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Sample records for surface-initiated kumada catalyst-transfer

  1. "Hairy" Poly(3-hexylthiophene) Particles Prepared via Surface-Initiated Kumada Catalyst-Transfer Polycondensation

    DEFF Research Database (Denmark)

    Senkovskyy, Volodymyr; Tkachov, Roman; Beryozkina, Tetyana

    2009-01-01

    electronics, was selectively grown by SI-KCTP from (nano)particles bearing surface-immobilized Ni catalysts supported by bidentate phosphorus ligands, that resulted in hairy (nano)particles with end-tethered P3HT chains. Densely grafted P3HT chains exhibit strongly altered optical properties compared...

  2. Mechanistic Implications for the Ni(I-Catalyzed Kumada Cross-Coupling Reaction

    Directory of Open Access Journals (Sweden)

    Linda Iffland

    2017-11-01

    Full Text Available Herein we report on the cross-coupling reaction of phenylmagnesium bromide with aryl halides using the well-defined tetrahedral Ni(I complex, [(TriphosNiICl] (Triphos = 1,1,1-tris(diphenylphosphinomethylethane. In the presence of 0.5 mol % [(TriphosNiICl], good to excellent yields (75–97% of the respective coupling products within a reaction time of only 2.5 h at room temperature were achieved. Likewise, the tripodal Ni(IIcomplexes [(κ2-TriphosNiIICl2] and [(κ3-TriphosNiIICl](X (X = ClO4, BF4 were tested as potential pre-catalysts for the Kumada cross-coupling reaction. While the Ni(II complexes also afford the coupling products in comparable yields, mechanistic investigations by UV/Vis and electron paramagnetic resonance (EPR spectroscopy indicate a Ni(I intermediate as the catalytically active species in the Kumada cross-coupling reaction. Based on experimental findings and density functional theory (DFT calculations, a plausible Ni(I-catalyzed reaction mechanism for the Kumada cross-coupling reaction is presented.

  3. Preparation and Structural Studies on Hybrid Core-Shell Nanoparticles Consisting of Silica Core and Conjugated Block Copolymer Shell Prepared by Surface-Initiated Polymerization

    Science.gov (United States)

    Chatterjee, Sourav; Karam, Tony; Rosu, Cornelia; Li, Xin; Do, Changwoo; Youm, Sang Gil; Haber, Louis; Russo, Paul; Nesterov, Evgueni

    Controlled Kumada catalyst-transfer polymerization occurring by chain-growth mechanism was developed for the synthesis of conjugated polymers and block copolymers from the surface of inorganic substrates such as silica nanoparticles. Although synthesis of conjugated polymers via Kumada polymerization became an established method for solution polymerization, carrying out the same reaction in heterogeneous conditions to form monodisperse polymer chains still remains a challenge. We developed and described a simple and efficient approach to the preparation of surface-immobilized layer of catalytic Ni(II) initiator, and demonstrated using it to prepare polymers and block copolymers on silica nanoparticle. The structure of the resulting hybrid nanostructures was thoroughly studied using small-angle neutron and X-ray scattering, thermal analysis, and optical spectroscopy. The photoexcitation energy transfer processes in the conjugated polymer shell were studied via steady-state and time resolved transient absorption spectroscopy. This study uncovered important details of the energy transfer, which will be discussed in this presentation.

  4. Precision synthesis of poly(3-hexylthiophene) from catalyst-transfer Suzuki-Miyaura coupling polymerization.

    Science.gov (United States)

    Yokozawa, Tsutomu; Suzuki, Ryosuke; Nojima, Masataka; Ohta, Yoshihiro; Yokoyama, Akihiro

    2011-06-01

    (t)Bu(3) PPd(Ph)Br (1)-catalyzed Suzuki-Miyaura coupling polymerization of 2-(4-hexyl-5-iodo-2-thienyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2) was investigated. Monomer 2 was polymerized with 1 at 0 °C in the presence of CsF and 18-crown-6 in THF containing a small amount of water to yield P3HT with a narrow molecular weight distribution and almost perfect head-to-tail regioregularity. The M(n) values increased up to 11,400 g · mol(-1) in proportion to the feed ratio of 2 to 1. The MALDI-TOF mass spectra showed that P3HT with moderate molecular weight uniformly had a phenyl group at one end and a hydrogen atom at the other, indicating involvement of a catalyst-transfer mechanism. Successive 1-catalyzed polymerization of fluorene monomer 3 and then 2 yielded a well-defined block copolymer of polyfluorene and P3HT. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Synthesis of cis - and trans-diisothiocyanato-bis(NHC) complexes of nickel(II) and applications in the Kumada-Corriu reaction

    KAUST Repository

    Jothibasu, Ramasamy

    2010-09-13

    Metathetical reaction of AgSCN with a series of trans-dihalido-bis(carbene) nickel(II) complexes in CH3CN readily afforded the novel diisothiocyanato-bis(carbene) complexes [Ni(NCS)2(NHC)2] (trans-2a, NHC = 1,3-diisopropylbenzimidazolin-2-ylidene; trans-2b, NHC = 1,3-diisobutylbenzimidazolin-2-ylidene; trans-2c, NHC = 1,3- dibenzylbenzimidazolin-2-ylidene; cis-2d, NHC = 1,3-di(2-propenyl) benzimidazolin-2-ylidene; cis-2e, NHC = 1-propyl-3-methylbenzimidazolin-2- ylidene) as greenish-yellow powders in moderate to good yields. While dihalido-bis(carbene) Ni(II) complexes exclusively form trans-complexes, a trans-cis isomerization occurs upon halido-isothiocyanato exchange with complexes bearing less bulky carbene ligands, i.e., cis-2d/e. DFT calculations indicated that this isomerization can be attributed to a reduced energy difference between trans- and cis-isomers of diisothiocyanato complexes. All complexes have been characterized by multinuclear NMR spectroscopy, ESI mass spectrometry, and X-ray diffraction analysis. A catalytic study revealed that cis-complexes generally exhibit greater activities in the Kumada-Corriu coupling reaction. © 2010 American Chemical Society.

  6. Substituent effects in surface-initiated ATRP of substituted styrenes

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Sampa, E-mail: ssaha@polymers.iitd.ac.in; Baker, Gregory L.

    2015-12-30

    Graphical abstract: - Highlights: • Suitably substituted styrenes can lead to rapid synthesis of uniform and thick polystyrene brushes (>100 nm in 1 h) from gold surface via surface initiated ATRP. • High growth rates were observed for styrenes substituted with electron withdrawing groups in meta/para positions. • Electron donors at meta sites show surprisingly fast growth rates, which may be due to steric inhibition of termination. • Surface polymerization rates for substituted styrenes followed the Hammett relation with ρ = 0.51, similar to conventional radical polymerization in solution. - Abstract: Surface initiated atom transfer radical polymerization (ATRP) of substituted styrenes leads to rapid synthesis of uniform and thick substituted polystyrene brushes (>100 nm in 1 h) from gold surface. High growth rates were observed for styrenes substituted with electron withdrawing groups in meta/para positions. The effects seen in surface and solution polymerizations are similar for styrenes with electron withdrawing groups, and for electron donors in ortho and para positions. However, electron donors at meta sites have surprisingly fast growth rates, which may be due to steric inhibition of termination. The overall surface polymerization rates for substituted styrenes was analyzed and found to follow the Hammett relation with ρ = 0.51. The ratio of k{sub p} to k{sub t}, is as an indicator of the likelihood that a reaction will reach high degrees of polymerization before termination.

  7. Polystyrene/magnesium hydroxide nanocomposite particles prepared by surface-initiated in-situ polymerization

    Science.gov (United States)

    Liu, Hui; Yi, Jianhong

    2009-03-01

    In order to avoid their agglomeration and incompatibility with hydrophobic polystyrene substrate, magnesium hydroxide nanoparticles were encapsulated by surface-initiated in-situ polymerization of styrene. The process contained two steps: electrostatic adsorption of initiator and polymerization of monomer on the surface of magnesium hydroxide. It was found that high adsorption ratio in the electrostatic adsorption of initiator could be attained only in acidic region, and the adsorption belonged to typical physical process. Compared to traditional in-situ polymerization, higher grafting ratio was obtained in surface-initiated in-situ polymerization, which can be attributed to weaker steric hindrance. Both Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) indicated that polystyrene/magnesium hydroxide nanocomposite particles had been successfully prepared by surface-initiated in-situ polymerization. The resulting samples were also analyzed and characterized by means of contact angle testing, dispersibility evaluation and thermogravimetric analysis.

  8. On surface-initiated atom transfer radical polymerization using diazonium chemistry to introduce the initiator layer

    DEFF Research Database (Denmark)

    Iruthayaraj, Joseph; Chernyy, Sergey; Lillethorup, Mie

    2011-01-01

    This work features the controllability of surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl methacrylate, initiated by a multilayered 2-bromoisobutyryl moiety formed via diazonium chemistry. The thickness as a function of polymerization time has been studied by varying...

  9. Protein repellent hydrophilic grafts prepared by surface-initiated atom transfer radical polymerization from polypropylene

    DEFF Research Database (Denmark)

    Fristrup, Charlotte Juel; Jankova Atanasova, Katja; Eskimergen, Rüya

    2012-01-01

    Grafting of poly(ethylene glycol)methacrylate (PEGMA) and N,N-dimethylacrylamide (DMAAm) from UV-initiator modified polypropylene (PP) was performed by Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP). The modification and hydrophilization of the PP substrates were confirmed...

  10. Polymer coating comprising 2-methoxyethyl acrylate units synthesized by surface-initiated atom transfer radical polymerization

    DEFF Research Database (Denmark)

    2011-01-01

    Source: US2012184029A The present invention relates to preparation of a polymer coating comprising or consisting of polymer chains comprising or consisting of units of 2-methoxyethyl acrylate synthesized by Surface-Initiated Atom Transfer Radical Polymerization (SI ATRP) such as ARGET SI ATRP...... or AGET SI ATRP and uses of said polymer coating....

  11. Functionalized polymer film surfaces via surface-initiated atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Hu, Y.; Li, J.S.; Yang, W.T.; Xu, F.J.

    2013-01-01

    The ability to manipulate and control the surface properties of polymer films, without altering the substrate properties, is crucial to their wide-spread applications. In this work, a simple one-step method for the direct immobilization of benzyl chloride groups (as the effective atom transfer radical polymerization (ATRP) initiators) on the polymer films was developed via benzophenone-induced coupling of 4-vinylbenzyl chloride (VBC). Polyethylene (PE) and nylon films were selected as examples of polymer films to illustrate the functionalization of film surfaces via surface-initiated ATRP. Functional polymer brushes of (2-dimethylamino)ethyl methacrylate, sodium 4-styrenesulfonate, 2-hydroxyethyl methacrylate and glycidyl methacrylate, as well as their block copolymer brushes, have been prepared via surface-initiated ATRP from the VBC-coupled PE or nylon film surfaces. With the development of a simple approach to the covalent immobilization of ATRP initiators on polymer film surfaces and the inherent versatility of surface-initiated ATRP, the surface functionality of polymer films can be precisely tailored. - Highlights: ► Atom transfer radical polymerization initiators were simply immobilized. ► Different functional polymer brushes were readily prepared. ► Their block copolymer brushes were also readily prepared

  12. Toward Improved Land Surface Initialization in Support of Regional WRF Forecasts at the Kenya Meteorological Department

    Science.gov (United States)

    Case. Jonathan; Mungai, John; Sakwa, Vincent; Kabuchanga, Eric; Zavodsky, Bradley T.; Limaye, Ashutosh S.

    2014-01-01

    Flooding and drought are two key forecasting challenges for the Kenya Meteorological Department (KMD). Atmospheric processes leading to excessive precipitation and/or prolonged drought can be quite sensitive to the state of the land surface, which interacts with the boundary layer of the atmosphere providing a source of heat and moisture. The development and evolution of precipitation systems are affected by heat and moisture fluxes from the land surface within weakly-sheared environments, such as in the tropics and sub-tropics. These heat and moisture fluxes during the day can be strongly influenced by land cover, vegetation, and soil moisture content. Therefore, it is important to represent the land surface state as accurately as possible in numerical weather prediction models. Enhanced regional modeling capabilities have the potential to improve forecast guidance in support of daily operations and high-end events over east Africa. KMD currently runs a configuration of the Weather Research and Forecasting (WRF) model in real time to support its daily forecasting operations, invoking the Nonhydrostatic Mesoscale Model (NMM) dynamical core. They make use of the National Oceanic and Atmospheric Administration / National Weather Service Science and Training Resource Center's Environmental Modeling System (EMS) to manage and produce the WRF-NMM model runs on a 7-km regional grid over eastern Africa. Two organizations at the National Aeronautics and Space Administration Marshall Space Flight Center in Huntsville, AL, SERVIR and the Short-term Prediction Research and Transition (SPoRT) Center, have established a working partnership with KMD for enhancing its regional modeling capabilities. To accomplish this goal, SPoRT and SERVIR will provide experimental land surface initialization datasets and model verification capabilities to KMD. To produce a land-surface initialization more consistent with the resolution of the KMD-WRF runs, the NASA Land Information System (LIS

  13. Fabrication of Robust and Antifouling Superhydrophobic Surfaces via Surface-Initiated Atom Transfer Radical Polymerization.

    Science.gov (United States)

    Xue, Chao-Hua; Guo, Xiao-Jing; Ma, Jian-Zhong; Jia, Shun-Tian

    2015-04-22

    Superhydrophobic surfaces were fabricated via surface-initiated atom transfer radical polymerization of fluorinated methacrylates on poly(ethylene terephthalate) (PET) fabrics. The hydrophobicity of the PET fabric was systematically tunable by controlling the polymerization time. The obtained superhydrophobic fabrics showed excellent chemical robustness even after exposure to different chemicals, such as acid, base, salt, acetone, and toluene. Importantly, the fabrics maintained superhydrophobicity after 2500 abrasion cycles, 100 laundering cycles, and long time exposure to UV irradiation. Also, the surface of the superhydrophobic fabrics showed excellent antifouling properties.

  14. Hydrophilization of Poly(ether ether ketone) Films by Surface-initiated Atom Transfer Radical Polymerization

    DEFF Research Database (Denmark)

    Fristrup, Charlotte Juel; Eskimergen, Rüya; Burkrinsky, J.T.

    2008-01-01

    -modified PEEK using Surface-Initiated Atom Transfer Radical Polymerization (SI ATRP). Surface reduction of PEEK to form hydroxyl groups [1, 2, 3] was .performed prior to the attachment of 2-bromoisobutyrate initiating groups. Each modification step of PEEK as well as the polymer grafting was followed...... and confirmed by ATR FTIR, water contact ang;le, and Thermal Gravimetric Analysis (TGA). The surface topography was evaluated by "Atomic Force Microscopy (AFM). X-ray Photoelectron Spectroscopy (XPS) has been used to investigate the degree of functionalization. The performed modification allowed for successful...

  15. Surface-Initiated Atom Transfer Radical Polymerization from Electrospun Mats: An Alternative to Nafion

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Dimitrov, Ivaylo; Tynelius, Oskar

    2017-01-01

    Proton exchange membranes for fuel cell applications are synthesized by surface-initiated(SI) atom transfer radical polymerization (ATRP). Poly(vinylidene fluoride-co-chlorotrifluoroethylene)is electrospun into 50 μm thick mat, which is then employed as multifunctionalinitiator for copper......-mediated SI ATRP of 4-styrene sulfonic acid sodium salt. Fine-tuning ofthe ATRP conditions allows adjustment of the membrane’sion exchange capacity by varying the loading of the graftedionomer. Structure and composition of the membranes areinvestigated by spectroscopic means and thermogravimetricanalysis...

  16. Design of UV-absorbing PVDF membrane via surface-initiated AGET ATRP

    Science.gov (United States)

    Dong, Li; Liu, Xiangdong; Xiong, Zhengrong; Sheng, Dekun; Zhou, Yan; Lin, Changhong; Yang, Yuming

    2018-03-01

    Herein, PVDF membranes with excellent UV-absorbing property were first synthesized through grafting the polymerizable low-molecular-weight organic UV-absorber 2-hydroxy-4-(3-methacryloxy-2-hydroxylpropoxy) benzophenone (BPMA) onto α-bromoester-functionalized PVDF membranes via the surface-initiated activator generated by electron transfer atom transfer radical polymerization (SI-AGET ATRP). The surface initiators were immobilized by the reaction between 2-bromoisobutyryl bromide (BIBB) and the hydroxylated PVDF membranes. PVDF-g-PBPMA membranes with different grafting densities were obtained by tuning the polymerization time and the modified membranes were characterized by 1H-NMR, FT-IR, XPS, SEM, UV-vis Spectrophotometer, TGA and DSC. The experimental results indicated that PBPMA chains were successfully introduced onto PVDF membranes. Most importantly, the PVDF-g-PBPMA membranes exhibited outstanding UV-shielding property. UV-vis transmittance spectra showed that most UV light below 360 nm could be absorbed by PVDF-g-PBPMA membranes and the whole UV light region (200-400 nm) can be blocked with the reaction time increased.

  17. Enhanced protein retention on poly(caprolactone) via surface initiated polymerization of acrylamide

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yuhao; Cai, Mengtan; He, Liu [College of Polymer Science and Engineering, Sichuan University, Chengdu 610065 (China); Luo, Xianglin, E-mail: luoxl@scu.edu.cn [College of Polymer Science and Engineering, Sichuan University, Chengdu 610065 (China); State Key Laboratory of Polymer Material and Engineering, Sichuan University, Chengdu 610065 (China)

    2016-01-01

    Graphical abstract: - Highlights: • Dense package of poly(acrylamide) on poly(caprolactone) surface was achieved by surface-initiated atom transfer radical polymerization. • Poly(acrylamide) grafted surface exhibited high protein retention ability. • Loaded protein was resistant to detachment and maintained its structure without denaturation. - Abstract: To enhance the biocompatibility or extend the biomedical application of poly(caprolactone) (PCL), protein retention on PCL surface is often required. In this study, poly(acrylamide) (PAAm) brushes were grown from PCL surface via surface-initiated atom transfer radical polymerization (SI-ATRP) and served as a protein-capturing platform. Grafted PAAm was densely packed on surface and exhibited superior protein retention ability. Captured protein was found to be resistant to washing under detergent environment. Furthermore, protein structure after being captured was investigated by circular dichroism (CD) spectroscopy, and the CD spectra verified that secondary structure of captured proteins was maintained, indicating no denaturation of protein happened for retention process.

  18. WRF Simulation over the Eastern Africa by use of Land Surface Initialization

    Science.gov (United States)

    Sakwa, V. N.; Case, J.; Limaye, A. S.; Zavodsky, B.; Kabuchanga, E. S.; Mungai, J.

    2014-12-01

    The East Africa region experiences severe weather events associated with hazards of varying magnitude. It receives heavy precipitation which leads to wide spread flooding and lack of sufficient rainfall in some parts results into drought. Cases of flooding and drought are two key forecasting challenges for the Kenya Meteorological Service (KMS). The source of heat and moisture depends on the state of the land surface which interacts with the boundary layer of the atmosphere to produce excessive precipitation or lack of it that leads to severe drought. The development and evolution of precipitation systems are affected by heat and moisture fluxes from the land surface within weakly-sheared environments, such as in the tropics and sub-tropics. These heat and moisture fluxes during the day can be strongly influenced by land cover, vegetation, and soil moisture content. Therefore, it is important to represent the land surface state as accurately as possible in numerical weather prediction models. Improved modeling capabilities within the region have the potential to enhance forecast guidance in support of daily operations and high-impact weather over East Africa. KMS currently runs a configuration of the Weather Research and Forecasting (WRF) model in real time to support its daily forecasting operations, invoking the Non-hydrostatic Mesoscale Model (NMM) dynamical core. They make use of the National Oceanic and Atmospheric Administration / National Weather Service Science and Training Resource Center's Environmental Modeling System (EMS) to manage and produce the WRF-NMM model runs on a 7-km regional grid over Eastern Africa.SPoRT and SERVIR provide land surface initialization datasets and model verification tool. The NASA Land Information System (LIS) provide real-time, daily soil initialization data in place of interpolated Global Forecast System soil moisture and temperature data. Model verification is done using the Model Evaluation Tools (MET) package, in order

  19. Surface modification of hydroxyapatite with poly(methyl methacrylate) via surface-initiated ATRP

    International Nuclear Information System (INIS)

    Wang Yan; Zhang Xi; Yan Jinliang; Xiao Yan; Lang Meidong

    2011-01-01

    This article describes the fabrication of hydroxyapatite (HAP) nanocomposites grafted with poly(methyl methacrylate) (PMMA). Surface-initiated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was carried out from hydroxyapatite particles derivatized with ATRP initiators. The structure and properties of the nanocomposites were investigated by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), differential scanning calorimeter (DSC) measurements, and contact angle analyses. TGA was used to estimate the grafting density of ATRP initiators (0.49 initiator/nm 2 ) and the amount of grafted PMMA on the HAP surface. The contact angle analyses indicated that grafting PMMA onto the HAP surface dramatically increased the hydrophobicity of the surface. Moreover, the HAP nanocomposites showed excellent dispersibility in both aqueous solution and organic solvent.

  20. Intelligent dual-responsive cellulose surfaces via surface-initiated ATRP.

    Science.gov (United States)

    Lindqvist, Josefina; Nyström, Daniel; Ostmark, Emma; Antoni, Per; Carlmark, Anna; Johansson, Mats; Hult, Anders; Malmström, Eva

    2008-08-01

    Novel thermo-responsive cellulose (filter paper) surfaces of N-isopropylacrylamide (NIPAAm) and pH-responsive cellulose surfaces of 4-vinylpyridine (4VP) have been achieved via surface-initiated ATRP. Dual-responsive (pH and temperature) cellulose surfaces were also obtained through the synthesis of block-copolymer brushes of PNIPAAm and P4VP. With changes in pH and temperature, these "intelligent" surfaces showed a reversible response to both individual triggers, as indicated by the changes in wettability from highly hydrophilic to highly hydrophobic observed by water contact angle measurements. Adjusting the composition of the grafted block-copolymer brushes allowed for further tuning of the wettability of these "intelligent" cellulose surfaces.

  1. Surface-initiated polymerization from barium titanate nanoparticles for hybrid dielectric capacitors.

    Science.gov (United States)

    Paniagua, Sergio A; Kim, Yunsang; Henry, Katherine; Kumar, Ritesh; Perry, Joseph W; Marder, Seth R

    2014-03-12

    A phosphonic acid is used as a surface initiator for the growth of polystyrene and polymethylmethacrylate (PMMA) from barium titanate (BTO) nanoparticles through atom transfer radical polymerization with activators regenerated by electron transfer. This results in the barium titanate cores embedded in the grafted polymer. The one-component system, PMMA-grafted-BTO, achieves a maximum extractable energy density of 2 J/cm(3) at a field strength of ∼220 V/μm, which exhibits a 2-fold increase compared to that of the composite without covalent attachment or the neat polymer. Such materials have potential applications in hybrid capacitors due to the high permittivity of the nanoparticles and the high breakdown strength, mechanical flexibility, and ease of processability due to the organic polymer. The synthesis, processing, characterization, and testing of the materials in capacitors are discussed.

  2. Hydrophilization of poly(ether ether ketone) films by surface-initiated atom transfer radical polymerization

    DEFF Research Database (Denmark)

    Fristrup, Charlotte Juel; Jankova Atanasova, Katja; Hvilsted, Søren

    2010-01-01

    Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) has been exploited to hydrophilize PEEK. The ketone groups on the PEEK surface were reduced to hydroxyl groups which were converted to bromoisobutyrate initiating sites for SI-ATRP. The modification steps were followed by contact...... angle measurements and XPS. Moreover, ATR FTIR has been used to confirm the formation of initiating groups. Grafting of PEGMA from PEEK was performed in aqueous solution. The presence of the PPEGMA grafts on PEEK was revealed by the thermograms from TGA whereas investigations with AFM rejected changes...... in the surface topography. Two possible applications arose from the hydrophilization of PEEK, metal deposition and protein repellency. The performed modification allowed for successful electroless deposition and good adhesion of nickel as well as copper....

  3. Surface modification of hydroxyapatite with poly(methyl methacrylate) via surface-initiated ATRP

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yan; Zhang Xi; Yan Jinliang; Xiao Yan [Shanghai Key Laboratory of Advanced Polymeric Materials, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China); Lang Meidong, E-mail: mdlang@ecust.edu.cn [Shanghai Key Laboratory of Advanced Polymeric Materials, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China)

    2011-05-01

    This article describes the fabrication of hydroxyapatite (HAP) nanocomposites grafted with poly(methyl methacrylate) (PMMA). Surface-initiated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was carried out from hydroxyapatite particles derivatized with ATRP initiators. The structure and properties of the nanocomposites were investigated by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), differential scanning calorimeter (DSC) measurements, and contact angle analyses. TGA was used to estimate the grafting density of ATRP initiators (0.49 initiator/nm{sup 2}) and the amount of grafted PMMA on the HAP surface. The contact angle analyses indicated that grafting PMMA onto the HAP surface dramatically increased the hydrophobicity of the surface. Moreover, the HAP nanocomposites showed excellent dispersibility in both aqueous solution and organic solvent.

  4. Nitroxide polymer brushes prepared by surface-initiated ARGET ATRP and their selective oxidation performances

    Directory of Open Access Journals (Sweden)

    S. J. Liu

    2014-11-01

    Full Text Available Polymer brushes with 2,2,6,6-tetramethyl-4-piperidyl methacrylate (TMPM units, grafted on the cross-linked polystyrene (PS microspheres, were synthesized via surface-initiated ARGET (activators regenerated by electron transfer ATRP (atom transfer radical polymerization. They were further oxidized to yield nitroxide polymer brushes containing nitroxide radical units (TEMPO. The obtained polymer brushes were characterized by Fourier transform infrared spectroscopy (FT-IR, scanning electron microscopy (SEM, transmission electron microscopy (TEM, electron spin resonance (ESR and gel permeation chromatography (GPC. The catalytic properties of nitroxide polymer brushes for selective oxidation of benzyl alcohol were investigated. The results showed that the performances were good and the yield was up to 96%. Furthermore, the block brush had similar catalyst properties to non-supported TEMPO in terms of activity and selectivity. It could be recovered by centrifugation. The unity of high catalyst property and easy recovery was achieved.

  5. Thermosensitive Nanocables Prepared by Surface-Initiated Atom Transfer Radical Polymerization

    Directory of Open Access Journals (Sweden)

    Wei Qingshan

    2008-01-01

    Full Text Available Abstract Thermosensitive nanocables consisting of Au nanowire cores and poly(N-isopropylacrylamide sheaths (denoted as Au/PNIPAAm were synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP. The formation of PNIPAAm sheath was verified by Fourier transform infrared (FTIR and hydrogen nuclear magnetic resonance (1H NMR spectroscopy. Transmission electron microscope (TEM results confirmed the core/shell structure of nanohybrids. The thickness and density of PNIPAAm sheaths can be adjusted by controlling the amount of cross-linker during the polymerization. Signature temperature response was observed from Au/cross-linked-PNIPAAm nanocables. Such smart nanocables show immense potentials as building blocks for novel thermosensitive nanodevices in future.

  6. Transitioning Enhanced Land Surface Initialization and Model Verification Capabilities to the Kenya Meteorological Department (KMD)

    Science.gov (United States)

    Case, Jonathan L.; Mungai, John; Sakwa, Vincent; Zavodsky, Bradley T.; Srikishen, Jayanthi; Limaye, Ashutosh; Blankenship, Clay B.

    2016-01-01

    Flooding, severe weather, and drought are key forecasting challenges for the Kenya Meteorological Department (KMD), based in Nairobi, Kenya. Atmospheric processes leading to convection, excessive precipitation and/or prolonged drought can be strongly influenced by land cover, vegetation, and soil moisture content, especially during anomalous conditions and dry/wet seasonal transitions. It is thus important to represent accurately land surface state variables (green vegetation fraction, soil moisture, and soil temperature) in Numerical Weather Prediction (NWP) models. The NASA SERVIR and the Short-term Prediction Research and Transition (SPoRT) programs in Huntsville, AL have established a working partnership with KMD to enhance its regional modeling capabilities. SPoRT and SERVIR are providing experimental land surface initialization datasets and model verification capabilities for capacity building at KMD. To support its forecasting operations, KMD is running experimental configurations of the Weather Research and Forecasting (WRF; Skamarock et al. 2008) model on a 12-km/4-km nested regional domain over eastern Africa, incorporating the land surface datasets provided by NASA SPoRT and SERVIR. SPoRT, SERVIR, and KMD participated in two training sessions in March 2014 and June 2015 to foster the collaboration and use of unique land surface datasets and model verification capabilities. Enhanced regional modeling capabilities have the potential to improve guidance in support of daily operations and high-impact weather and climate outlooks over Eastern Africa. For enhanced land-surface initialization, the NASA Land Information System (LIS) is run over Eastern Africa at 3-km resolution, providing real-time land surface initialization data in place of interpolated global model soil moisture and temperature data available at coarser resolutions. Additionally, real-time green vegetation fraction (GVF) composites from the Suomi-NPP VIIRS instrument is being incorporated

  7. On fatigue crack growth mechanisms of MMC: Reflection on analysis of 'multi surface initiations'

    International Nuclear Information System (INIS)

    Mkaddem, A.; El Mansori, M.

    2009-01-01

    This work attempts to examine the mechanisms of fatigue when cracks synergetically initiate in more than one site at the specimen surface. The metal matrix composites (MMC) i.e. silicon carbide particles reinforced aluminium matrix composites (Al/SiC p -MMC), seem to be good candidates to accelerate fatigue failures following multi surface initiations (MSI). Closure effects of MSI mechanisms on the variation of fatigue behaviour are explored for various stress states. Experiments were carried out using non pre-treated and pre-treated specimens. Using an Equivalent Ellipse Method (EEM), it is shown that the aspect of surface finish of specimen plays an important role on crack growth. Scanning Electron Microscope (SEM) inspections have lead to distinguishing the initiation regions from propagation regions and final separation regions. It is also revealed that the total lifetime of specimens is sensitive to heat treatment. Moreover, it is found that the appearance of MSI in cycled materials is more probable at high level of fatigue loads.

  8. PNIPAAm-grafted thermoresponsive microcarriers: Surface-initiated ATRP synthesis and characterization

    International Nuclear Information System (INIS)

    Çakmak, Soner; Çakmak, Anıl S.; Gümüşderelioğlu, Menemşe

    2013-01-01

    In this study, we developed novel thermoresponsive microcarriers as a powerful tool for cell culture and tissue engineering applications. For this purpose, two types of commercially available spherical microparticles (approximately 100 μm in diameter), dextran-based Sephadex® and vinyl acetate-based VA-OH (Biosynth®), were used and themoresponsive poly(N-isopropylacrylamide) (PNIPAAm) was grafted to the beads' surfaces by surface-initiated atom transfer radical polymerization (SI-ATRP). Initially, hydroxyl groups of microbeads were reacted with 2-bromopropionyl bromide to form ATRP macroinitiator. Then, NIPAAm was successfully polymerized from the initiator attached microbeads by ATRP with CuBr/2,2′-dipyridyl, catalyst complex. Furthermore, grafted and ungrafted microbeads were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscope (SEM), atomic force microscopy (AFM) and electron spectroscopy for chemical analysis (ESCA). The results of characterization studies confirmed that PNIPAAm was successfully grafted onto both dextran and vinyl acetate-based beads by means of ATRP reaction and thus, grafted microbeads gained thermoresponsive characteristics which will be evaluated for cell harvesting in further studies. Highlights: • PNIPAAm was grafted to the hydroxyl group carrying polymer beads by SI-ATRP. • Dex-g-PNIPAAm and VA-OH-g-PNIPAAm beads exhibited thermoresponsive characteristics. • They are appropriate candidates for microcarrier-facilitated cell cultures

  9. Biomimetic PEGylation of carbon nanotubes through surface-initiated RAFT polymerization.

    Science.gov (United States)

    Shi, Yingge; Zeng, Guanjian; Xu, Dazhuang; Liu, Meiying; Wang, Ke; Li, Zhen; Fu, Lihua; Zhang, Qingsong; Zhang, Xiaoyong; Wei, Yen

    2017-11-01

    Carbon nanotubes (CNTs) are a type of one-dimensional carbon nanomaterials that possess excellent physicochemical properties and have been potentially utilized for a variety of applications. Surface modification of CNTs with polymers is a general route to expand and improve the performance of CNTs and has attracted great research interest over the past few decades. Although many methods have been developed previously, most of these methods still showed some disadvantages, such as low efficiency, complex experimental procedure and harsh reaction conditions etc. In this work, we reported a practical and novel way to fabricate CNTs based polymer composites via the combination of mussel inspired chemistry and reversible addition fragmentation chain transfer (RAFT) polymerization. First, the amino group was introduced onto the surface of CNTs via self-polymerization of dopamine. Then, chain transfer agent can be immobilized on the amino groups functionalized CNTs to obtain CNT-PDA-CTA, which can be utilized for surface-initiated RAFT polymerization. A water soluble and biocompatible monomer poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) was adopted to fabricate pPEGMA functionalized CNTs through RAFT polymerization. The successful preparation of CNTs based polymer composites (CNT-pPEGMA) was confirmed by transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy in details. The CNT-pPEGMA showed good dispersibility and desirable biocompatibility, making them highly potential for biomedical applications. More importantly, a large number of CNTs based polymer composites could also be fabricated through the same strategy when different monomers were used due to the good monomer adaptability of RAFT polymerization. Therefore, this strategy should be a general method for preparation of various multifunctional CNTs based polymer composites. Copyright © 2017 Elsevier B.V. All rights

  10. Parameters Studies on Surface Initiated Rolling Contact Fatigue of Turnout Rails by Three-Level Unreplicated Saturated Factorial Design

    Directory of Open Access Journals (Sweden)

    Xiaochuan Ma

    2018-03-01

    Full Text Available Surface initiated rolling contact fatigue (RCF, mainly characterized by cracks and material stripping, is a common type of damage to turnout rails, which can not only shorten service life of turnout but also lead to poor running safety of vehicle. The rail surface initiated RCF of turnouts is caused by a long-term accumulation, the size and distribution of which are related to the dynamic parameters of the complicated vehicle-turnout system. In order to simulate the accumulation of rail damage, some random samples of dynamic parameters significantly influencing it should be input. Based on the three-level unreplicated saturated factorial design, according to the evaluation methods of H, P and B statistic values, six dynamic parameters that influence the rail surface initiated RCF in turnouts, namely running speed of vehicle, axle load, wheel-rail profiles, integral vertical track stiffness and wheel-rail friction coefficient, are obtained by selecting 13 dynamic parameters significantly influencing the dynamic vehicle-turnout interaction as the analysis factors, considering four dynamic response results, i.e., the normal wheel-rail contact force, longitudinal creep force, lateral creep force and wheel-rail contact patch area as the observed parameters. In addition, the rail surface initiated RCF behavior in turnouts under different wheel-rail creep conditions is analyzed, considering the relative motion of stock/switch rails. The results show that the rail surface initiated RCF is mainly caused by the tangential stress being high under small creep conditions, the normal and tangential stresses being high under large creep conditions, and the normal stress being high under pure spin creep conditions.

  11. Surface-Initiated Graft Atom Transfer Radical Polymerization of Methyl Methacrylate from Chitin Nanofiber Macroinitiator under Dispersion Conditions

    Directory of Open Access Journals (Sweden)

    Ryo Endo

    2015-08-01

    Full Text Available Surface-initiated graft atom transfer radical polymerization (ATRP of methyl methacrylate (MMA from self-assembled chitin nanofibers (CNFs was performed under dispersion conditions. Self-assembled CNFs were initially prepared by regeneration from a chitin ion gel with 1-allyl-3-methylimidazolium bromide using methanol; the product was then converted into the chitin nanofiber macroinitiator by reaction with α-bromoisobutyryl bromide in a dispersion containing N,N-dimethylformamide. Surface-initiated graft ATRP of MMA from the initiating sites on the CNFs was subsequently carried out under dispersion conditions, followed by filtration to obtain the CNF-graft-polyMMA film. Analysis of the product confirmed the occurrence of the graft ATRP on the surface of the CNFs.

  12. Coating and dispersion of ceramic nanoparticles by UV-ozone etching assisted surface-initiated living radical polymerization.

    Science.gov (United States)

    Arita, Toshihiko

    2010-10-01

    Commercially available unmodified ceramic nanoparticles (NPs) in dry powder state were surface-modified and dispersed in almost single-crystal size. The surface-initiated living radical polymerization after just UV-ozone soft etching enables one to graft polymers onto the surface of ceramic NPs and disperse them in solvents. Furthermore, a number of NPs were dispersed with single-crystal sizes. The technique developed here could be applied to almost all ceramic NPs including metal nitrides.

  13. Fabrication of luminescent hydroxyapatite nanorods through surface-initiated RAFT polymerization: Characterization, biological imaging and drug delivery applications

    Energy Technology Data Exchange (ETDEWEB)

    Heng, Chunning [Shaanxi Key Laboratory of Degradable Biomedical Materials, Shaanxi R& D Center of Biomaterials and Fermentation Engineering, School of Chemical and Engineering, Northwest University, Xi’an, 710069 (China); Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Zheng, Xiaoyan [Shaanxi Key Laboratory of Degradable Biomedical Materials, Shaanxi R& D Center of Biomaterials and Fermentation Engineering, School of Chemical and Engineering, Northwest University, Xi’an, 710069 (China); Liu, Meiying; Xu, Dazhuang; Huang, Hongye; Deng, Fengjie [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Hui, Junfeng, E-mail: huijunfeng@126.com [Shaanxi Key Laboratory of Degradable Biomedical Materials, Shaanxi R& D Center of Biomaterials and Fermentation Engineering, School of Chemical and Engineering, Northwest University, Xi’an, 710069 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wei, Yen, E-mail: weiyen@tsinghua.edu.cn [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing, 100084 (China)

    2016-11-15

    Highlights: • Hydrophobic hydroxyapatite nanorods were obtained from hydrothermal synthesis. • Surface initiated RAFT polymerization was adopted to surface modification of hydroxyapatite nanorods. • These modified hydroxyapatite nanorods showed high water dispersibility and biocompatibility. • These modified hydroxyapatite nanorods can be used for controlled drug delivery. - Abstract: Hydroxyapatite nanomaterials as an important class of nanomaterials, have been widely applied for different biomedical applications for their excellent biocompatibility, biodegradation potential and low cost. In this work, hydroxyapatite nanorods with uniform size and morphology were prepared through hydrothermal synthesis. The surfaces of these hydroxyapatite nanorods are covered with hydrophobic oleic acid, making them poor dispersibility in aqueous solution and difficult for biomedical applications. To overcome this issue, a simple surface initiated polymerization strategy has been developed via combination of the surface ligand exchange and reversible addition fragmentation chain transfer (RAFT) polymerization. Hydroxyapatite nanorods were first modified with Riboflavin-5-phosphate sodium (RPSSD) via ligand exchange reaction between the phosphate group of RPSSD and oleic acid. Then hydroxyl group of nHAp-RPSSD was used to immobilize chain transfer agent, which was used as the initiator for surface-initiated RAFT polymerization. The nHAp-RPSSD-poly(IA-PEGMA) nanocomposites were characterized by means of {sup 1}H nuclear magnetic resonance, Fourier transform infrared spectroscopy, fluorescence spectroscopy and thermal gravimetric analysis in detailed. The biocompatibility, biological imaging and drug delivery of nHAp-RPSSD-poly(IA-PEGMA) were also investigated. Results showed that nHAp-RPSSD-poly(IA-PEGMA) exhibited excellent water dispersibility, desirable optical properties, good biocompatibility and high drug loading capability, making them promising candidates for

  14. Preparation and controlled drug delivery applications of mesoporous silica polymer nanocomposites through the visible light induced surface-initiated ATRP

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Long; Liu, Meiying; Mao, Liucheng; Xu, Dazhuang; Wan, Qing; Zeng, Guangjian; Shi, Yingge [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wen, Yuanqing, E-mail: m18600788382@163.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wei, Yen, E-mail: weiyen@tsinghua.edu.cn [Department of Chemistry and The Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing, 100084 (China)

    2017-08-01

    Graphical abstract: A novel strategy for surface PEGylation of mesoporous silica nanoparticles was developed based on the light induced surface-initiated atom transfer radical polymerization. - Highlights: • Surface modification of silica nanoparticles through light induced surface-initiated ATRP. • MSNs-NH{sub 2}-poly(IA-co-PEGMA) nanocomposites show high water dispersity. • MSNs-NH{sub 2}-poly(IA-co-PEGMA) nanocomposites are promising for biomedical applications. • The light induced ATRP possesses many advantages as compared with traditional ATRP. - Abstract: The mesoporous materials with large pore size, high specific surface area and high thermal stability have been widely utilized in a variety of fields ranging from environmental remediation to separation and biomedicine. However, surface modification of these silica nanomaterials is required to endow novel properties and achieve better performance for most of these applications. In this work, a new method has been established for surface modification of mesoporous silica nanoparticles (MSNs) that relied on the visible light induced atom transfer radical polymerization (ATRP). In the procedure, the copolymers composited with itaconic acid (IA) and poly(ethylene glycol)methyl acrylate (PEGMA) were grafted from MSNs using IA and PEGMA as the monomers and 10-Phenylphenothiazine(PTH) as the organic catalyst. The successful preparation of final polymer nanocomposites (named as MSNs-NH{sub 2}-poly(IA-co-PEGMA)) were evidenced by a series of characterization techniques. More importantly, the anticancer agent cisplatin can be effectively loaded on MSNs-NH{sub 2}-poly(IA-co-PEGMA) and controlled release it from the drug-loading composites with pH responsive behavior. As compared with conventional ATRP, the light induced surface-initiated ATRP could also be utilized for preparation of various silica polymer nanocomposites under rather benign conditions (e.g. absent of transition metal ions, low polymerization

  15. Toward Improved Land Surface Initialization in Support of Regional WRF Forecasts at the Kenya Meteorological Service (KMS)

    Science.gov (United States)

    Case, Jonathan L.; Mungai, John; Sakwa, Vincent; Kabuchanga, Eric; Zavodsky, Bradley T.; Limaye, Ashutosh S.

    2014-01-01

    SPoRT/SERVIR/RCMRD/KMS Collaboration: Builds off strengths of each organization. SPoRT: Transition of satellite, modeling and verification capabilities; SERVIR-Africa/RCMRD: International capacity-building expertise; KMS: Operational organization with regional weather forecasting expertise in East Africa. Hypothesis: Improved land-surface initialization over Eastern Africa can lead to better temperature, moisture, and ultimately precipitation forecasts in NWP models. KMS currently initializes Weather Research and Forecasting (WRF) model with NCEP/Global Forecast System (GFS) model 0.5-deg initial / boundary condition data. LIS will provide much higher-resolution land-surface data at a scale more representative to regional WRF configuration. Future implementation of real-time NESDIS/VIIRS vegetation fraction to further improve land surface representativeness.

  16. Visible Light-Induced Metal Free Surface Initiated Atom Transfer Radical Polymerization of Methyl Methacrylate on SBA-15

    Directory of Open Access Journals (Sweden)

    Liang Ma

    2017-02-01

    Full Text Available Surface-initiated atom transfer radical polymerization (SI-ATRP is one of the most versatile techniques to modify the surface properties of materials. Recent developed metal-free SI-ATRP makes such techniques more widely applicable. Herein photo-induced metal-free SI-ATRP of methacrylates, such as methyl methacrylate, N-isopropanyl acrylamide, and N,N-dimethylaminoethyl methacrylate, on the surface of SBA-15 was reported to fabricate organic-inorganic hybrid materials. A SBA-15-based polymeric composite with an adjustable graft ratio was obtained. The structure evolution during the SI-ATRP modification of SBA-15 was monitored and verified by FT-IR, XPS, TGA, BET, and TEM. The obtained polymeric composite showed enhanced adsorption ability for the model compound toluene in aqueous conditions. This procedure provides a low-cost, readily available, and easy modification method to synthesize polymeric composites without the contamination of metal.

  17. Functionalization of vertically aligned carbon nanotubes with polystyrene via surface initiated reversible addition fragmentation chain transfer polymerization

    International Nuclear Information System (INIS)

    Macdonald, Thomas; Gibson, Christopher T.; Constantopoulos, Kristina; Shapter, Joseph G.; Ellis, Amanda V.

    2012-01-01

    Here we demonstrate the covalent attachment of vertically aligned (VA) acid treated single-walled carbon nanotubes (SWCNTs) onto a silicon substrate via dicyclohexylcarbodiimide (DCC) coupling chemistry. Subsequently, the pendant carboxyl moieties on the sidewalls of the VA-SWCNTs were derivatized to acyl chlorides, and then finally to bis(dithioester) moieties using a magnesium chloride dithiobenzoate salt. The bis(dithioester) moieties were then successfully shown to act as a chain transfer agent (CTA) in the reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in a surface initiated “grafting-from” process from the VA-SWCNT surface. Atomic force microscopy (AFM) verified vertical alignment of the SWCNTs and the maintenance thereof throughout the synthesis process. Finally, Raman scattering spectroscopy and AFM confirmed polystyrene functionalization.

  18. Toward Improved Land Surface Initialization in Support of Regional WRF Forecasts at the Kenya Meteorological Service (KMS)

    Science.gov (United States)

    Case, Johnathan L.; Mungai, John; Sakwa, Vincent; Kabuchanga, Eric; Zavodsky, Bradley T.; Limaye, Ashutosh S.

    2014-01-01

    Flooding and drought are two key forecasting challenges for the Kenya Meteorological Service (KMS). Atmospheric processes leading to excessive precipitation and/or prolonged drought can be quite sensitive to the state of the land surface, which interacts with the planetary boundary layer (PBL) of the atmosphere providing a source of heat and moisture. The development and evolution of precipitation systems are affected by heat and moisture fluxes from the land surface, particularly within weakly-sheared environments such as in the tropics and sub-tropics. These heat and moisture fluxes during the day can be strongly influenced by land cover, vegetation, and soil moisture content. Therefore, it is important to represent the land surface state as accurately as possible in land surface and numerical weather prediction (NWP) models. Enhanced regional modeling capabilities have the potential to improve forecast guidance in support of daily operations and high-impact weather over eastern Africa. KMS currently runs a configuration of the Weather Research and Forecasting (WRF) NWP model in real time to support its daily forecasting operations, making use of the NOAA/National Weather Service (NWS) Science and Training Resource Center's Environmental Modeling System (EMS) to manage and produce the KMS-WRF runs on a regional grid over eastern Africa. Two organizations at the NASA Marshall Space Flight Center in Huntsville, AL, SERVIR and the Shortterm Prediction Research and Transition (SPoRT) Center, have established a working partnership with KMS for enhancing its regional modeling capabilities through new datasets and tools. To accomplish this goal, SPoRT and SERVIR is providing enhanced, experimental land surface initialization datasets and model verification capabilities to KMS as part of this collaboration. To produce a land-surface initialization more consistent with the resolution of the KMS-WRF runs, the NASA Land Information System (LIS) is run at a comparable

  19. Preparation of polymeric silica composites through polydopamine-mediated surface initiated ATRP for highly efficient removal of environmental pollutants

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Qiang; Liu, Meiying; Wan, Qing; Jiang, Ruming; Mao, Liucheng; Zeng, Guangjian; Huang, Hongye; Deng, Fengjie [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wei, Yen [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing 100084 (China)

    2017-06-01

    In this study, we developed a new procedure to prepare monodispersed functionalized SiO{sub 2} (SiO{sub 2}-PDA-PDMC) composites via mussel inspired chemistry and surface initiated atom transfer radical polymerization (SI-ATRP). Samples were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA) measurements. TEM results showed that spherical morphology was unchanged after the functionalization. FT-IR results confirmed the successful modification with polydopamine (PDA) and the presence of poly-([2-(Methacryloyloxy) ethyl] trimethylammonium chloride) (PDMC) layer on the surface of SiO{sub 2} spheres. TGA data showed that the PDMC account for about 12.12 wt% in the sample of SiO{sub 2}-PDA-PDMC composites. The XPS analysis further confirmed the existence of PDMC on the surface of SiO{sub 2}-PDA-PDMC composites. The obtained SiO{sub 2}-PDA-PDMC composites were used as adsorbent for the removal of Congo red (CR) from aqueous solution to evaluate the performance in environment application. The effect of contact time, solution pH, initial CR concentration and temperature on the adsorption of CR onto SiO{sub 2}-PDA-PDMC composites was investigated. Adsorption results demonstrated that adsorption of CR onto SiO{sub 2}-PDA-PDMC composites was a fast and efficient process. The adsorption equilibrium reached within 60 min, and the adsorption process followed the pseudo-second-order model. The experimental data of isotherms were better described by the Freundlich model. Thermodynamic study depicted the endothermic nature of adsorption and the process was spontaneous. Results from the effect of solution pH on the CR adsorption showed that the acidic condition favors the adsorption and provided evidence for the contribution of PDMC on the SiO{sub 2}-PDA-PDMC composites in the removal of CR. This study suggests SiO{sub 2}-PDA-PDMC composites can be

  20. Poly(N-isopropylacrylamide) brushes grafted from cellulose nanocrystals via surface-initiated single-electron transfer living radical polymerization.

    Science.gov (United States)

    Zoppe, Justin O; Habibi, Youssef; Rojas, Orlando J; Venditti, Richard A; Johansson, Leena-Sisko; Efimenko, Kirill; Osterberg, Monika; Laine, Janne

    2010-10-11

    Cellulose nanocrystals (CNCs) or nanowhiskers produced from sulfuric acid hydrolysis of ramie fibers were used as substrates for surface chemical functionalization with thermoresponsive macromolecules. The CNCs were grafted with poly(N-isopropylacrylamide) brushes via surface-initiated single-electron transfer living radical polymerization (SI-SET-LRP) under various conditions at room temperature. The grafting process was confirmed via Fourier transform IR spectroscopy and X-ray photoelectron spectroscopy and the different molecular masses of the grafts were quantified and found to depend on the initiator and monomer concentrations used. No observable damage occurred to the CNCs after grafting, as determined by X-ray diffraction. Size exclusion chromatography analyses of polymer chains cleaved from the cellulose nanocrystals indicated that a higher degree of polymerization was achieved by increasing initiator or monomer loading, most likely caused by local heterogeneities yielding higher rates of polymerization. It is expected that suspension stability, interfacial interactions, friction, and other properties of grafted CNCs can be controlled by changes in temperature and provide a unique platform for further development of stimuli-responsive nanomaterials.

  1. Functionalization of regenerated cellulose membrane via surface initiated atom transfer radical polymerization for boron removal from aqueous solution.

    Science.gov (United States)

    Wei, Yu-Ting; Zheng, Yu-Ming; Chen, J Paul

    2011-05-17

    In this study, an adsorptive membrane was prepared for efficient boron removal. Poly(glycidyl methacrylate) was grafted on the surfaces of the regenerated cellulose (RC) membrane via surface-initiated atom transfer radical polymerization, and N-methylglucamine was used to further react with epoxide rings to introduce polyhydroxyl functional groups, which served as the major binding sites for boron. The pristine and modified membranes were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), dynamic water contact angle measurement, and scanning electron microscopy. It was shown that the designed functional groups were successfully grafted onto the RC membrane, and surface modification contributed to higher boron binding capability. The optimal pH range for boron adsorption was 4-8. Under a neutral pH condition, the maximum adsorption capacity of the modified membrane was determined to be 0.75 mmol/g, which was comparable with those of commercial resins. Studies of electrolyte influence indicated the formation of inner-sphere surface complexes on the membrane surface. The ATR-FTIR and XPS analyses showed that secondary alcohol and tertiary amine groups were mainly involved in boron adsorption, and tetrahedral boron complexes were found on the membrane surface.

  2. Optimisation of Surface-Initiated Photoiniferter-Mediated Polymerisation under Confinement, and the Formation of Block Copolymers in Mesoporous Films

    Directory of Open Access Journals (Sweden)

    Jessica C. Tom

    2017-10-01

    Full Text Available Nature as the ultimate inspiration can direct, gate, and selectively transport species across channels to fulfil a specific targeted function. Harnessing such precision over local structure and functionality at the nanoscale is expected to lead to indispensable developments in synthetic channels for application in catalysis, filtration and sensing, and in drug delivery. By combining mesoporous materials with localised charge-switchable poly(2-(dimethylaminoethyl methacrylate (PDMAEMA brushes, precisely controlling pore filling and exploring the possibility of incorporating two different responsive polymers, we hope to approach the precision control of natural systems in the absence of an external force. Here, we report a simple one-step approach to prepare a mesoporous silica thin film with ~8 nm pores functionalised with a photoiniferter by combining sol–gel chemistry and evaporation-induced self-assembly (EISA. We show that surface-initiated photoiniferter-mediated polymerisation (SI-PIMP allows the incorporation of a high polymer content up to geometrical pore blocking by the simple application of UV light in the presence of a monomer and solvent, proceeding in a controlled manner in pore sizes below 10 nm, with the potential to tune the material properties through the formation of surface-grafted block copolymers.

  3. Preparation and controlled drug delivery applications of mesoporous silica polymer nanocomposites through the visible light induced surface-initiated ATRP

    Science.gov (United States)

    Huang, Long; Liu, Meiying; Mao, Liucheng; Xu, Dazhuang; Wan, Qing; Zeng, Guangjian; Shi, Yingge; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

    2017-08-01

    The mesoporous materials with large pore size, high specific surface area and high thermal stability have been widely utilized in a variety of fields ranging from environmental remediation to separation and biomedicine. However, surface modification of these silica nanomaterials is required to endow novel properties and achieve better performance for most of these applications. In this work, a new method has been established for surface modification of mesoporous silica nanoparticles (MSNs) that relied on the visible light induced atom transfer radical polymerization (ATRP). In the procedure, the copolymers composited with itaconic acid (IA) and poly(ethylene glycol)methyl acrylate (PEGMA) were grafted from MSNs using IA and PEGMA as the monomers and 10-Phenylphenothiazine(PTH) as the organic catalyst. The successful preparation of final polymer nanocomposites (named as MSNs-NH2-poly(IA-co-PEGMA)) were evidenced by a series of characterization techniques. More importantly, the anticancer agent cisplatin can be effectively loaded on MSNs-NH2-poly(IA-co-PEGMA) and controlled release it from the drug-loading composites with pH responsive behavior. As compared with conventional ATRP, the light induced surface-initiated ATRP could also be utilized for preparation of various silica polymer nanocomposites under rather benign conditions (e.g. absent of transition metal ions, low polymerization temperature and short polymerization time). Taken together, we have developed a rather promising strategy method for fabrication of multifunctional MSNs-NH2-poly(IA-co-PEGMA) with great potential for biomedical applications.

  4. Data in support of dual-functionalized cellulose nanofibrils prepared through TEMPO-mediated oxidation and surface-initiated ATRP

    Directory of Open Access Journals (Sweden)

    Tzung-Yung Tsai

    2015-06-01

    Full Text Available We previously studied a suitably 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO-oxidized cellulose nanofibrils (TOCNs that can be further functionalized with initiating sites and overcame the obstacle of performing atom transfer radical polymerization (ATRP in the presence of neutral carboxylic acid sodium salt groups [1]. Herein, characterization of the modified TOCNs and of the products from surface-initiated (SI ATRP of the (nanocelluloses with styrene (St was performed using nuclear magnetic resonance (NMR, gel permeation chromatography (GPC, and contact angle (CA measurements. From the analysis of 1H NMR, a high purity of sacrificial initiator (i.e., 2-hydroxyethyl 2-bromoisobutyrate (HEBiB was confirmed. HEBiB was utilized to trace the SI ATRP with the generated free PSt. Gradually molecular weight evaluations were revealed from GPC analysis (ca. Mn=21,000 and Đ=1.10 using different TOCNs, implying the insignificant contribution to the kinetics from the grafted initiating sites. The TOCN-g-PSts were further characterized by contact angles and displayed an obvious reversibility between hydrophilicity and hydrophobicity in tens of minutes. These results illustrated a simple and facile approach for controlling the graft length and composition of TOCNs through SI ATRP.

  5. Hydrogel brushes grafted from stainless steel via surface-initiated atom transfer radical polymerization for marine antifouling

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jingjing, E-mail: jjwang1@hotmail.com; Wei, Jun

    2016-09-30

    Highlights: • Crosslinked hydrogel brushes were grafted from SS surfaces for marine antifouling. • All brush-coated SS surfaces could effectively reduce the adhesion of biofouling. • The antifouling efficacy increased with the crosslinking density of hydrogels. - Abstract: Crosslinked hydrogel brushes were grafted from stainless steel (SS) surfaces for marine antifouling. The brushes were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-methacryloyloxyethyl phosphorylcholine (MPC) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) respectively with different fractions of crosslinker in the feed. The grafted layers prepared with different thickness were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), ellipsometry and water contact angle measurements. With the increase in the fraction of crosslinker in the feed, the thickness of the grafted layer increased and the surface became smooth. All the brush-coated SS surfaces could effectively reduce the adhesion of bacteria and microalgae and settlement of barnacle cyprids, as compared to the pristine SS surface. The antifouling efficacy of the PEGMA polymer (PPEGMA)-grafted surface was higher than that of the MPC polymer (PMPC)-grafted surfaces. Furthermore, the crosslinked hydrogel brush-grafted surfaces exhibited better fouling resistance than the non-crosslinked polymer brush-grafted surfaces, and the antifouling efficacy increased with the crosslinking density. These hydrogel coatings of low toxicity and excellent anti-adhesive characteristics suggested their useful applications as environmentally friendly antifouling coatings.

  6. Formation of copper nanoparticles on poly(thymine) through surface-initiated enzymatic polymerization and its application for DNA detection.

    Science.gov (United States)

    Hu, Weiwen; Ning, Yong; Kong, Jinming; Zhang, Xueji

    2015-08-21

    Poly(thymine) (polyT) and double-stranded DNA (dsDNA) can act as efficient templates for the formation of copper nanoparticles (CuNPs) at a low concentration of CuSO4, and the formed CuNPs emit excellent fluorescence. In this work, we demonstrated a new and facile strategy for the highly sensitive and selective detection of DNA on streptavidin-functionalized magnetic beads (SA-MB) using DNA-templated CuNPs as the fluorescent probe. Target DNA (tDNA) was hybridized with the capture DNA that was immobilized on the surface of SA-MB. Surface initiated enzymatic polymerization (SIEP) was employed as the signal amplification method to generate the polyT at the 3' end of tDNA for the formation of CuNPs. The incorporation of polyT by SIEP resulted in ∼35.7 fold signal amplification compared to the dsDNA after hybridization without SIEP. A dose-response curve for detection of DNA was obtained, with a linear dynamic range of 0.1 nM to 10 nM. We showed that this method has a low pM limit of detection (LOD 98.2 pM) and it is also very sensitive to the mismatch type in a specific DNA sequence. In addition, it avoids rigorously controlled temperature, complex synthesis of the fluorescent probe and prelabeling of DNA strands and eliminates the use of sophisticated experimental techniques and equipment. Armed with these intriguing properties, the proposed system could provide an efficient tool for early diagnosis and risk assessment of malignancy.

  7. Protein adsorption resistance of PVP-modified polyurethane film prepared by surface-initiated atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Huihui; Qian, Bin; Zhang, Wei [Shanghai Key Laboratory of Functional Materials Chemistry and Research Center of Analysis and Test, East China University of Science and Technology, Shanghai 200237 (China); Lan, Minbo, E-mail: minbolan@ecust.edu.cn [Shanghai Key Laboratory of Functional Materials Chemistry and Research Center of Analysis and Test, East China University of Science and Technology, Shanghai 200237 (China); State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2016-02-15

    Highlights: • Antifouling PVP brushes were successfully grafted on PU films by SI-ATRP. • The effect of polymerization time on surface property and topography was studied. • Hydrophilicity and protein fouling resistance of PVP–PU films were greatly promoted. • Competitive adsorption of three proteins on PVP–PU films was evaluated. - Abstract: An anti-fouling surface of polyurethane (PU) film grafted with Poly(N-vinylpyrrolidone) (PVP) was prepared through surface-initiated atom transfer radical polymerization (SI-ATRP). And the polymerization time was investigated to obtain PU films with PVP brushes of different lengths. The surface properties and protein adsorption of modified PU films were evaluated. The results showed that the hydrophilicity of PU–PVP films were improved with the increase of polymerization time, which was not positive correlation with the surface roughness due to the brush structure. Additionally, the protein resistance performance was promoted when prolonging the polymerization time. The best antifouling PU–PVP (6.0 h) film reduced the adsoption level of bovine serum albumin (BSA), lysozyme (LYS), and brovin serum fibrinogen (BFG) by 93.4%, 68.3%, 85.6%, respectively, compared to the unmodified PU film. The competitive adsorption of three proteins indicated that LYS preferentially adsorbed on the modified PU film, while BFG had the lowest adsorption selectivity. And the amount of BFG on PU–PVP (6.0 h) film reduced greatly to 0.08 μg/cm{sup 2}, which was almost one-tenth of its adsorption from the single-protein system. Presented results suggested that both hydrophilicity and surface roughness might be the important factors in all cases of protein adsorption, and the competitive or selective adsorption might be related to the size of the proteins, especially on the non-charged films.

  8. Surface-initiated polymerization of 2-hydroxyethyl methacrylate from heterotelechelic oligoperoxide-coated .gamma.-Fe2O3 nanoparticles and their engulfment by mammalian cells

    Czech Academy of Sciences Publication Activity Database

    Horák, Daniel; Shagotova, Tetiana; Mitina, N.; Trchová, Miroslava; Boiko, N.; Babič, Michal; Stoika, R.; Kovářová, Jana; Hevus, O.; Beneš, Milan J.; Klyuchivska, O.; Holler, Petr; Zaichenko, A.

    2011-01-01

    Roč. 23, č. 10 (2011), s. 2637-2649 ISSN 0897-4756 R&D Projects: GA ČR GA203/09/1242; GA ČR GAP503/10/0664; GA AV ČR(CZ) KAN401220801 Institutional research plan: CEZ:AV0Z40500505 Keywords : 2-hydroxyethyl methacrylate * oligoperoxide * surface-initiated polymerization Subject RIV: CD - Macromolecular Chemistry Impact factor: 7.286, year: 2011

  9. Facile Preparation of Crosslinked Polymeric Nanocapsules via Combination of Surface-Initiated Atom Transfer Radical Polymerization and Ultraviolet Irradiated Crosslinking Techniques

    Directory of Open Access Journals (Sweden)

    Mu Bin

    2009-01-01

    Full Text Available Abstract A facile approach for the preparation of crosslinked polymeric nanocapsules was developed by the combination of the surface-initiated atom transfer radical polymerization and ultraviolet irradiation crosslinking techniques. The well-defined polystyrene grafted silica nanoparticles were prepared via the SI-ATRP of styrene from functionalized silica nanoparticles. Then the grafted polystyrene chains were crosslinked with ultraviolet irradiation. The cross-linked polystyrene nanocapsules with diameter of 20–50 nm were achieved after the etching of the silica nanoparticle templates with hydrofluoric acid. The strategy developed was confirmed with Fourier transform infrared, thermogravimetric analysis, and transmission electron microscopy.

  10. Surface grafting of zwitterionic polymers onto dye doped AIE-active luminescent silica nanoparticles through surface-initiated ATRP for biological imaging applications

    Science.gov (United States)

    Mao, Liucheng; Liu, Xinhua; Liu, Meiying; Huang, Long; Xu, Dazhuang; Jiang, Ruming; Huang, Qiang; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

    2017-10-01

    Aggregation-induced emission (AIE) dyes have recently been intensively explored for biological imaging applications owing to their outstanding optical feature as compared with conventional organic dyes. The AIE-active luminescent silica nanoparticles (LSNPs) are expected to combine the advantages both of silica nanoparticles and AIE-active dyes. Although the AIE-active LSNPs have been prepared previously, surface modification of these AIE-active LSNPs with functional polymers has not been reported thus far. In this work, we reported a rather facile and general strategy for preparation of polymers functionalized AIE-active LSNPs through the surface-initiated atom transfer radical polymerization (ATRP). The AIE-active LSNPs were fabricated via direct encapsulation of AIE-active dye into silica nanoparticles through a non-covalent modified Stöber method. The ATRP initiator was subsequently immobilized onto these AIE-active LSNPs through amidation reaction between 3-aminopropyl-triethoxy-silane and 2-bromoisobutyryl bromide. Finally, the zwitterionic 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) was selected as model monomer and grafted onto MSNs through ATRP. The characterization results suggested that LSNPs can be successfully modified with poly(MPC) through surface-initiated ATRP. The biological evaluation results demonstrated that the final SNPs-AIE-pMPC composites possess low cytotoxicity, desirable optical properties and great potential for biological imaging. Taken together, we demonstrated that AIE-active LSNPs can be fabricated and surface modified with functional polymers to endow novel functions and better performance for biomedical applications. More importantly, this strategy developed in this work could also be extended for fabrication of many other LSNPs polymer composites owing to the good monomer adoptability of ATRP.

  11. Surface polyPEGylation of Eu{sup 3+} doped luminescent hydroxyapatite nanorods through the combination of ligand exchange and metal free surface initiated atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Guangjian; Liu, Meiying [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Heng, Chunning [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Shaanxi Key Laboratory of Degradable Biomedical Materials, Shaanxi R& D Center of Biomaterials and Fermentation Engineering, School of Chemical and Engineering, Northwest University, Xi’an 710069 (China); Huang, Qiang; Mao, Liucheng; Huang, Hongye [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Hui, Junfeng [Shaanxi Key Laboratory of Degradable Biomedical Materials, Shaanxi R& D Center of Biomaterials and Fermentation Engineering, School of Chemical and Engineering, Northwest University, Xi’an 710069 (China); Deng, Fengjie, E-mail: fengjiedeng@aliyun.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wei, Yen, E-mail: weiyen@tsinghua.edu.cn [Department of Chemistry and The Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing 100084 (China)

    2017-03-31

    Highlights: • Surface modification of HAp nanorods through the combination of ligand exchange reaction and metal free SI-ATRP. • HAp-polyPEGMA displayed high water dispersibility, good biocompatibility and biological imaging capability. • Metal free ATRP can overcome the toxic and fluorescence quenching effects of metal catalysts of conventional ATRP. - Abstract: The Eu{sup 3+} doped luminescent hydroxyapatite (HAp) nanorods with uniform size and morphology can be synthesized by hydrothermal route. However, these HAp nanorods are coated by hydrophobic oleylamine, which makes them difficult to be dispersed in aqueous solution and impede their biomedical applications. In this work, Eu{sup 3+} doped luminescent polymers functionalized HAp nanorods were prepared through the combination of ligand exchange reaction and metal free surface initiated atom transfer radical polymerization (ATRP) method. In this procedure, the amino group functionalized HAp nanorods were first prepared by ligand exchange reaction using adenosine monophosphate (AMP) as ligand. Then the Br-containing initiators (HAp-Br) were introduced onto the surface of HAp-AMP nanorods through the amidation reaction. Finally, polymers functionalized HAp nanorods were prepared by metal free ATRP method using poly(ethylene glycol) methacrylate (PEGMA) as monomer and 10-phenylphenothiazine (PTH) as organic photocatalyst. The properties of these obtained HAp nanocomposites (HAP-polyPEGMA nanorods) were characterized by means of transmission electron microscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis in detail. The cell imaging of these HAP-polyPEGMA nanorods was examined using laser scanning confocal microscope to evaluate their biomedical applications. We demonstrated for the first time that hydrophobic luminescent HAp nanorods can be functionalized with polyPEGMA through the combination of ligand exchange reaction and metal free surface

  12. Examining the Impacts of High-Resolution Land Surface Initialization on Model Predictions of Convection in the Southeastern U.S.

    Science.gov (United States)

    Case, Jonathan L.; Kumar, Sujay V.; Santos, Pablo; Medlin, Jeffrey M.; Jedlovec, Gary J.

    2009-01-01

    One of the most challenging weather forecast problems in the southeastern U.S. is daily summertime pulse convection. During the summer, atmospheric flow and forcing are generally weak in this region; thus, convection typically initiates in response to local forcing along sea/lake breezes, and other discontinuities often related to horizontal gradients in surface heating rates. Numerical simulations of pulse convection usually have low skill, even in local predictions at high resolution, due to the inherent chaotic nature of these precipitation systems. Forecast errors can arise from assumptions within physics parameterizations, model resolution limitations, as well as uncertainties in both the initial state of the atmosphere and land surface variables such as soil moisture and temperature. For this study, it is hypothesized that high-resolution, consistent representations of surface properties such as soil moisture and temperature, ground fluxes, and vegetation are necessary to better simulate the interactions between the land surface and atmosphere, and ultimately improve predictions of local circulations and summertime pulse convection. The NASA Short-term Prediction Research and Transition (SPORT) Center has been conducting studies to examine the impacts of high-resolution land surface initialization data generated by offline simulations of the NASA Land Informatiot System (LIS) on subsequent numerical forecasts using the Weather Research and Forecasting (WRF) model (Case et al. 2008, to appear in the Journal of Hydrometeorology). Case et al. presents improvements to simulated sea breezes and surface verification statistics over Florida by initializing WRF with land surface variables from an offline LIS spin-up run, conducted on the exact WRF domain and resolution. The current project extends the previous work over Florida, focusing on selected case studies of typical pulse convection over the southeastern U.S., with an emphasis on improving local short-term WRF

  13. Poly(allyl methacrylate) functionalized hydroxyapatite nanocrystals via the combination of surface-initiated RAFT polymerization and thiol-ene protocol: a potential anticancer drug nanocarrier.

    Science.gov (United States)

    Bach, Long Giang; Islam, Md Rafiqul; Vo, Thanh-Sang; Kim, Se-Kwon; Lim, Kwon Taek

    2013-03-15

    Hydroxyapatite nanocrystals (HAP NCs) were encapsulated by poly(allyl methacrylate) (PolyAMA) employing controlled surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization of allyl methacrylate to afford HAP-PolyAMA nanohybrids. The subsequent thiol-ene coupling of nanohybrids with 2-mercaptosuccinic acid resulted HAP-Poly(AMA-COOH) possessing multicarboxyl group. The formation of the nanohybrids was confirmed by FT-IR and EDS analyses. The TGA and FE-SEM investigation were further suggested the grafting of PolyAMA onto HAP NCs. The utility of the HAP-PolyAMA nanohybrid as drug carrier was also explored. The pendant carboxyl groups on the external layers of nanohybrids were conjugated with anticancer drug cisplatin to afford HAP-Poly(AMA-COOH)/Pt complex. The formation of the complex was confirmed by FT-IR, XPS, and FE-SEM. In vitro evaluation of the synthesized complex as nanomedicine revealed its potential chemotherapeutic efficacy against cancer cell lines. Copyright © 2012 Elsevier Inc. All rights reserved.

  14. Surface modification of thermoplastic poly(vinyl alcohol)/saponite nanocomposites via surface-initiated atom transfer radical polymerization enhanced by air dielectric discharges barrier plasma treatment

    International Nuclear Information System (INIS)

    Zhen Weijun; Lu Canhui

    2012-01-01

    To improve the water resistance of thermoplastic poly(vinyl alcohol)/saponite nanocomposites (TPVA), a simple two-step method was developed for the covalent immobilization of atom transfer radical polymerization (ATRP) initiators on the TPVA surfaces enhanced by air dielectric barrier discharges (DBD) plasma treatment, and hydrophobic poly(methyl methacrylate) (PMMA) brushes were then grafted onto the surface of TPVA via surface-initiated atom transfer radical polymerization (SI-ATRP). The chemical composition, morphology and hydrophobicity of the modified TPVA surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The water resistance of the surface-functionalized PMMA was evaluated by the contact angle and water adsorption method. It was shown that air DBD plasma treatment activated the TPVA surface and accelerated the immobilization of ATRP initiator on the TPVA surface. Compared with TPVA control, TPVA modified by SI-ATRP can be grafted well-defined and covalently tethered network PMMA brushes onto the surface and the hydrophobicity of TPVA were significantly enhanced.

  15. A combination of "thiol-ene" click chemistry and surface initiated atom transfer radical polymerization: Fabrication of boronic acid functionalized magnetic graphene oxide composite for enrichment of glycoproteins.

    Science.gov (United States)

    Su, Jie; He, Xiwen; Chen, Langxing; Zhang, Yukui

    2018-04-01

    An efficient glycoproteins enrichment platform is one of vital preprocessing steps in biomarker research and in particular glycoproteomics. In this work, a well-defined boronic acid functionalized magnetic graphene oxide nanocomposite (Fe 3 O 4 -GO@PAAPBA) was synthesized for the selective enrichment of glycoproteins from complex biological samples via a novel strategy based on the "thiol-ene" click chemistry and surface initiated atom transfer radical polymerization (SI-ATRP). The initiator of ATRP was anchored to the surface of substrate through "thiol-ene" click reaction. The product Fe 3 O 4 -GO@PAAPBA was successfully synthesized in following SI-ATRP. The Fe 3 O 4 -GO@PAAPBA nanocomposite was characterized by transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM) and thermogravimetric analysis. The adsorption capacity of Fe 3 O 4 -GO@PAAPBA towards ovalbumin (OVA) and transferrin (Trf) is 471mgg -1 and 450mgg -1 , respectively. The nanocomposite also featured good selectivity to glycoproteins in the mixture of glycoproteins and non-glycoproteins at alkaline (pH 9.0) and physiological conditions (pH 7.4). Furthermore, it can be applied to extract glycoproteins directly from egg white samples. These results have indicated that Fe 3 O 4 -GO@PAAPBA was a potential affinity material in glycoprotein analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Surface-initiated ring-opening metathesis polymerization (SI-ROMP) to attach a tethered organic corona onto CdSe/ZnS core/shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Vatansever, Fatma, E-mail: vatansever.fatma@mgh.harvard.edu; Hamblin, Michael R., E-mail: hamblin@helix.mgh.harvard.edu [Massachusetts General Hospital, Wellman Center for Photomedicine (United States)

    2016-10-15

    Core–shell CdSe/ZnS quantum dots (QDs) are useful as tunable photostable fluorophores for multiple applications in industry, biology, and medicine. However, to achieve the optimum optical properties, the surface of the QDs must be passivated to remove charged sites that might bind extraneous substances and allow aggregation. Here we describe a method of growing an organic polymer corona onto the QD surface using the bottom-up approach of surface-initiated ring-opening metathesis polymerization (SI-ROMP) with Grubbs catalyst. CdSe/ZnS QDs were first coated with mercaptopropionic acid by displacing the original tri-octylphosphine oxide layer, and then reacted with 7-octenyl dimethyl chlorosilane. The resulting octenyl double bonds allowed the attachment of ruthenium alkylidene groups as a catalyst. A subsequent metathesis reaction with strained bicyclic monomers (norbornene-dicarbonyl chloride (NDC), and a mixture of NDC and norbornenylethylisobutyl-polyhedral oligomeric silsesquioxane (norbornoPOSS)) allowed the construction of tethered organic homo-polymer or co-polymer layers onto the QD. Compounds were characterized by FT-IR, 1H-NMR, X-ray photoelectron spectroscopy, differential scanning calorimetry, and transmission electron microscopy. Atomic force microscopy showed that the coated QDs were separate and non-aggregated with a range of diameter of 48–53 nm.

  17. Poly(glycidyl methacrylate) grafted CdSe quantum dots by surface-initiated atom transfer radical polymerization: Novel synthesis, characterization, properties, and cytotoxicity studies

    International Nuclear Information System (INIS)

    Bach, Long Giang; Islam, Md. Rafiqul; Lee, Doh Chang; Lim, Kwon Taek

    2013-01-01

    A novel approach for the synthesis of poly(glycidyl methacrylate) grafted CdSe quantum dot (QDs) (PGMA-g-CdSe) was developed. The PGMA-g-CdSe nanohybrids were synthesized by the surface-initiated atom transfer radical polymerization of glycidyl methacrylate from the surface of the strategic initiator, CdSe-BrIB QDs prepared by the interaction of 2-bromoisobutyryl bromide (BrIB) and CdSe-OH QDs. The structure, morphology, and optical property of the PGMA-g-CdSe nanohybrids were analyzed by FT-IR, XPS, TGA, XRD, TEM, and PL. The as-synthesized PGMA-g-CdSe nanohybrids having multi-epoxide groups were employed for the direct coupling of biotin via ring-opening reaction of the epoxide groups to afford the Biotin-f-PGMA-g-CdSe nanobioconjugate. The covalent immobilization of biotin onto PGMA-g-CdSe was confirmed by FT-IR, XPS, and EDX. Biocompatibility and imaging properties of the Biotin-f-PGMA-g-CdSe were investigated by MTT bioassay and PL analysis, respectively. The cell viability study suggested that the biocompatibility was significantly enhanced by the functionalization of CdSe QDs by biotin and PGMA.

  18. Ternary hybrid polymeric nanocomposites through grafting of polystyrene on graphene oxide-TiO{sub 2} by surface initiated atom transfer radical polymerization (SI-ATRP)

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Arvind; Bansal, Ankushi; Behera, Babita; Jain, Suman L.; Ray, Siddharth S., E-mail: ssray@iip.res.in

    2016-04-01

    A ternary hybrid of graphene oxide-titania-polystyrene (GO-TiO{sub 2}-PS) nanocomposite is developed where polystyrene composition is regulated by controlling growth of polymer chains and nanoarchitectonics is discussed. Graphene Oxide-TiO{sub 2} (GO-TiO{sub 2}) nanocomposite is prepared by in-situ hydrothermal method and the surface is anchored with α-bromoisobutyryl bromide to activate GO-TiO{sub 2} as initiator for polymerization. In-situ grafting of polystyrene through surface initiated atom transfer radical polymerization (SI- ATRP) on this Br-functionalized nano-composite initiator yields GO-TiO{sub 2}-PS ternary hybrid. Varying the monomer amount and keeping the concentration of initiator constant, polystyrene chain growth is regulated with narrow poly-dispersivity to achieve desired composition. This composite is well characterized by various analytical techniques like FTIR, XRD, DSC, SEM, TEM, and TGA. - Highlights: • Nanocomposite of ternary hybrid of GO-TiO{sub 2} with polystyrene. • PS is surface grafted on GO-TiO{sub 2}. • Polymer chain lengths are well regulated by SI-ATRP living polymerization. • Thermal stability of this hybrid is relatively high.

  19. Fabrication of an SPR Sensor Surface with Antifouling Properties for Highly Sensitive Detection of 2,4,6-Trinitrotoluene Using Surface-Initiated Atom Transfer Polymerization

    Directory of Open Access Journals (Sweden)

    Kiyoshi Toko

    2013-07-01

    Full Text Available In this study, we modified a surface plasmon resonance immunosensor chip with a polymer using surface-initiated atom transfer polymerization (SI-ATRP for the highly sensitive detection of 2,4,6-trinitrotoluene (TNT. To immobilize a TNT analogue on the polymer, mono-2-(methacryloyloxyethylsuccinate (MES, which has a carboxyl group, was used in this study. However, the anti-TNT antibody may adsorb non-specifically on the polymer surface by an electrostatic interaction because MES is negatively charged. Therefore, a mixed monomer with MES and diethylaminoethylmethacrylate (DEAEM, which has a tertiary amino group and is positively charged, was prepared to obtain electroneutrality for suppressing the nonspecific adsorption. The detection of TNT was performed by inhibition assay using the polymer surface. To ensure high sensitivity to TNT, the affinity between the surface and the antibody was optimized by controlling the density of the initiator for ATRP by mixing two types of self-assembled monolayer reagents. As a result, a limit of detection of 5.7 pg/mL (ppt for TNT was achieved using the optimized surface.

  20. Surface-Initiated Atom Transfer Radical Polymerization of Magnetite Nanoparticles with Statistical Poly(tert-butyl acrylate-poly(poly(ethylene glycol methyl ether methacrylate Copolymers

    Directory of Open Access Journals (Sweden)

    Patcharin Kanhakeaw

    2015-01-01

    Full Text Available This work presented the surface modification of magnetite nanoparticle (MNP with poly[(t-butyl acrylate-stat-(poly(ethylene glycol methyl ether methacrylate] copolymers (P[(t-BA-stat-PEGMA] via a surface-initiated “grafting from” atom transfer radical polymerization (ATRP. Loading molar ratio of t-BA to PEGMA was systematically varied (100 : 0, 75 : 25, 50 : 50, and 25 : 75, resp. such that the degree of hydrophilicity of the copolymers, affecting the particle dispersibility in water, can be fine-tuned. The reaction progress in each step of the synthesis was monitored via Fourier transform infrared spectroscopy (FTIR. The studies in the reaction kinetics indicated that PEGMA had higher reactivity than that of t-BA in the copolymerizations. Gel permeation chromatography (GPC indicated that the molecular weights of the copolymers increased with the increase of the monomer conversion. Transmission electron microscopy (TEM revealed that the particles were spherical with averaged size of 8.1 nm in diameter. Dispersibility of the particles in water was apparently improved when the copolymers were coated as compared to P(t-BA homopolymer coating. The percentages of MNP and the copolymer in the composites were determined via thermogravimetric analysis (TGA and their magnetic properties were investigated via vibrating sample magnetometry (VSM.

  1. Preparation of Mg(OH){sub 2} hybrid pigment by direct precipitation and graft onto cellulose fiber via surface-initiated atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiao, E-mail: wangxiao@dlpu.edu.cn [School of Textile and Materials Engineering, Dalian Polytechnic University, Dalian, Liaoning Province (China); Zhang, Yue; Lv, Lihua; Cui, Yongzhu; Wei, Chunyan [School of Textile and Materials Engineering, Dalian Polytechnic University, Dalian, Liaoning Province (China); Pang, Guibing [School of Mechanical Engineering and Automation, Dalian Polytechnic University, Dalian, Liaoning Province (China)

    2016-02-15

    Graphical abstract: - Highlights: • Adsorbed anionic dye molecules are conducive to preferential growth of (0 0 1) plane of Mg(OH){sub 2} crystal for Mg(OH){sub 2} pigments. • Uniform coverage of nanosized Mg(OH){sub 2} pigments on fiber surface is achieved via surface-initiated ATRP. • About 4 wt% of Mg(OH){sub 2} pigment on fiber surface shortens nearly half of burning time of cellulose. - Abstract: Mg(OH){sub 2} flame retardant hybrid pigment is synthesized through simultaneous solution precipitation and adsorption of anionic dyes (C.I. Acid Red 6). The Mg(OH){sub 2} hybrid pigment bearing vinyl groups after surface silane modification is immobilized onto the surface of bromo end-functional cellulose fiber by atom transfer radical polymerization (ATRP). The morphology and structure of Mg(OH){sub 2} pigments and cellulose fibers grafted with modified pigments are characterized. The thermal properties, flammability and color fastness of cellulose fibers grafted with modified pigments are measured. The results reveal that anionic dye molecules are adsorbed onto Mg(OH){sub 2} crystals and affect the formation of lamella-like Mg(OH){sub 2} crystals. The cellulose fiber grafted with modified Mg(OH){sub 2} hybrid pigment absorbs about four times heat more than original cellulose fiber with about 4% immobilization ratio of pigment, which shortens nearly half of afterflame time and afterglow time.

  2. An electrochemical aptasensor for detection of IFN-γ using graphene and a dual signal amplification strategy based on the exonuclease-mediated surface-initiated enzymatic polymerization.

    Science.gov (United States)

    Liu, Chang; Xiang, Guiming; Jiang, Dongneng; Liu, Linlin; Liu, Fei; Luo, Fukang; Pu, Xiaoyun

    2015-11-21

    Tuberculosis is one of the major health problems in the world. The cytokine interferon γ (IFN-γ) is associated with the disease-specific immune responses and is used as a tuberculosis diagnosis marker. In this study, a novel electrochemical aptasensor was developed for IFN-γ detection based on the exonuclease-catalyzed target recycling and the TdT-mediated cascade signal amplification. To construct the aptasensor, a previously hybridized double-stranded DNA (capture probe hybridization with a complementary IFN-γ binding aptamer) was immobilized on a gold nanoparticle-graphene (Au-Gra) nanohybrid film-modified electrode. In the presence of IFN-γ, the formation of an aptamer-IFN-γ complex leads to the liberation of the aptamer from the double-stranded DNA (dsDNA). Using exonuclease, the aptamer was selectively digested, and IFN-γ was released for the target recycling. A large amount of single-stranded capture probes formed and led to the hybridization with signal probe-labelled Au@Fe3O4. Then, the labelled signal probe sequences were catalyzed at the 3'-OH group by terminal deoxynucleotidyl transferase (TdT) to form a long single-stranded DNA structure. As a result, the electron mediator hexaammineruthenium(III) chloride ([Ru(NH3)6](3+)) electrostatically adsorbed onto DNA producing a strong electrochemical signal which can be used to quantitatively measure the IFN-γ levels. With the conducting nanomaterial Au-Gra as a substrate and the target recycling-based surface-initiated enzymatic polymerization-mediated signal amplification strategy, the proposed aptasensor displayed a broad linearity with a low detection limit of 0.003 ng mL(-1). Moreover, the resulting aptasensor exhibited good specificity, acceptable reproducibility and stability, which makes this method versatile and suitable for detecting IFN-γ and other biomolecules.

  3. Impact of Land Surface Initialization and Land-Atmosphere Coupling on the Prediction of the Indian Summer Monsoon with the CFSv2

    Directory of Open Access Journals (Sweden)

    Subhadeep Halder

    2018-01-01

    predictability and skill attributable to land initial conditions. Furthermore, incorrect representation of daily and sub-daily precipitation statistics over land also likely lead to errors in land-atmosphere coupling. Above all, the importance of accurate land surface initialization and land-atmosphere coupling in improving the Indian summer monsoon prediction on sub-seasonal to seasonal time scales is emphasized.

  4. Surface functionalized SiO2nanoparticles with cationic polymers via the combination of mussel inspired chemistry and surface initiated atom transfer radical polymerization: Characterization and enhanced removal of organic dye.

    Science.gov (United States)

    Huang, Qiang; Liu, Meiying; Mao, Liucheng; Xu, Dazhuang; Zeng, Guangjian; Huang, Hongye; Jiang, Ruming; Deng, Fengjie; Zhang, Xiaoyong; Wei, Yen

    2017-08-01

    Monodispersed SiO 2 particles functionalized with cationic polymers poly-((3-acrylamidopropyl)trimethylammonium chloride) (PAPTCl) were prepared using mussel inspired surface modification strategy and surface initiated atom transfer radical polymerization (SI-ATRP). Fourier transform infrared spectroscopy, transmission electron microscope, thermogravimetric analysis, X-ray photoelectron spectroscopy, and zeta potential were employed to characterize these SiO 2 samples. The adsorption performance of the functionalized SiO 2 (donated as SiO 2 -PDA-PAPTCl) towards anionic organic dye Congo red (CR) was investigated to evaluate their potential environmental applications. We demonstrated that the surface of SiO 2 particles can be successfully functionalized with cationic PAPTCl. The adsorption capability of as-prepared SiO 2 was found to increases from 28.70 and 106.65mg/g after surface grafted with cationic polymers. The significant enhancement in the adsorption capability of SiO 2 -PDA-PAPTCl is mainly attributed to the introduction of cationic polymers. More importantly, this strategy is expected to be promising for fabrication of many other functional polymer nanocomposites for environmental applications due to the universality of mussel inspired chemistry and well designability and good monomer adaptability of SI-ATRP. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. Surface-initiated atom-transfer radical polymerization of 3-O-methacryloyl-1,2:5,6-di- O-isopropylidene-alpha- D-glucofuranoside onto gold surface.

    Science.gov (United States)

    Yoon, Kuk Ro; Ramaraj, B; Lee, Seungho; Yu, Jong-Sung; Choi, Insung S

    2009-03-01

    A sugar-containing polymer was grown on gold surface by surface-initiated atom-transfer radical polymerization (SI-ATRP) of methacrylate monomer, 3-O-methacryloyl-1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranoside (MAIpGIc), using 1,4,8,11-tetraaza-1,4,8,11-tetramethylcyclotetradecane (Me(4)Cyclam) as ligand, 2-bromopropionyl moiety attached on the gold surface as initiator, and Copper(I) bromide as catalyst, respectively, in tetrahydrofuran (THF) medium. The resultant sugar film was characterized by polarized infrared external reflectance spectroscopy (PIERS), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), ellipsometry, and contact angle goniometry. The IR peaks characteristics of poly(3-O-methacryloyl-alpha,beta-D-glucopyranoside) (PMAGlc), broad O--H stretch at approximately 3400 cm(-1), and C==O ester stretch at approximately 1748 cm(-1) observed in PIERS spectra demonstrate the formation of PMAGlc on the gold surface. The AFM and SEM images show the polymer growth away from the gold surface without visible domain boundaries, and it further confirms the formation of sugar coating. The method described in the article would be beneficial in many areas, such as pathogen detection and biosensors, considering the biological importance of carbohydrate polymers. (c) 2008 Wiley Periodicals, Inc.

  6. Synthesis of Monodisperse Silica Particles Grafted with Concentrated Ionic Liquid-Type Polymer Brushes by Surface-Initiated Atom Transfer Radical Polymerization for Use as a Solid State Polymer Electrolyte

    Directory of Open Access Journals (Sweden)

    Takashi Morinaga

    2016-04-01

    Full Text Available A polymerizable ionic liquid, N,N-diethyl-N-(2-methacryloylethyl-N-methylammonium bis(trifluoromethylsulfonylimide (DEMM-TFSI, was polymerized via copper-mediated atom transfer radical polymerization (ATRP. The polymerization proceeded in a living manner producing well-defined poly(DEMM-TFSI of target molecular weight up to about 400 K (including a polycation and an counter anion. The accurate molecular weight as determined by a GPC analysis combined with a light scattering measurement, and the molecular weight values obtained exhibited good agreement with the theoretical values calculated from the initial molar ratio of DEMM-TFSI and the monomer conversion. Surface-initiated ATRP on the surface of monodisperse silica particles (SiPs with various diameters was successfully performed, producing SiPs grafted with well-defined poly(DEMM-TFSI with a graft density as high as 0.15 chains/nm2. Since the composite film made from the silica-particle-decorated polymer brush and ionic liquid shows a relatively high ionic conductivity, we have evaluated the relationship between the grafted brush chain length and the ionic conductivity.

  7. Impact of high resolution land surface initialization in Indian summer ...

    Indian Academy of Sciences (India)

    transpiration coupling. Most ..... T-test is performed for the EXP1 and EXP2 in this experiment, the results show that the differences in experiments are significant at 0.01 level. 3.2.2 Heat wave. Heat wave condition in June 2009 over the north.

  8. Stably Doped Conducting Polymer Nanoshells by Surface Initiated Polymerization.

    Science.gov (United States)

    Li, Junwei; Yoon, Soon Joon; Hsieh, Bao-Yu; Tai, Wanyi; O'Donnell, Matthew; Gao, Xiaohu

    2015-12-09

    Despite broad applications ranging from electronics to biomedical sensing and imaging, a long-standing problem of conducting polymers is the poor resistance to dedoping, which directly affects their signature electrical and optical properties. This problem is particularly significant for biomedical uses because of fast leaching of dopant ions in physiological environments. Here, we describe a new approach to engineer multimodal core-shell nanoparticles with a stably doped conductive polymer shell in biological environments. It was achieved by making a densely packed polymer brush rather than changing its molecular structure. Polyaniline (PANI) was used as a model compound due to its concentrated near-infrared (NIR) absorption. It was grafted onto a magnetic nanoparticle via a polydopamine intermediate layer. Remarkably, at pH 7 its conductivity is ca. 2000× higher than conventional PANI nanoshells. Similarly, its NIR absorption is enhanced by 2 orders of magnitude, ideal for photothermal imaging and therapy. Another surprising finding is its nonfouling property, even outperforming polyethylene glycol. This platform technology is also expected to open exciting opportunities in engineering stable conductive materials for electronics, imaging, and sensing.

  9. Impact of high resolution land surface initialization in Indian summer ...

    Indian Academy of Sciences (India)

    transpiration coupling. Most of the previous land surface ..... break spell during the 2009 monsoon season (EXP1: red line, EXP2: blue line) and observation: black line). (figure 4a). However, the rainfall over northeast region is less compared to the break ...

  10. Surface Initiated Polymerizations via e-ATRP in Pure Water

    NARCIS (Netherlands)

    Hosseiny, Seyed Schwan; van Rijn, Patrick

    2013-01-01

    Here we describe the combined process of surface modification with electrochemical atom transfer radical polymerization (e-ATRP) initiated from the surface of a modified gold-electrode in a pure aqueous solution without any additional supporting electrolyte. This approach allows for a very

  11. Surface Initiated Polymerizations via e-ATRP in Pure Water

    Directory of Open Access Journals (Sweden)

    Seyed Schwan Hosseiny

    2013-10-01

    Full Text Available Here we describe the combined process of surface modification with electrochemical atom transfer radical polymerization (e-ATRP initiated from the surface of a modified gold-electrode in a pure aqueous solution without any additional supporting electrolyte. This approach allows for a very controlled growth of the polymer chains leading towards a steady increase in film thickness. Electrochemical quartz crystal microbalance displayed a highly regular increase in surface confined mass only after the addition of the pre-copper catalyst which is reduced in situ and transformed into the catalyst. Even after isolation and washing of the modified electrode surface, reinitiation was achieved with retention of the controlled electrochemical ATRP reaction. This reinitiation after isolation proves the livingness of the polymerization. This approach has interesting potential for smart thin film materials and offers also the possibility of post-modification via additional electrochemical induced reactions.

  12. Comparing blends and blocks: Synthesis of partially fluorinated diblock polythiophene copolymers to investigate the thermal stability of optical and morphological properties

    Directory of Open Access Journals (Sweden)

    Pierre Boufflet

    2016-10-01

    Full Text Available The microstructure of the active blend layer has been shown to be a critically important factor in the performance of organic solar devices. Block copolymers provide a potentially interesting avenue for controlling this active layer microstructure in solar cell blends. Here we explore the impact of backbone fluorination in block copolymers of poly(3-octyl-4-fluorothiophenes and poly(3-octylthiophene (F-P3OT-b-P3OT. Two block co-polymers with varying block lengths were prepared via sequential monomer addition under Kumada catalyst transfer polymerisation (KCTP conditions. We compare the behavior of the block copolymer to that of the corresponding homopolymer blends. In both types of system, we find the fluorinated segments tend to dominate the UV–visible absorption and molecular vibrational spectral features, as well as the thermal behavior. In the block copolymer case, non-fluorinated segments appear to slightly frustrate the aggregation of the more fluorinated block. However, in situ temperature dependent Raman spectroscopy shows that the intramolecular order is more thermally stable in the block copolymer than in the corresponding blend, suggesting that such materials may be interesting for enhanced thermal stability of organic photovoltaic active layers based on similar systems.

  13. Surface-initiated phase transition in solid hydrogen under the high-pressure compression

    Science.gov (United States)

    Lei, Haile; Lin, Wei; Wang, Kai; Li, Xibo

    2018-03-01

    The large-scale molecular dynamics simulations have been performed to understand the microscopic mechanism governing the phase transition of solid hydrogen under the high-pressure compression. These results demonstrate that the face-centered-cubic-to-hexagonal close-packed phase transition is initiated first at the surfaces at a much lower pressure than in the volume and then extends gradually from the surface to volume in the solid hydrogen. The infrared spectra from the surface are revealed to exhibit a different pressure-dependent feature from those of the volume during the high-pressure compression. It is thus deduced that the weakening intramolecular H-H bonds are always accompanied by hardening surface phonons through strengthening the intermolecular H2-H2 coupling at the surfaces with respect to the counterparts in the volume at high pressures. This is just opposite to the conventional atomic crystals, in which the surface phonons are softening. The high-pressure compression has further been predicted to force the atoms or molecules to spray out of surface to degrade the pressure. These results provide a glimpse of structural properties of solid hydrogen at the early stage during the high-pressure compression.

  14. Surface-Initiated Polymerization by Means of Novel, Stable, Non-Ester-Based Radical Initiator

    Czech Academy of Sciences Publication Activity Database

    Bain, E. D.; Dawes, K.; Ozcam, A. E.; Hu, X.; Gorman, C. B.; Šrogl, Jiří; Genzer, J.

    2012-01-01

    Roč. 45, č. 9 (2012), s. 3802-3815 ISSN 0024-9297 Institutional support: RVO:61388963 Keywords : self -assembled monolayers * poly(acrylic acid) brushes * thermoresponsive polymer Subject RIV: CC - Organic Chemistry Impact factor: 5.521, year: 2012

  15. Surface-initiated Atom Transfer Radical Polymerization - a Technique to Develop Biofunctional Coatings

    DEFF Research Database (Denmark)

    Fristrup, Charlotte Juel; Jankova Atanasova, Katja; Hvilsted, Søren

    2009-01-01

    The initial formation of initiating sites for atom transfer radical polymerization (ATRP) on various polymer surfaces and numerous inorganic and metallic surfaces is elaborated. The subsequent ATRP grafting of a multitude of monomers from such surfaces to generate thin covalently linked polymer...

  16. Protein Compatible Polymer Brushes on Polymeric Substrates Prepared by Surface-Initiated Transfer Radica Polymerization

    DEFF Research Database (Denmark)

    Fristrup, Charlotte Juel; Eskimergen, Rüya; Burkrinsky, J.T.

    2008-01-01

    have been made with model systems of poly(ether ether ketone) (PEEK) films as they can easily be functionalized [1]. Moreover, the inert material polypropylene has successfully beel! activated using a photochemical method [2]. Different polymers including PEG-like matenals have been investigated...... when the PEEK films were modified. The surface roughness should either be unchanged or decreased as it 'will affect the protein adsorption [3]. 1. O. Noiset, C. Henneuse, Y.-J. Schneider, J. Marchand-Brynaert Macromolecules 30 (1997) 540-548 2. J. Huang, H. Murata, R.R. Koepsel, A.J. Russell, K...

  17. Hydrophobic modification of wood via surface-initiated ARGET ATRP of MMA

    Energy Technology Data Exchange (ETDEWEB)

    Fu Yanchun; Li Gang [Material Science and Engineering College, Northeast Forestry University, Harbin 150040 (China); Yu Haipeng, E-mail: yuhaipeng20000@yahoo.com.cn [Key laboratory of Bio-based Material Science and Technology of Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Material Science and Engineering College, Northeast Forestry University, Harbin 150040 (China); Liu Yixing, E-mail: yxl200488@sina.com [Key laboratory of Bio-based Material Science and Technology of Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Material Science and Engineering College, Northeast Forestry University, Harbin 150040 (China)

    2012-01-15

    To convert the hydrophilic surface of wood into a hydrophobic surface, the present study investigated activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) as a method of grafting methyl methacrylate (MMA) onto the wood surface. The wood treated with 2-bromoisobutyryl bromide and with the subsequently attached MMA via ARGET ATRP under different polymerization times (2 h, 4 h, 6 h, 8 h) were examined using scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. All the analyses confirmed that PMMA had been grafted onto the wood surface. Water contact angle measurement proved that the covering layer of PMMA on wood made the surface hydrophobic. Polymerization time had a positive influence on the contact angle value and higher contact angle can be produced with the prolongation of the polymerization time. When the reaction time was extended to 8 h, the contact angle of treated wood surface reached 130 Degree-Sign in the beginning, and remained at 116 Degree-Sign after 60 s. The ARGET ATRP method may raise an alteration on the wood surface modification.

  18. A Kumada Coupling Catalyst, [Ni{(Ph2P)2N(CH2)3Si(OCH3)3-P,P }Cl2], Bearing a Ligand for Direct Immobilization Onto Siliceous Mesoporous Molecular Sieves

    Czech Academy of Sciences Publication Activity Database

    Stamatopoulos, I.; Giannitsios, D.; Psycharis, V.; Raptopoulou, C. P.; Balcar, Hynek; Zukal, Arnošt; Svoboda, J.; Kyritsis, P.; Vohlídal, J.

    2015-01-01

    Roč. 2015, č. 18 (2015), s. 3038-3044 ISSN 1434-1948 R&D Projects: GA ČR GAP108/12/1143 Institutional support: RVO:61388955 Keywords : homogenous catalysis * heterogeneous catalysis * cross coupling Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.686, year: 2015

  19. Tunable Fluorescence of a Semiconducting Polythiophene Positioned on DNA Origami.

    Science.gov (United States)

    Zessin, Johanna; Fischer, Franziska; Heerwig, Andreas; Kick, Alfred; Boye, Susanne; Stamm, Manfred; Kiriy, Anton; Mertig, Michael

    2017-08-09

    A novel approach for the integration of π-conjugated polymers (CPs) into DNA-based nanostructures is presented. Using the controlled Kumada catalyst-transfer polycondensation, well-defined thiophene-based polymers with controllable molecular weight, specific end groups, and water-soluble oligoethylene glycol-based side chains were synthesized. The end groups were used for the easy but highly efficient click chemistry-based attachment of end-functionalized oligodeoxynucleotides (ODNs) with predesigned sequences. As demonstrated by surface plasmon resonance spectroscopy, the prepared block copolymers (BCPs), P3(EO) 3 T-b-ODN, comprising different ODN lengths and specific or repetitive sequences, undergo specific hybridization with complementary, thiol-functionalized ODNs immobilized on a gold surface. Furthermore, the site-specific attachment of the BCPs to DNA origami structures is studied. We demonstrate that a nanoscale object, that is, a single BCP with a single ODN handle, can be directed and bound to the DNA origami with reasonable yield, site-specificity, and high spatial density. On the basis of these results, we are able to demonstrate for the first time that optical properties of CP molecules densely immobilized on DNA origami can be locally fine-tuned by controlling the attractive π-π-stacking interactions between the CPs. In particular, we show that the fluorescence of the immobilized CP molecules can be significantly enhanced by surfactant-induced breakup of π-π-stacking interactions between the CP's backbones. Such molecular control over the emission intensity of the CPs can be valuable for the construction of sophisticated switchable nanophotonic devices and nanoscale biosensors.

  20. Surface-Initiated Atom Transfer Radical Polymerization and Electrografting Technique as a Means For Attaining Tailor-Made Polymer Coatings

    DEFF Research Database (Denmark)

    Chernyy, Sergey

    2012-01-01

    of the solution ATRP conditions and extending those conditions to the SI-ATRP. As a result, the new acetone/methyl methacrylate medium was found to be optimal for MMA polymerization both in the solution and on the surface. The reaction mixture was studied thoroughly; in addition to ex-situ techniques......Atom transfer radical polymerization initiated from a surface of various substrates (SI-ATRP) has become a progressively popular technique for obtaining thin polymer films with predetermined properties. The present work addresses the main features of SI-ATRP with respect to the controllability......, rates of polymerization, suitable monomers, reaction mixture compositions etc. An alternative potential-driven polymerization approach is discussed, although to a smaller extent. Chapter 1 provides an overview of controlled/living polymerization techniques with an accent made on ATRP. Different...

  1. Fabrication and evaluation of temperature responsive molecularly imprinted sorbents based on surface of yeast via surface-initiated AGET ATRP

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Jianming, E-mail: pjm@ujs.edu.cn; Hang, Hui; Li, Xiuxiu; Zhu, Wenjing; Meng, Minjia; Dai, Xiaohui; Dai, Jiangdong; Yan, Yongsheng

    2013-12-15

    Temperature responsive molecularly imprinted polymers (T-MIPs) were prepared based on the surface of yeast by electron transfer atom transfer radical polymerization (AGET ATRP). The as-prepared T-MIPs were charcterized by FT-IR, SEM, TGA and elemental analysis, which indicated that T-MIPs exhibited thermal stability and composed of temperature responsive imprinted layer. Then T-MIPs were evaluated as sorbents to selectively recognise and release cefalexin (CFX) molecules. The results suggested binding properties of T-MIPs were related to the testing temperature. The maximum adsorption capacity of T-MIPs at 303 K was 59.4 mg g{sup −1}, and the maximum release proportion for T-MIPs at 293 K in water for 24 h was 71.08%. The selective recognition experiments demonstrated high affinity and selectivity of T-MIPs towards CFX over competitive compounds, and the specific recognition of binding sites may be based on the distinct size, structure and functional group to the template molecules.

  2. Preparation of a polyacrylonitrile/multi-walled carbon nanotubes composite by surface-initiated atom transfer radical polymerization on a stainless steel wire for solid-phase microextraction.

    Science.gov (United States)

    Minet, Isabelle; Hevesi, Laszlo; Azenha, Manuel; Delhalle, Joseph; Mekhalif, Zineb

    2010-04-23

    We report on the fabrication and performances of a solid-phase microextraction (SPME) fiber based on a stainless steel wire coated with a covalently attached polyacrylonitrile (PAN)/multi-walled carbon nanotubes (MWCNTs) composite. This new coating is obtained by atom transfer radical polymerization (ATRP) of acrylonitrile mixed with MWCNTs. ATRP is initiated from 11-(2-bromo-2-methylpropionyloxy)-undecyl-phosphonic acid molecules grafted on the wire surface via the phosphonic acid group. The extraction performances of the fibers are assessed on different classes of compounds (polar, non-polar, aromatic, etc.) from water solutions by headspace extraction. The optimization of the parameters affecting the extraction efficiency of the target compounds was studied as well as the reproducibility and the repeatability of the fiber. The fibers sustain more than 200 extractions during which they remain chemically stable and maintain good performances (detection limits lower than 2 microg/l, repeatability, etc.). Considering their robustness together with their easy and inexpensive fabrication, these fibers could constitute promising alternatives to existing products. Copyright 2010 Elsevier B.V. All rights reserved.

  3. Synthesis of polyacrylonitrile-grafted cross-linked N-chlorosulfonamidated polystyrene via surface-initiated ARGET ATRP, and use of the resin in mercury removal after modification.

    Science.gov (United States)

    Zong, Guangxi; Chen, Hou; Qu, Rongjun; Wang, Chunhua; Ji, Naiyi

    2011-02-15

    A novel method of surface modification was developed via iron (III)-mediated atom transfer radical polymerization, with activators regenerated by electron transfer (ARGET ATRP) on the surfaces of polystyrene resin-supported N-chlorosulfonamide groups. The well-defined polyacrylonitrile (PAN) was grafted onto the surfaces of the polystyrene (PS). The graft reaction exhibited first-order kinetics with respect to the polymerization time in the low-monomer-conversion stage. The cyano group of PAN-g-PS was modified by NH(2)OH·HCl to yield amidoxime (AO) groups. The AO groups had been demonstrated to be an efficient Hg-specific sorbent, which can remove Hg(2+) from solutions. No interference arose from common metal ions, such as Pd(2+), Ag(+), and Cu(2+). Three adsorption-desorption cycles demonstrated that this resin is suitable for reuse without any considerable change in adsorption capacity. Copyright © 2010 Elsevier B.V. All rights reserved.

  4. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    The analysis revealed that the complexes possess a distorted octahedral geometry with the ligand coordinating in a uni-negative tridentate ONS fashion. The catalytic activity of complexes towards some C–C coupling reactions (viz., Kumada-Corriu, Suzuki-Miyaura and Sonogashira) has been examined. The complexes ...

  5. Nickel (II) complexes containing ONS donor ligands: Synthesis ...

    Indian Academy of Sciences (India)

    The analysis revealed that the complexes possess a distorted octahedral geometry with the ligand coordinating in a uni-negative tridentate ONS fashion. The catalytic activity of complexes towards some C–C coupling reactions (viz., Kumada-Corriu, Suzuki-Miyaura and Sonogashira) has been examined. The complexes ...

  6. Prevalence of parasitic infections of stray cats in Jammu, India

    African Journals Online (AJOL)

    ADEYEYE

    Gastrointestinal parasites of feral cats from. Christmas Island. Australian Veterinary. Journal, 86:60-63. Arai H, Fukuda Y, Hara T, Funakoshi Y, Kaneko S,. Yoshida T, Asahi H, Kumada M, Kato K &. Koyama T (1990). Prevalence of cryptosporidium infection among domestic cat in the Tokyo Metropolitan District,. Japan.

  7. Tentacle-type zwitterionic stationary phase prepared by surface-initiated graft polymerization of 3-[N,N-dimethyl-N-(methacryloyloxyethyl)-ammonium] propanesulfonate through peroxide groups tethered on porous silica.

    Science.gov (United States)

    Jiang, Wen; Irgum, Knut

    2002-09-15

    A novel stationary phase with tentacle-type zwitterionic interaction layer was synthesized by free radical graft polymerization of 3-[N,N-dimethyl-N-(methacryloyloxyethyl)ammonium]propanesulfonate (SPE) from the surface of Kromasil porous silica particles. The polymerization was initiated by thermal cleavage of tert-butylperoxy groups covalently attached to the particle surface, and the material therefore carries a tentacle-type polymeric interaction layer with 3-sulfopropylbetaine functional moieties. The composition of the surface graft was determined by elemental analysis, and the surface charge was measured using photon correlation spectroscopy. The measured zeta-potentials were close to 0 and nearly independent of pH, and the tentacle character of the interactive layers were evident from the lack of colloidal stability in the absence of salt (antipolyelectrolytic behavior) and a marked increase in column back-pressure when the concentration of perchloric acid or perchlorate salt was increased. The chromatographic properties were evaluated on columns packed with the functionalized material, and it was shown that this zwitterionic stationary phase could simultaneously and independently separate inorganic anions and cations using aqueous solutions of perchloric acid or perchlorate salts as eluents. The material was also capable of separating two acidic and three basic proteins in a single run, using gradient salt elution at constant pH.

  8. Controlled/living surface-initiated ATRP of antifouling polymer brushes from gold in PBS and blood sera as a model study for polymer modifications in complex biological media

    Czech Academy of Sciences Publication Activity Database

    Rodriguez-Emmenegger, Cesar; Hasan, E.; Pop-Georgievski, Ognen; Houska, Milan; Brynda, Eduard; Bologna Alles, A.

    2012-01-01

    Roč. 12, č. 4 (2012), s. 525-532 ISSN 1616-5187 R&D Projects: GA AV ČR KAN200670701; GA ČR GAP503/10/0664 Institutional research plan: CEZ:AV0Z40500505 Keywords : antifouling surfaces * atom-transfer radical polymerization ( ATRP ) * biocompatibility Subject RIV: EE - Microbiology, Virology Impact factor: 3.742, year: 2012

  9. Transition Metal Catalyzed Synthesis of Carboxylic Acids, Imines, and Biaryls

    DEFF Research Database (Denmark)

    Santilli, Carola; Madsen, Robert

    Dehydrogenative synthesis of carboxylic acids catalyzed by a ruthenium N- heterocycliccarbene complex. A new methodology for the synthesis of carboxylic acids from primary alcohols and hydroxide has been developed. The reaction is catalyzed by the ruthenium N-heterocycliccarbene complex [RuCl2(Ii...... to the carboxylic acids can be explained by the involvement of a competing Cannizzaro reaction. The scope of the dehydrogenation was further extended to linear and branched saturated aliphatic alcohols, although longer reaction times are necessary to ensure complete substrate conversions. The kinetic isotope effect...... the carboxylate.  Manganese catalyzed radical Kumada-type reaction between aryl halidesand aryl Grignard reagents. The reaction between aryl halides and aryl Grignard reagents catalyzed by MnCl2 has been extended to several methyl-substituted aryl iodide reagents byperforming the reaction at 120 ˚C in a microwave...

  10. Chain-growth cycloaddition polymerization via a catalytic alkyne [2 + 2 + 2] cyclotrimerization reaction and its application to one-shot spontaneous block copolymerization.

    Science.gov (United States)

    Sugiyama, Yu-ki; Kato, Rei; Sakurada, Tetsuya; Okamoto, Sentaro

    2011-06-29

    A cobalt-catalyzed alkyne [2 + 2 + 2] cycloaddition reaction has been applied to polymerizations yielding linear polymers via selective cross-cyclotrimerization of yne-diyne monomers, which occurs in a chain-growth manner. Additionally, through control of the alkyne reactivity of the two monomers, this method was efficiently applied to the spontaneous block copolymerization of their mixture. Here we present the proposed mechanism of the catalyst transfer process of this cycloaddition polymerization.

  11. Switching on elusive organometallic mechanisms with photoredox catalysis.

    Science.gov (United States)

    Terrett, Jack A; Cuthbertson, James D; Shurtleff, Valerie W; MacMillan, David W C

    2015-08-20

    Transition-metal-catalysed cross-coupling reactions have become one of the most used carbon-carbon and carbon-heteroatom bond-forming reactions in chemical synthesis. Recently, nickel catalysis has been shown to participate in a wide variety of C-C bond-forming reactions, most notably Negishi, Suzuki-Miyaura, Stille, Kumada and Hiyama couplings. Despite the tremendous advances in C-C fragment couplings, the ability to forge C-O bonds in a general fashion via nickel catalysis has been largely unsuccessful. The challenge for nickel-mediated alcohol couplings has been the mechanistic requirement for the critical C-O bond-forming step (formally known as the reductive elimination step) to occur via a Ni(III) alkoxide intermediate. Here we demonstrate that visible-light-excited photoredox catalysts can modulate the preferred oxidation states of nickel alkoxides in an operative catalytic cycle, thereby providing transient access to Ni(III) species that readily participate in reductive elimination. Using this synergistic merger of photoredox and nickel catalysis, we have developed a highly efficient and general carbon-oxygen coupling reaction using abundant alcohols and aryl bromides. More notably, we have developed a general strategy to 'switch on' important yet elusive organometallic mechanisms via oxidation state modulations using only weak light and single-electron-transfer catalysts.

  12. Enhanced Performance of Organic Thin Film Transistor Devices Using Hydroxyethyl-Terminated P3HT as the Active Layer.

    Science.gov (United States)

    Yeh, Je-Yuan; Tsiang, Raymond Chien-Chao

    2015-05-01

    Hydroxyethyl-terminated poly(3-hexylthiophene) (P3HT-OH) have been synthesized via a catalyst-transfer polycondensation using Grignard metathesis mediated by a nickel-based catalyst. This hydrophilic P3HT-OH is compared against the hydrophobic P3HT when used as an active layer on silicon dioxide (SiO2) wafer for organic thin-film-transistor (OTFT) fabrication. Hydroxyl groups at a 7.5% weight content lead to more chain regularity when polymer is bonded to SiO2 wafer surface and thus enhance the performance of OTFT Device, such as an 114.2% increase in ON/OFF ratio, an 12.4% increase in mobility, a 23.3% decrease in threshold voltage and a 30.1% decrease in surface roughness. Analysis and measurements reported in this paper have illustrated for the first time the feasibility of imparting hydrophilicity to the active layer for improving the OTFT performance.

  13. Development of heterogeneous catalysts for the conversion of levulinic acid to γ-valerolactone.

    Science.gov (United States)

    Wright, William R H; Palkovits, Regina

    2012-09-01

    γ-Valerolactone (GVL) has been identified as a potential intermediate for the production of fuels and chemicals based on renewable feedstocks. Numerous heterogeneous catalysts have been used for GVL production, alongside a range of reaction setups. This Minireview seeks to outline the development of heterogeneous catalysts for the targeted conversion of levulinic acid (LA) to GVL. Emphasis has been placed on discussing specific systems, including heterogeneous noble and base metal catalysts, transfer hydrogenation, and application of scCO₂ as reaction medium, with the aim of critically highlighting both the achievements and remaining challenges associated with this field. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Thermo-responsive and fluorescent cellulose nanocrystals grafted with polymer brushes

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Weibing [Nanjing Forestry Univ. (China); Georgia Inst. of Technology, Atlanta, GA (United States); Huang, Fang [Georgia Inst. of Technology, Atlanta, GA (United States); Pan, Shaobo [Georgia Inst. of Technology, Atlanta, GA (United States); Mu, Wei [Georgia Inst. of Technology, Atlanta, GA (United States); Meng, Xianzhi [Georgia Inst. of Technology, Atlanta, GA (United States); Yang, Haitao [Hubei Univ. of Technology, Wuhan (China); Xu, Zhaoyang [Nanjing Forestry Univ. (China); Ragauskas, Arthur J. [Georgia Inst. of Technology, Atlanta, GA (United States); Deng, Yulin [Georgia Inst. of Technology, Atlanta, GA (United States)

    2014-11-24

    Fluorescent and thermo-responsive cellulose nanocrystals (CNCs) with tuned polymer brushes were preparedviasurface initiated activators generated by electron transfer for atom transfer radical polymerization.

  15. [Humus composition of petroleum hydrocarbon-contaminated soil].

    Science.gov (United States)

    Feng, Jun; Tang, Li-Na; Zhang, Jin-Jing; Dou, Sen

    2008-05-01

    An abandoned petroleum well which had been exploited for about twenty years in Songyuan city of Jilin Province, China, was selected to study the compositions and characteristics of soil humus using revised humus composition method and Simon-Kumada method. Soil samples were collected at 0.5, 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5 and 10.5 m apart from the well head. Results show that the petroleum contents increase from 0.08 g/kg (10.5 m to the well head) to 153.3 g/kg (0.5 m to the well head). With the increase in petroleum content, the contents of soil organic carbon and water soluble organic carbon increase; for total soil humus, the contents of extractable humus (HE) and humic acid (HA) decrease whereas that of humin (HM) increase; the percentage of HA/HE (PQ 72.0%-8.05%) decrease and HM/HE ratio (31.4-76.7) increase; for different combined humus, the contents of loosely combined humus (HI) and stably combined humus (HII) have a decrease tendency while that of tightly combined humus (HIII) increase; the HI/HII ratio (0.19-0.39) shows an increase tendency, whereas HI/HIII ratio (0.032-0.003) and HII/HIII ratio (0.096-0.009) decrease; the PQs of HI (3.21%-1.42%) and HIII (58.1%-35.5%) also decrease, and the range of PQ change is less in HI than in HII; the color coefficient (deltalogk) of water soluble organic matter (WSOM) decreases, whereas no obvious change for HA. The above results indicate that petroleum hydrocarbon promotes the formation of HM but not HA. The decrease in HA is mainly due to the restraining effect of petroleum hydrocarbon on the formation of stably combined HA. Petroleum hydrocarbon leads molecular structure of WSOM more complex but no effect on molecular structure of HA.

  16. Virologic breakthrough in a patient with chronic hepatitis B by combination treatment with tenofovir disoproxil fumarate and entecavir

    Directory of Open Access Journals (Sweden)

    Suzuki F

    2014-06-01

    Full Text Available Fumitaka Suzuki,1,2 Hitomi Sezaki,1 Norio Akuta,1 Yoshiyuki Suzuki,1 Yusuke Kawamura,1 Tetsuya Hosaka,1 Masahiro Kobayashi,1 Satoshi Saitoh,1 Yasuji Arase,1 Kenji Ikeda,1 Mariko Kobayashi,3 Sachiyo Watahiki,3 Rie Mineta,3 Yukiko Suzuki,3 Hiromitsu Kumada1 1Department of Hepatology, Toranomon Hospital, Tokyo, Japan; 2Okinaka Memorial Institute for Medical Research, Tokyo, Japan; 3Research Institute for Hepatology, Toranomon Branch Hospital, Kawasaki, Japan Abstract: Tenofovir disoproxil fumarate (TDF is widely used to treat hepatitis B virus (HBV patients in the USA and Europe. No confirmed report of resistance selection during treatment with TDF in treatment-naïve and nucleoside/nucleotide analog-treated chronic hepatitis B patients has yet been reported. Here, we report for the first time a patient with chronic hepatitis B and cirrhosis who emerged with virologic breakthrough during combination therapy with TDF and entecavir (ETV, against ETV-resistant virus. A 51-year-old Japanese woman with hepatitis B e-antigen (HBeAg, whose genotype was C, received ETV monotherapy continuously followed by TDF and ETV combination therapy, because her HBV DNA levels had been >3.5 log copies/mL. At the start of combination therapy, amino acid substitutions of the reverse transcriptase (rt gene, rtL180M, rtT184I/M, and rtM204V, were detected. After this, serum HBV DNA decreased to less than 2.1 log copies/mL and remained at this level until 31 months of combination therapy, when it again began to increase. Amino acid substitutions of rtL180M, rtS202G, and rtM204V emerged and were associated with an increase in serum HBV DNA at virologic breakthrough. Long-term therapy with TDF against the ETV-resistant virus has the potential to induce virologic breakthrough and resistance, and careful follow-up should be carried out. Keywords: hepatitis B virus, resistant

  17. Micro-Spectroscopy as a Tool for Detecting Micron-Scale Mineral Variations Across a Rock Surface: An Example Using a Thin Section of Martian Meteorite ALH 84001

    Science.gov (United States)

    Dalton, J. Brad; Bishop, Janice L.

    2003-01-01

    Imaging spectroscopy is a powerful tool for mineral detection across broad spatial regions. A prototype micro-imaging spectrometer at NASA Ames is tested in this study on a scale of tens to hundreds of microns across rock surfaces. Initial measurements were performed in the visible spectral region on a thin section of martian meteorite ALH 84001.

  18. Polymer–clay nanocomposites via chemical grafting of ...

    Indian Academy of Sciences (India)

    mer matrices could lead to enhanced thermal stability (Phang et al 2005; Zhao and Wang 2006; Jin and Chang ... thus the resulting copolymers may be used as plastic resins, fibres or rubbers. It is the most common ... from clay nanoparticles via high-dose gamma-ray irradiation. (Wang et al 2007), surface-initiated redox ...

  19. Buried, Covalently Attached RGD Peptide Motifs in Poly(methacryllic) Brush Layers; The Effect of Brush Structure on Cell Adhesion

    NARCIS (Netherlands)

    Navarro, Melba; Benetti, Edmondo Maria; Zapotoczny, S.J.; Planell, Josep A.; Vancso, Gyula J.

    2008-01-01

    Iniferter-mediated surface-initiated photopolymerization was used to graft poly(methacrylic acid) (PMAA) brush layers obtained from surface-attached iniferters in self-assembled monolayers to a gold surface. The tethered chains were subsequently functionalized with the cell-adhesive

  20. INVESTIGATION OF THE SOLVENT FREE ISOMERISATION OF cis ...

    African Journals Online (AJOL)

    Preferred Customer

    diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and the results showed that the reaction was first order. A thermomicroscopic investigation of cis-Mo(CO)4[P(m-tolyl)3]2 revealed that the isomerisation was surface-initiated. KEY WORDS. KEY WORDS: Solventless reactions, Molybdenum, Isomerisation, ...

  1. Physicochemical and biological evaluation of poly(ethylene glycol) methacrylate grafted onto poly(dimethyl siloxane) surfaces for prosthetic devices

    NARCIS (Netherlands)

    Goncalves, Sara; Leiros, Ana; Van Kooten, Theo; Dourado, Fernando; Rodrigues, Ligia R.

    2013-01-01

    Poly(dimethyl siloxane) (PDMS) was surface-polymerized with poly(ethylene glycol)methacrylate (PEGMA) by surface-initiated atom transfer radical polymerization (SI-ATRP) in aqueous media at room temperature. Modification of the PDMS surface followed a three-step procedure: (i) PDMS surface

  2. Detection of early squats by axle box acceleration

    NARCIS (Netherlands)

    Molodova, M.

    2013-01-01

    This thesis discusses a new method for detection of short track irregularities, particularly squats, with axle box acceleration (ABA) measurements. A squat is a surface initiated short track defect, associated with high frequency vibrations of the wheel-rail system. High stresses in the contact

  3. Recent insights into the role of the contact pathway in thrombo-inflammatory disorders

    NARCIS (Netherlands)

    van Montfoort, Maurits L.; Meijers, Joost C. M.

    2014-01-01

    The contact pathway of coagulation consists of the proteins factor XI, factor XII, prekallikrein, and high-molecular-weight kininogen. Activation of the contact system leads to procoagulant and proinflammatory reactions. The contact system is essential for surface-initiated coagulation, as

  4. Smart polymer brush nanostructures guide the self-assembly of pore-spanning lipid bilayers with integrated membrane proteins

    NARCIS (Netherlands)

    de Groot, G.W.; Demarche, S.; Santonicola, M.G.; Tiefenauer, L.; Vancso, Gyula J.

    2014-01-01

    Nanopores in arrays on silicon chips are functionalized with pH-responsive poly(methacrylic acid) (PMAA) brushes and used as supports for pore-spanning lipid bilayers with integrated membrane proteins. Robust platforms are created by the covalent grafting of polymer brushes using surface-initiated

  5. Generic Top-Functionalization of Patterned Antifouling Zwitterionic Polymers on Indium Tin Oxide

    NARCIS (Netherlands)

    Li, Y.; Giesbers, M.; Zuilhof, H.

    2012-01-01

    This paper presents a novel surface engineering approach that combines photochemical grafting and surface-initiated atom transfer radical polymerization (SI-ATRP) to attach zwitterionic polymer brushes onto indium tin oxide (ITO) substrates. The photochemically grafted hydroxyl-terminated organic

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

    NARCIS (Netherlands)

    Bhairamadgi, N.S.; Pujari, S.P.; Leermakers, F.A.M.; Rijn, van C.J.M.; Zuilhof, H.

    2014-01-01

    A series of different thicknesses of fluoro poly(2,2,2-trifluoroethyl methacrylate) and its analogous nonfluoro poly(ethyl methacrylate) polymer brushes were prepared via surface-initiated ATRP (SI-ATRP) on Si(111) surfaces. The thiol-yne click reaction was used to immobilize the SI-ATRP initiator

  7. PDMS and MWCNT – How to Obtain an Efficient and Controlled Distribution of Conductive Fillers in PDMS

    DEFF Research Database (Denmark)

    Hassonueh, S. S.; Goswami, Kaustav; Skov, Anne Ladegaard

    .g. atom transfer radical polymerization (ATRP) using compatibilizing monomers. Through the surface initiated polymerization a thin coating of polymer is introduced on the MWCNT to prevent agglomeration and permit much easier dispersion into the targeted polymer such as a PDMS prepolymer. Through simple...

  8. Reasons for encounter and diagnoses of new outpatients at a small community hospital in Japan: an observational study

    Directory of Open Access Journals (Sweden)

    Takeshima T

    2014-06-01

    Full Text Available Taro Takeshima,1,2 Maki Kumada,3,4 Junichi Mise,5 Yoshinori Ishikawa,6 Hiromichi Yoshizawa,4 Takashi Nakamura,3,4 Masanobu Okayama,1 Eiji Kajii11Division of Community and Family Medicine, Center for Community Medicine, Jichi Medical University, Shimotsuke, Japan; 2Department of Healthcare Epidemiology, School of Public Health in the Graduate School of Medicine, Kyoto University, Kyoto, Japan; 3Division of The Project for Integration of Community Health, Center for Community Medicine, Jichi Medical University, Shimotsuke, Japan; 4Department of General Internal Medicine, Chikusei City Hospital, Chikusei, Japan; 5Division of Human Resources Development for Community Medicine, Center for Community Medicine, Jichi Medical University, Shimotsuke, Japan; 6Department of Surgery, Chikusei City Hospital, Chikusei, JapanPurpose: Although many new patients are seen at small hospitals, there are few reports of new health problems from such hospitals in Japan. Therefore, we investigated the reasons for encounter (RFE and diagnoses of new outpatients in a small hospital to provide educational resources for teaching general practice methods.Methods: This observational study was conducted at the Department of General Internal Medicine in a small community hospital between May 6, 2010 and March 11, 2011. We classified RFEs and diagnoses according to component 1, “Symptoms/Complaints”, and component 7, “Diagnosis/Diseases”, of the International Classification of Primary Care, 2nd edition (ICPC-2. We also evaluated the differences between RFEs observed and common symptoms from the guidelines Model Core Curriculum for Medical Students and Goals of Clinical Clerkship.Results: We analyzed the data of 1,515 outpatients. There were 2,252 RFEs (1.49 per encounter and 170 ICPC-2 codes. The top 30 RFE codes accounted for 80% of all RFEs and the top 55 codes accounted for 90%. There were 1,727 diagnoses and 196 ICPC-2 codes. The top 50 diagnosis codes accounted for

  9. Selective Degradation of Organic Pollutants Using an Efficient Metal-Free Catalyst Derived from Carbonized Polypyrrole via Peroxymonosulfate Activation.

    Science.gov (United States)

    Hu, Peidong; Su, Hanrui; Chen, Zhenyu; Yu, Chunyang; Li, Qilin; Zhou, Baoxue; Alvarez, Pedro J J; Long, Mingce

    2017-10-03

    Metal-free carbonaceous materials, including nitrogen-doped graphene and carbon nanotubes, are emerging as alternative catalysts for peroxymonosulfate (PMS) activation to avoid drawbacks of conventional transition metal-containing catalysts, such as the leaching of toxic metal ions. However, these novel carbocatalysts face relatively high cost and complex syntheses, and their activation mechanisms have not been well-understood. Herein, we developed a novel nitrogen-doped carbonaceous nanosphere catalyst by carbonization of polypyrrole, which was prepared through a scalable chemical oxidative polymerization. The defective degree of carbon substrate and amount of nitrogen dopants (i.e., graphitic nitrogen) were modulated by the calcination temperature. The product carbonized at 800 °C (CPPy-F-8) exhibited the best catalytic performance for PMS activation, with 97% phenol degradation efficiency in 120 min. The catalytic system was efficient over a wide pH range (2-9), and the reaction of phenol degradation had a relatively low activation energy (18.4 ± 2.7 kJ mol -1 ). The nitrogen-doped carbocatalyst activated PMS through a nonradical pathway. A two-step catalytic mechanism was extrapolated: the catalyst transfers electrons to PMS through active nitrogen species and becomes a metastable state of the catalyst (State I); next, organic substrates are oxidized and degraded by serving as electron donors to reduce State I. The catalytic process was selective toward degradation of various aromatic compounds with different substituents, probably depending on the oxidation state of State I and the ionization potential (IP) of the organics; that is, only those organics with an IP value lower than ca. 9.0 eV can be oxidized in the CPPy-F-8/PMS system.

  10. From Self-Assembled Monolayers to Coatings: Advances in the Synthesis and Nanobio Applications of Polymer Brushes

    Directory of Open Access Journals (Sweden)

    Myungwoong Kim

    2015-07-01

    Full Text Available In this review, we describe the latest advances in synthesis, characterization, and applications of polymer brushes. Synthetic advances towards well-defined polymer brushes, which meet criteria such as: (i Efficient and fast grafting, (ii Applicability on a wide range of substrates; and (iii Precise control of surface initiator concentration and hence, chain density are discussed. On the characterization end advances in methods for the determination of relevant physical parameters such as surface initiator concentration and grafting density are discussed. The impact of these advances specifically in emerging fields of nano- and bio-technology where interfacial properties such as surface energies are controlled to create nanopatterned polymer brushes and their implications in mediating with biological systems is discussed.

  11. Flexible particle array structures by controlling polymer graft architecture.

    Science.gov (United States)

    Choi, Jihoon; Dong, Hongchen; Matyjaszewski, Krzysztof; Bockstaller, Michael R

    2010-09-15

    Surface-initiated atom-transfer radical polymerization is used to synthesize particle brushes with controlled fraction of extended and relaxed conformations of surface-grafted chains. In the semidilute brush limit, the grafting of polymeric ligands is shown to facilitate the formation of ordered yet plastic-compliant particle array structures in which chain entanglements give rise to fracture through a polymer-like crazing process that dramatically increases the toughness and flexibility of the particle assembly.

  12. Modification Of Poly(glycidyl Methacrylate) Grafted Onto Crosslinked Pvc With Tertiary Amine Group And Use For Removing Acidic Dyes From Water

    OpenAIRE

    Yorgun, Gülden

    2009-01-01

    In this study, glycidylmethacrylate is grafted onto partially dehydrochlorinated poly(vinyl chloride) (DHPVC) using ATRP method and polymerization kinetics of the reaction is studied. Then, the polymeric resin was interacted with excess of diethylamine, giving a tertiary amine containing sorbent. Surface initiated polymerizations have been widely used to overcome inadequate properties of poly(vinylchloride) (PVC). Epoxy group is one of the most important type to be integrated into polymers. T...

  13. Magnetic-Field-Assisted Assembly of Ordered Multifunctional Ceramic Nanocomposites for Extreme Environments

    Science.gov (United States)

    2016-04-01

    165-168. 2. Chen, R., Maclaughlin, S., Botton, G., and Zhu, S. (2009). Preparation of Ni-g-polymer core–shell nanoparticles by surface-initiated...and Schmidt, M. (2012). Colloidal Crystallization and Structural Changes in Suspensions of Silica/ Magnetite Core–Shell Nanoparticles . Langmuir 28...inclusions. Electrospun mullite nanofibers with incorporated magnetic nanoparticles , SiC whiskers decorated with magnetic nanoparticles , and Nickel

  14. Monolithic Hierarchical Fractal Assemblies of Silica Nanoparticles Cross-Linked with Polynorbornene via ROMP: A Structure-Property Correlation from Molecular to Bulk through Nano

    Science.gov (United States)

    2012-08-23

    secondary particles, SANS, SAXS, rheology 1. INTRODUCTION Low-density, open- cell , nanoporous solids consisting of three- dimensional (3D) assemblies...metals and ceramics . The cross-linking process is akin to grafting polymers onto surfaces. It has been demonstrated with both grafting-to and grafting...Closer to our purposes, ROMP has been used in the surface-initiated mode by immobilizing suitable catalysts on surfaces to produce, in a grafting-from

  15. Surface Modification of Nanoporous 1,2-Polybutadiene by Atom Transfer Radical Polymerization or Click Chemistry

    DEFF Research Database (Denmark)

    Guo, Fengxiao; Jankova Atanasova, Katja; Schulte, Lars

    2010-01-01

    Surface-initiated atom transfer radical polymerization (ATRP) and click chemistry were used to obtain functional nanoporous polymers based oil nanoporous 1,2-polybutadiene (PB) with gyroid morphology. The ATRP monolith initiator was prepared by immobilizing bromoester initiators onto the pore walls...... ATRP-grafting of hydrophilic polyacrylates and click of MPEG, the originally hydrophobic samples transformed into hydrophilic nanoporous materials. The successful modification was confirmed by infrared spectroscopy, contact angle measurements and measurements of spontaneous water uptake, while...

  16. Preparation and Grafting Functionalization of Self-Assembled Chitin Nanofiber Film

    Directory of Open Access Journals (Sweden)

    Jun-ichi Kadokawa

    2016-07-01

    Full Text Available Chitin is a representative biomass resource comparable to cellulose. Although considerable efforts have been devoted to extend novel applications to chitin, lack of solubility in water and common organic solvents causes difficulties in improving its processability and functionality. Ionic liquids have paid much attention as solvents for polysaccharides. However, little has been reported regarding the dissolution of chitin with ionic liquids. The author found that an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr, dissolved chitin in concentrations up to ~4.8 wt % and the higher contents of chitin with AMIMBr gave ion gels. When the ion gel was soaked in methanol for the regeneration of chitin, followed by sonication, a chitin nanofiber dispersion was obtained. Filtration of the dispersion was subsequently carried out to give a chitin nanofiber film. A chitin nanofiber/poly(vinyl alcohol composite film was also obtained by co-regeneration approach. Chitin nanofiber-graft-synthetic polymer composite films were successfully prepared by surface-initiated graft polymerization technique. For example, the preparation of chitin nanofiber-graft-biodegradable polyester composite film was achieved by surface-initiated graft polymerization from the chitin nanofiber film. The similar procedure also gave chitin nanofiber-graft-polypeptide composite film. The surface-initiated graft atom transfer radical polymerization was conducted from a chitin macroinitiator film derived from the chitin nanofiber film.

  17. Surface modification of nanodiamond through metal free atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Guangjian; Liu, Meiying; Shi, Kexin; Heng, Chunning; Mao, Liucheng; Wan, Qing; Huang, Hongye [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Deng, Fengjie, E-mail: fengjiedeng@aliyun.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wei, Yen, E-mail: weiyen@tsinghua.edu.cn [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing, 100084 (China)

    2016-12-30

    Highlights: • Surface modification of ND with water soluble and biocompatible polymers. • Functionalized ND through metal free surface initiated ATRP. • The metal free surface initiated ATRP is rather simple and effective. • The ND-poly(MPC) showed high dispersibility and desirable biocompatibility. - Abstract: Surface modification of nanodiamond (ND) with poly(2-methacryloyloxyethyl phosphorylcholine) [poly(MPC)] has been achieved by using metal free surface initiated atom transfer radical polymerization (SI-ATRP). The ATRP initiator was first immobilized on the surface of ND through direct esterification reaction between hydroxyl group of ND and 2-bromoisobutyryl bromide. The initiator could be employed to obtain ND-poly(MPC) nanocomposites through SI-ATRP using an organic catalyst. The final functional materials were characterized by {sup 1}H nuclear magnetic resonance, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and thermo gravimetric analysis in detailed. All of these characterization results demonstrated that ND-poly(MPC) have been successfully obtained via metal free photo-initiated SI-ATRP. The ND-poly(MPC) nanocomposites shown enhanced dispersibility in various solvents as well as excellent biocompatibility. As compared with traditional ATRP, the metal free ATRP is rather simple and effective. More importantly, this preparation method avoided the negative influence of metal catalysts. Therefore, the method described in this work should be a promising strategy for fabrication of polymeric nanocomposites with great potential for different applications especially in biomedical fields.

  18. Moving to Sustainable Metals. Multifunctional Ligands in Catalytic, Outer Sphere C-H, N-H and O-H Activation

    Energy Technology Data Exchange (ETDEWEB)

    Crabtree, Robert [Yale Univ., New Haven, CT (United States)

    2015-03-03

    Much of our work during this grant period has emphasized green chemistry and sustainability. For example, we were able to convert glycerine, a waste byproduct of biodiesel production, into lactic acid, a compound with numerous applications, notably in the food and cosmetics industry, as well as being a source material for a biodegradable plastic. This work required a catalyst, that ceases to work after a certain lapse of time. We were able to identify the way in which this deactivation occurs by identifying some of the metal catalyst deactivation products. These proved to be multimetallic clusters containing up to six metals and up to 14 hydrogen atoms. Both the catalytic reaction itself and the deactivation structures are novel and unexpected. We have previously proposed that nitrogen heterocycles could be good energy carriers in a low CO2 future world. In another part of our study, we found catalysts for introduction of hydrogen, an energy carrier that is hard to store, into nitrogen heterocycles. The mechanism of this process proved to be unusual in that the catalyst transfers the H2 to the heterocycle in the form of H+ and H-, first transferring the H+ and only then the H-. In a third area of study, some of our compounds, originally prepared for DOE catalysis purposes, also proved useful in hydrocarbon oxidation and in water oxidation. The latter is important in solar-to-fuel work, because, by analogy with natural photosynthesis, the goal of the Yale Solar Group of four PIs is to convert sunlight to hydrogen and oxygen, which requires water splitting catalysts. The catalysts that proved useful mediate the latter reaction: water oxidation to oxygen. In a more technical study, we developed methods for distinguishing the case where catalysis is mediated by a soluble catalyst from cases where catalysis arises from a deposit of finely divided solid. One particular application involved electrocatalysis

  19. Influence of snow and soil moisture initialization on sub-seasonal predictability and forecast skill in boreal spring

    Science.gov (United States)

    Thomas, Jaison Ambadan; Berg, Aaron A.; Merryfield, William J.

    2016-07-01

    This study examines the influence of snow and soil moisture initialization on sub-seasonal potential and actual prediction skill of Canadian Climate Model version 3 (CanCM3) predictions of springtime (April-May) near surface air temperature. Four series of ten-member ensemble forecasts, initialized on 1st April where each series use different land surface initialization, were performed for the 20 year period 1986-2005. Potential predictability of temperature for extratropical Northern Hemisphere land is assessed using synthetic truth and signal-to-noise methods, and compared with actual prediction skills determined through validation against an ensemble mean of six reanalysis products. These metrics are computed for the forecasted 15 days averaged values of temperature at 15, 30 and 45 days lead times. Three of the four land surface initializations considered are intended to be realistic. These are obtained from the Canadian LAand Surface Scheme (CLASS) land surface component of the climate model driven off line with bias-corrected meteorological fields, with and without rescaling to the climate model's land climatology, and from climate model runs where the atmospheric component is constrained by reanalysis fields. A fourth land surface initialization that is intended to be unrealistic consists of a "scrambled" version of that obtained from rescaled offline-driven CLASS, in which each ensemble member is assigned values from a year other than the one being forecasted. Comparisons of forecasts using the scrambled and corresponding realistic land initializations indicate that the latter show higher potential predictability overall especially over North America and parts of Eurasia at all lead times. The higher potential predictability is primarily attributed to correct initialization of land surface variables, in particular the snow water equivalent, and the frozen and liquid components of soil moisture. Our results also indicate that predictability is governed

  20. Particle-size effect on the rate of TiO2 carbonizing

    International Nuclear Information System (INIS)

    Lekanova, T.L.; Ryabkov, Yu.I.; Sevbo, O.A.

    2003-01-01

    Dependence of recovery rate constant of titanium dioxide in TiO 2 -C system on the value of specific surface initial components at 1300 deg C was studied. It is shown that decrease in equivalent particle size of titanium dioxide and carbon particles in the range of 500-100 μm has a similar effect on increase in titanium dioxide recovery rate. Analysis of kinetic equations suggests diffusion character of titanium dioxide carbonizing at the values of initial components specific surface in excess of 100 m 2 /g [ru

  1. Fatigue Crack Propagation in a Gear Tooth in the Presence of an Inclusion

    Science.gov (United States)

    Agarwal, Vineet; Zagade, Pramod R.; Khan, Danish; Gautham, B. P.

    2014-05-01

    A computational model for studying the fatigue crack propagation characteristics in a gear tooth root in the presence of inclusions is presented. A step-by-step crack growth scheme is implemented to predict the crack path using the finite element method and linear elastic fracture mechanics. Paris law approach is used to model fatigue crack propagation. The effect of size and location of hard circular inclusion on the growth of a surface-initiated crack and service life in a gear tooth is studied.

  2. Synthesis of polymer/inorganic nanocomposite films using highly porous inorganic scaffolds.

    Science.gov (United States)

    Zhang, Huanjun; Popp, Matthias; Hartwig, Andreas; Mädler, Lutz

    2012-04-07

    Polymeric/inorganic nanocomposite films have been fabricated through a combination of flame-spray-pyrolysis (FSP) made inorganic scaffold and surface initiated polymerization of cyanoacrylate. The highly porous structure of pristine SnO(2) films allows the uptake of cyanoacrylate and the polymerization is surface initiated by the water adsorbed onto the SnO(2) surface. Scanning electron microscopy study reveals a nonlinear increase in the composite particle size and the film thickness with polymerization time. The structural change is rather homogeneous throughout the whole layer. The composite is formed mainly by an increase of the particle size and not by just filling the existing pores. High-resolution transmission electron microscopy imaging shows SnO(2) nanoparticles embedded in the polymeric matrix, constituting the nanocomposite material. Thermogravimetric analysis indicates that the porosity of the nanocomposite films decreases from 98% to 75%, resulting in a significant enhancement of the hardness of the films. DC conductivity measurements conducted in situ on the nanocomposite layer suggest a gradual increase in the layer resistance, pointing to a loss of connectivity between the SnO(2) primary particles as the polymerization proceeds. This journal is © The Royal Society of Chemistry 2012

  3. Programming nanostructures of polymer brushes by dip-pen nanodisplacement lithography (DNL)

    Science.gov (United States)

    Liu, Xuqing; Li, Yi; Zheng, Zijian

    2010-12-01

    We report a facile and versatile scanning probe based approach--dip-pen nanodisplacement lithography (DNL)--for manipulating nanostructures of polymer brushes. Nanostructured polymer brushes with sizes as small as 25 nm are made by DNL patterning of the initiator molecules and subsequent surface-initiated polymerization. Nanoconfinement effects including chain collapsing and spreading are observed in the nanopatterned polymer brushes. In addition to chemical structure, size, topography and shape, our approach can also readily program the grafting density, chain configuration, hierarchical structure and multiplexing of the polymer brushes, which allows for the realization of complex chemical surfaces.We report a facile and versatile scanning probe based approach--dip-pen nanodisplacement lithography (DNL)--for manipulating nanostructures of polymer brushes. Nanostructured polymer brushes with sizes as small as 25 nm are made by DNL patterning of the initiator molecules and subsequent surface-initiated polymerization. Nanoconfinement effects including chain collapsing and spreading are observed in the nanopatterned polymer brushes. In addition to chemical structure, size, topography and shape, our approach can also readily program the grafting density, chain configuration, hierarchical structure and multiplexing of the polymer brushes, which allows for the realization of complex chemical surfaces. Electronic supplementary information (ESI) available: LFM images of MUDBr patterns; digital image of irregular polymer brushes grown on gold caused by random diffusion of MUDBr through the air. See DOI: 10.1039/c0nr00565g

  4. Synthesis of Polymer Grafted Magnetite Nanoparticle with the Highest Grafting Density via Controlled Radical Polymerization

    Directory of Open Access Journals (Sweden)

    Babu Kothandapani

    2009-01-01

    Full Text Available Abstract The surface-initiated ATRP of benzyl methacrylate, methyl methacrylate, and styrene from magnetite nanoparticle is investigated, without the use of sacrificial (free initiator in solution. It is observed that the grafting density obtained is related to the polymerization kinetics, being higher for faster polymerizing monomer. The grafting density was found to be nearly 2 chains/nm2for the rapidly polymerizing benzyl methacrylate. In contrast, for the less rapidly polymerizing styrene, the grafting density was found to be nearly 0.7 chain/nm2. It is hypothesized that this could be due to the relative rates of surface-initiated polymerization versus conformational mobility of polymer chains anchored by one end to the surface. An amphiphilic diblock polymer based on 2-hydroxylethyl methacrylate is synthesized from the polystyrene monolayer. The homopolymer and block copolymer grafted MNs form stable dispersions in various solvents. In order to evaluate molecular weight of the polymer that was grafted on to the surface of the nanoparticles, it was degrafted suitably and subjected to gel permeation chromatography analysis. Thermogravimetric analysis, transmission electron microscopy, and Fourier transform infrared spectroscopy were used to confirm the grafting reaction.

  5. Evaluation of NU-WRF Rainfall Forecasts for IFloodS

    Science.gov (United States)

    Wu, Di; Peters-Lidard, Christa; Tao, Wei-Kuo; Petersen, Walter

    2016-01-01

    The Iowa Flood Studies (IFloodS) campaign was conducted in eastern Iowa as a pre- GPM-launch campaign from 1 May to 15 June 2013. During the campaign period, real time forecasts are conducted utilizing NASA-Unified Weather Research and Forecasting (NU-WRF) model to support the everyday weather briefing. In this study, two sets of the NU-WRF rainfall forecasts are evaluated with Stage IV and Multi-Radar Multi-Sensor (MRMS) Quantitative Precipitation Estimation (QPE), with the objective to understand the impact of Land Surface initialization on the predicted precipitation. NU-WRF is also compared with North American Mesoscale Forecast System (NAM) 12 kilometer forecast. In general, NU-WRF did a good job at capturing individual precipitation events. NU-WRF is also able to replicate a better rainfall spatial distribution compare with NAM. Further sensitivity tests show that the high-resolution makes a positive impact on rainfall forecast. The two sets of NU-WRF simulations produce very close rainfall characteristics. The Land surface initialization do not show significant impact on short term rainfall forecast, and it is largely due to the soil conditions during the field campaign period.

  6. Poly(lactic acid) Polymer Brushes as Dynamic Surfaces

    Science.gov (United States)

    Xu, Le Bo

    Degradable Poly(lactic acid), PLA, polymer brushes, were prepared to use as a temporary protective layer on a substrate. The PLA brushes degraded under basic conditions, which distinguished from bulk PLA, as well as PLA oligomer. The underlying substrate was able to be exposed with the removal of PLA brushes, resulting in a dynamic behavior. PLA brushes were grafted from silicon and gold substrates through surface initiated ring opening polymerization, ROP, of lactide catalyzed by tin octoate. The surface silanol groups on silicon and hydroxyl-terminated thiol self-assembled monolayers, SAMs, on gold were used as immobilized initiators for the surface initiated polymerization. The surface silanol groups worked equally well as the alcohol species to serve as initiator for the ROP of lactide. Synthesis conditions, such as temperature, monomer concentration and the type of catalyst and solvent, were explored to pursue the maximum brush thickness and well controlled growth on the surface. It was highlighted the different optimized synthesis conditions between the ROP in solution and the surface initiated ROP due to the equilibrium behavior of ROP. Both molecular weight and monomer conversion were considered in solution ROP. However, monomer conversion was not that important for surface ROP given merely trace amount of polymer was grafted on the surface as brushes. It was also demonstrated that the thickness of PLA brush could be tuned by varying either growth time or grafting density. The PLA brushes with a gradient thickness were prepared by gradually filling a reaction container with reactive solution. PLA brushes were able to be removed by immersing them in basic aqueous solution. The degradation of PLA brushes was found to be unique. Bulk PLA degraded under acidic conditions. The degradation of PLA oligomer occurred under both acidic and basic conditions. While the PLA brushes only degraded under basic conditions. The base-catalyzed degradation suggests the

  7. Sweet potato starch residue as starting material to prepare polyacrylonitrile adsorbent via SI-SET-LRP.

    Science.gov (United States)

    Hao, Zhihai; Wang, Dongju; Chen, Hou; Sun, Jinming; Xu, Yuanyuan

    2014-02-26

    Sweet potato starch residue (SPSR) was used as starting material to prepare an eco-friendly adsorbent. SPSR was modified by bromoacetyl bromide to obtain a macroinitiator for surface-initiated single electron transfer-living radical polymerization (SI-SET-LRP) of acrylonitrile (AN) catalyzed by La(0)/hexamethylenetetramine (HMTA) in N,N-dimethylformamide (DMF) in the presence of ascorbic acid (VC). The amidoxime (AO) adsorbent was prepared by the reaction of the graft copolymer bromoactylated sweet potato starch (BSPS)/polyacrylonitrile (BSPS-g-PAN) with hydroxylamine. The maximum adsorption capacity for Hg(II) was 4.03 mmol·g(-1). This simple method provided a novel approach to recycle and reuse agricultural residues for controlling heavy metal pollution.

  8. Preparation of poly(methyl methacrylate) grafted hydroxyapatite nanoparticles via reverse ATRP.

    Science.gov (United States)

    Wang, Yan; Xiao, Yan; Huang, Xiujuan; Lang, Meidong

    2011-08-15

    Surface-initiated reverse atom transfer radical polymerization (reverse ATRP) technical was successfully employed to modify hydroxyapatite (HAP) nanoparticles with poly(methyl methacrylate) (PMMA). The peroxide initiator moiety for reverse ATRP was covalently attached to the HAP surface through the surface hydroxyl groups. Reverse ATRP of methyl methacrylate (MMA) from the initiator-functionalized HAP was carried out, and the end bromide groups of grafted PMMA initiated ATRP of MMA subsequently. Fourier transformation infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA) and transmission electron microscopy (TEM) were employed to confirm the grafting and to characterize the nanoparticle structure. The grafted PMMA gave HAP nanoparticles excellent dispersibility in MMA monomer. As the amount of grafted PMMA increased, the dispersibility of surface-grafted HAP and the compressive strength of HAP/PMMA composites were improved. Copyright © 2011 Elsevier Inc. All rights reserved.

  9. Internal architecture of zwitterionic polymer brushes regulates nonfouling properties.

    Science.gov (United States)

    Huang, Chun-Jen; Li, Yuting; Krause, Jordan B; Brault, Norman D; Jiang, Shaoyi

    2012-06-14

    In this work, we study how film thickness and chain packing density affect the protein-resistant properties of polymer brushes in complex media. Polymer brushes based on dual-functional poly(carboxybetaine acrylamide) (pCB) were prepared via surface-initiated photoiniferter-mediated polymerization. By adjusting UV radiation time and solvent polarity, pCB films with different thicknesses can be achieved and characterized using an ellipsometer. The packing density of pCB polymer chains is directly related to the swelling ratio of swollen to collapsed film thicknesses. Results showed that the dry film thickness alone, used often in the literature, is not sufficient to correlate with nonfouling properties and the chain packing density must be considered for the design of nonfouling surface coatings. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Glycopolypeptide-encapsulated Mn-doped ZnS quantum dots for drug delivery: fabrication, characterization, and in vitro assessment.

    Science.gov (United States)

    Xu, Zhigang; Li, Bo; Tang, Wanjin; Chen, Tong; Zhang, Haixia; Wang, Qin

    2011-11-01

    In this work, glycopolypeptide nanoparticles (GPNPs) composed of Mn doped ZnS quantum dots (QDs) as core and glycopolypeptides as shell were synthesized through the surface initiated polymerization of N-carboxyanhydrides and surface condensation polymerization with carboxymethyldextran on amine-functionalized QDs. The loading and release behavior of ibuprofen on the GPNPs were investigated. The GPNPs exhibited not only high loading but also controlled release behavior. The cytotoxicity of the GPNPs was evaluated by incubating with HEK293T cell lines and they were shown to be of low cytotoxicity. They appear to be a very promising candidate for targeted drug delivery. Copyright © 2011 Elsevier B.V. All rights reserved.

  11. Poly(lauryl acrylate) and poly(stearyl acrylate) grafted multiwalled carbon nanotubes for polypropylene composites

    DEFF Research Database (Denmark)

    Daugaard, Anders Egede; Jankova Atanasova, Katja; Hvilsted, Søren

    2014-01-01

    Two new polymer grafts on an industrial grade multiwalled carbon nanotube (MWCNT) were prepared through a non-oxidative pathway employing controlled free radical polymerization for surface initiated polymer grafting. After photochemical introduction of an ATRP initiator onto the MWCNT......, polymerizations of lauryl or stearyl acrylate were performed, resulting in two novel polymer modifications on the MWCNT (poly(lauryl acrylate) or poly(stearyl acrylate)). The method was found to give time dependent loading of polymers as a function of time (up to 38 wt% for both acrylates), and showed a plateau...... in loading after 12 h of polymerization. The modified nanomaterials were melt mixed into polypropylene composites with very low filler loading (0.3 wt%), whereafter both the thermal and electrical properties were investigated by DSC and dielectric resonance spectroscopy. The electrical properties were found...

  12. Functionalization and Polymerization on the CNT Surfaces

    KAUST Repository

    Albuerne, Julio

    2013-07-01

    In this review we focus on the current status of using carbon nanotube (CNT) as a filler for polymer nanocomposites. Starting with the historical background of CNT, its distinct properties and the surface functionalization of the nanotube, the three different surface polymerization techniques, namely grafting "from", "to" and "through/in between" were discussed. Wider focus has been given on "grafting from" surface initiated polymerizations, including atom transfer radical polymerization (ATRP), reversible addition fragmentation chain-transfer (RAFT) Polymerization, nitroxide mediated polymerization (NMP), ring opening polymerization (ROP) and other miscellaneous polymerization methods. The grafting "to" and "through / in between" also discussed and compared with grafting from polymerization. The merits and shortcomings of all three grafting methods were discussed and the bottleneck issue in grafting from method has been highlighted. Furthermore the current and potential future industrial applications were deliberated. Finally the toxicity issue of CNTs in the final product has been reviewed with the limited available literature knowledge. © 2013 Bentham Science Publishers.

  13. A corrosion-protective coating based on a solution-processable polymer-grafted graphene oxide nanocomposite

    International Nuclear Information System (INIS)

    Qi, Kai; Sun, Yimin; Duan, Hongwei; Guo, Xingpeng

    2015-01-01

    Highlights: • Solution-processable polymer-grafted graphene nanocomposite is synthesized. • The nanocomposite exhibits synergistic properties of both building blocks. • The nanocomposite can be easily applied to form a protective coating on metals. • The coating can effectively prevent corrosion of copper substrate. - Abstract: A new type of solution-processable graphene coating has been synthesized by grafting polymethylmethacrylate (PMMA) brushes on graphene oxide (GO) via surface-initiated atom transfer radical polymerization (ATRP). One major finding is that the PMMA-grafted GO nanocomposite exhibits synergistic properties of both building blocks, i.e., permeation inhibition of GO and solubility of PMMA in a variety of solvents, which makes it compatible with commonly used coating methods to form uniform coatings with controlled thickness. Our results demonstrate that PMMA-grafted GO coating can effectively block charge transfer at the metal–electrolyte interface and prevent corrosion of the copper substrate under aggressive saline conditions

  14. Surface modification of silica nanoparticles by UV-induced graft polymerization of methyl methacrylate.

    Science.gov (United States)

    Kim, Sooyeon; Kim, Eunhye; Kim, Sungsoo; Kim, Woosik

    2005-12-01

    In this study we modified the surface of silica nanoparticles with methyl methacrylate by UV-induced graft polymerization. It is a surface-initiated polymerization reaction induced by ultraviolet irradiation. The resulting organic-inorganic nanocomposites were near-monodisperse and fabricated without homopolymerization of the monomer. Substantial increase in mean particle size was observed by SEM image analysis after UV-induced grafting of methyl methacrylate onto pure silica particles. FT-Raman spectroscopy and X-ray photoelectron spectroscopy studies of these materials revealed the successful grafting of methyl methacrylate onto the silica surface. The formation of a covalent bond between the grafted PMMA chains and silica surface was indicated by FT-Raman spectra. Thermogravimetric analysis of the PMMA-grafted silica particles indicated the polymer contents in good agreement with SEM photographs.

  15. Synthesis, structural characterization and antibacterial activity of cotton fabric modified with a hydrogel containing barium hexaferrite nanoparticles

    Science.gov (United States)

    Staneva, Desislava; Koutzarova, Tatyana; Vertruyen, Benedicte; Vasileva-Tonkova, Evgenia; Grabchev, Ivo

    2017-01-01

    Barium hexaferrite nanoparticles were synthesized by co-precipitation of Ba2+ and Fe3+ cations with NaOH under of high-power ultrasound. The nanoparticles were dispersed in an aqueous solution of the hydrogel precursors. This solution was used to impregnate the cotton fabric dyed with a photoinitiator. The composite material BaFe12O19 nanoparticles-hydrogel-cotton fabric was prepared by surface initiate photopolymerization under visible light. The modification of the cotton fabric and uniform distribution of the nanoparticles in the structure of the hydrogel were analyzed by scanning electron microscopy (SEM), IR spectroscopy, X-ray diffraction analysis (XRD), fluorescence and colourimetric analyses. The antibacterial efficacy of the material was evaluated against Gram-negative Escherichia coli and Pseudomonas aeruginosa.

  16. Mussel inspired polymerized P(TA-TETA) for facile functionalization of carbon nanotube

    Science.gov (United States)

    Si, Shuxian; Gao, Tingting; Wang, Junhao; Liu, Qinze; Zhou, Guowei

    2018-03-01

    This article describes a novel and effective approach for non-covalent modification of carbon nanotube (CNT) via the mussel inspired polymerization of tannic acid (TA) and triethylenetetramine (TETA) and subsequent surface initiated atom transfer radical polymerization (SI-ATRP). Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and photograph were used to study the successful preparation of polymer brush grafted CNT (CNT-P(TA-TETA)-PDMAEMA) composite as well as the pH-responsive behavior of the composite. Furthermore, by amine protonation and in situ reduction, gold nanoparticles were successfully uploaded and the catalytic property of CNT-P(TA-TETA)-PDMAEMA/Au was investigated. We believe that the surface functionalization strategy can be extended to graphene and other substrates, and the surface properties can be regulated by grafting polymer brushes with different functionalities.

  17. Automated coating procedures to produce poly(ethylene glycol) brushes in fused-silica capillaries

    DEFF Research Database (Denmark)

    Poulsen, Nicklas N; Østergaard, Jesper; Petersen, Nickolaj J

    2017-01-01

    the four model proteins cytochrome c, myoglobin, ovalbumin and human serum albumin in the pH range 3.4-8.4. Further, even samples containing 10% v/v plasma derived from human blood did not show signs of adsorbing to the coated capillaries. The covalent as well as the electrostatically adsorbed coating were...... both found to be stable and provided almost complete suppression of the electroosmotic flow in the pH range 3.4-8.4. The coating procedures may easily be integrated in fully automated capillary electrophoresis methodologies. This article is protected by copyright. All rights reserved........ Flexible and reliable approaches for preventing unwanted protein adsorption in separation science are thus in high demand. We therefore present new coating approaches based on an automated in-capillary surface initiated atom transfer radical polymerization process (covalent coating) as well...

  18. Expanded corn starch as a versatile material in atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate.

    Science.gov (United States)

    Bansal, Ankushi; Kumar, Arvind; Latha, Patnam Padma; Ray, Siddharth Sankar; Chatterjee, Alok Kumar

    2015-10-05

    Polymerization of styrene (St) and methyl methacrylate (MMA) was performed by surface initiated (SI) and activator generated by electron transfer (AGET) systems of atom transfer radical polymerization (ATRP) using renewable expanded corn starch (ECS) as a support. This prepared ECS is found to have V type crystallinity with 50 m(2)g(-1) surface area (<1m(2)g(-1) for corn starch (CS)) and average pore volume of 0.43 cm(3)g(-1) (<0.1cm(3)g(-1) for CS). In SI-ATRP, hydroxyl groups on ECS were converted into macro-initiator by replacing with 2-bromoisobutyryl bromide (BIBB) with a 0.06 degree of substitution determined from NMR. In AGET-ATRP, CuBr2/ligand complex get adsorbed on ECS (Cu(II)/ECS=10 wt.%) to catalyze the polymerization. Synthesized PS/PMMA was characterized by SEM, FT-IR, (1)H NMR. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Successful skin homografting from an identical twin in a severely burned patient.

    Science.gov (United States)

    Turk, Emin; Karagulle, Erdal; Turan, Hale; Oguz, Hakan; Abali, Ebru Sakallioglu; Ozcay, Necdet; Moray, Gokhan; Haberal, Mehmet

    2014-01-01

    Flame burns are a serious condition and usually have high morbidity and mortality because they affect large areas of the body surface as well as the lungs. In these patients, it is especially difficult to find healthy skin for grafting if they have more than 70% third-degree burns. Repeated autografting or synthetic wound care materials are the only treatment options to cover burned areas. Partial-thickness skin grafting from the patient's identical twin sibling may be an alternative treatment option, if possible. Here, we report a patient with severe flame injury treated with skin from his identical twin. The patient had third-degree burns covering 70% of his body surface. Initial treatment consisted of fluid and electrolyte replacement, daily wound care, and surgical debridements, as well as nutritional support. After initial treatment, we performed a successful skin grafting from his identical twin. Skin grafting between identical twins might be an alternate method for severely burned patients.

  20. Initiator-integrated 3D printing enables the formation of complex metallic architectures.

    Science.gov (United States)

    Wang, Xiaolong; Guo, Qiuquan; Cai, Xiaobing; Zhou, Shaolin; Kobe, Brad; Yang, Jun

    2014-02-26

    Three-dimensional printing was used to fabricate various metallic structures by directly integrating a Br-containing vinyl-terminated initiator into the 3D resin followed by surface-initiated atomic-transfer radical polymerization (ATRP) and subsequent electroless plating. Cu- and Ni-coated complex structures, such as microlattices, hollow balls, and even Eiffel towers, were prepared. Moreover, the method is also capable of fabricating ultralight cellular metals with desired structures by simply etching the polymer template away. By combining the merits of 3D printing in structure design with those of ATRP in surface modification and polymer-assisted ELP of metals, this universal, robust, and cost-effective approach has largely extended the capability of 3D printing and will make 3D printing technology more practical in areas of electronics, acoustic absorption, thermal insulation, catalyst supports, and others.

  1. Surface chemical reactions induced by molecules electronically-excited in the gas

    DEFF Research Database (Denmark)

    Petrunin, Victor V.

    2011-01-01

    and alignment are taking place, guiding all the molecules towards the intersections with the ground state PES, where transitions to the ground state PES will occur with minimum energy dissipation. The accumulated kinetic energy may be used to overcome the chemical reaction barrier. While recombination chemical...... beams inducing the reaction can be used to distinguish the new process we try to investigate from chemical reactions induced by photoexcitation within adsorbed molecules and/or gas phase photolysis.......We present a model suggesting high chemical activity of electronically-excited molecules colliding with an isolator surface. Initial photochemical event is accounted for as the result of molecular evolution on the electronically-excited potential energy surface (PES), where acceleration...

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

    Science.gov (United States)

    Wang, Zhanhua; Zuilhof, Han

    2016-07-05

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

  3. Examination of shaped charge liner shock loading

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, M.J.; Moore, T.W.; Lee, C.G.; Breithaupt, R.; Avara, G.R.

    1996-07-01

    A series of experiments was conducted for the purpose of achieving a more fundamental understanding of the shaped charge liner shock loading environment. The test configuration, representing the middle portion of a shaped charge, consists of a 50 mm deep, 100 mm tall, and 2 mm thick copper plate driven by 50 mm deep, 100 mm tall, tapered thickness wedge of LX-14. An electrically driven 50 mm square flyer is used to surface initiate the base of the LX-14 causing a plane detonation wave to propagate into the explosive wedge along the liner surface. Fabry-Perot laser velocimetry measures the particle velocity time history of the plate. The CTH and DYNA2D hydrocodes are used to simulate the experiments. Calculations of the velocity profiles are compared to the experimental results. The effects of mesh density, copper material failure and strength models, and explosive detonation models are discussed.

  4. Influence of microstructure and mean stress on the fatique behaviour of Ti-6Al-4V

    International Nuclear Information System (INIS)

    Steele, R.K.; McEvily, A.J.

    1977-01-01

    In previous fatigue studies of Ti-6Al-4V bar stock and forgings a number of findings of interest were encountered. These findings include the sub-surface initiation of fatigue cracks, a strong Bauschinger effect, cyclic softening, an influence of microstructural size on resistance to fatigue (particularly at R=0), and a dependency of cyclic-stress strain behavior on loading path. The present paper extends the work of the earlier investigations to cover a wider range of microstructures as well as cyclic loading conditions. The basic materials are forging and bar stock of the Ti-6Al-4V alloy with microstructural variations being achieved by different heat treating procedures. (Auth.)

  5. TiO2 patterns with wide photo-induced wettability change by a combination of reactive sputtering process and surface modification in a microfluidic channel

    Science.gov (United States)

    Kobayashi, Taizo; Konishi, Satoshi

    2015-11-01

    This paper reports the formation of TiO2 patterns with a wide range of photo-induced wettability switching from high hydrophobic to superhydrophilic states for on-chip liquid manipulation. TiO2 thin films with rough surface morphology were formed by a combination of optimised reactive sputtering and CF4 plasma etching. Octadecylphosphonic acid self-assembled monolayer (ODP-SAM) surface modification was applied to the surface-roughened TiO2 thin films in order to obtain a highly hydrophobic surface initially. Photocatalytic decomposition of ODP-SAM on the surface-roughened TiO2 by ultraviolet (UV) irradiation caused a wetting transition from the Cassie-Baxter state to the Wenzel state. Switching of the flow direction into branch channels was also demonstrated by utilising the photoresponsive wettability of the surface-modified TiO2 patterns on a fluidic chip.

  6. Macromolecular surface design: photopatterning of functional stable nitrile oxides.

    Science.gov (United States)

    Altintas, Ozcan; Glassner, Mathias; Rodriguez-Emmenegger, Cesar; Welle, Alexander; Trouillet, Vanessa; Barner-Kowollik, Christopher

    2015-05-04

    The efficient trapping of photogenerated thioaldehydes with functional shelf-stable nitrile oxides in a 1,3-dipolar cycloaddition is a novel and versatile photochemical strategy for polymer end-group functionalization and surface modification under mild and equimolar conditions. The modular ligation in solution was followed in detail by electrospray ionization mass spectrometry (ESI-MS). X-ray photoelectron spectroscopy (XPS) was employed to analyze the functionalized surfaces, whereas time-of-flight secondary-ion mass spectrometry (ToF-SIMS) confirmed the spatial control of the surface functionalization using a micropatterned shadow mask. Polymer brushes were grown from the surface in a spatially confined regime by surface-initiated atom transfer radical polymerization (SI-ATRP) as confirmed by TOF-SIMS, XPS as well as ellipsometry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. CdS/CdSe quantum dot co-sensitized graphene nanocomposites via polymer brush templated synthesis for potential photovoltaic applications

    Science.gov (United States)

    Yan, Junfeng; Ye, Qian; Wang, Xiaolong; Yu, Bo; Zhou, Feng

    2012-03-01

    CdS/CdSe quantum dot (QDs) co-sensitized graphene sheets have been obtained via polymer brush templated synthesis. Firstly, the anionic functional polymer (polymethacrylate cadmium) was grafted via the surface initiated atomic transfer radical polymerization (ATRP) using a macromolecular initiator, which contains polymerized pyrene units for chemical anchoring on graphene surface and alkyl bromines to initiate ATRP. Then, the coordinated cadmium in the polymer chains can act as a source precursor for QDs. After reaction, polymer brushes can be recovered and act as the nanoreactor via the absorption of cadmium ions by carboxylate groups. So, high density QDs can be multiply uploaded onto the graphene surface by repeated steps. The as-prepared composite materials exhibited significantly enhanced visible light response compared to plain graphene, and have potential applications as the platform to build solar cell assembles.

  8. CdS/CdSe quantum dot co-sensitized graphene nanocomposites via polymer brush templated synthesis for potential photovoltaic applications.

    Science.gov (United States)

    Yan, Junfeng; Ye, Qian; Wang, Xiaolong; Yu, Bo; Zhou, Feng

    2012-03-21

    CdS/CdSe quantum dot (QDs) co-sensitized graphene sheets have been obtained via polymer brush templated synthesis. Firstly, the anionic functional polymer (polymethacrylate cadmium) was grafted via the surface initiated atomic transfer radical polymerization (ATRP) using a macromolecular initiator, which contains polymerized pyrene units for chemical anchoring on graphene surface and alkyl bromines to initiate ATRP. Then, the coordinated cadmium in the polymer chains can act as a source precursor for QDs. After reaction, polymer brushes can be recovered and act as the nanoreactor via the absorption of cadmium ions by carboxylate groups. So, high density QDs can be multiply uploaded onto the graphene surface by repeated steps. The as-prepared composite materials exhibited significantly enhanced visible light response compared to plain graphene, and have potential applications as the platform to build solar cell assembles. This journal is © The Royal Society of Chemistry 2012

  9. Perspectives and Peptides of the Next Generation

    Science.gov (United States)

    Brogden, Kim A.

    Shortly after their discovery, antimicrobial peptides from prokaryotes and eukaryotes were recognized as the next potential generation of pharmaceuticals to treat antibiotic-resistant bacterial infections and septic shock, to preserve food, or to sanitize surfaces. Initial research focused on identifying the spectrum of antimicrobial agents, determining the range of antimicrobial activities against bacterial, fungal, and viral pathogens, and assessing the antimicrobial activity of synthetic peptides versus their natural counterparts. Subsequent research then focused on the mechanisms of antimicrobial peptide activity in model membrane systems not only to identify the mechanisms of antimicrobial peptide activity in microorganisms but also to discern differences in cytotoxicity for prokaryotic and eukaryotic cells. Recent, contemporary work now focuses on current and future efforts to construct hybrid peptides, peptide congeners, stabilized peptides, peptide conjugates, and immobilized peptides for unique and specific applications to control the growth of microorganisms in vitro and in vivo.

  10. Fouling-resistant polymer brush coatings

    KAUST Repository

    Thérien-Aubin, Héloïse

    2011-11-01

    A major problem to be addressed with thin composite films used in processes such as coatings or water purification is the biofouling of the surface. To address this problem in a model system, functionalized polyaramide membranes containing an atom transfer radical polymerization (ATRP) initiator were synthesized as a versatile approach to easily modify the surface properties of the polyaramide. Poly(methacrylic acid) brushes were grown using surface initiated ATRP followed by the functionalization of the poly(methacrylic acid) brushes with different side-chains chosen to reduce adhesion between the membrane and foulant. The relation between membrane fouling and the physicochemical properties of the surface was investigated in detail. © 2011 Elsevier Ltd. All rights reserved.

  11. Chlorine-induced modifications in the electronic structure of Ag surfaces: a metastable deexcitation spectroscopy and photoemission comparative study

    CERN Document Server

    Pasquali, L; Canepa, M; Staicu-Casagrande, E M; Esaulov, V A

    2003-01-01

    Surface-sensitive spectroscopic techniques, namely metastable deexcitation spectroscopy (MDS) and ultraviolet photoemission (UPS), have been applied to investigate the effects of chlorine chemisorption on the electronic properties (surface density of states and charge density) of Ag(100), Ag(110) and Ag(111) surfaces. Initial stages of chemisorption, up to the formation of a saturated Cl overlayer, have been examined. In particular, MDS permitted us to observe at low Cl gas exposure a progressive depletion of the Ag (5s) charge due to transfer and bonding with Cl atoms. From both MDS and UPS it was possible to observe the development of Cl (3p) bonding and anti-bonding states, the amount of their splitting increasing with coverage. Differences between chemisorption at the three surfaces have been noticed and they have been justified in terms of the different adatom packing and possible formation of small AgCl clusters (especially for the Ag(111) surface).

  12. Durable and Washable Antibacterial Copper Nanoparticles Bridged by Surface Grafting Polymer Brushes on Cotton and Polymeric Materials

    Directory of Open Access Journals (Sweden)

    Chufeng Sun

    2018-01-01

    Full Text Available To increase the durability of antibacterial coating on cotton and polymeric substrates, surface initiated grafting polymer brushes are introduced onto the substrates surface to bridge copper nanoparticles coatings and substrate. The morphologies of the composites consisting of the copper nanoparticles and polymer brushes were characterized with scanning electron microscopy (SEM. It was found that copper nanoparticles were uniformly and firmly distributed on the surfaces of the substrates by the polymer brushes; meanwhile, the reinforced concrete-like structures were formed in the composite materials. The substrates coated by the copper nanoparticles showed the efficient antibacterial activity against Staphylococcus aureus (S. aureus and Escherichia coli (E. coli even after washing by 30 cycles. The copper nanoparticles were tethered on the substrates by the strong chemical bonds, which led to the excellent washable fitness and durability. The change of the phase structure of the copper was analyzed to investigate the release mechanism of copper ions.

  13. Suppression of phase separation in $(AlAs)_{2ML} (InAs)_{2ML}$ superlattices using $Al_{0.48}In_{0.52}$ As monolayer insertions

    CERN Document Server

    Lee, S R; Follstaedt, D M

    2001-01-01

    Al/sub 0.48/In/sub 0.52/As monolayers (ML) are inserted at the binary-compound interfaces of (AlAs)/sub 2/ /sub ML/(InAs)/sub 2/ /sub ML/ short-period superlattices (SPSs) during growth on (001) In P. The insertion of Al/sub 0.48/In/sub 0.52/As interlayers greater than 2 ML thick tends to suppress the phase separation that normally occurs during molecular beam epitaxy of the SPS. The degree of suppression is a sensitive function of both the monolayer-scale thickness, and the intraperiod growth sequence, of the interlayers in the SPS. Given this sensitivity to monolayer-scale variations in the surface-region composition, we propose that cyclical phase transition of the reconstructed surface initiates SPS decomposition. (21 refs).

  14. Stratified polymer brushes from microcontact printing of polydopamine initiator on polymer brush surfaces.

    Science.gov (United States)

    Wei, Qiangbing; Yu, Bo; Wang, Xiaolong; Zhou, Feng

    2014-06-01

    Stratified polymer brushes are fabricated using microcontact printing (μCP) of initiator integrated polydopamine (PDOPBr) on polymer brush surfaces and the following surface initiated atom transfer radical polymerization (SI-ATRP). It is found that the surface energy, chemically active groups, and the antifouling ability of the polymer brushes affect transfer efficiency and adhesive stability of the polydopamine film. The stickiness of the PDOPBr pattern on polymer brush surfaces is stable enough to perform continuous μCP and SI-ATRP to prepare stratified polymer brushes with a 3D topography, which have broad applications in cell and protein patterning, biosensors, and hybrid surfaces. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Preparation and characterization of poly(glycidyl methacrylate)-grafted magnetic nanoparticles: Effects of the precursor concentration on polyol synthesis of Fe3O4 and [PMDETA]0/[CuBr2]0 ratios on SI-AGET ATRP

    Science.gov (United States)

    Jiang, Liping; Zhou, Xuyang; Wei, Guyun; Lu, Xiaoduo; Wei, Weiping; Qiu, Jianhua

    2015-12-01

    Polymer brushes based on poly(glycidyl methacrylate) (PGMA) have been successfully grafted from the surface of silica coated iron oxide (Fe3O4@SiO2) nanoparticles via surface-initiated activators generated by electron transfer atom transfer radical polymerization (SI-AGET ATRP). The size of the nanoparticles could be adjusted from 7.3 to 9.6 nm by varying the precursor concentration of iron(III) acetylacetonate. The Fe3O4 nanoparticles possessed a highly crystalline structure, and the saturation magnetization of the as-prepared magnetite was strongly related to the particle size. Furthermore, the grafted PGMA content on the magnetic nanoparticles could be controlled by varying the ligand to transition metal ratio in a N,N,N‧,N″,N″-pentamethyldiethylenetriamine (PMDETA)/CuBr2 catalyst system. The maximum grafted content was 23.1% at a ratio of [PMDETA]0/[CuBr2]0 = 2:1.

  16. Antiplatelet and thermally responsive poly(N-isopropylacrylamide) surface with nanoscale topography.

    Science.gov (United States)

    Chen, Li; Liu, Mingjie; Bai, Hao; Chen, Peipei; Xia, Fan; Han, Dong; Jiang, Lei

    2009-08-05

    Nanoscale topography was constructed on a thermally responsive poly(N-isopropylacrylamide) (PNIPAAm) surface by grafting the polymer from silicon nanowire arrays via surface-initiated atom transfer radical polymerization. The as-prepared surface showed largely reduced platelet adhesion in vitro both below and above the lower critical solution temperature (LCST) of PNIPAAm ( approximately 32 degrees C), while a smooth PNIPAAm surface exhibited antiadhesion to platelets only below the LCST. Contact angle and adhesive force measurements on oil droplets (1,2-dichloroethane) in water demonstrated that the nanoscale topography kept a relatively high ratio of water content on the as-prepared surface and played a key role in largely reducing the adhesion of platelets; however, this effect did not exist on the smooth PNIPAAm surface. The results can be used to extend the applications of PNIPAAm in the fields of biomaterials and biomedicine under human physiological temperature and provide a new strategy for fabricating other blood-compatible materials.

  17. New research progress of vegetable oil-based polyurethanes

    Directory of Open Access Journals (Sweden)

    Hongjie LIU

    2016-10-01

    Full Text Available This paper summarizes the latest progress for vegetable oil-based polyurethanes mainly from the view of thermoset and thermoplastic. Firstly, the modification methods for traditional thermoset polyurethane are introduced, including physical modification methods (filling and alloying and chemical modification methods (copolymerization grafting, crosslinking and interpenetrating polymer network. Materials used for physical modification mainly contain inorganic materials such as SiO2 and organic substances such as cellulose. Grafting copolymerization of styrene, acrylate and other monomers with polyurethane is the main method of chemical modification. The characteristics, preparations and application fields of thermoplastic polyurethane are reviewed, and the preparations, performances and applications of oleic acid-based thermoplastic polyurethane are chiefly presented. The development prospects of vegetable oil-based polyurethane are put forward. Surface-initiated living polymerization and other methods are used to controllable chemical modification of the traditional thermoset polyurethane and click chemistry method is uesd to promote multi-functionalization of the thermoplastic polyurethane.

  18. Surface modification of polysulfone membranes applied for a membrane reactor with immobilized alcohol dehydrogenase

    DEFF Research Database (Denmark)

    Hoffmann, Christian; Silau, Harald; Pinelo, Manuel

    2018-01-01

    Commercially available polysulfone (PSf) membranes with a polypropylene backing are used across a broad range of applications. However, the natural properties of the PSf surface sometimes limit their application. Here we present, how the surface of supported membranes can be heterogeneously...... activated by lithiation followed by functionalization with acid chlorides at 0 °C, permitting modification of commercial PSf membranes without compromising the mechanical integrity of the membrane. Post-functionalization polymer grafting was illustrated through both, a “grafting from” approach by surface...... initiated atom transfer radical polymerization (SI-ATRP) and by a “grafting to” approach exploiting Cu(I) catalyzed 1,3-cycloadditions of alkynes with azides (CuAAC) introducing hydrophilic polymers onto the membrane surface. Poly(1-vinyl imidazole) (pVim) grafted membranes were exploited as support...

  19. Red fluorescent chitosan nanoparticles grafted with poly(2-methacryloyloxyethyl phosphorylcholine) for live cell imaging.

    Science.gov (United States)

    Wang, Ke; Fan, Xingliang; Zhang, Xiaoyong; Zhang, Xiqi; Chen, Yi; Wei, Yen

    2016-08-01

    Poly(2-methacryloyloxyethyl phosphorylcholine) conjugated red fluorescent chitosan nanoparticles (GCC-pMPC) were facilely fabricated by "grafting from" method via surface initiated atom transfer radical polymerization (ATRP). Firstly, glutaraldehyde crosslinked red fluorescent chitosan nanoparticles (GCC NPs) with many amino groups and hydroxyl groups on their surface were prepared, which were then reacted with 2-bromoisobutyryl bromide to form GCC-Br; subsequently, poly(MPC) (pMPC) brushes were grafted onto GCC NPs surface using GCC-Br as initiator via ATRP. Compared with PEGylated nanoparticles, zwitterionic polymers modified nanoparticles demonstrated better performance in their cellular uptake. Moreover, the obtained GCC-pMPC demonstrated excellent water-dispersibility, biocompatibility, and photostability, which made them highly potential for long-term tracing applications. Importantly, the successful live cell imaging of GCC-pMPC would remarkably advance the research of their further bioapplications. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Chlorine-induced modifications in the electronic structure of Ag surfaces: a metastable deexcitation spectroscopy and photoemission comparative study

    International Nuclear Information System (INIS)

    Pasquali, L; Nannarone, S; Canepa, M; Staicu-Casagrande, E M; Esaulov, V A

    2003-01-01

    Surface-sensitive spectroscopic techniques, namely metastable deexcitation spectroscopy (MDS) and ultraviolet photoemission (UPS), have been applied to investigate the effects of chlorine chemisorption on the electronic properties (surface density of states and charge density) of Ag(100), Ag(110) and Ag(111) surfaces. Initial stages of chemisorption, up to the formation of a saturated Cl overlayer, have been examined. In particular, MDS permitted us to observe at low Cl gas exposure a progressive depletion of the Ag (5s) charge due to transfer and bonding with Cl atoms. From both MDS and UPS it was possible to observe the development of Cl (3p) bonding and anti-bonding states, the amount of their splitting increasing with coverage. Differences between chemisorption at the three surfaces have been noticed and they have been justified in terms of the different adatom packing and possible formation of small AgCl clusters (especially for the Ag(111) surface)

  1. Fabrication of surface plasmon resonance sensor surface with control of the nonspecific adsorption and affinity for the detection of 2,4,6-trinitrotoluene using an antifouling copolymer

    Directory of Open Access Journals (Sweden)

    Rui eYatabe

    2014-04-01

    Full Text Available We fabricated a surface plasmon resonance (SPR sensor using a hydrophilic polymer for the highly sensitive detection of 2,4,6-trinitrotoluene (TNT. The hydrophilic polymer was made from mono-2-(methacryloyloxyethylsuccinate (MES and 2-hydroxyethylmethacrylate (HEMA by surface-initiated atom transfer radical polymerization (SI-ATRP. The detection of TNT was carried out by displacement assay with the SPR measurement. In displacement assay, the affinity between anti-TNT antibody and the sensor surface, affects to the sensitivity. In the SPR measurement, nonspecific adsorption should be controlled because SPR sensor cannot discriminate between specific and nonspecific adsorption. Therefore, the affinity and nonspecific adsorption were controlled by changing the ratio of HEMA to MES. A detection limit of 0.4 ng/ml (ppb for TNT was achieved using a sensor surface with the lowest affinity without nonspecific adsorption.

  2. Hydrophilic nanoporous polystyrenes and 1,2-polybutadienes

    DEFF Research Database (Denmark)

    Guo, Fengxiao; Jankova Atanasova, Katja; Vigild, Martin Etchells

    2008-01-01

    Nanoporous polymers from ordered block copolymers having hydrophilic cavity surfaces were successfully prepared by two methodologies: ' 1. Nanoporous polystyrenes fromPtBA-b-PS diblock or PDMS-b-PtBA-b-PS triblock copolymer precursors by atom transfer radical polymerization (ATRP), or combination...... of living anionic polymerization~ and ATRP r~spectively. The one, PtBA block, can be modified to the hydrophilic PAA, where the dther, polydimethysiloxane (PDMS) block, can be fully degraded. Deprotection of the tert-butyl groups in PtBA and the selective etching of PDMS· chains were accomplished...... via surface-initiated ATRP. The nanoporous 1,2-PB precursor with gyroid morphology was prepared from the diblock copolymer 1,2-PB-b-PDMS after cross-linking the major 1,2-PB .. block, and etching the minor PDMS block. Then a bromoester i~itiator for ATRP was immobilized onto the pore walls using...

  3. Polymeric Nanocapsule from Silica Nanoparticle@Cross-linked Polymer Nanoparticles via One-Pot Approach

    Directory of Open Access Journals (Sweden)

    Shen Ruoping

    2009-01-01

    Full Text Available Abstract A facile strategy was developed here to prepare cross-linked polymeric nanocapsules (CP nanocapsules with silica nanoparticles as templates. The silica nanoparticle@cross-linked polymer nanoparticles were prepared by the encapsulation of the silica nanoparticles by the one-pot approach via surface-initiated atom transfer radical polymerization of hydroxyethyl acrylate in the presence ofN,N′-methylenebisacrylamide as a cross-linker from the initiator-modified silica nanoparticles. After the silica nanoparticle templates were etched with hydrofluoric acid, the CP nanocapsules with particle size of about 100 nm were obtained. The strategy developed was confirmed with Fourier transform infrared, thermogravimetric analysis and transmission electron microscopy.

  4. Colloidal lithography for fabricating patterned polymer-brush microstructures

    Directory of Open Access Journals (Sweden)

    Tao Chen

    2012-05-01

    Full Text Available We exploit a series of robust, but simple and convenient colloidal lithography (CL approaches, using a microsphere array as a mask or as a guiding template, and combine this with surface-initiated atom-transfer radical polymerization (SI-ATRP to fabricate patterned polymer-brush microstructures. The advantages of the CL technique over other lithographic approaches for the fabrication of patterned polymer brushes are (i that it can be carried out with commercially available colloidal particles at a relatively low cost, (ii that no complex equipment is required to create the patterned templates with micro- and nanoscale features, and (iii that polymer brush features are controlled simply by changing the size or chemical functionality of the microspheres or the substrate.

  5. Photothermal and biodegradable polyaniline/porous silicon hybrid nanocomposites as drug carriers for combined chemo-photothermal therapy of cancer.

    Science.gov (United States)

    Xia, Bing; Wang, Bin; Shi, Jisen; Zhang, Yu; Zhang, Qi; Chen, Zhenyu; Li, Jiachen

    2017-03-15

    To develop photothermal and biodegradable nanocarriers for combined chemo-photothermal therapy of cancer, polyaniline/porous silicon hybrid nanocomposites had been successfully fabricated via surface initiated polymerization of aniline onto porous silicon nanoparticles in our experiments. As-prepared polyaniline/porous silicon nanocomposites could be well dispersed in aqueous solution without any extra hydrophilic surface coatings, and showed a robust photothermal effect under near-infrared (NIR) laser irradiation. Especially, after an intravenous injection into mice, these biodegradable porous silicon-based nanocomposites as non-toxic agents could be completely cleared in body. Moreover, these polyaniline/porous silicon nanocomposites as drug carriers also exhibited an efficient loading and dual pH/NIR light-triggered release of doxorubicin hydrochloride (DOX, a model anticancer drug). Most importantly, assisted with NIR laser irradiation, polyaniline/PSiNPs nanocomposites with loading DOX showed a remarkable synergistic anticancer effect combining chemotherapy with photothermal therapy, whether in vitro or in vivo. Therefore, based on biodegradable PSiNPs-based nanocomposites, this combination approach of chemo-photothermal therapy would have enormous potential on clinical cancer treatments in the future. Considering the non-biodegradable nature and potential long-term toxicity concerns of photothermal nanoagents, it is of great interest and importance to develop biodegradable and photothermal nanoparticles with an excellent biocompatibility for their future clinical applications. In our experiments, we fabricated porous silicon-based hybrid nanocomposites via surface initiated polymerization of aniline, which showed an excellent photothermal effect, aqueous dispersibility, biodegradability and biocompatibility. Furthermore, after an efficient loading of DOX molecules, polyaniline/porous silicon nanocomposites exhibited the remarkable synergistic anticancer

  6. Preparation of grafted microspheres CPVA-g-PSSS and studies on their drug-carrying and colon-specific drug delivery properties

    International Nuclear Information System (INIS)

    Gao, Baojiao; Fang, Li; Men, Jiying; Zhang, Yanyan

    2013-01-01

    Sodium 4-styrene sulfonate (SSS) was graft-polymerized on the surfaces of crosslinked polyvinyl alcohol (CPVA) microspheres in a manner of surface-initiated graft-polymerization by using cerium salt-hydroxyl group redox initiation system, obtaining the grafted microspheres CPVA-g-PSSS. The chemical structure and physicochemical characters of CPVA-g-PSSS microspheres were fully characterized with infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and zeta potential determination. The aim of this work is to constitute a novel colon-specific drug delivery system via molecular design by using CPVA-g-PSSS microspheres as the drug-carrying material and by taking metronidazole (MTZ) as the model drug. The drug-carrying ability and mechanism of the grafted microspheres CPVA-g-PSSS for MTZ were investigated. Finally, in-vitro release tests for the drug-carrying microspheres were conducted. The experimental results show that in an acidic medium, the grafted microspheres CPVA-g-PSSS exhibit strong adsorption ability for MTZ by driving of electrostatic interaction, and have an adsorption capacity of 112 mg/g, displaying the high efficiency of drug-carrying. The in-vitro release behavior of the drug-carried microspheres is highly pH-sensitive. In the medium of pH = 1, the drug-carrying microspheres do not release the drug, whereas in the medium of pH = 7.4, a sudden delivery phenomenon of the drug will occur, displaying an excellent colon-specific drug delivery behavior. Highlights: ► A metronidazole colon-specific drug delivery was constituted using grafted polymeric microspheres. ► Grafted polymeric microspheres CPVA-g-PSSS were prepared via surface-initiated graft-polymerization. ► The release of the drug-carrying microspheres is highly pH-sensitive. ► The drug-carrying microspheres display an excellent colon-specific drug delivery behavior

  7. Molecularly imprinted polymer-matrix nanocomposite for enantioselective electrochemical sensing of D- and L-aspartic acid

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, Bhim Bali, E-mail: prof.bbpd@yahoo.com; Srivastava, Amrita; Tiwari, Mahavir Prasad

    2013-10-15

    A new molecularly imprinted polymer-matrix (titanium dioxide nanoparticle/multiwalled carbon nanotubes) nanocomposite was developed for the modification of pencil graphite electrode as an enantioselective sensing probe for aspartic acid isomers, prevalent at ultra trace level in aqueous and real samples. The nanocomposite having many shape complementary cavities was synthesized adopting surface initiated-activators regenerated by electron transfer for atom transfer radical polymerization. The proposed sensor has high stability, nanocomposite uniformity, good reproducibility, and enhanced electrocatalytic activity to respond oxidative peak current of L-aspartic acid quantitatively by differential pulse anodic stripping voltammetry, without any cross-reactivity in real samples. Under the optimized operating conditions, the L-aspartic acid imprinted modified electrode showed a wide linear response for L-aspartic acid within the concentration range 9.98–532.72 ng mL{sup −1}, with the minimum detection limit of 1.73–1.79 ng mL{sup −1} (S/N = 3) in aqueous and real samples. Almost similar stringent limit (1.79 ng mL{sup −1}) was obtained with cerebrospinal fluid which is typical for the primitive diagnosis of neurological disorders, caused by an acute depletion of L-aspartic acid biomarker, in clinical settings. Highlights: • We have adopted surface initiated-activators regenerated by electron transfer for atom transfer radical polymerization. • This approach takes advantage of the nanostructured ultrathin imprinted film. • Successful enantioselective sensing and ultratrace analysis of D- and L-aspartic acid. • Stringent detection limit without any non-specific false-positive contribution.

  8. Preparation of grafted microspheres CPVA-g-PSSS and studies on their drug-carrying and colon-specific drug delivery properties

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Baojiao, E-mail: gaobaojiao@126.com [Department of Chemical Engineering, North University of China, Taiyuan 030051, People' s Republic of China (China); Fang, Li [School of Chemistry and Chemical engineering, Shanxi University, Taiyuan 030006 (China); Men, Jiying; Zhang, Yanyan [Department of Chemical Engineering, North University of China, Taiyuan 030051, People' s Republic of China (China)

    2013-04-01

    Sodium 4-styrene sulfonate (SSS) was graft-polymerized on the surfaces of crosslinked polyvinyl alcohol (CPVA) microspheres in a manner of surface-initiated graft-polymerization by using cerium salt-hydroxyl group redox initiation system, obtaining the grafted microspheres CPVA-g-PSSS. The chemical structure and physicochemical characters of CPVA-g-PSSS microspheres were fully characterized with infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and zeta potential determination. The aim of this work is to constitute a novel colon-specific drug delivery system via molecular design by using CPVA-g-PSSS microspheres as the drug-carrying material and by taking metronidazole (MTZ) as the model drug. The drug-carrying ability and mechanism of the grafted microspheres CPVA-g-PSSS for MTZ were investigated. Finally, in-vitro release tests for the drug-carrying microspheres were conducted. The experimental results show that in an acidic medium, the grafted microspheres CPVA-g-PSSS exhibit strong adsorption ability for MTZ by driving of electrostatic interaction, and have an adsorption capacity of 112 mg/g, displaying the high efficiency of drug-carrying. The in-vitro release behavior of the drug-carried microspheres is highly pH-sensitive. In the medium of pH = 1, the drug-carrying microspheres do not release the drug, whereas in the medium of pH = 7.4, a sudden delivery phenomenon of the drug will occur, displaying an excellent colon-specific drug delivery behavior. Highlights: ► A metronidazole colon-specific drug delivery was constituted using grafted polymeric microspheres. ► Grafted polymeric microspheres CPVA-g-PSSS were prepared via surface-initiated graft-polymerization. ► The release of the drug-carrying microspheres is highly pH-sensitive. ► The drug-carrying microspheres display an excellent colon-specific drug delivery behavior.

  9. Neutral hydrophilic coatings for capillary electrophoresis prepared by controlled radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, Fabián H.; Gómez, Jorge E.; Espinal, José H.; Sandoval, Junior E., E-mail: junior.sandoval@correounivalle.edu.co

    2016-12-15

    In the present study, porous silica particles as well as impervious fused-silica wafers and capillary tubes were modified with hydrophilic polymers (hydroxylated polyacrylamides and polyacrylates), using a surface-confined grafting procedure based on atom transfer radical polymerization (ATRP) which was also surface-initiated from α-bromoisobutyryl groups. Initiator immobilization was achieved by hydrosilylation of allyl alcohol on hydride silica followed by esterification of the resulting propanol-bonded surface with α-bromoisobutyryl bromide. Elemental analysis, IR and NMR spectroscopies on silica micro-particles, atomic force microscopy, ellipsometry and profilometry on fused-silica wafers, as well as CE on fused-silica tubes were used to characterize the chemically modified silica substrate at different stages. We studied the effect of monomer concentration as well as cross-linker on the ability of the polymer film to reduce electroosmosis and to prevent protein adsorption (i. e., its non-fouling capabilities) and found that the former was rather insensitive to both parameters. Surface deactivation towards adsorption was somewhat more susceptible to monomer concentration and appeared also to be favored by a low concentration of the cross-linker. The results show that hydrophilic polyacrylamide and polyacrylate coatings of controlled thickness can be prepared by ATRP under very mild polymerization conditions (aqueous solvent, room temperature and short reaction times) and that the coated capillary tubes exhibit high efficiencies for protein separations (0.3–0.6 million theoretical plates per meter) as well as long-term hydrolytic stability under the inherently harsh conditions of capillary isoelectric focusing. Additionally, there was no adsorption of lysozyme on the coated surface as indicated by a complete recovery of the basic enzyme. Furthermore, since polymerization is confined to the inner capillary surface, simple precautions (e.g., solution

  10. Control the wettability of poly(n-isopropylacrylamide-co-1-adamantan-1-ylmethyl acrylate) modified surfaces: the more Ada, the bigger impact?

    Science.gov (United States)

    Shi, Xiu-Juan; Chen, Gao-Jian; Wang, Yan-Wei; Yuan, Lin; Zhang, Qiang; Haddleton, David M; Chen, Hong

    2013-11-19

    Surface-initiated SET-LRP was used to synthesize polymer brush containing N-isopropylacrylamide and adamantyl acrylate using Cu(I)Cl/Me6-TREN as precursor catalyst and isopropanol/H2O as solvent. Different reaction conditions were explored to investigate the influence of different parameters (reaction time, catalyst concentration, monomer concentration) on the polymerization. Copolymers with variable 1-adamantan-1-ylmethyl acrylate (Ada) content and comparable thickness were synthesized onto silicon surfaces. Furthermore, the hydrophilic and bioactive molecule β-cyclodextrin-(mannose)7 (CDm) was synthesized and complexed with adamantane via host-guest interaction. The effect of adamantane alone and the effect of CDm together with adamantane on the wettability and thermoresponsive property of surface were investigated in detail. Experimental and molecular structure analysis showed that Ada at certain content together with CDm has the greatest impact on surface wettability. When Ada content was high (20%), copolymer-CDm surfaces showed almost no CDm complexed with Ada as the result of steric hindrance.

  11. Role of step edges on the structure formation of α-6T on Ag(441)

    Science.gov (United States)

    Wagner, Thorsten; Fritz, Daniel Roman; Rudolfová, Zdena; Zeppenfeld, Peter

    2018-01-01

    Controlling the orientation of organic molecules on surfaces is important in order to tune the physical properties of the organic thin films and, thereby, increase the performance of organic thin film devices. Here, we present a scanning tunneling microscopy (STM) and photoelectron emission microscopy (PEEM) study of the deposition of the organic dye pigment α-sexithiophene (α-6T) on the vicinal Ag(441) surface. In the presence of the steps on the Ag(441) surface, the α-6T molecules exclusively align parallel to the step edges oriented along the [1 1 bar0]-direction of the substrate. The STM results further reveal that the adsorption of the α-6T molecules is accompanied by various restructuring of the substrate surface: Initially, the molecules prefer the Ag(551) building blocks of the Ag(441) surface. The Ag(551) termination of the terraces is then changed to a predominately Ag(331) one upon completion of the first α-6T monolayer. When closing the two layer thick wetting layer, the original ratio of Ag(331) and Ag(551) building blocks ( ≈ 1:1) is recovered, but a phase separation into microfacets, which are composed either of Ag(331) or of Ag(551) building blocks, is found.

  12. Green chemical functionalization of multiwalled carbon nanotubes with poly(ε-caprolactone) in ionic liquids

    International Nuclear Information System (INIS)

    Yang Yingkui; Qiu Shengqiang; He Chengen; He Wenjie; Yu Linjuan; Xie Xiaolin

    2010-01-01

    Multiwalled carbon nanotubes (MWNTs) have been successfully functionalized by free radical addition of 4,4'-azobis(4-cyanopentanol) in aqueous media to generate the terminal-hydroxyl-modified MWNTs (MWNT-OH), followed by surface-initiated in situ ring-opening polymerization of ε-caprolactone in 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF 4 ) to obtain poly(ε-caprolactone)-grafted MWNTs (MWNT-g-PCL). Spectroscopic methods in conjunction with electron microscopy clearly revealed that hairy PCL chains were chemically attached to the surface of MWNTs to form core-shell nanostructures with the latter as core and the former as shell. With increasing polymerization time from 2 to 8 h, the amount of the grafted-PCL synthesized in BmimBF 4 varies from 30.6 to 62.7 wt%, which is clearly higher than that (41.5 wt%) obtained in 1,2-dichlorobenzene under comparable conditions (8 h). The proposed methodology here uses water and room temperature ionic liquids (RTILs) as the reaction media and promises a green chemical process for functionalizing nanotubes.

  13. Improved surface hydrophilicity and antifouling property of polysulfone ultrafiltration membrane with poly(ethylene glycol) methyl ether methacrylate grafted graphene oxide nanofillers

    Science.gov (United States)

    Wang, Haidong; Lu, Xiaofei; Lu, Xinglin; Wang, Zhenghui; Ma, Jun; Wang, Panpan

    2017-12-01

    In this study, the GO-g-P(PEGMA) nanoplates were first synthesized by grafting hydrophilic poly (poly (ethylene glycol) methyl ether methacrylate) via surface-initiated atom transfer radical polymerization (SI-ATRP) method. A novel polysulfone (PSF) nanocomposite membrane using GO-g-P(PEGMA) nanoplates as nanofillers was fabricated. FTIR, TGA, 1H NMR, GPC and TEM were applied to verify the successful synthesis of the prepared nanoplates, while SEM, AFM, XPS, contact angle goniometry and filtration experiments were used to characterize the fabricated nanocomposite membranes. It was found that the new prepared nanofillers were well dispersed in organic PSF matrix, and the PSF/GO-g-P(PEGMA) nanocomposite membrane showed significant improvements in water flux and flux recovery rate. Based on the results of resistance-in-series model, the nanocomposite membrane exhibited superior resistance to the irreversible fouling. The excellent filtration and antifouling performance are attributed to the segregation of GO-g-P(PEMGA) nanofillers toward the membrane surface and the pore walls. Notably, the blended nanofillers appeared a stable retention in/on nanocomposite membrane after 30 days of washing time. The demonstrated method of synthesis GO-g-P(PEGMA) in this study can also be extended to preparation of other nanocomposite membrane in future.

  14. Study of Temperature Wave Propagation in Superfluid Helium Focusing on Radio-Frequency Cavity Cooling

    CERN Document Server

    Koettig, T; Avellino, S; Junginger, T; Bremer, J

    2015-01-01

    Oscillating Superleak Transducers (OSTs) can be used to localize quenches of superconducting radio-frequency cavities. Local hot spots at the cavity surface initiate temperature waves in the surrounding superfluid helium that acts as cooling fluid at typical temperatures in the range of 1.6 K to 2 K. The temperature wave is characterised by the properties of superfluid helium such as the second sound velocity. For high heat load densities second sound velocities greater than the standard literature values are observed. This fast propagation has been verified in dedicated small scale experiments. Resistors were used to simulate the quench spots under controlled conditions. The three dimensional propagation of second sound is linked to OST signals. The aim of this study is to improve the understanding of the OST signal especially the incident angle dependency. The characterised OSTs are used as a tool for quench localisation on a real size cavity. Their sensitivity as well as the time resolution was proven to b...

  15. Novel Resorbable and Osteoconductive Calcium Silicophosphate Scaffold Induced Bone Formation

    Directory of Open Access Journals (Sweden)

    Patricia Ros-Tárraga

    2016-09-01

    Full Text Available This aim of this research was to develop a novel ceramic scaffold to evaluate the response of bone after ceramic implantation in New Zealand (NZ rabbits. Ceramics were prepared by the polymer replication method and inserted into NZ rabbits. Macroporous scaffolds with interconnected round-shaped pores (0.5–1.5 mm = were prepared. The scaffold acted as a physical support where cells with osteoblastic capability were found to migrate, develop processes, and newly immature and mature bone tissue colonized on the surface (initially and in the material’s interior. The new ceramic induced about 62.18% ± 2.28% of new bone and almost complete degradation after six healing months. An elemental analysis showed that the gradual diffusion of Ca and Si ions from scaffolds into newly formed bone formed part of the biomaterial’s resorption process. Histological and radiological studies demonstrated that this porous ceramic scaffold showed biocompatibility and excellent osteointegration and osteoinductive capacity, with no interposition of fibrous tissue between the implanted material and the hematopoietic bone marrow interphase, nor any immune response after six months of implantation. No histological changes were observed in the various organs studied (para-aortic lymph nodes, liver, kidney and lung as a result of degradation products being released.

  16. Assimilation of SMOS Retrieved Soil Moisture into the Land Information System

    Science.gov (United States)

    Blankenship, Clay; Case, Jonathan; Zavodsky, Bradley; Jedlovec, Gary

    2014-01-01

    Soil moisture retrievals from the Soil Moisture and Ocean Salinity (SMOS) instrument are assimilated into the Noah land surface model (LSM) within the NASA Land Information System (LIS). Before assimilation, SMOS retrievals are bias-corrected to match the model climatological distribution using a Cumulative Distribution Function (CDF) matching approach. Data assimilation is done via the Ensemble Kalman Filter. The goal is to improve the representation of soil moisture within the LSM, and ultimately to improve numerical weather forecasts through better land surface initialization. We present a case study showing a large area of irrigation in the lower Mississippi River Valley, in an area with extensive rice agriculture. High soil moisture value in this region are observed by SMOS, but not captured in the forcing data. After assimilation, the model fields reflect the observed geographic patterns of soil moisture. Plans for a modeling experiment and operational use of the data are given. This work helps prepare for the assimilation of Soil Moisture Active/Passive (SMAP) retrievals in the near future.

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

    Science.gov (United States)

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

    2010-11-15

    A new and efficient approach to obtaining molecularly imprinted polymers (MIPs) with both pure water-compatible (i.e., applicable in the pure aqueous environments) and stimuli-responsive binding properties is described, whose proof-of-principle is demonstrated by the facile modification of the preformed MIP microspheres via surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAAm). The presence of poly(NIPAAm) (PNIPAAm) brushes on the obtained MIP microspheres was confirmed by FT-IR as well as the water dispersion and static contact angle experiments, and some quantitative information including the molecular weights and polydispersities of the grafted polymer brushes, the thickness of the polymer brush layers, and their grafting densities was provided. In addition, the binding properties of the ungrafted and grafted MIPs/NIPs in both methanol/water (4/1, v/v) and pure water solutions were also investigated. The introduction of PNIPAAm brushes onto the MIP microspheres has proven to significantly improve their surface hydrophilicity and impart stimuli-responsive properties to them, leading to their pure water-compatible and thermo-responsive binding properties. The application of the facile surface-grafting approach, together with the versatility of RAFT polymerization and the availability of many different functional monomers, makes the present methodology a general and promising way to prepare water-compatible and stimuli-responsive MIPs for a wide range of templates. Copyright © 2010 Elsevier B.V. All rights reserved.

  18. Temperature-Responsive Hierarchical Polymer Brushes Switching from Bactericidal to Cell Repellency.

    Science.gov (United States)

    Wang, Xianghong; Yan, Shunjie; Song, Lingjie; Shi, Hengchong; Yang, Huawei; Luan, Shifang; Huang, Yubin; Yin, Jinghua; Khan, Ather Farooq; Zhao, Jie

    2017-11-22

    Unlike conventional poly(N-isopropylacrylamide) (PNIPAM)-based surfaces switching from bactericidal activity to bacterial repellency upon decreasing temperature, we developed a hierarchical polymer architecture, which could maintain bactericidal activities at room temperature while presenting bacterial repellency at physiological temperature. In this architecture, a thermoresponsive bactericidal upper layer consisting of PNIPAM-based copolymer and vancomycin (Van) moieties was built on an antifouling poly(sulfobetaine methacrylate) (PSBMA) bottom layer via sequential surface-initiated photoiniferter-mediated polymerization. At room temperature below the lower critical solution temperature (LCST), the PNIPAM-based upper layer was stretchable, facilitating contact killing of bacteria by Van. At physiological temperature (above the LCST), the PNIPAM-based layer collapsed, thus leading to the burial of Van and exposure of bottom PSBMA brushes, finally displaying notable performances in bacterial inhibition, dead bacteria detachment, and biocompatibility, simultaneously. Our strategy provides a novel pathway in the rational design of temperature-sensitive switchable surfaces, which shows great advantages in the real-world infection-resistant applications.

  19. TMEM59 potentiates Wnt signaling by promoting signalosome formation.

    Science.gov (United States)

    Gerlach, Jan P; Jordens, Ingrid; Tauriello, Daniele V F; van 't Land-Kuper, Ineke; Bugter, Jeroen M; Noordstra, Ivar; van der Kooij, Johanneke; Low, Teck Y; Pimentel-Muiños, Felipe X; Xanthakis, Despina; Fenderico, Nicola; Rabouille, Catherine; Heck, Albert J R; Egan, David A; Maurice, Madelon M

    2018-04-09

    Wnt/β-catenin signaling controls development and adult tissue homeostasis by regulating cell proliferation and cell fate decisions. Wnt binding to its receptors Frizzled (FZD) and low-density lipoprotein-related 6 (LRP6) at the cell surface initiates a signaling cascade that leads to the transcription of Wnt target genes. Upon Wnt binding, the receptors assemble into large complexes called signalosomes that provide a platform for interactions with downstream effector proteins. The molecular basis of signalosome formation and regulation remains elusive, largely due to the lack of tools to analyze its endogenous components. Here, we use internally tagged Wnt3a proteins to isolate and characterize activated, endogenous Wnt receptor complexes by mass spectrometry-based proteomics. We identify the single-span membrane protein TMEM59 as an interactor of FZD and LRP6 and a positive regulator of Wnt signaling. Mechanistically, TMEM59 promotes the formation of multimeric Wnt-FZD assemblies via intramembrane interactions. Subsequently, these Wnt-FZD-TMEM59 clusters merge with LRP6 to form mature Wnt signalosomes. We conclude that the assembly of multiprotein Wnt signalosomes proceeds along well-ordered steps that involve regulated intramembrane interactions. Copyright © 2018 the Author(s). Published by PNAS.

  20. Synthesis of magnetic molecularly imprinted polymers by reversible addition fragmentation chain transfer strategy and its application in the Sudan dyes residue analysis.

    Science.gov (United States)

    Xie, Xiaoyu; Chen, Liang; Pan, Xiaoyan; Wang, Sicen

    2015-07-31

    Magnetic molecularly imprinted polymers (MMIPs) have become a hotspot owing to the dual functions of target recognition and magnetic separation. In this study, the MMIPs were obtained by the surface-initiated reversible addition fragmentation chain transfer (RAFT) polymerization using Sudan I as the template. The resultant MMIPs were characterized by transmission electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, vibrating sample magnetometer, and X-ray diffraction. Benefiting from the controlled/living property of the RAFT strategy, the uniform MIP layer was successfully grafted on the surface of RAFT agent-modified Fe3O4@SiO2 nanoparticles, favoring the fast mass transfer and rapid binding kinetics. The developed MMIPs were used as the solid-phase extraction sorbents to selectively extract four Sudan dyes (Sudan I, II, III, and IV) from chili powder samples. The recoveries of the spiked samples in chili powder samples ranged from 74.1 to 93.3% with RSD lower than 6.4% and the relative standard uncertainty lower than 0.029. This work provided a good platform for the extraction and removal of Sudan dyes in complicated matrixes and demonstrated a bright future for the application of the well-constructed MMIPs in the field of solid-phase extraction. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Distribution of 239Pu in the skeleton of the tree shrew (Tupaia belangeri) between 15 and 50 months after injection

    International Nuclear Information System (INIS)

    Sontag, W.; Seidel, A.

    1987-01-01

    The macroscopic and microscopic distribution of intramuscularly injected, essentially monomeric, 239 Pu was studied in the skeleton of the adult tree shrew (Tupaia belangeri). Data for between 15 and 50 months after injection are presented and compared with data from earlier time points. Between 83 and 500 days after injection nuclide content and wet weight of the skeleton decreased to a constant level at about 55% of maximum. The microscopic distribution was analysed in distal femora, proximal humerus, proximal tibia and lumbar vertebra over the whole time; additionally at some selected time points proximal femur, femur shaft, distal humerus and distal tibia were analysed. The initial endosteal surface activity ranged from 3.8 to 5.3 Bq/cm 2 , decreased to a minimum at about 1000 days after injection and increased thereafter. Similar behaviour was found for dose rate near bone surfaces (initially about 0.075 Gy/day on endosteal surfaces). In deep bone and deep marrow the dose rate was negligible, about 0.008 Gy/day and 0.001 Gy/day, respectively. The average cumulative dose 1500 days after injection was about 67 Gy on the endosteum; six times greater than the cumulative dose calculated from the mean concentration of plutonium in the whole skeleton. Tupaia data are compared to monkeys, dogs and rats. (author)

  2. GIFAD for He/KCl(001). Structure in the pattern for 〈 110 〉 incidence as a measure of the projectile-cation interaction

    Science.gov (United States)

    Bocan, G. A.; Gravielle, M. S.

    2018-04-01

    In this article we address grazing incidence fast atom diffraction (GIFAD) for the He/KCl(001) system, for which a systematic experimental study was recently reported [E. Meyer, Ph.D dissertation, Humboldt-Universität, Berlin, Germany, 2015]. Our theoretical model is built from a projectile-surface interaction obtained from Density Functional Theory (DFT) calculations and the Surface Initial-Value Representation (SIVR), which is a semi-quantum approach to describe the scattering process. For incidence along the 〈 100 〉 and 〈 110 〉 directions, we present and discuss the main features of our interaction potential, the dependence of the rainbow angle with the impact energy normal to the surface, and the simulated GIFAD patterns, which reproduce the main aspects of the reported experimental charts. The features of the diffraction charts for He/KCl(001) are related to the averaged equipotential curves of the system and a comparison is established with the case of He/LiF(001). The marked differences observed for 〈 110 〉 incidence are explained as due to the much larger size of the K+ ion relative to that of Li+.

  3. Polymer brushes for antibiofouling and lubrication

    Directory of Open Access Journals (Sweden)

    Wufang Yang

    2017-09-01

    Full Text Available Surface-initiated atom transfer radical polymerization (SI-ATRP could provide many merits for the preparation of polymer brush, such as the well-defined chemical configurations, gradient, architecture and thickness. To date, SI-ATRP has been a popular strategy to tailor the physicochemical properties of material interfaces. In this short review, the recent progresses of our group and others’ in preparing methodologies of polymer brushes through SI-ATRP are highlighted in detail, including the fundamental mechanistic and superior characteristics. Some novel SI-ATRP techniques which are trigged by external-stimuli and the preparation of micro/nanoscale polymer hierarchical architecture with tailorable chemical components are also emphasized. Besides, since the polymer brush with different chemical components (e.g., single-component and multi-components and multi-scale structural characteristics shows great impact on the physicochemical properties at interface and polymer brush are generally sensitive to the external stimuli, the polymer chains modified surfaces acted as smart materials show great potential in many fields. The application advancements of polymer brush are reviewed mainly in two aspects, including antibiofouling and lubrication. Finally, the opportunities and challenges for further application are addressed.

  4. Hydrogeology, Chemical and Microbial Activity Measurement Through Deep Permafrost

    Science.gov (United States)

    Stotler, R.L.; Frape, S.K.; Freifeld, B.M.; Holden, B.; Onstott, T.C.; Ruskeeniemi, T.; Chan, E.

    2011-01-01

    Little is known about hydrogeochemical conditions beneath thick permafrost, particularly in fractured crystalline rock, due to difficulty in accessing this environment. The purpose of this investigation was to develop methods to obtain physical, chemical, and microbial information about the subpermafrost environment from a surface-drilled borehole. Using a U-tube, gas and water samples were collected, along with temperature, pressure, and hydraulic conductivity measurements, 420 m below ground surface, within a 535 m long, angled borehole at High Lake, Nunavut, Canada, in an area with 460-m-thick permafrost. Piezometric head was well above the base of the permafrost, near land surface. Initial water samples were contaminated with drill fluid, with later samples values ???5??? lower than the local surface water. The fluid isotopic composition was affected by the permafrost-formation process. Nonbacteriogenic CH4 was present and the sample location was within methane hydrate stability field. Sampling lines froze before uncontaminated samples from the subpermafrost environment could be obtained, yet the available time to obtain water samples was extended compared to previous studies. Temperature measurements collected from a distributed temperature sensor indicated that this issue can be overcome easily in the future. The lack of methanogenic CH4 is consistent with the high sulfate concentrations observed in cores. The combined surface-drilled borehole/U-tube approach can provide a large amount of physical, chemical, and microbial data from the subpermafrost environment with few, controllable, sources of contamination. ?? 2010 The Author(s). Journal compilation ?? 2010 National Ground Water Association.

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

    Science.gov (United States)

    Lilge, Inga; Schönherr, Holger

    2016-01-26

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

  6. Buried, covalently attached RGD peptide motifs in poly(methacrylic acid) brush layers: the effect of brush structure on cell adhesion.

    Science.gov (United States)

    Navarro, Melba; Benetti, Edmondo M; Zapotoczny, Szczepan; Planell, Josep A; Vancso, G Julius

    2008-10-07

    Iniferter-mediated surface-initiated photopolymerization was used to graft poly(methacrylic acid) (PMAA) brush layers obtained from surface-attached iniferters in self-assembled monolayers to a gold surface. The tethered chains were subsequently functionalized with the cell-adhesive arginine-glycine-aspartic acid (RGD) motif. The modified brushes were extended by reinitiating the polymerization to obtain an additional layer of PMAA, thereby burying the peptide-functionalized segments inside the brush structure. Contact angle measurements and Fourier transform infrared (FTIR) spectroscopy were employed to characterize the wettability and the chemical properties of these platforms. Time of flight secondary ion mass spectroscopy (TOF-SIMS) measurements were performed to monitor the chemical composition of the polymer layer as a function of the distance to the gold surface and obtain information concerning the depth of the RGD motifs inside the brush structure. The brush thickness was evaluated as a function of the polymerization (i.e., UV-irradiation) time with atomic force microscopy (AFM) and ellipsometry. Cell adhesion tests employing human osteoblasts were performed on substrates with the RGD peptides exposed at the surface as well as covered by a PMAA top brush layer. Immunofluorescence studies demonstrated a variation of the cell morphology as a function of the position of the peptide units along the grafted chains.

  7. Predictability of soil moisture and river flows over France for the spring season

    Directory of Open Access Journals (Sweden)

    S. Singla

    2012-01-01

    Full Text Available Sources of spring predictability of the hydrological system over France were studied on a seasonal time scale over the 1960–2005 period. Two random sampling experiments were set up in order to test the relative importance of the land surface initial state and the atmospheric forcing. The experiments were based on the SAFRAN-ISBA-MODCOU hydrometeorological suite which computed soil moisture and river flow forecasts over a 8-km grid and more than 880 river-gauging stations. Results showed that the predictability of hydrological variables primarily depended on the seasonal atmospheric forcing (mostly temperature and total precipitation over most plains, whereas it mainly depended on snow cover over high mountains. However, the Seine catchment area was an exception as the skill mainly came from the initial state of its large and complex aquifers. Seasonal meteorological hindcasts with the Météo-France ARPEGE climate model were then used to force the ISBA-MODCOU hydrological model and obtain seasonal hydrological forecasts from 1960 to 2005 for the entire March-April-May period. Scores from this seasonal hydrological forecasting suite could thus be compared with the random atmospheric experiment. Soil moisture and river flow skill scores clearly showed the added value in seasonal meteorological forecasts in the north of France, contrary to the Mediterranean area where values worsened.

  8. A new Brazilian Passiflora leafminer: Spinivalva gaucha, gen. n., sp. n. (Lepidoptera, Gracillariidae, Gracillariinae), the first gracillariid without a sap-feeding instar.

    Science.gov (United States)

    Brito, Rosângela; Gonçalves, Gislene L; Vargas, Hector A; Moreira, Gilson R P

    2013-01-01

    Male, female, pupa, larva and egg of a new genus and species of Gracillariidae (Gracillariinae), Spinivalva gaucha Moreira and Vargas from southern Brazil are described and illustrated with the aid of optical and scanning electron microscopy. A preliminary analysis of mitochondrial DNA sequences including members of related lineages is also provided. The immature stages are associated with Passiflora actinia, Passiflora misera and Passiflora suberosa (Passifloraceae), and build mines on the adaxial leaf surface. Initially the mines are serpentine in shape, but later in larval ontogeny become a blotch type. Although the larvae are hypermetamorphic as in other Gracillariidae, there is no sap-feeding instar in Spinivalva gaucha; the larva feeds on the palisade parenchyma, thus producing granular frass during all instars. Pupation occurs outside the mine; prior to pupating, the larva excretes numerous bubbles that are placed in rows on the lateral margins of the cocoon external surface. This is the second genus of gracillariid moth described for the Atlantic Rain Forest, and the second gracillariid species known to be associated with Passifloraceae.

  9. Improved antifouling properties of photobioreactors by surface grafted sulfobetaine polymers.

    Science.gov (United States)

    Wang, Dongwei; Wu, Xia; Long, Lixia; Yuan, Xubo; Zhang, Qinghua; Xue, Shengzhang; Wen, Shumei; Yan, Chenghu; Wang, Jianming; Cong, Wei

    2017-11-01

    To improve the antifouling (AF) properties of photobioreactors (PBR) for microalgal cultivation, using trihydroxymethyl aminomethane (tris) as the linking agent, a series of polyethylene (PE) films grafted with sulfobetaine (PE-SBMA) with grafting density ranging from 23.11 to 112 μg cm -2 were prepared through surface-initiated atom transfer radical polymerization (SI-ATRP). It was found that the contact angle of PE-SBMA films decreased with the increase in the grafting density. When the grafting density was 101.33 μg cm -2 , it reached 67.27°. Compared with the PE film, the adsorption of protein on the PE-SBMA film decreased by 79.84% and the total weight of solid and absorbed microalgae decreased by 54.58 and 81.69%, respectively. Moreover, the transmittance of PE-SBMA film recovered to 86.03% of the initial value after cleaning, while that of the PE film recovered to only 47.27%. The results demonstrate that the AF properties of PE films were greatly improved on polySBMA-grafted surfaces.

  10. Molecularly imprinted polymer-matrix nanocomposite for enantioselective electrochemical sensing of D- and L-aspartic acid.

    Science.gov (United States)

    Prasad, Bhim Bali; Srivastava, Amrita; Tiwari, Mahavir Prasad

    2013-10-01

    A new molecularly imprinted polymer-matrix (titanium dioxide nanoparticle/multiwalled carbon nanotubes) nanocomposite was developed for the modification of pencil graphite electrode as an enantioselective sensing probe for aspartic acid isomers, prevalent at ultra trace level in aqueous and real samples. The nanocomposite having many shape complementary cavities was synthesized adopting surface initiated-activators regenerated by electron transfer for atom transfer radical polymerization. The proposed sensor has high stability, nanocomposite uniformity, good reproducibility, and enhanced electrocatalytic activity to respond oxidative peak current of L-aspartic acid quantitatively by differential pulse anodic stripping voltammetry, without any cross-reactivity in real samples. Under the optimized operating conditions, the L-aspartic acid imprinted modified electrode showed a wide linear response for L-aspartic acid within the concentration range 9.98-532.72 ng mL(-1), with the minimum detection limit of 1.73-1.79 ng mL(-1) (S/N=3) in aqueous and real samples. Almost similar stringent limit (1.79 ng mL(-1)) was obtained with cerebrospinal fluid which is typical for the primitive diagnosis of neurological disorders, caused by an acute depletion of L-aspartic acid biomarker, in clinical settings. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Modification of cellulose nanocrystal via SI-ATRP of styrene and the mechanism of its reinforcement of polymethylmethacrylate.

    Science.gov (United States)

    Yin, Y; Tian, X; Jiang, X; Wang, H; Gao, W

    2016-05-20

    Cellulose nanocrystal (CNC) is a promising strengthener but is used limitedly since its poor compatibility with organic materials. The graft polymerization of styrene via surface-initiated atom transfer radical polymerization (SI-ATRP) of cellulose nanocrystal is adopted to modify its thermo-stability and compatibility. The modified crystals have been dosed into polymethylmethacrylate (PMMA) nanocomposites by the solution casting. The polymeric layer on the surface of CNCs should improve the thermal stability of CNCs, and provide significant dispersibility and compatibilization for the nanocomposites. Thermogravimetry analysis proved that the initial degrade temperature of CNC was increased 50 °C with the modification. The scanning electronic microscope showed that the modified CNCs homogeneously dispersed in PMMA matrix. Breaking strength and elongation at break of the composites were improved, which was attributed to the reinforcement of CNCs modified with styrene. Transmittance of nanocomposite films measurement showed that the transmittance of PMMA/1%CNC was almost close to that of pure PMMA. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Assessing the Association Between Asthma and Air Quality in the Presence of Wildfires

    Science.gov (United States)

    Young, L. J.; Al-Hamdan, M. Z.; Lopiano, K. K.; Crosson, W. L.; Gotway, C. A.; DuClos, C.; Jordan, M.; Estes, M. G.; Luvall, J. C.; Estes, S. M.; Xu, X.; Holt, N. M.; Leary, E.

    2012-12-01

    Asthma hospital/emergency room (patient) data are used as the foundation for creating a health outcome indicator of human response to environmental air quality. Daily U.S. Environmental Protection Agency (EPA) Air Quality System (AQS) fine particulates (PM2.5) ground data and the U.S. National Aeronautical Space Administration (NASA) MODIS aerosol optical depth (AOD) data were acquired and processed for years of 2007 and 2008. Figure 1 shows the PM2.5 annual mean composite of all the 2007 B-spline daily surfaces. Initial models for predicting the number of weekly asthma cases within a Florida county has focused on environmental variables. Weekly maximums of PM2.5, relative humidity, and the proportions of the county with smoke and fire were the environmental variables included in the model. Cosine and sine functions of time were used to account for seasonality in asthma cases. Counties were considered to be random effects, thereby adjusting for differences in socio-demographics and other factors. The 2007 predictions for Miami-Dade county when using B-splines PM2.5 are displayed in Figures 2.; PM2.5 annual mean composite of all the 2007 daily surfaces developed using Al-Hamdan et al (2009) B-spline fitting algorithm ; Predicted and observed weekly asthma cases presenting to hospitals or emergency rooms in Miami-Dade county in Florida during 2007

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

    Science.gov (United States)

    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.

  14. Facile surface modification of silicone rubber with zwitterionic polymers for improving blood compatibility.

    Science.gov (United States)

    Liu, Pingsheng; Chen, Qiang; Yuan, Bo; Chen, Mengzhou; Wu, Shishan; Lin, Sicong; Shen, Jian

    2013-10-01

    A facile approach to modify silicone rubber (SR) membrane for improving the blood compatibility was investigated. The hydrophobic SR surface was firstly activated by air plasma, after which an initiator was immobilized on the activated surface for atom transfer radical polymerization (ATRP). Three zwitterionic polymers were then grafted from SR membrane via surface-initiated atom transfer radical polymerization (SI-ATRP). The surface composition, wettability, and morphology of the membranes before and after modification were characterized by X-ray photoelectron spectroscopy (XPS), static water contact angle (WCA) measurement, and atomic force microscopy (AFM). Results showed that zwitterionic polymers were successfully grafted from SR surfaces, which remarkably improved the wettability of the SR surface. The blood compatibility of the membranes was evaluated by protein adsorption and platelet adhesion tests in vitro. As observed, all the zwitterionic polymer modified surfaces have improved resistance to nonspecific protein adsorption and have excellent resistance to platelet adhesion, showing significantly improved blood compatibility. This work should inspire many creative uses of SR based materials for biomedical applications such as vessel, catheter, and microfluidics. Copyright © 2013 Elsevier B.V. All rights reserved.

  15. Immobilization of Poly(1,1-dimethysilacyclobutane by Means of Anionic Ring-Opening Polymerization on Organic Nanoparticles and Reinvestigation of Crystallization

    Directory of Open Access Journals (Sweden)

    Matthias Rehahn

    2013-03-01

    Full Text Available In the present study, the synthesis of poly(1,1-dimethylsilacyclobutane (PDMSB by anionic ring opening polymerization (ROP is reinvestigated, leading to narrowly distributed molar masses (polydispersities 1.04–1.15 in the range of 2.3 to 60 kg mol−1. Investigations of thermal behavior for low molar mass PDMSB revealed an untypical multiple peaks melting phenomenon, which at first glance, seems to be of the same origin as low molar mass poly(ethylene oxides. Small angle X-ray scattering (SAXS and X-ray diffraction (XRD measurements are done, proving the fast crystallization and subsequent recrystallization for investigated low molar mass samples. Synthetic attempts are expanded to the surface-initiated anionic ROP of 1,1-dimethylsilacyclobutane (DMSB monomer from the surface of cross-linked polystyrene (PS nanoparticles. Novel polycarbosilanes (PCS/organic core/shell particles are obtained, which are investigated by using transmission electron microscopy (TEM and dynamic light scattering (DLS experiments. First insights into the crystallization behavior of surface-attached PDMSB chains reveal that crystallization seems to be hindered.

  16. Novel Resorbable and Osteoconductive Calcium Silicophosphate Scaffold Induced Bone Formation

    Science.gov (United States)

    Ros-Tárraga, Patricia; Mazón, Patricia; Rodríguez, Miguel A.; Meseguer-Olmo, Luis; De Aza, Piedad N.

    2016-01-01

    This aim of this research was to develop a novel ceramic scaffold to evaluate the response of bone after ceramic implantation in New Zealand (NZ) rabbits. Ceramics were prepared by the polymer replication method and inserted into NZ rabbits. Macroporous scaffolds with interconnected round-shaped pores (0.5–1.5 mm = were prepared). The scaffold acted as a physical support where cells with osteoblastic capability were found to migrate, develop processes, and newly immature and mature bone tissue colonized on the surface (initially) and in the material’s interior. The new ceramic induced about 62.18% ± 2.28% of new bone and almost complete degradation after six healing months. An elemental analysis showed that the gradual diffusion of Ca and Si ions from scaffolds into newly formed bone formed part of the biomaterial’s resorption process. Histological and radiological studies demonstrated that this porous ceramic scaffold showed biocompatibility and excellent osteointegration and osteoinductive capacity, with no interposition of fibrous tissue between the implanted material and the hematopoietic bone marrow interphase, nor any immune response after six months of implantation. No histological changes were observed in the various organs studied (para-aortic lymph nodes, liver, kidney and lung) as a result of degradation products being released. PMID:28773906

  17. Superhydrophilic and underwater superoleophobic poly(sulfobetaine methacrylate)-grafted glass fiber filters for oil-water separation.

    Science.gov (United States)

    Liu, Qingsheng; Patel, Ankit A; Liu, Lingyun

    2014-06-25

    Oil-water separation is a major problem in industries such as oil production and wastewater treatment, where millions of gallons of oil-contaminated water are produced. Zwitterionic poly(sulfobetaine methacrylate) (pSBMA) is a superhydrophilic polymer due to its strong interaction with water via electrostatic interactions. By coating surfaces of filter media with such a superhydrophilic polymer, it is expected that one can effectively separate oil and water. In this work, pSBMA was grafted onto glass fiber surfaces using surface-initiated atom transfer radical polymerization (SI-ATRP). The in-air water contact angle of the pSBMA-treated glass was 8-15°, as compared to 31° for the control untreated glass, whereas the underwater-oil contact angle of the pSBMA-grafted glass was 162-169°, as compared to 142° for the control pristine glass, suggesting that the pSBMA-grafted glass slides are superhydrophilic and underwater superoleophobic. Such superhydrophilicity and underwater superoleophobicity were realized by modifying surface chemistry only, with no need to create rough surfaces. The pSBMA-grafted glass fiber filters demonstrated exceptional results at separating oil from water without even allowing miniscule amounts of visible oil to permeate through.

  18. Predictability of soil moisture and river flows over France for the spring season

    Science.gov (United States)

    Singla, S.; Céron, J.-P.; Martin, E.; Regimbeau, F.; Déqué, M.; Habets, F.; Vidal, J.-P.

    2012-01-01

    Sources of spring predictability of the hydrological system over France were studied on a seasonal time scale over the 1960-2005 period. Two random sampling experiments were set up in order to test the relative importance of the land surface initial state and the atmospheric forcing. The experiments were based on the SAFRAN-ISBA-MODCOU hydrometeorological suite which computed soil moisture and river flow forecasts over a 8-km grid and more than 880 river-gauging stations. Results showed that the predictability of hydrological variables primarily depended on the seasonal atmospheric forcing (mostly temperature and total precipitation) over most plains, whereas it mainly depended on snow cover over high mountains. However, the Seine catchment area was an exception as the skill mainly came from the initial state of its large and complex aquifers. Seasonal meteorological hindcasts with the Météo-France ARPEGE climate model were then used to force the ISBA-MODCOU hydrological model and obtain seasonal hydrological forecasts from 1960 to 2005 for the entire March-April-May period. Scores from this seasonal hydrological forecasting suite could thus be compared with the random atmospheric experiment. Soil moisture and river flow skill scores clearly showed the added value in seasonal meteorological forecasts in the north of France, contrary to the Mediterranean area where values worsened.

  19. Single- and double-slit collimating effects on fast-atom diffraction spectra

    Energy Technology Data Exchange (ETDEWEB)

    Gravielle, M.S., E-mail: msilvia@iafe.uba.ar; Miraglia, J.E.

    2016-09-01

    Diffraction patterns produced by fast He atoms grazingly impinging on a LiF(0 0 1) surface are investigated focusing on the influence of the beam collimation. Single- and double-slit collimating devices situated in front of the beam source are considered. To describe the scattering process we use the Surface Initial Value Representation (SIVR) approximation, which is a semi-quantum approach that incorporates a realistic description of the initial wave packet in terms of the collimating parameters. Our initial wave-packet model is based on the Van Cittert–Zernike theorem. For a single-slit collimation the width of the collimating aperture controls the shape of the azimuthal angle distribution, making different interference mechanisms visible, while the length of the slit affects the polar angle distribution. Additionally, we found that by means of a double-slit collimation it might be possible to obtain a wide polar angle distribution, which is associated with a large spread of the initial momentum perpendicular to the surface, derived from the uncertainty principle. It might be used as a simple way to probe the surface potential for different normal energies.

  20. Investigation of dielectric breakdown in silica-epoxy nanocomposites using designed interfaces.

    Science.gov (United States)

    Bell, Michael; Krentz, Timothy; Keith Nelson, J; Schadler, Linda; Wu, Ke; Breneman, Curt; Zhao, Su; Hillborg, Henrik; Benicewicz, Brian

    2017-06-01

    Adding nano-sized fillers to epoxy has proven to be an effective method for improving dielectric breakdown strength (DBS). Evidence suggests that dispersion state, as well as chemistry at the filler-matrix interface can play a crucial role in property enhancement. Herein we investigate the contribution of both filler dispersion and surface chemistry on the AC dielectric breakdown strength of silica-epoxy nanocomposites. Ligand engineering was used to synthesize bimodal ligands onto 15nm silica nanoparticles consisting of long epoxy compatible, poly(glycidyl methacrylate) (PGMA) chains, and short, π-conjugated, electroactive surface ligands. Surface initiated RAFT polymerization was used to synthesize multiple graft densities of PGMA chains, ultimately controlling the dispersion of the filler. Thiophene, anthracene, and terthiophene were employed as π-conjugated surface ligands that act as electron traps to mitigate avalanche breakdown. Investigation of the synthesized multifunctional nanoparticles was effective in defining the maximum particle spacing or free space length (L f ) that still leads to property enhancement, as well as giving insight into the effects of varying the electronic nature of the molecules at the interface on breakdown strength. Optimization of the investigated variables was shown to increase the AC dielectric breakdown strength of epoxy composites as much as 34% with only 2wt% silica loading. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. High fluorescence emission of carboxylic acid functionalized polystyrene/BaTiO{sub 3} nanocomposites and rare earth metal complexes: Preparation and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Cao, X. T.; Showkat, A. M.; Wang, Z.; Lim, K. T., E-mail: ktlim@pknu.ac.kr [Department of Imaging System Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

    2015-03-30

    Noble fluorescence nanocomposite compound based on barium titanate nanoparticles (BTO), polystyrene (PSt), and terbium ion (Tb{sup 3+}) was synthesized by a combination of surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization, Friedel-Crafts alkylation reaction and coordinate chemistry. Initially, a modification of surface of BTO was conducted by an exchange process with S-benzyl S’-trimethoxysilylpropyltrithiocarbonate to create macro-initiator for polymerization of styrene. Subsequently, aryl carboxylic acid functionalized polystyrene grafted barium titanate (BTO-g-PSt-COOH) was generated by substitution reaction between 4-(Chloromethyl) benzoic acid and PSt chains. The coordination of the nanohybrids with Tb{sup 3+} ions afforded fluorescent Tb{sup 3+} tagged aryl carboxylic acid functionalized polystyrene grafted barium titanate (BTO-g-PSt-Tb{sup 3+}) complexes. Structure, morphology, and fluorescence properties of nanohybrid complexes were investigated by respective physical and spectral studies. FT-IR and SEM analyses confirmed the formation of BTO-g-PSt-Tb{sup 3+}nanohybrids. Furthermore, TGA profiles demonstrated the grafting of aryl carboxylic acid functionalized polystyrene on BTO surface. Optical properties of BTO-g-PSt-Tb{sup 3+} complexes were investigated by fluorescence spectroscopy.

  2. Surface patterning with natural and synthetic polymers via an inverse electron demand Diels-Alder reaction employing microcontact chemistry.

    Science.gov (United States)

    Roling, Oliver; Mardyukov, Artur; Lamping, Sebastian; Vonhören, Benjamin; Rinnen, Stefan; Arlinghaus, Heinrich F; Studer, Armido; Ravoo, Bart Jan

    2014-10-21

    Bioorthogonal ligation methods are the focus of current research due to their versatile applications in biotechnology and materials science for post-functionalization and immobilization of biomolecules. Recently, inverse electron demand Diels-Alder (iEDDA) reactions employing 1,2,4,5-tetrazines as electron deficient dienes emerged as powerful tools in this field. We adapted iEDDA in microcontact chemistry (μCC) in order to create enhanced surface functions. μCC is a straightforward soft-lithography technique which enables fast and large area patterning with high pattern resolutions. In this work, tetrazine functionalized surfaces were reacted with carbohydrates conjugated with norbornene or cyclooctyne acting as strained electron rich dienophiles employing μCC. It was possible to create monofunctional as well as bifunctional substrates which were specifically addressable by proteins. Furthermore we structured glass supported alkene terminated self-assembled monolayers with a tetrazine conjugated atom transfer radical polymerization (ATRP) initiator enabling surface grafted polymerizations of poly(methylacrylate) brushes. The success of the surface initiated iEDDA via μCC as well as the functionalization with natural and synthetic polymers was verified via fluorescence and optical microscopy, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), atomic force microscopy (AFM) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR).

  3. Functional lignocellulosic materials prepared by ATRP from a wood scaffold

    Science.gov (United States)

    Cabane, Etienne; Keplinger, Tobias; Künniger, Tina; Merk, Vivian; Burgert, Ingo

    2016-01-01

    Wood, a natural and abundant source of organic polymers, has been used as a scaffold to develop novel wood-polymer hybrid materials. Through a two-step surface-initiated Atom Transfer Radical Polymerization (ATRP), the porous wood structure can be effectively modified with polymer chains of various nature. In the present study, polystyrene and poly(N-isopropylacrylamide) were used. As shown with various characterization techniques including confocal Raman microscopy, FTIR, and SEM/EDX, the native wood ultrastructure and features are retained and the polymer chains can be introduced deep within the wood, i.e. inside the wood cell walls. The physical properties of the new materials have been studied, and results indicate that the insertion of polymer chains inside the wood cell wall alters the intrinsic properties of wood to yield a hybrid composite material with new functionalities. This approach to the functionalization of wood could lead to the fabrication of a new class of interesting functional materials and promote innovative utilizations of the renewable resource wood. PMID:27506369

  4. Ultrasound data for laboratory calibration of an analytical model to calculate crack depth on asphalt pavements.

    Science.gov (United States)

    Franesqui, Miguel A; Yepes, Jorge; García-González, Cándida

    2017-08-01

    This article outlines the ultrasound data employed to calibrate in the laboratory an analytical model that permits the calculation of the depth of partial-depth surface-initiated cracks on bituminous pavements using this non-destructive technique. This initial calibration is required so that the model provides sufficient precision during practical application. The ultrasonic pulse transit times were measured on beam samples of different asphalt mixtures (semi-dense asphalt concrete AC-S; asphalt concrete for very thin layers BBTM; and porous asphalt PA). The cracks on the laboratory samples were simulated by means of notches of variable depths. With the data of ultrasound transmission time ratios, curve-fittings were carried out on the analytical model, thus determining the regression parameters and their statistical dispersion. The calibrated models obtained from laboratory datasets were subsequently applied to auscultate the evolution of the crack depth after microwaves exposure in the research article entitled "Top-down cracking self-healing of asphalt pavements with steel filler from industrial waste applying microwaves" (Franesqui et al., 2017) [1].

  5. Ultrasound data for laboratory calibration of an analytical model to calculate crack depth on asphalt pavements

    Directory of Open Access Journals (Sweden)

    Miguel A. Franesqui

    2017-08-01

    Full Text Available This article outlines the ultrasound data employed to calibrate in the laboratory an analytical model that permits the calculation of the depth of partial-depth surface-initiated cracks on bituminous pavements using this non-destructive technique. This initial calibration is required so that the model provides sufficient precision during practical application. The ultrasonic pulse transit times were measured on beam samples of different asphalt mixtures (semi-dense asphalt concrete AC-S; asphalt concrete for very thin layers BBTM; and porous asphalt PA. The cracks on the laboratory samples were simulated by means of notches of variable depths. With the data of ultrasound transmission time ratios, curve-fittings were carried out on the analytical model, thus determining the regression parameters and their statistical dispersion. The calibrated models obtained from laboratory datasets were subsequently applied to auscultate the evolution of the crack depth after microwaves exposure in the research article entitled “Top-down cracking self-healing of asphalt pavements with steel filler from industrial waste applying microwaves” (Franesqui et al., 2017 [1].

  6. High temperature measurement of water vapor absorption

    Science.gov (United States)

    Keefer, Dennis; Lewis, J. W. L.; Eskridge, Richard

    1985-01-01

    An investigation was undertaken to measure the absorption coefficient, at a wavelength of 10.6 microns, for mixtures of water vapor and a diluent gas at high temperature and pressure. The experimental concept was to create the desired conditions of temperature and pressure in a laser absorption wave, similar to that which would be created in a laser propulsion system. A simplified numerical model was developed to predict the characteristics of the absorption wave and to estimate the laser intensity threshold for initiation. A non-intrusive method for temperature measurement utilizing optical laser-beam deflection (OLD) and optical spark breakdown produced by an excimer laser, was thoroughly investigated and found suitable for the non-equilibrium conditions expected in the wave. Experiments were performed to verify the temperature measurement technique, to screen possible materials for surface initiation of the laser absorption wave and to attempt to initiate an absorption wave using the 1.5 kW carbon dioxide laser. The OLD technique was proven for air and for argon, but spark breakdown could not be produced in helium. It was not possible to initiate a laser absorption wave in mixtures of water and helium or water and argon using the 1.5 kW laser, a result which was consistent with the model prediction.

  7. A novel shortened electrospun nanofiber modified with a 'concentrated' polymer brush

    International Nuclear Information System (INIS)

    Yoshikawa, Chiaki; Zhang, Kun; Zawadzak, Ewelina; Kobayashi, Hisatoshi

    2011-01-01

    We report the fabrication of shortened electrospun polymer fibers with a well-defined concentrated polymer brush. We first prepared electrospun nanofibers from a random copolymer of styrene and 4-vinylbenzyl 2-bromopropionate, with number-average molecular weight M n =105 200 and weight-average molecular weight M w =296 700 (M w /M n =2.82). The fibers had a diameter of 593±74 nm and contained initiating sites for surface-initiated atom transfer radical polymerization (SI-ATRP). Then, SI-ATRP of hydrophilic styrene sodium sulfonate (SSNa) was carried out in the presence of a free initiator and the hydrophobic fibers. Gel permeation chromatography confirmed that M n and M w /M n values were almost the same for free polymers and graft polymers. M n agreed well with the theoretical prediction, and M w /M n was relatively low ( n , we calculated the graft density σ as 0.22 chains nm -2 . This value was nearly equal to the density obtained on silicon wafers (σ=0.24 chains nm -2 ), which is categorized into the concentrated brush regime. Finally, we mechanically cut the fibers with a concentrated poly(SSNa) brush by a homogenizer. With increasing cutting time, the fiber length became shorter and more homogenous (11±17 μm after 3 h). The shortened fibers exhibited excellent water dispersibility owing to the hydrophilic poly(SSNa) brush layer.

  8. Bohm's quantum potential as an internal energy

    Energy Technology Data Exchange (ETDEWEB)

    Dennis, Glen, E-mail: gdennis502@gmail.com [TPRU, Birkbeck College, University of London, London, WC1E 7HX (United Kingdom); Gosson, Maurice A. de, E-mail: maurice.de.gosson@univie.ac.at [University of Vienna, Faculty of Mathematics, NuHAG, Oskar-Morgenstern-Platz 1, 1090 Vienna (Austria); Hiley, Basil J., E-mail: b.hiley@bbk.ac.uk [TPRU, Birkbeck College, University of London, London, WC1E 7HX (United Kingdom)

    2015-06-26

    Highlights: • The quantum potential is seen as internal energy associated with a phase space region. • Fermi's trick shows that Bohm's particle is an extended structure in phase space. • We associate Bohm's quantum potential with a context-dependent energy redistribution. • A physically motivated derivation of Schrodinger's equation is provided. • We show the Fermi set associated with a 3-D coherent state contains a quantum blob. - Abstract: We pursue our discussion of Fermi's surface initiated by Dennis, de Gosson and Hiley and show that Bohm's quantum potential can be viewed as an internal energy of a quantum system, giving further insight into its role in stationary states. This implies that the ‘particle’ referred to in Bohm's theory is not a classical point-like object but rather has an extended structure in phase space which can be linked to the notion of a symplectic capacity, a topological feature of the underlying symplectic geometry. This structure provides us with a new, physically motivated derivation of Schrödinger's equation provided we interpret Gleason's theorem as a derivation of the Born rule from fundamental assumptions about quantum probabilities.

  9. Gold nanoparticles stabilized by poly(4-vinylpyridine) grafted cellulose nanocrystals as efficient and recyclable catalysts.

    Science.gov (United States)

    Zhang, Zhen; Sèbe, Gilles; Wang, Xiaosong; Tam, Kam C

    2018-02-15

    pH-responsive poly(4-vinylpyridine) (P4VP) grafted cellulose nanocrystals (P4VP-g-CNC) were prepared by Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) and subsequently used to stabilize gold nanoparticles (Au NPs) as efficient and recyclable nanocatalysts for the reduction of 4-nitrophenol (4NP). The presence of P4VP brushes on the CNC surface controlled the growth of Au NPs yielding smaller averaged diameter compared to Au NPs deposited directly on pristine CNC. The catalytic performances of pristine Au NPs, Au@CNC and Au@P4VP-g-CNC were compared by measuring the turnover frequency (TOF) for the catalytic reduction of 4NP. Compared to pristine Au NPs, the catalytic activity of Au@CNC and Au@P4VP-g-CNC were 10 and 24 times better. Moreover, the Au@P4VP-g-CNC material could be recovered via flocculation at pH>5, and the recycled nanocatalyst remained highly active. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Polymers for Combating Biocorrosion

    Directory of Open Access Journals (Sweden)

    Jing Guo

    2018-03-01

    Full Text Available Biocorrosion has been considered as big trouble in many industries and marine environments due to causing of great economic loss. The main disadvantages of present approaches to prevent corrosion include being limited by environmental factors, being expensive, inapplicable to field, and sometimes inefficient. Studies show that polymer coatings with anticorrosion and antimicrobial properties have been widely accepted as a novel and effective approach to prevent biocorrosion. The main purpose of this review is to summarize up the progressive status of polymer coatings used for combating microbial corrosion. Polymers used to synthesize protective coatings are generally divided into three categories: (i traditional polymers incorporated with biocides, (ii antibacterial polymers containing quaternary ammonium compounds, and (iii conductive polymers. The strategies to synthesize polymer coatings resort mainly to grafting antibacterial polymers from the metal substrate surface using novel surface-functionalization approaches, such as free radical polymerization, chemically oxidative polymerization, and surface-initiated atom transfer radical polymerization, as opposed to the traditional approaches of dip coating or spin coating.

  11. Surface-Tunable Bioluminescence Resonance Energy Transfer via Geometry-Controlled ZnO Nanorod Coordination.

    Science.gov (United States)

    Lim, Jun Hyung; Park, Geun Chul; Lee, Seung Muk; Lee, Jung Heon; Lim, Butaek; Hwang, Soo Min; Kim, Jung Ho; Park, Hansoo; Joo, Jinho; Kim, Young-Pil

    2015-07-01

    The use of ZnO nanorods (NRs) as an effective coordinator and biosensing platform to create bioluminescence resonance energy transfer (BRET) is reported. Herein, a hydrothermal approach is applied to obtain morphologically controlled ZnO NRs, which are directly bound to luciferase (Luc) and carboxy-modified quantum dot (QD) acting as a donor-acceptor pair for BRET. BRET efficiency varies significantly with the geometry of ZnO NRs, which modulates the coordination between hexahistidine-tagged Luc (Luc-His6 ) and QD, owing to the combined effect of the total surface area consisting of (001) and (100) planes and their surface polarities. Unlike typical QD-BRET reactions with metal ions (e.g., zinc ions), a geometry-controlled ZnO NR platform can facilitate the design of surface-initiated BRET sensors without being supplemented by copious metal ions: the geometry-controlled ZnO NR platform can therefore pave the way for nanostructure-based biosensors with enhanced analytical performance. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Novel pyrolyzed polyaniline-grafted silicon nanoparticles encapsulated in graphene sheets as Li-ion battery anodes.

    Science.gov (United States)

    Li, Zhe-Fei; Zhang, Hangyu; Liu, Qi; Liu, Yadong; Stanciu, Lia; Xie, Jian

    2014-04-23

    A simple method to fabricate graphene-encapsulated pyrolyzed polyaniline-grafted Si nanoparticles has been developed. Instead of using Si nanoparticles with a native oxide layer, HF-treated Si nanoparticles were employed in this work. The uniqueness of this method is that, first, a PANI layer over the Si nanoparticles was formed via the surface-initiated polymerization of aniline on the surface of aniline-functionalized Si nanoparticles; then, the PANI-grafted Si nanoparticles were wrapped by the GO sheets via π-π interaction and electrostatic attraction between the GO and the PANI. Finally, the GO and PANI were pyrolyzed, and this pyrolyzed PANI layer tightly binds the graphene sheets and the Si nanoparticles together in the composite. The composite materials exhibit better cycling stability and Coulombic efficiency as anodes in lithium ion batteries, as compared to pure Si nanoparticles and physically mixed graphene/Si composites. After 300 cycles at a current density of 2 A/g, the composite electrodes can still deliver a specific capacity of about 900 mAh/g, which corresponds to ∼76% capacity retention. The enhanced performance can be attributed to the absence of surface oxides, the better electronic conductivity, faster ion diffusion rate, and the strong interaction between the graphene sheets and the tightly bound carbon-coated Si nanoparticles.

  13. Fabrication of the Superhydrophobic Surface Inspired from Lotus-Effect

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Dae Hwan; Lim, Hyun Eui; Noh, Jeong Hyun; Kim, Wan Doo [Korea Instutite of Machinery and Materials, Daejeon (Korea, Republic of)

    2007-07-01

    Wettability of solid surfaces with liquids is governed by the chemical properties and the microstructure of the surfaces. We report on the preparation of liquid-repellent surfaces using surface-attached monolayers of perfluorinated polymer molecules on porous silica substrates. A covalent attachment of the polymer molecules to the substrate is achieved by generation of the polymer chains through starting a surface-initiated radical-chain polymerization of a fluorinated monomer. To this, self-assembled monolayers of azo initiators are attached to silica substrates, which are used to kick off the polymerization reaction in situ. The growth of the fluorinated polymer films and the characterization of the obtained surfaces by surface plasmon spectroscopy, XPS, and contact angle measurements is described. It is shown that perfluorinated polymer films can be grown with controlled thicknesses on flat and even on porous silica surfaces, essentially without changing the surface roughness. The combination of the low surface energy coating and the surface porosity allows generation of materials which are both water and oil repellent.

  14. Immobilization of α-amylase onto poly(glycidyl methacrylate) grafted electrospun fibers by ATRP

    International Nuclear Information System (INIS)

    Oktay, Burcu; Demir, Serap; Kayaman-Apohan, Nilhan

    2015-01-01

    In this study, novel α-amylase immobilized poly(vinyl alcohol) (PVA) nanofibers were prepared. The PVA nanofiber surfaces were functionalized with 2-bromoisobutyryl bromide (BiBBr) and followed by surface initiated atom transfer radical polymerization (SI-ATRP) of glycidyl methacrylate (GMA). The morphology of the poly(glycidyl methacrylate) (PGMA) grafted PVA nanofibers was characterized by scanning electron microscopy (SEM). Also PGMA brushes were confirmed by X-ray photo electron microscopy (XPS). α-Amylase was immobilized in a one step process onto the PGMA grafted PVA nanofiber. The characteristic properties of the immobilized and free enzymes were examined. The thermal stability of the enzyme was improved and showed maximum activity at 37 °C by immobilization. pH values of the maximum activity of the free and immobilized enzymes were also found at 6.0 and 6.5, respectively. Free enzyme lost its activity completely within 15 days. The immobilized enzyme lost only 23.8% of its activity within 30 days. - Highlights: • Electrospun photocrosslinkable PVA nanofiber was prepared. • PGMA brushes were conducted on PVA nanofiber via SI-ATRP. • The immobilized enzyme showed maximum activity at pH 6.0 and at 37 °C. • Functionalized nanofibers may be used as promising supports for enzyme immobilization

  15. Preparation of a novel Zr(4+)-immobilized metal affinity membrane for selective adsorption of phosphoprotein.

    Science.gov (United States)

    He, Maofang; Wang, Chaozhan; Wei, Yinmao

    2016-09-01

    In this study, a novel phosphate-Zr(4+) immobilized metal affinity membrane (IMAM) was prepared based on the surface initiated-atom transfer radical polymerization technique for the selective adsorption of phosphoprotein. The adsorption capacity and selectivity of the phosphate-Zr(4+) IMAM were evaluated by using the mixture of standard phosphoproteins (β-casein, ovalbumin) and nonphosphoproteins (bovine serum albumin and lysozyme) as model samples. The adsorption isotherms and competitive adsorption results demonstrated that the phosphate-Zr(4+) IMAM had higher binding capacity and selectivity for phosphoproteins over nonphosphoproteins. Moreover, the phosphate-Zr(4+) IMAM exhibited good re-usability and re-productivity. Finally, the phosphate-Zr(4+) IMAM was applied to separate phosphoprotein from real samples with high purity. Therefore, the as-prepared phosphate-Zr(4+) IMAM could be a promising affinity material for the efficient enrichment of phosphoprotein from complex bio-samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Guanidine-based polymer brushes grafted onto silica nanoparticles as efficient artificial phosphodiesterases.

    Science.gov (United States)

    Savelli, Claudia; Salvio, Riccardo

    2015-04-07

    Polymer brushes grafted to the surface of silica nanoparticles were fabricated by atom-transfer radical polymerization (ATRP) and investigated as catalysts in the cleavage of phosphodiesters. The surfaces of silica nanoparticles were functionalized with an ATRP initiator. Surface-initiated ATRP reactions, in varying proportions, of a methacrylate moiety functionalized with a phenylguanidine moiety and an inert hydrophilic methacrylate species afforded hybrid nanoparticles that were characterized with potentiometric titrations, thermogravimetric analysis, and SEM. The activity of the hybrid nanoparticles was tested in the transesterification of the RNA model compound 2-hydroxypropyl para-nitrophenylphosphate (HPNP) and diribonucleoside monophosphates. A high catalytic efficiency and a remarkable effective molarity, thus overcoming the effective molarities previously observed for comparable systems, indicate the existence of an effective cooperation of the guanidine/guanidinium units and a high level of preorganization in the nanostructure. The investigated system also exhibits a marked and unprecedented selectivity for the diribonucleoside sequence CpA. The results presented open up the way for a novel and straightforward strategy for the preparation of supramolecular catalysts. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Poly(ionic liquids) hollow nanospheres with PDMAEMA as joint support of highly dispersed gold nanoparticles for thermally adjustable catalysis

    International Nuclear Information System (INIS)

    He, Xiaoyan; Liu, Zhirong; Fan, Fuhong; Qiang, Shenglu; Cheng, Li; Yang, Wu

    2015-01-01

    A smart hollow hybrid system was prepared by introducing poly(2-(1-methylimidazolium 3-yl)-ethyl methacrylate chloride) (PMIMC) network, the temperature-responsive PDMAEMA brushes, and Au nanoparticles into silica nanoparticles through two-step surface-initiated atom transfer radical polymerization. TEM, FTIR, EDX, XRD, XPS, and TGA were used to characterize the morphology and structure of air@PMIMC–PDMAEMA–Au hairy hollow nanospheres. The result showed that Au nanoparticles with an average diameter of 1.5 ± 0.2 nm were homogeneously embedded inside the PMIMC–PDMAEMA shell. Catalytic activity of the as-synthesized air@PMIMC–PDMAEMA–Au hairy hollow nanospheres were investigated using the reduction of 4-nitrophenol with NaBH 4 as a model reaction. It was found that the joint structures of PMIMC hollow nanospheres and PDMAEMA brushes lead to production of the highly active and stable catalyst for reduction of 4-nitrophenol. Furthermore, the obtained air@PMIMC–PDMAEMA–Au hairy hollow nanospheres were found to have a thermally adjustable catalytic activity for the reduction of 4-nitrophenol

  18. Surface functionalization of aluminosilicate nanotubes with organic molecules

    Directory of Open Access Journals (Sweden)

    Wei Ma

    2012-02-01

    Full Text Available The surface functionalization of inorganic nanostructures is an effective approach for enriching the potential applications of existing nanomaterials. Inorganic nanotubes attract great research interest due to their one-dimensional structure and reactive surfaces. In this review paper, recent developments in surface functionalization of an aluminosilicate nanotube, “imogolite”, are introduced. The functionalization processes are based on the robust affinity between phosphate groups of organic molecules and the aluminol (AlOH surface of imogolite nanotubes. An aqueous modification process employing a water soluble ammonium salt of alkyl phosphate led to chemisorption of molecules on imogolite at the nanotube level. Polymer-chain-grafted imogolite nanotubes were prepared through surface-initiated polymerization. In addition, the assembly of conjugated molecules, 2-(5’’-hexyl-2,2’:5’,2’’-terthiophen-5-ylethylphosphonic acid (HT3P and 2-(5’’-hexyl-2,2’:5’,2’’-terthiophen-5-ylethylphosphonic acid 1,1-dioxide (HT3OP, on the imogolite nanotube surface was achieved by introducing a phosphonic acid group to the corresponding molecules. The optical and photophysical properties of these conjugated-molecule-decorated imogolite nanotubes were characterized. Moreover, poly(3-hexylthiophene (P3HT chains were further hybridized with HT3P modified imogolite to form a nanofiber hybrid.

  19. Multi-model assessment of the impact of soil moisture initialization on mid-latitude summer predictability

    Science.gov (United States)

    Ardilouze, Constantin; Batté, L.; Bunzel, F.; Decremer, D.; Déqué, M.; Doblas-Reyes, F. J.; Douville, H.; Fereday, D.; Guemas, V.; MacLachlan, C.; Müller, W.; Prodhomme, C.

    2017-12-01

    Land surface initial conditions have been recognized as a potential source of predictability in sub-seasonal to seasonal forecast systems, at least for near-surface air temperature prediction over the mid-latitude continents. Yet, few studies have systematically explored such an influence over a sufficient hindcast period and in a multi-model framework to produce a robust quantitative assessment. Here, a dedicated set of twin experiments has been carried out with boreal summer retrospective forecasts over the 1992-2010 period performed by five different global coupled ocean-atmosphere models. The impact of a realistic versus climatological soil moisture initialization is assessed in two regions with high potential previously identified as hotspots of land-atmosphere coupling, namely the North American Great Plains and South-Eastern Europe. Over the latter region, temperature predictions show a significant improvement, especially over the Balkans. Forecast systems better simulate the warmest summers if they follow pronounced dry initial anomalies. It is hypothesized that models manage to capture a positive feedback between high temperature and low soil moisture content prone to dominate over other processes during the warmest summers in this region. Over the Great Plains, however, improving the soil moisture initialization does not lead to any robust gain of forecast quality for near-surface temperature. It is suggested that models biases prevent the forecast systems from making the most of the improved initial conditions.

  20. Predictive Model for the Design of Zwitterionic Polymer Brushes: A Statistical Design of Experiments Approach.

    Science.gov (United States)

    Kumar, Ramya; Lahann, Joerg

    2016-07-06

    The performance of polymer interfaces in biology is governed by a wide spectrum of interfacial properties. With the ultimate goal of identifying design parameters for stem cell culture coatings, we developed a statistical model that describes the dependence of brush properties on surface-initiated polymerization (SIP) parameters. Employing a design of experiments (DOE) approach, we identified operating boundaries within which four gel architecture regimes can be realized, including a new regime of associated brushes in thin films. Our statistical model can accurately predict the brush thickness and the degree of intermolecular association of poly[{2-(methacryloyloxy) ethyl} dimethyl-(3-sulfopropyl) ammonium hydroxide] (PMEDSAH), a previously reported synthetic substrate for feeder-free and xeno-free culture of human embryonic stem cells. DOE-based multifunctional predictions offer a powerful quantitative framework for designing polymer interfaces. For example, model predictions can be used to decrease the critical thickness at which the wettability transition occurs by simply increasing the catalyst quantity from 1 to 3 mol %.

  1. Polyacrylamide-based inorganic hybrid flocculants with self-degradable property

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Xinfang [Materials and Metallurgical College, Northeastern University, Shenyang 110819 (China); Hebei Provincial Laboratory for Dielectric and Electrolyte Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China); Tao, Junshi; Li, Mingzhi; Zhu, Bishan; Li, Xuan; Ma, Zhiyu; Zhao, Tingjie; Wang, Bingzhu; Suo, Biao [Hebei Provincial Laboratory for Dielectric and Electrolyte Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China); Wang, Haiwang, E-mail: whwdbdx@126.com [Materials and Metallurgical College, Northeastern University, Shenyang 110819 (China); State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Hebei Provincial Laboratory for Dielectric and Electrolyte Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China); Yang, Jun, E-mail: jyang@ipe.ac.cn [State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Ye, Li, E-mail: yeli@iccas.ac.cn [Beijing National Laboratory for Molecular Sciences, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190 (China); Qi, Xiwei, E-mail: qxw@mail.neuq.edu.cn [Materials and Metallurgical College, Northeastern University, Shenyang 110819 (China); Hebei Provincial Laboratory for Dielectric and Electrolyte Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004 (China)

    2017-05-01

    Polyacrylamide (PAM)-based inorganic hybrid materials are of great potential as flocculants in soil-liquid separation. Herein, we reported the design of inorganic soil-TiO{sub 2}-PAM hybrid materials using a unique process, which involved coating of titanium dioxide (TiO{sub 2}) nanoparticles on the surface of inorganic soils and subsequent polymerization of acrylamide (AM) on these nanoparticles under visible light. Inorganic soils including kaolin, bentonite, montmorillonite and diatomaceous earth were used to control the volume and to reduce the cost, and the TiO{sub 2} nanoparticles accelerated PAM degradation. The nanoparticles initiated AM polymerization directly under visible light, thus providing a facile strategy for the synthesis of new organic-inorganic hybrid flocculants. The obtained hybrid materials were characterized using Fourier transform infrared spectroscopy and transmission electron microscopy. The degradation of PAM initiated by UV irradiation exceeded 24% in 2 h, depending on its initial concentration. - Highlights: • A new polyacrylamide (PAM)-based inorganic hybrid flocculants with self-degradable property was developed. • TiO{sub 2} nanoparticles show a unique surface-initiated property under the condition of visible light. • We designed a facile strategy for the synthesis of inorganic soil@TiO{sub 2}@PAM hybrid materials.

  2. Synthesis and characterization of PVP-functionalized superparamagnetic Fe3O4 nanoparticles as an MRI contrast agent

    Directory of Open Access Journals (Sweden)

    2010-06-01

    Full Text Available The magnetite (Fe3O4 nanoparticles (MNPs coated with poly(N-vinyl pyrrolidone (PVP via covalent bonds were prepared as T2 contrast agent for magnetic resonance imaging (MRI. The surface of MNPs was first coated with 3-(trimethoxysilyl propyl methacrylate (silan A by a silanization reaction to introduce reactive vinyl groups onto the surface, then poly(N-vinyl pyrrolidone was grafted onto the surface of modified-MNPs via surface-initiated radical polymerization. The obtained nanoparticles were characterized by FT-IR (Fourier transform infrared spectroscopy, XRD (X-ray diffraction, TEM (transmission electron microscopy, VSM (vibrating sample magnetometer, and TGA (thermogravimetric analysis. The MNPs had an average size of 14 nm and exhibited superparamagnetism and high saturation magnetization at room temperature. T2-weighted MRI images of PVP-grafted MNPs showed that the magnetic resonance signal is enhanced significantly with increasing nanoparticle concentration in water. The r1 and r2 values per millimole Fe, and r2/r1 value of the PVP-grafted MNPs were calculated to be 2.6 , 72.1, and 28.1(mmol/l–1•s–1, respectively. These results indicate that the PVP-grafted MNPs have great potential for application in MRI as a T2 contrast agent.

  3. Antifouling coatings via plasma polymerization and atom transfer radical polymerization on thin film composite membranes for reverse osmosis

    Science.gov (United States)

    Hirsch, Ulrike; Ruehl, Marco; Teuscher, Nico; Heilmann, Andreas

    2018-04-01

    A major drawback to otherwise highly efficient membrane-based desalination techniques like reverse osmosis (RO) is the susceptibility of the membranes to biofouling. In this work, a combination of plasma activation, plasma bromination and surface-initiated atom transfer radical polymerization (si-ATRP) of hydrophilic and zwitterionic monomers, namely hydroxyethyl methacrylate (HEMA), 2-methacryloyloxyethyl phosphorylcholine (MPC) and [2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), was applied to generate non-specific, anti-adhesive coatings on thin film composite (TFC) membranes. The antifouling effect of the coatings was shown by short-time batch as well as long-time steady state cultivation experiments with the microorganism Pseudomonas fluorescens. It could be shown that plasma functionalization and polymerization is possible on delicate thin film composite membranes without restricting their filtration performance. All modified membranes showed an increased resistance towards the adhesion of Pseudomonas fluorescens. On average, the biofilm coverage was reduced by 51.4-12.6% (for HEMA, SBMA, and MPC), the highest reduction was monitored for MPC with a biofilm reduction by 85.4%. The hydrophilic coatings applied did not only suppress the adhesion of Pseudomonas fluorescens, but also significantly increase the permeate flux of the membranes relative to uncoated membranes. The stability of the coatings was however not ideal and will have to be improved for future commercial use.

  4. Surface glycosylation of polysulfone membrane towards a novel complexing membrane for boron removal.

    Science.gov (United States)

    Meng, Jianqiang; Yuan, Jing; Kang, Yinlin; Zhang, Yufeng; Du, Qiyun

    2012-02-15

    In this study, a novel complexing membrane was synthesized for boron removal from aqueous solution. A glycopolymer, poly(2-gluconamidoethyl methacrylate) (PGAMA), was grafted onto the chloromethylated polysulfone (CMPSF) microporous membrane via surface-initiated ATRP (SIATRP). The glycosylated PSF (GlyPSF) membrane was characterized by attenuated total refection-Flourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM). It was demonstrated that PGAMA was successfully anchored onto the membrane surface and the grafting yield can be tuned in a wide range up to 5.9 mg/cm(2) by varying the polymerization time. The complexing membrane can adsorb boron rapidly with the equilibrium reached within 2h and has a remarkable high boron adsorption capacity higher than 2.0 mmol/g at optimized conditions. Freundlich, Langmuir, and Dubinin-Radushkevich adsorption isotherms were applied, and the data were best described by Langmuir model. Kinetic data were analyzed, and the data fitted very well to the pseudo-second-order rate expression. The optimal pH for boron uptake is in a wide range of 6-9, and the optimal initial boron concentration is over 300 mg/L. Studies of ionic strength effects indicated the formation of inner-sphere surface complexes. The complexed boron can be leached quantitatively under acid condition. Copyright © 2011 Elsevier Inc. All rights reserved.

  5. Structural Characterization of Aluminum (Oxy)hydroxide Films at the Muscovite (001)-Water Interface.

    Science.gov (United States)

    Lee, Sang Soo; Schmidt, Moritz; Fister, Timothy T; Nagy, Kathryn L; Sturchio, Neil C; Fenter, Paul

    2016-01-19

    The formation of Al (oxy)hydroxide on the basal surface of muscovite mica was investigated to understand how the structure of the substrate controls the nucleation and growth of secondary phases. Atomic force microscopy images showed that solid phases nucleated on the surface initially as two-dimensional islands that were ≤10 Å in height and ≤200 Å in diameter after 16-50 h of reaction in a 100 μM AlCl3 solution at pH 4.2 at room temperature. High-resolution X-ray reflectivity data indicated that these islands were gibbsite layers whose basic unit is composed of a plane of Al ions octahedrally coordinated to oxygen or hydroxyl groups. The formation of gibbsite layers is likely favored because of the structural similarity between its basal plane and the underlying mica surface. After 700-2000 h of reaction, a thicker and continuous film had formed on top of the initial gibbsite layers. X-ray diffraction data showed that this film was composed of diaspore that grew predominantly with its [040] and [140] crystallographic directions oriented along the muscovite [001] direction. These results show the structural characteristics of the muscovite (001) and Al (oxy)hydroxide film interface where presumed epitaxy had facilitated nucleation of metastable gibbsite layers which acted as a structural anchor for the subsequent growth of thermodynamically stable diaspore grown from a mildly acidic and Al-rich solution.

  6. Thermo- and pH-responsive polymer brushes-grafted gigaporous polystyrene microspheres as a high-speed protein chromatography matrix.

    Science.gov (United States)

    Qu, Jian-Bo; Xu, Yu-Liang; Liu, Jun-Yi; Zeng, Jing-Bin; Chen, Yan-Li; Zhou, Wei-Qing; Liu, Jian-Guo

    2016-04-08

    Dual thermo- and pH-responsive chromatography has been proposed using poly(N-isopropylacrylamide-co-butyl methacrylate-co-N,N-dimethylaminopropyl acrylamide) (P(NIPAM-co-BMA-co-DMAPAAM)) brushes grafted gigaporous polystyrene microspheres (GPM) as matrix. Atom transfer radical polymerization (ATRP) initiator was first coupled onto GPM through Friedel-Crafts acylation with 2-bromoisobutyryl bromide. The dual-responsive polymer brushes were then grafted onto GPM via surface-initiated ATRP. The surface composition, gigaporous structure, protein adsorption and dual-responsive chromatographic properties of the matrix (GPM-P(NIPAM-co-BMA-co-DMAPAAM) were characterized in detail. Results showed that GPM were successfully grafted with thermoresponsive cationic polymer brushes and that the gigaporous structure was well maintained. A column packed with GPM-P(NIPAM-co-BMA-co-DMAPAAM presented low backpressure, good permeability and appreciable thermo-responsibility. By changing pH of the mobile phase and temperature of the column in turn, the column can separate three model proteins at the mobile phase velocity up to 2528cmh(-1). A separation mechanism of this matrix was also proposed. All results indicate that the dual thermo- and pH-responsive chromatography matrix has great potentials in 'green' high-speed protein chromatography. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Design of a High Viscosity Couette Flow Facility for Patterned Surface Drag Measurements

    Science.gov (United States)

    Johnson, Tyler; Lang, Amy

    2009-11-01

    Direct drag measurements can be difficult to obtain with low viscosity fluids such as air or water. In this facility, mineral oil is used as the working fluid to increase the shear stress across the surface of experimental models. A mounted conveyor creates a flow within a plexiglass tank. The experimental model of a flat or patterned surface is suspended above a moving belt. Within the gap between the model and moving belt a Couette flow with a linear velocity profile is created. PIV measurements are used to determine the exact velocities and the Reynolds numbers for each experiment. The model is suspended by bars that connect to the pillow block housing of each bearing. Drag is measured by a force gauge connected to linear roller bearings that slide along steel rods. The patterned surfaces, initially consisting of 2-D cavities, are embedded in a plexiglass plate so as to keep the total surface area constant for each experiment. First, the drag across a flat plate is measured and compared to theoretical values for laminar Couette flow. The drag for patterned surfaces is then measured and compared to a flat plate.

  8. Amino acid-based zwitterionic polymers: antifouling properties and low cytotoxicity.

    Science.gov (United States)

    Li, Wenchen; Liu, Qingsheng; Liu, Lingyun

    2014-01-01

    A group of five amino acid containing zwitterionic vinyl monomers, based on serine, lysine, ornithine, glutamic acid, and aspartic acid, respectively, were proposed and developed for potential antifouling applications. Their polymer brushes were grafted on gold chips by surface-initiated photoiniferter-mediated polymerization. We then compared their performance in resisting protein adsorption from full human serum and plasma. All five polymers can reduce protein adsorption by more than 90% compared to the unmodified gold. The ornithine-based and aspartic acid-based poly(methacrylamide) can most strongly resist protein adsorption from serum and plasma, compared to the other three. The ability of surfaces to suppress bacterial adhesion is another criterion in evaluating antifouling properties of materials. Our results show that the five polymer-grafted surfaces can significantly suppress Escherichia coli K12 adhesion to 99% compared to the bare gold surface. The zwitterionic structure of amino acids, with homogenously distributed and balanced positive and negative charges, is responsible for the outstanding antifouling properties. Considering multiple potential applications (e.g. medical devices and drug delivery) of the antifouling materials, we further systematically evaluated the cytotoxicity of both monomers and polymer nanogels for all five materials at various concentrations. Very low cytotoxicity was observed for all tested amino acid-based monomers and nanogels, which is comparable or even lower than the traditional and some newly developed antifouling materials, which might be related to the biomimetic nature of amino acids.

  9. Picosecond laser micro/nano surface texturing of nickel for superhydrophobicity

    Science.gov (United States)

    Wang, X. C.; Wang, B.; Xie, H.; Zheng, H. Y.; Lam, Y. C.

    2018-03-01

    A single step direct picosecond laser texturing process was demonstrated to be able to obtain a superhydrophobic surface on a nickel substrate, a key material for mold fabrication in the manufacture of various devices, including polymeric microfluidic devices. A two-scale hierarchical surface structure of regular 2D array micro-bumps with nano-ripples was produced on a nickel surface. The laser textured surface initially showed superhydrophilicity with almost complete wetting of the structured surface just after laser treatment, then quickly changed to nearly superhydrophobic with a water contact angle (WCA) of 140° in less than 1 d, and finally became superhydrophobic with a WCA of more than 150° and a contact angle hysteresis (CAH) of less than 5°. The mechanism involved in the process is discussed in terms of surface morphology and surface chemistry. The ultra-fast laser induced NiO catalytic effect was thought to play a key role in modifying the surface chemistry so as to lower the surface energy. The developed process has the potential to improve the performance of nickel mold in the fabrication of microfluidic devices.

  10. Hydrophilic crosslinked-polymeric surface capable of effective suppression of protein adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Kamon, Yuri; Inoue, Naoko; Mihara, Erika; Kitayama, Yukiya; Ooya, Tooru; Takeuchi, Toshifumi, E-mail: takeuchi@gold.kobe-u.ac.jp

    2016-08-15

    Highlights: • Three hydrophilic crosslinked polymers were examined for protein adsorption. • All polymers showed low nonspecific adsorption of negatively charged proteins. • Poly(MMPC) showed the lowest adsorption for positively charged proteins. • Poly(MMPC) is able to reduce nonspecific adsorption of a wide range of proteins. - Abstract: We investigated the nonspecific adsorption of proteins towards three hydrophilic crosslinked-polymeric thin layers prepared by surface-initiated atom transfer radical polymerization using N,N′-methylenebisacrylamide, 2-(methacryloyloxy)ethyl-[N-(2-methacryloyloxy)ethyl]phosphorylcholine (MMPC), or 6,6′-diacryloyl-trehalose crosslinkers. Protein binding experiments were performed by surface plasmon resonance with six proteins of different pI values including α-lactalbumin, bovine serum albumin (BSA), myoglobin, ribonuclease A, cytochrome C, and lysozyme in buffer solution at pH 7.4. All of the obtained crosslinked-polymeric thin layers showed low nonspecific adsorption of negatively charged proteins at pH 7.4 such as α-lactalbumin, BSA, and myoglobin. Nonspecific adsorption of positively charged proteins including ribonuclease A, cytochrome C, and lysozyme was the lowest for poly(MMPC). These results suggest poly(MMPC) can effectively reduce nonspecific adsorption of a wide range of proteins that are negatively or positively charged at pH 7.4. MMPC is a promising crosslinker for a wide range of polymeric materials requiring low nonspecific protein binding.

  11. Functionalized carbon nanotube via distillation precipitation polymerization and its application in nafion-based composite membranes.

    Science.gov (United States)

    He, Guangwei; Zhao, Jing; Hu, Shen; Li, Lingqiao; Li, Zongyu; Li, Yifan; Li, Zhen; Wu, Hong; Yang, Xinlin; Jiang, Zhongyi

    2014-09-10

    The objective of this study is to develop a novel approach to in situ functionalizing multiwalled carbon nanotubes (MWCNTs) and exploring their application in Nafion-based composite membranes for efficient proton conduction. Covalent grafting of acrylate-modified MWCNTs with poly(methacrylic acid-co-ethylene glycol dimethacrylate), poly(vinylphosphonic acid-co-ethylene glycol dimethacrylate), and sulfonated poly(styrene-co-divinylbenzene) was achieved via surface-initiated distillation precipitation polymerization. The formation of core-shell structure was verified by TEM images, and polymer layers with thickness around 30 nm were uniformly covered on the MWCNTs. The graft yield reached up to 93.3 wt % after 80 min of polymerization. The functionalized CNTs (FCNTs) were incorporated into the Nafion matrix to prepare composite membranes. The influence of various functional groups (-COOH, -PO3H2, and -SO3H) in FCNTs on proton transport of the composite membranes was studied. The incorporation of FCNTs afforded the composite membranes significantly enhanced proton conductivities under reduced relative humidity. The composite membrane containing 5 wt % phosphorylated MWCNTs (PCNTs) showed the highest proton conductivity, which was attributed to the construction of lower-energy-barrier proton transport pathways by PCNTs, and excellent water-retention and proton-conduction properties of the cross-linked polymer in PCNTs. Moreover, the composite membranes exhibited an enhanced mechanical stability.

  12. Effect of wetting-drying cycles on soil desiccation cracking behaviour

    Directory of Open Access Journals (Sweden)

    Tang Chao-Sheng

    2016-01-01

    Full Text Available Better understanding the desiccation cracking process is essential in analysing drought effects on soil hydraulic and mechanical properties through consideration of the atmosphere-ground interaction. Laboratory tests were conducted to investigate the consequence of wetting-drying cycles on the initiation and propagation characteristics of desiccation cracks on soil surface. Initially saturated slurry specimens were prepared and subjected to five subsequent wetting-drying cycles. Image processing technique was employed to quantitatively analyze the morphology characteristics of crack patterns formed during each drying path. The results show that the desiccation cracking behaviour of soil is significantly affected by the wetting-drying cycles. Before the third wetting-drying cycle is reached, the surface crack ratio and the average crack width increases while the average clod area decreases with increasing the number of wetting-drying cycles. The number of intersections and crack segments per unit area reaches the peak values after the second wetting-drying cycle. After the third wetting-drying cycle is reached, the effect of increasing wetting-drying cycles on crack patterns is insignificant. Moreover, it is observed that the applied wetting-drying cycles are accompanied by a continual reconstruction of soil structure. The initial homogenous slurry structure is completely replaced with aggregated structure after the third cycles, and a significant increase in the inter-aggregate porosity can be observed.

  13. Dental plaque morphology as revealed by direct observation and by replicating techniques.

    Science.gov (United States)

    Lie, T; Gusberti, F

    1978-01-01

    The ability of four elastomer impression materials to reproduce details of bacterial plaque structures was studied by comparing areas of the replica models with corresponding areas of the replicated plaque. Plaque was grown on hydroxyapatite splint segments for 48 hours and replica models were made from three different resins. One of the resins, a methacrylate material, was not suited for this purpose due to its content of spherical particles. The polysulfide and polyether impression materials reacted with the heat curing epoxy resin, and less satisfactory results were obtained with cold curing epoxy resin. Best results were obtained by a combined use of low viscosity silicone impression materials and cold or heat curing epoxy resins as model materials. However, a considerable loss of detail occurred in the replica models compared with observations of plaque directly on splint surfaces. Outlines of individual bacteria could sometimes be seen in the models, but generally several cells seemed to fuse, and appeared like small globular structures where cells and pellicle were difficult to distinguish. The bacterial colonization started near the gingival border of the surface, initiated by attachment of individual bacteria to the pellicle surface.

  14. Assessing the Association Between Asthma and Air Quality in the Presence of Wildfires

    Science.gov (United States)

    Young, L. J.; Lopiano, K. K.; Xu, X.; Holt, N. M.; Leary, E.; Al-Hamdan, M. Z.; Crosson, W. L.; Estes, M. G.; Luvall, J. C.; Estes, S. M.; hide

    2012-01-01

    Asthma hospital/emergency room (patient) data are used as the foundation for creating a health outcome indicator of human response to environmental air quality. Daily U.S. Environmental Protection Agency (EPA) Air Quality System (AQS) fine particulates (PM2.5) ground data and the U.S. National Aeronautical Space Administration (NASA) MODIS aerosol optical depth (AOD) data were acquired and processed for years of 2007 and 2008. Figure 1 shows the PM2.5 annual mean composite of all the 2007 B-spline daily surfaces. Initial models for predicting the number of weekly asthma cases within a Florida county has focused on environmental variables. Weekly maximums of PM2.5, relative humidity, and the proportions of the county with smoke and fire were the environmental variables included in the model. Cosine and sine functions of time were used to account for seasonality in asthma cases. Counties were considered to be random effects, thereby adjusting for differences in socio ]demographics and other factors. The 2007 predictions for Miami ]Dade county when using B ]splines PM2.5 are displayed in Figures 2.

  15. Case study of elevated layers of high sulfate concentration

    International Nuclear Information System (INIS)

    McNaughton, D.J.; Orgill, M.M.

    1979-01-01

    During studies in August 1976 that were part of the Multi-State Atmospheric Power Production Pollutant Study (MAP3S), Alkezweeny et al., (1977) noted that in the Milwaukee urban plume, layers of relatively high sulfate concentrations occurred at high altitudes with respect to the boundary layer. This paper represents a progress report on studies undertaken to investigate possible causes for a bimodel vertical profile of sulfate concentrations. Data presented by Alkezweeny et al., (1977) serve as a basis for this study. Data from August 23, 1976, and August 24, 1978, indicate concentrations relatively high in sulfate, at 1000 and 6000 ft, respectively, with lower concentrations at lower altitudes. Concentrations of trace metals also indicate no peaks in the vertical concentration profiles above the surface. Initial studies of the high, elevated sulfate concentrations have centered on the August 23 measurements taken over southeast Wisconsin using synoptic data from the national weather service, emissions data from the national emissions data bank system (EPA), air quality data from the national air surveillance network (EPA), and satellite photographs from the EROS Data Center

  16. Bottle-Brush Brushes: Cylindrical Molecular Brushes of Poly(2-oxazoline) on Glassy Carbon

    KAUST Repository

    Zhang, Ning

    2009-07-28

    We report on the synthesis of brushes of bottle-brushes of poly(2-oxazoline)s on polished glassy carbon (GC) substrates. First, homogeneous and stable poly(2-isopropenyl-2-oxazoline) (PIPOx) brush layers with thicknesses up to 160 nm were created directly onto GC by the self-initiated photografting and photopolymerization (SIPGP) of 2-isopropenyl-2-oxazoline (IPOx). Kinetic studies reveal a linear increase in thickness with the polymerization time. In a second reaction, the pendant 2-oxazoline ring of the PIPOx brushes were used for the living cationic ring-opening polymerization (LCROP) with different substituted 2-oxazoline monomers to form the side chains. Also for the second surface-initiatedLCROPfrom the surface-bound macroinitiator brushes, the thickness increase with the polymerization time was found to be linear and reproducible. Characterization of the resulting bottle-brush brushes by FTIR spectroscopy,contact angle, and AFM indicates a high side chain grafting density and quantitative reactions. Finally, we have demonstrated the possibility of functionalizing the bottle-brush brushes side chain end groups with sterically demanding molecules. © 2009 American Chemical Society.

  17. Preparation of novel polyamine-type chelating resin with hyperbranched structures and its adsorption performance

    Science.gov (United States)

    Zhao, Wei; Wang, Huan; Li, Yuhong; Li, Chenxi

    2018-01-01

    This paper explored the method of combining atom transfer radical polymerization (ATRP) technology and hyperbranched polymer principle to prepare the high capacity chelating resin. First, surface-initiated atom transfer radical polymerization (SI-ATRP) method was used to graft glycidyl methacrylate (GMA) on chloromethylated cross-linked styrene-divinylbenzene resin, and then the novel polyamine chelating resin with a kind of hyperbranched structure was prepared through the amination reaction between amino group of (2-aminoethyl) triamine and epoxy group in GMA. This resin had a selective effect on As(V) and Cr(VI) at a relatively low pH and can be used for the disposal of waste water containing As(V) and Cr(VI). It had a relatively strong adsorption effect on Cu(II), Pb(II), Cd(II) and Cr(III) and can be used for the disposal of heavy metal ion waste water. The finding was that, the adsorption capacity of resin on the studied heavy metal ions was higher than that of the chelating resin synthesized by traditional technology and also higher than that of the resin modified by ATRP technology and bifunctional chelator, indicating that the combination of ATRP and hyperbranched polymer concept is an effective method to prepare chelating resin with high capacity. PMID:29515875

  18. 30 s Response Time of K+ Ion-Selective Hydrogels Functionalized with 18-Crown-6 Ether Based on QCM Sensor.

    Science.gov (United States)

    Zhang, Zhenxiao; Dou, Qian; Gao, Hongkai; Bai, Bing; Zhang, Yongmei; Hu, Debo; Yetisen, Ali K; Butt, Haider; Yang, Xiaoxia; Li, Congju; Dai, Qing

    2018-03-01

    Potassium detection is critical in monitoring imbalances in electrolytes and physiological status. The development of rapid and robust potassium sensors is desirable in clinical chemistry and point-of-care applications. In this study, composite supramolecular hydrogels are investigated: polyethylene glycol methacrylate and acrylamide copolymer (P(PEGMA-co-AM)) are functionalized with 18-crown-6 ether by employing surface initiated polymerization. Real-time potassium ion monitoring is realized by combining these compounds with quartz crystal microbalance. The device demonstrates a rapid response time of ≈30 s and a concentration detection range from 0.5 to 7.0 × 10 -3 m. These hydrogels also exhibit high reusability and K + ion selectivity relative to other cations in biofluids such as Na + , NH 4 + , Mg 2+ , and Ca 2+ . These results provide a new approach for sensing alkali metal ions using P(PEGMA-co-AM) hydrogels. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Cellulose nanocrystal-poly(oligo(ethylene glycol) methacrylate) brushes with tunable LCSTs.

    Science.gov (United States)

    Grishkewich, Nathan; Akhlaghi, Seyedeh Parinaz; Zhaoling, Yao; Berry, Richard; Tam, Kam C

    2016-06-25

    This paper reports on the synthesis of poly(oligoethylene glycol) methyl ether acrylate (POEGMA) grafted cellulose nanocrystals (CNCs) via surface initiated atom transfer radical polymerization (ATRP). An ATRP initiator (α-Bromoisobutyryl bromide) was covalently bonded to the surface of CNCs, followed by copolymerizing di(ethylene glycol) methyl ether methacrylate (MEO2MA) and oligoethylene glycol methyl ether methacrylate (OEGMA300) monomers from the surface using Cu(I)Br/2,2-dipyridal. Multiple POEGMA-g-CNC systems with varying MEO2MA/OEGMA300 content were synthesized, and they displayed a range of lower critical solution temperatures (LCSTs) in aqueous medium. μDSC endotherms and microstructural analysis indicated the collapse of POEGMA chains, followed by the aggregation of nanoparticles above their LCSTs. Cloud point measurements demonstrated a hysteresis in the heating and cooling of the POEGMA-g-CNC systems. It was found that the LCST of the nanoparticles could be tuned to between 23.8 to 63.8°C by adjusting the OEGMA300 content of the POEGMA brushes. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Energy storage in ferroelectric polymer nanocomposites filled with core-shell structured polymer@BaTiO3 nanoparticles: understanding the role of polymer shells in the interfacial regions.

    Science.gov (United States)

    Zhu, Ming; Huang, Xingyi; Yang, Ke; Zhai, Xing; Zhang, Jun; He, Jinliang; Jiang, Pingkai

    2014-11-26

    The interfacial region plays a critical role in determining the electrical properties and energy storage density of dielectric polymer nanocomposites. However, we still know a little about the effects of electrical properties of the interfacial regions on the electrical properties and energy storage of dielectric polymer nanocomposites. In this work, three types of core-shell structured polymer@BaTiO3 nanoparticles with polymer shells having different electrical properties were used as fillers to prepare ferroelectric polymer nanocomposites. All the polymer@BaTiO3 nanoparticles were prepared by surface-initiated reversible-addition-fragmentation chain transfer (RAFT) polymerization, and the polymer shells were controlled to have the same thickness. The morphology, crystal structure, frequency-dependent dielectric properties, breakdown strength, leakage currents, energy storage capability, and energy storage efficiency of the polymer nanocomposites were investigated. On the other hand, the pure polymers having the same molecular structure as the shells of polymer@BaTiO3 nanoparticles were also prepared by RAFT polymerization, and their electrical properties were provided. Our results show that, to achieve nanocomposites with high discharged energy density, the core-shell nanoparticle filler should simultaneously have high dielectric constant and low electrical conductivity. On the other hand, the breakdown strength of the polymer@BaTiO3-based nanocomposites is highly affected by the electrical properties of the polymer shells. It is believed that the electrical conductivity of the polymer shells should be as low as possible to achieve nanocomposites with high breakdown strength.

  1. Solvent Oligomerization during SEI Formation on Model Systems for Li-Ion Battery Anodes

    Energy Technology Data Exchange (ETDEWEB)

    Tavassol, Hadi; Buthker, Joseph W.; Ferguson, Glen A.; Curtiss, Larry A.; Gewirth, Andrew A.

    2012-01-01

    We report the results of electrochemical quartz crystal microbalance (EQCM), and matrix assisted laser desorption ionization (MALDI) time of flight (TOF) mass spectrometry (MS) measurements along with detailed calculations examining the formation of the solid electrolyte interphase (SEI) on battery anode electrodes. EQCM analysis of Au and Sn surfaces in propylene carbonate (PC) and a 1:1 mixture of ethylene carbonate and dimethyl carbonate (EC:DMC) showed major irreversible mass uptake by the electrode surface especially during the first five cycles between +2 and 0.1 V vs. Li/Li+. MALDI-MS on emersed electrodes showed that long chain (m/z = 3000 on PC) oligomerized species were present on Au surfaces in PC and EC:DMC solvents, where oligomerized species formed in PC solutions showed higher mass ratios. The repeating units of the oligomer, visible as oscillations in the MALDI-MS, vary with the type of the solvent and electrode material. Sn surfaces initially showed formation of long chain polymers, but this material was not in evidence on electrode emersed after five cycles, which likely arises as a consequence of the catalytic involvement of Sn in decomposition of initially formed species. Density functional theory (DFT) calculations of cyclic solvent molecules suggested a radical initiated polymerization mechanism and predict oligomer subunits consistent with the experimental results.

  2. Synthesis of HNTs@PEDOT composites via in situ chemical oxidative polymerization and their application in electrode materials

    Science.gov (United States)

    Wang, Fang; Zhang, Xianhong; Ma, Yuhong; Yang, Wantai

    2018-01-01

    The hybrid composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and halloysite nanotubes (HNTs) was synthesized by a two-step process. First, poly(sodium styrene sulfonate) (PSSNa) was grafted onto HNTs via surface initiated atom transfer radical polymerization. Then with the HNTs-g-PSS as a template and the grafted PSS chains as the counterion dopant, PEDOT was precipitated onto the template via in situ oxidization polymerization of EDOT to form HNTs@PEDOT hybrid composites. The conductivity of HNTs@PEDOT can reach up to 9.35 S/cm with the content of 40% HNTs-g-PSS, which increased almost 78 times than that of pure PEDOT (about 0.12 S/cm) prepared at the similar condition. Further treated with p-toluenesulfonic acid (TsOH) as external dopant, the conductivity of HNTs@PEDOT increased to 24.3 S/cm. The electrochemical properties of the composites were investigated with cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy with three-electrode cell configuration. The results showed that the capacitance of HNTs@PEDOT composite increased 55% than that of pure PEDOT.

  3. Direct fabrication of hybrid nanofibres composed of SiO2-PMMA nanospheres via electrospinning.

    Science.gov (United States)

    Zhang, Ran; Shang, Tinghua; Yang, Guang; Jia, Xiaolong; Cai, Qing; Yang, Xiaoping

    2016-08-01

    The direct fabrication of hybrid nanofibres composed of poly(methyl methacrylate)-grafted SiO2 (SiO2-PMMA) nanospheres via electrospinning was investigated in detail. SiO2-PMMA nanospheres were successfully prepared, with the SiO2 nanospheres synthesized via the Stober method, followed by in situ surface-initiated atom transfer radical polymerization of methyl methacrylate (MMA). Electrospinning was carried out with N,N-dimethylformamide (DMF) as the solvent to disperse SiO2-PMMA nanospheres. The size of the SiO2 core, the molecular weight of the PMMA shell and the concentration of the SiO2-PMMA/DMF solution all had substantial effects on the morphology and structure of electrospun nanofibres composed of SiO2-PMMA nanospheres. When these determining factors were well-tailored, it was found that one-dimensional necklace-like nanofibres were obtained, with SiO2-PMMA nanospheres aligned one by one along the fibre. The successful fabrication of nanofibres by directly electrospinning the SiO2-PMMA/DMF solution verified that polymer-grafted particles possess polymer-like characteristics, which endowed them with the ability to be processed into desirable shapes and structures. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Collective magnetic behavior of biocompatible systems of maghemite particles coated with functional polymer shells

    Energy Technology Data Exchange (ETDEWEB)

    Demchenko, P.; Nedelko, N. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Mitina, N. [Lviv Polytechnic National University, 12 Bandera, Lviv 79013 (Ukraine); Lewińska, S.; Dłużewski, P. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Greneche, J.M. [Institut des Molécules et Matériaux du Mans, IMMM UMR CNRS 6283, Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans (France); Ubizskii, S.; Navrotskyi, S.; Zaichenko, A. [Lviv Polytechnic National University, 12 Bandera, Lviv 79013 (Ukraine); Ślawska-Waniewska, A., E-mail: slaws@ifpan.edu.pl [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland)

    2015-04-01

    Three series of core–shell maghemite nanoparticles were prepared by a template synthesis using surface active oligoperoxides and further surface initiated grafting functional polymers, forming shell suitable for biomedical applications. Because the polymer shells prevent exchange coupling between maghemite particles, the overall magnetic properties of the samples studied are dominated by dipolar interparticle interactions. Only the sample with the highest polymer fraction displays superparamagnetic relaxation phenomena close to the room temperature. On cooling, the magnetostatic interactions lead to a disordered collective magnetic state that should be described in terms of a spin-glass phenomenology. This collective freezing cannot however be considered as a generic spin-glass phase transition at a well-defined temperature but rather as freezing to a metastable glass-like state of locally correlated structural domains (clusters) without a long-range order. A quasi static spin ordering is only achieved at temperatures much below the freezing temperature. - Highlights: • Core–shell γ-Fe{sub 2}O{sub 3}/polymer particles were prepared using new surface active oligoperoxides. • Grafting of particle shells with functional polymers, suitable for biomedical applications. • Magnetic properties of nanocomposites are dominated by dipolar interactions. • On cooling magnetostatic interactions lead to a spin-glass-like state. • The most diluted maghemite particles display superparamagnetism at 300 K.

  5. Antimicrobial activity of TiO{sub 2}:Ag nanocrystalline heterostructures: Experimental and theoretical insights

    Energy Technology Data Exchange (ETDEWEB)

    André, Rafaela S. [UFSCar – Universidade Federal de São Carlos, Department of Chemistry, 13565-905 São Carlos, SP (Brazil); Zamperini, Camila A. [UNESP – Universidade Estadual Paulista, Instituto de Química, 14801-907 Araraquara, SP (Brazil); Mima, Ewerton G. [UNESP – Universidade Estadual Paulista, Escola de Odontologia de Araraquara, Departamento de Materias Odontológicos e Próteses Dentárias, 14801-903 Araraquara, SP (Brazil); Longo, Valéria M., E-mail: valeria.longo@liec.ufscar.br [USP – Universidade de São Paulo, Instituto de Física de São Carlos, 13560-970 São Carlos, SP (Brazil); Albuquerque, Anderson R. [UNESP – Universidade Estadual Paulista, Grupo de Modelagem e Simulação Molecular, P.O. Box 477, CEP 17033-360 Bauru, SP (Brazil); Instituto Federal de Educação, Ciência e Tecnologia do Sertão Pernambucano, IFSetão-PE, 56400-000 Floresta, PE (Brazil); Sambrano, Júlio R. [UNESP – Universidade Estadual Paulista, Grupo de Modelagem e Simulação Molecular, P.O. Box 477, CEP 17033-360 Bauru, SP (Brazil); and others

    2015-09-28

    Highlights: • Greener hydrothermal process to obtain nanocrystalline TiO{sub 2} anatase with Ag nanoparticles. • Antifungal effect against planktonic cells of C. albicans and Staphylococcus aureus. • DFT calculations of anatase TiO{sub 2} and metallic Ag. • Mechanism for the formation of reactive species at surface. - Abstract: We report the synthesis and characterization of silver-decorated titanium dioxide (TiO{sub 2}:Ag) nanoparticles, as well as a discussion of their antimicrobial activity. This material was synthesized by microwave-assisted hydrothermal treatment and characterized by complementary techniques. The minimum inhibitory concentration and minimum bactericidal/fungicidal concentration of TiO{sub 2}:Ag nanoparticles against planktonic and biofilm-forming strains of methicillin-resistant Staphylococcus aureus, Candida species (spp.) and the total biofilm mass were determined. The basis of the biological activity of TiO{sub 2}:Ag was investigated by electronic analysis of the material using theoretical quantum chemical calculations. In the proposed mechanism of action, the impregnated semiconductor donates electrons to the forbidden band gaps in the metal, generating point defects, with partially located electrons and holes at the surface, initiating a radical process involving the solvent and biological target. Our results suggest that this TiO{sub 2}:Ag nanomaterial has potential for use in the development of new therapeutic agents.

  6. QCM-D studies of attachment and differential spreading of pre-osteoblastic cells on Ta and Cr surfaces.

    Science.gov (United States)

    Modin, Charlotte; Stranne, Anne-Louise; Foss, Morten; Duch, Mogens; Justesen, Jeannette; Chevallier, Jacques; Andersen, Lars K; Hemmersam, Anne G; Pedersen, Finn S; Besenbacher, Flemming

    2006-03-01

    The quartz crystal microbalance with dissipation (QCM-D) technique was employed to characterize initial cell adhesion in terms of attachment and spreading of pre-osteoblastic MC3T3-E1 cells on Ta and Cr surfaces. Evaluation of initial cell adhesion established a correlation between input cell number and the shifts in frequency (f) and dissipation (D). The f-shift was found to be much larger in serum-free medium as compared to a medium including serum; hence, initial cell adhesion was subsequently evaluated in serum-free medium. During the first hour of adhesion, we found a positive correlation between the QCM-D f-shift and the average area of the spread cells, as measured by cryo-scanning electron microscopy (cryo-SEM). Finally, the QCM-D technique was used to study cell adhesion on different metal oxide surfaces. Initial cell adhesion on Ta was found to induce a larger f-shift as compared to Cr, indicating larger spreading of cells on Ta. Cryo-SEM data confirmed that spreading of cells on Cr was on average only two-thirds the spreading on Ta. Our results demonstrate that the QCM-D technique is a versatile technique to quickly distinguish initial cell-surface interactions on different biomaterials.

  7. Surface modification of nanodiamond through metal free atom transfer radical polymerization

    Science.gov (United States)

    Zeng, Guangjian; Liu, Meiying; Shi, Kexin; Heng, Chunning; Mao, Liucheng; Wan, Qing; Huang, Hongye; Deng, Fengjie; Zhang, Xiaoyong; Wei, Yen

    2016-12-01

    Surface modification of nanodiamond (ND) with poly(2-methacryloyloxyethyl phosphorylcholine) [poly(MPC)] has been achieved by using metal free surface initiated atom transfer radical polymerization (SI-ATRP). The ATRP initiator was first immobilized on the surface of ND through direct esterification reaction between hydroxyl group of ND and 2-bromoisobutyryl bromide. The initiator could be employed to obtain ND-poly(MPC) nanocomposites through SI-ATRP using an organic catalyst. The final functional materials were characterized by 1H nuclear magnetic resonance, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and thermo gravimetric analysis in detailed. All of these characterization results demonstrated that ND-poly(MPC) have been successfully obtained via metal free photo-initiated SI-ATRP. The ND-poly(MPC) nanocomposites shown enhanced dispersibility in various solvents as well as excellent biocompatibility. As compared with traditional ATRP, the metal free ATRP is rather simple and effective. More importantly, this preparation method avoided the negative influence of metal catalysts. Therefore, the method described in this work should be a promising strategy for fabrication of polymeric nanocomposites with great potential for different applications especially in biomedical fields.

  8. Direct surface PEGylation of nanodiamond via RAFT polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Yingge [Department of Chemistry and Jiangxi Provincial Key Laboratory of New Energy Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Liu, Meiying [Department of Chemistry and Jiangxi Provincial Key Laboratory of New Energy Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wang, Ke [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing 100084 (China); Huang, Hongye; Wan, Qing [Department of Chemistry and Jiangxi Provincial Key Laboratory of New Energy Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Tao, Lei [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing 100084 (China); Fu, Lihua [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry and Jiangxi Provincial Key Laboratory of New Energy Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wei, Yen, E-mail: weiyen@tsinghua.edu.cn [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing 100084 (China)

    2015-12-01

    Graphical abstract: In this paper, we describe an efficient, practical and novel method to modify ND via direct immobilization of chain transfer agent for RAFT polymerization. - Highlights: • Surface PEGylation of ND via RAFT polymerization. • ND with high water dispersibility and excellent biocompatibility. • Controlled living polymerization. - Abstract: Nanodiamond (ND) is a novel class of carbon nanomaterials, which has been extensively investigated for biomedical applications because of its small size, high surface area and excellent biocompatibility. However, the biomedical applications of unmodified ND are still largely restricted because of their poor dispersibility in both aqueous and organic medium. In this work, we reported a novel strategy for the surface modification of ND via reversible addition fragmentation chain transfer (RAFT) polymerization. For preparation of the PEGylated ND (pPEGMA-ND), chain transfer agent (CTA) was immobilized onto ND through reaction between the hydroxyl group of ND and the carboxyl group of CTA, which was used as the initiator for surface-initiated RAFT polymerization. The successful preparation of pPEGMA-ND was characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectra and thermal gravimetric analysis in detail. Results demonstrated that pPEGMA-ND exhibited enhanced water dispersibility and desirable biocompatibility, making it promising for biomedical applications.

  9. Real-Time Packing Behavior of Core-Shell Silica@Poly(N-isopropylacrylamide Microspheres as Photonic Crystals for Visualizing in Thermal Sensing

    Directory of Open Access Journals (Sweden)

    Karthikeyan Manivannan

    2016-12-01

    Full Text Available We grafted thermo-responsive poly(N-isopropylacrylamide (PNIPAM brushes from monodisperse SiO2 microspheres through surface-initiated atom transfer radical polymerization (SI ATRP to generate core-shell structured SiO2@PNIPAM microspheres (SPMs. Regular-sized SPMs dispersed in aqueous solution and packed as photonic crystals (PCs in dry state. Because of the microscale of the SPMs, the packing behavior of the PCs in water can be observed by optical microscopy. By increasing the temperature above the lower critical solution temperature (LCST of PNIPAM, the reversible swelling and shrinking of the PNIPAM shell resulted in dispersion and precipitation (three-dimensional aggregation of the SPM in aqueous solution. The SPMs were microdispersed in a water layer to accommodate the aggregation along two dimensions. In the microdispersion, the SPMs are packed as PCs with microscale spacing between SPMs below the LCST. When the temperature is increased above the LCST, the microdispersed PCs exhibited a close-packed arrangement along two dimensions with decreased spacing between SPMs. The change in spacing with increasing temperature above the LCST resulted in a color change from red to blue, which could be observed by the naked eye at an incident angle. Thus, the SPM array could be applied as a visual temperature sensor.

  10. A method to modify PVDF microfiltration membrane via ATRP with low-temperature plasma pretreatment

    Energy Technology Data Exchange (ETDEWEB)

    Han, Yu [School of Marine Science, Ningbo University, Fenghua Road 818, Ningbo, 315211 (China); Ningbo University of Technology, Fenghua Road 201, Ningbo, 315211 (China); Song, Shuijun [School of Marine Science, Ningbo University, Fenghua Road 818, Ningbo, 315211 (China); Zhejiang University of Science Technology, Liuhe Road 318, Hangzhou, 310023 (China); Lu, Yin, E-mail: luyin@nbu.edu.cn [School of Marine Science, Ningbo University, Fenghua Road 818, Ningbo, 315211 (China); Zhu, Dongfa [School of Marine Science, Ningbo University, Fenghua Road 818, Ningbo, 315211 (China)

    2016-08-30

    Highlights: • We report a simple method to modify hydrophobic PVDF modification membrane. • Surface modification of PVDF membrane via ATRP with plasma pre-treatment. • ATRP grafting of SBMA onto the PVDF membrane surface form PVDF-g-SBMA membrane. • PVDF-g-SBMA membrane shows superior antifouling properties and hydrophilic. - Abstract: The hydrophilic modification of a polyvinylidene fluoride (PVDF) microfiltration membrane via pretreatment with argon plasma and direct surface-initiated atom transfer radical polymerization (ATRP) was studied. Both modified and unmodified PVDF membranes were characterized by Fourier transform infrared spectroscopy (FTIR), water contact angle, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and pore size distribution measurements. FTIR and XPS spectra confirmed that sulfobetaine methacrylate (SBMA) had been grafted onto the membrane surface. The initial contact angle decreased from 87.0° to 29.8° and a water drop penetrated into the modified membrane completely in 8 s. The pore size distribution of the modified membrane exhibited a smaller mean value than that of the original membrane. The antifouling properties of the modified PVDF membrane were evaluated by a filtration test using bovine serum albumin (BSA) solution. The results showed that the initial flux of the modified membrane increased from 2140.1 L/m{sup 2} h to 2812.7 L/m{sup 2} h and the equilibrium flux of BSA solution increased from 31 L/m{sup 2} h to 53 L/m{sup 2} h.

  11. Preparation and biocompatibility of grafted functional β-cyclodextrin copolymers from the surface of PET films

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yan, E-mail: yan_jiang_72@126.com [College of Materials Science and Engineering, Changzhou University, Changzhou 213164, Jiangsu (China); Liang, Yuan; Zhang, Hongwen [College of Materials Science and Engineering, Changzhou University, Changzhou 213164, Jiangsu (China); Zhang, Weiwei [College of Life Science, Agriculture and Forestry, Qiqihar University, Qiqihar 161006, Heilongjiang (China); Tu, Shanshan [College of Materials Science and Engineering, Changzhou University, Changzhou 213164, Jiangsu (China)

    2014-08-01

    The hydrophobic inert surface of poly(ethylene terephthalate) (PET) film has limited its practical bioapplications, in which case, better biocompatibility should be achieved by surface modification. In this work, the copolymer of functional β-cyclodextrin derivatives and styrene grafted surfaces was prepared via surface-initiated atom transfer radical polymerization (SI-ATRP) on initiator-immobilized PET. The structures, composition, properties, and surface morphology of the modified PET films were characterized by fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), contact angle measurement, and scanning electronic microscopy (SEM). The results show that the surface of PET films was covered by a thick targeted copolymer layer, and the hydrophobic surface of PET was changed into an amphiphilic surface. The copolymer-grafted surfaces were also shown good biocompatibility on which SGC-7901 A549 and A549/DDP cells readily attached and proliferated, demonstrating that the functional copolymer-grafted PET films could be a promising alternative to biomaterials especially for tissue engineering. - Highlights: • The PET film was grafted by functional β-CD copolymers, which owns amphiphilicity. • The surface of grafted PET film by copolymers enhanced the cell adhesion and growth. • The biocompatible PET film may be used in tissue engineering and cell cultivation.

  12. Surface Immobilization of pH-Responsive Polymer Brushes on Mesoporous Silica Nanoparticles by Enzyme Mimetic Catalytic ATRP for Controlled Cargo Release

    Directory of Open Access Journals (Sweden)

    Hang Zhou

    2016-08-01

    Full Text Available Peroxidase mimetic catalytic atom transfer radical polymerization (ATRP was first used to install tertiary amine-functionalized polymer brushes on the surface of mesoporous silica nanoparticles (MSNs in a facile and highly efficient manner. Poly(N,N-dimethylaminoethyl methacrylate (PDMAEMA brushes-grafted MSNs were fabricated by biocompatible deuterohemin-β-Ala-His-Thr-Val-Glu-Lys (DhHP-6-catalyzed surface-initiated ATRP (SI-ATRP. The resulting organic–inorganic hybrid nanocarriers were fully characterized by Fourier transform-infrared spectroscopy (FT-IR, thermogravimetric analysis (TGA, X-ray photoelectron spectroscopy (XPS, powder X-ray diffraction (XRD, SEM, TEM, Elemental analysis, Zeta-potential, and N2 adsorption–desorption isotherms, which demonstrated the successful coating of pH-responsive polymers on the MSN surface. Rhodamine 6G (Rh6G dyes were further loaded within the mesopores of this nanocarrier, and the release of Rh6G out of MSNs in a controlled fashion was achieved upon lowing the solution pH. The electrostatic repulsion of positively-charged tertiary ammonium of PDMAEMAs in acidic environments induced the stretching out of polymer brushes on MSN surfaces, thus opening the gates to allow cargo diffusion out of the mesopores of MSNs.

  13. Preparation and characterization of a thermoresponsive gigaporous medium for high-speed protein chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Qu, Jian-Bo, E-mail: jbqu@upc.edu.cn [State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580 (China); Chen, Yan-Li; Huan, Guan-Sheng [State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580 (China); Zhou, Wei-Qing [National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Liu, Jian-Guo; Zhu, Hu [State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580 (China); Zhang, Xiao-Yun, E-mail: zhangxy@upc.edu.cn [State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580 (China)

    2015-01-01

    Highlights: • A high-speed thermoresponsive bioseparation medium was prepared in two steps. • Non-specific adsorption of proteins on thermoresponsive medium was greatly reduced. • Separation of proteins was achieved by only adjusting column temperature. • It was able to separate proteins at the mobile phase velocity up to 2167 cm h{sup −1}. - Abstract: A high-speed thermoresponsive medium was developed by grafting poly(N-isopropylacrylamide-co-butyl methacrylate) (P(NIPAM-co-BMA)) brushes onto gigaporous polystyrene (PS) microspheres via surface-initiated atom transfer radical polymerization (ATRP) technique, which has strong mechanical strength, good chemical stability and high mass transfer rate for biomacromolecules. The gigaporous structure, surface chemical composition, static protein adsorption, and thermoresponsive chromatographic properties of prepared medium (PS–P(NIPAM-co-BMA)) were characterized in detail. Results showed that the PS microspheres were successfully grafted with P(NIPAM-co-BMA) brushes and that the gigaporous structure was robustly maintained. After grafting, the nonspecific adsorption of proteins on PS microspheres was greatly reduced. A column packed with PS–P(NIPAM-co-BMA) exhibited low backpressure and significant thermo-responsibility. By simply changing the column temperature, it was able to separate three model proteins at the mobile phase velocity up to 2167 cm h{sup −1}. In conclusion, the thermoresponsive polymer brushes grafted gigaporous PS microspheres prepared by ATRP are very promising in ‘green’ high-speed preparative protein chromatography.

  14. Facile surface modification of silicone rubber with zwitterionic polymers for improving blood compatibility

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Pingsheng [School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Chen, Qiang, E-mail: chem100@nju.edu.cn [School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); High Technology Research Institute of Nanjing University, Changzhou 213164 (China); Yuan, Bo; Chen, Mengzhou; Wu, Shishan; Lin, Sicong [School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Shen, Jian, E-mail: shenj1957@yahoo.com.cn [School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China)

    2013-10-15

    A facile approach to modify silicone rubber (SR) membrane for improving the blood compatibility was investigated. The hydrophobic SR surface was firstly activated by air plasma, after which an initiator was immobilized on the activated surface for atom transfer radical polymerization (ATRP). Three zwitterionic polymers were then grafted from SR membrane via surface-initiated atom transfer radical polymerization (SI-ATRP). The surface composition, wettability, and morphology of the membranes before and after modification were characterized by X-ray photoelectron spectroscopy (XPS), static water contact angle (WCA) measurement, and atomic force microscopy (AFM). Results showed that zwitterionic polymers were successfully grafted from SR surfaces, which remarkably improved the wettability of the SR surface. The blood compatibility of the membranes was evaluated by protein adsorption and platelet adhesion tests in vitro. As observed, all the zwitterionic polymer modified surfaces have improved resistance to nonspecific protein adsorption and have excellent resistance to platelet adhesion, showing significantly improved blood compatibility. This work should inspire many creative uses of SR based materials for biomedical applications such as vessel, catheter, and microfluidics. Highlights: • Facile surface modification of silicone rubber with functional brushes • Modified SR surfaces have improved resistance to nonspecific protein adsorption. • Modified SR surfaces have excellent resistance to platelet adhesion. • Zwitteironic surface significant improvement in blood compatibility • Could inspire many creative uses of SR based materials for biomedical.

  15. Immobilization of α-amylase onto poly(glycidyl methacrylate) grafted electrospun fibers by ATRP

    Energy Technology Data Exchange (ETDEWEB)

    Oktay, Burcu; Demir, Serap; Kayaman-Apohan, Nilhan, E-mail: napohan@marmara.edu.tr

    2015-05-01

    In this study, novel α-amylase immobilized poly(vinyl alcohol) (PVA) nanofibers were prepared. The PVA nanofiber surfaces were functionalized with 2-bromoisobutyryl bromide (BiBBr) and followed by surface initiated atom transfer radical polymerization (SI-ATRP) of glycidyl methacrylate (GMA). The morphology of the poly(glycidyl methacrylate) (PGMA) grafted PVA nanofibers was characterized by scanning electron microscopy (SEM). Also PGMA brushes were confirmed by X-ray photo electron microscopy (XPS). α-Amylase was immobilized in a one step process onto the PGMA grafted PVA nanofiber. The characteristic properties of the immobilized and free enzymes were examined. The thermal stability of the enzyme was improved and showed maximum activity at 37 °C by immobilization. pH values of the maximum activity of the free and immobilized enzymes were also found at 6.0 and 6.5, respectively. Free enzyme lost its activity completely within 15 days. The immobilized enzyme lost only 23.8% of its activity within 30 days. - Highlights: • Electrospun photocrosslinkable PVA nanofiber was prepared. • PGMA brushes were conducted on PVA nanofiber via SI-ATRP. • The immobilized enzyme showed maximum activity at pH 6.0 and at 37 °C. • Functionalized nanofibers may be used as promising supports for enzyme immobilization.

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

    Directory of Open Access Journals (Sweden)

    Babu Kothandapani

    2008-01-01

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

  17. Preparation of monodispersed macroporous core-shell molecularly imprinted particles and their application in the determination of 2,4-dichlorophenoxyacetic acid.

    Science.gov (United States)

    Liu, Yongliang; He, Yonghuan; Jin, Yulong; Huang, Yanyan; Liu, Guoquan; Zhao, Rui

    2014-01-03

    Porous polymers have aroused extensive attention due to their controllable porous structure in favor of mass transfer and binding capacity. In this work, the novel macroporous core-shell molecularly imprinted polymers (MIP) for selective recognition of 2,4-dichlorophenoxyacetic acid (2,4-D) were prepared by surface initiated atom transfer radical polymerization (si-ATRP). By using one-step swelling and polymerization method, the monodispersed macroporous poly(glycidyl methacrylate) (PGMA) particles were synthesized and used as supporting matrix for preparing surface MIP particles (PGMA@MIP). Thanks to the inner and outer surface-located binding cavities and the macroporous structure, the PGMA@MIPs revealed desirable efficiency for template removal and mass transfer, and thus excellent accessibility and affinity toward template 2,4-D. Moreover, PGMA@MIPs exhibited much higher selectivity toward 2,4-D than PGMA@NIPs. PGMA@MIP particles were directly used to selectively enrich 2,4-D from tap water and the recoveries of 2,4-D were obtained as 90.0-93.4% with relative standard division of 3.1-3.4% (n=3). The macroporous PGMA@MIPs also possessed steady and excellent reusable performance for 2,4-D in four extraction/stripping cycles. This novel macroporous core-shell imprinted material may become a powerful tool for rapid and efficient enrichment and separation of target compounds from the complicated samples. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. A novel self-catalyzed photoATRP strategy for preparation of fluorescent hydroxyapatite nanoparticles and their biological imaging

    Science.gov (United States)

    Jiang, Ruming; Liu, Meiying; Huang, Hongye; Huang, Long; Huang, Qiang; Wen, Yuanqing; Cao, Qian-yong; Tian, Jianwen; Zhang, Xiaoyong; Wei, Yen

    2018-03-01

    Hydroxyapatite (HAp), as an important biomaterial for the regeneration and reconstruction of bone tissue, has attracted more and more attention of researchers and scientists due to its unique structure and compositions. However, the preparation of fluorescent HAp with controllable morphology has achieved only limited success. In this work, we reported a novel strategy to construct the water dispersible fluorescent HAp nanorods via the combination of ligand exchange and metal-free atom transfer radical polymerization (ATRP). The Br-containing fluorescent HAp nanorods with controllable size and morphology were first prepared through hydrothermal treatment. A multifunctional organic molecule (named as PTH-Br) with aggregation-induced emission feature was immobilized on the surface of hydrophobic HAp nanorods through ligand exchange reaction. The PTH-Br could be used as the initiator and catalyst for surface-initiated metal-free ATRP using poly(ethylene glycol) methacrylate as monomer to obtain hydrophilic fluorescent HAp polymer nanoparticles. This strategy successfully endowed HAp nanorods excellent fluorescence properties and favorable water dispersibility but well preserved their regular morphology. Biological assays demonstrated that the HAp-PTH-poly(PEGMA) nanoparticles exhibited good biocompatibility and efficient cell uptake performance. Taken together, we have developed a rather facile strategy based on the surface ligand exchange reaction and metal-free photoATRP to fabricate fluorescent HAp with controllable size and morphology, high water dispersibility and biological properties. These HAp-PTH-poly(PEGMA) nanoparticles should be novel and promising candidates for biomedical applications.

  19. Functional lignocellulosic materials prepared by ATRP from a wood scaffold

    Science.gov (United States)

    Cabane, Etienne; Keplinger, Tobias; Künniger, Tina; Merk, Vivian; Burgert, Ingo

    2016-08-01

    Wood, a natural and abundant source of organic polymers, has been used as a scaffold to develop novel wood-polymer hybrid materials. Through a two-step surface-initiated Atom Transfer Radical Polymerization (ATRP), the porous wood structure can be effectively modified with polymer chains of various nature. In the present study, polystyrene and poly(N-isopropylacrylamide) were used. As shown with various characterization techniques including confocal Raman microscopy, FTIR, and SEM/EDX, the native wood ultrastructure and features are retained and the polymer chains can be introduced deep within the wood, i.e. inside the wood cell walls. The physical properties of the new materials have been studied, and results indicate that the insertion of polymer chains inside the wood cell wall alters the intrinsic properties of wood to yield a hybrid composite material with new functionalities. This approach to the functionalization of wood could lead to the fabrication of a new class of interesting functional materials and promote innovative utilizations of the renewable resource wood.

  20. Branched poly(ethyleneimine): a versatile scaffold for patterning polymer brushes by means of remote photocatalytic lithography

    Science.gov (United States)

    Panzarasa, Guido; Dübner, Matthias; Soliveri, Guido; Edler, Matthias; Griesser, Thomas

    2017-09-01

    Patterning of functional surfaces is one of the cornerstones of nanotechnology as it allows the fabrication of sensors and lab-on-a-chip devices. Here, the patterning of self-assembled monolayers of branched poly(ethyleneimine) (bPEI) on silica was achieved by means of remote photocatalytic lithography. Moreover, when 2-bromoisobutyryl-modified bPEI was used, the resulting pattern could be amplified by grafting polymer brushes by means of surface-initiated atom transfer radical polymerization. In contrast to previous reports for the patterning of bPEI, the present approach can be conducted in minutes instead of hours, reducing the exposure time to UV radiation and enhancing the overall efficiency. Furthermore, our approach is much more user-friendly, allowing a facile fabrication of patterned initiator-modified surfaces and the use of inexpensive instrumentation such as a low-power UV source and a simple photomask. Considering the versatility of bPEI as a scaffold for the development of biosensors, patterning by means of remote photocatalytic lithography will open new opportunities in a broad field of applications.

  1. Shear Thickening Electrolyte Built from Sterically Stabilized Colloidal Particles.

    Science.gov (United States)

    Shen, Brian H; Armstrong, Beth L; Doucet, Mathieu; Heroux, Luke; Browning, James F; Agamalian, Michael; Tenhaeff, Wyatt E; Veith, Gabriel M

    2018-03-21

    We present a method to prepare shear thickening electrolytes consisting of silica nanoparticles in conventional liquid electrolytes with limited flocculation. These electrolytes rapidly and reversibly stiffen to solidlike behaviors in the presence of external shear or high impact, which is promising for improved lithium ion battery safety, especially in electric vehicles. However, in initial chemistries the silica nanoparticles aggregate and/or sediment in solution over time. Here, we demonstrate steric stabilization of silica colloids in conventional liquid electrolyte via surface-tethered PMMA brushes, synthesized via surface-initiated atom transfer radical polymerization. The PMMA increases the magnitude of the shear thickening response, compared to the uncoated particles, from 0.311 to 2.25 Pa s. Ultrasmall-angle neutron scattering revealed a reduction in aggregation of PMMA-coated silica nanoparticles compared to bare silica nanoparticles in solution under shear and at rest, suggesting good stabilization. Conductivity tests of shear thickening electrolytes (30 wt % solids in electrolyte) at rest were performed with interdigitated electrodes positioned near the meniscus of electrolytes over the course of 24 h to track supernatant formation. Conductivity of electrolytes with bare silica increased from 10.1 to 11.6 mS cm -1 over 24 h due to flocculation. In contrast, conductivity of electrolytes with PMMA-coated silica remained stable at 6.1 mS cm -1 over the same time period, suggesting good colloid stability.

  2. Experimental study on soluble chemical transfer to surface runoff from soil.

    Science.gov (United States)

    Tong, Juxiu; Yang, Jinzhong; Hu, Bill X; Sun, Huaiwei

    2016-10-01

    Prevention of chemical transfer from soil to surface runoff, under condition of irrigation and subsurface drainage, would improve surface water quality. In this paper, a series of laboratory experiments were conducted to assess the effects of various soil and hydraulic factors on chemical transfer from soil to surface runoff. The factors include maximum depth of ponding water on soil surface, initial volumetric water content of soil, depth of soil with low porosity, type or texture of soil and condition of drainage. In the experiments, two soils, sand and loam, mixed with different quantities of soluble KCl were filled in the sandboxes and prepared under different initial saturated conditions. Simulated rainfall induced surface runoff are operated in the soils, and various ponding water depths on soil surface are simulated. Flow rates and KCl concentration of surface runoff are measured during the experiments. The following conclusions are made from the study results: (1) KCl concentration in surface runoff water would decrease with the increase of the maximum depth of ponding water on soil surface; (2) KCl concentration in surface runoff water would increase with the increase of initial volumetric water content in the soil; (3) smaller depth of soil with less porosity or deeper depth of soil with larger porosity leads to less KCl transfer to surface runoff; (4) the soil with finer texture, such as loam, could keep more fertilizer in soil, which will result in more KCl concentration in surface runoff; and (5) good subsurface drainage condition will increase the infiltration and drainage rates during rainfall event and will decrease KCl concentration in surface runoff. Therefore, it is necessary to reuse drained fertile water effectively during rainfall, without polluting groundwater. These study results should be considered in agriculture management to reduce soluble chemical transfer from soil to surface runoff for reducing non-point sources pollution.

  3. The Influence of Dissolved hydrogen on Nickel Alloy SCC: A Window to Fundamental Insight

    Energy Technology Data Exchange (ETDEWEB)

    D.S. Morton; S.A. Attanasio; G.A. Young; P.L. Andresen; T.M. Angeliu

    2000-10-12

    Prior stress corrosion crack growth rate (SCCGR) testing of nickel alloys as a function of the aqueous hydrogen concentration (i.e., the concentration of hydrogen dissolved in the water) has identified different functionalities at 338 and 360 C. These SCCGR dependencies have been uniquely explained in terms of the stability of nickel oxide. The present work evaluates whether the influence of aqueous hydrogen concentration on SCCGR is fundamentally due to effects on hydrogen absorption and/or corrosion kinetics. Hydrogen permeation tests were conducted to measure hydrogen pickup in and transport through the metal. Repassivation tests were performed in an attempt to quantify the corrosion kinetics. The aqueous hydrogen concentration dependency of these fundamental parameters (hydrogen permeation, repassivation) has been used to qualitatively evaluate the film-rupture/oxidation (FRO) and hydrogen assisted cracking (HAC) SCC mechanisms. This paper discusses the conditions that must be imposed upon these mechanisms to describe the known nickel alloy SCCGR aqueous hydrogen concentration functionality. Specifically, the buildup of hydrogen within Alloy 600 (measured through permeability) does not exhibit the same functionality as SCC with respect to the aqueous hydrogen concentration. This result implies that if HAC is the dominant SCC mechanism, then corrosion at isolated active path regions (i.e., surface initiation sites or cracks) must be the source of localized elevated detrimental hydrogen. Repassivation tests showed little temperature sensitivity over the range of 204 to 360 C. This result implies that for either the FRO or the HAC mechanism, corrosion processes (e.g., at a crack tip, in the crack wake, or on surfaces external to the crack) cannot by themselves explain the strong temperature dependence of nickel alloy SCC.

  4. A novel thermal and pH responsive drug delivery system based on ZnO@PNIPAM hybrid nanoparticles

    International Nuclear Information System (INIS)

    Tan, Licheng; Liu, Jian; Zhou, Weihua; Wei, Junchao; Peng, Zhiping

    2014-01-01

    A smart ZnO@PNIPAM hybrid was prepared by grafting thermal responsive poly(N-isopropylacrylamide) (PNIPAM) on zinc oxide (ZnO) nanoparticles via surface-initiated atom transfer radical polymerization (ATRP). The thermal gravimetric analysis (TGA) shows that the grafting amount of PNIPAM was about 38%, and the SEM images show that the PNIPAM chains can prevent the aggregation of ZnO nanoparticles. The responsive properties of ZnO@PNIPAM were measured by photoluminescence spectra, and the results demonstrate that the PNIPAM chains grafted on ZnO surfaces can realize reversible thermal responsive and photoluminescence properties. An anticancer drug, doxorubicin (Dox), was used as a model drug and loaded into the hybrid nanoparticles, and an in vitro drug release test implied that ZnO@PNIPAM could work as a thermal responsive drug delivery system. Furthermore, pH sensitive drug releases were carried out in acetate buffer at pH 5.0 and pH 6.0 and in water at pH 7.0, and the results showed evident pH dependency, showing its pH responsive properties. - Graphical abstract: In this manuscript, thermal responsive poly(N-isopropylacrylamide) (PNIPAM) was grafted on the surface of ZnO nanoparticles. The obtained ZnO@PNIPAM hybrid showed reversible thermal responsive photoluminescent properties, and can also work as a thermal and pH responsive drug delivery system. - Highlights: • The ZnO@PNIPAM hybrid was prepared via ATRP. • The ZnO@PNIPAM hybrid showed thermal responsive properties. • The ZnO@PNIPAM hybrid can work as a thermal and pH responsive drug delivery system

  5. Immobilization of poly(MPC) brushes onto titanium surface by combining dopamine self-polymerization and ATRP: Preparation, characterization and evaluation of hemocompatibility in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Wenyong; Yang, Ping; Li, Jingan; Li, Shiqi; Li, Peichuang; Zhao, Yuancong, E-mail: Zhaoyc7320@163.com; Huang, Nan

    2015-09-15

    Graphical abstract: The functional surface containing rich amino and hydroxyl groups was obtained by simple and easily dopamine self-polymerization. Poly (MPC) brushes were successfully immobilized on titanium surface by combining acylation reaction and ATRP. This chemical and biomimetic modified titanium surface effectively inhibits platelet adhesion and activation. - Highlights: • Polydopamine coating provides amino and hydroxyl groups for second reactivity. • Poly(MPC) brushes covalently immobilized on coating by surface initiated ATRP. • In vitro hemocompatibility of biomimetic modified Ti was better than unmodified. - Abstract: Poly(2-methacryloyloxyethyl phosphorylcholine(MPC)) has been studied in many biomedical fields because of good biocompatibility, such as hemocompatibility, inhibiting protein adhesion, antifouling, and so on. To achieve good hemocompatibility of titanium (Ti) surface, bio-inspired poly(MPC) brushes were grafted from Ti substrate covalently. In this work, the surface of Ti was first coated with polydopamine, and got a surface bearing −NH{sub 2} and −OH groups which could be bridged with poly(MPC) via atom transfer radical polymerization. Water contact angle decreased to 51.3° when titanium grafted with poly(MPC) brushes. The data of Infrared Spectroscopy and X-ray photoelectron spectroscopy (XPS) indicated that poly(MPC) was successfully grafted onto the surface of titanium. Platelet-rich plasma (PRP) adhesion test and lactate dehydrogenase (LDH) assay showed that the number of platelets adhered on the surface of modified-titanium was much less than that of unmodified titanium and platelets did not aggregate and distort. Thus, the simple and chemical method of immobilization of poly(MPC) brushes has potential application for improving hemocompatibility for cardiovascular stent and some other biomaterials.

  6. Chemical and mechanical interactions of interstitials with vanadium alloys

    Energy Technology Data Exchange (ETDEWEB)

    DiStefano, J.R.; Chitwood, L.D.; DeVan, J.H. [Oak Ridge National Laboratory, TN (United States)

    1996-04-01

    Oxidation studies of V-4Cr-4Ti were conducted in air and reduced oxygen partial pressures (10{sup 4}, 10{sup -5} and 10{sup -6} torr). Reaction rates were determined by weight change measurements and chemical analyses. Mechanical properties after the exposures were determined by room temperature tensile tests. In air at 400 and 500{degrees}C, oxide films form on the surface. Initially, rates are high but decrease with time reaching similiar values to those found in oxygen partial pressures at 10{sup -4}, 10{sup -5}, and 10{sup -6} torr. At 400{degrees}C, oxygen pick-up followed a logarithmic function of time and was confined to regions near the surface. Little change in room temperature tensile properties was noted for oxygen increase up to 1500 ppm. Thermal cycling specimens from 400{degrees}C to room temperature up to 14 times had no apparent effect on oxidation rate or tensile properties. At 500{degrees}C, oxygen pick-up appeared to follow a parabolic relation with time. Rates were {approx} 10 times those at 400{degrees}C and correspondingly larger oxygen increases occurred when compared with the 400{degrees}C tests after similiar time periods. This resulted in a significant decrease in total elongation after 240 h. At reduced oxygen partial pressures, rates were measured for times <100 h. Data are relatively sparse but generally show a slightly higher initial rate before slowing. At 400{degrees}C increases to {approx}200 ppm oxygen were found with no effect on room temperature elongation. At 500{degrees}C increase in oxygen of 2400 ppm after 50h/10{sup -5} torr resulted in a decrease of around 25% in room temperature elongation. By comparison, exposure to air at 500{degrees}C for 12 h caused nearly the same results.

  7. Real-time optical diagnosis of the rat brain exposed to a laser-induced shock wave: observation of spreading depolarization, vasoconstriction and hypoxemia-oligemia.

    Directory of Open Access Journals (Sweden)

    Shunichi Sato

    Full Text Available Despite many efforts, the pathophysiology and mechanism of blast-induced traumatic brain injury (bTBI have not yet been elucidated, partially due to the difficulty of real-time diagnosis and extremely complex factors determining the outcome. In this study, we topically applied a laser-induced shock wave (LISW to the rat brain through the skull, for which real-time measurements of optical diffuse reflectance and electroencephalogram (EEG were performed. Even under conditions showing no clear changes in systemic physiological parameters, the brain showed a drastic light scattering change accompanied by EEG suppression, which indicated the occurrence of spreading depression, long-lasting hypoxemia and signal change indicating mitochondrial energy impairment. Under the standard LISW conditions examined, hemorrhage and contusion were not apparent in the cortex. To investigate events associated with spreading depression, measurement of direct current (DC potential, light scattering imaging and stereomicroscopic observation of blood vessels were also conducted for the brain. After LISW application, we observed a distinct negative shift in the DC potential, which temporally coincided with the transit of a light scattering wave, showing the occurrence of spreading depolarization and concomitant change in light scattering. Blood vessels in the brain surface initially showed vasodilatation for 3-4 min, which was followed by long-lasting vasoconstriction, corresponding to hypoxemia. Computer simulation based on the inverse Monte Carlo method showed that hemoglobin oxygen saturation declined to as low as ∼35% in the long-term hypoxemic phase. Overall, we found that topical application of a shock wave to the brain caused spreading depolarization/depression and prolonged severe hypoxemia-oligemia, which might lead to pathological conditions in the brain. Although further study is needed, our findings suggest that spreading depolarization/depression is one of

  8. Electrical conductivity in Langmuir-Blodgett films of n-alkyl cyanobiphenyls using current sensing atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Gayathri, H. N.; Suresh, K. A., E-mail: suresh@cnsms.res.in [Centre for Nano and Soft Matter Sciences, P. B. No. 1329, Jalahalli, Bangalore 560013 (India)

    2015-06-28

    We report our studies on the nanoscale electrical conductivity in monolayers of n-alkyl cyanobiphenyl materials deposited on solid surface. Initially, the 8CB, 9CB, and 10CB monolayer films were prepared by the Langmuir technique at air-water interface and characterized by surface manometry and Brewster angle microscopy. The monolayer films were transferred on to solid substrates by the Langmuir-Blodgett (L-B) technique. The 8CB, 9CB, and 10CB monolayer L-B films were deposited on freshly cleaved mica and studied by atomic force microscope (AFM), thereby measuring the film thickness as ∼1.5 nm. The electrical conductivity measurements were carried out on 9CB and 10CB monolayer L-B films deposited onto highly ordered pyrolytic graphite using current sensing AFM. The nanoscale current-voltage (I-V) measurements show a non-linear variation. The nature of the curve indicates electron tunneling to be the mechanism for electrical conduction. Furthermore, analysis of the I-V curve reveals a transition in the electron conduction mechanism from direct tunneling to injection tunneling. From the transition voltage, we have estimated the values of barrier height for 9CB and 10CB to be 0.71 eV and 0.37 eV, respectively. For both 9CB and 10CB, the effective mass of electron was calculated to be 0.021 m{sub e} and 0.065 m{sub e}, respectively. These parameters are important in the design of molecular electronic devices.

  9. Preliminary results of laser-assisted sealing of hand-sewn canine esophageal anastomoses

    Science.gov (United States)

    Auteri, Joseph S.; Oz, Mehmet C.; Sanchez, Juan A.; Bass, Lawrence S.; Jeevanandam, Valluvan; Williams, Matthew R.; Smith, Craig R.; Treat, Michael R.

    1991-07-01

    Dehiscence rates of esophageal anastomoses range between 5 and 20%. Causative factors include ischemia, tension, foreign body reaction, microabscesses, and the negative pressure within the thoracic cavity. Laser assisted tissue sealing (LATS) has been shown to decrease anastomotic leakage rates in other tissues. Using a canine model the efficacy of LATS in enhancing single layer hand swen intrathoracic esophageal anastomoses was assessed. Via a left thoracotomy, paired two centimeter transverse incisions (one laser sealed, one control) were made in the proximal and distal esophagus in nine dogs. Both were sewn using a single layer of 4-0 polyglycolic acid. A combination of albumin (0.2 cc), sodium hyaluronate (0.4 cc), and indocyanine green (1 gtt) was applied to one of the randomly chosen hand sewn repairs. The albumin/hyaluronate combination is used to provide a protein matrix across the anastomosis for ingrowth of fibroblasts. Indocyanine green dye selectively absorbs at OM805 nm which matches the output of the diode laser (808 +/- 1 nm), thus improving uptake of laser energy by the targeted tissues. The anastomosis was then exposed to continuous wave diode laser energy for OM2 minutes at a power density of 9.6 W/cm2. The esophagus was recovered either at the time of sealing or two days postoperatively and infused with saline under pressure. Bursting pressures were considered the point of initial saline leakage. At time 0 there was no significant difference in bursting pressures between the LATS group and controls. However, at two days postoperatively controls burst at 121 +/- 14 mmHg while the laser assisted anastomoses burst at 295 +/- 35 mmHg (p anastomoses revealed minimal thermal injury to the mucosal surface initially, with some regeneration of mucosal lining at two days postoperatively. No foreign body reaction to the solder was noted. Laser reinforcement of single layer hand sewn esophageal anastomoses appears to increase bursting pressure and may result

  10. Do edible oils reduce bacterial colonization of enamel in situ?

    Science.gov (United States)

    Hannig, Christian; Kirsch, Jasmin; Al-Ahmad, Ali; Kensche, Anna; Hannig, Matthias; Kümmerer, Klaus

    2013-03-01

    Edible oils are an empiric approach for the prevention of oral diseases. The present in situ study investigated the effect of edible oils on initial bacterial colonization of enamel surfaces. Initial biofilm formation was performed on enamel specimens mounted on maxillary splints and carried by eight subjects. After 1 min of pellicle formation, rinses with safflower oil, olive oil and linseed oil were performed for 10 min. Application of chlorhexidine for 1 min served as positive control. Afterwards, the slabs were carried for 8 h overnight. Samples carried for 8 h without any rinse served as negative controls. The amount of adherent bacteria was determined by DAPI staining (4',6-diamidino-2-phenylindole) and live-dead staining (BacLight). Additionally, determination of colony forming units was performed after desorption of the bacteria. TEM evaluation was carried out after application of the rinses. The number of adherent bacteria on control samples was 6.1 ± 8.1 × 10(5)/cm(2) after 8 h (DAPI). Fluorescence microscopic data from DAPI staining and live-dead staining as well as from the determination of CFU revealed no significant effects of rinsing with oils on the amount of adherent bacteria compared to the non-rinsed control samples. However, with chlorhexidine a significant reduction in the number of bacteria by more than 85 % was achieved (DAPI, chlorhexidine: 8.2 ± 17.1 × 10(4)/cm(2)). The ratio of viable to dead bacteria was almost equal (1:1) irrespective of the rinse adopted as recorded with BacLight. TEM indicated accumulation of oil micelles at the pellicle's surface and modification of its ultrastructure. Rinses with edible oils have no significant impact on the initial pattern and amount of bacterial colonization on enamel over 8 h. Rinses with edible oils cannot be recommended for efficient reduction of oral biofilm formation.

  11. Uptake of pH-Sensitive Gold Nanoparticles in Strong Polyelectrolyte Brushes

    Directory of Open Access Journals (Sweden)

    Dikran Kesal

    2016-04-01

    Full Text Available The impact of electrostatic attraction on the uptake of gold nanoparticles (AuNPs into positively charged strong poly-[2-(Methacryloyloxy ethyl] trimethylammonium chloride (PMETAC polyelectrolyte brushes was investigated. In this work, PMETAC brushes were synthesized via surface-initiated atom transfer radical polymerization (Si-ATRP. PMETAC/AuNP composite materials were prepared by incubation of the polymer brush coated samples into 3-mercaptopropionic acid-capped AuNP (5 nm in diameter suspension. The electrostatic interactions were tuned by changing the surface charge of the AuNPs through variations in pH value, while the charge of the PMETAC brush was not affected. Atomic-force microscopy (AFM, ellipsometry, UV/Vis spectroscopy, gravimetric analysis and transmission electron microscopy (TEM were employed to study the loading and penetration into the polymer brush. The results show that the number density of attached AuNPs depends on the pH value and increases with increasing pH value. There is also strong evidence that the particle assembly is dependent on the pH value of the AuNP suspension. Incubation of PMETAC brushes in AuNP suspension at pH 4 led to the formation of a surface layer on top of the brush (2D assembly due to sterical hindrance of the clustered AuNPs, while incubation in AuNP suspension at pH 8 led to deeper particle penetration into the brush (3D assembly. The straightforward control of particle uptake and assembly by tuning the charge density of the nanoparticle surface is a valuable tool for the development of materials for colorimetric sensor applications.

  12. Incorporation of multilayered silver nanoparticles into polymer brushes as 3-dimensional SERS substrates and their application for bacteria detection

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Qian; Wang, Xiang-Dong; Tian, Ting; Chu, Li-Qiang, E-mail: chuliqiang@tust.edu.cn

    2017-06-15

    Highlights: • POEGMA/AgNPs composite film prepared via the in-stacking method is employed as 3D SERS substrate. • Control over POEGMA chain length is achieved via SI-ATRP method. • Influence of POEGMA chain length and in-stacking process on SERS performance is investigated. • The 3D SERS substrate is used for the ultrasensitive detection of ATP and S. aureus. - Abstract: Surface-enhanced Raman scattering (SERS) sensors have been extensively studied for ultrasensitive detection of diverse chemical or biological analytes. Facile fabrication of highly sensitive SERS substrates is believed to be of crucial importance in these analytical applications. In this regard, the preparation of 3-dimensional (3D) SERS substrates are explored via the incorporation of multilayered silver nanoparticles (AgNPs) into poly (oligo(ethylene glycol) methacrylate) (POEGMA) brushes by repeating the immersion-rinsing-drying steps for different lengths of time (i.e., the so-called in-stacking method). The POEGMA brushes of different chain lengths are synthesized by surface-initiated atom transfer radical polymerization (ATRP) with various reaction time. The resulting POEGMA/AgNP nanocomposites are characterized by FE-SEM, UV–vis and Raman spectroscopy. FE-SEM and UV–vis results indicate that the AgNPs are successfully incorporated into the POEGMA brushes with a 3D configuration. The nanocomposite films are employed as SERS substrates for the detection of a Raman reporter molecule (i.e., 4-aminothiophenol), giving rise to an enhancement factor of up to 1.29 × 10{sup 7} and also having relatively good uniformity and reproducibility. The obtained 3D SERS substrates are also used for the detection of a typical gram-positive bacterium, Staphylococcus aureus. The limit of detection is found to be as low as ca. 8 CFU/mL.

  13. A new approach to the problem of bulk-mediated surface diffusion.

    Science.gov (United States)

    Berezhkovskii, Alexander M; Dagdug, Leonardo; Bezrukov, Sergey M

    2015-08-28

    This paper is devoted to bulk-mediated surface diffusion of a particle which can diffuse both on a flat surface and in the bulk layer above the surface. It is assumed that the particle is on the surface initially (at t = 0) and at time t, while in between it may escape from the surface and come back any number of times. We propose a new approach to the problem, which reduces its solution to that of a two-state problem of the particle transitions between the surface and the bulk layer, focusing on the cumulative residence times spent by the particle in the two states. These times are random variables, the sum of which is equal to the total observation time t. The advantage of the proposed approach is that it allows for a simple exact analytical solution for the double Laplace transform of the conditional probability density of the cumulative residence time spent on the surface by the particle observed for time t. This solution is used to find the Laplace transform of the particle mean square displacement and to analyze the peculiarities of its time behavior over the entire range of time. We also establish a relation between the double Laplace transform of the conditional probability density and the Fourier-Laplace transform of the particle propagator over the surface. The proposed approach treats the cases of both finite and infinite bulk layer thicknesses (where bulk-mediated surface diffusion is normal and anomalous at asymptotically long times, respectively) on equal footing.

  14. Controlled in situ formation of polyacrylamide hydrogel on PET surface via SI-ARGET-ATRP for wound dressings

    Energy Technology Data Exchange (ETDEWEB)

    Nazari Pour, Sedigheh [Department of Chemistry, Faculty of Science, University of Manitoba, Winnipeg, Canada R3T 2N2 (Canada); Ghugare, Shivkumar V. [Department of Textile Science, Faculty of Human Ecology, University of Manitoba, Winnipeg, Canada R3T 2N2 (Canada); Wiens, Richard; Gough, Kathleen [Department of Chemistry, Faculty of Science, University of Manitoba, Winnipeg, Canada R3T 2N2 (Canada); Liu, Song, E-mail: Song.Liu@umanitoba.ca [Department of Chemistry, Faculty of Science, University of Manitoba, Winnipeg, Canada R3T 2N2 (Canada); Department of Textile Science, Faculty of Human Ecology, University of Manitoba, Winnipeg, Canada R3T 2N2 (Canada); Department of Biosystems Engineering, Faculty of Engineering, University of Manitoba, Winnipeg, Canada R3T 2N2 (Canada)

    2015-09-15

    Graphical abstract: - Highlights: • We grow poly(acrylamide) (PAM) hydrgol from a polymer surface in a controlled way. • Divinyl crosslinker doesn't compromise the control chain growth feature of ARGET-ATRP. • ATR-FTIR-FPA images (spatial resolution 220 nm) reveal a uniform grafting of PAM. • PAM grafted wound dressing can be dual functional: low-adherent and antibacterial. - Abstract: Well-defined polyacrylamide (PAM) hydrogel was synthesized on the surface of poly(ethylene terephthalate) (PET) film via surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET-ATRP). Following the deposition of an ATRP initiator (2-bromoisobutyrylbromide) on PET film, PAM hydrogel was grafted from the functionalized PET surface via ARGET-ATRP. XPS and FTIR-ATR confirmed that PAM hydrogel was successfully grafted on the PET surface. Results from AFM, SEM, and FTIR-FPA microscopic investigations showed that PAM hydrogel uniformly covers the surface of PET film. The grafting yield increases linearly with increasing reaction time, indicating that the growth of PAM hydrogel on the surface of PET is well controlled. In a cell adhesion assay, PAM hydrogel grafted PET films (PAM hydrogel-g-PET) showed low adhesion to keratinocyte cells. To impart PAM hydrogel-g-PET with antibacterial function, AgNPs were self-assembled along the amide side chains of PAM hydrogel. AgNPs loaded-PAM hydrogel-g-PET shows 99% reduction in the number of multidrug-resistant Pseudomonas aeruginosa within 3 h contact.

  15. Hydrogeology, chemical and microbial activity measurement through deep permafrost.

    Science.gov (United States)

    Stotler, Randy L; Frape, Shaun K; Freifeld, Barry M; Holden, Brian; Onstott, Tullis C; Ruskeeniemi, Timo; Chan, Eric

    2011-01-01

    Little is known about hydrogeochemical conditions beneath thick permafrost, particularly in fractured crystalline rock, due to difficulty in accessing this environment. The purpose of this investigation was to develop methods to obtain physical, chemical, and microbial information about the subpermafrost environment from a surface-drilled borehole. Using a U-tube, gas and water samples were collected, along with temperature, pressure, and hydraulic conductivity measurements, 420 m below ground surface, within a 535 m long, angled borehole at High Lake, Nunavut, Canada, in an area with 460-m-thick permafrost. Piezometric head was well above the base of the permafrost, near land surface. Initial water samples were contaminated with drill fluid, with later samples <40% drill fluid. The salinity of the non-drill fluid component was <20,000 mg/L, had a Ca/Na ratio above 1, with δ(18) O values ∼5‰ lower than the local surface water. The fluid isotopic composition was affected by the permafrost-formation process. Nonbacteriogenic CH(4) was present and the sample location was within methane hydrate stability field. Sampling lines froze before uncontaminated samples from the subpermafrost environment could be obtained, yet the available time to obtain water samples was extended compared to previous studies. Temperature measurements collected from a distributed temperature sensor indicated that this issue can be overcome easily in the future. The lack of methanogenic CH(4) is consistent with the high sulfate concentrations observed in cores. The combined surface-drilled borehole/U-tube approach can provide a large amount of physical, chemical, and microbial data from the subpermafrost environment with few, controllable, sources of contamination. Copyright © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.

  16. Biodegradable polymer brush as nanocoupled interface for improving the durability of polymer coating on metal surface.

    Science.gov (United States)

    Bedair, Tarek M; Cho, Youngjin; Joung, Yoon Ki; Han, Dong Keun

    2014-10-01

    Metal-based drug-eluting stents (DESs) have severe drawbacks such as peeling-off and cracking of the coated polymer. To prevent the fracture of polymer-coated layer and improve the durability of DES, poly(l-lactide) (PLLA) brushes were synthesized onto cobalt-chromium (Co-Cr or CC) surface through atom transfer radical polymerization (ATRP) of 2-hydroxyethylmethacrylate (HEMA) followed by surface-initiated ring opening polymerization (SI-ROP) of l-lactide. The polymer brushes were then characterized by attenuated total reflection-Fourier transform infrared (ATR-FTIR), water contact angle, ellipsometry, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). All of the unmodified and modified Co-Cr surfaces were coated with a matrix of poly(d,l-lactide) (PDLLA) and sirolimus (SRL). The in vitro drug release profile was measured for 70 days. The PLLA-modified Co-Cr showed a biphasic release pattern in the initial burst followed by a slow release. On the other hand, the unmodified Co-Cr showed fast drug release and detachment of the coated polymer layer due to the instability of the polymer layer on Co-Cr surface. In comparison, the PLLA-modified Co-Cr preserved a uniform coating without detachment even after 6 weeks of degradation test. The platelet morphology and low density of platelet adhered on the modified layer and the SRL-in-PDLLA coated Co-Cr surfaces demonstrated that these samples would be blood compatible. Therefore, the introduction of PLLA brush onto Co-Cr surface is proved to dramatically improve the durability of the coating layer, and it is a promising strategy to prevent the coating defects found in DESs. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Hydrogeology, chemical and microbial activity measurement through deep permafrost

    Energy Technology Data Exchange (ETDEWEB)

    Stotler, R.L.; Frape, S.K.; Freifeld, B.M.; Holden, B.; Onstott, T.C.; Ruskeeniemi, T.; Chan, E.

    2010-04-01

    Little is known about hydrogeochemical conditions beneath thick permafrost, particularly in fractured crystalline rock, due to difficulty in accessing this environment. The purpose of this investigation was to develop methods to obtain physical, chemical, and microbial information about the subpermafrost environment from a surface-drilled borehole. Using a U-tube, gas and water samples were collected, along with temperature, pressure, and hydraulic conductivity measurements, 420 m below ground surface, within a 535 m long, angled borehole at High Lake, Nunavut, Canada, in an area with 460-m-thick permafrost. Piezometric head was well above the base of the permafrost, near land surface. Initial water samples were contaminated with drill fluid, with later samples <40% drill fluid. The salinity of the non-drill fluid component was <20,000 mg/L, had a Ca/Na ratio above 1, with {delta}{sup 18}O values {approx}5{per_thousand} lower than the local surface water. The fluid isotopic composition was affected by the permafrost-formation process. Nonbacteriogenic CH{sub 4} was present and the sample location was within methane hydrate stability field. Sampling lines froze before uncontaminated samples from the subpermafrost environment could be obtained, yet the available time to obtain water samples was extended compared to previous studies. Temperature measurements collected from a distributed temperature sensor indicated that this issue can be overcome easily in the future. The lack of methanogenic CH{sub 4} is consistent with the high sulfate concentrations observed in cores. The combined surface-drilled borehole/U-tube approach can provide a large amount of physical, chemical, and microbial data from the subpermafrost environment with few, controllable, sources of contamination.

  18. Effect of denture cleaning on abrasion resistance and surface topography of polymerized CAD CAM acrylic resin denture base.

    Science.gov (United States)

    Shinawi, Lana Ahmed

    2017-05-01

    The application of computer-aided design computer-aided manufacturing (CAD CAM) technology in the fabrication of complete dentures, offers numerous advantages as it provides optimum fit and eliminates polymerization shrinkage of the acrylic base. Additionally, the porosity and surface roughness of CAD CAM resins is less compared to conventionally processed resins which leads to a decrease in the adhesion of bacteria on the denture base, which is associated with many conditions including halitosis and aspiration pneumonia in elderly denture wearers. To evaluate the influence of tooth brushing with dentifrices on CAD CAM resin blocks in terms of abrasion resistance, surface roughness and scanning electron photomicrography. This experimental study was carried out at the Faculty of Dentistry of King Abdulaziz University during 2016. A total of 40 rectangular shaped polymerized CAD CAM resin samples were subjected to 40.000 and 60.000 brushing strokes under a 200-gram vertical load simulating three years of tooth brushing strokes using commercially available denture cleaning dentifrice. Data were analyzed by SPSS version 20, using descriptive statistics and ANOVA. ANOVA test revealed a statistical significant weight loss of CAD CAM acrylic resin denture base specimens following 40.000 and 60.000 brushing strokes as well as a statistical significant change (p=0.0.5) in the surface roughness following brushing. The CAD CAM resin samples SEM baseline imaging revealed a relatively smooth homogenous surface, but following 40,000 and 60,000 brushing strokes, imaging displayed the presence of small scratches on the surface. CAD CAM resin displayed a homogenous surface initially with low surface roughness that was significantly affected following simulating three years of manual brushing, but despite the significant weight loss, the findings are within the clinically acceptable limits.

  19. Improving dielectric properties of BaTiO3/poly(vinylidene fluoride) composites by employing core-shell structured BaTiO3@Poly(methylmethacrylate) and BaTiO3@Poly(trifluoroethyl methacrylate) nanoparticles

    Science.gov (United States)

    Zhang, Xianhong; Zhao, Sidi; Wang, Fang; Ma, Yuhong; Wang, Li; Chen, Dong; Zhao, Changwen; Yang, Wantai

    2017-05-01

    Polymer based dielectric composites were fabricated through incorporation of core-shell structured BaTiO3 (BT) nanoparticles into PVDF matrix by means of solution blending. Core-shell structured BT nanoparticles with different shell composition and shell thickness were prepared by grafting methacrylate monomer (MMA or TFEMA) onto the surface of BT nanoparticles via surface initiated atom transfer radical polymerization (SI-ATRP). The content of the grafted polymer and the micro-morphology of the core-shell structured BT nanoparticles were investigated by thermo gravimetric analyses (TGA) and transmission electron microscopy (TEM), respectively. The dielectric properties were measured by broadband dielectric spectroscopy. The results showed that high dielectric constant and low dielectric loss are successfully realized in the polymer based composites. Moreover, the type of the grafted polymer and its content had different effect on the dielectric constant. In detail, the attenuation of dielectric constant was 16.6% for BT@PMMA1/PVDF and 10.7% for BT@PMMA2/PVDF composite in the range of 10 Hz to 100 kHz, in which the grafted content of PMMA was 5.5% and 8.0%, respectively. However, the attenuation of dielectric constant was 5.5% for BT@PTFEMA1/PVDF and 4.0% for BT@PTFEMA2/PVDF composite, in which the grafted content of PTFEMA was 1.5% and 2.0%, respectively. These attractive features of BT@PTFEMA/PVDF composites suggested that dielectric ceramic fillers modified with fluorinated polymer can be used to prepare high performance composites, especially those with low dielectric loss and high dielectric constant.

  20. Simulation of fluid flow and energy transport processes associated with high-level radioactive waste disposal in unsaturated alluvium

    Science.gov (United States)

    Pollock, David W.

    1986-01-01

    Many parts of the Great Basin have thick zones of unsaturated alluvium which might be suitable for disposing of high-level radioactive wastes. A mathematical model accounting for the coupled transport of energy, water (vapor and liquid), and dry air was used to analyze one-dimensional, vertical transport above and below an areally extensive repository. Numerical simulations were conducted for a hypothetical repository containing spent nuclear fuel and located 100 m below land surface. Initial steady state downward water fluxes of zero (hydrostatic) and 0.0003 m yr−1were considered in an attempt to bracket the likely range in natural water flux. Predicted temperatures within the repository peaked after approximately 50 years and declined slowly thereafter in response to the decreasing intensity of the radioactive heat source. The alluvium near the repository experienced a cycle of drying and rewetting in both cases. The extent of the dry zone was strongly controlled by the mobility of liquid water near the repository under natural conditions. In the case of initial hydrostatic conditions, the dry zone extended approximately 10 m above and 15 m below the repository. For the case of a natural flux of 0.0003 m yr−1 the relative permeability of water near the repository was initially more than 30 times the value under hydrostatic conditions, consequently the dry zone extended only about 2 m above and 5 m below the repository. In both cases a significant perturbation in liquid saturation levels persisted for several hundred years. This analysis illustrates the extreme sensitivity of model predictions to initial conditions and parameters, such as relative permeability and moisture characteristic curves, that are often poorly known.

  1. A novel shortened electrospun nanofiber modified with a 'concentrated' polymer brush

    Directory of Open Access Journals (Sweden)

    Chiaki Yoshikawa, Kun Zhang, Ewelina Zawadzak and Hisatoshi Kobayashi

    2011-01-01

    Full Text Available We report the fabrication of shortened electrospun polymer fibers with a well-defined concentrated polymer brush. We first prepared electrospun nanofibers from a random copolymer of styrene and 4-vinylbenzyl 2-bromopropionate, with number-average molecular weight Mn=105 200 and weight-average molecular weight Mw=296 700 (Mw/Mn=2.82. The fibers had a diameter of 593±74 nm and contained initiating sites for surface-initiated atom transfer radical polymerization (SI-ATRP. Then, SI-ATRP of hydrophilic styrene sodium sulfonate (SSNa was carried out in the presence of a free initiator and the hydrophobic fibers. Gel permeation chromatography confirmed that Mn and Mw/Mn values were almost the same for free polymers and graft polymers. Mn agreed well with the theoretical prediction, and Mw/Mn was relatively low (<1.3 in all the examined cases, indicating that this polymerization proceeded in a living manner. Using the values of the graft amount measured by Fourier transform infrared spectroscopy, the surface area, and Mn, we calculated the graft density σ as 0.22 chains nm−2. This value was nearly equal to the density obtained on silicon wafers (σ=0.24 chains nm−2, which is categorized into the concentrated brush regime. Finally, we mechanically cut the fibers with a concentrated poly(SSNa brush by a homogenizer. With increasing cutting time, the fiber length became shorter and more homogenous (11±17 μm after 3 h. The shortened fibers exhibited excellent water dispersibility owing to the hydrophilic poly(SSNa brush layer.

  2. Modelling the fate of persistent organic pollutants in Europe: parameterisation of a gridded distribution model

    International Nuclear Information System (INIS)

    Prevedouros, Konstantinos; MacLeod, Matthew; Jones, Kevin C.; Sweetman, Andrew J.

    2004-01-01

    A regionally segmented multimedia fate model for the European continent is described together with an illustrative steady-state case study examining the fate of γ-HCH (lindane) based on 1998 emission data. The study builds on the regionally segmented BETR North America model structure and describes the regional segmentation and parameterisation for Europe. The European continent is described by a 5 deg. x 5 deg. grid, leading to 50 regions together with four perimetric boxes representing regions buffering the European environment. Each zone comprises seven compartments including; upper and lower atmosphere, soil, vegetation, fresh water and sediment and coastal water. Inter-regions flows of air and water are described, exploiting information originating from GIS databases and other georeferenced data. The model is primarily designed to describe the fate of Persistent Organic Pollutants (POPs) within the European environment by examining chemical partitioning and degradation in each region, and inter-region transport either under steady-state conditions or fully dynamically. A test case scenario is presented which examines the fate of estimated spatially resolved atmospheric emissions of lindane throughout Europe within the lower atmosphere and surface soil compartments. In accordance with the predominant wind direction in Europe, the model predicts high concentrations close to the major sources as well as towards Central and Northeast regions. Elevated soil concentrations in Scandinavian soils provide further evidence of the potential of increased scavenging by forests and subsequent accumulation by organic-rich terrestrial surfaces. Initial model predictions have revealed a factor of 5-10 underestimation of lindane concentrations in the atmosphere. This is explained by an underestimation of source strength and/or an underestimation of European background levels. The model presented can further be used to predict deposition fluxes and chemical inventories, and it

  3. Macropinocytosis, mTORC1 and cellular growth control.

    Science.gov (United States)

    Yoshida, Sei; Pacitto, Regina; Inoki, Ken; Swanson, Joel

    2018-04-01

    The growth and proliferation of metazoan cells are driven by cellular nutrient status and by extracellular growth factors. Growth factor receptors on cell surfaces initiate biochemical signals that increase anabolic metabolism and macropinocytosis, an actin-dependent endocytic process in which relatively large volumes of extracellular solutes and nutrients are internalized and delivered efficiently into lysosomes. Macropinocytosis is prominent in many kinds of cancer cells, and supports the growth of cells transformed by oncogenic K-Ras. Growth factor receptor signaling and the overall metabolic status of the cell are coordinated in the cytoplasm by the mechanistic target-of-rapamycin complex-1 (mTORC1), which positively regulates protein synthesis and negatively regulates molecular salvage pathways such as autophagy. mTORC1 is activated by two distinct Ras-related small GTPases, Rag and Rheb, which associate with lysosomal membranes inside the cell. Rag recruits mTORC1 to the lysosomal surface where Rheb directly binds to and activates mTORC1. Rag is activated by both lysosomal luminal and cytosolic amino acids; Rheb activation requires phosphoinositide 3-kinase, Akt, and the tuberous sclerosis complex-1/2. Signals for activation of Rag and Rheb converge at the lysosomal membrane, and several lines of evidence support the idea that growth factor-dependent endocytosis facilitates amino acid transfer into the lysosome leading to the activation of Rag. This review summarizes evidence that growth factor-stimulated macropinocytosis is essential for amino acid-dependent activation of mTORC1, and that increased solute accumulation by macropinocytosis in transformed cells supports unchecked cell growth.

  4. Effect of denture cleaning on abrasion resistance and surface topography of polymerized CAD CAM acrylic resin denture base

    Science.gov (United States)

    Shinawi, Lana Ahmed

    2017-01-01

    Background The application of computer-aided design computer-aided manufacturing (CAD CAM) technology in the fabrication of complete dentures, offers numerous advantages as it provides optimum fit and eliminates polymerization shrinkage of the acrylic base. Additionally, the porosity and surface roughness of CAD CAM resins is less compared to conventionally processed resins which leads to a decrease in the adhesion of bacteria on the denture base, which is associated with many conditions including halitosis and aspiration pneumonia in elderly denture wearers. Aim To evaluate the influence of tooth brushing with dentifrices on CAD CAM resin blocks in terms of abrasion resistance, surface roughness and scanning electron photomicrography. Methods This experimental study was carried out at the Faculty of Dentistry of King Abdulaziz University during 2016. A total of 40 rectangular shaped polymerized CAD CAM resin samples were subjected to 40.000 and 60.000 brushing strokes under a 200-gram vertical load simulating three years of tooth brushing strokes using commercially available denture cleaning dentifrice. Data were analyzed by SPSS version 20, using descriptive statistics and ANOVA. Results ANOVA test revealed a statistical significant weight loss of CAD CAM acrylic resin denture base specimens following 40.000 and 60.000 brushing strokes as well as a statistical significant change (p=0.0.5) in the surface roughness following brushing. The CAD CAM resin samples SEM baseline imaging revealed a relatively smooth homogenous surface, but following 40,000 and 60,000 brushing strokes, imaging displayed the presence of small scratches on the surface. Conclusion CAD CAM resin displayed a homogenous surface initially with low surface roughness that was significantly affected following simulating three years of manual brushing, but despite the significant weight loss, the findings are within the clinically acceptable limits. PMID:28713496

  5. Original Ge-induced phenomena on various SiC(0 0 0 1) reconstructions

    Energy Technology Data Exchange (ETDEWEB)

    Ait-Mansour, K [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France); Dentel, D [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France); Kubler, L [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France); Diani, M [LSGM, Departement de Physique, Faculte des Sciences et Techniques, Tanger BP 416 (Morocco); Derivaz, M [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France); Bischoff, J L [Laboratoire de Physique et de Spectroscopie Electronique, UMR CNRS 7014, Universite de Haute Alsace, 68093 Mulhouse Cedex (France)

    2007-10-21

    Using complementary surface analysis techniques, we study the Ge growth on distinct SiC(0 0 0 1) reconstructions and elucidate complex mechanisms occurring by thermal activation. Two Si-rich reconstructions (3 x 3) and ({radical}3 x {radical}3)R30{sup 0}({radical}3), and one C-rich, (6{radical}3 x 6{radical}3)R30{sup 0}(6{radical}3), are concerned, on which Ge is found to grow in Stranski-Krastanov and Volmer-Weber modes, respectively. The best Ge-wetting layer is favoured on the {radical}3 (less Si-rich) because closest to a perfect truncated SiC(0 0 0 1) termination. At sufficiently high temperature, the Ge-wetting layer is organized in the form of a (4 x 4)Ge reconstruction for which we propose a first atomic model that is based on the 3 x 3 structure. Annealing Ge on the (3 x 3) and 6{radical}3 surfaces provokes spectacular successive 2D/3D and unusual 3D/2D transitions not only of Ge but also of Si and C, respectively, coming from the surface initial richness. In both cases, a phase separation is observed either in the 2D or 3D structures, which is unexpected for the Ge/Si binary system and somewhat usual for the Ge/C one. In the case of Ge on 6{radical}3, a special 2D heterostructure graphite/Ge/SiC is achieved at the atomic level. This acts as a Schottky barrier and then can be promising for future possible applications. (review article)

  6. Controlled in situ formation of polyacrylamide hydrogel on PET surface via SI-ARGET-ATRP for wound dressings

    International Nuclear Information System (INIS)

    Nazari Pour, Sedigheh; Ghugare, Shivkumar V.; Wiens, Richard; Gough, Kathleen; Liu, Song

    2015-01-01

    Graphical abstract: - Highlights: • We grow poly(acrylamide) (PAM) hydrgol from a polymer surface in a controlled way. • Divinyl crosslinker doesn't compromise the control chain growth feature of ARGET-ATRP. • ATR-FTIR-FPA images (spatial resolution 220 nm) reveal a uniform grafting of PAM. • PAM grafted wound dressing can be dual functional: low-adherent and antibacterial. - Abstract: Well-defined polyacrylamide (PAM) hydrogel was synthesized on the surface of poly(ethylene terephthalate) (PET) film via surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET-ATRP). Following the deposition of an ATRP initiator (2-bromoisobutyrylbromide) on PET film, PAM hydrogel was grafted from the functionalized PET surface via ARGET-ATRP. XPS and FTIR-ATR confirmed that PAM hydrogel was successfully grafted on the PET surface. Results from AFM, SEM, and FTIR-FPA microscopic investigations showed that PAM hydrogel uniformly covers the surface of PET film. The grafting yield increases linearly with increasing reaction time, indicating that the growth of PAM hydrogel on the surface of PET is well controlled. In a cell adhesion assay, PAM hydrogel grafted PET films (PAM hydrogel-g-PET) showed low adhesion to keratinocyte cells. To impart PAM hydrogel-g-PET with antibacterial function, AgNPs were self-assembled along the amide side chains of PAM hydrogel. AgNPs loaded-PAM hydrogel-g-PET shows 99% reduction in the number of multidrug-resistant Pseudomonas aeruginosa within 3 h contact

  7. Comparison of ONIX simulation results with experimental data from the BATMAN testbed for the study of negative ion extraction

    Science.gov (United States)

    Mochalskyy, Serhiy; Fantz, Ursel; Wünderlich, Dirk; Minea, Tiberiu

    2016-10-01

    The development of negative ion (NI) sources for the ITER neutral beam injector is strongly accompanied by modelling activities. The ONIX (Orsay Negative Ion eXtraction) code simulates the formation and extraction of negative hydrogen ions and co-extracted electrons produced in caesiated sources. In this paper the 3D geometry of the BATMAN extraction system, and the source characteristics such as the extraction and bias potential, and the 3D magnetic field were integrated in the model. Calculations were performed using plasma parameters experimentally obtained on BATMAN. The comparison of the ONIX calculated extracted NI density with the experimental results suggests that predictive calculations of the extraction of NIs are possible. The results show that for an ideal status of the Cs conditioning the extracted hydrogen NI current density could reach ~30 mA cm-2 at 10 kV and ~20 mA cm-2 at 5 kV extraction potential, with an electron/NI current density ratio of about 1, as measured in the experiments under the same plasma and source conditions. The dependency of the extracted NI current on the NI density in the bulk plasma region from both the modeling and the experiment was investigated. The separate distributions composing the NI beam originating from the plasma bulk region and the PG surface are presented for different NI plasma volume densities and NI emission rates from the plasma grid (PG) wall, respectively. The extracted current from the NIs produced at the Cs covered PG surface, initially moving towards the bulk plasma and then being bent towards the extraction surfaces, is lower compared to the extracted NI current from directly extracted surface produced ions.

  8. Direct surface grafting of mesoporous silica nanoparticles with phospholipid choline-containing copolymers through chain transfer free radical polymerization and their controlled drug delivery.

    Science.gov (United States)

    Huang, Long; Wu, Jing; Liu, Meiying; Mao, Liucheng; Huang, Hongye; Wan, Qing; Dai, Yanfeng; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

    2017-12-15

    Mesoporous silica nanoparticles have attracted considerable research attention due to their various applications. Surface modification of these mesoporous silica nanoparticles with polymers not only can improve their water dispersity but can also endow several new functions, such as drug loading and delivery or targeting capability. In this work, we report a novel strategy for the direct surface grafting of phospholipid choline-containing copolymers onto Santa Barbara Amorphous-15 (SBA-15) through surface-initiated chain transfer free radical polymerization. The SBA-15 was synthesized by hydrolysis of tetraethoxysilane in the presence of poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) under acidic synthetic conditions. Next, SBA-15 was subsequently modified with thiol groups by co-condensation with γ-mercaptopropyltrimethoxysilane to obtain SBA-15-SH. Finally, the copolymers were grafted on SBA-15-SH through chain transfer free radical polymerization using 2-methacryloyloxy ethyl phosphorylcholine (MPC) and itaconic acid (IA) as monomers. The SBA-15-based polymer composites (SBA-15-SH-poly(MPC-co-IA)) were used as matrices for controlled release of cisplatin (CDDP). The data from a series of characterization techniques indicated that the monomers were successfully grafted onto SBA-15. The resultant SBA-15-SH-poly(MPC-co-IA) composites showed many remarkable physicochemical properties, such as high water dispersity, desirable biocompatibility and high drug loading capacity. These features provide the SBA-15-SH-poly(MPC-co-IA) composites with considerable potential for biomedical applications. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Biomimetic polymeric superhydrophobic surfaces and nanostructures: from fabrication to applications.

    Science.gov (United States)

    Wen, Gang; Guo, ZhiGuang; Liu, Weimin

    2017-03-09

    Numerous research studies have contributed to the development of mature superhydrophobic systems. The fabrication and applications of polymeric superhydrophobic surfaces have been discussed and these have attracted tremendous attention over the past few years due to their excellent properties. In general, roughness and chemical composition, the two most crucial factors with respect to surface wetting, provide the basic criteria for yielding polymeric superhydrophobic materials. Furthermore, with their unique properties and flexible configurations, polymers have been one of the most efficient materials for fabricating superhydrophobic materials. This review aims to summarize the most recent progress in polymeric superhydrophobic surfaces. Significantly, the fundamental theories for designing these materials will be presented, and the original methods will be introduced, followed by a summary of multifunctional superhydrophobic polymers and their applications. The principles of these methods can be divided into two categories: the first involves adding nanoparticles to a low surface energy polymer, and the other involves combining a low surface energy material with a textured surface, followed by chemical modification. Notably, surface-initiated radical polymerization is a versatile method for a variety of vinyl monomers, resulting in controlled molecular weights and low polydispersities. The surfaces produced by these methods not only possess superhydrophobicity but also have many applications, such as self-cleaning, self-healing, anti-icing, anti-bioadhesion, oil-water separation, and even superamphiphobic surfaces. Interestingly, the combination of responsive materials and roughness enhances the responsiveness, which allows the achievement of intelligent transformation between superhydrophobicity and superhydrophilicity. Nevertheless, surfaces with poor physical and chemical properties are generally unable to withstand the severe conditions of the outside world

  10. Fibrous polymer grafted magnetic chitosan beads with strong poly(cation-exchange) groups for single step purification of lysozyme.

    Science.gov (United States)

    Bayramoglu, Gulay; Tekinay, Turgay; Ozalp, V Cengiz; Arica, M Yakup

    2015-05-15

    Lysozyme is an important polypetide used in medical and food applications. We report a novel magnetic strong cation exchange beads for efficient purification of lysozyme from chicken egg white. Magnetic chitosan (MCHT) beads were synthesized via phase inversion method, and then grafted with poly(glycidyl methacrylate) (p(GMA)) via the surface-initiated atom transfer radical polymerization (SI-ATRP). Epoxy groups of the grafted polymer, were modified into strong cation-exchange groups (i.e., sulfonate groups) in the presence of sodium sulfite. The MCTH and MCTH-g-p(GMA)-SO3H beads were characterized by ATR-FTIR, SEM, and VSM. The sulphonate groups content of the modified MCTH-g-p(GMA)-4 beads was found to be 0.53mmolg(-1) of beads by the potentiometric titration method. The MCTH-g-p(GMA)-SO3H beads were first used as an ion-exchange support for adsorption of lysozyme from aqueous solution. The influence of different experimental parameters such as pH, contact time, and temperature on the adsorption process was evaluated. The maximum adsorption capacity was found to be 208.7mgg(-1) beads. Adsorption of lysozyme on the MCTH-g-p(GMA)-SO3H beads fitted to Langmuir isotherm model and followed the pseudo second-order kinetic. More than 93% of the adsorbed lysozyme was desorbed using Na2CO3 solution (pH 11.0). The purity of the lysozyme was checked by HPLC and SDS gel electrophoresis. In addition, the MCTH-g-p(GMA)-SO3H beads prepared in this work showed promising potential for separation of various anionic molecules. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Sleep deprivation in the rat: XI. The effect of guanethidine-induced sympathetic blockade on the sleep deprivation syndrome.

    Science.gov (United States)

    Pilcher, J J; Bergmann, B M; Fang, V S; Refetoff, S; Rechtschaffen, A

    1990-06-01

    In earlier studies, rats totally deprived of sleep by a disk-over-water apparatus (TSD rats) had shown an increase in energy expenditure (EE) that could not be explained by increased motor activity or the metabolic expense of wakefulness. Excessive activation of a calorigenic mediator was a possibility, and norepinephrine-mediated sympathetic activation was the most likely candidate, because plasma norepinephrine (NE) levels had risen sharply in TSD rats. To determine whether this activation was necessary for increased EE in sleep deprived rats, the peripheral sympathetic blocking agent guanethidine (GU) was administered to six sleep-deprived (GD) rats and their yoked control (GC) rats. GU attenuated the increase in NE previously seen in TSD rats, but the increase in EE was not attenuated. Apparently, NE-mediated sympathetic activation was not critical for increased EE in sleep-deprived rats. On the other hand, plasma epinephrine (EPI) levels were significantly increased in GD (but not in GC) rats above those previously seen in TSD rats, suggesting the substitution of one calorigenic mediator for another in response to an abnormally elevated need for EE. Temperature data suggest that increased need for EE could arise from an elevated temperature setpoint and an inability to retain body heat. GD (but not GC) rats also showed other effects previously seen in TSD rats, including debilitated appearance; severe ulcerative and hyperkeratotic lesions on the tails and plantar surfaces; initially increased and later decreased body temperature; decreased plasma thyroxine; increased triiodothyronine-thyroxine ratio; and eventual death. Evidently, NE-mediated sympathetic activation was not critical to any of these effects, although a role for catecholamines cannot be ruled out.

  12. Teratosphaeria nubilosa, a serious leaf disease pathogen of Eucalyptus spp. in native and introduced areas.

    Science.gov (United States)

    Hunter, Gavin C; Crous, Pedro W; Carnegie, Angus J; Wingfield, Michael J

    2009-01-01

    Teratosphaeria nubilosa is a serious leaf pathogen of several Eucalyptus spp. This review considers the taxonomic history, epidemiology, host associations and molecular biology of T. nubilosa. Kingdom Fungi; Phylum Ascomycota; Class Dothideomycetes; Order Capnodiales; Family Teratosphaeriaceae; genus Teratosphaeria; species nubilosa. Pseudothecia hypophyllous, less so amphigenous, ascomata black, globose becoming erumpent, asci aparaphysate, fasciculate, bitunicate, obovoid to ellipsoid, straight or incurved, eight-spored, ascospores hyaline, non-guttulate, thin walled, straight to slightly curved, obovoid with obtuse ends, medially one-septate, slightly constricted at the median septum, tapering to both ends, ascospore germination type F, germinating from both ends, germ tubes growing parallel to the long axis of the spore with distortion of the primary ascospore cell. Teratosphaeria nubilosa is a primary pathogen of several Eucalyptus spp., including E. botryoides, E. bicostata, E. bridgesiana, E. cypellocarpa, E. dunnii, E. globulus ssp. bicostata, E. globulus ssp. globulus, E. globulus ssp. maidenii, E. globulus ssp. pseudoglobulus, E. grandis, E. gunnii, E. nitens, E. pilularis, E. quadrangulata, E. viminalis, E. grandis x E. resinifera and E. urophylla x E. globulus. Leaf spots predominantly occur on juvenile Eucalyptus foliage; however, T. nubilosa has also recently been found on mature Eucalyptus foliage. Leaf spots are amphigenous, varying in size from small spots that are round to irregular. Lesions enlarge and coalesce to form larger blotches over the leaf surface. Initial lesions appear as pale-green spots surrounded by purple margins and, once mature, are generally yellow to pale brown with dark-brown raised borders. Mycobank, http://www.mycobank.org; Mycosphaerella identification website, http://www.cbs.knaw.nl/mycosphaerella/BioloMICS.aspx.

  13. The role of polymer nanolayer architecture on the separation performance of anion-exchange membrane adsorbers: I. Protein separations.

    Science.gov (United States)

    Bhut, Bharat V; Weaver, Justin; Carter, Andrew R; Wickramasinghe, S Ranil; Husson, Scott M

    2011-11-01

    This contribution describes the preparation of strong anion-exchange membranes with higher protein binding capacities than the best commercial resins. Quaternary amine (Q-type) anion-exchange membranes were prepared by grafting polyelectrolyte nanolayers from the surfaces of macroporous membrane supports. A focus of this study was to better understand the role of polymer nanolayer architecture on protein binding. Membranes were prepared with different polymer chain graft densities using a newly developed surface-initiated polymerization protocol designed to provide uniform and variable chain spacing. Bovine serum albumin and immunoglobulin G were used to measure binding capacities of proteins with different size. Dynamic binding capacities of IgG were measured to evaluate the impact of polymer chain density on the accessibility of large size protein to binding sites within the polyelectrolyte nanolayer under flow conditions. The dynamic binding capacity of IgG increased nearly linearly with increasing polymer chain density, which suggests that the spacing between polymer chains is sufficient for IgG to access binding sites all along the grafted polymer chains. Furthermore, the high dynamic binding capacity of IgG (>130 mg/mL) was independent of linear flow velocity, which suggests that the mass transfer of IgG molecules to the binding sites occurs primarily via convection. Overall, this research provides clear evidence that the dynamic binding capacities of large biologics can be higher for well-designed macroporous membrane adsorbers than commercial membrane or resin ion-exchange products. Specifically, using controlled polymerization leads to anion-exchange membrane adsorbers with high binding capacities that are independent of flow rate, enabling high throughput. Results of this work should help to accelerate the broader implementation of membrane adsorbers in bioprocess purification steps. Copyright © 2011 Wiley Periodicals, Inc.

  14. Long-Life, Lightweight, Multi-Roller Traction Drives for Planetary Vehicle Surface Exploration

    Science.gov (United States)

    Klein, Richard C.; Fusaro, Robert L.; Dimofte, Florin

    2012-01-01

    NASA s initiative for Lunar and Martian exploration will require long lived, robust drive systems for manned vehicles that must operate in hostile environments. The operation of these mechanical drives will pose a problem because of the existing extreme operating conditions. Some of these extreme conditions include operating at a very high or very cold temperature, operating over a wide range of temperatures, operating in very dusty environments, operating in a very high radiation environment, and operating in possibly corrosive environments. Current drive systems use gears with various configurations of teeth. These gears must be lubricated with oil (or grease) and must have some sort of a lubricant resupply system. For drive systems, oil poses problems such as evaporation, becoming too viscous and eventually freezing at cold temperatures, being too thin to lubricate at high temperatures, being degraded by the radiation environment, being contaminated by the regolith (soil), and if vaporized (and not sealed), it will contaminate the regolith. Thus, it may not be advisable or even possible to use oil because of these limitations. An oil-less, compact traction vehicle drive is a drive designed for use in hostile environments like those that will be encountered on planetary surfaces. Initially, traction roller tests in vacuum were conducted to obtain traction and endurance data needed for designing the drives. From that data, a traction drive was designed that would fit into a prototype lunar rover vehicle, and this design data was used to construct several traction drives. These drives were then tested in air to determine their performance characteristics, and if any final corrections to the designs were necessary. A limitation with current speed reducer systems such as planetary gears and harmonic drives is the high-contact stresses that occur at tooth engagement and in the harmonic drive wave generator interface. These high stresses induce high wear of solid

  15. Ingenious route for ultraviolet-induced graft polymerization achieved on inorganic particle: Fabricating magnetic poly(acrylic acid) densely grafted nanocomposites for Cu{sup 2+} removal

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Qi, E-mail: roundzking@163.com [School of Environmental and Chemical Engineering, Shanghai University, 333 Nanchen Road, Shanghai, 200444 (China); Luo, Wenjun [Faculty of Material and Chemistry, China University of Geosciences, Wuhan, 430074 (China); Zhang, Xing [School of Environmental and Chemical Engineering, Shanghai University, 333 Nanchen Road, Shanghai, 200444 (China)

    2017-08-15

    Highlights: • A novel PAA brushes-decorated magnetic adsorbent was prepared successfully. • The preparation approach was simple, rapid, and efficient. • Densely polymer grafting can be achieved on inorganic substrate by the method. • The g-MNPs exhibits an outstanding adsorption performance for Cu{sup 2+}. • The Cu{sup 2+}-saturated adsorbent can be separated and regenerated easily. - Abstract: In this study, ultraviolet (UV)-induced graft technology is improved to be successfully applied on inorganic substrate for fabricating a novel poly(acrylic acid) (PAA) brushes-decorated magnetic nano-composite particles (g-MNPs) as a potential adsorbent toward Cu{sup 2+} ion. The most fascinating features of the resultant g-MNPs are the abundant and highly accessible carboxyl groups present in PAA brushes and the rapid separation from the medium by magnetic field after adsorption. Through the new and high-efficiency surface-initiated polymerization route, the densely PAA brushes was successfully immobilized on the MNPs surface with a high grafting yield of 88.3%. Excitingly, the g-MNPs exhibited an exceptional performance for Cu{sup 2+} adsorption, e.g., ultrahigh adsorption capacity (up to 152.1 mg g{sup −1}), rapid adsorption rate (within 30 min) and low residual concentration (below 1.3 ppm). Full kinetic and isotherm analysis as well as thermodynamic study were also undertaken, the results showed that Cu{sup 2+} adsorption followed Langmuir isotherm and the pseudo-second-order kinetic model, the adsorption rate was controlled by two sequential periods of external and intraparticle diffusion. According to the calculated value of thermodynamic parameters, the Cu{sup 2+} adsorption onto g-MNPs was a spontaneous endothermic process. Furthermore, the excellent reusability of the resultant adsorbent was also confirmed, which can keep above 95% adsorption capacity and desorption rate in 8 consecutive cycles.

  16. PNIPAAM modified mesoporous hydroxyapatite for sustained osteogenic drug release and promoting cell attachment

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Tao [The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) & Key Laboratory of Oral Biomedicine Ministry of Education, School & Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan 430079 (China); Tan, Lei [Key Laboratory of Biomedical Polymers of Ministry of Education, College of Chemistry and Molecular Science, Wuhan University, Wuhan 430072 (China); Cheng, Ning; Yan, Qi; Zhang, Yu-Feng [The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) & Key Laboratory of Oral Biomedicine Ministry of Education, School & Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan 430079 (China); Liu, Chuan-Jun, E-mail: cjliu@whu.edu.cn [Key Laboratory of Biomedical Polymers of Ministry of Education, College of Chemistry and Molecular Science, Wuhan University, Wuhan 430072 (China); Shi, Bin, E-mail: shibin_dentist@126.com [The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) & Key Laboratory of Oral Biomedicine Ministry of Education, School & Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan 430079 (China)

    2016-05-01

    This work presented a sustained release system of simvastatin (SIM) based on the mesoporous hydroxyapatite (MHA) capped with poly(N-isopropylacrylamide) (PNIPAAM). The MHA was prepared by using cetyltrimethylammonium bromide (CTAB) as a template and the modified PNIPAAM layer on the surface of MHA was fabricated through surface-initiated atom transfer radical polymerization (SI-ATRP). The SIM loaded MHA-PNIPAAM showed a sustained release of SIM at 37 °C over 16 days. The bone marrow mesenchymal stem cell (BMSC) proliferation was assessed by cell counting kit-8 (CCK-8) assay, and the osteogenic differentiation was evaluated by alkaline phosphatase (ALP) activity and Alizarin Red staining. The release profile showed that the release of SIM from MHA-SIM-PNIPAAM lasted 16 days and the cumulative amount of released SIM was almost seven-fold than MHA-SIM. Besides, SIM loaded MHA-PNIPAAM exhibited better performance on cell proliferation, ALP activity, and calcium deposition than pure MHA due to the sustained release of SIM. The quantity of ALP in MHA-SIM-PNIPAAM group was more than two fold than pure MHA group at 7 days. Compared to pure MHA, better BMSC attachment on PNIPAAM modified MHA was observed using fluorescent microscopy, indicating the better biocompatibility of MHA-PNIPAAM. - Highlights: • PNIPAAM modified mesoporous hydroxyapatite (MHA) was fabricated by SI-ATRP. • SIM loaded MHA-PNIPAAM continually released SIM in effect concentration for 16 days. • MHA-SIM-PNIPAAM behaved well on cell proliferation, ALP activity and calcium deposition.

  17. Hemocompatible surface of electrospun nanofibrous scaffolds by ATRP modification

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Wenjie [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Feng, Yakai, E-mail: yakaifeng@hotmail.com [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Key Laboratory of Systems Bioengineering of Ministry of Education, Tianjin University, Tianjin 300072 (China); Tianjin University-Helmholtz-Zentrum Geesthacht, Joint Laboratory for Biomaterials and Regenerative Medicine, Weijin Road 92, 300072 Tianjin (China); Wang, Heyun [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); School of Chemistry and Chemical Engineering, Shihezi University, Shihezi 832002 (China); Yang, Dazhi [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); An, Bo [Department of Orthopedics, Affiliated Hospital of Logistics University of Chinese People' s Armed Police Force, Tianjin 300162 (China); Zhang, Wencheng [Department of Physiology and Pathophysiology, Logistics University of Chinese People' s Armed Police Force, Tianjin 300162 (China); Khan, Musammir [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Guo, Jintang [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Tianjin University-Helmholtz-Zentrum Geesthacht, Joint Laboratory for Biomaterials and Regenerative Medicine, Weijin Road 92, 300072 Tianjin (China)

    2013-10-15

    The electrospun scaffolds are potential application in vascular tissue engineering since they can mimic the nano-sized dimension of natural extracellular matrix (ECM). We prepared a fibrous scaffold from polycarbonateurethane (PCU) by electrospinning technology. In order to improve the hydrophilicity and hemocompatibility of the fibrous scaffold, poly(ethylene glycol) methacrylate (PEGMA) was grafted onto the fiber surface by surface-initiated atom transfer radical polymerization (SI-ATRP) method. Although SI-ATRP has been developed and used for surface modification for many years, there are only few studies about the modification of electrospun fiber by this method. The modified fibrous scaffolds were characterized by SEM, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). The scaffold morphology showed no significant difference when PEGMA was grafted onto the scaffold surface. Based on the water contact angle measurement, the surface hydrophilicity of the scaffold surface was improved significantly after grafting hydrophilic PEGMA (P = 0.0012). The modified surface showed effective resistance for platelet adhesion compared with the unmodified surface. Activated partial thromboplastin time (APTT) of the PCU-g-PEGMA scaffold was much longer than that of the unmodified PCU scaffold. The cyto-compatibility of electrospun nanofibrous scaffolds was tested by human umbilical vein endothelial cells (HUVECs). The images of 7-day cultured cells on the scaffold surface were observed by SEM. The modified scaffolds showed high tendency to induce cell adhesion. Moreover, the cells reached out pseudopodia along the fibrous direction and formed a continuous monolayer. Hemolysis test showed that the grafted chains of PEGMA reduced blood coagulation. These results indicated that the modified electrospun nanofibrous scaffolds were potential application as artificial blood vessels. Highlights: • Electrospun nanofibrous scaffolds were successfully

  18. Porphyrin-functionalized porous polysulfone membrane towards an optical sensor membrane for sorption and detection of cadmium(II)

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Lizhi, E-mail: zhaolizhi_phd@163.com [State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tianjin Polytechnic University, Tianjin 300387 (China); Li, Min; Liu, Manman; Zhang, Yuecong [State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tianjin Polytechnic University, Tianjin 300387 (China); Wu, Chenglin [School of Pharmaceutical and Chemical Engineering, Taizhou University, Taizhou 317000, Zhejiang Province (China); Zhang, Yuzhong, E-mail: zhangyz2004cn@163.com [State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tianjin Polytechnic University, Tianjin 300387 (China)

    2016-01-15

    Highlights: • An optical sensor membrane is prepared by TMPyP and PNaSS-grafted PSF membrane. • The optical sensor membrane shows enhanced sorption for cadmium(II). • Visual and spectrophotometric detection can be achieved. • The functional membrane exhibits good stability and reusability. - Abstract: In this study, an optical sensor membrane was prepared for sorption and detection of cadmium(II) (Cd(II)) in aqueous solution. A polyanion, poly(sodium 4-styrenesulfonate) (PNaSS), was grafted onto the chloromethylated polysulfone (CMPSF) microporous membrane via surface-initiated ATRP. 5,10,15,20-tetrakis(4-N-methylpyridyl) porphyrin p-toluenesulfonate (TMPyP) was immobilized onto the PNaSS-grafted polysulfone (PSF-PNaSS) membrane through electrostatic interaction. The TMPyP-functionalized membrane exhibited an enhanced sorption for, and distinct color and spectral response to cadmium(II) (Cd(II)) in aqueous solution. Larger immobilization capacity of TMPyP on the membrane led to stronger sorption for Cd(II), and smaller one made the optical sensor have a faster (in minutes) and more sensitive response to the ion. The detection limit study indicated that the functional membrane with proper amount of TMPyP (<0.5 mg/g) could still have color and spectral response to Cd(II) solutions at an extreme low concentration (10{sup −4} mg/L). The optical sensor membrane exhibited good stability and reusability which made it efficient for various sorptive removal and detection applications.

  19. Hydrophilic PCU scaffolds prepared by grafting PEGMA and immobilizing gelatin to enhance cell adhesion and proliferation

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Changcan; Yuan, Wenjie; Khan, Musammir; Li, Qian [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Feng, Yakai, E-mail: yakaifeng@tju.edu.cn [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Key Laboratory of Systems Bioengineering of Ministry of Education, Tianjin University, Tianjin 300072 (China); Tianjin University-Helmholtz-Zentrum Geesthacht, Joint Laboratory for Biomaterials and Regenerative Medicine, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Chemical Engineering (Tianjin) Tianjin 300072 (China); Yao, Fanglian [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Key Laboratory of Systems Bioengineering of Ministry of Education, Tianjin University, Tianjin 300072 (China); Tianjin University-Helmholtz-Zentrum Geesthacht, Joint Laboratory for Biomaterials and Regenerative Medicine, Tianjin 300072 (China); Zhang, Wencheng, E-mail: wenchengzhang@yahoo.com [Department of Physiology and Pathophysiology, Logistics University of Chinese People' s Armed Police Force, Tianjin 300162 (China)

    2015-05-01

    Gelatin contains many functional motifs which can modulate cell specific adhesion, so we modified polycarbonate urethane (PCU) scaffold surface by immobilization of gelatin. PCU-g-gelatin scaffolds were prepared by direct immobilizing gelatins onto the surface of aminated PCU scaffolds. To increase the immobilization amount of gelatin, poly(ethylene glycol) methacrylate (PEGMA) was grafted onto PCU scaffolds by surface initiated atom transfer radical polymerization. Then, following amination and immobilization, PCU-g-PEGMA-g-gelatin scaffolds were obtained. Both modified scaffolds were characterized by chemical and biological methods. After immobilization of gelatin, the microfiber surface became rough, but the original morphology of scaffolds was maintained successfully. PCU-g-PEGMA-g-gelatin scaffolds were more hydrophilic than PCU-g-gelatin scaffolds. Because hydrophilic PEGMA and gelatin were grafted and immobilized onto the surface, the PCU-g-PEGMA-g-gelatin scaffolds showed low platelet adhesion, perfect anti-hemolytic activity and excellent cell growth and proliferation capacity. It could be envisioned that PCU-g-PEGMA-g-gelatin scaffolds might have potential applications in tissue engineering artificial scaffolds. - Graphical abstract: PCU-g-gelatin scaffolds were prepared by direct immobilizing gelatin onto the surface of aminated PCU scaffolds (method a). To increase the immobilization amount of gelatin, PEGMAs were grafted onto the scaffold surface by SI-ATRP. PCU-g-PEGMA-g-gelatin scaffolds were prepared by method b. The gelatin modified scaffolds exhibited high hydrophilicity, low platelet adhesion, perfect anti-hemolytic activity, and excellent cell adhesion and proliferation capacity. They might have potential applications as tissue engineering scaffolds for artificial blood vessels. - Highlights: • Hydrophilic scaffolds were prepared by grafting PEGMA and immobilization of gelatins. • Grafting PEGMA enhanced the immobilization amount of gelatin

  20. A novel thermal and pH responsive drug delivery system based on ZnO@PNIPAM hybrid nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Licheng; Liu, Jian; Zhou, Weihua [Department of Chemistry, Nanchang University, Nanchang 330031 (China); Wei, Junchao, E-mail: weijunchao@ncu.edu.cn [Department of Chemistry, Nanchang University, Nanchang 330031 (China); State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, 220 Handan Road, Shanghai 200433 (China); Peng, Zhiping [Department of Chemistry, Nanchang University, Nanchang 330031 (China)

    2014-12-01

    A smart ZnO@PNIPAM hybrid was prepared by grafting thermal responsive poly(N-isopropylacrylamide) (PNIPAM) on zinc oxide (ZnO) nanoparticles via surface-initiated atom transfer radical polymerization (ATRP). The thermal gravimetric analysis (TGA) shows that the grafting amount of PNIPAM was about 38%, and the SEM images show that the PNIPAM chains can prevent the aggregation of ZnO nanoparticles. The responsive properties of ZnO@PNIPAM were measured by photoluminescence spectra, and the results demonstrate that the PNIPAM chains grafted on ZnO surfaces can realize reversible thermal responsive and photoluminescence properties. An anticancer drug, doxorubicin (Dox), was used as a model drug and loaded into the hybrid nanoparticles, and an in vitro drug release test implied that ZnO@PNIPAM could work as a thermal responsive drug delivery system. Furthermore, pH sensitive drug releases were carried out in acetate buffer at pH 5.0 and pH 6.0 and in water at pH 7.0, and the results showed evident pH dependency, showing its pH responsive properties. - Graphical abstract: In this manuscript, thermal responsive poly(N-isopropylacrylamide) (PNIPAM) was grafted on the surface of ZnO nanoparticles. The obtained ZnO@PNIPAM hybrid showed reversible thermal responsive photoluminescent properties, and can also work as a thermal and pH responsive drug delivery system. - Highlights: • The ZnO@PNIPAM hybrid was prepared via ATRP. • The ZnO@PNIPAM hybrid showed thermal responsive properties. • The ZnO@PNIPAM hybrid can work as a thermal and pH responsive drug delivery system.

  1. Preparation and characterization of poly(glycidyl methacrylate)-grafted magnetic nanoparticles: Effects of the precursor concentration on polyol synthesis of Fe{sub 3}O{sub 4} and [PMDETA]{sub 0}/[CuBr{sub 2}]{sub 0} ratios on SI-AGET ATRP

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Liping; Zhou, Xuyang; Wei, Guyun; Lu, Xiaoduo; Wei, Weiping; Qiu, Jianhua

    2015-12-01

    Highlights: • The nanoparticle size of Fe{sub 3}O{sub 4} increased from 7.3 to 9.6 nm and the saturation magnetization of nanoparticles increased from 59 to 61 emu g{sup −1} with increasing the metal precursor concentration from 0.1 to 0.8 mol L{sup −1}, respectively. • The grafted content of PGMA increased from 4.1 to 23.1 wt% as the [PMDETA]{sub 0}/[CuBr{sub 2}]{sub 0} ratio decreased from 6:1 to 2:1. The PGMA-grafted Fe{sub 3}O{sub 4}@SiO{sub 2} magnetic microparticles were prepared by SI-AGET ATRP. - Abstract: Polymer brushes based on poly(glycidyl methacrylate) (PGMA) have been successfully grafted from the surface of silica coated iron oxide (Fe{sub 3}O{sub 4}@SiO{sub 2}) nanoparticles via surface-initiated activators generated by electron transfer atom transfer radical polymerization (SI-AGET ATRP). The size of the nanoparticles could be adjusted from 7.3 to 9.6 nm by varying the precursor concentration of iron(III) acetylacetonate. The Fe{sub 3}O{sub 4} nanoparticles possessed a highly crystalline structure, and the saturation magnetization of the as-prepared magnetite was strongly related to the particle size. Furthermore, the grafted PGMA content on the magnetic nanoparticles could be controlled by varying the ligand to transition metal ratio in a N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA)/CuBr{sub 2} catalyst system. The maximum grafted content was 23.1% at a ratio of [PMDETA]{sub 0}/[CuBr{sub 2}]{sub 0} = 2:1.

  2. Moving-Bed Process for Residue Hydrotreating Procédé à lit mobile pour l'hydrotraitement des résidus

    Directory of Open Access Journals (Sweden)

    Euzen J. P.

    2006-11-01

    the solid particles during the sequential withdrawal. It is the reason why the movement of the solid and, moreover, the residence time distribution of the catalyst particles have been especially followed. To this end, a new technique has been developed to measure the concentration of magnetically marked particles. Furthermore, a specific effort has been devoted to technological problems such as selection and developement of special valves able to insure efficient tightness between the various sections at elevated temperatures and pressures in the presence of solid particles. Another study has been devoted to the operation of addition and withdrawal of the catalyst to and from the reactor running at high pressure and temperature. The solid flows and the catalyst transfer conditions have been carefully studied and tested. Finally a demonstration unit has been built at a semi-industrial scale in a mini-refinery. It was a convincing way to check all the conclusions drawed from the developement step with models, smaller scale pilots and mock-ups. As the fluids and the catalyst were real industrial products, the feasibility of the whole process has been demonstrated. Therefore, a new industrial process using the countercurrent moving bed is now available and permits a very efficient use of the catalyst particles. Un grand nombre de procédés chimiques, pétrochimiques ou de raffinage nécessitent un contact entre 3 phases : un produit de base liquide, un réactif gazeux et un catalyseur solide. Il arrive souvent que l'activité du catalyseur soit réduite par un empoisonnement des sites actifs ou par des dépôts de coke. C'est particulièrement le cas des procédés utilisés dans l'hydrotraitement des résidus lourds. La durée de vie du catalyseur étant réduite, il est nécessaire de remplacer ou de régénérer fréquemment le catalyseur devenu inactif. Différentes solutions permettent d'effectuer ce travail tout en limitant les pertes de temps et de production

  3. Computer simulation of electronic excitation in atomic collision cascades

    Energy Technology Data Exchange (ETDEWEB)

    Duvenbeck, A.

    2007-04-05

    The impact of an keV atomic particle onto a solid surface initiates a complex sequence of collisions among target atoms in a near-surface region. The temporal and spatial evolution of this atomic collision cascade leads to the emission of particles from the surface - a process usually called sputtering. In modern surface analysis the so called SIMS technology uses the flux of sputtered particles as a source of information on the microscopical stoichiometric structure in the proximity of the bombarded surface spots. By laterally varying the bombarding spot on the surface, the entire target can be scanned and chemically analyzed. However, the particle detection, which bases upon deflection in electric fields, is limited to those species that leave the surface in an ionized state. Due to the fact that the ionized fraction of the total flux of sputtered atoms often only amounts to a few percent or even less, the detection is often hampered by rather low signals. Moreover, it is well known, that the ionization probability of emitted particles does not only depend on the elementary species, but also on the local environment from which a particle leaves the surface. Therefore, the measured signals for different sputtered species do not necessarily represent the stoichiometric composition of the sample. In the literature, this phenomenon is known as the Matrix Effect in SIMS. In order to circumvent this principal shortcoming of SIMS, the present thesis develops an alternative computer simulation concept, which treats the electronic energy losses of all moving atoms as excitation sources feeding energy into the electronic sub-system of the solid. The particle kinetics determining the excitation sources are delivered by classical molecular dynamics. The excitation energy calculations are combined with a diffusive transport model to describe the spread of excitation energy from the initial point of generation. Calculation results yield a space- and time-resolved excitation

  4. Development of degradable renewable polymers and stimuli-responsive nanocomposites

    Science.gov (United States)

    Eyiler, Ersan

    The overall goal of this research was to explore new living radical polymerization methods and the blending of renewable polymers. Towards this latter goal, polylactic acid (PLA) was blended with a new renewable polymer, poly(trimethylene-malonate) (PTM), with the aim of improving mechanical properties, imparting faster degradation, and examining the relationship between degradation and mechanical properties. Blend films of PLA and PTM with various ratios (5, 10, and 20 wt %) were cast from chloroform. Partially miscible blends exhibited Young's modulus and elongation-to-break values that significantly extend PLA's usefulness. Atomic force microscopy (AFM) data showed that incorporation of 10 wt% PTM into PLA matrix exhibited a Young's modulus of 4.61 GPa, which is significantly higher than that of neat PLA (1.69 GPa). The second part of the bioplastics study involved a one-week hydrolytic degradation study of PTM and another new bioplastic, poly(trimethylene itaconate) (PTI) using DI water (pH 5.4) at room temperature, and the effects of degradation on crystallinity and mechanical properties of these films were examined by differential scanning calorimetry (DSC) and AFM. PTI showed an increase in crystallinity with degradation, which was attributed to predominately degradation of free amorphous regions. Depending on the crystallinity, the elastic modulus increased at first, and decreased slightly. Both bulk and surface-tethered stimuli-responsive polymers were studied on amine functionalized magnetite (Fe3O4) nanoparticles. Stimuli-responsive polymers studied, including poly(N-isopropylacrylamide) (PNIPAM), poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), and poly(itaconic acid) (PIA), were grafted via surface-initiated aqueous atom transfer radical polymerization (SI-ATRP). Both Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) spectroscopies showed the progression of the grafting. The change in particle size as a

  5. NleC, a type III secretion protease, compromises NF-κB activation by targeting p65/RelA.

    Directory of Open Access Journals (Sweden)

    Hilo Yen

    Full Text Available The NF-κB signaling pathway is central to the innate and adaptive immune responses. Upon their detection of pathogen-associated molecular patterns, Toll-like receptors on the cell surface initiate signal transduction and activate the NF-κB pathway, leading to the production of a wide array of inflammatory cytokines, in attempt to eradicate the invaders. As a countermeasure, pathogens have evolved ways to subvert and manipulate this system to their advantage. Enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC are closely related bacteria responsible for major food-borne diseases worldwide. Via a needle-like protein complex called the type three secretion system (T3SS, these pathogens deliver virulence factors directly to host cells and modify cellular functions, including by suppressing the inflammatory response. Using gain- and loss-of-function screenings, we identified two bacterial effectors, NleC and NleE, that down-regulate the NF-κB signal upon being injected into a host cell via the T3SS. A recent report showed that NleE inhibits NF-κB activation, although an NleE-deficient pathogen was still immune-suppressive, indicating that other anti-inflammatory effectors are involved. In agreement, our present results showed that NleC was also required to inhibit inflammation. We found that NleC is a zinc protease that disrupts NF-κB activation by the direct cleavage of NF-κB's p65 subunit in the cytoplasm, thereby decreasing the available p65 and reducing the total nuclear entry of active p65. More importantly, we showed that a mutant EPEC/EHEC lacking both NleC and NleE (ΔnleC ΔnleE caused greater inflammatory response than bacteria carrying ΔnleC or ΔnleE alone. This effect was similar to that of a T3SS-defective mutant. In conclusion, we found that NleC is an anti-inflammatory bacterial zinc protease, and that the cooperative function of NleE and NleC disrupts the NF-κB pathway and accounts for most of the immune

  6. Nanocomposite Membrane via Magnetite Nanoparticle Assembly

    KAUST Repository

    Xie, Yihui

    2012-07-01

    Membrane technology is one of the most promising technologies for addressing the global water crisis as well as in many other applications. One of the drawbacks of current ultra- and nanofiltration membranes is the relatively broad pore size distribution. Block copolymer membranes with ultrahigh permeability and very regular pore sizes have been recently demonstrated with pores being formed by the supramolecular assembly of core/shell micelles. Our study aimed at developing an innovative and economically efficient alternative method to fabricate isoporous membrane by self-assembly of magnetic nanoparticle with a polystyrene shell, mimicking the behavior of block copolymer micelle. Fe3O4 nanoparticles of ~13 nm diameter were prepared by co-precipitation as cores. The initiator for ATRP was covalently bonded onto the surface of magnetic nanoparticles with two strategies. Then the surface initiated ATRP of styrene was carried out to functionalize nanoparticles with polystyrene through a “grafting from” method. Finally, the nanocomposite membrane was cast from 50 wt % Fe3O4@PS brush polymer solution in DMF via non solvent phase inversion. Microscopies reveal an asymmetric membrane with a dense thin layer on top of a porous sponge-like layer. This novel class of asymmetric membrane, based on the pure assembly of functionalized nanoparticles was prepared for the first time. The nanoparticles are well distributed however with no preferential order yet in the as-cast film.I would like to thank my committee chair and advisor, Prof. Suzana Nunes, and other committee members, Prof. Klaus-Viktor Peinemann and Prof. Gary Amy, for their guidance and support throughout the course of this research. My appreciation also goes to my colleagues in our group for useful discussions and suggestions. I also want to extend my gratitude to the staff from the KAUST Core Lab for Advanced Nanofabrication, Imaging and Characterization, especially Dr. Ali Reza Behzad, Dr. Rachid Sougrat, and

  7. OCT assisted identification of the grade of encrustation of urologic catheters

    Science.gov (United States)

    Sroka, Ronald; Püls, Michaela; Stepp, Herbert; Zilinberg, Katja; Bader, Markus; Weidlich, Patrick

    2013-06-01

    Introduction: Ureteric stenting is a commonly used endourologic procedure for temporary and long-term drainage of an obstructed upper urinary tract. The indication for ureteric stenting is obstruction due to intrinsic (intraureteral stones, strictures, or tumors) or extrinsic (for example compressing pelvic or retroperitoneal mass) causes. Despite the fact that stents do certainly have proven benefits in all fields of urology, there are potential morbidities. The most common problem of indwelling ureteral stents is infection. As foreign body in the urinary system, stents act as a nidus for bacteria colonization, crystallization and encrustation. Bacteria induced biofilm formation predisposes for the crystallization of lithogenic salts, such as calcium-phosphate, calcium-oxalate, magnesium-phosphate on the surface initiating stent encrustation. It was the objective of this study to evaluate whether optical coherence tomography (OCT) using both the surface and the endoluminal technique is feasible to investigate the locations and degree of encrustation process in clinically used ureteral stents. Patients and methods: After removal from patients, fourteen polyurethane JJ stents were investigated. A fresh JJ served as a control. The external surfaces were examined using an endoscopic surface OCT whereas the intraluminal surfaces were investigated by an endoluminal radial OCT device. The focus was on detection of encrustation or crystalline sedimentation. Results: In 12 female and 2 male patients, the median indwelling time of the ureteral catheter was 100 days (range 19- 217). Using the endoluminal OCT, the size and grade of intraluminal encrustation could be expressed as a percentage relating to the open lumen of the reference stent. The maximum encrustation observed resulted in a remaining unrestricted lumen of 15-35% compared to the reference. The luminal reduction caused by encrustation was significantly higher at the proximal end of the ureteral stent as compared

  8. Micro-Spectroscopic Chemical Imaging of Individual Identified Marine Biogenic and Ambient Organic Ice Nuclei (Invited)

    Science.gov (United States)

    Knopf, D. A.; Alpert, P. A.; Wang, B.; OBrien, R. E.; Moffet, R. C.; Aller, J. Y.; Laskin, A.; Gilles, M.

    2013-12-01

    Atmospheric ice formation represents one of the least understood atmospheric processes with important implications for the hydrological cycle and climate. Current freezing descriptions assume that ice active sites on the particle surface initiate ice nucleation, however, the nature of these sites remains elusive. Here, we present a new experimental method that allows us to relate physical and chemical properties of individual particles with observed water uptake and ice nucleation ability using a combination of micro-spectroscopic and optical single particle analytical techniques. We apply this method to field-collected particles and particles generated via bursting of bubbles produced by glass frit aeration and plunging water impingement jets in a mesocosm containing artificial sea water and bacteria and/or phytoplankton. The most efficient ice nuclei (IN) within a particle population are identified and characterized. Single particle characterization is achieved by computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy. A vapor controlled cooling-stage coupled to an optical microscope is used to determine the onsets of water uptake, immersion freezing, and deposition ice nucleation of the individual particles as a function of temperature (T) as low as 200 K and relative humidity (RH) up to water saturation. In addition, we perform CCSEM/EDX to obtain on a single particle level the elemental composition of the entire particle population. Thus, we can determine if the IN are exceptional in nature or belong to a major particle type class with respect to composition and size. We find that ambient and sea spray particles are coated by organic material and can induce ice formation under tropospheric relevant conditions. Micro-spectroscopic single particle analysis of the investigated particle samples invokes a potential

  9. Synthesis and property of nanoparticles in ionic liquids and their surface modification

    Science.gov (United States)

    Wang, Yong

    nanoparticles protected by capping agents were modified by coating with a layer of polystyrene through surface initiated atomic transfer radical polymerization. Their surface chemistry could be altered through the formation of complexation between capping agents and alpha-cyclodextrin. These surface-modified particles exhibited a good stability in aqueous environments.

  10. Polycaprolactone Nanocomposites Reinforced with Cellulose Nanocrystals Surface-Modified via Covalent Grafting or Physisorption: A Comparative Study.

    Science.gov (United States)

    Boujemaoui, Assya; Cobo Sanchez, Carmen; Engström, Joakim; Bruce, Carl; Fogelström, Linda; Carlmark, Anna; Malmström, Eva

    2017-10-11

    In the present work, cellulose nanocrystals (CNCs) have been surface-modified either via covalent grafting or through physisorption of poly(n-butyl methacrylate) (PBMA) and employed as reinforcement in PCL. Covalent grafting was achieved by surface-initiated atom transfer radical polymerization (SI-ATRP). Two approaches were utilized for the physisorption: using either micelles of poly(dimethyl aminoethyl methacrylate)-block-poly(n-butyl methacrylate) (PDMAEMA-b-PBMA) or latex nanoparticles of poly(dimethyl aminoethyl methacrylate-co-methacrylic acid)-block-poly(n-butyl methacrylate) (P(DMAEMA-co-MAA)-b-PBMA). Block copolymers (PDMAEMA-b-PBMA)s were obtained by ATRP and subsequently micellized. Latex nanoparticles were produced via reversible addition-fragmentation chain-transfer (RAFT) mediated surfactant-free emulsion polymerization, employing polymer-induced self-assembly (PISA) for the particle formation. For a reliable comparison, the amounts of micelles/latex particles adsorbed and the amount of polymer grafted onto the CNCs were kept similar. Two different chain lengths of PBMA were targeted, below and above the critical molecular weight for chain entanglement of PBMA (M n,c ∼ 56 000 g mol -1 ). Poly(ε-caprolactone) (PCL) nanocomposites reinforced with unmodified and modified CNCs in different weight percentages (0.5, 1, and 3 wt %) were prepared via melt extrusion. The resulting composites were evaluated by UV-vis, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and tensile testing. All materials resulted in higher transparency, greater thermal stability, and stronger mechanical properties than unfilled PCL and nanocomposites containing unmodified CNCs. The degradation temperature of PCL reinforced with grafted CNCs was higher than that of micelle-modified CNCs, and the latter was higher than that of latex-adsorbed CNCs with a long PBMA chain length. The results clearly indicate that covalent grafting is superior to

  11. Influence of soil management on water erosion and hydrological responses in semiarid agrosystems

    Science.gov (United States)

    De Alba, Saturnino; Alcazar, María; Ivón Cermeño, F.

    2014-05-01

    fallow (white fallow) with minimum tillage, 3) Organic fallow (Green fallow), 4) Delayed fallow, and 5) Chemical fallow with a no-tillage management. Additionally, there is an experimental plot presenting a simulation of abandonment and natural re-vegetation. This paper presents the main results, for a data series of 20 years (1993-2013) with special attention to the organic farming management results, regarding to the following research objectives: 1) Monitoring the hydrological and erosive responses of the different management systems; 2) Study of the role of key factors in soil erodibility affected by the management as soil physics and chemistry, surface cover and roughness, and soil and surface initial conditions (soil water content, surface roughness…); and, 3) Characterizing the seasonal variability of the rainfall erosivity.

  12. Instantaneous generation of charge-separated state on TiO₂ surface sensitized with plasmonic nanoparticles.

    Science.gov (United States)

    Long, Run; Prezhdo, Oleg V

    2014-03-19

    Photoexcitation of the plasmon band in metallic nanoparticles adsorbed on a TiO2 surface initiates many important photovoltaic and photocatalytic processes. The traditional view on the photoinduced charge separation involves excitation of a surface plasmon, its subsequent dephasing into electron-hole pairs, followed by electron transfer (ET) from the metal nanoparticle into TiO2. We use nonadiabatic molecular dynamics combined with time-domain density functional theory to demonstrate that an electron appears inside TiO2 immediately upon photoexcitation with a high probability (~50%), bypassing the intermediate step of electron-hole thermalization inside the nanoparticle. By providing a detailed, atomistic description of the charge separation, energy relaxation, and electron-hole recombination processes, the simulation rationalizes why the experimentally observed ultrafast photoinduced ET in an Au-TiO2 system is possible in spite of the fast energy relaxation. The simulation shows that the photogenerated plasmon is highly delocalized onto TiO2, and thus, it is shared by the electron donor and acceptor materials. In the 50% of the cases remaining after the instantaneous photogeneration of the charge-separated state, the electron injects into TiO2 on a sub-100 fs time scale by the nonadiabatic mechanism due to high density of acceptor states. The electron-phonon relaxation parallels the injection and is slower, resulting in a transient heating of the TiO2 surface by 40 K. Driven by entropy, the electron moves further into TiO2 bulk. If the electron remains trapped at the TiO2 surface, it recombines with the hole on a picosecond time scale. The obtained ET and recombination times are in excellent agreement with the experiment. The delocalized plasmon state observed in our study establishes a novel concept for plasmonic photosensitization of wide band gap semiconductors, leading to efficient conversion of photons to charge carriers and to hybrid materials with a wide

  13. Late Quaternary stratigraphy of an alluvial valley along an active convergence front: Interactions of fluvial processes, tectonic channel steering, and sea level in the eastern Ganges-Brahmaputra-Meghna River delta

    Science.gov (United States)

    Williams, L.; Goodbred, S. L.; Steckler, M. S.; Seeber, L.; Spiess, V.; Schwenk, T.; Palamenghi, L.; Akhter, S. H.; Mondal, D.; Hossain, S.

    2012-12-01

    Insights into how tectonics, alluvial channels, and sediment interact to build the stratigraphy in a tectonically active depositional basin can be discovered by studying the sediment record and the current geomorphology of a system. Tectonics is an influence on basins that often gets overlooked due to overriding controls such as sea level, climate, and sediment load. The area for this study is in the Ganges Brahmaputra Meghna Delta (GBMD) in close proximity to an active convergent thrust front. To investigate the stratigraphy, we drilled 48 cores along two approximately longitudinal transects, 25-60 km apart, each spanning ~100 km. The boreholes were drilled every 3-4 km to a maximum depth of 100 m. The transects are situated across an alluvial valley and are bounded to the west by a Pleistocene terrace (Madhupur Terrace) and to the east by a fold belt (Indo-Burman Fold Belt) that continues to deform due to active tectonics at the thrust front. A seismic cruise using a mini-GI gun was conducted in conjunction with this study along the current river channel and has shown evidence of folded sediment at depth, and field studies in the area have found outcropping anticlines thus aiding in the determination of transect location. Through analysis of aerial imagery and digital elevation models (DEMs) of the transects, abandoned channels once occupied by the alluvial channel are evidence of migration and avulsion occurring recently enough to be recorded on the land surface. Initial analysis of the sediment cores shows a dramatic contrast in the stratigraphy between the two transects despite lying along the same morphological reach of the GBMD. The northern transect is dominated by fine to medium sands throughout indicating a strong fluvial influence, while the southern transect is dominated by muds and finer sands at depth indicating a tidal estuarine influence. The stratigraphy and land surface are a consequence of the controls on the system and reflect channel behavior

  14. High-Resolution Specification of the Land and Ocean Surface for Improving Regional Mesoscale Model Predictions

    Science.gov (United States)

    Case, Jonathan L.; Lazarus, Steven M.; Splitt, Michael E.; Crosson, William L.; Lapenta, William M.; Jedlovec, Gary J.; Peters-Lidard, Christa D.

    2008-01-01

    The exchange of energy and moisture between the Earth's surface and the atmospheric boundary layer plays a critical role in many meteorological processes. High-resolution, accurate representations of surface properties such as sea-surface temperature (SST), soil temperature and moisture content, ground fluxes, and vegetation are necessary to better understand the Earth-atmosphere interactions and improve numerical predictions of sensible weather. The NASA Short-term Prediction Research and Transition (SPoRT) Center has been conducting separate studies to examine the impacts of high-resolution land-surface initialization data from the Goddard Space Flight Center Land Information System (LIS) on subsequent WRF forecasts, as well as the influence of initializing WRF with SST composites derived from the MODIS instrument. This current project addresses the combined impacts of using high-resolution lower boundary data over both land (LIS data) and water (MODIS SSTs) on the subsequent daily WRF forecasts over Florida during May 2004. For this experiment, the WRF model is configured to run on a nested domain with 9- km and 3-kin grid spacing, centered on the Florida peninsula and adjacent coastal waters of the Gulf of Mexico and Atlantic Ocean. A control configuration of WRF is established to take all initial condition data from the NCEP Eta model. Meanwhile, two WRF experimental runs are configured to use high-resolution initialization data from (1) LIS land-surface data only, and (2) a combination of LIS data and high-resolution MODIS SST composites. The experiment involves running 24-hour simulations of the control WRF configuration, the MS-initialized WRF, and the LIS+MODIS-initialized WRF daily for the entire month of May 2004. All atmospheric data for initial and boundary conditions for the Control, LIS, and LIS+MODIS runs come from the NCEP Eta model on a 40-km grid. Verification statistics are generated at land surface observation sites and buoys, and the impacts

  15. The Impact of Microphysics and Planetary Boundary Layer Physics on Model Simulation of U.S. Deep South Summer Convection

    Science.gov (United States)

    McCaul, Eugene W., Jr.; Case, Jonathan L.; Zavodsky, Bradley T.; Srikishen, Jayanthi; Medlin, Jeffrey M.; Wood, Lance

    2014-01-01

    Inspection of output from various configurations of high-resolution, explicit convection forecast models such as the Weather Research and Forecasting (WRF) model indicates significant sensitivity to the choices of model physics pararneterizations employed. Some of the largest apparent sensitivities are related to the specifications of the cloud microphysics and planetary boundary layer physics packages. In addition, these sensitivities appear to be especially pronounced for the weakly-sheared, multicell modes of deep convection characteristic of the Deep South of the United States during the boreal summer. Possible ocean-land sensitivities also argue for further examination of the impacts of using unique ocean-land surface initialization datasets provided by the NASA Short-term Prediction Research and Transition (SPoRn Center to select NOAAlNWS weather forecast offices. To obtain better quantitative understanding of these sensitivities and also to determine the utility of the ocean-land initialization data, we have executed matrices of regional WRF forecasts for selected convective events near Mobile, AL (MOB), and Houston, TX (HGX). The matrices consist of identically initialized WRF 24-h forecasts using any of eight microphysics choices and any of three planetary boWldary layer choices. The resulting 24 simulations performed for each event within either the MOB or HGX regions are then compared to identify the sensitivities of various convective storm metrics to the physics choices. Particular emphasis is placed on sensitivities of precipitation timing, intensity, and coverage, as well as amount and coverage oflightuing activity diagnosed from storm kinematics and graupel in the mixed phase layer. The results confirm impressions gleaned from study of the behavior of variously configured WRF runs contained in the ensembles produced each spring at the Center for the Analysis and Prediction of Storms, but with the benefit of more straightforward control of the

  16. Improving dielectric properties of BaTiO{sub 3}/poly(vinylidene fluoride) composites by employing core-shell structured BaTiO{sub 3}@Poly(methylmethacrylate) and BaTiO{sub 3}@Poly(trifluoroethyl methacrylate) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xianhong; Zhao, Sidi; Wang, Fang [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Ma, Yuhong, E-mail: mayh@mail.buct.edu.cn [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Engineering Research Center of Syntheses and Applications of Waterborne Polymers, Beijing University of Chemical Technology, 100029 (China); Wang, Li; Chen, Dong; Zhao, Changwen [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Engineering Research Center of Syntheses and Applications of Waterborne Polymers, Beijing University of Chemical Technology, 100029 (China); Yang, Wantai, E-mail: yangwt@mail.buct.edu.cn [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Engineering Research Center of Syntheses and Applications of Waterborne Polymers, Beijing University of Chemical Technology, 100029 (China)

    2017-05-01

    Highlights: • Core-shell structured BT@PMMA and BT@PTFEMA nanoparticles were synthesized. • The dispersity of BT nanoparticles in PVDF matrix was improved significantly. • Dielectric properties both of BT@PMMA/PVDF and BT@PTFEMA/PVDF composites were improved. • The frequency dependence of dielectric constant attenuation of BT@PTFEMA/PVDF composites was smaller than that of BT@PMMA/PVDF composites. - Abstract: Polymer based dielectric composites were fabricated through incorporation of core-shell structured BaTiO{sub 3} (BT) nanoparticles into PVDF matrix by means of solution blending. Core-shell structured BT nanoparticles with different shell composition and shell thickness were prepared by grafting methacrylate monomer (MMA or TFEMA) onto the surface of BT nanoparticles via surface initiated atom transfer radical polymerization (SI-ATRP). The content of the grafted polymer and the micro-morphology of the core-shell structured BT nanoparticles were investigated by thermo gravimetric analyses (TGA) and transmission electron microscopy (TEM), respectively. The dielectric properties were measured by broadband dielectric spectroscopy. The results showed that high dielectric constant and low dielectric loss are successfully realized in the polymer based composites. Moreover, the type of the grafted polymer and its content had different effect on the dielectric constant. In detail, the attenuation of dielectric constant was 16.6% for BT@PMMA1/PVDF and 10.7% for BT@PMMA2/PVDF composite in the range of 10 Hz to 100 kHz, in which the grafted content of PMMA was 5.5% and 8.0%, respectively. However, the attenuation of dielectric constant was 5.5% for BT@PTFEMA1/PVDF and 4.0% for BT@PTFEMA2/PVDF composite, in which the grafted content of PTFEMA was 1.5% and 2.0%, respectively. These attractive features of BT@PTFEMA/PVDF composites suggested that dielectric ceramic fillers modified with fluorinated polymer can be used to prepare high performance composites, especially

  17. Adjustment of surface chemical and physical properties with functionalized polymers to control cell adhesion

    Science.gov (United States)

    Zhou, Zhaoli

    Cell-surface interaction is crucial in many cellular functions such as movement, growth, differentiation, proliferation and survival. In the present work, we have developed several strategies to design and prepare synthetic polymeric materials with selected cues to control cell attachment. To promote neuronal cell adhesion on the surfaces, biocompatible, non-adhesive PEG-based materials were modified with neurotransmitter acetylcholine functionalities to produce hydrogels with a range of porous structures, swollen states, and mechanical strengths. Mice hippocampal cells cultured on the hydrogels showed differences in number, length of processes and exhibited different survival rates, thereby highlighting the importance of chemical composition and structure in biomaterials. Similar strategies were used to prepare polymer brushes to assess how topographical cues influence neuronal cell behaviors. The brushes were prepared using the "grown from" method through surface-initiated atom transfer radical polymerization (SI-ATRP) reactions and further patterned via UV photolithography. Protein absorption tests and hippocampal neuronal cell culture of the brush patterns showed that both protein and neuronal cells can adhere to the patterns and therefore can be guided by the patterns at certain length scales. We also prepared functional polymers to discourage attachment of undesirable cells on the surfaces. For example, we synthesized PEG-perfluorinated alkyl amphiphilic surfactants to modify polystyrene-block-poly(ethylene-ran-butylene)- block-polyisoprene (SEBI or K3) triblock copolymers for marine antifouling/fouling release surface coatings. Initial results showed that the polymer coated surfaces can facilitate removal of Ulva sporelings on the surfaces. In addition, we prepared both bioactive and dual functional biopassive/bioactive antimicrobial coatings based on SEBI polymers. Incubating the polymer coated surfaces with gram-positive bacteria (S. aureus), gram

  18. Enhanced binding capacity of boronate affinity adsorbent via surface modification of silica by combination of atom transfer radical polymerization and chain-end functionalization for high-efficiency enrichment of cis-diol molecules

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei; He, Maofang; Wang, Chaozhan; Wei, Yinmao, E-mail: ymwei@nwu.edu.cn

    2015-07-30

    Boronate affinity materials have been widely used for specific separation and preconcentration of cis-diol molecules, but most do not have sufficient capacity due to limited binding sites on the material surface. In this work, we prepared a phenylboronic acid-functionalized adsorbent with a high binding capacity via the combination of surface-initiated atom transfer radical polymerization (SI-ATRP) and chain-end functionalization. With this method, the terminal chlorides of the polymer chains were used fully, and the proposed adsorbent contains dense boronic acid polymers chain with boronic acid on the chain end. Consequently, the proposed adsorbent possesses excellent selectivity and a high binding capacity of 513.6 μmol g{sup −1} for catechol and 736.8 μmol g{sup −1} for fructose, which are much higher than those of other reported adsorbents. The dispersed solid-phase extraction (dSPE) based on the prepared adsorbent was used for extraction of three cis-diol drugs (i.e., epinephrine, isoprenaline and caffeic acid isopropyl ester) from plasma; the eluates were analyzed by HPLC-UV. The reduced amount of adsorbent (i.e., 2.0 mg) could still eliminate interferences efficiently and yielded a recovery range of 85.6–101.1% with relative standard deviations ranging from 2.5 to 9.7% (n = 5). The results indicated that the proposed strategy could serve as a promising alternative to increase the density of surface functional groups on the adsorbent; thus, the prepared adsorbent has the potential to effectively enrich cis-diol substances in real samples. - Highlights: • Boronate adsorbent is prepared via ATRP and chain-end functionalization. • The adsorbent has quite high binding capacity for cis-diols. • Binding capacity is easily manipulated by ATRP condition. • Chain-end functionalization can improve binding capacity significantly. • Reduced adsorbent is consumed in dispersed solid-phase extraction of cis-diols.

  19. Toward spatial control of gold nanorod surface functionalization

    Science.gov (United States)

    Eller, Jonathan R.

    Gold nanorods (GNRs) show much promise for applications in biological, optoelectronic and energy applications. The resonant generation of a localized surface plasmon resonance (LSPR) at the GNR surface results in interesting optical properties and unique interactions with molecules. Combined with their biocompatibility, ease of synthesis and facile surface functionalization, these anisotropic metal particles are excellent scaffolds for the study of the interactions between nanoscale surfaces and their chemical/biological environments. Regardless of the application, however, GNR utility will not be fully realized until the chemical nature of the surface is understood and controlled. GNRs can enhance various photophysical properties of molecules. In the case of two-photon absorption (TPA), cross-section enhancements have been shown to increase with strong distance-dependence. Here, a dual approach for the conjugation of a TPA chromophore to GNRs is presented, relying on layer-by- layer (LbL) polymer wrapping and direct thiol coating of the same parent chromophore structure. Together, these approaches allow for estimated chromophore-particle distances from products in the synthesis of site- selective silica-coated GNRs is demonstrated, and the thickness tunability of the resulting core-shell materials is investigated. The redox state of methoxy- terminated poly(ethylene glycol) thiol attached to GNRs is shown to be relevant in guiding the deposition of silica, providing an important insight into the design of anisotropic composite nanomaterials. Surface-initiated Atom transfer radical polymerization (SI-ATRP) is a popular method for grafting polymers from a surface. We demonstrate our ability to grow poly(N-isopropylacrylamide) (PNIPAM) shells on the GNR surface, toward a "smart" thermoresponsive polymer shell. The role of ligand choice, molar ratio of monomer to initiator and polymerization on presence and control of shell thickness are investigated. The introduction

  20. Interactions between endothelial progenitor cells (EPC) and titanium implant surfaces.

    Science.gov (United States)

    Ziebart, Thomas; Schnell, Anne; Walter, Christian; Kämmerer, Peer W; Pabst, Andreas; Lehmann, Karl M; Ziebart, Johanna; Klein, Marc O; Al-Nawas, Bilal

    2013-01-01

    Endothelial cells play an important role in peri-implant angiogenesis during early bone formation. Therefore, interactions between endothelial progenitor cells (EPCs) and titanium dental implant surfaces are of crucial interest. The aim of our in vitro study was to investigate the reactions of EPCs in contact with different commercially available implant surfaces. EPCs from buffy coats were isolated by Ficoll density gradient separation. After cell differentiation, EPC were cultured for a period of 7 days on different titanium surfaces. The test surfaces varied in roughness and hydrophilicity: acid-etched (A), sand-blasted-blasted and acid-etched (SLA), hydrophilic A (modA), and hydrophilic SLA (modSLA). Plastic and fibronectin-coated plastic surfaces served as controls. Cell numbers and morphology were analyzed by confocal laser scanning microscopy. Secretion of vascular endothelial growth factor (VEGF)-A was measured by enzyme-linked immunosorbent assay and expressions of iNOS and eNOS were investigated by real-time polymerase chain reaction. Cell numbers were higher in the control groups compared to the cells of titanium surfaces. Initially, hydrophilic titanium surfaces (modA and modSLA) showed lower cell numbers than hydrophobic surfaces (A and SLA). After 7 days smoother surfaces (A and modA) showed increased cell numbers compared to rougher surfaces (SLA and modSLA). Cell morphology of A, modA, and control surfaces was characterized by a multitude of pseudopodia and planar cell soma architecture. SLA and modSLA promoted small and plump cell soma with little quantity of pseudopodia. The lowest VEGF level was measured on A, the highest on modSLA. The highest eNOS and iNOS expressions were found on modA surfaces. The results of this study demonstrate that biological behaviors of EPCs can be influenced by different surfaces. The modSLA surface promotes an undifferentiated phenotype of EPCs that has the ability to secrete growth factors in great quantities. In

  1. Initial hafnium oxide growth on silicon(100) and gallium arsenide(100) substrates using TEMAH+water and TDMAH+water ALD processes

    Science.gov (United States)

    Hackley, Justin Cain

    Atomic layer deposition (ALD) is a cyclic growth process that is distinguished by a self-limiting, two-step surface reaction that results in precise growth control and high quality, conformal thin films. Due to the continuous downscaling of MOSFET devices, a large interest has recently developed in the ALD of high-kappa dielectric materials as gate oxide layers on Si and III-V substrates. The ALD of HfO2 is an established process; however, there is still controversy over the initial growth mechanisms on differently prepared Si surfaces. This motivated a comparison of the nucleation stage of HfO 2 films grown on OH-(Si-OH) and H-terminated (Si-H) Si(100) surfaces. Two different ALD chemistries are investigated, including tetrakis[ethylmethylamino]hafnium (Hf[N(CH3)(C2H5)]4), abbreviated as TEMAH, and tetrakis[dimethylamino]hafnium (Hf[N(CH3)2] 4, abbreviated as TDMAH. H2O is used as the oxidizing precursor. Deposition temperatures of 250-275°C result in a linear growth per cycle of 1 A/cycle. Techniques including Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), and transmission electron microscopy are used to examine the film interface and initial film growth. HfO2 films are also subjected to post-deposition anneals, and the film morphology is examined with X-ray diffraction, Fourier transform infrared spectroscopy and atomic force microscopy. GaAs MOSFET devices have long proven elusive due to the lack of a stable native oxide. Recent research into high-kappa dielectric materials for use in Si-based devices has presented many new options for insulating layers on GaAs. HfO2 growth on GaAs(100) from a TDMAH+H2O ALD process is studied here. Three different GaAs surface treatments are examined, including buffered oxide etch (BOE), NH4OH, and a simple acetone/methanol wash (to retain the native oxide surface). Initial HfO2 growth on these surfaces is characterized with RBS and SE. The interfacial

  2. The mARM spatially distributed soil evolution model: A computationally efficient modeling framework and analysis of hillslope soil surface organization

    Science.gov (United States)

    Cohen, Sagy; Willgoose, Garry; Hancock, Greg

    2009-09-01

    Hillslope surface armouring and weathering processes have received little attention in geomorphologic and hydrologic models due to their complexity and the uncertainty associated with them. Their importance, however, in a wide range of spatial processes is well recognized. A physically based armouring and weathering computer model (ARMOUR) has previously been used to successfully simulate the effect of these processes on erosion and soil grading at a hillslope scale. This model is, however, computationally complex and cannot realistically be applied over large areas or over long periods of time. A simplified process conceptualization approach is presented (named mARM) which uses a novel approach of modeling physical processes using transition matrices, which is orders of magnitude faster. We describe in detail the modeling framework. We calibrate and evaluate the model against ARMOUR simulations and show it matches ARMOUR for a range of conditions. The computational efficiency of mARM allowed us to easily examine time- and space-varying relationships between erosion and physical weathering rates at the hillslope scale. For erosion-dominated slopes the surface coarsens over time, while for weathering domination the surface fines over time. When erosion and weathering are comparable in scale a slope can be weathering-dominated upslope (where runoff and therefore erosion is low) and armouring-dominated downslope. In all cases, for a constant gradient slope the surface armour coarsens downslope as a result of a balance between erosion and weathering. Thus even for weathering-dominated slopes the surface grading catena is dependent on armouring through the balance between weathering and armouring. We also observed that for many slopes the surface initially armours but, after some period of time (space- and rate-dependent), weathering begins to dominate and the surface subsequently fines. Depending on the relative magnitude of armouring and weathering the final

  3. Past Holocene soil erosion modeling as a new way to decipher human-climate-environment interactions on natural geo-ecosystem over long time-scale.

    Science.gov (United States)

    Simonneau, Anaëlle; Di Giovanni, Christian; Chapron, Emmanuel

    2017-04-01

    Soil erosion is a global phenomenon dealing with both environmental, societal and economic issues. Soil erosion is also one of the key processes when it is a matter of Human-climate-environment interactions [1, 2] since if mechanical erosion of continental surfaces initially results from climatic forcing, it can be largely amplified by anthropogenic activities. Using multi-scalar datasets to model long-term (Holocene) erosion fluxes in contrasted areas, where human pressure is well documented by geoarchaeology, we address how landscape evolution, geomorphological processes, ecosystem response and human impacts have been connected over time. Beyond that, such interdisciplinary and integrative approach allow (1) to locally date, qualify, and in particular quantify, both climate variability (rainfall) and impacts of human activities on soils, and (2) to discuss of potential feedback mechanisms and the legacy of past socio-cultural systems on actual geo-ecosystems. Lacustrine sediment represents one of the more relevant natural archives in order to reconstruct environmental or climatic variability and human activities over the past thousand years. Over the last 50 years, the edges of lakes Paladru (low altitude site, 640 m a.s.l.) and Blanc Huez (high-altitude site, 2250 m a.s.l.), both located in Western French Alps and therefore sensitive to the same climatic influences, have been deeply studied by archaeologists who documented and dated periods of enhanced human pressures (agriculture, mining [3, 4]). In these two case-studies, we were therefore able to confront the specific calendars of local human activities with past landscape evolution (vegetation cover, 5) and soil erosion fluxes reconstituted from specific organic tracers quantified into the lacustrine sediments [3, 6]. Results demonstrated that, over the Holocene, climatic forcing, and more particularly glacial fluctuations, influenced human accessibility to high-altitude sites (lake Blanc Huez) and therefore

  4. Diagnostics and treatment of 1.3 GHz Nb cavities

    International Nuclear Information System (INIS)

    Tamashevich, Yegor

    2017-01-01

    The European XFEL and the International Linear Collider are based on superconducting rf cavities. In order to reach the theoretical gradient limits of the superconducting cavities it is necessary to increase the mechanical quality and chemical composition of the inner surface as well as to understand the reason for performance limitations. This work is based on the diagnosis of over 100 XFEL and HiGrade cavities whose performance was limited by several factors: field emission on dust or surface defects, low-field thermal breakdown caused by the defects, Q-slope etc. It was found that some defects were produced during the mechanical production of the cavity and were not removed by electro-chemical polishing, a standard processing technique of the inner cavity surface. On the other hand, some of the defects were produced during the electro-chemical polishing process as the surface initially had imperfections or inclusions of foreign material. One of the opportunities to overcome the aforementioned drawbacks is to replace the ''bulk'' electro-chemical polishing process by mechanical centrifugal barrel polishing. The parameters of the surface after each polishing step were studied using small samples, so called coupons. An undersurface layer was investigated using metallographic techniques and cross sectioning. The influence of centrifugal polishing on the specific parameters of a 9-cell cavity (field flatness, eccentricity etc.) was investigated. As a result, a single-step centrifugal barrel polishing process followed by a standard ''light'' electropolishing was proposed for industrial application. Although the performance-limiting mechanisms are understood in general, the origin of the quench of the cavity is often unclear. To determine the quench locations, a localisation tool for thermal breakdown using the ''second sound'' in superfluid helium has been used. All components of this tool were improved to

  5. Polymer surface engineering via thiol-mediated reactions

    Science.gov (United States)

    Hensarling, Ryan Matthew

    Synthesis of polymer brushes to decorate a surface with desired functionality typically involves surface-initiated polymerization (SIP) of functional, but non-reactive monomers. This approach suffers major drawbacks associated with synthesizing sufficiently thick polymer brushes containing surface-attached polymer chains of high molecular weight at high grafting density (i.e. cost, synthetic effort and functional group intolerance during polymerization). The research herein seeks to circumvent these limitations by the decoration of surfaces with polymer chains bearing specific pendent functional groups amenable to post-polymerization modification (PPM). In particular, this dissertation leverages PPM via a specific class of click reactions - thiol-click - that 1) enables the rapid generation of a diverse library of functional surfaces from a single substrates precursor, 2) utilizes a structurally diverse range of commercially available or easily attainable reagents, 3) proceeds rapidly to quantitative conversions under mild conditions and 4) opens the door to orthogonal and site-selective functionalization. In the first two studies, radical-mediated thiol-yne and base-catalyzed thiol-isocyanate reactions are demonstrated as modular platforms for the rapid and practical fabrication of highly functional, multicomponent surfaces under ambient conditions. Brush surfaces expressing a three-dimensional configuration of alkyne or isocyanate functionalities were modified with high efficiency and short reaction times using a library of commercially available thiols. In the third study, two routes to multifunctional brush surfaces were demonstrated utilizing orthogonal thiol-click reactions. In the first approach, alkyne-functionalized homopolymer brushes were modified with multiple thiols via a statistical, radical-mediated thiol-yne co-click reaction; and in the second approach, statistical copolymer brushes carrying two distinctly-addressable reactive moieties were

  6. Stratigraphy, age, and correlation of voluminous debris-avalanche events from an ancestral Egmont Volcano : implications for coastal plain construction and regional hazard assessment

    International Nuclear Information System (INIS)

    Alloway, B.V.; McComb, P.; Neall, V.; Vucetich, C.; Gibb, J.; Sherburn, S.; Stirling, M.W.

    2005-01-01

    Two previously unrecognised debris-avalanche deposits have been identified on the eastern flanks of Egmont Volcano beneath a thick mantle of tephric and andic soil material that has mostly subdued their topographic expression. The Ngaere Formation is a c. 23 14 C ka large volume (>5.85 km 3 ) debris-avalanche deposit that is widely distributed over 320-500 km 2 of the north-east, south-east, and south portions of the Egmont ring plain. The second deposit, Okawa Formation, is a c. 105 ka large volume (>3.62 km 3 ) debris-avalanche deposit that has been mapped over a minimum area of 255 km 2 in northern and north-eastern Taranaki. Both debris-avalanche formations contain axial facies with hummocks composed mainly of block-supported brecciated andesitic debris. A less conspicuous marginal facies, texturally resembling a mudflow, is more extensive. A third debris-avalanche deposit (Motunui Formation) is extensively preserved along the north Taranaki coast where it is truncated by a c. 127 ka wave cut surface (NT2) and closely overlies a c. 210 ka wave cut surface (NT3). The source of this debris-avalanche deposit is unknown. Side-scan sonar and shallow seismic profiling have been useful in accurately delineating the distribution of combined Okawa and Motunui debris-avalanche deposits in the offshore environment but cannot distinguish between the two deposits or enable onshore spatial and volumetric estimates for each unit to be revised. However, the widespread occurrence of debris-avalanche rock material offshore does emphasise the importance of this lag material altering the orientation of the coast influencing both wave climate and rates of coastal erosion. Similarly, the extensive onshore occurrence of debris-avalanche rock material appears to be a significant factor in widening of the north Taranaki coastal plain and preservation of the NT2 and NT3 uplifted marine terrace surfaces. Initiation of collapse by magmatically-induced seismicity is apparently common at

  7. Effect of micro-topography and undrained shear strength on soil erosion

    Science.gov (United States)

    Todisco, Francesca; Vergni, Lorenzo; Vinci, Alessandra; Torri, Dino

    2017-04-01

    An experiment to evaluate the effect of the pre-event soil surface conditions on the dynamics of the interrill erosion process was performed at the Masse experimental station (Italy) in a replicated 1mx1m plot, located in a 16% slope in a silt-clay-loam soil equipped with a nozzle-type rainfall simulator. Two experiments was performed, each experiment started from a just ploughed bare surface and included 3 simulations (I, II and III in the first experiment and IV, V and VI in the second experiment) carried out in the range of few days. A 30 min pre-wetting phase ensures almost constant initial soil moisture (mean=31%, CV=5%) and bulk density (mean=1.3 g/cm3, CV=3%). Rainfall intensity was maintained constant (mean=67mm/h, CV=2.7%). The independent variables were the initial soil surface conditions that, progressively modified by the rainfall runoff process, were different for the three subsequent simulations. The soil surface initial and final micro-topography and undrained shear strength, T, were monitored through photogrammetric surveys (with I-Phone 6plus) and Torvane test (with pocket-torvane, obliged shear surface at 0.5 cm from soil surface, plate diameter 5 cm, 0.2186 full scale complete revolution 360°, test done on saturated soil surface, with water standing at the surface). Runoff, Q, runoff coefficient, Qr, soil loss, SL and sediment concentration, C, were measured every 5 min. The particle size distribution were also determined. During the simulations Q increases monotonically with typically concave trend. Almost similar consideration can be made for the other variables. A higher frequency of the roughness, RR, (i.e. vertical distance between the surface and a reference horizontal plane, obtained by removing the slope effect) lower than a fixed amount, was measured at the final than the initial step of each simulation and within the single experiment between successive simulations. Therefore, the roughness decreases along with the Q, SL and C increase

  8. Hydrologic monitoring for Chicago’s Sustainable Streetscapes Program

    Science.gov (United States)

    Duncker, James J.; Morrow, William S.

    2016-04-05

    sanitary flow) and wet weather conditions (stormwater runoff in addition to the sanitary flow). Sanitary flow is the largest source of flow in the combined sewers during dry weather, and stormwater runoff and sanitary flow combine during wet weather. The sewer flow data allow engineers and scientists to calculate total runoff volume for selected storm events.Wells are located within the project corridor to record water levels and help determine the direction of movement of groundwater in response to rainfall and snowmelt. In urban settings with aging sewer systems, groundwater can seep into the sewers or combined sewage can seep from the sewers into the local groundwater system. The groundwater data are also important in evaluating the overall impacts of increased infiltration resulting from BMPs.Data from wells show the relative water levels of shallow groundwater, water levels in the combined sewer system, and nearby surface-water channels within the project corridor. In some aging urban sewer systems, the local combined sewer system lies below the water table and receives substantial amounts of groundwater inflow, which can significantly reduce the amount of additional water the sewer system can accept.The bioswale along the south side of West Cermak Road near South Throop Street functions to infiltrate stormwater runoff from the road. Stormwater on the road surface initially drains to the curb and then flows along the curb until it reaches a curb cut-out. Materials within the bioswale allow stormwater to infiltrate and reduce the load to the combined sewer.A common feature in urban areas are curbside catch basins that collect stormwater runoff from paved streets. Stormwater drains first to the curb and then flows along the curb to the catch basin. Lateral sewer pipe connects the catch basin to the combined sewer beneath the street. The use of permeable pavers along the curbs in the project study reach let stormwater infiltrate before it reaches the curb, thus reducing

  9. Advance and prospectus of seasonal prediction: assessment of the APCC/CliPAS 14-model ensemble retrospective seasonal prediction (1980-2004)

    Science.gov (United States)

    Wang, Bin; Lee, June-Yi; Kang, In-Sik; Shukla, J.; Park, C.-K.; Kumar, A.; Schemm, J.; Cocke, S.; Kug, J.-S.; Luo, J.-J.; Zhou, T.; Wang, B.; Fu, X.; Yun, W.-T.; Alves, O.; Jin, E. K.; Kinter, J.; Kirtman, B.; Krishnamurti, T.; Lau, N. C.; Lau, W.; Liu, P.; Pegion, P.; Rosati, T.; Schubert, S.; Stern, W.; Suarez, M.; Yamagata, T.

    2009-07-01

    Temperature (SST) anomalies are primary sources of atmospheric climate variability worldwide. The MME 1-month lead hindcast can predict, with high fidelity, the spatial-temporal structures of the first two leading empirical orthogonal modes of the equatorial SST anomalies for both boreal summer (JJA) and winter (DJF), which account for about 80-90% of the total variance. The major bias is a westward shift of SST anomaly between the dateline and 120°E, which may potentially degrade global teleconnection associated with it. The TCC score for SST predictions over the equatorial eastern Indian Ocean reaches about 0.68 with a 6-month lead forecast. However, the TCC score for Indian Ocean Dipole (IOD) index drops below 0.40 at a 3-month lead for both the May and November initial conditions due to the prediction barriers across July, and January, respectively. The MME prediction skills are well correlated with the amplitude of Niño 3.4 SST variation. The forecasts for 2 m air temperature are better in El Niño years than in La Niña years. The precipitation and circulation are predicted better in ENSO-decaying JJA than in ENSO-developing JJA. There is virtually no skill in ENSO-neutral years. Continuing improvement of the one-tier climate model’s slow coupled dynamics in reproducing realistic amplitude, spatial patterns, and temporal evolution of ENSO cycle is a key for long-lead seasonal forecast. Forecast of monsoon precipitation remains a major challenge. The seasonal rainfall predictions over land and during local summer have little skill, especially over tropical Africa. The differences in forecast skills over land areas between the CliPAS and DEMETER MMEs indicate potentials for further improvement of prediction over land. There is an urgent need to assess impacts of land surface initialization on the skill of seasonal and monthly forecast using a multi-model framework.

  10. Advance and prospectus of seasonal prediction: assessment of the APCC/CliPAS 14-model ensemble retrospective seasonal prediction (1980-2004)

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Bin; Lee, June-Yi; Fu, X.; Liu, P. [University of Hawaii, Department of Meteorology and International Pacific Research Center, IPRC, School of Ocean and Earth Science and Technology, Honolulu, HI (United States); Kang, In-Sik; Kug, J.S. [Seoul National University, School of Earth and Environmental Sciences, Seoul (Korea); Shukla, J.; Jin, E.K.; Kinter, J.; Kirtman, B. [George Mason University and COLA, Climate Dynamics Program, Calverton, MD (United States); Park, C.K. [APEC Climate Center, Busan (Korea); Kumar, A.; Schemm, J. [Climate Prediction Center/NCEP, Camp Springs, MD (United States); Cocke, S.; Krishnamurti, T. [Florida State University, Tallahassee, FL (United States); Luo, J.J. [Frontier Research Center for Global Chnage, Yokohama (Japan); Zhou, T.; Wang, B. [Chinese Academy of Sciences, LASG/Institute of Atmospheric Physics, Beijing (China); Yun, W.T. [Korean Meteorological Administration, Seoul (Korea); Alves, O. [Bureau of Meteorology Research Center, Melburne (Australia); Lau, N.C.; Rosati, T.; Stern, W. [Princeton University, Geophysical Fluid Dynamics Laboratory/NOAA, Princeton, NJ (United States); Lau, W.; Pegion, P.; Schubert, S.; Suarez, M. [Godard Space Flight Center/NASA, Greenbelt, MD (United States)

    2009-07-15

    Temperature (SST) anomalies are primary sources of atmospheric climate variability worldwide. The MME 1-month lead hindcast can predict, with high fidelity, the spatial-temporal structures of the first two leading empirical orthogonal modes of the equatorial SST anomalies for both boreal summer (JJA) and winter (DJF), which account for about 80-90% of the total variance. The major bias is a westward shift of SST anomaly between the dateline and 120 E, which may potentially degrade global teleconnection associated with it. The TCC score for SST predictions over the equatorial eastern Indian Ocean reaches about 0.68 with a 6-month lead forecast. However, the TCC score for Indian Ocean Dipole (IOD) index drops below 0.40 at a 3-month lead for both the May and November initial conditions due to the prediction barriers across July, and January, respectively. The MME prediction skills are well correlated with the amplitude of Nino 3.4 SST variation. The forecasts for 2 m air temperature are better in El Nino years than in La Nina years. The precipitation and circulation are predicted better in ENSO-decaying JJA than in ENSO-developing JJA. There is virtually no skill in ENSO-neutral years. Continuing improvement of the one-tier climate model's slow coupled dynamics in reproducing realistic amplitude, spatial patterns, and temporal evolution of ENSO cycle is a key for long-lead seasonal forecast. Forecast of monsoon precipitation remains a major challenge. The seasonal rainfall predictions over land and during local summer have little skill, especially over tropical Africa. The differences in forecast skills over land areas between the CliPAS and DEMETER MMEs indicate potentials for further improvement of prediction over land. There is an urgent need to assess impacts of land surface initialization on the skill of seasonal and monthly forecast using a multi-model framework. (orig.)

  11. Studies in Multifunctional Drug Development: Preparation and Evaluation of 11beta-Substituted Estradiol-Drug Conjugates, Cell Membrane Targeting Imaging Agents, and Target Multifunctional Nanoparticles

    Science.gov (United States)

    Dao, KinhLuan Lenny D.

    with an azido-tetraethylene glycol moiety that could be coupled to a complementary doxorubicin benzoyl hydrazone, functionalized with a propargyl tetraethylene glycol moiety. Huisgen [3+2] cycloaddition chemistry gave the final hybrid which was evaluated for receptor binding to demonstrate ER-affinity and for cytotoxicity in ER(+)-MCF-7 and ER(-)-MDA-MB-231 breast cancer cell lines. The anti-estrogen-doxorubicin hybrid demonstrated enhanced (>70-fold) selectivity for ER(+)-cells versus ER(-)-cells and enhanced efficacy compared to doxorubicin alone. The reversal of these effects by co-administration of estradiol demonstrated that the presence of the anti-estrogenic component was critical for selectivity and cytotoxicity in ER(+)-MCF-7 human breast cancer cells. The results suggest that this approach the basis for developing selective therapeutic agents for ER(+)-cancer cells with reduced effects on non-target tissues.1,2 The second study describes our use of 11beta-AE for targeting ER membrane targeting in hormone-dependent breast cancer, and of a urea-based prostate specific membrane antigen (PSMA) inhibitor for targeting PSMA membrane receptors in androgen-independent of prostate cancer. These derivatives were used to prepare a series of molecular imaging probes. We have successfully established our model compound, 11beta-AE radiolabeled with 18F-fluoro-OEG-azide, for in vivo imaging.3 The third study describes a strategy based on the design and synthesis of a multifunctional gold nanoparticulate (mfAuNPs) drug delivery system that can be used for prostate cancer therapy. We have utilized a convergent modular assembly approach to prepare individual components such as a) prostate specific membrane antigen (PSMA) ligands for targeting; b) pH-sensitive doxorubicin; and c) Re/99Tc chelating complex for radioimaging. The components can be assembled with a terminal lipoic acid or thiolated ethylene glycol oligomer for attachment to the Au surface. Initial in vitro studies