Science.gov

Sample records for 110k-calmodulin complex brush

  1. 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.

  2. Polymer brushes infiltrated by nanoparticles and applications to the nuclear pore complex

    NASA Astrophysics Data System (ADS)

    Opferman, Michael G.

    Systems of grafted polymers in the presence of additives are useful in a variety of contexts including industrial applications, solar cells, organic electronics, drug delivery, and nucleocytoplasmic transport. In this thesis, we will consider the morphologies that polymer brushes attain when exposed to a solution of additives (which we generically term "nanoparticles"), particularly when those nanparticles interact attractively with the polymers. We find that nanoparticles of this type can have a dramatic effect on the height of the polymer chains above the grafting surface, and they can induce highly non-uniform morphologies, including ones in which a dense layer of nanoparticles and monomers forms near the grafting surface. We consider especially the relevance of the system to several experiments performed on biopolymers in the nuclear pore complex when they interact attractively with transport factors that regulate nucleocytoplasmic transport. We find that, although these experiments appear to give inconsistent results, the inconsistencies can be reconciled through two simple models: the Alexander-de Gennes polymer brush, and the Milner-Witten-Cates polymer brush. Our findings should contribute to the understanding of the nuclear pore complex in that experiments can be better understood in the context of their relevant control parameters.

  3. Nuclear Pore Complex Protein Sequences Determine Overall Copolymer Brush Structure and Function?

    NASA Astrophysics Data System (ADS)

    Ando, David; Kim, Yongwoon; Zandi, Roya; Colvin, Michael; Rexach, Michael; Gopinathan, Ajay

    2015-03-01

    Disordered proteins are an interesting class of unfolded protein biopolymers which are functionally versatile. Their sequences are unconstrained by a sequence-structure relationship, and allow for a wide range of chemical and physical polymer properties. The Nuclear Pore Complex (NPC) contains over one hundred of such proteins (FG nups), which collectively function to regulate the exchange of all materials between the nucleus and cytoplasm. We perform coarse grained simulations of both individual FG nups and grafted rings of nups mimicking the in vivo geometry of the NPC, supplemented with polymer brush modeling. Our results indicate that different regions or ``blocks'' of an individual FG nup can have distinctly different forms of disorder, and that this property appears to be a conserved feature across eukarya. Furthermore, this block structure at the individual protein level is critical to the formation of a unique higher-order polymer brush architecture. Because the interactions between FG nups may be modulated by certain forms of transport factors, our results indicate that transitions between brush morphologies could play an important role in regulating transport across the NPC, suggesting novel forms of gated transport across membrane pores with wide biomimetic applicability.

  4. A protein complex in the brush-border membrane explains a Hartnup disorder allele.

    PubMed

    Kowalczuk, Sonja; Bröer, Angelika; Tietze, Nadine; Vanslambrouck, Jessica M; Rasko, John E J; Bröer, Stefan

    2008-08-01

    Protein absorption in the intestine is mediated by proteases and brush-border peptidases together with peptide and amino acid transporters. Neutral amino acids are generated by a variety of aminopeptidases and carboxypeptidases and are subsequently taken up by the amino acid transporter B(0)AT1 (SLC6A19), which is mutated in Hartnup disorder. Coexpression of B(0)AT1 together with the brush-border carboxypeptidase angiotensin-converting enzyme 2 (ACE2) in Xenopus laevis oocytes led to a dramatic increase of transporter expression at the oocyte surface. Other members of the SLC6 family were not stimulated by coexpression with ACE2. Addition of a peptide containing a carboxyterminal leucine residue to ACE2- and B(0)AT1-coexpressing oocytes caused inward currents due to Na(+)-leucine cotransport, demonstrating the formation of a metabolic complex. Coexpression of the Hartnup disorder causing mutation B(0)AT1(R240Q) showed reduced interaction with ACE2 and its renal paralogue collectrin. This would result in reduced surface expression in both kidney and intestine, thereby explaining the onset of the disorder in individuals carrying this mutation. PMID:18424768

  5. Complex microstructures of ABC triblock copolymer thin films directed by polymer brushes based on self-consistent field theory.

    PubMed

    Jiang, Zhibin; Xu, Chang; Qiu, Yu Dong; Wang, Xiaoliang; Zhou, Dongshan; Xue, Gi

    2014-01-01

    The morphology and the phase diagram of ABC triblock copolymer thin film directed by polymer brushes are investigated by the self-consistent field theory in three dimensions. The polymer brushes coated on the substrate can be used as a good soft template to tailor the morphology of the block copolymer thin films compared with those on the hard substrates. The polymer brush is identical with the middle block B. By continuously changing the composition of the block copolymer, the phase diagrams are constructed for three cases with the fixed film thickness and the brush density: identical interaction parameters, frustrated and non-frustrated cases. Some ordered complex morphologies are observed: parallel lamellar phase with hexagonally packed pores at surfaces (LAM3 (ll) -HFs), perpendicular lamellar phase with cylinders at the interface (LAM(⊥)-CI), and perpendicular hexagonally packed cylinders phase with rings at the interface (C2 (⊥)-RI). A desired direction (perpendicular or parallel to the coated surfaces) of lamellar phases or cylindrical phases can be obtained by varying the composition and the interactions between different blocks. The phase diagram of ABC triblock copolymer thin film wetted between the polymer brush-coated surfaces is very useful in designing the directed pattern of ABC triblock copolymer thin film. PMID:25114650

  6. Mechanistic Basis of Organization of the Harmonin/USH1C-Mediated Brush Border Microvilli Tip-Link Complex.

    PubMed

    Li, Jianchao; He, Yunyun; Lu, Qing; Zhang, Mingjie

    2016-01-25

    Brush border microvilli are actin-based protrusions lining the apical surface of epithelial cells in intestines and proximal tubules of kidneys. While brush border microvilli resemble the relatively well-characterized stereocilia of hair cells, the mechanistic basis of tip-link complex organization in microvilli is poorly understood. Here, we have biochemically and structurally characterized the following pairs of interactions: protocadherin 24 and Harmonin (also known as USH1C or AIE-75), Harmonin and myosin VIIb (MYO7B), Harmonin and ANKS4B, and ANKS4B and MYO7B. We show that Harmonin, ANKS4B, and MYO7B form a stable ternary complex for anchoring microvilli tip-link cadherins. Despite having only Harmonin in common, the microvilli and the stereocilia tip-link complexes are formed via strikingly similar interaction modes. These results not only provide insight into the mechanistic bases of brush border microvilli formation and maintenance but may also be valuable for understanding some gut and/or kidney diseases caused by perturbations of brush border microvilli structures. PMID:26812017

  7. 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 ...

  8. Ureteral retrograde brush biopsy

    MedlinePlus

    Biopsy - brush - urinary tract; Retrograde ureteral brush biopsy cytology; Cytology - ureteral retrograde brush biopsy ... to be biopsied is rubbed with the brush. Biopsy forceps may be used instead to collect a ...

  9. Stretching a polymer brush by making in situ cyclodextrin inclusion complexes.

    PubMed

    Joseph, Julie; Dreiss, Cécile A; Cosgrove, Terence

    2008-09-16

    The interaction between poly(ethylene oxide) (PEO) chains grafted onto polystyrene latex particles and alpha-, beta-, and gamma-cyclodextrins (CD) was studied by small-angle neutron scattering. The particles were contrast-matched to the solvent in order that only the scattering from the polymer layers was detected. The signal from the layers was fitted to a double-exponential volume fraction profile. The effects of adding cyclodextrin on the polymer profile are shown as a function of cyclodextrin concentration. The polymer layers are seen to extend on addition of CD, which is consistent with a complexation between the grafted PEO and the CD molecules. The effect is the strongest with alpha-CD. PMID:18712892

  10. 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 ...

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. Zwitterionic poly(amino acid methacrylate) brushes.

    PubMed

    Alswieleh, Abdullah M; Cheng, Nan; Canton, Irene; Ustbas, Burcin; Xue, Xuan; Ladmiral, Vincent; Xia, Sijing; Ducker, Robert E; El Zubir, Osama; Cartron, Michael L; Hunter, C Neil; Leggett, Graham J; Armes, Steven P

    2014-07-01

    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

  17. Rotating Brush Seal

    NASA Technical Reports Server (NTRS)

    Lattime, S. B.; Braun, M. J.; Choy. F. K.; Hendricks, R. C.; Steinetz, B. M.

    2006-01-01

    The proven technology of brush seals has been extended to the mitigation of problems arising from friction and wear at the bristle-rotor interface at high surface speeds. In prototype testing, the brush is mounted on, and free to rotate with the shaft, thus providing a complaint primary seal. A face seal positioned between the backing plate of the brush seal and the housing provides a secondary seal. The purpose of this paper is to demonstrate the interaction between the brush bristles and the shaft at high surface speeds as well as introduce a numerical model to simulate the bristle behavior. A test facility was constructed to study the effects of centrifugal forces on bristle deflection in a single rotating brush seal. The bristle-rotor interface was observed through a video camera, which utilized a high magnification borescope and a high frequency strobe light source. Rotational speeds of the rotor and the brush seal were measured by a magnetic and optical speed sensor, respectively. Preliminary results with speeds up to 11,000 rpm show no speed differential between the brush seal and rotor, or any instability problems associated with the brush seal. Bristle liftoff from the rotor is successfully captured on video.

  18. Flow visualization in a simulated brush seal

    NASA Technical Reports Server (NTRS)

    Braun, M. J.; Canacci, V.; Hendricks, R. C.

    1990-01-01

    A method to visualize and characterize the complex flow fields in simulated brush seals is presented. The brush seal configuration was tested in a water and then in an oil tunnel. The visualization procedure revealed typical regions that are rivering, jetting, vortical or lateral flows and exist upstream, downstream or within the seal. Such flows are engendered by variations in fiber void that are spatial and temporal and affect changes in seal leakage and stability. While the effects of interface motion for linear or cylindrical configurations have not been considered herein, it is believed that the observed flow fields characterize flow phenomenology in both circular and linear brush seals. The axial pressure profiles upstream, across and downstream of the brush in the oil tunnel have been measured under a variety of inlet pressure conditions and the ensuing pressure maps are presented and discussed.

  19. 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.

  20. Comb and brush acne.

    PubMed

    Petrozzi, J W

    1980-12-01

    Frequent combing or brushing of the hair may result in an exacerbation of existing acne or be the cause of localized acne. Because of today's hair styling habits and methods, this type of acne is commonly encountered but poorly appreciated by physicians. Patient education is the most important factor in the management of this condition. Comb and brush acne is another external factor to be added to the list of causes of "acne mechanica." PMID:6449356

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Temperature responsive behavior of polymer brush/polyelectrolyte multilayer composites.

    PubMed

    Micciulla, Samantha; Soltwedel, Olaf; Löhmann, Oliver; von Klitzing, Regine

    2016-01-28

    The complex interaction of polyelectrolyte multilayers (PEMs) physisorbed onto end-grafted polymer brushes with focus on the temperature-responsive behavior of the system is addressed in this work. The investigated brush/multilayer composite consists of a poly(styrene sulfonate)/poly(diallyldimethylammonium chloride) (PSS/PDADMAC) multilayer deposited onto the poly(N-isopropylacrylamide-b-dimethylaminoethyl methacrylate) P(NIPAM-b-DMAEMA) brush. Ellipsometry and neutron reflectometry were used to monitor the brush collapse with the thickness decrease as a function of temperature and the change in the monomer distribution perpendicular to the substrate at temperatures below, across and above the phase transition, respectively. It was found that the adsorption of PEMs onto polymer brushes had a hydrophobization effect on PDMAEMA, inducing the shift of its phase transition to lower temperatures, but without suppressing its temperature-responsiveness. Moreover, the diffusion of the free polyelectrolyte chains inside the charged brush was proved by comparing the neutron scattering length density profile of pure and the corresponding PEM-capped brushes, eased by the enhanced contrast between hydrogenated brushes and deuterated PSS chains. The results presented herein demonstrate the possibility of combining a temperature-responsive brush with polyelectrolyte multilayers without quenching the responsive behavior, even though significant interpolyelectrolyte interactions are present. This is of importance for the design of multicompartment coatings, where the brush can be used as a reservoir for the controlled release of substances and the multilayer on the top as a membrane to control the diffusion in/out by applying different stimuli. PMID:26612742

  9. Wire brush fastening device

    SciTech Connect

    Meigs, R.A.

    1993-08-31

    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. 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.

  11. 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.

  12. Interpenetrations in polymer brushes

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Amitabha; Nelson, Peter; Toral, Raúl

    1994-01-01

    We carry out Monte Carlo simulations in both lattice and off-lattice geometry, to study the configurational properties of a system of two polymer-coated plates. We compare our results with numerical and analytical self-consistent-field theories. For the short chain-lengths considered here, we find both compression and interpenetration of the polymer brushes as the plate separation is decreased, instead of the ``classical-limit'' picture of compression with no interpenetration.

  13. Brush seals for cryogenic applications

    NASA Astrophysics Data System (ADS)

    Proctor, Margaret P.

    1994-07-01

    This viewgraph presentation presents test results of brush seals for cryogenic applications. Leakage for a single brush seal was two to three times less than for a 12-tooth labyrinth seal. The maximum temperature rise for a single brush seal was less than 50 R and occurred at 25 psid across the seal and 35,000 rpm. A static blowout test demonstrated sealing capability up to 550 psid. The seal limit was not obtained. The power loss for a single brush at 35,000 rpm and 175 psid was 2.45 hp. Two brushes far apart leak less than two brushes tight packed. Rotor wear was approximately 0.00075 mils and bristle wear was 1-3 mils after 4-1/2 hours.

  14. Brush seals for cryogenic applications

    NASA Technical Reports Server (NTRS)

    Proctor, Margaret P.

    1994-01-01

    This viewgraph presentation presents test results of brush seals for cryogenic applications. Leakage for a single brush seal was two to three times less than for a 12-tooth labyrinth seal. The maximum temperature rise for a single brush seal was less than 50 R and occurred at 25 psid across the seal and 35,000 rpm. A static blowout test demonstrated sealing capability up to 550 psid. The seal limit was not obtained. The power loss for a single brush at 35,000 rpm and 175 psid was 2.45 hp. Two brushes far apart leak less than two brushes tight packed. Rotor wear was approximately 0.00075 mils and bristle wear was 1-3 mils after 4-1/2 hours.

  15. Isolation of renal brush borders.

    PubMed

    Morré, D James; Hammond, Timothy

    2007-03-01

    Methods are described to isolate intact brush borders and brush border membranes from renal cell homogenates. A rapid method yields sealed vesicles that reconstitute renal brush border transport. In one variation of this protocol, 10 to 20 mM CaCl2 or MgCl2 is added to aggregate non-brush border structures for subsequent removal by centrifugation. For analytical studies, guidance is provided for subsequent purification steps including preparative free-flow and aqueous two-phase partition. Marker enzymes and morphological parameters are included for assessment of yield and fraction purity. PMID:18228514

  16. Electrostatically anchored branched brush layers.

    PubMed

    Liu, Xiaoyan; Dedinaite, Andra; Rutland, Mark; Thormann, Esben; Visnevskij, Ceslav; Makuska, Ricardas; Claesson, Per M

    2012-11-01

    A novel type of block copolymer has been synthesized. It consists of a linear cationic block and an uncharged bottle-brush block. The nonionic bottle-brush block contains 45 units long poly(ethylene oxide) side chains. This polymer was synthesized with the intention of creating branched brush layers firmly physisorbed to negatively charged surfaces via the cationic block, mimicking the architecture (but not the chemistry) of bottle-brush molecules suggested to be present on the cartilage surface, and contributing to the efficient lubrication of synovial joints. The adsorption properties of the diblock copolymer as well as of the two blocks separately were studied on silica surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D) and optical reflectometry. The adsorption kinetics data highlight that the diblock copolymers initially adsorb preferentially parallel to the surface with both the cationic block and the uncharged bottle-brush block in contact with the surface. However, as the adsorption proceeds, a structural change occurs within the layer, and the PEO bottle-brush block extends toward solution, forming a surface-anchored branched brush layer. As the adsorption plateau is reached, the diblock copolymer layer is 46-48 nm thick, and the water content in the layer is above 90 wt %. The combination of strong electrostatic anchoring and highly hydrated branched brush structures provide strong steric repulsion, low friction forces, and high load bearing capacity. The strong electrostatic anchoring also provides high stability of preadsorbed layers under different ionic strength conditions. PMID:23046176

  17. Spontaneous Curvature of Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Sheiko, Sergei; da Silva, Marcelo; Shirvaniants, David; Rodrigues, Carlos; Beers, Kathryn; Matyjaszewski, Krzysztof; Potemkin, Igor; Moeller, Martin

    2003-03-01

    Experimental studies of cylindrical brushes on surfaces revealed peculiar shape of brush molecules with a curved backbone. According to scaling analysis, spontaneous bending of the backbone can be driven by entropic elasticity of the side chains: smaller extension of the chains is attained due to their asymmetric distribution with respect to the backbone. An equilibrium, i.e. spontaneous curvature results from the balance of the elasticity of the side chains and the elasticity of the interface. The curvature is predicted to increase with the side chain length. The system is of general interest because cylindrical brushes confined to a flat surface represent a two-dimensional cross-section of a planar brush grafted on both sides. Here we present systematic studies of cylindrical brushes with different length of the side chains. The curvature of cylindrical brushes confined to a flat substrate was investigated by atomic force microscopy. The method allowed visualization of individual molecules and quantitative analysis of their conformation. In agreement with theory, adsorbed brushes demonstrated spontaneous curvature, however the curvature was shown to decrease with the side chain length.

  18. 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.

  19. 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. PMID:25736601

  20. Stimuli Response of Cationic Polymer Brush Prepared by ATRP: Application in Peptide Fractionation.

    PubMed

    Scott, Colleen; Mitrovic, Bojan; Eastwood, Stephanie; Kinsel, Gary

    2014-08-01

    Random cationic copolymer brushes composed of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and N-isopropylacrylamide (NIPAAm) were synthesized using the atom transfer radical polymerization (ATRP) method. The effects of varying the monomer feed ratios (30:70 and 70:30 DMAEMA:NIPAAm) and polymerization times on the film height, morphology and stimuli response to pH of the brush were evaluated. While the polymerization time was found to have little influence on the properties of the brushes, the monomer feed ratios had a great impact. The 70 % DMAEMA polymer brush had similar height as the 30 % DMAEMA brush after 45 min; however, it had a greater response to pH and morphological change compared to the 30 % DMAEMA. The 70 % DMAEMA brush was used to demonstrate an efficient approach to alleviate the ion suppression effect in MALDI analysis of complex mixtures by effectively fractionating a binary mixture of peptides prior to MALDI-MS analysis. PMID:25253913

  1. Stimuli Response of Cationic Polymer Brush Prepared by ATRP: Application in Peptide Fractionation

    PubMed Central

    Scott, Colleen; Mitrovic, Bojan; Eastwood, Stephanie; Kinsel, Gary

    2014-01-01

    Random cationic copolymer brushes composed of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and N-isopropylacrylamide (NIPAAm) were synthesized using the atom transfer radical polymerization (ATRP) method. The effects of varying the monomer feed ratios (30:70 and 70:30 DMAEMA:NIPAAm) and polymerization times on the film height, morphology and stimuli response to pH of the brush were evaluated. While the polymerization time was found to have little influence on the properties of the brushes, the monomer feed ratios had a great impact. The 70 % DMAEMA polymer brush had similar height as the 30 % DMAEMA brush after 45 min; however, it had a greater response to pH and morphological change compared to the 30 % DMAEMA. The 70 % DMAEMA brush was used to demonstrate an efficient approach to alleviate the ion suppression effect in MALDI analysis of complex mixtures by effectively fractionating a binary mixture of peptides prior to MALDI-MS analysis. PMID:25253913

  2. Osmotic and Salted Brush Phase of Polyelectrolyte Brushes

    NASA Astrophysics Data System (ADS)

    Helm, Christane A.; Ahrens, Heiko; Förster, Stephan

    2004-03-01

    Amphiphilic block copolymers consisting of a fluid hydrophobic Poly(ethyletylene) (PEE), and a Poly(styrenesulfonate) (PSS) part form monolayers at the air/water interface. With x-ray reflectivity it is shown that the hydrophobic blocks of PEE_114PSS_83 and PEE_144PSS_136 constitute a nm-thick melt, while the polyelectrolyte forms an osmotically swollen brush with counterion incorporation. A slight thickness increase on monolayer compression is found which can be explained by the strong stretching of the brushes. Only at high salt conditions (above 0.1 M), the brush shrinks and the thickness scales with the molecular area (exponent -1/3), and with the salt concentration (exponent ca. -1/5). With Grazing Incidence Diffraction, the lateral order of the polyelectrolyte chains can be detected.

  3. Cryogenic Brush Seal Test Results

    NASA Technical Reports Server (NTRS)

    Proctor, Margaret P.; Walker, James F.

    1996-01-01

    Brush seals are compliant, contact seals that have long-life, low-leakage characteristics desirable for use in rocket engine turbopumps. 50.8-mm (2.0 inch) diameter brush seals with a nominal initial radial interference of 0.127-mm (0.005 inch) were tested in liquid nitrogen at shaft speeds up to 35,000 rpm and differential pressure loads up to 1.21 MPa (175 psi) per brush. The measured leakage rate of a single brush was 2-3 times less than that measured for a 12-tooth, 0.127-mm (0.005 inch) radial clearance labyrinth seal used as a baseline. Stage effects were studied and it was found that two brush seals with a large separation distance leaked less than two brushes tightly packed together. The maximum measured groove depth on the Inconel 718 rotor was 25.4 (mu)m (0.001 inch) after 4.31 hours of shaft rotation. The Haynes-25 bristles wore approximately 25.4-76.2 (mu)m (0.001-0.003 inch) under the same conditions. Three seal runner coatings, chromium carbide, Teflon impregnated chromium, and zirconium oxide, were tested in liquid hydrogen at 35,000 and 65,000 rpm with separate 50.8 mm diameter brush seals made of Haynes-25 bristles and having a nominal initial radial interference of 129 rpm. Two bare Inconel-718 rotors were also tested as a baseline. The test results revealed significant differences between the wear characteristics of the uncoated and coated seal runners. At both speeds the brush seal with the bare Inconel-718 seal runner exhibited significant bristle wear with excessive material transferring to the runner surface. In contrast, the coated seal runners inhibited the transfer and deposit of bristle material. The chromium carbide coating showed only small quantities of bristle material transferring to its surface. The Teflon impregnated chromium coating also inhibited material transfer and provided some lubrication. This coating, however, is self-sacrificing. The Teflon remained present on the low speed runner, but it was completely removed from the

  4. Mesoscale modeling of polyelectrolyte brushes with salt.

    PubMed

    Ibergay, Cyrille; Malfreyt, Patrice; Tildesley, Dominic J

    2010-06-01

    We report dissipative particle dynamics (DPD) simulations of a polyelectrolyte brush under athermal solvent conditions. The electrostatic interactions are calculated using the particle-particle particle-mesh (PPPM) method with charges distributed over the particles. The polymer beads, counterions, co-ions, and solvent particles are modeled explicitly. The DPD simulations show a dependence of the brush height on the grafting density and the charge fraction that is typical of the nonlinear osmotic brush regime. We report the effect of the addition of salt on the structural properties of the brush. In the case of a polyelectrolyte brush with a high surface coverage, the simulations reproduce the transition between the nonlinear osmotic brush regime where the thickness of the brush is independent of the salt concentration and the salted regime where the brush height decreases weakly with the salt concentration. PMID:20455593

  5. Swelling of polyelectrolyte and polyzwitterion brushes by humid vapors

    NASA Astrophysics Data System (ADS)

    Genzer, Jan; Galvin, Casey; Dimitriou, Michael; Satija, Sushil

    2015-03-01

    Swelling behavior of polyelectrolyte and polyzwitterion brushes derived from poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) in water vapor is investigated using a combination of neutron and X-ray reflectivity and spectroscopic ellipsometry over a wide range of relative humidity (RH) levels. The extent of swelling depends strongly on the nature of the side-chain chemistry. For parent PDMAEMA, there is an apparent enrichment of vapor at the polymer/air interface. Despite extensive swelling at high humidity level, no evidence of charge repulsion is found in weak or strong polyelectrolyte brushes. Polyzwitterionic brushes swell to a greater extent than the quaternized brushes studied. However, for RH levels beyond 70%, the polyzwitterionic brushes start to exclude water molecules, leading to a decline in water volume fraction from the maximum of 0.30 down to 0.10. Using a gradient in polymer chain grafting density, we provide evidence that this behavior stems from the formation of inter- and intramolecular zwitterionic complexes.

  6. 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

  7. Charge transferred in brush discharges

    NASA Astrophysics Data System (ADS)

    Talarek, M.; Kacprzyk, R.

    2015-10-01

    Electrostatic discharges from surfaces of plastic materials can be a source of ignition, when appear in explosive atmospheres. Incendivity of electrostatic discharges can be estimated using the transferred charge test. In the case of brush discharges not all the energy stored at the tested sample is released and the effective surface charge density (or surface potential) crater is observed after the discharge. Simplified model, enabling calculation of a charge transferred during electrostatic brush discharge, was presented. Comparison of the results obtained from the simplified model and from direct measurements of transferred charge are presented in the paper.

  8. 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.

  9. 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

  10. Brush seals for cryogenic applications

    NASA Technical Reports Server (NTRS)

    Proctor, Margaret P.

    1993-01-01

    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.

  11. 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.)

  12. Teach children to brush (image)

    MedlinePlus

    ... child's overall good health. Without proper dental care tooth decay and gum disease can lead to serious problems such as cavities and gingivitis, swollen and bleeding gums. Regular visits to the dentist, brushing twice each day, and flossing, are ways to ...

  13. Polymer brushes for molecular transport

    NASA Astrophysics Data System (ADS)

    Tu, Huilin

    Polymer brushes and self-assembled monolayers (SAMs) are used as solid-state, 2-dimensional transport media to confine molecular diffusion. Microcontact printing and photolithography combined with surface-initiated atom transfer radical polymerization (ATRP) are the major techniques to construct patterned polymer brushes. Fluorescence recovery after photobleaching (FRAP) is used to determine diffusion coefficients of fluorescent dye, Prodan, in the polymer brushes and SAMs. Similar diffusion coefficients of Prodan are found for the SAMs formed by chlorotrimethyl silane (CTS) and silanated poly(ethylene glycol) (PEG). No fluorescence recovery is observed on the octadecyltrichlorosilane (OTS) SAM or on the clean silica surface. Patterned poly(N-isopropylacrylamide) (PNIPAAm) brushes were fabricated on silica substrates by surface-initiated ATRP of N-isopropylacrylamide from a micropatterned initiator. Variable temperature ellipsometry indicated that the lower critical solution temperature (LCST) of the hydrated PNIPAAm brush was broad, occurring over the range of 20-35°C. FRAP results of Prodan in PNIPAAm layers indicate that bulk translational diffusion is very slow relative to other diffusion mechanisms. Poly(oligoethylene glycol acrylate) (POEGA) chains are grafted onto silica substrates by surface-initiated ATRP. The diffusion of Prodan in dry POEGA is very fast, which is attributable to the low glass transition temperature of POEGA. The diffusion of Prodan in POEGA under variable humidity can be described reasonably well using WLF equation. Patterned POEGA brushes are not able to confine Prodan to diffuse exclusively inside the polymer regions, and possible explanations are rotational diffusion and a combination of fast surface diffusion and slow bulk diffusion. PNIPAAm chains are tethered onto silica particles via surface-initiated polymerization. Thermal annealing slightly improved the crystallinity of the colloidal assembly. Video microscopy of the two

  14. Turbine-Driven Pipe-Cleaning Brush

    NASA Technical Reports Server (NTRS)

    Werlink, Rudy J.; Rowell, David E.

    1994-01-01

    Simple pipe-cleaning device includes small turbine wheel axially connected, by standoff, to circular brush. Turbine wheel turns on hub bearing attached to end of upstream cable. Turbine-and-brush assembly inserted in pipe with cable trailing upstream and brush facing downstream. Water or cleaning solution pumped through pipe. Cable held at upstream end, so it holds turbine and brush in pipe at location to be cleaned. Flow in pipe turns turbine, which turns wheel, producing desired cleaning action. In addition to brushing action, device provides even mixing of cleaning solution in pipe.

  15. 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

  16. 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.

  17. 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.

  18. Loop polymer brushes from polymer single crystals

    NASA Astrophysics Data System (ADS)

    Zhou, Tian; Li, Christopher

    2014-03-01

    Loop polymer brushes represent a category of polymer brushes with both chain ends being tethered to a surface or interface with sufficiently high density. Due to this morphological difference, loop brushes exhibit distinct properties compared with traditional polymer brushes with single chain end being tethered. In our study, α, ω-functionalized polycaprolactone (PCL) single crystals were prepared as templates for polymer brush synthesis. By carefully controlling crystallization condition and immobilization, looped polymer brushes were successfully prepared. Comprehensive studies on the morphology and physical properties of these polymer brushes were carried out using Atomic Force Microscopy and FTIR. Advantages of using this method include exclusive loop morphology, high grafting density, controlled tethering sites and tunable loop size.

  19. 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.

  20. Polyelectrolyte brushes: theory, modelling, synthesis and applications.

    PubMed

    Das, Siddhartha; Banik, Meneka; Chen, Guang; Sinha, Shayandev; Mukherjee, Rabibrata

    2015-11-28

    Polyelectrolyte (PE) brushes are a special class of polymer brushes (PBs) containing charges. Polymer chains attain "brush"-like configuration when they are grafted or get localized at an interface (solid-fluid or liquid-fluid) with sufficiently close proximity between two-adjacent grafted polymer chains - such a proximity triggers a particular nature of interaction between the adjacent polymer molecules forcing them to stretch orthogonally to the grafting interface, instead of random-coil arrangement. In this review, we discuss the theory, synthesis, and applications of PE brushes. The theoretical discussion starts with the standard scaling concepts for polymer and PE brushes; following that, we shed light on the state of the art in continuum modelling approaches for polymer and PE brushes directed towards analysis beyond the scaling calculations. A special emphasis is laid in pinpointing the cases for which the PE electrostatic effects can be de-coupled from the PE entropic and excluded volume effects; such de-coupling is necessary to appropriately probe the complicated electrostatic effects arising from pH-dependent charging of the PE brushes and the use of these effects for driving liquid and ion transport at the interfaces covered with PE brushes. We also discuss the atomistic simulation approaches for polymer and PE brushes. Next we provide a detailed review of the existing approaches for the synthesis of polymer and PE brushes on interfaces, nanoparticles, and nanochannels, including mixed brushes and patterned brushes. Finally, we discuss some of the possible applications and future developments of polymer and PE brushes grafted on a variety of interfaces. PMID:26399305

  1. Positron annihilation spectroscopy: a new frontier for understanding nanoparticle-loaded polymer brushes

    NASA Astrophysics Data System (ADS)

    Panzarasa, Guido; Aghion, Stefano; Soliveri, Guido; Consolati, Giovanni; Ferragut, Rafael

    2016-01-01

    Nanoparticle-loaded polymer brushes are powerful tools for the development of innovative devices. However, their characterization is challenging and arrays of different techniques are typically required to gain sufficient insight. Here we demonstrate for the first time the suitability of positron annihilation spectroscopy (PAS) to investigate, with unprecedented detail and without making the least damage to samples, the physico-chemical changes experienced by pH-responsive polymer brushes after protonation and after loading of silver nanoparticles. One of the most important findings is the depth profiling of silver nanoparticles inside the brushes. These results open up a completely new way to understand the structure and behavior of such complex systems.

  2. 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.

  3. 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.

  4. Brush seals for turbine engine fuel conservation

    NASA Technical Reports Server (NTRS)

    Sousa, Mike

    1994-01-01

    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.

  5. 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.

  6. Nanopatterned polymer brushes: conformation, fabrication and applications.

    PubMed

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

    2016-01-14

    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. PMID:26648412

  7. 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.

  8. Arbitrary and Parallel Nanofabrication of 3D Metal Structures with Polymer Brush Resists.

    PubMed

    Chen, Chaojian; Xie, Zhuang; Wei, Xiaoling; Zheng, Zijian

    2015-12-01

    3D polymer brushes are reported for the first time as ideal resists for the alignment-free nanofabrication of complex 3D metal structures with sub-100 nm lateral resolution and sub-10 nm vertical resolution. Since 3D polymer brushes can be serially fabricated in parallel, this method is effective to generate arbitrary 3D metal structures over a large area at a high throughput. PMID:26439441

  9. Controlled Synthesis of Polymer Brushes via Polymer Single Crystal Templates

    NASA Astrophysics Data System (ADS)

    Zhou, Tian

    A novel synthetic method of polymer brushes using polymer single crystals (PSCs) as solid-state templates is introduced in this study. PSC has a quasi-2D lamellae structure with polymer chains fold back-and-forth perpendicular to the lamellae surfaces. During crystallization, the chain ends are excluded from the unit cell onto the lamellae surfaces, which makes the material extremely versatile in its functionality. Such structure holds the unique capability to harvest nanoparticles, or being immobilized onto macroscopic flat surfaces. After dissolving PSCs in good solvent, polymer brushes are chemically tethered on either nanoparticles or flat macroscopic surfaces. Because the chain-folding structure can be conveniently tailored by changing the molecular weight of polymer and the crystallization temperature, the thickness, grafting density and morphology of resulted polymer brushes can be precisely controlled. As a model system, poly(?-caprolactone) with thiol or alkoxysilane terminal groups was used, and polymer brushes were successfully prepared on both nanoparticles and glass/Au flat surfaces. The structure-property relationships of the as-prepared polymer brushes were studied in detail using multiple characterization techniques. First of all, when functionalizing nanoparticles, by engineering the chain-folding structure of the PSCs, interesting complex nanostructures can be formed by nanoparticles including Janus nanoparticles and nanoparticle dimers. These unique structures render hybrid nanoparticles very interesting responsive behavior which have been studied in detail in this dissertation. When grafted onto a flat surface on the other hand, not only the molecular weight and grafting density can be precisely controlled, the tethering points of a single polymer chain can also be conveniently tailored, resulting polymer brushes with either tail or loop structures. Such difference in brush structure can significantly alter the properties of functional surface

  10. Compression induced phase transition of nematic brush: A mean-field theory study

    NASA Astrophysics Data System (ADS)

    Tang, Jiuzhou; Zhang, Xinghua; Yan, Dadong

    2015-11-01

    Responsive behavior of polymer brush to the external compression is one of the most important characters for its application. For the flexible polymer brush, in the case of low grafting density, which is widely studied by the Gaussian chain model based theory, the compression leads to a uniform deformation of the chain. However, in the case of high grafting density, the brush becomes anisotropic and the nematic phase will be formed. The normal compression tends to destroy the nematic order, which leads to a complex responsive behaviors. Under weak compression, chains in the nematic brush are buckled, and the bending energy and Onsager interaction give rise to the elasticity. Under deep compression, the responsive behaviors of the nematic polymer brush depend on the chain rigidity. For the compressed rigid polymer brush, the chains incline to re-orientate randomly to maximize the orientational entropy and its nematic order is destroyed. For the compressed flexible polymer brush, the chains incline to fold back to keep the nematic order. A buckling-folding transition takes place during the compressing process. For the compressed semiflexible brush, the chains are collectively tilted to a certain direction, which leads to the breaking of the rotational symmetry in the lateral plane. These responsive behaviors of nematic brush relate to the properties of highly frustrated worm-like chain, which is hard to be studied by the traditional self-consistent field theory due to the difficulty to solve the modified diffusion equation. To overcome this difficulty, a single chain in mean-field theory incorporating Monte Carlo simulation and mean-field theory for the worm-like chain model is developed in present work. This method shows high performance for entire region of chain rigidity in the confined condition.

  11. Compression induced phase transition of nematic brush: A mean-field theory study

    SciTech Connect

    Tang, Jiuzhou; Zhang, Xinghua; Yan, Dadong

    2015-11-28

    Responsive behavior of polymer brush to the external compression is one of the most important characters for its application. For the flexible polymer brush, in the case of low grafting density, which is widely studied by the Gaussian chain model based theory, the compression leads to a uniform deformation of the chain. However, in the case of high grafting density, the brush becomes anisotropic and the nematic phase will be formed. The normal compression tends to destroy the nematic order, which leads to a complex responsive behaviors. Under weak compression, chains in the nematic brush are buckled, and the bending energy and Onsager interaction give rise to the elasticity. Under deep compression, the responsive behaviors of the nematic polymer brush depend on the chain rigidity. For the compressed rigid polymer brush, the chains incline to re-orientate randomly to maximize the orientational entropy and its nematic order is destroyed. For the compressed flexible polymer brush, the chains incline to fold back to keep the nematic order. A buckling-folding transition takes place during the compressing process. For the compressed semiflexible brush, the chains are collectively tilted to a certain direction, which leads to the breaking of the rotational symmetry in the lateral plane. These responsive behaviors of nematic brush relate to the properties of highly frustrated worm-like chain, which is hard to be studied by the traditional self-consistent field theory due to the difficulty to solve the modified diffusion equation. To overcome this difficulty, a single chain in mean-field theory incorporating Monte Carlo simulation and mean-field theory for the worm-like chain model is developed in present work. This method shows high performance for entire region of chain rigidity in the confined condition.

  12. 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.

  13. 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 DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1090 Haidinger brush. (a) Identification. A...

  14. 21 CFR 884.1100 - Endometrial brush.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Endometrial brush. 884.1100 Section 884.1100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES OBSTETRICAL AND GYNECOLOGICAL DEVICES Obstetrical and Gynecological Diagnostic Devices § 884.1100 Endometrial brush. (a) Identification....

  15. 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 DEVICES OBSTETRICAL AND GYNECOLOGICAL DEVICES Obstetrical and Gynecological Diagnostic Devices § 884.1100 Endometrial brush. (a) Identification....

  16. 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.

  17. 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. PMID:26026947

  18. Semiflexible polymer brushes and the brush-mushroom crossover.

    PubMed

    Egorov, Sergei A; Hsu, Hsiao-Ping; Milchev, Andrey; Binder, Kurt

    2015-04-01

    Semiflexible polymers end-grafted to a repulsive planar substrate under good solvent conditions are studied by scaling arguments, computer simulations, and self-consistent field theory. Varying the chain length N, persistence length lp, and grafting density σg, the chain linear dimensions and distribution functions of all monomers and of the free chain ends are studied. Particular attention is paid to the limit of very small σg, where the grafted chains behave as "mushrooms" no longer interacting with each other. Unlike a flexible mushroom, which has a self-similar structure from the size (a) of an effective monomer up to the mushroom height (h/a ∝ N(v), ν ≈ 3/5), a semiflexible mushroom (like a free semiflexible chain) exhibits three different scaling regimes, h/a ∝ N for contour length L = Na < lp, a Gaussian regime, h/a ∝ (Llp)(1/2)/a for lp ≪ L ≪ R* ∝ (lp(2)/a), and a regime controlled by excluded volume, h/a ∝ (lp/a)(1/5)N(ν). The semiflexible brush is predicted to scale as h/a ∝ (lpaσg)(1/3)N in the excluded volume regime, and h/a ∝ (lpa(3)σ(2))(1/4)N in the Gaussian regime. Since in the volume taken by a semiflexible mushroom excluded-volume interactions are much weaker in comparison to a flexible mushroom, there occurs an additional regime where semiflexible mushrooms overlap without significant chain stretching. Moreover, since the size of a semiflexible mushroom is much larger than the size of a flexible mushroom with the same N, the crossover from mushroom to brush behavior is predicted to take place at much smaller densities than for fully flexible chains. The numerical results, however, confirm the scaling predictions only qualitatively; for chain lengths that are relevant for experiments, often intermediate effective exponents are observed due to extended crossovers. PMID:25687784

  19. Brushing Your Child’s Teeth

    MedlinePlus

    ... the toothpaste rather than swallowing it. For children under age 3, use just a small amount of toothpaste ... floss and brush your teeth every day. Children under age 6 may be able to handle a toothbrush ...

  20. 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. PMID:25994486

  1. 3D-patterned polymer brush surfaces

    NASA Astrophysics Data System (ADS)

    Zhou, Xuechang; Liu, Xuqing; Xie, Zhuang; Zheng, Zijian

    2011-12-01

    Polymer brush-based three-dimensional (3D) structures are emerging as a powerful platform to engineer a surface by providing abundant spatially distributed chemical and physical properties. In this feature article, we aim to give a summary of the recent progress on the fabrication of 3D structures with polymer brushes, with a particular focus on the micro- and nanoscale. We start with a brief introduction on polymer brushes and the challenges to prepare their 3D structures. Then, we highlight the recent advances of the fabrication approaches on the basis of traditional polymerization time and grafting density strategies, and a recently developed feature density strategy. Finally, we provide some perspective outlooks on the future directions of engineering the 3D structures with polymer brushes.

  2. 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.

  3. Water driven turbine/brush pipe cleaner

    NASA Astrophysics Data System (ADS)

    Werlink, Rudy J.

    1995-04-01

    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.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. Performance characteristics of brush seals for limited-life engines

    SciTech Connect

    Chupp, R.E. ); Dowler, C.A. )

    1993-04-01

    Brush seals are potential replacements for air-to-air labyrinth seals in gas turbine engines. An investigation has been conducted to determine the performance characteristics of brush seals for application in limited-life gas turbine engines. An elevated temperature, rotating test rig was designed and built to test labyrinth and brush seals in simulated subsonic and supersonic engine conditions. Results from initial tests for subsonic applications demonstrated that brush seals exhibit appreciably lower leakage compared to labyrinth seals, and thus offer significant engine performance improvements. Performance results have been obtained showing the effect of various brush seal parameters, including: initial interference, backplate gap, and multiple brush seals in series.

  9. Regression modeling and prediction of road sweeping brush load characteristics from finite element analysis and experimental results.

    PubMed

    Wang, Chong; Sun, Qun; Wahab, Magd Abdel; Zhang, Xingyu; Xu, Limin

    2015-09-01

    Rotary cup brushes mounted on each side of a road sweeper undertake heavy debris removal tasks but the characteristics have not been well known until recently. A Finite Element (FE) model that can analyze brush deformation and predict brush characteristics have been developed to investigate the sweeping efficiency and to assist the controller design. However, the FE model requires large amount of CPU time to simulate each brush design and operating scenario, which may affect its applications in a real-time system. This study develops a mathematical regression model to summarize the FE modeled results. The complex brush load characteristic curves were statistically analyzed to quantify the effects of cross-section, length, mounting angle, displacement and rotational speed etc. The data were then fitted by a multiple variable regression model using the maximum likelihood method. The fitted results showed good agreement with the FE analysis results and experimental results, suggesting that the mathematical regression model may be directly used in a real-time system to predict characteristics of different brushes under varying operating conditions. The methodology may also be used in the design and optimization of rotary brush tools. PMID:26123978

  10. 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).

  11. Two-stage eutectic metal brushes

    DOEpatents

    Hsu, John S [Oak Ridge, TN

    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.

  12. 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

  13. Improved molybdenum disulfide-silver motor brushes have extended life

    NASA Technical Reports Server (NTRS)

    Horton, J. C.; King, H. M.

    1964-01-01

    Motor brushes of proper quantities of molybdenum disulfide and copper or silver are manufactured by sintering techniques. Graphite molds are used. These brushes operate satisfactorily for long periods in normal atmosphere or in a high-vacuum environment.

  14. Plasticity of the brush border - the yin and yang of intestinal homeostasis.

    PubMed

    Delacour, Delphine; Salomon, Julie; Robine, Sylvie; Louvard, Daniel

    2016-03-01

    The brush border on the apical surface of enterocytes is a highly specialized structure well-adapted for efficient digestion and nutrient transport, whilst at the same time providing a protective barrier for the intestinal mucosa. The brush border is constituted of a densely ordered array of microvilli, protrusions of the plasma membrane, which are supported by actin-based microfilaments and interacting proteins and anchored in an apical network of actomyosin and intermediate filaments, the so-called terminal web. The highly dynamic, specialized apical domain is both an essential partner for the gut microbiota and an efficient signalling platform that enables adaptation to physiological stimuli from the external and internal milieu. Nevertheless, genetic alterations or various pathological stresses, such as infection, inflammation, and mechanical or nutritional alterations, can jeopardize this equilibrium and compromise intestinal functions. Long-time neglected, the intestinal brush-border shall be enlightening again as the central actor of the complex but essential intestinal homeostasis. Here, we review the processes and components involved in brush border organization and discuss pathological mechanisms that can induce brush border defects and their physiological consequences. PMID:26837713

  15. "Long life" DC brush motor for use on the Mars surveyor program

    NASA Technical Reports Server (NTRS)

    Braun, David; Noon, Don

    1998-01-01

    DC brush motors have several qualities which make them very attractive for space flight applications. Their mechanical commutation is simple and lightweight, requiring no external sensing and control in order to function properly. They are extremely efficient in converting electrical energy into mechanical energy. Efficiencies over 80% are not uncommon, resulting in high power throughput to weight ratios. However, the inherent unreliability and short life of sliding electrical contacts, especially in vacuum, have driven previous programs to utilize complex brushless DC or the less efficient stepper motors. The Mars Surveyor Program (MSP'98) and the Shuttle Radar Topography Mission (SRTM) have developed a reliable "long life" brush type DC motor for operation in low temperature, low pressure CO2 and N2, utilizing silver-graphite brushes. The original intent was to utilize this same motor for SRTM's space operation, but the results thus far have been unsatisfactory in vacuum. This paper describes the design, test, and results of this development.

  16. 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.

  17. Improvement of rotating brushes for surface cleaning

    NASA Astrophysics Data System (ADS)

    Baryshev, E. S.

    The general design, operation, and performance characteristics of the currently used aircraft-washing machines are briefly reviewed, and areas that need improvement are identified. In particular, specific recommendations are given concerning the improvement of the design of rotating brushes as one of the possible ways of improving the efficiency of mechanized washing.

  18. 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

  19. 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…

  20. 21 CFR 884.1100 - Endometrial brush.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... perforation, or a recent cesarean section, and (3) Design and testing: (i) The sampling component is covered... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Endometrial brush. 884.1100 Section 884.1100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED)...

  1. 21 CFR 884.1100 - Endometrial brush.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... perforation, or a recent cesarean section, and (3) Design and testing: (i) The sampling component is covered... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Endometrial brush. 884.1100 Section 884.1100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED)...

  2. 21 CFR 884.1100 - Endometrial brush.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... perforation, or a recent cesarean section, and (3) Design and testing: (i) The sampling component is covered... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Endometrial brush. 884.1100 Section 884.1100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED)...

  3. Multifunctional brushes made from carbon nanotubes

    NASA Astrophysics Data System (ADS)

    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.

  4. Charge Transport Properties in Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Moog, Mark; Tsui, Frank; Vonwald, Ian; You, Wei

    Electrical transport properties in poly(3-methyl)thiophene (P3MT) brushes have been studied. The P3MT brushes correspond to a new type of surface-tethered, vertically oriented conjugated molecular wires, sandwiched between two metallic electrodes to form the electrode-molecule-electrode (EME) devices. P3MT is a highly conjugated polymer, a ''workhorse'' material for organic electronics and photonics. The P3MT brushes were grown on ITO surfaces with controlled length (between 2 and 100 nm). The top electrodes were transfer-printed Au films with lateral dimensions between 200 nm and 50 μm. I-V and differential conductance measurements were performed using conductive AFM and 4-terminal techniques. Tunneling and field-emission measurements in EME devices with molecular lengths < 5 nm show HOMO mediated direct hole tunneling with energy barriers of 0.3 and 0.5 eV at the respective interfaces with ITO and Au. The transport properties in longer brushes are indicative of the two quasi-Ohmic interfaces with a characteristic offset in the conductance minimum of 0.12 V biased toward the ITO. Temperature dependent parameters have been examined at various molecular lengths. The drift mobility and the interplay between intra- and intermolecular transport have been investigated.

  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 PMID:27232497

  6. Adhesion and friction properties of polymer brushes: fluoro versus nonfluoro polymer brushes at varying thickness.

    PubMed

    Bhairamadgi, Nagendra S; Pujari, Sidharam P; Leermakers, Frans A M; van Rijn, Cees J M; Zuilhof, Han

    2014-03-01

    A series of different thicknesses of fluoro poly(2,2,2-trifluoroethyl methacrylate) and its analogous nonfluoro poly(ethyl methacrylate) polymer brushes were prepared via surface-initiated ATRP (SI-ATRP) on Si(111) surfaces. The thiol-yne click reaction was used to immobilize the SI-ATRP initiator with a high surface coverage, in order to achieve denser polymer brushes (grafting density from ~0.1 to 0.8 chains/nm(2)). All polymer brushes were characterized by static water contact angle measurements, infrared absorption reflection spectroscopy, and X-ray photoelectron spectroscopy. Adhesion and friction force measurements were conducted with silica colloidal probe atomic force microscopy (CP-AFM) under ambient and dry (argon) conditions. The fluoro poly(2,2,2-trifluoroethyl methacrylate) polymer showed a decrease in adhesion and friction with increasing thickness. The analogous nonfluoro poly(ethyl methacrylate) polymer brushes showed high adhesion and friction under ambient conditions. Friction coefficients down to 0.0057 (ambient conditions) and 0.0031 (dry argon) were obtained for poly(2,2,2-trifluoroethyl methacrylate) polymer brushes with 140 nm thickness, which are the lowest among these types of polymer brushes. PMID:24555721

  7. 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.

  8. 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.

  9. 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.

  10. New Development of Monte Carlo Techniques for Studying Bottle-brush Polymers

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiao-Ping

    Due to the complex characteristics of bottle-brush polymers, it became a challenge to develop an e_cient algorithm for studying such macromolecules under various solvent conditions or some constraints in the space by using computer simulations. In the limit of a bottle-brush polymer with a rather sti_ backbone (straight rigid backbone), we generalize the variant of the biased chain growth algorithm, the pruned-enriched Rosenbluth method, for simulating polymers with complex architecture, from star polymers to bottle-brush polymers, on the simple cubic lattice. With the high statistics of our Monte Carlo results, we check the theoretical predictions of side chain behavior and radial monomer density profile. For the comparison of the experimental data for bottle-brush polymers with a flexible backbone and flexible side chains, based on the bond fluctuation model we propose another fast Monte Carlo algorithm combining the local moves, the pivot move, and an adjustable simulation lattice box. By monitoring the autocorrelation functions of gyration radii for the side chains and for the backbone, we see that for fixed side chain length there is no change in the behavior of these two functions as the backbone length increases. Our extensive results cover the range which is accessible for the comparison to experimental data and for the checking of the theoretically predicted scaling laws.

  11. Effect of brushing on fluoride release from 3 bracket adhesives.

    PubMed

    Staley, Robert N; Mack, Steven J; Wefel, James S; Vargas, Marcos A; Jakobsen, Jane R

    2004-09-01

    The purpose of this in vitro study was to compare fluoride ion release from 3 orthodontic bracket adhesives with and without brushing the bracketed teeth with a fluoridated dentifrice. The bracket adhesives included a light-cured composite resin (Transbond; 3M Unitek, Monrovia, Calif), a fluoride-releasing composite resin (Advance; L D Caulk Division, Dentsply International, Milford, Del), and a resin-modified glass ionomer (Fuji Ortho LC; GC America, Alsip, Ill). The teeth in the control group were not bonded with brackets. Sixty extracted human teeth were randomly assigned to 6 groups of 10 each: (1) Transbond, brushed; (2) Advance, brushed; (3) Advance, not brushed; (4) Fuji, brushed; (5) Fuji, not brushed; and (6) control, brushed. After bonding, each tooth was placed in a sealed plastic test tube containing 4 ml of deionized water. The toothpaste used in brushing contained 0.15% weight per volume sodium fluoride, 1500 parts per million parts fluoride (Winter-fresh gel; Colgate-Palmolive Co., New York, NY). Brushing began 24 hours after the teeth were bonded and placed in deionized water. After brushing, the teeth were thoroughly rinsed with deionized water and returned to a sealed test tube. Fluoride measurements were taken before brushing began, at intervals of 72 hours for 22 days, and 90 and 93 days after bonding. Findings included: (1) brushing significantly increased the release of fluoride ions from the teeth in the composite resin and control groups, (2) the enamel crowns of the unbonded control teeth absorbed and re-released a substantial amount of fluoride ions obtained from the toothpaste, (3) the brushed group of teeth bonded with the fluoride-releasing composite resin released significantly more fluoride on the last 4 days that measurements were taken after brushing than the nonbrushed group bonded with the same adhesive, (4) the brushed group of teeth bonded with the resin-modified glass ionomer released significantly more fluoride on the last 4

  12. 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.

  13. Mechanisms for nano particle removal in brush scrubber cleaning

    NASA Astrophysics Data System (ADS)

    Huang, Yating; Guo, Dan; Lu, Xinchun; Luo, Jianbin

    2011-01-01

    A model describing the nano particle (<100 nm) removal behavior in brush scrubber cleaning is presented based on experiment results and theoretical analysis. The forces on the particles in different situations are analyzed and discussed. The adhesion forces of the van der Waals force, the electrostatic force, the brush load and the static friction between the particle and the wafer are calculated. The contact elastic force, hydrodynamic drag force and friction between the brush and the particle are considered as removal forces and are evaluated. The porous structure and roughness surface of brush material are considered in the hydrodynamic model to describe the brush deformation and the flow field in the cleaning process. The porous structure will result in decrease of hydrodynamic drag force. There are four situations of the particles relative to the brush roughness asperities for which the forces on the particle are different. When the particle is in contact with a brush asperity or on the wafer surface and in a semi-infinite fluid flow field, the particle may be removed by hydrodynamic force and elastic force in the presence of surfactant. When the particle is embedded in the brush asperity, the remove will realized when the friction caused by adhesion between the brush and the particle overcome the adhesion force between particle and wafer surface. The removed particles will be in the flow field or adhered on the brush surface and may redeposit on the wafer surface.

  14. Application of amorphous brush-plated

    NASA Astrophysics Data System (ADS)

    Zheng, M.; Zhu, Y.; Zheng, Z.

    1994-02-01

    The results obtained during industrial trials have shown that the service life of hot work dies can be increased by 33 to 180% using the brush plating technique to prepare amorphous coatings. The coatings possess a much higher hardness, lower friction coefficient at room and elevated temperatures, good scale resistance in addition to higher surface finish, compared to uncoated dies, and thus improve the tribological performance of the dies. In this work, a study of the crystallization process, its kinetics, and the hardness variations of the coatings has been made. According to the data obtained, it can be considered that the main reason for the success of amorphous brush-plated coatings is that, during the operation, crystallization and precipitation takes place instantaneously, which results in a strong secondary hardening effect, thus leading to an increase in the red hardness of the surface layers of dies, therefore ensuring higher thermal wear resistance of the dies.

  15. 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.

  16. 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

  17. Transparent Aluminium Oxide Coatings of Polymer Brushes.

    PubMed

    Micciulla, Samantha; Duan, XiaoFei; Strebe, Julia; Löhmann, Oliver; Lamb, Robert N; von Klitzing, Regine

    2016-04-11

    A novel method for the preparation of transparent Al2 O3 coatings of polymers is presented. An environmental-friendly sol-gel method is employed, which implies mild conditions and low costs. A thermoresponsive brush is chosen as a model surface. X-ray photoelectron spectroscopy is used to characterize the samples during the conversion of the precursor Al(OH)3 into oxide and to prove the mildness of the protocol. The study evidences a relation between lateral homogeneity of alumina and the wettability of the polymer surface by the precursor solution, while morphology and elasticity are dominated by the polymer properties. The study of the swelling behavior of the underneath brush reveals the absence of water uptake, proving the impermeability of the alumina layer. The broad chemical and structural variety of polymers, combined with the robustness of transparent alumina films, makes these composites promising as biomedical implants, protective sheets and components for electric and optical devices. PMID:26991543

  18. Steric interactions between two grafted polymer brushes

    NASA Astrophysics Data System (ADS)

    Ruckenstein, Eli; Li, Buqiang

    1997-07-01

    A lattice model and a generator-matrix method are employed to calculate the interaction force profile between two grafted polymer brushes. The correlation between neighboring bonds and the interdigitation between the two brushes are taken into account. The calculations show that the effect of incorporating the bond correlations is equivalent to an increase in the value of the polymer-solvent interaction parameter when the bond correlations are ignored. The interdigitation between the two brushes decreases the free energy of the system and consequently results in a smaller steric repulsion. A complete interdigitation occurs at a separation close to half the separation between the two plates for which the interaction force is zero. The model is compared with the experimental interaction force profiles for ten systems which involve poly(2-vinylpyridine)-polyisoprene (PVP-PI), poly(2-vinylpyridine)-polystyrene (PVP-PS) block copolymers as well as end-functionalized polystyrenes (PS-X). For most of the systems, the theoretical predictions are in good agreement with experiment. In addition, the present results are compared with the equations proposed by de Gennes, based on the assumption of a step distribution function for the segment density, and by Milner et al., based on the parabolic distribution of the segment density. Both equations neglected interdigitation. It is shown in this paper that the interdigitation is not negligible and that it can decrease by an order of magnitude the repulsive force.

  19. 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

  20. 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. PMID:26882214

  1. Optical brush: Imaging through permuted probes

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  2. Nanoscale contact mechanics of biocompatible polyzwitterionic brushes.

    PubMed

    Zhang, Zhenyu; Morse, Andrew J; Armes, Steven P; Lewis, Andrew L; Geoghegan, Mark; Leggett, Graham J

    2013-08-27

    Friction force microscopy has been used to demonstrate that biocompatible, lubricious poly(2-(methacryloyloxy)ethylphosphorylcholine) (PMPC) brushes exhibit different frictional properties depending on the medium (methanol, ethanol, 2-propanol, and water; the latter also with different quantities of added salt). The chemical functionalization of the probe (amine-, carboxylic acid-, and methyl-terminated probes were used) is not as important as the medium in determining the contact mechanics. For solvents such as methanol, where the adhesion between AFM probe and PMPC brushes is negligible, a linear friction-load relationship is observed. In contrast, the friction-load plot is nonlinear in ethanol or water, media in which stronger adhesion is measured. For ethanol, the data indicate Johnson-Kendall-Roberts (JKR) mechanics, whereas the Derjaguin-Muller-Toporov (DMT) model provided a good fit for the data acquired in water. Contact mechanics on zwitterionic PMPC brushes immersed in aqueous solutions of varying ionic strength followed the same trend, with high adhesion energies being correlated with a nonlinear friction-load relationship. These results can be rationalized by treating the friction force as the sum of a load-dependent term, attributed to molecular plowing, and an area-dependent shear term. In a good solvent for PMPC such as methanol, the shear term is negligible and the sliding interaction is dominated by molecular plowing. However, the adhesion energy is significantly larger in water and ethanol and the shear term is no longer negligible. PMID:23855771

  3. Polymer-brush lubrication: a review of recent theoretical advances.

    PubMed

    Kreer, T

    2016-04-13

    This review compiles recent theoretical advances to describe compressive and shear forces of polymer-brush bilayers, which consist of two opposing brushes in contact. Such model systems for polymer-brush lubrication are frequently used as a benchmark to gain insight into biological problems, e.g., synovial joint lubrication. Based on scaling theory, I derive conformational and collective properties of polymer-brush bilayers in equilibrium and out-of-equilibrium situations, such as shear forces in the linear and nonlinear response regimes of stationary shear and under non-stationary shear. Furthermore, I discuss the influence of macromolecular inclusions and electrostatic interactions on polymer-brush lubrication. Comparisons to alternative analytical approaches, experiments and numerical results are performed. Special emphasis is given to methods for simulating polymer-brush bilayers using molecular dynamics simulations. PMID:27029521

  4. Entanglements of End Grafted Polymer Brushes in a Polymeric Matrix

    NASA Astrophysics Data System (ADS)

    Grest, Gary S.; Hoy, Robert S.

    2007-03-01

    The entanglement of a polymer brush immersed in a melt of mobile polymer chains is studied by molecular dynamics simulations. A primitive path analysis (PPA) is carried out to identify the brush/brush, brush/melt and melt/melt entanglements as a function of distance from the substrate. The PPA characterizes the microscopic state of conformations of the polymer chain and is ideally suited to identify chain/chain entanglements. We use a new thin-chain PPA technique to eliminate spurious non-entangled inter chain contacts arising from excluded volume. As the grafting density of the brush increases we find that the entanglements of the brush with the melt decrease as the system crosses over from the wet to dry brush regime. Results are compared to brush/brush entanglements in an implicit solvent of varying solvent quality. Sandia is a multiprogram laboratory operated by Sandia Corp., a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  5. 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.

  6. Antifouling Properties of Fluoropolymer Brushes toward Organic Polymers: The Influence of Composition, Thickness, Brush Architecture, and Annealing.

    PubMed

    Wang, Zhanhua; Zuilhof, Han

    2016-07-01

    Fluoropolymer brushes are widely used to prevent nonspecific adsorption of commercial polymeric or biological materials due to their strongly hydrophobic character. Herein, a series of fluoropolymer brushes with different compositions, thicknesses and molecular architectures was prepared via surface-initiated atom transfer radical polymerization (ATRP). Subsequently, the antifouling properties of these fluoropolymer brushes against organic polymers were studied in detail using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements and polystyrene as a representative fouling polymer. Among all of the molecular architectures studied, homopolymerized methacrylate-based fluoropolymer brushes (PMAF17) show the best antifouling properties. Annealing the fluoropolymer brushes improves the antifouling property dramatically due to the reregulated surface composition. These fluoropolymer brushes can be combined with, e.g., micro- and nanostructuring and other advanced materials properties to yield even better long-term antifouling behavior under harsh environments. PMID:27332543

  7. 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

  8. 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

  9. Conformational properties of bottle-brush polymers

    NASA Astrophysics Data System (ADS)

    Denesyuk, N. A.

    2003-05-01

    General and renormalized perturbation theories are used to study the conformational properties of a bottle-brush molecule, composed of multiarmed polymer stars grafted regularly onto a flexible backbone. The end-to-end distances of the backbone and of an arm of the middle star are calculated within the first order of perturbation theory. For the high grafting densities of stars, the calculated expressions are generalized with the help of the scaling arguments to give the equivalent power laws. According to these laws, the molecule may adopt a sequence of three different conformations (star-rod-coil) as the length of the backbone grows.

  10. Conformational properties of bottle-brush polymers.

    PubMed

    Denesyuk, N A

    2003-05-01

    General and renormalized perturbation theories are used to study the conformational properties of a bottle-brush molecule, composed of multiarmed polymer stars grafted regularly onto a flexible backbone. The end-to-end distances of the backbone and of an arm of the middle star are calculated within the first order of perturbation theory. For the high grafting densities of stars, the calculated expressions are generalized with the help of the scaling arguments to give the equivalent power laws. According to these laws, the molecule may adopt a sequence of three different conformations (star-rod-coil) as the length of the backbone grows. PMID:12786171

  11. 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

  12. An all-aqueous route to polymer brush-modified membranes with remarkable permeabilites and protein capture rates

    PubMed Central

    Anuraj, Nishotha; Bhattacharjee, Somnath; Geiger, James H.; Baker, Gregory L.; Bruening, Merlin L.

    2011-01-01

    Microporous membranes are attractive for protein purification because convection rapidly brings proteins to binding sites. However, the low binding capacity of such membranes limits their applications. This work reports a rapid, aqueous procedure to create highly permeable, polymer brush-modified membranes that bind large amounts of protein. The synthetic method includes a 10-min adsorption of a macroinitiator in a hydroxylated nylon membrane and a subsequent 5-min aqueous atom transfer radical polymerization of 2-(methacryloyloxy)ethyl succinate from the immobilized initiator to form poly(acid) brushes. This procedure likely leads to more swollen, less dense brushes than polymerization from silane initiators, and thus requires less polymer to achieve the same binding capacity. The hydraulic permeability of the poly(acid) membranes is 4-fold higher than that of similar membranes prepared by growing brushes from immobilized silane initiators. These brush-containing nylon membranes bind 120 mg/cm3 of lysozyme using solution residence times as short as 35 ms, and when functionalized with nitrilotriacetate (NTA)-Ni2+ complexes, they capture 85 mg/cm3 of histidine6-tagged (His-tagged) Ubiquitin. Additionally the NTA-Ni2+-functionalized membranes isolate His-tagged myo-inositol-1-phosphate synthase directly from cell extracts and show >90% recovery of His-tagged proteins. PMID:22287817

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  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 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...

  20. 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...

  1. 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...

  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 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...

  4. 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...

  5. 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...

  6. 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…

  7. 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.

  8. Instability of Liquids in Flexible Fiber Brushes under Applied Pressure.

    PubMed

    Yamamoto, Tetsuya; Meng, Qingan; Liu, Huan; Jiang, Lei; Doi, Masao

    2016-04-01

    We theoretically predict the stability of liquid in a model brush made of flexible fibers for cases in which liquid is supplied from an ink reservoir. The volume of the liquid in the brush increases with increasing applied pressure by the reservoir, and the liquid shows instability at a critical pressure. When the fibers are shorter than a critical length, the end of the brush opens continuously with increasing applied pressure. The volume of the liquid that hangs from the open end of the brush increases with increasing applied pressure, and the liquid drops from the brush at the critical pressure, where the weight of the liquid becomes larger than the surface tension. In contrast, when the fibers are longer than the critical length, the end of the brush opens discontinuously to the maximal extent at the critical pressure. The discontinuous unbuckling is driven by the instability arising from the fact that the bending stiffness of the water surface, which bends together with the flexible fibers, decreases as the end of the brush opens, and it is thus a unique feature of brushes of flexible fibers. PMID:26967664

  9. Surface friction of hydrogels with well-defined polyelectrolyte brushes.

    PubMed

    Ohsedo, Yutaka; Takashina, Rikiya; Gong, Jian Ping; Osada, Yoshihito

    2004-08-01

    Hydrogels of poly(2-hydroxyethyl methacrylate) (PHEMA) with well-defined polyelectrolyte brushes of poly(sodium 4-styrenesulfonate) (PNaSS) of various molecular weights were synthesized, keeping the distance between the polymer brushes constant at ca. 20 nm. The effect of polyelectrolyte brush length on the sliding friction against a glass plate, an electrorepulsive solid substrate, was investigated in water in a velocity range of 7.5 x 10(-5) to 7.5 x 10(-2) m/s. It is found that the presence of polymer brush can dramatically reduce the friction when the polymer brushes are short. With an increase in the length of the polymer brush, this drag reduction effect only works at a low sliding velocity, and the gel with long polymer brushes even shows a higher friction than that of a normal network gel at a high sliding velocity. The strong polymer length and sliding velocity dependence indicate a dynamic mechanism of the polymer brush effect. PMID:15274553

  10. The Effects of a Brushing Procedure on Stereotypical Behavior

    ERIC Educational Resources Information Center

    Davis, Tonya N.; Durand, Shannon; Chan, Jeffrey M.

    2011-01-01

    In this study we analyzed the effects of a brushing protocol on stereotyped behavior of a young boy with autism. First, a functional analysis was conducted which showed that the participant's stereotypy was maintained by automatic reinforcement. Next, the Wilbarger Protocol, a brushing intervention, was implemented. An ABA design was implemented…

  11. 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...

  12. 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...

  13. 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...

  14. 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.

  15. Nanopatterned polymer brushes by reactive writing.

    PubMed

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

    2016-03-31

    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

  16. 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.

  17. 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.

  18. 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

  19. 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.

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

    DOE PAGESBeta

    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

  1. Physicochemical Properties of 'Particle Brush'-Based Materials: Using Polymer Graft Modification to Tailor Particle Interactions

    NASA Astrophysics Data System (ADS)

    Schmitt, Michael D.

    The advent of surface-initiated controlled radical polymerization techniques has allowed a new class of hybrid polymer-grafted nanoparticles, known as eparticle brushes,f to be realized. By grafting polymers from the surface, interactions between particles can be tuned using the precise control over graft architecture (i.e. chain length, dispersity, particle size, and grafting density) afforded by controlled radical polymerizations. Previously, a transition from particle-like to polymer-like interactions in small particles with increasing graft length has been observed. In the limit of long graft lengths, the polymer chains impart new interactions between particles, such as entanglements. These results outline a rich, but largely unexplored parameter space. The present thesis further elucidates the extent to which polymer graft modification facilitates new interaction types between particles and the dependence of those interactions on chain conformation. Specifically, the mechanical properties, processability, phase separation, and vibrational modes of particle brushes are examined. A dependence of the mechanical properties of particle brush assemblies on particle size is accurately captured by accounting for differences in chain conformation between particles of different sizes using a simple scaling model. Further tailoring of mechanical characteristics in weak particle brush assemblies can be achieved using appropriate homopolymer additives to form two-component systems. Improved mechanical properties are accompanied by a significant enhancement in particle processability that allows application of previously unusable processing methods. Considering more complex systems, mesoscale phase separation of nanoparticles is demonstrated for the first time by blending of particle brushes with different graft polymers. Polymer graft modification is seen to not only strengthen and introduce new interactions, but also tune particle properties. Vibrational modes of

  2. 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...

  3. 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

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

  4. 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...

  5. Effectiveness of gutter brushes in removing street sweeping waste.

    PubMed

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

    2010-02-01

    Litter on roadways has to be removed for hygiene and to reduce pollution, amongst other reasons. Therefore, the effective operation of street sweepers is important in the collection of solid waste. In this article, the effectiveness of gutter brushes of street sweepers in removing different debris types, namely medium-size gravel, small and fine particles, and wet thin debris is studied by means of sweeping tests using a brushing test rig. Two types of gutter brushes, cutting and F128, are tested under a variety of operating conditions. The experimental tests provide a means of identifying suitable ranges of brush penetration for the different debris types under defined operating parameters such as brush angle of attack, brush rotational speed, and sweeper velocity. These ranges may provide sufficiently high removal forces and avoid the occurrence of sweeping problems such as backward sweeping and inappropriate bristle-surface contact. Optimum operating parameters for the three debris types studied, as well as a mixture of all of them, are determined. Lastly, the results indicate that, as far as the sweeping effectiveness is concerned, the F128 brush is the preferred one for the cases studied. PMID:19879125

  6. pH- and Electro-Responsive Properties of Poly(acrylic acid) and Poly(acrylic acid)-block-poly(acrylic acid-grad-styrene) Brushes Studied by Quartz Crystal Microbalance with Dissipation Monitoring.

    PubMed

    Borisova, O V; Billon, L; Richter, R P; Reimhult, E; Borisov, O V

    2015-07-14

    We report on the synthesis of novel pH- and electro-responsive polyelectrolyte brushes from a gold substrate by direct one-step nitroxide-mediated polymerization of acrylic acid (AA) or copolymerization of AA and styrene (S). In the latter case, amphiphilic brushes of block-gradient copolymers PAA-b-(PAA-grad-PS) comprising one PAA block and one block with the gradient sequence of AA and S were obtained. The block-gradient copolymers are initiated from the surface by the start of the PAA block. The brushes were characterized by XPS and ellipsometry. (1)H NMR confirmed the gradient sequence of the PAA-grad-PS copolymer block. The pH- and electro-responsive properties of the brushes were studied by quartz crystal microbalance with dissipation monitoring (QCM-D) in combination with electrochemistry. This method provides evidence of swelling of the PAA brushes proportional to the contour length of the chains at elevated pH, whereas the response functions of the block-gradient copolymers are more complex and point to intermolecular aggregation in the brush at low pH. Monitoring of the changes in resonance frequency and dissipation of the QCM-D also demonstrates that application of negative voltage to the substrate leads to swelling of the brush; application of a positive voltage provokes only a transient collapse of the brush in proportion to the applied voltage. PMID:26070329

  7. 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.

  8. 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

  9. Sterilization effects of atmospheric cold plasma brush

    NASA Astrophysics Data System (ADS)

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

    2006-01-01

    This study investigated the sterilization effects of a brush-shaped plasma created at one atmospheric pressure. A population of 1.0×104-1.0×105 Escherichia coli or Micrococcus luteus bacteria was seeded in filter paper media and then subjected to Ar and/or Ar +O2 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.

  10. Brush Lettering II; Commercial and Advertising Art--Intermediate: 9185.01.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    This course outline has been prepared as a guide to help the student gain mastery in the proper brush techniques required for proficiency in brush lettering. The skills of Brush Lettering 1 are a prerequisite. Consisting of 135 clock hours, the course prepares the student to understand brush lettering for poster production and advertising layout.…

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

    PubMed

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

    2015-12-29

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

  12. Flow reduction in microchannels coated with a polymer brush.

    PubMed

    Lanotte, Luca; Guido, Stefano; Misbah, Chaouqi; Peyla, Philippe; Bureau, Lionel

    2012-09-25

    We report on the design of microchannels made of glass capillary coated with polymer brushes elaborated by the so-called "grafting-from" technique. We present measurements of velocity profiles for pressure-driven flows of water in such "hairy" capillaries. We show that the flow reduction induced by the presence of the brush is unexpectedly greater than what could be anticipated from simple geometric arguments on the reduction of the effective capillary diameter or from predictions by models describing the brush layer as a poro-elastic boundary. PMID:22935030

  13. High-Temperature, Flexible, Pressure-Assisted Brush Seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M.; Sirocky, Paul J.

    1993-01-01

    Ceramic-fibers brush and integral spring clip block hot, engine flows. High-temperature, pressure-assisted brush seal installed in movable panel in advanced hypersonic engine. Seal prevents flow of hot engine gas from penetrating gap between movable panel and adjacent stationary panel. Potential applications include sealing gaps in variable-geometry two-dimensional turbojet exhaust nozzles or sealing control surface gaps of hypersonic vehicles. Ceramic brush seals also used as structural seals in high-temperature furnaces or advanced ceramic heat exchangers.

  14. Brush/gold nanoparticle hybrids: effect of grafting density on the particle uptake and distribution within weak polyelectrolyte brushes.

    PubMed

    Christau, Stephanie; Möller, Tim; Yenice, Zuleyha; Genzer, Jan; von Klitzing, Regine

    2014-11-01

    The effect of the brush grafting density on the loading of 13 nm gold nanoparticles (AuNPs) into stimuli-responsive poly(N,N-(dimethylamino ethyl) methacrylate) (PDMAEMA) brushes anchored to flat impenetrable substrates is reported. Atom-transfer radical polymerization (ATRP) is used to grow polymer brushes via a "grafting from" approach from a 2-bromo-2-methyl-N-(3-(triethoxysilyl) propyl) propanamide (BTPAm)-covered silicon substrate. The grafting density is varied by using mixtures of initiator and a "dummy" molecule that is not able to initiate polymerization. A systematic study is carried out by varying the brush grafting density while keeping all of the other parameters constant. X-ray reflectivity is a suitable tool for investigating the spatial structure of the hybrid, and it is combined with scanning electron microscopy and UV/vis spectroscopy to study the particle loading and interpenetration of the particles within the polymer brush matrix. The particle uptake increases with decreasing grafting density and is highest for an intermediate grafting density because more space between the polymer chains is available. For very low grafting densities of PDMAEMA brushes, the particle uptake decreases because of a lack of the polymer matrix for the attachment of particles. The structure of the surface-grafted polymer chains changes after particle attachment. More water is incorporated into the brush matrix after particle immobilization, which leads to a swelling of the polymer chains in the hybrid material. Water can be removed from the brush by decreasing the relative humidity, which leads to brush shrinking and forces the AuNPs to get closer to each other. PMID:25275215

  15. The cell adhesion molecule Fasciclin2 regulates brush border length and organization in Drosophila renal tubules.

    PubMed

    Halberg, Kenneth A; Rainey, Stephanie M; Veland, Iben R; Neuert, Helen; Dornan, Anthony J; Klämbt, Christian; Davies, Shireen-Anne; Dow, Julian A T

    2016-01-01

    Multicellular organisms rely on cell adhesion molecules to coordinate cell-cell interactions, and to provide navigational cues during tissue formation. In Drosophila, Fasciclin 2 (Fas2) has been intensively studied due to its role in nervous system development and maintenance; yet, Fas2 is most abundantly expressed in the adult renal (Malpighian) tubule rather than in neuronal tissues. The role Fas2 serves in this epithelium is unknown. Here we show that Fas2 is essential to brush border maintenance in renal tubules of Drosophila. Fas2 is dynamically expressed during tubule morphogenesis, localizing to the brush border whenever the tissue is transport competent. Genetic manipulations of Fas2 expression levels impact on both microvilli length and organization, which in turn dramatically affect stimulated rates of fluid secretion by the tissue. Consequently, we demonstrate a radically different role for this well-known cell adhesion molecule, and propose that Fas2-mediated intermicrovillar homophilic adhesion complexes help stabilize the brush border. PMID:27072072

  16. The cell adhesion molecule Fasciclin2 regulates brush border length and organization in Drosophila renal tubules

    PubMed Central

    Halberg, Kenneth A.; Rainey, Stephanie M.; Veland, Iben R.; Neuert, Helen; Dornan, Anthony J.; Klämbt, Christian; Davies, Shireen-Anne; Dow, Julian A. T.

    2016-01-01

    Multicellular organisms rely on cell adhesion molecules to coordinate cell–cell interactions, and to provide navigational cues during tissue formation. In Drosophila, Fasciclin 2 (Fas2) has been intensively studied due to its role in nervous system development and maintenance; yet, Fas2 is most abundantly expressed in the adult renal (Malpighian) tubule rather than in neuronal tissues. The role Fas2 serves in this epithelium is unknown. Here we show that Fas2 is essential to brush border maintenance in renal tubules of Drosophila. Fas2 is dynamically expressed during tubule morphogenesis, localizing to the brush border whenever the tissue is transport competent. Genetic manipulations of Fas2 expression levels impact on both microvilli length and organization, which in turn dramatically affect stimulated rates of fluid secretion by the tissue. Consequently, we demonstrate a radically different role for this well-known cell adhesion molecule, and propose that Fas2-mediated intermicrovillar homophilic adhesion complexes help stabilize the brush border. PMID:27072072

  17. Controlled synthesis of photochromic polymer brushes by atom transfer radical polymerization.

    SciTech Connect

    Piech, Marcin; Bell, Nelson Simmons; Long, Timothy Michael

    2005-06-01

    This work reports on the grafting of methyl methacrylate polymer brushes containing spirobenzopyran pendant groups from flat silica surfaces and colloidal particles utilizing atom transfer radical polymerization (ATRP). The reaction conditions were optimized with respect to the kind of surface bound initiator, the type of halide and ligand used in the catalytic complex, the presence/absence of untethered initiator, and solvent type. This enabled synthesis of coatings up to 80 {+-} 3 nm thick with controlled spirobenzopyran content. While polymerization kinetics indicate the presence of chain termination reactions, the 'living' character of the process is confirmed by controlled formation of block copolymer brushes. UV/vis spectroscopy was used to characterize the UV-induced isomerization of spirobenzopyran to zwitterionic merocyanine and the thermal back-reaction. Spectral and kinetic analyses of this latter bleaching process points to the existence of free and associated merocyanines in the polymeric brush in both tetrahydrofuran and toluene. However, stabilization of merocyanine species by the polymer matrix is considerably greater in toluene with thermal back-reaction rates approaching those determined for solid dry films.

  18. Lipid rafts in epithelial brush borders: atypical membrane microdomains with specialized functions.

    PubMed

    Danielsen, E Michael; Hansen, Gert H

    2003-10-31

    Epithelial cells that fulfil high-throughput digestive/absorptive functions, such as small intestinal enterocytes and kidney proximal tubule cells, are endowed with a dense apical brush border. It has long been recognized that the microvillar surface of the brush border is organized in cholesterol/sphingolipid-enriched membrane microdomains commonly known as lipid rafts. More recent studies indicate that microvillar rafts, in particular those of enterocytes, have some unusual properties in comparison with rafts present on the surface of other cell types. Thus, microvillar rafts are stable rather than transient/dynamic, and their core components include glycolipids and the divalent lectin galectin-4, which together can be isolated as "superrafts", i.e., membrane microdomains resisting solubilization with Triton X-100 at physiological temperature. These glycolipid/lectin-based rafts serve as platforms for recruitment of GPI-linked and transmembrane digestive enzymes, most likely as an economizing effort to secure and prolong their digestive capability at the microvillar surface. However, in addition to microvilli, the brush border surface also consists of membrane invaginations between adjacent microvilli, which are the only part of the apical surface sterically accessible for membrane fusion/budding events. Many of these invaginations appear as pleiomorphic, deep apical tubules that extend up to 0.5-1 microm into the underlying terminal web region. Their sensitivity to methyl-beta-cyclodextrin suggests them to contain cholesterol-dependent lipid rafts of a different type from the glycolipid-based rafts at the microvillar surface. The brush border is thus an example of a complex membrane system that harbours at least two different types of lipid raft microdomains, each suited to fulfil specialized functions. This conclusion is in line with an emerging, more varied view of lipid rafts being pluripotent microdomains capable of adapting in size, shape, and content to

  19. 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

  20. 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

  1. 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

  2. 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

  3. 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).

  4. 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.

  5. 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 - ...

  6. Unique Tuft Test Facility Dramatically Reduces Brush Seal Development Costs

    NASA Technical Reports Server (NTRS)

    Fellenstein, James A.

    1997-01-01

    Brush seals have been incorporated in the latest turbine engines to reduce leakage and improve efficiency. However, the life of these seals is limited by wear. Studies have shown that optimal sealing characteristics for a brush seal occur before the interference fit between the brush and shaft is excessively worn. Research to develop improved tribopairs (brush and coating) with reduced wear and lower friction has been hindered by the lack of an accurate, low-cost, efficient test methodology. Estimated costs for evaluating a new material combination in an engine company seal test program are on the order of $100,000. To address this need, the NASA Lewis Research Center designed, built, and validated a unique, innovative brush seal tuft tester that slides a single tuft of brush seal wire against a rotating shaft under controlled loads, speeds, and temperatures comparable to those in turbine engines. As an initial screening tool, the brush seal tuft tester can tribologicaly evaluate candidate seal materials for 1/10th the cost of full-scale seal tests. Previous to the development of the brush seal tuft tester facility, most relevant tribological data had been obtained from full-scale seal tests conducted primarily to determine seal leakage characteristics. However, from a tribological point of view, these tests included the confounding effects of varying contact pressures, bristle flaring, high-temperature oxidation, and varying bristle contact angles. These confounding effects are overcome in tuft testing. The interface contact pressures can be either constant or varying depending on the tuft mounting device, and bristle wear can be measured optically with inscribed witness marks. In a recent cooperative program with a U.S. turbine engine manufacturer, five metallic wire candidates were tested against a plasma-sprayed Nichrome-bonded chrome carbide. The wire materials used during this collaboration were either nickel-chrome- or cobaltchrome-based superalloys. These

  7. 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.

  8. Chinese brushes: controllable liquid transfer in ratchet conical hairs.

    PubMed

    Wang, Qianbin; Su, Bin; Liu, Huan; Jiang, Lei

    2014-07-23

    The controllable liquid transfer of a Chinese brush is attributable to the unique anisotropic multi-scale structures of the freshly emergent hairs. A large mass of liquid an be dynamically balanced within the brush as a cooperative effect of the Laplace pressure difference, the asymmetrical retention force, and gravity. Inspired by this, a device is developed with parallel hairs that allows for direct writing of micro-lines. PMID:24781976

  9. Oral hygiene: a history of tongue scraping and brushing.

    PubMed

    Christen, A G; Swanson, B Z

    1978-02-01

    Tongue scraping and brushing have been practiced for hundreds of years but are still little appreciated or used by the public. Throughout the centuries, tongue scrapers have been constructed of thin, flexible strips of wood, various meals, ivory, mother-of-pearl, whalebone, celluloid, tortoiseshell, and plastic. Recent scientific evidence has validated the need to practice habitual and thorough tongue brushing as part of daily home oral hygiene procedures. PMID:342578

  10. Brush development for underwater ship hull coating maintenance

    NASA Astrophysics Data System (ADS)

    Tribou, Melissa Eileen

    Ship hull grooming has been proposed as an environmentally friendly method of maintaining ship hull coatings in a fouling-free condition. It is defined as the frequent and gentle cleaning of a ship hull coating to prevent the establishment of fouling. This research investigated the grooming tool properties and operational requirements needed to implement the method. The grooming tool needs to provide sufficient force to remove incipient fouling without damaging the surface and consume minimal energy. Research showed that a vertical rotating brush design containing brushes filled with angled polypropylene bristles provided an effective method. This brush system was able to successfully prevent incipient fouling from becoming established on a copper ablative and two silicone fouling release coatings when groomed on a weekly basis; however, biofilm was not completely controlled. Brush design and operational parameters in relation to brush normal forces were investigated and models were developed to understand the relationship between bristle stiffness, dimensions, and angular velocity. A preliminary look at wear found that bristle stiffness has an effect on the degree of marring of the surface of a silicone fouling release coating. The knowledge gained by this research may be used to optimize grooming brush design and operational parameters that can be applied to the design and deployment of low power autonomous underwater vehicles that will groom the ship while in port.

  11. Insertion of nanoparticles into polymer brush under variable solvent conditions.

    PubMed

    Egorov, S A

    2012-10-01

    In this work, two-dimensional lattice-based self-consistent field theory is used to study the free energy cost associated with the insertion of a nanoparticle into a polymer brush. The nanoparticle is modeled as a cylinder and the self-consistent field equations are formulated on a cylindrical lattice. The use of two-dimensional formalism makes it possible to take into account the distortion of the brush density profile due to the embedded nanoinclusion. The insertion free energy penalty is analyzed as a function of the particle size, the brush grafting density, and the solvent quality. In agreement with the earlier simulation work, we find that the insertion free energy cost increases both with the particle size and the brush grafting density and decreases with deteriorating solvent quality. For nanoparticles located deep inside the brush, the insertion free energy is shown to scale with either squared (good solvent) or cubed (poor solvent) monomer volume fraction profile, in agreement with the earlier theoretical results. For shallow nanoinclusions located close to the brush surface, the insertion free energy is shown to scale linearly with the monomer volume fraction profile under both good and theta solvent conditions, again in agreement with the earlier work. PMID:23039611

  12. Insertion of nanoparticles into polymer brush under variable solvent conditions

    NASA Astrophysics Data System (ADS)

    Egorov, S. A.

    2012-10-01

    In this work, two-dimensional lattice-based self-consistent field theory is used to study the free energy cost associated with the insertion of a nanoparticle into a polymer brush. The nanoparticle is modeled as a cylinder and the self-consistent field equations are formulated on a cylindrical lattice. The use of two-dimensional formalism makes it possible to take into account the distortion of the brush density profile due to the embedded nanoinclusion. The insertion free energy penalty is analyzed as a function of the particle size, the brush grafting density, and the solvent quality. In agreement with the earlier simulation work, we find that the insertion free energy cost increases both with the particle size and the brush grafting density and decreases with deteriorating solvent quality. For nanoparticles located deep inside the brush, the insertion free energy is shown to scale with either squared (good solvent) or cubed (poor solvent) monomer volume fraction profile, in agreement with the earlier theoretical results. For shallow nanoinclusions located close to the brush surface, the insertion free energy is shown to scale linearly with the monomer volume fraction profile under both good and theta solvent conditions, again in agreement with the earlier work.

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

    DOE PAGESBeta

    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

  14. Polymer brushes grafted to "passivated" silicon substrates using click chemistry.

    PubMed

    Ostaci, Roxana-Viorela; Damiron, Denis; Capponi, Simona; Vignaud, Guillaume; Léger, Liliane; Grohens, Yves; Drockenmuller, Eric

    2008-03-18

    We present herein a versatile method for grafting polymer brushes to passivated silicon surfaces based on the Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition (click chemistry) of omega-azido polymers and alkynyl-functionalized silicon substrates. First, the "passivation" of the silicon substrates toward polymer adsorption was performed by the deposition of an alkyne functionalized self-assembled monolayer (SAM). Then, three tailor-made omega-azido linear brush precursors, i.e., PEG-N3, PMMA-N3, and PS-N3 (Mn approximately 20,000 g/mol), were grafted to alkyne-functionalized SAMs via click chemistry in tetrahydrofuran. The SAM, PEG, PMMA, and PS layers were characterized by ellipsometry, scanning probe microscopy, and water contact angle measurements. Results have shown that the grafting process follows the scaling laws developed for polymer brushes, with a significant dependence over the weight fraction of polymer in the grafting solution and the grafting time. The chemical nature of the brushes has only a weak influence on the click chemistry grafting reaction and morphologies observed, yielding polymer brushes with thickness of ca. 6 nm and grafting densities of ca. 0.2 chains/nm2. The examples developed herein have shown that this highly versatile and tunable approach can be extended to the grafting of a wide range of polymer (pseudo-) brushes to silicon substrates without changing the tethering strategy. PMID:18247640

  15. Rotordynamic and leakage characteristics of a 4-stage brush seal

    NASA Astrophysics Data System (ADS)

    Conner, K. J.; Childs, D. W.

    1992-12-01

    Experimental results are presented for the direct and cross-coupled stiffness and damping coefficients as well as the leakage performance for a 4-stage brush seal. Variable test parameters include the inlet pressure, pressure ratio, shaft speed, fluid prerotation, and seal spacing. Direct damping is shown to increase with running speed; otherwise, the rotordynamic coefficients are relatively insensitive to changes in the test parameters. Cross-coupled stiffness is generally unchanged by increasing the inlet tangential velocity to the seals, suggesting that the brush seal is not affected by inlet swirl. Direct stiffness is shown to increase with frequency; however, the magnitudes of direct stiffness are always positive. Cross-coupled stiffness increases slightly with frequency; yet not as drastically as direct stiffness. Comparisons of test results for the 4-stage brush seal with an 8-cavity labyrinth showed superior rotordynamics performance for the brush seal; viz., large values for direct stiffness and lower values for the (destabilizing) cross-coupled stiffness coefficient. The damping for brush seals is smaller, but comparable to labyrinth seals. The whirl-frequency ratio is always smaller for the brush seal.

  16. 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

  17. 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.

  18. Dispersion of Mixed Brush Gold Nanorods in Polymer Matrices

    NASA Astrophysics Data System (ADS)

    Ferrier, Robert; Koski, Jason; Riggleman, Robert; Composto, Russell

    In this work we investigate, both experimentally and through hybrid particle/self-consistent field theoretic (hSCFT) calculations, the dispersion state of gold nanorods (AuNRs) grafted with homopolymer, bidispersed, or mixed polymer brushes. AuNRs are grafted with 11.5 kg/mol PS (HNRs), 11.5 kg/mol PS and 5.3 kg/mol PS (BNRs), or 11.5 kg/mol PS and 5 kg/mol poly(methyl methacrylate) (PMMA) (MBNRs) and cast in PS or PMMA films consisting of short to very long chains compared to the grafted brush. We further investigated the MBNR systems by varying the length of the PS brush. Overall, we find that the MBNRs dispersed markedly better than the other brush types (HNRs or BNRs) in PS matrices. We utilize hSCFT calculations, in particular potential of mean force (PMF) and brush profile calculations, to elucidate the thermodynamics of these systems. The PMFs and brush profiles exhibit similar trends for the BNRs and MBNRs where the short grafted chain forces the longer grafted chain away from the AuNR surface and promotes wetting by the matrix chains. The hSCFT calculations demonstrated qualitative trends consistent with the aggregation observed for AuNRs in PMMA matrices. Therefore, we have demonstrated that MBNR dispersion in polymer matrices is enhanced compared to the HNR and BNR cases, which extends the dispersion window for new combinations of nanorods and polymers.

  19. 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.

  20. 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).

  1. 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. PMID:25204365

  2. Response behavior of diblock copolymer brushes in explicit solvent

    NASA Astrophysics Data System (ADS)

    Gong, Kai; Marshall, Bennett D.; Chapman, Walter G.

    2012-10-01

    The understanding of phase behavior of copolymer brushes is of fundamental importance for the design of smart materials. In this paper, we have performed classical density functional theory calculations to study diblock copolymer brushes (A-B) in an explicit solvent which prefers the A block to B block. With increasing B-block length (NB), we find a structural transition of the copolymer brush from mixed to collapsed, partial-exposed, and exposed structure, which is qualitatively consistent with experiments. The phase transitions are attributed to the interplay between entropic cost of folding copolymer brushes and enthalpic effect of contact between unlike components. In addition, we examine the effect of different parameters, such as grafting density (ρg), the bottom block length (NA), and the chain length of solvent (NS) on the solvent response of copolymer brushes. The transition chain length (NB) increases with decreasing ρg and NA, and a smaller solvent molecule makes the collapsed structure less stable due to its lower penetration cost. Our results provide the insight to phase behavior of copolymer brushes in selective solvents from a molecular view.

  3. Spatial control over brush growth through sunlight-induced atom transfer radical polymerization using dye-sensitized TiO2 as a photocatalyst.

    PubMed

    Li, Bin; Yu, Bo; Zhou, Feng

    2014-07-01

    Simulated-sunlight induced atom transfer radical polymerization is used for spatial control over polymer brush growth by in situ photo-generation of the Cu(I) /L activator complex from its higher oxidation state Cu(II) /L deactivator complex using dye sensitized titanium dioxide nano-particles. The polymerization is well controlled under sunlight irradiation. Another attractive feature of this method is the possibility of creating various patterned surfaces of brushes using photomasks. When a nanoporous alumina oxide membrane is used as the template for confinement diffusion of photogenerated Cu(I) /L catalyst, patterns with sub-50 nm resolution are obtained. PMID:24740888

  4. 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

  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. What information can frictional properties of polymer brushes tell us?

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu; Moxey, Mark; Morse, Andrew; Armes, Steven; Lewis, Andrew; Geoghegan, Mark; Leggett, Graham

    2013-03-01

    We have used friction force microscopy (FFM) to quantitatively examine surface grown zwitterionic polymer brushes: poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC), and to establish the correlation between its frictional behaviour to other intrinsic properties. In a good solvent, it was found that the coefficient of friction (μ) decreased with increasing film thickness. We conclude that the amount of bound solvent increases as the brush length increases, causing the osmotic pressure to increase and yielding a reduced tendency for the brush layer to deform under applied load. When measured in a series of alcohol/water mixtures, a significant increase in μ was observed for ethanol/water mixtures at a volume fraction of 90%. This is attributed to brush collapse due to co-nonsolvency, leading to loss of hydration of the brush chains and hence substantially reduced lubrication. We show that single asperity contact mechanics is strongly dependent on solvent quality. Friction-load relationship was found linear in methanol (good solvent), but sub-linear in water and ethanol (moderate solvent).

  7. Supporting awareness through collaborative brushing and linking of tabular data.

    PubMed

    Hajizadeh, Amir Hossein; Tory, Melanie; Leung, Rock

    2013-12-01

    Maintaining an awareness of collaborators' actions is critical during collaborative work, including during collaborative visualization activities. Particularly when collaborators are located at a distance, it is important to know what everyone is working on in order to avoid duplication of effort, share relevant results in a timely manner and build upon each other's results. Can a person's brushing actions provide an indication of their queries and interests in a data set? Can these actions be revealed to a collaborator without substantially disrupting their own independent work? We designed a study to answer these questions in the context of distributed collaborative visualization of tabular data. Participants in our study worked independently to answer questions about a tabular data set, while simultaneously viewing brushing actions of a fictitious collaborator, shown directly within a shared workspace. We compared three methods of presenting the collaborator's actions: brushing & linking (i.e. highlighting exactly what the collaborator would see), selection (i.e. showing only a selected item), and persistent selection (i.e. showing only selected items but having them persist for some time). Our results demonstrated that persistent selection enabled some awareness of the collaborator's activities while causing minimal interference with independent work. Other techniques were less effective at providing awareness, and brushing & linking caused substantial interference. These findings suggest promise for the idea of exploiting natural brushing actions to provide awareness in collaborative work. PMID:24051785

  8. Isolation and characterization of rabbit kidney brush borders

    PubMed Central

    Quirk, S. J.; Robinson, G. B.

    1972-01-01

    1. Brush borders were isolated from rabbit kidney-cortex homogenates by rate-zonal centrifugation through a sucrose density gradient in a B-XIV zonal rotor, followed by differential centrifugation. 2. The method of preparation gave brush borders of high purity with a reasonable yield. The morphological appearance supported the evidence from enzymic and chemical investigations, that the brush borders were only slightly contaminated with endoplasmic reticulum, mitochondria, lysosomes and nuclei. 3. The molar ratio of cholesterol to phospholipid lay within the range found in other plasma membranes, but the carbohydrate content was double that found in liver plasma membranes. 4. Alkaline phosphatase, maltase, trehalase and aminopeptidase were major enzymic constituents of the brush borders, and had an approximately equal yield and enrichment, but none of these enzymes fulfilled the criteria for marker enzymes. 5. Mg2+-dependent and Na+,K+-dependent adenosine triphosphatases, although found in brush borders, had low yields and low enrichments. ImagesPLATE 2PLATE 1 PMID:4264701

  9. 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

  10. Specific ion modulated thermoresponse of poly(N-isopropylacrylamide) brushes.

    PubMed

    Humphreys, Ben A; Willott, Joshua D; Murdoch, Timothy J; Webber, Grant B; Wanless, Erica J

    2016-02-17

    The influence of specific anions on the equilibrium thermoresponse of poly(N-isopropylacrylamide) (pNIPAM) brushes has been studied using in situ ellipsometry, quartz crystal microbalance with dissipation (QCM-D) and static contact angle measurements between 20 and 45 °C in the presence of up to 250 mM acetate and thiocyanate anions in water. The thickness and changes in dissipation exhibited a broad swelling transition spanning approximately 15 °C from collapsed (high temperatures) to swollen conformation (low temperatures) while the brush surface wettability changed over approximately 2 °C. In the presence of the kosmotropic acetate anions, the measured lower critical solution temperature (LCST) by the three techniques was very similar and decreased linearly as a function of ionic strength. Conversely, increasing the concentration of the chaotropic thiocyanate anions raised the LCST of the pNIPAM brushes with variation in the measured LCST between the three techniques increasing with ionic strength. The thickness of the pNIPAM brush was seen to progressively increase with increasing thiocyanate concentration at all temperatures. It is proposed that specific ion binding of the chaotropic thiocyanate anion with pNIPAM amide moieties increases the electrostatic intra- and intermolecular repulsion within and between pNIPAM chains. This allows the brush to begin to swell at higher temperatures and to an overall greater extent. PMID:26840183

  11. Modeling bristle lift-off in idealized brush seal configurations

    NASA Technical Reports Server (NTRS)

    Modi, Vijay

    1993-01-01

    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.

  12. Evaluation of Internal Brushing on Pinch Weld Quality

    SciTech Connect

    Korinko, P

    2005-12-01

    Post machining operations such as borescope inspection can cause linear indications down the length of the bore of fill stems. Often these indications are removed or obscured using rotary wire brushing. This study evaluated the effect this mechanical operation may have on pinch weld quality when relatively cold welds were made. A total of four stems with two levels of brushing of both Type 304L and 21-6-9 stainless steels were tested. In addition, two each of the Type 304L stems were Nitradd cleaned and the other two were aqueously cleaned; all four 21-6-9 stems were aqueously cleaned. All of the brushed stem areas exhibited more surface anomalies based on borescope evaluation. On average, the bond rating was a higher value (worse) for the brushed areas than the unadulterated areas for both Type 304L and 21-6-9 stems. The test method used may have biased the results towards a lesser quality bond for the brushed areas so additional testing is recommended.

  13. Excluded volume effects in compressed polymer brushes: A density functional theory

    SciTech Connect

    Chen, Cangyi; Tang, Ping E-mail: fengqiu@fudan.edu.cn; Qiu, Feng E-mail: fengqiu@fudan.edu.cn; Shi, An-Chang

    2015-03-28

    A classical density functional theory (DFT) is applied to investigate the behavior of compressed polymer brushes composed of hard-sphere chains. The excluded volume interactions among the chain segments are explicitly treated. Two compression systems are used to study the behavior of brush-wall and brush-brush interactions. For the brush-brush systems, an obvious interpenetration zone has been observed. The extent of the interpenetration depends strongly on the grafting density. Furthermore, the repulsive force between the brush and wall or between the two brushes has been obtained as a function of the compression distance. Compared to the prediction of the analytic self-consistent field theory, such force increases more rapidly in the brush-wall compression with high polymer grafting densities or at higher compressions. In the brush-brush compression system, the interpenetration between the two compressed brushes creates a “softer” interaction. The influence of hard-sphere solvents on the behavior of compressed brushes is also discussed.

  14. Chemical and structural changes in a pH-responsive mixed polyelectrolyte brush studied by infrared ellipsometry.

    PubMed

    Hinrichs, Karsten; Aulich, Dennis; Ionov, Leonid; Esser, Norbert; Eichhorn, Klaus-Jochen; Motornov, Mikhail; Stamm, Manfred; Minko, Sergiy

    2009-09-15

    This work provides direct chemical and structural insight into pH-dependent changes of an ultrathin (d=12 nm) mixed polyelectrolyte brush. In-situ infrared spectroscopic ellipsometry was used for the first time to study the gradual pH-responsive behavior of the brush, constituted of weak anionic and cationic polyelectrolytes, poly(acrylic acid) (PAA) and poly(2-vinylpyridine) (P2VP), respectively. The pH-dependent infrared fingerprints in the mid-infrared spectral range were analyzed as a function of chemical and structural changes in the mixed brush caused by pH changes. Thereby, the IR spectra were directly correlated to different chemical states of the brush, giving previously not accessible new information on the ionization of the thin film. In contrast to other techniques (e.g., classical attenuated total reflection IR spectroscopy) we used almost plane Si-substrates for the IR ellipsometric approach with application of a single reflection mode. The optical path through Si is of minimal length, which makes a large spectral range accessible. For the most pronounced bands of the carboxyl group at 1718 cm(-1) and the carboxylate ion at 1565 cm(-1), the band amplitudes were correlated with the degree of ionization of the carboxylic groups. Interpretation of the pH-dependent changes in the spectral signature reveals gradual changes of the chemical structures of the mixed brush between three distinct switchable states: strongly ionized PAA at pH 10, strongly ionized P2VP at pH 2, and mainly nonionized functional groups in a "dry" PAA-P2VP polyelectrolyte complex in the range from pH=4 to pH=7. At intermediate pH, the IR spectra confirm the previously made hypothesis of the formation of a polyelectrolyte complex between P2VP and PAA in the mixed brush. From IR spectra it is also concluded that the polyelectrolyte complex is formed as a result of a small fraction of ionized functional groups. PMID:19572506

  15. 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.

  16. Surface and interface structure of diblock copolymer brushes

    NASA Astrophysics Data System (ADS)

    Akgun, Bulent

    The main objective of the work presented in this thesis is to understand the surface and interface structure and dynamics of diblock copolymer brushes (DCBs). DCBs are stimuli-responsive materials and the surface properties of a DCB can be changed from those characteristic of one polymer block to those characteristic of the other one by treating the DCB with a solvent selective for one of its blocks. For this purpose, polystyrene- block-polyacrylate or polyacrylate-block-polystyrene brushes were synthesized using the "grafting from" technique in combination with atom transfer radical polymerization (ATRP). In the first part of this project the internal structure of DCBs after the synthesis and surface rearrangement were investigated using neutron reflectivity (NR) and grazing incidence small angle X-ray scattering (GISAXS). It was found that the internal brush structure depends strongly on the synthesis sequence of polymer blocks and the value of chiN. For small values of chiN (chiN ≤ 11), a model of two layers with an interfacial region of finite width provides a good description of the data. The interface width is found to be larger for DCBs which have the polymer block with the lower surface energy synthesized next to the substrate. A three layer model must be used to describe the structure of DCBs of larger chiN values (chiN ≤ 23) and of sufficiently asymmetric composition. The necessity of including a third layer is consistent with the presence of a lateral ordering of some type in the center of the brush, as evidenced by correlation peaks in the GISAXS data. The spacing of the in-plane ordering varies with the thickness of the poly(methyl acrylate) (PMA) block. After a DCB is treated with a selective solvent, Bragg rods appear in the GISAXS pattern. The appearance of Bragg rods indicates the formation of a new 2D structure which has a lateral spacing on the order of the total thickness of the brush. The Bragg rods disappear upon heating to 80

  17. [Perforating injuries of the eyes caused by rotating steel brushes].

    PubMed

    Höh, H; Krannig, H J

    1990-03-01

    Three cases of perforating lamellating injuries to the eyes are described which illustrate the hazards of using rotating wire brushes. All three patients were home handymen who failed to take the customary safety precautions. In one case the eye injury was partially due to an inappropriate combination of tools (a low-speed wire brush used with a high-speed drill). In view of the constantly increasing popularity of DIY work tool manufacturers, social insurance funds, private insurance companies and public institutions are called upon to help reduce the frequency of accidents in the DIY sector through appropriate design, organizational measures and publicity campaigns. Practical proposals are outlined in this paper. Perforating eye injuries caused by wire brushes can easily be overlooked. Thorough ophthalmological examination is therefore essential, and a diagnostic intervention may be required. PMID:2342318

  18. 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.

  19. 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.

  20. Macromolecular Brushes as Stabilizers of Hydrophobic Solute Nanoparticles.

    PubMed

    Luo, Hanying; Raciti, David; Wang, Chao; Herrera-Alonso, Margarita

    2016-06-01

    Macromolecular brushes bearing poly(ethylene glycol) and poly(d,l-lactide) side chains were used to stabilize hydrophobic solute nanoparticles formed by a rapid change in solvent quality. Unlike linear diblock copolymers with the same hydrophilic and hydrophobic block chemistries, the brush copolymer enabled the formation of ellipsoidal β-carotene nanoparticles, which in cosolvent mixtures developed into rod-like structures, resulting from a combination of Ostwald ripening and particle aggregation. The stabilizing ability of the copolymer was highly dependent on the mobility of the hydrophobic component, influenced by its molecular weight. As shown here, asymmetric amphiphilic macromolecular brushes of this type may be used as hydrophobic drug stabilizers and potentially assist the shape control of nonspherical aggregate morphologies. PMID:27035279

  1. 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.

  2. Numerical simulations of plasma brush behavior in hybrid armatures

    NASA Astrophysics Data System (ADS)

    Hawke, R. S.; Pincosy, P. A.

    1993-01-01

    Hybrid armatures used to accelerate projectiles in railguns are often the consequence of using a solid armature or in some cases the preferred armature type. Although hybrid armatures are often used, their design has been empirical and their performance sporadic. As a first step towards understanding hybrid design and performance, we have begun a combined numerical simulation and experimental verification effort. This paper will describe numerical simulations performed with a quasi 1-D MHD code (CONFUSE) which has been applied to simulate the behavior of plasma brushes used in hybrid armatures. The simulations have provided estimates of the plasma brush length, resistive voltage drop and temperatures corresponding to a range of; 1) brush gap size, 2) fuse thickness, and 3) magnetic pressure. The results of these simulations is presented and discussed.

  3. 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.

  4. Scaling Behavior and Segment Concentration Profile of Densely Grafted Polymer Brushes Swollen in Vapor.

    PubMed

    Sun, Liang; Akgun, Bulent; Hu, Renfeng; Browning, James F; Wu, David T; Foster, Mark D

    2016-06-01

    The scaling of the thickness, hs, of a densely grafted polymer brush of chain length N and grafting density σ swollen in vapor agrees quantitatively with the scaling reported by Kuhl et al. for densely grafted brushes swollen in liquid. Deep in the brush, next to the substrate, the shape of the segment concentration profile is the same whether the brush is swollen by liquid or by vapor. Differences in the segment concentration profile are manifested primarily in the swollen brush interface with the surrounding fluid. The interface of the polymer brush swollen in vapor is much more abrupt than that of the same brush swollen in liquid. This has implications for the compressibility of the swollen brush surface and for fluctuations at that surface. PMID:27172089

  5. Doubly anchored nematic polymer brushes: Shear, field effects, and quasipiezoelectricity

    NASA Astrophysics Data System (ADS)

    Halperin, A.; Williams, D. R. M.

    1994-02-01

    The shear behavior of a doubly anchored brush of liquid-crystalline polymers immersed in a nematic solvent is investigated. In such a brush the grafted polymers bridge two plates. Remarkably, the Franck nematic elasticity in this system can dominate the shear modulus. In the presence of a field the system undergoes a Fréedericksz transition modified by the bridging polymers. In particular: (i) the polymeric elasticity affects the critical field Ec; (ii) the shear modulus vanishes as the field approaches Ec; and (iii) the nematic distortion couples to a shear strain. The system exhibits quasipiezoelectricity, which is nonlinear and is not associated with any inverse effect.

  6. 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…

  7. 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

  8. Thicker is better? Synthesis and evaluation of well-defined polymer brushes with controllable catalytic loadings.

    PubMed

    Fernandes, Antony E; Dirani, Ali; d'Haese, Cécile; Deumer, Gladys; Guo, Weiming; Hensenne, Peter; Nahra, Fady; Laloyaux, Xavier; Haufroid, Vincent; Nysten, Bernard; Riant, Olivier; Jonas, Alain M

    2012-12-01

    Polymer brushes (PBs) have been used as supports for the immobilization of palladium complexes on silicon surfaces. The polymers were grown by surface-initiated atom-transfer radical polymerization (SI-ATRP) and postdecorated with dipyridylamine (dpa) ligands. The pendant dpa units were in turn complexed with [Pd(OAc)(2)] to afford hybrid catalytic surfaces. A series of catalytic samples of various thicknesses (ca. 20-160 nm) and associated palladium loadings (ca. 10-45 nmol  cm(-2)) were obtained by adjusting the SI-ATRP reaction time and characterized by ellipsometry, X-ray reflectivity, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry (ICP-MS). ICP-MS revealed a near-linear relationship between thickness of the polymer brush and palladium content, which confirmed the robustness of the preparation and postmodification sequence presented herein, rendering possible the creation of functional architectures with predefined catalytic potential. The activities of the catalytic PBs were determined by systematically exploring a full range of substrate-to-catalyst ratios in a model palladium(0)-catalyzed reaction. Quantitative transformations were observed for loadings down to 0.03 mol % and a maximum turnover number (TON) of around 3500 was established for the system. Comparison of the catalytic performances evidenced a singular influence of the thickness on conversions and TONs. The limited recyclability of the hairy catalysts has been attributed to palladium leaching. PMID:23032959

  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. 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... INFORMATION CONTACT: Keysha Martinez (202-205-2136), Office of Investigations, U.S. International...

  11. Switching Shape of Cylindrical Brush Molecules at Interfaces

    NASA Astrophysics Data System (ADS)

    Sheiko, Sergei; da Silva, Marcelo; Prokhorova, Svetlana; Beers, Kathryn; Boerner, Hans; Matyjaszewski, Krzysztof

    2002-03-01

    Significant progress in polymer synthesis has been made towards preparation of three-dimensional macromolecules with well-defined shapes, interiors, and surface structures. The most prominent examples are dendrimers and cylindrical brushes. In contrast to solid particles, hyperbranched macromolecules retain flexibility of chain segments and demonstrate significant density fluctuations. They can be regarded as soft molecular particles, which can change their shape in response to changes in the surrounding environment. The conformational changes are particularly subtle for cylindrical brushes adsorbed to an interface. The surface breaks the molecular symmetry due to partial desorption of the side chains and due to uneven distribution of the side chains with respect to the backbone. The constraints imposed by the branching topology result in a number of distinct conformations and transitions between them. Recently, we have succeeded in monitoring of the conformational changes and motion of individual brush molecules using scanning force microscopy. The most peculiar properties of cylindrical brushes, namely axial contraction, conformational transitions, and persistent motion will be discussed.

  12. The Conformation of Thermoresponsive Polymer Brushes Probed by Optical Reflectivity.

    PubMed

    Varma, Siddhartha; Bureau, Lionel; Débarre, Delphine

    2016-04-01

    We describe a microscope-based optical setup that allows us to perform space- and time-resolved measurements of the spectral reflectance of transparent substrates coated with ultrathin films. This technique is applied to investigate the behavior in water of thermosensitive polymer brushes made of poly(N-isopropylacrylamide) grafted on glass. We show that spectral reflectance measurements yield quantitative information about the conformation and axial structure of the brushes as a function of temperature. We study how parameters such as grafting density and chain length affect the hydration state of a brush, and provide one of the few experimental evidences for the occurrence of vertical phase separation in the vicinity of the lower critical solution temperature of the polymer. The origin of the hysteretic behavior of poly(N-isopropylacrylamide) brushes upon cycling the temperature is also clarified. We thus demonstrate that our optical technique allows for in-depth characterization of stimuli-responsive polymer layers, which is crucial for the rational design of smart polymer coatings in actuation, gating, or sensing applications. PMID:26986181

  13. 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.

  14. 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...

  15. Self-organization of multivalent counterions in polyelectrolyte brushes

    NASA Astrophysics Data System (ADS)

    Wu, Jianzhong

    2013-03-01

    The structure and interfacial properties of a polyelectrolyte brush (PEB) depend on a broad range of parameters such as the polymer charge and grafting density, counterion valence, salt concentration, and solvent conditions. These properties are of fundamental importance in technological applications of PEBs including colloid stabilization, surface modification and lubrication, and in functioning of biological systems such as genome packaging in single-strand DNA/RNA viruses. Despite intensive studies by experiments, molecular simulations, and myriad analytical methods including scaling analyses, self-consistent-field theory, and most recently density functional theory, the behavior of PEBs in the presence of multivalent counterions remains poorly understood. In this talk, I will present a density functional method for polyelectrolyte brushes and discuss self-organization of multivalent counterions within highly charged polyelectrolyte brushes. The counterion-mediated attraction between polyions leads to a first-order phase transition similar to that for a neutral brush in a poor solvent. The self-organization of multivalent counterions results in a wavelike electrostatic potential and charge density that oscillate between positive and negative values.

  16. Patterned biofunctional poly(acrylic acid) brushes on silicon surfaces.

    PubMed

    Dong, Rong; Krishnan, Sitaraman; Baird, Barbara A; Lindau, Manfred; Ober, Christopher K

    2007-10-01

    Protein patterning was carried out using a simple procedure based on photolithography wherein the protein was not subjected to UV irradiation and high temperatures or contacted with denaturing solvents or strongly acidic or basic solutions. Self-assembled monolayers of poly(ethylene glycol) (PEG) on silicon surfaces were exposed to oxygen plasma through a patterned photoresist. The etched regions were back-filled with an initiator for surface-initiated atom transfer radical polymerization (ATRP). ATRP of sodium acrylate was readily achieved at room temperature in an aqueous medium. Protonation of the polymer resulted in patterned poly(acrylic acid) (PAA) brushes. A variety of biomolecules containing amino groups could be covalently tethered to the dense carboxyl groups of the brush, under relatively mild conditions. The PEG regions surrounding the PAA brush greatly reduced nonspecific adsorption. Avidin was covalently attached to PAA brushes, and biotin-tagged proteins could be immobilized through avidin-biotin interaction. Such an immobilization method, which is based on specific interactions, is expected to better retain protein functionality than direct covalent binding. Using biotin-tagged bovine serum albumin (BSA) as a model, a simple strategy was developed for immobilization of small biological molecules using BSA as linkages, while BSA can simultaneously block nonspecific interactions. PMID:17880179

  17. Conformational switching of modified guest chains in polymer brushes

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    Using a numerical quasi off-lattice self-consistent field method which describes heterogeneous chains of spherical monomers we study the case of a densely grafted polymer brush with a fraction of free chain ends being replaced by a modified end-group differing in size and solvent selectivity. We can confirm the observation from molecular dynamics simulations that upon changing the solvent conditions, a switching in location of end-groups which are bigger than monomers from a state "exposed" to the solvent (on the top of the brush) to a "hidden" state (inside the brush) takes place. Our numerical method allows a detailed study of the switching effect as a function of the relevant parameters, such as grafting density, chain length, size of end-groups and their volume fraction. We find that the switching effect is enhanced for long chains, low fractions of modified chains, and big end-groups. We consider the case of low fraction of modified chains in more detail using a test chain method. Here, we explore the optimal grafting density as a function of the size of the end-groups, where the switching is most sensitive. These values can be in the experimental range for end-groups which are at least 3-4 times bigger than the monomers. The end-groups can be realized by attaching nano-particles to the last monomer of a brush-chain.

  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. 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.

  20. 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.

  1. Adsorption of Anionic or Cationic Surfactants in Polyanionic Brushes and Its Effect on Brush Swelling and Fouling Resistance during Emulsion Filtration.

    PubMed

    Yang, Zhefei; Tarabara, Volodymyr V; Bruening, Merlin L

    2015-11-01

    Atom transfer radical polymerization of ionic monomers from membrane surfaces yields polyelectrolyte brushes that swell in water and repel oil droplets to resist fouling during filtration of oil-in-water emulsions. However, surfactant adsorption to polyelectrolyte brushes may overcome this fouling resistance. This work examines adsorption of cationic and anionic surfactants in polyanionic brushes and the effect of these surfactants on emulsion filtration. In situ ellipsometry with films on flat surfaces shows that brushes composed of poly(3-sulfopropyl methacrylate salts) (pSPMK) swell 280% in water and do not adsorb sodium dodecyl sulfate (SDS). pSPMK-modified microfiltration membranes reject >99.9% of the oil from SDS-stabilized submicron emulsions, and the specific flux through these modified membranes is comparable to that through NF270 nanofiltration membranes. Moreover, the brush-modified membranes show no decline in flux over a 12 h filtration, whereas the flux through NF270 membranes decreases by 98.7%. In contrast, pSPMK brushes adsorb large quantities of cetyltrimethylammonium bromide (CTAB), and at low chain densities the brushes collapse in the presence of this cationic surfactant. Filtration of CTAB-stabilized emulsions through pSPMK-modified membranes gives minimal oil rejection, presumably due to the brush collapse. Thus, the fouling resistance of polyelectrolyte brush-modified membranes clearly depends on the surfactant composition in a particular emulsion. PMID:26442835

  2. 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

  3. Block copolymer assembly on nanoscale patterns of polymer brushes formed by electrohydrodynamic jet printing.

    PubMed

    Onses, M Serdar; Ramírez-Hernández, Abelardo; Hur, Su-Mi; Sutanto, Erick; Williamson, Lance; Alleyne, Andrew G; Nealey, Paul F; de Pablo, Juan J; Rogers, John A

    2014-07-22

    Fundamental understanding of the self-assembly of domains in block copolymers (BCPs) and capabilities in control of these processes are important for their use as nanoscale templates in various applications. This paper focuses on the self-assembly of spin-cast and printed poly(styrene-block-methyl methacrylate) BCPs on patterned surface wetting layers formed by electrohydrodynamic jet printing of random copolymer brushes. Here, end-grafted brushes that present groups of styrene and methyl methacrylate in geometries with nanoscale resolution deterministically define the morphologies of BCP nanostructures. The materials and methods can also be integrated with lithographically defined templates for directed self-assembly of BCPs at multiple length scales. The results provide not only engineering routes to controlled formation of complex patterns but also vehicles for experimental and simulation studies of the effects of chemical transitions on the processes of self-assembly. In particular, we show that the methodology developed here provides the means to explore exotic phenomena displayed by the wetting behavior of BCPs, where 3-D soft confinement, chain elasticity, interfacial energies, and substrate's surface energy cooperate to yield nonclassical wetting behavior. PMID:24882265

  4. Post-Functionalized Polymer Brushes for Bio-Separation: Tuning GFP Adsorption via Functional Group Display

    NASA Astrophysics Data System (ADS)

    Diamanti, Steve; Arifuzzaman, Shafi; Genzer, Jan; Naik, Rajesh; Vaia, Richard

    2007-03-01

    An inexpensive and robust biosensor platform that can be tuned to separate and/or detect complex mixtures of biomolecules while minimizing reagents would be of great use for military, homeland security, and medical diagnostic applications. Gradient surfaces of poly(2-hydroxyethyl methacrylate) (PHEMA) brushes have been previously shown to spatially localize biomolecule binding, while minimizing non-specific adsorption of the same biomolecule on other regions of the gradient specimen. In order to further improve the specificity and to provide latent functionality for detection of the binding events, post-polymerization modification of PHEMA with various functional groups has been investigated. Using standard succinimide-based coupling, hydroxyl pendants of PHEMA brushes were conjugated to oligo-peptides, alkanes and oligo(ethylene glycol) (OEG) through an alpha-terminus primary amine. Ellipsometry, contact angle, XPS and ER-FTIR spectroscopy indicated that coupling occurred with efficiencies ranging from 10-40%. Post-functionalization of PHEMA with OEG and hexadecane allows manipulation of the hydrophilicity of the surface and thus tuning of Green Fluorescent Protein (GFP) binding.

  5. Synthesis of iron oxide rods coated with polymer brushes and control of their assembly in thin films.

    PubMed

    Huang, Yun; Ishige, Ryohei; Tsujii, Yoshinobu; Ohno, Kohji

    2015-01-27

    We investigated the surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl methacrylate (MMA) using monodisperse rod-type particles of iron oxide, β-FeOOH. The slow hydrolysis of iron(III) chloride yielded monodisperse β-FeOOH rods with an average length-to-width ratio, L/W, of 6 (L = 210 nm and W = 35 nm on average). The surfaces of the β-FeOOH rods were modified with a triethoxysilane derivative as an ATRP-initiating site, namely, (2-bromo-2-methyl)propionyloxypropyl triethoxysilane. The SI-ATRP of MMA, mediated by a copper complex, was performed using the initiator-coated β-FeOOH rods in the presence of a "sacrificial" free initiator. Well-defined poly(methyl methacrylate) (PMMA) brushes with molecular weights of up to 700,000 could be grafted on the β-FeOOH rods with a surface density as high as 0.3 chains/nm(2). The resultant polymer-brush-afforded hybrid rods exhibited high dispersibility in various solvents for PMMA without forming aggregates. Thin films were prepared by dip-coating from a suspension of the hybrid rods, and the rods were oriented in a specific direction in the films. The arrangement of the rods could be controlled by varying the chain length of the polymer brush and the withdrawal speed during the dip-coating process. PMID:25552325

  6. Wettability and antifouling behavior on the surfaces of superhydrophilic polymer brushes.

    PubMed

    Kobayashi, Motoyasu; Terayama, Yuki; Yamaguchi, Hiroki; Terada, Masami; Murakami, Daiki; Ishihara, Kazuhiko; Takahara, Atsushi

    2012-05-01

    The surface wettabilities of polymer brushes with hydrophobic and hydrophilic functional groups were discussed on the basis of conventional static and dynamic contact angle measurements of water and hexadecane in air and captive bubble measurements in water. Various types of high-density polymer brushes with nonionic and ionic functional groups were prepared on a silicon wafer by surface-initiated atom-transfer radical polymerization. The surface free energies of the brushes were estimated by Owens-Wendt equation using the contact angles of various probe liquids with different polarities. The decrease in the water contact angle corresponded to the polarity of fluoroalkyl, hydroxy, ethylene oxide, amino, carboxylic acid, ammonium salt, sulfonate, carboxybetaine, sulfobetaine, and phosphobetaine functional groups. The poly(2-perfluorooctylethyl acrylate) brush had a low surface free energy of approximately 8.7 mN/m, but the polyelectrolyte brushes revealed much higher surface free energies of 70-74 mN/m, close to the value for water. Polyelectrolyte brushes repelled both air bubbles and hexadecane in water. Even when the silicone oil was spread on the polyelectrolyte brush surfaces in air, once they were immersed in water, the oil quickly rolled up and detached from the brush surface. The oil detachment behavior observed on the superhydrophilic polyelectrolyte brush in water was explained by the low adhesion force between the brush and the oil, which could contribute to its excellent antifouling and self-cleaning properties. PMID:22500465

  7. Improved endoscopic retrograde cholangiopancreatography brush increases diagnostic yield of malignant biliary strictures

    PubMed Central

    Shieh, Frederick K; Luong-Player, Adelina; Khara, Harshit S; Liu, Haiyan; Lin, Fan; Shellenberger, Matthew J; Johal, Amitpal S; Diehl, David L

    2014-01-01

    AIM: To determine if a new brush design could improve the diagnostic yield of biliary stricture brushings. METHODS: Retrospective chart review was performed of all endoscopic retrograde cholangiopancreatography procedures with malignant biliary stricture brushing between January 2008 and October 2012. A standard wire-guided cytology brush was used prior to protocol implementation in July 2011, after which, a new 9 French wire-guided cytology brush (Infinity sampling device, US Endoscopy, Mentor, OH) was used for all cases. All specimens were reviewed by blinded pathologists who determined whether the sample was positive or negative for malignancy. Cellular yield was quantified by describing the number of cell clusters seen. RESULTS: Thirty-two new brush cases were compared to 46 historical controls. Twenty-five of 32 (78%) cases in the new brush group showed abnormal cellular findings consistent with malignancy as compared to 17 of 46 (37%) in the historical control group (P = 0.0003). There was also a significant increase in the average number of cell clusters of all sizes (21.1 vs 9.9 clusters, P = 0.0007) in the new brush group compared to historical controls. CONCLUSION: The use of a new brush design for brush cytology of biliary strictures shows increased diagnostic accuracy, likely due to improved cellular yield, as evidenced by an increase in number of cellular clusters obtained. PMID:25031790

  8. 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.

  9. pH-Responsive Behavior of Poly(acrylic acid) Brushes of Varying Thickness

    NASA Astrophysics Data System (ADS)

    Yadav, Vivek; Robertson, Megan; Conrad, Jacinta

    2015-03-01

    We have investigated the pH-dependent response of polyelectrolyte brushes of varying thickness. Our model system consists of poly(acrylic acid) brushes, which change from hydrophobic and neutral at low pH to hydrophilic and negatively charged at high pH, synthesized using a grafting-from approach at constant grafting density. As the polymer brush thickness increased, the brushes exhibited greater hysteresis in static water contact angle as a function of pH. We extracted the pKa of the polymer brushes from contact angle measurements. The relationship between the pKa and brush thickness depended on the order in which the brushes were exposed to solutions of varying pH: pKa decreased on increasing brush thickness when going from basic to acidic medium whereas pKa increased on increasing brush thickness when going from acidic to basic medium. We speculate that the origin of hysteresis can be explained by pH-dependent conformational changes in these polyelectrolyte brushes.

  10. 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

  11. 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).

  12. BABE - a brush cathode discharge for thermal fluctuation measurements

    NASA Astrophysics Data System (ADS)

    Ratynskaia, S.; Dilecce, G.; Tolias, P.

    2015-04-01

    For experimental tests of fluctuation theory in ideal plasmas and plasmas seeded with dust, the ideal environment would be that of stable quiescent plasma. In most laboratory plasmas the homogeneous state of the positive column is often unstable, rare exceptions are the so-called brush cathode discharges, proposed in the 60s, where a specially manufactured cathode allows stable operation in the abnormal glow regime and the only fluctuations present are those due the thermal motion of the particles. Such a device, the BAri Brush Electrode (BABE), has recently been built in a novel configuration that combines the advantages of the inverse design with those of the reflex geometry. The region between the two anodes is essentially field-free and extremely stable in wide range of plasma densities and collisionalities. Unprecedented low fluctuation levels of δn/n <= 10-5 in He and δn/n <= 5 × 10-6 in Ar discharges have been achieved.

  13. Origin of Lateral Nanoscale Heterogeneities in Weak Polyelectrolyte Brushes

    NASA Astrophysics Data System (ADS)

    Won, You-Yeon; Witte, Kevin; Hur, Jaehyun

    2009-03-01

    In this talk, we will first discuss experimental evidence of lateral nanoscale heterogeneities in a single-component weak polyelectrolyte brush system under zero to low salt conditions. Using an amphiphilic diblock copolymer, poly(2-(dimethylamino)ethyl methacrylate-b-n-butyl acrylate) (PDMAEMA-PnBA), for Langmuir film compression and Langmuir-Blodgett deposition on a hydrophobic substrate followed by fluid AFM imaging, we show the existence of regions of different brush heights, indicative of the thermodynamic instability (and resultant local clustering) of the PDMAEMA chains in the low-salt limit. Using SCF and scaling theories, we will also show that the lateral heterogeneities occur due to the combined effects of (i) the osmotic instability regulated by charge equilibrium and (ii) the hydrophobicity of the chains.

  14. 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.

  15. Toxicological study of ''Aralhex Brush'' and its two components

    SciTech Connect

    London, J.E.; Smith, D.M.

    1985-09-01

    The acute oral LD/sub 50/ values for the adhesive ''Aralhex Brush'' for mice and rats are greater than 5g/kg. According to classified guidelines, the mixture would be considered only slightly toxic or practically nontoxic in both species. Skin application studies in the rabbit with the adhesive demonstrated that it was cutaneously mildly irritating; however, based on the primary irritation index, the adhesive's two precursor components were nonirritating. The adhesive and components I were mildly irritating in the rabbit eye application studies and component II was non-irritating. The sensitization study in the guinea pig did not show ''Aralhex Brush'' or its two components to be sensitizers. 5 refs., 3 tabs.

  16. Directing cell migration using micropatterned and dynamically adhesive polymer brushes.

    PubMed

    Costa, Patricia; Gautrot, Julien E; Connelly, John T

    2014-06-01

    Micropatterning techniques, such as photolithography and microcontact printing, provide robust tools for controlling the adhesive interactions between cells and their extracellular environment. However, the ability to modify these interactions in real time and examine dynamic cellular responses remains a significant challenge. Here we describe a novel strategy to create dynamically adhesive, micropatterned substrates, which afford precise control of cell adhesion and migration over both space and time. Specific functionalization of micropatterned poly(ethylene glycol methacrylate) (POEGMA) brushes with synthetic peptides, containing the integrin-binding arginine-glycine-aspartic acid (RGD) motif, was achieved using thiol-yne coupling reactions. RGD activation of POEGMA brushes promoted fibroblast adhesion, spreading and migration into previously non-adhesive areas, and migration speed could be tuned by adjusting the surface ligand density. We propose that this technique is a robust strategy for creating dynamically adhesive biomaterial surfaces and a useful assay for studying cell migration. PMID:24508539

  17. Numerical simulation of flow in Brush Creek Valley, Colorado

    SciTech Connect

    Leone, J.M. Jr.; Lee, R.L.

    1987-06-01

    In this paper, we present some results from our three-dimensional, non-hydrostatic, finite element model applied to simulations of flow in Brush Creek Valley. These simulations are not intended to reproduce any particular experiment, but rather are to evaluate the qualitative performance of the model, to explore the major difficulties involved, and to begin sensitivity studies of the flows of interest. 2 refs., 11 figs.

  18. 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

  19. 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

  20. 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

  1. 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

  2. Multifunctional nanolayers via polymer brush approach: Synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Swaminatha Iyer, K. L.

    The strong effect of boundary surfaces on a material's performance is generally recognized. This is why in order to get materials with the desired performance, their surfaces are often modified before use. Ultrathin polymer films grafted to the surface can dramatically alter the surface properties of a substrate, such as conductivity, lubrication, adhesion, wettability, friction and biocompatibility. Moreover, if several functional polymers are used for the grafting, hybrid polymer layers can be synthesized and surfaces with responsive properties can be obtained. The ultimate goal of the current study is to fabricate and characterize nanolayers via polymer brush approach to modify surface properties of organic and inorganic substrates. Substrates were modified with polymer brushes using "grafting to", "grafting from" and physisorption techniques. The initial part of the investigation deals with the development and understanding of a "universal platform" to modify substrates using a macromolecular anchoring layer approach. It was demonstrated that the approach worked effectively on PET substrates. Finally, polymer brushes were successful fabricated to tune wettability of surfaces, develop stable silver/polymer nanocomposites and self-cleaning surfaces.

  3. 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.

  4. 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.

  5. 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. PMID:25830715

  6. Evidence to Support Tooth Brushing in Critically Ill Patients

    PubMed Central

    Ames, Nancy J.

    2012-01-01

    Tooth brushing in critically ill patients has been advocated by many as a standard of care despite the limited evidence to support this practice. Attention has been focused on oral care as the evidence accumulates to support an association between the bacteria in the oral microbiome and those respiratory pathogens that cause pneumonia. It is plausible to assume that respiratory pathogens originating in the oral cavity are aspirated into the lungs, causing infection. A recent study of the effects of a powered toothbrush on the incidence of ventilator-associated pneumonia was stopped early because of a lack of effect in the treatment group. This review summarizes the evidence that supports the effectiveness of tooth brushing in critically ill adults and children receiving mechanical ventilation. Possible reasons for the lack of benefit of tooth brushing demonstrated in clinical trials are discussed. Recommendations for future trials in critically ill patients are suggested. With increased emphasis being placed on oral care, the evidence that supports this intervention must be evaluated carefully. PMID:21532045

  7. 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.

  8. Protein Adsorption on Poly(N-isopropylacrylamide) Brushes: dependence on grafting density and chain collapse

    PubMed Central

    Xue, Changying; Yonet-Tanyeri, Nihan; Brouette, Nicolas; Sferrazza, Michele; Braun, Paul V.; Leckband, Deborah E.

    2012-01-01

    The protein resistance of poly(N-isopropylacrylamide) brushes grafted from silicon wafers was investigated as a function of the chain molecular weight, grafting density, and temperature. Above the lower critical solution temperature (LCST) of 32°C, the collapse of the water swollen chains, determined by ellipsometry, depends on the grafting density and molecular weight. Ellipsometry, radio assay, and fluorescence imaging demonstrated that, below the lower critical solution temperature, the brushes repel protein as effectively as oligoethylene oxide terminated monolayers. Above 32°C, very low levels of protein adsorb on densely grafted brushes, and the amounts of adsorbed protein increase with decreasing brush grafting densities. Brushes that do not exhibit a collapse transition also bind protein, even though the chains remain extended above the LCST. These findings suggest possible mechanisms underlying protein interactions with end-grafted PNIPAM brushes. PMID:21662243

  9. Electrokinetic Transport in Nanochannels Grafted with Polyelectrolyte Brushes with End-Charging

    NASA Astrophysics Data System (ADS)

    Das, Siddhartha; Chen, Guang

    2015-11-01

    Electrokinetic transport in nanochannels grafted with polyelectrolyte (PE) brushes is important for applications such as ion transport, ion manipulation, flow valving, etc. We discuss here a semi-analytical mean field theory approach to study electrokinetic transport in nanochannels grafted with polyelectrolyte brushes with end-charging. The model first probes the thermodynamics and the electrostatics of the PE brushes by appropriately accounting for the entropic (elastic), excluded volume, and electrostatic effects. The resulting knowledge on the electrostatic potential and the PE configuration is next used to obtain the electroosmotic transport. Results demonstrate the role of surface charges (at the end of the PE brushes) in modifying (shrinking or swelling) the brush height. This, in turn, alters the electroosmotic body force and the PE brush layer induced drag force on the fluid flow; therefore, the flow field eventually evolves from a non-trivial interplay of the PE electrostatic, entropic, and excluded volume effects.

  10. 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.

  11. Brush Effects on DNA Chips: Thermodynamics, Kinetics, and Design Guidelines

    PubMed Central

    Halperin, A.; Buhot, A.; Zhulina, E. B.

    2005-01-01

    In biology experiments, oligonucleotide microarrays are contacted with a solution of long nucleic acid targets. The hybridized probes thus carry long tails. When the surface density of the oligonucleotide probes is high enough, the progress of hybridization gives rise to a polyelectrolyte brush due to mutual crowding of the nucleic acid tails. The free-energy penalty associated with the brush modifies both the hybridization isotherms and the rate equations: the attainable hybridization is lowered significantly as is the hybridization rate. When the equilibrium hybridization fraction, xeq, is low, the hybridization follows a Langmuir type isotherm, xeq/(1 − xeq) = ctK where ct is the target concentration and K is the equilibrium constant. K is smaller than its bulk value by a factor (n/N)2/5 due to wall effects where n and N denote the number of bases in the probe and the target. At higher xeq, when the brush is formed, the leading correction is \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}x_{{\\mathrm{eq}}}/(1-x_{{\\mathrm{eq}}})=c_{{\\mathrm{t}}}K\\hspace{.167em}{\\mathrm{exp}}\\hspace{.167em} \\left \\left[-const^{\\prime} \\left \\left(x_{{\\mathrm{eq}}}^{2/3}-x_{{\\mathrm{B}}}^{2/3}\\right) \\right \\right] \\right \\end{equation*}\\end{document} where xB corresponds to the onset of the brush regime. The denaturation rate constant in the two regimes is identical. However, the hybridization rate constant in the brush regime is lower, the leading correction being \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{exp}}\\hspace{.167em} \\left \\left[-const^{\\prime} \\left \\left

  12. Swelling of chemical and physical planar brushes of gradient copolymers in a selective solvent.

    PubMed

    Venev, Sergey V; Potemkin, Igor I

    2014-09-14

    We propose a mean-field theory of chemical and physical planar brushes of linear gradient copolymers swollen in a selective solvent. The polymer chains are grafted to the substrate by the ends with the excess of insoluble monomer units, and the majority of the soluble units are located near the free ends of the chains. The grafting points are considered to be immobile (chemical brush) and mobile in-plane (physical brush). In the latter case the grafting density is determined from the equilibrium conditions (minimum of the free energy). A common peculiarity of the brushes of both types is that the polymer concentration gradually changes from a relatively high value near the substrate (collapsed region of the brush) to a small value near the free surface (swollen region of the brush). In the case of the chemical brush, a polymer depletion zone can appear in the middle of the brush if incompatibility between insoluble and soluble (A and B) units is high enough. Here the polymer density is even lower than near the free surface of the brush. The grafting density of the physical brush is inversely proportional to the chain length and increases with the decrease of the solvent quality for the insoluble (A) units. The latter can be accompanied by shrinkage of the brush thickness due to broad distribution of the insoluble units through the chain: a minor fraction of insoluble units near the free ends can aggregate with a major fraction of them near the substrate. As a result, the concentration of the soluble (B) units can have a maximum in the middle of the brush rather than near the free surface. PMID:25058377

  13. Anion-specific effects on the behavior of pH-sensitive polybasic brushes.

    PubMed

    Willott, Joshua D; Murdoch, Timothy J; Humphreys, Ben A; Edmondson, Steve; Wanless, Erica J; Webber, Grant B

    2015-03-31

    The anion-specific solvation and conformational behavior of weakly basic poly(2-dimethylamino)ethyl methacrylate (poly(DMA)), poly(2-diethylamino)ethyl methacrylate (poly(DEA)), and poly(2-diisopropylamino)ethyl methacrylate (poly(DPA)) brushes, with correspondingly increasing inherent hydrophobicity, have been investigated using in situ ellipsometric and quartz crystal microbalance with dissipation (QCM-D) measurements. In the osmotic brush regime, as the initial low concentration of salt is increased, the brushes osmotically swell by the uptake of solvent as they become charged and the attractive hydrophobic inter- and intrachain interactions are overcome. With increased ionic strength, the brushes move into the salted brush regime where they desolvate and collapse as their electrostatic charge is screened. Here, as the brushes collapse, they transition to more uniform and rigid conformations, which dissipate less energy, than similarly solvated brushes at lower ionic strength. Significantly, in these distinct regimes brush behavior is not only ionic strength dependent but is also influenced by the nature of the added salt based on its position in the well-known Hofmeister or lyotropic series, with potassium acetate, nitrate, and thiocyanate investigated. The strongly kosmotropic acetate anions display low affinity for the hydrophobic polymers, and largely unscreened electrosteric repulsions allow the brushes to remain highly solvated at higher acetate concentrations. The mildly chaotropic nitrate and strongly chaotropic thiocyanate anions exhibit a polymer hydrophobicity-dependent affinity for the brushes. Increasing thiocyanate concentration causes the brushes to collapse at lower ionic strength than for the other two anions. This study of weak polybasic brushes demonstrates the importance of all ion, solvent, and polymer interactions. PMID:25768282

  14. Protein microarrays based on polymer brushes prepared via surface-initiated atom transfer radical polymerization.

    PubMed

    Barbey, Raphael; Kauffmann, Ekkehard; Ehrat, Markus; Klok, Harm-Anton

    2010-12-13

    Polymer brushes represent an interesting platform for the development of high-capacity protein binding surfaces. Whereas the protein binding properties of polymer brushes have been investigated before, this manuscript evaluates the feasibility of poly(glycidyl methacrylate) (PGMA) and PGMA-co-poly(2-(diethylamino)ethyl methacrylate) (PGMA-co-PDEAEMA) (co)polymer brushes grown via surface-initiated atom transfer radical polymerization (SI-ATRP) as protein reactive substrates in a commercially available microarray system using tantalum-pentoxide-coated optical waveguide-based chips. The performance of the polymer-brush-based protein microarray chips is assessed using commercially available dodecylphosphate (DDP)-modified chips as the benchmark. In contrast to the 2D planar, DDP-coated chips, the polymer-brush-covered chips represent a 3D sampling volume. This was reflected in the results of protein immobilization studies, which indicated that the polymer-brush-based coatings had a higher protein binding capacity as compared to the reference substrates. The protein binding capacity of the polymer-brush-based coatings was found to increase with increasing brush thickness and could also be enhanced by copolymerization of 2-(diethylamino)ethyl methacrylate (DEAEMA), which catalyzes epoxide ring-opening of the glycidyl methacrylate (GMA) units. The performance of the polymer-brush-based microarray chips was evaluated in two proof-of-concept microarray experiments, which involved the detection of biotin-streptavidin binding as well as a model TNFα reverse assay. These experiments revealed that the use of polymer-brush-modified microarray chips resulted not only in the highest absolute fluorescence readouts, reflecting the 3D nature and enhanced sampling volume provided by the brush coating, but also in significantly enhanced signal-to-noise ratios. These characteristics make the proposed polymer brushes an attractive alternative to commercially available, 2D microarray

  15. Pericellular Brush and Mechanics of Guinea Pig Fibroblast Cells Studied with AFM.

    PubMed

    Dokukin, Maxim; Ablaeva, Yulija; Kalaparthi, Vivekanand; Seluanov, Andrei; Gorbunova, Vera; Sokolov, Igor

    2016-07-12

    The atomic force microscopy (AFM) indentation method combined with the brush model can be used to separate the mechanical response of the cell body from deformation of the pericellular layer surrounding biological cells. Although self-consistency of the brush model to derive the elastic modulus of the cell body has been demonstrated, the model ability to characterize the pericellular layer has not been explicitly verified. Here we demonstrate it by using enzymatic removal of hyaluronic content of the pericellular brush for guinea pig fibroblast cells. The effect of this removal is clearly seen in the AFM force-separation curves associated with the pericellular brush layer. We further extend the brush model for brushes larger than the height of the AFM probe, which seems to be the case for fibroblast cells. In addition, we demonstrate that an extension of the brush model (i.e., double-brush model) is capable of detecting the hierarchical structure of the pericellular brush, which, for example, may consist of the pericellular coat and the membrane corrugation (microridges and microvilli). It allows us to quantitatively segregate the large soft polysaccharide pericellular coat from a relatively rigid and dense membrane corrugation layer. This was verified by comparison of the parameters of the membrane corrugation layer derived from the force curves collected on untreated cells (when this corrugation membrane part is hidden inside the pericellular brush layer) and on treated cells after the enzymatic removal of the pericellular coat part (when the corrugations are exposed to the AFM probe). We conclude that the brush model is capable of not only measuring the mechanics of the cell body but also the parameters of the pericellular brush layer, including quantitative characterization of the pericellular layer structure. PMID:27410750

  16. An Experimental-Theoretical Analysis of Protein Adsorption on Peptidomimetic Polymer Brushes

    PubMed Central

    Lau, K.H. Aaron; Ren, Chunlai; Park, Sung Hyun; Szleifer, Igal; Messersmith, Phillip B.

    2012-01-01

    Surface-grafted water soluble polymer brushes are being intensely investigated for preventing protein adsorption to improve biomedical device function, prevent marine fouling, and enable applications in biosensing and tissue engineering. In this contribution, we present an experimental-theoretical analysis of a peptidomimetic polymer brush system with regard to the critical brush density required for preventing protein adsorption at varying chain lengths. A mussel adhesive-inspired DOPA-Lys pentapeptide surface grafting motif enabled aqueous deposition of our peptidomimetic polypeptoid brushes over a wide range of chain densities. Critical densities of 0.88 nm−2 for a relatively short polypeptoid 10-mer to 0.42 nm−2 for a 50-mer were identified from measurements of protein adsorption. The experiments were also compared with the protein adsorption isotherms predicted by a molecular theory. Excellent agreements in terms of both the polymer brush structure and the critical chain density were obtained. Furthermore, atomic force microscopy (AFM) imaging is shown to be useful in verifying the critical brush density for preventing protein adsorption. The present co-analysis of experimental and theoretical results demonstrates the significance of characterizing the critical brush density in evaluating the performance of an anti-fouling polymer brush system. The high fidelity of the agreement between the experiments and molecular theory also indicate that the theoretical approach presented can aid in the practical design of antifouling polymer brush systems. PMID:22107438

  17. Friction, wear, and noise of slip ring and brush contacts for synchronous satellite use.

    NASA Technical Reports Server (NTRS)

    Lewis, N. E.; Cole, S. R.; Glossbrenner, E. W.; Vest, C. E.

    1973-01-01

    A program is being conducted for testing of slip rings for synchronous orbit application. Instrumentation systems necessary for monitoring electrical noise, friction, and brush wear at atmospheric pressure and at less than 50 nanotorr have been developed. A multiplex scheme necessary for the simultaneous recording of brush displacement, friction, and electrical noise has also been developed. Composite brushes consisting of silver-molybdenum disulfide-graphite and silver-niobium diselenide-graphite have been employed on rings of coin silver and rhodium plate. Brush property measurements made included measurement of density, electrical resistivity, shear strength, and microstructure.

  18. 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.

  19. Evaluation of boronate-containing polymer brushes and gels as substrates for carbohydrate-mediated adhesion and cultivation of animal cells.

    PubMed

    Ivanov, Alexander E; Kumar, Ashok; Nilsang, Suthasinee; Aguilar, Maria-Rosa; Mikhalovska, Lyubov I; Savina, Irina N; Nilsson, Lars; Scheblykin, Ivan G; Kuzimenkova, Marina V; Galaev, Igor Yu

    2010-02-01

    Boronate-containing thin polyacrylamide gels (B-Gel), polymer brushes (B-Brush) and chemisorbed organosilane layers (B-COSL) were prepared on the surface of glass slides and studied as substrates for carbohydrate-mediated cell adhesion. B-COSL- and B-Brush-modified glass samples exhibited multiple submicron structures densely and irregularly distributed on the glass surface, as found by scanning electron microscopy and atomic force microscopy. B-Gel was ca. 0.1 mm thick and contained pores with effective size of 1-2 microm in the middle and of 5-20 microm on the edges of the gel sample as found by confocal laser scanning microscopy. Evidence for the presence of phenylboronic acid in the samples was given by time-of-flight secondary ion mass-spectrometry (ToF SIMS), contact angle measurements performed in the presence of fructose, and staining with Alizarin Red S dye capable of formation specific, fluorescent complexes with boronic acids. A comparative study of adhesion and cultivation of animal cells on the above substrates was carried out using murine hybridoma M2139 cell line as a model. M2139 cells adhered to the substrates in the culture medium without glucose or sodium pyruvate at pH 8.0, and then were cultivated in the same medium at pH 7.2 for 4 days. It was found that the substrates of B-Brush type were superior both regarding cell adhesion and viability of the adhered cells, among the substrates studied. MTT assay confirmed proliferation of M2139 cells on B-Brush substrates. Some cell adhesion was also registered in the macropores of B-Gel substrate. The effects of surface microstructure of the boronate-containing polymers on cell adhesion are discussed. Transparent glass substrates grafted with boronate-containing copolymers offer good prospects for cell adhesion studies and development of cell-based assays. PMID:19837569

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

    PubMed

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

    2014-06-01

    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 at high chain grafting densities, whereas the more height-mismatched system (System #3) is only microscopically phase separated under comparable brush density conditions even though the lateral

  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. 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

  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. PMID:24681929

  4. 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.

  5. 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.

  6. Description of fuel element brush assembly`s fabrication for 105-K west

    SciTech Connect

    Maassen, D. P.

    1997-10-15

    This report is a description of the process to redesign and fabricate, as well as, describe the features of the Fuel Element Brush Assembly used in the 105-K West Basin. This narrative description will identify problems that occurred during the redesigning and fabrication of the 105-K West Basin Fuel Element Brush Assembly and specifically address their solutions.

  7. The effects of variables in nickel brush plating on brazeability of superalloys

    NASA Astrophysics Data System (ADS)

    Moskowitz, M.

    1992-04-01

    Effects of the anode material and partial depletion of plating solution due to prolonged use on the brazeability of nickel-based alloys were investigated using Waspaloy sample panels brush-plated with sulfamate nickel under various plating conditions. It was found that the protective quality of brush plating was independent of the studied variables of the process.

  8. 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.

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

    DOE PAGESBeta

    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

  10. 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.

  11. A Colorimetric Interdental Probe as a Standard Method to Evaluate Interdental Efficiency of Interdental Brush

    PubMed Central

    Bourgeois, D.; Carrouel, F.; Llodra, J.C.; Bravo, M.; Viennot, S.

    2015-01-01

    The aim of this study is to evaluate the concordance between the empirical choice of interdental brushes of different diameters compared to the gold standard, the IAP CURAPROX© calibrating colorimetric probe. It is carried out with the aim of facilitating the consensus development of best practices. All the subjects’ interproximal spaces were evaluated using the reference technique (colorimetric probe), then after a time lapse of 1.2 ± 0.2 hours, using the empirical clinical technique (brushes) by the same examiner. Each examiner explored 3 subjects. The order the patients were examined with the colorimetric interdental probe (CIP) was random. 446 sites were selected in the study out of 468 potential sites. The correspondence of scores between interdental bushes vs. colorimetric probe is 43.0% [95%-CI: 38.5-47.6]. In 33.41% of the 446 sites, the brush is inferior to the probe; in 23.54% of cases, the brush is superior to the probe. Among the discrepancies there is thus a tendency for the subjects to use brushes with smaller diameter than that recommended by the colorimetric probe. This review has found very high-quality evidence that colorimetric probes plus interdental brushing is more beneficial than interdental brushing alone for increase the concordance between the empirical choice of interdental brushes of different diameters compared to the gold standard. Uncertainties remain and further research is required to provide detailed data on user satisfaction. PMID:26966470

  12. Oligonucleotide Immobilization and Hybridization on Aldehyde-Functionalized Poly(2-hydroxyethyl methacrylate) Brushes.

    PubMed

    Bilgic, Tugba; Klok, Harm-Anton

    2015-11-01

    DNA biosensing requires high oligonucleotide binding capacity interface chemistries that can be tuned to maximize probe presentation as well as hybridization efficiency. This contribution investigates the feasibility of aldehyde-functionalized poly(2-hydroxyethyl methacrylate) (PHEMA) brush-based interfaces for oligonucleotide binding and hybridization. These polymer brushes, which allow covalent immobilization of oligonucleotides, are prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) of HEMA followed by a postpolymerization oxidation step to generate side chain aldehyde groups. A series of polymer brushes covering a range of film thicknesses and grafting densities was investigated with regard to their oligonucleotide binding capacity as well as their ability to support oligonucleotide hybridization. Densely grafted brushes were found to have probe oligonucleotide binding capacities of up to ∼30 pmol/cm(2). Increasing the thickness of these densely grafted brush films, however, resulted in a decrease in the oligonucleotide binding capacity. Less densely grafted brushes possess binding capacities of ∼10 pmol/cm(2), which did not significantly depend on film thickness. The oligonucleotide hybridization efficiencies, however, were highest (93%) on those brushes that present the lowest surface concentration of the probe oligonucleotide. These results highlight the importance of optimizing the probe oligonucleotide surface concentration and binding interface chemistry. The versatility and tunability of the PHEMA-based brushes presented herein makes these films a very attractive platform for the immobilization and hybridization of oligonucleotides. PMID:26441148

  13. 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

  14. 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.

  15. Anomalous Shrinking-Swelling of Nanoconfined End-Charged Polyelectrolyte Brushes: Interplay of Confinement and Electrostatic Effects.

    PubMed

    Chen, Guang; Das, Siddhartha

    2016-07-14

    In this article, we model the structure and configuration of the end-charged polyelectrolyte (PE) brushes grafted on the inner walls of a nanochannel. When the confinement effect is weak, that is, d0 < h/2 (d0 is the PE brush height without electrostatic effects and h is the nanochannel half-height), d < d0 (d is the brush height with the electrostatic effects), that is, the brushes shrink due to the electrostatic effects. Furthermore, for this case, an increase in salt concentration increases d. On the contrary, for the case in which the confinement effect is strong (i.e., d0 > h/2), d > d0 (i.e., the electrostatic effects swell the brushes), and an increase in salt concentration decreases the brush height. These findings reveal that the behavior of the end-charged brushes shows three unique differences when compared to that of the standard PE brushes with charges along their entire backbone. These differences are (a) the presence of a distinct role of the confinement in dictating how the electrostatic effects mediated by the electric double layer govern the height of end-charged brushes, (b) electrostatic-effect-driven shrinking of end-charged brushes for d0 < h/2 (for backbone-charged brushes, the electrostatic effects always swell the brushes), and (c) swelling of end-charged brushes with an increase in salt concentration for d0 < h/2 (backbone-charged brushes always shrink with an increase in salt concentration). Such unique effects of confinement and electrostatics on PE brushes have not been reported previously, and we anticipate that these findings will shed new light on the structure and properties of PE-brush-functionalized nanochannels with implications in applications such as fabrication of functionalized-nanochannel-based nanofluidic diodes, valves, biosensors, current rectifiers, and so forth. PMID:27322913

  16. Hysteresis and bristle stiffening effects in brush seals

    NASA Astrophysics Data System (ADS)

    Basu, P.; Datta, A.; Loewenthal, R.; Short, J.; Johnson, R.

    1994-07-01

    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 may adversely affect 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.

  17. 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.

  18. Self-Assembly into Strands in Amphiphilic Polymer Brushes.

    PubMed

    Larin, Daniil E; Lazutin, Alexei A; Govorun, Elena N; Vasilevskaya, Valentina V

    2016-07-12

    The self-assembly of amphiphilic macromolecules end-grafted to a plane surface is studied using mean-field theory and computer simulations. Chain backbones are built from hydrophobic groups, whereas side groups are hydrophilic. The brush is immersed in a solvent, which can be good or poor, but on average is not far from θ conditions. It is demonstrated that the strong amphiphilicity of macromolecules at a monomer unit level leads to their self-assembly into a system of strands with a 2D hexagonal order in a cross-section parallel to the grafting plane. The structure period is determined by the length of side groups. In theory, this effect is explained by the orientation of strongly amphiphilic monomer units at a strand/solvent boundary that leads to an effective negative contribution to the surface tension. Computer simulations with molecular dynamics (MD) are used for a detailed study of the local brush structure. The aggregation number of strands grows with the increase of the grafting density and side group length. PMID:27267357

  19. Brush seal low surface speed hard-rub characteristics

    NASA Astrophysics Data System (ADS)

    Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

    1993-06-01

    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.

  20. Brush seal bristle flexure and hard-rub characteristics

    NASA Astrophysics Data System (ADS)

    Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

    1992-08-01

    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.

  1. Brush seal low surface speed 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.

  2. 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.

  3. Brush seal bristle flexure and hard-rub characteristics

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Carlile, Julie A.; Liang, Anita D.

    1992-01-01

    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.

  4. The plaque removal effects of single rinsings and brushings.

    PubMed

    Binney, A; Addy, M; Newcombe, R G

    1993-03-01

    Chemical plaque removal is one mechanism whereby an agent could improve oral hygiene and gingival health. As with toothpastes most agents, when delivered as rinses, would be considered adjunctive to mechanical tooth cleaning procedures. The aim of this study was to determine whether selected commercial rinses exhibited clinically significant plaque removal properties alone or when combined with toothbrushing with water or a toothpaste. A group of 12 volunteers took part in this single blind, randomized placebo-controlled, 12 cell cross-over study, employing 6 rinses. During each regimen subjects accumulated plaque from a zero baseline over 72 hours. Plaque removal was then measured by index and area after first a single rinse of product and second a subsequent brushing with water or toothpaste. Prebrushing rinsing removed less than 5% of the plaque with little difference between agents. No rinse was more adjunctive than water to postrinse brushings. Most statistically significant differences arose with the chlorhexidine rinse being apparently less effective. However, the possibility of a disclosing dye interaction cannot be discounted as explaining this anomalous result. This study could not support any claim of a direct prebrushing rinse benefit greater than that provided by water to mechanical plaque removal by any of the products tested. PMID:8463939

  5. A Brownian Dynamics study of dense DNA brushes.

    NASA Astrophysics Data System (ADS)

    Mercier, Jean-Francois; Slater, Gary W.; Mayer, Pascal

    2004-03-01

    Recently, a new way to amplify DNA, called solid phase amplification (SPA) has been introduced. Because SPA uses surface-bound primers, the amplification is limited to two-dimensional surfaces. This allows a large number of different DNA strands to be amplified in the same experiment. SPA amplification leads to the formation of dense DNA brushes where each molecule needs to bend (so that its end can find a matching primer) to successfully duplicate. We used united atom Brownian Dynamics simulations to model the DNA brushes found in SPA experiments. Our goal is to better understand the bending dynamics of grafted DNA molecules. In particular, we have investigated the time required for the free end to come close to the surface, and the average spatial distribution of those contacts, as a function of the chain density and distribution. We also examine the average and the distribution of fundamental quantities such as the radius of gyration and the end-to-end distance of the molecules. This work was supported by a Grant from the Natural Sciences and Engineering Research Council of Canada (NSERC) to GWS and by scholarships from NSERC, FCAR, OGSST, Manteia Predictive Medicine and the University of Ottawa to JFM.

  6. 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.

  7. Brush Seal Arrangement for the RS-68 Turbopump Set

    NASA Technical Reports Server (NTRS)

    Nunez, D.; Ransom, D.; Prueger, G.

    2006-01-01

    The nature of the RS-68 turbopumps requires that the hydrogen seals separating the pump from the turbine must have extremely low levels of leakage and be contained in small packages. Conventional seal technologies are not able to reasonably satisfy such design requirements. A review of experimental measurements and analysis publications suggests that brush seals are well suited for the design requirements. Brush seals are shown to have less leakage than conventional labyrinth and damper seals and have no adverse effects on the rotordynamics of the machine. The bulk-flow analysis presented by Hendricks et al. is used as a guideline to create a spreadsheet that provides mass flow through the seal and heat generated by the rubbing contact of the bristles on the shaft. The analysis is anchored to published data for LN2 and LH2 leakage tests. Finally, the analysis is used to design seals for both applications. It is observed that the most important analysis parameter is the thickness of the bristle pack and its relationship to seal clearance, lay angle and pressure drop.

  8. 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

  9. Elastic repulsion from polymer brush layers exhibiting high protein repellency.

    PubMed

    Inoue, Yuuki; Nakanishi, Tomoaki; Ishihara, Kazuhiko

    2013-08-27

    Hydrophilic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and poly(2-hydroxyethyl methacrylate) (PHEMA) brush layers with different thicknesses and graft densities were prepared to construct a model surface to elucidate protein-surface interactions. In particular, we focused on the steric repulsion of hydrophilic polymer layers as one of the surface properties that strongly influence protein adsorption and employed force-versus-distance (f-d) curve measurements obtained via atomic force microscopy to quantitatively evaluate the steric repulsion force, which is also referred to as the "elastic repulsion energy." We also analyzed direct interactions between the surface and proteins via the f-d curve, because these interactions trigger the protein-adsorption phenomenon. Protein-surface interactions were extremely suppressed at surfaces with high elastic repulsion energies and highly dense polymer brush structures, which is in contrast to those at surfaces with low elastic repulsion energies and low density of the grafted polymer layers. These results indicate that the elastic repulsion from the grafted polymer layer at the surface is an important parameter for controlling protein-surface interactions and protein adsorption phenomenon. PMID:23898820

  10. 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

  11. 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.

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

    DOE PAGESBeta

    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

  13. 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.

  14. 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.

  15. In situ spectroscopic ellipsometry of pH-responsive polymer brushes on gold substrates.

    PubMed

    Rauch, Sebastian; Uhlmann, Petra; Eichhorn, Klaus-Jochen

    2013-11-01

    The dynamic and reversible switching behaviour of polyelectrolyte brushes of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) toward changes of the pH value was studied by in situ VIS-spectroscopic ellipsometry (SE). For this, PDMAEMA brushes with three different molecular weights were synthesized via the "grafting from" method using surface initiated atom transfer radical polymerization. In detail, the applicability of different SE data modelling to describe the optical properties of the different brush layers in the swollen and collapsed state was investigated. Especially for the PDMAEMA brushes with a high molecular weight, an improved optical modelling of the experimental data could be achieved and revealed an exponential distribution of the PDMAEMA fraction in the brush layer. PMID:23812852

  16. 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

  17. Highly uniform hole spacing micro brushes based on aligned carbon nanotube arrays

    PubMed Central

    2013-01-01

    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. PMID:24274897

  18. 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

  19. Light-Induced Reversible Change of Roughness and Thickness of Photosensitive Polymer Brushes.

    PubMed

    Kopyshev, Alexey; Galvin, Casey J; Patil, Rohan R; Genzer, Jan; Lomadze, Nino; Feldmann, David; Zakrevski, Juri; Santer, Svetlana

    2016-07-27

    We investigate light-induced changes in thickness and roughness of photosensitive polymer brushes containing azobenzene cationic surfactants by atomic force microscopy (AFM) in real time during light irradiation. Because the cis-state of azobenzene unit requires more free volume than its trans counterpart, the UV light-induced expansion of polymer thin films associated with the trans-to-cis isomerism of azobenzene groups is expected to occur. This phenomenon is well documented in physisorbed polymer films containing azobenzene groups. In contrast, photosensitive polymer brushes show a decrease in thickness under UV irradiation. We have found that the azobenzene surfactants in their trans-state form aggregates within the brush. Under irradiation, the surfactants undergo photoisomerization to the cis-state, which is more hydrophilic. As a consequence, the aggregates within the brush are disrupted, and the polymer brush contracts. When subsequently irradiated with blue light the polymer brush thickness returns back to its initial value. This behavior is related to isomerization of the surfactant to the more hydrophobic trans-state and subsequent formation of surfactant aggregates within the polymer brush. The photomechanical function of the dry polymer brush, i.e., contraction and expansion, was found to be reversible with repeated irradiation cycles and requires only a few seconds for switching. In addition to the thickness change, the roughness of the brush also changes reversibly between a few Angstroms (blue light) and several nanometers (UV light). Photosensitive polymer brushes represent smart films with light responsive thickness and roughness that could be used for generating dynamic fluctuating surfaces, the function of which can be turned on and off in a controllable manner on a nanometer length scale. PMID:27351592

  20. Structure and collapse of a surface-grown strong polyelectrolyte brush on sapphire.

    PubMed

    Dunlop, Iain E; Thomas, Robert K; Titmus, Simon; Osborne, Victoria; Edmondson, Steve; Huck, Wilhelm T S; Klein, Jacob

    2012-02-14

    We have used neutron reflectometry to investigate the behavior of a strong polyelectrolyte brush on a sapphire substrate, grown by atom-transfer radical polymerization (ATRP) from a silane-anchored initiator layer. The initiator layer was deposited from vapor, following treatment of the substrate with an Ar/H(2)O plasma to improve surface reactivity. The deposition process was characterized using X-ray reflectometry, indicating the formation of a complete, cross-linked layer. The brush was grown from the monomer [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC), which carries a strong positive charge. The neutron reflectivity profile of the swollen brush in pure water (D(2)O) showed that it adopted a two-region structure, consisting of a dense surface region ∼100 Å thick, in combination with a diffuse brush region extending to around 1000 Å from the surface. The existence of the diffuse brush region may be attributed to electrostatic repulsion from the positively charged surface region, while the surface region itself most probably forms due to polyelectrolyte adsorption to the hydrophobic initiator layer. The importance of electrostatic interactions in maintaining the brush region is confirmed by measurements at high (1 M) added 1:1 electrolyte, which show a substantial transfer of polymer from the brush to the surface region, together with a strong reduction in brush height. On addition of 10(-4) M oppositely charged surfactant (sodium dodecyl sulfate), the brush undergoes a dramatic collapse, forming a single dense layer about 200 Å in thickness, which may be attributed to the neutralization of the monomers by adsorbed dodecyl sulfate ions in combination with hydrophobic interactions between these dodecyl chains. Subsequent increases in surfactant concentration result in slow increases in brush height, which may be caused by stiffening of the polyelectrolyte chains due to further dodecyl sulfate adsorption. PMID:22292571

  1. Cleaning by Brush-Scrubbing of Chemical Mechanical Polished Silicon Surfaces Using Ozonized Water and Diluted HF

    NASA Astrophysics Data System (ADS)

    Kurokawa, Yoshiaki; Hirose, Harumichi; Moriya, Takahiko; Kimura, Chouichi

    1999-09-01

    A new process for scrubbing chemical-mechanical-polished silicon wafer surfaces with a brush (brush-scrubbing process) was developed. The scrubbing is performed in two stages; the first stage involves a wet treatment using ozonized water and dilute HF. The second stage involves scrubbing with a Poly(vinyl alcohol)(PVA) brush. After scrubbing, the number of residual particles, metal and carbonaceous contamination, and surface roughness of the silicon wafer surface were evaluated. It was determined that this new brush-scrubbing process efficiently removed particles from chemical mechanical polishedsilicon surfaces. Finally, a model explaining the new brush-scrubbingprocess is constructed.

  2. Oxidation and Volatilization from Tungsten Brush High Heat Flux Armor During High Temperature Steam Exposure

    SciTech Connect

    Smolik, Galen Richard; Pawelko, Robert James; Anderl, Robert Andrew; Petti, David Andrew

    2000-05-01

    Tungsten brush accommodates thermal stresses and high heat flux in fusion reactor components such as plasma facing surfaces or armor. However, inherently higher surface areas are introduced with the brush design. We have tested a specific design of tungsten brush in steam between 500 and 1100°C. Hydrogen generation and tungsten volatilization rates were determined to address fusion safety issues. The brush prepared from 3.2-mm diameter welding rods had a packing density of 85 percent. We found that both hydrogen generation and tungsten volatilization from brush, fixtured to represent a unit within a larger component, were less than projections based upon the total integrated surface area (TSA). Steam access and the escape of hydrogen and volatile oxide from void spaces within the brush are restricted compared to specimens with more direct diffusion pathways to the test environment. Hydrogen generation rates from restrained specimens based on normal surface area (NSA) remain about five times higher than rates based on total surface areas from specimens with direct steam access. Volatilization rates from restrained specimens based upon normal surface area (NSA) were only 50 percent higher than our historic cumulative maximum flux plot (CMFP) for tungsten. This study has shown that hydrogen generation and tungsten volatilization from brush do not scale according to predictions with previously determined rates, but in fact, with higher packing density could approach those from flat surfaces.

  3. Dense Poly(ethylene glycol) Brushes Reduce Adsorption and Stabilize the Unfolded Conformation of Fibronectin.

    PubMed

    Faulón Marruecos, David; Kastantin, Mark; Schwartz, Daniel K; Kaar, Joel L

    2016-03-14

    Polymer brushes, in which polymers are end-tethered densely to a grafting surface, are commonly proposed for use as stealth coatings for various biomaterials. However, although their use has received considerable attention, a mechanistic understanding of the impact of brush properties on protein adsorption and unfolding remains elusive. We investigated the effect of the grafting density of poly(ethylene glycol) (PEG) brushes on the interactions of the brush with fibronectin (FN) using high-throughput single-molecule tracking methods, which directly measure protein adsorption and unfolding within the brush. We observed that, as grafting density increased, the rate of FN adsorption decreased; however, surface-adsorbed FN unfolded more readily, and unfolded molecules were retained on the surface for longer residence times relative to those of folded molecules. These results, which are critical for the rational design of PEG brushes, suggest that there is a critical balance between protein adsorption and conformation that underlies the utility of such brushes in physiological environments. PMID:26866385

  4. Effect of Process Parameters on Particle Removal Efficiency in Poly(vinyl alcohol) Brush Scrubber Cleaning

    NASA Astrophysics Data System (ADS)

    An, Joonho; Lee, Hyunseop; Kim, Hyoungjae; Jeong, Haedo

    2012-02-01

    Wafer cleaning is one of the most critical processes in the semiconductor device manufacturing. Poly(vinyl alcohol) (PVA) brush scrubber cleaning is much attractive when compared with traditional wet-batch cleaning which causes the cross-contamination among the wafers in a bath and environmental issues with huge amount of chemical and deionized water (DIW) usages. The mechanical forces generated from PVA brush contact can remove the particles on a wafer surface under low concentration of chemical solution without cross-contamination. In this research, we monitored the change of the dynamic forces including normal and friction force generated by PVA brush contacts during cleaning process, and also investigated the effects of scrubbing conditions of PVA brush overlap and velocity, and the surface tension (low- or high-hydrophilic) of the wafer on the particle removal efficiency. The results show that the driving mechanism to remove the particle on a wafer surface can be changed by the PVA brush overlap and velocity condition such as the hydrodynamic drag force in the brush soft contact condition and friction force in the brush hard contact condition. The particle removal efficiency is higher under the low-hydrophilic surface having a low surface tension compared to high-hydrophilic surface.

  5. Design optimization of a brush turbine with a cleaner/water based solution

    NASA Astrophysics Data System (ADS)

    Kim, Rhyn H.

    1994-10-01

    Recently, a fluid turbine which has a brush attached to it has been designed and tested with water as fluid. The purpose of the turbine-brush is to clean up fouling in a tube. The Montreal Protocol prohibits the use of CFC products from refrigeration industry or from industry in general as a cleanser in 1996. Alternatives for the cleansers, devices or a combination of alternative devices with a cleanser should be found. One of the methods is to develop a device which cleans fouling with a cleaning medium. In this paper, we describe a turbine connected with a brush. However, the turbine with the brush should be simple and easy to install. This device is a combined small liquid turbine with a brush. The turbine is activated by the liquid flowing through the tube. Then the turbine turns the brush cleaning fouling along the tube. Based on the energy conservation and the Bernoulli equation along with an empirical relationship of drag force obtained from an experimental apparatus, a relationship of the rotational speed, the number of blades, and geometric variables of the turbine-brush was obtained. The predicted rotational speeds were compared with the experimental observations. Further work was recommended for improvements.

  6. 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

  7. Design optimization of a brush turbine with a cleaner/water based solution

    NASA Technical Reports Server (NTRS)

    Kim, Rhyn H.

    1994-01-01

    Recently, a fluid turbine which has a brush attached to it has been designed and tested with water as fluid. The purpose of the turbine-brush is to clean up fouling in a tube. The Montreal Protocol prohibits the use of CFC products from refrigeration industry or from industry in general as a cleanser in 1996. Alternatives for the cleansers, devices or a combination of alternative devices with a cleanser should be found. One of the methods is to develop a device which cleans fouling with a cleaning medium. In this paper, we describe a turbine connected with a brush. However, the turbine with the brush should be simple and easy to install. This device is a combined small liquid turbine with a brush. The turbine is activated by the liquid flowing through the tube. Then the turbine turns the brush cleaning fouling along the tube. Based on the energy conservation and the Bernoulli equation along with an empirical relationship of drag force obtained from an experimental apparatus, a relationship of the rotational speed, the number of blades, and geometric variables of the turbine-brush was obtained. The predicted rotational speeds were compared with the experimental observations. Further work was recommended for improvements.

  8. 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

  9. Impact of self-tongue brushing on taste perception in Thai older adults: A pilot study.

    PubMed

    Madiloggovit, Jirakate; Chotechuang, Nattida; Trachootham, Dunyaporn

    2016-01-01

    Oral hygiene influences taste, affecting appetite and nutrition in older adults. However, the impact of self-administered tongue brushing on their taste perceptions was unclear. This pilot study (N = 44) was aimed to observe the changes in taste thresholds using Filter Paper Disc after tongue brushing in Thai older adults. Based on the results, continuous tongue brushing for 3 months reduced tongue coat (p < 0.01) and improved subjective taste in 74% of participants. Sweet and salty recognition thresholds were reduced in both anterior and posterior tongue, while sour and bitter thresholds were reduced only in posterior tongue. No changes in umami (savory) were observed. Daily brushing was more effective than weekly brushing in improving the sweet and bitter tastes. The data suggested that tongue brushing could improve perception of multiple tastes and daily tongue brushing was recommended as routine personal care for older adults. This study supports further investigation in a randomized-controlled setting. PMID:26747405

  10. Biomimetic polymer brushes containing tethered acetylcholine analogs for protein and hippocampal neuronal cell patterning.

    PubMed

    Zhou, Zhaoli; Yu, Panpan; Geller, Herbert M; Ober, Christopher K

    2013-02-11

    This paper describes a method to control neuronal cell adhesion and differentiation with both chemical and topographic cues by using a spatially defined polymer brush pattern. First, biomimetic methacrylate polymer brushes containing tethered neurotransmitter acetylcholine functionalities in the form of dimethylaminoethyl methacrylate or free hydroxyl-terminated poly(ethylene glycol) units were prepared using the "grown from" method through surface-initiated atom transfer radical polymerization reactions. The surface properties of the resulting brushes were thoroughly characterized with various techniques and hippocampal neuronal cell culture on the brush surfaces exhibit cell viability and differentiation comparable to, or even better than, those on commonly used poly-l-lysine coated glass coverslips. The polymer brushes were then patterned via UV photolithography techniques to provide specially designed surface features with different sizes (varying from 2 to 200 μm) and orientations (horizontal and vertical). Protein absorption experiments and hippocampal neuronal cell culture tests on the brush patterns showed that both protein and neurons can adhere to the patterns and therefore be guided by such patterns. These results also demonstrate that, because of their unique chemical composition and well-defined nature, the developed polymer brushes may find many potential applications in cell-material interactions studies and neural tissue engineering. PMID:23336729

  11. Surface Dynamics of Free PS Chains on Chemically Identical Polymer Brushes: An XPCS Study

    NASA Astrophysics Data System (ADS)

    Ugur, Gokce; Akgun, Bulent; Jiang, Zhang; Narayanan, Suresh; Brittain, William J.; Foster, Mark D.

    2009-03-01

    We found no relaxation of fluctuations of the brush surfaces within the range of time (0.2 -1100 s) and length scale (0.6-3 um) studied by X-ray photon correlation spectroscopy(XPCS). This is true for PS brushes of thicknesses of 9 - 101 nm and grafting density of 0.12-0.6 chains/nm^2 at temperatures up to 130C above bulk Tg. Results on the dynamics of a layer of untethered 2.2k PS chains on top of a PS brush surface show that placing the PS chains atop the brush dramatically slows down the surface relaxations of the film surface. As the ratio of the thickness of the layer of untethered chains to the thickness of the highly dense brush drops below ˜0.5, the surface relaxations become too slow to be observed readily with XPCS. Reducing grafting density of the underlying brush markedly slows the surface dynamics. The surface dynamics of the layer of ``free'' PS chains are coupled with those of the underlying brush.

  12. Control of Cell Attachment and Spreading on Poly(acrylamide) Brushes with Varied Grafting Density.

    PubMed

    Lilge, Inga; Schönherr, Holger

    2016-01-26

    To achieve spatial control of fibroblast cell attachment and spreading on a biocompatible polymer coating, the effect of poly(acrylamide) (PAAm) brushes with varied grafting density was investigated. The synthesis of the brushes was performed by surface-initiated atom transfer radical polymerization (SI-ATRP). Gold substrates were modified with binary self-assembled monolayers (SAMs) of an initiator and 16-mercaptohexadecanoic acid (MHDA) as an "inert" thiol to initiate the ATRP of AAm. By using different mixtures for the binary SAMs, a series of polymer brushes with varied grafting densities were prepared. The fractional coverage of surface bound initiator was determined by grazing incidence Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and contact angle measurements. A linear relationship between the Br/S ratio determined by XPS and ToF-SIMS versus the fraction of initiator on the surface determined by water contact angle measurements was observed. The varied initiation concentration on the gold substrates yielded PAAm brushes with different thicknesses, indicating a transition from mushroom to brush regimes with increasing grafting density. Thereby we achieved exquisite control of the degree of cell adhesion. Cell attachment experiments with NIH 3T3 fibroblast cells revealed cell spreading on PAAm brushes with low grafting densities (initiator fractional coverage <0.2) as well as a complete passivation by polymer brushes with higher grafting densities. PMID:26771447

  13. Brush plating of tin(II) selenide thin films

    NASA Astrophysics Data System (ADS)

    Subramanian, B.; Sanjeeviraja, C.; Jayachandran, M.

    2002-01-01

    Brush plating technique has been adopted for the first time to coat tin selenide thin film on tin oxide coated conducting substrates at room temperature, 50°C and 60°C. Uniform and pinhole free films were deposited at potentials 5.0 V. XRD analyses show the polycrystalline nature of the films with orthorhombic structure. Optical studies show the indirect nature with a bandgap of 1.0 eV. SEM pictures show smooth and uniform surface morphology with a grain size of about 0.3 μm. Film roughness was characterized by atomic force microscopy. Mott-Schottky plot has been drawn to evaluate the semiconductor parameters.

  14. Gingival abrasion and recession in manual and oscillating–rotating power brush users

    PubMed Central

    Rosema, NAM; Adam, R; Grender, JM; Van der Sluijs, E; Supranoto, SC; Van der Weijden, GA

    2014-01-01

    Objective To assess gingival recession (GR) in manual and power toothbrush users and evaluate the relationship between GR and gingival abrasion scores (GA). Methods This was an observational (cross-sectional), single-centre, examiner-blind study involving a single-brushing exercise, with 181 young adult participants: 90 manual brush users and 91 oscillating–rotating power brush users. Participants were assessed for GR and GA as primary response variables. Secondary response variables were the level of gingival inflammation, plaque score reduction and brushing duration. Pearson correlation was used to describe the relationship between number of recession sites and number of abrasions. Prebrushing (baseline) and post-brushing GA and plaque scores were assessed and differences analysed using paired tests. Two-sample t-test was used to analyse group differences; ancova was used for analyses of post-brushing changes with baseline as covariate. Results Overall, 97.8% of the study population had at least one site of ≥1 mm of gingival recession. For the manual group, this percentage was 98.9%, and for the power group, this percentage was 96.7% (P = 0.621). Post-brushing, the power group showed a significantly smaller GA increase than the manual group (P = 0.004); however, there was no significant correlation between number of recession sites and number of abrasions for either group (P ≥ 0.327). Conclusions Little gingival recession was observed in either toothbrush user group; the observed GR levels were comparable. Lower post-brushing gingival abrasion levels were seen in the power group. There was no correlation between gingival abrasion as a result of brushing and the observed gingival recession following use of either toothbrush. PMID:24871587

  15. Temperature Dependence of the Surface and Volume Hydrophilicity of Hydrophilic Polymer Brushes.

    PubMed

    Zhuang, Pengyu; Dirani, Ali; Glinel, Karine; Jonas, Alain M

    2016-04-12

    The temperature-dependence of the volume and surface hydrophilicity of a series of water-swollen dense polymer brushes is measured by contact angle measurements in the captive bubble configuration, by ellipsometry, and by quartz crystal microbalance with dissipation monitoring (QCM-D). Thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and poly(di(methoxyethoxy)ethyl methacrylate) (PMEO2MA), strongly hydrophilic poly(N,N-dimethylacrylamide) (PDMA) and poly(oligo(ethylene glycol) methacrylate) (POEGMA), and weakly hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) brushes were synthesized by surface-initiated atom-transfer radical polymerization (SI-ATRP). Conditions leading to reproducible measurements of the contact angle are first provided, giving access to the surface hydrophilicity. Volume hydrophilicity is quantified by measuring the swelling of the brushes, either by QCM-D or by ellipsometry. A model-free methodology is proposed to analyze the QCM-D data. Comparison between the acoustic and optical swelling coefficients shows that QCM-D is sensitive to the maximal thickness of swollen brushes, while ellipsometry provides an integral thickness. Diagrams of surface versus volume hydrophilicity of the brushes finally lead to identify two types of behavior: strongly water-swollen brushes exhibit a progressive decrease of volume hydrophilicity with temperature, while surface hydrophilicity changes moderately; weakly water-swollen brushes have a close-to-constant volume hydrophilicity, while surface hydrophilicity decreases with temperature. Thermoresponsive brushes abruptly switch from one behavior to the other, and do not exhibit an abrupt change of surface hydrophilicity across their collapse transition contrarily to a common erroneous belief. In general, there is no direct correlation between surface and volume hydrophilicity, because surface properties are dependent on the details of conformation and composition at the surface, whereas volume properties

  16. Preparation and characterization of optical-functional diblock copolymer brushes on hollow sphere surface via atom transfer radical polymerization

    SciTech Connect

    Wang, Li-Ping; Li, Wen-Zhi; Zhao, Li-Min; Zhang, Chun-Juan; Wang, Yan-Dong; Kong, Li-Li; Li, Ling-Ling

    2010-09-15

    The optical-functional poly(methyl methacrylate)-block-Tb complex diblock copolymer brushes grafted from hollow sphere surface via atom transfer radical polymerization were investigated in this work. A sufficient amount of azo initiator was introduced onto hollow sphere surface firstly. Then the monomer methyl methacrylate was polymerized via surface-initiated reverse atom transfer radical polymerization using azo group modified hollow sphere as initiator. Following, the poly(methyl methacrylate) modified hollow sphere was used as maroinitiator for surface-initiated atom transfer radical polymerization of Tb complex. The samples were characterized by Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance, gel permeation chromatographer and transmission electron microscopy, respectively. The results indicated that the poly(methyl methacrylate) had grafted from hollow sphere surface and the average diameter of hollow core was about 1 {mu}m. The optical properties of the poly(methyl methacrylate)-block-Tb copolymer modified hollow sphere were also reported.

  17. Stimuli-responsive surfaces using polyampholyte polymer brushes prepared via atom transfer radical polymerization.

    PubMed

    Ayres, Neil; Cyrus, Crystal D; Brittain, William J

    2007-03-27

    The synthesis of AB diblock copolymer polyampholyte polymer brushes of the type Si/SiO2//poly(acrylic acid-b-vinyl pyridine) prepared using atom transfer radical polymerization is reported. Both 2- and 4-vinyl pyridine have been used. The diblock polyampholyte polymer brushes demonstrate stimuli-responsive behavior with respect to pH, showing both polyelectrolyte and polyampholyte effects. Furthermore, we have quaternized the 4-vinyl pyridine segments to form a mixed weak/strong, or annealed/quenched, polyelectrolyte system. The quaternized polymer brush exhibits different pH-responsive behavior, with decreasing film thickness being observed with increasing pH. PMID:17319701

  18. A sequence of calculation of the modes of dimensional combined processing by an electrode brush

    NASA Astrophysics Data System (ADS)

    Ryazantsev, A. Yu; Kirillov, O. N.; Smolentsev, V. P.; Totay, A. V.

    2016-04-01

    In the article the way of calculation of the modes of dimensional processing by an electrode brush is considered. The choice of a liquid working environment is presented. A calculation of tension in electrodes and forces of the technological current realized during processing is given. A choice of a clip of wire bunches in a processing zone, feeding an electrode brush to a non-rigid work piece. The recommended technological indicators of the process of the finishing combined treatment by an electrode brush are presented.

  19. Controlled cell adhesion on poly(dopamine) interfaces photopatterned with non-fouling brushes.

    PubMed

    Rodriguez-Emmenegger, Cesar; Preuss, Corinna M; Yameen, Basit; Pop-Georgievski, Ognen; Bachmann, Michael; Mueller, Jan O; Bruns, Michael; Goldmann, Anja S; Bastmeyer, Martin; Barner-Kowollik, Christopher

    2013-11-13

    Bioinspired poly(dopamine) (PDA) films are merged with antifouling poly(MeOEGMA) brushes utilizing a nitrile imine-mediated tetrazole-ene cycloaddition (NITEC)-based phototriggered surface encoding protocol. The antifouling brushes were photopatterned on PDA surfaces, leading cells to form confluent layers in the non-irradiated sections, while no adhesion occurred on the brushes resulting in a remarkably precise cell pattern. The presented strategy paves the way for the design of tailor-made patterned cell interfaces. PMID:23999835

  20. Development of the Upgraded DC Brush Gear Motor for Spacebus Platforms

    NASA Technical Reports Server (NTRS)

    Berning, Robert H.; Viout, Olivier

    2010-01-01

    The obsolescence of materials and processes used in the manufacture of traditional DC brush gear motors has necessitated the development of an upgraded DC brush gear motor (UBGM). The current traditional DC brush gear motor (BGM) design was evaluated using Six-Sigma process to identify potential design and production process improvements. The development effort resulted in a qualified UBGM design which improved manufacturability and reduced production costs. Using Six-Sigma processes and incorporating lessons learned during the development process also improved motor performance for UBGM making it a more viable option for future use as a deployment mechanism in space flight applications.

  1. A hybrid floating brush seal (HFBS) for improved sealing and wear performance in turbomachinery applications

    NASA Astrophysics Data System (ADS)

    Lattime, Scott Byran

    A conceptually new type of seal has been developed for gas turbine applications which dramatically reduces wear and leakage associated with current labyrinth and brush seal technologies. The Hybrid Floating Brush Seal (HFBS) combines brush seal and film riding face seal technologies to create a hybrid seal that allows both axial and radial excursions of the sealed shaft, while simultaneously eliminating interface surface speeds (friction and heat) between the rotor and the brush material that characterize standard brush seal technology. A simple test rig was designed to evaluate feasibility of the HFBS under relatively low pressures and rotational speeds (50psig, 5krpm). A second test stand was created to study the effects of centrifugal force on bristle deflection. A third test facility was constructed for prototype development and extensive room temperature testing at moderate pressures and fairly high rotational speeds (100psig, 40krpm). This test rig also allowed the evaluation of the HFBS during axial movement of a rotating shaft. An analytical model to predict the effects of centrifugal force on the bristles of a rotating brush seal was developed. Room temperature analysis of the HFBS proved successful for relatively high operating rotational velocities at moderate pressures with very acceptable leakage rates for gas turbine engines. Brush seals were able to track rotor speeds up to 24krpm while maintaining sealing integrity. The HFBS's ability to function under axial shaft displacement and synchronous dynamic radial loading was also proven successful. Hydrodynamic performance of the face seal was proven to provide adequate stiffness and load carrying capacity to keep the brush seal from contacting the face seal at pressure drops across the brush of up to 100psi. Leakage performance over standard brush seal and labyrinth technology was quite dramatic. The HFBS showed its sealing advantage using much higher radial interference between the rotor and the bristle

  2. Experimental and theoretical rotordynamic stiffness coefficients for a three-stage brush seal

    NASA Astrophysics Data System (ADS)

    Pugachev, A. O.; Deckner, M.

    2012-08-01

    Experimental and theoretical results are presented for a multistage brush seal. Experimental stiffness is obtained from integrating circumferential pressure distribution measured in seal cavities. A CFD analysis is used to predict seal performance. Bristle packs are modeled by the porous medium approach. Leakage is predicted well by the CFD method. Theoretical stiffness coefficients are in reasonable agreement with the measurements. Experimental results are also compared with a three-teeth-on-stator labyrinth seal. The multistage brush seal gives about 60% leakage reduction over the labyrinth seal. Rotordynamic stiffness coefficients are also improved: the brush seal has positive direct stiffness and smaller cross-coupled stiffness.

  3. Wire grill brush bristle as an unusual foreign body: report of two pediatric cases.

    PubMed

    Arganbright, Jill M; Bruegger, Daniel E; Sykes, Kevin J; Wei, Julie L

    2012-03-01

    Wire grill brushes are commonly used for cleaning grill grates. Accidental ingestion of a wire bristle from a grill-cleaning brush is a rarely reported foreign body, with only three prior case reports. Although scarce in the literature, we encountered two pediatric cases at the regional children's hospital within 1 year. By presenting these two cases, our goal was to raise awareness of this potentially hazardous foreign body. Additionally, we raise a consumer safety issue associated with the use of wire grill-cleaning brushes as there are currently no ingestion hazard warnings on these products. Laryngoscope,, 2011. PMID:22231656

  4. Unipolar brush cell: a potential feedforward excitatory interneuron of the cerebellum.

    PubMed

    Diño, M R; Schuerger, R J; Liu, Y; Slater, N T; Mugnaini, E

    2000-01-01

    Unipolar brush cells are a class of interneurons in the granular layer of the mammalian cerebellum that receives excitatory mossy fiber synaptic input in the form of a giant glutamatergic synapse. Previously, it was shown that the unipolar brush cell axon branches within the granular layer, giving rise to large terminals. Single mossy fiber stimuli evoke a prolonged burst of firing in unipolar brush cells, which would be distributed to postsynaptic targets within the granular layer. Knowledge of the ultrastructure of the unipolar brush cell terminals and of the cellular identity of its postsynaptic targets is required to understand how unipolar brush cells contribute to information processing in the cerebellar circuit. To investigate the unipolar brush cell axon and its targets, unipolar brush cells were patch-clamped in fresh parasagittal slices from rat cerebellar vermis with electrodes filled with Lucifer Yellow and Biocytin, and examined by confocal fluorescence and electron microscopy. Biocytin was localized with diaminobenzidine chromogen or gold-conjugated, silver-intensified avidin. Light microscopic examination revealed a single thin axon emanating from the unipolar brush cell soma that gave rise to 2-3 axon collaterals terminating in mossy fiber-like rosettes in the granular layer, typically within a few hundred microm of the soma. In some cases, axon collaterals crossed the white matter within the same folium before terminating in the adjacent granular layer. Electron microscopic examination of serial ultrathin sections revealed that proximal unipolar brush cell axons and axon collaterals were unmyelinated and devoid of synaptic contacts. However, the rosette-shaped enlargements of each collateral formed the central component of glomeruli where they were surrounded by dendrites of granule cells and/or other unipolar brush cells, with which they formed asymmetric synaptic contacts. A long-latency repetitive burst of polysynaptic activity was observed in

  5. Patterned Poly(acrylic acid) Brushes Containing Gold Nanoparticles for Peptide Detection by Surface-Assisted Laser Desorption/Ionization Mass Spectrometry.

    PubMed

    Sangsuwan, Arunee; Narupai, Benjaporn; Sae-ung, Pornpen; Rodtamai, Sasithon; Rodthongkum, Nadnudda; Hoven, Voravee P

    2015-11-01

    Patterned poly(acrylic acid) (PAA) brushes was successfully generated via photolithography and surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylic acid as verified by water contact angle measurements and FT-IR analysis. The carboxyl groups of PAA brushes can act as reducing moieties for in situ synthesis of gold nanoparticles (AuNPs), without the use of additional reducing agent. The formation of AuNPs was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy. The glass surface-modified by PAA brushes and immobilized with AuNPs (AuNPs-PAA) can be used as a substrate for SALDI-MS analysis, which is capable of detecting both small peptides having m/z ≤ 600 (glutathione) and large peptides having m/z ≥ 1000 (bradykinin, ICNKQDCPILE) without the interference from matrix signal suggesting that AuNPs were stably trapped within the PAA brushes and the carboxyl groups of PAA can serve as internal proton source. By employing AuNPs as the capture probe, the AuNPs-PAA substrate can selectively identify thiol-containing peptides from the peptide mixtures with LOD as low as 0.1 and 0.05 nM for glutathione and ICNKQDCPILE, respectively. An ability to selectively detect ICNKQDCPILE in a diluted human serum is also demonstrated. The patterned format together with its high sensitivity and selectivity render this newly developed substrate a potential platform for high-throughput analysis of other biomarkers, especially those with low molecular weight in complex biological samples. PMID:26434604

  6. Brush in the bath of active particles: Anomalous stretching of chains and distribution of particles

    NASA Astrophysics Data System (ADS)

    Li, Hui-shu; Zhang, Bo-kai; Li, Jian; Tian, Wen-de; Chen, Kang

    2015-12-01

    The interaction between polymer brush and colloidal particles has been intensively studied in the last two decades. Here, we consider a flat chain-grafted substrate immersed in a bath of active particles. Simulations show that an increase in the self-propelling force causes an increase in the number of particles that penetrate into the brush. Anomalously, the particle density inside the main body of the brush eventually becomes higher than that outside the brush at very large self-propelling force. The grafted chains are further stretched due to the steric repulsion from the intruded particles. Upon the increase of the self-propelling force, distinct stretching behaviors of the chains were observed for low and high grafting densities. Surprisingly, we find a weak descent of the average end-to-end distance of chains at high grafting density and very large force which is reminiscent of the compression effect of a chain in the active bath.

  7. Brush in the bath of active particles: Anomalous stretching of chains and distribution of particles.

    PubMed

    Li, Hui-shu; Zhang, Bo-kai; Li, Jian; Tian, Wen-de; Chen, Kang

    2015-12-14

    The interaction between polymer brush and colloidal particles has been intensively studied in the last two decades. Here, we consider a flat chain-grafted substrate immersed in a bath of active particles. Simulations show that an increase in the self-propelling force causes an increase in the number of particles that penetrate into the brush. Anomalously, the particle density inside the main body of the brush eventually becomes higher than that outside the brush at very large self-propelling force. The grafted chains are further stretched due to the steric repulsion from the intruded particles. Upon the increase of the self-propelling force, distinct stretching behaviors of the chains were observed for low and high grafting densities. Surprisingly, we find a weak descent of the average end-to-end distance of chains at high grafting density and very large force which is reminiscent of the compression effect of a chain in the active bath. PMID:26671400

  8. Efficacy of plaque-removal using interdental brushes and waxed dental floss.

    PubMed

    Bergenholtz, A; Olsson, A

    1984-06-01

    The plaque-removing efficacy when using waxed dental floss and three interdental brushes was compared in an intraindividual clinical trial. Nine adult patients treated for periodontal disease, with a reduced but healthy periodontium and large interdental spaces were subjects in the study. Each subject tested the four interdental cleaning aids in random sequence over a 2-wk period. The duration of the study was 8 wk. The results indicated that the use of interdental brushes is preferable to that of dental floss in cleaning interdental areas where the papilla is missing. No difference in achieved cleanliness was noted after use of the different interdental brushes tested. No gingival damage or damage to the hard tissue of the teeth was observed after use of interdental brushes or dental floss. PMID:6589735

  9. Friction, wear and noise of slip ring and brush contacts for synchronous satellite use.

    NASA Technical Reports Server (NTRS)

    Lewis, N. E.; Cole, S. R.; Glossbrenner, E. W.; Vest, C. E.

    1972-01-01

    A program is being conducted for testing of slip rings for synchronous orbit application. Instrumentation systems necessary for monitoring electrical noise, friction, and brush wear at atmospheric pressure and at less than 50 ntorr have been developed. A multiplex scheme necessary for the simultaneous recording of brush displacement, friction, and electrical noise has also been developed. Composite brushes consisting of silver-molybdenum disulfide-graphite and silver-niobium diselenide-graphite have been employed on rings of coin silver and rhodium plate. Four contact combinations have been tested during an ambient condition run-in at 150 rpm and a humidity sequence at 0.1 rpm. The first six months of the two year vacuum test at 0.1 rpm have been completed. Electrical noise, friction and brush wear data recorded during these periods have been analyzed.

  10. Brush seal performance and durability issues based on T-700 engine test results

    NASA Astrophysics Data System (ADS)

    Hendricks, R. C.

    1994-03-01

    The integrity and performance of brush seals have been established. Severe bench and engine tests have shown high initial wear or run-in rates, material smearing at the interface, and bristle and rub-runner wear, but the brush seals did not fail. Short-duration (46 hr) experimental T-700 engine testing of the compressor discharge seal established over 1-percent engine performance gain (brush versus labyrinth). Long-term gains were established only as leakage comparisons, with the brush at least 20 percent better at controlling leakage. Long-term materials issues, such as wear and ultimately seal life, remain to be resolved. Future needs are cited for materials and analysis tools that account for heat generation, thermomechanical behavior, and tribological pairing to enable original equipment manufacturers to design high-temperature, high-surface-speed seals with confidence.

  11. Peptides Displayed as High Density Brush Polymers Resist Proteolysis and Retain Bioactivity

    PubMed Central

    2015-01-01

    We describe a strategy for rendering peptides resistant to proteolysis by formulating them as high-density brush polymers. The utility of this approach is demonstrated by polymerizing well-established cell-penetrating peptides (CPPs) and showing that the resulting polymers are not only resistant to proteolysis but also maintain their ability to enter cells. The scope of this design concept is explored by studying the proteolytic resistance of brush polymers composed of peptides that are substrates for either thrombin or a metalloprotease. Finally, we demonstrate that the proteolytic susceptibility of peptide brush polymers can be tuned by adjusting the density of the polymer brush and offer in silico models to rationalize this finding. We contend that this strategy offers a plausible method of preparing peptides for in vivo use, where rapid digestion by proteases has traditionally restricted their utility. PMID:25314576

  12. Brushes and picks used on nails during the surgical scrub to reduce bacteria: a randomised trial.

    PubMed

    Tanner, J; Khan, D; Walsh, S; Chernova, J; Lamont, S; Laurent, T

    2009-03-01

    Though brushes are no longer used on the hands and forearms during the surgical scrub, they are still widely used on the nails. The aim of this study was to determine whether nail picks and nail brushes are effective in providing additional decontamination during a surgical hand scrub. A total of 164 operating department staff were randomised to undertake one of the following three surgical hand-scrub protocols: chlorhexidine only; chlorhexidine and a nail pick; or chlorhexidine and a nail brush. Bacterial hand sampling was conducted before and 1h after scrubbing using a modified version of the glove juice method. No statistically significant differences in bacterial numbers were found between any two of the three intervention groups. Nail brushes and nail picks used during surgical hand scrubs do not decrease bacterial numbers and are unnecessary. PMID:19162371

  13. Brush Seal Performance and Durability Issues Based on T-700 Engine Test Results

    NASA Technical Reports Server (NTRS)

    Hendricks, R. C.

    1994-01-01

    The integrity and performance of brush seals have been established. Severe bench and engine tests have shown high initial wear or run-in rates, material smearing at the interface, and bristle and rub-runner wear, but the brush seals did not fail. Short-duration (46 hr) experimental T-700 engine testing of the compressor discharge seal established over 1-percent engine performance gain (brush versus labyrinth). Long-term gains were established only as leakage comparisons, with the brush at least 20 percent better at controlling leakage. Long-term materials issues, such as wear and ultimately seal life, remain to be resolved. Future needs are cited for materials and analysis tools that account for heat generation, thermomechanical behavior, and tribological pairing to enable original equipment manufacturers to design high-temperature, high-surface-speed seals with confidence.

  14. Influence of Cutting Time on Brush Response: Implications for Herbivory in Linear (Transportation) Corridors

    NASA Astrophysics Data System (ADS)

    Rea, Roy V.; Child, Kenneth N.; Spata, David P.; MacDonald, Douglas

    2007-08-01

    An experiment was conducted to determine the influence the time of brush-cutting can have on plant regrowth and attractiveness to herbivores that browse in linear corridors. The influence of cutting time on leaf flush and senescence, shoot morphometry, and biomass was measured for 3 consecutive years after initial brush-cutting. Results indicate that morphological and phenological attributes of three woody deciduous plants were influenced by the timing of brush-cutting for up to 3 years after initial cutting. Brush-cutting generally stimulated plants to produce larger than normal shoots and delay leaf senescence. The degree to which plants were affected, however, varied with the timing of initial cutting and the species in question. Generally, plants cut later in the year resprouted more vigorously and were taller in the third year after cutting but produced less overall biomass than when cut earlier. In the years following brush-cutting, plants cut earlier flushed leaves earlier in the spring but delayed leaf senescence in the fall when compared to uncut controls. Results of these trials suggest that brush-cutting time influences plant response and several plant attributes known to influence plant attractiveness to moose and other herbivores. We therefore recommend that roadside and railside vegetation management plans consider the influence of cutting time on plant regrowth. Such considerations can ensure that brush is cut to reduce the attractiveness of plant regrowth in these linear corridors, reduce the utilization of such brush by herbivores, and, as such, mitigate collision risk between motorists and herbivores such as moose.

  15. Tooth brushing frequency in Mexican schoolchildren and associated socio-demographic, socioeconomic, and dental variables

    PubMed Central

    Casanova-Rosado, Alejandro José; Medina-Solís, Carlo Eduardo; Casanova-Rosado, Juan Fernando; Vallejos-Sánchez, Ana Alicia; Minaya-Sánchez, Mirna; Mendoza-Rodríguez, Martha; Márquez-Rodríguez, Sonia; Maupomé, Gerardo

    2014-01-01

    Background Tooth brushing (with fluoridated toothpaste) is the most cost-effective intervention in dentistry and it is widely recommended to preserve good oral health. We aimed to determine the frequency of tooth brushing and the variables associated with this practice in schoolchildren living in southeast Mexico. Material/Methods A cross-sectional study was carried out in 1644 schoolchildren, 6 to 13 years old. Questionnaires with socio-demographic, socioeconomic, and dental variables were administered to mothers/guardians of children. The dependent variable was the frequency of tooth brushing, which was categorized as 0 = tooth brushing less than once a day and 1 = tooth brushing at least once a day. A logistic regression model was used to evaluate the final results. Results Mean age was 9.06±2.02 years and 49.1% were girls. The prevalence of tooth brushing at least once a day was 49.8%. In the multivariate model, characteristics related to tooth brushing frequency (p<0.05) were: older age (OR=1.11), being female (OR=1.64), having a larger family (OR=0.87), having had a visit to a dentist during the year preceding the study (OR=1.37), and having had fluoride applications by a professional (OR=1.39). Conclusions The results suggested that different variables (demographic, socioeconomic and dental) are associated with the frequency of tooth brushing. Family size (proxy variable for socioeconomic status) may indicate certain oral health inequalities in this population. PMID:24907713

  16. Dissipative particle dynamics simulations in the grand canonical ensemble: applications to polymer brushes.

    PubMed

    Goujon, Florent; Malfreyt, Patrice; Tildesley, Dominic J

    2004-04-19

    We have used the dissipative particle dynamics (DPD) method in the grand canonical ensemble to study the compression of grafted polymer brushes in good solvent conditions. The force-distance profiles calculated from DPD simulations in the grand canonical ensemble are in very good agreement with the self-consistent field (SCF) theoretical models and with experimental results for two polystyrene brush layers grafted onto mica surfaces in toluene. PMID:15139218

  17. Influence of cutting time on brush response: implications for herbivory in linear (transportation) corridors.

    PubMed

    Rea, Roy V; Child, Kenneth N; Spata, David P; MacDonald, Douglas

    2007-08-01

    An experiment was conducted to determine the influence the time of brush-cutting can have on plant regrowth and attractiveness to herbivores that browse in linear corridors. The influence of cutting time on leaf flush and senescence, shoot morphometry, and biomass was measured for 3 consecutive years after initial brush-cutting. Results indicate that morphological and phenological attributes of three woody deciduous plants were influenced by the timing of brush-cutting for up to 3 years after initial cutting. Brush-cutting generally stimulated plants to produce larger than normal shoots and delay leaf senescence. The degree to which plants were affected, however, varied with the timing of initial cutting and the species in question. Generally, plants cut later in the year resprouted more vigorously and were taller in the third year after cutting but produced less overall biomass than when cut earlier. In the years following brush-cutting, plants cut earlier flushed leaves earlier in the spring but delayed leaf senescence in the fall when compared to uncut controls. Results of these trials suggest that brush-cutting time influences plant response and several plant attributes known to influence plant attractiveness to moose and other herbivores. We therefore recommend that roadside and railside vegetation management plans consider the influence of cutting time on plant regrowth. Such considerations can ensure that brush is cut to reduce the attractiveness of plant regrowth in these linear corridors, reduce the utilization of such brush by herbivores, and, as such, mitigate collision risk between motorists and herbivores such as moose. PMID:17557175

  18. Hysteretic memory in pH-response of water contact angle on poly(acrylic acid) brushes.

    PubMed

    Yadav, Vivek; Harkin, Adrienne V; Robertson, Megan L; Conrad, Jacinta C

    2016-04-13

    We investigated the pH-dependent response of flat polyacid brushes of varying length and dispersity in the extended brush regime. Our model system consisted of poly(acrylic acid) brushes, which change from hydrophobic and neutral at low pH to hydrophilic and negatively charged at high pH, synthesized on silicon substrates using a grafting-from approach at constant grafting density. We observed three trends in the pH-response: first, the dry brush thickness increased as the pH was increased for brushes above a critical length, and this effect was magnified as the dispersity increased; second, the water contact angle measured at low pH was larger for brushes of greater dispersity; and third, brushes of sufficient dispersity exhibited hysteretic memory behavior in the pH-dependence of the contact angle, in which the contact angle upon increasing and decreasing pH differed. As a consequence, the pKa of the brushes measured upon increasing pH was consistently higher than that measured upon decreasing pH. The observed pH response is consistent with proposed changes in the conformation and charge distribution of the polyelectrolyte brushes that depend on the direction of pH change and the dispersity of the brushes. PMID:26979270

  19. A computational study of brush seal contact loads with friction

    NASA Astrophysics Data System (ADS)

    Aksit, Mahmut Faruk

    The brush seal is emerging as a new technology to effectively control cooling and leakage flows in gas turbine engines. With their superior leakage performance, they show the potential to replace current labyrinth seals in gas turbine engines. Because the bristles slide against the rotor surface, wear at the contact becomes a major concern as it determines the life and efficiency of the seal. To optimize seal life and efficiency, an in-depth study of the factors causing the seal stiffness is needed, and a good choice of materials must be made. Although considerable research has been done on material selection and tribopairs, a brief survey reveals the lack of reliable analyses to evaluate contact loads, and to address heat transfer issues. As material pairs have been optimized for most cases, understanding and management of contact loads hold the key for further improvements in seal life. The complicated nature of bristle behavior under various combinations of pressure load and rotor interference requires computer analysis to study details that may not be available through analytical formulations. In an attempt to meet this need, this study presents a 3-D finite element model of a brush seal. The model consists of a representative bristle bundle with a backing plate and a rotor surface. Every bristle is defined by a number of 3-D quadratic beam elements. Bristles are fixed at the top nodes, while they are free to move in any direction at the tip touching the rotor surface. The model consists of 10 to 13 circumferential rows of bristles. The number of rows are based on the actual packing thickness of the seal modeled. Unlike previous analytical studies on brush seal contact loads, this work includes nonlinear frictional effects between the bristles. Frictional effects are known to drastically change the seal behavior, and are crucial in determining the contact forces. The model applies the available published experimental data to define the boundary conditions and

  20. Anti-biofouling properties of an amphoteric polymer brush constructed on a glass substrate.

    PubMed

    Kitano, Hiromi; Kondo, Takuya; Kamada, Tomohiro; Iwanaga, Shintaroh; Nakamura, Makoto; Ohno, Kohji

    2011-11-01

    An amphoteric copolymer brush of methacrylic acid (MA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) was prepared by reversible addition-fragmentation chain-transfer (RAFT) polymerization using both a free chain transfer agent (n-butylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid) and a radical initiator (4,4'-azobis(4-cyanopentanoic acid)) covalently fixed to a glass substrate. An aqueous solution of the copolymer, Poly(MA-r-DMAEMA), which was simultaneously obtained in liquid phase, had a sufficiently small polydispersity in its molecular weight. The copolymer brush showed effective suppression of non-specific adsorption of bovine serum albumin and egg white lysozyme to the brush. In contrast, both negatively charged PolyMA and positively charged PolyDMAEMA brushes significantly adsorbed the proteins irrespective of their net charges. Upon ion beam irradiation, furthermore, a hollow space with a designed shape could be made on the glass substrate, and both HEK293 and HepG2 cells non-specifically adhered to the space, forming aggregates, while no adhesion to the non-treated area on the brush was observed. These results suggest that the amphoteric polymer brushes will be useful materials for biomedical applications. PMID:21820283

  1. Particles without a Box: Brush-first Synthesis of Photodegradable PEG Star Polymers under Ambient Conditions

    PubMed Central

    Liu, Jenny; Gao, Angela Xiaodi; Johnson, Jeremiah A.

    2013-01-01

    Convenient methods for the rapid, parallel synthesis of diversely functionalized nanoparticles will enable discovery of novel formulations for drug delivery, biological imaging, and supported catalysis. In this report, we demonstrate parallel synthesis of brush-arm star polymer (BASP) nanoparticles by the "brush-first" method. In this method, a norbornene-terminated poly(ethylene glycol) (PEG) macromonomer (PEG-MM) is first polymerized via ring-opening metathesis polymerization (ROMP) to generate a living brush macroinitiator. Aliquots of this initiator stock solution are added to vials that contain varied amounts of a photodegradable bis-norbornene crosslinker. Exposure to crosslinker initiates a series of kinetically-controlled brush+brush and star+star coupling reactions that ultimately yields BASPs with cores comprised of the crosslinker and coronas comprised of PEG. The final BASP size depends on the amount of crosslinker added. We carry out the synthesis of three BASPs on the benchtop with no special precautions to remove air and moisture. The samples are characterized by gel permeation chromatography (GPC); results agreed closely with our previous report that utilized inert (glovebox) conditions. Key practical features, advantages, and potential disadvantages of the brush-first method are discussed. PMID:24145552

  2. Membrane-enhanced surface acoustic wave analysis of grafted polymer brushes

    NASA Astrophysics Data System (ADS)

    Brass, David A.; Shull, Kenneth R.

    2008-04-01

    An analysis is developed for the frequency response of a quartz crystal resonator (often referred to as a quartz crystal microbalance) that is modified with a grafted solvent-swollen polymer brush and placed in contact with a membrane capping layer. The shear wave generated at the resonator surface couples into the membrane layer with an efficiency that is strongly dependent on the thickness of the swollen brush layer. As a result, the resonant frequency changes by a maximum amount that is closely approximated by the Sauerbrey shift for the capping layer. The calculated shift substantially decreases for increases in the brush thickness of approximately 10nm, which gives a net frequency response that is extremely sensitive to the degree of swelling of the polymer brush. An optimum capping layer thickness is determined by balancing the Sauerbrey shift against dissipative effects that weaken the crystal resonance. This optimum membrane thickness depends only weakly on the properties of the membrane material and is in the micron range. Detailed multilayer calculations are presented for the specific case of a poly(ethylene glycol) brush swollen with water and brought into contact with an elastomeric water-permeable membrane. These calculations confirm that the method is sensitive to the properties of the brush layer in the experimentally relevant thickness regime. Connections are also made to conceptually simpler two and three layer models of the acoustic impedance of the material systems that are brought into contact with the resonator.

  3. Poly(acrylic acid) brushes pattern as a 3D functional biosensor surface for microchips

    NASA Astrophysics Data System (ADS)

    Wang, Yan-Mei; Cui, Yi; Cheng, Zhi-Qiang; Song, Lu-Sheng; Wang, Zhi-You; Han, Bao-Hang; Zhu, Jin-Song

    2013-02-01

    Poly(acrylic acid) (PAA) brushes, a novel three dimensional (3D) precursor layer of biosensor or protein microarrays, possess high protein loading level and low non-specific protein adsorption. In this article, we describe a simple and convenient way to fabricate 3D PAA brushes pattern by microcontact printing (μCP) and characterize it with FT-IR and optical microscopy. The carboxyl groups of PAA brushes can be applied to covalently immobilize protein for immunoassay. Thriving 3D space made by patterning PAA brushes thin film is available to enhance protein immobilization, which is confirmed by measuring model protein interaction between human immunoglobulin G (H-IgG) and goat anti-H-IgG (G-H-IgG) with fluorescence microscopy and surface plasmon resonance imaging (SPRi). As expected, the SPRi signals of H-IgG coating on 3D PAA brushes pattern and further measuring specific binding with G-H-IgG are all larger than that of 3D PAA brushes without pattern and 2D bare gold surface. We further revealed that this surface can be used for high-throughput screening and clinical diagnosis by label-free assaying of Hepatitis-B-Virus surface antibody (HBsAb) with Hepatitis-B-Virus surface antigen (HBsAg) concentration array chip. The linearity range for HBsAb assay is wider than that of conventional ELISA method.

  4. Putative interaction of brush cells with bicarbonate secreting cells in the proximal corpus mucosa.

    PubMed

    Eberle, Julia Anna-Maria; Müller-Roth, Kai L; Widmayer, Patricia; Chubanov, Vladimir; Gudermann, Thomas; Breer, Heinz

    2013-01-01

    The gastric epithelium is protected from the highly acidic luminal content by alkaline mucus which is secreted from specialized epithelial cells. In the stomach of mice strong secretion of alkaline fluid was observed at the "gastric groove," the border between corpus and fundus mucosa. Since this region is characterized by numerous brush cells it was proposed that these cells might secrete alkaline solution as suggested for brush cells in the bile duct. In fact, it was found that in this region multiple cells express elements which are relevant for the secretion of bicarbonate, including carbonic anhydrase (CAII), the cystic fibrosis transmembrane conductance regulator (CFTR) and the Na(+)/H(+) exchanger (NHE1). However, this cell population was distinct from brush cells which express the TRP-channel TRPM5 and are considered as putative sensory cells. The location of both cell populations in close proximity implies the possibility for a paracrine interaction. This view was substantiated by the finding that brush cells express prostaglandin synthase-1 (COX-1) and the neighboring cells a specific receptor type for prostaglandins. The notion that brush cells may be able to sense a local acidification was supported by the observation that they express the channel PKD1L3 which contributes to the acid responsiveness of gustatory sensory cells. The results support the concept that brush cells may sense the luminal content and influence via prostaglandins the secretion of alkaline solution. PMID:23874305

  5. Evaluation of Brushing as a Lunar Dust Mitigation Strategy for Thermal Control Surfaces

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Journey, Khrissaundra; Christopher, Steven; Davis, Shanon

    2011-01-01

    Evaluation of brushing to remove lunar simulant dust from thermal control surfaces is described. First, strip brushes made with nylon, PTFE, or Thunderon (Nihon Sanmo Dyeing Company Ltd.) bristles were used to remove JSC-1AF dust from AZ93 thermal control paint or aluminized FEP (AlFEP) thermal control surface under ambient laboratory conditions. Nylon and PTFE bristles removed a promising amount of dust from AZ93, and nylon and Thunderon bristles from AlFEP. But when these were tested under simulated lunar conditions in the lunar dust adhesion bell jar (LDAB), they were not effective. In a third effort, seven brushes made up of three different materials, two different geometries, and different bristle lengths and thicknesses were tested under laboratory conditions against AZ93 and AlFEP. Two of these brushes, the Zephyr fiberglass fingerprint brush and the Escoda nylon fan brush, removed over 90 percent of the dust, and so were tested in the fourth effort in the LDAB. They also performed well under these conditions recovering 80 percent or more of the original thermal performance (solar absorptance/thermal emittance) of both AZ93 and AgFEP after 20 strokes, and 90 or more percent after 200 strokes

  6. Evaluation of Brushing as a Lunar Dust Mitigation Strategy for Thermal Control Surfaces

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Journey, Hhrissaundra; Christopher, Steven; Davis, Shanon

    2011-01-01

    Evaluation of brushing to remove lunar simulant dust from thermal control surfaces is described. First, strip brushes made with nylon, PTFE, or Thunderon bristles were used to remove JSC-1AF dust from AZ93 thermal control paint or aluminized FEP (AlFEP) thermal control surface under ambient laboratory conditions. Nylon and PTFE bristles removed a promising amount of dust from AZ93, and nylon and Thunderon bristles from AlFEP. But when these were tested under simulated lunar conditions in the lunar dust adhesion bell jar (LDAB), they were not effective. In a third effort, seven brushes made up of three different materials, two different geometries, and different bristle lengths and thicknesses were tested under laboratory conditions against AZ93 and AlFEP. Two of these brushes, the Zephyr fiberglass fingerprint brush and the Escoda nylon fan brush, removed over 90 percent of the dust, and so were tested in the fourth effort in the LDAB. They also performed well under these conditions recovering 80 percent or more of the original thermal performance (solar absorptance/thermal emittance) of both AZ93 and AgFEP after 20 strokes, and 90 or more percent after 200 strokes.

  7. Effect of colloidal substrate curvature on pH-responsive polyelectrolyte brush growth.

    PubMed

    Cheesman, Benjamin T; Neilson, Alexander J G; Willott, Joshua D; Webber, Grant B; Edmondson, Steve; Wanless, Erica J

    2013-05-21

    Coatings consisting of polymer brushes are an effective way to modify solid interfaces. Polymer brush-modified hybrid particles have been prepared by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP) of 2-(diethylamino)ethyl methacrylate (DEA) on silica particles. We have optimized the synthesis with respect to changing the reducing agent, temperature, and reaction solvent from an aqueous ethanol mixture to an aqueous methanol mixture. Our flexible electrostatically adsorbed macroinitiator approach allows for the modification of a variety of surfaces. Polybasic brushes have been grown on silica particles of different sizes, from 120 to 840 nm in diameter, as well as on wafers, and a comparison of the products has allowed the effect of surface curvature to be elucidated. An examination of the thickness of the dry brush and the aqueous hydrodynamic brush at both pH 7 and at 4 demonstrated that growth increased substantially with substrate curvature for particles with a diameter below 450 nm. This is attributed to the increasing separation between active chain ends, reducing the rate of termination. This is believed to be the first time that this effect has been demonstrated experimentally. Furthermore, we have seen that polymer brush growth on planar wafers was significantly reduced when the reaction mixture was stirred. PMID:23617419

  8. Assembly and Characterization of Well Defined High Molecular Weight Poly(p-phenylene) Polymer Brushes

    SciTech Connect

    Alonzo Calderon, Jose E; Kilbey, II, S Michael; Ankner, John Francis; Britt, Phillip F; Chen, Jihua; Dadmun, Mark D; Deng, Suxiang; Hong, Kunlun; Mays, Jimmy; Messman, Jamie M; Sumpter, Bobby; Swader, Onome A; Yu, Xiang; Bredas, Jean-Luc E; Malagoli, Massimo

    2011-01-01

    The assembly and characterization of well-defined, end-tethered poly(p-phenylene) (PPP) brushes having high molecular weight, low polydispersity and high 1,4-stereoregularity are presented. The PPP brushes are formed using a precursor route that relies on either self-assembly or spin coating of high molecular weight (degrees of polymerizations 54, 146, and 238) end-functionalized poly(1,3-cyclohexadiene) (PCHD) chains from benzene solutions onto silicon or quartz substrates, followed by aromatization of the end-attached PCHD chains on the surface. The approach allows the thickness (grafting density) of the brushes to be easily varied. The dry brushes before and after aromatization are characterized by ellipsometry, atomic force microscopy, grazing angle attenuated total reflectance Fourier transform infrared spectroscopy, and UV-Vis spectroscopy. The properties of the PPP brushes are compared with those of films made using oligo-paraphenylenes and with ab initio density functional theory simulations of optical properties. Our results suggest conversion to fully aromatized, end-tethered PPP polymer brushes having effective conjugation lengths of 5 phenyl units.

  9. Design criteria for brush commutation in high speed traveling wave coilguns

    SciTech Connect

    Snow, W.R.; Willig, R.L. )

    1991-01-01

    Barrel current in a traveling wave coilgun must be commutated on and off and remain synchronized with the position of the armature coils. Brushes on the armature can be used to satisfy these two requirements. First, they provide synchronization of the currents by being physically attached to the armature coil. Second, they provide a means of shorting the turns of the barrel so that motion induced commutation can take place. Motion induced commutation is the process where the current in a shorted barrel turn is caused to rise or fall because of the voltage induced by the moving armature. This change in barrel current must take place during the time the turn is shorted by the brush. Residual current in the trailing edge of the brush must be made small at the instant the circuit is opened to minimize arcing. A set of design criteria are presented for designing a brush commutated coilgun so as to achieve the required synchronous commutation. The design variables include the barrel coil configuration and its pitch, the armature coil configuration and its number of turns, and the brush length. The number of turns in the barrel undergoing commutation at the same instant in time is directly related to the length of the brush. In this paper the results of applying the design criteria to a specific design are presented.

  10. 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

  11. The synthesis of hydrogels with controlled distribution of polymer brushes in hydrogel network

    NASA Astrophysics Data System (ADS)

    Sun, YuWei; Zhou, Chao; Zhang, AoKai; Xu, LiQun; Yao, Fang; Cen, Lian; Fu, Guo-Dong

    2014-11-01

    Poly(ethylene glycol) (PEG) hydrogels with 3-dimensionally controlled well-defined poly(N-isopropylacrylamide) (poly(NIPAAm)) brushes were prepared by combined copper(I)-catalyzed azide-alkyne cycloaddition ("Click Chemistry") and atom transfer radical polymerization (ATRP). The resulting hydrogels were presented as representatives with their detailed synthesis routes and characterization. HPEG-S-poly(NIPAAm) is a hydrogel with poly(NIPAAm) brushes mainly grafted on surface, whereas HPEG-G-poly(NIPAAm) has a gradiently decreased poly(NIPAAm) brushes in their chain length from surface to inside. On the other hand, poly(NIPAAm) brushes in HPEG-U-poly(NIPAAm) are uniformly dispersed throughout the whole hydrogel network. Successful preparation of HPEG-S-poly(NIPAAm), HPEG-G-poly(NIPAAm) and HPEG-U-poly(NIPAAm) were ascertained by X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. Optical properties and thermal behaviors of these hydrogels were evaluated by UV-visible transmittance spectra and differential scanning calorimetry (DSC). Hence, the flexibility and controllability of the synthetic strategy in varying the distribution of polymer brushes and hydrogel properties was demonstrated. Hydrogels with tunable and well-defined 3-dimensional poly(NIPAAm) polymer brushes could be tailor-designed to find potential applications in smart devices or skin dressing, such as for diabetics as they have special optical and thermal behaviors.

  12. Putative interaction of brush cells with bicarbonate secreting cells in the proximal corpus mucosa

    PubMed Central

    Eberle, Julia Anna-Maria; Müller-Roth, Kai L.; Widmayer, Patricia; Chubanov, Vladimir; Gudermann, Thomas; Breer, Heinz

    2013-01-01

    The gastric epithelium is protected from the highly acidic luminal content by alkaline mucus which is secreted from specialized epithelial cells. In the stomach of mice strong secretion of alkaline fluid was observed at the “gastric groove,” the border between corpus and fundus mucosa. Since this region is characterized by numerous brush cells it was proposed that these cells might secrete alkaline solution as suggested for brush cells in the bile duct. In fact, it was found that in this region multiple cells express elements which are relevant for the secretion of bicarbonate, including carbonic anhydrase (CAII), the cystic fibrosis transmembrane conductance regulator (CFTR) and the Na+/H+ exchanger (NHE1). However, this cell population was distinct from brush cells which express the TRP-channel TRPM5 and are considered as putative sensory cells. The location of both cell populations in close proximity implies the possibility for a paracrine interaction. This view was substantiated by the finding that brush cells express prostaglandin synthase-1 (COX-1) and the neighboring cells a specific receptor type for prostaglandins. The notion that brush cells may be able to sense a local acidification was supported by the observation that they express the channel PKD1L3 which contributes to the acid responsiveness of gustatory sensory cells. The results support the concept that brush cells may sense the luminal content and influence via prostaglandins the secretion of alkaline solution. PMID:23874305

  13. Poly(N-isopropylacrylamide)-Based Mixed Brushes: A Computer Simulation Study.

    PubMed

    Léonforte, Fabien; Müller, Marcus

    2015-06-17

    Temperature-sensitive poly(N-isopropylacrylamide) (PNIPAM) polymer brushes of fixed molecular weight and grafting density are modeled in the framework of a coarse-grained model with soft, nonbonded interactions and an implicit solvent. This model has been developed to address experimentally relevant, large invariant degrees of polymerization, and nonbonded interactions are expressed via a third-order (virial) expansion of the equation of state. The choice of interaction parameters is intended to mimic the swelling behavior of PNIPAM in water as the temperature increases toward the lower critical solution temperature (T(LCST)). Results of molecular dynamics simulations for one component brushes are compared to experimental data. Mixed brushes incorporating small and large amounts of grafted poly(ethylene glycol) polymers are then considered. The effects of mixing polymer components on the response of the mixed brushes to temperature changes are monitored, and the results are compared to experimental data. In the end, two design principles for biomolecule triggering using temperature-sensitive mixed polymer brushes with functional and switchable end-groups are proposed and studied. This work is in favor of establishing qualitative rules for the design, optimization, and comprehension of binary polymer brushes for bioengineering purposes. PMID:25634688

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

    PubMed

    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

  15. Novel temperature-responsive polymer brushes with carbohydrate residues facilitate selective adhesion and collection of hepatocytes

    NASA Astrophysics Data System (ADS)

    Idota, Naokazu; Ebara, Mitsuhiro; Kotsuchibashi, Yohei; Narain, Ravin; Aoyagi, Takao

    2012-12-01

    Temperature-responsive glycopolymer brushes were designed to investigate the effects of grafting architectures of the copolymers on the selective adhesion and collection of hypatocytes. Homo, random and block sequences of N-isopropylacrylamide and 2-lactobionamidoethyl methacrylate were grafted on glass substrates via surface-initiated atom transfer radical polymerization. The galactose/lactose-specific lectin RCA120 and HepG2 cells were used to test for specific recognition of the polymer brushes containing galactose residues over the lower critical solution temperatures (LCSTs). RCA120 showed a specific binding to the brush surfaces at 37 °C. These brush surfaces also facilitated the adhesion of HepG2 cells at 37 °C under nonserum conditions, whereas no adhesion was observed for NIH-3T3 fibroblasts. When the temperature was decreased to 25 °C, almost all the HepG2 cells detached from the block copolymer brush, whereas the random copolymer brush did not release the cells. The difference in releasing kinetics of cells from the surfaces with different grafting architectures can be explained by the correlated effects of significant changes in LCST, mobility, hydrophilicity and mechanical properties of the grafted polymer chains. These findings are important for designing ‘on-off’ cell capture/release substrates for various biomedical applications such as selective cell separation.

  16. Dynamics of polymeric brushes: End exchange and bridging kinetics

    NASA Astrophysics Data System (ADS)

    Johner, A.; Joanny, J. F.

    1993-01-01

    We study some dynamical aspects of grafted polymer layers in a solvent. The structure of the brush is described in a θ solvent by the self-consistent mean field theory and in a good solvent using scaling laws. The Rouse-Zimm model including hydrodynamic interactions is used for the dynamic properties. A given chain end explores the entire thickness of a free grafted layer in a time Te proportional to the cube of the thickness. The exploration time is much larger than the Rouse time that characterizes the relaxation of the fluctuations of the chains conformations. In a θ-solvent we give a detailed study of the relaxation of the density of a few labeled chain ends towards its equilibrium value. The bridging kinetics between a grafting plate and a plate adsorbing the free ends is also discussed. When adsorption proceeds, an exclusion zone grows in the vicinity of the adsorbing plate. To cross the exclusion zone and adsorb, a chain end must overcome an energy barrier. The typical adsorption time is the first passage time through this barrier. Except in the very late stages where the fraction of chains η forming bridges saturates at its equilibrium value, the energy barrier against adsorption increases as a power law of η and the bridging fraction increases very slowly (logarithmically) with time. Both weak bridging where only a small fraction of chains form bridges and total bridging where all the chains form bridges are studied.

  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. Small intestinal brush border enzymes in cystic fibrosis.

    PubMed

    Van Biervliet, S; Eggermont, E; Carchon, H; Veereman, G; Deboeck, K

    1999-01-01

    The study concerns the maltase, saccharase, lactase and alkaline phosphatase activity in small intestinal biopsy specimens from 61 consecutively admitted, untreated, Caucasian cystic fibrosis patients. A group of 319 age matched controls admitted during the same time period for undefined gastrointestinal or nutritional disorders acted as the controls. In order to eliminate morphological damage as a confounding factor, the enzyme activities were studied in small intestinal biopsy specimens having both normal stereomicroscopic and histological features. It was shown that neither maltase nor saccharase activity was different in the two groups, in contrast to lactase and alkaline phophatase activity, that was significantly lower in cystic fibrosis patients. The differences could not be explained by the nutritional status as judged by the body mass index. Lactase activity is known to be easily affected by numerous enteropathies. As the information on alkaline phosphatase activity is limited, the low activity is discussed in more detail. Taking into account the literature data, the low alkaline phosphatase activity is tentatively attributed either to enhanced release from the brush border or to the faulty handling of alkaline phophatase protein in the post-golgi compartments secondary to the accumulation of incorrectly glycosylated CFTR in the same cell structures. PMID:10547891

  19. 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-1brush interface.

  20. 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

  1. 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

  2. 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

  3. Abrasion of eroded root dentine brushed with different toothpastes.

    PubMed

    De Menezes, Márcio; Turssi, Cecilia Pedroso; Hara, Anderson Takeo; Messias, Danielle Cristine Furtado; Serra, Mônica Campos

    2004-09-01

    This study evaluated the surface roughness change and wear provided by different dentifrices on root dentine previously exposed to erosive challenges. According to a randomized complete block design, 150 slabs of bovine root dentine (6 x 3 x 2 mm) were ground flat and polished. In an area of 4 x 3 mm on the dentine surface, specimens were submitted to five erosive/abrasive events, each one composed by: exposure to Sprite Diet or distilled water for 5 min, then to a remineralizing solution for 1 min, and simulation of 5,000 brushing strokes. Four dentifrices--regular (RE), baking soda (BS), whitening (WT) and tartar control (TC)--and distilled water (CO), used as control, were compared. Final texture and the wear depth were evaluated using a profilometer. ANOVA did not show significant interaction, indicating that the effect of dentifrices on both surface roughness change and wear did not depend on whether or not the dentine was eroded ( p>0.05). There was no difference between abrasion of eroded and sound dentine. The Tukey's test revealed that WT, BS and TC provided the highest increase in surface roughness differing from RE and CO. TC yielded the deepest wear of root dentine, whereas RE and CO, the shallowest. No significant difference in wear among BS, TC and WT were observed. Within the limitations of this study, the data showed that abrasion of both eroded and sound root dentine was dependent on the dentifrice used. PMID:15146320

  4. Cordon bleu promotes the assembly of brush border microvilli

    PubMed Central

    Grega-Larson, Nathan E.; Crawley, Scott W.; Erwin, Amanda L.; Tyska, Matthew J.

    2015-01-01

    Microvilli are actin-based protrusions found on the surface of diverse cell types, where they amplify membrane area and mediate interactions with the external environment. In the intestinal tract, these protrusions play central roles in nutrient absorption and host defense and are therefore essential for maintaining homeostasis. However, the mechanisms controlling microvillar assembly remain poorly understood. Here we report that the multifunctional actin regulator cordon bleu (COBL) promotes the growth of brush border (BB) microvilli. COBL localizes to the base of BB microvilli via a mechanism that requires its proline-rich N-terminus. Knockdown and overexpression studies show that COBL is needed for BB assembly and sufficient to induce microvillar growth using a mechanism that requires functional WH2 domains. We also find that COBL acts downstream of the F-BAR protein syndapin-2, which drives COBL targeting to the apical domain. These results provide insight into a mechanism that regulates microvillar growth during epithelial differentiation and have significant implications for understanding the maintenance of intestinal homeostasis. PMID:26354418

  5. Drilling Deeper into tooth brushing skills: Is proactive interference an under-recognized factor in oral hygiene behavior change?

    PubMed Central

    Thavarajah, Rooban; Kumar, Madan; Mohandoss, Anusa Arunachalam

    2015-01-01

    Proper tooth brushing is a seemingly simple motor activity that can promote oral health. Applying health theories, such as the Information-Motivation-Behavioral Skills (IMB) model, Motivational Interviewing (MI) and Integrated Health Coaching (IHC), may help optimize tooth brushing technique in those with suboptimal skills. Some motor activities, including tooth brushing, may over time become rote and unconscious actions, such that an existing habit can inhibit new learning, i.e., exert proactive interference on learning the new skill. Proactive interference may impede the acquisition of new tooth brushing skills; thus, in this report, we: (1) Review how the habit of tooth brushing is formed; (2) Postulate how proactive interference could impede the establishment of proper tooth brushing retraining; (3) Discuss the merits of this hypothesis; and (4) Provide guidance for future work in this topic within the context of an approach to behavior change that integrates IMB, MI and IHC methodology. PMID:26457238

  6. Development of Self-Assembled Nanoscale Templates via Microphase Separation Induced by Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Chu, Elza

    Phase separation in soft matter has been the crucial element in generating hybrid materials, such as polymer blends and mixed polymer brushes. This dissertation discusses two methods of developing self-assembled nanoscale templates via microphase separation induced by polymer brush synthesis. This work introduces a novel soft substrate approach with renewable grafting sites where polyacrylamide is "grafted through" chitosan soft substrates. The mechanism of grafting leads to ordered arrays of filament-like nanostructures spanning the chitosan-air interface. Additionally, the chemical composition of the filaments allows for post-chemical modification to change the physical properties of the filaments, and subsequently tailor surfaces for specific application. Unlike traditional materials, multi-functional or "smart" materials, such as binary polymer brushes (BPB) are capable of spontaneously changing the spatial distribution of functional groups and morphology at the surface upon external stimuli. Although promising in principle, the limited range of available complementary polymers with common non-selective solvents confines the diversity of usable materials and restricts any further advancement in the field. This dissertation also covers the fabrication and characterization of responsive nanoscale polystyrene templates or "mosaic" brushes that are capable of changing interfacial composition upon exposure to varying solvent qualities. Using a "mosaic" brush template is a unique approach that allows the fabrication of strongly immiscible polymer BPB without the need for a common solvent. The synthesis of such BPB is exemplified by two strongly immiscible polymers, i.e. polystyrene (polar) and polyacrylamide (non-polar), where polyacrylamide brush is "graft through" a Si-substrate modified with the polystyrene collapsed "mosaic" brush. The surface exhibits solvent-triggered responses, as well as application potential for anti-biofouling.

  7. Effect of toothbrushes and denture brushes on heat-polymerized acrylic resins.

    PubMed

    de Freitas Pontes, Karina Matthes; de Holanda, Janaína Câncio; Fonteles, Cristiane Sa Roriz; Pontes, Cassio de Barros; Lovato da Silva, Cláudia Helena; Paranhos, Helena de Freitas Oliveira

    2016-01-01

    It is important to choose an appropriate brush for denture cleaning to prevent damage to the surface properties of prosthetic devices. The purpose of this study was to evaluate the abrasiveness of toothbrushes and denture brushes on boiled and microwave-processed acrylic resins. Specimens of 4 resin brands were prepared (n = 30). Five brands of brushes (n = 6) were used in a toothbrushing machine, first for 17,800 strokes and then for an additional 35,600 strokes (total of 53,400), at a load of 200 g. An analytical balance and a profilometer were used to assess the weight and surface roughness, respectively, before and after 17,800 and 53,400 strokes. Analysis of variance and Tukey tests were used for data analysis (α = 0.05). Weight loss increased with time, while surface roughness remained the same. There were no statistically significant differences among toothbrushes and denture brushes in the resulting weight loss (17,800 strokes, 1.83 mg; 53,400 strokes, 3.78 mg) or surface roughness (17,800 or 53,400 strokes, 0.14 µm). The weight loss values after 53,400 brush strokes indicated that Clássico (2.28 mg) and VIPI Wave (2.75 mg) presented significantly greater abrasion resistance than Lucitone 550 (3.36 mg) and Onda-Cryl (2.85 mg) (P < 0.05). The type of brush and the polymerization method did not influence resin wear after brushing. PMID:26742168

  8. Access to Interdental Brushing in Periodontal Healthy Young Adults: A Cross-Sectional Study

    PubMed Central

    Santamaria, Julie; Bravo, Manuel; Bourgeois, Denis

    2016-01-01

    Purpose Interdental diameter space is largely undefined in adults, which compromises the decision support for daily interdental cleaning during routine practice in individual oral prophylaxis. This study assesses the distribution of diameter access of interdental spaces in an 18- to 25-year-old adult population free of periodontal disease. Methods In March-April 2015, a cross-sectional study using random sampling was performed at the University Lyon 1, France. The interproximal dental spaces of 99 individuals were examined using a colorimetric calibrated probe associated with the corresponding calibrated interdental brush (IDB). Results Of the 2,408 out of 2,608 sites, the overall accessibility prevalence of any interdental brushing was 92.3%. In total, 80.6% of the sites required interdental brushes with smaller diameters (0.6–0.7 mm). In anterior sites, the diameter of the interdental brushes used was smaller (55.8% of IDB with 0.6 mm) than the diameter of the interdental brushes used in posterior sites (26.1% of IDB with 0.6 mm) (p < 0.01). The adjusted ORs indicate a significant association with the location of the sites (approximately doubling the risk of bleeding, i.e., OR = 1.9, in posterior sites). Conclusions Most interdental sites can be cleaned using interdental brushes. Even in healthy people, interdental hygiene requirements are very high. Strengthening the oral hygiene capacity by specifically using interdental brushes can have an effect on the health of the entire population. Screening of the accessibility of the interdental space should be a component of a routine examination for all patients. PMID:27192409

  9. Quantitative evaluation of interaction force between functional groups in protein and polymer brush surfaces.

    PubMed

    Sakata, Sho; Inoue, Yuuki; Ishihara, Kazuhiko

    2014-03-18

    To understand interactions between polymer surfaces and different functional groups in proteins, interaction forces were quantitatively evaluated by force-versus-distance curve measurements using atomic force microscopy with a functional-group-functionalized cantilever. Various polymer brush surfaces were systematically prepared by surface-initiated atom transfer radical polymerization as well-defined model surfaces to understand protein adsorption behavior. The polymer brush layers consisted of phosphorylcholine groups (zwitterionic/hydrophilic), trimethylammonium groups (cationic/hydrophilic), sulfonate groups (anionic/hydrophilic), hydroxyl groups (nonionic/hydrophilic), and n-butyl groups (nonionic/hydrophobic) in their side chains. The interaction forces between these polymer brush surfaces and different functional groups (carboxyl groups, amino groups, and methyl groups, which are typical functional groups existing in proteins) were quantitatively evaluated by force-versus-distance curve measurements using atomic force microscopy with a functional-group-functionalized cantilever. Furthermore, the amount of adsorbed protein on the polymer brush surfaces was quantified by surface plasmon resonance using albumin with a negative net charge and lysozyme with a positive net charge under physiological conditions. The amount of proteins adsorbed on the polymer brush surfaces corresponded to the interaction forces generated between the functional groups on the cantilever and the polymer brush surfaces. The weakest interaction force and least amount of protein adsorbed were observed in the case of the polymer brush surface with phosphorylcholine groups in the side chain. On the other hand, positive and negative surfaces generated strong forces against the oppositely charged functional groups. In addition, they showed significant adsorption with albumin and lysozyme, respectively. These results indicated that the interaction force at the functional group level might be

  10. Light-responsive polymer surfaces via postpolymerization modification of grafted polymer-brush structures.

    PubMed

    Dübner, Matthias; Spencer, Nicholas D; Padeste, Celestino

    2014-12-16

    Light-induced, spatially well-defined, reversible switching of surface properties enables the creation of remote-controlled smart surfaces. We have taken advantage of the unique high-resolution structuring capabilities of extreme ultraviolet (EUV) interference lithography to produce nanostructured photoresponsive polymer brushes. Patterns of poly(glycidyl methacrylate) (PGMA) and poly(methacrylic acid) (PMAA) were grafted from two different 100 μm thick fluoropolymer substrates by means of a radiation-initiated, grafting-from approach based on free-radical polymerization (FRP). Photochromic properties were introduced via novel one- or two-step postpolymerization modifications with spiropyran (SP) derivatives, which allowed us to control the number of photochromic groups on the polymer brushes. Depending on the degree of functionalization and the local chemical environment, the SP moieties can open upon UV-light exposure to form zwitterionic, deeply colored, and fluorescent merocyanines (MCs) and reclose to the colorless SP configuration via thermal or visible light-induced relaxation. Switching kinetics were studied by means of time-resolved fluorescence microscopy and compared with kinetic measurements of the SP moiety in solution. The results indicated the importance, for the intensity of the switching, of the local chemical environment provided by both the polymer brush and added solvents, and showed the predominant influence on the ring-closing kinetics of polar solvents, which stabilize the MC form. To allow further characterization of the polymer-brush arrangements on a macroscopic scale, similar, but unstructured brush systems were grafted from fluoropolymers after large-area activation using EUV radiation or argon plasma. All steps of the postpolymerization modification were characterized in detail using attenuated total reflection infrared (ATR-IR) spectroscopy. Furthermore, a light-induced reversible static-contact-angle switch with a range of up to 15

  11. Adhesion and friction properties of fluoropolymer brushes: on the tribological inertness of fluorine.

    PubMed

    Bhairamadgi, Nagendra S; Pujari, Sidharam P; van Rijn, Cees J M; Zuilhof, Han

    2014-10-28

    The effects of fluorination on the adhesion and friction properties of covalently bound poly(fluoroalkyl methacrylate) polymer brushes (thickness ∼80 nm) were systematically investigated. Si(111) surfaces were functionalized with a covalently bound initiator via a thiol-yne click reaction to have a high surface coverage for initiator immobilization. Surface-initiated atom-transfer radical polymerization (SI-ATRP) was employed for the synthesis of four different fluoropolymer brushes (SPFx, where x = 0, 3, 7, or 17 F atoms per monomer), based on fluoroalkyl methacrylates. All polymer brushes were characterized with static contact angle measurements, X-ray photoelectron spectroscopy (XPS), and infrared absorption reflection spectroscopy (IRRAS). The polymer brushes exhibited an excellent hydrophobicity, with static water contact angles of up to 121° depending on the number of fluorine atoms per side chain in fluoroalkyl methacrylate. The degree of swelling was precisely studied by using ellipsometry in different solvents such as acetone, hexadecane, hexafluoroisopropanol, nonafluorobutyl methyl ether, and Fluorinert FC-40. The polymer brushes have shown nanoscale swelling behavior in all solvents except hexadecane. The grafting density decreased upon increasing fluorine content in polymer brushes from 0.65 chains/nm(2) (SPF0) to 0.10 chains/nm(2) (SPF17) as observed in Fluorinert FC-40 as a good solvent. Adhesion and friction force measurements were conducted with silica colloidal probe atomic force microscopy (CP-AFM) under ambient, dry (argon), and lubricating fluid conditions. SPF17 showed the lowest coefficient of friction 0.005 under ambient condition (RH = 44 ± 2%) and a further decrease with 50% under fluidic conditions. These polymer brushes also showed adhesion forces as low as 6.9 nN under ambient conditions, which further went down to 0.003 nN under fluidic conditions (Fluorinert FC-40 and hexadecane) at 10 nN force. PMID:25313839

  12. Effects of carbon brush anode size and loading on microbial fuel cell performance in batch and continuous mode

    NASA Astrophysics Data System (ADS)

    Lanas, Vanessa; Ahn, Yongtae; Logan, Bruce E.

    2014-02-01

    Larger scale microbial fuel cells (MFCs) require compact architectures to efficiently treat wastewater. We examined how anode-brush diameter, number of anodes, and electrode spacing affected the performance of the MFCs operated in fed-batch and continuous flow mode. All anodes were initially tested with the brush core set at the same distance from the cathode. In fed-batch mode, the configuration with three larger brushes (25 mm diameter) produced 80% more power (1240 mW m-2) than reactors with eight smaller brushes (8 mm) (690 mW m-2). The higher power production by the larger brushes was due to more negative and stable anode potentials than the smaller brushes. The same general result was obtained in continuous flow operation, although power densities were reduced. However, by moving the center of the smaller brushes closer to the cathode (from 16.5 to 8 mm), power substantially increased from 690 to 1030 mW m-2 in fed batch mode. In continuous flow mode, power increased from 280 to 1020 mW m-2, resulting in more power production from the smaller brushes than the larger brushes (540 mW m-2). These results show that multi-electrode MFCs can be optimized by selecting smaller anodes, placed as close as possible to the cathode.

  13. The pathogenic antigen of Heymann nephritis is a membrane glycoprotein of the renal proximal tubule brush border.

    PubMed Central

    Kerjaschki, D; Farquhar, M G

    1982-01-01

    Purified brush border fractions prepared from rat kidneys were solubilized in detergent, iodinated, and subjected to immunoprecipitation to identify the pathogenic antigen present in brush border membranes that is responsible for the production of Heymann nephritis (HN). Purified IgG prepared from the sera of rabbits or rats immunized with a crude cortical preparation, known as Fx1A, precipitated multiple peptides, whereas IgG eluted from glomeruli of rats with active or passive HN specifically immunoprecipitated a single large glycoprotein (Mr = 330,000). This protein (gp330) was subsequently purified by gel filtration and lentil lectin affinity chromatography from detergent-solubilized brush border membranes. When rats were immunized with purified gp330, they developed anti-brush border antibodies and active HN. IgG prepared from the serum of rats with active HN caused passive HN when injected into normal recipients. Rats immunized against brush border membrane proteins depleted of gp330 developed anti-brush border antibodies but did not develop HN. Further analysis of gp330 indicated that it is solubilized by detergent treatment of isolated brush border microvilli, and its antigenic component is released from intact microvilli by trypsin. By immunoperoxidase staining it was localized to the luminal side of the brush border membranes. These results indicate that (i) gp330 is the pathogenic antigen of HN; (ii) the antigen is a glycoprotein of the brush border membrane; and (iii) it is disposed with its pathogenic domain(s) facing the tubule lumen. Images PMID:6752952

  14. 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.

  15. 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.

  16. 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.

  17. Mechanism of Nanoparticle Actuation by Responsive Polymer Brushes: From Reconfigurable Composite Surfaces to Plasmonic Effects

    SciTech Connect

    Tokarev, I.; Nykypanchuk, D.; Roiter, Y.; Minko, I.; Minko, S.

    2011-11-14

    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. Evaluation of brush plated alloys as substitutes for tank plated hard chromium

    SciTech Connect

    Durham, H.B.; Hooper, A.M.

    1995-11-01

    This paper summarizes results obtained from a test program conducted in cooperation with Tinker Air Force Base (TAFB) in 1993 for the purpose of evaluating the potential of using brush plated alloys as replacements for tank plated hard chromium which is used in the overhaul of jet engines. Tank plating is energy expensive and generates waste products in several of the plating steps. Test specimens used in this study were fabricated from carbon steel, chromium-based stainless steel, and nickel-based stainless steel. Baseline specimens were tank plated with hard chromium or with a soft nickel capped with hard chromium. The specimens were tested for fatigue, thickness, microhardness, Taber wear, and Falex pin and vee block wear. All test were conducted in accordance with standard procedures of the American Society for Testing and Materials (ASTM). Test results obtained from the baseline specimens were compared with those obtained from specimens which had been coated with the three brush plated layered alloy solutions used in this evaluation. Results of this study show that brush plated alloy coatings appear promising as alternatives to tank plated hard chromium. Some data quality problems were encountered during testing, so at this time, definitive statements concerning the use of brush plating alloys as an acceptable alternative to tank plated hard chromium in critical TAFB maintenance, cannot be made. Although these tests results are not positive for TAFB`s operation, users of hard chromium tank plating with less critical applications may find brush plated coatings a suitable alternative. 1 ref.

  19. Structure of bottle brush polymers on surfaces: weak versus strong adsorption.

    PubMed

    Hsu, Hsiao-Ping; Paul, Wolfgang; Binder, Kurt

    2011-12-01

    Large-scale Monte Carlo simulations are presented for a coarse-grained model of cylindrical molecular brushes adsorbed on a flat structureless substrate, varying both the chain length N of the side chains and the backbone chain length N(b). For the case of good solvent conditions, both the cases of weak adsorption (only 10 to 15% of the monomers being bound to the surface) and strong adsorption (~40% of the monomers being bound to the surface, forcing the bottle brush into an almost 2D conformation) are studied. We focus on the scaling of the total linear dimensions of the cylindrical brush with both chain lengths N and N(b), demonstrating a crossover from rod-like behavior (for not very large N(b)) to the scaling of 2D self-avoiding walks. Despite the fact that snapshot pictures suggest a "worm-like" picture as a coarse-grained description of such cylindrical brushes, the Kratky-Porod worm-like chain model fails because there is no regime where Gaussian statistics applies. We compare the stiffness (orientational correlations of backbone bonds, persistence length estimates, etc.) of the adsorbed bottle brush polymers with their corresponding 3D nonadsorbed counterparts. Consequences for the discussion of pertinent experiments are briefly discussed. PMID:21751800

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

    PubMed

    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

    2015-06-17

    The protein-adsorbing and -repelling properties of various smart nanometer-thin polymer brushes containing poly(N-isopropylacrylamide) and poly(acrylic acid) with high potential for biosensing and biomedical applications are studied by in situ infrared-spectroscopic ellipsometry (IRSE). IRSE is a highly sensitive nondestructive technique that allows protein adsorption on polymer brushes to be investigated in an aqueous environment as external stimuli, such as temperature and pH, are varied. These changes are relevant to conditions for regulation of protein adsorption and desorption for biotechnology, biocatalysis, and bioanalytical applications. Here brushes are used as model surfaces for controlling protein adsorption of human serum albumin and human fibrinogen. The important finding of this work is that IRSE in the in situ experiments in protein solutions can distinguish between contributions of polymer brushes and proteins. The vibrational bands of the polymers provide insights into the hydration state of the brushes, whereas the protein-specific amide bands are related to changes of the protein secondary structure. PMID:25668395

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

    DOE PAGESBeta

    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

  2. Improved adhesion between PMMA and stainless steel modified with PMMA brushes.

    PubMed

    Shimizu, Kyoko; Malmos, Kristoffer; Holm, Allan Hjarbæk; Pedersen, Steen Uttrup; Daasbjerg, Kim; Hinge, Mogens

    2014-12-10

    In this work, various lengths and densities of poly(methyl methacrylate) (PMMA) brushes were synthesized on stainless steel (SS) surfaces via surface initiated atom transfer radical polymerization. Subsequently, the joints between the bulk PMMA and the PMMA brushed stainless steel were obtained by injection molding, and for these the degree of adhesion was assessed by tensile testing. Several conditions are required to facilitate the mixing between the brushes and the bulk polymer and to reduce the residual stress at the interface: preheating of the SS samples before the injection molding; a long packing time; and a mold temperature above the glass transition temperature (Tg) of PMMA during the injection molding. This treatment leads to a cohesive failure in the bulk PMMA. It was observed that the stress concentrated at the rim, due to contraction of bulk PMMA during cooling, results in a weak adhesion at the rim of the joint. A combination of high density and long brush length of PMMA film provides better adhesion. The large number of PMMA brush chains apparently promotes good penetration into the bulk PMMA chains and ultimately results in high adhesion strength. PMID:25348044

  3. Brush Scrub Cleaning after Spraying Ozonized Water on Si Wafer Treated by Chemical Mechanical Polishing

    NASA Astrophysics Data System (ADS)

    Kurokawa, Yoshiaki; Hayashi, Kounosuke; Nishimura, Eriko; Saito, Reiko; Maki, Kunisuke

    2008-09-01

    To clean the surface of 300-mm-diameter silicon wafers treated by chemical mechanical polishing (CMP), the following steps were performed: (1) the wafer surfaces were first terminated with hydrogen using an etching solution of hydrofluoric acid, and (2) the wafers were then spun while ozonized water was sprayed before brush scrub cleaning was performed. The number of particles more than 100 nm in diameter remaining on the wafer decreased linearly with increasing time after spraying ozonized water for approximately 5 s before brush scrub cleaning. The wafers had fewer than 10 particles after spraying ozonized water for approximately 15 s followed by brush scrub cleaning. Such a cleaning effect was not accomplished when the ozonized water was not sprayed. A model of the brush scrub cleaning process is discussed from the view point that an oxide film is first formed on the wafer surface where no particles are adhered, and then grows laterally beneath the particles. The force then applied by the brush scrubber overcomes the adhesion force between the particles and the wafer, which results in their removal when the oxide layer reaches a sufficient thickness. The growth of the oxide film was confirmed by observing the spectra obtained by attenuated total reflectance spectroscopy (ATR) using a Fourier transform infrared spectroscope (FTIR) and by X-ray photoelectron spectroscopy (XPS).

  4. When hatchlings outperform adults: locomotor development in Australian brush turkeys (Alectura lathami, Galliformes)

    PubMed Central

    Dial, Kenneth P.; Jackson, Brandon E.

    2011-01-01

    Within Galliformes, megapods (brush turkey, malleefowl, scrubfowl) exhibit unique forms of parental care and growth. Hatchlings receive no post-hatching parental care and exhibit the most exaggerated precocial development of all extant birds, hatching with fully developed, flight-capable forelimbs. Rather than flying up to safety, young birds preferentially employ wing-assisted incline running. Newly hatched Australian brush turkeys (Alectura lathami) are extraordinarily proficient at negotiating all textured inclined surfaces and can flap-walk up inclines exceeding the vertical. Yet, as brush turkeys grow, their forelimb-dependent locomotor performance declines. In an attempt to elucidate how hatchlings perform so well, we analysed hindlimb forces and forelimb kinematics. We measured ground reaction forces (GRFs) for animals spanning the entire growth range (110–2000 g) as they ascended a variably positioned inclined ramp that housed a forceplate. These data are compared with a similar dataset for a chukar partridge (Alectoris chukar) that exhibit a growth strategy typical of most other Galliformes and that demonstrate improved incline performance with increasing age. The brush turkeys' ontogenetic decline in incline running performance is accompanied by loss of traction at steep angles, reduced GRFs and increased wing-loading. We hypothesize that Australian brush turkeys, in contrast to other Galliformes, develop from forelimb-dominated young that exploit a variable terrain (e.g. mound nests, boulders, embankments, cliffs, bushes and trees) into hindlimb-dominated adults dependent on size and running speed to avoid predation. PMID:21047855

  5. ARGET–ATRP Synthesis and Characterization of PNIPAAm Brushes for Quantitative Cell Detachment Studies

    PubMed Central

    Shivapooja, Phanindhar; Ista, Linnea K.; Canavan, Heather E.; Lopez, Gabriel P.

    2012-01-01

    Stimuli responsive (or “smart”) polymer brushes represent a non-toxic approach for achieving release of biofouling layers. Thermo-responsive poly(N-isopropylacrylamide) (PNIPAAm) polymer brushes have been shown to modulate bacterial adhesion and release through transition between temperatures above and below the lower critical solution temperature (LCST ~32 °C) of PNIPAAm in water. In this article, we describe a convenient method to synthesize grafted PNIPAAm brushes over large areas for biological studies using a relatively simple and rapid method which allows atom transfer radical polymerization (ATRP) in presence of air using the activator regenerated electron transfer (ARGET) mechanism. PNIPAAm brushes were characterized using X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectroscopy, Fourier transform infrared spectroscopy, ellipsometry, and contact angle measurements. Our studies demonstrate that uniform, high purity PNIPAAm brushes with controlled and high molecular weight can be easily produced over large areas using ARGET–ATRP. We also report the use of a spinning disk apparatus to systematically and quantitatively study the detachment profiles of bacteria from PNIPAAm surfaces under a range (0–400 dyne/cm2) of shear stresses. PMID:22589075

  6. Probing carbonyl-water hydrogen-bond interactions in thin polyoxazoline brushes.

    PubMed

    Kroning, Annika; Furchner, Andreas; Adam, Stefan; Uhlmann, Petra; Hinrichs, Karsten

    2016-03-01

    Temperature-responsive oxazoline-based polymer brushes have gained increased attention as biocompatible surfaces. In aqueous environment, they can be tuned between hydrophilic and hydrophobic behavior triggered by a temperature stimulus. This transition is connected with changes in molecule-solvent interactions and results in a switching of the brushes between swollen and collapsed states. This work studies the temperature-dependent interactions between poly(2-oxazoline) brushes and water. In detail, thermoresponsive poly(2-cyclopropyl-2-oxazoline), nonresponsive hydrophilic poly(2-methyl-2-oxazoline), as well as a copolymer of the two were investigated with in situ infrared ellipsometry. Focus was put on interactions of the brushes' carbonyl groups with water molecules. Different polymer-water interactions could be observed and assigned to hydrogen bonding between C=O groups and water molecules. The switching behavior of the brushes in the range of 20-45 °C was identified by frequency shifts and intensity changes of the amide I band. PMID:26746164

  7. Assembly and Characterization ofWell-DefinedHigh-Molecular-Weight Poly(p-phenylene) Polymer Brushes

    SciTech Connect

    Chen, Jihua; Dadmun, Mark D; Mays, Jimmy; Messman, Jamie M; Hong, Kunlun; Britt, Phillip F; Sumpter, Bobby G; Alonzo Calderon, Jose E; Kilbey, II, S Michael; Ankner, John Francis; Bredas, Jean-Luc E; Malagoli, Massimo; Deng, Suxiang; Swader, Onome A; Yu, Xiang

    2011-01-01

    The assembly and characterization of well-de ned, end-tethered poly- (p-phenylene) (PPP) brushes having high molecular weight, low polydispersity and high 1,4-stereoregularity are presented. The PPP brushes are formed using a precursor route that relies on either self-assembly or spin coating of high molecular weight (degrees of poly- merizations 54, 146, and 238) end-functionalized poly(1,3-cyclohexadiene) (PCHD) chains from benzene solutions onto silicon or quartz substrates, followed by aromatization of the end-attached PCHD chains on the surface. The approach allows the thickness (grafting density) of the brushes to be easily varied. The dry brushes before and after aromatization are characterized by ellipsometry, atomic force microscopy, grazing angle attenuated total re ectance Fourier transform infrared spectroscopy, and UV-Vis spectros- copy. The properties of the PPP brushes are compared with those of lms made using oligo- paraphenylenes and with ab initio density functional theory simulations of optical proper- ties. Our results suggest conversion to fully aromatized, end-tetheredPPPpolymerbrusheshaving eective conjugation lengths of 5 phenyl units.

  8. Design criteria for brush commutation in high speed traveling wave coilguns

    NASA Astrophysics Data System (ADS)

    Snow, W. R.; Willig, R. L.

    1991-01-01

    Barrel current in a traveling wave coilgun must be commutated on and off, and remain synchronized with the position of the armature coils. Brushes on the armature can be used to satisfy these two requirements, providing synchronization of the currents by being physically attached to the armature coil and provide a means of shorting the turns of the barrel so that motion-induced commutation can take place. This change in barrel current must take place during the time the turn is shorted by the brush. Residual current in the trailing edge of the brush must be made small at the instant the circuit is opened to minimize arcing. A set of design criteria are presented for designing a brush-commutated coilgun so as to achieve the required synchronous commutation. The numer of turns in the barrel undergoing commutation at the same instant in time is directly related to the length of the brush. The results of applying the design criteria to a specific design are presented.

  9. Tunable polymer brush/Au NPs hybrid plasmonic arrays based on host-guest interaction.

    PubMed

    Fang, Liping; Li, Yunfeng; Chen, Zhaolai; Liu, Wendong; Zhang, Junhu; Xiang, Siyuan; Shen, Huaizhong; Li, Zibo; Yang, Bai

    2014-11-26

    The fabrication of versatile gold nanoparticle (Au NP) arrays with tunable optical properties by a novel host-guest interaction are presented. The gold nanoparticles were incorporated into polymer brushes by host-guest interaction between β-cyclodextrin (β-CD) ligand of gold nanoparticles and dimethylamino group of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA). The gold nanoparticle arrays were prepared through the template of PDMAEMA brush patterns which were fabricated combining colloidal lithography and surface-initiated atom-transfer radical polymerization (SI-ATRP). The structure parameters of gold nanoparticle patterns mediated by polymer brushes such as height, diameters, periods and distances, could be easily tuned by tailoring the etching time or size of colloidal spheres in the process of colloidal lithography. The change of optical properties induced by different gold nanoparticle structures was demonstrated. The direct utilization of PDMAEMA brushes as guest avoids a series of complicated modification process and the PDMAEMA brushes can be grafted on various substrates, which broaden its applications. The prepared gold naoparticle arrays are promising in applications of nanosensors, memory storage and surface enhanced spectroscopy. PMID:25347749

  10. Stimuli-responsive spherical brushes based on D-galactopyranose and 2-(dimethylamino)ethyl methacrylate.

    PubMed

    Arslan, Hülya; Pfaff, André; Lu, Yan; Stepanek, Petr; Müller, Axel H E

    2014-01-01

    Stimuli-responsive spherical brushes composed of 6-O-methacryloyl-1,2:3,4-di-O-isopropylidene-D-galactopyranose (MAIGal) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) are prepared via atom transfer radical polymerization (ATRP) using cross-linked polystyrene nanoparticles covered with a thin layer of 2-(2-bromoisobutyryloxy)ethyl methacrylate (BIEM) as ATRP initiator by the "grafting from" approach. The stimuli-responsive behavior of the deprotected spherical PMAGal-b-PDMAEMA block copolymer brushes is investigated by dynamic light scattering and cryogenic transmission electron microscopy. A brush with arms containing 160 MAGal and 170 DMAEMA monomer units shows a significant contraction of the hydrodynamic radius from 20 to 70 °C at pH = 8 with a cloud point at ≈40 °C, whereas no LCST is detected at pH = 6 and 7 due to the protonation of the DMAEMA units. Aggregates occur at low temperatures and pH 8 due to intermolecular interactions between the chains of different brushes, which disappear above LCST, when the PDMAEMA chains fold back to the core of the brushes, exposing the glycopolymer chains to the outside. PMID:24106068

  11. Profilometric analysis of two composite resins’ surface repolished after tooth brush abrasion with three polishing systems

    PubMed Central

    Uppal, Mudit; Ganesh, Arathi; Balagopal, Suresh; Kaur, Gurleen

    2013-01-01

    Aim: To evaluate the effect of three polishing protocols that could be implemented at recall on the surface roughness of two direct esthetic restorative materials. Materials and Methods: Specimens (n = 40) measuring 8 mm (length) × 5 mm (width) × 4 mm (height) were fabricated in an acrylic mold using two light-cured resin-based materials (microfilled composite and microhybrid composite). After photopolymerization, all specimens were finished and polished with one of three polishing protocols (Enhance, One Gloss, and Sof-Lex polishing systems). The average surface roughness of each treated specimen was determined using 3D optical profilometer. Next all specimens were brushed 60,000 times with nylon bristles at 7200 rpm using crosshead brushing device with equal parts of toothpaste and water used as abrasive medium. The surface roughness of each specimen was measured after brushing followed by repolishing with one of three polishing protocols, and then, the final surface roughness values were determined. Results: The data were analyzed using one-way and two-factor analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD). Significant difference (P < 0.05) in surface roughness was observed. Simulated brushing following initial polishing procedure significantly roughened the surface of restorative material (P < 0.05). Conclusion: Polishing protocols can be used to restore a smooth surface on esthetic restorative materials following simulated tooth brushing. PMID:23956531

  12. Experimental determination of optimum gutter brush parameters and road sweeping criteria for different types of waste.

    PubMed

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

    2011-06-01

    The removal ability of gutter brushes for road sweeping for various debris types and different sweeping parameters is studied through experimental tests. The brushing test rig used comprises two commercial gutter brushes, a concrete test bed, and an asphalt test road with a gutter of 0.25 cm width and 10° slope. The brush-surface contact area is determined by sweeping sand on the concrete test bed. Sweeping problems are identified and discussed, and sweeping criteria for the different debris types are suggested. Also, optimum sweeping parameters are proposed for each debris type. In addition, debris removal mechanisms are discussed and analysed. The results indicate that for large heavy debris such as stones and gravel, it is not difficult to achieve large removal forces, because the steel bristles are relatively stiff. Conversely, high removal forces are not needed for particles of millimetre or micron sizes, but bristle curvature has to be appropriate to remove particles from road concavities. Finally, it is found that mud, especially dry mud on a rough surface, is the hardest debris to sweep, requiring a brush with a large tilt angle and a very large penetration to produce large removal forces. PMID:21277186

  13. Particles Bridge the Gap -- Relevance of Polymer Graft Architecture on the Properties of Particle Brush Assemblies

    NASA Astrophysics Data System (ADS)

    Bockstaller, Michael

    2011-03-01

    Current interest in the assembly of ligand-coated nanoparticles into 2D and 3D array structures is driven by the opportunities for novel material technologies that derive from the interactions within nanoparticle superlattice structures. A common challenge in the solution-based assembly of particle superlattice structures is the propensity of hard-sphere type particle assemblies to crack formation and brittle fracture during solvent evaporation. Recent progress in controlled radical polymerization offers novel opportunities for polymer-stabilized particle systems (particle brushes) as building blocks of particle superlattice structures. This contribution will discuss synthetic strategies to realize particle brush systems with well defined polymer graft-architecture in the dense or semi-dilute brush regime and discuss the effect of polymer grafting on the structure formation and cohesive interactions in particle brush assemblies. In particular, it will be demonstrated chain entanglements between surface-grafted chains give rise to fracture through polymer-like crazing thus dramatically increasing the toughness and flexibility of the particle assembly. The modulus and toughness of polymer nanocomposites synthesized by self-assembly of particle brush systems will be shown to exceed those of ``conventional'' particle-filled polymer composites -- a result that will be interpreted as a consequence of the particular conformational constraints of surface grafted chains. The author acknowledges financial support by AFOSR and DTRA.

  14. On the self-assembly of brush block copolymers in thin films.

    PubMed

    Hong, Sung Woo; Gu, Weiyin; Huh, June; Sveinbjornsson, Benjamin R; Jeong, Gajin; Grubbs, Robert Howard; Russell, Thomas P

    2013-11-26

    We describe a simple route to fabricate two dimensionally well-ordered, periodic nanopatterns using the self-assembly of brush block copolymers (brush BCPs). Well-developed lamellar microdomains oriented perpendicular to the substrate are achieved, without modification of the underlying substrates, and structures with feature sizes greater than 200 nm are generated due to the reduced degree of chain entanglements of brush BCPs. A near-perfect linear scaling law was found for the period, L, as a function of backbone degree of polymerization (DP) for two series of brush BCPs. The exponent increases slightly from 0.99 to 1.03 as the side chain molecular weight increases from ∼2.4 to ∼4.5 kg/mol(-1) and saturated with further increase in the side chain molecular weight due to the entropic penalty associated with the packing of the side chains. Porous templates and scaffolds from brush BCP thin films are also obtained by selective etching of one component. PMID:24156297

  15. Eccentricity effects on leakage of a brush seal at low speeds

    NASA Technical Reports Server (NTRS)

    Schlumberger, Julie A.; Proctor, Margaret P.; Hendricks, Robert C.

    1991-01-01

    The effects of eccentricity on brush seal leakage at low rotational speeds were investigated. Included are the leakage results for ambient temperature air and nearly saturated streams at three different rotor eccentricities at both 0 and 400 rpm. A brush seal with a nominal bore diameter of 13.647 cm. (5.3730 in.) was used. It had a radial concentric interference of 0.071 cm (0.0028 in.) and a fence height of 0.0927 cm (0.0365 in.). There were 1060 bristles per centimeter of circumference (2690 bristles per inch of circumference). Rotor eccentricities of 0.003, 0.010, 0.038, and 0.043 cm (0.001, 0.004, 0.015, and 0.017 in.) were achieved by using bushings with different offsets. The results were compared with an annular seal model (FLOWCAL) for air and to a standard labyrinth seal model for steam. The annular seal model was also compared with a bulk flow model of a concentric brush seal in air. Large eccentricities did not damage the brush seals or their Haynes 25 bristles. However, the 304 stainless steel rotor did not show wear, indicating a harder surface is needed. Only the stream data showed hysteresis and were affected by shaft rotation. The brush seal had lower leakage rates than those predicted for comparable annular and labyrinth seals (conventional) because of the large clearances those seals require to accommodate large shaft excursions.

  16. N-hydroxymethyl acrylamide polymer brush and its application in catalyzing coupling reaction.

    PubMed

    Fu, Zhihua; Zhang, Na; Liu, Jie; Li, Tiesheng; Xu, Wenjian; Wang, Fei; Wang, Tao; Zhai, Zhen; Liu, Linlin; Mao, Luyan; Wu, Yangjie

    2013-03-15

    Poly (N-hydroxy methyl acrylamide)-grafted silicon, glass, and quartz surfaces were successfully prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) with methyl alcohol/water mixtures as solvents and CuCl/2,2-dipyridyl as a catalyst. The modified surfaces were characterized by water contact angle, atomic force microscope (AFM), Fluorescence spectrophotometer, Low-angle X-ray diffraction (LAXRD), and X-ray Photoelectron Spectroscopy (XPS). The results showed that the homogeneous and well hydrophilic N-hydroxymethyl acrylamide polymer brushes (NHAM-brushes), which had high hydrophilic properties and the added advantage of providing 3-D coatings with higher binding capacities, were obtained successfully. Cyclopalladated arylimine functionalized polymer brushes were also obtained by reacting HAM-brushes with N,N'-Carbonyldiimidazole (CDI) and cyclopalladated arylimine. The catalyst functionalized PHAM-brushes had good catalytic activity in heterogeneous compared to homogeneous catalyst and exhibited much improved stability and recyclability over time in Suzuki cross-coupling reaction. PMID:23375806

  17. Glassy dynamics of poly(2-vinyl-pyridine) brushes with varying grafting density.

    PubMed

    Neubauer, Nils; Winkler, René; Tress, Martin; Uhlmann, Petra; Reiche, Martin; Kipnusu, Wycliffe Kiprop; Kremer, Friedrich

    2015-04-21

    The molecular dynamics of poly(2-vinyl-pyridine) (P2VP) brushes is measured by Broadband Dielectric Spectroscopy (BDS) in a wide temperature (250 K to 440 K) and broad spectral (0.1 Hz to 1 MHz) range. This is realized using nanostructured, highly conductive silicon electrodes being separated by silica spacers as small as 35 nm. A "grafting-to"-method is applied to prepare the P2VP-brushes with five different grafting densities (0.030 nm(-2) to 0.117 nm(-2)), covering the "true-brush" regime with highly stretched coils and the "mushroom-to-brush" transition regime. The film thickness ranges between 1.8 to 7.1 (±0.2) nm. Two relaxations are observed, an Arrhenius-like process being attributed to fluctuations in the poly(glycidyl-methacrylate) (PGMA) linker used for the grafting reaction and the segmental dynamics (dynamic glass transition) of the P2VP brushes. The latter is characterized by a Vogel-Fulcher-Tammann dependence similar to bulk P2VP. The results can be comprehended considering the length scale on which the dynamic glass transition (≤1 nm) takes place. PMID:25740018

  18. Oral health promotion for schoolchildren – evaluation of a pragmatic approach with emphasis on improving brushing skills

    PubMed Central

    Livny, Alon; Vered, Yuval; Slouk, Liat; Sgan-Cohen, Harold D

    2008-01-01

    Background Preventive dentistry has traditionally emphasized improvement of oral hygiene. School-based programs, often delivered by dental hygienists or other health educators, are usually limited to dental knowledge provision. The present study focused on promotion of health behavior. The objectives were to evaluate the effect of a pragmatic educational program on tooth brushing skills of young schoolchildren. Methods The population consisted of 196 first grade children in Jerusalem. One dentist interviewed the children and evaluated base-line brushing skills, applying simple visual index, based on dividing the dentition to eight different segments. a trained hygienist then educated the children, emphasizing brushing skills. A simple "scrubbing" brushing method was taught for all dental surfaces. Four months later a second examination was conducted, applying same evaluation methods. Results At base-line 92% of the children had brushed the labial surfaces of front teeth, but only 8% brushed the inner surfaces of posterior teeth. Only 32% brushed occlusal surfaces. These levels significantly increased after four months: 98% now brushed the labial surfaces; 43% brushed inner surfaces of posterior teeth, 87% brushed occlusal surfaces (p < 0.001). The average number of dental "areas" brushed had increased (among the eight areas recorded) from 2.8 to 5.7 (p < 0.0001). Conclusion This method of behavioural instruction emphasized improvement of personal manual skills specifically for those areas of the dentition which demand most efforts in oral hygiene promotion. These results are of practical help in improving future health education programs by the health promotion team. PMID:18237389

  19. Distribution and phenotypes of unipolar brush cells in relation to the granule cell system of the rat cochlear nuclear nucleus

    PubMed Central

    Diño, Maria. R.; Mugnaini, Enrico

    2009-01-01

    In most mammals the cochlear nuclear complex (CN) contains a distributed system of granule cells (GCS), whose parallel fiber axons innervate the dorsal cochlear nucleus (DCN). Like their counterpart in cerebellum, CN granules are innervated by mossy fibers of various origins. The GCS is complemented by unipolar brush (UBCs) and Golgi cells, and by stellate and cartwheel cells of the DCN. This cerebellum-like microcircuit modulates the activity of the DCN’s main projection neurons, the pyramidal, giant and tuberculoventral neurons, and is thought to improve auditory performance by integrating acoustic and proprioceptive information. In this paper, we focus on the UBCs, a chemically heterogeneous neuronal population, using antibodies to calretinin, mGluR1α epidermal growth factor substrate 8 (Eps8) and the transcription factor Tbr2. Eps8 and Tbr2 labeled most of the CN’s UBCs, if not the entire population, while calretinin and mGluR1α distinguished two largely separate subsets with overlapping distributions. By double labeling with antibodies to Tbr2 and the α6 GABAA-receptor subunit, we found that UBCs populate all regions of the GCS and occur at remarkably high densities in the DCN and subpeduncular corner, but rarely in the lamina. Although GCS subregions likely share the same microcircuitry, their dissimilar UBC densities suggest they may be functionally distinct. UBCs and granules are also present in regions previously not included in the GCS, namely the rostrodorsal magnocellular portions of VCN, vestibular nerve root, trapezoid body, spinal tract and sensory and principal nuclei of the trigeminal nerve, and cerebellar peduncles. The UBC’s dendritic brush receives AMPA- and NMDA-mediated input from an individual mossy fiber, favoring singularity of input, and its axon most likely forms several mossy fiber-like endings that target numerous granule cells and other UBCs, as in the cerebellum. The UBCs therefore, may amplify afferent signals temporally and

  20. Streaming Potential and Energy Conversion in Nanochannel Grafted With Poly-Zwitterion Brushes

    NASA Astrophysics Data System (ADS)

    Patwary, Jahin; Chen, Guang; Das, Siddhartha

    2015-11-01

    Here we study the streaming potential and electrochemomechanical energy conversion in nanochannels grafted with poly-zwitterion (PZ) brushes. PZs are polymer molecules consisting of negative and positive charge centres simultaneously; depending on the bulk pH, the extent of dissociation differs at each of these charge centres, yielding a particular net charge on the PZ molecule. This PZ charge, therefore, develops a pH dependent electrostatics of the PZ brushes grafted at the naochannel walls. We develop a self-consistent field theory model to calculate this electrostatics by appropriately accounting for the explicit hydrogen ion concentration. Secondly, we use this electrostatics to calculate the streaming potential and the resulting electrochemomechanical energy conversion in nanochannels grafted with poly-zwitterion (PZ) brushes. Our results indicate distinct influences of pH, bulk ion concentration, and the ionization parameters of the PZs in regulating the nanochannel energy conversion. Bridge to the Doctorate Fellowship - LSAMP Committee.

  1. Highly efficient antibacterial surface grafted with a triclosan-decorated poly(N-hydroxyethylacrylamide) brush.

    PubMed

    Wu, Hai-Xia; Tan, Lei; Tang, Zhao-Wen; Yang, Mei-Yan; Xiao, Jian-Yun; Liu, Chuan-Jun; Zhuo, Ren-Xi

    2015-04-01

    This work presented a highly efficient antibacterial Ti-surface which was grafted with poly(N-hydroxyethylacrylamide) (PHEAA) brush and further decorated with triclosan (TCS). The modified surfaces were characterized using contact angle measurements, X-ray photoelectron spectroscopy, and attenuated total reflectance Fourier transform infrared. The antibacterial performance of the modified surfaces was evaluated using the Streptococcus mutans and Actinomyces naeslundii attachment test. The Ti surface with PHEAA brush (Ti-PHEAA) was able to resist the adhesion of the bacteria, while the TCS-decorated Ti surface (Ti-TCS) showed the capability of killing the bacteria adhered on the surface. As we coupled the TCS to the PHEAA brush, the surface showed highly efficient antibacterial performance due to the combination of the resistance to the bacteria adhesion and its activity of killing bacteria. PMID:25756367

  2. Scaling behavior of a brush-homopolymer interface in the limit of high grafting density

    NASA Astrophysics Data System (ADS)

    Matsen, M. W.

    2005-04-01

    The interface between a polymer brush and a chemically equivalent homopolymer is examined using self-consistent field theory (SCFT). Focusing on ultrahigh grafting densities, we extract how the properties scale with the brush thickness, L, and compare with predictions based on strong-stretching theory (SST). Although the scaling exponents are consistent, the overall agreement is poor. We attribute this to the inaccurate way the SST-based calculation treats chain fluctuations at the extremity of the brush. This accounts for a previous disagreement between SCFT and SST in regards to autophobic dewetting, and brings into question a number of other SST predictions. Our conclusion is that SST requires a more sophisticated treatment of finite-stretching corrections, along the lines of that proposed by Likhtman and Semenov [Europhys. Lett. 51, 307 (2000)].

  3. New Poly(amino acid methacrylate) Brush Supports the Formation of Well-Defined Lipid Membranes

    PubMed Central

    2015-01-01

    A novel poly(amino acid methacrylate) brush comprising zwitterionic cysteine groups (PCysMA) was utilized as a support for lipid bilayers. The polymer brush provides a 12-nm-thick cushion between the underlying hard support and the aqueous phase. At neutral pH, the zeta potential of the PCysMA brush was ∼−10 mV. Cationic vesicles containing >25% DOTAP were found to form a homogeneous lipid bilayer, as determined by a combination of surface analytical techniques. The lipid mobility as measured by FRAP (fluorescence recovery after photobleaching) gave diffusion coefficients of ∼1.5 μm2 s–1, which are comparable to those observed for lipid bilayers on glass substrates. PMID:25746444

  4. Inhibitory effect for proliferation of oral bacteria in dogs by tooth brushing and application of toothpaste

    PubMed Central

    WATANABE, Kazuhiro; KIJIMA, Saku; NONAKA, Chie; MATSUKAWA, Yuki; YAMAZOE, Kazuaki

    2016-01-01

    To investigate inhibitory effect for oral bacterial proliferation, we divided 12 dogs into 3 groups; scaling alone (C; control group), brushing (B) and application of toothpaste (P). Before scaling (Pre) and at 0 to 8 weeks after scaling (0–8 w), we collected oral bacteria from the dental surface every week and counted them using a bacterial counter. The results demonstrated a significant reduction in the number of oral bacteria for group B relative to Pre and group C, as well as for group P relative to group C at 5–7 w. Consequently, brushing may inhibit an increase in the number of oral bacteria, and toothpaste may be effective at a certain level, although not more than that of brushing. PMID:27062999

  5. Characterization of Swollen States of Polyelectrolyte Brushes in Salt Solution by Neutron Reflectivity

    NASA Astrophysics Data System (ADS)

    Kobayashi, Motoyasu; Mitamura, Koji; Terada, Masami; Yamada, Norifumi L.; Takahara, Atsushi

    2011-01-01

    Cationic and zwitterionic polyelectrolyte brushes on quartz substrate were synthesized by surface-initiated atom transfer radical polymerization of 2-(methacryloyloxy)-ethyltrimethylammonium chloride (MTAC) and 2-(methacryloyloxy)ethyl phosphorylcholine (MPC). The effects of ionic strength on brush structure are investigated by neutron reflectivity (NR) in NaCl deuterium oxide (D2O) solutions. We observed that poly(MTAC) chains were drastically shrunk at concentrations above 0.1 M NaCl/D2O, which may be the change in charge-screening effect against ions on poly(MTAC). On the other hand, effect of salt concentration on a swollen state of poly(MPC) brush was negligible, even at the high concentration (5.0 M) close to saturation. The behaviour of poly(MPC) in salt aqueous solution is completely different from that of poly(MTAC), which may arise from the unique interaction properties, neutral nature, and hydrated water structure of phosphorylcholine units.

  6. Core-shell-corona-structured polyelectrolyte brushes-grafting magnetic nanoparticles for water harvesting.

    PubMed

    Liu, Guoqiang; Cai, Meirong; Wang, Xiaolong; Zhou, Feng; Liu, Weimin

    2014-07-23

    A novel superhydrophilic material, charged polymer brushes-grafted magnetic core-shell-corona composite nanoparticles (Fe3O4@SiO2@PSPMA), was developed to harvest water through the hydration effect. Because of both the strong hydration capability and the good swelling performance, the negatively charged polymer brushes, PSPMA brushes, endow the composite nanoparticles with superhydrophilicity and a good water-absorbing performance like a sponge, while the magnetic Fe3O4 cores allow easy separation of Fe3O4@SiO2@PSPMA nanoparticles with absorbed water from oil/water mixture under an external magnetic field. The functional particles have the capability of harvesting water droplets whether floating on an oil surface or in the oil. This water-absorbing material uses selective wettability to harvest water and achieve oil-water separation and may be useful in finding novel approaches for recycling water from sewage and removing water in the petroleum industry. PMID:24955817

  7. Integrity testing of brush seal in shroud ring of T-700 engine

    NASA Astrophysics Data System (ADS)

    Hendricks, Robert C.; Griffin, Thomas A.; Bobula, George B.; Bill, Robert C.; Howe, Harold W.

    1992-08-01

    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 30 hr of cyclic and steady-state data were taken with surface speeds to 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.

  8. Rotordynamic coefficient test results for a four-stage brush seal

    NASA Astrophysics Data System (ADS)

    Conner, Kelly J.; Childs, Dara W.

    1993-06-01

    Experimental results are presented for the direct and cross-coupled stiffness and direct damping coefficients for a four-stage brush seal. Variable test parameters include the inlet pressure, pressure ratio, shaft speed, fluid prerotation, and seal spacing. Direct damping slightly increases with running speed; otherwise, the rotordynamic coefficients are relatively insensitive to changes in the test parameters. Cross-coupled stiffness is generally unchanged by increasing the inlet tangential velocity to the seals, in contrast to conventional labyrinth seals. Comparisons of test results for the four-stage brush seal with an eight-cavity labyrinth showed superior rotordynamic performance for the brush seal, namely, larger values for direct stiffness and lower values for the (destabilizing) cross-coupled stiffness coefficient.

  9. A brush-shaped air plasma jet operated in glow discharge mode at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Li, Xuechen; Bao, Wenting; Jia, Pengying; Di, Cong

    2014-07-01

    Using ambient air as working gas, a direct-current plasma jet is developed to generate a brush-shaped plasma plume with fairly large volume. Although a direct-current power supply is used, the discharge shows a pulsed characteristic. Based on the voltage-current curve and fast photography, the brush-shaped plume, like the gliding arc plasma, is in fact a temporal superposition of a moving discharge filament in an arched shape. During it moves away from the nozzle, the discharge evolves from a low-current arc into a normal glow in one discharge cycle. The emission profile is explained qualitatively based on the dynamics of the plasma brush.

  10. Immobilization of enzymes on 2-hydroxyethyl methacrylate and glycidyl methacrylate copolymer brushes.

    PubMed

    Ren, Tanchen; Mao, Zhengwei; Moya, Sergio Enrique; Gao, Changyou

    2014-08-01

    The immobilization of enzymes is of paramount importance to maintain their activity and stability. In this study, surface-initiated atom-transfer radical polymerization was applied to prepare poly(2-hydroxyethyl methacrylate)-block-poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate) brushes on glass slides. The polymerization kinetics was followed by using a quartz crystal microbalance with dissipation monitoring and ellipsometry in terms of mass and thickness growth, respectively. The surface chemical compositions of the obtained polymer brushes were characterized by X-ray photoelectron spectroscopy. Their mass, thickness, and enzyme-immobilization ability could be easily tuned by the initiator reaction time, monomer ratio, and polymerization time. The antibacterial activity and stability of the immobilized lysozymes were studied by fluorescent staining and bacteria lysis assay, which revealed that the lysozymes on the copolymer brushes had good stability during storage at 4 °C for up to 30 days. PMID:24962678

  11. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  13. Mesoscopic simulation of entanglements using dissipative particle dynamics: application to polymer brushes.

    PubMed

    Goujon, Florent; Malfreyt, Patrice; Tildesley, Dominic J

    2008-07-21

    We use a simple spring-spring repulsion to model entanglements between polymers in dissipative particle dynamics (DPD) simulations. The model is applied to a polymer brushes system to study lubrication. We demonstrate that this method leads to mechanical equilibrium in polymer brushes using the normal DPD time step. The number of bond crossings is calculated to provide a quantitative description of the entanglement. We demonstrate that it is possible to avoid 99% of the bond crossings with the values of spring-spring repulsion that can be used without significantly decreasing the time step. A shear force is applied to the system to study the effect of the decrease in the bond crossings on the structure and rheological properties of the brushes. In particular, we show how the friction coefficient increases with the decrease in the bond crossings of the polymers. PMID:18647043

  14. New poly(amino acid methacrylate) brush supports the formation of well-defined lipid membranes.

    PubMed

    Blakeston, Anita C; Alswieleh, Abdullah M; Heath, George R; Roth, Johannes S; Bao, Peng; Cheng, Nan; Armes, Steven P; Leggett, Graham J; Bushby, Richard J; Evans, Stephen D

    2015-03-31

    A novel poly(amino acid methacrylate) brush comprising zwitterionic cysteine groups (PCysMA) was utilized as a support for lipid bilayers. The polymer brush provides a 12-nm-thick cushion between the underlying hard support and the aqueous phase. At neutral pH, the zeta potential of the PCysMA brush was ∼-10 mV. Cationic vesicles containing >25% DOTAP were found to form a homogeneous lipid bilayer, as determined by a combination of surface analytical techniques. The lipid mobility as measured by FRAP (fluorescence recovery after photobleaching) gave diffusion coefficients of ∼1.5 μm(2) s(-1), which are comparable to those observed for lipid bilayers on glass substrates. PMID:25746444

  15. Inhibitory effect for proliferation of oral bacteria in dogs by tooth brushing and application of toothpaste.

    PubMed

    Watanabe, Kazuhiro; Kijima, Saku; Nonaka, Chie; Matsukawa, Yuki; Yamazoe, Kazuaki

    2016-08-01

    To investigate inhibitory effect for oral bacterial proliferation, we divided 12 dogs into 3 groups; scaling alone (C; control group), brushing (B) and application of toothpaste (P). Before scaling (Pre) and at 0 to 8 weeks after scaling (0-8 w), we collected oral bacteria from the dental surface every week and counted them using a bacterial counter. The results demonstrated a significant reduction in the number of oral bacteria for group B relative to Pre and group C, as well as for group P relative to group C at 5-7 w. Consequently, brushing may inhibit an increase in the number of oral bacteria, and toothpaste may be effective at a certain level, although not more than that of brushing. PMID:27062999

  16. Brush-Coated Nanoparticle Polymer Thin Films: structure-mechanical-optical properties

    SciTech Connect

    Green, Peter F.

    2015-01-13

    Executive Summary Our work was devoted to understanding the structure and properties of a class of thin film polymer nanocomposites (PNCs). PNCs are composed of polymer hosts into which nanoparticles (metallic nanoparticles, quantum dots, nanorods, C60, nanotubes) are incorporated. PNCs exhibit a diverse range of functional properties (optical, electronic, mechanical, biomedical, structural), determined in part by the chemical composition of the polymer host and the type of nanoparticle. The properties PNCs rely not only on specific functional, size-dependent, behavior of the nanoparticles, but also on the dispersion, and organizational order in some cases, inter-nanoparticle separation distances, and on relative interactions between the nanoparticles and the host. Therefore the scientific challenges associated with understanding the interrelations between the structure and function/properties of PNCs are far more complex than may be understood based only on the knowledge of the compositions of the constituents. The challenges of understanding the structure-function behavior of PNCs are further compounded by the fact that control of the dispersion of the nanoparticles within the polymer hosts is difficult; one must learn how to disperse inorganic particles within an organic host. The goal of this proposal was to develop an understanding of the connection between the structure and the thermal (glass transition), mechanical and optical properties of a specific class of PNCs. Specifically PNCs composed of polymer chain grafted gold nanoparticles within polymer hosts. A major objective was to understand how to develop basic principles that enable the fabrication of functional materials possessing optimized morphologies and combinations of materials properties. Accomplishments: We developed: (1) fundamental principles that enabled the creation of thin film PNCs possessing more complex morphologies of homopolymers and block copolymer micellar systems [1-6]; (2) a new

  17. 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. PMID:25679494

  18. Improving optical contact for functional near‑infrared brain spectroscopy and imaging with brush optodes

    PubMed Central

    Khan, Bilal; Wildey, Chester; Francis, Robert; Tian, Fenghua; Delgado, Mauricio R.; Liu, Hanli; MacFarlane, Duncan; Alexandrakis, George

    2012-01-01

    A novel brush optode was designed and demonstrated to overcome poor optical contact with the scalp that can occur during functional near infrared spectroscopy (fNIRS) and imaging due to light obstruction by hair. The brush optodes were implemented as an attachment to existing commercial flat-faced (conventional) fiber bundle optodes. The goal was that the brush optodes would thread through hair and improve optical contact on subjects with dense hair. Simulations and experiments were performed to assess the magnitude of these improvements. FNIRS measurements on 17 subjects with varying hair colors (blonde, brown, and black) and hair densities (0–2.96 hairs/mm2) were performed during a finger tapping protocol for both flat and brush optodes. In addition to reaching a study success rate of almost 100% when using the brush optode extensions, the measurement setup times were reduced by a factor of three. Furthermore, the brush optodes enabled improvements in the activation signal-to-noise ratio (SNR) by up to a factor of ten as well as significant (p < 0.05) increases in the detected area of activation (dAoA). The measured improvements in SNR were matched by Monte Carlo (MC) simulations of photon propagation through scalp and hair. In addition, an analytical model was derived to mathematically estimate the observed light power losses due to different hair colors and hair densities. Interestingly, the derived analytical formula produced excellent estimates of the experimental data and MC simulation results despite several simplifying assumptions. The analytical model enables researchers to readily estimate the light power losses due to obstruction by hair for both flat-faced fiber bundles and individual fibers for a given subject. PMID:22567582

  19. Examining Scientific and Technical Writing Strategies in the 11th Century Chinese Science Book "Brush Talks from Dream Brook"

    ERIC Educational Resources Information Center

    Zhang, Yuejiao

    2013-01-01

    This article examines the influential Chinese science book "Brush Talks from Dream Brook," written by Shen Kuo in the 11th century. I suggest that "Brush Talks" reveals a tension between institutionalized science and science in the public, and a gap between the making of scientific knowledge and the communication of such…

  20. Development of an integrated multi-platform approach for assessing brush management conservation efforts in semiarid rangelands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Millions of dollars have been spent on brush management, or removal of unwanted woody vegetation, as a conservation practice to control the presence of woody species. Land managers need an inexpensive means of monitoring the effects of brush management conservation methods for decreasing degradatio...

  1. 78 FR 61330 - Subzone 141F, Authorization of Production Activity, John D. Brush & Co., dba Sentry Group, (Safes...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-03

    ... public comment (78 FR 34335, 6-7-2013). The FTZ Board has determined that no further review of the... Foreign-Trade Zones Board Subzone 141F, Authorization of Production Activity, John D. Brush & Co., dba... activity to the Foreign-Trade Zones (FTZ) Board on behalf of John D. Brush & Co., dba Sentry Group,...

  2. Coupling pH-responsive polymer brushes to electricity: switching thickness and creating waves of swelling or collapse.

    PubMed

    Dunderdale, Gary J; Fairclough, J Patrick A

    2013-03-19

    Electrolysis of water is proposed as a method to couple the pH-responsive behavior of polymer brushes to an electrical stimulus. It is shown that an electrode in close proximity to a pH-responsive polymer brush can change the local solution pH, inducing either swelling or collapse of the polymer brush. By alternating the bias of the voltage applied to the electrode, either acidic or alkaline conditions can be generated, and reproducible cycles of polymer brush swelling and collapse can be achieved. It was found that the length of time which the electrical stimulus is applied to the electrodes can be as short as 10 s and that, once "switched", polymer brushes remain in the switched state for many minutes after the electrical stimulus is turned off. In other experiments, two electrodes were positioned 10 cm apart with a pH-responsive brush in between. Under these conditions waves of either acidic or alkaline solution pH could be generated which caused a coincident wave of polymer brush swelling or collapse. These waves originate from one electrode and travel across the brush surface toward the opposite electrode with a velocity of ~40 μm s(-1). PMID:23441938

  3. A corrosion resistant cerium oxide based coating on aluminum alloy 2024 prepared by brush plating

    NASA Astrophysics Data System (ADS)

    Tang, Junlei; Han, Zhongzhi; Zuo, Yu; Tang, Yuming

    2011-01-01

    Cerium oxide based coatings were prepared on AA2024 Al alloy by brush plating. The characteristic of this technology is that hydrogen peroxide, which usually causes the plating solution to be unstable, is not necessary in the plating electrolyte. The coating showed laminated structures and good adhesive strength with the substrate. X-ray diffraction and X-ray photoelectron spectroscopy analysis showed that the coatings were composed of Ce(III) and Ce(IV) oxides. The brush plated coatings on Al alloys improved corrosion resistance. The influence of plating parameters on structure and corrosion resistance of the cerium oxide based coating was studied.

  4. Strain rate sensitivity of a nanocrystalline Cu synthesized by electric brush plating

    NASA Astrophysics Data System (ADS)

    Jiang, Zhonghao; Liu, Xianli; Li, Guangyu; Jiang, Qing; Lian, Jianshe

    2006-04-01

    A method for synthesizing bulk nanocrystalline Cu by an electric brush-plating technique is reported. This brush-plated nanocrystalline Cu has a fine (26nm) and quite uniform grain structure and predominant high-angle grain boundaries. A pronounced strain rate sensitivity of the stress with an m of 0.104 and the Coble creep and a subsequent transition to the power-law creep were observed in room temperature tensile and creep tests. The dominant grain boundary deformation due to the truly nanocrystalline structure of this nanocrystalline Cu is responsible for the observed strain rate sensitivity.

  5. Bottle-brush polymers as an intermediate between star and cylindrical polymers.

    PubMed

    Denesyuk, N A

    2003-09-01

    We present a theoretical study of a single bottle-brush molecule, which consists of multiarmed polymer stars grafted densely onto a stiff backbone. Mean-field approximation and a variational approach are used to calculate the dominant trajectories of the grafted chains, the shape of the molecule, and the segment density distribution around the backbone. All these properties are calculated for an arbitrary relationship between the size of the backbone and that of a grafted star. Hence cylindrical comb copolymer brushes and spherically symmetric polymer stars are considered as the limiting cases of the present problem. PMID:14524794

  6. Bottle-brush polymers as an intermediate between star and cylindrical polymers

    NASA Astrophysics Data System (ADS)

    Denesyuk, N. A.

    2003-09-01

    We present a theoretical study of a single bottle-brush molecule, which consists of multiarmed polymer stars grafted densely onto a stiff backbone. Mean-field approximation and a variational approach are used to calculate the dominant trajectories of the grafted chains, the shape of the molecule, and the segment density distribution around the backbone. All these properties are calculated for an arbitrary relationship between the size of the backbone and that of a grafted star. Hence cylindrical comb copolymer brushes and spherically symmetric polymer stars are considered as the limiting cases of the present problem.

  7. Submicron Patterning of Polymer Brushes: An Unexpected Discovery from Inkjet Printing of Polyelectrolyte Macroinitiators.

    PubMed

    Parry, Adam V S; Straub, Alexander J; Villar-Alvarez, Eva M; Phuengphol, Takdanai; Nicoll, Jonathan E R; W K, Xavier Lim; Jordan, Lianne M; Moore, Katie L; Taboada, Pablo; Yeates, Stephen G; Edmondson, Steve

    2016-07-27

    Using an electrostatic-based super inkjet printer we report the high-resolution deposition of polyelectrolyte macroinitiators and subsequent polymer brush growth using SI-ARGET-ATRP. We go on to demonstrate for the first time a submicron patterning phenomenon through the addition of either a like charged polyelectrolyte homopolymer or through careful control of ionic strength. As a result patterning of polymer brushes down to ca. 300 nm is reported. We present a possible mechanistic model and consider how this may be applied to other polyelectrolyte-based systems as a general method for submicron patterning. PMID:27400396

  8. Esophageal aspergillosis in cytologic brushings: report of two cases associated with acute myelogenous leukemia.

    PubMed

    Bergman, Simon; Geisinger, Kim R

    2004-05-01

    Aspergillus, which commonly involves the sinonasal region and upper respiratory tract, is reported for the first time in esophageal brushings in two immunocompromised patients with a history of acute myelogenous leukemia (AML). Aspergillus species was identified in both cases in smears as scattered three-dimensional groups of fungi with 45 degrees angle branching. One case had a local esophageal noninvasive form, while the other, in addition to the esophagus, had disseminated to the spleen. Although Aspergillus is an uncommon cause of esophagitis in immunocompromised patients, its presence may be associated with an extremely poor prognosis as both expired shortly after detecting this fungus on esophageal brushings. PMID:15108234

  9. Rapid synthesis of polymer brush surfaces via microwave-assisted surface-initiated radical polymerization.

    PubMed

    Guo, Wei; Hensarling, Ryan M; LeBlanc, Arthur L; Hoff, Emily A; Baranek, Austin D; Patton, Derek L

    2012-05-14

    Microwave-assisted surface-initiated radical polymerization (μW-SIP) is demonstrated for the rapid synthesis of polymer brush surfaces on two-dimensional substrates. μW-SIP is carried out at constant temperature and microwave power allowing comparison with conventional SIP carried out in an oil bath at the same effective solution temperature. We show μW-SIP enables significant enhancements (up to 39-fold increase) in brush thickness at reduced reaction times for a range of monomer types (i.e. acrylamides, acrylates, methacrylates, and styrene). The effects of reaction time, monomer concentration, and microwave power on film thickness are explored. PMID:22514123

  10. Real-time x-ray scattering study of the initial growth of organic crystals on polymer brushes

    SciTech Connect

    An, Sung Yup; Ahn, Kwangseok; Kim, Doris Yangsoo; Lee, Dong Ryeol; Lee, Hyun-Hwi; Cho, Jeong Ho

    2014-04-21

    We studied the early-stage growth structures of pentacene organic crystals grown on polymer brushes using real-time x-ray scattering techniques. In situ x-ray reflectivity and atomic force microscopy analyses revealed that at temperatures close to the glass transition temperature of polymer brush, the pentacene overlayer on a polymer brush film showed incomplete condensation and 3D island structures from the first monolayer. A growth model based on these observations was used to quantitatively analyze the real-time anti-Bragg x-ray scattering intensities measured during pentacene growth to obtain the time-dependent layer coverage of the individual pentacene monolayers. The extracted total coverage confirmed significant desorption and incomplete condensation in the pentacene films deposited on the polymer brushes. These effects are ascribed to the change in the surface viscoelasticity of the polymer brushes around the glass transition temperature.

  11. Fabrication of protein-resistant blend based on PVDF-HFP and amphiphilic brush copolymer made from PMMA and PEGMA

    NASA Astrophysics Data System (ADS)

    Hwangbo, Kyung-Hee; Kim, Yu-Jeong; Cho, Kuk Young

    2012-12-01

    Polymeric blends provide a facile route to obtaining materials with various synergistic properties arising from the individual components. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), a hydrophobic polymer, is finding new applications in polymer electrolytes, membranes, and heat-resistant structural materials owing to its high thermal stability, mechanical strength, and weatherability. In this report, blends of PVDF-HFP and polymer brush were prepared with enhanced water uptake and protein resistance, which are important requirements for membranes used in food and biological applications. Polymer brush is composed of poly(methyl methacrylate) main chains, which are miscible with PVDF-HFP, and hydrophilic poly(ethylene glycol) (PEG) brush chains. Incorporation of PEG chains through the polymer brush structure not only enhanced water uptake and protein adsorption resistance but also produced a well-distributed morphology of the blending components through the matrix as evidenced by observation of the morphology after selective extraction of polymer brush from the matrix.

  12. Effect of pH on Swelling Behavior of Polyelectrolyte Brushes Produced via Surface Confined Atom Transfer Radical Polymerization.

    NASA Astrophysics Data System (ADS)

    Sankhe, Amit

    2005-03-01

    Surface-tethered polyelectrolyte brushes comprised of poly (itaconic acid) (PIA) and poly(methacrylic acid) (PMAA) were grown using surface-confined atom transfer radical polymerization (ATRP). The surface- tethered initiator monolayer was formed by self-assembling 2-bromoisobutyryl bromide terminated thiol molecules on gold coated silicon substrates. This polymerization initiator molecule and a copper-based organometallic catalyst allowed tethered polyelectrolyte chains to be grown via radical polymerization at room temperature in aqueous solutions. The behavior of these polyelectrolyte brushes as a function of pH was studied using a phase modulated ellipsometery. The presentation explains how the brushes are affected by external conditions such as the pH of the contacting solution. As the polymer brushes already exist in the charged state, addition of neutral water or salt solution did not affect the polymer brush height, however a decrease of thickness with pH is found.

  13. Cationic polymer brush-modified cellulose nanocrystals for high-affinity virus binding

    NASA Astrophysics Data System (ADS)

    Rosilo, Henna; McKee, Jason R.; Kontturi, Eero; Koho, Tiia; Hytönen, Vesa P.; Ikkala, Olli; Kostiainen, Mauri A.

    2014-09-01

    -initiated atom-transfer radical polymerization of poly(N,N-dimethylaminoethyl methacrylate) and subsequent quaternization of the polymer pendant amino groups. The cationic polymer brush-modified CNCs maintained excellent dispersibility and colloidal stability in water and showed a ζ-potential of +38 mV. Dynamic light scattering and electron microscopy showed that the modified CNCs electrostatically bind cowpea chlorotic mottle virus and norovirus-like particles with high affinity. Addition of only a few weight percent of the modified CNCs in water dispersions sufficed to fully bind the virus capsids to form micrometer-sized assemblies. This enabled the concentration and extraction of the virus particles from solution by low-speed centrifugation. These results show the feasibility of the modified CNCs in virus binding and concentrating, and pave the way for their use as transduction enhancers for viral delivery applications. Electronic supplementary information (ESI) available: CNC surface chain fraction and degree of substitution after BriBBr modification, NMR spectra of the SI-ATRP reaction mixture at 0 and 120 min, conversion of the DMAEMA monomer during SI-ATRP, DLS size distribution profiles of CNCs and CNC-g-P(QDMAEMA), TEM images of NoV-VLPs and their complexes with CNC-g-P(QDMAEMA) at 0 mM NaCl. See DOI: 10.1039/c4nr03584d

  14. Daily reduction of oral malodor with the use of a sonic tongue brush combined with an antibacterial tongue spray in a randomized cross-over clinical investigation.

    PubMed

    Saad, S; Gomez-Pereira, P; Hewett, K; Horstman, P; Patel, J; Greenman, J

    2016-03-01

    The objective of this clinical investigation was to test the effectiveness on breath odor of a newly designed sonic tongue brush (TongueCare+, TC). It consists of a soft silicone brush optimally designed based on the tongue's anatomy to remove bacterial biofilm from the tongue's complex surface, and it is coupled with a sonic power toothbrush handle. TC was used in combination with an antibacterial tongue spray (BreathRx, BRx) containing 0.09% cetylpyridinium chloride and 0.7% zinc gluconate. A total of 21 participants with oral malodor exceeding the threshold for recognition took part in this cross-over clinical investigation, which consisted of a single use of four treatment arms with one week washout period in between. The treatments consisted of: (1) TC  +  BRx, (2) TC  +  water, (3) BRx and (4) water. Malodor levels and bacterial density were monitored up to 6 h by organoleptic scoring and selective plating, respectively. The organoleptic score and bacterial density were significantly lower after using TC  +  BRx compared to all alternative treatments at all time points. A significant decrease in both parameters was detected after a single use of TC  +  BRx, from levels characteristic of high oral malodor, to barely noticeable levels after treatment and this was maintained up to 6 h. Moreover, we identified a significant positive correlation between bacterial density and organoleptic score, confirming that bacterial tongue biofilm is the root cause of oral malodor in these subjects. The results of this clinical investigation demonstrated that the combined treatment of a sonic tongue brush with the antibacterial tongue spray is able to deliver more than 6 h of fresh breath following a single use. The clinical investigation was registered at the ISRCTN registry under study identification number ISRCTN38199132. PMID:26869586

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

    PubMed Central

    2014-01-01

    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. PMID:24948900

  16. Aluminum hydroxide coating thickness measurements and brushing tests on K West Basin fuel elements

    SciTech Connect

    Pitner, A.L.

    1998-09-11

    Aluminum hydroxide coating thicknesses were measured on fuel elements stored in aluminum canisters in K West Basin using specially developed eddy current probes . The results were used to estimate coating inventories for MCO fuel,loading. Brushing tests successfully demonstrated the ability to remove the coating if deemed necessary prior to MCO loading.

  17. Numerical investigation of the contraction of neutral-charged diblock copolymer brushes in electric fields.

    PubMed

    Chen, Yuwei; Li, Haiming; Zhu, Yuejin; Tong, Chaohui

    2016-03-31

    Using self-consistent field theory (SCFT), the contraction of neutral-charged A-B diblock copolymer brushes in electric fields generated by opposite surface charges on two parallel electrodes has been numerically investigated. The diblock copolymer chains were grafted with the free end of the neutral block to one electrode and immersed in a salt-free solution sandwiched between the two electrodes. The numerical results reveal that the charged monomers, A-B joint segment and the tail exhibit bimodal distributions under external electric fields, which are absent for homopolymer polyelectrolyte brushes. The dependences of the relative populations and peak positions of the two modes on various parameters such as block ratio, grafting density, chain length and strength of the applied electric field were systematically examined and the underlining mechanisms were elucidated. It was found in this study that, if the total amount of surface charges on the grafting electrode is no more than that of the counter-ions in the system, overall charge neutrality is generally maintained inside the brushes when including the contribution of surface charges on the grafting electrode. In such a case, the counter-ions expelled from the brushes are highly enriched in the immediate vicinity of the second electrode and an approximate charge balance between these expelled counter-ions and the opposite surface charges on the second electrode is achieved. PMID:26912335

  18. Brush seal leakage performance with gaseous working fluids at static and low rotor speed conditions

    NASA Technical Reports Server (NTRS)

    Carlile, Julie A.; Hendricks, Robert C.; Yoder, Dennis A.

    1992-01-01

    The leakage performance of a brush seal with gaseous working fluids at static and low rotor speed conditions was studied. The leakage results included for air, helium, and carbon dioxide at several bristle/rotor interferences. Also, the effects of packing a lubricant into the bristles and also of reversing the pressure drop across the seal were studied. Results were compared to that of an annular seal at similar operating conditions. In order to generalize the results, they were correlated using corresponding state theory. The brush seal tested had a bore diameter of 3.792 cm (1.4930 in.), a fence height of 0.0635 cm (0.025 in.), and 1800 bristles/cm circumference (4500 bristles/in. circumference). Various bristle/rotor radial interferences were achieved by using a tapered rotor. The brush seal reduced the leakage in comparison to the annular seal, up to 9.5 times. Reversing the pressure drop across the brush seal produced leakage rates approximately the same as that of the annular seal. Addition of a lubricant reduced the leakage by 2.5 times. The air and carbon dioxide data were successfully correlated using corresponding state theory. However, the helium data followed a different curve than the air and carbon dioxide data.

  19. EVALUATING THE IMPACT OF BRUSH CLEARING ON RECHARGE TO A KARST AQUIFER

    EPA Science Inventory

    My hypothesis is that brush removal will increase recharge, and this will be reflected in drip rate and drip water chemistry in the cave below. The results from this study should contribute to the understanding of how environmental variables affect karst hydrology. This stu...

  20. Binary Mixed Homopolymer Brushes Tethered to Cellulose Nanocrystals: A Step Towards Compatibilized Polyester Blends.

    PubMed

    Mincheva, Rosica; Jasmani, Latifah; Josse, Thomas; Paint, Yoann; Raquez, Jena-Marie; Gerbaux, Pascal; Eyley, Samuel; Thielemans, Wim; Dubois, Philippe

    2016-09-12

    This article reports on the successful preparation and characterization of cellulose nanocrystals (CNCs) surface-modified with polylactide (PLA) and poly(butylene succinate) (PBS) binary mixed homopolymer brushes. Their synthesis was designed as a three-step procedure combining polyester synthesis and surface-modification of CNCs with simultaneous polyester grafting via a heterogeneous copper(I)-catalyzed azide-alkyne cycloaddition reaction. For comparison, single homopolymer brushes tethered to CNCs (PLLA-g-CNC and PBSBDEMPAM-g-CNC) were obtained applying the same procedure. The hairy nanoparticles were characterized in terms of chemical composition and thermal properties. Spectroscopic analyses suggested "rippled" microphase separation of both immiscible homopolyesters in the mixed brushes, while others showed impeded homopolyester crystallization after surface-grafting. A synergistic relationship between the polyesters and CNCs was also suggested, i.e., the polyester grafting increases the CNC thermal resistance, while CNC presence imparts char formation. The as-obtained binary homopolymer brushes tethered to nanoparticles makes these surface-modified cellulosic nanomaterials attractive as compatibilization/reinforcement agents for PLA/PBS blends. PMID:27434410

  1. Electrochemical deposition and surface-initiated RAFT polymerization: protein and cell-resistant PPEGMEMA polymer brushes.

    PubMed

    Tria, Maria Celeste R; Grande, Carlos David T; Ponnapati, Ramakrishna R; Advincula, Rigoberto C

    2010-12-13

    This paper introduces a novel and versatile method of grafting protein and cell-resistant poly(poly ethylene glycol methyl ether methacrylate) (PPEGMEMA) brushes on conducting Au surface. The process started with the electrochemical deposition and full characterization of an electro-active chain transfer agent (CTA) on the Au surface. The electrochemical behavior of the CTA was investigated by cyclic voltammetry (CV) while the deposition and stability of the CTA on the surface were confirmed by ellipsometry, contact angle, and X-ray photoelectron spectroscopy (XPS). The capability of the electrodeposited CTA to mediate surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization on both the polymethyl methacrylate (PMMA; model polymer) and PPEGMEMA brushes was demonstrated by the increase in thicknesses of the films after polymerization. Contact angles also decreased with the incorporation of the more hydrophilic brushes. Significant changes in the morphologies of the films before and after polymerization were also observed with atomic force microscopy (AFM) analyses. Furthermore, XPS results showed an increase in the O 1s peak intensity relative to C 1s after polymerizations, which confirmed the grafting of polyethyleneglycol (PEG) bearing brushes. The ability of the PPEGMEMA-modified Au surface to resist nonspecific adhesion of proteins and cells was monitored and confirmed by XPS, ellipsometry, contact angle, AFM, and fluorescence imaging. The new method presented has potential application as robust protein and cell-resistant coatings for electrically conducting electrodes and biomedical devices. PMID:21028799

  2. Magnetite/Polymer Brush Nanocomposites with Switchable Uptake Behavior Toward Methylene Blue.

    PubMed

    Dolatkhah, Asghar; Wilson, Lee D

    2016-03-01

    The grafting from approach was used to prepare pH-responsive polyacid brushes using poly(itaconic acid) (PIA) and poly(acrylic acid) (PAA) at the amine functional groups of chitosan. Hybrid materials consisting of polymer brushes and magnetite nanoparticles (MNPs) were also prepared. The products were structurally characterized and displayed reversible pH-responsive behavior and controlled adsorption/desorption of methylene blue (MB). Switchable binding of MB involves cooperative effects due to conformational changes of brushes and swelling phenomena in solution which arise from response to changes in pH. Above the pKa, magnetic nanocomposites (MNCs) are deprotonated and display enhanced electrostatic interactions with high MB removal efficiency (>99%). Below the pKa, MNCs undergo self-assembly and release the cationic dye. The switchable binding of MB and the structure of the polymer brush between collapsed and extended forms relate to changes in osmotic pressure due to reversible ionization of acid groups at variable pH. Reversible adsorption-desorption with variable binding affinity and regeneration ability was demonstrated after five cycles. PMID:26751742

  3. SECURING CONTAINERIZED HAZARDOUS WASTES BY ENCAPSULATION WITH SPRAY-ON/BRUSH-ON RESINS

    EPA Science Inventory

    Methods were investigated for securing containerized hazardous wastes in the field with spray-on or brush-on resins at ambient temperatures. Laboratory-scale, cylindrical specimens of containerized sodium chloride (which simulated soluble salts containing heavy metals) were fabri...

  4. The synergistic effects of slip ring-brush design and materials

    NASA Technical Reports Server (NTRS)

    Lewis, N. E.; Cole, S. R.; Glossbrenner, E. W.

    1974-01-01

    The design, fabrication, and subsequent testing of four power slip rings for synchronous orbit application are described. The synergistic effects of contact materials and slip ring-brush design are studied by means of frequent and simultaneous recording of friction, wear, and electrical noise. Data generated during the test period are presented along with post test analysis data.

  5. Effect of salt on the compression of polyelectrolyte brushes in a theta solvent.

    PubMed

    Matsen, M W

    2012-02-01

    Classical strong-stretching theory (SST) predicts that, as opposing polyelectrolyte brushes are compressed together in a salt-free theta solvent, they contract so as to maintain a finite polymer-free gap, which offers a potential explanation for the ultra-low frictional forces observed in experiments despite the application of large normal forces. However, the SST ignores chain fluctuations, which would tend to close the gap resulting in physical contact and in turn significant friction. In a preceding study, we examined the effect of fluctuations using self-consistent field theory (SCFT) and illustrated that high normal forces can still be applied before the gap is destroyed. We now look at the effect of adding salt. It is found to reduce the long-range interaction between the brushes but has little effect on the short-range part, provided the concentration does not enter the salted-brush regime. Consequently, the maximum normal force between two planar brushes at the point of contact is remarkably unaffected by salt. For the crossed-cylinder geometry commonly used in experiments, however, there is a gradual reduction because in this case the long-range part of the interaction contributes to the maximum normal force. PMID:22367602

  6. Microbiological contamination of packer head brushes in United States commercial shell egg processing plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the United States, eggs are washed, checked for cleanliness, defect eggs are culled, and are then packed into cartons or flats based on weight. One of the last parts of egg washing machinery to come into contact with the eggs prior to packaging is packer head brushes. A sanitation study of shel...

  7. Brush seal leakage performance with gaseous working fluids at static and low rotor speed conditions

    NASA Technical Reports Server (NTRS)

    Carlile, Julie A.; Hendricks, Robert C.; Yoder, Dennis A.

    1992-01-01

    The leakage performance of a brush seal with gaseous working fluids at static and low rotor speed conditions was studied. The leakage results are included for air, helium, and carbon dioxide at several bristle/rotor interferences. Also, the effects of packing a lubricant into the bristles and also of reversing the pressure drop across the seal were studied. Results were compared to that of an annular seal at similar operating conditions. In order to generalize the results, they were correlated using corresponding state theory. The brush seal tested had a bore diameter of 3.792 cm (1.4930 in), a fence height of 0.0635 cm (0.025 in), and 1800 bristles/cm circumference (4500 bristles/in circumference). Various bristle/rotor radial interferences were achieved by using a tapered rotor. The brush seal reduced the leakage in comparison to the annular seal, up to 9.5 times. Reversing the pressure drop across the brush seal produced leakage rates approx. the same as that of the annular seal. Addition of a lubricant reduced the leakage by 2.5 times. The air and carbon dioxide data were successfully correlated using corresponding state theory. However, the helium data followed a different curve than the air and carbon dioxide data.

  8. Thermal-reversible, size-selective desorption of nanoparticles from polymer brushes

    NASA Astrophysics Data System (ADS)

    Vaia, Richard; Diamanti, Steve; Arifuzzaman, Shafi; Genzer, Jan

    2008-03-01

    The ability to reversibly modulate surface energy and chemistry will provide new opportunities for future separation and sensing technologies. Post-polymerization functionalization of covalently-tethered polymer brushes affords a robust platform technology for these goals. Using standard succinimide-based coupling, hydroxyl pendants of poly(2-hydroxyethyl methacrylate) (PHEMA) brushes were conjugated to oligo-peptides, alkanes, fluoroalkanes, and oligo(ethylene glycol) (OEG) through an alpha-terminus primary amine. Coupling of these different chemical moieties allows tailoring of the surface energy (θH2O˜40--110^o), that combined with PHEMA grafting density and molecular weight (MW), leads to tunable adsorption of analytes. OEG-modified PHEMA brushes exhibit thermal-reversible desorption of analytes that is size-selective. For example, Au NPs of larger size are liberated from the brushes at shorter heating times; hence mixtures of Au NPs of different sizes can be sequentially released by controlling substrate heating. The impact of electrolyte content, Au NP surface chemistry, coupling efficiency and OEG MW is discussed to elucidate the detailed molecular mechanisms dominating the size and temperature-dependent OEG-Au NP binding efficiency.

  9. Brush Talk at the Conversation Table: Interaction between L1 and L2 Speakers of Chinese

    ERIC Educational Resources Information Center

    Hwang, Menq-Ju

    2009-01-01

    Chinese characters are used in both Chinese and Japanese writing systems. When literate speakers of either language experience problems in finding or understanding words, they often resort to using Chinese characters or "kanji" (i.e., Chinese characters used in Japanese writing) in their talk, a practice known as "brush talk" ("bitan" in Chinese,…

  10. AN INTERDISCIPLINARY APPROACH TO VALUING WATER FROM BRUSH CONTROL: JOURNAL ARTICLE

    EPA Science Inventory

    NRMRL-CIN-1652 Lemberg**, B., Mjelde, J.W., Connor, R., Griffin, R.C., Rosenthal, W.D., and Stuth, J.W. An Interdisciplinary Approach to Valuing Water from Brush Control. Journal of American Water Resources Association (Warwick, J.J. (Ed.), USA: American Water Resources Assoc....

  11. Simulation of tracer concentration data in the Brush Creek Drainage flow using an integrated puff model

    SciTech Connect

    Rao, K. S.; Eckman, R. M.; Hosker, R. P., Jr.

    1989-07-01

    During the 1984 ASCOT field study in Brush Creek Valley, two perfluorocarbon tracers were released into the nocturnal drainage flow at two different heights. The resulting surface concentrations were sampled at 90 sites, and vertial concentration profiles at 11 sites. These detailed tracer measurements provide a valuable dataset for developing and testing models of pollutant transport and dispersion in valleys.

  12. Small Bowel Perforations by Metallic Grill Brush Bristles: Clinical Presentations and Opportunity for Prevention.

    PubMed

    Sordo, Salvador; Holloway, Travis L; Woodard, Russell L; Conway, Bruce E; Liao, Lillian F; Eastridge, Brian J; Myers, John G; Stewart, Ronald M; Dent, Daniel L

    2016-05-01

    Increasing reports on the incidental ingestion of metallic bristles from barbeque grill cleaning brushes have been reported. We sought to describe the clinical presentation and grilling habits of patients presenting after ingesting metallic bristles in an attempt to identify risk factors. We performed a chart review of six patients with documented enteric injury from metallic bristles. Subjects were contacted and administered a survey focused on the events surrounding the bristle ingestion. We arranged for in-home visits to inspect the grill and grill brush whenever possible. Of the six subjects identified, three (50%) were male, five (83%) were white, and they ranged in age from 18 to 65 years (mean 42.5). All complained of abdominal pain. All bristles were identified by CT scan. Three patients underwent laparoscopic enterorrhaphy, and two underwent laparotomy. The remaining patients did not require intervention. None had replaced their grill brush in at least two years. Surgeon's awareness of this unusual injury is important to identify and manage this problem. Alternative methods to clean the grill should be sought and grill brushes should be replaced at least every two years. PMID:27215721

  13. On the shape of bottle-brush macromolecules: Systematic variation of architectural parameters

    NASA Astrophysics Data System (ADS)

    Rathgeber, Silke; Pakula, Tadeusz; Wilk, Agnieszka; Matyjaszewski, Krzysztof; Beers, Kathryn L.

    2005-03-01

    We measured the form factor of bottle-brush macromolecules under good solvent conditions with small-angle neutron scattering and static light scattering. The systems under investigation are brushes, synthesized via the grafting-from route, built from a poly(alkyl methacrylate) backbone to which poly(n-butyl acrylate) side chains are densely grafted. The aim of our work is to study how the systematic variation of structural parameters such as the side chain length and backbone length change the conformation of the polymer brushes in solution. All spectra can be consistently described by a model, considering the bottle-brush polymers as flexible rods with internal density fluctuations. Parameters discussed are (1) the contour length per main chain monomer lb, (2) the fractal dimension of the side chains Ds, as well as (3) the fractal dimension D, and (4) the Kuhn length λk of the overall brush. lb=0.253±0.008nm is found to be independent of the side chain length and equal to the value found for the bare main chain, indicating a strongly stretched conformation for the backbone due to the presence of the side chains. The fractal dimension of the side chains is determined to be Ds=1.75±0.07 which is very close to the value of 1/0.588≈1.70 expected for a three-dimensional self-avoiding random walk (3D-SAW) under good solvent conditions. On larger length scales the overall brush appears to be a 3D-SAW itself (D=1.64±0.08) with a Kuhn-step length of λk=70±4nm. The value is independent of the side chain length and 46 times larger than the Kuhn length of the bare backbone (λk=1.8±0.2nm). The ratio of Kuhn length to brush diameter λk/d⩾20 determines whether lyotropic behavior can be expected or not. Since longer side chains do not lead to more persistent structures, λk/d decreases from 8 to 4 with increasing side chain length and lyotropic behavior becomes unlikely.

  14. Anti-biofouling properties of a telomer brush with pendent glucosylurea groups.

    PubMed

    Kitano, Hiromi; Hayashi, Atsushi; Takakura, Hajime; Suzuki, Hisatomo; Kanayama, Naoki; Saruwatari, Yoshiyuki

    2009-08-18

    A thiol-group-carrying telomer with pendent D-glucosylurea groups [poly(glucosylureaethyl methacrylate)-SH (PolyGUMA-SH)] was obtained by reversible addition-fragmentation chain-transfer (RAFT) polymerization of GUMA in the presence of 4,4'-azobis(4-cyanopentanoic acid) (initiator) and 4-cyanopentanoic acid dithiobenzoate (chain-transfer agent) and subsequent reduction with NaBH4. The thiol-carrying telomer was accumulated on both a gold electrode and a colloidal gold-immobilized glass substrate as proven by cyclic voltammetry using hydroquinone as a probe, and the increase in absorbance at 550 nm was ascribable to localized surface plasmon resonance (LSPR), respectively. The adsorption of various proteins to the surface of the telomer brush was examined by the LSPR method, too. The PolyGUMA brush showed a significant resistance against nonspecific adsorption of proteins, such as lysozyme, bovine serum albumin, immunoglobulin G, and fibrinogen. Furthermore, sugar-binding proteins, concanavalin A (Con A, with an affinity for mannose and glucose) and wheat germ agglutinin (WGA, with an affinity for N-acetylglucosamine), were not adsorbed to the GUMA-carrying brush, which is in contrast with the prompt and distinct binding of these proteins to the telomer brushes composed of 2-methacryloyloxyethyl D-glucopyranoside (Con A) and 1-O-(6'-methacrylamido)hexyl-2-N-acetoamido-2-deoxy-D-glucopyranoside residues (WGA). The glucosylurea-group-carrying telomer brush prepared here might be quite useful to provide a "bio-inert (anti-biofouling)" surface in biomedical fields. PMID:19518093

  15. Liquid crystal-based glucose biosensor functionalized with mixed PAA and QP4VP brushes.

    PubMed

    Khan, Mashooq; Park, Soo-Young

    2015-06-15

    4-Cyano-4'-pentylbiphenyl (5CB) in a transmission electron microscopy (TEM) grid was developed for glucose detection by coating with a monolayer of mixed polymer brushes using poly(acrylicacid-b-4-cynobiphenyl-4'-oxyundecylacrylate) (PAA-b-LCP) and quaternized poly(4-vinylpyridine-b-4-cynobiphenyl-4'-oxyundecylacrylate) (QP4VP-b-LCP) (LCP stands for liquid crystal polymer) at the 5CB/aqueous interface. The resultant 5CB in TEM grid was functionalized with the PAA and QP4VP brushes, which were strongly anchored by the LCP block. The PAA brush rendered the 5CB/aqueous interface pH-responsive and the QP4VP brush immobilized glucose oxidase (GOx) through electrostatic interactions without the aid of coupling agents. The glucose was detected through a homeotropic-to-planar orientational transition of the 5CB observed through a polarized optical microscope (POM) under crossed polarizers. The optimum immobilization with a 0.78 µM GOx solution on the dual-brush-coated TEM grid enabled glucose detection at concentrations higher than 0.5 mM with response times shorter than 180 s. This TEM grid glucose sensor provided a linear response of birefringence of the 5CB to glucose concentrations ranging from 0.5 to 11 mM with a Michaelis-Menten constant (Km) of 1.67 mM. This new and sensitive glucose biosensor has the advantages of low production cost, simple enzyme immobilization, high enzyme sensitivity and stability, and easy detection with POM, and may be useful for prescreening the glucose level in the human body. PMID:25617751

  16. Four DNA methylation biomarkers in biliary brush samples accurately identify the presence of cholangiocarcinoma

    PubMed Central

    Andresen, Kim; Boberg, Kirsten Muri; Vedeld, Hege Marie; Honne, Hilde; Jebsen, Peter; Hektoen, Merete; Wadsworth, Christopher A.; Clausen, Ole Petter; Lundin, Knut E.A.; Paulsen, Vemund; Foss, Aksel; Mathisen, Øystein; Aabakken, Lars; Schrumpf, Erik; Lothe, Ragnhild A.

    2015-01-01

    Early detection of the highly aggressive malignancy cholangiocarcinoma (CCA) remains a challenge but has the potential to render the tumor curable by surgical removal. This study evaluates a biomarker panel for the diagnosis of CCA by DNA methylation analyses of biliary brush samples. The methylation status of 13 candidate genes (CDO1, CNRIP1, DCLK1, FBN1, INA, MAL, SEPT9, SFRP1, SNCA, SPG20, TMEFF2, VIM, and ZSCAN18) was investigated in 93 tissue samples (39 CCAs and 54 nonmalignant controls) using quantitative methylation‐specific polymerase chain reaction. The 13 genes were further analyzed in a test series of biliary brush samples (15 CCAs and 20 nonmalignant primary sclerosing cholangitis controls), and the methylation status of the four best performing markers was validated (34 CCAs and 34 primary sclerosing cholangitis controls). Receiver operating characteristic curve analyses were used to evaluate the performance of individual biomarkers and the combination of biomarkers. The 13 candidate genes displayed a methylation frequency of 26%‐82% in tissue samples. The four best‐performing genes (CDO1, CNRIP1, SEPT9, and VIM) displayed individual methylation frequencies of 45%‐77% in biliary brushes from CCA patients. Across the test and validation biliary brush series, this four‐gene biomarker panel achieved a sensitivity of 85% and a specificity of 98%, with an area under the receiver operating characteristic curve of 0.944. Conclusion: We report a straightforward biomarker assay with high sensitivity and specificity for CCA, outperforming standard brush cytology, and suggest that the biomarker panel, potentially in combination with cytological evaluation, may improve CCA detection, particularly among primary sclerosing cholangitis patients. (Hepatology 2015;61:1651–1659) PMID:25644509

  17. In situ evaluation of different remineralization periods to decrease brushing abrasion of demineralized enamel.

    PubMed

    Attin, T; Knöfel, S; Buchalla, W; Tütüncü, R

    2001-01-01

    The aim of the present in situ study was to evaluate the effect of different periods of intraoral remineralization to decrease the susceptibility of previously demineralized enamel against toothbrushing abrasion. Six human enamel specimens (A-F) were recessed in the buccal aspects of each of eight intraoral appliances which were worn for 21 days by 8 panelists. Demineralization of the samples was performed twice a day extraorally in the acidic beverage Sprite Light for 90 s. Subsequently, the enamel specimens were brushed at different times. Specimen A was brushed immediately after the demineralization. The remaining samples B-E were brushed after the intraoral appliances had been worn for various periods of remineralization: specimen B, 10 min; C, 20 min; D, 30 min and E, 60 min, respectively. Specimen F was only demineralized and remineralized, but not brushed. After 21 days, enamel wear was measured with a laser profilometer. The following values (mean +/- standard deviation) were obtained: specimen A, 6.78+/-2.71 microm; B, 5.47+/-3.39 microm; C, 6.06+/-3.18 microm; D, 5.43+/-2.58 microm; E 4.78+/-2.57 microm, and F 0.66+/-1.11 micro;m. Analysis of variance revealed a significant influence of remineralization period on abrasive wear. However, even after a remineralization period of 60 min the wear was significantly increased as compared to the demineralized, but not brushed control. It is concluded that (1) abrasion resistance of softened enamel increases with remineralization period and (2) at least 60 min should elapse before toothbrushing after an erosive attack. PMID:11385203

  18. 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. PMID:26061866

  19. Liquid crystalline polymers in good nematic solvents: Free chains, mushrooms, and brushes

    SciTech Connect

    Williams, D.R.M. . Lab. de Physique de la Matiere Condensee); Halperin, A. . Dept. of Materials)

    1993-08-02

    The swelling of main chain liquid crystalline polymers (LCPs) in good nematic solvents is theoretically studied, focusing on brushes of terminally anchored, grafted LCPs. The analysis is concerned with long LCPs, of length L, with n[sub 0] >> 1 hairpin defects. The extension behavior of the major axis, R[parallel], of these ellipsoidal objects gives rise to an Ising elasticity with a free energy penalty of F[sub el](R[parallel])/kT [approx] n[sub 0] [minus] n[sub 0](1 [minus] R[parallel][sup 2]/L[sup 2])[sup 1/2]. The theory of the extension behavior enables the formulation of a Flory type theory of swelling of isolated LCPs yielding R[parallel] [approx] exp(2U[sub h]/5kT)N[sup 3/5] and R [perpendicular] [approx] exp([minus]U[sub h]/10kT)N[sup 3/5], with N the degree of polymerization and U[sub h] the hairpin energy. It also allows the generalization of the Alexander model for polymer brushes to the case of grafted LCPs. The behavior of LCP brushes depends on the alignment imposed by the grafting surface and the liquid crystalline solvent. A tilting phase transition is predicted as the grafting density is increased for a surface imposing homogeneous, parallel anchoring. A related transition is expected upon compression of a brush subject to homeotropic, perpendicular alignment. The effect of magnetic or electric fields on these phase transitions is also studied. The critical magnetic/electric field for the Frederiks transition can be lowered to arbitrarily small values by using surfaces coated by brushes of appropriate density.

  20. Evaluation of a brushing machine for estimating density of spider mites on grape leaves.

    PubMed

    Macmillan, Craig D; Costello, Michael J

    2015-12-01

    Direct visual inspection and enumeration for estimating field population density of economically important arthropods, such as spider mites, provide more information than alternative methods, such as binomial sampling, but is laborious and time consuming. A brushing machine can reduce sampling time and perhaps improve accuracy. Although brushing technology has been investigated and recommended as a useful tool for researchers and integrated pest management practitioners, little work to demonstrate the validity of this technique has been performed since the 1950's. We investigated the brushing machine manufactured by Leedom Enterprises (Mi-Wuk Village, CA, USA) for studies on spider mites. We evaluated (1) the mite recovery efficiency relative to the number of passes of a leaf through the brushes, (2) mite counts as generated by the machine compared to visual counts under a microscope, (3) the lateral distribution of mites on the collection plate and (4) the accuracy and precision of a 10% sub-sample using a double-transect counting grid. We found that about 95% of mites on a leaf were recovered after five passes, and 99% after nine passes, and mite counts from brushing were consistently higher than those from visual inspection. Lateral distribution of mites was not uniform, being highest in concentration at the center and lowest at the periphery. The 10% double-transect pattern did not result in a significant correlation with the total plate count at low mite density, but accuracy and precision improved at medium and high density. We suggest that a more accurate and precise sample may be achieved using a modified pattern which concentrates on the center plus some of the adjacent area. PMID:26459377

  1. Wettability of terminally anchored polymer brush layers on a polyamide surface.

    PubMed

    Varin, Kari J Moses; Cohen, Yoram

    2014-12-15

    Surface wettability of terminally anchored hydrophilic polymer brush layers on polyamide-silicon (PA-Si) surfaces was evaluated with respect to surface topography at the nanoscale. Hydrophilic polyvinylpyrrolidone (PVP) and polyacrylamide (PAAm) brush layers were synthesized via graft polymerization onto a PA-Si surface previously activated by surface treatment with atmospheric pressure plasma. Hydrophilicity (or wettability) of the PA substrate, as quantified by the free energy of hydration, was increased upon surface coverage with the PVP and PAAm brush layers by 13-24% (-101.4 to -111.3 mJ/m(2)) and 19-37% (-106.1 to -122.4 mJ/m(2)), respectively. Surface hydrophilicity increased with both increasing surface roughness (0.55-2.89 nm and 1.54-5.84 nm for PVP and PAAm, respectively) and polymer volume (1.3×10(6)-7.3×10(6) nm(3)/μm(2) and 3.3×10(6)-2.8×10(7) nm(3)/μm(2) for PVP and PAAm surfaces, respectively). The present study suggests that a specific level of surface wettability can be attained by tailor-designing the polymer brush layer's physicochemical characteristics (e.g., surface roughness, wettability, and polymer water affinity) by adjusting surface topography and surface chemistry, which are controlled by surface activation and polymerization conditions. The above indicates that there is merit in structuring various surfaces with hydrophilic brush layers to increase surface wettability in membrane filtration, biomedical devices, and lubrication applications. PMID:25305445

  2. The plaque-removing efficacy of a single-tufted brush on the lingual and buccal surfaces of the molars

    PubMed Central

    Lee, Dong-Won

    2011-01-01

    Purpose To test the plaque-removal efficacy of a single-tufted toothbrush on the posterior molars compared with a flat-trimmed toothbrush. Methods Forty-nine subjects were selected. Professional instruction and written brushing instructions were given. After thorough supra-gingival scaling and polishing, all subjects were asked to abstain from oral hygiene procedures for 24 hours prior to the first experiment. The subjects were randomized to a treatment sequence. The modified Quigley and Hein plaque index was recorded pre- and post-tooth brushing, at 6 surfaces of the posterior molars. After a wash-out period, all the remaining plaque was removed professionally. Twenty-four hours of brushing abstinence was again performed. The plaque index was recorded pre- and post-tooth brushing after the subjects were given the second toothbrush in the cross-over sequence. Results The percentage reductions in plaque scores achieved with the single-tufted brushes were significantly higher than those of the flat-trimmed brush at the maxillary buccal interproximal, marginal and mandibular lingual interproximal site. The other locations showed no significant difference. Conclusions The results of the present study implied that the single-tufted brush could be an effective tool for the removal of plaque at some, but not all, sites of the posterior molars. PMID:21811688

  3. Photo-induced in situ crosslinking of polymer brushes with dimethyl maleimide moieties for dynamically stimulating stem cell differentiation.

    PubMed

    Arisaka, Yoshinori; Nishijima, Yuka; Yusa, Shin-Ichi; Takeda, Naoya

    2016-09-01

    We designed photo-crosslinkable polymer brushes with dimethylmaleimide moieties, in order to demonstrate dynamic stimulation of cell differentiation in mesenchymal stem cells (MSCs). The polymer brushes were synthesized by surface-initiated reversible addition fragmentation chain transfer polymerization using dimethylmaleimide ethyl methacrylate and methyl methacrylate on a chain transfer agent-immobilized glass surface. The polymer brushes were crosslinked by photodimerization of the dimethylmaleimide moieties within polymer chains with stem cells present on the surface. In order to evaluate the effects of in situ photo-induced crosslinking of the polymer brushes on gene expression of stem cells, human bone marrow MSCs were cultured under static and dynamic culture conditions for 7 days. Expression of the osteocalcin (Ocn) gene in MSCs was used as an indicator of osteoblast differentiation under dynamic culture conditions. Structural conversion from non-crosslinked polymer brushes to crosslinked polymer brushes increased the expression of Ocn by 1.4-fold in the presence of adhered cells, compared with non-crosslinked polymer brushes under static culture conditions. These results suggest that MSCs recognized surface conversion from non-crosslinked to crosslinked structures, which resulted in altered differentiation lineages. Therefore, photo-crosslinkable surfaces with dimethyl maleimide moieties are potential novel materials for dynamically stimulating MSC differentiation. PMID:27255343

  4. The Wear Behavior of Brush-Plated Ni-W-Co/SiC Composite Layer with Oil Lubrication

    NASA Astrophysics Data System (ADS)

    Xu, Jiang; Liu, Wenjin

    The wear behavior of brush-plating a Ni-W-Co/SiC composite layer on 1045 steel with oil lubrication is investigated. The composite layer is determined by OM, XRD and TEM. The worn surface of the plated layer is observed with SEM and laser profile analysis. The composition and average size of worn debris are analyzed by means of ferrograph and fluid spectrum. The results show that the brush-plated composite layer with added SiC particles reveals high wear resistance compared to the Ni-W-Co brush-plated layer.

  5. Grafting of Poly(methyl methacrylate) Brushes from Magnetite Nanoparticles Using a Phosphonic Acid Based Initiator by Ambient Temperature Atom Transfer Radical Polymerization (ATATRP)

    PubMed Central

    2008-01-01

    Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom transfer radical polymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis. This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried out in the presence of CuBr/PMDETA complex, without a sacrificial initiator, and the grafting density is found to be as high as 0.90 molecules/nm2. The organic–inorganic hybrid material thus prepared shows exceptional stability in organic solvents unlike unfunctionalized magnetite nanoparticles which tend to flocculate. The polymer brushes of various number average molecular weights were prepared and the molecular weight was determined using size exclusion chromatography, after degrafting the polymer from the magnetite core. Thermogravimetric analysis, X-ray photoelectron spectra and diffused reflection FT-IR were used to confirm the grafting reaction.

  6. 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

  7. Structural state of the Na+/D-glucose cotransporter in calf kidney brush-border membranes. Target size analysis of Na+-dependent phlorizin binding and Na+-dependent D-glucose transport.

    PubMed

    Lin, J T; Szwarc, K; Kinne, R; Jung, C Y

    1984-11-01

    Target sizes of the renal sodium-D-glucose cotransport system in brush-border membranes of calf kidney cortex were estimated by radiation inactivation. In brush-border vesicles irradiated at -50 degrees C with 1.5 MeV electron beams, sodium-dependent phlorizin binding, and Na+-dependent D-glucose tracer exchange decreased exponentially with increasing doses of radiation (0.4-4.4 Mrad). Inactivation of phlorizin binding was due to a reduction in the number of high-affinity phlorizin binding sites but not in their affinity. The molecular weight of the Na+-dependent phlorizin binding unit was estimated to be 230 000 +/- 38 000. From the tracer exchange experiments a molecular weight of 345 000 +/- 24 500 was calculated for the D-glucose transport unit. The validity of these target size measurements was established by concomitant measurements of two brush-border enzymes, alkaline phosphatase and gamma-glutamyltransferase, whose target sizes were found to be 68 570 +/- 2670 and 73 500 +/- 2270, respectively. These findings provide further evidence for the assumption that the sodium-D-glucose cotransport system is a multimeric structure, in which distinct complexes are responsible for phlorizin binding and D-glucose translocation. PMID:6148966

  8. Chemical bath deposition of textured and compact zinc oxide thin films on vinyl-terminated polystyrene brushes

    PubMed Central

    Blumenstein, Nina J; Hofmeister, Caroline G; Lindemann, Peter; Huang, Cheng; Baier, Johannes; Leineweber, Andreas; Wöll, Christof; Schimmel, Thomas

    2016-01-01

    Summary In this study we investigated the influence of an organic polystyrene brush on the deposition of ZnO thin films under moderate conditions. On a non-modified SiOx surface, island growth is observed, whereas the polymer brush induces homogeneous film growth. A chemical modification of the polystyrene brushes during the mineralization process occurs, which enables stronger interaction between the then polar template and polar ZnO crystallites in solution. This may lead to oriented attachment of the crystallites so that the observed (002) texture arises. Characterization of the templates and the resulting ZnO films were performed with ζ-potential and contact angle measurements as well as scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). Infrared spectroscopy (IR) measurements were used to investigate the polystyrene brushes before and after modification. PMID:26925358

  9. Chemical bath deposition of textured and compact zinc oxide thin films on vinyl-terminated polystyrene brushes.

    PubMed

    Blumenstein, Nina J; Hofmeister, Caroline G; Lindemann, Peter; Huang, Cheng; Baier, Johannes; Leineweber, Andreas; Walheim, Stefan; Wöll, Christof; Schimmel, Thomas; Bill, Joachim

    2016-01-01

    In this study we investigated the influence of an organic polystyrene brush on the deposition of ZnO thin films under moderate conditions. On a non-modified SiO x surface, island growth is observed, whereas the polymer brush induces homogeneous film growth. A chemical modification of the polystyrene brushes during the mineralization process occurs, which enables stronger interaction between the then polar template and polar ZnO crystallites in solution. This may lead to oriented attachment of the crystallites so that the observed (002) texture arises. Characterization of the templates and the resulting ZnO films were performed with ζ-potential and contact angle measurements as well as scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). Infrared spectroscopy (IR) measurements were used to investigate the polystyrene brushes before and after modification. PMID:26925358

  10. 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

  11. The effect of pre-milking teat-brushing on milk processing time in an automated milking system.

    PubMed

    Jago, Jenny G; Davis, Kendra L; Copeman, Peter J; Woolford, Murray M

    2006-05-01

    Cow throughput in an automatic milking system (AMS) is limited by system parameters such as the time required for pre-milking udder preparation and cup attachment, physiological responses of the cow (such as milk let-down and milking-out rate), milking machine features and cow behaviour. A single-factor cross-over design was used to investigate the effect of pre-milking teat brushing on milk processing time in an AMS operating in an extensive grazing farming system. Teat brushing consisted of two roller brushes tracking up each teat three times (total brushing time of up to 45 s/cow). Cows were allocated to one of two treatment groups with either no brushing (NB) or brushing (B) for a 4-week period before being changed to the other treatment. Teat brushing resulted in shorter average cups-on-time (B = 506.1 s, NB = 541.0 s, P = 0.0001), longer average milk processing time (B = 10.30 min, NB = 9.76 min, P = 0.001) and no difference in daily milk yield (B = 14.67, NB = 14.71 kg/cow, P = 0.826). There was no difference between the two treatments in the success of cup attachment (B = 3.76%, NB = 5.10% unsuccessful milking attempts, P = 0.285). The estimated time cost of pre-milking teat brushing was 53 min for every 100 milkings, equivalent to an additional 5-6 milkings for every 100 milkings by an AMS. The importance of these potential time savings is discussed in relation to automatic milking in farming systems that aim for a lower per cow milking frequency and high ratio of cows to AMS. PMID:16476173

  12. Regular Tooth Brushing is Associated with a Decreased Risk of Metabolic Syndrome According to a Medical Check-Up Database.

    PubMed

    Tsutsumi, Chiyo; Kakuma, Tatsuyuki

    2015-01-01

    Associations have been reported between periodontal disease and increased cardiovascular disease risk, as well as between healthy self-reported tooth brushing behavior and reduced cardiovascular disease risk. We examined the association between self-reported tooth brushing behavior and the risk of metabolic syndrome (MetS) using a large medical check-up database. A total of 12,548 medical checkup records from a medical screening center in a city in southwest Japan were assessed. Subjects were aged 30 to 59 years. As lifestyle is associated with both tooth brushing and MetS, many lifestyle variables were considered as potential confounders. Logistic regression model were employed with a list of 127 lifestyle variables. Twenty variables associated with both tooth brushing and MetS were selected for both males and females. Furthermore, final confounding variables were selected by principal component analysis to avoid collinearity problems. The association of tooth brushing and MetS was evaluated for males and females separately by calculating adjusted odds ratios (ORs) with selected confounders plus age. The association between daily tooth brushing frequency and MetS risk for both genders was significant after adjusting for confounders, with the risk of MetS decreasing with increased frequency of daily tooth brushing (adjusted OR = 0.57 (95%Cl:0.48-0.81), 0.50 (95%Cl:0.35-0.71), 0.42 (95%Cl: 0.29-0.61) for males and adjusted OR = 0.65 (95%Cl:0.48-0.87), 0.44 (95%Cl:0.32-0.62) for females). Therefore, oral hygiene, including the frequency of tooth brushing as a significant component, may be an important factor in preventing MetS. PMID:25810422

  13. The Temperature-Sensitive brush Mutant of the Legume Lotus japonicus Reveals a Link between Root Development and Nodule Infection by Rhizobia[C][W][OA

    PubMed Central

    Maekawa-Yoshikawa, Makoto; Müller, Judith; Takeda, Naoya; Maekawa, Takaki; Sato, Shusei; Tabata, Satoshi; Perry, Jillian; Wang, Trevor L.; Groth, Martin; Brachmann, Andreas; Parniske, Martin

    2009-01-01

    The brush mutant of Lotus japonicus exhibits a temperature-dependent impairment in nodule, root, and shoot development. At 26°C, brush formed fewer nodules, most of which were not colonized by rhizobia bacteria. Primary root growth was retarded and the anatomy of the brush root apical meristem revealed distorted cellular organization and reduced cell expansion. Reciprocal grafting of brush with wild-type plants indicated that this genotype only affected the root and that the shoot phenotype was a secondary effect. The root and nodulation phenotype cosegregated as a single Mendelian trait and the BRUSH gene could be mapped to the short arm of chromosome 2. At 18°C, the brush root anatomy was rescued and similar to the wild type, and primary root length, number of infection threads, and nodule formation were partially rescued. Superficially, the brush root phenotype resembled the ethylene-related thick short root syndrome. However, treatment with ethylene inhibitor did not recover the observed phenotypes, although brush primary roots were slightly longer. The defects of brush in root architecture and infection thread development, together with intact nodule architecture and complete absence of symptoms from shoots, suggest that BRUSH affects cellular differentiation in a tissue-dependent way. PMID:19176723

  14. Major vegetation types, climatological data, and solar radiation calculations for Colorado's Brush Creek valley

    SciTech Connect

    Whiteman, C.D.; Lambeth, R.; Allwine, K.J.

    1987-04-01

    In this report we present information on the vegetative cover, climate, and solar radiation for the Brush Creek valley. A brief vegetative survey was made on October 3, 1984, to identify the vegetation types in the lowest 8 km of the valley; the reader is cautioned that this included only a small part of the Brush Creek valley. The intent was to identify the principal vegetation types, with no attempt to use available scientific sampling techniques to determine accurate relative frequencies of the vegetation types. Nevertheless, the site survey has allowed us to identify the major species of vegetation, and to make reasonably accurate differentiations of both major vegetation types on valley surfaces (the valley floor, two sidewalls, and ridgetops) and the relative abundance of major vegetation types on each surface.

  15. Residual stress induced wetting variation on electric brush-plated Cu film

    NASA Astrophysics Data System (ADS)

    Meng, Ke-Ke; Jiang, Yue; Jiang, Zhong-Hao; Lian, Jian-She; Jiang, Qing

    2014-03-01

    Nanocrystalline Cu film with a mirror surface finishing is prepared by the electric brush-plating technique. The as-prepared Cu film exhibits a superhydrophilic behavior with an apparent water contact angle smaller than 10°. A subsequent increase in the water contact angle and a final wetting transition from inherent hydrophilicity with water contact angle smaller than 90° to apparent hydrophobicity with water contact angle larger than 90° are observed when the Cu film is subjected to natural aging. Analysis based on the measurement of hardness with nanoindentation and the theory of the bond-order-length-strength correlation reveals that this wetting variation on the Cu film is attributed to the relaxation of residual stress generated during brush-plating deposition and a surface hydrophobization role associated with the broken bond polarization induced by surface nanostructure.

  16. Electric Double Layer electrostatics of spherical polyelectrolyte brushes with pH-dependent charge density

    NASA Astrophysics Data System (ADS)

    Li, Hao; Chen, Guang; Sinha, Shayandev; Das, Siddhartha; Soft Matter, Interfaces,; Energy Laboratory (Smiel) Team

    Understanding the electric double layer (EDL) electrostatics of spherical polyelectrolyte (PE) brushes, which are spherical particles grafted with PE layers, is essential for appropriate use of PE-grfated micro-nanoparticles for targeted drug delivery, oil recovery, water harvesting, emulsion stabilization, emulsion breaking, etc. Here we elucidate the EDL electrostatics of spherical PE brushes for the case where the PE exhibits pH-dependent charge density. This pH-dependence necessitates the consideration of explicit hydrogen ion concentration, which in turn dictates the distribution of monomers along the length of the grafted PE. This monomer distribution is shown to be a function of the nature of the sphere (metallic or a charged or uncharged dielectric or a liquid-filled sphere). All the calculations are performed for the case where the PE electrostatics can be decoupled from the PE elastic and excluded volume effects. Initial predictions are also provided for the case where such decoupling is not possible.

  17. Treatment of enterococcus faecalis bacteria by a helium atmospheric cold plasma brush with oxygen addition

    SciTech Connect

    Chen Wei; Huang Jun; Wang Xingquan; Lv Guohua; Zhang Guoping; Du Ning; Liu Xiaodi; Guo Lihong; Yang Size

    2012-07-01

    An atmospheric cold plasma brush suitable for large area and low-temperature plasma-based sterilization is designed. Results demonstrate that the He/O{sub 2} plasma more effectively kills Enterococcus faecalis than the pure He plasma. In addition, the sterilization efficiency values of the He/O{sub 2} plasma depend on the oxygen fraction in Helium gas. The atmospheric cold plasma brush using a proper ratio of He/O{sub 2} (2.5%) reaches the optimum sterilization efficiency. After plasma treatment, the cell structure and morphology changes can be observed by the scanning electron microscopy. Optical emission measurements indicate that reactive species such as O and OH play a significant role in the sterilization process.

  18. Treatment of enterococcus faecalis bacteria by a helium atmospheric cold plasma brush with oxygen addition

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Huang, Jun; Du, Ning; Liu, Xiao-Di; Wang, Xing-Quan; Lv, Guo-Hua; Zhang, Guo-Ping; Guo, Li-Hong; Yang, Si-Ze

    2012-07-01

    An atmospheric cold plasma brush suitable for large area and low-temperature plasma-based sterilization is designed. Results demonstrate that the He/O2 plasma more effectively kills Enterococcus faecalis than the pure He plasma. In addition, the sterilization efficiency values of the He/O2 plasma depend on the oxygen fraction in Helium gas. The atmospheric cold plasma brush using a proper ratio of He/O2 (2.5%) reaches the optimum sterilization efficiency. After plasma treatment, the cell structure and morphology changes can be observed by the scanning electron microscopy. Optical emission measurements indicate that reactive species such as O and OH play a significant role in the sterilization process.

  19. Synthesis and conformational characterization of functional di-block copolymer brushes for microarray technology

    NASA Astrophysics Data System (ADS)

    Di Carlo, Gabriele; Damin, Francesco; Armelao, Lidia; Maccato, Chiara; Unlu, Selim; Spuhler, Philipp S.; Chiari, Marcella

    2012-02-01

    Surface initiated polymerization (SIP) coupled with reversible addition-fragmentation chain transfer polymerization (RAFT) was used to functionalize microarray glass slides with block polymer brushes. N,N-dimethylacrylamide (DMA) and N-acryloyloxysuccinimide (NAS) (graft-poly[DMA-b-(DMA-co-NAS)]) brushes, with di-block architecture, were prepared from a novel RAFT chain transfer agent bearing a silanating moiety (RAFT silane) directly anchored onto the glass surfaces. Conformational characterization of the coatings was performed by Self Spectral Interference Fluorescence Microscopy (SSFM), an innovative technique that describes the location of a fluorescent DNA molecule relative to a surface with sub-nanometer accuracy. X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) were used to characterize the coatings composition and morphology.

  20. Fabrication of DNA Polymer Brush Arrays by Destructive Micropatterning and Rolling-Circle Amplification

    PubMed Central

    Barbee, Kristopher D.; Chandrangsu, Matt; Huang, Xiaohua

    2011-01-01

    A method for fabricating DNA polymer brush arrays using photolithography and plasma etching followed by solid-phase enzymatic DNA amplification is reported. After attaching oligonucleotide primers to the surface of a glass coverslip, a thin layer of photoresist is spin-coated on the glass and patterned via photolithography to generate an array of posts in the resist. An oxygen-based plasma is then used to destroy the exposed oligonucleotide primers. The glass coverslip with the primer array is assembled into a microfluidic chip and DNA polymer brushes are synthesized on the oligonucleotide array by rolling-circle DNA amplification. We have demonstrated that the linear polymers can be rapidly synthesized in situ with a high degree of control over their density and length. PMID:21305694