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Sample records for adsorbed molecular brush

  1. Molecular Adsorber Coating

    NASA Technical Reports Server (NTRS)

    Straka, Sharon; Peters, Wanda; Hasegawa, Mark; Hedgeland, Randy; Petro, John; Novo-Gradac, Kevin; Wong, Alfred; Triolo, Jack; Miller, Cory

    2011-01-01

    A document discusses a zeolite-based sprayable molecular adsorber coating that has been developed to alleviate the size and weight issues of current ceramic puck-based technology, while providing a configuration that more projects can use to protect against degradation from outgassed materials within a spacecraft, particularly contamination-sensitive instruments. This coating system demonstrates five times the adsorption capacity of previously developed adsorber coating slurries. The molecular adsorber formulation was developed and refined, and a procedure for spray application was developed. Samples were spray-coated and tested for capacity, thermal optical/radiative properties, coating adhesion, and thermal cycling. Work performed during this study indicates that the molecular adsorber formulation can be applied to aluminum, stainless steel, or other metal substrates that can accept silicate-based coatings. The coating can also function as a thermal- control coating. This adsorber will dramatically reduce the mass and volume restrictions, and is less expensive than the currently used molecular adsorber puck design.

  2. Adsorption of enzymes to stimuli-responsive polymer brushes: Influence of brush conformation on adsorbed amount and biocatalytic activity.

    PubMed

    Koenig, Meike; Bittrich, Eva; König, Ulla; Rajeev, Bhadra Lakshmi; Müller, Martin; Eichhorn, Klaus-Jochen; Thomas, Sabu; Stamm, Manfred; Uhlmann, Petra

    2016-10-01

    Polyelectrolyte brushes can be utilized to immobilize enzymes on macroscopic surfaces. This report investigates the influence of the pH value of the surrounding medium on the amount and the activity of enzymes adsorbed to poly(2-vinylpyridine) and poly(acrylic acid) brushes, as well as the creation of thermoresponsive biocatalytically active coatings via the adsorption of enzymes onto a mixed brush consisting of a polyelectrolyte and temperature-sensitive poly(N-isopropylacryl amide). Spectroscopic ellipsometry and attenuated total reflection-Fourier transform infrared spectroscopy are used to monitor the adsorption process. Additionally, infrared spectra are evaluated in terms of the secondary structure of the enzymes. Glucose oxidase is used as a model enzyme, where the enzymatic activity is measured after different adsorption conditions. Poly(acrylic acid) brushes generally adsorb larger amounts of enzyme, while less glucose oxidase is found on poly(2-vinylpyridine), which however exhibits higher specific activity. This difference in activity could be attributed to a difference in secondary structure of the adsorbed enzyme. For glucose oxidase adsorbed to mixed brushes, switching of enzymatic activity between an active state at 20°C and a less active state at 40°C as compared to the free enzyme in solution is observed. However, this switching is strongly depending on pH in mixed brushes of poly(acrylic acid) and poly(N-isopropylacryl amide) due to interactions between the polymers.

  3. Adsorption of enzymes to stimuli-responsive polymer brushes: Influence of brush conformation on adsorbed amount and biocatalytic activity.

    PubMed

    Koenig, Meike; Bittrich, Eva; König, Ulla; Rajeev, Bhadra Lakshmi; Müller, Martin; Eichhorn, Klaus-Jochen; Thomas, Sabu; Stamm, Manfred; Uhlmann, Petra

    2016-10-01

    Polyelectrolyte brushes can be utilized to immobilize enzymes on macroscopic surfaces. This report investigates the influence of the pH value of the surrounding medium on the amount and the activity of enzymes adsorbed to poly(2-vinylpyridine) and poly(acrylic acid) brushes, as well as the creation of thermoresponsive biocatalytically active coatings via the adsorption of enzymes onto a mixed brush consisting of a polyelectrolyte and temperature-sensitive poly(N-isopropylacryl amide). Spectroscopic ellipsometry and attenuated total reflection-Fourier transform infrared spectroscopy are used to monitor the adsorption process. Additionally, infrared spectra are evaluated in terms of the secondary structure of the enzymes. Glucose oxidase is used as a model enzyme, where the enzymatic activity is measured after different adsorption conditions. Poly(acrylic acid) brushes generally adsorb larger amounts of enzyme, while less glucose oxidase is found on poly(2-vinylpyridine), which however exhibits higher specific activity. This difference in activity could be attributed to a difference in secondary structure of the adsorbed enzyme. For glucose oxidase adsorbed to mixed brushes, switching of enzymatic activity between an active state at 20°C and a less active state at 40°C as compared to the free enzyme in solution is observed. However, this switching is strongly depending on pH in mixed brushes of poly(acrylic acid) and poly(N-isopropylacryl amide) due to interactions between the polymers. PMID:27447452

  4. Molecular interaction forces generated during protein adsorption to well-defined polymer brush surfaces.

    PubMed

    Sakata, Sho; Inoue, Yuuki; Ishihara, Kazuhiko

    2015-03-17

    The molecular interaction forces generated during the adsorption of proteins to surfaces were examined by the force-versus-distance (f-d) curve measurements of atomic force microscopy using probes modified with appropriate molecules. Various substrates with polymer brush layers bearing zwitterionic, cationic, anionic, and hydrophobic groups were systematically prepared by surface-initiated atom transfer radical polymerization. Surface interaction forces on these substrates were analyzed by the f-d curve measurements using probes with the same polymer brush layer as the substrate. Repulsive forces, which decreased depending on the ionic strength, were generated between cationic or anionic polyelectrolyte brush layers; these were considered to be electrostatic interaction forces. A strong adhesive force was detected between hydrophobic polymer brush layers during retraction; this corresponded to the hydrophobic interaction between two hydrophobic polymer layers. In contrast, no significant interaction forces were detected between zwitterionic polymer brush layers. Direct interaction forces between proteins and polymer brush layers were then quantitatively evaluated by the f-d curve measurements using protein-immobilized probes consisting of negatively charged albumin and positively charged lysozyme under physiological conditions. In addition, the amount of protein adsorbed on the polymer brush layer was quantified by surface plasmon resonance measurements. Relatively large amounts of protein adsorbed to the polyelectrolyte brush layers with opposite charges. It was considered that the detachment of the protein after contact with the polymer brush layer hardly occurred due to salt formation at the interface. Both proteins adsorbed significantly on the hydrophobic polymer brush layer, which was due to hydrophobic interactions at the interface. In contrast, the zwitterionic polymer brush layer exhibited no significant interaction force with proteins and suppressed

  5. Interaction between brush layers of bottle-brush polyelectrolytes: molecular dynamics simulations.

    PubMed

    Russano, Daniel; Carrillo, Jan-Michael Y; Dobrynin, Andrey V

    2011-09-01

    Interactions between tethered layers composed of aggrecan (charged bottle-brush) macromolecules are responsible for the molecular origin of cartilage biomechanical behavior. To elucidate the role of the electrostatic forces in interaction between bottle-brush layers, we have performed molecular dynamics simulations of charged and neutral bottle-brush macromolecules tethered to substrates. In the case of charged bottle-brush layers, the disjoining pressure P between two brush layers in salt-free solutions increases with decreasing distance D between substrates as P ∝ D(-1.8). A stronger dependence of the disjoining pressure P on the surface separation D was observed for neutral bottle-brushes, P ∝ D(-4.6), in the same interval of disjoining pressures. These scaling laws for dependence of disjoining pressure P on distance D are due to bending energy of the bottle-brush macromolecules within compressed brush layers. The weaker distance dependence observed in polyelectrolyte bottle-brushes is due to interaction between counterion clouds surrounding the bottle-brush macromolecules preventing strong brush overlap.

  6. Conductive Nanowires Templated by Molecular Brushes.

    PubMed

    Raguzin, Ivan; Stamm, Manfred; Ionov, Leonid

    2015-10-21

    In this paper, we report the fabrication of conductive nanowires using polymer bottle brushes as templates. In our approach, we synthesized poly(2-dimethylamino)ethyl methacrylate methyl iodide quaternary salt brushes by two-step atom transfer radical polymerization, loaded them with palladium salt, and reduced them in order to form metallic nanowires with average lengths and widths of 300 and 20 nm, respectively. The obtained nanowires were deposited between conductive gold pads and were connected to them by sputtering of additional pads to form an electric circuit. We connected the nanowires in an electric circuit and demonstrated that the conductivity of these nanowires is around 100 S·m(-1). PMID:26418290

  7. Polymer brushes with nanoinclusions under shear: A molecular dynamics investigation

    PubMed Central

    Milchev, A.; Dimitrov, D. I.; Binder, K.

    2010-01-01

    We use molecular dynamics simulations with a dissipative particle dynamics thermostat to study the behavior of nanosized inclusions (colloids) in a polymer brush under shear whereby the solvent is explicitly included in the simulation. The brush is described by a bead-spring model for flexible polymer chains, grafted on a solid substrate, while the polymer-soluble nanoparticles in the solution are taken as soft spheres whose diameter is about three times larger than that of the chain segments and the solvent. We find that the brush number density profile, as well as the density profiles of the nanoinclusions and the solvent, remains insensitive to strong shear although the grafted chains tilt in direction of the flow. The thickness of the penetration layer of nanoinclusions, as well as their average concentration in the brush, stays largely unaffected even at the strongest shear. Our result manifests the remarkable robustness of polymer brushes with embedded nanoparticles under high shear which could be of importance for technological applications. PMID:21045924

  8. Black Molecular Adsorber Coatings for Spaceflight Applications

    NASA Technical Reports Server (NTRS)

    Abraham, Nithin Susan; Hasegawa, Mark Makoto; Straka, Sharon A.

    2014-01-01

    The molecular adsorber coating is a new technology that was developed to mitigate the risk of on-orbit molecular contamination on spaceflight missions. The application of this coating would be ideal near highly sensitive, interior surfaces and instruments that are negatively impacted by outgassed molecules from materials, such as plastics, adhesives, lubricants, epoxies, and other similar compounds. This current, sprayable paint technology is comprised of inorganic white materials made from highly porous zeolite. In addition to good adhesion performance, thermal stability, and adsorptive capability, the molecular adsorber coating offers favorable thermal control characteristics. However, low reflectivity properties, which are typically offered by black thermal control coatings, are desired for some spaceflight applications. For example, black coatings are used on interior surfaces, in particular, on instrument baffles for optical stray light control. Similarly, they are also used within light paths between optical systems, such as telescopes, to absorb light. Recent efforts have been made to transform the white molecular adsorber coating into a black coating with similar adsorptive properties. This result is achieved by optimizing the current formulation with black pigments, while still maintaining its adsorption capability for outgassing control. Different binder to pigment ratios, coating thicknesses, and spray application techniques were explored to develop a black version of the molecular adsorber coating. During the development process, coating performance and adsorption characteristics were studied. The preliminary work performed on black molecular adsorber coatings thus far is very promising. Continued development and testing is necessary for its use on future contamination sensitive spaceflight missions.

  9. Black molecular adsorber coatings for spaceflight applications

    NASA Astrophysics Data System (ADS)

    Abraham, Nithin S.; Hasegawa, Mark M.; Straka, Sharon A.

    2014-09-01

    The molecular adsorber coating is a new technology that was developed to mitigate the risk of on-orbit molecular contamination on spaceflight missions. The application of this coating would be ideal near highly sensitive, interior surfaces and instruments that are negatively impacted by outgassed molecules from materials, such as plastics, adhesives, lubricants, epoxies, and other similar compounds. This current, sprayable paint technology is comprised of inorganic white materials made from highly porous zeolite. In addition to good adhesion performance, thermal stability, and adsorptive capability, the molecular adsorber coating offers favorable thermal control characteristics. However, low reflectivity properties, which are typically offered by black thermal control coatings, are desired for some spaceflight applications. For example, black coatings are used on interior surfaces, in particular, on instrument baffles for optical stray light control. Similarly, they are also used within light paths between optical systems, such as telescopes, to absorb light. Recent efforts have been made to transform the white molecular adsorber coating into a black coating with similar adsorptive properties. This result is achieved by optimizing the current formulation with black pigments, while still maintaining its adsorption capability for outgassing control. Different binder to pigment ratios, coating thicknesses, and spray application techniques were explored to develop a black version of the molecular adsorber coating. During the development process, coating performance and adsorption characteristics were studied. The preliminary work performed on black molecular adsorber coatings thus far is very promising. Continued development and testing is necessary for its use on future contamination sensitive spaceflight missions.

  10. Development and Testing of Molecular Adsorber Coatings

    NASA Technical Reports Server (NTRS)

    Abraham, Nithin; Hasegawa, Mark; Straka, Sharon

    2012-01-01

    The effect of on-orbit molecular contamination has the potential to degrade the performance of spaceflight hardware and diminish the lifetime of the spacecraft. For example, sensitive surfaces, such as optical surfaces, electronics, detectors, and thermal control surfaces, are vulnerable to the damaging effects of contamination from outgassed materials. The current solution to protect these surfaces is through the use of zeolite coated ceramic adsorber pucks. However, these pucks and its additional complex mounting hardware requirements result in several disadvantages, such as size, weight, and cost related concerns, that impact the spacecraft design and the integration and test schedule. As a result, a new innovative molecular adsorber coating was developed as a sprayable alternative to mitigate the risk of on-orbit molecular contamination. In this study, the formulation for molecular adsorber coatings was optimized using various binders, pigment treatment methods, binder to pigment ratios, thicknesses, and spray application techniques. The formulations that passed coating adhesion and vacuum thermal cycling tests were further tested for its adsorptive capacity. Accelerated molecular capacitance tests were performed in an innovatively designed multi-unit system containing idealized contaminant sources. This novel system significantly increased the productivity of the testing phase for the various formulations that were developed. Work performed during the development and testing phases has demonstrated successful application of molecular adsorber coatings onto metallic substrates, as well as, very promising results for the adhesion performance and the molecular capacitance of the coating. Continued testing will assist in the qualification of molecular adsorber coatings for use on future contamination sensitive spaceflight missions.

  11. Polymer Brushes under Shear: Molecular Dynamics Simulations Compared to Experiments.

    PubMed

    Singh, Manjesh K; Ilg, Patrick; Espinosa-Marzal, Rosa M; Kröger, Martin; Spencer, Nicholas D

    2015-04-28

    Surfaces coated with polymer brushes in a good solvent are known to exhibit excellent tribological properties. We have performed coarse-grained equilibrium and nonequilibrium molecular dynamics (MD) simulations to investigate dextran polymer brushes in an aqueous environment in molecular detail. In a first step, we determined simulation parameters and units by matching experimental results for a single dextran chain. Analyzing this model when applied to a multichain system, density profiles of end-tethered polymer brushes obtained from equilibrium MD simulations compare very well with expectations based on self-consistent field theory. Simulation results were further validated against and correlated with available experimental results. The simulated compression curves (normal force as a function of surface separation) compare successfully with results obtained with a surface forces apparatus. Shear stress (friction) obtained via nonequilibrium MD is contrasted with nanoscale friction studies employing colloidal-probe lateral force microscopy. We find good agreement in the hydrodynamic regime and explain the observed leveling-off of the friction forces in the boundary regime by means of an effective polymer-wall attraction.

  12. Graft copolymer composed of cationic backbone and bottle brush-like side chains as a physically adsorbed coating for protein separation by capillary electrophoresis.

    PubMed

    Zhou, Dan; Xiang, Lina; Zeng, Rongju; Cao, Fuhu; Zhu, Xiaoxi; Wang, Yanmei

    2011-12-01

    To stabilize electroosmotic flow (EOF) and suppress protein adsorption onto the silica capillary inner wall, a cationic hydroxyethylcellulose-graft-poly (poly(ethylene glycol) methyl ether methacrylate) (cat-HEC-g-PPEGMA) graft copolymer composed of cationic backbone and bottle brush-like side chains was synthesized for the first time and used as a novel physically adsorbed coating for protein separation by capillary electrophoresis. Reversed (anodal) and very stable EOF was obtained in cat-HEC-g-PPEGMA-coated capillary at pH 2.2-7.8. The effects of degree of cationization, PEGMA grafting ratio, PEGMA molecular mass, and buffer pH on the separation of basic proteins were investigated. A systematic comparative study of protein separation in bare and HEC-coated capillaries and in cat-HEC-g-PPEGMA-coated capillary was also performed. The basic proteins can be well separated in cat-HEC-g-PPEGMA-coated capillary over the pH range of 2.8-6.8 with good repeatability and high separation efficiency, because the coating combines good protein-resistant property of bottle brush-like PPEGMA side chains with excellent coating ability of cat-HEC backbone. Besides its success in separation of basic proteins, the cat-HEC-g-PPEGMA coating was also superior in the fast separation of other protein samples, such as protein mixture, egg white, and saliva, which indicates that it is a promising coating for further proteomics analysis. PMID:22038787

  13. NASA Applications of Molecular Adsorber Coatings

    NASA Technical Reports Server (NTRS)

    Abraham, Nithin S.

    2015-01-01

    The Molecular Adsorber Coating (MAC) is a new, innovative technology that was developed to reduce the risk of molecular contamination on spaceflight applications. Outgassing from materials, such as plastics, adhesives, lubricants, silicones, epoxies, and potting compounds, pose a significant threat to the spacecraft and the lifetime of missions. As a coating made of highly porous inorganic materials, MAC offers impressive adsorptive capabilities that help capture and trap contaminants. Past research efforts have demonstrated the coating's promising adhesion performance, optical properties, acoustic durability, and thermal stability. These results advocate its use near or on surfaces that are targeted by outgassed materials, such as internal optics, electronics, detectors, baffles, sensitive instruments, thermal control coatings, and vacuum chamber test environments. The MAC technology has significantly progressed in development over the recent years. This presentation summarizes the many NASA spaceflight applications of MAC and how the coatings technology has been integrated as a mitigation tool for outgassed contaminants. For example, this sprayable paint technology has been beneficial for use in various vacuum chambers for contamination control and hardware bake-outs. The coating has also been used in small instrument cavities within spaceflight instrument for NASA missions.

  14. Multiarm molecular brushes: effect of the number of arms on the molecular weight polydispersity and surface ordering.

    PubMed

    Boyce, Jamie R; Shirvanyants, David; Sheiko, Sergei S; Ivanov, Dimitri A; Qin, Shuhui; Börner, Hans; Matyjaszewski, Krzysztof

    2004-07-01

    Individual molecules of multiarm starlike molecular brushes were visualized by atomic force microscopy. In the studied series of brushes, the number of arms varied from one for a linear chain to four, while the length of the side chains was kept approximately constant. Molecular visualization provided a unique opportunity for independent size characterization of the brush arms separately from that of the entire molecule. In agreement with the Schulz-Flory theory for chain coupling, the polydispersity of the total length was significantly lower than that of the arm length. The variation in polydispersity had an effect on molecular ordering. Lateral compression of the starlike brushes caused a transition from an extended dendritic-like conformation to a compact disklike conformation. In contrast to one-, two-, and three-arm brushes, the four-arm molecules with a lower polydispersity index of 1.04 demonstrated local hexagonal order.

  15. Polyphosphazene Based Star-Branched and Dendritic Molecular Brushes.

    PubMed

    Henke, Helena; Posch, Sandra; Brüggemann, Oliver; Teasdale, Ian

    2016-05-01

    A new synthetic procedure is described for the preparation of poly(organo)phosphazenes with star-branched and star dendritic molecular brush type structures, thus describing the first time it has been possible to prepare controlled, highly branched architectures for this type of polymer. Furthermore, as a result of the extremely high-arm density generated by the phosphazene repeat unit, the second-generation structures represent quite unique architectures for any type of polymer. Using two relativity straight forward iterative syntheses it is possible to prepare globular highly branched polymers with up to 30 000 functional end groups, while keeping relatively narrow polydispersities (1.2-1.6). Phosphine mediated polymerization of chlorophosphoranimine is first used to prepare three-arm star polymers. Subsequent substitution with diphenylphosphine moieties gives poly(organo)phosphazenes to function as multifunctional macroinitiators for the growth of a second generation of polyphosphazene arms. Macrosubstitution with Jeffamine oligomers gives a series of large, water soluble branched macromolecules with high-arm density and hydrodynamic diameters between 10 and 70 nm. PMID:27027404

  16. Polyphosphazene Based Star-Branched and Dendritic Molecular Brushes.

    PubMed

    Henke, Helena; Posch, Sandra; Brüggemann, Oliver; Teasdale, Ian

    2016-05-01

    A new synthetic procedure is described for the preparation of poly(organo)phosphazenes with star-branched and star dendritic molecular brush type structures, thus describing the first time it has been possible to prepare controlled, highly branched architectures for this type of polymer. Furthermore, as a result of the extremely high-arm density generated by the phosphazene repeat unit, the second-generation structures represent quite unique architectures for any type of polymer. Using two relativity straight forward iterative syntheses it is possible to prepare globular highly branched polymers with up to 30 000 functional end groups, while keeping relatively narrow polydispersities (1.2-1.6). Phosphine mediated polymerization of chlorophosphoranimine is first used to prepare three-arm star polymers. Subsequent substitution with diphenylphosphine moieties gives poly(organo)phosphazenes to function as multifunctional macroinitiators for the growth of a second generation of polyphosphazene arms. Macrosubstitution with Jeffamine oligomers gives a series of large, water soluble branched macromolecules with high-arm density and hydrodynamic diameters between 10 and 70 nm.

  17. Polyphosphazene Based Star-Branched and Dendritic Molecular Brushes

    PubMed Central

    Henke, Helena; Posch, Sandra; Brüggemann, Oliver; Teasdale, Ian

    2016-01-01

    A new synthetic procedure is described for the preparation of poly(organo)phosphazenes with star-branched and star dendritic molecular brush type structures, thus describing the first time it has been possible to prepare controlled, highly branched architectures for this type of polymer. Furthermore, as a result of the extremely high-arm density generated by the phosphazene repeat unit, the second-generation structures represent quite unique architectures for any type of polymer. Using two relativity straight forward iterative syntheses it is possible to prepare globular highly branched polymers with up to 30 000 functional end groups, while keeping relatively narrow polydispersities (1.2–1.6). Phosphine mediated polymerization of chlorophosphoranimine is first used to prepare three-arm star polymers. Subsequent substitution with diphenylphosphine moieties gives poly(organo)phosphazenes to function as multifunctional macroinitiators for the growth of a second generation of polyphosphazene arms. Macrosubstitution with Jeffamine oligomers gives a series of large, water soluble branched macromolecules with high-arm density and hydrodynamic diameters between 10 and 70 nm. PMID:27027404

  18. Volumetric Interpretation of Protein Adsorption: Capacity Scaling with Adsorbate Molecular Weight and Adsorbent Surface Energy

    PubMed Central

    Parhi, Purnendu; Golas, Avantika; Barnthip, Naris; Noh, Hyeran; Vogler, Erwin A.

    2009-01-01

    Silanized-glass-particle adsorbent capacities are extracted from adsorption isotherms of human serum albumin (HSA, 66 kDa), immunoglobulin G (IgG, 160 kDa), fibrinogen (Fib, 341 kDa), and immunoglobulin M (IgM, 1000 kDa) for adsorbent surface energies sampling the observable range of water wettability. Adsorbent capacity expressed as either mass-or-moles per-unit-adsorbent-area increases with protein molecular weight (MW) in a manner that is quantitatively inconsistent with the idea that proteins adsorb as a monolayer at the solution-material interface in any physically-realizable configuration or state of denaturation. Capacity decreases monotonically with increasing adsorbent hydrophilicity to the limit-of-detection (LOD) near τo = 30 dyne/cm (θ~65o) for all protein/surface combinations studied (where τo≡γlvocosθ is the water adhesion tension, γlvo is the interfacial tension of pure-buffer solution, and θ is the buffer advancing contact angle). Experimental evidence thus shows that adsorbent capacity depends on both adsorbent surface energy and adsorbate size. Comparison of theory to experiment implies that proteins do not adsorb onto a two-dimensional (2D) interfacial plane as frequently depicted in the literature but rather partition from solution into a three-dimensional (3D) interphase region that separates the physical surface from bulk solution. This interphase has a finite volume related to the dimensions of hydrated protein in the adsorbed state (defining “layer” thickness). The interphase can be comprised of a number of adsorbed-protein layers depending on the solution concentration in which adsorbent is immersed, molecular volume of the adsorbing protein (proportional to MW), and adsorbent hydrophilicity. Multilayer adsorption accounts for adsorbent capacity over-and-above monolayer and is inconsistent with the idea that protein adsorbs to surfaces primarily through protein/surface interactions because proteins within second (or higher

  19. Investigations of Mechanical Properties of Polymer Brushes and Hydrogels Through Molecular Dynamics Simulation

    NASA Astrophysics Data System (ADS)

    Ou, Yangpeng

    In this thesis, the forces between surfaces coated with polyelectrolye brushes and polymer gels were investigated via molecular dynamics simulation on a computer workstation that I built. The first project investigated the reasons for why grafted polyelectrolye brushes have smaller friction coefficients than grafted neutral polymer brushes. The flexible neutral polymer brush is treated as a bead-spring model, and the polyelectrolyte brush is treated the same way except that each bead is charged and there are counterions present to neutralize the charge. We investigated the friction coefficient, monomer density, and brush penetration for the two kinds of brushes with both the same grafting density and the same normal force under good solvent conditions. We found that polyelectrolyte brushes have smaller friction coefficients in both simulations. We present evidence that the reason for this is that the extra normal force contribution provided by the counterion osmotic pressure that exists for polyelectrolyte brushes permits them to support the same load as identical neutral polymer brushes of higher grafting density. Because of the resulting lower monomer density for the charged brushes, fewer monomer collisions take place per unit time, resulting in a lower friction coefficient. The second project investigated interactions between two grafted polymer gels. Unlike polyelectrolyte polymer brushes, polymer chains are linked to other neighboring polymer chains. We studied a defect-free network of diamond-like topology containing 8 tetra-functional nodes linked by 16 non-crossing chains. We studied the shear force, friction coefficient, and density profiles of these polymer gels. We found that polymer gels have very small friction coefficients in our simulation, which is consistent with previous experimental measurements. In order to understand and explain this very low friction coefficient behavior, we computed the interpenetrations between two polymer gels, the

  20. Synthesis and CO₂ adsorption properties of molecularly imprinted adsorbents.

    PubMed

    Zhao, Yi; Shen, Yanmei; Bai, Lu; Hao, Rongjie; Dong, Liyan

    2012-02-01

    A series of molecularly imprinted adsorbents of CO(2) were developed by molecular self-assembly procedures, using ethanedioic acid, acrylamide, and ethylene glycol dimethacrylate as template, functional monomer, and cross-linker, respectively. Textural properties of these adsorbents were characterized by N(2) adsorption experiment, thermo-gravimetric analysis, and Fourier transform infrared spectroscopy. CO(2) adsorption capacities of adsorbents were investigated by thermo-gravimetric balance under 15% CO(2)/85% Ar atmosphere. Adsorption selectivity of CO(2) was studied by fixed-bed adsorption/desorption experiments. All the adsorbents displayed good thermal stability at 200 °C. Among them, MIP1b, with the higher amine content, exhibited the largest CO(2) capacity, which maintained steady after 50 adsorption-desorption cycles. Although MIP3 showed the highest specific surface, the CO(2) capacity was lower than that of MIP1b. CO(2) adsorption mechanism of molecularly imprinted adsorbents was determined to be physical sorption according to the adsorption enthalpies integrated from the DSC heatflow profiles. The calculated separation factors of CO(2) under 15% CO(2)/85% N(2) atmosphere were above 100 for all adsorbents.

  1. Equilibrium molecular theory of two-dimensional adsorbate drops on surfaces of heterogeneous adsorbents

    NASA Astrophysics Data System (ADS)

    Tovbin, Yu. K.

    2016-08-01

    A molecular statistical theory for calculating the linear tension of small multicomponent droplets in two-dimensional adsorption systems is developed. The theory describes discrete distributions of molecules in space (on a scale comparable to molecular size) and continuous distributions of molecules (at short distances inside cells) in their translational and vibrational motions. Pair intermolecular interaction potentials (the Mie type potential) in several coordination spheres are considered. For simplicity, it is assumed that distinctions in the sizes of mixture components are slight and comparable to the sizes of adsorbent adsorption centers. Expressions for the pressure tensor components inside small droplets on the heterogeneous surface of an adsorbent are obtained, allowing calculations of the thermodynamic characteristics of a vapor-fluid interface, including linear tension. Problems in refining the molecular theory are discussed: describing the properties of small droplets using a coordination model of their structure, considering the effect an adsorbate has on the state of a near-surface adsorbent region, and the surface heterogeneity factor in the conditions for the formation of droplets.

  2. From adsorption to condensation: the role of adsorbed molecular clusters.

    PubMed

    Yaghoubian, Sima; Zandavi, Seyed Hadi; Ward, C A

    2016-08-01

    The adsorption of heptane vapour on a smooth silicon substrate with a lower temperature than the vapour is examined analytically and experimentally. An expression for the amount adsorbed under steady state conditions is derived from the molecular cluster model of the adsorbate that is similar to the one used to derive the equilibrium Zeta adsorption isotherm. The amount adsorbed in each of a series of steady experiments is measured using a UV-vis interferometer, and gives strong support to the amount predicted to be adsorbed. The cluster distribution is used to predict the subcooling temperature required for the adsorbed vapour to make a disorder-order phase transition to become an adsorbed liquid, and the subcooling temperature is found to be 2.7 ± 0.4 K. The continuum approach for predicting the thickness of the adsorbed liquid film originally developed by Nusselt is compared with that measured and is found to over-predict the thickness by three-orders of magnitude. PMID:27426944

  3. Static and dynamic properties of polymer brush with topological ring structures: Molecular dynamic simulation

    NASA Astrophysics Data System (ADS)

    Wan, Wu-Bing; Lv, Hong-Hong; Merlitz, Holger; Wu, Chen-Xu

    2016-10-01

    By defining a topological constraint value (rn), the static and dynamic properties of a polymer brush composed of moderate or short chains with different topological ring structures are studied using molecular dynamics simulation, and a comparison with those of linear polymer brush is also made. For the center-of-mass height of the ring polymer brush scaled by chain length h ˜ N ν , there is no significant difference of exponent from that of a linear brush in the small topological constraint regime. However, as the topological constraint becomes stronger, one obtains a smaller exponent. It is found that there exists a master scaling power law of the total stretching energy scaled by chain length N for moderate chain length regime, F ene ˜ Nρ ν , for ring polymer brushes, but with a larger exponent ν than 5/6, indicating an influence of topological constraint to the dynamic properties of the system. A topological invariant of free energy scaled by 5/4 is found. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374243 and 11574256).

  4. Lotus Dust Mitigation Coating and Molecular Adsorber Coating

    NASA Technical Reports Server (NTRS)

    O'Connor, Kenneth M.; Abraham, Nithin S.

    2015-01-01

    NASA Goddard Space Flight Center has developed two unique coating formulations that will keep surfaces clean and sanitary and contain contaminants.The Lotus Dust Mitigation Coating, modeled after the self-cleaning, water-repellant lotus leaf, disallows buildup of dust, dirt, water, and more on surfaces. This coating, has been successfully tested on painted, aluminum, glass, silica, and some composite surfaces, could aid in keeping medical assets clean.The Molecular Adsorber Coating is a zeolite-based, sprayable molecular adsorber coating, designed to prevent outgassing in materials in vacuums. The coating works well to adsorb volatiles and contaminates in manufacturing and processing, such as in pharmaceutical production. The addition of a biocide would also aid in controlling bacteria levels.

  5. Method of recovering adsorbed liquid compounds from molecular sieve columns

    DOEpatents

    Burkholder, Harvey R.; Fanslow, Glenn E.

    1983-01-01

    Molecularly adsorbed volatile liquid compounds are recovered from molecular sieve adsorbent columns by directionally applying microwave energy to the bed of the adsorbent to produce a mixed liquid-gas effluent. The gas portion of the effluent generates pressure within the bed to promote the discharge of the effluent from the column bottoms. Preferably the discharged liquid-gas effluent is collected in two to three separate fractions, the second or intermediate fraction having a substantially higher concentration of the desorbed compound than the first or third fractions. The desorption does not need to be assisted by passing a carrier gas through the bed or by applying reduced pressure to the outlet from the bed.

  6. Method of recovering adsorbed liquid compounds from molecular sieve columns

    DOEpatents

    Burkholder, H.R.; Fanslow, G.E.

    1983-12-20

    Molecularly adsorbed volatile liquid compounds are recovered from molecular sieve adsorbent columns by directionally applying microwave energy to the bed of the adsorbent to produce a mixed liquid-gas effluent. The gas portion of the effluent generates pressure within the bed to promote the discharge of the effluent from the column bottoms. Preferably the discharged liquid-gas effluent is collected in two to three separate fractions, the second or intermediate fraction having a substantially higher concentration of the desorbed compound than the first or third fractions. The desorption does not need to be assisted by passing a carrier gas through the bed or by applying reduced pressure to the outlet from the bed. 8 figs.

  7. One-pot synthesis of molecular bottle-brush functionalized single-walled carbon nanotubes with superior dispersibility in water.

    PubMed

    Deng, Yong; Hu, Qin; Yuan, Qiulin; Wu, Yan; Ling, Ying; Tang, Haoyu

    2014-01-01

    Molecular bottle-brush functionalized single-walled carbon nanotubes (SWCNTs) with superior dispersibility in water are prepared by a one-pot synthetic methodology. Elongating the main-chain and side-chain length of molecular bottle-brushes can further increase SWCNT dispersibility. They show significant enhancement of SWCNT dispersibility up to four times higher than those of linear molecular functionalized SWCNTs. PMID:24307218

  8. Development of the Molecular Adsorber Coating for Spacecraft and Instrument Interiors

    NASA Technical Reports Server (NTRS)

    Abraham, Nithin

    2011-01-01

    On-orbit Molecular Contamination occurs when materials outgas and deposit onto very sensitive interior surfaces of the spacecraft and instruments. The current solution, Molecular Adsorber Pucks, has disadvantages, which are reviewed. A new innovative solution, Molecular Adsorber Coating (MAC), is currently being formulated, optimized, and tested. It is a sprayable alternative composed of Zeolite-based coating with adsorbing properties.

  9. Incorporation of molecular adsorbers into future Hubble Space Telescope instruments

    NASA Astrophysics Data System (ADS)

    Thomson, Shaun R.; Hansen, Patricia A.; Chen, Philip T.; Triolo, Jack J.; Carosso, Nancy P.

    1996-11-01

    The Hubble Space Telescope (HST) has been designed to accommodate changeout and/or repair of many of the primary instruments and subsystem components, in an effort to prolong the useful life of this orbiting observatory. In order to achieve the science goals established for this observatory, many HST instruments must operate in regimes that are greatly influenced by the presence of on-orbit propagated contaminants. To insure that the required performance of each instrument is not compromised due to these contaminant effects, great efforts have been made to minimize the level of on-orbit contamination. These efforts include careful material selection, performing extensive pre-flight vacuum bakeouts of parts and assemblies, assuring instrument assembly is carried out in strict cleanroom environments, performing precision cleaning of various parts, and most recently, the incorporation of a relatively new technology -- molecular adsorbers -- into the basic design of future replacement instruments. Molecular adsorbers were included as part of the wide field/planetary camera 2 (WFPC-2) instrument, which was integrated into the HST during the servicing mission 1 (SM1) in 1993. It is generally recognized that these adsorbers aided in the reductio of on-orbit contamination levels for the WFPC-2 instrument. This technology is now being implemented as part of the basic design for several new instruments being readied for the servicing mission 2 (SM2), scheduled for early 1997. An overview of the concept, design, applications, and to-date testing and predicted benefits associated with the molecular adsorbers within these new HST instruments are presented and discussed in this paper.

  10. Graphene symmetry-breaking with molecular adsorbates: modeling and experiment

    NASA Astrophysics Data System (ADS)

    Groce, M. A.; Hawkins, M. K.; Wang, Y. L.; Cullen, W. G.; Einstein, T. L.

    2012-02-01

    Graphene's structure and electronic properties provide a framework for understanding molecule-substrate interactions and developing techniques for band gap engineering. Controlled deposition of molecular adsorbates can create superlattices which break the degeneracy of graphene's two-atom unit cell, opening a band gap. We simulate scanning tunneling microscopy and spectroscopy measurements for a variety of organic molecule/graphene systems, including pyridine, trimesic acid, and isonicotinic acid, based on density functional theory calculations using VASP. We also compare our simulations to ultra-high vacuum STM and STS results.

  11. Molecular switches from benzene derivatives adsorbed on metal surfaces

    PubMed Central

    Liu, Wei; Filimonov, Sergey N.; Carrasco, Javier; Tkatchenko, Alexandre

    2013-01-01

    Transient precursor states are often experimentally observed for molecules adsorbing on surfaces. However, such precursor states are typically rather short-lived, quickly yielding to more stable adsorption configurations. Here we employ first-principles calculations to systematically explore the interaction mechanism for benzene derivatives on metal surfaces, enabling us to selectively tune the stability and the barrier between two metastable adsorption states. In particular, in the case of the tetrachloropyrazine molecule, two equally stable adsorption states are identified with a moderate and conceivably reversible barrier between them. We address the feasibility of experimentally detecting the predicted bistable behaviour and discuss its potential usefulness in a molecular switch. PMID:24157660

  12. Molecular Factors in Dendritic Cell Responses to Adsorbed Glycoconjugates

    PubMed Central

    Hotaling, Nathan A.; Cummings, Richard D.; Ratner, Daniel M.; Babensee, Julia E.

    2014-01-01

    Carbohydrates and glycoconjugates have been shown to exert pro-inflammatory effects on the dendritic cell (DC), supporting pathogen-induced innate immunity and antigen processing, as well as immunosuppressive effects in the tolerance to self-proteins. Additionally, the innate inflammatory response to implanted biomaterials has been hypothesized to be mediated by inflammatory cells interacting with adsorbed proteins, many of which are glycosylated. However, the molecular factors relevant for surface displayed glycoconjugate modulation of DC phenotype are unknown. Thus, in this study, a model system was developed to establish the role of glycan composition, density, and carrier cationization state on DC response. Thiol modified glycans were covalently bound to a model protein carrier, maleimide functionalized bovine serum albumin (BSA), and the number of glycans per BSA modulated. Additionally, the carrier isoelectric point was scaled from a pI of ~4.0 to ~10.0 using ethylenediamine (EDA). The DC response to the neoglycoconjugates adsorbed to wells of a 384 well plate was determined via a high throughput assay. The underlying trends in DC phenotype in relation to conjugate properties were elucidated via multivariate general linear models. It was found that glycoconjugates with more than 20 glycans per carrier had the greatest impact on the pro-inflammatory response from DCs, followed by conjugates having an isoelectric point above 9.5. Surfaces displaying terminal α1–2 linked mannose structures were able to increase the inflammatory DC response to a greater extent than did any other terminal glycan structure. The results herein can be applied to inform the design of the next generation of combination products and biomaterials for use in future vaccines and implanted materials. PMID:24746228

  13. Modulation of the molecular spintronic properties of adsorbed copper corroles

    PubMed Central

    Wu, Fan; Liu, Jie; Mishra, Puneet; Komeda, Tadahiro; Mack, John; Chang, Yi; Kobayashi, Nagao; Shen, Zhen

    2015-01-01

    The ability to modulate the spin states of adsorbed molecules is in high demand for molecular spintronics applications. Here, we demonstrate that the spin state of a corrole complex can be tuned by expanding its fused ring as a result of the modification to the d–π interaction between the metal and ligand. A bicyclo[2.2.2]octadiene-fused copper corrole can readily be converted into a tetrabenzocorrole radical on an Au(111) substrate during the sublimation process. In the scanning tunnelling spectroscopy spectrum, a sharp Kondo resonance appears near the Fermi level on the corrole ligand of the tetrabenzocorrole molecule. In contrast, a non-fused-ring-expanded copper corrole molecule, copper 5,10,15-triphenylcorrole, shows no such Kondo feature. Mapping of the Kondo resonance demonstrates that the spin distribution of the tetrabenzocorrole molecule can be further modified by the rotation of the meso-aryl groups, in a manner that could lead to applications in molecular spintronics. PMID:26112968

  14. Voltammetric sensor for barbituric acid based on a sol-gel derivated molecularly imprinted polymer brush grafted to graphite electrode.

    PubMed

    Patel, Amit Kumar; Sharma, Piyush Sindhu; Prasad, Bhim Bali

    2009-04-17

    A voltammetric sensor based on a molecularly imprinted polymer (MIP) brush grafted to sol-gel film on graphite electrode is reported for the selective and sensitive analysis of barbituric acid (BA) in aqueous, blood plasma, and urine samples. The modified electrode was preanodised at +1.6 V (vs. saturated calomel electrode), where encapsulated BA involved hydrophobically induced hydrogen bondings, in MIP cavities exposed at the film/solution interface, at pH 7.0. Scanning electron microscopy (SEM) was employed to characterise the surface morphology of the resultant imprinted film of MIP brush. The differential pulse, cathodic stripping voltammetry (DPCSV) technique was employed to investigate the binding performance of the sol-gel-modified imprinted polymer brush, which yielded a linear response in the range of 4.95-100.00 microg mL(-1) of BA with a detection limit of 1.6 microg mL(-1) (S/N=3). PMID:19135515

  15. Lubrication by glycoprotein brushes.

    NASA Astrophysics Data System (ADS)

    Zappone, Bruno; Ruths, Marina; Greene, George W.; Israelachvili, Jacob

    2006-03-01

    Grafted polyelectrolyte brushes show excellent lubricating properties under water and have been proposed as a model to study boundary lubrication in biological system. Lubricin, a glycoprotein of the synovial fluid, is considered the major boundary lubricant of articular joints. Using the Surface Force Apparatus, we have measured normal and friction forces between model surfaces (negatively charged mica, positively charged poly-lysine and aminothiol, hydrophobic alkanethiol) bearing adsorbed layers of lubricin. Lubricin layers acts like a versatile anti-adhesive, adsorbing on all the surfaces considered and creating a repulsion similar to the force between end-grafted polymer brushes. Analogies with polymer brushes also appear from bridging experiment, where proteins molecules are end-adsorbed on two opposing surfaces at the same time. Lubricin `brushes' show good lubricating ability at low applied pressures (P<0.5MPa), especially on negatively charged surfaces like mica. At higher load, the adsorbed layers wears and fails lubricating the surfaces, while still protecting the underlying substrate from wearing. Lubricin might thus be a first example of biological polyelectrolytes providing `brush-like' lubrication and wear-protection.

  16. The feasibility of molecular testing on cell blocks created from brush tip washings in the assessment of peripheral lung lesions

    PubMed Central

    Christie, Michael; Beaty, Anne; Lunke, Sebastian; Taylor, Graham; Irving, Louis; Steinfort, Daniel

    2016-01-01

    Background With the rapid development of genotype-guided therapies, molecular testing is becoming important in the management of lung cancer. Bronchoscopy is one of the most common investigations performed to diagnose and investigate lung cancer. Given the limited samples often produced by bronchoscopy, this study aims to evaluate the feasibility of performing molecular testing on cell blocks created from bronchoscope cytology brush tip washings (BTW). Methods Patients with positive brush cytology for tumour cells had cell blocks created from the BTW. Mutations were detected using amplicon-based massively parallel sequencing of targeted regions of EGFR, KRAS, and BRAF genes. Results A total of 45 patients were included in this study. Of those, 91% had adequate specimens for molecular analysis and 66% of patients with adenocarcinoma had mutations detected. Bronchial brush tip wash cell blocks were the sole specimen available for molecular testing in 27 (60%) patients. Conclusions The findings of this study demonstrate that molecular testing can be performed on cell blocks created from BTW and this technique may allow for an increase in bronchoscope specimens amenable to molecular testing without further increasing morbidity and mortality. PMID:27747008

  17. Comparison of the detection of periodontal pathogens in bacteraemia after tooth brushing by culture and molecular techniques

    PubMed Central

    Figuero, Elena; González, Itziar; O´Connor, Ana; Diz, Pedro; Álvarez, Maximiliano; Herrera, David; Sanz, Mariano

    2016-01-01

    Background The prevalence and amounts of periodontal pathogens detected in bacteraemia samples after tooth brushing-induced by means of four diagnostic technique, three based on culture and one in a molecular-based technique, have been compared in this study. Material and Methods Blood samples were collected from thirty-six subjects with different periodontal status (17 were healthy, 10 with gingivitis and 9 with periodontitis) at baseline and 2 minutes after tooth brushing. Each sample was analyzed by three culture-based methods [direct anaerobic culturing (DAC), hemo-culture (BACTEC), and lysis-centrifugation (LC)] and one molecular-based technique [quantitative polymerase chain reaction (qPCR)]. With culture any bacterial isolate was detected and quantified, while with qPCR only Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans were detected and quantified. Descriptive analyses, ANOVA and Chi-squared tests, were performed. Results Neither BACTEC nor qPCR detected any type of bacteria in the blood samples. Only LC (2.7%) and DAC (8.3%) detected bacteraemia, although not in the same patients. Fusobacterium nucleatum was the most frequently detected bacterial species. Conclusions The disparity in the results when the same samples were analyzed with four different microbiological detection methods highlights the need for a proper validation of the methodology to detect periodontal pathogens in bacteraemia samples, mainly when the presence of periodontal pathogens in blood samples after tooth brushing was very seldom. Key words:Bacteraemia, periodontitis, culture, PCR, tooth brushing. PMID:26946197

  18. Early molecular adsorbents recirculating system treatment of Amanita mushroom poisoning.

    PubMed

    Kantola, Taru; Kantola, Teemu; Koivusalo, Anna-Maria; Höckerstedt, Krister; Isoniemi, Helena

    2009-10-01

    Acute poisoning due to ingestion of hepatotoxic Amanita sp. mushrooms can result in a spectrum of symptoms, from mild gastrointestinal discomfort to life-threatening acute liver failure. With conventional treatment, Amanita phalloides mushroom poisoning carries a substantial risk of mortality and many patients require liver transplantation. The molecular adsorbent recirculating system (MARS) is an artificial liver support system that can partly compensate for the detoxifying function of the liver by removing albumin-bound and water-soluble toxins from blood. This treatment has been used in acute liver failure to enable native liver recovery and as a bridging treatment to liver transplantation. The aim of the study is to evaluate the outcome of 10 patients with Amanita mushroom poisoning who were treated with MARS. The study was a retrospectively analyzed case series. Ten adult patients with accidental Amanita poisoning of varying severity were treated in a liver disease specialized intensive care unit from 2001 to 2007. All patients received MARS treatment and standard medical therapy for mushroom poisoning. The demographic, laboratory, and clinical data from each patient were recorded upon admission. The one-year survival and need for liver transplantation were documented. The median times from mushroom ingestion to first-aid at a local hospital and to MARS treatment were 18 h (range 14-36 h) and 48 h (range 26-78 h), respectively. All 10 patients survived longer than one year. One patient underwent a successful liver transplantation. No serious adverse side-effects were observed with the MARS treatment. In conclusion, MARS treatment seems to offer a safe and effective treatment option in Amanita mushroom poisoning.

  19. The Wide Field/Planetary Camera 2 (WFPC-2) molecular adsorber

    NASA Technical Reports Server (NTRS)

    Barengoltz, Jack; Moore, Sonya; Soules, David; Voecks, Gerald

    1995-01-01

    A device has been developed at the Jet Propulsion Laboratory, California Institute of Technology, for the adsorption of contaminants inside a space instrument during flight. The molecular adsorber was developed for use on the Wide Field Planetary Camera 2, and it has been shown to perform at its design specifications in the WFPC-2. The basic principle of the molecular adsorber is a zeolite-coated ceramic honeycomb. The arrangement is efficient for adsorption and also provides the needed rigidity to retain the special zeolite coating during the launch vibrational environment. The adsorber, on other forms, is expected to be useful for all flight instruments sensitive to internal sources of contamination. Typically, some internal contamination is unavoidable. A common design solution is to increase the venting to the exterior. However, for truly sensitive instruments, the external contamination environment is more severe. The molecular adsorber acts as a one-way vent to solve this problem. Continued development is planned for this device.

  20. Proper Brushing

    MedlinePlus

    ... 3 teeth using a vibrating back & forth rolling motion. A rolling motion is when the brush makes contact with the ... gumline. Gently brush using back, forth, and rolling motion along all of the inner tooth surfaces. Tilt ...

  1. Smart Adsorbents with Photoregulated Molecular Gates for Both Selective Adsorption and Efficient Regeneration.

    PubMed

    Cheng, Lei; Jiang, Yao; Yan, Ni; Shan, Shu-Feng; Liu, Xiao-Qin; Sun, Lin-Bing

    2016-09-01

    Selective adsorption and efficient regeneration are two crucial issues for adsorption processes; unfortunately, only one of them instead of both is favored by traditional adsorbents with fixed pore orifices. Herein, we fabricated a new generation of smart adsorbents through grafting photoresponsive molecules, namely, 4-(3-triethoxysilylpropyl-ureido)azobenzene (AB-TPI), onto pore orifices of the support mesoporous silica. The azobenzene (AB) derivatives serve as the molecular gates of mesopores and are reversibly opened and closed upon light irradiation. Irradiation with visible light (450 nm) causes AB molecules to isomerize from cis to trans configuration, and the molecular gates are closed. It is easy for smaller adsorbates to enter while difficult for the larger ones, and the selective adsorption is consequently facilitated. Upon irradiation with UV light (365 nm), the AB molecules are transformed from trans to cis isomers, promoting the desorption of adsorbates due to the opened molecular gates. The present smart adsorbents can consequently benefit not only selective adsorption but also efficient desorption, which are exceedingly desirable for adsorptive separation but impossible for traditional adsorbents with fixed pore orifices. PMID:27559985

  2. Synthesis and characterization of polymer brushes for controlled adsorption of proteins

    NASA Astrophysics Data System (ADS)

    Hoy, Olha

    Performance of biomedical devices to a large extent depends on the interactions between the device surface and the biological liquids/protein molecules. To achieve controllable interactions between the device and biomolecules and still retain the required mechanical strength on the whole, modification of the surface is often done. In the present study surface properties were modified through a polymer brush approach. After the modification, surfaces gain tunability toward protein adsorption. Mixed polymer brushes consisting of protein repelling and protein attractive components were used, with a "grafting to" method employed for the synthesis of polymer layers. First, poly(ethylene glycol), the protein repelling component of the mixed polymer brush, was tethered to the surface. Then, polyacrylic acid-b-polystyrene (the protein attractive component) was grafted on top of the previous layer. As one part of this study, the temperature dependence of grafting of the mixed brush components was studied. Surface morphology and surface properties of the mixed polymer brush were altered by treating the brush with different organic solvents. Changes in surface morphology and properties resulting from the solvent treatment were studied in dry conditions and in aqueous media. Hydrophobic interactions of the mixed polymer brush in different pH environments were also estimated. Synthesized mixed polymer brushes demonstrated a clear dependency between the external stimuli applied to the brush and the amount of the protein adsorbed onto the brush surface, allowing an effective control of protein adsorption. Attraction forces between the protein molecules and surface of he mixed polymer brush were measured using AFM and these supported the findings from the protein adsorption studies. 2-D molecular imprinting of the polymer brush approach was used to synthesize a surface with controlled positioning of the protein molecules on the surface. Protein adsorption onto the surface of the

  3. Polymer brushes: Tools for surface design

    NASA Astrophysics Data System (ADS)

    Ober, Christopher

    2011-03-01

    Polymers brushes are ideal materials for interfacing with biological systems as they share many of the same molecular components and properties. Polymer brushes provide remarkable screening power in shielding a substrate from the environment through both steric and charge interactions. However, the majority of biomolecular species will still non-specifically bind to polymer brush surfaces unless some care is given to molecular design. Several polymer brush systems are described to control interaction of biomacromolecules and cells by design of specific and non-specific interactions in polymer brush architectures. ``Grown from'' and block copolymer brushes are described, both of which provide excellent substrates for study of brush surfaces. Examples of polymer brushes used for sensor creation and for investigation of cellular interaction are given. Brushes used in non-fouling coatings tailored for marine applications and in which amphiphilic structures play an important role are also described. Support from both NSF and ONR is gratefully acknowledged.

  4. Molecular recognition using nanotube-adsorbed polymer phases: nanotube antibodies

    PubMed Central

    Zhang, Jingqing; Landry, Markita P.; Barone, Paul W.; Kim, Jong-Ho; Lin, Shangchao; Ulissi, Zachary W.; Lin, Dahua; Mu, Bin; Heller, Daniel A.; Boghossian, Ardemis A.; Hilmer, Andrew J.; Rwei, Alina; Hinckley, Allison C.; Kruss, Sebastian; Shandell, Mia A.; Nair, Nitish; Blake, Steven; Sen, Fatih; Sen, Selda; Croy, Robert G.; Li, Deyu; Yum, Kyungsuk; Ahn, Jin-Ho; Jin, Hong; Essigmann, John M.; Blankschtein, Daniel; Strano, Michael S.

    2016-01-01

    Molecular recognition is central to the design of therapeutics, chemical catalysis and sensors. Motifs for doing so most commonly involve biological structures such as antibodies and aptamers. The key to such biological recognition consists of a folded and constrained heteropolymer that, via intra-molecular forces, forms a unique three dimensional structure that creates a binding pocket or an interface able to recognize a specific molecule. In this work, we demonstrate that synthetic heteropolymers can be alternatively constrained by adsorption around a nanoparticle, and specifically a single walled carbon nanotube (SWNT), forming a corona phase and resulting in a new form of molecular recognition of specific molecules. The phenomenon is shown to be generic, with new heteropolymer recognition complexes demonstrated for three distinct examples: Riboflavin, l-thyroxine, and estradiol, each predicted using a 2D thermodynamic model of surface interactions. The dissociation constants are continuously tunable by perturbing the chemical structure of the heteropolymer. Moreover, these complexes can be used as new types of spatial-temporal sensors based on modulation of SWNT photoemission in the near-infrared, as we show by tracking riboflavin diffusion in murine macrophages. PMID:24270641

  5. Shock compression and flash-heating of molecular adsorbates on the picosecond time scale

    NASA Astrophysics Data System (ADS)

    Berg, Christopher Michael

    An ultrafast nonlinear coherent laser spectroscopy termed broadband multiplex vibrational sum-frequency generation (SFG) with nonresonant suppression was employed to monitor vibrational transitions of molecular adsorbates on metallic substrates during laser-driven shock compression and flash-heating. Adsorbates were in the form of well-ordered self-assembled monolayers (SAMs) and included molecular explosive simulants, such as nitroaromatics, and long chain-length alkanethiols. Based on reflectance measurements of the metallic substrates, femtosecond flash-heating pulses were capable of producing large-amplitude temperature jumps with DeltaT = 500 K. Laser-driven shock compression of SAMs produced pressures up to 2 GPa, where 1 GPa ≈ 1 x 104 atm. Shock pressures were estimated via comparison with frequency shifts observed in the monolayer vibrational transitions during hydrostatic pressure measurements in a SiC anvil cell. Molecular dynamics during flash-heating and shock loading were probed with vibrational SFG spectroscopy with picosecond temporal resolution and sub-nanometer spatial resolution. Flash-heating studies of 4-nitrobenzenethiolate (NBT) on Au provided insight into effects from hot-electron excitation of the molecular adsorbates at early pump-probe delay times. At longer delay times, effects from the excitation of SAM lattice modes and lower-energy NBT vibrations were shown. In addition, flash-heating studies of alkanethiolates demonstrated chain disordering behaviors as well as interface thermal conductances across the Au-SAM junction, which was of specific interest within the context of molecular electronics. Shock compression studies of molecular explosive simulants, such as 4-nitrobenzoate (NBA), demonstrated the proficiency of this technique to observe shock-induced molecular dynamics, in this case orientational dynamics, on the picosecond time scale. Results validated the utilization of these refined shock loading techniques to probe the shock

  6. Evaluation of an atomic force microscopy pull-off method for measuring molecular weight and polydispersity of polymer brushes: effect of grafting density.

    PubMed

    Goodman, Diane; Kizhakkedathu, Jayachandran N; Brooks, Donald E

    2004-07-20

    The accuracy of the molecular weights Mn and polydispersities of polymer brushes, determined by stretching the grafted chains using atomic force microscopy (AFM) and measuring the contour length distribution, was evaluated as a function of grafting density sigma. Poly(N,N-dimethylacrylamide) brushes were prepared by surface initiated atom transfer radical polymerization on latex particles with sigma ranging between 0.17 and 0.0059 chains/nm2 and constant Mn. The polymer, which could be cleaved from the grafting surface by hydrolysis and characterized by gel permeation chromatography (GPC), had a Mn of 30,600 and polydispersity (PDI) of 1.35. The Mn determined by the AFM technique for the higher density brushes agreed quite well with the GPC results but was significantly underestimated for the lower sigma. At high grafting density in good solvent, the extended structure of the brush increases the probability of forming segment-tip contacts located at the chain end. When the distance between chains approached twice the radius of gyration of the polymer, the transition from brush to mushroom structure presumably enabled the formation of a larger number of segment-tip contacts having separations smaller than the contour length, which explains the discrepancy between the two methods at low sigma. The PDI was typically higher than that obtained by GPC, suggesting that sampling of chains with above average contour length occurs at a frequency that is greater than their spatial distribution.

  7. Characterization and control of molecular ordering on adsorbate-induced reconstructed surfaces

    NASA Astrophysics Data System (ADS)

    Pai, Woei Wu; Hsu, C. L.; Lin, K. C.; Sin, L. Y.; Tang, Tong B.

    2005-02-01

    Understanding molecular ordering is a critical step in achieving molecular self-assembly for the fabrication of nanomaterials, and molecular ordering in the adsorption of large molecules on atomically flat surfaces can be characterized with precision by scanning tunneling microscopy (STM). Complications arise therein from the expanded possibility of various adsorption structures, conformations and surface reconstructions. Here we present two cases of C 60 adsorbed on Ag(1 0 0) and Cu(1 1 1) that illustrate the importance of competitive interactions in the presence of adsorbate-induced reconstruction. In both studies, strong STM contrasts derive from topographic features arising from reconstructed substrates. C 60/Ag(1 0 0) presents a unique uniaxially incommensurate molecular packing. We have also found that one can control molecular ordering with a stepped surface to produce a single-domain film. In C 60/Cu(1 1 1), we are able to obtain metastable, yet well-defined, molecular ordering with precise annealing procedures. These metastable states exhibit a clear correlation between molecular contrast patterns and the adlayer rotation angle, as a consequence of competitive interactions between optimizing C 60 bonding at preferred reconstructive sites and C 60-C 60 repulsion. Finer control of selective preparation of these metastable structures offers a plausible way of fabricating nanostructures by design.

  8. Application of the Molecular Adsorber Coating Technology on the Ionospheric Connection Explorer Program

    NASA Technical Reports Server (NTRS)

    Abraham, Nithin S.; Hasegawa, Mark M.; Secunda, Mark S.

    2016-01-01

    The Molecular Adsorber Coating (MAC) is a zeolite based highly porous coating technology that was developed by NASA Goddard Space Flight Center (GSFC) to capture outgassed contaminants, such as plastics, adhesives, lubricants, silicones, epoxies, potting compounds, and other similar materials. This paper describes the use of the MAC technology to address molecular contamination concerns on NASAs Ionospheric Connection Explorer (ICON) program led by the University of California (UC) Berkeleys Space Sciences Laboratory. The sprayable paint technology was applied onto plates that were installed within the instrument cavity of ICONs Far Ultraviolet Imaging Spectrograph (FUV). However, due to the instruments particulate sensitivity, the coating surface was vibrationally cleaned through simulated acoustics to reduce the risk of particle fall-out contamination. This paper summarizes the coating application efforts on the FUV adsorber plates, the simulated laboratory acoustic level cleaning test methods, particulation characteristics, and future plans for the MAC technology.

  9. Molecular adsorbates as probes of the local properties of doped graphene

    PubMed Central

    Pham, Van Dong; Joucken, Frédéric; Repain, Vincent; Chacon, Cyril; Bellec, Amandine; Girard, Yann; Rousset, Sylvie; Sporken, Robert; Santos, Maria Cristina dos; Lagoute, Jérôme

    2016-01-01

    Graphene-based sensors are among the most promising of graphene’s applications. The ability to signal the presence of molecular species adsorbed on this atomically thin substrate has been explored from electric measurements to light scattering. Here we show that the adsorbed molecules can be used to sense graphene properties. The interaction of porphyrin molecules with nitrogen-doped graphene has been investigated using scanning tunneling microscopy and ab initio calculations. Molecular manipulation was used to reveal the surface below the adsorbed molecules allowing to achieve an atomic-scale measure of the interaction of molecules with doped graphene. The adsorbate’s frontier electronic states are downshifted in energy as the molecule approaches the doping site, with largest effect when the molecule sits over the nitrogen dopant. Theoretical calculations showed that, due to graphene’s high polarizability, the adsorption of porphyrin induces a charge rearrangement on the substrate similar to the image charges on a metal. This charge polarization is enhanced around nitrogen site, leading to an increased interaction of molecules with their image charges on graphene. Consequently, the molecular states are stabilized and shift to lower energies. These findings reveal the local variation of polarizability induced by nitrogen dopant opening new routes towards the electronic tuning of graphene. PMID:27097555

  10. Selective adsorption of modified nucleoside cancer biomarkers by hybrid molecularly imprinted adsorbents.

    PubMed

    Iwanowska, Agnieszka; Yusa, Shin-Ichi; Nowakowska, Maria; Szczubiałka, Krzysztof

    2016-08-01

    Modified adenosine nucleosides have been proposed to be potential DNA-based biomarkers for early diagnosis of tumor and a promising tool for the development of noninvasive prediction systems. However, the low concentration of modified adenosine nucleosides in physiological fluids makes them challenging for both quantitative and qualitative determination. Therefore, materials, which are potentially useful for selective adsorption of nucleobase-containing compounds, were obtained. To obtain the adsorbents, the silica gel particles were coated layer-by-layer with films of the polymers with different combinations of polymers containing thymine groups. Next, the microspheres were irradiated with UV light in the presence of 2'-deoxyadenosine or 5'-deoxy-5'-(methylthio)adenosine, as template molecules, which resulted in the photodimerization of thymine moieties and molecular imprinting of adsorbed modified adenosine compounds. The selectivity of the adsorption was significantly enhanced by the photoimprinting process. Eventually, the imprinted particles have shown an improved ability to recognize mainly 2'-deoxyadenosine and 5'-deoxy-5'-(methylthio)adenosine molecules. The best performing adsorbent was obtained using modified natural polysaccharides. The studied materials could serve as promising adsorbents of biomarkers for tumor diagnostics. PMID:27296785

  11. An efficient approach to obtaining water-compatible and stimuli-responsive molecularly imprinted polymers by the facile surface-grafting of functional polymer brushes via RAFT polymerization.

    PubMed

    Pan, Guoqing; Zhang, Ying; Guo, Xianzhi; Li, Chenxi; Zhang, Huiqi

    2010-11-15

    A new and efficient approach to obtaining molecularly imprinted polymers (MIPs) with both pure water-compatible (i.e., applicable in the pure aqueous environments) and stimuli-responsive binding properties is described, whose proof-of-principle is demonstrated by the facile modification of the preformed MIP microspheres via surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAAm). The presence of poly(NIPAAm) (PNIPAAm) brushes on the obtained MIP microspheres was confirmed by FT-IR as well as the water dispersion and static contact angle experiments, and some quantitative information including the molecular weights and polydispersities of the grafted polymer brushes, the thickness of the polymer brush layers, and their grafting densities was provided. In addition, the binding properties of the ungrafted and grafted MIPs/NIPs in both methanol/water (4/1, v/v) and pure water solutions were also investigated. The introduction of PNIPAAm brushes onto the MIP microspheres has proven to significantly improve their surface hydrophilicity and impart stimuli-responsive properties to them, leading to their pure water-compatible and thermo-responsive binding properties. The application of the facile surface-grafting approach, together with the versatility of RAFT polymerization and the availability of many different functional monomers, makes the present methodology a general and promising way to prepare water-compatible and stimuli-responsive MIPs for a wide range of templates.

  12. Multilayer graphene nanostructure separate CO2/CH4 mixture: Combining molecular simulations with ideal adsorbed solution theory

    NASA Astrophysics Data System (ADS)

    Cheng, Huiyuan; Lei, Guangping

    2016-09-01

    The molecular simulations (Grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations) combined with ideal adsorbed solution theory (IAST) are adopted to investigate the adsorption of CO2, CH4 and their mixture in multilayer graphene nanostructure. The effects of pressure, temperature and pre-adsorbed water on the separation behaviors are examined. The IAST accurately predict the loading of two species, but it has a slight deviation for the selectivity predictions. It is beneficial to the CO2/CH4 mixture separation by reducing temperature or pre-adsorbing some water. Due to additional adsorbate-H2O interactions, the diffusivities of two species drop down as the pre-adsorbed water content increases.

  13. Contributions of the substrate electric field to the molecular adsorbate optical nonlinearities

    SciTech Connect

    Zouari, M.; Villaeys, A.A.

    2005-10-15

    The nonlinear optical response of an adsorbate, whose structure is altered by the inhomogeneous electrostatic field of the substrate, has been evaluated with a particular emphasis on the sum-frequency generation process. In the limiting case of an homogeneous electrostatic field, besides the contributions associated with the induced dipole moments, we have additional contributions which only exist if the adsorbed molecule has permanent dipole moments. Also, the Franck-Condon factors of the unperturbed molecule weight the internal couplings induced by the electrostatic field. For the more general inhomogeneous electrostatic field case, while the main observations remain valid, the Franck-Condon factors are modified by the molecular structure changes induced by the electrostatic field. In addition, we have a strong redistribution of the vibronic couplings resulting from the analytical Q dependence of the partial charge distribution which is a signature of the field inhomogeneities.

  14. Explicit Solvent Simulations of Friction between Brush Layers of Charged and Neutral Bottle-Brush Macromolecules

    NASA Astrophysics Data System (ADS)

    Carrillo, J.-M. Y.; Brown, W. M.; Dobrynin, A. V.

    2013-03-01

    We study friction between charged and neutral brush layers of bottle-brush macromolecules using molecular dynamics simulations. The deformation of the bottle-brush macromolecules under the shear were studied as a function of the substrate separation and shear stress. For charged bottle-brush layers we study effect of the added salt on the brush lubricating properties to elucidate factors responsible for energy dissipation in charged and neutral brush systems. Our simulations have shown that for both charged and neutral brush systems the main deformation mode of the bottle-brush macromolecule is associated with the backbone deformation. This deformation mode manifests itself in the backbone deformation ratio, α, and shear viscosity, η, to be universal functions of the Weissenberg number W. The value of the friction coefficient, μ, and viscosity, η, are larger for the charged bottle-brush coatings in comparison with those for neutral brushes at the same separation distance, D, between substrates. The additional energy dissipation generated by brush sliding in charged bottle-brush systems is due to electrostatic coupling between bottle-brush and counterion motion. This coupling weakens as salt concentration, cs, increases resulting in values of the viscosity, η, and friction coefficient, μ, approaching corresponding values obtained for neutral brush systems. NSF DMR-1004576

  15. Explicit Solvent Simulations of Friction between Brush Layers of Charged and Neutral Bottle-Brush Macromolecules

    SciTech Connect

    Carrillo, Jan-Michael; Brown, W Michael; Dobrynin, Andrey

    2012-01-01

    We study friction between charged and neutral brush layers of bottle-brush macromolecules using molecular dynamics simulations. In our simulations the solvent molecules were treated explicitly. The deformation of the bottle-brush macromolecules under the shear were studied as a function of the substrate separation and shear stress. For charged bottle-brush layers we study effect of the added salt on the brush lubricating properties to elucidate factors responsible for energy dissipation in charged and neutral brush systems. Our simulations have shown that for both charged and neutral brush systems the main deformation mode of the bottle-brush macromolecule is associated with the backbone deformation. This deformation mode manifests itself in the backbone deformation ratio, , and shear viscosity, , to be universal functions of the Weissenberg number W. The value of the friction coefficient, , and viscosity, , are larger for the charged bottle-brush coatings in comparison with those for neutral brushes at the same separation distance, D, between substrates. The additional energy dissipation generated by brush sliding in charged bottle-brush systems is due to electrostatic coupling between bottle-brush and counterion motion. This coupling weakens as salt concentration, cs, increases resulting in values of the viscosity, , and friction coefficient, , approaching corresponding values obtained for neutral brush systems.

  16. Atomic and molecular oxygen adsorbed on (111) transition metal surfaces: Cu and Ni

    SciTech Connect

    López-Moreno, S.; Romero, A. H.

    2015-04-21

    Density functional theory is used to investigate the reaction of oxygen with clean copper and nickel [111]-surfaces. We study several alternative adsorption sites for atomic and molecular oxygen on both surfaces. The minimal energy geometries and adsorption energies are in good agreement with previous theoretical studies and experimental data. From all considered adsorption sites, we found a new O{sub 2} molecular precursor with two possible dissociation paths on the Cu(111) surface. Cross barrier energies for the molecular oxygen dissociation have been calculated by using the climbing image nudge elastic band method, and direct comparison with experimental results is performed. Finally, the structural changes and adsorption energies of oxygen adsorbed on surface when there is a vacancy nearby the adsorption site are also considered.

  17. Molecular adsorbent recirculating system as artificial support therapy for liver failure: a meta-analysis.

    PubMed

    Vaid, Arjun; Chweich, Haval; Balk, Ethan M; Jaber, Bertrand L

    2012-01-01

    Molecular Adsorbent Recirculating System (MARS) is an artificial liver support system that has been developed for patients with liver failure until the liver regains function or as a bridge to transplantation. We conducted a meta-analysis to examine the efficacy of this promising therapy. We searched MEDLINE, EMBASE, and the Cochrane Registry of Controlled Trials databases, and abstracts from the proceedings of several scientific meetings. Patients with acute, acute on chronic, and hyperacute liver failure were included and we compared MARS with standard medical therapy. Randomized and nonrandomized controlled trials were included and Molecular Adsorbent Recirculating System was the intervention used. We evaluated net change in total bilirubin levels, improvement in hepatic encephalopathy and mortality. Nine randomized controlled trials and one nonrandomized controlled study met criteria and were included. By meta-analysis, MARS resulted in a significant decrease in total bilirubin levels (net change -7.0 mg/dl; 95% CI -10.4, -3.7; p < 0.001) and in an improvement in the West-Haven grade of hepatic encephalopathy (odds ratio [OR] 3.0; 95% CI 1.9, 5.0; p < 0.001). There was no beneficial effect on mortality (OR 0.91; 95% CI 0.64, 1.31; p = 0.62). The limitations of this study include a small sample size, an inability to blind with significant heterogeneity among studies, and variable definitions of liver failure. The Molecular Adsorbent Recirculating System is associated with a significant improvement in total bilirubin levels and hepatic encephalopathy but has no impact on survival. Large studies are required to assess the merit of this promising therapy on patient-centered outcomes. PMID:22210651

  18. Adsorbate shape selectivity: Separation of the HF/134a azeotrope over carbogenic molecular sieve

    SciTech Connect

    Hong, A.; Mariwala, R.K.; Kane, M.S.; Foley, H.C.

    1995-03-01

    Experimental evidence is provided for adsorptive shape selectivity in the separation of the azeotrope between HF and 1,1,1,2-tetrafluoroethane (134a) over pyrolyzed poly(furfuryl alcohol)-derived carbogenic molecular sieve (PPFA-CMS). The separation can be accomplished over coconut charcoal or Carbosieve G on the basis of the differences in the extent of equilibrium adsorption of HF and 134a. On these adsorbents 134a is more strongly bound than HF, thus it elutes much more slowly from the bed. The heat of adsorption for 134a in the vicinity of 200 C on Carbosieve G is {approximately}8.8 kcal/mol. In contrast, when the same azeotropic mixture is separated over PPFA-CMS prepared at 500 C, 134a is not adsorbed. As a result 134a elutes from the bed first, followed by HF. The reversal is brought about by the narrower pore size and pore size distribution of the PPFA-CMS versus that for Carbosieve G. Thus the separation over PPFA-CMS is an example of adsorbate shape selectivity and represents a limiting case of kinetic separation.

  19. Electronic Friction-Based Vibrational Lifetimes of Molecular Adsorbates: Beyond the Independent-Atom Approximation.

    PubMed

    Rittmeyer, Simon P; Meyer, Jörg; Juaristi, J Iñaki; Reuter, Karsten

    2015-07-24

    We assess the accuracy of vibrational damping rates of diatomic adsorbates on metal surfaces as calculated within the local-density friction approximation (LDFA). An atoms-in-molecules (AIM) type charge partitioning scheme accounts for intramolecular contributions and overcomes the systematic underestimation of the nonadiabatic losses obtained within the prevalent independent-atom approximation. The quantitative agreement obtained with theoretical and experimental benchmark data suggests the LDFA-AIM scheme as an efficient and reliable approach to account for electronic dissipation in ab initio molecular dynamics simulations of surface chemical reactions. PMID:26252696

  20. Photoinduced Reconfiguration Cycle in a Molecular Adsorbate Layer Studied by Femtosecond Inner-Shell Photoelectron Spectroscopy

    SciTech Connect

    Dachraoui, H.; Michelswirth, M.; Bartz, P.; Pfeiffer, W.; Heinzmann, U.; Siffalovic, P.; Schaefer, C.; Schnatwinkel, B.; Mattay, J.; Drescher, M.

    2011-03-11

    A time-resolved study of core-level chemical shifts in a monolayer of aromatic molecules reveals complex photoinduced reaction dynamics. The combination of electron spectroscopy for chemical analysis and ultrashort pulse excitation in the extreme ultraviolet allows performing time-correlated 4d-core-level spectroscopy of iodine atoms that probe the local chemical environment in the adsorbate molecule. The selectivity of the method unveils metastable molecular configurations that appear about 50 ps after the excitation and are efficiently quenched back to the ground state.

  1. Thermoresponsive PDMAEMA Brushes: Effect of Gold Nanoparticle Deposition.

    PubMed

    Yenice, Zuleyha; Schön, Sebastian; Bildirir, Hakan; Genzer, Jan; von Klitzing, Regine

    2015-08-13

    The paper addresses the effect of gold nanoparticle (Au-NP) deposition on the thermoresponsive volume phase transition of the weak polyelectrolyte poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes. PDMAEMA brushes were synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP). The PDMAEMA/Au-NP composite brushes were fabricated by immersing the brush modified wafer in the Au-NP suspension. Atomic force microscopy (AFM), ellipsometry, and scanning electron microscopy (SEM) have been employed to characterize the neat PDMAEMA brushes and PDMAEMA/Au-NP composite brushes. All neat PDMAEMA brushes swelled below the volume phase transition temperature and collapsed with increasing temperature over a broad temperature range independent of the initial brush thickness. Water uptake of the brushes is also independent of initial brush thickness. The adsorption of the charged Au-NPs significantly affects the degree of swelling and the thermoresponsive properties of the brushes. PDMAEMA/Au-NP composite brushes do not exhibit any noticeable phase transition at the experimental temperature range irrespective of the initial brush thickness. The reason for this behavior is attributed to a combination of the following: the decreased conformational entropy of the Au-NP adsorbed polymer chains, the increased hydrophilicity of the system due to the charged Au-NPs, and the ≈13 nm diameter Au-NPs causing steric hindrance. We have also shown that the AFM full-indentation method can be successfully applied to determine the polymer brush thicknesses. PMID:26132296

  2. Adsorption separation of carbon dioxide from flue gas by a molecularly imprinted adsorbent.

    PubMed

    Zhao, Yi; Shen, Yanmei; Ma, Guoyi; Hao, Rongjie

    2014-01-01

    CO2 separation by molecularly imprinted adsorbent from coal-fired flue gas after desulfurization system has been studied. The adsorbent was synthesized by molecular imprinted technique, using ethanedioic acid, acrylamide, and ethylene glycol dimethacrylate as the template, functional monomer, and cross-linker, respectively. According to the conditions of coal-fired flue gas, the influencing factors, including adsorption temperature, desorption temperature, gas flow rate, and concentrations of CO2, H2O, O2, SO2, and NO, were studied by fixed bed breakthrough experiments. The experimental conditions were optimized to gain the best adsorption performance and reduce unnecessary energy consumption in future practical use. The optimized adsorption temperature, desorption temperature, concentrations of CO2, and gas flow rate are 60 °C, 80 °C, 13%, and 170 mL/min, respectively, which correspond to conditions of practical flue gases to the most extent. The CO2 adsorption performance was nearly unaffected by H2O, O2, and NO in the flue gas, and was promoted by SO2 within the emission limit stipulated in the Chinese emission standards of air pollutants for a thermal power plant. The maximum CO2 adsorption capacity, 0.57 mmol/g, was obtained under the optimized experimental conditions, and the SO2 concentration was 150 mg/m(3). The influence mechanisms of H2O, O2, SO2, and NO on CO2 adsorption capacity were investigated by infrared spectroscopic analysis. PMID:24410306

  3. On-demand degrafting and the study of molecular weight and grafting density of poly(methyl methacrylate) brushes on flat silica substrates.

    PubMed

    Patil, Rohan R; Turgman-Cohen, Salomon; Šrogl, Jiří; Kiserow, Douglas; Genzer, Jan

    2015-03-01

    We report on degrafting of surface-anchored poly(methyl methacrylate) (PMMA) brushes from flat silica-based substrates using tetrabutylammonium fluoride (TBAF) and determining their molecular weight distribution (MWD) using size exclusion chromatography (SEC). The grafted PMMA layer was synthesized using surface-initiated atom transfer radical polymerization (SI-ATRP) of MMA for polymerization times ranging from 6 to 24 h. X-ray photoelectron spectroscopy, ellipsometry, and time-of-flight secondary ion mass spectrometry were employed in tandem to characterize the degrafting process. The SEC eluograms were fit to various polymer distributions, namely Zimm-Schulz, ATRP in continuous stirred tank reactor, Wesslau, Schulz-Flory, and Smith et al. The ATRP model gives the best fit to the experimental data. The dry PMMA brush thickness and the number-average molecular weight (obtained from the MWD) suggest that the grafting density of the PMMA grafts is independent of polymerization time, indicating well-controlled/living growth of MMA. The observed polydispersity index (PDI) was higher than that generally observed in bulk grown polymers under similar conditions, indicating an effect due to chain confinement and crowding. We detect small but noticeable dependence of the polymer brush grafting density on the inhibitor/catalyst ratio. Higher inhibitor/catalyst ratio offers better control with lower early terminations, which results in a small increase in the apparent grafting density of the chains.

  4. Custom-tailored adsorbers: A molecular dynamics study on optimal design of ion exchange chromatography material.

    PubMed

    Lang, Katharina M H; Kittelmann, Jörg; Pilgram, Florian; Osberghaus, Anna; Hubbuch, Jürgen

    2015-09-25

    The performance of functionalized materials, e.g., ion exchange resins, depends on multiple resin characteristics, such as type of ligand, ligand density, the pore accessibility for a molecule, and backbone characteristics. Therefore, the screening and identification process for optimal resin characteristics for separation is very time and material consuming. Previous studies on the influence of resin characteristics have focused on an experimental approach and to a lesser extent on the mechanistic understanding of the adsorption mechanism. In this in silico study, a previously developed molecular dynamics (MD) tool is used, which simulates any given biomolecule on resins with varying ligand densities. We describe a set of simulations and experiments with four proteins and six resins varying in ligand density, and show that simulations and experiments correlate well in a wide range of ligand density. With this new approach simulations can be used as pre-experimental screening for optimal adsorber characteristics, reducing the actual number of screening experiments, which results in a faster and more knowledge-based development of custom-tailored adsorbers.

  5. Interaction between two polyelectrolyte brushes.

    PubMed

    Kumar, N Arun; Seidel, Christian

    2007-08-01

    We report molecular dynamics simulations on completely charged polyelectrolyte brushes grafted to two parallel surfaces. The pressure Pi is evaluated as a function of separation D between the two grafting planes. For decreasing separation, Pi shows several regimes distinguished by their scaling with D which reflects the different physical nature of the various regimes. At weak compression the pressure obeys the 1D power law predicted by scaling theory of an ideal gas of counterions in the osmotic brush regime. In addition we find that the brushes shrink as they approach each other trying to avoid interpenetration. At higher compressions where excluded volume interactions become important, we obtain scaling exponents between -2 at small grafting density rho(a) and -3 at large rho(a). This behavior indicates a transition from a brush under good solvent condition to the melt regime with increasing grafting density. PMID:17929998

  6. Molecular Insights into the pH-Dependent Adsorption and Removal of Ionizable Antibiotic Oxytetracycline by Adsorbent Cyclodextrin Polymers

    PubMed Central

    Zhang, Yu; Cai, Xiyun; Xiong, Weina; Jiang, Hao; Zhao, Haitong; Yang, Xianhai; Li, Chao; Fu, Zhiqiang; Chen, Jingwen

    2014-01-01

    Effects of pH on adsorption and removal efficiency of ionizable organic compounds (IOCs) by environmental adsorbents are an area of debate, because of its dual mediation towards adsorbents and adsorbate. Here, we probe the pH-dependent adsorption of ionizable antibiotic oxytetracycline (comprising OTCH2+, OTCH±, OTC−, and OTC2−) onto cyclodextrin polymers (CDPs) with the nature of molecular recognition and pH inertness. OTCH± commonly has high adsorption affinity, OTC− exhibits moderate affinity, and the other two species have negligible affinity. These species are evidenced to selectively interact with structural units (e.g., CD cavity, pore channel, and network) of the polymers and thus immobilized onto the adsorbents to different extents. The differences in adsorption affinity and mechanisms of the species account for the pH-dependent adsorption of OTC. The mathematical equations are derived from the multiple linear regression (MLR) analysis of quantitatively relating adsorption affinity of OTC at varying pH to adsorbent properties. A combination of the MLR analysis for OTC and molecular recognition of adsorption of the species illustrates the nature of the pH-dependent adsorption of OTC. Based on this finding, γ-HP-CDP is chosen to adsorb and remove OTC at pH 5.0 and 7.0, showing high removal efficiency and strong resistance to the interference of coexisting components. PMID:24465975

  7. Molecular characterization of a family of metalloendopeptidases from the intestinal brush border of Haemonchus contortus.

    PubMed

    Newlands, G F J; Skuce, P J; Nisbet, A J; Redmond, D L; Smith, S K; Pettit, D; Smith, W D

    2006-09-01

    Substantial protection against the economically important parasitic nematode Haemonchus contortus has been achieved by immunizing sheep with a glycoprotein fraction isolated from the intestinal membranes of the worm (H-gal-GP). Previous studies showed that one of the major components of H-gal-GP is a family of at least 4 zinc metalloendopeptidases, designated MEPs 1-4. This paper describes aspects of the molecular architecture of this protease family, including the proteomic analysis of the MEP fraction of the H-gal-GP complex. These enzymes belong to the M13 zinc metalloendopeptidase family (EC 3.4.24.11), also known as neutral endopeptidases or neprilysins. The sequences of MEPs 1 and 3 suggested a typical Type II integral membrane protein structure, whilst MEPs 2 and 4 had putative cleavable signal peptides, typical of secreted proteins. Proteomic analysis of H-gal-GP indicated that the extracellular domain of all 4 MEPs had been cleaved close to the transmembrane region/signal peptide with additional cleavage sites mid-way along the polypeptide. MEP3 was present as a homo-dimer in H-gal-GP, whereas MEP1 or MEP2 formed hetero-dimers with MEP4. It was found that expression of MEP3 was confined to developing 4th-stage larvae and to adult worms, the stages of Haemonchus which feed on blood. MEP-like activity was detected in the H-gal-GP complex over a broad pH range (5-9). Since all 4 MEPs must share a similar microenvironment in the complex, this suggests that each might have a different substrate specificity. PMID:16740178

  8. Review article: the molecular adsorbents recirculating system (MARS) in liver failure.

    PubMed

    Sen, S; Mookerjee, R P; Davies, N A; Williams, R; Jalan, R

    2002-12-01

    In recent years different artificial liver support systems are being developed for use in patients with acute decompensation of chronic liver disease or acute liver failure. The molecular adsorbents recirculating system (MARS), a device in which patient's blood is dialysed across an albumin-impregnated membrane against a recirculated albumin-containing solution, seems to be effective in removing albumin-bound toxins, such as fatty acids, bile acids and bilirubin. Although the clinical experience with MARS is scarce, some pilot studies have reported its effectiveness at improving liver function and hepatic encephalopathy in patients with acute decompensation of chronic liver disease, and renal function in patients with hepatorenal syndrome type I. Data regarding MARS experience in acute liver failure and in primary graft dysfunction are encouraging but limited. Its real usefulness in these settings is, at present, under evaluation in randomized controlled clinical trials.

  9. A Comprehensive Study of Hydrogen Adsorbing to Amorphous Water ice: Defining Adsorption in Classical Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Dupuy, John L.; Lewis, Steven P.; Stancil, P. C.

    2016-11-01

    Gas–grain and gas–phase reactions dominate the formation of molecules in the interstellar medium (ISM). Gas–grain reactions require a substrate (e.g., a dust or ice grain) on which the reaction is able to occur. The formation of molecular hydrogen (H2) in the ISM is the prototypical example of a gas–grain reaction. In these reactions, an atom of hydrogen will strike a surface, stick to it, and diffuse across it. When it encounters another adsorbed hydrogen atom, the two can react to form molecular hydrogen and then be ejected from the surface by the energy released in the reaction. We perform in-depth classical molecular dynamics simulations of hydrogen atoms interacting with an amorphous water-ice surface. This study focuses on the first step in the formation process; the sticking of the hydrogen atom to the substrate. We find that careful attention must be paid in dealing with the ambiguities in defining a sticking event. The technical definition of a sticking event will affect the computed sticking probabilities and coefficients. Here, using our new definition of a sticking event, we report sticking probabilities and sticking coefficients for nine different incident kinetic energies of hydrogen atoms [5–400 K] across seven different temperatures of dust grains [10–70 K]. We find that probabilities and coefficients vary both as a function of grain temperature and incident kinetic energy over the range of 0.99–0.22.

  10. OZONE REACTION WITH N-ALDEHYDES (N=4-10), BENZALDEHYDE, ETHANOL, ISOPROPANOL, AND N-PROPANOL ADSORBED ON A DUAL-BED GRAPHITIZED CARBON/CARBON MOLECULAR SIEVE ADSORBENT CARTRIDGE

    EPA Science Inventory

    Ozone reacts with n-aldehydes (n = 4 - 10), benzaldehyde, ethanol, isopropanol, and n-propanol adsorbed on a dual-bed graphitized carbon/carbon molecular sieve adsorbent cartridge. Destruction of n-aldehydes increases with n number and with ozone concentration. In some samp...

  11. Molecular resonant dissociation of surface-adsorbed molecules by plasmonic nanoscissors

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenglong; Sheng, Shaoxiang; Zheng, Hairong; Xu, Hongxing; Sun, Mengtao

    2014-04-01

    The ability to break individual bonds or specific modes in chemical reactions is an ardently sought goal by chemists and physicists. While photochemistry based methodologies are very successful in controlling e.g. photocatalysis, photosynthesis and the degradation of plastic, it is hard to break individual molecular bonds for those molecules adsorbed on the surface because of the weak light-absorption in molecules and the redistribution of the resulting vibrational energy both inside the molecule and to its surrounding environment. Here we show how to overcome these obstacles with a plasmonic hot-electron mediated process and demonstrate a new method that allows the sensitive control of resonant dissociation of surface-adsorbed molecules by `plasmonic' scissors. To that end, we used a high-vacuum tip-enhanced Raman spectroscopy (HV-TERS) setup to dissociate resonantly excited NC2H6 fragments from Malachite green. The surface plasmons (SPs) excited at the sharp metal tip not only enhance the local electric field to harvest the light incident from the laser, but crucially supply `hot electrons' whose energy can be transferred to individual bonds. These processes are resonant Raman, which result in some active chemical bonds and then weaken these bonds, followed by dumping in lots of indiscriminant energy and breaking the weakest bond. The method allows for sensitive control of both the rate and probability of dissociation through their dependence on the density of hot electrons, which can be manipulated by tuning the laser intensity or tunneling current/bias voltage in the HV-TERS setup, respectively. The concepts of plasmonic scissors open up new versatile avenues for the deep understanding of in situ surface-catalyzed chemistry.The ability to break individual bonds or specific modes in chemical reactions is an ardently sought goal by chemists and physicists. While photochemistry based methodologies are very successful in controlling e.g. photocatalysis

  12. Fragmentation of molecular adsorbates by electron and ion bombardment: methoxy chemistry on Al(111)

    SciTech Connect

    Basu, P.; Chen, J.G.; Ng, L.; Colaianni, M.L.; Yates, J.T.

    1988-08-15

    High-resolution electron-energy-loss spectroscopy (HR)EELS has been used successfully to provide direct spectroscopic evidence regarding details of the molecular fragmentation of methoxy (CH3O) on Al(lll) caused by energetic electron and ion beams. Chemisorbed methoxy on Al(lll) is produced by heating of absorbed CH3OH. Irradiation of CH3O(a) by either energetic (approx 300 eV) electrons or Ar+ ions results in C-O and C-H bond scission with simultaneous formation of Al-O and Al-C bonds. During electron stimulated desorption the CH3O(a) species undergo sequential fragmentation first to CHx groups that are captured by the surface and in the final decay process to adsorbed carbon. C-O bonds in CH3O9a) are depleted preferentially compared to C-H bonds in CHx(a) species. The electron-induced sequential fragmentation of the patent CH3 group (from methoxy) to resultant CHx(a) occurs with an efficiency approx. 3 orders of magnitude greater than the subsequent process of CHx(a)=C(a). Cross sections for various bond scission processes in electron and ion bombardment have been estimated.

  13. Molecular simulations of intermediate and long alkanes adsorbed on graphite: tuning of non-bond interactions.

    PubMed

    Firlej, Lucyna; Kuchta, Bogdan; Roth, Michael W; Wexler, Carlos

    2011-04-01

    The interplay between the torsional potential energy and the scaling of the 1-4 van der Waals and Coulomb interactions determines the stiffness of flexible molecules. In this paper we demonstrate for the first time that the precise value of the nonbond scaling factor (SF)--often a value assumed without justification--has a significant effect on the critical properties and mechanisms of systems undergoing a phase transition, and that, for accurate simulations, this scaling factor is highly dependent on the system under consideration. In particular, by analyzing the melting of n-alkanes (hexane C6, dodecane C12, tetracosane C24) on graphite, we show that the SF is not constant over varying alkane chain lengths when the structural correlated transformations are concerned. Instead, monotonic decrease of SF with the molecular length drives a cross-over between two distinct mechanisms for melting in such systems. In a broad sense we show that the choice for SF in any simulation containing adsorbed or correlated long molecules needs to be carefully considered.

  14. Meta-analysis of survival with the molecular adsorbent recirculating system for liver failure

    PubMed Central

    He, Guo-Lin; Feng, Lei; Duan, Chong-Yang; Hu, Xiang; Zhou, Chen-Jie; Cheng, Yuan; Pan, Ming-Xin; Gao, Yi

    2015-01-01

    This study aims to assess the treatment effects of the molecular adsorbent recirculating system (MARS) in patients with acute and acute-on-chronic liver failure. We searched MEDLINE, EMBASE, and the Cochrane Controlled Trials Registry database between January 1966 and January 2014. We included randomized controlled trials, which compared the treatment effects of MARS with standard medical treatment. Study quality assessed according to Consolidated Standards of Reporting Trials (CONSORT) criteria. The risk ratio was used as the effect-size measure according to a fixed-effects model. The search strategy revealed 72 clinical studies, 10 of which were randomized controlled trials that met the criteria and were included. Four addressed ALF (93 patients) and six addressed AOCLF (453 patients). The mean CONSORT score was 15 (range 10-20). By meta-analysis, MARS significantly improved survival in ALF (risk ratio 0.61; 95% CI 0.38, 0.97; P = 0.04). There was no significant survival benefit in AOCLF (risk ratio 0.88; 95% CI 0.74, 1.06; P = 0.16). MARS significantly improved survival in patients with acute liver failure, however, there is no evidence that it improved survival in patients with acute-on-chronic liver failure. In conclusion, the present meta-analysis indicates that MARS therapy can improve survival in patients with ALF. It is necessary to develop MARS treatment because of the increasing demand for liver transplantation and the risk of liver failure. PMID:26770295

  15. Extracorporeal Elimination of Piperacillin/Tazobactam during Molecular Adsorbent Recirculating System Therapy.

    PubMed

    Personett, Heather A; Larson, Scott L; Frazee, Erin N; Nyberg, Scott L; El-Zoghby, Ziad M

    2015-08-01

    Use of the Molecular Adsorbent Recirculating System (MARS) as a liver support device continues to grow worldwide. Various components of the MARS circuit remove both protein-bound and water-soluble molecules. Little is known about the extent of the enhanced clearance mechanisms used in MARS therapy on drug elimination. Of particular interest to acute care practitioners is the impact of MARS on antibiotic clearance, as suboptimal concentrations of such drugs can negatively impact patient outcomes. The properties of piperacillin/tazobactam suggest that elimination may be enhanced in the setting of MARS therapy. We describe two cases in which this was studied. Piperacillin concentrations were determined at various points within the MARS circuit, and patient serum concentrations were reported throughout the dosing interval while receiving MARS therapy. Piperacillin concentrations in both cases were in excess of the desired goal minimum inhibitory concentrations for treatment of gram-negative infections. Use of an extended-infusion strategy of piperacillin/tazobactam 3.375 or 4.5 g given every 8 hours maintained desired serum levels throughout the dosing interval. To our knowledge, this is the second published report on the use of piperacillin/tazobactam during MARS therapy. These case reports reveal successful dosing strategies for patients requiring piperacillin/tazobactam while receiving MARS therapy, as well as quantify the influence of individual MARS elements on drug extraction. PMID:26289310

  16. Molecular dynamics simulations of Palmitic acid adsorbed on NaCl

    NASA Astrophysics Data System (ADS)

    Lovrić, Josip; Brizquez, Stéphane; Duflot, Denis; Monnerville, Maurice; Pouilly, Brigitte; Toubin, Céline

    2015-04-01

    The aerosol and gases effects in the atmosphere play an important role on health, air quality and climate, affecting both political decisions and economic activities around the world [1]. Among the several approaches of studying the origin of these effects, computational modeling is of fundamental importance, providing insights on the elementary chemical processes. Sea salts are the most important aerosol in the troposphere (109T/year) [2]. Our theoretical work consists in modeling a (100) NaCl surface coated with palmitic acid (PA) molecules. Molecular dynamics simulations are carried out with the GROMACS package [3], in the NPT ensemble at different temperatures, different PA coverages and various humidity. We focus on two aspects of the PA organization at the salt surface: the first one is related to transition in molecular orientation of the adsorbate as a function of PA coverage. The second one implies the effect of humidity, by adding water molecules, on the organization of the fatty acid at the salt surface, and especially on the occurrence of PA isolated islands as observed in the experiments [4]. For high humidity conditions, PA are removed from the salt surface and form islands on top of the water. This effect is enhanced when temperature increases. Acknowledgments: this research has been supported by the CaPPA project (Chemical and Physical Properties of the Atmosphere), funded by the French National Research Agency (ANR) through the PIA (Programme d'Investissement d'Avenir) under contract ANR-10-LABX-005. [1] O. Boucher et al, 5th Assessment Report IPCC, (2013) [2] B. J. Finlayson-Pitts, Chem. Rev.103, 4801-4822 (2003) [3] http://www.gromacs.org/ [4] S. Sobanska et al, private communication

  17. Cylindrical Brushes

    NASA Astrophysics Data System (ADS)

    Schmidt

    1998-03-01

    Homopolymerization of macromonomers, i.e. polymerizable oligomers, yields macromolecules of cylindrical shape, because the main chain is considerably stretched due to the steric overcrowding of the side chains.(M. Wintermantel et al., Macromolecules 1996, 29,978.) Irrespective of the chemical nature of the macromonomer (styrene, methylmethacrylate, vinylpyridine, propylene) the chain stiffness in terms of the Kuhn statistical segment length lk lies in the range of 50 nm < lk < 200 nm. In accordance to the high degree of stiffness polymacromonomers form lyotropic liquid crystalline phases in solution and in the bulk.(M. Wintermantel et. al, Angew. Chemie 1995, 107, 1606.) Upon drying a dilute solution on mica or silicon wafer ordered monolayers are formed.(S.S. Sheiko et al., Langmuir 1997, 13, 5368.)^, (P. Dziezok et al., Angew. Chemie 1997, 00, 000.) Recently, stable monolayers of polyvinylpyridine macromonomers were successfully prepared on a Langmuir-Blodgett trough. Up to 15 monolayers were transferred onto a planar silicon wafer and characterized by x-ray reflection. The individual brush molecules within the monolayer could be visualized by atomic force microscopy. Frequently occurring hairpin formations by one molecule could not yet be explained. AFM on isolated, single molecules, however, have confirmed the cylindrical structure of polymacromonomers.

  18. Molecular layer-by-layer self-assembly and mercury sensing characteristics of novel brush polymers bearing thymine moieties.

    PubMed

    Jung, Jungwoon; Kim, Jin Chul; Rho, Yecheol; Kim, Mihee; Kwon, Wonsang; Kim, Heesoo; Ree, Moonhor

    2011-07-01

    Two new brush polyoxyethylenes bearing thymine moieties at the bristle ends have been synthesized as model polymers in which the chemical loading of the thymine functional group into the polymer is maximized: poly(oxy(11-thyminoacetyloxyundecylthiomethyl)ethylene) (PECH(S)-T) and poly(oxy(11-thyminoacetyloxyundecylsulfonylmethyl)ethylene) (PECH(SO(2))-T). These brush polymers are thermally stable up to around 225 °C, and their glass transitions occur in the range 23-27 °C, but they have significantly different properties despite the similarity of their chemical structures. In particular, PECH(SO(2))-T films exhibit better performance in sensing mercury ions than PECH(S)-T films. These differences were found to originate in the differences between their morphological structures. The PECH(SO(2))-T film has a multi-bilayer structure without interdigitation, in which the layers stack along the out-of-plane of the film and provide a thymine-rich surface. In contrast, the PECH(S)-T film is amorphous with a relatively low population of thymine moieties at the surface. This study demonstrated that a thymine-rich surface is required for recyclable thymine-based polymers to provide highly improved sensitivity and selectivity as well as full reversibility in the sensing of mercury ions. A thymine-rich surface can be achieved with a brush polymer bearing thymine moieties that can self-assemble into a multi-bilayer structure. Because of the thymine-rich surface, the PECH(SO(2))-T thin films even in only 6 nm thickness demonstrate the detection of mercury ions in aqueous solutions with a detection limit of 10(-6) M. PMID:21650219

  19. Molecular separations with breathing metal-organic frameworks: modelling packed bed adsorbers.

    PubMed

    Van Assche, Tom R C; Baron, Gino V; Denayer, Joeri F M

    2016-03-14

    Various metal-organic framework (MOFs) adsorbents show peculiar adsorption behaviour as they can adopt different crystal phases, each phase with its own adsorption characteristics. Besides external stimuli such as temperature or light, different species of guest adsorbate can trigger a transition (breathing) of the host structure at a different pressure. Such phase transitions also occur during dynamic separations on a packed bed of adsorbent, where the concentrations of the adsorbates vary throughout axial column distance and time. This work presents a general strategy to model the adsorption behavior of such phase changing adsorbents during column separations and focuses on remarkable model predictions for pure components and binary mixtures in diluted and non-diluted conditions. During binary breakthrough experiments, the behaviour of flexible adsorbents is quite complex. A succession of complete or even partial phase transformations (resulting in phase coexistence) can occur during the adsorption process. A variety of unusual breakthrough profiles is observed for diluted binary mixtures. Simulations reveal at least five types of breakthrough profiles to emerge. The occurrence of these cases can be rationalized by the hodograph technique, combined with the phase diagram of the adsorbent. The remarkable experimental breakthrough profiles observed for ortho-xylene/ethylbenzene (diluted) and CO2/CH4 (non-diluted) separation on the flexible MIL-53 framework can be rationalized by application of the proposed model strategy. PMID:26885972

  20. Polymer composite adsorbents using particles of molecularly imprinted polymers or aluminium oxide nanoparticles for treatment of arsenic contaminated waters.

    PubMed

    Önnby, L; Pakade, V; Mattiasson, B; Kirsebom, H

    2012-09-01

    Removal of As(V) by adsorption from water solutions was studied using three different synthetic adsorbents. The adsorbents, (a) aluminium nanoparticles (Alu-NPs, <50 nm) incorporated in amine rich cryogels (Alu-cryo), (b) molecular imprinted polymers (<38 μm) in polyacrylamide cryogels (MIP-cryo) and (c) thiol functionalised cryogels (SH-cryo) were evaluated regarding material characteristics and arsenic removal in batch test and continuous mode. Results revealed that a composite design with particles incorporated in cryogels was a successful means for applying small particles (nano- and micro- scale) in water solutions with maintained adsorption capacity and kinetics. Low capacity was obtained from SH-cryo and this adsorbent was hence excluded from the study. The adsorption capacities for the composites were 20.3 ± 0.8 mg/g adsorbent (Alu-cryo) and 7.9 ± 0.7 mg/g adsorbent (MIP-cryo) respectively. From SEM images it was seen that particles were homogeneously distributed in Alu-cryo and heterogeneously distributed in MIP-cryo. The particle incorporation increased the mechanical stability and the polymer backbones of pure polyacrylamide (MIP-cryo) were of better stability than the amine containing polymer backbone (Alu-cryo). Both composites worked well in the studied pH range of pH 2-8. Adsorption tested in real wastewater spiked with arsenic showed that co-ions (nitrate, sulphate and phosphate) affected arsenic removal for Alu-cryo more than for MIP-cryo. Both composites still adsorbed well in the presence of counter-ions (copper and zinc) present at low concentrations (μg/l). The unchanged and selective adsorption in realistic water observed for MIP-cryo was concluded to be due to a successful imprinting, here controlled using a non-imprinted polymer (NIP). A development of MIP-cryo is needed, considering its low adsorption capacity.

  1. Lubrication and load-bearing properties of human salivary pellicles adsorbed ex vivo on molecularly smooth substrata.

    PubMed

    Harvey, Neale M; Yakubov, Gleb E; Stokes, Jason R; Klein, Jacob

    2012-01-01

    In a series of Surface Force Balance experiments, material from human whole saliva was adsorbed to molecularly smooth mica substrata (to form an 'adsorbed salivary film'). Measurements were taken of normal (load bearing, F (n)) and shear (frictional, F (s)*) forces between two interacting surfaces. One investigation involved a salivary film formed by overnight adsorption from undiluted, centrifuged saliva, with the adsorbed film rinsed with pure water before measurement. Measurements were taken under pure water and 70 mM NaNO(3). In a second investigation, a film was formed from and measured under a solution of 7% filtered saliva in 10 mM NaNO(3). F (n) results for both systems showed purely repulsive layers, with an uncompressed thickness of 35-70 nm for the diluted saliva investigation and, prior to the application of shear, 11 nm for the rinsed system. F (s)* was essentially proportional to F (n) for all systems and independent of shear speed (in the range 100-2000 nm s(-1)), with coefficients of friction μ ≈ 0.24 and μ ≈ 0.46 for the unrinsed and rinsed systems, respectively. All properties of the rinsed system remained similar when the pure water measurement environment was changed to 70 mM NaNO(3). For all systems studied, shear gave rise to an approximately threefold increase in the range of normal forces, attributed to the ploughing up of adsorbed material during shear to form debris that stood proud of the adsorbed layer. The results provide a microscopic demonstration of the wear process for a salivary film under shear and may be of particular interest for understanding the implications for in vivo oral lubrication under conditions such as rinsing of the mouth cavity. The work is interpreted in light of earlier studies that showed a structural collapse and increase in friction for an adsorbed salivary film in an environment of low ionic strength.

  2. Molecular dynamics study of n-alcohols adsorbed on an aqueous electrolyte solution

    NASA Astrophysics Data System (ADS)

    Daiguji, Hirofumi

    2001-07-01

    The distribution of normal alcohol (n-alcohol) on water and the effect of salt on the structural and dynamical properties of n-alcohol on aqueous electrolyte solutions were investigated using molecular dynamics simulation. The stability of the alcohol distribution was studied for three types of n-alcohol (n-propanol, C3H7OH; n-heptanol, C7H15OH; and n-undecanol, C11H23OH), four or five concentrations of alcohol, and three concentrations of salt. The simulation results reveal the following. The distribution of n-propanol on water is homogeneous at all n-alcohol concentrations studied here and the distribution of n-heptanol and n-undecanol on water is heterogeneous. The n-alcohol concentration at which fluctuations in the alcohol distribution begin to increase depends on the length of the hydrocarbon chain of the n-alcohol. Salt concentration affects the surface excess concentration of n-alcohol and the stability of the adsorbed layer of n-alcohol. The degree of each effect depends on the length of the hydrocarbon chain of the n-alcohol. For n-undecanol, the surface structure of n-alcohol is independent of salt concentration because interaction between the hydrocarbon chains is sufficiently strong. In absorption refrigeration technology, to enhance the absorption rate of water vapor into a highly concentrated aqueous electrolyte solution, a small amount of alcohols is added to the aqueous electrolyte solution, which induces cellular convection referred to as Marangoni instability. Among the three types of n-alcohol studied here, only n-heptanol induces strong cellular convection. The simulations reveal two required conditions for Marangoni instability: generation of fluctuations in the alcohol distribution on water, and strong correlation between the structural and dynamical properties and salt concentration. Among the three types of n-alcohol studied here, based on the simulations, only n-heptanol satisfies both conditions.

  3. Nonequilibrium Molecular Dynamics Simulations of Organic Friction Modifiers Adsorbed on Iron Oxide Surfaces.

    PubMed

    Ewen, James P; Gattinoni, Chiara; Morgan, Neal; Spikes, Hugh A; Dini, Daniele

    2016-05-10

    For the successful development and application of lubricants, a full understanding of the nanoscale behavior of complex tribological systems is required, but this is difficult to obtain experimentally. In this study, we use nonequilibrium molecular dynamics (NEMD) simulations to examine the atomistic structure and friction properties of commercially relevant organic friction modifier (OFM) monolayers adsorbed on iron oxide surfaces and lubricated by a thin, separating layer of hexadecane. Specifically, acid, amide, and glyceride OFMs, with saturated and Z-unsaturated hydrocarbon tail groups, are simulated at various surface coverages and sliding velocities. At low and medium coverage, the OFMs form liquidlike and amorphous monolayers, respectively, which are significantly interdigitated with the hexadecane lubricant, resulting in relatively high friction coefficients. At high coverage, solidlike monolayers are formed for all of the OFMs, which, during sliding, results in slip planes between well-defined OFM and hexadecane layers, yielding a marked reduction in the friction coefficient. When present at equal surface coverage, OFMs with saturated and Z-unsaturated tail groups are found to yield similar structure and friction behavior. OFMs with glyceride head groups yield significantly lower friction coefficients than amide and particularly carboxylic acid head groups. For all of the OFMs and coverages simulated, the friction coefficient is found to increase linearly with the logarithm of sliding velocity; however, the gradient of this increase depends on the coverage. The structure and friction details obtained from these simulations agree well with experimental results and also shed light on the relative tribological performance of these OFMs through nanoscale structural variations. This has important implications in terms of the applicability of NEMD to aid the development of new formulations to control friction.

  4. Brushing your infant's teeth

    MedlinePlus

    ... gov/ency/patientinstructions/000769.htm Brushing Your Child’s Teeth To use the sharing features on this page, ... how to brush their teeth on their own. Tooth and Gum Care for Young Children You should ...

  5. Adsorbed Proteins Influence the Biological Activity and Molecular Targeting of Nanomaterials

    SciTech Connect

    Dutta, Debamitra; Sundaram, S. K.; Teeguarden, Justin G.; Riley, Brian J.; Fifield, Leonard S.; Jacobs, Jon M.; Addleman, Raymond S.; Kaysen, George A.; Moudgil, Brij M.; Weber, Thomas J.

    2007-11-01

    The possible combination of unique physicochemical properties operating at unique sites of action within cells and tissues has led to considerable uncertainty surrounding nanomaterial toxic potential. Here we have investigated the relative importance of proteins adsorbed onto nanomaterial surfaces in guiding uptake and toxicity to determine whether a priori identification of adsorbed proteins will contribute to nanomaterial toxicity assessment. Albumin was identified as the major protein adsorbed onto single walled carbon nanotubes (SWCNTs) following incubation with fetal bovine or human serum/plasma, but not when plasma from the Nagase Analbuminemic Rat (NAR) was used, and precoating SWCNTs with a non-ionic surfactant (Pluronic F127) inhibited albumin adsorption. Damaged or structurally altered albumin is rapidly cleared by scavenger receptors. In the RAW 264.7 macrophage-like model, we observed that SWCNTs inhibited the induction of cyclooxygenase-2 (Cox-2) by lipopolysaccharide (LPS; 1 ng/ml, 6 hr) and this anti-inflammatory response was inhibited by fucoidan (scavenger receptor antagonist) and by precoating SWCNTs with Pluronic F127. Fucoidan also reduced the uptake of fluorescent SWCNTs (Alexa647) in RAW 264.7 cells. Albumin-coated SWCNTs reduced LPS-mediated Cox-2 induction. SWCNTs did not appear to reduce binding of a fluorescent LPS (Alexa488) to RAW 264.7 cells. The profile of proteins adsorbed onto amorphous silica (50 – 1000 nm) was qualitatively different, relative to SWCNTs, and coating amorphous silica with Pluronic F127 dramatically reduced protein binding and toxicity. Collectively, these observations are consistent with an important role for adsorbed proteins in guiding nanomaterial disposition and toxicity.

  6. Molecular Structure and Equilibrium Forces of Bovine Submaxillary Mucin Adsorbed at a Solid-Liquid Interface.

    PubMed

    Zappone, Bruno; Patil, Navinkumar J; Madsen, Jan B; Pakkanen, Kirsi I; Lee, Seunghwan

    2015-04-21

    By combining dynamic light scattering, circular dichroism spectroscopy, atomic force microscopy, and surface force apparatus, the conformation of bovine submaxillary mucin in dilute solution and nanomechanical properties of mucin layers adsorbed on mica have been investigated. The samples were prepared by additional chromatographic purification of commercially available products. The mucin molecule was found to have a z-average hydrodynamic diameter of ca. 35 nm in phosphate buffered solution, without any particular secondary or tertiary structure. The contour length of the mucin is larger than, yet of the same order of magnitude as the diameter, indicating that the molecule can be modeled as a relatively rigid polymeric chain due to the large persistence length of the central glycosylated domain. Mucin molecules adsorbed abundantly onto mica from saline buffer, generating polymer-like, long-ranged, repulsive, and nonhysteretic forces upon compression of the adsorbed layers. Detailed analysis of such forces suggests that adsorbed mucins had an elongated conformation favored by the stiffness of the central domain. Acidification of aqueous media was chosen as means to reduce mucin-mucin and mucin-substrate electrostatic interactions. The hydrodynamic diameter in solution did not significantly change when the pH was lowered, showing that the large persistence length of the mucin molecule is due to steric hindrance between sugar chains, rather than electrostatic interactions. Remarkably, the force generated by an adsorbed layer with a fixed surface coverage also remained unaltered upon acidification. This observation can be linked to the surface-protective, pH-resistant role of bovine submaxillary mucin in the variable environmental conditions of the oral cavity. PMID:25806669

  7. MARS (Molecular Adsorbent Recirculating System): experience in 34 cases of acute liver failure.

    PubMed

    Novelli, Gilnardo; Rossi, Massimo; Pretagostini, Renzo; Poli, Luca; Novelli, Luigi; Berloco, Pasquale; Ferretti, Giancarlo; Iappelli, Massimo; Cortesini, Raffaello

    2002-01-01

    As reported in the literature, the mortality rates for patients with Acute Hepatic Failure (AHF) approaches 80% in cases in which liver transplantation is not possible. Post-transplant mortality mostly depends on the severity of the neurological condition at the time of the operation (20% in I-II degree coma patients and 44% in III degree coma patients). The primary indications for liver transplantation in AHF are Fulminant Hepatitis (FH)(93%), Subfulminant Hepatitis (5%) and other indications (2%). Other causes of AHF are Primary Non-Function (PNF) and Delayed Function (DF), which occur in 7-10%. Therefore it becomes necessary to monitor the patients with a Liver Support Device to be able to improve the clinical condition of the patients before liver transplantation (LT). In our experience we used the Molecular Adsorbent Recirculating System (MARS) (MARS Monitor; Teraklin AG, Rostock Germany), which enables the selective removal of albumin-bound substances accumulating in liver failure by the use of albumin-enriched dialysate. The system is used as a bridging device to orthotopic liver transplantation (OLT) of patients with FHF. We studied 34 patients, including 16 males and 18 females: 9 were affected by Primary-Non-Function (PNF), nine by Fulminant Hepatitis (FH), six by Delayed-Non-Function (DNF), and ten by Acute on Chronic Hepatic Failure (AOCHF). The average age of the patients was 41.8 years and the average number of applications was 6.4; the median length of application was about eight hours. The parameters that we monitored, before and after each treatment, were neurological status (EEG, cerebral CT, Glasgow Coma Score), haemodynamic parameters, acid base equilibrium, and blood gas analysis. We also monitored hepatic and renal function. In addition, the clinical conditions of the patients were monitored using kidney and liver ultrasound/ultrasonography (US). Inclusion criteria were bilirubin > 15 mg/dL, ammonia > 160 micro g/dL and a Glasgow Coma Score

  8. Removal of molecular adsorbates on gold nanoparticles using sodium borohydride in water.

    PubMed

    Ansar, Siyam M; Ameer, Fathima S; Hu, Wenfang; Zou, Shengli; Pittman, Charles U; Zhang, Dongmao

    2013-03-13

    The mechanism of sodium borohydride removal of organothiols from gold nanoparticles (AuNPs) was studied using an experimental investigation and computational modeling. Organothiols and other AuNP surface adsorbates such as thiophene, adenine, rhodamine, small anions (Br(-) and I(-)), and a polymer (PVP, poly(N-vinylpyrrolidone)) can all be rapidly and completely removed from the AuNP surfaces. A computational study showed that hydride derived from sodium borohydride has a higher binding affinity to AuNPs than organothiols. Thus, it can displace organothiols and all the other adsorbates tested from AuNPs. Sodium borohydride may be used as a hazard-free, general-purpose detergent that should find utility in a variety of AuNP applications including catalysis, biosensing, surface enhanced Raman spectroscopy, and AuNP recycle and reuse.

  9. Restoring effect of selenium on the molecular content, structure and fluidity of diabetic rat kidney brush border cell membrane.

    PubMed

    Gurbanov, Rafig; Bilgin, Mehmet; Severcan, Feride

    2016-04-01

    Diabetic kidney disease (DKD) is a dominant factor standing for kidney impairments during diabetes. In this study, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to disclose the diabetes-induced structural changes in the kidney and evaluate the effects of selenium on diabetes. The increase in the area of the olefinic band indicated increased amount of lipid peroxidation end products in diabetic kidney brush border cell membrane. Moreover, saturated lipid content of this cell membrane considerably diminished. DKD was found to disrupt lipid order and cause a decrease in membrane dynamics. However, the administration of selenium at low and medium doses was shown to improve these conditions by changing the lipid contents toward control values, restoring the ordered structure of the lipids and membrane dynamics. Curve-fitting and artificial neural network (ANN) analyses of secondary structures of proteins demonstrated a relative increase in α-helix and reduction in the β-sheet during diabetes in comparison to the control group, which were ameliorated following selenium treatment at low and medium doses. These findings were further confirmed by applying hierarchical cluster analysis (HCA) and principal component analysis (PCA). A clear separation of the experimental groups was obtained with high heterogeneity in the lipid and protein regions. These chemometric analyses showed that the low and medium doses of selenium-treated diabetic groups are successfully segregated from the diabetic group and clustered closer to the control. The study suggests that medium and, more predominantly, low-dose selenium treatment can be efficient in eliminating diabetes-induced structural alterations.

  10. Restoring effect of selenium on the molecular content, structure and fluidity of diabetic rat kidney brush border cell membrane.

    PubMed

    Gurbanov, Rafig; Bilgin, Mehmet; Severcan, Feride

    2016-04-01

    Diabetic kidney disease (DKD) is a dominant factor standing for kidney impairments during diabetes. In this study, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to disclose the diabetes-induced structural changes in the kidney and evaluate the effects of selenium on diabetes. The increase in the area of the olefinic band indicated increased amount of lipid peroxidation end products in diabetic kidney brush border cell membrane. Moreover, saturated lipid content of this cell membrane considerably diminished. DKD was found to disrupt lipid order and cause a decrease in membrane dynamics. However, the administration of selenium at low and medium doses was shown to improve these conditions by changing the lipid contents toward control values, restoring the ordered structure of the lipids and membrane dynamics. Curve-fitting and artificial neural network (ANN) analyses of secondary structures of proteins demonstrated a relative increase in α-helix and reduction in the β-sheet during diabetes in comparison to the control group, which were ameliorated following selenium treatment at low and medium doses. These findings were further confirmed by applying hierarchical cluster analysis (HCA) and principal component analysis (PCA). A clear separation of the experimental groups was obtained with high heterogeneity in the lipid and protein regions. These chemometric analyses showed that the low and medium doses of selenium-treated diabetic groups are successfully segregated from the diabetic group and clustered closer to the control. The study suggests that medium and, more predominantly, low-dose selenium treatment can be efficient in eliminating diabetes-induced structural alterations. PMID:26850735

  11. Ceramic brush seals development

    NASA Technical Reports Server (NTRS)

    Howe, Harold

    1994-01-01

    The following topics are discussed in this viewgraph presentation: ceramic brush seals, research and development, manufacturing, brazed assembly development, controlling braze flow, fiber selection, and braze results.

  12. Modeling adsorption: Investigating adsorbate and adsorbent properties

    NASA Astrophysics Data System (ADS)

    Webster, Charles Edwin

    1999-12-01

    Surface catalyzed reactions play a major role in current chemical production technology. Currently, 90% of all chemicals are produced by heterogeneously catalyzed reactions. Most of these catalyzed reactions involve adsorption, concentrating the substrate(s) (the adsorbate) on the surface of the solid (the adsorbent). Pore volumes, accessible surface areas, and the thermodynamics of adsorption are essential in the understanding of solid surface characteristics fundamental to catalyst and adsorbent screening and selection. Molecular properties such as molecular volumes and projected molecular areas are needed in order to convert moles adsorbed to surface volumes and areas. Generally, these molecular properties have been estimated from bulk properties, but many assumptions are required. As a result, different literature values are employed for these essential molecular properties. Calculated molar volumes and excluded molecular areas are determined and tabulated for a variety of molecules. Molecular dimensions of molecules are important in the understanding of molecular exclusion as well as size and shape selectivity, diffusion, and adsorbent selection. Molecular dimensions can also be used in the determination of the effective catalytic pore size of a catalyst. Adsorption isotherms, on zeolites, (crystalline mineral oxides) and amorphous solids, can be analyzed with the Multiple Equilibrium Analysis (MEA) description of adsorption. The MEA produces equilibrium constants (Ki), capacities (ni), and thermodynamic parameters (enthalpies, ΔHi, and entropies, ΔSi) of adsorption for each process. Pore volumes and accessible surface areas are calculated from the process capacities. Adsorption isotherms can also be predicted for existing and new adsorbate-adsorbent systems with the MEA. The results show that MEA has the potential of becoming a standard characterization method for microporous solids that will lead to an increased understanding of their behavior in gas

  13. Isocyanide ligands adsorbed on metal surfaces: applications in catalysis, nanochemistry, and molecular electronics.

    PubMed

    Angelici, Robert J; Lazar, Mihaela

    2008-10-20

    Knowledge of the coordination chemistry and reactivity of isocyanide ligands in transition-metal complexes forms the basis for understanding the adsorption and reactions of isocyanides on metal surfaces. In this overview, we explore reactions (often catalytic) of isocyanides adsorbed on metal surfaces that reflect their patterns of reactivity in metal complexes. We also examine applications of isocyanide adsorption to the stabilization of metal nanoparticles, the functionalization of metal electrodes, and the creation of conducting organic-metal junctions in molecule-scale electronic devices.

  14. Method for Controlling Electrical Properties of Single-Layer Graphene Nanoribbons via Adsorbed Planar Molecular Nanoparticles

    NASA Astrophysics Data System (ADS)

    Tanaka, Hirofumi; Arima, Ryo; Fukumori, Minoru; Tanaka, Daisuke; Negishi, Ryota; Kobayashi, Yoshihiro; Kasai, Seiya; Yamada, Toyo Kazu; Ogawa, Takuji

    2015-07-01

    A simple method for fabricating single-layer graphene nanoribbons (sGNRs) from double-walled carbon nanotubes (DWNTs) was developed. A sonication treatment was employed to unzip the DWNTs by inducing defects in them through annealing at 500 °C. The unzipped DWNTs yielded double-layered GNRs (dGNRs). Further sonication allowed each dGNR to be unpeeled into two sGNRs. Purification performed using a high-speed centrifuge ensured that more than 99% of the formed GNRs were sGNRs. The changes induced in the electrical properties of the obtained sGNR by the absorption of nanoparticles of planar molecule, naphthalenediimide (NDI), were investigated. The shape of the I-V curve of the sGNRs varied with the number of NDI nanoparticles adsorbed. This was suggestive of the existence of a band gap at the narrow-necked part near the NDI-adsorbing area of the sGNRs.

  15. Method for Controlling Electrical Properties of Single-Layer Graphene Nanoribbons via Adsorbed Planar Molecular Nanoparticles

    PubMed Central

    Tanaka, Hirofumi; Arima, Ryo; Fukumori, Minoru; Tanaka, Daisuke; Negishi, Ryota; Kobayashi, Yoshihiro; Kasai, Seiya; Yamada, Toyo Kazu; Ogawa, Takuji

    2015-01-01

    A simple method for fabricating single-layer graphene nanoribbons (sGNRs) from double-walled carbon nanotubes (DWNTs) was developed. A sonication treatment was employed to unzip the DWNTs by inducing defects in them through annealing at 500 °C. The unzipped DWNTs yielded double-layered GNRs (dGNRs). Further sonication allowed each dGNR to be unpeeled into two sGNRs. Purification performed using a high-speed centrifuge ensured that more than 99% of the formed GNRs were sGNRs. The changes induced in the electrical properties of the obtained sGNR by the absorption of nanoparticles of planar molecule, naphthalenediimide (NDI), were investigated. The shape of the I-V curve of the sGNRs varied with the number of NDI nanoparticles adsorbed. This was suggestive of the existence of a band gap at the narrow-necked part near the NDI-adsorbing area of the sGNRs. PMID:26205209

  16. Method for Controlling Electrical Properties of Single-Layer Graphene Nanoribbons via Adsorbed Planar Molecular Nanoparticles.

    PubMed

    Tanaka, Hirofumi; Arima, Ryo; Fukumori, Minoru; Tanaka, Daisuke; Negishi, Ryota; Kobayashi, Yoshihiro; Kasai, Seiya; Yamada, Toyo Kazu; Ogawa, Takuji

    2015-01-01

    A simple method for fabricating single-layer graphene nanoribbons (sGNRs) from double-walled carbon nanotubes (DWNTs) was developed. A sonication treatment was employed to unzip the DWNTs by inducing defects in them through annealing at 500 °C. The unzipped DWNTs yielded double-layered GNRs (dGNRs). Further sonication allowed each dGNR to be unpeeled into two sGNRs. Purification performed using a high-speed centrifuge ensured that more than 99% of the formed GNRs were sGNRs. The changes induced in the electrical properties of the obtained sGNR by the absorption of nanoparticles of planar molecule, naphthalenediimide (NDI), were investigated. The shape of the I-V curve of the sGNRs varied with the number of NDI nanoparticles adsorbed. This was suggestive of the existence of a band gap at the narrow-necked part near the NDI-adsorbing area of the sGNRs. PMID:26205209

  17. Influence of molecular structure and adsorbent properties on sorption of organic compounds to a temperature series of wood chars.

    PubMed

    Lattao, Charisma; Cao, Xiaoyan; Mao, Jingdong; Schmidt-Rohr, Klaus; Pignatello, Joseph J

    2014-05-01

    Chars from wildfires and soil amendments (biochars) are strong adsorbents that can impact the fate of organic compounds in soil, yet the effects of solute and adsorbent properties on sorption are poorly understood. We studied sorption of benzene, naphthalene, and 1,4-dinitrobenzene from water to a series of wood chars made anaerobically at different heat treatment temperatures (HTT) from 300 to 700 °C, and to graphite as a nonporous, unfunctionalized reference adsorbent. Peak suppression in the NMR spectrum by sorption of the paramagnetic relaxation probe TEMPO indicated that only a small fraction of char C atoms lie near sorption sites. Sorption intensity for all solutes maximized with the 500 °C char, but failed to trend regularly with N2 or CO2 surface area, micropore volume, mesopore volume, H/C ratio, O/C ratio, aromatic fused ring size, or HTT. A model relating sorption intensity to a weighted sum of microporosity and mesoporosity was more successful. Sorption isotherm linearity declined progressively with carbonization of the char. Application of a thermodynamic model incorporating solvent-water and char-graphite partition coefficients permitted for the first time quantification of steric (size exclusion in pores) and π-π electron donor-acceptor (EDA) free energy contributions, relative to benzene. Steric hindrance for naphthalene increases exponentially from 9 to 16 kJ/mol (∼ 1.6-2.9 log units of sorption coefficient) with the fraction of porosity in small micropores. π-π EDA interactions of dinitrobenzene contribute -17 to -19 kJ/mol (3-3.4 log units of sorption coefficient) to sorption on graphite, but less on chars. π-π EDA interaction of naphthalene on graphite is small (-2 to 2 kJ/mol). The results show that sorption is a complex function of char properties and solute molecular structure, and not very predictable on the basis of readily determined char properties.

  18. Influence of molecular structure and adsorbent properties on sorption of organic compounds to a temperature series of wood chars.

    PubMed

    Lattao, Charisma; Cao, Xiaoyan; Mao, Jingdong; Schmidt-Rohr, Klaus; Pignatello, Joseph J

    2014-05-01

    Chars from wildfires and soil amendments (biochars) are strong adsorbents that can impact the fate of organic compounds in soil, yet the effects of solute and adsorbent properties on sorption are poorly understood. We studied sorption of benzene, naphthalene, and 1,4-dinitrobenzene from water to a series of wood chars made anaerobically at different heat treatment temperatures (HTT) from 300 to 700 °C, and to graphite as a nonporous, unfunctionalized reference adsorbent. Peak suppression in the NMR spectrum by sorption of the paramagnetic relaxation probe TEMPO indicated that only a small fraction of char C atoms lie near sorption sites. Sorption intensity for all solutes maximized with the 500 °C char, but failed to trend regularly with N2 or CO2 surface area, micropore volume, mesopore volume, H/C ratio, O/C ratio, aromatic fused ring size, or HTT. A model relating sorption intensity to a weighted sum of microporosity and mesoporosity was more successful. Sorption isotherm linearity declined progressively with carbonization of the char. Application of a thermodynamic model incorporating solvent-water and char-graphite partition coefficients permitted for the first time quantification of steric (size exclusion in pores) and π-π electron donor-acceptor (EDA) free energy contributions, relative to benzene. Steric hindrance for naphthalene increases exponentially from 9 to 16 kJ/mol (∼ 1.6-2.9 log units of sorption coefficient) with the fraction of porosity in small micropores. π-π EDA interactions of dinitrobenzene contribute -17 to -19 kJ/mol (3-3.4 log units of sorption coefficient) to sorption on graphite, but less on chars. π-π EDA interaction of naphthalene on graphite is small (-2 to 2 kJ/mol). The results show that sorption is a complex function of char properties and solute molecular structure, and not very predictable on the basis of readily determined char properties. PMID:24758543

  19. Formation of Molecular Networks: Tailored Quantum Boxes and Behavior of Adsorbed CO in Them

    NASA Astrophysics Data System (ADS)

    Wyrick, Jon; Sun, Dezheng; Kim, Dae-Ho; Cheng, Zhihai; Lu, Wenhao; Zhu, Yeming; Luo, Miaomiao; Kim, Yong Su; Rotenberg, Eli; Kim, Kwangmoo; Einstein, T. L.; Bartels, Ludwig

    2011-03-01

    We show that the behavior of CO adsorbed into the pores of large regular networks on Cu(111) is significantly affected by their nano-scale lateral confinement and that formation of the networks themselves is directed by the Shockley surface state. Saturation coverages of CO are found to exhibit persistent dislocation lines; at lower coverages their mobility increases. Individual CO within the pores titrate the surface state, providing crucial information for understanding formation of the network as a result of optimization of the number N of electrons bound within each pore. Determination of N is based on quinone-coverage-dependent UPS data and an analysis of states of particles in a pore-shaped box (verified by CO's titration); a wide range of possible pore shapes and sizes has been considered. Work at UCR supported by NSF CHE 07-49949; at UMD by NSF CHE 07-50334 & UMD NSF-MRSEC DMR 05-20471.

  20. Molecular sieve adsorbents and membranes for applications in the production of renewable fuels and chemicals

    NASA Astrophysics Data System (ADS)

    Ranjan, Rajiv

    Metal organic frameworks (MOF), a new class of porous materials, have emerged as promising candidate for gas storage, separation membrane and chemical sensors. We used secondary growth method to grow microporous metal organic framework (MMOF) films on porous alumina supports. Examination of the film using SEM and XRD showed that the crystals were well inter-grown and preferentially oriented. Gas permeation study showed that membranes were defect free and moderate selectivity was achieved for H2/N2 gas pairs. The next project had to do with ethanol production from lignocellulosic biomass as an alternate energy source. However, toxic inhibitors produced from the hydrolysis of biomass decrease ethanol yield during the fermentation process. We demonstrated the use of zeolites for the pretreatment of hydrolyzate in order to remove inhibitors like 5-Hydroxymethylfurfuraldehyde (HMF) and furfural from aqueous solution. Zeolites exhibit preferential adsorption of the inhibitors and in effect improve the ethanol yield during fermentation. Ideal Adsorbed Solution Theory (IAST) was also used to predict adsorption isotherms for HMF-furfural mixtures using single component adsorption data. We also studied production of HMF, a potential substitute as a building block for plastic and chemical production, from renewable biomass resources. Catalytic dehydration of fructose for HMF production faces problems like low conversion and yield. Dimethyl sulfoxide (DMSO) can be used as the solvent as well as the catalyst resulting in high HMF yield. We studied a reaction-separation system for this dehydration reaction where the product (HMF) could be recovered by selective adsorption on solid adsorbents from the reaction mixture.

  1. Formation of gold nanoparticle assemblies in responsive polymer brushes

    NASA Astrophysics Data System (ADS)

    Christau, Stephanie; von Klitzing, Regine; Genzer, Jan

    2014-03-01

    The modification of surfaces by means of polymer brushes has become an active area of research during the past few years due to numerous potential applications of such systems in nano- and biotechnology. The structure and conformation of a brush depends on external stimuli such as pH, temperature or solvent type and can be manipulated by varying these attributes. This stimulus-response can be exploited for the development of smart surfaces and for sensor applications. Furthermore, brushes can be used as 3D matrices for immobilization of nanoparticles. In this study, responsive brushes are used as a matrix for the attachment of gold nanoparticles (AuNPs); this hybrid system exhibits intriguing optical properties due to the surface plasmon resonance of the AuNPs. We address the effect of some system parameters such as synthetic procedure, brush thickness, brush grafting density, particle size and particle incubation time on the characteristics of the resultant particle-impregnated brushes. We also discuss the spatial distribution of the AuNPs inside the brush with regard to the particle size, brush density and brush molecular weight.

  2. Albumin dialysis with molecular adsorbent recirculating system (MARS) for the treatment of hepatic encephalopathy in liver failure.

    PubMed

    Kobashi-Margáin, Ramón A; Gavilanes-Espinar, Juan G; Gutiérrez-Grobe, Ylse; Gutiérrez-Jiménez, Angel A; Chávez-Tapia, Norberto; Ponciano-Rodríguez, Guadalupe; Uribe, Misael; Méndez Sánchez, Nahum

    2011-06-01

    Acute, acute-on-chronic and chronic liver diseases are major health issues worldwide, and most cases end with the need for liver transplantation. Up to 90% of the patients die waiting for an organ to be transplanted. Hepatic encephalopathy is a common neuropsychiatric syndrome that usually accompanies liver failure and impacts greatly on the quality of life. The molecular adsorbent recirculating system (MARS) is a recently developed form of artificial liver support that functions on a base of albumin dialysis. It facilitates the dialysis of albumin-bound and water-soluble toxins, allowing the patient to survive and even improving some clinical features of liver failure. The following manuscript reviews the technical features of MARS operation and some of the clinical trials that analyze the efficacy of the system in the therapy of liver diseases.

  3. Surface-enhanced nonlinear optical effects and detection of adsorbed molecular monolayers

    SciTech Connect

    Shen, Y.R.; Chen, C.K.; Heinz, T.F.; Ricard, D.

    1981-01-01

    The observation of a number of surface-enhanced nonlinear optical effects is discussed. The feasibility of using second-harmonic generation to detect the adsorption of molecular monolayers on a metal surface in an electrolytic solution is shown.

  4. Anisotropic orientational motion of molecular adsorbates at the air-water interface

    SciTech Connect

    Zimdars, D.; Dadap, J.I.; Eisenthal, K.B.; Heinz, T.F.

    1999-04-29

    The ultrafast orientational motions of coumarin 314 (C314) adsorbed at the air/water interface were investigated by time-resolved surface second harmonic generation (TRSHG). The theory and method of using TRSHG to detect both out-of-plane and in-plane orientational motions are discussed. The interfacial solute motions were found to be anisotropic, with differing out-of-plane and in-plane reorientation time constants. This report presents the first direct observation of in-plane orientational motion of a molecule (C314) at the air/water interface using TRSHG. The in-plane reorientation time constant is 600 {+-} 40 ps. The out-of-plane reorientation time constant is 350 {+-} 20 ps. The out-of-plane orientational motion of C314 is similar to the previous results on rhodamine 6G at the air/water interface which indicated increased interfacial friction compared with bulk aqueous solution. The surface reorientation times are 2--3 times slower than the bulk isotropic orientational diffusion time.

  5. Almond brush module cutter

    SciTech Connect

    Zohns, M.A.; Jenkins, B.M.; Mehlschau, J.J.; Morrison, D.

    1983-06-01

    This paper addresses the design, construction, and evaluation of an almond brush module cutter. The module cutter is one link in a system which processes tree prunings for fuel and fiber. This system includes a modified cotton module builder, a module mover, the cutter, and a tub grinder. An economic analysis of the cutter is presented along with the problems involved in cutting brush modules.

  6. Degrafting of polymer brushes from substrates enables insight about the brush structure and facilitates surface patterning

    NASA Astrophysics Data System (ADS)

    Patil, Rohan; Turgman-Cohen, Salomon; Srogl, Jiri; Kiserow, Douglas; Genzer, Jan

    Polymers end-grafted to surfaces or interfaces, commonly referred to as polymer brushes, enable tailoring physico-chemical properties of material surfaces. Many applications of polymer brushes require information about the molecular weight (MW) and grafting density (GD) of polymer brushes. For brushes synthesized by surface initiated polymerization (SIP) determining these attributes was always a challenge. We have developed a simple method of measuring MW and GD of these systems by degrafting SIP from silica-based surfaces by using tetrabutyl ammonium fluoride (TBAF), which attacks selectively Si-O bonds and enables complete degrafting of poly(methyl methacrylate) (PMMA) brushes from silica based substrates without damaging the backbone. The rate of PMMA degrafting decreases with reaction time and depends on the concentration of TBAF, temperature, and the initial GD of the system. The molecular weight distribution of the degrafted PMMA was measured using size exclusion chromatography. The GD was calculated from known MW and dry thickness of the PMMA brush. Spatial patterns of degrafted regions on the substrate can be prepared by either localizing the TBAF to certain regions or by gradually immersing homogeneous samples into TBAF solution.

  7. Nuclear transport receptor binding avidity triggers a self-healing collapse transition in FG-nucleoporin molecular brushes

    PubMed Central

    Schoch, Rafael L.; Kapinos, Larisa E.; Lim, Roderick Y. H.

    2012-01-01

    Conformational changes at supramolecular interfaces are fundamentally coupled to binding activity, yet it remains a challenge to probe this relationship directly. Within the nuclear pore complex, this underlies how transport receptors known as karyopherins proceed through a tethered layer of intrinsically disordered nucleoporin domains containing Phe-Gly (FG)-rich repeats (FG domains) that otherwise hinder passive transport. Here, we use nonspecific proteins (i.e., BSA) as innate molecular probes to explore FG domain conformational changes by surface plasmon resonance. This mathematically diminishes the surface plasmon resonance refractive index constraint, thereby providing the means to acquire and correlate height changes in a surface-tethered FG domain layer to Kap binding affinities in situ with respect to their relative spatial arrangements. Stepwise measurements show that FG domain collapse is caused by karyopherin β1 (Kapβ1) binding at low concentrations, but this gradually transitions into a reextension at higher Kapβ1 concentrations. This ability to self-heal is intimately coupled to Kapβ1-FG binding avidity that promotes the maximal incorporation of Kapβ1 into the FG domain layer. Further increasing Kapβ1 to physiological concentrations leads to a “pileup” of Kapβ1 molecules that bind weakly to unoccupied FG repeats at the top of the layer. Therefore, binding avidity does not hinder fast transport per se. Revealing the biophysical basis underlying the form–function relationship of Kapβ1-FG domain behavior results in a convergent picture in which transport and mechanistic aspects of nuclear pore complex functionality are reconciled. PMID:23043112

  8. Molecular adsorbates on HOPG: Toward modulation of graphene density of states

    NASA Astrophysics Data System (ADS)

    Groce, Michelle; Einstein, Theodore; Cullen, William

    2013-03-01

    Ordered molecular superlattices, particularly those made of planar aromatics with their attendant pi orbitals, have the potential to break the graphene sublattice degeneracy and create a band gap. Trimesic acid (TMA) is a promising candidate due to its self-assembly into symmetry-breaking superlattices nearly commensurate with that of graphene. We have used the graphite (0001) surface as a model system to explore the impact of TMA thin films on band structure. By examining correlations between STM topography and STS maps of corresponding regions, we are able to investigate the effects of TMA on the local density of states. Work supported by the University of Maryland NSF-MRSEC, DMR 0520471 and Shared Experimental Facilities.

  9. Molecular recognition using corona phase complexes made of synthetic polymers adsorbed on carbon nanotubes.

    PubMed

    Zhang, Jingqing; Landry, Markita P; Barone, Paul W; Kim, Jong-Ho; Lin, Shangchao; Ulissi, Zachary W; Lin, Dahua; Mu, Bin; Boghossian, Ardemis A; Hilmer, Andrew J; Rwei, Alina; Hinckley, Allison C; Kruss, Sebastian; Shandell, Mia A; Nair, Nitish; Blake, Steven; Şen, Fatih; Şen, Selda; Croy, Robert G; Li, Deyu; Yum, Kyungsuk; Ahn, Jin-Ho; Jin, Hong; Heller, Daniel A; Essigmann, John M; Blankschtein, Daniel; Strano, Michael S

    2013-12-01

    Understanding molecular recognition is of fundamental importance in applications such as therapeutics, chemical catalysis and sensor design. The most common recognition motifs involve biological macromolecules such as antibodies and aptamers. The key to biorecognition consists of a unique three-dimensional structure formed by a folded and constrained bioheteropolymer that creates a binding pocket, or an interface, able to recognize a specific molecule. Here, we show that synthetic heteropolymers, once constrained onto a single-walled carbon nanotube by chemical adsorption, also form a new corona phase that exhibits highly selective recognition for specific molecules. To prove the generality of this phenomenon, we report three examples of heteropolymer-nanotube recognition complexes for riboflavin, L-thyroxine and oestradiol. In each case, the recognition was predicted using a two-dimensional thermodynamic model of surface interactions in which the dissociation constants can be tuned by perturbing the chemical structure of the heteropolymer. Moreover, these complexes can be used as new types of spatiotemporal sensors based on modulation of the carbon nanotube photoemission in the near-infrared, as we show by tracking riboflavin diffusion in murine macrophages.

  10. Molecular recognition using corona phase complexes made of synthetic polymers adsorbed on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhang, Jingqing; Landry, Markita P.; Barone, Paul W.; Kim, Jong-Ho; Lin, Shangchao; Ulissi, Zachary W.; Lin, Dahua; Mu, Bin; Boghossian, Ardemis A.; Hilmer, Andrew J.; Rwei, Alina; Hinckley, Allison C.; Kruss, Sebastian; Shandell, Mia A.; Nair, Nitish; Blake, Steven; Şen, Fatih; Şen, Selda; Croy, Robert G.; Li, Deyu; Yum, Kyungsuk; Ahn, Jin-Ho; Jin, Hong; Heller, Daniel A.; Essigmann, John M.; Blankschtein, Daniel; Strano, Michael S.

    2013-12-01

    Understanding molecular recognition is of fundamental importance in applications such as therapeutics, chemical catalysis and sensor design. The most common recognition motifs involve biological macromolecules such as antibodies and aptamers. The key to biorecognition consists of a unique three-dimensional structure formed by a folded and constrained bioheteropolymer that creates a binding pocket, or an interface, able to recognize a specific molecule. Here, we show that synthetic heteropolymers, once constrained onto a single-walled carbon nanotube by chemical adsorption, also form a new corona phase that exhibits highly selective recognition for specific molecules. To prove the generality of this phenomenon, we report three examples of heteropolymer-nanotube recognition complexes for riboflavin, L-thyroxine and oestradiol. In each case, the recognition was predicted using a two-dimensional thermodynamic model of surface interactions in which the dissociation constants can be tuned by perturbing the chemical structure of the heteropolymer. Moreover, these complexes can be used as new types of spatiotemporal sensors based on modulation of the carbon nanotube photoemission in the near-infrared, as we show by tracking riboflavin diffusion in murine macrophages.

  11. A molecular dynamics study on the transport of a charged biomolecule in a polymeric adsorbent medium and its adsorption onto a charged ligand.

    PubMed

    Riccardi, E; Wang, J-C; Liapis, A I

    2010-08-28

    The transport of a charged adsorbate biomolecule in a porous polymeric adsorbent medium and its adsorption onto the covalently immobilized ligands have been modeled and investigated using molecular dynamics modeling and simulations as the third part of a novel fundamental methodology developed for studying ion-exchange chromatography based bioseparations. To overcome computational challenges, a novel simulation approach is devised where appropriate atomistic and coarse grain models are employed simultaneously and the transport of the adsorbate is characterized through a number of locations representative of the progress of the transport process. The adsorbate biomolecule for the system studied in this work changes shape, orientation, and lateral position in order to proceed toward the site where adsorption occurs and exhibits decreased mass transport coefficients as it approaches closer to the immobilized ligand. Furthermore, because the ligands are surrounded by counterions carrying the same type of charge as the adsorbate biomolecule, it takes the biomolecule repeated attempts to approach toward a ligand in order to displace the counterions in the proximity of the ligand and to finally become adsorbed. The formed adsorbate-ligand complex interacts with the counterions and polymeric molecules and is found to evolve slowly and continuously from one-site (monovalent) interaction to multisite (multivalent) interactions. Such a transition of the nature of adsorption reduces the overall adsorption capacity of the ligands in the adsorbent medium and results in a type of surface exclusion effect. Also, the adsorption of the biomolecule also presents certain volume exclusion effects by not only directly reducing the pore volume and the availability of the ligands in the adjacent regions, but also causing the polymeric molecules to change to more compact structures that could further shield certain ligands from being accessible to subsequent adsorbate molecules. These

  12. A molecular dynamics study on the transport of a charged biomolecule in a polymeric adsorbent medium and its adsorption onto a charged ligand

    NASA Astrophysics Data System (ADS)

    Riccardi, E.; Wang, J.-C.; Liapis, A. I.

    2010-08-01

    The transport of a charged adsorbate biomolecule in a porous polymeric adsorbent medium and its adsorption onto the covalently immobilized ligands have been modeled and investigated using molecular dynamics modeling and simulations as the third part of a novel fundamental methodology developed for studying ion-exchange chromatography based bioseparations. To overcome computational challenges, a novel simulation approach is devised where appropriate atomistic and coarse grain models are employed simultaneously and the transport of the adsorbate is characterized through a number of locations representative of the progress of the transport process. The adsorbate biomolecule for the system studied in this work changes shape, orientation, and lateral position in order to proceed toward the site where adsorption occurs and exhibits decreased mass transport coefficients as it approaches closer to the immobilized ligand. Furthermore, because the ligands are surrounded by counterions carrying the same type of charge as the adsorbate biomolecule, it takes the biomolecule repeated attempts to approach toward a ligand in order to displace the counterions in the proximity of the ligand and to finally become adsorbed. The formed adsorbate-ligand complex interacts with the counterions and polymeric molecules and is found to evolve slowly and continuously from one-site (monovalent) interaction to multisite (multivalent) interactions. Such a transition of the nature of adsorption reduces the overall adsorption capacity of the ligands in the adsorbent medium and results in a type of surface exclusion effect. Also, the adsorption of the biomolecule also presents certain volume exclusion effects by not only directly reducing the pore volume and the availability of the ligands in the adjacent regions, but also causing the polymeric molecules to change to more compact structures that could further shield certain ligands from being accessible to subsequent adsorbate molecules. These

  13. David Adler Lectureship Award Talk: Friction and energy dissipation mechanisms in adsorbed molecules and molecularly thin films

    NASA Astrophysics Data System (ADS)

    Krim, Jacqueline

    2015-03-01

    Studies of the fundamental origins of friction have undergone rapid progress in recent years, with the development of new experimental and computational techniques for measuring and simulating friction at atomic length and time scales. The increased interest has sparked a variety of discussions and debates concerning the nature of the atomic-scale and quantum mechanisms that dominate the dissipative process by which mechanical energy is transformed into heat. Measurements of the sliding friction of physisorbed monolayers and bilayers can provide information on the relative contributions of these various dissipative mechanisms. Adsorbed films, whether intentionally applied or present as trace levels of physisorbed contaminants, moreover are ubiquitous at virtually all surfaces. As such, they impact a wide range of applications whose progress depends on precise control and/or knowledge of surface diffusion processes. Examples include nanoscale assembly, directed transport of Brownian particles, material flow through restricted geometries such as graphene membranes and molecular sieves, passivation and edge effects in carbon-based lubricants, and the stability of granular materials associated with frictional and frictionless contacts. Work supported by NSFDMR1310456.

  14. Chemical Potential of Triethylene Glycol Adsorbed on Surfaces Relevant to Gas Transport and Processing - Studies Using Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Kvamme, B.; Olsen, R.; Sjöblom, S.; Leirvik, K. N.; Kuznetsova, T.

    2014-12-01

    Natural gas will inevitably contain trace amounts of water and other impurities during different stages of processing and transport. Glycols, such as triethylene glycol (TEG), will in many cases follow the water. The glycol contents of the gas can originate from preceding glycol-drying units or it can be a residue from the direct injection of glycols used to prevent hydrate formation. Thus, it is important to know how glycol contents will affect the different paths leading to hydrate formation. Glycols may in some cases dominate the condensed water phase. If this occurs, it will lead to the well-documented shift in the hydrate stability curve, due to the altered activity of the water. A great deal of information on the molecular path of a glycol through the system can be obtained from calculating the chemical potential. Due to difficulties in measuring interfacial chemical potentials, these often need to be estimated using theoretical tools. We used molecular dynamics (MD) to study how TEG behaves in the vicinity of mineral surfaces such as calcite and hematite. Many methods exist for estimating chemical potentials based on MD trajectories. These include techniques such as free energy perturbation theory (FEP) and thermodynamic integration (TI). Such methods require sufficient sampling of configurations where free energy is to be estimated. Thus, it can be difficult to estimate chemical potentials on surfaces. There are several methods to circumvent this problem, such as blue moon sampling and umbrella sampling. These have been considered and the most important have been used to estimate chemical potentials of TEG adsorbed on the mineral surfaces. The resulting chemical potentials were compared to the chemical potential of TEG in bulk water, which was estimated using temperature thermodynamic integration.

  15. Adsorbent and adsorbent bed for materials capture and separation processes

    SciTech Connect

    Liu, Wei

    2011-01-25

    A method device and material for performing adsorption wherein a fluid mixture is passed through a channel in a structured adsorbent bed having a solid adsorbent comprised of adsorbent particles having a general diameter less than 100 um, loaded in a porous support matrix defining at least one straight flow channel. The adsorbent bed is configured to allow passage of a fluid through said channel and diffusion of a target material into said adsorbent under a pressure gradient driving force. The targeted molecular species in the fluid mixture diffuses across the porous support retaining layer, contacts the adsorbent, and adsorbs on the adsorbent, while the remaining species in the fluid mixture flows out of the channel.

  16. Detection of molecular oxygen adsorbate during room-temperature oxidation of Si(100)2 × 1 surface: In situ synchrotron radiation photoemission study

    NASA Astrophysics Data System (ADS)

    Yoshigoe, Akitaka; Yamada, Yoichi; Taga, Ryo; Ogawa, Shuichi; Takakuwa, Yuji

    2016-10-01

    Synchrotron radiation photoelectron spectroscopy during the oxidation of a Si(100)2 × 1 surface at room temperature revealed the existence of molecularly adsorbed oxygen, which was considered to be absent. The O 1s spectrum of such oxidation was found to be similar to that of Si(111)7 × 7 surface oxidation. Also, molecular oxygen appeared after the initial surface oxides were formed, indicating that it was not a precursor for dissociation oxygen adsorption on a clean surface. Considering this finding, we have proposed presumable structural models for atomic configurations, where molecular oxygen resided on the oxidized silicon with two oxygen atoms at the backbonds.

  17. Bidirectional Brush Seals

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Wilson, Jack; Wu, Tom; Flower, Ralph

    1997-01-01

    Presented is a study of the use of a set of I.D./O.D. bidirectional press seals to reduce the leakage losses in a wave rotor. Relative to the baseline configuration, data indicate the use of brush seals enhanced wave rotor efficiency from 36 to 45 percent at low leakages (small rotor endwall gap spacings) and from 15 to 33 percent at high leakages (larger endwall gap spacings). These brush seals are capable of sealing positive or negative pressure drops with respect to the axial direction. Surface tribology for these tests suggested little evidence of grooving although the bristles appeared polished.

  18. On-demand degrafting of polymer brushes prepared by controlled radical polymerization on flat silica substrates

    NASA Astrophysics Data System (ADS)

    Patil, Rohan; Srogl, Jiri; Kiserow, Douglas; Genzer, Jan

    2014-03-01

    Polymer brush degrafting refers to the removal of grafted polymer chains from the substrate without harming the polymer chemical structure. We grow poly(methyl methacrylate) (PMMA) brushes on flat silicon substrates using atom transfer radical polymerization (ATRP) and remove them from the surface by exposing the samples to tetrabutyl ammonium fluoride. We then analyze the polymer molecular weight of degrafted PMMA chains by size exclusion chromatography. The kinetics of PMMA brush degrafting exhibits double exponential behavior suggesting a transition from `brush' to `mushroom' regime. The dry brush thickness increases initially with increasing polymerization time. At longer reaction times, the thickness starts to plateau due to loss in the living nature of ATRP. We examine the relationship between the brush dry thickness and molecular weight and show that grafting density of the PMMA brush does not remain constant over the course of polymerization but reduces with time.

  19. Brush potential curve tracer

    DOEpatents

    Finch, Hilvan A.

    1987-01-01

    A device for analyzing commutating characteristics of a motor or generator includes a holder for supporting a plurality of probes adjacent a brush of the motor or generator. Measurements of electrical current characteristics in each of the probes provides information useful in analyzing operation of the machine. Methods for employing a device in accordance with the invention are also disclosed.

  20. Smart photonic carbon brush

    NASA Astrophysics Data System (ADS)

    Morozov, Oleg G.; Kuznetsov, Artem A.; Morozov, Gennady A.; Nureev, Ilnur I.; Sakhabutdinov, Airat Z.; Faskhutdinov, Lenar M.; Artemev, Vadim I.

    2016-03-01

    Aspects of the paper relate to a wear monitoring system for smart photonic carbon brush. There are many applications in which regular inspection is not feasible because of a number of factors including, for example, time, labor, cost and disruptions due to down time. Thus, there is a need for a system that can monitor the wear of a component while the component is in operation or without having to remove the component from its operational position. We propose a new smart photonic method for characterization of carbon brush wear. It is based on the usage of advantages of the multiplicative response of FBG and LPFG sensors and its double-frequency probing. Additional measuring parameters are the wear rate, the brush temperature, the engine rotation speed, the hangs control, and rotor speed. Sensor is embedded in brush. Firstly the change of sensor length is used to measure wear value and its central wavelength shift for temperature ones. The results of modeling and experiments are presented.

  1. A Brush-Creeper

    ERIC Educational Resources Information Center

    Mak, Se-yuen; Wong, Siu-ling

    2006-01-01

    In this note, we introduce a simple homemade toy called the brush-creeper, which can glide forward with no propellers, limbs, wheels, and seemingly no movement of any kind that can push forward against the ground. The toy arouses pupils' interest and their incentive to ask "Why?" in lessons related to friction.

  2. Brush potential curve tracer

    DOEpatents

    Finch, H.A.

    1985-06-21

    A device for analyzing commutating characteristics of a motor or generator includes a holder for supporting a plurality of probes adjacent a brush of the motor or generator. Measurements of electrical current characteristics of the probes provides information useful in analyzing operation of the machine. Methods for employing a device in accordance with the invention are also disclosed.

  3. Addition of Molecular Adsorbent Recirculating System (MARS®) Albumin Dialysis for the Preoperative Management of Jaundiced Patients with Hilar Cholangiocarcinoma

    PubMed Central

    Regimbeau, Jean-Marc; Fuks, David; Chapuis-Roux, Emilie; Yzet, Thierry; Cosse, Cyril; Bartoli, Eric; N'Guyen-Khac, Eric; Robert, Brice; Lobjoie, Eric

    2013-01-01

    The preoperative management of hilar cholangiocarcinoma (HC) with jaundice focuses on decreasing the total serum bilirubin level (SBL) by performing preoperative biliary drainage (PBD). However, it takes about 6–8 weeks for the SBL to fall at a sufficient extent. The objective of this preliminary study was to evaluate the impact of Molecular Adsorbent Recirculating System (MARS®) dialysis (in association with PBD) on SBL decrease. From January 2010 to January 2011, we prospectively selected all jaundiced patients admitted to our university hospital for resectable HC and requiring PBD prior to major hepatectomy. The PBD was followed by 3 sessions of MARS dialysis over a period of 72 h. A total of 10 patients with HC were screened and two of them were included (Bismuth-Corlette stage IIIa, gender ratio 1, median age 68 years). The initial SBL in the two patients was 328 and 242 μmol/l, respectively. After three MARS dialysis sessions, the SBL had fallen by 30 and 52%, respectively. After the end of each session, there was a SBL rebound of about 10 μmol/l. The MARS decreased the serum creatinine level, the platelet count and the prothrombin index, but did not modify the serum albumin level. Pruritus disappeared after one and two sessions, respectively. MARS-related morbidity included hypotension (n = 1), tachycardia (n = 1), thrombocytopenia (n = 2) and anaemia (n = 1). When combined with PBD, MARS dialysis appears to accelerate the decrease in SBL and thus may enable earlier surgery. This hypothesis must be validated in a larger study. PMID:24163652

  4. Computer Simulations of Bottle Brushes: From Melts to Soft Networks

    SciTech Connect

    Cao, Zhen; Carrillo, Jan-Michael Y.; Sheiko, Sergei S.; Dobrynin, Andrey V.

    2015-07-13

    We use a combination of Molecular dynamics simulations and analytical calculations, and study dens bottle-brush systems in a melt and network State. Analysis of our simulation results shows that bottle-brush macromolecules in melt behave as ideal chains with effective Kuhn length bK. Simulations show that the bottle-brush-induced bending rigidity is due to an entropy decrease caused by redistribution of the side chains upon backbone bending. The Kuhn length of the bottle:brushes increases with increasing the side-chain degree of polymerization nsc as bK proportional to nsc0.46. Moreover, this model of bottle brush macromolecules is extended to describe mechanical properties of bottle brush networks in linear and nonlinear deformation regimes. In the linear deformation regime, the network shear modulus scales with the degree of polymerization of the side chains as G0 proportional to (nsc + 1)-1 as long as the ratio of the Kuhn length, bK, to the size of the fully extended bottle-brush backbone between cross-links, R-max, is smaller than unity, bK/Rmax << 1. Bottle-brush networks With bK/Rmax proportional to 1 demonstrate behavior similar to that of networks Of semiflexible chains with G0 proportional to nsc-0.5. Finally, in the nonlinear network deformation regime, the deformation-dependent shear modulus is a universal function of the first strain invariant I1 and bottle-brush backbone deformation ratio beta describing stretching ability of the bottle-brush backbone between cross-links.

  5. Computer Simulations of Bottle Brushes: From Melts to Soft Networks

    DOE PAGES

    Cao, Zhen; Carrillo, Jan-Michael Y.; Sheiko, Sergei S.; Dobrynin, Andrey V.

    2015-07-13

    We use a combination of Molecular dynamics simulations and analytical calculations, and study dens bottle-brush systems in a melt and network State. Analysis of our simulation results shows that bottle-brush macromolecules in melt behave as ideal chains with effective Kuhn length bK. Simulations show that the bottle-brush-induced bending rigidity is due to an entropy decrease caused by redistribution of the side chains upon backbone bending. The Kuhn length of the bottle:brushes increases with increasing the side-chain degree of polymerization nsc as bK proportional to nsc0.46. Moreover, this model of bottle brush macromolecules is extended to describe mechanical properties of bottlemore » brush networks in linear and nonlinear deformation regimes. In the linear deformation regime, the network shear modulus scales with the degree of polymerization of the side chains as G0 proportional to (nsc + 1)-1 as long as the ratio of the Kuhn length, bK, to the size of the fully extended bottle-brush backbone between cross-links, R-max, is smaller than unity, bK/Rmax << 1. Bottle-brush networks With bK/Rmax proportional to 1 demonstrate behavior similar to that of networks Of semiflexible chains with G0 proportional to nsc-0.5. Finally, in the nonlinear network deformation regime, the deformation-dependent shear modulus is a universal function of the first strain invariant I1 and bottle-brush backbone deformation ratio beta describing stretching ability of the bottle-brush backbone between cross-links.« less

  6. Shedding light on azopolymer brush dynamics by fluorescence correlation spectroscopy.

    PubMed

    Kollarigowda, R H; De Santo, I; Rianna, C; Fedele, C; Manikas, A C; Cavalli, S; Netti, P A

    2016-09-14

    Understanding the response to illumination at a molecular level as well as characterising polymer brush dynamics are key features that guide the engineering of new light-stimuli responsive materials. Here, we report on the use of a confocal microscopy technique that was exploited to discern how a single molecular event such as the photoinduced isomerisation of azobenzene can affect an entire polymeric material at a macroscopic level leading to photodriven mass-migration. For this reason, a set of polymer brushes, containing azobenzene (Disperse Red 1, DR) on the side chains of poly(methacrylic acid), was synthesised and the influence of DR on the polymer brush dynamics was investigated for the first time by Fluorescence Correlation Spectroscopy (FCS). Briefly, two dynamics were observed, a short one coming from the isomerisation of DR and a long one related to the brush main chain. Interestingly, photoinduced polymer aggregation in the confocal volume was observed. PMID:27491890

  7. Modeling helical polymer brushes using self-consistent field theory (SCFT)

    NASA Astrophysics Data System (ADS)

    Mahalik, Jyoti; Sumpter, Bobby; Kumar, Rajeev

    We investigate structure of helical polymer brushes in terms of segment density distribution and local helical ordering using SCFT. A flexible chain model with vector potential was used to model liquid crystalline-like ordering in the brushes. The effects of surface grafting density, polymer molecular weight and the solvent quality on the brush structure were investigated. For densely grafted polymer brushes or the brushes made up of high molecular weight polymers, immersed in good quality solvent, stronger orientational ordering was found near the edge of the brushes (i.e., far from the grafting surface). Furthermore, an increase in the orientational ordering near the grafted end was found with decrease in solvent quality or decrease in molecular weight and decrease in surface grafting density. Computer Science and Mathematics Division, Oak Ridge National Laboratory.

  8. Wire brush fastening device

    DOEpatents

    Meigs, R.A.

    1995-09-19

    A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus. 13 figs.

  9. Wire brush fastening device

    DOEpatents

    Meigs, Richard A.

    1995-01-01

    A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus.

  10. Adsorbent phosphates

    NASA Technical Reports Server (NTRS)

    Watanabe, S.

    1983-01-01

    An adsorbent which uses as its primary ingredient phosphoric acid salts of zirconium or titanium is presented. Production methods are discussed and several examples are detailed. Measurements of separating characteristics of some gases using the salts are given.

  11. Molecular dynamics simulations of SDS, DTAB, and C12E8 monolayers adsorbed at the air/water surface in the presence of DSEP.

    PubMed

    Pang, Jinyu; Wang, Yajing; Xu, Guiying; Han, Tingting; Lv, Xin; Zhang, Jian

    2011-03-24

    The properties of adsorbed monolayers of three hydrocarbon surfactants with the same hydrophobic tail, sodium dodecyl sulfate (SDS), dodecyltrimethylammonium bromide (DTAB) and octaethylene glycol dodecyl ether (C(12)E(8)) at the air/water surface in the absence and presence of a dimethylsiloxane ethoxylate-propoxylate (DSEP) were studied via molecular dynamics simulations to compare the effect of the headgroups on the aggregation behaviors of surfactant mixtures. The structures and dynamical properties of the monolayers were greatly affected after adding DSEP. In the presence of DSEP, SDS monolayer was better ordered and more compact, whereas C(12)E(8) monolayer was relatively disordered. Some DTAB molecules immerged into water, and the others adsorbed at the surface were in less compact but well-ordered arrangement. The reason for the appearance of different types of monolayers was also discussed, with the goal of providing a theoretical approach for their further applications.

  12. In Situ Infrared Ellipsometry for Protein Adsorption Studies on Ultrathin Smart Polymer Brushes in Aqueous Environment

    SciTech Connect

    Kroning, Annika; Furchner, Andreas; Aulich, Dennis; Bittrich, Eva; Rauch, Sebastian; Uhlmann, Petra; Eichhorn, Klaus-Jochen; Seeber, Michael; Luzinov, Igor; Kilbey, S. Michael; Lokitz, Bradley S.; Minko, Sergiy; Hinrichs, Karsten

    2015-02-10

    The protein-adsorbing and -repelling properties of various smart nanometer-thin polymer brushes with high potential for biosensing and biomedical applications are studied by in-situ infrared-spectroscopic ellipsometry (IRSE). IRSE as a highly sensitive non-destructive technique allows us to investigate protein adsorption on polymer brushes in aqueous environment in dependence of external stimuli like temperature and pH. These stimuli are, for instance, relevant in switchable mixed brushes containing poly(N-isopropyl acrylamide) and poly(acrylic acid), respectively. We use such brushes as model surfaces for controlling protein adsorption of human serum albumin and human fibrinogen. IRSE can distinguish between polymer-specific vibrational bands, which yield insights into the hydration state of the brushes, and changes in the protein-specific amide bands, which are related to changes of the protein secondary structure.

  13. In Situ Infrared Ellipsometry for Protein Adsorption Studies on Ultrathin Smart Polymer Brushes in Aqueous Environment

    DOE PAGES

    Kroning, Annika; Furchner, Andreas; Aulich, Dennis; Bittrich, Eva; Rauch, Sebastian; Uhlmann, Petra; Eichhorn, Klaus-Jochen; Seeber, Michael; Luzinov, Igor; Kilbey, S. Michael; et al

    2015-02-10

    The protein-adsorbing and -repelling properties of various smart nanometer-thin polymer brushes with high potential for biosensing and biomedical applications are studied by in-situ infrared-spectroscopic ellipsometry (IRSE). IRSE as a highly sensitive non-destructive technique allows us to investigate protein adsorption on polymer brushes in aqueous environment in dependence of external stimuli like temperature and pH. These stimuli are, for instance, relevant in switchable mixed brushes containing poly(N-isopropyl acrylamide) and poly(acrylic acid), respectively. We use such brushes as model surfaces for controlling protein adsorption of human serum albumin and human fibrinogen. IRSE can distinguish between polymer-specific vibrational bands, which yield insights intomore » the hydration state of the brushes, and changes in the protein-specific amide bands, which are related to changes of the protein secondary structure.« less

  14. The structure, energetics, and nature of the chemical bonding of phenylthiol adsorbed on the Au(111) surface: implications for density-functional calculations of molecular-electronic conduction.

    PubMed

    Bilić, Ante; Reimers, Jeffrey R; Hush, Noel S

    2005-03-01

    The adsorption of phenylthiol on the Au(111) surface is modeled using Perdew and Wang density-functional calculations. Both direct molecular physisorption and dissociative chemisorption via S-H bond cleavage are considered as well as dimerization to form disulfides. For the major observed product, the chemisorbed thiol, an extensive potential-energy surface is produced as a function of both the azimuthal orientation of the adsorbate and the linear translation of the adsorbate through the key fcc, hcp, bridge, and top binding sites. Key structures are characterized, the lowest-energy one being a broad minimum of tilted orientation ranging from the bridge structure halfway towards the fcc one. The vertically oriented threefold binding sites, often assumed to dominate molecular electronics measurements, are identified as transition states at low coverage but become favored in dense monolayers. A similar surface is also produced for chemisorption of phenylthiol on Ag(111); this displays significant qualitative differences, consistent with the qualitatively different observed structures for thiol chemisorption on Ag and Au. Full contours of the minimum potential energy as a function of sulfur translation over the crystal face are described, from which the barrier to diffusion is deduced to be 5.8 kcal mol(-1), indicating that the potential-energy surface has low corrugation. The calculated bond lengths, adsorbate charge and spin density, and the density of electronic states all indicate that, at all sulfur locations, the adsorbate can be regarded as a thiyl species that forms a net single covalent bond to the surface of strength 31 kcal mol(-1). No detectable thiolate character is predicted, however, contrary to experimental results for alkyl thiols that indicate up to 20%-30% thiolate involvement. This effect is attributed to the asymptotic-potential error of all modern density functionals that becomes manifest through a 3-4 eV error in the lineup of the adsorbate and

  15. Counterion-mediated protein adsorption into polyelectrolyte brushes.

    PubMed

    He, Su-Zhen; Merlitz, Holger; Sommer, Jens-Uwe; Wu, Chen-Xu

    2015-09-01

    We present molecular dynamics simulations of the interaction of fullerene-like, inhomogeneously charged proteins with polyelectrolyte brushes. A motivation of this work is the experimental observation that proteins, carrying an integral charge, may enter like-charged polymer brushes. Simulations of varying charge distributions on the protein surfaces are performed to unravel the physical mechanism of the adsorption. Our results prove that an overall neutral protein can be strongly driven into polyelectrolyte brush whenever the protein features patches of positive and negative charge. The findings reported here give further evidence that the strong adsorption of proteins is also driven by entropic forces due to counterion release, since charged patches on the surface of the proteins can act as multivalent counterions of the oppositely charged polyelectrolyte chains. A corresponding number of mobile co- and counterions is released from the brush and the vicinity of the proteins so that the entropy of the total system increases. PMID:26385737

  16. Tension amplification in tethered layers of bottle-brush polymers

    DOE PAGES

    Leuty, Gary M.; Tsige, Mesfin; Grest, Gary S.; Rubinstein, Michael

    2016-02-26

    In this paper, molecular dynamics simulations of a coarse-grained bead–spring model have been used to study the effects of molecular crowding on the accumulation of tension in the backbone of bottle-brush polymers tethered to a flat substrate. The number of bottle-brushes per unit surface area, Σ, as well as the lengths of the bottle-brush backbones Nbb (50 ≤ Nbb ≤ 200) and side chains Nsc (50 ≤ Nsc ≤ 200) were varied to determine how the dimensions and degree of crowding of bottle-brushes give rise to bond tension amplification along the backbone, especially near the substrate. From these simulations, wemore » have identified three separate regimes of tension. For low Σ, the tension is due solely to intramolecular interactions and is dominated by the side chain repulsion that governs the lateral brush dimensions. With increasing Σ, the interactions between bottle-brush polymers induce compression of the side chains, transmitting increasing tension to the backbone. For large Σ, intermolecular side chain repulsion increases, forcing side chain extension and reorientation in the direction normal to the surface and transmitting considerable tension to the backbone.« less

  17. Distribution of Chains in Polymer Brushes Produced by a “Grafting From” Mechanism

    DOE PAGES

    Martinez, Andre P.; Carrillo, Jan-Michael Y.; Dobrynin, Andrey V.; Adamson, Douglas H.

    2016-01-11

    The molecular weight and polydispersity of the chains in a polymer brush are critical parameters determining the brush properties. However, the characterization of polymer brushes is hindered by the vanishingly small mass of polymer present in brush layers. In this study, in order to obtain sufficient quantities of polymer for analysis, polymer brushes were grown from high surface area fibrous nylon membranes by ATRP. We synthesized the brushes with varying surface initiator densities, polymerization times, and amounts of sacrificial initiator, then cleaved from the substrate, and analyzed by GPC and NMR. Characterization showed that the surface-grown polymer chains were moremore » polydisperse and had lower average molecular weight compared to solution-grown polymers synthesized concurrently. Furthermore, the molecular weight distribution of the polymer brushes was observed to be bimodal, with a low molecular weight population of chains representing a significant mass fraction of the polymer chains at high surface initiator densities. Moreover, the origin of this low MW polymer fraction is proposed to be the termination of growing chains by recombination during the early stages of polymerization, a mechanism confirmed by molecular dynamics simulations of brush polymerization.« less

  18. Computer simulations of the mechanical response of brushes on the surface of cancerous epithelial cells

    PubMed Central

    Goicochea, A. Gama; Guardado, S. J. Alas

    2015-01-01

    We report a model for atomic force microscopy by means of computer simulations of molecular brushes on surfaces of biological interest such as normal and cancerous cervical epithelial cells. Our model predicts that the force needed to produce a given indentation on brushes that can move on the surface of the cell (called “liquid” brushes) is the same as that required for brushes whose ends are fixed on the cell’s surface (called “solid” brushes), as long as the tip of the microscope covers the entire area of the brush. Additionally, we find that cancerous cells are softer than normal ones, in agreement with various experiments. Moreover, soft brushes are found to display larger resistance to compression than stiff ones. This phenomenon is the consequence of the larger equilibrium length of the soft brushes and the cooperative association of solvent molecules trapped within the brushes, which leads to an increase in the osmotic pressure. Our results show that a careful characterization of the brushes on epithelial cells is indispensable when determining the mechanical response of cancerous cells. PMID:26315877

  19. Computer simulations of the mechanical response of brushes on the surface of cancerous epithelial cells

    NASA Astrophysics Data System (ADS)

    Goicochea, A. Gama; Guardado, S. J. Alas

    2015-08-01

    We report a model for atomic force microscopy by means of computer simulations of molecular brushes on surfaces of biological interest such as normal and cancerous cervical epithelial cells. Our model predicts that the force needed to produce a given indentation on brushes that can move on the surface of the cell (called “liquid” brushes) is the same as that required for brushes whose ends are fixed on the cell’s surface (called “solid” brushes), as long as the tip of the microscope covers the entire area of the brush. Additionally, we find that cancerous cells are softer than normal ones, in agreement with various experiments. Moreover, soft brushes are found to display larger resistance to compression than stiff ones. This phenomenon is the consequence of the larger equilibrium length of the soft brushes and the cooperative association of solvent molecules trapped within the brushes, which leads to an increase in the osmotic pressure. Our results show that a careful characterization of the brushes on epithelial cells is indispensable when determining the mechanical response of cancerous cells.

  20. Glyoxal-Urea-Formaldehyde Molecularly Imprinted Resin as Pipette Tip Solid-Phase Extraction Adsorbent for Selective Screening of Organochlorine Pesticides in Spinach.

    PubMed

    Yang, Chen; Lv, Tianwei; Yan, Hongyuan; Wu, Gaochan; Li, Haonan

    2015-11-01

    A new kind of glyoxal-urea-formaldehyde molecularly imprinted resin (GUF-MIR) was synthesized by a glyoxal-urea-formaldehyde (GUF) gel imprinting method with 4,4'-dichlorobenzhydrol as a dummy template. The obtained GUF-MIR was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) and applied as a selective adsorbent of miniaturized pipet tip solid-phase extraction (PT-SPE) for the separation and extraction of three organochlorine pesticides (dicofol (DCF), dichlorodiphenyl dichloroethane (DDD), and tetradifon) in spinach samples. The proposed pretreatment procedures of spinach samples involved only 5.0 mg of GUF-MIR, 0.7 mL of MeOH-H2O (1:1, v/v) (washing solvent), and 0.6 mL of cyclohexane-ethyl acetate (9:1, v/v) (elution solvent). In comparison with other adsorbents (such as silica gel, C18, NH2-silica gel, and neutral alumina (Al2O3-N)), GUF-MIR showed higher adsorption and purification capacity for DCF, DDD, and tetradifon in aqueous solution. The average recoveries at three spiked levels ranged from 89.1% to 101.9% with relative standard deviations (RSDs) ≤ 7.1% (n = 3). The presented GUF-MIR-PT-SPE method combines the advantages of molecularly imprinted polymers (MIPs), GUF, and PT-SPE and can be used in polar solutions with high affinity and selectivity to the analytes in complex samples.

  1. Polymer absorption in dense polymer brushes vs. polymer adsorption on the brush-solvent interface

    NASA Astrophysics Data System (ADS)

    Milchev, Andrey; Binder, Kurt

    2014-06-01

    Molecular-dynamics simulations of a coarse-grained model of a dense brush of flexible polymers (of type A) interacting with a long flexible macromolecule (of type B) are presented, considering the case of an attractive AB interaction, while effective interactions between AA and BB pairs of monomers are repulsive. Varying the strength \\varepsilon_{AB} of the attraction between unlike monomers, an adsorption transition at some critical value \\varepsilon^c_{AB} is found, where the B-chain is bound to the brush-solvent interface, similar to the adsorption on a planar solid substrate. However, when \\varepsilon_{AB} is much higher than \\varepsilon^c_{AB} , the long macromolecule is gradually “sucked in” the brush, developing many pieces that are locally stretched in the z-direction perpendicular to the substrate, in order to fit between the brush chains. The resulting hairpin-like structures of the absorbed chain shows up via oscillatory decay of the bond vector autocorrelation function. Chain relaxation is only possible via reptation.

  2. Stereoregular polyacrylamide and its copolymer brushes: Preparation and surface characters

    NASA Astrophysics Data System (ADS)

    Jiang, Jianguo; Wang, Xiaoshu; Lu, Xiaoyan; Lu, Yun

    2008-12-01

    Two kinds of polymer brushes, the single one with stereospecific polyacrylamide (PAAM) chains and the dual-component one with random poly(methyl methacrylate) (PMMA) segments grafting from stereospecific PAAM chains, were prepared on silicon wafer for the first time by combining the immobilization of initiator and the stereospecific living radical in situ polymerization. With the addition of the Lewis acid AlCl 3 into the polymerization system, the PAAM brushes obtained exhibited an increased stereospecificity as well as a decreased hydrophilicity, which might attribute to the reduced thickness of PAAM brushes on the silicon wafer and the handicap of the free rotation of the stereospecific molecular chain. The smoother surface morphology of the stereospecific PAAM brushes shown in AFM images was in good agreement with the experimental data of water contact angle. Also, block amphiphilic copolymer brushes were prepared with the stereospecific PAAM formed first on silicon wafer as the anchored-initiator and revealed a novel surface self-assembly behavior after being treated with different solvent such as toluene or water. The stereospecificity of PAAM chains in the polymer brushes could be modulated by adjusting reaction conditions according to the requirement of applications for surface hydrophilicity.

  3. Examination of the molecular mechanism of SH reagent-induced inhibition of the intestinal brush-border membrane Na+/phosphate cotransporter.

    PubMed

    Peerce, B E; Cedilote, M; Clarke, R D

    1995-10-01

    SH residues on the rabbit intestinal brush-border membrane Na+/phosphate cotransporter were examined using a variety of SH specific reagents, proteolytic digestion and HPLC separation of SH-labeled cotransporter, and partial reaction assays. Of the seven SH-containing peptide fragments on the non-denatured non-reduced cotransporter six peptides were labeled: five SH-containing peptides were labeled with acrylodan or IAF (iodoacetamidofluorescein) and three peptides were labeled with IAEDANS. One SH-containing peptide was labeled with IAEDANS or fluorescein maleimide only. Selective SH labeling conditions employing acrylodan and IAEDANS were used to identify the environments of these SH-containing peptides in the native cotransporter. The nature of SH reagent-induced inhibition of Na(+)-dependent phosphate uptake was examined using substrate-induced conformational changes, and substrate-induced changes in IAEDANS and acrylodan fluorescence of the SH-labeled Na+/phosphate cotransporter. The results indicate that five of the SH-labeled peptides sense the Na(+)-induced conformational change, three peptides sense the Na++ difluorophosphate-induced conformational change, and one peptide senses only the Na++ monofluorophosphate-induced conformational change. Five of the SH-labeled peptides are passive participants in the substrate-induced conformational changes with only SH 51 involved in cotransporter function. Alkylation of SH 51 resulted in a cotransporter conformation which differed from the substrate-mediated conformations and was characterized by increased monofluorophosphate sensitivity.

  4. 'King George Island' Brushed

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Annotated Version

    This mosaic was made from frames acquired by the microscopic imager on NASA's Mars Exploration Rover Spirit during Spirit's 1,031 Martian day, or sol, on the red planet (Nov. 27, 2006). It shows a rock target called 'King George Island' after the target was brushed by the rover's rock abrasion tool. The mosaic covers approximately 6 centimeters (2.4 inches) across and shows the granular nature of the rock exposure. The grains are typically about 1 millimeter (.04 inches) wide. Data from the rover's Moessbauer spectrometer provides evidence that they have an enhanced amount of the mineral hematite relative to surrounding soils.

  5. Acid effect on excited Auramine-O molecular rotor relaxations in solution and adsorbed on insulin fibrils

    NASA Astrophysics Data System (ADS)

    Simkovitch, R.; Akulov, K.; Erez, Y.; Amdursky, N.; Gepshtein, R.; Schwartz, T.; Huppert, D.

    2015-09-01

    Steady-state and time-resolved UV-Vis spectroscopy techniques were employed to study the non-radiative process of Auramine-O (AuO). We focused our attention on the ultrafast nonradiative decay of Auramine-O in water and on the acid effect on Auramine-O spectroscopy. We found that weak acids like formic acid shorten the excited-state decay times of both the emission and the transient pump-probe spectra of Auramine-O. We found three time domains in the relaxation of the excited states back to the ground state. In mixtures of acetic and formic acids, the three decay times associated with the relaxation process are shorter in the presence of formic acid in Auramine-O solutions. We qualitatively explain the very large non-radiative rate in water and in formic-acetic acid mixtures by a protic nonradiative model proposed by Sobolewski and Domcke. The steady-state emission spectrum of AuO adsorbed on insulin fibrils consists of two bands assigned to protonated and deprotonated forms and the emission intensity increases by three orders of magnitude. We conclude that the nonradiative process prevails in the liquid state, whereas when AuO is adsorbed on fibrils the nonradiative rate is reduced by three orders of magnitude and thus enables a slow ESPT process to occur.

  6. Transcription rates in DNA brushes.

    PubMed

    Yamamoto, Tetsuya; Safran, S A

    2015-04-21

    We theoretically predict the rate of transcription (TX) in DNA brushes by introducing the concept of TX dipoles that takes into account the unidirectional motion of enzymes (RNAP) along DNA during transcription as correlated pairs of sources and sinks in the relevant diffusion equation. Our theory predicts that the TX rates dramatically change upon the inversion of the orientation of the TX dipoles relative to the substrate because TX dipoles modulate the concentrations of RNAP in the solution. Comparing our theory with experiments suggests that, in some cases, DNA chain segments are relatively uniformly distributed in the brush, in contrast to the parabolic profile expected for flexible polymer brushes.

  7. Current developments in brush seals

    NASA Astrophysics Data System (ADS)

    Loewenthal, Bob

    1994-07-01

    The objective of the brush seal development program is to develop a comprehensive design methodology for brush seals using application requirements from engine manufacturers and experimental characterization of seal design and tribological pairs. The goals are to substantially lower leakage compared to labyrinth seals, seal life consistent with man-rated mission requirements, to investigate single and multiple staged brush seals, temperature up to 1200 F and surface speed up to 900 fps, and pressure drop across the seal of 50 psid. Test results are presented in viewgraph format.

  8. Precise control of surface electrostatic forces on polymer brush layers with opposite charges for resistance to protein adsorption.

    PubMed

    Sakata, Sho; Inoue, Yuuki; Ishihara, Kazuhiko

    2016-10-01

    Various molecular interaction forces are generated during protein adsorption process on material surfaces. Thus, it is necessary to control them to suppress protein adsorption and the subsequent cell and tissue responses. A series of binary copolymer brush layers were prepared via surface-initiated atom transfer radical polymerization, by mixing the cationic monomer unit and anionic monomer unit randomly in various ratios. Surface characterization revealed that the constructed copolymer brush layers exhibited an uniform super-hydrophilic nature and different surface potentials. The strength of the electrostatic interaction forces operating on these mixed-charge copolymer brush surfaces was evaluated quantitatively using force-versus-distance (f-d) curve measurements by atomic force microscopy (AFM) and probes modified by negatively charged carboxyl groups or positively charged amino groups. The electrostatic interaction forces were determined based on the charge ratios of the copolymer brush layers. Notably, the surface containing equivalent cationic/anionic monomer units hardly interacted with both the charged groups. Furthermore, the protein adsorption force and the protein adsorption mass on these surfaces were examined by AFM f-d curve measurement and surface plasmon resonance measurement, respectively. To clarify the influence of the electrostatic interaction on the protein adsorption behavior on the surface, three kinds of proteins having negative, positive, and relatively neutral net charges under physiological conditions were used in this study. We quantitatively demonstrated that the amount of adsorbed proteins on the surfaces would have a strong correlation with the strength of surface-protein interaction forces, and that the strength of surface-protein interaction forces would be determined from the combination between the properties of the electrostatic interaction forces on the surfaces and the charge properties of the proteins. Especially, the

  9. Molecular orientation of molybdate ions adsorbed on goethite nanoparticles revealed by polarized in situ ATR-IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Davantès, Athénaïs; Lefèvre, Grégory

    2016-11-01

    The speciation of species adsorbed on nanoparticles is a major concern for several fields, as environmental pollution and remediation, surface functionalization, or catalysis. Attenuated total reflectance infrared spectroscopy (ATR-IR) was amongst the rare methods able to give in situ information about the geometry of surface complexes on nanoparticles. A new possibility using this technique is illustrated here with the MoO42 -/goethite system. Using deuterated goethite to avoid spectral interferences, adsorption of molybdate ions on a spontaneous oriented film of nanoparticles has been followed using a polarized infrared beam. From the decomposition of spectra in the x, y and z directions, a monodentate surface complex on the {101} faces has been found as the most probable geometry. This result demonstrates that polarized ATR-IR allows to characterize in more details adsorption mode at the atomic scale, in comparison with usual ATR-IR spectroscopy.

  10. On the widths of Stokes lines in Raman scattering from molecules adsorbed at metal surfaces and in molecular conduction junctions

    NASA Astrophysics Data System (ADS)

    Gao, Yi; Galperin, Michael; Nitzan, Abraham

    2016-06-01

    Within a generic model we analyze the Stokes linewidth in surface enhanced Raman scattering (SERS) from molecules embedded as bridges in molecular junctions. We identify four main contributions to the off-resonant Stokes signal and show that under zero voltage bias (a situation pertaining also to standard SERS experiments) and at low bias junctions only one of these contributions is pronounced. The linewidth of this component is determined by the molecular vibrational relaxation rate, which is dominated by interactions with the essentially bosonic thermal environment when the relevant molecular electronic energy is far from the metal(s) Fermi energy(ies). It increases when the molecular electronic level is close to the metal Fermi level so that an additional vibrational relaxation channel due to electron-hole (eh) exciton in the molecule opens. Other contributions to the Raman signal, of considerably broader linewidths, can become important at larger junction bias.

  11. Natural gas cleanup: Evaluation of a molecular sieve carbon as a pressure swing adsorbent for the separation of methane/nitrogen mixtures

    SciTech Connect

    Grimes, R.W.

    1994-06-01

    This report describes the results of a preliminary evaluation to determine the technical feasibility of using a molecular sieve carbon manufactured by the Takeda Chemical Company of Japan in a pressure owing adsorption cycle for upgrading natural gas (methane) contaminated with nitrogen. Adsorption tests were conducted using this adsorbent in two, four, and five-step adsorption cycles. Separation performance was evaluated in terms of product purity, product recovery, and sorbent productivity for all tests. The tests were conducted in a small, single-column adsorption apparatus that held 120 grams of the adsorbent. Test variables included adsorption pressure, pressurization rate, purge rate and volume, feed rate, and flow direction in the steps from which the product was collected. Sorbent regeneration was accomplished by purging the column with the feed gas mixture for all but one test series where a pure methane purge was used. The ratio between the volumes of the pressurization gas and the purge gas streams was found to be an important factor in determining separation performance. Flow rates in the various cycle steps had no significant effect. Countercurrent flow in the blow-down and purge steps improved separation performance. Separation performance appears to improve with increasing adsorption pressure, but because there are a number of interrelated variables that are also effected by pressure, further testing will be needed to verify this. The work demonstrates that a molecular sieve carbon can be used to separate a mixture of methane and nitrogen when used in a pressure swing cycle with regeneration by purge. Further work is needed to increase product purity and product recovery.

  12. Surface Grafted Polysarcosine as a Peptoid Antifouling Polymer Brush

    PubMed Central

    Lau, King Hang Aaron; Ren, Chunlai; Sileika, Tadas S.; Park, Sung Hyun; Szleifer, Igal; Messersmith, Phillip B.

    2012-01-01

    Poly(N-substituted glycine) “peptoids” are a class of peptidomimetic molecules receiving significant interest as engineered biomolecules. Sarcosine (i.e. poly(N-methyl glycine)) has the simplest sidechain chemical structure of this family. In this contribution, we demonstrate that surface-grafted polysarcosine (PSAR) brushes exhibit excellent resistance to non-specific protein adsorption and cell attachment. Polysarcosine was coupled to a mussel adhesive protein inspired DOPA-Lys pentapeptide, which enabled solution grafting and control of the surface chain density of the PSAR brushes. Protein adsorption was found to decrease monotonically with increasing grafted chain densities, and protein adsorption could be completely inhibited above certain critical chain densities specific to different polysarcosine chain-lengths. The dependence of protein adsorption on chain length and density was also investigated by a molecular theory. PSAR brushes at high chain length and density were shown to resist fibroblast cell attachment over a 7 wk period, as well as resist the attachment of some clinically relevant bacteria strains. The excellent antifouling performance of PSAR may be related to the highly hydrophilic character of polysarcosine, which was evident from high-pressure liquid chromatography measurements of polysarcosine and water contact angle measurements of the PSAR brushes. Peptoids have been shown to resist proteolytic degradation and polysarcosine could be produced in large quantities by N-carboxy anhydride polymerization. In summary, surface grafted polysarcosine peptoid brushes hold great promise for antifouling applications. PMID:23101930

  13. Analysis of structural changes in active site of luciferase adsorbed on nanofabricated hydrophilic Si surface by molecular-dynamics simulations

    SciTech Connect

    Nishiyama, Katsuhiko; Hoshino, Tadatsugu

    2007-05-21

    Interactions between luciferase and a nanofabricated hydrophilic Si surface were explored by molecular-dynamics simulations. The structural changes in the active-site residues, the residues affecting the luciferin binding, and the residues affecting the bioluminescence color were smaller on the nanofabricated hydrophilic Si surface than on both a hydrophobic Si surface and a hydrophilic Si surface. The nanofabrication and wet-treatment techniques are expected to prevent the decrease in activity of luciferase on the Si surface.

  14. Biomass-based palm shell activated carbon and palm shell carbon molecular sieve as gas separation adsorbents.

    PubMed

    Sethupathi, Sumathi; Bashir, Mohammed Jk; Akbar, Zinatizadeh Ali; Mohamed, Abdul Rahman

    2015-04-01

    Lignocellulosic biomass has been widely recognised as a potential low-cost source for the production of high added value materials and proved to be a good precursor for the production of activated carbons. One of such valuable biomasses used for the production of activated carbons is palm shell. Palm shell (endocarp) is an abundant by-product produced from the palm oil industries throughout tropical countries. Palm shell activated carbon and palm shell carbon molecular sieve has been widely applied in various environmental pollution control technologies, mainly owing to its high adsorption performance, well-developed porosity and low cost, leading to potential applications in gas-phase separation using adsorption processes. This mini-review represents a comprehensive overview of the palm shell activated carbon and palm shell carbon molecular sieve preparation method, physicochemical properties and feasibility of palm shell activated carbon and palm shell carbon molecular sieve in gas separation processes. Some of the limitations are outlined and suggestions for future improvements are pointed out.

  15. The Use of the Molecular Adsorber Coating Technology to Mitigate Vacuum Chamber Contamination During Pathfinder Testing for the James Webb Space Telescope

    NASA Technical Reports Server (NTRS)

    Abraham, Nithin S.; Hasegawa, Mark M.; Wooldridge, Eve M.; Henderson-Nelson, Kelly A.

    2016-01-01

    As a coating made of highly porous zeolite materials, the Molecular Adsorber Coating (MAC) was developed to capture outgassed molecular contaminants, such as hydrocarbons and silicones. For spaceflight applications, the adsorptive capabilities of the coating can alleviate on-orbit outgassing concerns on or near sensitive surfaces and instruments within the spacecraft. Similarly, this sprayable paint technology has proven to be significantly beneficial for ground based space applications, in particular, for vacuum chamber environments. This paper describes the recent use of the MAC technology during Pathfinder testing of the Optical Ground Support Equipment (OGSE) for the James Webb Space Telescope (JWST) at NASA Johnson Space Center (JSC). The coating was used as a mitigation tool to entrap persistent outgassed contaminants, specifically silicone based diffusion pump oil, from within JSC's cryogenic optical vacuum chamber test facility called Chamber A. This paper summarizes the sample fabrication, installation, laboratory testing, post-test chemical analysis results, and future plans for the MAC technology, which was effectively used to protect the JWST test equipment from vacuum chamber contamination.

  16. Adhesion and friction properties of polymer brushes on rough surfaces: a gradient approach.

    PubMed

    Ramakrishna, Shivaprakash N; Espinosa-Marzal, Rosa M; Naik, Vikrant V; Nalam, Prathima C; Spencer, Nicholas D

    2013-12-10

    The effect of nanoscale surface roughness on the lubrication properties of a polymer brush in a good solvent has been investigated. Friction and adhesion forces were measured by means of polyethylene colloidal-probe AFM across a 12 nm silica particle gradient before and after the adsorption of a poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG) polymer brush. The adsorption and conformation of the polymer chains were studied with multiple transmission and reflection infrared (MTR-IR) spectroscopy. The results show that prior to the adsorption of PLL-g-PEG on the gradient surface, the friction is high at the smooth end of the gradient while it decreases toward the rough end. Moreover, there is a direct correlation between friction and adhesion. Upon adsorption of the brushes, adhesion vanishes. In this case, a higher frictional force between the PEG-coated particle gradient substrate and the polyethylene sphere is observed at the rough end of the gradient in comparison to the smooth end. In spite of the increased adsorbed mass of PLL-g-PEG at the rough end of the gradient, theory and simulations show that the high curvature of the nanoparticles leads to a less swollen PEG brush in comparison to PEG brushes adsorbed on a planar surface, resulting in a lower repulsion, which can explain the observed increase in friction with particle density.

  17. Air Force brush seal programs

    NASA Astrophysics Data System (ADS)

    Dowler, Connie

    1993-10-01

    Aggressive pursuit of increased performance in gas turbine engines is driving the thermodynamic cycle to higher pressure ratios, bypass ratios, and turbine inlet temperatures. As these parameters increase, internal air system and resultant thermodynamic cycle losses increase. This conflict of reducing internal airflows while increasing thermodynamic efficiency and performance is putting more emphasis on improvements to the internal flow system. One improvement that has been and continues to be pursued by the Air Force for both man-rated and expendable turbine engine applications is the brush seal. This presentation briefly describes both past and current brush seal research and development programs and gives a summary of demonstrator and developmental engine testing of brush seals.

  18. Shaping the intestinal brush border

    PubMed Central

    Crawley, Scott W.; Mooseker, Mark S.

    2014-01-01

    Epithelial cells from diverse tissues, including the enterocytes that line the intestinal tract, remodel their apical surface during differentiation to form a brush border: an array of actin-supported membrane protrusions known as microvilli that increases the functional capacity of the tissue. Although our understanding of how epithelial cells assemble, stabilize, and organize apical microvilli is still developing, investigations of the biochemical and physical underpinnings of these processes suggest that cells coordinate cytoskeletal remodeling, membrane-cytoskeleton cross-linking, and extracellular adhesion to shape the apical brush border domain. PMID:25422372

  19. Brush seals for cryogenic applications

    NASA Astrophysics Data System (ADS)

    Proctor, Margaret P.

    1993-11-01

    Brush seals are compliant, contacting seals and have significantly lower leakage than labyrinth seals in gas turbine applications. Their characteristics of long life and low leakage make them candidates for use in rocket engine turbopumps. Two-inch diameter brush seals with a nominal 0.005 inch radial interference were tested in liquid nitrogen at shaft speeds up to 35,000 rpm and pressure drops up to 175 psid per seal. A labyrinth seal was also tested to provide a baseline. Performance, staging effects, and wear results are presented.

  20. Brush/Fin Thermal Interfaces

    NASA Technical Reports Server (NTRS)

    Knowles, Timothy R.; Seaman, Christopher L.; Ellman, Brett M.

    2004-01-01

    Brush/fin thermal interfaces are being developed to increase heat-transfer efficiency and thereby enhance the thermal management of orbital replaceable units (ORUs) of electronic and other equipment aboard the International Space Station. Brush/fin thermal interfaces could also be used to increase heat-transfer efficiency in terrestrial electronic and power systems. In a typical application according to conventional practice, a replaceable heat-generating unit includes a mounting surface with black-anodized metal fins that mesh with the matching fins of a heat sink or radiator on which the unit is mounted. The fins do not contact each other, but transfer heat via radiation exchange. A brush/fin interface also includes intermeshing fins, the difference being that the gaps between the fins are filled with brushes made of carbon or other fibers. The fibers span the gap between intermeshed fins, allowing heat transfer by conduction through the fibers. The fibers are attached to the metal surfaces as velvet-like coats in the manner of the carbon fiber brush heat exchangers described in the preceding article. The fiber brushes provide both mechanical compliance and thermal contact, thereby ensuring low contact thermal resistance. A certain amount of force is required to intermesh the fins due to sliding friction of the brush s fiber tips against the fins. This force increases linearly with penetration distance, reaching 1 psi (6.9 kPa) for full 2-in. (5.1 cm) penetration for the conventional radiant fin interface. Removal forces can be greater due to fiber buckling upon reversing the sliding direction. This buckling force can be greatly reduced by biasing the fibers at an angle perpendicularly to the sliding direction. Means of containing potentially harmful carbon fiber debris, which is electrically conductive, have been developed. Small prototype brush/fin thermal interfaces have been tested and found to exhibit temperature drops about onesixth of that of conventional

  1. Macroscopic lateral heterogeneity observed in a laterally mobile immiscible mixed polyelectrolyte-neutral polymer brush

    SciTech Connect

    Lee, Hoyoung; Tsouris, Vasilios; Lim, Yunho; Mustafa, Rafid; Choi, Je; Choi, Yun Hwa; Park, Hae-Woong; Meron, Mati; Lin, Binhua; Won, You-Yeon

    2014-07-11

    We studied mixed poly(ethylene oxide) (PEO) and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes. The question we attempted to answer was: when the chain grafting points are laterally mobile, how will this lateral mobility influence the structure and phase behavior of the mixed brush? Three different model mixed PEO/PDMAEMA brush systems were prepared: (1) a laterally mobile mixed brush by spreading onto the air–water interface a mixture of poly(ethylene oxide)–poly(n-butyl acrylate) (PEO–PnBA) and poly(2-(dimethylamino)ethyl methacrylate)–poly(n-butyl acrylate) (PDMAEMA–PnBA) diblock copolymers (the specific diblock copolymers used will be denoted as PEO113–PnBA100 and PDMAEMA118–PnBA100, where the subscripts refer to the number-average degrees of polymerization of the individual blocks), (2) a mobility-restricted (inseparable) version of the above mixed brush prepared using a PEO–PnBA–PDMAEMA triblock copolymer (denoted as PEO113–PnBA89–PDMAEMA120) having respective brush molecular weights matched with those of the diblock copolymers, and (3) a different laterally mobile mixed PEO and PDMAEMA brush prepared from a PEO113–PnBA100 and PDMAEMA200–PnBA103 diblock copolymer combination, which represents a further more height-mismatched mixed brush situation than described in (1). These three mixed brush systems were investigated by surface pressure–area isotherm and X-ray (XR) reflectivity measurements. These experimental data were analyzed within the theoretical framework of a continuum self-consistent field (SCF) polymer brush model. The combined experimental and theoretical results suggest that the mobile mixed brush derived using the PEO113–PnBA100 and PDMAEMA118–PnBA100 combination (i.e., mixed brush System #1) undergoes a lateral macroscopic phase separation

  2. 21 CFR 884.1100 - Endometrial brush.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Endometrial brush. 884.1100 Section 884.1100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL... Endometrial brush. (a) Identification. An endometrial brush is a device designed to remove samples of...

  3. Neutron reflectivity study of the swollen structure of polyzwitterion and polyeletrolyte brushes in aqueous solution.

    PubMed

    Kobayashi, Motoyasu; Ishihara, Kazuhiko; Takahara, Atsushi

    2014-01-01

    The swollen brush structures of polycation and zwitterionic polymer brushes, such as poly(2-methacryloyloxyethyltrimethylammonium chloride) (PMTAC), poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), and poly[3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate] (PMAPS), in aqueous solutions of various ionic strengths were characterized by neutron reflectivity (NR) measurements. A series of the polyelectrolyte brushes were prepared by surface-initiated controlled radical polymerization on silicon substrates. A high-graft-density PMTAC brush in salt-free water (D2O) adopted a two-region step-like structure consisting of a shrunk region near the Si substrate surface and a diffuse brush region with a relatively stretched chain structure at the solution interface. The diffuse region of PMTAC was reduced with increase in salt (NaCl) concentration. The PMAPS brush in D2O formed a collapsed structure due to the strong molecular interaction between betaine groups, while significant increase in the swollen thickness was observed in salt aqueous solution. In contrast, no change was observed in the depth profile of the swollen PMPC brush in D2O with various salt concentrations. The unique solution behaviors of zwitterionic polymer brushes were described. PMID:25178564

  4. Wear of metal fiber brushes

    NASA Astrophysics Data System (ADS)

    Brown, Lloyd Perryman, Jr.

    The goal of this dissertation was determining the wear mechanism of metal fiber brushes on commutators and slip rings with the goal of achieving the lowest possible wear rate. To this end, metal fiber brushes were operated, while conducting direct current, on gold-plated copper rotors with and without unfilled gaps to simulate slip rings and commutators, respectively. Wear rates on unfilled-groove commutators were found to be only modestly higher than on slip ring style rotors. Three possible causes for enhanced metal fiber brush wear on commutators were considered: (i) accelerated "adhesive" wear controlled by contact spots, (ii) fatigue induced wear and (iii) "fiber chopping". Similarly, SEM analysis of fiber tips and wear particles produced scant, if any, evidence of fiber chopping, which would occur as, again, fiber tips extend elastically into the commutator grooves and small slices of them would be "chopped" off by oncoming edges of commutator bars. Finally considered was "modified chopping", wherein fiber tips would be dragged over groove edges, resulting in tensile fracture and chopping. Only a single fiber fragment showed damage that might be compatible with that mechanism. Moreover, the fact that it was exemplified by a single tenuous case, rules it out as significant. The same conclusion also follows from comparing commutator wear rates with that on slip rings. These show good correlation in terms of effective brush pressure, which on commutators is increased because only bars conduct current and gaps do not support load. (Abstract shortened by UMI.)

  5. Role of Structure and Glycosylation of Adsorbed Protein Films in Biolubrication

    PubMed Central

    Veeregowda, Deepak H.; Busscher, Henk J.; Vissink, Arjan; Jager, Derk-Jan; Sharma, Prashant K.; van der Mei, Henny C.

    2012-01-01

    Water forms the basis of lubrication in the human body, but is unable to provide sufficient lubrication without additives. The importance of biolubrication becomes evident upon aging and disease, particularly under conditions that affect secretion or composition of body fluids. Insufficient biolubrication, may impede proper speech, mastication and swallowing, underlie excessive friction and wear of articulating cartilage surfaces in hips and knees, cause vaginal dryness, and result in dry, irritated eyes. Currently, our understanding of biolubrication is insufficient to design effective therapeutics to restore biolubrication. Aim of this study was to establish the role of structure and glycosylation of adsorbed protein films in biolubrication, taking the oral cavity as a model and making use of its dynamics with daily perturbations due to different glandular secretions, speech, drinking and eating, and tooth brushing. Using different surface analytical techniques (a quartz crystal microbalance with dissipation monitoring, colloidal probe atomic force microscopy, contact angle measurements and X-ray photo-electron spectroscopy), we demonstrated that adsorbed salivary conditioning films in vitro are more lubricious when their hydrophilicity and degree of glycosylation increase, meanwhile decreasing their structural softness. High-molecular-weight, glycosylated proteins adsorbing in loops and trains, are described as necessary scaffolds impeding removal of water during loading of articulating surfaces. Comparing in vitro and in vivo water contact angles measured intra-orally, these findings were extrapolated to the in vivo situation. Accordingly, lubricating properties of teeth, as perceived in 20 volunteers comprising of equal numbers of male and female subjects, could be related with structural softness and glycosylation of adsorbed protein films on tooth surfaces. Summarizing, biolubrication is due to a combination of structure and glycosylation of adsorbed protein

  6. Planar dipolar polymer brush: field theoretical investigations

    NASA Astrophysics Data System (ADS)

    Mahalik, Jyoti; Kumar, Rajeev; Sumpter, Bobby

    2015-03-01

    Physical properties of polymer brushes bearing monomers with permanent dipole moments and immersed in a polar solvent are investigated using self-consistent field theory (SCFT). It is found that mismatch between the permanent dipole moments of the monomer and the solvent plays a significant role in determining the height of the polymer brush. Sign as well as magnitude of the mismatch determines the extent of collapse of the polymer brush. The mismatch in the dipole moments also affects the force-distance relations and interpenetration of polymers in opposing planar brushes. In particular, an attractive force between the opposing dipolar brushes is predicted for stronger mismatch parameter. Furthermore, effects of added monovalent salt on the structure of dipolar brushes will also be presented. This investigation highlights the significance of dipolar interactions in affecting the physical properties of polymer brushes. Csmd division, Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37831, USA.

  7. Brush Seals for Improved Steam Turbine Performance

    NASA Technical Reports Server (NTRS)

    Turnquist, Norman; Chupp, Ray; Baily, Fred; Burnett, Mark; Rivas, Flor; Bowsher, Aaron; Crudgington, Peter

    2006-01-01

    GE Energy has retrofitted brush seals into more than 19 operating steam turbines. Brush seals offer superior leakage control compared to labyrinth seals, owing to their compliant nature and ability to maintain very tight clearances to the rotating shaft. Seal designs have been established for steam turbines ranging in size from 12 MW to over 1200 MW, including fossil, nuclear, combined-cycle and industrial applications. Steam turbines present unique design challenges that must be addressed to ensure that the potential performance benefits of brush seals are realized. Brush seals can have important effects on the overall turbine system that must be taken into account to assure reliable operation. Subscale rig tests are instrumental to understanding seal behavior under simulated steam-turbine operating conditions, prior to installing brush seals in the field. This presentation discusses the technical challenges of designing brush seals for steam turbines; subscale testing; performance benefits of brush seals; overall system effects; and field applications.

  8. Molecular Adsorbent Recirculating System (MARS(®)) removal of piperacillin/tazobactam in a patient with acetaminophen-induced acute liver failure.

    PubMed

    Ruggero, M A; Argento, A C; Heavner, M S; Topal, J E

    2013-04-01

    The objective of this study was to illustrate the pharmacokinetic removal of piperacillin/tazobactam in an anuric patient on Molecular Adsorbent Recirculating System (MARS(®)). The patient was a 32-year-old woman who presented to a medical intensive care unit with acute liver failure secondary to an acetaminophen overdose. While awaiting transplant, she was started on MARS therapy as a bridge to liver transplant and empirically started on piperacillin/tazobactam therapy. MARS is an extracorporeal hemofiltration device, which incorporates a continuous venovenous hemofiltration (CVVHD) machine linked to an albumin-enriched dialysate filter to normalize excess electrolytes, metabolic waste, and protein-bound toxins. In addition to protein-bound waste, MARS removes water-soluble, low molecular-weight molecules. The patient received piperacillin/tazobactam 4.5 g infused intravenously over 3 h. A steep decline in serum levels occurred between hours 4 and 6 while MARS continued and no antibiotic was infused. The elimination rate constant (k(e)) for the removal of piperacillin in this patent was 0.453 h(-1) and the half-life (λ) was 1.53 h. The k(e) was 2.9-fold higher than with CVVHD alone and the λ was 3.7-fold shorter. Low levels of piperacillin are achieved during MARS therapy, but in the treatment of more resistant organisms, such as Pseudomonas aeruginosa, these low levels may not be adequate to achieve bactericidal activity. Drug levels following a standard infusion of 30 min would likely be even lower. Formalized pharmacokinetic studies of piperacillin/tazobactam removal in patients on MARS therapy are necessary to make clear dosing recommendations.

  9. Nanoparticle organization in sandwiched polymer brushes.

    PubMed

    Curk, Tine; Martinez-Veracoechea, Francisco J; Frenkel, Daan; Dobnikar, Jure

    2014-05-14

    The organization of nanoparticles inside grafted polymer layers is governed by the interplay of polymer-induced entropic interactions and the action of externally applied fields. Earlier work had shown that strong external forces can drive the formation of colloidal structures in polymer brushes. Here we show that external fields are not essential to obtain such colloidal patterns: we report Monte Carlo and molecular dynamics simulations that demonstrate that ordered structures can be achieved by compressing a "sandwich" of two grafted polymer layers, or by squeezing a coated nanotube, with nanoparticles in between. We show that the pattern formation can be efficiently controlled by the applied pressure, while the characteristic length-scale, that is, the typical width of the patterns, is sensitive to the length of the polymers. Based on the results of the simulations, we derive an approximate equation of state for nanosandwiches. PMID:24707901

  10. Dendritic brushes under theta and poor solvent conditions.

    PubMed

    Gergidis, Leonidas N; Kalogirou, Andreas; Charalambopoulos, Antonios; Vlahos, Costas

    2013-07-28

    The effects of solvent quality on the internal stratification of polymer brushes formed by dendron polymers up to third generation were studied by means of molecular dynamics simulations with Langevin thermostat. The distributions of polymer units, of the free ends, the radii of gyration, and the back folding probabilities of the dendritic spacers were studied at the macroscopic states of theta and poor solvent. For high grafting densities we observed a small decrease in the height of the brush as the solvent quality decreases. The internal stratification in theta solvent was similar to the one we found in good solvent, with two and in some cases three kinds of populations containing short dendrons with weakly extended spacers, intermediate-height dendrons, and tall dendrons with highly stretched spacers. The differences increase as the grafting density decreases and single dendron populations were evident in theta and poor solvent. In poor solvent at low grafting densities, solvent micelles, polymeric pinned lamellae, spherical and single chain collapsed micelles were observed. The scaling dependence of the height of the dendritic brush at high density brushes for both solvents was found to be in agreement with existing analytical results. PMID:23902025

  11. Non-biofouling property of well-defined concentrated polymer brushes.

    PubMed

    Yoshikawa, Chiaki; Qiu, Jun; Huang, Chih-Feng; Shimizu, Yoshihisa; Suzuki, Junji; van den Bosch, Edith

    2015-03-01

    The non-biofouling properties of polymer brushes of poly(2-hydroxyethyl methacrylate) (PHEMA), poly(2-hydroxyethyl acrylate) (PHEA), and poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA) were comprehensively studied by varying graft densities (i.e., semi-dilute and concentrated regimes) and the thicknesses at the dry state of 2 and 10 nm. Semi-dilute polymer brushes (SDPBs) were prepared by grafting-to method and concentrated polymer brushes (CPBs) were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP). The adsorptions of proteins with different sizes were investigated on the brushes by quartz crystal microbalance (QCM) from a view point of size-exclusion effect specific to the CPBs. We confirmed that due to the size exclusion effect, the CPBs of all the three much suppressed proteins adsorption and human umbilical vein endothelial cell (HUVEC) adhesion compared with the corresponding SDPBs. In order to investigate what type of proteins adsorbed on the brushes to trigger cell adhesion, we identified adsorbed proteins from fetal bovine serum on the brushes using a high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Proteins were only detected on the SDPBs. Interestingly, the number and type of identified proteins were different on the SDPBs, indicating that chemical composition of the SDPBs affects protein adsorption, hence the cell adhesion. The adsorption mechanism on the SDPBs could be due to the combination of protein-polymer interaction and physical inclusion, whereas CPBs exhibit size exclusion effect combined with neutral hydrophilic nature of polymer, thereby, that provides excellent non-biofouling property.

  12. Nanotribology of charged polymer brushes

    NASA Astrophysics Data System (ADS)

    Klein, Jacob

    Polymers at surfaces, whose modern understanding may be traced back to early work by Sam Edwards1, have become a paradigm for modification of surface properties, both as steric stabilizers and as remarkable boundary lubricants2. Charged polymer brushes are of particular interest, with both technological implications and especially biological relevance where most macromolecules are charged. In the context of biolubrication, relevant in areas from dry eye syndrome to osteoarthritis, charged polymer surface phases and their complexes with other macromolecules may play a central role. The hydration lubrication paradigm, where tenaciously-held yet fluid hydration shells surrounding ions or zwitterions serve as highly-efficient friction-reducing elements, has been invoked to understand the excellent lubrication provided both by ionized3 and by zwitterionic4 brushes. In this talk we describe recent advances in our understanding of the nanotribology of such charged brush systems. We consider interactions between charged end-grafted polymers, and how one may disentangle the steric from the electrostatic surface forces5. We examine the limits of lubrication by ionized brushes, both synthetic and of biological origins, and how highly-hydrated zwitterionic chains may provide extremely effective boundary lubrication6. Finally we describe how the lubrication of articular cartilage in the major joints, a tribosystem presenting some of the greatest challenges and opportunities, may be understood in terms of a supramolecular synergy between charged surface-attached polymers and zwitterionic groups7. Work supported by European Research Council (HydrationLube), Israel Science Foundation (ISF), Petroleum Research Fund of the American Chemical Society, ISF-NSF China Joint Program.

  13. Chain Length and Grafting Density Dependent Enhancement in the Hydrolysis of Ester-Linked Polymer Brushes.

    PubMed

    Melzak, Kathryn A; Yu, Kai; Bo, Deng; Kizhakkedathu, Jayachandran N; Toca-Herrera, José L

    2015-06-16

    Poly(N,N-dimethylacrylamide) (PDMA) brushes with different grafting density and chain length were grown from an ester group-containing initiator using surface-initiated polymerization. Hydrolysis of the PDMA chains from the surface was monitored by measuring thickness of the polymer layer by ellipsometry and extension length by atomic force microscopy. It was found that the initial rate of cleavage of one end-tethered PDMA chains was dependent on the grafting density and chain length; the hydrolysis rate was faster for high grafting density brushes and brushes with higher molecular weights. Additionally, the rate of cleavage of polymer chains during a given experiment changed by up to 1 order of magnitude as the reaction progressed, with a distinct transition to a lower rate as the grafting density decreased. Also, polymer chains undergo selective cleavage, with longer chains in a polydisperse brush being preferentially cleaved at one stage of the hydrolysis reaction. We suggest that the enhanced initial hydrolysis rates seen at high grafting densities and high chain lengths are due to mechanical activation of the ester bond connecting the polymer chains to the surface in association with high lateral pressure within the brush. These results have implications for the preparation of polymers brushes, their stability under harsh conditions, and the analysis of polymer brushes from partial hydrolysates. PMID:26010390

  14. Simple leakage flow model for brush seals

    NASA Astrophysics Data System (ADS)

    Chupp, Raymond E.; Dowler, Constance A.; Holle, Glenn F.

    1991-06-01

    Brush seals are potential replacements for some or most of the air-to-air labyrinth seals in gas turbine engines. A simple flow model is presented to generalize brush seal leakage performance throughout the range of test and application environments. The model uses a single parameter, effective brush thickness, to correlate flow through the seal. This effective brush thickness is a measure of the compactness of the bristle bed. Initial model results have been obtained using leakage flow data from two investigators. The results indicate that this simple single parameter model gives insight into the active nature of a brush seal and approximately accounts for the effect of fluid temperature, especially at the higher pressure ratios, where brush seals are commonly applied.

  15. Stimuli-sensitive intrinsically disordered protein brushes

    NASA Astrophysics Data System (ADS)

    Srinivasan, Nithya; Bhagawati, Maniraj; Ananthanarayanan, Badriprasad; Kumar, Sanjay

    2014-10-01

    Grafting polymers onto surfaces at high density to yield polymer brush coatings is a widely employed strategy to reduce biofouling and interfacial friction. These brushes almost universally feature synthetic polymers, which are often heterogeneous and do not readily allow incorporation of chemical functionalities at precise sites along the constituent chains. To complement these synthetic systems, we introduce a biomimetic, recombinant intrinsically disordered protein that can assemble into an environment-sensitive brush. This macromolecule adopts an extended conformation and can be grafted to solid supports to form oriented protein brushes that swell and collapse dramatically with changes in solution pH and ionic strength. We illustrate the value of sequence specificity by using proteases with mutually orthogonal recognition sites to modulate brush height in situ to predictable values. This study demonstrates that stimuli-responsive brushes can be fabricated from proteins and introduces them as a new class of smart biomaterial building blocks.

  16. Tooth brushing inhibits oral bacteria in dogs.

    PubMed

    Watanabe, Kazuhiro; Hayashi, Kotaro; Kijima, Saku; Nonaka, Chie; Yamazoe, Kazuaki

    2015-10-01

    In this study, scaling, polishing and daily tooth brushing were performed in 20 beagle dogs, and the number of oral bacteria was determined using a bacterial counter. The dogs were randomized into the scaling (S), scaling + polishing (SP), scaling + tooth daily brushing (SB) and scaling + polishing + tooth daily brushing (SPB) groups. Samples were collected from the buccal surface of the maxillary fourth premolars of the dogs immediately after scaling and every week thereafter from weeks 1 to 8. Throughout the study, the number of bacteria was significantly lower in the SB and SPB groups compared with the S group. The findings suggest that daily tooth brushing inhibited oral bacterial growth in the dogs.

  17. Nanopatterned polymer brushes: conformation, fabrication and applications

    NASA Astrophysics Data System (ADS)

    Yu, Qian; Ista, Linnea K.; Gu, Renpeng; Zauscher, Stefan; López, Gabriel P.

    2015-12-01

    Surfaces with end-grafted, nanopatterned polymer brushes that exhibit well-defined feature dimensions and controlled chemical and physical properties provide versatile platforms not only for investigation of nanoscale phenomena at biointerfaces, but also for the development of advanced devices relevant to biotechnology and electronics applications. In this review, we first give a brief introduction of scaling behavior of nanopatterned polymer brushes and then summarize recent progress in fabrication and application of nanopatterned polymer brushes. Specifically, we highlight applications of nanopatterned stimuli-responsive polymer brushes in the areas of biomedicine and biotechnology.

  18. Brush seals for turbine engine fuel conservation

    NASA Astrophysics Data System (ADS)

    Sousa, Mike

    1994-07-01

    The program objective is to demonstrate brush seals for replacing labyrinth seals in turboprop engines. The approach taken was to design and procure brush seals with assistance from Sealol, modify and instrument an existing T407 low pressure turbine test rig, replace inner balance piston and outer balance piston labyrinth seals with brush seals, conduct cyclic tests to evaluate seal leakage at operating pressures and temperatures, and evaluate effect of seal pack width and rotor eccentricity. Results are presented in viewgraph format and show that brush seals offer performance advantages over labyrinth seals.

  19. Development of a Brush Seals Program Leading to Ceramic Brush Seals

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Flower, Ralph; Howe, Harold

    1994-01-01

    Some events of a U.S. Army/NASA Lewis Research Center brush seals program are reviewed, and the development of ceramic brush seals is described. Some preliminary room-temperature flow data are given, and the results of testing metallic brushes in cryogenic nitrogen are discussed.

  20. The structures and dynamics of atomic and molecular adsorbates on metal surfaces by scanning tunneling microscopy and low energy electron diffraction

    SciTech Connect

    Yoon, Hyungsuk Alexander

    1996-12-01

    Studies of surface structure and dynamics of atoms and molecules on metal surfaces are presented. My research has focused on understanding the nature of adsorbate-adsorbate and adsorbate-substrate interactions through surface studies of coverage dependency and coadsorption using both scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). The effect of adsorbate coverage on the surface structures of sulfur on Pt(111) and Rh(111) was examined. On Pt(111), sulfur forms p(2x2) at 0.25 ML of sulfur, which transforms into a more compressed ({radical}3x{radical}3)R30{degrees} at 0.33 ML. On both structures, it was found that sulfur adsorbs only in fcc sites. When the coverage of sulfur exceeds 0.33 ML, it formed more complex c({radical}3x7)rect structure with 3 sulfur atoms per unit cell. In this structure, two different adsorption sites for sulfur atoms were observed - two on fcc sites and one on hcp site within the unit cell.

  1. Brush seal numerical simulation: Concepts and advances

    NASA Technical Reports Server (NTRS)

    Braun, M. J.; Kudriavtsev, V. V.

    1994-01-01

    The development of the brush seal is considered to be most promising among the advanced type seals that are presently in use in the high speed turbomachinery. The brush is usually mounted on the stationary portions of the engine and has direct contact with the rotating element, in the process of limiting the 'unwanted' leakage flows between stages, or various engine cavities. This type of sealing technology is providing high (in comparison with conventional seals) pressure drops due mainly to the high packing density (around 100 bristles/sq mm), and brush compliance with the rotor motions. In the design of modern aerospace turbomachinery leakage flows between the stages must be minimal, thus contributing to the higher efficiency of the engine. Use of the brush seal instead of the labyrinth seal reduces the leakage flow by one order of magnitude. Brush seals also have been found to enhance dynamic performance, cost less, and are lighter than labyrinth seals. Even though industrial brush seals have been successfully developed through extensive experimentation, there is no comprehensive numerical methodology for the design or prediction of their performance. The existing analytical/numerical approaches are based on bulk flow models and do not allow the investigation of the effects of brush morphology (bristle arrangement), or brushes arrangement (number of brushes, spacing between them), on the pressure drops and flow leakage. An increase in the brush seal efficiency is clearly a complex problem that is closely related to the brush geometry and arrangement, and can be solved most likely only by means of a numerically distributed model.

  2. Brush seal numerical simulation: Concepts and advances

    NASA Astrophysics Data System (ADS)

    Braun, M. J.; Kudriavtsev, V. V.

    1994-07-01

    The development of the brush seal is considered to be most promising among the advanced type seals that are presently in use in the high speed turbomachinery. The brush is usually mounted on the stationary portions of the engine and has direct contact with the rotating element, in the process of limiting the 'unwanted' leakage flows between stages, or various engine cavities. This type of sealing technology is providing high (in comparison with conventional seals) pressure drops due mainly to the high packing density (around 100 bristles/sq mm), and brush compliance with the rotor motions. In the design of modern aerospace turbomachinery leakage flows between the stages must be minimal, thus contributing to the higher efficiency of the engine. Use of the brush seal instead of the labyrinth seal reduces the leakage flow by one order of magnitude. Brush seals also have been found to enhance dynamic performance, cost less, and are lighter than labyrinth seals. Even though industrial brush seals have been successfully developed through extensive experimentation, there is no comprehensive numerical methodology for the design or prediction of their performance. The existing analytical/numerical approaches are based on bulk flow models and do not allow the investigation of the effects of brush morphology (bristle arrangement), or brushes arrangement (number of brushes, spacing between them), on the pressure drops and flow leakage. An increase in the brush seal efficiency is clearly a complex problem that is closely related to the brush geometry and arrangement, and can be solved most likely only by means of a numerically distributed model.

  3. Size exclusion chromatography of quantum dots by utilizing nanoparticle repelling surface of concentrated polymer brush

    NASA Astrophysics Data System (ADS)

    Arita, Toshihiko; Yoshimura, Tomoka; Adschiri, Tadafumi

    2010-08-01

    We have found that the concentrated poly(methyl methacrylate) (PMMA) brush showed the very good nanoparticles (NPs) repellency in its good solvent, e.g. tetrahydrofuran (THF). Whereas the oil- and hydro-phobic (fluorinated), hydrophobic and hydrophilic surfaces adsorbed a lot of NPs. The repellency of NPs did not depend on the surface nature of the NPs. Preparing absorption free columns for size exclusion chromatography (SEC) may enable us to separate quantum dots (QDs) and NPs according to their size. By installing the concentrated PMMA brush into silica monolith columns, we tried to achieve SEC of QDs and NPs. The concentrated PMMA brush immobilized silica monolith columns were prepared by surface initiated atom transfer polymerization of MMA. As a result, we have succeeded in separating QDs according to their size. This SEC system may be advantageous because it can be used in good solvents of the brush regardless of the stability of the surface modifier layer on the NPs.We have found that the concentrated poly(methyl methacrylate) (PMMA) brush showed the very good nanoparticles (NPs) repellency in its good solvent, e.g. tetrahydrofuran (THF). Whereas the oil- and hydro-phobic (fluorinated), hydrophobic and hydrophilic surfaces adsorbed a lot of NPs. The repellency of NPs did not depend on the surface nature of the NPs. Preparing absorption free columns for size exclusion chromatography (SEC) may enable us to separate quantum dots (QDs) and NPs according to their size. By installing the concentrated PMMA brush into silica monolith columns, we tried to achieve SEC of QDs and NPs. The concentrated PMMA brush immobilized silica monolith columns were prepared by surface initiated atom transfer polymerization of MMA. As a result, we have succeeded in separating QDs according to their size. This SEC system may be advantageous because it can be used in good solvents of the brush regardless of the stability of the surface modifier layer on the NPs. Electronic

  4. Nanostructure and salt effect of zwitterionic carboxybetaine brush at the air/water interface.

    PubMed

    Matsuoka, Hideki; Yamakawa, Yuta; Ghosh, Arjun; Saruwatari, Yoshiyuki

    2015-05-01

    Zwitterionic amphiphilic diblock copolymer, poly(ethylhexyl acrylate)-b-poly(carboxybetaine) (PEHA-b-PGLBT), was synthesized by the reversible addition-fragmentation chain transfer (RAFT) method with precise control of block length and polydispersity. The polymers thus obtained were spread onto the water surface to form a polymer monolayer. The fundamental property and nanostructure of the block copolymer monolayer were systematically studied by the surface pressure-molecular area (π-A) isotherm, Brewster angle microscopy (BAM), and X-ray reflectivity (XR) techniques. The π values of the monolayer increased by compression in relatively larger A regions. After showing a large plateau region by compression, the π value sharply increased at very small A regions, suggesting the formation of poly(GLBT) brush formation just beneath the water surface. The domain structure of μm size was observed by BAM in the plateau region. XR profiles for the monolayer at higher surface pressure regions clearly showed the PGLBT brush formation in addition to PGLBT carpet layer formation under the hydrophobic PEHA layer on the water surface, as was observed for both anionic and cationic brush layer in the water surface monolayer studied previously. The critical brush density, where the PGLBT brush is formed, was estimated to be about 0.30 chains/nm(2) for the (EHA)45-b-(GLBT)60 monolayer, which is relatively large compared to other ionic brushes. This observation is consistent with the fact that the origin of brush formation is mainly steric hindrance between brush chains. The brush thickness increased by compression and also by salt addition, unlike the normal ionic brush (anionic and cationic), whose thickness tended to decrease, i.e., shrink, by salt addition. This might be a character unique to the zwitterionic brush, and its origin is thought to be transition to an ionic nature from the almost nonionic inner salt caused by salt addition since both the cation and anion of the

  5. Dual wound dc brush motor gearhead

    NASA Technical Reports Server (NTRS)

    Henson, Barrie W.

    1986-01-01

    The design requirements, the design, development tests and problems, the qualification and life test and the findings of the strip examination of a dual wound DC brushed motor gearhead are described. It is the only space qualified dual wound dc brushed motor gearhead in Europe.

  6. Brush-Wheel Samplers for Planetary Exploration

    NASA Technical Reports Server (NTRS)

    Rivellini, Tommaso

    2003-01-01

    A report proposes brush-wheel mechanisms for acquiring samples of soils from remote planets. In simplest terms, such a mechanism would contain brush wheels that would be counter-rotated at relatively high speed. The mechanism would be lowered to the ground from a spacecraft or other exploratory vehicle. Upon contact with the ground, the counter-rotating brush wheels would kick soil up into a collection chamber. Thus, in form and function, the mechanism would partly resemble traditional street and carpet sweepers. The main advantage of using of brush wheels (in contradistinction to cutting wheels or other, more complex mechanisms) is that upon encountering soil harder than expected, the brushes could simply deflect and the motor(s) could continue to turn. That is, sufficiently flexible brushes would afford resistance to jamming and to overloading of the motors used to rotate the brushes, and so the motors could be made correspondingly lighter and less power hungry. Of course, one could select the brush stiffnesses and motor torques and speeds for greatest effectiveness in sampling soil of a specific anticipated degree of hardness.

  7. 21 CFR 886.1090 - Haidinger brush.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Haidinger brush. 886.1090 Section 886.1090 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL... brush is an AC-powered device that provides two conical brushlike images with apexes touching which...

  8. 21 CFR 886.1090 - Haidinger brush.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Haidinger brush. 886.1090 Section 886.1090 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL... brush is an AC-powered device that provides two conical brushlike images with apexes touching which...

  9. 21 CFR 886.1090 - Haidinger brush.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Haidinger brush. 886.1090 Section 886.1090 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL... brush is an AC-powered device that provides two conical brushlike images with apexes touching which...

  10. 21 CFR 886.1090 - Haidinger brush.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Haidinger brush. 886.1090 Section 886.1090 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL... brush is an AC-powered device that provides two conical brushlike images with apexes touching which...

  11. 21 CFR 886.1090 - Haidinger brush.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Haidinger brush. 886.1090 Section 886.1090 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL... brush is an AC-powered device that provides two conical brushlike images with apexes touching which...

  12. A Brush Seals Program Modeling and Developments

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Flower, Ralph; Howe, Harold

    1996-01-01

    Some events of a U.S. Army/NASA Lewis Research Center brush seals program are reviewed, and the development of ceramic brush seals is described. Some preliminary room-temperature flow data are modeled and compare favorably to the results of Ergun.

  13. Liquid Crystalline Phases of Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Amini, Kiana; Abukhdeir, Nasser; Matsen, Mark

    The phase behavior of liquid-crystal polymeric brushes in solvent are investigated using self-consistent field theory. The polymers are modeled as freely-jointed chain consisting of N rigid segments. The isotropic interactions between the polymer and the solvent are treated using the standard Flory-Huggins theory, while the anisotropic liquid-crystalline (LC) interactions between rigid segments are taken into account using the Mayer-Saupe theory. For weak LC interactions, the brush exhibits the conventional parabolic-like profile, while for strong LC interactions, the polymers crystallize into a dense brush with a step-like profile. At intermediate interaction strengths, we find the microphase-segregated phase observed previously for lattice-model calculations. In this phase, the brush exhibits a crystalline layer next to the grafting surface with an external layer similar to the conventional brush. This work was supported by NSERC of Canada.

  14. Protein patterning by UV-induced photodegradation of poly(oligo(ethylene glycol) methacrylate) brushes.

    PubMed

    Alang Ahmad, Shahrul; Hucknall, Angus; Chilkoti, Ashutosh; Leggett, Graham J

    2010-06-15

    The UV photodegradation of protein-resistant poly(oligo(ethylene glycol) methacrylate) (POEGMA) bottle-brush films, grown on silicon oxide by surface-initiated atom radical transfer polymerization, was studied using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Exposure to light with a wavelength of 244 nm caused a loss of polyether units from the brush structure and the creation of aldehyde groups that could be derivatized with amines. An increase was measured in the coefficient of friction of the photodegraded polymer brush compared to the native brush, attributed to the creation of a heterogeneous surface film, leading to increased energy dissipation through film deformation and the creation of new polar functional groups at the surface. Exposure of the films through a photomask yielded sharp, well-defined patterns. Analysis of topographical images showed that physical removal of material occurred during exposure, at a rate of 1.35 nm J(-1) cm(2). Using fluorescence microscopy, the adsorption of labeled proteins onto the exposed surfaces was studied. It was found that protein strongly adsorbed to exposed areas, while the masked regions retained their protein resistance. Exposure of the film to UV light from a scanning near-field optical microscope yielded submicrometer-scale patterns. These data indicate that a simple, rapid, one-step photoconversion of the poly(OEGMA) brush occurs that transforms it from a highly protein-resistant material to one that adsorbs protein and can covalently bind amine-containing molecules and that this photoconversion can be spatially addressed with high spatial resolution.

  15. Chain-length dependence of the dissociation dynamics of oriented molecular adsorbates: n-alkyl bromides on GaAs(110)

    SciTech Connect

    Khan, K.A.; Camillone, N. III; Osgood, R.M. Jr.

    1999-07-01

    Brominated hydrocarbons adsorbed on semiconductor surfaces serve as ideal model systems for investigating the photoinduced chemistry of oriented molecules in the condensed phase. Under UV irradiation these adsorbates dissociate via attachment of photoexcited substrate electrons giving rise to energetic alkyl and surface-bound bromine fragments. In this report the authors describe the effect on the fragmentation dynamics due to systematic variation of the complexity (alkyl chain length) of the adsorbate. Increasing the length of the alkyl chain leads to distinct changes in the alkyl fragment angular distributions. For methyl bromide, the angular distribution is dominated by a focused beam of directly ejected hyperthermal methyl radicals at 44{degree} (in the [0{bar 1}] direction) from the surface normal. While a similar direct beam is observed for ethyl and propyl bromide, inelastic scattering of these fragments is found to result in increased importance of a slower diffuse cos{sup n} {theta} desorption. In addition, significant retention of alkyl fragments is detected by postirradiation thermal desorption measurements for these longer-chain homologues. Increasing the number of degrees of freedom of the adsorbate is also observed to dramatically alter the energetics of the ejection of the photofragments from the surface. As the number of carbons in the fragment is increased from one to three, the average energy of the directly ejected radicals decreases from 1.48 to 1.1 to 0.69 eV (UV incident at {lambda} = 193 nm). Variations in the energy and angular distributions are discussed in terms of initial adsorbate orientation, energy partitioning into rovibrational modes, and influence of radical-surface interactions.

  16. Mechanism of nanoparticle actuation by responsive polymer brushes: from reconfigurable composite surfaces to plasmonic effects.

    PubMed

    Roiter, Yuri; Minko, Iryna; Nykypanchuk, Dmytro; Tokarev, Ihor; Minko, Sergiy

    2012-01-01

    The mechanism of nanoparticle actuation by stimuli-responsive polymer brushes triggered by changes in the solution pH was discovered and investigated in detail in this study. The finding explains the high spectral sensitivity of the composite ultrathin film composed of a poly(2-vinylpyridine) (P2VP) brush that tunes the spacing between two kinds of nanoparticles-gold nanoislands immobilized on a transparent support and gold colloidal particles adsorbed on the brush. The optical response of the film relies on the phenomenon of localized surface plasmon resonances in the noble metal nanoparticles, giving rise to an extinction band in visible spectra, and a plasmon coupling between the particles and the islands that has a strong effect on the band position and intensity. Since the coupling is controlled by the interparticle spacing, the pH-triggered swelling-shrinking transition in the P2VP brush leads to pronounced changes in the transmission spectra of the hybrid film. It was not established in the previous publications how the actuation of gold nanoparticles within a 10-15 nm interparticle distance could result in the 50-60 nm shift in the absorbance maximum in contrast to the model experiments and theoretical estimations of several nanometer shifts. In this work, the extinction band was deconvoluted into four spectrally separated and overlapping contributions that were attributed to different modes of interactions between the particles and the islands. These modes came into existence due to variations in the thickness of the grafted polymeric layer on the profiled surface of the islands. In situ atomic force microscopy measurements allowed us to explore the behavior of the Au particles as the P2VP brush switched between the swollen and collapsed states. In particular, we identified an interesting, previously unanticipated regime when a particle position in a polymer brush was switched between two distinct states: the particle exposed to the surface of the

  17. Preparation and Friction Force Microscopy Measurements of Immiscible, Opposing Polymer Brushes

    PubMed Central

    de Beer, Sissi; Kutnyanszky, Edit; Müser, Martin H.; Vancso, G. Julius

    2014-01-01

    Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low friction at the interface. Nevertheless, these systems can be sensitive to wear due to interdigitation of the opposing brushes. In a recent publication, we have shown via molecular dynamics simulations and atomic force microscopy experiments, that using an immiscible polymer brush system terminating the substrate and the slider surfaces, respectively, can eliminate such interdigitation. As a consequence, wear in the contacts is reduced. Moreover, the friction force is two orders of magnitude lower compared to traditional miscible polymer brush systems. This newly proposed system therefore holds great potential for application in industry. Here, the methodology to construct an immiscible polymer brush system of two different brushes each solvated by their own preferred solvent is presented. The procedure how to graft poly(N-isopropylacrylamide) (PNIPAM) from a flat surface and poly(methyl methacrylate) (PMMA) from an atomic force microscopy (AFM) colloidal probe is described. PNIPAM is solvated in water and PMMA in acetophenone. Via friction force AFM measurements, it is shown that the friction for this system is indeed reduced by two orders of magnitude compared to the miscible system of PMMA on PMMA solvated in acetophenone. PMID:25590429

  18. Preparation and friction force microscopy measurements of immiscible, opposing polymer brushes.

    PubMed

    de Beer, Sissi; Kutnyanszky, Edit; Müser, Martin H; Vancso, G Julius

    2014-12-24

    Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low friction at the interface. Nevertheless, these systems can be sensitive to wear due to interdigitation of the opposing brushes. In a recent publication, we have shown via molecular dynamics simulations and atomic force microscopy experiments, that using an immiscible polymer brush system terminating the substrate and the slider surfaces, respectively, can eliminate such interdigitation. As a consequence, wear in the contacts is reduced. Moreover, the friction force is two orders of magnitude lower compared to traditional miscible polymer brush systems. This newly proposed system therefore holds great potential for application in industry. Here, the methodology to construct an immiscible polymer brush system of two different brushes each solvated by their own preferred solvent is presented. The procedure how to graft poly(N-isopropylacrylamide) (PNIPAM) from a flat surface and poly(methyl methacrylate) (PMMA) from an atomic force microscopy (AFM) colloidal probe is described. PNIPAM is solvated in water and PMMA in acetophenone. Via friction force AFM measurements, it is shown that the friction for this system is indeed reduced by two orders of magnitude compared to the miscible system of PMMA on PMMA solvated in acetophenone.

  19. Binary Polymer Brushes of Strongly Immiscible Polymers.

    PubMed

    Chu, Elza; Babar, Tashnia; Bruist, Michael F; Sidorenko, Alexander

    2015-06-17

    The phenomenon of microphase separation is an example of self-assembly in soft matter and has been observed in block copolymers (BCPs) and similar materials (i.e., supramolecular assemblies (SMAs) and homo/block copolymer blends (HBCs)). In this study, we use microphase separation to construct responsive polymer brushes that collapse to generate periodic surfaces. This is achieved by a chemical reaction between the minor block (10%, poly(4-vinylpyridine)) of the block copolymer and a substrate. The major block of polystyrene (PS) forms mosaic-like arrays of grafted patches that are 10-20 nm in size. Depending on the nature of the assembly (SMA, HBC, or neat BCP) and annealing method (exposure to vapors of different solvents or heating above the glass transition temperature), a range of "mosaic" brushes with different parameters can be obtained. Successive grafting of a secondary polymer (polyacrylamide, PAAm) results in the fabrication of binary polymer brushes (BPBs). Upon being exposed to specific selective solvents, BPBs may adopt different conformations. The surface tension and adhesion of the binary brush are governed by the polymer occupying the top stratum. The "mosaic" brush approach allows for a combination of strongly immiscible polymers in one brush. This facilitates substantial contrast in the surface properties upon switching, previously only possible for substrates composed of predetermined nanostructures. We also demonstrate a possible application of such PS/PAAm brushes in a tunable bioadhesion-bioadhesive (PS on top) or nonbioadhesive (PAAm on top) surface as revealed by Escherichia coli bacterial seeding.

  20. Hydrophobic Porous Material Adsorbs Small Organic Molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Hickey, Gregory S.

    1994-01-01

    Composite molecular-sieve material has pore structure designed specifically for preferential adsorption of organic molecules for sizes ranging from 3 to 6 angstrom. Design based on principle that contaminant molecules become strongly bound to surface of adsorbent when size of contaminant molecules is nearly same as that of pores in adsorbent. Material used to remove small organic contaminant molecules from vacuum systems or from enclosed gaseous environments like closed-loop life-support systems.

  1. Zwitterionic Poly(amino acid methacrylate) Brushes

    PubMed Central

    2014-01-01

    A new cysteine-based methacrylic monomer (CysMA) was conveniently synthesized via selective thia-Michael addition of a commercially available methacrylate-acrylate precursor in aqueous solution without recourse to protecting group chemistry. Poly(cysteine methacrylate) (PCysMA) brushes were grown from the surface of silicon wafers by atom-transfer radical polymerization. Brush thicknesses of ca. 27 nm were achieved within 270 min at 20 °C. Each CysMA residue comprises a primary amine and a carboxylic acid. Surface zeta potential and atomic force microscopy (AFM) studies of the pH-responsive PCysMA brushes confirm that they are highly extended either below pH 2 or above pH 9.5, since they possess either cationic or anionic character, respectively. At intermediate pH, PCysMA brushes are zwitterionic. At physiological pH, they exhibit excellent resistance to biofouling and negligible cytotoxicity. PCysMA brushes undergo photodegradation: AFM topographical imaging indicates significant mass loss from the brush layer, while XPS studies confirm that exposure to UV radiation produces surface aldehyde sites that can be subsequently derivatized with amines. UV exposure using a photomask yielded sharp, well-defined micropatterned PCysMA brushes functionalized with aldehyde groups that enable conjugation to green fluorescent protein (GFP). Nanopatterned PCysMA brushes were obtained using interference lithography, and confocal microscopy again confirmed the selective conjugation of GFP. Finally, PCysMA undergoes complex base-catalyzed degradation in alkaline solution, leading to the elimination of several small molecules. However, good long-term chemical stability was observed when PCysMA brushes were immersed in aqueous solution at physiological pH. PMID:24884533

  2. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...

  3. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...

  4. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...

  5. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...

  6. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...

  7. Cholinergic urethral brush cells are widespread throughout placental mammals.

    PubMed

    Deckmann, Klaus; Krasteva-Christ, Gabriela; Rafiq, Amir; Herden, Christine; Wichmann, Judy; Knauf, Sascha; Nassenstein, Christina; Grevelding, Christoph G; Dorresteijn, Adriaan; Chubanov, Vladimir; Gudermann, Thomas; Bschleipfer, Thomas; Kummer, Wolfgang

    2015-11-01

    We previously identified a population of cholinergic epithelial cells in murine, human and rat urethrae that exhibits a structural marker of brush cells (villin) and expresses components of the canonical taste transduction signaling cascade (α-gustducin, phospholipase Cβ2 (PLCβ2), transient receptor potential cation channel melanostatin 5 (TRPM5)). These cells serve as sentinels, monitoring the chemical composition of the luminal content for potentially hazardous compounds such as bacteria, and initiate protective reflexes counteracting further ingression. In order to elucidate cross-species conservation of the urethral chemosensory pathway we investigated the occurrence and molecular make-up of urethral brush cells in placental mammals. We screened 11 additional species, at least one in each of the five mammalian taxonomic units primates, carnivora, perissodactyla, artiodactyla and rodentia, for immunohistochemical labeling of the acetylcholine synthesizing enzyme, choline acetyltransferase (ChAT), villin, and taste cascade components (α-gustducin, PLCβ2, TRPM5). Corresponding to findings in previously investigated species, urethral epithelial cells with brush cell shape were immunolabeled in all 11 mammals. In 8 species, immunoreactivities against all marker proteins and ChAT were observed, and double-labeling immunofluorescence confirmed the cholinergic nature of villin-positive and chemosensory (TRPM5-positive) cells. In cat and horse, these cells were not labeled by the ChAT antiserum used in this study, and unspecific reactions of the secondary antiserum precluded conclusions about ChAT-expression in the bovine epithelium. These data indicate that urethral brush cells are widespread throughout the mammalian kingdom and evolved not later than about 64.5millionyears ago. PMID:26044348

  8. Cholinergic urethral brush cells are widespread throughout placental mammals.

    PubMed

    Deckmann, Klaus; Krasteva-Christ, Gabriela; Rafiq, Amir; Herden, Christine; Wichmann, Judy; Knauf, Sascha; Nassenstein, Christina; Grevelding, Christoph G; Dorresteijn, Adriaan; Chubanov, Vladimir; Gudermann, Thomas; Bschleipfer, Thomas; Kummer, Wolfgang

    2015-11-01

    We previously identified a population of cholinergic epithelial cells in murine, human and rat urethrae that exhibits a structural marker of brush cells (villin) and expresses components of the canonical taste transduction signaling cascade (α-gustducin, phospholipase Cβ2 (PLCβ2), transient receptor potential cation channel melanostatin 5 (TRPM5)). These cells serve as sentinels, monitoring the chemical composition of the luminal content for potentially hazardous compounds such as bacteria, and initiate protective reflexes counteracting further ingression. In order to elucidate cross-species conservation of the urethral chemosensory pathway we investigated the occurrence and molecular make-up of urethral brush cells in placental mammals. We screened 11 additional species, at least one in each of the five mammalian taxonomic units primates, carnivora, perissodactyla, artiodactyla and rodentia, for immunohistochemical labeling of the acetylcholine synthesizing enzyme, choline acetyltransferase (ChAT), villin, and taste cascade components (α-gustducin, PLCβ2, TRPM5). Corresponding to findings in previously investigated species, urethral epithelial cells with brush cell shape were immunolabeled in all 11 mammals. In 8 species, immunoreactivities against all marker proteins and ChAT were observed, and double-labeling immunofluorescence confirmed the cholinergic nature of villin-positive and chemosensory (TRPM5-positive) cells. In cat and horse, these cells were not labeled by the ChAT antiserum used in this study, and unspecific reactions of the secondary antiserum precluded conclusions about ChAT-expression in the bovine epithelium. These data indicate that urethral brush cells are widespread throughout the mammalian kingdom and evolved not later than about 64.5millionyears ago.

  9. Effectiveness of oscillatory gutter brushes in removing street sweeping waste.

    PubMed

    Vanegas-Useche, Libardo V; Abdel-Wahab, Magd M; Parker, Graham A

    2015-09-01

    In this paper, the novel concept of oscillatory gutter brushes of road sweepers is studied experimentally. Their effectiveness in removing different debris types is studied by means of a brushing test rig. The debris types dealt with are medium-size gravel, small and fine particles, wet thin debris, and compacted debris. The performance of two types of brushes, cutting and F128, under diverse operating conditions is investigated. The purpose of the tests is to ascertain whether brush oscillations superimposed onto brush rotation improve sweeping effectiveness. According to the results, brush oscillations seem to be useful for increasing brushing effectiveness in the case of bonded particles and wet thin debris, especially for bonded debris, but they seem to be of no value for other loosed debris. Also, appropriate values of brush penetration, sweeper speed, brush angle of attack, rotational speed, and frequency of brush speed oscillations, for the debris types studied are provided.

  10. Preparation of a thick polymer brush layer composed of poly(2-methacryloyloxyethyl phosphorylcholine) by surface-initiated atom transfer radical polymerization and analysis of protein adsorption resistance.

    PubMed

    Inoue, Yuuki; Onodera, Yuya; Ishihara, Kazuhiko

    2016-05-01

    The purpose of this study was to prepare a thick polymer brush layer composed of poly(2-methacryloyloxyethyl phosphorylcholine (MPC)) and assess its resistance to protein adsorption from the dissolved state of poly(MPC) chains in an aqueous condition. The thick poly(MPC) brush layer was prepared through the surface-initiated atom transfer radical polymerization (SI-ATRP) of MPC with a free initiator from an initiator-immobilized substrate at given [Monomer]/[Free initiator] ratios. The ellipsometric thickness of the poly(MPC) brush layers could be controlled by the polymerization degree of the poly(MPC) chains. The thickness of the poly(MPC) brush layer in an aqueous medium was larger than that in air, and this tendency became clearer when the polymerization degree of the poly(MPC) increased. The maximum thickness of the poly(MPC) brush layer in an aqueous medium was around 110 nm. The static air contact angle of the poly(MPC) brush layer in water indicated a reasonably hydrophilic nature, which was independent of the thickness of the poly(MPC) brush layer at the surface. This result occurred because the hydrated state of the poly(MPC) chains is not influenced by the environment surrounding them. Finally, as measured with a quartz crystal microbalance, the amount of protein adsorbed from a fetal bovine serum solution (10% in phosphate-buffered saline) on the original substrate was 420 ng/cm(2). However, the poly(MPC) brush layer reduced this value dramatically to less than 50 ng/cm(2). This effect was independent of the thickness of the poly(MPC) brush layer for thicknesses between 20 nm and about 110 nm. These results indicated that the surface covered with a poly(MPC) brush layer is a promising platform to avoid biofouling and could also be applied to analyze the reactions of biological molecules with a high signal/noise ratio.

  11. Designing of dynamic polyethyleneimine (PEI) brushes on polyurethane (PU) ureteral stents to prevent infections.

    PubMed

    Gultekinoglu, Merve; Tunc Sarisozen, Yeliz; Erdogdu, Ceren; Sagiroglu, Meral; Aksoy, Eda Ayse; Oh, Yoo Jin; Hinterdorfer, Peter; Ulubayram, Kezban

    2015-07-01

    Permanent antibacterial coatings have been developed by brush-like polyethyleneimine (PEI) on polyurethane (PU) ureteral stents since bacterial adhesion and biofilm formation with the following encrustation on stent surface limit their long term usage. In order to control or prevent bacterial infections; PEI chains with two different molecular weights (Mn: 1800 or 60,000 Da) were covalently attached on the polyurethane (PU) surface by "grafting to" approach to obtain a brush-like structure. Then, PEI brushes were alkylated with bromohexane to enhance the disruption of bacterial membranes with increasing polycationic character. X-ray Photoelectron and Infrared Spectroscopy investigations confirmed that PEI grafting and alkylation steps were performed successfully. Surface roughness in dry state increased dramatically from 65.8 nm to 277.7 nm and 145.2 nm for short chain PEI and long chain PEI grafted samples, respectively. Both low and high molecular weight PEI grafts exhibited a brush-like structure and potent antibacterial activity by lowering the adherence of Klebsiella pneumonia, Escherichia coli and Proteus mirabilis species up to two orders of magnitude without any cytotoxic effect on L929 and G/G cells. Thus, permanent bactericidal activity was achieved by the contact-active strategy of dynamic PEI brush-like structures on polyurethane ureteral stent.

  12. Tribopair evaluation of brush seal applications

    NASA Astrophysics Data System (ADS)

    Derby, J.; England, R.

    1992-07-01

    Brush seal technology is currently being viewed as having high potential for improving jet engine efficiency by reducing the secondary flow leakage relative to layrinth seals. The selection of appropriate materials for brush seal bristles and coatings should be done in light of the tribological behavior at elevated temperature and speed. Seven candidate coatings and seven bristle alloys have been evaluated for friction and wear behavior at high temperature and high sliding speed conditions for the purpose of identifying materials which can extend brush seal performance. Four tribopairs are discussed in detail and a material combination is identified which can lower frictional heating during high radial excursion conditions by up to 50 percent, and extend the life of the brush seal through improved resistance to oxidation and wear, as compared to the standards today.

  13. Three-Wheel Brush-Wheel Sampler

    NASA Technical Reports Server (NTRS)

    Duckworth, Geoffrey A.; Liu, Jun; Brown, Mark G.

    2010-01-01

    A new sampler is similar to a common snow blower, but is robust and effective in sample collection. The brush wheels are arranged in a triangle shape, each driven by a brushless DC motor and planetary gearhead embedded in the wheel shaft. Its speed can be varied from 800 - 2,000 rpm, depending on the surface regolith resistance. The sample-collecting flow path, and internal features, are designed based on flow dynamics, and the sample-collecting rates have consistently exceeded the requirement under various conditions that span the range of expected surface properties. The brush-wheel sampler (BWS) is designed so that the flow channel is the main body of the apparatus, and links the brush-wheel assembly to the sample canister. The combination of the three brush wheels, the sample flow path, and the canister location make sample collection, storage, and transfer an easier task.

  14. Touch- and Brush-Spinning of Nanofibers.

    PubMed

    Tokarev, Alexander; Asheghali, Darya; Griffiths, Ian M; Trotsenko, Oleksandr; Gruzd, Alexey; Lin, Xin; Stone, Howard A; Minko, Sergiy

    2015-11-01

    Robust, simple, and scalable touch- and brush-spinning methods for the drawing of nanofibers, core-shell nanofibers, and their aligned 2D and 3D meshes using polymer solutions and melts are discussed.

  15. Responsive polymer brushes for controlled nanoparticle exposure

    NASA Astrophysics Data System (ADS)

    Akkilic, Namik; Leermakers, Frans A. M.; de Vos, Wiebe M.

    2015-10-01

    We propose the design of a novel mixed polymer brush system that could act as a selective sensor with a distinct on-off switch. In the proposed system, a (single) nanoparticle (such as an antibody) is end-attached to a responsive chain, which is surrounded by a brush of nonresponsive chains. The collapse of the responsive chain leads to a protected state, where the nanoparticle is hidden in the polymer brush, while swelling of the responsive chain brings the nanoparticle outside of the brush into an exposed and active state. We investigate this system by numerical self-consistent field theory and predict a first-order like transition between the active state and the protective state at a critical decrease in solvent quality for the responsive chain. We show that by careful design of the brush parameters such as grafting density and chain length, for a given particle size, it is possible to fine-tune the desired switching mechanism.We propose the design of a novel mixed polymer brush system that could act as a selective sensor with a distinct on-off switch. In the proposed system, a (single) nanoparticle (such as an antibody) is end-attached to a responsive chain, which is surrounded by a brush of nonresponsive chains. The collapse of the responsive chain leads to a protected state, where the nanoparticle is hidden in the polymer brush, while swelling of the responsive chain brings the nanoparticle outside of the brush into an exposed and active state. We investigate this system by numerical self-consistent field theory and predict a first-order like transition between the active state and the protective state at a critical decrease in solvent quality for the responsive chain. We show that by careful design of the brush parameters such as grafting density and chain length, for a given particle size, it is possible to fine-tune the desired switching mechanism. Electronic supplementary information (ESI) available: Brush density profiles for different grafting

  16. Water driven turbine/brush pipe cleaner

    NASA Technical Reports Server (NTRS)

    Werlink, Rudy J. (Inventor)

    1995-01-01

    Assemblies are disclosed for cleaning the inside walls of pipes and tubes. A first embodiment includes a small turbine with angled blades axially mounted on one end of a standoff support. An O-ring for stabilizing the assembly within the pipe is mounted in a groove within the outer ring. A replaceable circular brush is fixedly mounted on the opposite end of the standoff support and can be used for cleaning tubes and pipes of various diameters, lengths and configurations. The turbine, standoff support, and brush spin in unison relative to a hub bearing that is fixedly attached to a wire upstream of the assembly. The nonrotating wire is for retaining the assembly in tension and enabling return of the assembly to the pipe entrance. The assembly is initially placed in the pipe or tube to be cleaned. A pressurized water or solution source is provided at a required flow-rate to propel the assembly through the pipe or tube. The upstream water pressure propels and spins the turbine, standoff support and brush. The rotating brush combined with the solution cleans the inside of the pipe. The solution flows out of the other end of the pipe with the brush rotation controlled by the flow-rate. A second embodiment is similar to the first embodiment but instead includes a circular shaped brush with ring backing mounted in the groove of the exterior ring of the turbine, and also reduces the size of the standoff support or eliminates the standoff support.

  17. Mechanism of nanoparticle actuation by responsive polymer brushes: from reconfigurable composite surfaces to plasmonic effects

    NASA Astrophysics Data System (ADS)

    Roiter, Yuri; Minko, Iryna; Nykypanchuk, Dmytro; Tokarev, Ihor; Minko, Sergiy

    2011-12-01

    The mechanism of nanoparticle actuation by stimuli-responsive polymer brushes triggered by changes in the solution pH was discovered and investigated in detail in this study. The finding explains the high spectral sensitivity of the composite ultrathin film composed of a poly(2-vinylpyridine) (P2VP) brush that tunes the spacing between two kinds of nanoparticles--gold nanoislands immobilized on a transparent support and gold colloidal particles adsorbed on the brush. The optical response of the film relies on the phenomenon of localized surface plasmon resonances in the noble metal nanoparticles, giving rise to an extinction band in visible spectra, and a plasmon coupling between the particles and the islands that has a strong effect on the band position and intensity. Since the coupling is controlled by the interparticle spacing, the pH-triggered swelling-shrinking transition in the P2VP brush leads to pronounced changes in the transmission spectra of the hybrid film. It was not established in the previous publications how the actuation of gold nanoparticles within a 10-15 nm interparticle distance could result in the 50-60 nm shift in the absorbance maximum in contrast to the model experiments and theoretical estimations of several nanometer shifts. In this work, the extinction band was deconvoluted into four spectrally separated and overlapping contributions that were attributed to different modes of interactions between the particles and the islands. These modes came into existence due to variations in the thickness of the grafted polymeric layer on the profiled surface of the islands. In situ atomic force microscopy measurements allowed us to explore the behavior of the Au particles as the P2VP brush switched between the swollen and collapsed states. In particular, we identified an interesting, previously unanticipated regime when a particle position in a polymer brush was switched between two distinct states: the particle exposed to the surface of the

  18. Rotating Intershaft Brush Seal Project

    NASA Technical Reports Server (NTRS)

    Krawiecki, Stephen; Mehta, Jayesh; Holloway, Gary

    2006-01-01

    The pursuit of high Mach number flight presents several challenges to the airframe and engine design engineers. Most obvious is the resulting high temperatures encountered as the aircraft approaches Mach 3 and above. The encountered high temperatures and shaft speeds of engines require rethinking in the areas of material selections, component design and component operating life. In the area of sump compartment sealing, one of the most difficult sealing applications is the sealing of an engine s rear sump. Normally this sump will need some method of sealing between two rotating shafts. This sealing operation is done with an intershaft seal. The aft sump region also presents an additional design requirement for the intershaft seal. This region has to absorb the engine s thermal growth, which means that in the seal area, axial movement, on the order of 0.30 in., between the rotating shafts must be tolerated. A new concept or new technology of sealing an intershaft sump configuration is being developed. This concept, called a rotating intershaft brush seal has key attributes that will allow this seal to perform better, in the demanding environment of sealing an aft sump with two rotating shafts, when compared to today s sealing technology of labyrinth and carbon sea

  19. Poly(oligo(ethylene glycol)acrylamide) brushes by surface initiated polymerization: effect of macromonomer chain length on brush growth and protein adsorption from blood plasma.

    PubMed

    Kizhakkedathu, Jayachandran N; Janzen, Johan; Le, Yevgeniya; Kainthan, Rajesh K; Brooks, Donald E

    2009-04-01

    Three hydrolytically stable polyethyleneglycol (PEG)-based N-substituted acrylamide macromonomers, methoxypolyethyleneglycol (350) acrylamide (MPEG350Am) methoxypolyethyleneglycol (750) acrylamide(MPEG750Am) and methoxypolyethyleneglycol (2000)acrylamide (MPEG2000Am) with increasing PEG chain length were synthesized. Surface-initiated aqueous atom transfer radical polymerization (ATRP) using CuCl/1,1,4,7,10,10-hexamethyl triethylene tetramine (HMTETA) catalyst was utilized to generate dense polymer brushes from these monomers via an ester linker group on the surface of model polystyrene (PS) particles. The molecular weight, hydrodynamic thickness, and graft densities of the grafted polymer layers were controlled by changing the reaction parameters of monomer concentration, addition of Cu(II)Cl2, and sodium chloride. The graft densities of surface-grafted brushes decreased with increasing PEG macromonomer chain length, 350 > 750 > 2000, under similar experimental conditions. The molecular weight of grafts increased with increase in monomer concentration, and only selected conditions produced narrow distributed polymer chains. The molecular weight of grafted polymer chains differs significantly to those formed in solution. The hydrodynamic thicknesses of the grafted polymer layers were fitted to the Daoud and Cotton model (DCM) for brush height on spherical surfaces. The results show that the size of the pendent groups on the polymer chains has a profound effect on the hydrodynamic thickness of the brush for a given degree of polymerization. The new PEG-based surfaces show good protection against nonspecific protein adsorption from blood plasma compared to the bare surface. Protein adsorption decreased with increasing surface density of grafted polymer chains. Poly(MPEG750Am) brushes were more effective in preventing protein adsorption than poly(MPEG350Am) even at low graft densities, presumably due to the increase in PEG content in the grafted layer. PMID:19708153

  20. Adsorption characteristics of brush polyelectrolytes on silicon oxynitride revealed by dual polarization interferometry.

    PubMed

    Bijelic, Goran; Shovsky, Alexander; Varga, Imre; Makuska, Ricardas; Claesson, Per M

    2010-08-01

    Adsorption properties of bottle-brush polyelectrolytes have been investigated using dual polarization interferometry (DPI), which provides real time monitoring of adsorbed layer thickness and refractive index. The adsorption on silicon oxynitride was carried out from aqueous solution with no added inorganic salt, and the adsorbed polyelectrolyte layer was subsequently rinsed with NaCl solutions of increasing concentration. The bottle-brush polyelectrolytes investigated in this study have different ratios of permanent cationic charged segments and uncharged PEO side chains. Both the cationic groups and the PEO side chains have affinity for silica-like surfaces, and thus contribute to the adsorption process that becomes rather complex. Adsorption properties in water, responses to changes in ionic strength of the surrounding medium, adsorption kinetics and the layer structure are all strongly dependent on the ratio between backbone charges and side chains. The results are interpreted in terms of competitive adsorption of segments with different chemical nature. The adsorption kinetics is relatively fast, taking only tens to hundreds of seconds when adsorbed from dilute 100 ppm solutions. The DPI technique was found to be suitable for studying such rapid adsorption processes, including determination of the initial adsorption kinetics. We expect that the effects observed in this study are of general importance for synthetic and biological polymers carrying segments of different nature.

  1. Cold plasma brush generated at atmospheric pressure

    SciTech Connect

    Duan Yixiang; Huang, C.; Yu, Q. S.

    2007-01-15

    A cold plasma brush is generated at atmospheric pressure with low power consumption in the level of several watts (as low as 4 W) up to tens of watts (up to 45 W). The plasma can be ignited and sustained in both continuous and pulsed modes with different plasma gases such as argon or helium, but argon was selected as a primary gas for use in this work. The brush-shaped plasma is formed and extended outside of the discharge chamber with typical dimension of 10-15 mm in width and less than 1.0 mm in thickness, which are adjustable by changing the discharge chamber design and operating conditions. The brush-shaped plasma provides some unique features and distinct nonequilibrium plasma characteristics. Temperature measurements using a thermocouple thermometer showed that the gas phase temperatures of the plasma brush are close to room temperature (as low as 42 deg. C) when running with a relatively high gas flow rate of about 3500 ml/min. For an argon plasma brush, the operating voltage from less than 500 V to about 2500 V was tested, with an argon gas flow rate varied from less than 1000 to 3500 ml/min. The cold plasma brush can most efficiently use the discharge power as well as the plasma gas for material and surface treatment. The very low power consumption of such an atmospheric argon plasma brush provides many unique advantages in practical applications including battery-powered operation and use in large-scale applications. Several polymer film samples were tested for surface treatment with the newly developed device, and successful changes of the wettability property from hydrophobic to hydrophilic were achieved within a few seconds.

  2. Size selective hydrophobic adsorbent for organic molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K. (Inventor); Hickey, Gregory S. (Inventor)

    1997-01-01

    The present invention relates to an adsorbent formed by the pyrolysis of a hydrophobic silica with a pore size greater than 5 .ANG., such as SILICALITE.TM., with a molecular sieving polymer precursor such as polyfurfuryl alcohol, polyacrylonitrile, polyvinylidene chloride, phenol-formaldehyde resin, polyvinylidene difluoride and mixtures thereof. Polyfurfuryl alcohol is the most preferred. The adsorbent produced by the pyrolysis has a silicon to carbon mole ratio of between about 10:1 and 1:3, and preferably about 2:1 to 1:2, most preferably 1:1. The pyrolysis is performed as a ramped temperature program between about 100.degree. and 800.degree. C., and preferably between about 100.degree. and 600.degree. C. The present invention also relates to a method for selectively adsorbing organic molecules having a molecular size (mean molecular diameter) of between about 3 and 6 .ANG. comprising contacting a vapor containing the small organic molecules to be adsorbed with the adsorbent composition of the present invention.

  3. Synthesis of mimic molecularly imprinted ordered mesoporous silica adsorbent by thermally reversible semicovalent approach for pipette-tip solid-phase extraction-liquid chromatography fluorescence determination of estradiol in milk.

    PubMed

    Wang, Lu; Yan, Hongyuan; Yang, Chunliu; Li, Zan; Qiao, Fengxia

    2016-07-22

    A mimic molecularly imprinted ordered mesoporous silica (MIOMS) adsorbent was prepared utilizing a thermally reversible semicovalent approach. The thermally reversible covalent template-monomer complex was firstly synthesized by employing 4,4'-sulfonyldiphenol (BPS) and (3-isocyanatopropyl) triethoxysilane (ICPTES) as template and monomer, respectively. The template-monomer complex was incorporated into ordered mesoporous silica via a simple self-assembly process. The adsorption experiment illustrated that the imprint-removed silica (MIOMS-ir) had higher special recognition ability (250μgg(-1)) for estradiol (E2) than the non-imprinted silica (NIOMS-ir) (25μgg(-1)). MIOMS-ir was applied as an adsorbent in pipette-tip solid-phase extraction (PT-SPE) coupled with liquid chromatography-fluorescence detector (LC-FLD) for determination of E2 in milk samples. Under the optimized conditions, only 3mg of the adsorbent, 0.3mL of water as washing solvent, and 0.5mL of acetonitrile-acetic acid (96:4, v/v) as elution solvent were used in the pretreatment procedure of milk samples. Good calibration linearity was obtained in a range of 25ngL(-1) to 1000ngL(-1), and the recoveries at three spiked levels were ranged from 95.4% to 107.0% with relative standard deviations (RSDs) ≤3.1% (n=3). The proposed MIOMS-ir-PT-SPE-LC-FLD method combined the advantages of PT-SPE and ordered mesoporous material such as ease assembly, low cost, high extraction efficiency and large specific surface area, so it is a potential pretreatment strategy for the extraction and determination of E2 in complex milk samples. PMID:27328886

  4. Determination of the Actual Contact Surface of a Brush Contact

    NASA Technical Reports Server (NTRS)

    Holm, Ragnar

    1944-01-01

    The number of partial contact surfaces of a brush-ring contact is measured by means of a statistical method. The particular brush is fitted with wicks - that is, insulated and cemented cylinders of brush material, terminating in the brush surface. The number of partial contact surfaces can be computed from the length of the rest periods in which such wicks remain without current. Resistance measurements enable the determination of the size of the contact surfaces. The pressure in the actual contact surface of a recently bedded brush is found to be not much lower than the Brinell hardness of the brush.

  5. Monomer volume fraction profiles in pH responsive planar polyelectrolyte brushes

    DOE PAGES

    Mahalik, Jyoti P.; Yang, Yubo; Deodhar, Chaitra V.; Ankner, John Francis; Lokitz, Bradley S.; Kilbey, II, S. Michael; Sumpter, Bobby G.; Kumar, Rajeev

    2016-03-06

    Spatial dependencies of monomer volume fraction profiles of pH responsive polyelectrolyte brushes were investigated using field theories and neutron reflectivity experiments. In particular, planar polyelectrolyte brushes in good solvent were studied and direct comparisons between predictions of the theories and experimental measurements are presented. The comparisons between the theories and the experimental data reveal that solvent entropy and ion-pairs resulting from adsorption of counterions from the added salt play key roles in affecting the monomer distribution and must be taken into account in modeling polyelectrolyte brushes. Furthermore, the utility of this physics-based approach based on these theories for the predictionmore » and interpretation of neutron reflectivity profiles in the context of pH responsive planar polyelectrolyte brushes such as polybasic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and polyacidic poly(methacrylic acid) (PMAA) brushes is demonstrated. The approach provides a quantitative way of estimating molecular weights of the polymers polymerized using surface-initiated atom transfer radical polymerization.« less

  6. Growing Embossed Nanostructures of Polymer Brushes on Wet-Etched Silicon Templated via Block Copolymers

    PubMed Central

    Lu, Xiaobin; Yan, Qin; Ma, Yinzhou; Guo, Xin; Xiao, Shou-Jun

    2016-01-01

    Block copolymer nanolithography has attracted enormous interest in chip technologies, such as integrated silicon chips and biochips, due to its large-scale and mass production of uniform patterns. We further modified this technology to grow embossed nanodots, nanorods, and nanofingerprints of polymer brushes on silicon from their corresponding wet-etched nanostructures covered with pendent SiHx (X = 1–3) species. Atomic force microscopy (AFM) was used to image the topomorphologies, and multiple transmission-reflection infrared spectroscopy (MTR-IR) was used to monitor the surface molecular films in each step for the sequential stepwise reactions. In addition, two layers of polymethacrylic acid (PMAA) brush nanodots were observed, which were attributed to the circumferential convergence growth and the diffusion-limited growth of the polymer brushes. The pH response of PMAA nanodots in the same region was investigated by AFM from pH 3.0 to 9.0. PMID:26841692

  7. A theoretical study of colloidal forces near an amphiphilic polymer brush

    NASA Astrophysics Data System (ADS)

    Wu, Jianzhong

    2011-03-01

    Polymer-based ``non-stick'' coatings are promising as the next generation of effective, environmentally-friendly marine antifouling systems that minimize nonspecific adsorption of extracellular polymeric substances (EPS). However, design and development of such systems are impeded by the poor knowledge of polymer-mediated interactions of biomacromolecules with the protected substrate. In this work, a polymer density functional theory (DFT) is used to predict the potential of mean force between spherical biomacromolecules and amphiphilic copolymer brushes within a coarse-grained model that captures essential nonspecific interactions such as the molecular excluded volume effects and the hydrophobic energies. The relevance of theoretical results for practical control of the EPS adsorption is discussed in terms of the efficiency of different brush configurations to prevent biofouling. It is shown that the most effective antifouling surface may be accomplished by using amphiphilic brushes with a long hydrophilic backbone and a hydrophobic end at moderate grafting density.

  8. Quantum chemical investigation on the role of Li adsorbed on anatase (101) surface nano-materials on the storage of molecular hydrogen.

    PubMed

    Srinivasadesikan, V; Raghunath, P; Lin, M C

    2015-06-01

    Lithiation of TiO2 has been shown to enhance the storage of hydrogen up to 5.6 wt% (Hu et al. J Am Chem Soc 128:11740-11741, 2006). The mechanism for the process is still unknown. In this work we have carried out a study on the adsorption and diffusion of Li atoms on the surface and migration into subsurface layers of anatase (101) by periodic density functional theory calculations implementing on-site Coulomb interactions (DFT+U). The model consists of 24 [TiO2] units with 11.097 × 7.655 Å(2) surface area. Adsorption energies have been calculated for different Li atoms (1-14) on the surface. A maximum of 13 Li atoms can be accommodated on the surface at two bridged O, Ti-O, and Ti atom adsorption sites, with 83 kcal mol(-1) adsorption energy for a single Li atom adsorbed between two bridged O atoms from where it can migrate into the subsurface layer with 27 kcal mol(-1) energy barrier. The predicted adsorption energies for H2 on the lithiated TiO2 (101) surface with 1-10 Li atoms revealed that the highest adsorption energies occurred on 1-Li, 5-Li, and 9-Li surfaces with 3.5, 4.4, and 7.6 kcal mol(-1), respectively. The values decrease rapidly with additional H2 co-adsorbed on the lithiated surfaces; the maximum H2 adsorption on the 9Li-TiO2(a) surface was estimated to be only 0.32 wt% under 100 atm H2 pressure at 77 K. The result of Bader charge analysis indicated that the reduction of Ti occurred depending on the Li atoms covered on the TiO2 surface.

  9. Motor Brush Testing for Mars and Vacuum

    NASA Technical Reports Server (NTRS)

    Noon, Don E.

    1999-01-01

    Brush motors have been qualified and flown successfully on Mars missions, but upcoming missions require longer life and higher power. A test program was therefore undertaken to identify the best brush material for operation in the Mars atmosphere. Six different brush materials were used in 18 identical motors and operated under various load conditions for a period of four weeks in low-pressure CO2. All motors performed acceptably, with accumulated motor revolutions between 98 and 144 million revolutions, depending on load. A proprietary silver-graphite material from Superior Carbon (SG54-27) appears to be the best choice for long life, but even the stock copper-graphite brushes performed reliably with acceptable wear. The motors from the CO2 test were then cleaned and run in vacuum for 2 weeks. The difference in results was dramatic, with 5 motors failing catastrophically and wear rates increasing by orders of magnitude for the SG54-27 material. Three brush materials survived the test with no failures: SG54-27 with a proprietary Ball Aerospace impregnation, a silver-graphite-molybdenum disulfide material from Superior Carbon (SG59), and a copper sulfide-graphite material also from Superior Carbon (BG91).

  10. Bidirectional Brush Seals: Post-Test Analysis

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Wilson, Jack; Wu, Tom Y.; Flower, Ralph; Mullen, Robert L.

    1997-01-01

    A post-test analysis of a set of inside-diameter/outside-diameter (ID/OD) bidirectional brush seals used in three-port wave rotor tests was undertaken to determine brush bristle and configuration wear, pullout, and rotor coating wear. The results suggest that sharp changes in the pressure profiles were not well reflected in bristle tip configuration patterns or wear. Also, positive-to-negative changes in axial pressure gradients appeared to have little effect on the backing plates. Although the brushes had similar porosities, they had very different unpacked arrays. This difference could explain the departure of experimental data from computational fluid dynamics flow predictions for well-packed arrays at higher pressure drops. The rotor wear led to "car-track" scars (upper and lower wear bands) with a whipped surface between the bands. Those bands may have resulted from bristle stiffening at the fence and gap plates during alternate portions of the rotor cycle. Within the bristle response range the wear surface reflected the pressure distribution effect on bristle motion. No sacrificial metallurgical data were taken. The bristles did wear, with correspondingly more wear on the ID brush configurations than on the OD configurations; the complexity in constructing the ID brush was a factor.

  11. Discriminatory bio-adhesion over nano-patterned polymer brushes

    NASA Astrophysics Data System (ADS)

    Gon, Saugata

    Surfaces functionalized with bio-molecular targeting agents are conventionally used for highly-specific protein and cell adhesion. This thesis explores an alternative approach: Small non-biological adhesive elements are placed on a surface randomly, with the rest of the surface rendered repulsive towards biomolecules and cells. While the adhesive elements themselves, for instance in solution, typically exhibit no selectivity for various compounds within an analyte suspension, selective adhesion of targeted objects or molecules results from their placement on the repulsive surface. The mechanism of selectivity relies on recognition of length scales of the surface distribution of adhesive elements relative to species in the analyte solution, along with the competition between attractions and repulsions between various species in the suspension and different parts of the collecting surface. The resulting binding selectivity can be exquisitely sharp; however, complex mixtures generally require the use of multiple surfaces to isolate the various species: Different components will be adhered, sharply, with changes in collector composition. The key feature of these surface designs is their lack of reliance on biomolecular fragments for specificity, focusing entirely on physicochemical principles at the lengthscales from 1 - 100 nm. This, along with a lack of formal patterning, provides the advantages of simplicity and cost effectiveness. This PhD thesis demonstrates these principles using a system in which cationic poly-L-lysine (PLL) patches (10 nm) are deposited randomly on a silica substrate and the remaining surface is passivated with a bio-compatible PEG brush. TIRF microscopy revealed that the patches were randomly arranged, not clustered. By precisely controlling the number of patches per unit area, the interfaces provide sharp selectivity for adhesion of proteins and bacterial cells. For instance, it was found that a critical density of patches (on the order of

  12. Microstructured poly(2-oxazoline) bottle-brush brushes on nanocrystalline diamond.

    PubMed

    Hutter, Naima A; Reitinger, Andreas; Zhang, Ning; Steenackers, Marin; Williams, Oliver A; Garrido, Jose A; Jordan, Rainer

    2010-05-01

    We report on the preparation of microstructured poly(2-oxazoline) bottle-brush brushes (BBBs) on nanocrystalline diamond (NCD). Structuring of NCD was performed by photolithography and plasma treatment to result in a patterned NCD surface with oxidized and hydrogenated areas. Self-initiated photografting and photopolymerization (SIPGP) of 2-isopropenyl-2-oxazoline (IPOx) resulted in selective grafting of poly(2-isopropenyl-2-oxazoline) (PIPOx) polymer brushes only at the oxidized NCD areas. Structured PIPOx brushes were converted by methyl triflate into the polyelectrolyte brush macroinitiator for the living cationic ring-opening polymerization (LCROP) of 2-oxazolines. The LCROP was performed with 2-ethyl-2-oxazoline (EtOx) as well as 2-(carbazolyl)ethyl-2-oxazoline (CarbOx) as monomers, resulting in structured bottle-brush brushes (BBB) with different pendant side chains and functionalities. FT-IR spectroscopy, fluorescence microscopy, and AFM measurements indicated a high side chain grafting density as well as quantitative and selective reactions. Poly(2-oxazoline) BBBs containing hole conducting carbazole moieties on NCD as electrode material may open the way to advanced amperometric biosensing systems.

  13. LM2500+ Brush Seal Case Study

    NASA Technical Reports Server (NTRS)

    Haaser, Fred G.

    2006-01-01

    The LM2500+ industrial aeroderivative gas turbine, a 25% enhanced power derivative of the LM2500 gas turbine, recently completed its development test program during the period 5/96 - 10/96. Early in the engine program a Quality Function Deployment (QFD) process was used to determine customer needs for this project.The feedback obtained from the QFD process showed without doubt that gas turbine customers now emphasize product reliability and availability at the top of their needs. One area of development on the LM2500+ was to investigate the use of a brush seal as a means to reduce undesirable turbine cooling leakages within the turbine mid frame in order to enhance part life. This presentation presents a case study on the factors that went into evaluating a brush seal during engine test, test results, and the ultimate decision not to implement the brush seal for cost and other reasons.

  14. Two-stage eutectic metal brushes

    SciTech Connect

    Hsu, John S

    2009-07-14

    A two-stage eutectic metal brush assembly having a slip ring rigidly coupled to a shaft, the slip ring being electrically coupled to first voltage polarity. At least one brush is rigidly coupled to a second ring and slidingly engaged to the slip ring. Eutectic metal at least partially fills an annulus between the second ring and a stationary ring. At least one conductor is rigidly coupled to the stationary ring and electrically coupled to a second voltage polarity. Electrical continuity is maintained between the first voltage polarity and the second voltage polarity. Periodic rotational motion is present between the stationary ring and the second ring. Periodic rotational motion is also present between the brush and the slip ring.

  15. Pathogenesis of mucosal injury in the blind loop syndrome. Brush border enzyme activity and glycoprotein degradation.

    PubMed

    Jonas, A; Flanagan, P R; Forstner, G G

    1977-12-01

    The effect of intestinal bacterial over-growth on brush border hydrolases and brush border glycoproteins was studied in nonoperated control rats, control rats with surgically introduced jejunal self-emptying blind loops, and rats with surgically introduced jejunal self-filling blind loops. Data were analyzed from blind loop segments, segments above and below the blind loops, and three corresponding segments in the nonoperated controls. Rats with self-filling blind loops had significantly greater fat excretion than controls and exhibited significantly lower conjugated:free bile salt ratios in all three segments. Maltase, sucrase, and lactase activities were significantly reduced in homogenates and isolated brush borders from the self-filling blind loop, but alkaline phosphatase was not affected. The relative degradation rate of homogenate and brush border glycoproteins was assessed by a double-isotope technique involving the injection of d-[6-(3)H]glucosamine 3 h and d-[U-(14)C]glucosamine 19 h before sacrifice, and recorded as a (3)H:(14)C ratio. The relative degradation rate in both homogenate and brush border fractions was significantly greater in most segments from rats with self-filling blind loops. In the upper and blind loop segments from rats with self-filling blind loops, the (3)H:(14)C ratios were higher in the brush border membrane than in the corresponding homogenates, indicating that the increased rates of degradation primarily involve membrane glycoproteins. Incorporation of d-[6-(3)H]glucosamine by brush border glycoproteins was not reduced in rats with self-filling blind loops, suggesting that glycoprotein synthesis was not affected. Polyacrylamide gel electrophoresis of brush border glycoproteins from the contaminated segments indicated that the large molecular weight glycoproteins, which include many of the surface hydrolases, were degraded most rapidly. Brush border maltase, isolated by immunoprecipitation, had (3)H:(14)C ratios characteristic of

  16. Using specialized adsorbents for remediation

    SciTech Connect

    Hochmuth, D.P.; Grant, A.

    1995-11-01

    This paper describes two remediation case studies in which specialized adsorbents were used. In one case, the adsorbents were used to treat effluent from a soil vapor extraction system. In the other case, the adsorbents were used to treat air from a groundwater air stripper. The specialized adsorbents effectively removed volatile organic compounds from each air stream.

  17. Synthesis and antibacterial properties of ZnO brush pens

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Zhang, Rong; Li, Yilin; Weng, Yuan; Liang, Weiquan; Zhang, Wenfeng; Zheng, Weitao; Hu, Haimei

    2015-12-01

    In this paper, ZnO with a novel hierarchical nanostructure has been synthesized by a new solution method. The novel hierarchical structure is named a ‘brush pen’. The biocompatibility and antibacterial properties of ZnO brush pens have been evaluated. The results demonstrate that ZnO brush pens show good antibacterial activity against Staphylococcus aureus.

  18. Polymer brushes in cylindrical pores: Simulation versus scaling theory

    NASA Astrophysics Data System (ADS)

    Dimitrov, D. I.; Milchev, A.; Binder, K.

    2006-07-01

    The structure of flexible polymers endgrafted in cylindrical pores of diameter D is studied as a function of chain length N and grafting density σ, assuming good solvent conditions. A phenomenological scaling theory, describing the variation of the linear dimensions of the chains with σ, is developed and tested by molecular dynamics simulations of a bead-spring model. Different regimes are identified, depending on the ratio of D to the size of a free polymer N3/5. For D >N3/5 a crossover occurs for σ =σ*=N-6/5 from the "mushroom" behavior (Rgx=Rgy=Rgz=N3/5) to the behavior of a flat brush (Rgz=σ1/3N,Rgx=Rgy=σ-1/12N1/2), until at σ**=(D /N)3 a crossover to a compressed state of the brush, [Rgz=D,Rgx=Rgy=(N3D /4σ)1/8brush. These predictions are compared to the computer simulations. From the latter, extensive results on monomer density and free chain end distributions are also obtained, and a discussion of pertinent theories is given. In particular, it is shown that for large D the brush height is an increasing function of D-1.

  19. Clinical evaluation of supplementing tongue brushing to most advocated regime of tooth brushing.

    PubMed

    Gulati, M S; Gupta, L

    1998-03-01

    Tongue, because of its surface texture contributes significantly in plaque formation and accumulation, has remained a neglected part in the oral cavity. The study conducted on twenty students aged 18 to 23 years, was undertaken to clinically evaluate the role of supplementing tongue brushing to most advocated regime of tooth brushing. In both the phases of the study, plaque scoring was done daily and oral debris was collected on the eighth day. It was observed that tongue brushing when supplemented to the most advocated regime of tooth brushing that is, immediately after breakfast in the morning and immediately after dinner at night significantly reduced the initial rate of plaque formation and total plaque accumulation.

  20. Regenerative adsorbent heat pump

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    1991-01-01

    A regenerative adsorbent heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system and at least a portion of the heat of adsorption. A series of at least four compressors containing an adsorbent is provided. A large amount of heat is transferred from compressor to compressor so that heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.

  1. Adsorption of plasma proteins and fibronectin on poly(hydroxylethyl methacrylate) brushes of different thickness and their relationship with adhesion and migration of vascular smooth muscle cells

    PubMed Central

    Deng, Jun; Ren, Tanchen; Zhu, Jiyu; Mao, Zhengwei; Gao, Changyou

    2014-01-01

    The surface-grafted poly(hydroxylethyl methacrylate) (PHEMA) molecules were demonstrated to show a brush state regardless of their molecular length (molecular weight). Adsorption of proteins from 10% fetal bovine serum (FBS), fibronectin (Fn) and bovine serum albumin (BSA) was quantified by ellipsometry, revealing that the amounts of FBS and Fn decreased monotonously along with the increase of PHEMA thickness, whereas not detectable for BSA when the PHEMA thickness was larger than 6 nm. Radio immunoassay found that the adsorption of Fn from 10% FBS had no significant difference regardless of the PHEMA thickness. However, ELISA results showed that the Arg-Gly-Asp (RGD) activity of adsorbed Fn decreased with the increase of PHEMA thickness. By comparison of cellular behaviors of vascular smooth muscle cells (VSMCs) being cultured in vitro in the normal serum-containing medium and the Fn-depleted serum-containing medium, the significant role of Fn on modulating the adhesion and migration of VSMCs was verified. Taking account all the results, the Fn adsorption model and its role on linking the biomaterials surface to the VSMCs behaviors are proposed. PMID:26814446

  2. Numerical self-consistent field theory study of the response of strong polyelectrolyte brushes to external electric fields

    SciTech Connect

    Tong, Chaohui

    2015-08-07

    The response of strong polyelectrolyte (PE) brushes grafted on an electrode to electric fields generated by opposite surface charges on the PE-grafted electrode and a second parallel electrode has been numerically investigated by self-consistent field theory. The influences of grafting density, average charge fraction, salt concentration, and mobile ion size on the variation of the brush height against an applied voltage bias were investigated. In agreement with molecular dynamics simulation results, a higher grafting density requires a larger magnitude of voltage bias to achieve the same amount of relative change in the brush height. In the experimentally relevant parameter regime of the applied voltage, the brush height becomes insensitive to the voltage bias when the grafting density is high. Including the contribution of surface charges on the grafting electrode, overall charge neutrality inside the PE brushes is generally maintained, especially for PE brushes with high grafting density and high average charge fraction. Our numerical study further reveals that the electric field across the two electrodes is highly non-uniform because of the complex interplay between the surface charges on the electrodes, the charges on the grafted PE chains, and counterions.

  3. Chinese Brush Calligraphy Character Retrieval and Learning

    ERIC Educational Resources Information Center

    Zhuang, Yueting; Zhang, Xiafen; Lu, Weiming; Wu, Fei

    2007-01-01

    Chinese brush calligraphy is a valuable civilization legacy and a high art of scholarship. It is still popular in Chinese banners, newspaper mastheads, university names, and celebration gifts. There are Web sites that try to help people enjoy and learn Chinese calligraphy. However, there lacks advanced services such as content-based retrieval or…

  4. Multifunctional brushes made from carbon nanotubes.

    PubMed

    Cao, Anyuan; Veedu, Vinod P; Li, Xuesong; Yao, Zhaoling; Ghasemi-Nejhad, Mehrdad N; Ajayan, Pulickel M

    2005-07-01

    Brushes are common tools for use in industry and our daily life, performing a variety of tasks such as cleaning, scraping, applying and electrical contacts. Typical materials for constructing brush bristles include animal hairs, synthetic polymer fibres and metal wires (see, for example, ref. 1). The performance of these bristles has been limited by the oxidation and degradation of metal wires, poor strength of natural hairs, and low thermal stability of synthetic fibres. Carbon nanotubes, having a typical one-dimensional nanostructure, have excellent mechanical properties, such as high modulus and strength, high elasticity and resilience, thermal conductivity and large surface area (50-200 m2 g(-1)). Here we construct multifunctional, conductive brushes with carbon nanotube bristles grafted on fibre handles, and demonstrate their several unique tasks such as cleaning of nanoparticles from narrow spaces, coating of the inside of holes, selective chemical adsorption, and as movable electromechanical brush contacts and switches. The nanotube bristles can also be chemically functionalized for selective removal of heavy metal ions.

  5. Scaling Relationships for Spherical Polymer Brushes Revisited.

    PubMed

    Chen, Guang; Li, Hao; Das, Siddhartha

    2016-06-16

    In this short paper, we revisit the scaling relationships for spherical polymer brushes (SPBs), i.e., polymer brushes grafted to rigid, spherical particles. Considering that the brushes can be described to be encased in a series of hypothetical spherical blobs, we identify significant physical discrepancies in the model of Daoud and Cotton (Journal of Physics, 1982), which is considered to be the state of the art in scaling modeling of SPBs. We establish that the "brush" configuration of the polymer molecules forming the SPBs is possible only if the swelling ratio (which is the ratio of the end-to-end length of the blob-encased polymer segment to the corresponding coil-like polymer segment) is always less than unity-a notion that has been erroneously overlooked in the model of Daoud and Cotton. We also provide new scaling arguments that (a) establish this swelling (or more appropriately shrinking) ratio as a constant (less than unity) for the case of "good" solvent, (b) recover the scaling predictions for blob dimension and monomer number and monomer concentration distributions within the blob, and

  6. Phototriggered functionalization of hierarchically structured polymer brushes.

    PubMed

    de los Santos Pereira, Andres; Kostina, Nina Yu; Bruns, Michael; Rodriguez-Emmenegger, Cesar; Barner-Kowollik, Christopher

    2015-06-01

    The precise design of bioactive surfaces, essential for the advancement of many biomedical applications, depends on achieving control of the surface architecture as well as on the ability to attach bioreceptors to antifouling surfaces. Herein, we report a facile avenue toward hierarchically structured antifouling polymer brushes of oligo(ethylene glycol) methacrylates via surface-initiated atom transfer radical polymerization (SI-ATRP) presenting photoactive tetrazole moieties, which permitted their functionalization via nitrile imine-mediated tetrazole-ene cyclocloaddition (NITEC). A maleimide-functional ATRP initiator was photoclicked to the side chains of a brush enabling a subsequent polymerization of carboxybetaine acrylamide to generate a micropatterned graft-on-graft polymer architecture as evidenced by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Furthermore, the spatially resolved biofunctionalization of the tetrazole-presenting brushes was accessed by the photoligation of biotin-maleimide and subsequent binding of streptavidin. The functionalized brushes bearing streptavidin were able to resist the fouling from blood plasma (90% reduction with respect to bare gold). Moreover, they were employed to demonstrate a model biosensor by immobilization of a biotinylated antibody and subsequent capture of an antigen as monitored in real time by surface plasmon resonance. PMID:25961109

  7. Bioadhesive control of plasma proteins and blood cells from umbilical cord blood onto the interface grafted with zwitterionic polymer brushes.

    PubMed

    Chang, Yu; Chang, Yung; Higuchi, Akon; Shih, Yu-Ju; Li, Pei-Tsz; Chen, Wen-Yih; Tsai, Eing-Mei; Hsiue, Ging-Ho

    2012-03-01

    In this work, bioadhesive behavior of plasma proteins and blood cells from umbilical cord blood (UCB) onto zwitterionic poly(sulfobetaine methacrylate) (polySBMA) polymer brushes was studied. The surface coverage of polySBMA brushes on a hydrophobic polystyrene (PS) well plate with surface grafting weights ranging from 0.02 mg/cm(2) to 0.69 mg/cm(2) can be effectively controlled using the ozone pretreatment and thermal-induced radical graft-polymerization. The chemical composition, grafting structure, surface hydrophilicity, and hydration capability of prepared polySBMA brushes were determined to illustrate the correlations between grafting properties and blood compatibility of zwitterionic-grafted surfaces in contact with human UCB. The protein adsorption of fibrinogen in single-protein solutions and at complex medium of 100% UCB plasma onto different polySBMA brushes with different grafting coverage was measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. The grafting density of the zwitterionic brushes greatly affects the PS surface, thus controlling the adsorption of fibrinogen, the adhesion of platelets, and the preservation of hematopoietic stem and progenitor cells (HSPCs) in UCB. The results showed that PS surfaces grafted with polySBMA brushes possess controllable hydration properties through the binding of water molecules, regulating the bioadhesive and bioinert characteristics of plasma proteins and blood platelets in UCB. Interestingly, it was found that the polySBMA brushes with an optimized grafting weight of approximately 0.1 mg/cm(2) at physiologic temperatures show significant hydrated chain flexibility and balanced hydrophilicity to provide the best preservation capacity for HSPCs stored in 100% UCB solution for 2 weeks. This work suggests that, through controlling grafting structures, the hemocompatible nature of grafted zwitterionic polymer brushes makes them well suited to the molecular design of regulated

  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.

  9. Nonlinearity in the rotational dynamics of Haidinger's brushes

    NASA Astrophysics Data System (ADS)

    Rothmayer, Mark; Dultz, Wolfgang; Frins, Erna; Zhan, Qiwen; Tierney, Dennis; Schmitzer, Heidrun

    2007-10-01

    Haidinger's brushes are an entoptic effect of the human visual system that enables us to detect polarized light. However, individual perceptions of Haidinger's brushes can vary significantly. We find that the birefringence of the cornea influences the rotational motion and the contrast of Haidinger's brushes and may offer an explanation for individual differences. We have devised an experimental setup to simulate various phase shifts of the cornea and found a switching effect in the rotational dynamics of Haidinger's brushes. In addition, age related macular degeneration reduces the polarization effect of the macula and thus also leads to changes in the brush pattern.

  10. Effects of brush seal morphology on leakage and pressure drops

    NASA Technical Reports Server (NTRS)

    Braun, M. J.; Yang, Y.; Hendricks, R. C.

    1991-01-01

    Research on brush seals which was undertaken earlier by Braun et al. (1990) is continued. Particular attention is given to the effects of brush positioning, design, and morphology on sealing surfaces, fluid leakage, and associated pressure drops. It is found that both the structure and the design of the brush are important to its performance. High resistance to the flow of the brush/fence combination can result in catastrophic failure of the brush, while at lower flow resistances, the failure is more gradual.

  11. Brushes of semiflexible polymers in equilibrium and under flow in a super-hydrophobic regime.

    PubMed

    Speyer, K; Pastorino, C

    2015-07-21

    We performed molecular dynamics simulations to study the equilibrium and flow properties of a liquid in a nano-channel with confining surfaces coated with a layer of grafted semiflexible polymers. The coverage spans a wide range of grafting densities from essentially isolated chains to dense brushes. The end-grafted polymers were described by a bead spring model with a harmonic potential to include the bond stiffness of the chains. We varied the rigidity of the chains, from fully flexible polymers to rigid rods, in which the configurational entropy of the chains is negligible. The brush-liquid interaction was tuned to obtain a super-hydrophobic channel, in which the liquid did not penetrate the polymer brush, giving rise to a Cassie-Baxter state. Equilibrium properties such as brush height and bending energy were measured, varying the grafting density and the stiffness of the polymers. We also studied the characteristics of the brush-liquid interface and the morphology of the polymer chains supporting the liquid for different bending rigidities. Non-equilibrium simulations were performed, moving the walls of the channel in opposite directions at constant speed, obtaining a Couette velocity profile in the bulk liquid. The molecular degrees of freedom of the polymers were studied as a function of the Weissenberg number. Also, the violation of the no-slip boundary condition and the slip properties were analyzed as a function of the shear rate, grafting density and bending stiffness. At high grafting densities, a finite slip length independent of the shear rate or bending constant was found, while at low grafting densities a very interesting non-monotonic dependence on the bending constant is observed.

  12. Arsenic(III, V) adsorption on a goethite-based adsorbent in the presence of major co-existing ions: Modeling competitive adsorption consistent with spectroscopic and molecular evidence

    NASA Astrophysics Data System (ADS)

    Kanematsu, Masakazu; Young, Thomas M.; Fukushi, Keisuke; Green, Peter G.; Darby, Jeannie L.

    2013-04-01

    Adsorption of the two oxyanions, arsenate (As(V)) and arsenite (As(III)), on a common goethite-based granular porous adsorbent is studied in the presence of major co-existing ions in groundwater (i.e., phosphate, silicic acid, sulfate, carbonate, magnesium, and calcium) and predicted using the extended triple layer model (ETLM), a dipole modified single-site triple layer surface complexation model consistent with spectroscopic and molecular evidence. Surface species of all ions were selected according to the previous ETLM studies and published experimental spectroscopic/theoretical molecular information. The adsorption equilibrium constants for all ions were determined using adsorption data obtained in single-solute systems. The adsorption equilibrium constants referenced to the site-occupancy standard state (indicated by Kθ) were compared with those for goethite in the literature if available. The values of these constants for the goethite-based adsorbent are found to be close to the values for goethite previously studied. These "constrained" adsorption equilibrium constants determined in single-solute systems were used in the ETLM to predict the competitive interactions of As(III, V) with the co-existing ions in binary-solute systems. The ETLM is capable of predicting As(III, V) adsorption in the presence of oxyanions (phosphate, silicic acid, sulfate, and carbonate). This study presents the first successful and systematic prediction of the competitive interactions of As(III, V) with these oxyanions using the ETLM. The ETLM prediction of surface (and aqueous) speciation also provides insights into the distinct adsorption behavior of As(III, V) in the presence of the oxyanions. Magnesium and calcium significantly enhanced As(V) adsorption at higher pH values, while they had little effect on As(III) adsorption. The enhanced adsorption of As(V), however, could not be predicted by the ETLM using the surface species proposed in previous ETLM studies. Further studies

  13. Preparation of High Purity, High Molecular-Weight Chitin from Ionic Liquids for Use as an Adsorbate for the Extraction of Uranium from Seawater

    SciTech Connect

    Rogers, Robin

    2013-12-21

    Ensuring a domestic supply of uranium is a key issue facing the wider implementation of nuclear power. Uranium is mostly mined in Kazakhstan, Australia, and Canada, and there are few high-grade uranium reserves left worldwide. Therefore, one of the most appealing potential sources of uranium is the vast quantity dissolved in the oceans (estimated to be 4.4 billion tons worldwide). There have been research efforts centered on finding a means to extract uranium from seawater for decades, but so far none have resulted in an economically viable product, due in part to the fact that the materials that have been successfully demonstrated to date are too costly (in terms of money and energy) to produce on the necessary scale. Ionic Liquids (salts which melt below 100{degrees}C) can completely dissolve raw crustacean shells, leading to recovery of a high purity, high molecular weight chitin powder and to fibers and films which can be spun directly from the extract solution suggesting that continuous processing might be feasible. The work proposed here will utilize the unprecedented control this makes possible over the chitin fiber a) to prepare electrospun nanofibers of very high surface area and in specific architectures, b) to modify the fiber surfaces chemically with selective extractant capacity, and c) to demonstrate their utility in the direct extraction and recovery of uranium from seawater. This approach will 1) provide direct extraction of chitin from shellfish waste thus saving energy over the current industrial process for obtaining chitin; 2) allow continuous processing of nanofibers for very high surface area fibers in an economical operation; 3) provide a unique high molecular weight chitin not available from the current industrial process, leading to stronger, more durable fibers; and 4) allow easy chemical modification of the large surface areas of the fibers for appending uranyl selective functionality providing selectivity and ease of stripping. The

  14. Surface modification and characterization of carbon spheres by grafting polyelectrolyte brushes

    NASA Astrophysics Data System (ADS)

    Zhang, Qi; Li, Houbin; Zhang, Pan; Liu, Liangliang; He, Yuhang; Wang, Yali

    2014-06-01

    Modified carbon spheres (CSPBs) were obtained by grafting poly(diallyl dimethyl ammonium chloride) (p-DMDAAC) on the surface of carbon spheres (CSs). It can be viewed as a kind of cation spherical polyelectrolyte brushes (CSPBs), which consist of carbon spheres as core and polyelectrolytes as shell. The method of synthesizing carbon spheres was hydrothermal reaction. Before the polyelectrolyte brushes were grafted, azo initiator [4,4'-Azobis(4-cyanovaleric acyl chloride)] was attached to the carbon spheres' surface through hydroxyl groups. CSPBs were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), conductivity meter, and system zeta potential. The results showed that compared with carbon spheres, the conductivity and zeta potential on CSPBs increased from 9.98 to 49.24 μS/cm and 11.6 to 42.5 mV, respectively, after the polyelectrolyte brushes were grafted. The colloidal stability in water was enhanced, and at the same time, the average diameter of the CSPBs was found to be 173 nm, and the average molecular weight and grafted density of the grafted polyelectrolyte brushes were 780,138 g/mol and 4.026 × 109/nm2, respectively.

  15. Removal of acutely hazardous pharmaceuticals from water using multi-template imprinted polymer adsorbent.

    PubMed

    Venkatesh, Avinash; Chopra, Nikita; Krupadam, Reddithota J

    2014-05-01

    Molecularly imprinted polymer adsorbent has been prepared to remove a group of recalcitrant and acutely hazardous (p-type) chemicals from water and wastewaters. The polymer adsorbent exhibited twofold higher adsorption capacity than the commercially used polystyrene divinylbenzene resin (XAD) and powdered activated carbon adsorbents. Higher adsorption capacity of the polymer adsorbent was explained on the basis of high specific surface area formed during molecular imprinting process. Freundlich isotherms drawn showed that the adsorption of p-type chemicals onto polymer adsorbent was kinetically faster than the other reference adsorbents. Matrix effect on adsorption of p-type chemicals was minimal, and also polymer adsorbent was amenable to regeneration by washing with water/methanol (3:1, v/v) solution. The polymer adsorbent was unaltered in its adsorption capacity up to 10 cycles of adsorption and desorption, which will be more desirable in cost reduction of treatment compared with single-time-use activated carbon. PMID:24499987

  16. Polyelectrolyte brushes: a novel stable lubrication system in aqueous conditions.

    PubMed

    Kobayashi, Motoyasu; Terada, Masami; Takahara, Atsushi

    2012-01-01

    Surface-initiated controlled radical copolymerizations of 2-dimethylaminoethyl methacrylate (DMAEMA), 2-(methacryloyloxy)ethyl phosphorylcholine (MPC), 2-(methacryloyloxy)ethyltrimethylammonium chloride) (MTAC), and 3-sulfopropyl methacrylate potassium salt (SPMK) were carried out on a silicon wafer and glass ball to prepare polyelectrolyte brushes with excellent water wettability. The frictional coefficient of the polymer brushes was recorded on a ball-on-plate type tribometer by linear reciprocating motion of the brush specimen at a selected velocity of 1.5 x 10(-3) m s-1 under a normal load of 0.49 N applied to the stationary glass ball (d = 10 mm) at 298 K. The poly(DMAEMA-co-MPC) brush partially cross-linked by bis(2-iodoethoxy)ethane maintained a relatively low friction coefficient around 0.13 under humid air (RH > 75%) even after 200 friction cycles. The poly(SPMK) brush revealed an extremely low friction coefficient around 0.01 even after 450 friction cycles. We supposed that the abrasion of the brush was prevented owing to the good affinity of the poly(SPMK) brush for water forming a water lubrication layer, and electrostatic repulsive interactions among the brushes bearing sulfonic acid groups. Furthermore, the poly(SPMK-co-MTAC) brush with a chemically cross-linked structure showed a stable low friction coefficient in water even after 1400 friction cycles under a normal load of 139 MPa, indicating that the cross-linking structure improved the wear resistance of the brush layer.

  17. Vision, healing brush, and fiber bundles

    NASA Astrophysics Data System (ADS)

    Georgiev, Todor

    2005-03-01

    The Healing Brush is a tool introduced for the first time in Adobe Photoshop (2002) that removes defects in images by seamless cloning (gradient domain fusion). The Healing Brush algorithms are built on a new mathematical approach that uses Fibre Bundles and Connections to model the representation of images in the visual system. Our mathematical results are derived from first principles of human vision, related to adaptation transforms of von Kries type and Retinex theory. In this paper we present the new result of Healing in arbitrary color space. In addition to supporting image repair and seamless cloning, our approach also produces the exact solution to the problem of high dynamic range compression of17 and can be applied to other image processing algorithms.

  18. Lubrication at physiological pressures by polyzwitterionic brushes.

    PubMed

    Chen, Meng; Briscoe, Wuge H; Armes, Steven P; Klein, Jacob

    2009-03-27

    The very low sliding friction at natural synovial joints, which have friction coefficients of mu < 0.002 at pressures up to 5 megapascals or more, has to date not been attained in any human-made joints or between model surfaces in aqueous environments. We found that surfaces in water bearing polyzwitterionic brushes that were polymerized directly from the surface can have mu values as low as 0.0004 at pressures as high as 7.5 megapascals. This extreme lubrication is attributed primarily to the strong hydration of the phosphorylcholine-like monomers that make up the robustly attached brushes, and may have relevance to a wide range of human-made aqueous lubrication situations.

  19. Lubrication at Physiological Pressures by Polyzwitterionic Brushes

    NASA Astrophysics Data System (ADS)

    Chen, Meng; Briscoe, Wuge H.; Armes, Steven P.; Klein, Jacob

    2009-03-01

    The very low sliding friction at natural synovial joints, which have friction coefficients of μ < 0.002 at pressures up to 5 megapascals or more, has to date not been attained in any human-made joints or between model surfaces in aqueous environments. We found that surfaces in water bearing polyzwitterionic brushes that were polymerized directly from the surface can have μ values as low as 0.0004 at pressures as high as 7.5 megapascals. This extreme lubrication is attributed primarily to the strong hydration of the phosphorylcholine-like monomers that make up the robustly attached brushes, and may have relevance to a wide range of human-made aqueous lubrication situations.

  20. Mechanism of nanoparticle actuation by responsive polymer brushes: from reconfigurable composite surfaces to plasmonic effects

    NASA Astrophysics Data System (ADS)

    Roiter, Yuri; Minko, Iryna; Nykypanchuk, Dmytro; Tokarev, Ihor; Minko, Sergiy

    2011-12-01

    The mechanism of nanoparticle actuation by stimuli-responsive polymer brushes triggered by changes in the solution pH was discovered and investigated in detail in this study. The finding explains the high spectral sensitivity of the composite ultrathin film composed of a poly(2-vinylpyridine) (P2VP) brush that tunes the spacing between two kinds of nanoparticles--gold nanoislands immobilized on a transparent support and gold colloidal particles adsorbed on the brush. The optical response of the film relies on the phenomenon of localized surface plasmon resonances in the noble metal nanoparticles, giving rise to an extinction band in visible spectra, and a plasmon coupling between the particles and the islands that has a strong effect on the band position and intensity. Since the coupling is controlled by the interparticle spacing, the pH-triggered swelling-shrinking transition in the P2VP brush leads to pronounced changes in the transmission spectra of the hybrid film. It was not established in the previous publications how the actuation of gold nanoparticles within a 10-15 nm interparticle distance could result in the 50-60 nm shift in the absorbance maximum in contrast to the model experiments and theoretical estimations of several nanometer shifts. In this work, the extinction band was deconvoluted into four spectrally separated and overlapping contributions that were attributed to different modes of interactions between the particles and the islands. These modes came into existence due to variations in the thickness of the grafted polymeric layer on the profiled surface of the islands. In situ atomic force microscopy measurements allowed us to explore the behavior of the Au particles as the P2VP brush switched between the swollen and collapsed states. In particular, we identified an interesting, previously unanticipated regime when a particle position in a polymer brush was switched between two distinct states: the particle exposed to the surface of the

  1. Forces of Interaction between Surfaces Bearing Looped Polymer Brushes in Good Solvent.

    SciTech Connect

    Alonzo, Jose; Mays, Jimmy; Kilbey, II, S Michael

    2009-01-01

    In a previous publication we suggested [Huang et al., Macromolecules, 2008, 41, 1745-1752] that looped polymer brushes formed by tethering chains by both ends to a surface may exhibit a polydispersity-like effect due to a distribution of distances between tethering points, leading to segment density profiles dominated by a long and diffuse exponentially-decaying tail. To study this issue in more detail, the force profiles (forces of interaction as a function of separation distance) of a series of looped polymer brushes made by preferential adsorption of poly(2-vinylpyridine)-polystyrene-poly(2-vinylpyridine) (PVP-b-PS-b-PVP) triblock copolymers of varying molecular weight and asymmetry ratio are measured using the surface forces apparatus. The force profiles are analyzed using an equivalent diblock model, which considers the triblock copolymer brushes as being comprised of two diblock copolymers of half the PS molecular weight. While scaling the dependencies of the interaction energy and distance on molecular weight, the tethering density and segment size coalesce the measured force profiles to the universal profile, it is necessary to include polydispersity in the description of the equilibrium structure. This is done using the self-consistent field model of Milner et al. [Macromolecules, 1988, 21, 2610-2619]. For looped brushes formed from the symmetric and moderately symmetric triblock copolymers we find that the polydispersity due to molecular weight distribution effectively accounts for the observed force profiles. On the other hand, agreement between the measured and predicted force profiles of looped brushes formed from highly asymmetric copolymers at low degrees-of-compression is achieved only if a much smaller value of the polydispersity index is used in the fitting. The implication of these results is that the shape of the segment density profiles is not due to the previously proposed anchor-induced polydispersity arising due to loop formation; however in

  2. Synthesis of metronidazole-imprinted molecularly imprinted polymers by distillation precipitation polymerization and their use as a solid-phase adsorbent and chromatographic filler.

    PubMed

    Liu, Jiang; Zhang, Lu; Li Han Song, Le; Liu, Yuan; Tang, Hui; Li, Yingchun

    2015-04-01

    Metronidazole-imprinted polymers with superior recognition properties were prepared by a novel strategy called distillation-precipitation polymerization. The as-obtained polymers were characterized by Fourier-transform infrared spectroscopy, laser particle size determination and scanning electron microscopy, and their binding performances were evaluated in detail by static, kinetic and dynamic rebinding tests, and Scatchard analysis. The results showed that when the fraction of the monomers was 5 vol% in the whole reaction system, the prepared polymers afforded good morphology, monodispersity, and high adsorption capacity and excellent selectivity to the target molecule, metronidazole. The optimal binding performance is 12.41 mg/g for metronidazole just before leakage occurred and 38.51 mg/g at saturation in dynamic rebinding tests. Metronidazole-imprinted polymers were further applied as packing agents in solid-phase extraction and as chromatographic filler, both of which served for the detection of metronidazole in fish tissue. The results illustrated the recoveries of spiked samples ranged from 82.97 to 87.83% by using molecularly imprinted solid-phase extraction combined with a C18 commercial column and 93.7 to 101.2% by directly using the polymer-packed chromatographic column. The relative standard deviation of both methods was less than 6%. PMID:25594306

  3. Molecular dynamics simulation of the interfacial structure of [C(n)mim][PF6] adsorbed on a graphite surface: effects of temperature and alkyl chain length.

    PubMed

    Dou, Q; Sha, M L; Fu, H Y; Wu, G Z

    2011-05-01

    The structures and diffusion behaviors of a series of ionic liquids [C(n)mim][PF(6)] (n = 1, 4, 8 and 12) on a graphite surface have been investigated by means of molecular dynamics simulation. It was found that three or four ordering layers of ionic liquids were formed near the graphite surface, and this layering structure was stable over the temperature range investigated. At the liquid/vacuum interface, the ionic liquid with a butyl chain had a monolayer ordering surface, while [C(8)mim][PF(6)] and [C(12)mim][PF(6)] exhibited a bilayer ordering with a polar domain sandwiched between two orientational nonpolar domains. More impressively, the simulated results showed that for the ionic liquids with alkyl chains longer than C(4), the adjacent alkyl chains in the whole film tended to be parallel to each other, with the imidazolium rings packed closely together. This indicated that the ionic liquids have a better regulated short-range structure than was previously expected. It was also found that both in the bottom layer and in the bulk region, the diffusion of the alkyl chains was much faster than that of the polar groups. However, as the alkyl chain length increased, the charge delocalization in the cation and the enhanced van der Waals interaction between the nonpolar groups contributed by reducing this difference in the diffusivity of major groups.

  4. Antifouling Polymer Brushes Displaying Antithrombogenic Surface Properties.

    PubMed

    de los Santos Pereira, Andres; Sheikh, Sonia; Blaszykowski, Christophe; Pop-Georgievski, Ognen; Fedorov, Kiril; Thompson, Michael; Rodriguez-Emmenegger, Cesar

    2016-03-14

    The contact of blood with artificial materials generally leads to immediate protein adsorption (fouling), which mediates subsequent biological processes such as platelet adhesion and activation leading to thrombosis. Recent progress in the preparation of surfaces able to prevent protein fouling offers a potential avenue to mitigate this undesirable effect. In the present contribution, we have prepared several types of state-of-the-art antifouling polymer brushes on polycarbonate plastic substrate, and investigated their ability to prevent platelet adhesion and thrombus formation under dynamic flow conditions using human blood. Moreover, we compared the ability of such brushes--grafted on quartz via an adlayer analogous to that used on polycarbonate--to prevent protein adsorption from human blood plasma, assessed for the first time by means of an ultrahigh frequency acoustic wave sensor. Results show that the prevention of such a phenomenon constitutes one promising route toward enhanced resistance to thrombus formation, and suggest that antifouling polymer brushes could be of service in biomedical applications requiring extensive blood-material surface contact.

  5. Optical brush: Imaging through permuted probes.

    PubMed

    Heshmat, Barmak; Lee, Ik Hyun; Raskar, Ramesh

    2016-01-01

    The combination of computational techniques and ultrafast imaging have enabled sensing through unconventional settings such as around corners, and through diffusive media. We exploit time of flight (ToF) measurements to enable a flexible interface for imaging through permuted set of fibers. The fibers are randomly distributed in the scene and are packed on the camera end, thus making a brush-like structure. The scene is illuminated by two off-axis optical pulses. Temporal signatures of fiber tips in the scene are used to localize each fiber. Finally, by combining the position and measured intensity of each fiber, the original input is reconstructed. Unlike conventional fiber bundles with packed set of fibers that are limited by a narrow field of view (FOV), lack of flexibility, and extended coaxial precalibration, the proposed optical brush is flexible and uses off-axis calibration method based on ToF. The enabled brush form can couple to other types of ToF imaging systems. This can impact probe-based applications such as, endoscopy, tomography, and industrial imaging and sensing. PMID:26868954

  6. Optical brush: Imaging through permuted probes

    PubMed Central

    Heshmat, Barmak; Lee, Ik Hyun; Raskar, Ramesh

    2016-01-01

    The combination of computational techniques and ultrafast imaging have enabled sensing through unconventional settings such as around corners, and through diffusive media. We exploit time of flight (ToF) measurements to enable a flexible interface for imaging through permuted set of fibers. The fibers are randomly distributed in the scene and are packed on the camera end, thus making a brush-like structure. The scene is illuminated by two off-axis optical pulses. Temporal signatures of fiber tips in the scene are used to localize each fiber. Finally, by combining the position and measured intensity of each fiber, the original input is reconstructed. Unlike conventional fiber bundles with packed set of fibers that are limited by a narrow field of view (FOV), lack of flexibility, and extended coaxial precalibration, the proposed optical brush is flexible and uses off-axis calibration method based on ToF. The enabled brush form can couple to other types of ToF imaging systems. This can impact probe-based applications such as, endoscopy, tomography, and industrial imaging and sensing. PMID:26868954

  7. Helicobacter (Campylobacter) pylori in gastric brushing cytology.

    PubMed

    Edmonds, P R; Carrozza, M J; Ruggiero, F M; Calafati, S A; Jann, R C

    1992-01-01

    Helicobacter (formerly Campylobacter) pylori is frequently associated with chronic gastritis and peptic ulcer and has been implicated as an etiologic agent. Identification of H. pylori is important for specific treatment with antibiotics and bismuth compounds. We studied 27 patients who presented with symptoms of gastritis or peptic ulcer on whom paired gastric biopsies and gastric brushings for cytology had been performed. Biopsies were stained with H & E and Warthin-Starry or Giemsa for H. pylori. Previously, Papanicolaou-stained brushings were restained with Giemsa and reviewed blindly by two cytologists. Cytologic examination revealed the characteristic 1-3 mu curved or spiral gram-negative bacilli embedded in mucus in 12 of 27 (44%) of cases. Biopsies showed H. pylori in 13 of 27 (48%) of cases. Cytology and histology were concordant in 22 of 27 (81%) of cases. Three cases were positive on biopsy, negative on cytology; two of these were unsatisfactory cytology specimens. Two cases were positive on cytology, negative on biopsy, apparently sampling artifacts. Papanicolaou-stained slides were scored for several morphologic parameters; numbers of acute and chronic inflammatory cells and degree of cytologic atypia. None of these were predictive of the presence of H. pylori. We conclude that Giemsa-stained gastric brushings are a useful complement to gastric biopsies in establishing the diagnosis of H. pylori.

  8. Professional brushing study comparing the effectiveness of sonic brush heads with manual toothbrushes: a single blinded, randomized clinical trial.

    PubMed

    Pelka, Anna-Kristina; Nagler, Tonia; Hopp, Imke; Petschelt, Anselm; Pelka, Matthias Anton

    2011-08-01

    The aim of this study was to evaluate the plaque removal efficacy of four toothbrushes: the Philips Sonicare Elite with medium and mini brush heads, the Elmex Sensitive, and the American Dental Association (ADA) reference toothbrush. This study was a randomized, controlled, investigator-blinded, four-brush crossover design study, which examined plaque removal following a consecutive repeated use. All brushes were used on each participant in a randomly assigned quadrant of the mouth. A total of 90 subjects participated in the study. Prior to the experiment, they received a professional prophylaxis and were requested to refrain from toothbrushing for 48 h. Teeth were professionally brushed consecutively for 10 to 90 s per quadrant. A Turesky-modified Quigley Hein Index score was assessed at baseline and after each brushing interval by one blinded investigator. Results showed reduction of mean plaque scores for all brushes with time from 10 to 90 s. After 30 s (2-min whole mouth equivalent) of brushing, the Sonicare brushes cleaned 19, the ADA brush 16, and the Elmex Sensitive 10 of in average 28 tooth surfaces. With time, the number of additional cleaned surfaces decreased. Time is an important variable in the evaluation of plaque-removing efficacy since absolute efficacy increases with time and differs per toothbrush. No differences could be found between the two brush heads of the Sonicare.

  9. Behavior of Surface-Anchored Poly(acrylic acid) Brushes with Grafting Density Gradients on Solid Substrates: 1. Experiment

    SciTech Connect

    Wu,T.; Gong, P.; Szleifer, I.; Vicek, P.; Subr, V.; Genzer, J.

    2007-01-01

    We describe experiments pertaining to the formation of surface-anchored poly(acrylic acid) (PAA) brushes with a gradual variation of the PAA grafting densities on flat surfaces and provide detailed analysis of their properties. The PAA brush gradients are generated by first covering the substrate with a molecular gradient of the polymerization initiator, followed by the 'grafting from' polymerization of tert-butyl acrylate (tBA) from these substrate-bound initiator centers, and finally converting the PtBA into PAA. We use spectroscopic ellipsometry to measure the wet thickness of the grafted PAA chains in aqueous solutions at three different pH values (4, 5.8, and 10) and a series of ionic strengths (IS). Our measurements reveal that at low grafting densities, s, the wet thickness of the PAA brush (H) remains relatively constant, the polymers are in the mushroom regime. Beyond a certain value of s, the macromolecules enter the brush regime, where H increases with increasing s. For a given s, H exhibits a nonmonotonic behavior as a function of the IS. At large IS, the H is small because the charges along PAA are completely screened by the excess of the external salt. As IS decreases, the PAA enters the so-called salt brush (SB) regime, where H increases. At a certain value of IS, H reaches a maximum and then decreases again. The latter is a typical brush behavior in so-called osmotic brush (OB) regime. We provide detailed discussion of the behavior of the grafted PAA chains in the SB and OB regimes.

  10. Development of a novel antifouling platform for biosensing probe immobilization from methacryloyloxyethyl phosphorylcholine-containing copolymer brushes.

    PubMed

    Akkahat, Piyaporn; Kiatkamjornwong, Suda; Yusa, Shin-ichi; Hoven, Voravee P; Iwasaki, Yasuhiko

    2012-04-01

    The immobilization of thiol-terminated poly[(methacrylic acid)-ran-(2-methacryloyloxyethyl phosphorylcholine)] (PMAMPC-SH) brushes on gold-coated surface plasmon resonance (SPR) chips was performed using the "grafting to" approach via self-assembly formation. The copolymer brushes provide both functionalizability and antifouling characteristics, desirable features mandatorily required for the development of an effective platform for probe immobilization in biosensing applications. The carboxyl groups from the methacrylic acid (MA) units were employed for attaching active biomolecules that can act as sensing probes for biospecific detection of target molecules, whereas the 2-methacryloyloxyethyl phosphorylcholine (MPC) units were introduced to suppress unwanted nonspecific adsorption. The detection efficiency of the biotin-immobilized PMAMPC brushes with the target molecule, avidin (AVD), was evaluated in blood plasma in comparison with the conventional 2D monolayer of 11-mercaptoundecanoic acid (MUA) and homopolymer brushes of poly(methacrylic acid) (PMA) also immobilized with biotin using the SPR technique. Copolymer brushes with 79 mol % MPC composition and a molecular weight of 49.3 kDa yielded the platform for probe immobilization with the best performance considering its high S/N ratio as compared with platforms based on MUA and PMA brushes. In addition, the detection limit for detecting AVD in blood plasma solution was found to be 1.5 nM (equivalent to 100 ng/mL). The results have demonstrated the potential for using these newly developed surface-attached PMAMPC brushes for probe immobilization and subsequent detection of designated target molecules in complex matrices such as blood plasma and clinical samples.

  11. Electrolyte-induced collapse of a polyelectrolyte brush

    NASA Astrophysics Data System (ADS)

    Biesalski, M.; Johannsmann, D.; Rühe, J.

    2004-05-01

    We have investigated the electrolyte-induced collapse of a polyelectrolyte brush covalently attached to a planar solid surface. Positively charged poly-4-vinyl [N-methyl-pyridinium] (MePVP) brushes were prepared in situ at the surface by free radical chain polymerization using a surface-immobilized initiator monolayer ("grafting from" technique) and 4-vinylpyridine as the monomer, followed by a polymer-analogous quaternization reaction. The height of the brushes was measured as a function of the external salt concentration via multiple-angle null ellipsometry. As predicted by mean-field theory, the height of the MePVP brushes remains unaffected by the addition of low amounts of external salt. At higher salt concentrations the brush height decreases. The extent to which the brush shrinks strongly depends on the nature of the salt present in the environment. MePVP brushes collapse to almost the dry layer thickness upon the addition of potassium iodide to a contacting aqueous medium. In contrast, the collapse of MePVP brushes having bromide or chloride counterions is much less pronounced. These brushes remain in a highly swollen state even after large amounts of salt have been added to the solution.

  12. Unoccupied electronic states in adsorbate systems

    NASA Astrophysics Data System (ADS)

    Bertel, E.

    1991-11-01

    Experimental work on unoccupied electronic states in adsorbate systems on metallic substrates is reviewed with emphasis on recent developments. The first part is devoted to molecular adsorbates. Weakly chemisorbed hydrocarbons are briefly discussed. An exhaustive inverse photoemission (IPE) study of the CO bond to the transition metals Ni, Pb, and Pt is presented. Adsorbed NO is taken as an example to demonstrate the persisting discrepancies in the interpretation of IPE spectra. Atomic adsorbates are discussed in the second part. The quantum well state model is applied to interpret the surface states in reconstructing and non-reconstructing adsorption systems of alkali metals and hydrogen. A recent controversy on the unoccupied electronic states of the Cu(110)/O p(2×1) surface is critically reviewed. The quantum well state model is then compared to tight binding and local-density-functional calculations of the unoccupied bands and the deficiencies of the various approaches are pointed out. Finally, the relation between the surface state model and more chemically oriented models of surface bonding is briefly discussed.

  13. Effect of Frequency of Brushing Teeth on Plaque and Calculus Accumulation, and Gingivitis in Dogs.

    PubMed

    Harvey, Colin; Serfilippi, Laurie; Barnvos, Donald

    2015-01-01

    The efficacy of brushing the teeth of beagle dogs in a randomized, controlled, blinded study design using a clearly-defined brushing technique was evaluated for 4 brushing frequencies: brushing daily, brushing every other day, brushing weekly and brushing every other week, compared with no brushing in a control group of dogs. All dogs were fed a standard dry kibble diet during the study. Standard plaque, calculus, and gingivitis indices were used to score the teeth. A 'clean tooth' model was used. No gingival or non-gingival lacerations or other signs of injury to oral tissues were found at the end of the 28 day trial period. Brushing more frequently had greater effectiveness in retarding accumulation of plaque and calculus, and reducing the severity of pre-existing gingivitis. Brushing daily or every other day produced statistically significant improved results compared with brushing weekly or every other week. Based on the results of this study, daily brushing is recommended.

  14. Effect of Frequency of Brushing Teeth on Plaque and Calculus Accumulation, and Gingivitis in Dogs.

    PubMed

    Harvey, Colin; Serfilippi, Laurie; Barnvos, Donald

    2015-01-01

    The efficacy of brushing the teeth of beagle dogs in a randomized, controlled, blinded study design using a clearly-defined brushing technique was evaluated for 4 brushing frequencies: brushing daily, brushing every other day, brushing weekly and brushing every other week, compared with no brushing in a control group of dogs. All dogs were fed a standard dry kibble diet during the study. Standard plaque, calculus, and gingivitis indices were used to score the teeth. A 'clean tooth' model was used. No gingival or non-gingival lacerations or other signs of injury to oral tissues were found at the end of the 28 day trial period. Brushing more frequently had greater effectiveness in retarding accumulation of plaque and calculus, and reducing the severity of pre-existing gingivitis. Brushing daily or every other day produced statistically significant improved results compared with brushing weekly or every other week. Based on the results of this study, daily brushing is recommended. PMID:26197686

  15. Brush cells in the human duodenojejunal junction: an ultrastructural study

    PubMed Central

    Morroni, Manrico; Cangiotti, Angela Maria; Cinti, Saverio

    2007-01-01

    Brush cells have been identified in the respiratory and gastrointestinal tract mucosa of many mammalian species. In humans they are found in the respiratory tract and the gastrointestinal apparatus, in both the stomach and the gallbladder. The function of brush cells is unknown, and most morphological data have been obtained in rodents. To extend our knowledge of human brush cells, we performed an ultrastructural investigation of human small intestine brush cells. Six brush cells identified in five out of more than 300 small intestine biopsies performed for gastrointestinal tract disorders were examined by transmission electron microscopy. Five brush cells were located on the surface epithelium and one in a crypt. The five surface brush cells were characterized by a narrow apical pole from which emerged microvilli that were longer and thicker than those of enterocytes. The filamentous core extended far into the cell body without forming the terminal web. Caveolae were abundant. Filaments were in the form of microfilaments and intermediate filaments. Cytoplasmic projections containing filaments were found on the basolateral surface of brush cells. In a single cell, axons containing vesicles and dense core granules were in close contact both with the basal and the lateral surface of the cell. The crypt brush cell appeared less mature. We concluded that human small intestine brush cells share a similar ultrastructural biology with those of other mammals. They are polarized and well-differentiated cells endowed with a distinctive cytoskeleton. The observation of nerve fibres closely associated with brush cells, never previously described in humans, lends support to the hypothesis of a receptor role for these cells. PMID:17509089

  16. Modeling of polymer brush grafted nanoparticles for algal harvesting

    NASA Astrophysics Data System (ADS)

    Goins, Jason

    Microalgae derived biofuel shows great potential as a replacement to petroleum based fuels. However, industrial scale and economical production of fuel from microalgae suffer from an expensive dewatering step brought on by the organism's specific cell properties. A retrievable, paramagnetic nanoparticle polyelectrolyte brush (NPPB) has been designed as a flocculation agent to provide a low cost method in collecting algal biomass in biofuel production. In conjunction with experiment, subsequent theoretical investigations have been conducted in order to understand experimental observations and inform future design. A strategy has been implemented to provide informative descriptions for the relationship between flocculation agent parameters and dewatering efficiency. We studied the effect altering the degree of polymerization and monomer charge fraction had on the harvesting efficiency by considering flocculation as the criteria for harvesting. As the number of charges on the polymer backbone of the NPPB is increased, less NPPB concentrations are required to achieve equal harvesting efficiencies. This is a result of needing less NPPB to completely screen the effective charge on the algae surface. However, the Debye length limits the amount of charge on the algae surface one NPPB can screen. Using the free energy calculations for the complete set of pair interactions between the NPPB and the algae, we determined how many adsorbed NPPB were required in order for the force between coated algae to become attractive at some algae surface separation. This corresponded to the NPPB bridging two algae surfaces. NPPB with higher monomer charge fractions and degree of polymerizations led to a stronger bridging bond and larger bridging gap that could outweigh the algae pair repulsion. Optimized structures maximize these effects.

  17. Light-chain binding sites on renal brush-border membranes

    SciTech Connect

    Batuman, V.; Dreisbach, A.W.; Cyran, J.

    1990-05-01

    Immunoglobulin light chains are low-molecular-weight proteins filtered at the renal glomerulus and catabolized within the proximal tubular epithelium. Excessive production and urinary excretion of light chains are associated with renal dysfunction. They also interfere with proximal renal tubule epithelial functions in vitro. We studied the binding of 125I-labeled kappa- and lambda-light chains, obtained from the urine of multiple myeloma patients, to rat and human renal proximal tubular brush-border membranes. Light-chain binding to brush borders was also demonstrated immunologically by flow cytometry. Computer analysis of binding data was consistent with presence of a single class of low-affinity, high-capacity, non-cooperative binding sites with relative selectivity for light chains on both rat and human kidney brush-border membranes. The dissociation constants of light chains ranged from 1.6 X 10(-5) to 1.2 X 10(-4) M, and maximum binding capacity ranged from 4.7 +/- 1.3 X 10(-8) to 8.0 +/- 0.9 X 10(-8) (SD) mol/mg protein at 25 degrees C. Kappa- and lambda-light chains competed with each other for binding with comparable affinity constants. Competition by albumin and beta-lactoglobulin, however, was much weaker, suggesting relative site selectivity for light chains. These binding sites probably function as endocytotic receptors for light chains and possibly other low-molecular-weight proteins.

  18. Flows in Pinned Arrays Simulating Brush Seals

    NASA Technical Reports Server (NTRS)

    Hendricks, R.C.; Kudriavtsev, V. V.; Braun, M. J.; Athavale, M. M.

    1996-01-01

    Flows through idealized pin arrays were investigated using an unstructured grid finite difference model and the simplified Ergun model to predict leakage flows and pressure drops in brush seals. The models are in good agreement in the laminar region with departures in the laminar-turbulent transition region defined by the simplified Ergun model. No local disturbances in the velocity or pressure fields, symptomatic of turbulence were found in the numerical results. The simplified model failed to predict the pressure drop of a 32-pin anisotropic array. Transitional and anisotropic behavior requires

  19. Hollow-fiber-based adsorbers for gas separation by pressure-swing adsorption

    SciTech Connect

    Feng, X.; Pan, C.Y.; McMinis, C.W.; Ivory, J.; Ghosh, D.

    1998-07-01

    Hollow-fiber-based adsorbers for gas separation by pressure-swing adsorption (PSA) was studied experimentally. The high efficiency of hollow-fiber-based adsorbers for gas separation was illustrated by hydrogen separation using fine-powder-activated carbon and molecular sieve as adsorbents. The adsorption equilibrium and dynamics of the hollow-fiber adsorbers were determined. The pressure drop of the gas flowing through the adsorbers was also examined. The adsorbers were tested for hydrogen separation from nitrogen, carbon dioxide, and a multicomponent gas mixture simulating ammonia synthesis purge gas. The PSA systems using the hollow-fiber adsorbers were very effective for hydrogen purification. The high separation efficiency is derived from the fast mass-transfer rate and low pressure drop, two key features of hollow-fiber-based adsorbers.

  20. 16 CFR Figure 8 to Part 1610 - Brush

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...

  1. 16 CFR Figure 9 to Part 1610 - Brushing Device Template

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 9 Figure 9 to Part 1610—Brushing...

  2. 16 CFR Figure 9 to Part 1610 - Brushing Device Template

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 9 Figure 9 to Part 1610—Brushing...

  3. 16 CFR Figure 8 to Part 1610 - Brush

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...

  4. 16 CFR Figure 7 to Part 1610 - Brushing Device

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...

  5. 16 CFR Figure 7 to Part 1610 - Brushing Device

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...

  6. Improved Steam Turbine Leakage Control with a Brush Seal Design

    NASA Astrophysics Data System (ADS)

    Turnquist, Norman; Chupp, Raymond E.; Pastrana, Ryan; Wolfe, Chris; Burnett, Mark

    2002-10-01

    This paper presents an improved steam turbine leakage control system with a brush seal design. The contents include: 1) Typical Design Characteristics; 2) Typical Brush Seal Locations; 3) Reduced Leakage Rates; 4) Performance Benefits; 5) System Considerations; 6) Rotor Dynamics; 7) Laboratory Tests and 8) Field Experience.

  7. Preliminary experimental results for a cryogenic brush seal configuration

    NASA Astrophysics Data System (ADS)

    Carlile, J. A.; Hendricks, R. C.; Hibbs, R. I.; McVey, S. E.; Scharrer, J. K.

    1993-06-01

    Preliminary fluid nitrogen flow data are reported for a five-brush, ceramic-coated-rub-runner brush seal system, where the brushes and the rub runner were placed at each end of a centrally pressurized multifunction tester ('back-to-back' set of brushes) and tested at rotor speeds of 0, 10, 18, and 22.5 krpm. After testing, both the brushes and the ceramic-coated rub runner appeared pristine. The coating withstood both the thermomechanical and dynamic loadings with minor wear track scarring. The bristle tips showed some indication of material shearing (smearing) wear. The Ergun porous flow equation was applied to the brush seal data. The Ergun relation, which required heuristic information to characterize the coefficients, fit the gaseous data but was in poor agreement with the fluid results. The brush seal exit conditions were two phase. Two-phase, choked-flow design charts were applied but required one data point at each rotor speed to define the (C(sub f)A x Constant) flow and area coefficients. Reasonable agreement between prediction and data was found, as expected, but such methods are not to be construed as two-phase-flow brush seal analyses.

  8. Preliminary experimental results for a cryogenic brush seal configuration

    NASA Astrophysics Data System (ADS)

    Carlile, J. A.; Hendricks, R. C.; Hibbs, R. I.; McVey, S. E.; Scharrer, J. K.

    1993-06-01

    Preliminary fluid nitrogen flow data are reported for a five-brush, ceramic-coated-rub-runner brush seal system, where the brushes and the rub runner were placed at each end of a centrally pressurized multifunction tester ('back-to-back' set of brushes) and tested at rotor speeds of 0, 10, 18, and 22.5 krpm. After testing, both the brushes and the ceramic-coated rub runner appeared pristine. The coating withstood both the thermomechanical and dynamic loadings with minor wear track scarring. The bristle tips showed some indication of material shearing (smearing) wear. The Ergun (1952) porous flow equation was applied to the brush seal data. The Ergun relation fit the gaseous data but was in poor agreement with the fluid results. The brush seal exit conditions were two phase. Two-phase, choked-flow design charts were applied but required one data point at each rotor speed to define the flow and area coefficients. Reasonable agreement between prediction and data was found, but such methods are not to be construed as two-phase-flow brush seal analyses.

  9. 75 FR 39706 - Natural Bristle Paint Brushes From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-12

    ... the antidumping duty order on natural bristle paint brushes from China (75 FR 21347, April 23, 2010... revoke the order on June 16, 2010 (75 FR 34097). In light of these developments, the Commission is... COMMISSION Natural Bristle Paint Brushes From China AGENCY: United States International Trade...

  10. Effects of material choices on brush seal performance

    NASA Astrophysics Data System (ADS)

    Atkinson, Edward; Bristol, Brent

    1992-09-01

    This paper discusses some of the initial hot and cold material testing undertaken in a brush seal development program. It describes the effects of material selection on relative wear and leakage of brush seals. Criteria for ranking wear couples are addressed.

  11. 75 FR 18237 - Natural Bristle Paint Brushes From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-09

    ... party group response to its notice of institution (74 FR 56666, November 2, 2009) was adequate and that... COMMISSION Natural Bristle Paint Brushes From China AGENCY: United States International Trade Commission... duty order on natural bristle paint brushes from China. SUMMARY: The Commission hereby gives...

  12. 16 CFR Figure 7 to Part 1610 - Brushing Device

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...

  13. 16 CFR Figure 7 to Part 1610 - Brushing Device

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...

  14. 16 CFR Figure 8 to Part 1610 - Brush

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...

  15. 16 CFR Figure 9 to Part 1610 - Brushing Device Template

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 9 Figure 9 to Part 1610—Brushing...

  16. 16 CFR Figure 9 to Part 1610 - Brushing Device Template

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 9 Figure 9 to Part 1610—Brushing...

  17. 16 CFR Figure 9 to Part 1610 - Brushing Device Template

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 9 Figure 9 to Part 1610—Brushing...

  18. 16 CFR Figure 8 to Part 1610 - Brush

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...

  19. 16 CFR Figure 7 to Part 1610 - Brushing Device

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...

  20. 16 CFR Figure 8 to Part 1610 - Brush

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...

  1. A Critique of the Brushing for Life Programme

    ERIC Educational Resources Information Center

    Downer, Martin C.; Drugan, Caroline S.; Blinkhorn, Anthony S.

    2006-01-01

    Background and objective: Brushing for Life is intended to promote regular brushing of children's teeth with fluoride toothpaste. The programme is delivered by health visitors who provide toothbrushes, toothpaste and dental health education material at children's 8, 18 and 36 month development checks. The purpose of the present paper was to…

  2. Computer simulations of adsorbed liquid crystal films

    NASA Astrophysics Data System (ADS)

    Wall, Greg D.; Cleaver, Douglas J.

    2003-01-01

    The structures adopted by adsorbed thin films of Gay-Berne particles in the presence of a coexisting vapour phase are investigated by molecular dynamics simulation. The films are adsorbed at a flat substrate which favours planar anchoring, whereas the nematic-vapour interface favours normal alignment. On cooling, a system with a high molecule-substrate interaction strength exhibits substrate-induced planar orientational ordering and considerable stratification is observed in the density profiles. In contrast, a system with weak molecule-substrate coupling adopts a director orientation orthogonal to the substrate plane, owing to the increased influence of the nematic-vapour interface. There are significant differences between the structures adopted at the two interfaces, in contrast with the predictions of density functional treatments of such systems.

  3. Sliding Friction at a Rubber/Brush Interface

    NASA Astrophysics Data System (ADS)

    Bureau, Lionel

    2004-03-01

    The friction of poly(dimethylsiloxane) (PDMS) rubber networks sliding, at low velocity (3 nm.s-1molecular parameters which are the grafting density and the molecular weight of the tethered chains. We thus show that frictional dissipation is governed, at high grafting densities, by the rheology of a thin entangled layer confined outside the elastomer, whereas at low grafting density, where chains can be considered as independent, friction enhancement is due to pull-out of the chains ends which penetrate into the network during sliding. This latter result provides a strong evidence for friction controlled by arm retraction relaxation of the grafted chains, as proposed by Rubinstein et al. in a model of slippage at a network/brush interface.

  4. Nanopatterned polymer brushes by reactive writing

    NASA Astrophysics Data System (ADS)

    Nawroth, Jonas F.; Neisser, Claudia; Erbe, Artur; Jordan, Rainer

    2016-03-01

    Polymer brush patterns were prepared by a combination of electron beam induced damage in self-assembled monolayers (SAMs), creating a stable carbonaceous deposit, and consecutive self-initiated photografting and photopolymerization (SIPGP). This newly applied technique, reactive writing (RW), is investigated with 1H,1H,2H,2H-perfluorooctyltriethoxysilane SAM (PF-SAM) on silicon oxide, which, when modified by RW, can be selectively functionalized by SIPGP. With the monomer N,N-dimethylaminoethyl methacrylate (DMAEMA), we demonstrate the straightforward formation of polymer brush gradients and single polymer lines of sub-100 nm lateral dimensions, with high contrast to the PF-SAM background. The lithography parameters acceleration voltage, irradiation dose, beam current and dwell time were systematically varied to identify the optimal conditions for the maximum conversion of the SAM into a carbonaceous deposit. The results of this approach were compared to patterns prepared by carbon templating (CT) under analogous conditions, revealing a dwell time dependency, which differs from earlier reports. This new technique expands the range of CT by giving the opportunity to not only vary the chemistry of the created polymer patterns with monomer choice but also vary the chemistry of the surrounding substrate.

  5. Nanopatterned polymer brushes by reactive writing.

    PubMed

    Nawroth, Jonas F; Neisser, Claudia; Erbe, Artur; Jordan, Rainer

    2016-04-14

    Polymer brush patterns were prepared by a combination of electron beam induced damage in self-assembled monolayers (SAMs), creating a stable carbonaceous deposit, and consecutive self-initiated photografting and photopolymerization (SIPGP). This newly applied technique, reactive writing (RW), is investigated with 1H,1H,2H,2H-perfluorooctyltriethoxysilane SAM (PF-SAM) on silicon oxide, which, when modified by RW, can be selectively functionalized by SIPGP. With the monomer N,N-dimethylaminoethyl methacrylate (DMAEMA), we demonstrate the straightforward formation of polymer brush gradients and single polymer lines of sub-100 nm lateral dimensions, with high contrast to the PF-SAM background. The lithography parameters acceleration voltage, irradiation dose, beam current and dwell time were systematically varied to identify the optimal conditions for the maximum conversion of the SAM into a carbonaceous deposit. The results of this approach were compared to patterns prepared by carbon templating (CT) under analogous conditions, revealing a dwell time dependency, which differs from earlier reports. This new technique expands the range of CT by giving the opportunity to not only vary the chemistry of the created polymer patterns with monomer choice but also vary the chemistry of the surrounding substrate. PMID:26902916

  6. Brush seal shaft wear resistant coatings

    NASA Astrophysics Data System (ADS)

    Howe, Harold

    1995-03-01

    Brush seals suffer from high wear, which reduces their effectiveness. This work sought to reduce brush seal wear by identifying and testing several industry standard coatings. One of the coatings was developed for this work. It was a co-sprayed PSZ with boron-nitride added for a high temperature dry lubricant. Other coatings tested were a PSZ, chrome carbide and a bare rotor. Testing of these coatings included thermal shocking, tensile testing and wear/coefficient of friction testing. Wear testing consisted of applying a coating to a rotor and then running a sample tuft of SiC ceramic fiber against the coating. Surface speeds at point of contact were slightly over 1000 ft/sec. Rotor wear was noted, as well as coefficient of friction data. Results from the testing indicates that the oxide ceramic coatings cannot withstand the given set of conditions. Carbide coatings will not work because of the need for a metallic binder, which oxidizes in the high heat produced by friction. All work indicated a need for a coating that has a lubricant contained within itself and the coating must be resistant to an oxidizing environment.

  7. Adapting low-adhesive thin films from mixed polymer brushes.

    PubMed

    Sheparovych, Roman; Motornov, Mikhail; Minko, Sergiy

    2008-12-16

    The concept of the responsive/adaptive mixed polymer brushes was applied to the development of the thin film coatings possessing low adhesive properties that were evaluated with AFM probes in different media. Mixed brushes composed of polydimethylsiloxane (PDMS) and polyethyleneoxide (PEO) revealed a selective layered segregation in air and water. Immersion of the sample into an aqueous environment drove PEO chains to the brush-water interface while upon drying the surface undergoing reconstruction and was occupied with PDMS. Low interfacial energies of PDMS in air and PEO in water provided low-adhesive properties of the PDMS-PEO brushes to the probes in both media due to the spontaneous and rapid reconstruction of the mixed brush.

  8. Simple effective thickness model for circular brush seals

    NASA Astrophysics Data System (ADS)

    Dowler, Constance A.; Chupp, Raymond E.; Holle, Glenn F.

    1992-07-01

    Brush seals are being investigated as replacements for some of the labyrinth seals in gas turbine engines. A relatively simple flow model approach has been presented to generalize brush seal leakage throughout the range of test and application environments. The model uses a single parameter, effective brush thickness, to correlate flow through the seal. A revision to the flow model is presented in this paper to account for seal curvature, which is especially important for smaller diameter brush seals. The revised model has been applied to leakage flow data from five sources. The results demonstrate the utility of the flow model approach in correlating the performance of brush seals having different design geometries. The revised model is shown to effectively account for the effect of seal curvature.

  9. Rod-like polyelectrolyte brushes with mono- and multivalent counterions

    NASA Astrophysics Data System (ADS)

    Fazli, H.; Golestanian, R.; Hansen, P. L.; Kolahchi, M. R.

    2006-02-01

    A model of rod-like polyelectrolyte brushes in the presence of monovalent and multivalent counterions but with no added salt is studied using Monte Carlo simulation. The average height of the brush, the histogram of rod conformations, and the counterion density profile are obtained for different values of the grafting density of the charge-neutral wall. For a domain of grafting densities, the brush height is found to be relatively insensitive to the density due to a competition between counterion condensation and inter-rod repulsion. In this regime, multivalent counterions collapse the brush in the form of linked clusters. Nematic order emerges at high grafting densities, resulting in an abrupt increase of the brush height.

  10. Evaluating the Thickness of Multivalent Glycopolymer Brushes for Lectin Binding.

    PubMed

    Lazar, Jaroslav; Park, Hyunji; Rosencrantz, Ruben R; Böker, Alexander; Elling, Lothar; Schnakenberg, Uwe

    2015-08-01

    Electrochemical impedance spectroscopy (EIS) is applied for investigating binding of lectins to multivalent glycopolymer brushes grafted from interdigital gold microelectrodes. By variation of the measuring frequency, EIS allows simultaneous analysis of binding at different subnanometer distances from the sensor surfaces. In this way, the binding dynamics along the brushes are quantified, giving an idea about the motion of the lectin through the brush layer. Two different brush lengths are investigated, revealing distinct dynamics of lectin binding due to changing topology of the brushes. Moreover, very low K D values in the nanomolar range are obtained. This unique platform may be used as sophisticated biosensor for detailed investigation of high-affinity protein binding to poly-mer layers. PMID:26096302

  11. Applications of Polymer Brushes in Protein Analysis and Purification

    NASA Astrophysics Data System (ADS)

    Jain, Parul; Baker, Gregory L.; Bruening, Merlin L.

    2009-07-01

    This review examines the application of polymer brush-modified flat surfaces, membranes, and beads for protein immobilization and isolation. Modification of porous substrates with brushes yields membranes that selectively bind tagged proteins to give 99% pure protein at capacities as high as 100 mg of protein per cubic centimeter of membrane. Moreover, enrichment of phosphopeptides on brush-modified matrix-assisted laser desorption/ionization (MALDI) plates allows detection and characterization of femtomole levels of phosphopeptides by MALDI mass spectrometry. Because swollen hydrophilic brushes can resist nonspecific protein adsorption while immobilizing a high density of proteins, they are attractive as substrates for protein microarrays. This review highlights the advantages of polymer brush-modified surfaces over self-assembled monolayers and identifies some research needs in this area.

  12. Polyelectrolyte brushes: a novel stable lubrication system in aqueous conditions.

    PubMed

    Kobayashi, Motoyasu; Terada, Masami; Takahara, Atsushi

    2012-01-01

    Surface-initiated controlled radical copolymerizations of 2-dimethylaminoethyl methacrylate (DMAEMA), 2-(methacryloyloxy)ethyl phosphorylcholine (MPC), 2-(methacryloyloxy)ethyltrimethylammonium chloride) (MTAC), and 3-sulfopropyl methacrylate potassium salt (SPMK) were carried out on a silicon wafer and glass ball to prepare polyelectrolyte brushes with excellent water wettability. The frictional coefficient of the polymer brushes was recorded on a ball-on-plate type tribometer by linear reciprocating motion of the brush specimen at a selected velocity of 1.5 x 10(-3) m s-1 under a normal load of 0.49 N applied to the stationary glass ball (d = 10 mm) at 298 K. The poly(DMAEMA-co-MPC) brush partially cross-linked by bis(2-iodoethoxy)ethane maintained a relatively low friction coefficient around 0.13 under humid air (RH > 75%) even after 200 friction cycles. The poly(SPMK) brush revealed an extremely low friction coefficient around 0.01 even after 450 friction cycles. We supposed that the abrasion of the brush was prevented owing to the good affinity of the poly(SPMK) brush for water forming a water lubrication layer, and electrostatic repulsive interactions among the brushes bearing sulfonic acid groups. Furthermore, the poly(SPMK-co-MTAC) brush with a chemically cross-linked structure showed a stable low friction coefficient in water even after 1400 friction cycles under a normal load of 139 MPa, indicating that the cross-linking structure improved the wear resistance of the brush layer. PMID:23285641

  13. 75 FR 44939 - Natural Bristle Paint Brushes and Brush Heads from the People's Republic of China: Final Results...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-30

    ... FR 5580 (February 14, 1986) and Amended Antidumping Duty Order; Natural Bristle Paint Brushes and Brush Heads From the People's Republic of China, 51 FR 8342 (March 11, 1986) (``Order''). On May 7, 2010... Order, 75 FR 34097 (June 16, 2010) (``Initiation and Preliminary Results''). As noted above, we...

  14. 75 FR 13489 - Natural Bristle Paint Brushes and Brush Heads from the People's Republic of China: Final Results...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-22

    ... (``Sunset'') Review, 74 FR 56593 (November 2, 2009) (``Sunset Initiation''); see also Antidumping Duty Order; Natural Bristle Paint Brushes and Brush Heads From the People's Republic of China, 51 FR 5580 (February 14...'s Republic of China, 51 FR 8342 (March 11, 1986) (``Order''). Based on the notice of intent...

  15. 75 FR 34097 - Natural Bristle Paint Brushes and Brush Heads From the People's Republic of China: Notice of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-16

    ... Brushes and Paint Brush Heads from the People's Republic of China, 51 FR 5580 (Feb. 14, 1986) and Amended... China, 51 FR 8342 (March 11, 1986) (``Order''). The domestic industry submitted a letter to the... Republic of China: Final Results of the Expedited Sunset Review of the Antidumping Duty Order, 75 FR...

  16. Ultraviolet and electron radiation induced fragmentation of adsorbed ferrocene

    SciTech Connect

    Welipitiya, D.; Green, A.; Woods, J.P.; Dowben, P.A.; Robertson, B.W.; Byun, D.; Zhang, J.

    1996-06-01

    From thermal desorption spectroscopy we find that ferrocene, Fe(C{sub 5}H{sub 5}){sub 2}, adsorbs and desorbs associatively on Ag(100). Photoemission results indicate that the initially adsorbed surface species closely resembles that of molecular ferrocene. The shift in photoemission binding energies relative to the gas phase is largely independent of the molecular orbital. We find that ultraviolet light does lead to partial fragmentation of the ferrocene and that the molecular fragments are much more strongly bound to the surface than the associatively adsorbed ferrocene. Since fragmentation occurs only in the presence of incident radiation, selective area deposition from this class of molecules is possible. Using a focused electron beam in a scanning transmission electron microscope, we show that selective area deposition of features with resolution of a few hundred angstroms is readily achieved. {copyright} {ital 1996 American Institute of Physics.}

  17. Methane Recovery from Gaseous Mixtures Using Carbonaceous Adsorbents

    NASA Astrophysics Data System (ADS)

    Buczek, Bronisław

    2016-06-01

    Methane recovery from gaseous mixtures has both economical and ecological aspect. Methane from different waste gases like mine gases, nitrogenated natural gases and biogases can be treated as local source for production electric and heat energy. Also occurs the problem of atmosphere pollution with methane that shows over 20 times more harmful environmental effect in comparison to carbon dioxide. One of the ways utilisation such gases is enrichment of methane in the PSA technique, which requires appropriate adsorbents. Active carbons and carbon molecular sieve produced by industry and obtained in laboratory scale were examined as adsorbent for methane recuperation. Porous structure of adsorbents was investigated using densimetry measurements and adsorption of argon at 77.5K. On the basis of adsorption data, the Dubinin-Radushkevich equation parameters, micropore volume (Wo) and characteristics of energy adsorption (Eo) as well as area micropores (Smi) and BET area (SBET) were determined. The usability of adsorbents in enrichment of the methane was evaluated in the test, which simulate the basic stages of PSA process: a) adsorbent degassing, b) pressure raise in column by feed gas, c) cocurrent desorption with analysis of out flowing gas. The composition of gas phase was accepted as the criterion of the suitability of adsorbent for methane separation from gaseous mixtures. The relationship between methane recovery from gas mixture and texture parameters of adsorbents was found.

  18. A new numerical approach to dense polymer brushes and surface instabilities

    NASA Astrophysics Data System (ADS)

    Romeis, D.; Merlitz, H.; Sommer, J.-U.

    2012-01-01

    We present a numerical self-consistent field (SCF) method which describes freely jointed chains of spherical monomers applied to densely grafted polymer brushes. We discuss both the Flory-Huggins model and the Carnahan-Starling equation of state and show the latter being preferable within our model at polymer volume fractions above 10%. We compare the results of our numerical method with data from molecular dynamics (MD) simulations [G.-L. He, H. Merlitz, J.-U. Sommer, and C.-X. Wu, Macromolecules 40, 6721 (2007)] and analytical SCF calculations [P. M. Biesheuvel, W. M. de Vos, and V. M. Amoskov, Macromolecules 41, 6254 (2008)] and obtain close agreement between the density profiles up to high grafting densities. In contrast to prior numerical and analytical studies of densely grafted polymer brushes our method provides detailed information about chain configurations including fluctuation, depletion, and packing effects. Using our model we could study the recently discovered instability of densely grafted polymer brushes with respect to slight variations of individual chain lengths, driven by fluctuation effects [H. Merlitz, G.-L. He, C.-X. Wu, and J.-U. Sommer, Macromolecules 41, 5070 (2008)]. The obtained results are in very close agreement with corresponding MD simulations.

  19. Role of hydrogen bonding in solubility of poly(N-isopropylacrylamide) brushes in sodium halide solutions

    NASA Astrophysics Data System (ADS)

    Xin-Jun, Zhao; Zhi-Fu, Gao

    2016-07-01

    By employing molecular theory, we systematically investigate the shift of solubility of poly(N-isopropylacrylamide) (PNIPAM) brushes in sodium halide solutions. After considering PNIPAM–water hydrogen bonds, water–anion hydrogen bonds, and PNIPAM–anion bonds and their explicit coupling to the PNIPAM conformations, we find that increasing temperature lowers the solubility of PNIPAM, and results in a collapse of the layer at high enough temperatures. The combination of the three types of bonds would yield a decrease in the solubility of PNIPAM following the Hofmeister series: NaCl>NaBr>NaI. PNIPAM–water hydrogen bonds are affected by water–anion hydrogen bonds and PNIPAM–anion bonds. The coupling of polymer conformations and the competition among the three types of bonds are essential for describing correctly a decrease in the solubility of PNIPAM brushes, which is determined by the free energy associated with the formation of the three types of bonds. Our results agree well with the experimental observations, and would be very important for understanding the shift of the lower critical solution temperature of PNIPAM brushes following the Hofmeister series. Project supported by the National Natural Science Foundation of China (Grant Nos. 21264016, 11464047, and 21364016) and the Joint Funds of Xinjiang Natural Science Foundation, China (Grant No. 2015211C298).

  20. Spin-Casting Polymer Brush Films for Stimuli-Responsive and Anti-Fouling Surfaces.

    PubMed

    Xu, Binbin; Feng, Chun; Hu, Jianhua; Shi, Ping; Gu, Guangxin; Wang, Lei; Huang, Xiaoyu

    2016-03-01

    Surfaces modified with amphiphilic polymers can dynamically alter their physicochemical properties in response to changes of their environmental conditions; meanwhile, amphiphilic polymer coatings with molecular hydrophilic and hydrophobic patches, which can mitigate biofouling effectively, are being actively explored as advanced coatings for antifouling materials. Herein, a series of well-defined amphiphilic asymmetric polymer brushes containing hetero side chains, hydrophobic polystyrene (PS) and hydrophilic poly(ethylene glycol) (PEG), was employed to prepare uniform thin films by spin-casting. The properties of these films were investigated by water contact angle, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and quartz crystal microbalance (QCM). AFM showed smooth surfaces for all films with the roughness less than 2 nm. The changes in water contact angle and C/O ratio (XPS) evidenced the enrichment of PEG or PS chains at film surface after exposed to selective solvents, indicative of stimuli- responsiveness. The adsorption of proteins on PEG functionalized surface was quantified by QCM and the results verified that amphiphilic polymer brush films bearing PEG chains could lower or eliminate protein-material interactions and resist to protein adsorption. Cell adhesion experiments were performed by using HaCaT cells and it was found that polymer brush films possess good antifouling ability. PMID:26905980

  1. Electronic structure of benzene adsorbed on Ni and Cu surfaces

    SciTech Connect

    Weinelt, M.; Nilsson, A.; Wassdahl, N.

    1997-04-01

    Benzene has for a long time served as a prototype adsorption system of large molecules. It adsorbs with the molecular plane parallel to the surface. The bonding of benzene to a transition metal is typically viewed to involve the {pi} system. Benzene adsorbs weakly on Cu and strongly on Ni. It is interesting to study how the adsorption strength is reflected in the electronic structure of the adsorbate-substrate complex. The authors have used X-ray Emission (XE) and X-ray Absorption (XA) spectroscopies to selectively study the electronic states localized on the adsorbed benzene molecule. Using XES the occupied states can be studies and with XAS the unoccupied states. The authors have used beamline 8.0 and the Swedish endstation equipped with a grazing incidence x-ray spectrometer and a partial yield absorption detector. The resolution in the XES and XAS were 0.5 eV and 0.05 eV, respectively.

  2. Sterilization effects of atmospheric cold plasma brush

    SciTech Connect

    Yu, Q.S.; Huang, C.; Hsieh, F.-H.; Huff, H.; Duan Yixiang

    2006-01-02

    This study investigated the sterilization effects of a brush-shaped plasma created at one atmospheric pressure. A population of 1.0x10{sup 4}-1.0x10{sup 5} Escherichia coli or Micrococcus luteus bacteria was seeded in filter paper media and then subjected to Ar and/or Ar+O{sub 2} plasmas. A complete kill of the Micrococcus luteus required about 3 min argon plasma exposures. With oxygen addition into the argon plasma gas streams, a complete kill of the bacteria needed only less than 1 min plasma exposure for Micrococcus luteus and about 2 min exposure for Escherichia coli. The plasma treatment effects on the different bacteria cell structures were examined using scanning electron microscopy.

  3. Color of smoke from brush fires.

    PubMed

    Lynch, David K; Bernstein, Lawrence S

    2008-12-01

    Smoke clouds from brush fires usually appear reddish or brownish when viewed from below in transmission, while a thin smoke cloud or part of a thick cloud near its periphery is noticeably bluish. Yet, when viewed from above in backscatter, the smoke appears bluish-white. We present observations of smoke clouds and explain their varied colors using a simple one-dimensional two-stream multiple scattering/absorbing radiative transfer approach for a model cloud whose particles are much smaller than the wavelength of visible light, the Rayleigh limit. The colors are purely the result of Rayleigh scattering and are not significantly influenced by the intrinsic color (wavelength-dependent albedo) of the particles.

  4. Thermal Conductance of Poly(3-methylthiophene) Brushes.

    PubMed

    Roy, Anandi; Bougher, Thomas L; Geng, Rugang; Ke, Yutian; Locklin, Jason; Cola, Baratunde A

    2016-09-28

    A wide variety of recent work has demonstrated that the thermal conductivity of polymers can be improved dramatically through the alignment of polymer chains in the direction of heat transfer. Most of the polymeric samples exhibit high conductivity in either the axial direction of a fiber or in the in-plane direction of a thin film, while the most useful direction for thermal management is often the cross-plane direction of a film. Here we show poly(3-methylthiophene) brushes grafted from phosphonic acid monolayers using surface initiated polymerization can exhibit through-plane thermal conductivity greater than 2 W/(m K), a 6-fold increase compared to spin-coated poly(3-hexylthiophene) samples. The thickness of these films (10-40 nm) is somewhat less than that required in most applications, but the method demonstrates a route toward higher thermal conductivity in covalently grafted, aligned polymer films. PMID:27579585

  5. Macroion Interaction at Polyelectrolyte Brush Interfaces

    NASA Astrophysics Data System (ADS)

    Qu, Chen

    2015-03-01

    The effect of macroions, including synthetic polyelectrolytes, DNA and proteins, on the structure and surface properties of charged polymer thin films remains inadequately understood partially due to the complexity involving the hydrophobic effect and the conformational change of polymeric macroions. In this work, we explore a group of inorganic nanocluster based macroions, hydrophilic polyoxometalates (POMs) of robust nanocluster structure and carrying high surface charges (~ 2-42 negative charges) to investigate their interaction with surface tethered poly-2-vinylpyridine (P2VP) brush-like thin films immersed in aqueous solution. We observe the collapse of swollen P2VP chains by adding POM macroions of increased concentration by AFM, QCM and contact goniometer measurements, in sharp contrast to the increased chain stretching by adding monovalent salts. A careful comparison is made between distinct POMs based on their charge, size and chemical nature. These findings serve as a good reference for theoretical model modification and design of new mesoporous composite membranes.

  6. Brushing abrasion of luting cements under neutral and acidic conditions.

    PubMed

    Buchalla, W; Attin, T; Hellwig, E

    2000-01-01

    Four resin based materials (Compolute Aplicap, ESPE; Variolink Ultra, Vivadent; C&B Metabond, Parkell and Panavia 21, Kuraray), two carboxylate cements (Poly-F Plus, Dentsply DeTrey and Durelon Maxicap, ESPE), two glass-ionomer cements (Fuji I, GC and Ketac-Cem Aplicap, ESPE), one resin-modified glass ionomer cement (Vitremer, 3M) one polyacid-modified resin composite (Dyract Cem, Dentsply DeTrey) and one zinc phosphate cement (Harvard, Richter & Hoffmann) were investigated according to their brushing resistance after storage in neutral and acidic buffer solutions. For this purpose 24 cylindrical acrylic molds were each filled with the materials. After hardening, the samples were stored for seven days in 100% relative humidity and at 37 degrees C. Subsequently, they were ground flat and polished. Then each specimen was covered with an adhesive tape leaving a 4 mm wide window on the cement surface. Twelve samples of each material were stored for 24 hours in a buffer solution with a pH of 6.8. The remaining 12 samples were placed in a buffer with a pH of 3.0. All specimens were then subjected to a three media brushing abrasion (2,000 strokes) in an automatic brushing machine. Storage and brushing were performed three times. After 6,000 brushing strokes per specimen, the tape was removed. Brushing abrasion was measured with a computerized laser profilometer and statistically analyzed with ANOVA and Tukey's Standardized Range Test (p < or = 0.05). The highest brushing abrasion was found for the two carboxylate cements. The lowest brushing abrasion was found for one resin based material, Compolute Aplicap. With the exception of three resin-based materials, a lower pH led to a higher brushing abrasion.

  7. Orbital tomography for highly symmetric adsorbate systems

    NASA Astrophysics Data System (ADS)

    Stadtmüller, B.; Willenbockel, M.; Reinisch, E. M.; Ules, T.; Bocquet, F. C.; Soubatch, S.; Puschnig, P.; Koller, G.; Ramsey, M. G.; Tautz, F. S.; Kumpf, C.

    2012-10-01

    Orbital tomography is a new and very powerful tool to analyze the angular distribution of a photoemission spectroscopy experiment. It was successfully used for organic adsorbate systems to identify (and consequently deconvolute) the contributions of specific molecular orbitals to the photoemission data. The technique was so far limited to surfaces with low symmetry like fcc(110) oriented surfaces, owing to the small number of rotational domains that occur on such surfaces. In this letter we overcome this limitation and present an orbital tomography study of a 3,4,9,10-perylene-tetra-carboxylic-dianhydride (PTCDA) monolayer film adsorbed on Ag(111). Although this system exhibits twelve differently oriented molecules, the angular resolved photoemission data still allow a meaningful analysis of the different local density of states and reveal different electronic structures for symmetrically inequivalent molecules. We also discuss the precision of the orbital tomography technique in terms of counting statistics and linear regression fitting algorithm. Our results demonstrate that orbital tomography is not limited to low-symmetry surfaces, a finding which makes a broad field of complex adsorbate systems accessible to this powerful technique.

  8. Tuning ice nucleation with counterions on polyelectrolyte brush surfaces

    PubMed Central

    He, Zhiyuan; Xie, Wen Jun; Liu, Zhenqi; Liu, Guangming; Wang, Zuowei; Gao, Yi Qin; Wang, Jianjun

    2016-01-01

    Heterogeneous ice nucleation (HIN) on ionic surfaces is ubiquitous in a wide range of atmospheric aerosols and at biological interfaces. Despite its great importance in cirrus cloud formation and cryopreservation of cells, organs, and tissues, it remains unclear whether the ion-specific effect on ice nucleation exists. Benefiting from the fact that ions at the polyelectrolyte brush (PB)/water interface can be reversibly exchanged, we report the effect of ions on HIN on the PB surface, and we discover that the distinct efficiency of ions in tuning HIN follows the Hofmeister series. Moreover, a large HIN temperature window of up to 7.8°C is demonstrated. By establishing a correlation between the fraction of ice-like water molecules and the kinetics of structural transformation from liquid- to ice-like water molecules at the PB/water interface with different counterions, we show that our molecular dynamics simulation analysis is consistent with the experimental observation of the ion-specific effect on HIN. PMID:27386581

  9. Tuning ice nucleation with counterions on polyelectrolyte brush surfaces.

    PubMed

    He, Zhiyuan; Xie, Wen Jun; Liu, Zhenqi; Liu, Guangming; Wang, Zuowei; Gao, Yi Qin; Wang, Jianjun

    2016-06-01

    Heterogeneous ice nucleation (HIN) on ionic surfaces is ubiquitous in a wide range of atmospheric aerosols and at biological interfaces. Despite its great importance in cirrus cloud formation and cryopreservation of cells, organs, and tissues, it remains unclear whether the ion-specific effect on ice nucleation exists. Benefiting from the fact that ions at the polyelectrolyte brush (PB)/water interface can be reversibly exchanged, we report the effect of ions on HIN on the PB surface, and we discover that the distinct efficiency of ions in tuning HIN follows the Hofmeister series. Moreover, a large HIN temperature window of up to 7.8°C is demonstrated. By establishing a correlation between the fraction of ice-like water molecules and the kinetics of structural transformation from liquid- to ice-like water molecules at the PB/water interface with different counterions, we show that our molecular dynamics simulation analysis is consistent with the experimental observation of the ion-specific effect on HIN. PMID:27386581

  10. Anomalous structure and scaling of ring polymer brushes

    NASA Astrophysics Data System (ADS)

    Reith, D.; Milchev, A.; Virnau, P.; Binder, K.

    2011-07-01

    A comparative simulation study of polymer brushes formed by grafting at a planar surface either flexible linear polymers (chain length NL) or (non-catenated) ring polymers (chain length NR=2NL) is presented. Two distinct off-lattice models are studied, one by Monte Carlo methods, the other by molecular dynamics, using a fast implementation on graphics processing units (GPUs). It is shown that the monomer density profiles ρ(z) in the z-direction perpendicular to the surface for rings and linear chains are practically identical, ρR(2NL,z)=ρL(NL, z). The same applies to the pressure, exerted on a piston at height z, as well. While the gyration radii components of rings and chains in the z-direction coincide, too, and increase linearly with NL, the transverse components differ, even with respect to their scaling properties: Rgxy(L)~NL1/2, Rgxy(R)~NL0.4. These properties are interpreted in terms of the statistical properties known for ring polymers in dense melts.

  11. Thickness Dependence of Bovine Serum Albumin Adsorption on Thin Thermoresponsive Poly(diethylene glycol) Methyl Ether Methacrylate Brushes by Surface Plasmon Resonance Measurements.

    PubMed

    Wassel, Ekram; Jiang, Siyu; Song, Qimeng; Vogt, Stephan; Nöll, Gilbert; Druzhinin, Sergey I; Schönherr, Holger

    2016-09-13

    This study reports on the dependence of the temperature-induced changes in the properties of thin thermoresponsive poly(diethylene glycol) methyl ether methacrylate (PDEGMA) layers of end-tethered chains on polymer thickness and grafting density. PDEGMA layers with a dry ellipsometric thickness of 5-40 nm were synthesized by surface-initiated atom transfer radical polymerization on gold. To assess the temperature-induced changes, the adsorption of bovine serum albumin (BSA) was investigated systematically as a function of film thickness, temperature, and grafting density by surface plasmon resonance (SPR), complemented by wettability and quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. BSA adsorption on PDEGMA brushes is shown to differ significantly above and below an apparent transition temperature. This surface transition temperature was found to depend linearly on the PDEGMA thickness and changed from 35 °C at 5 nm thickness to 48 °C at 23 nm. Similarly, a change of the grafting density enables the adjustment of this transition temperature presumably via a transition from the mushroom to the brush regime. Finally, BSA that adsorbed irreversibly on polymer brushes at temperatures above the transition temperature can be desorbed by reducing the temperature to 25 °C, underlining the reversibly switchable properties of PDEGMA brushes in response to temperature changes.

  12. Protein interactions with bottle-brush polymer layers: Effect of side chain and charge density ratio probed by QCM-D and AFM.

    PubMed

    Olanya, Geoffrey; Thormann, Esben; Varga, Imre; Makuska, Ricardas; Claesson, Per M

    2010-09-01

    Silica surfaces were coated with a range of cationic bottle-brush polymers with 45 units long poly(ethylene oxide) side chains, and their efficiency in reducing protein adsorption was probed by QCM-D, reflectometry and AFM. Preadsorbed layers formed by bottle-brush polymers with different side chain to charge ratio was exposed to two proteins with different net charge, lysozyme and BSA. The reduction in protein adsorption was found to depend on both the type of protein and on the nature of the polyelectrolyte layer. The most pronounced reduction in protein adsorption was achieved when the fraction of charged backbone segments was in the range 0.25-0.5 equivalent to a fraction of poly(ethylene oxide) side chains of 0.75-0.5. It was concluded that these polymers have enough electrostatic attachment points to ensure a strong binding to the surface, and at the same time a sufficient amount of poly(ethylene oxide) side chains to counteract protein adsorption. In contrast, a layer formed by a highly charged polyelectrolyte without side chains was unable to resists protein adsorption. On such a layer the adsorption of negatively charged BSA was strongly enhanced, and positively charged lysozyme adsorbed to a similar extent as to bare silica. AFM colloidal probe force measurement between silica surfaces with preadsorbed layers of bottle-brush polymers were conducted before and after exposure to BSA and lysozyme to gain insight into how proteins were incorporated in the bottle-brush polymer layers.

  13. Thickness Dependence of Bovine Serum Albumin Adsorption on Thin Thermoresponsive Poly(diethylene glycol) Methyl Ether Methacrylate Brushes by Surface Plasmon Resonance Measurements.

    PubMed

    Wassel, Ekram; Jiang, Siyu; Song, Qimeng; Vogt, Stephan; Nöll, Gilbert; Druzhinin, Sergey I; Schönherr, Holger

    2016-09-13

    This study reports on the dependence of the temperature-induced changes in the properties of thin thermoresponsive poly(diethylene glycol) methyl ether methacrylate (PDEGMA) layers of end-tethered chains on polymer thickness and grafting density. PDEGMA layers with a dry ellipsometric thickness of 5-40 nm were synthesized by surface-initiated atom transfer radical polymerization on gold. To assess the temperature-induced changes, the adsorption of bovine serum albumin (BSA) was investigated systematically as a function of film thickness, temperature, and grafting density by surface plasmon resonance (SPR), complemented by wettability and quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. BSA adsorption on PDEGMA brushes is shown to differ significantly above and below an apparent transition temperature. This surface transition temperature was found to depend linearly on the PDEGMA thickness and changed from 35 °C at 5 nm thickness to 48 °C at 23 nm. Similarly, a change of the grafting density enables the adjustment of this transition temperature presumably via a transition from the mushroom to the brush regime. Finally, BSA that adsorbed irreversibly on polymer brushes at temperatures above the transition temperature can be desorbed by reducing the temperature to 25 °C, underlining the reversibly switchable properties of PDEGMA brushes in response to temperature changes. PMID:27531168

  14. The entropies of adsorbed molecules.

    PubMed

    Campbell, Charles T; Sellers, Jason R V

    2012-10-31

    Adsorbed molecules are involved in many reactions on solid surface that are of great technological importance. As such, there has been tremendous effort worldwide to learn how to predict reaction rates and equilibrium constants for reactions involving adsorbed molecules. Theoretical calculation of both the rate and equilibrium constants for such reactions requires knowing the entropy and enthalpy of the adsorbed molecule. While much effort has been devoted to measuring and calculating the enthalpies of well-defined adsorbates, few measurements of the entropies of adsorbates have been reported. We present here a new way to determine the standard entropies of adsorbed molecules (S(ad)(0)) on single crystal surfaces from temperature programmed desorption data, prove its accuracy by comparison to entropies measured by equilibrium methods, and apply it to published data to extract new entropies. Most importantly, when combined with reported entropies, we find that at high coverage, they linearly track the entropy of the gas-phase molecule at the same temperature (T), such that S(ad)(0)(T) = 0.70 S(gas)(0)(T) - 3.3R (R = the gas constant), with a standard deviation of only 2R over a range of 50R. These entropies, which are ~2/3 of the gas, are huge compared to most theoretical predictions. This result can be extended to reliably predict prefactors in the Arrhenius rate constant for surface reactions involving such species, as proven here for desorption. PMID:23033909

  15. In-Plane Ordering in Diblock Copolymer Brushes.

    NASA Astrophysics Data System (ADS)

    Akgun, Bulent; Ugur, Gokce; Brittain, William J.; Foster, Mark D.; Li, Xuefa; Wang, Jin

    2007-03-01

    Internal and surface structures of polystyrene-b-polyacrylate and polyacrylate-b-polystyrene diblock copolymer brushes have been studied using grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM). Each asymmetric, as-deposited diblock brush that contains a poly(methyl acrylate) (PMA) block shows an in-plane structure with a spacing comparable to the PMA layer thickness. The correlation length of the in-plane ordering is about the nearest neighbor distance and grows with annealing at 180^o C. After a brush is treated with a solvent selective for the bottom block, Bragg rods appear in the GISAXS pattern. The lateral spacing corresponding to the Bragg rods is on the order of the brush total thickness. This lateral correlation is also detected by power spectral density analysis of AFM images of the samples' surfaces. The Bragg rods disappear upon heating to 80^o C.

  16. Surface wave excitations and backflow effect over dense polymer brushes

    PubMed Central

    Biagi, Sofia; Rovigatti, Lorenzo; Sciortino, Francesco; Misbah, Chaouqi

    2016-01-01

    Polymer brushes are being increasingly used to tailor surface physicochemistry for diverse applications such as wetting, adhesion of biological objects, implantable devices and much more. Here we perform Dissipative Particle Dynamics simulations to study the behaviour of dense polymer brushes under flow in a slit-pore channel. We discover that the system displays flow inversion at the brush interface for several disconnected ranges of the imposed flow. We associate such phenomenon to collective polymer dynamics: a wave propagating on the brush surface. The relation between the wavelength, the amplitude and the propagation speed of the flow-generated wave is consistent with the solution of the Stokes equations when an imposed traveling wave is assumed as the boundary condition (the famous Taylor’s swimmer). PMID:26975329

  17. Surface wave excitations and backflow effect over dense polymer brushes.

    PubMed

    Biagi, Sofia; Rovigatti, Lorenzo; Sciortino, Francesco; Misbah, Chaouqi

    2016-01-01

    Polymer brushes are being increasingly used to tailor surface physicochemistry for diverse applications such as wetting, adhesion of biological objects, implantable devices and much more. Here we perform Dissipative Particle Dynamics simulations to study the behaviour of dense polymer brushes under flow in a slit-pore channel. We discover that the system displays flow inversion at the brush interface for several disconnected ranges of the imposed flow. We associate such phenomenon to collective polymer dynamics: a wave propagating on the brush surface. The relation between the wavelength, the amplitude and the propagation speed of the flow-generated wave is consistent with the solution of the Stokes equations when an imposed traveling wave is assumed as the boundary condition (the famous Taylor's swimmer). PMID:26975329

  18. Surface wave excitations and backflow effect over dense polymer brushes

    NASA Astrophysics Data System (ADS)

    Biagi, Sofia; Rovigatti, Lorenzo; Sciortino, Francesco; Misbah, Chaouqi

    2016-03-01

    Polymer brushes are being increasingly used to tailor surface physicochemistry for diverse applications such as wetting, adhesion of biological objects, implantable devices and much more. Here we perform Dissipative Particle Dynamics simulations to study the behaviour of dense polymer brushes under flow in a slit-pore channel. We discover that the system displays flow inversion at the brush interface for several disconnected ranges of the imposed flow. We associate such phenomenon to collective polymer dynamics: a wave propagating on the brush surface. The relation between the wavelength, the amplitude and the propagation speed of the flow-generated wave is consistent with the solution of the Stokes equations when an imposed traveling wave is assumed as the boundary condition (the famous Taylor’s swimmer).

  19. 1. Building a brush dam. Location unknown. Photographer: Unknown, no ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. Building a brush dam. Location unknown. Photographer: Unknown, no date. Source: Salt River Project Archives (SRPA) - Tempe Canal, South Side Salt River in Tempe, Mesa & Phoenix, Tempe, Maricopa County, AZ

  20. Dense brushes of stiff polymers or filaments in fluid flow

    NASA Astrophysics Data System (ADS)

    Römer, F.; Fedosov, D. A.

    2015-03-01

    Dense filamentous brush-like structures are present in many biological interfacial systems (e.g., glycocalyx layer in blood vessels) to control their surface properties. Such structures can regulate the softness of a surface and modify fluid flow. In this letter, we propose a theoretical model which predicts quantitatively flow-induced deformation of a dense brush of stiff polymers or filaments, whose persistence length is larger or comparable to their contour length. The model is validated by detailed mesoscopic simulations and characterizes different contributions to brush deformation including hydrodynamic friction due to flow and steric excluded-volume interactions between grafted filaments. This theoretical model can be used to describe the effect of a stiff-polymer brush on fluid flow and to aid in the quantification of experiments.

  1. Keep Kids' Mouths Healthy: Brush 2min2X

    MedlinePlus

    ... Kids’ Teeth Teeth Helpful Resources Links Keep Kids’ Mouths Healthy Roll over or click the time line below for healthy mouth information. Email Link Kids' Care Timeline Brush 2min2x - ...

  2. Astronauts Culbertson and Bursch brush their teeth on Discovery's middeck

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Astronauts Frank L. Culbertson (right), mission commander, and Daniel W. Bursch, mission specialist, brush their teeth on Discovery's middeck. Two sleep restraints form part of the backdrop for the photograph.

  3. Coat thickness dependent adsorption of hydrophobic molecules at polymer brushes

    NASA Astrophysics Data System (ADS)

    Smiatek, Jens; Heuer, Andreas; Wagner, Hendrik; Studer, Armido; Hentschel, Carsten; Chi, Lifeng

    2013-01-01

    We study the adsorption properties of hydrophobic test particles at polymer brushes with different coat thicknesses via mesoscopic dissipative particle dynamics simulations. Our findings indicate stronger free energies of adsorption at thin polymer brushes. The reason for this difference is mainly given by entropic contributions due to different elastic deformations of the coatings. The numerical findings are supported by analytical calculations and are in good qualitative agreement to experimental fluorescence intensity results.

  4. High temperature, flexible pressure-actuated, brush seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor); Sirocky, Paul J. (Inventor)

    1991-01-01

    A high temperature, flexible brush seal comprises a bundle of fibers or bristles held tightly together and secured at one end with a backing plate. The assembly includes a secondary spring-clip having one end anchored to the brush seal backing plate. An alternate embodiment of the seal utilizes a metal bellows containing coolant holes. Another embodiment of the seal uses non-circular cross-sectional fibers which may be square, rectangular or hexagonal in cross section.

  5. Fibre evaluation for spacecraft cleaning. [vacuum brush materials

    NASA Technical Reports Server (NTRS)

    Jensen, W. M.

    1976-01-01

    The employment of vacuum brushes utilizing sable tail hair for the physical removal of particulates from spacecraft surfaces has become problematical in connection with a lack of compatibility of the bristle with sterilization and biological decontamination procedures required for spacecraft cleaning. An investigation was, therefore, conducted to find a suitable fiber which can replace sable bristle. Felor fiber was found to have the best properties for use in a motorized cleaning brush.

  6. Brush cytology: a reliable method to detect Helicobacter pylori.

    PubMed

    Dalla Libera, M; Pazzi, P; Carli, G; Contato, E; Piva, I; Scagliarini, R; Merighi, A; Ricci, N; Gullini, S

    1996-06-01

    This study was conducted to verify the reliability of brush cytology in detecting Helicobacter pylori in an unselected group of patients with duodenal ulcer (DU) and nonulcer dyspepsia (NUD). Endoscopy was performed on 416 consecutive patients: group A, 94 with active DU; group B, 176 patients with DU after omeprazole (n = 78), ranitidine (n = 43), or triple anti-H. pylori therapy (n = 55); and group C, 146 patients with NUD. During endoscopy, the gastric mucosa was brushed and two biopsy samples from the antrum and body were obtained for histology. In 65 patients, culture of the brush-collected materials also was performed as was that from of biopsy samples. The overall frequency of H. pylori presence detected by brush cytology was significantly higher compared with that of histology (p < 0.001), particularly in group A (p < 0.05), group C (p < 0.05), and in patients with DU after omeprazole treatment (p < 0.01), but not in patients with DU after ranitidine or anti-H. pylori treatment. The overall frequency of H. pylori-positive cultures from the brush-collected material was higher compared with cultures from the biopsy samples (38.5% vs. 24.6%), particularly in the NUD group (32.6% vs. 16.3%). Brush cytology is more sensitive than histology, besides being faster and cheaper, for the assessment of H. pylori infection, particularly when the density of the bacteria is low.

  7. Polyelectrolyte brushes in mixed ionic medium studied via intermolecular forces

    NASA Astrophysics Data System (ADS)

    Farina, Robert; Laugel, Nicolas; Pincus, Philip; Tirrell, Matthew

    2011-03-01

    The vast uses and applications of polyelectrolyte brushes make them an attractive field of research especially with the growing interest in responsive materials. Polymers which respond via changes in temperature, pH, and ionic strength are increasingly being used for applications in drug delivery, chemical gating, etc. When polyelectrolyte brushes are found in either nature (e.g., surfaces of cartilage and mammalian lung interiors) or commercially (e.g., skin care products, shampoo, and surfaces of medical devices) they are always surrounded by mixed ionic medium. This makes the study of these brushes in varying ionic environments extremely relevant for both current and future potential applications. The polyelectrolyte brushes in this work are diblock co-polymers of poly-styrene sulfonate (N=420) and poly-t-butyl styrene (N=20) which tethers to a hydrophobic surface allowing for a purely thermodynamic study of the polyelectrolyte chains. Intermolecular forces between two brushes are measured using the SFA. As multi-valent concentrations are increased, the brushes collapse internally and form strong adhesion between one another after contact (properties not seen in a purely mono-valent environment).

  8. Cues to Action as Motivators for Children's Brushing.

    PubMed

    Walker, Kimberly K; Steinfort, Erin L; Keyler, Maria J

    2015-01-01

    Dental caries is the most common chronic childhood disease. Home self-care procedures are the most important strategies to prevent tooth decay. Brushing is the most important single intervention for the prevention of tooth decay, yet compliance is not practiced and there is limited understanding of children's behavioral decisions. Guided by the Health Belief Model, this study consisted of eight focus groups with children in the second through fifth grades at three different socioeconomic-level school districts to determine the cues to action that are motivating or can motivate their brushing behavior. Results indicated children are primarily motivated to brush for aesthetic reasons, mainly due to viewed media pictures of "perfect" teeth. Other less commonly expressed motivations for brushing stemmed from interpersonal connections, such as relatives with dentures. Social media, on the other hand, played a key role in some children's understanding of more advanced oral health connections such as links between cardiovascular and oral disease, and smoking and oral cancer. These links were viewed as threatening to children to motivate better brushing. Additionally, the study found that home computers can be used as an external motivator to deliver tailored messages to encourage better brushing.

  9. The Unusual Conformational Behavior of Polyzwitterionic Brushes in Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Mao, Jun; Chen, Wei; Yuan, Guangcui; Yu, Jing; Tirrell, Matthew

    Polyzwitterions constitute a peculiar class of polyelectrolytes, which are electrically neutral polymers containing both a positive and a negative charge on each repeating unit. Surfaces coated with polyzwitterionic brushes are resistant to the nonspecific accumulation of proteins and microorganisms, making them excellent candidates for a wide range of antifouling applications, from biocompatible medical devices to marine coatings. The surrounding environment can dramatically influence the conformational behavior of polyzwitterionic brushes. High-density polyzwitterionic brushes poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) were synthesized using surface initiated atom-transfer radical polymerization, and neutron reflectivity (NR) measurements were performed to investigate the ionic strength dependence of the conformational behaviors of PMPC brushes in monovalent salt solutions. Despite the numerous observations of normal pure polyelectrolyte brushes, NR results showed that both the densely concentrated layer near the substrate surface and the relatively swollen layer into the solution have been observed in different q range in a single neutron reflectivity profile. These results will definitely help us to better understand the relationship between the solution behaviors of zwitterionic polymer brushes and their antifouling properties.

  10. Effect of Salt on Phosphorylcholine-based Zwitterionic Polymer Brushes.

    PubMed

    Zhang, Zhenyu; Moxey, Mark; Alswieleh, Abdullah; Morse, Andrew J; Lewis, Andrew L; Geoghegan, Mark; Leggett, Graham J

    2016-05-24

    A quantitative investigation of the responses of surface-grown biocompatible brushes of poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) to different types of salt has been carried out using ellipsometry, quartz crystal microbalance (QCM) measurements, and friction force microscopy. Both cations and anions of varying valency over a wide range of concentrations were examined. Ellipsometry shows that the height of the brushes is largely independent of the ionic strength, confirming that the degree of swelling of the polymer is independent of the ionic character of the medium. In contrast, QCM measurements reveal significant changes in mass and dissipation to the PMPC brush layer, suggesting that ions bind to phosphorylcholine (PC) groups in PMPC molecules, which results in changes in the stiffness of the brush layer, and the binding affinity varies with salt type. Nanotribological measurements made using friction force microscopy show that the coefficient of friction decreases with increasing ionic strength for a variety of salts, supporting the conclusion drawn from QCM measurements. It is proposed that the binding of ions to the PMPC molecules does not change their hydration state, and hence the height of the surface-grown polymeric brushes. However, the balance of the intra- and intermolecular interactions is strongly dependent upon the ionic character of the medium between the hydrated chains, modulating the interactions between the zwitterionic PC pendant groups and, consequently, the stiffness of the PMPC molecules in the brush layer. PMID:27133955

  11. Isomerization reactions on single adsorbed molecules.

    PubMed

    Morgenstern, Karina

    2009-02-17

    Molecular switches occur throughout nature. In one prominent example, light induces the isomerization of retinal from the compact 11-cis form to the elongated all-trans form, a conversion that triggers the transformation of light into a neural impulse in the eye. Applying these natural principles to synthetic systems offers a promising way to construct smaller and faster nanoelectronic devices. In such systems, electronic switches are essential components for storage and logical operations. The development of molecular switches on the single-molecule level would represent a major step toward incorporating molecules as building units into nanoelectronic circuits. Molecular switches must be both reversible and bistable. To meet these requirements, a molecule must have at least two different thermally stable forms and a way to repeatedly interconvert between those forms based on changes in light, heat, pressure, magnetic or electric fields, pH, mechanical forces, or electric currents. The conversion should be connected to a measurable change in electronic, optical, magnetic, or mechanical properties. Because isomers can differ significantly in physical and chemical properties, isomerization could serve as a molecular switching mechanism. Integration of molecular switches into larger circuits will probably require arranging them on surfaces, which will require a better understanding of isomerization reactions in these environments. In this Account, we describe our scanning tunneling microscopy studies of the isomerization of individual molecules adsorbed on metal surfaces. Investigating chlorobenzene and azobenzene derivatives on the fcc(111) faces of Ag, Cu, and Au, we explored the influence of substituents and the substrate on the excitation mechanism of the isomerization reaction induced by inelastically tunneling electrons. We achieved an irreversible configurational (cis-trans) isomerization of individual 4-dimethyl-amino-azobenzene-4-sulfonic acid molecules on Au

  12. RADIOLYSIS OF ORGANIC COMPOUNDS IN THE ADSORBED STATE

    DOEpatents

    Sutherland, J.W.; Allen, A.O.

    1961-10-01

    >A method of forming branch chained hydrocarbons by means of energetic penetrating radiation is described. A solid zeolite substrate is admixed with a cobalt ion and is irradiated with a hydrocarbon adsorbed therein. Upon irradiation with gamma rays, there is an increased yield of branched and lower molecular straight chain compounds. (AEC)

  13. Atomic force microscopy study of the interaction between adsorbed poly(ethylene oxide) layers: effects of surface modification and approach velocity.

    PubMed

    McLean, Scott C; Lioe, Hadi; Meagher, Laurence; Craig, Vincent S J; Gee, Michelle L

    2005-03-15

    The interaction forces between layers of the triblock copolymer Pluronic F108 adsorbed onto hydrophobic radio frequency glow discharge (RFGD) thin film surfaces and hydrophilic silica, in polymer-free 0.15 M NaCl solution, have been measured using the atomic force microscope (AFM) colloid probe technique. Compression of Pluronic F108 layers adsorbed on the hydrophobic RFGD surfaces results in a purely repulsive force due to the steric overlap of the layers, the form of which suggests that the PEO chains adopt a brush conformation. Subsequent fitting of these data to the polymer brush models of Alexander-de Gennes and Milner, Witten, and Cates confirms that the adsorbed Pluronic F108 adsorbs onto hydrophobic surfaces as a polymer brush with a parabolic segment density profile. In comparison, the interaction between Pluronic F108 layers adsorbed on silica exhibits a long ranged shallow attractive force and a weaker steric repulsion. The attractive component is reasonably well described by van der Waals forces, but polymer bridging cannot be ruled out. The weaker steric component of the force suggests that the polymer is less densely packed on the surface and is less extended into solution, existing as polymeric isolated mushrooms. When the surfaces are driven together at high piezo ramp velocities, an additional repulsive force is measured, attributable to hydrodynamic drainage forces between the surfaces. In comparing theoretical predictions of the hydrodynamic force to the experimentally obtained data, agreement could only be obtained if the flow profile of the aqueous solution penetrated significantly into the polymer brush. This finding is in line with the theoretical predictions of Milner and provides further evidence that the segment density profile of the adsorbed polymer brush is parabolic. A velocity dependent additional stepped repulsive force, reminiscent of a solvation oscillatory force, is also observed when the adsorbed layers are compressed under high

  14. Rotary adsorbers for continuous bulk separations

    DOEpatents

    Baker, Frederick S.

    2011-11-08

    A rotary adsorber for continuous bulk separations is disclosed. The rotary adsorber includes an adsorption zone in fluid communication with an influent adsorption fluid stream, and a desorption zone in fluid communication with a desorption fluid stream. The fluid streams may be gas streams or liquid streams. The rotary adsorber includes one or more adsorption blocks including adsorbent structure(s). The adsorbent structure adsorbs the target species that is to be separated from the influent fluid stream. The apparatus includes a rotary wheel for moving each adsorption block through the adsorption zone and the desorption zone. A desorption circuit passes an electrical current through the adsorbent structure in the desorption zone to desorb the species from the adsorbent structure. The adsorbent structure may include porous activated carbon fibers aligned with their longitudinal axis essentially parallel to the flow direction of the desorption fluid stream. The adsorbent structure may be an inherently electrically-conductive honeycomb structure.

  15. A Case Study of Truncated Electrostatics for Simulation of Polyelectrolyte Brushes on GPU Accelerators

    SciTech Connect

    Nguyen, Trung D; Carrillo, Jan-Michael; Dobrynin, Andrey; Brown, W Michael

    2013-01-01

    Numerous issues have disrupted the trend for increasing computational performance with faster CPU clock frequencies. In order to exploit the potential performance of new computers, it is becoming increasingly desirable to re-evaluate computational physics methods and models with an eye towards towards approaches that allow for increased concurrency and data locality. The evaluation of long-range Coulombic interactions is a common bottleneck for molecular dynamics simulations. Enhanced truncation approaches have been proposed as an alternative method and are particularly well suited for many-core architectures and GPUs due to the inherent fine-grain parallelism that can be exploited. In this paper, we compare efficient truncation-based approximations to evaluation of electrostatic forces with the more traditional particle-particle particle-mesh (P3M) method for molecular dynamics simulation of polyelectrolyte brush layers. We show that with the use of GPU accelerators, large parallel simulations using P3M can be greater than 3 times faster due to a reduction in the mesh-size required. Alternatively, using a truncation-based scheme can improve performance even further. This approach can be up to 3.9 times faster than GPU-accelerated P3M for many polymer systems and results in accurate calculation of shear velocities and disjoining pressures for brush layers. For configurations with highly non-uniform charge distributions, however, we find that it is more efficient to use P3M; for these systems, computationally efficient parameterizations of the truncation-based approach do not produce accurate counterion density profiles or brush morphologies.

  16. A Case Study of Truncated Electrostatics for Simulation of Polyelectrolyte Brushes on GPU Accelerators.

    PubMed

    Nguyen, Trung Dac; Carrillo, Jan-Michael Y; Dobrynin, Andrey V; Brown, W Michael

    2013-01-01

    Numerous issues have disrupted the trend for increasing computational performance with faster CPU clock frequencies. In order to exploit the potential performance of new computers, it is becoming increasingly desirable to re-evaluate computational physics methods and models with an eye toward approaches that allow for increased concurrency and data locality. The evaluation of long-range Coulombic interactions is a common bottleneck for molecular dynamics simulations. Enhanced truncation approaches have been proposed as an alternative method and are particularly well-suited for many-core architectures and GPUs due to the inherent fine-grain parallelism that can be exploited. In this paper, we compare efficient truncation-based approximations to evaluation of electrostatic forces with the more traditional particle-particle particle-mesh (P(3)M) method for the molecular dynamics simulation of polyelectrolyte brush layers. We show that with the use of GPU accelerators, large parallel simulations using P(3)M can be greater than 3 times faster due to a reduction in the mesh-size required. Alternatively, using a truncation-based scheme can improve performance even further. This approach can be up to 3.9 times faster than GPU-accelerated P(3)M for many polymer systems and results in accurate calculation of shear velocities and disjoining pressures for brush layers. For configurations with highly nonuniform charge distributions, however, we find that it is more efficient to use P(3)M; for these systems, computationally efficient parametrizations of the truncation-based approach do not produce accurate counterion density profiles or brush morphologies.

  17. Affinity Adsorbents Based on Carriers Activated by Epoxy-compounds

    NASA Astrophysics Data System (ADS)

    Klyashchitskii, B. A.; Kuznetsov, P. V.

    1984-10-01

    The review is devoted to the synthesis and applications of affinity adsorbents based on carriers activated by epoxy-compounds. The methods for the introduction of epoxy-groups into carriers of different chemical types are discussed and conditions for the immobilisation of three-dimensional spacers and low-molecular-weight and polymeric ligands on carriers containing epoxy-groups are considered. Data are presented on the properties and applications of adsorbents of this type in affinity chromatography. The bibliography includes 144 references.

  18. Hydrogen molecule on lithium adsorbed graphene: A DFT study

    NASA Astrophysics Data System (ADS)

    Kaur, Gagandeep; Gupta, Shuchi; Gaganpreet, Dharamvir, Keya

    2016-05-01

    Electronic structure calculations for the adsorption of molecular hydrogen on lithium (Li) decorated and pristine graphene have been studied systematically using SIESTA code [1] within the framework of the first-principle DFT under the Perdew-Burke-Ernzerhof (PBE) form of the generalized gradient approximation (GGA)[2], including spin polarization. The energy of adsorption of hydrogen molecule on graphene is always enhanced by the presence of co-adsorbed lithium. The most efficient adsorption configuration is when H2 is lying parallel to lithium adsorbed graphene which is in contrast to its adsorption on pristine graphene (PG) where it prefers perpendicular orientation.

  19. The Impact of Enzyme Orientation and Electrode Topology on the Catalytic Activity of Adsorbed Redox Enzymes

    PubMed Central

    McMillan, Duncan G. G.; Marritt, Sophie J.; Kemp, Gemma L.; Gordon-Brown, Piers; Butt, Julea N.; Jeuken, Lars J. C.

    2014-01-01

    It is well established that the structural details of electrodes and their interaction with adsorbed enzyme influences the interfacial electron transfer rate. However, for nanostructured electrodes, it is likely that the structure also impacts on substrate flux near the adsorbed enzymes and thus catalytic activity. Furthermore, for enzymes converting macro-molecular substrates it is possible that the enzyme orientation determines the nature of interactions between the adsorbed enzyme and substrate and therefore catalytic rates. In essence the electrode may impede substrate access to the active site of the enzyme. We have tested these possibilities through studies of the catalytic performance of two enzymes adsorbed on topologically distinct electrode materials. Escherichia coli NrfA, a nitrite reductase, was adsorbed on mesoporous, nanocrystalline SnO2 electrodes. CymA from Shewanella oneidensis MR-1 reduces menaquinone-7 within 200 nm sized liposomes and this reaction was studied with the enzyme adsorbed on SAM modified ultra-flat gold electrodes. PMID:24634538

  20. The Impact of Enzyme Orientation and Electrode Topology on the Catalytic Activity of Adsorbed Redox Enzymes.

    PubMed

    McMillan, Duncan G G; Marritt, Sophie J; Kemp, Gemma L; Gordon-Brown, Piers; Butt, Julea N; Jeuken, Lars J C

    2013-11-01

    It is well established that the structural details of electrodes and their interaction with adsorbed enzyme influences the interfacial electron transfer rate. However, for nanostructured electrodes, it is likely that the structure also impacts on substrate flux near the adsorbed enzymes and thus catalytic activity. Furthermore, for enzymes converting macro-molecular substrates it is possible that the enzyme orientation determines the nature of interactions between the adsorbed enzyme and substrate and therefore catalytic rates. In essence the electrode may impede substrate access to the active site of the enzyme. We have tested these possibilities through studies of the catalytic performance of two enzymes adsorbed on topologically distinct electrode materials. Escherichia coli NrfA, a nitrite reductase, was adsorbed on mesoporous, nanocrystalline SnO2 electrodes. CymA from Shewanella oneidensis MR-1 reduces menaquinone-7 within 200 nm sized liposomes and this reaction was studied with the enzyme adsorbed on SAM modified ultra-flat gold electrodes.

  1. 76 FR 70760 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-American Brush...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-15

    ... Brush Manufacturers Association Notice is hereby given that, on October 12, 2011, pursuant to Section 6... Act''), American Brush Manufacturers Association (``ABMA'') has filed written notifications... organization is: American Brush Manufacturers Association, Aurora, IL. The nature and scope of ABMA's...

  2. Contamination Impact of Station Brush Fire on Cleanroom Facilities

    NASA Technical Reports Server (NTRS)

    Carey, Phil; Blakkolb, Brian

    2010-01-01

    Brush and forest fires, both naturally occurring and anthropogenic in origin, in proximity to space flight hardware processing facilities raise concerns about the threat of contamination resulting from airborne particulate and molecular components of smoke. Perceptions of the severity of the threat are possibly heightened by the high sensitivity of the human sense of smell to some components present in the smoke of burning vegetation.On August 26th, 2009, a brushfire broke out north of Pasadena, California, two miles from the Jet Propulsion Laboratory. The Station Fire destroyed over 160,000 acres, coming within a few hundred yards of JPL. Smoke concentrations on Lab were very heavy over several days. All Lab operations were halted, and measures were taken to protect personnel, critical hardware, and facilities. Evaluation of real-time cleanroom monitoring data, visualinspection of facilities, filter systems, and analysis of surface cleanliness samples revealed facility environments andhardware were minimally effected.Outside air quality easily exceeded Class Ten Million. Prefilters captured most large ash and soot; multi-stage filtration greatly minimized the impact on the HEPA/ULPA filters. Air quality in HEPA filtered spacecraft assembly cleanrooms remained within Class 10,000 specification throughout. Surface cleanliness was inimally affected, as large particles were effectively removed from the airstream, and sub-micron particles have extremely long settling rates. Approximate particulate fallout within facilities was 0.00011% area coverage/day compared to 0.00038% area coverage/day during normal operations. Deposition of condensable airborne components, as measured in real time, peaked at approximately1.0 ng/cm2/day compared to 0.05 ng/cm2/day nominal.

  3. Contamination impact of station brush fire on cleanroom facilities

    NASA Astrophysics Data System (ADS)

    Carey, Philip A.; Blakkolb, Brian K.

    2010-08-01

    Brush and forest fires, both naturally occurring and anthropogenic in origin, in proximity to space flight hardware processing facilities raise concerns about the threat of contamination resulting from airborne particulate and molecular components of smoke. Perceptions of the severity of the threat are possibly heightened by the high sensitivity of the human sense of smell to some components present in the smoke of burning vegetation. On August 26th, 2009, a brushfire broke out north of Pasadena, California, two miles from the Jet Propulsion Laboratory. The Station Fire destroyed over 160,000 acres, coming within a few hundred yards of JPL. Smoke concentrations on Lab were very heavy over several days. All Lab operations were halted, and measures were taken to protect personnel, critical hardware, and facilities. Evaluation of real-time cleanroom monitoring data, visual inspection of facilities, filter systems, and analysis of surface cleanliness samples revealed facility environments and hardware were minimally effected. Outside air quality easily exceeded Class Ten Million. Prefilters captured most large ash and soot; multi-stage filtration greatly minimized the impact on the HEPA/ULPA filters. Air quality in HEPA filtered spacecraft assembly cleanrooms remained within Class 10,000 specification throughout. Surface cleanliness was minimally affected, as large particles were effectively removed from the airstream, and sub-micron particles have extremely long settling rates. Approximate particulate fallout within facilities was 0.00011% area coverage/day compared to 0.00038% area coverage/day during normal operations. Deposition of condensable airborne components, as measured in real time, peaked at approximately 1.0 ng/cm2/day compared to 0.05 ng/cm2/day nominal.

  4. Dendritic brushes under good solvent conditions: a simulation study.

    PubMed

    Gergidis, Leonidas N; Kalogirou, Andreas; Vlahos, Costas

    2012-12-11

    The structural properties of polymer brushes, formed by dendron polymers up to the third generation, were studied by means of Brownian dynamics simulations for the macroscopic state of good solvent. The distributions of polymer units, of the free ends, of the dendrons centers of mass, and of the units of every dendritic generation and the radii of gyration necessary for the understanding of the internal stratification of brushes were calculated. Previous self-consistent field theory numerical simulations of first-generation dendritic brushes suggested that at high grafting densities two kinds of populations are evident, one of short dendrons having weakly extended spacers and another with tall dendrons having strongly stretched spacers. These Brownian dynamics calculations provided a more complicated picture of dendritic brushes, revealing different populations of short, tall, and in some cases intermediate height dendrons, depending on the dendron generation and spacer length. The scaling dependence of the height and the span of the dendritic brush on the grafting density and other parameters were found to be in good agreement with existing theoretical results for good solvents. PMID:23134236

  5. Modeling bristle lift-off in idealized brush seal configurations

    NASA Astrophysics Data System (ADS)

    Modi, Vijay

    1993-10-01

    We attempt in this paper to develop a model for the flow through brush seals and determine their elastic behavior in order to predict the dependence of brush/journal clearance on geometry and operating conditions. Several idealizations regarding brush seal configuration, flow conditions, and elastic behavior are made in the analysis in order to determine closed form parametric dependence. This formulation assumes that there is no initial interference between the bristle tip and the rotor. Also, interbristle, bristle-backing plate, and bristle-rotor friction is neglected. The bristle bundle or the brush seal as it is alternately called is assumed homogeneous and isotropic on a macroscopic scale so that a physical property like permeability is uniform. The fluid is assumed to be homogeneous, incompressible, viscous, and flowing under steady conditions. A schematic of a brush seal is shown. If the nominal bristle-shaft interference is absent then under static conditions the bristles may deflect axially due to the imposed pressure differential. This axial deflection may create a clearance permitting leakage flow in excess of that which occurs through the porous matrix formed by the bristle bundles. Under dynamic conditions the Couette flow created by shaft motion could be strong enough to cause bristle deflection and once again a clearance may develop. The paper proposes a means to determine this clearance (or at least describe its parametric dependence on geometry and operating conditions) under static as well as dynamic conditions.

  6. Control of nanoparticle formation using the constrained dewetting of polymer brushes

    NASA Astrophysics Data System (ADS)

    Lee, Thomas; Hendy, Shaun C.; Neto, Chiara

    2015-02-01

    We have used coarse-grained molecular dynamics simulations to investigate the use of pinned micelles formed by the constrained dewetting of polymer brushes to act as a template for nanoparticle formation. The evaporation of a thin film containing a dissolved solute from a polymer brush was modeled to study the effect of solubility, concentration, grafting density, and evaporation rate on the nucleation and growth of nanoparticles. Control over particle nucleation could be imposed when the solution was dilute enough such that particle nucleation occurred following the onset of constrained dewetting. We predict that nanoparticles with sizes on the order of 1 nm to 10 nm could be produced from a range of organic molecules under experimentally accessible conditions. This method could allow the functionality of organic materials to potentially be imparted onto surfaces without the need for synthetic modification of the functional molecule, and with control over particle size and aggregation, for application in the preparation of surfaces with useful optical, pharmaceutical, or electronic properties.We have used coarse-grained molecular dynamics simulations to investigate the use of pinned micelles formed by the constrained dewetting of polymer brushes to act as a template for nanoparticle formation. The evaporation of a thin film containing a dissolved solute from a polymer brush was modeled to study the effect of solubility, concentration, grafting density, and evaporation rate on the nucleation and growth of nanoparticles. Control over particle nucleation could be imposed when the solution was dilute enough such that particle nucleation occurred following the onset of constrained dewetting. We predict that nanoparticles with sizes on the order of 1 nm to 10 nm could be produced from a range of organic molecules under experimentally accessible conditions. This method could allow the functionality of organic materials to potentially be imparted onto surfaces without the

  7. Adsorbate-induced curvature and stiffening of graphene.

    PubMed

    Svatek, Simon A; Scott, Oliver R; Rivett, Jasmine P H; Wright, Katherine; Baldoni, Matteo; Bichoutskaia, Elena; Taniguchi, Takashi; Watanabe, Kenji; Marsden, Alexander J; Wilson, Neil R; Beton, Peter H

    2015-01-14

    The adsorption of the alkane tetratetracontane (TTC, C44H90) on graphene induces the formation of a curved surface stabilized by a gain in adsorption energy. This effect arises from a curvature-dependent variation of a moiré pattern due to the mismatch of the carbon-carbon separation in the adsorbed molecule and the period of graphene. The effect is observed when graphene is transferred onto a deformable substrate, which in our case is the interface between water layers adsorbed on mica and an organic solvent, but is not observed on more rigid substrates such as boron nitride. Our results show that molecular adsorption can be influenced by substrate curvature, provide an example of two-dimensional molecular self-assembly on a soft, responsive interface, and demonstrate that the mechanical properties of graphene may be modified by molecular adsorption, which is of relevance to nanomechanical systems, electronics, and membrane technology. PMID:25469625

  8. Adsorbate-Induced Curvature and Stiffening of Graphene

    PubMed Central

    2014-01-01

    The adsorption of the alkane tetratetracontane (TTC, C44H90) on graphene induces the formation of a curved surface stabilized by a gain in adsorption energy. This effect arises from a curvature-dependent variation of a moiré pattern due to the mismatch of the carbon–carbon separation in the adsorbed molecule and the period of graphene. The effect is observed when graphene is transferred onto a deformable substrate, which in our case is the interface between water layers adsorbed on mica and an organic solvent, but is not observed on more rigid substrates such as boron nitride. Our results show that molecular adsorption can be influenced by substrate curvature, provide an example of two-dimensional molecular self-assembly on a soft, responsive interface, and demonstrate that the mechanical properties of graphene may be modified by molecular adsorption, which is of relevance to nanomechanical systems, electronics, and membrane technology. PMID:25469625

  9. Integrity testing of brush seal in a T-700 engine

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Griffin, Thomas A.; Bobula, George A.; Bill, Robert C.; Howe, Harold W.

    1993-01-01

    A split-ring brush seal was fabricated, installed between two labyrinth-honeycomb shroud seals, and tested in the fourth-stage turbine of a T-700 engine. The annealed Haynes 25 bristles rubbed directly against the nonconditioned, irregular Rene 80 turbine blade shroud surface. A total of 21 hr of cyclic and steady-state data were taken with surface speeds of 335 m/s (1100 ft/s) and shroud temperatures to 620 C (1150 F). Wear appeared to be rapid initially, with an orange flash of hot brush fragments during the first engine startup, to minimal after 10 hr of operation. The brush survived the testing but experienced some bristle pullouts and severe bristle wear; some turbine interface wear and possible material transfer was noted. Future design concerns center on tribological behavior at the interface with or without lubricants.

  10. A bulk flow model of a brush seal system

    NASA Technical Reports Server (NTRS)

    Hendricks, R. C.; Schlumberger, S.; Braun, M. J.; Choy, F.; Mullen, R. L.

    1991-01-01

    Fibers can be readily fabricated into a variety of seal configurations that are compliant and responsive to high speed or lightly loaded systems. A linear, circular, or contoured brush seal system is a contact seal consisting of the bristle pattern and hardened interface. When compared to a labyrinth seal, the brush seal system is superior and features low leakage, dynamic stability, and permits compliant structures. But in turn, the system usually requires a hardened smooth interface and permits only limited pressure drops. Wear life and wear debris for operations with static or dynamic excitation are largely undetermined. A seal system involves control of fluid within specific boundaries. The brush and rub ring (or rub surface) form a seal system. Design similitudes, a bulk flow model, and rub ring (interface) coatings are discussed. The bulk flow model calculations are based on flows in porous media and filters. The coatings work is based on experience and expanded to include current practice.

  11. Integrity testing of brush seal in a T-700 engine

    NASA Astrophysics Data System (ADS)

    Hendricks, Robert C.; Griffin, Thomas A.; Bobula, George A.; Bill, Robert C.; Howe, Harold W.

    1993-10-01

    A split-ring brush seal was fabricated, installed between two labyrinth-honeycomb shroud seals, and tested in the fourth-stage turbine of a T-700 engine. The annealed Haynes 25 bristles rubbed directly against the nonconditioned, irregular Rene 80 turbine blade shroud surface. A total of 21 hr of cyclic and steady-state data were taken with surface speeds of 335 m/s (1100 ft/s) and shroud temperatures to 620 C (1150 F). Wear appeared to be rapid initially, with an orange flash of hot brush fragments during the first engine startup, to minimal after 10 hr of operation. The brush survived the testing but experienced some bristle pullouts and severe bristle wear; some turbine interface wear and possible material transfer was noted. Future design concerns center on tribological behavior at the interface with or without lubricants.

  12. A new tribological test for candidate brush seal materials evaluation

    SciTech Connect

    Fellenstein, J.A.; DellaCorte, C.

    1994-10-01

    A new tribological test for candidate brush seal materials evaluation has been developed. The sliding contact between the brush seal wires and their mating counterface journal is simulated by testing a small tuft of wire against the outside diameter of a high speed rotating shaft. The test configuration is similar to a standard block on ring geometry. The new tester provides the capability to measure both the friction and wear of candidate wire and counterface materials under controlled loading conditions in the gram to kilogram range. A wide test condition latitude of speeds (1 to 27 m/s), temperatures (25 to 700C), and loads (0.5 to 10 N) enables the simulation of many of the important tribological parameters found in turbine engine brush seals. This paper describes the new test rig and specimen configuration and presents initial data for candidate seal materials comparing tuft test results and wear surface morphology to field tested seal components.

  13. An Overview of Non-Metallic Brush Seal Technology

    NASA Technical Reports Server (NTRS)

    Ruggiero, Eric J.

    2009-01-01

    Non-metallic brush seals are ultra-low flow sealing elements ideal for low pressure differentials (<30 psid) and low temperature (typically <300 degF) applications. The compliant bristle pack of a non-metallic brush seal is advantageous in terms of sealing capability during transients. However, if not designed properly, the bristle pack compliance can be detrimental to the performance of the seal. GE GLobal Research has investigated the stiffness and heat generation properties of non-metallic brush seals made from Kevlar and Carbon Fiber. The presentation will review the progress made on the design points of the seals, as well as highlight some current commercial applications of the technology.

  14. A New Tribological Test for Candidate Brush Seal Materials Evaluation

    NASA Technical Reports Server (NTRS)

    Fellenstein, James A.; Dellacorte, Christopher

    1994-01-01

    A new tribological test for candidate brush seal materials evaluation has been developed. The sliding contact between the brush seal wires and their mating counterface journal is simulated by testing a small tuft of wire against the outside diameter of a high speed rotating shaft. The test configuration is similar to a standard block on ring geometry. The new tester provides the capability to measure both the friction and wear of candidate wire and counterface materials under controlled loading conditions in the gram to kilogram range. A wide test condition latitude of speeds (1 to 27 m/s), temperatures (25 to 700 C), and loads (0.5 to 10 N) enables the simulation of many of the important tribological parameters found in turbine engine brush seals. This paper describes the new test rig and specimen configuration and presents initial data for candidate seal materials comparing tuft test results and wear surface morphology to field tested seal components.

  15. Trends in adsorbate induced core level shifts

    NASA Astrophysics Data System (ADS)

    Nilsson, Viktor; Van den Bossche, Maxime; Hellman, Anders; Grönbeck, Henrik

    2015-10-01

    Photoelectron core level spectroscopy is commonly used to monitor atomic and molecular adsorption on metal surfaces. As changes in the electron binding energies are convoluted measures with different origins, calculations are often used to facilitate the decoding of experimental signatures. The interpretation could in this sense benefit from knowledge on trends in surface core level shifts for different metals and adsorbates. Here, density functional theory calculations have been used to systematically evaluate core level shifts for (111) and (100) surfaces of 3d, 4d, and 5d transition metals upon CO, H, O and S adsorption. The results reveal trends and several non-intuitive cases. Moreover, the difficulties correlating core level shifts with charging and d-band shifts are underlined.

  16. Apparatus to measure chemical wear of carbon brushes

    NASA Astrophysics Data System (ADS)

    Kosky, P. G.; Peters, H. C.; Spiro, C. L.; Lamby, E. J.; McKee, D. W.

    1985-07-01

    It has been inferred for several years that the wear of a carbon brush at a sliding interface of a dc machine is influenced by chemical factors. Previously, the difficulties of isolating and measuring chemical factors in such circumstances have discouraged specific verification. An apparatus is described that hermetically seals a selected polarity brush and uses an artificial atmosphere of humidified oxygen and argon to simulate air. By monitoring the ratio of mass spectrometric peaks of CO+2 to 36Ar+, a consistent rise is observed in the amount of CO2 present. The amount of carbon thus gasified exceeded 25% of the total carbon lost.

  17. Effective Antisense Gene Regulation via Noncationic, Polyethylene Glycol Brushes.

    PubMed

    Lu, Xueguang; Jia, Fei; Tan, Xuyu; Wang, Dali; Cao, Xueyan; Zheng, Jiamin; Zhang, Ke

    2016-07-27

    Negatively charged nucleic acids are often complexed with polycationic transfection agents before delivery. Herein, we demonstrate that a noncationic, biocompatible polymer, polyethylene glycol, can be used as a transfection vector by forming a brush polymer-DNA conjugate. The brush architecture provides embedded DNA strands with enhanced nuclease stability and improved cell uptake. Because of the biologically benign nature of the polymer component, no cytotoxicity was observed. This approach has the potential to address several long-lasting challenges in oligonucleotide therapeutics. PMID:27420413

  18. A comparative study of stain removal with two electric toothbrushes and a manual brush.

    PubMed

    Moran, J M; Addy, M; Newcombe, R G

    1995-01-01

    Recent studies have suggested that a sonic electric toothbrush is more effective than a manual brush at removing extrinsic dental stain. There have been few studies of the comparative stain removal properties of different electric brushes. The study reported here was conducted to compare the efficacy of the sonic toothbrush (Sonicare) with an oscillating/rotating brush (Braun Oral-B Plaque Remover) and a conventional manual brush (Crest Complete). The study was a single-blind, randomized, cross-over design, balanced for residual effects and employing 24 subjects. Stain was enhanced over a 21-day period by twice-daily rinses with chlorhexidine and frequent intakes of tea and/or coffee. At the end of each period, tooth stain intensity and area, tongue stain intensity and area, lower lingual calculus and subjective tooth sensitivity were recorded together with preference for the brushes determined at the study's completion. Similar levels of tongue staining were recorded for the three periods, with no significant differences between the three groups. Tooth stain intensity, for most sites, was not significantly different between the three groups. For mean total stain area and for lingual and lingual interproximal sites, a significant reduction in stain was seen following use of the oscillating/rotating brush compared to the manual brush. The reductions in stain with the sonic brush were not significantly different from the manual brush. With the exception of maximum stain intensity, there were no significant differences between the oscillating/rotating and sonic brushes. Significantly less tooth sensitivity was found following use of the oscillating/rotating brush compared to both the manual and sonic brushes. All three brushes were found to be safe, but volunteer preference significantly and predominantly favored the oscillating/rotating brush. The results suggest that the oscillating/rotating brush is superior to a manual brush for stain removal.

  19. Polypeptoid Brushes by Surface-Initiated Polymerization of N-Substituted Glycine N-Carboxyanhydrides

    PubMed Central

    Schneider, Maximilian; Fetsch, Corinna; Amin, Ihsan; Jordan, Rainer; Luxenhofer, Robert

    2013-01-01

    Polypeptoid brushes were synthesized by surface-initiated polymerization of N-substituted glycine N-carboxyanhydrides (NNCAs) on self assembled amine monolayers. Using the presented grafting from approach, polypeptoid brush thicknesses of approx. 40 nm could be obtained as compared previously reported brush thicknesses of 4 nm. Moreover, hydrophilic, hydrophobic and amphiphilic polymer brushes were realized which are expected to have valuable applic-tions as non-fouling surfaces and as model or references systems for surface grafted polypeptides. PMID:23663172

  20. Brush Lettering I; Commercial and Advertising Art--Basic: 9183.05.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    The course outline has been prepared as a guide to help the students gain mastery in the proper brush techniques required for efficiency in brush lettering. The student is first given an orientation to the materials and equipment used, and the preparation of tempera paints for brush lettering. After this introduction, the student is guided through…

  1. EFFICACY OF BIOFILM DISCLOSING AGENT AND OF THREE BRUSHES IN THE CONTROL OF COMPLETE DENTURE CLEANSING

    PubMed Central

    da Silva, Cláudia Helena Lovato; Paranhos, Helena de Freitas Oliveira

    2006-01-01

    Objective: This report evaluated the efficacy of three brushes and one biofilm disclosing agent in complete denture cleansing. Methods: Twenty-seven wearers of maxillary dentures were distributed into three groups and received different brushes: Oral B40, conventional toothbrush (Oral B); Denture, denture-specific brush (Condor); Johnson & Johnson, denture-specific brush (Johnson & Johnson). The 60-day experimental period was divided into two techniques: I - brushing (brush associated with a paste - Dentu Creme, Dentco) three times a day; II - brushing and daily application of 1% neutral red on the denture internal surface. Biofilm quantification was carried out weekly and the areas with dye biofilm were obtained by means of Image Tool 2.02 software. Results: Biofilm removal was more effective during Technique II (Wilcoxon test: p=0.01) for the three groups of brushes. When the brushes were compared in Technique I, the Kruskal Wallis test indicated statistical difference between Denture X Johnson & Johnson and Denture X Oral B40, in which the Denture was more efficient. For Technique II, there was no statistical difference between brushes (p>0.05). Conclusion: The disclosed application promoted more efficacy on biofilm removal, regardless of the brush used. Denture (Condor) was more efficient than the other brushes during Technique I. PMID:19089247

  2. Structure of polymer layers adsorbed from concentrated solutions

    NASA Astrophysics Data System (ADS)

    Auvray, Loïc; Auroy, Philippe; Cruz, Margarida

    1992-06-01

    We study by neutron scattering the interfacial strucuture of poly(dimethylsiloxane) layers irreversibly adsorbed from concentrated solutions or melts. We first measure the thickness h of the layers swollen by a good solvent as a function of the chain polymerisation index N and of the polymer volume fraction in the initial solution Φ. The relation h ≈ N^{0.8}Φ^{0.3}, recently predicted from an analogy between irreversibly adsorbed layers and grafted polymer brushes, describes well our results. We can therefore deduce that there is at least one large loop of about N monomers per adsorbed chain. We also study the shape of the polymer concentration profile in the layers by measuring on two samples the polymer-solid partial structure factor, that is proportional to the Fourier transform of the profile. The model of pseudobrushes predicts a concentration decay varying with the distance of the wall z as z^{-2/5}. This power law profile accounts quantitatively for the angular variation of the polymer-solid cross structure factor but it is difficult to distinguish it without anbiguity from less singular profiles. It implies that the adsorption of PDMS onto silica is sufficiently strong and fast to quench completely the loop distribution in the initial layer. Nous étudions par diffusion de neutrons la structure interfaciale de couches de poly(diméthylsiloxane) irréversiblement adsorbées sur de la silice à partir de solutions semidiluées et de fondus. Nous mesurons d'abord l'épaisseur h des couches gonflées par un bon solvant en fonction du degré de polymérisation des chaînes N et de la fraction volumique dans la solution initiale Φ. La relation h≈ N^{0.8}Φ^{0.3} récemment prédite à partir de l'analogie entre couches irréversiblement adsorbées et brosses de polymères greffés décrit bien nos résultats. Nous en déduisons qu'il existe au moins une grande boucle d'environ N monomères par chaîne adsorbée. Nous étudions aussi la forme du profil de

  3. Supercritical fluid regeneration of adsorbents

    NASA Astrophysics Data System (ADS)

    Defilippi, R. P.; Robey, R. J.

    1983-05-01

    The results of a program to perform studies supercritical (fluid) carbon dioxide (SCF CO2) regeneration of adsorbents, using samples of industrial wastewaters from manufacturing pesticides and synthetic solution, and to estimate the economics of the specific wastewater treatment regenerations, based on test data are given. Processing costs for regenerating granular activated carbon GAC) for treating industrial wastewaters depend on stream properties and regeneration throughput.

  4. Adsorbed polyelectrolyte coatings decrease Fe(0) nanoparticle reactivity with TCE in water: conceptual model and mechanisms.

    PubMed

    Phenrat, Tanapon; Liu, Yueqiang; Tilton, Robert D; Lowry, Gregory V

    2009-03-01

    The surfaces of reactive nanoscale zerovalent iron (NZVI) particles used for in situ groundwater remediation are modified with polymers or polyelectrolytes to enhance colloidal stability and mobility in the subsurface. However, surface modification decreases NZVI reactivity. Here, the TCE dechlorination rate and reaction products are measured as a function of adsorbed polyelectrolyte mass for three commercially available polyelectrolytes used for NZVI surface modification including poly(styrene sulfonate) (PSS), carboxymethyl cellulose (CMC), and polyaspartate (PAP). The adsorbed mass, extended layer thickness, and TCE-polyelectrolyte partition coefficient are measured and used to explain the effect of adsorbed polyelectrolyte on NZVI reactivity. For all modifiers, the dechlorination rate constant decreased nonlinearly with increasing surface excess, with a maximum of a 24-fold decrease in reactivity. The TCE dechlorination pathways were not affected. Consistent with Scheutjens-Fleer theory for homopolymer adsorption, the nonlinear relationship between the dechlorination rate and the surface excess of adsorbed polyelectrolyte suggests that adsorbed polyelectrolyte decreases reactivity primarily by blocking reactive surface sites at low surface excess where they adsorb relatively flat onto the NZVI surface, and by a combination of site blocking and decreasing the aqueous TCE concentration at the NZVI surface due to partitioning of TCE to adsorbed polyelectrolytes. This explanation is also consistent with the effect of adsorbed polyelectrolyte on acetylene formation. This conceptual model should apply to other medium and high molecular weight polymeric surface modifiers on nanoparticles, and potentially to adsorbed natural organic matter.

  5. Improving Brush Polymer Infrared One-Dimensional Photonic Crystals via Linear Polymer Additives

    SciTech Connect

    Macfarlane, Robert J.; Kim, Bongkeun; Lee, Byeongdu; Weitekamp, Raymond A.; Bates, Christopher M.; Lee, Siu Fung; Chang, Alice B.; Delaney, Kris T.; Fredrickson, Glen H.; Atwater, Harry A.; Grubbs, Robert H.

    2014-12-17

    Brush block copolymers (BBCPs) enable the rapid fabrication of self-assembled one-dimensional photonic crystals with photonic band gaps that are tunable in the UV-vis-IR, where the peak wavelength of reflection scales with the molecular weight of the BBCPs. Due to the difficulty in synthesizing very large BBCPs, the fidelity of the assembled lamellar nanostructures drastically erodes as the domains become large enough to reflect IR light, severely limiting their performance as optical filters. To overcome this challenge, short linear homopolymers are used to swell the arrays to ~180% of the initial domain spacing, allowing for photonic band gaps up to~1410 nm without significant opacity in the visible, demonstrating improved ordering of the arrays. Additionally, blending BBCPs with random copolymers enables functional groups to be incorporated into the BBCP array without attaching them directly to the BBCPs. The addition of short linear polymers to the BBCP arrays thus offers a facile means of improving the self-assembly and optical properties of these materials, as well as adding a route to achieving films with greater functionality and tailorability, without the need to develop or optimize the processing conditions for each new brush polymer synthesized.

  6. Novel lubricated surface of titanium alloy based on porous structure and hydrophilic polymer brushes

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Xiong, Dangsheng; Niu, Yuxiang

    2014-10-01

    On the purpose of improving the tribological properties of titanium alloy through mimicking natural articular cartilage, porous structure was prepared on the surface of Ti6Al4V alloy by anodic oxidation method, and then hydrophilic polymer brushes were grafted onto its surface. Surface morphology of porous oxidized film was investigated by metalloscope and scanning electron microscope (SEM). The composition and structure of modified surface were characterized by Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR/ATR), and the wettability was also evaluated. Friction and wear properties of modified alloys sliding against ultra-high molecular weight polyethylene (UHMWPE) were tested by a pin-on-disc tribometer in physiological saline. The results showed that, the optimum porous structure treated by anodic oxidation formed when the voltage reached as high as 100 V. Hydrophilic monomers [Acrylic acid (AA) and 3-dimethyl-(3-(N-methacrylamido) propyl) ammonium propane sulfonate (DMMPPS)] were successfully grafted onto porous Ti6Al4V surface to form polymer brushes by UV radiation. The change of contact angle showed that wettability of modified Ti6Al4V was improved significantly. The friction coefficient of modified Ti6Al4V was much lower and more stable than untreated ones. The lowest friction coefficient was obtained when the sample was anodized at 100 V and grafted with DMMPPS, and the value was 0.132. The wear of modified samples was also obviously improved.

  7. Control of nanoparticle formation using the constrained dewetting of polymer brushes

    NASA Astrophysics Data System (ADS)

    Lee, Thomas; Hendy, Shaun C.; Neto, Chiara

    2015-03-01

    We have used coarse-grained molecular dynamics simulations to investigate the use of pinned micelles formed by the constrained dewetting of polymer brushes to act as a template for nanoparticle formation. The evaporation of a thin film containing a dissolved solute from a polymer brush was modeled to study the effect of solubility, concentration, grafting density, and evaporation rate on the nucleation and growth of nanoparticles. Control over particle nucleation could be imposed when the solution was dilute enough such that particle nucleation occurred following the onset of constrained dewetting. We predict that nanoparticles with sizes on the order of 1 nm to 10 nm could be produced from a range of organic molecules under experimentally accessable conditions. This method could allow the functionality of organic materials to be imparted onto surfaces without the need for synthetic modification of the functional molecule, and with control over particle size and aggregation, allowing for the preparation of surfaces with useful optical, pharmaceutical, or electronic properties. Now at Department of Civil and Environmental Engineering, Massachusettes Institute of Technology, Cambridge, MA.

  8. A new fate for old cells: brush cells and related elements

    PubMed Central

    Sbarbati, A; Osculati, F

    2005-01-01

    Over the past 50 years, hundreds of studies have described those cells that are characterized by a brush of rigid apical microvilli with long rootlets, and which are found in the digestive and respiratory apparatuses. These cells have been given names such as brush cells, tuft cells, fibrillovesicular cells, multivesicular cells and caveolated cells. More recently, it has been realized that all these elements may represent a single cell type, probably with a chemosensory role, even if other functions (e.g. secretory or absorptive) seem to be possible. Very recent developments have permitted a partial definition of the chemical code characterizing these elements, revealing the presence of molecules involved in chemoreceptorial cell signalling. A molecular cascade, similar to those characterizing the gustatory epithelium, seems to be present in these elements. These new data suggest that these elements can be considered solitary chemosensory cells with the presence of the apical ‘brush’ as an inconsistent feature. They seem to comprise a diffuse chemosensory system that covers large areas (probably the whole digestive and respiratory apparatuses) with analogies to chemosensory systems described in aquatic vertebrates. PMID:15817103

  9. Some metallographic results for brush bristles and brush segments of a shroud ring brush seal tested in a T-700 engine

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Griffin, Thomas A.; Bobula, George A.; Bill, Robert C.; Hull, David R.; Csavina, Kristine R.

    1994-01-01

    Post-test investigation of a T-700 engine brush seal found regions void of bristles ('yanked out'), regions of bent-over bristles near the inlet, some 'snapped' bristles near the fence, and a more uniform smeared bristle interface between the first and last axial rows of bristles. Several bristles and four brush segments were cut from the brush seal, wax mounted, polished, and analyzed. Metallographic analysis of the bristle near the rub tip showed tungsten-rich phases uniformly distributed throughout the bristle, no apparent change within 1 mu m of the interface, and possibly a small amount of titanium, which would represent a transfer from the rotor. Analysis of the bristle wear face showed nonuniform tungsten, which is indicative of material resolidification. The cut end contained oxides and internal fractures; the worn end was covered with oxide scale. Material losses due to wear and elastoplastic deformation within the shear zone and third-body lubrication effects in the contact zone are discussed.

  10. Some metallographic results for brush bristles and brush segments of a shroud ring brush seal tested in a T-700 engine

    NASA Astrophysics Data System (ADS)

    Hendricks, Robert C.; Griffin, Thomas A.; Bobula, George A.; Bill, Robert C.; Hull, David R.; Csavina, Kristine R.

    1994-07-01

    Post-test investigation of a T-700 engine brush seal found regions void of bristles ('yanked out'), regions of bent-over bristles near the inlet, some 'snapped' bristles near the fence, and a more uniform smeared bristle interface between the first and last axial rows of bristles. Several bristles and four brush segments were cut from the brush seal, wax mounted, polished, and analyzed. Metallographic analysis of the bristle near the rub tip showed tungsten-rich phases uniformly distributed throughout the bristle, no apparent change within 1 mu m of the interface, and possibly a small amount of titanium, which would represent a transfer from the rotor. Analysis of the bristle wear face showed nonuniform tungsten, which is indicative of material resolidification. The cut end contained oxides and internal fractures; the worn end was covered with oxide scale. Material losses due to wear and elastoplastic deformation within the shear zone and third-body lubrication effects in the contact zone are discussed.

  11. Charge regulation and local dielectric function in planar polyelectrolyte brushes

    SciTech Connect

    Kumar, Rajeev; Sumpter, Bobby G; Kilbey, II, S Michael

    2012-01-01

    Understanding the effect of inhomogeneity on the charge regulation and dielectric properties, and how it depends on the conformational characteristics of the macromolecules is a long-standing problem. In order to address this problem, we have developed a field-theory to study charge regulation and local dielectric function in planar polyelectrolyte brushes. The theory is used to study a polyacid brush, which is comprised of chains end-grafted at the solid-fluid interface, in equilibrium with a bulk solution containing monovalent salt ions, solvent molecules, and pH controlling acid. In particular, we focus on the effects of the concentration of added salt and pH of the bulk in determining the local charge and dielectric function. Our theoretical investigations reveal that the dipole moment of the ion-pairs formed as a result of counterion adsorption on the chain backbones play a key role in affecting the local dielectric function. For polyelectrolytes made of monomers having dipole moments lower than the solvent molecules, dielectric decrement is predicted inside the brush region. However, the formation of ion-pairs (due to adsorption of counterions coming from the dissociation of added salt) more polar than the solvent molecules is shown to increase the magnitude of the dielectric function with respect to its bulk value. Furthermore, an increase in the bulk salt concentration is shown to increase the local charge inside the brush region.

  12. Brush Seal Would Impede Flow Of Hot Gas

    NASA Technical Reports Server (NTRS)

    Carroll, Paul F.; Easter, Barry P.

    1993-01-01

    Proposed brush seal helps prevent recirculating flow of hot combustion gases from reaching bellows seal located deep in gap in wall of combustion chamber. More durable, more tolerant of irregularities, and easier to install. Seals also helpful in impeding deleterious flows of hot gases in other combustion chambers such as those of furnaces and turbomachines.

  13. AN INTERDISCIPLINARY APPROACH TO VALUING WATER FROM BRUSH CONTROL

    EPA Science Inventory

    An analytical methodology utilizing models from three disciplines is developed to assess the viability of brush control for wate yield in the Frio River Basin, TX. Ecological, hydrologic, and economic models are used to portray changes in forage production and water supply result...

  14. Adsorbed molecules in external fields: Effect of confining potential.

    PubMed

    Tyagi, Ashish; Silotia, Poonam; Maan, Anjali; Prasad, Vinod

    2016-12-01

    We study the rotational excitation of a molecule adsorbed on a surface. As is well known the interaction potential between the surface and the molecule can be modeled in number of ways, depending on the molecular structure and the geometry under which the molecule is being adsorbed by the surface. We explore the effect of change of confining potential on the excitation, which is largely controlled by the static electric fields and continuous wave laser fields. We focus on dipolar molecules and hence we restrict ourselves to the first order interaction in field-molecule interaction potential either through permanent dipole moment or/and the molecular polarizability parameter. It is shown that confining potential shapes, strength of the confinement, strongly affect the excitation. We compare our results for different confining potentials. PMID:27387127

  15. Dynamics in Adsorbed Homopolymer Layers: Entanglements and Osmotic Effects

    NASA Astrophysics Data System (ADS)

    Santore, Maria; Mubarekyan, Ervin

    2001-03-01

    This work seeks the dynamic mechanism for the exchange of homopolymer chains between a dilute solution and a layer adsorbed at the solid-liquid interface. With the model system of polyethylene oxide (PEO) adsorbed onto silica from aqueous solution, it is shown that the behavior of saturated interfaces compared to starved layers reveals an interesting trend: The characteristic self exchange time is dependent only on coverage, not molecular weight, for chains of 100K or less. Therefore, it is concluded that classical entanglements do not play a role below 100K. For all molecular weights, when the coverage of 0.2 mg/m2 is exceeded, the interfacial dynamics become slow. At lower coverages, chains lie flat in train, with no loops or tails, and no lateral interactions either. The onset of slow dynamics at higher coverages may be a result of both surface crowding and the resistance of loops and tails to new chains approaching the layer.

  16. Method And Apparatus For Regenerating Nox Adsorbers

    DOEpatents

    Driscoll, J. Joshua; Endicott, Dennis L.; Faulkner, Stephen A.; Verkiel, Maarten

    2006-03-28

    Methods and apparatuses for regenerating a NOx adsorber coupled with an exhaust of an engine. An actuator drives a throttle valve to a first position when regeneration of the NOx adsorber is desired. The first position is a position that causes the regeneration of the NOx adsorber. An actuator drives the throttle valve to a second position while regeneration of the NOx adsorber is still desired. The second position being a position that is more open than the first position and operable to regenerate a NOx adsorber.

  17. Comparison of bronchial brushing and sputum in detection of pediatric pulmonary tuberculosis.

    PubMed

    Chen, Qiao-Pei; Ren, Shi-Feng; Wang, Xin-Feng; Wang, Mao-Shui

    2016-01-27

    The retrospective study aimed to evaluate the diagnostic value of bronchial brushing and sputum using acid fast bacilli smear, mycobacterial culture and real-time PCR in detection of pediatric pulmonary tuberculosis, sensitivity and specificity of bronchial brushing and sputum examined by the three methods were calculated and compared to each other. Data showed there were no significant difference in sensitivity between bronchial brushing and matched sputum using each method. But the specificity of real-time PCR on bronchial brushing was lower than on sputum. Compared with bronchial brushing, sputum was better specimen in detection of pediatric pulmonary tuberculosis.

  18. Design optimization of a brush turbine with a cleaner/water based solution

    NASA Technical Reports Server (NTRS)

    Kim, Rhyn H.

    1995-01-01

    Recently, a turbine-brush was analyzed based on the energy conservation and the force momentum equation with an empirical relationship of the drag coefficient. An equation was derived to predict the rotational speed of the turbine-brush in terms of the blade angle, number of blades, rest of geometries of the turbine-brush and the incoming velocity. Using the observed flow conditions, drag coefficients were determined. Based on the experimental values as boundary conditions, the turbine-brush flows were numerically simulated to understand first the nature of the flows, and to extend the observed drag coefficient to a flow without holding the turbine-brush.

  19. Improving Electrical Conductivity, Thermal Stability, and Solubility of Polyaniline-Polypyrrole Nanocomposite by Doping with Anionic Spherical Polyelectrolyte Brushes

    NASA Astrophysics Data System (ADS)

    Su, Na

    2015-07-01

    The extent to which anionic spherical polyelectrolyte brushes (ASPB) as dopant improved the performance of polyaniline-polypyrrole (PANI-PPy) nanocomposite was investigated. Different characterization and analytical methods including Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD) confirmed that ASPB serving as dopant could improve the comprehensive properties of PANI-PPy nanocomposite. It was different from dopants such as SiO2, poly(sodium- p-styrenesulfonate) (PSS), and canonic spherical polyelectrolyte brushes (CSPB) which only enhanced the performance of PANI-PPy nanocomposite on one or two sides. The electrical conductivity of (PANI-PPy)/ASPB nanocomposite at room temperature was 8.3 S/cm, which was higher than that of PANI-PPy (2.1 S/cm), (PANI-PPy)/PSS (6.8 S/cm), (PANI-PPy)/SiO2 (7.2 S/cm), and (PANI-PPy)/CSPB (2.2 S/cm). Meanwhile, (PANI-PPy)/ASPB nanocomposite possessed enhanced thermal stability and good solubility. In addition, the effects of polymerization temperature, the molecular weight of grafted polyelectrolyte brushes, and storage time on electrical conductivity were discussed.

  20. Hydrologic Effects of Brush Management in Central Texas

    NASA Astrophysics Data System (ADS)

    Banta, J. R.; Slattery, R.

    2011-12-01

    Encroachment of woody vegetation into traditional savanna grassland ecosystems in central Texas has largely been attributed to land use practices of settlers, most notably overgrazing and fire suppression. Implementing brush management practices (removing the woody vegetation and allowing native grasses to reestablish in the area), could potentially change the hydrology in a watershed. The U.S. Geological Survey, in cooperation with several local, State, and Federal cooperators, studied the hydrologic effects of ashe juniper (Juniperus ashei) removal as a brush management conservation practice in the Honey Creek State Natural Area in Comal County, Tex. Two adjacent watersheds of 104 and 159 hectares were used in a paired study. Rainfall, streamflow, evapotranspiration (Bowen ratio method), and water quality data were collected in both watersheds. Using a hydrologic mass balance approach, rainfall was allocated to surface-water runoff, evapotranspiration, and groundwater recharge. Groundwater recharge was not directly measured, but estimated as the residual of the hydrologic mass balance. After hydrologic data were collected in both watersheds for 3 years, approximately 80 percent of the woody vegetation (ashe juniper) was selectively removed from the 159 hectare watershed (treatment watershed). Brush management was not implemented in the other (reference) watershed. Hydrologic data were collected in both watersheds for six years after brush management implementation. The resulting data were examined for differences in the hydrologic budget between the reference and treatment watersheds as well as between pre- and post-brush management periods to assess effects of the treatment. Preliminary results indicate there are differences in the hydrologic budget as well as water quality between the watersheds during pre- and post-treatment periods.

  1. Brushing behavior among young adolescents: does perceived severity matter

    PubMed Central

    2014-01-01

    Background Oral health is a basis for general health and well-being and affects physical and psychological aspects of the human life. The aim of this study was to determine the power of the health belief model in general and the role of perceived severity and its components in particular in predicting tooth brushing behavior among young adolescents. Methods This was a cross sectional study of a sample of female students grade four in Rasht (a metropolitan in north Iran) in 2012. A systematic random sampling method was applied to recruit students. They were asked to respond to a designed questionnaire containing items on brushing behavior based on the health belief model. In this study for the first time perceived severity and perceived barriers were divided into two parts, perceived subjective and objective severity and perceived physical and psychological barriers and were treated as independent variables. Logistic regression analysis was performed in order to identify the variables that predict the desirable behavior (brushing twice a day or more). Results In all 265 female students were entered into the study. Of these, only 17.4% reported that they were brushing at least twice a day (desirable behavior). The results obtained from the logistic regression analysis indicated that perceived objective severity (OR = 0.37, 95% CI = 0.21- 0.66, P = 0.001) and feeling less perceived psychological barriers (OR = 2.60, 95% CI = 1.50- 4.52, P = 0.001) were the significant predicting factors for brushing twice a day. Conclusion The findings suggest that perceived objective severity and perceived psychological barriers play important role in adapting a desirable health behavior among young adolescents. PMID:24397588

  2. Brush-eating device promises reforestation, wood energy aid

    SciTech Connect

    Blackman, T.

    1981-01-01

    An invention which began as a low-ground-pressure skidder developed into a machine which clears brush, thins plantations, and can harvest wood for energy. First came the notion of an extra-low-ground-pressure log skidder. A swinging chopper was added to the front to clear the skid roads. Working in manzanita brush 10 to 12 foot tall, and with stems up to 18 inches in diameter, the Shar 20 can clear one to two and a half acres an hour. The 30 will be able to clear two to five acres an hour. The big machine will have two chopper heads rotating in opposite directions to force the chopped wood into a chipper built into the machine. Chips will be blown to a van following the harvester so they can be used for hog fuel or as feedstock for methanol production. The head spins at a relatively slow 450 rpm - a safety factor. Surrounding brush catches most of the cut material, but an occasional chunk of wood does fly several yards. Companies are paying more attention to reforestation. Clearing the land will leave a mulch-like debris on the ground. This offers some shade and helps retain soil moisture. Even when brush is harvested for energy, about 10% of the material is left on the ground. California's Department of Forestry wants to start a five-year clearing cycle for the chaparral stands, ''mowing'' a million acres a year and returning every fifth year to reclear the brush. California alone has 27 million acres of brushland not suitable for timber. A brushy acre averages from 30 to 200 tons of wood at 10% moisture content. The machines are designed to run at up to 12 mph when moving.

  3. Adsorption and desorption behavior of asphaltene on polymer-brush-immobilized surfaces.

    PubMed

    Higaki, Yuji; Hatae, Kaoru; Ishikawa, Tatsuya; Takanohashi, Toshimasa; Hayashi, Jun-ichiro; Takahara, Atsushi

    2014-11-26

    The adsorption behavior of a model compound for surface-active component of asphaltenes, N-(1-hexylheptyl)-N'-(12-carboxylicdodecyl) perylene-3,4,9,10-tetracarboxylic bisimide (C5Pe), and detachment behavior of asphaltene deposit films for high-density polymer brushes were investigated. Zwitterionic poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate (PMAPS) brushes and hydrophobic poly(n-hexyl methacrylate) (PHMA) brushes exhibit less C5Pe adsorption than poly(methyl methacrylate) (PMMA). The asphaltene deposit films on the PHMA brush detached in a model oil (toluene/n-heptane=1/4 (v/v)), and the asphaltene films on the PMAPS brush detached in water. The antifouling character was explained by the interface free energy for the polymer-brush/asphaltenes (γSA) and polymer-brush/toluene (γSO). PMID:25370500

  4. Evaluation of multi-brush anode systems in microbial fuel cells.

    PubMed

    Lanas, Vanessa; Logan, Bruce E

    2013-11-01

    The packing density of anodes in microbial fuel cells (MFCs) was examined here using four different graphite fiber brush anode configurations. The impact of anodes on performance was studied in terms of carbon fiber length (brush diameter), the number of brushes connected in parallel, and the wire current collector gage. MFCs with different numbers of brushes (one, three or six) set perpendicular to the cathode all produced similar power densities (1200 ± 40 mW/m(2)) and coulombic efficiencies (60% ± 5%). Reducing the number of brushes by either disconnecting or removing them reduced power, demonstrating the importance of anode projected area covering the cathode, and therefore the need to match electrode projected areas to maintain high performance. Multi-brush reactors had the same COD removal as single-brush systems (>90%). The use of smaller Ti wire gages did not affect power generation, which will enable the use of less metal, reducing material costs. PMID:24063821

  5. Theoretical speed and current density limits for different types of electrical brushes

    NASA Astrophysics Data System (ADS)

    Kuhlmann-Wilsdorf, D.

    1984-03-01

    Theoretical performance limits based on the criterion of flash temperature are investigated for monolithic Ag-C brushes, Cu-on-Cu brushes with elastic contact spots, and 'QM' brushes (Quantum Mechanical brushes with ultrathin metal fibers), in which ordinary current conduction is significantly supplemented by electron tunneling peripherally about the contact spots. Equations are developed for the contact spot radii and heat input rates for frictional and electrical heating at the contact spots. Typical data for the flash temperatures are calculated for the high-speed approximation for plastic and elastic contact spots. The low-speed approximation is used for QM brushes. It is concluded that metal fiber and/or QM brushes may represent the best solution to the brush problem for electromagnetic launching.

  6. Adsorption and desorption behavior of asphaltene on polymer-brush-immobilized surfaces.

    PubMed

    Higaki, Yuji; Hatae, Kaoru; Ishikawa, Tatsuya; Takanohashi, Toshimasa; Hayashi, Jun-ichiro; Takahara, Atsushi

    2014-11-26

    The adsorption behavior of a model compound for surface-active component of asphaltenes, N-(1-hexylheptyl)-N'-(12-carboxylicdodecyl) perylene-3,4,9,10-tetracarboxylic bisimide (C5Pe), and detachment behavior of asphaltene deposit films for high-density polymer brushes were investigated. Zwitterionic poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate (PMAPS) brushes and hydrophobic poly(n-hexyl methacrylate) (PHMA) brushes exhibit less C5Pe adsorption than poly(methyl methacrylate) (PMMA). The asphaltene deposit films on the PHMA brush detached in a model oil (toluene/n-heptane=1/4 (v/v)), and the asphaltene films on the PMAPS brush detached in water. The antifouling character was explained by the interface free energy for the polymer-brush/asphaltenes (γSA) and polymer-brush/toluene (γSO).

  7. Structural characterization of adsorbed helical and beta-sheet peptides

    NASA Astrophysics Data System (ADS)

    Samuel, Newton Thangadurai

    Adsorbed peptides on surfaces have potential applications in the fields of biomaterials, tissue engineering, peptide microarrays and nanobiotechnology. The surface region, the "biomolecular interface" between a material and the biological environment, plays a crucial role in these applications. As a result, characterization of adsorbed peptide structure, especially with respect to identity, concentration, spatial distribution, conformation and orientation, is important. The present research employs NEXAFS (near-edge X-ray absorption fine structure spectroscopy) and SFG (sum frequency generation spectroscopy) to provide information about the adsorbed peptide structure. Soft X-ray NEXAFS is a synchrotron-based technique which typically utilizes polarized X-rays to interrogate surfaces under ultra-high vacuum conditions. SFG is a non-linear optical technique which utilizes a combination of a fixed visible and a tunable infrared laser beams to generate a surface-vibrational spectrum of surface species. SFG has the added advantage of being able to directly analyze the surface-structure at the solid-liquid interface. The main goals of the present research were twofold: characterize the structure of adsorbed peptides (1) ex situ using soft X-ray NEXAFS, and (2) in situ using non-linear laser spectroscopy (SFG). Achieving the former goal involved first developing a comprehensive characterization of the carbon, nitrogen and oxygen k-edge NEXAFS spectra for amino acids, and then using a series of helical and beta-sheet peptides to demonstrate the sensitivity of polarization-dependent NEXAFS to secondary structure of adsorbed peptides. Characterizing the structure of adsorbed peptides in situ using SFG involved developing a model system to probe the solid-liquid interface in situ; demonstrating the ability to probe the molecular interactions and adsorbed secondary structure; following the time-dependent ordering of the adsorbed peptides; and establishing the ability to obtain

  8. Evaluation of gaseous fluorocarbon adsorption isotherms on porous adsorbents under high pressure

    SciTech Connect

    Kaliappan, S.; Furuya, E.G.; Noll, K.E.; Chang, H.T.; Wang, H.C.

    1996-11-01

    In this study data have been collected to aid in the design of a control system that will remove fluorocarbons by adsorbing onto porous adsorbents. A bench scale experimental adsorption system had been designed using high accuracy MKS pressure transducers of 10,000 torr (two nos.) and a 100 torr connected to digital readout units. Tetrafluoromethane (CF{sub 4}) one of the fluorinated carbon family has been selected to evaluate the adsorption characteristics on porous adsorbents. The CF{sub 4} was charged to a sample reservoir in the test system at 200 psig pressure and at 22 C was allowed into an adsorption chamber at small increment of pressure rise. The pressure drop, using a Valydine PS 309 differential pressure gauge from the sample reservoir and the pressure buildup in the adsorption chamber were measured and the amount of CF{sub 4} adsorbed onto the adsorbents was calculated using ideal gas law. Various adsorbents, molecular sieve 13X, Silicagel (14 x 20), Beads Activated Carbon, Granular Activated Carbons PCB 6 x 16, BPL 4 x 10, F300, and F400 had been studied. It has been found that GAC-PCB 6 x 16 has the highest adsorbing capacity of 0.51 gm/gm at the conditions established. GAC-F300 had the second highest adsorbing capacity of 0.413 gm/gm, among all the adsorbents tested. The isotherms were analyzed using several equations employing both two parameters and three parameters. The relationship between the constants and physical properties of adsorbent solids and adsorbate molecules is discussed. The result of this study will be utilized to design a pressure swing fluorocarbon adsorption system that can be economically (using recycle of the collected fluorocarbons) applied to fluorocarbon removal in the electronic industry.

  9. Electrophoresis and dielectric dispersion of spherical polyelectrolyte brushes.

    PubMed

    Ahualli, Silvia; Ballauff, Matthias; Arroyo, Francisco J; Delgado, Ángel V; Jiménez, María L

    2012-11-27

    Spherical polyelectrolyte brushes (SPBs) consist of a rigid core on which polyelectrolyte chains are grafted in such a way that in certain conditions (low ionic strength and high charge of the chains) the polymer chains extend radially toward the liquid medium. Because of the hairy-like structure of the polymer brushes, the typical soft-particle approach used for explaining the behavior of polyelectrolyte-coated particles must be modified, using the assumptions that the density of charged segments in the polymer chains decreases with the squared distance to the rigid core surface and that the same happens to the friction between the brushes and the surrounding fluid. Interest in clarifying the electrokinetics of these systems is not just academic. It has recently been found experimentally (Jiménez et al., Soft Matter 2011, 7, 3758-3762) that the response of concentrated suspensions of spherical polyelectrolyte brushes in the presence of alternating electric fields shows a number of unexpected features. Both dielectric and dynamic electrophoretic mobility spectra (respectively, dependences of the electric permittivity and the AC electrophoretic mobility on the frequency of the applied field) showed very special aspects, with giant values of the mobility and an unusually strong dielectric relaxation in the kHz region. In the present paper we give a full account of the electrodynamics of such systems, based on a cell model for describing the hydrodynamic and electrical interactions between the particles. It is found that the low-frequency dynamic mobility of SPBs is much higher than that of rigid particles of comparable size and charge, making any interpretation based on zeta potential estimations of very limited applicability. The very characteristic feature of SPBs in concentrated suspensions, namely, the enhanced alpha relaxation, can be explained by considering an adequate description of the field-induced perturbations in the counterion and co-ion concentrations

  10. Liquid Crystalline Block Copolymers with Brush Type Architecture: Toward Functional Membranes by Magnetic Field Alignment

    NASA Astrophysics Data System (ADS)

    Choo, Youngwoo; Gopinadhan, Manesh; Mahajan, Lalit; Kasi, Rajeswari; Osuji, Chinedum

    2015-03-01

    We introduce a novel liquid crystalline block copolymer with brush type architecture for membrane applications by magnetic field directed self-assembly. Ring-opening metathesis of n-alkyloxy cyanobiphenyl and polylactide (PLA) functionalized norbornene monomers provides efficient polymerization yielding low polydispersity block copolymers. The molecular weight of the PLA side chains, spacer length of the cyanobiphenyl mesogens are systematically varied to form well-ordered BCP morphologies at varying volume fractions. Interestingly, the system features morphology dependent anchoring condition where mesogens adopt planar anchoring on cylindrical interface while homeotropic anchoring was preferred on a planar block interface. The minority PLA domains from highly aligned materials can be readily degraded by hydrolysis to produce vertically aligned nanoporous polymer films which exhibit reversible thermal switching behavior. The polymers introduced here provide a versatile platform for scalable fabrication of aligned membranes and further functional materials based on such templates. This work was supported by NSF(CCMI-1246804).

  11. Electronic Transport of the Adsorbed Trigonal Graphene Flake: A First Principles Calculation

    NASA Astrophysics Data System (ADS)

    Tan, Xun-Qiong

    2014-12-01

    Based on the non-equilibrium Green's function method combined with the density functional theory, we investigate the transport properties of a zigzag trigonal graphene flake (zTGF) adsorbed by a single atom (F or H) or a single group (OH or CH3) at the central site and connected to two symmetric Au electrodes by Au-S bonds. The results show that the OH adsorption can enhance the conductance, followed by the negative differential resistance effects, while the conductance for the zTGF adsorbed by H and CH3 is lowered obviously, and rectifying characteristics can be observed for the H-adsorbed system. The adsorbing action alters the molecular level position and the spatial distribution of the molecular orbital, leading to different transport properties.

  12. Competition between Displacement and Dissociation of a Strong Acid Compared to a Weak Acid Adsorbed on Silica Particle Surfaces: The Role of Adsorbed Water.

    PubMed

    Fang, Yuan; Tang, Mingjin; Grassian, Vicki H

    2016-06-16

    The adsorption of nitric (HNO3) and formic (HCOOH) acids on silica particle surfaces and the effect of adsorbed water have been investigated at 296 K using transmission FTIR spectroscopy. Under dry conditions, both nitric and formic acids adsorb reversibly on silica. Additionally, the FTIR spectra show that both of these molecules remain in the protonated form. At elevated relative humidities (RH), adsorbed water competes both for surface adsorption sites with these acids as well as promotes their dissociation to hydronium ions and the corresponding anions. Compared to HNO3, the extent of dissociation is much smaller for HCOOH, very likely because it is a weaker acid. This study provides valuable insights into the interaction of HNO3 and HCOOH with silica surface on the molecular level and further reveals the complex roles of surface-adsorbed water in atmospheric heterogeneous chemistry of mineral dust particles-many of these containing silica.

  13. Competition between Displacement and Dissociation of a Strong Acid Compared to a Weak Acid Adsorbed on Silica Particle Surfaces: The Role of Adsorbed Water.

    PubMed

    Fang, Yuan; Tang, Mingjin; Grassian, Vicki H

    2016-06-16

    The adsorption of nitric (HNO3) and formic (HCOOH) acids on silica particle surfaces and the effect of adsorbed water have been investigated at 296 K using transmission FTIR spectroscopy. Under dry conditions, both nitric and formic acids adsorb reversibly on silica. Additionally, the FTIR spectra show that both of these molecules remain in the protonated form. At elevated relative humidities (RH), adsorbed water competes both for surface adsorption sites with these acids as well as promotes their dissociation to hydronium ions and the corresponding anions. Compared to HNO3, the extent of dissociation is much smaller for HCOOH, very likely because it is a weaker acid. This study provides valuable insights into the interaction of HNO3 and HCOOH with silica surface on the molecular level and further reveals the complex roles of surface-adsorbed water in atmospheric heterogeneous chemistry of mineral dust particles-many of these containing silica. PMID:27220375

  14. UV-induced protonation of molecules adsorbed on ice surfaces at low temperature.

    PubMed

    Moon, Eui-Seong; Lee, Chang-Woo; Kim, Joon-Ki; Park, Seong-Chan; Kang, Heon

    2008-05-21

    UV irradiation of ice films adsorbed with methylamine molecules induces protonation of the adsorbate molecules at low temperature (50-130 K). The observation indicates that long-lived protonic defects are created in the ice film by UV light, and they transfer protons to the adsorbate molecules via tunneling mechanism at low temperature. The methylammonium ion formed by proton transfer remains to be stable at the ice surface. It is suggested that this solid-phase protonation might play a significant role in the production of molecular ions in interstellar clouds.

  15. Ligand conjugation to bimodal poly(ethylene glycol) brush layers on microbubbles.

    PubMed

    Chen, Cherry C; Borden, Mark A

    2010-08-17

    Using microbubbles as model systems, we examined molecular diffusion and binding to colloidal surfaces in bimodal poly(ethylene glycol) (PEG) brush layers. A microbubble is a gaseous colloidal particle with a diameter of less than 10 mum, of which the surface comprises amphiphilic phospholipids self-assembled to form a lipid monolayer shell. Due to the compressible gas core, microbubbles provide a sensitive acoustic response and are currently used as ultrasound contrast agents. Similar to the design of long circulating liposomes, PEG chains are typically incorporated into the shell of microbubbles to form a steric barrier against coalescence and adsorption of macromolecules to the microbubble surface. We introduced a buried-ligand architecture (BLA) design where the microbubble surface was coated with a bimodal PEG brush. After microbubbles were generated, fluorescent ligands with different molecular weights were conjugated to the tethered functional groups on the shorter PEG chains, while the longer PEG chains served as a shield to protect these ligands from exposure to the surrounding environment. BLA microbubbles reduced the binding of macromolecules (>10 kDa) to the tethers due to the steric hindrance of the PEG overbrush while allowing the uninhibited attachment of small molecules (<1 kDa). Roughly 40% less fluorescein-conjugated streptavidin (SA-FITC) bound to BLA microbubbles compared to exposed-ligand architecture (ELA) microbubbles. The binding of SA-FITC to BLA microbubbles suggested a possible phase separation between the lipid species on the surface leading to populations of revealed and concealed ligands. Ligand conjugation kinetics was independent of microbubble size, regardless of ligand size or microbubble architecture. We observed, for the first time, streptavidin-induced surface structure formation for ELA microbubbles and proposed that this phenomenon may be correlated to flow cytometry scattering measurements. We therefore demonstrated the

  16. Adsorption, Lubrication, and Wear of Lubricin on Model Surfaces: Polymer Brush-Like Behavior of a Glycoprotein

    PubMed Central

    Zappone, Bruno; Ruths, Marina; Greene, George W.; Jay, Gregory D.; Israelachvili, Jacob N.

    2007-01-01

    Using a surface force apparatus, we have measured the normal and friction forces between layers of the human glycoprotein lubricin, the major boundary lubricant in articular joints, adsorbed from buffered saline solution on various hydrophilic and hydrophobic surfaces: i), negatively charged mica, ii), positively charged poly-lysine and aminothiol, and iii), hydrophobic alkanethiol monolayers. On all these surfaces lubricin forms dense adsorbed layers of thickness 60–100 nm. The normal force between two surfaces is always repulsive and resembles the steric entropic force measured between layers of end-grafted polymer brushes. This is the microscopic mechanism behind the antiadhesive properties showed by lubricin in clinical tests. For pressures up to ∼6 atm, lubricin lubricates hydrophilic surfaces, in particular negatively charged mica (friction coefficient μ = 0.02–0.04), much better than hydrophobic surfaces (μ > 0.3). At higher pressures, the friction coefficient is higher (μ > 0.2) for all surfaces considered and the lubricin layers rearrange under shear. However, the glycoprotein still protects the underlying substrate from damage up to much higher pressures. These results support recent suggestions that boundary lubrication and wear protection in articular joints are due to the presence of a biological polyelectrolyte on the cartilage surfaces. PMID:17142292

  17. Stability against brushing abrasion and the erosion-protective effect of different fluoride compounds.

    PubMed

    Wiegand, A; Schneider, S; Sener, B; Roos, M; Attin, T

    2014-01-01

    This study aimed to analyse the impact of brushing on the protective effect of different fluoride solutions on enamel and dentin erosion. Bovine enamel and dentin specimens were rinsed once with TiF4, AmF, SnF2 (0.5 M F, 2 min) or water (control). Specimens were either left unbrushed or brushed with 10, 20, 50, 100 or 500 brushing strokes in an automatic brushing machine (2 N, non-fluoridated toothpaste slurry). Ten specimens per group were eroded with hydrochloric acid (HCl) (pH 2.3) for 60 s, and calcium release into the acid was determined by atomic absorption spectroscopy. Additionally, enamel and dentin surfaces were analysed by X-ray energy-dispersive spectroscopy (EDS) (n = 6/group) and scanning electron microscopy (SEM) (n = 2/group) before brushing and after 500 brushing strokes. Statistical analysis (p < 0.05) was performed by three- and one-way ANOVA (calcium release) or repeated measures ANOVA (EDS). TiF4, AmF and SnF2 reduced the erosive calcium loss in unbrushed specimens to 58-67% (enamel) and 23-31% (dentin) of control. Calcium release increased with increasing brushing strokes prior to erosion and amounted to 70-88% (enamel) and 45-78% (dentin) of control after 500 brushing strokes. Brushing reduced the surface concentration of fluoride (AmF), tin (SnF2) and titanium (TiF4). SEM revealed that surface precipitates were affected by long-term brushing. Brushing reduced the protective potential of TiF4, AmF and SnF2 solutions. However, considering a small number of brushing strokes, the protective effect of fluoride solutions is only slightly affected by brushing abrasion.

  18. A novel fiber-based adsorbent technology

    SciTech Connect

    Reynolds, T.A.

    1997-10-01

    In this Phase I Small Business Innovation Research program, Chemica Technologies, Inc. is developing an economical, robust, fiber-based adsorbent technology for removal of heavy metals from contaminated water. The key innovation is the development of regenerable adsorbent fibers and adsorbent fiber cloths that have high capacity and selectivity for heavy metals and are chemically robust. The process has the potential for widespread use at DOE facilities, mining operations, and the chemical process industry.

  19. Brush border intestinal enzymes after multiple daily fractionation

    SciTech Connect

    Becciolini, A.; Giache, V.; Balzi, M.; Morrone, A.

    1987-03-01

    The modifications in brush border enzyme activity of the epithelial cell of the small intestine were studied after multiple daily fractionation (MDF) of 3 Gy X and 3 Gy X 2 X 2 (12 h split). Disaccharase and dipeptidase activities changed in the same way after irradiation. The results show that both total doses caused the three known phases of increase, decrease, and a return to normal. With MDF, activity at the end of irradiation was similar to or greater than that of controls and remained higher longer than a single dose of 8 Gy. However, the return to normal occurred sooner than after a single dose of 8 Gy. After 11 days, circadian oscillations of brush border enzyme activity appeared similar to those of controls in many segments of the intestine, reaching the highest activity during the night and the lowest in the afternoon.

  20. Brushed Target on Rock 'Champagne' in Gusev Crater

    NASA Technical Reports Server (NTRS)

    2005-01-01

    NASA's Mars Exploration Rover Spirit took this microscopic image of a target called 'Bubbles' on a rock called 'Champagne' after using its rock abrasion tool to brush away a coating of dust. The circular brushed area is about 5 centimeters (2 inches) across. This rock is different from rocks out on the plains of Gusev Crater but is similar to other rocks in this area of the 'Columbia Hills' in that it has higher levels of phosphorus. Plagioclase, a mineral commonly found in igneous rocks, is also present in these rocks, according to analysis with the minature thermal emission spectrometer. By using the alpha particle X-ray spectrometer to collect data over multiple martian days, or sols, scientists are also beginning to get measurements of trace elements in these rocks. Spirit took the images that are combined into this mosaic on sol 354 (Dec. 30, 2004).

  1. Electrocatalysis of CO2 Reduction in Brush Polymer Ion Gels.

    PubMed

    McNicholas, Brendon J; Blakemore, James D; Chang, Alice B; Bates, Christopher M; Kramer, Wesley W; Grubbs, Robert H; Gray, Harry B

    2016-09-01

    The electrochemical characterization of brush polymer ion gels containing embedded small-molecule redox-active species is reported. Gels comprising PS-PEO-PS triblock brush polymer, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm-TFSI), and some combination of ferrocene (Fc), cobaltocenium (CoCp2(+)), and Re(bpy)(CO)3Cl (1) exhibit diffusion-controlled redox processes with diffusion coefficients approximately one-fifth of those observed in neat BMIm-TFSI. Notably, 1 dissolves homogeneously in the interpenetrating matrix domain of the ion gel and displays electrocatalytic CO2 reduction to CO in the gel. The catalytic wave exhibits a positive shift versus Fc(+/0) compared with analogous nonaqueous solvents with a reduction potential 450 mV positive of onset and 90% Faradaic efficiency for CO production. These materials provide a promising and alternative approach to immobilized electrocatalysis, creating numerous opportunities for application in solid-state devices.

  2. Oxalate transport by anion exchange across rabbit ileal brush border.

    PubMed Central

    Knickelbein, R G; Aronson, P S; Dobbins, J W

    1986-01-01

    This study demonstrates the presence of oxalate transporters on the brush border membrane of rabbit ileum. We found that an inside alkaline (pH = 8.5 inside, 6.5 outside) pH gradient stimulated [14C]oxalate uptake 10-fold at 1 min with a fourfold accumulation above equilibrated uptake at 5 min. 1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonate (disodium salt; DIDS) profoundly inhibited the pH-gradient stimulated oxalate uptake. Using an inwardly directed K+ gradient and valinomycin, we found no evidence for potential sensitive oxalate uptake. In contrast to Cl:HCO3 exchange, HCO3 did not stimulate oxalate uptake more than was seen with a pH gradient in the absence of HCO3. An outwardly directed Cl gradient (50 mM inside, 5 mM outside) stimulated oxalate uptake 10-fold at 1 min with a fivefold accumulation above equilibrated uptake. Cl-stimulated oxalate uptake was largely inhibited by DIDS. Addition of K+ and nigericin only slightly decreased the Cl gradient-stimulated oxalate uptake, which indicates that this stimulation was not primarily due to the Cl gradient generating an inside alkaline pH gradient via Cl:OH exchange. Further, an outwardly directed oxalate gradient stimulated 36Cl uptake. These results suggested that both oxalate:OH and oxalate:Cl exchange occur on the brush border membrane. To determine if one or both of these exchanges were on contaminating basolateral membrane, the vesicle preparation was further fractionated into a brush border and basolateral component using sucrose density gradient centrifugation. Both exchangers localized to the brush border component. A number of organic anions were examined (outwardly directed gradient) to determine if they could stimulate oxalate and Cl uptake. Only formate and oxaloacetate were found to stimulate oxalate and Cl uptake. An inwardly directed Na gradient only slightly stimulated oxalate uptake, which was inhibited by DIDS. PMID:3003149

  3. Electrochemical redox responsive polymeric micelles formed from amphiphilic supramolecular brushes.

    PubMed

    Feng, Anchao; Yan, Qiang; Zhang, Huijuan; Peng, Liao; Yuan, Jinying

    2014-05-11

    The end-decorated homopolymer poly(ε-caprolactone)-ferrocene threaded onto a β-cyclodextrin-functionalized main-chain polymer can form a class of amphiphilic noncovalent graft copolymers based on the host-guest interactions of the terminal groups on the side chains. These new supramolecular polymer brushes can further self-assemble into micellar aggregates that exhibit reversible assembly and disassembly behavior under an electrochemical redox trigger, which opens up a new route to building dynamic block copolymer topologies.

  4. Taurine transport in renal brush-border-membrane vesicles.

    PubMed Central

    Rozen, R; Tenenhouse, H S; Scriver, C R

    1979-01-01

    Taurine transport in isolated brush-border-membrane vesicles from rat kidney is concentrative and it is driven by the Na+ gradient and transmembrane potential difference; binding is not a significant component of net uptake. The Na+-dependent component of net uptake is saturable with an apparent Km of 17 microM. The taurine-transport mechanism is selective for beta-amino compounds. PMID:486101

  5. Quasiparticle excitations of adsorbates on doped graphene

    NASA Astrophysics Data System (ADS)

    Lischner, Johannes; Wickenburg, Sebastian; Wong, Dillon; Karrasch, Christoph; Wang, Yang; Lu, Jiong; Omrani, Arash A.; Brar, Victor; Tsai, Hsin-Zon; Wu, Qiong; Corsetti, Fabiano; Mostofi, Arash; Kawakami, Roland K.; Moore, Joel; Zettl, Alex; Louie, Steven G.; Crommie, Mike

    Adsorbed atoms and molecules can modify the electronic structure of graphene, but in turn it is also possible to control the properties of adsorbates via the graphene substrate. In my talk, I will discuss the electronic structure of F4-TCNQ molecules on doped graphene and present a first-principles based theory of quasiparticle excitations that captures the interplay of doping-dependent image charge interactions between substrate and adsorbate and electron-electron interaction effects on the molecule. The resulting doping-dependent quasiparticle energies will be compared to experimental scanning tunnelling spectra. Finally, I will also discuss the effects of charged adsorbates on the electronic structure of doped graphene.

  6. Distribution of metal and adsorbed guest species in zeolites

    SciTech Connect

    Chmelka, B.F.

    1989-12-01

    Because of their high internal surface areas and molecular-size cavity dimensions, zeolites are used widely as catalysts, shape- selective supports, or adsorbents in a variety of important chemical processes. For metal-catalyzed reactions, active metal species must be dispersed to sites within the zeolite pores that are accessible to diffusing reactant molecules. The distribution of the metal, together with transport and adsorption of reactant molecules in zeolite powders, are crucial to ultimate catalyst performance. The nature of the metal or adsorbed guest distribution is known, however, to be dramatically dependent upon preparatory conditions. Our objective is to understand, at the molecular level, how preparatory treatments influence the distribution of guest species in zeolites, in order that macroscopic adsorption and reaction properties of these materials may be better understood. The sensitivity of xenon to its adsorption environment makes {sup 129}Xe NMR spectroscopy an important diagnostic probe of metal clustering and adsorbate distribution processes in zeolites. The utility of {sup 129}Xe NMR depends on the mobility of the xenon atoms within the zeolite-guest system, together with the length scale of the sample heterogeneity being studied. In large pore zeolites containing dispersed guest species, such as Pt--NaY, {sup 129}Xe NMR is insensitive to fine structural details at room temperature.

  7. Ligand-Driven Phase Separation in Binary Particle Brush Materials

    NASA Astrophysics Data System (ADS)

    Bockstaller, Michael; Schmitt, Michael; Zhang, Jianan; Yan, Jiajun; Matyjaszewski, Krzysztof

    The tethering of polymer chains to the surface of nanoparticles (to form so-called `particle brush materials') has emerged as an effective means to enable the bottom-up assembly of one-component hybrid materials with controlled microstructure and improved mechanical stability as well as novel optical or acoustic properties. The polymer-like interactions and response of these particle-brush materials suggest intriguing new opportunities to control structure formation in multicomponent particle mixtures. This contribution will demonstrate that polymer-ligand interactions can drive phase separation processes in mixed particle systems that share analogies to those of regular binary polymer blends. The role of particle size, density and degree of polymerization of tethered chains as well as the interaction parameter between the distinct tethered chains on the mechanism and kinetics of phase separation processes in mixed particle brush systems will be discussed. Ligand-driven phase separation will be shown to enable the efficient fabrication of monochromatic domain structured in mixed quantum dot systems that might find application in next generation quantum dot-enabled LEDs. Support by the National Science Foundation (via Grant DMR-1410845) is gratefully acknowledged.

  8. Interpretation of charge transfer measurements of brush discharges

    NASA Astrophysics Data System (ADS)

    Chowdhury, Kanchan; von Pidoll, Ulrich; Moeckel, Dieter; Langer, Tim; Beyer, Michael

    2011-06-01

    In the present work, experimental results on the measurement of the total charge on a charged insulating sheet before and after a provoked brush discharge, their difference "C", the induced charge "A" when approaching an earthed microprocessor operated hand-Coulombmeter, and the transferred charge "B" at the instance of the discharge are presented. "B" is identical with the value measured by the hand-Coulombmeter within the expected measurement uncertainty. Due to observed corona losses and multiple brush discharges independent of each other, "B" correlates better with the incendivity than "C". The quotient B/C was closer to 1 than calculated in the literature but shows all predicted trends. The results obtained can be used for correct estimation of the incendivity of brush discharges between 10 nC and 90 nC. There is no need to change the existing threshold limits of 60 nC, 30 nC and 10 nC for the explosion groups IIA, IIB and IIC hitherto used in standards for zone 1.

  9. Hierarchical structure formation of cylindrical brush polymer-surfactant complexes.

    PubMed

    Cong, Yang; Gunari, Nikhil; Zhang, Bin; Janshoff, Andreas; Schmidt, Manfred

    2009-06-01

    The complex formation of cylindrical brush polymers with poly(l-lysine) side chains (PLL) and sodium dodecyl sulfate (SDS) can induce a helical conformation of the cylindrical brush polymer in aqueous solution (Gunari, N.; Cong, Y.; Zhang, B.; Fischer, K.; Janshoff, A.; Schmidt, M. Macromol. Rapid Commun. 2008, 29, 821-825). Herein, we have systematically investigated the influence of surfactant, salt, and pH on the supramolecular structure formation. The cylindrical brush polymers and their complexes with surfactants were directly visualized by atomic force microscopy in air and in aqueous solution. The alkyl chain length (measured by the carbon number, n) of the surfactant plays a key role. While helical structures were formed with n=10, 11, and 12, no helices were observed with n<10 and n>13. Addition of salt destroys the helical structures as do pH conditions below 4 and above 6, most probably because the polymer-surfactant complexes start to disintegrate. Circular dichroism was utilized to monitor the PLL side chain conformation and clearly revealed that beta-sheet formation of the side chains induces the helical conformation of the atactic main chain. PMID:19326944

  10. Structural analysis of paintings based on brush strokes

    NASA Astrophysics Data System (ADS)

    Sablatnig, Robert; Kammerer, Paul; Zolda, Ernestine

    1998-05-01

    The origin of works of art can often not be attributed to a certain artist. Likewise it is difficult to say whether paintings or drawings are originals or forgeries. In various fields of art new technical methods are used to examine the age, the state of preservation and the origin of the materials used. For the examination of paintings, radiological methods like X-ray and infra-red diagnosis, digital radiography, computer-tomography, etc. and color analyzes are employed to authenticate art. But all these methods do not relate certain characteristics in art work to a specific artist -- the artist's personal style. In order to study this personal style of a painter, experts in art history and image processing try to examine the 'structural signature' based on brush strokes within paintings, in particular in portrait miniatures. A computer-aided classification and recognition system for portrait miniatures is developed, which enables a semi- automatic classification and forgery detection based on content, color, and brush strokes. A hierarchically structured classification scheme is introduced which separates the classification into three different levels of information: color, shape of region, and structure of brush strokes.

  11. Reduced Water Density in a Poly(ethylene oxide) Brush

    SciTech Connect

    Lee, Hoyoung; Kim, Dae Hwan; Park, Hae-Woong; Mahynski, Nathan A.; Kim, Kyungil; Meron, Mati; Lin, Binhua; Won, You-Yeon

    2012-09-05

    A model poly(ethylene oxide) (PEO) brush system, prepared by spreading a poly(ethylene oxide)-poly(n-butyl acrylate) (PEO-PnBA) amphiphilic diblock copolymer onto an air-water interface, was investigated under various grafting density conditions by using the X-ray reflectivity (XR) technique. The overall electron density profiles of the PEO-PnBA monolayer in the direction normal to the air-water interface were determined from the XR data. From this analysis, it was found that inside of the PEO brush, the water density is significantly lower than that of bulk water, in particular, in the region close to the PnBA-water interface. Separate XR measurements with a PnBA homopolymer monolayer confirm that the reduced water density within the PEO-PnBA monolayer is not due to unfavorable contacts between the PnBA surface and water. The above result, therefore, lends support to the notion that PEO chains provide a hydrophobic environment for the surrounding water molecules when they exist as polymer brush chains.

  12. A Nanosecond Pulsed Plasma Brush for Surface Decontamination

    NASA Astrophysics Data System (ADS)

    Neuber, Johanna; Malik, Muhammad; Song, Shutong; Jiang, Chunqi

    2015-11-01

    This work optimizes a non-thermal, atmospheric pressure plasma brush for surface decontamination. The generated plasma plumes with a maximum length of 2 cm are arranged in a 5 cm long, brush-like array. The plasma was generated in ambient air with <= 10 kV, 200 ns pulses at a repetition rate of 1.5 kHz. The energy per pulse and average power are in the range of 1-3 mJ and 0.5-1.5 W, respectively. Helium containing varying concentrations of water vapor was evaluated as the carrier gas and was fed into the plasma chamber at a rate varying between 1 to 7 SLPM. Optimization of the cold plasma brush for surface decontamination was tested in a study of the plasma inactivation of two common pathogens, Staphylococcus aureus and Acinetobacter baumannii. Laminate surfaces inoculated with over-night cultured bacteria were subject to the plasma treatment for varying water concentrations in He, flow rates and discharge voltages. It was found that increasing the water content of the feed gas greatly enhanced the bactericidal effect. Emission spectroscopy was performed to identify the reactive plasma species that contribute to this variation. Additional affiliation: Frank Reidy Research Center for Bioelectrics

  13. The uranium from seawater program at PNNL: Overview of marine testing, adsorbent characterization, adsorbent durability, adsorbent toxicity, and deployment studies

    DOE PAGES

    Gill, Gary A.; Kuo, Li -Jung; Janke, Christopher James; Park, Jiyeon; Jeters, Robert T.; Bonheyo, George T.; Pan, Horng -Bin; Wai, Chien; Khangaonkar, Tarang P.; Bianucci, Laura; et al

    2016-02-07

    The Pacific Northwest National Laboratory's (PNNL) Marine Science Laboratory (MSL) located along the coast of Washington State is evaluating the performance of uranium adsorption materials being developed for seawater extraction under realistic marine conditions with natural seawater. Two types of exposure systems were employed in this program: flow-through columns for testing of fixed beds of individual fibers and pellets and a recirculating water flume for testing of braided adsorbent material. Testing consists of measurements of the adsorption of uranium and other elements from seawater as a function of time, typically 42 to 56 day exposures, to determine the adsorbent capacitymore » and adsorption rate (kinetics). Analysis of uranium and other trace elements collected by the adsorbents was conducted following strong acid digestion of the adsorbent with 50% aqua regia using either Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) or Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The ORNL 38H adsorbent had a 56 day adsorption capacity of 3.30 ± 0.68 g U/ kg adsorbent (normalized to a salinity of 35 psu), a saturation adsorption capacity of 4.89 ± 0.83 g U/kg of adsorbent material (normalized to a salinity of 35 psu) and a half-saturation time of 28 10 days. The AF1 adsorbent material had a 56 day adsorption capacity of 3.9 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu), a saturation capacity of 5.4 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu) and a half saturation time of 23 2 days. The ORNL amidoxime-based adsorbent materials are not specific for uranium, but also adsorb other elements from seawater. The major doubly charged cations in seawater (Ca and Mg) account for a majority of the cations adsorbed (61% by mass and 74% by molar percent). For the ORNL AF1 adsorbent material, U is the 4th most abundant element adsorbed by mass and 7th most abundant by molar percentage. Marine testing

  14. Molecular Plasmonics.

    PubMed

    Wilson, Andrew J; Willets, Katherine A

    2016-06-12

    In this review, we survey recent advances in the field of molecular plasmonics beyond the traditional sensing modality. Molecular plasmonics is explored in the context of the complex interaction between plasmon resonances and molecules and the ability of molecules to support plasmons self-consistently. First, spectroscopic changes induced by the interaction between molecular and plasmonic resonances are discussed, followed by examples of how tuning molecular properties leads to active molecular plasmonic systems. Next, the role of the position and polarizability of a molecular adsorbate on surface-enhanced Raman scattering signals is examined experimentally and theoretically. Finally, we introduce recent research focused on using molecules as plasmonic materials. Each of these examples is intended to highlight the role of molecules as integral components in coupled molecule-plasmon systems, as well as to show the diversity of applications in molecular plasmonics.

  15. Molecular Plasmonics

    NASA Astrophysics Data System (ADS)

    Wilson, Andrew J.; Willets, Katherine A.

    2016-06-01

    In this review, we survey recent advances in the field of molecular plasmonics beyond the traditional sensing modality. Molecular plasmonics is explored in the context of the complex interaction between plasmon resonances and molecules and the ability of molecules to support plasmons self-consistently. First, spectroscopic changes induced by the interaction between molecular and plasmonic resonances are discussed, followed by examples of how tuning molecular properties leads to active molecular plasmonic systems. Next, the role of the position and polarizability of a molecular adsorbate on surface-enhanced Raman scattering signals is examined experimentally and theoretically. Finally, we introduce recent research focused on using molecules as plasmonic materials. Each of these examples is intended to highlight the role of molecules as integral components in coupled molecule-plasmon systems, as well as to show the diversity of applications in molecular plasmonics.

  16. Complete braided adsorbent for marine testing to demonstrate 3g-U/kg-adsorbent

    SciTech Connect

    Janke, Chris; Yatsandra, Oyola; Mayes, Richard; none,; Gill, Gary; Li-Jung, Kuo; Wood, Jordana; Sadananda, Das

    2014-04-30

    ORNL has manufactured four braided adsorbents that successfully demonstrated uranium adsorption capacities ranging from 3.0-3.6 g-U/kg-adsorbent in marine testing at PNNL. Four new braided and leno woven fabric adsorbents have also been prepared by ORNL and are currently undergoing marine testing at PNNL.

  17. Bowl inversion of surface-adsorbed sumanene.

    PubMed

    Jaafar, Rached; Pignedoli, Carlo A; Bussi, Giovanni; Aït-Mansour, Kamel; Groening, Oliver; Amaya, Toru; Hirao, Toshikazu; Fasel, Roman; Ruffieux, Pascal

    2014-10-01

    Bowl-shaped π-conjugated compounds offer the possibility to study curvature-dependent host-guest interactions and chemical reactivity in ideal model systems. For surface-adsorbed π bowls, however, only conformations with the bowl opening pointing away from the surface have been observed so far. Here we show for sumanene on Ag(111) that both bowl-up and bowl-down conformations can be stabilized. Analysis of the molecular layer as a function of coverage reveals an unprecedented structural phase transition involving a bowl inversion of one-third of the molecules. On the basis of scanning tunneling microscopy (STM) and complementary atomistic simulations, we develop a model that describes the observed phase transition in terms of a subtle interplay between inversion-dependent adsorption energies and intermolecular interactions. In addition, we explore the coexisting bowl-up and -down conformations with respect to host-guest binding of methane. STM reveals a clear energetic preference for methane binding to the concave face of sumanene. PMID:25181621

  18. Reversible Swelling of Chitosan and Quaternary Ammonium Modified Chitosan Brush Layers: Effect of pH and Counter Anion Size and Functionality.

    PubMed

    Lee, Hyun-Su; Yee, Michael Q; Eckmann, Yonaton Y; Hickok, Noreen J; Eckmann, David M; Composto, Russell J

    2012-10-01

    This study investigates the swelling of grafted polycationic brushes as a function of pH and anion type. The brushes are chitosan (CH) and chitosans with 27% and 51% degree of substitution (DS) of quaternary ammonium salt, denoted as CH-Q(25) and CH-Q(50), respectively. The water content and swelling behaviors are monitored using in situ quartz-crystal microbalance with dissipation (QCM-D). The pH varies from ~3.5 to 8.5, and the counter anion types include chloride, acetate, and citrate. At fixed pH, the water content and brush swelling increase as the DS increases. Whereas the CH-Q(50) brush layer shows symmetric swelling with a minimum near pH = 4.5, the swelling of CH and CH-Q(25) is relatively constant as pH decreases from 8.2 to 5.5, and then begins to increase near pH 4. These studies indicate that the symmetric swelling of CH-Q(50) is likely attributed to increasing protonation of primary amines for pH values below pH 6.5 and the quaternary ammonium salts above pH 6.5. At pH 4, the swelling of the CH brush increases upon exchanging the smaller chloridewith a bulkier acetate anion, which is less effective at screening intra/inter molecular repulsion. In contrast, upon exchanging the acetate with trifunctional citrate, CH and CH-Q(25) brushes collapse by 53 and 42%, respectively, because the citrate forms ionic cross-links. To test antibacterial properties, silicon oxide, CH and CH-Q(50) brush layers are exposed to 10(7)-10(8) cfu/ml of S. aureus for two days at 37 °C and exposed to stepped shear stresses in 2 min intervals. Whereas an S. aureus biofilm adheres strongly to silicon oxide and CH for stresses up to 12 dyne/cm(2), biofilms on CH-Q(50) detach at a relatively low shear stress, 1.5 dyne/cm(2). Due to their high degree of swelling that can be tuned via pH, counterion size and type, chitosan and quaternary modified chitosans have potential as responsive coatings for applications including MEMS/NEMS devices and drug eluting implants. PMID:23209343

  19. Potential effects of tooth-brushing on human dentin wear following exposure to acidic soft drinks.

    PubMed

    Choi, S; Park, K-H; Cheong, Y; Moon, S W; Park, Y-G; Park, H-K

    2012-08-01

    This study used scanning electron microscopy and atomic force microscopy to examine the short-term potential effects of brushing time and the start-time of tooth-brushing after demineralization on primary dentin wear in vitro. Thirty-six noncarious primary central incisors were assigned to 12 experimental groups. Exposure to cola drinks was used to initiate the demineralization process. Three brushing times (5, 15 and 30 s) and four start-times of brushing (0, 30, 60 and 120 min) after an erosive attack were used for the abrasion process. Tooth-brushing the softened dentin surface led to increases in the open tubular fraction and microstructural changes on the dentin surface. Brushing immediately after exposure to cola resulted in the greatest irreversible dentin loss, whereas brushing 60 or 120 min after pretreatment resulted in the least irreversible dentin loss. However, brushing time had no effect on the irreversible loss of dentin wear. Based on these experimental results, tooth-brushing should be performed at least 60 min after consuming a cola drink to achieve the desired tooth cleaning and avoid the introduction of surface lesions on dentin.

  20. Scaling Laws for liquid and ion transport in nanochannels grafted with polyelectrolyte brushes

    NASA Astrophysics Data System (ADS)

    Chen, Guang; Sinha, Shayandev; Das, Siddhartha; Soft Matter, Interfaces,; Energy Laboratory (Smiel) Team

    Grafting nanochannels with polyelectrolyte (PE) brushes renders tremendous functionality to the nanochannels, making them capable of applications such as ion manipulation, ion sensing, current rectification, nanofluidic diode fabrication, and flow control. PE brush is a special case of polymers at interfaces; such brush-like structure is possible only when the grafting density (σ) is beyond a critical value. In this study, we shall propose scaling laws that identify σ-N(N is the size of the PE molecule) combination that simultaneously ensure that the grafted PE molecules adopt ''brush''-like configuration and the height of the PE brushes are smaller than the nanochannel half height. Secondly, we pinpoint the scaling conditions where the electrostatic effects associated with the PE brushes can be decoupled from the corresponding PE excluded volume and elastic effects; such de-coupling has tremendous connotation in context of modeling of electrostatics and transport at PE-brush-covered interfaces. Thirdly, we provide scaling arguments to quantify the dependence of the flow penetration depth into the PE brush as a function of the σ-N combination. Finally, our scaling estimates pinpoint the conditions where the flow or electric field induced deformation of the grafted nanochannel PE brushes can be neglected while modeling the pressure-driven or electroosmotic transport or ionic current in such nanochannels.

  1. Database of Novel and Emerging Adsorbent Materials

    National Institute of Standards and Technology Data Gateway

    SRD 205 NIST/ARPA-E Database of Novel and Emerging Adsorbent Materials (Web, free access)   The NIST/ARPA-E Database of Novel and Emerging Adsorbent Materials is a free, web-based catalog of adsorbent materials and measured adsorption properties of numerous materials obtained from article entries from the scientific literature. Search fields for the database include adsorbent material, adsorbate gas, experimental conditions (pressure, temperature), and bibliographic information (author, title, journal), and results from queries are provided as a list of articles matching the search parameters. The database also contains adsorption isotherms digitized from the cataloged articles, which can be compared visually online in the web application or exported for offline analysis.

  2. NOx adsorber and method of regenerating same

    DOEpatents

    Endicott, Dennis L.; Verkiel, Maarten; Driscoll, James J.

    2007-01-30

    New technologies, such as NOx adsorber catalytic converters, are being used to meet increasingly stringent regulations on undesirable emissions, including NOx emissions. NOx adsorbers must be periodically regenerated, which requires an increased fuel consumption. The present disclosure includes a method of regenerating a NOx adsorber within a NOx adsorber catalytic converter. At least one sensor positioned downstream from the NOx adsorber senses, in the downstream exhaust, at least one of NOx, nitrous oxide and ammonia concentrations a plurality of times during a regeneration phase. The sensor is in communication with an electronic control module that includes a regeneration monitoring algorithm operable to end the regeneration phase when a time rate of change of the at least one of NOx, nitrous oxide and ammonia concentrations is after an expected plateau region begins.

  3. Fluorescence dynamics of microsphere-adsorbed sunscreens

    NASA Astrophysics Data System (ADS)

    Krishnan, R.

    2005-03-01

    Sunscreens are generally oily substances which are prepared in organic solvents, emulsions or dispersions with micro- or nanoparticles. These molecules adsorb to and integrate into skin cells. In order to understand the photophysical properties of the sunscreen, we compare steady-state and time-resolved fluorescence in organic solvent of varying dielectric constant ɛ and adsorbed to polystyrene microspheres and dispersed in water. Steady-state fluorescence is highest and average fluorescence lifetime longest in toluene, the solvent of lowest ɛ. However, there is no uniform dependence on ɛ. Sunscreens PABA and padimate-O show complex emission spectra. Microsphere-adsorbed sunscreens exhibit highly non-exponential decay, illustrative of multiple environments of the adsorbed molecule. The heterogeneous fluorescence dynamics likely characterizes sunscreen adsorbed to cells.

  4. Inorganic chemically active adsorbents (ICAAs)

    SciTech Connect

    Ally, M.R.; Tavlarides, L.

    1997-10-01

    Oak Ridge National Laboratory (ORNL) researchers are developing a technology that combines metal chelation extraction technology and synthesis chemistry. They begin with a ceramic substrate such as alumina, titanium oxide or silica gel because they provide high surface area, high mechanical strength, and radiolytic stability. One preparation method involves silylation to hydrophobize the surface, followed by chemisorption of a suitable chelation agent using vapor deposition. Another route attaches newly designed chelating agents through covalent bonding by the use of coupling agents. These approaches provide stable and selective, inorganic chemically active adsorbents (ICAAs) tailored for removal of metals. The technology has the following advantages over ion exchange: (1) higher mechanical strength, (2) higher resistance to radiation fields, (3) higher selectivity for the desired metal ion, (4) no cation exchange, (5) reduced or no interference from accompanying anions, (6) faster kinetics, and (7) easy and selective regeneration. Target waste streams include metal-containing groundwater/process wastewater at ORNL`s Y-12 Plant (multiple metals), Savannah River Site (SRS), Rocky Flats (multiple metals), and Hanford; aqueous mixed wastes at Idaho National Engineering Laboratory (INEL); and scrubber water generated at SRS and INEL. Focus Areas that will benefit from this research include Mixed Waste, and Subsurface Contaminants.

  5. Adsorption of high salinity surfactant systems and sacrificial agents for EOR on model adsorbents

    SciTech Connect

    Volz, H.V.

    1988-05-01

    In chemical flooding processes for enhanced oil recovery, chemical adsorption is a major factor which may limit the applicability of these processes. Under typical high salinity conditions of West German oil reservoirs (100 to 200 kg/m/sup 3/ of total dissolved solids) adsorption experiments with single and multi-component surfactant systems and with and without the use of sacrificial agents on model adsorbents were carried out, adsorbents being calcium benetonite, illite, kaolinite, dickite, prochlorite, and quartz. It can be shown that polyethylene glycols of appropriate molecular weight, which were used as sacrificial agents, adsorb specifically on calcium bentonite or quartz, whereas on kaolnite they form an adsorbing complex together with the surfactant. Based on experimental results specific coverages of sacrificial agents and surfactants are calculated.

  6. Assembly and organization of poly(3-hexylthiophene) brushes and their potential use as novel anode buffer layers for organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Alonzo, José; Kochemba, W. Michael; Pickel, Deanna L.; Ramanathan, Muruganathan; Sun, Zhenzhong; Li, Dawen; Chen, Jihua; Sumpter, Bobby G.; Heller, William T.; Kilbey, S. Michael, II

    2013-09-01

    Buffer layers that control electrochemical reactions and physical interactions at electrode/film interfaces are key components of an organic photovoltaic cell. Here the structure and properties of layers of semi-rigid poly(3-hexylthiophene) (P3HT) chains tethered at a surface are investigated, and these functional systems are applied in an organic photovoltaic device. Areal density of P3HT chains is readily tuned through the choice of polymer molecular weight and annealing conditions, and insights from optical absorption spectroscopy and semiempirical quantum calculation methods suggest that tethering causes intrachain defects that affect co-facial π-stacking of brush chains. Because of their ability to modify oxide surfaces, P3HT brushes are utilized as an anode buffer layer in a P3HT-PCBM (phenyl-C61-butyric acid methyl ester) bulk heterojunction device. Current-voltage characterization shows a significant enhancement in short circuit current, suggesting the potential of these novel nanostructured buffer layers to replace the PEDOT:PSS buffer layer typically applied in traditional P3HT-PCBM solar cells.Buffer layers that control electrochemical reactions and physical interactions at electrode/film interfaces are key components of an organic photovoltaic cell. Here the structure and properties of layers of semi-rigid poly(3-hexylthiophene) (P3HT) chains tethered at a surface are investigated, and these functional systems are applied in an organic photovoltaic device. Areal density of P3HT chains is readily tuned through the choice of polymer molecular weight and annealing conditions, and insights from optical absorption spectroscopy and semiempirical quantum calculation methods suggest that tethering causes intrachain defects that affect co-facial π-stacking of brush chains. Because of their ability to modify oxide surfaces, P3HT brushes are utilized as an anode buffer layer in a P3HT-PCBM (phenyl-C61-butyric acid methyl ester) bulk heterojunction device

  7. Proton conduction of polyAMPS brushes on titanate nanotubes

    PubMed Central

    Feng, Jun; Huang, Yaqin; Tu, Zhengkai; Zhang, Haining; Pan, Mu; Tang, Haolin

    2014-01-01

    Proton conducting materials having reasonable proton conductivity at low humidification conditions are critical for decrease in system complexity and improvement of power density for polymer electrolyte membrane fuel cells. This study shows that polyelectrolyte brushes on titanate nanotubes formed through surface-initiated free radical polymerization exhibit less humidity-dependent proton conduction because of the high grafting density of polymer electrolyte chains and well-distribution of ionic groups. The results described in this study provide an idea for design of new proton conductors with effective ion transport served at relatively low humidification levels. PMID:25169431

  8. Infrared radiation emerging from smoke produced by brush fires

    NASA Technical Reports Server (NTRS)

    Weinman, J. A.; Olson, W. S.; Harshvardhan, M.

    1981-01-01

    The IR radiative transport properties of brush fire smoke clouds, computed for a model with finite horizontal dimensions as well as the more common plane-parallel model, are presented. The finite model is a three-dimensional version of the two-stream approximation applied to cubic clouds of steam, carbon, and silicates. Assumptions are made with regard to the shape and size distributions of the smoke particles. It is shown that 11.5-micron radiometry can detect fires beneath smoke clouds if the path integrated mass density of the smoke is less than or equal to 3 g/sq m.

  9. Infrared radiation emerging from smoke produced by brush fires.

    PubMed

    Weinman, J A; Harshvardhan, H; Olson, W S

    1981-01-15

    This study presents the IR radiative transport properties of brush fire smoke clouds computed for a model with finite horizontal dimensions as well as the more common plane-parallel model. The finite model is a 3-D version of the two-stream approximation applied to cubic clouds of steam, carbon, and silicates. Assumptions are made with regard to the shape and size distributions of the smoke particles. It is shown that 11.5-microm radiometry can detect fires beneath smoke clouds if the path integrated mass density of the smoke is less, similar3 g/m(2).

  10. A Modified Tactile Brush Algorithm for Complex Touch Gestures

    SciTech Connect

    Ragan, Eric

    2015-01-01

    Several researchers have investigated phantom tactile sensation (i.e., the perception of a nonexistent actuator between two real actuators) and apparent tactile motion (i.e., the perception of a moving actuator due to time delays between onsets of multiple actuations). Prior work has focused primarily on determining appropriate Durations of Stimulation (DOS) and Stimulus Onset Asynchronies (SOA) for simple touch gestures, such as a single finger stroke. To expand upon this knowledge, we investigated complex touch gestures involving multiple, simultaneous points of contact, such as a whole hand touching the arm. To implement complex touch gestures, we modified the Tactile Brush algorithm to support rectangular areas of tactile stimulation.

  11. Electrochemical redox responsive polymeric micelles formed from amphiphilic supramolecular brushes.

    PubMed

    Feng, Anchao; Yan, Qiang; Zhang, Huijuan; Peng, Liao; Yuan, Jinying

    2014-05-11

    The end-decorated homopolymer poly(ε-caprolactone)-ferrocene threaded onto a β-cyclodextrin-functionalized main-chain polymer can form a class of amphiphilic noncovalent graft copolymers based on the host-guest interactions of the terminal groups on the side chains. These new supramolecular polymer brushes can further self-assemble into micellar aggregates that exhibit reversible assembly and disassembly behavior under an electrochemical redox trigger, which opens up a new route to building dynamic block copolymer topologies. PMID:24681929

  12. Protein Mediators of Sterol Transport Across Intestinal Brush Border Membrane

    PubMed Central

    Brown, J. Mark; Yu, Liqing

    2012-01-01

    Dysregulation of cholesterol balance contributes significantly to atherosclerotic cardiovascular disease (ASCVD), the leading cause of death in the United States. The intestine has the unique capability to act as a gatekeeper for entry of cholesterol into the body, and inhibition of intestinal cholesterol absorption is now widely regarded as an attractive non-statin therapeutic strategy for ASCVD prevention. In this chapter we discuss the current state of knowledge regarding sterol transport across the intestinal brush border membrane. The purpose of this work is to summarize substantial progress made in the last decade in regards to protein-mediated sterol trafficking, and to discuss this in the context of human disease. PMID:20213550

  13. Heat transfer to the adsorbent in solar adsorption cooling device

    NASA Astrophysics Data System (ADS)

    Pilat, Peter; Patsch, Marek; Papucik, Stefan; Vantuch, Martin

    2014-08-01

    The article deals with design and construction of solar adsorption cooling device and with heat transfer problem in adsorber. The most important part of adsorption cooling system is adsorber/desorber containing adsorbent. Zeolith (adsorbent) type was chosen for its high adsorption capacity, like a coolant was used water. In adsorber/desorber occur, at heating of adsorbent, to heat transfer from heat change medium to the adsorbent. The time required for heating of adsorber filling is very important, because on it depend flexibility of cooling system. Zeolith has a large thermal resistance, therefore it had to be adapted the design and construction of adsorber. As the best shows the tube type of adsorber with double coat construction. By this construction is ensured thin layer of adsorbent and heating is quick in all volume of adsorbent. The process of heat transfer was experimentally measured, but for comparison simulated in ANSYS, too.

  14. Adsorbed natural gas storage with activated carbon

    SciTech Connect

    Sun, Jian; Brady, T.A.; Rood, M.J.

    1996-12-31

    Despite technical advances to reduce air pollution emissions, motor vehicles still account for 30 to 70% emissions of all urban air pollutants. The Clean Air Act Amendments of 1990 require 100 cities in the United States to reduce the amount of their smog within 5 to 15 years. Hence, auto emissions, the major cause of smog, must be reduced 30 to 60% by 1998. Natural gas con be combusted with less pollutant emissions. Adsorbed natural gas (ANG) uses adsorbents and operates with a low storage pressure which results in lower capital costs and maintenance. This paper describes the production of an activated carbon adsorbent produced from an Illinois coal for ANG.

  15. States of water adsorbed on perindopril crystals

    NASA Astrophysics Data System (ADS)

    Stepanov, V. A.; Khmelevskaya, V. S.; Bogdanov, N. Yu.; Gorchakov, K. A.

    2011-10-01

    The relationship between the structural state of adsorbed water, the crystal structure of the substances, and the solubility of the perindopril salt C19H32N2O5 · C4H11N in water was studied by IR spectroscopy and X-ray diffractometry. The high-frequency shift of the stretching vibrations of adsorbed water and the solubility depend on the crystal structure of the drug substance. A reversible chemical reaction occurred between the adsorbed water and the perindopril salt.

  16. Comparison of adsorbents for H2S and D4 removal for biogas conversion in a solid oxide fuel cell.

    PubMed

    Sigot, Léa; Ducom, Gaëlle; Benadda, Belkacem; Labouré, Claire

    2016-01-01

    Biogas contains trace compounds detrimental for solid oxide fuel cell (SOFC) application, especially sulphur-containing compounds and volatile organic silicon compounds (VOSiCs). It is therefore necessary to remove these impurities from the biogas for fuelling an SOFC. In this paper, dynamic lab-scale adsorption tests were performed on synthetic polluted gas to evaluate the performance of a polishing treatment to remove hydrogen sulphide (H2S - sulphur compound) and octamethylcyclotetrasiloxane (D4 - VOSiC). Three kinds of adsorbents were tested: an activated carbon, a silica gel (SG) and a zeolite (Z). Z proved to be the best adsorbent for H2S removal, with an adsorbed quantity higher than [Formula: see text] at the SOFC tolerance limit. However, as concerns D4 removal, SG was the most efficient adsorbent, with an adsorbed quantity of about 184 mgD4/gSG at the SOFC tolerance limit. These results could not be explained by structural characteristics of the adsorbents, but they were partly explained by chemical interactions between the adsorbate and the adsorbent. In these experiments, internal diffusion was the controlling step, Knudsen diffusion being predominant to molecular diffusion. As Z was also a good adsorbent for D4 removal, competition phenomena were investigated with Z for the simultaneous removal of H2S and D4. It was shown that H2S retention was dramatically decreased in the presence of D4, probably due to D4 polymerization resulting in pore blocking.

  17. Modification of Ti6Al4V substrates with well-defined zwitterionic polysulfobetaine brushes for improved surface mineralization.

    PubMed

    Liu, Pingsheng; Domingue, Emily; Ayers, David C; Song, Jie

    2014-05-28

    Osteoconductive mineral coatings are beneficial for improving the osteointegration of metallic orthopedic/dental implants, but achieving adequate structural integration between the surface minerals and underlying metallic substrates has been a significant challenge. Here, we report covalent grafting of zwitterionic poly(sulfobetaine methacrylate) (pSBMA) brushes on the Ti6Al4V substrates to promote the surface-mineralization of hydroxyapatite with enhanced surface mineral coverage and mineral-substrate interfacial adhesion. We first optimized the atom transfer radical polymerization (ATRP) conditions for synthesizing pSBMA polymers in solution. Well-controlled pSBMA polymers (relative molecular weight up to 26 kD, PDI = 1.17) with high conversions were obtained when the ATRP was carried out in trifluoroethanol/ionic liquid system at 60 °C. Applying identical polymerization conditions, surface-initiated atom transfer radical polymerization (SI-ATRP) was carried out to graft zwitterionic pSBMA brushes (PDI < 1.20) from the Ti6Al4V substrates, generating a stable superhydrophilic and low-fouling surface coating without compromising the bulk mechanic property of the Ti6Al4V substrates. The zwitterionic pSBMA surface brushes, capable of attracting both cationic and anionic precursor ions during calcium phosphate apatite mineralization, increased the surface mineral coverage from 32% to 71%, and significantly reinforced the attachment of the apatite crystals on the Ti6Al4V substrate. This facile approach to surface modification of metallic substrates can be exploited to generate multifunctional polymer coatings and improve the performance of metallic implants in skeletal tissue engineering and orthopedic and dental care. PMID:24828749

  18. Modification of Ti6Al4V Substrates with Well-defined Zwitterionic Polysulfobetaine Brushes for Improved Surface Mineralization

    PubMed Central

    2015-01-01

    Osteoconductive mineral coatings are beneficial for improving the osteointegration of metallic orthopedic/dental implants, but achieving adequate structural integration between the surface minerals and underlying metallic substrates has been a significant challenge. Here, we report covalent grafting of zwitterionic poly(sulfobetaine methacrylate) (pSBMA) brushes on the Ti6Al4V substrates to promote the surface-mineralization of hydroxyapatite with enhanced surface mineral coverage and mineral-substrate interfacial adhesion. We first optimized the atom transfer radical polymerization (ATRP) conditions for synthesizing pSBMA polymers in solution. Well-controlled pSBMA polymers (relative molecular weight up to 26kD, PDI = 1.17) with high conversions were obtained when the ATRP was carried out in trifluoroethanol/ionic liquid system at 60 °C. Applying identical polymerization conditions, surface-initiated atom transfer radical polymerization (SI-ATRP) was carried out to graft zwitterionic pSBMA brushes (PDI < 1.20) from the Ti6Al4V substrates, generating a stable superhydrophilic and low-fouling surface coating without compromising the bulk mechanic property of the Ti6Al4V substrates. The zwitterionic pSBMA surface brushes, capable of attracting both cationic and anionic precursor ions during calcium phosphate apatite mineralization, increased the surface mineral coverage from 32% to 71%, and significantly reinforced the attachment of the apatite crystals on the Ti6Al4V substrate. This facile approach to surface modification of metallic substrates can be exploited to generate multifunctional polymer coatings and improve the performance of metallic implants in skeletal tissue engineering and orthopedic and dental care. PMID:24828749

  19. Non-linear optical studies of adsorbates: Spectroscopy and dynamics

    SciTech Connect

    Zhu, Xiangdong.

    1989-08-01

    In the first part of this thesis, we have established a systematic procedure to apply the surface optical second-harmonic generation (SHG) technique to study surface dynamics of adsorbates. In particular, we have developed a novel technique for studies of molecular surface diffusions. In this technique, the laser-induced desorption with two interfering laser beams is used to produce a monolayer grating of adsorbates. The monolayer grating is detected with diffractions of optical SHG. By monitoring the first-order second-harmonic diffraction, we can follow the time evolution of the grating modulation from which we are able to deduce the diffusion constant of the adsorbates on the surface. We have successfully applied this technique to investigate the surface diffusion of CO on Ni(111). The unique advantages of this novel technique will enable us to readily study anisotropy of a surface diffusion with variable grating orientation, and to investigate diffusion processes of a large dynamic range with variable grating spacings. In the second part of this work, we demonstrate that optical infrared-visible sum-frequency generation (SFG) from surfaces can be used as a viable surface vibrational spectroscopic technique. We have successfully recorded the first vibrational spectrum of a monolayer of adsorbates using optical infrared-visible SFG. The qualitative and quantitative correlation of optical SFG with infrared absorption and Raman scattering spectroscopies are examined and experimentally demonstrated. We have further investigated the possibility to use transient infrared-visible SFG to probe vibrational transients and ultrafast relaxations on surfaces. 146 refs.

  20. Effect of brushing with sonic and counterrotational toothbrushes on the bond strength of orthodontic brackets.

    PubMed

    Hansen, P A; Killoy, W; Masterson, K

    1999-01-01

    The purpose of this study was to evaluate the effect of brushing with both a sonic and mechanical counter rotary power toothbrush on the bond strength of orthodontic brackets. Forty-five extracted teeth were divided into three random groups and had orthodontic brackets bonded to them. One group was brushed with a counterrotational toothbrush, the Interplak, one group with a sonic toothbrush, the Sonicare, and a third group was not brushed and was held as a control. After the equivalent of 2 years brushing, the teeth were placed in an Instron machine and the shear force to remove the brackets was recorded. Group 1, the counter rotary power brush, had a mean of 107.5 kg/cm2, the second group, the sonic brush, had a mean of 79.7 kg/cm2, and the control group had a mean of 125. 4 kg/cm2. Single factor analysis of variance followed by the Fisher-Hayter Multiple Comparison Procedure showed a statistically significant difference between the sonic power brush and the control (P <.01), but no significant difference between the counter rotary and the control (P >.05). There was no significant difference between the two power brushes (P >.05).

  1. 46 CFR 108.187 - Ventilation for brush type electric motors in classified spaces.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... spaces. 108.187 Section 108.187 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A... Ventilation for brush type electric motors in classified spaces. Ventilation for brush type electric motors in... the motors may cause unsafe conditions. Accommodation Spaces...

  2. Supramolecular Magnetic Brushes: The Impact of Dipolar Interactions on the Equilibrium Structure

    PubMed Central

    2015-01-01

    The equilibrium structure of supramolecular magnetic filament brushes is analyzed at two different scales. First, we study the density and height distributions for brushes with various grafting densities and chain lengths. We use Langevin dynamics simulations with a bead–spring model that takes into account the cross-links between the surface of the ferromagnetic particles, whose magnetization is characterized by a point dipole. Magnetic filament brushes are shown to be more compact near the substrate than nonmagnetic ones, with a bimodal height distribution for large grafting densities. This latter feature makes them also different from brushes with electric dipoles. Next, in order to explain the observed behavior at the filament scale, we introduce a graph theory analysis to elucidate for the first time the structure of the brush at the scale of individual beads. It turns out that, in contrast to nonmagnetic brushes, in which the internal structure is determined by random density fluctuations, magnetic forces introduce a certain order in the system. Because of their highly directional nature, magnetic dipolar interactions prevent some of the random connections to be formed. On the other hand, they favor a higher connectivity of the chains’ free and grafted ends. We show that this complex dipolar brush microstructure has a strong impact on the magnetic response of the brush, as any weak applied field has to compete with the dipole–dipole interactions within the crowded environment. PMID:26538768

  3. Towards controlled polymer brushes via a self-assembly-assisted-grafting-to approach

    PubMed Central

    Zhou, Tian; Qi, Hao; Han, Lin; Barbash, Dmitri; Li, Christopher Y.

    2016-01-01

    Precise synthesis of polymer brushes to modify the surface of nanoparticles and nanodevices for targeted applications has been one of the major focuses in the community for decades. Here we report a self-assembly-assisted-grafting-to approach to synthesize polymer brushes on flat substrates. In this method, polymers are pre-assembled into two-dimensional polymer single crystals (PSCs) with functional groups on the surface. Chemically coupling the PSCs onto solid substrates leads to the formation of polymer brushes. Exquisite control of the chain folding in PSCs allows us to obtain polymer brushes with well-defined grafting density, tethering points and brush conformation. Extremely high grafting density (2.12 chains per nm2) has been achieved in the synthesized single-tethered polymer brushes. Moreover, polymer loop brushes have been successfully obtained using oddly folded PSCs from telechelic chains. Our approach combines some of the important advantages of conventional ‘grafting-to' and ‘grafting-from' methods, and is promising for tailored synthesis of polymer brushes. PMID:27009369

  4. Analytic models of regularly branched polymer brushes using the self-consistent mean field theory

    NASA Astrophysics Data System (ADS)

    LeSher, Daniel

    2015-10-01

    Polymer brushes consist of multiple monomers connected together with one of the polymer chain's ends attached to a surface. Polymer brushes have shown great promise for a wide variety of applications including drug delivery dendrimer systems and as tunable brushes that can change their shape and physical properties in response to changes in their environment. Regularly branched polymer brushes which are structured as a function of their chemical indices are investigated here using the self-consistent mean field theory for electrically neutral polymers. The brushes were described using weighting functions, f(n), were n was the fewest number of monomers from a specified location to a free end. Brushes with weighting functions of the form f(n)=nb, f(n)=ebn, as well as f(n)=dan when d 2 and alpha > 2 were found to match the parabolic free chain end profile expected, while it was determined that polymer brushes described using f(n)=n b must be very small in order to remain in equilibrium. However, brushes described by f(n)=2G(N-n) N and f(n)2n were found to be unstable for real, positive values of the potential of the system.

  5. Towards controlled polymer brushes via a self-assembly-assisted-grafting-to approach

    NASA Astrophysics Data System (ADS)

    Zhou, Tian; Qi, Hao; Han, Lin; Barbash, Dmitri; Li, Christopher Y.

    2016-03-01

    Precise synthesis of polymer brushes to modify the surface of nanoparticles and nanodevices for targeted applications has been one of the major focuses in the community for decades. Here we report a self-assembly-assisted-grafting-to approach to synthesize polymer brushes on flat substrates. In this method, polymers are pre-assembled into two-dimensional polymer single crystals (PSCs) with functional groups on the surface. Chemically coupling the PSCs onto solid substrates leads to the formation of polymer brushes. Exquisite control of the chain folding in PSCs allows us to obtain polymer brushes with well-defined grafting density, tethering points and brush conformation. Extremely high grafting density (2.12 chains per nm2) has been achieved in the synthesized single-tethered polymer brushes. Moreover, polymer loop brushes have been successfully obtained using oddly folded PSCs from telechelic chains. Our approach combines some of the important advantages of conventional `grafting-to' and `grafting-from' methods, and is promising for tailored synthesis of polymer brushes.

  6. Process Of Bonding A Metal Brush Structure To A Planar Surface Of A Metal Substrate

    DOEpatents

    Slattery, Kevin T.; Driemeyer, Daniel E.; Wille; Gerald W.

    1999-11-02

    Process for bonding a metal brush structure to a planar surface of a metal substrate in which an array of metal rods are retained and immobilized at their tips by a common retention layer formed of metal, and the brush structure is then joined to a planar surface of a metal substrate via the retention layer.

  7. PERVAPORATION USING ADSORBENT-FILLED MEMBRANES

    EPA Science Inventory

    Membranes containing selective fillers, such as zeolites and activated carbon, can improve the separation by pervaporation. Applications of adsorbent-filled membranes in pervaporation have been demonstrated by a number of studies. These applications include removal of organic co...

  8. Computer simulation of bottle-brush polymers with flexible backbone: Good solvent versus theta solvent conditions

    NASA Astrophysics Data System (ADS)

    Theodorakis, Panagiotis E.; Hsu, Hsiao-Ping; Paul, Wolfgang; Binder, Kurt

    2011-10-01

    By molecular dynamics simulation of a coarse-grained bead-spring-type model for a cylindrical molecular brush with a backbone chain of Nb effective monomers to which with grafting density σ side chains with N effective monomers are tethered, several characteristic length scales are studied for variable solvent quality. Side chain lengths are in the range 5 ⩽ N ⩽ 40, backbone chain lengths are in the range 50 ⩽ Nb ⩽ 200, and we perform a comparison to results for the bond fluctuation model on the simple cubic lattice (for which much longer chains are accessible, Nb ⩽ 1027, and which corresponds to an athermal, very good, solvent). We obtain linear dimensions of the side chains and the backbone chain and discuss their N-dependence in terms of power laws and the associated effective exponents. We show that even at the theta point the side chains are considerably stretched, their linear dimension depending on the solvent quality only weakly. Effective persistence lengths are extracted both from the orientational correlations and from the backbone end-to-end distance; it is shown that different measures of the persistence length (which would all agree for Gaussian chains) are not mutually consistent with each other and depend distinctly both on Nb and the solvent quality. A brief discussion of pertinent experiments is given.

  9. Graphene transistors with multifunctional polymer brushes for biosensing applications.

    PubMed

    Hess, Lucas H; Lyuleeva, Alina; Blaschke, Benno M; Sachsenhauser, Matthias; Seifert, Max; Garrido, Jose A; Deubel, Frank

    2014-06-25

    Exhibiting a combination of exceptional structural and electronic properties, graphene has a great potential for the development of highly sensitive sensors. To date, many challenging chemical, biochemical, and biologic sensing tasks have been realized based on graphene. However, many of these sensors are rather unspecific. To overcome this problem, for instance, the sensor surface can be modified with analyte-specific transducers such as enzymes. One problem associated with the covalent attachment of such biomolecular systems is the introduction of crystal defects that have a deleterious impact on the electronic properties of the sensor. In this work, we present a versatile platform for biosensing applications based on polymer-modified CVD-grown graphene transistors. The functionalization method of graphene presented here allows one to integrate several functional groups within surface-bound polymer brushes without the introduction of additional defects. To demonstrate the potential of this polymer brush functionalization scaffold, we modified solution-gated graphene field-effect transistors with the enzyme acetylcholinesterase and a transducing group, allowing the detection of the neurotransmitter acetylcholine. Taking advantage of the transducing capability of graphene transistors and the versatility of polymer chemistry and enzyme biochemistry, this study presents a novel route for the fabrication of highly sensitive, multipurpose transistor sensors that can find application for a multitude of biologically relevant analytes. PMID:24866105

  10. Brushing of attribute clouds for the visualization of multivariate data.

    PubMed

    Jänicke, Heike; Böttinger, Michael; Scheuermann, Gerik

    2008-01-01

    The visualization and exploration of multivariate data is still a challenging task. Methods either try to visualize all variables simultaneously at each position using glyph-based approaches or use linked views for the interaction between attribute space and physical domain such as brushing of scatterplots. Most visualizations of the attribute space are either difficult to understand or suffer from visual clutter. We propose a transformation of the high-dimensional data in attribute space to 2D that results in a point cloud, called attribute cloud, such that points with similar multivariate attributes are located close to each other. The transformation is based on ideas from multivariate density estimation and manifold learning. The resulting attribute cloud is an easy to understand visualization of multivariate data in two dimensions. We explain several techniques to incorporate additional information into the attribute cloud, that help the user get a better understanding of multivariate data. Using different examples from fluid dynamics and climate simulation, we show how brushing can be used to explore the attribute cloud and find interesting structures in physical space.

  11. Brush seal bristle flexure and hard-rub characteristics

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

    1993-01-01

    The bristles of a 38.1-mm (1.5-in.) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in.) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in.) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in.) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in.) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping', and hot spots and streaks were found. With a smooth-plug rotor, post-test leakage increased 30 percent over pretest leakage.

  12. Brush seal bristle flexure and hard-rub characteristics

    NASA Astrophysics Data System (ADS)

    Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

    1993-10-01

    The bristles of a 38.1-mm (1.5-in.) diameter brush seal were flexed by a tapered, 40-tooth rotor operating at 2600 rpm that provided sharp leading-edge impact of the bristles with hard rubbing of the rotor lands. Three separate tests were run with the same brush accumulating over 1.3 x 10(exp 9) flexure cycles while deteriorating 0.2 mm (0.008 in.) radially. In each, the test bristle incursion depth varied from 0.130 to 0.025 mm (0.005 to 0.001 in.) or less (start to stop), and in the third test the rotor was set 0.25 mm (0.010 in.) eccentric. Runout varied from 0.025 to 0.076 mm (0.001 to 0.003 in.) radially. The bristles wore but did not pull out, fracture, or fragment. Bristle and rotor wear debris were deposited as very fine, nearly amorphous, highly porous materials at the rotor groove leading edges and within the rotor grooves. The land leading edges showed irregular wear and the beginning of a convergent groove that exhibited sharp, detailed wear at the land trailing edges. Surface grooving, burnishing, 'whipping', and hot spots and streaks were found. With a smooth-plug rotor, post-test leakage increased 30 percent over pretest leakage.

  13. Hysteresis and bristle stiffening effects of conventional brush seals

    NASA Astrophysics Data System (ADS)

    Basu, P.; Datta, A.; Johnson, R.; Loewenthal, R.; Short, J.

    1993-06-01

    Extensive testing of conventional brush seals has identified the phenomena of bristle 'hysteresis' and 'stiffening' with pressure as their two major drawbacks. Subsequent to any differential movement of the runner into the bristle pack due to its radial excursions or centrifugal/thermal growths, the displaced bristles do not recover against the frictional forces between them and the backing plate. As a result, a significant leakage increase is observed following any runner movement. Furthermore, the bristle pack exhibits a considerable stiffening effect with the application of pressure. This phenomenon adversely affects the life of the seal and the runner due to a highly increased mechanical contact pressure at the sliding interface. In comparison with these conventional design seals, the characteristics of an improved design, known as the 'low hysteresis' design, are presented here. This design shows a substantially lower degree of the detrimental effects mentioned above. This type of seal can maintain its reduced leakage characteristics throughout the running cycle with runner excursions and growths. The bristles also do not show any stiffening, up to a certain pressure threshold. Therefore, this seal also has a potential for a longer life than a brush seal of conventional design.

  14. Protein adsorption properties of OEG monolayers and dense PNIPAM brushes probed by neutron reflectivity

    NASA Astrophysics Data System (ADS)

    Brouette, N.; Xue, C.; Haertlein, M.; Moulin, M.; Fragneto, G.; Leckband, D. E.; Halperin, A.; Sferrazza, M.

    2012-11-01

    The structure of dense poly(N-isopropylacrylamide) (PNIPAM) brushes and oligo(ethylene glycol) (OEG) monolayers has been probed using neutron reflectometry and ellipsometry. The PNIPAM brush is swollen below the Lower Critical Solution Temperature (LCST) of 32 ∘C and is collapsed at 37 ∘C. Neutron reflectivity shows that below the LCST, the brush is described by a two-layer model: an inner dense layer and a hydrated outer layer. Above the LCST the collapsed brush forms a homogenous layer. With a fully deuterated myoglobin protein to increase the neutron scattering length density contrast, the reflectivity data show no detectable primary adsorption on the grafted OEG surface. A bound on the ternary adsorption onto PNIPAM chains forming dense brushes below and above the LCST is obtained.

  15. Highly uniform hole spacing micro brushes based on aligned carbon nanotube arrays.

    PubMed

    Yang, Zhi; Zhu, Xingzhong; Huang, Xiaolu; Cheng, Yingwu; Liu, Yun; Geng, Huijuan; Wu, Yue; Su, Yanjie; Wei, Hao; Zhang, Yafei

    2013-11-25

    Highly uniform hole spacing micro brushes were fabricated based on aligned carbon nanotube (CNT) arrays synthesized by chemical vapor deposition method with the assistance of anodic aluminum oxide (AAO) template. Different micro brushes from CNT arrays were constructed on silicon, glass, and polyimide substrates, respectively. The micro brushes had highly uniform hole spacing originating from the regularly periodic pore structure of AAO template. The CNT arrays, serving as bristles, were firmly grafted on the substrates. The brushes can easily clean particles with scale of micrometer on the surface of silicon wafer and from the narrow spaces between the electrodes in a series of cleaning experiments. The results show the potential application of the CNT micro brushes as a cleaning tool in microelectronics manufacture field.

  16. Highly uniform hole spacing micro brushes based on aligned carbon nanotube arrays

    NASA Astrophysics Data System (ADS)

    Yang, Zhi; Zhu, Xingzhong; Huang, Xiaolu; Cheng, Yingwu; Liu, Yun; Geng, Huijuan; Wu, Yue; Su, Yanjie; Wei, Hao; Zhang, Yafei

    2013-11-01

    Highly uniform hole spacing micro brushes were fabricated based on aligned carbon nanotube (CNT) arrays synthesized by chemical vapor deposition method with the assistance of anodic aluminum oxide (AAO) template. Different micro brushes from CNT arrays were constructed on silicon, glass, and polyimide substrates, respectively. The micro brushes had highly uniform hole spacing originating from the regularly periodic pore structure of AAO template. The CNT arrays, serving as bristles, were firmly grafted on the substrates. The brushes can easily clean particles with scale of micrometer on the surface of silicon wafer and from the narrow spaces between the electrodes in a series of cleaning experiments. The results show the potential application of the CNT micro brushes as a cleaning tool in microelectronics manufacture field.

  17. DNA Polymer Brush Patterning through Photocontrollable Surface-Initiated DNA Hybridization Chain Reaction.

    PubMed

    Huang, Fujian; Zhou, Xiang; Yao, Dongbao; Xiao, Shiyan; Liang, Haojun

    2015-11-18

    The fabrication of DNA polymer brushes with spatial resolution onto a solid surface is a crucial step for biochip research and related applications, cell-free gene expression study, and even artificial cell fabrication. Here, for the first time, a DNA polymer brush patterning method is reported based on the photoactivation of an ortho-nitrobenzyl linker-embedded DNA hairpin structure and a subsequent surface-initiated DNA hybridization chain reaction (HCR). Inert DNA hairpins are exposed to ultraviolet light irradiation to generate DNA duplexes with two active sticky ends (toeholds) in a programmable manner. These activated DNA duplexes can initiate DNA HCR to generate multifunctional patterned DNA polymer brushes with complex geometrical shapes. Different multifunctional DNA polymer brush patterns can be fabricated on certain areas of the same solid surface using this method. Moreover, the patterned DNA brush surface can be used to capture target molecules in a desired manner.

  18. Tooth brushing pattern classification using three-axis accelerometer and magnetic sensor for smart toothbrush.

    PubMed

    Lee, Kang-Hwi; Lee, Jeong-Whan; Kim, Kyeong-Seop; Kim, Dong-Jun; Kim, Kyungho; Yang, Heui-Kyung; Jeong, Keesam; Lee, Byungchae

    2007-01-01

    The concept of intelligent toothbrush, capable of monitoring brushing motion, orientation through the grip axis, during toothbrushing was suggested in our previous study. In this study, we describe a tooth brushing pattern classification algorithm using three-axis accelerometer and three-axis magnetic sensor. We have found that inappropriate tooth brushing pattern showed specific moving patterns. In order to trace the position and orientation of toothbrush in a mouth, we need to know absolute coordinate information of toothbrush. By applying tilt-compensated azimuth (heading) calculation algorithm, which is generally used in small telematics devices, we could find the inclination and orientation information of toothbrush. To assess the feasibility of the proposed algorithm, 8 brushing patterns were preformed by 6 individual healthy subjects. The proposed algorithm showed the detection ratio of 98%. This study showed that the proposed monitoring system was conceived to aid dental care personnel in patient education and instruction in oral hygiene regarding brushing style. PMID:18002931

  19. Lectin binding studies on a glycopolymer brush flow-through biosensor by localized surface plasmon resonance.

    PubMed

    Rosencrantz, Ruben R; Nguyen, Vu Hoa; Park, Hyunji; Schulte, Christine; Böker, Alexander; Schnakenberg, Uwe; Elling, Lothar

    2016-08-01

    A localized surface plasmon resonance biosensor in a flow-through configuration was applied for investigating kinetics of lectin binding to surface-grafted glycopolymer brushes. Polycarbonate filter membranes with pore sizes of 400 nm were coated with a 114-nm thick gold layer and used as substrate for surface-initiated atom-transfer radical polymerization of a glycomonomer. These grafted from glycopolymer brushes were further modified with two subsequent enzymatic reactions on the surface to yield an immobilized trisaccharide presenting brush. Specific binding of lectins including Clostridium difficile toxin A receptor domain to the glycopolymer brush surface could be investigated in a microfluidic setup with flow-through of the analytes and transmission surface plasmon resonance spectroscopy. Graphical abstract Glycopolymer brushes serve as high affinity ligands for lectin and toxin interactions in a sensitive, disposable flow-through LSPR biosensor. PMID:27277814

  20. Regenerable activated bauxite adsorbent alkali monitor probe

    DOEpatents

    Lee, Sheldon H. D.

    1992-01-01

    A regenerable activated bauxite adsorber alkali monitor probe for field applications to provide reliable measurement of alkali-vapor concentration in combustion gas with special emphasis on pressurized fluidized-bed combustion (PFBC) off-gas. More particularly, the invention relates to the development of a easily regenerable bauxite adsorbent for use in a method to accurately determine the alkali-vapor content of PFBC exhaust gases.

  1. Regenerable activated bauxite adsorbent alkali monitor probe

    DOEpatents

    Lee, S.H.D.

    1992-12-22

    A regenerable activated bauxite adsorber alkali monitor probe for field applications to provide reliable measurement of alkali-vapor concentration in combustion gas with special emphasis on pressurized fluidized-bed combustion (PFBC) off-gas. More particularly, the invention relates to the development of a easily regenerable bauxite adsorbent for use in a method to accurately determine the alkali-vapor content of PFBC exhaust gases. 6 figs.

  2. Mesoporous Silica: A Suitable Adsorbent for Amines

    PubMed Central

    2009-01-01

    Mesoporous silica with KIT-6 structure was investigated as a preconcentrating material in chromatographic systems for ammonia and trimethylamine. Its adsorption capacity was compared to that of existing commercial materials, showing its increased adsorption power. In addition, KIT-6 mesoporous silica efficiently adsorbs both gases, while none of the employed commercial adsorbents did. This means that KIT-6 Mesoporous silica may be a good choice for integrated chromatography/gas sensing micro-devices. PMID:20628459

  3. A novel hydrophilic polymer-brush pattern for site-specific capture of blood cells from whole blood.

    PubMed

    Hou, Jianwen; Shi, Qiang; Ye, Wei; Fan, Qunfu; Shi, Hengchong; Wong, Shing-Chung; Xu, Xiaodong; Yin, Jinghua

    2015-03-11

    A novel hydrophilic PAMPS-PAAm brush pattern is fabricated to selectively capture blood cells from whole blood. PAMPS brushes provide antifouling surfaces to resist protein and cell adhesion while PAAm brushes effectively entrap targeted proteins for site-specific and cell-type dependent capture of blood cells. PMID:25469596

  4. Metallographic Analysis of Brush Bristle and Integrity Testing of Brush Seal in Shroud Ring of T-700 Engine

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Griffin, Thomas A.; Bobula, George A.; Bill, Robert C.; Hull, David R.; Csavina, Kristine R.

    1995-01-01

    Post-test investigation of a T-700 engine brush seal found regions void of bristles ('yanked out'), regions of bent-over bristles near the inlet, some 'snapped' bristles near the fence, and a more uniform 'smeared' bristle interface between the first and last axial rows of bristles. Several bristles were cut from the brush seal, wax mounted, polished, and analyzed. Metallographic analysis of the bristles near the rub tip showed tungsten-rich phases uniformly distributed throughout the bristle with no apparent change within 1 to 2 micron of the interface except for possibly a small amount of titanium, which would represent a transfer from the rotor. Analysis of the bristle wear face showed nonuniform tungsten, which is indicative of material resolidification. The cut end contained oxides and internal fractures; the worn end was covered with oxide scale. Material losses due to wear and elastoplastic deformation within the shear zone and third-body lubrication effects in the contact zone are discussed.

  5. Chain dimensions in free and immobilized brush states of polysulfobetaine in aqueous solution at various salt concentrations

    NASA Astrophysics Data System (ADS)

    Terayama, Y.; Arita, H.; Ishikawa, T.; Kikuchi, M.; Mitamura, K.; Kobayashi, M.; Yamada, N. L.; Takahara, A.

    2011-01-01

    The chain dimensions of free and immobilized polysulfobetaine in aqueous solution at various salt concentrations were investigated by size-exclusion chromatography with multiangle light scattering and neutron reflectivity measurement, respectively. The dependence of the z-average mean square radius of gyration (z1/2) on the weight-average molecular weight (Mw) of free poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfo-nate) (MAPS) in aqueous solution at salt concentrations of 74, 100, 200, and 500 mM was described by the perturbed wormlike chain model using the chain stiffness parameter λ-1 the molar mass per unit contour length ML, and the excluded volume effect B. B increased from 0 to 1.8 nm with increasing salt concentration to 500 mM due to the screening of attractive electrostatic interaction between ammonium cations and sulfonyl anions by salt ions. The swollen structure of the poly(MAPS) brush in D2O changed from a shrunken state to a relatively extended state with increasing salt concentration from 0 to 500 mM NaCl/D2O solution. The thickness of the swollen poly(MAPS) brush in 500 mM NaCl/D2O was 9.0 times greater than 2z1/2 of free poly(MAPS) due to high osmotic pressure generated by the excluded volume effect of densely grafted polymer chains.

  6. Fabrication of ultrahydrophobic poly(lauryl acrylate) brushes on silicon wafer via surface-initiated atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Öztürk, Esra; Turan, Eylem; Caykara, Tuncer

    2010-11-01

    In this report, ultrahydrophobic poly(lauryl acrylate) [poly(LA)] brushes were synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) of lauryl acrylate (LA) in N,N-dimethylformamide (DMF) at 90 °C. The formation of ultrahydrophobic poly(LA) films, whose thickness can be turned by changing polymerization time, is evidenced by using the combination of ellipsometry, X-ray photoelectron spectroscopy (XPS), grazing angle attenuated total reflectance-Fourier transform infrared spectroscopy (GATR-FTIR), atomic force microscopy (AFM), gel permeation chromatography (GPC), and water contact angle measurements. The SI-ATRP can be conducted in a well-controlled manner, as revealed by the linear kinetic plot, linear evolution of number-average molecular weights ( M) versus monomer conversions, and the relatively narrow PDI (<1.28) of the grafted poly(LA) chains. The calculation of grafting parameters from experimental measurements indicated the synthesis of densely grafted poly(LA) films and allowed us to predict a "brushlike" conformation for the chains in good solvent. The poly(LA) brushes exhibited high water contact angle of 163.3 ± 2.8°.

  7. Rapid fabrication of poly(DL-lactide) nanofiber scaffolds with tunable degradation for tissue engineering applications by air-brushing

    PubMed Central

    Behrens, Adam M; Kim, Jeffrey; Hotaling, Nathan; Seppala, Jonathan E; Kofinas, Peter; Tutak, Wojtek

    2016-01-01

    Polymer nanofiber based materials have been widely investigated for use as tissue engineering scaffolds. While promising, these materials are typically fabricated through techniques that require significant time or cost. Here we report a rapid and cost effective air-brushing method for fabricating nanofiber scaffolds using a simple handheld apparatus, compressed air, and a polymer solution. Air-brushing also facilities control over the scaffold degradation rate without adversely impacting architecture. This was accomplished through a one step blending process of high (Mw ≈ 100 000 g mol−1) and low (Mw ≈ 25 000 g mol−1) molecular weight poly(DL-lactide) (PDLLA) polymers at various ratios (100:0, 70:30 and 50:50). Through this approach, we were able to control fiber scaffold degradation rate while maintaining similar fiber morphology, scaffold porosity, and bulk mechanical properties across all of the tested compositions. The impact of altered degradation rates was biologically evaluated in human bone marrow stromal cell (hBMSC) cultures for up to 16 days and demonstrated degradation rate dependence of both total DNA concentration and gene regulation. PMID:27121660

  8. Assembly and organization of poly(3-hexylthiophene) brushes and their potential use as novel anode buffer layers for organic photovoltaics.

    PubMed

    Alonzo, José; Kochemba, W Michael; Pickel, Deanna L; Ramanathan, Muruganathan; Sun, Zhenzhong; Li, Dawen; Chen, Jihua; Sumpter, Bobby G; Heller, William T; Kilbey, S Michael

    2013-10-01

    Buffer layers that control electrochemical reactions and physical interactions at electrode/film interfaces are key components of an organic photovoltaic cell. Here the structure and properties of layers of semi-rigid poly(3-hexylthiophene) (P3HT) chains tethered at a surface are investigated, and these functional systems are applied in an organic photovoltaic device. Areal density of P3HT chains is readily tuned through the choice of polymer molecular weight and annealing conditions, and insights from optical absorption spectroscopy and semiempirical quantum calculation methods suggest that tethering causes intrachain defects that affect co-facial π-stacking of brush chains. Because of their ability to modify oxide surfaces, P3HT brushes are utilized as an anode buffer layer in a P3HT-PCBM (phenyl-C₆₁-butyric acid methyl ester) bulk heterojunction device. Current-voltage characterization shows a significant enhancement in short circuit current, suggesting the potential of these novel nanostructured buffer layers to replace the PEDOT:PSS buffer layer typically applied in traditional P3HT-PCBM solar cells.

  9. Rapid fabrication of poly(DL-lactide) nanofiber scaffolds with tunable degradation for tissue engineering applications by air-brushing.

    PubMed

    Behrens, Adam M; Kim, Jeffrey; Hotaling, Nathan; Seppala, Jonathan E; Kofinas, Peter; Tutak, Wojtek

    2016-01-01

    Polymer nanofiber based materials have been widely investigated for use as tissue engineering scaffolds. While promising, these materials are typically fabricated through techniques that require significant time or cost. Here we report a rapid and cost effective air-brushing method for fabricating nanofiber scaffolds using a simple handheld apparatus, compressed air, and a polymer solution. Air-brushing also facilities control over the scaffold degradation rate without adversely impacting architecture. This was accomplished through a one step blending process of high (M w  ≈  100 000 g mol(-1)) and low (M w  ≈  25 000 g mol(-1)) molecular weight poly(DL-lactide) (PDLLA) polymers at various ratios (100:0, 70:30 and 50:50). Through this approach, we were able to control fiber scaffold degradation rate while maintaining similar fiber morphology, scaffold porosity, and bulk mechanical properties across all of the tested compositions. The impact of altered degradation rates was biologically evaluated in human bone marrow stromal cell (hBMSC) cultures for up to 16 days and demonstrated degradation rate dependence of both total DNA concentration and gene regulation. PMID:27121660

  10. Selective Response of Mesoporous Silicon to Adsorbants with Nitro Groups

    SciTech Connect

    McLeod, John A.; Kurmaev, Ernst Z.; Sushko, Petr V.; Boyko, Teak D.; Levitsky, Igor A.; Moewes, Alexander

    2012-01-30

    We demonstrate that the electronic structure of mesoporous silicon is affected by adsorption of nitrobased explosive molecules in a compound-selective manner. This selective response is demonstrated by probing the adsorption of two nitro-based molecular explosives (trinitrotoluene and cyclotrimethylenetrinitramine) and a nonexplosive nitro-based aromatic molecule (nitrotoluene) on mesoporous silicon using soft X-ray spectroscopy. The Si atoms strongly interact with adsorbed molecules to form Si-O and Si-N bonds, as evident from the large shifts in emission energy present in the Si L2,3 X-ray emission spectroscopy (XES) measurements. Furthermore, we find that the energy gap (band gap) of mesoporous silicon changes depending on the adsorbant, as estimated from the Si L2,3 XES and 2p X-ray absorption spectroscopy (XAS) measurements. Our ab initio molecular dynamics calculations of model compounds suggest that these changes are due to spontaneous breaking of the nitro groups upon contacting surface Si atoms. This compound-selective change in electronic structure may provide a powerful tool for the detection and identification of trace quantities of airborne explosive molecules.

  11. Insight into the adsorption of PPCPs by porous adsorbents: Effect of the properties of adsorbents and adsorbates.

    PubMed

    Zhu, Zengyin; Xie, Jiawen; Zhang, Mancheng; Zhou, Qing; Liu, Fuqiang

    2016-07-01

    Adsorption is an efficient method for removal of pharmaceuticals and personal care products (PPCPs). Magnetic resins are efficient adsorbents for water treatment and exhibit potential for PPCP removal. In this study, the magnetic hypercrosslinked resin Q100 was used for adsorption of PPCPs. The adsorption behavior of this resin was compared with those of two activated carbons, namely, Norit and F400D. Norit exhibited the fastest adsorption kinetics, followed by Q100. Norit featured a honeycomb shape and long-range ordered pore channels, which facilitated the diffusion of PPCPs. Moreover, the large average pore size of Q100 reduced diffusion resistance. The adsorbed amounts of 11 PPCPs on the three adsorbents increased with increasing adsorbate hydrophobicity. For Q100, a significant linear correlation was observed between the adsorption performance for PPCPs and hydrophobicity (logD value) of adsorbates (R(2) = 0.8951); as such, PPCPs with high logD values (>1.69) could be efficiently removed. Compared with those of Norit and F400D, the adsorption performance of Q100 was less affected by humic acid because of the dominant hydrophobic interaction. Furthermore, Q100 showed improved regeneration performance, which renders it promising for PPCP removal in practical applications. PMID:27131811

  12. Liposomes remain intact when complexed with polycationic brushes.

    PubMed

    Yaroslavov, Alexander A; Sybachin, Andrei V; Schrinner, Marc; Ballauff, Matthias; Tsarkova, Larisa; Kesselman, Ellina; Schmidt, Judith; Talmon, Yeshayahu; Menger, Fredric M

    2010-05-01

    Anionic liposomes adsorb onto the surface of spherical polymer particles bearing grafted linear cationic macromolecules. The size, shape, and encapsulation ability of the liposomes remain unchanged upon adsorption, thus providing immobilized self-organizing containers that have potential applications in the biomedical field. PMID:20387892

  13. Dynamics of an unconstrained oscillatory flicking brush for road sweeping

    NASA Astrophysics Data System (ADS)

    Vanegas Useche, L. V.; Abdel Wahab, M. M.; Parker, G. A.

    2007-11-01

    This article studies the dynamics of a freely rotating flicking brush by means of a mathematical model. The bristles are treated as cantilever prismatic beams subjected to small deflections. A solution of the equation of motion for their forced transverse vibration is obtained through the normal-mode method. A novel oscillatory motion is superimposed onto the rotary motion of the brush. Two functions of oscillation are investigated: a sinusoidal angular velocity and a novel function, named after the authors 'VAP' (Vanegas Useche, Abdel Wahab, Parker), developed to provide small shaft accelerations. The VAP function may be a square wave, a triangle wave, or a smooth wave between them, depending on the value of a smoothness parameter, b. The results indicate that the maximum bending moment, stress, and deflection are independent of the mean angular velocity, are proportional to its alternating component, and increase linearly with the mount radius and the sine of the mount angle. In addition, the behaviour of the brush is strongly affected by the frequency of oscillation, the type of function, the value of b, and bristle wear, amongst other parameters. For the sinusoidal and VAP function, resonance occurs at the bristle natural frequencies. Moreover, the VAP function tends to produce a condition similar to resonance also at odd fractions of the natural frequencies. This phenomenon may be accentuated or reduced, by adjusting the value of b, and be expedited or impeded, by the selection of the frequency. The results of this work may also be applied to the case of a small-deflection cantilever beam, when the transverse external force is a sinusoidal, square, or triangle wave or when it is given by the new VAP function. Finally, the VAP wave may enable to excite a condition similar to resonance not only at the natural frequencies of the beam, but also at odd fractions of them. Small frequencies may be required to achieve a resonant behaviour of a high-frequency mode

  14. A study on Effective Thermal Conductivity of Packed Bed of Adsorbent Including Water

    NASA Astrophysics Data System (ADS)

    Hirasawa, Yoshio; Ohta, Ryuma; Takegoshi, Eisyun

    In the present study, an effective thermal conductivity of the packed bed of an adsorbent including water was measured experimentally by using the transient hot wire method in temperature range from about -40°C to room temperature. Zeolite particle and activated carbon particle were employed as the adsorbent. The water included in the adsorbent was classified to three kinds; namely, the adsorbed water in the adsorption site with a nanometer order in particle, the osmosis water existing in gap with lager size than the adsorption site and the free water around particle. The measurement was performed with changing the mass ratio of adsorbed water and osmosis water and was also performed for the particle filled by the free water. As the results, the effective thermal conductivity of the packed bed increased with the increase of temperature except the case containing free water. In zeolite, the effective thermal conductivity of the packed bed of particles with adsorbed water became bigger than that of the desorbed particle about 10% though the adsorbed water was trapped in the adsorption site as a single molecular in zeolite particle. In activated carbon, the effective thermal conductivity was larger than that of desorbed particle about 20%. Next, in the packed bed of particle with the osmosis water, the effective thermal conductivity indicated about two times of that of particle with the adsorbed water. In the packed bed of particle filled by free water, the effective thermal conductivity increased suddenly under 0°C. It is considered that the thermal conductivity of ice affected seriously to the effective thermal conductivity because ice was the continuous phase in the bed.

  15. Evaluation of Hydrogen Isotope Exchange Methodology on Adsorbents for Tritium Removal

    DOE PAGES

    Morgan, Gregg A.; Xiao, S. Xin

    2015-03-06

    The Savannah River National Laboratory has demonstrated a potential process that can be used to remove tritium from tritiated water using Pt-catalyzed molecular sieves. The process is an elemental isotope exchange process in which H2 (when flowed through the molecular sieves) will exchange with the adsorbed water, D2O, leaving H2O adsorbed on the molecular sieves. Various formulations of catalyzed molecular sieve material were prepared using two different techniques, Pt-implantation and Pt-ion exchange. This technology has been demonstrated for a protium (H) and deuterium (D) system, but can also be used for the removal of tritium from contaminated water (T2O, HTO,more » and DTO) using D2 (or H2)« less

  16. Evaluation of Hydrogen Isotope Exchange Methodology on Adsorbents for Tritium Removal

    SciTech Connect

    Morgan, Gregg A.; Xiao, S. Xin

    2015-03-06

    The Savannah River National Laboratory has demonstrated a potential process that can be used to remove tritium from tritiated water using Pt-catalyzed molecular sieves. The process is an elemental isotope exchange process in which H2 (when flowed through the molecular sieves) will exchange with the adsorbed water, D2O, leaving H2O adsorbed on the molecular sieves. Various formulations of catalyzed molecular sieve material were prepared using two different techniques, Pt-implantation and Pt-ion exchange. This technology has been demonstrated for a protium (H) and deuterium (D) system, but can also be used for the removal of tritium from contaminated water (T2O, HTO, and DTO) using D2 (or H2)

  17. Evaluation of hydrogen isotope exchange methodology on adsorbents for tritium removal

    SciTech Connect

    Morgan, G.A.; Xin Xiao, S.

    2015-03-15

    The Savannah River National Laboratory has demonstrated a potential process that can be used to remove tritium from tritiated water using Pt-catalyzed molecular sieves. The process is an elemental isotope exchange process in which H{sub 2} (when flowed through the molecular sieves) will exchange with the adsorbed water, D{sub 2}O, leaving H{sub 2}O adsorbed on the molecular sieves. Various formulations of catalyzed molecular sieve material were prepared using two different techniques, Pt-implantation and Pt-ion exchange. This technology has been demonstrated for a protium (H) and deuterium (D) system, but can also be used for the removal of tritium from contaminated water (T{sub 2}O, HTO, and DTO) using D{sub 2} (or H{sub 2}). (authors)

  18. Enhanced stability of low fouling zwitterionic polymer brushes in seawater with diblock architecture.

    PubMed

    Quintana, Robert; Gosa, Maria; Jańczewski, Dominik; Kutnyanszky, Edit; Vancso, G Julius

    2013-08-27

    The successful implementation of zwitterionic polymeric brushes as antifouling materials for marine applications is conditioned by the stability of the polymer chain and the brush-anchoring segment in seawater. Here we demonstrate that robust, antifouling, hydrophilic polysulfobetaine-based brushes with diblock architecture can be fabricated by atom-transfer radical polymerization (ATRP) using initiator-modified surfaces. Sequential living-type polymerization of hydrophobic styrene or methyl methacrylate and commercially available hydrophilic sulfobetaine methacrylamide (SBMAm) monomer is employed. Stability enhancement is accomplished by protecting the siloxane anchoring bond of brushes on the substrate, grafted from silicon oxide surfaces. The degradation of unprotected PSBMAm brushes is clearly evident after a 3 month immersion challenge in sterilized artificial seawater. Ellipsometry and atomic force microscopy (AFM) measurements are used to follow changes in coating thickness and surface morphology. Comparative stability results indicate that surface-tethered poly(methyl methacrylate) and polystyrene hydrophobic blocks substantially improve the stability of zwitterionic brushes in an artificial marine environment. In addition, differences between the hydration of zwitterionic brushes in fresh and salt water are discussed to provide a better understanding of hydration and degradation processes with the benefit of improved design of polyzwitterionic coatings. PMID:23876125

  19. Nitroxide polymer brushes grafted onto silica nanoparticles as cathodes for organic radical batteries

    NASA Astrophysics Data System (ADS)

    Lin, Hsiao-Chien; Li, Chia-Chen; Lee, Jyh-Tsung

    2011-10-01

    Nitroxide polymer brushes grafted on silica nanoparticles as binder-free cathodes for organic radical batteries have been investigated. Scanning electron microscopy, transmission electron microscopy, infrared spectroscopy and electron spin resonance confirm that the nitroxide polymer brushes are successfully grafted onto silica nanoparticles via surface-initiated atom transfer radical polymerization. The thermogravimetric analysis results indicate that the onset decomposition temperature of these nitroxide polymer brushes is found to be ca. 201 °C. The grafting density of the nitroxide polymer brushes grafted on silica nanoparticles is 0.74-1.01 chains nm-2. The results of the electrochemical quartz crystal microbalance indicate that the non-crosslinking nitroxide polymer brushes prevent the polymer from dissolving into organic electrolytes. Furthermore, the electrochemical results show that the discharge capacity of the polymer brushes is 84.9-111.1 mAh g-1 at 10 C and the cells with the nitroxide polymer brush electrodes have a very good cycle-life performance of 96.3% retention after 300 cycles.

  20. Synthesis and Biomedical Applications of Poly((meth)acrylic acid) Brushes.

    PubMed

    Qu, Zhenyuan; Xu, Hong; Gu, Hongchen

    2015-07-15

    Poly((meth)acrylic acid) (P(M)AA) brushes possess a number of distinctive properties that are particularly attractive for biomedical applications. This minireview summarizes recent advances in the synthesis and biomedical applications of P(M)AA brushes and brushes containing P(M)AA segments. First, we review different surface-initiated polymerization (SIP) methods, with a focus on recent progress in the surface-initiated controlled/living radical polymerization (SI-CLRP) techniques used to generate P(M)AA brushes with a tailored structure. Next, we discuss biomolecule immobilization methods for P(M)AA brushes, including physical adsorption, covalent binding, and affinity interactions. Finally, typical biomedical applications of P(M)AA brushes are reviewed, and their performance is discussed based on their unique properties. We conclude that P(M)AA brushes are promising biomaterials, and more potential biomedical applications are expected to emerge with the further development of synthetic techniques and increased understanding of their interactions with biological systems.