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Sample records for ionic surfaces implications

  1. Stability of Secondary and Tertiary Structures of Virus-Like Particles Representing Noroviruses: Effects of pH, Ionic Strength, and Temperature and Implications for Adhesion to Surfaces

    PubMed Central

    Samandoulgou, Idrissa; Hammami, Riadh; Morales Rayas, Rocio; Fliss, Ismail

    2015-01-01

    Loss of ordered molecular structure in proteins is known to increase their adhesion to surfaces. The aim of this work was to study the stability of norovirus secondary and tertiary structures and its implications for viral adhesion to fresh foods and agrifood surfaces. The pH, ionic strength, and temperature conditions studied correspond to those prevalent in the principal vehicles of viral transmission (vomit and feces) and in the food processing and handling environment (pasteurization and refrigeration). The structures of virus-like particles representing GI.1, GII.4, and feline calicivirus (FCV) were studied using circular dichroism and intrinsic UV fluorescence. The particles were remarkably stable under most of the conditions. However, heating to 65°C caused losses of β-strand structure, notably in GI.1 and FCV, while at 75°C the α-helix content of GII.4 and FCV decreased and tertiary structures unfolded in all three cases. Combining temperature with pH or ionic strength caused variable losses of structure depending on the particle type. Regardless of pH, heating to pasteurization temperatures or higher would be required to increase GII.4 and FCV adhesion, while either low or high temperatures would favor GI.1 adhesion. Regardless of temperature, increased ionic strength would increase GII.4 adhesion but would decrease GI.1 adhesion. FCV adsorption would be greater at refrigeration, pasteurization, or high temperature combined with a low salt concentration or at a higher NaCl concentration regardless of temperature. Norovirus adhesion mediated by hydrophobic interaction may depend on hydrophobic residues normally exposed on the capsid surface at pH 3, pH 8, physiological ionic strength, and low temperature, while at pasteurization temperatures it may rely more on buried hydrophobic residues exposed upon structural rearrangement. PMID:26296729

  2. Hybridization of ionic levels at metal surfaces

    NASA Astrophysics Data System (ADS)

    Kürpick, P.; Thumm, U.

    1998-09-01

    We investigated the hybridization of He+, Li2+, and Be3+ ionic levels and the creation of surface resonances for nuclear charges Z=2, 3, and 4 near an Al surface. Starting from a two-center basis set expansion with hydrogenic wave functions on the ion site and jellium wave functions in the metal half space, we calculate the self-energy for ion-surface system in the fixed-ion approximation. We obtain convergence by using a rather small set of bound ionic states. This ideally suits this method for the generation of adiabatic basis states that can be used in time-dependent close-coupling calculations for slow ion-surface collisions. We compare our resonance energies and widths with other theoretical approaches, discuss electronic density profiles, and analyze resonances in terms of Stark states.

  3. Ionic surface electrical conductivity in sandstone

    NASA Astrophysics Data System (ADS)

    Glover, Paul W. J.; Meredith, Philip G.; Sammonds, Peter R.; Murrell, Stanley A. F.

    1994-11-01

    Recent analyses of complex conductivity measurements have indicated that high-frequency dispersions encountered in rocks saturated with low-salinity fluids are due to ionic surface conduction and that the form of these dispersions may be dependent upon the nature of the pore and crack surfaces within the rock (Ruffet et al., 1991). Unfortunately, the mechanisms of surface conduction are not well understood, and no model based on rigorous physical principles exists. This paper is split into two parts: an experimental section followed by the development of a theoretical description of adsorption of ions onto mineral surfaces. We have made complex conductivity measurements upon samples of sandstone saturated with a range of different types and concentrations of aqueous solution with a frequency range of 20 Hz to 1 MHz. The frequency dependence of complex conductivity was analyzed using the empirical model of Cole and Cole (1941). The 'fractal' surface models of Le Mehaute and Crepy (1983), Po Zen Wong (1987), the Ruffet el at. (1991) were used to calculate apparent fractal pore surface dimensions for samples saturated with different solution types and concentrations. These showed a pronounced decrease of apparent fractal surface dimension with decreasing electrolyte concentration and a decrease of apparent fractal dimension with increasing relative ionic radius of the dominant cation in solution. A model for ionic surface concentration (ISCOM I) has been developed as the first step in producing a rigorous physicochemical model of surface conduction in quartz-dominated rocks. The results from ISCOM I show that quartz surfaces are overwhelmingly dominated by adsorbed Na(+) when saturated with NaCl solutions of salinities and pH found in actual geological situations. ISCOM I also shows that the concentration threshold for dominance of surface conduction over bulk conduction is aided by depletion of ions from the bulk fluid as a result of their adsorption onto the mineral

  4. Layering of ionic liquids on rough surfaces

    NASA Astrophysics Data System (ADS)

    Sheehan, Alexis; Jurado, L. Andres; Ramakrishna, Shivaprakash N.; Arcifa, Andrea; Rossi, Antonella; Spencer, Nicholas D.; Espinosa-Marzal, Rosa M.

    2016-02-01

    Understanding the behavior of ionic liquids (ILs) either confined between rough surfaces or in rough nanoscale pores is of great relevance to extend studies performed on ideally flat surfaces to real applications. In this work we have performed an extensive investigation of the structural forces between two surfaces with well-defined roughness (<9 nm RMS) in 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide by atomic force microscopy. Statistical studies of the measured layer thicknesses, layering force, and layering frequency reveal the ordered structure of the rough IL-solid interface. Our work shows that the equilibrium structure of the interfacial IL strongly depends on the topography of the contact.Understanding the behavior of ionic liquids (ILs) either confined between rough surfaces or in rough nanoscale pores is of great relevance to extend studies performed on ideally flat surfaces to real applications. In this work we have performed an extensive investigation of the structural forces between two surfaces with well-defined roughness (<9 nm RMS) in 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide by atomic force microscopy. Statistical studies of the measured layer thicknesses, layering force, and layering frequency reveal the ordered structure of the rough IL-solid interface. Our work shows that the equilibrium structure of the interfacial IL strongly depends on the topography of the contact. Electronic supplementary information (ESI) available: Optimized geometries and sizes for [HMIM] Ntf2, SEM images of the smooth and rough colloids, frequency of occurrence of layering in the resolved force-distance curves for all investigated systems with [HMIM] Ntf2, layer size and layering force measured with a sharp tip on mica for the same IL, and results of the kinetics experiments. See DOI: 10.1039/c5nr07805a

  5. Ionic Liquids Can Permanently Modify Porous Silicon Surface Chemistry.

    PubMed

    Trivedi, Shruti; Coombs, Sidney G; Wagle, Durgesh V; Bhawawet, Nakara; Baker, Gary A; Bright, Frank V

    2016-08-01

    To develop ionic liquid/porous silicon (IL/pSi) microarrays we have contact pin-printed 20 hydrophobic and hydrophilic ionic liquids onto as-prepared, hydrogen-passivated porous silicon (ap-pSi) and then determined the individual IL spot size, shape and associated pSi surface chemistry. The results reveal that the hydrophobic ionic liquids oxidize the ap-pSi slightly. In contrast, the hydrophilic ionic liquids lead to heavily oxidized pSi (i.e., ox-pSi). The strong oxidation arises from residual water within the hydrophilic ILs that is delivered from these ILs into the ap-pSi matrix causing oxidation. This phenomenon is less of an issue in the hydrophobic ILs because their water solubility is substantially lower. PMID:27405109

  6. Ionic-charge modification at the surface of polar crystals

    SciTech Connect

    Watson, R.E.; Davenport, J.W.

    1983-05-15

    A simple variational principle has been applied to obtain a bound on the change in ionic charge of a polar crystal between the surface and the interior. Central to the estimate is the assumption that the energy involves terms analytic in the ionic charge q and that these may be treated as a sum of Madelung, intra-atomic, and interatomic (overlap and hybridization) contributions. The Madelung terms are calculated explicitly, the intra-atomic contributions are obtained from the following paper (Phys. Rev. B 27, 6428 (1983)), and the change in interatomic terms on going from the bulk to the surface is estimated by scaling with coordination number. The results do not replace detailed quantum-mechanical calculations but they are simple computationally, and they suggest trends in the competition between the Madelung potential, which encourages ion charging, and hybridization, which discourages ionic charging, both at the surface and in the interior of a crystal. Nonpolar surfaces are of principal concern but one polar surface is considered indicating that the charge disturbance penetrates much further in from the surface than it does in nonpolar cases where the effect is largely limited to the first layer of atoms.

  7. Corrosion prevention of magnesium surfaces via surface conversion treatments using ionic liquids

    DOEpatents

    Qu, Jun; Luo, Huimin

    2016-09-06

    A method for conversion coating a magnesium-containing surface, the method comprising contacting the magnesium-containing surface with an ionic liquid compound under conditions that result in decomposition of the ionic liquid compound to produce a conversion coated magnesium-containing surface having a substantially improved corrosion resistance relative to the magnesium-containing surface before said conversion coating. Also described are the resulting conversion-coated magnesium-containing surface, as well as mechanical components and devices containing the conversion-coated magnesium-containing surface.

  8. Weighing the surface charge of an ionic liquid.

    PubMed

    Hjalmarsson, Nicklas; Wallinder, Daniel; Glavatskih, Sergei; Atkin, Rob; Aastrup, Teodor; Rutland, Mark W

    2015-10-14

    Electrochemical quartz crystal microbalance has been used to measure changes in the composition of the capacitive electrical double layer for 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)-trifluorophosphate, an ionic liquid, in contact with a gold electrode surface as a function of potential. The mass difference between the cation and anion means that the technique can effectively "weigh" the surface charge accurately with high temporal resolution. This reveals quantitatively how changing the potential alters the ratio of cations and anions associated with the electrode surface, and thus the charge per unit area, as well as the kinetics associated with these interfacial processes. The measurements reveal that it is diffusion of co-ions into the interfacial region rather than expulsion of counterions that controls the relaxation. The measured potential dependent double layer capacitance experimentally validates recent theoretical predictions for counterion overscreening (low potentials) and crowding (high potentials) at electrode surfaces. This new capacity to quantitatively measure ion composition is critical for ionic liquid applications ranging from batteries, capacitors and electrodeposition through to boundary layer structure in tribology, and more broadly provides new insight into interfacial processes in concentrated electrolyte solutions. PMID:26370450

  9. Surface confined ionic liquid as a stationary phase for HPLC

    SciTech Connect

    Wang, Qian; Baker, Gary A; Baker, Sheila N; Colon, Luis

    2006-01-01

    Trimethoxysilane ionosilane derivatives of room temperature ionic liquids based on alkylimidazolium bromides were synthesized for attachment to silica support material. The derivatives 1-methyl-3-(trimethoxysilylpropyl)imidazolium bromide and 1-butyl-3-(trimethoxysilylpropyl)imidazolium bromide were used to modify the surface of 3 {micro}m diameter silica particles to act as the stationary phase for HPLC. The modified particles were characterized by thermogravimetric analysis (TGA) and {sup 13}C and {sup 29}Si NMR spectroscopies. The surface modification procedure rendered particles with a surface coverage of 0.84 {micro}mol m{sup -2} for the alkylimidazolium bromide. The ionic liquid moiety was predominantly attached to the silica surface through two siloxane bonds of the ionosilane derivative (63%). Columns packed with the modified silica material were tested under HPLC conditions. Preliminary evaluation of the stationary phase for HPLC was performed using aromatic carboxylic acids as model compounds. The separation mechanism appears to involve multiple interactions including ion exchange, hydrophobic interaction, and other electrostatic interactions.

  10. Imidazolium-based ionic liquids grafted on solid surfaces.

    PubMed

    Xin, Bingwei; Hao, Jingcheng

    2014-01-01

    Supported ionic liquids (SILs), which refer to ionic liquids (ILs) immobilized on supports, are among the most important derivatives of ILs. The immobilization process of ILs can transfer their desired properties to substrates. Combination of the advantages of ILs with those of support materials will derive novel performances while retaining properties of both moieties. SILs have been widely applied in almost all of fields involving ILs, and have brought about drastic expansion of the ionic liquid area. As green media in organic catalytic reactions, based on utilizing the ability of ILs to stabilize the catalysts, they have many advantages over free ILs, including avoiding the leaching of ILs, reducing their amount, and improving the recoverability and reusability of both themselves and catalysts. This has critical significance from both environmental and economical points of view. As novel functional materials in surface science and material chemistry, SILs are ideal surface modifying agents. They can modify and improve the properties of solids, such as wettability, lubricating property, separation efficiency and electrochemical response. With the achievements in the field of ILs, using magnetic nanoparticles (MNPs) to SILs has drawn increasing attention in catalytic reactions and separation technologies, and achieved substantial progress. The combination of MNPs and ILs renders magnetic SILs, which exhibit the unique properties of ILs as well as facile separation by an external magnetic field. In this article, we focus on imidazolium-based ILs covalently grafted to non-porous and porous inorganic materials. The excellent stability and durability of this kind of SILs offer a great advantage compared with free ILs and IL films physically adsorbed on substrates without covalent bonds. Including examples from our own research, we overview mainly the applications and achievements of covalent-linked SILs in catalytic reactions, surface modification, separation

  11. Computer simulation of the structure of ionic surfaces and interfaces

    SciTech Connect

    Wolf, D.

    1994-09-01

    The classic Madelung problem, i.e., the divergence associated with the r{sup {minus}1} term in the Coulomb potential of condensed ionic systems, was recently cast into an absolutely convergent form that is readily evaluated by direct lattice summation, revealing a net r{sup {minus}5} range of this potential. This realization that Coulomb interactions in condensed systems can actually be rather short ranged (if the system is overall neutral) permits novel physical insights into their structure and energetics to be gained. As an example, the authors demonstrate that an understanding of the range and the nature of the convergence of the Coulomb potential leads naturally to the prediction, verified here by computer simulations for rocksalt-structured surfaces, that all surfaces in predominantly ionic materials should be fundamentally reconstructed. The work also provides a conceptual framework for the theoretical treatment of polar surfaces and interfaces, as demonstrated here for the case of the (111) stacking fault and of the (111) twin boundary in the rocksalt structure.

  12. Effect of Ionic Strength and Surface Charge on Convective Deposition.

    PubMed

    Joshi, Kedar; Muangnapoh, Tanyakorn; Stever, Michael D; Gilchrist, James F

    2015-11-17

    Particle-particle and particle-substrate interactions play a crucial role in capillary driven convective self-assembly for continuous deposition of particles. This systematic study demonstrates the nontrivial effects of varying surface charge and ionic strength of monosized silica microspheres in water on the quality of the deposited monolayer. Increase in particle surface charge results a broader range of parameters that result in monolayer deposition which can be explained considering the particle-substrate electrostatic repulsion in solution. Resulting changes in the coating morphology and microstructure at different solution conditions were observed using confocal microscopy enabling correlation of order to disorder transitions with relative particle stability. These results, in part, may explain similar results seen by Muangnapoh et al., 2013 in vibration-assisted convective deposition. PMID:26501996

  13. Photoresponsive Self-Assembly of Surface Active Ionic Liquid.

    PubMed

    Wu, Aoli; Lu, Fei; Sun, Panpan; Gao, Xinpei; Shi, Lijuan; Zheng, Liqiang

    2016-08-16

    A novel photoresponsive surface active ionic liquid (SAIL) 1-(4-methyl azobenzene)-3-tetradecylimidazolium bromide ([C14mimAzo]Br) with azobenzene located in the headgroup was designed. Reversible vesicle formation and rupture can be finely controlled by photostimuli without any additives in the aqueous solution of the single-tailed ionic liquid. The photoisomerization of the azobenzene derivative was investigated by (1)H NMR and UV-vis spectroscopy. Density functional theory (DFT) calculations further demonstrate that trans-[C14mimAzo]Br has less negative interaction energy, which is beneficial to aggregate formation in water. The incorporation of trans-azobenzene group increases the hydrophobicity of the headgroup and reduces the electrostatic repulsion by delocalization of charge, which are beneficial to the formation of vesicles. However, the bend of cis-azobenzene makes the cis-isomers have no ability to accumulate tightly, which induces the rupture of vesicles. Our work paves a convenient way to achieve controlled topologies and self-assembly of single SAIL. PMID:27445115

  14. Multiscale implications of stress-induced ionic polymer transducer sensing

    NASA Astrophysics Data System (ADS)

    Zangrilli, Ursula Therese

    Ionic Polymer Transducers (IPTs) can act as both actuators and sensors. As actuators, the energy density values are much better than PZT or PVDF materials. As sensors, IPTs are extraordinarily sensitive and have the potential to be used in any mode of deformation. However, application of IPT sensors is limited because of a lack of understanding of their fundamental physics. In this work, the main focus will be to explore and develop a better understanding of how IPTs function with respect to shear deformation. In turn, the results developed here will improve upon the state of understanding of IPT sensors in general and potentially expand meaningful application opportunities. Because IPT active response is a multiscale phenomenon, this study adopts a multiscale modeling framework. Of interest are the interplay among the polymeric backbone of the ionic polymer, the diluent present in the hydrophilic regions of the polymer and the interspersed electrode particulate. To begin, this work improves upon a past multiscale modeling framework for the polymer backbone based upon Rotational Isomeric State Theory such that the effects of material anisotropy may be considered. This is potentially significant in light of the polymer manufacturing process. These modeling results are then incorporated into a model of the diluent movement within the ionic transport regions of the IPT. The electrical current predictions are based upon streaming potential theories. Finally, this model incorporates viscoelastic behavior in order to develop a better understanding of the coupling of these two systems (the polymer and the diluent) and how this coupling influence affects the expected current output over time.

  15. Fluorination effects on the thermodynamic, thermophysical and surface properties of ionic liquids

    PubMed Central

    Reis, P. M.; Carvalho, P. J.; Lopes-da-Silva, J. A.; Esperança, J. M. S. S.; Araújo, J. M. M.; Rebelo, L. P. N.; Freire, M. G.; Pereiro, A. B.

    2016-01-01

    This paper reports the thermal, thermodynamic, thermophysical and surface properties of eight ionic liquids with fluorinated alkyl side chain lengths equal or greater than four carbon atoms. Melting and decomposition temperatures were determined together with experimental densities, surface tensions, refractive indices, dynamic viscosities and ionic conductivities in a temperature interval ranging from 293.15 to 353.15 K. The surface properties of these fluorinated ionic liquids were discussed and several thermodynamic functions, as well as critical temperatures, were estimated. Coefficients of isobaric thermal expansion, molecular volumes and free volume effects were calculated from experimental values of density and refractive index and compared with previous data. Finally, Walden plots were used to evaluate the ionicity of the investigated ionic liquids.

  16. Mesoporous and biocompatible surface active silica aerogel synthesis using choline formate ionic liquid.

    PubMed

    Meera, Kamal Mohamed Seeni; Sankar, Rajavelu Murali; Jaisankar, Sellamuthu N; Mandal, Asit Baran

    2011-09-01

    In this paper, we report the preparation and characterization of mesoporous and biocompatible transparent silica aerogel by the sol-gel polymerization of tetraethyl orthosilicate using ionic liquid. Choline cation based ionic liquid allows the silica framework to form in a non collapsing environment and controls the pore size of the gel. FT-IR spectra reveal the interaction of ionic liquid with surface -OH of the gel. DSC thermogram giving the evidence of confinement of ionic liquid within the silica matrix, which helps to avoid the shrinkage of the gel during the aging process. Nitrogen sorption measurements of gel prepared with ionic liquid exhibit a low surface area of 100.53 m2/g and high average pore size of 3.74 nm. MTT assay proves the biocompatibility and cell viability of the prepared gels. This new nanoporous silica material can be applied to immobilize biological molecules, which may retain their stability over a longer period. PMID:21565470

  17. Influence of ionic strength on the surface charge and interaction of layered silicate particles.

    PubMed

    Liu, Jing; Miller, Jan D; Yin, Xihui; Gupta, Vishal; Wang, Xuming

    2014-10-15

    The surface charge densities and surface potentials of selected phyllosilicate surfaces were calculated from AFM surface force measurements and reported as a function of ionic strength at pH 5.6. The results show that the silica faces of clay minerals follow the constant surface charge model because of isomorphous substitution in the silica tetrahedral layer. A decreasing surface charge density sequence was observed as follows: muscovite silica face>kaolinite silica face>talc silica face, which is expected to be due to the extent of isomorphous substitution. In contrast, at pH 5.6, the alumina face and the edge surface of kaolinite follow the constant surface potential model with increasing ionic strength, and the surface charge density increased with increasing ionic strength. The cluster size of suspended kaolinite particles at pH 5.6 was found to increase with increasing ionic strength due to an increase in the surface charge density for the alumina face and the edge surface. However, the cluster size decreased at 100mM KCl as a result of an unexpected decrease in the surface charge of the alumina face. When the ionic strength continued to increase above 100mM KCl, the van der Waals attraction dominated and larger clusters of micron size were stabilized. PMID:25086721

  18. Correlating Humidity-Dependent Ionically Conductive Surface Area with Transport Phenomena in Proton-Exchange Membranes

    SciTech Connect

    He, Qinggang; Kusoglu, Ahmet; Lucas, Ivan T.; Clark, Kyle; Weber, Adam Z.; Kostecki, Robert

    2011-08-01

    The objective of this effort was to correlate the local surface ionic conductance of a Nafion? 212 proton-exchange membrane with its bulk and interfacial transport properties as a function of water content. Both macroscopic and microscopic proton conductivities were investigated at different relative humidity levels, using electrochemical impedance spectroscopy and current-sensing atomic force microscopy (CSAFM). We were able to identify small ion-conducting domains that grew with humidity at the surface of the membrane. Numerical analysis of the surface ionic conductance images recorded at various relative humidity levels helped determine the fractional area of ion-conducting active sites. A simple square-root relationship between the fractional conducting area and observed interfacial mass-transport resistance was established. Furthermore, the relationship between the bulk ionic conductivity and surface ionic conductance pattern of the Nafion? membrane was examined.

  19. Interfacial structure and orientation of confined ionic liquids on charged quartz surfaces.

    PubMed

    Wang, Yong-Lei; Laaksonen, Aatto

    2014-11-14

    Atomistic molecular dynamics simulations have been performed to study microscopic ionic structures and orientational preferences of absorbed [BMIM] cations and four paired anions ([BF4], [PF6], [TFO] and [TF2N]) on quartz surfaces. Two chemically different quartz surface models were adopted: one is saturated with silanol Si(OH)2 groups, and the other one is covered by silane SiH2 groups, respectively. Simulation results reveal that dense ionic layers, characterized by distinct mass, number, charge and electron densities, are formed in quartz interfacial region. The orientational preferences of confined ionic groups are characterized with different features depending on the size and shape of anionic groups, and the quartz surface charge. The [BMIM] cations attach exclusively onto the negatively charged Si(OH)2 surface. The imidazolium rings lie preferentially perpendicular to Si(OH)2 surface, to which the directly connected methyl and butyl chains are oriented and elongated along Si(OH)2 surface, respectively. The anions are mainly absorbed on positively charged SiH2 surface. The main axes of asymmetric [TFO] and [TF2N] anions are perpendicular and parallel to SiH2 surface, respectively. Such distinct structural and orientational preferences of confined ionic groups attribute to the strong electrostatic interactions and the formation of hydrogen bonds between confined ionic species and quartz interfacial groups. PMID:25260202

  20. Study of tribochemical decomposition of ionic liquids on a nascent steel surface

    NASA Astrophysics Data System (ADS)

    Lu, Renguo; Mori, Shigeyuki; Kobayashi, Kimihiro; Nanao, Hidetaka

    2009-08-01

    Tribological properties and the decomposition process of ionic liquids (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide and 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide) on a nascent surface of bearing steel 52100 were investigated by a ball-on-disk friction tester in a vacuum chamber equipped with a quadrupole mass spectrometer (Q-MS). Ionic liquids exhibited better tribological properties than synthetic hydrocarbon oil (multialkylated cyclopentane (MAC)) in high vacuum conditions. The induction period for decomposition of MAC was about 10 km, while no obvious gaseous products were observed for ionic liquids even after a sliding distance of 22 km under the same mechanical conditions. The mass spectra indicated that both the anionic and cationic moieties of ionic liquids decomposed on the nascent steel surface during friction processes. The cationic moiety with a longer alkyl chain was more difficult to decompose on the nascent steel surface than that with a shorter alkyl chain. XPS analysis revealed that the tribofilm formed by ionic liquid was mainly composed of FeF 2 and FeS, which deactivated the nascent surface. As a result, desorption rate of gaseous products decreased appreciably comparing with MAC. The critical load for the mechanical activation of the decomposition correspondingly increased from 1.1 N of MAC to 8 N of ionic liquids.

  1. Simulation of ionic surfaces from an absolutely convergent solution of the Madelung problem

    SciTech Connect

    Wolf, D.

    1995-04-01

    The classic Madelung problem is cast into an absolutely convergent form that is readily evaluated by direct lattice summation, revealing a net r{sup {minus}5} range of the net Coulomb potential in ionic crystals and liquids. The realization that Coulomb interactions in condensed systems can actually be rather short ranged (provided the system is overall neutral) leads to the prediction, verified by computer simulations for rocksalt-structure surfaces, that all surfaces in predominantly ionic crystals should be fundamentally reconstructed. The work also provides a conceptual framework for the theoretical treatment of polar surfaces, as demonstrated for the case of the (111) surfaces of NaCl and MgO.

  2. Surface Physicochemistry and Ionic Strength Affects eDNA’s Role in Bacterial Adhesion to Abiotic Surfaces

    PubMed Central

    Regina, Viduthalai R.; Lokanathan, Arcot R.; Modrzyński, Jakub J.; Sutherland, Duncan S.; Meyer, Rikke L.

    2014-01-01

    Extracellular DNA (eDNA) is an important structural component of biofilms formed by many bacteria, but few reports have focused on its role in initial cell adhesion. The aim of this study was to investigate the role of eDNA in bacterial adhesion to abiotic surfaces, and determine to which extent eDNA-mediated adhesion depends on the physicochemical properties of the surface and surrounding liquid. We investigated eDNA alteration of cell surface hydrophobicity and zeta potential, and subsequently quantified the effect of eDNA on the adhesion of Staphylococcus xylosus to glass surfaces functionalised with different chemistries resulting in variable hydrophobicity and charge. Cell adhesion experiments were carried out at three different ionic strengths. Removal of eDNA from S. xylosus cells by DNase treatment did not alter the zeta potential, but rendered the cells more hydrophilic. DNase treatment impaired adhesion of cells to glass surfaces, but the adhesive properties of S. xylosus were regained within 30 minutes if DNase was not continuously present, implying a continuous release of eDNA in the culture. Removal of eDNA lowered the adhesion of S. xylosus to all surfaces chemistries tested, but not at all ionic strengths. No effect was seen on glass surfaces and carboxyl-functionalised surfaces at high ionic strength, and a reverse effect occurred on amine-functionalised surfaces at low ionic strength. However, eDNA promoted adhesion of cells to hydrophobic surfaces irrespective of the ionic strength. The adhesive properties of eDNA in mediating initial adhesion of S. xylosus is thus highly versatile, but also dependent on the physicochemical properties of the surface and ionic strength of the surrounding medium. PMID:25122477

  3. Probing the interaction of ionic liquids with graphene using surface-enhanced Raman spectroscopy

    SciTech Connect

    Mahurin, Shannon Mark; Dai, Sheng; Surwade, Sumedh P.; Crespo, Marcos

    2015-12-17

    We report an in situ measurement of the interaction of an imidazolium-based room temperature ionic liquid with both pure silver and a graphene-over-silver electrode under an applied electrochemical potential. At a negative applied potential, overall signal intensity increased indicating enhanced ionic liquid concentration at both silver and graphene electrodes. Vibrational modes associated with the imidazolium ring exhibited greater intensity enhancements and larger peak shifts compared with the anion indicating that the cation adsorbs with the ring and alkyl chain parallel to the electrode surface for both silver and graphene. In contrast to the silver, the surface enhanced Raman spectra of the ionic liquid near graphene showed shifts in the cation peaks even at no applied potential because of the strong π–π interaction between the ionic liquid and the graphene. Furthermore, the intensity of the graphene peak decreased in the presence of ionic liquid possibly due to the interaction between the ionic liquid and graphene. In conclusion, these results illustrate the effectiveness of surface-enhanced Raman spectroscopy to investigate electrolyte interactions with graphene at the liquid/electrode interface.

  4. Probing the interaction of ionic liquids with graphene using surface-enhanced Raman spectroscopy

    DOE PAGESBeta

    Mahurin, Shannon Mark; Dai, Sheng; Surwade, Sumedh P.; Crespo, Marcos

    2015-12-17

    We report an in situ measurement of the interaction of an imidazolium-based room temperature ionic liquid with both pure silver and a graphene-over-silver electrode under an applied electrochemical potential. At a negative applied potential, overall signal intensity increased indicating enhanced ionic liquid concentration at both silver and graphene electrodes. Vibrational modes associated with the imidazolium ring exhibited greater intensity enhancements and larger peak shifts compared with the anion indicating that the cation adsorbs with the ring and alkyl chain parallel to the electrode surface for both silver and graphene. In contrast to the silver, the surface enhanced Raman spectra ofmore » the ionic liquid near graphene showed shifts in the cation peaks even at no applied potential because of the strong π–π interaction between the ionic liquid and the graphene. Furthermore, the intensity of the graphene peak decreased in the presence of ionic liquid possibly due to the interaction between the ionic liquid and graphene. In conclusion, these results illustrate the effectiveness of surface-enhanced Raman spectroscopy to investigate electrolyte interactions with graphene at the liquid/electrode interface.« less

  5. New Alkylether-Thiazolium Room-Temperature Ionic Liquid Lubricants: Surface Interactions and Tribological Performance.

    PubMed

    Espinosa, Tulia; Sanes, José; Bermúdez, María-Dolores

    2016-07-20

    The use of newly synthesized alkylether-thiazolium ionic liquids as lubricants is described for the first time. Two ionic liquids composed of a thiazolium cation and a bis(trifluoromethanesulfonyl)amide ([Th][Tf2N]) or dicyanamide ([Th][(NC)2N]) anion have been studied, and their tribological behavior has been compared with that of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([Im][Tf2N]) in pin-on-disk tests using sapphire balls against AISI 52100 or AISI 316L steels. All ionic liquids show higher contact angles on AISI 316L steel than on AISI 52100, the lowest values found for ([Im][Tf2N]) on both steel surfaces. AISI 52100 shows similar friction coefficients for all lubricants, and negligible wear rates for the ionic liquids containing the bis(trifluoromethanesulfonyl)amide anion. Immersion tests show no corrosion of AISI 52100 in imidazolium or thiazolium bis(trifluoromethanesulfonyl)amide ionic liquids. AISI 316L shows similar friction coefficients for both bis(trifluoromethanesulfonyl)amide ionic liquids, but the lowest wear rate is obtained for [Th][Tf2N]. An increase in friction coefficient and wear rate is observed for thiazolium dicyanamide. This increase is related to a tribocorrosion process due to decomposition of the thiazolium cation. XPS shows the formation of iron sulfide on the wear track on AISI 316L after lubrication with thiazolium dicyanamide. No tribocorrosion processes take place for the [Tf2N] ionic liquids. PMID:27348604

  6. A study of the ionic conduction of mica surface by admittance spectroscopy

    NASA Astrophysics Data System (ADS)

    Dolci, D.; Aloisi, G.; Lanzi, L.; Carlà, M.

    2007-08-01

    The ionic conduction on the surface of humid mica has been analyzed by admittance spectroscopy as a function of relative humidity for different surface treatments. Measurements at low frequency indicate that water adsorption proceeds first in the form of a strongly adsorbed uniform thin layer, then with the formation of highly inhomogeneous thick aggregates.

  7. Polymerization process for carboxyl containing polymers utilizing oil soluble ionic surface active agents

    SciTech Connect

    Uebele, C.E.; Ball, L.E.; Jorkasky, R.J. II; Wardlow, E. Jr.

    1987-09-08

    This patent describes a method for polymerizing olefinically unsaturated carboxylic acid monomers containing at least one activated carbon to carbon olefinic double bond and at least one carboxyl group. The monomers are polymerized in an organic media consisting essentially of organic liquids, in the presence of free radical forming catalysts and at least one oil soluble ionic surface active agent selected from the group consisting of: (a) anionic surface active agents; (b) cationic surface active agents; and (c) amphoteric surface active agents.

  8. Wire-to-Plate Surface Dielectric Barrier Discharge and Induced Ionic Wind

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Liu, Lijuan; Li, Ben; Ouyang, Jiting

    2016-06-01

    The electrical and mechanical characteristics of the wire-to-plate surface dielectric barrier discharge and the induced ionic wind are investigated experimentally. The different temporal behaviors in positive and negative half-cycles are studied by time-resolved images. It is shown that the discharge and the light emission are generally stronger in the positive half cycle. The discharge is inhomogeneous and propagates in streamer mode; however, in the negative half-cycle, the discharge appears visually uniformly and operates in the diffuse mode. The surface discharge can produce ionic wind about several m/s above the dielectric surface. There exists an optimal width of the grounded electrode to produce a larger plasma area or active wind region. Increasing of the applied voltage or normalized dielectric constant leads to a larger wind velocity. The performance of ionic wind on flow control is visualized by employing a smoke stream. supported by National Natural Science Foundation of China (Nos. 11175017 and 11475019)

  9. Magadiite Templated High Surface Area Graphene-Type Carbons from Metal-Halide based Ionic Liquids

    SciTech Connect

    Fulvio, Pasquale F; Hillesheim, Patrick C; Bauer, John C; Mahurin, Shannon Mark; Dai, Sheng; Arend, Nikolas

    2013-01-01

    Freestanding silicon films with a thickness ranging from 1 nm to several micrometers were prepared by Cat-CVD onto ionic liquid ([BMIM][BF4]) surfaces for the first time. The films, obtained without a solid substrate, can be facilely characterized by TEM and AFM to study the film formation and growth process.

  10. Accelerated CO2 transport on surface of AgO nanoparticles in ionic liquid BMIMBF4

    PubMed Central

    Ji, Dahye; Kang, Yong Soo; Kang, Sang Wook

    2015-01-01

    The AgO nanoparticles were utilized for a CO2 separation membrane. The AgO nanoparticles were successfully generated in ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIMBF4) by favorable interaction between the surface of particles and the counteranion of BMIMBF4. The generated AgO nanoparticles were confirmed by TEM, and the average size was 20 nm. Coordinative interactions of dissociated AgO particles with BMIM+BF4− were investigated by FT-Raman spectroscopy. When the ionic liquid BMIMBF4 containing AgO nanoparticles was utilized as a CO2 separation membrane, the separation performance was largely enhanced. PMID:26549605

  11. Ionic Behavior in Highly Concentrated Aqueous Solutions Nanoconfined between Discretely Charged Silicon Surfaces.

    PubMed

    Qiu, Yinghua; Ma, Jian; Chen, Yunfei

    2016-05-17

    Through molecular dynamics simulations considering thermal vibration of surface atoms, ionic behaviors in concentrated NaCl solutions confined between discretely charged silicon surfaces have been investigated. The electric double layer structure was found to be sensitive to the density and distribution of surface charges. Due to the discreteness of the surface charge, a slight charge inversion appeared which depended on the surface charge density, bulk concentration, and confinement. In the nanoconfined NaCl solutions concentrated from 0.2 to 4.0 M, the locations of accumulation layers for Na(+) and Cl(-) ions remained stable, but their peak values increased. The higher the concentration was, the more obvious the charge inversion appeared. In 4.0 M NaCl solution, Na(+) and Cl(-) ions show obvious alternating layered distributions which may correspond to the solidification found in experiments. By changing surface separation, the confinement had a large effect on the ionic distribution. As both surfaces approached each other, many ions and water molecules were squeezed out of the confined space. Two adjacent layers in ion or water distribution profiles can be forced closer to each other and merge together. From ionic hydration analysis, the coordination number of Na(+) ions in highly confined space was much lower than that in the bulk. PMID:27137990

  12. Peculiar surface behavior of some ionic liquids based on active pharmaceutical ingredients

    NASA Astrophysics Data System (ADS)

    Restolho, José; Mata, José Luis; Saramago, Benilde

    2011-02-01

    The ionic liquids based on biologically active cations and anions, commonly designated by ionic liquids based on active pharmaceutical ingredients (ILs-APIs), are interesting compounds for use in pharmaceutical applications. Lidocaine docusate, ranitidine docusate, and didecyldimethylammonium ibuprofen are examples of promising ILs-APIs that were recently synthesized. They were submitted to biological testing and calorimetric measurements, but nothing is known about their surface properties. In this work, we measured the surface tension and the contact angles on both hydrophilic and hydrophobic surfaces in a temperature range as wide as possible. Based on the wettability data, the polarity fractions were estimated using the Fowkes theory. The peculiar surface behavior observed was tentatively attributed to the presence of mesophases.

  13. Peculiar surface behavior of some ionic liquids based on active pharmaceutical ingredients.

    PubMed

    Restolho, José; Mata, José Luis; Saramago, Benilde

    2011-02-21

    The ionic liquids based on biologically active cations and anions, commonly designated by ionic liquids based on active pharmaceutical ingredients (ILs-APIs), are interesting compounds for use in pharmaceutical applications. Lidocaine docusate, ranitidine docusate, and didecyldimethylammonium ibuprofen are examples of promising ILs-APIs that were recently synthesized. They were submitted to biological testing and calorimetric measurements, but nothing is known about their surface properties. In this work, we measured the surface tension and the contact angles on both hydrophilic and hydrophobic surfaces in a temperature range as wide as possible. Based on the wettability data, the polarity fractions were estimated using the Fowkes theory. The peculiar surface behavior observed was tentatively attributed to the presence of mesophases. PMID:21341864

  14. Study of surface-bonded dicationic ionic liquids as stationary phases for hydrophilic interaction chromatography.

    PubMed

    Qiao, Lizhen; Li, Hua; Shan, Yuanhong; Wang, Shuangyuan; Shi, Xianzhe; Lu, Xin; Xu, Guowang

    2014-02-21

    In the present study, several geminal dicationic ionic liquids based on 1,4-bis(3-allylimidazolium)butane and 1,8-bis(3-allylimidazolium)octane in combination with different anions bromide and bis(trifluoromethanesulphonyl)imide were prepared and then bonded to the surface of 3-mercaptopropyl modified silica materials through the "thiol-ene" click chemistry as stationary phases for hydrophilic interaction chromatography (HILIC). Compared with their monocationic analogues, the dicationic ionic liquids stationary phases presented effective retention and good selectivity for typical hydrophilic compounds under HILIC mode with the column efficiency as high as 130,000 plates/m. Moreover, the influence of different alkyl chain spacer between dications and combined anions on the retention behavior and selectivity of the dicationic ionic liquids stationary phases under HILIC mode was displayed. The results indicated that the longer linkage chain would decrease the hydrophilicity and retention on the dicationic ionic liquid stationary phase, and while differently combined anions had no difference due to the exchangeability under the common HILIC mobile phase with buffer salt. Finally, the retention mechanism was investigated by evaluating the effect of chromatographic factors on retention, including the water content in the mobile phase, the mobile phase pH and buffer salt concentration. The results showed that the dicationic ionic liquids stationary phases presented a mixed-mode retention behavior with HILIC mechanism and anion exchange. PMID:24484692

  15. Influence of Nanosegregation on the Surface Tension of Fluorinated Ionic Liquids.

    PubMed

    Luís, Andreia; Shimizu, Karina; Araújo, João M M; Carvalho, Pedro J; Lopes-da-Silva, José A; Canongia Lopes, José N; Rebelo, Luís Paulo N; Coutinho, João A P; Freire, Mara G; Pereiro, Ana B

    2016-06-21

    We have investigated, both theoretically and experimentally, the balance between the presence of alkyl and perfluoroalkyl side chains on the surface organization and surface tension of fluorinated ionic liquids (FILs). A series of ionic liquids (ILs) composed of 1-alkyl-3-methylimidazolium cations ([CnC1im] with n = 2, 4, 6, 8, 10, or 12) combined with the perfluorobutanesulfonate anion was used. The surface tensions of the investigated liquid salts are considerably lower than those reported for non-fluorinated ionic liquids. The most surprising and striking feature is the identification, for the first time, of a minimum at n = 8 in the surface tension versus the length of the IL cation alkyl side chain. Supported by molecular dynamics (MD) simulations, it was found that this trend is a result of the competition between the two nonpolar domains (perfluorinated and aliphatic) pointing toward the gas-liquid interface, a phenomenon which occurs in ILs with perfluorinated anions. Furthermore, these ILs present the lowest surface entropy reported to date. PMID:27218210

  16. Surface science and model catalysis with ionic liquid-modified materials.

    PubMed

    Steinrück, H-P; Libuda, J; Wasserscheid, P; Cremer, T; Kolbeck, C; Laurin, M; Maier, F; Sobota, M; Schulz, P S; Stark, M

    2011-06-17

    Materials making use of thin ionic liquid (IL) films as support-modifying functional layer open up a variety of new possibilities in heterogeneous catalysis, which range from the tailoring of gas-surface interactions to the immobilization of molecularly defined reactive sites. The present report reviews recent progress towards an understanding of "supported ionic liquid phase (SILP)" and "solid catalysts with ionic liquid layer (SCILL)" materials at the microscopic level, using a surface science and model catalysis type of approach. Thin film IL systems can be prepared not only ex-situ, but also in-situ under ultrahigh vacuum (UHV) conditions using atomically well-defined surfaces as substrates, for example by physical vapor deposition (PVD). Due to their low vapor pressure, these systems can be studied in UHV using the full spectrum of surface science techniques. We discuss general strategies and considerations of this approach and exemplify the information available from complementary methods, specifically photoelectron spectroscopy and surface vibrational spectroscopy. PMID:21520462

  17. Surface morphology implications on Langmuir probe measurements

    NASA Astrophysics Data System (ADS)

    Suresh, Padmashri

    2011-12-01

    Langmuir probes are extensively employed to study the plasmas in space and laboratory environments. Successful measurements require a comprehensive modeling of both the plasma environment and the probe conditions in the form of current collection models. In this thesis, the surface morphology implications on the probe current collection are investigated. This problem is applied and solved in the context of a CubeSat regime. The first problem that is investigated is the consequence of surface structural variability on the current measurements. A new model for dealing with non-uniformity of the probe surface structure is developed in this paper. This model is applied to analyze the Langmuir probe data from a sounding rocket mission that was subjected to surface structural non-homogeneities. This model would be particularly useful for CubeSat platforms where elaborate probe design procedures are not feasible. The second problem that is investigated is the surface area implications on Langmuir probe measurements. It has been established that surface area ratio of the spacecraft to that of the probe needs to be sufficiently large to make successful plasma measurements. CubeSats would therefore pose a challenge for employing Langmuir-type instruments to study the space plasma. We inspect the feasibility of making plasma measurements using Langmuir probes subjected to CubeSat area constraints. This analysis is done for a forthcoming Utah State University (USU)/Space Dynamics Lab (SDL) CubeSat mission.

  18. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    SciTech Connect

    Roberts, J.G.

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  19. Neptunium (V) Adsorption to a Halophilic Bacterium Under High Ionic Strength Conditions: A Surface Complexation Modeling Approach

    SciTech Connect

    Ams, David A

    2012-06-11

    Rationale for experimental design: Np(V) -- important as analog for Pu(V) and for HLW scenarios; High ionic strength -- relevant to salt-based repositories such as the WIPP; Halophilic microorganisms -- representative of high ionic strength environments. For the first time showed: Significant adsorbant to halophilic microorganisms over entire pH range under high ionic strength conditions; Strong influence of ionic strength with increasing adsorption with increasing ionic strength (in contrast to trends of previous low ionic strength studies); Effect of aqueous Np(V) and bacterial surface site speciation on adsorption; and Developed thermodynamic models that can be incorporated into geochemical speciation models to aid in the prediction of the fate and transport of Np(V) in more complex systems.

  20. Equilibrium and stability of polarization in ultrathin ferroelectric films with ionic surface compensation.

    SciTech Connect

    Stephenson, G. B.; Highland, M. J.

    2011-01-01

    Thermodynamic theory is developed for the ferroelectric phase transition of an ultrathin film in equilibrium with a chemical environment that supplies ionic species to compensate its surface. Equations of state and free energy expressions are developed based on Landau-Ginzburg-Devonshire theory, using electrochemical equilibria to provide ionic compensation boundary conditions. Calculations are presented for a monodomain PbTiO{sub 3} (001) film coherently strained to SrTiO{sub 3} with its exposed surface and its electronically conducting bottom electrode in equilibrium with a controlled oxygen partial pressure. The stability and metastability boundaries of phases of different polarization are determined as a function of temperature, oxygen partial pressure, and film thickness. Phase diagrams showing polarization and internal electric field are presented. At temperatures below a thickness-dependent Curie point, high or low oxygen partial pressure stabilizes positive or negative polarization, respectively. Results are compared to the standard cases of electronic compensation controlled by either an applied voltage or charge across two electrodes. Ionic surface compensation through chemical equilibrium with an environment introduces new features into the phase diagram. In ultrathin films, a stable nonpolar phase can occur between the positive and negative polar phases when varying the external chemical potential at fixed temperature, under conditions where charged surface species are not present in sufficient concentration to stabilize a polar phase.

  1. Nanoscale Lubrication of Ionic Surfaces Controlled via a Strong Electric Field

    PubMed Central

    Strelcov, Evgheni; Kumar, Rajeev; Bocharova, Vera; Sumpter, Bobby G.; Tselev, Alexander; Kalinin, Sergei V.

    2015-01-01

    Frictional forces arise whenever objects around us are set in motion. Controlling them in a rational manner means gaining leverage over mechanical energy losses and wear. This paper presents a way of manipulating nanoscale friction by means of in situ lubrication and interfacial electrochemistry. Water lubricant is directionally condensed from the vapor phase at a moving metal-ionic crystal interface by a strong confined electric field, thereby allowing friction to be tuned up or down via an applied bias. The electric potential polarity and ionic solid solubility are shown to strongly influence friction between the atomic force microscope (AFM) tip and salt surface. An increase in friction is associated with the AFM tip digging into the surface, whereas reducing friction does not influence its topography. No current flows during friction variation, which excludes Joule heating and associated electrical energy losses. The demonstrated novel effect can be of significant technological importance for controlling friction in nano- and micro-electromechanical systems. PMID:25623295

  2. Nanoscale lubrication of ionic surfaces controlled via a strong electric field

    SciTech Connect

    Strelcov, Evgheni; Bocharova, Vera; Sumpter, Bobby G.; Tselev, Alexander; Kalinin, Sergei V.; Kumar, Rajeev

    2015-01-27

    Frictional forces arise whenever objects around us are set in motion. Controlling them in a rational manner means gaining leverage over mechanical energy losses and wear. This paper presents a way of manipulating nanoscale friction by means of in situ lubrication and interfacial electrochemistry. Water lubricant is directionally condensed from the vapor phase at a moving metal-ionic crystal interface by a strong confined electric field, thereby allowing friction to be tuned up or down via an applied bias. The electric potential polarity and ionic solid solubility are shown to strongly influence friction between the atomic force microscope (AFM) tip and salt surface. An increase in friction is associated with the AFM tip digging into the surface, whereas reducing friction does not influence its topography. No current flows during friction variation, which excludes Joule heating and associated electrical energy losses. Lastly, the demonstrated novel effect can be of significant technological importance for controlling friction in nano- and micro-electromechanical systems.

  3. Nanoscale Lubrication of Ionic Surfaces Controlled via a Strong Electric Field

    NASA Astrophysics Data System (ADS)

    Strelcov, Evgheni; Kumar, Rajeev; Bocharova, Vera; Sumpter, Bobby G.; Tselev, Alexander; Kalinin, Sergei V.

    2015-01-01

    Frictional forces arise whenever objects around us are set in motion. Controlling them in a rational manner means gaining leverage over mechanical energy losses and wear. This paper presents a way of manipulating nanoscale friction by means of in situ lubrication and interfacial electrochemistry. Water lubricant is directionally condensed from the vapor phase at a moving metal-ionic crystal interface by a strong confined electric field, thereby allowing friction to be tuned up or down via an applied bias. The electric potential polarity and ionic solid solubility are shown to strongly influence friction between the atomic force microscope (AFM) tip and salt surface. An increase in friction is associated with the AFM tip digging into the surface, whereas reducing friction does not influence its topography. No current flows during friction variation, which excludes Joule heating and associated electrical energy losses. The demonstrated novel effect can be of significant technological importance for controlling friction in nano- and micro-electromechanical systems.

  4. Surface-modified silica colloidal crystals: nanoporous films and membranes with controlled ionic and molecular transport.

    PubMed

    Zharov, Ilya; Khabibullin, Amir

    2014-02-18

    Nanoporous membranes are important for the study of the transport of small molecules and macromolecules through confined spaces and in applications ranging from separation of biomacromolecules and pharmaceuticals to sensing and controlled release of drugs. For many of these applications, chemists need to gate the ionic and molecular flux through the nanopores, which in turn depends on the ability to control the nanopore geometry and surface chemistry. Most commonly used nanoporous membrane materials are based on polymers. However, the nanostructure of polymeric membranes is not well-defined, and their surface is hard to modify. Inorganic nanoporous materials are attractive alternatives for polymers in the preparation of nanoporous membranes. In this Account, we describe the preparation and surface modification of inorganic nanoporous films and membranes self-assembled from silica colloidal spheres. These spheres form colloidal crystals with close-packed face centered cubic lattices upon vertical deposition from colloidal solutions. Silica colloidal crystals contain ordered arrays of interconnected three dimensional voids, which function as nanopores. We can prepare silica colloidal crystals as supported thin films on various flat solid surfaces or obtain free-standing silica colloidal membranes by sintering the colloidal crystals above 1000 °C. Unmodified silica colloidal membranes are capable of size-selective separation of macromolecules, and we can surface-modify them in a well-defined and controlled manner with small molecules and polymers. For the surface modification with small molecules, we use silanol chemistry. We grow polymer brushes with narrow molecular weight distribution and controlled length on the colloidal nanopore surface using atom transfer radical polymerization or ring-opening polymerization. We can control the flux in the resulting surface-modified nanoporous films and membranes by pH and ionic strength, temperature, light, and small molecule

  5. Potentiostatic control of ionic liquid surface film formation on ZE41 magnesium alloy.

    PubMed

    Efthimiadis, Jim; Neil, Wayne C; Bunter, Andrew; Howlett, Patrick C; Hinton, Bruce R W; MacFarlane, Douglas R; Forsyth, Maria

    2010-05-01

    The generation of potentially corrosion-resistant films on light metal alloys of magnesium have been investigated. Magnesium alloy, ZE41 [Mg-Zn-Rare Earth (RE)-Zr, nominal composition approximately 4 wt % Zn, approximately 1.7 wt % RE (Ce), approximately 0.6 wt % Zr, remaining balance, Mg], was exposed under potentiostatic control to the ionic liquid trihexyl(tetradecyl)phosphonium diphenylphosphate, denoted [P(6,6,6,14)][DPP]. During exposure to this IL, a bias potential, shifted from open circuit, was applied to the ZE41 surface. Electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) were used to monitor the evolution of film formation on the metal surface during exposure. The EIS data indicate that, of the four bias potentials examined, applying a potential of -200 mV versus OCP during the exposure period resulted in surface films of greatest resistance. Both EIS measurements and scanning electron microscopy (SEM) imaging indicate that these surfaces are substantially different to those formed without potential bias. Time of flight-secondary ion mass spectrometry (ToF-SIMS) elemental mapping of the films was utilized to ascertain the distribution of the ionic liquid cationic and anionic species relative to the microstructural surface features of ZE41 and indicated a more uniform distribution compared with the surface following exposure in the absence of a bias potential. Immersion of the treated ZE41 specimens in a chloride contaminated salt solution clearly indicated that the ionic liquid generated surface films offered significant protection against pitting corrosion, although the intermetallics were still insufficiently protected by the IL and hence favored intergranular corrosion processes. PMID:20433137

  6. Modification of Hydrophilic and Hydrophobic Surfaces Using an Ionic-Complementary Peptide

    PubMed Central

    Yang, Hong; Fung, Shan-Yu; Pritzker, Mark; Chen, P.

    2007-01-01

    Ionic-complementary peptides are novel nano-biomaterials with a variety of biomedical applications including potential biosurface engineering. This study presents evidence that a model ionic-complementary peptide EAK16-II is capable of assembling/coating on hydrophilic mica as well as hydrophobic highly ordered pyrolytic graphite (HOPG) surfaces with different nano-patterns. EAK16-II forms randomly oriented nanofibers or nanofiber networks on mica, while ordered nanofibers parallel or oriented 60° or 120° to each other on HOPG, reflecting the crystallographic symmetry of graphite (0001). The density of coated nanofibers on both surfaces can be controlled by adjusting the peptide concentration and the contact time of the peptide solution with the surface. The coated EAK16-II nanofibers alter the wettability of the two surfaces differently: the water contact angle of bare mica surface is measured to be <10°, while it increases to 20.3±2.9° upon 2 h modification of the surface using a 29 µM EAK16-II solution. In contrast, the water contact angle decreases significantly from 71.2±11.1° to 39.4±4.3° after the HOPG surface is coated with a 29 µM peptide solution for 2 h. The stability of the EAK16-II nanofibers on both surfaces is further evaluated by immersing the surface into acidic and basic solutions and analyzing the changes in the nanofiber surface coverage. The EAK16-II nanofibers on mica remain stable in acidic solution but not in alkaline solution, while they are stable on the HOPG surface regardless of the solution pH. This work demonstrates the possibility of using self-assembling peptides for surface modification applications. PMID:18091996

  7. Molecular dynamics investigation of the ionic liquid/enzyme interface: application to engineering enzyme surface charge.

    PubMed

    Burney, Patrick R; Nordwald, Erik M; Hickman, Katie; Kaar, Joel L; Pfaendtner, Jim

    2015-04-01

    Molecular simulations of the enzymes Candida rugosa lipase and Bos taurus α-chymotrypsin in aqueous ionic liquids 1-butyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium ethyl sulfate were used to study the change in enzyme-solvent interactions induced by modification of the enzyme surface charge. The enzymes were altered by randomly mutating lysine surface residues to glutamate, effectively decreasing the net surface charge by two for each mutation. These mutations resemble succinylation of the enzyme by chemical modification, which has been shown to enhance the stability of both enzymes in ILs. After establishing that the enzymes were stable on the simulated time scales, we focused the analysis on the organization of the ionic liquid substituents about the enzyme surface. Calculated solvent charge densities show that for both enzymes and in both solvents that changing positively charged residues to negative charge does indeed increase the charge density of the solvent near the enzyme surface. The radial distribution of IL constituents with respect to the enzyme reveals decreased interactions with the anion are prevalent in the modified systems when compared to the wild type, which is largely accompanied by an increase in cation contact. Additionally, the radial dependence of the charge density and ion distribution indicates that the effect of altering enzyme charge is confined to short range (≤1 nm) ordering of the IL. Ultimately, these results, which are consistent with that from prior experiments, provide molecular insight into the effect of enzyme surface charge on enzyme stability in ILs. PMID:25641162

  8. Concentration dependence of nanoparticle surface coverage for ionic self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Kim, Vincent; Simpson, Brian; Seredinski, Andrew; Schwen, Eric; Mazilu, Dan; Mazilu, Irina

    2014-03-01

    We investigate the concentration dependence of the surface coverage of thin films that consist of silica nanoparticles deposited on the substrates via the ISAM (ionically self-assembled monolayers) technique. Several experiments were conducted in order to investigate the factors that affected the quality of the coatings and one significant factor observed was the concentration of the colloidal silica solution. Using SEM micrographs, we analyzed the surface coverage and compared it to the analytical results obtained using a cooperative sequential adsorption model. The results we obtained matched the linear relation between particle density and the inverse of the concentration predicted by the theory.

  9. Surface-active ionic liquids in micellar catalysis: impact of anion selection on reaction rates in nucleophilic substitutions.

    PubMed

    Cognigni, Alice; Gaertner, Peter; Zirbs, Ronald; Peterlik, Herwig; Prochazka, Katharina; Schröder, Christian; Bica, Katharina

    2016-05-21

    A series of surface-active ionic liquids based on the 1-dodecyl-3-methylimidazolium cation and different anions such as halides and alkylsulfates was synthesized. The aggregation behavior of these ionic liquids in water was characterized by surface tension, conductivity measurements and UV-Vis spectroscopy in order to determine the critical micelle concentration (CMC) and to provide aggregation parameters. The determination of surface activity and aggregation properties of amphiphilic ionic liquids was accompanied by SAXS studies on selected surface-active ionic liquids. The application of these surface-active ionic liquids with different anions was tested in nucleophilic substitution reactions for the degradation of organophosphorus compounds. Kinetic studies via UV-Vis spectrophotometry showed a strong acceleration of the reaction in the micellar system compared to pure water. In addition, an influence of the anion was observed, resulting in a correlation between the anion binding to the micelle and the reaction rate constants, indicating that the careful choice of the surface-active ionic liquid can considerably affect the outcome of reactions. PMID:27121134

  10. Physically and chemically stable ionic liquid-infused textured surfaces showing excellent dynamic omniphobicity

    SciTech Connect

    Miranda, Daniel F.; Urata, Chihiro; Masheder, Benjamin; Dunderdale, Gary J.; Hozumi, Atsushi; Yagihashi, Makoto

    2014-05-01

    A fluorinated and hydrophobic ionic liquid (IL), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, effectively served as an advantageous lubricating liquid for the preparation of physically and chemically stable omniphobic surfaces based on slippery liquid-infused porous surfaces. Here, we used particulate microstructures as supports, prepared by the chemical vapor deposition of 1,3,5,7-tetramethylcyclotetrasiloxane and subsequent surface modification with (3-aminopropyl)triethoxysilane. Confirmed by SEM and contact angle measurements, the resulting IL-infused microtextured surfaces are smooth and not only water but also various low surface tension liquids can easily slide off at low substrate tilt angles of <5°, even after exposure to high temperature, vacuum, and UV irradiation.

  11. Life Sciences Implications of Lunar Surface Operations

    NASA Technical Reports Server (NTRS)

    Chappell, Steven P.; Norcross, Jason R.; Abercromby, Andrew F.; Gernhardt, Michael L.

    2010-01-01

    The purpose of this report is to document preliminary, predicted, life sciences implications of expected operational concepts for lunar surface extravehicular activity (EVA). Algorithms developed through simulation and testing in lunar analog environments were used to predict crew metabolic rates and ground reaction forces experienced during lunar EVA. Subsequently, the total metabolic energy consumption, the daily bone load stimulus, total oxygen needed, and other variables were calculated and provided to Human Research Program and Exploration Systems Mission Directorate stakeholders. To provide context to the modeling, the report includes an overview of some scenarios that have been considered. Concise descriptions of the analog testing and development of the algorithms are also provided. This document may be updated to remain current with evolving lunar or other planetary surface operations, assumptions and concepts, and to provide additional data and analyses collected during the ongoing analog research program.

  12. Surface interactions, corrosion processes and lubricating performance of protic and aprotic ionic liquids with OFHC copper

    NASA Astrophysics Data System (ADS)

    Espinosa, Tulia; Sanes, José; Jiménez, Ana-Eva; Bermúdez, María-Dolores

    2013-05-01

    In order to select possible candidates for use as lubricants or as precursors of surface coatings, the corrosion and surface interactions of oxygen-free high conductivity (OFHC) copper with two new protic (PIL) and four aprotic (APIL) room-temperature ionic liquids have been studied. The PILs, with no heteroatoms in their composition, are the triprotic di[(2-hydroxyethyl)ammonium] succinate (MSu) and the diprotic di[bis-(2-hydroxyethyl)ammonium] adipate (DAd). The four APILs contain imidazolium cations with short or long alkyl chain substituents and reactive anions: 1-ethyl-3-methylimidazolium phosphonate ([EMIM]EtPO3H); 1-ethyl-3-methylimidazolium octylsulfate ([EMIM]C8H17SO4); 1-hexyl-3-methylimidazolium tetrafluoroborate ([HMIM]BF4) and 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF6). Contact angles between the ionic liquids and OFHC copper surface were measured. Mass and roughness changes of OFHC copper after 168 h in contact with the ionic liquids have been determined. Copper surfaces were studied by XRD, SEM-EDX and XPS surface analysis. FTIR spectra of the liquid phases recovered after being in contact with the copper surface were compared with that of the neat ionic liquids. The lowest corrosion rate is observed for the diprotic ammonium adipate PIL (DAd), which gives low mass and surface roughness changes and forms adsorbed layers on copper, while the triprotic ammonium succinate salt (MSu) produces a severe corrosive attack by reaction with copper to form a blue crystalline solid, which has been characterized by FTIR and thermal analysis (TGA). All imidazolium APILs react with copper, with different results as a function of the anion. As expected, [EMIM]C8H17SO4 reacts with copper to form the corresponding copper sulphate salt. [EMIM]EtPO3H produces severe corrosion to form a phosphonate-copper soluble phase. [HMIM]BF4 gives rise to the highest roughness increase of the copper surface. [HMIM]PF6 shows the lowest mass and roughness changes of

  13. Nearest Neighbor Hopping conduction observed with ionic liquid induced silicon surface states

    NASA Astrophysics Data System (ADS)

    Nelson, Jj; Reich, K. V.; Sammon, M.; Shklovskii, B. I.; Goldman, A. M.

    A two-dimensional hole gas can be created on the surface of a bulk Si wafer by using an ionic liquid in an electric double layer transistor configuration (EDLT). EDLTs are useful in observing metal to insulator and superconductor to insulator transitions due to record high carrier densities of 1015 cm-2 that can be achieved. In some cases the high carrier densities are due in part to oxidation of the sample surface. With an EDLT configuration we have observed a 2D insulator-to metal transition with low mobility Si at the highest reported critical carrier density. The experiment reported here is designed to promote electrostatic carrier induction over electrochemical reactions and is focused on carrier densities near 1011 cm-2. At such a low densities we observe nearest neighbor hopping conduction on the surface of Si. This observation suggests that the ionic liquid covering the surface should be treated as a series of discrete charges that can act as a platform to better understand EDLT physics at higher carrier densities. This work was supported in part by the National Science Foundation under Grant NSF-1263316.

  14. Thermodynamic Control of Two-Dimensional Molecular Ionic Nanostructures on Metal Surfaces.

    PubMed

    Jeon, Seokmin; Doak, Peter W; Sumpter, Bobby G; Ganesh, Panchapakesan; Maksymovych, Petro

    2016-08-23

    Bulk molecular ionic solids exhibit fascinating electronic properties, including electron correlations, phase transitions, and superconducting ground states. In contrast, few of these phenomena have been observed in low-dimensional molecular structures, including thin films, nanoparticles, and molecular blends, not in the least because most of such structures have been composed of nearly closed-shell molecules. It is therefore desirable to develop low-dimensional ionic molecular structures that can capture potential applications. Here, we present detailed analysis of monolayer-thick structures of the canonical TTF-TCNQ (tetrathiafulvalene 7,7,8,8-tetracyanoquinodimethane) system grown on low-index gold and silver surfaces. The most distinctive property of the epitaxial growth is the wide abundance of stable TTF/TCNQ ratios, in sharp contrast to the predominance of a 1:1 ratio in the bulk. We propose the existence of the surface phase diagram that controls the structures of TTF-TCNQ on the surfaces and demonstrate phase transitions that occur upon progressively increasing the density of TCNQ while keeping the surface coverage of TTF fixed. Based on direct observations, we propose the binding motif behind the stable phases and infer the dominant interactions that enable the existence of the rich spectrum of surface structures. Finally, we also show that the surface phase diagram will control the epitaxy beyond monolayer coverage. Multiplicity of stable surface structures, the corollary rich phase diagram, and the corresponding phase transitions present an interesting opportunity for low-dimensional molecular systems, particularly if some of the electronic properties of the bulk can be preserved or modified in the surface phases. PMID:27458890

  15. Thermodynamic Control of Two-Dimensional Molecular Ionic Nanostructures on Metal Surfaces

    DOE PAGESBeta

    Jeon, Seokmin; Doak, Peter W.; Sumpter, Bobby G.; Ganesh, Panchapakesan; Maksymovych, Petro

    2016-07-26

    Bulk molecular ionic solids exhibit fascinating electronic properties, including electron correlations, phase transitions and superconducting ground states. In contrast, few of these phenomena have so far been observed in low-dimensional molecular structures, including thin films, nanoparticles and molecular blends, not in the least because most of such structures have so far been composed of nearly closed-shell molecules. It is therefore desirable to develop low-dimensional molecular structures of ionic molecules toward fundamental studies and potential applications. Here we present detailed analysis of monolayer-thick structures of the canonical TTF-TCNQ (tetrathiafulvalene 7,7,8,8-tetracyanoquinodimethane) system grown on low-index gold and silver surfaces. The most distinctivemore » property of the epitaxial growth is the wide abundance of stable TTF/TCNQ ratios, in sharp contrast to the predominance of 1:1 ratio in the bulk. We propose the existence of the surface phase-diagram that controls the structures of TTF-TCNQ on the surfaces, and demonstrate phase-transitions that occur upon progressively increasing the density of TCNQ while keeping the surface coverage of TTF fixed. Based on direct observations, we propose the binding motif behind the stable phases and infer the dominant interactions that enable the existence of the rich spectrum of surface structures. Finally, we also show that the surface phase diagram will control the epitaxy beyond monolayer coverage. Multiplicity of stable surface structures, the corollary rich phase diagram and the corresponding phase-transitions present an interesting opportunity for low-dimensional molecular systems, particularly if some of the electronic properties of the bulk can be preserved or modified in the surface phases.« less

  16. Self-assembly of nanoparticles on the surface of ionic crystals: Structural properties

    NASA Astrophysics Data System (ADS)

    Nikolic, K.; Murugesan, M.; Forshaw, M.; Cunningham, D.; Martinez-Albertos, J.-L.; Moore, B. D.

    2007-07-01

    With a suitable combination of ligand-stabilised nanoparticle suspension and ionic salt solutions, it is possible to produce microcrystals that are coated with nanoparticles. The self-assembly process of coating microcrystals by gold nanoparticles (NP) is mediated by the crystal lattice. This is the so-called CLAMS process - a generic process for self-organisation of nanoparticles on the surface of crystals [M. Murugeshan, D. Cunningham, J.-L. Martnez-Albertos, R. Vrcelj, B.D. Moore, Chem. Commun. (2005) 2677]. We are exploring here the structural properties of these self-assembled structures by using different imaging techniques.

  17. Chemical and heating treatments of ionic monolayer-protected clusters (IMPCs) with different surface counter anions.

    PubMed

    Choo, Hosun; Isaacs, Steven R; Small, Adam; Parmley, Seth; Shon, Young-Seok

    2007-12-01

    This paper shows an in-depth study on the chemical and thermal responses of two ionic monolayer-protected gold clusters (Oct(4)N(+-)Br- and Oct(4)N(+-)O(3)SS-IMPCs). Two IMPCs displayed completely different phase-transfer behaviors when the solutions were in contact with the aqueous solution containing N-(2-mercaptopropionyl)glycine (tiopronin). Not Oct(4)N(+-)O(3)SS-IMPCs but Oct(4)N(+-)Br-IMPCs experienced a facile phase transfer from the organic layer to the aqueous layer, which was resulted from the displacement of ionic ligands by tiopronin monolayers on the gold nanoparticle surface. When the toluene solution containing Oct(4)N(+-)Br-IMPCs was treated with the aqueous solution containing NaCl salts, the UV-vis spectrum of the solution containing Oct(4)N(+-)Br-IMPCs undertook a fast spectral evolution caused by decomposition/agglomeration of IMPCs. In contrast, Oct(4)N(+-)O(3)SS-IMPCs exhibited much higher stability against the NaCl treatments. The Oct(4)N(+-)O(3)SS-IMPCs also displayed a superior thermal stability at relatively high temperature of approximately 110 degrees C. Core size evolutions of Oct(4)N(+-)O(3)SS-IMPCs without a fast decomposition or aggregation of clusters were also observed during solid-state heating treatments at approximately 150 and approximately 200 degrees C. These results support that the presence of different anions clearly affect the overall stability of ionic nanoparticles. The stronger binding property of thiosulfate anions compared to bromide anions with gold nanoparticle surfaces makes Oct(4)N(+-)O(3)SS-IMPCs chemically more inert and thermally more stable. PMID:17719060

  18. Straightforward approach to graft bioactive polysaccharides onto polyurethane surfaces using an ionic liquid

    NASA Astrophysics Data System (ADS)

    Bigot, Sandra; Louarn, Guy; Kébir, Nasreddine; Burel, Fabrice

    2014-09-01

    Surface properties directly affect the performance of a material in a biological environment. In this study, the goal was to develop a simple procedure allowing the grafting of antibacterial polysaccharides onto biomedical grade polyurethanes (e.g. Tecothane®). Thus, a straightforward chemical pathway involving an isothiocyanate-alcohol reaction in an ionic liquid (IL) was developed. PU isothiocyanted surfaces (PU-NCS) were first prepared by reacting p-phenylene diisothiocyanate with the surface urethane groups. Then, unmodified bioactive seaweed polysaccharides were directly grafted onto the surface, in mild conditions. The selected IL, i.e. 1-ethyl-3-methyl imidazolium phosphate, was of particular interest since this liquid worked as solvent for p-phenylene diisothiocyanate and the polysaccharides and as catalyst for the grafting reactions. Successful grafting of the different polysaccharides was attested by changes in the surface functional groups, using X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) showed that polysaccharide grafting, slightly increased the surface roughness from 1.9 to more than 7 nm. Contact angle with water decreased from 88° (for native PU) to around 75° after polysaccharide grafting, attesting a more hydrophilic surface. This procedure would be transposed to the grafting onto PU surfaces of any macromolecule of interest bearing hydroxyl, thiol or amine groups.

  19. New insights into the fundamental chemical nature of ionic liquid film formation on magnesium alloy surfaces.

    PubMed

    Forsyth, Maria; Neil, Wayne C; Howlett, Patrick C; Macfarlane, Douglas R; Hinton, Bruce R W; Rocher, Nathalie; Kemp, Thomas F; Smith, Mark E

    2009-05-01

    Ionic liquids (ILs) based on trihexyltetradecylphosphonium coupled with either diphenylphosphate or bis(trifluoromethanesulfonyl)amide have been shown to react with magnesium alloy surfaces, leading to the formation a surface film that can improve the corrosion resistance of the alloy. The morphology and microstructure of the magnesium surface seems critical in determining the nature of the interphase, with grain boundary phases and intermetallics within the grain, rich in zirconium and zinc, showing almost no interaction with the IL and thereby resulting in a heterogeneous surface film. This has been explained, on the basis of solid-state NMR evidence, as being due to the extremely low reactivity of the native oxide films on the intermetallics (ZrO2 and ZnO) with the IL as compared with the magnesium-rich matrix where a magnesium hydroxide and/or carbonate inorganic surface is likely. Solid-state NMR characterization of the ZE41 alloy surface treated with the IL based on (Tf)2N(-) indicates that this anion reacts to form a metal fluoride rich surface in addition to an organic component. The diphenylphosphate anion also seems to undergo an additional chemical process on the metal surface, indicating that film formation on the metal is not a simple chemical interaction between the components of the IL and the substrate but may involve electrochemical processes. PMID:20355890

  20. Nanoscale lubrication of ionic surfaces controlled via a strong electric field

    DOE PAGESBeta

    Strelcov, Evgheni; Bocharova, Vera; Sumpter, Bobby G.; Tselev, Alexander; Kalinin, Sergei V.; Kumar, Rajeev

    2015-01-27

    Frictional forces arise whenever objects around us are set in motion. Controlling them in a rational manner means gaining leverage over mechanical energy losses and wear. This paper presents a way of manipulating nanoscale friction by means of in situ lubrication and interfacial electrochemistry. Water lubricant is directionally condensed from the vapor phase at a moving metal-ionic crystal interface by a strong confined electric field, thereby allowing friction to be tuned up or down via an applied bias. The electric potential polarity and ionic solid solubility are shown to strongly influence friction between the atomic force microscope (AFM) tip andmore » salt surface. An increase in friction is associated with the AFM tip digging into the surface, whereas reducing friction does not influence its topography. No current flows during friction variation, which excludes Joule heating and associated electrical energy losses. Lastly, the demonstrated novel effect can be of significant technological importance for controlling friction in nano- and micro-electromechanical systems.« less

  1. Self-assembling array of magnetoelectrostatic jets from the surface of a superparamagnetic ionic liquid.

    PubMed

    King, Lyon B; Meyer, Edmond; Hopkins, Mark A; Hawkett, Brian S; Jain, Nirmesh

    2014-12-01

    Electrospray is a versatile technology used, for example, to ionize biomolecules for mass spectrometry, create nanofibers and nanowires, and propel spacecraft in orbit. Traditionally, electrospray is achieved via microfabricated capillary needle electrodes that are used to create the fluid jets. Here we report on multiple parallel jetting instabilities realized through the application of simultaneous electric and magnetic fields to the surface of a superparamagnetic electrically conducting ionic liquid with no needle electrodes. The ionic liquid ferrofluid is synthesized by suspending magnetic nanoparticles in a room-temperature molten salt carrier liquid. Two ILFFs are reported: one based on ethylammonium nitrate (EAN) and the other based on EMIM-NTf2. The ILFFs display an electrical conductivity of 0.63 S/m and a relative magnetic permeability as high as 10. When coincident electric and magnetic fields are applied to these liquids, the result is a self-assembling array of emitters that are composed entirely of the colloidal fluid. An analysis of the magnetic surface stress induced on the ILFF shows that the electric field required for transition to spray can be reduced by as much as 4.5 × 10(7) V/m compared to purely electrostatic spray. Ferrofluid mode studies in nonuniform magnetic fields show that it is feasible to realize arrays with up to 16 emitters/mm(2). PMID:25372842

  2. Effects of PCB Substrate Surface Finish, Flux, and Phosphorus Content on Ionic Contamination

    NASA Astrophysics Data System (ADS)

    Bacior, M.; Sobczak, N.; Siewiorek, A.; Kudyba, A.; Homa, M.; Nowak, R.; Dziula, M.; Masłoń, S.

    2015-02-01

    The ionic contamination on printed circuit boards (PCB) having different surface finishes was examined using ionograph. The study was performed at the RT on three types of PCBs covered with: (i) hot air solder leveling (HASL LF), (ii) electroless nickel immersion gold (ENIG), and (iii) organic surface protectant (OSP), all on Cu substrates, as well as two types of fluxes, namely EF2202 and RF800. In the group of boards without soldered components, the lowest average value of contamination was for the ENIG 18 µm surface (0.01 μg NaCl/cm2). Boards with soldered components were more contaminated (from 0.29 μg NaCl/cm2 for the HASL LF 18 µm surface). After spraying boards with fluxing agents, the values of contaminants were the highest. The influence of phosphorus content in Ni-P layer of ENIG finish on ionic contamination was examined. In the group of PCBs with Au coating, the smallest amount of surface contaminants (0.32 μg NaCl/cm2) was for Ni-2-5%P layer. PCBs with Ni-11%P layer were higher contaminated (0.47 μg NaCl/cm2), and another with Ni-8%P layer had 0.81 μg NaCl/cm2. PCBs without Au coating, had the lowest contamination (0.48 μg NaCl/cm2) at phosphorous content equal 11%P. Higher contamination (0.67 μg NaCl/cm2) was at 2-5%P, up to 1.98 μg NaCl/cm2 for 8% of P. Boards with Au finish have lower value of contamination than identical boards without Au layer thus contributing to better reliability of electronic assemblies, since its failures due to current leakage and corrosion can be caused by contaminants.

  3. The behavior of internal surfaces of cleavage in ionic crystals under thermoelectric influence

    NASA Astrophysics Data System (ADS)

    Karyev, Leonid; Zanina, Anna; Feodorov, Victor

    2016-01-01

    The behavior of internal surfaces of cleavage fracture in ionic crystals under complex thermoelectric effect was investigated. The experiment was carried out in case of normal and parallel orientation of the electric field lines to the investigated surface. Our basic research method lies in simultaneous influence of thermal and electric fields on the crystal. In case of normal orientation of electric field lines to the crack surface the formation of dislocation rosettes in temperature range of impurity conduction was observed. In the temperature range of intrinsic conduction authors detected the formation of single crystal outgrowths on the positively charged surface. The shape of rosettes and outgrowths depends on their relative location to the crack tip. When outgrowth reaches the opposite negatively charged surface it forms a bridge between cleavage shores. In these areas the restoration of continuity was observed. In case of parallel orientation of electric field lines to the surface authors observed the appearance of a new phase in the form of a jelly-like substance on the crack surface. The crack faces had a closing tendency due to the directed diffusion of cations to the crack edges.

  4. Controlled ionic condensation at the surface of a native extremophile membrane

    NASA Astrophysics Data System (ADS)

    Contera, Sonia Antoranz; Voïtchovsky, Kislon; Ryan, John F.

    2010-02-01

    At the nanoscale level biological membranes present a complex interface with the solvent. The functional dynamics and relative flexibility of membrane components together with the presence of specific ionic effects can combine to create exciting new phenomena that challenge traditional theories such as the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory or models interpreting the role of ions in terms of their ability to structure water (structure making/breaking). Here we investigate ionic effects at the surface of a highly charged extremophile membrane composed of a proton pump (bacteriorhodopsin) and archaeal lipids naturally assembled into a 2D crystal. Using amplitude-modulation atomic force microscopy (AM-AFM) in solution, we obtained sub-molecular resolution images of ion-induced surface restructuring of the membrane. We demonstrate the presence of a stiff cationic layer condensed at its extracellular surface. This layer cannot be explained by traditional continuum theories. Dynamic force spectroscopy experiments suggest that it is produced by electrostatic correlation mediated by a Manning-type condensation of ions. In contrast, the cytoplasmic surface is dominated by short-range repulsive hydration forces. These findings are relevant to archaeal bioenergetics and halophilic adaptation. Importantly, they present experimental evidence of a natural system that locally controls its interactions with the surrounding medium and challenges our current understanding of biological interfaces.At the nanoscale level biological membranes present a complex interface with the solvent. The functional dynamics and relative flexibility of membrane components together with the presence of specific ionic effects can combine to create exciting new phenomena that challenge traditional theories such as the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory or models interpreting the role of ions in terms of their ability to structure water (structure making/breaking). Here we

  5. Surface science of Cs, CsO and CsI ionic layers on Pt(111)

    NASA Astrophysics Data System (ADS)

    Drnec, Jakub

    surface structures observed by LEED during the coadsorption of Cs and I are in good agreement with atomic arrangements predicted for ionic layers. The validity of this conclusion and the general behavior of ionic layers was checked by an electrostatic energy calculation for various structures.

  6. Effective work functions for ionic and electronic emissions from mono- and polycrystalline surfaces

    NASA Astrophysics Data System (ADS)

    Kawano, Hiroyuki

    2008-02-01

    The effective work functions ( ϕ+, ϕe and ϕ-) for positive-ionic, electronic, and negative-ionic emissions from mono- and polycrystalline surfaces are surveyed comprehensively and also investigated critically for the main purposes of (1) evaluating the most probable values of ϕ+, ϕe and ϕ- for a variety of surface species, (2) explicating both thermionic contrasts (Δ ϕ∗ ≡ ϕ+ - ϕe and Δ ϕ∗∗ ≡ ϕ- - ϕe) and their dependence on experimental conditions, and (3) demonstrating the necessity of employing ϕ+ (not ϕe) for quantitative analysis of those data on positive ion emission from polycrystalline surfaces. Careful examination of both theoretical results and experimental data on the work functions yield several conclusions. By both theory and experiment, clean monocrystalline surfaces are verified to have Δ ϕ∗ = 0.0 eV within an error of ±0.05 eV. Next, as the density of local surface irregularities increases, the homogeneity in the work function over the whole surface area decreases and, hence, Δ ϕ∗ increases. Also, the most probable values of ϕ+ and ϕe are recommended for many mono- and polycrystalline surfaces, mostly (∼70%) with a standard deviation of ±0.02-0.08 eV. Compared with the probable or typical values of ϕe accepted in influential handbooks, the most probable values of ϕe recommended here are typically (∼70%) equal to each other within a narrow gap of less than ∼0.1 eV, but some (∼20%) are different by ∼0.2 eV or more (up to ∼1 eV). Furthermore, polycrystalline surfaces of Nb, Mo, Ta, W, Re, Ir, Pt, etc. hold Δ ϕ∗ ≈ 0.3-0.8 eV since each surface has a mean value that is different between ϕ+ and ϕe. Also, at the degree of monocrystallization ( δm) below ∼50%, the theoretical value of Δ ϕ∗ depends little on δm and agrees well with experimental data on each polycrystalline surface. As δm increases beyond ∼80%, Δ ϕ∗ decreases rapidly to 0, showing again a good agreement between theory

  7. Clean surface processing of rubrene single crystal immersed in ionic liquid by using frequency modulation atomic force microscopy

    SciTech Connect

    Yokota, Yasuyuki; Hara, Hisaya; Morino, Yusuke; Bando, Ken-ichi; Imanishi, Akihito; Fukui, Ken-ichi; Uemura, Takafumi; Takeya, Jun

    2014-06-30

    Surface processing of a rubrene single crystal immersed in ionic liquids is valuable for further development of low voltage transistors operated by an electric double layer. We performed a precise and clean surface processing based on the tip-induced dissolution of rubrene molecules at the ionic liquid/rubrene single crystal interfaces by using frequency modulation atomic force microscopy. Molecular resolution imaging revealed that the tip-induced dissolution proceeded via metastable low density states derived from the anisotropic intermolecular interactions within the crystal structure.

  8. Determination of Surface Charge of Titanium Dioxide (Anatase) at High Ionic Strength

    NASA Astrophysics Data System (ADS)

    Schoonen, M. A.; Strongin, D. R.

    2014-12-01

    Charge development on mineral surfaces is an important control on the fate of minor and trace elements in a wide range of environments, including in possible radioactive waste repositories. Formation waters have often a high ionic strength. In this study, we determined the zeta potential (ζ) of anatase in potassium chloride solutions with concentrations up to 3M (25°C). The zeta potential is the potential at the hydrodynamic shear plane. In this study, we made use of the electro-acoustic effect. This effect is based on the development of a measureable potential/current when the electrical double layer outside the shearplane is separated from a charged particle through rapid oscillation induced by a sound wave. The advantage of this type of measurement is that the particles are not subjected to a high electric field (common to typical zeta potential measurements), which leads to electrode reactions and a shift of solution pH. Measurements were collected by subtracting the ion vibration current (IVI) due to the presence of potassium and chloride ions from the CVI. The correction is necessary for measurements in solutions with I > 0.25 M. This subtraction was done at each of the measurement conditions by centrifuging the slurrly, measuring the IVI of the supernatant, reconstituting the slurry, and then measuring CVI of the slurry. Subtraction of IVI at each condition is critical because IVI changes with pH and accounts for most of raw signal. The results show that the anatase isoelectric point shifts from a pH ~6.5 to a value of ~4.5 at 1M KCl. At ionic strength in excess of 1 M KCl, the surface appears to be slightly negatively charged accross the pH range accessible by this technique (pH 2.5-10). The loss of an isoelectric point suggests that KCl is no longer an indifferent electrolyte at 1 M KCl and higher. The results are in disagreement with earlier measurements in which anatase was shown to have a positive charge at high ionic strength across the pH scale. The

  9. Temperature-dependent surface-enrichment effects of imidazolium-based ionic liquids.

    PubMed

    Kolbeck, Claudia; Deyko, Alexey; Matsuda, Takashi; Kohler, Florian T U; Wasserscheid, Peter; Maier, Florian; Steinrück, Hans-Peter

    2013-11-11

    We present the first systematic study of the influence of temperature on the degree of surface enrichment of 1-alkyl-3-methylimidazolium-based ionic liquids (ILs). Using angle-resolved X-ray photoelectron spectroscopy, we demonstrate that the degree of surface enrichment strongly decreases with increasing temperature for all the studied ILs. For ILs with the same cation, but different anions, [C8 C1 Im]Br, [C8 C1 Im][TfO] and [C8 C1 Im][Tf2 N], no significant differences of the temperature-induced partial loss of surface enrichment are found. Measurements for [C4 C1 Im][TfO], [C8 C1 Im][TfO] and [C18 C1 Im][TfO] indicate a small effect of the chain length. For [C18 C1 Im][TfO], a continuous decrease of alkyl surface enrichment is found with increasing temperature, with no abrupt changes at the phase-transition temperature from the smectic A to the isotropic phase, indicating that the surface enrichment is not affected by this phase transition. PMID:24123477

  10. Adsorbed and near surface structure of ionic liquids at a solid interface.

    PubMed

    Segura, Juan José; Elbourne, Aaron; Wanless, Erica J; Warr, Gregory G; Voïtchovsky, Kislon; Atkin, Rob

    2013-03-01

    The structure of solid-ionic liquid (IL) interfaces has been characterised with unprecedented clarity by employing a range of atomic force microscopy (AFM) imaging techniques and tip pressures appropriate for the system under study. Soft contact and amplitude-modulation (AM) AFM imaging have been used to elucidate the lateral structure of ILs adsorbed onto mica, and in the near surface ion layers. Data is presented for ethylammonium nitrate (EAN) and 1-ethyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)imide (EMIm TFSI). Whereas EAN is a protic IL that forms a nanostructured sponge phase in the bulk, EMIm TFSI is aprotic and has weak (or absent) bulk association structure. Comparison of results obtained for the two liquids elucidates how the strength of bulk liquid morphology effects lateral organisation at the surface, and any effect of IL class, i.e. protic versus aprotic. Imaging reveals EAN self assembles at the solid surface in a worm-like morphology, whereas EMIm cations adsorb in a more isolated fashion, but still in rows templated by the mica surface. To the authors' knowledge, the wormlike structures present at the EAN-mica interface are the smallest self-assembled aggregates ever imaged on a solid surface. PMID:23361257

  11. Surface Tensions of Ionic Liquids: Non-Regular Trend Along the Number of Cyano Groups

    PubMed Central

    Almeida, Hugo F. D.; Carvalho, Pedro J.; Kurnia, Kiki A.; Lopes-da-Silva, José A.; Coutinho, João A. P.; Freire, Mara G.

    2016-01-01

    Ionic liquids (ILs) with cyano-functionalized anions are a set of fluids that are still poorly characterized despite their remarkably low viscosities and potential applications. Aiming at providing a comprehensive study on the influence of the number of –CN groups through the surface tension and surface organization of ILs, the surface tensions of imidazolium-based ILs with cyano-functionalized anions were determined at atmospheric pressure and in the (298.15 to 343.15) K temperature range. The ILs investigated are based on 1-alkyl-3-methylimidazolium cations (alkyl = ethyl, butyl and hexyl) combined with the [SCN]-, [N(CN)2]−, [C(CN)3]− and [B(CN)4]-anions. Although the well-known trend regarding the surface tension decrease with the increase of the size of the aliphatic moiety at the cation was observed, the order obtained for the anions is more intricate. For a common cation and at a given temperature, the surface tension decreases according to: [N(CN)2]- > [SCN]- > [C(CN)3]- > [B(CN)4]-. Therefore, the surface tension of this homologous series does not decrease with the increase of the number of –CN groups at the anion as has been previously shown by studies performed with a more limited matrix of ILs. A maximum in the surface tension and critical temperature was observed for [N(CN)2]-based ILs. Furthermore, a minimum in the surface entropy, indicative of a highly structured surface, was found for the same class of ILs. All these evidences seem to be a result of stronger hydrogen-bonding interactions occurring in [N(CN)2]-based ILs, when compared with the remaining CN-based counterparts, and as sustained by cation-anion interaction energies derived from the Conductor Like Screening Model for Real Solvents (COSMO-RS).

  12. Emission spectrum of holmium atoms excited during ionic sputtering of a surface

    SciTech Connect

    Pop, S. S.; Braslavets, V. V.; Evdokimov, S. A.

    1988-08-01

    The article shows the fundamental possibility of using the bombardment of the surface of solids by kilo V ions for exciting the emission spectrum of particles of the target material and for obtaining spectroscopic data. The method is tested by studying the emission spectra of holmium as an example. It is shown that the sensitivity of the method can be substantially increased by using the so-called chemical effect, i.e., the effect of strengthening the spectral lines of sputtered excited metal atoms during bombardment of the target in the presence of oxygen. It is proposed that the chemical effect, which takes place only for atomic lines, in contrast to ionic ones, can also be used for simplifying the identification of atomic lines. It is noted that the proposed method is suitable for studying the atomic spectra of any solids, including refractory and chemically reactive substances.

  13. Fabrication of localized surface plasmon resonance fiber probes using ionic self-assembled gold nanoparticles.

    PubMed

    Wan, Miao; Luo, Pengfei; Jin, Jiayi; Xing, Jiong; Wang, Zhiyong; Wong, Stephen T C

    2010-01-01

    An nm-thickness composite gold thin film consisting of gold nanoparticles and polyelectrolytes is fabricated through ionic self-assembled multilayers (ISAM) technique and is deposited on end-faces of optical fibers to construct localized surface plasmon resonance (LSPR) fiber probes. We demonstrate that the LSPR spectrum induced by ISAM gold films can be fine-tuned through the ISAM procedure. We investigate variations of reflection spectra of the probe with respect to the layer-by-layer adsorption of ISAMs onto end-faces of fibers, and study the spectral variation mechanism. Finally, we demonstrated using this fiber probe to detect the biotin-streptavidin bioconjugate pair. ISAM adsorbed on optical fibers potentially provides a simple, fast, robust, and low-cost, platform for LSPR biosensing applications. PMID:22163561

  14. Surface study of metal-containing ionic liquids by means of photoemission and absorption spectroscopies

    NASA Astrophysics Data System (ADS)

    Caporali, Stefano; Pedio, Maddalena; Chiappe, Cinzia; Pomelli, Christian S.; Acres, Robert G.; Bardi, Ugo

    2016-06-01

    The vacuum/liquid interface of different ionic liquids obtained by dissolving bistriflimide salts of Ag, Al, Cu, Ni, and Zn in 1-butyl-3-methylimidazolium bistriflimide ([bmim][Tf2N]) was investigated under vacuum using AR-XPS and NEXAFS. The XPS spectra show chemical shifts of the nitrogen of the bistriflimide anion as a function of the metal type, indicating different strength of the coordination bonds. In silver bearing ILs, silver ions were found to be only weakly coordinated. On the contrary, Ni, Cu, Zn, and especially Al exhibit large chemical shifts attributable to strong interaction with the bistriflimide ions. The outermost surface was enriched with or depleted of metal ions as a function of the nature of the metals. Nickel and zinc tend to slightly concentrate at the surface while copper, silver, and especially aluminum are depleted at the surface. We also observed that the aliphatic alkyl chains of the cations tend to protrude outside the surface in all systems studied. However, the presence of metals generally increases the amount of bistriflimide at the vacuum/liquid interface.

  15. Grafting of ionic liquids on stainless steel surface for antibacterial application.

    PubMed

    Pang, Li Qing; Zhong, Li Juan; Zhou, Hui Fang; Wu, Xue E; Chen, Xiao Dong

    2015-02-01

    Stainless steel (SS) is favored for many uses due to its excellent chemical resistance, thermal stability and mechanical properties. Biofilms can be formed on stainless steel and may lead to serious hygiene problems and economic losses in many areas, e.g. food processing, public infrastructure and healthcare. For the first time, our work endeavored to make SS having antibacterial properties, ionic liquids (ILs) were grafted on SS surface via silane treatment followed by thiol-ene click reaction. The chemical structure and composition of the ILs grafted stainless-steel coupon surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. The antibacterial activity has been investigated, and the results showed that the ILs grafted SS surface exhibited significant antibacterial effects against Gram-negative Escherichia coli. Additionally, the results obtained here indicated that the ILs used here having bromide anion showed much better antibacterial activity against E. coli than the corresponding ILs with tetrafluoroborate and hexafluorophosphate as anions. These results obtained here can help to design novel and more efficient stainless steel having antibacterial surface. PMID:25561415

  16. Composition of the outermost layer and concentration depth profiles of ammonium nitrate ionic liquid surfaces.

    PubMed

    Ridings, Christiaan; Warr, Gregory G; Andersson, Gunther G

    2012-12-14

    Differences in the surface structure of protic ionic liquids (ILs) with three different cations and a common anion; ethyl-, propyl- and 2-hydroxyethyl- (or ethanol-) ammonium nitrate (EAN, PAN and EtAN, respectively) have been observed by neutral impact collision ion scattering spectroscopy (NICISS) and metastable induced electron spectroscopy/ultraviolet photoelectron spectroscopy (MIES/UPS). NICISS is used to determine the concentration depth profiles of the elements in each IL and it reveals an enrichment of cation alkyl chains of PAN and EtAN in the outermost layer compared to EAN, and a corresponding depletion of nitrate from the outermost layer of the EtAN surface. MIES probes the molecular orbitals of only the species in the outermost layer of a sample and confirms that, while both the anion and the cation are present to some degree at the surface of all three ILs, the cation is enriched to a greater extent at the surface of PAN and EtAN compared to EAN. PMID:23103987

  17. Contact angles and wettability of ionic liquids on polar and non-polar surfaces.

    PubMed

    Pereira, Matheus M; Kurnia, Kiki A; Sousa, Filipa L; Silva, Nuno J O; Lopes-da-Silva, José A; Coutinho, João A P; Freire, Mara G

    2015-12-21

    Many applications involving ionic liquids (ILs) require the knowledge of their interfacial behaviour, such as wettability and adhesion. In this context, herein, two approaches were combined aiming at understanding the impact of the IL chemical structures on their wettability on both polar and non-polar surfaces, namely: (i) the experimental determination of the contact angles of a broad range of ILs (covering a wide number of anions of variable polarity, cations, and cation alkyl side chain lengths) on polar and non-polar solid substrates (glass, Al-plate, and poly-(tetrafluoroethylene) (PTFE)); and (ii) the correlation of the experimental contact angles with the cation-anion pair interaction energies generated by the Conductor-like Screening Model for Real Solvents (COSMO-RS). The combined results reveal that the hydrogen-bond basicity of ILs, and thus the IL anion, plays a major role through their wettability on both polar and non-polar surfaces. The increase of the IL hydrogen-bond accepting ability leads to an improved wettability of more polar surfaces (lower contact angles) while the opposite trend is observed on non-polar surfaces. The cation nature and alkyl side chain lengths have however a smaller impact on the wetting ability of ILs. Linear correlations were found between the experimental contact angles and the cation-anion hydrogen-bonding and cation ring energies, estimated using COSMO-RS, suggesting that these features primarily control the wetting ability of ILs. Furthermore, two-descriptor correlations are proposed here to predict the contact angles of a wide variety of ILs on glass, Al-plate, and PTFE surfaces. A new extended list is provided for the contact angles of ILs on three surfaces, which can be used as a priori information to choose appropriate ILs before a given application. PMID:26554705

  18. Interaction of Ionic Liquids with Lipid Biomembrane: Implication from Supramolecular Assembly to Cytotoxicity

    NASA Astrophysics Data System (ADS)

    Jing, Benxin; Lan, Nan; Zhu, Y. Elaine

    2013-03-01

    An explosion in the research activities using ionic liquids (ILs) as new ``green'' chemicals in several chemical and biomedical processes has resulted in the urgent need to understand their impact in term of their transport and toxicity towards aquatic organisms. Though a few experimental toxicology studies have reported that some ionic liquids are toxic with increased hydrophobicity of ILs while others are not, our understanding of the molecular level mechanism of IL toxicity remains poorly understood. In this talk, we will discuss our recent study of the interaction of ionic liquids with model cell membranes. We have found that the ILs could induce morphological change of lipid bilayers when a critical concentration is exceeded, leading to the swelling and tube-like formation of lipid bilayers. The critical concentration shows a strong dependence on the length of hydrocarbon tails and hydrophobic counterions. By SAXS, Langmuir-Blodgett (LB) and fluorescence microscopic measurement, we have confirmed that tube-like lipid complexes result from the insertion of ILs with long hydrocarbon chains to minimize the hydrophobic interaction with aqueous media. This finding could give insight to the modification and adoption of ILs for the engineering of micro-organisms.

  19. Electrostatics in ionic solution : work and energy, charge regulation, and in homogeneous surfaces

    NASA Astrophysics Data System (ADS)

    Boon, N. J. H.

    2012-01-01

    This thesis concerns the electrostatic properties of charged objects that are immersed into an ionic solvent, for example water with dissolved salt. Typically, the ions inside such a solvent form layers of countercharge close to the charged objects, causing `screening' of the charges. By employing Density Functional Theory (DFT) one is able integrate out the degrees of freedom of the ions and find relations that describe the effective electrostatic properties of the charged objects. One finds that for a large parameter regime the electrostatic potential everywhere in the solvent should satisfy the well established Poisson-Boltzmann equation. We study the electrostatic capacity of porous electrodes in salt water, and derive a method to reversibly extract electric energy from salinity gradients that occur for example at an estuary where sea- and river water meet. However, in the main part of this thesis we consider charged colloidal particles, and study the effect of internal porosity as well as heterogeneities in the surface-charge density (patchy particles) on colloid-colloid interactions. In a far-field analysis we derive equations that describe these interactions for particles with nonvanishing multipole moments, for example `Janus' colloids with a strong dipole component. If such particles locally have a high surface charge density, then the nonlinear dependence of the counterion density on the local charge density leads to a generalisation of charge renormalisation from purely monopolar to dipolar, quadrupolar, etc., including `mode couplings'. In a more detailed approach, which turns out to be important for colloidal particles at smaller distances from each other, we consider the chemical processes that lead to surface charge, and specify a parameter regime in which charging can be described by a single `chargeability' parameter. As we show in this thesis, the phase diagrams we obtain within this regime have many similarities with a `constant surface potential

  20. Preparation and characterization of ultrathin dual-layer ionic liquid lubrication film assembled on silica surfaces.

    PubMed

    Pu, Jibin; Wang, Liping; Mo, Yufei; Xue, Qunji

    2011-02-15

    A novel ultrathin dual-layer film, which contained both bonded and mobile phases in ionic liquids (ILs) layer, was fabricated successfully on a silicon substrate modified by a self-assembled monolayer (SAM). The formation and surface properties of the films were analyzed using ellipsometer, water contact angle meter, attenuated total reflectance Fourier transform infrared spectroscopy, multi-functional X-ray photoelectron spectroscopy, and atomic force microscope. Meanwhile, the adhesive and nanotribological behaviors of the films were evaluated by a homemade colloidal probe. A ball-on-plate tribometer was used to evaluate the microtribological performances of the films. Compared with the single-layer ILs film deposited directly on the silicon surface, the as-prepared dual-layer film shows the improved tribological properties, which is attributed to the special chemical structure and outstanding physical properties of the dual-layer film, i.e., the strong adhesion between bonded phase of ILs and silicon substrate via the chemical bonding with SAM, the interlinked hydrogen bonds among the molecules, and two-phase structure composed of steady bonded phase with load-carrying capacity and flowable mobile phase with self-replenishment property. PMID:21111428

  1. Phenomenological Transition of an Aluminum Surface in an Ionic Liquid and Its Beneficial Implementation in Batteries.

    PubMed

    Shvartsev, B; Gelman, D; Amram, D; Ein-Eli, Y

    2015-12-29

    Aluminum (Al) electrochemical dissolution in organic nonaqueous media and room temperature ionic liquids (RTILs) is partially hampered by the presence of a native oxide. In this work, Al activation in EMIm(HF)2.3F RTIL is reported. It was confirmed that as a result of the interaction of Al with the RTIL, a new film is formed instead of the pristine oxide layer. Aluminum surface modifications result in a transformation from a passive state to the active behavior of the metal. This was confirmed via the employment of electrochemical methods and characterization by XPS, AFM, and TEM. It was shown that the pristine oxide surface film dissolves in EMIm(HF)2.3F, allowing an Al-O-F layer to be formed instead. This newly built up layer dramatically restricts Al corrosion while enabling high rates of Al anodic dissolution. These beneficial features allow the implementation of Al as an anode in advanced portable power sources, such as aluminum-air batteries. PMID:26636468

  2. Anisotropic surface roughness enhances the bending response of ionic polymer-metal composite (IPMC) artificial muscles

    NASA Astrophysics Data System (ADS)

    Stoimenov, Boyko L.; Rossiter, Jonathan M.; Mukai, Toshiharu

    2007-01-01

    Demands from the fields of bio-medical engineering and biologically-inspired robotics motivate a growing interest in actuators with properties similar to biological muscle, including ionic polymer-metal composites (IPMC), the focus of this study. IPMC actuators consist of an ion-conductive polymer membrane, coated with thin metal electrodes on both sides and bend when voltage is applied. Some of the advantages of IPMC actuators are their softness, lack of moving parts, easy miniaturization, light weight and low actuation voltage. When used in bio-mimetic robotic applications, such as a snake-like swimming robot, locomotion speed can be improved by increasing the bending amplitude. However, it cannot be improved much by increasing the driving voltage, because of water electrolysis. To enhance the bending response of IPMCs we created a "preferred" bending direction by anisotropic surface modification. Introduction of anisotropic roughness with grooves across the length of the actuator improved the bending response by a factor of 2.1. Artificially introduced cracks on the electrodes in direction, in which natural cracks form by bending, improved bending response by a factor of 1.6. Anisotropic surface modification is an effective method to enhance the bending response of IPMC actuators and does not compromise their rigidity under loads perpendicular to the bending plane.

  3. A step toward the development of high-temperature stable ionic liquid-in-oil microemulsions containing double-chain anionic surface active ionic liquid.

    PubMed

    Rao, Vishal Govind; Banerjee, Chiranjib; Ghosh, Surajit; Mandal, Sarthak; Kuchlyan, Jagannath; Sarkar, Nilmoni

    2013-06-20

    Owing to their fascinating properties and wide range of potential applications, interest in nonaqueous microemulsions has escalated in the past decade. In the recent past, nonaqueous microemulsions containing ionic liquids (ILs) have been utilized in performing chemical reactions, preparation of nanomaterials, synthesis of nanostructured polymers, and drug delivery systems. The most promising fact about IL-in-oil microemulsions is their high thermal stability compared to that of aqueous microemulsions. Recently, surfactant-like properties of surface active ionic liquids (SAILs) have been used for preparation of microemulsions with high-temperature stability and temperature insensitivity. However, previously described methods present a limited possibility of developing IL-in-oil microemulsions with a wide range of thermal stability. With our previous work, we introduced a novel method of creating a huge number of IL-in-oil microemulsions (Rao, V. G.; Ghosh, S.; Ghatak, C.; Mandal, S.; Brahmachari, U.; Sarkar, N. J. Phys. Chem. B2012, 116, 2850-2855), composed of a SAIL as a surfactant, room-temperature ionic liquids as a polar phase, and benzene as a nonpolar phase. The use of benzene as a nonpolar solvent limits the application of the microemulsions to temperatures below 353 K. To overcome this limitation, we have synthesized N,N-dimethylethanolammonium 1,4-bis(2-ethylhexyl) sulfosuccinate (DAAOT), which was used as a surfactant. DAAOT in combination with isopropyl myristate (IPM, as an oil phase) and ILs (as a polar phase) produces a huge number of high-temperature stable IL-in-oil microemulsions. By far, this is the first report of a huge number of high-temperature stable IL-in-oil microemulsions. In particular, we demonstrate the wide range of thermal stability of [C6mim][TF2N]/DAAOT/IPM microemulsions by performing a phase behavior study, dynamic light scattering measurements, and (1)H NMR measurements and by using coumarin-480 (C-480) as a fluorescent probe

  4. Surface structured platinum electrodes for the electrochemical reduction of carbon dioxide in imidazolium based ionic liquids.

    PubMed

    Hanc-Scherer, Florin A; Montiel, Miguel A; Montiel, Vicente; Herrero, Enrique; Sánchez-Sánchez, Carlos M

    2015-10-01

    The direct CO2 electrochemical reduction on model platinum single crystal electrodes Pt(hkl) is studied in [C2mim(+)][NTf2(-)], a suitable room temperature ionic liquid (RTIL) medium due to its moderate viscosity, high CO2 solubility and conductivity. Single crystal electrodes represent the most convenient type of surface structured electrodes for studying the impact of RTIL ion adsorption on relevant electrocatalytic reactions, such as surface sensitive electrochemical CO2 reduction. We propose here based on cyclic voltammetry and in situ electrolysis measurements, for the first time, the formation of a stable adduct [C2mimH-CO2(-)] by a radical-radical coupling after the simultaneous reduction of CO2 and [C2mim(+)]. It means between the CO2 radical anion and the radical formed from the reduction of the cation [C2mim(+)] before forming the corresponding electrogenerated carbene. This is confirmed by the voltammetric study of a model imidazolium-2-carboxylate compound formed following the carbene pathway. The formation of that stable adduct [C2mimH-CO2(-)] blocks CO2 reduction after a single electron transfer and inhibits CO2 and imidazolium dimerization reactions. However, the electrochemical reduction of CO2 under those conditions provokes the electrochemical cathodic degradation of the imidazolium based RTIL. This important limitation in CO2 recycling by direct electrochemical reduction is overcome by adding a strong acid, [H(+)][NTf2(-)], into solution. Then, protons become preferentially adsorbed on the electrode surface by displacing the imidazolium cations and inhibiting their electrochemical reduction. This fact allows the surface sensitive electro-synthesis of HCOOH from CO2 reduction in [C2mim(+)][NTf2(-)], with Pt(110) being the most active electrode studied. PMID:26307480

  5. Effects of Electrode Surface Morphology on the Transduction of Ionic Polymer-Metal Composites

    NASA Astrophysics Data System (ADS)

    Palmre, Viljar

    Ionic polymer-metal composites (IPMCs) are innovative smart materials that exhibit electromechanical and mechanoelectrical transduction (conversion of electrical input into mechanical deformation and vice versa). Due to low driving voltage (< 5 V) and ability to operate in aqueous environment, IPMCs are attractive for developing soft actuators and sensors for underwater robots and medical devices. This dissertation focuses on investigating the effects of electrode surface morphology in the transduction of Pt and Pd-Pt electrodes-based IPMCs, with the aim to improve the electrode surface design and thereby enhance the transduction performance of the material. Firstly, the synthesis techniques are developed to control and manipulate the surface structure of the mentioned electrodes through the electroless plating process. Using these techniques, IPMCs with different electrode surface structures are fabricated. The changes in the electrode surface morphology and the resulting effects on the material's electromechanical, mechanoelectrical, electrochemical and mechanical properties area examined and analyzed. This study shows that increasing the impregnation-reduction cycles under appropriate conditions leads to the formation and growth of platinum nanoparticles with sharp tips and edges---called Pt nanothorn assemblies---at the polymer-electrode interface. IPMCs designed with such nanostructured Pt electrodes are first to be reported. The experiments demonstrate that the formation and growth of Pt nanothorn assemblies at the electrode interface increases considerably the total transported charge during the transduction, thereby increasing significantly the displacement and blocking force output of IPMC. The improvement of the mentioned electromechanical properties was 3--5 times, depending on the input voltage and frequency used. Also, the peak mechanoelectrically induced voltage increased somewhat, although the overall effect of the surface structure was relatively

  6. A novel urea-functionalized surface-confined octadecylimidazolium ionic liquid silica stationary phase for reversed-phase liquid chromatography.

    PubMed

    Zhang, Mingliang; Tan, Ting; Li, Zhan; Gu, Tongnian; Chen, Jia; Qiu, Hongdeng

    2014-10-24

    One-pot synthesis of surface-confined ionic liquid functionalized silica spheres was proposed using N-(3-aminopropyl)imidazole, γ-isopropyltriethoxysilane and 1-bromooctadecane as starting materials. The surface modification of the silica spheres was successful with a high surface density of octadecylimidazolium, enabling the utilization of this new urea-functionalized ionic liquid-grafted silica material as stationary phase for high-performance liquid chromatography in reversed-phase mode. The long aliphatic chain combined with the multiple polar group embedded in the ligands imparted the new stationary phase fine selectivity towards PAH isomers and polar aromatics and higher affinity for phenolic compounds. The unique features of the new material, especially the effect of the urea group on the retention were elucidated by mathematic modeling. PMID:25249489

  7. Ionic liquid activated Bacillus subtilis lipase A variants through cooperative surface substitutions.

    PubMed

    Zhao, Jing; Jia, Ning; Jaeger, Karl-Erich; Bocola, Marco; Schwaneberg, Ulrich

    2015-10-01

    The interest in performing enzyme-catalyzed reactions in amphiphilic systems, e.g., imidazolium-based ionic liquids (ILs) or surfactants, has been increased over the past decades. Directed protein evolution has been successful in tailoring enzymes for desired properties. Herein, nine IL-resistant Bacillus subtilis lipase A variants, particularly an IL-activated variant M1 (M134N/N138S/L140S), were identified by directed evolution. For instance, variant M2 (M134R/L140S) showed almost doubled specific activity (16.9 vs. 9.4 U/mg) and resistance (233% vs. 111%) at 9 vol% 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([C4 mim][TfO]) compared with wild-type. The specific activities and resistance of purified individual single and double variants have been studied in five different IL-aqueous mixtures. The re-activation of lipase variant M1 (not wild-type) at high IL concentration was attributed to the cooperative effect of three surface substitutions (M134N, N138S, L140S) near the substrate-binding cleft. The presence of IL/substrate clusters under assay conditions was likely related to the re-activation effect. This study provides first example of IL-activated lipase variant generated by protein engineering, and helps to better understand the protein-IL interaction. PMID:25899108

  8. Stimuli-responsive surface localized ionic cluster (SLICs) formation from nonspherical colloidal particles.

    PubMed

    Lestage, David J; Urban, Marek W

    2005-07-19

    Structural features of phospholipids provide a unique opportunity for utilizing these amphiphilic species to stabilize the synthesis of colloidal dispersion particles by controlling concentration levels relative to dispersion synthesis components. 1,2-Bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DCPC) phospholipid was utilized as cosurfactant in the synthesis of sodium dioctyl sulfosuccinate (SDOSS) stabilized methyl methacrylate/n-butyl acrylate (MMA/nBA) colloidal dispersions. Aqueous dispersions containing various concentration levels of DCPC result in the formation of cocklebur particle morphologies, and when prepared in the presence of Ca2+ and annealed at various temperatures, stimuli-responsive behaviors of coalesced films were elucidated. The formation of surface localized ionic clusters (SLICs) at the film-air (F-A) and film-substrate (F-S) interfaces is shown to be responsive to concentration levels of DCPC, Ca2+/DCPC ratios, and temperature. These studies show that it is possible to control stratification and mobility to the F-A and F-S interfaces during and after coalescence. Using attenuated total reflectance Fourier transform infrared (ATR-FTIR) and internal reflection infrared imaging (IRIRI) spectroscopies, molecular entities responsible for SLIC formation were determined. These studies also show that stimuli-responsive behaviors during film formation can be controlled by colloidal solution morphologies and synergistic interactions of individual components. PMID:16008384

  9. Identification of helicity-dependent photocurrents from topological surface states in Bi2Se3 gated by ionic liquid.

    PubMed

    Duan, Junxi; Tang, Ning; He, Xin; Yan, Yuan; Zhang, Shan; Qin, Xudong; Wang, Xinqiang; Yang, Xuelin; Xu, Fujun; Chen, Yonghai; Ge, Weikun; Shen, Bo

    2014-01-01

    Dirac-like surface states on surfaces of topological insulators have a chiral spin structure with spin locked to momentum, which is interesting in physics and may also have important applications in spintronics. In this work, by measuring the tunable helicity-dependent photocurrent (HDP), we present an identification of the HDP from the Dirac-like surface states at room temperature. It turns out that the total HDP has two components, one from the Dirac-like surface states, and the other from the surface accumulation layer. These two components have opposite directions. The clear gate tuning of the electron density as well as the HDP signal indicates that the surface band bending and resulted surface accumulation are successfully modulated by the applied ionic liquid gate, which provides a promising way to the study of the Dirac-like surface states and also potential applications in spintronic devices. PMID:24809330

  10. Ionic liquid lubrication: influence of ion structure, surface potential and sliding velocity.

    PubMed

    Li, Hua; Rutland, Mark W; Atkin, Rob

    2013-09-21

    Colloid probe atomic force microscopy (AFM) has been employed to investigate the nanotribology of the ionic liquid (IL)-Au(111) interface. Data is presented for four ILs, 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([EMIM] FAP), 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([BMIM] FAP), 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM] FAP) and 1-butyl-3-methylimidazolium iodide ([BMIM] I), at different Au(111) surface potentials. Lateral forces vary as a function of applied surface potential and ion structure because the composition of the confined ion layer changes from cation-enriched (at negative potentials) to mixed (at 0 V), and to anion-enriched (at positive potentials). ILs with FAP(-) anions all exhibit similar nanotribology: low friction at negative potentials and higher friction at positive potentials. [BMIM] I displays the opposite behaviour, as an I(-) anion-enriched layer is more lubricating than either the [BMIM](+) or FAP(-) layers. The effect of cation charged group (charge-delocalised versus charged-localised) was investigated by comparing [BMIM] FAP with 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([Py(1,4)] FAP). [BMIM] FAP is less lubricating at negative potentials, but more lubricating at positive potentials. This indicated that even at positive potentials the cation concentration in the boundary layer is sufficiently high to influence lubricity. The influence of sliding velocity on lateral force was investigated for the [EMIM] FAP-Au(111) system. At neutral potentials the behaviour is consistent with a discontinuous sliding process. When a positive or negative potential bias is applied, this effect is less pronounced as the colloid probe slides along a better defined ion plane. PMID:23836254

  11. Preparation and evaluation of surface-bonded tricationic ionic liquid silica as stationary phases for high-performance liquid chromatography.

    PubMed

    Qiao, Lizhen; Shi, Xianzhe; Lu, Xin; Xu, Guowang

    2015-05-29

    Two tricationic ionic liquids were prepared and then bonded onto the surface of supporting silica materials through "thiol-ene" click chemistry as new stationary phases for high-performance liquid chromatography. The obtained columns of tricationic ionic liquids were evaluated respectively in the reversed-phase liquid chromatography (RPLC) mode and hydrophilic interaction liquid chromatography (HILIC) mode, and possess ideal column efficiency of 80,000 plates/m in the RPLC mode with naphthalene as the test solute. The tricationic ionic liquid stationary phases exhibit good hydrophobic and shape selectivity to hydrophobic compounds, and RPLC retention behavior with multiple interactions. In the HILIC mode, the retention and selectivity were evaluated through the efficient separation of nucleosides and bases as well as flavonoids, and the typical HILIC retention behavior was demonstrated by investigating retention changes of hydrophilic solutes with water volume fraction in mobile phase. The results show that the tricationic ionic liquid columns possess great prospect for applications in analysis of hydrophobic and hydrophilic samples. PMID:25890438

  12. Electromechanical model for a self-sensing ionic polymer-metal composite actuating device with patterned surface electrodes

    NASA Astrophysics Data System (ADS)

    Kruusamäe, Karl; Brunetto, Paola; Punning, Andres; Kodu, Margus; Jaaniso, Raivo; Graziani, Salvatore; Fortuna, Luigi; Aabloo, Alvo

    2011-12-01

    This paper further discusses a concept of creating a self-sensing ionic polymer-metal composite (IPMC) actuating device with patterned surface electrodes where the actuator and sensor elements are separated by a grounded shielding electrode. Different patterning methods are discussed and compared in detail; the presented experimental data give an understanding of the qualitative properties of the patterns created. Finally, an electromechanical model of the device is proposed and validated.

  13. Surface osteosarcoma: Clinical features and therapeutic implications

    PubMed Central

    Nouri, H.; Ben Maitigue, M.; Abid, L.; Nouri, N.; Abdelkader, A.; Bouaziz, M.; Mestiri, M.

    2015-01-01

    Introduction Surface osteosarcoma are rare variant of osteosarcoma that include parosteal osteosarcoma, periosteal osteosarcoma and high grade surface osteosarcoma. These lesions have different clinical presentation and biological behavior compared to conventional osteosarcoma, and hence need to be managed differently. Goal The aim of this study is to analyze the clinico-pathological features and outcome of a series of surface osteosarcoma in an attempt to define the adequate treatment of this rare entity. Patient and method It is a retrospective and bicentric study of 18 surface osteosarcoma that were seen at the KASSAB’s Institute and SAHLOUL Hospital from 2006 to 2013. The authors reviewed the clinical and radiologic features, histologic sections, treatments, and outcomes in this group of patients. Results Seven patients were male (38.9%) and 11 were female (61.1%) with mean age of 25 years (range from 16 to 55 years). Eleven lesions were in the femur and 7 in the tibia. We identified 11 parosteal osteosarcoma (six of them were dedifferentiated), 3 periosteal osteosarcoma and 4 high grade surface osteosarcoma. Six patients had neoadjuvant chemotherapy and all lesions had surgical resection. Margins were wide in 15 cases and intra lesional in 3 cases. Histological response to chemotherapy was poor in all cases. The mean follow up was 34.5 months. Six patients (33.3%) presented local recurrence and 8 patients (44.4%) presented lung metastases. Six patients (33.3%) died from the disease after a mean follow up of 12 months (6–30 months); all of them had high grade lesions. Conclusion Histological grade of malignancy is the main point to assess in surface osteosarcoma since it determines treatment and prognosis. Low grade lesions should be treated by wide resection, while high grade lesions need more aggressive surgical approach associated to post operative chemotherapy. PMID:26730360

  14. Effect of Ions and Ionic Strength on Surface Plasmon Absorption of Single Gold Nanowires.

    PubMed

    Baral, Susil; Green, Andrew J; Richardson, Hugh H

    2016-06-28

    The local temperature change from a single optically excited gold nanowire, lithographically prepared on Al0.94Ga0.06N embedded with Er(3+) ions, is measured in air, pure water, and various concentrations of aqueous solutions of ionic solutes of NaCl, Na2SO4, and MgSO4. The absorption cross section of the nanowire under pure water (2.25 × 10(-14) m(2)) and different solution ionic strength is measured from the slopes of temperature change versus laser intensity plots. Addition of charges into the solution decreases the amount of heat generated during optical excitation of the gold nanostructures because the absorption cross section of the gold nanowire is attenuated. A Langmuir-type behavior of the absorption cross section with ionic strength is observed that is identified with an increase in the occupancy of screened interfacial charges. The absorption cross section of the nanowire decreases with ionic strength until a saturation value of 9 × 10(-15) m(2), where saturation in the occupancy of screened interfacial charge occurs. Dynamic measurements of temperature for a single gold nanowire immersed in a microchannel flow cell show a sharp and fast temperature drop for the flow of ionic solution compared to the pure (deionized) water, suggesting that the technique can be developed as a sensor probe to detect the presence of ions in solution. PMID:27215955

  15. Self-assembled thin film of imidazolium ionic liquid on a silicon surface: Low friction and remarkable wear-resistivity

    NASA Astrophysics Data System (ADS)

    Gusain, Rashi; Kokufu, Sho; Bakshi, Paramjeet S.; Utsunomiya, Toru; Ichii, Takashi; Sugimura, Hiroyuki; Khatri, Om P.

    2016-02-01

    Imidazolium-hexafluorophosphate (ImPF6) ionic liquid thin film is prepared on a silicon surface using 3-chloropropyltrimethoxysilane as a bifunctional chemical linker. XPS result revealed the covalent grafting of ImPF6 thin film on a silicon surface. The atomic force microscopic images demonstrated that the ImPF6 thin film is composed of nanoscopic pads/clusters with height of 3-7 nm. Microtribological properties in terms of coefficient of friction and wear-resistivity are probed at the mean Hertzian contact pressure of 0.35-0.6 GPa under the rotational sliding contact. The ImPF6 thin film exhibited low and steady coefficient of friction (μ = 0.11) along with remarkable wear-resistivity to protect the underlying silicon substrate. The low shear strength of ImPF6 thin film, the covalent interaction between ImPF6 ionic liquid thin film and underlying silicon substrate, and its regular grafting collectively reduced the friction and improved the anti-wear property. The covalently grafted ionic liquid thin film further shows immense potential to expand the durability and lifetime of M/NEMS based devices with significant reduction of the friction.

  16. Electrochemical Deposition of Niobium onto the Surface of Copper Using a Novel Choline Chloride-Based Ionic Liquid

    SciTech Connect

    Wixtroma, Alex I.; Buhlera, Jessica E.; Reece, Charles E.; Abdel-Fattah, Tarek M.

    2013-06-01

    Recent research has shown that choline chloride-based solutions can be used to replace acid-based electrochemical polishing solutions. In this study niobium metal was successfully deposited on the surface of copper substrate via electrochemical deposition using a novel choline chloride-based ionic liquid. The niobium metal used for deposition on the Cu had been dissolved in the solution from electrochemical polishing of a solid niobium piece prior to the deposition. The visible coating on the surface of the Cu was analyzed using scanning electron microscopy (SEM) and electron dispersive x-ray spectroscopy (EDX). This deposition method effectively recycles previously dissolved niobium from electrochemical polishing.

  17. Synthesis and micellar properties of surface-active ionic liquids: 1-alkyl-3-methylimidazolium chlorides.

    PubMed

    El Seoud, Omar A; Pires, Paulo Augusto R; Abdel-Moghny, Thanaa; Bastos, Erick L

    2007-09-01

    A series of surface-active ionic liquids, RMeImCl, has been synthesized by the reaction of purified 1-methylimidazole and 1-chloroalkanes, RCl, R=C(10),C(12),C(14), and C(16), respectively. Adsorption and aggregation of these surfactants in water have been studied by surface tension measurement. Additionally, solution conductivity, electromotive force, fluorescence quenching of micelle-solubilized pyrene, and static light scattering have been employed to investigate micelle formation. The following changes resulted from an increase in the length of R: an increase of micelle aggregation number; a decrease of: minimum area/surfactant molecule at solution/air interface; critical micelle concentration, and degree of counter-ion dissociation. Theoretically-calculated aggregation numbers and those based on quenching of pyrene are in good agreement. Gibbs free energies of adsorption at solution/air interface, DeltaG(ads)(0), and micelle formation in water, DeltaG(mic)(0), were calculated, and compared to those of three surfactant series, alkylpyridinium chlorides, RPyCl, alkylbenzyldimethylammonium chlorides, RBzMe(2)Cl, and benzyl(3-acylaminoethyl)dimethylammonium chlorides, R(')AEtBzMe(2)Cl, respectively. Contributions to the above-mentioned Gibbs free energies from surfactant methylene groups (in the hydrophobic tail) and the head-group were calculated. For RMeImCl, the former energy is similar to that of other cationic surfactants. The corresponding free energy contribution of the head-group to DeltaG(mic)(0) showed the following order: RPyCl approximately RBzMe(2)Cl>RMeImCl>R(')AEtBzMe(2)Cl. The head-groups of the first two surfactant series are more hydrophobic than the imidazolium ring of RMeImCl, this should favor their aggregation. Micellization of RMeImCl, however, is driven by a relatively strong hydrogen-bonding between the chloride ion and the hydrogens in the imidazolium ring, in particular the relatively acidic H2. This interaction more than compensates for

  18. Effect of alkyl chain length and hydroxyl group functionalization on the surface properties of imidazolium ionic liquids.

    PubMed

    Pensado, Alfonso S; Costa Gomes, Margarida F; Canongia Lopes, José N; Malfreyt, Patrice; Pádua, Agílio A H

    2011-08-14

    Properties of the surface of ionic liquids, such as surface tension, ordering, and charge and density profiles, were studied using molecular simulation. Two types of modification in the molecular structure of imidazolium cations were studied: the length of the alkyl side chain and the presence of a polar hydroxyl group at the end of the side chain. Four ionic liquids were considered: 1-ethyl-3-methylimidazolium tetrafluoroborate, [C(2)C(1)im][BF(4)]; 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate, [C(2)OHC(1)im][BF(4)]; 1-octyl-3-methylimidazolium tetrafluoroborate, [C(8)C(1)im][BF(4)] and 1-(8-hydroxyoctyl)-3-methylimidazolium tetrafluoroborate, [C(8)OHC(1)im][BF(4)]. The surface tension was calculated using both mechanical and thermodynamic definitions, with consistent treatment of the long-range corrections. The simulations reproduce the available experimental values of surface tension with a maximum deviation of ±10%. This energetic characterization of the interface is completed by microscopic structural analysis of orientational ordering at the interface and density profiles along the direction normal to the interface. The presence of the hydroxyl group modifies the local structure at the interface, leading to a less organized liquid phase. The results allow us to relate the surface tension to the structural ordering at the liquid-vacuum interface. PMID:21643581

  19. Release and formation of surface-localized ionic clusters (SLICs) into phospholipid rafts from colloidal solutions during coalescence.

    PubMed

    Lestage, David J; Urban, Marek W

    2005-03-15

    Stimuli-responsive behavior of phospholipids in the presence of ionic surfactants utilized in synthesis of MMA/nBA colloidal particles was investigated. Utilizing 1-myristoyl-2-hydroxy-sn-glycero-phosphocholine (MHPC) phospholipid, and sodium dioctyl sulfosuccinate (SDOSS) surfactant as dispersing media in H(2)O, narrow unimodal particle size distributions of methyl methacrylate (MMA)/n-butyl acrylate (nBA) copolymers were synthesized. The particle diameters were 154 nm when a SDOSS/MHPC mixture was used and 161 nm using MHPC as the only surface-stabilizing species. When such colloidal dispersions are exposed to 1.7, 3.3, and 6.7 mM aqueous CaCl(2) and KCl electrolyte solutions, surface-localized ionic clusters are generated at the film-air interface that may serve as lipid rafts composed of crystalline phases of MHPC deposited on poly(MMA)/nBA films. These studies illustrate that it is possible to control release and morphology developments of surface phospholipid rafts on artificial surfaces. PMID:15752001

  20. Adhesion of CO2 on hydrated mineral surfaces and its implications to geologic carbon sequestration

    NASA Astrophysics Data System (ADS)

    Wang, S.; Clarens, A. F.; Tao, Z.; Persily, S. M.

    2013-12-01

    Most mineral surfaces are water wetting, which has important implications for the transport of non-aqueous phase liquids, such as CO2, through porous media. In this work, contact angle experiments were carried out wherein unusual wetting behavior was observed between mineral surfaces and liquid or supercritical CO2 under certain geochemical conditions. This behavior can be understood in the context of adhesion between the CO2 and the mineral surface. When adhesion occurs, the wettability characteristics of the surfaces are significantly altered. More importantly, the CO2 exhibits a strong affinity for the surface and is highly resistant to shear forces in the aqueous phase. A static pendant drop method was used on a variety of polished mineral surfaces to measure contact angles. The composition of the aqueous phase (e.g., pH, ionic strength) and the characteristics of the mineral surface (e.g., composition, roughness), were evaluated to understand their impact on the prevalence of adhesion. Pressure and temperature conditions were selected to represent those that would be prevalent in geologic carbon sequestration (GCS) or during leakage from target repositories. Adhesion was widely observed on phlogopite mica, silica, and calcite surfaces with roughness on the order of ~10 nanometers. CO2 exhibited no adhesion on mineral surfaces with higher roughness (e.g., quartz). On smoother surfaces, the CO2 is thought to have more effective contact area with the mineral, enabling the weak van der Waals forces that drive most adhesion processes. Brine chemistry also had an important role in controlling CO2 adhesion. Increases in CO2 partial pressure and ionic strength both increased the incidence of adhesion. The addition of strong acid or strong base permanently inhibited the development of adhesion. These results suggest that the development of adhesion between the CO2 and the mineral surface is dependent on the integrity and thickness of the hydration layer between the CO2

  1. Polymeric ionic liquid and carbon black composite as a reusable supporting electrolyte: modification of the electrode surface.

    PubMed

    Yoo, Seung Joon; Li, Long-Ji; Zeng, Cheng-Chu; Little, R Daniel

    2015-03-16

    One of the major impediments to using electroorganic synthesis is the need for large amounts of a supporting electrolyte to ensure the passage of charge. Frequently this causes separation and waste problems. To address these issues, a polymeric ionic liquid-Super P carbon black composite has been formulated. The system enables electrolyses to be performed without adding an additional supporting electrolyte, and its efficient recovery and reuse. In addition, the ability of the composite to modify the electrode surface in situ leads to improved kinetics. A practical consequence is that one can decrease catalyst loading without sacrificing efficiency. PMID:25619992

  2. Surface history of Mercury - Implications for terrestrial planets

    NASA Technical Reports Server (NTRS)

    Murray, B. C.; Strom, R. G.; Trask, N. J.; Gault, D. E.

    1975-01-01

    A plausible surface history of Mercury is presented which is suggested by Mariner 10 television pictures. Five periods are postulated which are delineated by successive variations in the modification of the surface by external and internal processes: accretion and differentiation, terminal heavy bombardment, formation of the Caloris basin, flooding of that basin and other areas, and light cratering accumulated on the smooth plains. Each period is described in detail; the overall history is compared with the surface histories of Venus, Mars, and the moon; and the implications of this history for earth are discussed. It is tentatively concluded that: Mercury is a differentiated planet most likely composed of a large iron core enclosed by a relatively thin silicate layer; heavy surface bombardment occurred about four billion years ago, which probably affected all the inner planets, and was followed by a period of volcanic activity; no surface modifications caused by tectonic, volcanic, or atmospheric processes took place after the volcanic period.

  3. Surface modification of compressor steels using thermally assisted ionic diffusion in the titanium plasma of a vacuum arc discharge

    NASA Astrophysics Data System (ADS)

    Muboyadzhyan, S. A.; Azarovskii, E. N.

    2015-11-01

    The thermally stimulated ionic diffusion (ionic modification) of titanium ions at the surfaces of EP866 and EI961 compressor steels is considered in the plasma of the high-current vacuum-arc discharge (VAD) in an ion-plasma MAP-3 plant. The dependences of the sample temperature in the sputtering chamber of the ion-plasma MAP-3 plant and the rate of specific change of the sample mass on the bias voltage at a VAD current of 300 A are obtained. The elemental composition of the surface layers of the samples subjected to ion treatment is studied. It is shown that, at a VAD current of 300 A and a bias voltage up to 400 V, the compressor steel sample temperature does not exceed 440°C and the inversion voltage, which determines the transition from coating condensation to ion etching of a substrate, is ~360 V for EP866 steel and ~390 V for EI961 steel. The corrosion resistance of the compressor steels modified at a VAD current of 300 A is investigated.

  4. Decay behavior of screened electrostatic surface forces in ionic liquids: the vital role of non-local electrostatics.

    PubMed

    Kjellander, Roland

    2016-07-28

    Screened electrostatic surface forces, also called double layer forces, between surfaces in ionic liquids can, depending on the circumstances, decay in an exponentially damped, oscillatory manner or in a plain exponential way (the latter as in dilute electrolyte solutions where ion-ion correlations are very weak). The occurrence of both of these behaviors in dense ionic liquids, where ion-ion correlations are very strong, is analyzed in the current work using exact statistical mechanics formulated in a manner that is physically transparent. A vital ingredient in understanding the decay behaviors is the fact that electrostatics in dense electrolytes have a non-local nature caused by the strong correlations. It is shown that the effects of non-locality can be elucidated by a remarkably simple, general expression for the decay parameter κ that replaces the classical expression for the inverse Debye length κDH of the Debye-Hückel (DH) and non-linear Poisson-Boltzmann approximations. This exact expression is valid for both the plain exponential and the oscillatory cases. It shows how strong correlations can give rise to plain exponential decay with a long decay length. Such a decay can arise from anion-cation associations of various kinds, for instance transient ion pairing or association caused by many-body correlations; ion pairing is a possibility but not a necessity for this to occur. Theoretical analysis is done for systems consisting of ions with an arbitrary shape and internal charge density and immersed planar walls with arbitrary internal charge distribution and any short-range ion-surface interaction. The screened electrostatic surface force between two walls is at large separations proportional to the product of effective surface charge densities of each wall. For the oscillatory case, each wall contributes with a phase shift to the oscillations of the interaction. PMID:27356099

  5. Surface modification of PCC with guar gum using organic titanium ionic crosslinking agent and its application as papermaking filler.

    PubMed

    Xie, Wei; Song, Zhanqian; Liu, Zhenhua; Qian, Xueren

    2016-10-01

    Utilized the principles of guar gum (GG) gelation and crosslinking, a novel modified precipitated calcium carbonate (MPCC) papermaking filler was prepared by using organic titanium (OT) ionic crosslinking agent. The MPCC was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). FTIR results confirmed that GG had been coated on the surface of PCC particles, XPS analysis indicated the presence of titanium atoms on MPCC particles, and SEM and XRD results showed that the modification treatment did change the surface morphology and crystal structure of PCC particles. The handsheet testing results showed that the strength properties of handsheets were obviously improved when using MPCC as papermaking filler, and the optimum preparation conditions of MPCC were obtained. This research suggests that the GG modified PCC by using OT as crosslinking agent can be used to manufacture high filler content paper products. PMID:27312620

  6. Influence of Water on the Interfacial Nanostructure and Wetting of [Rmim][NTf2] Ionic Liquids at Mica Surfaces.

    PubMed

    Wang, Zhantao; Li, Hua; Atkin, Rob; Priest, Craig

    2016-09-01

    The effect of water concentration on the interfacial nanostructure and wetting behavior of a family of ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [Rmim][NTf2], at the surface of mica was investigated by contact angle measurement and atomic force microscopy (AFM). AFM reveals that interfacial layers of ILs observed at the surface of mica for "dry" ILs are not present for water-saturated ILs. The interaction of the IL ions of [Rmim][NTf2] with water molecules through hydrogen bonding is suspected to disrupt IL ion layering and precursor film growth on mica. Without the IL precursor film, contact angle relaxation of "wet" ILs on mica is less significant and ambient vapor adsorption becomes more important in determining the macroscopic wetting behavior. PMID:27486675

  7. Structural and metal-insulator transitions in ionic liquid-gated Ca3Ru2O7 surface

    NASA Astrophysics Data System (ADS)

    Puls, Conor P.; Cai, Xinxin; Zhang, Yuhe; Peng, Jin; Mao, Zhiqiang; Liu, Ying

    2014-06-01

    We report the fabrication and measurements of ionic liquid gated Hall bar devices prepared on the ab face of a thin Ca3Ru2O7 flake exfoliated from bulk single crystals that were grown by a floating zone method. The devices were categorized into two types: those with their electrical transport properties dominated by c-axis transport in type A or that of the in-plane in type B devices. Bulk physical phenomena, including a magnetic transition near 56 K, a structural and metal-insulator transition at a slightly lower temperature, as well as the emergence of a highly unusual metallic state as the temperature is further lowered, were found in both types of devices. However, the Shubnikov-de Haas oscillations were found in type A but not type B devices, most likely due to enhanced disorder on the flake surface. Finally, the ionic liquid gating of a type B device revealed a shift in critical temperature of the structural and metal-insulator transition, suggesting that this transition is tunable by the electric field effect.

  8. Protein imprinted ionic liquid polymer on the surface of multiwall carbon nanotubes with high binding capacity for lysozyme.

    PubMed

    Yuan, Shifang; Deng, Qiliang; Fang, Guozhen; Wu, Jianhua; Li, Wangwang; Wang, Shuo

    2014-06-01

    In this research, ionic liquid as functional monomer to prepare molecularly imprinted polymers for protein recognition was for the first time demonstrated, in which, 1-vinyl-3-butylimidazolium chloride was selected as functional monomer, acrylamide as co-functional monomer and lysozyme (Lyz) as template protein to synthesize imprinted polymers on the surface of multiwall carbon nanotubes in aqueous medium. The results indicated that ionic liquid was helpful to improve binding capacity of imprinted polymers, which had a maximum binding capacity of 763.36 mg/g in the optimum adsorption conditions. The prepared imprinted polymers had a fast adsorption rate and a much higher adsorption capacity than the corresponding non-imprinted polymers, with the difference in adsorption capacity up to 258.31 mg/g. The obtained polymer was evaluated by Lyz, bovine serum albumin (BSA), bovine hemoglobin (BHb), equine myoglobin (MB) and cytochrome c (Cyt c). The selectivity factor (β) for Lyz/BSA, Lyz/Mb, Lyz/BHb, and Lyz/Cyt c were 7.17, 2.12, 1.76 and 1.57, respectively, indicating the imprinted polymers had a good selectivity. Easy preparation of the imprinted polymers as well as high ability and selectivity to adsorb template proteins makes this polymer attractive and broadly applicable in biomacromolecular separation, biotechnology and sensors. PMID:24835511

  9. Spatially resolved electrochemistry in ionic liquids: surface structure effects on triiodide reduction at platinum electrodes.

    PubMed

    Aaronson, Barak D B; Lai, Stanley C S; Unwin, Patrick R

    2014-02-25

    Understanding the relationship between electrochemical activity and electrode structure is vital for improving the efficiency of dye-sensitized solar cells. Here, the reduction of triiodide to iodide in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]) room temperature ionic liquid (RTIL) is investigated on polycrystalline platinum using scanning electrochemical cell microscopy (SECCM) and correlated to the crystallographic orientation from electron backscatter diffraction (EBSD). Although the rate determining step in all grains was the first electron transfer, significant grain-dependent variations in activity were revealed, with grains with a dominant (110) crystallographic character exhibiting higher catalytic activity compared to those with a major (100) orientation. The SECCM technique is demonstrated to resolve heterogeneity in activity, highlighting that methods incorporating polycrystalline electrodes miss vital details for understanding and optimizing electrocatalysts. An additional advantage of the SECCM over single-crystal techniques is its ability to probe high index facets. PMID:24479903

  10. Coherent excitations at the neutral-ionic transition: Femtosecond dynamics on diabatic potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Cavatorta, Lorenzo; Painelli, Anna; Soos, Zoltán G.

    2015-05-01

    Upon decreasing temperature (Tc˜81 K) tetrathiafulvalene-chloranil (TTF-CA) undergoes a discontinuous phase transition from a neutral regular stack to an ionic dimerized stack. The same system may undergo a phase transition upon photoexcitation. We discuss the early time (<3 ps) dynamics following ultrafast (<20 fs) excitation of TTF-CA crystals either near or far from the neutral-ionic transition (T ˜90 and 260 K, respectively). Adopting a modified Hubbard model with linear coupling of electrons to a zone-center lattice (dimerization) phonon and to a molecular vibration, both assumed to be harmonic, we are able to quantitatively reproduce coherent oscillations recently reported for this system [H. Uemura and H. Okamoto, Phys. Rev. Lett. 105, 258302 (2010), 10.1103/PhysRevLett.105.258302; T. Miyamoto, H. Uemura, and H. Okamoto, J. Phys. Soc. Jpn. 81, 073703 (2012), 10.1143/JPSJ.81.073703]. We demonstrate that the microscopic model with parameters optimized for ground state properties of TTF-CA also applies to the coherent dynamics following photoexcitation. The modulation of the frequency of coherent molecular oscillations at the frequency of the lattice phonon emerges naturally as due to strong anharmonic coupling between the two harmonic vibrational degrees of freedom through coupling to delocalized electrons. Detailed comparison with experiment validates the model and sheds light on other aspects of photoinduced dynamics, including the almost instantaneous transfer of several electrons upon absorption of a single photon, as due to a cooperative effect of electronic correlations and molecular vibrations.

  11. Effect of π-π+ stacking on the layering of ionic liquids confined to an amorphous carbon surface.

    PubMed

    Gong, Xiao; Kozbial, Andrew; Rose, Franck; Li, Lei

    2015-04-01

    In the current paper, AFM studies were conducted on nanometer-thick ionic liquids (ILs) confined to an amorphous carbon (AC) surface, which is critical to the design of the next-generation media lubricant for hard disk drives (HDDs). The results indicated that the existence of the delocalized ring in the cation is critical to layering of ILs. Extended layering was observed only when there is imidazolium ring in the cation. When the imidazolium ring is replaced by an aliphatic moiety, "drop-on-layer" (dewetting) structure was observed. On the basis of the experimental results, we proposed that π-π+ stacking between sp(2) carbon in the AC and the imidazolium cation in the ILs is the key to the extended layering of ILs at the ILs/AC interface. PMID:25808335

  12. Asteroid surface materials - Mineralogical characterizations and cosmological implications

    NASA Technical Reports Server (NTRS)

    Gaffey, M. J.; Mccord, T. B.

    1977-01-01

    The theoretical basis for the interpretation of diagnostic spectral features is examined and previous characterizations of asteroid surface materials are considered. A summary is provided of results reported by Gaffey and McCord (1977) who have utilized the most sophisticated interpretive techniques available to interpret the spectral reflectance data of about 65 asteroids for mineralogic and petrologic information. Cosmological implications related to the study of asteroid surface materials are also considered, taking into account source bodies for the meteorites, postaccretionary thermal history, significant factors of asteroid thermal history, and the Apollo and Amor asteroids. It is found that the asteroids exhibit surface materials made up of assemblages of meteoritic minerals. The relative abundance of meteorite types reaching the earth's surface is very different from the population of mineralogic types on asteroid surfaces. The earth-crossing or -approaching asteroids apparently derive from a restricted source region or population which is very strongly depleted in the C2-like assemblages that dominate the belt as a whole.

  13. Impact of Environmental Conditions (pH, Ionic Strength, And Electrolyte Type) On The Surface Charge And Aggregation Of Silver Nanoparticles Suspensions

    EPA Science Inventory

    The impact of capping agents and environmental conditions (pH, ionic strength, and background electrolytes) on surface charge and aggregation potential of silver nanoparticles (AgNPs) suspensions were investigated. Capping agents are chemicals used in the synthesis of nanopartic...

  14. Adsorption of a Textile Dye on Commercial Activated Carbon: A Simple Experiment to Explore the Role of Surface Chemistry and Ionic Strength

    ERIC Educational Resources Information Center

    Martins, Angela; Nunes, Nelson

    2015-01-01

    In this study, an adsorption experiment is proposed using commercial activated carbon as adsorbent and a textile azo dye, Mordant Blue-9, as adsorbate. The surface chemistry of the activated carbon is changed through a simple oxidation treatment and the ionic strength of the dye solution is also modified, simulating distinct conditions of water…

  15. A comprehensive physics-based model encompassing variable surface resistance and underlying physics of ionic polymer-metal composite actuators

    NASA Astrophysics Data System (ADS)

    Shen, Qi; Palmre, Viljar; Stalbaum, Tyler; Kim, Kwang J.

    2015-09-01

    The ionic polymer-metal composite (IPMC) is an emerging smart material in actuation and sensing applications, such as artificial muscles, underwater actuators, and advanced medical devices. However, the effect of the change in surface electrode properties on the actuating of IPMC has not been well studied. To address this problem, we theoretically predict and experimentally investigate the dynamic electro-mechanical response of the IPMC thin-strip actuator. A model of the IPMC actuator is proposed based on the Poisson-Nernst-Planck equations for ion transport and charge dynamics in the polymer membrane, while a physical model for the change of surface resistance of the electrodes of the IPMC due to deformation is also incorporated. By incorporating these two models, a complete, dynamic, physics-based model for IPMC actuators is presented. To verify the model, IPMC samples were prepared and experiments were conducted. The results show that the theoretical model can accurately predict the actuating performance of IPMC actuators over a range of dynamic conditions. Additionally, the charge dynamics inside the polymer during the oscillation of the IPMC is presented. It is also shown that the charge at the boundary mainly affects the induced stress of the IPMC. The current study is beneficial for the comprehensive understanding of the surface electrode effect on the performance of IPMC actuators.

  16. Roles of ionic strength and biofilm roughness on adhesion kinetics of Escherichia coli onto groundwater biofilm grown on PVC surfaces

    PubMed Central

    Janjaroen, Dao; Ling, Fangqiong; Monroy, Guillermo; Derlon, Nicolas; Mogenroth, Eberhard; Boppart, Stephen A.; Liu, Wen-Tso; Nguyen, Thanh H.

    2013-01-01

    Mechanisms of Escherichia coli attachment on biofilms grown on PVC coupons were investigated. Biofilms were grown in CDC reactors using groundwater as feed solution over a period up to 27 weeks. Biofilm physical structure was characterized at the micro- and meso-scales using Scanning Electron Microscopy (SEM) and Optical Coherence Tomography (OCT), respectively. Microbial community diversity was analyzed with Terminal Restricted Fragment Length Polymorphism (T-RFLP). Both physical structure and microbial community diversity of the biofilms were shown to be changing from 2 weeks to 14 weeks, and became relatively stable after 16 weeks. A parallel plate flow chamber coupled with an inverted fluorescent microscope was also used to monitor the attachment of fluorescent microspheres and E. coli on clean PVC surfaces and biofilms grown on PVC surfaces for different ages. Two mechanisms of E. coli attachment were identified. The adhesion rate coefficients (kd) of E. coli on nascent PVC surfaces and 2-week biofilms increased with ionic strength. However, after biofilms grew for 8 weeks, the adhesion was found to be independent of solution chemistry. Instead, a positive correlation between kd and biofilm roughness as determined by OCT was obtained, indicating that the physical structure of biofilms could play an important role in facilitating the adhesion of E. coli cells. PMID:23497979

  17. X-ray reflectometry studies on the effect of water on the surface structure of [C4mpyr][NTf2] ionic liquid.

    PubMed

    Lauw, Y; Horne, M D; Rodopoulos, T; Webster, N A S; Minofar, B; Nelson, A

    2009-12-28

    The effect of water on the surface structure of 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonylimide [C(4)mpyr][NTf(2)] ionic liquid was investigated using X-ray reflectometry. The measured reflectivity data suggests a significant amount of water is adsorbed at the surface, with the first layer from the gas (nitrogen)-liquid phase boundary mainly occupied by a mixture of cations and water. Beyond the cation + water layer, the scattering length density increases towards the bulk value, indicating a decreasing amount of water and cations, and/or an increasing amount of anions. The orientation of the butyl chain of cation at the phase boundary and the population of water at the surface were described based on results from an independent molecular dynamics (MD) simulation. We show that the presence of water in the ionic liquid has a non-monotonic effect on the overall thickness of the surface. At low water content, the addition of water does not change the surface thickness since water is mainly present in the bulk. As the water content increases, the surface swells before eventually shrinking down close to the solubility limit of water. The non-monotonic surface thickness is used to explain the anomalous trend of surface tension in ionic liquid-water mixtures reported in the literature. PMID:20024422

  18. High surface area electrodes in ionic polymer transducers: Numerical and experimental investigations of the electro-chemical behavior

    NASA Astrophysics Data System (ADS)

    Akle, Barbar J.; Habchi, Wassim; Wallmersperger, Thomas; Akle, Etienne J.; Leo, Donald J.

    2011-04-01

    Ionomeric polymer transducer (IPT) is an electroactive polymer that has received considerable attention due to its ability to generate large bending strain (>5%) and moderate stress at low applied voltages (±2 V). Ionic polymer transducers consist of an ionomer, usually Nafion, sandwiched between two electrically conductive electrodes. A novel fabrication technique denoted as the direct assembly process (DAP) enabled controlled electrode architecture in ionic polymer transducers. A DAP built transducer consists of two high surface area electrodes made of electrically conducting particles uniformly distributed in an ionomer matrix sandwiching an ionomer membrane. The purpose of this paper is to investigate and simulate the effect of these high surface area particles on the electro-chemical response of an IPT. Theoretical investigations as well as experimental verifications are performed. The model used consists of a convection-diffusion equation describing the chemical field as well as a Poisson equation describing the electrical field. The two-dimensional model incorporates highly conductive particles randomly distributed in the electrode area. Traditionally, these kinds of electrodes were simulated with boundary conditions representing flat electrodes with a large dielectric permittivity at the polymer boundary. This model enables the design of electrodes with complicated geometrical patterns. In the experimental section, several transducers are fabricated using the DAP process on Nafion 117 membranes. The architecture of the high surface area electrodes in these samples is varied. The concentration of the high surface area RuO2 particles is varied from 30 vol% up to 60 vol% at a fixed thickness of 30 μm, while the overall thickness of the electrode is varied from 10 μm up to 40 μm at a fixed concentration of 45%. The flux and charge accumulation in the materials are measured experimentally and compared to the results of the numerical simulations. Trends of

  19. Low-energy reactive ion scattering as a probe of surface femtochemical reaction: H+ and H- formation on ionic compound surfaces

    NASA Astrophysics Data System (ADS)

    Souda, R.; Suzuki, T.; Kawanowa, H.; Asari, E.

    1999-01-01

    Capture and loss of valence electrons during low-energy (50-500 eV) proton scattering from some alkali-halide surfaces such as LiCl, NaCl, and KF have been investigated in comparison with those from the TiO2(110) and Cs-adsorbed Si(100) surfaces. The primary H+ ion survives neutralization when scattered from the highly ionized target species existing on the surface. For H- ion formation, a close atomic encounter with individual target ions is found to be important; the H- ion is formed more efficiently on the cationic site than on the anionic site despite the fact that the valence electron is spacially localized on the latter. This is because the charge state of scattered hydrogen is determined during a transient chemisorption state and amphoteric hydrogen tends to be coordinated negatively (positively) on the cationic site (the anionic site). The final charge state of scattered hydrogen is fixed at a certain bond-breaking distance (˜5.0 a.u.) from the surface where the well-defined atomic orbital of hydrogen evolves. The competing nonlocal resonance tunneling is suppressed at the ionic-compound surfaces due to the existence of a large band gap, so that hydrogen is scattered without losing the memory of such a transient chemisorption state.

  20. Aggregation Behavior of Imidazolium-Based Surface-Active Ionic Liquids with Photoresponsive Cinnamate Counterions in the Aqueous Solution.

    PubMed

    Bi, Yanhui; Zhao, Liuchen; Hu, Qiongzheng; Gao, Yan'an; Yu, Li

    2015-11-24

    Two imidazolium-based surface active ionic liquids (SAILs) with photoresponsive cinnamate aromatic counterions, viz. 1-dodecyl-3-methylimidazolium cinnamate ([C12mim][CA]) and 1-dodecyl-3-methylimidazolium para-hydroxy-cinnamate ([C12mim][PCA]), were newly synthesized, and their self-assembly behaviors in aqueous solutions were systematically explored. Results of surface tension and conductivity measurements show that both [C12mim][CA] and [C12mim][PCA] display a superior surface activity in aqueous solutions compared to the common imidazolium-based SAIL, 1-dodecyl-3-methylimidazolium bromide (C12mimBr), which implies the incorporation of cinnamate aromatic counterions can promote the micellar formation. Furthermore, [C12mim][CA] shows higher surface activity due to the higher hydrophobicity of its counterion in comparison to [C12mim][PCA] that has a hydroxyl group. Both hexagonal liquid-crystalline phase (H1) and cubic liquid-crystalline phase (V2) were constructed in the [C12mim][CA] aqueous solutions. In contrast, the [C12mim][PCA]/H2O system only exhibits a single hexagonal liquid-crystalline phase (H1) in a broad concentration region. These lyotropic liquid crystal (LLC) phases were comprehensively characterized by polarized optical microscopy (POM), small-angle X-ray scattering (SAXS), and rheometer. Investigation on the temperature-dependent self-assembly nanostructures demonstrates that the higher temperature leads to a looser arrangement. Under UV irradiation, trans-cis photoisomerization of the phenylalkene group results in inferior surface activity of the prepared SAILs in aqueous solution with higher cmc values. Moreover, UV light irradiation induces obvious change of the structural parameters without altering the LLC phases. This work is expected to enrich the investigations of phase behaviors formed in SAILs systems and receive particular attention due to their unique properties and potential applications in drug delivery, biochemistry, materials

  1. Effect of dynamic diffusion of air, nitrogen, and helium gaseous media on the microhardness of ionic crystals with juvenile surfaces

    NASA Astrophysics Data System (ADS)

    Klyavin, O. V.; Fedorov, V. Yu.; Chernov, Yu. M.; Shpeizman, V. V.

    2015-09-01

    The load dependences of the microhardness of surface layers of NaCl and LiF ionic single crystals with juvenile surfaces and surfaces exposed to air for a long time measured in the air, nitrogen, and helium gaseous media have been investigated. It has been found that there is a change in the sign of the derivative of the microhardness as a function of the load for LiF crystals indented in helium and after their aging in air, as well as a weaker effect of the nitrogen and air gaseous media on the studied dependences as compared to NaCl crystals. It has also been found that, after the aging of the surface of NaCl crystals in air, there is a change in the sign of the derivative of the microhardness in the nitrogen and air gaseous media, as well as a pronounced change in the microhardness as a function of the time of aging the samples in air as compared to the weaker effect of the gaseous medium for LiF crystals. The obtained data have been analyzed in terms of the phenomenon of dislocation-dynamic diffusion of particles from the external medium into crystalline materials during their plastic deformation along the nucleating and moving dislocations. It has been shown that this phenomenon affects the microhardness through changes in the intensity of dislocation multiplication upon the formation of indentation rosettes in different gaseous media. The performed investigation of the microhardness of the juvenile surface of NaCl and LiF crystals in different gaseous media has revealed for the first time a different character of dislocation-dynamic diffusion of these media in a "pure" form.

  2. Ionic liquid-aqueous solution ultrasonic-assisted extraction of three kinds of alkaloids from Phellodendron amurense Rupr and optimize conditions use response surface.

    PubMed

    Wang, Wenchao; Li, Qingyong; Liu, Yuhui; Chen, Binbin

    2015-05-01

    In this paper, we chose diffident kinds of ionic liquids to optimal selection an optimal one to extract alkaloids from Phellodendron amurense Rupr. Four ionic liquids with diffident carbon chains or anions have been investigated and 1-butyl-3-methylimidazolium bromide with best productivity. Then, selections have been optimized in different conditions, including concentration of ionic liquid, time for ultrasonic treatment, ultrasonic power and solid-liquid ratio. Moreover, three conditions have been comprehensively assessment by response surface methodology, the optimal conditions were determined as follows ultrasonic power 100 W, extraction time 75 min and ratio of solvent to raw material 1:14. Under these conditions, the yield% (MIX) was 106.7% (extracted by heat reflux being defined 100%). Comparing with other methods, the advantages are saving conserving, time saving, high yield% and especially pollution-free. PMID:25443277

  3. Molecular dynamics simulations of the liquid surface of the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide: structure and surface tension.

    PubMed

    Sanmartín Pensado, Alfonso; Malfreyt, Patrice; Pádua, Agílio A H

    2009-11-01

    Molecular dynamics simulations of the liquid-vacuum interface of the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide were performed with an all-atom force field. Structural properties of the interface, such as orientational ordering and density profiles, were calculated. The hexyl side chain of the cation is likely to protrude outward from the surface layer. There is a region with enhanced density from that of the bulk where the cation preferably slants with the imidazolium ring tending to be perpendicular to the interface. The surface tensions are calculated using mechanical and thermodynamic definitions via profiles along the direction normal to the interface. We also discuss the different contributions to the surface tension due to the repulsion-dispersion and electrostatic interactions. The use of local pressure profiles provides an explanation to the systematic problems encountered by several researchers to obtain accurate values of the surface tension at low temperature. Even when macroscopically the system looks in equilibrium, locally this is not accomplished. PMID:19863141

  4. SURFACE COMPLEXATION OF ACTINIDES WITH IRON OXIDES: IMPLICATIONS FOR RADIONUCLIDE TRANSPORT IN NEAR-SURFACE AQUIFERS

    SciTech Connect

    J.L. Jerden Jr.; A.J. Kropf; Y. Tsai

    2005-08-25

    The surface complexation of actinides with iron oxides plays a key role in actinide transport and retardation in geosphere-biosphere systems. The development of accurate actinide transport models therefore requires a mechanistic understanding of surface complexation reactions (i.e. knowledge of chemical speciation at mineral/fluid interfaces). Iron oxides are particularly important actinide sorbents due to their pH dependent surface charges, relatively high surface areas and ubiquity in oxic and suboxic near-surface systems. In this paper we present results from field and laboratory investigations that elucidate the mechanisms involved in binding uranium and neptunium to iron oxide mineral substrates in near neutral groundwaters. The field study involved sampling and characterizing uranium-bearing groundwaters and solids from a saprolite aquifer overlying an unmined uranium deposit in the Virginia Piedmont. The groundwaters were analyzed by inductively coupled mass spectrometry and ion chromatography and the aquifer solids were analyzed by electron microprobe. The laboratory study involved a series of batch sorption tests in which U(VI) and Np(V) were reacted with goethite, hematite and magnetite in simulated groundwaters. The pH, ionic strength, aging time, and sorbent/sorbate ratios were varied in these experiments. The oxidation state and coordination environment of neptunium in solutions and sorbents from the batch tests were characterized by X-ray absorption spectroscopy (XAS) at the Advanced Photon Source, Argonne National Laboratory. Results from this work indicate that, in oxidizing near-surface aquifers, the dissolved concentration of uranium may be limited to less than 30 parts per billion due to uptake by iron oxide mineral coatings and the precipitation of sparingly soluble U(VI) phosphate minerals. Results from the batch adsorption tests showed that, in near neutral groundwaters, a significant fraction of the uranium and neptunium adsorbed as strongly

  5. Membrane interactions in nerve myelin. I. Determination of surface charge from effects of pH and ionic strength on period.

    PubMed Central

    Inouye, H.; Kirschner, D. A.

    1988-01-01

    We have used x-ray diffraction to study the interactions between myelin membranes in the sciatic nerve (PNS) and optic nerve (CNS) as a function of pH (2-10) and ionic strength (0-0.18). The period of myelin was found to change in a systematic manner with pH and ionic strength. PNS periods ranged from 165 to 250 A or more, while CNS periods ranged from 150 to 230 A. The native periods were observed only near physiological ionic strength at neutral or alkaline pH. The smallest periods were observed in the pH range 2.5-4 for PNS myelin and pH 2.5-5 for CNS myelin. The minimum period was also observed for PNS myelin after prolonged incubation in distilled water. At pH 4, within these acidic pH ranges, myelin period increased slightly with ionic strength; however, above these ranges, the period increased with pH and decreased with ionic strength. Electron density profiles calculated at different pH and ionic strength showed that the major structural alteration underlying the changes in period was in the width of the aqueous space at the extracellular apposition of membranes; the width of the cytoplasmic space was virtually constant. Assuming that the equilibrium myelin periods are determined by a balance of nonspecific forces/i.e., the electrostatic repulsion force and the van der Walls attractive force, as well as the short-range repulsion force (hydration force, or steric stabilization), then values in the period-dependency curve can be used to define the isoelectric pH and exclusion length of the membrane. The exclusion length, which is related to the minimum period at isoelectric pH, was used to calculate the electrostatic repulsion force given the other forces. The electrostatic repulsion was then used to calculate the surface potential, which in turn was used to calculate the surface charge density (at different pH and ionic strength). We found the negative surface charge increases with pH at constant ionic strength and with ionic strength at constant pH. We

  6. Energetic atomic and ionic oxygen textured optical surfaces for blood glucose monitoring

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A. (Inventor)

    2007-01-01

    Disclosed is a method and the resulting product thereof comprising a solid light-conducting fiber with a point of attachment and having a textured surface site consisting a textured distal end prepared by being placed in a vacuum and then subjected to directed hyperthermal beams comprising oxygen ions or atoms. The textured distal end comprises cones or pillars that are spaced upon from each other by less than 1 micron and are extremely suitable to prevent cellular components of blood from entering the valleys between the cones or pillars so as to effectively separate the cellular components in the blood from interfering with optical sensing of the glucose concentration for diabetic patients.

  7. Holey graphene nanosheets with surface functional groups as high-performance supercapacitors in ionic-liquid electrolyte.

    PubMed

    Yang, Cheng-Hsien; Huang, Po-Ling; Luo, Xu-Feng; Wang, Chueh-Han; Li, Chi; Wu, Yi-Hsuan; Chang, Jeng-Kuei

    2015-05-22

    Pores and surface functional groups are created on graphene nanosheets (GNSs) to improve supercapacitor properties in a butylmethylpyrrolidinium-dicyanamide (BMP-DCA) ionic liquid (IL) electrolyte. The GNS electrode exhibits an optimal capacitance of 330 F g(-1) and a satisfactory rate capability within a wide potential range of 3.3 V at 25 °C. Pseudocapacitive effects are confirmed using X-ray photoelectron spectroscopy. Under the same conditions, carbon nanotube and activated carbon electrodes show capacitances of 80 and 81 F g(-1) , respectively. Increasing the operation temperature increases the conductivity and decreases the viscosity of the IL electrolyte, further improving cell performance. At 60 °C, a symmetric-electrode GNS supercapacitor with the IL electrolyte is able to deliver maximum energy and power densities of 140 Wh kg(-1) and 52.5 kW kg(-1) (based on the active material on both electrodes), respectively, which are much higher than the 20 Wh kg(-1) and 17.8 kW kg(-1) obtained for a control cell with a conventional organic electrolyte. PMID:25900279

  8. Polypeptide nanogels with hydrophobic moieties in the cross-linked ionic cores: Synthesis, characterization and implications for anticancer drug delivery

    PubMed Central

    Kim, Jong Oh; Oberoi, Hardeep S.; Desale, Swapnil; Kabanov, Alexander V.; Bronich, Tatiana K.

    2014-01-01

    Polymer nanogels have gained considerable attention as a potential platform for drug delivery applications. Here we describe the design and synthesis of novel polypeptide-based nanogels with hydrophobic moieties in the cross-linked ionic cores. Diblock copolymer, poly(ethylene glycol)-b-poly(L-glutamic acid), hydrophobically modified with L-phenylalanine methyl ester moieties was used for controlled template synthesis of nanogels with small size (ca. 70 nm in diameter) and narrow particle size distribution. Steady-state and time-resolved fluorescence studies using coumarin C153 indicated the existence of hydrophobic domains in the ionic cores of the nanogels. Stable doxorubicin-loaded nanogels were prepared at high drug capacity (30 w/w%). We show that nanogels are enzymatically-degradable leading to accelerated drug release under simulated lysosomal acidic pH. Furthermore, we demonstrate that the nanogel-based formulation of doxorubicin is well tolerated and exhibit an improved antitumor activity compared to a free doxorubicin in an ovarian tumor xenograft mouse model. Our results signify the point to a potential of these biodegradable nanogels as attractive carriers for delivery of chemotherapeutics. PMID:23998716

  9. Layering and shear properties of an ionic liquid, 1-ethyl-3-methylimidazolium ethylsulfate, confined to nano-films between mica surfaces.

    PubMed

    Perkin, Susan; Albrecht, Tim; Klein, Jacob

    2010-02-14

    We report high-resolution measurements of the forces between two atomically smooth solid surfaces across a film of 1-ethyl-3-methylimidazolium ethylsulfate ionic liquid, for film thickness down to a single ion diameter. For films thinner than approximately 2 nm oscillatory structural forces are observed as the surface separation decreases and pairs of ion layers are squeezed out of the film. Strikingly, measurements of the shear stress of the ionic liquid film reveal low friction coefficients which are 1-2 orders of magnitude smaller than for analogous films of non-polar molecular liquids, including standard hydrocarbon lubricants, up to ca. 1 MPa pressure. We attribute this to the geometric and charge characteristics of the ionic liquid: the irregular shapes of the ions lead to a low shear stress, while the strong coulombic interactions between the ions and the charged confining surfaces lead to a robust film which is maintained between the shearing surfaces when pressure is applied across the film. PMID:20119601

  10. Energetic Atomic and Ionic Oxygen Textured Optical Surfaces for Blood Glucose Monitoring

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A. (Inventor)

    2007-01-01

    Disclosed is a method and the resulting product thereof comprising a solid light-conducting fiber with a point of attachment and having a textured surface site consisting of a textured distal end prepared by being placed in a vacuum and then subjected to directed hyperthermal beams comprising oxygen ions or atoms. The textured distal end comprises cones or pillars that are spaced upon from each other by less than 1 micron and are extremely suitable to prevent cellular components of blood from entering the valleys between the cones or pillars so as to effectively separate the cellular components in the blood from interfering with optical sensing of the glucose concentration for diabetic patients.

  11. The liquid surface of chiral ionic liquids as seen from molecular dynamics simulations combined with intrinsic analysis

    SciTech Connect

    Lísal, Martin

    2013-12-07

    We present molecular-level insight into the liquid/gas interface of two chiral room-temperature ionic liquids (RTILs) derived from 1-n-butyl-3-methylimidazolium bromide ([bmim][Br]); namely, (R)-1-butyl-3-(3-hydroxy-2-methylpropyl)imidazolium bromide (hydroxypropyl) and 1-butyl-3-[(1R)-nopyl]imidazolium bromide (nopyl). We use our currently developed force field which was validated against the experimental bulk density, heat of vaporization, and surface tension of [bmim][Br]. The force field for the RTILs adopts the Chemistry at Harvard Molecular Mechanics (CHARMM) parameters for the intramolecular and repulsion-dispersion interactions along with the reduced partial atomic charges based on ab initio calculations. The net charges of the ions are around ±0.8e, which mimic the anion to cation charge transfer and many-body effects. Molecular dynamics simulations in the slab geometry combined with the intrinsic interface analysis are employed to provide a detailed description of the RTIL/gas interface in terms of the structural and dynamic properties of the interfacial, sub-interfacial, and central layers at a temperature of 300 K. The focus is on the comparison of the liquid/gas interface for the chiral RTILs with the interface for parent [bmim][Br]. The structure of the interface is elucidated by evaluating the surface roughness, intrinsic atomic density profiles, and orientation ordering of the cations. The dynamics of the ions at the interfacial region is characterized by computing the survival probability, and normal and lateral self-diffusion coefficients in the layers.

  12. The liquid surface of chiral ionic liquids as seen from molecular dynamics simulations combined with intrinsic analysis.

    PubMed

    Lísal, Martin

    2013-12-01

    We present molecular-level insight into the liquid/gas interface of two chiral room-temperature ionic liquids (RTILs) derived from 1-n-butyl-3-methylimidazolium bromide ([bmim][Br]); namely, (R)-1-butyl-3-(3-hydroxy-2-methylpropyl)imidazolium bromide (hydroxypropyl) and 1-butyl-3-[(1R)-nopyl]imidazolium bromide (nopyl). We use our currently developed force field which was validated against the experimental bulk density, heat of vaporization, and surface tension of [bmim][Br]. The force field for the RTILs adopts the Chemistry at Harvard Molecular Mechanics (CHARMM) parameters for the intramolecular and repulsion-dispersion interactions along with the reduced partial atomic charges based on ab initio calculations. The net charges of the ions are around ±0.8e, which mimic the anion to cation charge transfer and many-body effects. Molecular dynamics simulations in the slab geometry combined with the intrinsic interface analysis are employed to provide a detailed description of the RTIL/gas interface in terms of the structural and dynamic properties of the interfacial, sub-interfacial, and central layers at a temperature of 300 K. The focus is on the comparison of the liquid/gas interface for the chiral RTILs with the interface for parent [bmim][Br]. The structure of the interface is elucidated by evaluating the surface roughness, intrinsic atomic density profiles, and orientation ordering of the cations. The dynamics of the ions at the interfacial region is characterized by computing the survival probability, and normal and lateral self-diffusion coefficients in the layers. PMID:24320388

  13. NMR, surface tension and conductance study to investigate host-guest inclusion complexes of three sequential ionic liquids with β-cyclodextrin in aqueous media

    NASA Astrophysics Data System (ADS)

    Barman, Siti; Ekka, Deepak; Saha, Subhadeep; Roy, Mahendra Nath

    2016-08-01

    Host-guest inclusion complexes of three sequential cationic room temperature surface active ionic liquids, benzyltrialkylammonium chloride [(C6H5CH2)N(CnH2n+1)3Cl; where n = 1, 2, 4] with β-cyclodextrin in aqueous media have been studied using surface tension, conductance and NMR spectroscopy. All the studies have suggested that the hydrophobic benzyl group of ionic liquids is encapsulated inside into the cavity of β-cyclodextrin and played a crucial role in supporting the formation of inclusion complexes. The variation of the thermodynamic parameters with guest size, shape is used to draw inferences about contributions to the overall binding by means of the driving forces, viz., hydrophobic effect, steric hindrance, van der Waal force, and electrostatic force.

  14. Electropolishing of stainless steels in a choline chloride based ionic liquid: an electrochemical study with surface characterisation using SEM and atomic force microscopy.

    PubMed

    Abbott, Andrew P; Capper, Glen; McKenzie, Katy J; Glidle, Andrew; Ryder, Karl S

    2006-09-28

    We have studied the anodic dissolution (electropolishing) of various stainless steel alloys in an ionic liquid comprising a 2 : 1 stoichiometric mix of ethylene glycol (EG) and choline chloride. We have used a combination of electrochemical and spectroscopic methods together with in situ liquid probe microscopy. We discuss the role and influence of the surface oxide passivation layer, characterized here by X-ray photoelectron spectroscopy (XPS) and linear sweep voltammetry, on the polishing process. We address the question of dealloying during the polish in order to contribute to our understanding of the viability of the ionic liquid as a replacement industrial electropolishing medium; the current commercial process uses a corrosive mixture of phosphoric and sulfuric acids. Also, we present data from ex situ and in situ liquid AFM studies giving both a qualitative and quantitative insight into the nature and scale of morphological changes at the steel surface during the polishing process. PMID:16971989

  15. Implications of the Differential Toxicological Effects of III-V Ionic and Particulate Materials for Hazard Assessment of Semiconductor Slurries.

    PubMed

    Jiang, Wen; Lin, Sijie; Chang, Chong Hyun; Ji, Zhaoxia; Sun, Bingbing; Wang, Xiang; Li, Ruibin; Pon, Nanetta; Xia, Tian; Nel, André E

    2015-12-22

    Because of tunable band gaps, high carrier mobility, and low-energy consumption rates, III-V materials are attractive for use in semiconductor wafers. However, these wafers require chemical mechanical planarization (CMP) for polishing, which leads to the generation of large quantities of hazardous waste including particulate and ionic III-V debris. Although the toxic effects of micron-sized III-V materials have been studied in vivo, no comprehensive assessment has been undertaken to elucidate the hazardous effects of submicron particulates and released III-V ionic components. Since III-V materials may contribute disproportionately to the hazard of CMP slurries, we obtained GaP, InP, GaAs, and InAs as micron- (0.2-3 μm) and nanoscale (<100 nm) particles for comparative studies of their cytotoxic potential in macrophage (THP-1) and lung epithelial (BEAS-2B) cell lines. We found that nanosized III-V arsenides, including GaAs and InAs, could induce significantly more cytotoxicity over a 24-72 h observation period. In contrast, GaP and InP particulates of all sizes as well as ionic GaCl3 and InCl3 were substantially less hazardous. The principal mechanism of III-V arsenide nanoparticle toxicity is dissolution and shedding of toxic As(III) and, to a lesser extent, As(V) ions. GaAs dissolves in the cell culture medium as well as in acidifying intracellular compartments, while InAs dissolves (more slowly) inside cells. Chelation of released As by 2,3-dimercapto-1-propanesulfonic acid interfered in GaAs toxicity. Collectively, these results demonstrate that III-V arsenides, GaAs and InAs nanoparticles, contribute in a major way to the toxicity of III-V materials that could appear in slurries. This finding is of importance for considering how to deal with the hazard potential of CMP slurries. PMID:26549624

  16. The formation of carbonic and silicon dioxide structured films through the decomposition of molecules on the surface of ionic crystals under the action of IR femtosecond laser radiation

    NASA Astrophysics Data System (ADS)

    Kompanets, V. O.; Laptev, V. B.; Pigul’skii, S. V.; Ryabov, E. A.; Chekalin, S. V.; Blank, V. D.; Denisov, V. N.; Kravchuk, K. S.; Kulnitskiy, B. A.; Perezhogin, I. A.

    2016-06-01

    This study relates to the formation of carbon and silicon dioxide films that occurs as a result of the decomposition of organic and silicon-containing molecules on the surface of ionic crystals under IR femtosecond laser radiation of moderate intensity (~1011 W cm‑2) without molecular decomposition in the gas phase. We found that transparent graphite oxide films formed in the case of CO2 molecule decomposition.

  17. Changes in zeta potential of imidazolium ionic liquids modified minerals--Implications for determining mechanism of adsorption.

    PubMed

    Markiewicz, Marta; Mrozik, Wojciech; Rezwan, Kurosch; Thöming, Jorg; Hupka, Jan; Jungnickel, Christian

    2013-01-01

    As the amount of industrial processes involving ionic liquids (ILs) increase the question of their environmental fate awaits an answer. Should ILs become a source of pollution they will primarily be found in soils and water. Interaction of imidazolium IL with soils is a complex interplay of many parameters making predicting their fate and mobility a challenging task. In order to shed more light on the mechanism of adsorption in soils we examined the interactions of imidazolium ILs with the major component of soils, namely mineral fraction. Within this work adsorption on kaolinite and quartz was investigated in terms of adsorption isotherms, partition coefficients and changes of zeta potentials of clays modified by ILs aggregates. The zeta potential was found to be dependent on the alkyl chain length of the imidazolium homologues. It can therefore be concluded that although adsorption seems to rely on electrostatic attraction, at least in the initial stage, the hydrophobicity of molecules is just as significant. PMID:23079161

  18. Halogen-free ionic liquid as an additive in zinc(II)-selective electrode: surface analyses as correlated to the membrane activity.

    PubMed

    Al-Asousi, Maryam F; Shoukry, Adel F; Bu-Olayan, Abdul Hadi

    2012-05-30

    Two conventional Zn(II) polyvinyl chloride (PVC) membrane electrodes have been prepared and characterized. They were based on dibenzo-24-crown-8 (DBC) as a neutral carrier, dioctyl phthalate (DOP) as a plasticizer, and potassium tetrakis (p-chlorophenyl) borate, KTpClPB or the halogen-free ionic liquid, tetraoctylammonium dodecylbenzene sulfonate [TOA][DBS] as an additive. The use of ionic liquid has been found to enhance the selectivity of the sensor. For each electrode, the surfaces of two membranes were investigated using X-ray photoelectron, ion-scattering spectroscopy and atomic force microscopy. One of the two membranes was conditioned by soaking it for 24 h in a 1.0×10(-3) M Zn(NO(3))(2) solution and the second was soaked in bi-distilled water for the same interval (24 h). Comparing the two surfaces indicated the following: (a) the high selectivity in case of using [TOA][DBS] as an additive is due to the extra mediation caused by the ionic liquid and (b) the working mechanism of the electrode is based on phase equilibrium at the surface of the membrane associated with ion transport through the bulk of the membrane. PMID:22608433

  19. Influence of Lithium Solutes on Double-Layer Structure of Ionic Liquids.

    PubMed

    Smith, Alexander M; Perkin, Susan

    2015-12-01

    The ionic liquid-electrode interface has attracted much recent interest owing to its importance for development of energy storage devices; however, the important step of adding electro-active ions is not yet well understood at the molecular level. Using direct force measurements across confined electrolyte films, we study the effect of added lithium-ion solute on the double-layer structure of an ionic liquid electrolyte with molecular resolution. We find anionic clusters involving lithium can persist adjacent to the surfaces, and in many cases, this inhibits direct adsorption of lithium ions to the negative surface. Two apparently similar ionic liquid solvents show diverging properties, with one facilitating and the other preventing direct Li-ion adsorption onto the negative surface. The results have implications for the selection of ionic liquids as electrolytes in lithium-ion batteries. PMID:26580815

  20. Wormlike micelles with photoresponsive viscoelastic behavior formed by surface active ionic liquid/azobenzene derivative mixed solution.

    PubMed

    Bi, Yanhui; Wei, Hongtu; Hu, Qiongzheng; Xu, Wenwen; Gong, Yanjun; Yu, Li

    2015-04-01

    The UV-light-stimulated self-assembly behavior of a surface active ionic liquid (SAIL), 1-hexadecyl-3-methylimidazolium bromide (C16mimBr), with an azobenzene derivative, sodium azobenzene 4-carboxylate (AzoCOONa), was investigated in aqueous solution. The properties and structures of the aggregates, formed at a concentration ratio equal to 2:1 ([C16mimBr]:[AzoCOONa]), were comprehensively characterized by rheometer and cryogenic transmission electron microscopy. Initially, viscoelastic wormlike micelles with a viscosity of 0.65 Pa·s were constructed in the C16mimBr/AzoCOONa system. Upon irradiation by UV light (365 nm), particularly fascinating is that the wormlike micelles become much longer and more entangled, exhibiting a high viscosity of 6.9 Pa·s. This can be attributed to photoisomerization of the AzoCOONa molecule from trans to cis form. It is the first time that, with exposure to UV or visible light, the aggregate type of the photoresponsive system has remained unchanged, with only a change of internal property parameters. The cation-π interaction prevailing over the hydrophobic interaction and electrostatic interaction between C16mimBr and AzoCOONa molecules is supposed to be responsible for this peculiar phase behavior. The wormlike micelles constructed with the SAIL and photosensitive additive exhibit controllable viscoelastic behavior in the photoresponsive process. In addition, the average contour length of wormlike micelles was found to slightly decrease with the increase of temperature. We expect this system will receive particular attention due to its unique properties and potential applications in drug delivery, biochemistry, and materials science, etc. PMID:25763685

  1. 5-Methyl Salicylic Acid-Induced Thermo Responsive Reversible Transition in Surface Active Ionic Liquid Assemblies: A Spectroscopic Approach.

    PubMed

    Roy, Arpita; Dutta, Rupam; Banerjee, Pavel; Kundu, Sangita; Sarkar, Nilmoni

    2016-07-19

    This article describes the formation of stable unilamellar vesicles involving surface active ionic liquid (SAIL), 1-hexadecyl-3-methylimidazolium chloride (C16mimCl), and 5-methyl salicylic acid (5mS). Turbidity, dynamic light scattering (DLS), transmission electron microscopy (TEM), and viscosity measurements suggest that C16mimCl containing micellar aggregates are transformed to elongated micelle and finally into vesicular aggregates with the addition of 5mS. Besides, we have also investigated the photophysical aspects of a hydrophobic (coumarin 153, C153) and a hydrophilic molecule (rhodamine 6G (R6G) perchlorate) during 5mS-induced micelle to vesicle transition. The rotational motion of C153 becomes slower, whereas faster motion is observed for R6G during micelle to vesicle transition. Moreover, the fluorescence correlation spectroscopy (FCS) measurements suggest that the translational diffusion of hydrophobic probe becomes slower in C16mimCl-5mS aggregates in comparison to C16mimCl micelle. However, a reverse trend in translational diffusion motion of hydrophilic molecule has been observed in C16mimCl-5mS aggregates. Moreover, we have also found that the C16mimCl-5mS containing vesicles are transformed into micelles upon enhanced temperature, and it is further confirmed by turbidity, DLS measurements that this transition is a reversible one. Finally, temperature-induced rotational motion of C153 and R6G has been monitored in C16mimCl-5mS aggregates to get a complete scenario regarding the temperature-induced vesicle to micelle transition. PMID:27345738

  2. Cigarette Smoke Toxins Deposited on Surfaces: Implications for Human Health

    PubMed Central

    Martins-Green, Manuela; Adhami, Neema; Frankos, Michael; Valdez, Mathew; Goodwin, Benjamin; Lyubovitsky, Julia; Dhall, Sandeep; Garcia, Monika; Egiebor, Ivie; Martinez, Bethanne; Green, Harry W.; Havel, Christopher; Yu, Lisa; Liles, Sandy; Matt, Georg; Destaillats, Hugo; Sleiman, Mohammed; Gundel, Laura A.; Benowitz, Neal; Jacob, Peyton; Hovell, Melbourne; Winickoff, Jonathan P.; Curras-Collazo, Margarita

    2014-01-01

    Cigarette smoking remains a significant health threat for smokers and nonsmokers alike. Secondhand smoke (SHS) is intrinsically more toxic than directly inhaled smoke. Recently, a new threat has been discovered – Thirdhand smoke (THS) – the accumulation of SHS on surfaces that ages with time, becoming progressively more toxic. THS is a potential health threat to children, spouses of smokers and workers in environments where smoking is or has been allowed. The goal of this study is to investigate the effects of THS on liver, lung, skin healing, and behavior, using an animal model exposed to THS under conditions that mimic exposure of humans. THS-exposed mice show alterations in multiple organ systems and excrete levels of NNAL (a tobacco-specific carcinogen biomarker) similar to those found in children exposed to SHS (and consequently to THS). In liver, THS leads to increased lipid levels and non-alcoholic fatty liver disease, a precursor to cirrhosis and cancer and a potential contributor to cardiovascular disease. In lung, THS stimulates excess collagen production and high levels of inflammatory cytokines, suggesting propensity for fibrosis with implications for inflammation-induced diseases such as chronic obstructive pulmonary disease and asthma. In wounded skin, healing in THS-exposed mice has many characteristics of the poor healing of surgical incisions observed in human smokers. Lastly, behavioral tests show that THS-exposed mice become hyperactive. The latter data, combined with emerging associated behavioral problems in children exposed to SHS/THS, suggest that, with prolonged exposure, they may be at significant risk for developing more severe neurological disorders. These results provide a basis for studies on the toxic effects of THS in humans and inform potential regulatory policies to prevent involuntary exposure to THS. PMID:24489722

  3. Ionic Blocks

    ERIC Educational Resources Information Center

    Sevcik, Richard S.; Gamble, Rex; Martinez, Elizabet; Schultz, Linda D.; Alexander, Susan V.

    2008-01-01

    "Ionic Blocks" is a teaching tool designed to help middle school students visualize the concepts of ions, ionic compounds, and stoichiometry. It can also assist high school students in reviewing their subject mastery. Three dimensional blocks are used to represent cations and anions, with color indicating charge (positive or negative) and size…

  4. Effects of ionic strength on the surface tension and nonequilibrium interfacial characteristics of poly(sodium styrenesulfonate)/dodecyltrimethylammonium bromide mixtures.

    PubMed

    Ábrahám, Ágnes; Kardos, Attila; Mezei, Amália; Campbell, Richard A; Varga, Imre

    2014-05-01

    We rationalize the surface tension behavior and nonequilibrium interfacial characteristics of high molecular weight poly(sodium styrenesulfonate)/dodecyltrimethylammonium bromide (NaPSS/DTAB) mixtures with respect to the ionic strength. Excellent agreement is achieved between experimental data and our recent empirical model [Langmuir 2013, 29, 11554], which is based on the lack of colloidal stability of bulk aggregates in the phase separation region and has no free fitting parameters. We show that the size of a surface tension peak positioned at the edge of the phase separation region can be suppressed by the addition of inert electrolyte, which lowers the critical micelle concentration in relation to the phase separation region. Such manipulation of the peak is possible for the 100 ppm NaPSS/DTAB system because there is a high free surfactant concentration in the phase separation region. The close agreement of our model with the experimental data of samples in the phase separation region with respect to the ionic strength indicates that the surface tension behavior can be rationalized in terms of comprehensive precipitation regardless of whether there is a peak or not. The time scale of precipitation for the investigated system is on the order of one month, which emphasizes the need to understand the dynamic changes in the state of bulk aggregation in order to rationalize the surface properties of strongly interacting mixtures; steady state surface properties measured in the interim period will represent samples far from equilibrium. We show also that the surface properties of samples of low ionic strength outside the equilibrium phase separation region can be extreme opposites depending on the sample history, which is attributed to the generation of trapped nonequilibrium states. This work highlights the need to validate the underlying nature of oppositely charged polyelectrolyte/surfactant systems prior to the interpretation of experimental data within an

  5. Taylor cones of ionic liquids from capillary tubes as sources of pure ions: The role of surface tension and electrical conductivity

    NASA Astrophysics Data System (ADS)

    Garoz, D.; Bueno, C.; Larriba, C.; Castro, S.; Romero-Sanz, I.; Fernandez de la Mora, J.; Yoshida, Y.; Saito, G.

    2007-09-01

    The emissions of Taylor cones from a wide range of ionic liquids (ILs) have been tested in vacuo in an attempt to identify what physical properties favor the purely ionic regime (PIR). This regime is well known in the case of Taylor cones of liquid metals. For nonmetallic liquids, it has been previously observed in conventional (capillary tube) electrospray sources at room temperature only for the room temperature molten salt (ionic liquid) EMI -BF4 (EMI =1-ethyl-3-methylimidazolium). A large number of other ILs and their mixtures have been studied here, most of which (but not all) are unable to reach the PIR at room temperature. Based on these results and additional theoretical considerations, strong support is assembled for the notion that the PIR is favored by ILs not only of high electrical conductivity but also of high surface tension. This hypothesis is confirmed by tests with three recently synthesized ILs, EMI -GaCl4, EMI -C(CN)3, and EMI -N(CN)2, all of which combine exceptional surface tension and electrical conductivity, and all of which reach the PIR at room temperature far more readily than EMI -BF4.

  6. Hydrophobic and Ionic-Interactions in Bulk and Confined Water with Implications for Collapse and Folding of Proteins

    NASA Astrophysics Data System (ADS)

    Vaitheeswaran, S.; Chen, Jie; Thirumalai, D.

    2011-10-01

    Water and water-mediated interactions determine the thermodynamics and kinetics of protein folding, protein aggregation and self-assembly in confined spaces. To obtain insights into the role of water in the context of folding problems, we describe computer simulations of a few related model systems. The dynamics of collapse of eicosane shows that upon expulsion of water the linear hydrocarbon chain adopts an ordered helical hairpin structure with 1.5 turns. The structure of dimer of eicosane molecules has two well ordered helical hairpins that are stacked perpendicular to each other. As a prelude to studying folding in confined spaces we used simulations to understand changes in hydrophobic and ionic interactions in nano-sized water droplets. Solvation of hydrophobic and charged species change drastically in nano-scale water droplets. Hydrophobic species are localized at the boundary. The tendency of ions to be at the boundary where water density is low increases as the charge density decreases. The interactions between hydrophobic, polar, and charged residue are also profoundly altered in confined spaces. Using the results of computer simulations and accounting for loss of chain entropy upon confinement we argue and then demonstrate, using simulations in explicit water, that ordered states of generic amphiphilic peptide sequences should be stabilized in cylindrical nanopores.

  7. p-Si(1 1 1):H/ionic liquid interface investigated through a combination of electrochemical measurements and reflection high energy electron diffraction surface analysis in vacuum

    NASA Astrophysics Data System (ADS)

    Watanabe, Ko; Maruyama, Shingo; Matsumoto, Yuji

    2016-07-01

    A combination study of electrochemical measurements and reflection high energy electron diffraction (RHEED) surface analysis experiments in a vacuum was first demonstrated to characterize a p-Si(1 1 1):H/ionic liquid interface. Mott-Schottky plot analysis was made to successfully not only evaluate the acceptor density and flat band potential of the p-Si(1 1 1):H, but also get some insight into its surface states. Furthermore, the electric double layer capacitance and specific adsorption properties at the IL/Si(1 1 1):H interface as well as the electrochemical interface stability will be discussed in this paper.

  8. Lubrication of starch in ionic liquid-water mixtures: Soluble carbohydrate polymers form a boundary film on hydrophobic surfaces.

    PubMed

    Yakubov, Gleb E; Zhong, Lei; Li, Ming; Boehm, Michael W; Xie, Fengwei; Beattie, David A; Halley, Peter J; Stokes, Jason R

    2015-11-20

    Soluble starch polymers are shown to enhance the lubrication of ionic liquid-water solvent mixtures in low-pressure tribological contacts between hydrophobic substrates. A fraction of starch polymers become highly soluble in 1-ethyl-3-methylimidazolium acetate (EMIMAc)-water solvents with ionic liquid fraction ≥60wt%. In 65wt% EMIMAc, a small amount of soluble starch (0.33wt%) reduces the boundary friction coefficient by up to a third in comparison to that of the solvent. This low-friction is associated with a nanometre thick film (ca. 2nm) formed from the amylose fraction of the starch. In addition, under conditions where there is a mixture of insoluble starch particles and solubilised starch polymers, it is found that the presence of dissolved amylose enhances the lubrication of starch suspensions between roughened substrates. These findings open up the possibility of utilising starch biopolymers, as well as other hydrocolloids, for enhancing the performance of ionic liquid lubricants. PMID:26344308

  9. Long-range electrostatic screening in ionic liquids.

    PubMed

    Gebbie, Matthew A; Dobbs, Howard A; Valtiner, Markus; Israelachvili, Jacob N

    2015-06-16

    Electrolyte solutions with high concentrations of ions are prevalent in biological systems and energy storage technologies. Nevertheless, the high interaction free energy and long-range nature of electrostatic interactions makes the development of a general conceptual picture of concentrated electrolytes a significant challenge. In this work, we study ionic liquids, single-component liquids composed solely of ions, in an attempt to provide a novel perspective on electrostatic screening in very high concentration (nonideal) electrolytes. We use temperature-dependent surface force measurements to demonstrate that the long-range, exponentially decaying diffuse double-layer forces observed across ionic liquids exhibit a pronounced temperature dependence: Increasing the temperature decreases the measured exponential (Debye) decay length, implying an increase in the thermally driven effective free-ion concentration in the bulk ionic liquids. We use our quantitative results to propose a general model of long-range electrostatic screening in ionic liquids, where thermally activated charge fluctuations, either free ions or correlated domains (quasiparticles), take on the role of ions in traditional dilute electrolyte solutions. This picture represents a crucial step toward resolving several inconsistencies surrounding electrostatic screening and charge transport in ionic liquids that have impeded progress within the interdisciplinary ionic liquids community. More broadly, our work provides a previously unidentified way of envisioning highly concentrated electrolytes, with implications for diverse areas of inquiry, ranging from designing electrochemical devices to rationalizing electrostatic interactions in biological systems. PMID:26040001

  10. Long-range electrostatic screening in ionic liquids

    PubMed Central

    Gebbie, Matthew A.; Dobbs, Howard A.; Valtiner, Markus; Israelachvili, Jacob N.

    2015-01-01

    Electrolyte solutions with high concentrations of ions are prevalent in biological systems and energy storage technologies. Nevertheless, the high interaction free energy and long-range nature of electrostatic interactions makes the development of a general conceptual picture of concentrated electrolytes a significant challenge. In this work, we study ionic liquids, single-component liquids composed solely of ions, in an attempt to provide a novel perspective on electrostatic screening in very high concentration (nonideal) electrolytes. We use temperature-dependent surface force measurements to demonstrate that the long-range, exponentially decaying diffuse double-layer forces observed across ionic liquids exhibit a pronounced temperature dependence: Increasing the temperature decreases the measured exponential (Debye) decay length, implying an increase in the thermally driven effective free-ion concentration in the bulk ionic liquids. We use our quantitative results to propose a general model of long-range electrostatic screening in ionic liquids, where thermally activated charge fluctuations, either free ions or correlated domains (quasiparticles), take on the role of ions in traditional dilute electrolyte solutions. This picture represents a crucial step toward resolving several inconsistencies surrounding electrostatic screening and charge transport in ionic liquids that have impeded progress within the interdisciplinary ionic liquids community. More broadly, our work provides a previously unidentified way of envisioning highly concentrated electrolytes, with implications for diverse areas of inquiry, ranging from designing electrochemical devices to rationalizing electrostatic interactions in biological systems. PMID:26040001

  11. Electrochemical synthesis and surface characterization of poly(3,4-ethylenedioxythiophene) films grown in an ionic liquid.

    PubMed

    Ahmad, Shahzada; Deepa, M; Singh, S

    2007-11-01

    We report a facile method to synthesize poly(3,4-ethylenedioxythiophene) (PEDOT) films at room temperature in a waterproof ionic liquid, 1-ethyl-3-methylimidazolium bis(perfluoroethylsulfonyl)imide (EMIPFSI), by electropolymerization. The ionic liquid leads to the formation of randomly oriented nanofibers and particles confined to submicrometer-sized domains in the film microstructure. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray (EDX) studies provide information about the intercalation of the cation apart from the reported anion in the polymer film, and on how the imidazolium ion controls the growth of PEDOT nanostructures. PMID:17915903

  12. Inelastic and Reactive Scattering Dynamics of Hyperthermal Oxygen Atoms on Ionic Liquid Surfaces: [emim][NTf{sub 2}] and [C{sub 12}mim][NTf{sub 2}

    SciTech Connect

    Wu Bohan; Zhang Jianming; Minton, Timothy K.; McKendrick, Kenneth G.; Slattery, John M.; Yockel, Scott; Schatz, George C.

    2011-05-20

    Collisions of hyperthermal oxygen atoms, with an average translational energy of 520 kJ mol{sup -1}, on continuously refreshed ionic liquids, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([emim][NTf{sub 2}]) and 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C{sub 12}mim][NTf{sub 2}]), were studied with the use of a beam-surface scattering technique. Time-of-flight and angular distributions of inelastically scattered O and reactively scattered OH and H{sub 2}O were collected for various angles of incidence with the use of a rotatable mass spectrometer detector. For both O and OH, two distinct scattering processes were identified, which can be empirically categorized as thermal and non-thermal. Non-thermal scattering is more probable for both O and OH products. The observation of OH confirms that at least some reactive sites, presumably alkyl groups, must be exposed at the surface. The ionic liquid with the longer alkyl chain, [C{sub 12}mim][NTf{sub 2}], is substantially more reactive than the liquid with the shorter alkyl chain, [emim][NTf{sub 2}], and proportionately much more so than would be predicted simply from stoichiometry based on the number of abstractable hydrogen atoms. Molecular dynamics models of these surfaces shed light on this change in reactivity. The scattering behavior of O is distinctly different from that of OH. However, no such differences between inelastic and reactive scattering dynamics have been seen in previous work on pure hydrocarbon liquids, in particular the benchmark, partially branched hydrocarbon, squalane (C{sub 30}H{sub 62}). The comparison between inelastic and reactive scattering dynamics indicates that inelastic scattering from the ionic liquid surfaces takes place predominantly at non-reactive sites that are effectively stiffer than the reactive alkyl chains, with a higher proportion of collisions sampling such sites for [emim][NTf{sub 2}] than for [C{sub 12}mim][NTf{sub 2}].

  13. Allylic ionic liquid electrolyte-assisted electrochemical surface passivation of LiCoO2 for advanced, safe lithium-ion batteries

    PubMed Central

    Mun, Junyoung; Yim, Taeeun; Park, Jang Hoon; Ryu, Ji Heon; Lee, Sang Young; Kim, Young Gyu; Oh, Seung M.

    2014-01-01

    Room-temperature ionic liquid (RTIL) electrolytes have attracted much attention for use in advanced, safe lithium-ion batteries (LIB) owing to their nonvolatility, high conductivity, and great thermal stability. However, LIBs containing RTIL-electrolytes exhibit poor cyclability because electrochemical side reactions cause problematic surface failures of the cathode. Here, we demonstrate that a thin, homogeneous surface film, which is electrochemically generated on LiCoO2 from an RTIL-electrolyte containing an unsaturated substituent on the cation (1-allyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, AMPip-TFSI), can avert undesired side reactions. The derived surface film comprised of a high amount of organic species from the RTIL cations homogenously covered LiCoO2 with a <25 nm layer and helped suppress unfavorable thermal reactions as well as electrochemical side reactions. The superior performance of the cell containing the AMPip-TFSI electrolyte was further elucidated by surface, electrochemical, and thermal analyses. PMID:25168309

  14. Allylic ionic liquid electrolyte-assisted electrochemical surface passivation of LiCoO2 for advanced, safe lithium-ion batteries.

    PubMed

    Mun, Junyoung; Yim, Taeeun; Park, Jang Hoon; Ryu, Ji Heon; Lee, Sang Young; Kim, Young Gyu; Oh, Seung M

    2014-01-01

    Room-temperature ionic liquid (RTIL) electrolytes have attracted much attention for use in advanced, safe lithium-ion batteries (LIB) owing to their nonvolatility, high conductivity, and great thermal stability. However, LIBs containing RTIL-electrolytes exhibit poor cyclability because electrochemical side reactions cause problematic surface failures of the cathode. Here, we demonstrate that a thin, homogeneous surface film, which is electrochemically generated on LiCoO2 from an RTIL-electrolyte containing an unsaturated substituent on the cation (1-allyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, AMPip-TFSI), can avert undesired side reactions. The derived surface film comprised of a high amount of organic species from the RTIL cations homogenously covered LiCoO2 with a <25 nm layer and helped suppress unfavorable thermal reactions as well as electrochemical side reactions. The superior performance of the cell containing the AMPip-TFSI electrolyte was further elucidated by surface, electrochemical, and thermal analyses. PMID:25168309

  15. Allylic ionic liquid electrolyte-assisted electrochemical surface passivation of LiCoO2 for advanced, safe lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Mun, Junyoung; Yim, Taeeun; Park, Jang Hoon; Ryu, Ji Heon; Lee, Sang Young; Kim, Young Gyu; Oh, Seung M.

    2014-08-01

    Room-temperature ionic liquid (RTIL) electrolytes have attracted much attention for use in advanced, safe lithium-ion batteries (LIB) owing to their nonvolatility, high conductivity, and great thermal stability. However, LIBs containing RTIL-electrolytes exhibit poor cyclability because electrochemical side reactions cause problematic surface failures of the cathode. Here, we demonstrate that a thin, homogeneous surface film, which is electrochemically generated on LiCoO2 from an RTIL-electrolyte containing an unsaturated substituent on the cation (1-allyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, AMPip-TFSI), can avert undesired side reactions. The derived surface film comprised of a high amount of organic species from the RTIL cations homogenously covered LiCoO2 with a <25 nm layer and helped suppress unfavorable thermal reactions as well as electrochemical side reactions. The superior performance of the cell containing the AMPip-TFSI electrolyte was further elucidated by surface, electrochemical, and thermal analyses.

  16. Band effects on inelastic scattering of low-energy ions from metallic and ionic surfaces: A formalism beyond the adiabatic molecular-orbitals calculation

    NASA Astrophysics Data System (ADS)

    García, Evelina A.; Goldberg, E. C.

    1998-03-01

    Charge exchange and inelastic excitation processes have been analyzed in the scattering of low-energy He+ from metallic and ionic surfaces. An Anderson-like Hamiltonian is proposed, where the parameters are defined taking into account the electronic band structure of the surface as well as the atomic nature of the interaction between the projectile and the target atoms. The time-dependent collisional process is solved by using a Green-function formalism, which allows us to calculate not only the charge-state probabilities but also the one-electron interband excitations in the solid. Competitive effects of the hybridizations among the localized state at the projectile site and the localized and extended surface states are contemplated. In this way we can explain the observed energy dependences of the neutralization probability, as well as the occurrence of energy-loss processes due to the excitation of valence and core surface electrons induced by the collision.

  17. Leaching of metal(loid)s from a construction material: influence of the particle size, specific surface area and ionic strength.

    PubMed

    Schmukat, A; Duester, L; Ecker, D; Schmid, H; Heil, C; Heininger, P; Ternes, T A

    2012-08-15

    Construction materials are tested worldwide for a potential release of dangerous substances to prevent adverse effects on humans and biota. It is crucial to identify and understand the processes which are decisive for the release of hazardous substances. The current study compares the results of different test methods. Taking copper slag as model material, the influence of material particle size, eluant composition and ionic strength was tested. Ionic strength and salinity significantly influenced the release of metal(loid)s in the water phase. Furthermore, it was elucidated that colloids can cause methodological artefacts. The available specific surface area exhibited a positive correlation with the release of hazardous substances. The specific surface areas of materials were determined by the Brunauer, Emmett and Teller model (BET) and four other methods. The aluminium foil method showed the best results with regard to the statistical uncertainty, compared to a 3D laser scanning method. With help of the roughness factor λ it is possible to compare the results from surface area measurements with different material particle sizes (0-250 mm). This comparability offers the potential to match the release of metal(loid)s from laboratory studies with field applications and catchment area calculations/modelling, based on the release per m(2). PMID:22683212

  18. Surface melting of clusters and implications for bulk matter

    NASA Astrophysics Data System (ADS)

    Cheng, Hai-Ping; Berry, R. Stephen

    1992-06-01

    Surface melting on clusters is investigated by a combination of analytic modeling and computer simulation. Homogeneous argonlike clusters bound by Lennard-Jones forces and Cu-like clusters bound by ``embedded-atom'' potentials are the systems considered. Molecular-dynamics calculations have been carried out for clusters with 40-147 atoms. Well below the bulk melting temperature, the surfaces become very soft, exhibiting well-defined diffusion constants even while the cores remain nearly rigid and solidlike. The simulations, particularly animations, of atomic motion reveal that the surface melting is associated not with amorphous, random surface structures in constant, irregular motion, but rather with large-amplitude, organized, collective motion of most of the surface atoms accompanied by a few detached atoms (``floaters'') and holes. At any time, a few of the surface atoms are out of the surface layer, leaving vacancies; these promoted particles wander diffusively, the holes also but less so; the floaters occasionally exchange with atoms in the surface layer. This result is the basis for an analytic, statistical model. The caloric curves, particularly the latent heats, together with the results from an analytical model, show that surface melting of clusters is a ``phase change'' different from the homogeneous melting of clusters.

  19. Ionic compound mediated rearrangement of 3, 4, 9, 10-perylene tetracarboxylic dianhydride molecules on Ag(100) surface

    NASA Astrophysics Data System (ADS)

    Guo, Qinmin; Huang, Min; Lu, Shuangzan; Cao, Gengyu

    2015-07-01

    Tailoring of the assembly structure of organic molecular monolayer is of great importance to improve the performance of molecular devices. In this work, a typical ionic compound, namely KCl, was used to mediate the rearrangement of 3, 4, 9, 10-perylene tetracarboxylic dianhydride (PTCDA) monolayer on Ag(100). Combined scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) results indicate that both molecule and molecular superlattice would rotate after the dosing of KCl. The density functional theory calculation shows that KCl would exist in the form of molecules rather than ions on Ag(100) and demonstrates that experimentally observed structural transition induced by KCl molecules is energetically favored.

  20. Ionic compound mediated rearrangement of 3, 4, 9, 10-perylene tetracarboxylic dianhydride molecules on Ag(100) surface.

    PubMed

    Guo, Qinmin; Huang, Min; Lu, Shuangzan; Cao, Gengyu

    2015-07-10

    Tailoring of the assembly structure of organic molecular monolayer is of great importance to improve the performance of molecular devices. In this work, a typical ionic compound, namely KCl, was used to mediate the rearrangement of 3, 4, 9, 10-perylene tetracarboxylic dianhydride (PTCDA) monolayer on Ag(100). Combined scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) results indicate that both molecule and molecular superlattice would rotate after the dosing of KCl. The density functional theory calculation shows that KCl would exist in the form of molecules rather than ions on Ag(100) and demonstrates that experimentally observed structural transition induced by KCl molecules is energetically favored. PMID:26080855

  1. Synthesis, COSMO-RS analysis and optical properties of surface modified ZnS quantum dots using ionic liquids

    NASA Astrophysics Data System (ADS)

    Shahid, Robina; Muhammad, Nawshad; Gonfa, Girma; Toprak, Muhammet S.; Muhammed, Mamoun

    2015-10-01

    Zinc sulfide (ZnS) quantum dots (QDs) were synthesized using the microwave assisted ionic liquid (MAIL) route. Three ionic liquids (ILs), namely, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4]), trihexyl(tetradecyl) phosphonium bis(trifluoromethanesulfonyl) amide ([P6,6,6,14][TSFA]) and trihexyl(tetradecyl) phosphonium chloride ([P6,6,6,14][Cl]) were used in this study. The size and structure of the QDs were characterized by high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) pattern, respectively. The synthesized QDs were of wurtzite crystalline structure with size less than 5 nm. The QDs were more uniformly distributed while using the phosponium based ILs as a reaction medium during synthesis. The optical properties were investigated by UV-vis absorption and photoluminescence (PL) emission spectroscopy. The optical properties of QDs showed the quantum confinement effect in their absorption and the effect of cation and anion structural moiety was observed on their bandedge emission. The QDs emission intensity was measured higher for [P6,6,6,14][Cl] due to their better dispersion as well as high charge density of Cl anion. The capability of the ILs in stabilizing the QDs was interpreted by density functional theory (DFT) computations. The obtained results are in good agreement with the theoretical prediction.

  2. Ionic self-assembly affords mesoporous ionic networks by crosslinking linear polyviologens with polyoxometalate clusters.

    PubMed

    Chen, Guojian; Hou, Wei; Li, Jing; Wang, Xiaochen; Zhou, Yu; Wang, Jun

    2016-03-21

    Ionic-bonded mesoporous ionic networks were prepared by the ionic self-assembly of polyoxometalate (POM) clusters with linear cationic polyviologens in water. The POM-enriched PMIN-2(V) possesses a high surface area up to 120 m(2) g(-1), exhibiting superior non-noble metal heterogeneous catalytic performance in the ambient aerobic selective oxidation of 5-hydroxymethylfurfural. PMID:26898883

  3. Multi-scale surface-groundwater interactions: Processes and Implications

    NASA Astrophysics Data System (ADS)

    Packman, A. I.; Harvey, J. W.; Worman, A.; Cardenas, M. B.; Schumer, R.; Jerolmack, D. J.; Tank, J. L.; Stonedahl, S. H.

    2009-05-01

    Site-based investigations of stream-subsurface interactions normally focus on a limited range of spatial scales - typically either very shallow subsurface flows in the hyporheic zone, or much larger scale surface- groundwater interactions - but subsurface flows are linked across this entire continuum. Broad, multi-scale surface-groundwater interactions produce complex patterns in porewater flows, and interfacial fluxes do not average in a simple fashion because of the competitive effects of flows induced at different scales. For example, reach-scale stream-groundwater interactions produce sequences of gaining and losing reaches that can either suppress or enhance local-scale hyporheic exchange. Many individual topographic features also produce long power-law tails in surface residence time distributions, and the duration of these tails is greatly extended by interactions over a wide range of spatial scales. Simultaneous sediment transport and landscape evolution further complicates the analysis of porewater flow dynamics in rivers. Finally, inhomogeneity in important biogeochemical processes, particularly microbial processes that are stimulated near the sediment- water interface, leads to a great degree of non-linearity in chemical transformation rates in stream channels. This high degree of complexity in fluvial systems requires that careful approaches be used to extend local observations of hyporheic exchange and associated nutrient, carbon, and contaminant transformations to larger spatial scales. It is important to recognize that conventional advection-dispersion models are not expected to apply, and instead anomalous transport models must be used. Unfortunately, no generally applicable model is available for stream-groundwater interactions at the present time. Alternative approaches for modeling conservative and reactive transport will be discussed, and a strategy articulated for coping with the complexity of coupled surface-subsurface dynamics in fluvial

  4. Interaction of ionic liquids with noble metal surfaces: structure formation and stability of [OMIM][TFSA] and [EMIM][TFSA] on Au(111) and Ag(111).

    PubMed

    Uhl, Benedikt; Huang, Hsinhui; Alwast, Dorothea; Buchner, Florian; Behm, R Jürgen

    2015-10-01

    Aiming at a comprehensive understanding of the interaction of ionic liquids (ILs) with metal surfaces we have investigated the adsorption of two closely related ILs, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][TFSA] and 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide [OMIM][TFSA], with two noble metal surfaces, Au(111) and Ag(111), under ultrahigh vacuum (UHV) conditions using scanning tunneling microscopy (STM). At room temperature, the ILs form a 2D liquid on either of the two surfaces, while at lower temperatures they condense into two-dimensional (2D) islands which exhibit ordered structures or a short-range ordered 2D glass structure. Comparison of the adlayer structures formed in the different adsorption systems and also with those determined recently for n-butyl-n-methylpyrrolidinium [TFSA](-) adlayers on Ag(111) and Au(111) (B. Uhl et al., Beilstein J. Nanotechnol., 2013, 4, 903) gains detailed insight into the adsorption geometry of the IL ions on the surface. The close similarity of the adlayer structures indicates that (i) the structure formation is dominated by the tendency to optimize the anion adsorption geometry, and that (ii) also in the present systems the cation adsorbs with the alkyl chain pointing up from the surface. PMID:26305417

  5. The Effect of Microporous Polymeric Support Modification on Surface and Gas Transport Properties of Supported Ionic Liquid Membranes

    PubMed Central

    Akhmetshina, Alsu A.; Davletbaeva, Ilsiya M.; Grebenschikova, Ekaterina S.; Sazanova, Tatyana S.; Petukhov, Anton N.; Atlaskin, Artem A.; Razov, Evgeny N.; Zaripov, Ilnaz I.; Martins, Carla F.; Neves, Luísa A.; Vorotyntsev, Ilya V.

    2015-01-01

    Microporous polymers based on anionic macroinitiator and toluene 2,4-diisocyanate were used as a support for 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) immobilization. The polymeric support was modified by using silica particles associated in oligomeric media, and the influence of the modifier used on the polymeric structure was studied. The supported ionic liquid membranes (SILMs) were tested for He, N2, NH3, H2S, and CO2 gas separation and ideal selectivities were calculated. The high values of ideal selectivity for ammonia-based systems with permanent gases were observed on polymer matrixes immobilized with [bmim][PF6] and [emim][Tf2N]. The modification of SILMs by nanosize silica particles leads to an increase of NH3 separation relatively to CO2 or H2S. PMID:26729177

  6. Metallic 2D Surface State of Silicon by Ionic Liquid gating and observation of Reentrant Insulating behavior

    NASA Astrophysics Data System (ADS)

    Nelson, J. J.; Goldman, A. M.

    2015-03-01

    Metal insulator transitions are usually observed in high mobility and low carrier density 2D electron systems. There are several open questions regarding the metallic state including its existence in the limit of zero temperature. The current experimental focus is on the production of higher mobility samples to push the critical carrier density to even lower values, which will increase the effects of the Coulomb interaction. Here we report an unexpected result, the observation of the onset of a metallic state at high carrier densities in silicon gated with the ionic liquid DEME-TFSI. In addition we have observed a return to the insulating state as the carrier density was further increased. This reentrant insulting behavior is an effect that was recently predicted. Supported in part by NSF/DMR-1263316. Part of this work was carried out at the Minnesota Nanocenter.

  7. Identifying the ionically bound cell wall and intracellular glycoside hydrolases in late growth stage Arabidopsis stems: implications for the genetic engineering of bioenergy crops

    PubMed Central

    Wei, Hui; Brunecky, Roman; Donohoe, Bryon S.; Ding, Shi-You; Ciesielski, Peter N.; Yang, Shihui; Tucker, Melvin P.; Himmel, Michael E.

    2015-01-01

    Identifying the cell wall-ionically bound glycoside hydrolases (GHs) in Arabidopsis stems is important for understanding the regulation of cell wall integrity. For cell wall proteomics studies, the preparation of clean cell wall fractions is a challenge since cell walls constitute an open compartment, which is more likely to contain a mixture of intracellular and extracellular proteins due to cell leakage at the late growth stage. Here, we utilize a CaCl2-extraction procedure to isolate non-structural proteins from Arabidopsis whole stems, followed by the in-solution and in-gel digestion methods coupled with Nano-LC-MS/MS, bioinformatics and literature analyses. This has led to the identification of 75 proteins identified using the in-solution method and 236 proteins identified by the in-gel method, among which about 10% of proteins predicted to be secreted. Together, eight cell wall proteins, namely AT1G75040, AT5G26000, AT3G57260, AT4G21650, AT3G52960, AT3G49120, AT5G49360, and AT3G14067, were identified by the in-solution method; among them, three were the GHs (AT5G26000, myrosinase 1, GH1; AT3G57260, β-1,3-glucanase 2, GH17; AT5G49360, bifunctional XYL 1/α-L-arabinofuranosidase, GH3). Moreover, four more GHs: AT4G30270 (xyloglucan endotransferase, GH16), AT1G68560 (bifunctional α-l-arabinofuranosidase/XYL, GH31), AT1G12240 (invertase, GH32) and AT2G28470 (β-galactosidase 8, GH35), were identified by the in-gel solution method only. Notably, more than half of above identified GHs are xylan- or hemicellulose-modifying enzymes, and will likely have an impact on cellulose accessibility, which is a critical factor for downstream enzymatic hydrolysis of plant tissues for biofuels production. The implications of these cell wall proteins identified at the late growth stage for the genetic engineering of bioenergy crops are discussed. PMID:26029221

  8. Identifying the ionically bound cell wall and intracellular glycoside hydrolases in late growth stage Arabidopsis stems: Implications for the genetic engineering of bioenergy crops

    SciTech Connect

    Wei, Hui; Brunecky, Roman; Donohoe, Bryon S.; Ding, Shi -You; Ciesielski, Peter N.; Yang, Shihui; Tucker, Melvin P.; Himmel, Michael E.

    2015-05-13

    Identifying the cell wall-ionically bound glycoside hydrolases (GHs) in Arabidopsis stems is important for understanding the regulation of cell wall integrity. For cell wall proteomics studies, the preparation of clean cell wall fractions is a challenge since cell walls constitute an open compartment, which is more likely to contain a mixture of intracellular and extracellular proteins due to cell leakage at the late growth stage. Here, for this study, we utilize a CaCl2-extraction procedure to isolate non-structural proteins from Arabidopsis whole stems, followed by the in-solution and in-gel digestion methods coupled with Nano-LC-MS/MS, bioinformatics and literature analyses. This has led to the identification of 75 proteins identified using the in-solution method and 236 proteins identified by the in-gel method, among which about 10% of proteins predicted to be secreted. Together, eight cell wall proteins, namely AT1G75040, AT5G26000, AT3G57260, AT4G21650, AT3G52960, AT3G49120, AT5G49360, and AT3G14067, were identified by the in-solution method; among them, three were the GHs (AT5G26000, myrosinase 1, GH1; AT3G57260, β-1,3-glucanase 2, GH17; AT5G49360, bifunctional XYL 1/α-L-arabinofuranosidase, GH3). Moreover, four more GHs: AT4G30270 (xyloglucan endotransferase, GH16), AT1G68560 (bifunctional α-l-arabinofuranosidase/XYL, GH31), AT1G12240 (invertase, GH32) and AT2G28470 (β-galactosidase 8, GH35), were identified by the in-gel solution method only. Notably, more than half of above identified GHs are xylan- or hemicellulose-modifying enzymes, and will likely have an impact on cellulose accessibility, which is a critical factor for downstream enzymatic hydrolysis of plant tissues for biofuels production. Finally, the implications of these cell wall proteins identified at the late growth stage for the genetic engineering of bioenergy crops are discussed.

  9. Identifying the ionically bound cell wall and intracellular glycoside hydrolases in late growth stage Arabidopsis stems: Implications for the genetic engineering of bioenergy crops

    DOE PAGESBeta

    Wei, Hui; Brunecky, Roman; Donohoe, Bryon S.; Ding, Shi -You; Ciesielski, Peter N.; Yang, Shihui; Tucker, Melvin P.; Himmel, Michael E.

    2015-05-13

    Identifying the cell wall-ionically bound glycoside hydrolases (GHs) in Arabidopsis stems is important for understanding the regulation of cell wall integrity. For cell wall proteomics studies, the preparation of clean cell wall fractions is a challenge since cell walls constitute an open compartment, which is more likely to contain a mixture of intracellular and extracellular proteins due to cell leakage at the late growth stage. Here, for this study, we utilize a CaCl2-extraction procedure to isolate non-structural proteins from Arabidopsis whole stems, followed by the in-solution and in-gel digestion methods coupled with Nano-LC-MS/MS, bioinformatics and literature analyses. This has ledmore » to the identification of 75 proteins identified using the in-solution method and 236 proteins identified by the in-gel method, among which about 10% of proteins predicted to be secreted. Together, eight cell wall proteins, namely AT1G75040, AT5G26000, AT3G57260, AT4G21650, AT3G52960, AT3G49120, AT5G49360, and AT3G14067, were identified by the in-solution method; among them, three were the GHs (AT5G26000, myrosinase 1, GH1; AT3G57260, β-1,3-glucanase 2, GH17; AT5G49360, bifunctional XYL 1/α-L-arabinofuranosidase, GH3). Moreover, four more GHs: AT4G30270 (xyloglucan endotransferase, GH16), AT1G68560 (bifunctional α-l-arabinofuranosidase/XYL, GH31), AT1G12240 (invertase, GH32) and AT2G28470 (β-galactosidase 8, GH35), were identified by the in-gel solution method only. Notably, more than half of above identified GHs are xylan- or hemicellulose-modifying enzymes, and will likely have an impact on cellulose accessibility, which is a critical factor for downstream enzymatic hydrolysis of plant tissues for biofuels production. Finally, the implications of these cell wall proteins identified at the late growth stage for the genetic engineering of bioenergy crops are discussed.« less

  10. Ocean Surface Circulation with Implication for Marine Debris Distribution

    NASA Astrophysics Data System (ADS)

    Hafner, Jan; Maximenko, Nikolai; Niiler, Peter

    2010-05-01

    Modern, multi-instrumental Global Ocean Observing System (GOOS) includes satellites and in situ observations, monitoring the ocean state at the highest accuracy and resolution ever. By combining data of satellite altimetry, surface drifters, wind and gravity, ocean currents can be assessed globally and at research quality. The map of the mean surface currents shows a complex pattern of oceanic fronts and gyres. Distinct are the convergences of Ekman currents in subtropical gyres that, through the Sverdrup mechanism, are feeding anticyclonic circulation in the gyres. Drifter trajectories can also be utilized to simulate the evolution of the marine debris. Main problem is the inhomogeneous drifter data density, both due to convergence/divergence of the ocean currents and due to the drifter deployment scheme. A model constructed from statistics of the drifters exchange between small bins corrects this bias and was run from the uniform initial condition to study the fate of debris in the ocean. In addition to such actively studied debris accumulation areas as the Great Garbage Patch in the North Pacific, a new so far unrecognized, the world-strongest convergence is discovered in the South Pacific from the model solution. The same model reveals a complex pattern of convergence/divergence on the cold/warm flanks of major oceanic fronts. This pattern is studied in the framework of nonlinear interaction between Ekman drift and geostrophic baroclinic fronts outcropping at the sea surface. Results are generalized to assess the dynamics of internal Ekman layer distributed along the thermocline and controlling the secondary circulation at the fronts.

  11. Catalytic peptide hydrolysis by mineral surface: Implications for prebiotic chemistry

    NASA Astrophysics Data System (ADS)

    Marshall-Bowman, Karina; Ohara, Shohei; Sverjensky, Dimitri A.; Hazen, Robert M.; Cleaves, H. James

    2010-10-01

    The abiotic polymerization of amino acids may have been important for the origin of life, as peptides may have been components of the first self-replicating systems. Though amino acid concentrations in the primitive oceans may have been too dilute for significant oligomerization to occur, mineral surface adsorption may have provided a concentration mechanism. As unactivated amino acid polymerization is thermodynamically unfavorable and kinetically slow in aqueous solution, we studied mainly the reverse reaction of polymer degradation to measure the impact of mineral surface catalysis on peptide bonds. Aqueous glycine (G), diglycine (GG), diketopiperazine (DKP), and triglycine (GGG) were reacted with minerals (calcite, hematite, montmorillonite, pyrite, rutile, or amorphous silica) in the presence of 0.05 M, pH 8.1, KHCO 3 buffer and 0.1 M NaCl as background electrolyte in a thermostatted oven at 25, 50 or 70 °C. Below 70 °C, reaction kinetics were too sluggish to detect catalytic activity over amenable laboratory time-scales. Minerals were not found to have measurable effects on the degradation or elongation of G, GG or DKP at 70 °C in solution. At 70 °C pyrite was the most catalytic mineral with detectible effects on the degradation of GGG, although several others also displayed catalytic behavior. GGG degraded ˜1.5-4 times faster in the presence of pyrite than in control reactions, depending on the ratio of solution concentration to mineral surface area. The rate of pyrite catalysis of GGG hydrolysis was found to be saturable, suggesting the presence of discrete catalytic sites on the mineral surface. The mineral-catalyzed degradation of GGG appears to occur via a GGG → DKP + G mechanism, rather than via GGG → GG + G, as in solution-phase reactions. These results are compatible with many previous findings and suggest that minerals may have assisted in peptide synthesis in certain geological settings, specifically by speeding the approach to equilibrium

  12. Connexin-47 and connexin-32 in gap junctions of oligodendrocyte somata, myelin sheaths, paranodal loops and Schmidt-Lanterman incisures: implications for ionic homeostasis and potassium siphoning.

    PubMed

    Kamasawa, N; Sik, A; Morita, M; Yasumura, T; Davidson, K G V; Nagy, J I; Rash, J E

    2005-01-01

    The subcellular distributions and co-associations of the gap junction-forming proteins connexin 47 and connexin 32 were investigated in oligodendrocytes of adult mouse and rat CNS. By confocal immunofluorescence light microscopy, abundant connexin 47 was co-localized with astrocytic connexin 43 on oligodendrocyte somata, and along myelinated fibers, whereas connexin 32 without connexin 47 was co-localized with contactin-associated protein (caspr) in paranodes. By thin-section transmission electron microscopy, connexin 47 immunolabeling was on the oligodendrocyte side of gap junctions between oligodendrocyte somata and astrocytes. By freeze-fracture replica immunogold labeling, large gap junctions between oligodendrocyte somata and astrocyte processes contained much more connexin 47 than connexin 32. Along surfaces of internodal myelin, connexin 47 was several times as abundant as connexin 32, and in the smallest gap junctions, often occurred without connexin 32. In contrast, connexin 32 was localized without connexin 47 in newly-described autologous gap junctions in Schmidt-Lanterman incisures and between paranodal loops bordering nodes of Ranvier. Thus, connexin 47 in adult rodent CNS is the most abundant connexin in most heterologous oligodendrocyte-to-astrocyte gap junctions, whereas connexin 32 is the predominant if not sole connexin in autologous ("reflexive") oligodendrocyte gap junctions. These results clarify the locations and connexin compositions of heterologous and autologous oligodendrocyte gap junctions, identify autologous gap junctions at paranodes as potential sites for modulating paranodal electrical properties, and reveal connexin 47-containing and connexin 32-containing gap junctions as conduits for long-distance intracellular and intercellular movement of ions and associated osmotic water. The autologous gap junctions may regulate paranodal electrical properties during saltatory conduction. Acting in series and in parallel, autologous and

  13. Secondary craters on Europa and implications for cratered surfaces.

    PubMed

    Bierhaus, Edward B; Chapman, Clark R; Merline, William J

    2005-10-20

    For several decades, most planetary researchers have regarded the impact crater populations on solid-surfaced planets and smaller bodies as predominantly reflecting the direct ('primary') impacts of asteroids and comets. Estimates of the relative and absolute ages of geological units on these objects have been based on this assumption. Here we present an analysis of the comparatively sparse crater population on Jupiter's icy moon Europa and suggest that this assumption is incorrect for small craters. We find that 'secondaries' (craters formed by material ejected from large primary impact craters) comprise about 95 per cent of the small craters (diameters less than 1 km) on Europa. We therefore conclude that large primary impacts into a solid surface (for example, ice or rock) produce far more secondaries than previously believed, implying that the small crater populations on the Moon, Mars and other large bodies must be dominated by secondaries. Moreover, our results indicate that there have been few small comets (less than 100 m diameter) passing through the jovian system in recent times, consistent with dynamical simulations. PMID:16237437

  14. A new strategy to prepare giant vesicles from surface active ionic liquids (SAILs): a study of protein dynamics in a crowded environment using a fluorescence correlation spectroscopic technique.

    PubMed

    Banerjee, Chiranjib; Roy, Arpita; Kundu, Niloy; Banik, Debasis; Sarkar, Nilmoni

    2016-06-01

    A simple procedure for the preparation of giant vesicles using surface active ionic liquids (SAILs) has been provided in this paper. SAILs, used to form vesicles, were synthesized by replacing the cationic part of Aerosol OT (AOT) with cations having alkyl chains of different lengths (ammonium and imidazolium cations). The number of carbons in the alkyl chains of the cations was varied from eight to sixteen. From the observed results, the formation of giant vesicles is found to be dependent on the alkyl chain length as well as the organic moieties of the respective cations. These giant vesicles were characterized using fluorescence lifetime imaging microscopy (FLIM). The conformational dynamics of bovine serum albumin (BSA) inside these giant vesicles was determined using fluorescence correlation spectroscopy (FCS) to get an idea about the protein dynamics in a constrained environment. The interaction of the giant vesicles with the protein was confirmed by the change in the diffusion coefficient and the conformational fluctuation time. PMID:27173474

  15. Drainage pits in cohesionless materials: implications for surface of Phobos.

    PubMed

    Horstman, K C; Melosh, H J

    1989-09-10

    Viking orbiter images show grooves and chains of pits crossing the surface of Phobos, many of which converge toward the large crater Stickney or its antipode. Although it has been proposed that the pits and grooves are chains of secondary craters, their morphology and geometric relations suggest that they are the surface traces of fractures in the underlying solid body of Phobos. Several models have been proposed to explain the pits, of which the most plausible are gas venting and drainage of regolith into open fractures. the latter mechanism is best supported by the image data and is the mechanism studied in this investigation. Drainage pits and fissures are modeled experimentally by using two rigid substrate plates placed edge to edge and covered by uniform thicknesses of dry fragmental debris (simulated regolith). Fracture extension is simulated by drawing the plates apart, allowing drainage of regolith into the newly created void. A typical drainage experiment begins with a shallow depression on the surface of the regolith, above the open fissure. Increased drainage causes local drainage pits to form; continued drainage causes the pits to coalesce, forming a cuspate groove. The resulting experimental patterns of pits and grooves have pronounced similarities to those observed on Phobos. Characteristics such as lack of raised rims, linearity of grooves and chains of pits, uniform spacing of pits, and progression from discrete pits to cuspate grooves are the same in the experiments and on Phobos. In contrast, gas-venting pits occur in irregular chains and have raised rims. These experiments thus indicate that the Phobos grooves and pits formed as drainage structures. The pit spacing in an experiment is measured at the time that the maximum number of pits forms, prior to groove development. The average pit spacing is compared to the regolith thickness for each material. Regression line fits indicate that the average spacing of drainage pits in unconsolidated

  16. The global topography of Mars and implications for surface evolution

    NASA Technical Reports Server (NTRS)

    Smith, D. E.; Zuber, M. T.; Solomon, S. C.; Phillips, R. J.; Head, J. W.; Garvin, J. B.; Banerdt, W. B.; Muhleman, D. O.; Pettengill, G. H.; Neumann, G. A.; Lemoine, F. G.; Abshire, J. B.; Aharonson, O.; Brown, C. D.; Hauck, S. A.; Ivanov, A. B.; McGovern, P. J.; Zwally, H. J.; Duxbury, T. C.

    1999-01-01

    Elevations measured by the Mars Orbiter Laser Altimeter have yielded a high-accuracy global map of the topography of Mars. Dominant features include the low northern hemisphere, the Tharsis province, and the Hellas impact basin. The northern hemisphere depression is primarily a long-wavelength effect that has been shaped by an internal mechanism. The topography of Tharsis consists of two broad rises. Material excavated from Hellas contributes to the high elevation of the southern hemisphere and to the scarp along the hemispheric boundary. The present topography has three major drainage centers, with the northern lowlands being the largest. The two polar cap volumes yield an upper limit of the present surface water inventory of 3.2 to 4.7 million cubic kilometers.

  17. The global topography of Mars and implications for surface evolution.

    PubMed

    Smith, D E; Zuber, M T; Solomon, S C; Phillips, R J; Head, J W; Garvin, J B; Banerdt, W B; Muhleman, D O; Pettengill, G H; Neumann, G A; Lemoine, F G; Abshire, J B; Aharonson, O; Brown, C D; Hauck, S A; Ivanov, A B; McGovern, P J; Zwally, H J; Duxbury, T C

    1999-05-28

    Elevations measured by the Mars Orbiter Laser Altimeter have yielded a high-accuracy global map of the topography of Mars. Dominant features include the low northern hemisphere, the Tharsis province, and the Hellas impact basin. The northern hemisphere depression is primarily a long-wavelength effect that has been shaped by an internal mechanism. The topography of Tharsis consists of two broad rises. Material excavated from Hellas contributes to the high elevation of the southern hemisphere and to the scarp along the hemispheric boundary. The present topography has three major drainage centers, with the northern lowlands being the largest. The two polar cap volumes yield an upper limit of the present surface water inventory of 3.2 to 4.7 million cubic kilometers. PMID:10348732

  18. Thermal anomaly on Mimas surface: Implications on its regolith structure

    NASA Astrophysics Data System (ADS)

    Ferrari, C.; Lucas, A.

    2015-10-01

    Thanks to the Cassini CIRS infrared spectrometer,Howett et al. [1] have discovered a large scale thermal anomaly on the surface of Saturn satellite Mimas. This anomaly translates into a dichotomy in thermal inertia between leading and trailing faces of this synchronous icy satellite: the leading face (region R2) exhibits a high thermal inertia,Γ =66 ± 23 J/m 2/K/s 1/2, compared to the trailing one(region R1), where Γ < 16 J/m2/K/s1/2. The pattern appears to be well correlated with a color anomaly (Schenk et al. [2]) in visible light, also observed on other Saturn moons. It maybe due to the alter ation of their leading face by a focused bombardment of highly energetic electrons.This is thought to increase the contact between regolith grains by gluing them, improving thus the thermal conductivity or decrea sing porosity.

  19. Change of electrostatic potential of mean force between two curved surfaces due to different salt composition, ion valence and size under certain ionic strength

    NASA Astrophysics Data System (ADS)

    Zhou, Shiqi

    2016-02-01

    Change of an electrostatic potential of mean force (EPMF) between two cylindrical rod surfaces with salt composition, ion valence, and ion size at a constant ionic strength of 0.3 M is studied by a classical density functional theory (CDFT) in a primitive model electrolyte solution. Several novel observations are made: (i) strength of a so-called like charge attraction (LCA) reduces in an invariable manner with the salt solution changing from single 2:1 electrolyte to mixture of 2:1 and 1:1 type electrolytes of varying concentration ratios; the change is even over entire range of the composition variation under low surface charge strength, and tends to be insensitive to the composition variation in the presence of the divalent counter-ion, and more and more drastic at a critical point the divalent counter-ion disappears, respectively, as the surface charge strength becomes big enough. (ii) Both monovalent counter-ion and co-ion diameters have only a marginal effect on both the LCA strength and equilibrium distance, and the former "abnormally" affects less than the latter. (iii) Depending on the surface charge strength considered, the divalent counter-ion diameter influences the LCA strength in solution comprised of 2:1 type and 1:1 type electrolytes, monotonously or non-monotonously. All of these findings provide forceful support for a recently proposed hydrogen-bonding style mechanism explaining the LCA.

  20. Impact of ionic strength of growth on the physiochemical properties, structure, and adhesion of Listeria monocytogenes polyelectrolyte brushes to a silicon nitride surface in water.

    PubMed

    Gordesli, Fatma Pinar; Abu-Lail, Nehal I

    2012-12-15

    The adhesion energies between pathogenic Listeria monocytogenes EGDe to a model surface of silicon nitride were quantified using atomic force microscopy (AFM) in water for cells grown in pure media (as the control) and in media of four different ionic strengths of added NaCl (IS of 0.05 M, 0.1 M, 0.3 M and 0.5 M NaCl). The physiochemical properties of L. monocytogenes EGDe surface brushes were shown to have a strong influence on the adhesion of the microbe to the silicon nitride surface. The transitions in the adhesion energies, physiochemical properties, and the structure of bacterial surface polyelectrolyte brushes were observed for the cells grown in the media of 0.1M added NaCl. Our results suggested that the highest long-range electrostatic repulsion which was partially balanced by the Liftshitz-van der Waals attraction for the cells grown at 0.1M was responsible for the highest energy barrier to adhesion for these cells as predicted by the soft-particle analysis of DLVO theory and the lower adhesion measured by AFM. PMID:23010316

  1. Enhanced super-hydrophobic and switching behavior of ZnO nanostructured surfaces prepared by simple solution--immersion successive ionic layer adsorption and reaction process.

    PubMed

    Suresh Kumar, P; Sundaramurthy, J; Mangalaraj, D; Nataraj, D; Rajarathnam, D; Srinivasan, M P

    2011-11-01

    A simple and cost-effective successive ionic layer adsorption and reaction (SILAR) method was adopted to fabricate hydrophobic ZnO nanostructured surfaces on transparent indium-tin oxide (ITO), glass and polyethylene terephthalate (PET) substrates. ZnO films deposited on different substrates show hierarchical structures like spindle, flower and spherical shape with diameters ranging from 30 to 300 nm. The photo-induced switching behaviors of ZnO film surfaces between hydrophobic and hydrophilic states were examined by water contact angle and X-ray photoelectron spectroscopy (XPS) analysis. ZnO nanostructured films had contact angles of ~140° and 160°±2 on glass and PET substrates, respectively, exhibiting hydrophobic behavior without any surface modification or treatment. Upon exposure to ultraviolet (UV) illumination, the films showed hydrophilic behavior (contact angle: 15°±2), which upon low thermal stimuli revert back to its original hydrophobic nature. Such reversible and repeatable switching behaviors were observed upon cyclical exposure to ultraviolet radiation. These biomimetic ZnO surfaces exhibit good anti-reflective properties with lower reflectance of 9% for PET substrates. Thus, the present work is significant in terms of its potential application in switching devices, solar coatings and self-cleaning smart windows. PMID:21831394

  2. An ultrasensitive lysozyme chemiluminescence biosensor based on surface molecular imprinting using ionic liquid modified magnetic graphene oxide/β-cyclodextrin as supporting material.

    PubMed

    Duan, Huimin; Wang, Xiaojiao; Wang, Yanhui; Sun, Yuanling; Li, Jianbo; Luo, Chuannan

    2016-04-28

    In this work, ionic liquid modified Fe3O4@dopamine/graphene oxide/β-cyclodextrin (ILs-Fe3O4@DA/GO/β-CD) was used as supporting material to synthesize surface molecularly imprinted polymer (SMIP) which then was introduced into chemiluminescence (CL) to achieve an ultrasensitive and selective biosensor for determination of lysozyme (Lys). ILs and β-CD was applied to provide multiple binding sites to prepare Lys SMIP and Fe3O4@DA was designed to make the product separate easily and prevent the aggregation of GO which could improve absorption capacity for its large specific surface area. The ILs-Fe3O4@DA/GO/β-CD-SMIP showed high adsorption capacity (Q = 101 mg/g) to Lys in the adsorption isotherm assays. The adsorption equilibrium was reached within 10 min for all the concentrations, attributing to the binding sites situated exclusively at the surface, and the adsorption model followed Langmuir isotherm. Under the suitable CL conditions, the proposed biosensor could response Lys linearly in the range of 1.0 × 10(-9)-8.0 × 10(-8) mg/mL with a detection limit of 3.0 × 10(-10) mg/mL. When used in practical samples in determination of Lys, the efficient biosensor exhibited excellent result with the recoveries ranging from 94% to 112%. PMID:27046214

  3. Ionic Conductivity of Mesostructured Yttria-Stabilized Zirconia Thin Films with Cubic Pore Symmetry—On the Influence of Water on the Surface Oxygen Ion Transport.

    PubMed

    Elm, Matthias T; Hofmann, Jonas D; Suchomski, Christian; Janek, Jürgen; Brezesinski, Torsten

    2015-06-10

    Thermally stable, ordered mesoporous thin films of 8 mol % yttria-stabilized zirconia (YSZ) were prepared by solution-phase coassembly of chloride salt precursors with an amphiphilic diblock copolymer using an evaporation-induced self-assembly process. The resulting material is of high quality and exhibits a well-defined three-dimensional network of pores averaging 24 nm in diameter after annealing at 600 °C for several hours. The wall structure is polycrystalline, with grains in the size range of 7 to 10 nm. Using impedance spectroscopy, the total electrical conductivity was measured between 200 and 500 °C under ambient atmosphere as well as in dry atmosphere for oxygen partial pressures ranging from 1 to 10(-4) bar. Similar to bulk YSZ, a constant ionic conductivity is observed over the whole oxygen partial pressure range investigated. In dry atmosphere, the sol-gel derived films have a much higher conductivity, with different activation energies for low and high temperatures. Overall, the results indicate a strong influence of the surface on the transport properties in cubic fluorite-type YSZ with high surface-to-volume ratio. A qualitative defect model which includes surface effects (annihilation of oxygen vacancies as a result of water adsorption) is proposed to explain the behavior and sensitivity of the conductivity to variations in the surrounding atmosphere. PMID:25984884

  4. Study of the effect of tribo-materials and surface finish on the lubricant performance of new halogen-free room temperature ionic liquids

    NASA Astrophysics Data System (ADS)

    Saurín, N.; Minami, I.; Sanes, J.; Bermúdez, M. D.

    2016-03-01

    The present work evaluates different materials and surface finish in the presence of newly designed, hydrophobic halogen-free room temperature ionic liquids (RTILs) as lubricants. A reciprocating tribo-tester was employed with steel-ceramic and steel-thermosetting epoxy resin contacts under boundary lubrication conditions. Four different tetraalkylphosphonium organosilanesulfonate RTILs provided excellent lubricating performance, with friction coefficients as low as 0.057, and non-measurable wear for the higher roughness machine-finish stainless steel flat against sapphire balls, in the case of the lubricants containing the 2-trimethylsilylethanesulfonate anion. Higher friction coefficients of the order of 0.1 and wear volumes of the order of 10-4 mm3 were observed for the lower roughness fine-finished flat stainless steel surface. All RTILs prevent wear of epoxy resin against stainless steel balls, with friction coefficients in the range of 0.03-0.06. EDX analysis shows the presence of RTILs on the stainless steel surfaces after the tribological tests. Under the experimental conditions, no corrosive processes were observed.

  5. Tetracene Aggregation on Polar and Nonpolar Surfaces: Implications for Singlet Fission.

    PubMed

    Strong, Steven E; Eaves, Joel D

    2015-04-01

    In molecular crystals that exhibit singlet fission, quantum yields depend strongly on intermolecular configurations that control the relevant electronic couplings. Here, we explore how noncovalent interactions between molecules and surfaces stabilize intermolecular structures with strong singlet fission couplings. Using molecular dynamics simulations, we studied the aggregation patterns of tetracene molecules on a solid surface as a function of surface polarity. Even at low surface concentrations, tetracene self-assembled into nanocrystallites where about 10-20% of the clustered molecules were part of at least one herringbone structure. The herringbone structure is the native structure of crystalline tetracene, which exhibits a high singlet fission quantum yield. Increasing the polarity of the surface reduced both the amount of clustering and the relative number of herringbone configurations, but only when the dipoles on the surface were orientationally disordered. These results have implications for the application of singlet fission in dye-sensitized solar cells. PMID:26262973

  6. Influence of Ionic Inorganic Solutes on Self-Assembly and Polymerization Processes Related to Early Forms of Life: Implications for a Prebiotic Aqueous Medium

    NASA Astrophysics Data System (ADS)

    Monnard, Pierre-Alain; Apel, Charles L.; Kanavarioti, Anastassia; Deamer, David W.

    2002-06-01

    A commonly accepted view is that life began in a marine environment, which would imply the presence of inorganic ions such as Na+, Cl-, Mg2+, Ca2+, and Fe2+. We have investigated two processes relevant to the origin of life - membrane self-assembly and RNA polymerization - and established that both are adversely affected by ionic solute concentrations much lower than those of contemporary oceans. In particular, monocarboxylic acid vesicles, which are plausible models of primitive membrane systems, are completely disrupted by low concentrations of divalent cations, such as magnesium and calcium, and by high sodium chloride concentrations as well. Similarly, a nonenzymatic, nontemplated polymerization of activated RNA monomers in ice/eutectic phases (in a solution of low initial ionic strength) yields oligomers with >80% of the original monomers incorporated, but polymerization in initially higher ionic strength aqueous solutions is markedly inhibited. These observations suggest that cellular life may not have begun in a marine environment because the abundance of ionic inorganic solutes would have significantly inhibited the chemical and physical processes that lead to self-assembly of more complex molecular systems.

  7. SORPTION OF CU AND ZN TO KAOLINITE AND IRON OXIDE: EFFECTS OF HUMIC ACID AND IONIC STRENGTH AND IMPLICATIONS FOR STORMWATER RUNOFF

    EPA Science Inventory

    Heavy metals are common pollutants in wet weather flows and urban waterways. Changes in ionic strength, whether from mixing with saline waters, road salt, or from the large osmotic adjustment needed for the Microtox toxicity assay, affect the aqueous chemistry of stormwater runof...

  8. Nonlinear ionic pulses along microtubules.

    PubMed

    Sekulić, D L; Satarić, B M; Tuszynski, J A; Satarić, M V

    2011-05-01

    Microtubules are cylindrically shaped cytoskeletal biopolymers that are essential for cell motility, cell division and intracellular trafficking. Here, we investigate their polyelectrolyte character that plays a very important role in ionic transport throughout the intra-cellular environment. The model we propose demonstrates an essentially nonlinear behavior of ionic currents which are guided by microtubules. These features are primarily due to the dynamics of tubulin C-terminal tails which are extended out of the surface of the microtubule cylinder. We also demonstrate that the origin of nonlinearity stems from the nonlinear capacitance of each tubulin dimer. This brings about conditions required for the creation and propagation of solitonic ionic waves along the microtubule axis. We conclude that a microtubule plays the role of a biological nonlinear transmission line for ionic currents. These currents might be of particular significance in cell division and possibly also in cognitive processes taking place in nerve cells. PMID:21604102

  9. Surface structure of imidazolium-based ionic liquids: Quantitative comparison between simulations and high-resolution RBS measurements

    NASA Astrophysics Data System (ADS)

    Nakajima, Kaoru; Nakanishi, Shunto; Lísal, Martin; Kimura, Kenji

    2016-03-01

    Elemental depth profiles of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([CnMIM][TFSI], n = 4, 6, 8) are measured using high-resolution Rutherford backscattering spectroscopy (HRBS). The profiles are compared with the results of molecular dynamics (MD) simulations. Both MD simulations and HRBS measurements show that the depth profiles deviate from the uniform stoichiometric composition in the surface region, showing preferential orientations of ions at the surface. The MD simulations qualitatively reproduce the observed HRBS profiles but the agreement is not satisfactory. The observed discrepancy is ascribed to the capillary waves. By taking account of the surface roughness induced by the capillary waves, the agreement becomes almost perfect.

  10. Effects of Ionic Strength on Bacteriophage MS2 Behavior and Their Implications for the Assessment of Virus Retention by Ultrafiltration Membranes ▿

    PubMed Central

    Furiga, Aurelie; Pierre, Gwenaelle; Glories, Marie; Aimar, Pierre; Roques, Christine; Causserand, Christel; Berge, Mathieu

    2011-01-01

    Bacteriophage MS2 is widely used as a surrogate to estimate pathogenic virus elimination by membrane filtration processes used in water treatment. Given that this water technology may be conducted with different types of waters, we focused on investigating the effects of ionic strength on MS2 behavior. For this, MS2 was analyzed while suspended in solutions of various ionic strengths, first in a batch experiment and second during membrane ultrafiltration, and quantified using (i) quantitative reverse transcriptase PCR (qRT-PCR), which detects the total number of viral genomes, (ii) qRT-PCR without the RNA extraction step, which reflects only particles with a broken capsid (free RNA), and (iii) the PFU method, which detects only infectious viruses. At the beginning of the batch experiments using solutions containing small amounts of salts, losses of MS2 infectivity (90%) and broken particles (20%) were observed; these proportions did not change during filtration. In contrast, in high-ionic-strength solutions, bacteriophage kept its biological activity under static conditions, but it quickly lost its infectivity during the filtration process. Increasing the ionic strength decreased both the inactivation and the capsid breakup in the feed suspension and increased the loss of infectivity in the filtration retentate, while the numbers of MS2 genomes were identical in both experiments. In conclusion, the effects of ionic strength on MS2 behavior may significantly distort the results of membrane filtration processes, and therefore, the combination of classical and molecular methods used here is useful for an effective validation of the retention efficiency of ultrafiltration membranes. PMID:21075898

  11. Interactional behavior of the polyelectrolyte poly sodium 4-styrene sulphonate (NaPSS) with imidazolium based surface active ionic liquids in an aqueous medium.

    PubMed

    Sharma, Renu; Kamal, Ajar; Kang, Tejwant Singh; Mahajan, Rakesh Kumar

    2015-09-28

    The present study aims to develop an understanding of the interactions between an anionic polyelectrolyte, poly sodium 4-styrene sulphonate (NaPSS), and cationic surface active imidazolium based ionic liquids (SAILs), [Cnmim][Cl] (n = 10, 12, 14) using a multi-technique approach. Various physicochemical and electrochemical techniques such as surface tension, conductivity, fluorescence, isothermal titration calorimetry (ITC), dynamic light scattering (DLS), turbidity, potentiometry, cyclic voltammetry (CV), and differential pulse voltammetry (DPV) are employed to obtain comprehensive information about NaPSS-SAIL interactions. Different stages of interaction, corresponding to the critical aggregation concentration (cac), critical saturation concentration (Cs) and critical micelle concentration (cmc) have been observed owing to the strong electrostatic and hydrophobic interactions, and the results obtained from different techniques complement each other very well. The results extracted from DLS and turbidity measurements clearly indicated that the size of the micelle like aggregates first decreases and then increases in the presence of polyelectrolyte. The binding isotherms obtained using potentiometry show a concentration dependence and the highly co-operative nature of the interactions which is attributed to aggregation of the polyelectrolyte-SAIL complexes. The diffusion coefficients (Dm) of the electroactive probe in the pure and NaPSS-SAIL mixed systems were obtained, which were further used to obtain the values of the micellar self-diffusion coefficients (D) and inter-micellar interaction parameters (kd). PMID:26300416

  12. Facile Fabrication of a Silver Nanoparticle Immersed, Surface-Enhanced Raman Scattering Imposed Paper Platform through Successive Ionic Layer Absorption and Reaction for On-Site Bioassays.

    PubMed

    Kim, Wansun; Kim, Yeon-Hee; Park, Hun-Kuk; Choi, Samjin

    2015-12-23

    We introduce a novel, facile, rapid, low-cost, highly reproducible, and power-free synthesizable fabrication method of paper-based silver nanoparticle (AgNP) immersed surface-enhanced Raman scattering (SERS) platform, known as the successive ionic layer absorption and reaction (SILAR) method. The rough and porous properties of the paper led to direct synthesis of AgNPs on the surface as well as in the paper due to capillary effects, resulting in improved plasmon coupling with interparticles and interlayers. The proposed SERS platform showed an enhancement factor of 1.1 × 10(9), high reproducibility (relative standard deviation of 4.2%), and 10(-12) M rhodamine B highly sensitive detection limit by optimizing the SILAR conditions including the concentration of the reactive solution (20/20 mM/mM AgNO3/NaBH4) and the number of SILAR cycles (six). The applicability of the SERS platform was evaluated using two samples including human cervical fluid for clinical diagnosis of human papillomavirus (HPV) infection, associated with cervical cancer, and a malachite green (MG) solution for fungicide and parasiticide in aquaculture, associated with human carcinogenesis. The AgNP-immersed SERS-functionalized platform using the SILAR technique allowed for high chemical structure sensitivity without additional tagging or chemical modification, making it a good alternative for early clinical diagnosis of HPV infection and detection of MG-activated human carcinogenesis. PMID:26619139

  13. Analysis of passive surface-wave noise in surface microseismic data and its implications

    USGS Publications Warehouse

    Forghani-Arani, F.; Willis, M.; Haines, S.; Batzle, M.; Davidson, M.

    2011-01-01

    Tight gas reservoirs are projected to be a major portion of future energy resources. Because of their low permeability, hydraulic fracturing of these reservoirs is required to improve the permeability and reservoir productivity. Passive seismic monitoring is one of the few tools that can be used to characterize the changes in the reservoir due to hydraulic fracturing. Although the majority of the studies monitoring hydraulic fracturing exploit down hole microseismic data, surface microseismic monitoring is receiving increased attention because it is potentially much less expensive to acquire. Due to a broader receiver aperture and spatial coverage, surface microseismic data may be more advantageous than down hole microseismic data. The effectiveness of this monitoring technique, however, is strongly dependent on the signal-to-noise ratio of the data. Cultural and ambient noise can mask parts of the waveform that carry information about the subsurface, thereby decreasing the effectiveness of surface microseismic analysis in identifying and locating the microseismic events. Hence, time and spatially varying suppression of the surface-wave noise ground roll is a critical step in surface microseismic monitoring. Here, we study a surface passive dataset that was acquired over a Barnett Shale Formation reservoir during two weeks of hydraulic fracturing, in order to characterize and suppress the surface noise in this data. We apply techniques to identify the characteristics of the passive ground roll. Exploiting those characteristics, we can apply effective noise suppression techniques to the passive data. ?? 2011 Society of Exploration Geophysicists.

  14. Frost grain size metamorphism - Implications for remote sensing of planetary surfaces

    NASA Technical Reports Server (NTRS)

    Clark, R. N.; Fanale, F. P.; Zent, A. P.

    1983-01-01

    The effective grain size of a material on a planetary surface affects the strength of absorption features observed in the reflectance of a particulate surface. In the case of a planetary surface containing volatile ices, the absorption characteristics can change in connection with processes leading to a change in the grain size of the material. The present investigation is concerned with an evaluation regarding the occurrence of such processes and the implications for remote sensing applications. It is found that quantitative modeling of the kinetics of grain growth and destruction by thermal and nonthermal processes can provide a means to reconcile apparent optical paths in the volatile portions of planetary surfaces with the physical history of those surfaces. Attention is also given to conditions in the case of the Pluto/Triton system, Uranus and Saturnian satellites, and the Galilean system.

  15. Charging Properties of Cassiterite (alpha-SnO2) Surfaces in NaCl and RbCl Ionic Media.

    SciTech Connect

    Rosenqvist, Jorgen K; Machesky, Michael L.; Vlcek, Lukas; Wesolowski, David J

    2009-09-01

    The acid-base properties of cassiterite ({alpha}-SnO{sub 2}) surfaces at 10-50 C were studied using potentiometric titrations of powder suspensions in aqueous NaCl and RbCl media. The proton sorption isotherms exhibited common intersection points in the pH range of 4.0-4.5 under all conditions, and the magnitude of charging was similar but not identical in NaCl and RbCl. The hydrogen bonding configuration at the oxide-water interface, obtained from classical molecular dynamics (MD) simulations, was analyzed in detail, and the results were explicitly incorporated in calculations of protonation constants for the reactive surface sites using the revised MUSIC model. The calculations indicated that the terminal SnOH{sub 2} group is more acidic than the bridging Sn{sub 2}OH group, with protonation constants (log K{sub H}) of 3.60 and 5.13 at 25 C, respectively. This is contrary to the situation on the isostructural {alpha}-TiO{sub 2} (rutile), apparently because of the difference in electronegativity between Ti and Sn. MD simulations and speciation calculations indicated considerable differences in the speciation of Na{sup +} and Rb{sup +}, despite the similarities in overall charging. Adsorbed sodium ions are almost exclusively found in bidentate surface complexes, whereas adsorbed rubidium ions form comparable numbers of bidentate and tetradentate complexes. Also, the distribution of adsorbed Na{sup +} between the different complexes shows a considerable dependence on the surface charge density (pH), whereas the distribution of adsorbed Rb{sup +} is almost independent of pH. A surface complexation model (SCM) capable of accurately describing both the measured surface charge and the MD-predicted speciation of adsorbed Na{sup +}/Rb{sup +} was formulated. According to the SCM, the deprotonated terminal group (SnOH{sup -0.40}) and the protonated bridging group (Sn{sub 2}OH{sup +0.36}) dominate the surface speciation over the entire pH range of this study (2.7-10). The

  16. Charging Properties of Cassiterite (alpha-SnO2) surfaces in NaCl and RbCl Ionic Media.

    SciTech Connect

    Rosenqvist, Jorgen K; Machesky, Michael L.; Vlcek, Lukas; Wesolowski, David J

    2009-09-01

    The acid-base properties of cassiterite (alpha-SnO2) surfaces at 10-50 degrees C were studied using potentiometric titrations of powder suspensions in aqueous NaCl and RbCl media. The proton sorption isotherms exhibited common intersection points in the pH range of 4.0-4.5 under all conditions, and the magnitude of charging was similar but not identical in NaCl and RbCl. The hydrogen bonding configuration at the oxide-water interface, obtained from classical molecular dynamics (MD) simulations, was analyzed in detail, and the results were explicitly incorporated in calculations of protonation constants for the reactive surface sites using the revised MUSIC model. The calculations indicated that the terminal SnOH2 group is more acidic than the bridging Sn2OH group, with protonation constants (log KH) of 3.60 and 5.13 at 25 degrees C, respectively. This is contrary to the situation on the isostructural alpha-TiO2 (rutile), apparently because of the difference in electronegativity between Ti and Sn. MD simulations and speciation calculations indicated considerable differences in the speciation of Na+ and Rb+, despite the similarities in overall charging. Adsorbed sodium ions are almost exclusively found in bidentate surface complexes, whereas adsorbed rubidium ions form comparable numbers of bidentate and tetradentate complexes. Also, the distribution of adsorbed Na+ between the different complexes shows a considerable dependence on the surface charge density (pH), whereas the distribution of adsorbed Rb+ is almost independent of pH. A surface complexation model (SCM) capable of accurately describing both the measured surface charge and the MD-predicted speciation of adsorbed Na+/Rb+ was formulated. According to the SCM, the deprotonated terminal group (SnOH(-0.40)) and the protonated bridging group (Sn2OH+0.36) dominate the surface speciation over the entire pH range of this study (2.7-10). The complexation of medium cations increases significantly with increasing

  17. Evaporites, surface roughness, and inundation in a playa dust source; implications of surface composition for erodibility

    NASA Astrophysics Data System (ADS)

    Tollerud, H.; Fantle, M.

    2013-12-01

    An understanding of fundamental controls on dust emission is critical in order to predict and model geochemical fluxes in the Earth system. Crucial parameters for dust emission include surface properties such as roughness, strength, and composition, which affect the erodibility of surface sediments. Accordingly, knowledge of the processes that govern surface properties is vital for predicting geochemical dust fluxes. In this study, we examine the spatial distribution of mineralogy within a playa dust source (Black Rock Desert, NV, USA) and its association with the spatial distribution of annual inundation, and employ a numerical model to assess the importance of transport by inundation for producing the distribution of mineralogy that we observe. Additionally, we experimentally investigate the effect of evaporite mineralogy on the development of surface roughness in a playa analog surface. We hypothesize that evaporite minerals in playa surface crusts reduce erodibility by contributing to sediment aggregation, promoting smoothing of the surface and a decrease in the availability of particles for saltation. Heterogeneity in surface mineralogy will then affect erodibility. Thus, it is useful to identify controls on the distribution of mineralogy (specifically evaporites) across a playa dust source. In particular, a connection between inundation and surface heterogeneity suggests that inundation could influence erodibility. Semi-quantitative X-ray diffraction analysis of surface sediments from the Black Rock Desert shows that evaporite content is variable; halite content varies from 0-40 wt%, and calcite from 2-15 wt%, with average sediment compositions of 30% quartz, 45% clay, and 10% plagioclase. Average calcite content is lower (7.6%) for sites within the inundated area of the previous year's playa lake (detected using MODIS satellite imagery; band 6, 1640 nm) than for sites outside this area (average calcite content 9.5%). Sites inundated the previous year are

  18. Scratching the surface of ice: Interfacial phase transitions and their kinetic implications

    NASA Astrophysics Data System (ADS)

    Limmer, David

    The surface structure of ice maintains a high degree of disorder down to surprisingly low temperatures. This is due to a number of underlying interfacial phase transitions that are associated with incremental changes in broken symmetry relative to the bulk crystal. In this talk I summarize recent work attempting to establish the nature and locations of these different phase transitions as well as how they depend on external conditions and nonequilibrium driving. The implications of this surface disorder is discussed in the context of simple kinetic processes that occur at these interfaces. Recent experimental work on the roughening transition is highlighted.

  19. Model for oxygen recombination on silicon-dioxide surfaces. II - Implications toward reentry heating

    NASA Technical Reports Server (NTRS)

    Jumper, E. J.; Seward, W. A.

    1992-01-01

    This paper briefly reviews the model for recombination of oxygen on a silicon-dioxide surface presented in detail in a previous paper. New data supporting the model is also presented. The ramifications of the model toward the production of excited molecular oxygen is examined as it pertains to surface heating. A reentry simulation is given and compared to STS-2 reentry data, and conclusions are drawn as to the implications of the recombination model toward reentry heating. A possible buffering of the heating above a critical temperature associated with the physics of the model is also discussed.

  20. Ionic Liquids Database- (ILThermo)

    National Institute of Standards and Technology Data Gateway

    SRD 147 Ionic Liquids Database- (ILThermo) (Web, free access)   IUPAC Ionic Liquids Database, ILThermo, is a free web research tool that allows users worldwide to access an up-to-date data collection from the publications on experimental investigations of thermodynamic, and transport properties of ionic liquids as well as binary and ternary mixtures containing ionic liquids.

  1. Examination of 1-methylimidazole series ionic liquids in the extraction of flavonoids from Chamaecyparis obtuse leaves using a response surface methodology.

    PubMed

    Tang, Baokun; Lee, Yu Jin; Lee, Yu Ri; Row, Kyung Ho

    2013-08-15

    Ionic liquids (ILs) are a new type of reagent that has accelerated research in extraction technology. On the other hand, few studies have systematically applied 1-methylimidazole ([MIM]) series ILs to the extraction of bioactive compounds from plants. In this study, [MIM] series ILs were used to extract four bioactive flavonoids, such as dihydrokaempferol, quercitrin, amentoflavone and myricetin, from Chamaecyparis obtuse (CO) leaves. First, a screen of the extraction method and solvent revealed the [MIM] series ILs to be suitable as additives in methanol in Soxhlet extraction. Second, an examination of a range of cations and anions of [MIM] series ILs for extraction revealed 1-decyl-3-methylimidazolium bromide ([DMIM][Br]) to be the best selection as an additive in methanol for the Soxhlet extraction of flavonoids from (CO) leaves. Finally, some factors of extraction, such as temperature, time and amount of samples, were examined systematically using a response surface methodology (RSM). Based on the above optimization, 2.41, 3.47, 0.76 and 3.15mg/g of dihydrokaempferol, quercitrin, amentoflavone and myricetin, respectively, were extracted from 15g of CO leaves by 2.5mgmL(-1) of [DMIM][Br] as additives in 200mL of methanol in Soxhlet extraction at 200°C for 8h. This study highlights the potential of [MIM] series ILs as promising reagents for the extraction of bioactive compounds from plants. PMID:23845390

  2. Process optimization of deposition conditions of PbS thin films grown by a successive ionic layer adsorption and reaction (SILAR) method using response surface methodology

    NASA Astrophysics Data System (ADS)

    Yücel, Ersin; Yücel, Yasin; Beleli, Buse

    2015-07-01

    In this study, lead sulfide (PbS) thin films were synthesized by a successive ionic layer adsorption and reaction (SILAR) method with different pH, dipping time and dipping cycles. Response surface methodology (RSM) and central composite design (CCD) were successfully used to optimize the PbS films deposition parameters and understand the significance and interaction of the factors affecting the film quality. 5-level-3-factor central composite design was employed to evaluate the effects of the deposition parameters (pH, dipping time and dipping cycles) on the response (the optical band gap of the films). Data obtained from RSM were subjected to the analysis of variance (ANOVA) and analyzed using a second order polynomial equation. The optimal conditions for the PbS films deposition have been found to be: pH of 9.1, dipping time of 10 s and dipping cycles of 10 cycles. The predicted band gap of PbS film was 2.13 eV under the optimal conditions. Verification experiment (2.24 eV) confirmed the validity of the predicted model. The film structures were characterized by X-ray diffractometer (XRD). Morphological properties of the films were studied with a scanning electron microscopy (SEM). The optical properties of the films were investigated using a UV-visible spectrophotometer.

  3. Surface Adsorption and Micelle Formation of Polyoxyethylene-type Nonionic Surfactants in Mixtures of Water and Hydrophilic Imidazolium-type Ionic Liquid.

    PubMed

    Misono, Takeshi; Okada, Kohei; Sakai, Kenichi; Abe, Masahiko; Sakai, Hideki

    2016-06-01

    The interfacial properties of polyoxyethylene alkyl ether-type nonionic surfactants (CnEm) were studied in a hydrophilic room-temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4), in the presence of water. These properties were assessed using static surface tension, pyrene fluorescence, and dynamic light scattering measurements. The interfacial properties were strongly dependent on the solution composition. Increased water concentration lowered the critical micelle concentration (cmc). The cmc was also affected by the lengths of both the alkyl and polyoxyethylene chains, but a greater impact was observed for the alkyl chain length. These results indicate that micellization occurs as a result of solvophobic interaction between surfactant molecules in the water/bmimBF4 mixed solutions, similar to aqueous surfactant systems. The cloud point phenomenon was observed for CnEm with a relatively low hydrophilic-lipophilic balance (HLB) value, and the relationship between the cloud point and water/bmimBF4 composition exhibited a convex upward curve. Furthermore, the mixing of bmimBF4 with water increased the surfactant solubility for water-rich compositions, suggesting that bmimBF4 acts as a chaotropic salt. PMID:27181249

  4. Chemical interactions between the present-day Martian atmosphere and surface minerals: Implications for sample return

    NASA Technical Reports Server (NTRS)

    Prinn, Ronald; Fegley, Bruce

    1988-01-01

    Thermochemical and photochemical reactions between surface minerals and present-day atmospheric constituents are predicted to produce microscopic effects on the surface of mineral grains. Relevant reactions hypothesized in the literature include conversions of silicates and volcanic glasses to clay minerals, conversion of ferrous to ferric compounds, and formation of carbonates, nitrates, and sulfates. These types of surface-atmosphere weathering of minerals, biological potential of the surface environment, and atmospheric stability in both present and past Martian epochs. It is emphasized that the product of these reactions will be observable and interpretable on the microscopic surface layers of Martian surface rocks using modern techniques with obvious implications for sample return from Mars. Macroscopic products of chemical weathering reactions in past Martian epochs are also expected in Martian surface materials. These products are expected not only as a result of reactions similar to those proceeding today but also due to aqueous reactions in past epochs in which liquid water was putatively present. It may prove very difficult or impossible, however, to determine definitively from the relic macroscopic product alone either the exact weathering process which led to its formation of the identity of its weathering parent mineral. The enormous advantages of studying the Martian chemical weathering by investigating the microscopic products of present-day chemical reactions on sample surfaces are very apparent.

  5. Identification of ionic chloroacetanilide-herbicide metabolites in surface water and groundwater by HPLC/MS using negative ion spray

    USGS Publications Warehouse

    Ferrer, I.; Thurman, E.M.; Barcelo, D.

    1997-01-01

    Solid-phase extraction (SPE) was combined with high-performance liquid chromatography/high-flow pneumatically assisted electrospray mass spectrometry (HPLC/ESP/MS) for the trace analysis of oxanilic and sulfonic acids of acetochlor, alachlor, and metolachlor. The isolation procedure separated the chloroacetanilide metabolites from the parent herbicides during the elution from C18 cartridges using ethyl acetate for parent compounds, followed by methanol for the anionic metabolites. The metabolites were separated chromatographically using reversed-phase HPLC and analyzed by negative-ion MS using electrospray ionization in selected ion mode. Quantitation limits were 0.01 ??g/L for both the oxanilic and sulfonic acids based on a 100-mL water sample. This combination of methods represents an important advance in environmental analysis of chloroacetanilide-herbicide metabolites in surface water and groundwater for two reasons. First, anionic chloroacetanilide metabolites are a major class of degradation products that are readily leached to groundwater in agricultural areas. Second, anionic metabolites, which are not able to be analyzed by conventional methods such as liquid extraction and gas chromatography/mass spectrometry, are effectively analyzed by SPE and high-flow pneumatically assisted electrospray mass spectrometry. This paper reports the first HPLC/MS identification of these metabolites in surface water and groundwater.

  6. Correlations between VIMS and RADAR data over the surface of Titan: Implications for Titan's surface properties.

    NASA Astrophysics Data System (ADS)

    Tosi, Federico; Orosei, Roberto; Seu, Roberto; Coradini, Angioletta; Lunine, Jonathan; Filacchione, Gianrico; Capaccioni, Fabrizio; Cerroni, Priscilla; Brown, Robert

    2010-05-01

    We present new results combining the VIMS and RADAR data on Titan's surface. In RADAR data we consider two geophysical quantities: the normalized backscatter cross-section obtained from the scatterometer measurement, corrected for the incidence angle, and the calibrated antenna temperature determined from the radiometer measurement, as found in publicly available data products. In VIMS data, combining spatial and spectral information, we have selected some atmospheric windows in the spectral range between 2 and 5 μm, providing the best optical depth to measure surface reflectance. The two RADAR parameters are combined with VIMS data, with estimated errors, to produce an aggregate data set, that we process using multivariate classification methods to identify homogeneous taxonomic units in the multivariate space of the samples. The use of data sets from different instruments onboard the Cassini spacecraft has the potential to deepen our understanding of the nature of the surface. Our analysis relies on the G-mode method, which has been successfully used in the past for the classification of such diverse data sets as lunar rock samples, asteroids and planetary surfaces. Due to the large number of data of Titan, the classification work proceeds in several steps. In a previous work (Tosi et al., 2010), we analyzed the data acquired in Titan flybys: T3, T4, T8, T13 and T16, covering mostly the major bright and dark features seen around the equator, combined with VIMS infrared data, in order to validate the classification method. Now we focus on flybys: T23, T25, T28, T30, and T43, covering also regions of Titan located at higher latitudes, and partly including the polar regions. The obtained results are generally in agreement with previous work devoted both to the analysis of the scatterometry data through physical models and to the correlation between SAR and radiometry data at a high resolution scale. This evidence, evaluated for the first time through a multivariate

  7. Correlations between VIMS and RADAR data over the surface of Titan: Implications for Titan's surface properties

    NASA Astrophysics Data System (ADS)

    Tosi, F.; Orosei, R.; Seu, R.; Coradini, A.; Lunine, J. I.; Filacchione, G.; Capaccioni, F.; Cerroni, P.; Brown, R. H.; Cassini Vims; Radar Teams

    2010-04-01

    We present new results combining the VIMS and RADAR data on Titan's surface. In RADAR data we consider two geophysical quantities: the normalized backscatter cross-section obtained from the scatterometer measurement, corrected for the incidence angle, and the calibrated antenna temperature determined from the radiometer measurement, as found in publicly available data products. In VIMS data, combining spatial and spectral information, we have selected some atmospheric windows in the spectral range between 2 and 5 μm, providing the best optical depth to measure surface reflectance. The two RADAR parameters are combined with VIMS data, with estimated errors, to produce an aggregate data set, that we process using multivariate classification methods to identify homogeneous taxonomic units in the multivariate space of the samples. The use of data sets from different instruments onboard the Cassini spacecraft has the potential to deepen our understanding of the nature of the surface. Our analysis relies on the G-mode method, which has been successfully used in the past for the classification of such diverse data sets as lunar rock samples, asteroids and planetary surfaces. Due to the large number of data of Titan, the classification work proceeds in several steps. In a previous work (Tosi et al., 2010), we analyzed the data acquired in Titan flybys: T3, T4, T8, T13 and T16, covering mostly the major bright and dark features seen around the equator, combined with VIMS infrared data, in order to validate the classification method. Now we focus on flybys: T23, T25, T28, T30, and T43, covering also regions of Titan located at higher latitudes, and partly including the polar regions. The obtained results are generally in agreement with previous work devoted both to the analysis of the scatterometry data through physical models and to the correlation between SAR and radiometry data at a high resolution scale. This evidence, evaluated for the first time through a multivariate

  8. Ionic Surfactant Binding to pH-Responsive Polyelectrolyte Brush-Grafted Nanoparticles in Suspension and on Charged Surfaces.

    PubMed

    Riley, John K; An, Junxue; Tilton, Robert D

    2015-12-29

    The interactions between silica nanoparticles grafted with a brush of cationic poly(2-(dimethylamino) ethyl methacrylate) (SiO2-g-PDMAEMA) and anionic surfactant sodium dodecyl sulfate (SDS) is investigated by dynamic light scattering, electrophoretic mobility, quartz crystal microbalance with dissipation, ellipsometry, and atomic force microscopy. SiO2-g-PDMAEMA exhibits pH-dependent charge and size properties which enable the SDS binding to be probed over a range of electrostatic conditions and brush conformations. SDS monomers bind irreversibly to SiO2-g-PDMAEMA at low surfactant concentrations (∼10(-4) M) while exhibiting a pH-dependent threshold above which cooperative, partially reversible SDS binding occurs. At pH 5, SDS binding induces collapse of the highly charged and swollen brush as observed in the bulk by DLS and on surfaces by QCM-D. Similar experiments at pH 9 suggest that SDS binds to the periphery of the weakly charged and deswollen brush and produces SiO2-g-PDMAEMA/SDS complexes with a net negative charge. SiO2-g-PDMAEMA brush collapse and charge neutralization is further confirmed by colloidal probe AFM measurements, where reduced electrosteric repulsions and bridging adhesion are attributed to effects of the bound SDS. Additionally, sequential adsorption schemes with SDS and SiO2-g-PDMAEMA are used to enhance deposition relative to SiO2-g-PDMAEMA direct adsorption on silica. This work shows that the polyelectrolyte brush configuration responds in a more dramatic fashion to SDS than to pH-induced changes in ionization, and this can be exploited to manipulate the structure of adsorbed layers and the corresponding forces of compression and friction between opposing surfaces. PMID:26649483

  9. Year-round observations of water-soluble ionic species and trace metals in Sapporo aerosols: implication for significant contributions from terrestrial biological sources in Northeast Asia

    NASA Astrophysics Data System (ADS)

    Pavuluri, C. M.; Kawamura, K.; Mihalopoulos, N.; Fu, P.

    2013-03-01

    High aerosol loadings are prevalent in the atmosphere of East Asia, where the aerosols impact the Earth's climate system and human health; however, their sources and seasonal variations are not clearly understood. To better understand the sources of water-soluble ionic species and trace metals in Northeast Asia, we studied atmospheric aerosol samples collected in Sapporo, northern Japan for one-year period. SO42- (average 3.47 ± 1.03 μg m-3) was found as the most abundant ionic species, which accounted for on average 43 ± 15% of the measured total ionic mass followed by Cl- (13 ± 12%) ≈ NO3- ≈ Na+ > NH4+ > Ca2+ > Mg2+ > K+ > MSA-. Among the metals determined, Ca was found as the most abundant (45 ± 5.2%) followed by Fe (27 ± 4.5%), Al (21± 3.1%), Zn (3.2 ± 1.7), Ti, Mn, Ni, Pb, Cu, V, As, Cr and Cd. Based on factor analysis, linear relations of selected species with biomarkers, and backward air mass trajectories, we found that long-range atmospheric transport of soil dust (∼ 33%) from arid regions of Mongolia and/or Northeast China is a major source for Sapporo aerosols as well as terrestrial biogenic emissions (≥ 24%) including microbial activities and biomass burning mostly from distant source region(s) (e.g. Siberia). We also found that the contributions of soil dust to the aerosols maximized in early spring whereas those of vegetational emissions maximized in spring/summer. Contributions of microbial activities to aerosols peaked in autumn whereas forest fires/biomass burning peaked in autumn/winter. On the contrary, fossil fuel combustion/industrial activities and oceanic emissions to Sapporo aerosols are suggested to be rather minor. This study also suggests that fungal spores contribute to some trace metals (i.e. Ni, Cu, As) while pollen contributes to Zn in aerosols.

  10. How does the surface charge of ionic surfactant and cholesterol forming vesicles control rotational and translational motion of rhodamine 6G perchlorate (R6G ClO₄)?

    PubMed

    Ghosh, Surajit; Roy, Arpita; Banik, Debasis; Kundu, Niloy; Kuchlyan, Jagannath; Dhir, Anjali; Sarkar, Nilmoni

    2015-03-01

    The rotational dynamics and translational diffusion of a hydrophilic organic molecule, rhodamine 6G perchlorate (R6G ClO4) in small unilamellar vesicles formed by two different ionic surfactants, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), with cholesterol have been investigated using fluorescence spectroscopic methods. Moreover, in this article the formation of vesicle using anionic surfactant, SDS at different cholesterol-to-surfactant molar ratio (expressed by Q value (Q = [cholesterol]/[surfactant])) has also been reported. Visual observation, dynamic light scattering (DLS) study, turbidity measurement, steady state fluorescence anisotropy (r0) measurement, and eventually microscopic images reveal the formation of small unilamellar vesicles in aqueous solution. Also, in this study, an attempt has been made to observe whether the cationic probe molecule, rhodamine 6G (R6G) experiences similar or different microenvironment in cholesterol-SDS and cholesterol-CTAB assemblies with increase in cholesterol concentration. The influence of cholesterol on rotational and translational diffusion of R6G molecules has been investigated by monitoring UV-vis absorption, fluorescence, time-resolved fluorescence anisotropy, and finally fluorescence correlation spectroscopy (FCS) measurements. In cholesterol-SDS assemblies, due to the strong electrostatic attractive interaction between the negatively charged surface of vesicle and cationic R6G molecules, the rotational and diffusion motion of R6G becomes slower. However, in cholesterol-CTAB aggregates, the enhanced hydrophobicity and electrostatic repulsion induces the migration of R6G from vesicle bilayer to aqueous phase. The experimental observations suggest that the surface charge of vesicles has a stronger influence than the hydrophobicity of the vesicle bilayer on the rotational and diffusion motion of R6G molecules. PMID:25643899

  11. Correlations between VIMS and RADAR data over the surface of Titan: Implications for Titan's surface properties

    NASA Astrophysics Data System (ADS)

    Tosi, F.; Orosei, R.; Seu, R.; Coradini, A.; Lunine, J. I.; Filacchione, G.; Capaccioni, F.; Cerroni, P.; Flamini, E.; Brown, R. H.; Cruikshank, D. P.; Lopes, R. M.

    2010-12-01

    We present new results combining the VIMS and RADAR medium resolution data on Titan’s surface. In RADAR data we consider two geophysical quantities: the normalized backscatter cross-section obtained from the scatterometer measurement, corrected for the incidence angle, and the calibrated antenna temperature determined from the radiometer measurement, as found in publicly available data products. In VIMS data, combining spatial and spectral information, we have selected some atmospheric windows in the spectral range between 2 and 5 μm, providing the best optical depth to measure surface reflectance. The two RADAR parameters are combined with VIMS data, with estimated errors, to produce an aggregate data set, that we process using multivariate classification methods to identify homogeneous taxonomic units in the multivariate space of the samples. Such units in fact reveal compositional trends in the surface, that are likely related to different abundances of simple ices and/or hydrocarbons. Our analysis relies on the G-mode method, which has been successfully used in the past for the classification of such diverse data sets as lunar rock samples, asteroids and planetary surfaces. Due to the large number of data of Titan, the classification work proceeds in several steps. In a previous work (Tosi et al., 2010), we analyzed the data acquired in Titan flybys: T3, T4, T8, T13 and T16, covering mostly the major bright and dark features seen around the equator, combined with VIMS infrared data, in order to validate the classification method. Now we focus on flybys: T23, T25, T28, T30, and T43, covering also regions of Titan located at higher latitudes, and partly including the polar regions. The obtained results are generally in agreement with previous work devoted both to the analysis of the scatterometry data through physical models and to the correlation between SAR and radiometry data at a high resolution scale. This classification can be expanded and refined as new

  12. Ionic Graphitization of Ultrathin Films of Ionic Compounds.

    PubMed

    Kvashnin, A G; Pashkin, E Y; Yakobson, B I; Sorokin, P B

    2016-07-21

    On the basis of ab initio density functional calculations, we performed a comprehensive investigation of the general graphitization tendency in rocksalt-type structures. In this paper, we determine the critical slab thickness for a range of ionic cubic crystal systems, below which a spontaneous conversion from a cubic to a layered graphitic-like structure occurs. This conversion is driven by surface energy reduction. Using only fundamental parameters of the compounds such as the Allen electronegativity and ionic radius of the metal atom, we also develop an analytical relation to estimate the critical number of layers. PMID:27333810

  13. Interactions between glycine derivatives and mineral surfaces: Implications for the origins of life on planetary surfaces

    NASA Astrophysics Data System (ADS)

    Marshall-Bowman, K. J.; Cleaves, H. J.; Sverjensky, D. A.; Hazen, R. M.

    2009-12-01

    Various mechanisms could have delivered amino acids to the prebiotic Earth (Miller and Orgel 1974). The polymerization of amino acids may have been important for the origin of life, as peptides may have been components for the first self-replicating systems (Kauffman 1971; Yao et al 1998). Though amino acid concentrations in the primitive oceans were likely too dilute for significant oligomerization to occur (Cleaves et al 2009), mineral surface adsorption may have concentrated these biomolecules (Bernal 1951; Lambert 2008). Few studies have examined the catalytic effects of mineral surfaces on aqueous peptide oligomerization or degradation. As unactivated amino acid polymerization is thermodynamically unfavorable and kinetically slow in aqueous solution, we studied the reverse reaction of polymer degradation to measure potential mineral catalysis. Glycine (G) derivatives glycylglycine (GG), diketopiperazine (DKP), and glycylglycylglycine (GGG) were reacted with different minerals (calcite, hematite, montmorillonite, rutile, amorphous silica, and pyrite) in the presence of 0.05 M pH 8.1 KHCO3 buffer and 0.1 M NaCl as background electrolyte. Experiments were performed by reacting the aqueous amino acid derivative-mineral mixtures in a thermostatted oven (modified to accommodate a mechanical rotator) at 25°, 50° or 70°C. Samples were removed after 30, 60, 90, and 140 hours. Samples were then analyzed using high performance liquid chromatography to quantify the products. Besides mineral catalysis, it was determined that degradation of GGG proceeds principally via a GGG → DKP + G mechanism, rather than via GGG → GG + G. Below 70°C kinetics were generally too sluggish to detect catalytic activity over reasonable laboratory time-scales at this pH. At 70°C, pyrite was the only mineral with detectible catalytic effects on the degradation of GGG. GGG degraded ~ 1.5 - 4 x faster in the presence of pyrite than in control reactions, depending on the ratio of solution

  14. Hot surface ionic line emission and cold K-inner shell emission from petawatt-laser irradiated Cu foil targets

    SciTech Connect

    Theobald, W; Akli, K; Clarke, R; Delettrez, J A; Freeman, R R; Glenzer, S; Green, J; Gregori, G; Heathcote, R; Izumi, N; King, J A; Koch, J A; Kuba, J; Lancaster, K; MacKinnon, A J; Key, M; Mileham, C; Myatt, J; Neely, D; Norreys, P A; Park, H; Pasely, J; Patel, P; Regan, S P; Sawada, H; Shepherd, R; Snavely, R; Stephens, R B; Stoeckl, C; Storm, M; Zhang, B; Sangster, T C

    2005-12-13

    A hot, T{sub e} {approx} 2- to 3-keV surface plasma was observed in the interaction of a 0.7-ps petawatt laser beam with solid copper-foil targets at intensities >10{sup 20} W/cm{sup 2}. Copper K-shell spectra were measured in the range of 8 to 9 keV using a single-photon-counting x-ray CCD camera. In addition to K{sub {alpha}} and K{sub {beta}} inner-shell lines, the emission contained the Cu He{sub {alpha}} and Ly{sub {alpha}} lines, allowing the temperature to be inferred. These lines have not been observed previously with ultrafast laser pulses. For intensities less than 3 x 10{sup 18} W/cm{sup 2}, only the K{sub {alpha}} and K{sub {beta}} inner-shell emissions are detected. Measurements of the absolute K{sub {alpha}} yield as a function of the laser intensity are in agreement with a model that includes refluxing and confinement of the suprathermal electrons in the target volume.

  15. Direct Mapping of Ionic Transport in a Si Anode on the Nanoscale: Time Domain Electrochemical Strain Spectroscopy Study

    SciTech Connect

    Jesse, Stephen; Balke, Nina; Eliseev, Eugene; Tselev, Alexander; Dudney, Nancy J; Morozovska, Anna N; Kalinin, Sergei V

    2011-01-01

    Local Li-ion transport in amorphous silicon is studied on the nanometer scale using time domain electrochemical strain microscopy (ESM). A strong variability of ionic transport controlled by the anode surface morphology is observed. The observed relaxing and nonrelaxing response components are discussed in terms of local and global ionic transport mechanisms, thus establishing the signal formation mechanisms in ESM. This behavior is further correlated with local conductivity measurements. The implications of these studies for Si-anode batteries are discussed. The universal presence of concentrationstrain coupling suggests that ESM and associated time and voltage spectroscopies can be applied to a broad range of electrochemical systems ranging from batteries to fuel cells.

  16. Experimental and DFT studies on the aggregation behavior of imidazolium-based surface-active ionic liquids with aromatic counterions in aqueous solution.

    PubMed

    Xu, Wenwen; Wang, Tao; Cheng, Ni; Hu, Qiongzheng; Bi, Yanhui; Gong, Yanjun; Yu, Li

    2015-02-01

    Two imidazolium-based surface-active ionic liquids with aromatic counterions, namely, 1-dodecyl-3-methylimidazolium salicylate (C12mimSal) and 1-dodecyl-3-methylimidazolium 3-hydroxy-2-naphthoate (C12mimHNC), were synthesized, and their aggregate behavior in aqueous solutions was systematically explored. Surface tension and conductivity measurements indicate that both C12mimSal and C12mimHNC show superior surface activity compared to the common imidazolium-based SAIL with the same hydrocarbon chain length, 1-dodecyl-3-methylimidazolium bromide (C12mimBr). This result demonstrates that the incorporation of aromatic counterions favors the formation of micelles. C12mimHNC displays a higher surface activity than C12mimSal, resulting from the different hydrophobicities of the counterions. In comparison with C12mimBr, C12mimSal not only can form hexagonal liquid-crystalline phase (H1) in aqueous solution, but also exhibits a broad region of cubic liquid-crystalline phase (V2) at higher concentration. As for the C12mimHNC/H2O system, a lamellar liquid-crystalline (L(α)) phase was observed. These lyotropic liquid crystals (LLCs) were characterized by polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS). Structural parameters calculated from SAXS patterns suggest that a higher concentration of the SAIL leads to a denser arrangement whereas a higher temperature results in the opposite effect. The rheological results manifest that the formed H1 phase in the C12mimSal/H2O system exhibits an impressive viscoelastic behavior, indicated by a modulus (G' and G″) that is 1 order of magnitude higher than that of C12mimBr. Density functional theory (DFT) calculations reveal that C12mimSal has a more negative interaction energy with a water molecule and the Sal(-) counterion presents a stronger electronegativity than the HNC(-) counterion. The specific phase behavior of the C12mimSal/H2O and C12mimHNC/H2O systems can be attributed to the strong synergic

  17. A sol-gel derived pH-responsive bovine serum albumin molecularly imprinted poly(ionic liquids) on the surface of multiwall carbon nanotubes.

    PubMed

    Liu, Mingming; Pi, Jiangyan; Wang, Xiaojie; Huang, Rong; Du, Yamei; Yu, Xiaoyang; Tan, Wenfeng; Liu, Fan; Shea, Kenneth J

    2016-08-17

    A pH-responsive surface molecularly imprinted poly(ionic liquids) (MIPILs) was prepared on the surface of multiwall carbon nanotubes (MWCNTs) by a sol-gel technique. The material was synthesized using a 3-aminopropyl triethoxysilane modified multiwall carbon nanotube (MWCNT-APTES) as the substrate, bovine serum albumin (BSA) as the template molecule, an alkoxy-functionalized IL 1-(3-trimethoxysilyl propyl)-3-methyl imidazolium chloride ([TMSPMIM]Cl) as both the functional monomer and the sol-gel catalyst, and tetraethoxysilane (TEOS) as the crosslinking agent. The molecular interaction between BSA and [TMSPMIM]Cl was quantitatively evaluated by UV-vis spectroscopy prior to polymerization so as to identify an optimal template/monomer ratio and the most suitable pH value for the preparation of the MWCNTs@BSA-MIPILs. This strategy was found to be effective to overcome the problems of trial-and-error protocol in molecular imprinting. The optimum synthesis conditions were as follows: template/monomer ratio 7:20, crosslinking agent content 2.0-2.5 mL, temperature 4 °C and pH 8.9 Tris-HCl buffer. The influence of incubation pH on adsorption was also studied. The result showed that the imprinting effect and selectivity improved significantly with increasing incubation pH from 7.7 to 9.9. This is mainly because the non-specific binding from electrostatic and hydrogen bonding interactions decreased greatly with the increase of pH value, which made the specific binding affinity from shape selectivity strengthened instead. The polymers synthesized under the optimal conditions were then characterized by BET surface area measurement, FTIR, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The adsorption capacity, imprinting effect, selective recognition and reusability were also evaluated. The as-prepared MWCNTs@BSA-MIPILs were also found to have a number of advantages including high surface area (134.2 m(2) g(-1)), high adsorption capacity (55.52

  18. Spectra of Fe-Ti silicate glasses - Implications to remote-sensing of planetary surfaces

    NASA Technical Reports Server (NTRS)

    Nolet, D. A.; Burns, R. G.; Flamm, S. L.; Besancon, J. R.

    1979-01-01

    Optical spectra of synthetic Fe-Ti silicate glasses and the temperature variations of the spectral features were investigated. The spectra are assigned to absorptions due to crystal field (CF) transitions in Ti(3+), Fe(2+) in octahedral coordination, and Fe(2+) in tetrahedral coordination, and to metal-metal and oxygen-metal charge transfer (CT) transitions which contribute to the near ultraviolet absorption edge. Temperature variations of the optical bands have been studied to explore implications for remote sensing. Caution is urged in the use of the absorption edge as a measure of TiO2 concentrations on planetary surfaces and in regolith samples.

  19. A new theory of bubble stability: Implications for nanobubbles at surfaces and in bulk solution

    NASA Astrophysics Data System (ADS)

    Craig, Vincent

    2013-11-01

    Nanobubbles on hydrophobic surfaces can be imaged using Atomic Force Microscopy and are implicated in the very long-range attraction measured between hydrophobic surfaces. However, the widely accepted theory of bubble dissolution predicts that small bubbles under the influence of Laplace pressure should rapidly dissolve resulting in bubble lifetimes of less than a second. Such short lifetimes should preclude nanobubbles from having an effect on surface force measurements or being observed by AFM, yet nanobubbles are readily observed by AFM and widely implicated in force measurements between hydrophobic surfaces. This has led to a number of attempts at describing their unexpected stability, though no explanation is currently widely accepted. Additionally, nanobubbles have contact angles substantially greater (measured through the more dense liquid phase) than the equivalent macroscopic contact angle. It is clear that nanobubbles at surfaces pose a number of problems that are yet to be resolved. Additionally, recent reports of long-lived nanobubbles in bulk solution add to the mystery. Here we present a new theory describing the stability of nanobubbles. We calculate their lifetimes as a function of gas supersaturation and explain the long lifetimes observed. The same theory predicts that bulk nanobubbles should be stable under certain circumstances. Further, in an extension of this work we explain the difference in contact angle between the nanoscopic and macroscopic measurements and describe in detail the process by which nanobubbles are formed during solvent exchange. Experimental evidence is presented supporting this new approach and showing that this theoretical framework has parallels in other nucleated systems. This work was supported by an ARC Future Fellowship.

  20. Process optimization studies of 10-Hydroxycamptothecin (HCPT)-loaded folate-conjugated chitosan nanoparticles by SAS-ionic crosslink combination using response surface methodology (RSM)

    NASA Astrophysics Data System (ADS)

    Zhao, Xiuhua; Jiang, Ru; Zu, Yuangang; Wang, Ying; Zhao, Qi; Zu, Baishi; Zhao, Dongmei; Wang, Meixiang; Sun, Zhiqiang

    2012-01-01

    10-Hydroxycamptothecin (HCPT) is a well-established topoisomerase I inhibitor of a broad spectrum of cancers. However, poor aqueous solubility, low instability, and toxicity to normal tissues have limited its clinical development. A novel HCPT-containing drug carrier system was developed to overcome these disadvantages. The response surface methodology was used to optimize the process of preparing HCPT-chitosan nanoparticles (HCPT-CSNPs) by the SAS-ionic crosslink (supercritical antisolvent SAS) combination method; the resulting HCPT-CSNPs were then conjugated with folate for specific targeting. A central composite design, composed of four independent variables, namely, chitosan concentration, TPP concentration, HCPT nanoparticle concentration, and crosslink time, was applied in the modeling process. The mean particle size and drug entrapment efficiency (DEE) of HCPT-CSNPs were chosen as response variables. The interactive effects of the four independent variables on the response variables were also studied. Nanoparticle characteristics such as morphology, DEE, and mean particle size were investigated. The optimum conditions for preparing HCPT-CSNPs were determined as follows: folate-coupled chitosan concentration 2.46 mg/ml, TPP concentration 7.73 mg/ml, HCPT nanoparticle concentration 0.48 mg/ml, and crosslinking time 47.4 min. Optimum conditions for preparing desired HCPT-CSNPs with a mean particle size of 173.5 nm and entrapment efficiency of 77.3% were obtained. The resulting folate-conjugated HCPT-CSNPs (FA-HCPT-CSNPs) reveal that the amount of folate conjugation was 197.64 mg/g CS. FA-HCPT-CSNPs used in drug carrier systems could have potential value in HCPT-sensitive tumors.

  1. Quantized friction across ionic liquid thin films.

    PubMed

    Smith, Alexander M; Lovelock, Kevin R J; Gosvami, Nitya Nand; Welton, Tom; Perkin, Susan

    2013-10-01

    Ionic liquids - salts in the liquid state under ambient conditions - are of great interest as precision lubricants. Ionic liquids form layered structures at surfaces, yet it is not clear how this nano-structure relates to their lubrication properties. We measured the friction force between atomically smooth solid surfaces across ionic liquid films of controlled thickness in terms of the number of ion layers. Multiple friction-load regimes emerge, each corresponding to a different number of ion layers in the film. In contrast to molecular liquids, the friction coefficients differ for each layer due to their varying composition. PMID:23942943

  2. Acidic Ionic Liquids.

    PubMed

    Amarasekara, Ananda S

    2016-05-25

    Ionic liquid with acidic properties is an important branch in the wide ionic liquid field and the aim of this article is to cover all aspects of these acidic ionic liquids, especially focusing on the developments in the last four years. The structural diversity and synthesis of acidic ionic liquids are discussed in the introduction sections of this review. In addition, an unambiguous classification system for various types of acidic ionic liquids is presented in the introduction. The physical properties including acidity, thermo-physical properties, ionic conductivity, spectroscopy, and computational studies on acidic ionic liquids are covered in the next sections. The final section provides a comprehensive review on applications of acidic ionic liquids in a wide array of fields including catalysis, CO2 fixation, ionogel, electrolyte, fuel-cell, membrane, biomass processing, biodiesel synthesis, desulfurization of gasoline/diesel, metal processing, and metal electrodeposition. PMID:27175515

  3. The effect of ionic strength on the adsorption of H{sup +}, Cd{sup 2+}, Pb{sup 2+}, and Cu{sup 2+} by Bacillus subtilis and Bacillus licheniformis: A surface complexation model

    SciTech Connect

    Daughney, C.J.; Fein, J.B.

    1998-02-01

    To quantify metal adsorption onto bacterial surfaces, recent studies have applied surface complexation theory to model the specific chemical and electrostatic interactions occurring at the solution-cell wall interface. However, to date, the effect of ionic strength on these interactions has not been investigated. In this study, the authors perform acid-base titrations of suspensions containing Bacillus subtilis or Bacillus licheniformis in 0.01 or 0.1 M NaNO{sub 3}, and they evaluate the constant capacitance and basic Stern double-layer models for their ability to describe ionic-strength-dependent behavior. The constant capacitance model provides the best description of the experimental data. The constant capacitance model parameters vary between independently grown bacterial cultures, possibly due to cell wall variation arising from genetic exchange during reproduction. The authors perform metal-B. subtilis and metal-B. licheniformis adsorption experiments using Cd, Pb, and Cu, and they solve for stability constants describing metal adsorption onto distinct functional groups on the bacterial cell walls. They find that these stability constants vary substantially but systematically between the two bacterial species at the two different ionic strengths.

  4. Wettability by Ionic Liquids.

    PubMed

    Liu, Hongliang; Jiang, Lei

    2016-01-01

    Ionic liquids (ILs) have become particularly attractive recently because they have demonstrated themselves to be important construction units in the broad fields of chemistry and materials science, from catalysis and synthesis to analysis and electrochemistry, from functional fluids to clean energy, from nanotechnology to functional materials. One of the greatest issues that determines the performance of ILs is the wettability of correlated surfaces. In this concept article, the key developments and issues in IL wettability are surveyed, including the electrowetting of ILs in gas-liquid-solid systems and liquid-liquid-solid systems, ILs as useful probe fluids, the superwettability of Ils, and future directions in IL wettability. This should generate extensive interest in the field and encourage more scientists to engage in this area to tackle its scientific challenges. PMID:26619157

  5. Understanding global cycling of atmosphere-surface exchangeable pollutants and its implications

    NASA Astrophysics Data System (ADS)

    Selin, N. E.; Giang, A.; Song, S.; Pike-thackray, C.; Friedman, C. L.

    2014-12-01

    We combine modeling approaches with data analysis to provide quantitative constraints on the global biogeochemical cycling of pollutants such as mercury (Hg) and persistent organic pollutants (POPs). These pollutants, released by human activities, continue to cycle between land, ocean, and atmosphere surfaces, extending their effective lifetimes in the environment. Measurement data are limited for all of these substances, providing few constraints on the magnitude of surface-atmosphere fluxes and thus the timescales of their cycling. This limits our ability to trace emissions to impacts for these substances, particularly in the context of both ongoing policies and climate change. We present a suite of modeling and analysis tools, including uncertainty analysis, that can provide quantitative constraints on cycling for these data-limited problems, and we illustrate their applicability through examples of Hg and selected POPs. Specifically, we summarize recent insights from inverse modeling of mercury, polynomial chaos-based methods for PAHs. Finally, we assess how uncertainty in timescales affects the entire emissions-to-impacts pathway for atmosphere-surface exchangeable pollutants. We discuss the implications of this analysis for policies under the Stockholm and Minamata Conventions.

  6. Facet personality and surface-level diversity as team mental model antecedents: implications for implicit coordination.

    PubMed

    Fisher, David M; Bell, Suzanne T; Dierdorff, Erich C; Belohlav, James A

    2012-07-01

    Team mental models (TMMs) have received much attention as important drivers of effective team processes and performance. Less is known about the factors that give rise to these shared cognitive structures. We examined potential antecedents of TMMs, with a specific focus on team composition variables, including various facets of personality and surface-level diversity. Further, we examined implicit coordination as an important outcome of TMMs. Results suggest that team composition in terms of the cooperation facet of agreeableness and racial diversity were significantly related to team-focused TMM similarity. TMM similarity was also positively predictive of implicit coordination, which mediated the relationship between TMM similarity and team performance. Post hoc analyses revealed a significant interaction between the trust facet of agreeableness and racial diversity in predicting TMM similarity. Results are discussed in terms of facilitating the emergence of TMMs and corresponding implications for team-related human resource practices. PMID:22468847

  7. Surface-enhanced Raman spectroscopy at single-molecule scale and its implications in biology.

    PubMed

    Wang, Yuling; Irudayaraj, Joseph

    2013-02-01

    Single-molecule (SM) spectroscopy has been an exciting area of research offering significant promise and hope in the field of sensor development to detect targets at ultra-low levels down to SM resolution. To the experts and developers in the field of surface-enhanced Raman spectroscopy (SERS), this has often been a challenge and a significant opportunity for exploration. Needless to say, the opportunities and excitement of this multidisciplinary area impacts span the fields of physics, chemistry and engineering, along with a significant thrust in applications constituting areas in medicine, biology, environment and agriculture among others. In this review, we will attempt to provide a quick snapshot of the basics of SM-SERS, nanostructures and devices that can enable SM Raman measurement. We will conclude with a discussion on SERS implications in biomedical sciences. PMID:23267180

  8. New and revised 14C dates for Hawaiian surface lava flows: Paleomagnetic and geomagnetic implications

    USGS Publications Warehouse

    Pressline, N.; Trusdell, F.A.; Gubbins, David

    2009-01-01

    Radiocarbon dates have been obtained for 30 charcoal samples corresponding to 27 surface lava flows from the Mauna Loa and Kilauea volcanoes on the Island of Hawaii. The submitted charcoal was a mixture of fresh and archived material. Preparation and analysis was undertaken at the NERC Radiocarbon Laboratory in Glasgow, Scotland, and the associated SUERC Accelerator Mass Spectrometry facility. The resulting dates range from 390 years B.P. to 12,910 years B.P. with corresponding error bars an order of magnitude smaller than previously obtained using the gas-counting method. The new and revised 14C data set can aid hazard and risk assessment on the island. The data presented here also have implications for geomagnetic modelling, which at present is limited by large dating errors. Copyright 2009 by the American Geophysical Union.

  9. Surface-enhanced Raman spectroscopy at single-molecule scale and its implications in biology

    PubMed Central

    Wang, Yuling; Irudayaraj, Joseph

    2013-01-01

    Single-molecule (SM) spectroscopy has been an exciting area of research offering significant promise and hope in the field of sensor development to detect targets at ultra-low levels down to SM resolution. To the experts and developers in the field of surface-enhanced Raman spectroscopy (SERS), this has often been a challenge and a significant opportunity for exploration. Needless to say, the opportunities and excitement of this multidisciplinary area impacts span the fields of physics, chemistry and engineering, along with a significant thrust in applications constituting areas in medicine, biology, environment and agriculture among others. In this review, we will attempt to provide a quick snapshot of the basics of SM-SERS, nanostructures and devices that can enable SM Raman measurement. We will conclude with a discussion on SERS implications in biomedical sciences. PMID:23267180

  10. Ionic liquid lubrication at electrified interfaces

    NASA Astrophysics Data System (ADS)

    Kong, Lingling; Huang, Wei; Wang, Xiaolei

    2016-06-01

    The lubrication performances of ionic liquids at electrified interfaces have been investigated by using a reciprocating sliding tribometer. Experimental results indicated that the lubricity of the confined ionic liquids was markedly affected by the application of external electric field and strong interface electric field strength could result in high friction. The influence was more pronounced for the ionic liquid with a shorter alkyl side chain in particular. The main reason of the friction increment might be ascribed to the electrically influenced surface adsorption where the charged ions were structured to form robust and ordered layers.

  11. Asteroid Compositions and Surface Processes: Some Possible New Implications from Meteorite Studies

    NASA Astrophysics Data System (ADS)

    Sears, D. W. G.; Akridge, G. D.

    1997-07-01

    We have been exploring the idea that chondrules and chondrites formed in the regolith of asteroid-sized bodies made dynamic by the passage of gases from the interior. Such a process explains better than current ideas two of the chief properties of meteorites, their small deviations from solar Fe/Si and the abundance of chondrules. Variations in Fe/Si arise as a result of the separation of metal and silicates as gravity and aerodynamic drag sort the components by size and mass. Impact into a losely consolidated surface, new developments in chondrule chronology and regolith evolution, make the formation of chondrules by impact seem more viable than once thought. These ideas not only offer a new scenario for chondrite formation, but they have implications for asteroid studies. The proposed process is probably fairly rare, as it requires enough heat to dehydrate and mobilize the surface, but not enough to melt. Thus ordinary chondrites (i.e., unmelted dry surface) are probably rare and most asteroids are either igneous (i.e., once partially or fully melted) or CI/CM like (i.e., water-rich). Asteroid reflectance spectra, meteorite cosmic ray exposure ages, and induced thermoluminescence data for H chondrites, suggest that ordinary chondrites are coming from a very limited number of parent asteroids, such as 6 Hebe in the case of the H chondrites. Ordinary chondrites are overrepresented among terrestrial falls because only objects near resonances can send meteorites to Earth and because the earth's atmosphere screens all but the toughest meteorites. If these ideas have any merit, then there is no need to invoke space weathering or other devices to explain why asteroid surface compositions are so unlike the compositions of the major meteorite classes.

  12. Tidal Distortion of Titan: Implications for Surface Features and Tidal Measurements

    NASA Astrophysics Data System (ADS)

    Sohl, F.; Hussmann, H.; Coustenis, A.; Knapmeyer, M.; Lange, C.; Solomonidou, A.; Stephan, K.; Wagner, F. W.

    2012-04-01

    Titan is unique due to its similarity to the Earth and terrestrial planets in spite of the satellite's ice-rich bulk composition. Gravitational field data acquired by the Cassini spacecraft suggest that Titan's interior is composed of a mixture of rock and ice and is only partly differentiated. Titan is tidally locked with respect to Saturn and thereby subject to periodic tidal forcing of its interior and surface. Based on interior structure models and assumptions on rheological properties of planetary materials (i.e. ice, rock, water-ammonia ocean), we compute the elastic body tide Love numbers h2, k2, and l2 in order to describe Titan's tidal response. Key parameters, e.g., tidally-induced changes of local gravity, tilt relative to the direction of gravity, and areal strain are then given by linear combinations of h2, k2, and l2. We find peak-to-peak amplitudes of tidally-induced surface displacement and tilt variation on the order of up to a few tens of metres and a few arc seconds, respectively. Based on the obtained variations of tidal parameters, we will address possible implications for morphotectonic surface features and compositional heterogeneity on Titan. In addition, we will address possible measurements of global tidal distortion by using a network of several small landed stations. Each of those would have to carry an instrument suite to monitor tidally-induced changes of local gravity, tilt relative to the direction of gravity, and areal strain at the surface of Titan. Furthermore, tidal stresses are expected to induce significant seismic activity comparable to tidally-induced quakes on the Moon, and possibly along with seismicity induced by localized cryovolcanic activity.

  13. Long tails in regional surface temperature probability distributions with implications for extremes under global warming

    NASA Astrophysics Data System (ADS)

    Ruff, Tyler W.; Neelin, J. David

    2012-02-01

    Prior work has shown that probability distributions of column water vapor and several passive tropospheric chemical tracers exhibit longer-than-Gaussian (approximately exponential) tails. The tracer-advection prototypes explaining the formation of these long-tailed distributions motivate exploration of observed surface temperature distributions for non-Gaussian tails. Stations with long records in various climate regimes in National Climatic Data Center Global Surface Summary of Day observations are used to examine tail characteristics for daily average, maximum and minimum surface temperature probability distributions. Each is examined for departures from a Gaussian fit to the core (here approximated as the portion of the distribution exceeding 30% of the maximum). While the core conforms to Gaussian for most distributions, roughly half the cases exhibit non-Gaussian tails in both winter and summer seasons. Most of these are asymmetric, with a long, roughly exponential, tail on only one side. The shape of the tail has substantial implications for potential changes in extreme event occurrences under global warming. Here the change in the probability of exceeding a given threshold temperature is quantified in the simplest case of a shift in the present-day observed distribution. Surface temperature distributions with long tails have a much smaller change in threshold exceedances (smaller increases for high-side and smaller decreases for low-side exceedances relative to exceedances in current climate) under a given warming than do near-Gaussian distributions. This implies that models used to estimate changes in extreme event occurrences due to global warming should be verified regionally for accuracy of simulations of probability distribution tails.

  14. High-Surface-Area CO2 Sponge: High Performance CO2 Scrubbing Based on Hollow Fiber-Supported Designer Ionic Liquid Sponges

    SciTech Connect

    2010-09-01

    IMPACCT Project: The team from ORNL and Georgia Tech is developing a new technology that will act like a sponge, integrating a new, alcohol-based ionic liquid into hollow fibers (magnified image, right) to capture CO2 from the exhaust produced by coal-fired power plants. Ionic liquids, or salts that exist in liquid form, are promising materials for carbon capture and storage, but their tendency to thicken when combined with CO2 limits their efficiency and poses a challenge for their development as a cost-effective alternative to current-generation solutions. Adding alcohol to the mix limits this tendency to thicken in the presence of CO2 but can also make the liquid more likely to evaporate, which would add significantly to the cost of CO2 capture. To solve this problem, ORNL is developing new classes of ionic liquids with high capacity for absorbing CO2. ORNL’s sponge would reduce the cost associated with the energy that would need to be diverted from power plants to capture CO2 and release it for storage.

  15. Adsorption of CO on oxide and water ice surfaces - Implications for the Martian atmosphere

    NASA Technical Reports Server (NTRS)

    Leu, M.-T.; Blamont, J. E.; Anbar, A. D.; Keyser, L. F.; Sander, S. P.

    1992-01-01

    The adsorption of carbon monoxide (CO) on water ice and on the oxides Fe2O3, Fe3O4, Al2O3, SiO2, CaO, MgO, and TiO2 (rutile and anatase) has been investigated in a flow reactor. A mass spectrometer was employed as a detector to monitor the temporal concentrations of CO. Adsorption coefficients as large as 1 x 10 exp -4 were measured for CO on TiO2 solids in helium at 196 K. The fractional surface coverage for CO on TiO2 solids in helium was also determined to be approximately 10 percent at 196 K. The upper limits of the fractional surface coverage for the other oxides (Fe2O3, Fe3O4, Al2O3, SiO2, CaO, and MgO) and water ice were also measured to be less than 1 percent. The implications for the stability of CO2 in the Martian atmosphere and the 'CO hole' observed by the Phobos/ISM experiment are discussed.

  16. Fundamental studies of the chemisorption of organosulfur compounds on Au(111). Implications for molecular self-assembly on gold surfaces

    SciTech Connect

    Nuzzo, R.G.; Zegarski, B.R.; Dubois, L.H.

    1987-02-04

    Studies of the adsorption of methanethiol and dimethyl disulfide on an Au(111) surface under UHV conditions are described. Both adsorbates bind strongly, with the bonding of the disulfide being greatly favored. It is found that, under these conditions, the disulfide bond is dissociated to give a stable surface thiolate. Adsorption of methanethiol does not involve cleavage of the S-H bond. The implications of these results for solution adsorption experiments and the thermodynamics characterizing monolayer formation are discussed.

  17. Unravelling the secrets of Cs controlled secondary ion formation: Evidence of the dominance of site specific surface chemistry, alloying and ionic bonding

    NASA Astrophysics Data System (ADS)

    Wittmaack, Klaus

    2013-03-01

    implantation can be evaluated as a function of Cs coverage.The summarised results imply that secondary ions are commonly not formed by charge transfer between an escaping atom and the electronic system of the sample but are already emitted as ions. The probability of ion formation appears to be controlled by the local ionic character of the alkali-target atom bonds, i.e., by the difference in electronegativity between the involved elements as well as by the electron affinity and the ionisation potential of the departing atom. This idea is supported by the finding that Si- yields exhibit the same very strong dependence on Cs coverage as Si+ and O- yields on the oxygen fraction in oxygen loaded Si. Most challenging to theoreticians is the finding that the ionisation probability is independent of the emission velocity of sputtered ions. This phenomenon cannot be rationalised along established routes of thinking. Different concepts need to be explored. An old, somewhat exotic idea takes account of the heavy perturbation created for a very short period of time at the site of ion emission (dynamic randomisation). Molecular dynamics simulations are desirable to clarify the issue. Ultimately it may be possible to describe all phenomena of enhanced or suppressed secondary ion formation, produced either by surface loading with alkali atoms or by enforced surface oxidation, on the basis of a single universal model. There is plenty of room for exciting new studies.

  18. Unravelling the secrets of Cs controlled secondary ion formation: Evidence of the dominance of site specific surface chemistry, alloying and ionic bonding

    NASA Astrophysics Data System (ADS)

    Wittmaack, Klaus

    2013-03-01

    implantation can be evaluated as a function of Cs coverage. The summarised results imply that secondary ions are commonly not formed by charge transfer between an escaping atom and the electronic system of the sample but are already emitted as ions. The probability of ion formation appears to be controlled by the local ionic character of the alkali-target atom bonds, i.e., by the difference in electronegativity between the involved elements as well as by the electron affinity and the ionisation potential of the departing atom. This idea is supported by the finding that Si- yields exhibit the same very strong dependence on Cs coverage as Si+ and O- yields on the oxygen fraction in oxygen loaded Si. Most challenging to theoreticians is the finding that the ionisation probability is independent of the emission velocity of sputtered ions. This phenomenon cannot be rationalised along established routes of thinking. Different concepts need to be explored. An old, somewhat exotic idea takes account of the heavy perturbation created for a very short period of time at the site of ion emission (dynamic randomisation). Molecular dynamics simulations are desirable to clarify the issue. Ultimately it may be possible to describe all phenomena of enhanced or suppressed secondary ion formation, produced either by surface loading with alkali atoms or by enforced surface oxidation, on the basis of a single universal model. There is plenty of room for exciting new studies.

  19. Noble metal ionic catalysts.

    PubMed

    Hegde, M S; Madras, Giridhar; Patil, K C

    2009-06-16

    Because of growing environmental concerns and increasingly stringent regulations governing auto emissions, new more efficient exhaust catalysts are needed to reduce the amount of pollutants released from internal combustion engines. To accomplish this goal, the major pollutants in exhaust-CO, NO(x), and unburned hydrocarbons-need to be fully converted to CO(2), N(2), and H(2)O. Most exhaust catalysts contain nanocrystalline noble metals (Pt, Pd, Rh) dispersed on oxide supports such as Al(2)O(3) or SiO(2) promoted by CeO(2). However, in conventional catalysts, only the surface atoms of the noble metal particles serve as adsorption sites, and even in 4-6 nm metal particles, only 1/4 to 1/5 of the total noble metal atoms are utilized for catalytic conversion. The complete dispersion of noble metals can be achieved only as ions within an oxide support. In this Account, we describe a novel solution to this dispersion problem: a new solution combustion method for synthesizing dispersed noble metal ionic catalysts. We have synthesized nanocrystalline, single-phase Ce(1-x)M(x)O(2-delta) and Ce(1-x-y)Ti(y)M(x)O(2-delta) (M = Pt, Pd, Rh; x = 0.01-0.02, delta approximately x, y = 0.15-0.25) oxides in fluorite structure. In these oxide catalysts, Pt(2+), Pd(2+), or Rh(3+) ions are substituted only to the extent of 1-2% of Ce(4+) ion. Lower-valent noble metal ion substitution in CeO(2) creates oxygen vacancies. Reducing molecules (CO, H(2), NH(3)) are adsorbed onto electron-deficient noble metal ions, while oxidizing (O(2), NO) molecules are absorbed onto electron-rich oxide ion vacancy sites. The rates of CO and hydrocarbon oxidation and NO(x) reduction (with >80% N(2) selectivity) are 15-30 times higher in the presence of these ionic catalysts than when the same amount of noble metal loaded on an oxide support is used. Catalysts with palladium ion dispersed in CeO(2) or Ce(1-x)Ti(x)O(2) were far superior to Pt or Rh ionic catalysts. Therefore, we have demonstrated that the

  20. Ab initio study of EMIM-BF4 crystal interaction with a Li (100) surface as a model for ionic liquid/Li interfaces in Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Valencia, Hubert; Kohyama, Masanori; Tanaka, Shingo; Matsumoto, Hajime

    2009-12-01

    We examined the atomic and electronic structures of an interface between a 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMIM-BF4) ionic-liquid crystal and a Li(100) surface by periodic density-functional calculations, as a model for a room-temperature ionic-liquid (RTIL) electrolyte/Li interface at a Li-ion battery electrode. Results are compared with our previous theoretical study of the EMIM-BF4 molecular adsorption on Li surfaces [H. Valencia et al., Phys. Rev. B 78, 205402 (2008)]. For the EMIM-BF4 crystal structure, the present projector augmented wave scheme with the generalized gradient approximation can reproduce rather correct intramolecular structures as well as satisfactory short-ranged intermolecular distances, while long-range intermolecular distances are overestimated due to the lack of correct description of long-range dispersive interactions. We constructed a coherent crystal/crystal interface model where four EMIM-BF4 pairs are stacked on a p(4×3) Li (100) surface cell so as to simulate RTIL-layer deposition on a Li surface. We observed significant attraction of surface Li ions toward contacting BF4- anions, counterbalanced by electron transfer toward EMIM+ cations near the interface, revealing the tendency of easy ionization of Li and Lix-BF4 cluster formation, coupled with the reduction of EMIM+. These features are similar to those observed in the EMIM-BF4 molecular adsorption, while these have been proved to occur in the crystal-layer adsorption. We examined the adhesive energy, wetability, and detailed electronic structure at the crystal/crystal interface.

  1. Stability of Ionic Colloidal Crystals (ICCs)

    NASA Astrophysics Data System (ADS)

    Maskaly, Garry R.; Garcia, R. Edwin; Carter, W. Craig; Chiang, Yet-Ming

    2003-03-01

    Ionic colloidal crystals (ICCs) are here defined as ordered multicomponent colloids formed by attractive electrostatic interactions. Compared to previous approaches to colloidal crystallization, the ICC approach holds the potential for self-assembly of a wide range of structures not easily accessible by other methods. In this work, the colloid-chemical conditions under which ICCs are stable have been theoretically analyzed. A model is presented in which two dimensionless parameters are found to fully characterize an ICC system. We calculate the Madelung constant for ICCs of several classical ionic crystal structures as a function of these two parameters, and discuss the parallels between the ICC Madelung constants and the classical ionic case. Experimentally accessible regions of surface charge, particle sizes, salt concentration, and temperature where ionic colloidal crystallization should be possible are identified.

  2. Quantized ionic conductance in nanopores

    SciTech Connect

    Zwolak, Michael; Lagerqvist, Johan; Di Ventra, Massimilliano

    2009-01-01

    Ionic transport in nanopores is a fundamentally and technologically important problem in view of its ubiquitous occurrence in biological processes and its impact on DNA sequencing applications. Using microscopic calculations, we show that ion transport may exhibit strong non-liDearities as a function of the pore radius reminiscent of the conductance quantization steps as a function of the transverse cross section of quantum point contacts. In the present case, however, conductance steps originate from the break up of the hydration layers that form around ions in aqueous solution. Once in the pore, the water molecules form wavelike structures due to multiple scattering at the surface of the pore walls and interference with the radial waves around the ion. We discuss these effects as well as the conditions under which the step-like features in the ionic conductance should be experimentally observable.

  3. The effects of steam on the surface properties of palygorskite: Implications for palygorskite-water interactions

    NASA Astrophysics Data System (ADS)

    Kadakia, Abhy

    decreased by 40-50% after steam treatment. The reduced affinity for water and EGME may represent a reduced affinity for polar molecules in general. These results, particularly the XPS spectra and the observed large changes in rheological properties, suggest that steam altered the H + ion environment and/or concentration on palygorskite's surface. Exposing palygorskite to steam may have significant implications for its industrial applications, adversely affecting some applications and enhancing others.

  4. The flexible structure of the K24S28 region of Leucine-Rich Amelogenin Protein (LRAP) bound to apatites as a function of surface type, calcium, mutation, and ionic strength

    SciTech Connect

    Lu, Junxia; Burton, Sarah D.; Xu, Yimin; Buchko, Garry W.; Shaw, Wendy J.

    2014-07-11

    Leucine-Rich Amelogenin Protein (LRAP) is a member of the amelogenin family of biomineralization proteins, proteins which play a critical role in enamel formation. Recent studies have revealed the structure and orientation of the N- and C-terminus of LRAP bound to hydroxyapatite (HAP), a surface used as an analog of enamel. The structure of one region, K24 to S28, was found to be sensitive to phosphorylation of S16, the only naturally observed site of serine phosphorylation in LRAP, suggesting that the residues from K24 to S28 may sit at a key region of structural flexibility and play a role in the protein’s function. In this work, we investigated the sensitivity of the structure and orientation of this region when bound to HAP as a function of several factors which may vary during enamel formation to influence structure: the ionic strength (0.05 M, 0.15 M, 0.2 M), the calcium concentration (0.07 mM and 0.4 mM), and the surface to which it is binding (HAP and carbonated apatite (CAP), a more direct mimic of enamel). A naturally occurring mutation found in amelogenin (T21I), was also investigated. The structure in the K24S28 region of the protein was found to be sensitive to these conditions, with the CAP surface and excess Ca2+ (8:1 [Ca2+]:[LRAP-K24S28(+P)]) resulting in a much tighter helix, while low ionic strength relaxed the helical structure. Higher ionic strength and the point mutation did not result in any structural change in this region. The distance of the backbone of K24 from the surface was most sensitive to excess Ca2+ and in the T21I-mutation. Collectively, these data suggest that the protein is able to accommodate structural changes while maintaining its interaction with the surface, and provides further evidence of the structural sensitivity of the K24 to S28 region, a sensitivity that may contribute to function in biomineralization. This research was supported by NIH-NIDCR Grant DE-015347. The research was performed at the Pacific Northwest

  5. The flexible structure of the K24S28 region of Leucine-Rich Amelogenin Protein (LRAP) bound to apatites as a function of surface type, calcium, mutation, and ionic strength

    PubMed Central

    Lu, Jun-xia; Burton, Sarah D.; Xu, Yimin S.; Buchko, Garry W.; Shaw, Wendy J.

    2014-01-01

    Leucine-Rich Amelogenin Protein (LRAP) is a member of the amelogenin family of biomineralization proteins, proteins which play a critical role in enamel formation. Recent studies have revealed the structure and orientation of the N- and C-terminus of LRAP bound to hydroxyapatite (HAP), a surface used as an analog of enamel. The structure of one region, K24 to S28, was found to be sensitive to phosphorylation of S16, the only naturally observed site of serine phosphorylation in LRAP, suggesting that K24S28 may sit at a key region of structural flexibility and play a role in the protein's function. In this work, we investigated the sensitivity of the structure and orientation of this region when bound to HAP as a function of several factors which may vary during enamel formation to influence structure: the ionic strength (0.05, 0.15, 0.2 M), the calcium concentration (0.07 and 0.4 mM), and the surface to which it is binding [HAP and carbonated apatite (CAP), a more direct mimic of enamel]. A naturally occurring mutation found in amelogenin (T21I) was also investigated. The structure in the K24S28 region of the protein was found to be sensitive to these conditions, with the CAP surface and excess Ca2+ (8:1 [Ca2+]:[LRAP-K24S28(+P)]) resulting in a tighter helix, while low ionic strength relaxed the helical structure. Higher ionic strength and the point mutation did not result in any structural change in this region. The distance of the backbone of K24 from the surface was most sensitive to excess Ca2+ and in the T21I-mutation. Collectively, these data suggest that phosphorylated LRAP is able to accommodate structural changes while maintaining its interaction with the surface, and provides further evidence of the structural sensitivity of the K24S28 region, a sensitivity that may contribute to function in biomineralization. PMID:25071599

  6. Ionic liquids behave as dilute electrolyte solutions

    PubMed Central

    Gebbie, Matthew A.; Valtiner, Markus; Banquy, Xavier; Fox, Eric T.; Henderson, Wesley A.; Israelachvili, Jacob N.

    2013-01-01

    We combine direct surface force measurements with thermodynamic arguments to demonstrate that pure ionic liquids are expected to behave as dilute weak electrolyte solutions, with typical effective dissociated ion concentrations of less than 0.1% at room temperature. We performed equilibrium force–distance measurements across the common ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]) using a surface forces apparatus with in situ electrochemical control and quantitatively modeled these measurements using the van der Waals and electrostatic double-layer forces of the Derjaguin–Landau–Verwey–Overbeek theory with an additive repulsive steric (entropic) ion–surface binding force. Our results indicate that ionic liquids screen charged surfaces through the formation of both bound (Stern) and diffuse electric double layers, where the diffuse double layer is comprised of effectively dissociated ionic liquid ions. Additionally, we used the energetics of thermally dissociating ions in a dielectric medium to quantitatively predict the equilibrium for the effective dissociation reaction of [C4mim][NTf2] ions, in excellent agreement with the measured Debye length. Our results clearly demonstrate that, outside of the bound double layer, most of the ions in [C4mim][NTf2] are not effectively dissociated and thus do not contribute to electrostatic screening. We also provide a general, molecular-scale framework for designing ionic liquids with significantly increased dissociated charge densities via judiciously balancing ion pair interactions with bulk dielectric properties. Our results clear up several inconsistencies that have hampered scientific progress in this important area and guide the rational design of unique, high–free-ion density ionic liquids and ionic liquid blends. PMID:23716690

  7. Surface wind variability and its implications for the Yucatan basin-Caribbean Sea dynamics

    NASA Astrophysics Data System (ADS)

    PéRez-Santos, IváN.; Schneider, Wolfgang; Sobarzo, Marcus; Montoya-SáNchez, Raúl; Valle-Levinson, Arnoldo; GarcéS-Vargas, José

    2010-10-01

    Sea surface wind data from the QuikSCAT satellite and two meteorological stations collected over 1 decade (1999-2008) were used to study the dominant time scales of the wind regime in the Yucatan basin. Wind data were used to quantify its implications on regional hydrodynamics by evaluating Ekman pumping and Ekman transport. The annual cycle of surface wind revealed different features than the Caribbean wind regime with a relative wind stress maximum observed in the Yucatan basin in June caused by the Caribbean low-level jet. The strongest wind stress occurred during November presumably due to the collapse of the Atlantic warm pool. This feature provides new evidence of the importance of local atmosphere-ocean coupling. Synoptic scale variability was detected during fall and winter, leaving spring and summer almost free from these activities. Empirical orthogonal functions revealed three dominant time scales of variability: an annual scale in mode 1 (46.3% of the total variance), a synoptic scale in mode 2 (27.7%), and a semiannual scale in mode 3 (6.4%). The third mode featured extreme pulses (six tropical storms and nine hurricanes). Ekman transport was found to contribute the most (93%) to total transport, whereas Ekman pumping contributed only 7%. However, upwelling induced by Ekman pumping persisted during some synoptic pulses, underscoring the importance of tropical storms and hurricanes. Offshore Ekman transport over the continental shelf north of the Yucatan Peninsula favored upwelling all year long. Onshore transport toward the coasts of southern Cuba and the eastern Yucatan Peninsula favored downwelling.

  8. Diverse policy implications for future ozone and surface UV in a changing climate

    NASA Astrophysics Data System (ADS)

    Butler, A. H.; Daniel, J. S.; Portmann, R. W.; Ravishankara, A. R.; Young, P. J.; Fahey, D. W.; Rosenlof, K. H.

    2016-06-01

    Due to the success of the Montreal Protocol in limiting emissions of ozone-depleting substances, concentrations of atmospheric carbon dioxide, nitrous oxide, and methane will control the evolution of total column and stratospheric ozone by the latter half of the 21st century. As the world proceeds down the path of reducing climate forcing set forth by the 2015 Conference of the Parties to the United Nations Framework Convention on Climate Change (COP 21), a broad range of ozone changes are possible depending on future policies enacted. While decreases in tropical stratospheric ozone will likely persist regardless of the future emissions scenario, extratropical ozone could either remain weakly depleted or even increase well above historical levels, with diverse implication for ultraviolet (UV) radiation. The ozone layer’s dependence on future emissions of these gases creates a complex policy decision space for protecting humans and ecosystems, which includes unexpected options such as accepting nitrous oxide emissions in order to maintain historical column ozone and surface UV levels.

  9. Growth kinetics of step edges on celestite (0 0 1) surfaces as a function of temperature, saturation state, ionic strength, and aqueous strontium:sulfate ratio: An in-situ atomic force microscopy study

    NASA Astrophysics Data System (ADS)

    Bracco, Jacquelyn N.; Gooijer, Yiscka; Higgins, Steven R.

    2016-02-01

    Step velocities on the celestite (0 0 1) surface have been measured as a function of temperature (23-45 °C), saturation state (S = 1.1-2.2), ionic strength (I = 0.01, 0.06, and 0.1 M), and aqueous strontium:sulfate ratio (r = 0.01-100) using atomic force microscopy (AFM). Celestite growth hillocks were flanked by [0 1 0]-aligned step edges, which are polar, and step edges vicinal to <1 2 0>, which are non-polar. [0 1 0] step velocities increased with temperature and saturation state, however step velocities did not vary significantly with ionic strength. Step velocities were non-linear with saturation state, suggesting a change in mechanism at high S as compared with low S. At constant S, the step velocities were maximized at r = 1 and decreased significantly at extreme r, demonstrating the governing role of solute stoichiometry. We successfully fit the step velocity data as a function of r using the Stack and Grantham (2010) nucleation and propagation model. Based on the results as a function of ionic strength and r, the mechanism at low S is likely ion-by-ion attachment to the step with an activation energy of 75 (±10) kJ mol-1. At high S the mechanism is a combination of the one at low S and possibly attachment of a neutral species such as an ion pair with an activation energy of 43 (±9) kJ mol-1.

  10. Growth kinetics of step edges on celestite (0 0 1) surfaces as a function of temperature, saturation state, ionic strength, and aqueous strontium:sulface ratio: An in-situ atomic force microscopy study

    SciTech Connect

    Bracco, Jacquelyn N.; Gooijer, Yiscka; Higgins, Steven R.

    2015-12-12

    Step velocities on the celestite (0 0 1) surface have been measured as a function of temperature (23–45 °C), saturation state (S = 1.1–2.2), ionic strength (I = 0.01, 0.06, and 0.1 M), and aqueous strontium:sulfate ratio (r = 0.01–100) using atomic force microscopy (AFM). Celestite growth hillocks were flanked by [0 1 0]-aligned step edges, which are polar, and step edges vicinal to <1 2 0>, which are non-polar. [0 1 0] step velocities increased with temperature and saturation state, however step velocities did not vary significantly with ionic strength. Step velocities were non-linear with saturation state, suggesting a change in mechanism at high S as compared with low S. At constant S, the step velocities were maximized at r = 1 and decreased significantly at extreme r, demonstrating the governing role of solute stoichiometry. We successfully fit the step velocity data as a function of r using the Stack and Grantham (2010) nucleation and propagation model. Based on the results as a function of ionic strength and r, the mechanism at low S is likely ion-by-ion attachment to the step with an activation energy of 75 (±10) kJ mol–1. In conclusion, at high S the mechanism is a combination of the one at low S and possibly attachment of a neutral species such as an ion pair with an activation energy of 43 (±9) kJ mol–1.

  11. Growth kinetics of step edges on celestite (0 0 1) surfaces as a function of temperature, saturation state, ionic strength, and aqueous strontium:sulface ratio: An in-situ atomic force microscopy study

    DOE PAGESBeta

    Bracco, Jacquelyn N.; Gooijer, Yiscka; Higgins, Steven R.

    2015-12-12

    Step velocities on the celestite (0 0 1) surface have been measured as a function of temperature (23–45 °C), saturation state (S = 1.1–2.2), ionic strength (I = 0.01, 0.06, and 0.1 M), and aqueous strontium:sulfate ratio (r = 0.01–100) using atomic force microscopy (AFM). Celestite growth hillocks were flanked by [0 1 0]-aligned step edges, which are polar, and step edges vicinal to <1 2 0>, which are non-polar. [0 1 0] step velocities increased with temperature and saturation state, however step velocities did not vary significantly with ionic strength. Step velocities were non-linear with saturation state, suggesting amore » change in mechanism at high S as compared with low S. At constant S, the step velocities were maximized at r = 1 and decreased significantly at extreme r, demonstrating the governing role of solute stoichiometry. We successfully fit the step velocity data as a function of r using the Stack and Grantham (2010) nucleation and propagation model. Based on the results as a function of ionic strength and r, the mechanism at low S is likely ion-by-ion attachment to the step with an activation energy of 75 (±10) kJ mol–1. In conclusion, at high S the mechanism is a combination of the one at low S and possibly attachment of a neutral species such as an ion pair with an activation energy of 43 (±9) kJ mol–1.« less

  12. Electron-transfer reactions of cobalt(III) complexes. 1. The kinetic investigation of the reduction of various surfactant cobalt(III) complexes by iron(II) in surface active ionic liquids

    NASA Astrophysics Data System (ADS)

    Nagaraj, Karuppiah; Senthil Murugan, Krishnan; Thangamuniyandi, Pilavadi; Sakthinathan, Subramanian

    2015-05-01

    The kinetics of outer sphere electron transfer reaction of surfactant cobalt(III) complex ions, cis-[Co(en)2(C12H25NH2)2]3+ (1), cis-[Co(dp)2(C12H25NH2)2]3+ (2), cis-[Co(trien)(C12H25NH2)2]3+ (3), cis-[Co(bpy)2(C12H25NH2)2]3+ (4) and cis-[Co(phen)2(C12H25NH2)2]3+ (5) (en: ethylenediamine, dp: diaminopropane, trien : triethylenetetramine, bpy: 2,2‧-bipyridyl, phen: 1,10-phenanthroline and C12H25NH2 : dodecylamine) have been interrogated by Fe2+ ion in ionic liquid (1-butyl-3-methylimidazoliumbromide) medium at different temperatures (298, 303, 308, 313, 318 and 323 K) by the spectrophotometry method under pseudo first order conditions using an excess of the reductant. Experimentally the reactions were found to be of second order and the electron transfer as outer sphere. The second order rate constant for the electron transfer reaction in ionic liquids was found to increase with increase in the concentration of all these surfactant cobalt(III) complexes. Among these complexes (from en to phen ligand), complex containing the phenanthroline ligand rate is higher compared to other complexes. By assuming the outer sphere mechanism, the results have been explained based on the presence of aggregated structures containing cobalt(III) complexes at the surface of ionic liquids formed by the surfactant cobalt(III) complexes in the reaction medium. The activation parameters (enthalpy of activation ΔH‡ and entropy of activation ΔS‡) of the reaction have been calculated which substantiate the kinetics of the reaction.

  13. Optimization of Ionic Liquid Based Simultaneous Ultrasonic- and Microwave-Assisted Extraction of Rutin and Quercetin from Leaves of Velvetleaf (Abutilon theophrasti) by Response Surface Methodology

    PubMed Central

    Zhao, Chunjian; Lu, Zhicheng; He, Xin; Li, Zhao; Shi, Kunming; Yang, Lei; Fu, Yujie; Zu, Yuangang

    2014-01-01

    An ionic liquids based simultaneous ultrasonic and microwave assisted extraction (ILs-UMAE) method has been proposed for the extraction of rutin (RU), quercetin (QU), from velvetleaf leaves. The influential parameters of the ILs-UMAE were optimized by the single factor and the central composite design (CCD) experiments. A 2.00 M 1-butyl-3-methylimidazolium bromide ([C4mim]Br) was used as the experimental ionic liquid, extraction temperature 60°C, extraction time 12 min, liquid-solid ratio 32 mL/g, microwave power of 534 W, and a fixed ultrasonic power of 50 W. Compared to conventional heating reflux extraction (HRE), the RU and QU extraction yields obtained by ILs-UMAE were, respectively, 5.49 mg/g and 0.27 mg/g, which increased, respectively, 2.01-fold and 2.34-fold with the recoveries that were in the range of 97.62–102.36% for RU and 97.33–102.21% for QU with RSDs lower than 3.2% under the optimized UMAE conditions. In addition, the shorter extraction time was used in ILs-UMAE, compared with HRE. Therefore, ILs-UMAE was a rapid and an efficient method for the extraction of RU and QU from the leaves of velvetleaf. PMID:25243207

  14. Widespread Surface Weathering on Early Mars: possible implication on the Past Climate

    NASA Astrophysics Data System (ADS)

    Loizeau, Damien; Carter, John; Mangold, Nicolas; Poulet, François; Rossi, Angelo P.; Allemand, Pascal; Lozac'h, Loïc; Quantin, Cathy; Bibring, Jean-Pierre

    2015-04-01

    The recent discovery of widespread hydrous clays on Mars with OMEGA/Mars Express and CRISM/MRO indicates that diverse and widespread aqueous environments existed on Mars, from the surface to kilometric depths [1, 2]. The study of the past habitability and past climates of the planet requires assessing the importance of sustained surface water vs. subsurface water in its aqueous history. Vertical sequences of Al-rich clays on top of Fe/Mg-rich clays in the top tens of meters of the surface are identified on Mars [3-6] (see figure 1) and interpreted as possible weathering profiles, similar to cases of pedogenesis on Earth (e.g. [7, 8]). A global study of these clay sequences has recently been published by Carter et al. [9]. This following work presents detailed geological analysis, performed for each identified candidate, in order to constrain their age and origin. With the increasing availability of CTX and HiRISE stereoimages, we investigate the thickness of the altered sequences, the age of the altered units and the different geological contexts to further understand the weathering process(es), and their possible implication on the past climate. The types of geologic settings where the interpreted weathering profiles are observed are much varied: from basin floor to plateaus, in apparent massive rocks to finely layered rocks. Besides, the number and variety of sequences is/was likely larger. However, in term of chronology, the alteration seems to have stopped in a relatively limited period of time for the studied cases, between 3.8 and 3.6 Ga. This would point to a formation due to a global process that enabled liquid water at the surface and pedogenesis in various regions, on various terrains, from late Noachian to early Hesperian. This global process would imply regular, widely distributed ice or precipitations in large regions of Mars at that time. If weathering occurred before that time, during the early or middle Noachian, the sequences may have been erased

  15. Estimating dermal transfer of copper particles from the surfaces of pressure-treated lumber and implications for exposure.

    PubMed

    Platten, William E; Sylvest, Nicholas; Warren, Casey; Arambewela, Mahendranath; Harmon, Steve; Bradham, Karen; Rogers, Kim; Thomas, Treye; Luxton, Todd Peter

    2016-04-01

    Lumber pressure-treated with micronized copper was examined for the release of copper and copper micro/nanoparticles using a surface wipe method to simulate dermal transfer. In 2003, the wood industry began replacing CCA treated lumber products for residential use with copper based formulations. Micronized copper (nano to micron sized particles) has become the preferred treatment formulation. There is a lack of information on the release of copper, the fate of the particles during dermal contact, and the copper exposure level to children from hand-to-mouth transfer. For the current study, three treated lumber products, two micronized copper and one ionic copper, were purchased from commercial retailers. The boards were left to weather outdoors for approximately 1year. Over the year time period, hand wipe samples were collected periodically to determine copper transfer from the wood surfaces. The two micronized formulations and the ionic formulation released similar levels of total copper. The amount of copper released was high initially, but decreased to a constant level (~1.5mgm(-2)) after the first month of outdoor exposure. Copper particles were identified on the sampling cloths during the first two months of the experiment, after which the levels of copper were insufficient to collect interpretable data. After 1month, the particles exhibited minimal changes in shape and size. At the end of 2-months, significant deterioration of the particles was evident. Based on the wipe sample data, a playground visit may result in a potential exposure to 2.58mg of copper, which is near or exceeds the daily tolerable upper intake limits for children under the age of 8, if completely ingested through hand-to-mouth transfer. While nanoparticles were found, there is not enough information to estimate the exposure from the released particles due to a lack of published literature on copper carbonate. PMID:26826852

  16. The Implications of the Moon-Forming Impact for Terrestrial Oxidation State and Surface Water Stability

    NASA Astrophysics Data System (ADS)

    Wade, J.; Wood, B. J.; van Hinsberg, V.

    2014-12-01

    The fraction of the Moon made from Earth at the time of the moon-forming impact and the amount of impactor it contains are major questions concerning the origin of the Earth-Moon system. Earth's mantle and the Moon are distinctive in their FeO contents and some trace element ratios (e.g. Nb/Ta) but identical in their isotopes of O, Si, W, Ti and Cr. The latter observation implies that they are made from exactly the same material but the former implies the opposite. Due to the pressure-dependence and redox-sensitive nature of W partitioning between metallic core and silicate mantle, the identical W isotopic ratios of both bodies is hard to reconcile. One possible solution is that the impactor and the proto-Earth were not only of similar composition but also essentially the same size - a rather unlikely coincidence. An alternative scenario which we have modeled chemically and isotopically is that the proto-Earth, with a higher mantle FeO content than present, was struck by an early-formed, highly-reduced impactor. The core of the impactor merged with that of Earth, as depicted in most simulations. The moon, containing a similar proportion of impactor material to that of the Earth (<15%), can be viewed as a 'snap-shot' of proto-Earth's mantle. This produced a Moon identical to the Earth's mantle in isotopic composition, but with elevated mantle Nb/Ta and FeO contents. Evidence of FeO-rich domains in Archaean mantle (Francis, Lithos v.71, 2003) would be consistent with an FeO-rich terrestrial protomantle. Changes in mantle FeO content have implications for the stability of liquid H2O at the surface. More FeO-rich mantles (e.g Mars) generate basalts which are more susceptible to serpentinisation and hence to the consumption of surface water. Thus we can argue that the impactor delivered volatiles to the Earth and the ability to retain water in surface reservoirs.

  17. Ionically-mediated electromechanical hysteresis in transition metal oxides

    SciTech Connect

    Kim, Yunseok; Kumar, Amit; Jesse, Stephen; Kalinin, Sergei V

    2012-01-01

    Electromechanical activity, remanent polarization states, and hysteresis loops in paraelectric TiO2 and SrTiO3 are observed. The coupling between the ionic dynamics and incipient ferroelectricity in these materials is analyzed using extended Ginsburg Landau Devonshire (GLD) theory. The possible origins of electromechanical coupling including ionic dynamics, surface-charge induced electrostriction, and ionically-induced ferroelectricity are identified. For the latter, the ionic contribution can change the sign of first order GLD expansion coefficient, rendering material effectively ferroelectric. These studies provide possible explanation for ferroelectric-like behavior in centrosymmetric transition metal oxides.

  18. Encapsulated ionic liquids (ENILs): from continuous to discrete liquid phase.

    PubMed

    Palomar, Jose; Lemus, Jesus; Alonso-Morales, Noelia; Bedia, Jorge; Gilarranz, Miguel A; Rodriguez, Juan J

    2012-10-14

    Encapsulated ionic liquid (ENIL) material was developed, consisting of ionic liquid (IL) introduced into carbon submicrocapsules. ENILs contain >85% w/w of IL but discretized in submicroscopic encapsulated drops, drastically increasing the surface contact area with respect to the neat fluid. ENIL materials were here tested for gas separation processes, obtaining a drastic increase in mass transfer rate. PMID:22935733

  19. Measured and modeled albedos of sea-ice surfaces with implications for Snowball Earth

    NASA Astrophysics Data System (ADS)

    Carns, Regina C.

    surface to emulate the light from an overcast sky. We created a crust of hydrohalite and used this "albedo dome" method to measure albedo of the crust as it developed and dissolved. Using these measurements along with a radiative transfer code, we inferred the complex refractive index for hydrohalite and developed a parameterization for the albedo of hydrohalite crusts of any thickness. These results have implications for Earthlike exoplanets with sizable oceans, which would also be susceptible to ice-albedo feedback. The formation of hydrohalite in sub-eutectic sea ice and the development of a lag deposit in cold, dry conditions could intensify the positive feedback that leads to Snowball conditions. This work shows that the albedo of hydrohalite is much higher than that of snow in the near-infrared, which could make the formation of hydrohalite crusts particularly important to the climates of planets that orbit M-dwarf stars, which output a large fraction of their energy in the near-infrared.

  20. The bounding-surfaces record of a barrier spit from Huangqihai Lake, North China: implications for coastal barrier boundary hierarchy

    NASA Astrophysics Data System (ADS)

    Shan, Xin; Yu, Xinghe; Clift, Peter D.; Wang, Tianyi; Tan, Chengpeng; Jin, Lina

    2016-09-01

    Ground-penetrating radar and trenching studies of a barrier spit on the north shore of Huangqihai Lake were made, that reveal important implications for the coastal washover barrier boundary hierarchy and interpretations of this depositional record. A four-fold hierarchy bounding-surface model, representing different levels of impact and genesis, is defined. Each level of the hierarchy is enclosed by a distinct kind of surface characterized by different ground-penetrating radar reflection features, sedimentary characteristics (color, grain size, sorting, rounding and sedimentary structures) and origin. We suggest that this hierarchical model can be applied to any coastal washover barrier deposits.

  1. Tuning Hydrated Nanoceria Surfaces: Experimental/Theoretical Investigations of Ion Exchange and Implications in Organic and Inorganic Interactions

    PubMed Central

    Vincent, Abhilash; Inerbaev, Talgat M.; Babu, Suresh; Karakoti, Ajay S.; Self, William T.; Masunov, Artëm E.; Seal, Sudipta

    2010-01-01

    Long term stability and surface properties of colloidal nanoparticles have significance in many applications. Here, surface charge modified hydrated cerium oxide nanoparticles (CNPs, also known as nanoceria) are synthesized and their dynamic ion exchange interactions with the surrounding medium are investigated in detail. Time dependent Zeta (ζ) potential (ZP) variations of CNPs are demonstrated as a useful characteristic for optimizing their surface properties. The surface charge reversal of CNPs observed with respect to time, concentration, temperature and doping is correlated to the surface modification of CNPs in aqueous solution and the ion exchange reaction between the surface protons (H+) and the neighboring hydroxyls ions (OH−). Using density functional theory (DFT) calculations, we have demonstrated that the adsorption of H+ ions on the CNP surface is kinetically more favorable while the adsorption of OH− ions on CNPs is thermodynamically more favorable. The importance of selecting CNPs with appropriate surface charges and the implications of dynamic surface charge variations are exemplified with applications in microelectronics and biomedical.\\ PMID:20131920

  2. Applications of ionic liquids.

    PubMed

    Patel, Divia Dinesh; Lee, Jong-Min

    2012-06-01

    Ionic liquids have recently gained popularity in the scientific community owing to their special properties and characteristics. One of the reasons why ionic liquids have been termed "green solvents" is due to their negligible vapour pressure. Their use in electrochemical, biological and metal extraction applications is discussed. Wide research has been carried out for their use in batteries, solar panels, fuel cells, drug deliveries and biomass pretreatments. This work aims to consolidate the various findings from previous works in these areas. PMID:22711528

  3. On the implications of the Surface Water and Ocean Topography (SWOT) mission for hydrologic science and applications (Invited)

    NASA Astrophysics Data System (ADS)

    Lettenmaier, D. P.

    2010-12-01

    The SWOT mission will provide surface water elevation and extent information with unprecedented accuracy and spatial resolution globally. All of the implications of thedata that SWOT will produce for the hydrologic science and applications communities are not yet apparent. The SWOT data will, however, certainly offer groundbreaking opportunities for estimation of two key terms in the land surface water budget: surface water storage (in almost all water bodies with surface area exceeding about 1 km2) and derived discharge for many of the world’s large rivers (widths greater than roughly 100-250 m). Among just a few of the science questions that the observations should allow us to address are a) what are the dynamics of floods and overbank flows in large rivers? b) what is the contribution of long-term, seasonal, and interannual storage in reservoirs, lakes, and wetlands to sea level? c) what is the magnitude of surface water storage changes at seasonal to decadal time scales and continental spatial scales relative to soil moisture and groundwater? d) what will be the implications of SWOT-based estimates of reservoir storage and storage change to the management of transboundary rivers? These quite likely are among just a few of the questions that SWOT will help elucidate. Others no doubt will arise from creative analyses of SWOT data in combination with data from other missions I conclude with a discussion of mechanisms that will help foster a community to investigate these and other questions, and the implications of a SWOT data policy.

  4. Ionic liquids as novel solvents for ionic polymer transducers

    NASA Astrophysics Data System (ADS)

    Bennett, Matthew D.; Leo, Donald J.

    2004-07-01

    The use of ionic liquids as solvents for ionic polymer (specifically, Nafion) transducers is demonstrated. Ionic liquids are attractive for this application because of their high inherent stability. Ionic liquids are salts that exist as liquids at room temperature and have no measureable vapor pressure. Therefore, the use of ionic liquids as solvents for ionic polymer transducers can eliminate the traditional problem of water evaporation in these devices. Another benefit of the use of ionic liquids in this way is the reduction or elimination of the characteristic back-relaxation common in water-solvated ionic polymer actuators. The results demonstrate that the viscosity of the ionic liquid and the degree to which the ionic liquid swells the membrane are the important physical parameters to consider. Five ionic liquids were studied, based on substituted pyrrolidinium, phosphonium, or imidazolium cations and fluoroanions. Of these five ionic liquids, transduction is demonstrated in three of them and the best results are obtained with 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid. This substance has an electrochemical stability window of 4.1 V, a melting point of -10 °C, and a viscosity of 35-45 cP [19]. Results demonstrate that platinum-plated Nafion transducers solvated with this ionic liquid exhibit sensing and actuation responses and that these transducers are stable in air. Endurance testing of this sample reveals a decrease in the free strain of only 25 % after 250,000 actuation cycles in air.

  5. Ionic liquids in refinery desulfurization: comparison between biphasic and supported ionic liquid phase suspension processes.

    PubMed

    Kuhlmann, Esther; Haumann, Marco; Jess, Andreas; Seeberger, Andreas; Wasserscheid, Peter

    2009-01-01

    The desulfurization of fuel compounds in the presence of ionic liquids is reported. For this purpose, the desulfurization efficiency of a variety of imidazolium phosphate ionic liquids has been tested. Dibenzothiophene/dodecane and butylmercaptan/decane mixtures were used as model systems. Single-stage extractions reduced the sulfur content from 500 ppm to 200 ppm. In multistage extractions the sulfur content could be lowered to less than 10 ppm within seven stages. Regeneration of the ionic liquid was achieved by distillation or re-extraction procedures. Supported ionic liquid phase (SILP) materials, obtained by dispersing the ionic liquid as a thin film on highly porous silica, exhibited a significantly higher extraction performance owing to their larger surface areas, reducing the sulfur content to less than 100 ppm in one stage. Multistage extraction with these SILP materials reduced the sulfur level to 50 ppm in the second stage. The SILP technology offers very efficient utilization of ionic liquids and circumvents mass transport limitations because of the small film thickness and large surface area, and allows application of the simple packed-bed column extraction technique. PMID:19798713

  6. Near infrared imaging of the surface of Venus and implications for crustal composition

    NASA Astrophysics Data System (ADS)

    Müller, N.; Helbert, J.

    2009-04-01

    . Generation of felsic crust is unlikely under the current climatic and tectonic regime on Venus. The lunar highland crust is believed to be a remnant of an magma ocean [Taylor 1974]. Enrichment in silica as in the continental crust of Earth requires recycling of water into the mantle [Campbell and Taylor 1984]. The surface of Venus is extremely dry and Venus and crustal recycling by plate tectonics does not operate at present. Any crust with felsic bulk composition had to be created during the early history of the planet. In a stratigraphic analysis tessera terrain predates all units it is in contact with [Ivanov and Head 1996]. Tessera terrain is defined by an extensive history of tectonic deformation. Assuming that tessera highlands indeed represent less dense crustal blocks created early in the history of Venus, implications arise from their persistence on the surface of Venus regarding resurfacing mechanism, crustal recycling and thermal evolution. If tessera highlands are enriched in silica relative to basalt this implies existence of a primordial ocean on Venus [Hashimoto et al. 2008]. In either case Venus would even more closely resemble the Earth-Moon system than previously assumed, making Venus an excellent subject for general studies of earth-like planets. Basilevsky, A. T.,et al. (1997), The Resurfacing History of Venus, in Venus II, pp. 1047-1084. Hashimoto, et al. (2008), Galileo Near Infrared Mapping Spectrometer (NIMS) Data Suggests Felsic Highland Crust on Venus, JGR, in press. Ivanov, M. A., et al. (1996), Tessera terrain on Venus: A survey of the global distribution, characteristics, and relation to surrounding units from Magellan data, JGR, 101, 14,861-14,908. Mueller, N., et al. (2008), Venus surface thermal emission at one micrometer in VIRTIS imaging observations - evidence for variation of crust and mantle differentiation conditions, JGR , in press. Nikolaeva, O. V., et al. (1992), Evidence on the crustal dichotomy, pp. 129-139, Venus Geology

  7. Elucidation of the effect of ionic liquid pretreatment on rice husk via structural analyses

    PubMed Central

    2012-01-01

    Background In the present study, three ionic liquids, namely 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc), and 1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM]DEP), were used to partially dissolve rice husk, after which the cellulose were regenerated by the addition of water. The aim of the investigation is to examine the implications of the ionic liquid pretreatments on rice husk composition and structure. Results From the attenuated total reflectance Fourier transform-infrared (ATR FT-IR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) results, the regenerated cellulose were more amorphous, less crystalline, and possessed higher structural disruption compared with untreated rice husk. The major component of regenerated cellulose from [BMIM]Cl and [EMIM]DEP pretreatments was cellulose-rich material, while cellulose regenerated from [EMIM]OAc was a matrix of cellulose and lignin. Cellulose regenerated from ionic pretreatments could be saccharified via enzymatic hydrolysis, and resulted in relatively high reducing sugars yields, whereas enzymatic hydrolysis of untreated rice husk did not yield reducing sugars. Rice husk residues generated from the ionic liquid pretreatments had similar chemical composition and amorphousity to that of untreated rice husk, but with varying extent of surface disruption and swelling. Conclusions The structural architecture of the regenerated cellulose and rice husk residues showed that they could be used for subsequent fermentation or derivation of cellulosic compounds. Therefore, ionic liquid pretreatment is an alternative in the pretreatment of lignocellulosic biomass in addition to the conventional chemical pretreatments. PMID:22958710

  8. Surface Electrical Conductivity Prediction by Soil Moisture and Electromagnetic Mapping Techniques: Implication for Landmine Detection Technologies

    NASA Astrophysics Data System (ADS)

    Katsube, J.; McNairn, H.; Keating, P. K.; Das, Y.; Dyke, L.; Best, M. E.; Singhroy, V.; Connell-Madore, S.; Hunter, J.; Klassen, R.; Dilabio, R.; Moore, A.

    2004-05-01

    Electrical conductivity (EC) can be a source of significant signal interference in landmine detection, implying that there is a necessity for soil EC prediction in order to carry out safe demining operations in landmine affected countries in the world. A fundamental study on soil EC mechanisms and their relationship to moisture content has been carried out in order to increase the soil EC prediction accuracy when using data from various sensors, such as remote sensing, airborne and surficial electromagnetic (EM) methods. Results indicate that soil moisture consists of free water filling pore spaces and bound water which forms adsorbed water layers on the grain surfaces. The response of these two water phases to drying rates and EC are very different, to the extent that a moist clay poor soil may have low EC but a dry clay rich soil may have higher EC. This is a result of not only the bound water layers being a significant source of EC, but of the capillary component of the free water reacting differently to the different grain-sizes of the soil. The capillary water forms important electrical conductive bridges between the adsorbed water layers on the grains that constitute the soil. This implies that information on soil texture, mineralogy and their distribution are required for accurate EC prediction. Whereas information on these soil characteristics may be acquired by remote sensing and soil maps, soil moisture content is likely to vary from the time of data acquisition to that of demining operations, implying methods to predict these changes are required. In addition, soil type inhomogeniety, such as vertical and horizontal variation can also be a source of inaccuracies in moisture and EC predictions. However, these investigations also indicate that a wide band electrical frequency signal may have the possibility of providing information on, not only metallic mineral content, but on pore space, clay mineral type and water content. In addition, applications of

  9. Ionic electrostatic excitations along biological membranes

    NASA Astrophysics Data System (ADS)

    Moradi, Afshin

    2011-02-01

    A theoretical analysis of ionic electrostatic excitations of a charged biological membrane is presented within the framework of the fluid theory for surface ions inside and outside the cell, in conjunction with the Poisson's equation. General expressions of dispersion relations are obtained for electrostatic oscillations of intrinsic cellular with different shapes and symmetries.

  10. Structure of clean and hydrated α-Al2O3 (1102) surfaces: implication on surface charge.

    PubMed

    Tougerti, Asma; Méthivier, Christophe; Cristol, Sylvain; Tielens, Frederik; Che, Michel; Carrier, Xavier

    2011-04-14

    Periodic DFT calculations coupled to a first-principle thermodynamic approach have allowed us to establish a surface phase diagram for the different terminations of the α-Al(2)O(3) (1102) surface in various temperature and water pressure conditions. Theoretical results are compared with previous experimental data from the literature. Under a wide range of temperature and water pressure (including ambient conditions) the most stable surface (denoted C2_1H(2)O in this work) is terminated with singly coordinated hydroxyls on four-fold coordinated aluminium (Al(4C)-μ(1)-OH) while most existing surface models are only considering six-fold coordinated surface Al atoms as in the bulk structure of alumina. The presence of more acidic Al(4C)-μ(1)-OH sites helps explain the low Point of Zero Charge (PZC) (between 5 and 6) determined from the onset of Mo oxoanions adsorption on (1102) single crystal wafers. It is also postulated that another termination (corresponding to the hydration of the non-polar, stoichiometric surface, stable in dehydrated conditions) may be observed in aqueous solution depending on the surface preparation conditions. PMID:21380472

  11. Micro-porous surfaces in controlled drug delivery systems: design and evaluation of diltiazem hydrochloride controlled porosity osmotic pump using non-ionic surfactants as pore-former.

    PubMed

    Adibkia, Khosro; Ghanbarzadeh, Saeed; Shokri, Mohammad Hosein; Arami, Zahra; Arash, Zeinab; Shokri, Javad

    2014-06-01

    The major problem associated with conventional drug delivery systems is unpredictable plasma concentrations. The aim of this study was to design a controlled porosity osmotic pump (CPOP) of diltiazem hydrochloride to deliver the drug in a controlled manner. CPOP tablets were prepared by incorporation of drug in the core and subsequent coating with cellulose acetate as semi-permeable membrane. Non-ionic surfactants were applied as pore-formers as well. The effect of pore-formers concentration on the in vitro release of diltiazem was also studied. The formulations were compared based on four comparative parameters, namely, total drug released after 24 h (D24 h), lag-time (tL), squared correlation coefficient of zero order equation (RSQzero) and mean percent deviation from zero order kinetic (MPDzero). Results of scanning electron microscopy studies exhibited formation of pores in the membrane from where the drug release occurred. It was revealed that drug release rate was directly proportional to the concentration of the pore-formers. The value of D24 h in the formulations containing Tween 80 (10%) and Brij 35 (5%) were found to be more than 94.9%, and drug release followed zero order kinetic (RSQzero > 0.99 and MPDzero < 8%) with acceptable tL (lower than 1 h). PMID:23763379

  12. Effects of surface roughening of Nafion 117 on the mechanical and physicochemical properties of ionic polymer–metal composite (IPMC) actuators

    NASA Astrophysics Data System (ADS)

    Wang, Yanjie; Zhu, Zicai; Liu, Jiayu; Chang, Longfei; Chen, Hualing

    2016-08-01

    In this paper, the surface of a Nafion membrane was roughened by the sandblasting method, mainly considering the change of sandblasting time and powder size. The roughened surfaces were characterized in terms of their topography from the confocal laser scanning microscope (CLSM) and SEM. The key surface parameters, such as Sa (the arithmetical mean deviation of the specified surface profile), SSA (the surface area ratio before and after roughening) and the area measurement on the histogram from the CLSM images, were extracted and evaluated from the roughened membranes. Also, the detailed change in surface and interfacial electrodes were measured and discussed together with the surface resistance, equivalent modulus, capacitance and performances of IPMC actuators based on the roughened membranes. The results show that a suitable sandblasting condition, resulting in the decrease in the bending stiffness and the increase in the interface area closely related to the capacitance, can effectively increase the electromechanical responses of IPMCs. Although the surface roughening by sandblasting caused a considerable lowering of mechanical strength, it was very effective for enlarging the interfacial area between Nafion membrane and the electrode layers, and for forming a penetrated electrode structure, which facilitated improvement of the surface resistance and capacitance characteristics of IPMCs. In this work, a quantitative relationship was built between the topography of Nafion membrane surface and electromechanical performance of IPMCs by means of sandblasting.

  13. Mantle viscosity stratification and flow geometry - Implications for surface motions on earth and Venus

    NASA Technical Reports Server (NTRS)

    Kiefer, Walter S.

    1993-01-01

    For a fixed heat flow, the surface flow velocity of a convecting layer is not strongly sensitive to the variation of viscosity as a function of depth. Thus, the inferred absence of a low viscosity asthenosphere on Venus can not account for the limited surface motions there. The surface velocity is dependent on the convective geometry. Cartesian geometry convection can produce large surface velocities if the high viscosity surface layer is broken in places by weak zones. On the other hand, a high viscosity surface layer may inhibit the development of large surface velocities in axisymmetric convection.

  14. Mantle viscosity stratification and flow geometry - Implications for surface motions on earth and Venus

    NASA Astrophysics Data System (ADS)

    Kiefer, W. S.

    1993-02-01

    For a fixed heat flow, the surface flow velocity of a convecting layer is not strongly sensitive to the variation of viscosity as a function of depth. Thus, the inferred absence of a low viscosity asthenosphere on Venus can not account for the limited surface motions there. The surface velocity is dependent on the convective geometry. Cartesian geometry convection can produce large surface velocities if the high viscosity surface layer is broken in places by weak zones. On the other hand, a high viscosity surface layer may inhibit the development of large surface velocities in axisymmetric convection.

  15. Unravelling nanoconfined films of ionic liquids

    SciTech Connect

    Lee, Alpha A.; Vella, Dominic; Goriely, Alain; Perkin, Susan

    2014-09-07

    The confinement of an ionic liquid between charged solid surfaces is treated using an exactly solvable 1D Coulomb gas model. The theory highlights the importance of two dimensionless parameters: the fugacity of the ionic liquid, and the electrostatic interaction energy of ions at closest approach, in determining how the disjoining pressure exerted on the walls depends on the geometrical confinement. Our theory reveals that thermodynamic fluctuations play a vital role in the “squeezing out” of charged layers as the confinement is increased. The model shows good qualitative agreement with previous experimental data, with all parameters independently estimated without fitting.

  16. Effects of engineered nano-titanium dioxide on pore surface properties and phosphorus adsorption of sediment: its environmental implications.

    PubMed

    Luo, Zhuanxi; Wang, Zhenhong; Wei, Qunshan; Yan, Changzhou; Liu, Feng

    2011-09-15

    Understanding the environmental safety and human health implications of engineered nanoparticles (ENPs) is of worldwide importance. As an important ENPs, engineered nano-TiO(2) (Enano-TiO(2)) may have been substantially deposited in aquatic sediments because of its widely uses. Sediment pore surface properties would be thus significantly influenced due to the large surface area of Enano-TiO(2). In this study, Enano-TiO(2) was found to greatly impact on sediment pore surface properties. The attachment of Enano-TiO(2) particles to sediment surfaces enhanced markedly BET specific surface area and t-Plot external specific surface area, and thereby increased sediment phosphorus (P) adsorption maximum (S(max)). Contrarily, the fill of Enano-TiO(2) particles into the micropores of sediments could significantly reduce t-Plot micropore specific surface area, and cause slight decrease in sediment P binding energy (K). Clearly, P sorbed in sediment would be easily released because of the decreasing P binding energy of the sediment with elevated Enano-TiO(2). Enano-TiO(2) would thus cause aggravated endogenous pollution in water if such sediment was re-suspended on disturbance. The results obtained in this study contribute to our increasing knowledge of how to regulate physicochemical behavior of pollutants in sediments under the influences of Enano-TiO(2) and/or similar ENPs. PMID:21794978

  17. Implications of time-delayed feedback control on limit cycle oscillation of a two-dimensional supersonic lifting surface,

    NASA Astrophysics Data System (ADS)

    Yu, P.; Chen, Z.; Librescu, L.; Marzocca, P.

    2007-07-01

    In this paper, the problem of implications of time delay feedback control of a two-dimensional supersonic lifting surface on the flutter boundary and on its character, that is, benign or catastrophic, is addressed. In this context, the structural and aerodynamic nonlinearities are included in the aeroelastic governing equations. The model and the associated theory are developed for linear and nonlinear plunging and pitching full-state proportional and velocity feedback controls. Center manifold reduction and normal form theory are applied to investigate the stability in the post-flutter flight speed regimes. Numerical simulations are carried out to determine the implications of time delay in the considered controls, but are restricted to the cases of proportional feedback control and no structural damping.

  18. Selective Ionic Transport Pathways in Phosphorene.

    PubMed

    Nie, Anmin; Cheng, Yingchun; Ning, Shoucong; Foroozan, Tara; Yasaei, Poya; Li, Wen; Song, Boao; Yuan, Yifei; Chen, Lin; Salehi-Khojin, Amin; Mashayek, Farzad; Shahbazian-Yassar, Reza

    2016-04-13

    Despite many theoretical predictions indicating exceptionally low energy barriers of ionic transport in phosphorene, the ionic transport pathways in this two-dimensional (2D) material has not been experimentally demonstrated. Here, using in situ aberration-corrected transmission electron microscopy (TEM) and density functional theory, we studied sodium ion transport in phosphorene. Our high-resolution TEM imaging complemented by electron energy loss spectroscopy demonstrates a precise description of anisotropic sodium ions migration along the [100] direction in phosphorene. This work also provides new insight into the effect of surface and the edge sites on the transport properties of phosphorene. According to our observation, the sodium ion transport is preferred in zigzag edge rather than the armchair edge. The use of this highly selective ionic transport property may endow phosphorene with new functionalities for novel chemical device applications. PMID:26986876

  19. Water Contaminant Mitigation in Ionic Liquid Propellant

    NASA Technical Reports Server (NTRS)

    Conroy, David; Ziemer, John

    2009-01-01

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

  20. Role of Ionic Strength in Staphylococcal Cell Aggregation.

    PubMed

    Vanzieleghem, Thomas; Couniot, Numa; Herman-Bausier, Philippe; Flandre, Denis; Dufrêne, Yves F; Mahillon, Jacques

    2016-07-26

    Cell aggregation plays a key role in biofilm formation and pathogenesis of Staphylococcus species. Although the molecular basis of aggregation in Staphylococci has already been extensively investigated, the influence of environmental factors, such as ionic strength, remains poorly understood. In this paper, we report a new type of cellular aggregation of Staphylococci that depends solely on ionic strength. Seven strains out of 14, all belonging to staphylococcal species, formed large cell clusters within minutes in buffers of ionic strength ranging from 1.5 to 50 mM, whereas isolates belonging to other Gram-positive species did not display this phenotype. Atomic force microscopy (AFM) with chemically functionalized tips provided direct evidence that ionic strength modulates cell surface adhesive properties through changes in cell surface charge. The optimal ionic strength for aggregation was found to be strain dependent, but in all cases, bacterial aggregates formed at an ionic strength of 1.5-50 mM were rapidly dispersed in a solution of higher ionic strength, indicating a reversibility of the cell aggregation process. These findings suggest that some staphylococcal isolates can respond to ionic strength as an external stimulus to trigger rapid cell aggregation in a way that has not yet been reported. PMID:27364477

  1. Surface-attached cells, biofilms and biocide susceptibility: implications for hospital cleaning and disinfection.

    PubMed

    Otter, J A; Vickery, K; Walker, J T; deLancey Pulcini, E; Stoodley, P; Goldenberg, S D; Salkeld, J A G; Chewins, J; Yezli, S; Edgeworth, J D

    2015-01-01

    Microbes tend to attach to available surfaces and readily form biofilms, which is problematic in healthcare settings. Biofilms are traditionally associated with wet or damp surfaces such as indwelling medical devices and tubing on medical equipment. However, microbes can survive for extended periods in a desiccated state on dry hospital surfaces, and biofilms have recently been discovered on dry hospital surfaces. Microbes attached to surfaces and in biofilms are less susceptible to biocides, antibiotics and physical stress. Thus, surface attachment and/or biofilm formation may explain how vegetative bacteria can survive on surfaces for weeks to months (or more), interfere with attempts to recover microbes through environmental sampling, and provide a mixed bacterial population for the horizontal transfer of resistance genes. The capacity of existing detergent formulations and disinfectants to disrupt biofilms may have an important and previously unrecognized role in determining their effectiveness in the field, which should be reflected in testing standards. There is a need for further research to elucidate the nature and physiology of microbes on dry hospital surfaces, specifically the prevalence and composition of biofilms. This will inform new approaches to hospital cleaning and disinfection, including novel surfaces that reduce microbial attachment and improve microbial detachment, and methods to augment the activity of biocides against surface-attached microbes such as bacteriophages and antimicrobial peptides. Future strategies to address environmental contamination on hospital surfaces should consider the presence of microbes attached to surfaces, including biofilms. PMID:25447198

  2. Chemistry of Frozen NaCl and MgSO4 Brines - Implications for Surface Expression of Europa's Ocean Composition

    NASA Astrophysics Data System (ADS)

    Johnson, P. V.; Hodyss, R. P.; Choukroun, M.; Vu, T. H.

    2015-12-01

    The composition of Europa's subsurface ocean is a critical determinant of its habitability, but current analysis of the ocean composition is limited to its expression on the Europan surface. While there is observational evidence indicating that ocean materials make their way to the surface, our understanding of the chemical processes that can alter this material under Europan surface conditions is limited. We present experimental data on the chemistry of mixed solutions of NaCl and MgSO4 as they are frozen to 100 K, replicating the conditions that may occur when subsurface ocean fluids are emplaced onto Europa's surface. Confocal micro-Raman spectroscopy is used to study the formation of salts during the freezing process, and the interaction of ions in the frozen brines. Our data indicate that mixed aqueous solutions of NaCl and MgSO4 form Na2SO4 and MgCl2 preferentially when frozen, rather than making NaCl and MgSO4 precipitates. The detection of epsomite (MgSO4Ÿ•7H2O) on Europa's surface may therefore imply an ocean composition relatively low in sodium, unless radiolytic chemistry converts MgCl2 to MgSO4 as suggested by Hand and Brown 2013 (ApJ 145 110). These results have important implications for the interpretation of remote sensing data of Europa's surface.

  3. Electroplating Using Ionic Liquids

    NASA Astrophysics Data System (ADS)

    Abbott, Andrew P.; Frisch, Gero; Ryder, Karl S.

    2013-07-01

    Electroplating is a key technology in many large-scale industrial applications such as corrosion-resistant and decorative coatings. Issues with current aqueous processes, such as toxicity of reagents and low current efficiencies, can often be overcome by using ionic liquids, and this approach has turned ionometallurgy into a fast-growing area of research. This review outlines the interactions in ionic liquids that are responsible for the advantageous properties of these solvents in electroplating. It summarizes recent research in which these properties have been analyzed or exploited and highlights fundamental issues in research and technology that need to be addressed.

  4. Sorption mechanisms of Sr and Pb on zeolitized tuffs from the Nevada test site as a function of pH and ionic strength

    SciTech Connect

    Um, Wooyong; Papelis, Charalambos

    2003-11-01

    The sorption of divalent strontium, Sr{sup 2+}, and divalent lead, Pb{sup 2+}, on zeolitized tuffs from the Nevada Test Site (NTS) was investigated using macroscopic batch sorption experiments and x-ray absorption spectroscopy (XAS) as a function of geochemical parameters, including pH, ionic strength, and type of background electrolyte. The sorption of Sr{sup 2+} is dependent on the ionic strength of the medium and independent of pH, suggesting that Sr{sup 2+} sorption is controlled by ion exchange at permanent charge sites. At higher ionic strengths, background electrolyte cations compete effectively with Sr{sup 2+} for cation exchange sites and Sr{sup 2+} sorption is suppressed. At the two lower ionic strengths (0.01 and 0.1 M), Pb{sup 2+} sorption is also consistent with adsorption by cation exchange. At the highest ionic strength (1.0 M), however, exclusion of Pb{sup 2+} from cation exchange sites resulted in pH dependent adsorption, consistent with sorption on amphoteric surface hydroxyl sites or formation of surface precipitates. XAS was used to test these hypotheses. Based on XAS data, Sr{sup 2+} formed hydrated surface complexes coordinated with approximately eight oxygen atoms at an average distance of 2.60 ({+-}0.02) {angstrom}, regardless of conditions, consistent with the formation of mononuclear, outer-sphere surface complexes at the Ca2 site in the B channel of clinoptilolite. The coordination environment of sorbed Pb{sup 2+} was more complex and a function of pH and ionic strength. The first shell consisted of two to three oxygen atoms at an average distance of 2.20 ({+-}0.02) {angstrom}. At low pH and ionic strength, XAS data were consistent with Pb{sup 2+} adsorption at the Na1 and Ca2 cation exchange sites in channels A and B of clinoptilolite, respectively. At the highest ionic strength (1.0 M) and low pH, XAS provides evidence for formation of Pb{sup 2+} monodentate, corner-sharing inner-sphere complexes, while at higher pH, XAS analysis is

  5. Direct Mapping of Ionic Transport in a Si Anode on the Nanoscale: Time Domain Electrochemical Strain Spectroscopy Study

    SciTech Connect

    Jesse, Stephen; Balke, Nina; Eliseev, Eugene; Tselev, Alexander; Dudney, Nancy J.; Morozovska, Anna N.; Kalinin, Sergei V.

    2011-12-27

    Local Li-ion transport in amorphous silicon is studied on the nanometer scale using time domain electrochemical strain microscopy (ESM). A strong variability of ionic transport controlled by the anode surface morphology is observed. The observed relaxing and nonrelaxing response components are discussed in terms of local and global ionic transport mechanisms, thus establishing the signal formation mechanisms in ESM. This behavior is further correlated with local conductivity measurements. The implications of these studies for Si-anode batteries are discussed. The universal presence of concentration–strain coupling suggests that ESM and associated time and voltage spectroscopies can be applied to a broad range of electrochemical systems ranging from batteries to fuel cells.

  6. Direct mapping of ionic transport in Si-anode on the nanoscale: time domain electrochemical strain spectroscopy study

    SciTech Connect

    Jesse, Stephen; Balke, Nina; Eliseev, E. A.; Tselev, Alexander; Dudney, Nancy J; Morozovska, A. N.; Kalinin, Sergei V

    2011-01-01

    Local Li-ion transport in amorphous silicon is studied on the nanometer scale using time domain electrochemical strain microscopy (ESM). A strong variability of ionic transport controlled by the anode surface morphology is observed. The observed relaxing and nonrelaxing response components are discussed in terms of local and global ionic transport mechanisms, thus establishing the signal formation mechanisms in ESM. This behavior is further correlated with local conductivity measurements. The implications of these studies for Si-anode batteries are discussed. The universal presence of concentration-strain coupling suggests that ESM and associated time and voltage spectroscopies can be applied to a broad range of electrochemical systems ranging from batteries to fuel cells.

  7. The Development of Surface Roughness and Implications for Cellular Attachment in Biomedical Applications

    NASA Technical Reports Server (NTRS)

    Banks, Bruce; Miller, Sharon; deGroh, Kim; Chan, Amy; Sahota, Mandeep

    2001-01-01

    The application of a microscopic surface texture produced by ion beam sputter texturing to the surfaces of polymer implants has been shown to result in significant increases in cellular attachment compared to smooth surface implants in animal studies. A collaborative program between NASA Glenn Research Center and the Cleveland Clinic Foundation has been established to evaluate the potential for improving osteoblast attachment to surfaces that have been microscopically roughened by atomic oxygen texturing. The range of surface textures that are feasible depends upon both the texturing process and the duration of treatment. To determine whether surface texture saturates or continues to increase with treatment duration, an effort was conducted to examine the development of surface textures produced by various physical and chemical erosion processes. Both experimental tests and computational modeling were performed to explore the growth of surface texture with treatment time. Surface texturing by means of abrasive grit blasting of glass, stainless steel, and polymethylmethacry I ate surfaces was examined to measure the growth in roughness with grit blasting duration by surface profilometry measurements. Laboratory tests and computational modeling was also conducted to examine the development of texture on Aclar(R) (chlorotfifluoroethylene) and Kapton(R) polyimide, respectively. For the atomic oxygen texturing tests of Aclar(R), atomic force microscopy was used to measure the development of texture with atomic oxygen fluence. The results of all the testing and computational modeling support the premise that development of surface roughness obeys Poisson statistics. The results indicate that surface roughness does not saturate but increases as the square root of the treatment time.

  8. Communication: Salt-induced water orientation at a surface of non-ionic surfactant in relation to a mechanism of Hofmeister effect

    SciTech Connect

    Hishida, Mafumi; Kaneko, Yohei; Okuno, Masanari; Yamamura, Yasuhisa; Ishibashi, Taka-aki; Saito, Kazuya

    2015-05-07

    The behavior of water molecules at the surface of nonionic surfactant (monomyristolein) and effects of monovalent ions on the behavior are investigated using the heterodyne-detected vibrational sum frequency generation spectroscopy. It is found that water molecules at the surface are oriented with their hydrogen atoms pointing to the bulk, and that the degree of orientation depends on the anion strongly but weakly on the cation. With measured surface potentials in those saline solutions, it is concluded that the heterogeneous distribution of anions and cations in combination with the nonionic surfactant causes the water orientation. This heterogeneous distribution well explains the contrasting order of anions and cations with respect to the ion size in the Hofmeister series.

  9. Fun with Ionic Compounds

    ERIC Educational Resources Information Center

    Logerwell, Mollianne G.; Sterling, Donna R.

    2007-01-01

    Ionic bonding is a fundamental topic in high school chemistry, yet it continues to be a concept that students struggle to understand. Even if they understand atomic structure and ion formation, it can be difficult for students to visualize how ions fit together to form compounds. This article describes several engaging activities that help…

  10. Synthesis of ionic liquids

    DOEpatents

    Dai, Sheng; Luo, Huimin

    2011-11-01

    Ionic compounds which are liquids at room temperature are formed by the method of mixing a neutral organic ligand with the salt of a metal cation and its conjugate anion. The liquids are hydrophobic, conductive and stable and have uses as solvents and in electrochemical devices.

  11. Synthesis of ionic liquids

    DOEpatents

    Dai, Sheng [Knoxville, TN; Luo, Huimin [Knoxville, TN

    2008-09-09

    Ionic compounds which are liquids at room temperature are formed by the method of mixing a neutral organic liqand with the salt of a metal cation and its conjugate anion. The liquids are hydrophobic, conductive and stable and have uses as solvents and in electrochemical devices.

  12. Carbenes from ionic liquids.

    PubMed

    Hollóczki, Oldamur; Nyulászi, László

    2014-01-01

    In the last decade an explosive development has been observed in the fields of both ionic liquids (ILs) as potential chemically inert solvents with many possible technical applications, and N-heterocyclic carbenes (NHCs) as catalysts with superb performance. Since the cations of many ILs can be deprotonated by strong bases yielding NHCs, this two fields are inherently connected. It has only recently been recognized that some of the commonly used basic anions of the ILs (such as acetate) are able to deprotonate azolium cations. While the resulting NHC could clearly be observed in the vapor phase, in the liquid - where the mutual electrostatic interactions within the ion network stabilize the ion pairs - the neutral NHC cannot be detected by commonly used analytical techniques; however, from these ionic liquids NHCs can be trapped, e.g., by complex formation, or more importantly these ILs can be directly used as catalysts, since the NHC content is sufficiently large for these applications. Apart from imidazole-2-ylidenes, the formation of other highly reactive neutral species ("abnormal carbenes," 2-alkylideneimidazoles, pyridine-ylidenes or pyridinium-ylides) is feasible in highly basic ionic liquids. The cross-fertilizing overlap between the two fields may provide access to a great advance in both areas, and we give an overview here on the results published so far, and also on the remaining possibilities and challenges in the concept of "carbenes from ionic liquids." PMID:23539381

  13. Surface defects on ZnO nanowires: implications for design of sensors

    NASA Astrophysics Data System (ADS)

    Spencer, Michelle J. S.; Wong, Kester W. J.; Yarovsky, Irene

    2012-08-01

    Surface defects are commonly believed to be fundamentally important to gas-sensor performance. We examine the effect of gas coverage and ethanol orientation on its adsorption on the stoichiometric and oxygen deficient (1 0\\bar {1}0) nanowire surface. Our density functional theory calculations show that ethanol adsorbs in multiple stable configurations at coverages between 1/4 and 1 ML, highlighting the ability of ZnO to detect ethanol. Ethanol prefers to bind to a surface Zn via the adsorbate oxygen atom and, if a surface oxygen atom is in close proximity, the molecule is further stabilized by formation of a hydrogen bond between the hydrogen of the hydroxyl group and the surface oxygen. Two primary adsorption configurations were identified and have different binding strengths that could be distinguished experimentally by the magnitude of their OH stretching frequency. Our findings show that ethanol adsorbed on the oxygen deficient ZnO(1 0\\bar {1}0) surface has a reduced binding strength. This is due to either the lack of a hydrogen bond (due to a deficiency in surface oxygen) or to surface reconstruction that occurs on the defect surface that weakens the hydrogen bond interaction. This reduced binding on the oxygen deficient surface is in contrast to the defect enhanced gas-sensor interaction for other gases. Despite this difference, ethanol still acts as a reducing gas, donating electrons to the surface and decreasing the band gap. We show that multiple adsorbed ethanol molecules prefer to be orientated parallel to each other to facilitate the hydrogen bonding to the defect-free surface for enhanced interaction.

  14. Quantitative assessment of interfacial interactions with rough membrane surface and its implications for membrane selection and fabrication in a MBR.

    PubMed

    Chen, Jianrong; Mei, Rongwu; Shen, Liguo; Ding, Linxian; He, Yiming; Lin, Hongjun; Hong, Huachang

    2015-03-01

    The interfacial interactions between a foulant particle and rough membrane surface in a submerged membrane bioreactor (MBR) were quantitatively assessed by using a new-developed method. It was found that the profile of total interaction versus separation distance was complicated. There were an energy barrier and two negative energy ranges in the profile. Further analysis showed that roughness scale significantly affected the strength and properties of interfacial interactions. It was revealed that there existed a critical range of roughness scale within which the total energy in the separation distance ranged from 0 to several nanometers was continually repulsive. Decrease in foulant size would increase the strength of specific interaction energy, but did not change the existence of a critical roughness scale range. These findings suggested the possibility to "tailor" membrane surface morphology for membrane fouling mitigation, and thus gave significant implications for membrane selection and fabrication in MBRs. PMID:25553567

  15. Modifications of microvascular EC surface modulate phototoxicity of a porphycene anti-ICAM-1 immunoconjugate; therapeutic implications

    PubMed Central

    Rosàs, Elisabet; Santomá, Pablo; Duran-Frigola, Miquel; Hernandez, Bryan; Llinàs, Maria C.; Ruiz-González, Rubén; Nonell, Santi; Sánchez-García, David; Edelman, Elazer R.; Balcells, Mercedes

    2013-01-01

    Inflammation and shear stress can upregulate expression of cellular adhesion molecules in endothelial cells (EC). The modified EC surface becomes a mediating interface between the circulating blood elements and the endothelium, and grants opportunity for immunotherapy. In photodynamic therapy (PDT), immunotargeting might overcome the lack of selectivity of currently used sensitizers. In this study, we hypothesized that differential ICAM-1 expression modulates the effects of a drug targeted to surface ICAM-1. A novel porphycene-anti-ICAM-1 conjugate was synthesized and applied to treat endothelial cells from macro and microvasculature. Results show that the conjugate induces phototoxicity in inflamed, but not in healthy, microvascular EC. Conversely, macrovascular EC exhibited phototoxicity regardless of their state. These findings have two major implications; the relevance of ICAM-1 as a modulator of drug effects in microvasculature, and the potential of the porphycene bioconjugate as a promising novel PDT agent. PMID:23844929

  16. Implications of surface noise for the motional coherence of trapped ions

    NASA Astrophysics Data System (ADS)

    Talukdar, I.; Gorman, D. J.; Daniilidis, N.; Schindler, P.; Ebadi, S.; Kaufmann, H.; Zhang, T.; Häffner, H.

    2016-04-01

    Electric noise from metallic surfaces is a major obstacle towards quantum applications with trapped ions due to motional heating of the ions. Here, we discuss how the same noise source can also lead to pure dephasing of motional quantum states. The mechanism is particularly relevant at small ion-surface distances, thus imposing a constraint on trap miniaturization. By means of a free induction decay experiment, we measure the dephasing time of the motion of a single ion trapped 50 μ m above a Cu-Al surface. From the dephasing times we extract the integrated noise below the secular frequency of the ion. We find that none of the most commonly discussed surface noise models for ion traps describes both the observed heating as well as the measured dephasing satisfactorily. Thus, our measurements provide a benchmark for future models for the electric noise emitted by metallic surfaces.

  17. Ceres: predictions for near-surface water ice stability and implications for plume generating processes

    USGS Publications Warehouse

    Titus, Timothy N.

    2015-01-01

    This paper will constrain the possible sources and processes for the formation of recently observed H2O vapor plumes above the surface of the dwarf planet Ceres. Two hypotheses have been proposed: (1) cryovolcanism where the water source is the mantle and the heating source is still unknown or (2) comet-like sublimation where near-surface water ice is vaporized by seasonally increasing solar insolation. We test hypothesis #2, comet-like near-surface sublimation, by using a thermal model to examine the stability of water-ice in the near surface. For a reasonable range of physical parameters (thermal inertia, surface roughness, slopes), we find that water ice is only stable at latitudes higher than ~40-60 degrees. These results indicate that either (a) the physical properties of Ceres are unlike our expectations or (b) an alternative to comet-like sublimation, such as the cryovolcanism hypothesis, must be invoked.

  18. Biocatalytic transformations in ionic liquids.

    PubMed

    van Rantwijk, Fred; Madeira Lau, Rute; Sheldon, Roger A

    2003-03-01

    Room temperature ionic liquids are non-volatile, thermally stable and highly polar; they are also moderately hydrophilic solvents. Here, we discuss their use as reaction media for biocatalysis. Enzymes of widely diverging types are catalytically active in ionic liquids or aqueous biphasic ionic liquid systems. Lipases, in particular, maintain their activity in anhydrous ionic liquid media; the (enantio)selectivity and operational stability are often better than in traditional media. The unconventional solvent properties of ionic liquids have been exploited in biocatalyst recycling and product recovery schemes that are not feasible with traditional solvent systems. PMID:12628370

  19. Water organization between oppositely charged surfaces: Implications for protein sliding along DNA a)

    NASA Astrophysics Data System (ADS)

    Marcovitz, Amir; Naftaly, Aviv; Levy, Yaakov

    2015-02-01

    Water molecules are abundant in protein-DNA interfaces, especially in their nonspecific complexes. In this study, we investigated the organization and energetics of the interfacial water by simplifying the geometries of the proteins and the DNA to represent them as two equally and oppositely charged planar surfaces immersed in water. We found that the potential of mean force for bringing the two parallel surfaces into close proximity comprises energetic barriers whose properties strongly depend on the charge density of the surfaces. We demonstrated how the organization of the water molecules into discretized layers and the corresponding energetic barriers to dehydration can be modulated by the charge density on the surfaces, salt, and the structure of the surfaces. The 1-2 layers of ordered water are tightly bound to the charged surfaces representing the nonspecific protein-DNA complex. This suggests that water might mediate one-dimensional diffusion of proteins along DNA (sliding) by screening attractive electrostatic interactions between the positively charged molecular surface on the protein and the negatively charged DNA backbone and, in doing so, reduce intermolecular friction in a manner that smoothens the energetic landscape for sliding, and facilitates the 1D diffusion of the protein.

  20. Water organization between oppositely charged surfaces: implications for protein sliding along DNA.

    PubMed

    Marcovitz, Amir; Naftaly, Aviv; Levy, Yaakov

    2015-02-28

    Water molecules are abundant in protein-DNA interfaces, especially in their nonspecific complexes. In this study, we investigated the organization and energetics of the interfacial water by simplifying the geometries of the proteins and the DNA to represent them as two equally and oppositely charged planar surfaces immersed in water. We found that the potential of mean force for bringing the two parallel surfaces into close proximity comprises energetic barriers whose properties strongly depend on the charge density of the surfaces. We demonstrated how the organization of the water molecules into discretized layers and the corresponding energetic barriers to dehydration can be modulated by the charge density on the surfaces, salt, and the structure of the surfaces. The 1-2 layers of ordered water are tightly bound to the charged surfaces representing the nonspecific protein-DNA complex. This suggests that water might mediate one-dimensional diffusion of proteins along DNA (sliding) by screening attractive electrostatic interactions between the positively charged molecular surface on the protein and the negatively charged DNA backbone and, in doing so, reduce intermolecular friction in a manner that smoothens the energetic landscape for sliding, and facilitates the 1D diffusion of the protein. PMID:25725757

  1. Intensity of nightside MARSIS AIS surface reflections and implications for low-altitude ionospheric densities

    NASA Astrophysics Data System (ADS)

    Němec, F.; Morgan, D. D.; Diéval, C.; Gurnett, D. A.

    2015-04-01

    Spacecraft radar sounding signals at frequencies higher than the ionospheric peak plasma frequency are not reflected by the ionosphere. Instead, they make it to the ground where they are reflected by the planetary surface. We analyze the intensity of the surface reflections measured by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) ionospheric radar sounder on board the Mars Express spacecraft. Apart from the surface reflectivity and the spacecraft altitude, the detected intensity of surface reflections is controlled primarily by the signal attenuation during the ionospheric propagation. We focus on the nightside region, where the ionospheric densities in the main layer are too low to cause a significant attenuation and allow sampling of the surface reflections at frequencies down to 3 MHz. The attenuation occurs mainly at altitudes below 100 km, where the electron-neutral collision frequency is a maximum. The intensity of surface reflections can thus serve as a proxy for electron densities at low altitudes not accessible by the direct ionospheric radar sounding. We analyze the intensity of surface reflections as a function of relevant controlling parameters. The intensity of surface reflections is lower at higher solar zenith angles on the nightside and during the periods of larger solar activity. Moreover, it exhibits a seasonal variation that is related to the dust storm occurrence. The intensity of surface reflections is lower in areas of closed magnetic field lines, suggesting that nightside electron densities behave rather differently at low altitudes than at higher altitudes. This is confirmed by comparison with simultaneous observations of the main ionospheric layer.

  2. The mineralogic evolution of the Martian surface through time: Implications from chemical reaction path modeling studies

    NASA Technical Reports Server (NTRS)

    Plumlee, G. S.; Ridley, W. I.; Debraal, J. D.; Reed, M. H.

    1993-01-01

    Chemical reaction path calculations were used to model the minerals that might have formed at or near the Martian surface as a result of volcano or meteorite impact driven hydrothermal systems; weathering at the Martian surface during an early warm, wet climate; and near-zero or sub-zero C brine-regolith reactions in the current cold climate. Although the chemical reaction path calculations carried out do not define the exact mineralogical evolution of the Martian surface over time, they do place valuable geochemical constraints on the types of minerals that formed from an aqueous phase under various surficial and geochemically complex conditions.

  3. Dissolving Polymers in Ionic Liquids.

    NASA Astrophysics Data System (ADS)

    Hoagland, David; Harner, John

    2009-03-01

    Dissolution and phase behavior of polymers in ionic liquids have been assessed by solution characterization techniques such as intrinsic viscosity and light scattering (static and dynamic). Elevated viscosity proved the greatest obstacle. As yet, whether principles standard to conventional polymer solutions apply to ionic liquid solutions is uncertain, especially for polymers such as polyelectrolytes and hydrophilic block copolymers that may specifically interact with ionic liquid anions or cations. For flexible polyelectrolytes (polymers releasing counterions into high dielectric solvents), characterization in ionic liquids suggests behaviors more typical of neutral polymer. Coil sizes and conformations are approximately the same as in aqueous buffer. Further, several globular proteins dissolve in a hydrophilic ionic liquid with conformations analogous to those in buffer. General principles of solubility, however, remain unclear, making predictions of which polymer dissolves in which ionic liquid difficult; several otherwise intractable polymers (e.g., cellulose, polyvinyl alcohol) dissolve and can be efficiently functionalized in ionic liquids.

  4. Lidar-derived Correlations Between Lower-tropospheric Column and Surface Ozone: Implications for Satellite Observations

    NASA Astrophysics Data System (ADS)

    Senff, C. J.; Langford, A. O.; Alvarez, R. J. _II, II; Kirgis, G.; Choukulkar, A.; Brewer, A.; Banta, R. M.; Weickmann, A. M.; Sandberg, S.; Olson, E.

    2015-12-01

    One of the data products that will be provided by the TEMPO satellite mission is 0-2 km ozone column concentration. To make inferences about surface air quality from this data product, the relationship between lower-tropospheric column and surface ozone concentrations and their diurnal, seasonal, and spatial variations have to be well understood. To characterize these relationships, we have used ozone profile observations obtained with NOAA's truck-based, scanning TOPAZ ozone lidar from several recent field campaigns including Discover-AQ Houston and Colorado, the Uintah Basin Wintertime Ozone Study (UBWOS), and the Las Vegas Ozone Study (LVOS). The TOPAZ lidar is ideally suited for this kind of study because it provides ozone profiles from about 15 m above ground level (AGL) up to 3 km AGL at high spatial and temporal resolution. We have used the lidar observations closest to the ground as a proxy for surface ozone and compared them to the 0-2 km AGL average column ozone concentrations measured with the lidar. Results from the Discover-AQ Colorado campaign show that in the afternoon, when the boundary layer (BL) was deep and well mixed, ozone column and surface concentrations agreed quite well. However, during the morning hours, ozone column concentrations were significantly higher than those at the surface, because ozone was depleted in a shallow surface layer due to titration and deposition, whereas ozone levels in the residual layer aloft remained moderately high. The analysis of column and surface ozone correlations using ozone lidar observations from the Discover-AQ Houston, UBWOS and LVOS campaigns is currently underway. The results from these studies will provide additional insights into the relationship between column and surface ozone, in particular their variation as a function of measurement location and season, and their dependence on BL processes such as mixed layer height evolution, land-sea breeze circulation, and terrain-induced flows.

  5. Implications of Adhesion Studies for Dust Mitigation on Thermal Control Surfaces

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Berkebile, Stephen P.

    2012-01-01

    Experiments measuring the adhesion forces under ultrahigh vacuum conditions (10 (exp -10) torr) between a synthetic volcanic glass and commonly used space exploration materials have recently been described. The glass has a chemistry and surface structure typical of the lunar regolith. It was found that Van der Waals forces between the glass and common spacecraft materials was negligible. Charge transfer between the materials was induced by mechanically striking the spacecraft material pin against the glass plate. No measurable adhesion occurred when striking the highly conducting materials, however, on striking insulating dielectric materials the adhesion increased dramatically. This indicates that electrostatic forces dominate over Van der Waals forces under these conditions. The presence of small amounts of surface contaminants was found to lower adhesive forces by at least two orders of magnitude, and perhaps more. Both particle and space exploration material surfaces will be cleaned by the interaction with the solar wind and other energetic processes and stay clean because of the extremely high vacuum (10 (exp -12) torr) so the atomically clean adhesion values are probably the relevant ones for the lunar surface environment. These results are used to interpret the results of dust mitigation technology experiments utilizing textured surfaces, work function matching surfaces and brushing. They have also been used to reinterpret the results of the Apollo 14 Thermal Degradation Samples experiment.

  6. Infiltration on sloping surfaces: Laboratory experimental evidence and implications for infiltration modeling

    NASA Astrophysics Data System (ADS)

    Morbidelli, Renato; Saltalippi, Carla; Flammini, Alessia; Cifrodelli, Marco; Corradini, Corrado; Govindaraju, Rao S.

    2015-04-01

    Infiltration on sloping surfaces occupies an important role in our understanding of surface and subsurface hydrology. Previous studies have provided conflicting results about the role of slope on infiltration. Here, our main objective is to highlight, by well-controlled experiments, the slope role in the absence of the conflicting contributions generated by other physical processes observed in previous studies under natural or laboratory conditions. The experimental program was designed to resolve some of the confounding factors such as lower impermeable boundary condition, range of rainfall rates relative to soil saturated hydraulic conductivity, surface sealing, and erosion of top soil. The experimental apparatus consists of a box containing a natural bare soil with slope angle γ chosen between 0° and 10°, two sensors of surface and deep flow, one probe for moisture content and an artificial rainfall generator. The primary experimental results suggest that under steady conditions and rainfall rate, r, greater than saturated hydraulic conductivity, Ks, the deep flow, Qd, decreases with increasing slope angle, γ, up to a value leading to Qd(γ = 1°)/Qd(γ = 10°) equal to ≈4 which is in contrast with the results provided in a few earlier papers. Furthermore, in sloping bare soils surface runoff is produced even for r < Ks. Finally, we discuss the link between Qd(γ) and the shear stress at the soil surface as a guideline in the determination of an effective saturated hydraulic conductivity to be incorporated in the existing horizontal infiltration models.

  7. Adhesion energy between mica surfaces: Implications for the frictional coefficient under dry and wet conditions

    NASA Astrophysics Data System (ADS)

    Sakuma, Hiroshi

    2013-12-01

    frictional strength of faults is a critical factor that contributes to continuous fault slip and earthquake occurrence. Frictional strength can be reduced by the presence of sheet-structured clay minerals. In this study, two important factors influencing the frictional coefficient of minerals were quantitatively analyzed by a newly developed computational method based on a combination of first-principles study and thermodynamics. One factor that helps reduce the frictional coefficient is the low adhesion energy between the layers under dry conditions. Potassium ions on mica surfaces are easily exchanged with sodium ions when brought into contact with highly concentrated sodium-halide solutions. We found that the surface ion exchange with sodium ions reduces the adhesion energy, indicating that the frictional coefficient can be reduced under dry conditions. Another factor is the lubrication caused by adsorbed water films on mineral surfaces under wet conditions. Potassium and sodium ions on mica surfaces have a strong affinity for water molecules. In order to remove the adsorbed water molecules confined between mica surfaces, a differential compressive stress of the order of tens of gigapascals was necessary at room temperature. These water molecules inhibit direct contact between mineral surfaces and reduce the frictional coefficient. Our results imply that the frictional coefficient can be modified through contact with fluids depending on their salt composition. The low adhesion energy between fault-forming minerals and the presence of an adsorbed water film is a possible reason for the low frictional coefficient observed at continuous fault slip zones.

  8. Improvement of SOFC electrodes using mixed ionic-electronic conductors

    SciTech Connect

    Matsuzaki, Y.; Hishinuma, M.

    1996-12-31

    Since the electrode reaction of SOFC is limited to the proximity of a triple phase boundary (TPB), the local current density at the electrode and electrolyte interface is larger than mean current density, which causes large ohmic and electrode polarization. This paper describes an application of mixed ionic-electronic conductors to reduce such polarization by means of (1) enhancing ionic conductivity of the electrolyte surface layer by coating a high ionic conductors, and (2) reducing the local current density by increasing the electrochemically active sites.

  9. Mesoscale studies of ionic closed membranes with polyhedral geometries

    NASA Astrophysics Data System (ADS)

    Olvera de la Cruz, Monica

    2016-06-01

    Large crystalline molecular shells buckle spontaneously into icosahedra while multicomponent shells buckle into various polyhedra. Continuum elastic theory explains the buckling of closed shells with one elastic component into icosahedra. A generalized elastic model, on the other hand, describes the spontaneous buckling of inhomogeneous shells into regular and irregular polyhedra. By co-assembling water-insoluble anionic (-1) amphiphiles with cationic (3+) amphiphiles, we realized ionic vesicles. Results revealed that surface crystalline domains and the unusual shell shapes observed arise from the competition of ionic correlations with charge-regulation. We explain here the mechanism by which these ionic membranes generate a mechanically heterogeneous vesicle.

  10. Biological implications of the hydrodynamics of swimming at or near the surface and in shallow water.

    PubMed

    Blake, R W

    2009-03-01

    The origins and effects of wave drag at and near the surface and in shallow water are discussed in terms of the dispersive waves generated by streamlined technical bodies of revolution and by semi-aquatic and aquatic animals with a view to bearing on issues regarding the design and function of autonomous surface and underwater vehicles. A simple two-dimensional model based on energy flux, allowing assessment of drag and its associated wave amplitude, is applied to surface swimming in Lesser Scaup ducks and is in good agreement with measured values. It is argued that hydrodynamic limitations to swimming at speeds associated with the critical Froude number ( approximately 0.5) and hull speed do not necessarily set biological limitations as most behaviours occur well below the hull speed. From a comparative standpoint, the need for studies on the hull displacement of different forms is emphasized. For forms in surface proximity, drag is a function of both Froude and Reynolds numbers. Whilst the depth dependence of wave drag is not particularly sensitive to Reynolds number, its magnitude is, with smaller and slower forms subject to relatively less drag augmentation than larger, faster forms that generate additional resistance due to ventilation and spray. A quasi-steady approach to the hydrodynamics of swimming in shallow water identifies substantial drag increases relative to the deeply submerged case at Froude numbers of about 0.9 that could limit the performance of semi-aquatic and aquatic animals and autonomous vehicles. A comparative assessment of fast-starting trout and upside down catfish shows that the energy losses of fast-starting fish are likely to be less for fish in surface proximity in deep water than for those in shallow water. Further work on unsteady swimming in both circumstances is encouraged. Finally, perspectives are offered as to how autonomous surface and underwater vehicles in surface proximity and shallow water could function to avoid

  11. Atomic-scale surface roughness of rutile and implications for organic molecule adsorption.

    PubMed

    Livi, Kenneth J T; Schaffer, Bernhard; Azzolini, David; Seabourne, Che R; Hardcastle, Trevor P; Scott, Andrew J; Hazen, Robert M; Erlebacher, Jonah D; Brydson, Rik; Sverjensky, Dimitri A

    2013-06-11

    Crystal surfaces provide physical interfaces between the geosphere and biosphere. It follows that the arrangement of atoms at the surfaces of crystals profoundly influences biological components at many levels, from cells through biopolymers to single organic molecules. Many studies have focused on the crystal-molecule interface in water using large, flat single crystals. However, little is known about atomic-scale surface structures of the nanometer- to micrometer-sized crystals of simple metal oxides typically used in batch adsorption experiments under conditions relevant to biogeochemistry and the origins of life. Here, we present atomic-resolution microscopy data with unprecedented detail of the circumferences of nanosized rutile (α-TiO2) crystals previously used in studies of the adsorption of protons, cations, and amino acids. The data suggest that one-third of the {110} faces, the largest faces on individual crystals, consist of steps at the atomic scale. The steps have the orientation to provide undercoordinated Ti atoms of the type and abundance for adsorption of amino acids as inferred from previous surface complexation modeling of batch adsorption data. A remarkably uniform pattern of step proportions emerges: the step proportions are independent of surface roughness and reflect their relative surface energies. Consequently, the external morphology of rutile nanometer- to micrometer-sized crystals imaged at the coarse scale of scanning electron microscope images is not an accurate indicator of the atomic smoothness or of the proportions of the steps present. Overall, our data strongly suggest that amino acids attach at these steps on the {110} surfaces of rutile. PMID:23675906

  12. Variability of the temporal bone surface's topography: implications for otologic surgery

    NASA Astrophysics Data System (ADS)

    Lecoeur, Jérémy; Noble, Jack H.; Balachandran, Ramya; Labadie, Robert F.; Dawant, Benoit M.

    2012-02-01

    Otologic surgery is performed for a variety of reasons including treatment of recurrent ear infections, alleviation of dizziness, and restoration of hearing loss. A typical ear surgery consists of a tympanomastoidectomy in which both the middle ear is explored via a tympanic membrane flap and the bone behind the ear is removed via mastoidectomy to treat disease and/or provide additional access. The mastoid dissection is performed using a high-speed drill to excavate bone based on a pre-operative CT scan. Intraoperatively, the surface of the mastoid component of the temporal bone provides visual feedback allowing the surgeon to guide their dissection. Dissection begins in "safe areas" which, based on surface topography, are believed to be correlated with greatest distance from surface to vital anatomy thus decreasing the chance of injury to the brain, large blood vessels (e.g. the internal jugular vein and internal carotid artery), the inner ear, and the facial nerve. "Safe areas" have been identified based on surgical experience with no identifiable studies showing correlation of the surface with subsurface anatomy. The purpose of our study was to investigate whether such a correlation exists. Through a three-step registration process, we defined a correspondence between each of twenty five clinically-applicable temporal bone CT scans of patients and an atlas and explored displacement and angular differences of surface topography and depth of critical structures from the surface of the skull. The results of this study reflect current knowledge of osteogenesis and anatomy. Based on two features (distance and angular difference), two regions (suprahelical and posterior) of the temporal bone show the least variability between surface and subsurface anatomy.

  13. Super ionic conductive glass

    DOEpatents

    Susman, Sherman; Volin, Kenneth J.

    1984-01-01

    An ionically conducting glass for use as a solid electrolyte in a power or secondary cell containing an alkali metal-containing anode and a cathode separated by an alkali metal ion conducting glass having an ionic transference number of unity and the general formula: A.sub.1+x D.sub.2-x/3 Si.sub.x P.sub.3-x O.sub.12-2x/3, wherein A is a network modifier for the glass and is an alkali metal of the anode, D is an intermediate for the glass and is selected from the class consisting of Zr, Ti, Ge, Al, Sb, Be, and Zn and X is in the range of from 2.25 to 3.0. Of the alkali metals, Na and Li are preferred and of the intermediate, Zr, Ti and Ge are preferred.

  14. Super ionic conductive glass

    DOEpatents

    Susman, S.; Volin, K.J.

    Described is an ionically conducting glass for use as a solid electrolyte in a power or secondary cell containing an alkali metal-containing anode and a cathode separated by an alkali metal ion conducting glass having an ionic transference number of unity and the general formula: A/sub 1 + x/D/sub 2-x/3/Si/sub x/P/sub 3 - x/O/sub 12 - 2x/3/, wherein A is a network modifier for the glass and is an alkali metal of the anode, D is an intermediate for the glass and is selected from the class consisting of Zr, Ti, Ge, Al, Sb, Be, and Zn and X is in the range of from 2.25 to 3.0. Of the alkali metals, Na and Li are preferred and of the intermediate, Zr, Ti and Ge are preferred.

  15. Ionic Strength Modulation of the Free Energy Landscape of Aβ40 Peptide Fibril Formation.

    PubMed

    Abelein, Axel; Jarvet, Jüri; Barth, Andreas; Gräslund, Astrid; Danielsson, Jens

    2016-06-01

    Protein misfolding and formation of cross-β structured amyloid fibrils are linked to many neurodegenerative disorders. Although recently developed quantitative approaches have started to reveal the molecular nature of self-assembly and fibril formation of proteins and peptides, it is yet unclear how these self-organization events are precisely modulated by microenvironmental factors, which are known to strongly affect the macroscopic aggregation properties. Here, we characterize the explicit effect of ionic strength on the microscopic aggregation rates of amyloid β peptide (Aβ40) self-association, implicated in Alzheimer's disease. We found that physiological ionic strength accelerates Aβ40 aggregation kinetics by promoting surface-catalyzed secondary nucleation reactions. This promoted catalytic effect can be assigned to shielding of electrostatic repulsion between monomers on the fibril surface or between the fibril surface itself and monomeric peptides. Furthermore, we observe the formation of two different β-structured states with similar but distinct spectroscopic features, which can be assigned to an off-pathway immature state (Fβ*) and a mature stable state (Fβ), where salt favors formation of the Fβ fibril morphology. Addition of salt to preformed Fβ* accelerates transition to Fβ, underlining the dynamic nature of Aβ40 fibrils in solution. On the basis of these results we suggest a model where salt decreases the free-energy barrier for Aβ40 folding to the Fβ state, favoring the buildup of the mature fibril morphology while omitting competing, energetically less favorable structural states. PMID:27171340

  16. Is the boundary layer of an ionic liquid equally lubricating at higher temperature?

    PubMed

    Hjalmarsson, Nicklas; Atkin, Rob; Rutland, Mark W

    2016-03-23

    Atomic force microscopy has been used to study the effect of temperature on normal forces and friction for the room temperature ionic liquid (IL) ethylammonium nitrate (EAN), confined between mica and a silica colloid probe at 25 °C, 50 °C, and 80 °C. Force curves revealed a strong fluid dynamic influence at room temperature, which was greatly reduced at elevated temperatures due to the reduced liquid viscosity. A fluid dynamic analysis reveals that bulk viscosity is manifested at large separation but that EAN displays a nonzero slip, indicating a region of different viscosity near the surface. At high temperatures, the reduction in fluid dynamic force reveals step-like force curves, similar to those found at room temperature using much lower scan rates. The ionic liquid boundary layer remains adsorbed to the solid surface even at high temperature, which provides a mechanism for lubrication when fluid dynamic lubrication is strongly reduced. The friction data reveals a decrease in absolute friction force with increasing temperature, which is associated with increased thermal motion and reduced viscosity of the near surface layers but, consistent with the normal force data, boundary layer lubrication was unaffected. The implications for ILs as lubricants are discussed in terms of the behaviour of this well characterised system. PMID:26976694

  17. Stabilization of MgAl2O4 spinel surfaces via doping

    NASA Astrophysics Data System (ADS)

    Hasan, Md. M.; Dholabhai, Pratik P.; Castro, Ricardo H. R.; Uberuaga, Blas P.

    2016-07-01

    Surface structure of complex oxides plays a vital role in processes such as sintering, thin film growth, and catalysis, as well as being a critical factor determining the stability of nanoparticles. Here, we report atomistic calculations of the low-index stoichiometric magnesium aluminate spinel (MgAl2O4) surfaces, each with two different chemical terminations. High temperature annealing was used to explore the potential energy landscape and provide more stable surface structures. We find that the lowest energy surface is {100} while the highest energy surface is {111}. The surfaces were subsequently doped with three trivalent dopants (Y3+, Gd3+, La3+) and one tetravalent dopant (Zr4+) and both the surface segregation energies of the dopants and surface energies of the doped surface were determined. All of the dopants reduce the surface energy of spinel, though this reduction in energy depends on both the size and valence of the dopant. Dopants with larger ionic radius tend to segregate to the surface more strongly and reduce the surface energy to a greater extent. Furthermore, the ionic valence of the dopants seems to have a stronger influence on the segregation than does ionic size. For both undoped and doped spinel, the predicted crystal shape is dominated by {100} surfaces, but the relative fraction of the various surfaces changes with doping due to the unequal changes in energy, which has implications on equilibrium nanoparticle shapes and therefore on applications sensitive to surface properties.

  18. Stabilization of MgAl2O4 spinel surfaces via doping

    DOE PAGESBeta

    Hasan, Md. M.; Dholabhai, Pratik P.; Castro, Ricardo H. R.; Uberuaga, Blas P.

    2016-07-01

    Here, the surface structure of complex oxides plays a vital role in processes such as sintering, thin film growth, and catalysis, as well as being a critical factor determining the stability of nanoparticles. We report atomistic calculations of the low-index stoichiometric magnesium aluminate spinel (MgAl2O4) surfaces, each with two different chemical terminations. High temperature annealing was used to explore the potential energy landscape and provide more stable surface structures. We find that the lowest energy surface is {100} while the highest energy surface is {111}. The surfaces were subsequently doped with three trivalent dopants (Y3+, Gd3+, La3+) and one tetravalentmore » dopant (Zr4+) and both the surface segregation energies of the dopants and surface energies of the doped surface were determined. All of the dopants reduce the surface energy of spinel, though this reduction in energy depends on both the size and valence of the dopant. Dopants with larger ionic radius tend to segregate to the surface more strongly and reduce the surface energy to a greater extent. Furthermore, the ionic valence of the dopants seems to have a stronger influence on the segregation than does ionic size. For both undoped and doped spinel, the predicted crystal shape is dominated by {100} surfaces, but the relative fraction of the various surfaces changes with doping due to the unequal changes in energy, which has implications on equilibrium nanoparticle shapes and therefore on applications sensitive to surface properties.« less

  19. Thermodynamic estimation: Ionic materials

    SciTech Connect

    Glasser, Leslie

    2013-10-15

    Thermodynamics establishes equilibrium relations among thermodynamic parameters (“properties”) and delineates the effects of variation of the thermodynamic functions (typically temperature and pressure) on those parameters. However, classical thermodynamics does not provide values for the necessary thermodynamic properties, which must be established by extra-thermodynamic means such as experiment, theoretical calculation, or empirical estimation. While many values may be found in the numerous collected tables in the literature, these are necessarily incomplete because either the experimental measurements have not been made or the materials may be hypothetical. The current paper presents a number of simple and relible estimation methods for thermodynamic properties, principally for ionic materials. The results may also be used as a check for obvious errors in published values. The estimation methods described are typically based on addition of properties of individual ions, or sums of properties of neutral ion groups (such as “double” salts, in the Simple Salt Approximation), or based upon correlations such as with formula unit volumes (Volume-Based Thermodynamics). - Graphical abstract: Thermodynamic properties of ionic materials may be readily estimated by summation of the properties of individual ions, by summation of the properties of ‘double salts’, and by correlation with formula volume. Such estimates may fill gaps in the literature, and may also be used as checks of published values. This simplicity arises from exploitation of the fact that repulsive energy terms are of short range and very similar across materials, while coulombic interactions provide a very large component of the attractive energy in ionic systems. Display Omitted - Highlights: • Estimation methods for thermodynamic properties of ionic materials are introduced. • Methods are based on summation of single ions, multiple salts, and correlations. • Heat capacity, entropy

  20. 3-Methylpiperidinium ionic liquids.

    PubMed

    Belhocine, Tayeb; Forsyth, Stewart A; Gunaratne, H Q Nimal; Nieuwenhuyzen, Mark; Nockemann, Peter; Puga, Alberto V; Seddon, Kenneth R; Srinivasan, Geetha; Whiston, Keith

    2015-04-28

    A wide range of room temperature ionic liquids based on the 3-methylpiperdinium cation core were produced from 3-methylpiperidine, which is a derivative of DYTEK® A amine. First, reaction with 1-bromoalkanes or 1-bromoalkoxyalkanes generated the corresponding tertiary amines (Rmβpip, R = alkyl or alkoxyalkyl); further quaternisation reactions with the appropriate methylating agents yielded the quaternary [Rmmβpip]X salts (X(-) = I(-), [CF3CO2](-) or [OTf](-); Tf = -SO2CF3), and [Rmmβpip][NTf2] were prepared by anion metathesis from the corresponding iodides. All [NTf2](-) salts are liquids at room temperature. [Rmmβpip]X (X(-) = I(-), [CF3CO2](-) or [OTf](-)) are low-melting solids when R = alkyl, but room temperature liquids upon introduction of ether functionalities on R. Neither of the 3-methylpiperdinium ionic liquids showed any signs of crystallisation, even well below 0 °C. Some related non-C-substituted piperidinium and pyrrolidinium analogues were prepared and studied for comparison. Crystal structures of 1-hexyl-1,3-dimethylpiperidinium tetraphenylborate, 1-butyl-3-methylpiperidinium bromide, 1-(2-methoxyethyl)-1-methylpiperidinium chloride and 1-(2-methoxyethyl)-1-methylpyrrolidinium bromide are reported. Extensive structural and physical data are collected and compared to literature data, with special emphasis on the systematic study of the cation ring size and/or asymmetry effects on density, viscosity and ionic conductivity, allowing general trends to be outlined. Cyclic voltammetry shows that 3-methylpiperidinium ionic liquids, similarly to azepanium, piperidinium or pyrrolidinium counterparts, are extremely electrochemically stable; the portfolio of useful alternatives for safe and high-performing electrolytes is thus greatly extended. PMID:25669485

  1. Cyclic phosphonium ionic liquids

    PubMed Central

    Mukhlall, Joshua A; Romeo, Alicia R; Gohdo, Masao; Ramati, Sharon; Berman, Marc; Suarez, Sophia N

    2014-01-01

    Summary Ionic liquids (ILs) incorporating cyclic phosphonium cations are a novel category of materials. We report here on the synthesis and characterization of four new cyclic phosphonium bis(trifluoromethylsulfonyl)amide ILs with aliphatic and aromatic pendant groups. In addition to the syntheses of these novel materials, we report on a comparison of their properties with their ammonium congeners. These exemplars are slightly less conductive and have slightly smaller self-diffusion coefficients than their cyclic ammonium congeners. PMID:24605146

  2. VOC and HAP recovery using ionic liquids

    SciTech Connect

    Michael R. Milota : Kaichang Li

    2007-05-29

    During the manufacture of wood composites, paper, and to a lesser extent, lumber, large amounts of volatile organic compounds (VOCs) such as terpenes, formaldehyde, and methanol are emitted to air. Some of these compounds are hazardous air pollutants (HAPs). The air pollutants produced in the forest products industry are difficult to manage because the concentrations are very low. Presently, regenerative thermal oxidizers (RTOs and RCOs) are commonly used for the destruction of VOCs and HAPs. RTOs consume large amounts of natural gas to heat air and moisture. The combustion of natural gas generates increased CO2 and NOx, which have negative implications for global warming and air quality. The aforementioned problems are addressed by an absorption system containing a room-temperature ionic liquid (RTIL) as an absorbent. RTILs are salts, but are in liquid states at room temperature. RTILs, an emerging technology, are receiving much attention as replacements for organic solvents in industrial processes with significant cost and environmental benefits. Some of these processes include organic synthesis, extraction, and metal deposition. RTILs would be excellent absorbents for exhausts from wood products facilities because of their unique properties: no measurable vapor pressure, high solubility of wide range of organic compounds, thermal stability to 200°C (almost 400°F), and immisciblity with water. Room temperature ionic liquids were tested as possible absorbents. Four were imidizolium-based and were eight phosphonium-based. The imidizolium-based ionic liquids proved to be unstable at the conditions tested and in the presence of water. The phosphonium-based ionic liquids were stable. Most were good absorbents; however, cleaning the contaminates from the ionic liquids was problematic. This was overcome with a higher temperature (120°C) than originally proposed and a very low pressure (1 kPa. Absorption trials were conducted with tetradecy

  3. Effect of blood storage on erythrocyte/wall interactions: implications for surface charge and rigidity.

    PubMed

    Godin, C; Caprani, A

    1997-01-01

    In this report, we study, under flow conditions, the interactions of stored erythrocytes with an artificial surface: a microelectrode whose charge density ranges from -15 to +27 microC/cm2. Interactions consist of red cells slowly circulating on the microelectrode and exerting a real contact with the electrode. Interaction is detected and measured by transient fluctuations of the electrolyte resistance obtained by impedance measurement of the microelectrode. Effects of aging induced by storage of whole blood at 4 degrees C show that the surface charge of erythrocytes rapidly decreases when blood is stored for more than 6 days under our experimental conditions. In comparison with trypsin-treated erythrocytes, an eight day storage induces a 60% decrease in the surface charge of red cells. After two weeks of storage, red cells are no longer negatively charged, presumably because of removal of sialic acid. Cells rigidity is significant after 6 days of storage and influences the electrical contact. Membrane rigidity increase could arise from the surface charge decrease. Finally the surface charge decrease could be importance in the use of stored blood. PMID:9232845

  4. LIMEX '87 ice surface characteristics - Implications for C-band SAR backscatter signatures

    NASA Technical Reports Server (NTRS)

    Drinkwater, Mark R.

    1989-01-01

    Ice surface characterization data collected in 1987, during the Labrador Sea Ice Margin Experiment, are analyzed to estimate the changes in snow and ice properties at the onset of melt. Surface measurements were made from an ice research vessel on several days (some of which had coincident remote-sensing flights) at a number of locations in the marginal ice zone. These data are used as input parameters in a simple scattering model to simulate the effects of variations in material properties upon C-band scattering signatures. Snow moisture and large-scale surface roughness are demonstrated to have the largest effect upon HH polarization scattering cross-section sigma(HH)(O) and large differences are predicted between undeformed floe surfaces and deformed or undulating rough ice surfaces. Using a parametric approach, an approximate picture of rough and smooth ice signatures and their relative contrast are provided. The models reproduce a trend observed in synthetic aperture radar (SAR) images of increasing backscatter contrast between deformed and underformed ice over an early period of warning: such observations are consistent with the results of analysis of SAR images to date. The model also reproduces a calibrated SAR-derived signature with a reasonable degree of accuracy.

  5. Beryllium in the Galactic halo - Surface abundances from standard, diffusive, and rotational stellar evolution, and implications

    NASA Technical Reports Server (NTRS)

    Deliyannis, Constantine P.; Pinsonneault, Marc H.

    1990-01-01

    The recently observed upper limits to the beryllium abundances in population II stars are much lower than population I detections. This difference reflects an intrinsic difference in the initial abundances and is not caused by different degrees of depletion driven by stellar evolution processes from similar initial abundances. Evolutionary sequences of models from the early premain sequence to beyond the turnoff that correspond to halo dwarfs with Fe/H abundances of -1.3, -2.3, and -3.3 are constructed, and standard, diffusive, and rotational mechanisms are used to estimate a maximal possible beryllium depletion. Halo star models in the T(eff) range 6000 to 5000 K might be rotationally depleted by a factor of 1.5-2, and the total depletion should be no more than (conservatively) a factor of 3. Implications for cosmology, cosmic-ray theory, and Galactic chemical evolution are discussed.

  6. VARIABILITY OF SURFACE FLOWS ON THE SUN AND THE IMPLICATIONS FOR EXOPLANET DETECTION

    SciTech Connect

    Makarov, Valeri V.

    2010-05-20

    The published Mount Wilson Doppler-shift measurements of the solar velocity field taken in 1967-1982 are revisited with a more accurate model, which includes two terms representing the meridional flow and three terms corresponding to the convective limb shift. Integration of the recomputed data over the visible hemisphere reveals significant variability of the net radial velocity at characteristic time scales of 0.1-10 years, with a standard deviation of 1.4 m s{sup -1}. This result is supported by independent published observations. The implications for exoplanet detection include reduced sensitivity of the Doppler method to Earth-like planets in the habitable zone, and an elevated probability of false detections at periods of a few to several years.

  7. Surface properties of bacillus subtilis determined by acid/base titrations, and the implications for metal adsorption in fluid-rock systems

    SciTech Connect

    Fein, J.B.; Davis, T.A.

    1996-10-01

    Bacteria are ubiquitous in low temperature aqueous systems, but quantifying their effects on aqueous mass transport remains a problem. Numerous studies have qualitatively examined the metal binding capacity of bacterial cell walls. However, quantitative thermodynamic modeling of metal-bacteria-mineral systems requires a detailed knowledge of the surface properties of the bacterial functional groups. In this study, we have conducted acid/base titrations of suspensions of B. subtilis, a common subsurface species whose surface properties are largely controlled by carboxyl groups. Titrations were conducted between pH 2 and 11 at several ionic strengths. The data are analyzed using a constant capacitance model to account for the surface electric field effects on the acidity constant. The pK{sub a} value that best fits the titration data is 3.9 {plus_minus} 0.3. This result represents the first step toward quantifying bacteria-metal and mineral-bacteria-metal interactions using equilibrium thermodynamics.

  8. Ionic liquid based multifunctional double network gel

    NASA Astrophysics Data System (ADS)

    Ahmed, Kumkum; Higashihara, Tomoya; Arafune, Hiroyuki; Kamijo, Toshio; Morinaga, Takashi; Sato, Takaya; Furukawa, Hidemitsu

    2015-04-01

    Gels are a promising class of soft and wet materials with diverse application in tissue engineering and bio-medical purpose. In order to accelerate the development of gels, it is required to synthesize multi-functional gels of high mechanical strength, ultra low surface friction and suitable elastic modulus with a variety of methods and new materials. Among many types of gel ionic gel made from ionic liquids (ILs) could be used for diverse applications in electrochemical devices and in the field of tribology. IL, a promising materials for lubrication, is a salt with a melting point lower than 100 °C. As a lubricant, ILs are characterized by an extremely low vapor pressure, high thermal stability and high ion conductivity. In this work a novel approach of making double network DN ionic gel using IL has been made utilizing photo polymerization process. A hydrophobic monomer Methyl methacrylate (MMA) has been used as a first network and a hydrophobic IL monomer, N,N-diethyl-N-(2-mthacryloylethyl)-N-methylammonium bistrifluoromethylsulfonyl)imide (DEMM-TFSI) has been used as a second network using photo initiator benzophenon and crosslinker triethylene glycol dimethacrylate (TEGDMA). The resulting DN ionic gel shows transparency, flexibility, high thermal stability, good mechanical toughness and low friction coefficient value which can be a potential candidate as a gel slider in different mechanical devices and can open a new area in the field of gel tribology.

  9. The spectral and physical properties of metal in meteorite assemblages - Implications of asteroid surface materials

    NASA Technical Reports Server (NTRS)

    Gaffey, M. J.

    1986-01-01

    One of the objectives of the present paper is related to a definition of the spectral contribution of the nickel-iron metal component in meteoritic assemblages. Another objective is the elucidation of the chemical, physical, and petrographic properties of the metal grains which affect the spectral signature in asteroid surface materials. It is pointed out that an improved understanding of the spectral and physical properties of metal in asteroid regoliths should permit an improved characterization of these objects, and, in particular, a better evaluation of the differentiated or undifferentiated nature of the S-type and M-type asteroids. Attention is given to the spectra of iron and nickel-iron metals, the spectral effects of metal in chondritic assemblages, the spectral reflectance of metal grains in ordinary chondrites, the nature of the surfaces of chondritic metal grains, the origin of coats on chondritic metal grains, and the fragmentation of metal on asteroid surfaces.

  10. Spatial organization of surface nanobubbles and its implications in their formation process.

    PubMed

    Lhuissier, Henri; Lohse, Detlef; Zhang, Xuehua

    2014-02-21

    We study the size and spatial distribution of surface nanobubbles formed by the solvent exchange method to gain insight into the mechanism of their formation. The analysis of Atomic Force Microscopy (AFM) images of nanobubbles formed on a hydrophobic surface reveals that the nanobubbles are not randomly located, which we attribute to the role of the history of nucleation during the formation. Moreover, the size of each nanobubble is found to be strongly correlated with the area of the bubble-depleted zone around it. The precise correlation suggests that the nanobubbles grow by diffusion of the gas from the bulk rather than by diffusion of the gas adsorbed on the surface. Lastly, the size distribution of the nanobubbles is found to be well described by a log-normal distribution. PMID:24983101

  11. Mars - Near-infrared spectral reflectance of surface regions and compositional implications

    NASA Astrophysics Data System (ADS)

    McCord, T. B.; Clark, R. N.; Singer, R. B.

    1982-04-01

    Both morphological and compositional information are needed to define and characterize surface geologic units on Mars. A description is presented of new, near-infrared spectra (0.65 to 2.50 micrometers) for 11 regions on the Martian surface observed in 1978. The high photometric quality of these data combined with increased near-infrared spectral coverage provide new information about the spectral behavior and, therefore, the composition and physical nature of Martian surface materials. The spectral reflectances were obtained with the aid of a 2.2-m telescope located on Mauna Kea, Hawaii. A cooled (to 77 K) circular variable filter spectrometer with an InSb detector was used to measure alternatively Mars and the standard star Beta Geminorum. Attention is given to general spectral characteristics, the dark region composition, spectral evidence for water, and the 2.3 micrometer absorption.

  12. Nitric Acid-Sea Salt Reactions: Implications for Nitrogen Deposition to Water Surfaces.

    NASA Astrophysics Data System (ADS)

    Pryor, S. C.; Sørensen, L. L.

    2000-05-01

    Many previous studies have indicated the importance of nitric acid (HNO3) reactions on sea salt particles for flux divergence of HNO3 in the marine surface layer. The potential importance of this reaction in determining the spatial and temporal patterns of nitrogen dry deposition to marine ecosystems is investigated using models of sea spray generation and particle- and gas-phase dry deposition. Under horizontally homogeneous conditions with near-neutral stability and for wind speeds between 3.5 and 10 m s1, transfer of HNO3 to the particle phase to form sodium nitrate may decrease the deposition velocity of nitrogen by over 50%, leading to greater horizontal transport prior to deposition to the sea surface. Conversely, for wind speeds above 10 m s1, transfer of nitrogen to the particle phase would increase the deposition rate and hence decrease horizontal transport prior to surface removal.

  13. Age of Lunar Meteorite LAP02205 and Implications for Impact-Sampling of Planetary Surfaces

    NASA Technical Reports Server (NTRS)

    Nyquist, L. E.; Shih, C.-Y.; Reese, Y.; Bogard, D. D.

    2005-01-01

    We have measured the age of lunar meteorite LAP02205 by the Rb-Sr and Ar-Ar methods. Sm-Nd analyses are in progress. The Rb-Sr and Ar-Ar ages indicate a crystallization age of approx. 3 Ga. Comparing the ages of LAP02205 and other lunar mare basaltic meteorites to mare surface ages based on the density of impact craters shows no significant bias in impact- sampling of lunar mare surfaces. Comparing the isotopic and geochemical data for LAP02205 to those for other lunar mare basalts suggests that it is a younger variant of the type of volcanism that produced the Apollo 12 basalts. Representative impact-sampling of the lunar surface

  14. Cell surface reactivity of Synechococcus sp. PCC 7002: Implications for metal sorption from seawater

    NASA Astrophysics Data System (ADS)

    Liu, Yuxia; Alessi, D. S.; Owttrim, G. W.; Petrash, D. A.; Mloszewska, A. M.; Lalonde, S. V.; Martinez, R. E.; Zhou, Qixing; Konhauser, K. O.

    2015-11-01

    The past two decades have seen a significant advancement in our understanding of bacterial surface chemistry and the ability of microbes to bind metals from aqueous solutions. Much of this work has been aimed at benthic, mat-forming species in an effort to model the mechanisms by which microbes may exert control over metal contaminant transport in soils and groundwater. However, there is a distinct paucity of information pertaining to the surface chemistry of marine planktonic species, and their ability to bind trace metals from the ocean's photic zone. To this end, the surface properties of the cyanobacterium Synechococcus sp. PCC 7002 were studied as this genus is one of the dominant marine phytoplankton, and as such, contributes significantly to metal cycling in the ocean's photic zone. Zeta potential measurement indicates that the cell surfaces display a net negative charge. This was supported by potentiometric titration and Fourier transform infrared spectroscopy analyses demonstrating that the cells are dominated by surface proton releasing ligands, including carboxyl, phosphoryl and amino functional groups, with a total ligand density of 34.18 ± 1.62 mmol/g (dry biomass). Cd adsorption experiments further reveal that carboxyl groups play a primary role in metal adsorption, with 1.0 g of dry biomass binding an equivalent of 7.05 × 10-5 M of Cd from solution at pH = 8. To put this value into context, in 1 L of seawater, and with an open-ocean population of Synechococcus of 105 cells/mL in the photic zone, approximately 10 nmol of Cd could potentially be adsorbed by the cyanobacteria; an amount equivalent to seawater Cd concentrations. Although we have only focused on one microbial species and one metal cation, and we have not considered trace element assimilation, our results highlight the potential role of surface sorption by phytoplankton in the cycling of metals in the ocean.

  15. Subsurface Emission Effects in AMSR-E Measurements: Implications for Land Surface Microwave Emissivity Retrieval

    NASA Technical Reports Server (NTRS)

    Galantowicz, John F.; Moncet, Jean-Luc; Liang, Pan; Lipton, Alan E.; Uymin, Gennady; Prigent, Catherine; Grassotti, Christopher

    2011-01-01

    An analysis of land surface microwave emission time series shows that the characteristic diurnal signature associated with subsurface emission in sandy deserts carry over to arid and semi-arid region worldwide. Prior work found that diurnal variation of Special Sensor Microwave/Imager (SSM/I) brightness temperatures in deserts was small relative to International Satellite Cloud Climatology Project land surface temperature (LST) variation and that the difference varied with surface type and was largest in sand sea regions. Here we find more widespread subsurface emission effects in Advanced Microwave Scanning Radiometer-EOS (AMSR-E) measurements. The AMSR-E orbit has equator crossing times near 01:30 and 13 :30 local time, resulting in sampling when near-surface temperature gradients are likely to be large and amplifying the influence of emission depth on effective emitting temperature relative to other factors. AMSR-E measurements are also temporally coincident with Moderate Resolution Imaging Spectroradiometer (MODIS) LST measurements, eliminating time lag as a source of LST uncertainty and reducing LST errors due to undetected clouds. This paper presents monthly global emissivity and emission depth index retrievals for 2003 at 11, 19, 37, and 89 GHz from AMSR-E, MODIS, and SSM/I time series data. Retrieval model fit error, stability, self-consistency, and land surface modeling results provide evidence for the validity of the subsurface emission hypothesis and the retrieval approach. An analysis of emission depth index, emissivity, precipitation, and vegetation index seasonal trends in northern and southern Africa suggests that changes in the emission depth index may be tied to changes in land surface moisture and vegetation conditions

  16. Casimir Torque between Topological Insulators: a Physical Implication of the Surface State Hexagonal Warping Effect

    NASA Astrophysics Data System (ADS)

    Chen, Liang; Chang, Kai

    We use a variation of the Lifshitz formula to calculate the anisotropic Casimir energy density between two topological insulators in the vacuum. We find that the hexagonal warping effect can induce a Casimir torque between the two topological insulators, Tc ~ sin (6 θ) with twisted angle θ. The maximal Casimir torque at θ = π / 12 is estimated to be ~10-19 N . m / rad for Bi2Te3 on the [111] surface when the distance between the two topological insulators is about 20 nm and the surface areas are taken to be ~ 1 cm2 .

  17. Implications of old, glaciated surfaces at high elevations in the Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Brocklehurst, S. H.; Granger, D. E.; Whipple, K. X.

    2002-12-01

    Among the numerous arêtes and sharp peaks at the crest of the Sierra Nevada, California, are a number of remarkably low relief, diamict-covered surfaces. We propose that these widespread, enigmatic, old surfaces represent former glacial valley floors. The head of Sardine Canyon is a beheaded cirque. Thick piles of diamict and gruss attest to the absence of any recent glaciation. At the point where the valley floor is truncated by the cliffs leading down into the Golden Trout Lake basin, we found boulders of a distinct biotite leucogranite not found elsewhere within the Sardine Canyon basin. Furthermore, glacial polish on the undersides of these boulders indicates that they were transported into place by a glacier. Cosmogenic exposure age dating on a large, flat boulder just downvalley of these erratics suggests that there has not been a cirque glacier in the basin in the last ~190 ka. This exposure age represents a minimum time since glaciation in the basin due to an unknown amount of erosion of the rock surface. The cirque on the western side of Baxter Pass is in the process of being beheaded. The deposit here is much coarser than that in Sardine Canyon, and exposure dates in the range ~20-50 ka confirm that this surface is younger. At the other extreme in terms of age, the isolated, small patch of diamict on the northeastern ridge of University Peak is surrounded on all sides by steep cliffs, and presumably represents a much more advanced stage in the evolution of these surfaces than Sardine Canyon. Given the variety of ages for these surfaces, and modelling studies that have shown that glacial headwall erosion is an important process, we infer that the glacial drainages of the eastern Sierra Nevada are subject to a cycle of drainage capture and relief inversion events, similar to the evolution of fluvial drainage networks. These processes produce diamict-covered surfaces at various stages of evolution from clearly U-shaped forms to stranded, flatter surfaces at

  18. Tailoring biomaterial surface properties to modulate host-implant interactions: implication in cardiovascular and bone therapy

    PubMed Central

    Pacelli, Settimio; Manoharan, Vijayan; Desalvo, Anna; Lomis, Nikita; Jodha, Kartikeya Singh

    2016-01-01

    Host body response to a foreign medical device plays a critical role in defining its fate post implantation. It is thus important to control host-material interactions by designing innovative implant surfaces. In the recent years, biochemical and topographical features have been explored as main target to produce this new type of bioinert or bioresponsive implants. The review discusses specific biofunctional materials and strategies to achieve a precise control over implant surface properties and presents possible solutions to develop next generation of implants, particularly in the fields of bone and cardiovascular therapy.

  19. Orbital Radar Response of Near Surface Materials in Southern Egypt and Implications for Cenozoic History

    NASA Astrophysics Data System (ADS)

    Maxwell, T. A.; Grant, J. A.; Johnston, A. K.

    2004-05-01

    Although the existence of "trunk" and tributary drainage channels beneath the sand in the northeast Sahara has been known for two decades, data from the SIR-C mission continues to be useful in solving geologic problems and understanding the radar response from specific types of near surface materials. In the Kiseiba Oasis region of southwest Egypt, SIR-C data revealed a complex tributary pattern of varying brightness that indicated the presence of paleodrainage not noted in the field. The orbital imaging radar uniquely specified key areas for detailed field studies that were not apparent in visible wavelengths. Twenty-two trenches up to 3 m deep, hundreds of shallow pits, several auger holes, and ground penetrating radar reveal that this area has had a history of fluctuating climatic conditions responsible for excavation and enlargement of the local depression by fluvial erosion and preservation of relict surfaces by aeolian blanketing of sand sheet deposits. The resulting near-surface stratigraphy is a complex mixture of fluvial pebble lags in the subsurface and on the surface, where aeolian mixing and local transport have modified the original geometry. In L-band (23 cm wavelength) SIR-C data, a hierarchy of returned signal strength and geometric patterns enables us to predict the type of surface and near-surface materials, sequentially from shallow bedrock to subsurface and surficial lags to sand sheet-veneered weathered anhydrite. Integrating the pattern of sedimentary deposits with relict channels and interfluves enables a better understanding of the origin of the Kiseiba-Dungul depression and its Cenozoic history. What was once thought to be a continuous deposit of Eocene limestone from southern Egypt into northern Sudan is cast in doubt as even the most optimistic estimates of scarp retreat don't permit hundred's of kms of retreat to the present position. Instead, the E-W pattern of the depression, the relict hills, and fracture zones all suggest structural

  20. A much warmer Earth surface for most of geologic time: implications to biotic weathering

    NASA Technical Reports Server (NTRS)

    Schwartzman, D. W.; McMenamin, M.

    1993-01-01

    The authors present two scenarios for the temperature history of Earth. One scenario is conventional, the other relies on a warmer history. Both scenarios include surface cooling determined by the evolution of the biosphere and are similar until the Proterozoic period. The warmer scenario requires a higher plant/lichen terrestrial biota to increase weathering intensity. Justification for a warmer surface includes period temperatures from the oxygen isotope record of coexisting phosphates and cherts, an upper limit of 58 degrees C from primary gypsum precipitation, and the lack of fractionation of sulfur isotopes between sulfide and sulfates in Archean sediments.

  1. Evidence for a basalt-free surface on Mercury and implications for internal heat.

    PubMed

    Jeanloz, R; Mitchell, D L; Sprague, A L; de Pater, I

    1995-06-01

    Microwave and mid-infrared observations reveal that Mercury's surface contains less FeO + TiO2 and at least as much feldspar as the lunar highlands. The results are compatible with the high albedo (brightness) of Mercury's surface at visible wavelengths in suggesting a rock and soil composition that is devoid of basalt, the primary differentiate of terrestrial mantles. The occurrence of a basalt-free, highly differentiated crust is in accord with recent models of the planet's thermal evolution and suggests that Mercury has retained a hot interior as a result of a combination of inefficient mantle convection and minimal volcanic heat loss. PMID:7770770

  2. An ionic electro-active actuator made with graphene film electrode, chitosan and ionic liquid

    NASA Astrophysics Data System (ADS)

    He, Qingsong; Yu, Min; Yang, Xu; Kim, Kwang Jin; Dai, Zhendong

    2015-06-01

    A newly developed ionic electro-active actuator composed of an ionic electrolyte layer sandwiched between two graphene film layers was investigated. Scanning electronic microscopy observation and x-ray diffraction analysis showed that the graphene sheets in the film stacked in a nearly face-to-face fashion but did not restack back to graphite, and the resulting graphene film with low sheet resistance (10 Ω sq-1) adheres well to the electrolyte membrane. Contact angle measurement showed the surface energy (37.98 mJ m-2) of the ionic electrolyte polymer is 2.67 times higher than that (14.2 mJ m-2) of the Nafion membrane, contributing to the good adhesion between the graphene film electrode and the electrolyte membrane. An electric double-layer is formed at the interface between the graphene film electrode and the ionic electrolyte membrane under the input potential, resulting in a higher capacitance of 27.6 mF cm-2. We report that this ionic actuator exhibits adequate bending strain, ranging from 0.032 to 0.1% (305 to 945 μm) as functions of voltage.

  3. Ozone-surface interactions: Investigations of mechanisms, kinetics, mass transport, and implications for indoor air quality

    SciTech Connect

    Morrison, Glenn C.

    1999-12-01

    In this dissertation, results are presented of laboratory investigations and mathematical modeling efforts designed to better understand the interactions of ozone with surfaces. In the laboratory, carpet and duct materials were exposed to ozone and measured ozone uptake kinetics and the ozone induced emissions of volatile organic compounds. To understand the results of the experiments, mathematical methods were developed to describe dynamic indoor aldehyde concentrations, mass transport of reactive species to smooth surfaces, the equivalent reaction probability of whole carpet due to the surface reactivity of fibers and carpet backing, and ozone aging of surfaces. Carpets, separated carpet fibers, and separated carpet backing all tended to release aldehydes when exposed to ozone. Secondary emissions were mostly n-nonanal and several other smaller aldehydes. The pattern of emissions suggested that vegetable oils may be precursors for these oxidized emissions. Several possible precursors and experiments in which linseed and tung oils were tested for their secondary emission potential were discussed. Dynamic emission rates of 2-nonenal from a residential carpet may indicate that intermediate species in the oxidation of conjugated olefins can significantly delay aldehyde emissions and act as reservoir for these compounds. The ozone induced emission rate of 2-nonenal, a very odorous compound, can result in odorous indoor concentrations for several years. Surface ozone reactivity is a key parameter in determining the flux of ozone to a surface, is parameterized by the reaction probability, which is simply the probability that an ozone molecule will be irreversibly consumed when it strikes a surface. In laboratory studies of two residential and two commercial carpets, the ozone reaction probability for carpet fibers, carpet backing and the equivalent reaction probability for whole carpet were determined. Typically reaction probability values for these materials were 10

  4. The footprint of Alaskan tundra fires during the past half-century: implications for surface properties and radiative forcing

    USGS Publications Warehouse

    Rocha, Adrian V.; Loranty, Michael M.; Higuera, Phil E.; Mack, Michelle C.; Hu, Feng Sheng; Jones, Benjamin M.; Breen, Amy L.; Rastetter, Edward B.; Goetz, Scott J.; Shaver, Gus R.

    2012-01-01

    Recent large and frequent fires above the Alaskan arctic circle have forced a reassessment of the ecological and climatological importance of fire in arctic tundra ecosystems. Here we provide a general overview of the occurrence, distribution, and ecological and climate implications of Alaskan tundra fires over the past half-century using spatially explicit climate, fire, vegetation and remote sensing datasets for Alaska. Our analyses highlight the importance of vegetation biomass and environmental conditions in regulating tundra burning, and demonstrate that most tundra ecosystems are susceptible to burn, providing the environmental conditions are right. Over the past two decades, fire perimeters above the arctic circle have increased in size and importance, especially on the North Slope, indicating that future wildfire projections should account for fire regime changes in these regions. Remote sensing data and a literature review of thaw depths indicate that tundra fires have both positive and negative implications for climatic feedbacks including a decadal increase in albedo radiative forcing immediately after a fire, a stimulation of surface greenness and a persistent long-term (>10 year) increase in thaw depth. In order to address the future impact of tundra fires on climate, a better understanding of the control of tundra fire occurrence as well as the long-term impacts on ecosystem carbon cycling will be required.

  5. Mechanisms of Chromate, Selenate, and Sulfate Adsorption on Al-Substituted Ferrihydrite: Implications for Ferrihydrite Surface Structure and Reactivity.

    PubMed

    Johnston, Chad P; Chrysochoou, Maria

    2016-04-01

    Ferrihydrite is a nanocrystalline Fe (hydr)oxide and important sink for environmental contaminants. Although Fe (hydr)oxides are rarely pure in natural systems, little is known about the effects of structural impurities such as Al on the surface properties and reactivity of ferrihydrite. In this study, we characterized the adsorption mechanisms of chromate, selenate, and sulfate on Al-substituted ferrihydrite (0, 6, 12, 18, and 24 mol % Al) using in situ attenuated total reflection Fourier transform infrared spectroscopy. Spectral data sets recorded as a function of pH were processed using a multivariate curve resolution technique to identify which types of surface species form and to generate their concentration profiles as a function of pH and Al content. Results show a significant increase in relative fraction of outer-sphere complexes for all three oxyanions with increasing Al substitution. In addition, the effect of Al substitution is found to be mechanism-specific in the case of chromate, with bidentate complexes disproportionately suppressed over monodentate complexes at higher Al contents. Overall, our findings have important implications for the fate of chromate, selenate, and sulfate in subsurface environments and offer new insight into the surface reactivity of Al-ferrihydrite. PMID:26900715

  6. The role of the surface on microglia function: implications for central nervous system tissue engineering

    PubMed Central

    Pires, Liliana R.; Rocha, Daniela N.; Ambrosio, Luigi; Pêgo, Ana Paula

    2015-01-01

    In tissue engineering, it is well accepted that a scaffold surface has a decisive impact on cell behaviour. Here we focused on microglia—the resident immune cells of the central nervous system (CNS)—and on their response to poly(trimethylene carbonate-co-ε-caprolactone) (P(TMC-CL)) fibrous and flat surfaces obtained by electrospinning and solvent cast, respectively. This study aims to provide cues for the design of instructive surfaces that can contribute to the challenging process of CNS regeneration. Cell morphology was evidently affected by the substrate, mirroring the surface main features. Cells cultured on flat substrates presented a round shape, while cells with elongated processes were observed on the electrospun fibres. A higher concentration of the pro-inflammatory cytokine tumour necrosis factor-α was detected in culture media from microglia on fibres. Still, astrogliosis is not exacerbated when astrocytes are cultured in the presence of microglia-conditioned media obtained from cultures in contact with either substrate. Furthermore, a significant percentage of microglia was found to participate in the process of myelin phagocytosis, with the formation of multinucleated giant cells being observed only on films. Altogether, the results presented suggest that microglia in contact with the tested substrates may contribute to the regeneration process, putting forward P(TMC-CL) substrates as supporting matrices for nerve regeneration. PMID:25540243

  7. The role of the surface on microglia function: implications for central nervous system tissue engineering.

    PubMed

    Pires, Liliana R; Rocha, Daniela N; Ambrosio, Luigi; Pêgo, Ana Paula

    2015-02-01

    In tissue engineering, it is well accepted that a scaffold surface has a decisive impact on cell behaviour. Here we focused on microglia-the resident immune cells of the central nervous system (CNS)-and on their response to poly(trimethylene carbonate-co-ε-caprolactone) (P(TMC-CL)) fibrous and flat surfaces obtained by electrospinning and solvent cast, respectively. This study aims to provide cues for the design of instructive surfaces that can contribute to the challenging process of CNS regeneration. Cell morphology was evidently affected by the substrate, mirroring the surface main features. Cells cultured on flat substrates presented a round shape, while cells with elongated processes were observed on the electrospun fibres. A higher concentration of the pro-inflammatory cytokine tumour necrosis factor-α was detected in culture media from microglia on fibres. Still, astrogliosis is not exacerbated when astrocytes are cultured in the presence of microglia-conditioned media obtained from cultures in contact with either substrate. Furthermore, a significant percentage of microglia was found to participate in the process of myelin phagocytosis, with the formation of multinucleated giant cells being observed only on films. Altogether, the results presented suggest that microglia in contact with the tested substrates may contribute to the regeneration process, putting forward P(TMC-CL) substrates as supporting matrices for nerve regeneration. PMID:25540243

  8. Regional variations in magnetic properties of surface sediments in the Qaidam Basin and their paleoenvironmental implications

    NASA Astrophysics Data System (ADS)

    Zan, Jinbo; Fang, Xiaomin; Yan, Maodu; Zhang, Zhiguo; Zhang, Dawen

    2015-11-01

    The Qaidam Basin is the largest intermontane basin on the northeastern edge of the Tibetan Plateau. At present, systematic rock magnetic studies of surface sediments in this basin are scarce because of the vast area and poor accessibility. In this paper, multi-parameter rock magnetic investigations of surface sediments from a wide area in the Qaidam Basin have been conducted. We find that pseudo-single domain and multidomain ferrimagnetic minerals (i.e. magnetite and maghemite) dominate the magnetic properties of surface sediments in the basin. Surface sediments from the western part of the basin exhibit the lowest magnetic concentration values χ, χARM and SIRM. In contrast, samples from the upwind sides of the basin and the eastern margin of the basin show the highest magnetic concentration values. The spatial distribution of magnetic parameters in the Qaidam Basin suggest that wind environments and the supply of clastic sediments possibly provide the main control on the regional variations of magnetic parameters. Our results also provide new insights into the mechanisms of magnetic variations of late Pliocene lacustrine sediments in the western Qaidam Basin.

  9. GROUNDWATER-SURFACE WATER EXCHANGE AND IMPLICATIONS FOR LARGE RIVER RESTORATION

    EPA Science Inventory

    Movement of river water into and out of high-porosity alluvial deposits can have an important influence on surface water quality and aquatic habitat. In our study of a 60-km reach of the Willamette River in Oregon, USA, we: 1) used tracers to estimate the rate of exchange betw...

  10. Temperature Dependence of Cryogenic Ammonia-Water Ice Mixtures and Implications for Icy Satellite Surfaces

    NASA Technical Reports Server (NTRS)

    Dalton, J. B., III; Curchin, J. M.; Clark, R. N.

    2001-01-01

    Infrared spectra of ammonia-water ice mixtures reveal temperature-dependent absorption bands due to ammonia. These features, at 1.04, 2.0, and 2.25 microns, may shed light on the surface compositions of the Galilean and Saturnian satellites. Additional information is contained in the original extended abstract.

  11. Ecological filtering and plant traits variation across quarry geomorphological surfaces: implication for restoration.

    PubMed

    Gilardelli, Federica; Sgorbati, Sergio; Armiraglio, Stefano; Citterio, Sandra; Gentili, Rodolfo

    2015-05-01

    Revegetation patterns after quarry abandonment have been widely studied from several ecological points of view, but a trait-based approach is still lacking. The aim of this study was to characterise the plant species assemblages and the associated functional traits filtered on different geomorphological surfaces in abandoned limestone quarry areas: artificial cliffs, embankments, and platforms. We then verified if species with certain traits were better able to overcome the dispersal and environmental filters necessary for establishment. To this aim, we analyzed 113 vegetation plots and collected data on 25 morphological, ecological, and dispersal traits to detect species adaptaions across these man-made environments. As a case study, we investigated the extraction basin of Botticino (Lombardy, Italy), the second largest in Italy. The results obtained by SIMPER and CCA analyses showed that rockiness, stoniness, slope, elevation, and time of surfaces are the main filters that varied across quarries and affected plant assemblages at the macro-scale level. Across the three geomorphological surfaces (meso-scale) of quarries, more specific abiotic filters selecting species were found. In turn, traits differentiation according to the three main geomorphological surfaces of quarry emphasized that further filters acting at the micro-scale imply differences in dispersal mechanisms and resource availability. This work highlighted the utility to study species assemblages and environmental filters to address quarry restoration according to the type of geomorphological surface. The investigation of some traits (chorological form, life forms, seed dispersal,s and plant height) can furnish some interesting indications for practice individuating further abiotic filters acting at the micro-scale. PMID:25662933

  12. Ecological Filtering and Plant Traits Variation Across Quarry Geomorphological Surfaces: Implication for Restoration

    NASA Astrophysics Data System (ADS)

    Gilardelli, Federica; Sgorbati, Sergio; Armiraglio, Stefano; Citterio, Sandra; Gentili, Rodolfo

    2015-05-01

    Revegetation patterns after quarry abandonment have been widely studied from several ecological points of view, but a trait-based approach is still lacking. The aim of this study was to characterise the plant species assemblages and the associated functional traits filtered on different geomorphological surfaces in abandoned limestone quarry areas: artificial cliffs, embankments, and platforms. We then verified if species with certain traits were better able to overcome the dispersal and environmental filters necessary for establishment. To this aim, we analyzed 113 vegetation plots and collected data on 25 morphological, ecological, and dispersal traits to detect species adaptaions across these man-made environments. As a case study, we investigated the extraction basin of Botticino (Lombardy, Italy), the second largest in Italy. The results obtained by SIMPER and CCA analyses showed that rockiness, stoniness, slope, elevation, and time of surfaces are the main filters that varied across quarries and affected plant assemblages at the macro-scale level. Across the three geomorphological surfaces (meso-scale) of quarries, more specific abiotic filters selecting species were found. In turn, traits differentiation according to the three main geomorphological surfaces of quarry emphasized that further filters acting at the micro-scale imply differences in dispersal mechanisms and resource availability. This work highlighted the utility to study species assemblages and environmental filters to address quarry restoration according to the type of geomorphological surface. The investigation of some traits (chorological form, life forms, seed dispersal,s and plant height) can furnish some interesting indications for practice individuating further abiotic filters acting at the micro-scale.

  13. Saturn's Titan: Surface change, ammonia, and implications for atmospheric and tectonic activity

    USGS Publications Warehouse

    Nelson, R.M.; Kamp, L.W.; Matson, D.L.; Irwin, P.G.J.; Baines, K.H.; Boryta, M.D.; Leader, F.E.; Jaumann, R.; Smythe, W.D.; Sotin, C.; Clark, R.N.; Cruikshank, D.P.; Drossart, P.; Pearl, J.C.; Hapke, B.W.; Lunine, J.; Combes, M.; Bellucci, G.; Bibring, J.-P.; Capaccioni, F.; Cerroni, P.; Coradini, A.; Formisano, V.; Filacchione, G.; Langevin, R.Y.; McCord, T.B.; Mennella, V.; Nicholson, P.D.; Sicardy, B.

    2009-01-01

    Titan is known to have a young surface. Here we present evidence from the Cassini Visual and Infrared Mapping Spectrometer that it is currently geologically active. We report that changes in the near-infrared reflectance of a 73,000 km2 area on Titan (latitude 26° S, longitude 78° W) occurred between July 2004 and March of 2006. The reflectance of the area increased by a factor of two between July 2004 and March–April 2005; it then returned to the July 2004 level by November 2005. By late December 2005 the reflectance had surged upward again, establishing a new maximum. Thereafter, it trended downward for the next three months. Detailed spectrophotometric analyses suggest these changes happen at or very near the surface. The spectral differences between the region and its surroundings rule out changes in the distribution of the ices of reasonably expected materials such as H2O, CO2, and CH4 as possible causes. Remarkably, the change is spectrally consistent with the deposition and removal of NH3 frost over a water ice substrate. NH3 has been proposed as a constituent of Titan's interior and has never been reported on the surface. The detection of NH3 frost on the surface might possibly be explained by episodic effusive events occur which bring juvenile ammonia from the interior to the surface. If so, its decomposition would feed nitrogen to the atmosphere now and in the future. The lateral extent of the region exceeds that of active areas on the Earth (Hawaii) or Io (Loki).

  14. Nickel Alloy Primary Water Bulk Surface and SCC Corrosion Film Analytical Characterization and SCC Mechanistic Implications

    SciTech Connect

    Morton, D.; Lewis, N.; Hanson, M.; Rice, S.; Sanders, P.

    2007-04-18

    Alloy 600 corrosion coupon tests were performed: (1) to quantify the temperature dependency of general corrosion and (2) to characterize the composition and structure of bulk surface corrosion films for comparison with ongoing primary water SCC (PWSCC) crack tip corrosion film analyses. Results suggest that the thermal activation energy of Alloy 600 corrosion is consistent with the thermal activation energy of nickel alloy PWSCC. Analytical investigations of the structure and composition of Alloy 600 bulk surface corrosion oxides revealed a duplex (inner and outer) oxide layer structure. The outer layer is discontinuous and comprised of relatively large (1 to 3 {micro}m) nickel ferrite crystals and smaller ({approx}0.1 {micro}m) chromium containing nickel ferrite crystals. The inner layer consists of a relatively continuous chromite spinel (major phase) and chromia (Cr{sub 2}O{sub 3} minor phase) which formed through non-selective oxidation. Chromia and dealloyed Alloy 600 (highly Ni enriched metal) were only observed at 337 C (640 F) and only along the boundaries of deformation induced fine grains and subcells. Specimens having deformation free surfaces exhibited continuous uniform inner chromite spinel oxide layers. Specimens with machining induced surface deformation produced non-uniform inner layer oxides (chromite spinel, Cr{sub 2}O{sub 3} and unoxidized material). PWSCC crack tip oxides, in contrast, were fine grain (no duplex structure) and consisted of both chromium rich spinels and ''NiO'' structure oxides. Generally, nickel rich oxides were more abundant under more oxidized conditions (reduced coolant hydrogen) and spinel rich crack tip oxides were favored under more reducing conditions (increased coolant hydrogen). Bulk surface corrosion film thickness did not correlate with observed SCC growth rates. These results suggest that corrosion is not the rate controlling step of PWSCC but rather that PWSCC and corrosion have a common rate controlling sub

  15. Can environmental conditions trigger cyanobacterial surfaces and following carbonate formation: implication for biomineralization and biotechnology

    NASA Astrophysics Data System (ADS)

    Paulo, C.; Dittrich, M.; Zhu, T.

    2015-12-01

    In this presentation we will give an overview what kind of the factors may trigger carbonate formations at the cell surfaces under a variety of environmental conditions. As examples, we will present the results from our recent studies on formation of calcium carbonates, dolomites and bio-cements. The extracellular polymeric substances (EPS) in the Synechococcuscell envelope are recognized key players in the nucleation of carbonates in marine and freshwater environments. Yet, little is known about a nutrient contents control over the molecular composition of Synechococcus cell envelope, and consequently, biomineralization. In the first study, we investigated how a variation of the phosphorus (P) in the growth media can lead to changes in the surface reactivity of the cells and impact their ability to form carbonates. The objective of the second study is to gain insights into the spatial distribution of cyanobacterial EPS and dolomite from different sediment layers of Khor Al-Adaid sabkha (Qatar). Here, we characterized microbial mats on molecular level in respect of organic and inorganic components using in-situ 2D Raman spectroscopy and Atomic Force Microscopy (AFM) were used. Additionally, 2D chemical maps of sediment layers documented spectral characterizations of minerals and organic matter of microbial origins at high spatial resolution. Finally, we will show the results from the experiments with auto-phototrophic cyanobacteria Gloeocapsa PCC73106, which habitat on the monument surfaces, towards its application for bio-concrete, a product of microbial carbonate precipitation. We studied the biomineralization in biofilm forming Gloeocapsa PCC73106 on the concrete surface as a pre-requirement for microbial carbonate precipitation. Biomineralization on the concrete surface by live cells and killed cells were compared with that under the abiotic condition. Our experiments allow us to conclude that environmental conditions play a significant role in the control of

  16. The implication of nonradiative energy fluxes dominating Greenland ice sheet exceptional ablation area surface melt in 2012

    NASA Astrophysics Data System (ADS)

    Fausto, Robert S.; As, Dirk; Box, Jason E.; Colgan, William; Langen, Peter L.; Mottram, Ruth H.

    2016-03-01

    During two exceptionally large July 2012 multiday Greenland ice sheet melt episodes, nonradiative energy fluxes (sensible, latent, rain, and subsurface collectively) dominated the ablation area surface energy budget of the southern and western ice sheet. On average the nonradiative energy fluxes contributed up to 76% of daily melt energy at nine automatic weather station sites in Greenland. Comprising 6% of the ablation period, these powerful melt episodes resulted in 12-15% of the south and west Greenland automatic weather station annual ablation totals. Analysis of high resolution (~5 km) HIRHAM5 regional climate model output indicates widespread dominance of nonradiative energy fluxes across the western ablation area during these episodes. Yet HIRHAM5 still underestimates melt by up to 56% during these episodes due to a systematic underestimation of turbulent energy fluxes typical of regional climate models. This has implications for underestimating future melt, when exceptional melt episodes are expected to occur more frequently.

  17. Fast Conversion of Ionic Liquids and Poly(Ionic Liquid)s into Porous Nitrogen-Doped Carbons in Air

    PubMed Central

    Men, Yongjun; Ambrogi, Martina; Han, Baohang; Yuan, Jiayin

    2016-01-01

    Ionic liquids and poly(ionic liquid)s have been successfully converted into nitrogen-doped porous carbons with tunable surface area up to 1200 m2/g at high temperatures in air. Compared to conventional carbonization process conducted under inert gas to produce nitrogen-doped carbons, the new production method was completed in a rather shorter time without noble gas protection. PMID:27070588

  18. Fast Conversion of Ionic Liquids and Poly(Ionic Liquid)s into Porous Nitrogen-Doped Carbons in Air.

    PubMed

    Men, Yongjun; Ambrogi, Martina; Han, Baohang; Yuan, Jiayin

    2016-01-01

    Ionic liquids and poly(ionic liquid)s have been successfully converted into nitrogen-doped porous carbons with tunable surface area up to 1200 m²/g at high temperatures in air. Compared to conventional carbonization process conducted under inert gas to produce nitrogen-doped carbons, the new production method was completed in a rather shorter time without noble gas protection. PMID:27070588

  19. Surface Uplift History of the Central Andes: Implications for the Growth of Orogenic Plateaus

    NASA Astrophysics Data System (ADS)

    Garzione, C. N.; Hoke, G. D.; Libarkin, J. C.; MacFadden, B. J.; Withers, S.

    2007-05-01

    Sedimentation, paleoelevation, and incision histories provide important constraints on the timing and magnitude of regional surface uplift of mountain belts that point to specific processes that led to surface uplift. The sedimentary record and stable isotopic compositions of carbonates are used to reconstruct the late Miocene subsidence history, paleoenvironment, and paleoelevation of the northern Altiplano basin. Multiple paleoelevation proxies, including paleoleaf physiognomy, δ18O paleoaltimetry, and Δ47 paleothermometry, suggest that the Altiplano rose by 2.5±0.5 km to 3.5±0.5 km to its current elevation between ~10 and 7 Ma. Geomorphic evidence from widespread, low-relief paleosurfaces on both the eastern and western flanks of the Andes also shows that the onset of rapid incision of paleosurfaces occurred between ~10 and 6.5 Ma over the entire width of the mountain belt and over at least 5° latitude. Stream profile analysis of the drainage systems that incise these paleosurfaces has been inferred to reflect ~1 to 2 km of surface uplift of the flanks of the Andes. Combining geomorphic evidence with paleoelevation constraints, the paleotopographic evolution of the Andes is reconstructed over the late Miocene. Late Miocene regional surface uplift requires the removal of mantle lithosphere as the dominant geodynamic mechanism for raising the plateau during this time. However, crustal thickening and redistribution of crust by erosion/sedimentation and/or lower crustal flow set the limit of surface uplift. Regional surface uplift of the Andean plateau in the late Miocene predicts a decrease in the horizontal deviatoric stress in the plateau that is consistent with observations of upper crustal shortening, sedimentation rates, and magmatism in the plateau. Shortening ceased across the plateau between 10 and 7 Ma, coincident with widespread ignimbrite eruptions and an abrupt decrease in sedimentation rates. The combination of geodynamic processes that appear to

  20. Seasonal changes in Titan's weather patterns and the evolution and implications of accompanying surface changes

    NASA Astrophysics Data System (ADS)

    Turtle, Elizabeth; McEwen, Alfred

    2012-07-01

    Post-equinox changes in Titan's atmospheric circulation brought clouds and extensive methane rain to low latitudes [1,2]. Observations by Cassini ISS over the ensuing ~1.5 yr revealed surface changes to be short-lived; few rain-darkened areas persisted through 2011. In an unsaturated permeable medium, infiltration rates are >20 mm/week [3], so persistence of surface liquids over several months suggests that either an impermeable layer or the local methane table lies close to the surface. Evaporation rates >1 mm/week are predicted at low latitudes [4] and 20 mm/week has been documented at Titan's poles [5], thus areas where darkening persisted must be saturated ground at the level of a methane table or have had ponded liquid 2.5-50 cm deep. Several smaller areas of surface brightening were also observed, a phenomenon that is less well understood. Cassini VIMS spectra of these regions do not match clouds or other surface units [6]. Interpretations include cleaning by runoff [2] or deposition of a fine-grained volatile solid as the result of evaporative cooling of the surface [6]. In general, brightening has persisted longer than darkening, but these areas are also reverting to their original appearance, possibly due to evaporation/sublimation of the bright material or re-deposition of darker hydrocarbons by aeolian transport or precipitation from the atmosphere. Cassini and Earth-based observers monitor Titan frequently, but few clouds have been observed since Fall 2010, which may indicate that enough methane was removed from the atmosphere and the lapse rate stabilized sufficiently that activity will not resume until the onset of convection at mid-northern latitudes later in northern spring. A similar lapse followed a 2004 outburst of south-polar clouds [7], which also appeared to produce significant rainfall [8]. [1] Turtle et al., GRL 38, L03203, doi:10.1029/2010GL046266, 2011. [2] Turtle et al., Science 331, 10.1126/science.1201063. 2011. [3] Hayes et al., GRL 35

  1. Hot electron dynamics at semiconductor surfaces: Implications for quantum dot photovoltaics

    NASA Astrophysics Data System (ADS)

    Tisdale, William A., III

    Finding a viable supply of clean, renewable energy is one of the most daunting challenges facing the world today. Solar cells have had limited impact in meeting this challenge because of their high cost and low power conversion efficiencies. Semiconductor nanocrystals, or quantum dots, are promising materials for use in novel solar cells because they can be processed with potentially inexpensive solution-based techniques and because they are predicted to have novel optoelectronic properties that could enable the realization of ultra-efficient solar power converters. However, there is a lack of fundamental understanding regarding the behavior of highly-excited, or "hot," charge carriers near quantum-dot and semiconductor interfaces, which is of paramount importance to the rational design of high-efficiency devices. The elucidation of these ultrafast hot electron dynamics is the central aim of this Dissertation. I present a theoretical framework for treating the electronic interactions between quantum dots and bulk semiconductor surfaces and propose a novel experimental technique, time-resolved surface second harmonic generation (TR-SHG), for probing these interactions. I then describe a series of experimental investigations into hot electron dynamics in specific quantum-dot/semiconductor systems. A two-photon photoelectron spectroscopy (2PPE) study of the technologically-relevant ZnO(1010) surface reveals ultrafast (sub-30fs) cooling of hot electrons in the bulk conduction band, which is due to strong electron-phonon coupling in this highly polar material. The presence of a continuum of defect states near the conduction band edge results in Fermi-level pinning and upward (n-type) band-bending at the (1010) surface and provides an alternate route for electronic relaxation. In monolayer films of colloidal PbSe quantum dots, chemical treatment with either hydrazine or 1,2-ethanedithiol results in strong and tunable electronic coupling between neighboring quantum dots

  2. Geomorphic adjustment to hydrologic modifications along a meandering river: Implications for surface flooding on a floodplain

    NASA Astrophysics Data System (ADS)

    Edwards, Brandon L.; Keim, Richard F.; Johnson, Erin L.; Hupp, Cliff R.; Marre, Saraline; King, Sammy L.

    2016-09-01

    Responses of large regulated rivers to contemporary changes in base level are not well understood. We used field measurements and historical analysis of air photos and topographic maps to identify geomorphic trends of the lower White River, Arkansas, USA, in the 70 years following base-level lowering at its confluence with the Mississippi River and concurrent with flood control by dams. Incision was identified below a knickpoint area upstream of St. Charles, AR, and increases over the lowermost ~90 km of the study site to ~2 m near the confluence with the Mississippi River. Mean bankfull width increased by 30 m (21%) from 1930 to 2010. Bank widening appears to be the result of flow regulation above the incision knickpoint and concomitant with incision below the knickpoint. Hydraulic modeling indicated that geomorphic adjustments likely reduced flooding by 58% during frequent floods in the incised, lowermost floodplain affected by backwater flooding from the Mississippi River and by 22% above the knickpoint area. Dominance of backwater flooding in the incised reach indicates that incision is more important than flood control on the lower White River in altering flooding and also suggests that the Mississippi River may be the dominant control in shaping the lower floodplain. Overall, results highlight the complex geomorphic adjustment in large river-floodplain systems in response to anthropogenic modifications and their implications, including reduced river-floodplain connectivity.

  3. Modelling interstellar physics and chemistry: implications for surface and solid-state processes.

    PubMed

    Williams, David; Viti, Serena

    2013-07-13

    We discuss several types of regions in the interstellar medium of the Milky Way and other galaxies in which the chemistry appears to be influenced or dominated by surface and solid-state processes occurring on or in interstellar dust grains. For some of these processes, for example, the formation of H₂ molecules, detailed experimental and theoretical approaches have provided excellent fundamental data for incorporation into astrochemical models. In other cases, there is an astrochemical requirement for much more laboratory and computational study, and we highlight these needs in our description. Nevertheless, in spite of the limitations of the data, it is possible to infer from astrochemical modelling that surface and solid-state processes play a crucial role in astronomical chemistry from early epochs of the Universe up to the present day. PMID:23734052

  4. Spatial Arrangment of Organic Compounds on a Model Mineral Surface: Implications for Soil Organic Matter Stabilization

    SciTech Connect

    Petridis, Loukas; Ambaye, Haile Arena; Jagadamma, Sindhu; Kilbey, S. Michael; Lokitz, Bradley S; Lauter, Valeria; Mayes, Melanie

    2014-01-01

    The complexity of the mineral organic carbon interface may influence the extent of stabilization of organic carbon compounds in soils, which is important for global climate futures. The nanoscale structure of a model interface was examined here by depositing films of organic carbon compounds of contrasting chemical character, hydrophilic glucose and amphiphilic stearic acid, onto a soil mineral analogue (Al2O3). Neutron reflectometry, a technique which provides depth-sensitive insight into the organization of the thin films, indicates that glucose molecules reside in a layer between Al2O3 and stearic acid, a result that was verified by water contact angle measurements. Molecular dynamics simulations reveal the thermodynamic driving force behind glucose partitioning on the mineral interface: The entropic penalty of confining the less mobile glucose on the mineral surface is lower than for stearic acid. The fundamental information obtained here helps rationalize how complex arrangements of organic carbon on soil mineral surfaces may arise

  5. Crystal fractionation in the SNC meteorites: Implications for surface units on Mars

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.

    1987-01-01

    Almost all rock types in the SNC meteorites are cumulates, products of magma differentiation by crystal fractionation (addition or removal of crystals). If the SNC meteorites are from the surface of Mars or near sub-surface, then most of the igneous units on Mars are differentiated. Basaltic units probably experienced minor to moderate differentiation, but ultrabasic units probably experienced extreme differentiation. Products of this differentiation may include Fe-rich gabbro, pyroxenite, peridotite (and thus serpentine), and possibly massive sulfides. The SNC meteorites include ten lithologies (three in EETA79001), eight of which are crystal cumulates. The other lithologies, EETA79001 A and B are subophitic basalts. The cumulate lithologies ALHA77005 and EETA79001 C were not fully described or discussed.

  6. Volatile organic compounds in the marine troposphere and surface oceans: methods, measurements and biogeochemical implications

    NASA Astrophysics Data System (ADS)

    Hudson, Edward

    2010-09-01

    Volatile organic compounds (VOCs), among them non-methane hydrocarbons (NMHCs) and low molecular weight carbonyl compounds (aldehydes and ketones), affect the oxidative capacity of the atmosphere and thus pollutant lifetimes and global climate. VOCs in the surface oceans may be transported into, or derived from, the atmosphere. This thesis describes the development and optimization of chromatographic and preconcentration methods to determine volatile organic compounds (VOCs) in surface seawater and marine air, and their use to explore VOC distribution and fluxes at the seaair interface. It includes the first measurements of many carbonyl compounds in temperate and subarctic marine waters and the first estimates of fluxes of several aldehydes from the ocean surface into the marine atmosphere. Sea surface air, size-fractionated marine aerosols, and surface ocean water dissolved organic matter were simultaneously sampled in the Nordic seas. Nineteen C2-C7 NMHCs were quantified in the air samples. Site-to-site variability in NMHC concentrations was high, suggesting variable, local sources. The aerosols consisted mainly of inorganic marine material, but a culturable bacterium identified as Micrococcus luteus was also isolated from the 9.9 -- 18 mum fraction, suggesting organic matter may be transferred from the surface oceans to the atmosphere by marine aerosols. Lastly, a number of VOCs, including acetone, were detected in the seawater samples using solid-phase microextraction (SPME), leading to the subsequent development of an SPME application for carbonyl compounds in seawater. A mobile, economical and solventless method for the detection and quantification of carbonyl compounds in seawater, a matrix of global importance, was developed. The compounds were derivatized using O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine (PFBHA)and then pre-concentrated by SPME for gas chromatography with mass spectrometric (GC/MS) or flame ionization (GC-FID) detection. The method was

  7. Surface properties of the Orgueil meteorite - Implications for the early history of solar system volatiles

    NASA Technical Reports Server (NTRS)

    Fanale, F. P.; Cannon, W. A.

    1974-01-01

    The Kr and H2O adsorption properties of Orgueil were studied. Dehydration by stepwise calcination produced a tenfold change in its B.E.T. surface area, which increased to 120 and then fell to 40 square meters per gram. Water exchangeability was measured by water regain from lab air between calcination cycles. Dehydration at room temperature showed that Orgueil contained 6 per cent by weight of water adsorbed on free surfaces. These results are consistent with an identification of Orgueil as montmorillonite, although chemical data conflict with this. High D/H ratios in CI carbonaceous chondrites may result from D enrichment in OH- groups during equilibration of dispersed phyllosilicate dust with preplanetary nebula gas at temperatures much less than 0 C.

  8. Groundwater-surface water interactions in a large semi-arid floodplain: implications for salinity management

    NASA Astrophysics Data System (ADS)

    Lamontagne, Sébastien; Leaney, Fred W.; Herczeg, Andrew L.

    2005-10-01

    Flow regulation and water diversion for irrigation have considerably impacted the exchange of surface water between the Murray River and its floodplains. However, the way in which river regulation has impacted groundwater-surface water interactions is not completely understood, especially in regards to the salinization and accompanying vegetation dieback currently occurring in many of the floodplains. Groundwater-surface water interactions were studied over a 2 year period in the riparian area of a large floodplain (Hattah-Kulkyne, Victoria) using a combination of piezometric surface monitoring and environmental tracers (Cl-, 2H, and 18O). Despite being located in a local and regional groundwater discharge zone, the Murray River is a losing stream under low flow conditions at Hattah-Kulkyne. The discharge zone for local groundwater, regional groundwater and bank recharge is in the floodplain within 1 km of the river and is probably driven by high rates of transpiration by the riparian Eucalyptus camaldulensis woodland. Environmental tracers data suggest that the origin of groundwater is principally bank recharge in the riparian zone and a combination of diffuse rainfall recharge and localized floodwater recharge elsewhere in the floodplain. Although the Murray River was losing under low flows, bank discharge occurred during some flood recession periods. The way in which the water table responded to changes in river level was a function of the type of stream bank present, with point bars providing a better connection to the alluvial aquifer than the more common clay-lined banks. Understanding the spatial variability in the hydraulic connection with the river channel and in vertical recharge following inundations will be critical to design effective salinity remediation strategies for large semi-arid floodplains.

  9. Atmosphere-Surface Exchange of Reactive Nitrogen and its Implications for PM2.5

    NASA Astrophysics Data System (ADS)

    Wentworth, G.; Murphy, J. G.; Gregoire, P.; Tevlin, A.; Hems, R.; Cheyne, C.

    2012-12-01

    Recently it has been suggested that the surface-atmosphere exchange of both ammonia (NH3) and nitrous acid (HONO) can occur in a bidirectional fashion governed by a compensation point (i.e. the atmospheric mixing ratio where the flux changes direction). The compensation point corresponds to the gas phase mixing ratio that is in equilibrium with the dissolved constituents at the surface (soil water, plant tissue), governed by solubility and acid dissociation constants. Direct calculation of compensation point values is not trivial, because of the dependence on soil temperature, moisture, pH and the nitrogen distribution in the system. The presence of atmospheric particulate matter can further influence surface flux by providing a reactive sink for trace gases in the atmosphere. An accurate understanding of the factors governing bidirectional flux is required in order for air quality models to accurately predict trace gas mixing ratios, aerosol composition and spatial patterns of nitrogen deposition. A field study was conducted in southwestern Ontario during the summer of 2012 to measure the atmospheric and surface components of the system to provide observational constraints to test our understanding of the bi-directional exchange of reactive nitrogen. An Ambient Ion Monitor Ion Chromatograph (AIM-IC) was used to quantify the water-soluble trace gases (NH3, SO2, HNO3, HCl, and HONO) as well as water-soluble ions in PM2.5 with hourly time resolution. The same IC methods were used in an offline fashion to monitor soil ammonium, nitrite and nitrate composition. Challenges in selecting sampling and extraction protocols that can provide representative soil pH and nitrogen content are discussed.

  10. Plasma sterilization of poly lactic acid ultrasound contrast agents: surface modification and implications for drug delivery.

    PubMed

    Eisenbrey, John R; Hsu, Jennifer; Wheatley, Margaret A

    2009-11-01

    Poly lactic acid (PLA) ultrasound contrast agents (CA) have been developed previously in our laboratory for ultrasound (US) imaging, as well as surface coated with doxorubicin to create a potential targeted platform of chemotherapeutic delivery using focused US. However, we have previously found it impossible to sterilize these agents while at the same time maintaining their acoustic properties, a task that would probably require fabrication within a clean facility. The purpose of this paper is to investigate the feasibility of using plasma to sterilize these CA while maintaining maximum echogenicity, a step that would greatly facilitate in vivo investigations. Effects of plasma exposure time (1, 3 and 6 min) and intensity (low-10 mA, 6.8 W; medium-15 mA, 10.5 W; and high-25 mA, 18 W) on the CAs' acoustic properties, surface morphology, zeta potential, capacity to carry chemotherapeutics and overall sterility are described. Both increases in plasma intensity and exposure time increased CA zeta potential and also significantly increased drug payload. High-intensity plasma exposure for 3 min was found to be an optimal sterilization protocol for maximal (100%) preservation of CA echogenicity. Plasma exposure resulted in sterile samples and maintained original CA enhancement of 20 dB and acoustic half-life over 75 min, while increasing CA zeta potential by 11 mV and doxorubicin loading efficiency by 10%. This study not only shows how a highly temperature- and pressure-sensitive agent can be sterilized using plasma, but also that surface modification can be used to increase surface binding of the drug. PMID:19766380

  11. Surface Electrical Potentials of Root Cell Plasma Membranes: Implications for Ion Interactions, Rhizotoxicity, and Uptake

    PubMed Central

    Wang, Yi-Min; Kinraide, Thomas B.; Wang, Peng; Hao, Xiu-Zhen; Zhou, Dong-Mei

    2014-01-01

    Many crop plants are exposed to heavy metals and other metals that may intoxicate the crop plants themselves or consumers of the plants. The rhizotoxicity of heavy metals is influenced strongly by the root cell plasma membrane (PM) surface’s electrical potential (ψ0). The usually negative ψ0 is created by negatively charged constituents of the PM. Cations in the rooting medium are attracted to the PM surface and anions are repelled. Addition of ameliorating cations (e.g., Ca2+ and Mg2+) to the rooting medium reduces the effectiveness of cationic toxicants (e.g., Cu2+ and Pb2+) and increases the effectiveness of anionic toxicants (e.g., SeO42− and H2AsO4−). Root growth responses to ions are better correlated with ion activities at PM surfaces ({IZ}0) than with activities in the bulk-phase medium ({IZ}b) (IZ denotes an ion with charge Z). Therefore, electrostatic effects play a role in heavy metal toxicity that may exceed the role of site-specific competition between toxicants and ameliorants. Furthermore, ψ0 controls the transport of ions across the PM by influencing both {IZ}0 and the electrical potential difference across the PM from the outer surface to the inner surface (Em,surf). Em,surf is a component of the driving force for ion fluxes across the PM and controls ion-channel voltage gating. Incorporation of {IZ}0 and Em,surf into quantitative models for root metal toxicity and uptake improves risk assessments of toxic metals in the environment. These risk assessments will improve further with future research on the application of electrostatic theory to heavy metal phytotoxicity in natural soils and aquatic environments. PMID:25493475

  12. Ionic Grease Lubricants: Protic [Triethanolamine][Oleic Acid] and Aprotic [Choline][Oleic Acid].

    PubMed

    Mu, Liwen; Shi, Yijun; Ji, Tuo; Chen, Long; Yuan, Ruixia; Wang, Huaiyuan; Zhu, Jiahua

    2016-02-01

    Ionic liquid lubricants or lubricant additives have been studied intensively over past decades. However, ionic grease serving as lubricant has rarely been investigated so far. In this work, novel protic [triethanolamine][oleic acid] and aprotic [choline][oleic acid] ionic greases are successfully synthesized. These ionic greases can be directly used as lubricants without adding thickeners or other additives. Their distinct thermal and rheological properties are investigated and are well-correlated to their tribological properties. It is revealed that aprotic ionic grease shows superior temperature- and pressure-tolerant lubrication properties over those of protic ionic grease. The lubrication mechanism is studied, and it reveals that strong physical adsorption of ionic grease onto friction surface plays a dominating role for promoted lubrication instead of tribo-chemical film formation. PMID:26815603

  13. Amorphization of quartz by friction: Implication to silica-gel lubrication of fault surfaces

    NASA Astrophysics Data System (ADS)

    Nakamura, Yu; Muto, Jun; Nagahama, Hiroyuki; Shimizu, Ichiko; Miura, Takashi; Arakawa, Ichiro

    2012-11-01

    To understand physico-chemical processes at real contacts (asperities) on fault surfaces, we conducted pin-on-disk friction experiments at room temperature, using single crystalline quartz disks and quartz pins. Velocity weakening from friction coefficient μ ˜ 0.6 to 0.4 was observed under apparent normal stresses of 8-19 (18 > 19), when the slip rate was increased from 0.003 to 2.6 m/s. Frictional surfaces revealed ductile deformation of wear materials. The Raman spectra of frictional tracks showed blue shifts and broadening of quartz main bands, and appearance of new peaks at 490-520 and 610 cm-1. All these features are indicative of pressure- and strain-induced amorphization of quartz. The mapping analyses of Fourier transform infrared (FT-IR) spectroscopy at room dry conditions suggest selective hydration of wear materials. It is possible that the strained Si-O-Si bridges in amorphous silica preferentially react with water to form silica-gel. In natural fault systems, amorphous materials would be produced at real fault contacts and accumulate over the fault surfaces with displacements. Subsequent hydration would lead to significant reduction of fault strength during slip.

  14. Vitrification darkening of rock powders - Implications for optical properties of the lunar surface

    NASA Technical Reports Server (NTRS)

    Nash, D. B.; Conel, J. E.

    1973-01-01

    Laboratory experiments show that albedoes as low as those on the moon can be produced by vacuum vitrification and associated chemical fractionation of ordinary terrestrial basaltic material. Vitrification is established as an unequivocal process that can account for the low albedo and apparent local darkening with age of the lunar surface. The spectral reflectance curves of glass powders are significantly different than those of the parent rock mineralogy; thus, the presence of ubiquitous glass in lunar surface material complicates compositional determinations by interpretation of spectral reflectance curves. Vitrification of rocks on the moon may highly modify the chemical composition of the resulting glass; thus, glass fragments found in lunar fines cannot be assumed to represent bulk parent rock material. Progressive impact vitrification of lunar surface material throughout the moon's history may have led to a fine-grain, opaque, refractory-rich material we call 'ultimate glass.' This unidentified and, at this point, hypothetical component may exist in dark regolith material; if found, it may be a useful indicator of regolith maturity.

  15. Carbon and steel surfaces modified by Leptothrix discophora SP-6: characterization and implications.

    PubMed

    Nguyen, Tuan Anh; Lu, Yuzhuo; Yang, Xinghong; Shi, Xianming

    2007-12-01

    Leptothrix discophora SP-6, a type of manganese(Mn)-oxidizing bacteria, has been known to accumulate Mn oxides from the aqueous environment and thus play a key role in microbiologically influenced corrosion by increasing the electrochemical potential of steel and other metals. Similarly, this bacterium was found to modify the surface of glassy carbon in aqueous solution and increase its potential (i.e., ennoblement). In the latter case, biomineralized Mn oxides can be used as cathodic reactants for a new generation of microbial fuel cells featuring a biocathode. In this preliminary study, factors affecting the biofilm formation and biomineralization processes were examined. The inflow of air into the culture medium was found essential to sustain the ennoblement of substrate electrodes. The OCP and FESEM/EDS data indicated that a smoother initial substrate surface generally led to better ennoblement. Polarizing the carbon electrode at +500 mV(SCE) for 15 min was found to facilitate the ennoblement on carbon electrodes, and so did coating it with a poly(L-lysine) layer. Independent of substrate material, initial surface roughness, and pretreatment, there were three parameters in the EIS equivalent circuit that correlated well with the OCP indicating the level of ennoblement by L. discophora SP-6, i.e., electrolyte resistance, double-layer capacitance, and low-frequencies capacitance. These fascinating findings merit further investigation as they may shed light on the fundamental bacteria/substrate interactions and help advance the knowledge base needed forthe engineering applications. PMID:18186327

  16. Pyrolysis of surface-immobilized model compounds: Mechanistic implications for the thermal chemistry of coal

    SciTech Connect

    Britt, P F; Poutsma, M L

    1990-01-01

    Our research has been investigating the potential role that the cross-linked network structure of coal may play in perturbing free-radical reactions associated with coal thermolysis. This may be particularly important in the thermal conversion of coal at low temperatures, e.g., 350--400{degree}C, where bonds begin to break but most of the residual framework is retained. In order to assess the potential impact of restricted transport on thermal reaction pathways, we have modeled the phenomenon experimentally by studying organic model compounds that are covalently linked to an inert silica surface. The experimental methodology and significant results from studies of the thermolysis of surface-attached Ph(CH{sub 2}){sub n}Ph (n = 0--4) at 345--400{degree}C will be briefly surveyed. Initial results from studies of two-component surfaces will also be presented that reveal the role of radical migration, via facile hydrogen shuttling, in modifying the effects of diffusional constraints. 13 refs., 5 figs.

  17. Solar Wind Sputtering of Lunar Surface Materials: Role and Some Possible Implications of Potential Sputtering

    NASA Technical Reports Server (NTRS)

    Barghouty, A. F.; Adams, J. H., Jr.; Meyer, F.; Reinhold, c.

    2010-01-01

    Solar-wind induced sputtering of the lunar surface includes, in principle, both kinetic and potential sputtering. The role of the latter mechanism, however, in many focused studies has not been properly ascertained due partly to lack of data but can also be attributed to the assertion that the contribution of solar-wind heavy ions to the total sputtering is quite low due to their low number density compared to solar-wind protons. Limited laboratory measurements show marked enhancements in the sputter yields of slow-moving, highly-charged ions impacting oxides. Lunar surface sputtering yields are important as they affect, e.g., estimates of the compositional changes in the lunar surface, its erosion rate, as well as its contribution to the exosphere as well as estimates of hydrogen and water contents. Since the typical range of solar-wind ions at 1 keV/amu is comparable to the thickness of the amorphous rim found on lunar soil grains, i.e. few 10s nm, lunar simulant samples JSC-1A AGGL are specifically enhanced to have such rims in addition to the other known characteristics of the actual lunar soil particles. However, most, if not all laboratory studies of potential sputtering were carried out in single crystal targets, quite different from the rim s amorphous structure. The effect of this structural difference on the extent of potential sputtering has not, to our knowledge, been investigated to date.

  18. Magnitude of global contraction on Mars from analysis of surface faults: Implications for martian thermal history

    NASA Astrophysics Data System (ADS)

    Nahm, Amanda L.; Schultz, Richard A.

    2011-01-01

    Faults provide a record of a planet's crustal stress state and interior dynamics, including volumetric changes related to long-term cooling. Previous work has suggested that Mars experienced a pulse of large-scale global contraction during Hesperian time. Here we evaluate the evidence for martian global contraction using a recent compilation of thrust faults. Fault-related strains were calculated for wrinkle ridges and lobate scarps to provide lower and upper bounds, respectively, on the magnitude of global contraction from contractional structures observed on the surface of Mars. During the hypothesized pulse of global contraction, contractional strain of -0.007% to -0.13% is indicated by the structures, corresponding to decreases in planetary radius of 112 m to 2.24 km, respectively. By contrast, consideration of all recognized thrust faults regardless of age produces a globally averaged contractional strain of -0.011% to -0.22%, corresponding to a radius decrease of 188 m to 3.77 km since the Early Noachian. The amount of global contraction predicted by thermal models is larger than what is recorded by the faults at the surface, paralleling similar studies for Mercury and the Moon, which suggests that observations of fault populations at the surface may provide tighter bounds on planetary thermal evolution than models alone.

  19. Identification of polymer surface adsorbed proteins implicated in pluripotent human embryonic stem cell expansion.

    PubMed

    Hammad, Moamen; Rao, Wei; Smith, James G W; Anderson, Daniel G; Langer, Robert; Young, Lorraine E; Barrett, David A; Davies, Martyn C; Denning, Chris; Alexander, Morgan R

    2016-08-16

    Improved biomaterials are required for application in regenerative medicine, biosensing, and as medical devices. The response of cells to the chemistry of polymers cultured in media is generally regarded as being dominated by proteins adsorbed to the surface. Here we use mass spectrometry to identify proteins adsorbed from a complex mouse embryonic fibroblast (MEF) conditioned medium found to support pluripotent human embryonic stem cell (hESC) expansion on a plasma etched tissue culture polystyrene surface. A total of 71 proteins were identified, of which 14 uniquely correlated with the surface on which pluripotent stem cell expansion was achieved. We have developed a microarray combinatorial protein spotting approach to test the potential of these 14 proteins to support expansion of a hESC cell line (HUES-7) and a human induced pluripotent stem cell line (ReBl-PAT) on a novel polymer (N-(4-Hydroxyphenyl) methacrylamide). These proteins were spotted to form a primary array yielding several protein mixture 'hits' that enhanced cell attachment to the polymer. A second array was generated to test the function of a refined set of protein mixtures. We found that a combination of heat shock protein 90 and heat shock protein-1 encourage elevated adherence of pluripotent stem cells at a level comparable to fibronectin pre-treatment. PMID:27466628

  20. Thermal convection in a rotating spherical body with free surface: Implications for Saturn's moon Iapetus

    NASA Astrophysics Data System (ADS)

    Kuchta, Milan; Čadek, O.; Tobie, G.

    2012-10-01

    We present a new numerical tool to simulate thermal cooling and spin evolution of a rotating body with freely deformable surface and complex rheology. While the long-term mechanical properties of the body are mimicked by visco-plastic rheology including different creep mechanisms, its despinning is controlled by Andrá de visco-elastic model. Variabledensity approximation (sticky air) and implicit description of the surface are combined in order to track the surface evolution. We use this tool to investigate the shape of Saturn's moon Iapetus, whose topography shows enigmatic remnant features from the moon's early history when the spin rate and temperature were significantly higher than at present. Our model is characterized by three parameters: the initial temperature (ranging from 230 to 270 K), the initial rotational period (8-15 hours), and the grain size of ice (0.01-100 mm) defining the relative role of diffusion creep in total deformation. For these three parameters, we systematically explore the model space and show for which combinations of parameters the body can be effectively despun while maintaining its strongly flattened shape. Our results indicate that the despinning of Iapetus could not occur without interaction with an external body.

  1. Conjunctive Surface and Groundwater Management in Utah. Implications for Oil Shale and Oil Sands Development

    SciTech Connect

    Keiter, Robert; Ruple, John; Tanana, Heather; Holt, Rebecca

    2011-12-01

    Unconventional fuel development will require scarce water resources. In an environment characterized by scarcity, and where most water resources are fully allocated, prospective development will require minimizing water use and seeking to use water resources in the most efficient manner. Conjunctive use of surface and groundwater provides just such an opportunity. Conjunctive use includes two main practices: First, integrating surface water diversions and groundwater withdrawals to maximize efficiency and minimize impacts on other resource users and ecological processes. Second, conjunctive use includes capturing surplus or unused surface water and injecting or infiltrating that water into groundwater aquifers in order to increase recharge rates. Conjunctive management holds promise as a means of addressing some of the West's most intractable problems. Conjunctive management can firm up water supplies by more effectively capturing spring runoff and surplus water, and by integrating its use with groundwater withdrawals; surface and groundwater use can be further integrated with managed aquifer recharge projects. Such integration can maximize water storage and availability, while simultaneously minimizing evaporative loss, reservoir sedimentation, and surface use impacts. Any of these impacts, if left unresolved, could derail commercial-scale unconventional fuel development. Unconventional fuel developers could therefore benefit from incorporating conjunctive use into their development plans. Despite its advantages, conjunctive use is not a panacea. Conjunctive use means using resources in harmony to maximize and stabilize long-term supplies it does not mean maximizing the use of two separate but interrelated resources for unsustainable short-term gains and it cannot resolve all problems or provide water where no unappropriated water exists. Moreover, conjunctive use may pose risks to ecological values forgone when water that would otherwise remain in a stream is

  2. Groundwater and surface water discharge from an abandoned tailings impoundment: Implications for watershed water quality

    NASA Astrophysics Data System (ADS)

    Moncur, M. C.; Ptacek, C. J.; Blowes, D. W.; Birks, S. J.

    2006-12-01

    Release of acid drainage from mine-waste disposal areas is a problem of international scale. Drainage from sulfide-rich waste can result in contaminated surface waters, directly through surface runoff and indirectly, from discharge of contaminated groundwater flow. Camp Lake, located in Northern Manitoba, receives both direct and indirect drainage from an abandoned tailings impoundment, which has severely affected the quality of the downstream watershed. Nearly a century of sulfide oxidation at this mine site has resulted in extremely high concentrations of oxidation products in the surface water and groundwater discharging from the two tailings impoundments, both of which flow into an adjacent semi-isolated shallow bay in Camp Lake. The incorporation of these aqueous effluents has altered the composition of the lake water, which in turn has modified the physical limnology of the lake. The various sources of water and solutes to the lake (surface inflows, perched water table, primary water table) contribute varying concentrations of metals to the overall contaminant loadings to the lake, and can be characterized by distinct 3H, δ18O, and δ2H compositions. Geochemical profiles of the water column indicate that, despite its shallow depth (6 m), the bay is stratified throughout the year. The greatest accumulation of dissolved metals and SO4 is in the lower portion of the water column, with concentrations up to 8500 mg/L Fe, 20,000 mg/L SO4, 30 mg/L Zn, and 100 mg/L Al, including elevated concentrations of Cu, Cd, Pb, and Ni. This stratification is mirrored in the δ18O, δ2H and d-excess profiles within the lake water column, with an evaporatively enriched surface layer overlying the isotopically lighter, higher d-excess hypolimnion. Despite meromictic conditions and very high solute concentrations being limited to the semi-isolated bay, the annual loadings of acid, sulfate, and metals from Camp Lake to the adjacent lake are extremely large, and fluctuate seasonally

  3. Implications of the MESSENGER Discovery of High Sulfur Abundance on the Surface of Mercury

    NASA Astrophysics Data System (ADS)

    Zolotov, M. Y.; Sprague, A. L.; Nittler, L. R.; Weider, S. Z.; Starr, R. D.; Evans, L. G.; Boynton, W. V.; Goldsten, J. O.; Hauck, S. A.; Solomon, S. C.

    2011-12-01

    The unusually high S content detected in Mercury's surface materials with the MESSENGER X-ray Spectrometer (XRS) constrains surface mineralogy, petrology, and the redox state of magmas and rocks. This discovery along with the low FeO content in surface silicates indicates a low oxygen fugacity (fO2) in corresponding melts and the occurrence of S in sulfides, which could be abundant in surface rocks. The detected high S content could reflect anomalously high (up to 8-10 wt%) solubility of sulfide S in extremely reduced magmas. The high bulk S/Fe ratio also suggests the presence of S in sulfides of Mg, Ca, Mn, and Cr, which occur in enstatite chondrites. Although the presence of some troilite (FeS) is possible, niningerite, (Mg, Fe, Mn)S, could be the most abundant sulfide. Niningerite could be partially responsible for Mercury's low surface albedo, its unusual reflectance spectrum at visible and near-infrared wavelengths, and the relatively high neutron absorption, because Mn is a strong neutron absorber. The presence of abundant niningerite would also imply a lower Mg/Si ratio in silicates than in bulk surface materials. It follows that Mg-rich mafic lavas could be present instead of, or in addition to, ultramafic lavas (komatiites). The occurrence of Mg-silicates (enstatite and forsterite) in Mercury's regolith as inferred from mid-infrared spectroscopy, together with the postulated presence of niningerite, helps characterize fO2 and fS2 in corresponding melts. If fS2 is controlled by the Fe-metal-Fe-sulfide equilibrium, the silicate-sulfide equilibria set fO2 values. For temperature less than 1700 K the evaluated values are less than 5.5 log fO2 units below the iron-wüstite buffer (IW-5.5). Lower temperatures and analogous considerations for Ca and Mn silicate-sulfide equilibria lead to lower fO2 values. For Fe-metal-saturated melts at 1700 K the fO2 value is IW-5.5 and corresponds to ~0.1 mol % FeO, which could be considered as an upper limit in magmas and

  4. Energy Crops and their Implications on Soil Carbon Sequestration, Surface Energy and Water Balance

    NASA Astrophysics Data System (ADS)

    Song, Y.; Barman, R.; Jain, A. K.

    2011-12-01

    The quest to meet growing energy demand with low greenhouse gas emissions has increased attention on the potential of existing and advanced biomass energy crops. Potential energy crops include row crops such as corn, and perennial grasses such as switchgrass. However, a massive expansion of bioenergy crops raises many questions such as: how and where to grow energy crops; and what will be the impacts of growing large scale biofuel crops on the terrestrial hydrological cycle, the surface energy budget, soil carbon sequestration and the concurrent effects on the climate system. An integrated modeling system is being developed with in the framework of a land surface model, the Integrated Science Assessment Model (ISAM), and being applied to address these questions.This framework accounts for the biophysical, physiological and biogeochemical systems governing important processes that regulate crop growth including water, energy and nutrient cycles within the soil-plant-atmosphere system. One row crop (Corn) and two energy crops (Switchgrass and Miscanthus) are studied in current framework. Dynamic phenology processes and parameters for simulating each crop have been developed using observed data from a north to south gradient of field trial sites. This study will specifically focus on the agricultural regions in the US and in Europe. The potential productivity of these three crops will be assessed in terms of carbon sequestration, surface energy and water balance and their spatial variability. This study will help to quantify the importance of various environmental aspects towards modeling bioenergy crops and to better understand the spatial and temporal dynamics of bioenergy crop yields.

  5. Spatiotemporal dynamics of surface water networks across a global biodiversity hotspot—implications for conservation

    NASA Astrophysics Data System (ADS)

    Tulbure, Mirela G.; Kininmonth, Stuart; Broich, Mark

    2014-11-01

    The concept of habitat networks represents an important tool for landscape conservation and management at regional scales. Previous studies simulated degradation of temporally fixed networks but few quantified the change in network connectivity from disintegration of key features that undergo naturally occurring spatiotemporal dynamics. This is particularly of concern for aquatic systems, which typically show high natural spatiotemporal variability. Here we focused on the Swan Coastal Plain, a bioregion that encompasses a global biodiversity hotspot in Australia with over 1500 water bodies of high biodiversity. Using graph theory, we conducted a temporal analysis of water body connectivity over 13 years of variable climate. We derived large networks of surface water bodies using Landsat data (1999-2011). We generated an ensemble of 278 potential networks at three dispersal distances approximating the maximum dispersal distance of different water dependent organisms. We assessed network connectivity through several network topology metrics and quantified the resilience of the network topology during wet and dry phases. We identified ‘stepping stone’ water bodies across time and compared our networks with theoretical network models with known properties. Results showed a highly dynamic seasonal pattern of variability in network topology metrics. A decline in connectivity over the 13 years was noted with potential negative consequences for species with limited dispersal capacity. The networks described here resemble theoretical scale-free models, also known as ‘rich get richer’ algorithm. The ‘stepping stone’ water bodies are located in the area around the Peel-Harvey Estuary, a Ramsar listed site, and some are located in a national park. Our results describe a powerful approach that can be implemented when assessing the connectivity for a particular organism with known dispersal distance. The approach of identifying the surface water bodies that act as

  6. Assessing metaldehyde concentrations in surface water catchments and implications for drinking water abstraction

    NASA Astrophysics Data System (ADS)

    Asfaw, Alemayehu; Shucksmith, James; Smith, Andrea; Cherry, Katherine

    2015-04-01

    Metaldehyde is an active ingredient in agricultural pesticides such as slug pellets, which are heavily applied to UK farmland during the autumn application season. There is current concern that existing drinking water treatment processes may be inadequate in reducing potentially high levels of metaldehyde in surface waters to below the UK drinking water quality regulation limit of 0.1 µg/l. In addition, current water quality monitoring methods can miss short term fluctuations in metaldehyde concentration caused by rainfall driven runoff, hampering prediction of the potential risk of exposure. Datasets describing levels, fate and transport of metaldehyde in river catchments are currently very scarce. This work presents results from an ongoing study to quantify the presence of metaldehyde in surface waters within a UK catchment used for drinking water abstraction. High resolution water quality data from auto-samplers installed in rivers are coupled with radar rainfall, catchment characteristics and land use data to i) understand which hydro-meteorological characteristics of the catchment trigger the peak migration of metaldehyde to surface waters; ii) assess the relationship between measured metaldehyde levels and catchment characteristics such as land use, topographic index, proximity to water bodies and runoff generation area; iii) describe the current risks to drinking water supply and discuss mitigation options based on modelling and real-time control of water abstraction. Identifying the correlation between catchment attributes and metaldehyde generation will help in the development of effective catchment management strategies, which can help to significantly reduce the amount of metaldehyde finding its way into river water. Furthermore, the effectiveness of current water quality monitoring strategy in accurately quantifying the generation of metaldehyde from the catchment and its ability to benefit the development of effective catchment management practices

  7. Dissimilarity between temperature-humidity in the atmospheric surface layer and implications for estimates of evaporation

    NASA Astrophysics Data System (ADS)

    Cancelli, D. M.; Dias, N. L.; Chamecki, M.

    2012-12-01

    In several methods used in water resources to estimate evaporation from land and water surfaces, a fundamental assumption is that temperature (T) and specific humidity (q) fluctuations behave similarly in the atmospheric surface layer (ASL). In the Energy-Budget Bowen Ratio method it is assumed that both eddy diffusivities are equal, while in the variance method it is often assumed that all the Monin-Obukhov Similarity (MOS) functions for the two scalars are equal. However, it is well-known that the T-q similarity does not always hold and that the dissimilarity found in practice can significantly impact the estimates of evaporation. Given the frequent dissimilarity between temperature and humidity, two important problems arise. The first one is related to the choice of the function used to characterize scalar similarity, given that not all commonly used functions are equally capable of identifying scalar dissimilarity. The second problem is associated with the identification of the physical mechanisms behind scalar dissimilarity in each particular case: local advection, nonstationarity, surface heterogeneity, active/passive roles of the scalars, entrainment fluxes at the top of the atmospheric boundary layer are typically cited as possible causes, but seldom a convincing argument is presented. In this work we combine experimental data and numerical simulations to study similarity between T and q in the ASL. Data measured over a lake in Brazil suggests a strong relationship between scalar similarity and the balance between local production and dissipation of scalar variance, which is in practice related to the strength of the surface forcing. Scalar variance and covariance budgets are used to derive a set of dimensionless Scalar Flux numbers that are capable of diagnosing the balance between gradient production and molecular dissipation of scalar variance and covariance. Experimental data shows that these Scalar Flux numbers are good predictors of scalar (dis

  8. Effects of Varying Surface Inclines and Suit Pressure: Implications on Space Suit Design

    NASA Technical Reports Server (NTRS)

    Clowers, Kurt; Clark, Timothy; Harvill, Lauren; Morency, Richard; Rajulu, Sudhakar

    2008-01-01

    Suited human performance studies in reduced gravity environments to date include limited observations from Apollo Lunar surface Extravehicular Activities (EVA) and from previous studies conducted in partial gravity simulation environments. The Constellation Program EVA Systems Project office has initiated tests to develop design requirements for the next generation Lunar EVA suit. Theses studies were conducted in the Space Vehicle Mock-Up Facility (SVMF) at Johnson Space Center from which the results provided recommendations for suit weight, mass, center of gravity, pressure, and suit kinematic constraints that optimize human performance in partial gravity environments.

  9. Seasonal changes in Titan's weather patterns and the evolution and implications of accompanying surface changes

    NASA Astrophysics Data System (ADS)

    Turtle, E. P.; Perry, J.; McEwen, A. S.; Barbara, J. M.; Del Genio, A. D.; West, R. A.; Barnes, J. W.; Hayes, A.; Lorenz, R. D.; Lunine, J. I.; Stofan, E. R.; Schaller, E. L.; Lopes, R. M.; Ray, T. L.

    2012-12-01

    Post-equinox changes in Titan's atmospheric circulation brought clouds and extensive methane rain to Titan's low latitudes [1,2]. Observations by Cassini ISS over the ~2 years since the storm revealed most of the changes to be short-lived; only a few darkened patches persisted through Fall 2011. In an unsaturated permeable medium, infiltration rates exceed 20 mm/week [3], so persistence of surface liquids over several months suggests either a shallow impermeable layer or that the local methane table lies close to the surface. Evaporation rates greater than 1 mm/week are predicted in equatorial regions [4] and rates of 20 mm/week have been documented at Titan's poles [5], thus areas where darkening persisted must be saturated ground at the level of a methane table or have had liquid ponded to depths of 2.5-50 cm. Several smaller areas of surface brightening were also observed, a phenomenon that is less well understood. Cassini VIMS spectra of these regions do not match those of clouds or other surface units [6, 7]. Interpretations include cleaning by runoff [2] or deposition of a fine-grained volatile solid as the result of evaporative cooling [6, 7]. In general, brightening has persisted longer than darkening, but these areas are also reverting to their original appearance, which could constrain rates of evaporation/sublimation of the bright material or re-deposition of darker hydrocarbons by aeolian transport or precipitation from the atmosphere. Cassini and Earth-based observers monitor Titan frequently (typically at least a few times per month), but few clouds have been observed since Fall 2010, which may indicate that enough methane was removed from the atmosphere and the lapse rate stabilized sufficiently that activity will not resume until the onset of convection at mid-northern latitudes later in northern spring. A similar lapse followed a 2004 outburst of south-polar clouds [8], which also appeared to produce significant rainfall [9]. [1] Turtle et al., GRL

  10. Evolution of Titan's equinoctial weather patterns and accompanying surface changes and implications thereof

    NASA Astrophysics Data System (ADS)

    Turtle, E. P.; Perry, J. E.; Barnes, J. W.; McEwen, A. S.; Barbara, J. M.; Del Genio, A. D.; Hayes, A. G.; West, R. A.; Lorenz, R. D.; Schaller, E. L.; Lunine, J. I.; Ray, T. L.; Lopes, R. M. C.; Stofan, E. R.

    2012-04-01

    Post-equinox changes in Titan's atmospheric circulation brought clouds and extensive methane rain to Titan's low latitudes [1,2]. Observations by Cassini ISS over the ~1.5 years since the storm revealed most of the changes to be short-lived; only a few darkened patches persisted through Fall 2011. In an unsaturated permeable medium, infiltration rates are >20 mm/week [3], so persistence of surface liquids over several months suggests either a shallow impermeable layer or that the local methane table lies close to the surface. Evaporation rates >1 mm/week are predicted in equatorial regions [4] and rates of 20 mm/week have been documented at the poles [5], thus areas where darkening persisted must be saturated ground at the level of a methane table or have had liquid ponded to depths of 2.5-50 cm. Several smaller areas of surface brightening were also observed, a phenomenon that is less well understood. Cassini VIMS spectra of these regions do not match those of clouds or other surface units [6, 7]. Interpretations include cleaning by runoff [2] or deposition of fresh methane ice [6, 7]. In general, brightening has persisted longer than darkening, but these areas are also reverting to their original appearance, which could constrain the rate of re-deposition of darker hydrocarbon materials by aeolian transport or possibly precipitation of aerosols from the atmosphere. Although we monitor Titan frequently (at least a few times per month), little cloud activity has been observed since Fall 2010. This lack of clouds may indicate that the outbreak removed enough methane from the atmosphere and the lapse rate stabilized sufficiently that activity will not resume until the onset of convection at mid-northern latitudes later in northern spring. A similar lapse followed a large outbreak of south-polar clouds in Fall 2004 [8], which also appeared to produce significant rainfall [9]. References: [1] Turtle et al., GRL 38, L03203, doi: 10.1029/2010GL046266, 2011. [2] Turtle et

  11. Revisiting the Phoenix TECP data: Implications for regolith control of near-surface humidity on Mars

    NASA Astrophysics Data System (ADS)

    Rivera-Valentin, Edgard G.; Chevrier, Vincent F.

    2015-06-01

    We analyze the recalibrated in situ humidity measurements by the Phoenix lander, which landed at 68.2°N, 234.3°E and operated from Ls 78° through Ls 148°, ∼152 sols. Vapor pressures demonstrate significant day-night variations with values ranging from 0.005 Pa to 0.37 Pa, an order of magnitude lower than previously reported, and evening derived enthalpies less than that for a purely ice deposition-driven process, suggesting other water vapor sinks may contribute to the near-surface humidity at the martian polar regions.

  12. Surface roughness effect on ultracold neutron interaction with a wall and implications for computer simulations

    SciTech Connect

    Steyerl, A.; Malik, S. S.; Desai, A. M.; Kaufman, C.

    2010-05-15

    We review the diffuse scattering and the loss coefficient in ultracold neutron reflection from slightly rough surfaces, report a surprising reduction in loss coefficient due to roughness, and discuss the possibility of transition from quantum treatment to ray optics. The results are used in a computer simulation of neutron storage in a recent neutron lifetime experiment that reported a large discrepancy of neutron lifetime with the current particle data value. Our partial reanalysis suggests the possibility of systematic effects that were not included in this publication.

  13. Oxidized basalts on the surface of Venus: Compositional implications of measured spectral properties

    NASA Technical Reports Server (NTRS)

    Pieters, C. M.; Patterson, W.; Pratt, S.; Head, J. W.; Garvin, J.

    1987-01-01

    Venera Lander reflectance data are compared with high temperature spectra of the same basaltic materials. The dark, flat unoxidized basalts are still inconsistent with the Venera data in the near-infrared. Basaltic material with a ferric component, however, would satisfy both the increase in reflectance beyond 0.7 microns as well as the dark, relatively colorless character in the visible. Therefore, it is concluded that besaltic surfaces of Venus represented by these measurements either contain minerals with uncommon characteristics, or, more likely, are relatively oxidized.

  14. Plot-scale field experiment of surface hydrologic processes with EOS implications

    NASA Technical Reports Server (NTRS)

    Laymon, Charles A.; Macari, Emir J.; Costes, Nicholas C.

    1992-01-01

    Plot-scale hydrologic field studies were initiated at NASA Marshall Space Flight Center to a) investigate the spatial and temporal variability of surface and subsurface hydrologic processes, particularly as affected by vegetation, and b) develop experimental techniques and associated instrumentation methodology to study hydrologic processes at increasingly large spatial scales. About 150 instruments, most of which are remotely operated, have been installed at the field site to monitor ground atmospheric conditions, precipitation, interception, soil-water status, and energy flux. This paper describes the nature of the field experiment, instrumentation and sampling rationale, and presents preliminary findings.

  15. Chemical abundances in low surface brightness galaxies: Implications for their evolution

    NASA Technical Reports Server (NTRS)

    Mcgaugh, S. S.; Bothun, G. D.

    1993-01-01

    Low Surface Brightness (LSB) galaxies are an important but often neglected part of the galaxy content of the universe. Their importance stems both from the selection effects which cause them to be under-represented in galaxy catalogs, and from what they can tell us about the physical processes of galaxy evolution that has resulted in something other than the traditional Hubble sequence of spirals. An important constraint for any evolutionary model is the present day chemical abundances of LSB disks. Towards this end, spectra for a sample of 75 H 2 regions distributed in 20 LSB disks galaxies were obtained. Structurally, this sample is defined as having B(0) fainter than 23.0 mag arcsec(sup -2) and scale lengths that cluster either around 3 kpc or 10 kpc. In fact, structurally, these galaxies are very similar to the high surface brightness spirals which define the Hubble sequence. Thus, our sample galaxies are not dwarf galaxies but instead have masses comparable to or in excess of the Milky Way. The basic results from these observations are summarized.

  16. pH-dependent mineral release and surface properties of cornstraw biochar: agronomic implications.

    PubMed

    Silber, A; Levkovitch, I; Graber, E R

    2010-12-15

    Surface charge and pH-dependent nutrient release properties of cornstraw biochar were examined to elucidate its potential agronomic benefits. Kinetics of element release was characterized by rapid H(+) consumption and rapid, pH-dependent P, Ca, and Mg release, followed by zero-order H(+) consumption and mineral dissolution reactions. Initial K release was not pH-dependent, nor was it followed by a zero-order reaction at any pH. Rapid and constant rate P releases were significant, having the potential to substitute substantial proportions of P fertilizer. K releases were also significant and may replace conventional K fertilizers, however, not long-term plant demand. The cation exchange capacity (CEC) of the biochar leached with a mild acidic solution increased linearly from 179 to 888 mmol(c) (kg C)(-1) over a pH range of 4-8, while the anion exchange capacity of 154 mmol(c) (kg C)(-1) was constant over the same pH range. Since native soil organic constituents have much higher CEC values (average 2800 mmol(c) (kg C)(-1) at pH 7), improved soil fertility as a result of enhanced cation retention by the biochar probably will be favorable only in sandy and low organic matter soils, unless surface oxidation during aging significantly increases its CEC. PMID:21090742

  17. Surface energetics and protein-protein interactions: analysis and mechanistic implications.

    PubMed

    Peri, Claudio; Morra, Giulia; Colombo, Giorgio

    2016-01-01

    Understanding protein-protein interactions (PPI) at the molecular level is a fundamental task in the design of new drugs, the prediction of protein function and the clarification of the mechanisms of (dis)regulation of biochemical pathways. In this study, we use a novel computational approach to investigate the energetics of aminoacid networks located on the surface of proteins, isolated and in complex with their respective partners. Interestingly, the analysis of individual proteins identifies patches of surface residues that, when mapped on the structure of their respective complexes, reveal regions of residue-pair couplings that extend across the binding interfaces, forming continuous motifs. An enhanced effect is visible across the proteins of the dataset forming larger quaternary assemblies. The method indicates the presence of energetic signatures in the isolated proteins that are retained in the bound form, which we hypothesize to determine binding orientation upon complex formation. We propose our method, BLUEPRINT, as a complement to different approaches ranging from the ab-initio characterization of PPIs, to protein-protein docking algorithms, for the physico-chemical and functional investigation of protein-protein interactions. PMID:27050828

  18. Rayed craters on Dione: Implication for the dominant surface alteration process

    NASA Astrophysics Data System (ADS)

    Hirata, Naoyuki; Miyamoto, Hideaki

    2016-08-01

    From recently-acquired, high-resolution images obtained by the Cassini spacecraft, we examine the patterns and spatial distributions of rayed craters on Dione. We identify 29 rayed craters with diameters larger than 2 km on Dione's surface. The density of rayed craters and theoretical cratering rates indicate that the retention time for rays on Dione can be approximately 1-50 My. Such a short retention time is interpreted to be due to bombardment of plasma and E-ring particles, as well as implantation of dark particles (presumably the same dark material found on Hyperion, Iapetus, and other saturnian satellites). We also find that when the ray system of Creusa crater was formed, it extended over most of the surface of Dione. Later, the ray system deposited on the trailing hemisphere might have been partially erased, mostly due to implantation of dark particles, which may have also removed other bright ray systems in that region. The pattern of Creusa's ray system implies that the implantation of the dark material occurred more recent than both the age of Creusa crater and the typical retention time for rays on Dione.

  19. Characterizing heavy metal build-up on urban road surfaces: implication for stormwater reuse.

    PubMed

    Liu, An; Liu, Liang; Li, Dunzhu; Guan, Yuntao

    2015-05-15

    Stormwater reuse is increasingly popular in the worldwide. In terms of urban road stormwater, it commonly contains toxic pollutants such as heavy metals, which could undermine the reuse safety. The research study investigated heavy metal build-up characteristics on urban roads in a typical megacity of South China. The research outcomes show the high variability in heavy metal build-up loads among different urban road sites. The degree of traffic congestion and road surface roughness was found to exert a more significant influence on heavy metal build-up rather than traffic volume. Due to relatively higher heavy metal loads, stormwater from roads with more congested traffic conditions or rougher surfaces might be suitable for low-water-quality required activities while the stormwater from by-pass road sections could be appropriate for relatively high-water-quality required purposes since the stormwater could be relatively less polluted. Based on the research outcomes, a decision-making process for heavy metals based urban road stormwater reuse was proposed. The new finding highlights the importance to undertaking a "fit-for-purpose" road stormwater reuse strategy. Additionally, the research results can also contribute to enhancing stormwater reuse safety. PMID:25687783

  20. Surface temperatures of the Mid-Pliocene North Atlantic Ocean: Implications for future climate

    USGS Publications Warehouse

    Dowsett, H.J.; Chandler, M.A.; Robinson, M.M.

    2009-01-01

    The Mid-Pliocene is the most recent interval in the Earth's history to have experienced warming of the magnitude predicted for the second half of the twenty-first century and is, therefore, a possible analogue for future climate conditions. With continents basically in their current positions and atmospheric CO2 similar to early twenty-first century values, the cause of Mid-Pliocene warmth remains elusive. Understanding the behaviour of the North Atlantic Ocean during the Mid-Pliocene is integral to evaluating future climate scenarios owing to its role in deep water formation and its sensitivity to climate change. Under the framework of the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) sea surface reconstruction, we synthesize Mid-Pliocene North Atlantic studies by PRISM members and others, describing each region of the North Atlantic in terms of palaeoceanography. We then relate Mid-Pliocene sea surface conditions to expectations of future warming. The results of the data and climate model comparisons suggest that the North Atlantic is more sensitive to climate change than is suggested by climate model simulations, raising the concern that estimates of future climate change are conservative. ?? 2008 The Royal Society.

  1. Surface energetics and protein-protein interactions: analysis and mechanistic implications

    PubMed Central

    Peri, Claudio; Morra, Giulia; Colombo, Giorgio

    2016-01-01

    Understanding protein-protein interactions (PPI) at the molecular level is a fundamental task in the design of new drugs, the prediction of protein function and the clarification of the mechanisms of (dis)regulation of biochemical pathways. In this study, we use a novel computational approach to investigate the energetics of aminoacid networks located on the surface of proteins, isolated and in complex with their respective partners. Interestingly, the analysis of individual proteins identifies patches of surface residues that, when mapped on the structure of their respective complexes, reveal regions of residue-pair couplings that extend across the binding interfaces, forming continuous motifs. An enhanced effect is visible across the proteins of the dataset forming larger quaternary assemblies. The method indicates the presence of energetic signatures in the isolated proteins that are retained in the bound form, which we hypothesize to determine binding orientation upon complex formation. We propose our method, BLUEPRINT, as a complement to different approaches ranging from the ab-initio characterization of PPIs, to protein-protein docking algorithms, for the physico-chemical and functional investigation of protein-protein interactions. PMID:27050828

  2. Surface Crystallization of Cloud Droplets: Implications for Climate Change and Ozone Depletion

    NASA Technical Reports Server (NTRS)

    Tabazadeh, A.; Djikaev, Y. S.; Reiss, H.; Gore, Warren J. (Technical Monitor)

    2002-01-01

    The process of supercooled liquid water crystallization into ice is still not well understood. Current experimental data on homogeneous freezing rates of ice nucleation in supercooled water droplets show considerable scatter. For example, at -33 C, the reported freezing nucleation rates vary by as much as 5 orders of magnitude, which is well outside the range of measurement uncertainties. Until now, experimental data on the freezing of supercooled water has been analyzed under the assumption that nucleation of ice took place in the interior volume of a water droplet. Here, the same data is reanalyzed assuming that the nucleation occurred "pseudoheterogeneously" at the air (or oil)-liquid water interface of the droplet. Our analysis suggest that the scatter in the nucleation data can be explained by two main factors. First, the current assumption that nucleation occurs solely inside the volume of a water droplet is incorrect. Second, because the nucleation process most likely occurs on the surface, the rates of nuclei formation could differ vastly when oil or air interfaces are involved. Our results suggest that ice freezing in clouds may initiate on droplet surfaces and such a process can allow for low amounts of liquid water (approx. 0.002 g per cubic meters) to remain supercooled down to -40 C as observed in the atmosphere.

  3. Surface and bulk properties of chromium oxide: Implications for reduction by methane

    NASA Astrophysics Data System (ADS)

    Skjelbred, Kristin M.; Åstrand, Per-Olof; Støvneng, Jon Andreas; Andersson, Stefan

    2015-12-01

    A computational method for Cr2O3 and Cr3C2 has been established based on a systematic investigation of functionals, basis sets and corrections for dispersion, self-interaction and relativistic effects. The suggested method comprises of the PBE functional with Grimme's dispersion correction, the TZ2P basis set with a frozen core of up to 2p for chromium and 1s for oxygen and carbon, and with the zeroth-order regular approximation for relativistic effects, and is in good agreement with experimental results for both bulk crystals and surface structures. Self-interactions have been corrected for by the DFT+U approach, but it still gives band gaps significantly different from the experimental band gap. We have also calculated the adsorption energy of methane on a chromium terminated (0001) Cr2O3 surface, and the significance of dispersion and self-interaction corrections for the adsorption of methane on Cr2O3 was found to be substantial.

  4. Surface temperatures of the Mid-Pliocene North Atlantic Ocean: implications for future climate.

    PubMed

    Dowsett, Harry J; Chandler, Mark A; Robinson, Marci M

    2009-01-13

    The Mid-Pliocene is the most recent interval in the Earth's history to have experienced warming of the magnitude predicted for the second half of the twenty-first century and is, therefore, a possible analogue for future climate conditions. With continents basically in their current positions and atmospheric CO2 similar to early twenty-first century values, the cause of Mid-Pliocene warmth remains elusive. Understanding the behaviour of the North Atlantic Ocean during the Mid-Pliocene is integral to evaluating future climate scenarios owing to its role in deep water formation and its sensitivity to climate change. Under the framework of the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) sea surface reconstruction, we synthesize Mid-Pliocene North Atlantic studies by PRISM members and others, describing each region of the North Atlantic in terms of palaeoceanography. We then relate Mid-Pliocene sea surface conditions to expectations of future warming. The results of the data and climate model comparisons suggest that the North Atlantic is more sensitive to climate change than is suggested by climate model simulations, raising the concern that estimates of future climate change are conservative. PMID:18852090

  5. Surface-induced assembly of apolipoprotein A-I: Implications for symmetry-driven non-cooperative clustering

    NASA Astrophysics Data System (ADS)

    Winford, Sidney; Tobin, Moriah; Gross, Eitan

    2012-03-01

    In condensed matter physics the geometry of a crystal is determined by the mechanism of condensation. In biology, the link between clustering mechanisms and the shape of a protein crystal is not well defined. To gain more insight into the problem, we studied clustering of apolipoprotein A-I (apo A-I) on a solid surface using AFM. The amyloidogenic protein apo A-I is the main protein component of high density lipoprotein and thus reduces the risk of atherosclerosis. We found that apo A-I clustered to form nano-scale, symmetrical clusters on mica. Statistical analysis of size distribution for several thousand clusters suggested that the clustering reaction followed a non-cooperative kinetic scheme characterized by a single equilibrium constant of 0.92·106 M-1 and a change in free energy (ΔG) of -0.03 kJ mole-1/residue. This is close to ΔG of-0.04 kJ mole-1/residue for apo A-I binding to phospholipid membrane; and 30-fold smaller than ΔG for β-amyloid formation by apo A-I. The high symmetry of the clusters is consistent with an isotropic diffusion coefficient of protein monomers on the surface of the substrate. This previously unrecognized link between protein clustering mechanism and the symmetry of the growth pattern may have important implications in medicine, pharmaceutics and polymer science.

  6. Surface exploration of a room-temperature ionic liquid-chitin composite film decorated with electrochemically deposited PdFeNi trimetallic alloy nanoparticles by pattern recognition: an elegant approach to developing a novel biotin biosensor.

    PubMed

    Gholivand, Mohammad-Bagher; Jalalvand, Ali R; Goicoechea, Hector C; Paimard, Giti; Skov, Thomas

    2015-01-01

    In this study, a novel biosensing system for the determination of biotin (BTN) based on electrodeposition of palladium-iron-nickel (PdFeNi) trimetallic alloy nanoparticles (NPs) onto a glassy carbon electrode (GCE) modified with a room-temperature ionic liquid (RTIL)-chitin (Ch) composite film (PdFeNi/ChRTIL/GCE) is established. NPs have a wide range of applications in science and technology and their sizes are often measured using transmission electron microscopy (TEM) or X-ray diffraction. Here, we used a pattern recognition method (digital image processing, DIP) for measuring particle size distributions (PSDs) from scanning electron microscopic (SEM) images in the presence of an uneven background. Different depositions were performed by varying the number of cyclic potential scans (N) during electroreduction step. It was observed that the physicochemical properties of the deposits were correlated to the performance of the PdFeNi/ChRTIL/GCE with respect to BTN assay. The best results were obtained for eight electrodeposition cyclic scans, where small-sized particles (19.54 ± 6.27 nm) with high density (682 particles µm(-2)) were obtained. Under optimized conditions, a linear range from 2.0 to 44.0 × 10(-9) mol L(-1) and a limit of detection (LOD) of 0.6 × 10(-9) mol L(-1) were obtained. The PdFeNi/ChRTIL nanocomposite showed excellent compatibility, enhanced electron transfer kinetics, large electroactive surface area, and was highly sensitive, selective, and stable toward BTN determination. Finally, the PdFeNi/ChRTIL/GCE was satisfactorily applied to the determination of BTN in infant milk powder, liver, and egg yolk samples. PMID:25281100

  7. Ionic liquids, electrolyte solutions including the ionic liquids, and energy storage devices including the ionic liquids

    SciTech Connect

    Gering, Kevin L.; Harrup, Mason K.; Rollins, Harry W.

    2015-12-08

    An ionic liquid including a phosphazene compound that has a plurality of phosphorus-nitrogen units and at least one pendant group bonded to each phosphorus atom of the plurality of phosphorus-nitrogen units. One pendant group of the at least one pendant group comprises a positively charged pendant group. Additional embodiments of ionic liquids are disclosed, as are electrolyte solutions and energy storage devices including the embodiments of the ionic liquid.

  8. Early history of Vesta: implications for the surface morphology and composition

    NASA Astrophysics Data System (ADS)

    Turrini, D.; Coradini, A.; Formisano, M.; Carli, C.; Magni, G.

    2011-12-01

    The Dawn mission inserted into orbit around Vesta on 15 July 2011 and is presently gathering data on the morphology and the composition of the asteroid. In order to fully exploit the data that the Dawn mission is supplying to probe the ancient past of our Solar System, we need to be able to understand how the present state of Vesta is linked to its origin and its secular evolution. The spectral connection between Vesta and the Howardite-Eurcrite-Diogenite (HED) suite of meteorites suggests that Vesta formed very early in the history of the Solar System and differentiated on a Ma-long timescale due to the decay of short-lived radioactive nuclides (see Keil 2002 and references therein). Short after the differentiation process ended, Vesta started to cool down quickly, so that on a 10 Ma timescale its molten mantle would be topped by a thick solid layer (Formisano et al. 2011). Across the same timespan, Jupiter and the other giant planets would form in the outer Solar System and trigger a primordial phase of bombardment on the other already formed planetary bodies (Turrini et al. 2011, Coradini et al. 2011). Such primordial bombardment is expected to excavate the solid crust of Vesta and to cause local to regional effusive phenomena (Turrini et al. 2011). Moreover, due to the relatively high escape speed from Vesta, most of the excavated material would fall back on the asteroid as an ejecta blanket. Here we discuss the timescale of the formation and evolution of Vesta and the implications for the interpretation of the data that the Dawn mission is collecting while orbiting the asteroid. Bibliography 1. Coradini A., Turrini D., Federico C., Magni G. (2011). Vesta and Ceres: crossing the history of the Solar System. Space Science Reviews, DOI: 10.1007/s11214-011-9792-x. 2. Formisano M., Federico C., Coradini A. (2011). Vesta Thermal Models. EPSC-DPS Joint Meeting 2011, Nantes, France. 3. Keil K. (2002). Geological History of Asteroid 4 Vesta: The Smallest Terrestrial

  9. Implications from Near-Shoemaker Imaging of Eros for Small-Scale Structure and Surface Sampling

    NASA Technical Reports Server (NTRS)

    Chapman, C. R.

    2000-01-01

    What we know about asteroids has always been bifurcated by the enormous gap between astronomical studies of small, distant bodies, and the close-up laboratory measurements of hand-sample sized meteorites. The gulf has been narrowed somewhat by improvements in Earth-based astronomical techniques (e.g. Hubble Space Telescope, radar, adaptive optics) and especially by spacecraft fly-bys of asteroids. But the Near Earth Asteroid Rendezvous (NEAR)-Shoemaker mission has gone considerably more in the direction of bridging the gap. Any consideration of intelligent sample-return from an asteroid must be based on the best possible knowledge of the asteroid at the spatial scales pertinent to operations at the asteroid and of the sample/s. Otherwise, we are in danger of succumbing to the 'Martian Horror Story' that Bruce Murray, in the 1960's, envisioned might impair our exploration of the surface of the red planet if we tried to land on it without first bolstering the information content of our database about Mars, especially at high resolutions. NEAR-Shoemaker is helping to bridge that gap in the case of Eros. The best resolution obtained by the Galileo spacecraft on Ida was 25 m/pixel. As of this writing, NEAR has already obtained images with resolutions at least five times better (information content 25 times better) and vastly better images may be available at the time of this Workshop from the late October low flyby. Already, we are seeing that the Martian horror story looks tame compared with Eros. Everywhere we have landed on Mars, the surface has been covered with rocks and boulders, with much higher spatial coverage than seen anywhere on the lunar surface. We have, in fact, been rather lucky that none of our Martian landers have tipped over so far, and there were justified fears in the early aftermath of last year's failure of Mars Polar Lander that it had suffered from inadequate high-resolution characterization of polar regions on Mars (the failure is now known to

  10. Possible Tuff Rings in the Beagle 2 Landing Area and Implications for Sub-surface Volatiles

    NASA Astrophysics Data System (ADS)

    Rothery, D. A.; Seabrook, A. M.; Bridges, J.; Wright, I. P.

    2001-12-01

    Isidis Planitia, which contains the December 2003 landing site for Beagle 2, is a basin at the edge of the northern hemisphere martian lowlands. Crater counts date most of this plains material at close to the Hesperian-Amazonian boundary. There is a dearth of small craters (<120m) that presumably reflects mainly aeolian erosion and/or burial. Superimposed on this surface are tens of thousands of cones, sometimes occurring singly but often in chains. Individual cones are several hundred metres across and up to 300m high. Summits are about half the diameter of the base, and are often occupied by an apparently shallow summit crater. Where most abundant, cones occupy about 10% of the surface area of Isidis. The cones show a wide variety of degradation, ranging from apparently pristine to severely eroded. Such differences can be noted even in adjacent edifices, but there is also a basin-wide trend towards more degraded morphology from SW to NE. The range in morphologies presumably reflects an age-range, and we think it unlikely that the cones can have been produced as mud volcanoes in response to catastrophic sediment loading of the basin because this would have led to a relatively brief single episode of cone formation. We therefore prefer a volcanic origin. We reject the rootless cone hypothesis, because, in contrast to examples elsewhere on Mars, the Isidis cones do not appear to be built on a lava surface. Lack of identifiable lava flows emanating from any of the studied cones makes a scoria cone origin unliklely. Instead, we suggest that the cones are analogs to tuff cones. These are produced on Earth when magma encounters a wet subsoil, leading to an explosive eruption with a water:magma ratio of about 10:1. On Mars, the volatile trapped at depth within the Isidis sediments could be either water or carbon dioxide. Further arguments in favor of a volcanic origin for the cones are the chains that could reflect deep-seated fractures through which magma was supplied

  11. Surface Processes on Small Planetary Bodies: Implications for the Origins of Chondritic Meteorites

    NASA Astrophysics Data System (ADS)

    Akridge, David Glen

    I have conducted both experimental and theoretical work concerning the formation conditions of chondritic meteorites. This work has focused on the size-sorting of chondrules and metal grains, metal abundance in chondrites, gas phase reactions, and the thermal history of meteorite parent bodies containing substantial regoliths. Although many of the major chondritic properties have been assumed to be the result of nebula processes, it is suggested here that the release of volatiles in a parent body regolith would cause gas phase reactions indistinguishable from those occurring in the nebula. The escaping volatiles from either radiogenic 26Al or impact heating could create a dynamic surface dust layer on planetesimals leading to the physical separation of regolith grains of differing size and densities. The thermal history of an H-chondrite parent body (Asteroid 6 Hebe) was numerically modeled using 26Al as the primary heat source. The three layer model consisted of an interior of solid rock overlain by a megaregolith and regolith surfaces coverings. Appropriate porosities, bulk densities, and thermal conductivities were used for each zone. Regolith and megaregolith thicknesses were varied to see which numerical run best matched the metamorphic characteristics of H-chondrites. The results show surprisingly shallow burial depths for most H-chondrites. A moderate 2 km regolith insulates the interior so that H3-6 chondrites can all be formed in the regolith or upper megaregolith. Predicted peak temperatures, cooling rates, and formation time intervals agree well with data obtained from H-chondrites. The release of volatiles (primarily water) during parent body heating events could cause fluidization in the regolith if the upward moving gas flow rate reached a minimum critical velocity. At this minimum velocity particulates are free to move with fluid-like behavior and may segregate based on size and density characteristics. Fluidization experiments at atmospheric and

  12. Nanoporous membranes with electrochemically switchable, chemically stabilized ionic selectivity

    NASA Astrophysics Data System (ADS)

    Small, Leo J.; Wheeler, David R.; Spoerke, Erik D.

    2015-10-01

    Nanopore size, shape, and surface charge all play important roles in regulating ionic transport through nanoporous membranes. The ability to control these parameters in situ provides a means to create ion transport systems tunable in real time. Here, we present a new strategy to address this challenge, utilizing three unique electrochemically switchable chemistries to manipulate the terminal functional group and control the resulting surface charge throughout ensembles of gold plated nanopores in ion-tracked polycarbonate membranes 3 cm2 in area. We demonstrate the diazonium mediated surface functionalization with (1) nitrophenyl chemistry, (2) quinone chemistry, and (3) previously unreported trimethyl lock chemistry. Unlike other works, these chemistries are chemically stabilized, eliminating the need for a continuously applied gate voltage to maintain a given state and retain ionic selectivity. The effect of surface functionalization and nanopore geometry on selective ion transport through these functionalized membranes is characterized in aqueous solutions of sodium chloride at pH = 5.7. The nitrophenyl surface allows for ionic selectivity to be irreversibly switched in situ from cation-selective to anion-selective upon reduction to an aminophenyl surface. The quinone-terminated surface enables reversible changes between no ionic selectivity and a slight cationic selectivity. Alternatively, the trimethyl lock allows ionic selectivity to be reversibly switched by up to a factor of 8, approaching ideal selectivity, as a carboxylic acid group is electrochemically revealed or hidden. By varying the pore shape from cylindrical to conical, it is demonstrated that a controllable directionality can be imparted to the ionic selectivity. Combining control of nanopore geometry with stable, switchable chemistries facilitates superior control of molecular transport across the membrane, enabling tunable ion transport systems.Nanopore size, shape, and surface charge all play

  13. Nanoporous membranes with electrochemically switchable, chemically stabilized ionic selectivity

    NASA Astrophysics Data System (ADS)

    Small, Leo J.; Wheeler, David R.; Spoerke, Erik D.

    2015-10-01

    Nanopore size, shape, and surface charge all play important roles in regulating ionic transport through nanoporous membranes. The ability to control these parameters in situ provides a means to create ion transport systems tunable in real time. Here, we present a new strategy to address this challenge, utilizing three unique electrochemically switchable chemistries to manipulate the terminal functional group and control the resulting surface charge throughout ensembles of gold plated nanopores in ion-tracked polycarbonate membranes 3 cm2 in area. We demonstrate the diazonium mediated surface functionalization with (1) nitrophenyl chemistry, (2) quinone chemistry, and (3) previously unreported trimethyl lock chemistry. Unlike other works, these chemistries are chemically stabilized, eliminating the need for a continuously applied gate voltage to maintain a given state and retain ionic selectivity. The effect of surface functionalization and nanopore geometry on selective ion transport through these functionalized membranes is characterized in aqueous solutions of sodium chloride at pH = 5.7. The nitrophenyl surface allows for ionic selectivity to be irreversibly switched in situ from cation-selective to anion-selective upon reduction to an aminophenyl surface. The quinone-terminated surface enables reversible changes between no ionic selectivity and a slight cationic selectivity. Alternatively, the trimethyl lock allows ionic selectivity to be reversibly switched by up to a factor of 8, approaching ideal selectivity, as a carboxylic acid group is electrochemically revealed or hidden. By varying the pore shape from cylindrical to conical, it is demonstrated that a controllable directionality can be imparted to the ionic selectivity. Combining control of nanopore geometry with stable, switchable chemistries facilitates superior control of molecular transport across the membrane, enabling tunable ion transport systems.Nanopore size, shape, and surface charge all play

  14. Thermal evolution of a differentiated Ganymede and implications for surface features

    SciTech Connect

    Kirk, R.L.; Stevenson, D.J.

    1987-01-01

    Thermodynamic models are developed for the processes which controlled the evolution of the surface Ganymede, an icy Jovian satellite assumed to have a rock-rich core surrounded by a water-ice mantle. Account is taken of a heat pulse which would have arisen from a Rayleigh-Taylor instability at a deep-seated liquid-solid water interface, rapid fracturing from global stresses imposed by warm ice diapiric upwelling, impacts by large meteorites, and resurfacing by ice flows (rather than core formation). Comparisons are made with existing models for the evolution of Callisto, and the difficulties in defining a mechanism which produced the groove terrain of Ganymede are discussed. 100 references.

  15. Rotational dynamics of water molecules near biological surfaces with implications for nuclear quadrupole relaxation.

    PubMed

    Braun, Daniel; Schmollngruber, Michael; Steinhauser, Othmar

    2016-09-21

    Based on Molecular Dynamics simulations of two different systems, the protein ubiquitin dissolved in water and an AOT reverse micelle, we present a broad analysis of the single particle rotational dynamics of water. A comprehensive connection to NQR, which is a prominent experimental method in this field, is developed, based on a reformulation of its theoretical framework. Interpretation of experimental NQR results requires a model which usually assumes that the NQR experiences retardation only in the first hydration shell. Indeed, the present study shows that this first-shell model is correct. Moreover, previous experimental retardation factors are quantitatively reproduced. All of this is seemingly contradicted by results of other methods, e.g., dielectric spectroscopy, responsible for a long-standing debate in this field. Our detailed analysis shows that NQR omits important information contained in overall water dynamics, most notably, the retardation of the water dipole axis in the electric field exerted by a biological surface. PMID:27546227

  16. Global climate impacts of bioenergy from forests: implications from biogenic CO2 fluxes and surface albedo

    NASA Astrophysics Data System (ADS)

    Cherubini, Francesco; Bright, Ryan; Strømman, Anders

    2013-04-01

    Production of biomass for bioenergy can alter biogeochemical and biogeophysical mechanisms, thus affecting local and global climate. Recent scientific developments mainly embraced impacts from land use changes resulting from area-expanded biomass production, with several extensive insights available. Comparably less attention, however, is given to the assessment of direct land surface-atmosphere climate impacts of bioenergy systems under rotation such as in plantations and forested ecosystems, whereby land use disturbances are only temporary. In this work, we assess bioenergy systems representative of various biomass species (spruce, pine, aspen, etc.) and climatic regions (US, Canada, Norway, etc.), for both stationary and vehicle applications. In addition to conventional greenhouse gas (GHG) emissions through life cycle activities (harvest, transport, processing, etc.), we evaluate the contributions to global warming of temporary effects resulting from the perturbation in atmospheric carbon dioxide (CO2) concentration caused by the timing of biogenic CO2 fluxes and in surface reflectivity (albedo). Biogenic CO2 fluxes on site after harvest are directly measured through Net Ecosystem Productivity (NEP) chronosequences from flux towers established at the interface between the forest canopy and the atmosphere and are inclusive of all CO2 exchanges occurring in the forest (e.g., sequestration of CO2 in growing trees, emissions from soil respiration and decomposition of dead organic materials). These primary data based on empirical measurements provide an accurate representation of the forest carbon sink behavior over time, and they are used in the elaboration of high-resolution IRFs for biogenic CO2 emissions. Chronosequence of albedo values from clear-cut to pre-harvest levels are gathered from satellite data (MODIS black-sky shortwave broadband, Collection 5, MCD43A). Following the cause-effect chain from emissions to damages, through radiative forcing and changes

  17. Radioactive elements on Mercury's surface from MESSENGER: implications for the planet's formation and evolution.

    PubMed

    Peplowski, Patrick N; Evans, Larry G; Hauck, Steven A; McCoy, Timothy J; Boynton, William V; Gillis-Davis, Jeffery J; Ebel, Denton S; Goldsten, John O; Hamara, David K; Lawrence, David J; McNutt, Ralph L; Nittler, Larry R; Solomon, Sean C; Rhodes, Edgar A; Sprague, Ann L; Starr, Richard D; Stockstill-Cahill, Karen R

    2011-09-30

    The MESSENGER Gamma-Ray Spectrometer measured the average surface abundances of the radioactive elements potassium (K, 1150 ± 220 parts per million), thorium (Th, 220 ± 60 parts per billion), and uranium (U, 90 ± 20 parts per billion) in Mercury's northern hemisphere. The abundance of the moderately volatile element K, relative to Th and U, is inconsistent with physical models for the formation of Mercury requiring extreme heating of the planet or its precursor materials, and supports formation from volatile-containing material comparable to chondritic meteorites. Abundances of K, Th, and U indicate that internal heat production has declined substantially since Mercury's formation, consistent with widespread volcanism shortly after the end of late heavy bombardment 3.8 billion years ago and limited, isolated volcanic activity since. PMID:21960624

  18. Color variations on Ceres derived by Dawn/VIR: Implications for the surface composition

    NASA Astrophysics Data System (ADS)

    Zambon, F.; De Sanctis, M. C.; Tosi, F.; Longobardo, A.; Palomba, E.; Carrozzo, G.; Combe, J.-Ph.; Li, J.-Y.; McFadden, L. A.; Marchi, S.; Jaumann, R.; Schoeder, S.; Ciarniello, M.; Raponi, A.; Frigeri, A.; Ammannito, E.; Russell, C. T.; Raymond, C. A.

    2015-10-01

    Ceres, the second target of the Dawn mission [1], with a diameter of ˜952 km, is the largest object in the main asteroid belt [2], and classified as a dwarf planet. More than two years after departure from Vesta, Dawn finally arrived to Ceres. During the approach phase, the spacecraft acquired data with unprecedented spatial resolution. Previous work based on Hubble Space Telescope (HST) data, highlight regions with different albedo variation in the UV-VIS range [3] (Fig. 1). The Visible and InfraRed (VIR) mapping spectrometer onboard Dawn covers the overall wavelength range between 0.25 and 5.1 μm [4]. VIR will enable the first comprehensive compositional mapping of Ceres, focusing on the possible presence of water ice, salts, organics and volatiles, and surface thermal properties [5].

  19. The tidal loss of satellite-orbiting objects and its implications for the lunar surface

    NASA Technical Reports Server (NTRS)

    Reid, M. J.

    1973-01-01

    The solar system is composed of numerous bodies orbiting the sun, and numerous satellites orbiting planets. However, no objects greater than a kilometer in diameter are known to orbit satellites. Theoretical arguments are used to show that most objects orbiting satellites ultimately would be destroyed by tidal interactions. This may explain why such objects have not been observed. These arguments are applied to objects orbiting the moon. The ages and sizes of most of the circular mare basins are compatible with the lifetimes and crater sizes expected for impacts by objects caught in decaying lunar orbits. The morphology of a few circular mare basins (Crisium, Serenitatis, and possibly Imbrium) indicates that they could have been formed by such impacts. Thus, the lunar surface may provide a record of impacts due to objects caught in tidally decaying lunar orbits.

  20. Earthing: health implications of reconnecting the human body to the Earth's surface electrons.

    PubMed

    Chevalier, Gaétan; Sinatra, Stephen T; Oschman, James L; Sokal, Karol; Sokal, Pawel

    2012-01-01

    Environmental medicine generally addresses environmental factors with a negative impact on human health. However, emerging scientific research has revealed a surprisingly positive and overlooked environmental factor on health: direct physical contact with the vast supply of electrons on the surface of the Earth. Modern lifestyle separates humans from such contact. The research suggests that this disconnect may be a major contributor to physiological dysfunction and unwellness. Reconnection with the Earth's electrons has been found to promote intriguing physiological changes and subjective reports of well-being. Earthing (or grounding) refers to the discovery of benefits-including better sleep and reduced pain-from walking barefoot outside or sitting, working, or sleeping indoors connected to conductive systems that transfer the Earth's electrons from the ground into the body. This paper reviews the earthing research and the potential of earthing as a simple and easily accessed global modality of significant clinical importance. PMID:22291721

  1. Multichannel surface recordings on the visual cortex: implications for a neuroprosthesis

    NASA Astrophysics Data System (ADS)

    Chelvanayagam, D. K.; Vickery, R. M.; Kirkcaldie, M. T. K.; Coroneo, M. T.; Morley, J. W.

    2008-06-01

    Using a multi-channel platinum surface electrode array, recordings from cat primary visual cortex were obtained in response to visual stimuli, and electrical stimuli delivered using the elements of the array itself. Neural responses to electrical stimuli were consistent, regardless of stimulus polarity or leading phase (biphasic), although thresholds were lower for monophasic than biphasic pulses. Both visual and electrical stimuli reliably evoked responses with characteristic components, which interacted with each other in a nonlinear summation showing first facilitation then suppression during the window of interaction. The chronaxie for eliciting threshold cortical responses was about 100 µs, and the charge density with a pulse width of 50-100 µs was around 55 µC cm-2. These data form the basis of understanding the types of cortical responses to stimuli delivered by devices suitable for chronic implantation.

  2. Adsorption of HO(x) on aerosol surfaces - Implications for the atmosphere of Mars

    NASA Technical Reports Server (NTRS)

    Anbar, A. D.; Leu, M.-T.; Nair, H. A.; Yung, Y. L.

    1993-01-01

    The potential impact of heterogeneous chemistry on the abundance and distribution of HO(x) in the Martian atmosphere is investigated using observational data on dust and ice aerosol distributions combined with an updated photochemical model. Critical parameters include the altitude distributions of aerosols and the surface loss coefficients of HO2 on dust and ice in the lower atmosphere and of H on ice above 40 km. Results of calculations indicate that adsorption of HO2 on dust, or ice near 30 km, can deplete OH abundances in the lower atmosphere by 10 percent or more and that the adsorption of H on ice at 50 km can result in even larger OH depletions (this effect is localized to altitudes greater than 40 km, where CO oxidation is relatively unimportant).

  3. Synthesis of Ionic Colloidal Crystals (ICCs)

    NASA Astrophysics Data System (ADS)

    Maskaly, Garry R.; Garcia, R. Edwin; Carter, W. Craig; Chiang, Yet-Ming

    2003-03-01

    Binary ionic colloidal crystals (ICCs) have been produced by ordered heterocoagulation of colloidal mixtures of silica (negative surface charge) and polystyrene functionalized with amidine (positive surface charge) suspended in isopropanol. Experimental conditions predicted by the theoretical model discussed in a separate talk have been implemented to obtain heterocoagulation of these particles in the rocksalt structure. To our knowledge, this is the first experimental demonstration of the ICC concept. The importance of various experimental parameters on ICC formation is discussed. Particle dynamics simulations are carried out to provide insight into the kinetics of ICCs. Potential applications are discussed.

  4. Retrodicting the Cenozoic evolution of the mantle: Implications for dynamic surface topography

    NASA Astrophysics Data System (ADS)

    Glišović, Petar; Forte, Alessandro; Rowley, David; Simmons, Nathan; Grand, Stephen

    2014-05-01

    Seismic tomography is the essential starting ingredient for constructing realistic models of the mantle convective flow and for successfully predicting a wide range of convection-related surface observables. However, the lack of knowledge of the initial thermal state of the mantle in the geological past is still an outstanding problem in mantle convection. The resolution of this problem requires models of 3-D mantle evolution that yield maximum consistency with a wide suite of geophysical constraints. Quantifying the robustness of the reconstructed thermal evolution is another major concern. We have carried out mantle dynamic simulations (Glišović & Forte, EPSL 2014) using a pseudo-spectral solution for compressible-flow thermal convection in 3-D spectral geometry that directly incorporate: 1) joint seismic-geodynamic inversions of mantle density structure with constraints provided by mineral physics data (Simmons et al., GJI 2009); and 2) constraints on mantle viscosity inferred by inversion of a suite of convection-related and glacial isostatic adjustment data sets (Mitrovica & Forte, EPSL 2004) characterised by Earth-like Rayleigh numbers. These time-reversed convection simulations reveal how the buoyancy associated with hot, active upwellings is a major driver of the mantle-wide convective circulation and the changes in dynamic topography at the Earth's surface. These simulations reveal, for example, a stable and long-lived superplume under the East Pacific Rise (centred under the Easter and Pitcairn hotspots) that was previously identified by Rowley et al. (AGU 2011, Nature in review) on the basis of plate kinematic data. We also present 65 Myr reconstructions of the Reunion plume that gave rise to the Deccan Traps.

  5. Soil Iodine Determination in Deccan Syneclise, India: Implications for Near Surface Geochemical Hydrocarbon Prospecting

    SciTech Connect

    Mani, Devleena; Kumar, T. Satish; Rasheed, M. A.; Patil, D. J.; Dayal, A. M.; Rao, T. Gnaneshwar; Balaram, V.

    2011-03-15

    The association of iodine with organic matter in sedimentary basins is well documented. High iodine concentration in soils overlying oil and gas fields and areas with hydrocarbon microseepage has been observed and used as a geochemical exploratory tool for hydrocarbons in a few studies. In this study, we measure iodine concentration in soil samples collected from parts of Deccan Syneclise in the west central India to investigate its potential application as a geochemical indicator for hydrocarbons. The Deccan Syneclise consists of rifted depositional sites with Gondwana-Mesozoic sediments up to 3.5 km concealed under the Deccan Traps and is considered prospective for hydrocarbons. The concentration of iodine in soil samples is determined using ICP-MS and the values range between 1.1 and 19.3 ppm. High iodine values are characteristic of the northern part of the sampled region. The total organic carbon (TOC) content of the soil samples range between 0.1 and 1.3%. The TOC correlates poorly with the soil iodine (r{sup 2} < 1), indicating a lack of association of iodine with the surficial organic matter and the possibility of interaction between the seeping hydrocarbons and soil iodine. Further, the distribution pattern of iodine compares well with two surface geochemical indicators: the adsorbed light gaseous hydrocarbons (methane through butane) and the propane-oxidizing bacterial populations in the soil. The integration of geochemical observations show the occurrence of elevated values in the northern part of the study area, which is also coincident with the presence of exposed dyke swarms that probably serve as conduits for hydrocarbon microseepage. The corroboration of iodine with existing geological, geophysical, and geochemical data suggests its efficacy as one of the potential tool in surface geochemical exploration of hydrocarbons. Our study supports Deccan Syneclise to be promising in terms of its hydrocarbon prospects.

  6. Layered convection in Io: Implications for short-wavelength surface topography and heat flow

    NASA Astrophysics Data System (ADS)

    Shahnas, M. H.; Pysklywec, R. N.; Peltier, W. R.

    2013-07-01

    Io, one of the four Galilean moons of Jupiter is remarkable for its extensive volcanism and extreme interior tidal heating. The tidal heating likely yields a very low viscosity asthenosphere and consequently a very high Rayleigh number of O(1012) for convection in the interior. In a state of quasi-steady balance the internally generated heat must be transported from the interior to the base of the Io lithosphere and exhausted to space. The mechanisms whereby the convective radial heat transfer is evacuated involve both conduction and volcanism. Despite Io's ubiquitous volcanism, only 4% of its mountains (montes) appear to have a volcanic origin and most of the mountainous regions seem to be related to tectonic processes. By employing an original control volume based numerical model we investigate the style of convection in the interior of Io and the correlation of the scale of convection with the Ionian surface heat flux and topography. Our control volume results support the existence of significant asthenospheric heating and demonstrate that short wavelength features of the surface heat flux are well correlated in scale to an expected layered intra-lithospheric style small-scale convection. These numerical analyses suggest that the amplitude of the short wavelength topography of Io is expected to be on the order of a few hundreds of meters. The model results also demonstrate that the Ionian highs cannot be produced by a lithospheric flexure process above the hot upwellings and therefore other tectonic events, such as have previously been suggested; must be responsible for the formation of the high Ionian mountains that reach in excess of 17 km in elevation.

  7. Comparison of bipolar and unipolar ionic diodes

    SciTech Connect

    Vlassiouk, Ivan V

    2010-01-01

    Nanoporous ionic diodes, as well as devices for manipulating ions and molecules in a solution, have attracted a great deal of interest from researchers in various fields from the fundamental point of view. Ionic diodes allow the ions to be transported in one direction and block the transport in the other. There are two types of diodes that have been realized experimentally. A bipolar diode contains a junction between two zones of the pore walls with positive and negative surface charges. A unipolar diode contains a zone that is neutral and a zone that is charged. In this paper we discuss differences in operation of the diodes with a special emphasis on the sensitivity of their performance to the lengths of the charged and neutral zones. We also show that a bipolar diode offers more asymmetric current-voltage curves than a unipolar diode.

  8. Complex source mechanisms of mining-induced seismic events - implications for surface effects

    NASA Astrophysics Data System (ADS)

    Orlecka-Sikora, B.; Cesca, S.; Lasocki, S.; Rudzinski, L.; Lizurek, L.; Wiejacz, P.; Urban, P.; kozlowska, M.

    2012-04-01

    The seismicity of Legnica-Głogów Copper District (LGCD) is induced by mining activities in three mines: Lubin, Rudna and Polkowice-Sieroszowice. Ground motion caused by strong tremors might affect local infrastructure. "Żelazny Most" tailings pond, the biggest structure of this type in Europe, is here under special concern. Due to surface objects protection, Rudna Mine has been running ground motion monitoring for several years. From June 2010 to June 2011 unusually strong and extensive surface impact has been observed for 6 mining tremors induced in one of Rudna mining sections. The observed peak ground acceleration (PGA) for both horizontal and vertical component were in or even beyond 99% confidence interval for prediction. The aim of this paper is analyze the reason of such unusual ground motion. On the basis of registrations from Rudna Mine mining seismological network and records from Polish Seismological Network held by the Institute of Geophysics Polish Academy of Sciences (IGF PAN), the source mechanisms of these 6 tremors were calculated using a time domain moment tensor inversion. Furthermore, a kinematic analysis of the seismic source was performed, in order to determine the rupture planes orientations and rupture directions. These results showed that in case of the investigated tremors, point source models and shear fault mechanisms, which are most often assumed in mining seismology, are invalid. All analyzed events indicate extended sources with non-shear mechanism. The rapture planes have small dip angles and the rupture starts at the tremors hypocenter and propagates in the direction opposite to the plane dip. The tensional component plays here also big role. These source mechanisms well explain such observed strong ground motion, and calculated synthetic PGA values well correlates with observed ones. The relationship between mining tremors were also under investigation. All subsequent tremors occurred in the area of increased stress due to

  9. Incompletely Mixed Surface Transient Storage Zones at River Restoration Structures: Modeling Implications

    NASA Astrophysics Data System (ADS)

    Endreny, T. A.; Robinson, J.

    2012-12-01

    River restoration structures, also known as river steering deflectors, are designed to reduce bank shear stress by generating wake zones between the bank and the constricted conveyance region. There is interest in characterizing the surface transient storage (STS) and associated biogeochemical processing in the STS zones around these structures to quantify the ecosystem benefits of river restoration. This research explored how the hydraulics around river restoration structures prohibits application of transient storage models designed for homogenous, completely mixed STS zones. We used slug and constant rate injections of a conservative tracer in a 3rd order river in Onondaga County, NY over the course of five experiments at varying flow regimes. Recovered breakthrough curves spanned a transect including the main channel and wake zone at a j-hook restoration structure. We noted divergent patterns of peak solute concentration and times within the wake zone regardless of transect location within the structure. Analysis reveals an inhomogeneous STS zone which is frequently still loading tracer after the main channel has peaked. The breakthrough curve loading patterns at the restoration structure violated the assumptions of simplified "random walk" 2 zone transient storage models which seek to identify representative STS zones and zone locations. Use of structure-scale Weiner filter based multi-rate mass transfer models to characterize STS zones residence times are similarly dependent on a representative zone location. Each 2 zone model assumes 1 zone is a completely mixed STS zone and the other a completely mixed main channel. Our research reveals limits to simple application of the recently developed 2 zone models, and raises important questions about the measurement scale necessary to identify critical STS properties at restoration sites. An explanation for the incompletely mixed STS zone may be the distinct hydraulics at restoration sites, including a constrained

  10. Surface Elevation Changes in West Antarctica from Satellite Altimetry: Mass Balance Implications

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Brenner, Anita C.; Cornejo, Helen; Koblinsky, Chester J. (Technical Monitor)

    2001-01-01

    Time-series of surface elevation change, which are constructed from 7-years (1992-1999) of ERS-1 and 2 satellite radar altimeter data of Antarctica, show significant seasonal, inter-annual, and long-term changes. Elevation time-series are created from altimeter crossovers among 90-day data periods on a 50 km grid to 81.5 degrees S and fit with a multivariate linear/sinusoidal function to give the average rate of elevation change (dH/dt) and account for seasonal changes. On the major Ronne, Filchner, and Ronne ice shelves, the dH/dt are small or near zero. In contrast, the ice shelves of the Antarctic Peninsula and along the West Antarctic coast appear to be thinning significantly, with a 23 +/- 3 cm a(exp -1) surface elevation decrease on the Larsen ice shelf and a 65 +/- 4 cm a(exp -1) decrease on the Dotson ice shelf. Significant elevation decreases are obtained over most of the drainage basins of the Pine Island and Thwaites glaciers. Significant increases are obtained over most of the other grounded ice in Marie Byrd Land, the Antarctic Peninsula, and Coates Land. Over the sector from 85 degrees W to 115 degrees W, which includes the Pine Island and Thwaites basins, the average elevation is significantly decreasing by 8.1 cm a(exp -1). The corresponding ice thickness change is about -11 cm a(exp -1), with a corresponding mass loss of 82 Gt a(exp -1), and a 0.22 mm a(exp -1) contribution to global sea level rise. In terms of elevation change, the decrease in the Pine Island-Thwaites sector is largely balanced by the increase in the Marie Byrd Land, but only balanced by about 1/4 in terms of ice thickness change and contribution to sea level rise. The overall average elevation change for the grounded ice is + 1.2 cm a(exp -1). Using an average bedrock uplift of 2.5 cm a(exp -1), implies an average ice thickness decrease of 1.3 cm a(exp -1), a mass loss of 22 Gt a(exp -1), and a 0.06 mm a(exp -1) contribution to global sea level rise.

  11. Survival of endospores of Bacillus subtilis on spacecraft surfaces under simulated martian environments: . implications for the forward contamination of Mars

    NASA Astrophysics Data System (ADS)

    Schuerger, Andrew C.; Mancinelli, Rocco L.; Kern, Roger G.; Rothschild, Lynn J.; McKay, Christopher P.

    2003-10-01

    Experiments were conducted in a Mars simulation chamber (MSC) to characterize the survival of endospores of Bacillus subtilis under high UV irradiation and simulated martian conditions. The MSC was used to create Mars surface environments in which pressure (8.5 mb), temperature (-80, -40, -10, or +23 °C), gas composition (Earth-normal N 2/O 2 mix, pure N 2, pure CO 2, or a Mars gas mix), and UV-VIS-NIR fluence rates (200-1200 nm) were maintained within tight limits. The Mars gas mix was composed of CO 2 (95.3%), N 2 (2.7%), Ar (1.7%), O 2 (0.2%), and water vapor (0.03%). Experiments were conducted to measure the effects of pressure, gas composition, and temperature alone or in combination with Mars-normal UV-VIS-NIR light environments. Endospores of B. subtilis, were deposited on aluminum coupons as monolayers in which the average density applied to coupons was 2.47×10 6 bacteria per sample. Populations of B. subtilis placed on aluminum coupons and subjected to an Earth-normal temperature (23 °C), pressure (1013 mb), and gas mix (normal N 2/O 2 ratio) but illuminated with a Mars-normal UV-VIS-NIR spectrum were reduced by over 99.9% after 30 sec exposure to Mars-normal UV fluence rates. However, it required at least 15 min of Mars-normal UV exposure to reduce bacterial populations on aluminum coupons to non-recoverable levels. These results were duplicated when bacteria were exposed to Mars-normal environments of temperature (-10 °C), pressure (8.5 mb), gas composition (pure CO 2), and UV fluence rates. In other experiments, results indicated that the gas composition of the atmosphere and the temperature of the bacterial monolayers at the time of Mars UV exposure had no effects on the survival of bacterial endospores. But Mars-normal pressures (8.5 mb) were found to reduce survival by approximately 20-35% compared to Earth-normal pressures (1013 mb). The primary implications of these results are (a) that greater than 99.9% of bacterial populations on sun

  12. Temperature dependence of Fe/++/ crystal field spectra - Implications to mineralogical mapping of planetary surfaces

    NASA Technical Reports Server (NTRS)

    Sung, C.-M.; Singer, R. B.; Parkin, K. M.; Burns, R. G.; Osborne, M.

    1977-01-01

    Results are reported of Fe(++) crystal field spectral measurements for olivines and pyroxenes up to 400 C. The results are correlated with crystal structure data at elevated temperatures, and the validity of remote-sensed identifications of minerals on hot surfaces of the moon and Mercury is assessed. Two techniques were used to obtain spectra of minerals at elevated temperatures using a spectrophotometer. One employed a diamond cell assembly or a specially designed sample holder to measure polarized absorption spectra of heated single crystals. For the other technique, a sample holder was designed to attach to a diffuse reflectance accessory to produce reflectance spectra of heated powdered samples. Polarized absorption spectra of forsterite at 20-400 C are shown in a graph. Other graphs show the temperature dependence of Fe(++) crystal field bands in olivines, the diffuse reflectance spectra of olivine at 40-400 C, the polarization absorption spectra of orthopyroxene at 30-400 C, the diffuse reflectance spectra of pigeonite at 40-400 C, and unpolarized absorption spectra of lunar pyroxene from Apollo 15 rock 15058.

  13. Volatile transport on Venus and implications for surface geochemistry and geology

    NASA Technical Reports Server (NTRS)

    Brackett, Robert A.; Fegley, Bruce; Arvidson, Raymond E.

    1995-01-01

    The high vapor pressure of volatile metal halides and chalcogenides (e.g., of Cu, Zn, Sn, Pb, As, Sb, Bi) at typical Venus surface temperatures, coupled with the altitude-dependent temperature gradient of approximately 8.5 K/km, is calculated to transport volatile metal vapors to the highlands of Venus, where condensation and accumulation will occur. The predicted geochemistry of volatile metals on Venus is supported by observations of CuCl in volcanic gases at Kilauea and Nyiragongo, and large enrichments of these and other volatile elements in terrestrial volcanic aerosols. A one-dimensional finite difference vapor transport model shows the diffusive migration of a thickness of 0.01 to greater than 10 microns/yr of moderately to highly volatile phases (e.g., metal halides and chalcogenides) from the hot lowlands (740 K) to the cold highlands (660 K) on Venus. The diffusive transport of volatile phases on Venus may explain the observed low emissivity of the Venusian highlands, hazes at 6-km altitude observed by two Pioneer Venus entry probes, and the Pioneer Venus entry probe anomalies at 12.5 km.

  14. Enzyme catalysis in ionic liquids.

    PubMed

    Kragl, Udo; Eckstein, Marrit; Kaftzik, Nicole

    2002-12-01

    Ionic liquids offer new possibilities for the application of solvent engineering to biocatalytic reactions. Although in many cases ionic liquids have simply been used to replace organic solvents, they have often led to improved process performance. Unlike conventional organic solvents, ionic liquids possess no vapor pressure, are able to dissolve many compounds, and can be used to form two-phase systems with many solvents. To date, reactions involving lipases have benefited most from the use of ionic liquids, but the use of ionic liquids with other enzymes and in whole-cell processes has also been described. In some cases, remarkable results with respect to yield, (enantio)selectivity or enzyme stability were observed. PMID:12482515

  15. Contrasting strike-slip motions on thrust and normal faults: Implications for space-geodetic monitoring of surface deformation

    NASA Astrophysics Data System (ADS)

    Hampel, Andrea; Li, Tao; Maniatis, Georgios

    2013-04-01

    emphasizes that understanding fault-parallel slip components and associated surface displacements is essential for inferring regional deformation patterns from space-geodetic and fault-slip data. References: Cheloni, D., N. D'Agostino, E. D'Anastasio, A. Avallone, S. Mantenuto, R. Giuliani, M. Mattone, S. Calcaterra, P. Gambino, D. Dominici, F. Radicioni, G. Fastellini (2010) Coseismic and initial post-seismic slip of the 2009 Mw 6.3 L'Aquila earthquake, Italy, from GPS measurements: Geophysical Journal International, 181, 1539-1546. Hampel, A., T. Li, G. Maniatis (in press) Contrasting strike-slip motions on thrust and normal faults: Implications for space-geodetic monitoring of surface deformation: Geology. Hsu, Y.-J., S.-B Yu, H.-Y. Chen (2009) Coseismic and postseismic deformation associated with the 2003 Chengkung, Taiwan, earthquake: Geophysical Journal International, 176, 420-430. Jackson, J.A., J. Gagnepain, G. Houseman, G.C.P. King, P. Papadimitriou, C. Soufleris, J. Virieux (1982) Seismicity, normal faulting, and the geomorphological development of the Gulf of Corinth (Greece): The Corinth earthquakes of February and March 1981: Earth and Planetary Science Letters, 57, 377-397. Roberts, G.P., I. Koukouvelas (1996) Structural and seismological segmentation of the Gulf of Corinth fault system: Implications for models of fault growth: Annali di Geofisica, 39, 619-646. Serpelloni, E., L. Anderlini, M.E. Belardinelli (2012) Fault geometry, coseismic-slip distribution and Coulomb stress change associated with the 2009 April 6, Mw 6.3, L'Aquila earthquake from inversion of GPS displacements: Geophysical Journal International, 188, 473-489.

  16. Alteration Assemblages in Martian Meteorites: Implications for Near-Surface Processes

    NASA Astrophysics Data System (ADS)

    Bridges, J. C.; Catling, D. C.; Saxton, J. M.; Swindle, T. D.; Lyon, I. C.; Grady, M. M.

    2001-04-01

    The SNC (Shergotty-Nakhla-Chassigny) meteorites have recorded interactions between martian crustal fluids and the parent igneous rocks. The resultant secondary minerals - which comprise up to ~1 vol.% of the meteorites - provide information about the timing and nature of hydrous activity and atmospheric processes on Mars. We suggest that the most plausible models for secondary mineral formation involve the evaporation of low temperature (25 - 150 °C) brines. This is consistent with the simple mineralogy of these assemblages - Fe-Mg-Ca carbonates, anhydrite, gypsum, halite, clays - and the chemical fractionation of Ca-to Mg-rich carbonate in ALH84001 "rosettes". Longer-lived, and higher temperature, hydrothermal systems would have caused more silicate alteration than is seen and probably more complex mineral assemblages. Experimental and phase equilibria data on carbonate compositions similar to those present in the SNCs imply low temperatures of formation with cooling taking place over a short period of time (e.g. days). The ALH84001 carbonate also probably shows the effects of partial vapourisation and dehydration related to an impact event post-dating the initial precipitation. This shock event may have led to the formation of sulphide and some magnetite in the Fe-rich outer parts of the rosettes. Radiometric dating (K-Ar, Rb-Sr) of the secondary mineral assemblages in one of the nakhlites (Lafayette) suggests that they formed between 0 and 670 Myr, and certainly long after the crystallisation of the host igneous rocks. Crystallisation of ALH84001 carbonate took place 0.5 Gyr after the parent rock. These age ranges and the other research on these assemblages suggest that environmental conditions conducive to near-surface liquid water have been present on Mars periodically over the last ~1 Gyr. This fluid activity cannot have been continuous over geological time because in that case much more silicate alteration would have taken place in the meteorite parent

  17. The Evolution and Development of the Lunar Regolith and Implications for Lunar Surface Operations and Construction

    NASA Technical Reports Server (NTRS)

    McKay, David

    2009-01-01

    The lunar regolith consists of about 90% submillimeter particles traditionally termed lunar soil. The remainder consists of larger particles ranging up to boulder size rocks. At the lower size end, soil particles in the 10s of nanometer sizes are present in all soil samples. Lunar regolith overlies bedrock which consists of either lava flows in mare regions or impact-produced megaregolith in highland regions. Lunar regolith has been produced over billions of years by a combination of breaking and communition of bedrock by meteorite bombardment coupled with a variety of complex space weathering processes including solar wind implantation, solar flare and cosmic ray bombardment with attendant radiation damage, melting, vaporization, and vapor condensation driven by impact, and gardening and turnover of the resultant soil. Lunar regolith is poorly sorted compared to most terrestrial soils, and has interesting engineering properties including strong grain adhesion, over-compacted soil density, an abundance of agglutinates with sharp corners, and a variety of properties related to soil maturity. The NASA program has supported a variety of engineering test research projects, the production of bricks by solar or microwave sintering, the production of concrete, the in situ sintering and glazing of regolith by microwave, and the extraction of useful resources such as oxygen, hydrogen, iron, aluminum, silicon and other products. Future requirements for a lunar surface base or outpost will include construction of protective berms, construction of paved roadways, construction of shelters, movement and emplacement of regolith for radiation shielding and thermal control, and extraction of useful products. One early need is for light weight but powerful digging, trenching, and regolith-moving equipment.

  18. Ground state of Ho atoms on Pt(111) metal surfaces: Implications for magnetism

    NASA Astrophysics Data System (ADS)

    Karbowiak, M.; Rudowicz, C.

    2016-05-01

    We investigated the ground state of Ho atoms adsorbed on the Pt(111) surface, for which conflicting results exist. The density functional theory (DFT) calculations yielded the Ho ground state as | Jz=±8 > . Interpretation of x-ray absorption spectroscopy and x-ray magnetic circular dichroism spectra and the magnetization curves indicated the ground state as | Jz=±6 > . Superposition model is employed to predict the crystal-field (CF) parameters based on the structural data for the system Ho/Pt(111) obtained from the DFT modeling. Simultaneous diagonalization of the free-ion (HFI) and the trigonal CF Hamiltonian (HCF) within the whole configuration 4 f10 of H o3 + ion was performed. The role of the trigonal CF terms, neglected in the pure uniaxial CF model used previously for interpretation of experimental spectra, is found significant, whereas the sixth-rank CF terms may be neglected in agreement with the DFT predictions. The results provide substantial support for the experimental designation of the | Jz=±6 > ground state, albeit with subtle difference due to admixture of other | Jz> states, but run against the DFT-based designation of the | Jz=±8 > ground state. A subtle splitting of the ground energy level with the state (predominantly), | Jz=±6 > is predicted. This paper provides better insight into the single-ion magnetic behavior of the Ho/Pt(111) system by helping to resolve the controversy concerning the Ho ground state. Experimental techniques with greater resolution powers are suggested for direct confirmation of this splitting and C3 v symmetry experienced by the Ho atom.

  19. Succinimidyl Ester Surface Chemistry: Implications of the Competition between Aminolysis and Hydrolysis on Covalent Protein Immobilization

    PubMed Central

    2015-01-01

    N-Hydroxysuccinimide (NHS) ester terminal groups are commonly used to covalently couple amine-containing biomolecules (e.g., proteins and peptides) to surfaces via amide linkages. This one-step aminolysis is often performed in buffered aqueous solutions near physiological pH (pH 6 to pH 9). Under these conditions, the hydrolysis of the ester group competes with the amidization process, potentially degrading the efficiency of the coupling chemistry. The work herein examines the efficiency of covalent protein immobilization in borate buffer (50 mM, pH 8.50) using the thiolate monolayer formed by the chemisorption of dithiobis (succinimidyl propionate) (DSP) on gold films. The structure and reactivity of these adlayers are assessed via infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), electrochemical reductive desorption, and contact angle measurements. The hydrolysis of the DSP-based monolayer is proposed to follow a reaction mechanism with an initial nucleation step, in contrast to a simple pseudo first-order reaction rate law for the entire reaction, indicating a strong dependence of the interfacial reaction on the packing and presence of defects in the adlayer. This interpretation is used in the subsequent analysis of IR-ERS kinetic plots which give a heterogeneous aminolysis rate constant, ka, that is over 3 orders of magnitude lower than that of the heterogeneous hydrolysis rate constant, kh. More importantly, a projection of these heterogeneous kinetic rates to protein immobilization suggests that under coupling conditions in which low protein concentrations and buffers of near physiological pH are used, proteins are more likely physically adsorbed rather than covalently linked. This result is paramount for biosensors that use NHS chemistry for protein immobilization due to effects that may arise from noncovalently linked proteins. PMID:25317495

  20. Seismic imaging of the upper mantle beneath the northern Central Andean Plateau: Implications for surface topography

    NASA Astrophysics Data System (ADS)

    Ward, K. M.; Zandt, G.; Beck, S. L.; Wagner, L. S.

    2015-12-01

    Extending over 1,800 km along the active South American Cordilleran margin, the Central Andean Plateau (CAP) as defined by the 3 km elevation contour is second only to the Tibetan Plateau in geographic extent. The uplift history of the 4 km high Plateau remains uncertain with paleoelevation studies along the CAP suggesting a complex, non-uniform uplift history. As part of the Central Andean Uplift and the Geodynamics of High Topography (CAUGHT) project, we use surface waves measured from ambient noise and two-plane wave tomography to image the S-wave velocity structure of the crust and upper mantle to investigate the upper mantle component of plateau uplift. We observe three main features in our S-wave velocity model including (1), a high velocity slab (2), a low velocity anomaly above the slab where the slab changes dip from near horizontal to a normal dip, and (3), a high-velocity feature in the mantle above the slab that extends along the length of the Altiplano from the base of the Moho to a depth of ~120 km with the highest velocities observed under Lake Titicaca. A strong spatial correlation exists between the lateral extent of this high-velocity feature beneath the Altiplano and the lower elevations of the Altiplano basin suggesting a potential relationship. Non-uniqueness in our seismic models preclude uniquely constraining this feature as an uppermost mantle feature bellow the Moho or as a connected eastward dipping feature extending up to 300 km in the mantle as seen in deeper mantle tomography studies. Determining if the high velocity feature represents a small lithospheric root or a delaminating lithospheric root extending ~300 km into the mantle requires more integration of observations, but either interpretation shows a strong geodynamic connection with the uppermost mantle and the current topography of the northern CAP.

  1. Ionic Vapor Composition in Pyridinium-Based Ionic Liquids.

    PubMed

    Chaban, Vitaly V; Prezhdo, Oleg V

    2016-05-26

    Strong electrostatic interactions in ionic compounds make vaporization a complex process. The gas phase can contain a broad range of ionic clusters, and the cluster composition can differ greatly from that in the liquid phase. Room-temperature ionic liquids (RTILs) constitute a complicated case due to their ionic nature, asymmetric structure, and a huge versatility of ions and ionic clusters. This work reports vapor-liquid equilibria and vapor compositions of butylpyridinium (BPY) RTILs formed with hexafluorophosphate (PF6), trifluoromethanesulfonate (TF), and bis(trifluoromethanesulfonyl)imide (TFSI) anions. Unlike inorganic crystals, the pyridinium-based RTILs contain significant percentages of charged clusters in the vapor phase. Ion triplets and ion quadruplets each constitute up to 10% of the vapor phase composition. Triples prevail over quadruples in [BPY][PF6] due to the size difference of the cation and the anion. The percentage of charged ionic clusters in the gas phase is in inverse proportion to the mass of the anion. The largest identified vaporized ionic cluster comprises eight ions, with a formation probability below 1%. Higher temperature fosters formation of larger clusters due to an increase of the saturated vapor density. PMID:27165866

  2. MEAN-FIELD THEORY AND COMPUTATION OF ELECTROSTATICS WITH IONIC CONCENTRATION DEPENDENT DIELECTRICS *

    PubMed Central

    LI, BO; WEN, JIAYI; ZHOU, SHENGGAO

    2015-01-01

    We construct a mean-field variational model to study how the dependence of dielectric coefficient (i.e., relative permittivity) on local ionic concentrations affects the electrostatic interaction in an ionic solution near a charged surface. The electrostatic free-energy functional of ionic concentrations, which is the key object in our model, consists mainly of the electrostatic potential energy and the ionic ideal-gas entropy. The electrostatic potential is determined by Poisson’s equation in which the dielectric coefficient depends on the sum of concentrations of individual ionic species. This dependence is assumed to be qualitatively the same as that on the salt concentration for which experimental data are available and analytical forms can be obtained by the data fitting. We derive the first and second variations of the free-energy functional, obtain the generalized Boltzmann distributions, and show that the free-energy functional is in general nonconvex. To validate our mathematical analysis, we numerically minimize our electrostatic free-energy functional for a radially symmetric charged system. Our extensive computations reveal several features that are significantly different from a system modeled with a dielectric coefficient independent of ionic concentration. These include the non-monotonicity of ionic concentrations, the ionic depletion near a charged surface that has been previously predicted by a one-dimensional model, and the enhancement of such depletion due to the increase of surface charges or bulk ionic concentrations. PMID:26877718

  3. Contrasting optical properties of surface waters across the Fram Strait and its potential biological implications

    NASA Astrophysics Data System (ADS)

    Pavlov, Alexey K.; Granskog, Mats A.; Stedmon, Colin A.; Ivanov, Boris V.; Hudson, Stephen R.; Falk-Petersen, Stig

    2015-03-01

    Underwater light regime is controlled by distribution and optical properties of colored dissolved organic matter (CDOM) and particulate matter. The Fram Strait is a region where two contrasting water masses are found. Polar water in the East Greenland Current (EGC) and Atlantic water in the West Spitsbergen Current (WSC) differ with regards to temperature, salinity and optical properties. We present data on absorption properties of CDOM and particles across the Fram Strait (along 79° N), comparing Polar and Atlantic surface waters in September 2009 and 2010. CDOM absorption of Polar water in the EGC was significantly higher (more than 3-fold) compared to Atlantic water in the WSC, with values of absorption coefficient, aCDOM(350), m- 1 of 0.565 ± 0.100 (in 2009) and 0.458 ± 0.117 (in 2010), and 0.138 ± 0.036 (in 2009) and 0.153 ± 0.039 (in 2010), respectively. An opposite pattern was observed for particle absorption with higher absorption found in the eastern part of the Fram Strait. Average values of particle absorption (aP(440), m- 1) were 0.016 ± 0.013 (in 2009) and 0.014 ± 0.011 (in 2010), and 0.047 ± 0.012 (in 2009) and 0.016 ± 0.014 (in 2010), respectively for Polar and Atlantic water. Thus absorption of light in eastern part of the Fram Strait is dominated by particles - predominantly phytoplankton, and the absorption of light in the western part of the strait is dominated by CDOM, with predominantly terrigenous origin. As a result the balance between the importance of CDOM and particulates to the total absorption budget in the upper 0-10 m shifts across Fram Strait. Under water spectral irradiance profiles were generated using ECOLIGHT 5.4.1 and the results indicate that the shift in composition between dissolved and particulate material does not influence substantially the penetration of photosynthetic active radiation (PAR, 400-700 nm), but does result in notable differences in ultraviolet (UV) light penetration, with higher attenuation in the

  4. The topography of Ceres and implications for the formation of linear surface structures

    NASA Astrophysics Data System (ADS)

    Buczkowski, D.; Otto, K.; Ruesch, O.; Scully, J. E. C.; Williams, D. A.; Mest, S. C.; Schenk, P.; Jaumann, R.; Nathues, A.; Preusker, F.; Park, R. S.; Raymond, C. A.; Russell, C. T.

    2015-12-01

    NASA's Dawn spacecraft began orbiting the dwarf planet Ceres in April 2015. Framing Camera data from the Approach (1.3 km/px) and Survey (415 m/px) orbits include digital terrain models derived from processing stereo images. These models have supported various scientific studies of the surface. The eastern hemisphere of Ceres is topographically higher than the western hemisphere. Some of linear structures on Ceres (which include grooves, pit crater chains, fractures and troughs) appear to be radial to the large basins Urvara and Yalode, and most likely formed due to impact processes. However, set of regional linear structures (RLS) that do not have any obvious relationship to impact craters are found on the eastern hemisphere topographic high region. Many of the longer RLS are comprised of smaller structures that have linked together, suggestive of en echelon fractures. Polygonal craters, theorized to form when pervasive subsurface fracturing affects crater formation [1], are widespread on Ceres [2], and those proximal to the RLS have straight crater rims aligned with the grooves and troughs, suggesting that the RLS are fracture systems. A cross-section of one RLS is displayed in FC images of the Occator crater wall. Comparing these images to the digital terrain models show 1) that the structure dips ~60º and 2) there is downward motion on the hanging wall, implying normal faulting. The digital terrain models also reveal the presence of numerous positive relief features with sub-circular shapes. These dome-like features have been tentatively interpreted as volcanic/magmatic features [3]; other possibilities include salt domes. Analog models of domal uplift in areas of regional extension [4] predict patterns of linear structures similar to those observed in the RLS near Occator. Utilizing topography data provided by the Ceres digital terrain models, we assess the relationship between the RLS and nearby domes and topographic high regions to determine the mechanism

  5. Present-Day Surface Changes on Mars: Implications for Recent Climate Variability and Habitability

    NASA Astrophysics Data System (ADS)

    McEwen, A. S.; Dundas, C. M.; Diniega, S.; Byrne, S.; Bridges, N. T.; Hansen, C. J.

    2012-12-01

    With the high-resolution and repeat-image capability of MRO/HiRISE, we have been documenting present-day surface activity. This activity includes seasonal defrosting (spots, fans, etc.), changes in polar deposits, new impacts, migrating sand dunes, enlargement of gullies, and a variety of slope flows. What does this tell us about possible environmental change and habitability? Perhaps the key result is that previous suggestions of recent climate change on Mars may have been somewhat exaggerated. One such suggestion is that the enlargement of pits in the south polar residual cap indicates present-day global warming. However, recent models of continuous sublimation and redeposition of the CO2 predict a suite of landforms that have been observed to exist today (Byrne, 2009, AREPS 37, 535). Another suggestion is that mid-latitude gullies formed by melting snow or shallow ice after a recent period of high obliquity, but HiRISE observations have shown rapid and widespread gully activity in the present climate (Diniega et al., 2010, Geology 38, 1047; Dundas et al., 2012, Icarus 220, 124; Dundas et al., this conference). Likewise, suggestions that Mars needed a significantly higher atmospheric density to explain the presence of well-preserved sand dunes have been countered by observations of widespread current activity (Bridges et al., 2012, Geology 40, 31; Bridges et al., 2012, Nature 485, 339). These observations do not rule out significantly different past climate conditions but do suggest that their effects were less pronounced, at least in recent times. There are features that do not appear active today; one example is the transverse aeolian ridges. Also, the mid-latitude icy lobate flows and ice-rich mantles have not shown current activity, appear to have partially sublimated, and are likely remnants of recent past climates. Ground ice excavated by new craters is observed closer to the equator than predicted for the present atmospheric water vapor content, but

  6. Theoretical Predictions for Surface Brightness Fluctuations and Implications for Stellar Populations of Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Liu, Michael C.; Charlot, Stéphane; Graham, James R.

    2000-11-01

    We compute theoretical predictions for surface brightness fluctuations (SBFs) of single-burst stellar populations (SSPs) using models optimized for this purpose. We present results over a wide range of ages (from 1 to 17 Gyr) and metallicities (from 1/200 to 2.5 times solar) and for a comprehensive set of ground-based and space-based optical and infrared bandpasses. Our models agree well with existing SBF observations of Milky Way globular clusters and elliptical galaxies. Our results also provide refined theoretical calibrations and k-corrections that are needed to use SBFs as standard candles. We suggest that SBF distance measurements can be improved by (1) using a filter around 1 μm to minimize the influence of stellar population variations, and (2) using the integrated V-K galaxy color instead of V-Ic to calibrate I-band SBF distances. In addition, we show that available SBF observations set useful constraints on current population synthesis models, and we suggest SBF-based tests for future models. The existing SBF data favor particular choices of stellar evolutionary tracks and spectral libraries among the several choices allowed by comparisons based on only the integrated properties of galaxies. Also, the tightness of the empirical I-band SBF calibration as a function of V-Ic galaxy color is a useful constraint. It suggests that the model uncertainties in the lifetimes of the post-main-sequence evolutionary phases are probably less than +/-50% and that the initial mass function in elliptical galaxies is probably not much steeper than that in the solar neighborhood. Finally, we analyze the potential of SBFs for probing unresolved stellar populations in elliptical galaxies. Since SBFs depend on the second moment of the stellar luminosity function, they are sensitive to the brightest giant stars and provide complementary information to commonly used integrated light and spectra. In particular, we find that optical/near-infrared SBFs are much more sensitive to

  7. Graphene/Ionic liquid composite films and ion exchange.

    PubMed

    Mo, Yufei; Wan, Yunfang; Chau, Alicia; Huang, Fuchuan

    2014-01-01

    Wettability of graphene is adjusted by the formation of various ionic surfaces combining ionic liquid (IL) self-assembly with ion exchange. The functionalized ILs were designed and synthesized with the goal of obtaining adjustable wettability. The wettability of the graphene surface bearing various anions was measured systematically. The effect of solvent systems on ion exchange ratios on the graphene surface has also been investigated. Meanwhile, the mechanical properties of the graphene/IL composite films were investigated on a nanometer scale. The elasticity and adhesion behavior of the thin film was determined with respected to the indentation deformation by colloid probe nanoindentation method. The results indicate that anions played an important role in determining graphene/IL composite film properties. In addition, surface wetting and mechanics can be quantitatively determined according to the counter-anions on the surface. This study might suggest an alternate way for quantity detection of surface ions by surface force. PMID:24970602

  8. Graphene/Ionic Liquid Composite Films and Ion Exchange

    NASA Astrophysics Data System (ADS)

    Mo, Yufei; Wan, Yunfang; Chau, Alicia; Huang, Fuchuan

    2014-06-01

    Wettability of graphene is adjusted by the formation of various ionic surfaces combining ionic liquid (IL) self-assembly with ion exchange. The functionalized ILs were designed and synthesized with the goal of obtaining adjustable wettability. The wettability of the graphene surface bearing various anions was measured systematically. The effect of solvent systems on ion exchange ratios on the graphene surface has also been investigated. Meanwhile, the mechanical properties of the graphene/IL composite films were investigated on a nanometer scale. The elasticity and adhesion behavior of the thin film was determined with respected to the indentation deformation by colloid probe nanoindentation method. The results indicate that anions played an important role in determining graphene/IL composite film properties. In addition, surface wetting and mechanics can be quantitatively determined according to the counter-anions on the surface. This study might suggest an alternate way for quantity detection of surface ions by surface force.

  9. Graphene/Ionic Liquid Composite Films and Ion Exchange

    PubMed Central

    Mo, Yufei; Wan, Yunfang; Chau, Alicia; Huang, Fuchuan

    2014-01-01

    Wettability of graphene is adjusted by the formation of various ionic surfaces combining ionic liquid (IL) self-assembly with ion exchange. The functionalized ILs were designed and synthesized with the goal of obtaining adjustable wettability. The wettability of the graphene surface bearing various anions was measured systematically. The effect of solvent systems on ion exchange ratios on the graphene surface has also been investigated. Meanwhile, the mechanical properties of the graphene/IL composite films were investigated on a nanometer scale. The elasticity and adhesion behavior of the thin film was determined with respected to the indentation deformation by colloid probe nanoindentation method. The results indicate that anions played an important role in determining graphene/IL composite film properties. In addition, surface wetting and mechanics can be quantitatively determined according to the counter-anions on the surface. This study might suggest an alternate way for quantity detection of surface ions by surface force. PMID:24970602

  10. Electrodeposition in Ionic Liquids.

    PubMed

    Zhang, Qinqin; Wang, Qian; Zhang, Suojiang; Lu, Xingmei; Zhang, Xiangping

    2016-02-01

    Due to their attractive physico-chemical properties, ionic liquids (ILs) are increasingly used as deposition electrolytes. This review summarizes recent advances in electrodeposition in ILs and focuses on its similarities and differences with that in aqueous solutions. The electrodeposition in ILs is divided into direct and template-assisted deposition. We detail the direct deposition of metals, alloys and semiconductors in five types of ILs, including halometallate ILs, air- and water-stable ILs, deep eutectic solvents (DESs), ILs with metal-containing cations, and protic ILs. Template-assisted deposition of nanostructures and macroporous structures in ILs is also presented. The effects of modulating factors such as deposition conditions (current density, current density mode, deposition time, temperature) and electrolyte components (cation, anion, metal salts, additives, water content) on the morphology, compositions, microstructures and properties of the prepared materials are highlighted. PMID:26530378

  11. A New Class of Ionic Liquids: Anion Amphiprotic Ionic Liquids.

    PubMed

    Treskow, Marcel; Pitawala, Jagath; Arenz, Sven; Matic, Aleksandar; Johansson, Patrik

    2012-08-16

    We here present a new class of protic ionic liquids, anion amphiprotic ionic liquids (AAILs). These materials are protonation equilibrium free protic ionic liquids and interesting in their own right by not following the classical Brønsted acid-base neutralization concept. Due to the very simple synthesis route applied and their stable basic chemistry, we believe in a potential use for manifold applications. This is supported by the combination of practical material properties, foremost, a general intrinsic stability versus reversal of the formation reaction toward neutral species, broad liquidus ranges, long-term thermal stabilities, high conductivities, protic characteristics, and a general stability versus water. PMID:26295756

  12. Cratering and penetration experiments in aluminum and teflon: Implications for space-exposed surfaces

    NASA Astrophysics Data System (ADS)

    Hörz, Friedrich

    2012-04-01

    and V, however, is very systematic. This has led to new and detailed calibration curves, permitting the reconstruction of Dp from the measurement of either crater diameter or penetration-hole size in Al1100 and TeflonFEP targets of arbitrary thickness. We also placed witness plates behind penetrated targets to intercept the down-range debris plume, which is generally a mixture of both target and impactor fragments and melts. These witness plates also reveal that the debris plume systematically and diagnostically depends on D*. Thick targets shed spall debris only, and target thickness must be less than crater depth (Tc) to allow projectile material on the witness plate. Concentric plume patterns, accented by characteristic "hole saw" rings, characterize penetrated Al-targets at D* = 1-10, but they give way to distinctly radial geometries at D* = 10-20. Most of the target debris occupies the periphery of the plume, while the projectile fragments or melts reside in its central parts. The periphery of the plume is also typically more fine-grained than its center. At D* > 50, the exit plume is dominated by solid projectile fragments that progressively coagulate and overlap with each other, giving rise to compound craters. The latter have irregular crater interiors on account of the heterogeneous mass distribution of a collisionally produced, aggregate impactor. Similarly, complex craters are observed on LDEF and Stardust and they are produced by aggregate cosmic-dust particles containing large, dense components within a relatively low-density, fine-grained matrix. The witness-plate observations can also be used to address the enigmatic clustering of impact sites observed on Stardust's aerogel and aluminum surfaces. We suggest that this clustering is difficult to produce by the collision of particles from comet Wild 2 with the Stardust spacecraft, and that it is more likely due to particle disaggregation in the comet's coma.

  13. A framework model for investigating the export of phosphorus to surface waters in forested watersheds: Implications to management.

    PubMed

    Santos, R M B; Sanches Fernandes, L F; Pereira, M G; Cortes, R M V; Pacheco, F A L

    2015-12-01

    The present study was developed in four sub-basins of rivers Cávado and Douro, located in the North of mainland Portugal. The goal was to identify main stressors as well as driving and attenuating processes responsible for the presence of phosphorus in masses of surface water in those catchments. To accomplish the goal, the basins were selected where a quality station was present at the outlet, the forest occupation was greater than 75% and the phosphorus concentrations have repeatedly exceeded the threshold for the good ecological status in the period 2000-2006. Further, in two basins the quality station was installed in a lotic (free-flow water) environment whereas in the other two was placed in a lentic (dammed water) environment. The ArcMap GIS-based software package was used for the spatial analysis of stressors and processes. The yields of phosphorus vary widely across the studied basins, from 0.2-30 kg·ha(-1)·yr(-1). The results point to post-fire soil erosion and hardwood clear cuttings as leading factors of phosphorus exports across the watersheds, with precipitation intensity being the key variable of erosion. However, yields can be attenuated by sediment deposition along the pathway from burned or managed areas to water masses. The observed high yields and concentrations of phosphorus in surface water encompass serious implications for water resources management in the basins, amplified in the lentic cases by potential release of phosphorus from lake sediments especially during the summer season. Therefore, a number of measures were proposed as regards wildfire combat, reduction of phosphorus exports after tree cuts, attenuation of soil erosion and improvement of riparian buffers, all with the purpose of preventing phosphorus concentrations to go beyond the regulatory good ecological status. PMID:26225737

  14. Strong sea surface cooling in the eastern equatorial Pacific and implications for Galápagos Penguin conservation

    NASA Astrophysics Data System (ADS)

    Karnauskas, K. B.; Jenouvrier, S.; Brown, C. W.; Murtugudde, R.

    2015-08-01

    The Galápagos is a flourishing yet fragile ecosystem whose health is particularly sensitive to regional and global climate variations. The distribution of several species, including the Galápagos Penguin, is intimately tied to upwelling of cold, nutrient-rich water along the western shores of the archipelago. Here we show, using reliable, high-resolution sea surface temperature observations, that the Galápagos cold pool has been intensifying and expanding northward since 1982. The linear cooling trend of 0.8°C/33 yr is likely the result of long-term changes in equatorial ocean circulation previously identified. Moreover, the northward expansion of the cold pool is dynamically consistent with a slackening of the cross-equatorial component of the regional trade winds—leading to an equatorward shift of the mean position of the Equatorial Undercurrent. The implied change in strength and distribution of upwelling has important implications for ongoing and future conservation measures in the Galápagos.

  15. Effect of the environmental humidity on the bulk, interfacial and nanoconfined properties of an ionic liquid.

    PubMed

    Jurado, L Andres; Kim, Hojun; Rossi, Antonella; Arcifa, Andrea; Schuh, Jonathon K; Spencer, Nicholas D; Leal, Cecilia; Ewoldt, Randy H; Espinosa-Marzal, Rosa M

    2016-08-10

    With reference to our previous surface-force study on 1-hexyl-3-methylimidazolium ethylsulfate ([HMIM] EtSO4) using an extended surface forces apparatus, which showed an ordered structure within the nanoconfined dry ionic liquid (IL) between mica surfaces that extended up to ∼60 nm from the surface, this work focuses on the influence of the environmental humidity on the bulk, interfacial and nanoconfined structure of [HMIM] EtSO4. Infrared spectroscopy and rheometry reflect the changes in chemical and physical properties of the bulk IL due to the uptake of water when exposed to ambient humidity, while wide-angle X-ray scattering shows a mild swelling of the bulk nanostructure, and the AFM sharp tip reveals an additional surface layer at the mica-IL interface. When the water-containing [HMIM] EtSO4 is nanoconfined between two mica surfaces, no long-range order is detected, in contrast to the results obtained for the dry IL, which demonstrates that the presence of water can prevent the liquid-to-solid transformation of this IL. A combination of techniques and the calculated Bjerrum length indicate that water molecules weaken interionic electrostatic and hydrogen-bonding interactions, which lessens ion-ion correlations. Our work shows that the solid-like behavior of the nanoconfined IL strongly depends on the presence of absorbed water and hence, it has implications with regard to the correct interpretation of laboratory studies and their extension to real applications in lubrication. PMID:27430333

  16. Osmotic Pressure in Ionic Microgel Dispersions

    NASA Astrophysics Data System (ADS)

    Denton, Alan R.; Tang, Qiyun

    2015-03-01

    Microgels are microscopic gel particles, typically 10-1000 nm in size, that are swollen by a solvent. Hollow microgels (microcapsules) can encapsulate cargo, such as dye molecules or drugs, in their solvent-filled cavities. Their sensitive response to environmental conditions (e.g., temperature, pH) and influence on flow properties suit microgels to widespread applications in the chemical, pharmaceutical, food, and consumer care industries. When dispersed in water, polyelectrolyte gels become charged through dissociation of counterions. The electrostatic contribution to the osmotic pressure inside and outside of ionic microgels influences particle swelling and bulk materials properties, including thermodynamic, structural, optical, and rheological properties. Within the primitive and cell models of polyelectrolyte solutions, we derive an exact statistical mechanical formula for the contribution of mobile microions to the osmotic pressure within ionic microgels. Using Poisson-Boltzmann theory, we validate this result by explicitly calculating ion distributions across the surface of an ionic microgel and the electrostatic contribution to the osmotic pressure. Within a coarse-grained one-component model, we further chart the limits of the cell model for salty dispersions. This work was supported by the National Science Foundation under Grant No. DMR-1106331.

  17. Ionic Liquids with Ammonium Cations as Lubricants or Additives

    SciTech Connect

    Qu, Jun; Blau, Peter Julian; Dai, Sheng; Luo, Huimin; Truhan, Jr., John J

    2006-01-01

    Friction and wear are estimated to cost 6% of the US gross national product, or around $700 billion annually. A new class of more effective lubricants could lead to huge energy savings. Limited recent literature has suggested potential for using room-temperature ionic liquids as lubricants, however only a few out of millions (or more) of species have been evaluated. Recent ORNL work discovered a new category of ionic liquids with ammonium cations that have demonstrated promising lubricating properties as net lubricants or lubricant additives, particularly in lubricating difficult-to-lubricate metals like aluminum. More than 30% friction reduction has been observed on ammonium-based ionic liquids compared to conventional hydrocarbon oils. The inherent polarity of ionic liquids is believed to provide strong adhesion to contact surfaces and form a boundary lubricating film leading to friction and wear reductions. Other advantages of ionic liquids include (1) negligible volatility, (2) high thermal stability, (3) non-flammability, and (4) better intrinsic properties that eliminate the necessity of many expensive lubricant additives. With very flexible molecular structures, this new class of lubricants, particularly ammonium-based ionic liquids, can be tailored to fit a big variety of applications including but not limited to bearings, combustion engines, MEMS, and metal forming.

  18. Thermal boundary conductance of hydrophilic and hydrophobic ionic liquids

    NASA Astrophysics Data System (ADS)

    Oyake, Takafumi; Sakata, Masanori; Yada, Susumu; Shiomi, Junichiro

    2015-03-01

    A solid/liquid interface plays a critical role for understanding mechanisms of biological and physical science. Moreover, carrier density of the surface is dramatically enhanced by electric double layer with ionic liquid, salt in the liquid state. Here, we have measured the thermal boundary conductance (TBC) across an interface of gold thin film and ionic liquid by using time-domain thermoreflectance technique. Following the prior researches, we have identified the TBC of two interfaces. One is gold and hydrophilic ionic liquid, N,N-Diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate (DEME-BF4), which is a hydrophilic ionic liquid, and the other is N,N-Diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide (DEME-TFSI), which is a hydrophobic ionic liquid. We found that the TBC between gold and DEME-TFIS (19 MWm-2K-1) is surprisingly lower than the interface between gold and DEME-BF4 (45 MWm-2K-1). With these data, the importance of the wetting angle and ion concentration for the thermal transport at the solid/ionic liquid interface is discussed. Part of this work is financially supported by Japan Society for the Promotion of Science (JSPS) and Japan Science and Technology Agency. The author is financially supported by JSPS Fellowship.

  19. Employing ionic liquids to deposit cellulose on PET fibers.

    PubMed

    Textor, Torsten; Derksen, Leonie; Gutmann, Jochen S

    2016-08-01

    Several ionic liquids are excellent solvents for cellulose. Starting from that finishing of PET fabrics with cellulose dissolved in ionic liquids like 1-ethyl-3-methyl imidazolium acetate, diethylphosphate and chloride, or the chloride of butyl-methyl imidazolium has been investigated. Finishing has been carried out from solutions of different concentrations, using microcrystalline cellulose or cotton and by employing different cross-linkers. Viscosity of solutions has been investigated for different ionic liquids, concentrations, cellulose sources, linkers and temperatures. Since ionic liquids exhibit no vapor pressure, simple pad-dry-cure processes are excluded. Before drying the ionic liquid has to be removed by a rinsing step. Accordingly rinsing with fresh ionic liquid followed by water or the direct rinsing with water have been tested. The amount of cellulose deposited has been investigated by gravimetry, zinc chloride iodine test as well as reactive dyeing. Results concerning wettability, water up-take, surface resistance, wear-resistance or washing stability are presented. PMID:27112860

  20. Application of Ionic Liquids in High Performance Reversed-Phase Chromatography

    PubMed Central

    Wang, Ye; Tian, Minglei; Bi, Wentao; Row, Kyung Ho

    2009-01-01

    Ionic liquids, considered “green” chemicals, are widely used in many areas of analytical chemistry due to their unique properties. Recently, ionic liquids have been used as a kind of novel additive in separation and combined with silica to synthesize new stationary phase as separation media. This review will focus on the properties and mechanisms of ionic liquids and their potential applications as mobile phase modifier and surface-bonded stationary phase in reversed-phase high performance liquid chromatography (RP-HPLC). Ionic liquids demonstrate advantages and potential in chromatographic field. PMID:19582220

  1. Lithium ion conductive behavior of TiO2 nanotube/ionic liquid matrices

    PubMed Central

    2014-01-01

    A series of TiO2 nanotube (TNT)/ionic liquid matrices were prepared, and their lithium ion conductive properties were studied. SEM images implied that ionic liquid was dispersed on the whole surface of TNT. Addition of TNT to ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMImTFSA)) resulted in significant increase of ionic conductivity. Furthermore, lithium transference number was also largely enhanced due to the interaction of anion with TNT. Vogel-Fulcher-Tammann parameter showed higher carrier ion number for TNT/BMImTFSA in comparison with BMImTFSA. PMID:25313300

  2. High Current Ionic Diode Using Homogeneously Charged Asymmetric Nanochannel Network Membrane.

    PubMed

    Choi, Eunpyo; Wang, Cong; Chang, Gyu Tae; Park, Jungyul

    2016-04-13

    A high current ionic diode is achieved using an asymmetric nanochannel network membrane (NCNM) constructed by soft lithography and in situ self-assembly of nanoparticles with uniform surface charge. The asymmetric NCNM exhibits high rectified currents without losing a rectification ratio because of its ionic selectivity gradient and differentiated electrical conductance. Asymmetric ionic transport is analyzed with diode-like I-V curves and visualized via fluorescent dyes, which is closely correlated with ionic selectivity and ion distribution according to variation of NCNM geometries. PMID:26990504

  3. Analysis of very-high-resolution Galileo images of Europa: Implications for small-scale structure and surface evolution

    NASA Astrophysics Data System (ADS)

    Leonard, E. J.; Pappalardo, R. T.; Yin, A.; Prockter, L. M.; Patthoff, D. A.

    2014-12-01

    The Galileo Solid State Imager (SSI) recorded nine very high-resolution frames (8 at 12 m/pixel and 1 at 6 m/pixel) during the E12 flyby of Europa in Dec. 1997. To understand the implications for the small-scale structure and evolution of Europa, we mosaicked these frames (observations 12ESMOTTLE01 and 02, incidence ≈18°, emission ≈77°) into their regional context (part of observation 11ESREGMAP01, 220 m/pixel, incidence ≈74°, emission ≈23°), despite their very different viewing and lighting conditions. We created a map of geological units based on morphology, structure, and albedo along with stereoscopic images where the frames overlapped. The highly diverse units range from: high albedo sub-parallel ridge and grooved terrain; to variegated-albedo hummocky terrain; to low albedo and relatively smooth terrain. We classified and analyzed the diverse units solely based on the high-resolution image mosaic, prior to comparison to the context image, to obtain an in-depth look at possible surface evolution and underlying formational processes. We infer that some of these units represent different stages and forms of resurfacing, including cryovolcanic and tectonic resurfacing. However, significant morphological variation among units in the region indicates that there are different degrees of resurfacing at work. We have created candidate morphological sequences that provide insight into the conversion of ridged plains to chaotic terrain—generally, a process of subduing formerly sharp features through tectonic modification and/or cryovolcanism. When the map of the high-resolution area is compared to the regional context, features that appear to be one unit at regional resolution are comprised of several distinct units at high resolution, and features that appear to be smooth in the context image are found to show distinct textures. Moreover, in the context image, transitions from ridged units to disrupted units appear to be gradual; however the high

  4. Seasonal cycles in radium and barium within a subterranean estuary: Implications for groundwater derived chemical fluxes to surface waters

    NASA Astrophysics Data System (ADS)

    Gonneea, Meagan Eagle; Mulligan, Ann E.; Charette, Matthew A.

    2013-10-01

    There is increasing evidence that submarine groundwater discharge (SGD) is an important source of water and dissolved materials to the ocean. One of the primary tracers of this process is the quartet of radium isotopes (223Ra, 224Ra, 226Ra and 228Ra), whereby excess activities in surface waters can often be attributed to an input supplied via SGD. This approach requires the radium end member activity to be well constrained, however, natural variability in groundwater radium may span several orders of magnitude. Therefore, this variability is usually the main driver of uncertainties in volumetric SGD estimates. To investigate the physical and biogeochemical controls on groundwater radium activities, we conducted a three-year time series of radium and barium, a chemical analogue for radium, within the subterranean estuary of a coastal aquifer (Waquoit Bay, MA, USA). Gonneea et al. (2013) demonstrated that movement of the salinity interface within the subterranean estuary is driven by changes in the hydraulic gradient between groundwater level and sea level height. For Waquoit Bay, seasonal scale sea level change, not groundwater level, was the main driver in hydraulic gradient fluctuations. Seasonal changes in groundwater chemistry can be attributed to the resulting movement of the salinity transition zone between terrestrial and marine groundwater. Landward movement of the interface results in a large release of radium isotopes (226Ra = 1400 dpm 100 L-1) and barium (3000 nmol kg-1) associated with an increase in groundwater salinity. The magnitude of these releases cannot be explained by in situ production or weathering alone, but is likely due to salinity driven desorption from surface-bound sediment inventory. The timing of these peak concentrations is not always in phase with model-derived estimates of SGD; as a result, the groundwater concentration rather than the water flux is the main driver of Ra and Ba inputs to Waquoit Bay surface waters. The behavior of

  5. Screening of ionic cores in partially ionized plasmas within linear response

    SciTech Connect

    Gericke, D. O.; Vorberger, J.; Wuensch, K.; Gregori, G.

    2010-06-15

    We employ a pseudopotential approach to investigate the screening of ionic cores in partially ionized plasmas. Here, the effect of the tightly bound electrons is condensed into an effective potential between the (free) valence electrons and the ionic cores. Even for weak electron-ion coupling, the corresponding screening clouds show strong modifications from the Debye result for elements heavier than helium. Modifications of the theoretically predicted x-ray scattering signal and implications on measurements are discussed.

  6. Mixed ionic-electronic conductor-based radiation detectors and methods of fabrication

    DOEpatents

    Conway, Adam; Beck, Patrick R; Graff, Robert T; Nelson, Art; Nikolic, Rebecca J; Payne, Stephen A; Voss, Lars; Kim, Hadong

    2015-04-07

    A method of fabricating a mixed ionic-electronic conductor (e.g. TlBr)-based radiation detector having halide-treated surfaces and associated methods of fabrication, which controls polarization of the mixed ionic-electronic MIEC material to improve stability and operational lifetime.

  7. Thermophysical properties of phosphonium-based ionic liquids

    PubMed Central

    Bhattacharjee, Arijit; Lopes-da-Silva, José A.; Freire, Mara G.; Coutinho, João A. P.; Carvalho, Pedro J.

    2015-01-01

    Experimental data for density, viscosity, refractive index and surface tension of four phosphonium-based ionic liquids were measured in the temperature range between (288.15 and 353.15) K and at atmospheric pressure. The ionic liquids considered include tri(isobutyl) methylphosphonium tosylate, [Pi(444)1][Tos], tri(butyl)methylphosphonium methylsulfate, [P4441][CH3SO4], tri(butyl)ethylphosphonium diethylphosphate, [P4442][(C2H5O)2PO2], and tetraoctylphosphonium bromide, [P8888][Br]. Additionally, derivative properties, such as the isobaric thermal expansion coefficient, the surface thermodynamic properties and the critical temperatures for the investigated ionic liquids were also estimated and are presented and discussed. Group contribution methods were evaluated and fitted to the density, viscosity and refractive index experimental data. PMID:26435574

  8. Stress-relaxation behavior in gels with ionic and covalent crosslinks

    NASA Astrophysics Data System (ADS)

    Zhao, Xuanhe; Huebsch, Nathaniel; Mooney, David J.; Suo, Zhigang

    2010-03-01

    Long-chained polymers in alginate hydrogels can form networks by either ionic or covalent crosslinks. This paper shows that the type of crosslinks can markedly affect the stress-relaxation behavior of the gels. In gels with only ionic crosslinks, stress relaxes mainly through breaking and subsequent reforming of the ionic crosslinks, and the time scale of the relaxation is independent of the size of the sample. By contrast, in gels with only covalent crosslinks, stress relaxes mainly through migration of water, and the relaxation slows down as the size of the sample increases. Implications of these observations are discussed.

  9. Surface Charge Visualization at Viable Living Cells.

    PubMed

    Perry, David; Paulose Nadappuram, Binoy; Momotenko, Dmitry; Voyias, Philip D; Page, Ashley; Tripathi, Gyanendra; Frenguelli, Bruno G; Unwin, Patrick R

    2016-03-01

    Scanning ion conductance microscopy (SICM) is demonstrated to be a powerful technique for quantitative nanoscale surface charge mapping of living cells. Utilizing a bias modulated (BM) scheme, in which the potential between a quasi-reference counter electrode (QRCE) in an electrolyte-filled nanopipette and a QRCE in bulk solution is modulated, it is shown that both the cell topography and the surface charge present at cellular interfaces can be measured simultaneously at high spatial resolution with dynamic potential measurements. Surface charge is elucidated by probing the properties of the diffuse double layer (DDL) at the cellular interface, and the technique is sensitive at both low-ionic strength and under typical physiological (high-ionic strength) conditions. The combination of experiments that incorporate pixel-level self-referencing (calibration) with a robust theoretical model allows for the analysis of local surface charge variations across cellular interfaces, as demonstrated on two important living systems. First, charge mapping at Zea mays root hairs shows that there is a high negative surface charge at the tip of the cell. Second, it is shown that there are distinct surface charge distributions across the surface of human adipocyte cells, whose role is the storage and regulation of lipids in mammalian systems. These are new features, not previously recognized, and their implications for the functioning of these cells are highlighted. PMID:26871001

  10. Ionic Liquid Crystals: Versatile Materials.

    PubMed

    Goossens, Karel; Lava, Kathleen; Bielawski, Christopher W; Binnemans, Koen

    2016-04-27

    This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions. PMID:27088310

  11. Special Report: Solid Ionic Conductors.

    ERIC Educational Resources Information Center

    Shriver, Duward F.; Farrington, Gregory C.

    1985-01-01

    Solid ionic conductors are unusual materials that may find valuable applications in devices ranging from high-energy density batteries to lasers. The nature of these materials and their potential uses are discussed. (JN)

  12. Novel approaches to ionic chromatography

    SciTech Connect

    Dasgupta, P.K.

    1990-11-01

    Research during this reporting period, continued on ionic chromatography. Major progress has been made towards on-line on-demand generation of ultrapure chemicals by electrochemical means. The concentration of the generated material is governed electrochemically.

  13. Survival of endospores of Bacillus subtilis on spacecraft surfaces under simulated martian environments: implications for the forward contamination of Mars

    NASA Technical Reports Server (NTRS)

    Schuerger, Andrew C.; Mancinelli, Rocco L.; Kern, Roger G.; Rothschild, Lynn J.; McKay, Christopher P.

    2003-01-01

    Experiments were conducted in a Mars simulation chamber (MSC) to characterize the survival of endospores of Bacillus subtilis under high UV irradiation and simulated martian conditions. The MSC was used to create Mars surface environments in which pressure (8.5 mb), temperature (-80, -40, -10, or +23 degrees C), gas composition (Earth-normal N2/O2 mix, pure N2, pure CO2, or a Mars gas mix), and UV-VIS-NIR fluence rates (200-1200 nm) were maintained within tight limits. The Mars gas mix was composed of CO2 (95.3%), N2 (2.7%), Ar (1.7%), O2 (0.2%), and water vapor (0.03%). Experiments were conducted to measure the effects of pressure, gas composition, and temperature alone or in combination with Mars-normal UV-VIS-NIR light environments. Endospores of B. subtilis, were deposited on aluminum coupons as monolayers in which the average density applied to coupons was 2.47 x 10(6) bacteria per sample. Populations of B. subtilis placed on aluminum coupons and subjected to an Earth-normal temperature (23 degrees C), pressure (1013 mb), and gas mix (normal N2/O2 ratio) but illuminated with a Mars-normal UV-VIS-NIR spectrum were reduced by over 99.9% after 30 sec exposure to Mars-normal UV fluence rates. However, it required at least 15 min of Mars-normal UV exposure to reduce bacterial populations on aluminum coupons to non-recoverable levels. These results were duplicated when bacteria were exposed to Mars-normal environments of temperature (-10 degrees C), pressure (8.5 mb), gas composition (pure CO2), and UV fluence rates. In other experiments, results indicated that the gas composition of the atmosphere and the temperature of the bacterial monolayers at the time of Mars UV exposure had no effects on the survival of bacterial endospores. But Mars-normal pressures (8.5 mb) were found to reduce survival by approximately 20-35% compared to Earth-normal pressures (1013 mb). The primary implications of these results are (a) that greater than 99.9% of bacterial populations on

  14. Ionic Liquid Epoxy Resin Monomers

    NASA Technical Reports Server (NTRS)

    Paley, Mark S. (Inventor)

    2013-01-01

    Ionic liquid epoxide monomers capable of reacting with cross-linking agents to form polymers with high tensile and adhesive strengths. Ionic liquid epoxide monomers comprising at least one bis(glycidyl) N-substituted nitrogen heterocyclic cation are made from nitrogen heterocycles corresponding to the bis(glycidyl) N-substituted nitrogen heterocyclic cations by a method involving a non-nucleophilic anion, an alkali metal cation, epichlorohydrin, and a strong base.

  15. Evaluation of cation-anion interaction strength in ionic liquids.

    PubMed

    Fernandes, Ana M; Rocha, Marisa A A; Freire, Mara G; Marrucho, Isabel M; Coutinho, João A P; Santos, Luís M N B F

    2011-04-14

    Electrospray ionization mass spectrometry with variable collision induced dissociation of the isolated [(cation)(2)anion](+) and/or [(anion)(2)cation](-) ions of imidazolium-, pyridinium-, pyrrolidinium-, and piperidinium-based ionic liquids (ILs) combined with a large set of anions, such as chloride, tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, and bis[(trifluoromethyl)sulfonyl]imide, was used to carry out a systematic and comprehensive study on the ionic liquids relative interaction energies. The results are interpreted in terms of main influences derived from the structural characteristics of both anion and cation. On the basis of quantum chemical calculations, the effect of the anion upon the dissociation energies of the ionic liquid pair, and isolated [(cation)(2)anion](+) and/or [(anion)(2)cation](-) aggregates, were estimated and are in good agreement with the experimental data. Both experimental and computational results indicate an energetic differentiation between the cation and the anion to the ionic pair. Moreover, it was found that the quantum chemical calculations can describe the trend obtained for the electrostatic cation-anion attraction potential. The impact of the cation-anion interaction strengths in the surface tension of ionic liquids is further discussed. The surface tensions dependence on the cation alkyl chain length, and on the anion nature, follows an analogous pattern to that of the relative cation-anion interaction energies determined by mass spectrometry. PMID:21425809

  16. Hydrophobic ionic liquids

    DOEpatents

    Koch, V.R.; Nanjundiah, C.; Carlin, R.T.

    1998-10-27

    Ionic liquids having improved properties for application in non-aqueous batteries, electrochemical capacitors, electroplating, catalysis and chemical separations are disclosed. Exemplary compounds have one of the following formulas shown in a diagram wherein R{sub 1}, R{sub 2}, R{sub 3}, R{sub 4}, R{sub 5}, and R{sub 6} are either H; F; separate alkyl groups of from 1 to 4 carbon atoms, respectively, or joined together to constitute a unitary alkylene radical of from 2 to 4 carbon atoms forming a ring structure converging on N; or separate phenyl groups; and wherein the alkyl groups, alkylene radicals or phenyl groups may be substituted with electron withdrawing groups, preferably F-, Cl-, CF{sub 3}-, SF{sub 5}-, CF{sub 3}S-, (CF{sub 3}){sub 2}CHS- or (CF{sub 3}){sub 3}CS-; and X{sup {minus}} is a non-Lewis acid-containing polyatomic anion having a van der Waals volume exceeding 100 {angstrom}{sup 3}. 4 figs.

  17. Hydrophobic ionic liquids

    DOEpatents

    Koch, Victor R.; Nanjundiah, Chenniah; Carlin, Richard T.

    1998-01-01

    Ionic liquids having improved properties for application in non-aqueous batteries, electrochemical capacitors, electroplating, catalysis and chemical separations are disclosed. Exemplary compounds have one of the following formulas: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are either H; F; separate alkyl groups of from 1 to 4 carbon atoms, respectively, or joined together to constitute a unitary alkylene radical of from 2 to 4 carbon atoms forming a ring structure converging on N; or separate phenyl groups; and wherein the alkyl groups, alkylene radicals or phenyl groups may be substituted with electron withdrawing groups, preferably F--, Cl--, CF.sub.3 --, SF.sub.5 --, CF.sub.3 S--, (CF.sub.3).sub.2 CHS-- or (CF.sub.3).sub.3 CS--; and X.sup.- is a non-Lewis acid-containing polyatomic anion having a van der Waals volume exceeding 100 .ANG..sup.3.

  18. Force microscopy of layering and friction in an ionic liquid

    NASA Astrophysics Data System (ADS)

    Hoth, Judith; Hausen, Florian; Müser, Martin H.; Bennewitz, Roland

    2014-07-01

    The mechanical properties of the ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl) trifluorophosphate ([Py1,4][FAP]) in confinement between a SiOx and a Au(1 1 1) surface are investigated by means of atomic force microscopy (AFM) under electrochemical control. Up to 12 layers of ion pairs can be detected through force measurements while approaching the tip of the AFM to the surface. The particular shape of the force versus distance curve is explained by a model for the interaction between tip, gold surface and ionic liquid, which assumes an exponentially decaying oscillatory force originating from bulk liquid density correlations. Jumps in the tip-sample distance upon approach correspond to jumps of the compliant force sensor between branches of the oscillatory force curve. Frictional force between the laterally moving tip and the surface is detected only after partial penetration of the last double layer between tip and surface.

  19. Force microscopy of layering and friction in an ionic liquid.

    PubMed

    Hoth, Judith; Hausen, Florian; Müser, Martin H; Bennewitz, Roland

    2014-07-16

    The mechanical properties of the ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl) trifluorophosphate ([Py1,4][FAP]) in confinement between a SiOx and a Au(1 1 1) surface are investigated by means of atomic force microscopy (AFM) under electrochemical control. Up to 12 layers of ion pairs can be detected through force measurements while approaching the tip of the AFM to the surface. The particular shape of the force versus distance curve is explained by a model for the interaction between tip, gold surface and ionic liquid, which assumes an exponentially decaying oscillatory force originating from bulk liquid density correlations. Jumps in the tip-sample distance upon approach correspond to jumps of the compliant force sensor between branches of the oscillatory force curve. Frictional force between the laterally moving tip and the surface is detected only after partial penetration of the last double layer between tip and surface. PMID:24919549

  20. Interaction of nonionic surfactant AEO9 with ionic surfactants*

    PubMed Central

    Zhang, Zhi-guo; Yin, Hong

    2005-01-01

    The interaction in two mixtures of a nonionic surfactant AEO9 (C12H25O(CH2CH2O)9H) and different ionic surfactants was investigated. The two mixtures were AEO9/sodium dodecyl sulfate (SDS) and AEO9/cetyltrimethylammonium bromide (CTAB) at molar fraction of AEO9, α AEO9=0.5. The surface properties of the surfactants, critical micelle concentration (CMC), effectiveness of surface tension reduction (γ CMC), maximum surface excess concentration (Γ max) and minimum area per molecule at the air/solution interface (A min) were determined for both individual surfactants and their mixtures. The significant deviations from ideal behavior (attractive interactions) of the nonionic/ionic surfactant mixtures were determined. Mixtures of both AEO9/SDS and AEO9/CTAB exhibited synergism in surface tension reduction efficiency and mixed micelle formation, but neither exhibited synergism in surface tension reduction effectiveness. PMID:15909351

  1. High performance ultracapacitors with carbon nanomaterials and ionic liquids

    DOEpatents

    Lu, Wen; Henry, Kent Douglas

    2012-10-09

    The present invention is directed to the use of carbon nanotubes and/or electrolyte structures in various electrochemical devices, such as ultracapacitors having an ionic liquid electrolyte. The carbon nanotubes are preferably aligned carbon nanotubes. Compared to randomly entangled carbon nanotubes, aligned carbon nanotubes can have better defined pore structures and higher specific surface areas.

  2. Quantifying small-scale temporal surface change on glaciers and salt pans using terrestrial laser scanning: implications for modelling ablation and dust emission

    NASA Astrophysics Data System (ADS)

    Nield, J. M.; Wiggs, G. F. S.; Leyland, J.; Darby, S. E.; King, J.; Eckardt, F. D.; Chiverrell, R. C.; Vircavs, L. H.; Jacobs, B.

    2012-04-01

    Physical surface roughness is important in glacial and desert environments as it influences aerodynamic roughness, which in turn determines the ability of the wind to contribute to the turbulent heat flux component of the energy balance for glacial ice ablation or the likelihood of a surface emitting dust. Surface microtopography has traditionally been quantified by single 2D transects, but little is known about how these surfaces vary over time and the feedback between surface properties and other geomorphic processes. Terrestrial laser scanning (TLS) is the perfect tool to examine geomorphic microtopography over large spatial areas relatively quickly with the opportunity for repeat temporal measurements. Here we present examples of daily and weekly surface change measured on the Sua Pan, Botswana and the Svínafellsjökull, Iceland with mm accuracy using TLS. For the first time it is possible to quantify salt crust plucking and extrusion events and elucidate links between surface and wind shear interactions, as well as possible changes in aerodynamic roughness over time as surfaces evolve. Clear patterning is evident, with crust expansion limited to topographic highs. Likewise, we illustrate examples of measured daily ablation rates and patterns, and allude to implications for energy balance modelling by improving estimates of aerodynamic roughness. Specific ice patterning includes melt water eroding channels, the unique interactions of surface debris (volcanic ash from the 21 - 30 May 2011 eruption of Grímsvötn) melting out from the glacier and surface water forming a diverse microtopography of debris cones, cryoconite holes and perched blocks. However, whilst TLS represents a step-change in our ability to move from small transect derived roughness measurements to complete 3D surface change, detecting change on mobile surfaces through time is challenging, and linking surface properties to other point-based process measurements can be problematic.

  3. Dual Ionic and Organic Nature of Ionic Liquids

    PubMed Central

    Shi, Rui; Wang, Yanting

    2016-01-01

    Inherited the advantages of inorganic salts and organic solvents, ionic liquids (ILs) exhibit many superior properties allowing them promising green solvents for the future. Although it has been widely acknowledged that the unique features of ILs originate from their dual ionic and organic nature, its microscopic physical origin still remains blurry. In this work, by comparing the ion/molecule cage structures obtained from molecular dynamics simulations for seven prototypic liquids—a molten inorganic salt, four ILs, a strongly polar organic solvent, and a weakly polar organic solvent, we have revealed that the depth of the cage energy landscape characterizes the ionic nature of ILs, whereas the slope and curvature of its mimimum determine the organic nature of ILs. This finding advances our understanding of ILs and thus will help their efficient utilization as well as the systematic design of novel functionalized ILs. PMID:26782660

  4. Dual Ionic and Organic Nature of Ionic Liquids

    NASA Astrophysics Data System (ADS)

    Shi, Rui; Wang, Yanting

    2016-01-01

    Inherited the advantages of inorganic salts and organic solvents, ionic liquids (ILs) exhibit many superior properties allowing them promising green solvents for the future. Although it has been widely acknowledged that the unique features of ILs originate from their dual ionic and organic nature, its microscopic physical origin still remains blurry. In this work, by comparing the ion/molecule cage structures obtained from molecular dynamics simulations for seven prototypic liquids—a molten inorganic salt, four ILs, a strongly polar organic solvent, and a weakly polar organic solvent, we have revealed that the depth of the cage energy landscape characterizes the ionic nature of ILs, whereas the slope and curvature of its mimimum determine the organic nature of ILs. This finding advances our understanding of ILs and thus will help their efficient utilization as well as the systematic design of novel functionalized ILs.

  5. Dual Ionic and Organic Nature of Ionic Liquids.

    PubMed

    Shi, Rui; Wang, Yanting

    2016-01-01

    Inherited the advantages of inorganic salts and organic solvents, ionic liquids (ILs) exhibit many superior properties allowing them promising green solvents for the future. Although it has been widely acknowledged that the unique features of ILs originate from their dual ionic and organic nature, its microscopic physical origin still remains blurry. In this work, by comparing the ion/molecule cage structures obtained from molecular dynamics simulations for seven prototypic liquids--a molten inorganic salt, four ILs, a strongly polar organic solvent, and a weakly polar organic solvent, we have revealed that the depth of the cage energy landscape characterizes the ionic nature of ILs, whereas the slope and curvature of its mimimum determine the organic nature of ILs. This finding advances our understanding of ILs and thus will help their efficient utilization as well as the systematic design of novel functionalized ILs. PMID:26782660

  6. Electrotunable Lubricity with Ionic Liquid Nanoscale Films

    PubMed Central

    Fajardo, O. Y.; Bresme, F.; Kornyshev, A. A.; Urbakh, M.

    2015-01-01

    One of the main challenges in tribology is finding the way for an in situ control of friction without changing the lubricant. One of the ways for such control is via the application of electric fields. In this respect a promising new class of lubricants is ionic liquids, which are solvent-free electrolytes, and their properties should be most strongly affected by applied voltage. Based on a minimal physical model, our study elucidates the connection between the voltage effect on the structure of the ionic liquid layers and their lubricating properties. It reveals two mechanisms of variation of the friction force with the surface charge density, consistent with recent AFM measurements, namely via the (i) charge effect on normal and in-plane ordering in the film and (ii) swapping between anion and cation layers at the surfaces. We formulate conditions that would warrant low friction coefficients and prevent wear by resisting “squeezing-out” of the liquid under compression. These results give a background for controllable variation of friction. PMID:25572127

  7. Infrared spectroscopy of weathering products in a terrestrial glacial environment: Implications for cold weathering on planetary surfaces

    NASA Astrophysics Data System (ADS)

    Rutledge, A. M.; Christensen, P. R.; Havig, J. R.

    2011-12-01

    Geologic features on Mars show evidence of modification by water and water ice. Past obliquity variations are hypothesized to have allowed the formation and stability of ground ice near the equator, possibly promoting the accumulation of glaciers. Massive ice deposits, including probable glacial and periglacial features have also been observed in the east Hellas Basin and Deuteronilus Mensae regions, located at the midlatitudes of Mars. These features indicate present-day, near-surface ice has been in contact with geologic materials, creating an environment in which cold weathering processes could have been occurring, and might still be at work. Weathering processes in cold terrestrial environments are not well understood, and processes acting on subglacial and englacial sediments and rocks are not well characterized due to the remote location of many glaciers and the difficulty of collecting samples. The types of weathering products and energy sources produced in a glacial environment will drive the overall energy budget for any microbial communities present. The subglacial energy budget for microbes thus has implications in the search for life on other planets, making glacial and periglacial terrains excellent sites for future exploration. However, planetary ice deposits are difficult to study due to their sensitive nature and are thus limited to observation from orbit at present. It is therefore a key concern to better understand the types materials and alteration products that can be observed and constrained from orbital data. In this study, we characterize the types of weathering products present in a glacial system using ground-truthed remote sensing techniques. Robertson Glacier, Alberta, Canada (115°20'W, 50°44'N) provides an excellent testbed for this technique as it is accessible, and its recent and continuing retreat allows fresh subglacial and englacial sediments to be sampled. Samples of bedrock and glacially altered rock and sediments were collected