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Sample records for brush border probed

  1. Probing endocytosis from the enterocyte brush border using fluorescent lipophilic dyes: lipid sorting at the apical cell surface.

    PubMed

    Danielsen, E Michael

    2015-05-01

    The small intestinal brush border is a specialized cell membrane that needs to withstand the solubilizing effect of bile salts during assimilation of dietary nutrients and to achieve detergent resistance; it is highly enriched in glycolipids organized in lipid raft microdomains. In the present work, the fluorescent lipophilic probes FM 1-43 (N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl)pyridinium dibromide), FM 4-64 (N-(3-triethylammoniumpropyl)-4-(6-(4-(diethylamino) phenyl)hexatrienyl)pyridinium dibromide), TMA-DPH (1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene p-toluenesulfonate), and CellMask Orange plasma membrane stain were used to study endocytosis from the enterocyte brush border of organ-cultured porcine mucosal explants. All the dyes readily incorporated into the brush border but were not detectably endocytosed by 5 min, indicating a slow uptake compared with other cell types. At later time points, FM 1-43 clearly appeared in distinct punctae in the terminal web region, previously shown to represent early endosomes (TWEEs). In contrast, the other dyes were relatively "endocytosis resistant" to varying degrees for periods up to 2 h, indicating an active sorting of lipids in the brush border prior to internalization. For some of the dyes, a diphenylhexatriene motif in the lipophilic tail seemed to confer the relative endocytosis resistance. Lipid sorting by selective endocytosis therefore may be a process in the enterocytes aimed to generate and maintain a unique lipid composition in the brush border.

  2. Shaping the intestinal brush border

    PubMed Central

    Crawley, Scott W.; Mooseker, Mark S.

    2014-01-01

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

  3. 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.

  4. 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

  5. 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

  6. Protein Mediators of Sterol Transport Across Intestinal Brush Border Membrane

    PubMed Central

    Brown, J. Mark; Yu, Liqing

    2012-01-01

    Dysregulation of cholesterol balance contributes significantly to atherosclerotic cardiovascular disease (ASCVD), the leading cause of death in the United States. The intestine has the unique capability to act as a gatekeeper for entry of cholesterol into the body, and inhibition of intestinal cholesterol absorption is now widely regarded as an attractive non-statin therapeutic strategy for ASCVD prevention. In this chapter we discuss the current state of knowledge regarding sterol transport across the intestinal brush border membrane. The purpose of this work is to summarize substantial progress made in the last decade in regards to protein-mediated sterol trafficking, and to discuss this in the context of human disease. PMID:20213550

  7. Optical brush: Imaging through permuted probes.

    PubMed

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

    2016-01-01

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

  8. 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

  9. Order-disorder phase transition and lipid dynamics in rabbit small intestinal brush border membranes. Effect of proteins.

    PubMed

    Mütsch, B; Gains, N; Hauser, H

    1983-12-20

    The total lipids extracted from brush border membranes form smectic lamellar phases when dispersed in water. 31P broad-band nuclear magnetic resonance (NMR) shows that between body temperature (37 degrees C) and freezing of the solvent, the extracted lipids form bilayers with the lipid molecules undergoing fast anisotropic motion. This is also true for the lipids present in the brush border membrane. The electron spin resonance (ESR) results obtained with various hydrophobic spin probes incorporated in either brush border vesicle membranes or their extracted lipids are consistent with this interpretation. By use of a variety of chemically different spin-labels, the temperature dependence of brush border membranes and their extracted lipids was probed. The temperature dependence of various ESR spectral parameters shows discontinuities that, by comparison with differential scanning calorimetry, are assigned to a lipid thermotropic phase transition. Differential scanning calorimetry shows that the lipid in brush border membranes undergoes a broad, reversible phase transition of low enthalpy between 10 and 30 degrees C, with a peak temperature of about 25 degrees C. Hence, the brush border membrane of rabbit small intestine functions in the liquid-crystalline state, well above the peak temperature and also above the upper limit of the lipid phase transition. Therefore, in itself, the thermotropic lipid phase transition is unlikely to play a physiological role. The low enthalpy of the lipid phase transition, indicative of a lack of cooperativity, is primarily attributed to the relatively high cholesterol content and to heterogeneity in the lipid composition of this membrane [Hauser, H., Howell, K., Dawson, R. M. C., & Bowyer, D. E. (1980) Biochim. Biophys. Acta 602, 567-577].(ABSTRACT TRUNCATED AT 250 WORDS)

  10. Ontogeny of Na/H antiporter activity in rabbit renal brush border membrane vesicles.

    PubMed Central

    Beck, J C; Lipkowitz, M S; Abramson, R G

    1991-01-01

    The development of the Na/H antiporter was studied in renal brush border membrane vesicles (BBMV) from fetal and adult rabbits using isotopic and fluorescent techniques. The kinetics of the antiporter studied by 22Na+ uptake revealed that the Vmax was only 25% of that in the adult; however, the Km's for Na+ were not significantly different. These data were confirmed by a fluorescent assay using the pH-sensitive probe, acridine orange: the Vmax was significantly lower in the fetal BBMV. Conductive Na+ movement was estimated from amiloride-insensitive 22Na+ uptake and the rate of alkalinization induced by K+, an ion whose relative conductance was found to be similar to that of Na+. Although relative Na+ conductance was significantly greater in fetal BBMV, the lower Vmax in fetal vesicles could not be ascribed to this factor. Maternal administration of betamethasone (50 micrograms/kg intramuscularly) for 2 d before delivery significantly increased the Vmax of the antiporter to levels observed in the adult; Km was unaffected. Na/K ATPase activity increased fourfold after betamethasone, but the specific activities of four brush border marker enzymes and the kinetics of Na(+)-glucose cotransport were unchanged. These data indicate that there is a developmental increase in brush border Na/H exchange which is the result of an increase in the number and/or the turnover number of the carriers. Further, these data suggest that the postnatal increase in antiporter activity may be related to the surge in glucocorticoid concentration that occurs perinatally. Images PMID:1645751

  11. Immune Complex Tubulointerstitial Nephritis Due to Autoantibodies to the Proximal Tubule Brush Border.

    PubMed

    Rosales, Ivy A; Collins, A Bernard; do Carmo, Paula Alves S; Tolkoff-Rubin, Nina; Smith, R Neal; Colvin, Robert B

    2016-02-01

    Immune complex tubulointerstitial nephritis due to antibodies to brush border antigens of the proximal tubule has been demonstrated experimentally and rarely in humans. Our patient developed ESRD and early recurrence after transplantation. IgG and C3 deposits were conspicuous in the tubular basement membrane of proximal tubules, corresponding to deposits observed by electron microscopy. Rare subepithelial deposits were found in the glomeruli. The patient had no evidence of SLE and had normal complement levels. Serum samples from the patient reacted with the brush border of normal human kidney, in contrast with the negative results with 20 control serum samples. Preliminary characterization of the brush border target antigen excluded megalin, CD10, and maltase. We postulate that antibodies to brush border antigens cause direct epithelial injury, accumulate in the tubular basement membrane, and elicit an interstitial inflammatory response.

  12. 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

  13. Small molecule pinocytosis and clathrin-dependent endocytosis at the intestinal brush border: Two separate pathways into the enterocyte.

    PubMed

    Michael Danielsen, E; Hansen, Gert H

    2016-02-01

    Pinocytosis at the small intestinal brush border was studied in postweaned porcine cultured mucosal explants, using the fluorescent polar probes Alexa hydrazide (AH, MW 570), Texas red dextran (TRD, MW ~ 3000), and Cascade blue dextran (CBD, MW ~ 10,000). Within 1 h, AH appeared in a string of subapical punctae in enterocytes, indicative of an ongoing constitutive pinocytosis. By comparison, TRD was taken up less efficiently into the same compartment, and no intracellular labeling of CBD was detectable, indicating that only small molecules are pinocytosed from the postweaned gut lumen. AH remained in the terminal web region in EEA-1-positive endosomes (“TWEEs”) for at least 2 h, implying that the pinocytic uptake does not proceed towards a transcytic pathway. Like AH, cholera toxin B subunit (CTB) was readily internalized, but the two probes appeared in completely non-overlapping subapical compartments, indicating the existence of two different uptake mechanisms operating simultaneously at the brush border. CTB is internalized by clathrin-dependent receptor mediated endocytosis, but surprisingly the toxin also caused a rapid disappearance from the apical cell surface of two major brush border enzymes, alkaline phosphatase and aminopeptidase N, demonstrating the disruptive effect of this pathway. By immunofluorescence, caveolin-1 was hardly detectable in enterocytes, arguing against a caveolae-mediated uptake of AH, whereas the pinocytosis/phagocytosis inhibitors dimethyl amiloride and cytochalasin D both arrested AH uptake. We propose that the constitutive pinocytic mechanism visualized by AH contributes to maintenance of membrane homeostasis and to enrich the contents of lipid raft constituents at the brush border.

  14. Uptake of barbituric acid derivatives in small intestinal brush border membrane vesicles from retinyl palmitate-treated rats.

    PubMed

    Tanii, H; Horie, T

    2000-08-01

    Brush border membrane was prepared from the small intestinal (jejunum) cells along the crypt-villus axis. The fluorescence spectra of 1,8-anilinonaphthalene sulfonic acid and the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene were measured in the brush border membrane vesicle suspension. The hydrophobicity of brush border membrane was found to be in the order villus tip >mid villus >lower villus. The fluidity of brush border membrane was in the order villus tip brush border membrane vesicles was well correlated with their partition coefficients (isopentyl acetate/water). No significant difference was observed between the uptake of hexobarbital by brush border membrane vesicles from the villus tip and lower villus. When retinyl palmitate was administered to rats, the fluidity of brush border membrane was found to be higher in the retinyl palmitate-treated rats than in the control rats. However, no significant difference in the uptake of hexobarbital by brush border membrane vesicles was observed between the retinyl palmitate-administered rats and the control rats. Thus, the retinyl palmitate treatment seems unlikely to affect the passively transported ligands like barbituric acid derivatives in brush border membrane vesicles. PMID:10989945

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

    PubMed

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

    1977-12-01

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

  16. 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.

  17. Reevaluation of brush border motility: calcium induces core filament solation and microvillar vesiculation

    PubMed Central

    Burgess, DR; Prum, BE

    1982-01-01

    The report that microvillar cores of isolated, demembranated brush borders retract into the terminal web in the presence of Ca(++) and ATP has been widely cited as an example of Ca(++)-regulated nonmuscle cell motility. Because of recent findings that microvillar core actin filaments are cross-linked by villin which, in the presence of micromolar Ca(++), fragments actin filaments, we used the techniques of video enhanced differential interference contrast, immunofluorescence, and phase contrast microscopy and thin-section electron microscopy (EM) to reexamine the question of contraction of isolated intestinal cell brush borders. Analysis of video enhanced light microscopic images of Triton- demembranated brush borders treated with a buffered Ca(++) solution shows the cores disintegrating with the terminal web remaining intact; membranated brush borders show the microvilli to vesiculate with Ca(++). Using Ca(++)/EGTA buffers, it is found that micromolar free Ca(++) causes core filament dissolution in membranated or demembranated brush borders, Ca(++) causes microvillar core solation followed by complete vesiculation of the microvillar membrane. The lengths of microvilli cores and rootlets were measured in thin sections of membranated and demembranated controls, in Ca(++)-, Ca(++) + ATP-, and in ATP-treated brush borders. Results of these measurements show that Ca(++) alone causes the complete solation of the microvillar cores, yet the rootlets in the terminal web region remain of normal length. These results show that microvilli do not retract into the terminal web in response to Ca(++) and ATP but rather that the microvillar cores disintegrate. NBD-phallicidin localization of actin and fluorescent antibodies to myosin reveal a circumferential band of actin and myosin in mildly permeabilized cells in the region of the junctional complex. The presence of these contractile proteins in this region, where other studies have shown a circumferential band of thin filaments

  18. Comparison of intestinal brush-border 95-Kdalton polypeptide and alpha- actinins

    PubMed Central

    1980-01-01

    To explore the suggestion that alpha-actinin cross-links actin filaments to the microvillar membrane (Mooseker and Tilney, 1975, J. Cell Biol. 67:725--743; Mooseker, 1976, J. Cell Biol. 71-417--433), we have assessed the possible relatedness of alpha-actinin and the brush- border 95-kdalton protein by four independent criteria: antigenicity, mobility on SDS gels, extractability in nonionic detergents, and peptide maps. We have found that anti-chicken gizzard alpha-actinin stains the junctional complex region of intact cells (Craig and Pardo, 1979, J. Cell Biol. 80:203--210) but does not stain isolated brush borders even though these structures contain a 95-kdalton polypeptide. Lack of staining is not caused by failure of the antibody to penetrate, as antiactin stains both the terminal web and the microvilli of isolated brush borders. By the antibody SDS gel overlay technique, we have established that anti-gizzard alpha-actinin recognizes homologous molecules in chicken skeletal and cardiac muscles, as well as in intestinal epithelial cells, but fails to recognize the brush-border 95- kdalton polypeptide. Conversely, anti-95-kdalton polypeptide does not recognize gizzard alpha-actinin. On high-resolution SDS polyacrylamide gel electrophoresis, alpha-actinin and brush-border 95-kdalton protein exhibit distinct mobilities. The two proteins also differ in their ability to be extracted in nonionic mobilities. The two proteins also differ in their ability to be extracted in nonionic detergent: epithelial cell immunoreactive alpha-actinin is soluble in NP-40, whereas 95-kdalton protein is insoluble. Finally, two-dimensional peptide mapping of iodinated tryptic peptides, as well as one- dimensional fingerprinting of partial tryptic, chymotryptic, papain, and S. aureus V8 protease digests, have revealed less than 5% homology between gizzard alpha-actinin and brush-border 95-kdalton polypeptide. The data suggest that there is no major structural homology between gizzard

  19. Brush border peptidases and arylamidases in the experimental blind loop syndrome of the rat.

    PubMed

    Mazzacca, G; Musella, S; Andria, G; D'Agostino, L; Cimino, L; Budillon, G

    1977-10-01

    Peptidase and arylamidase activities were assessed in purified brush borders from jejunum of rats with surgically created blind loops. The blind loop segment and the jejunum proximal and distal to the blind loop were studied. Comparable jejunal segments from control rats were also studied. The blind loop syndrome was documented by presence of macrocytic anemia. Enzyme activities were determined on purified brush borders. In rats with the blind loop syndromes enzymatic activities hydrolizing sucrose, L-Leucyl-beta-naphthylamide, L-lysyl-beta-naphthylamide, alpha-L-glutamyl-beta-naphthylamide, L-phenylalanyl-alanine and L-leucyl-glycine were significantly reduced as compared to controls (P less than 0.001). After a short course of antibiotic therapy enzymatic activities returned to normal. Our findings suggest a reversible intestinal mucosa damage in the rat with blind loop syndrome.

  20. Exposure to Engineered Nanomaterial Results in Disruption of Brush Borders in Epithelia Models in vitro

    NASA Astrophysics Data System (ADS)

    Faust, James J.

    Engineered nanoparticles (NP; 10-9 m) have found use in a variety of consumer goods and medical devices because of the unique changes in material properties that occur when synthesized on the nanoscale. Although many definitions for nanoparticle exist, from the perspective of size, nanoparticle is defined as particles with diameters less than 100 nm in any external dimension. Examples of their use include titanium dioxide added as a pigment in products intended to be ingested by humans, silicon dioxide NPs are used in foods as an anticaking agent, and gold or iron oxide NPs can be used as vectors for drug delivery or contrast agents for specialized medical imaging. Although the intended use of these NPs is often to improve human health, it has come to the attention of investigators that NPs can have unintended or even detrimental effects on the organism. This work describes one such unintended effect of NP exposure from the perspective of exposure via the oral route. First, this Dissertation will explain an event referred to as brush border disruption that occurred after nanoparticles interacted with an in vitro model of the human intestinal epithelium. Second, this Dissertation will identify and characterize several consumer goods that were shown to contain titanium dioxide that are intended to be ingested. Third, this Dissertation shows that sedimentation due to gravity does not artifactually result in disruption of brush borders as a consequence of exposure to food grade titanium dioxide in vitro. Finally, this Dissertation will demonstrate that iron oxide nanoparticles elicited similar effects after exposure to an in vitro brush border expressing model of the human placenta. Together, these data suggest that brush border disruption is not an artifact of the material/cell culture model, but instead represents a bona fide biological response as a result of exposure to nanomaterial.

  1. 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

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

    SciTech Connect

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

    1990-05-01

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

  3. Calcium uptake by brush-border and basolateral membrane vesicles in chick duodenum

    SciTech Connect

    Takito, J.; Shinki, T.; Sasaki, T.; Suda, T. )

    1990-01-01

    Calcium uptake was compared between duodenal brush-border membrane vesicles (BBMV) and basolateral membrane vesicles (BLMV) isolated from vitamin D-deficient chicks and those injected with 625 ng of 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3). The uptake by BBMV in the 1 alpha,25-(OH)2D3-treated birds attained a maximum (280% of the control) at 12 h and was maintained at an elevated level (210%) at 24 h after the injection of the vitamin. In contrast, ATP-dependent calcium uptake by BLMV reached a maximum (185% of the control) at 6 h and decreased to the control level at 24 h. The kinetic analysis revealed that 1 alpha,25(OH)2D3 increased Vmax values without any changes in apparent Km values in both BBMV and BLMV. The activity of ATP-dependent calcium uptake was localized exclusively in the basolateral membrane, and the activity was inhibited by vanadate (IC50, 1 microM), but not by oligomycin, theophylline, calmodulin, trifluoperazine, or calbindin D28K. These results indicate that calcium transport through both the brush-border and basolateral membranes is involved in the 1 alpha,25(OH)2D3-dependent intestinal calcium absorption. The initiation of calcium absorption by 1 alpha,25(OH)2D3 appears to be due to an increase in the rate of calcium efflux at the basolateral membrane rather than the rate at the brush-border membrane.

  4. The stimulative effect of diffusion potential on enoxacin uptake across rat intestinal brush-border membranes.

    PubMed

    Hirano, T; Iseki, K; Miyazaki, S; Takada, M; Kobayashi, M; Sugawara, M; Miyazaki, K

    1994-08-01

    Evidence of a membrane potential dependence for enoxacin uptake by rat intestinal brush-border membrane vesicles has been found. The transient overshooting uptake of enoxacin disappeared in the voltage-clamped brush-border membrane vesicles in the presence of an outward H(+)-gradient. Momentary dissipation of the H(+)-gradient itself by carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP) did not affect the uptake of enoxacin. In contrast, enoxacin uptake was depressed by an interior positive K(+)-diffusion potential induced by valinomycin. Furthermore, not only the outward H(+)-gradient but also an inward Cl(-)-gradient caused a stimulating effect on enoxacin uptake, and the stimulation by the Cl(-)-gradient was dissipated by using voltage-clamped membrane vesicles. These results indicate that enoxacin transportation across the brush-border membrane is dependent on the ionic diffusion potential. On the other hand, neither Gly-Gly nor guanidine had any effect on enoxacin uptake by the membrane vesicles in the presence of an inward (for Gly-Gly) or outward (for guanidine) H(+)-gradient as a driving force for each transport system. Therefore, it seems that enoxacin transport through the intestinal epithelia does not participate in the carrier-mediated transport systems for Gly-Gly and guanidine.

  5. 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

  6. 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

  7. Specific binding of lactoferrin to brush-border membrane: Ontogeny and effect of glycan chain

    SciTech Connect

    Davidson, L.A.; Loennerdal, B. )

    1988-04-01

    Bioavailability of iron from human milk is exceptionally high. It has been suggested that lactoferrin, the major iron-binding protein in human milk, may participate in this high iron bioavailability from milk. The authors examined the interaction of lactoferrin with the intestinal brush-border membrane using the rhesus monkeys as a model. Brush-border membrane vesicles were prepared from monkeys of various ages. Binding studies with {sup 59}Fe-labeled human and monkey lactoferrin were performed to examine interaction of lactoferrin with the brush-border membrane. Specific saturable binding of lactoferrin was found at all ages studied. The dissociation constant for lactoferrin-receptor binding was 9 {times} 10{sup {minus}6} M. In contrast, no binding of serum transferrin or bovine lactoferrin occurred. Removal of fucose from the lactoferrin glycans resulted in a significant decrease in binding. It was concluded that lactoferrin in milk may function in the process of iron absorption through interaction with a small intestinal receptor and that fucosylated glycans on the carbohydrate chain of lactoferrin are necessary for receptor recognition.

  8. Shiga toxin exposure modulates intestinal brush border membrane functional proteins in rabbit ileum.

    PubMed

    Chopra, Puja; Verma, Dinesh; Khullar, Madhu; Sapru, Sunita; Mahmood, Safrun

    2006-02-01

    The activities of lactase, sucrase and alkaline phosphatase (AP) were studied in intestinal brush border membranes of control and toxin-treated rabbits. Purified Shiga toxin (Stx) exposure to ileal mucosa inhibited activities of brush border enzymes by 50%. Kinetic analysis revealed that the observed decrease in BBM enzyme activities was due to reduced V(max) with no change in the affinity constants of the systems. The observed changes in enzyme activities were corroborated by Western Blot analysis of lactase, sucrase and AP. The mRNA levels encoding sucrase and lactase proteins in control and Shiga toxin-treated rabbit ileum did not show any change in the rabbit ileum. Histopathological analysis showed short, blunt villi with increased number of inflammatory cells in the lamina propria and extrusion of cells in to the lumen of Stx-treated rabbit ileum. The present findings suggest that Shiga toxin act by inhibiting protein synthesis of these brush border functional proteins beyond their transcriptional level and by the direct damage to intestinal epithelium, which could be implicated in the pathogenesis of diarrhea.

  9. Generation of Stable Lipid Raft Microdomains in the Enterocyte Brush Border by Selective Endocytic Removal of Non-Raft Membrane

    PubMed Central

    Danielsen, E. Michael; Hansen, Gert H.

    2013-01-01

    The small intestinal brush border has an unusually high proportion of glycolipids which promote the formation of lipid raft microdomains, stabilized by various cross-linking lectins. This unique membrane organization acts to provide physical and chemical stability to the membrane that faces multiple deleterious agents present in the gut lumen, such as bile salts, digestive enzymes of the pancreas, and a plethora of pathogens. In the present work, we studied the constitutive endocytosis from the brush border of cultured jejunal explants of the pig, and the results indicate that this process functions to enrich the contents of lipid raft components in the brush border. The lipophilic fluorescent marker FM, taken up into early endosomes in the terminal web region (TWEEs), was absent from detergent resistant membranes (DRMs), implying an association with non-raft membrane. Furthermore, neither major lipid raft-associated brush border enzymes nor glycolipids were detected by immunofluorescence microscopy in subapical punctae resembling TWEEs. Finally, two model raft lipids, BODIPY-lactosylceramide and BODIPY-GM1, were not endocytosed except when cholera toxin subunit B (CTB) was present. In conclusion, we propose that constitutive, selective endocytic removal of non-raft membrane acts as a sorting mechanism to enrich the brush border contents of lipid raft components, such as glycolipids and the major digestive enzymes. This sorting may be energetically driven by changes in membrane curvature when molecules move from a microvillar surface to an endocytic invagination. PMID:24124585

  10. Generation of stable lipid raft microdomains in the enterocyte brush border by selective endocytic removal of non-raft membrane.

    PubMed

    Danielsen, E Michael; Hansen, Gert H

    2013-01-01

    The small intestinal brush border has an unusually high proportion of glycolipids which promote the formation of lipid raft microdomains, stabilized by various cross-linking lectins. This unique membrane organization acts to provide physical and chemical stability to the membrane that faces multiple deleterious agents present in the gut lumen, such as bile salts, digestive enzymes of the pancreas, and a plethora of pathogens. In the present work, we studied the constitutive endocytosis from the brush border of cultured jejunal explants of the pig, and the results indicate that this process functions to enrich the contents of lipid raft components in the brush border. The lipophilic fluorescent marker FM, taken up into early endosomes in the terminal web region (TWEEs), was absent from detergent resistant membranes (DRMs), implying an association with non-raft membrane. Furthermore, neither major lipid raft-associated brush border enzymes nor glycolipids were detected by immunofluorescence microscopy in subapical punctae resembling TWEEs. Finally, two model raft lipids, BODIPY-lactosylceramide and BODIPY-GM1, were not endocytosed except when cholera toxin subunit B (CTB) was present. In conclusion, we propose that constitutive, selective endocytic removal of non-raft membrane acts as a sorting mechanism to enrich the brush border contents of lipid raft components, such as glycolipids and the major digestive enzymes. This sorting may be energetically driven by changes in membrane curvature when molecules move from a microvillar surface to an endocytic invagination.

  11. Enzymatic and transport characteristics of isolated snake renal brush-border membranes

    SciTech Connect

    Benyajati, S.; Dantzler, W.H. )

    1988-07-01

    Brush-border membranes (BBM) or proximal tubules were isolated from the kidney of the garter snake (Thamnophis sirtalis) by a procedure involving hypotonic lysis, Ca precipitation, and differential centrifugation. The isolated membranes were enriched 15-fold in brush-border enzyme activities (alkaline phosphatase, {gamma}-glutamyl transpeptidase) compared with whole kidney homogenates and were substantially free of other contaminating membranes. The yield of the BBM preparation was 40%. The BBM vesicular transport of several organic solutes was characterized by a rapid filtration technique at 25{degree}C. D-glucose, p-aminohippurate (PAH), and urate entered the same osmotically active space and binding was minimal. An uptake overshoot for 3-O-methyl-D-glucose by reptilian BBM was observed only in the presence of an inwardly directed NaCl gradient and was abolished by 0.1 mM phlorizin. Reptilian BBM exhibited Na-gradient-stimulated uptake of PAH (90 {mu}M) with an overshoot that was inhibited by other organic acids and by 4-acetamido-4{prime}-isothiocyanostilbene-2,2{prime}-disulfonic acid (SITS). In contrast, urate uptake appeared to be Na independent and not appreciably affected by other organic anions or SITS. The presence of specific transport systems for organic solutes in the isolated membrane preparation distinctly characterizes the BBM of reptilian kidney.

  12. Aboral changes in D-glucose transport by human intestinal brush-border membrane vesicles.

    PubMed Central

    Bluett, M K; Abumrad, N N; Arab, N; Ghishan, F K

    1986-01-01

    D-Glucose transport was investigated in isolated brush-border membrane vesicles from human small intestine. Characteristics of D-glucose transport from the jejunum were compared with that in the mid and terminal ileum. Jejunal and mid-ileal D-glucose transport was Na+-dependent and electrogenic. The transient overshoot of jejunal D-glucose transport was significantly greater than corresponding values in mid-ileum. The terminal ileum did not exhibit Na+-dependent D-glucose transport, but did exhibit Na+-dependent taurocholate transport. Na+-glucose co-transport activity as measured by tracer-exchange experiments was greatest in the jejunum, and diminished aborally. We conclude that D-glucose transport in man is Na+-dependent and electrogenic in the proximal intestine and directly related to the activity of D-glucose-Na+ transporters present in the brush-border membranes. D-Glucose transport in the terminal ileum resembles colonic transport of D-glucose. PMID:3800877

  13. Fractionation of renal brush border membrane proteins with Triton X-114 phase partitioning.

    PubMed

    Vachon, V; Pouliot, J F; Laprade, R; Béliveau, R

    1991-01-01

    Analysis of brush border membrane proteins by gel electrophoresis has revealed a complex polypeptide composition. We have investigated the use of Triton X-114 phase partitioning to fractionate such proteins on the basis of their degree of hydrophobicity. Each of the fractions was composed of a complex but distinct set of proteins. Most proteins were solubilized by Triton X-114 and partitioned into the detergent-poor fraction. Trehalase, gamma-glutamyl transpeptidase, and leucine aminopeptidase were well solubilized (greater than 80%) and enriched 5.1-, 3.9-, and 2.5-fold in the detergent-rich fraction. In contrast, alkaline phosphatase and 5'-nucleotidase were poorly solubilized. The specific activities of these enzymes were increased 2.7- and 2.3-fold in the insoluble protein fraction. Maltase was almost completely solubilized and partitioned into the detergent-poor fraction with a small enrichment factor (1.3). These results suggest that Triton X-114 phase partitioning could be useful as a first step in the purification of many brush border membrane proteins.

  14. The Secretion and Action of Brush Border Enzymes in the Mammalian Small Intestine.

    PubMed

    Hooton, Diane; Lentle, Roger; Monro, John; Wickham, Martin; Simpson, Robert

    2015-01-01

    Microvilli are conventionally regarded as an extension of the small intestinal absorptive surface, but they are also, as latterly discovered, a launching pad for brush border digestive enzymes. Recent work has demonstrated that motor elements of the microvillus cytoskeleton operate to displace the apical membrane toward the apex of the microvillus, where it vesiculates and is shed into the periapical space. Catalytically active brush border digestive enzymes remain incorporated within the membranes of these vesicles, which shifts the site of BB digestion from the surface of the enterocyte to the periapical space. This process enables nutrient hydrolysis to occur adjacent to the membrane in a pre-absorptive step. The characterization of BB digestive enzymes is influenced by the way in which these enzymes are anchored to the apical membranes of microvilli, their subsequent shedding in membrane vesicles, and their differing susceptibilities to cleavage from the component membranes. In addition, the presence of active intracellular components of these enzymes complicates their quantitative assay and the elucidation of their dynamics. This review summarizes the ontogeny and regulation of BB digestive enzymes and what is known of their kinetics and their action in the peripheral and axial regions of the small intestinal lumen.

  15. Uptake mechanism of trientine by rat intestinal brush-border membrane vesicles.

    PubMed

    Tanabe, R; Kobayashi, M; Sugawara, M; Iseki, K; Miyazaki, K

    1996-05-01

    The uptake characteristics of trientine by rat intestinal brush-border membrane vesicles were studied. The uptake characteristics of trientine were similar to those of the physiological polyamines with respect to the excessive accumulation in vesicles, the pH dependency, the temperature dependency and the ineffectiveness of K+ diffusion potential (inside negative). The initial uptake of trientine was saturable with a K(m) value of 1.13 mM, which was larger than that of spermine and spermidine. Furthermore, the uptake rate of trientine was dose-dependently inhibited by spermine and spermidine. Spermine competitively inhibited the uptake of trientine with a Ki value of 18.6 microM, and it was close to the K(m) value for spermine (30.4 microM). These data suggested that the uptake of trientine was similar to that of spermine and spermidine in rat small intestinal brush-border membrane vesicles, and these polyamines seem to inhibit the absorption of trientine from the gastrointestinal tract.

  16. Detection of renal brush border membrane enzymes for evaluation of renal injury in neonatal scleredema

    PubMed Central

    Ren, Qing; Zhang, Yongjun; Yang, Jinying; Wei, Lixia; Zhao, Lili; Yang, Qiaozhi

    2015-01-01

    Objective: To evaluate renal brush border membrane enzymes in urine as an indicator for renal injury in neonatal scleredema (NS). Methods: Sixty nine NS patients in our hospital were enrolled and divided into mild group and moderate/severe group. Patients were further randomly divided into therapy and control subgroups for 7 days ligustrazine administration. Urine samples were collected to detect renal brush border membrane enzymes (RBBME) by ELISA and β2-microglobulin (β2-MG) by radioimmunoassay (RIA). The results were compared with those of 30 normal neonates. Data were statistically analyzed using SPSS13.0 software. Results: Both RBBME and β2-MG were found to be higher in urine in NS patients than normal controls (P < 0.01). Level of RBBME increased with the severity of NS (P <0.05), while urinary β2-MG did not (P >0.05). After being treated with ligustrazine, a medicine for renal function recovery, both RBBME and β2-MG were similarly significantly decreased comparing to untreated groups (P < 0.05). 79.7% of NS patients showed abnormal RBBME while only 52.2% had an abnormal urinary β2-MG (χ2=11.65,P < 0.01). Conclusion: RBBME was more sensitive than β2-MG in reflecting the renal injury in NS. Examination of RBBME effectively reflected the recovery of renal injury after treatment with ligustrazine. PMID:25878616

  17. Thyroid hormones increase Na -H exchange activity in renal brush border membranes

    SciTech Connect

    Kinsella, J.; Sacktor, B.

    1985-06-01

    Na -H exchange activity, i.e., amiloride-sensitive Na and H flux, in renal proximal tubule brush border (luminal) membrane vesicles was increased in the hyperthyroid rat and decreased in the hypothyroid rat, relative to the euthyroid animal. A positive correlation was found between Na -H exchange activity and serum concentrations of thyroxine (T4) and triiodothyronine (T3). The thyroid status of the animal did not alter amiloride-insensitive Na uptake. The rate of passive pH gradient dissipation was higher in membrane vesicles from hyperthyroid rats compared to the rate in vesicles from hypothyroid animals, a result which would tend to limit the increase in Na uptake in vesicles from hyperthyroid animals. Na -dependent phosphate uptake was increased in membrane vesicles from hyperthyroid rats; Na -dependent D-glucose and L-proline uptakes were not changed by the thyroid status of the animal. The effect of thyroid hormones in increasing the uptake of Na in the brush border membrane vesicle is consistent with the action of the hormones in enhancing renal Na reabsorption.

  18. H+ V-ATPase-Energized Transporters in Brush Border Membrane Vesicles from Whole Larvae of Aedes Aegypti

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Brush Border Membrane vesicles (BBMVs) from Whole larvae of Aedes aegypti (AeBBMVWs ) contain an H+ V-ATPase (V), a Na+/H+ antiporter, NHA1 (A) and a Na+-coupled, nutrient amino acid transporter, NAT8 (N), VAN for short. All V-ATPase subunits are present in the Ae. aegypti genome and in the vesicles...

  19. Association and dissociation of Escherichia coli heat-stable enterotoxin from rat brush border membrane receptors

    SciTech Connect

    Cohen, M.B.; Thompson, M.R.; Overmann, G.J.; Giannella, R.A.

    1987-02-01

    Escherichia coli heat-stable enterotoxin (ST) binds to receptors on rat intestinal cells and brush border membranes (BBM). We devised experiments to examine the reversibility of ST binding. We found that both /sup 125/I-labeled ST and native ST were spontaneously dissociable from the BBM receptor. Radiolabeled ST bound to BBM was also dissociated by the addition of avid goat anti-ST antiserum. Furthermore, using a computer program for analysis of ligand binding, we calculated an apparent Ka of 10(8) liters/mol from competitive inhibition and saturation-binding data. This is significantly lower than the value previously reported by others. Our findings, of a lower Ka and a reversible ST-binding process, suggest that a therapeutic strategy of removing bound ST from its receptor or competing with the enterocyte receptor for unbound ST might be successful in terminating ST-induced secretion.

  20. Multiple sodium-dependent nucleoside transport systems in bovine renal brush-border membrane vesicles.

    PubMed Central

    Williams, T C; Jarvis, S M

    1991-01-01

    Na(+)-dependent nucleoside transport was examined in bovine renal brush-border membrane vesicles. Two separate Na+/nucleoside cotransporters were shown to be present: (1) a system specific for purine nucleosides and uridine, designated as the N1 carrier, and (2) an Na(+)-dependent nucleoside transporter that accepts pyrimidine nucleosides, adenosine and analogues of adenosine, designated as the N2 system. Both systems exhibit a high affinity for nucleosides (apparent Km values approximately 10 microM), are insensitive to inhibition by facilitated-diffusion nucleoside transport inhibitors, are rheogenic and exhibit a high specificity for Na+. Na+ increases the affinity of the influx of guanosine and thymidine, nucleosides that serve as model permeants for the N1 and N2 nucleoside transporters respectively. The Na+/nucleoside coupling stoichiometry is consistent with 1:1 for both carriers. PMID:2001243

  1. Developmental pattern of rat intestinal brush-border enzymic proteins along the villus--crypt axis.

    PubMed

    Simon, P M; Kedinger, M; Raul, F; Grenier, J F; Haffen, K

    1979-02-15

    At various postnatal stages, intestinal epithelial cells were isolated sequentially from villus tip to crypt base by successive EDTA treatments. According to the localization of marker enzymic activities, isolated cells were pooled into three cell compartments: villus (V), lower villus and upper crypt (VC) and crypt (C). Purified brush-border-membrane proteins were separated by 7.5%-polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. Enzymic activities could be assigned to some protein bands: maltase/glucoamylase (protein band 3), sucrase-isomaltase (protein bands 3 and 6), lactase (protein band 5) and alkaline phosphatase (region of protein bands 8 and 9). The findings suggest the following. (1) Sucrase-isomaltase activities appeared in compartment C at 17 days with a simultaneous increase of the pre-existing protein band 3 and appearance of a well-defined protein band in position 6; the enzymic complex remained still present in the crypt cells until adulthood. From the day 21 onwards, sucrase-isomaltase was detected in compartments VC and V. (2) Lactase was only present in the three cell compartments until day 21; at this developmental stage its activity completely disappeared from compartment C, in spite of the persistence of a weak protein band. (3) Alkaline phosphatase activity could be detected as a single peak corresponding to protein band 9 in all three cell compartments until day 21; thereafter it was replaced by two peaks of activity showing a less precise correlation with the well-defined protein bands 8 and 9. In the crypt cells of the adult rat, however, the preweaning situation, which was regularly observed, is an unexpected phenomenon. (4) Maltase and glucoamylase did not display any marked qualitative or quantitative modifications either along the villus-crypt axis or during the period of postnatal development studied. Evidence is given from the present data that each brush-border enzyme investigated has a specific

  2. Brush border Myosin Ia has tumor suppressor activity in the intestine

    PubMed Central

    Mazzolini, Rocco; Dopeso, Higinio; Mateo-Lozano, Silvia; Chang, Wakam; Rodrigues, Paulo; Bazzocco, Sarah; Alazzouzi, Hafid; Landolfi, Stefania; Hernández-Losa, Javier; Andretta, Elena; Alhopuro, Pia; Espín, Eloy; Armengol, Manel; Tabernero, Josep; Ramón y Cajal, Santiago; Kloor, Matthias; Gebert, Johannes; Mariadason, John M.; Schwartz, Simo; Aaltonen, Lauri A.; Mooseker, Mark S.; Arango, Diego

    2012-01-01

    The loss of the epithelial architecture and cell polarity/differentiation is known to be important during the tumorigenic process. Here we demonstrate that the brush border protein Myosin Ia (MYO1A) is important for polarization and differentiation of colon cancer cells and is frequently inactivated in colorectal tumors by genetic and epigenetic mechanisms. MYO1A frame-shift mutations were observed in 32% (37 of 116) of the colorectal tumors with microsatellite instability analyzed, and evidence of promoter methylation was observed in a significant proportion of colon cancer cell lines and primary colorectal tumors. The loss of polarization/differentiation resulting from MYO1A inactivation is associated with higher tumor growth in soft agar and in a xenograft model. In addition, the progression of genetically and carcinogen-initiated intestinal tumors was significantly accelerated in Myo1a knockout mice compared with Myo1a wild-type animals. Moreover, MYO1A tumor expression was found to be an independent prognostic factor for colorectal cancer patients. Patients with low MYO1A tumor protein levels had significantly shorter disease-free and overall survival compared with patients with high tumoral MYO1A (logrank test P = 0.004 and P = 0.009, respectively). The median time-to-disease recurrence in patients with low MYO1A was 1 y, compared with >9 y in the group of patients with high MYO1A. These results identify MYO1A as a unique tumor-suppressor gene in colorectal cancer and demonstrate that the loss of structural brush border proteins involved in cell polarity are important for tumor development. PMID:22307608

  3. 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.

  4. Effects of dimethylsulfoxide and mercurial sulfhydryl reagents on water and solute permeability of rat kidney brush border membranes.

    PubMed

    van Hoek, A N; de Jong, M D; van Os, C H

    1990-12-14

    The effects of dimethylsulfoxide, DMSO, and mercurial sulfhydryl reagents have been studied on water and small solute permeability of rat renal brush border membrane vesicles. Water and solute permeability was measured by mixing membrane vesicles with hypertonic solutions in a stopped-flow apparatus and following osmotically-induced changes in vesicular volume via changes in scattered light intensity. The rate constant of the fast osmotic shrinkage is proportional to the osmotic water permeability, while the rate constant of the slow reswelling phase is proportional to the solute permeability. Using mannitol as the osmotic agent, the osmotic shrinkage of rat renal brush border membrane vesicles followed a biphasic time course. 80% of the vesicles shrunk with a rate constant of approx. 50 s-1 and 20% with a rate constant of approx. 2 s-1. DMSO decreased dose-dependently the amplitude of the fast osmotic shrinkage, without affecting its rate constant. In contrast to DMSO, HgCl2 decreased the rate constant but not the amplitude of the fast osmotic shrinkage of renal brush border vesicles. Between 40-50 microM HgCl2, the inhibition of the fast osmotic shrinkage was completed. DMSO and HgCl2 increase the activation energy of water permeation in renal membranes from 3 to 12-15 kcal/mol. DMSO and HgCl2 did not affect the rate constant of the slow osmotic shrinkage of renal membrane vesicles and were also without effect on osmotic shrinkage of small intestinal brush border and pure phospholipid vesicles. In renal brush border membranes, HgCl2 at low concentrations (less than 10 microM) increased by 15-fold the permeability to NaCl and urea but not to mannitol, an effect which precedes the inhibition of water permeability at higher HgCl2 concentrations. The increase in small solute permeability was irreversible while the inhibition of water permeability could be reversed with cysteine and dithiothreitol. We conclude that water and small solute pathways in rat renal brush

  5. Radiation inactivation studies of renal brush border water and urea transport

    SciTech Connect

    Verkman, A.S.; Dix, J.A.; Seifter, J.L.; Skorecki, K.L.; Jung, C.Y.; Ausiello, D.A.

    1985-12-01

    Radiation inactivation was used to determine the nature and molecular weight of water and urea transport pathways in brush border membrane vesicles (BBMV) isolated from rabbit renal cortex. BBMV were frozen to -50 degrees C, irradiated with 1.5 MeV electrons, thawed, and assayed for transport or enzyme activity. The freezing process had no effect on enzyme or transport kinetics. BBMV alkaline phosphatase activity gave linear ln(activity) vs. radiation dose plots with a target size of 68 +/- 3 kDa, similar to previously reported values. Water and solute transport were measured using the stopped-flow light-scattering technique. The rates of acetamide and osmotic water transport did not depend on radiation dose (0-7 Mrad), suggesting that transport of these substances does not require a protein carrier. In contrast, urea and thiourea transport gave linear ln(activity) vs. dose curves with a target size of 125-150 kDa; 400 mM urea inhibited thiourea flux by -50% at 0 and 4.7 Mrad, showing that radiation does not affect inhibitor binding to surviving transporters. These studies suggest that BBMV urea transport requires a membrane protein, whereas osmotic water transport does not.

  6. The effects of ethanol administration on brush border membrane glycolipids in rat intestine.

    PubMed

    Grewal, Ravneet K; Mahmood, Akhtar

    2010-09-01

    Ethanol ingestion is well known to induce morphological and biochemical changes in intestine and is responsible for intestinal dysfunctions. Luminal surface of enterocytes is rich in glycolipids, but the effects of ethanol ingestion on membrane glycolipids are not well characterized. In the present study, rats were given 1 mL of 30% ethanol daily for 15, 25, 35, and 56 days. Ethanol feeding for 15 days did not affect glycolipid pattern in microvillus membranes, but the levels of cerebrosides (glucosylceramide, lactosylceramide, globotriasyloceramide) were enhanced in rats fed with ethanol for 35 or 56 days compared with controls. In contrast, the content of fucolipids and gangliosides was reduced in rats on ethanol ingestion for 35 or 56 days. The observed changes in membrane glycolipids were substantiated using biotinylated lectins Jacalin (affinity for N-acetylgalactosamine) and Aleuria aurantia (affinity for α-l-fucose). The incorporation of [(14)C]-mannose and [(14)C]-glucosamine revealed an increase (P<.01) in glucosamination and reduction (P<.01) in mannosylation of glycolipids from ethanol-fed rats for 45 days compared with controls. These findings were further characterized by autoradiography of the glycolipids separated on thin layer chromatograms. These findings indicate that ethanol ingestion modulates the glycolipids composition of brush borders, resulting in generalized aberration of intestinal glycosylation in chronic alcoholism in rats. PMID:20708369

  7. Renal brush-border Na/sup +/-H/sup +/ exchange activity in the aging rat

    SciTech Connect

    Kinsella, J.L.; Sacktor, B.

    1987-04-01

    Amiloride-sensitive Na/sup +/-H/sup +/ exchange activity in brush-border membrane vesicles isolated from male rat proximal tubules was decreased in the senescent rat (24 mo) compared with the young adult (6 mo). There was no significant loss in Na/sup +/-H/sup +/ exchange activity in the kidneys of animals between 6 and 18 mo of age. Amiloride-insensitive /sup 22/Na/sup +/ uptake and the rate of pH gradient dissipation were not altered during aging. The decrease in sodium-dependent (/sup 32/P) phosphate transport preceded the decline in Na/sup +/-H/sup +/ exchange activity by at least 6 mo. Sodium-dependent D-(/sup 3/H) glucose transport was not significantly altered during aging. Thus various renal plasma membrane transport functions were affected differently in the aging rat. The decrease in Na/sup +/-H/sup +/ exchange activity during aging contrasted with the increase in exchange activity reported previously in acute ablation models of chronic renal failure.

  8. Na-dependent L-proline transport by eel intestinal brush-border membrane vesicles

    SciTech Connect

    Vilella, S.; Ahearn, G.A.; Cassano, G.; Storelli, C. University of Hawaii at Manoa, Honolulu )

    1988-10-01

    L-({sup 3}H)proline uptake by brush-border membrane vesicles prepared from intestinal mucosa of the European eel, Anguilla anguilla, was stimulated by a transmembrane Na gradient (out > in.) Kinetic analysis of L-proline influx, under short-circuited membrane potential conditions, indicated the presence of an apparent single Na-dependent carrier process and a nonsaturable transfer component with an apparent diffusional permeability (P) of 1.53 {plus minus} 0.35 {mu}l{center dot}mg protein{sup {minus}1}{center dot}min{sup {minus}1}. An imposed transmembrane potential (inside negative) increased apparent L-proline binding affinity (lowered K{sub app}) without appreciably altering maximal amino acid influx (J{sub max}). Hill analysis of L-proline influx over a wide range of external Na concentrations indicated a 1:1 stoichiometry for Na-proline cotransport. Use of amino acid inhibitors of L-proline influx suggested that L-proline transfer may occur by either a classical Na-dependent A System with a wide substrate specificity or by the combination of Na-dependent PHE (phenylalanine preferring) and IMINO (proline, {alpha}-methylaminoisobutyric acid preferring) Systems.

  9. Natural Selection at the Brush-Border: Adaptations to Carbohydrate Diets in Humans and Other Mammals

    PubMed Central

    Pontremoli, Chiara; Mozzi, Alessandra; Forni, Diego; Cagliani, Rachele; Pozzoli, Uberto; Menozzi, Giorgia; Vertemara, Jacopo; Bresolin, Nereo; Clerici, Mario; Sironi, Manuela

    2015-01-01

    Dietary shifts can drive molecular evolution in mammals and a major transition in human history, the agricultural revolution, favored carbohydrate consumption. We investigated the evolutionary history of nine genes encoding brush-border proteins involved in carbohydrate digestion/absorption. Results indicated widespread adaptive evolution in mammals, with several branches experiencing episodic selection, particularly strong in bats. Many positively selected sites map to functional protein regions (e.g., within glucosidase catalytic crevices), with parallel evolution at SI (sucrase-isomaltase) and MGAM (maltase-glucoamylase). In human populations, five genes were targeted by positive selection acting on noncoding variants within regulatory elements. Analysis of ancient DNA samples indicated that most derived alleles were already present in the Paleolithic. Positively selected variants at SLC2A5 (fructose transporter) were an exception and possibly spread following the domestication of specific fruit crops. We conclude that agriculture determined no major selective event at carbohydrate metabolism genes in humans, with implications for susceptibility to metabolic disorders. PMID:26319403

  10. Direct effect of vanadium on citrate uptake by rat renal brush border membrane vesicles (BBMV).

    PubMed

    Sato, Kazuhiro; Kusaka, Yukinori; Akino, Hironobu; Kanamaru, Hiroshi; Okada, Kenichiro

    2002-07-01

    Vanadium pentoxide is used as a catalyst and a ferrovanadium alloy ingredient in automotive steels and in jet engines and airframes. In addition, vanadium is found in fuel oils. Thus, occupational exposures to vanadium pentoxide and trioxide may occur during the cleaning of oil-fired ship boilers, and from oil-fired power station boilers. Occupational exposure to vanadium pentoxide induces green tongue, asthmatic symptoms and albuminuria with cast. Urinary citrate is freely filtered at the glomerulus, and its reabsorption in the proximal tubule is the major determinant of the rate of renal excretion. In this study, we exposed rat renal brush border membrane vesicles (BBMV) to vanadium pentoxide and examined their citrate uptake characteristics. The preincubation of BBMV with 1 mM V2O5 for 8 hours significantly inhibited citrate uptake compared with that of BBMV without V2O5, preincubation. These findings indicate that the preincubation of BBMV with vanadium pentoxide results in a time-dependent inhibition of citrate uptake by BBMV. These findings might contribute to nephrotoxicity in vanadium exposure. PMID:12141377

  11. Sulfate uptake by crustacean hepatopancreatic brush border membrane vesicles. [Homarus americanus

    SciTech Connect

    Gerencser, G.A.; Cattey, M.A; Ahearn, G.A. Univ. of Hawaii, Honolulu )

    1990-02-26

    Purified brush border membrane vesicles (BBMV) were prepared from Atlantic lobster (Homarus americanus) hepatopancreas using differential centrifugation and Mg{sup +2} precipitation techniques. Uptake of 0.1 mM {sup 35}SO{sub 4}{sup {minus}2} was stimulated by pre-loading vesicles with Cl{sup {minus}} leading to a transient accumulation of isotope more than twice that at equilibrium. Pre-loading with HCO{sub 3}{sup {minus}} or gluconate had no effect on sulfate uptake. No stimulation of {sup 35}SO{sub 4}{sup {minus}2} was observed in the presence of inwardly directed Na{sup +} or tetramethylammonium{sup +} gradients. Uptake of the divalent anion was strongly stimulated by inwardly directed proton gradients (pH{sub o} < pH{sub i}) and markedly inhibited by outwardly directed proton gradients (pH{sub o} > pH{sub i}). {sup 35}SO{sub 4}{sup {minus}2}/Cl{sup {minus}} exchange was enhanced by imposing a transmembrane inside positive K{sup +} diffusion potential and inhibited by a membrane potential of the opposite polarity (K{sup +}/valinomycin). Results suggest the presence of a proton-dependent, electrogenic anion antiport mechanism in BBMV isolated from the crustacean hepatopancreas.

  12. Heparin blocks /sup 125/I-calmodulin internalization by isolated rat renal brush border membrane vesicles

    SciTech Connect

    Meezan, E.; Elgavish, A.; Roden, L.; Wallace, R.W.

    1986-03-05

    /sup 125/I-Calmodulin is internalized by isolated rat renal brush border membrane vesicles (BBV) in a time, temperature and calcium dependent manner. Internalization of /sup 125/I-calmodulin into the osmotically sensitive space of BBV was distinguished from binding of the ligand to the outer BBV surface by examining the interaction of ligand and BBV at different medium osmolarities (300-1100 mosm), uptake was inversely proportional to medium osmolarity. Internalized /sup 125/I-calmodulin was intact and Western blots of solubilized BBV with /sup 125/I-calmodulin demonstrated the presence of several calmodulin-binding proteins of 143, 118, 50, 47.5, 46.5 and 35 kilodaltons which could represent potential intravesicular binding sites for the ligand. Heparin and the related glycosaminoglycan heparin sulfate both showed a dose-dependent inhibition (0.5-50 ..mu..g/ml) of /sup 125/I-calmodulin uptake by BBV, but other sulfated and nonsulfated glycosaminoglycans including chondroitin sulfates, keratan sulfate and hyaluronic acid showed little or no inhibitory effect. Desulfation of heparin virtually abolished the inhibition of uptake while depolymerization reduced it. Heparin did not block the binding of /sup 125/I-calmodulin to BBV proteins as assessed by Western blotting technique suggesting its effect was on internalization of the ligand rather than on its association with internal membrane proteins.

  13. Characterization of L-carnitine transport by rat kidney brush-border-membrane vesicles.

    PubMed Central

    Stieger, B; O'Neill, B; Krähenbühl, S

    1995-01-01

    In the presence of a 100 mM Na+ gradient, transport of L-carnitine into rat renal brush-border-membrane vesicles was linear over 30 s and showed an overshoot at 5 min. The uptake of L-carnitine was clearly less active in the presence of other cations such as Li+, K+, Cs+ or choline. In the presence of a Na+ gradient, L-carnitine uptake after 20 s was much higher for chloride as an anion than for SCN-, NO3-, gluconate or SO4(2-). In comparison with conditions with inside positive or no membrane potential, transport was higher in vesicles with an inside negative membrane potential, suggesting an electrogenic mechanism. The kinetic characterization of the Na(+)-dependent portion of L-carnitine transport revealed two transport systems with Km values of 17.4 +/- 3.9 microM and 15.0 +/- 6.0 mM, respectively. The transport could be inhibited in a concentration-dependent fashion by structural analogues such as butyrobetaine, L-acetylcarnitine, trimethyl-lysine and D-carnitine, but not by L-arginine or glycinebetaine. PMID:7626031

  14. Dietary regulation of intestinal brush-border sugar and amino acid transport in carnivores.

    PubMed

    Buddington, R K; Chen, J W; Diamond, J M

    1991-10-01

    The ability of omnivores and herbivores to regulate reversibly their intestinal brush-border nutrient transporters is functionally related to the unpredictably variable composition of their natural diets. To determine whether carnivores are able similarly to regulate the activities of their intestinal nutrient transporters, we fed to three species of vertebrates that are carnivorous as adults (cats, mink, and leopard frogs) diets with either at least 50% digestible carbohydrate or with negligible carbohydrate levels. Rates of transport for the sugars glucose and fructose and the amino acids (AAs) aspartate, leucine, lysine, and proline were measured throughout the intestine (only proline and glucose in the frogs) by an in vitro everted-sleeve method. Although all three species consume much carbohydrate during early development, only the mink was able to regulate sugar transporter activity in response to changes in levels of dietary carbohydrate. In contrast, the sugar transporters of the cat were unresponsive to varying carbohydrate levels, and long-term feeding of a high-carbohydrate diet caused down-regulation of sugar transport in frogs. Of the three species, only the mink is a member of a family that includes omnivorous species, whereas all members of the families to which the cat and frog belong are carnivorous as adults. All three species were able to regulate rates of AA transport, though the patterns and magnitude of the responses differed between species as well as between AAs, suggesting independent regulation of some AA transporters.(ABSTRACT TRUNCATED AT 250 WORDS)

  15. Effects of ethanol in vitro on rat intestinal brush-border membranes.

    PubMed

    Hunter, C K; Treanor, L L; Gray, J P; Halter, S A; Hoyumpa, A; Wilson, F A

    1983-07-13

    Ethanol, at concentrations found in the intestinal lumen after moderate drinking, has been shown to inhibit carrier-mediated intestinal transport processes. This inhibition could occur by direct interaction with membrane transporters, dissipation of the energy producing Na+ electrochemical gradient and/or nonspecific alteration of membrane integrity. The latter alteration may be reflected by changes in membrane fluidity, chemical composition or vesicular size. These possibilities were examined with studies in purified brush border membrane vesicles of rat intestine. Ethanol inhibited concentrative Na+-dependent D-glucose uptake in a dose-dependent manner. In contrast, ethanol did not inhibit concentrative D-glucose uptake under conditions of D-glucose trans-stimulation in the absence of a Na+ electrochemical gradient. Ethanol also inhibited initial, concentrative Na+-dependent taurocholic acid uptake, as well as equilibrium uptake. That ethanol exerted a dual effect on transport by increasing membrane conductance for Na+ while decreasing intravesicular space was supported by direct studies of Na+ uptake. Morphometric analysis confirmed that ethanol-treated membranes had a decreased intravesicular size when compared to untreated membranes. Finally, membrane fluidity measured by EPR showed that ethanol had a significant fluidizing effect without producing qualitative changes in membrane proteins, as determined by SDS gel electrophoresis. These results suggest that ethanol inhibits carrier-mediated transport by dissipation of the Na+ electrochemical gradient and alteration of membrane integrity rather than by direct interaction with membrane transporter.

  16. Developmental aspects of proline transport in rat renal brush border membranes.

    PubMed

    Medow, M S; Roth, K S; Goldmann, D R; Ginkinger, K; Hsu, B Y; Segal, S

    1986-10-01

    Proline uptake by rat renal brush border membrane vesicles from animals 7 days of age and older has been examined to delineate developmental changes in membrane function that may underlie the physiological hyperprolinuria of young animals. Although the two proline transport systems normally present in adult membranes were found in membranes from young animals, the proline "overshoot" resulting from a sodium ion gradient is minimal and increases with age of the animal from which the membranes were isolated. This is associated with a severalfold faster entry of 22Na into vesicles of the 7-day-old animal compared to entry into membranes prepared from adult kidneys. The very rapid dissipation of the sodium gradient thus diminishing the driving force for transmembrane proline movement may explain the changes in proline overshoot observed in membranes from young animals. The altered sodium permeability is consistent with the fact that young animals have a generalized inability to reabsorb other amino acids whose transport is known to be sodium gradient stimulated. PMID:3463985

  17. Inhibition of beta-amino acid transport by diamide does not involve the brush border membrane surface

    SciTech Connect

    Chesney, R.W.; Gusowski, N.; Albright, P.

    1985-01-01

    Diamide (dicarboxylic acid bis-(N,N-dimethylamide) has been shown in previous studies to block the uptake of the beta-amino acid taurine at its high affinity transport site in rat renal cortex slices. Diamide may act by increasing the efflux of taurine from the slice. Studies performed in rat slices again indicate enhanced efflux over 8-12 minutes. The time course of reduced glutathione (GSH) depletion from renal cortex is similar, indicating a potential interaction between GSH depletion and inhibition of taurine accumulation. The effect of 9 mM diamide on the Na+ -dependent accumulation of taurine (10 and 250 microM) by brush border membrane vesicles was examined, and the taurine uptake value both initially and at equilibrium was the same in the presence and absence of diamide. Isolation of the brush border surface and subsequent transport studies of taurine are not influenced by diamide. Thus, diamide inhibition of taurine uptake does not involve physiochemical alteration of the membrane surface where active amino acid transport occurs, despite the thiol-oxidizing properties of this agent. Further, these studies suggest that diamide either acts at the basolateral surface, rather than the brush border surface of rat renal cortex or requires the presence of an intact tubule, capable of metabolism, prior to its inhibitory action.

  18. Effect of chronic (4 weeks) ingestion of ethanol on transport of proline into intestinal brush border membrane vesicles

    SciTech Connect

    Beesley, R.C.; Jones, T.D.

    1986-03-01

    Hamsters were separated into two groups and fed liquid diets ad lib. Controls were given a diet similar to that described by DeCarli and Lieber while alcoholics received the same diet containing 5% ethanol isocalorically substituted for sucrose. The volume of diet consumed daily and the gain in body weights of alcoholics were not significantly different from those of controls. After four weeks the animals were sacrificed and the upper third of the small intestine was used to prepare brush border membrane vesicles. In the presence of a Na/sup +/ gradient, uptake of proline into vesicles prepared from both groups was rapid, reaching a maximum accumulation in 1 to 2 min and then decreasing to the equilibrium level. To normalize the results, the amount of proline take up at each time point was divided by the amount present at equilibrium. From the normalized data it was concluded that both the rate of uptake and the maximum accumulation of proline into brush border membrane vesicles isolated from alcoholics were significantly less than those obtained with vesicles from controls. These results suggest that chronic ingestion of ethanol results in a reduction in Na/sup +/-dependent transport of proline across the brush border membrane and, thus, may contribute to the malnutrition which is frequently associated with chronic alcoholism.

  19. Demonstration of high-affinity folate binding activity associated with the brush border membranes of rat kidney.

    PubMed Central

    Selhub, J; Rosenberg, I H

    1978-01-01

    Folate binding activity of high affinity was identified in the particulate fractions of rat kidney homogenates. This binding activity cofractionated with alkaline phosphatase and maltase, two brush border membranes markers. With an enriched preparation of brush border membranes, freed of endogenous folate by acid treatment, the binding of [3H]olate was found to be saturable (Kb = 4.2 X 10(-11)M) and rapid. Binding was optimal at pH 6.4-7.7. At neutral pH, competition for binding with [3H]folic acid required 1.45 equivalents of pteroylheptaglutamate, 6.25 equivalents of N5-methyltetrathydrofolate, 29 equivalents of methotrexate, and 125 equivalents of N5-formyltetrahydrofolate. At alkaline pH, N5-methyltetrahydrofolate was as effective a competitor as folic acid. In view of reports that renal tubular reabsorption of folate includes an initial tight binding step, the binding activity associated with the brush border membranes may participate in this process. PMID:28521

  20. In vitro effect of ethanol on sodium and glucose transport in rabbit renal brush border membrane vesicles.

    PubMed

    Parenti, P; Giordana, B; Hanozet, G M

    1991-11-18

    The effect of ethanol on sodium and glucose transport in rabbit renal brush border membrane vesicles was examined. When membrane vesicles were preincubated in the presence of ethanol the sodium-dependent D-glucose uptake was significantly inhibited. This effect, as suggested by O'Neill et al. (1986) FEBS Lett. 194, 183-188, may be due to a faster collapse of the Na+ gradient. As a matter of fact, the amiloride-insensitive sodium pathway was increased by ethanol in our brush border membrane preparation. However, sodium/D-glucose cotransport was inhibited by ethanol, although to a lesser degree, also in the absence of a sodium gradient. In addition, ethanol inhibited glucose-dependent sodium uptake, suggesting that a direct interaction with the translocator was involved. This conclusion was also supported by kinetic measurements showing a decrease of Vmax and an increase in Km for glucose in membrane vesicles treated with ethanol. Moreover, ethanol influenced the interaction of phlorizin with the cotransporter: uptake experiments performed in the presence of the two inhibitors demonstrated that phlorizin and ethanol behave as not mutually exclusive inhibitors of D-glucose transport. These data indicate that in rabbit renal brush border membranes ethanol not only affects the 'passive pathway', i.e. the sodium permeability, but it also directly interferes with carrier functions.

  1. Sulfate transport by chick renal tubule brush-border and basolateral membranes

    SciTech Connect

    Renfro, J.L.; Clark, N.B.; Metts, R.E.; Lynch, M.A.

    1987-01-01

    Brush-border and basolateral membrane vesicles (BBMV and BLMV, respectively) were prepared from chick kidney by a calcium precipitation method and by centrifugation on an 8% Percoll self-generating gradient, respectively. In BBMV a 100-mM Na gluconate gradient, out>in, caused concentrative (/sup 35/S) sulfate uptake approximately fivefold greater at 1 min than at 60 min (equilibrium) whether or not the membranes were short-circuited with 100 mM K gluconate, in=out, plus 20 ..mu..g valinomycin/mg protein. A 48-mM HCO/sub 3//sup -/ gradient, in>out, stimulated a 2.5-fold higher uptake at 1 min than at 60 min, and short circuiting as above had no effect on the magnitude of this response. Imposition of a H/sup +/ gradient caused concentrative uptake fourfold higher at 1 min than at equilibrium. Short circuiting as above or addition of 0.1 mM carbonyl cyanide m-chlorophenylhydrazone (CCCP) significantly inhibited the pH gradient effect. Creation of an inside positive electrical potential with 100 mM K gluconate, out>in, plus valinomycin, also caused concentrative sulfate uptake. Based on inhibitor/competitor effects, these are distinct sulfate transport processes. In chick BLMV, imposition of an HCO/sub 3//sup -/ gradient, in>out, produced concentrative sulfate uptake. 4-Acetamido-4'-isothiocyanostilbene 2,2'-disulfonic acid disodium at 0.1 mM was an effective inhibitor of BLMV bicarbonate-sulfate exchange.

  2. Bacillus thuringiensis delta-endotoxin binding to brush border membrane vesicles of rice stem borers.

    PubMed

    Alcantara, Edwin P; Aguda, Remedios M; Curtiss, April; Dean, Donald H; Cohen, Michael B

    2004-04-01

    The receptor binding step in the molecular mode of action of five delta-endotoxins (Cry1Ab, Cry1Ac, Cry1C, Cry2A, and Cry9C) from Bacillus thuringiensis was examined to find toxins with different receptor sites in the midgut of the striped stem borer (SSB) Chilo suppressalis (Walker) and yellow stem borer (YSB) Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae). Homologous competition assays were used to estimate binding affinities (K(com)) of (125)I-labelled toxins to brush border membrane vesicles (BBMV). The SSB BBMV affinities in decreasing order was: Cry1Ab = Cry1Ac > Cry9C > Cry2A > Cry1C. In YSB, the order of decreasing affinities was: Cry1Ac > Cry1Ab > Cry9C = Cry2A > Cry1C. The number of binding sites (B(max)) estimated by homologous competition binding among the Cry toxins did not affect toxin binding affinity (K(com)) to both insect midgut BBMVs. Results of the heterologous competition binding assays suggest that Cry1Ab and Cry1Ac compete for the same binding sites in SSB and YSB. Other toxins bind with weak (Cry1C, Cry2A) or no affinity (Cry9C) to Cry1Ab and Cry1Ac binding sites in both species. Cry2A had the lowest toxicity to 10-day-old SSB and Cry1Ab and Cry1Ac were the most toxic. Taken together, the results of this study show that Cry1Ab or Cry1Ac could be combined with either Cry1C, Cry2A, or Cry9C for more durable resistance in transgenic rice. Cry1Ab should not be used together with Cry1Ac because a mutation in one receptor site could diminish binding of both toxins. PMID:15027071

  3. Leucine transport in brush border membrane vesicles from freshwater insect larvae.

    PubMed

    Forcella, Matilde; Berra, Elisa; Giacchini, Roberto; Parenti, Paolo

    2006-11-01

    Leucine transport across brush border membrane vesicles prepared from four insect species common to European freshwater streams has been characterized. The species studied were: Ephemera danica (Ephemeroptera: Ephemeridae), Isoperla grammatica (Plecoptera: Perlodidae), Hydropsyche pellucidula (Trichoptera: Hydropsychidae), and Hybomitra bimaculata (Diptera: Tabanidae). The transport differed among the studied taxa for several features, including pH and sodium dependence, substrate affinity and specificity, and efficiency. In H. pellucidula and E. danica, leucine uptake was higher at pH 7.4 than at more alkaline or acidic pH values, whereas in I. grammatica and H. bimaculata, the uptake was rather constant when pH varied from 5.0 to 7.4, then strongly decreased at pH 8.8. All but E. danica displayed a transient intravescicular leucine accumulation in the presence of sodium, suggesting the existence of a cation-leucine symport mechanism. The sodium dependence ranged according to the following order: H. pellucidula > I. grammatica > H. bimaculata > E. danica. Moreover, in H. pellucidula and I. grammatica, the sodium-dependence was stronger at pH 8.8 than at pH 7.4. In E. danica, leucine uptake was sodium-independent at all pH values. The highest value of V(max) (45.3 pmol.s(-1).mg proteins(-1)) was in E. danica, which, however, displayed the lowest affinity (K(m) 137 muM) when compared to the kinetic parameters of other taxa. The V(max) and K(m) values were: 40 and 52.5, 32.1 and 12.5, and 4.5 and 230 for H. bimaculata, H. pellucidula, and I. grammatica, respectively. The obtained results are discussed within our current knowledge of amino acid transport systems in insects.

  4. Binding of Yersinia enterocolitica to rabbit intestinal brush border membranes, mucus, and mucin.

    PubMed Central

    Mantle, M; Basaraba, L; Peacock, S C; Gall, D G

    1989-01-01

    Mucus and its gel-forming glycoprotein component, mucin, are thought to protect the gastrointestinal tract from enteric pathogens by inhibiting their attachment to enterocytes. In this study, we investigated interactions between Yersinia enterocolitica (isogenic strains of virulent and nonvirulent organisms) and crude mucus, highly purified mucin, and brush border membranes (BBMs) isolated from the upper mid-, and distal small intestine and the proximal colon of the rabbit. Adherence of radiolabeled bacteria was assessed to BBMs, mucus, and mucin immobilized in polystyrene microtiter plate wells. Virulent Y. enterocolitica showed saturable binding to mucus, mucin, and BBMs from all four regions of the intestinal tract, although adherence to BBMs was appreciably greater than that to mucus or mucin. Maximal binding of bacteria was higher to BBMs from the distal small intestine and the proximal colon than to those from the upper and mid-small intestine, which may in part explain why the organism localizes to the ileo-caecal regions of the gut. Adherence of virulent Y. enterocolitica to BBMs was significantly reduced in the presence of homologous mucus or mucin preparations. Binding of virulent bacteria appears to depend on plasmid-encoded proteins located on the outer surface membrane, since (i) the isogenic strain lacking the virulence plasmid showed markedly less binding to all BBM, mucus, and mucin preparations; (ii) growth of the virulent strain at 25 degrees C, which inactivates its plasmid, significantly diminished binding to BBMs, mucus, and mucin; and (iii) mild proteolysis substantially decreased adherence of virulent bacteria to BBMs. Compared with rabbit intestinal and colonic mucins, binding of virulent Y. enterocolitica was significantly greater to purified human intestinal mucin and significantly less to rat intestinal mucin. These findings provide support for the role of mucus and mucin in host defense by preventing adherence of virulent Y

  5. Proline transport by brush-border membrane vesicles of lobster antennal glands

    SciTech Connect

    Behnke, R.D.; Wong, R.K.; Huse, S.M.; Reshkin, S.J.; Ahearn, G.A. )

    1990-02-01

    Purified brush-border membrane vesicles (BBMV) of lobster antennal gland labyrinth and bladder were separately formed by a magnesium precipitation technique. L-(3H)proline uptake was stimulated by a transmembrane NaCl gradient (outside (o) greater than inside (i)) to a greater extent in BBMV from labyrinth than those from the bladder. Detailed study of the labyrinth proline-transport processes revealed a specific dependence on NaCl, with negligible stimulatory effects by NaSCN, Na-gluconate, or KCl. A transmembrane proton gradient (o greater than i) was without stimulatory effect on proline transport. A transmembrane potential difference alone, in the presence of equilibrated NaCl and L-(3H)proline, led to net influx of the labeled amino acid, suggesting that the uptake process was electrogenic and capable of bringing about the net transfer of positive charge to the vesicle interior. Although a transmembrane Na gradient alone, in the presence of equilibrated Cl and L-(3H)proline, was able to bring about the net influx of the amino acid, a transmembrane Cl gradient alone under Na- and L-(3H)proline-equilibrated conditions was not, suggesting that only the Na gradient could energize the carrier process through cotransport, while the anion served an essential activating role. Proline influx by these vesicles occurred by the combination of at least one saturable Michaelis-Menten carrier system (apparent Kt = 0.37 mM; apparent JM = 1.19 nmol.mg protein-1.10 s-1) and apparent diffusion (P = 0.33 nmol.mg protein-1.10 s-1.mM-1). Static head analysis of the transport process suggested a cotransport stoichiometry of 2 Na:1 proline with essential activation by Cl ion.

  6. Characterization of calcium binding to brush-border membranes from rat duodenum.

    PubMed Central

    Miller, A; Li, S T; Bronner, F

    1982-01-01

    The Ca2+-binding properties of isolated brush-border membranes at physiological ionic strength and pH were examined by rapid Millipore filtration. A comprehensive analysis of the binding data suggested the presence of two types of Ca2+-binding sites. The high-affinity sites, Ka = (6.3 +/- 3.3) X 10(5) M-1 (mean +/- S.E.M.), bound 0.8 +/- 0.1 nmol of Ca2+/mg of protein and the low-affinity sites, Ka = (2.8 +/- 0.3) X 10(2) M-1, bound 33 +/- 3.5 nmol of Ca2+/mg of protein. The high-affinity site exhibited a selectivity for Ca2+, since high concentrations of competing bivalent cations were required to inhibit Ca2+ binding. The relative effectiveness of the competing cations (1 and 10 mM) for the high-affinity site was Mn2+ approximately equal to Sr2+ greater than Ba2+ greater than Mg2+. Data from the pH studies, treatment of the membranes with carbodi-imide and extraction of phospholipids with aqueous acetone and NH3 provided evidence that the low-affinity sites were primarily phospholipids and the high-affinity sites were either phosphoprotein or protein with associated phospholipid. Two possible roles for the high-affinity binding sites are suggested. Either high-affinity Ca2+ binding is involved with specific enzyme activities or Ca2+ transport across the luminal membrane occurs via a Ca2+ channel which contains a high-affinity Ca2+-specific binding site that may regulate the intracellular Ca2+ concentration and gating of the channel. PMID:7165733

  7. Hormone induced expression of brush border lactase in suckling rat intestine.

    PubMed

    Chaudhry, Kamaljit Kaur; Mahmood, Safrun; Mahmood, Akhtar

    2008-05-01

    The postnatal development of intestine is associated with a decline in brush border lactase activity in rodents. This is similar to adulthood hypolactasia, a phenomenon prevalent in humans worldwide. In the present study, the effect of luminal proteases from adult rat intestine was studied in vitro on intestinal lactase activity in saline control, thyroxine, insulin and cortisone treated rat pups. Lactase levels were determined by enzyme analysis and Western blotting. mRNA levels encoding lactase were determined by Northern blotting. Administration of thyroxine for 4 days reduced (P<0.05) lactase activity, but insulin treatment had no effect in 8-day-old rat intestine. However, cortisone administration augmented (P<0.01) lactase activity, under these conditions. Western blot analysis showed decreased lactase signal corresponding to 220-kDa protein band in thyroxine treated animals. However, the intensity of lactase signal was high in cortisone treated animals compared to controls. mRNA levels encoding lactase showed a 6.8-kb mRNA transcript in saline and hormone treated rats. mRNA levels encoding lactase were increased in cortisone treated animals but were reduced in thyroxine injected pups compared to controls. Microvillus membranes from saline (P<0.01) and thyroxine (P<0.05) or insulin (P<0.01) treated rats upon incubation with luminal wash from adult rat intestine showed a significant decline in lactase activity. These findings suggest that thyroxine, insulin or cortisone induced changes in lactase expression in suckling rat intestine make it susceptible to luminal proteases, which may in part be responsible for observed maturational decline in lactase activity in adult rat intestine.

  8. Ezetimibe Promotes Brush Border Membrane-to-Lumen Cholesterol Efflux in the Small Intestine.

    PubMed

    Nakano, Takanari; Inoue, Ikuo; Takenaka, Yasuhiro; Ono, Hiraku; Katayama, Shigehiro; Awata, Takuya; Murakoshi, Takayuki

    2016-01-01

    Ezetimibe inhibits Niemann-Pick C1-like 1 (NPC1L1), an apical membrane cholesterol transporter of enterocytes, thereby reduces intestinal cholesterol absorption. This treatment also increases extrahepatic reverse cholesterol transport via an undefined mechanism. To explore this, we employed a trans-intestinal cholesterol efflux (TICE) assay, which directly detects circulation-to-intestinal lumen 3H-cholesterol transit in a cannulated jejunal segment, and found an increase of TICE by 45%. To examine whether such increase in efflux occurs at the intestinal brush border membrane(BBM)-level, we performed luminal perfusion assays, similar to TICE but the jejunal wall was labelled with orally-given 3H-cholesterol, and determined elevated BBM-to-lumen cholesterol efflux by 3.5-fold with ezetimibe. Such increased efflux probably promotes circulation-to-lumen cholesterol transit eventually; thus increases TICE. Next, we wondered how inhibition of NPC1L1, an influx transporter, resulted in increased efflux. When we traced orally-given 3H-cholesterol in mice, we found that lumen-to-BBM 3H-cholesterol transit was rapid and less sensitive to ezetimibe treatment. Comparison of the efflux and fractional cholesterol absorption revealed an inverse correlation, indicating the efflux as an opposite-regulatory factor for cholesterol absorption efficiency and counteracting to the naturally-occurring rapid cholesterol influx to the BBM. These suggest that the ezetimibe-stimulated increased efflux is crucial in reducing cholesterol absorption. Ezetimibe-induced increase in cholesterol efflux was approximately 2.5-fold greater in mice having endogenous ATP-binding cassette G5/G8 heterodimer, the major sterol efflux transporter of enterocytes, than the knockout counterparts, suggesting that the heterodimer confers additional rapid BBM-to-lumen cholesterol efflux in response to NPC1L1 inhibition. The observed framework for intestinal cholesterol fluxes may provide ways to modulate the flux

  9. Ezetimibe Promotes Brush Border Membrane-to-Lumen Cholesterol Efflux in the Small Intestine

    PubMed Central

    Nakano, Takanari; Inoue, Ikuo; Takenaka, Yasuhiro; Ono, Hiraku; Katayama, Shigehiro; Awata, Takuya; Murakoshi, Takayuki

    2016-01-01

    Ezetimibe inhibits Niemann-Pick C1-like 1 (NPC1L1), an apical membrane cholesterol transporter of enterocytes, thereby reduces intestinal cholesterol absorption. This treatment also increases extrahepatic reverse cholesterol transport via an undefined mechanism. To explore this, we employed a trans-intestinal cholesterol efflux (TICE) assay, which directly detects circulation-to-intestinal lumen 3H-cholesterol transit in a cannulated jejunal segment, and found an increase of TICE by 45%. To examine whether such increase in efflux occurs at the intestinal brush border membrane(BBM)-level, we performed luminal perfusion assays, similar to TICE but the jejunal wall was labelled with orally-given 3H-cholesterol, and determined elevated BBM-to-lumen cholesterol efflux by 3.5-fold with ezetimibe. Such increased efflux probably promotes circulation-to-lumen cholesterol transit eventually; thus increases TICE. Next, we wondered how inhibition of NPC1L1, an influx transporter, resulted in increased efflux. When we traced orally-given 3H-cholesterol in mice, we found that lumen-to-BBM 3H-cholesterol transit was rapid and less sensitive to ezetimibe treatment. Comparison of the efflux and fractional cholesterol absorption revealed an inverse correlation, indicating the efflux as an opposite-regulatory factor for cholesterol absorption efficiency and counteracting to the naturally-occurring rapid cholesterol influx to the BBM. These suggest that the ezetimibe-stimulated increased efflux is crucial in reducing cholesterol absorption. Ezetimibe-induced increase in cholesterol efflux was approximately 2.5-fold greater in mice having endogenous ATP-binding cassette G5/G8 heterodimer, the major sterol efflux transporter of enterocytes, than the knockout counterparts, suggesting that the heterodimer confers additional rapid BBM-to-lumen cholesterol efflux in response to NPC1L1 inhibition. The observed framework for intestinal cholesterol fluxes may provide ways to modulate the flux

  10. In Vivo, Villin Is Required for Ca2+-Dependent F-Actin Disruption in Intestinal Brush Borders

    PubMed Central

    Ferrary, Evelyne; Cohen-Tannoudji, Michel; Pehau-Arnaudet, Gérard; Lapillonne, Alexandre; Athman, Rafika; Ruiz, Tereza; Boulouha, Lilia; El Marjou, Fatima; Doye, Anne; Fontaine, Jean-Jacques; Antony, Claude; Babinet, Charles; Louvard, Daniel; Jaisser, Frédéric; Robine, Sylvie

    1999-01-01

    Villin is an actin-binding protein localized in intestinal and kidney brush borders. In vitro, villin has been demonstrated to bundle and sever F-actin in a Ca2+-dependent manner. We generated knockout mice to study the role of villin in vivo. In villin-null mice, no noticeable changes were observed in the ultrastructure of the microvilli or in the localization and expression of the actin-binding and membrane proteins of the intestine. Interestingly, the response to elevated intracellular Ca2+ differed significantly between mutant and normal mice. In wild-type animals, isolated brush borders were disrupted by the addition of Ca2+, whereas Ca2+ had no effect in villin-null isolates. Moreover, increase in intracellular Ca2+ by serosal carbachol or mucosal Ca2+ ionophore A23187 application abolished the F-actin labeling only in the brush border of wild-type animals. This F-actin disruption was also observed in physiological fasting/refeeding experiments. Oral administration of dextran sulfate sodium, an agent that causes colonic epithelial injury, induced large mucosal lesions resulting in a higher death probability in mice lacking villin, 36 ± 9.6%, compared with wild-type mice, 70 ± 8.8%, at day 13. These results suggest that in vivo, villin is not necessary for the bundling of F-actin microfilaments, whereas it is necessary for the reorganization elicited by various signals. We postulate that this property might be involved in cellular plasticity related to cell injury. PMID:10459016

  11. Uptake of /sup 75/Se-selenite by brush border membrane vesicles from chick duodenum stimulated by vitamin D

    SciTech Connect

    Mykkanen, H.M.; Wasserman, R.H.

    1989-02-01

    Brush border membrane vesicles were isolated from mucosal homogenates of duodena from normal, rachitic and vitamin D-treated rachitic chicks using a discontinuous sucrose gradient, and further purified by glycerol gradient centrifugation. In vitro uptake of 75Se-selenite by purified brush border membrane vesicles was studied using a rapid filtration technique. The time course of 75Se uptake was non-linear; rapid initial binding was followed by a gradual decrease in the rate of uptake until an equilibrium value was reached at 60-120 min. The initial binding at 36 s was not affected by selenite concentration in the incubation buffer, while the fractional rate of uptake between the 36 s and 2 min time periods was clearly lower with 1 mM Se than with 4-100 microM Se. 75Se uptake did not show any dependency on the external Na-gradient, nor could it be inhibited by other anions (arsenate, phosphate). Treatment of rachitic chicks either with cholecalciferol (500 Iu, 72 h) or with 1,25(OH)2-cholecalciferol (0.5 microgram given 16 h prior to isolation of the vesicles) significantly enhanced 75Se uptake. A threefold excess of mannitol in the outside buffer reduced 75Se uptake by vesicles from vitamin D-deficient and D-treated chicks 60% and 35% respectively, but had no effect on vesicles from vitamin D-treated chicks preloaded with 75Se. Neither saponin treatment nor excess cold selenite could release the label from the vesicles preloaded with 75Se. These data are compatible with the hypothesis that selenite easily crosses the brush border membrane into the intravesicular space and, once inside, is tightly bound by the membrane.

  12. Squalamine, a novel cationic steroid, specifically inhibits the brush-border Na+/H+ exchanger isoform NHE3.

    PubMed

    Akhter, S; Nath, S K; Tse, C M; Williams, J; Zasloff, M; Donowitz, M

    1999-01-01

    Squalamine, an endogenous molecule found in the liver and other tissues of Squalus acanthias, has antibiotic properties and causes changes in endothelial cell shape. The latter suggested that its potential targets might include transport proteins that control cell volume or cell shape. The effect of purified squalamine was examined on cloned Na+/H+ exchanger isoforms NHE1, NHE2, and NHE3 stably transfected in PS120 fibroblasts. Squalamine (1-h pretreatment) decreased the maximal velocity of rabbit NHE3 in a concentration-dependent manner (13, 47, and 57% inhibition with 3, 5, and 7 micrograms/ml, respectively) and also increased K'[H+]i. Squalamine did not affect rabbit NHE1 or NHE2 function. The inhibitory effect of squalamine was 1) time dependent, with no effect of immediate addition and maximum effect with 1 h of exposure, and 2) fully reversible. Squalamine pretreatment of the ileum for 60 min inhibited brush-border membrane vesicle Na+/H+ activity by 51%. Further investigation into the mechanism of squalamine's effects showed that squalamine required the COOH-terminal 76 amino acids of NHE3. Squalamine had no cytotoxic effect at the concentrations studied, as indicated by monitoring lactate dehydrogenase release. These results indicate that squalamine 1) is a specific inhibitor of the brush-border NHE isoform NHE3 and not NHE1 or NHE2, 2) acts in a nontoxic and fully reversible manner, and 3) has a delayed effect, indicating that it may influence brush-border Na+/H+ exchanger function indirectly, through an intracellular signaling pathway or by acting as an intracellular modulator. PMID:9886929

  13. Hypothyroidism increases osmotic water permeability (Pf) in the developing renal brush border membrane.

    PubMed

    Mulder, Jaap; Haddad, Maha N; Vernon, Kimberly; Baum, Michel; Quigley, Raymond

    2003-06-01

    The osmotic water permeability (Pf) of the rabbit proximal tubule brush border membrane vesicles (BBMV) increases during maturation and is mediated by an increase in aquaporin-1 (AQP1) protein expression. Serum thyroid hormone levels increase after birth and have been shown to play a role in the maturation of other renal transport functions. We examined the hypothesis that thyroid hormone plays a role in the maturational increase in osmotic water permeability. Hypothyroidism was induced by addition of 0.1% propylthiouracil (PTU) to the drinking water of pregnant rabbits (starting 9 d before delivery) and was continued until the rabbits were studied as adults (9-11 wk). Some animals received thyroid hormone replacement by daily injection with triiodothyronine (T3; 10 microg/100 g body weight) for three days before study. Pf was found to be higher in BBMV from hypothyroid (82.7 +/- 5.5 microm/s) than from euthyroid (60.6 +/- 4.0 microm/s) and T3-replacement rabbits (69.0 +/- 5.0 microm/s) (p < 0.05). The activation energy (Ea; in kcal/deg.mol) of Pf was not different among the three experimental groups (euthyroid 5.6 +/- 0.9, hypothyroid 4.9 +/- 0.8, T3-replacement 5.0 +/- 1.0; p = NS), nor was the percentage mercury inhibition of Pf (euthyroid 66.5 +/- 5.3, hypothyroid 74.2 +/- 3.2 and T3-replacement 73.1 +/- 4.3; p = NS). AQP1 expression, measured by immunoblotting, was highest in BBMV from hypothyroid rabbits (p < 0.05). Membrane fluidity, measured as steady-state generalized polarization (GP) of Laurdan, which is inversely related to membrane fluidity, was significantly different between the three groups (GP: euthyroid 0.307 +/- 0.004, hypothyroid 0.271 +/- 0.004 and T3-replacement 0.287 +/- 0.003; for all p < 0.05). These data demonstrate that the maturational increase in thyroid hormone levels is not responsible for the maturational increase in water transport. Surprisingly, congenital hypothyroidism in rabbits is associated with an increased Pf when rabbits

  14. Characterization of the fetal glucose transporter in rabbit kidney. Comparison with the adult brush border electrogenic Na+-glucose symporter.

    PubMed Central

    Beck, J C; Lipkowitz, M S; Abramson, R G

    1988-01-01

    Glucose transport was characterized in rabbit renal brush border membrane vesicles (BBMV) of the fetus late in gestation. Highly purified, osmotically reactive fetal BBMV contained a glucose transporter that was qualitatively indistinguishable from that in the adult: both are concentrative, Na+ dependent, electrogenic, stereospecific, and sensitive to phlorizin. Although the apparent Km for glucose is similar in the fetus and adult, the Vmax is significantly higher in the adult. When the membrane potential was clamped with a protonophore, this difference diminished; however, Vmax remained significantly higher in adult BBMV. This postnatal increase in Vmax was paralleled by a similar increase in the number of phlorizin binding sites. These findings indicate that the maturational increase in glucose transport is, in part, consequent to a more favorable electrical potential for Na+-dependent glucose transport and, in part, the result of the insertion of new transporters. The homogenate activity of several brush border enzymes also demonstrated significant maturational increases. The magnitude of these changes was variable and enzyme dependent. These combined observations suggest that mature expression of membrane proteins (transporters and enzymes) occurs at different stages of development of renal proximal tubule cells. PMID:3403709

  15. Binding Analyses of Bacillus thuringiensis Cry δ-Endotoxins Using Brush Border Membrane Vesicles of Ostrinia nubilalis

    PubMed Central

    Hua, Gang; Masson, Luke; Jurat-Fuentes, Juan Luis; Schwab, George; Adang, Michael J.

    2001-01-01

    Transgenic corn expressing the Bacillus thuringiensis Cry1Ab gene is highly insecticidal to Ostrinia nubilalis (European corn borer) larvae. We ascertained whether Cry1F, Cry9C, or Cry9E recognizes the Cry1Ab binding site on the O. nubilalis brush border by three approaches. An optical biosensor technology based on surface plasmon resonance measured binding of brush border membrane vesicles (BBMV) injected over a surface of immobilized Cry toxin. Preincubation with Cry1Ab reduced BBMV binding to immobilized Cry1Ab, whereas preincubation with Cry1F, Cry9C, or Cry9E did not inhibit BBMV binding. BBMV binding to a Cry1F-coated surface was reduced when vesicles were preincubated in Cry1F or Cry1Ab but not Cry9C or Cry9E. A radioligand approach measured 125I-Cry1Ab toxin binding to BBMV in the presence of homologous (Cry1Ab) and heterologous (Cry1Ac, Cry1F, Cry9C, or Cry9E) toxins. Unlabeled Cry1Ac effectively competed for 125I-Cry1Ab binding in a manner comparable to Cry1Ab itself. Unlabeled Cry9C and Cry9E toxins did not inhibit 125I-Cry1Ab binding to BBMV. Cry1F inhibited 125I-Cry1Ab binding at concentrations greater than 500 nM. Cry1F had low-level affinity for the Cry1Ab binding site. Ligand blot analysis identified Cry1Ab, Cry1Ac, and Cry1F binding proteins in BBMV. The major Cry1Ab signals on ligand blots were at 145 kDa and 154 kDa, but a strong signal was present at 220 kDa and a weak signal was present at 167 kDa. Cry1Ac and Cry1F binding proteins were detected at 220 and 154 kDa. Anti-Manduca sexta aminopeptidase serum recognized proteins of 145, 154, and 167 kDa, and anti-cadherin serum recognized the 220 kDa protein. We speculate that isoforms of aminopeptidase and cadherin in the brush border membrane serve as Cry1Ab, Cry1Ac, and Cry1F binding proteins. PMID:11157257

  16. High affinity 3H-Phe uptake by brush border membrane vesicles from whole larvae of Aedes aegypti (AaBMVw)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Brush border membrane vesicles from whole Aedes aegypti larvae (AaBBMVw) are confirmed to be valid preparations for membrane transport studies. The Abdul-Rauf and Ellar method was used to isolate AaBBMVw that were frozen, stored for several months, transported to a distant site, thawed and used to s...

  17. Effects of different Brush Border Membrane Vesicle isolation protocols on proteomic analysis of Cry1Ac binding proteins from the midgut of Helicoverpa armigera

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The brush border membrane vesicles (BBMV) isolated from midgut cells of insect have been widely used for studying of the binding receptors and action mode of Cry proteins produced by Bacillus thuringiensis (Bt). There are several methods for isolating insect BBMV used in one-dimension electrophoresi...

  18. Microbial sphingomyelinase induces RhoA-mediated reorganization of the apical brush border membrane and is protective against invasion.

    PubMed

    Saslowsky, David E; Thiagarajah, Jay R; McCormick, Beth A; Lee, Jean C; Lencer, Wayne I

    2016-04-01

    The apical brush border membrane (BBM) of intestinal epithelial cells forms a highly structured and dynamic environmental interface that serves to regulate cellular physiology and block invasion by intestinal microbes and their products. How the BBM dynamically responds to pathogenic and commensal bacterial signals can define intestinal homeostasis and immune function. We previously found that in model intestinal epithelium, the conversion of apical membrane sphingomyelin to ceramide by exogenous bacterial sphingomyelinase (SMase) protected against the endocytosis and toxicity of cholera toxin. Here we elucidate a mechanism of action by showing that SMase induces a dramatic, reversible, RhoA-dependent alteration of the apical cortical F-actin network. Accumulation of apical membrane ceramide is necessary and sufficient to induce the actin phenotype, and this coincides with altered membrane structure and augmented innate immune function as evidenced by resistance to invasion by Salmonella. PMID:26864627

  19. Microbial sphingomyelinase induces RhoA-mediated reorganization of the apical brush border membrane and is protective against invasion

    PubMed Central

    Saslowsky, David E.; Thiagarajah, Jay R.; McCormick, Beth A.; Lee, Jean C.; Lencer, Wayne I.

    2016-01-01

    The apical brush border membrane (BBM) of intestinal epithelial cells forms a highly structured and dynamic environmental interface that serves to regulate cellular physiology and block invasion by intestinal microbes and their products. How the BBM dynamically responds to pathogenic and commensal bacterial signals can define intestinal homeostasis and immune function. We previously found that in model intestinal epithelium, the conversion of apical membrane sphingomyelin to ceramide by exogenous bacterial sphingomyelinase (SMase) protected against the endocytosis and toxicity of cholera toxin. Here we elucidate a mechanism of action by showing that SMase induces a dramatic, reversible, RhoA-dependent alteration of the apical cortical F-actin network. Accumulation of apical membrane ceramide is necessary and sufficient to induce the actin phenotype, and this coincides with altered membrane structure and augmented innate immune function as evidenced by resistance to invasion by Salmonella. PMID:26864627

  20. Kinetics of D-glucose and L-leucine transport into sheep and pig intestinal brush border membrane vesicles.

    PubMed

    Wolffram, S; Eggenberger, E; Scharrer, E

    1986-01-01

    The kinetic parameters (Vmax, Kt) of Na+-dependent D-glucose transport into brush border membrane vesicles (BBMV) from sheep and pig jejunum were determined. Due to the fermentation of ingested carbohydrates in the rumen the small intestine of ruminants (sheep) has to absorb much less glucose than the small intestine of monogastric omnivores (pigs) or herbivores. Kinetic analysis of the concentration dependence of D-glucose transport revealed a ten-fold smaller Vmax value combined with a five times lower Kt value in sheep BBMV compared with pig BBMV. The Vmax value for L-leucine transport did not differ between the two species investigated, whereas the Kt value in the sheep exceeded that in the pig. It is concluded from these results that the mechanism for Na+-dependent D-glucose transport in ruminants is adapted to the small amounts of carbohydrates reaching the small intestine.

  1. Cytokine modulation of Na(+)-dependent glutamine transport across the brush border membrane of monolayers of human intestinal Caco-2 cells.

    PubMed Central

    Souba, W W; Copeland, E M

    1992-01-01

    Previous studies have demonstrated that Na(+)-dependent brush border glutamine transport is diminished in septic patients. To examine the potential regulation of this decreased transport by endotoxin, cytokines, or glucocorticoids, the human intestinal Caco-2 cell line was studied in vitro. Na(+)-dependent glutamine transport across the apical brush border membrane was assayed in confluent monolayers of differentiated cells that were 10 days old. Uptake of 50 microM glutamine was determined after a 12-hour incubation with varying doses (10 to 1000 U/mL) of tumor necrosis factor-alpha, interleukin-1, interleukin-6, interferon-gamma, and various combinations of these cytokines. Studies were also done in cells incubated with E. coli endotoxin (1 micrograms/mL) or dexamethasone (1 and 10 microM). Endotoxin, tumor necrosis factor, interleukin-1, and interleukin-6 alone and in combination did not significantly reduce Na(+)-dependent glutamine transport across the brush border of Caco-2 cells. Dexamethasone decreased glutamine transport by 20%, but this decrease was not apparent for 48 hours. Interferon consistently decreased glutamine transport by 30%; this was due to a reduction in carrier maximal transport velocity (3427 +/- 783 pmol/mg protein/minute in controls versus 2279 +/- 411 in interferon, p less than 0.05) rather than a change in Km (276 +/- 29 microM in controls versus 333 +/- 74 in interferon, p = not interferon + dexamethasone + tumor necrosis factor + interleukin-1 resulted in a 38% decrease in transport activity. Cytokines and glucocorticoids may work independently and synergistically in regulating Na(+)-dependent brush border glutamine transport in human intestinal cells. Whether these signal molecules play a central role in the cause of the diminished brush border glutamine transport that occurs in septic patients requires further study. PMID:1616390

  2. (Na+ + K+)-ATPase and plasma membrane polarity of intestinal epithelial cells: presence of a brush border antigen in the distal large intestine that is immunologically related to beta subunit

    PubMed Central

    1989-01-01

    The previously produced monoclonal antibody IEC 1/48 against cultured rat intestinal crypt cells (Quaroni, A., and K. J. Isselbacher. 1981. J. Natl. Cancer Inst. 67:1353-1362) was extensively characterized and found to be directed against the beta subunit of (Na+ + K+)-ATPase as assessed by immunological and enzymatic criteria. Under nondenaturing conditions the antibody precipitated the alpha-beta enzyme complex (98,000 and 48,000 Mr). This probe, together with the monoclonal antibody C 62.4 against the alpha subunit (Kashgarian, M., D. Biemesderfer, M. Caplan, and B. Forbush. 1985. Kidney Int. 28:899-913), was used to localize (Na+ + K+)-ATPase in epithelial cells along the rat intestinal tract by immunofluorescence and immunoelectron microscopy. Both antibodies exclusively labeled the basolateral membrane of small intestine and proximal colon epithelial cells. However, in the distal colon, IEC 1/48, but not C 62.4, also labeled the brush border membrane. The cross-reacting beta-subunit-like antigen on the apical cell pole was tightly associated with isolated brush borders but was apparently devoid of (Na+ + K+)-ATPase activity. Subcellular fractionation of colonocytes in conjunction with limited proteolysis and surface radioiodination of intestinal segments suggested that the cross-reacting antigen in the brush border may be very similar to the beta subunit. The results support the notion that in the small intestine and proximal colon the enzyme subunits are exclusively targeted to the basolateral membrane while in the distal colon nonassembled beta subunit or a beta-subunit-like protein is also transported to the apical cell pole. PMID:2549076

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

    PubMed

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

    2012-04-01

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

  4. K⁺-dependent ³H-D-glucose transport by hepatopancreatic brush border membrane vesicles of a marine shrimp.

    PubMed

    Obi, Ijeoma E; Sterling, Kenneth M; Ahearn, Gregory A

    2013-01-01

    The effects of sodium, potassium, sugar inhibitors, and membrane potential on ³H-D-glucose uptake by hepatopancreatic epithelial brush border membrane vesicles (BBMV) of the Atlantic marine shrimp, Litopenaeus setiferus, were investigated. Brush border membrane vesicles were prepared using a MgCl₂/EGTA precipitation method and uptake experiments were conducted using a high speed filtration technique. ³H-D-Glucose uptake was stimulated by both sodium and potassium and these transport rates were almost doubled in the presence of an inside-negative-induced membrane potential. Kinetics of ³H-D-glucose influx were hyperbolic functions of both external Na⁺ or K⁺, and an induced membrane potential increased influx J(max) and lowered K(m) in both salts. ³H-D-Glucose influx versus [glucose] in both Na⁺ or K⁺ media also displayed Michaelis-Menten properties that were only slightly affected by induced membrane potential. Phloridzin was a poor inhibitor of 0.5 mM ³H-D-glucose influx, requiring at least 5 mM in NaCl and 10 mM in KCl to significantly reduce hexose transport. Several sugars (D-galactose, α-methyl-D-gluco-pyranoside, unlabeled D-glucose, D-fructose, and D-mannose) were used at 75 mM as potential inhibitors of 0.1 mM ³H-D-glucose influx. Only unlabeled D-glucose, D-fructose, and D-mannose significantly (p < 0.05) reduced labeled glucose transport. An additional experiment using increasing concentrations of D-mannose (0, 10, 25, 75, and 100 mM) showed this hexose to be an effective inhibitor of 0.1 mM ³H-D-glucose uptake at concentrations of 75 mM and higher. As a whole these results suggest that ³H-D-glucose transport by hepatopancreatic BBMV occurs by a carrier system that is able to use both Na⁺ and K⁺ as drivers, is enhanced by membrane potential, is relatively refractory to phloridzin, and is only inhibited by itself, D-fructose, and D-mannose. These properties are similar to those exhibited by the mammalian SLC5A9/SGLT4 transporter

  5. Uptake and binding of /sup 125/I-calmodulin by isolated rat renal brush border membrane vesicles

    SciTech Connect

    Meezan, E.; Elgavish, A.; Wallace, R.W.

    1986-05-01

    The authors have investigated the interaction of /sup 125/I-calmodulin with isolated rat renal brush border membrane vesicles (BBV) using an experimental protocol which allows us to distinguish between ligand binding to the outside of the vesicles vs. uptake and possible binding to the vesicle interior. By examining the association of /sup 125/I-calmodulin with BBV as a function of medium osmolarity (300-1100 mosm) to alter intravesicular space, virtually all ligand interaction with BBV was found to represent uptake of intact /sup 125/I-calmodulin into the intravesicular space. Uptake appeared specific by the following criteria: (1) it was largely calcium dependent (2) it was inhibited in a dose dependent fashion by calmodulin and the homologous protein troponin C, but not by unrelated proteins (lysozyme, cytochrome C, insulin) (3) it was inhibited by known calmodulin antagonists (calmidazolium, mellitin, trifluoperazine). Calmodulin uptake may be followed by binding of /sup 125/I-calmodulin to intravesicular BBV proteins; calmodulin-binding proteins in BBV with molecular weights of 143K, 118K, 50K, 47.5K, 46.5K and 35K were identified by Western blotting techniques. The specific association of /sup 125/I-calmodulin with isolated BBV is of interest in regard to the possible role of this calcium regulatory protein in the protein reabsorptive and ion transport functions of this renal tubular membrane fraction.

  6. Influence of class B scavenger receptors on cholesterol flux across the brush border membrane and intestinal absorption.

    PubMed

    Nguyen, David V; Drover, Victor A; Knopfel, Martin; Dhanasekaran, Padmaja; Hauser, Helmut; Phillips, Michael C

    2009-11-01

    To learn more about how the step of cholesterol uptake into the brush border membrane (BBM) of enterocytes influences overall cholesterol absorption, we measured cholesterol absorption 4 and 24 h after administration of an intragastric bolus of radioactive cholesterol in mice with scavenger receptor class B, type 1 (SR-BI) and/or cluster determinant 36 (CD36) deleted. The cholesterol absorption efficiency is unaltered by deletion of either one or both of the receptors. In vitro determinations of the cholesterol uptake specific activity of the BBM from the mice reveal that the scavenger receptors facilitate cholesterol uptake into the proximal BBM. It follows that cholesterol uptake into the BBM is not normally rate-limiting for the cholesterol absorption process in vivo; a subsequent step, such as NPC1L1-mediated transfer from the BBM into the interior of the enterocyte, is rate-limiting. The absorption of dietary cholesterol after 4 h in mice lacking SR-BI and/or CD36 and fed a high-fat/high-cholesterol diet is delayed to more distal regions of the small intestine. This effect probably arises because ATP binding cassette half transporters G5 and G8-mediated back flux of cholesterol from the BBM to the lumen of the small intestine limits absorption and causes the local cholesterol uptake facilitated by SR-BI and CD36 to become rate-limiting under this dietary condition. PMID:19454765

  7. Cadmium inhibition of L-alanine transport into renal brush border membrane vesicles isolated from the winter flounder (Pseudopleuronectes americanus)

    SciTech Connect

    Bevan, C.; Kinne-Saffran, E.; Foulkes, E.C.; Kinne, R.K. )

    1989-12-01

    Using isolated brush border membrane vesicles from the kidney of the winter flounder (Pseudopleuronectes americanus), we have studied the effect of cadmium on L-alanine transport. Pretreatment of vesicles with 0.1 mM Cd{sup 2+} resulted in inhibition of L-alanine uptake in the presence of a NaCl (but not KCl) gradient. Inhibition was due to a specific interaction with the sodium-alanine cotransport system and not a change in the driving forces for alanine transport, since Cd{sup 2+} did not affect sodium-dependent D-glucose uptake. The effect of Cd{sup 2+} on Na{sup +}-alanine cotransport showed mixed-type inhibition which is only partially reversible by EDTA. Cd{sup 2+} uptake itself was shown to be time and temperature dependent, resulting in binding to both sides of the membrane. No direct correlation was possible between inhibition of L-alanine transport and the amount of Cd{sup 2+} taken up by the membranes. Nevertheless, the striking time dependence of the effect of Cd{sup 2+} on sodium-dependent L-alanine uptake and the inability of EDTA to reverse the inhibitory action of Cd{sup 2+} suggest that Cd{sup 2+} inhibits Na+-alanine cotransport at the cytoplasmic side of the membrane.

  8. Exploring the Midgut Transcriptome and Brush Border Membrane Vesicle Proteome of the Rice Stem Borer, Chilo suppressalis (Walker)

    PubMed Central

    Peng, Chuanhua; Wang, Xiaoping; Li, Fei; Lin, Yongjun

    2012-01-01

    The rice stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), is one of the most detrimental pests affecting rice crops. The use of Bacillus thuringiensis (Bt) toxins has been explored as a means to control this pest, but the potential for C. suppressalis to develop resistance to Bt toxins makes this approach problematic. Few C. suppressalis gene sequences are known, which makes in-depth study of gene function difficult. Herein, we sequenced the midgut transcriptome of the rice stem borer. In total, 37,040 contigs were obtained, with a mean size of 497 bp. As expected, the transcripts of C. suppressalis shared high similarity with arthropod genes. Gene ontology and KEGG analysis were used to classify the gene functions in C. suppressalis. Using the midgut transcriptome data, we conducted a proteome analysis to identify proteins expressed abundantly in the brush border membrane vesicles (BBMV). Of the 100 top abundant proteins that were excised and subjected to mass spectrometry analysis, 74 share high similarity with known proteins. Among these proteins, Western blot analysis showed that Aminopeptidase N and EH domain-containing protein have the binding activities with Bt-toxin Cry1Ac. These data provide invaluable information about the gene sequences of C. suppressalis and the proteins that bind with Cry1Ac. PMID:22666467

  9. Myosin Ia is required for CFTR brush border membrane trafficking and ion transport in the mouse small intestine.

    PubMed

    Kravtsov, Dmitri V; Caputo, Christina; Collaco, Anne; Hoekstra, Nadia; Egan, Marie E; Mooseker, Mark S; Ameen, Nadia A

    2012-08-01

    In enterocytes of the small intestine, endocytic trafficking of CFTR channels from the brush border membrane (BBM) to the subapical endosomes requires the minus-end motor, myosin VI (Myo6). The subapical localization of Myo6 is dependent on myosin Ia (Myo1a) the major plus-end motor associated with the BBM, suggestive of functional synergy between these two motors. In villus enterocytes of the Myo1a KO mouse small intestine, CFTR accumulated in syntaxin-3 positive subapical endosomes, redistributed to the basolateral domain and was absent from the BBM. In colon, where villi are absent and Myo1a expression is low, CFTR exhibited normal localization to the BBM in the Myo1a KO similar to WT. cAMP-stimulated CFTR anion transport in the small intestine was reduced by 58% in the KO, while anion transport in the colon was comparable to WT. Co-immunoprecipitation confirmed the association of CFTR with Myo1a. These data indicate that Myo1a is an important regulator of CFTR traffic and anion transport in the BBM of villus enterocytes and suggest that Myo1a may power apical CFTR movement into the BBM from subapical endosomes. Alternatively, it may anchor CFTR channels in the BBM of villus enterocytes as was proposed for Myo1a's role in BBM localization of sucrase-isomaltase. PMID:22510086

  10. Freeze-thaw and high-voltage discharge allow macromolecule uptake into ileal brush-border vesicles

    SciTech Connect

    Donowitz, M.; Emmer, E.; McCullen, J.; Reinlib, L.; Cohen, M.E.; Rood, R.P.; Madara, J.; Sharp, G.W.G.; Murer, H.; Malmstrom, K.

    1987-06-01

    High-voltage discharge or one cycle of freeze-thawing are shown to transiently permeabilize rabbit ileal brush-border membrane vesicles to macromolecules. Uptake of the radiolabeled macromolecule dextran, mol wt 70,000, used as a marker for vesicle permeability, was determined by a rapid filtration technique, with uptake defined as substrate associated with the vesicle and releasable after incubation of vesicles with 0.1% saponin. Dextran added immediately after electric shock (2000 V) or at the beginning of one cycle of freeze-thawing was taken up approximately eightfold compared with control. ATP also was taken up into freeze-thawed vesicles, whereas there was no significant uptake into control vesicles. The increase in vesicle permeability was reversible, based on Na-dependent D-glucose uptake being decreased when studied 5 but not 15 min after electric shock, and was not significantly decreased after completion of one cycle of freeze-thawing. In addition, adenosine 3',5'-cyclic monophosphate and Ca/sup 2 +/-calmodulin-dependent protein kinase activity were similar in control vesicles and vesicles exposed to high-voltage discharge or freeze-thawing. Also, vesicles freeze-thawed with (/sup 32/P)ATP demonstrated increased phosphorylation compared with nonfrozen vesicles, while freeze-thawing did not alter vesicle protein as judged by Coomassie blue staining. These techniques should allow intestinal membrane vesicles to be used for studies of intracellular control of transport processes, for instance, studies of protein kinase regulation of transport.

  11. Probing biofouling resistant polymer brush surfaces by atomic force microscopy based force spectroscopy.

    PubMed

    Schön, Peter; Kutnyanszky, Edit; ten Donkelaar, Bas; Santonicola, M Gabriella; Tecim, Tugba; Aldred, Nick; Clare, Anthony S; Vancso, G Julius

    2013-02-01

    The protein repellency and biofouling resistance of zwitterionic poly(sulfobetaine methacrylate)(pSBMA) brushes grafted via surface initiated polymerization (SIP) from silicon and glass substrata was assessed using atomic force microscopy (AFM) adherence experiments. Laboratory settlement assays were conducted with cypris larvae of the barnacle Balanus amphitrite. AFM adherence includes the determination of contact rupture forces when AFM probe tips are withdrawn from the substratum. When the surface of the AFM tip is modified, adherence can be assessed with chemical specifity using a method known as chemical force microscopy (CFM). In this study, AFM tips were chemically functionalized with (a) fibronectin- here used as model for a nonspecifically adhering protein - and (b) arginine-glycine-aspartic acid (RGD) peptide motifs covalently attached to poly(methacrylic acid) (PMAA) brushes as biomimics of cellular adhesion receptors. Fibronectin functionalized tips showed significantly reduced nonspecific adhesion to pSBMA-modified substrata compared to bare gold (2.3±0.75 nN) and octadecanethiol (ODT) self-assembled monolayers (1.3±0.75 nN). PMAA and PMAA-RGD modified probes showed no significant adhesion to pSBMA modified silicon substrata. The results gathered through AFM protein adherence studies were complemented by laboratory fouling studies, which showed no adhesion of cypris larvae of Balanus amphitrite on pSBMA. With regard to its unusually high non-specific adsorption to a wide variety of materials the behavior of fibronectin is analogous to the barnacle cyprid temporary adhesive that also binds well to surfaces differing in polarity, charge and free energy. The antifouling efficacy of pSBMA may, therefore, be directly related to the ability of this surface to resist nonspecific protein adsorption. PMID:23138001

  12. Effect of dietary fatty acids on jejunal and ileal oleic acid uptake by rat brush border membrane vesicles.

    PubMed

    Prieto, R M; Stremmel, W; Sales, C; Tur, J A

    1996-04-18

    To test the effect of dietary fatty acids on fatty acid uptake, the influx kinetics of a representative long-chain fatty acid, 3H-oleic acid, in both the jejunum and ileum of rats has been studied using brush border membrane vesicles (BBMV). Animals were fed with semipurified diets containing 5 g fat/100 g diet, as corn oil (control group), safflower oil (unsaturated group) and coconut oil hydrogenated (saturated group). With increasing unbound oleate concentration in the medium, the three dietary groups showed saturable kinetics in both jejunal and ileal BBMV (controls: Vmax = 0.15 +/- 0.01 nmol x mg protein-1 x 5 min-1 and Km = 136 +/- 29.1 nmol for jejunum, and Vmax = 0.23 +/- 0.03 nmol x mg protein-1 x 5 min-1 and Km = 196 +/- 50.3 nmol for ileum; unsaturated: Vmax = 0.28 +/- 0.05 nmol x mg protein-1 x 5 min-1 and Km = 242.7 +/- 91.8 nmol for jejunum, and Vmax = 1.29 +/- 0.06 nmol x mg protein-1 x 5 min-1 and Km = 509.8 +/- 97.5 nmol for ileum; saturated: Vmax = 0.03 +/- 0.01 nmol x mg protein-1 x 5 min-1 and Km = 124.5 +/- 72.6 nmol for jejunum, and Vmax = 0.04 +/- 0.01 nmol x mg protein -1.5 min-1 and Km = 205.6 +/- 85.3 nmol for ileum). These results support the theory that feeding an isocaloric diet containing only unsaturated fatty acids enhanced oleic acid uptake, and feeding an isocaloric diet containing only saturated fatty acids decreased oleic acid uptake. The results obtained in the present work also show the adaptative ability of jejunum and ileum to the type of dietary fat.

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

    PubMed

    Gurbanov, Rafig; Bilgin, Mehmet; Severcan, Feride

    2016-04-01

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

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

    PubMed

    Gurbanov, Rafig; Bilgin, Mehmet; Severcan, Feride

    2016-04-01

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

  15. Binding kinetics of Clostridium difficile toxins A and B to intestinal brush border membranes from infant and adult hamsters

    SciTech Connect

    Rolfe, R.D. )

    1991-04-01

    This study was undertaken to determine if the relative resistance of neonates and infants to Clostridium difficile-associated intestinal disease can be related to age-dependent differences in intestinal receptors for C. difficile toxins A and B. Brush border membranes (BBMs) from the small intestines of adult and infant hamsters were examined for their ability to bind radiolabeled toxins A and B. (125I)toxin A bound to both infant and adult hamster BBMs at physiological temperature, whereas (125I)toxin B did not bind to the BBMs under any of the conditions examined. The number of (125I)toxin A molecules bound at saturation was approximately 4 x 10(10) per micrograms of membrane protein for adult BBMs and 1 x 10(11) per micrograms of membrane protein for infant BBMs. Scatchard plot analysis suggested the presence of a single class of toxin A binding sites on both infant and adult hamster BBMs. Maximal binding capacity and Kd values were 0.63 pmol/mg of protein and 66.7 nM, respectively, for the infant BBMs, and 0.24 pmol/mg of protein and 27 nM, respectively, for the adult BBMs. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analyses of extracted BBM proteins revealed differences in the proteins of infant and adult BBMs. However, there were not any detectable differences in the protein bands which bound (125I)toxin A between infant and adult hamsters. The results from these investigations indicate that differences in the binding kinetics of toxins A and/or B to infant and adult hamster BBMs do not account for the observed differences in their susceptibility to C. difficile-associated intestinal disease.

  16. Dexamethasone modulates rat renal brush border membrane phosphate transporter mRNA and protein abundance and glycosphingolipid composition.

    PubMed Central

    Levi, M; Shayman, J A; Abe, A; Gross, S K; McCluer, R H; Biber, J; Murer, H; Lötscher, M; Cronin, R E

    1995-01-01

    Glucocorticoids are important regulators of renal phosphate transport. This study investigates the role of alterations in renal brush border membrane (BBM) sodium gradient-dependent phosphate transport (Na-Pi cotransporter) mRNA and protein abundance in the dexamethasone induced inhibition of Na-Pi cotransport in the rat. Dexamethasone administration for 4 d caused a 1.5-fold increase in the Vmax of Na-Pi cotransport (1785 +/- 119 vs. 2759 +/- 375 pmol/5 s per mg BBM protein in control, P < 0.01), which was paralleled by a 2.5-fold decrease in the abundance of Na-Pi mRNA and Na-Pi protein. There was also a 1.7-fold increase in BBM glucosylceramide content (528 +/- 63 vs. 312 +/- 41 ng/mg BBM protein in control, P < 0.02). To determine whether the alteration in glucosylceramide content per se played a functional role in the decrease in Na-Pi cotransport, control rats were treated with the glucosylceramide synthase inhibitor, D-threo-1-phenyl-2-decanoyl-amino-3-morpholino-1-propanol (PDMP). The resultant 1.5-fold decrease in BBM glucosylceramide content (199 +/- 19 vs. 312 +/- 41 ng/mg BBM protein in control, P < 0.02) was associated with a 1.4-fold increase in Na-Pi cotransport activity (1422 +/- 73 vs. 1048 +/- 85 pmol/5 s per mg BBM protein in control, P < 0.01), and a 1.5-fold increase in BBM Na-Pi protein abundance. Thus, dexamethasone-induced inhibition of Na-Pi cotransport is associated with a decrease in BBM Na-Pi cotransporter abundance, and an increase in glucosylceramide. Since primary alteration in BBM glucosylceramide content per se directly and selectively modulates BBM Na-Pi cotransport activity and Na-Pi protein abundance, we propose that the increase in BBM glucosylceramide content plays an important role in mediating the inhibitory effect of dexamethasone on Na-Pi cotransport activity. Images PMID:7615789

  17. Specificity of Bacillus thuringiensis endotoxins is correlated with the presence of high-affinity binding sites in the brush border membrane of target insect midguts

    SciTech Connect

    Hofmann, C.; Vanderbruggen, H.; Hoefte, H.; Van Rie, J.; Jansens, S.; Van Mellaert, H. )

    1988-11-01

    Binding studies were performed with two {sup 125}I-labeled Bacillus thuringiensis {delta}-endotoxins on brush border membrane vesicles prepared from the larval midgut of the tobacco hornworm Manduca sexta or the cabbage butterfly Pieris brassicae. One {delta}-endotoxin, Bt2-protoxin, is a 130-kDa recombinant crystalline protein from B. thuringiensis subsp. berliner. It kills larvae of both insect species. The active Bt2-toxin is a 60-kDa proteolytic fragment of the Bt2-protoxin. It binds saturably and with high affinity to brush border membrane vesicles from the midgut of both species. The other {delta}-endotoxin, Bt4412-protoxin, is a 136-kDa crystalline protein from B. thuringiensis subsp. thuringiensis, which is highly toxic for P. brassicae, but not for M. sexta larvae. Bt4412-toxin, obtained after proteolytic activation of Bt4412-protoxin, shows high-affinity saturable binding to P. brassicae vesicles but not to M. sexta vesicles. The correlation between toxicity and specific binding is further strengthened by competition studies. Other B. thuringiensis {delta}-endotoxins active against M. sexta compete for binding of {sup 125}I-labeled Bt2-toxin to M. sexta vesicles, whereas toxins active against dipteran or coleopteran larvae do not compete. Bt2-toxin and Bt4412-toxin bind to different sites on P. brassicae vesicles.

  18. Modulatory effect of thyroid hormones on uptake of phosphate and other solutes across luminal brush border membrane of kidney cortex.

    PubMed

    Yusufi, A N; Murayama, N; Keller, M J; Dousa, T P

    1985-06-01

    The mechanism whereby thyroid hormones modulate the transport properties of luminal brush border membrane (BBM) of renal proximal tubules was studied in thyroparathyroidectomized rats. Administration of both T4 and T3 increased BBM capacity for Na+ gradient-dependent uptake of phosphate (Pi) by BBM vesicles (BBMV). This effect of thyroid hormones was present in thyroparathyroidectomized and hypophysectomized rats, and it was not blocked by a saturating dose of propranolol. The stimulatory effect of T3 and T4 on BBM transport of Pi was dose dependent in the range of 5.2-520 nmol/100 g BW. Pretreatment of rats with inhibitors of 5'-monodeiodinase (5'-DI), iopanoic acid or ipodate, prevented the increase in serum T3 in rats injected with T4, but it did not diminish the increase in BBM transport of Pi. Administration of iopanoic acid and ipodate also prevented a 5-fold increase in 5'-DI activity in renal cortical tissue elicited by T4 administration. Treatment with T3 resulted in an increase of Pi transport across BBM from kidneys of rats subjected to dietary Pi deprivation due either to total fasting or to feeding of a low Pi diet. Further, T3 administration enhanced amiloride-sensitive Na+-H+ countertransport across BBM, but the uptake of 22Na+ by BBMV in the absence of pH gradient was not changed. The Na+ gradient-dependent uptake of L-[3H]proline by BBMV was slightly decreased, but the uptake of [14C]citrate was not changed in response to T3. Administration of T3 increased Pi transport in BBMV prepared from juxtamedullary cortex, but not in BBMV from superficial cortex. Conversely, the rate of Na+-H+ countertransport was enhanced, and the enzymatic activity of alkaline phosphatase was decreased in BBMV from superficial cortex; no changes in these parameters were found in BBMV from juxtamedullary cortex. Our results indicate that the stimulatory effect of administered T3 and/or T4 on renal BBM transport of Pi is distinct from the modulatory effect of dietary Pi

  19. Combining colloidal probe atomic force and reflection interference contrast microscopy to study the compressive mechanics of hyaluronan brushes.

    PubMed

    Attili, Seetharamaiah; Richter, Ralf P

    2012-02-14

    We describe a method that combines colloidal probe atomic force microscopy (AFM) and reflection interference contrast microscopy (RICM) to characterize the mechanical properties of thin and solvated polymer films. When analyzing polymer films, a fundamental problem in colloidal probe AFM experiments is to determine the distance at closest approach between the probe and the substrate on which the film is deposited. By combining AFM and RICM in situ, forces and absolute distances can be measured simultaneously. Using the combined setup, we quantify the compressive mechanics of films of the polysaccharide hyaluronan that is end-grafted to a supported lipid bilayer. The experimental data, and comparison with polymer theory, show that hyaluronan films are well-described as elastic, very soft and highly solvated polymer brushes. The data on these well-defined films should be a useful reference for the investigation of the more complex hyaluronan-rich coats that surround many living cells.

  20. Brush border membrane vesicle and Caco-2 cell line: Two experimental models for evaluation of absorption enhancing effects of saponins, bile salts, and some synthetic surfactants

    PubMed Central

    Moghimipour, Eskandar; Tabassi, Sayyed Abolghassem Sajadi; Ramezani, Mohammad; Handali, Somayeh; Löbenberg, Raimar

    2016-01-01

    The aim of this study was to investigate the influence of absorption enhancers in the uptake of hydrophilic compounds. The permeation of the two hydrophilic drug models gentamicin and 5 (6)-carboxyfluorescein (CF) across the brush border membrane vesicles and Caco-2 cell lines were evaluated using total saponins of Acanthophyllum squarrosum, Quillaja saponaria, sodium lauryl sulfate, sodium glycocholate, sodium taurodeoxycholate, and Tween 20 as absorption enhancers. Transepithelial electrical resistance (TEER) measurement was utilized to assess the paracellular permeability of cell lines. Confocal laser scanning microscopy (CLSM) was performed to obtain images of the distribution of CF in Caco-2 cells. These compounds were able to loosen tight junctions, thus increasing paracellular permeability. CLSM confirmed the effect of these absorption enhancers on CF transport across Caco-2 lines and increased the Caco-2 permeability via transcellular route. It was also confirmed that the decrease in TEER was transient and reversible after removal of permeation enhancers. PMID:27429925

  1. A Tenebrio molitor GPI-anchored alkaline phosphatase is involved in binding of Bacillus thuringiensis Cry3Aa to brush border membrane vesicles.

    PubMed

    Zúñiga-Navarrete, Fernando; Gómez, Isabel; Peña, Guadalupe; Bravo, Alejandra; Soberón, Mario

    2013-03-01

    Bacillus thuringiensis Cry toxins recognizes their target cells in part by the binding to glycosyl-phosphatidyl-inositol (GPI) anchored proteins such as aminopeptidase-N (APN) or alkaline phosphatases (ALP). Treatment of Tenebrio molitor brush border membrane vesicles (BBMV) with phospholipase C that cleaves out GPI-anchored proteins from the membranes, showed that GPI-anchored proteins are involved in binding of Cry3Aa toxin to BBMV. A 68 kDa GPI-anchored ALP was shown to bind Cry3Aa by toxin overlay assays. The 68 kDa GPI-anchored ALP was preferentially expressed in early instar larvae in comparison to late instar larvae. Our work shows for the first time that GPI-anchored ALP is important for Cry3Aa binding to T. molitor BBMV suggesting that the mode of action of Cry toxins is conserved in different insect orders.

  2. A Tenebrio molitor GPI-anchored alkaline phosphatase is involved in binding of Bacillus thuringiensis Cry3Aa to brush border membrane vesicles.

    PubMed

    Zúñiga-Navarrete, Fernando; Gómez, Isabel; Peña, Guadalupe; Bravo, Alejandra; Soberón, Mario

    2013-03-01

    Bacillus thuringiensis Cry toxins recognizes their target cells in part by the binding to glycosyl-phosphatidyl-inositol (GPI) anchored proteins such as aminopeptidase-N (APN) or alkaline phosphatases (ALP). Treatment of Tenebrio molitor brush border membrane vesicles (BBMV) with phospholipase C that cleaves out GPI-anchored proteins from the membranes, showed that GPI-anchored proteins are involved in binding of Cry3Aa toxin to BBMV. A 68 kDa GPI-anchored ALP was shown to bind Cry3Aa by toxin overlay assays. The 68 kDa GPI-anchored ALP was preferentially expressed in early instar larvae in comparison to late instar larvae. Our work shows for the first time that GPI-anchored ALP is important for Cry3Aa binding to T. molitor BBMV suggesting that the mode of action of Cry toxins is conserved in different insect orders. PMID:22743140

  3. Brush border membrane vesicle and Caco-2 cell line: Two experimental models for evaluation of absorption enhancing effects of saponins, bile salts, and some synthetic surfactants.

    PubMed

    Moghimipour, Eskandar; Tabassi, Sayyed Abolghassem Sajadi; Ramezani, Mohammad; Handali, Somayeh; Löbenberg, Raimar

    2016-01-01

    The aim of this study was to investigate the influence of absorption enhancers in the uptake of hydrophilic compounds. The permeation of the two hydrophilic drug models gentamicin and 5 (6)-carboxyfluorescein (CF) across the brush border membrane vesicles and Caco-2 cell lines were evaluated using total saponins of Acanthophyllum squarrosum, Quillaja saponaria, sodium lauryl sulfate, sodium glycocholate, sodium taurodeoxycholate, and Tween 20 as absorption enhancers. Transepithelial electrical resistance (TEER) measurement was utilized to assess the paracellular permeability of cell lines. Confocal laser scanning microscopy (CLSM) was performed to obtain images of the distribution of CF in Caco-2 cells. These compounds were able to loosen tight junctions, thus increasing paracellular permeability. CLSM confirmed the effect of these absorption enhancers on CF transport across Caco-2 lines and increased the Caco-2 permeability via transcellular route. It was also confirmed that the decrease in TEER was transient and reversible after removal of permeation enhancers. PMID:27429925

  4. Mechanism of cis- and trans-substrate interactions at the tetraethylammonium/H+ exchanger of rabbit renal brush-border membrane vesicles

    SciTech Connect

    Wright, S.H.; Wunz, T.M.

    1988-12-25

    The kinetic basis for trans-effects of intravesicular substrates on the uptake of the organic cation, tetraethylammonium (TEA), into rabbit renal brush-border membrane vesicles (BBMV) was studied. Preloading BBMV with 1, 2, or 4 mM TEA stimulated the initial rate of uptake and the total net accumulation of 0.1 mM (TH)TEA. The stimulatory effect of intravesicular TEA on the initial rate of uptake was a saturable function of the trans-TEA concentration, with a half-maximal effect noted at an intravesicular concentration of 0.28 mM. A 1 mM trans-concentration of TEA increased the Jmax of (TH)TEA uptake (from 4.3 to 6.8 nmol.mg-1.min-1) without affecting the apparent Kt. An outwardly directed H+ gradient also increased Jmax (to 10.7 nmol.mg-1.min-1), although the addition of an outwardly directed TEA gradient did not produce further increases in the rate of TEA uptake. External H+ acted as a competitive inhibitor of TEA uptake, and an increase in external (H+) (from 32 nM to 100 nM) produced an increase in the apparent Kt for TEA transport (from 0.12 to 0.26 mM) without affecting the Jmax. The results suggested that TEA and H+ compete for a common site or set of mutually exclusive sites on the cytoplasmic and luminal aspects of TEA/H+ exchanger in the renal brush border, and that these sites have a similar affinity for TEA.

  5. Experimental type II diabetes and related models of impaired glucose metabolism differentially regulate glucose transporters at the proximal tubule brush border membrane.

    PubMed

    Chichger, Havovi; Cleasby, Mark E; Srai, Surjit K; Unwin, Robert J; Debnam, Edward S; Marks, Joanne

    2016-06-01

    What is the central question of this study? Although SGLT2 inhibitors represent a promising treatment for patients suffering from diabetic nephropathy, the influence of metabolic disruption on the expression and function of glucose transporters is largely unknown. What is the main finding and its importance? In vivo models of metabolic disruption (Goto-Kakizaki type II diabetic rat and junk-food diet) demonstrate increased expression of SGLT1, SGLT2 and GLUT2 in the proximal tubule brush border. In the type II diabetic model, this is accompanied by increased SGLT- and GLUT-mediated glucose uptake. A fasted model of metabolic disruption (high-fat diet) demonstrated increased GLUT2 expression only. The differential alterations of glucose transporters in response to varying metabolic stress offer insight into the therapeutic value of inhibitors. SGLT2 inhibitors are now in clinical use to reduce hyperglycaemia in type II diabetes. However, renal glucose reabsorption across the brush border membrane (BBM) is not completely understood in diabetes. Increased consumption of a Western diet is strongly linked to type II diabetes. This study aimed to investigate the adaptations that occur in renal glucose transporters in response to experimental models of diet-induced insulin resistance. The study used Goto-Kakizaki type II diabetic rats and normal rats rendered insulin resistant using junk-food or high-fat diets. Levels of protein kinase C-βI (PKC-βI), GLUT2, SGLT1 and SGLT2 were determined by Western blotting of purified renal BBM. GLUT- and SGLT-mediated d-[(3) H]glucose uptake by BBM vesicles was measured in the presence and absence of the SGLT inhibitor phlorizin. GLUT- and SGLT-mediated glucose transport was elevated in type II diabetic rats, accompanied by increased expression of GLUT2, its upstream regulator PKC-βI and SGLT1 protein. Junk-food and high-fat diet feeding also caused higher membrane expression of GLUT2 and its upstream regulator PKC

  6. Membrane insertion of the Bacillus thuringiensis Cry1Ab toxin: single mutation in domain II block partitioning of the toxin into the brush border membrane.

    PubMed

    Nair, Manoj S; Liu, Xinyan Sylvia; Dean, Donald H

    2008-05-27

    The umbrella and penknife models hypothesize that insecticidal Bacillus thuringiensis Cry toxins partition into the apical membrane of the insect midgut by insertion of only two alpha-helices from domain I of the protein, alpha-helices 4 and 5 in the case of the umbrella model and alpha-helices 5 and 6 in the case of the penknife model. Neither model envisages membrane partitioning by domains II and III. In this study, we present data suggesting that mutations in the domain II residue, F371, affect insertion of the whole toxin into Manduca sexta brush border membrane vesicles (BBMVs). Using steady state fluorescence measurements combined with a proteinase K protection assay, we show that mutants of F371 have lost their ability to insert into the BBMV, even though binding to cadherin is almost unaffected. The study also identifies a difference in partitioning of toxins into artificial lipid vesicles (SUVs) as opposed to native BBMVs. While the F371 mutations block insertion of domains I and II into BBMVs, they only block domain II insertion into SUVs. Bioassay and voltage clamping of midguts also confirm the fluorescence data that the noninserting mutants are nontoxic. Our study leads us to propose that, in contrast to previous models of individual free helices inserting into the membrane, the toxin enters into the membrane as a whole molecule or oligomers of the molecule, wherein the domain II residue F371 has a vital role to play in membrane insertion. PMID:18457427

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

    PubMed

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

    1995-10-01

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

  8. Effect of medium-chain glycerides on the membrane transport of D-glucose and sulfanilic acid in the intestinal brush-border membrane vesicles.

    PubMed

    Sagara, K; Higaki, K; Yamazaki, A; Hashida, M; Sezaki, H

    1990-01-01

    To clarify the influence of medium-chain glycerides (MCG) on a biological membrane, we investigated the membrane transport of D-glucose and sulfanilic acid in the brush-border membrane (BBM) vesicles pretreated with MCG. The size distribution of the BBM vesicles determined by electron microscopic observation was not significantly different between the vesicles incorporated with MCG and those of the control. However, the amount of D-glucose taken up by the vesicles at an equilibrated stage (30 min) was significantly decreased in the MCG-treated ones based on unit content of protein. Based on these results we estimated the membrane transport of D-glucose and sulfanilic acid in consideration of vesiculation or filter-capturing efficiency in MCG-treated vesicles. The rates of Na+ gradient-independent D-glucose transport and sulfanilic acid transport were significantly greater in MCG-treated vesicles than in the control. On the other hand, the magnitude of overshooting effect in Na+ gradient-dependent uptake of D-glucose in MCG-treated vesicles was maintained similar to the control. Comparison of kinetic parameters for active D-glucose transport at different concentrations indicated that Km and Vmax were not significantly different between MCG-treated and the control vesicles. These results indicated that passive diffusion of D-glucose and sulfanilic acid was significantly increased but Na(+)-glucose cotransporter was not significantly changed by the incorporation of MCG in the intestinal BBM vesicles.

  9. Interaction of Lysinibacillus sphaericus Cry48Aa/Cry49Aa toxin with midgut brush-border membrane fractions from Culex quinquefasciatus larvae.

    PubMed

    Guo, Q-Y; Hu, X-M; Cai, Q-X; Yan, J-P; Yuan, Z-M

    2016-04-01

    The Cry48Aa/Cry49Aa mosquitocidal toxin from Lysinibacillus sphaericus was uniquely composed of a three-domain (Cry) toxin and binary (Bin) toxin-like protein, with high toxicity against Culex spp. However, its mode of action against the target mosquitoes is still unknown. In this study, Cry48Aa, Cry49Aa and its N- and C-terminal truncated proteins were expressed and purified, and the binding affinities of the purified proteins with midgut brush-border membrane fractions (BBMFs) from Culex quin-quefasciatus larvae were performed. The results showed that both Cry48Aa and Cry49Aa have specific and high binding affinity to BBMFs, with dissociation constants of 9.5 ± 1.8 and 25.4 ± 3.8 nM, respectively. Competition assays demonstrated that Cry49Aa C-terminal derivatives were able to bind to the BBMFs, whereas Far-Western dot blot analysis revealed that its N-terminal constructs interacted with Cry48Aa. Nevertheless, larvicidal activity was almost lost when Cry49Aa truncated proteins, either individually or in pairs, combined with Cry48Aa. It is concluded that Cry49Aa is responsible for receptor binding and interaction with Cry48Aa and plays an important role in the mechanism of action of these two-component toxins. PMID:26748768

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

    PubMed

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

    2010-09-01

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

  11. Chronic and selective inhibition of basolateral membrane Na-K-ATPase uniquely regulates brush border membrane Na absorption in intestinal epithelial cells

    PubMed Central

    Manoharan, Palanikumar; Gayam, Swapna; Arthur, Subha; Palaniappan, Balasubramanian; Singh, Soudamani; Dick, Gregory M.

    2015-01-01

    Na-K-ATPase, an integral membrane protein in mammalian cells, is responsible for maintaining the favorable intracellular Na gradient necessary to promote Na-coupled solute cotransport processes [e.g., Na-glucose cotransport (SGLT1)]. Inhibition of brush border membrane (BBM) SGLT1 is, at least in part, due to the diminished Na-K-ATPase in villus cells from chronically inflamed rabbit intestine. The aim of the present study was to determine the effect of Na-K-ATPase inhibition on the two major BBM Na absorptive pathways, specifically Na-glucose cotransport and Na/H exchange (NHE), in intestinal epithelial (IEC-18) cells. Na-K-ATPase was inhibited using 1 mM ouabain or siRNA for Na-K-ATPase-α1 in IEC-18 cells. SGLT1 activity was determined as 3-O-methyl-d-[3H]glucose uptake. Na-K-ATPase activity was measured as the amount of inorganic phosphate released. Treatment with ouabain resulted in SGLT1 inhibition at 1 h but stimulation at 24 h. To further characterize this unexpected stimulation of SGLT1, siRNA silencing was utilized to inhibit Na-K-ATPase-α1. SGLT1 activity was significantly upregulated by Na-K-ATPase silencing, while NHE3 activity remained unaltered. Kinetics showed that the mechanism of stimulation of SGLT1 activity was secondary to an increase in affinity of the cotransporter for glucose without a change in the number of cotransporters. Molecular studies demonstrated that the mechanism of stimulation was not secondary to altered BBM SGLT1 protein levels. Chronic and direct silencing of basolateral Na-K-ATPase uniquely regulates BBM Na absorptive pathways in intestinal epithelial cells. Specifically, while BBM NHE3 is unaffected, SGLT1 is stimulated secondary to enhanced affinity of the cotransporter. PMID:25652450

  12. Role of N-linked oligosaccharides in the transport activity of the Na+/H+ antiporter in rat renal brush-border membrane

    SciTech Connect

    Yusufi, A.N.; Szczepanska-Konkel, M.; Dousa, T.P.

    1988-09-25

    The role of N-linked oligosaccharide side chains in the biogenesis and function of Na+-coupled transporters in renal luminal brush-border membrane (BBM) is not known. We examined the question of how in vivo inhibition by alkaloid swainsonine of alpha-mannosidase, a key enzyme in processing of glycoproteins in the Golgi apparatus, affects Na+/H+ antiport and Na+/Pi symport as well as activities of other transporters and enzymes in rat renal BBM. Administration of swainsonine to thyroparathyroidectomized rats, control or treated with 3,5,3'-triiodothyronine, markedly decreased the rate of Na+/H+ antiport, but had no effect on the rate of Na+/Pi symport across renal BBM vesicles (BBMV). Moreover, administration of swainsonine did not change activities of Na+ gradient, ((extravesicular Na+) greater than (intravesicular Na+))-dependent transport of D-glucose, L-proline, or the amiloride-insensitive 22Na+ uptake by BBMV; the activities of the BBM enzymes alkaline phosphatase, gamma-glutamyltransferase, or leucine aminopeptidase in BBMV were also not changed. The in vitro enzymatic deglycosylation of BBM by incubating freshly isolated BBMV with bacterial endoglycosidase F also resulted in a decreased rate of Na+/H+ antiport, but not Na+-coupled symports of Pi, L-proline, and D-glucose, or the activities of the BBM enzymes were not significantly affected. Similar incubation with endoglycosidase H was without effect on any of these parameters. Both the modification of BBMV glycoproteins by administration fo swainsonine in vivo as well as the in vitro incubation of BBMV with endoglycosidase F resulted in a decrease of the apparent Vmax of Na+/H+ antiport, but did not change the apparent Km of this antiporter for extravesicular Na+ and did not increase H+ conductance of BBM.

  13. Chronic and selective inhibition of basolateral membrane Na-K-ATPase uniquely regulates brush border membrane Na absorption in intestinal epithelial cells.

    PubMed

    Manoharan, Palanikumar; Gayam, Swapna; Arthur, Subha; Palaniappan, Balasubramanian; Singh, Soudamani; Dick, Gregory M; Sundaram, Uma

    2015-04-15

    Na-K-ATPase, an integral membrane protein in mammalian cells, is responsible for maintaining the favorable intracellular Na gradient necessary to promote Na-coupled solute cotransport processes [e.g., Na-glucose cotransport (SGLT1)]. Inhibition of brush border membrane (BBM) SGLT1 is, at least in part, due to the diminished Na-K-ATPase in villus cells from chronically inflamed rabbit intestine. The aim of the present study was to determine the effect of Na-K-ATPase inhibition on the two major BBM Na absorptive pathways, specifically Na-glucose cotransport and Na/H exchange (NHE), in intestinal epithelial (IEC-18) cells. Na-K-ATPase was inhibited using 1 mM ouabain or siRNA for Na-K-ATPase-α1 in IEC-18 cells. SGLT1 activity was determined as 3-O-methyl-D-[(3)H]glucose uptake. Na-K-ATPase activity was measured as the amount of inorganic phosphate released. Treatment with ouabain resulted in SGLT1 inhibition at 1 h but stimulation at 24 h. To further characterize this unexpected stimulation of SGLT1, siRNA silencing was utilized to inhibit Na-K-ATPase-α1. SGLT1 activity was significantly upregulated by Na-K-ATPase silencing, while NHE3 activity remained unaltered. Kinetics showed that the mechanism of stimulation of SGLT1 activity was secondary to an increase in affinity of the cotransporter for glucose without a change in the number of cotransporters. Molecular studies demonstrated that the mechanism of stimulation was not secondary to altered BBM SGLT1 protein levels. Chronic and direct silencing of basolateral Na-K-ATPase uniquely regulates BBM Na absorptive pathways in intestinal epithelial cells. Specifically, while BBM NHE3 is unaffected, SGLT1 is stimulated secondary to enhanced affinity of the cotransporter.

  14. Mutations in domain I interhelical loops affect the rate of pore formation by the Bacillus thuringiensis Cry1Aa toxin in insect midgut brush border membrane vesicles.

    PubMed

    Lebel, Geneviève; Vachon, Vincent; Préfontaine, Gabrielle; Girard, Frédéric; Masson, Luke; Juteau, Marc; Bah, Aliou; Larouche, Geneviève; Vincent, Charles; Laprade, Raynald; Schwartz, Jean-Louis

    2009-06-01

    Pore formation in the apical membrane of the midgut epithelial cells of susceptible insects constitutes a key step in the mode of action of Bacillus thuringiensis insecticidal toxins. In order to study the mechanism of toxin insertion into the membrane, at least one residue in each of the pore-forming-domain (domain I) interhelical loops of Cry1Aa was replaced individually by cysteine, an amino acid which is normally absent from the activated Cry1Aa toxin, using site-directed mutagenesis. The toxicity of most mutants to Manduca sexta neonate larvae was comparable to that of Cry1Aa. The ability of each of the activated mutant toxins to permeabilize M. sexta midgut brush border membrane vesicles was examined with an osmotic swelling assay. Following a 1-h preincubation, all mutants except the V150C mutant were able to form pores at pH 7.5, although the W182C mutant had a weaker activity than the other toxins. Increasing the pH to 10.5, a procedure which introduces a negative charge on the thiol group of the cysteine residues, caused a significant reduction in the pore-forming abilities of most mutants without affecting those of Cry1Aa or the I88C, T122C, Y153C, or S252C mutant. The rate of pore formation was significantly lower for the F50C, Q151C, Y153C, W182C, and S252C mutants than for Cry1Aa at pH 7.5. At the higher pH, all mutants formed pores significantly more slowly than Cry1Aa, except the I88C mutant, which formed pores significantly faster, and the T122C mutant. These results indicate that domain I interhelical loop residues play an important role in the conformational changes leading to toxin insertion and pore formation.

  15. Brush border myosin-I truncated in the motor domain impairs the distribution and the function of endocytic compartments in an hepatoma cell line.

    PubMed Central

    Durrbach, A; Collins, K; Matsudaira, P; Louvard, D; Coudrier, E

    1996-01-01

    Myosins I, a ubiquitous monomeric class of myosins that exhibits actin-based motor properties, are associated with plasma and/or vesicular membranes and have been suggested as players for trafficking events between cell surface and intracellular membranous structures. To investigate the function of myosins 1, we have transfected a mouse hepatoma cell line (BWTG3) with cDNAs encoding the chicken brush border myosin-I (BBMI) and two variants truncated in the motor domain. One variant is deleted of the first 446 amino acids and thereby lacks the ATP binding site, whereas the other is deleted of the entire motor domain and lacks the ATP and actin binding sites. We have observed (i) that significant amounts of the truncated variants are recovered with membrane fractions after cell fractionation, (ii) that they codistribute with a compartment containing alpha2-macroglobulin internalized for 30 min as determined by fluorescent microscopy, (iii) that the production of BBMI-truncated variants impairs the distribution of the acidic compartment and ligands internalized for 30 min, and (iv) that the production of the truncated variant containing the actin binding site decreases the rate of alpha2-macroglobulin degradation whereas the production of the variant lacking the ATP binding site and the actin binding site increases the rate of a2-macroglobulin degradation. These observations indicate that the two truncated variants have a dominant negative effect on the distribution and the function of the endocytic compartments. We propose that an unidentified myosin-I might contribute to the distribution of endocytic compartments in a juxtanuclear position and/or to the regulation of the delivery of ligands to the degradative compartment in BWTG3 cells. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:8692943

  16. An NSP4-dependant mechanism by which rotavirus impairs lactase enzymatic activity in brush border of human enterocyte-like Caco-2 cells.

    PubMed

    Beau, Isabelle; Cotte-Laffitte, Jacqueline; Géniteau-Legendre, Monique; Estes, Mary K; Servin, Alain L

    2007-09-01

    Lactase-phlorizin hydrolase (LPH, EC 3.2.1.23-62) is a brush border membrane (BBM)-associated enzyme in intestinal cells that hydrolyse lactose, the most important sugar in milk. Impairing in lactase activity during rotavirus infection has been described in diseased infants but the mechanism by which the functional lesion occurs remains unknown. We undertook a study to elucidate whether rotavirus impairs the lactase enzymatic activity in BBM of human enterocyte cells. In this study we use cultured human intestinal fully differentiated enterocyte-like Caco-2 cells to demonstrate how the lactase enzymatic activity at BBM is significantly decreased in rhesus monkey rotavirus (RRV)-infected cells. We found that the decrease in enzyme activity is not dependent of the Ca(2+)- and cAMP-dependent signalling events triggered by the virus. The LPH biosynthesis, stability, and expression of the protein at the BBM of infected cells were not modified. We provide evidence that in RRV-infected cells the kinetic of lactase enzymatic activity present at the BBM was modified. Both BBM(control) and BBM(RRV) have identical K(m) values, but hydrolyse the substrate at different rates. Thus, the BBM(RRV) exhibits almost a 1.5-fold decreased V(max) than that of BBM(control) and is therefore enzymatically less active than the latter. Our study demonstrate conclusively that the impairment of lactase enzymatic activity at the BBM of the enterocyte-like Caco-2 cells observed during rotavirus infection results from an inhibitory action of the secreted non-structural rotavirus protein NSP4.

  17. Increased calcium absorption in prehypertensive spontaneously hypertensive rat. Role of serum 1,25-dihydroxyvitamin D3 levels and intestinal brush border membrane fluidity.

    PubMed Central

    Lau, K; Langman, C B; Gafter, U; Dudeja, P K; Brasitus, T A

    1986-01-01

    Changes in Ca absorption have been described in the spontaneously hypertensive rat (SHR) compared with Wistar-Kyoto (WKy) rats. In 3.5-wk-old SHR and age-matched WKy controls, we measured direct arterial blood pressure, Ca absorption, and serum 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] levels and small intestine brush border membrane (BBM) fluidity and lipid composition. The two objectives were (a) to define the nature of the absorptive changes before detectable hypertension and (b) to evaluate the potential mechanism(s). We found that even at this normotensive stage (106 +/- 4 vs. 107 +/- 2 torr for the female and 109 +/- 3 vs. 104 +/- 3 torr for the male), the SHR (a) absorbed more Ca (1.46 +/- 0.06 vs. 1.14 +/- 0.08 mmol/d and 1.53 +/- 0.06 vs. 1.28 +/- 0.06 mmol/d, respectively) and retained more Ca, (b) had higher serum 1,25(OH)2D3 levels (340 +/- 36 vs. 160 +/- 18 pg/ml and 230 +/- 25 vs. 150 +/- 16 pg/ml, respectively), and (c) possessed BBM with increased fluidity and with reduced fatty acyl saturation index owing to decreased stearic (32.2 +/- 2.6% vs. 38.2 +/- 0.9%) but increased linoleic acids (12.2 +/- 2.0% vs. 7.6 +/- 1.6%). These results demonstrate increased Ca absorption in prehypertensive SHR associated with increased serum 1,25(OH)2D3 levels, increased intestinal BBM fluidity, and reduced saturation index, which singly or in combination could produce the changes in intestinal Ca transport. PMID:3760184

  18. Brush potential curve tracer

    DOEpatents

    Finch, Hilvan A.

    1987-01-01

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

  19. 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.

  20. Proper Brushing

    MedlinePlus

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

  1. Resistance in a laboratory population of Culex quinquefasciatus (Diptera: Culicidae) to Bacillus sphaericus binary toxin is due to a change in the receptor on midgut brush-border membranes.

    PubMed

    Nielsen-Leroux, C; Charles, J F; Thiéry, I; Georghiou, G P

    1995-02-15

    Direct binding experiments with isolated brush border membrane fractions (BBMF) from larvae of a susceptible laboratory strain of Culex quinquefasciatus Say, indicated the presence of a single class of Bacillus sphaericus binary toxin receptors. The dissociation constant (Kd) was approximately 11 nM and the maximum binding capacity (Bmax) approximately 8 pmol/mg BBMF protein. Similar binding experiments with a field population of C. quinquefasciatus that had been selected in the laboratory to more than 100,000-fold resistance to B. sphaericus binary toxin failed to reveal the presence of any specific binding. Thus this resistant strain had lost the functional receptor for B. sphaericus toxin. The binding characteristics of BBMF from the F1 larval progeny (susceptible females x resistant males) were very close to those of the parental susceptible strain, consistent with the resistance being recessive. PMID:7883005

  2. Identification of ABCC2 as a binding protein of Cry1Ac on brush border membrane vesicles from Helicoverpa armigera by an improved pull-down assay.

    PubMed

    Zhou, Zishan; Wang, Zeyu; Liu, Yuxiao; Liang, Gemei; Shu, Changlong; Song, Fuping; Zhou, Xueping; Bravo, Alejandra; Soberón, Mario; Zhang, Jie

    2016-08-01

    Cry1Ac toxin-binding proteins from Helicoverpa armigera brush border membrane vesicles were identified by an improved pull-down method that involves coupling Cry1Ac to CNBr agarose combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS). According to the LC-MS/MS results, Cry1Ac toxin could bind to six classes of aminopeptidase-N, alkaline phosphatase, cadherin-like protein, ATP-binding cassette transporter subfamily C protein (ABCC2), actin, ATPase, polycalin, and some other proteins not previously characterized as Cry toxin-binding molecules such as dipeptidyl peptidase or carboxyl/choline esterase and some serine proteases. This is the first report that suggests the direct binding of Cry1Ac toxin to ABCC2 in H. armigera. PMID:27037552

  3. Differential Association of the Na+/H+ Exchanger Regulatory Factor (NHERF) Family of Adaptor Proteins with the Raft-and the Non-Raft Brush Border Membrane Fractions of NHE3

    PubMed Central

    Sultan, Ayesha; Luo, Min; Yu, Qin; Riederer, Brigitte; Xia, Weiliang; Chen, Mingmin; Lissner, Simone; Gessner, Johannes E.; Donowitz, Mark; Yun, C. Chris; deJonge, Hugo; Lamprecht, Georg; Seidler, Ursula

    2014-01-01

    Background/Aims Trafficking, brush border membrane (BBM) retention, and signal-specific regulation of the Na+/H+ exchanger NHE3 is regulated by the Na+/H+ Exchanger Regulatory Factor (NHERF) family of PDZ-adaptor proteins, which enable the formation of multiprotein complexes. It is unclear, however, what determines signal specificity of these NHERFs. Thus, we studied the association of NHE3, NHERF1 (EBP50), NHERF2 (E3KARP), and NHERF3 (PDZK1) with lipid rafts in murine small intestinal BBM. Methods Detergent resistant membranes (“lipid rafts”) were isolated by floatation of Triton X-incubated small intestinal BBM from a variety of knockout mouse strains in an Optiprep step gradient. Acid-activated NHE3 activity was measured fluorometrically in BCECF-loaded microdissected villi, or by assessment of CO2/HCO3− mediated increase in fluid absorption in perfused jejunal loops of anethetized mice. Results NHE3 was found to partially associate with lipid rafts in the native BBM, and NHE3 raft association had an impact on NHE3 transport activity and regulation in vivo. NHERF1, 2 and 3 were differentially distributed to rafts and non-rafts, with NHERF2 being most raft-associated and NHERF3 entirely non-raft associated. NHERF2 expression enhanced the localization of NHE3 to membrane rafts. The use of acid sphingomyelinase-deficient mice, which have altered membrane lipid as well as lipid raft composition, allowed us to test the validity of the lipid raft concept in vivo. Conclusions The differential association of the NHERFs with the raft-associated and the non-raft fraction of NHE3 in the brush border membrane is one component of the differential and signal-specific NHE3 regulation by the different NHERFs. PMID:24297041

  4. 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.

  5. Cylindrical Brushes

    NASA Astrophysics Data System (ADS)

    Schmidt

    1998-03-01

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

  6. 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 ...

  7. 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.

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

    PubMed

    Sheparovych, Roman; Motornov, Mikhail; Minko, Sergiy

    2008-12-16

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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 'King George Island' Brushed

    NASA Technical Reports Server (NTRS)

    2006-01-01

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

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

  17. 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.

  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. Interaction between two polyelectrolyte brushes.

    PubMed

    Kumar, N Arun; Seidel, Christian

    2007-08-01

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

  20. Polymer brushes: Tools for surface design

    NASA Astrophysics Data System (ADS)

    Ober, Christopher

    2011-03-01

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

  1. Border Battle.

    PubMed

    Berlin, Joey

    2015-11-01

    The Texas Medical Association, the Texas Alliance for Patient Access, and other organizations ask for reversal of a court ruling that allows a Texas negligence case to proceed in New Mexico. The case is sounding alarms all over Texas' medical community, conjuring fears that if the Supreme Court upholds the application of New Mexico law, it could have a significant impact on Texas doctors who operate near the state's vast borders and treat out-of-state patients.

  2. Iraq Border

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In an area north of the city of Al-Basrah, Iraq, which borders Iran, a former wetland has been drained and walled off. Now littered with minefields and gun emplacments, it is a staging area for military exercises. This image was acquired by Landsat 7's Enhanced Thematic Mapper plus (ETM+) sensor on January 24, 2001. This is a false-color composite image made using near-infrared, red, and green wavelengths. The image has also been sharpened using the sensor's panchromatic band. Image provided by the USGS EROS Data Center Satellite Systems Branch

  3. Air Force brush seal programs

    NASA Astrophysics Data System (ADS)

    Dowler, Connie

    1993-10-01

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

  4. 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.

  5. 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

  6. 21 CFR 884.1100 - Endometrial brush.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

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

  7. 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.)

  8. 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.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  11. 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.

  12. A novel approach for measuring the intrinsic nanoscale thickness of polymer brushes by means of atomic force microscopy: application of a compressible fluid model

    NASA Astrophysics Data System (ADS)

    Cuellar, José Luis; Llarena, Irantzu; Iturri, Jagoba J.; Donath, Edwin; Moya, Sergio Enrique

    2013-11-01

    The thickness of a poly(sulfo propyl methacrylate) (PSPM) brush is determined by Atomic Force Microscopy (AFM) imaging as a function of the loading force at different ionic strengths, ranging from Milli-Q water to 1 M NaCl. Imaging is performed both with a sharp tip and a colloidal probe. The brush thickness strongly depends both on the applied load and on the ionic strength. A brush thickness of 150 nm is measured in Millipore water when applying the minimal loading force. Imaging with an 8 μm silica particle as a colloidal probe results in a thickness of 30 nm larger than that measured with the tip. Increasing the ionic strength causes the well known reduction of the thickness of the brush. The apparent thickness of the brush decreases with increasing loading forces. An empirical model analogous to that of a compressible fluid is applied to describe the dependence of the apparent thickness of the brush with loading force. The model comprises three ionic strength dependent parameters for the brush: thickness at infinite compression, energy, and cohesive force. The meaning and significance of these parameters are discussed. A particular advantage of the model is that it allows for determination of the brush thickness at zero loading force.The thickness of a poly(sulfo propyl methacrylate) (PSPM) brush is determined by Atomic Force Microscopy (AFM) imaging as a function of the loading force at different ionic strengths, ranging from Milli-Q water to 1 M NaCl. Imaging is performed both with a sharp tip and a colloidal probe. The brush thickness strongly depends both on the applied load and on the ionic strength. A brush thickness of 150 nm is measured in Millipore water when applying the minimal loading force. Imaging with an 8 μm silica particle as a colloidal probe results in a thickness of 30 nm larger than that measured with the tip. Increasing the ionic strength causes the well known reduction of the thickness of the brush. The apparent thickness of the brush

  13. 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.

  14. Simple leakage flow model for brush seals

    NASA Astrophysics Data System (ADS)

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

    1991-06-01

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

  15. Stimuli-sensitive intrinsically disordered protein brushes

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  16. Tooth brushing inhibits oral bacteria in dogs.

    PubMed

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

    2015-10-01

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

  17. Nanopatterned polymer brushes: conformation, fabrication and applications

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  18. Brush seals for turbine engine fuel conservation

    NASA Astrophysics Data System (ADS)

    Sousa, Mike

    1994-07-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  20. 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

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

    PubMed

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

    2014-12-24

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

  2. 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.

  3. 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.

  4. 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.

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

    PubMed

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

    2011-09-01

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

  6. 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.

  7. 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.

  8. 21 CFR 886.1090 - Haidinger brush.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

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

  9. 21 CFR 886.1090 - Haidinger brush.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

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

  10. 21 CFR 886.1090 - Haidinger brush.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

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

  11. 21 CFR 886.1090 - Haidinger brush.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

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

  12. 21 CFR 886.1090 - Haidinger brush.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

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

  13. 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.

  14. Liquid Crystalline Phases of Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Amini, Kiana; Abukhdeir, Nasser; Matsen, Mark

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

  15. Border Trade Facilitation System

    SciTech Connect

    Goldsmith, Steven Y.

    1999-06-07

    System for managing commercial trans-border shipments via the Internet. This application assists geographically distributed commercial and governmental users with the transshipment of goods across the U.S. - Mexico border.

  16. A novel approach for measuring the intrinsic nanoscale thickness of polymer brushes by means of atomic force microscopy: application of a compressible fluid model.

    PubMed

    Cuellar, José Luis; Llarena, Irantzu; Iturri, Jagoba J; Donath, Edwin; Moya, Sergio Enrique

    2013-12-01

    The thickness of a poly(sulfo propyl methacrylate) (PSPM) brush is determined by Atomic Force Microscopy (AFM) imaging as a function of the loading force at different ionic strengths, ranging from Milli-Q water to 1 M NaCl. Imaging is performed both with a sharp tip and a colloidal probe. The brush thickness strongly depends both on the applied load and on the ionic strength. A brush thickness of 150 nm is measured in Millipore water when applying the minimal loading force. Imaging with an 8 μm silica particle as a colloidal probe results in a thickness of 30 nm larger than that measured with the tip. Increasing the ionic strength causes the well known reduction of the thickness of the brush. The apparent thickness of the brush decreases with increasing loading forces. An empirical model analogous to that of a compressible fluid is applied to describe the dependence of the apparent thickness of the brush with loading force. The model comprises three ionic strength dependent parameters for the brush: thickness at infinite compression, energy, and cohesive force. The meaning and significance of these parameters are discussed. A particular advantage of the model is that it allows for determination of the brush thickness at zero loading force.

  17. Binary Polymer Brushes of Strongly Immiscible Polymers.

    PubMed

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

    2015-06-17

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

  18. 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

  19. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

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

  20. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

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

  1. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

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

  2. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

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

  3. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

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

  4. 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

  5. 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.

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

    PubMed

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

    2013-12-10

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

  7. Tribopair evaluation of brush seal applications

    NASA Astrophysics Data System (ADS)

    Derby, J.; England, R.

    1992-07-01

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

  8. 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.

  9. Touch- and Brush-Spinning of Nanofibers.

    PubMed

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

    2015-11-01

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

  10. Responsive polymer brushes for controlled nanoparticle exposure

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  11. 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.

  12. 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

  13. 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

  14. 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.

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

    NASA Technical Reports Server (NTRS)

    Holm, Ragnar

    1944-01-01

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

  16. The Border Pedagogy Revisited

    ERIC Educational Resources Information Center

    Kazanjian, Christopher John

    2011-01-01

    Border pedagogy is a multicultural educational approach utilized in multicultural settings to help students understand their histories and experiences and how it affects their identities and cultures. The approach seeks to produce intellectuals that transcend physical and metaphysical boundaries. The goal of border pedagogy is to remove cultural…

  17. 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).

  18. 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.

  19. Artificial periodontal defects and frequency of tooth brushing in beagle dogs (I). Clinical findings after creation of the defects.

    PubMed

    Corba, N H; Jansen, J; Fidler, V

    1986-02-01

    This investigation was designed to determine the influence of different frequencies of tooth brushing on artificial periodontal defects in the beagle dog shortly after creation. In 12 beagle dogs, periodontal defects were created using elastic bands placed in the sulci below the gingival margin after having cut the dento-gingival fibres to the level of the alveolar bone. This active phase of creating defects lasted for 6 weeks. 6 premolars in the lower jaw were used (2P2, 3P3, 4P4). After removal of the elastic bands, the 12 dogs were distributed into 3 groups of 4 dogs each. Each group was brushed with a certain frequency, i.e., 7 times, 3 times or once a week. Plaque index, gingival index and probing depth, using a constant force probe, were assessed interproximally. The experiment lasted for 24 weeks. For hypothesis testing, a brushing effect was calculated for each dog. Furthermore, an analysis was performed based on the absolute scores at week 24. From the statistical analysis, it was concluded that in artificially-induced periodontal defects in beagle dogs immediately after creation, brushing 7 times a week is superior to brushing 3 times a week to establish and maintain gingival health.

  20. Artificial periodontal defects and frequency of tooth brushing in beagle dogs (II). Clinical findings after a period of healing.

    PubMed

    Corba, N H; Jansen, J; Pilot, T

    1986-03-01

    This investigation was designed to determine the influence of different frequencies of tooth brushing on artificial periodontal defects in the beagle dog after a period of healing. In 12 beagle dogs, periodontal defects were created using elastic bands placed in the sulci below the gingival margin after having cut the dento-gingival fibres to the level of the alveolar bone crest. This active phase of creating defects lasted for 6 weeks. After removal of the elastic bands, the created defects were left undisturbed during the remainder of the pre-experimental period (12 weeks). 6 premolars in the lower jaw were used (2P2, 3P3, 4P4). After the pre-experimental period, the 12 dogs were distributed into 3 groups of 4 dogs each. Each group was brushed with a certain frequency, i.e., 7 times, 3 times or once a week. Registrations of plaque index, gingival index and probing depth using a constant force probe were carried out on approximal surfaces. The experiment lasted for 24 weeks. A brushing effect was calculated for each dog to include information on all within-dog and between-dog variations. It was shown in relation to artificially-induced periodontal defects in beagle dogs that after a period of healing, brushing 7 times a week is superior to brushing 3 times a week in establishing and maintaining gingival health.

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

    PubMed

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

    2010-05-01

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

  2. LM2500+ Brush Seal Case Study

    NASA Technical Reports Server (NTRS)

    Haaser, Fred G.

    2006-01-01

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

  3. Two-stage eutectic metal brushes

    SciTech Connect

    Hsu, John S

    2009-07-14

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

  4. 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.

  5. Bordering on environmental disaster.

    PubMed Central

    Schmidt, C W

    2000-01-01

    Millions of people live on the U.S.-Mexico border, drawn by employment opportunities from industry and agriculture, and booming growth is expected to continue in the coming decades. But the influx of people has long outstripped the capacity of border towns and cities to provide for their citizens, and a large percentage of the population lives in sprawling, underserviced shantytowns. Although investment in environmental infrastructure on both sides has led to improvements, shortages among necessities such as drinking water, wastewater treatment, and solid waste disposal are at crisis levels. In addition, a host of diseases including gastrointestinal infections, asthma, tuberculosis, multiple myeloma, systemic lupus erythematosus, hepatitis A, neural tube defects, and lead poisoning have been linked to environmental conditions on the border. Ongoing binational studies are attempting to define the breadth of the public and environmental health crisis and find ways to help make the border a healthier place. PMID:10903625

  6. Border cells versus border-like cells: are they alike?

    PubMed

    Driouich, Azeddine; Durand, Caroline; Cannesan, Marc-Antoine; Percoco, Giuseppe; Vicré-Gibouin, Maité

    2010-09-01

    Roots of many plants are known to produce large numbers of 'border' cells that play a central role in root protection and the interaction of the root with the rhizosphere. Unlike border cells, border-like cells were described only recently in the model plant Arabidopsis thaliana and other Brassicaceae species and very little is known about the functional properties of border-like cells as compared with 'classical' border cells. To stimulate discussion and future research on this topic, the function of border cells and the way border-like cells are organized, maintained, and possibly involved in plant protection is discussed here.

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

    PubMed

    Gulati, M S; Gupta, L

    1998-03-01

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

  8. 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…

  9. Multifunctional brushes made from carbon nanotubes.

    PubMed

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

    2005-07-01

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

  10. 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

  11. 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

  12. 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.

  13. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  15. Electric double layer electrostatics of pH-responsive spherical polyelectrolyte brushes in the decoupled regime.

    PubMed

    Li, Hao; Chen, Guang; Das, Siddhartha

    2016-11-01

    Understanding the behavior and properties of spherical polyelectrolyte brushes (SPEBs), which are polyelectrolyte brushes grafted to a spherical core, is fundamental to many applications in biomedical, chemical and petroleum engineering as well as in pharmaceutics. In this paper, we study the pH-responsive electrostatics of such SPEBs in the decoupled regime. In the first part of the paper, we derive the scaling conditions in terms of the grafting density of the PEs on the spherical core that ensure that the analysis can be performed in the decoupled regime. In such a regime the elastic and the excluded volume effects of polyelectrolyte brushes (PEBs) can be decoupled from the electrostatic effects associated with the PE charge and the induced EDL. As a consequence the PE brush height, assumed to be dictated by the balance of the elastic and excluded volume effects, can be independent of the electrostatic effects. In the second part, we quantify the pH-responsive electrostatics of the SPEBs - we pinpoint that the radial monomer distribution for a given brush molecule exhibit a non-unique cubic distribution that decays away from the spherical core. Such a monomer distribution ensures that the hydrogen ion concentration is appropriately accounted for in the description of the SPEB thermodynamics. We anticipate that the present analysis, which provides possibly one of the first models for probing the electrostatics of pH-responsive SPEBs in a thermodynamically-consistent framework, will be vital for understanding the behavior of a large number of entities ranging from PE-coated NPs and stealth liposomes to biomolecules like bacteria and viruses.

  16. 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.

  17. Model tests of living brush mattresses made of shrub and tree willows as bank protection at navigable waters

    NASA Astrophysics Data System (ADS)

    Sokopp, Manuel

    2014-05-01

    The embankment stability at navigable waters suffers from hydraulic loads, like strong ship induced waves, resulting hydropeaking and strong water-level fluctuations. Willow brush mattresses can reduce erosion at the embankments of rivers and increase bank stability. Due to experiences gained in the project "Alternative Technical-Biological Bank Protection on Inland Water-ways" the Federal Waterways Engineering and Research Institute commissioned a more detailed investigation of protective functions of willow brush mattresses respectively the differences between brush mattresses made of pure shrub (Salix viminalis) or tree willows (Salix alba) at water ways with high ship-induced hydraulic loads. This paper shows the upcoming research methods of the years 2014 to 2016. The protective functions of two different willow brush mattresses and the congruence between soil, hydraulics and willow sprouts movement will be investigated in a wave basin by measuring flow velocity with ADVs (Acoustic Doppler Velocimeters) installed near the soil surface and in different embankment areas, the pore water pressure with probes in different soil layers, the wave height with ultrasound probes and the willow movements with permanently installed cameras while flooding the basin as well as measuring the erosion afterwards. These flooding test series will be conducted two times during the vegetation period. The shear strength of the tree willow rooted soil will be examined in different soil layers with a shear load frame. The results will be compared with the data of shear strength tests of same aged brush mattresses made of shrub willows, which have already been carried out by the Federal Waterways Engineering and Research Institute. The filtering capability of the soil covering branches and the near surface willow roots will be investigated by growing willow brush mattresses in sample boxes. Those can be repeatedly moved up and down into a diving pool while measuring pore water pressure

  18. 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.

  19. 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.

  20. 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.

  1. Lubrication at physiological pressures by polyzwitterionic brushes.

    PubMed

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

    2009-03-27

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

  2. 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

  3. Lubrication at Physiological Pressures by Polyzwitterionic Brushes

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

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

  4. Antifouling Polymer Brushes Displaying Antithrombogenic Surface Properties.

    PubMed

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

    2016-03-14

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

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

    PubMed

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

    1992-01-01

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

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

    PubMed

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

    2011-08-01

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

  7. "Border Sexualities, Border Families in Schools": Queering Education

    ERIC Educational Resources Information Center

    Ryan, John

    2012-01-01

    This essay reviews Maria Pallotta-Chiarolli's (2010) Lambda Award-winning monograph "Border Sexualities, Border Families in Schools", in which queer and mestizage pedagogies frame a groundbreaking and highly accessible exploration of the issues that sexual border dwellers experience. Her particular focus areas are bisexual "sexually fluid"…

  8. "Over the River": Border Childhoods and Border Crossings at Niagara

    ERIC Educational Resources Information Center

    Helleiner, Jane

    2007-01-01

    Drawing on interviews with Canadian borderlanders, this article examines childhood experiences with the Canada--US border in the mid-1980s to early 1990s. The retrospective accounts of childhood border experiences demonstrate how childhood was produced and experienced in border crossings and how the production of childhood intersected with a…

  9. 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.

  10. Binding of isolectins from red kidney bean (Phaseolus vulgaris) to purified rat brush-border membranes.

    PubMed

    Boldt, D H; Banwell, J G

    1985-12-13

    Ingestion of red kidney bean phytohemagglutinin causes impaired growth and intestinal malabsorption, and facilitates bacterial colonization in the small intestine of weanling rats. We have studied interactions of the highly purified phytohemagglutinin erythroagglutinating (E4) and mitogenic (L4) isolectins with microvillous membrane vesicles prepared from rat small intestines. E4 and L4 were radioiodinated with 125I by the chloramine-T technique. E4 and L4 isolectins both bound to microvillous membrane vesicles. Binding was saturable and reversible. Each mg of membrane protein bound 744 +/- 86 micrograms E4 and 213 +/- 21 micrograms L4. The apparent Ka for E4 and L4 binding was 2.5 x 10(-6) and 13.0 x 10(-6) M-1, respectively. Binding of each 125I-labelled isolectin was abolished by 100-fold excess of unlabelled isolectin. In each case binding also was inhibited by appropriate oligosaccharide inhibitors, indicating that isolectin-microvillous membrane interactions were mediated by carbohydrate recognition. Patterns of saccharide inhibition of isolectin binding were different for E4 and L4. Competitive binding experiments demonstrated mutual noncompetitive inhibition of E4 and L4 binding consistent with steric hindrance. Therefore, E4 and L4 each bound to its own set of receptors. Based on the known saccharide specificities of E4 and L4, these data indicate that there are differences in expression of complex asparagine-linked biantennary and tri- or tetraantennary oligosaccharides at the microvillous surface. The data also provide the possibility that direct interactions of one or more phytohemagglutinin isolectins with intestinal mucosa in vivo may contribute to the antinutritional effects associated with ingestion of crude red kidney beans. PMID:4063394

  11. Phase separation of rat intestinal brush border membrane proteins using Triton X-114.

    PubMed

    Tiruppathi, C; Alpers, D H; Seetharam, B

    1986-03-01

    Rat intestinal microvillus membrane contains at least 24 polypeptides, of which 18 can be solubilized using Triton X-114 at 4 degrees C. Upon phase separation at 32 degrees C, 11 proteins separated nearly completely into the detergent-rich phase, while 9 proteins were found exclusively in the aqueous phase. Enzymes which were uniquely included in the detergent phase were alkaline phosphatase, leucine aminopeptidase, gamma-glutamyl transpeptidase, and Ca2+-Mg2+ ATPase. The proteins which were excluded from the detergent phase and found exclusively in the aqueous phase included the disaccharidases (glucoamylase, sucrase-isomaltase, trehalase, lactase) and the ileal receptor for the intrinsic factor-cobalamin complex. Integral membrane proteins can thus be separated during solubilization into two groups prior to further purification or characterization.

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

    PubMed

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

    2006-09-01

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

  13. Thiolation of polycarbophil enhances its inhibition of intestinal brush border membrane bound aminopeptidase N.

    PubMed

    Bernkop-Schnürch, A; Zarti, H; Walker, G F

    2001-11-01

    The purpose of this study was to evaluate the potential of polycarbophil-cysteine conjugates (PCP-Cys) as an oral excipient to protect leucine enkephalin (leu-enkp) from enzymatic degradation by the intestinal mucosa. Cysteine was covalently linked to polycarbophil by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC). Inhibitory activity was tested towards isolated aminopeptidase N and excised intact pig intestinal mucosa, with native mucus. Aminopeptidase N activity was assayed spectrophotometrically using L-leucine p-nitroanilide (leu-pNA) as a synthetic substrate and against the model peptide drug leu-enkp, by high-performance liquid chromatography (HPLC). Free cysteine at 6.3 and 63 microM (pH 6) significantly (p < 0.05) inhibited aminopeptidase N activity, and PCP-Cys (0.25% w/v, pH 6) had a significantly (p < 0.05) greater inhibitory effect than PCP on the aminopeptidase N activity towards both substrates. PCP-Cys completely protected leu-enkp against aminopeptidase N activity over a 2-h incubation period, whereas 83 +/- 4 and 60 +/- 7% remained stable in the presence of PCP and buffer only, respectively. Leu-enkp in the absence and presence of PCP (0.25% w/v) at pH 6 was completely digested by the intact intestinal mucosa at the 60- and 90-min incubation time points, respectively, whereas in the presence of PCP-Cys (0.25% w/v, pH 6) 11 +/- 3.5% of leu-enkp remained at the 120-min time point. Thiolation of PCP increased the stability of leu-enkp against the enzymatic degradation by aminopeptidase N and the intact intestinal mucosa, identifying a promising new excipient for peroral delivery of peptides.

  14. ZINC UPTAKE BY LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  15. FERRIREDUCTASE ACTIVITY IN LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES (BBMV). (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  16. CALCIUM TRANSPORT PROCESSES OF LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  17. Alterations in gut microflora populations and brush border functionality following intra-amniotic daidzein administration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Daidzein is an isoflavone found primarily in soybean and various soy-based products such as tofu. In the intestines, daidzein is reductively transformed to its constituent metabolites equol and O-desmethylangolensin. Although the ingestion of daidzein has been associated with marked physiological im...

  18. Dicyclohexylcarbodiimide (DCCD) sensitive organic cation/H/sup +/ antiporter in renal brush border membrane vesicles (BBMV)

    SciTech Connect

    Sokol, P.P.; Holohan, P.D.; Ross, C.R.

    1986-03-01

    We tested the hypothesis that organic cation transport in BBMV is coupled to the countertransport of a H/sup +/ by employing a prototypic organic cation, N/sup 1/-methylnicotinamide (NMN), and a rapid filtration assay. Two H/sup +/ gradient uncouplers, carbonyl cyanide m-chlorophenylhydrazone (CCCP)/sub 3/ and gramicidin D were effective in dissipating H/sup +/ driven (/sup 3/H)NMN transport. Nigericin, a K/sup +//H/sup +/ exchanger, generated a H/sup +/ gradient in situ which drove the net accumulation of NMN. The molecular mechanism of H/sup +/ coupling was examined employing DCCD, a hydrophobic carbodiimide, which inactivates essential carboxylate groups, the putative H/sup +/ receptor. DCCD inactivated NMN transport irreversibly with an IC/sub 50/ of 2.6..mu..M whereas the hydrophilic carbodiimide, 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide, did not. DCCD inactivation followed pseudo-first-order kinetics and was not affected by NMN. A double logarithmic plot of the apparent rate constants vs. (DCCD) gave a slope of 0.8. The data are consistent with a simple bimolecular reaction mechanism and imply that one molecule of DCCD inactivates one carboxylate group per active transport unit. The results show that (1) the transport of organic cations is coupled to the countermovement of a H/sup +/ and (2) a carboxylate group is essential for H/sup +/ binding and translocation.

  19. 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.

  20. 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

  1. Astronomers without borders

    NASA Astrophysics Data System (ADS)

    Simmons, Mike

    2011-06-01

    ``Astronomers Without Borders'' is a new global organisational dedicated to furthering understanding and goodwill across national and cultural boundaries using the universal appeal of astronomy and space science. A growing network of affiliate organisations brings together clubs, magazines and other organizations involved in astronomy and space science. Forums, galleries, video conferences and other interactive technologies are used to connect participants around the world. Sharing of resources and direct connections through travel programs are also planned. One project, ``The World at Night'' (TWAN), has become an Special Project of IYA2009. TWAN creates wide-angle images of the night sky in important natural and historic settings around the world, dramatically demonstrating the universal nature and appeal of the night sky. ``Astronomers Without Borders'' is also a leader of the 100 Hours of Astronomy IYA2009 Global Cornerstone Project.

  2. Metrics for border management systems.

    SciTech Connect

    Duggan, Ruth Ann

    2009-07-01

    There are as many unique and disparate manifestations of border systems as there are borders to protect. Border Security is a highly complex system analysis problem with global, regional, national, sector, and border element dimensions for land, water, and air domains. The complexity increases with the multiple, and sometimes conflicting, missions for regulating the flow of people and goods across borders, while securing them for national security. These systems include frontier border surveillance, immigration management and customs functions that must operate in a variety of weather, terrain, operational conditions, cultural constraints, and geopolitical contexts. As part of a Laboratory Directed Research and Development Project 08-684 (Year 1), the team developed a reference framework to decompose this complex system into international/regional, national, and border elements levels covering customs, immigration, and border policing functions. This generalized architecture is relevant to both domestic and international borders. As part of year two of this project (09-1204), the team determined relevant relative measures to better understand border management performance. This paper describes those relative metrics and how they can be used to improve border management systems.

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

    NASA Astrophysics Data System (ADS)

    Milchev, Andrey; Binder, Kurt

    2014-06-01

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

  4. 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

  5. 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

  6. Efficacy and safety of BrushPicks, a new cleaning aid, compared to the use of Glide floss.

    PubMed

    Yankell, Samuel L; Shi, Xiuren; Emling, Robert C

    2002-01-01

    The objective of this double-blind, four-week clinical study was to evaluate the efficacy of BrushPicks, a new cleaning aid, and Glide floss on the reduction of plaque area, gingivitis and bleeding on probing, and to monitor safety when these products were used in addition to toothbrushing with an ADA-Accepted toothbrush (Oral-B P35) and an ADA-Accepted fluoride-containing dentifrice (Crest Regular). No special instructions on or supervision of product use was conducted, other than requesting twice-a-day (morning and evening) use of the assigned products. Following a baseline examination, 63 qualifying adult male and female subjects from the Philadelphia, Pennsylvania area were randomized into two groups. Subjects were also told to use their assigned dental aid after each toothbrushing. Examinations for efficacy and safety were repeated after two and four weeks' use of the products. Sixty-two subjects completed all aspects of the study. There were no untoward side effects attributed to product use, reported or observed, at the two- or four-week examination times. At baseline, there were no significant differences in plaque, gingivitis or bleeding on probing mean scores between the BrushPicks and Glide floss groups. At the two- and four-week evaluation times, both the BrushPicks and Glide floss had numerically lower plaque scores compared to baseline levels. The only statistically significant reduction (p < 0.01) was in the BrushPicks group, comparing the week two mean with the baseline value. Gingivitis (GI) at four weeks was statistically (p < 0.05) lower in the BrushPicks group as compared to the Glide floss mean value. When the changes in scores from baseline to two weeks and to four weeks were assessed, the mean GI score for the Glide floss group was significantly lower at two weeks (p < 0.01) compared to baseline, and also from two weeks to four weeks (p < 0.001). The change in mean GI score for the Glide floss group from baseline to four weeks was also

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

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

    NASA Astrophysics Data System (ADS)

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

    2002-10-01

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

  14. Preliminary experimental results for a cryogenic brush seal configuration

    NASA Astrophysics Data System (ADS)

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

    1993-06-01

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

  15. Preliminary experimental results for a cryogenic brush seal configuration

    NASA Astrophysics Data System (ADS)

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

    1993-06-01

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

  16. 75 FR 39706 - Natural Bristle Paint Brushes From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-12

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

  17. 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.

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. 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...

  8. 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…

  9. 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.

  10. Nanopatterned polymer brushes by reactive writing.

    PubMed

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

    2016-04-14

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

  11. Brush seal shaft wear resistant coatings

    NASA Astrophysics Data System (ADS)

    Howe, Harold

    1995-03-01

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

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

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

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

    PubMed

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

    2015-08-01

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

  15. 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.

  16. Atmospheric Science Without Borders

    NASA Astrophysics Data System (ADS)

    Panday, Arnico; Praveen, Ps; Adhikary, Bhupesh; Bhave, Prakash; Surapipith, Vanisa; Pradhan, Bidya; Karki, Anita; Ghimire, Shreta; Thapa, Alpha; Shrestha, Sujan

    2016-04-01

    The Indo-Gangetic Plains (IGP) in northern South Asia are among the most polluted and most densely populated places in the world, and they are upwind of vulnerable ecosystems in the Himalaya mountains. They are also fragmented across 5 countries between which movement of people, data, instruments and scientific understanding have been very limited. ICIMOD's Atmosphere Initiative has for the past three years been working on filling data gaps in the region, while facilitating collaborations across borders. It has established several atmospheric observatories at low and mid elevations in Bhutan and Nepal that provide new data on the inflow of pollutants from the IGP towards the mountains, as well as quantify the effects of local emissions on air quality in mountain cities. EGU will be the first international conference where these data will be presented. ICIMOD is in the process of setting up data servers through which data from the region will be shared with scientists and the general public across borders. Meanwhile, to promote cross-border collaboration among scientists in the region, while addressing an atmospheric phenomenon that affects the lives of the several hundred million people, ICIMOD' Atmosphere Initiative has been coordinating an interdisciplinary multi-year study of persistent winter fog over the Indo-Gangetic Plains, with participation by researchers from Pakistan, India, China, Nepal, Bhutan and Bangladesh. Using a combination of in-situ measurements and sample collection, remote sensing, modeling and community based research, the researchers are studying how changing moisture availability and air pollution have led to increases in fog frequency and duration, as well as the fog's impacts on local communities and energy demand that may affect air pollution emissions. Preliminary results of the Winter 2015-2016 field campaign will be shown.

  17. 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.

  18. 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

  19. 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

  20. Mentors without Borders.

    PubMed

    Muenke, Maximilian

    2016-09-01

    Mentors without Borders is a proposed international mentoring network that allows trainee geneticists to identify mentors from a list of volunteers who are not at one's own institution. It is an experiment, a matchmaker between a junior and a senior professional. These mentors do not replace the mentors at the home institution but allow the mentee, if desired, to identify mentors outside of their own institution. We envision that different ways of communicating and/or different mentor-mentee relationships may prove beneficial to the trainee and the mentor. PMID:27652276

  1. Collaborating Across Borders

    NASA Astrophysics Data System (ADS)

    Flatten, Amy

    Physicists transcend national boundaries, ethnic differences, and scientific disciplines to address globally shared problems and questions. This talk will highlight how scientists have collaborated across borders - both geographic and scientific - to achieve ground-breaking discoveries through international scientific cooperation. The speaker also will address how international collaborations will be even more crucial for addressing future challenges faced by the physics community, such as building large-scale research facilities, strengthening scientific capacity in developing countries, fostering ''science for diplomacy'' in times of political tensions and other critical issues.

  2. 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...

  3. 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...

  4. 75 FR 34097 - Natural Bristle Paint Brushes and Brush Heads From the People's Republic of China: Notice of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-16

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

  5. 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.

  6. Color of smoke from brush fires.

    PubMed

    Lynch, David K; Bernstein, Lawrence S

    2008-12-01

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

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

    PubMed

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

    2016-09-28

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

  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. 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.

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

    PubMed

    Buchalla, W; Attin, T; Hellwig, E

    2000-01-01

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

  11. Crossing borders for science.

    PubMed

    Schultheiss, Sebastian J; Yang, Joshua SungWoo; Iwasaki, Wataru; Lin, Shu-Hsi; Jean, Angela; Michaut, Magali

    2014-03-01

    Exchanging ideas with like-minded, enthusiastic people interested in the same topic is crucial for the advancement of a scientist's career. Several Regional Student Groups (RSGs) of the International Society for Computational Biology (ISCB) Student Council have cooperated in the last six years to organize scientific workshops and conferences. With motivated students, it is possible to create a memorable event for fellow scientists; in doing so, the organizers gain valuable experiences. While collaborating across borders and time zones can be difficult, feedback from event organizers was always positive. When limited resources are juxtaposed with great ideas and a network of contacts, the outcome is always an amazing experience, despite organizers being separated geographically across different countries.

  12. Life on the Hardened Border

    ERIC Educational Resources Information Center

    Miller, Bruce Granville

    2012-01-01

    The many Coast Salish groups distributed on both sides of the United States-Canada border on the Pacific coast today face significant obstacles to cross the international border, and in some cases are denied passage or intimidated into not attempting to cross. The current situation regarding travel by Aboriginal people reflects the "hardening" of…

  13. Microsensors for border patrol applications

    NASA Astrophysics Data System (ADS)

    Falkofske, Dwight; Krantz, Brian; Shimazu, Ron; Berglund, Victor

    2005-05-01

    A top concern in homeland security efforts is the lack of ability to monitor the thousands of miles of open border with our neighbors. It is not currently feasible to continually monitor the borders for illegal intrusions. The MicroSensor System (MSS) seeks to achieve a low-cost monitoring solution that can be efficiently deployed for border patrol applications. The modifications and issues regarding the unique requirements of this application will be discussed and presented. The MicroSensor System was developed by the Defense Microelectronics Activity (DMEA) for military applications, but border patrol applications, with their unique sensor requirements, demand careful adaptation and modification from the military application. Adaptation of the existing sensor design for border applications has been initiated. Coverage issues, communications needs, and other requirements need to be explored for the border patrol application. Currently, border patrol has a number of deficiencies that can be addressed with a microsensor network. First, a distributed networked sensor field could mitigate the porous border intruder detection problem. Second, a unified database needs to be available to identify aliens attempting to cross into the United States. This database needs to take unique characteristics (e.g. biometrics, fingerprints) recovered from a specialized field unit to reliably identify intruders. Finally, this sensor network needs to provide a communication ability to allow border patrol officers to have quick access to intrusion information as well as equipment tracking and voice communication. MSS already addresses the sensing portion of the solution, including detection of acoustic, infrared, magnetic, and seismic events. MSS also includes a low-power networking protocol to lengthen the battery life. In addition to current military requirements, MSS needs a solar panel solution to extend its battery life to 5 years, and an additional backbone communication link

  14. 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

  15. In-Plane Ordering in Diblock Copolymer Brushes.

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

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

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

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

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

    NASA Astrophysics Data System (ADS)

    Römer, F.; Fedosov, D. A.

    2015-03-01

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

  2. 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 - ...

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  6. 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.

  7. 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

  8. 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.

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

    PubMed

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

    1996-06-01

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

  10. 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).

  11. 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.

  12. 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.

  13. 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

  14. Polymer-nanocomposite brush-like architectures as an all-solid electrolyte matrix.

    PubMed

    Gowneni, Soujanya; Ramanjaneyulu, Kota; Basak, Pratyay

    2014-11-25

    Herein, we report on polymer-nanocomposites with brush-like architectures and evaluate their feasibility as an all-solid electrolyte matrix supporting Li(+)-ion conduction. Showcased as a first example in the domain of electrolyte research, the study probes several key factors, such as (i) core morphology, (ii) surface modifiers/functionality, (iii) grafting length, and (iv) density of the brushes, and determines their role on the overall electrochemical properties of these nanostructured organic-inorganic hybrids. Nanostructured titania was synthesized via wet-chemical approaches using either controlled hydrolysis or hydrothermal methods. Exercising suitable control on reaction parameters led to well-defined morphologies/phases, such as nanoparticles, nanospindles, nanourchins, nanorods or nanotubes, in either anatase, rutile or mixed forms. Covalent anchoring on titania nanostructures was achieved using dopamine, gallic acid and glycerol as small organic moieties. A one-pot process of priming the available surface functional groups postmodification with isocyanate chemistry was followed by grafting polyethylene glycol monomethyl ethers of desired chain lengths. Finally, complexation with lithium salt yielded electrolyte compositions where the ethylene oxide (EO) fractions aid in ion-solvation with ease. The synthesized materials were characterized in detail employing XRD, TEM, DRS-UV, FTIR, micro-Raman, TG-DTA and DSC at each stage to confirm the products and ascertain the physicochemical properties. Comprehensive evaluation using temperature-step electrochemical impedance spectroscopy (EIS) of these brush-like nanocomposites provided crucial leads toward establishing a plausible physical model for the system and understanding the mechanism of ion transport in these all-solid matrices. The preliminary results on ionic conductivity (σ) obtained for some of the compositions are estimated to be within the range of ∼10(-4) to 10(-5) S cm(-1) in the temperature

  15. 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.

  16. 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

  17. Advanced border monitoring sensor system

    NASA Astrophysics Data System (ADS)

    Knobler, Ronald A.; Winston, Mark A.

    2008-04-01

    McQ has developed an advanced sensor system tailored for border monitoring that has been delivered as part of the SBInet program for the Department of Homeland Security (DHS). Technology developments that enhance a broad range of features are presented in this paper, which address the overall goal of the system to improving unattended ground sensor system capabilities for border monitoring applications. Specifically, this paper addresses a system definition, communications architecture, advanced signal processing to classify targets, and distributed sensor fusion processing.

  18. 76 FR 70760 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-American Brush...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-15

    ... Brush Manufacturers Association Notice is hereby given that, on October 12, 2011, pursuant to Section 6... Act''), American Brush Manufacturers Association (``ABMA'') has filed written notifications... organization is: American Brush Manufacturers Association, Aurora, IL. The nature and scope of ABMA's...

  19. Dendritic brushes under good solvent conditions: a simulation study.

    PubMed

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

    2012-12-11

    The structural properties of polymer brushes, formed by dendron polymers up to the third generation, were studied by means of Brownian dynamics simulations for the macroscopic state of good solvent. The distributions of polymer units, of the free ends, of the dendrons centers of mass, and of the units of every dendritic generation and the radii of gyration necessary for the understanding of the internal stratification of brushes were calculated. Previous self-consistent field theory numerical simulations of first-generation dendritic brushes suggested that at high grafting densities two kinds of populations are evident, one of short dendrons having weakly extended spacers and another with tall dendrons having strongly stretched spacers. These Brownian dynamics calculations provided a more complicated picture of dendritic brushes, revealing different populations of short, tall, and in some cases intermediate height dendrons, depending on the dendron generation and spacer length. The scaling dependence of the height and the span of the dendritic brush on the grafting density and other parameters were found to be in good agreement with existing theoretical results for good solvents. PMID:23134236

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

    PubMed Central

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

    2010-01-01

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

  1. 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.

  2. 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

  3. Real-time Monitoring of Surface-Initiated Atom Transfer Radical Polymerization Using Silicon Photonic Microring Resonators: Implications for Combinatorial Screening of Polymer Brush Growth Conditions

    PubMed Central

    Limpoco, F. Ted; Bailey, Ryan C.

    2011-01-01

    We directly monitor in parallel and in real-time the temporal profiles of polymer brushes simultaneously grown via multiple ATRP reaction conditions on a single substrate using arrays of silicon photonic microring resonators. In addition to probing relative polymerization rates, we also show the ability to evaluate the dynamic properties of the in situ grown polymers. Taken together, this presents a powerful new platform for studying modified interfaces that may allow for the combinatorial optimization of surface initiated polymerization conditions. PMID:21899288

  4. Integrity testing of brush seal in a T-700 engine

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    A split-ring brush seal was fabricated, installed between two labyrinth-honeycomb shroud seals, and tested in the fourth-stage turbine of a T-700 engine. The annealed Haynes 25 bristles rubbed directly against the nonconditioned, irregular Rene 80 turbine blade shroud surface. A total of 21 hr of cyclic and steady-state data were taken with surface speeds of 335 m/s (1100 ft/s) and shroud temperatures to 620 C (1150 F). Wear appeared to be rapid initially, with an orange flash of hot brush fragments during the first engine startup, to minimal after 10 hr of operation. The brush survived the testing but experienced some bristle pullouts and severe bristle wear; some turbine interface wear and possible material transfer was noted. Future design concerns center on tribological behavior at the interface with or without lubricants.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. The link between border crossing and obesity.

    PubMed

    Molina, Marisa A; Ayala, Guadalupe X; Baquero, Barbara; Madanat, Hala; Garcini, Luz

    2015-04-01

    Research examining border crossing and health has focused on substance abuse, healthcare utilization and air pollution. Living in border communities allows for frequent crossing and exposure to different sociocultural and structural environments. Given high rates of obesity among Latinos and the large percentage living in border communities, it is important to consider the relationship between border crossing and obesity. This study explored the relationship between frequency of border crossing, obesigenic behaviors, measured obesity, and chronic disease. Multistage sampling methods were used to recruit 397 Latino adults living in border communities in South San Diego County. Selected participants completed a face-to-face interview and height and weight measurements. More frequent border crossing was associated with more fast food consumption and a greater reported diagnosis of high cholesterol. Understanding the extent to which border crossing is associated with obesigenic behaviors and chronic disease is important for developing relevant interventions along the border.

  11. The link between border crossing and obesity.

    PubMed

    Molina, Marisa A; Ayala, Guadalupe X; Baquero, Barbara; Madanat, Hala; Garcini, Luz

    2015-04-01

    Research examining border crossing and health has focused on substance abuse, healthcare utilization and air pollution. Living in border communities allows for frequent crossing and exposure to different sociocultural and structural environments. Given high rates of obesity among Latinos and the large percentage living in border communities, it is important to consider the relationship between border crossing and obesity. This study explored the relationship between frequency of border crossing, obesigenic behaviors, measured obesity, and chronic disease. Multistage sampling methods were used to recruit 397 Latino adults living in border communities in South San Diego County. Selected participants completed a face-to-face interview and height and weight measurements. More frequent border crossing was associated with more fast food consumption and a greater reported diagnosis of high cholesterol. Understanding the extent to which border crossing is associated with obesigenic behaviors and chronic disease is important for developing relevant interventions along the border. PMID:24442511

  12. Apparatus to measure chemical wear of carbon brushes

    NASA Astrophysics Data System (ADS)

    Kosky, P. G.; Peters, H. C.; Spiro, C. L.; Lamby, E. J.; McKee, D. W.

    1985-07-01

    It has been inferred for several years that the wear of a carbon brush at a sliding interface of a dc machine is influenced by chemical factors. Previously, the difficulties of isolating and measuring chemical factors in such circumstances have discouraged specific verification. An apparatus is described that hermetically seals a selected polarity brush and uses an artificial atmosphere of humidified oxygen and argon to simulate air. By monitoring the ratio of mass spectrometric peaks of CO+2 to 36Ar+, a consistent rise is observed in the amount of CO2 present. The amount of carbon thus gasified exceeded 25% of the total carbon lost.

  13. 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

  14. A comparative study of stain removal with two electric toothbrushes and a manual brush.

    PubMed

    Moran, J M; Addy, M; Newcombe, R G

    1995-01-01

    Recent studies have suggested that a sonic electric toothbrush is more effective than a manual brush at removing extrinsic dental stain. There have been few studies of the comparative stain removal properties of different electric brushes. The study reported here was conducted to compare the efficacy of the sonic toothbrush (Sonicare) with an oscillating/rotating brush (Braun Oral-B Plaque Remover) and a conventional manual brush (Crest Complete). The study was a single-blind, randomized, cross-over design, balanced for residual effects and employing 24 subjects. Stain was enhanced over a 21-day period by twice-daily rinses with chlorhexidine and frequent intakes of tea and/or coffee. At the end of each period, tooth stain intensity and area, tongue stain intensity and area, lower lingual calculus and subjective tooth sensitivity were recorded together with preference for the brushes determined at the study's completion. Similar levels of tongue staining were recorded for the three periods, with no significant differences between the three groups. Tooth stain intensity, for most sites, was not significantly different between the three groups. For mean total stain area and for lingual and lingual interproximal sites, a significant reduction in stain was seen following use of the oscillating/rotating brush compared to the manual brush. The reductions in stain with the sonic brush were not significantly different from the manual brush. With the exception of maximum stain intensity, there were no significant differences between the oscillating/rotating and sonic brushes. Significantly less tooth sensitivity was found following use of the oscillating/rotating brush compared to both the manual and sonic brushes. All three brushes were found to be safe, but volunteer preference significantly and predominantly favored the oscillating/rotating brush. The results suggest that the oscillating/rotating brush is superior to a manual brush for stain removal.

  15. Polypeptoid Brushes by Surface-Initiated Polymerization of N-Substituted Glycine N-Carboxyanhydrides

    PubMed Central

    Schneider, Maximilian; Fetsch, Corinna; Amin, Ihsan; Jordan, Rainer; Luxenhofer, Robert

    2013-01-01

    Polypeptoid brushes were synthesized by surface-initiated polymerization of N-substituted glycine N-carboxyanhydrides (NNCAs) on self assembled amine monolayers. Using the presented grafting from approach, polypeptoid brush thicknesses of approx. 40 nm could be obtained as compared previously reported brush thicknesses of 4 nm. Moreover, hydrophilic, hydrophobic and amphiphilic polymer brushes were realized which are expected to have valuable applic-tions as non-fouling surfaces and as model or references systems for surface grafted polypeptides. PMID:23663172

  16. 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…

  17. 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

  18. On Borders: From Ancient to Postmodern Times

    NASA Astrophysics Data System (ADS)

    Bellezza, G.

    2013-11-01

    The article deals with the evolution of the concept of borders between human groups and with its slow evolution from the initial no men's land zones to the ideal single-dimension linear borders. In ancient times the first borders were natural, such as mountain ranges or large rivers until, with the development of Geodesy, astronomical borders based on meridians and parallels became a favourite natural base. Actually, Modern States adopted these to fix limits in unknown conquered territories. The postmodern thought led give more importance to cultural borders until, in the most recent times, is becoming rather impossible to fix borders in the virtual cyberspace.

  19. 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.

  20. Some metallographic results for brush bristles and brush segments of a shroud ring brush seal tested in a T-700 engine

    NASA Astrophysics Data System (ADS)

    Hendricks, Robert C.; Griffin, Thomas A.; Bobula, George A.; Bill, Robert C.; Hull, David R.; Csavina, Kristine R.

    1994-07-01

    Post-test investigation of a T-700 engine brush seal found regions void of bristles ('yanked out'), regions of bent-over bristles near the inlet, some 'snapped' bristles near the fence, and a more uniform smeared bristle interface between the first and last axial rows of bristles. Several bristles and four brush segments were cut from the brush seal, wax mounted, polished, and analyzed. Metallographic analysis of the bristle near the rub tip showed tungsten-rich phases uniformly distributed throughout the bristle, no apparent change within 1 mu m of the interface, and possibly a small amount of titanium, which would represent a transfer from the rotor. Analysis of the bristle wear face showed nonuniform tungsten, which is indicative of material resolidification. The cut end contained oxides and internal fractures; the worn end was covered with oxide scale. Material losses due to wear and elastoplastic deformation within the shear zone and third-body lubrication effects in the contact zone are discussed.

  1. Dendritic brushes under theta and poor solvent conditions.

    PubMed

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

    2013-07-28

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

  2. Charge regulation and local dielectric function in planar polyelectrolyte brushes

    SciTech Connect

    Kumar, Rajeev; Sumpter, Bobby G; Kilbey, II, S Michael

    2012-01-01

    Understanding the effect of inhomogeneity on the charge regulation and dielectric properties, and how it depends on the conformational characteristics of the macromolecules is a long-standing problem. In order to address this problem, we have developed a field-theory to study charge regulation and local dielectric function in planar polyelectrolyte brushes. The theory is used to study a polyacid brush, which is comprised of chains end-grafted at the solid-fluid interface, in equilibrium with a bulk solution containing monovalent salt ions, solvent molecules, and pH controlling acid. In particular, we focus on the effects of the concentration of added salt and pH of the bulk in determining the local charge and dielectric function. Our theoretical investigations reveal that the dipole moment of the ion-pairs formed as a result of counterion adsorption on the chain backbones play a key role in affecting the local dielectric function. For polyelectrolytes made of monomers having dipole moments lower than the solvent molecules, dielectric decrement is predicted inside the brush region. However, the formation of ion-pairs (due to adsorption of counterions coming from the dissociation of added salt) more polar than the solvent molecules is shown to increase the magnitude of the dielectric function with respect to its bulk value. Furthermore, an increase in the bulk salt concentration is shown to increase the local charge inside the brush region.

  3. 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.

  4. 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...

  5. Comparison of bronchial brushing and sputum in detection of pediatric pulmonary tuberculosis.

    PubMed

    Chen, Qiao-Pei; Ren, Shi-Feng; Wang, Xin-Feng; Wang, Mao-Shui

    2016-01-27

    The retrospective study aimed to evaluate the diagnostic value of bronchial brushing and sputum using acid fast bacilli smear, mycobacterial culture and real-time PCR in detection of pediatric pulmonary tuberculosis, sensitivity and specificity of bronchial brushing and sputum examined by the three methods were calculated and compared to each other. Data showed there were no significant difference in sensitivity between bronchial brushing and matched sputum using each method. But the specificity of real-time PCR on bronchial brushing was lower than on sputum. Compared with bronchial brushing, sputum was better specimen in detection of pediatric pulmonary tuberculosis.

  6. 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.

  7. 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.

  8. Brushing behavior among young adolescents: does perceived severity matter

    PubMed Central

    2014-01-01

    Background Oral health is a basis for general health and well-being and affects physical and psychological aspects of the human life. The aim of this study was to determine the power of the health belief model in general and the role of perceived severity and its components in particular in predicting tooth brushing behavior among young adolescents. Methods This was a cross sectional study of a sample of female students grade four in Rasht (a metropolitan in north Iran) in 2012. A systematic random sampling method was applied to recruit students. They were asked to respond to a designed questionnaire containing items on brushing behavior based on the health belief model. In this study for the first time perceived severity and perceived barriers were divided into two parts, perceived subjective and objective severity and perceived physical and psychological barriers and were treated as independent variables. Logistic regression analysis was performed in order to identify the variables that predict the desirable behavior (brushing twice a day or more). Results In all 265 female students were entered into the study. Of these, only 17.4% reported that they were brushing at least twice a day (desirable behavior). The results obtained from the logistic regression analysis indicated that perceived objective severity (OR = 0.37, 95% CI = 0.21- 0.66, P = 0.001) and feeling less perceived psychological barriers (OR = 2.60, 95% CI = 1.50- 4.52, P = 0.001) were the significant predicting factors for brushing twice a day. Conclusion The findings suggest that perceived objective severity and perceived psychological barriers play important role in adapting a desirable health behavior among young adolescents. PMID:24397588

  9. 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.

  10. The impact of Border policy effect on cross-border ethnic areas

    NASA Astrophysics Data System (ADS)

    Bie, Q. L.; Zhou, S. Y.; Li, C. S.

    2013-11-01

    Boundary effect analysis is related to border policy making in the cross-border ethnic area. The border effect literatures show that geographic boundaries have obvious impacts on economic, social and cultural relations in both sides of a nation border. Particularly in cross-border ethnic areas, each ethnic group has strong internal spatial structure relevance, and the boundary effect is more obvious. However, most of China's border areas are cross-border ethnic areas, each of border issues is unique. Under this perspective, we analyze the border effects of various boundaries can provide basis for formulating border management policies. For small scale of cross-border ethnic minority areas, how to formulate the boundary management policy is a good question to explore. This paper is demonstrated by a study of the impact of border management policies in Dehong Dai and Jingpo Autonomous Prefecture in Yunnan Province at the border area to Burma. The comparative method is used to analysis the border management policies in past 50 decades for the border area of Yunnan Province .This research aims to define trends within border policy and its influences to national security. This paper also examines Wendy Brown's liberal theory of border management policy. We found that it is not suitable for Sino-Burma border area. The conclusion is that the changes or instability of international economic and political situation has more influence to this cross-border ethnic area, and only innovative policy will be effective in cross-border ethnic area. So the border management policies should reflect the change of international context.

  11. 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

  12. Evaluation of multi-brush anode systems in microbial fuel cells.

    PubMed

    Lanas, Vanessa; Logan, Bruce E

    2013-11-01

    The packing density of anodes in microbial fuel cells (MFCs) was examined here using four different graphite fiber brush anode configurations. The impact of anodes on performance was studied in terms of carbon fiber length (brush diameter), the number of brushes connected in parallel, and the wire current collector gage. MFCs with different numbers of brushes (one, three or six) set perpendicular to the cathode all produced similar power densities (1200 ± 40 mW/m(2)) and coulombic efficiencies (60% ± 5%). Reducing the number of brushes by either disconnecting or removing them reduced power, demonstrating the importance of anode projected area covering the cathode, and therefore the need to match electrode projected areas to maintain high performance. Multi-brush reactors had the same COD removal as single-brush systems (>90%). The use of smaller Ti wire gages did not affect power generation, which will enable the use of less metal, reducing material costs. PMID:24063821

  13. Theoretical speed and current density limits for different types of electrical brushes

    NASA Astrophysics Data System (ADS)

    Kuhlmann-Wilsdorf, D.

    1984-03-01

    Theoretical performance limits based on the criterion of flash temperature are investigated for monolithic Ag-C brushes, Cu-on-Cu brushes with elastic contact spots, and 'QM' brushes (Quantum Mechanical brushes with ultrathin metal fibers), in which ordinary current conduction is significantly supplemented by electron tunneling peripherally about the contact spots. Equations are developed for the contact spot radii and heat input rates for frictional and electrical heating at the contact spots. Typical data for the flash temperatures are calculated for the high-speed approximation for plastic and elastic contact spots. The low-speed approximation is used for QM brushes. It is concluded that metal fiber and/or QM brushes may represent the best solution to the brush problem for electromagnetic launching.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  15. 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).

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

    PubMed

    Sakata, Sho; Inoue, Yuuki; Ishihara, Kazuhiko

    2016-10-01

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

  17. Spectrophotometric probe

    DOEpatents

    Prather, William S.; O'Rourke, Patrick E.

    1994-01-01

    A support structure bearing at least one probe for making spectrophotometric measurements of a fluid using a source of light and a spectrophotometer. The probe includes a housing with two optical fibers and a planoconvex lens. A sleeve bearing a mirror surrounds the housing. The lens is separated from the mirror by a fixed distance, defining an interior space for receiving a volume of the fluid sample. A plurality of throughholes extending through the sleeve communicate between the sample volume and the exterior of the probe, all but one hole bearing a screen. A protective jacket surrounds the probe. A hollow conduit bearing a tube is formed in the wall of the probe for venting any air in the interior space when fluid enters. The probe is held at an acute angle so the optic fibers carrying the light to and from the probe are not bent severely on emergence from the probe.

  18. Spectrophotometric probe

    DOEpatents

    Prather, W.S.; O'Rourke, P.E.

    1994-08-02

    A support structure is described bearing at least one probe for making spectrophotometric measurements of a fluid using a source of light and a spectrophotometer. The probe includes a housing with two optical fibers and a planoconvex lens. A sleeve bearing a mirror surrounds the housing. The lens is separated from the mirror by a fixed distance, defining an interior space for receiving a volume of the fluid sample. A plurality of throughholes extending through the sleeve communicate between the sample volume and the exterior of the probe, all but one hole bearing a screen. A protective jacket surrounds the probe. A hollow conduit bearing a tube is formed in the wall of the probe for venting any air in the interior space when fluid enters. The probe is held at an acute angle so the optic fibers carrying the light to and from the probe are not bent severely on emergence from the probe. 3 figs.

  19. Border-ownership-dependent tilt aftereffect

    NASA Astrophysics Data System (ADS)

    von der Heydt, Rüdiger; Macuda, Todd; Qiu, Fangtu T.

    2005-10-01

    Single-cell recordings from macaque visual cortex have shown orientation-selective neurons in area in V2 code for border ownership [J. Neurosci. 20, 6594 (2000)]: Each piece of contrast border is represented by two pools of neurons whose relative firing rate indicates the side of border ownership. Here we show that the human visual cortex uses a similar coding scheme by demonstrating a border-ownership-contingent tilt aftereffect. The aftereffect was specific for the adapted location, indicating that the adapted neurons have small receptive fields. We conclude that figure-ground organization is represented by border-ownership-selective neurons at early stages in the human visual cortex.

  20. Passive Neutron Detection at Borders

    SciTech Connect

    Kouzes, Richard T.; Siciliano, Edward R.; Ely, James H.; Keller, Paul E.; McConn, Ronald J.

    2008-03-01

    Radiation portal monitor systems have been deployed to screen for illicit trafficking of radioactive materials at international border crossings. This report reviews some of the neutron detection requirements and capabilities of passive detection systems used for such applications. Simulations show the effects of cargo materials on neutron spectra, different detector geometries, using a large-array of neutron detectors, and the effects of backgrounds including “ship effect” neutrons.

  1. Cross-border reprogenetic services.

    PubMed

    Couture, V; Drouin, R; Tan, S-L; Moutquin, J-M; Bouffard, C

    2015-01-01

    The purpose of this review is to synthesize the current knowledge on the international movement of patients and biopsied embryo cells for pre-implantation genetic diagnosis and its different applications. Thus far, few attempts have been made to identify the specific nature of this phenomenon called 'cross-border reprogenetic services'. There is scattered evidence, both empirical and speculative, suggesting that these services raise major issues in terms of service provision, risks for patients and the children-to-come, the legal liabilities of physicians, as well as social justice. To compile this evidence, this review uses the narrative overview protocol combined with thematic analysis. Five major themes have emerged from the literature at the conjunction of cross-border treatments and reprogenetics: 'scope', 'scale', 'motivations', 'concerns', and 'governance'. Similar themes have already been observed in the case of other medical tourism activities, but this review highlights their singularity with reprogenetic services. It emphasizes the diagnostic and autologous feature of reprogenetics, the constant risk of misdiagnosis, the restriction on certain tests for medically controversial conditions, and the uncertain accessibility of genetic counseling in cross-border settings.

  2. Cross-border reprogenetic services.

    PubMed

    Couture, V; Drouin, R; Tan, S-L; Moutquin, J-M; Bouffard, C

    2015-01-01

    The purpose of this review is to synthesize the current knowledge on the international movement of patients and biopsied embryo cells for pre-implantation genetic diagnosis and its different applications. Thus far, few attempts have been made to identify the specific nature of this phenomenon called 'cross-border reprogenetic services'. There is scattered evidence, both empirical and speculative, suggesting that these services raise major issues in terms of service provision, risks for patients and the children-to-come, the legal liabilities of physicians, as well as social justice. To compile this evidence, this review uses the narrative overview protocol combined with thematic analysis. Five major themes have emerged from the literature at the conjunction of cross-border treatments and reprogenetics: 'scope', 'scale', 'motivations', 'concerns', and 'governance'. Similar themes have already been observed in the case of other medical tourism activities, but this review highlights their singularity with reprogenetic services. It emphasizes the diagnostic and autologous feature of reprogenetics, the constant risk of misdiagnosis, the restriction on certain tests for medically controversial conditions, and the uncertain accessibility of genetic counseling in cross-border settings. PMID:24798608

  3. Electrophoresis and dielectric dispersion of spherical polyelectrolyte brushes.

    PubMed

    Ahualli, Silvia; Ballauff, Matthias; Arroyo, Francisco J; Delgado, Ángel V; Jiménez, María L

    2012-11-27

    Spherical polyelectrolyte brushes (SPBs) consist of a rigid core on which polyelectrolyte chains are grafted in such a way that in certain conditions (low ionic strength and high charge of the chains) the polymer chains extend radially toward the liquid medium. Because of the hairy-like structure of the polymer brushes, the typical soft-particle approach used for explaining the behavior of polyelectrolyte-coated particles must be modified, using the assumptions that the density of charged segments in the polymer chains decreases with the squared distance to the rigid core surface and that the same happens to the friction between the brushes and the surrounding fluid. Interest in clarifying the electrokinetics of these systems is not just academic. It has recently been found experimentally (Jiménez et al., Soft Matter 2011, 7, 3758-3762) that the response of concentrated suspensions of spherical polyelectrolyte brushes in the presence of alternating electric fields shows a number of unexpected features. Both dielectric and dynamic electrophoretic mobility spectra (respectively, dependences of the electric permittivity and the AC electrophoretic mobility on the frequency of the applied field) showed very special aspects, with giant values of the mobility and an unusually strong dielectric relaxation in the kHz region. In the present paper we give a full account of the electrodynamics of such systems, based on a cell model for describing the hydrodynamic and electrical interactions between the particles. It is found that the low-frequency dynamic mobility of SPBs is much higher than that of rigid particles of comparable size and charge, making any interpretation based on zeta potential estimations of very limited applicability. The very characteristic feature of SPBs in concentrated suspensions, namely, the enhanced alpha relaxation, can be explained by considering an adequate description of the field-induced perturbations in the counterion and co-ion concentrations

  4. 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

  5. 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.

  6. Stability against brushing abrasion and the erosion-protective effect of different fluoride compounds.

    PubMed

    Wiegand, A; Schneider, S; Sener, B; Roos, M; Attin, T

    2014-01-01

    This study aimed to analyse the impact of brushing on the protective effect of different fluoride solutions on enamel and dentin erosion. Bovine enamel and dentin specimens were rinsed once with TiF4, AmF, SnF2 (0.5 M F, 2 min) or water (control). Specimens were either left unbrushed or brushed with 10, 20, 50, 100 or 500 brushing strokes in an automatic brushing machine (2 N, non-fluoridated toothpaste slurry). Ten specimens per group were eroded with hydrochloric acid (HCl) (pH 2.3) for 60 s, and calcium release into the acid was determined by atomic absorption spectroscopy. Additionally, enamel and dentin surfaces were analysed by X-ray energy-dispersive spectroscopy (EDS) (n = 6/group) and scanning electron microscopy (SEM) (n = 2/group) before brushing and after 500 brushing strokes. Statistical analysis (p < 0.05) was performed by three- and one-way ANOVA (calcium release) or repeated measures ANOVA (EDS). TiF4, AmF and SnF2 reduced the erosive calcium loss in unbrushed specimens to 58-67% (enamel) and 23-31% (dentin) of control. Calcium release increased with increasing brushing strokes prior to erosion and amounted to 70-88% (enamel) and 45-78% (dentin) of control after 500 brushing strokes. Brushing reduced the surface concentration of fluoride (AmF), tin (SnF2) and titanium (TiF4). SEM revealed that surface precipitates were affected by long-term brushing. Brushing reduced the protective potential of TiF4, AmF and SnF2 solutions. However, considering a small number of brushing strokes, the protective effect of fluoride solutions is only slightly affected by brushing abrasion.

  7. 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).

  8. Electrocatalysis of CO2 Reduction in Brush Polymer Ion Gels.

    PubMed

    McNicholas, Brendon J; Blakemore, James D; Chang, Alice B; Bates, Christopher M; Kramer, Wesley W; Grubbs, Robert H; Gray, Harry B

    2016-09-01

    The electrochemical characterization of brush polymer ion gels containing embedded small-molecule redox-active species is reported. Gels comprising PS-PEO-PS triblock brush polymer, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm-TFSI), and some combination of ferrocene (Fc), cobaltocenium (CoCp2(+)), and Re(bpy)(CO)3Cl (1) exhibit diffusion-controlled redox processes with diffusion coefficients approximately one-fifth of those observed in neat BMIm-TFSI. Notably, 1 dissolves homogeneously in the interpenetrating matrix domain of the ion gel and displays electrocatalytic CO2 reduction to CO in the gel. The catalytic wave exhibits a positive shift versus Fc(+/0) compared with analogous nonaqueous solvents with a reduction potential 450 mV positive of onset and 90% Faradaic efficiency for CO production. These materials provide a promising and alternative approach to immobilized electrocatalysis, creating numerous opportunities for application in solid-state devices.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. Interpretation of charge transfer measurements of brush discharges

    NASA Astrophysics Data System (ADS)

    Chowdhury, Kanchan; von Pidoll, Ulrich; Moeckel, Dieter; Langer, Tim; Beyer, Michael

    2011-06-01

    In the present work, experimental results on the measurement of the total charge on a charged insulating sheet before and after a provoked brush discharge, their difference "C", the induced charge "A" when approaching an earthed microprocessor operated hand-Coulombmeter, and the transferred charge "B" at the instance of the discharge are presented. "B" is identical with the value measured by the hand-Coulombmeter within the expected measurement uncertainty. Due to observed corona losses and multiple brush discharges independent of each other, "B" correlates better with the incendivity than "C". The quotient B/C was closer to 1 than calculated in the literature but shows all predicted trends. The results obtained can be used for correct estimation of the incendivity of brush discharges between 10 nC and 90 nC. There is no need to change the existing threshold limits of 60 nC, 30 nC and 10 nC for the explosion groups IIA, IIB and IIC hitherto used in standards for zone 1.

  14. Hierarchical structure formation of cylindrical brush polymer-surfactant complexes.

    PubMed

    Cong, Yang; Gunari, Nikhil; Zhang, Bin; Janshoff, Andreas; Schmidt, Manfred

    2009-06-01

    The complex formation of cylindrical brush polymers with poly(l-lysine) side chains (PLL) and sodium dodecyl sulfate (SDS) can induce a helical conformation of the cylindrical brush polymer in aqueous solution (Gunari, N.; Cong, Y.; Zhang, B.; Fischer, K.; Janshoff, A.; Schmidt, M. Macromol. Rapid Commun. 2008, 29, 821-825). Herein, we have systematically investigated the influence of surfactant, salt, and pH on the supramolecular structure formation. The cylindrical brush polymers and their complexes with surfactants were directly visualized by atomic force microscopy in air and in aqueous solution. The alkyl chain length (measured by the carbon number, n) of the surfactant plays a key role. While helical structures were formed with n=10, 11, and 12, no helices were observed with n<10 and n>13. Addition of salt destroys the helical structures as do pH conditions below 4 and above 6, most probably because the polymer-surfactant complexes start to disintegrate. Circular dichroism was utilized to monitor the PLL side chain conformation and clearly revealed that beta-sheet formation of the side chains induces the helical conformation of the atactic main chain. PMID:19326944

  15. 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.

  16. 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.

  17. 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

  18. Chronic hypercapnia enhances V sub max of Na-H antiporter of renal brush-border membranes

    SciTech Connect

    Talor, Z.; Yang, Wuchang; Shuffield, J.; Sack, E.; Arruda, J.A.L. )

    1987-09-01

    Chronic hypercapnia is associated with increased proximal HCO{sub 3} reabsorption that is thought to be mediated by a Na-H antiporter. The authors hypothesized that chronic hypercapnia would be associated either with increased V{sub max} or with decreased K{sub m} of the Na-H antiporter. To test this hypothesis they made rabbits hypercapnic for 48 h by exposure to 10% CO{sub 2}. In both control and hypercapnic animals, cortical luminal membranes were enriched over the homogenate 16-fold in alkaline phosphatase and 10-fold in maltase activity. The kinetic activity of the Na-H antiporter was measured by the dissipation of the quenching of acridine orange by addition of different Na concentrations. Chronic hypercapnic rabbits had significantly higher V{sub max} of the Na-H antiporter of luminal membranes than controls. The K{sub m}, however, was not different between control and hypercapnic rabbits. {sup 22}Na uptake in presence of an outwardly directed pH gradient was significantly higher in vesicles from hypercapnic rabbits than controls. Amiloride inhibited the Na-H antiporter (as assessed by acridine orange quenching or {sup 22}Na uptake) to the same degree in membranes from both control and hypercapnic rabbits. The uptake of D-({sup 3}H)glucose by luminal membranes was not different between control and hypercapnic rabbits, indicating a specific enhancement of the Na-H antiporter. Thus chronic hypercapnia, but not acute hypercapnia, induces a selective and specific increase in the V{sub max} of Na-H antiporter, and this may mediate the adaptation to chronic hypercapnia.

  19. CHARACTERIZATION OF A BRUSH BORDER FERRIREDUCTASE IN LOBSTER HEPATOPANCREATIC EPITHELIAL CELLS AND ITS POSSIBLE ROLE IN IRON TRANSPORT. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  20. Severity of tubular brush border damage in cadmium-polluted area (Jinzu River Basin): clinical role of urinary trehalase

    SciTech Connect

    Nakano, M.; Aoshima, K.; Katoh, T.; Teranishi, H.; Kasuya, M.; Katoh, K.

    1987-12-01

    Urinary trehalase activity and leucine aminopeptidase activity were parabolically correlated with urinary ..beta..-microglobulin, and these enzymes were observed to be biphasic in relation to urinary ..beta..-microglobulin when the study populations included patients of Itai-itai disease and inhabitants of a cadmium-polluted area. Furthermore, urinary trehalase activity was parabolically correlated with urinary total protein and urinary glucose. From these results it is inferred that by measuring both urinary trehalase and urinary ..beta../sub 2/-microglobulin, one can elucidate the degree of tubular damage.

  1. ZINC STIMULATES L-PROLINE TRANSPORT BY THE IMINO SYSTEM IN LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  2. CD2+ AND H+ STIMULATE UPTAKE OF 59FE2+ IN LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  3. Binding of Bacillus thuringiensis Cry1A toxins with brush border membrane vesicles of maize stem borer (Chilo partellus Swinhoe).

    PubMed

    Sharma, Priyanka; Nain, Vikrant; Lakhanpaul, Suman; Kumar, P A

    2011-02-01

    Maize stem borer (Chilo partellus) is a major insect pest of maize and sorghum in Asia and Africa. Bacillus thuringiensis (Bt) δ-endotoxins have been found effective against C. partellus, both in diet-overlay assay and in transgenic plants. Gene stacking as one of the resistance management strategies in Bt maize requires an understanding of receptor sharing and binding affinity of δ-endotoxins. In the present study, binding affinity of three fluorescein isothiocyanate labeled Cry1A toxins showed high correlation with the toxicity of respective δ-endotoxins. Competitive binding studies showed that Cry1Ab toxins share some of the binding sites with Cry1Aa and Cry1Ac with low affinity and that Cry1Ab may have additional binding sites that are unavailable to the other two toxins tested. PMID:20831871

  4. 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.

  5. 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

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

    NASA Astrophysics Data System (ADS)

    Hoy, Olha

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

  7. A model for international border management systems.

    SciTech Connect

    Duggan, Ruth Ann

    2008-09-01

    To effectively manage the security or control of its borders, a country must understand its border management activities as a system. Using its systems engineering and security foundations as a Department of Energy National Security Laboratory, Sandia National Laboratories has developed such an approach to modeling and analyzing border management systems. This paper describes the basic model and its elements developed under Laboratory Directed Research and Development project 08-684.

  8. An effective technique for denture border evaluation.

    PubMed

    Phoenix, R D; DeFreest, C F

    1997-09-01

    Proper extension and adjustment of denture borders is a critical component in successful removable prosthodontic treatment. Unfortunately, commonly marketed disclosing media may not provide appropriate viscosities for the accurate assessment of denture border extensions. This article provides a technique for the mixing, unit-dose packaging, and utilization of a disclosing medium that is extremely well-suited for denture border applications. The technique employs commonly available materials and compiles with current "unit-dose" guidelines.

  9. Potential effects of tooth-brushing on human dentin wear following exposure to acidic soft drinks.

    PubMed

    Choi, S; Park, K-H; Cheong, Y; Moon, S W; Park, Y-G; Park, H-K

    2012-08-01

    This study used scanning electron microscopy and atomic force microscopy to examine the short-term potential effects of brushing time and the start-time of tooth-brushing after demineralization on primary dentin wear in vitro. Thirty-six noncarious primary central incisors were assigned to 12 experimental groups. Exposure to cola drinks was used to initiate the demineralization process. Three brushing times (5, 15 and 30 s) and four start-times of brushing (0, 30, 60 and 120 min) after an erosive attack were used for the abrasion process. Tooth-brushing the softened dentin surface led to increases in the open tubular fraction and microstructural changes on the dentin surface. Brushing immediately after exposure to cola resulted in the greatest irreversible dentin loss, whereas brushing 60 or 120 min after pretreatment resulted in the least irreversible dentin loss. However, brushing time had no effect on the irreversible loss of dentin wear. Based on these experimental results, tooth-brushing should be performed at least 60 min after consuming a cola drink to achieve the desired tooth cleaning and avoid the introduction of surface lesions on dentin.

  10. 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.

  11. The Armchair at the Borders: The "Messy" Ideas of Borders and Border Epistemologies within Multicultural Science Education Scholarship

    ERIC Educational Resources Information Center

    Carter, Lyn

    2010-01-01

    This paper aims to further articulate multicultural science education scholarship. In particular, it explores the notions of borders and border epistemologies as intellectual resources to think again about the challenges of science education in the global world that demand more sophisticated concepts to unravel some of its complexities. It…

  12. International Issues, High-Stakes Testing, and Border Pedagogy: Social Studies at Border High School

    ERIC Educational Resources Information Center

    Cashman, Timothy G.; McDermott, Benjamin R.

    2013-01-01

    A recently constructed border wall stands within walking distance of Border High School (BHS) and was created to impede the flow of people, goods, fauna, and contraband from Mexico into the United States (U.S.). The reality, however, is that this geopolitical border is fluid, allowing connections between sociopolitical zones. The researchers…

  13. The Intersectionality of Border Pedagogy and Latino/a Youth: Enacting Border Pedagogy in Multiple Spaces

    ERIC Educational Resources Information Center

    Ramirez, Pablo C.; Ross, Lydia; Jimenez-Silva, Margarita

    2016-01-01

    In this one-year qualitative study, the authors examined how border pedagogy is enacted by two Latino/a high school teachers in a border community in Southern California. Through classroom observations, the authors documented powerful student discussions that named complex borders (Giroux, 1992) that existed in their daily lives. We drew from…

  14. 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

  15. Proton conduction of polyAMPS brushes on titanate nanotubes

    PubMed Central

    Feng, Jun; Huang, Yaqin; Tu, Zhengkai; Zhang, Haining; Pan, Mu; Tang, Haolin

    2014-01-01

    Proton conducting materials having reasonable proton conductivity at low humidification conditions are critical for decrease in system complexity and improvement of power density for polymer electrolyte membrane fuel cells. This study shows that polyelectrolyte brushes on titanate nanotubes formed through surface-initiated free radical polymerization exhibit less humidity-dependent proton conduction because of the high grafting density of polymer electrolyte chains and well-distribution of ionic groups. The results described in this study provide an idea for design of new proton conductors with effective ion transport served at relatively low humidification levels. PMID:25169431

  16. 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.

  17. 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.

  18. Infrared radiation emerging from smoke produced by brush fires.

    PubMed

    Weinman, J A; Harshvardhan, H; Olson, W S

    1981-01-15

    This study presents the IR radiative transport properties of brush fire smoke clouds computed for a model with finite horizontal dimensions as well as the more common plane-parallel model. The finite model is a 3-D version of the two-stream approximation applied to cubic clouds of steam, carbon, and silicates. Assumptions are made with regard to the shape and size distributions of the smoke particles. It is shown that 11.5-microm radiometry can detect fires beneath smoke clouds if the path integrated mass density of the smoke is less, similar3 g/m(2).

  19. 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.

  20. 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

  1. Border Pedagogy Cafes: Grassroots Conversations that Matter

    ERIC Educational Resources Information Center

    Necochea, Juan; Cline, Zulmara

    2008-01-01

    This exploratory study uses qualitative methods to analyze the impact of conversations in the Border Pedagogy "Cafes" on more than 500 binational educators from the Tijuana/San Diego area on the U.S.-Mexico border. Four important themes emerged from the analysis that describe the impact of the cafes and offer a strong foundation on which to build…

  2. Teaching Orthodox Religious Education on the Border

    ERIC Educational Resources Information Center

    Berglund, Jenny

    2014-01-01

    In geographical areas bordering those of other states, the function of educational systems, as the means for states to foster their citizens, is challenged by ambiguities and tensions connected to intercultural experiences. In this article, I illustrate some of the findings from a project that studies religious education in four border areas…

  3. Researching Transfronterizo Literacies in Texas Border Colonias

    ERIC Educational Resources Information Center

    Smith, Patrick H.; Murillo, Luz A.

    2012-01-01

    This study examines literacies practiced in bilingual households located in emerging communities along the Texas-Mexico border known as border colonias. Drawing on theoretical notions of space as geographic and temporal, the simultaneity of global and local forces at work in colonias, and expressions of agency that are "in between" accommodation…

  4. Optical probe

    DOEpatents

    Hencken, Kenneth; Flower, William L.

    1999-01-01

    A compact optical probe is disclosed particularly useful for analysis of emissions in industrial environments. The instant invention provides a geometry for optically-based measurements that allows all optical components (source, detector, rely optics, etc.) to be located in proximity to one another. The geometry of the probe disclosed herein provides a means for making optical measurements in environments where it is difficult and/or expensive to gain access to the vicinity of a flow stream to be measured. Significantly, the lens geometry of the optical probe allows the analysis location within a flow stream being monitored to be moved while maintaining optical alignment of all components even when the optical probe is focused on a plurality of different analysis points within the flow stream.

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

    PubMed

    Kobayashi, Motoyasu; Ishihara, Kazuhiko; Takahara, Atsushi

    2014-01-01

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

  6. Effect of brushing with sonic and counterrotational toothbrushes on the bond strength of orthodontic brackets.

    PubMed

    Hansen, P A; Killoy, W; Masterson, K

    1999-01-01

    The purpose of this study was to evaluate the effect of brushing with both a sonic and mechanical counter rotary power toothbrush on the bond strength of orthodontic brackets. Forty-five extracted teeth were divided into three random groups and had orthodontic brackets bonded to them. One group was brushed with a counterrotational toothbrush, the Interplak, one group with a sonic toothbrush, the Sonicare, and a third group was not brushed and was held as a control. After the equivalent of 2 years brushing, the teeth were placed in an Instron machine and the shear force to remove the brackets was recorded. Group 1, the counter rotary power brush, had a mean of 107.5 kg/cm2, the second group, the sonic brush, had a mean of 79.7 kg/cm2, and the control group had a mean of 125. 4 kg/cm2. Single factor analysis of variance followed by the Fisher-Hayter Multiple Comparison Procedure showed a statistically significant difference between the sonic power brush and the control (P <.01), but no significant difference between the counter rotary and the control (P >.05). There was no significant difference between the two power brushes (P >.05).

  7. 46 CFR 108.187 - Ventilation for brush type electric motors in classified spaces.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... spaces. 108.187 Section 108.187 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A... Ventilation for brush type electric motors in classified spaces. Ventilation for brush type electric motors in... the motors may cause unsafe conditions. Accommodation Spaces...

  8. 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

  9. 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

  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. 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

  12. 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.

  13. 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.

  14. Alcohol abuse and dependence among U.S.-Mexico border and non-border Mexican Americans

    PubMed Central

    Caetano, Raul; Caetano Vaeth, Patrice A.; Mills, Britain A.; Rodriguez, Lori A.

    2012-01-01

    BACKGROUND This paper examines the prevalence, the symptom profile, and the drinking and sociodemographic predictors of current (past 12 month) DSM-IV alcohol abuse and dependence among Mexican Americans living along the U.S.-Mexico border and those living in metropolitan areas away from the border. METHODS Respondents in the non-border areas (primarily Houston and Los Angeles) constitute a multistage probability sample (N=1,288) of these areas, interviewed as part of the 2006 Hispanic Americans Baseline Alcohol Survey (HABLAS). Respondents in the border area (N=1,307) constitute a household probability sample of Mexican Americans living on the border. In both surveys, data were collected during computer assisted interviews conducted in respondents’ homes. The HABLAS and the border sample response rates were 76% and 67%, respectively. RESULTS Although bivariate analyses revealed no overall differences between border and non-border locations, (negative) age trends were more pronounced on the border for male abuse and for dependence among both genders. Among females aged 18–29, border residence was linked to significantly higher rates of dependence. In multivariable analyses, the prevalence of male abuse declined more rapidly with age on the border than off the border. Other unique predictors of male abuse were Jewish/other religion and weekly volume of alcohol consumption. Being married or out of the workforce, attaining a higher education, no religious preference, and weekly volume uniquely predicted female dependence. Age and weekly volume uniquely predicted male dependence. CONCLUSIONS The prevalence of alcohol use disorders among Mexican Americans on and off the U.S.-Mexico border largely mirrors previously documented patterns of alcohol consumption in these areas. For young Mexican-American women in particular, border residence is linked to heightened vulnerability to alcohol dependence. PMID:23278433

  15. 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

  16. Brushing of attribute clouds for the visualization of multivariate data.

    PubMed

    Jänicke, Heike; Böttinger, Michael; Scheuermann, Gerik

    2008-01-01

    The visualization and exploration of multivariate data is still a challenging task. Methods either try to visualize all variables simultaneously at each position using glyph-based approaches or use linked views for the interaction between attribute space and physical domain such as brushing of scatterplots. Most visualizations of the attribute space are either difficult to understand or suffer from visual clutter. We propose a transformation of the high-dimensional data in attribute space to 2D that results in a point cloud, called attribute cloud, such that points with similar multivariate attributes are located close to each other. The transformation is based on ideas from multivariate density estimation and manifold learning. The resulting attribute cloud is an easy to understand visualization of multivariate data in two dimensions. We explain several techniques to incorporate additional information into the attribute cloud, that help the user get a better understanding of multivariate data. Using different examples from fluid dynamics and climate simulation, we show how brushing can be used to explore the attribute cloud and find interesting structures in physical space.

  17. 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.

  18. 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.

  19. 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.

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

    PubMed

    Yang, Zhi; Zhu, Xingzhong; Huang, Xiaolu; Cheng, Yingwu; Liu, Yun; Geng, Huijuan; Wu, Yue; Su, Yanjie; Wei, Hao; Zhang, Yafei

    2013-11-25

    Highly uniform hole spacing micro brushes were fabricated based on aligned carbon nanotube (CNT) arrays synthesized by chemical vapor deposition method with the assistance of anodic aluminum oxide (AAO) template. Different micro brushes from CNT arrays were constructed on silicon, glass, and polyimide substrates, respectively. The micro brushes had highly uniform hole spacing originating from the regularly periodic pore structure of AAO template. The CNT arrays, serving as bristles, were firmly grafted on the substrates. The brushes can easily clean particles with scale of micrometer on the surface of silicon wafer and from the narrow spaces between the electrodes in a series of cleaning experiments. The results show the potential application of the CNT micro brushes as a cleaning tool in microelectronics manufacture field.

  1. 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.

  2. 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.

  3. DNA Polymer Brush Patterning through Photocontrollable Surface-Initiated DNA Hybridization Chain Reaction.

    PubMed

    Huang, Fujian; Zhou, Xiang; Yao, Dongbao; Xiao, Shiyan; Liang, Haojun

    2015-11-18

    The fabrication of DNA polymer brushes with spatial resolution onto a solid surface is a crucial step for biochip research and related applications, cell-free gene expression study, and even artificial cell fabrication. Here, for the first time, a DNA polymer brush patterning method is reported based on the photoactivation of an ortho-nitrobenzyl linker-embedded DNA hairpin structure and a subsequent surface-initiated DNA hybridization chain reaction (HCR). Inert DNA hairpins are exposed to ultraviolet light irradiation to generate DNA duplexes with two active sticky ends (toeholds) in a programmable manner. These activated DNA duplexes can initiate DNA HCR to generate multifunctional patterned DNA polymer brushes with complex geometrical shapes. Different multifunctional DNA polymer brush patterns can be fabricated on certain areas of the same solid surface using this method. Moreover, the patterned DNA brush surface can be used to capture target molecules in a desired manner.

  4. 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

  5. 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

  6. 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

  7. 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

  8. Semantic Borders and Incomplete Understanding.

    PubMed

    Silva-Filho, Waldomiro J; Dazzani, Maria Virgínia

    2016-03-01

    In this article, we explore a fundamental issue of Cultural Psychology, that is our "capacity to make meaning", by investigating a thesis from contemporary philosophical semantics, namely, that there is a decisive relationship between language and rationality. Many philosophers think that for a person to be described as a rational agent he must understand the semantic content and meaning of the words he uses to express his intentional mental states, e.g., his beliefs and thoughts. Our argument seeks to investigate the thesis developed by Tyler Burge, according to which our mastery or understanding of the semantic content of the terms which form our beliefs and thoughts is an "incomplete understanding". To do this, we discuss, on the one hand, the general lines of anti-individualism or semantic externalism and, on the other, criticisms of the Burgean notion of incomplete understanding - one radical and the other moderate. We defend our understanding that the content of our beliefs must be described in the light of the limits and natural contingencies of our cognitive capacities and the normative nature of our rationality. At heart, anti-individualism leads us to think about the fact that we are social creatures, living in contingent situations, with important, but limited, cognitive capacities, and that we receive the main, and most important, portion of our knowledge simply from what others tell us. Finally, we conclude that this discussion may contribute to the current debate about the notion of borders.

  9. Semantic Borders and Incomplete Understanding.

    PubMed

    Silva-Filho, Waldomiro J; Dazzani, Maria Virgínia

    2016-03-01

    In this article, we explore a fundamental issue of Cultural Psychology, that is our "capacity to make meaning", by investigating a thesis from contemporary philosophical semantics, namely, that there is a decisive relationship between language and rationality. Many philosophers think that for a person to be described as a rational agent he must understand the semantic content and meaning of the words he uses to express his intentional mental states, e.g., his beliefs and thoughts. Our argument seeks to investigate the thesis developed by Tyler Burge, according to which our mastery or understanding of the semantic content of the terms which form our beliefs and thoughts is an "incomplete understanding". To do this, we discuss, on the one hand, the general lines of anti-individualism or semantic externalism and, on the other, criticisms of the Burgean notion of incomplete understanding - one radical and the other moderate. We defend our understanding that the content of our beliefs must be described in the light of the limits and natural contingencies of our cognitive capacities and the normative nature of our rationality. At heart, anti-individualism leads us to think about the fact that we are social creatures, living in contingent situations, with important, but limited, cognitive capacities, and that we receive the main, and most important, portion of our knowledge simply from what others tell us. Finally, we conclude that this discussion may contribute to the current debate about the notion of borders. PMID:26111737

  10. Metallographic Analysis of Brush Bristle and Integrity Testing of Brush Seal in Shroud Ring of T-700 Engine

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Griffin, Thomas A.; Bobula, George A.; Bill, Robert C.; Hull, David R.; Csavina, Kristine R.

    1995-01-01

    Post-test investigation of a T-700 engine brush seal found regions void of bristles ('yanked out'), regions of bent-over bristles near the inlet, some 'snapped' bristles near the fence, and a more uniform 'smeared' bristle interface between the first and last axial rows of bristles. Several bristles were cut from the brush seal, wax mounted, polished, and analyzed. Metallographic analysis of the bristles near the rub tip showed tungsten-rich phases uniformly distributed throughout the bristle with no apparent change within 1 to 2 micron of the interface except for possibly a small amount of titanium, which would represent a transfer from the rotor. Analysis of the bristle wear face showed nonuniform tungsten, which is indicative of material resolidification. The cut end contained oxides and internal fractures; the worn end was covered with oxide scale. Material losses due to wear and elastoplastic deformation within the shear zone and third-body lubrication effects in the contact zone are discussed.

  11. Dynamics of an unconstrained oscillatory flicking brush for road sweeping

    NASA Astrophysics Data System (ADS)

    Vanegas Useche, L. V.; Abdel Wahab, M. M.; Parker, G. A.

    2007-11-01

    This article studies the dynamics of a freely rotating flicking brush by means of a mathematical model. The bristles are treated as cantilever prismatic beams subjected to small deflections. A solution of the equation of motion for their forced transverse vibration is obtained through the normal-mode method. A novel oscillatory motion is superimposed onto the rotary motion of the brush. Two functions of oscillation are investigated: a sinusoidal angular velocity and a novel function, named after the authors 'VAP' (Vanegas Useche, Abdel Wahab, Parker), developed to provide small shaft accelerations. The VAP function may be a square wave, a triangle wave, or a smooth wave between them, depending on the value of a smoothness parameter, b. The results indicate that the maximum bending moment, stress, and deflection are independent of the mean angular velocity, are proportional to its alternating component, and increase linearly with the mount radius and the sine of the mount angle. In addition, the behaviour of the brush is strongly affected by the frequency of oscillation, the type of function, the value of b, and bristle wear, amongst other parameters. For the sinusoidal and VAP function, resonance occurs at the bristle natural frequencies. Moreover, the VAP function tends to produce a condition similar to resonance also at odd fractions of the natural frequencies. This phenomenon may be accentuated or reduced, by adjusting the value of b, and be expedited or impeded, by the selection of the frequency. The results of this work may also be applied to the case of a small-deflection cantilever beam, when the transverse external force is a sinusoidal, square, or triangle wave or when it is given by the new VAP function. Finally, the VAP wave may enable to excite a condition similar to resonance not only at the natural frequencies of the beam, but also at odd fractions of them. Small frequencies may be required to achieve a resonant behaviour of a high-frequency mode

  12. The U.S.-Mexico Border Infectious Disease Surveillance Project: Establishing Binational Border Surveillance

    PubMed Central

    Waterman, Stephen; Lucas, Carlos Alvarez; Falcon, Veronica Carrion; Morales, Pablo Kuri; Lopez, Luis Anaya; Peter, Chris; Gutiérrez, Alejandro Escobar; Gonzalez, Ernesto Ramirez; Flisser, Ana; Bryan, Ralph; Valle, Enrique Navarro; Rodriguez, Alfonso; Hernandez, Gerardo Alvarez; Rosales, Cecilia; Ortiz, Javier Arias; Landen, Michael; Vilchis, Hugo; Rawlings, Julie; Leal, Francisco Lopez; Ortega, Luis; Flagg, Elaine; Conyer, Roberto Tapia; Cetron, Martin

    2003-01-01

    In 1997, the Centers for Disease Control and Prevention, the Mexican Secretariat of Health, and border health officials began the development of the Border Infectious Disease Surveillance (BIDS) project, a surveillance system for infectious diseases along the U.S.-Mexico border. During a 3-year period, a binational team implemented an active, sentinel surveillance system for hepatitis and febrile exanthems at 13 clinical sites. The network developed surveillance protocols, trained nine surveillance coordinators, established serologic testing at four Mexican border laboratories, and created agreements for data sharing and notification of selected diseases and outbreaks. BIDS facilitated investigations of dengue fever in Texas-Tamaulipas and measles in California–Baja California. BIDS demonstrates that a binational effort with local, state, and federal participation can create a regional surveillance system that crosses an international border. Reducing administrative, infrastructure, and political barriers to cross-border public health collaboration will enhance the effectiveness of disease prevention projects such as BIDS. PMID:12533288

  13. The U.S.-Mexico Border Infectious Disease Surveillance project: establishing bi-national border surveillance.

    PubMed

    Weinberg, Michelle; Waterman, Stephen; Lucas, Carlos Alvarez; Falcon, Veronica Carrion; Morales, Pablo Kuri; Lopez, Luis Anaya; Peter, Chris; Gutiérrez, Alejandro Escobar; Gonzalez, Ernesto Ramirez; Flisser, Ana; Bryan, Ralph; Valle, Enrique Navarro; Rodriguez, Alfonso; Hernandez, Gerardo Alvarez; Rosales, Cecilia; Ortiz, Javier Arias; Landen, Michael; Vilchis, Hugo; Rawlings, Julie; Leal, Francisco Lopez; Ortega, Luis; Flagg, Elaine; Conyer, Roberto Tapia; Cetron, Martin

    2003-01-01

    In 1997, the Centers for Disease Control and Prevention, the Mexican Secretariat of Health, and border health officials began the development of the Border Infectious Disease Surveillance (BIDS) project, a surveillance system for infectious diseases along the U.S.-Mexico border. During a 3-year period, a binational team implemented an active, sentinel surveillance system for hepatitis and febrile exanthems at 13 clinical sites. The network developed surveillance protocols, trained nine surveillance coordinators, established serologic testing at four Mexican border laboratories, and created agreements for data sharing and notification of selected diseases and outbreaks. BIDS facilitated investigations of dengue fever in Texas-Tamaulipas and measles in California-Baja California. BIDS demonstrates that a binational effort with local, state, and federal participation can create a regional surveillance system that crosses an international border. Reducing administrative, infrastructure, and political barriers to cross-border public health collaboration will enhance the effectiveness of disease prevention projects such as BIDS.

  14. The U.S.-Mexico Border Infectious Disease Surveillance project: establishing bi-national border surveillance.

    PubMed

    Weinberg, Michelle; Waterman, Stephen; Lucas, Carlos Alvarez; Falcon, Veronica Carrion; Morales, Pablo Kuri; Lopez, Luis Anaya; Peter, Chris; Gutiérrez, Alejandro Escobar; Gonzalez, Ernesto Ramirez; Flisser, Ana; Bryan, Ralph; Valle, Enrique Navarro; Rodriguez, Alfonso; Hernandez, Gerardo Alvarez; Rosales, Cecilia; Ortiz, Javier Arias; Landen, Michael; Vilchis, Hugo; Rawlings, Julie; Leal, Francisco Lopez; Ortega, Luis; Flagg, Elaine; Conyer, Roberto Tapia; Cetron, Martin

    2003-01-01

    In 1997, the Centers for Disease Control and Prevention, the Mexican Secretariat of Health, and border health officials began the development of the Border Infectious Disease Surveillance (BIDS) project, a surveillance system for infectious diseases along the U.S.-Mexico border. During a 3-year period, a binational team implemented an active, sentinel surveillance system for hepatitis and febrile exanthems at 13 clinical sites. The network developed surveillance protocols, trained nine surveillance coordinators, established serologic testing at four Mexican border laboratories, and created agreements for data sharing and notification of selected diseases and outbreaks. BIDS facilitated investigations of dengue fever in Texas-Tamaulipas and measles in California-Baja California. BIDS demonstrates that a binational effort with local, state, and federal participation can create a regional surveillance system that crosses an international border. Reducing administrative, infrastructure, and political barriers to cross-border public health collaboration will enhance the effectiveness of disease prevention projects such as BIDS. PMID:12533288

  15. Conductivity Probe

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Thermal and Electrical Conductivity Probe (TECP) for NASA's Phoenix Mars Lander took measurements in Martian soil and in the air.

    The needles on the end of the instrument were inserted into the Martian soil, allowing TECP to measure the propagation of both thermal and electrical energy. TECP also measured the humidity in the surrounding air.

    The needles on the probe are 15 millimeters (0.6 inch) long.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  16. 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

  17. Nitroxide polymer brushes grafted onto silica nanoparticles as cathodes for organic radical batteries

    NASA Astrophysics Data System (ADS)

    Lin, Hsiao-Chien; Li, Chia-Chen; Lee, Jyh-Tsung

    2011-10-01

    Nitroxide polymer brushes grafted on silica nanoparticles as binder-free cathodes for organic radical batteries have been investigated. Scanning electron microscopy, transmission electron microscopy, infrared spectroscopy and electron spin resonance confirm that the nitroxide polymer brushes are successfully grafted onto silica nanoparticles via surface-initiated atom transfer radical polymerization. The thermogravimetric analysis results indicate that the onset decomposition temperature of these nitroxide polymer brushes is found to be ca. 201 °C. The grafting density of the nitroxide polymer brushes grafted on silica nanoparticles is 0.74-1.01 chains nm-2. The results of the electrochemical quartz crystal microbalance indicate that the non-crosslinking nitroxide polymer brushes prevent the polymer from dissolving into organic electrolytes. Furthermore, the electrochemical results show that the discharge capacity of the polymer brushes is 84.9-111.1 mAh g-1 at 10 C and the cells with the nitroxide polymer brush electrodes have a very good cycle-life performance of 96.3% retention after 300 cycles.

  18. Synthesis and Biomedical Applications of Poly((meth)acrylic acid) Brushes.

    PubMed

    Qu, Zhenyuan; Xu, Hong; Gu, Hongchen

    2015-07-15

    Poly((meth)acrylic acid) (P(M)AA) brushes possess a number of distinctive properties that are particularly attractive for biomedical applications. This minireview summarizes recent advances in the synthesis and biomedical applications of P(M)AA brushes and brushes containing P(M)AA segments. First, we review different surface-initiated polymerization (SIP) methods, with a focus on recent progress in the surface-initiated controlled/living radical polymerization (SI-CLRP) techniques used to generate P(M)AA brushes with a tailored structure. Next, we discuss biomolecule immobilization methods for P(M)AA brushes, including physical adsorption, covalent binding, and affinity interactions. Finally, typical biomedical applications of P(M)AA brushes are reviewed, and their performance is discussed based on their unique properties. We conclude that P(M)AA brushes are promising biomaterials, and more potential biomedical applications are expected to emerge with the further development of synthetic techniques and increased understanding of their interactions with biological systems.

  19. 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

  20. Functional polymer brushes via surface-initiated atom transfer radical graft polymerization for combating marine biofouling.

    PubMed

    Yang, Wen Jing; Neoh, Koon-Gee; Kang, En-Tang; Lee, Serina Siew Chen; Teo, Serena Lay-Ming; Rittschof, Daniel

    2012-01-01

    Dense and uniform polymer brush coatings were developed to combat marine biofouling. Nonionic hydrophilic, nonionic hydrophobic, cationic, anionic and zwitterionic polymer brush coatings were synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-hydroxyethyl methacrylate, 2,3,4,5,6-pentafluorostyrene, 2-(methacryloyloxy)ethyl trimethylammonium chloride, 4-styrenesulfonic acid sodium and N,N'-dimethyl-(methylmethacryloyl ethyl) ammonium propanesulfonate, respectively. The functionalized surfaces had different efficacies in preventing adsorption of bovine serum albumin (BSA), adhesion of the Gram-negative bacterium Pseudomonas sp. NCIMB 2021 and the Gram-positive Staphylococcus aureus, and settlement of cyprids of the barnacle Amphibalanus amphitrite (=Balanus amphitrite). The nonionic hydrophilic, anionic and zwitterionic polymer brushes resisted BSA adsorption during a 2 h exposure period. The nonionic hydrophilic, cationic and zwitterionic brushes exhibited resistance to bacterial fouling (24 h exposure) and cyprid settlement (24 and 48 h incubation). The hydrophobic brushes moderately reduced protein adsorption, and bacteria and cyprid settlement. The anionic brushes were least effective in preventing attachment of bacteria and barnacle cyprids. Thus, the best approach to combat biofouling involves a combination of nonionic hydrophilic and zwitterionic polymer brush coatings on material surfaces. PMID:22963034

  1. 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.

  2. Biomimetic Polymer Brushes Containing Tethered Acetylcholine Analogs for Protein and Hippocampal Neuronal Cell Patterning

    PubMed Central

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

    2013-01-01

    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 (DMAEMA), or free hydroxyl-terminated poly(ethylene glycol) (PEG) units were prepared using the “grown from” method through surface-initiated atom transfer radical polymerization (SI-ATRP) 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 µm 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

  3. Salt-Responsive Zwitterionic Polymer Brushes with Tunable Friction and Antifouling Properties.

    PubMed

    Yang, Jintao; Chen, Hong; Xiao, Shengwei; Shen, Mingxue; Chen, Feng; Fan, Ping; Zhong, Mingqiang; Zheng, Jie

    2015-08-25

    Development of smart, multifunction materials is challenging but important for many fundamental and industrial applications. Here, we synthesized and characterized zwitterionic poly(3-(1-(4-vinylbenzyl)-1H-imidazol-3-ium-3-yl)propane-1-sulfonate) (polyVBIPS) brushes as ion-responsive smart surfaces via the surface-initiated atom transfer radical polymerization. PolyVBIPS brushes were carefully characterized for their surface morphologies, compositions, wettability, and film thicknesses by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), contact angle, and ellipsometer, respectively. Salt-responsive, switching properties of polyVBIPS brushes on surface hydration, friction, and antifouling properties were further examined and compared both in water and in salt solutions with different salt concentrations and counterion types. Collective data showed that polyVBIPS brushes exhibited reversible surface wettability switching between in water and saturated NaCl solution. PolyVBIPS brushes in water induced the larger protein absorption, higher surface friction, and lower surface hydration than those in salt solutions, exhibiting "anti-polyelectrolyte effect" salt responsive behaviors. At appropriate ionic conditions, polyVBIPs brushes were able to switch to superlow fouling surfaces (<0.3 ng/cm(2) protein adsorption) and superlow friction surfaces (u ∼ 10(-3)). The relationship between brush structure and its salt-responsive performance was also discussed. This work provides new zwitterionic surface-responsive materials with controllable antifouling and friction capabilities for multifunctional applications.

  4. 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

  5. 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.

  6. Ultrasensitive ELISA using enzyme-loaded nanospherical brushes as labels.

    PubMed

    Qu, Zhenyuan; Xu, Hong; Xu, Ping; Chen, Kaimin; Mu, Rong; Fu, Jianping; Gu, Hongchen

    2014-10-01

    Improving the detection sensitivity of enzyme-linked immunosorbent assay (ELISA) is of utmost importance for meeting the demand of early disease diagnosis. Herein we report an ultrasensitive ELISA system using horseradish peroxidase (HRP)-loaded nanospherical poly(acrylic acid) brushes (SPAABs) as labels. HRP was covalently immobilized in SPAABs with high capacity and activity via an efficient "chemical conjugation after electrostatic entrapment" (CCEE) process, thus endowing SPAABs with high amplification capability as labels. The periphery of SPAAB-HRP was further utilized to bind a layer of antibody with high density for efficient capture of analytes owing to the three-dimensional architecture of SPAABs. Using human chorionic gonadotrophin (hCG) as a model analyte, the SPAAB-amplified system drastically boosted the detection limit of ELISA to 0.012 mIU mL(-1), a 267-fold improvement as compared to conventional ELISA systems.

  7. Experience with a flexible-brush dust-feed mechanism

    SciTech Connect

    Milliman, E.M.; Chang, D.P.Y.; Moss, O.R.

    1980-05-01

    The difficulties of redispersing fine solid particles in a consistent manner are well known. Production of solid aerosols by redispersing bulk powders can be separated into two problems: feeding bulk powder at a desired rate, and dispersion of agglomerates within the bulk powder to produce an aerosol. A novel design for the feeding of bulk powders at the low rates suitable for exposure chamber studies is described. Principal advantages of the dust-feed mechanism are: excellent stability over periods approaching 24 hr; low construction cost; simplicity of design; ability to handle powders which are difficult to compact into a dust cake; wide operational limits on feed rates. The device is not a positive displacement feeder, so that a calibration curve of mass output rate versus brush rotational speed must be developed for each type of dust dispensed.

  8. Piercing an interface with a brush: Collaborative stiffening

    NASA Astrophysics Data System (ADS)

    Chiodi, F.; Roman, B.; Bico, J.

    2010-05-01

    The hairs of a painting brush withdrawn from a wetting liquid self-assemble into clumps whose sizes rely on a balance between liquid surface tension and hairs bending rigidity. Here we study the situation of an immersed carpet in an evaporating liquid bath: the free extremities of the hairs are forced to pierce the liquid interface. The compressive capillary force on the tip of flexible hairs leads to buckling and collapse. However we find that the spontaneous association of hairs into stronger bundles may allow them to resist capillary buckling. We explore in detail the different structures obtained and compare them with similar patterns observed in micro-structured surfaces such as carbon nanotubes "forests".

  9. Training mentally retarded adolescents to brush their teeth.

    PubMed

    Horner, R D; Keilitz, I

    1975-01-01

    The need for self-care by retarded individuals in behaviors such as brushing teeth led to the development and evaluation of a comprehensive toothbrushing program that included a task analysis and training procedure specific to each component of the task analysis. Eight mentally retarded adolescents, in two groups, individually received acquisition training that included scheduled opportunities for independent performances, verbal instruction, modelling, demonstration, and physical assistance. The first group of four subjects received token plus social reinforcement; the second received only social reinforcement. All eight subjects showed improved toothbrushing behaviors when compared to baseline. Six of the eight subjects correctly performed all toothbrushing steps in two of three consecutive sessions. The study emphasizes the need for systematic program development and evaluation.

  10. 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.

  11. Diagnosis of bile duct cancer by bile cytology: usefulness of post-brushing biliary lavage fluid

    PubMed Central

    Sugimoto, Shinya; Matsubayashi, Hiroyuki; Kimura, Hirokazu; Sasaki, Keiko; Nagata, Kaori; Ohno, Sachiyo; Uesaka, Katsuhiko; Mori, Keita; Imai, Kenichiro; Hotta, Kinichi; Takizawa, Kohei; Kakushima, Naomi; Tanaka, Masaki; Kawata, Noboru; Ono, Hiroyuki

    2015-01-01

    Background: Pathologic evidence of biliary diseases can be obtained from cytology in addition to endoscopic retrograde cholangiopancreatography (ERCP); however, the diagnostic effectiveness is not satisfactory. Study aim: This retrospective, single-center study evaluated the efficacy of various sampling methods for the cytologic diagnosis of bile duct cancer. Patients and methods: Biliary samples included bile that was simply aspirated, brush smear, brush-rinsed saline, and post-brushing biliary lavage fluid. A set of samples was compared for cytologic efficacy in 76 patients with surgically proven bile duct cancer and in 50 patients with benign biliary stricture. Results: The cytologic sensitivity for diagnosing biliary cancer was 34 % with aspirated bile, 32 % with brush smear, 43 % with brush-rinsed saline, and 70 % with post-brushing biliary lavage fluid, in contrast to the null false-positive result in the benign cases. The sensitivity of cytology was significantly higher with post-brushing lavage fluid than with the other three sampling methods (P < 0.0001), and post-brushing lavage fluid improved the cumulative sensitivity by 24 % (P = 0.002). The sensitivity of biliary cytology was also associated with the amount of aspirated bile (P = 0.01) and with the aspiration site (P = 0.03). The rate of cancer positivity in a cytology set differed according to the tumor macroscopic type (85 % in the protruding type vs. 40 % in the flat type; P = 0.003), and according to the size of the cancer (87 % for tumors ≥ 50 mm vs. 66 % for tumors < 50 mm; P = 0.02). Conclusions: Post-brushing biliary lavage fluid cytology provides superior diagnostic efficacy, and its addition to ERCP procedures is recommended for obtaining cytologic evidence of bile duct cancer. PMID:26357678

  12. 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.

  13. 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

  14. Growth Factor-Bearing Polymer Brushes--Versatile Bioactive Substrates Influencing Cell Response.

    PubMed

    Psarra, Evmorfia; Foster, Elena; König, Ulla; You, Jungmok; Ueda, Yuichiro; Eichhorn, Klaus-J; Müller, Martin; Stamm, Manfred; Revzin, Alexander; Uhlmann, Petra

    2015-11-01

    In this study we present the development of responsive nanoscale substrates exhibiting cell-guiding properties based on incorporated bioactive signaling cues. The investigative approach considered the effect of two different surface-bound growth factors (GFs) on cell behavior and response: hepatocyte growth factor (HGF) and basic fibroblast growth factor (bFGF). Two surface biofunctionalization strategies were explored in order to conceive versatile, bioactive thin polymer brush films. Polymer brushes made of tethered poly(acrylic)acid (PAA) polymer layers with a high grafting density of polymer chains were biofunctionalized with GFs either by physisorption or chemisorption. Both GFs showed high binding efficiencies to PAA brushes based on their initial loading concentrations. The GF release kinetics can be distinguished depending on the applied biofunctionalization method. Specifically, a high initial burst followed by a constant slow release was observed in the case of both physisorbed HGF and bFGF. In contrast, the release kinetics of chemisorbed GFs were quite different. Remarkably, chemisorbed HGF remained bound to the brush surface for over 1 week, whereas 50% of chemisorbed bFGF was released slowly. Furthermore, the effect of these GF-biofunctionalized PAA brushes on different cells was investigated. A human hepatoma cell line (HepG2) was used to analyze the bioactivity of HGF-modified PAA brushes by measuring cell growth inhibition and scattering effects. Additionally, the differentiation of mouse embryonic stem cells (mESCs) toward endoderm was studied on bFGF-modified PAA brush surfaces. Finally, the results illustrate that PAA brushes, particularly those biofunctionalized with chemisorbed GFs, produce an expected measurable effect on both cell types. Therefore, PAA polymer brushes biofunctionalized with GFs can be used as bioactive cell culture substrates with tuned efficiency. PMID:26447354

  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. Deposition of zwitterionic polymer brushes in a dense gas medium.

    PubMed

    Puniredd, Sreenivasa Reddy; Jayaraman, Sundaramurthy; Gandhimathi, Chinnasamy; Ramakrishna, Seeram; Venugopal, Jayarama Reddy; Yeo, Tin Wei; Guo, Shifeng; Quintana, Robert; Jańczewski, Dominik; Srinivasan, M P

    2015-06-15

    Poly(sulfobetaine methacrylate) (PSBMA) films known for their resistance to nonspecific protein adsorption, cell/bacterial adhesion and biofilm formation were produced by surface initiated polymerization on a silicon surface via a batch reaction system in CO2 expanded liquid (CO2-EL) medium. Atom transfer radical polymerization (ATRP) was carried out using 2,2'-bipyridyl as ligand and CuBr as a catalyst in water/methanol mixture with trichloro[4-(chloromethyl)phenyl]silane (CMPS) used as the initiating species. The films were grown in the CO2-EL environment at a range of conditions and thickness up to 10nm. In contrast to films produced by conventional solvent systems at atmospheric pressure, the polymer films grown by the CO2-EL process showed uniform thickness and pin-hole free topography. Most importantly, the CO2-EL processed PSBMA films showed no trace of copper (used as the catalyst), thus obviating the need for post-deposition processing and avoiding adverse effects of the metal leaching during service. Finally, PSBMA films from both the conventional and CO2-EL processes were exposed to Human mesenchymal stem cells (hMSCs) and the results showed that, while in both the cases the cell proliferation rate was inhibited by the charged polymeric brush surface, the CO2-EL-processed brush exhibited inhibition to a larger extent due to the reduced occurrence of pinholes. The process can be easily exploited effectively when carrying out surface initiated polymerization on non-flat topographies, such as in trenches and nanostructured features with high aspect ratios. PMID:25728486

  17. Pollution Probe.

    ERIC Educational Resources Information Center

    Chant, Donald A.

    This book is written as a statement of concern about pollution by members of Pollution Probe, a citizens' anti-pollution group in Canada. Its purpose is to create public awareness and pressure for the eventual solution to pollution problems. The need for effective government policies to control the population explosion, conserve natural resources,…

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

    PubMed

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

    2015-05-01

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

  19. 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.

  20. 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.

  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. Comparison between observed children's tooth brushing habits and those reported by mothers

    PubMed Central

    2011-01-01

    Background Information bias can occur in epidemiological studies and compromise scientific outcomes, especially when evaluating information given by a patient regarding their own health. The oral habits of children reported by their mothers are commonly used to evaluate tooth brushing practices and to estimate fluoride intake by children. The aim of the present study was to compare observed tooth-brushing habits of young children using fluoridated toothpaste with those reported by mothers. Methods A sample of 201 mothers and their children (aged 24-48 months) from Montes Claros, Brazil, took part in a cross-sectional study. At day-care centres, the mothers answered a self-administered questionnaire on their child's tooth-brushing habits. The structured questionnaire had six items with two to three possible answers. An appointment was then made with each mother/child pair at day-care centres. The participants were asked to demonstrate the tooth-brushing practice as usually performed at home. A trained examiner observed and documented the procedure. Observed tooth brushing and that reported by mothers were compared for overall agreement using Cohen's Kappa coefficient and the McNemar test. Results Cohen's Kappa values comparing mothers' reports and tooth brushing observed by the examiner ranged from poor-to-good (0.00-0.75). There were statistically significant differences between observed tooth brushing habits and those reported by mothers (p < 0.001). When observed by the examiner, the frequencies of dentifrice dispersed on all bristles (35.9%), children who brushed their teeth alone (33.8%) and those who did not rinse their mouths during brushing (42.0%) were higher than those reported by the mothers (12.1%, 18.9% and 6.5%, respectively; p < 0.001). Conclusions In general, there was low agreement between observed tooth brushing and mothers' reports. Moreover, the different methods of estimation resulted in differences in the frequencies of tooth brushing habits

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

    NASA Astrophysics Data System (ADS)

    Ou, Yangpeng

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

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

    PubMed

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

    2016-01-15

    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.

  5. 75 FR 41842 - Northern Border Pipeline Company; Notice of Application

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-19

    ... Energy Regulatory Commission Northern Border Pipeline Company; Notice of Application July 12, 2010. Take notice that on July 2, 2010, Northern Border Pipeline Company (Northern Border), 717 Texas Street... Northern Border's mainline system in Bureau County, Illinois, to a point of interconnection with...

  6. Fabrication and Optimization of Brush-Printed n-type Bi2Te3 Thick Films for Thermoelectric Cooling Devices

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Zhao, Wen-yu; Zhou, Hong-yu; Mu, Xin; He, Dan-qi; Zhu, Wan-ting; Wei, Ping; Wu, Han; Zhang, Qing-jie

    2016-03-01

    A simple, efficient and rapid brush-printing method has been developed for preparation of n-type Bi2Te2.7Se0.3 films approximately 100-150 μm thick. X-ray diffraction, scanning electron microscopy, electron probe microanalysis, and four-point probe measurements were used to characterize the crystal structure, composition, microstructure, and electrical properties of the films. The results showed that all the n-type Bi2Te2.7Se0.3 thick films were composed of single-phase Bi2Te2.7Se0.3; the grains in the films were randomly distributed in the low-temperature-annealed samples and predominantly oriented along the (00 l) plane in samples annealed at temperatures >673 K. σ and the absolute value of α first increased substantially with increasing the annealing temperature in the range 573-673 K then decreased when the annealing temperature was increased further. The dependence of σ and α on annealing temperature may be reasonably explained on the basis of the change in the microstructure induced by annealing. The performance of a prototype cooling device containing n-type Bi2Te2.7Se0.3 thick films was evaluated for temperature differences produced by use of different DC currents.

  7. Cross-border mobility and social networks: Laotians seeking medical treatment along the Thai border.

    PubMed

    Bochaton, Audrey

    2015-01-01

    Drawing upon research conducted on cross-border patients living in Laos and seeking care in Thailand, this paper examines the important role played by social networks in patients' decision-making and on the itineraries they choose to seek treatment on the Thai side of the border. Due to the vastly contrasting situations between the two countries in terms of healthcare supply, and considering Laotians' increasing demand for high quality healthcare, a number of them have managed to satisfy their needs by combining cross-border treatment with the use of the healthcare facilities provided by their own country. This study consisted first of household surveys conducted in five border areas (2006-2007) in Laos in order to quantify and map out cross-border healthcare-related travel patterns. Afterwards, interviews were conducted with cross-border patients (55), Laotian and Thai medical doctors (6), Thai social workers (5), and officials working in public institutions (12). While socioeconomic and spatial factors partly explain cross-border mobility, patients' social networks significantly influence treatment itineraries throughout the decision-making process, including logistical and financial considerations. The social networks existing at different geographical levels (neighbourhood, regional and global) are therefore a powerful analytical tool not only for understanding the emergence of these cross-border movements but also for justifying them in an authoritarian political environment such as Lao PDR's. PMID:25454637

  8. Cross-border mobility and social networks: Laotians seeking medical treatment along the Thai border.

    PubMed

    Bochaton, Audrey

    2015-01-01

    Drawing upon research conducted on cross-border patients living in Laos and seeking care in Thailand, this paper examines the important role played by social networks in patients' decision-making and on the itineraries they choose to seek treatment on the Thai side of the border. Due to the vastly contrasting situations between the two countries in terms of healthcare supply, and considering Laotians' increasing demand for high quality healthcare, a number of them have managed to satisfy their needs by combining cross-border treatment with the use of the healthcare facilities provided by their own country. This study consisted first of household surveys conducted in five border areas (2006-2007) in Laos in order to quantify and map out cross-border healthcare-related travel patterns. Afterwards, interviews were conducted with cross-border patients (55), Laotian and Thai medical doctors (6), Thai social workers (5), and officials working in public institutions (12). While socioeconomic and spatial factors partly explain cross-border mobility, patients' social networks significantly influence treatment itineraries throughout the decision-making process, including logistical and financial considerations. The social networks existing at different geographical levels (neighbourhood, regional and global) are therefore a powerful analytical tool not only for understanding the emergence of these cross-border movements but also for justifying them in an authoritarian political environment such as Lao PDR's.

  9. pH-regulated ionic current rectification in conical nanopores functionalized with polyelectrolyte brushes.

    PubMed

    Zeng, Zhenping; Ai, Ye; Qian, Shizhi

    2014-02-14

    Mimicking biological ion channels capable of pH-regulated ionic transport, synthetic nanopores functionalized with pH-tunable polyelectrolyte (PE) brushes have been considered as versatile tools for active transport control of ions, fluids, and bioparticles on the nanoscale. The ionic current rectification (ICR) phenomenon through a conical nanopore functionalized with PE brushes whose charge highly depends upon the local solution properties (i.e., pH and background salt concentration) is studied theoretically for the first time. The results show that the rectification magnitude, as well as the preferential rectification direction, is sensitive to the pH stimulus. The bulk concentration of the background salt can also significantly influence the charge of the PE brushes and accordingly affect the ICR phenomenon. The obtained results provide an insightful understanding of the pH-regulated ICR and guidelines for designing nanopores functionalized with PE brushes for pH-tunable applications.

  10. Electron spectroscopy analysis of contact surfaces in the wear of carbon brushes against copper commutators

    NASA Astrophysics Data System (ADS)

    Savage, D. E.; Lagally, M. G.; Schrader, M. E.

    Carbon brushes and copper commutator strips have been analyzed by a combination of techniques to investigate possible surface-related phenomena in the excessive wear of carbon brushes in motors and generators. X-ray photoelectron spectroscopy, scanning Auger microscopy, optical microscopy, scanning electron microscopy, and energy-dispersive X-ray analysis were used in this study. A thin SiO 2 film, of the order of 30 Å on the brushes, and of the order of several hundred Å on the commutators, was correlated with high wear and is believed to be the chief cause of the excessive wear. Possible models for the effect of SiO 2 on carbon brush wear are discussed.

  11. 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.

  12. 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

  13. 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.

  14. Helicobacter pylori in gastroduodenal diseases: rapid identification by endoscopic brush cytology.

    PubMed

    De Francesco, F; Nicòtina, P A; Picciotto, M; Martines, F; Ferlazzo, G; d'Aquino, A

    1993-08-01

    Previous reports showed Helicobacter pylori (H. pylori) in type B gastritis-affected stomachs. This study was carried out to compare H. pylori staining effectiveness on biopsy to brush cytology. Tissue and brush parallel samples of gastric mucosa with abnormal or normal appearances were examined: 57.6% H. pylori-positive pieces from the antrum and 19.2% from the body were found, versus 65.3% and 25% H. pylori-positive brush smears, respectively. H. pylori resembling organisms were mainly related to chronic and acute antral inflammations and were often associated with higher amounts of round-shaped cocco-bacteria. In addition, H. pylori direct stain on brushing is proposed as the most rapid and reliable method for the routine diagnosis of Helicobacter pylori infection, in both ulcer or nonulcer gastritis.

  15. 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.

  16. Thermally modulated retention of lymphoctytes on polymer-brush-grafted glass beads.

    PubMed

    Nagase, Kenichi; Mukae, Naoto; Kikuchi, Akihiko; Okano, Teruo

    2012-03-01

    Thermoresponsive PIPAAm-brush-grafted glass beads are prepared through siATRP and their physicochemical properties are characterized by micro-nitrogen analysis, XPS, and contact angle measurements. The amount of grafted PIPAAm on glass bead surfaces can be controlled by varying the ATRP reaction time, leading to a modulation of the temperature-dependent wettability of the prepared surfaces. To evaluate a possible use of the beads as cell separation matrices, loading with rat lymphocytes from mesenteric lymph nodes is studied. The results show that the interaction between PIPAAm brushes and lymphocytes can be controlled by modulating PIPAAm brush length and temperature. The PIPAAm-brush-grafted beads might therefore be useful as effective cell separation matrices.

  17. 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.

  18. Network communities within and across borders

    PubMed Central

    Cerina, Federica; Chessa, Alessandro; Pammolli, Fabio; Riccaboni, Massimo

    2014-01-01

    We investigate the impact of borders on the topology of spatially embedded networks. Indeed territorial subdivisions and geographical borders significantly hamper the geographical span of networks thus playing a key role in the formation of network communities. This is especially important in scientific and technological policy-making, highlighting the interplay between pressure for the internationalization to lead towards a global innovation system and the administrative borders imposed by the national and regional institutions. In this study we introduce an outreach index to quantify the impact of borders on the community structure and apply it to the case of the European and US patent co-inventors networks. We find that (a) the US connectivity decays as a power of distance, whereas we observe a faster exponential decay for Europe; (b) European network communities essentially correspond to nations and contiguous regions while US communities span multiple states across the whole country without any characteristic geographic scale. We confirm our findings by means of a set of simulations aimed at exploring the relationship between different patterns of cross-border community structures and the outreach index. PMID:24686380

  19. Network communities within and across borders.

    PubMed

    Cerina, Federica; Chessa, Alessandro; Pammolli, Fabio; Riccaboni, Massimo

    2014-01-01

    We investigate the impact of borders on the topology of spatially embedded networks. Indeed territorial subdivisions and geographical borders significantly hamper the geographical span of networks thus playing a key role in the formation of network communities. This is especially important in scientific and technological policy-making, highlighting the interplay between pressure for the internationalization to lead towards a global innovation system and the administrative borders imposed by the national and regional institutions. In this study we introduce an outreach index to quantify the impact of borders on the community structure and apply it to the case of the European and US patent co-inventors networks. We find that (a) the US connectivity decays as a power of distance, whereas we observe a faster exponential decay for Europe; (b) European network communities essentially correspond to nations and contiguous regions while US communities span multiple states across the whole country without any characteristic geographic scale. We confirm our findings by means of a set of simulations aimed at exploring the relationship between different patterns of cross-border community structures and the outreach index. PMID:24686380

  20. Network communities within and across borders

    NASA Astrophysics Data System (ADS)

    Cerina, Federica; Chessa, Alessandro; Pammolli, Fabio; Riccaboni, Massimo

    2014-04-01

    We investigate the impact of borders on the topology of spatially embedded networks. Indeed territorial subdivisions and geographical borders significantly hamper the geographical span of networks thus playing a key role in the formation of network communities. This is especially important in scientific and technological policy-making, highlighting the interplay between pressure for the internationalization to lead towards a global innovation system and the administrative borders imposed by the national and regional institutions. In this study we introduce an outreach index to quantify the impact of borders on the community structure and apply it to the case of the European and US patent co-inventors networks. We find that (a) the US connectivity decays as a power of distance, whereas we observe a faster exponential decay for Europe; (b) European network communities essentially correspond to nations and contiguous regions while US communities span multiple states across the whole country without any characteristic geographic scale. We confirm our findings by means of a set of simulations aimed at exploring the relationship between different patterns of cross-border community structures and the outreach index.

  1. 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

  2. Performance of bile aspiration plus brushing to diagnose malignant biliary strictures during endoscopic retrograde cholangiopancreatography

    PubMed Central

    Roth, Gael S.; Bichard, Philippe; Fior-Gozlan, Michele; Roth, Hubert; Auroux, Jean; Risse, Olivier; Letoublon, Christian; Laverrière, Marie Hélène; Bricault, Ivan; Leroy, Vincent; Decaens, Thomas

    2016-01-01

    Background and study aims: Endobiliary brushing during endoscopic retrograde cholangiopancreatography (ERCP) is the main technique used to diagnose a malignant stricture, but has a poor sensitivity. This study evaluated the diagnostic performance of bile aspiration associated with biliary brushing during ERCP to diagnose a malignant stricture, compared to brushing alone. Patients and methods: Between January 2007 and December 2012, all consecutive patients undergoing ERCP to treat a biliary stricture were included. After a biliary sphincterotomy, 3 mL to 10 mL of bile was aspirated into the brush catheter and collected in a dry sterile tube before and after brushing (to yield three samples). Brushing was performed as commonly recommended. Results: One hundred eleven patients (68 males, 43 females) were included; mean age 67 ± 15.4 years. A final diagnosis of malignant stricture was established in 51 patients, including 43 cholangiocarcinomas; 60 patients had benign strictures. Specificity (Sp) and positive predictive values were 100% for all samples. The diagnostic performance of the three-sample combination of bile aspiration + brushing + bile aspiration was significantly greater than brushing alone (P = 0.004): sensitivity (Se) = 84.3 % vs. Se = 66.7 %. The three-sample combination gave a negative predictive value of 88.2 %, and a diagnostic accuracy of 92.8 %. When suspicious results were added to malignant results as positive results, the three-sample combination gave Sp = 91.7 % and Se = 94.1 %. Conclusions: In cases of biliary stricture, conducting bile aspiration before and after brushing significantly increased the ability to diagnose a malignant stricture with a sensitivity of 84.3 % (P = 0.004). PMID:27652308

  3. Development of a directly patterned low-surface-energy polymer brush in supercritical carbon dioxide.

    PubMed

    Rastogi, Abhinav; Paik, Marvin Y; Ober, Christopher K

    2009-09-01

    Carbon dioxide (CO2) is a sustainable solvent because it is nonflammable, exhibits a relatively low toxicity, and is naturally abundant. As a selective, nonpolar solvent, supercritical CO2 (scCO2) is an ideal fit for the development of low-surface-energy polymers. The development of directly patterned poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) brushes in scCO2 was investigated. PTFEMA, in particular, was selected over other fluorinated polymers because of its very high electron-beam (e-beam) sensitivity. PTFEMA brushes were grown on silicon substrates via controlled surface-initiated atom-transfer radical polymerization of TFEMA. Surface analysis techniques including ellipsometry, contact-angle goniometry, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy were used to characterize the thickness, hydrophilicity, roughness, and chemical composition of the polymer brushes. PTFEMA brushes were directly patterned in a single step using e-beam lithography and were processed in an environmentally benign scCO2 solvent. Tapping-mode AFM imaging confirmed the successful e-beam patterning and development of these brushes. The sensitivity of PTFEMA brushes toward direct patterning with the e-beam, followed by scCO2 development, was studied and compared to development in tetrahydrofuran solvent. Using this direct-patterning method, followed by dry development in scCO2, highly resolved nanostructured polymer brush lines down to 78 nm could be prepared. This method can be generalized to prepare fluorinated low-surface-energy polymer brush surfaces in a single step for various applications. PMID:20355827

  4. 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.

  5. Degradable Polycaprolactone and Polylactide Homopolymer and Block Copolymer Brushes Prepared by Surface-Initiated Polymerization with Triazabicyclodecene and Zirconium Catalysts.

    PubMed

    Grubbs, Joe B; Arnold, Rachelle M; Roy, Anandi; Brooks, Karson; Bilbrey, Jenna A; Gao, Jing; Locklin, Jason

    2015-09-22

    Surface-initiated ring-opening polymerization (SI-ROP) of polycaprolactone (PCL) and polylactide (PLA) polymer brushes with controlled degradation rates were prepared on oxide substrates. PCL brushes were polymerized from hydroxyl-terminated monolayers utilizing triazabicyclodecene (TBD) as the polymerization catalyst. A consistent brush thickness of 40 nm could be achieved with a reproducible unique crystalline morphology. The organocatalyzed PCL brushes were chain extended using lactide in the presence of zirconium n-butoxide to successfully grow PCL/PLA block copolymer (PCL-b-PLA) brushes with a final thickness of 55 nm. The degradation properties of "grafted from" PCL brush and the PCL-b-PLA brush were compared to "grafted to" PCL brushes, and we observed that the brush density plays a major role in degradation kinetics. Solutions of methanol/water at pH 14 were used to better solvate the brushes and increase the kinetics of degradation. This framework enables a control of degradation that allows for the precise removal of these coatings.

  6. 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

  7. Preparation of plasmonic vesicles from amphiphilic gold nanocrystals grafted with polymer brushes

    PubMed Central

    Song, Jibin; Huang, Peng; Chen, Xiaoyuan

    2016-01-01

    Gold nanovesicles contain multiple nanocrystals within a polymeric coating. The strong plasmonic coupling between adjacent nanoparticles in their vesicular shell makes ultrasensitive biosensing and bioimaging possible. In our laboratory, multifunctional plasmonic vesicles are assembled from amphiphilic gold nanocrystals (such as gold nanoparticles and gold nanorods) coated with mixed hydrophilic and hydrophobic polymer brushes or amphiphilic diblock co-polymer brushes. To fulfill the different requirements of biomedical applications, different polymers that are either pH=responsive, photoactive or biodegradable can be used to form the hydrophobic brush, while the hydrophilicity is maintained by polyethylene glycol (PEG). This protocol covers the preparation, surface functionalization and self-assembly of amphiphilic gold nanocrystals grafted covalently with polymer brushes. The protocol can be completed within 2 d. The preparation of amphiphilic gold nanocrystals, coated with amphiphilic diblock polymer brushes using a ‘grafting to’ method or mixed hydrophilic and hydrophobic polymer brushes using tandem ‘grafting to’ and ‘grafting from’ methods, is described. We also provide detailed procedures for the preparation and characterization of pH-responsive plasmonic gold nanovesicles from amphiphilic gold nanocrystals using a film-rehydration method that can be completed within ~3 d. PMID:27763624

  8. 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.

  9. Grafting of PMMA brushes layer on Cu surface to create a stable superhydrophobic surface

    NASA Astrophysics Data System (ADS)

    Zhang, Junhong; Cai, Junyan; Li, Ming

    2016-11-01

    In this paper, poly(methyl methacrylate) (PMMA) brushes were grafted on Cu micro-cone structured substrate by a simple one-step cathodic electro-initiated polymerization method which was carried out in aqueous solution at room temperature in the open air. The PMMA brushes were continuous, uniform and thickness-controllable, and it covalently bonded to the Cu surface. In the brushes, nitrophenyl moieties acted as cross-linker between PMMA chains. After removed from the solution followed by treated with water, the PMMA brushes (basically a hydrophilic material)/micro-cone structured Cu surface was hydrophilic with water contact angle (CA) of 74.4°. However, it exhibited superhydrophobicity by treating it in the acetone. The conversion from hydrophilic surface to superhydrophobic one may due to rearrangement of nitrophenyl moieties and PMMA chains at the topmost of the brushes. In addition, its water CA increased with grafting time of the brushes from 145° to about 166°, because there was no available space in thinner film for group reorientation. The surface was conversed to hydrophilic again after treated with hot water, but it was still superhydrophobic after treated in water at room temperature. This revealed that the group reorientation also easily occurred in hot water like in the acetone. More importantly, the surface retained good superhydrophobic stability in acidic environment and in long-time storage. Furthermore, the superhydrophobic surface had excellent resistance that can provide effective protection for the bare Cu substrate.

  10. 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.

  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. 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

  13. 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.

  14. Polymer Brush Surfaces Showing Superhydrophobicity and Air-Bubble Repellency in a Variety of Organic Liquids.

    PubMed

    Dunderdale, Gary J; England, Matt W; Urata, Chihiro; Hozumi, Atsushi

    2015-06-10

    Silicon (Si) substrates were modified with polyalkyl methacrylate brushes having different alkyl chain lengths (C(n), where n = 1, 4, 8, and 18) using ARGET-ATRP at ambient temperature without purging the reaction solution of oxygen. The dynamic hydrophobicity of these polymer brush-covered Si surfaces when submerged in a variety of organic solvents (1-butanol, dichloromethane, toluene, n-hexane) depended markedly on the alkyl chain length and to a lesser extent polymer solubility. Long-chain poly(stearyl methacrylate) brushes (C(n) = 18) submerged in toluene showed excellent water-repellant properties, having large advancing/receding contact angles (CAs) of 169°/168° with negligible CA hysteresis (1°). Whereas polymer brushes with short alkyl-chain (C(n) ≤ 4) had significantly worse water drop mobility because of small CAs (as low as 125°/55°) and large CA hysteresis (up to 70°). However, such poor dynamic dewetting behavior of these surfaces was found to significantly improve when water drops impacted onto the surfaces at moderate velocities. Under these conditions, all brush surfaces were able to expel water drops from their surface. In addition, our brush surfaces were also highly repellant toward air bubbles under all conditions, irrespective of C(n) or polymer solubility. These excellent surface properties were found to be vastly superior to the performance of conventional perfluoroalkylsilane-derived surfaces. PMID:25988214

  15. Surface roughness and color change of a composite: influence of beverages and brushing.

    PubMed

    Lepri, Cesar Penazzo; Palma-Dibb, Regina Guenka

    2012-01-01

    This study evaluated the influence of beverages and brushing on the surface roughness(SR) and color change(∆E) of a composite resin.For this, 120-disks(10 mm×2 mm) of composite resin(Filtek-Z250) were prepared and polished. Initials SR(Ra-μm) and color(CIELab-system) were measured with rugosimeter and spectrophotometer; specimens were divided into four groups(red wine, soft drink, sugar cane spirit, or artificial saliva=control) and three subgroups(without brushing; brushed with Colgate or with Close-Up). Specimens were immersed in the beverage 5×/day, for 5', over 30 day, being two subgroups brushed(120 strokes/day). Color was measuredat 15th day, 30th day and after repolishment; SR at 30th day. ∆E-values were statistically different after immersion in the beverages(p<0.05). Red wine promoted the highest alteration, followed by soft drink=sugar cane spirit and finally saliva. At 30th day, specimens exhibited ∆E higher than 15th day; after repolishing, ∆E was similar to 15th day. Beverages and brushing negatively influenced the SR. Therefore, ∆E and SR can be influenced by beverages and brushing. PMID:22864226

  16. Affect of Brush Seals on Wave Rotor Performance Assessed

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The NASA Lewis Research Center's experimental and theoretical research shows that wave rotor topping can significantly enhance gas turbine engine performance levels. Engine-specific fuel consumption and specific power are potentially enhanced by 15 and 20 percent, respectively, in small (e.g., 400 to 700 hp) and intermediate (e.g., 3000 to 5000 hp) turboshaft engines. Furthermore, there is potential for a 3- to 6-percent specific fuel consumption enhancement in large (e.g., 80,000 to 100,000 lbf) turbofan engines. This wave-rotor-enhanced engine performance is accomplished within current material-limited temperature constraints. The completed first phase of experimental testing involved a three-port wave rotor cycle in which medium total pressure inlet air was divided into two outlet streams, one of higher total pressure and one of lower total pressure. The experiment successfully provided the data needed to characterize viscous, partial admission, and leakage loss mechanisms. Statistical analysis indicated that wave rotor product efficiency decreases linearly with the rotor to end-wall gap, the square of the friction factor, and the square of the passage of nondimensional opening time. Brush seals were installed to further minimize rotor passage-to-cavity leakage. The graph shows the effect of brush seals on wave rotor product efficiency. For the second-phase experiment, which involves a four-port wave rotor cycle in which heat is added to the Brayton cycle in an external burner, a one-dimensional design/analysis code is used in conjunction with a wave rotor performance optimization scheme and a two-dimensional Navier-Stokes code. The purpose of the four-port experiment is to demonstrate and validate the numerically predicted four-port pressure ratio versus temperature ratio at pressures and temperatures lower than those that would be encountered in a future wave rotor/demonstrator engine test. Lewis and the Allison Engine Company are collaborating to investigate

  17. Optical Force Probe Microscopy of the Pericellular Matrix

    NASA Astrophysics Data System (ADS)

    McLane, Louis T.; Chang, Patrick; Granqvist, Anna; Boehm, Heike; Kramer, Anthony; Curtis, Jennifer E.

    2012-02-01

    The pericellular matrix is a microns-thick grafted polymer film on the surface of cells. Its structure and mechanics influence processes as diverse as filtration, cell adhesion, proliferation, migration, cancer metastasis and possibly mechanotransduction. Optical force probe microscopy enables dynamic and equilibrium measurements of this polymer film on living cells. We show that equilibrium force measurements can be related to the osmotic pressure in the pericellular matrix, leading to a prediction of a spatially varying correlation length (mesh size) profile ranging from ˜100 nm at the cell surface to 1000 nm near the edge of the cell coat. Assuming the film is brush-like, comparison to polymer brush theory provides estimates of the equilibrium brush length and the grafting density at the surface. The equilibrium length is consistent with that observed during dynamic force measurements, and the grafting density is close to that of maximal packing for the large, space filling molecules in the system - i.e. tethered polymers populated by semi-flexible side chains with cross sections ˜80 x 400 nm^2.

  18. Control of Japanese honeysuckle in wildlife borders

    USGS Publications Warehouse

    Warbach, O.

    1953-01-01

    1. Japanese honeysuckle, an exotic that can be either a pest or an asset in different localities, makes maintenance of wildlife plantings in the Southeast a difficult problem. 2. A herbicide applied during the winter and strong enough to kill dormant woody plants will stop the spread of honeysuckle from a woods edge for at least two years. 3. A low-percentage 2,4-D water spray applied to honeysuckle growing in bicolor lespedeza borders at a time when honeysuckle is starting growth and bicolor is still dormant will selectively destroy the vine without injuring the border. 4. Studies on control of honeysuckle in multiflora rose, shrub borders, and contour hedges by herbicides are planned for the future.

  19. Formation and separation of root border cells.

    PubMed

    Driouich, Azeddine; Durand, Caroline; Vicré-Gibouin, Maïté

    2007-01-01

    Plant roots release a large number of border cells into the rhizosphere, which are believed to play a key role in root development and health. The formation and loss of these cells from the root cap region is a developmentally regulated process that is also controlled by phytohormones and environmental factors. The separation of border cells involves the complete dissociation of individual cells from each other and from root tissue. This process requires the activity of cell wall-degrading enzymes that solubilize the cell wall connections between cells. We present and discuss the solubilization process with an emphasis on pectin-degrading enzymes as well as the recently discovered root border-like cells of Arabidopsis thaliana.

  20. BTFS: The Border Trade Facilitation System

    SciTech Connect

    Phillips, L.R.

    1999-03-18

    The author demonstrates the Border Trade Facilitation System (BTFS), an agent-based bilingual e-commerce system built to expedite the regulation, control, and execution of commercial trans-border shipments during the delivery phase. The system was built to serve maquila industries at the US/Mexican border. The BTFS uses foundation technology developed here at Sandia Laboratories' Advanced Information Systems Lab (AISL), including a distributed object substrate, a general-purpose agent development framework, dynamically generated agent-human interaction via the World-Wide Web, and a collaborative agent architecture. This technology is also the substrate for the Multi-Agent Simulation Management System (MASMAS) proposed for demonstration at this conference. The BTFS executes authenticated transactions among agents performing open trading over the Internet. With the BTFS in place, one could conduct secure international transactions from any site with an Internet connection and a web browser. The BTFS is currently being evaluated for commercialization.