WorldWideScience

Sample records for k30-diclofenac-ldh nanohybrid dispersion

  1. Superior SWNT dispersion by amino acid based amphiphiles: designing biocompatible cationic nanohybrids.

    Science.gov (United States)

    Brahmachari, Sayanti; Das, Dibyendu; Das, Prasanta Kumar

    2010-11-28

    Stable aqueous SWNT dispersion up to 92% was achieved using amino acid based amphiphiles through a structure-property investigation. The nanohybrids showed remarkable serum stability and biocompatibility to mammalian cells.

  2. Improving the physical properties of starch using a new kind of water dispersible nano-hybrid reinforcement.

    Science.gov (United States)

    Morales, Noé J; Candal, Roberto; Famá, Lucía; Goyanes, Silvia; Rubiolo, Gerardo H

    2015-08-20

    Plasticized cassava starch matrix composites reinforced by a multi-wall carbon nanotube (MWCNT)-hercynite (FeAl2O4) nanomaterial were developed. The hybrid nanomaterial consists of FeAl2O4 nanoparticles anchored strongly to the surface of the MWCNT. This nano-hybrid filler shows an irregular geometry, which provides a strong mechanical interlocking with the matrix, and excellent stability in water, ensuring a good dispersion in the starch matrix. The composite containing 0.04wt.% of the nano-hybrid filler displays increments of 370% in the Young's modulus, 138% in tensile strength and 350% in tensile toughness and a 70% decrease in water vapor permeability relative to the matrix material. All of these significant improvements are explained in terms of the nano-hybrid filler homogenous dispersion and its high affinity with both plasticizers, glycerol and water, which induces crystallization without deterioration of the tensile toughness.

  3. Fabrication of stable aqueous dispersions of graphene using gellan gum as a reducing and stabilizing agent and its nanohybrids

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Ding; Zhang, Fei; Zhang, Hongbin, E-mail: hbzhang@sjtu.edu.cn

    2015-01-15

    An environment-friendly method for the reduction of graphene oxide (GO) was developed by utilizing the acid polysaccharide of gellan gum (GG) as both a reducing and a stabilizing agent. The reduction process of GO was monitored by UV–Vis spectroscopy and the factors that affect the reduction of GO, such as the molecular weight of GG, the weight ratio of GG/GO, pH and reaction temperature, were studied. A mechanism for reduction of GO with GG and the optimum reaction condition were proposed. The obtained reduced graphene oxide (RGO) that bears adsorbed GG (G-RGO) was characterized by Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, Thermogravimetric analysis, Raman spectroscopy, X-ray photoelectron spectroscopy and Atomic force microscopy. The results showed that GG can efficiently reduce GO and adsorb onto the RGO nanosheets giving a stable G-RGO aqueous dispersion. Parameters affecting the stability of G-RGO aqueous dispersion, such as pH and ionic strength, were also studied. This work promised a new green strategy for large scale production of RGO with highlighting multiple functions of the natural, nontoxic and biodegradable macromolecule of GG. Moreover, GG was found to be able to promote reducing HAuCl{sub 4}, AgNO{sub 3} or H{sub 2}PtCl{sub 6} to Au, Ag or Pt nanoparticles respectively onto G-RGO surfaces providing noble metal nanoparticle-G-RGO nanohybrids that exhibit good electrochemical activities with potential applications in the fields of catalysis and energy storage. - Highlights: • A green method for preparation of reduced graphene oxide (RGO) was developed. • Gellan gum (GG) was used as both a reducing and a stabilizing agent. • RGO nanosheets can be dispersed stably in aqueous medium by adsorption of GG. • RGO containing GG can be used as a template to prepare noble metal nanohybrids. • These obtained nanohybrids exhibit good electrochemical activities.

  4. Synthesis and properties of highly dispersed ionic silica-poly(ethylene oxide) nanohybrids.

    KAUST Repository

    Fernandes, Nikhil J

    2013-02-04

    We report an ionic hybrid based on silica nanoparticles as the anion and amine-terminated poly(ethylene oxide) (PEO) as a cation. The charge on the nanoparticle anion is carried by the surface hydroxyls. SAXS and TEM reveal an exceptional degree of dispersion of the silica in the polymer and high degree of order in both thin film and bulk forms. In addition to better dispersion, the ionic hybrid shows improved flow characteristics compared to silica/PEO mixtures in which the ionic interactions are absent.

  5. Optical dispersion parameters and stability of poly (9, 9‧-di-n-octylfluorenyl-2.7-diyl)/ZnO nanohybrid films: towards organic photovoltaic applications

    Science.gov (United States)

    El-Bashir, S. M.; Alenazi, W. K.; AlSalhi, M. S.

    2017-02-01

    Conjugated polymer nanohybrid films were prepared from poly (9,9‧-di-n-octylfluorenyl-2.7-diyl) (PFO) and zinc oxide (ZnO) nanoparticles. ZnO nanopowder was prepared by the solgel method, different ratios of PFO/ZnO nanohybrids have been prepared using solution blending method. Then, the blends were spin-coated onto glass substrates at 2000 rpm for 1 min. and subsequently dried at room temperature. XRD and TEM were used to determine the structural properties, while UV–Vis and photoluminescence spectrophotometers were employed to investigate the optical properties of the films. The spectral distribution of specular reflectance were used to calculate the refractive index n (λ) and the optical dispersion parameters were determined according to Wemple and Didomenico (WD) model. The effect of ZnO NPs on the direct and indirect band gap energies, photo- and thermal stability was also discussed. A significant enhancement in the light emitting properties has been observed by increasing the concentration of ZnO NPs.

  6. Novel nanohybrid MTA compositions

    DEFF Research Database (Denmark)

    Lovschall, Henrik; Ranjkesh, Bahram

    capping. and that it is a highly biocompatible material. MTA has as drawbacks high costs, potential discoloration, and 3h setting time (1). Novel technology developed at Aarhus University is basis for novel nano-hybrid MTA (called iMTA) with fast setting time and fluoride release. iMTA contain a slightly...

  7. Novel nanohybrid MTA compositions

    DEFF Research Database (Denmark)

    Lovschall, Henrik; Ranjkesh, Bahram

    Original Mineral Trioxide Aggregate (MTA) has been recommended for various uses in endodontics. MTA is a calcia, silica, alumina containing hydraulic cement with long setting time, calcium hydroxide release, and high pH. It possesses antibacterial and sealing properties. Interestingly, recent...... studies describe hydroxyapatite crystals form over MTA when it comes in contact with simulated physiological tissue fluid. On the basis of available evidence it appears that MTA efficiently develop superior marginal adaptation in humid environments. Observations suggest MTA is suitable material for pulp...... capping. and that it is a highly biocompatible material. MTA has as drawbacks high costs, potential discoloration, and 3h setting time (1). Novel technology developed at Aarhus University is basis for novel nano-hybrid MTA (called iMTA) with fast setting time and fluoride release. iMTA contain a slightly...

  8. Layered zinc hydroxide–ibuprofen nanohybrids: synthesis and characterization

    Indian Academy of Sciences (India)

    Hafezeh Nabipour; Moayad Hossaini Sadr

    2015-10-01

    The nonsteroidal anti-inflammatory drug (NSAID), ibuprofen (IBU) anion, was intercalated into the layered zinc hydroxide (LZH) to form a new organic–inorganic nanohybrid. Then, IBU–LZH nanohybrid was dispersed into chitosan for the formation of the nanocomposite. The IBU–LZH nanohybrid was characterized by powder X-ray diffraction (PXRD) to study intercalation, scanning electron microscopy (SEM) for the investigation of surface morphology, Fourier transform infrared (FTIR) spectrophotometer to study the chemical interactions and thermal gravimetric analysis/derivative thermogravimetric analysis (TGA/DTG) for understanding the thermal stability. The PXRD patterns showed that the IBU was successfully intercalated into the interlay space of LZHs as monolayers and the basal spacing of LZH increased from 9.57 to 19.54 Å. The FTIR analyses confirmed the formation of the host–guest nanohybrid. The DTG studies revealed that the thermal stability of IBU was increased after the intercalation into LZH. The in vitro release study of IBU from IBU–LZH and IBU–LZH/chitosan nanocomposite was investigated in phosphate buffer saline (PBS) solution of pH 4.8 and 7.4. The drug release from the LZH was studied by ultraviolet–visible (UV–vis) spectroscopy.

  9. Engineering of a Pluronic F127 functionalized magnetite/graphene nanohybrid for chemophototherapy.

    Science.gov (United States)

    Li, Yongyong; Liu, Jiaqiang; Dong, Haiqing; Liu, Guangzhen; Hu, Haiqing

    2014-02-14

    In this study, a multifunctional graphene based nanohybrid, termed as GN/Fe3O4/PF127, is engineered via a facile one-pot process consisting of simultaneous reduction of graphene oxide/Fe3O4 and subsequent assembly of Pluronic F127 (PF127) onto graphene nanosheets (GNs). The unique aromatic and planar structure of GNs allows the attachment of multiple functional components including MRI contrast agent (Fe3O4 nanoparticles) and an aromatic anticancer drug like doxorubicin (DOX), as well as PF127 coating which imparts physiological dispersivity and stability to the nanohybrid. The successful assembly process is revealed by TEM observation, size and FITR monitoring. In contrast with the primitive graphene or its oxide derivative, the resulting GN/Fe3O4/PF127 nanohybrids have shown high biological dispersion and MRI effect for diagnosis due to the incorporation of superparamagnetic Fe3O4 nanoparticles without evident cytotoxicity. Moreover, the GN/Fe3O4/PF127 nanohybrid exhibits a photothermal effect due to the considerable optical absorption in the near-infrared region of GNs. The GN/Fe3O4/PF127 nanohybrid could be a further platform for chemophototherapy assisted by the therapeutic DOX. Cellular toxicity assays indicated that the DOX-loaded GN/Fe3O4/PF127 nanohybrid showed a remarkable cytotoxicity to HeLa cells and the cytotoxic effect was intensified when subjected to photoirradiation. Confocal laser scanning microscopy (CLSM) and flow cytometric analysis (FCAS) revealed that the nanohybrid could be easily uptaken into HeLa cells.

  10. A novel fabrication of a high performance SiO2-graphene oxide (GO) nanohybrids: Characterization of thermal properties of epoxy nanocomposites filled with SiO2-GO nanohybrids.

    Science.gov (United States)

    Haeri, S Z; Ramezanzadeh, B; Asghari, M

    2017-05-01

    In this study it has been aimed to enhance the thermal resistance of epoxy coating through incorporation of SiO2-GO nanohybrids. SiO2-GO nanohybrids were synthesized through one-step sol-gel route using a mixture of Tetraethylorthosilane (TEOS) and 3-Aminopropyl triethoxysilane (APTES) silanes. The SiO2-GO nanohybrids were prepared at various hydrolysis times of 24, 48 and 72h. Then 0.2wt.% of GO and SiO2-GO nanohybrids were separately incorporated into the epoxy coating. Results revealed that amino functionalized SiO2 nanoparticles with particle size around 20-30nm successfully synthesized on the basal plane of GO. Results showed significant improvement of dispersion and interfacial interactions between nanohybrids and epoxy composite arising from covalent bonding between the SiO2-GO and the epoxy matrix. It was found that the thermal resistance of SiO2-GO nanohybrids and SiO2-GO/Epoxy nanocomposite was noticeably higher than GO and epoxy matrix, respectively.

  11. Hyaluronic acid-decorated graphene oxide nanohybrids as nanocarriers for targeted and pH-responsive anticancer drug delivery.

    Science.gov (United States)

    Song, Erqun; Han, Weiye; Li, Cheng; Cheng, Dan; Li, Lingrui; Liu, Lichao; Zhu, Guizhi; Song, Yang; Tan, Weihong

    2014-08-13

    A novel nanohybrid of hyaluronic acid (HA)-decorated graphene oxide (GO) was fabricated as a targeted and pH-responsive drug delivery system for controlling the release of anticancer drug doxorubicin (DOX) for tumor therapy. For the preparation, DOX was first loaded onto GO nanocarriers via π-π stacking and hydrogen-bonding interactions, and then it was decorated with HA to produce HA-GO-DOX nanohybrids via H-bonding interactions. In this strategy, HA served as both a targeting moiety and a hydrophilic group, making the as-prepared nanohybrids targeting, stable, and disperse. A high loading efficiency (42.9%) of DOX on the nanohybrids was also obtained. Cumulative DOX release from HA-GO-DOX was faster in pH 5.3 phosphate-buffered saline solution than that in pH 7.4, providing the basis for pH-response DOX release in the slightly acidic environment of tumor cells, while the much-slower DOX release from HA-GO-DOX than DOX showed the sustained drug-release capability of the nanohybrids. Fluorescent images of cellular uptake and cell viability analysis studies illustrated that these HA-GO-DOX nanohybrids significantly enhanced DOX accumulation in HA-targeted HepG2 cancer cells compared to HA-nontargeted RBMEC cells and subsequently induced selective cytotoxicity to HepG2 cells. In vivo antitumor efficiency of HA-GO-DOX nanohybrids showed obviously enhanced tumor inhibition rate for H22 hepatic cancer cell-bearing mice compared with free DOX and the GO-DOX formulation. These studies suggest that the HA-GO-DOX nanohybrids have potential clinical applications for anticancer drug delivery.

  12. Metal Fe{sup 3+} ions assisted synthesis of highly monodisperse Ag/SiO{sub 2} nanohybrids and their antibacterial activity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Nianchun; Xue, Feng [College of Material Science and Engineering, South China University of Technology, Guangzhou 510641 (China); Yu, Xiang [Analytical and Testing Center, Jinan University, Guangzhou 510632 (China); Zhou, Huihua [Guangdong East Sunshine Pharmaceutical Co., Ltd., Dongguan 523871 (China); Ding, Enyong, E-mail: eyding@scut.edu.cn [College of Material Science and Engineering, South China University of Technology, Guangzhou 510641 (China)

    2013-02-15

    Graphical abstract: TEM images of the Ag/SiO{sub 2}-2 nanohybrids. The homogeneous and more mono-disperse Ag nanoparticles deposit on SiO{sub 2} spheres. Through this method, Ag nanoparticles are easily formed on the surface of SiO{sub 2} compared to other methods. Highlights: Black-Right-Pointing-Pointer We prepared homogeneous and mono-dispersed Ag/SiO{sub 2}-2 nanohybrids by adding Fe{sup 3+} ions. Black-Right-Pointing-Pointer The Ag/SiO{sub 2}-2 nanohybrids had core(SiO{sub 2})-shell(Ag) structure. Black-Right-Pointing-Pointer The Ag/SiO{sub 2}-2 nanohybrids exhibited excellent antibacterial activity against bacteria. Black-Right-Pointing-Pointer The reaction temperature was lower and the yield of Ag/SiO{sub 2}-2 nanohybrids were higher. - Abstract: Highly monodispersed Ag/SiO{sub 2} nanohybrids with excellent antibacterial property were synthesized by using DMF as a reducing agent and employing an additional redox potential of metal Fe{sup 3+} ion as a catalytic agent. The obtained Ag/SiO{sub 2}-2 nanohybrids of about 240 nm were highly monodispersity and uniformity by adding trace Fe{sup 3+} ions into the reaction which Ag{sup +} reacted with N,N-dimethyl formamide (DMF) at 70 Degree-Sign C. Compared to the conventional techniques, which need long time and high temperature for silica coating of Ag nanoparticles, this new method was capable of synthesizing monodispersed, uniform, high yield Ag/SiO{sub 2} nanohybrids. The electron was transferred from the Fe{sup 2+} ion to the Ag{sup +} ion to accelerate the nucleation of silver nanoparticles. The chemical structures, morphologies and properties of the Ag/SiO{sub 2} nanohybrids were characterized by X-ray diffraction (XRD), (High-resolution, Scanning transmission) transmission electron microscopy (TEM, HRTEM and STEM), and X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy (UV-vis) and test of antibacterial. The results demonstrated that the silver nanoparticles supported on the surface of Si

  13. Graphene oxide based nanohybrid proton exchange membranes for fuel cell applications: An overview.

    Science.gov (United States)

    Pandey, Ravi P; Shukla, Geetanjali; Manohar, Murli; Shahi, Vinod K

    2017-02-01

    In the context of many applications, such as polymer composites, energy-related materials, sensors, 'paper'-like materials, field-effect transistors (FET), and biomedical applications, chemically modified graphene was broadly studied during the last decade, due to its excellent electrical, mechanical, and thermal properties. The presence of reactive oxygen functional groups in the grapheme oxide (GO) responsible for chemical functionalization makes it a good candidate for diversified applications. The main objectives for developing a GO based nanohybrid proton exchange membrane (PEM) include: improved self-humidification (water retention ability), reduced fuel crossover (electro-osmotic drag), improved stabilities (mechanical, thermal, and chemical), enhanced proton conductivity, and processability for the preparation of membrane-electrode assembly. Research carried on this topic may be divided into protocols for covalent grafting of functional groups on GO matrix, preparation of free-standing PEM or choice of suitable polymer matrix, covalent or hydrogen bonding between GO and polymer matrix etc. Herein, we present a brief literature survey on GO based nano-hybrid PEM for fuel cell applications. Different protocols were adopted to produce functionalized GO based materials and prepare their free-standing film or disperse these materials in various polymer matrices with suitable interactions. This review article critically discussed the suitability of these PEMs for fuel cell applications in terms of the dependency of the intrinsic properties of nanohybrid PEMs. Potential applications of these nanohybrid PEMs, and current challenges are also provided along with future guidelines for developing GO based nanohybrid PEMs as promising materials for fuel cell applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Photoactive Zn(II)Porphyrin–multi-walled carbon nanotubes nanohybrids through covalent β-linkages

    Energy Technology Data Exchange (ETDEWEB)

    Lipińska, Monika E., E-mail: m.e.lipinska@gmail.com [REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto (Portugal); Rebelo, Susana L.H., E-mail: susana.rebelo@fc.up.pt [REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto (Portugal); Pereira, M. Fernando R., E-mail: fpereira@fe.up.pt [Laboratório de Catálise e Materiais (LCM), Laboratório Associado LSRE/LCM, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto (Portugal); Figueiredo, José L., E-mail: jlfig@fe.up.pt [Laboratório de Catálise e Materiais (LCM), Laboratório Associado LSRE/LCM, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto (Portugal); Freire, Cristina, E-mail: acfreire@fc.up.pt [REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto (Portugal)

    2013-12-16

    Donor–acceptor nanohybrids by a covalent linkage between the β-position of a Zn(II)Porphyrin and multi-walled carbon nanotubes are reported for the first time, in a closer analogy to the natural light harvesting systems, which are based on β-substituted porphyrinoid structures, the chlorophylls. An unique and direct connection was established through the immobilization of the Zn(II)(β-NH{sub 2}-tetraphenylporphyrin), using diazonium chemistry, in order to afford i) a short and conjugated linkage between the two aromatic systems and ii) an amide bond resulting from a three-step functionalization synthesis. Electronic and steady-state fluorescence spectroscopies confirmed high photoinduced electron communication through the β-linkage when compared to analogous meso-phenyl linkers, stating its positive effect. The procedure involving the amide linkage allowed higher chromophore loadings; however, the direct conjugated bond showed improved photoinduced activity and a different emission pattern that can be associated with intense communication within the expanded π-system MWCNT–metalloporphyrin. - Graphical abstract: Preparation and photo-induced activity of two donor–acceptor nanohybrids is reported based on different linkages through β-position of porphyrin core to MWCNT, direct conjugation and amide bond. - Highlights: • β-linked Zn(II)Porphyrin–MWCNT nanohybrids were prepared through direct or amide bond. • Efficient and mild functionalizations were achieved using diazonium chemistry. • Good nanohybrid dispersibility was obtained in low boiling point solvent. • Nanohybrids showed strong photoinduced electronic transfer. • The emission quenching was higher for the π-expanded system.

  15. Dispersal

    Science.gov (United States)

    Clobert, J.; Danchin, E.; Dhondt, A.A.; Nichols, J.D.

    2001-01-01

    The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that so many species and ecosystems face major environmental threats from habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between patches of habitat can be crucial to ensuring their survival. This book provides a timely and wide-ranging overview of the study of dispersal and incorporates much of the latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species and community levels are considered. The potential of new techniques and models for studying dispersal, drawn from molecular biology and demography, is also explored. Perspectives and insights are offered from the fields of evolution, conservation biology and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.

  16. Preparation of magnetic photocatalyst nanohybrid decorated by polyoxometalate for the degradation of a pharmaceutical pollutant under solar light.

    Science.gov (United States)

    Bastami, Tahereh Rohani; Ahmadpour, Ali

    2016-05-01

    Magnetic polyoxometalate nanohybrid was prepared by the surface modification of γ-Fe2O3/SrCO3 nanoparticles with PW 12 O 40 (3 -) polyoxometalate (POM) anions. The results of Fourier transform infrared (FTIR) and energy-dispersive X-ray (EDX) confirm the presence of POM on the surface of γ-Fe2O3/SrCO3 nanoparticles. TEM results revealed the ellipsoid-like structure of nanohybrid which was 23 nm in length and 6 nm in width. The activity of the photocatalyst was investigated by the photocatalytic degradation of ibuprofen (IBP) in an aqueous solution under solar light. It was found that in comparison with the γ-Fe2O3/SrCO3, the degradation of IBP after 2-h exposure to the solar light irradiation was significantly higher for POM-γ-Fe2O3/SrCO3 nanohybrids. The degradation of IBP was enhanced by the addition of H2O2 to the air saturated solution, while the addition of NaHCO3 and isopropanol restricted the degradation process. In the presence of H2O2, the Fenton photocatalyst degradation under solar light irradiation led to relatively complete degradation of IBP. Furthermore, the photocatalytic activity and magnetization properties of this magnetic photocatalyst nanohybrid provide a promising solution for the degradation of water pollutants and photocatalyst recovery. Graphical Abstract Schematic illustration for preparation of POM-γ-Fe2O3/SrCO3 nanohybrid and photocatalytic reaction of IBP on POM-γ-Fe2O3/SrCO3 nanohybrid.

  17. Preparation of surface-modified lanthanum fluoride-graphene oxide nanohybrids and evaluation of their tribological properties as lubricant additive in liquid paraffin

    Science.gov (United States)

    Yang, Cuizhen; Hou, Xiao; Li, Zhiwei; Li, Xiaohong; Yu, Laigui; Zhang, Zhijun

    2016-12-01

    Oleic acid surface-modified Lanthanum trifluoride-graphene oxide (OA-LaF3-GO) nanohybrids were successfully prepared by surface modification technology. The morphology and phase structure of as-prepared samples were analyzed by means of X-ray diffraction and transmission electron microscopy, Fourier transform infrared spectrometry, Raman spectrometry and thermogravimetry. The results revealed that OA were bonded onto the surface of LaF3-GO nanohybrids. Subsequently, the tribological properties of OA-LaF3-GO nanohybrids as lubricant additive in liquid paraffin were evaluated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined on a scanning electron microscope with an energy dispersive spectrometer. Tribological results showed that OA-LaF3-GO nanohybrids had excellent friction reduction and antiwear ability at the loading of 0.5 wt.% OA-LaF3-GO nanohybrids, compared to liquid paraffin alone. The results of energy dispersive spectrometer revealed that improved tribological properties resulted from OA-LaF3-GO could transfer to the rubbed steel surface and decompose to form protective layers, which help to improve tribological properties.

  18. Characterization and Curing Kinetics of Epoxy/Silica Nano-Hybrids

    Directory of Open Access Journals (Sweden)

    Cheng-Fu Yang

    2015-10-01

    Full Text Available The sol-gel technique was used to prepare epoxy/silica nano-hybrids. The thermal characteristics, curing kinetics and structure of epoxy/silica nano-hybrids were studied using differential scanning calorimetry (DSC, 29Si nuclear magnetic resonance (NMR and transmission electron microscopy (TEM. To improve the compatibility between the organic and inorganic phases, a coupling agent was used to modify the diglycidyl ether of bisphenol A (DGEBA epoxy. The sol-gel technique enables the silica to be successfully incorporated into the network of the hybrids, increasing the thermal stability and improving the mechanical properties of the prepared epoxy/silica nano-hybrids. An autocatalytic mechanism of the epoxy/SiO2 nanocomposites was observed. The low reaction rate of epoxy in the nanocomposites is caused by the steric hindrance in the network of hybrids that arises from the consuming of epoxide group in the network of hybrids by the silica. In the nanocomposites, the nano-scale silica particles had an average size of approximately 35 nm, and the particles were well dispersed in the epoxy matrix, according to the TEM images.

  19. Characterization and Curing Kinetics of Epoxy/Silica Nano-Hybrids

    Science.gov (United States)

    Yang, Cheng-Fu; Wang, Li-Fen; Wu, Song-Mao; Su, Chean-Cheng

    2015-01-01

    The sol-gel technique was used to prepare epoxy/silica nano-hybrids. The thermal characteristics, curing kinetics and structure of epoxy/silica nano-hybrids were studied using differential scanning calorimetry (DSC), 29Si nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM). To improve the compatibility between the organic and inorganic phases, a coupling agent was used to modify the diglycidyl ether of bisphenol A (DGEBA) epoxy. The sol-gel technique enables the silica to be successfully incorporated into the network of the hybrids, increasing the thermal stability and improving the mechanical properties of the prepared epoxy/silica nano-hybrids. An autocatalytic mechanism of the epoxy/SiO2 nanocomposites was observed. The low reaction rate of epoxy in the nanocomposites is caused by the steric hindrance in the network of hybrids that arises from the consuming of epoxide group in the network of hybrids by the silica. In the nanocomposites, the nano-scale silica particles had an average size of approximately 35 nm, and the particles were well dispersed in the epoxy matrix, according to the TEM images. PMID:28793616

  20. Scratch resistance of a polycarbonate + organoclay nanohybrid

    Directory of Open Access Journals (Sweden)

    2009-10-01

    Full Text Available A polycarbonate-based nanohybrid has been created containing 1 wt% of Bentone 2010, an organically modified montmorillonite. A micro-section on the nanohybrid obtained using focused ion beam (FIB and field emission scanning electron microscopy (FESEM was employed to observe the orientation of the nanoclay inside a polycarbonate (PC matrix in the cross-section FIB-milled face. A micro-scratch tester was used to measure the scratch resistance in terms of residual (healing depth Rh under progressive load and in sliding wear. Effects of the number of scratches, normal load and scratch velocity have been evaluated as a function of nanoclay orientation. In sliding wear (multiple scratching along the same groove, our nanohybrid reaches residual depth values that remain constant after a certain number of scratches, a manifestation of strain hardening. The number of scratches to induce strain hardening decreases as the normal applied load increases. SEM was used to characterize deformation and wear mechanisms that operate on contacts and the results related to the wear data.

  1. Massive dielectric properties enhancement of MWCNTs/CoFe2O4 nanohybrid for super capacitor applications

    Science.gov (United States)

    Khan, Muhammad Zarrar; Gul, Iftikhar Hussain; Anwar, Humaira; Ameer, Shahid; Khan, Ahmad Nawaz; Khurram, Aqeel Ahsan; Nadeem, Kashif; Mumtaz, Muhammad

    2017-02-01

    Nanohybrids of CoFe2O4/MWCNTs with increasing MWCNTs loading from 0.0%, 0.5%, 1%, 1.5%, 2% and 5% by weight were prepared by a novel method of dispersion using ortho-xylene as a dispersive medium for the first time. In our current research, nanoparticles of cobalt ferrite were synthesized via wet chemical co-precipitation route. Non-magnetic MWCNTs matrix was dispersed uniformly in the synthesized ferrite nanoparticles using ortho-xylene as a polar solvent. and Impedance Analyzer were utilized to effectively investigate the synthesized nanohybrid. The obtained X-Ray Powder Diffraction (XRD) images confirm the pure Face Centered Cubic (FCC) single phase of CoFe2O4/MWCNTs nanohybrid. The average crystallite size remains within the range of 26±6 nm. Scanning Electron Microscopy (SEM) results showed aggregation of ferrite nanoparticles on MWCNTs. Fourier Transform Infrared Spectroscopy (FTIR) was utilized to study the band positions. The dielectric properties were found to be massively enhanced with increased loadings of MWCNTs. The dielectric constant (ε/) was massively enhanced from 45 for pure cobalt ferrites to 4.32×1012 for 5% MWCNTs loading at 100 Hz. The dielectric and tangent losses also increased from 21 and 0.47 for pure cobalt ferrites to 2.33×1017 and 5.39×104 at 100 Hz for 5% MWCNTs loading respectively indicating that this area of research should further be exploited in the realm of super capacitors applications.

  2. Visible-light driven photocatalytic degradation of methylene-violet by rGO/Fe{sub 3}O{sub 4}/ZnO ternary nanohybrid structures

    Energy Technology Data Exchange (ETDEWEB)

    Thangavel, Srinivas [Nanomaterials Research Lab ( NmRL ), Department of Nanoscience and Technology, Karunya University, Coimbatore 641 114, Tamil Nadu (India); Center of Excellence in Advanced Materials and Green Technologies, Department of Chemical Engineering and Material Science, Amrita Vishwa Vidyapeetham, Coimbatore 641 112, Tamil Nadu (India); Thangavel, Sakthivel [Nanomaterials Research Lab ( NmRL ), Department of Nanoscience and Technology, Karunya University, Coimbatore 641 114, Tamil Nadu (India); Department of Mechanical Engineering, Jeju National University, Jeju 690-756 (Korea, Republic of); Raghavan, Nivea [Nanomaterials Research Lab ( NmRL ), Department of Nanoscience and Technology, Karunya University, Coimbatore 641 114, Tamil Nadu (India); Krishnamoorthy, Karthikeyan [Department of Mechanical Engineering, Jeju National University, Jeju 690-756 (Korea, Republic of); Venugopal, Gunasekaran, E-mail: gunasekaran@karunya.edu [Nanomaterials Research Lab ( NmRL ), Department of Nanoscience and Technology, Karunya University, Coimbatore 641 114, Tamil Nadu (India); Solid State Electronics Lab, Research Institute of Electrical Communication, Tohoku University, Katahira, Sendai 980-8577 (Japan)

    2016-04-25

    A novel ternary nanohybrid structure was constructed with reduced graphene-oxide/iron-oxide/zinc-oxide (rGO/Fe{sub 3}O{sub 4}/ZnO) via a facile hydrothermal method. The structural, morphological and optical properties were explored using X-ray diffraction, scanning electron microscope (SEM) with energy dispersive spectra and photoluminescence (PL) studies. The functional groups of ternary nanohybrid were characterized by Fourier transform-infrared spectroscopy. SEM images confirm the presence of two-dimensional GO sheets, one dimensional Fe{sub 3}O{sub 4} and ZnO nanorods. The PL spectra showed the quenching effect which has been observed from the reduction of electron–hole recombination in hybrid. Degradation efficiency of this system was evaluated and compared with pure ZnO and Fe{sub 3}O{sub 4}/ZnO. Under visible light condition, the ternary nanohybrid has shown an excellent photocatalytic degradation of methylene-violet dye. The degradation efficiency of rGO/Fe{sub 3}O{sub 4}/ZnO was systematically analyzed by absorption spectra and total organic carbon removal techniques. Our experimental results will show the potential way for the development of futuristic rGO based nanohybrids as an effective photocatalytic materials for waste-water treatment and environmental remedial applications. - Graphical abstract: A new ternary nanohybrid has been constructed with 1D Fe{sub 3}O{sub 4}–ZnO and 2D rGO sheets to utilize as visible-light photocatalyst. Highly active photocatalyst has been prepared by a feasible hydrothermal approach. For the first time, rGO/Fe{sub 3}O{sub 4}/ZnO ternary nanohybrid exhibits a superior photocatalytic activity towards the degradation of methylene-violet (dye) and the same can be used for environmental remediation applications. - Highlights: • Ternary nanohybrid constructed with 1D ZnO, Fe{sub 3}O{sub 4} and 2D rGO. • Aggregation free rGO/Fe{sub 3}O{sub 4}/ZnO nanohybrid exhibits superior photocatalytic activity. • rGO boost up

  3. Spectroscopical properties of organic/metal nanohybrids.

    Science.gov (United States)

    Dellepiane, Giovanna; Cuniberti, Carla; Alloisio, Marina; Demartini, Anna

    2010-03-28

    The aim of our work was to prepare stable nanohybrids of controlled size and shape consisting of a noble metal core decorated with polydiacetylenes (PDAs). Due to the combination of the outstanding linear and nonlinear optical properties of the polydiacetylenic chains with the electromagnetic field-enhancing capability of metal nanostructures, these novel composites can find potential application in different fields. In particular, the different colours exhibited by PDAs in relation to the chemical nature of the monomer and the polymerization procedure, as well as in response to environmental perturbations, make them excellent materials for the fabrication of sensing devices. On the basis of our previous work on PDA self-assembled monolayers on flat metal surfaces, the results of which are briefly reported, we prepared differently-shaped gold and silver nanocores (spheres, cages) coated with various diacetylenic monomers having end-groups able to firmly anchor to the metal surface. These nanohybrids exhibit in aqueous colloidal solution an enhanced photochemical polymerization monitored step by step with UV-Vis and SERS techniques. It is shown that in these stable assemblies an intra-particle polymerization takes place and that the dominant PDA form is conditioned by the core size and geometry. While the nanoparticles are SERS active in the visible, the nanocages should be excellent SERS substrates from the visible to the near infrared regions.

  4. Shell-Controlled Photoluminescence in CdSe/CNT Nanohybrids

    Directory of Open Access Journals (Sweden)

    Si Hua-Yan

    2009-01-01

    Full Text Available Abstract A new type of nanohybrids containing carbon nanotubes (CNTs and CdSe quantum dots (QDs was prepared using an electrostatic self-assembly method. The CdSe QDs were capped by various mercaptocarboxylic acids, including thioglycolic acid (TGA, dihydrolipoic acid (DHLA and mercaptoundecanoic acid (MUA, which provide shell thicknesses of ~5.2, 10.6 and 15.2 Å, respectively. The surface-modified CdSe QDs are then self-assembled onto aridine orange-modified CNTs via electrostatic interaction to give CdSe/CNT nanohybrids. The photoluminescence (PL efficiencies of the obtained nanohybrids increase significantly with the increase of the shell thickness, which is attributed to a distance-dependent photo-induced charge-transfer mechanism. This work demonstrates a simple mean for fine tuning the PL properties of the CdSe/CNT nanohybrids and gains new insights to the photo-induced charge transfer in such nanostructures.

  5. Facile Low-Temperature Synthesis of Carbon Nanotube/ Nanohybrids with Enhanced Visible-Light-Driven Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    Yunlong Xie

    2012-01-01

    Full Text Available We demonstrate a facile and novel chemical precipitation strategy for the accurate coating of TiO2 nanoparticles on the surface of carbon nanotubes (CNTs to form CNT/TiO2 nanohybrids, which only requires titanium sulfate and CNTs as starting materials and reacts in the alkaline solution at 60°C for 6 h. Using this process, the as-prepared hybrid structures preserved the good dispersity and uniformity of initial CNTs. Furthermore, the CNT/TiO2 nanohybrids show a broad blue luminescence at 469 nm and exhibit significantly enhanced photocatalytic activity for the degradation of rhodamine B (RhB under visible-light irradiation, which is about 1.5 times greater than that of commercial Degussa P25 TiO2 nanoparticles. It is believed that this facile chemical precipitation strategy is scalable and its application can be extended to synthesize other CNT/oxide nanohybrids for various applications.

  6. Novel sulfonated poly (ether ether ketone)/phosphonic acid-functionalized titania nanohybrid membrane by an in situ method for direct methanol fuel cells

    Science.gov (United States)

    Wu, Hong; Cao, Ying; Li, Zhen; He, Guangwei; Jiang, Zhongyi

    2015-01-01

    Sulfonated poly (ether ether ketone)/phosphonic acid-functionalized titania nanohybrid membranes are prepared by an in situ method using titanium tetrachloride (TiCl4) as inorganic precursor and amino trimethylene phosphonic acid (ATMP) as modifier. Phosphonic acid-functionalized titania nanoparticles with a uniform particle size of ∼50 nm are formed and dispersed homogeneously in the SPEEK matrix with good interfacial compatibility. Accordingly, the nanohybrid membranes display remarkably enhanced proton conduction property due to the incorporation of additional sites for proton transport and the formation of well-connected channels by bridging the hydrophilic domains in SPEEK matrix. The nanohybrid membrane with 6 wt. % of phosphonic acid-functionalized titania nanoparticles exhibits the highest proton conductivity of 0.334 S cm-1 at 65 °C and 100% RH, which is 63.7% higher than that of pristine SPEEK membrane. Furthermore, the as-prepared nanohybrid membranes also show elevated thermal and mechanical stabilities as well as decreased methanol permeability.

  7. Multifunctional CNTs nanohybrids decorated with magnetic and fluorescent nanoparticles layer-by-layer

    Indian Academy of Sciences (India)

    Li Liu; Wei Jiang; Lei Yao; Xi-Wen Yang; Bin-Hua Chen; Shi-Xi Wu; Feng-Sheng Li

    2013-06-01

    Fe3O4/CNTs nanocomposites, which were prepared by polyol-medium in situ high-temperature decomposition of Fe()3 using PVP as stabilizing agent andmodified with SDS, were further decorated with high-quality ZnS nanocrystal via a wet technique in glycol solution. The obtained ZnS/Fe3O4/CNTs nanohybrids were characterized by XRD, FT–IR, Raman microscope, TEM, EDS, XPS, VSM and fluorophotometers. Results indicated that magnetic Fe3O4 nanoparticles and fluorescent ZnS nanocrystal were uniformly dispersed on the surface of CNTs layer-by-layer with PVP and SDS as stabilizing agent and ion-capture agent, respectively. The novel multi-functional nanohybrids exhibit super-paramagnetic properties with a saturation magnetization about 6.795 emu g-1 at room temperature and show a strong emission band at 367 nm with a broad shoulder around 342–483 nm due to the interactions and/or background emissions of Fe3O4 and CNTs. The superparamagnetic and fluorescent properties of obtained products are promising for potential applications in magnetically guided and fluorescence tracing drug delivery systems.

  8. Heterostructured layered aluminosilicate-itraconazole nanohybrid for drug delivery system.

    Science.gov (United States)

    Yang, Jae-Hun; Jung, Hyun; Kim, Su Yeon; Yo, Chul Hyun; Choy, Jin-Ho

    2013-11-01

    A nanohybrid, consisting of layered aluminosilicate as a host material and itraconazole as a guest molecule, was successfully synthesized through the interfacial intercalation reaction across the boundary between water and water-immiscible liquid at the various pH. According to the powder X-ray diffraction pattern, the basal spacing of the intraconazole-layered aluminosilicate nanohybrid increased from 14.7 to 22.7 A depending on the pH of the aqueous suspension. The total amounts of itraconazole in the hybrids were determined to be 2.3-25.4 wt% by HPLC analysis. The in vivo pharmacokinetics study was performed in rats in order to compare the absorptions of itraconazole for the itraconazole-layered aluminosilicate nanohybrid and a commercial product, Sporanox. The pharmacokinetic data for the nanohybrid and Sporanox showed that the mean area under the plasma concentration-time curve (AUC, 2477 +/- 898 ng x hr/mL and 2630 +/- 953 ng x hr/mL, respectively) and maximum concentration (Cmax, 225.4 +/- 77.4 ng x hr/mL and 223.6 +/- 51.9 ng x hr/mL, respectively), were within the bioequivalence (BE) range. Therefore, we concluded that this drug-layered aluminosilicate nanohybrid system has a great potential for its application in formulation of poorly soluble drugs.

  9. Silica-Gentamicin Nanohybrids: Synthesis and Antimicrobial Action

    Directory of Open Access Journals (Sweden)

    Dina Ahmed Mosselhy

    2016-03-01

    Full Text Available Orthopedic applications commonly require the administration of systemic antibiotics. Gentamicin is one of the most commonly used aminoglycosides in the treatment and prophylaxis of infections associated with orthopedic applications, but gentamicin has a short half-life. However, silica nanoparticles (SiO2 NPs can be used as elegant carriers for antibiotics to prolong their release. Our goal is the preparation and characterization of SiO2-gentamicin nanohybrids for their potential antimicrobial administration in orthopedic applications. In vitro gentamicin release profile from the nanohybrids (gentamicin-conjugated SiO2 NPs prepared by the base-catalyzed precipitation exhibited fast release (21.4% during the first 24 h and further extension with 43.9% release during the five-day experiment. Antimicrobial studies of the SiO2-gentamicin nanohybrids versus native SiO2 NPs and free gentamicin were performed against Bacillus subtilis (B. subtilis, Pseudomonas fluorescens (P. fluorescens and Escherichia coli (E. coli. SiO2-gentamicin nanohybrids were most effective against B. subtilis. SiO2 NPs play no antimicrobial role. Parallel antimicrobial studies for the filter-sterilized gentamicin were performed to assess the effect of ultraviolet (UV-irradiation on gentamicin. In summary, the initial fast gentamicin release fits the need for high concentration of antibiotics after orthopedic surgical interventions. Moreover, the extended release justifies the promising antimicrobial administration of the nanohybrids in bone applications.

  10. Fire and Gas Barrier Properties of Poly(styrene-co-acrylonitrile Nanocomposites Using Polycaprolactone/Clay Nanohybrid Based-Masterbatch

    Directory of Open Access Journals (Sweden)

    S. Benali

    2008-01-01

    Full Text Available Exfoliated nanocomposites are prepared by dispersion of poly(ε-caprolactone (PCL grafted montmorillonite nanohybrids used as masterbatches in poly(styrene-co-acrylonitrile (SAN. The PCL-grafted clay nanohybrids with high inorganic content are synthesized by in situ intercalative ring-opening polymerization of ε-caprolactone between silicate layers organomodified by alkylammonium cations bearing two hydroxyl functions. The polymerization is initiated by tin alcoholate species derived from the exchange reaction of tin(II bis(2-ethylhexanoate with the hydroxyl groups borne by the ammonium cations that organomodified the clay. These highly filled PCL nanocomposites (25 wt% in inorganics are dispersed as masterbatches in commercial poly(styrene-co-acrylonitrile by melt blending. SAN-based nanocomposites containing 3 wt% of inorganics are accordingly prepared. The direct blend of SAN/organomodified clay is also prepared for sake of comparison. The clay dispersion is characterized by wide-angle X-ray diffraction (WAXD, atomic force microscopy (AFM, and solid state NMR spectroscopy measurements. The thermal properties are studied by thermogravimetric analysis. The flame retardancy and gas barrier resistance properties of nanocomposites are discussed both as a function of the clay dispersion and of the matrix/clay interaction.

  11. Ultrasonic-electrodeposition of PtPd alloy nanoparticles on ionic liquid-functionalized graphene paper: towards a flexible and versatile nanohybrid electrode

    Science.gov (United States)

    Sun, Yimin; Zheng, Huaming; Wang, Chenxu; Yang, Mengmeng; Zhou, Aijun; Duan, Hongwei

    2016-01-01

    Here we fabricate a new type of flexible and versatile nanohybrid paper electrode by ultrasonic-electrodeposition of PtPd alloy nanoparticles on freestanding ionic liquid (IL)-functionalized graphene paper, and explore its multifunctional applications in electrochemical catalysis and sensing systems. The graphene-based paper materials demonstrate intrinsic flexibility, exceptional mechanical strength and high electrical conductivity, and therefore can serve as an ideal freestanding flexible electrode for electrochemical devices. Furthermore, the functionalization of graphene with IL (i.e., 1-butyl-3-methylimidazolium tetrafluoroborate) not only increases the electroactive surface area of a graphene-based nanohybrid paper electrode, but also improves the adhesion and dispersion of metal nanoparticles on the paper surface. These unique attributes, combined with the merits of an ultrasonic-electrodeposition method, lead to the formation of PtPd alloy nanoparticles on IL-graphene paper with high loading, uniform distribution, controlled morphology and favourable size. Consequently, the resultant nanohybrid paper electrode exhibits remarkable catalytic activity as well as excellent cycle stability and improved anti-poisoning ability towards electrooxidation of fuel molecules such as methanol and ethanol. Furthermore, for nonenzymatic electrochemical sensing of some specific biomarkers such as glucose and reactive oxygen species, the nanohybrid paper electrode shows high selectivity, sensitivity and biocompatibility in these bio-catalytic processes, and can be used for real-time tracking hydrogen peroxide secretion by living human cells. All these features demonstrate its promising application as a versatile nanohybrid electrode material in flexible and lightweight electrochemical energy conversion and biosensing systems such as bendable on-chip power sources, wearable/implantable detectors and in vivo micro-biosensors.Here we fabricate a new type of flexible and

  12. Controlled building of CdSe@ZnS/Au and CdSe@ZnS/ Au2S/Au nanohybrids

    Institute of Scientific and Technical Information of China (English)

    Raquel E. Galian[1; Pilar Diaz[1; Antonio Ribera[1; Alejandro Rincon-Bertolin[1; Said Agouram[2; Julia Perez-Prieto[1

    2015-01-01

    The addition of Au3. to spherical amine-capped CdSe@ZnS nanoparticles in toluene at room temperature and under darkness can lead to ternary CdSe@ZnS/Au nanohybrids. We demonstrate that this happens only when the nanoparticles possess a relatively thin ZnS shell, thus showing that thickness plays a key role in gold deposition on the CdSe@ZnS nanoparticle surface. Our hypothesis is that the amine ligand acts as the reductant of Au3+ ions into Au+ ions, whose affinity for sulfur would keep them at the CdSe@ZnS surface. This interaction stabilizes the Au+ ion, making it less prone to reduction than a non-coordinated Au+ ion. In CdSe@ZnS with a thin shell, Au+ ions at the surface of, or most probably within, the ZnS shell cause the transfer of Cd2+ ions into the solution. Subsequently, the core Se2- anion, which is a better reductant than the shell S2- reduces Au+ ions to Au(0), and large gold nanoparticles (AuNPs) are quickly deposited on the CdSe@ZnS surface in room temperature process, leading to ternary CdSe@ZnS/Au nanohybrids. In solution, these ternary nanohybrids progressively transform into quaternary CdSe@ZnS/Au2S/Au nanohybrids due to the reaction of the shell S2- anion with the remaining Au+ at the CdSe@ZnS surface, thus leading to the growth of Au2S nanoparticles on the CdSe@ZnS surface while Zn concomitantly leaches from the nanohybrid into the solution. Photoirradiation of the heterostructures with visible light enhances their emission efficiency. Comparatively, irradiation of the precursors, i.e., CdSe@ZnS nanoparticles, causes a drastic decrease in their emission accompanied by a blue shift of their emission maximum. The optical properties of these nanohybrids were analyzed by absorption and fluorescence (steady-state and time-resolved) spectroscopy, and the composition of the samples and the chemical states were determined by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy

  13. Preparation and characterization of superparamagnetic graphene oxide nanohybrids anchored with Fe{sub 3}O{sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jung Hee [Department of Chemistry, Hannam University, 461-6 Jeon min-dong, Yuseoung-gu, Daejeon 305-811 (Korea, Republic of); Ramaraj, B. [Research and Development Department, Central Institute of Plastics Engineering and Technology (CIPET), 630, Phase IV, GIDC, Vatva, Ahmedabad 382445 (India); Yoon, Kuk Ro, E-mail: kryoon@hannam.ac.kr [Department of Chemistry, Hannam University, 461-6 Jeon min-dong, Yuseoung-gu, Daejeon 305-811 (Korea, Republic of)

    2014-01-15

    Highlights: • A new method for fabrication of GPO–Fe{sub 3}O{sub 4} nanostructured hybrid was demonstrated. • The FT-IR analysis of nanohybrid shows infrared peaks characteristic of amide link. • EDX spectrum shows intense peaks for Iron along with carbon and oxygen peaks. • SEM images confirm the presence of Fe{sub 3}O{sub 4} nanoparticles on the GPO surface. • This nanohybrid is a potential material for electromagnetic devices and biomedicine. -- Abstract: We describe a novel method for the preparation of a graphene oxide (GPO) – magnetic nanoparticle (Fe{sub 3}O{sub 4}) (GPO–Fe{sub 3}O{sub 4}) nanostructured hybrids by a simple and effective method. In this method, the fabrication of multi-component nanostructure system involves covalent attachment of GPO with Fe{sub 3}O{sub 4} through dopamine (do) (GPO–do-Fe{sub 3}O{sub 4}). Optical microscopy (OM), ultraviolet spectroscopy (UV), Fourier transform infrared (FT-IR) spectroscopy, energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were used to demonstrate the successful attachment of Fe{sub 3}O{sub 4} to GPO. It was found that the fabricated nanohybrid shows superparamagnetic behavior and allows rapid separation under an external-magnetic field. The FT-IR analysis of GPO–do-Fe{sub 3}O{sub 4} nanohybrid shows infrared (IR) peaks characteristic of amide (-CO-NH-) link on the surface of GPO. TGA analysis clearly shows two major stages of thermal degradation, different from the pattern of observed for dopamine coated Fe{sub 3}O{sub 4} surface. An EDX spectrum of GPO–do-Fe{sub 3}O{sub 4} shows intense peaks for Iron (Fe) along with carbon and oxygen peaks. SEM images further support the FT-IR and TGA results and confirm the presence of Fe{sub 3}O{sub 4} on GPO surface. Thus, the resultant GPO–do-Fe{sub 3}O{sub 4} nanohybrid system carries both electrical and magnetic properties, which are important for applications ranging from

  14. Carbon nanotube-acridine nanohybrids: spectroscopic characterization of photoinduced electron transfer.

    Science.gov (United States)

    Mackiewicz, Nicolas; Delaire, Jacques A; Rutherford, A William; Doris, Eric; Mioskowski, Charles

    2009-01-01

    Single-walled carbon nanotubes (NT) were covalently functionalized with either 9-phenyl acridine (PhA) or 10-methyl-9-phenyl acridinium (PhMeA(+)). Absorption and fluorescence properties of acridine derivatives tethered to the nanotubes were studied in homogeneous dispersions. Exciplex emission was observed for NT functionalized with 9-phenylacridine. This phenomenon was attributed to an "intramolecular" interaction between excited phenyl acridine and carbon nanotubes. Interestingly, reverse photoinduced electron transfer from the nanotube to 10-methyl-9-phenylacridinium was detected for the NT-PhMeA(+) nanohybrid. This electron transfer led to a strong quenching of the acridinium fluorescence and to the formation of a metastable acridine radical. Evidence for the formation of this radical was obtained by ESR studies.

  15. Incorporation of Nanohybrid Films of Silica into Recycled Polystyrene Matrix

    Directory of Open Access Journals (Sweden)

    Genoveva Hernández-Padrón

    2015-01-01

    Full Text Available An alternative for the reutilization of polystyrene waste containers consisting in creating a hybrid material made of SiO2 nanoparticles embedded in a matrix of recycled polystyrene (PSR has been developed. Recycled polystyrene functionalized (PSRF was used to influence the morphological and antifog properties by the sol-gel synthesis of nanohybrid silica. To this end, silica nanoparticles were produced from alkoxide precursors in the presence of recycled polystyrene. The functionalization of this polymeric matrix was with the purpose of uniting in situ carboxyl and silanol groups during the sol-gel process. In this way, opaque or transparent solid substrates can be obtained, with each of these endowed with optical conditions that depend on the amount of reactants employed to prepare each nanohybrid specimen. The nanohybrids were labelled as SiO2/PSR (HPSR and SiO2/PSRF (HPSRF and their properties were then compared to those of commercial polystyrene (PS. All the prepared samples were used for coating glass substrates. The hydrophobicity of the resultant coatings was determined through contact angle measurement. The nanohybrid materials were characterized by FT-IR and 1H-NMR techniques. Additionally, TGA and SEM were employed to determine their thermal and textural properties.

  16. Silicon nanohybrid-based surface-enhanced Raman scattering sensors.

    Science.gov (United States)

    Wang, Houyu; Jiang, Xiangxu; Lee, Shuit-Tong; He, Yao

    2014-11-01

    Nanomaterial-based surface-enhanced Raman scattering (SERS) sensors are highly promising analytical tools, capable of ultrasensitive, multiplex, and nondestructive detection of chemical and biological species. Extensive efforts have been made to design various silicon nanohybrid-based SERS substrates such as gold/silver nanoparticle (NP)-decorated silicon nanowires, Au/Ag NP-decorated silicon wafers (AuNP@Si), and so forth. In comparison to free AuNP- and AgNP-based SERS sensors, the silicon nanohybrid-based SERS sensors feature higher enhancement factors (EFs) and excellent reproducibility, since SERS hot spots are efficiently coupled and stabilized through interconnection to the semiconducting silicon substrates. Consequently, in the past decade, giant advancements in the development of silicon nanohybrid-based SERS sensors have been witnessed for myriad sensing applications. In this review, the representative achievements related to the design of high-performance silicon nanohybrid-based SERS sensors and their use for chemical and biological analysis are reviewed in a detailed way. Furthermore, the major opportunities and challenges in this field are discussed from a broad perspective and possible future directions.

  17. Effect of organic solvents compared to sandblasting on the repair bond strength of nanohybrid and nanofilled composite resins.

    Science.gov (United States)

    Brum, Rafael Torres; Vieira, Sergio; Freire, Andrea; Mazur, Rui Fernando; De Souza, Evelise Machado; Rached, Rodrigo Nunes

    2017-01-01

    This study evaluated the effect of different surface treatments on the repair bond strength of nanohybrid (Empress Direct) and nanofilled (Filtek Z350 XT) composite resins. A total of 120 specimens of each material (7.5 x 4.5 x 3 mm) were prepared and polished with SiC paper. Half of the specimens were kept in water for seven days and the other half for six months; they were then divided into six groups according to the type of surface treatment: negative control (no treatment), Al2O3sandblasted, liquid acetone, acetone gel, liquid alcohol and alcohol gel. Following application of the silane coupling agent and the adhesive system, composite resin cylinders were fabricated on the specimens and light cured (20 seconds). The same composite resins were used for the repair. Additionally, ten intact specimens of each composite resin (without repair) were prepared (positive control). The specimens were then loaded to failure in the microshear mode. Three additional specimens were fabricated in each group, and the surface treatments were analyzed by atomic force microscopy, energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM). The nanofilled composite resin showed higher cohesive strength and repair bond strength than the nanohybrid composite resin. The aging process affected the repair bond strength of the nanofilled composite resin. Al2O3sandblasting was more efficient for the nanofilled composite resin and promoted greater surface roughness in both materials. The solvents demonstrated higher efficacy for the nanohybrid composite resin. The strengths resulting from the solvents were material dependent, and Al2O3sandblasting resulted in superior repair bond strength in both materials.

  18. Electrocatalytic Applications of Graphene–Metal Oxide Nanohybrid Materials

    DEFF Research Database (Denmark)

    Halder, Arnab; Zhang, Minwei; Chi, Qijin

    2016-01-01

    of graphenebased composite materials, graphene–metal oxide nanohybrids hold great promise to‐ ward engineering efficient electrocatalysts and have attracted increasing interest in both scientific communities and industrial partners around the world. The goal of this chapter is primarily set on an overview...... of cutting-edge developments in graphene–metal oxide nanohybrid materials, with the recently reported results from worldwide research groups. This chapter is presented first with an introduction, followed by synthetic meth‐ ods and structural characterization of nanocomposites, an emphasis......Development of state-of-the-art electrocatalysts using commercially available precursors with low cost is an essential step in the advancement of next-generation electrochemical energy storage/conversion systems. In this regard, noble metal-free and graphene-sup‐ ported nanocomposites...

  19. Chitosan-mediated synthesis of carbon nanotube-gold nanohybrids

    Institute of Scientific and Technical Information of China (English)

    GRAVEL; Edmond; FOILLARD; Stéphanie; DORIS; Eric

    2010-01-01

    Metal-nanotube nanohybrids were produced by in situ synthesis and stabilization of gold nanoparticles on chitosan-functionalized carbon nanotubes.The formation of gold nanoparticles from tetrachloroauric acid was observed after only a few minutes of contact with the functionalized nanotubes,at room temperature.These results suggest that adsorption of chitosan at the surface of carbon nanotubes permits smooth reduction of the metallic salt and efficient anchoring of gold nanoparticles to the nanotubes.

  20. Electrocatalytic oxidation behavior of NADH at Pt/Fe{sub 3}O{sub 4}/reduced-graphene oxide nanohybrids modified glassy carbon electrode and its determination

    Energy Technology Data Exchange (ETDEWEB)

    Roushani, Mahmoud, E-mail: mahmoudroushani@yahoo.com [Department of Chemistry, Faculty of Sciences, Ilam University, Ilam, 69315516 (Iran, Islamic Republic of); Hoseini, S. Jafar [Department of Chemistry, Faculty of Sciences, Yasouj University, Yasouj, 7591874831 (Iran, Islamic Republic of); Azadpour, Mitra [Department of Chemistry, Faculty of Sciences, Ilam University, Ilam, 69315516 (Iran, Islamic Republic of); Heidari, Vahid; Bahrami, Mehrangiz; Maddahfar, Mahnaz [Department of Chemistry, Faculty of Sciences, Yasouj University, Yasouj, 7591874831 (Iran, Islamic Republic of)

    2016-10-01

    We have developed Pt/Fe{sub 3}O{sub 4}/reduced-graphene oxide nanohybrids modified glassy carbon (Pt/Fe{sub 3}O{sub 4}/RGO/GC) electrode as a novel system for the preparation of electrochemical sensing platform. Characterization of as-made composite was determined using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and energy-dispersive analysis of X-ray (EDAX) where the Pt, Fe, Si, O and C elements were observed. The Pt/Fe{sub 3}O{sub 4}/RGO/GC electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect between Pt, Fe{sub 3}O{sub 4} and RGO, the nanohybrid exhibited excellent performance toward dihydronicotinamide adenine dinucleotide (NADH) oxidation in 0.1 M phosphate buffer solution, pH 7.0, with a low detection limit of 5 nM. - Highlights: • Preparation of a novel electrochemical sensing platform system • Excellent performance of Pt/Fe{sub 3}O{sub 4}/reduced-graphene oxide nanohybrids • Dihydronicotinamide adenine dinucleotide oxidation with a low detection limit of 5 nM.

  1. The effect of toothbrush bristle stiffness on nanohybrid surface roughness

    Science.gov (United States)

    Zairani, O.; Irawan, B.; Damiyanti, M.

    2017-08-01

    The surface of a restoration can be affected by toothpaste containing abrasive agents and the stiffness of toothbrush bristles. Objective: To identify the effect of toothbrush bristle stiffness on nanohybrid surface roughness. Methods: Sixteen nanohybrid specimens were separated into two groups. The first group was brushed using soft-bristle toothbrushes, and the second group was brushed using medium-bristle toothbrushes. Media such as aqua bides was used for brushing in both groups. Brushing was done 3 times for 5 minutes. Surface roughness was measured initially and at 5, 10, and 15 minutes using a surface roughness tester. Results: The results, tested with One-Way ANOVA and Independent Samples t Test, demonstrated that after brushing for 15 minutes, the soft-bristle toothbrush group showed a significantly different value (p < 0.05) of nanohybrid surface roughness. The group using medium-bristle toothbrushes showed the value of nano hybrid surface roughness significant difference after brushing for 10 minutes. Conclusion: Roughness occurs more rapidly when brushing with medium-bristle tooth brushes than when brushing with soft-bristle toothbrushes.

  2. Effect Aging Conditions on the Repair Bond Strength of a Microhybrid and a Nanohybrid Resin Composite

    NARCIS (Netherlands)

    Ozcan, Mutlu; Cura, Cenk; Brendeke, Johannes

    2010-01-01

    Purpose This study evaluated the effect of different aging methods on the repair bond strength and failure types of a microhybrid and a nanohybrid composite Materials and Methods Disk shaped microhybrid (Quadrant Anterior Shine-QA) and nanohybrid (Tetric EvoCeram TE) resin composite specimens (N = 1

  3. Effect Aging Conditions on the Repair Bond Strength of a Microhybrid and a Nanohybrid Resin Composite

    NARCIS (Netherlands)

    Ozcan, Mutlu; Cura, Cenk; Brendeke, Johannes

    2010-01-01

    Purpose This study evaluated the effect of different aging methods on the repair bond strength and failure types of a microhybrid and a nanohybrid composite Materials and Methods Disk shaped microhybrid (Quadrant Anterior Shine-QA) and nanohybrid (Tetric EvoCeram TE) resin composite specimens (N =

  4. Reflectometric measurement of n-hexane adsorption on ZnO2 nanohybrid film modified by hydrophobic gold nanoparticles

    Science.gov (United States)

    Sebők, Dániel; Csapó, Edit; Ábrahám, Nóra; Dékány, Imre

    2015-04-01

    Zinc-peroxide/poly(styrenesulfonate) nanohybrid thin films (containing 20 bilayers: [ZnO2/PSS]20, d ∼ 500 nm) were prepared using layer-by-layer (LbL) method. The thin film surface was functionalized by different surface modifying agents (silanes, alkylthiols and hydrophobized nanoparticles). Based on the experimental results of quartz crystal microbalance (QCM) and contact angle measurements (as prequalifications) the octanethiol covered gold nanoparticles (OT-AuNPs) were selected for further vapour adsorption studies. Reflectometric interference spectroscopy (RIfS) was used to measure n-hexane vapour adsorption on the original and modified nanohybrid films in a gas flow platform. The thin film provides only the principle of the measurement (by interference phenomenon), the selectivity and hydrophobicity is controlled and enhanced by surface functionalization (by dispersion interaction between the alkyl chains). The interference pattern shift (Δλ) caused by the increase of the optical thickness of the thin film due to vapour adsorption was investigated. It was found that due to the surface functionalization by hydrophobic nanoparticles the effect of water vapour adsorption decreased significantly, while for n-hexane opposite tendency was observed (the effective refractive index and thus the interference pattern shift increased drastically). The correlation between QCM technique and optical method (RIfS) was specified: linear specific adsorbed amount vs. wavelength shift calibration curves were determined in the pr = 0-0.4 relative vapour pressure range. The thin film is suitable for sensorial application (e.g. volatile organic compound/VOC sensor).

  5. ZnO–PDMS Nanohybrids: A Novel Optical Sensing Platform for Ethanol Vapor Detection at Room Temperature

    KAUST Repository

    Klini, Argyro

    2015-01-08

    © 2014 American Chemical Society. A new optical gas sensor platform based on highly luminescent ZnO-polymer nanohybrids is demonstrated. The nanohybrids consist of ZnO nanoparticles, typically 125 (±25) nm in size, dispersed in an inert cross-linked polydimethylsiloxane (PDMS) matrix. Upon exposure to ethanol-enriched air at room temperature, the nanocomposites exhibit a clear increase in their photoluminescence (PL) emission, which shows a nearly Langmuir dependence on the alcohol vapor pressure. The response time is on the order of 50 s, particularly at low ethanol concentrations. The limit of ethanol vapor detection (LOD) is as low as 0.4 Torr, while the sensor remains unaffected by the presence of water vapor, demonstrating the potential of the ZnO-PDMS system as an optical gas sensing device. The interaction of the ZnO nanoparticles with molecular oxygen plays an essential role on the overall performance of the sensor, as shown in comparative experiments performed in the presence and absence of atmospheric air. Notably, O2 was found to be quite effective in accelerating the sensor recovery process compared to N2 or vacuum.

  6. Controlled-release of Avermectin from Organically Modified Hydrotalcite-like Compound Nanohybrids

    Institute of Scientific and Technical Information of China (English)

    QIU,Depeng; LI,Yonghai; FU,Xiying; JIANG,Zhen; ZHAO,Xinyan; WANG,Tian; HOU,Wanguo

    2009-01-01

    The intercalation of avermectin (AVM)into sodium dodecyl sulfate(SDS)modified hydrotalcite-like com-pounds(HTlc) was carried out using an evaporating solvent enhanced intercalation method to obtain AVM-SDS-HTlc nanohybrids. It was found that the nanohybrids could well control the release of avermectin, showing the nanohybrids are a potential pesticide controlled-release formulation.The release of avermectin from AVM-SDS-HTlc nanohybrids is dependent on the pH.temperature and the presence of electrolyte in release me-dium. Acidic medium and higher temperature and the presence of electrolytes may induce the higher release rate of avermectin. The release process of avermectin from AVM-SDS-HTlc nanohybrids can be described by pseudo-first-order release kinetics, and the activation energy of release is 279 kJ/mol.

  7. A Novel Soluble Tin(IV Porphyrin Modified Single-Walled Carbon Nanotube Nanohybrid With Light Harvesting Properties

    Directory of Open Access Journals (Sweden)

    Jian-Yu Zheng

    2008-01-01

    Full Text Available A dihydroxotin(IV porphyrin functionalized single-walled carbon nanotubes (SWNTs nanohybrid is obtained. Solubility of the nanohybrid in organic solvents is determined by UV-Vis-NIR absorption spectroscopy. Electron absorption and fluorescence spectra investigations demonstrate that efficient electron transfer occurs within the nanohybrid at the photoexcited state and the charge-separated state of the nanohybrid is observed by transient absorption spectrum. The results illustrate that this soluble electron donor–acceptor nanohybrid might be a good candidate as a light harvesting material in molecular photoelectronic devices.

  8. Architectured morphologies of chemically prepared NiO/MWCNTs nanohybrid thin films for high performance supercapacitors.

    Science.gov (United States)

    Gund, Girish S; Dubal, Deepak P; Shinde, Sujata S; Lokhande, Chandrakant D

    2014-03-12

    The preparation of nanostructured metal oxide decorated on multiwalled carbon nanotubes (MWCNTs) nanohybrid films through simple, scalable, additive-free, binderless, and cost-effective route has fascinated significant attention not only in fundamental research areas but also its commercial applications, in order to reduce the growing environmental pollution and the cost of electrode fabrication. Here, we report the fabrication of highly flexible electrode with NiO/MWCNTs nanohybrid thin films directly on stainless steel substrate using successive ionic layer adsorption and reaction (SILAR) method. The impact of ratio of adsorption and reaction cycles on structural, surface areas and electrochemical properties of NiO/MWCNTs nanohybrids was investigated. X-ray diffraction measurements confirm the hybridization and face centered cubic (FCC) crystal structure of NiO in NiO/MWCNTs nanohybrids. In addition, these nanohybrids exhibit excellent surface properties such as uniform surface morphology, good surface area, pore volume, and uniform pore size distribution. The electrochemical tests demonstrate the highest specific capacitance of 1727 F g(-1) at 5 mA cm(-2) of current density with 91% capacitance retention after 2000 cycles. In addition, the Ragone plot confirms the better power and energy densities for all NiO/MWCNTs nanohybrids. The attractive electrochemical capacitive activity revealed by NiO/MWCNTs nanohybrid electrode proposes that it is an auspicious respondent for future energy storage application.

  9. Photothermal and mechanical stimulation of cells via dualfunctional nanohybrids

    Science.gov (United States)

    Chechetka, Svetlana A.; Doi, Motomichi; Pichon, Benoit P.; Bégin-Colin, Sylvie; Miyako, Eijiro

    2016-11-01

    Stimulating cells by light is an attractive technology to investigate cellular function and deliver innovative cell-based therapy. However, current techniques generally use poorly biopermeable light, which prevents broad applicability. Here, we show that a new type of composite nanomaterial, synthesized from multi-walled carbon nanotubes, magnetic iron nanoparticles, and polyglycerol, enables photothermal and mechanical control of Ca2+ influx into cells overexpressing transient receptor potential vanilloid type-2. The nanohybrid is simply operated by application of highly biotransparent near-infrared light and a magnetic field. The technology may revolutionize remote control of cellular function.

  10. Synthesis and characterization of nanohybrid of montmorillonite and zinc oxide

    Energy Technology Data Exchange (ETDEWEB)

    Chagas, Beatriz S.; Mendes, Luis C.; Brito, Alice S., E-mail: biachagas@ima.ufrj.b [Universidade Federal do Rio de Janeiro (IMA/UFRJ), RJ (Brazil). Inst. de Macromoleculas Profa. Eloisa Mano

    2009-07-01

    Zinc oxide-aluminosilicate nanohybrids through a hydrothermal reaction of a colloidal suspension of exfoliated montmorillonite nanosheets and zinc oxide in acid solution, performed in three different routes, were synthesized. The products were characterized by wide angle X-ray diffraction (WAXD). In all routes, it was found that the intercalation of zinc oxide into the host montmorillonite gallery was successfully performed so that the crystalline peaks of the montmorillonite and zinc oxide were suppressed from the X-ray patterns. The use of ultrasound decreased the reaction time.(author)

  11. Real-time tracking of hydrogen peroxide secreted by live cells using MnO{sub 2} nanoparticles intercalated layered doubled hydroxide nanohybrids

    Energy Technology Data Exchange (ETDEWEB)

    Asif, Muhammad; Aziz, Ayesha [Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074 (China); Dao, Anh Quang [Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074 (China); Hue Industrial College, 70 Nguyen Hue, Hue, Thua Thien Hue, 531081 (Viet Nam); Hakeem, Abdul; Wang, Haitao; Dong, Shuang; Zhang, Guoan [Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074 (China); Xiao, Fei [Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074 (China); Shenzhen Institute of Huazhong University of Science & Technology, Shenzhen, 518000 (China); Liu, Hongfang, E-mail: liuhf@hust.edu.cn [Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074 (China); Shenzhen Institute of Huazhong University of Science & Technology, Shenzhen, 518000 (China)

    2015-10-22

    We report a facile and green method for the fabrication of new type of electrocatalysts based on MnO{sub 2} nanoparticles incorporated on MgAl LDH P-type semiconductive channel and explore its practical applications as high-performance electrode materials for electrochemical biosensor. A series of MgAl layered doubled hydroxide (LDH) nanohybrids with fixed Mg/Al (M{sup 2+}/M{sup 3+} atomic ratio of 3) and varied amount of MnCl{sub 2}.4H{sub 2}O are fabricated by a facile co-precipitation method. This approach demonstrates the combination of distinct properties including excellent intercalation features of LDH for entrapping nanoparticles and high loading of MnO{sub 2} nanoparticles in the host layers of LDH. Among all samples, Mn5–MgAl with 0.04% loaded manganese has a good crystalline morphology. A well-dispersed MnO{sub 2} nanoparticles encapsulated into the host matrix of hydrotalcite exhibit enhanced electrocatalytic activity towards the reduction of H{sub 2}O{sub 2} as well as excellent stability, selectivity and reproducibility due to synergistic effect of good catalytic ability of MnO{sub 2} and conductive MgAl LDH. Glass carbon electrode (GCE) modified with Mn5–MgAl possesses a wide linear range of 0.05–78 mM, lowest detection limit 5 μM (S/N = 3) and detection sensitivity of 0.9352 μAmM{sup −1}. This outstanding performance enables it to be used for real-time tracking of H{sub 2}O{sub 2} secreted by live HeLa cells. This work may provide new insight in clinical diagnosis, on-site environmental analysis and point of care testing devices. - Highlights: • MnO{sub 2}MgAl nanohybrids have been fabricated by a facile and robust co-precipitation approach. • MgAl layered doubled hydroxide can be used for the intercalation of MnO{sub 2} nanoparticles. • MgAl layered doubled hydroxide nanohybrid serves as p-type semiconductive channel for efficient electrocatalysis. • The nanohybrid electrode demonstrates excellent electrochemical performance

  12. Enhanced cellular uptake of protoporphyrine IX/linolenic acid-conjugated spherical nanohybrids for photodynamic therapy.

    Science.gov (United States)

    Lee, Hye-In; Kim, Young-Jin

    2016-06-01

    Protoporphyrin IX (PpIX) has wide applications in photodynamic diagnosis and photodynamic therapy (PDT) in many human diseases. However, poor water solubility and cancer cell localization limit its direct application for PDT. We improved the water-solubility and cellular internalization of PpIX to enhance PDT efficacy by developing biocompatible PpIX/linolenic acid-conjugated polyhedral oligomeric silsesquioxane (PPLA) nanohybrids. The resulting PPLA nanohybrids exhibited a quasi-spherical shape with a size of gastric cancer cells. These results imply that the PPLA nanohybrid system may be applicable in PDT.

  13. High-yield Synthesis of Nanohybrid Shish-kebab Polyethylene-carbon Nanotube Structure

    Institute of Scientific and Technical Information of China (English)

    CUI Chaojie; QIAN Weizhong; ZHAO Mengqiang; XU Guanghui; NIE Jingqi; JIA Xilai; WEI Fei

    2013-01-01

    We report a novel method to prepare nanohybrid shish-kebab (NHSK) structure of polyethylene (PE) and carbon nanotube (CNT),Pristine CNTs without surface modification with high concentration was effectively dispersed in xylene solution by a simple shearing method,which induces the quick crystallization of PE in xylene to form a novel NHSK structure with more dense and smaller PE kebab on CNT axis.The flocculated NHSK product was transferred quickly from the xylene solution to the ethanol solution,in order to shorten the preparation time.The freeze-drying method was used in vacuum instead of high-temperature drying to avoid the aggregation of NHSK product.These improvements allow the formation of NHSK with an absolute yield of 200 mg·h-1,which is 2000 folds of that reported previously.It is favorable to apply this structured material in high performance nanocomposite,by improving the compatibility of CNTs in polymer and the interracial force between CNTs and polymer.

  14. Thermal Degradation Studies of Polyurethane/POSS Nanohybrid Elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Lewicki, J P; Pielichowski, K; TremblotDeLaCroix, P; Janowski, B; Todd, D; Liggat, J J

    2010-03-05

    Reported here is the synthesis of a series of Polyurethane/POSS nanohybrid elastomers, the characterization of their thermal stability and degradation behavior at elevated temperatures using a combination of Thermal Gravimetric Analysis (TGA) and Thermal Volatilization Analysis (TVA). A series of PU elastomers systems have been formulated incorporating varying levels of 1,2-propanediol-heptaisobutyl-POSS (PHIPOSS) as a chain extender unit, replacing butane diol. The bulk thermal stability of the nanohybrid systems has been characterized using TGA. Results indicate that covalent incorporation of POSS into the PU elastomer network increase the non-oxidative thermal stability of the systems. TVA analysis of the thermal degradation of the POSS/PU hybrid elastomers have demonstrated that the hybrid systems are indeed more thermally stable when compared to the unmodified PU matrix; evolving significantly reduced levels of volatile degradation products and exhibiting a {approx}30 C increase in onset degradation temperature. Furthermore, characterization of the distribution of degradation products from both unmodified and hybrid systems indicate that the inclusion of POSS in the PU network is directly influencing the degradation pathways of both the soft and hard block components of the elastomers: The POSS/PU hybrid systems show reduced levels of CO, CO2, water and increased levels of THF as products of thermal degradation.

  15. Dynamism of Stimuli-Responsive Nanohybrids: Environmental Implications

    Directory of Open Access Journals (Sweden)

    Jaime Plazas-Tuttle

    2015-06-01

    Full Text Available Nanomaterial science and design have shifted from generating single passive nanoparticles to more complex and adaptive multi-component nanohybrids. These adaptive nanohybrids (ANHs are designed to simultaneously perform multiple functions, while actively responding to the surrounding environment. ANHs are engineered for use as drug delivery carriers, in tissue-engineered templates and scaffolds, adaptive clothing, smart surface coatings, electrical switches and in platforms for diversified functional applications. Such ANHs are composed of carbonaceous, metallic or polymeric materials with stimuli-responsive soft-layer coatings that enable them to perform such switchable functions. Since ANHs are engineered to dynamically transform under different exposure environments, evaluating their environmental behavior will likely require new approaches. Literature on polymer science has established a knowledge core on stimuli-responsive materials. However, translation of such knowledge to environmental health and safety (EHS of these ANHs has not yet been realized. It is critical to investigate and categorize the potential hazards of ANHs, because exposure in an unintended or shifting environment could present uncertainty in EHS. This article presents a perspective on EHS evaluation of ANHs, proposes a principle to facilitate their identification for environmental evaluation, outlines a stimuli-based classification for ANHs and discusses emerging properties and dynamic aspects for systematic EHS evaluation.

  16. Controlling the Morphology of Nano-Hybrid Materials

    Directory of Open Access Journals (Sweden)

    Abdullah I.A. Jaafari

    2010-01-01

    Full Text Available Problem statement: It is known that layer double hydroxide is one of the nano ordered layered compounds and possesses plate-like morphology if carefully crystallized. Approach: In this study, Co-Sn LDH consisting of divalent and tetravalent cations was prepared with new morphology. XRD patterns of the prepared Co-Sn LDH showed that the interlayer spacing of the LDH was 0.78 nm and SEM image showed nano-needles structure. Results: By intercalation reaction with monocarboxylic acids at room temperature, XRD patterns indicated that the interlayered spacing increased to 3-4.8 nm and formed organic-inorganic nano-hybrid materials. Also, SEM images showed that the nano-needles structure of Co-Sn LDH changes to plate like-structure. Conclusion: Thermal analyses (TG, DTG and DTA and Infrared spectrum confirmed the intercalation processes of n-capric acid and n-stearic acid inside Co-Sn LDH and the formation of nano-hybrid materials.

  17. A nanohybrid system for taste masking of sildenafil

    Directory of Open Access Journals (Sweden)

    Lee JH

    2012-03-01

    Full Text Available Ji-Hee Lee1,*, Goeun Choi1,*, Yeon-Ji Oh1, Je Won Park1, Young Bin Choy3, Mung Chul Park1, Yeo Joon Yoon1, Hwa Jeong Lee2, Hee Chul Chang4, Jin-Ho Choy1 1Center for Intelligent Nano-Bio Materials (CINBM, Department of Bioinspired Science and Department of Chemistry and Nano Science, 2Division of Life and Pharmaceutical Sciences and College of Pharmacy, Ewha Womans University, Seoul, Korea; 3Department of Biomedical Engineering, College of Medicine and Institute of Medical and Biological Engineering, Medical Research Center, Seoul National University, Seoul, Korea; 4Global Strategy Center and Pharmaceutical Research Institute, Daewoong Pharmaceutical Co., Ltd., Seoul, Korea*These authors contributed equally to this workAbstract: A nanohybrid was prepared with an inorganic clay material, montmorillonite (MMT, for taste masking of sildenafil (SDN. To further improve the taste-masking efficiency and enhance the drug-release rate, we coated the nanohybrid of SDN–MMT with a basic polymer, polyvinylacetal diethylaminoacetate (AEA. Powder X-ray diffraction and Fourier transform infrared experiments showed that SDN was successfully intercalated into the interlayer space of MMT. The AEA-coated SDN–MMT nanohybrid showed drug release was much suppressed at neutral pH (release rate, 4.70 ± 0.53%, suggesting a potential for drug taste masking at the buccal cavity. We also performed in vitro drug release experiments in a simulated gastric fluid (pH = 1.2 and compared the drug-release profiles of AEA-coated SDN–MMT and Viagra®, an approved dosage form of SDN. As a result, about 90% of SDN was released from the AEA-coated SDN–MMT during the first 2 hours while almost 100% of drug was released from Viagra®. However, an in vivo experiment showed that the AEA-coated SDN–MMT exhibited higher drug exposure than Viagra®. For the AEA-coated SDN–MMT, the area under the plasma concentration–time curve from 0 hours to infinity (AUC0-∞ and maximum

  18. Immediate repair bond strengths of microhybrid, nanohybrid and nanofilled composites after different surface treatments

    NARCIS (Netherlands)

    Rinastiti, Margareta; Siswomihardjo, Widowati; Busscher, Henk J.; Ozcan, Mutlu

    2010-01-01

    Objectives: To evaluate immediate repair bond strengths and failure types of resin composites with and without surface conditioning and characterize the interacting composite surfaces by their surface composition and roughness. Methods: Microhybrid, nanohybrid and nanofilled resin composites were ph

  19. Acetyl salicylic acid–ZnAl layered double hydroxide functional nanohybrid for skin care application

    CSIR Research Space (South Africa)

    Mosangi, Damodar

    2016-10-01

    Full Text Available to the formulation with pure ASA. From these studies, we can conclude that the in situ intercalation of an LDH–ASA nanohybrid system is a promising alternative active ingredient for topical cosmetic emulsions....

  20. In Vivo Remote Control of Reactions in Caenorhabditis elegans by Using Supramolecular Nanohybrids of Carbon Nanotubes and Liposomes.

    Science.gov (United States)

    Miyako, Eijiro; Chechetka, Svetlana A; Doi, Motomichi; Yuba, Eiji; Kono, Kenji

    2015-08-17

    A supramolecular nanohybrid based on carbon nanotubes and liposomes that is highly biocompatible and capable of permeation through cells is described. The nanohybrid can be loaded with a variety of functional molecules and is structurally controlled by near-infrared laser irradiation for the release of molecules from the nanohybrids in a targeted manner via microscopy. We implemented the controlled release of molecules from the nanohybrids and demonstrated remote regulation of the photoinduced nanohybrid functions. As a proof of principle, nanohybrids loaded with amiloride were successfully used in the spatiotemporally targeted blocking of amiloride-sensitive mechanosensory neurons in living Caenorhabditis elegans. Our prototype could inspire new designs for biomimetic parasitism and symbiosis, and biologically active nanorobots for the higher-level manipulation of organisms.

  1. Mg–Al layered double hydroxide–methotrexate nanohybrid drug delivery system: Evaluation of efficacy

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Jui [Central Glass and Ceramic Research Institute, CSIR, 196 Raja S.C. Mullick Road, Kolkata-700032 (India); Roychowdhury, Susanta [Indian Institute of Chemical Biology, CSIR, Kolkata-700032 (India); Sengupta, Somoshree [Central Glass and Ceramic Research Institute, CSIR, 196 Raja S.C. Mullick Road, Kolkata-700032 (India); Ghosh, Swapankumar, E-mail: swapankumar.ghosh2@mail.dcu.ie [Central Glass and Ceramic Research Institute, CSIR, 196 Raja S.C. Mullick Road, Kolkata-700032 (India)

    2013-05-01

    Mg–Al layered double hydroxide nanoparticles were synthesized by one-pot co-precipitation method and anticancerous drug methotrexate was incorporated into it by in-situ ion exchange. The LDH–MTX nanohybrid produced moderately stable suspension in water, as predicted by zeta potential measurement. X-ray diffraction revealed that the basal spacing increased to nearly twice the same for pristine LDH on MTX intercalation. Thermogravimetric analyses confirmed an increase in thermal stability of the intercalated drug in the LDH framework. A striking enhancement in efficacy/sensitivity of MTX on the HCT-116 cells was obtained when intercalated within the LDH layers, as revealed by the attainment of half maximal inhibitory concentration of LDH–MTX nanohybrid by 48 h, whereas, bare MTX required 72 h for the same. The MTX release from MgAl-LDH–MTX hybrids in phosphate buffer saline at pH 7.4 followed a relatively slow, first order kinetics and was complete within 8 days following diffusion and crystal dissolution mechanism. Highlights: ► MgAl-LDH–methotrexate nanohybrid synthesized by one-pot synthetic strategy ► IC{sub 50} for LDH–MTX indicates the efficacy of nanohybrid as an efficient drug carrier. ► XRD and TEM study on nanohybrid revealed successful intercalation of methotrexate. ► TG analyses showed ∼ 13.1 wt.% of methotrexate loading into the nanohybrid.

  2. Cell Mapping for Nanohybrid Circuit Architecture Using Genetic Algorithm

    Institute of Scientific and Technical Information of China (English)

    Zhu-Fei Chu; Yin-Shui Xia; Lun-Yao Wang

    2012-01-01

    Nanoelectronics constructed by nanoscale devices seems promising for the advanced development of integrated circuits (ICs). However,the lack of computer aided design (CAD) tools seriously hinders its development and applications.To investigate the cell mapping task in CAD flow,we present a genetic algorithm (GA) based method for Cmos/nanowire/MOLecular hybrid (CMOL),which is a nanohybrid circuit architecture.By designing several crossover operators and analyzing their performance,an efficient crossover operator is proposed.Combining a mutation operator,a GA based algorithm is presented and tested on the International Symposium on Circuits and Systems (ISCAS) benchmarks.The results show that the proposed method not only can obtain better area utilization and smaller delay,but also can handle larger benchmarks with CPU time improvement compared with the published methods.

  3. Profile of Fluoride Release from a Nanohybrid Composite Resin

    Directory of Open Access Journals (Sweden)

    Raquel Assed Bezerra Silva

    2015-02-01

    Full Text Available The aim of this study was to evaluate in vitro the amount and profile of fluoride release from a fluoride-containing nanohybrid composite resin (Tetric® N-Ceram by direct potentiometry. Thirty specimens (5 mm diameter x 3 mm high; n=10/material were made of Tetric® N-Ceram, Vitremer® resin-modified glass ionomer cement (RMGIC (positive control or Filtek® Z350 nanofill composite resin (negative control. The specimens were stored individually in plastic tubes containing 1 mL of artificial saliva at 37°C, which was daily renewed during 15 days. At each renewal of saliva, the amount of fluoride ions released in the solution was measured using a fluoride ion-selective electrode with ion analyzer, and the values obtained in mV were converted to ppm (µg/mL. Data were analyzed statistically by ANOVA and Tukey’s post-hoc test at a significance level of 5%. The results showed that the resins Tetric® N-Ceram and Filtek® Z350 did not release significant amounts of fluoride during the whole period of evaluation (p>0.05. Only Vitremer® released significant amounts of fluoride ions during the 15 days of the experiment, with greater release in first 2 days (p0.05. In conclusion, the nanohybrid composite resin Tetric® N-Ceram did not present in vitro fluoride-releasing capacity throughout the 15 days of study.

  4. Novel CuCo2O4/graphitic carbon nitride nanohybrids: Highly effective catalysts for reducing CO generation and fire hazards of thermoplastic polyurethane nanocomposites.

    Science.gov (United States)

    Shi, Yongqian; Yu, Bin; Zhou, Keqing; Yuen, Richard K K; Gui, Zhou; Hu, Yuan; Jiang, Saihua

    2015-08-15

    Novel spinel copper cobaltate (CuCo2O4)/graphitic carbon nitride (g-C3N4) (named C-CuCo2O4) nanohybrids with different weight ratios of g-C3N4 to CuCo2O4 were successfully synthesized via a facile hydrothermal method. Then the nanohybrids were added into the thermoplastic polyurethane (TPU) matrix to prepare TPU nanocomposites using a master batch-melt compounding approach. Morphological analysis indicated that CuCo2O4 nanoparticles were uniformly distributed on g-C3N4 nanosheets. Thermal analysis revealed that C-CuCo2O4-7 (proportion of g-C3N4 to CuCo2O4 of 93/7) was an optimal nanohybrid for the properties improvement of TPU. Incorporation of C-CuCo2O4-7 into TPU led to significant improvements in the onset decomposition temperature, temperature at maximal mass loss rate and char yields. The heat release rate and total heat release of TPU/C-CuCo2O4-7 decreased by 37% and 31.3%, respectively, compared with those of pure TPU. Furthermore, the amounts of pyrolysis gaseous products, including combustible volatiles and carbon monoxide (CO), were remarkably reduced, whereas, non-flammable gas (carbon dioxide) increased. Excellent dispersion of C-CuCo2O4-7 in TPU host was achieved, due to the synergistic effect between g-C3N4 and CuCo2O4. Enhancements in the thermal stability and flame retardancy were attributed to the explanations that g-C3N4 nanosheets showed the physical barrier effect and catalytic nitrogen monoxide (NO) decomposition, and that CuCo2O4 catalyzes the reaction of CO with NO and increased char residues. Copyright © 2015. Published by Elsevier B.V.

  5. pH-sensitive Laponite(®)/doxorubicin/alginate nanohybrids with improved anticancer efficacy.

    Science.gov (United States)

    Gonçalves, Mara; Figueira, Priscilla; Maciel, Dina; Rodrigues, João; Qu, Xue; Liu, Changsheng; Tomás, Helena; Li, Yulin

    2014-01-01

    The efficacy of the anticancer drug doxorubicin (Dox) is limited by an insufficient cellular uptake and drug resistance, which is partially due to ion trapping in acidic environments such as the extracellular environment of solid tumors and the interior of endolysosome vesicles. Herein, we describe the preparation and in vitro evaluation of a new type of nanohybrid for anticancer drug delivery which is capable of carrying a high load of the cationic Dox through the cell membrane. In addition, the nanohybrids use the acidic environment of the endolysosomes to release the drug, simultaneously helping to disrupt the endolysosomes and diminishing endolysosome Dox trapping. Furthermore, as the nanohybrid carriers are capable of sustained drug delivery, those that remain in the cytoplasm and still contain Dox are expected to exert a prolonged anticancer activity. Briefly, Dox is loaded onto biocompatible anionic Laponite(®) (LP) nanodisks with a high aspect ratio (25 nm in diameter and 0.92 nm in thickness) through strong electrostatic interactions to get Dox-loaded LP disks. Alginate (AG), a biocompatible natural polymer, is then coated onto the Dox-loaded LP disks (LP/Dox/AG nanohybrids) to prevent the burst release of the drug. The results demonstrate that the nanohybrids have a high encapsulation efficiency (80.8 ± 10.6%), are sensitive to pH and display a sustained drug release behavior. Cell culture experiments indicate that the LP/Dox/AG nanohybrids can be effectively internalized by CAL-72 cells (an osteosarcoma cell line), and exhibit a remarkable higher cytotoxicity to cancer cells than the free Dox. The merits of Laponite(®)/alginate nanohybrids, such as biocompatibility, high loading capacity and stimulus responsive release of cationic chemotherapeutic drugs, render them as excellent platforms for drug delivery.

  6. Synthesis and Characterization of Porous Carbon-MoS2 Nanohybrid Materials for Charge-Enhanced Electrocatalysis

    NARCIS (Netherlands)

    Dolinska, J.; Chidambaram, A.; Adamkiewicz, W.; Estili, M.; Lisowski, W.; Iwan, M.; Palys, B.; Sudholter, E.J.R.; Marken, F.; Opallo, M.; Rassaei, L.

    2016-01-01

    Porous carbon nanohybrids are promising materials as high-performance electrodes for both sensing and energy conversion applications. This is mainly due to their high specific surface area and specific physicochemical properties. Here, new porous nanohybrid materials are developed based on exfoliate

  7. Anticancer Activity of Ferulic Acid-Inorganic Nanohybrids Synthesized via Two Different Hybridization Routes, Reconstruction and Exfoliation-Reassembly

    Directory of Open Access Journals (Sweden)

    Hyoung-Jun Kim

    2013-01-01

    Full Text Available We have successfully prepared nanohybrids of biofunctional ferulic acid and layered double hydroxide nanomaterials through reconstruction and exfoliation-reassembly routes. From X-ray diffraction and infrared spectroscopy, both nanohybrids were determined to incorporate ferulic acid molecules in anionic form. Micrsocopic results showed that the nanohybrids had average particle size of 150 nm with plate-like morphology. As the two nanohybridization routes involved crystal disorder and random stacking of layers, the nanohybrids showed slight alteration in z-axis crystallinity and particle size. The zeta potential values of pristine and nanohybrids in deionized water were determined to be positive, while those in cell culture media shifted to negative values. According to the in vitro anticancer activity test on human cervical cancer HeLa cells, it was revealed that nanohybrids showed twice anticancer activity compared with ferulic acid itself. Therefore we could conclude that the nanohybrids of ferulic acid and layered double hydroxide had cellular delivery property of intercalated molecules on cancer cell lines.

  8. Meso-Molding Three-Dimensional Macroporous Perovskites: A New Approach to Generate High-Performance Nanohybrid Catalysts

    DEFF Research Database (Denmark)

    Arandiyan, Hamidreza; Scott, Jason; Wang, Yuan

    2016-01-01

    Newly designed 3D highly ordered macro/mesoporous multifunctional La1-xCexCoO3 nanohybrid frameworks with a 2D hexagonal mesostructure were fabricated via facile meso-molding in a three-dimensionally macroporous perovskite (MTMP) route. The nanohybrid framework exhibited excellent catalytic...

  9. Preparation of zinc hydroxystannate-decorated graphene oxide nanohybrids and their synergistic reinforcement on reducing fire hazards of flexible poly (vinyl chloride)

    Science.gov (United States)

    Gao, Tingting; Chen, Laicheng; Li, Zhiwei; Yu, Laigui; Wu, Zhishen; Zhang, Zhijun

    2016-04-01

    A novel flame retardant, zinc hydroxystannate-decorated graphene oxide (ZHS/GO) nanohybrid, was successfully prepared and well characterized. Herein, the ZHS nanoparticles could not only enhance the flame retardancy of GO with the synergistic flame-retardant effect of ZHS but also prevent the restack of GO to improve the mechanical properties of poly (vinyl chloride) (PVC) matrix. The structure characterization showed ZHS nanoparticles were bonded onto the surface of GO nanosheets and the ZHS nanoparticles were well distributed on the surface of GO. Subsequently, resulting ZHS/GO was introduced into flexible PVC and fire hazards and mechanical properties of PVC nanocomposites were investigated. Compared to neat PVC, thermogravimetric analysis exhibited that the addition of ZHS/GO into PVC matrix led to an improvement of the charring amount and thermal stability of char residue. Moreover, the incorporation of 5 wt.% ZHS/GO imparted excellent flame retardancy to flexible PVC, as shown by increased limiting oxygen index, reduced peak heat release rate, and total heat release tested by an oxygen index meter and a cone calorimeter, respectively. In addition, the addition of ZHS/GO nanohybrids decreased the smoke products and increased the tensile strength of PVC. Above-excellent flame-retardant properties are generally attributed to the synergistic effect of GO and ZHS, containing good dispersion of ZHS/GO in PVC matrix, the physical barrier of GO, and the catalytic char function of ZHS.

  10. Synthesis and controlled release properties of 2,4-dichlorophenoxy acetate–zinc layered hydroxide nanohybrid

    Energy Technology Data Exchange (ETDEWEB)

    Bashi, Abbas M., E-mail: abbasmatrood@yahoo.com [Department of Medical Analysis, Faculty of Medical Science, Karbala University (Iraq); Hussein, Mohd Zobir; Zainal, Zulkarnain [Chemistry Department Faculty of Science-UPM (Malaysia); Tichit, Didier [Institut Charles Gerhardt UMR 5253 CNRS/UM2/ENSCM/UM1, Matériaux Avancés pour la Catalyse et la Santé, 8 rue Ecole Normale, 34296 Montpellier Cedex 5 (France)

    2013-07-15

    Direct reaction of ZnO with 2,4-dichlorophenoxyacetic acid (24D) solutions of different concentrations allows obtaining new organic–inorganic nanohybrid materials formed by intercalation of 24D into interlayers of zinc layered hydroxide (ZLH). XRD patterns show a progressive evolution of the structure as 24D concentration increases. The nanohybrid obtained at higher 24D concentration (24D–ZLH(0.4)) reveals a well ordered layered structure with two different basal spacings at 25.2 Å and 24 Å. The FTIR spectrum showing the vibrations bands of the functional groups of 24D and of the ZLH confirms the intercalation. SEM images are in agreement with the structural evolution observed by XRD and reveal the ribbon morphology of the nanohybrids. The release studies of 24D showed a rapid release of 94% for the first 100 min governed by the pseudo-second order kinetic model. - Graphical abstract: The phenomenon indicates that the optical energy gap is enlarged with the increase of molar concentrations in 2,4-dichlorophenoxy acetate anion content into ZnO to create a ZLH–24D nanohybrid. - Highlights: • Nanohybrid was synthesized from 2,4-dichlorophenoxy acetate with-Zinc LHD, using wet chemistry. • Characterized using SEM, TEM, EDX, FTIR, XRD and TGA. • Ribbon-shaped 24D–Zn-layered hydroxide nanoparticles with (003) diffractions of 2.5 nm phase were synthesized.

  11. A general strategy for nanohybrids synthesis via coupled competitive reactions controlled in a hybrid process.

    Science.gov (United States)

    Wang, Rongming; Yang, Wantai; Song, Yuanjun; Shen, Xiaomiao; Wang, Junmei; Zhong, Xiaodi; Li, Shuai; Song, Yujun

    2015-01-01

    A new methodology based on core alloying and shell gradient-doping are developed for the synthesis of nanohybrids, realized by coupled competitive reactions, or sequenced reducing-nucleation and co-precipitation reaction of mixed metal salts in a microfluidic and batch-cooling process. The latent time of nucleation and the growth of nanohybrids can be well controlled due to the formation of controllable intermediates in the coupled competitive reactions. Thus, spatiotemporal-resolved synthesis can be realized by the hybrid process, which enables us to investigate nanohybrid formation at each stage through their solution color changes and TEM images. By adjusting the bi-channel solvents and kinetic parameters of each stage, the primary components of alloyed cores and the second components of transition metal doping ZnO or Al2O3 as surface coatings can be successively formed. The core alloying and shell gradient-doping strategy can efficiently eliminate the crystal lattice mismatch in different components. Consequently, varieties of gradient core-shell nanohybrids can be synthesized using CoM, FeM, AuM, AgM (M = Zn or Al) alloys as cores and transition metal gradient-doping ZnO or Al2O3 as shells, endowing these nanohybrids with unique magnetic and optical properties (e.g., high temperature ferromagnetic property and enhanced blue emission).

  12. Doxorubicin loaded 17β-estradiol based SWNT dispersions for target specific killing of cancer cells.

    Science.gov (United States)

    Ghosh, Moumita; Das, Prasanta Kumar

    2016-06-01

    The present work reports the synthesis of a 17β-estradiol based amphiphiles comprising of polyethylene glycol (PEG) moiety linked through succinic acid that non-covalently dispersed (76%) the single walled carbon nanotubes (SWNTs) in water. The superior exfoliation of carbon nanotubes was characterized by microscopic and spectroscopic studies. Significant stability of these SWNT dispersions was observed in the presence of protein in cell culture media and the nanohybrids were highly biocompatible toward mammalian cells. Anticancer drug doxorubicin loaded on these nanohybrids was selectively delivered within estrogen receptor rich cancer cells, MCF7 (breast cancer cell) and A549 (lung cancer cell). Microscopic studies showed the localization of doxorubicin within the cancer cell nucleus whereas no such localization was observed in ER negative cells. Both these ER positive cancer cells were killed by ∼3 fold higher efficiency than that of ER negative MDA-MB-231 (advanced breast cancer cell) and HeLa cells that are deprived of estrogen receptors. Thus, judiciously designed estradiol based nanohybrids proved to be excellent tool for SWNT dispersion and also for selectively killing of ER positive cancer cells. To the best of our knowledge, for the first time non-covalently modified SWNTs by estradiol based amphiphilic dispersing agent have been used for selective killing of ER positive cancer cells by doxorubicin loaded on dispersed SWNTs. It holds immense promise to be exploited as a cancer therapeutic agent.

  13. Photophysical properties of fluorescent PMMA/SiO{sub 2} nanohybrids for solar energy applications

    Energy Technology Data Exchange (ETDEWEB)

    El-Bashir, S.M., E-mail: elbashireg@yahoo.com [Department of Physics and Astronomy, Science College, King Saud University, Riyadh 11451 (Saudi Arabia)

    2012-07-15

    This work concerning the photophysical properties of fluorescent nanohybrid films based on poly(methylmethacrylate) (PMMA) doped with coumarin dyestuff and entrapped with different concentrations of hydrophilic nanosilica. Spectroscopic tools were applied in order to determine the optimum concentration of nanosilica for the best optical properties for a matrix used as fluorescent solar concentrator. The optical constants and photoluminescence spectra of fluorescent nanohybrid films showed an enhancement of the photon trapping efficiency and matrix stability by increasing the concentration of SiO{sub 2} nanoparticles. - Highlights: Black-Right-Pointing-Pointer Fluorescent PMMA/SiO{sub 2} nanohybrids were prepared and studied. Black-Right-Pointing-Pointer Adding small amounts of hydrophilic SiO{sub 2} nanoparticles to PMMA enhances its optical properties. Black-Right-Pointing-Pointer These hybrids are promising matrices for luminescent solar concentrators (LSCs).

  14. Avatar DNA Nanohybrid System in Chip-on-a-Phone

    Science.gov (United States)

    Park, Dae-Hwan; Han, Chang Jo; Shul, Yong-Gun; Choy, Jin-Ho

    2014-05-01

    Long admired for informational role and recognition function in multidisciplinary science, DNA nanohybrids have been emerging as ideal materials for molecular nanotechnology and genetic information code. Here, we designed an optical machine-readable DNA icon on microarray, Avatar DNA, for automatic identification and data capture such as Quick Response and ColorZip codes. Avatar icon is made of telepathic DNA-DNA hybrids inscribed on chips, which can be identified by camera of smartphone with application software. Information encoded in base-sequences can be accessed by connecting an off-line icon to an on-line web-server network to provide message, index, or URL from database library. Avatar DNA is then converged with nano-bio-info-cogno science: each building block stands for inorganic nanosheets, nucleotides, digits, and pixels. This convergence could address item-level identification that strengthens supply-chain security for drug counterfeits. It can, therefore, provide molecular-level vision through mobile network to coordinate and integrate data management channels for visual detection and recording.

  15. Nanohybrid based on antibiotic encapsulated layered double hydroxide as a drug delivery system.

    Science.gov (United States)

    Khan, Sher Bahadar; Alamry, Khalid A; Alyahyawi, Nedaa A; Asiri, Abdullah M; Arshad, Muhammad Nadeem; Marwani, Hadi M

    2015-02-01

    Nanohybrid of cefuroxime (CFO) with layered double hydroxide (LDH) has been prepared, and the rate of dissolution and bioavailability of CFO using nanohybrid as a drug delivery system has been broadly studied. The intercalation process was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The CFO contents were found to be 19.0 wt% in the nanohybrid. The release mechanism of CFO was investigated with respect to anion and pH of the dissolution media such as gastric, intestinal and blood simulated media. The effect of pH was evaluated on the release of CFO from nanohybrid, and the dissolution of CFO from the nanohybrid was found to be a slow process at pH 4.0, 6.8, and 7.4. Further the addition of Cl ion and PAM in release media did not affect the release rate of drug at pH 4.0 and 6.8, while at pH 7.4, Cl ion and PAM have significant role on the drug release. At pH 1.2, the release study shows that LDH dissolved in the acidic medium and CFO released in its molecular form. The release behavior suggests two mechanisms that are responsible for the release of CFO from nanohybrid: weathering (dependent on the pH) and ion exchange (highly dependent on the anions). Surface reactions mediated by solid weathering ruled the release in gastric fluid, whereas anion exchange determined CFO release in lysosomal, intestinal, and blood medium. In order to evaluate the drug release mechanism, the released data were fitted by mathematical models describing various kinetic.

  16. Nonlinear Optical Properties of a MMA-Silica Nanohybrid Material Doped with Rhodamine 6G

    Directory of Open Access Journals (Sweden)

    J. Lima-Gutiérrez

    2013-01-01

    Full Text Available A novel nanohybrid material based on MMA-Silica has been synthesized with an organic dye dopant (R6G to tailor the optical properties. This novel material can be used on several devices such as active laser media for an organic solid state laser, OLEDs, or as a characterization media for new organic dye molecules. Thin films were deposited by dip-coating and characterized by absorption and reflection UV-VIS, photoluminescence, SEM, and Z-scan technique to verify their nonlinear behavior. R6G dye dopant has been used to verify that the nanohybrid matrix does not inhibit its optical properties.

  17. Maghemite and poly-DL-alanine based core–shell multifunctional nanohybrids for environmental protection and biomedicine applications

    Energy Technology Data Exchange (ETDEWEB)

    Covaliu, Cristina Ileana, E-mail: cristina_covaliu@yahoo.com [University Politehnica of Bucharest, Faculty of Biotechnical Systems Engineering, Bucharest (Romania); Paraschiv, Gigel; Biriş, Sorin-Ştefan [University Politehnica of Bucharest, Faculty of Biotechnical Systems Engineering, Bucharest (Romania); Jitaru, Ioana; Vasile, Eugeniu [University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, Bucharest (Romania); Diamandescu, Lucian [National Institute of Materials Physics, Bucharest (Romania); Velickovic, Tanja Cirkovic; Krstic, Maja [University of Belgrade, Faculty of Chemistry, Belgrade (Serbia); Ionita, Valentin [University Politehnica of Bucharest, Faculty of Electrical Engineering, Bucharest (Romania); Iovu, Horia [University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, Bucharest (Romania); Matei, Ecaterina [University Politehnica of Bucharest, Faculty of Materials Science and Engineering, Bucharest (Romania)

    2013-11-15

    This paper deals with the synthesis of two nanohybrid materials based on maghemite (γ-Fe{sub 2}O{sub 3}) and poly-DL-alanine using a two-step procedure consisting of maghemite nanoparticles synthesis by microemulsion method and nanohybrids obtaining by coating of maghemite nanoparticles with poly-DL-alanine biopolymer in two different molar ratios (H1:5 and H1:15). The maghemite and their corresponding nanohybrids were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoemission spectroscopy, Mössbauer spectroscopy, Transmission electron microscopy, High resolution transmission electron microscopy with selected area electron diffraction and Atomic absorption spectroscopy. The two nanohybrids under the investigation have the average particle sizes of 22 nm and 23 nm. The Fourier transform infrared spectroscopy spectra and X-ray photoemission spectroscopy data indicate the existence of some interactions between the maghemite nanoparticles and poly-DL-alanine shell. The saturation magnetization values for maghemite and the two nanohybrids determined by a Vibrating Sample Magnetometer correspond to a typical superparamagnetic behavior suitable for applying in biomedical field. Also, with respect of biomedical application the biological activity of maghemite and its corresponding nanohybrids was investigated on healthy human cells (PBMC) and cancerous cells (HeLa). Furthermore, in order to support the multifunctionality of the γ-Fe{sub 2}O{sub 3} sample and nanohybrids we also investigated their wastewater treatment properties by measuring the removal efficiency of heavy metal Cd (II) ions.

  18. Emergent Properties and Toxicological Considerations for Nanohybrid Materials in Aquatic Systems.

    Science.gov (United States)

    Saleh, Navid B; Afrooz, A R M Nabiul; Bisesi, Joseph H; Aich, Nirupam; Plazas-Tuttle, Jaime; Sabo-Attwood, Tara

    2014-06-03

    Conjugation of multiple nanomaterials has become the focus of recent materials development. This new material class is commonly known as nanohybrids or "horizon nanomaterials". Conjugation of metal/metal oxides with carbonaceous nanomaterials and overcoating or doping of one metal with another have been pursued to enhance material performance and/or incorporate multifunctionality into nano-enabled devices and processes. Nanohybrids are already at use in commercialized energy, electronics and medical products, which warrant immediate attention for their safety evaluation. These conjugated ensembles likely present a new set of physicochemical properties that are unique to their individual component attributes, hence increasing uncertainty in their risk evaluation. Established toxicological testing strategies and enumerated underlying mechanisms will thus need to be re-evaluated for the assessment of these horizon materials. This review will present a critical discussion on the altered physicochemical properties of nanohybrids and analyze the validity of existing nanotoxicology data against these unique properties. The article will also propose strategies to evaluate the conjugate materials' safety to help undertake future toxicological research on the nanohybrid material class.

  19. Emergent Properties and Toxicological Considerations for Nanohybrid Materials in Aquatic Systems

    Directory of Open Access Journals (Sweden)

    Navid B. Saleh

    2014-06-01

    Full Text Available Conjugation of multiple nanomaterials has become the focus of recent materials development. This new material class is commonly known as nanohybrids or “horizon nanomaterials”. Conjugation of metal/metal oxides with carbonaceous nanomaterials and overcoating or doping of one metal with another have been pursued to enhance material performance and/or incorporate multifunctionality into nano-enabled devices and processes. Nanohybrids are already at use in commercialized energy, electronics and medical products, which warrant immediate attention for their safety evaluation. These conjugated ensembles likely present a new set of physicochemical properties that are unique to their individual component attributes, hence increasing uncertainty in their risk evaluation. Established toxicological testing strategies and enumerated underlying mechanisms will thus need to be re-evaluated for the assessment of these horizon materials. This review will present a critical discussion on the altered physicochemical properties of nanohybrids and analyze the validity of existing nanotoxicology data against these unique properties. The article will also propose strategies to evaluate the conjugate materials’ safety to help undertake future toxicological research on the nanohybrid material class.

  20. Polymeric nanohybrids and functionalized carbon nanotubes as drug delivery carriers for cancer therapy.

    Science.gov (United States)

    Prakash, Satya; Malhotra, Meenakshi; Shao, Wei; Tomaro-Duchesneau, Catherine; Abbasi, Sana

    2011-11-01

    The scope of nanotechnology to develop target specific carriers to achieve higher therapeutic efficacy is gaining importance in the pharmaceutical and other industries. Specifically, the emergence of nanohybrid materials is posed to edge over chemotherapy and radiation therapy as cancer therapeutics. This is primarily because nanohybrid materials engage controlled production parameters in the making of engineered particles with specific size, shape, and other essential properties. It is widely expressed that these materials will significantly contribute to the next generation of medical care technology and pharmaceuticals in areas of disease diagnosis, disease prevention and many other treatment procedures. This review focuses on the currently used nanohybrid materials, polymeric nanoparticles and nanotubes, which show great potential as effective drug delivery systems for cancer therapy, as they can be grafted with cell-specific receptors and intracellular targeting molecules for the targeted delivery of therapeutics. Specifically, this article focuses on the current status, recent advancements, potentials and limitations of polymeric nanohybrids and functionalized carbon nanotubes as drug delivery carriers.

  1. A novel magnetic/photoluminescence bifunctional nanohybrid for the determination of trypsin.

    Science.gov (United States)

    Xia, Tingting; Ma, Qiang; Hu, Tianyu; Su, Xingguang

    2017-08-01

    In this work, we have designed a novel kind of nanohybrid with magnetic and photoluminescence (PL) property for trypsin detection. The modified magnetic Fe3O4 nanoparticles (MNPs) with polydopamine (PDA) and human serum albumin (HSA) were prepared through a one step self-polymerization under mild condition. The polydopamine (PDA) coating on MNPs can improve the biocompatibility of the MNP-PDA-HAS composite due to its hydrophilicity and multifunctional groups. When MNP-PDA-HSA composite was added into the Anti-HSA modified CdTe QDs (anti-HSA-QDs), HSA on the MNP-PDA-HSA composite was captured by the site of anti-HSA-QDs to form MNP-PDA-HSA/anti-HSA-QDs nanohybrid. Therefore, the photoluminescence of QDs can be quenched by Fe3O4 nanoparticles due to the electron transfer. In the presence of trypsin, the protein (anti-HSA) was digested by trypsin and QDs was separated from the nanohybrid surface. As a result, the photoluminescence intensity of QDs was recovered. The magnetic/luminescent bifunctional nanohybrid displayed excellent analytical performance for the detection of trypsin in the range of 0.5-30μg/mL with a low detection limit of 0.25μg/mL. Copyright © 2017. Published by Elsevier B.V.

  2. Carbon quantum dot-NO photoreleaser nanohybrids for two-photon phototherapy of hypoxic tumors.

    Science.gov (United States)

    Fowley, Colin; McHale, Anthony P; McCaughan, Bridgeen; Fraix, Aurore; Sortino, Salvatore; Callan, John F

    2015-01-04

    We report a conjugate between carbon quantum dots and a NO photoreleaser able to photogenerate the anticancer NO radical via an energy transfer mechanism. This nanohybrid proved toxic to cancer cells in vitro and significantly reduced tumor volume in mice bearing human xenograft BxPC-3 pancreatic tumors upon two-photon excitation with the highly biocompatible 800 nm light.

  3. Encapsulation of Conjugated Oligomers in Single-Walled Carbon Nanotubes : Towards Nanohybrids for Photonic Devices

    NARCIS (Netherlands)

    Loi, Maria Antonietta; Gao, Jia; Cordella, Fabrizio; Blondeau, Pascal; Menna, Enzo; Bartova, Barbora; Hebert, Cecile; Lazar, Sorin; Botton, Gianluigi A.; Milko, Matus; Ambrosch-Draxl, Claudia

    2010-01-01

    Visible-light emitting single-walled carbon nanotubes (SWNTs)/organic hybrids have been successfully synthesized and promise to be a photon source to be used in future optoelectronic devices. The nanohybrids are "peapods" having sexithiophene molecules inside the hollow space of SWNTs. High-resoluti

  4. Encapsulation of Conjugated Oligomers in Single-Walled Carbon Nanotubes: Towards Nanohybrids for Photonic Devices

    NARCIS (Netherlands)

    Loi, M.A.; Gao, Jia; Cordella, Fabrizio; Blondeau, Pascal; Menna, Enzo; Bartova, Barbora; Hebert, Cecile; Lazar, Sorin; Botton, Gianluigi A.; Milko, Matus; Ambrosch-Draxl, Claudia

    2010-01-01

    {Visible-light emitting single-walled carbon nanotubes (SWNTs)/organic hybrids have been successfully synthesized and promise to be a photon source to be used in future optoelectronic devices. The nanohybrids are ``peapods{''} having sexithiophene molecules inside the hollow space of SWNTs. High-res

  5. Cooperative dehydrogenation of N-heterocycles using a carbon nanotube-rhodium nanohybrid.

    Science.gov (United States)

    Jawale, Dhanaji V; Gravel, Edmond; Shah, Nimesh; Dauvois, Vincent; Li, Haiyan; Namboothiri, Irishi N N; Doris, Eric

    2015-05-04

    Rhodium nanoparticles were anchored on carbon nanotubes and the resulting nanohybrid was studied as co-catalyst, along with tert-butylcatechol, for the dehydrogenation of various N-heterocycles. The co-catalytic system operates in high yields, under the mildest conditions reported so far, and can be applied to a wide variety of secondary amine-containing scaffolds.

  6. Sodium alginate stabilized silver nanoparticles-silica nanohybrid and their antibacterial characteristics.

    Science.gov (United States)

    Pandey, Sadanand; Ramontja, James

    2016-12-01

    Due to the problem of resistance of many infectious agents to the usual treatments, this study addresses the ways of obtaining and using new sodium alginate stabilized-silver/mesoporous silica (Na-Alg-s-AgNPs@SiO2) nanohybrid as antimicrobial agents. Capping AgNPs with a shell of mesoporous SiO2 is a system to build the increase biocompatibility of AgNPs. In this work, we report a simple and green way to deal with setting up a uniform sodium alginate-stabilized silver nanoparticles embedded mesoporous silica (Na-Alg-s-AgNPs@SiO2 nanohybrid). The synthesized nanocomposite was characterized using transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra, and ultraviolet-visible (UV-vis) absorption spectra, which exhibited that AgNPs with average of size of ∼7nm were consistently and compactly deposited in the nanocomposite. The nanohybrid demonstrated excellent antibacterial activity against both Gram negative (-ve) and Gram positive (+ve) bacteria. Thus, the developed Na-Alg-s-AgNPs@SiO2 nanohybrid has a potential to be used for various antibacterial applications in biotechnology and biomedical fields.

  7. Development of antiproliferative nanohybrid compound with controlled release property using ellagic acid as the active agent

    Directory of Open Access Journals (Sweden)

    Hussein MZ

    2011-07-01

    Full Text Available Mohd Zobir Hussein1,2, Samer Hasan Al Ali2, Zulkarnain Zainal2, Muhammad Nazrul Hakim31Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA, 2Department of Chemistry, Faculty of Science, 3Department of Biomedical Science, Faculty of Medicine and Health Science, Universiti Putra Malaysia, Selangor, MalaysiaAbstract: An ellagic acid (EA–zinc layered hydroxide (ZLH nanohybrid (EAN was synthesized under a nonaqueous environment using EA and zinc oxide (ZnO as the precursors. Powder X-ray diffraction showed that the basal spacing of the nanohybrid was 10.4 Å, resulting in the spatial orientation of EA molecules between the interlayers of 22.5° from z-axis with two negative charges at 8,8′ position of the molecules pointed toward the ZLH interlayers. FTIR study showed that the intercalated EA spectral feature is generally similar to that of EA, but with bands slightly shifted. This indicates that some chemical bonding of EA presence between the nanohybrid interlayers was slightly changed, due to the formation of host–guest interaction. The nanohybrid is of mesopores type with 58.8% drug loading and enhanced thermal stability. The release of the drug active, EA from the nanohybrid was found to be sustained and therefore has good potential to be used as a drug controlled-release formulation. In vitro bioassay study showed that the EAN has a mild effect on the hepatocytes cells, similar to its counterpart, free EA.Keywords: ellagic acid, nonaqueous solution, ZnO, zinc-layered hydroxide, viability test

  8. Electrochemical Reduction of Oxygen on Anthraquinone/Carbon Nanotubes Nanohybrid Modified Glassy Carbon Electrode in Neutral Medium

    Directory of Open Access Journals (Sweden)

    Zheng Gong

    2013-01-01

    Full Text Available The electrochemical behaviors of monohydroxy-anthraquinone/multiwall carbon nanotubes (MHAQ/MWCNTs nanohybrid modified glassy carbon (MHAQ/MWCNTs/GC electrodes in neutral medium were investigated; also reported was their application in the electrocatalysis of oxygen reduction reaction (ORR. The resulting MHAQ/MWCNTs nanohybrid was characterized by scanning electron microscope (SEM and transmission electron microscope (TEM. It was found that the ORR at the MHAQ/MWCNTs/GC electrode occurs irreversibly at a potential about 214 mV less negative than at a bare GC electrode in pH 7.0 buffer solution. Cyclic voltammetric and rotating disk electrode (RDE techniques indicated that the MHAQ/MWCNTs nanohybrid has high electrocatalytic activity for the two-electron reduction of oxygen in the studied potential range. The kinetic parameters of ORR at the MHAQ/MWCNTs nanohybrid modified GC electrode were also determined by RDE and EIS techniques.

  9. One-pot synthesis of CaAl-layered double hydroxide–methotrexate nanohybrid for anticancer application

    Indian Academy of Sciences (India)

    MANJUSHA CHAKRABORTY; MANOJ K MITRA; JUI CHAKRABORTY

    2017-10-01

    One-pot (co-precipitation) synthesis route was employed for the first time to synthesize pristine CaAl-layereddouble hydroxide (LDH) and in-situ intercalation of the anticancer drug methotrexate (MTX) to prepare CaAl-LDH–MTXnanohybrid. An increase in the interplanar spacing of the (003) plane from 8.6 $\\AA$ in pristine CaAl-LDH bilayered structureto 18.26 $\\AA$ in CaAl-LDH–MTX nanohybrid indicated successful intercalation of anionic MTX into the interlayer space ofCaAl-LDH. This was supported by the transmission electron micrographs, which showed an increase in average interlayerspacing from 8.7 $\\AA$ in pristine LDH to 18.31 $\\AA$ in LDH–MTX nanohybrid. Particle size and morphology analysis of pristineCaAl-LDH and LDH–MTX nanohybrid using both dynamic light scattering (DLS) technique and transmission electronmicroscopy (TEM) indicated a decrease in average particle size in LDH–MTX nanohybrid as compared with that of pristineLDH. Thermogravimetric analyses (TGA) revealed an enhancement in decomposition temperature of MTX bound to CaAl-LDH nanohybrid to 380$^{\\circ}$C as compared with 290$^{\\circ}$C in pure MTX molecule, indicating enhanced thermal stability, which supports stable electrostatic interaction of MTX within the interlayer position of LDH. CHN (carbon hydrogen nitrogen) analysis revealed nearly 49 wt% of MTX loading into CaAl-LDH, which closely matched with the result obtained from TGA of the nanohybrid. Cumulative release of MTX from CaAl-LDH–MTX in phosphate buffer solution showed a non-lineardependence with incubation time. Release mechanism of MTX from LDH–MTX nanohybrid was governed by diffusionmechanism at physiological pH of 7.4. The in vitro cytotoxicity study of LDH–MTX nanohybrid using MG-63 humanosteosarcoma cell line indicated enhanced inhibition of the cancer cell proliferation compared with the MTX drug alone.

  10. Engineering of (10-hydroxycamptothecin intercalated layered double hydroxide)@liposome nanocomposites with excellent water dispersity

    Science.gov (United States)

    Zhang, Yongfang; Wu, Xiaowen; Mi, Yuwei; Li, Haiping; Hou, Wanguo

    2017-09-01

    A hierarchical nanocomposite of 10-hydroxycamptothecin (HCPT), a nonionic and lipophilic anticancer drug, intercalated layered double hydroxide (LDH) encapsulated in liposomes was constructed. HCPT molecules were first incorporated into sodium cholate (Ch) micelles, and the resultant negatively charged HCPT-loaded Ch micelles were then co-assembled with positively charged LDH single-layer nanosheets, forming a HCPT/Ch intercalated LDH (HCPT-Ch-LDH) host-gest nanohybrid. The nanohybrid particles were further coated with liposomes (LSs), gaining a core-shell nanocomposite, denoted as (HCPT-Ch-LDH)@LS. The so-obtained samples were characterized using TEM, SAXS, FT-IR, DLS, and elemental analyses. Special emphasis was placed on the effect of liposome-coating for the HCPT-Ch-LDH on its water dispersity and drug-release. The results showed that the nanocomposite has excellent water dispersity and enhanced drug sustained-release performance in comparison with the HCPT-Ch-LDH, demonstrating that the liposome-coating for drug-LDH nanohybrids is an effective strategy to enhance their water dispersity and sustained-release performances. This work provides an effective strategy for engineering of LDH-based delivery systems for nonionic and lipophilic drugs.

  11. Anticancer Drug-Incorporated Layered Double Hydroxide Nanohybrids and Their Enhanced Anticancer Therapeutic Efficacy in Combination Cancer Treatment

    Directory of Open Access Journals (Sweden)

    Tae-Hyun Kim

    2014-01-01

    Full Text Available Objective. Layered double hydroxide (LDH nanoparticles have been studied as cellular delivery carriers for anionic anticancer agents. As MTX and 5-FU are clinically utilized anticancer drugs in combination therapy, we aimed to enhance the therapeutic performance with the help of LDH nanoparticles. Method. Anticancer drugs, MTX and 5-FU, and their combination, were incorporated into LDH by reconstruction method. Simply, LDHs were thermally pretreated at 400°C, and then reacted with drug solution to simultaneously form drug-incorporated LDH. Thus prepared MTX/LDH (ML, 5-FU/LDH (FL, and (MTX + 5-FU/LDH (MFL nanohybrids were characterized by X-ray diffractometer, scanning electron microscopy, infrared spectroscopy, thermal analysis, zeta potential measurement, dynamic light scattering, and so forth. The nanohybrids were administrated to the human cervical adenocarcinoma, HeLa cells, in concentration-dependent manner, comparing with drug itself to verify the enhanced therapeutic efficacy. Conclusion. All the nanohybrids successfully accommodated intended drug molecules in their house-of-card-like structures during reconstruction reaction. It was found that the anticancer efficacy of MFL nanohybrid was higher than other nanohybrids, free drugs, or their mixtures, which means the multidrug-incorporated LDH nanohybrids could be potential drug delivery carriers for efficient cancer treatment via combination therapy.

  12. Facile synthesis of Au-ZnO plasmonic nanohybrids for highly efficient photocatalytic degradation of methylene blue

    Science.gov (United States)

    Kuriakose, Sini; Sahu, Kavita; Khan, Saif A.; Tripathi, A.; Avasthi, D. K.; Mohapatra, Satyabrata

    2017-02-01

    Au-ZnO plasmonic nanohybrids were synthesized by a facile two step process. In the first step, nanostructured ZnO thin films were prepared by carbothermal evaporation followed by thermal annealing in oxygen atmosphere. Deposition of ultrathin Au films onto the nanostructured ZnO thin films by sputtering combined with thermal annealing resulted in the formation of Au-ZnO plasmonic nanohybrid thin films. The structural, optical, plasmonic and photocatalytic properties of the Au-ZnO nanohybrid thin films were studied. XRD studies on the Au-ZnO hybrid thin films revealed the presence of Au and ZnO nanostructures. UV-visible absorption studies showed two peaks corresponding to the excitonic absorption of ZnO nanostructures in the UV region and the surface plasmon resonance (SPR) absorption of Au nanoparticles in the visible region. The Au-ZnO nanohybrid thin films annealed at 400 °C showed enhanced photocatalytic activity as compared to nanostructrured ZnO thin films towards sun light driven photocatalytic degradation of methylene blue (MB) dye in water. The observed enhanced photocatalytic activity of Au-ZnO plasmonic nanohybrids is attributed to the efficient suppression of the recombination of photogenerated charge carriers in ZnO due to the strong electron scavenging action of Au nanoparticles combined with the improved sun light utilization capability of Au-ZnO nanohybrids coming from the plasmonic response of Au nanoparticles decorating ZnO nanostructures.

  13. UV-assisted photocatalytic synthesis of highly dispersed Ag nanoparticles supported on DNA decorated graphene for quantitative iodide analysis.

    Science.gov (United States)

    Kong, Fen-Ying; Li, Wei-Wei; Wang, Jing-Yi; Wang, Wei

    2015-07-15

    Herein, we report, for the first time, the synthesis of reduced graphene oxide-DNA-Ag (RGO-DNA-Ag) nanohybrids by ultraviolet (UV) irradiation of aqueous solutions of GO and Ag ions in the presence of DNA. The morphology and microstructure characterizations of the resultant nanohybrids reveal that the proposed method leads to the simultaneous reduction of GO and Ag ions together with efficient dispersion of Ag nanoparticles on the surface of RGO sheets. This simple and fast synthesis route is carried out at ambient conditions without using any additional chemical reducing agents, which has the potential to provide new avenues for the green fabrication of various RGO-based nanomaterials. Additionally, the RGO-DNA-Ag nanohybrids can be utilized as a novel sensing interfacial for direct determination of iodide by simple differential pulse voltammetry (DPV), without requiring any preceding preconcentration of the analyte. Based on the RGO-DNA-Ag nanohybrids modified electrode, a wide linear range of 1μM-1mM and a low detection limit of 0.2μM were obtained. This sensitive and direct method of analysis can be applied successfully to the determination of iodide in real samples.

  14. Effect of aggressive beverage on the color stability of different nano-hybrid resin based composite

    Directory of Open Access Journals (Sweden)

    Hicham Oday Nuaimi

    2014-01-01

    Full Text Available Background: The purpose of this study was to evaluate the color stability of different types of nano-hybrid resin based composite restorative materials upon exposure to aggressive staining solutions (coffee and tea over time. The color of all specimens before and after storage in the solutions were measured by a spectrophotometer based on CIE Lab system that is recommended by the American Dental Association and the color differences thereby is calculated. Materials and Methods: The color differences of three nano-hybrid composites after immersion for 30 days in tea and coffee as aggressive beverage solutions. Results: Within the limitations of the study, Venus Diamond was found the most color stable in tea, while Ceram X was shown the most color stable in coffee. There were statistically significant differences between Filtek 350 XT in tea and coffee storage (P 0.005. Conclusion: Staining solutions are significant factors that affect color stability of composite resins.

  15. 2D quasi-ordered nitrogen-enriched porous carbon nanohybrids for high energy density supercapacitors

    Science.gov (United States)

    Kan, Kan; Wang, Lei; Yu, Peng; Jiang, Baojiang; Shi, Keying; Fu, Honggang

    2016-05-01

    Two-dimensional (2D) quasi-ordered nitrogen-enriched porous carbon (QNPC) nanohybrids, with the characteristics of an ultrathin graphite nanosheet framework and thick quasi-ordered nitrogen-doped carbon cladding with a porous texture, have been synthesized via an in situ polymerization assembly method. In the synthesis, the expandable graphite (EG) is enlarged by an intermittent microwave method, and then aniline monomers are intercalated into the interlayers of the expanded EG with the assistance of a vacuum. Subsequently, the intercalated aniline monomers could assemble on the interlayer surface of the expanded EG, accompanied by the in situ polymerization from aniline monomers to polyaniline. Meanwhile, the expanded EG could be exfoliated to graphite nanosheets. By subsequent pyrolysis and activation processes, the QNPC nanohybrids could be prepared. As supercapacitor electrodes, a typical QNPC12-700 sample derived from the precursor containing an EG content of 12%, with a high level of nitrogen doping of 5.22 at%, offers a high specific capacitance of 305.7 F g-1 (1 A g-1), excellent rate-capability and long-term stability. Notably, an extremely high energy density of 95.7 Wh kg-1 at a power density of 449.7 W kg-1 in an ionic liquid electrolyte can be achieved. The unique structural features and moderate heteroatom doping of the QNPC nanohybrids combines electrochemical double layer and faradaic capacitance contributions, which make these nanohybrids ideal candidates as electrode materials for high-performance energy storage devices.Two-dimensional (2D) quasi-ordered nitrogen-enriched porous carbon (QNPC) nanohybrids, with the characteristics of an ultrathin graphite nanosheet framework and thick quasi-ordered nitrogen-doped carbon cladding with a porous texture, have been synthesized via an in situ polymerization assembly method. In the synthesis, the expandable graphite (EG) is enlarged by an intermittent microwave method, and then aniline monomers are

  16. Graphene Paper Doped with Chemically Compatible Prussian Blue Nanoparticles as Nanohybrid Electrocatalyst

    DEFF Research Database (Denmark)

    Zhu, Nan; Han, Shuang; Gan, Shiyu

    2013-01-01

    Along with reduced graphene oxide (RGO), water soluble Prussian blue nanoparticles (PBNPs, around 6 nm) are synthesized and broadly characterized. These two types of highly stable, low‐cost and chemically compatible nanomaterials are exploited as building ingredients to prepare electrically...... oxidation and detection of glucose. The present work demonstrates a facile and highly reproducible way to construct free‐standing and flexible graphene paper doped with electroactive catalyst. Thanks to high stability, low‐cost and efficient electrocatalytic characteristics, this kind of nanohybrid material...... enhanced and functionally endorsed nanohybrid electrocatalysts, which are further transformed into free‐standing graphene papers. PBNPs doped graphene papers show highly efficient electrocatalysis towards reduction of hydrogen peroxide and can be used alone as flexible chemical sensors for potential...

  17. Nanohybrids Near-Field Optical Microscopy: From Image Shift to Biosensor Application

    Directory of Open Access Journals (Sweden)

    Nayla El-Kork

    2016-01-01

    Full Text Available Near-Field Optical Microscopy is a valuable tool for the optical and topographic study of objects at a nanometric scale. Nanoparticles constitute important candidates for such type of investigations, as they bear an important weight for medical, biomedical, and biosensing applications. One, however, has to be careful as artifacts can be easily reproduced. In this study, we examined hybrid nanoparticles (or nanohybrids in the near-field, while in solution and attached to gold nanoplots. We found out that they can be used for wavelength modulable near-field biosensors within conditions of artifact free imaging. In detail, we refer to the use of topographic/optical image shift and the imaging of Local Surface Plasmon hot spots to validate the genuineness of the obtained images. In summary, this study demonstrates a new way of using simple easily achievable comparative methods to prove the authenticity of near-field images and presents nanohybrid biosensors as an application.

  18. Peculiarities of Properties of the GaSe (InSe Nanohybrids, Synthesized under Lighting

    Directory of Open Access Journals (Sweden)

    F.O. Ivashchyshyn

    2016-11-01

    Full Text Available In this paper, new technological approach to the synthesis of multilayered nanostructures was proposed. It increased sensory properties of these nanostructures and their application for highly efficient nonelectrochemical accumulation of electrical energy. In particular, it was shown, that the field of the light wave, imposed in the process of nanohybrid formation, significantly affected the changes, caused by encapsulation of thiourea, on impedance, spectrum of thermally stimulated depolarisation currents (TSD, loss tangent tg δ and dielectric constant ε. As a result, both the application of nanohybrids GaSe as highly effective photovaricap structures and accumulation of energy on the quantum level at infralowfrequency range were investigated. In addition, a huge negative photo-capacitive phenomenon and the appearance of electromotive force in a constant magnetic field («spin battery» phenomenon in nanohibryds were found.

  19. A bentonite-gold nanohybrid as a heterogeneous green catalyst for selective oxidation of silanes.

    Science.gov (United States)

    Maya, R J; John, Jubi; Varma, R Luxmi

    2016-08-23

    A highly efficient, environmentally benign and reusable heterogeneous bentonite-gold nanohybrid catalyst was designed and synthesized. This heterogeneous catalyst could efficaciously catalyse the oxidation of organosilanes to silanols. The reaction is 98.7% atom economical and the products were obtained in excellent yield without the formation of disiloxanes as byproducts. The catalyst was also well applicable for the gram scale preparation of silanols.

  20. Tailoring of physical properties in highly filled experimental nanohybrid resin composites.

    Science.gov (United States)

    Pick, Bárbara; Pelka, Matthias; Belli, Renan; Braga, Roberto R; Lohbauer, Ulrich

    2011-07-01

    To assess the elastic modulus (EM), volumetric shrinkage (VS), and polymerization shrinkage stress (PSS) of experimental highly filled nanohybrid composites as a function of matrix composition, filler distribution, and density. One regular viscosity nanohybrid composite (Grandio, VOCO, Germany) and one flowable nanohybrid composite (Grandio Flow, VOCO) were tested as references along with six highly filled experimental nanohybrid composites (four Bis-GMA-based, one UDMA-based, and one Ormocer®-based). The experimental composites varied in filler size and density. EM values were obtained from the "three-point bending" load-displacement curve. VS was calculated with Archimedes' buoyancy principle. PSS was determined in 1-mm thick specimens placed between two (poly)methyl methacrylate rods (Ø=6mm) attached to an universal testing machine. Data were analyzed using oneway ANOVA, Tukey's test (α=0.05), and linear regression analyses. The flowable composite exhibited the highest VS and PSS but lowest EM. The PSS was significantly lower with Ormocer. The EM was significantly higher among experimental composites with highest filler levels. No significant differences were found between all other experimental composites regarding VS and PSS. Filler density and size did not influence EM, VS, or PSS. Neither the filler configuration nor matrix composition in the investigated materials significantly influenced composite shrinkage and mechanical properties. The highest filled experimental composite seemed to increase EM by keeping VS and PSS low; however, matrix composition seemed to be the determinant factor for shrinkage and stress development. The Ormocer, with reduced PSS, deserves further investigation. Filler size and density did not influence the tested parameters. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  1. Magnetic nanohybrids loaded with bimetal core-shell-shell nanorods for bacteria capture, separation, and near-infrared photothermal treatment.

    Science.gov (United States)

    Hu, Bo; Wang, Ning; Han, Lu; Chen, Ming-Li; Wang, Jian-Hua

    2015-04-20

    A novel antimicrobial nanohybrid based on near-infrared (NIR) photothermal conversion is designed for bacteria capture, separation, and sterilization (killing). Positively charged magnetic reduced graphene oxide with modification by polyethylenimine (rGO-Fe3 O4 -PEI) is prepared and then loaded with core-shell-shell Au-Ag-Au nanorods to construct the nanohybrid rGO-Fe3 O4 -Au-Ag-Au. NIR laser irradiation melts the outer Au shell and exposes the inner Ag shell, which facilitates controlled release of the silver shell. The nanohybrids combine physical photothermal sterilization as a result of the outer Au shell with the antibacterial effect of the inner Ag shell. In addition, the nanohybrid exhibits high heat conductivity because of the rGO and rapid magnetic-separation capability that is attributable to Fe3 O4 . The nanohybrid provides a significant improvement of bactericidal efficiency with respect to bare Au-Ag-Au nanorods and facilitates the isolation of bacteria from sample matrixes. A concentration of 25 μg mL(-1) of nanohybrid causes 100 % capture and separation of Escherichia coli O157:H7 (1×10(8) cfu mL(-1) ) from an aqueous medium in 10 min. In addition, it causes a 22 °C temperature rise for the surrounding solution under NIR irradiation (785 nm, 50 mW cm(-2) ) for 10 min. With magnetic separation, 30 μg mL(-1) of nanohybrid results in a 100 % killing rate for E. coli O157:H7 cells. The facile bacteria separation and photothermal sterilization is potentially feasible for environmental and/or clinical treatment.

  2. Effect of silver contents in cellulose nanocrystal/silver nanohybrids on PHBV crystallization and property improvements.

    Science.gov (United States)

    Zhang, Heng; Yu, Hou-Yong; Wang, Chuang; Yao, Juming

    2017-10-01

    Ternary nanocomposites including cellulose nanocrystals/silver nanohybrids (CNC-Ag) and biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were prepared by using solution casting. The effect of different AgNPs contents in the nanohybrids on crystallization ability and properties of PHBV was comprehensively investigated. Compared to binary PHBV/CNC nanocomposite, the ternary nanocomposites with high AgNPs contents showed larger improvements in the thermal stability, mechanical, barrier, overall migration and antibacterial properties. The property transitions at various AgNPs contents were due to transition of the nanohybrids induced PHBV crystallization ability (from single CNC nucleation to synergistic nucleation of CNC and AgNPs), and increased crystallinity without compromising the amounts of hydrogen bonds. Especially, the PHBV/CNC-Ag-1.7 showed the good barrier property and lower migration levels in food simulants, high antibacterial ratio of 99.9% and biocompatibility to human MG-63 cells, suggesting its potential application in food packaging related materials. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Effect of whitening dentifrices on the surface roughness of a nanohybrid composite resin.

    Science.gov (United States)

    da Rosa, Gabriela Migliorin; da Silva, Luciana Mendonça; de Menezes, Márcio; do Vale, Hugo Felipe; Regalado, Diego Ferreira; Pontes, Danielson Guedes

    2016-01-01

    The present study verified the influence of whitening dentifrices on the surface roughness of a nanohybrid composite resin. Thirty-two specimens were prepared with Filtek™ Z350 XT (3M/ESPE) and randomly divided into four groups (n = 08) that were subjected to brushing simulation equivalent to the period of 1 month. The groups assessed were a control group with distilled water (G1), Colgate Total 12 Professional Clean (G2), Sensodyne Extra Whitener Extra Fresh (G3), and Colgate Luminous White (G4). A sequence of 90 cycles was performed for all the samples. The initial roughness of each group was analyzed by the Surface Roughness Tester (TR 200-TIME Group Inc., CA, USA). After the brushing period, the final roughness was measured, and the results were statistically analyzed using nonparametric Kruskal-Wallis and Dunn tests for intergroup roughness comparison in the time factor. For intragroup and "Δ Final - Initial" comparisons, the Wilcoxon test and (one-way) ANOVA were, respectively, performed (α = 0.05). The roughness mean values before and after brushing showed no statistically significant difference when the different dentifrices were used. None of the dentifrices analyzed increased significantly the nanohybrid composite resin surface roughness in a 1 month of tooth brushing simulation. These results suggest that no hazardous effect on the roughness of nanohybrid composite resin can be expected when whitening dentifrices are used for a short period. Similar studies should be conducted to analyze other esthetic composite materials.

  4. Bandgap Narrowing of Titanium Dioxide by Iron Doping for Enhanced Photocatalytic Performance of Nanohybrids with CNTs

    Science.gov (United States)

    Khang, Nguyen Cao; Thanh, Do Minh; Van Minh, Nguyen

    2016-10-01

    Fe-doped TiO2/carbon nanotube (CNT) nanohybrids have been synthesized by a hydrolysis method. The samples were characterized by scanning electron microscopy, high-resolution transmission electron microscopy (HR-TEM), x-ray diffraction analysis, and ultraviolet-visible (UV-Vis) optical absorption spectroscopy. HR-TEM reveals Fe-doped TiO2 nanoparticles of about 8 nm in size attached to CNT sidewalls. Compared with TiO2, the UV-Vis spectra of all the nanohybrid materials exhibited red-shift with increased absorbance in the visible range. The photocatalytic performance was tested by photocatalytic degradation of methylene blue (MB) and methylene orange (MO) under visible-light irradiation. The results suggest that Fe-doped TiO2/CNT nanohybrid catalysts exhibit much higher dye degradation activity compared with neat TiO2, with the highest activity being observed for 6% Fe-doped TiO2. The experimental results were combined with density functional theory calculations of electronic band structure and density of states to understand the bonding states between TiO2 and CNTs, proving that the TiO2/CNT system is stable.

  5. Thin-Film LSCs Based on PMMA Nanohybrid Coatings: Device Optimization and Outdoor Performance

    Directory of Open Access Journals (Sweden)

    S. M. El-Bashir

    2013-01-01

    Full Text Available This study concerns the design optimization of thin-film luminescent solar concentrators (TLSCs based on polymethylmethacrylate (PMMA/silica nanohybrid films doped with coumarin dyestuffs specialized in coloring plastics. Two designs of TLSCs had been prepared and characterized. The first consists of a transparent nanohybrid layer coated on a fluorescent PMMA substrate. The second design is the ordinary configuration in which fluorescent nanohybrid layer is coated on a transparent PMMA substrate. The investigation of the spectral properties and efficiency parameters recommended the best solar energy conversion efficiency for the second design. The outdoor performance of optimized TLSC was also evaluated under clear sky conditions of Riyadh city, and the hourly values of the optical efficiency, ηopt, were calculated for one year. The best performance was achieved in summer since the short circuit current for PV cell was doubled after being attached to TLSC and the value of ηopt reached 40% which is higher than other values recorded before due to the abundant solar energy potential in the Arabian Peninsula.

  6. Sonochemical fabrication of Cu{sub 2}O@C/graphene nanohybrid with a hierarchical architecture

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jiasheng [School of Chemical Engineering, University of Ulsan, Ulsan 680-749 (Korea, Republic of); College of Chemistry, Chemical Engineering and Food Safety, Bohai University, 19 Sci-tech Road, Jinzhou 121013 (China); Dang, Dinh Khoi; Chung, Jin Suk; Hur, Seung Hyun; Choi, Won Mook [School of Chemical Engineering, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Kim, Eui Jung, E-mail: ejkim@ulsan.ac.kr [School of Chemical Engineering, University of Ulsan, Ulsan 680-749 (Korea, Republic of)

    2014-12-15

    A three-dimensional Cu{sub 2}O@C/graphene nanohybrid hierarchical sphere-like architecture has been successfully synthesized by a sonochemical method. The as-prepared nanocomposite has been characterized using various techniques including powder X-ray diffraction, scanning electron microscopy, field emission transmission electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and Fourier transmission infrared spectrometry. Secondary big hierarchical Cu{sub 2}O@C spheres (diameter of ∼200 nm) consist of primary small Cu{sub 2}O@C spheres (diameter of 5–10 nm), which are uniformly distributed on the graphene surface. In the primary small Cu{sub 2}O@C sphere, amorphous carbon is formed by the oxidation–reduction reaction between 1-aminopyrene and copper(II) acetate in the sonochemical process. Our facile sonochemical method may apply to the preparation of other metal oxide/graphene hierarchical nanohybrids. - Highlights: • The Cu{sub 2}O@C/graphene nanohybrid hierarchical architecture was obtained. • Secondary big hierarchical Cu{sub 2}O@C spheres (diameter of ∼200 nm) consist of primary small Cu{sub 2}O@C spheres (diameter of 5–10 nm). • 1-Aminopyrene serves as a “binding agent” operating through the π–π interactions.

  7. A pH-responsive layered double hydroxide (LDH)-phthalocyanine nanohybrid for efficient photodynamic therapy.

    Science.gov (United States)

    Li, Xing-Shu; Ke, Mei-Rong; Huang, Wei; Ye, Chun-Hong; Huang, Jian-Dong

    2015-02-16

    A pH-responsive nanohybrid (LDH-ZnPcPS4 ), in which a highly hydrophilic zinc(II) phthalocyanine tetra-α-substituted with 4-sulfonatophenoxy groups (ZnPcPS4 ) is incorporated with a cationic layered double hydroxide (LDH) based on electrostatic interaction, has been specially designed and prepared through a facile co-precipitation approach. ZnPcPS4 is an excellent singlet-oxygen generator with strong absorption at the near-infrared region (692 nm) in cellular culture media, whereas the photoactivities of ZnPcPS4 were remarkably inhibited after incorporation with the LDH. The nanohybrid is essentially stable in aqueous media at pH 7.4; nevertheless, in slightly acidic media of pH 6.5 or 5.0, ZnPcPS4 can be efficiently released from the LDH matrix, thus leading to restoration of the photoactivities. The nanohybrid shows a high photocytotoxicity against HepG2 cells as a result of much more efficient cellular uptake and preferential accumulation in lysosomes, whereby the acidic environment leads to the release of ZnPcPS4 . The IC50 value of LDH-ZnPcPS4 is as low as 0.053 μM, which is 24-fold lower than that of ZnPcPS4 . This work provides a facile approach for the fabrication of photosensitizers with high photocytotoxicity, potential tumor selectivity, and rapid clearance character.

  8. MoS2/Ag nanohybrid: A novel matrix with synergistic effect for small molecule drugs analysis by negative-ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

    Science.gov (United States)

    Zhao, Yaju; Deng, Guoqing; Liu, Xiaohui; Sun, Liang; Li, Hui; Cheng, Quan; Xi, Kai; Xu, Danke

    2016-09-21

    This paper reports a facile synthesis of molybdenum disulfide nanosheets/silver nanoparticles (MoS2/Ag) hybrid and its use as an effective matrix in negative ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The nanohybrid exerts a strong synergistic effect, leading to high performance detection of small molecule analytes including amino acids, peptides, fatty acids and drugs. The enhancement of laser desorption/ionization (LDI) efficiency is largely attributed to the high surface roughness and large surface area for analyte adsorption, better dispersibility, increased thermal conductivity and enhanced UV energy absorption as compared to pure MoS2. Moreover, both Ag nanoparticles and the edge of the MoS2 layers function as deprotonation sites for proton capture, facilitating the charging process in negative ion mode and promoting formation of negative ions. As a result, the MoS2/Ag nanohybrid proves to be a highly attractive matrix in MALDI-TOF MS, with desired features such as high desorption/ionization efficiency, low fragmentation interference, high salt tolerance, and no sweet-spots for mass signal. These characteristic properties allowed for simultaneous analysis of eight different drugs and quantification of acetylsalicylic acid in the spiked human serum. This work demonstrates for the first time the fabrication and application of a novel MoS2/Ag hybrid, and provides a new platform for use in the rapid and high throughput analysis of small molecules by mass spectrometry.

  9. Carboxylated or Aminated Polyaniline—Multiwalled Carbon Nanotubes Nanohybrids for Immobilization of Cellobiose Dehydrogenase on Gold Electrodes

    Directory of Open Access Journals (Sweden)

    Johannes Tanne

    2014-10-01

    Full Text Available Polymer-multiwalled carbon nanotube (MWCNT nanohybrids, which differ in surface charge have been synthesized to study the bioelectrocatalysis of adsorbed cellobiose dehydrogenase (CDH from Phanerochaete sordida on gold electrodes. To obtain negatively charged nanohybrids, poly(3-amino-4-methoxybenzoic acid-co-aniline (P(AMB-A was covalently linked to the surface of MWCNTs while modification with p-phenylenediamine (PDA converted the COOH-groups to positively charged amino groups. Fourier transform infrared spectroscopy (FTIR measurements verified the p-phenylenediamine (PDA modification of the polymer-CNT nanohybrids. The positively charged nanohybrid MWCNT-P(AMB-A-PDA promoted direct electron transfer (DET of CDH to the electrode and bioelectrocatalysis of lactose was observed. Amperometric measurements gave an electrochemical response with KMapp = 8.89 mM and a current density of 410 nA/cm2 (15 mM lactose. The catalytic response was tested at pH 3.5 and 4.5. Interference by ascorbic acid was not observed. The study proves that DET between the MWCNT-P(AMB-A-PDA nanohybrids and CDH is efficient and allows the sensorial detection of lactose.

  10. Comparison of drug delivery potentials of surface functionalized cobalt and zinc ferrite nanohybrids for curcumin in to MCF-7 breast cancer cells

    Science.gov (United States)

    Sawant, V. J.; Bamane, S. R.; Shejwal, R. V.; Patil, S. B.

    2016-11-01

    The functionalization and surface engineering of CoFe2O4 and ZnFe2O4 nanoparticles were performed by coating with PEG and Chitosan respectively using simple wet co-precipitation. Then multiactive therapeutic drug curcumin was loaded to form drug delivery nanohybrids by precipitation. These nanohybrids were characterized separately using UV-vis, FTIR, PL spectroscopy, XRD, VSM, SEM and TEM analysis. The moderate antibacterial activities of the nanohybrids were elaborated by in vitro antibacterial screening on Escherichia coli and Staphylococcus aureus. The anticancer potentials, apoptotic effects and enhanced drug delivery properties of these nanohybrids were confirmed and compared on MCF-7 cells by in vitro MTT assay. The drug delivery activities for hydrophobic drug and anticancer effects of chitosan coated zinc ferrite functionalized nanoparticles were higher than PEG coated cobalt ferrite nanohybrids.

  11. Magnetite (Fe{sub 3}O{sub 4})-filled carbon nanofibers as electro-conducting/superparamagnetic nanohybrids and their multifunctional polymer composites

    Energy Technology Data Exchange (ETDEWEB)

    Das, Arindam; Raffi, Muhammad; Megaridis, Constantine, E-mail: cmm@uic.edu [University of Illinois at Chicago, Department of Mechanical and Industrial Engineering (United States); Fragouli, Despina [Istituto Italiano di Tecnologia, Smart Materials, Nanophysics (Italy); Innocenti, Claudia [Universita di Firenze, INSTM Research Unit and Department of Chemistry (Italy); Athanassiou, Athanassia [Istituto Italiano di Tecnologia, Smart Materials, Nanophysics (Italy)

    2015-01-15

    A mild-temperature, nonchemical technique is used to produce a nanohybrid multifunctional (electro-conducting and magnetic) powder material by intercalating iron oxide nanoparticles in large aspect ratio, open-ended, hollow-core carbon nanofibers (CNFs). Single-crystal, superparamagnetic Fe{sub 3}O{sub 4} nanoparticles (10 nm average diameter) filled the CNF internal cavity (diameter <100 nm) after successive steps starting with dispersion of CNFs and magnetite nanoparticles in aqueous or organic solvents, sequencing or combining sonication-assisted capillary imbibition and concentration-driven diffusion, and finally drying at mild temperatures. The influence of several process parameters—such as sonication type and duration, concentration of solids dispersed in solvent, CNF-to-nanoparticle mass ratio, and drying temperature—on intercalation efficiency (evaluated in terms of particle packing in the CNF cavity) was studied using electron microscopy. The magnetic CNF powder was used as a low-concentration filler in poly(methyl methacrylate) to demonstrate thin free-standing polymer films with simultaneous magnetic and electro-conducting properties. Such films could be implemented in sensors, optoelectromagnetic devices, or electromagnetic interference shields.

  12. A Randomized 10-year Prospective Follow-up of Class II Nanohybrid and Conventional Hybrid Resin Composite Restorations

    DEFF Research Database (Denmark)

    van Dijken, Jan Wv; Pallesen, Ulla

    2014-01-01

    Purpose: To evaluate the 10-year durability of a nanohybrid resin composite in Class II restorations in a randomized controlled intraindividual comparison with its conventional hybrid resin composite predecessor. Materials and Methods: Each of 52 participants received at least two Class II...... restorations that were as similar as possible. The cavities were chosen at random to be restored with a nanohybrid resin composite (Excite/Tetric EvoCeram (TEC); n = 61) and a conventional hybrid (Excite/Tetric Ceram (TC); n = 61). The restorations were evaluated with slightly modified USPHS criteria...... investigated resin composites. Conclusion: The nanohybrid and the conventional hybrid resin composite showed good clinical effectiveness in extensive Class II restorations during the 10-year study....

  13. Comparison of surface roughness of nanofilled and nanohybrid composite resins after polishing with a multi-step technique

    Science.gov (United States)

    Itanto, B. S. H.; Usman, M.; Margono, A.

    2017-08-01

    To compare the surface roughness of nanofilled and nanohybrid composite resins after polishing using a multi-step technique. 40 composite resin specimens were divided into two groups (20 nanofilled specimens using Filtek Z350 XT [group A] and 20 nanohybrid specimens using Filtek Z250 XT [group B]), prepared, and then polished. After immersion in artificial saliva for 24 hours, the surface roughness was measured with a surface roughness tester. The mean surface roughness results along with the standard deviation of group A were 0.0967 μm ± 0.0174, while the results of group B were 0.1217 μm ± 0.0244. Statistically (with p = 0.05), there were significant differences between each group. The surface roughness of a nanofilled composite resin after polishing with a multi-step technique is better than that of a nanohybrid composite resin.

  14. Versatile Core-Shell Nanoparticle@Metal-Organic Framework Nanohybrids: Exploiting Mussel-Inspired Polydopamine for Tailored Structural Integration.

    Science.gov (United States)

    Zhou, Jiajing; Wang, Peng; Wang, Chenxu; Goh, Yi Ting; Fang, Zheng; Messersmith, Phillip B; Duan, Hongwei

    2015-07-28

    We report a versatile strategy based on the use of multifunctional mussel-inspired polydopamine for constructing well-defined single-nanoparticle@metal-organic framework (MOF) core-shell nanohybrids. The capability of polydopamine to form a robust conformal coating on colloidal substrates of any composition and to direct the heterogeneous nucleation and growth of MOFs makes it possible for customized structural integration of a broad range of inorganic/organic nanoparticles and functional MOFs. Furthermore, the unique redox activity of polydopamine adds additional possibilities to tailor the functionalities of the nanohybrids by sandwiching plasmonic/catalytic metal nanostructures between the core and shell via localized reduction. The core-shell nanohybrids, with the molecular sieving effect of the MOF shell complementing the intrinsic properties of nanoparticle cores, represent a unique class of nanomaterials of considerable current interest for catalysis, sensing, and nanomedicine.

  15. Novel mesoporous NiO/HTiNbO5 nanohybrids with high visible-light photocatalytic activity and good biocompatibility

    Science.gov (United States)

    Zhai, Zheng; Yang, Xiaoyan; Xu, Lin; Hu, Chenhui; Zhang, Lihong; Hou, Wenhua; Fan, Yining

    2012-01-01

    Mesoporous nanohybrids of NiO nanoparticles and HTiNbO5 nanosheets have been successfully synthesized by first exfoliating layered HTiNbO5 in tetrabutylammonium hydroxide (TBAOH) to obtain HTiNbO5 nanosheets, then reassembling with a nickel precursor and finally heating with urea. The resulting samples were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, photoluminescence spectroscopy (PL) and N2 adsorption-desorption measurements. It was found that the as-prepared nanohybrids had a relatively large interlayer spacing of 1.05 nm. After calcination, the titanoniobate nanosheet was still retained and the pore size of the resulting nanohybrids became larger. Compared with the original HTiNbO5, the obtained nanohybrids were mesoporous with a greatly expanded surface area (~75-115 m2 g-1), a much strengthened absorption in the UV light region and a visible-light response. Nickel atoms were present in the form of Ni-O in the nanohybrid, and NiO nanoparticles were homogeneously distributed with an average particle size of 2-3 nm, giving rise to the visible light response. The catalytic activities of the obtained samples were evaluated by the photodegradation of RhB solution under visible light irradiation. The introduction of urea during the calcination process not only increased the thermal stability and surface area, but also decreased the rate of recombination of photogenerated holes and electrons, leading to a greatly enhanced photocatalytic activity of the resulting nanohybrids. The dye molecules were mainly degraded to aliphatic organic compounds and partially mineralized to CO2 and/or CO, rather than being simply decolorized. In addition, cell viability results for HepG2 cells show that the as-prepared sample have good biocompatibility.

  16. Self-Assembled α-Fe2O3 mesocrystals/graphene nanohybrid for enhanced electrochemical capacitors.

    Science.gov (United States)

    Yang, Shuhua; Song, Xuefeng; Zhang, Peng; Sun, Jing; Gao, Lian

    2014-06-12

    Self-assembled α-Fe2O3 mesocrystals/graphene nanohybrids have been successfully synthesized and have a unique mesocrystal porous structure, a large specific surface area, and high conductivity. Mesocrystal structures have recently attracted unparalleled attention owing to their promising application in energy storage as electrochemical capacitors. However, mesocrystal/graphene nanohybrids and their growth mechanism have not been clearly investigated. Here we show a facile fabrication of short rod-like α-Fe2O3 mesocrystals/graphene nanohybrids by self-assembly of FeOOH nanorods as the primary building blocks on graphene under hydrothermal conditions, accompanied and promoted by concomitant phase transition from FeOOH to α-Fe2O3. A systematic study of the formation mechanism is also presented. The galvanostatic charge/discharge curve shows a superior specific capacitance of the as-prepared α-Fe2O3 mesocrystals/graphene nanohybrid (based on total mass of active materials), which is 306.9 F g(-1) at 3 A g(-1) in the aqueous electrolyte under voltage ranges of up to 1 V. The nanohybrid with unique sufficient porous structure and high electrical conductivity allows for effective ion and charge transport in the whole electrode. Even at a high discharge current density of 10 A g(-1), the enhanced ion and charge transport still yields a higher capacitance (98.2 F g(-1)), exhibiting enhanced rate capability. The α-Fe2O3 mesocrystal/graphene nanohybrid electrode also demonstrates excellent cyclic performance, which is superior to previously reported graphene-based hematite electrode, suggesting it is highly stable as an electrochemical capacitor.

  17. Synthesis and optical enhancement of amorphous carbon nanotubes/silver nanohybrids via chemical route at low temperature.

    Science.gov (United States)

    Han, Tan Kim; Fen, Leo Bey; Nee, Ng Meng; Johan, Mohd Rafie

    2014-01-01

    We report the synthesis of amorphous carbon nanotubes/silver (αCNTs/Ag) nanohybrids via simple chemical route without additional reactant and surfactant at low temperature. Field emission scanning microscope (FESEM) and transmission electron microscope (TEM) confirmed formation of CNTs. X-ray diffraction (XRD) pattern confirmed the amorphous phase of carbon and the formation of Ag nanoparticles crystalline phase. Raman spectra revealed the amorphous nature of α CNTs. UV-visible spectroscopy showed enhancement of optical properties of α CNTs/Ag nanohybrids.

  18. Enzyme-guided plasmonic biosensor based on dual-functional nanohybrid for sensitive detection of thrombin.

    Science.gov (United States)

    Yan, Jing; Wang, Lida; Tang, Longhua; Lin, Lei; Liu, Yang; Li, Jinghong

    2015-08-15

    Rapid and sensitive methodologies for the detection of protein are in urgent requirement for clinic diagnostics. Localized surface plasmon resonance (LSPR) of metal nanostructures has the potential to circumvent this problem due to its sensitive optical properties and strong electromagnetic near-field enhancements. In this work, an enzyme mediated plasmonic biosensor on the basis of a dual-functional nanohybrid was developed for the detection of thrombin. By utilizing LSPR-responsive nanohybrid and anaptamer-enzyme conjugated reporting probe, the sensing platform brings enhanced signal, stability as well as simplicity. Enzymatic reaction catalyzed the reduction of Au(3+) to Au° in situ, further leading to the rapid crystal growth of gold nanoparticles (AuNPs). The LSPR absorbance band and color changed company with the nanoparticle generation, which can be real-time monitoring by UV-visible spectrophotometer and naked eye. Nanohybrid constructed by gold and magnetic nanoparticles acts as a dual functional plasmonic unit, which not only plays the role of signal production, but also endows the sensor with the function of magnetic separation. Simultaneously, the introduction of enzyme effectively regulates the programming crystal growth of AuNPs. In addition, enzyme also serves as signal amplifier owing to its high catalysis efficiency. The response of the plasmonic sensor varies linearly with the logarithmic thrombin concentration up to 10nM with a limit of detection of 200 pM. The as-proposed strategy shows good analytical performance for thrombin determination. This simple, disposable method is promising in developing universal platforms for protein monitoring, drug discovery and point-of-care diagnostics.

  19. Fracture Toughness of Nanohybrid and Hybrid Composites Stored Wet and Dry up to 60 Days

    Directory of Open Access Journals (Sweden)

    Sookhakiyan M

    2017-03-01

    Full Text Available Statement of Problem: Patients’ demand for tooth-colored restoratives in the posterior region is increasing. Clinicians use universal nanohybrid resin composites for both anterior and posterior regions. There are few published reports comparing fracture toughness of nonohybrids and that of hybrid composite stored wet and dry. Objectives: To investigate the fracture toughness of three nanohybrids compared to that of a hybrid resin composite stored dry or wet up to 60 days, using four- point bending test. Materials and Methods: Four resin composites were used: three nanohybrids; Filtek Supreme (3M, Ice (SDI, TPH3 (Dentsply and one hybrid Filtek P60 (3M. For each material, 40 rectangular notched beam specimens were prepared with dimensions of 30 mm × 5mm × 2mm. The specimens were randomly divided into 4 groups (n = 10 and stored at 37ºC either in distilled water or dry for 1 and 60 days. The specimens were placed on the four-point test jig and subjected to force (N using universal testing machine loaded at a crosshead speed of 0.5mm/min and maximum load at specimen failure was recorded and KIc was calculated. Results: Three-way ANOVA showed a significant interaction between all the factors (all p < .0001. Except for TPH3, all tested materials showed significantly higher KIc when stored dry than stored wet (p < 0.05. After 1 day of dry storage, Ice showed the highest KIc (2.04 ± 0.32 followed by Filtek P60 and the lowest was for Filtek Supreme (1.39 ± 0.13. The effect of time on fracture toughness was material dependent. Conclusions: Wet storage adversely affected the fracture toughness of almost all materials. Keeping the restoration dry in the mouth may increase their fracture toughness. Therefore, using a coating agent on the surface of restoration may protect them from early water uptake and increase their strength during a time period.

  20. Effect of whitening dentifrices on the surface roughness of a nanohybrid composite resin

    Science.gov (United States)

    da Rosa, Gabriela Migliorin; da Silva, Luciana Mendonça; de Menezes, Márcio; do Vale, Hugo Felipe; Regalado, Diego Ferreira; Pontes, Danielson Guedes

    2016-01-01

    Objectives: The present study verified the influence of whitening dentifrices on the surface roughness of a nanohybrid composite resin. Materials and Methods: Thirty-two specimens were prepared with Filtek™ Z350 XT (3M/ESPE) and randomly divided into four groups (n = 08) that were subjected to brushing simulation equivalent to the period of 1 month. The groups assessed were a control group with distilled water (G1), Colgate Total 12 Professional Clean (G2), Sensodyne Extra Whitener Extra Fresh (G3), and Colgate Luminous White (G4). A sequence of 90 cycles was performed for all the samples. The initial roughness of each group was analyzed by the Surface Roughness Tester (TR 200-TIME Group Inc., CA, USA). After the brushing period, the final roughness was measured, and the results were statistically analyzed using nonparametric Kruskal–Wallis and Dunn tests for intergroup roughness comparison in the time factor. For intragroup and “Δ Final − Initial” comparisons, the Wilcoxon test and (one-way) ANOVA were, respectively, performed (α = 0.05). Results: The roughness mean values before and after brushing showed no statistically significant difference when the different dentifrices were used. None of the dentifrices analyzed increased significantly the nanohybrid composite resin surface roughness in a 1 month of tooth brushing simulation. Conclusions: These results suggest that no hazardous effect on the roughness of nanohybrid composite resin can be expected when whitening dentifrices are used for a short period. Similar studies should be conducted to analyze other esthetic composite materials. PMID:27095891

  1. Effect of Common Drinks on the Color Stability of Microhybrid and Nanohybrid Composites in Children

    Directory of Open Access Journals (Sweden)

    Hesameddin Seddighi

    Full Text Available Introduction: In spite of numerous developments in resin composites products, their color stability is still a major problem particularly in pediatric dentistry, since frequent visits of children is of great importantance due to their behavior management, regardless of the problems pertaining to aesthetic and additional expenses. The purpose of this study was to evaluate the effect of common children drinks on the color stability of nanohybrid and microhybrid resin composites.Materials & Methods: In this experimental study, 80 disk samples (with diameter of 10 mm and depth of 2 mm of microhybrid (point4 Kerr and nanohybrid (Herculite XRV Ultra Kerr resin composites were prepared. (categorized in 2 groups of 40.Then the samples of each group were divided into five subgroups of eight and were immersed in five different solutions (orange juice, red grape juice, fanta coke, chocolate milk and distilled water as the control group for 4 hours daily for a period of 10 days. The color of samples was measured by a spectrophotometer at the beginning of the study and after staining using CIE lab system. The data were analysed by 2-Way ANOVA test.Results: 2-Way ANOVA showed that there was no significant statistical difference between the microhybrid (P4 and nanohybrid (HCU resin composites with respect to the degree of staining in the mentioned solutions (P=0.29. Moreover 2-way ANOVA showed that type of the drink has a significant effect on the degree of staining of materials (P< 0.001.Conclusions: It doesn’t seem that the new nanocomposites have any considerable advantage to microhybrid resin composites regarding staining. Also regarding these results, colored drinks especially red grape juice and chocolate milk are not recommended in the first days after composite filling.

  2. Efficacy and safety of nanohybrids comprising silver nanoparticles and silicate clay for controlling Salmonella infection

    Directory of Open Access Journals (Sweden)

    Bau IJ

    2012-05-01

    Full Text Available Shu-Her Chiao,1* Siou-Hong Lin,1* Ching-I Shen,2* Jiunn-Wang Liao,3 I-Jiuan Bau,1 Jiun-Chiou Wei,4 Li-Ping Tseng,1 Shan-hui Hsu,4 Ping-Shan Lai,2 Shinn-Zong Lin,5–7 Jiang-Jen Lin,4 Hong-Lin Su,1,8 1Department of Life Sciences, Agricultural Biotechnology Center, National Chung Hsing University, 2Department of Chemistry, Agricultural Biotechnology Center, National Chung Hsing University, 3Graduate Institute of Veterinary Pathobiology, Agricultural Biotechnology Center, National Chung Hsing University, Taichung, Taiwan; 4Institute of Polymer Science and Engineering, National Taiwan University, Taipei, Taiwan; 5Center for Neuropsychiatry, China Medical University and Hospital, Taichung, Taiwan; 6Department of Neurosurgery, China Medical University Beigan Hospital, Yunlin, Taiwan; 7Graduate Institute of Immunology, China Medical University, Taichung, Taiwan; 8Department of Physical Therapy, China Medical University, Taichung, Taiwan*These three authors contributed equallyAbstract: Developing effective and safe drugs is imperative for replacing antibiotics and controlling multidrug-resistant microbes. Nanoscale silicate platelet (NSP and its nanohybrid, silver nanoparticle/NSP (AgNP/NSP, have been developed, and the nanohybrids show a strong and general antibacterial activity in vitro. Here, their efficacy for protecting Salmonella-infected chicks from fatality and septicemia was evaluated. Both orally administrated NSP and AgNP/NSP, but not AgNPs alone, effectively reduced the systemic Salmonella infection and mortality. In addition, quantitative Ag analyses demonstrated that Ag deposition from AgNP/NSP in the intestines was less than that from conventional AgNPs, indicating that the presence of NSP for immobilizing AgNPs reduced Ag accumulation in tissue and improved the safety of AgNPs. These in vivo results illustrated that both NSP and AgNP/NSP nanohybrid represent potential agents for controlling enteric bacterial infections.Keywords: silver

  3. Comparison of drug delivery potentials of surface functionalized cobalt and zinc ferrite nanohybrids for curcumin in to MCF-7 breast cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, V.J., E-mail: v11131@rediffmail.com [Department of Chemistry, Smt.K.W.College, Sangli, MS 416416 (India); Bamane, S.R. [Department of Chemistry, Raja Shripatrao Bhagwantrao College, Aundh, Satara, MS (India); Shejwal, R.V. [L.B.S. College, Satara, MS (India); Patil, S.B. [A.Birnale College of Pharmacy, Sangli, MS (India)

    2016-11-01

    The functionalization and surface engineering of CoFe{sub 2}O{sub 4} and ZnFe{sub 2}O{sub 4} nanoparticles were performed by coating with PEG and Chitosan respectively using simple wet co-precipitation. Then multiactive therapeutic drug curcumin was loaded to form drug delivery nanohybrids by precipitation. These nanohybrids were characterized separately using UV–vis, FTIR, PL spectroscopy, XRD, VSM, SEM and TEM analysis. The moderate antibacterial activities of the nanohybrids were elaborated by in vitro antibacterial screening on Escherichia coli and Staphylococcus aureus. The anticancer potentials, apoptotic effects and enhanced drug delivery properties of these nanohybrids were confirmed and compared on MCF-7 cells by in vitro MTT assay. The drug delivery activities for hydrophobic drug and anticancer effects of chitosan coated zinc ferrite functionalized nanoparticles were higher than PEG coated cobalt ferrite nanohybrids. - Highlights: • CoFe{sub 2}O{sub 4} and ZnFe{sub 2}O{sub 4} nanoparticles were surface functionalized with PEG and Chitosan respectively. • Hydrophobic multi therapeutic anticancer drug curcumin was loaded into these nanohybrids and their structure, morphologies were confirmed. • The effects of PEG and Chitosan coating over ferrites for curcumin release have been elaborated, and the Chitosan coated curcumin loaded Zinc ferrite nanohybrid exhibited higher drug delivery and anticancer effects.

  4. Application of Graphene Oxide-MnFe2O4 Magnetic Nanohybrids as Magnetically Separable Adsorbent for Highly Efficient Removal of Arsenic from Water

    Science.gov (United States)

    Huong, Pham Thi Lan; Huy, Le Thanh; Phan, Vu Ngoc; Huy, Tran Quang; Nam, Man Hoai; Lam, Vu Dinh; Le, Anh-Tuan

    2016-05-01

    In this work, a functional magnetic nanohybrid consisting of manganese ferrite magnetic nanoparticles (MnFe2O4) deposited onto graphene oxide (GO) nanosheets was successfully synthesized using a modified co-precipitation method. The as-prepared GO-MnFe2O4 magnetic nanohybrids were characterized using x-ray diffraction, transmission electron microscopy, Fourier transformed infrared spectroscopy, and vibrating sample magnetometer measurements. Adsorption experiments were performed to evaluate the adsorption capacities and efficient removal of arsenic of the nanohybrid and compared with bare MnFe2O4 nanoparticles and GO nanosheets. Our obtained results reveal that the adsorption process of the nanohybrids was well fitted with a pseudo-second-order kinetic equation and a Freundlich isotherm model; the maximum adsorption capacity and removal efficiency of the nanohybrids obtained ~240.385 mg/g and 99.9% with a fast response of equilibrium adsorption time ~20 min. The larger adsorption capacity and shorter equilibrium time of the GO-MnFe2O4 nanohybrids showed better performance than that of bare MnFe2O4 nanoparticles and GO nanosheets. The advantages of reusability, magnetic separation, high removal efficiency, and quick kinetics make these nanohybrids very promising as low-cost adsorbents for fast and effective removal of arsenic from water.

  5. Novel nanohybrid materials for the effective removal of phosphates and nitrates from liquid effluents

    Science.gov (United States)

    Eroglu, Ela; Haniff Wahid, M.; Boulos, Ramiz A.; Chen, Xianjue; Eggers, Paul K.; Toster, Jeremiah; D'Alonzo, Nicholas J.; Smith, Steven M.; Raston, Colin L.

    2014-05-01

    Within our research group, various types of nanofabrication processes have been applied for creating novel nanohybrid materials, including the immobilization of some microorganisms with electrospun nanofibres1, laminar nanomaterials (i.e. graphene and graphene oxide)2,3, microfibers of human hair4, and magnetic nanoparticles impregnated in polymer5. These approaches afford nanohybrid materials with microalgal cells1-5 or diatom frustules6 for the removal of waste pollutants, mainly nitrate and phosphate ions, while establishing a new paradigm in the field. Aside from these immobilization studies, we also investigated the improvement of nitrate removal with exfoliated graphene sheets in the presence of p-phosphonic acid calix[8]arene molecules.7 Various material characterization techniques such as scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and Raman spectroscopy were used for the characterization of the novel nanohybrid materials, while fluorescence microscopy and chlorophyll content analysis were mainly used for monitoring the viability and growth pattern of the microalgal cells. Nitrate and phosphate analyses were carried out by following HACH® standard methods. In this talk, a brief overview of the fabrication processes of these nanohybrid materials and their application for wastewater treatment will be highlighted. 1. E. Eroglu, V. Agarwal, M. Bradshaw, X. Chen, S.M. Smith, C.L. Raston and K.S. Iyer, Green Chemistry, 2012, 14(10), 2682 - 2685. 2. M.H. Wahid, E. Eroglu, X. Chen, S.M. Smith and C.L. Raston, Green Chemistry, 2013, 15(3), 650-655. 3. M.H. Wahid, E. Eroglu, X. Chen, S.M. Smith and C.L. Raston, RSC Advances, 2013, 3(22), 8180-8183. 4. R.A. Boulos, E. Eroglu, X. Chen, A. Scaffidi, J. Toster, B. Edwards and C.L. Raston, Green Chemistry, 2013, 15(5), 1268-1273. 5. E. Eroglu, N.J. D'Alonzo, S.M. Smith and C.L. Raston, Nanoscale, 2013, 5(7), 2627-2631. 6. J. Toster, I. Kusumawardani, E. Eroglu, K.S. Iyer, F

  6. Nanohybrid TiO2/carbon black sensor for NO2 gas

    Institute of Scientific and Technical Information of China (English)

    Wei-Jen Liou; Hong-Ming Lin

    2007-01-01

    A nanohybrid sensor of nanosized TiO2-coated carbon black particles, prepared by sol-gel technology for the detection of NO2 gas, has been developed. The response of the electric resistance of the hybrid sensor to NO2 concentration is investigated, showing that the sensitivity of the hybrid sensor is raised as certain ratio of the TiO2 content in the sensor. Easy and cheap to fabricate, the hybrid TiO2/carbon black promises to be a practical sensor for detecting NO2 gas.

  7. Aqueously Dispersed Silver Nanoparticle-Decorated Boron Nitride Nanosheets for Reusable, Thermal Oxidation-Resistant Surface Enhanced Raman Spectroscopy (SERS) Devices

    Science.gov (United States)

    Lin, Yi; Bunker, Christopher E.; Fernandos, K. A. Shiral; Connell, John W.

    2012-01-01

    The impurity-free aqueous dispersions of boron nitride nanosheets (BNNS) allowed the facile preparation of silver (Ag) nanoparticle-decorated BNNS by chemical reduction of an Ag salt with hydrazine in the presence of BNNS. The resultant Ag-BNNS nanohybrids remained dispersed in water, allowing convenient subsequent solution processing. By using substrate transfer techniques, Ag-BNNS nanohybrid thin film coatings on quartz substrates were prepared and evaluated as reusable surface enhanced Raman spectroscopy (SERS) sensors that were robust against repeated solvent washing. In addition, because of the unique thermal oxidation-resistant properties of the BNNS, the sensor devices may be readily recycled by short-duration high temperature air oxidation to remove residual analyte molecules in repeated runs. The limiting factor associated with the thermal oxidation recycling process was the Ostwald ripening effect of Ag nanostructures.

  8. Aqueously Dispersed Silver Nanoparticle-Decorated Boron Nitride Nanosheets for Reusable, Thermal Oxidation-Resistant Surface Enhanced Raman Spectroscopy (SERS) Devices

    Science.gov (United States)

    Lin, Yi; Bunker, Christopher E.; Fernandos, K. A. Shiral; Connell, John W.

    2012-01-01

    The impurity-free aqueous dispersions of boron nitride nanosheets (BNNS) allowed the facile preparation of silver (Ag) nanoparticle-decorated BNNS by chemical reduction of an Ag salt with hydrazine in the presence of BNNS. The resultant Ag-BNNS nanohybrids remained dispersed in water, allowing convenient subsequent solution processing. By using substrate transfer techniques, Ag-BNNS nanohybrid thin film coatings on quartz substrates were prepared and evaluated as reusable surface enhanced Raman spectroscopy (SERS) sensors that were robust against repeated solvent washing. In addition, because of the unique thermal oxidation-resistant properties of the BNNS, the sensor devices may be readily recycled by short-duration high temperature air oxidation to remove residual analyte molecules in repeated runs. The limiting factor associated with the thermal oxidation recycling process was the Ostwald ripening effect of Ag nanostructures.

  9. Drug delivery system for an anticancer agent, chlorogenate-Zn/Al-layered double hydroxide nanohybrid synthesised using direct co-precipitation and ion exchange methods

    Science.gov (United States)

    Barahuie, Farahnaz; Hussein, Mohd Zobir; Arulselvan, Palanisamy; Fakurazi, Sharida; Zainal, Zulkarnain

    2014-09-01

    A nano-structured drug-inorganic clay hybrid involving an active anticancer compound, which is chlorogenic acid (CA) intercalated into Zn/Al-layered double hydroxide, has been assembled via ion-exchange and co-precipitation methods to form a nanohybrid CZAE (a chlorogenic acid-Zn/Al nanohybrid synthesised using an ion-exchange method) and CZAC (a chlorogenic acid-Zn/Al nanohybrid synthesised using a direct method), respectively. The X-ray diffraction (XRD) results confirmed that the CA-LDH had a hybrid structure in which the anionic chlorogenate is arranged between the interlayers as a horizontal monolayer at 90 and 20° angles from the x axis for CZAE and CZAC, respectively. Both nanohybrids have the properties of mesoporous materials. The high loading percentage of chlorogenic acid (approximately 43.2% for CZAE and 45.3% for CZAC) with basal spacings of 11.7 and 12.6 Å for CZAE and CZAC, respectively, corroborates the successful intercalation of chlorogenic acid into the interlayer gallery of layered double hydroxides. Free chlorogenic acid and the synthesised nanocomposites (CZAE, CZAC) were assessed for their cytotoxicity against various cancer cells. The Fourier transform infrared data supported the formation of both nanohybrids, and a thermal analysis showed that the nanohybrids are more thermally stable than their counterparts. The chlorogenate shows a sustained release, and the release rate of chlorogenate from CZAE and CZAC nanohybrids at pH 7.4 is remarkably lower than that at pH 4.8 due to their different release mechanisms. The release rate of chlorogenate from both nanohybrids can be described as pseudo-second order. The present investigation revealed the potential of the nanohybrids to enhance the in vitro anti-tumour effect of chlorogenic acid in liver and lung cancer cells in vitro.

  10. Study on binding and fluorescence energy transfer efficiency of Rhodamine B with Pluronic F127-gold nanohybrid using optical spectroscopy methods

    Science.gov (United States)

    Antonisamy, Jenif Dsouza; Swain, Jitendriya; Dash, Sasmita

    2017-02-01

    This work focuses on the binding efficiency and fluorescence resonance energy transfer (FRET) of fluorescent dye Rhodamine B (Rh B) to Pluronic F127-gold nanohybrid. The formation of gold nanoparticles inside Rh B doped Pluronic F127 copolymer have been characterized using dynamic light scattering study, HR-TEM images, UV-visible spectra and fluorescence studies. Fluorescence quenching and the constant fluorescence lifetime of the Rhodamine B present in the cavity of Pluronic F127-gold nanohybrid suggested a strong binding ability (3.5 × 103 L mol- 1), static nature of quenching and better energy transfer efficiency of fluorescent dye towards Pluronic F127-gold (Au) nanohybrids.

  11. Effect of supercritical CO2 on the morphology and fluorescent behavior of fluorinated polyylidenefluorenes derivative/graphene oxide nanohybrids

    NARCIS (Netherlands)

    Li, Jing; Zheng, Shijun; Wang, Xiaobo; Yang, Hongxia; Loos, Katja; Xu, Qun

    2015-01-01

    Fluorinated polyylidenefluorenes derivative, poly [(9-ylidene-{2-tetradecyloxy-5-tetrafluorophthalimide-phenyl}fluorenyl-2,7-diyl)-alt-(1,4-phenyl)] (PFFB)/graphene oxide (GO) nanohybrids (SC-PFFB/GO) were successfully fabricated via a facile method with the assistance of supercritical CO2 (SC CO2).

  12. Fabrication of Alternate Stacking MnO2/MoS2 Layered Nanohybrid by a Sonochemistry Technology

    Institute of Scientific and Technical Information of China (English)

    SU Zhi-Kui; CUI Yan-Hua; TANG Xiu-Hua; ZHOU Qing; LIU Zong-Huai

    2008-01-01

    Layered manganese oxide was delaminated in a tetramethylammonium hydroxide by sonicating treatment for hated MnO2 colloid by ultrasonic treatment, and alternate stacking MnO2/MoS2 nanohybrid with a novel layered structure was fabricated by using a sonochemistry technology. A new hybridization method between two kinds of inorganic nanosheets with the same charge character was developed.

  13. Effect of supercritical CO2 on the morphology and fluorescent behavior of fluorinated polyylidenefluorenes derivative/graphene oxide nanohybrids

    NARCIS (Netherlands)

    Li, Jing; Zheng, Shijun; Wang, Xiaobo; Yang, Hongxia; Loos, Katja; Xu, Qun

    2015-01-01

    Fluorinated polyylidenefluorenes derivative, poly [(9-ylidene-{2-tetradecyloxy-5-tetrafluorophthalimide-phenyl}fluorenyl-2,7-diyl)-alt-(1,4-phenyl)] (PFFB)/graphene oxide (GO) nanohybrids (SC-PFFB/GO) were successfully fabricated via a facile method with the assistance of supercritical CO2 (SC CO2).

  14. Effects of surface conditioning on repair bond strengths of non-aged and aged microhybrid, nanohybrid, and nanofilled composite resins

    NARCIS (Netherlands)

    Rinastiti, Margareta; Siswomihardjo, Widowati; Busscher, Henk J.; Ozcan, Mutlu

    2011-01-01

    This study evaluates effects of aging on repair bond strengths of microhybrid, nanohybrid, and nanofilled composite resins and characterizes the interacting surfaces after aging. Disk-shaped composite specimens were assigned to one of three aging conditions: (1) thermocycling (5,000x, 5-55 degrees

  15. Detection of alprazolam with a lab on paper economical device integrated with urchin like Ag@ Pd shell nano-hybrids.

    Science.gov (United States)

    Narang, Jagriti; Malhotra, Nitesh; Singhal, Chaitali; Mathur, Ashish; Pn, Anoop Krishna; Pundir, C S

    2017-11-01

    We present results of the studies relating to fabrication of a microfluidic biosensor chip based on urchin like Ag@ Pd shell nano-hybrids that is capable of sensing alprazolam through electrochemical detection. Using this chip we demonstrate, with high reliability and in a time efficient manner, the detection of alprazolam present in buffer solutions at clinically relevant concentrations. Methylene blue (MB) was also doped as redox transition substance for sensing alprazolam. Nano-hybrids modified EμPAD showed wide linear range 1-300ng/ml and low detection limit of 0.025ng/l. Low detection limit can further enhance its suitability for forensic application. Nano-hybrids modified EμPAD was also employed for determination of drug in real samples such as human urine. Reported facile lab paper approach integrated with urchin like Ag@ Pd shell nano-hybrids could be well applied for the determination of serum metabolites. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Effects of surface conditioning on repair bond strengths of non-aged and aged microhybrid, nanohybrid, and nanofilled composite resins

    NARCIS (Netherlands)

    Rinastiti, Margareta; Siswomihardjo, Widowati; Busscher, Henk J.; Ozcan, Mutlu

    2011-01-01

    This study evaluates effects of aging on repair bond strengths of microhybrid, nanohybrid, and nanofilled composite resins and characterizes the interacting surfaces after aging. Disk-shaped composite specimens were assigned to one of three aging conditions: (1) thermocycling (5,000x, 5-55 degrees C

  17. Facile synthesis of the necklace-like graphene oxide-multi-walled carbon nanotube nanohybrid and its application in electrochemical sensing of azithromycin.

    Science.gov (United States)

    Zhang, Kaixin; Lu, Limin; Wen, Yangping; Xu, Jingkun; Duan, Xuemin; Zhang, Long; Hu, Dufen; Nie, Tao

    2013-07-17

    A novel electrochemical platform was designed for the determination of Azithromycin (Azi), a widely used macrolide antibiotic, by combining the hydrophilic properties of graphene oxide (GO) and the excellent electronic and antifouling properties of multi-walled carbon nanotubes (MWCNTs). Stable MWCNTs aqueous dispersion has been prepared using GO nano-sheets as surfactant and the obtained GO-MWCNTs nanohybrid was characterized by UV-vis spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy and electrochemical impedance spectroscopy, which confirmed that GO nano-sheets were attached onto the wall of MWCNTs to form a necklace-like structure. Electrochemical results obviously reveal that the oxidation peak currents of Azi obtained at the GC electrode modified with GO-MWCNTs hybrid are much higher than those at the MWCNTs/GC, GO/GC and bare GC electrodes. Under optimized conditions, the anodic peak current was linear to the concentration of Azi in the range from 0.1 to 10 μM with the detection limit of 0.07 μM. To further validate its possible application, the proposed method was successfully used for the determination of Azi in pharmaceutical formulations with satisfactory results. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Preparation and theophylline delivery applications of novel PMAA/MWCNT-COOH nanohybrid hydrogels.

    Science.gov (United States)

    Zhang, Chang-Hu; Luo, Yan-Ling; Chen, Ya-Shao; Wei, Qing-Bo; Fan, Li-Hua

    2009-01-01

    A series of nanohybrid hydrogels was designed and developed based on a hydrogen bond self-assembly of poly(methacrylic acid) (PMAA) networks and carboxyl-functionalized multi-walled carbon nanotubes (MWCNT-COOH). The nanohybrid hydrogels show low micropore densities and large mesh sizes with an increase in MWCNT-COOH content. Particularly, the hydrogels containing 10 wt% MWCNT-COOH was observed to collapse at pore walls because of large holes, which is believed to be responsible for high swelling. The ability of the MWCNT-COOH to self-associate with PMAA or water molecules via hydrogen-bonding interactions and an additional electrostatic repulsion govern both pH response of the network and drug release. Increasing pH values causes equilibrium swelling ratios and accumulative release to be elevated. On the other hand, modified mechanical behavior can be obtained under a low content of the MWCNT-COOH in that the high MWCNT-COOH filling effects the formation of PMAA gel networks. Swelling and controlled release profiles of theophylline could be modulated by changing pH values, introducing the MWCNT-COOH and adjusting the proportions of the MWCNT-COOH component.

  19. Anti-inflammatory drug incorporation into polymeric nano-hybrids for local controlled release.

    Science.gov (United States)

    Sammartino, G; Marenzi, G; Tammaro, L; Bolognese, A; Calignano, A; Costantino, U; Califano, L; Mastrangelo, F; Tetè, S; Vittoria, V

    2005-01-01

    In this paper we present the formulation, preparation and characterization of new polymeric composite materials containing a nano-hybrid to be used for the controlled molecular delivery of an anti-inflammatory molecule, Diclofenac. The nano-hybrid consists of a layer of double hydroxide of an Mg-Al hydrotalcite type, in which we replaced the chloride anions present in the host galleries with Diclofenac anions by a simple ion-exchange reaction. Different amounts of the hybrid material were incorporated in polycaprolactone and processed as films of 0.15 mm thickness. The composite materials were analyzed by X-ray diffractometry, thermogravimetry and for their mechanical properties, and showed properties even better than those for the pristine polymer. The release process of the anti-inflammatory molecules was very interesting and promising for tuneable drug delivery. It consists of two stages: a first stage, very rapid as a burst in which a small fraction of the drug is released, and of a second stage that is much slower, extending for longer and longer periods. The parameters influencing the drug release were individuated and discussed.

  20. Carbon nanohybrids used as catalysts and emulsifiers for reactions in biphasic aqueous/organic systems

    Institute of Scientific and Technical Information of China (English)

    Daniel E. Resasco

    2014-01-01

    This mini-review summarizes some novel aspects of reactions conducted in aqueous/organic emul-sions stabilized by carbon nanohybrids functionalized with catalytic species. Carbon nanohybrids represent a family of solid catalysts that not only can stabilize water-oil emulsions in the same fash-ion as Pickering emulsions, but also catalyze reactions at the liquid/liquid interface. Several exam-ples are discussed in this mini-review. They include (a) aldol condensation-hydrodeoxygenation tandem reactions catalyzed by basic (MgO) and metal (Pd) catalysts, respectively; (b) Fischer-Tropsch synthesis catalyzed by carbon-nanotube-supported Ru;and (c) emulsion polymerization of styrene for the production of conductive polymer composites. Conducting these reactions in emul-sion generates important advantages, such as increased liquid/liquid interfacial area that conse-quently means faster mass transfer rates of molecules between the two phases, effective separation of products from the reaction mixture by differences in the water-oil solubility, and significant changes in product selectivity that can be adjusted by modifying the emulsion characteristics.

  1. Understanding supercapacitors based on nano-hybrid materials with interfacial conjugation

    Institute of Scientific and Technical Information of China (English)

    George Z. Chen

    2013-01-01

    The recent fast development of supercapacitors, also known scientifically as electrochemical capacitors, has benefited significantly from synthesis, characterisations and electrochemistry of nanoma-terials. Herein, the principle of supercapacitors is explained in terms of performance characteristics and charge storage mechanisms, i.e. double layer (or interfacial) capacitance and pseudo-capacitance. The semiconductor band model is applied to qualitatively account for the pseudo-capacitance in association with rectangular cyclic voltammograms (CVs) and linear galvanostatic charging and discharging plots (GCDs), aiming to differentiate supercapacitors from rechargeable batteries. The invalidity of using peak shaped CVs and non-linear GCDs for capacitance measurement is highlighted. A selective review is given to the nano-hybrid materials between carbon nanotubes and redox active materials such as electronically conducting polymers and transition metal oxides. A new concept,“interfacial conjugation”, is introduced to reflect the capacitance enhancement resulting from π-π stacking interactions at the interface between two materials with highly conjugated chemical bonds. The prospects of carbon nanotubes and graphenes for supercapacitor applications are briefly compared and discussed. Hopefully, this article can help readers to understand supercapacitors and nano-hybrid materials so that further developments in materials design and synthesis, and device engineering can be more efficient and objective.

  2. Spinel LiMn2O4 nanohybrid as high capacitance positive electrode material for supercapacitors

    Science.gov (United States)

    Wang, F. X.; Xiao, S. Y.; Zhu, Y. S.; Chang, Z.; Hu, C. L.; Wu, Y. P.; Holze, R.

    2014-01-01

    A LiMn2O4 nanohybrid consisting of nanotubes, nanorods and nanoparticles has been synthesized using α-MnO2 nanotubes from hydrothermal reaction as a precursor. It is characterized with X-ray diffraction, field emission scanning electron and transmission electron microscopy. A formation mechanism is proposed. As a positive electrode material for supercapacitors, it exhibits a high specific discharge capacitance of 415 F g-1 at 0.5 A g-1 in 0.5 mol l-1 Li2SO4 aqueous solution. Even at 10 A g-1, it still has a specific discharge capacitance of 208 F g-1. The energy density of the asymmetric supercapacitor using activated carbon as the negative electrode and LiMn2O4-nanohybrid as the positive electrode in the aqueous solution in the voltage range of 0-1.8 V presents 29.8 Wh kg-1 at power density of 90 W kg-1. In addition, the cycling behavior of the asymmetric supercapacitor is good.

  3. Remarkably enhanced photocatalytic activity by sulfur-doped titanium dioxide in nanohybrids with carbon nanotubes

    Science.gov (United States)

    Khang, Nguyen Cao; Van, Duong Quoc; Thuy, Nguyen Minh; Minh, Nguyen Van; Minh, Phan Ngoc

    2016-12-01

    TiO2 doped S nanohybrids with carbon nanotubes (CNTs) were synthesized with CNTs, thiourea and TiO2 nanoparticles. The result indicated that the TiO2 nanoparticles with about 8 nm in size are attached on the sidewall of CNTs. The nanohybrids material can absorb at longer wavelength and the absorption even covers the whole range of visible region than that only TiO2 nanoparticles. Application of the catalysts to photocatalytic degradation of methylene blue (MB) was tested under visible light irradiation. The result suggests that a high MB degradation activity of S-TiO2/CNTs due to a reduce band gap of TiO2 when S is doped, and the decrease in the possibility of electron-hole recombination by CNTs. In addition, the density functional-theory (DFT) calculations of the electronic band structures and density of states (DOS) to understand the bonding states between TiO2 and CNTs, proved that the TiO2/CNTs system is stable.

  4. Organo/layered double hydroxide nanohybrids used to remove non ionic pesticides.

    Science.gov (United States)

    Chaara, D; Bruna, F; Ulibarri, M A; Draoui, K; Barriga, C; Pavlovic, I

    2011-11-30

    The preparation and characterization of organo/layered double hydroxide nanohybrids with dodecylsulfate and sebacate as interlayer anion were studied in detail. The aim of the modification of the layered double hydroxides (LDHs) was to change the hydrophilic character of the interlayer to hydrophobic to improve the ability of the nanohybrids to adsorb non-ionic pesticides such as alachlor and metolachlor from water. Adsorption tests were conducted on organo/LDHs using variable pH values, contact times and initial pesticide concentrations (adsorption isotherms) in order to identify the optimum conditions for the intended purpose. Adsorbents and adsorption products were characterized several physicochemical techniques. The adsorption test showed that a noticeable increase of the adsorption of the non-ionic herbicides was produced. Based on the results, the organo/LDHs could be good adsorbents to remove alachlor and metolachlor from water. Different organo/LDHs complexes were prepared by a mechanical mixture and by adsorption. The results show that HTSEB-based complex displays controlled release properties that reduce metolachlor leaching in soil columns compared to a technical product and the other formulations. The release was dependent on the nature of the adsorbent used to prepare the complexes. Thus, it can be concluded that organo/LDHs might act as suitable supports for the design of pesticide slow release formulations with the aim of reducing the adverse effects derived from rapid transport losses of the chemical once applied to soils.

  5. Mg-Al layered double hydroxide-methotrexate nanohybrid drug delivery system: evaluation of efficacy.

    Science.gov (United States)

    Chakraborty, Jui; Roychowdhury, Susanta; Sengupta, Somoshree; Ghosh, Swapankumar

    2013-05-01

    Mg-Al layered double hydroxide nanoparticles were synthesized by one-pot co-precipitation method and anticancerous drug methotrexate was incorporated into it by in-situ ion exchange. The LDH-MTX nanohybrid produced moderately stable suspension in water, as predicted by zeta potential measurement. X-ray diffraction revealed that the basal spacing increased to nearly twice the same for pristine LDH on MTX intercalation. Thermogravimetric analyses confirmed an increase in thermal stability of the intercalated drug in the LDH framework. A striking enhancement in efficacy/sensitivity of MTX on the HCT-116 cells was obtained when intercalated within the LDH layers, as revealed by the attainment of half maximal inhibitory concentration of LDH-MTX nanohybrid by 48 h, whereas, bare MTX required 72 h for the same. The MTX release from MgAl-LDH-MTX hybrids in phosphate buffer saline at pH7.4 followed a relatively slow, first order kinetics and was complete within 8 days following diffusion and crystal dissolution mechanism.

  6. Phosphorescent quantum dots/ethidium bromide nanohybrids based on photoinduced electron transfer for DNA detection

    Science.gov (United States)

    Bi, Lin; Yu, Yuan-Hua

    2015-04-01

    Mercaptopropionic acid-capped Mn-doped ZnS quantum dots/ethidium bromide (EB) nanohybrids were constructed for photoinduced electron transfer (PIET) and then used as a room-temperature phosphorescence (RTP) probe for DNA detection. EB could quench the RTP of Mn-doped ZnS QDs by PIET, thereby forming Mn-doped ZnS QDs/EB nanohybrids and storing RTP. Meanwhile, EB could be inserted into DNA and EB could be competitively desorbed from the surface of Mn-doped ZnS QDs by DNA, thereby releasing the RTP of Mn-doped ZnS QDs. Based on this mechanism, a RTP sensor for DNA detection was developed. Under optimal conditions, the detection limit for DNA was 0.045 mg L-1, the relative standard deviation was 1.7%, and the method linear ranged from 0.2 to 20 mg L-1. The proposed method was applied to biological fluids, in which satisfactory results were obtained.

  7. Effect of different polishing systems on the surface roughness of nano-hybrid composites

    Directory of Open Access Journals (Sweden)

    Brijesh Patel

    2016-01-01

    Full Text Available Objective: The study aimed to investigate the influence of different polishing systems on the surface roughness of nano-hybrid composite resins. Background: Different shapes of polishing systems are available according to the site of work. To minimize variability, a new system with single shape is developed that can be utilized in both anterior as well as posterior teeth. Materials and Methods: Seventy composite discs were fabricated using Teflon well (10 mm × 3 mm. Two main group of nano-hybrid composite Group I - Filtek Z350 and Group II - Tetric N-Ceram were used (n = 35 for each group. Both groups were further divided into four subgroups. Subgroup a - OneGloss (n = 10, Subgroup b - PoGo (n = 10, Subgroup c - Sof-Lex spiral (n = 10, Subgroup d - Mylar strip (control, n = 5. Samples were polished according to the manufacturer′s recommendations. Surface roughness test was performed using contact profilometer. The obtained data were analyzed using the one-way analysis of variance test. Result: Tetric N-Ceram produced smoother surfaces than Filtek Z350 (P < 0.05. Mylar strip and "PoGo" created equally smooth surfaces, while significantly rougher surfaces were obtained after applications of "Sof-Lex spiral" and "OneGloss" (P < 0.05. Conclusion: Polishing ability of Tetric N-Ceram is better than Filtek Z350 XT. "PoGo" seems to be a better polishing system than "OneGloss" and "Sof-Lex Spiral."

  8. Geometry in Biomimetic Network: Double Gyroid to Pseudo-Single Gyroid in Nanohybrid Materials

    Science.gov (United States)

    Hsueh, Han-Yu; Ho, Rong-Ming; Hung, Yu-Chueh; Ling, Yi-Chun; Hasegawa, Hirokazu

    2013-03-01

    Biological systems have developed delicately arranged micro- and architectures to produce striking optical effects since millions of years ago. Inspired by the textures of butterfly wings with single gyroid (SG) structure, herein, we aim to fabricate biocompatible and robust materials with SG-like structure in nanometer size so as to give new materials with unprecedented optical properties for applications. Biommicking from the biological photonic structures of butterfly wings, a double gyroid (DG) structure in nanometer size is obtained from the self-assembly of polystyrene-b-poly(L-lactide) (PS-PLLA). To acquire robust backbone networks, inorganic networks in polymer matrix are fabricated by using the hydrolyzed PS-PLLA with DG structure as a template for sol-gel reaction. Owing to the soft polymer matrix, two co-continuous inorganic networks embedded in the polymer matrix can be rearranged by thermal annealing at temperature above the glass transition of the polymer. Consequently, the rearrangement of these inorganic networks leads the formation of SG-like structure possessing unique nanohybrids with ordered texture. This unique nanomaterials with SG-like structure is referred as a pseudo-SG (p-SG) nanohybrids.

  9. Inhibition of Multimolecular RNA-Protein Interactions Using Multitarget-Directed Nanohybrid System.

    Science.gov (United States)

    Jeong, Woo-Jin; Kye, Mahnseok; Han, So-Hee; Choi, Jun Shik; Lim, Yong-Beom

    2017-04-05

    Multitarget-directed ligands (MTDLs) are hybrid ligands obtained by covalently linking active pharmacophores that can act on different targets. We envision that the concept of MTDLs can also be applied to supramolecular bioinorganic nanohybrid systems. Here, we report the inhibition of multimolecular RNA-protein complexes using multitarget-directed peptide-carbon nanotube hybrids (SPCHs). One of the most well-characterized and important RNA-protein interactions, a Rev-response element (RRE) RNA:Rev protein:Crm1 protein interaction system in human immunodeficiency virus type-1, was used as a model of multimolecular RNA-protein interactions. Although all previous studies have targeted only one of the interaction interfaces, that is, either the RRE:Rev interface or the RRE-Rev complex:Crm1 interface, we here have developed multitarget-directed SPCHs that could target both interfaces because the supramolecular nanosystem could be best suited for inhibiting multimolecular RNA-protein complexes that are characterized by large and complex molecular interfaces. The results showed that the single target-directed SPCHs were inhibitory to the single interface comprised only of RNA and protein in vitro, whereas multitarget-directed SPCHs were inhibitory to the multimolecular RNA-protein interfaces both in vitro and in cellulo. The MTDL nanohybrids represent a novel nanotherapeutic system that could be used to treat complex disease targets.

  10. Synthesis and characterization of MnS2/reduced graphene oxide nanohybrids for with photocatalytic and antibacterial activity.

    Science.gov (United States)

    Fakhri, Ali; Kahi, Delaram Salehpour

    2017-01-01

    A facile one-step hydrothermal route was developed here to prepare MnS2/reduced graphene oxide nanohybrids. The crystal morphologies could be controlled by adjusting the solvent, surfactant, and pH of the precursor solution. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV-Vis absorption spectra, and photoluminescence spectra (PL), were used to characterize the structures of the samples were used to characterize the structures of the samples, and the specific surface area was determined using the Brunauer-Emmett-Teller (BET) method. The thickness of the MnS2 nanoparticles and MnS2/reduced graphene oxide nanohybrids were measured to be about 20 and 5nm, respectively. The total pore volume and specific surface area were 0.540 and 1.173cm(3)g(-1) and 45.91 and 98.23m(2)g(-1) for pure MnS2 and MnS2/r-GO hybrids, respectively. Carbophenothion as an insecticide photodegradation was used to estimate the photocatalytic activity of the MnS2/reduced graphene oxide nanohybrids morphologies under UV light. The Carbophenothion hardly decomposed during photolysis over a period of 45min. The rate constant, k value, for the photocatalysis of Carbophenothion by MnS2/reduced graphene oxide nanohybrids under UV light radiation is 0.134min(-1). The antibacterial properties of the nanohybrids were evaluated by determining their minimum inhibitory and bactericidal concentrations (MIC and MBC), using a broth microdilution assay for Escherichia coli (E. coli) bacteria. The MIC and MBC values are 4.0 and 32.0μg/mL. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Large pore volume mesoporous copper particles and scaffold microporous carbon material obtained from an inorganic-organic nanohybrid material, copper-succinate-layered hydroxide.

    Science.gov (United States)

    Ghotbi, Mohammad Yeganeh; Bagheri, Narjes; Sadrnezhaad, S K

    2011-10-01

    Copper-succinate-layered hydroxide (CSLH), a new nanohybrid material, was synthesized as an inorganic-organic nanohybrid, in which organic moiety was intercalated between the layers of a single cation layered material, copper hydroxide nitrate. Microporous scaffold carbon material was obtained by thermal decomposition of the nanohybrid at 500 °C under argon atmosphere followed by acid washing process. Furthermore, the heat-treated product of the nanohybrid at 600 °C was ultrafine mesoporous metallic copper particles. The results of this study confirmed the great potential of CSLH to produce the carbon material with large surface area (580 m(2)/g) and high pore volume copper powder (2.04 cm(3)/g).

  12. Drug delivery system for an anticancer agent, chlorogenate-Zn/Al-layered double hydroxide nanohybrid synthesised using direct co-precipitation and ion exchange methods

    Energy Technology Data Exchange (ETDEWEB)

    Barahuie, Farahnaz [Materials Synthesis and Characterization Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Hussein, Mohd Zobir, E-mail: mzobir@putra.upm.edu.my [Materials Synthesis and Characterization Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Arulselvan, Palanisamy [Laboratory of Vaccines and Immunotherapeutics, Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Fakurazi, Sharida [Laboratory of Vaccines and Immunotherapeutics, Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Department of Human Anatomy, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Zainal, Zulkarnain [Materials Synthesis and Characterization Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia)

    2014-09-15

    A nano-structured drug-inorganic clay hybrid involving an active anticancer compound, which is chlorogenic acid (CA) intercalated into Zn/Al-layered double hydroxide, has been assembled via ion-exchange and co-precipitation methods to form a nanohybrid CZAE (a chlorogenic acid-Zn/Al nanohybrid synthesised using an ion-exchange method) and CZAC (a chlorogenic acid-Zn/Al nanohybrid synthesised using a direct method), respectively. The X-ray diffraction (XRD) results confirmed that the CA-LDH had a hybrid structure in which the anionic chlorogenate is arranged between the interlayers as a horizontal monolayer at 90 and 20° angles from the x axis for CZAE and CZAC, respectively. Both nanohybrids have the properties of mesoporous materials. The high loading percentage of chlorogenic acid (approximately 43.2% for CZAE and 45.3% for CZAC) with basal spacings of 11.7 and 12.6 Å for CZAE and CZAC, respectively, corroborates the successful intercalation of chlorogenic acid into the interlayer gallery of layered double hydroxides. Free chlorogenic acid and the synthesised nanocomposites (CZAE, CZAC) were assessed for their cytotoxicity against various cancer cells. The Fourier transform infrared data supported the formation of both nanohybrids, and a thermal analysis showed that the nanohybrids are more thermally stable than their counterparts. The chlorogenate shows a sustained release, and the release rate of chlorogenate from CZAE and CZAC nanohybrids at pH 7.4 is remarkably lower than that at pH 4.8 due to their different release mechanisms. The release rate of chlorogenate from both nanohybrids can be described as pseudo-second order. The present investigation revealed the potential of the nanohybrids to enhance the in vitro anti-tumour effect of chlorogenic acid in liver and lung cancer cells in vitro. - Highlights: • We intercalated chlorogenic into Zn/Al-layered double hydroxide by ion-exchange and coprecipitation methods. • The two methods gave nanocomposites

  13. Preparation and characterization of an anti-inflammatory agent based on a zinc-layered hydroxide-salicylate nanohybrid and its effect on viability of Vero-3 cells

    Directory of Open Access Journals (Sweden)

    Ramli M

    2013-01-01

    Full Text Available Munirah Ramli,1,2 Mohd Zobir Hussein,1,3 Khatijah Yusoff41Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, Serdang, Selangor, 2Department of Industrial Biotechnology, Faculty of Biosciences and Bioengineering, Universiti Teknologi Malaysia, Skudai, Johor, 3Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor, 4Department of Microbiology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Selangor, MalaysiaAbstract: A new organic-inorganic nanohybrid based on zinc-layered hydroxide intercalated with an anti-inflammatory agent was synthesized through direct reaction of salicylic acid at various concentrations with commercially available zinc oxide. The basal spacing of the pure phase nanohybrid was 15.73 Å, with the salicylate anions arranged in a monolayer form and an angle of 57 degrees between the zinc-layered hydroxide interlayers. Fourier transform infrared study further confirmed intercalation of salicylate into the interlayers of zinc-layered hydroxide. The loading of salicylate in the nanohybrid was estimated to be around 29.66%, and the nanohybrid exhibited the properties of a mesoporous-type material, with greatly enhanced thermal stability of the salicylate compared with its free counterpart. In vitro cytotoxicity assay revealed that free salicylic acid, pure zinc oxide, and the nanohybrid have a mild effect on viability of African green monkey kidney (Vero-3 cells.Keywords: anti-inflammatory, salicylic acid, zinc-layered hydroxide, zinc oxide, nanohybrid, cytotoxicity

  14. Low-temperature solution-processable Ni(OH)2 ultrathin nanosheet/N-graphene nanohybrids for high-performance supercapacitor electrodes.

    Science.gov (United States)

    Chang, Haixin; Kang, Jianli; Chen, Luyang; Wang, Junqiang; Ohmura, Kazuyo; Chen, Na; Fujita, Takeshi; Wu, Hongkai; Chen, Mingwei

    2014-06-07

    A novel and facile strategy is developed to fabricate highly nitrogen-doped graphene (N-graphene) based layered, quasi-two-dimensional nanohybrids with ultrathin nanosheet nanocrystals using a low-temperature, solution processing method for high-performance supercapacitor electrodes. High N doping can be achieved together with one of the lowest oxygen content in chemically reduced graphene and related nanohybrids at low temperature by large-scale residue defects of chemically reduced graphene. The layered, quasi-two-dimensional nanohybrids or heterostructures of ultrathin Ni(OH)2 nanosheet nanocrystal/N-graphene can be applied in supercapacitor electrodes with ultrahigh capacitances of ∼1551 F g(-1), excellent rate performance in the scan measurements (from 2 mV s(-1) to 100 mV s(-1)) and in the discharge tests (from 1.5 A g(-1) to 30 A g(-1)) and good cycling stability. Moreover, the capacitance of Ni(OH)2 nanosheet/N-graphene nanohybrids is two and one orders of magnitude higher than that for pure nanocrystals and for the physical mixture of nanocrystal/N-graphene, respectively. Electron transfer in supercapacitor electrodes based on nanohybrids is over 100 times faster than that in electrodes from pure nanocrystals and several tens of times faster than that in electrodes from nanocrystal/N-graphene mixtures. This low-temperature method may provide a low-cost, solution-processable and easily scalable route to high-performance graphene nanohybrid electrodes for energy applications.

  15. The Influence of Surface Polish and Beverages on the Roughness of Nanohybrid and Microhybri Resin Composites

    Directory of Open Access Journals (Sweden)

    Sadeghi M

    2016-03-01

    Full Text Available Statement of the Problem: Surface roughness is a key factor in the aesthetics of restorative dentistry as it can determine the clinical quality and success of restorative materials. The chemical process of dissolution in the presence of mechanical forces can accelerate the surface roughness of tooth-coloured restorative materials. Objectives: To determine the degree of surface roughness of a microhybrid and a nanohybrid resin composite after polishing and immersion in various solutions. Materials and Methods: Two resin composites were used : a microhybrid (Gradia direct, GC, and a nanohybrid (Ice, SDI. A total of 54 disc-shaped specimens were prepared for each composite and immersed in distilled water incubated at 37 °C for 24 hours. After 24 h, the baseline measurement for surface roughness (Ra was performed and the specimens were divided into 3 groups of 18 and tested with unpolished or after polishing with Sof-Lex disc and Enhance point systems. Specimens in each group were subdivided into 3 subgroups (n = 6 and immersed in 3 solutions (distilled water, coffee, and cola for 7 days incubated at 37 °C. After 7 days, the specimens were rinsed with tap water for 10 seconds, dried with paper towel and Ra was measured again. Two randomly selected specimens of each group were sputter coated with gold and examined using a Field-Emission Scanning Electron Microscope (SEM. Results: Gradia direct showed a greater Ra than ice in all solutions for all polishing systems (p < 0.001. Specimens polished with Enhance point revealed a significantly greater roughness than Sof-Lex discs and both showed greater Ra than unpolished specimens. Specimens immersed in coffee exhibited significantly greater surface roughness than that of distilled water (p < 0.05 and cola (p < 0.001. Conclusions: Nano-hybrid composite showed a significantly smoother surface than microhybrid. Coffee exhibited the highest Ra compared to distilled water and cola. Enhance point revealed

  16. CdS-Graphene Nanohybrids: Facile Ultrasonic Synthesis and Photocatalytic Performance%CdS/石墨烯纳米复合材料的超声化学法制备及光催化性能

    Institute of Scientific and Technical Information of China (English)

    周田; 陈炳地; 姚爱华; 王德平

    2013-01-01

    CdS/graphene nanohybrids were synthesized by a facile ultrasonic method. Their morphology, microstructure, optical property and photocatalytic activity under visible light were characterized by TEM、FE-SEM、XRD、UV-Vis and PL. The results show that ultrasonic condition enables small-sized, well-dispersed CdS nanoparticles to anchor firmly on the graphene sheets. Due to the good absorption property and the reduction of electron-hole pair recombination in CdS, the CdS/graphene nanohybrids exhibit high photo-stability and excellent photocatalytic performance for the degradation of methyl orange with a maximum removal rate of more than 90% in 30 min under visible light irradiation, and also no detectable changes of photocatalytic performance were observed during three cycles.%采用超声化学法制备了CdS/石墨烯纳米复合材料,通过TEM、FE-SEM、XRD、UV-Vis等对该复合材料的结构、形貌及其光学和可见光光催化性能进行了表征.结果表明,超声化学法不仅合成过程简单,而且石墨烯表面所负载的CdS纳米粒子尺寸小、分散性好,与石墨烯的结合牢固.由于石墨烯优异的吸附性能和对载流子的高迁移率,CdS/石墨烯纳米复合材料显示出较高的可见光光催化性和光稳定性,30 min内甲基橙的降解率即可达到90%以上,且3次重复实验过程中光催化效果接近.

  17. Effects of three surface conditioning techniques on repair bond strength of nanohybrid and nanofilled composites

    Directory of Open Access Journals (Sweden)

    Negin Nassoohi

    2015-01-01

    Full Text Available Background: Repair bond strength of different composite resins has been assessed in few studies. In addition, reports on the efficacy of surface treatments are debated. Therefore, this in vitro study was conducted to evaluate the effect of three surface treatments on two nanocomposites versus a microhybrid composite. Materials and Methods: In this experimental study, 135 composite blocks (45 specimens per composite of microhybrid (Filtek Supreme Z250, 3M ESPE, USA, nanohybrid (Filtek Supreme XT, 3M ESPE, and nanofilled (Filtek Supreme Z350, 3M ESPE were thermocycled (5000 rounds and then surface roughened (except in a control group of 9 specimens of three composite types. Each composite type was divided into three subgroups of surface treatments: (1 Bur abrading and phosphoric acid (PA etching, (2 sandblasting and PA etching, and (3 hydrofluoric etching and silane application (n = 15 × 9, complying with ISO TR11405. Composite blocks were repaired with the same composite type but of a different color. Microtensile bond strength and modes of failure were analyzed statistically using two-way analyses of variance, Tukey and Chi-square tests (α = 0.05. Results: There were significant differences between three composite resins (P < 0.0001 and treatment techniques (P < 0.0001. Their interaction was nonsignificant (P = 0.228. The difference between nanofilled and nanohybrid was not significant. However, the microhybrid composite showed a significantly higher bond strength (Tukey P < 0.05. Sandblasting was significantly superior to the other two methods, which were not different from each other. Conclusion: Within the limitations of this in vitro study, it seems that microhybrid composite might have higher repair strengths than two evaluated nanocomposites. Among the assessed preparation techniques, sandblasting followed by PA etching might produce the highest bond strength.

  18. Biocompatible magnetite/gold nanohybrid contrast agents via green chemistry for MRI and CT bioimaging.

    Science.gov (United States)

    Narayanan, Sreeja; Sathy, Binulal N; Mony, Ullas; Koyakutty, Manzoor; Nair, Shantikumar V; Menon, Deepthy

    2012-01-01

    Magnetite/gold (Fe(3)O(4)/Au) hybrid nanoparticles were synthesized from a single iron precursor (ferric chloride) through a green chemistry route using grape seed proanthocyanidin as the reducing agent. Structural and physicochemical characterization proved the nanohybrid to be crystalline, with spherical morphology and size ~35 nm. Magnetic resonance imaging and magnetization studies revealed that the Fe(3)O(4) component of the hybrid provided superparamagnetism, with dark T(2) contrast and high relaxivity (124.2 ± 3.02 mM(-1) s(-1)). Phantom computed tomographic imaging demonstrated good X-ray contrast, which can be attributed to the presence of the nanogold component in the hybrid. Considering the potential application of this bimodal nanoconstruct for stem cell tracking and imaging, we have conducted compatibility studies on human Mesenchymal Stem Cells (hMSCs), wherein cell viability, apoptosis, and intracellular reactive oxygen species (ROS) generation due to the particle-cell interaction were asessed. It was noted that the material showed good biocompatibility even for high concentrations of 500 μg/mL and up to 48 h incubation, with no apoptotic signals or ROS generation. Cellular uptake of the nanomaterial was visualized using confocal microscopy and prussian blue staining. The presence of the nanohybrids were clearly visualized in the intracytoplasmic region of the cell, which is desirable for efficient imaging of stem cells in addition to the cytocompatible nature of the hybrids. Our work is a good demonstrative example of the use of green aqueous chemistry through the employment of phytochemicals for the room temperature synthesis of complex hybrid nanomaterials with multimodal functionalities.

  19. Relative biocompatibility of micro-hybrid and nano-hybrid light-activated composite resins.

    Science.gov (United States)

    Olabisi Arigbede, Abiodun; Folasade Adeyemi, Bukola; Femi-Akinlosotu, Omowumi

    2017-01-01

    Background. In vitro studies have revealed a direct association between resin content and cytotoxicity of composite resins; however, implantation studies in this regard are sparse. This study investigates the relationship between filler content of composite resins and biocompatibility. Methods. This research employed twelve 180‒200-gr male Wistar rats, 1 nano-hybrid (Prime-Dent Inc.) and 1 micro-hybrid (Medental Inc.) composite resins containing 74% and 80‒90% filler content, respectively. The samples were assessed on the 2nd, 14th and 90th day of implantation. Four rats were allocated to each day in this experimental study. A section of 1.5mm long cured nano-hybrid and micro-hybrid materials were implanted into the right and left upper and lower limbs of the rats, respectively. Eight samples were generated on each day of observation. Inflammation was graded according to the criteria suggested by Orstavik and Major. Pearson's chi-squared test was employed to determine the relationship between the tissue responses of the two materials. Statistical significance was set at P composite resins with higher filler content elicited a significantly lower grade of inflammation irrespective of the duration (χ=20.000, df=8, P=0.010) while the composite resins with lower filler content elicited a significantly lower inflammatory response on the 90th day (χ=4.000, df=1, P=0.046). Conclusion. The composite resins with higher filler content generally elicited significantly lower grades of inflammation, and the composite resins with lower filler content exhibited significantly lower inflammatory response on the 90th day of implantation.

  20. Hydrothermal synthesis of silico-manganese nanohybrid for Cu(II) adsorption from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Qiufeng, E-mail: zhuqiufeng@th.btbu.edu.cn; Wang, Liting; An, Zehuan; Ye, Hong; Feng, Xudong

    2016-05-15

    Highlights: • A novel silico-manganese nanohybrid adsorbent (SMNA) was synthesized by a hydrothermal method. • The adsorption capacities of the SMNA for Cu(II) are lower pH dependency. • As-adsorbents are very efficient at low metal concentration and substantial amounts of Cu(II) can be removed from aqueous solution. - Abstract: A novel silico-manganese nanohybrid adsorbent (SMNA) was synthesized by a facile hydrothermal method, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR) and zeta potential measurement. The adsorption of Cu(II) ions from aqueous solution on the SMNA was investigated with variations in contact time, pH and initial Cu(II) concentration. The results showed that hydrothermal method would generate nanowire/nanorod incomplete crystallite (δ-MnO{sub 2}) adsorbent. The adsorption of Cu(II) onto SMNA increased sharply within 25 min and reached equilibrium gradually. The maximum adsorption capacities of SMNA for Cu(II) were ∼40–88 mg g{sup −1}, which was lower than δ-MnO{sub 2} (92.42 mg g{sup −1}) but had a lower pH dependency. As compared with δ-MnO{sub 2}, higher adsorption capacities of SMNA (7.5–15 wt% of silica doping amount) for Cu(II) could be observed when pH of the aqueous solution was low (<4). The pseudo-second-order model was the best choice to describe the adsorption behavior of Cu(II) onto SMNA, suggesting that the removal of Cu(II) by the as-prepared adsorbents was dominated by migration of Cu(II). The possibility of Cu(II) recovery was also investigated and it revealed that SMNA was a promising recyclable adsorbent for removal of heavy metal ions in water and wastewater treatment.

  1. Effects of three surface conditioning techniques on repair bond strength of nanohybrid and nanofilled composites

    Science.gov (United States)

    Nassoohi, Negin; Kazemi, Haleh; Sadaghiani, Morad; Mansouri, Mona; Rakhshan, Vahid

    2015-01-01

    Background: Repair bond strength of different composite resins has been assessed in few studies. In addition, reports on the efficacy of surface treatments are debated. Therefore, this in vitro study was conducted to evaluate the effect of three surface treatments on two nanocomposites versus a microhybrid composite. Materials and Methods: In this experimental study, 135 composite blocks (45 specimens per composite) of microhybrid (Filtek Supreme Z250, 3M ESPE, USA), nanohybrid (Filtek Supreme XT, 3M ESPE), and nanofilled (Filtek Supreme Z350, 3M ESPE) were thermocycled (5000 rounds) and then surface roughened (except in a control group of 9 specimens of three composite types). Each composite type was divided into three subgroups of surface treatments: (1) Bur abrading and phosphoric acid (PA) etching, (2) sandblasting and PA etching, and (3) hydrofluoric etching and silane application (n = 15 × 9, complying with ISO TR11405). Composite blocks were repaired with the same composite type but of a different color. Microtensile bond strength and modes of failure were analyzed statistically using two-way analyses of variance, Tukey and Chi-square tests (α = 0.05). Results: There were significant differences between three composite resins (P < 0.0001) and treatment techniques (P < 0.0001). Their interaction was nonsignificant (P = 0.228). The difference between nanofilled and nanohybrid was not significant. However, the microhybrid composite showed a significantly higher bond strength (Tukey P < 0.05). Sandblasting was significantly superior to the other two methods, which were not different from each other. Conclusion: Within the limitations of this in vitro study, it seems that microhybrid composite might have higher repair strengths than two evaluated nanocomposites. Among the assessed preparation techniques, sandblasting followed by PA etching might produce the highest bond strength. PMID:26759592

  2. EFFECT OF SURFACE SEALING ON STAIN RESISTANCE OF A NANO-HYBRID RESIN COMPOSITE*

    Directory of Open Access Journals (Sweden)

    Günçe SAYGI

    2015-04-01

    Full Text Available Purpose: This study investigated the influence of sealant application on stain resistance of a nanohybrid resin composite compared to the efficacy of a bonding agent used as a surface sealant on prolonging color stability of the resin composite. Materials and Methods: 28 disc-shaped materials were prepared from a nano-hybrid resin composite Filtek Z550 and assigned to four groups: G1K: nonsealed; G2:Adper Single Bond; G3: Fortify ; G4: Biscover LV. After 24 h storage in distilled water at 37˚C, all specimens were subjected to thermocycling and immersed into coffee solution. Color measurements were performed using spectrophotometer (VITA Easyshade; Vident according to CIEL*a*b* system. Results: Color change values were significantly different among the groups in each evaluation period except for after thermocycling (p<0.05. For 7 days evaluation period, the difference between G3 and G4 group was statistically significant while G4 exhibited statistically significant differences (p<0.05 and p<0.0001 respectively compared to control (G1 in 14 day whereas no significant difference was found between GI and GII in 28-day evaluation period. However, ΔE values of sealed specimens (GIII, GIV differed significantly from non-sealed (GI specimens after 28 days of immersion in coffee solution (p<0.05 and p<0.0001 respectively. Conclusion: It may be concluded that using a bonding agent as a surface sealant does not increase stain resistance of resin composites of the sealants evaluated. Biscover LV showed the highest efficacy to prolong color stability of the resin composite.

  3. Clay-chitosan-gold nanoparticle nanohybrid: Preparation and application for assembly and direct electrochemistry of myoglobin

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Xiaojuan; Mai Zhibin [School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Kang Xinhuang [College of Science, Guangdong Ocean University, Zhanjiang 524088 (China); Dai Zong [School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Zou Xiaoyong [School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)], E-mail: ceszxy@mail.sysu.edu.cn

    2008-05-30

    A biocompatible nanohybrid material (clay/AuCS) based on clay, chitosan and gold nanoparticles was explored. The material could provide a favorable microenvironment for proteins to realize the direct electron transfer on glassy carbon electrodes (GCE). Myoglobin (Mb), as a model protein to investigate the nanohybrid, was immobilized between the clay/AuCS film and another clay layer. Mb in the system exhibited a pair of well-defined and quasi-reversible redox peaks at -0.160 V (vs. saturated Ag/AgCl electrode) in 0.1 M PBS (pH 7.0), corresponding to its heme Fe{sup III}/Fe{sup II} redox couples. UV-vis spectrum suggested that Mb retained its native conformation in the system. Basal plane spacing of clay obtained by X-ray diffraction (XRD) indicated that there was an intercalation-exfoliation-restacking process among Mb, AuCS and clay during the modified film drying. Excellent biocatalytic activity of Mb in the modified system was exemplified by the reduction of hydrogen peroxide and nitrite. The linear range of H{sub 2}O{sub 2} determination was from 3.9 x 10{sup -5} to 3.0 x 10{sup -3} M with a detection limit of 7.5 {mu}M based on the signal to noise ratio of 3. The kinetic parameters such as {alpha} (charge transfer coefficient), k{sub s} (electron transfer rate constant) and K{sub m} (Michaelis-Menten constant) were evaluated to be 0.55, 2.66 {+-} 0.15 s{sup -1} and 5.10 mM, respectively.

  4. Dispersion Forces

    CERN Document Server

    Buhmann, Stefan Yoshi

    2012-01-01

    In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...

  5. Synthesis and characterization of model silica-gold core-shell nanohybrid systems to demonstrate plasmonic enhancement of fluorescence

    Science.gov (United States)

    Roy, Shibsekhar; Dixit, Chandra K.; Woolley, Robert; O'Kennedy, Richard; McDonagh, Colette

    2012-08-01

    In this work, gold-silica plasmonic nanohybrids have been synthesized as model systems which enable tuning of dye fluorescence enhancement/quenching interactions. For each system, a dye-doped silica core is surrounded by a 15 nm spacer region, which in turn is surrounded by gold nanoparticles (GNPs). The GNPs are either covalently conjugated via mercapto silanization to the spacer or encapsulated in a separate external silica shell. The intermediate spacer region can be either dye doped or left undoped to enable quenching and plasmonic enhancement effects respectively. The study indicates that there is a larger enhancement effect when GNPs are encapsulated in the outer shell compared to the system of external conjugation. This is due to the environmental shielding provided by shell encapsulation compared to the exposure of the GNPs to the solvent environment for the externally conjugated system. The fluorescence signal enhancement of the nanohybrid systems was evaluated using a standard HRP-anti-HRP fluorescence based assay platform.

  6. Deposition of Layer-by-layer Inorganic-organic Nano-hybrid Ultrathin Films onto SBA-15

    Institute of Scientific and Technical Information of China (English)

    Han Ming DING; Li Ping WANG; Yong Kui SHAN; Ming Yuan HE

    2003-01-01

    Deposition of inorganic-organic nano-hybrid ultrathin films onto mesoporous silicate materials has been proven possible by using layer-by-layer assembly method. In combination with sol-gel method, titania, subsequently dye molecules (or polymer) were successfully fabricated onto the inner wall of SBA-15. Their structures were preliminarily characterized by FTIR and solid-state UV-Vis spectroscopy, thermal analysis, and BET surface area measurements, respectively.

  7. Enhanced microwave absorption properties and mechanism of core/shell structured magnetic nanoparticles/carbon-based nanohybrids

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Xiaosi, E-mail: sci.xsqi@gzu.edu.cn [Physics Department, Guizhou University, Guiyang 550025 (China); Nanjing National Laboratory of Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Hu, Qi; Xu, Jianle; Xie, Ren; Bai, Zhongchen; Jiang, Yang; Qin, Shuijie [Physics Department, Guizhou University, Guiyang 550025 (China); Zhong, Wei, E-mail: wzhong@nju.edu.cn [Nanjing National Laboratory of Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China); Du, Youwei [Nanjing National Laboratory of Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Nanjing University, Nanjing 210093 (China)

    2016-09-15

    Graphical abstract: In the article, core/shell Fe{sub 3}O{sub 4}/C, Fe/helical carbon nanotubes were synthesized selectively. The results indicated that the optimum reflection loss (RL) could reach −47.1 dB at 17.39 GHz with a matching thickness of 1.39 mm. The absorption bandwidth with the RL below −20 dB was up to 11.59 GHz. Moreover, based on the obtained results, the possibly enhanced microwave absorption mechanisms were also discussed in detail. - Highlights: • An efficient scheme was designed to synthesize core/shell magnetic nanoparticles/carbon-based hybrids. • By controlling the temperature, different categories of core/shell nanohybrids were synthesized. • The obtained Fe/CNT hybrid exhibits enhanced microwave absorption property. • Enhanced microwave absorbing mechanism was discussed in detail. - Abstract: An efficient scheme was designed to selectively synthesize different categories of core/shell structured magnetic nanoparticles/carbon-based nanohybrids such as Fe{sub 3}O{sub 4}/C and Fe/helical carbon nanotubes (HCNTs) through the decomposition of acetylene directly over Fe{sub 2}O{sub 3} nanotubes by controlling the pyrolysis temperature. The measured electromagnetic parameters indicated that the Fe/HCNT nanohybrids exhibited enhanced microwave absorption properties, which may be related to their special structures. The optimum reflection loss (RL) could reach −47.1 dB at 17.39 GHz with a matching thickness of 1.39 mm. The absorption bandwidth with the RL values below −20 dB was up to 11.59 GHz. Moreover, based on the obtained results, the possible enhanced EM absorption mechanisms were also discussed in detail. The results show excellent microwave absorption materials that are lightweight, have strong absorption and a wide absorption frequency band may be realized in these nanohybrids.

  8. Facile synthesis and enhanced photocatalytic activity of single-crystalline nanohybrids for the removal of organic pollutants

    Science.gov (United States)

    Pervaiz, Erum; Liu, Honghong; Yang, Minghui

    2017-03-01

    This study focused on the synthesis of α-MoO3/rGO (rGO, reduced graphene oxide). One-dimensional nanohybrids under mild conditions and a low temperature wet chemical route produced highly pure single-crystalline orthorhombic α-MoO3 on GO sheets. Four nanohybrids, labeled as GMO-0, GMO-1, GMO-2 and GMO-3, were synthesized with different mass chargings of GO (0 mg, 40 mg, 60 mg and 100 mg, respectively). The photocatalytic performance for reduction of organic pollutants was analyzed. The presence of different amounts of GO in the prepared metal oxide hybrids altered the performance of the material as elaborated by the Brunauer-Emmett-Teller surface area, UV-visible diffuse reflectance spectra and the resulting reduction of organic dyes depicted by photocatalytic experiments. GO as a support material and active co-catalyst decreased the band gap of α-MoO3 (2.82 eV) to lower values (2.51 eV), rendering the prepared hybrids usable for visible-light-induced photocatalysis. The large specific surface area (72 m2 g-1) of the mesoporous α-MoO3/rGO nanohybrid made it an efficient photocatalyst for the elimination of azo dyes. Very fast reduction (100%) of Rhodamine B was observed in a few minutes, while Congo Red was degraded by 76% in 10 min, leading to the formation of stable intermediates that were completely neutralized in 12-14 h under light irradiation. The amount of GO loaded in the samples was limited to a point to achieve better results. After that, increasing the amount of GO decreased the extent of degradation due to the presence of a higher electron acceptor. Photocatalytic experiments revealed the synergistic effect, high selectivity of the prepared nanohybrids and degradation of azo dyes. The kinetics of the degradation reaction were studied and found to follow a pseudo first-order reaction.

  9. Improving photocurrent generation: supramolecularly and covalently functionalized single-wall carbon nanotubes-polymer/porphyrin donor-acceptor nanohybrids.

    Science.gov (United States)

    Rahman, G M Aminur; Troeger, Anna; Sgobba, Vito; Guldi, Dirk M; Jux, Norbert; Tchoul, Maxim N; Ford, Warren T; Mateo-Alonso, Aurelio; Prato, Maurizio

    2008-01-01

    Novel nanohybrids based on covalently and noncovalently functionalized single-wall carbon nanotubes (SWNTs) have been prepared and assembled for the construction of photoactive electrodes. Polymer-grafted SWNTs were synthesized by free-radical polymerization of (vinylbenzyl)trimethylammonium chloride. Poly[(vinylbenzyl)trimethylammonium chloride] (PVBTAn+) was also noncovalently wrapped around SWNTs to form stable, positively charged SWNT/PVBTAn+ suspensions in water. Versatile donor-acceptor nanohybrids were prepared by using the electrostatic/van der Waals interactions between covalent SWNT-PVBTAn+ and/or noncovalent SWNT/PVBTAn+ and porphyrins (H2P8- and/or ZnP8-). Several spectroscopic, microscopic, transient, and photoelectrochemical measurements were taken to characterize the resulting supramolecular complexes. Photoexcitation of the nanohybrids afforded long-lived radical ion pairs with lifetimes as long as 2.2 micros. In the final part, photoactive electrodes were constructed by using a layer-by-layer technique on an indium tin oxide covered glass support. Photocurrent measurements gave remarkable internal photon-to-current efficiencies of 3.81 and 9.90 % for the covalent ZnP8-/SWNT-PVBTAn+ and noncovalent ZnP8-/SWNT/PVBTAn+ complex, respectively, when a potential of 0.5 V was applied.

  10. Photocatalytic degradation of organic contaminants under solar light using carbon dot/titanium dioxide nanohybrid, obtained through a facile approach

    Science.gov (United States)

    Hazarika, Deepshikha; Karak, Niranjan

    2016-07-01

    In the present study, a novel, simple and green method was developed to synthesize highly luminescent nitrogen containing carbon dot (CD) using carbon resources like bio-based citric acid and glycerol in the presence of cost free cow urine. The as-synthesized CD showed exciting wavelength dependent down- and up-conversion flourescence properties. To utilize the advantage of up-conversion flourescence, a nanohybrid (CD@TiO2) was synthesized from the above carbon resources and titanium butoxide through a facile one pot single step hydrothermal protocol. Nanomaterials like bare TiO2 and nanohybrid of TiO2 in presence of CD (CD/TiO2) were also synthesized for comparison purpose. The optical properties and structural characteristics of the prepared CD, bare TiO2, CD@TiO2 and CD/TiO2 were examined by Fourier transform infrared (FTIR), UV-vis and fluorescence spectroscopic, scanning electron microscopic (SEM), transmission electron microscopic (TEM) and X-ray diffraction (XRD) studies. The elemental compositions of bare CD and CD@TiO2 nanohybrid were obtained from EDX analyses. The poor crystalline nature and narrow distribution of spherical CD and anatase form of TiO2 were confirmed from XRD and TEM studies. Amongst the studied nanomaterials, CD@TiO2 exhibited the most promising photocatalytic degradation of organic pollutants like benzene and phenol as well as an anthrogenic pesticide under sunlight.

  11. Integrating nanohybrid membranes of reduced graphene oxide: chitosan: silica sol gel with fiber optic SPR for caffeine detection.

    Science.gov (United States)

    Kant, Ravi; Tabassum, Rana; Gupta, Banshi D

    2017-05-12

    Caffeine is the most popular psychoactive drug consumed in the world for improving alertness and enhancing wakefulness. However, caffeine consumption beyond limits can result in lot of physiological complications in human beings. In this work, we report a novel detection scheme for caffeine integrating nanohybrid membranes of reduced graphene oxide (rGO) in chitosan modified silica sol gel (rGO: chitosan: silica sol gel) with fiber optic surface plasmon resonance. The chemically synthesized nanohybrid membrane forming the sensing route has been dip coated over silver coated unclad central portion of an optical fiber. The sensor works on the mechanism of modification of dielectric function of sensing layer on exposure to analyte solution which is manifested in terms of red shift in resonance wavelength. The concentration of rGO in polymer network of chitosan and silica sol gel and dipping time of the silver coated probe in the solution of nanohybrid membrane have been optimized to extricate the supreme performance of the sensor. The optimized sensing probe possesses a reasonably good sensitivity and follows an exponentially declining trend within the entire investigating range of caffeine concentration. The sensor boasts of an unparalleled limit of detection value of 1.994 nM and works well in concentration range of 0-500 nM with a response time of 16 s. The impeccable sensor methodology adopted in this work combining fiber optic SPR with nanotechnology furnishes a novel perspective for caffeine determination in commercial foodstuffs and biological fluids.

  12. Interstratified nanohybrid assembled by alternating cationic layered double hydroxide nanosheets and anionic layered titanate nanosheets with superior photocatalytic activity.

    Science.gov (United States)

    Lin, Bizhou; Sun, Ping; Zhou, Yi; Jiang, Shaofeng; Gao, Bifen; Chen, Yilin

    2014-09-15

    Oppositely charged 2D inorganic nanosheets of ZnAl-layered double hydroxide and layered titanate were successfully assembled into an interstratified nanohybrid through simply mixing the corresponding nanosheet suspensions. Powder X-ray diffraction and high-resolution transmission electron microscope clearly revealed that the component nanosheets in the as-obtained nanohybrid ZnAl-Ti3O7 retain the 2D sheet skeletons of the pristine materials and that the two kinds of nanosheets are well arranged in a layer-by-layer alternating fashion with a basal spacing of about 1.3 nm, coincident with the thickness summation of the two component nanosheets. The effective interfacial heterojunction between them and the high specific surface area resulted in that the nanohybrid exhibits a superior photocatalytic activity in the degradation of methylene blue with a reaction constant k of 2.81 × 10(-2)min(-1), which is about 9 and 4 times higher than its precursors H2Ti3O7 and ZnAl-LDH, respectively. Based on UV-vis, XPS and photoelectrochemical measurements, a proposed photoexcitation model was provided to understand its photocatalytic behavior.

  13. Integrating nanohybrid membranes of reduced graphene oxide: chitosan: silica sol gel with fiber optic SPR for caffeine detection

    Science.gov (United States)

    Kant, Ravi; Tabassum, Rana; Gupta, Banshi D.

    2017-05-01

    Caffeine is the most popular psychoactive drug consumed in the world for improving alertness and enhancing wakefulness. However, caffeine consumption beyond limits can result in lot of physiological complications in human beings. In this work, we report a novel detection scheme for caffeine integrating nanohybrid membranes of reduced graphene oxide (rGO) in chitosan modified silica sol gel (rGO: chitosan: silica sol gel) with fiber optic surface plasmon resonance. The chemically synthesized nanohybrid membrane forming the sensing route has been dip coated over silver coated unclad central portion of an optical fiber. The sensor works on the mechanism of modification of dielectric function of sensing layer on exposure to analyte solution which is manifested in terms of red shift in resonance wavelength. The concentration of rGO in polymer network of chitosan and silica sol gel and dipping time of the silver coated probe in the solution of nanohybrid membrane have been optimized to extricate the supreme performance of the sensor. The optimized sensing probe possesses a reasonably good sensitivity and follows an exponentially declining trend within the entire investigating range of caffeine concentration. The sensor boasts of an unparalleled limit of detection value of 1.994 nM and works well in concentration range of 0-500 nM with a response time of 16 s. The impeccable sensor methodology adopted in this work combining fiber optic SPR with nanotechnology furnishes a novel perspective for caffeine determination in commercial foodstuffs and biological fluids.

  14. Highly efficient catalytic reductive degradation of various organic dyes by Au/CeO₂-TiO₂ nano-hybrid

    Indian Academy of Sciences (India)

    PRANJAL SAIKIA; ABU T MIAH; PARTHA P DAS

    2017-01-01

    Highly improved catalytic reductive degradation of different organic dyes, in the presence of excess NaBH₄ over Au/CeO₂-TiO₂ nano-hybrid as the catalyst is reported in this study. CeO₂-TiO₂ nanocomposite was prepared by a facile co-precipitation method using ultra-high dilute aqueous solutions. Small amount of Au (only 1 wt%) was loaded onto the nanocomposite material by deposition-precipitation with urea (DPU) method to fabricate the ternary Au/CeO₂-TiO₂ nano-hybrid. The catalysts were characterized by the representative techniques like XRD, BET surface area, ICP-AES, UV-Vis diffuse reflectance spectroscopy, TEM and XPS. The Au/CeO₂-TiO₂ nano-hybrid along with NaBH₄ exhibited remarkable catalytic activities towards all the probed dyes, namely Methylene Blue, Methyl Orange, Congo Red, Rhodamine B and Malachite Green, with a degradation efficiency of ~100% in a short reaction time. The degradation reaction followed pseudo-first-order kinetics with respect to the concentration of the dye. Different parameters that affect the rate of the reaction are discussed. A plausible mechanism for methylene blue degradation has also been proposed.

  15. Photocatalytic degradation of organic contaminants under solar light using carbon dot/titanium dioxide nanohybrid, obtained through a facile approach

    Energy Technology Data Exchange (ETDEWEB)

    Hazarika, Deepshikha; Karak, Niranjan, E-mail: karakniranjan@gmail.com

    2016-07-15

    Highlights: • Nitrogen containing carbon dot and carbon dot/TiO{sub 2} nanohybrid (CD@TiO{sub 2}) are synthesized without any additional doping of passivating agent. • The photocatalytic efficacy of CD@TiO{sub 2} is found to be the best as compared to the bare TiO{sub 2}, CD and nanohybrid of TiO{sub 2} in presence of carbon dot. • Up-conversion luminescence of CD promotes the degradation activity of synthesized CD@TiO{sub 2} under visible light. • The hazardous contaminants like phenol, benzene and pesticide are efficiently degraded by CD@TiO{sub 2} under normal sunlight. - Abstract: In the present study, a novel, simple and green method was developed to synthesize highly luminescent nitrogen containing carbon dot (CD) using carbon resources like bio-based citric acid and glycerol in the presence of cost free cow urine. The as-synthesized CD showed exciting wavelength dependent down- and up-conversion flourescence properties. To utilize the advantage of up-conversion flourescence, a nanohybrid (CD@TiO{sub 2}) was synthesized from the above carbon resources and titanium butoxide through a facile one pot single step hydrothermal protocol. Nanomaterials like bare TiO{sub 2} and nanohybrid of TiO{sub 2} in presence of CD (CD/TiO{sub 2}) were also synthesized for comparison purpose. The optical properties and structural characteristics of the prepared CD, bare TiO{sub 2}, CD@TiO{sub 2} and CD/TiO{sub 2} were examined by Fourier transform infrared (FTIR), UV–vis and fluorescence spectroscopic, scanning electron microscopic (SEM), transmission electron microscopic (TEM) and X-ray diffraction (XRD) studies. The elemental compositions of bare CD and CD@TiO{sub 2} nanohybrid were obtained from EDX analyses. The poor crystalline nature and narrow distribution of spherical CD and anatase form of TiO{sub 2} were confirmed from XRD and TEM studies. Amongst the studied nanomaterials, CD@TiO{sub 2} exhibited the most promising photocatalytic degradation of organic

  16. Effect of Preheating and Precooling on the Flexural Strength and Modulus of Elasticity of Nanohybrid and Silorane-based Composite

    Directory of Open Access Journals (Sweden)

    Farahnaz Sharafeddin

    2015-09-01

    Full Text Available Statement of the Problem: Composite resin may be used in different temperatures; it is crucial to determine the effect of temperature on mechanical properties of nanohybrid and silorane-based composite. Purpose: This in vitro study compared the flexural strength and modulus of elasticity of nanohybrid and silorane-based resin composite, at 4˚C, room temperature (25˚C, and 45˚C. Materials and Method: In this experimental study, 60 specimens were prepared in a metal split mold (2×2×25mm. Two different resin composites, Filtek Z250 XT (3M/ ESPE and Filtek P90 (3M/ESPE, were evaluated. The material were inserted into split molds at room temperature, 4˚C or 45˚C and cured with LED (1200 mW/cm2 for 20 seconds in four points (n=10. Then, a three-point bending test was performed using a universal testing machine at a crosshead speed of 0.5 mm/min for measuring the flexural strength and flexural modulus of samples. The data were analyzed by the two-way ANOVA and Tukey test (p< 0.05. Results: The mean highest flexural strength was observed at 45˚C, showing statistically significant difference with flexural strength at 4˚C (p= 0.0001 and 25˚C (p= 0.003 regardless of the type of resin composite. The flexural modulus at 45˚C was highest, showing the statistically significant difference with flexural modulus at 4˚C (p= 0.0001 and 25˚C (p= 0.002. The flexural modulus was statistically different between nanohybrid and silorane-based resin composite (p= 0.01 in 25˚C and 45˚C, but there were no statistically significant differences between flexural strength of Filtek Z250 XT and Filtek P90 regardless of the temperatures (p= 0.062. Conclusion: Preheating the resin composite at 45˚C improves flexural strength and modulus of nanohybrid and silorane-based resin composite. However, flexural strength and modulus of the tested materials were not affected by precooling. The flexural modulus of nanohybrid resin composite was significantly higher than

  17. Dispersion Modeling.

    Science.gov (United States)

    Budiansky, Stephen

    1980-01-01

    This article discusses the need for more accurate and complete input data and field verification of the various models of air pollutant dispension. Consideration should be given to changing the form of air quality standards based on enhanced dispersion modeling techniques. (Author/RE)

  18. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil biodeg

  19. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil

  20. Fracture Toughness Evaluation of Hybrid and Nano-hybrid Resin Composites after Ageing under Acidic Environment

    Directory of Open Access Journals (Sweden)

    Ferooz M

    2015-03-01

    Full Text Available Statement of Problem: Tooth-coloured restorative materials are brittle with the major shortcomings of sensitivity to flaws and defects. Although various mechanical properties of resin composites have been studied, no fracture toughness test data for nano-hybrid composites under acidic condition for a long period of time has been published. Objectives: To compare the fracture toughness (KIc of two types of resin composites under tensile loading and to assess the effect of distilled water and lactic acid on the resistance of the restoratives to fracture after three months of immersion. Materials and Methods: Four resin composites were used: three nanohybrids [EsteliteSigma Quick (Kuraray, Luna (SDI, Paradigm (3M/ESPE] and one hybrid, Rok (SDI. The specimens were prepared using a custom-made polytetrafluorethylene split mould, stored in distilled water (pH 6.8 or 0.01mol/L lactic acid (pH 4 and conditioned at 37°C for 24 hours, 1 or 3 months. They were loaded under tensile stress using a universal testing machine; the maximum load (N to the specimen failure was recorded and the fracture toughness (KIc was calculated. Data were analysed by ANOVA and Tukey’s test using SPSS, version 18. Results: The results of two-way ANOVA did not show a significant combined effect of material, time, and storage medium on fracture toughness (p= 0.056. However, there was a strong interaction between materials and time (p=0.001 when the storage medium were ignored. After 24 h of immersion in distilled water, Paradigm revealed the highest KIc values followed by Rok, Luna and Estelite. Immersion in either distilled water or lactic acid significantly decreased the fracture toughness of almost all materials as time interval increased. Conclusions: Paradigm showed the highest fracture toughness followed by Rok, Luna and Estelite respectively. As time increased, KIc significantly decreased for almost all resin composites except for Luna which showed a slight decrease

  1. Two-year clinical comparison of a flowable-type nano-hybrid composite and a paste-type composite in posterior restoration.

    Science.gov (United States)

    Hirata-Tsuchiya, Shizu; Yoshii, Shinji; Ichimaru-Suematsu, Miki; Washio, Ayako; Saito, Noriko; Urata, Mariko; Hanada, Kaori; Morotomi, Takahiko; Kitamura, Chiaki

    2017-08-01

    The purpose of the present study was to compare the clinical efficacy between a flowable-type nano-hybrid composite and a paste-type composite for posterior restoration. Of 62 posterior teeth in 33 patients (mean age: 34.1 years), 31 were filled with a paste-type composite (Heliomolar [HM] group), and another 31 with a flowable nano-hybrid composite (MI FIL [MI] group). Clinical efficacy was evaluated at 2 years after the restoration. There were no differences for retention, surface texture deterioration, anatomical form change, deterioration of marginal adaptation, and secondary caries, while a statistical difference was found for marginal discoloration, which was significantly greater in the HM group (P composites showed that the flowable nano-hybrid composite could be an effective esthetic material for posterior restoration. © 2016 John Wiley & Sons Australia, Ltd.

  2. Free-Standing Graphene Oxide-Palygorskite Nanohybrid Membrane for Oil/Water Separation.

    Science.gov (United States)

    Zhao, Xueting; Su, Yanlei; Liu, Yanan; Li, Yafei; Jiang, Zhongyi

    2016-03-01

    Graphene oxide (GO) is an emerging kind of building block for advanced membranes with tunable passageway for water molecules. To synergistically manipulate the channel and surface structures/properties of GO-based membranes, the different building blocks are combined and the specific interfacial interactions are designed in this study. With vacuum-assisted filtration self-assembly, palygorskite nanorods are intercalated into adjacent GO nanosheets, and GO nanosheets are assembled into laminate structures through π-π stacking and cation cross-linking. The palygorskite nanorods in the free-standing GOP nanohybrid membranes take a 3-fold role, rendering enlarged mass transfer channels, elevating hydration capacity, and creating hierarchical nanostructures of membrane surfaces. Accordingly, the permeate fluxes from 267 L/(m(2) h) for GO membrane to 1867 L/(m(2) h) for GOP membrane. The hydration capacity and hierarchical nanostructures synergistically endow GOP membranes with underwater superoleophobic and low oil-adhesive water/membrane interfaces. Moreover, by rationally imparting chemical and physical joint defense mechanisms, the GOP membranes exhibit outstanding separation performance and antifouling properties for various oil-in-water emulsion systems (with different concentration, pH, or oil species). The high water permeability, high separation efficiency, as well as superior anti-oil-fouling properties of GOP membranes enlighten the great prospects of graphene-based nanostructured materials in water purification and wastewater treatment.

  3. Bio-nanohybrids of quantum dots and photoproteins facilitating strong nonradiative energy transfer.

    Science.gov (United States)

    Seker, Urartu Ozgur Safak; Mutlugun, Evren; Hernandez-Martinez, Pedro Ludwig; Sharma, Vijay K; Lesnyak, Vladimir; Gaponik, Nikolai; Eychmüller, Alexander; Demir, Hilmi Volkan

    2013-08-01

    Utilization of light is crucial for the life cycle of many organisms. Also, many organisms can create light by utilizing chemical energy emerged from biochemical reactions. Being the most important structural units of the organisms, proteins play a vital role in the formation of light in the form of bioluminescence. Such photoproteins have been isolated and identified for a long time; the exact mechanism of their bioluminescence is well established. Here we show a biomimetic approach to build a photoprotein based excitonic nanoassembly model system using colloidal quantum dots (QDs) for a new bioluminescent couple to be utilized in biotechnological and photonic applications. We concentrated on the formation mechanism of nanohybrids using a kinetic and thermodynamic approach. Finally we propose a biosensing scheme with an ON/OFF switch using the QD-GFP hybrid. The QD-GFP hybrid system promises strong exciton-exciton coupling between the protein and the quantum dot at a high efficiency level, possessing enhanced capabilities of light harvesting, which may bring new technological opportunities to mimic biophotonic events.

  4. The effect of different beverages on surface hardness of nanohybrid resin composite and giomer

    Directory of Open Access Journals (Sweden)

    Saijai Tanthanuch

    2014-01-01

    Full Text Available Aims: To investigate the effects of five beverages (apple cider, orange juice, Coca-Cola, coffee, and beer on microhardness and surface characteristic changes of nanohybrid resin composite and giomer. Materials and Methods: Ninety-three specimens of each resin composite and giomer were prepared. Before immersion, baseline data of Vicker′s microhardness was recorded and surface characteristics were examined using scanning electron microscopy (SEM. Five groups of discs (n = 18 were alternately immersed in 25 mL of each beverage for 5 s and in 25 mL of artificial saliva for 5 s for 10 cycles. Specimens were then stored in artificial saliva for 24 h. This process was repeated for 28 days. After immersion, specimens were evaluated and data were analyzed by two-way repeated analysis of variance (ANOVA, Tukey′s honestly significant difference (HSD, and a t-test (α = 0.05. Results: Microhardness of all groups significantly decreased after being immersed in the tested beverages (P < 0.05. SEM photomicrographs presented surface degradation of all groups. Conclusions: The effect of these beverages on the surface of both restorative materials also depended upon the exposure time and chemical composition of the restorative materials and beverages.

  5. Hydrothermal synthesis of silico-manganese nanohybrid for Cu(II) adsorption from aqueous solution

    Science.gov (United States)

    Zhu, Qiufeng; Wang, Liting; An, Zehuan; Ye, Hong; Feng, Xudong

    2016-05-01

    A novel silico-manganese nanohybrid adsorbent (SMNA) was synthesized by a facile hydrothermal method, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR) and zeta potential measurement. The adsorption of Cu(II) ions from aqueous solution on the SMNA was investigated with variations in contact time, pH and initial Cu(II) concentration. The results showed that hydrothermal method would generate nanowire/nanorod incomplete crystallite (δ-MnO2) adsorbent. The adsorption of Cu(II) onto SMNA increased sharply within 25 min and reached equilibrium gradually. The maximum adsorption capacities of SMNA for Cu(II) were ∼40-88 mg g-1, which was lower than δ-MnO2 (92.42 mg g-1) but had a lower pH dependency. As compared with δ-MnO2, higher adsorption capacities of SMNA (7.5-15 wt% of silica doping amount) for Cu(II) could be observed when pH of the aqueous solution was low (removal of Cu(II) by the as-prepared adsorbents was dominated by migration of Cu(II). The possibility of Cu(II) recovery was also investigated and it revealed that SMNA was a promising recyclable adsorbent for removal of heavy metal ions in water and wastewater treatment.

  6. Ultrasensitive cardiac troponin I antibody based nanohybrid sensor for rapid detection of human heart attack.

    Science.gov (United States)

    Bhatnagar, Deepika; Kaur, Inderpreet; Kumar, Ashok

    2017-02-01

    An ultrasensitive cardiac troponin I antibody conjugated with graphene quantum dots (GQD) and polyamidoamine (PAMAM) nanohybrid modified gold electrode based sensor was developed for the rapid detection of heart attack (myocardial infarction) in human. Screen printed gold (Au) electrode was decorated with 4-aminothiophenol for amine functionalization of the Au surface. These amino groups were further coupled with carboxyl functionalities of GQD with EDC-NHS reaction. In order to enhance the sensitivity of the sensor, PAMAM dendrimer was successively embedded on GQD through carbodiimide coupling to provide ultra-high surface area for antibody immobilization. The activated cardiac troponin I (cTnI) monoclonal antibody was immobilized on PAMAM to form nanoprobe for sensing specific heart attack marker cTnI. Various concentrations of cardiac marker, cTnI were electrochemically measured using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in human blood serum. The modifications on sensor surface were characterized by FTIR and AFM techniques. The sensor is highly specific to cTnI and showed negligible response to non-specific antigens. The sensitivity of the sensor was 109.23μAcm(-2)μg(-1) and lower limit of detection of cTnI was found 20fgmL(-1).

  7. Dual nutraceutical nanohybrids of folic acid and calcium containing layered double hydroxides

    Science.gov (United States)

    Kim, Tae-Hyun; Oh, Jae-Min

    2016-01-01

    Dual nutraceutical nanohybrids consisting of organic nutrient, folic acid (FA), and mineral nutrient, calcium, were prepared based on layered double hydroxide (LDH) structure. Among various hybridization methods such as coprecipitation, ion exchange, solid phase reaction and exfoliation-reassembly, it was found that exfoliation-reassembly was the most effective in terms of intercalation of FA moiety between Ca-containing LDH layers. X-ray diffraction patterns and infrared spectra indicated that FA molecules were well stabilized in the interlayer space of LDHs through electrostatic interaction. From the atomic force and scanning electron microscopic studies, particle thickness of LDH was determined to be varied with tens, a few and again tens of nanometers in pristine, exfoliated and reassembled state, respectively, while preserving particle diameter. The result confirmed layer-by-layer hybrid structure of FA and LDHs was obtained by exfoliation-reassembly. Solid UV-vis spectra showed 2-dimensional molecular arrangement of FA moiety in hybrid, exhibiting slight red shift in n→π* and π→π* transition. The chemical formulae of FA intercalated Ca-containing LDH were determined to Ca1.30Al(OH)4.6FA0.74·3.33H2O and Ca1.53Fe(OH)5.06FA2.24·9.94H2O by inductively coupled plasma-atomic emission spectroscopy, high performance liquid chromatography and thermogravimetry, showing high nutraceutical content of FA and Ca.

  8. The effect of red and white wine on color changes of nanofilled and nanohybrid resin composites

    Science.gov (United States)

    Tanthanuch, Saijai; Peerasukprasert, Thanwalee; Chanmanee, Nilobon; Chaisomboonphun, Parnchanok; Rodklai, Apisara

    2016-01-01

    Objectives This study investigated the effect of red and white wine on color changes of nanofilled and nanohybrid resin composite. Materials and Methods Sixty specimens of each resin composite were prepared. Baseline data color values were recorded using a spectrophotometer. Three groups of discs (n = 20) were then alternately immersed in red, white wine, and deionized water (as a control) for twenty five minutes and artificial saliva for five minutes for four cycles. Specimens were then stored in artificial saliva for twenty two hours. This process was repeated for five days following immersion in artificial saliva for two days. Subsequently, the process was repeated again. Data were analyzed by two-way repeated ANOVA, one-way ANOVA, and Tukey's HSD. Results Red wine caused significantly higher color change (ΔE* > 3.3) than did white wine and deionized water (p resin composite (p resin composite restorative materials depended upon the physical and chemical composition of the restorative materials and the types of wine. PMID:27200281

  9. Effects of staining and bleaching on a nanohybrid composite with or without surface sealant

    Science.gov (United States)

    Halacoglu, Derya Merve; Yamanel, Kıvanc; Basaran, Saffet; Tuncer, Duygu; Celik, Cigdem

    2016-01-01

    Objective: The effect of different staining solutions and a bleaching procedure on color stability and surface roughness of a nanohybrid resin composite were evaluated with or without liquid resin polishing (RP). Materials and Methods: Ninety-six disc-shaped resin composite specimens (A1 Shade, Z550 Filtek 3M ESPE, St. Paul, MN, USA) were prepared and divided randomly into two groups (n = 48). Liquid RP (BisCover LV, Bisco Inc., Schaumburg, IL, USA) was applied in one group (RP) and not in the other (P). Specimen color and surface roughness were determined using a colorimeter and profilometer, respectively. After baseline measurements, each group was divided into four subgroups (n = 12) for immersion in a control (distilled water) or three different staining solutions (ice tea, red wine, and cola) for 1 week. Color and surface roughness were then reevaluated. After measurements, all specimens were bleached using a 35% hydrogen peroxide gel. The color and surface roughness of the specimens were reevaluated. Statistical Analysis: Data were subjected to an analysis of variance for repeated measurements among the groups (P 0.05). Discoloration in the red wine group was higher than for the other staining solutions for the RP (P < 0.001) and P groups (P = 0.018). Conclusion: Application of liquid RP did not enhance the color stability and surface roughness of the composite resin restoration. PMID:27403054

  10. Preparation of graphene oxide-silver nanoparticle nanohybrids with highly antibacterial capability.

    Science.gov (United States)

    Zhu, Zhijun; Su, Min; Ma, Lan; Ma, Lina; Liu, Dianjun; Wang, Zhenxin

    2013-12-15

    A simple method based on electrostatic interactions was utilized to assemble silver nanoparticles (AgNPs) to graphene oxide (GO) sheets. This method allows conjugation of AgNPs with desired morphologies (densities, sizes and shapes) onto GO. In this process, poly(diallyldimethylammonium chloride) (PDDA) was introduced as an adhesive agent. The as-prepared graphene oxide-AgNPs composites (GO-AgNPs) have enhanced colloid stability and photo-stability than that of AgNPs. After conjugating to GO sheets, the antibacterial activities of AgNPs against Gram negative (G-) bacterial strain (Escherichia coli, E. coli) and Gram positive (G+) bacterial strain (Bacillus subtilis, B. subtilis) have been improved significantly. The antibacterial activity of GO-AgNPs is dependent on the size of AgNPs, i.e. the small AgNPs modified GO sheets show more effective antibacterial capability than that of large AgNPs modified GO sheets. Compared with AgNPs, the enhanced antibacterial activity of GO-AgNPs might not only be due to high stability of AgNPs anchored on GO sheets, but also the positive charged surface of hybrids which increases the electrostatic interaction of bacterial cell membrane with nanohybrids.

  11. Influence of finish line on the marginal seal of nanohybrid composite crowns after periodontal scaling: a microleakage study.

    Science.gov (United States)

    Angerame, D; De Biasi, M; Del Lupo, V; Bevilacqua, L; Zarone, F; Sorrentino, R

    2015-10-01

    The aim of the present microleakage study was to assess the sealing ability of nanohybrid composite crowns with different finish lines exposed to simulated mechanical periodontal treatment (SMPT). After sample size calculation (α=0.05; β=0.20; δ=1.0; σ=0.8), sixty extracted mandibular molars were divided into four groups (N.=15): G1, 90° shoulder; G2, beveled 90° shoulder; G3, 90° shoulder and SMPT; G4, beveled 90° shoulder and SMPT. Tooth preparations were carried out by means of diamond burs and Arkansas stones. The buildup of crowns was performed with a nanohybrid composite on master casts obtained after polyether impressions and crowns were cemented with self-adhesive cement. Groups G3 and G4 were subjected to the equivalent of five years of semestral mechanical periodontal scaling with Gracey curettes (2-mm long strokes, 5 N). Samples were immersed into a methylene blue supersaturated solution for 10 minutes. Microleakage was measured by stereomicroscopic observation of multiple sections of the samples and leakage data underwent statistical analysis with non-parametric tests. Marginal microleakage was 1.53±1.27% and 17.60±12.72% of the length of the adhesive interface in G1 and G2, respectively. SMPT reduced dye penetration (P<0.001) with G3 not leaking at all and G4 leaking along the 5.58±1.84% of the adhesive interface. The bevel preparation significantly worsened the marginal seal both in control and treated crowns (P<0.001). Microleakage of nanohybrid composite crowns increased by adding a bevel to a 90° shoulder preparation and diminished after SMPT.

  12. Functionalization of polyhedral oligomeric silsesquioxanes with bis(hydroxyethyl) ester and preparation of the corresponding degradable nanohybrids

    Institute of Scientific and Technical Information of China (English)

    Bing Tao Wang; Yan Zhang; Ping Zhang; Zheng Ping Fang

    2012-01-01

    One novel difunctionalized polyhedral oligomeric silsesquioxanes (POSS) derivative was designed and synthesized by a convenient method with high yield.1H NMR and FT-IR characterizations suggested that Michael addition reaction successfully took place between 2-hydroxyethyl acrylate (HEA) and aminopropylisobutyl POSS (POSS-NH2) under mild conditions,which finally formed bi(hydroxyethyl) ester-functionalized POSS derivatives (BH-POSS).Due to the similar functional groups and high reactivity,BH-POSS could be easily incorporated into the main-chain of biodegradable aliphatic-aromatic copolyesters PBTL via in situ melt polycondensation to prepare corresponding degradable nanohybrids with high mechanical properties.

  13. Dual nutraceutical nanohybrids of folic acid and calcium containing layered double hydroxides

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae-Hyun; Oh, Jae-Min, E-mail: jaemin.oh@yonsei.ac.kr

    2016-01-15

    Dual nutraceutical nanohybrids consisting of organic nutrient, folic acid (FA), and mineral nutrient, calcium, were prepared based on layered double hydroxide (LDH) structure. Among various hybridization methods such as coprecipitation, ion exchange, solid phase reaction and exfoliation-reassembly, it was found that exfoliation-reassembly was the most effective in terms of intercalation of FA moiety between Ca-containing LDH layers. X-ray diffraction patterns and infrared spectra indicated that FA molecules were well stabilized in the interlayer space of LDHs through electrostatic interaction. From the atomic force and scanning electron microscopic studies, particle thickness of LDH was determined to be varied with tens, a few and again tens of nanometers in pristine, exfoliated and reassembled state, respectively, while preserving particle diameter. The result confirmed layer-by-layer hybrid structure of FA and LDHs was obtained by exfoliation-reassembly. Solid UV–vis spectra showed 2-dimensional molecular arrangement of FA moiety in hybrid, exhibiting slight red shift in n→π* and π→π* transition. The chemical formulae of FA intercalated Ca-containing LDH were determined to Ca{sub 1.30}Al(OH){sub 4.6}FA{sub 0.74}·3.33H{sub 2}O and Ca{sub 1.53}Fe(OH){sub 5.06}FA{sub 2.24}·9.94H{sub 2}O by inductively coupled plasma-atomic emission spectroscopy, high performance liquid chromatography and thermogravimetry, showing high nutraceutical content of FA and Ca. - Highlights: • We successfully intercalated FA molecules into Ca-containing LDHs. • Exfoliation-reassembly was proven to be the most effective. • The interaction between LDH and FA were studied by FT-IR and UV–vis spectra. • Thermal stability of FA were enhanced by electrostatic interaction with LDH layers.

  14. Epigallocatechin Gallate/Layered Double Hydroxide Nanohybrids: Preparation, Characterization, and In Vitro Anti-Tumor Study.

    Directory of Open Access Journals (Sweden)

    Seyedeh Sara Shafiei

    Full Text Available In recent years, nanotechnology in merging with biotechnology has been employed in the area of cancer management to overcome the challenges of chemopreventive strategies in order to gain promising results. Since most biological processes occur in nano scale, nanoparticles can act as carriers of certain drugs or agents to deliver it to specific cells or targets. In this study, we intercalated Epigallocatechin-3-Gallate (EGCG, the most abundant polyphenol in green tea, into Ca/Al-NO3 Layered double hydroxide (LDH nanoparticles, and evaluated its efficacy compared to EGCG alone on PC3 cell line. The EGCG loaded LDH nanohybrids were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy (TEM and nanosizer analyses. The anticancer activity of the EGCG-loaded LDH was investigated in prostate cancer cell line (PC3 while the release behavior of EGCG from LDH was observed at pH 7.45 and 4.25. Besides enhancing of apoptotic activity of EGCG, the results showed that intercalation of EGCG into LDH can improve the anti- tumor activity of EGCG over 5-fold dose advantages in in-vitro system. Subsequently, the in-vitro release data showed that EGCG-loaded LDH had longer release duration compared to physical mixture, and the mechanism of diffusion through the particle was rate-limiting step. Acidic attack was responsible for faster release of EGCG molecules from LDH at pH of 4.25 compared to pH of 7.4. The results showed that Ca/Al-LDH nanoparticles could be considered as an effective inorganic host matrix for the delivery of EGCG to PC3 cells with controlled release properties.

  15. The in vitro sustained release profile and antitumor effect of etoposide-layered double hydroxide nanohybrids

    Directory of Open Access Journals (Sweden)

    Qin LL

    2013-05-01

    Full Text Available Lili Qin,1 Mei Wang,2 Rongrong Zhu,3 Songhui You,1 Ping Zhou,1 Shilong Wang31Department of Physical Education, Tongji University, Shanghai, People's Republic of China; 2Department of Chemistry, Tongji University, Shanghai, People's Republic of China; 3School of Life Science and Technology, Tongji University, Shanghai, People's Republic of ChinaAbstract: Magnesium-aluminum layered double hydroxides intercalated with antitumor drug etoposide (VP16 were prepared for the first time using a two-step procedure. The X-ray powder diffraction data suggested the intercalation of VP16 into layers with the increased basal spacing from 0.84–1.18 nm was successful. Then, it was characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis, and transmission electron microscopy. The prepared nanoparticles, VP16-LDH, showed an average diameter of 62.5 nm with a zeta potential of 20.5 mV. Evaluation of the buffering effect of VP16-LDH indicated that the nanohybrids were ideal for administration of the drugs that treat human stomach irritation. The loading amount of intercalated VP16 was 21.94% and possessed a profile of sustained release. The mechanism of VP16-LDH release in the phosphate buffered saline solution at pH 7.4 is likely controlled by the diffusion of VP16 anions from inside to the surface of LDH particles. The in vitro cytotoxicity and antitumor assays indicated that VP16-LDH hybrids were less toxic to GES-1 cells while exhibiting better antitumor efficacy on MKN45 and SGC-7901 cells. These results imply that VP16-LDH is a potential antitumor drug for a broad range of gastric cancer therapeutic applications.Keywords: layered double hydroxides, etoposide, drug delivery, antitumor effect, sustained release

  16. In vitro toothbrushing abrasion of dental resin composites: packable, microhybrid, nanohybrid and microfilled materials

    Directory of Open Access Journals (Sweden)

    Rafael Ratto de Moraes

    2008-06-01

    Full Text Available This study evaluated weight loss and surface roughening after toothbrushing of different resin composites: one packable (Solitaire 2, Heraeus Kulzer, one microhybrid (Charisma, Heraeus Kulzer, one nanohybrid (Simile, Pentron and one microfilled (Durafill VS, Heraeus Kulzer. Cylindrical specimens (n = 20 were prepared. Half of the samples were submitted to 60,000 strokes, at 4 Hz, with a dentifrice-water slurry. Control samples (n = 10 remained stored at 37°C. Pre- and post-abrasion parameters for weight (mg and surface roughness (Ra, µm were determined on an analytical balance and a surface profilometer. Data were separately submitted to Repeated Measures ANOVA and Tukey's test (a = 0.05. Percentages of weight loss were analyzed by ANOVA and Tukey's test (a = 0.05. The relationship between both evaluations was assessed by Pearson's test (a = 0.05. The means (% for weight loss (standard deviation were 0.65(0.2, 0.93(0.2, 1.25(0.6 and 1.25(0.4 for Simile, Durafill, Charisma and Solitaire, respectively. Baseline roughness means ranged from 0.065(0.01, 0.071(0.01, 0.066(0.02 and 0.074(0.01 for Simile, Durafill, Charisma and Solitaire, respectively, to 0.105(0.04, 0.117(0.03, 0.161(0.03 and 0.214(0.07 after testing. The composites with larger fillers presented higher weight loss and roughening than the finer materials (p < 0.05. For both evaluations, control specimens showed no significant alteration. No significant relationship between loss of weight and roughness alteration was detected (r = 0.322, p = 0.429.

  17. Aripiprazole-montmorillonite: a new organic-inorganic nanohybrid material for biomedical applications.

    Science.gov (United States)

    Oh, Yeon-Ji; Choi, Goeun; Choy, Young Bin; Park, Je Won; Park, Jung Hyun; Lee, Hwa Jeong; Yoon, Yeo Joon; Chang, Hee Chul; Choy, Jin-Ho

    2013-04-08

    Poor aqueous solubility and the unpleasant taste of aripiprazole (APZ) have been recurring problems, owing to its low bioavailability and low patient tolerance, respectively. Herein, we prepared a nanohybrid system that was based on a bentonite clay material, montmorillonite (MMT), which could both mask the taste and enhance the solubility of APZ (i.e., APZ-MMT). To further improve the efficacy of this taste masking and drug solubility, APZ-MMT was also coated with a cationic polymer, polyvinylacetal diethylamino acetate (AEA). In vitro dissolution tests at neutral pH showed that the amount of drug that was released from the AEA-coated APZ-MMT was greatly suppressed (<1%) for the first 3 min, thus suggesting that AEA-coated APZ-MMT has strong potential for the taste masking of APZ. Notably, in simulated gastric juice at pH 1.2, the total percentage of APZ that was released within the first 2 h increased up to 95% for AEA-coated APZ-MMT. Furthermore, this in vitro release profile was also similar to that of Abilify®, a commercially available medication. In vivo experiments by using Sprague-Dawley rats were also performed to compare the pharmacokinetics of AEA-coated APZ-MMT and Abilify®. AEA-coated APZ-MMT exhibited about 20% higher systemic exposure of APZ and its metabolite, dehydro-APZ, compared with Abilify®. Therefore, a new MMT-based nanovehicle, which is coated with a cationic polymer, can act as a promising delivery system for both taste masking and for enhancing the bioavailability of APZ. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. One year comparative clinical evaluation of EQUIA with resin-modified glass ionomer and a nanohybrid composite in noncarious cervical lesions

    Directory of Open Access Journals (Sweden)

    Deepa Sunil Vaid

    2015-01-01

    Full Text Available Aims: Comparative evaluation of EQUIA with a resin-modified glass ionomer cement (RMGIC; GC Gold Label glass ionomer light cured universal restorative cement and a nanohybrid composite (Tetric N-Ceram in noncarious cervical lesions (NCCLs. Background: To establish the most suitable material for the restoration of NCCLs. Settings and Design: In vivo study. Materials and Methods: Eighty-seven NCCLs were randomly restored with EQUIA, a RMGIC, and a nanohybrid composite. Clinical evaluation of the restorations was done following the Unites States Public Health criteria by a single-blinded investigator. Data were formulated, and statistical analysis was done by Chi-square test. Statistical Analysis Used: Chi-square test. Results: No significant difference was found between EQUIA, RMGIC, and nanohybrid composite at 1-month, at 6 months, and at 1-year (P > 0.05. Conclusions: EQUIA, resin-modified glass ionomer, and nanohybrid composite performed equally at 1-month, 6 months, and 1-year follow-up periods.

  19. Anionic clay as the drug delivery vehicle: tumor targeting function of layered double hydroxide-methotrexate nanohybrid in C33A orthotopic cervical cancer model.

    Science.gov (United States)

    Choi, Goeun; Piao, Huiyan; Alothman, Zeid A; Vinu, Ajayan; Yun, Chae-Ok; Choy, Jin-Ho

    2016-01-01

    Methotrexate (MTX), an anticancer agent, was successfully intercalated into the anionic clay, layered double hydroxides to form a new nanohybrid drug. The coprecipitation and subsequent hydrothermal method were used to prepare chemically, structurally, and morphologically well-defined two-dimensional drug-clay nanohybrid. The resulting two-dimensional drug-clay nanohybrid showed excellent colloidal stability not only in deionized water but also in an electrolyte solution of Dulbecco's Modified Eagle's Medium with 10% fetal bovine serum, in which the average particle size in colloid and the polydispersity index were determined to be around 100 and 0.250 nm, respectively. The targeting property of the nanohybrid drug was confirmed by evaluating the tumor-to-blood and tumor-to-liver ratios of the MTX with anionic clay carrier, and these ratios were compared to those of free MTX in the C33A orthotopic cervical cancer model. The biodistribution studies indicated that the mice treated with the former showed 3.5-fold higher tumor-to-liver ratio and fivefold higher tumor-to-blood ratio of MTX than those treated with the latter at 30 minutes postinjection.

  20. Nanohybrids of Mg/Al layered double hydroxide and long-chain (C18) unsaturated fatty acid anions: Structure and sorptive properties

    Science.gov (United States)

    Long-chain (C18) unsaturated fatty acid anions, elaidate (ELA), oleate (OLE), linoleate (LINO), and linolenate (LINOLEN), were intercalated into Mg/Al (3:1) layered double hydroxide (LDH) and the resultant organo-LDH nanohybrid materials were characterized and subsequently evaluated as sorbents of s...

  1. A six-year prospective randomized study of a nano-hybrid and a conventional hybrid resin composite in Class II restorations

    DEFF Research Database (Denmark)

    van Dijken, Jan W V; Pallesen, Ulla

    2013-01-01

    The objective of this 6 year prospective randomized equivalence trial was to evaluate the long-term clinical performance of a new nano-hybrid resin composite (RC) in Class II restorations in an intraindividual comparison with its well-established conventional hybrid RC predecessor....

  2. One-step approach to prepare magnetic iron oxide/reduced graphene oxide nanohybrid for efficient organic and inorganic pollutants removal

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Suman; Karak, Niranjan, E-mail: karakniranjan@yahoo.com

    2014-04-01

    An environmentally friendly effective technique was demonstrated to prepare iron oxide/reduced graphene oxide nanohybrid (IO/RGO) at room temperature by using banana peel ash aqueous extract as the base source and Colocasia esculenta leaves aqueous extract as the reducing agent. The nanohybrid was characterized by Fourier transform infrared spectroscopy, X-ray diffractometry, transmission electron microscopy, vibrating sample magnetometry, Raman spectroscopy and thermal studies. The results indicated the decoration of superparamagnetic IO nanoparticles on the surface of the RGO. Both organic and inorganic pollutants were effectively removed from the contaminated water (for Pb{sup 2+} and Cd{sup 2+} within 10 min, whereas for tetrabromobisphenol A within 30 min) by IO/RGO. The study revealed that adsorption followed pseudo-second order kinetics and isotherms were well described by the Langmuir model in all the cases. The thermodynamics parameters (ΔG°, ΔS° and ΔH°) were calculated from the temperature dependent isotherms and indicated that the adsorptions were endothermic and spontaneous. - Highlights: • Eco-friendly one step preparation of iron oxide/reduced graphene oxide nanohybrid. • The nanohybrid has excellent pollutants removal capacity from contaminated water. • Superparamagnetic iron oxide nanoparticles help in easy recycle. • The adsorption processes of pollutants are endothermic and spontaneous.

  3. Synthesis and characterization of a Noble metal Enhanced Optical Nanohybrid (NEON): a high brightness detection platform based on a dye-doped silica nanoparticle.

    Science.gov (United States)

    Roy, Shibsekhar; Dixit, Chandra K; Woolley, Robert; O'Kennedy, Richard; McDonagh, Colette

    2012-05-29

    A highly bright and photostable, fluorescent nanohybrid particle is presented which consists of gold nanoparticles (GNPs) embedded in dye-doped silica in a core-shell configuration. The dye used is the near-infrared emitting 4,5-benzo-5'-(iodoacetaminomethyl)-1',3,3,3',3'-pentamethyl-1-(4-sulfobutyl) indodicarbo cyanine. The nanohybrid architecture comprises a GNP core which is separated from a layer of dye molecules by a 15 nm buffer layer and has an outer protective, undoped silica shell. Using this architecture, a brightness factor of 550 has been achieved compared to the free dye. This hybrid system, referred to as Noble metal Enhanced Optical Nanohybrid (NEON) in this paper, is the first nanohybrid construct to our knowledge which demonstrates such tunable fluorescence property. NEON has enhanced photostability compared to the free dye and compared to a control particle without GNPs. Furthermore, the NEON particle, when used as a fluorescent label in a model bioassay, shows improved performance over assays using a conventional single dye molecule label.

  4. Graphene Oxide/Silver Nanohybrid as Multi-functional Material for Highly Efficient Bacterial Disinfection and Detection of Organic Dye

    Science.gov (United States)

    Tam, Le Thi; Dinh, Ngo Xuan; Van Cuong, Nguyen; Van Quy, Nguyen; Huy, Tran Quang; Ngo, Duc-The; Mølhave, Kristian; Le, Anh-Tuan

    2016-10-01

    In this work, a multi-functional hybrid system consisting of graphene oxide and silver nanoparticles (GO-Ag NPs) was successfully synthesized by using a two-step chemical process. We firstly demonstrated noticeable bactericidal ability of the GO-Ag hybrid system. We provide more chemo-physical evidence explaining the antibacterial behavior of GO-Ag nanohybrid against Gram-negative Escherichia Coli and Gram-positive Staphylococcus aureus in light of ultrastructural damage analyses and Ag1+ ions release rate onto the cells/medium. A further understanding of the mode of antimicrobial action is very important for designing and developing advanced antimicrobial systems. Secondly, we have also demonstrated that the GO-Ag nanohybrid material could be used as a potential surface enhanced Raman scattering (SERS) substrate to detect and quantify organic dyes, e.g., methylene blue (MB), in aqueous media. Our findings revealed that the GO-Ag hybrid system showed better SERS performance of MB detection than that of pure Ag-NPs. MB could be detected at a concentration as low as 1 ppm. The GO-Ag-based SERS platform can be effectively used to detect trace concentrations of various types of organic dyes in aqueous media. With the aforementioned properties, the GO-Ag hybrid system is found to be very promising as a multi-functional material for advanced biomedicine and environmental monitoring applications.

  5. Strongly coupled CdS/graphene quantum dots nanohybrids for highly efficient photocatalytic hydrogen evolution: unraveling the essential roles of graphene quantum dots

    KAUST Repository

    Lei, Yonggang

    2017-05-23

    It have been recognized that the coupling of graphene quantum dots (GQDs) with semiconductor photocatalysts endow the resulting nanocomposites with enhanced photocatalytic performances, however, the essential roles of GQDs have not been clearly revealed yet. Herein, we report that a high efficiency of the photocatalytic H2 evolution was achieved using strongly coupled nanohybrids of CdS with GQDs (CdS/GQDs) as visible-light-driven photocatalysts. CdS/GQDs nanohybrids were synthesized by a facile hydrothermal method in which the crystallization of CdS precursor and coupling of GQDs could be accomplished in one-step. GQDs are firmly decorated on the surface of CdS nanoparticles, forming “dot-on-particle” heterodimer structures. GQDs have no significant influence on the crystallite structure of CdS but render the nanohybrids with strong light absorption at the wavelength beyond the band edge of CdS. Under visible light irradiation (≥420nm), CdS/GQDs nanohybrids reach the highest H2 production rate of 95.4μmol·h−1, about 2.7 times higher than that of pure CdS nanoparticles, at GQDs content of 1.0wt %, and the apparent quantum efficiency (AQE) was determined to be 4.2% at 420nm. Incident light-wavelength dependent experiments reveal that the light absorption of CdS dominated the performance of nanohybrids, and the excess light absorption coming from GQDs hardly contributes to the observed higher activity. Photocurrent response, steady-state and time-resolved PL, and EIS measurements suggest that the high activity of CdS/GQDs is attributed predominantly to the graphene-like nature of GQDs, which can act as an efficient electron acceptor to induce an efficient charge separation. This work clearly reveals that GQDs mainly played a role of electron acceptor instead of a photosensitizer in enhancing the photocatalytic H2 evolution performances of CdS/GQDs nanohybrids, which offers a new insight to understand the essential roles of GQDs in semiconductor

  6. CdTe/聚乳酸纳米杂化材料的制备及其荧光性能%Preparation and fluorescence properties of CdTe/poly ( lactic acid) nanohybrids

    Institute of Scientific and Technical Information of China (English)

    王昌祝; 程玉鹏; 王彩凤; 陈莉; 陈苏

    2012-01-01

    以十二烷基胺(DDA)为表面修饰剂,将巯基水相法合成的CdTe纳米晶转移至有机溶剂三氯甲烷中,然后采用“物理共混法”实现了CdTe/聚乳酸(CdTe/PLA)纳米杂化材料及其透明荧光膜的制备.通过紫外-可见光谱仪(UV -vis)、荧光(PL)、紫外透射反射分析仪等表征方法考察相转移前后CdTe纳米晶的光学性能,并系统研究了CdTe/PLA纳米杂化材料的荧光性能.结果表明:相转移后CdTe纳米晶的粒径未发生明显变化,其量子产率却提高了;所制备的CdTe/PLA纳米杂化材料具有优越的荧光性能,CdTe纳米晶在聚合物中仍然保持良好的分散性和较好的量子尺寸效应.%Under the direction of dodecylamine (DDA), CdTe nanocrystals prepared by the thio-aqueous synthetic approach were transferred from water to organic solvent CHC13. Subsequently,CdTe/Poly(lactic acid) (CdTe/PLA) nanohybrids were prepared by the "physical blending" method. Their optical properties before and after the phase transfer were characterized by UV-vis absorption,photoluminescence (PL) and ultraviolet transmission reflection measurements. The results showed that the particle size of CdTe nanocrystals was kept unchanged while their quantum yields increased during the phase transfer process. The spectroscopic studies revealed that CdTe/PLA nanohybrids had good photoluminescence properties. CdTe nanocrystals were well dispersed in the polymer matrices to show good quantum size effect.

  7. Dispersed Indeterminacy

    CERN Document Server

    Fayngold, Moses

    2013-01-01

    A state of a single particle can be represented by a quantum blob in the corresponding phase space, or a patch (granule) in its 2-D subspace. Its area is frequently stated to be no less than, implying that such a granule is an indivisible quantum of the 2-D phase space. But this is generally not true, as is evident, for instance, from representation of some states in the basis of innately discrete observables like angular momentum. Here we consider some dispersed states involving the evanescent waves different from that in the total internal reflection. Such states are represented by a set of separated granules with individual areas, but with the total indeterminacy . An idealized model has a discrete Wigner function and is described by a superposition of eigenstates with eigenvalues and forming an infinite periodic array of dots on the phase plane. The question about the total indeterminacy in such state is discussed. We argue that the eigenstates corresponding to the considered EW cannot be singled out by a...

  8. Effect of Organo-Modified Nanoclay on the Thermal and Bulk Structural Properties of Poly(3-hydroxybutyrate-Epoxidized Natural Rubber Blends: Formation of Multi-Components Biobased Nanohybrids

    Directory of Open Access Journals (Sweden)

    Ali Salehabadi

    2014-06-01

    Full Text Available Multi-component nanohybrids comprising of organo-modified montmorillonite (MMT and immiscible biopolymer blends of poly(3-hydroxybutyrate (PHB and epoxidized natural rubber (ENR-50 were prepared by solvent casting technique. The one and three dimensional morphology of PHB/ENR-50/MMT systems were studied using Polarizing Optical Microscopy (POM and Scanning Electron Microscopy (SEM. Differential scanning calorimetry (DSC technique was used to evaluate the thermal properties of the nanohybrids. The melting temperature (Tm and enthalpy of melting (ΔHm of PHB decrease with respect to the increase in ENR-50 as well as MMT content. The non-isothermal decomposition of the nanohybrids was studied using thermogravimetric (TG-DTG analysis. FTIR-ATR spectra supported ring opening of the epoxide group via reaction with carboxyl group of PHB and amines of organic modifier. The reaction mechanism towards the formation of the nanohybrids is proposed.

  9. Immediate vs delayed repair bond strength of a nanohybrid resin composite.

    Science.gov (United States)

    El-Askary, Farid S; El-Banna, Ahmed H; van Noort, Richard

    2012-06-01

    To evaluate both the immediate and water-stored repair tensile bond strength (TBS) of a nanohybrid resin composite using different bonding protocols. One hundred sixty half hourglass-shaped slabs were prepared. Eighty half-slabs were wet ground immediately after light curing using high-speed abrasive burs, while the other half-slabs were stored in water for one month (delayed) and then wet ground for repair. Each set of the 80 repaired slabs was split into two groups to be tested for TBS after 24 h or 1 month of water storage. For all repaired slabs, either immediate or delayed, four bonding procedures were used involving wet and dry bonding with a 3-step etch-and-rinse adhesive with or without silane pretreatment. TBS tests were performed at a crosshead speed of 0.5 mm/min. To determine the cohesive strength of the resin composite itself, which served as the reference, additional whole slabs were prepared and tested in tension after a 24-h (n = 10) and a 1-month storage period (n = 10). Failure modes were evaluated using a stereomicroscope at 40X magnification. Three-way ANOVA was run to test the effect of water storage, testing time, bonding protocols, and their interactions on the repair TBS, which was given as a percentage of the reference values. For the immediate repair groups, the repair TBS ranged from 40% to 61.9% after 24-h storage and from 26% to 53.1% after 1-month water storage compared to the TBS of the whole slabs. For the delayed repair group, the repaired TBS ranged from 47.2% to 63.6% for the 24-h repairs and from 32.2% to 44.2% for the test groups stored in water for 1 month. Three-way ANOVA revealed that water storage had no significant effect on the repair TBS (p = 0.619). Both testing time and bonding protocols had a significant effect on the repair TBS (p = 0.001). The interactions between the independent variables (water storage, testing time, and bonding protocols) had no significant effect (p = 0.067). The repair bond strength was

  10. Hertzian Load-bearing Capacity of Hybrid and Nano-hybrid Resin Composites Stored Dry and Wet

    Directory of Open Access Journals (Sweden)

    Farmani S

    2016-03-01

    Full Text Available Statement of Problem: Hertzian indentation test has been proven to be an efficient and reliable alternative upon Vickers hardness test. This method has been used to test dental ceramics, amalgams, glass ionomers and luting cements.There is limited published information about the load-bearing capacity of resin composites using Hertizian indentation test. Objectives: To investigate the load-bearing capacity of hybrid and nano-hybrid resin composites stored dry or wet up to 30 days, using Hertzian indentation test. Materials and Methods: Three resin composites were used: two nano-hybrids (Filtek Supreme, and Luna and one hybrid, (Rok. A total of 108 disc-shaped specimens (1mm thick x 10 mm diameter were prepared using polyethylene mould. The specimens of each material were randomly divided into 6 groups of 6 (n=6 and stored at 370C either in distilled water or dry for 1, 7 and 30 days. The specimens were tested using Hertzian jig aligned in the universal testing machine. The specimen was placed on the top of a disc-shaped substrate. The load was applied at the center of each specimen and the load at the first crack was recorded. Data were analyzed by ANOVA, Tukey’sand student’s t-test using SPSS version 18.0. Results: Three-way ANOVA showed a significant interaction between all the factors (p = .0001. The load bearing capacity of almost all materials reduced significantly in the wet condition in comparison with the dry condition (p = .0001. After seven days of immersion in distilled water, Filtek Supreme had significantly lower values than those of Rok and Luna, there was no significant differences between materials in the dry condition. Conclusions:In contrast to dry condition, the load-bearing capacity of specimens stored in distilled water decreased significantly over the 30 days of immersion. The load bearing capacity of nano-hybrid composites tested in this study was shown to be comparable with that of the hybrid composite.

  11. Seed dispersal in fens

    NARCIS (Netherlands)

    Middleton, Beth; van Diggelen, Rudy; Jensen, Kai

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and

  12. Functional carbons and carbon nanohybrids for the catalytic conversion of biomass to renewable chemicals in the condensed phase

    Energy Technology Data Exchange (ETDEWEB)

    Matthiesen, John; Hoff, Thomas; Liu, Chi; Pueschel, Charles; Rao, Radhika; Tessonnier, Jean-Philippe

    2014-06-01

    The production of chemicals from lignocellulosic biomass provides opportunities to synthesize chemicals with new functionalities and grow a more sustainable chemical industry. However, new challenges emerge as research transitions from petrochemistry to biorenewable chemistry. Compared to petrochemisty, the selective conversion of biomass-derived carbohydrates requires most catalytic reactions to take place at low temperatures (< 300°C) and in the condensed phase to prevent reactants and products from degrading. The stability of heterogeneous catalysts in liquid water above the normal boiling point represents one of the major challenges to overcome. Herein, we review some of the latest advances in the field with an emphasis on the role of carbon materials and carbon nanohybrids in addressing this challenge.

  13. Functional carbons and carbon nanohybrids for the catalytic conversion of biomass to renewable chemicals in the condensed phase

    Institute of Scientific and Technical Information of China (English)

    John Matthiesen; Thomas Hoff; Chi Liu; Charles Pueschel; Radhika Rao; Jean-Philippe Tessonnier

    2014-01-01

    The production of chemicals from lignocellulosic biomass provides opportunities to synthesize chemicals with new functionalities and grow a more sustainable chemical industry. However, new challenges emerge as research transitions from petrochemistry to biorenewable chemistry. Com-pared to petrochemisty, the selective conversion of biomass-derived carbohydrates requires most catalytic reactions to take place at low temperatures (<300 °C) and in the condensed phase to pre-vent reactants and products from degrading. The stability of heterogeneous catalysts in liquid water above the normal boiling point represents one of the major challenges to overcome. Herein, we review some of the latest advances in the field with an emphasis on the role of carbon materials and carbon nanohybrids in addressing this challenge.

  14. Shear-bond-strength of orthodontic brackets to aged nano-hybrid composite-resin surfaces using different surface preparation.

    Science.gov (United States)

    Demirtas, Hatice Kubra; Akin, Mehmet; Ileri, Zehra; Basciftci, Faruk Ayhan

    2015-01-01

    The aim of this study was to evaluate the effects of different surface preparation methods on the shear bond strength (SBS) of orthodontic metal brackets to aged nano-hybrid resin composite surfaces in vitro. A total of 100 restorative composite resin discs, 6 mm in diameter and 3 mm thick, were obtained and treated with an ageing procedure. After ageing, the samples were randomly divided as follows according to surface preparation methods: (1)Control, (2)37% phosphoric acid gel, (3)Sandblasting, (4)Diamond bur, (5)Air-flow and 20 central incisor teeth were used for the control etched group. SBS test were applied on bonded metal brackets to all samples. SBS values and residual adhesives were evaluated. Analysis of variance showed a significant difference (phybrid composite resin surfaces.

  15. Carbon Nanotube-based Nanohybrid Materials as Counter Electrode for Highly Efficient Dye-sensitized Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ji-Soo; Sim, Eun-Ju; Dao, Van-Duong; Choi, Ho-Suk [Chungnam National University, Daejeon (Korea, Republic of)

    2016-04-15

    In this study, we present an excellent approach for easily and uniformly immobilizing Pt, Au and bimetallic PtAu nanoparticles (NPs) on a multi-walled carbon nanotube (MWNT)-coated layer through dry plasma reduction. The NPs are stably and uniformly immobilized on the surface of MWNTs and the nanohybrid materials are applied to counter electrode (CE) of dye-sensitized solar cells (DSCs). The electrochemical properties of CEs are examined through cyclic voltammogram, electrochemical impedance spectroscopy, and Tafel measurements. As a result, both electrochemical catalytic activity and electrical conductivity are highest for PtAu/MWNT electrode. The DSC employing PtAu/MWNT CE exhibits power conversion efficiency of 7.9%. The efficiency is better than those of devices with MWNT (2.6%), AuNP/MWNT (2.7%) and PtNP/MWNT (7.5%) CEs.

  16. Synthesis, characterization and catalytic activity of Ag-acidfuchsin nanohybrid system towards the ring opening polymerization of ε-caprolactone.

    Science.gov (United States)

    Meenarathi, B; Palanikumar, S; Kannammal, L; Anbarasan, R

    2015-01-25

    The acidfuchsin (AF) decorated Ag nanoparticle (NP) was synthesized and its ability towards the ring opening polymerization (ROP) of ε-caprolactone (CL) was studied under N2 atmosphere at 160 °C in the presence of stannous octoate (SO) as a catalyst. Both the nanohybrid and nanocomposites were characterized by various analytical tools like Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, fluorescence spectroscopy, gel permeation chromatography (GPC), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The number of binding site from the fluorescence spectrum confirmed that all the functional groups present in AF might have been involved in the ROP of CL. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. High-Performance Capacitive Deionization Disinfection of Water with Graphene Oxide-graft-Quaternized Chitosan Nanohybrid Electrode Coating.

    Science.gov (United States)

    Wang, Yilei; El-Deen, Ahmed G; Li, Peng; Oh, Bernice H L; Guo, Zanru; Khin, Mya Mya; Vikhe, Yogesh S; Wang, Jing; Hu, Rebecca G; Boom, Remko M; Kline, Kimberly A; Becker, David L; Duan, Hongwei; Chan-Park, Mary B

    2015-10-27

    Water disinfection materials should ideally be broad-spectrum-active, nonleachable, and noncontaminating to the liquid needing sterilization. Herein, we demonstrate a high-performance capacitive deionization disinfection (CDID) electrode made by coating an activated carbon (AC) electrode with cationic nanohybrids of graphene oxide-graft-quaternized chitosan (GO-QC). Our GO-QC/AC CDID electrode can achieve at least 99.9999% killing (i.e., 6 log reduction) of Escherichia coli in water flowing continuously through the CDID cell. Without the GO-QC coating, the AC electrode alone cannot kill the bacteria and adsorbs a much smaller fraction (<82.8 ± 1.8%) of E. coli from the same biocontaminated water. Our CDID process consists of alternating cycles of water disinfection followed by electrode regeneration, each a few minutes duration, so that this water disinfection process can be continuous and it only needs a small electrode voltage (2 V). With a typical brackish water biocontamination (with 10(4) CFU mL(-1) bacteria), the GO-QC/AC electrodes can kill 99.99% of the E. coli in water for 5 h. The disinfecting GO-QC is securely attached on the AC electrode surface, so that it is noncontaminating to water, unlike many other chemicals used today. The GO-QC nanohybrids have excellent intrinsic antimicrobial properties in suspension form. Further, the GO component contributes toward the needed surface conductivity of the CDID electrode. This CDID process offers an economical method toward ultrafast, contaminant-free, and continuous killing of bacteria in biocontaminated water. The proposed strategy introduces a green in situ disinfectant approach for water purification.

  18. Anionic clay as the drug delivery vehicle: tumor targeting function of layered double hydroxide-methotrexate nanohybrid in C33A orthotopic cervical cancer model

    Directory of Open Access Journals (Sweden)

    Choi G

    2016-01-01

    Full Text Available Goeun Choi,1 Huiyan Piao,1 Zeid A Alothman,2 Ajayan Vinu,3 Chae-Ok Yun,4 Jin-Ho Choy1 1Center for Intelligent Nano-Bio Materials, Department of Chemistry and Nano Science, Ewha Womans University, Seoul, Korea; 2Advanced Materials Research Chair, Chemistry Department, College of Science, King Saud University, Riyadh, Saudi Arabia; 3Future Industries Institute, University of South Australia, Mawson Lakes, SA, Australia; 4Department of Bioengineering, College of Engineering, Hanyang University, Seoul, Korea Abstract: Methotrexate (MTX, an anticancer agent, was successfully intercalated into the anionic clay, layered double hydroxides to form a new nanohybrid drug. The coprecipitation and subsequent hydrothermal method were used to prepare chemically, structurally, and morphologically well-defined two-dimensional drug-clay nanohybrid. The resulting two-dimensional drug-clay nanohybrid showed excellent colloidal stability not only in deionized water but also in an electrolyte solution of Dulbecco’s Modified Eagle’s Medium with 10% fetal bovine serum, in which the average particle size in colloid and the polydispersity index were determined to be around 100 and 0.250 nm, respectively. The targeting property of the nanohybrid drug was confirmed by evaluating the tumor-to-blood and tumor-to-liver ratios of the MTX with anionic clay carrier, and these ratios were compared to those of free MTX in the C33A orthotopic cervical cancer model. The biodistribution studies indicated that the mice treated with the former showed 3.5-fold higher tumor-to-liver ratio and fivefold higher tumor-to-blood ratio of MTX than those treated with the latter at 30 minutes postinjection. Keywords: anionic clay, biodistribution, cervical cancer, colloidal stability, layered double hydroxide, methotrexate 

  19. New non-toxic transition metal nanocomplexes and Zn complex-silica xerogel nanohybrid: Synthesis, spectral studies, antibacterial, and antitumor activities

    Science.gov (United States)

    Shebl, Magdy; Saif, M.; Nabeel, Asmaa I.; Shokry, R.

    2016-08-01

    A new chromone Schiff base and its complexes of Cu(II), Ni(II), Co(II), Fe(III), Zn(II), Cd(II), and UO2(VI) as well as Zn(II) complex-silica xerogel nanohybrid were successfully prepared in a nano domain with crystalline or amorphous structures. Structures of the Schiff base and its complexes were investigated by elemental and thermal analyses, IR, 1H NMR, electronic, ESR, mass spectra, XRD, and TEM, as well as conductivity and magnetic susceptibility measurements. The spectroscopic data revealed that the Schiff base ligand behaves as a monobasic tridentate ligand. The coordination sites with metal ions are γ-pyrone oxygen, azomethine nitrogen, and oxygen of the carboxylic group. The metal complexes exhibited octahedral geometry, except Cu(II) complex, which has a square planar geometry and UO2(VI) complex, in which uranium ion is hepta-coordinated. Transmission electron microscope (TEM) analysis showed that Ni(II) and Zn(II) complexes have aggregated spheres and rod morphologies, respectively. TEM images of Zn(II) complex-silica xerogel nanohybrid showed a nanosheet morphology with 46 nm average size and confirmed that the complex was uniformly distributed into the silica pores. The obtained nanocomplexes were tested as antimicrobial and antitumor agents. The results showed that Zn(II) nanocomplex and Zn(II) complex-silica xerogel nanohybrid have high activity. The toxicity test on mice showed that Zn(II) complex and Zn(II) complex-silica xerogel nanohybrid have lower toxicity than cisplatin.

  20. Mesoporous layer-by-layer ordered nanohybrids of layered double hydroxide and layered metal oxide: highly active visible light photocatalysts with improved chemical stability.

    Science.gov (United States)

    Gunjakar, Jayavant L; Kim, Tae Woo; Kim, Hyo Na; Kim, In Young; Hwang, Seong-Ju

    2011-09-28

    Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O(2) generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) and layered titanium oxide. The layer-by-layer ordering of two kinds of 2D nanosheets is evidenced by powder X-ray diffraction and cross-sectional high resolution-transmission electron microscopy. Upon the interstratification process, the original in-plane atomic arrangements and electronic structures of the component nanosheets remain intact. The obtained heterolayered nanohybrids show a strong absorption of visible light and a remarkably depressed photoluminescence signal, indicating an effective electronic coupling between the two component nanosheets. The self-assembly between 2D inorganic nanosheets leads to the formation of highly porous stacking structure, whose porosity is controllable by changing the ratio of layered titanate/Zn-Cr-LDH. The resultant heterolayered nanohybrids are fairly active for visible light-induced O(2) generation with a rate of ∼1.18 mmol h(-1) g(-1), which is higher than the O(2) production rate (∼0.67 mmol h(-1) g(-1)) by the pristine Zn-Cr-LDH material, that is, one of the most effective visible light photocatalysts for O(2) production, under the same experimental condition. This result highlights an excellent functionality of the Zn-Cr-LDH-layered titanate nanohybrids as efficient visible light active photocatalysts. Of prime interest is that the chemical stability of the Zn-Cr-LDH is significantly improved upon the hybridization, a result of the protection of the LDH lattice by highly stable titanate layer. The present findings clearly demonstrate that the layer-by-layer-ordered assembly between inorganic 2D nanosheets is quite effective not only in improving the photocatalytic activity of the component semiconductors but also in synthesizing novel porous LDH-based hybrid materials with improved chemical

  1. Preparation of zinc hydroxystannate-decorated graphene oxide nanohybrids and their synergistic reinforcement on reducing fire hazards of flexible poly (vinyl chloride)

    OpenAIRE

    Gao, Tingting; Chen, Laicheng; Li, Zhiwei; Yu, Laigui; Wu, Zhishen; Zhang, Zhijun

    2016-01-01

    A novel flame retardant, zinc hydroxystannate-decorated graphene oxide (ZHS/GO) nanohybrid, was successfully prepared and well characterized. Herein, the ZHS nanoparticles could not only enhance the flame retardancy of GO with the synergistic flame-retardant effect of ZHS but also prevent the restack of GO to improve the mechanical properties of poly (vinyl chloride) (PVC) matrix. The structure characterization showed ZHS nanoparticles were bonded onto the surface of GO nanosheets and the ZHS...

  2. Single-step preparation of TiO2/MWCNT Nanohybrid materials by laser pyrolysis and application to efficient photovoltaic energy conversion.

    Science.gov (United States)

    Wang, Jin; Lin, Yaochen; Pinault, Mathieu; Filoramo, Arianna; Fabert, Marc; Ratier, Bernard; Bouclé, Johann; Herlin-Boime, Nathalie

    2015-01-14

    This paper presents the continuous-flowand single-step synthesis of a TiO2/MWCNT (multiwall carbon nanotubes) nanohybrid material. The synthesis method allows achieving high coverage and intimate interface between the TiO2particles and MWCNTs, together with a highly homogeneous distribution of nanotubes within the oxide. Such materials used as active layer in theporous photoelectrode of solid-state dye-sensitized solar cells leads to a substantial performance improvement (20%) as compared to reference devices.

  3. NiFe layered double hydroxide/reduced graphene oxide nanohybrid as an efficient bifunctional electrocatalyst for oxygen evolution and reduction reactions

    Science.gov (United States)

    Zhan, Tianrong; Zhang, Yumei; Liu, Xiaolin; Lu, SiSi; Hou, Wanguo

    2016-11-01

    Highly active and low-cost bifunctional electrocatalysts for oxygen evolution and reduction reactions (OER and ORR) hold a heart position for the renewable energy technologies such as metal-air batteries and fuel cells. Here, we reported the synthesis of NiFe layered double hydroxide/reduced graphene oxide (NiFe-LDH/rGO) nanohybrid via the facile solvothermal method followed by chemical reduction. The template role of surfactant and the hybridization of rGO supplied the NiFe-LDH/rGO catalyst with a porous nanostructure and an enhanced conductivity, favoring both mass transport and charge communication of electrocatalytic reactions. The NiFe-LDH/rGO composite not only displayed highly efficient OER activity in alkaline solution with a low onset overpotential of 240 mV, but also only needed an overpotential of 250 mV to reach the 10 mA cm-2 current density. The NiFe-LDH/rGO nanohybrid also offered excellent ORR catalytic activity with onset potential at 0.796 V in alkaline media. The rotating-disk and rotating-ring-disk electrodes both revealed that the ORR on NiFe-LDH/rGO mainly involved a direct four-electron reaction pathways accompanying part of the two-electron process. The excellent bifunctional activity of the NiFe-LDH/rGO nanohybrid could be attributed to the synergistic effects of rGO and NiFe-LDH components due to the strongly coupled interactions.

  4. Adsorption of Cd(II), Cu(II) and Ni(II) ions by cross-linking chitosan/rectorite nano-hybrid composite microspheres.

    Science.gov (United States)

    Zeng, Lixuan; Chen, Yufei; Zhang, Qiuyun; Guo, Xingmei; Peng, Yanni; Xiao, Huijuan; Chen, Xiaocheng; Luo, Jiwen

    2015-10-05

    Chitosan/rectorie (CTS/REC) nano-hybrid composite microsphere was prepared by changing the proportion of CTS/REC with 2:1, 3:1 and 4:1. Compared with the pure cross-linking chitosan microsphere, the nano-hybrid composite microsphere was proved to have better sorption capacity of Cd(II), Cu(II) and Ni(II), especially 2:1(CTS/REC-1). The adsorption behavior of the microsphere of Cd(II), Cu(II) and Ni(II) was investigated in single and binary metal systems. In single system, the equilibrium studies showed that the adsorption of Cd(II), Cu(II) and Ni(II) followed the Langmuir model and the pseudo-second-order kinetic model. The negative values of (ΔG) suggested that the adsorption process was spontaneous. In binary system, the combined action of the metals was found to be antagonistic and the metal sorption followed the order of Cu(II)>Cd(II)>Ni(II). The regeneration studies indicated that EDTA desorbed Cd(II), Cu(II) and Ni(II) from cross-linking microspheres better than HCl. The FT-IR and XPS spectra showed that coordination bonds were formed between Cd(II), Cu(II) and Ni(II) and the nitrogen atoms of cross-linking CTS/REC nano-hybrid composite microspheres.

  5. Ultrasensitive electrochemical DNA biosensor based on functionalized gold clusters/graphene nanohybrids coupling with exonuclease III-aided cascade target recycling.

    Science.gov (United States)

    Wang, Wei; Bao, Ting; Zeng, Xi; Xiong, Huayu; Wen, Wei; Zhang, Xiuhua; Wang, Shengfu

    2017-05-15

    In this work, a novel and ultrasensitive electrochemical biosensor was constructed for DNA detection based on functionalized gold clusters/graphene nanohybrids (AuNCs/GR nanobybrids) and exonuclease III (Exo III)-aided cascade target recycling. By utilizing the capacity of GR as universal template, different metal nanoclusters including AuNCs/GR nanobybrids and PtNCs/GR nanohybrids were synthesized through convenient ultrasonic method. Exo III-aided cascade recycling was initiated by target DNA, generating the final cleavage product (S2), which acted as a linkage between capture probe and the functionalized metal nanoclusters/GR conjugates in the construction of the biosensor. The AuNCs/GR-DNA-enzyme conjugates acted as interfaces of enzyme-catalyzed silver deposition reaction, achieving DNA detection ranging from 0.02 fM to 20 pM with a detection limit of 0.057 fM. In addition, PtNCs/GR-DNA conjugates presented peroxidase-like activity and the functionalized PtNCs/GR nanohybrids-based electrochemical biosensor also realized DNA detection by catalyzing the 3,3',5,5'-tetramethylbenzidine-hydrogen peroxide (TMB-H2O2) system to produce electrochemical signal. This metal clusters/GR-based multiple-amplified electrochemical biosensor provided an universal method for DNA detection. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Novel Nanohybrids Derived from the Attachment of FePt Nanoparticles on Carbon Nanotubes

    NARCIS (Netherlands)

    Tsoufis, Theodoros; Tomou, Aphrodite; Gournis, Dimitrios; Douvalis, Alexios P.; Panagiotopoulos, Ioannis; Kooi, Bart; Georgakilas, Vasilios; Arfaoui, Imad; Bakas, Thomas

    2008-01-01

    Multiwalled carbon nanotubes (MWCNTs) were used as nanotemplates for the dispersion and stabilization of FePt nanoparticles (NPs). Pre-formed capped FePt NPs were connected to the MWCNTs external surface via covalent binding through organic linkers. Free FePt NPs and MWCNTs-FePt hybrids were anneale

  7. Chemically stable and reusable nano zero-valent iron/graphite-like carbon nitride nanohybrid for efficient photocatalytic treatment of Cr(VI) and rhodamine B under visible light

    Science.gov (United States)

    Liang, Zhiyu; Wen, Qingjuan; Wang, Xiu; Zhang, Fuwei; Yu, Yan

    2016-11-01

    Graphite-like carbon nitride (g-C3N4) displays strong potential applications in visible-light photocatalytic for water treatment, but its applications are greatly restricted by high recombination probability of photo-generated electron-hole pairs, as well as a weak reduction ability toward the heavy metals. In this work, we reported the synthesis of nZVI-g-C3N4 nano-hybrid with highly efficiency toward the photodegradation of RhB and Cr(VI) under the visible light irradiation. The nZVI nanoparticles can well be immobilized and dispersed on the surface of g-C3N4 nanosheets by a facile borohydride-reduction method. As-synthesized nZVI-g-C3N4 has an improved photocatalytic activity much better than that of the pure g-C3N4, wherein over 92.9% of Cr(VI) and 99.9% of RhB can be removed by using nZVI-g-C3N4. The nZVI particles not only contributes to the reduction and immobilization of Cr(VI), but also accelerates the photocatalytic degradation efficiency of RhB due to a lower recombination rate of photoexcited holes and electrons. Moreover, nZVI-g-C3N4 preserves superior photodegradation efficiency after five experimental cycles. It can be attributed that nZVI-g-C3N4 photocatalyst is chemically stable, and part of nZVI can be recovered by g-C3N4. We believe that, the composite of nZVI-g-C3N4 reported here could provide guidance for the design of efficient and reusable materials to remove both the organic compounds and heavy metal ions from waste waters.

  8. Dispersing powders in liquids

    CERN Document Server

    Nelson, RD

    1988-01-01

    This book provides powder technologists with laboratory procedures for selecting dispersing agents and preparing stable dispersions that can then be used in particle size characterization instruments. Its broader goal is to introduce industrial chemists and engineers to the phenomena, terminology, physical principles, and chemical considerations involved in preparing and handling dispersions on a commercial scale. The book introduces novices to: - industrial problems due to improper degree of dispersion; - the nomenclature used in describing particles; - the basic physica

  9. Organic-inorganic Polymer Nano-hybrids Based on Sol-gel Reaction

    Institute of Scientific and Technical Information of China (English)

    Yoshiki; Chujo

    2007-01-01

    1 Results Nano-ordered composite materials consisting of organic polymers and inorganic materials have been attracting attention for the purpose of the creation of high-performance or high-functional polymeric materials. Especially,the word of "polymer hybrid" claims the blends of organic and inorganic components at nano-level dispersion. By using this idea,an enhancement of mechanical strength of organic polymers with silica particles is possible.High transparency of this material is another important ...

  10. Effect of food/oral-simulating liquids on dynamic mechanical thermal properties of dental nanohybrid light-cured resin composites.

    Science.gov (United States)

    Vouvoudi, Evangelia C; Sideridou, Irini D

    2013-08-01

    The purpose of this work was the study of the effect of food/oral simulating liquids on the dynamic mechanical thermal properties (viscoelastic properties) of current commercial dental light-cured resin composites characterized as nanohybrids. These nanohybrids were Grandio, Protofill-nano and Tetric EvoCeram. The properties were determined under dry conditions (1h at 37°C after light-curing) and also after storage in dry air, distilled water, artificial saliva SAGF(®) or ethanol/water solution (75 vol%) at 37°C for up 1, 7, 30 or 90 days. Dynamic mechanical thermal analysis tests were performed on a Diamond Dynamic Mechanical Analyzer in bending mode. A frequency of 1Hz and a temperature range of 25-185°C were applied, while the heating rate of 2°C/min was selected to cover mouth temperature and the materials' likely Tg. Storage modulus, loss modulus and tangent delta were plotted against temperature over this period. The Tg of composites was obtained as the temperature indicated by tanδ peak. Moreover, the maximum height of tanδ peak, the width at the half of tanδ maximum and a parameter known as "ζ" parameter were determined. All composites analyzed 1h after light-curing and 1 day in air or in food/oral simulating liquids showed two Tg. All composites stored for 7, 30 or 90 days in any medium showed unique Tg value. Also among the various properties studied the most sensible in the structural changes of composites seems to be the Tg. Storage of composites in dry air at 37°C which is very close to their Tg (40°C) for 1 or 7 days caused post curing reactions, while storage for 30 or 90 days has no further effect on composites. Storage in water or artificial saliva 37°C for 1 or 7 days caused post curing reactions, while storage for 30 or 90 days seems to cause plasticization effect affecting some parameters analogously. Storage in ethanol/water solution (75vol%) 37°C for 1 or 7 days caused also post curing reactions, while storage for 30 or 90 days

  11. Gold Nanoparticle-Quantum Dot Fluorescent Nanohybrid: Application for Localized Surface Plasmon Resonance-induced Molecular Beacon Ultrasensitive DNA Detection

    Science.gov (United States)

    Adegoke, Oluwasesan; Park, Enoch Y.

    2016-11-01

    In biosensor design, localized surface plasmon resonance (LSPR)-induced signal from gold nanoparticle (AuNP)-conjugated reporter can produce highly sensitive nanohybrid systems. In order to retain the physicochemical properties of AuNPs upon conjugation, high colloidal stability in aqueous solution is needed. In this work, the colloidal stability with respect to the zeta potential (ZP) of four negatively charged thiol-functionalized AuNPs, thioglycolic (TGA)-AuNPs, 3-mercaptopropionic acid (MPA)-AuNPs, l-cysteine-AuNPs and l-glutathione (GSH)-AuNPs, and a cationic cyteamine-capped AuNPs was studied at various pHs, ionic strength, and NP concentration. A strong dependence of the ZP charge on the nanoparticle (NP) concentration was observed. High colloidal stability was exhibited between pH 3 and 9 for the negatively charged AuNPs and between pH 3 and 7 for the cationic AuNPs. With respect to the ionic strength, high colloidal stability was exhibited at ≤104 μM for TGA-AuNPs, l-cysteine-AuNPs, and GSH-AuNPs, whereas ≤103 μM is recommended for MPA-AuNPs. For the cationic AuNPs, very low ionic strength of ≤10 μM is recommended due to deprotonation at higher concentration. GSH-AuNPs were thereafter bonded to SiO2-functionalized alloyed CdZnSeS/ZnSe1.0S1.3 quantum dots (SiO2-Qdots) to form a plasmon-enhanced AuNP-SiO2-Qdots fluorescent nanohybrid. The AuNP-SiO2-Qdots conjugate was afterward conjugated to a molecular beacon (MB), thus forming an ultrasensitive LSPR-induced SiO2-Qdots-MB biosensor probe that detected a perfect nucleotide DNA sequence at a concentration as low as 10 fg/mL. The limit of detection was 11 fg/mL (1.4 fM) while the biosensor probe efficiently distinguished between single-base mismatch and noncomplementary sequence target.

  12. Dispersion y dinamica poblacional

    Science.gov (United States)

    Dispersal behavior of fruit flies is appetitive. Measures of dispersion involve two different parameter: the maximum distance and the standard distance. Standard distance is a parameter that describes the probalility of dispersion and is mathematically equivalent to the standard deviation around ...

  13. Seed dispersal in fens

    NARCIS (Netherlands)

    Middleton, Beth; van Diggelen, Rudy; Jensen, Kai

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and redu

  14. Eight-year randomized clinical evaluation of Class II nanohybrid resin composite restorations bonded with a one-step self-etch or a two-step etch-and-rinse adhesive

    DEFF Research Database (Denmark)

    van Dijken, Jan WV; Pallesen, Ulla

    2015-01-01

    Objectives: The aimof this study is to observe the durability of Class II nanohybrid resin composite restorations, placed with two different adhesive systems, in an 8-year follow-up. Methods: Seventy-eight participants received at random at least two Class II restorations of the ormocer......-based nanohybrid resin composite (Ceram X) bonded with either a one-step self-etch adhesive (Xeno III) or a control two-step etch-and-rinse adhesive (Excite). The 165 restorations were evaluated using slightly modified United States Public Health Services (USPHS) criteria at baseline and then yearly during 8 years...... and no significant difference in overall clinical performance between the two adhesives. Fracture was the main reason for failure. Clinical relevance: The one-step self-etch adhesive showed a good long-term clinical effectiveness in combination with the nanohybrid resin composite in Class II restorations....

  15. Heteroaggregation of Graphene Oxide with Nanometer- and Micrometer-Sized Hematite Colloids: Influence on Nanohybrid Aggregation and Microparticle Sedimentation.

    Science.gov (United States)

    Feng, Yiping; Liu, Xitong; Huynh, Khanh An; McCaffery, J Michael; Mao, Liang; Gao, Shixiang; Chen, Kai Loon

    2017-06-20

    Heteroaggregation of graphene oxide (GO) with nanometer- and micrometer-sized hematite colloids, which are naturally present in aquatic systems, is investigated in this study. The heteroaggregation rates between GO and hematite nanoparticles (HemNPs) were quantified by dynamic light scattering, while the heteroaggregation between GO and micrometer-sized hematite particles (HemMPs) was examined through batch adsorption and sedimentation experiments. The heteroaggregation rates of GO with HemNPs first increased and then decreased with increasing GO/HemNP mass concentration ratios. The conformation of GO-HemNP heteroaggregates at different GO/HemNP mass concentration ratios was observed through transmission electron microscopy imaging. Initially, GO underwent heteroaggregation with HemNPs through electrostatic attraction to form primary heteroaggregates, which were further bridged by GO to form bigger clusters. At high GO/HemNP mass concentration ratios where GO outnumbered HemNPs, heteroaggregation resulted in the formation of stable GO-HemNP nanohybrids that have a critical coagulation concentration of 308 mM NaCl at pH 5.2. In the case of HemMPs, GO adsorbed readily on the microparticles and, at an optimal GO/HemMP ratio of ∼0.002, the sedimentation of HemMPs was the fastest, most likely because of the formation of "electrostatic patches" leading to favorable aggregation of the microparticles.

  16. Effect of SiO2-acryl nanohybrid coating layers on transparent conducting oxide-poly(ethylene terephthalate) superstrate.

    Science.gov (United States)

    Kang, Y T; Kang, D P; Kang, D J; Chung, I D

    2013-05-01

    SiO2-acryl nanohybrid coating layers were produced by hybridizing acrylic resin and surface-modified colloidal silica (CS) nanoparticles. First, CS nanoparticles were modified with methyltrimethoxysilane (MTMS) and vinyltrimethoxysilane (VTMS) by a sol-gel process. The surface-modified CS nanoparticles were then solvent-exchanged to be homogeneous in acrylic resin. The Hybrid materials were mixed in variation with the amount of surface-modified CS nanoparticles, coated with poly(ethylene terephthalate) (PET), then finally cured by UV light to obtain a hybrid coating layer. Field emission scanning electron microscopy (FE-SEM), particle size analysis (using a Zetasizer), and atomic force microscopy (AFM) were performed to determine the morphology of the hybrid thin-films. Thermogravimetric analysis (TGA) was used to investigate the thermal properties. Fourier-transform infrared (FTIR), ultraviolet-visible (UVNis) spectroscopies, and pencil hardness were used to obtain the details of chemical structures, optical properties, and hardness, respectively. The hybrid thin films had shown to be enhanced properties compared to their urethane acrylate prepolymer (UAP) coating film.

  17. Magneto-conductive encryption assisted by third-order nonlinear optical effects in carbon/metal nanohybrids

    Science.gov (United States)

    García-Merino, J. A.; Mercado-Zúñiga, C.; Martínez-González, C. L.; Torres-SanMiguel, C. R.; Vargas-García, J. R.; Torres-Torres, C.

    2017-03-01

    The influence of a magnetic field on electrical conductivity and the third-order nonlinear optical properties exhibited by carbon nanotubes decorated with platinum nanoparticles is reported. The experimental and numerical results of the nonlinear magneto-optics, magneto-conductivity and photo-thermal processes were analyzed. The simultaneous impact of optical absorptive nonlinearities and the magnetic field in the sample allowed us to encrypt information in the electronic signals by designing an exclusive-OR logic gate scheme. The samples were prepared in film form using a spray pyrolysis route and a chemical vapor deposition approach. The characterization of the morphological nature of the multiwall nanotubes was evaluated by transmission electron microscopy and x-ray techniques. A vectorial two-wave mixing method was conducted by using nanosecond pulses at 532 nm in order to estimate the nonlinear optical behavior in the nanohybrid materials explored. An important enhancement in the phonon-band-structured transport from the inclusion of nanoparticles in the nanotubes was numerically calculated. A distinguished modification in the transient dynamics of the photo-thermal transitions and Kerr nonlinearities was pointed out to be due to the metallic nanoparticles incorporated in the sample. An extraordinary evolution of the magneto-conductivity, together with a strong change in the optical Kerr transmittance exposed to the magnetic field in propagation through the nanostructures, was observed.

  18. Emerging integrated nanohybrid drug delivery systems to facilitate the intravenous-to-oral switch in cancer chemotherapy.

    Science.gov (United States)

    Luo, Cong; Sun, Jin; Du, Yuqian; He, Zhonggui

    2014-02-28

    Nanohybrid drug delivery systems have presented lots of characteristic advantages as an efficient strategy to facilitate oral drug delivery. Nonetheless, oral administration of chemotherapy agents by nanoparticulate delivery technology still faces great challenges owing to the multiple biobarriers ranging from poorly physicochemical properties of drugs, to complex gastrointestinal disposition and to presystemic metabolism. This review briefly analyzes a series of biobarriers hindering oral absorption and describes the multiple aspects for facilitating the intravenous-to-oral switch in cancer therapy. Moreover, the developed nanoparticulate drug delivery strategies to overcome the above obstacles are provided, including metabolic enzyme inhibition, enteric-coated nanocarriers, bioadhesive and mucus-penetrating strategies, P-gp inhibition and active targeting. On these foundations, the emerging trends of integrated hybrid nanosystems in response to the present low-efficiency drug delivery of any single approach are summarized, such as mixed polymeric micelles and nanocomposite particulate systems. Finally, the recent advances of high-efficiency hybrid nanoparticles in oral chemotherapy are highlighted, with special attention on integrated approach to design drug delivery nanosystems.

  19. Clinical Evaluation of Silorane and Nano-hybrid Resin Composite Restorations in Class II Cavities up to 3 Years.

    Science.gov (United States)

    Öztürk-Bozkurt, F; Toz, T; Kara-Tuncer, A; Gözükara-Bağ, H; Özcan, M

    In this study, the clinical performance of a silorane-based resin composite (SC) vs a nano-hybrid resin composite (NHC) was evaluated in Class II cavities. From January 2012 to February 2013, a total of 29 patients (eight men, 21 women; mean age, 24 ± 5 years) received 29 pairs of restorations using both SC (Filtek Silorane, 3M ESPE) and NHC (Filtek Z550, 3M ESPE) materials. Patients were followed until February 2015. One operator performed all restorations using the corresponding adhesive resins according to the manufacturers' instructions. Two calibrated independent examiners evaluated the restorations at one week, six months, and then annually using the modified United States Public Health Service (USPHS) criteria for anatomic form, marginal adaptation, color match, surface roughness, marginal discoloration, secondary caries, and postoperative sensitivity. Changes in the USPHS parameters were analyzed with the McNemar test (α=0.05). The mean observation period was 31.2 months. Marginal adaptation was the only parameter that showed a significant difference and was worse for SC than NHC (p=0.012). At the final recall, 17 restorations from the SC group and five from the NHC group received a score of 1 (explorer catches). These scores were significantly different between baseline and final recall for SC (p0.05). Both NHC and SC performed similarly in Class II restorations up to three years except for marginal adaptation, for which the latter demonstrated significant deterioration at the final recall compared with baseline.

  20. Molecular dynamics simulations on the relationship between the elastic parameters and the molecular structures of nano-hybrid POSS materials

    Institute of Scientific and Technical Information of China (English)

    ZENG Fan-lin; SUN Yi; HU Li-jiang

    2006-01-01

    To research the relationship between the elastic parameters and the molecular structures of nano hybrid polyhedral oligomeric silsesquioxanes (POSS) materials, the mechanical properties at different temperatures for three POSS polymers with different molecular architectures, polymerlized norbornene POSS homopolymer (PNPOSS, pedant architecture), γ - (2, 3 glycidoxy) propyl diaminoethane POSS polymer (GPDP, catena architecture) and trimethoxysilylcyclopentyl POSS polymer (TSCP, cage -cage network architecture) were obtained by molecular dynamics simulations based on the Compass force-field. Results indicate that the molecular architectures of the POSS polymers have great influence on the reinforced effects. The effect of the cage-cage network architecture is best, while that of the catena architecture takes second place and the pedant architecture has the least influence comparatively. The reinforced effects of the POSS monomers were examined. The influences of the temperatures on these effects were analyzed also. It may provide some basis for the reasonable applications of the excellent mechanical properties of the organic-inorganic nano-hybrid materials. It may also provide references for exploitation and design of the POSS materials.

  1. Facile synthesis of titania/hyperbranched polyglycidol nanohybrids with controllable morphologies: from solid spheres, capsules to tubes

    Energy Technology Data Exchange (ETDEWEB)

    Li Haiqing; Zhang Lin; Jo, Jung Kyu; Ha, Chang-Sik; Shchipunov, Yury A.; Kim, Il, E-mail: ilkim@pusan.ac.kr [Pusan National University, WCU Center for Synthetic Polymer Bioconjugate Hybrid Materials, Department of Polymer Science and Engineering (Korea, Republic of)

    2011-05-15

    Titania/Hyperbranched polyglycidol (HBP) nanohybrids with tunable morphologies have been synthesized via a sol-gel process at ambient temperature. One-shot addition of varied amounts of titanium precursor tetraisopropoxide (TTIP) yields spherical titania/HBP solid particles with tunable size, while a controlled addition of TTIP results in spherical titania/HBP capsules. The average outer and inner diameters of the resultant capsules are also controllable according to the amount of TTIP via an Oswald ripening process. In addition, the modality of additional water supplied in the reaction systems can tune the morphologies of the resulting titania/HBP particles from nanocapsules to nanotubes owing to the accelerated hydrolysis rate of TTIP. The tunability in morphologies of the titania/HBP nanostructures ranging from solid spheres, capsules to tubes could be attributed to the self-assembly of a large amount of titania/HBP aggregates in a rapid, controlled and anisotropic manner, respectively. Surprisingly, by means of HBP contained in the resulting titania/HBP nanostructures, the gold nanoparticles are in situ generated and encapsulated into titania/HBP matrix in the absence of additional reducing agent. The as-prepared gold nanoparticles functionalized titania/HBP hybrids exhibit excellent catalytic function toward the reduction of 4-nitrophenol. This strategy demonstrates a typical example for functionalizing the titania/HBP hybrids targeted to specific applications.

  2. Fabrication of silica-decorated graphene oxide nanohybrids and the properties of composite epoxy coatings research

    Science.gov (United States)

    Ma, Yu; Di, Haihui; Yu, Zongxue; Liang, Ling; Lv, Liang; Pan, Yang; Zhang, Yangyong; Yin, Di

    2016-01-01

    With the purpose of preparing anticorrosive coatings, solvent-based epoxy resins often serve as raw material. Unfortunately, plentiful micro-pores are fabricated via solvent evaporation in the resin' curing process, which is an intrinsic shortcoming and it is thus necessary to obstacle their micro-pore for enhancing antiseptic property. To reduce the intrinsic defect and increase the corrosion resistance of coating, we synthesize a series of SiO2-GO hybrids through anchoring silica (SiO2) on graphene oxide (GO) sheets with the help of 3-aminopropyltriethoxysilane and 3-glycidoxypropyltrimethoxysilane, and disperse the hybrids into epoxy resin at a low weight fraction of 2%. Furthermore, we investigate the appropriate preparation proportion of SiO2-GO hybrids (namely: SiO2-GO (1:5)). The electrochemical impedance spectroscopy (EIS) test and coatings' morphology monitoring in corrosion process reveal that the anticorrosive performance of epoxy coatings is significantly enhanced by incorporation of SiO2-GO (1:5) hybrids to epoxy compared with neat epoxy and other nanofillers including SiO2 or GO at the same contents. The superiority of the SiO2-GO (1:5) hybrids is related to their excellent dispersion in resin and sheet-like structure.

  3. Amphiphilic polymer-mediated formation of laponite-based nanohybrids with robust stability and pH sensitivity for anticancer drug delivery.

    Science.gov (United States)

    Wang, Guoying; Maciel, Dina; Wu, Yilun; Rodrigues, João; Shi, Xiangyang; Yuan, Yuan; Liu, Changsheng; Tomás, Helena; Li, Yulin

    2014-10-08

    The development of pH-sensitive drug delivery nanosystems that present a low drug release at the physiological pH and are able to increase the extent of the release at a lower pH value (like those existent in the interstitial space of solid tumors (pH 6.5) and in the intracellular endolysosomal compartments (pH 5.0)) is very important for an efficient and safe cancer therapy. Laponite (LP) is a synthetic silicate nanoparticle with a nanodisk structure (25 nm in diameter and 0.92 nm in thickness) and negative-charged surface, which can be used for the encapsulation of doxorubicin (DOX, a cationic drug) through electrostatic interactions and exhibit good pH sensitivity in drug delivery. However, the colloidal instability of LP still limits its potential clinical applications. In this study, we demonstrate an elegant strategy to develop stable Laponite-based nanohybrids through the functionalization of its surface with an amphiphile PEG-PLA copolymer by a self-assembly process. The hydrophobic block of PEG-PLA acts as an anchor that binds to the surface of drug-loaded LP nanodisks, maintaining the core structure, whereas the hydrophilic PEG part serves as a protective stealth shell that improves the whole stability of the nanohybrids under physiological conditions. The resulting nanocarriers can effectively load the DOX drug (the encapsulation efficiency is 85%), and display a pH-enhanced drug release behavior in a sustained way. In vitro biological evaluation indicated that the DOX-loaded nanocarriers can be effectively internalized by CAL-72 cells (an osteosarcoma cell line), and exhibit a remarkable higher anticancer cytotoxicity than free DOX. The merits of Laponite/PEG-PLA nanohybrids, such as good cytocompatibility, excellent physiological stability, sustained pH-responsive release properties, and improved anticancer activity, make them a promising platform for the delivery of other therapeutic agents beyond DOX.

  4. Dispersion management with metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M.

    2017-03-07

    An apparatus, system, and method to counteract group velocity dispersion in fibers, or any other propagation of electromagnetic signals at any wavelength (microwave, terahertz, optical, etc.) in any other medium. A dispersion compensation step or device based on dispersion-engineered metamaterials is included and avoids the need of a long section of specialty fiber or the need for Bragg gratings (which have insertion loss).

  5. Vowel dispersion in Truku

    OpenAIRE

    Chiang, Wen-yu; Chiang, Fang-mei

    2013-01-01

    This study investigates the dispersion of vowel space in Truku, an endangered Austronesian language in Taiwan. Adaptive Dispersion (Liljencrants and Lindblom, 1972; Lindblom, 1986, 1990) proposes that the distinctive sounds of a language tend to be positioned in phonetic space in a way that maximizes perceptual contrast. For example, languages with large vowel inventories tend to expand the overall acoustic vowel space. Adaptive Dispersion predicts that the distance between the point vowels w...

  6. Seed dispersal in fens

    Science.gov (United States)

    Middleton, B.; Van Diggelen, R.; Jensen, K.

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and reducing genetic exchange. Species in fragmented wetlands may have lower reproductive success, which can lead to biodiversity loss. While fens may have always been relatively isolated from each other, they have become increasingly fragmented in modern times within agricultural and urban landscapes in both Europe and North America. Dispersal by water, animals and wind has been hampered by changes related to development in landscapes surrounding fens. Because the seeds of certain species are long-lived in the seed bank, frequent episodes of dispersal are not always necessary to maintain the biodiversity of fens. However, of particular concern to restoration is that some dominant species, such as the tussock sedge Carex stricta, may not disperse readily between fens. Conclusions: Knowledge of seed dispersal can be used to maintain and restore the biodiversity of fens in fragmented landscapes. Given that development has fragmented landscapes and that this situation is not likely to change, the dispersal of seeds might be enhanced by moving hay or cattle from fens to damaged sites, or by reestablishing lost hydrological connections. ?? IAVS; Opulus Press.

  7. Visualizing Dispersion Interactions

    Science.gov (United States)

    Gottschalk, Elinor; Venkataraman, Bhawani

    2014-01-01

    An animation and accompanying activity has been developed to help students visualize how dispersion interactions arise. The animation uses the gecko's ability to walk on vertical surfaces to illustrate how dispersion interactions play a role in macroscale outcomes. Assessment of student learning reveals that students were able to develop…

  8. Visualizing Dispersion Interactions

    Science.gov (United States)

    Gottschalk, Elinor; Venkataraman, Bhawani

    2014-01-01

    An animation and accompanying activity has been developed to help students visualize how dispersion interactions arise. The animation uses the gecko's ability to walk on vertical surfaces to illustrate how dispersion interactions play a role in macroscale outcomes. Assessment of student learning reveals that students were able to develop…

  9. The effect of solvatochromism on the interfacial morphology of P3HT-CdS nanowire nanohybrids.

    Science.gov (United States)

    Rodd, Christopher M; Agarwal, Ritesh

    2013-08-14

    Increasing performance in organic/inorganic bulk heterojunctions hybrid photovoltaic systems hinges not only on the structure of the inorganic component but also on the morphology of the polymeric component. Changing the morphology of the organic component is a facile way of changing the morphology of the interface between the inorganic and organic components in the bulk heterojunction system. Engineering this interface to more efficiently split photogenerated excitons and transport these carriers to electrodes can increase the efficiency of photovoltaic devices. In this report, we investigate the effect of solvent quality on the morphology of the poly(3-hexylthiophene)-2,5-diyl (P3HT) polymer-semiconductor interface (solvatochromism). We have found that creating more order within the P3HT main chain in solution and prior to deposition has a profound effect on the nature of the P3HT-CdS nanowire interface. Solvents with a larger difference in solubility parameter, Δδ, relative to P3HT, such as methanol and isopropanol, create larger rod domains in the P3HT main chain and result in larger domains of crystalline P3HT at the interface. Solvents with similar solubility parameters as P3HT, such as pyridine and hexanol, create relatively shorter rod domains in the main chain and, as a result, nanohybrids with reduced crystallinity. The results of this paper further cement the importance of manipulating the rod-coil transition in the conducting polymers such as P3HT to improve the crystallinity at the polymer-semiconductor interface that can easily be scaled up to improve the efficiency of bulk heterojunction photovoltatic systems.

  10. Synthesis of heterostructured Pd@TiO{sub 2}/TiOF{sub 2} nanohybrids with enhanced photocatalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xixia [State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum, Qingdao, Shandong 266580 (China); Wei, Guijuan [Department of Materials Physics and Chemistry, College of Science, China University of Petroleum, Qingdao, Shandong 266580 (China); Liu, Junxue [State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum, Qingdao, Shandong 266580 (China); Wang, Zhaojie [Department of Materials Physics and Chemistry, College of Science, China University of Petroleum, Qingdao, Shandong 266580 (China); An, Changhua, E-mail: anchh@upc.edu.cn [State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum, Qingdao, Shandong 266580 (China); Department of Materials Physics and Chemistry, College of Science, China University of Petroleum, Qingdao, Shandong 266580 (China); Zhang, Jun [State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum, Qingdao, Shandong 266580 (China)

    2016-08-15

    Highlights: • TiO{sub 2}/TiOF{sub 2} nanohybrids was synthesized via a two-step solvothermal method. • TiO{sub 2}/TiOF{sub 2} exhibited superior photoactivity in comparison with TiOF{sub 2} or TiO{sub 2}. • The photocatalytic activity was further improved by loading Pd nanoparticles. • Synergistic effect between TiOF{sub 2} and TiO{sub 2} was responsible for the enhanced photocatalytic performance over TiO{sub 2}/TiOF{sub 2}. - Abstract: TiO{sub 2}/TiOF{sub 2} heterostructured nanocomposites has been synthesized through a solvothermal method and characterized by X-ray diffraction, scanning electronic microscopy, transmission electronic microscopy, nitrogen adsorption–desorption isotherms, UV–vis and photo-luminescent spectroscopy. It was found that, compared with single TiOF{sub 2} or TiO{sub 2}, the as-prepared TiO{sub 2}/TiOF{sub 2} nanocomposites exhibited superior photoactivity towards the degradation of organic pollutants, i.e. rhodamine B and solar hydrogen evolution. The results are in accordance with the prohibition of photogenerated electrons and holes recombination in these two samples under light illumination. The photocatalytic activity can be further boosted by introducing Pd nanoparticles onto the surfaces of TiO{sub 2}/TiOF{sub 2} through a simple deposition method without using any stabilizers, which is probably attributed to the enhanced visible-light absorption as well as the facilitated charge-carrier separation after the introduction of Pd nanoparticles. The synergistic effect between TiOF{sub 2} and TiO{sub 2} was discussed and was responsible for the enhancement of their activity in comparison with single counterpart.

  11. Effects of surface conditioning on repair bond strengths of non-aged and aged microhybrid, nanohybrid, and nanofilled composite resins.

    Science.gov (United States)

    Rinastiti, Margareta; Özcan, Mutlu; Siswomihardjo, Widowati; Busscher, Henk J

    2011-10-01

    This study evaluates effects of aging on repair bond strengths of microhybrid, nanohybrid, and nanofilled composite resins and characterizes the interacting surfaces after aging. Disk-shaped composite specimens were assigned to one of three aging conditions: (1) thermocycling (5,000 ×, 5-55 °C), (2) storage in water at 37 °C for 6 months, or (3) immersion in citric acid at 37 °C, pH 3 for 1 week; a non-aged group acted as the control. Two surface conditionings were selected: intermediate adhesive resin application (IAR-application) and chairside silica coating followed by silanization and its specific IAR-application (SC-application). Composite resins, of the same kind as their substrate, were adhered onto the substrates, and repair shear bond strengths were determined, followed by failure type evaluation. Filler particle exposure was determined by X-ray photoelectron spectroscopy and surface roughness analyzed using scanning electron and atomic force microscopy. Surface roughness increased in all composite resins after aging, but filler particle exposure at the surface only increased after thermocycling and citric acid immersion. Composite resin type, surface conditioning, and aging method significantly influenced the repair bond strengths (p water storage. Repair bond strengths in aged composite resins after IAR-application were always lower in non-aged ones, while SC-application led to higher bond strengths than IAR-application after thermocycling and water storage. In addition, SC-application led to more cohesive failures than after IAR-application, regardless the aging method.

  12. Perfect Dispersive Medium

    CERN Document Server

    Gupta, Shulabh

    2015-01-01

    Dispersion is at the heart of all ultrafast real-time signal processing systems across the entire electromagnetic spectrum ranging from radio-frequencies to optics. However, following Kramer-Kronig relations, these signal processing systems have been plagued with the parasitic amplitude distortions due to frequency dependent, and non-flat amplitude transmission of naturally dispersive media. This issue puts a serious limitation on the applicability and performance of these signal processing systems. To solve the above mentioned issue, a perfect dispersive medium is proposed in this work, which artificially violates the Kramer-Kronig relations, while satisfying all causality requirements. The proposed dispersive metamaterial is based on loss-gain metasurface pairs and exhibit a perfectly flat transmission response along with arbitrary dispersion in a broad bandwidth, thereby solving a seemingly unavoidable issue in all ultrafast signal processing systems. Such a metamaterial is further shown using sub-waveleng...

  13. Evolution of dispersal distance.

    Science.gov (United States)

    Durrett, Rick; Remenik, Daniel

    2012-03-01

    The problem of how often to disperse in a randomly fluctuating environment has long been investigated, primarily using patch models with uniform dispersal. Here, we consider the problem of choice of seed size for plants in a stable environment when there is a trade off between survivability and dispersal range. Ezoe (J Theor Biol 190:287-293, 1998) and Levin and Muller-Landau (Evol Ecol Res 2:409-435, 2000) approached this problem using models that were essentially deterministic, and used calculus to find optimal dispersal parameters. Here we follow Hiebeler (Theor Pop Biol 66:205-218, 2004) and use a stochastic spatial model to study the competition of different dispersal strategies. Most work on such systems is done by simulation or nonrigorous methods such as pair approximation. Here, we use machinery developed by Cox et al. (Voter model perturbations and reaction diffusion equations 2011) to rigorously and explicitly compute evolutionarily stable strategies.

  14. Eight-year randomized clinical evaluation of Class II nanohybrid resin composite restorations bonded with a one-step self-etch or a two-step etch-and-rinse adhesive

    DEFF Research Database (Denmark)

    van Dijken, Jan WV; Pallesen, Ulla

    2015-01-01

    Objectives: The aimof this study is to observe the durability of Class II nanohybrid resin composite restorations, placed with two different adhesive systems, in an 8-year follow-up. Methods: Seventy-eight participants received at random at least two Class II restorations of the ormocer-based nan......Objectives: The aimof this study is to observe the durability of Class II nanohybrid resin composite restorations, placed with two different adhesive systems, in an 8-year follow-up. Methods: Seventy-eight participants received at random at least two Class II restorations of the ormocer......-based nanohybrid resin composite (Ceram X) bonded with either a one-step self-etch adhesive (Xeno III) or a control two-step etch-and-rinse adhesive (Excite). The 165 restorations were evaluated using slightly modified United States Public Health Services (USPHS) criteria at baseline and then yearly during 8 years...... and no significant difference in overall clinical performance between the two adhesives. Fracture was the main reason for failure. Clinical relevance: The one-step self-etch adhesive showed a good long-term clinical effectiveness in combination with the nanohybrid resin composite in Class II restorations....

  15. Four-year clinical evaluation of Class II nano-hybrid resin composite restorations bonded with a one-step self-etch and a two-step etch-and-rinse adhesive

    DEFF Research Database (Denmark)

    van Dijken, Jan W V; Pallesen, Ulla

    2011-01-01

    The objective of this prospective clinical trial was to evaluate the 4-year clinical performance of an ormocer-based nano-hybrid resin composite (Ceram X; Dentsply/DeTrey) in Class II restorations placed with a one-step self-etch (Xeno III; Dentsply/DeTrey) and two-step etch-and-rinse adhesive...

  16. Synthesis of free-standing carbon nanohybrid by directly growing carbon nanotubes on air-sprayed graphene oxide paper and its application in supercapacitor

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Li; Jiang, Wenchao; Yuan, Yang; Goh, Kunli; Yu, Dingshan [School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459 (Singapore); Wang, Liang [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Chen, Yuan, E-mail: chenyuan@ntu.edu.sg [School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459 (Singapore)

    2015-04-15

    We report the synthesis of a free-standing two dimensional carbon nanotube (CNT)-reduced graphene oxide (rGO) hybrid by directly growing CNTs on air-sprayed GO paper. As a result of the good integration between CNTs and thermally reduced GO film during chemical vapor deposition, excellent electrical conductivity (2.6×10{sup 4} S/m), mechanical flexibility (electrical resistance only increases 1.1% after bent to 90° for 500 times) and a relatively large surface area (335.3 m{sup 2}/g) are achieved. Two-electrode supercapacitor assembled using the CNT–rGO hybrids in ionic liquid electrolyte (1-ethyl-3-methylimidazolium tetrafluoroborate) shows excellent stability upon 500 bending cycles with the gravimetric energy density measuring 23.7 Wh/kg and a power density of 2.0 kW/kg. Furthermore, it shows an impedance phase angle of −64.4° at a frequency of 120 Hz, suggesting good potentials for 120 Hz alternating current line filtering applications. - Graphical abstract: Flexible and highly conductive carbon nanotube-reduced graphene oxide nanohybrid. - Highlights: • Direct growth of carbon nanotubes by chemical vapor deposition on air-sprayed graphene oxide paper. • Two-dimensional carbon nanohybrid with excellent conductivity and mechanical flexibility. • Supercapacitor with excellent performance stability upon mechanical deformation for flexible electronics applications. • Supercapacitor with high impedance phase angle for 120 Hz alternating current line filtering applications.

  17. Hierarchical Cobalt Hydroxide and B/N Co-Doped Graphene Nanohybrids Derived from Metal-Organic Frameworks for High Energy Density Asymmetric Supercapacitors

    Science.gov (United States)

    Tabassum, Hassina; Mahmood, Asif; Wang, Qingfei; Xia, Wei; Liang, Zibin; Qiu, Bin; Zhao, Ruo; Zou, Ruqiang

    2017-02-01

    To cater for the demands of electrochemical energy storage system, the development of cost effective, durable and highly efficient electrode materials is desired. Here, a novel electrode material based on redox active β-Co(OH)2 and B, N co-doped graphene nanohybrid is presented for electrochemical supercapacitor by employing a facile metal-organic frameworks (MOFs) route through pyrolysis and hydrothermal treatment. The Co(OH)2 could be firmly stabilized by dual protection of N-doped carbon polyhedron (CP) and B/N co-doped graphene (BCN) nanosheets. Interestingly, the porous carbon and BCN nanosheets greatly improve the charge storage, wettability, and redox activity of electrodes. Thus the hybrid delivers specific capacitance of 1263 F g‑1 at a current density of 1A g‑1 with 90% capacitance retention over 5000 cycles. Furthermore, the new aqueous asymmetric supercapacitor (ASC) was also designed by using Co(OH)2@CP@BCN nanohybrid and BCN nanosheets as positive and negative electrodes respectively, which leads to high energy density of 20.25 Whkg‑1. This device also exhibits excellent rate capability with energy density of 15.55 Whkg‑1 at power density of 9331 Wkg‑1 coupled long termed stability up to 6000 cycles.

  18. Core-Shell Structure of Gold Nanoparticles with Inositol Hexaphosphate Nanohybrids for Label-Free and Rapid Detection by SERS Nanotechnology

    Directory of Open Access Journals (Sweden)

    Andreas H. H. Mevold

    2015-01-01

    Full Text Available Gold nanoparticles bound with inositol hexaphosphate (IP6 (AuNPs/IP6 were prepared by in situ reduction of various concentrations of IP6 (0~320 µM through modified Frens method for surface-enhanced Raman scattering (SERS detection. The resultant AuNPs/IP6 were subject to characterization including UV/Vis spectroscopy, transmission electron microscopy (TEM, dynamic light scattering (DLS, zeta potential, and X-ray photoelectron spectroscopy (XPS. The results showed that AuNPs with 65 µM of IP6 would result in a core AuNPs-shell (IP6 layer structure, which exhibited the strongest SERS signal, due to the “hot spot effect” generated from the 1-2 nm interparticle gaps of AuNPs/IP6 nanohybrids (ionic interaction of IP6 and Au+. Furthermore, the reaction kinetics of Au and IP6 were also investigated in this work. Higher concentration of IP6 (190 and 260 µM will make AuNPs become irregularly shaped, because IP6 is a basic salt and served as a pH mediator. The morphology and distribution of AuNPs were greatly improved by addition of 65 µM of IP6. This novel AuNPs/IP6 nanohybrid showed great stability and Raman enhancement. It is promising in the application of rapid and label-free biological detection of bacteria or tumor cells.

  19. Hierarchical Cobalt Hydroxide and B/N Co-Doped Graphene Nanohybrids Derived from Metal-Organic Frameworks for High Energy Density Asymmetric Supercapacitors

    Science.gov (United States)

    Tabassum, Hassina; Mahmood, Asif; Wang, Qingfei; Xia, Wei; Liang, Zibin; Qiu, Bin; zhao, Ruo; Zou, Ruqiang

    2017-01-01

    To cater for the demands of electrochemical energy storage system, the development of cost effective, durable and highly efficient electrode materials is desired. Here, a novel electrode material based on redox active β-Co(OH)2 and B, N co-doped graphene nanohybrid is presented for electrochemical supercapacitor by employing a facile metal-organic frameworks (MOFs) route through pyrolysis and hydrothermal treatment. The Co(OH)2 could be firmly stabilized by dual protection of N-doped carbon polyhedron (CP) and B/N co-doped graphene (BCN) nanosheets. Interestingly, the porous carbon and BCN nanosheets greatly improve the charge storage, wettability, and redox activity of electrodes. Thus the hybrid delivers specific capacitance of 1263 F g−1 at a current density of 1A g−1 with 90% capacitance retention over 5000 cycles. Furthermore, the new aqueous asymmetric supercapacitor (ASC) was also designed by using Co(OH)2@CP@BCN nanohybrid and BCN nanosheets as positive and negative electrodes respectively, which leads to high energy density of 20.25 Whkg−1. This device also exhibits excellent rate capability with energy density of 15.55 Whkg−1 at power density of 9331 Wkg−1 coupled long termed stability up to 6000 cycles. PMID:28240224

  20. Clinical performance of Class I nanohybrid composite restorations with resin-modified glass-ionomer liner and flowable composite liner: A randomized clinical trial

    Science.gov (United States)

    Suhasini, Krishtipati; Madhusudhana, Koppolu; Suneelkumar, Chinni; Lavanya, Anumula; Chandrababu, K. S.; Kumar, Perisetty Dinesh

    2016-01-01

    Background: Liners play a vital role in minimizing polymerization shrinkage stress by elastic bonding concept and increase the longevity and favorable outcome for composite restorations. Aims: The aim of this study was to evaluate the clinical performance of nanohybrid composite restorations using resin-modified glass-ionomer and flowable composite liners. Settings and Design: A single-centered, double-blinded randomized clinical trial, with split-mouth design and equal allocation ratio that was conducted in the Department of Conservative Dentistry and Endodontics. Materials and Methods: In forty patients, a total of eighty Class I restorations were placed with resin-modified glass-ionomer cement (RMGIC) liner (FUJI II LC, GC America) in one group and flowable composite liner (smart dentin replacement/SDR, Dentsply Caulk, Milford, DE, USA) in another group. All restorations were clinically evaluated by two examiners, immediately (baseline), 3, 6, and 12 months using US Public Health Service modified criteria. Statistical Analysis Used: Statistical analysis was performed using McNemar's test (P < 0.05). Results: There was no significant difference in the color match, marginal discoloration, surface roughness, and marginal adaptation. Restorations with RMGIC liner group show 20% Bravo scores on anatomic form at 12 months but are still clinically acceptable. Conclusion: Nanohybrid composite restorations with RMGIC (Fuji II LC) and flowable composite liner (SDR) demonstrated clinically acceptable performance after 12 months. PMID:27994310

  1. General Solvent-dependent Strategy toward Enhanced Oxygen Reduction Reaction in Graphene/Metal Oxide Nanohybrids: Effects of Nitrogen-containing Solvent

    Science.gov (United States)

    Kao, Wei-Yao; Chen, Wei-Quan; Chiu, Yu-Hsiang; Ho, Yu-Hsuan; Chen, Chun-Hu

    2016-11-01

    A general solvent-dependent protocol directly influencing the oxygen reduction reaction (ORR) in metal oxide/graphene nanohybrids has been demonstrated. We conducted the two-step synthesis of cobalt oxide/N-doped graphene nanohybrids (CNG) with solvents of water, ethanol, and dimethylformamide (DMF), representing tree typical categories of aqueous, polar organic, and organic N-containing solvents commonly adopted for graphene nanocomposites preparation. The superior ORR performance of the DMF-hybrids can be attributed to the high nitrogen-doping, aggregation-free hybridization, and unique graphene porous structures. As DMF is the more effective N-source, the spectroscopic results support a catalytic nitrogenation potentially mediated by cobalt-DMF coordination complexes. The wide-distribution of porosity (covering micro-, meso-, to macro-pore) and micron-void assembly of graphene may further enhance the diffusion kinetics for ORR. As the results, CNG by DMF-synthesis exhibits the high ORR activities close to Pt/C (i.e. only 8 mV difference of half-wave potential with electron transfer number of 3.96) with the better durability in the alkaline condition. Additional graphene hybrids comprised of iron and manganese oxides also show the superior ORR activities by DMF-synthesis, confirming the general solvent-dependent protocol to achieve enhanced ORR activities.

  2. Rates of Gravel Dispersion

    Science.gov (United States)

    Haschenburger, J. K.

    2010-12-01

    Sediment transfers in gravel-bed rivers involve the three-dimensional dispersion of mixed size sediment. From a kinematics standpoint, few studies are available to inform on the streamwise and vertical rates of sediment dispersion in natural channels. This research uses a gravel tracing program to quantify dispersion rates over 19 flood seasons. Empirical observations come from Carnation Creek, a small gravel-bed river with large woody debris located on the west coast of Vancouver Island, Canada. Frequent floods and the relatively limited armor layer facilitate streambed activity and relatively high bedload transport rates, typically under partial sediment transport conditions. Over 2500 magnetically tagged stones, ranging in size from 16 to 180 mm, were deployed on the bed surface between 1989 and 1992 in four generations. To quantify gravel dispersion over distances up to 2.6 km, observations are taken from 11 recoveries. Over 280 floods capable of moving bedload occurred during this period, with five exceeding the estimated bankfull discharge. Streamwise dispersion is quantified by virtual velocity, while dispersion into the streambed is quantified by a vertical burial rate. The temporal trend in streamwise dispersion rates is described by a power function. Initial virtual velocities decline rapidly from around 1.4 m/hr to approach an asymptote value of about 0.2 m/hr. The rapid change corresponds to a significant increase in the proportion of buried tracers due to vertical mixing. Initial burial rates reflect the magnitude of the first flood after tracer deployment and range from 0.07 to 0.46 cm/hr depending on tracer generation. Burial rates converge to about 0.06 cm/hr after the fourth flood season and then gradually decline to about 0.01 cm/hr. Thus, the rate of streamwise dispersion exceeds that of vertical dispersion by three orders of magnitude when the movement of sediment routinely activated by floods is considered.

  3. Organic/Inorganic Nano-hybrids with High Dielectric Constant for Organic Thin Film Transistor Applications

    Science.gov (United States)

    Yu, Yang-Yen; Jiang, Ai-Hua; Lee, Wen-Ya

    2016-11-01

    The organic material soluble polyimide (PI) and organic-inorganic hybrid PI-barium titanate (BaTiO3) nanoparticle dielectric materials (IBX, where X is the concentration of BaTiO3 nanoparticles in a PI matrix) were successfully synthesized through a sol-gel process. The effects of various BaTiO3 contents on the hybrid film performance and performance optimization were investigated. Furthermore, pentacene-based organic thin film transistors (OTFTs) with PI-BaTiO3/polymethylmethacrylate or cyclic olefin copolymer (COC)-modified gate dielectrics were fabricated and examined. The hybrid materials showed effective dispersion of BaTiO3 nanoparticles in the PI matrix and favorable thermal properties. X-ray diffraction patterns revealed that the BaTiO3 nanoparticles had a perovskite structure. The hybrid films exhibited high formability and planarity. The IBX hybrid dielectric films exhibited tunable insulating properties such as the dielectric constant value and capacitance in ranges of 4.0-8.6 and 9.2-17.5 nF cm-2, respectively. Adding the modified layer caused the decrease of dielectric constant values and capacitances. The modified dielectric layer without cross-linking displayed a hydrophobic surface. The electrical characteristics of the pentacene-based OTFTs were enhanced after the surface modification. The optimal condition for the dielectric layer was 10 wt% hybrid film with the COC-modified layer; moreover, the device exhibited a threshold voltage of 0.12 V, field-effect mobility of 4.32 × 10-1 cm2 V-1 s-1, and on/off current of 8.4 × 107.

  4. Dispersive hydrodynamics: Preface

    Science.gov (United States)

    Biondini, G.; El, G. A.; Hoefer, M. A.; Miller, P. D.

    2016-10-01

    This Special Issue on Dispersive Hydrodynamics is dedicated to the memory and work of G.B. Whitham who was one of the pioneers in this field of physical applied mathematics. Some of the papers appearing here are related to work reported on at the workshop "Dispersive Hydrodynamics: The Mathematics of Dispersive Shock Waves and Applications" held in May 2015 at the Banff International Research Station. This Preface provides a broad overview of the field and summaries of the various contributions to the Special Issue, placing them in a unified context.

  5. Preference of multi-walled carbon nanotube (MWCNT) to single-walled carbon nanotube (SWCNT) and activated carbon for preparing silica nanohybrid pickering emulsion for chemical enhanced oil recovery (C-EOR)

    Science.gov (United States)

    AfzaliTabar, M.; Alaei, M.; Ranjineh Khojasteh, R.; Motiee, F.; Rashidi, A. M.

    2017-01-01

    The aim of this research was to determine the best nano hybrid that can be used as a Pickering emulsion Chemical Enhanced Oil Recovery (C-EOR). Therefore, we have prepared different carbon structures nano hybrids with SiO2 nano particles with different weight percent using sol-gel method. The as-prepared nano materials were characterized with X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM) and Thermal Gravimetric Analysis (TGA). Pickering emulsions of these nanohybrids were prepared at pH=7 in ambient temperature and with distilled water. Stability of the mentioned Pickering emulsions was controlled for one month. Emulsion phase morphology was investigated using optical microscopic imaging. Evaluation results demonstrated that the best sample is the 70% MWCNT/SiO2 nanohybrid. Stability of the selected nanohybrid (70% MWCNT/SiO2 nanohybrid) was investigated by alteration of salinity, pH and temperature. Results showed that the mentioned Pickering emulsion has very good stability at 0.1%, 1% salinity, moderate and high temperature (25 °C and 90 °C) and neutral and alkaline pH (7, 10) that is suitable for the oil reservoirs conditions. The effect of the related nano fluid on the wettability of carbonate rock was investigated by measuring the contact angle and interfacial tension. Results show that the nanofluid could significantly change the wettability of the carbonate rock from oil wet to water wet and can decrease the interfacial tension. Therefore, the 70% MWCNT/SiO2 nanohybrid Pickering emulsion can be used for Chemical Enhanced Oil Recovery (C-EOR).

  6. Dispersion forces in methane

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; Coulon, P.; Luyckx, R.

    1977-01-01

    The coefficients of the R-6 and R-7 terms in the series representation of the dispersion interaction between two methane molecules and between methane and helium, neon and argon are calculated by a variation method.

  7. 纳米粒子原位杂化酚醛/炭纤维烧蚀防热研究%Studies on ablative and heat-resistant properties of in-situ nano-hybrid PF/CF composite

    Institute of Scientific and Technical Information of China (English)

    刘乃亮; 齐暑华; 李春华; 理莎莎; 付东升

    2011-01-01

    SiC,SiO2 and A12O3 three nano-hybrid phenol formaldehyde resin (PF) were prepared by in-situ hybridization method, respectively. Scanning electron microscopy (SEM) observation showed that nanoparticles dispersed well in the composite and formed the "sea-island" structure with PF. Thermal gravity analysis (TG-DTG) demonstrated three stages in the process of PF thermal degradation,and the calculated results by Kissinger method illustrated that nanoparticles can reduce the thermal decomposition activation energy at the first stage and increase it at the second stage. Wear tests explained that nanoparticles can increase PF reinforced carbon fiber ( CF) composite wear property. Oxygen-acetylene ablation tests indicated that nanoparticles can increase the ablative resistance of PF/CF composite.%采用原位杂化方法分别制备了SiC、SiO2和Al2 O3 3种纳米粒子杂化酚醛树脂,扫描电镜观察发现,纳米粒子均匀分散在酚醛树脂中,与酚醛树脂形成“海-岛”结构;热重分析结果显示,纳米粒子杂化酚醛树脂的降解过程分为3个阶段,通过Kissinger法对杂化酚醛树脂热分解活化能进行计算,发现纳米粒子能够降低树脂第1阶段的热分解活化能,而提高了树脂在第2阶段的热分解活化能;磨耗性能测试显示纳米粒子可提高酚醛树脂/炭纤维耐磨性能;氧—乙炔烧蚀法测试表明,纳米粒子能提高酚醛树脂/炭纤维复合材料的耐烧蚀性能.

  8. Chemically stable and reusable nano zero-valent iron/graphite-like carbon nitride nanohybrid for efficient photocatalytic treatment of Cr(VI) and rhodamine B under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Zhiyu; Wen, Qingjuan; Wang, Xiu; Zhang, Fuwei [Key Laboratory of Eco-materials Advanced Technology (Fuzhou University), Fujian Province University (China); College of Materials Science and Engineering, Fuzhou University, New Campus, Minhou, Fujian Province 350108 (China); Yu, Yan, E-mail: yuyan@fzu.edu.cn [Key Laboratory of Eco-materials Advanced Technology (Fuzhou University), Fujian Province University (China); College of Materials Science and Engineering, Fuzhou University, New Campus, Minhou, Fujian Province 350108 (China)

    2016-11-15

    Highlights: • NZVI-g-C{sub 3}N{sub 4} efficiently photodegrades the organic/inorganic pollutants. • Fe{sup 0} improves the charge separation efficiency of g-C{sub 3}N{sub 4}. • A possible recover mechanism of nZVI-g-C{sub 3}N{sub 4} was proposed. - Abstract: Graphite-like carbon nitride (g-C{sub 3}N{sub 4}) displays strong potential applications in visible-light photocatalytic for water treatment, but its applications are greatly restricted by high recombination probability of photo-generated electron-hole pairs, as well as a weak reduction ability toward the heavy metals. In this work, we reported the synthesis of nZVI-g-C{sub 3}N{sub 4} nano-hybrid with highly efficiency toward the photodegradation of RhB and Cr(VI) under the visible light irradiation. The nZVI nanoparticles can well be immobilized and dispersed on the surface of g-C{sub 3}N{sub 4} nanosheets by a facile borohydride-reduction method. As-synthesized nZVI-g-C{sub 3}N{sub 4} has an improved photocatalytic activity much better than that of the pure g-C{sub 3}N{sub 4}, wherein over 92.9% of Cr(VI) and 99.9% of RhB can be removed by using nZVI-g-C{sub 3}N{sub 4}. The nZVI particles not only contributes to the reduction and immobilization of Cr(VI), but also accelerates the photocatalytic degradation efficiency of RhB due to a lower recombination rate of photoexcited holes and electrons. Moreover, nZVI-g-C{sub 3}N{sub 4} preserves superior photodegradation efficiency after five experimental cycles. It can be attributed that nZVI-g-C{sub 3}N{sub 4} photocatalyst is chemically stable, and part of nZVI can be recovered by g-C{sub 3}N{sub 4}. We believe that, the composite of nZVI-g-C{sub 3}N{sub 4} reported here could provide guidance for the design of efficient and reusable materials to remove both the organic compounds and heavy metal ions from waste waters.

  9. Fickian dispersion is anomalous

    Science.gov (United States)

    Cushman, John H.; O'Malley, Dan

    2015-12-01

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.

  10. A novel photoluminescent nanohybrid of poly(ε-caprolactone) grafted Mg/Al layered double hydroxides and Tb{sup 3+} ions: Synthesis and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Bach, Long Giang [Department of Imaging System Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Center for Advanced Materials Research, Nguyen Tat Thanh Unviersity, Ho Chi Minh City (Viet Nam); Islam, Md. Rafiqul [Department of Imaging System Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Energy and Mineral Resources Division, Ministry of Power, Energy and Mineral Resources, Government of the People’s Republic of Bangladesh, Dhaka 1000 (Bangladesh); Cao, Xuan Thang [Department of Imaging System Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Park, Jong Myung [Surface Engineering Laboratory, Graduate Institute of Ferrous Technology, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Lim, Kwon Taek, E-mail: ktlim@pknu.ac.kr [Department of Imaging System Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

    2014-01-05

    Highlights: • The photoluminescent LDHs-PCL-Tb{sup 3+} nanohybrid was successfully synthesized. • Structure and morphology of LDHs-g-PCL-Tb{sup 3+} were investigated by FT-IR, SEM, and TGA. • XPS and EDS analyses further suggested the formation of LDHs-g-PCL-Tb{sup 3+}. • Optical property of LDHs-g-PCL-Tb{sup 3+} was investigated by PL. -- Abstract: This paper demonstrates a systematic study of the synthesis and characterization of the hybrid of Mg–Al layer double hydroxides (LDHs), poly(ε-caprolactone) (PCL), and terbium ions (Tb{sup 3+}). The hybrid LDH-g-PCL-Tb{sup 3+}-1,10-phenanthroline (Phen) was prepared by the combination of ring opening polymerization (ROP), click chemistry, and coordination chemistry. First, LDHs with a molar ratio of Mg/Al = 2 were prepared by the co-precipitation method, which was subsequently functionalized with (3-chloropropyl) trimethoxysilane in order to introduce azide groups through the reaction of chlorine with sodium azide. Meanwhile, the acetylene functionalized PCL was prepared by ROP of ε-CL, followed by esterification of the hydroxyl groups using succinic anhydride. The click reaction of alkyne-PCL and N{sub 3}-LDHs successfully afforded LDH-g-PCL, which was coordinated with Tb{sup 3+} ions in the presence of Phen. The structure and properties of the nanohybrids were investigated by FT-IR, XPS, EDS, SEM, and TGA analyses. The data indicate the coordination of Tb{sup 3+} ions with LDH-g-PCL nanohybrids. The content of Tb{sup 3+} ions in the LDH-g-PCL-Tb{sup 3+}-Phen complex was calculated to be 8.7% (w/w). The LDH-g-PCL-Tb{sup 3+}-Phen complexes showed four emission bands with high fluorescence intensity centered at 489 nm ({sup 5}D{sub 4} → {sup 7}F{sub 6}), 546 nm ({sup 5}D{sub 4} → {sup 7}F{sub 5}), 586 nm ({sup 5}D{sub 4} → {sup 7}F{sub 4}) and 623 nm ({sup 5}D{sub 4} → {sup 7}F{sub 3}) with excitation at 328 nm ({sup 3}F{sub 6} → {sup 5}G{sub 6}). The stability of LDH-g-PCL-Tb{sup 3+}-Phen complexes

  11. Cyano-bridged coordination polymer hydrogel-derived Sn-Fe binary oxide nanohybrids with structural diversity: from 3D, 2D, to 2D/1D and enhanced lithium-storage performance

    Science.gov (United States)

    Zhang, Weiyu; Zhu, Xiaoshu; Chen, Xuguang; Zhou, Yiming; Tang, Yawen; Ding, Liangxin; Wu, Ping

    2016-05-01

    Metal oxide nanohybrids with uniform dimensions and controlled architectures possess unique compositional and structural superiorities, and thus harbor promising potential for a series of applications in energy, catalysis, and sensing systems. Herein, we propose a facile, general, and scalable cyano-bridged coordination polymer hydrogel-derived thermal-oxidation route for the construction of main-group metal and transition-metal heterometallic oxide nanohybrids with controlled constituents and architectures. The formation of Sn-Fe binary oxide nanohybrids has been demonstrated as an example by using cyano-bridged Sn(iv)-Fe(ii) bimetallic coordination polymer hydrogels (i.e., SnCl4-K4Fe(CN)6 cyanogels, Sn-Fe cyanogels) as precursors. The physicochemical properties of Sn-Fe cyanogels with different Sn/Fe ratios have been systematically examined, and it is found that perfect Sn-Fe cyanogels without unbridged Sn(iv) or Fe(ii) can be formed with Sn/Fe ratios from 2 : 1 to 1 : 2. More importantly, the simple adjustment of Sn/Fe ratios in the Sn-Fe cyanogel precursors can realize flexible dimensional control of the Sn-Fe binary oxide nanohybrids, and 2D/1D SnO2-Fe2O3 hierarchitectures, 2D SnO2-Fe2O3 nanosheets, and 3D SnO2-Fe2O3 networks have been synthesized using the Sn-Fe 1 : 2, Sn-Fe 1 : 1, and Sn-Fe 2 : 1 cyanogels as precursors, respectively. To demonstrate their compositional/structural superiorities and potential applications, the lithium-storage utilization of the Sn-Fe binary oxide nanohybrids has been selected as an objective application, and the nanohybrids exhibit Sn/Fe ratio-dependent lithium-storage performance. As a representative example, the 2D/1D SnO2-Fe2O3 hierarchitectures manifest markedly enhanced Li-storage performance in terms of reversible capacities and cycling stability in comparison with their constituent units, i.e., bare SnO2 nanosheets and Fe2O3 nanorods. The proposed cyanogel-derived thermal-oxidation strategy could open up new

  12. Coping with power dispersion?

    DEFF Research Database (Denmark)

    2014-01-01

    The last decades have witnessed a significant shift in policy competences away from central governments in Europe. The reallocation of competences spans over three dimensions: upwards; sideways; and downwards. This collection takes the dispersion of powers as a starting point and seeks to assess...... how the actors involved cope with the new configurations. In this introduction, we discuss the conceptualization of power dispersion and highlight the ways in which the contributions add to this research agenda. We then outline some general conclusions and end by indicating future avenues of research...

  13. Preparation and Investigation Performance of Water- Based Epoxy Coating Containing Supercritical CO2 Synthesized SelfDoped Polyaniline-Expanded Graphite Nanohybrids As A Anti Corrosion Pigment

    Directory of Open Access Journals (Sweden)

    M.R.Baghezadeh

    2017-03-01

    Full Text Available In this research, self- doped polyaniline- expanded graphite nanohybrid (SPEG was synthesized by supercritical CO2 method and the anti-corrosion performance of SPEG in water- based epoxy coatings was considered. For this purpose, SPEG was introduced into water- based hardener and epoxy resin, separately via direct mixing under an ultrasonic homogenizer. The distribution of SPEG in both matrices was studied by zeta sizer, XRD and TEM characterization methods. The corrosion behavior of coatings was characterized salt spray and electrochemical impedance spectroscopy (EIS in 3.5 % NaCl solution. The results showed that coatings prepared by using SPEG in water-based hardener had the best corrosion resistance.

  14. Magnetic solid phase extraction of gemfibrozil from human serum and pharmaceutical wastewater samples utilizing a β-cyclodextrin grafted graphene oxide-magnetite nano-hybrid.

    Science.gov (United States)

    Abdolmohammad-Zadeh, Hossein; Talleb, Zeynab

    2015-03-01

    A magnetic solid phase extraction method based on β-cyclodextrin (β-CD) grafted graphene oxide (GO)/magnetite (Fe3O4) nano-hybrid as an innovative adsorbent was developed for the separation and pre-concentration of gemfibrozil prior to its determination by spectrofluorometry. The as-prepared β-CD/GO/Fe3O4 nano-hybrid possesses the magnetism property of Fe3O4 nano-particles that makes it easily manipulated by an external magnetic field. On the other hand, the surface modification of GO by β-CD leads to selective separation of the target analyte from sample matrices. The structure and morphology of the synthesized adsorbent were characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. The experimental factors affecting the extraction/pre-concentration and determination of the analyte were investigated and optimized. Under the optimized experimental conditions, the calibration graph was linear in the range between 10 and 5000 pg mL(-1) with a correlation coefficient of 0.9989. The limit of detection and enrichment factor for gemfibrozil were 3 pg mL(-1) and 100, respectively. The maximum sorption capacity of the adsorbent for gemfibrozil was 49.8 mg g(-1). The method was successfully applied to monitoring gemfibrozil in human serum and pharmaceutical wastewaters samples with recoveries in the range of 96.0-104.0% for the spiked samples. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Non-enzymatic electrochemical biosensor based on Pt NPs/RGO-CS-Fc nano-hybrids for the detection of hydrogen peroxide in living cells.

    Science.gov (United States)

    Bai, Zhihao; Li, Guiyin; Liang, Jingtao; Su, Jing; Zhang, Yue; Chen, Huaizhou; Huang, Yong; Sui, Weiguo; Zhao, Yongxiang

    2016-08-15

    A highly sensitive non-enzymatic electrochemical sensor based on platinum nanoparticles/reduced graphene oxide-chitosan-ferrocene carboxylic acid nano-hybrids (Pt NPs/RGO-CS-Fc biosensor) was developed for the measurement of hydrogen peroxide (H2O2). The RGO-CS-Fc nano-hybrids was prepared and characterized by UV-vis spectrum, Fourier transform infrared spectroscopy, transmission electron microscopy, Raman spectrometer and electrochemical impedance spectroscopy. Under optimal experimental conditions, the Pt NPs/RGO-CS-Fc biosensor showed outstanding catalytic activity toward H2O2 reduction. The current response of the biosensor presented a linear relationship with H2O2 concentration from 2.0×10(-8)M to 3.0×10(-6)M with a correlation coefficient of R(2)=0.9968 and with logarithm of H2O2 concentration from 6.0×10(-6)M to 1.0×10(-2)M with a correlation coefficient of R(2)=0.9887, the low detection limit of 20nM was obtained at the signal/noise (S/N) ratio of 3. Moreover, the Pt NPs/RGO-CS-Fc biosensor exhibited excellent anti-interference capability and reproducibility for the detection of H2O2. The biosensor was also successfully applied for the detection of H2O2 from living cells containing normal and cancer cells. All these results prove that the Pt NPs/RGO-CS-Fc biosensor has the potential application in clinical diagnostics to evaluate oxidative stress of different living cells.

  16. A new nanohybrid material constructed from Keggin-type polyoxometalate and Cd(II) semicarbazone Schiff base complex with excellent adsorption properties for the removal of cationic dye pollutants

    Science.gov (United States)

    Farhadi, Saeed; Amini, Mostafa M.; Dusek, Michal; Kucerakova, Monika; Mahmoudi, Farzaneh

    2017-02-01

    A novel nanohybrid material containing a Cd(II) semicarbazone Schiff base complex and phosphomolybdic acid, [Cd(H2L+)6][H2L]+4[PMo12O40]4·18CH3OH·4H2O (1), [HL = pyridine-2-carbaldehyde semicarbazone] was prepared by a simple sonochemical route and characterized by 1HNMR, 13CNMR, FT-IR, UV-vis, PXRD, FESEM, TG-DTA and BET-BJH surface area analysis. Also the single crystal 1, was characterized by single-crystal X-ray diffraction analysis. It crystallizes in the triclinic system with space group P-1 and is assembled into 3D supramolecular structure via hydrogen intermolecular interactions. The nanohybrid 1 was tested for the adsorption and removal of organic dyes such as methylene blue (MB), Rhodamine B (RhB) and methyl orange (MO) from aqueous solutions. The effects of parameters such as the dosage of adsorbent, the initial concentration and pH of dye solution were investigated on the removal efficiency of methylene blue. The nanohybrid 1 exhibited excellent adsorption ability towards cationic dyes. Moreover, it could be easily separated from the reaction solution and recycled up to three times without significant loss of adsorption activity.

  17. Eight-year randomized clinical evaluation of Class II nanohybrid resin composite restorations bonded with a one-step self-etch or a two-step etch-and-rinse adhesive

    DEFF Research Database (Denmark)

    van Dijken, Jan WV; Pallesen, Ulla

    2015-01-01

    Objectives: The aimof this study is to observe the durability of Class II nanohybrid resin composite restorations, placed with two different adhesive systems, in an 8-year follow-up. Methods: Seventy-eight participants received at random at least two Class II restorations of the ormocer-based nan......Objectives: The aimof this study is to observe the durability of Class II nanohybrid resin composite restorations, placed with two different adhesive systems, in an 8-year follow-up. Methods: Seventy-eight participants received at random at least two Class II restorations of the ormocer......-based nanohybrid resin composite (Ceram X) bonded with either a one-step self-etch adhesive (Xeno III) or a control two-step etch-and-rinse adhesive (Excite). The 165 restorations were evaluated using slightly modified United States Public Health Services (USPHS) criteria at baseline and then yearly during 8 years....... Results: One hundred and fifty-eight restorations were evaluated after 8 years. Three participants with five restorations (three Xeno III, two Excite) were registered as dropouts. Twenty-one failed restorations (13.3 %) were observed during the follow-up. Twelve in the one-step self-etch adhesive group...

  18. Spatially Dispersed Employee Recovery

    DEFF Research Database (Denmark)

    Hvass, Kristian Anders; Torfadóttir, Embla

    2014-01-01

    Employee recovery addresses either employee well-being or management's practices in aiding employees in recovering themselves following a service failure. This paper surveys the cabin crew at a small, European, low-cost carrier and investigates employees' perceptions of management practices to aid...... personnel achieve service recovery. Employee recovery within service research often focuses on front-line employees that work in a fixed location, however a contribution to the field is made by investigating the recovery of spatially dispersed personnel, such as operational personnel in the transport sector......, who have a work place away from a fixed or central location and have minimal management contact. Results suggest that the support employees receive from management, such as recognition, information sharing, training, and strategic awareness are all important for spatially dispersed front...

  19. Light dispersion in space

    Science.gov (United States)

    Barbosa, L. C.

    2015-09-01

    Considering an idea of F. Arago in 1853 regarding light dispersion through the light ether in the interstellar space, this paper presents a new idea on an alternative interpretation of the cosmological red shift of the galaxies in the universe. The model is based on an analogy with the temporal material dispersion that occurs with light in the optical fiber core. Since intergalactic space is transparent, according to the model, this phenomenon is related to the gravitational potential existing in the whole space. Thus, it is possible to find a new interpretation to Hubble's constant. In space, light undergoes a dispersion process in its path, which is interpreted by a red shift equation of the type Δz = HL, since H = (d2n/dλ2 Δv Δλ), where H means the Hubble constant, n is the refractive index of the intergalactic space, Δλ is the spectral width of the extragalactic source, and Δv is the variation of the speed of light caused by the gravitational potential. We observe that this "constant" is governed by three new parameters. Light traveling the intergalactic space undergoes red shift due to this mechanism, while light amplitude decreases with time, and the wavelength always increases, thus producing the same type of behavior given by Hubble's Law. It can be demonstrated that the dark matter phenomenon is produced by the apparent speed of light of the stars on the periphery of the galaxies, without the existence of dark energy. Based on this new idea, the model of the universe is static, lacking expansion. Other phenomena may be interpreted based on this new model of the universe. We have what we call temporal gravitational dispersion of light in space produced by the variations of the speed of light, due to the presence of the gravitational potential in the whole space.

  20. Disabling Radiological Dispersal Terror

    Energy Technology Data Exchange (ETDEWEB)

    Hart, M

    2002-11-08

    Terror resulting from the use of a radiological dispersal device (RDD) relies upon an individual's lack of knowledge and understanding regarding its significance. Disabling this terror will depend upon realistic reviews of the current conservative radiation protection regulatory standards. It will also depend upon individuals being able to make their own informed decisions merging perceived risks with reality. Preparation in these areas will reduce the effectiveness of the RDD and may even reduce the possibility of its use.

  1. Nozzle for electric dispersion reactor

    Science.gov (United States)

    Sisson, Warren G.; Basaran, Osman A.; Harris, Michael T.

    1995-01-01

    A nozzle for an electric dispersion reactor includes two concentric electrodes, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode.

  2. Validity condition of separating dispersion of PCFs into material dispersion and geometrical dispersion

    Institute of Scientific and Technical Information of China (English)

    Wei Wang; Lantian Hou; Zhaolun Liu; Guiyao Zhou

    2009-01-01

    When using normalized dispersion method for the dispersion design of photonic crystal fibers(PCFs),it is vital that the group velocity dispersion of PCF can be seen as the sum of geometrical dispersion and material dispersion.However,the error induced by this way of calculation will deteriorate the final results.Taking 5 ps/(km·nm)and 5% as absolute error and relative error limits,respectively,the structure parameter boundaries of PCFs about when separating total dispersion into geometrical and material components is valid are provided for wavelength shorter than 1700 nm.By using these two criteria together,it is adequate to evaluate the simulatcd dispersion of PCFs when normalized dispersion method is employed.

  3. INFLUENCE OF CHROMATIC DISPERSION, DISPERSION SLOPE, DISPERSION CURVATURE ON MICROWAVE GENERATION USING TWO CASCADE MODULATORS

    OpenAIRE

    Mandeep Singh; S.K. Raghuwanshi

    2013-01-01

    This work presents a theoretical study of harmonic generation of microwave signals after detection of a modulated optical carrier in cascaded two electro-optic modulators. Dispersion is one of the major limiting factors for microwave generation in microwave photonics. In this paper, we analyze influence of chromatic dispersion, dispersion slope, dispersion curvature on microwave generation using two cascaded MZMs and it has been found that output intensity of photodetector reduces when disper...

  4. Developing a dispersant spraying capability

    Energy Technology Data Exchange (ETDEWEB)

    Gill, S.D.

    1979-01-01

    In developing a national dispersant spraying capability, the Canadian Coast Guard (CCG) has undertaken a modification program to enable the conventional offshore spraying gear to be mounted on almost any vessel of convenience. Smaller, more versatile inshore spraying vessels and pumps have been designed and built. With the popularization of concentrated dispersants, the inshore pumping equipment can be used aboard hovercraft for special application situations. A program of acquiring mobile dispersant storage tanks has been undertaken with auxiliary equipment that will facilitate the shipment of dispersants in bulk by air freight. Work also has commenced on extending the dispersant application program to include the CCG fleet of helicopters.

  5. Dispersion Interactions in Water Clusters.

    Science.gov (United States)

    Guidez, Emilie B; Gordon, Mark S

    2017-05-18

    The importance of dispersion forces in water clusters is examined using the effective fragment potential (EFP) method. Since the original EFP1 water potential does not include dispersion, a dispersion correction to the EFP1 potential (EFP1-D) was derived and implemented. The addition of dispersion to the EFP1 potential yields improved geometries for water clusters that contain 2-6 molecules. The importance of the odd E7 contribution to the dispersion energy is investigated. The E7 dispersion term is repulsive for all of the water clusters studied here and can have a magnitude that is as large as half of the E6 value. The E7 term therefore contributes to larger intermolecular distances for the optimized geometries. Inclusion of many-body effects and/or higher order terms may be necessary to further improve dispersion energies and optimized geometries.

  6. Spurious dispersion effects at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Prat, Eduard

    2009-07-15

    The performance of the Free-Electron Laser (FEL) process imposes stringent demands on the transverse trajectory and size of the electron beam. Since transverse dispersion changes off-energy particle trajectories and increases the effective beam size, dispersion must be controlled. This thesis treats the concept of dispersion in linacs, and analyses the impact of dispersion on the electron beam and on the FEL process. It presents generation mechanisms for spurious dispersion, quantifying its importance for FLASH (Free-electron Laser in Hamburg) and the XFEL (European X-ray Free-Electron Laser). A method for measuring and correcting dispersion and its implementation in FLASH is described. Experiments of dispersion e ects on the transverse beam quality and on the FEL performance are presented. (orig.)

  7. Quantum optical rotatory dispersion

    Science.gov (United States)

    Tischler, Nora; Krenn, Mario; Fickler, Robert; Vidal, Xavier; Zeilinger, Anton; Molina-Terriza, Gabriel

    2016-01-01

    The phenomenon of molecular optical activity manifests itself as the rotation of the plane of linear polarization when light passes through chiral media. Measurements of optical activity and its wavelength dependence, that is, optical rotatory dispersion, can reveal information about intricate properties of molecules, such as the three-dimensional arrangement of atoms comprising a molecule. Given a limited probe power, quantum metrology offers the possibility of outperforming classical measurements. This has particular appeal when samples may be damaged by high power, which is a potential concern for chiroptical studies. We present the first experiment in which multiwavelength polarization-entangled photon pairs are used to measure the optical activity and optical rotatory dispersion exhibited by a solution of chiral molecules. Our work paves the way for quantum-enhanced measurements of chirality, with potential applications in chemistry, biology, materials science, and the pharmaceutical industry. The scheme that we use for probing wavelength dependence not only allows one to surpass the information extracted per photon in a classical measurement but also can be used for more general differential measurements. PMID:27713928

  8. QT dispersion and P wave dispersion in patients with fibromyalgia.

    Science.gov (United States)

    Yolbaş, Servet; Yıldırım, Ahmet; Düzenci, Deccane; Karakaya, Bülent; Dağlı, Mustafa Necati; Koca, Süleyman Serdar

    2016-12-01

    Fibromyalgia (FM) is a chronic disease characterized by widespread pain. Somatic complaints associated with the cardiovascular system, such as chest pain and palpitations, are frequently seen in FM patients. P and QT dispersions are simple and inexpensive measurements reflecting the regional heterogeneity of atrial and ventricular repolarization, respectively. QT dispersion can cause serious ventricular arrhythmias. The aim of the present study was to evaluate QT dispersion and P wave dispersion in patients with FM. The study involved 48 FM patients who fulfilled the established criteria and 32 healthy controls (HC). A standard 12-lead electrocardiogram was performed on all participants. QT dispersion was defined as the difference between the longest and the shortest QT intervals. Similarly, the differences between the shortest and longest P waves were defined as P wave dispersion. The QT dispersion and corrected QT dispersion were shorter in the FM group compared with the HC group (pdispersion value, there was no significant difference between the FM and HC groups (p=0.088). Longer QT and P wave dispersions are not problems in patients with FM. Therefore, it may be concluded that fibromyalgia does not include an increased risk of atrial and/or ventricular arrhythmias.

  9. SMED - Sulphur MEditerranean Dispersion

    Science.gov (United States)

    Salerno, Giuseppe G.; Sellitto, Pasquale; Corradini, Stefano; Di Sarra, Alcide Giorgio; Merucci, Luca; Caltabiano, Tommaso; La Spina, Alessandro

    2016-04-01

    Emissions of volcanic gases and particles can have profound impacts on terrestrial environment, atmospheric composition, climate forcing, and then on human health at various temporal and spatial scales. Volcanic emissions have been identified as one of the largest sources of uncertainty in our understanding of recent climate change trends. In particular, a primary role is acted by sulphur dioxide emission due to its conversion to volcanic sulphate aerosol via atmospheric oxidation. Aerosols may play a key role in the radiative budget and then in photochemistry and tropospheric composition. Mt. Etna is one of the most prodigious and persistent emitters of gasses and particles on Earth, accounting for about 10% of global average volcanic emission of CO2 and SO2. Its sulphur emissions stand for 0.7 × 106 t S/yr9 and then about 10 times bigger than anthropogenic sulphur emissions in the Mediterranean area. Centrepiece of the SMED project is to advance the understanding of volcanogenic sulphur dioxide and sulphate aerosol particles dispersion and radiative impact on the downwind Mediterranean region by an integrated approach between ground- and space-based observations and modelling. Research is addressed by exploring the potential relationship between proximal SO2 flux and aerosol measured remotely in the volcanic plume of Mt. Etna between 2000 and 2014 and distal aerosol ground-based measurements in Lampedusa, Greece, and Malta from AERONET network. Ground data are combined with satellite multispectral polar and geostationary imagers able to detect and retrieve volcanic ash and SO2. The high repetition time of SEVIRI (15 minutes) will ensure the potential opportunity to follow the entire evolution of the volcanic cloud, while, the higher spatial resolution of MODIS (1x1 km2), are exploited for investigating the probability to retrieve volcanic SO2 abundances from passive degassing. Ground and space observations are complemented with atmospheric Lagrangian model

  10. Dispersive transport across interfaces

    Science.gov (United States)

    Berkowitz, Brian; Adler, Pierre

    2015-04-01

    Experiments demonstrating asymmetrical dispersive transport of a conservative tracer across interfaces between different porous materials have recently been performed. Here, this phenomenon is studied numerically on the pore scale. The flow field is derived by solving the Stokes equation. The dispersive transport is simulated by a large number of particles undergoing random walks under the simultaneous action of convection and diffusion. Two main two-dimensional configurations are studied; each consists of two segments (called coarse and fine) with the same structure, porosity, and length along the main flow, but different characteristic solid/pore sizes. One structure consists of two channels containing cavities of different sizes, and the second of square "grains" of different sizes. At time t=0, a large number of particles is injected (as a pulse) around a given cross-section. The corresponding breakthrough curves (BTCs) are registered as functions of time at six different cross sections. Calculations are made twice; in the first case (CtoF), particles are injected in the coarse side and are transported towards the fine one; in the second one (FtoC), the opposite case is studied. These calculations are performed for various Péclet numbers (Pe). Comparison of the resulting BTCs shows features that are similar to experimental observations, but with qualitative and quantitative differences. The influences of the medium, of the injection and observation planes, and of Pe are detailed and discussed. A BTC for pulse injection can be characterized by its maximum M(t_M) and the time tM at which it occurs. The observed differences for channels bounded by cavities are very small. However for the granular structures, M(t_M) is always larger for FtoC than for CtoF ; tM depends on all the parameters, namely Pe, the size ratio between the large and small grains, the injection and the observation planes. The numerical results are systematically compared with solutions of one

  11. Amplified Dispersive Optical Tomography

    CERN Document Server

    Goda, Keisuke; Jalali, Bahram

    2008-01-01

    Optical coherence tomography (OCT) has proven to be a powerful technique for studying tissue morphology in ophthalmology, cardiology, and endomicroscopy. Its performance is limited by the fundamental trade-off between the imaging sensitivity and acquisition speed -- a predicament common in virtually all imaging systems. In this paper, we circumvent this limit by using distributed Raman post-amplification of the reflection from the sample. We combine the amplification with simultaneously performed dispersive Fourier transformation, a process that maps the optical spectrum into an easily measured time-domain waveform. The Raman amplification enables measurement of weak signals which are otherwise buried in noise. It extends the depth range without sacrificing the acquisition speed or causing damage to the sample. As proof of concept, single-shot imaging with 15 dB improvement in sensitivity at an axial scan rate of 36.6 MHz is demonstrated.

  12. Natural dispersion revisited.

    Science.gov (United States)

    Johansen, Øistein; Reed, Mark; Bodsberg, Nils Rune

    2015-04-15

    This paper presents a new semi-empirical model for oil droplet size distributions generated by single breaking wave events. Empirical data was obtained from laboratory experiments with different crude oils at different stages of weathering. The paper starts with a review of the most commonly used model for natural dispersion, which is followed by a presentation of the laboratory study on oil droplet size distributions formed by breaking waves conducted by SINTEF on behalf of the NOAA/UNH Coastal Response Research Center. The next section presents the theoretical and empirical foundation for the new model. The model is based on dimensional analysis and contains two non-dimensional groups; the Weber and Reynolds number. The model was validated with data from a full scale experimental oil spill conducted in the Haltenbanken area offshore Norway in July 1982, as described in the last section of the paper.

  13. Piezoelectric coupling in a field-effect transistor with a nanohybrid channel of ZnO nanorods grown vertically on graphene.

    Science.gov (United States)

    Quang Dang, Vinh; Kim, Do-Il; Thai Duy, Le; Kim, Bo-Yeong; Hwang, Byeong-Ung; Jang, Mi; Shin, Kyung-Sik; Kim, Sang-Woo; Lee, Nae-Eung

    2014-12-21

    Piezoelectric coupling phenomena in a graphene field-effect transistor (GFET) with a nano-hybrid channel of chemical-vapor-deposited Gr (CVD Gr) and vertically aligned ZnO nanorods (NRs) under mechanical pressurization were investigated. Transfer characteristics of the hybrid channel GFET clearly indicated that the piezoelectric effect of ZnO NRs under static or dynamic pressure modulated the channel conductivity (σ) and caused a positive shift of 0.25% per kPa in the Dirac point. However, the GFET without ZnO NRs showed no change in either σ or the Dirac point. Analysis of the Dirac point shifts indicated transfer of electrons from the CVD Gr to ZnO NRs due to modulation of their interfacial barrier height under pressure. High responsiveness of the hybrid channel device with fast response and recovery times was evident in the time-dependent behavior at a small gate bias. In addition, the hybrid channel FET could be gated by mechanical pressurization only. Therefore, a piezoelectric-coupled hybrid channel GFET can be used as a pressure-sensing device with low power consumption and a fast response time. Hybridization of piezoelectric 1D nanomaterials with a 2D semiconducting channel in FETs enables a new design for future nanodevices.

  14. 2D/2D nano-hybrids of γ-MnO₂ on reduced graphene oxide for catalytic ozonation and coupling peroxymonosulfate activation.

    Science.gov (United States)

    Wang, Yuxian; Xie, Yongbing; Sun, Hongqi; Xiao, Jiadong; Cao, Hongbin; Wang, Shaobin

    2016-01-15

    Two-dimensional reduced graphene oxide (2D rGO) was employed as both a shape-directing medium and support to fabricate 2D γ-MnO2/2D rGO nano-hybrids (MnO2/rGO) via a facile hydrothermal route. For the first time, the 2D/2D hybrid materials were used for catalytic ozonation of 4-nitrophenol. The catalytic efficiency of MnO2/rGO was much higher than either MnO2 or rGO only, and rGO was suggested to play the role for promoting electron transfers. Quenching tests using tert-butanol, p-benzoquinone, and sodium azide suggested that the major radicals responsible for 4-nitrophenol degradation and mineralization are O2(-) and (1)O2, but not ·OH. Reusability tests demonstrated a high stability of the materials in catalytic ozonation with minor Mn leaching below 0.5 ppm. Degradation mechanism, reaction kinetics, reusability and a synergistic effect between catalytic ozonation and coupling peroxymonosulfate (PMS) activation were also discussed.

  15. Cross-linked branching nanohybrid polymer electrolyte with monodispersed TiO2 nanoparticles for high performance lithium-ion batteries

    Science.gov (United States)

    Ma, Cheng; Zhang, Jinfang; Xu, Mingquan; Xia, Qingbing; Liu, Jiatu; Zhao, Shuai; Chen, Libao; Pan, Anqiang; Ivey, Douglas G.; Wei, Weifeng

    2016-06-01

    Nanohybrid polymer electrolytes (NHPE) with ceramic particles have attracted significant attention owing to their improvement in electrochemical performance. However, particle aggregation and weak nanoparticle/polymer matrix interaction restrict their further application in lithium-ion batteries (LIBs). We demonstrate a facile in-situ polymerization/crystallization method to synthesize a homogeneous TiO2-grafted NHPE with a cross-linked branching structure, comprised of ion-conducting poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and non-polar stearyl methacrylate (SMA). This technique is different from existing methods of blending functionalized ceramic particles into the polymer matrix. Highly monodispersed TiO2 nanocrystals enhance the effective interfacial interactions between particles and polymer matrix, which suppress the crystallization of ethylene oxide (EO) groups and facilitate forming continuously interconnected ion-conducting channels. Moreover, an increased dissociation degree of Li salt can also be achieved. The TiO2-grafted NHPE exhibits superior electrochemical properties with an ionic conductivity of 1.1 × 10-4 S cm-1 at 30 °C, a high lithium ion transference number and excellent interfacial compatibility with the lithium electrode. In particular, a lithium-ion battery based on TiO2-grafted NHPE demonstrates good C-rate performance, as well as excellent cycling stability with an initial discharge capacity of 153.5 mAh g-1 and a capacity retention of 96% after 300 cycles at 1 C (80 °C).

  16. Degree of conversion of micro-hybrid, nano-hybrid and Ormocer composites using LED and QTH light-curing units

    Directory of Open Access Journals (Sweden)

    Seied Mostafa Fatemi

    2012-01-01

    Full Text Available Background and Aims: The aim of this study was to measure the degree of conversion (DC of three types of composite resins (micro-hybrid, nano-hybrid and Ormocer with different light curing units (LED LCU and QTH LCU in two depths.Materials and Methods: Three commercially available dental resin composites were used in this study: (Tetric Ceram, Ivoclar Vivadent, Liechtenstein-A2 shade, (Tetric Evoceram, Ivoclar Vivadent, Liechtenstein-A2 shade, (Ceram X, Dentsply, Germany-M2 shade. Specimens were divided into two groups, 5 specimens were photo-activated by QTH unit (Coltolux 75-Colten and the other five specimens were cured by LED (Demi-Kerr. Then each specimen was sectioned at the top surface and at 2-mm depth. The DC was measured by FT-IR(Bruker-tensor 27. The data were analyzed by 3-way ANOVA test.Results: There was significant difference between tested composite resins (P<0.001. The results of top surfaces were significantly different from those observed at 2-mm depth (P<0.001. The type of curing unit affected the polymerization of Ceram X resin composite.Conclusion: This study showed a significant difference in the degree of conversion in different thicknesses within three groups of resin composites.

  17. Core-shell yolk-shell Si@C@Void@C nanohybrids as advanced lithium ion battery anodes with good electronic conductivity and corrosion resistance

    Science.gov (United States)

    Xie, Jian; Tong, Liang; Su, Liwei; Xu, Yawei; Wang, Lianbang; Wang, Yuanhao

    2017-02-01

    Yolk-shell Si@void@C nanostructure has greatly improved the low Li+/electron conductivity and buffered the huge volume variation of Si, whereas the surface corrosion and passivation of the Si yolks in electrolytes still limit the lithium storage capability. Herein, core-shell yolk-shell Si@C@void@C nanohybrids were proposed and successfully prepared for the first time. Compared with Si@void@C, the newly-proposed structure introduced core-shell Si@C nanoparticles as the yolks instead. Such extra carbon shell can not only decrease the electrical resistance between Si yolks and hollow carbon shells but also effectively protect Si yolks from electrolyte corrosion, i.e., the formation of Li2SiF6 layers on Si surface confirmed by X-ray diffraction and transmission electron microscopy. As a result, the Si@C@void@C electrodes exhibited remarkably enhanced reversible capacity, cycling stability (∼1366 mA h g-1 after 50 cycles at 500 mA g-1, with a capacity retention of ∼71% with respect to the initial reversible capacity of 1910 mAh g-1 at 100 mA g-1), and rate performance (with a capacity retention of ∼60% at 4000 mA g-1). This work shows the paramount role of the inner carbon shell of Si@C@void@C in limiting the electrolyte corrosion and probably improving the electronic conductivity.

  18. Carbon Nitride-Aromatic Diimide-Graphene Nanohybrids: Metal-Free Photocatalysts for Solar-to-Hydrogen Peroxide Energy Conversion with 0.2% Efficiency.

    Science.gov (United States)

    Kofuji, Yusuke; Isobe, Yuki; Shiraishi, Yasuhiro; Sakamoto, Hirokatsu; Tanaka, Shunsuke; Ichikawa, Satoshi; Hirai, Takayuki

    2016-08-10

    Solar-to-chemical energy conversion is a challenging subject for renewable energy storage. In the past 40 years, overall water splitting into H2 and O2 by semiconductor photocatalysis has been studied extensively; however, they need noble metals and extreme care to avoid explosion of the mixed gases. Here we report that generating hydrogen peroxide (H2O2) from water and O2 by organic semiconductor photocatalysts could provide a new basis for clean energy storage without metal and explosion risk. We found that carbon nitride-aromatic diimide-graphene nanohybrids prepared by simple hydrothermal-calcination procedure produce H2O2 from pure water and O2 under visible light (λ > 420 nm). Photoexcitation of the semiconducting carbon nitride-aromatic diimide moiety transfers their conduction band electrons to graphene and enhances charge separation. The valence band holes on the semiconducting moiety oxidize water, while the electrons on the graphene moiety promote selective two-electron reduction of O2. This metal-free system produces H2O2 with solar-to-chemical energy conversion efficiency 0.20%, comparable to the highest levels achieved by powdered water-splitting photocatalysts.

  19. Synthesis mechanism, enhanced visible-light-photocatalytic properties, and photogenerated hydroxyl radicals of PS@CdS core–shell nanohybrids

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Han, E-mail: wanghan960070@126.com; Xu, Qian [China University of Petroleum, State Key Laboratory of Heavy Oil Processing (China); Zheng, Xing, E-mail: znhk113@163.com [Beijing ZNHK Science and Technology Development Co., LTD (China); Han, Wenqing [Baotou Light Industry and Vocational Technical College (China); Zheng, Jingtang, E-mail: jtzheng03@163.com; Jiang, Bo; Xue, Qinzhong; Wu, Mingbo [China University of Petroleum, State Key Laboratory of Heavy Oil Processing (China)

    2014-12-15

    In this study, spherical polystyrene (PS)@CdS core–shell structure nanoparticles (CSNPs) were prepared by sonochemical method. The influences of the surfactant PVP, the order of adding precursors, the molar ratio of S/Cd, and the reaction time on structure were carefully studied. Results of SEM, TEM, EDS, XRD, and FT-IR showed that the as-prepared nanohybrids have a typical core–shell structure with 260 nm core and a uniform shell with thickness ranging from 10 to 30 nm, both PVP and the order of adding precursors were the controlling parameters. In addition, the as-synthesized PS@CdS CSNPs exhibited much higher photocatalytic activity for RhB under visible light irradiation compared with pure CdS, which should be attributed to their synergic effect between core and shell, amount of hydroxyl groups on the surface, good monodispersity, and so on. Besides, the production of photogenerated hydroxyl radical ({sup •}OH) was in accordance with the RhB decolorization efficiency from the prepared PS@CdS CSNPs. It indicated that {sup •}OH was the main active oxygen species in the photocatalytic process.

  20. A facile approach to prepare crumpled CoTMPyP/electrochemically reduced graphene oxide nanohybrid as an efficient electrocatalyst for hydrogen evolution reaction

    Science.gov (United States)

    Ma, Juanjuan; Liu, Lin; Chen, Qian; Yang, Min; Wang, Danping; Tong, Zhiwei; Chen, Zhong

    2017-03-01

    Elaborate design and synthesis of efficient and stable non-Pt electrocatalysts for some renewable energy related conversion/storage processes are one of the major goals of sustainable chemistry. Herein, we report a facile method to fabricate Co porphyrin functionalized electrochemically reduced graphene oxide (CoTMPyP/ERGO) thin film by direct assembly of oppositely charged tetrakis(N-methylpyridyl) porphyrinato cobalt (CoTMPyP) and GO nanosheets under mild conditions followed by an electrochemical reduction procedure. STEM analysis confirms that CoTMPyP nanoaggregates are homogeneously distributed over the graphene surface. The electrochemical properties of CoTMPyP/ERGO were investigated by cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy. The results demonstrate that CoTMPyP/ERGO nanohybrid film can serve as excellent electrocatalyst for hydrogen evolution in alkaline solution with high activity and stability. The intimate contact and efficient electron transfer between CoTMPyP and ERGO, as well as the crumpled structure, contribute to the improvement of the electrocatalytic performance.

  1. Adhesion and inactivation of Gram-negative and Gram-positive bacteria on photoreactive TiO2/polymer and Ag-TiO2/polymer nanohybrid films

    Science.gov (United States)

    Tallósy, Szabolcs Péter; Janovák, László; Nagy, Elisabeth; Deák, Ágota; Juhász, Ádám; Csapó, Edit; Buzás, Norbert; Dékány, Imre

    2016-05-01

    The aim of this study was to develop photoreactive surface coatings, possessing antibacterial properties and can be activated under visible light illumination (λmax = 405 nm) using LED-light source. The photocatalytically active titanium dioxide (TiO2) was functionalized with silver nanoparticles (Ag NPs) and immobilized in polyacrylate based nanohybrid thin film in order to facilitate visible light activity (λAg/TiO2,max = 500 nm). First, the photocatalytic activity was modelled by following ethanol vapor degradation. The plasmonic functionalization resulted in 15% enhancement of the activity compared to pure TiO2. The photoreactive antimicrobial (5 log reduction of cfu in 2 h) surface coatings are able to inactivate clinically relevant pathogen strains (methicillin resistant Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa) within short time (60-120 min) due to the formed and quantified reactive oxygen species (ROS). The existence of electrostatic interactions between the negatively charged bacteria (from -0.89 to -3.19 μeq/109 cfu) and positively charged photocatalyst particles (in the range of +0.38 and +12.3 meq/100 g) was also proven by charge titration measurements. The surface inactivation of the bacteria and the photocatalytic degradation of the cell wall component were also confirmed by fluorescence and transmission electron microscopic observations, respectively. According to the results an effective sterilizing system and prevention strategy can be developed and carried out against dangerous microorganisms in health care.

  2. Acoustic Rectification in Dispersive Media

    Science.gov (United States)

    Cantrell, John H.

    2008-01-01

    It is shown that the shapes of acoustic radiation-induced static strain and displacement pulses (rectified acoustic pulses) are defined locally by the energy density of the generating waveform. Dispersive properties are introduced analytically by assuming that the rectified pulses are functionally dependent on a phase factor that includes both dispersive and nonlinear terms. The dispersion causes an evolutionary change in the shape of the energy density profile that leads to the generation of solitons experimentally observed in fused silica.

  3. Progress in urban dispersion studies

    DEFF Research Database (Denmark)

    Batchvarova, E.; Gryning, Sven-Erik

    2006-01-01

    The present Study addresses recent achievements in better representation Of the urban area structure in meteorology and dispersion parameterisations. The setup and Main Outcome of several recent dispersion experiments in Urban areas and their use in model validation are discussed. The maximum...... BUBBLE Tracer Experiment) the horizontal spread of the plume corresponds to a Lagrangian time scale bigger than the value for ground Sources. Turbulence measurements LIP to 3-5 times the building height Lire needed for direct use in dispersion Calculations....

  4. Seed dispersal of desert annuals.

    Science.gov (United States)

    Venable, D Lawrence; Flores-Martinez, Arturo; Muller-Landau, Helene C; Barron-Gafford, Greg; Becerra, Judith X

    2008-08-01

    We quantified seed dispersal in a guild of Sonoran Desert winter desert annuals at a protected natural field site in Tucson, Arizona, USA. Seed production was suppressed under shrub canopies, in the open areas between shrubs, or both by applying an herbicide prior to seed set in large, randomly assigned removal plots (10-30 m diameter). Seedlings were censused along transects crossing the reproductive suppression borders shortly after germination. Dispersal kernels were estimated for Pectocarya recurvata and Schismus barbatus from the change in seedling densities with distance from these borders via inverse modeling. Estimated dispersal distances were short, with most seeds traveling less than a meter. The adhesive seeds of P. recurvata went farther than the small S. barbatus seeds, which have no obvious dispersal adaptation. Seeds dispersed farther downslope than upslope and farther when dispersing into open areas than when dispersing into shrubs. Dispersal distances were short relative to the pattern of spatial heterogeneity created by the shrub and open space mosaic. This suggests that dispersal could contribute to local population buildup, possibly facilitating species coexistence. Overall, these results support the hypothesis that escape in time via delayed germination is likely to be more important for desert annuals than escape in space.

  5. Statistical Thermodynamics of Disperse Systems

    DEFF Research Database (Denmark)

    Shapiro, Alexander

    1996-01-01

    Principles of statistical physics are applied for the description of thermodynamic equilibrium in disperse systems. The cells of disperse systems are shown to possess a number of non-standard thermodynamic parameters. A random distribution of these parameters in the system is determined....... On the basis of this distribution, it is established that the disperse system has an additional degree of freedom called the macro-entropy. A large set of bounded ideal disperse systems allows exact evaluation of thermodynamic characteristics. The theory developed is applied to the description of equilibrium...

  6. INFLUENCE OF CHROMATIC DISPERSION, DISPERSION SLOPE, DISPERSION CURVATURE ON MICROWAVE GENERATION USING TWO CASCADE MODULATORS

    Directory of Open Access Journals (Sweden)

    Mandeep Singh

    2013-03-01

    Full Text Available This work presents a theoretical study of harmonic generation of microwave signals after detection of a modulated optical carrier in cascaded two electro-optic modulators. Dispersion is one of the major limiting factors for microwave generation in microwave photonics. In this paper, we analyze influence of chromatic dispersion, dispersion slope, dispersion curvature on microwave generation using two cascaded MZMs and it has been found that output intensity of photodetector reduces when dispersion term up to fifth order are added. We have used the two cascaded Mach-Zehnder Modulators for our proposed model and tried to show the dispersion effect with the help of modulation depth factor of MZM, which have been not discussed earlier.

  7. The NET effect of dispersants

    NARCIS (Netherlands)

    Marieke Zeinstra-Helfrich; Wierd Koops; Albertinka J. Murk

    2015-01-01

    Application of chemical dispersants or mechanical dispersion on surface oil is a trade-off between surface effects (impact of floating oil) and sub-surface effects (impact of suspended oil). Making an informed decision regarding such response, requires insight in the induced change in fate and

  8. Fermion dispersion in axion medium

    OpenAIRE

    Mikheev, N. V.; Narynskaya, E. N.

    2008-01-01

    The interaction of a fermion with the dense axion medium is investigated for the purpose of finding an axion medium effect on the fermion dispersion. It is shown that axion medium influence on the fermion dispersion under astrophysical conditions is negligible small if the correct Lagrangian of the axion-fermion interaction is used.

  9. Large deviations in Taylor dispersion

    Science.gov (United States)

    Kahlen, Marcel; Engel, Andreas; Van den Broeck, Christian

    2017-01-01

    We establish a link between the phenomenon of Taylor dispersion and the theory of empirical distributions. Using this connection, we derive, upon applying the theory of large deviations, an alternative and much more precise description of the long-time regime for Taylor dispersion.

  10. Pigment dispersion syndrome

    Directory of Open Access Journals (Sweden)

    C.S. Sandhya

    2013-10-01

    Full Text Available We report of the rare occurrence of pigment dispersion syndrome (PDS with posterior subcapsular cataract in both eyes in a young male patient. The patient presented with complaints of progressive decrease in vision of one year duration. The patient also had high myopia with mild iridodonesis, phacodonesis and anterior insertion of zonules. Classical signs of PDS like Krukenberg's spindle on the posterior corneal surface were evident on slit lamp examination; transillumination defects in the iris could not be elicited by retroillumination as the iris was heavily pigmented. Gonioscopy revealed heavy and uniform pigmentation of trabecular meshwork. Evidence of a characteristic iris configuration on optical coherence tomography (OCT, namely, posterior bowing of iris in the mid periphery suggested the diagnosis of PDS. This case highlights the importance of OCT in identifying the iris configuration characteristically seen in PDS even in the absence of transillumination defects in the iris and reiterates the need to look for subtle signs like phacodonesis which are important when surgical intervention is planned.

  11. Dispersion in unit disks

    CERN Document Server

    Dumitrescu, Adrian

    2009-01-01

    We present two new approximation algorithms with (improved) constant ratios for selecting $n$ points in $n$ unit disks such that the minimum pairwise distance among the points is maximized. (I) A very simple $O(n \\log{n})$-time algorithm with ratio 0.5110 for disjoint unit disks. In combination with an algorithm of Cabello \\cite{Ca07}, it yields a $O(n^2)$-time algorithm with ratio of 0.4487 for dispersion in $n$ not necessarily disjoint unit disks. (II) A more sophisticated LP-based algorithm with ratio 0.6495 for disjoint unit disks that uses a linear number of variables and constraints, and runs in polynomial time. The algorithm introduces a novel technique which combines linear programming and projections for approximating distances. The previous best approximation ratio for disjoint unit disks was 1/2. Our results give a partial answer to an open question raised by Cabello \\cite{Ca07}, who asked whether 1/2 could be improved.

  12. Dispersal and migration

    Directory of Open Access Journals (Sweden)

    Schwarz, C.

    2004-06-01

    Full Text Available Ringing of birds unveiled many aspects of avian migration and dispersal movements. However, there is even much more to be explored by the use of ringing and other marks. Dispersal is crucial in understanding the initial phase of migration in migrating birds as it is to understand patterns and processes of distribution and gene flow. So far, the analysis of migration was largely based on analysing spatial and temporal patters of recoveries of ringed birds. However, there are considerable biases and pitfalls in using recoveries due to spatial and temporal variation in reporting probabilities. Novel methods are required for future studies separating the confounding effects of spatial and temporal heterogeneity of recovery data and heterogeneity of the landscape as well. These novel approaches should aim a more intensive and novel use of the existing recovery data by taking advantage of, for instance, dynamic and multistate modeling, should elaborate schemes for future studies, and should also include other marks that allow a more rapid data collection, like telemetry, geolocation and global positioning systems, and chemical and molecular markers. The latter appear to be very useful in the delineating origin of birds and connectivity between breeding and non–breeding grounds. Many studies of migration are purely descriptive. However, King and Brooks (King & Brooks, 2004 examine if movement patterns of dolphins change after the introduction of a gillnet ban. Bayesian methods are an interesting approach to this problem as they provide a meaningful measure of the probability that such a change occurred rather than simple yes/no response that is often the result of classical statistical methods. However, the key difficulty of a general implementation of Bayesian methods is the complexity of the modelling —there is no general userfriendly package that is easily accessible to most scientists. Drake and Alisauskas (Drake & Alisauskas, 2004 examine the

  13. Air Flow and Dispersion Section

    Energy Technology Data Exchange (ETDEWEB)

    Slinn, W. G.N.; Nicola, P. W.; Powell, D. C.; Davis, W. E.

    1976-03-01

    There are eight papers in this section. Some of the fundamentals of atmospheric dispersion of pollutants are examined with theoretical analyses as well as detailed experimental investigations. Emphasis has been placed on analyzing and summarizing previous experimental dispersion data with more realistic and fundamentally sound approaches to plume behavior. The goal is to finalize improved short-range dispersion models from existing data, removing inconsistencies and inadequacies in presently applied assessment models. Dispersion and transport efforts in the future should aim toward evaluating plume behavior on meso and regional scales. The complex features of flow and dispersion through storms, and in the vicinity of significant terrain characteristics influencing local to regional circulations must receive future emphasis. (auth)

  14. Nano-Bio Engineered Carbon Dot-Peptide Functionalized Water Dispersible Hyperbranched Polyurethane for Bone Tissue Regeneration.

    Science.gov (United States)

    Gogoi, Satyabrat; Maji, Somnath; Mishra, Debasish; Devi, K Sanjana P; Maiti, Tapas Kumar; Karak, Niranjan

    2017-03-01

    The present study delves into a combined bio-nano-macromolecular approach for bone tissue engineering. This approach relies on the properties of an ideal scaffold material imbued with all the chemical premises required for fostering cellular growth and differentiation. A tannic acid based water dispersible hyperbranched polyurethane is fabricated with bio-nanohybrids of carbon dot and four different peptides (viz. SVVYGLR, PRGDSGYRGDS, IPP, and CGGKVGKACCVPTKLSPISVLYK) to impart target specific in vivo bone healing ability. This polymeric bio-nanocomposite is blended with 10 wt% of gelatin and examined as a non-invasive delivery vehicle. In vitro assessment of the developed polymeric system reveals good osteoblast adhesion, proliferation, and differentiation. Aided by this panel of peptides, the polymeric bio-nanocomposite exhibits in vivo ectopic bone formation ability. The study on in vivo mineralization and vascularization reveals the occurrence of calcification and blood vessel formation. Thus, the study demonstrates carbon dot/peptide functionalized hyperbranched polyurethane gel for bone tissue engineering application.

  15. Dispersive suspended microextraction.

    Science.gov (United States)

    Yang, Zhong-Hua; Liu, Yu; Lu, Yue-Le; Wu, Tong; Zhou, Zhi-Qiang; Liu, Dong-Hui

    2011-11-14

    A novel sample pre-treatment technique termed dispersive suspended microextraction (DSME) coupled with gas chromatography-flame photometric detection (GC-FPD) has been developed for the determination of eight organophosphorus pesticides (ethoprophos, malathion, chlorpyrifos, isocarbophos, methidathion, fenamiphos, profenofos, triazophos) in aqueous samples. In this method, both extraction and two phases' separation process were performed by the assistance of magnetic stirring. After separating the two phases, 1 μL of the suspended phase was injected into GC for further instrument analysis. Varieties of experiment factors which could affect the experiment results were optimized and the following were selected: 12.0 μL p-xylene was selected as extraction solvent, extraction speed was 1200 rpm, extraction time was 30 s, the restoration speed was 800 rpm, the restoration time was 8 min, and no salt was added. Under the optimum conditions, limits of detections (LODs) varied between 0.01 and 0.05 μg L(-1). The relative standard deviation (RSDs, n=6) ranged from 4.6% to 12.1%. The linearity was obtained by five points in the concentration range of 0.1-100.0 μg L(-1). Correlation coefficients (r) varied from 0.9964 to 0.9995. The enrichment factors (EFs) were between 206 and 243. In the final experiment, the developed method has been successfully applied to the determination of organophosphorus pesticides in wine and tap water samples and the obtained recoveries were between 83.8% and 101.3%. Compared with other pre-treatment methods, DSME has its own features and could achieve satisfied results for the analysis of trace components in complicated matrices.

  16. Wave-equation dispersion inversion

    KAUST Repository

    Li, Jing

    2016-12-08

    We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.

  17. Chemical synthesis of Fe{sub 3}O{sub 4}–graphene oxide nanohybrids as building blocks for magnetic and conductive membranes

    Energy Technology Data Exchange (ETDEWEB)

    Thu, Tran Viet, E-mail: tranvietthu@gmail.com [Electronics-Inspired Interdisciplinary Research Institute, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi 441-8580, Aichi (Japan); Sandhu, Adarsh [Electronics-Inspired Interdisciplinary Research Institute, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi 441-8580, Aichi (Japan); Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi 441-8580, Aichi (Japan)

    2014-11-15

    Graphical abstract: - Highlights: • Fe{sub 3}O{sub 4} nanocrystals are uniformly grown on graphene oxide (GO) at high density. • GO sheets act as physical substrate and surfactants for the growth of Fe{sub 3}O{sub 4}. • The saturation magnetization of the Fe{sub 3}O{sub 4}–GO hybrids is controlled. • Conductive membrane is formed by filtration of Fe{sub 3}O{sub 4}–GO suspension. - Abstract: We have developed a facile and scalable method for synthesising superparamagnetic Fe{sub 3}O{sub 4} nanocrystals (NCs) anchored on graphene oxide (GO) sheets by a co-precipitation reaction. As-synthesized Fe{sub 3}O{sub 4}–GO nanohybrids (NHs) were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, field-emission scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometer. Fe{sub 3}O{sub 4} NCs with a narrow size distribution (4.5 ± 0.6 nm) were uniformly decorated over GO surface at high density. The GO sheets act as two-dimensional substrates and surfactants for the growth and adhesion of Fe{sub 3}O{sub 4} NCs. Structural changes induced in the GO due to Fe{sub 3}O{sub 4} decoration were clearly observed using Raman spectroscopy. The magnetic properties of Fe{sub 3}O{sub 4}–GO NHs could be tuned by varying Fe{sub 3}O{sub 4} content and a saturation magnetization as high as 39.2 emu g{sup −1} was achieved. Fe{sub 3}O{sub 4}–GO NHs in their colloidal suspension were used as building blocks to fabricate magnetic and electrically conductive membranes by a vacuum-assisted assembly process.

  18. Preparation of Poly(MA-alt--olefin-C6,8,12,18)/Silica Nanohybrids via in situ generated nanofillers for use as a dual function organonanofiller

    Indian Academy of Sciences (India)

    Deni̇z Demi̇rcan; Günay Ki̇barer; Zaki̇r M O Rzayev

    2015-11-01

    Four types of copolymer-silica nanocomposites have been prepared via ring-opening grafting of -aminopropyltrimethoxysilane (APTS) as reactive coupling agent onto preformed copolymers of maleic anhydride (MA) with 1-hexene, 1-octene, 1-dodecene and 1-octadecene and in situ hydrolysis (polycondensation) of side-chain ethoxysilane groups and tetraethoxysilane as a precursor in the presence of HCl catalyst. The copolymers of MA with 1-hexene, 1-octene and 1-dodecene were synthesized by free radical polymerization and another MA copolymer with 1-octadecene was supplied commercially as matrix copolymer. Chemical/physical structures, thermal behavior and morphology investigations of the generated hybrids were performed by FTIR, 13C, 29Si-NMR, TGA, SEM and TEM analysis methods. Nano-level hybridization through covalent bonding (amidization) between the anhydride unit of copolymers and amine group of APTS was observed, and nanosilica networks (hydrolysis) were obtained through acid catalyzed co-polycondensation of TEOS and ethoxysilane fragments from both coupling agent and precursor. Agreeing with 29Si-NMR and TGA quantitative analysis results, the degree of hydrolysis of ethoxysilane groups varied from 51.0 to 60.9%, and the content of in situ generated silica particles was found to be around 70.7-75.7%. Thermal properties and thermal stability of the obtained hybrids were found to be enhanced with silica content. SEM analysis confirmed the formation of nanostructural hybrids with relatively fine distributed nanoparticles. TEM analyses of all the nanohybrids indicate the formation of spherical morphologies. These novel copolymer hybrids are expected to be a promising and efficient organonanofiller for the preparation of polymer nanocomposites with both dual functionality and compatibilizer effects.

  19. Dispersion scenarios over complex terrain

    DEFF Research Database (Denmark)

    Thykier-Nielsen, S.; Mikkelsen, T.; Moreno, J.

    1993-01-01

    A presentation of preliminary results from a real-time simulation of full-scale dispersion experiments carried out over complex terrain in Northern Spain is given. Actual wind and turbulence measurements as observed during the experiments were analysed and used as input data for a series of simul......A presentation of preliminary results from a real-time simulation of full-scale dispersion experiments carried out over complex terrain in Northern Spain is given. Actual wind and turbulence measurements as observed during the experiments were analysed and used as input data for a series...... are suitable for subsequent comparison with observed mean dispersion data when they become available....

  20. Dispersion Decay and Scattering Theory

    CERN Document Server

    Komech, Alexander

    2012-01-01

    A simplified, yet rigorous treatment of scattering theory methods and their applications Dispersion Decay and Scattering Theory provides thorough, easy-to-understand guidance on the application of scattering theory methods to modern problems in mathematics, quantum physics, and mathematical physics. Introducing spectral methods with applications to dispersion time-decay and scattering theory, this book presents, for the first time, the Agmon-Jensen-Kato spectral theory for the Schr?dinger equation, extending the theory to the Klein-Gordon equation. The dispersion decay plays a crucial role i

  1. Preparation of Graphene/Gold Nano-Hybrid Using Diamine Linker as Effective Surface-Enhanced Raman Scattering Platforms.

    Science.gov (United States)

    Yoon, Sang Su; Lee, Wonoh; Byun, Joon Hyung; Lee, Jea Uk

    2015-11-01

    Development of simple and efficient method for the large-scale production of gaphene/metal nanoparticle hybrids is highly desirable for practical applications, such as catalyst, energy generation and storage, optoelectronics, and sensors. Here, we present a facile approach for the preparation of graphene/gold nanoparticle (AuNP) hybrids by simply mixing the functionalized graphene oxide and AuNPs in aqueous media. Among various functionalized graphene sheets, amine-functionalized graphene oxide (GO-NH2) is used as the hybrid platform due to its synthetic convenience, good dispersity, scalable production with low cost, and positive charge on the surfacce, which could immobilize the AuNPs on the graphene sheets via electrostatic interaction. The synthesized graphene/AgNP hybrids show high surface-enhanced Raman scattering (SERS) sensitivity due to the combined effects of the high contents of amine functional groups on the GO-NH2 surface to adsorb more AgNPs and the electromagnetic enhancement of AgNPs.

  2. Surfactant-free, low band gap conjugated polymer nanoparticles and polymer:fullerene nanohybrids with potential for organic photovoltaics.

    Science.gov (United States)

    Wang, Suxiao; Singh, Amita; Walsh, Nichola; Redmond, Gareth

    2016-06-17

    Stable, aqueous dispersions of nanoparticles based on the low band gap polymers poly [2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (APFO-3) and poly [N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) were prepared, using a flexible, surfactant-free reprecipitation method, and characterized by a variety of optical techniques. Light scattering measurements indicated average nanoparticle hydrodynamic diameters of approximately 40 nm. The particles presented wide-bandwidth absorption and photoluminescence excitation spectra with high absorption cross-sections on the order of 10(-12) cm(2). Nanoparticle emission spectra were significantly red-shifted, with decreased emission quantum yields and lifetimes, consistent with increased inter-polymer chain interactions in the condensed phase. Single particle photoluminescence studies highlighted the multi-chromophoric nature of the polymer nanoparticles and confirmed their favorable photostabilities. When the nanoparticles were doped with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), the correspondence of photoluminescence emission quenching, quantum yield decreases, emission lifetime shortening, and increased non-radiative rates with increasing PCBM concentration suggested efficient photo-induced donor-to-acceptor charge transfer between the conjugated polymers and the fullerene dopants co-localized in the nanoparticle cores. Taken together, the data suggest that these surfactant-free hybrid nanomaterials may be useful for integration with future nanostructured organic photovoltaics technologies.

  3. Synthesis of PtNi Alloy Nanoparticles on Graphene-Based Polymer Nanohybrids for Electrocatalytic Oxidation of Methanol

    Directory of Open Access Journals (Sweden)

    Tung-Yuan Yung

    2016-12-01

    Full Text Available We have successfully produced bimetallic PtNi alloy nanoparticles on poly(diallyldimethylammonium chloride (PDDA-modified graphene nanosheets (PtNi/PDDA-G by the “one-pot” hydrothermal method. The size of PtNi alloy nanoparticles is approximately 2–5 nm. The PDDA-modified graphene nanosheets (PDDA-G provides an anchored site for metal precursors; hence, the PtNi nanoparticles could be easily bond on the PDDA-G substrate. PtNi alloy nanoparticles (2–5 nm display a homogenous alloy phase embedded on the PDDA-G substrate, evaluated by Raman, X-ray diffractometer (XRD, thermal gravity analysis (TGA, electron surface chemical analysis (ESCA, and electron energy loss spectroscopy (EELS. The Pt/Ni ratio of PtNi alloy nanoparticles is ~1.7, examined by the energy dispersive spectroscopy (EDS spectra of transmitting electron microscopy (EDS/TEM spectra and mapping technique. The methanol electro-oxidation of PtNi/PDDA-G was evaluated by cyclic voltammetry (CV in 0.5 M of H2SO4 and 0.5 M of CH3OH. Compared to Pt on carbon nanoparticles (Pt/C and Pt on Graphene (Pt/G, the PtNi/PDDA-G exhibits the optimal electrochemical surface area (ECSA, methanol oxidation reaction (MOR activity, and durability by chrono amperometry (CA test, which can be a candidate for MOR in the electro-catalysis of direct methanol fuel cells (DMFC.

  4. The conservation physiology of seed dispersal

    National Research Council Canada - National Science Library

    Graeme D. Ruxton; H. Martin Schaefer

    2012-01-01

    ...—dispersal interactions. We argue that large-bodied seed dispersers may be particularly important for plant conservation because seed dispersal of large-seeded plants is often more specialized and because large-bodied...

  5. Superradiant scattering of dispersive fields

    CERN Document Server

    Richartz, Maurício; Weinfurtner, Silke; Liberati, Stefano

    2013-01-01

    Motivated by analogue models of classical and quantum field theory in curved spacetimes and their recent experimental realizations, we consider wave scattering processes of dispersive fields exhibiting two extra degrees of freedom. In particular, we investigate how standard superradiant scattering processes are affected by subluminal or superluminal modifications of the dispersion relation. We analyze simple 1-dimensional toy-models based on fourth-order corrections to the standard second order wave equation and show that low-frequency waves impinging on generic scattering potentials can be amplified during the process. In specific cases, by assuming a simple step potential, we determine quantitatively the deviations in the amplification spectrum that arise due to dispersion, and demonstrate that the amplification can be further enhanced due to the presence of extra degrees of freedom. We also consider dispersive scattering processes in which the medium where the scattering takes place is moving with respect ...

  6. Asphaltene dispersants as demulsification aids

    Energy Technology Data Exchange (ETDEWEB)

    Manek, M.B.

    1995-11-01

    Destabilization of petroleum asphaltenes may cause a multitude of problems in crude oil recovery and production. One major problem is their agglomeration at the water-oil interface of crude oil emulsions. Once agglomeration occurs, destabilized asphaltenes can form a thick pad in the dehydration equipment, which significantly reduces the demulsification rate. Certain polymeric dispersants increase asphaltene solubilization in hydrocarbon media, and when used in conjunction with emulsion breakers, facilitate the demulsification process. Two case studies are presented that demonstrate how asphaltene dispersants can efficiently inhibit pad formation and help reduce demulsifier dosage. Criteria for dispersant application and selection are discussed, which include the application of a novel laboratory technique to assess asphaltene stabilization in the crude oil. The technique monitors asphaltene agglomeration while undergoing titration with an incompatible solvent (precipitant). The method was used to evaluate stabilization of asphaltenes in the crude oil and to screen asphaltene dispersants.

  7. The Effect of Single, Binary and Ternary Anions of Chloride, Carbonate and Phosphate on the Release of 2,4-Dichlorophenoxyacetate Intercalated into the Zn–Al-layered Double Hydroxide Nanohybrid

    Directory of Open Access Journals (Sweden)

    Zainal Zulkarnain

    2009-01-01

    Full Text Available Abstract Intercalation of beneficial anion into inorganic host has lead to an opportunity to synthesize various combinations of new organic–inorganic nanohybrids with various potential applications; especially, for the controlled release formulation and storage purposes. Investigation on the release behavior of 2,4-dichlorophenoxyacetate (2,4-D intercalated into the interlayer of Zn–Al-layered double hydroxide (ZAN have been carried out using single, binary and ternary aqueous systems of chloride, carbonate and phosphate. The release behavior of the active agent 2,4-D from its double-layered hydroxide nanohybrid ZANDI was found to be of controlled manner governed by pseudo-second order kinetics. It was found that carbonate medium yielded the highest accumulated release of 2,4-D, while phosphate in combination with carbonate and/or nitrate speeds up the release rate of 2,4-D. These results indicate that it is possible to design and develop new delivery system of latex stimulant compound with controlled release property based on 2,4-D that is known as a substance to increase latex production of rubber tree,Hevea brasiliensis.

  8. A Crucial Role of Rh Substituent Ion in Photoinduced Internal Electron Transfer and Enhanced Photocatalytic Activity of CdS-Ti(5.2-x)/6 Rhx /2 O2 Nanohybrids.

    Science.gov (United States)

    Lee, Jang Mee; Jin, Hyung Bin; Kim, In Young; Jo, Yun Kyung; Hwang, Jung-Wook; Wang, Kang-Kyun; Kim, Min Gyu; Kim, Yong-Rok; Hwang, Seong-Ju

    2015-11-18

    The photocatalytic activity and photostability of CdS quantum dot (QD) can be remarkably enhanced by hybridization with Rh-substituted layered titanate nanosheet even at very low Rh substitution rate (Rh(3+)/Rh(4+) ions for Ti(4+) ions in layered titanate is quite effective in enhancing an electronic coupling between hybridized CdS and titanate components via the formation of interband Rh 4d states. A crucial role of Rh substituent ion in the internal electron transfer is obviously evidenced from in situ X-ray absorption spectroscopy showing the elongation of (RhO) bond under visible light irradiation. This is the first spectroscopic evidence for the important role of substituent ion in the photoinduced electron transfer of hybrid-type photocatalyst. The CdS-Ti(5.2-x)/6 Rhx/2O2 nanohybrids show much higher photocatalytic activity for H2 production and better photostability than do CdS and unsubstituted CdS-TiO2 nanohybrid. This result is ascribable to the enhancement of visible light absorptivity, the depression of electron-hole recombination, and the enhanced hole curing of CdS upon Rh substitution. The present study underscores that the hybridization with composition-controlled inorganic nanosheet provides a novel efficient methodology to optimize the photo-related functionalities of semiconductor nanocrystal. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Dispersion engineering for integrated nanophotonics

    CERN Document Server

    Vanbésien, Olivier

    2014-01-01

    This book shows how dispersion engineering in two dimensional dielectric photonic crystals can provide new effects for the precise control of light propagation for integrated nanophotonics.Dispersion engineering in regular and graded photonic crystals to promote anomalous refraction effects is studied from the concepts to experimental demonstration via nanofabrication considerations. Self collimation, ultra and negative refraction, second harmonic generation, mirage and invisibility effects which lead to an unprecedented control of light propagation at the (sub-)wavelength scale for the

  10. Dispersion in alluvial convergent estuaries

    Science.gov (United States)

    Zhang, Zhilin; Savenije, Hubert H. G.

    2016-04-01

    The Van der Burgh's equation for longitudinal effective dispersion is a purely empirical method with practical implications. Its application to the effective tidal average dispersion under equilibrium conditions appears to have excellent performance in a wide range of alluvial estuaries. In this research, we try to find out the physical meaning of Van der Burgh's coefficient. Researchers like MacCready, Fischer, Kuijper, Hansen and Rattray have tried to split up dispersion into its constituents which did not do much to explain overall behaviour. In addition, traditional literature on dispersion is mostly related to flumes with constant cross-section. This research is about understanding the Van der Burgh's coefficient facing the fact that natural estuaries have exponentially varying cross-section. The objective is to derive a simple 1-D model considering both longitudinal and lateral mixing processes based on field observations (theoretical derivation). To that effect, we connect dispersion with salinity using the salt balance equation. Then we calculate the salinity along the longitudinal direction and compare it to the observed salinity. Calibrated dispersion coefficients in a range of estuaries are then compared with new expressions for the Van der Burgh's coefficient K and it is analysed if K varies from estuary to estuary. The set of reliable data used will be from estuaries: Kurau, Perak, Bernam, Selangor, Muar, Endau, Maputo, Thames, Corantijn, Sinnamary, Mae Klong, Lalang, Limpopo, Tha Chin, Chao Phraya, Edisto and Elbe.

  11. Dispersion properties of photonic Bandgap Fibres

    DEFF Research Database (Denmark)

    Broeng, Jes; Barkou, Stig Eigil; Søndergaard, Thomas

    1999-01-01

    Dispersion properties of new low-index core photonic crystal fibres are presented. Both wideband nearzero despersion and very large dispersion is shown possible in the 1550 nm wavelength range.......Dispersion properties of new low-index core photonic crystal fibres are presented. Both wideband nearzero despersion and very large dispersion is shown possible in the 1550 nm wavelength range....

  12. Dispersion Management with Higher Order Mode Fibers

    Institute of Scientific and Technical Information of China (English)

    Siddharth Ramachandran

    2003-01-01

    Dispersion compensation with few-mode fibers is emerging as a promising technique that can provide full dispersion and dispersion-slope compensation. The inherent modal path diversity of these fibers allows implementation of static as well as tunable dispersion management schemes. In addition, the low nonlinearityof this technology can improve system OSNR, leading to enhancements in transmission distances.

  13. Dispersion Management with Higher Order Mode Fibers

    Institute of Scientific and Technical Information of China (English)

    Siddharth; Ramachandran

    2003-01-01

    Dispersion compensation with few-mode fibers is emerging as a promising technique that can provide full dispersion and dispersion-slope compensation. The inherent modal path diversity of these fibers allows implementation of static as well as tunable dispersion management schemes. In addition, the low non-linearity of this technology can improve system OSNR, leading to enhancements in transmission distances.

  14. HYPERBRANCHED POLYMERIC DISPERSANTS AND NON-AQUEOUS PIGMENT DISPERSIONS

    NARCIS (Netherlands)

    ANDRE, XAVIER; Bernaerts, Katrien

    2011-01-01

    A polymeric dispersant having a hyperbranched polyurethane architecture obtained by reacting a polyisocyanate core with a mixture of a) 40 to 65 mol% of an anchor represented by Formula (I) and/or (II) wherein n represents an integer selected from 0 to 7; and X and Y each independently represent a p

  15. Hyperbranched polymeric dispersants and non-aqueous pigment dispersions

    NARCIS (Netherlands)

    ANDRE, XAVIER; Bernaerts, Katrien

    2012-01-01

    The invention discloses a polymeric dispersant having a hyperbranched polyurethane architecture obtained by reacting a polyisocyanate core with a mixture of a) 40 to 65 mol% of an anchor represented by Formula (I) and/or (II) wherein n represents an integer selected from 0 to 7; and X and Y each ind

  16. HYPERBRANCHED POLYMERIC DISPERSANTS AND NON-AQUEOUS PIGMENT DISPERSIONS

    NARCIS (Netherlands)

    ANCRE, XAVIER; BERNAERTS, KATRIEN; ANDRE, XAVIER

    2012-01-01

    A polymeric dispersant having a hyperbranched polyurethane architecture obtained by reacting a polyisocyanate core with a mixture of: a) 40 to 65 mol % of an anchor represented by Formula (I) and/or (II): wherein n represents an integer selected from 0 to 7; and X and Y each independently represent

  17. Stochastic models for atmospheric dispersion

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager

    2003-01-01

    Simple stochastic differential equation models have been applied by several researchers to describe the dispersion of tracer particles in the planetary atmospheric boundary layer and to form the basis for computer simulations of particle paths. To obtain the drift coefficient, empirical vertical...... velocity distributions that depend on height above the ground both with respect to standard deviation and skewness are substituted into the stationary Fokker/Planck equation. The particle position distribution is taken to be uniform *the well/mixed condition( and also a given dispersion coefficient...

  18. A generalized advection dispersion equation

    Indian Academy of Sciences (India)

    Abdon Atangana

    2014-02-01

    This paper examines a possible effect of uncertainties, variability or heterogeneity of any dynamic system when being included in its evolution rule; the notion is illustrated with the advection dispersion equation, which describes the groundwater pollution model. An uncertain derivative is defined; some properties of the operator are presented. The operator is used to generalize the advection dispersion equation. The generalized equation differs from the standard equation in four properties. The generalized equation is solved via the variational iteration technique. Some illustrative figures are presented.

  19. Dispersion scenarios over complex terrain

    DEFF Research Database (Denmark)

    Thykier-Nielsen, S.; Mikkelsen, T.; Moreno, J.

    1993-01-01

    A presentation of preliminary results from a real-time simulation of full-scale dispersion experiments carried out over complex terrain in Northern Spain is given. Actual wind and turbulence measurements as observed during the experiments were analysed and used as input data for a series of simul......A presentation of preliminary results from a real-time simulation of full-scale dispersion experiments carried out over complex terrain in Northern Spain is given. Actual wind and turbulence measurements as observed during the experiments were analysed and used as input data for a series...

  20. Dispersion of halloysite loaded with natural antimicrobials into pectins: Characterization and controlled release analysis.

    Science.gov (United States)

    Gorrasi, Giuliana

    2015-01-01

    This paper reports the preparation and characterization of green composites based on pectins and nano-hybrids composed of halloysite nanotubes (HNTs) loaded with rosemary essential oil. Different hybrid percentages were mixed into a pectin matrix, by ball milling in the presence of water. Cast films were obtained and analyzed. Structural organization and physical properties (thermal, mechanical, barrier to water vapor) were correlated to the nano-hybrid content. A preliminary study on the kinetics of release of the rosmarinic acid, chosen as a model molecule, was also performed. This work showed the potential of these systems in the active packaging field where controlled release of active species is required.

  1. Sol-Gel与在位聚合联用制备分散良好的纳米杂化材料%SOL-GEL IN-SITU POLYMERIZATION TO PREPARE WELL-DISPERSED NANO-HYBRID COMPOSITE

    Institute of Scientific and Technical Information of China (English)

    郭卫红; 汪济奎; 唐颂超; 唐芳琼; 徐种德

    2003-01-01

    采用Sol-Gel法与在位聚合相结合的方法,使正硅酸乙酯在聚合物单体中进行水解、缩聚,然后再加入引发剂使单体聚合,制得了稳定分散的纳米粒子杂化的聚合物材料,该材料性能优良,具有很好的透明度.在保持树脂光学性能的前提下,材料的抗冲击性能有所改善.对其结构与性能进行了表征.

  2. On Dispersion in Visual Photoreceptors

    NARCIS (Netherlands)

    Stavenga, D.G.; Barneveld, H.H. van

    1975-01-01

    An idealized visual pigment absorbance spectrum is used together with a Kramers-Kronig dispersion relation to calculate the contribution of the visual pigment to the refractive index of the fly photoreceptor. It appears that an absorption coefficient of 0.010 µm-1 results in a refractive index varia

  3. Magnetic exciton dispersion in praseodymium

    DEFF Research Database (Denmark)

    Rainford, B. D.; Houmann, Jens Christian Gylden

    1971-01-01

    Measurements of the dispersion of magnetic excitons have been made in a single crystal of praseodymium metal using inelastic neutron scattering. A preliminary analysis of the data yields the first detailed information about the exchange interactions and the crystal field splittings in the light...

  4. Dispersion-Enhanced Laser Gyroscope

    Science.gov (United States)

    Smith, David D.; Chang, Hongrok; Arissian, L.; Diels, J. C.

    2008-01-01

    We analyze the effect of a highly dispersive element placed inside a modulated optical cavity on the frequency and amplitude of the output modulation to determine the conditions for enhanced gyroscopic sensitivities. The element is treated as both a phase and amplitude filter, and the time-dependence of the cavity field is considered. Both atomic gases (two-level and multi-level) and optical resonators (single and coupled) are considered and compared as dispersive elements. We find that it is possible to simultaneously enhance the gyro scale factor sensitivity and suppress the dead band by using an element with anomalous dispersion that has greater loss at the carrier frequency than at the side-band frequencies, i.e., an element that simultaneously pushes and intensifies the perturbed cavity modes, e.g. a two-level absorber or an under-coupled optical resonator. The sensitivity enhancement is inversely proportional to the effective group index, becoming infinite at a group index of zero. However, the number of round trips required to reach a steady-state also becomes infinite when the group index is zero (or two). For even larger dispersions a steady-state cannot be achieved, and nonlinear dynamic effects such as bistability and periodic oscillations are predicted in the gyro response.

  5. DIMO, a plant dispersal model

    NARCIS (Netherlands)

    Wamelink, G.W.W.; Jochem, R.; Greft, van der J.G.M.; Franke, J.; Malinowska, A.H.; Geertsema, W.; Prins, A.H.; Ozinga, W.A.; Hoek, van der D.C.J.; Grashof-Bokdam, C.J.

    2014-01-01

    Due to human activities many natural habitats have become isolated. As a result the dispersal of many plant species is hampered. Isolated populations may become extinct and have a lower probability to become reestablished in a natural way. Moreover, plant species may be forced to migrate to new area

  6. Molecular mobility in glassy dispersions

    Science.gov (United States)

    Mehta, Mehak; McKenna, Gregory B.; Suryanarayanan, Raj

    2016-05-01

    Dielectric spectroscopy was used to characterize the structural relaxation in pharmaceutical dispersions containing nifedipine (NIF) and either poly(vinyl) pyrrolidone (PVP) or hydroxypropyl methylcellulose acetate succinate (HPMCAS). The shape of the dielectric response (permittivity versus log time) curve was observed to be independent of temperature. Thus, for the pure NIF as well as the dispersions, the validity of the time-temperature superposition principle was established. Furthermore, though the shape of the full dielectric response varied with polymer concentration, the regime related to the α- or structural relaxation was found to superimpose for the dispersions, though not with the response of the NIF itself. Hence, there is a limited time-temperature-concentration superposition for these systems as well. Therefore, in this polymer concentration range, calculation of long relaxation times in these glass-forming systems becomes possible. We found that strong drug-polymer hydrogen bonding interactions improved the physical stability (i.e., delayed crystallization) by reducing the molecular mobility. The strength of hydrogen bonding, structural relaxation time, and crystallization followed the order: NIF-PV P>NIF-HPMCAS>NIF. With an increase in polymer concentration, the relaxation times were longer indicating a decrease in molecular mobility. The temperature dependence of relaxation time, in other words fragility, was independent of polymer concentration. This is the first application of the superposition principle to characterize structural relaxation in glassy pharmaceutical dispersions.

  7. Wireless Communication over Dispersive Channels

    NARCIS (Netherlands)

    Fang, K.

    2010-01-01

    Broadband wireless communication systems require high transmission rates, where the bandwidth of the transmitted signal is larger than the channel coherence bandwidth. This gives rise to time dispersion of the transmitted symbols or frequency-selectivity with different frequency components exhibitin

  8. Molecular mobility in glassy dispersions

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, Mehak [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Pharmaceutics; McKenna, Gregory B. [Texas Tech Univ., Lubbock, TX (United States). Dept. of Chemical Engineering; Suryanarayanan, Raj [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Pharmaceutics

    2016-05-27

    Dielectric spectroscopy was used to characterize the structural relaxation in pharmaceutical dispersions containing nifedipine (NIF) and either poly(vinyl) pyrrolidone (PVP) or hydroxypropyl methylcellulose acetate succinate (HPMCAS). The shape of the dielectric response (permittivity versus log time) curve was observed to be independent of temperature. Thus, for the pure NIF as well as the dispersions, the validity of the time-temperature superposition principle was established. Furthermore, though the shape of the full dielectric response varied with polymer concentration, the regime related to the α- or structural relaxation was found to superimpose for the dispersions, though not with the response of the NIF itself. Hence, there is a limited time-temperature-concentration superposition for these systems as well. Therefore, in this polymer concentration range, calculation of long relaxation times in these glass-forming systems becomes possible. We found that strong drug-polymer hydrogen bonding interactions improved the physical stability (i.e., delayed crystallization) by reducing the molecular mobility. The strength of hydrogen bonding, structural relaxation time, and crystallization followed the order: NIF$-$PV P>NIF$-$HPMCAS>NIF. With an increase in polymer concentration, the relaxation times were longer indicating a decrease in molecular mobility. The temperature dependence of relaxation time, in other words fragility, was independent of polymer concentration. This is the first application of the superposition principle to characterize structural relaxation in glassy pharmaceutical dispersions.

  9. Dispersion-enhanced laser gyroscope

    Science.gov (United States)

    Smith, David D.; Chang, Hongrok; Arissian, L.; Diels, J. C.

    2008-11-01

    We analyze the effect of a highly dispersive element placed inside a modulated optical cavity on the frequency and amplitude of the output modulation to determine the conditions for enhanced gyroscopic sensitivities. The element is treated as both a phase and amplitude filter, and the time dependence of the cavity field is considered. Both atomic gases (two level and multilevel) and optical resonators (single and coupled) are considered and compared as dispersive elements. We find that it is possible to simultaneously enhance the gyro scale factor sensitivity and suppress the dead band by using an element with anomalous dispersion that has greater loss at the carrier frequency than at the sideband frequencies, i.e., an element that simultaneously pushes and intensifies the perturbed cavity modes, e.g. a two-level absorber or an undercoupled optical resonator. The sensitivity enhancement is inversely proportional to the effective group index, becoming infinite at a group index of zero. However, the number of round trips required to reach a steady state also becomes infinite when the group index is zero (or two). For even larger dispersions a steady state cannot be achieved, and nonlinear dynamic effects such as bistability and periodic oscillations are predicted in the gyro response.

  10. Seed dispersal: Size does matter

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ Many small seed-eating rodents bury their food in an erratic manner called scatter-hoarding because they are unable to defend one large hoard. This process has a complicated influence on seed dispersal,as shown in the work by ZHANG Zhibin at the CAS Institute of Zoology and hisco-workers.

  11. Anomalous dispersions of `hedgehog' particles

    Science.gov (United States)

    Bahng, Joong Hwan; Yeom, Bongjun; Wang, Yichun; Tung, Siu On; Hoff, J. Damon; Kotov, Nicholas

    2015-01-01

    Hydrophobic particles in water and hydrophilic particles in oil aggregate, but can form colloidal dispersions if their surfaces are chemically camouflaged with surfactants, organic tethers, adsorbed polymers or other particles that impart affinity for the solvent and increase interparticle repulsion. A different strategy for modulating the interaction between a solid and a liquid uses surface corrugation, which gives rise to unique wetting behaviour. Here we show that this topographical effect can also be used to disperse particles in a wide range of solvents without recourse to chemicals to camouflage the particles' surfaces: we produce micrometre-sized particles that are coated with stiff, nanoscale spikes and exhibit long-term colloidal stability in both hydrophilic and hydrophobic media. We find that these `hedgehog' particles do not interpenetrate each other with their spikes, which markedly decreases the contact area between the particles and, therefore, the attractive forces between them. The trapping of air in aqueous dispersions, solvent autoionization at highly developed interfaces, and long-range electrostatic repulsion in organic media also contribute to the colloidal stability of our particles. The unusual dispersion behaviour of our hedgehog particles, overturning the notion that like dissolves like, might help to mitigate adverse environmental effects of the use of surfactants and volatile organic solvents, and deepens our understanding of interparticle interactions and nanoscale colloidal chemistry.

  12. An Introduction to Dispersive Interactions

    Science.gov (United States)

    Taddei, M. M.; Mendes, T. N. C.; Farina, C.

    2010-01-01

    Dispersive forces are a kind of van der Waals intermolecular force which could only be fully understood with the establishment of quantum mechanics and, in particular, of quantum electrodynamics. In this pedagogical paper, we introduce the subject in a more elementary approach, aiming at students with basic knowledge of quantum mechanics. We…

  13. Dispersive mudslide-induced tsunamis

    Directory of Open Access Journals (Sweden)

    A. Rubino

    1998-01-01

    Full Text Available A nonlinear nested model for mudslide-induced tsunamis is proposed in which three phases of the life of the wave, i.e. the generation, far-field propagation and costal run-up are described by means of different mathematical models, that are coupled through appropriate matching procedures. The generation and run-up dynamics are simulated through a nonlinear shallow-water model with movable lateral boundaries: in the generation region two active layers are present, the lower one describing the slide descending on a sloping topography. For the intermediate phase, representing wave propagation far from the generation region, the hydrostatic assumption is not assumed as appropriate in general and, therefore, a nonlinear model allowing for weak phase dispersion, namely a Kadomtsev-Petviashvili equation, is used. This choice is made in order to assess the relevance of dispersive features such as solitary waves and dispersive tails. It is shown that in some realistic circumstances dispersive mudslide-induced tsunami waves can be produced over relatively short, distances. In such cases the use of a hydrostatic model throughout the whole tsunami history turns out to give erroneous results. In particular, when solitary waves are generated during the tsunami propagation in the open sea, the resulting run-up process yields peculiar wave forms leading to amplified coastal inundations with respect to a mere hydrostatic context.

  14. Interdependence of waveguide and material dispersion.

    Science.gov (United States)

    Marcuse, D

    1979-09-01

    Theoretical work on dispersion in single-mode fibers sometimes uses the assumption that waveguide dispersion D(w) and material dispersion D(m) are separate effects that contribute additively to the total amount of dispersion D(m+w). Using Gloge's LP-mode approximation we compute the dispersion of the LP(0l) (HE(11)) mode by solving the eigenvalue equation taking dispersion of core and cladding materials into account. The dispersion of the LP(01) mode is computed by numerical differentiation of the solution of the eigenvalue equation. The difference D(m+w) - D(w) is compared to waveguide dispersion D(w), which is computed by ignoring the dispersive properties of the core and cladding materials. We find large percentage deviations between D(m+w) - D(m) and D(w). The assumption of additivity of material and waveguide dispersion is thus not quite correct. However, because of the small contribution of waveguide dispersion to the total dispersion of the LP(01) mode, even a large percentage error in the waveguide dispersion has little influence on the over-all dispersion of the LP(01) mode.

  15. Adhesion and inactivation of Gram-negative and Gram-positive bacteria on photoreactive TiO{sub 2}/polymer and Ag–TiO{sub 2}/polymer nanohybrid films

    Energy Technology Data Exchange (ETDEWEB)

    Tallósy, Szabolcs Péter [Institute of Clinical Microbiology, Faculty of Medicine, University of Szeged, H-6725 Szeged, Semmelweis u. 6 (Hungary); Department of Physical Chemistry and Materials Sciences, University of Szeged, H-6720 Szeged, Aradi v.t.1 (Hungary); Janovák, László [Department of Physical Chemistry and Materials Sciences, University of Szeged, H-6720 Szeged, Aradi v.t.1 (Hungary); Nagy, Elisabeth [Institute of Clinical Microbiology, Faculty of Medicine, University of Szeged, H-6725 Szeged, Semmelweis u. 6 (Hungary); Deák, Ágota [Department of Physical Chemistry and Materials Sciences, University of Szeged, H-6720 Szeged, Aradi v.t.1 (Hungary); Juhász, Ádám; Csapó, Edit [MTA-SZTE Supramolecular and Nanostructured Materials Research Group, Department of Medical Chemistry, Faculty of Medicine, H-6720 Szeged, Dóm tér 8 (Hungary); Buzás, Norbert [Department of Health Economics, Faculty of Medicine, University of Szeged, H-6720 Szeged, Szőkefalvi-Nagy Béla u. 6 (Hungary); Dékány, Imre, E-mail: i.dekany@chem.u-szeged.hu [MTA-SZTE Supramolecular and Nanostructured Materials Research Group, Department of Medical Chemistry, Faculty of Medicine, H-6720 Szeged, Dóm tér 8 (Hungary)

    2016-05-15

    Highlights: • Surface reactivity of TiO{sub 2} and Ag–TiO{sub 2} nanohybrid films were tested by photooxidation. • Photocatalyst–bacteria interactions were defined by surface charge determination. • Higher surface charge induces stronger adhesion between the bacteria and the NPs. • Inactivation of GR+/GR− bacteria by hydroxyl radicals depends on cell wall structure. • The cell wall degradation of bacteria was proven with TEM and fluorescence studies - Abstract: The aim of this study was to develop photoreactive surface coatings, possessing antibacterial properties and can be activated under visible light illumination (λ{sub max} = 405 nm) using LED-light source. The photocatalytically active titanium dioxide (TiO{sub 2}) was functionalized with silver nanoparticles (Ag NPs) and immobilized in polyacrylate based nanohybrid thin film in order to facilitate visible light activity (λ{sub Ag/TiO2,max} = 500 nm). First, the photocatalytic activity was modelled by following ethanol vapor degradation. The plasmonic functionalization resulted in 15% enhancement of the activity compared to pure TiO{sub 2}. The photoreactive antimicrobial (5 log reduction of cfu in 2 h) surface coatings are able to inactivate clinically relevant pathogen strains (methicillin resistant Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa) within short time (60–120 min) due to the formed and quantified reactive oxygen species (ROS). The existence of electrostatic interactions between the negatively charged bacteria (from −0.89 to −3.19 μeq/10{sup 9} cfu) and positively charged photocatalyst particles (in the range of +0.38 and +12.3 meq/100 g) was also proven by charge titration measurements. The surface inactivation of the bacteria and the photocatalytic degradation of the cell wall component were also confirmed by fluorescence and transmission electron microscopic observations, respectively. According to the results an effective sterilizing system and

  16. CdS:Mn quantum dot-functionalized g-C3N4 nanohybrids as signal-generation tags for photoelectrochemical immunoassay of prostate specific antigen coupling DNAzyme concatamer with enzymatic biocatalytic precipitation.

    Science.gov (United States)

    Zhang, Kangyao; Lv, Shuzhen; Lin, Zhenzhen; Tang, Dianping

    2017-09-15

    A new photoelectrochemical (PEC) immunosensor based on Mn-doped CdS quantum dots (CdS:Mn QDs) on g-C3N4 nanosheets was developed for the sensitive detection of prostate specific antibody (PSA) in biological fluids. The signal derived from the as-synthesized Cd:Mn QDs-functionalized g-C3N4 nanohybrids via a hydrothermal method and was amplified through DNAzyme concatamers on gold nanoparticles accompanying enzymatic biocatalytic precipitation. Experimental results by UV-vis absorption spectra and photoluminescence revealed that CdS:Mn QDs/g-C3N4 nanohybrids exhibited higher photocurrent than those of CdS:Mn QDs and g-C3N4 alone. Upon addition of target PSA, a sandwich-type immunoreaction was carried out between capture antibodies and the labeled detection antibodies. Accompanying introduction of gold nanoparticles, the labeled initiator strands on the AuNPs triggered hybridization chain reaction and the formation of DNAzyme concatamers in the presence of hemin. The formed DNAzyme catalyzed 4-chloro-1-naphthol (4-CN) to produce an insoluble/insulating precipitate on the Mn:CdS QDs/g-C3N4, and blocked the light harvesting of Mn:CdS QDs/g-C3N4, thus resulting in the decreasing photocurrent. Under optimal conditions, the immunosensor exhibited good photocurrent responses for determination of target PSA, and allowed detection of PSA at a concentration as low as 3.8pgmL(-1). The specificity, reproducibility and precision of this system were acceptable. Significantly, this methodology was further evaluated for analyzing human serum samples, giving well-matched results with referenced PSA enzyme-linked immunosorbent assay (ELISA) method. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Analysis of Wave Nonlinear Dispersion Relation

    Institute of Scientific and Technical Information of China (English)

    LI Rui-jie; TAO Jian-fu

    2005-01-01

    The nonlinear dispersion relations and modified relations proposed by Kirby and Hedges have the limitation of intermediate minimum value. To overcome the shortcoming, a new nonlinear dispersion relation is proposed. Based on the summarization and comparison of existing nonlinear dispersion relations, it can be found that the new nonlinear dispersion relation not only keeps the advantages of other nonlinear dispersion relations, but also significantly reduces the relative errors of the nonlinear dispersion relations for a range of the relative water depth of 1<kh<1.5 and has sufficient accuracy for practical purposes.

  18. Dispersion compensation based on prism compressor

    Science.gov (United States)

    Liu, Hongying; Lan, Tian; Chen, Xiaomei; Ni, Guoqiang

    2017-04-01

    A prism compressor can compensate dispersion of femtosecond light pulses travelling in air for laser ranging. An accurate expression of the group delay dispersion (GDD) of a prism compressor at arbitrary incident angle and at arbitrary incident point is obtained, which is of benefit to finely compensating dispersion of femtosecond pulses. Influences of several parameters on group delay dispersion are analyzed for the active compensation of dispersion of femtosecond pulses. These expressions are convenient to applications of intra- and extra-cavity dispersion compensation of ultra-short laser pulses, as well as fine compensation of satellite laser ranging and laser altimetry.

  19. Seed dispersal distances: a typology based on dispersal modes and plant traits

    OpenAIRE

    Vittoz, P.; Engler, R.

    2007-01-01

    The ability of plants to disperse seeds may be critical for their survival under the current constraints of landscape fragmentation and climate change. Seed dispersal distance would therefore be an important variable to include in species distribution models. Unfortunately, data on dispersal distances are scarce, and seed dispersion models only exist for some species with particular dispersal modes. To overcome this lack of knowledge, we propose a simple approach to estimate seed dispersal di...

  20. Nanocomposites from Stable Dispersions of Carbon Nanotubes in Polymeric Matrices Using Dispersion Interaction

    Science.gov (United States)

    Wise, Kristopher Eric (Inventor); Park, Cheol (Inventor); Kang, Jin Ho (Inventor); Siochi, Emilie J. (Inventor); Harrison, Joycelyn S. (Inventor)

    2016-01-01

    Stable dispersions of carbon nanotubes (CNTs) in polymeric matrices include CNTs dispersed in a host polymer or copolymer whose monomers have delocalized electron orbitals, so that a dispersion interaction results between the host polymer or copolymer and the CNTs dispersed therein. Nanocomposite products, which are presented in bulk, or when fabricated as a film, fiber, foam, coating, adhesive, paste, or molding, are prepared by standard means from the present stable dispersions of CNTs in polymeric matrices, employing dispersion interactions, as presented hereinabove.

  1. Hawking Radiation in Dispersive Media

    CERN Document Server

    Robertson, Scott James

    2011-01-01

    Hawking radiation, despite its presence in theoretical physics for over thirty years, remains elusive and undetected. It also suffers, in its original context of gravitational black holes, from conceptual difficulties. Of particular note is the trans-Planckian problem, which is concerned with the apparent origin of the radiation in absurdly high frequencies. In order to gain better theoretical understanding and, it is hoped, experimental verification of Hawking radiation, much study is being devoted to systems which model the spacetime geometry of black holes, and which, by analogy, are also thought to emit Hawking radiation. These analogue systems typically exhibit dispersion, which regularizes the wave behaviour at the horizon but does not lend itself well to analytic treatment, thus rendering Hawking's prediction less secure. A general analytic method for dealing with Hawking radiation in dispersive systems has proved difficult to find. This thesis presents new numerical and analytic results for Hawking em...

  2. Coupling constant in dispersive model

    Indian Academy of Sciences (India)

    R Saleh-Moghaddam; M E Zomorrodian

    2013-11-01

    The average of the moments for event shapes in + - → hadrons within the context of next-to-leading order (NLO) perturbative QCD prediction in dispersive model is studied. Moments used in this article are $\\langle 1 - T \\rangle, \\langle ρ \\rangle, \\langle B_{T} \\rangle$ and $\\langle B_{W} \\rangle$. We extract , the coupling constant in perturbative theory and α0 in the non-perturbative theory using the dispersive model. By fitting the experimental data, the values of $(M_{Z^{°}})$ = 0.1171 ± 0.00229 and 0 ($_{I} = 2{\\text{GeV}}$) = 0.5068 ± 0.0440 are found. Our results are consistent with the above model. Our results are also consistent with those obtained from other experiments at different energies. All these features are explained in this paper.

  3. Statistical description of turbulent dispersion

    Science.gov (United States)

    Brouwers, J. J. H.

    2012-12-01

    We derive a comprehensive statistical model for dispersion of passive or almost passive admixture particles such as fine particulate matter, aerosols, smoke, and fumes in turbulent flow. The model rests on the Markov limit for particle velocity. It is in accordance with the asymptotic structure of turbulence at large Reynolds number as described by Kolmogorov. The model consists of Langevin and diffusion equations in which the damping and diffusivity are expressed by expansions in powers of the reciprocal Kolmogorov constant C0. We derive solutions of O(C00) and O(C0-1). We truncate at O(C0-2) which is shown to result in an error of a few percentages in predicted dispersion statistics for representative cases of turbulent flow. We reveal analogies and remarkable differences between the solutions of classical statistical mechanics and those of statistical turbulence.

  4. Study of Dispersion Coefficient Channel

    Science.gov (United States)

    Akiyama, K. R.; Bressan, C. K.; Pires, M. S. G.; Canno, L. M.; Ribeiro, L. C. L. J.

    2016-08-01

    The issue of water pollution has worsened in recent times due to releases, intentional or not, of pollutants in natural water bodies. This causes several studies about the distribution of pollutants are carried out. The water quality models have been developed and widely used today as a preventative tool, ie to try to predict what will be the concentration distribution of constituent along a body of water in spatial and temporal scale. To understand and use such models, it is necessary to know some concepts of hydraulic high on their application, including the longitudinal dispersion coefficient. This study aims to conduct a theoretical and experimental study of the channel dispersion coefficient, yielding more information about their direct determination in the literature.

  5. Dispersion engineering of surface plasmons.

    Science.gov (United States)

    Mandel, Isroel M; Bendoym, Igor; Jung, Young U; Golovin, Andrii B; Crouse, David T

    2013-12-30

    In this work, it is shown how the shapes of surface plasmon dispersion curves can be engineered by manipulating the distribution of the electromagnetic fields in multilayer structures, which themselves are controlled by the free electron density in metal-like materials, such as doped semiconductors in the THz spectral range. By having a nonuniform free electron density profile, reduced relative to that in typical bulk metals, the electromagnetic fields of surface plasmons are distributed in different metallic materials that have different complex dielectric permittivities. As the in-plane component of surface plasmon's wave-vector increases, they become more confined to a particular layer of the multilayer structure and have energies that are predictable by considering the permittivity of the layer in which the fields are most concentrated. Unusual and arbitrary shapes of surface plasmon dispersion curves can be designed, including stair steps and dovetails shapes.

  6. Tachyonic Dispersion in Coherent Networks

    CERN Document Server

    Chong, Y D

    2015-01-01

    We propose a technique to realize a tachyonic band structure in a coherent network, such as an array of coupled ring resonators. This is achieved by adding "PT symmetric" spatially-balanced gain and loss to each node of the network. In a square-lattice network, the quasi-energy bandstructure exhibits a tachyonic dispersion relation, centered at either the center or corner of the Brillouin zone. There is one tachyonic hyperboloid in each gap, unlike in PT-symmetric tight-binding honeycomb lattices where the hyperboloids occur in pairs. The dispersion relation can be probed by measuring the peaks in transmission across a finite network as the gain/loss parameter is varied.

  7. Ability Dispersion and Team Performance

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    What is the effect of dispersed levels of cognitive ability of members of a (business) team on their team's performance? This paper reports the results of a field experiment in which 573 students in 49 teams start up and manage real companies under identical circumstances for one year. We ensured...... exogenous variation in -otherwise random- team composition by assigning students to teams based on their measured cognitive abilities (Raven test). Each team performs a variety of tasks, often involving complex decision making. The key result of the experiment is that the performance of business teams first...... increases and then decreases with ability dispersion. We seek to understand this finding by developing a model in which team members of different ability levels form sub-teams with other team members with similar ability levels to specialize in different productive tasks. Diversity spreads production over...

  8. Ability Dispersion and Team Performance

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    What is the effect of dispersed levels of cognitive ability of members of a (business) team on their team's performance? This paper reports the results of a field experiment in which 573 students in 49 (student) teams start up and manage real companies under identical circumstances for one year. We...... ensured exogenous variation in otherwise random team composition by assigning students to teams based on their measured cognitive abilities. Each team performs a variety of tasks, often involving complex decision making. The key result of the experiment is that the performance of business teams first...... increases and then decreases with ability dispersion. We seek to understand this finding by developing a model in which team members of different ability levels form sub- teams with other team members with similar ability levels to specialize in different productive tasks. Diversity spreads production over...

  9. Ability Dispersion and Team Performance

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    What is the effect of dispersed levels of cognitive ability of members of a (business) team on their team's performance? This paper reports the results of a field experiment in which 573 students in 49 teams start up and manage real companies under identical circumstances. We ensured exogenous...... variation in - otherwise random - team composition by assigning students to teams based on their measured cognitive abilities (Raven test). Each team performs a variety of tasks, often involving complex decision making. The key result of the experiment is that the performance of business teams first...... increases and then decreases with ability dispersion. We seek to understand this finding by developing a model in which team members of different ability levels form sub-teams with other team members with similar ability levels to specialize in different productive tasks. Diversity spreads production over...

  10. Faraday anomalous dispersion optical tuners

    Science.gov (United States)

    Wanninger, P.; Valdez, E. C.; Shay, T. M.

    1992-01-01

    Common methods for frequency stabilizing diode lasers systems employ gratings, etalons, optical electric double feedback, atomic resonance, and a Faraday cell with low magnetic field. Our method, the Faraday Anomalous Dispersion Optical Transmitter (FADOT) laser locking, is much simpler than other schemes. The FADOT uses commercial laser diodes with no antireflection coatings, an atomic Faraday cell with a single polarizer, and an output coupler to form a compound cavity. This method is vibration insensitive, thermal expansion effects are minimal, and the system has a frequency pull in range of 443.2 GHz (9A). Our technique is based on the Faraday anomalous dispersion optical filter. This method has potential applications in optical communication, remote sensing, and pumping laser excited optical filters. We present the first theoretical model for the FADOT and compare the calculations to our experimental results.

  11. Hydrodynamic dispersion within porous biofilms

    KAUST Repository

    Davit, Y.

    2013-01-23

    Many microorganisms live within surface-associated consortia, termed biofilms, that can form intricate porous structures interspersed with a network of fluid channels. In such systems, transport phenomena, including flow and advection, regulate various aspects of cell behavior by controlling nutrient supply, evacuation of waste products, and permeation of antimicrobial agents. This study presents multiscale analysis of solute transport in these porous biofilms. We start our analysis with a channel-scale description of mass transport and use the method of volume averaging to derive a set of homogenized equations at the biofilm-scale in the case where the width of the channels is significantly smaller than the thickness of the biofilm. We show that solute transport may be described via two coupled partial differential equations or telegrapher\\'s equations for the averaged concentrations. These models are particularly relevant for chemicals, such as some antimicrobial agents, that penetrate cell clusters very slowly. In most cases, especially for nutrients, solute penetration is faster, and transport can be described via an advection-dispersion equation. In this simpler case, the effective diffusion is characterized by a second-order tensor whose components depend on (1) the topology of the channels\\' network; (2) the solute\\'s diffusion coefficients in the fluid and the cell clusters; (3) hydrodynamic dispersion effects; and (4) an additional dispersion term intrinsic to the two-phase configuration. Although solute transport in biofilms is commonly thought to be diffusion dominated, this analysis shows that hydrodynamic dispersion effects may significantly contribute to transport. © 2013 American Physical Society.

  12. Dispersed Fringe Sensing Analysis - DFSA

    Science.gov (United States)

    Sigrist, Norbert; Shi, Fang; Redding, David C.; Basinger, Scott A.; Ohara, Catherine M.; Seo, Byoung-Joon; Bikkannavar, Siddarayappa A.; Spechler, Joshua A.

    2012-01-01

    Dispersed Fringe Sensing (DFS) is a technique for measuring and phasing segmented telescope mirrors using a dispersed broadband light image. DFS is capable of breaking the monochromatic light ambiguity, measuring absolute piston errors between segments of large segmented primary mirrors to tens of nanometers accuracy over a range of 100 micrometers or more. The DFSA software tool analyzes DFS images to extract DFS encoded segment piston errors, which can be used to measure piston distances between primary mirror segments of ground and space telescopes. This information is necessary to control mirror segments to establish a smooth, continuous primary figure needed to achieve high optical quality. The DFSA tool is versatile, allowing precise piston measurements from a variety of different optical configurations. DFSA technology may be used for measuring wavefront pistons from sub-apertures defined by adjacent segments (such as Keck Telescope), or from separated sub-apertures used for testing large optical systems (such as sub-aperture wavefront testing for large primary mirrors using auto-collimating flats). An experimental demonstration of the coarse-phasing technology with verification of DFSA was performed at the Keck Telescope. DFSA includes image processing, wavelength and source spectral calibration, fringe extraction line determination, dispersed fringe analysis, and wavefront piston sign determination. The code is robust against internal optical system aberrations and against spectral variations of the source. In addition to the DFSA tool, the software package contains a simple but sophisticated MATLAB model to generate dispersed fringe images of optical system configurations in order to quickly estimate the coarse phasing performance given the optical and operational design requirements. Combining MATLAB (a high-level language and interactive environment developed by MathWorks), MACOS (JPL s software package for Modeling and Analysis for Controlled Optical

  13. Dispersion as a Survival Strategy

    Science.gov (United States)

    Junior, Valdivino Vargas; Machado, Fábio Prates; Roldán-Correa, Alejandro

    2016-08-01

    We consider stochastic growth models to represent population subject to catastrophes. We analyze the subject from different set ups considering or not spatial restrictions, whether dispersion is a good strategy to increase the population viability. We find out it strongly depends on the effect of a catastrophic event, the spatial constraints of the environment and the probability that each exposed individual survives when a disaster strikes.

  14. Faraday anomalous dispersion optical filters

    Science.gov (United States)

    Shay, T. M.; Yin, B.; Alvarez, L. S.

    1993-01-01

    The effect of Faraday anomalous dispersion optical filters on infrared and blue transitions of some alkali atoms is calculated. A composite system is designed to further increase the background noise rejection. The measured results of the solar background rejection and image quality through the filter are presented. The results show that the filter may provide high transmission and high background noise rejection with excellent image quality.

  15. The dispersal of protoplanetary discs

    Directory of Open Access Journals (Sweden)

    Ercolano Barbara

    2013-04-01

    Full Text Available Protoplanetary discs are a natural consequence of the star formation process and as such are ubiquitous around low-mass stars. They are fundamental to planet formation as they hold the reservoir of material from which planets form. Their evolution and final dispersal and the timescales that regulate these process are therefore of particular interest. In this contribution I will review the observational evidence for the dispersal of discs being dominated by two timescales and for the final dispersal to occur quickly and from the inside out. I will discuss the current theoretical models, including X-ray photoevaporation, showing that the latter provides a natural explanation to the observed behaviour and review supporting and contrasting evidence. I will finally introduce a new mechanism based on the interaction between planet formation and photoevaporation that may explain a particular class of transition discs with large inner holes and high accretion rates that are problematic for photoevaporation models and planet formation models alone.

  16. Chromatic Dispersion Estimation in Digital Coherent Receivers

    DEFF Research Database (Denmark)

    Soriano, Ruben Andres; Hauske, Fabian N.; Guerrero Gonzalez, Neil

    2011-01-01

    Polarization-diverse coherent demodulation allows to compensate large values of accumulated linear distortion by digital signal processing. In particular, in uncompensated links without optical dispersion compensation, the parameter of the residual chromatic dispersion (CD) is vital to set...

  17. Stochastic differential equations and turbulent dispersion

    Science.gov (United States)

    Durbin, P. A.

    1983-01-01

    Aspects of the theory of continuous stochastic processes that seem to contribute to an understanding of turbulent dispersion are introduced and the theory and philosophy of modelling turbulent transport is emphasized. Examples of eddy diffusion examined include shear dispersion, the surface layer, and channel flow. Modeling dispersion with finite-time scale is considered including the Langevin model for homogeneous turbulence, dispersion in nonhomogeneous turbulence, and the asymptotic behavior of the Langevin model for nonhomogeneous turbulence.

  18. Optical angular momentum in dispersive media

    CERN Document Server

    Philbin, T G

    2012-01-01

    The angular momentum density and flux of light in a dispersive, rotationally symmetric medium are derived from Noether's theorem. Optical angular momentum in a dispersive medium has no simple relation to optical linear momentum, even if the medium is homogeneous. A circularly polarized monochromatic beam in a homogeneous, dispersive medium carries a spin angular momentum per unit energy of $\\pm\\omega^{-1}$, as in vacuum. This result demonstrates the non-trivial interplay of dispersive contributions to optical angular momentum and energy.

  19. Dispersion climatology in a coastal zone

    DEFF Research Database (Denmark)

    Larsen, Søren Ejling; Gryning, Sven-Erik

    1986-01-01

    system should be used to describe the dispersion. This dispersion classification scheme is used to organize 3 years of data from two meteorological masts, one placed directly at a shoreline and the other roughly 1 km inland. Differences in the dispersion climatology over land and water are studied...

  20. Dispersion properties of photonic crystal fibres

    DEFF Research Database (Denmark)

    Bjarklev, Anders Overgaard; Broeng, Jes; Dridi, Kim;

    1998-01-01

    Approximate dispersion and bending properties of all-silica two-dimensional photonic crystal fibres are characterised by the combination of an effective-index model and classical analysis tools for optical fibres. We believe for the first time to have predicted the dispersion properties of photonic...... crystal fibres. The results strongly indicate that these fibres have potential applications as dispersion managing components...

  1. Going against the flow: a case for upstream dispersal and detection of uncommon dispersal events

    NARCIS (Netherlands)

    Wubs, E.R.J.; Fraaije, Rob G.A.; Groot, de G.A.; Erkens, R.H.J.; Garsen, Annemarie G.; Kleyheeg, Erik; Raven, Bart M.; Soons, Merel B.

    2016-01-01

    1.Dispersal and colonisation are key processes determining species survival, and their importance is increasing as a consequence of ongoing habitat fragmentation, land-use change and climate change. Identification of long-distance dispersal events, including upstream dispersal, and of the dispersal

  2. Going against the flow: a case for upstream dispersal and detection of uncommon dispersal events

    NARCIS (Netherlands)

    Wubs, E. R. Jasper; Fraaije, Rob G. A.; de Groot, G. Arjen; Erkens, Roy H. J.; Garssen, Annemarie G.; Kleyheeg, Erik; Raven, Bart M.; Soons, Merel B.

    2016-01-01

    * Dispersal and colonisation are key processes determining species survival, and their importance is increasing as a consequence of ongoing habitat fragmentation, land-use change and climate change. Identification of long-distance dispersal events, including upstream dispersal, and of the dispersal

  3. Broadband dispersion compensation using microstructure fibers

    Institute of Scientific and Technical Information of China (English)

    Xia Zhang; Xiaomin Ren; Yongzhao Xu; Zinan Wang; Yongqing Huang; Xue Chen

    2007-01-01

    Beijing University of Posts and Telecommunications, Beijing 100876Dispersion and dispersion slope compensation of 10-Gb/s pulses using microstructure fibers (MFs) is demonstrated experimentally. A 26-m MF is used to compensate the dispersion of 2-km standard singe mode fiber in a 20-nm range in C band. The experimental results show that a significant improvement can be achieved in the quality of the observed pulses with the dispersion compensation. Moreover, the further research shows that the MF can compensate the anomalous dispersion of a single mode fiber within ±0.27 ps/(nm·km) over a 50-nm wavelength range from 1520 to 1570 nm.

  4. Normal-dispersion microresonator Kerr frequency combs

    Directory of Open Access Journals (Sweden)

    Xue Xiaoxiao

    2016-06-01

    Full Text Available Optical microresonator-based Kerr frequency comb generation has developed into a hot research area in the past decade. Microresonator combs are promising for portable applications due to their potential for chip-level integration and low power consumption. According to the group velocity dispersion of the microresonator employed, research in this field may be classified into two categories: the anomalous dispersion regime and the normal dispersion regime. In this paper, we discuss the physics of Kerr comb generation in the normal dispersion regime and review recent experimental advances. The potential advantages and future directions of normal dispersion combs are also discussed.

  5. Dispersion of coupled mode-gap cavities

    CERN Document Server

    Lian, Jin; Yüce, Emre; De Rossi, Sylvain Combrié Alfredo; Mosk, Allard P

    2015-01-01

    The dispersion of a CROW made of photonic crystal mode-gap cavities is pronouncedly asymmetric. This asymmetry cannot be explained by the standard tight binding model. We show that the fundamental cause of the asymmetric dispersion is the fact that the cavity mode profile itself is dispersive, i.e., the mode wave function depends on the driving frequency, not the eigenfrequency. This occurs because the photonic crystal cavity resonances do not form a complete set. By taking into account the dispersive mode profile, we formulate a mode coupling model that accurately describes the asymmetric dispersion without introducing any new free parameters.

  6. Bilayer dispersion-flattened waveguides with four zero-dispersion wavelengths.

    Science.gov (United States)

    Guo, Yuhao; Jafari, Zeinab; Agarwal, Anu M; Kimerling, Lionel C; Li, Guifang; Michel, Jurgen; Zhang, Lin

    2016-11-01

    We propose a new type of bilayer dispersion-flattened waveguides that have four zero-dispersion wavelengths. Low and flat dispersion can be achieved by using two different material combinations, with a much smaller index contrast as compared to the previously proposed slot-assisted dispersion-flattened waveguides. Without using a nano-slot, dispersion becomes less sensitive to waveguide dimensions, which is highly desirable for high-yield device fabrication. Ultra-low dispersion, high nonlinearity, and fabrication-friendly design would make it promising for practical implementation of nonlinear photonic functions. The proposed waveguide configuration deepens our understanding of the dispersion flattening principle.

  7. Minimal dispersion refractive index profiles.

    Science.gov (United States)

    Feit, M D

    1979-09-01

    The analogy between optics and quantum mechanics is exploited by considering a 2-D quantum system whose Schroedinger equation is closely related to the wave equation for light propagation in an optical fiber. From this viewpoint, Marcatili's condition for minimal-dispersion-refractive-index profiles, and the Olshansky- Keck formula for rms pulse spreading in an alpha-profile fiber may be derived without recourse to the WKB approximation. Besides affording physical insight into these results, the present approach points out a possible limitation in their application to real fibers.

  8. Dispersive nanoSQUID magnetometry

    Science.gov (United States)

    Levenson-Falk, E. M.; Antler, N.; Siddiqi, I.

    2016-11-01

    We describe the theory and implementation of a dispersive magnetometer based on an aluminum nanoSQUID. The nanoSQUID consists of a superconducting loop interrupted by two variable-thickness weak-link nanobridge Josephson junctions. When the nanoSQUID is placed in parallel with a lumped-element capacitor, it acts as the inductive element in a resonant tank circuit. By performing microwave reflectometry on the circuit, the SQUID inductance can be measured, providing a sensitive meter of the flux threading the SQUID loop. In this review we provide the theoretical basis for the device, describe design and operation considerations, and present characterization results on several devices.

  9. Nonlinear Dispersion Effect on Wave Transformation

    Institute of Scientific and Technical Information of China (English)

    LI Ruijie; Dong-Young LEE

    2000-01-01

    A new nonlinear dispersion relation is given in this paper, which can overcome the limitation of the intermediate minimum value in the dispersion relation proposed by Kirby and Dalrymple (1986), and which has a better approximation to Hedges' empirical relation than the modilied relations by Hedges (1987). Kirby and Dahymple (1987) for shallow waters. The new dispersion relation is simple in form. thus it can be used easily in practice. Meanwhile. a general explicil approximalion to the new dispersion rela tion and olher nonlinear dispersion relations is given. By use of the explicit approximation to the new dispersion relation along with the mild slope equation taking inlo account weakly nonlinear effect, a mathematical model is obtained, and it is applied to laboratory data. The results show that the model developed vith the new dispersion relation predicts wave translornation over complicated topography quite well.

  10. Incorporating patterns of disperser behaviour into models of seed dispersal and its effects on estimated dispersal curves.

    Science.gov (United States)

    Westcott, David A; Bentrupperbäumer, Joan; Bradford, Matt G; McKeown, Adam

    2005-11-01

    The processes determining where seeds fall relative to their parent plant influence the spatial structure and dynamics of plant populations and communities. For animal dispersed species the factors influencing seed shadows are poorly understood. In this paper we test the hypothesis that the daily temporal distribution of disperser behaviours, for example, foraging and movement, influences dispersal outcomes, in particular the shape and scale of dispersal curves. To do this, we describe frugivory and the dispersal curves produced by the southern cassowary, Casuarius casuarius, the only large-bodied disperser in Australia's rainforests. We found C. casuarius consumed fruits of 238 species and of all fleshy-fruit types. In feeding trials, seeds of 11 species were retained on average for 309 min (+/-256 SD). Sampling radio-telemetry data randomly, that is, assuming foraging occurs at random times during the day, gives an estimated average dispersal distance of 239 m (+/-207 SD) for seeds consumed by C. casuarius. Approximately 4% of seeds were dispersed further than 1,000 m. However, observation of wild birds indicated that foraging and movement occur more frequently early and late in the day. Seeds consumed early in the day were estimated to receive dispersal distances 1.4 times the 'random' average estimate, while afternoon consumed seeds received estimated mean dispersal distances of 0.46 times the 'random' estimate. Sampling movement data according to the daily distribution of C. casuarius foraging gives an estimated mean dispersal distance of 337 m (+/-194 SD). Most animals' behaviour has a non-random temporal distribution. Consequently such effects should be common and need to be incorporated into seed shadow estimation. Our results point to dispersal curves being an emergent property of the plant-disperser interaction rather than being a property of a plant or species.

  11. Introduction to nonlinear dispersive equations

    CERN Document Server

    Linares, Felipe

    2015-01-01

    This textbook introduces the well-posedness theory for initial-value problems of nonlinear, dispersive partial differential equations, with special focus on two key models, the Korteweg–de Vries equation and the nonlinear Schrödinger equation. A concise and self-contained treatment of background material (the Fourier transform, interpolation theory, Sobolev spaces, and the linear Schrödinger equation) prepares the reader to understand the main topics covered: the initial-value problem for the nonlinear Schrödinger equation and the generalized Korteweg–de Vries equation, properties of their solutions, and a survey of general classes of nonlinear dispersive equations of physical and mathematical significance. Each chapter ends with an expert account of recent developments and open problems, as well as exercises. The final chapter gives a detailed exposition of local well-posedness for the nonlinear Schrödinger equation, taking the reader to the forefront of recent research. The second edition of Introdu...

  12. Modeling the dispersion in electromechanically coupled myocardium

    Science.gov (United States)

    Eriksson, Thomas S. E.; Prassl, Anton J.; Plank, Gernot; Holzapfel, Gerhard A.

    2014-01-01

    SUMMARY We present an approach to model the dispersion of fiber and sheet orientations in the myocardium. By utilizing structure parameters, an existing orthotropic and invariant-based constitutive model developed to describe the passive behavior of the myocardium is augmented. Two dispersion parameters are fitted to experimentally observed angular dispersion data of the myocardial tissue. Computations are performed on a unit myocardium tissue cube and on a slice of the left ventricle indicating that the dispersion parameter has an effect on the myocardial deformation and stress development. The use of fiber dispersions relating to a pathological myocardium had a rather big effect. The final example represents an ellipsoidal model of the left ventricle indicating the influence of fiber and sheet dispersions upon contraction over a cardiac cycle. Although only a minor shift in the pressure–volume (PV) loops between the cases with no dispersions and with fiber and sheet dispersions for a healthy myocardium was observed, a remarkably different behavior is obtained with a fiber dispersion relating to a diseased myocardium. In future simulations, this dispersion model for myocardial tissue may advantageously be used together with models of, for example, growth and remodeling of various cardiac diseases. PMID:23868817

  13. Modeling the dispersion in electromechanically coupled myocardium.

    Science.gov (United States)

    Eriksson, Thomas S E; Prassl, Anton J; Plank, Gernot; Holzapfel, Gerhard A

    2013-11-01

    We present an approach to model the dispersion of fiber and sheet orientations in the myocardium. By utilizing structure parameters, an existing orthotropic and invariant-based constitutive model developed to describe the passive behavior of the myocardium is augmented. Two dispersion parameters are fitted to experimentally observed angular dispersion data of the myocardial tissue. Computations are performed on a unit myocardium tissue cube and on a slice of the left ventricle indicating that the dispersion parameter has an effect on the myocardial deformation and stress development. The use of fiber dispersions relating to a pathological myocardium had a rather big effect. The final example represents an ellipsoidal model of the left ventricle indicating the influence of fiber and sheet dispersions upon contraction over a cardiac cycle. Although only a minor shift in the pressure-volume (PV) loops between the cases with no dispersions and with fiber and sheet dispersions for a healthy myocardium was observed, a remarkably different behavior is obtained with a fiber dispersion relating to a diseased myocardium. In future simulations, this dispersion model for myocardial tissue may advantageously be used together with models of, for example, growth and remodeling of various cardiac diseases.

  14. Research progress in avian dispersal behavior

    Institute of Scientific and Technical Information of China (English)

    Yang LIU; Zhengwang ZHANG

    2008-01-01

    Dispersal, defined as a linear spreading move-ment of individuals away from others of the population is a fundamental characteristic of organisms in nature. Dispersal is a central concept in ecological, behavioral and evolutionary studies, driven by different forces such as avoidance of inbreeding depression, density-dependent competition and the need to change breeding locations. By effective dispersal, organisms can enlarge their geo-graphic range and adjust the dynamic, sex ratio and gen-etic compositions of a population. Birds are one of the groups that are studied intensively by human beings. Due to their diurnal habits, diverse life history strategies and complex movement, birds are also ideal models for the study of dispersal behaviors. Certain topics of avian dispersal including sex-biased, asymmetric dispersal caused by differences in body conditions, dispersal pro-cesses, habitat selection and long distance dispersal are discussed here. Bird-ringing or marking, radio-telemetry and genetic markers are useful tools widely applied in dispersal studies. There are three major challenges regard-ing theoretical study and methodology research of dis-persal: (1) improvement in research methodology is needed, (2) more in-depth theoretical research is neces-sary, and (3) application of theoretical research into the conservation efforts for threatened birds and the manage-ment of their habitats should be carried out immediately.

  15. Soliton trapping of dispersive waves in photonic crystal fiber with two zero dispersive wavelengths.

    Science.gov (United States)

    Wang, Weibin; Yang, Hua; Tang, Pinghua; Zhao, Chujun; Gao, Jing

    2013-05-06

    Based on the generalized nonlinear Schrödinger equation, we present a numerical study of trapping of dispersive waves by solitons during supercontinuum generation in photonic crystal fibers pumped with femtosecond pulses in the anomalous dispersion region. Numerical simulation results show that the generated supercontinuum is bounded by two branches of dispersive waves, namely blue-shifted dispersive waves (B-DWs) and red-shifted dispersive waves (R-DWs). We find a novel phenomenon that not only B-DWs but also R-DWs can be trapped by solitons across the zero-dispersion wavelength when the group-velocity matching between the soliton and the dispersive wave is satisfied, which may led to the generation of new spectral components via mixing of solitons and dispersive waves. Mixing of solitons with dispersive waves has been shown to play an important role in shaping not only the edge of the supercontinuum, but also its central part around the higher zero-dispersion wavelength. Further, we show that the phenomenon of soliton trapping of dispersive waves in photonic crystal fibers with two zero-dispersion wavelengths has a very close relationship with pumping power and the interval between two zero-dispersion wavelengths. In order to clearly display the evolution of soliton trapping of dispersive waves, the spectrogram of output pulses is observed using cross-correlation frequency-resolved optical gating technique (XFROG).

  16. Dispersed publication of editorial research

    DEFF Research Database (Denmark)

    Rosenberg, Jacob; Pommergaard, Hans-Christian; Vinther, Siri

    2015-01-01

    INTRODUCTION: There seems to be no dedicated journals available for publication of editorial research in the biomedical sciences; that is research into editorial or publication process issues involving the scientific approach to writing, reviewing, editing and publishing. It is unknown where papers...... concerning these issues are typically published. We therefore set out to study the distribution of such papers in the biomedical literature. METHODS: In this pilot study, we conducted a MEDLINE search for papers on editorial research published in the year 2012. RESULTS: We found 445 articles published in 311...... journals with a median of one article per journal (range: 1-17). CONCLUSION: The publication of papers on editorial research seems to be dispersed. In order to increase the visibility of this research field, it may be reasonable to establish well-defined platforms such as dedicated journals or journal...

  17. Stochastic models for atmospheric dispersion

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager

    2003-01-01

    Simple stochastic differential equation models have been applied by several researchers to describe the dispersion of tracer particles in the planetary atmospheric boundary layer and to form the basis for computer simulations of particle paths. To obtain the drift coefficient, empirical vertical...... positions close to the boundaries. Different rules have been suggested in the literature with justifications based on simulation studies. Herein the relevant stochastic differential equation model is formulated in a particular way. The formulation is based on the marginal transformation of the position...... dependent particle velocity into a position independent Gaussian velocity. Boundary conditions are obtained from Itos rule of stochastic differentiation. The model directly point at a canonical rule of reflection for the approximating random walk with finite time step. This reflection rule is different from...

  18. Dispersion based beam tilt correction

    CERN Document Server

    Guetg, Marc W; Prat, Eduard; Reiche, Sven

    2013-01-01

    In Free Electron Lasers (FEL), a transverse centroid misalignment of longitudinal slices in an electron bunch reduces the effective overlap between radiation field and electron bunch and therefore the FEL performance. The dominant sources of slice misalignments for FELs are the incoherent and coherent synchrotron radiation within bunch compressors as well as transverse wake fields in the accelerating cavities. This is of particular importance for over-compression which is required for one of the key operation modes for the SwissFEL planned at the Paul Scherrer Institute. The centroid shift is corrected using corrector magnets in dispersive sections, e.g. the bunch compressors. First and second order corrections are achieved by pairs of sextupole and quadrupole magnets in the horizontal plane while skew quadrupoles correct to first order in the vertical plane. Simulations and measurements at the SwissFEL Injector Test Facility are done to investigate the proposed correction scheme for SwissFEL. This paper pres...

  19. Post-crash fuel dispersal

    Energy Technology Data Exchange (ETDEWEB)

    Tieszen, S.R.

    1997-03-01

    This paper is a brief overview of work over the last several decades in understanding what occurs to jet fuel stored in aircraft fuel tanks on impact with the ground. Fuel dispersal is discussed in terms of the overall crash dynamics process and impact regimes are identified. In a generic sense, the types of flow regimes which can occur are identified and general descriptions of the processes are given. Examples of engineering level tools, both computational and experimental, which have applicability to analyzing the complex environments are presented. Finally, risk based decision is discussed as a quick means of identifying requirements for development of preventative or mitigation strategies, such as further work on the development of an anti-misting agent.

  20. Dispersion relations for unphysical particles

    Science.gov (United States)

    Siringo, Fabio

    2017-03-01

    Generalized dispersion relations are discussed for unphysical particles, e.g. confined degrees of freedom that are not present in the physical spectra but can give rise to observable bound states. While in general the propagator of the unphysical particles can have complex poles and cannot be reconstructed from the knowledge of the imaginary part, under reasonable assumptions the missing piece of information is shown to be in the rational function that contains the poles and must be added to the integral representation. For pure Yang-Mills theory, the rational part and the spectral term are identified in the explicit analytical expressions provided by the massive expansion of the gluon propagator. The multi particle spectral term turns out to be very small and the simple rational part provides, from first principles, an approximate propagator that is equivalent to the tree-level result of simple phenomenological models like the refined Gribov-Zwanziger model.

  1. Dispersion and suburbanisation. New ethnoscapes.

    Directory of Open Access Journals (Sweden)

    Pau Serra del Pozo

    2011-11-01

    Full Text Available There are many deviations from the simple scheme of ethnic enclaves or ethnic centralities today, even in contemporary Little Havana in Miami. This scheme tends to be diluted by three processes: 1 the decentralization of some immigrant residents towards the suburbs or urban periphery; these suburban immigrants may be more settled or affluent than recent immigrants living in inner-city communities; 2 the dispersal of entrepreneurs of a particular ethnic minority in a large metropolitan area; and 3 the emergence and coexistence of multiple ethnic groups in the same zone or area. The three processes gradually cause the loss of the unity of the residententrepreneur coethnic tandem in the same neighbourhood.

  2. Dispersed publication of editorial research

    DEFF Research Database (Denmark)

    Rosenberg, Jacob; Pommergaard, Hans-Christian; Vinther, Siri;

    2015-01-01

    INTRODUCTION: There seems to be no dedicated journals available for publication of editorial research in the biomedical sciences; that is research into editorial or publication process issues involving the scientific approach to writing, reviewing, editing and publishing. It is unknown where papers...... concerning these issues are typically published. We therefore set out to study the distribution of such papers in the biomedical literature. METHODS: In this pilot study, we conducted a MEDLINE search for papers on editorial research published in the year 2012. RESULTS: We found 445 articles published in 311...... journals with a median of one article per journal (range: 1-17). CONCLUSION: The publication of papers on editorial research seems to be dispersed. In order to increase the visibility of this research field, it may be reasonable to establish well-defined platforms such as dedicated journals or journal...

  3. Dispersion Properties of TIRPCF under Compton Scattering

    Institute of Scientific and Technical Information of China (English)

    HAO Dong-shan; YU Ding-chen

    2006-01-01

    The dispersion properties in the short wavelength region of total internal reflective photonic crystal fiber(TIRPCF) in Compton scattering have been studied by using the model of the equivalent twin waveguide soliton coupling,dispersion management solitons and effective refractive index. It is shown that the positive dispersion of the cladding waveguide of TIRPCF and the negative dispersion of its core waveguide are quickly increased by the square of the collision non-elastic composition between the electron and photons,and they are lessened by the increase of the electron absorption photon number. Under the one-photon nonlinear Compton scattering,the method of the compensated probing laser diffraction by the phase hole induced by the stationary pumping laser in the cladding waveguide enables the average dispersion value of TIRPCF to be close to zero,and the zero dispersion point quickly shifts to the short wavelength region.

  4. EPDM/POSS 纳米杂化材料防火性能及力学性能的研究%Study on Fire Behavior and Mechanical Properties of EPDM/POSS Nano-hybrid Material

    Institute of Scientific and Technical Information of China (English)

    谭莲影; 程志; 穆洪帅; 朱田鑫; 苏韧伟

    2016-01-01

    EPDM/POSS nano-hybrid material was prepared using EPDM as raw rubber material, octavinyl-polyhedral oligomeric silsesquioxane (OVP)and intumescent flame retardant system (IFR) as additives,and the thermal properties,smoke properties and mechanical properties were tested by TGA,cone calorimetry and smoke density etc..The results showed that,compared to the pure EPDM material,adding OVP could effectively increase the thermal stability,flame retarding ability and me-chanical properties of the EPDM/POSS nano-hybrid material.When the amount of OVP was just 3phr,the thermal decomposition temperature was increased by 27.5°,while the peak HRR value was lowered by 9.2%.Besides,the tensile strength was strengthened by 26.5%,smoke density decreased as well.All these observations illustrated that OVP could significantly improve the comprehensive properties of the EPDM/POSS nano-hybird material.%以三元乙丙橡胶(EPDM)为原料,笼形八乙烯基硅倍半氧烷(OVP)及膨胀阻燃体系(IFR)为添加剂,制备了 EPDM/POSS 纳米杂化材料,并使用热重分析仪、锥形量热仪及烟密度箱等测试了其热性能、烟火性能及力学性能。结果表明,与纯 EPDM 胶料相比,添加了 OVP 的 EPDM/POSS 杂化材料的热稳定性、阻燃性能及力学性能均有所提升,当 OVP 加入3份时,起始热分解温度提高27.5℃,峰值热释放速率降低9.2%,拉伸强度提高26.5%,烟密度显著降低,说明 OVP 可提升 EPDM/POSS 杂化材料的综合性能。

  5. Formulation of disperse systems science and technology

    CERN Document Server

    Tadros, Tharwat F

    2014-01-01

    This book presents comprehensively the science and technology behind the formulation of disperse systems like emulsions, suspensions, foams and others. Starting with a general introduction, the book covers a broad range of topics like the role of different classes of surfactants, stability of disperse systems, formulation of different dispersions, evaluation of formulations and many more. Many examples are included, too. Written by the experienced author and editor Tharwart Tadros, this book is indispensable for every scientist working in the field.

  6. Electrostatic Stabilization of Graphene in Organic Dispersions

    OpenAIRE

    Rodgers, Andrew N J; Velicky, Matej; Dryfe, Robert A.W.

    2015-01-01

    The exfoliation of graphite to give graphene dispersions in nonaqueous solvents is an important area with regards to scalable production of graphene in bulk quantities and its ultimate application in devices. Understanding the mechanisms governing the stability of these dispersions is therefore of both scientific interest and technological importance. Herein, we have used addition of an indifferent electrolyte to perturb few-layer graphene dispersions in a nonaqueous solvent (1,2-dichloroetha...

  7. Phonon dispersion and heat capacity in polyfuran

    Science.gov (United States)

    Ali, Parvej; Srivastava, Seema; Ali Khan, Irfan; Gupta, V. D.; Ansari, Saif-ul-Islam

    A study of the normal modes of vibration and their dispersion in polyfuran (Pfu) based on the Urey-Bradley force field is reported. It provides a detailed interpretation of IR and Raman spectra. Characteristic features of dispersion curves such as regions of high density-of-states, repulsion and character mixing of dispersive modes are discussed. Predictive values of heat capacity as a function of temperature are calculated.

  8. Signal velocity for anomalous dispersive waves

    Energy Technology Data Exchange (ETDEWEB)

    Mainardi, F. (Bologna Univ. (Italy))

    1983-03-11

    The concept of signal velocity for dispersive waves is usually identified with that of group velocity. When the dispersion is anomalous, this interpretation is not correct since the group velocity can assume nonphysical values. In this note, by using the steepest descent method first introduced by Brillouin, the phase velocity is shown to be the signal velocity when the dispersion is anomalous in the full range of frequencies.

  9. Bed-Load Dispersion: A Literature Review

    Science.gov (United States)

    2016-12-01

    However, the work of Phillips et al. (2013) suggested that the asymptotic limit of bed-load dispersion is super- dispersive. Fischer et al. (1979...Olinde and Johnson 2015, Phillips et al. 2013, Martin et al. 2012 and 2014). Campagnol et al. (2015) showed that if the particles are exhibiting...vertical dispersion. Journal of Geophysical Research: Earth Surface 119(9): 1818–1832. Phillips , C. B., R. L. Martin, and D. J. Jerolmack. 2013

  10. The conservation physiology of seed dispersal.

    Science.gov (United States)

    Ruxton, Graeme D; Schaefer, H Martin

    2012-06-19

    At a time when plant species are experiencing increasing challenges from climate change, land-use change, harvesting and invasive species, dispersal has become a very important aspect of plant conservation. Seed dispersal by animals is particularly important because some animals disperse seeds to suitable sites in a directed fashion. Our review has two aims: (i) to highlight the various ways plant dispersal by animals can be affected by current anthropogenic change and (ii) to show the important role of plant and (particularly) animal physiology in shaping seed-dispersal interactions. We argue that large-bodied seed dispersers may be particularly important for plant conservation because seed dispersal of large-seeded plants is often more specialized and because large-bodied animals are targeted by human exploitation and have smaller population sizes. We further argue that more specialized seed-dispersal systems on island ecosystems might be particularly at risk from climate change both owing to small population sizes involved but also owing to the likely thermal specialization, particularly on tropical islands. More generally, the inherent vulnerability of seed-dispersal mutualisms to disruption driven by environmental change (as well as their ubiquity) demands that we continue to improve our understanding of their conservation physiology.

  11. Black Brant X third stage dispersion dynamics

    Science.gov (United States)

    Montag, W. H.; Maksimovic, V. M.; Lindahl, J. E.

    1982-01-01

    The successful development of the Black Brant X (BBX) launch vehicle resulted from the application of a gyroscopically stabilized, unguided third stage motor configuration. Design analyses indicated sufficient gyroscopic stability and acceptable impact dispersion could be realized by optimizing second/third stage separation time. By flying an unguided third stage motor, significant program cost savings were realized. One flight test and two operational missions demonstrated the feasibility of utilizing gyroscopic stability to achieve satisfactory trajectory dispersion on a high performance rocket. A detailed assessment of the major dispersion contributors identified for the first three BBX missions is presented, offering important insight into the dispersion sensitivity of unguided, spin-stabilized flight.

  12. RHEOLOGICAL BEHAVIOR OF EPOXY RESIN WATERBORNE DISPERSIONS

    Institute of Scientific and Technical Information of China (English)

    Zhen-zhong Yang; Yuan-ze Xu; De-lu Zhao

    2001-01-01

    The waterborne dispersions of epoxy resin were prepared by the phase inversion emulsification technique.Rheological behavior and its relationship with the structural change of the systems were studied. It was shown that the concentrated dispersions were highly viscoelastic and pseudoplastic, which was attributed to the formation of a physical network among the waterborne particles via hydrogen bond. The dilute dispersions were Newtonian fluids. The discrete clusters composed of small waterborne particles were found in diluted dispersions. With increasing solid content, there existed a structural transition via percolation through a cluster-cluster aggregation mode to form the physical network, which was qualitatively evidenced by the TEM morphologies.``

  13. Dispersal of Engineered Male Aedes aegypti Mosquitoes.

    Science.gov (United States)

    Winskill, Peter; Carvalho, Danilo O; Capurro, Margareth L; Alphey, Luke; Donnelly, Christl A; McKemey, Andrew R

    2015-11-01

    Aedes aegypti, the principal vector of dengue fever, have been genetically engineered for use in a sterile insect control programme. To improve our understanding of the dispersal ecology of mosquitoes and to inform appropriate release strategies of 'genetically sterile' male Aedes aegypti detailed knowledge of the dispersal ability of the released insects is needed. The dispersal ability of released 'genetically sterile' male Aedes aegypti at a field site in Brazil has been estimated. Dispersal kernels embedded within a generalized linear model framework were used to analyse data collected from three large scale mark release recapture studies. The methodology has been applied to previously published dispersal data to compare the dispersal ability of 'genetically sterile' male Aedes aegypti in contrasting environments. We parameterised dispersal kernels and estimated the mean distance travelled for insects in Brazil: 52.8 m (95% CI: 49.9 m, 56.8 m) and Malaysia: 58.0 m (95% CI: 51.1 m, 71.0 m). Our results provide specific, detailed estimates of the dispersal characteristics of released 'genetically sterile' male Aedes aegypti in the field. The comparative analysis indicates that despite differing environments and recapture rates, key features of the insects' dispersal kernels are conserved across the two studies. The results can be used to inform both risk assessments and release programmes using 'genetically sterile' male Aedes aegypti.

  14. Selection of Dispersivity in Groundwater Risk Assessment

    Institute of Scientific and Technical Information of China (English)

    武晓峰; 唐杰

    2004-01-01

    The Domenico model is used in combination with ASTM E 1739 in a Tier 2 risk assessment of chlorinated organic solvents contaminated groundwater sites to predict potential contaminant concentration in groundwater down-gradient from the point of exposure (POE). A knowledge of the dispersivity parameters is necessary for carrying out this calculation. A constant longitudinal dispersivity of 10 m is often used in analytical and numerical calculation. However, because of the scale effect of dispersion, two other main approaches are currently often used. From the viewpoint of conservative principle in risk assessment, it is necessary to determine which dispersivity data will give a higher predicted concentration, corresponding to a more conservative risk calculation. Generally, it is considered that a smaller dispersivity leads to a higher predicted concentration. This assumption is correct when dispersion is the only natural attenuation factor. However, degradation of commonly encountered chlorinated organic solvents in environment under natural condition has been widely reported. Calculations given in this paper of several representative cases show that a general consideration of the influence of dispersivity on concentration prediction is not always correct when a degradation term is included in the calculation. To give a conservative risk calculation, the scale effect of dispersion is considered. Calculations also show that the dispersivity parameters need to be determined by considering the POE distance from the source, the groundwater velocity, and the degradation rate of the contaminant.

  15. The conservation physiology of seed dispersal

    Science.gov (United States)

    Ruxton, Graeme D.; Schaefer, H. Martin

    2012-01-01

    At a time when plant species are experiencing increasing challenges from climate change, land-use change, harvesting and invasive species, dispersal has become a very important aspect of plant conservation. Seed dispersal by animals is particularly important because some animals disperse seeds to suitable sites in a directed fashion. Our review has two aims: (i) to highlight the various ways plant dispersal by animals can be affected by current anthropogenic change and (ii) to show the important role of plant and (particularly) animal physiology in shaping seed–dispersal interactions. We argue that large-bodied seed dispersers may be particularly important for plant conservation because seed dispersal of large-seeded plants is often more specialized and because large-bodied animals are targeted by human exploitation and have smaller population sizes. We further argue that more specialized seed-dispersal systems on island ecosystems might be particularly at risk from climate change both owing to small population sizes involved but also owing to the likely thermal specialization, particularly on tropical islands. More generally, the inherent vulnerability of seed-dispersal mutualisms to disruption driven by environmental change (as well as their ubiquity) demands that we continue to improve our understanding of their conservation physiology. PMID:22566677

  16. Discrete dispersion models and their Tweedie asymptotics

    DEFF Research Database (Denmark)

    Jørgensen, Bent; Kokonendji, Célestin C.

    2016-01-01

    in this approach, whereas several overdispersed discrete distributions, such as the Neyman Type A, Pólya-Aeppli, negative binomial and Poisson-inverse Gaussian, turn out to be Poisson-Tweedie factorial dispersion models with power dispersion functions, analogous to ordinary Tweedie exponential dispersion models...... with power variance functions. Using the factorial cumulant generating function as tool, we introduce a dilation operation as a discrete analogue of scaling, generalizing binomial thinning. The Poisson-Tweedie factorial dispersion models are closed under dilation, which in turn leads to a Poisson...

  17. Dispersal-mediated trophic interactions can generate apparent patterns of dispersal limitation in aquatic metacommunities

    NARCIS (Netherlands)

    Verreydt, D.; De Meester, L.; Decaestecker, E.; Villena, M.J.; Van der Gucht, K.; Vannormelingen, P.; Vyverman, W.; Declerck, S.A.J.

    2012-01-01

    Dispersal is a major organising force in metacommunities, which may facilitate compositional responses of local communities to environmental change and affect ecosystem function. Organism groups differ widely in their dispersal abilities and their communities are therefore expected to have different

  18. Who dispersed the seeds? The use of DNA barcoding in frugivory and seed dispersal studies

    National Research Council Canada - National Science Library

    González‐Varo, Juan P; Arroyo, Juan M; Jordano, Pedro; Gilbert, M

    2014-01-01

    ... ‘which species dispersed the seeds’. This is essential for assessing how multiple frugivore species contribute distinctly to critical dispersal events such as seed delivery to safe sites, long...

  19. Pollen Forecast and Dispersion Modelling

    Science.gov (United States)

    Costantini, Monica; Di Giuseppe, Fabio; Medaglia, Carlo Maria; Travaglini, Alessandro; Tocci, Raffaella; Brighetti, M. Antonia; Petitta, Marcello

    2014-05-01

    The aim of this study is monitoring, mapping and forecast of pollen distribution for the city of Rome using in-situ measurements of 10 species of common allergenic pollens and measurements of PM10. The production of daily concentration maps, associated to a mobile phone app, are innovative compared to existing dedicated services to people who suffer from respiratory allergies. The dispersal pollen is one of the most well-known causes of allergic disease that is manifested by disorders of the respiratory functions. Allergies are the third leading cause of chronic disease and it is estimated that tens millions of people in Italy suffer from it. Recent works reveal that during the last few years there was a progressive increase of affected subjects, especially in urban areas. This situation may depend: on the ability to transport of pollutants, on the ability to react between pollutants and pollen and from a combination of other irritants, existing in densely populated and polluted urban areas. The methodology used to produce maps is based on in-situ measurements time series relative to 2012, obtained from networks of air quality and pollen stations in the metropolitan area of Rome. The monitoring station aerobiological of University of Rome "Tor Vergata" is located at the Department of Biology. The instrument used to pollen monitoring is a volumetric sampler type Hirst (Hirst 1952), Model 2000 VPPS Lanzoni; the data acquisition is carried out as reported in Standard UNI 11008:2004 - "Qualità dell'aria - Metodo di campionamento e conteggio dei granuli pollinici e delle spore fungine aerodisperse" - the protocol that describes the procedure for measuring of the concentration of pollen grains and fungal spores dispersed into the atmosphere, and reported in the "Manuale di gestione e qualità della R.I.M.A" (Travaglini et. al. 2009). All 10 allergenic pollen are monitored since 1996. At Tor Vergata university is also operating a meteorological station (SP2000, CAE

  20. Who dispersed the seeds? The use of DNA barcoding in frugivory and seed dispersal studies

    OpenAIRE

    González-Varo, Juan P.; J.M. Arroyo; Jordano, Pedro

    2014-01-01

    Assessing dispersal events in plants faces important challenges and limitations. A methodological issue that limits advances in our understanding of seed dissemination by frugivorous animals is identifying 'which species dispersed the seeds'. This is essential for assessing how multiple frugivore species contribute distinctly to critical dispersal events such as seed delivery to safe sites, long-distance dispersal and the colonization of non-occupied habitats. Here, we describe DNA-barcoding ...

  1. Personality-dependent dispersal cancelled under predation risk.

    Science.gov (United States)

    Cote, Julien; Fogarty, Sean; Tymen, Blaise; Sih, Andrew; Brodin, Tomas

    2013-12-22

    Dispersal is a fundamental life-history trait for many ecological processes. Recent studies suggest that dispersers, in comparison to residents, display various phenotypic specializations increasing their dispersal inclination or success. Among them, dispersers are believed to be consistently more bold, exploratory, asocial or aggressive than residents. These links between behavioural types and dispersal should vary with the cause of dispersal. However, with the exception of one study, personality-dependent dispersal has not been studied in contrasting environments. Here, we used mosquitofish (Gambusia affinis) to test whether personality-dependent dispersal varies with predation risk, a factor that should induce boldness or sociability-dependent dispersal. Corroborating previous studies, we found that dispersing mosquitofish are less social than non-dispersing fish when there was no predation risk. However, personality-dependent dispersal is negated under predation risk, dispersers having similar personality types to residents. Our results suggest that adaptive dispersal decisions could commonly depend on interactions between phenotypes and ecological contexts.

  2. Does an ant-dispersed plant, Viola reichenbachiana, suffer from reduced seed dispersal under inundation disturbances?

    NARCIS (Netherlands)

    Prinzing, A.; Dauber, J.; Hammer, E.; Hammouti, N.; Bohning-Gaese, K.

    2008-01-01

    Many plant species use ants as seed dispersers. This dispersal mode is considered to be susceptible to disturbances, but the effect of natural, small-scale disturbances is still unknown. We investigated how small-scale disturbances due to inundation affect seed dispersal in Viola reichenbachiana, a

  3. Speciation of As(III)/As(V) in water samples by a magnetic solid phase extraction based on Fe₃O₄/Mg-Al layered double hydroxide nano-hybrid followed by chemiluminescence detection.

    Science.gov (United States)

    Abdolmohammad-Zadeh, Hossein; Talleb, Zeynab

    2014-10-01

    A novel magnetic solid phase extraction method was developed for the speciation of As(III)/As(V) in aqueous solutions utilizing Fe3O4-doped Mg-Al layered double hydroxide (LDH) as a nano-sorbent. The method is based on the separation and pre-concentration of As(V) by Fe3O4/Mg-Al LDH nano-hybrid prior to determination by a chemiluminescence (CL) technique. The CL route involves the oxidation of luminol by vanadomolybdoarsenate heteropoly acid in a basic media. Since the existing cations cannot be adsorbed by positively charged layers of the LDH and other potentially interferent anions had no considerable effect on the CL reaction, it provides a very selective and sensitive determination approach for As(V). The determination of total arsenic and hence indirectly As(III) involve the pre-oxidation of As(III) to As(V) by a mixture of hydrogen peroxide and potassium hydroxide. Several factors affecting the extraction and determination of the analyte were investigated and optimized. Under optimum conditions, the calibration graph was linear in the range of 5.0-5000 ng L(-1). The limit of detection and enrichment factor was 2.0 ng L(-1) and 80, respectively. The method was validated by the analysis of a standard reference material (NIST SRM 1643e), and successfully applied to the speciation of arsenic in several water samples with recoveries in the range of 93.3-106.7% for the spiked samples.

  4. Dispersion-induced nonlinearities in semiconductors

    DEFF Research Database (Denmark)

    Mørk, Jesper; Mecozzi, A.

    2002-01-01

    A dispersive and saturable medium is shown, under very general conditions, to possess ultrafast dynamic behaviour due to non-adiabatic polarisation dynamics. Simple analytical expressions relating the effect to the refractive index dispersion of a semiconductor ire derived and the magnitude...... of the equivalent Kerr coefficient is shown to be in qualitative agreement with measurements on active semiconductor waveguides....

  5. Relativistic energy loss in a dispersive medium

    DEFF Research Database (Denmark)

    Houlrik, Jens Madsen

    2002-01-01

    The electron energy loss in a dispersive medium is obtained using macroscopic electrodynamics taking advantage of a static frame of reference. Relativistic corrections are described in terms of a dispersive Lorentz factor obtained by replacing the vacuum velocity c by the characteristic phase...

  6. Van der Waals forces and spatial dispersion

    OpenAIRE

    2009-01-01

    A version of the Green's functions theory of the Van der Waals forces which can be conveniently used in the presence of spatial dispersion is presented. The theory is based on the fluctuation-dissipation theorem and is valid for interacting bodies, separated by vacuum. Objections against theories acounting for the spatial dispersion are discussed.

  7. Are western juniper seeds dispersed through diplochory?

    Science.gov (United States)

    Seed dispersal of western juniper (Juniperus occidentalis) appears to be convergent on a strategy utilized by fruit-bearing trees in that this conifer produces fleshy female cones (a.k.a., juniper “berries”) that are consumed by frugivorous birds, which then disperse the seeds through endozoochory b...

  8. Dispersive and erodible soils - fundamental differences

    CSIR Research Space (South Africa)

    Paige-Green, P

    2008-11-01

    Full Text Available Dispersive, erodible and slaking soils are prevalent over wide areas of South Africa. Each of these materials increases the cost of construction, but dispersive soils are likely to lead to far more serious problems, particularly in dam construction...

  9. Phonon dispersion relation of liquid metals

    Indian Academy of Sciences (India)

    P B Thakor; P N Gajjar; A R Jani

    2009-06-01

    The phonon dispersion curves of some liquid metals, viz. Na ( = 1), Mg ( = 2), Al ( = 3) and Pb ( = 4), have been computed using our model potential. The charged hard sphere (CHS) reference system is applied to describe the structural information. Our model potential along with CHS reference system is capable of explaining the phonon dispersion relation for monovalent, divalent, trivalent and tetravalent liquid metals.

  10. Membranes as separators of dispersed emulsion phases

    NARCIS (Netherlands)

    Lefferts, A.G.

    1997-01-01

    The reuse or discharge of industrial waste waters, containing small fractions of dispersed oil, requires a purification treatment for which membranes can be used. If only little oil is present, removal of the dispersed phase might be preferable to the more commonly applied removal of the

  11. Hominoid dispersal patterns and human evolution.

    Science.gov (United States)

    Koenig, Andreas; Borries, Carola

    2012-05-01

    Recent advances in DNA and isotope analyses have allowed tentative reconstructions of dispersal strategies of Plio-Pleistocene hominins.(1,2) Comparing their findings to dispersal patterns of some extant apes and humans suggested groups of related males and unrelated females in Neandertals indicating patrilocality(2) and Pan-like male philopatry in australopiths.(1) Here we review the demographic, ethnographic, and genetic evidence of dispersal patterns in extant apes and humans and compare the results to the suggestions for Plio-Pleistocene hominins. We find that alternative dispersal patterns, for example among gorillas or gibbons, could explain the findings of related or natal males in a confined geographic area. Based on sexual size dimorphism, we speculate that gorillas might currently be the best model for reconstructing dispersal in robust australopiths. Given that the sexual size dimorphism in other australopiths is still hotly debated, the question of which hominoid model best matches their dispersal pattern must remain unanswered. Neandertal dispersal patterns have been compared to patrilocality of modern humans. However, the latter is related to the advent of food production. Consequently, hunter-gatherers exhibiting primarily multilocality appear to be the better comparison for Neandertals. Overall, human-like patrilocality and Pan-like male philopatry appear to be poor models for the reconstruction of dispersal patterns in Plio-Pleistocene hominins. Copyright © 2012 Wiley Periodicals, Inc.

  12. Seed dispersal effectiveness revisited: a conceptual review.

    Science.gov (United States)

    Schupp, Eugene W; Jordano, Pedro; Gómez, José María

    2010-10-01

    Growth in seed dispersal studies has been fast-paced since the seed disperser effectiveness (SDE) framework was developed 17 yr ago. Thus, the time is ripe to revisit the framework in light of accumulated new insight. Here, we first present an overview of the framework, how it has been applied, and what we know and do not know. We then introduce the SDE landscape as the two-dimensional representation of the possible combinations of the quantity and the quality of dispersal and with elevational contours representing isoclines of SDE. We discuss the structure of disperser assemblages on such landscapes. Following this we discuss recent advances and ideas in seed dispersal in the context of their impacts on SDE. Finally, we highlight a number of emerging issues that provide insight into SDE. Overall, the SDE framework successfully captures the complexities of seed dispersal. We advocate an expanded use of the term dispersal encompassing the multiple recruitment stages from fruit to adult. While this entails difficulties in estimating SDE, it is a necessary expansion if we are to understand the central relevance of seed dispersal in plant ecology and evolution.

  13. Method of dispersing a hydrocarbon using bacteria

    Science.gov (United States)

    Tyndall, Richard L.

    1996-01-01

    New protozoan derived microbial consortia and method for their isolation are provided. Consortia and bacteria isolated therefrom are useful for treating wastes such as trichloroethylene and trinitrotoluene. Consortia, bacteria isolated therefrom, and dispersants isolated therefrom are useful for dispersing hydrocarbons such as oil, creosote, wax, and grease.

  14. 21 CFR 178.3725 - Pigment dispersants.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Pigment dispersants. 178.3725 Section 178.3725 Food... regulation, the substances listed in this section may be safely used as pigment dispersants in food-contact... not to exceed 0.45 percent by weight of the pigment. The pigmented articles may contact all...

  15. "Dispersion modeling approaches for near road

    Science.gov (United States)

    Roadway design and roadside barriers can have significant effects on the dispersion of traffic-generated pollutants, especially in the near-road environment. Dispersion models that can accurately simulate these effects are needed to fully assess these impacts for a variety of app...

  16. Relativistic energy loss in a dispersive medium

    DEFF Research Database (Denmark)

    Houlrik, Jens Madsen

    2002-01-01

    The electron energy loss in a dispersive medium is obtained using macroscopic electrodynamics taking advantage of a static frame of reference. Relativistic corrections are described in terms of a dispersive Lorentz factor obtained by replacing the vacuum velocity c by the characteristic phase...

  17. Uncertainty in spatially explicit animal dispersal models

    NARCIS (Netherlands)

    Mooij, W.M.; DeAngelis, D.L.

    2003-01-01

    Uncertainty in estimates of survival of dispersing animals is a vexing difficulty in conservation biology. The current notion is that this uncertainty decreases the usefulness of spatially explicit population models in particular. We examined this problem by comparing dispersal models of three level

  18. Blends of ascarosides regulate dispersal in nematodes

    Science.gov (United States)

    Blends of ascarosides regulate dispersal in nematodes Presenter: Dr. Fatma Kaplan Dispersal is an important behavior for many organisms. It can easily be observed when infectious juveniles of entomopathogenic nematodes (Steinernema and Heterorhabditis) leave a consumed insect host. Dauer larvae of ...

  19. Intermolecular forces: a solution to dispersion interactions.

    Science.gov (United States)

    Shimizu, Ken D

    2013-12-01

    London dispersion forces have been cited as an important factor in protein folding, drug–receptor interactions, and catalyst selectivities. However, careful analysis of a model system finds that the dispersion interactions are only minor contributors to the formation of complexes in solution.

  20. Chromatic Dispersion Estimation in Digital Coherent Receivers

    DEFF Research Database (Denmark)

    Soriano, Ruben Andres; Hauske, Fabian N.; Guerrero Gonzalez, Neil;

    2011-01-01

    Polarization-diverse coherent demodulation allows to compensate large values of accumulated linear distortion by digital signal processing. In particular, in uncompensated links without optical dispersion compensation, the parameter of the residual chromatic dispersion (CD) is vital to set the ac...

  1. Dispersed and decentralised settlement system

    Directory of Open Access Journals (Sweden)

    Andrej Černe

    2004-01-01

    Full Text Available In the process of reintegration of the urban system new settlements are emerging on theurban rim, transitional zones are reurbanised, derelict areas within the cities are being developedand degraded urban areas of derelict industrial complexes are being renaturalised. Inthe periphery combined research and production parks are being set up, in the open landscapeintegrated business, trade and recreational centres are springing up. Decentralisationand recentralisation of focal points of development accompany the contemporary processesof reurbanisation and suburbanisation – they are simultaneous and move in two-direction i.e. to and from the city. We understand them as manifestation of a dynamic balance amongcontradiction existing between the centre and the rim. Deindustrialisation and relocation ofproduction and distribution from the centres of gravity to the periphery generate extensivedegraded urban areas within cities and between the city and suburbs. The periphery is beingurbanised with the creation of new, dispersed and nonhierachical poles of development, andthe city and inner city is undergoing reurbanization. The general environmental conditionsin the city and in the countryside are being equalised, the potentials of development arebeing sought in the comparative advantages of local conditions: be it attractive urban districts,be it suburban entities or countryside areas.

  2. Dispersive internal long wave models

    Energy Technology Data Exchange (ETDEWEB)

    Camassa, R.; Choi, W.; Holm, D.D. [Los Alamos National Lab., NM (United States); Levermore, C.D.; Lvov, Y. [Univ. of Arizona, Tucson, AZ (United States)

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). This work is a joint analytical and numerical study of internal dispersive water wave propagation in a stratified two-layer fluid, a problem that has important geophysical fluid dynamics applications. Two-layer models can capture the main density-dependent effects because they can support, unlike homogeneous fluid models, the observed large amplitude internal wave motion at the interface between layers. The authors have derived new model equations using multiscale asymptotics in combination with the method they have developed for vertically averaging velocity and vorticity fields across fluid layers within the original Euler equations. The authors have found new exact conservation laws for layer-mean vorticity that have exact counterparts in the models. With this approach, they have derived a class of equations that retain the full nonlinearity of the original Euler equations while preserving the simplicity of known weakly nonlinear models, thus providing the theoretical foundation for experimental results so far unexplained.

  3. Taylor dispersion analysis of mixtures.

    Science.gov (United States)

    Cottet, Hervé; Biron, Jean-Philippe; Martin, Michel

    2007-12-01

    Taylor dispersion analysis (TDA) is a fast and simple method for determining hydrodynamic radii. In the case of sample mixtures, TDA, as the other nonseparative methods, leads to an average diffusion coefficient on the different molecules constituting the mixture. We set in this work the equations giving, on a consistent basis, the average values obtained by TDA with detectors with linear response functions. These equations confronted TDA experiments of sample mixtures containing different proportions of a small molecule and a polymer standard. Very good agreement between theory and experiment was obtained. In a second part of this work, on the basis of monomodal or bimodal molar mass distributions of polymers, the different average diffusion coefficients corresponding to TDA were compared to the z-average diffusion coefficient (D(z)) obtained from dynamic light scattering (DLS) experiments and to the weight average diffusion coefficient (D(w)). This latter value is sometimes considered as the most representative of the sample mixture. From these results, it appears that, for monomodal distribution and relatively low polydispersity (I = 1.15), the average diffusion coefficient generally derived from TDA is very close to Dw. However, for highly polydisperse samples (e.g., bimodal polydisperse distributions), important differences could be obtained (up to 35% between TDA and D(w)). In all the cases, the average diffusion coefficient obtained by TDA for a mass concentration detector was closer to the Dw value than the z-average obtained by DLS.

  4. Databases of surface wave dispersion

    Directory of Open Access Journals (Sweden)

    L. Boschi

    2005-06-01

    Full Text Available Observations of seismic surface waves provide the most important constraint on the elastic properties of the Earth’s lithosphere and upper mantle. Two databases of fundamental mode surface wave dispersion were recently compiled and published by groups at Harvard (Ekström et al., 1997 and Utrecht/Oxford (Trampert and Woodhouse, 1995, 2001, and later employed in 3-d global tomographic studies. Although based on similar sets of seismic records, the two databases show some significant discrepancies. We derive phase velocity maps from both, and compare them to quantify the discrepancies and assess the relative quality of the data; in this endeavour, we take careful account of the effects of regularization and parametrization. At short periods, where Love waves are mostly sensitive to crustal structure and thickness, we refer our comparison to a map of the Earth’s crust derived from independent data. On the assumption that second-order effects like seismic anisotropy and scattering can be neglected, we find the measurements of Ekström et al. (1997 of better quality; those of Trampert and Woodhouse (2001 result in phase velocity maps of much higher spatial frequency and, accordingly, more difficult to explain and justify geophysically. The discrepancy is partly explained by the more conservative a priori selection of data implemented by Ekström et al. (1997. Nevertheless, it becomes more significant with decreasing period, which indicates that it could also be traced to the different measurement techniques employed by the authors.

  5. Pay Dispersion and Performance in Teams

    DEFF Research Database (Denmark)

    Bucciol, Alessandro; Foss, Nicolai J; Piovesan, Marco

    2014-01-01

    Extant research offers conflicting predictions about the effect of pay dispersion on team performance. We collected a unique dataset from the Italian soccer league to study the effect of intra-firm pay dispersion on team performance, under different definitions of what constitutes a "team......". This peculiarity of our dataset can explain the conflicting evidence. Indeed, we also find positive, null, and negative effects of pay dispersion on team performance, using the same data but different definitions of team. Our results show that when the team is considered to consist of only the members who directly...... contribute to the outcome, high pay dispersion has a detrimental impact on team performance. Enlarging the definition of the team causes this effect to disappear or even change direction. Finally, we find that the detrimental effect of pay dispersion is due to worse individual performance, rather than...

  6. High-dispersive mirrors for femtosecond lasers.

    Science.gov (United States)

    Pervak, V; Teisset, C; Sugita, A; Naumov, S; Krausz, F; Apolonski, A

    2008-07-07

    We report on the development of highly dispersive mirrors for chirped-pulse oscillators (CPO) and amplifiers (CPA). In this proof-of-concept study, we demonstrate the usability of highly dispersive multilayer mirrors for high-energy femtosecond oscillators, namely for i) a chirped-pulse Ti:Sa oscillator and ii) an Yb:YAG disk oscillator. In both cases a group delay dispersion (GDD) of the order of 2x10(4) fs(2) was introduced, accompanied with an overall transmission loss as low as approximately 2 per cent. This unprecedented combination of high dispersion and low loss over a sizeable bandwidth with multilayer structures opens the prospects for femtosecond CPA systems equipped with a compact, alignment-insensitive all-mirror compressors providing compensation of GDD as well as higher-order dispersion.

  7. Rheological behaviour of heated potato starch dispersions

    Science.gov (United States)

    Juszczak, L.; Witczak, M.; Ziêba, T.; Fortuna, T.

    2012-10-01

    The study was designed to investigate the rheological properties of heated potato starch dispersions. Water suspensions of starch were heated at 65, 80 or 95°C for 5, 15, 30 or 60 min. The dispersions obtained were examined for granule size distribution and rheology. It was found that the starch dispersions significantly differed in both respects. The mean diameters of starch granules were largest for the dispersion heated at 65°C and smallest for that heated at 95°C. As the heating temperature was raised, the yield stresses and consistency coefficients decreased, while the flow behaviour indexes and Casson plastic viscosities increased. There were also differences in the viscoelastic properties of the dispersions: for those heated at 65°C the storage and loss moduli increased with heating time whereas for those heated at 80°C both moduli decreased.

  8. Shock waves in dispersive Eulerian fluids

    CERN Document Server

    Hoefer, M A

    2013-01-01

    The long time behavior of an initial step resulting in a dispersive shock wave (DSW) for the one-dimensional isentropic Euler equations regularized by generic, third order dispersion is considered by use of Whitham averaging. Under modest assumptions, the jump conditions (DSW locus and speeds) for admissible, weak DSWs are characterized and found to depend only upon the sign of dispersion (convex or concave) and a general pressure law. Two mechanisms leading to the breakdown of this simple wave DSW theory for sufficiently large jumps are identified: a change in the sign of dispersion, leading to gradient catastrophe in the modulation equations, and the loss of genuine nonlinearity in the modulation equations. Large amplitude DSWs are constructed for several particular dispersive fluids with differing pressure laws modeled by the generalized nonlinear Schr\\"{o}dinger equation. These include superfluids (Bose-Einstein condensates and ultracold Fermions) and "optical fluids". Estimates of breaking times for smoo...

  9. Flow properties of acetylated chickpea protein dispersions.

    Science.gov (United States)

    Liu, Li H; Hung, Tran V

    2010-06-01

    Chickpea protein concentrate was acetylated with acetic anhydride at 5 levels. Acetylated chickpea protein (ACP) dispersions at 3 levels (6%, 45%, and 49%) were chosen for this flow property study. Effects of protein concentration, temperature, concentrations of salt addition and particularly, degree of acetylation on these properties were examined. Compared with native chickpea proteins, the ACP dispersions exhibited a strong shear thinning behavior. Within measured temperature range (15 to 55 degrees C), the apparent viscosities of native chickpea protein dispersions were temperature independent; those of ACP dispersions were thermally affected. The flow index (n), consistency coefficient (m), apparent yield stress, and apparent viscosities of ACP dispersions increased progressively up to 45% acetylation but decreased at 49% acetylation level. Conformational studies by gel filtration suggested that chickpea proteins were associated or polymerized at up to 45% acetylation but the associated subunits gradually dissociated to smaller units at higher levels (49%) of acetylation.

  10. Pay Dispersion and Performance in Teams

    DEFF Research Database (Denmark)

    Bucciol, Alessandro; Foss, Nicolai J; Piovesan, Marco

    2014-01-01

    Extant research offers conflicting predictions about the effect of pay dispersion on team performance. We collected a unique dataset from the Italian soccer league to study the effect of intra-firm pay dispersion on team performance, under different definitions of what constitutes a "team......". This peculiarity of our dataset can explain the conflicting evidence. Indeed, we also find positive, null, and negative effects of pay dispersion on team performance, using the same data but different definitions of team. Our results show that when the team is considered to consist of only the members who directly...... contribute to the outcome, high pay dispersion has a detrimental impact on team performance. Enlarging the definition of the team causes this effect to disappear or even change direction. Finally, we find that the detrimental effect of pay dispersion is due to worse individual performance, rather than...

  11. Pay Dispersion and Performance in Teams

    Science.gov (United States)

    Bucciol, Alessandro; Foss, Nicolai J.; Piovesan, Marco

    2014-01-01

    Extant research offers conflicting predictions about the effect of pay dispersion on team performance. We collected a unique dataset from the Italian soccer league to study the effect of intra-firm pay dispersion on team performance, under different definitions of what constitutes a “team”. This peculiarity of our dataset can explain the conflicting evidence. Indeed, we also find positive, null, and negative effects of pay dispersion on team performance, using the same data but different definitions of team. Our results show that when the team is considered to consist of only the members who directly contribute to the outcome, high pay dispersion has a detrimental impact on team performance. Enlarging the definition of the team causes this effect to disappear or even change direction. Finally, we find that the detrimental effect of pay dispersion is due to worse individual performance, rather than a reduction of team cooperation. PMID:25397615

  12. Laboratory effectiveness testing of oil spill dispersants

    Energy Technology Data Exchange (ETDEWEB)

    Fingas, M.F.; Kyle, D.A.; Wang, Z.; Handfield, D.; Ianuzzi, D.; Ackerman, F. [Environment Canada, Ottawa, Ontario (Canada)

    1995-06-01

    Dispersant effectiveness tests are reviewed. Studies have been conducted of the variances among several standard regulatory tests. Three main causes of differences have been identified, oil-to-water ratio, settling time and energy. Energy can be partially compensated for in high energy tests by correcting for natural dispersion. With this correction and with high oil-to-water ratios and a settling time of at least 10 minutes, five apparatuses yield very similar results for a variety of oils and dispersants. Recent studies into the energy variation of dispersant tests show that the energy level varies in many apparatuses. The repeatability of energy levels in apparatus is largely responsible for the variation in dispersant effectiveness values in certain apparatus. Studies of analytical procedures show that traditional extraction and analysis methods cause a bias to results. Methods to overcome these difficulties are presented.

  13. Modulation instability in the weak dispersion regime of a dispersion modulated passive fiber-ring cavity.

    Science.gov (United States)

    Copie, François; Conforti, Matteo; Kudlinski, Alexandre; Trillo, Stefano; Mussot, Arnaud

    2017-05-15

    We present a theoretical and experimental study of the modulation instability process in a dispersion oscillating passive fiber-ring resonator in the low dispersion region. Generally, the modulation of the dispersion along the cavity length is responsible for the emergence of a regime characterised by multiple parametric resonances (or Faraday instabilities). We show that, under weak dispersion conditions, a huge number of Faraday sidebands can grow under the influence of fourth order dispersion. We specifically designed a piecewise uniform fiber-ring cavity and report on experiments that confirm our theoretical predictions. We recorded the dynamics of this system revealing strong interactions between the different sidebands in agreement with numerical simulations.

  14. Seed dispersal by pulp consumers, not "legitimate" seed dispersers, increases Guettarda viburnoides population growth.

    Science.gov (United States)

    Loayza, Andrea P; Knight, Tiffany

    2010-09-01

    We examined the effect of seed dispersal by Purplish Jays (Cyanocorax cyanomelas; pulp consumers) and the Chestnut-eared Araçari (Pteroglossus castanotis; "legitimate" seed dispersers) on population growth of the small tree Guettarda viburnoides (Rubiaceae) in northeastern Bolivian savannas. Because each bird species differs with respect to feeding and post-feeding behavior, we hypothesized that seed dispersal by each species will contribute differently to the rate of increase of G. viburnoides, but that seed dispersal by either species will increase population growth when compared to a scenario with no seed dispersal. To examine the effects of individual dispersers on the future population size of G. viburnoides, we projected population growth rate using demographic models for G. viburnoides that explicitly incorporate data on quantitative and qualitative aspects of seed dispersal by each frugivore species. Our model suggests that seed dispersal by C. cyanomelas leads to positive population growth of G. viburnoides, whereas seed dispersal by P. castanotis has a detrimental effect on the population growth of this species. To our knowledge, this is the first study to report negative effects of a "legitimate" seed disperser on the population dynamics of the plant it consumes. Our results stress the importance of incorporating frugivore effects into population projection matrices, to allow a comprehensive analysis of the effectiveness of different dispersers for plant population dynamics.

  15. 基于表面等离子体共振效应的Ag(Au)/半导体纳米复合光催化剂的研究进展%Research progress of Ag(Au)/semiconductor nanohybrid photocatalysts based on surface plasmon resonance

    Institute of Scientific and Technical Information of China (English)

    邵先坤; 郝勇敢; 刘同宣; 胡路阳; 王媛媛; 李本侠

    2016-01-01

    由具有表面等离子体共振(surface plasmon resonance,SPR)效应的贵金属(Ag、Au等)纳米粒子和半导体纳米结构组成的纳米复合光催化剂具有优异的可见光光催化活性,成为新型光催化材料的研究热点之一。本文综述了Ag(Au)/半导体纳米复合光催化剂的制备方法、基本性质以及光催化应用方面的一些重要研究进展;重点介绍了Ag(Au)等纳米粒子的表面等离子共振增强可见光催化活性的机理,以及Ag(Au)纳米粒子与不同类型半导体复合的光催化剂的光催化性能,其中所涉及的半导体包括金属氧化物、硫化物和其他一些半导体;本领域未来几年的研究热点将集中于新型高效的 Ag(Au)/半导体纳米复合光催化剂的微结构调控及其用于可见光驱动有机反应的机理研究。本文为基于SPR效应构建Ag(Au)/半导体纳米复合光催化剂的研究提供了有力的参考依据,并且指出Ag(Au)/半导体纳米复合光催化剂的研究是发展可见光高效光催化剂的重要方向。%Nanohybrid photocatalysts composed of noble metal nanoparticles (Ag,Au,etc.) with surface plasmon resonance (SPR) effect and semiconductor nanostructures have become one of the research hotspots in the field of advanced photocatalysis because of their excellent photocatalytic activity under visible light irradiation. This review summarized some significant research progress about the basic properties,preparation methods and the photocatalytic applications of the plasmonic Ag(Au)/semiconductor nanohybrid photocatalysts. We emphatically introduced the mechanism for the enhanced effect of Ag(Au) nanoparticles with SPR on visible light response photocatalytic activity,as well as the photocatalytic performance of the nanohybrid photocatalysts composed of Ag(Au) nanoparticles and different types of semiconductors,including metal oxides,metal chalcogenides and other semiconductors. The research in this

  16. Generalized dispersive wave emission in nonlinear fiber optics.

    Science.gov (United States)

    Webb, K E; Xu, Y Q; Erkintalo, M; Murdoch, S G

    2013-01-15

    We show that the emission of dispersive waves in nonlinear fiber optics is not limited to soliton-like pulses propagating in the anomalous dispersion regime. We demonstrate, both numerically and experimentally, that pulses propagating in the normal dispersion regime can excite resonant dispersive radiation across the zero-dispersion wavelength into the anomalous regime.

  17. Shear Flow Dispersion Under Wave and Current

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The longitudinal dispersion of solute in open channel flow with short period progressive waves is investigated. The waves induce second order drift velocity in the direction of propagation and enhance the mixing process in concurrent direction. The 1-D wave-period-averaged dispersion equation is derived and an expression for the wave-current induced longitudinal dispersion coefficient (WCLDC) is proposed based on Fischer's expression (1979) for dispersion in unidirectional flow. The result shows that the effect of waves on dispersion is mainly due to the cross-sectional variation of the drift velocity. Furthermore, to obtain a more practical expression of the WCLDC, the longitudinal dispersion coefficient due to Seo and Cheong (1998) is modified to incluee the effect of drift velocity. Laboratory experiments have been conducted to verify the proposed expression. The experimental results, together with dimensional analysis, show that the wave effect can be reflected by the ratio between the wave amplitude and wave period. A comparative study between the cases with and without waves demonstrates that the magnitude of the longitudinal dispersion coefficient is increased under the presence of waves.

  18. Acorn dispersal estimated by radio-tracking.

    Science.gov (United States)

    Pons, Josep; Pausas, Juli G

    2007-10-01

    Bird-dispersed seeds are difficult to track, especially in the case of long-distance dispersal events. To estimate the oak dispersal distance and the seed shadow generated by the European jay (Garrulus glandarius), we inserted radio-transmitters in 239 acorns, placed them in bird-feeders and then located them by radio-tracking. Using this methodology we located the exact caching site of 94 Quercus ilex and 54 Q. suber acorns and determined the caching habitat characteristics (vegetation type, distance, spatial distribution). The results show that: (1) there is no differences in the dispersal distance distribution between the different acorn species or sizes, (2) dispersal distances range from approximately 3 m up to approximately 550 m (mean = 68.6 m; median = 49.2 m), (3) recently abandoned fields and forest tracks were the sites preferred by jays to cache acorns, whereas fields and shrublands were avoided and (4) seed shadows showed acorn aggregation zones (i.e. clusters of caches) close to the feeder as well as isolated caches at longer distances. The results also suggest that radio-transmitters are a cheap and reliable way to determine seed shadows and quantify both seed dispersal and post-dispersal seed predation for medium to large seeds.

  19. Stationary one-dimensional dispersive shock waves

    CERN Document Server

    Kartashov, Yaroslav V

    2011-01-01

    We address shock waves generated upon the interaction of tilted plane waves with negative refractive index defect in defocusing media with linear gain and two-photon absorption. We found that in contrast to conservative media where one-dimensional dispersive shock waves usually exist only as nonstationary objects expanding away from defect or generating beam, the competition between gain and two-photon absorption in dissipative medium results in the formation of localized stationary dispersive shock waves, whose transverse extent may considerably exceed that of the refractive index defect. One-dimensional dispersive shock waves are stable if the defect strength does not exceed certain critical value.

  20. DISPERSION OF CYLINDRICAL PARTICLES IN TURBULENT FLOWS

    Institute of Scientific and Technical Information of China (English)

    GAO Zhen-yu; LIN Jian-zhong

    2004-01-01

    With consideration of the Stokes drag and virtual mass force, the equations for mean and fluctuating velocities in rotation and translation were given for rigid cylindrical particles moving in a turbulent flow. Then the rotational and translational dispersion coefficients of particle were derived. The relationships between the dispersion coefficients and flow length scale as well as particle characteristic parameters were analyzed. The resulting dispersion coefficients were proved to decrease as the particle length increases. The conclusions are helpful for the further research on the motion of cylindrical particles in turbulent flows.

  1. Inverse scattering of dispersive stratified structures

    CERN Document Server

    Skaar, Johannes

    2012-01-01

    We consider the inverse scattering problem of retrieving the structural parameters of a stratified medium consisting of dispersive materials, given knowledge of the complex reflection coefficient in a finite frequency range. It is shown that the inverse scattering problem does not have a unique solution in general. When the dispersion is sufficiently small, such that the time-domain Fresnel reflections have durations less than the round-trip time in the layers, the solution is unique and can be found by layer peeling. Numerical examples with dispersive and lossy media are given, demonstrating the usefulness of the method for e.g. THz technology.

  2. Dispersion and fall out of heavier particles

    DEFF Research Database (Denmark)

    Astrup, Poul

    2016-01-01

    they may like gasses and aerosols be transported more or less far by the wind. The present paper focuses on the growth of plumes of such particles larger and heavier than aerosols and transported by the wind. Implementation in existing decision support puff dispersion programs requires a parameterization...... of this growth, and two reasonable describing parameterizations have been found, one in the literature, one proposed here, and both are compared to experimental work found in the literature. The parameterization from the literature has been implemented in the dispersion program RIMPUFF, which has subsequently...... shown that the effect on fall out to a large extent overrules the effect on the dispersion of such particles....

  3. Plasma Dispersion Function for the Kappa Distribution

    Science.gov (United States)

    Podesta, John J.

    2004-01-01

    The plasma dispersion function is computed for a homogeneous isotropic plasma in which the particle velocities are distributed according to a Kappa distribution. An ordinary differential equation is derived for the plasma dispersion function and it is shown that the solution can be written in terms of Gauss' hypergeometric function. Using the extensive theory of the hypergeometric function, various mathematical properties of the plasma dispersion function are derived including symmetry relations, series expansions, integral representations, and closed form expressions for integer and half-integer values of K.

  4. Seed dispersal effectiveness revisited: a conceptual review

    OpenAIRE

    Schupp, Eugene W.; JORDANO, Pedro; Gómez Reyes, José M.

    2010-01-01

    Growth in seed dispersal studies has been fast-paced since the seed disperser effec- tiveness (SDE) framework was developed 17 yr ago. Thus, the time is ripe to revisit the framework in light of accumulated new insight. Here, we first present an over- view of the framework, how it has been applied, and what we know and do not know. We then introduce the SDE landscape as the two-dimensional representa- tion of the possible combinations of the quantity and the quality of dispersal and with ele...

  5. Dispersion Method Using Focused Ultrasonic Field

    Science.gov (United States)

    Kim, Jungsoon; Kim, Moojoon; Ha, Kanglyel; Chu, Minchul

    2010-07-01

    The dispersion of powders into liquids has become one of the most important techniques in high-tech industries and it is a common process in the formulation of various products, such as paint, ink, shampoo, beverages, and polishing media. In this study, an ultrasonic system with a cylindrical transducer is newly introduced for pure nanoparticle dispersion. The acoustics pressure field and the characteristics of the shock pulse caused by cavitation are investigated. The frequency spectrum of the pulse from the collapse of air bubbles in the cavitation is analyzed theoretically. It was confirmed that a TiO2 water suspension can be dispersed effectively using the suggested system.

  6. Modeling and Simulation of Aerial Dispersion on Piston Dispersal Mechanism%Modeling and Simulation of Aerial Dispersion on Piston Dispersal Mechanism

    Institute of Scientific and Technical Information of China (English)

    陶如意; 王浩; 黄蓓

    2011-01-01

    For the aerial dispersing interior ballistic process and submunition exterior ballistic initial conditions of cluster munition with piston maximum travel limit, a novel model is established, and the numerical simulation is performed. The piston maximum travel limit and the effect of reaction force on carrier body are researched using the internal ballistic model. Guide tube, cluster munition rotating and submunition assembly are analyzed using the submunition initial external ballistic model. The computational results are consistent with the practical process and the experimental data, and prove the rationality of this model. The theoretical methods are presented for the construction design and dispersion analysis of piston dispersal mechanism.

  7. High-Multipolar Effects on Dispersive Forces

    CERN Document Server

    Noguez, C; Esquivel-Sirvent, R; Villarreal, C; Noguez, Cecilia; Roman-Velazquez, Carlos E.

    2003-01-01

    We show that the dispersive force between a spherical nanoparticle (with a radius $\\le$ 100 nm) and a substrate is enhanced by several orders of magnitude when the sphere is near to the substrate. We calculate exactly the dispersive force in the non-retarded limit by incorporating the contributions to the interaction from of all the multipolar electromagnetic modes. We show that as the sphere approaches the substrate, the fluctuations of the electromagnetic field, induced by the vacuum and the presence of the substrate, the dispersive force is enhanced by orders of magnitude. We discuss this effect as a function of the size of the sphere.

  8. Physical models of polarization mode dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Menyuk, C.R.; Wai, P.K.A. [Univ. of Maryland, Baltimore, MD (United States)

    1995-12-31

    The effect of randomly varying birefringence on light propagation in optical fibers is studied theoretically in the parameter regime that will be used for long-distance communications. In this regime, the birefringence is large and varies very rapidly in comparison to the nonlinear and dispersive scale lengths. We determine the polarization mode dispersion, and we show that physically realistic models yield the same result for polarization mode dispersion as earlier heuristic models that were introduced by Poole. We also prove an ergodic theorem.

  9. Distorted-distance models for directional dispersal: a general framework with application to a wind-dispersed tree

    NARCIS (Netherlands)

    Putten, van B.; Visser, M.D.; Muller-Landau, H.C.; Jansen, P.A.

    2012-01-01

    1. Seed and pollen dispersal is often directionally biased, because of the inherent directionality of wind and many other dispersal vectors. Nevertheless, the vast majority of studies of seed and pollen dispersal fit isotropic dispersal kernels to data, implicitly assuming that dispersal is equally

  10. Distorted-distance models for directional dispersal: a general framework with application to a wind-dispersed tree

    NARCIS (Netherlands)

    Putten, van B.; Visser, M.D.; Muller-Landau, H.C.; Jansen, P.A.

    2012-01-01

    1. Seed and pollen dispersal is often directionally biased, because of the inherent directionality of wind and many other dispersal vectors. Nevertheless, the vast majority of studies of seed and pollen dispersal fit isotropic dispersal kernels to data, implicitly assuming that dispersal is equally

  11. Optimisation of dispersion parameters of Gaussian plume model for CO₂ dispersion.

    Science.gov (United States)

    Liu, Xiong; Godbole, Ajit; Lu, Cheng; Michal, Guillaume; Venton, Philip

    2015-11-01

    The carbon capture and storage (CCS) and enhanced oil recovery (EOR) projects entail the possibility of accidental release of carbon dioxide (CO2) into the atmosphere. To quantify the spread of CO2 following such release, the 'Gaussian' dispersion model is often used to estimate the resulting CO2 concentration levels in the surroundings. The Gaussian model enables quick estimates of the concentration levels. However, the traditionally recommended values of the 'dispersion parameters' in the Gaussian model may not be directly applicable to CO2 dispersion. This paper presents an optimisation technique to obtain the dispersion parameters in order to achieve a quick estimation of CO2 concentration levels in the atmosphere following CO2 blowouts. The optimised dispersion parameters enable the Gaussian model to produce quick estimates of CO2 concentration levels, precluding the necessity to set up and run much more complicated models. Computational fluid dynamics (CFD) models were employed to produce reference CO2 dispersion profiles in various atmospheric stability classes (ASC), different 'source strengths' and degrees of ground roughness. The performance of the CFD models was validated against the 'Kit Fox' field measurements, involving dispersion over a flat horizontal terrain, both with low and high roughness regions. An optimisation model employing a genetic algorithm (GA) to determine the best dispersion parameters in the Gaussian plume model was set up. Optimum values of the dispersion parameters for different ASCs that can be used in the Gaussian plume model for predicting CO2 dispersion were obtained.

  12. Dispersal Timing: Emigration of Insects Living in Patchy Environments.

    Directory of Open Access Journals (Sweden)

    Milica Lakovic

    Full Text Available Dispersal is a life-history trait affecting dynamics and persistence of populations; it evolves under various known selective pressures. Theoretical studies on dispersal typically assume 'natal dispersal', where individuals emigrate right after birth. But emigration may also occur during a later moment within a reproductive season ('breeding dispersal'. For example, some female butterflies first deposit eggs in their natal patch before migrating to other site(s to continue egg-laying there. How breeding compared to natal dispersal influences the evolution of dispersal has not been explored. To close this gap we used an individual-based simulation approach to analyze (i the evolution of timing of breeding dispersal in annual organisms, (ii its influence on dispersal (compared to natal dispersal. Furthermore, we tested (iii its performance in direct evolutionary contest with individuals following a natal dispersal strategy. Our results show that evolution should typically result in lower dispersal under breeding dispersal, especially when costs of dispersal are low and population size is small. By distributing offspring evenly across two patches, breeding dispersal allows reducing direct sibling competition in the next generation whereas natal dispersal can only reduce trans-generational kin competition by producing highly dispersive offspring in each generation. The added benefit of breeding dispersal is most prominent in patches with small population sizes. Finally, the evolutionary contests show that a breeding dispersal strategy would universally out-compete natal dispersal.

  13. Differential Contribution of Frugivores to Complex Seed Dispersal Patterns

    National Research Council Canada - National Science Library

    P. Jordano; C. Garcia; J. A. Godoy; J. L. Garcia-Castaño

    2007-01-01

    .... However, data are lacking on species-specific variation in two central aspects of seed dispersal, distance of dispersal and probability of dispersal among populations through long-distance transport...

  14. The Flying Sunflower: A Seed Dispersal Project.

    Science.gov (United States)

    Buege, Douglas J.

    1999-01-01

    Describes an open-ended activity in which students build a "plant" that launches its seeds as far as possible to study the dispersal strategies of various plants. Recommends extension activities for elementary- and secondary-level students. (WRM)

  15. Training for Internationalization through Domestic Geographical Dispersion

    DEFF Research Database (Denmark)

    Santangelo, Grazia D.; Stucchi, Tamara

    organizational learning, we seek to solve this puzzle in relation to the internationalization of Indian BGs. In particular, we argue that in heterogeneous domestic emerging markets BG’s geographical dispersion across sub-national states provides training for internationalization. To internationalize successfully......, BGs need to develop the capability of managing geographically dispersed units in institutional heterogeneous contexts. Domestic geographical dispersion would indeed help the BG dealing with different regulations, customers and infrastructures. However, there is less scope for such training as BGs...... become more internationally experienced, and the benefits of domestic geographical dispersions are limited by the degree of urbanization of sub-national states. We test our argument on a sample of 693 Indian BGs over the period 2001-2010....

  16. A dispersive approach to Sudakov resummation

    CERN Document Server

    Gardi, Einan

    2007-01-01

    We present a general all-order formulation of Sudakov resummation in QCD in terms of dispersion integrals. We show that the Sudakov exponent can be written as a dispersion integral over spectral density functions, weighted by characteristic functions that encode information on power corrections. The characteristic functions are defined and computed analytically in the large-beta_0 limit. The spectral density functions encapsulate the non-Abelian nature of the interaction. They are defined by the time-like discontinuity of specific effective charges (couplings) that are directly related to the familiar Sudakov anomalous dimensions and can be computed order-by-order in perturbation theory. The dispersive approach provides a realization of Dressed Gluon Exponentiation, where Sudakov resummation is enhanced by an internal resummation of running-coupling corrections. We establish all-order relations between the scheme-invariant Borel formulation and the dispersive one, and address the difference in the treatment o...

  17. Sex-biased dispersal of human ancestors.

    Science.gov (United States)

    Sugiyama, Yukimaru

    2017-07-01

    Some anthropologists and primatologists have argued that, judging by extant chimpanzees and humans, which are female-biased dispersers, the common ancestors of humans and chimpanzees were also female-biased dispersers. It has been thought that sex-biased dispersal patterns have been genetically transmitted for millions of years. However, this character has changed many times with changes in environment and life-form during human evolution and historical times. I examined life-form and social organization of nonhuman primates, among them gatherers (foragers), hunter-gatherers, agriculturalists, industrialists, and modern and extant humans. I conclude that dispersal patterns changed in response to environmental conditions during primate and human evolution. © 2017 Wiley Periodicals, Inc.

  18. Revised state diagram of Laponite dispersions.

    Science.gov (United States)

    Mongondry, Philippe; Tassin, Jean François; Nicolai, Taco

    2005-03-15

    We propose a state diagram of charged disk-like mineral particle (Laponite) dispersions as a function of the Laponite concentration (C) and the concentration of added salt (C(s)), based on simple observation and light-scattering measurements. At low C or high C(s) the dispersions separate into two domains due to sedimentation of Laponite aggregates, while at high C and low C(s) they form homogeneous gels that do not flow upon tube reversal. The aggregation rate and the structure factor of the Laponite dispersions is determined with light scattering as a function of C and C(s). We discuss in detail the controversy on the origin of gelation of Laponite dispersions in the absence of added salt. We argue that aggregation rather than glass formation causes gelation.

  19. Theoretical Considerations in Developing Amorphous Solid Dispersions

    DEFF Research Database (Denmark)

    Laitinen, Riikka; Priemel, Petra Alexandra; Surwase, Sachin;

    2014-01-01

    Before pursuing the laborious route of amorphous solid dispersion formulation and development, which is the topic of many of the subsequent chapters in this book, the formulation scientist would benefit from a priori knowledge whether the amorphous route is a viable one for a given drug and how...... to their glass-forming ability and glass stability. In the main parts of this chapter, we review theoretical approaches to determine amorphous drug polymer miscibility and crystalline drug polymer solubility, as a prerequisite to develop amorphous solid dispersions (glass solutions)....... much solubility improvement, and hence increase in bioavailability, can be expected, and what forms of solid dispersion have been developed in the past. In this chapter, we therefore initially define the various forms of solid dispersions, and then go on to discuss properties of pure drugs with respect...

  20. Experimental measurement of dispersion coefficients for gases

    Energy Technology Data Exchange (ETDEWEB)

    De Delgado, E. [National University at Comahue (Brazil); Da Franca Correa, A.C. [State Univ. of Campinas (Brazil)

    2001-06-01

    A series of experiments were conducted on dispersion, a phenomenon by which molecules of two miscible fluids diffuse into one another when they come into contact with each other. Both longitudinal and transverse diffusion is a result of forced flow. Longitudinal dispersion occurs in the direction of flow, while transverse dispersion occurs perpendicular to the direction of flow. This study focused on measuring longitudinal dispersion coefficients on natural gas displaced by an inert gas (nitrogen) at very low pressure. The experiments were carried out at two different pressure ranges on unconsolidated porous media at a Gas Plant Laboratory near Neuquen, Argentina. Two different types of porous media were used, a plastic hose and a metallic slim tube. They were each filled twice with both natural and synthetic sand grains. The study provided a better understanding of how gases behave at low pressures. 4 refs., 4 tabs., 5 figs.

  1. Pulse dispersion in hollow optical waveguides

    Science.gov (United States)

    Ben-David, M.; Ilev, Ilko K.; Waynant, Ronald W.; Gannot, Israel

    2005-09-01

    A study of laser (near- and mid-infrared) pulse dispersion in hollow waveguides is presented. We developed an analytical model to describe the pulse dispersion in hollow waveguides and compared our theoretical calculations with measurements done by us and also by two other groups. The pulse dispersion was experimentally measured for a short Q-switched Er:YAG laser in the nanosecond range and for femtosecond Ti:sapphire laser pulses transmitted by hollow optical waveguides. For analytical calculation of the pulse dispersion in these waveguides, a refined ray tracing program was developed. This approach took into account roughness of the internal reflecting and refracting inner layers. A comparison analysis between the measurements and calculations conducted at identical parameters demonstrates good correlation between theoretical and experimental results.

  2. Transport and dispersion on offshore banks

    Energy Technology Data Exchange (ETDEWEB)

    Hannah, C. [Department of Fisheries and Oceans, Dartmouth, NS (Canada). Bedford Inst. of Oceanography

    2000-07-01

    Basic principles of developing a model of benthic boundary layer transport of the vertical distribution of sediments to generate estimates of drift and dispersion are described. The application of local benthic boundary layer transport to the Hibernia, Cohasset and Georges Bank fields show inter-regional variations associated with water depth and current strength. At Cohasset no significant impact of drift or dispersion was observed during five days of simulation. At Georges Bank modelled currents and local benthic boundary layer transport predicted impacts from drilling waste disposal as a function of settling velocity and location on the Bank. Dispersion due to horizontal shear in the currents on the northern flank was clearly evident in the sheared distribution of the particles. The dispersion produced increased diffusivity compared with a local benthic boundary layer transport application. 6 refs., 2 figs.

  3. Dispersion forces between noble gas atoms

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; Luyckx, R.; Coulon, P.

    1978-01-01

    The coefficients of the R-6, R -8, and R-10 terms in the series representation of the dispersion interaction between helium, neon, and argon at distance R are calculated using an elementary variation method.

  4. Dispersive shock waves with nonlocal nonlinearity

    CERN Document Server

    Barsi, Christopher; Sun, Can; Fleischer, Jason W

    2007-01-01

    We consider dispersive optical shock waves in nonlocal nonlinear media. Experiments are performed using spatial beams in a thermal liquid cell, and results agree with a hydrodynamic theory of propagation.

  5. Dispersive shock waves with nonlocal nonlinearity.

    Science.gov (United States)

    Barsi, Christopher; Wan, Wenjie; Sun, Can; Fleischer, Jason W

    2007-10-15

    We consider dispersive optical shock waves in nonlocal nonlinear media. Experiments are performed using spatial beams in a thermal liquid cell, and results agree with a hydrodynamic theory of propagation.

  6. SCIPUFF - a generalized hazard dispersion model

    Energy Technology Data Exchange (ETDEWEB)

    Sykes, R.I.; Henn, D.S.; Parker, S.F.; Gabruk, R.S. [Titan Research and Technology, Princeton, NJ (United States)

    1996-12-31

    One of the more popular techniques for efficiently representing the dispersion process is the Gaussian puff model, which uses a collection of Lagrangian puffs with Gaussian concentration profiles. SCIPUFF (Second-order Closure Integrated Puff) is an advanced Gaussian puff model. SCIPUFF which uses second-order turbulence closure techniques to relate the dispersion rates to measurable turbulent velocity statistics, providing a wide range of applicability. In addition, the closure model provides a prediction of the statistical variance in the concentration field which can be used to estimate the uncertainty in the dispersion prediction resulting from the inherent uncertainty in the wind field. SCIPUFF has been greatly extended from a power plant plume model to describe more general source characteristics, material properties, and longer range dispersion. In addition, a Graphical User Interface has been developed to provide interactive problem definition and output display. This presentation describes the major features of the model, and presents several example calculations.

  7. Nonlinear Dispersion Relation in Wave Transformation

    Institute of Scientific and Technical Information of China (English)

    李瑞杰; 严以新; 曹宏生

    2003-01-01

    A nonlinear dispersion relation is presented to model the nonlinear dispersion of waves over the whole range of possible water depths. It reduces the phase speed over-prediction of both Hedges′ modified relation and Kirby and Dalrymple′s modified relation in the region of 1<kh<1.5 for small wave steepness and maintains the monotonicity in phase speed variation for large wave steepness. And it has a simple form. By use of the new nonlinear dispersion relation along with the mild slope equation taking into account weak nonlinearity, a mathematical model of wave transformation is developed and applied to laboratory data. The results show that the model with the new dispersion relation can predict wave transformation over complicated bathymetry satisfactorily.

  8. Bird deterrent and dispersal systems: Research update

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report is a research update on bird deterrent and dispersal systems by the Petroleum Association for Conservation of the Canadian Environment. The purpose of...

  9. Tackifier Dispersions to Make Pressure Sensitive Adhesives

    Energy Technology Data Exchange (ETDEWEB)

    None

    2003-02-01

    Development of new processes for tackifier dispersion could improve the production of pressure sensitive adhesives. Pressure sensitive adhesives (PSAs) have the ability to adhere to different surfaces with manual or finger pressure.

  10. Chirped mirrors with low dispersion ripple.

    Science.gov (United States)

    Pervak, V; Naumov, S; Krausz, F; Apolonski, A

    2007-10-17

    We demonstrate a chirped dielectric multilayer mirror (CM) with controlled reflectivity and dispersion in the wavelength range 760-840 nm. It exhibits a reflectivity of >99.9% and a mean group delay dispersion (GDD) of about -30 fs(2) with a theoretical GDD ripple of less than 0.5 fs(2) in the working spectral range. Deviations of the measured GDD from the calculated one are restricted to less than +/- 3 fs(2), limited by our measurement system. Simulations reveal that a dispersive delay line composed of 120 bounces off these mirrors introduces negligible distortion to a femtosecond pulse and largely preserves its contrast. The mirrors constitute an ideal tool for precision intracavity or extracavity dispersion control in the range of several thousand fs(2), particularly if pulses with high contrast are to be generated.

  11. Seed Dispersal Potential of Asian Elephants

    DEFF Research Database (Denmark)

    Harich, Franziska K.; Treydte, Anna Christina; Ogutu, Joseph Ochieng

    2016-01-01

    Elephants, the largest terrestrial mega-herbivores, play an important ecological role in maintaining forest ecosystem diversity. While several plant species strongly rely on African elephants (Loxodonta africana; L. cyclotis) as seed dispersers, little is known about the dispersal potential...... of Asian elephants (Elephas maximus). We examined the effects of elephant fruit consumption on potential seed dispersal using the example of a tree species with mega-faunal characteristics, Dillenia indica L., in Thailand. We conducted feeding trials with Asian elephants to quantify seed survival and gut...... with the longest GPT displayed the highest germination success over time. Unexpectedly, seeds planted with dung had longer germination times than those planted without. We conclude that D. indica does not solely depend on but benefits from dispersal by elephants. The declining numbers of these mega-faunal seed...

  12. Modeling electrical dispersion phenomena in Earth materials

    Directory of Open Access Journals (Sweden)

    D. Patella

    2008-06-01

    Full Text Available It is illustrated that IP phenomena in rocks can be described using conductivity dispersion models deduced as solutions to a 2nd-order linear differential equation describing the motion of a charged particle immersed in an external electrical field. Five dispersion laws are discussed, namely: the non-resonant positive IP model, which leads to the classical Debye-type dispersion law and by extension to the Cole-Cole model, largely used in current practice; the non-resonant negative IP model, which allows negative chargeability values, known in metals at high frequencies, to be explained as an intrinsic physical property of earth materials in specific field cases; the resonant flat, positive or negative IP models, which can explain the presence of peak effects at specific frequencies superimposed on flat, positive or negative dispersion spectra.

  13. Frictionless dispersive hydrodynamics of Stokes flows

    CERN Document Server

    Maiden, Michelle D; Anderson, Dalton V; Schubert, Marika E; Hoefer, Mark A

    2016-01-01

    Effectively frictionless, dispersive flow characterizes superfluids, nonlinear optical diffraction, and geophysical fluid interfaces. Dispersive shock waves (DSWs) and solitons are fundamental nonlinear excitations in these media, but DSW studies to date have been severely constrained by a loss of coherence. Here we report on a novel dispersive hydrodynamics testbed: the effectively frictionless flow of interfacial waves between two high contrast, low Reynolds' number Stokes fluids. This system enables high fidelity observations of large amplitude DSWs, found to agree quantitatively with a nonlinear wave averaging theory. We then report on observations of highly coherent phenomena including DSW backflow, the refraction or absorption of solitons by DSWs, and multi-phase DSW-DSW merger. The complex, coherent, nonlinear mixing of DSWs and solitons observed here are universal features of dissipationless, dispersive hydrodynamic flows.

  14. Adsorption of an anionic dispersant on lignite

    Energy Technology Data Exchange (ETDEWEB)

    Yavuz, R.; Kucukbayrak, S. [Istanbul Technical University, Istanbul (Turkey). Dept. of Chemical Engineering, Chemical & Metallurgical Engineering Faculty

    2001-12-01

    Since coal is not a homogeneous substance but a mixture of carbonaceous materials and mineral matter, it has a variety of surface properties. Therefore, it is not easy to control the properties of coal suspensions by simply adjusting variables, such as pH and/or electrolyte. A chemical agent needs to be added to control the properties of the coal suspensions. The adsorption behavior of an anionic dispersant in the presence of a wetting agent using some Turkish lignite samples was investigated. The effects of dispersant concentration, temperature and pH on the dispersant adsorption were studied systematically, and the experimental results are presented. Pellupur B69 as a dispersant, commercial mixture of formaldehyde condensate sodium salt of naphthalene sulphonic acid, and Texapon N{sub 2}5 as a wetting agent, a sodium lauryl ether sulfate, have been used.

  15. Dispersion of Human Capital and Economic Growth

    OpenAIRE

    Jungsoo Park

    2004-01-01

    Based on a theoretical consideration of human capital production technology, this study empirically investigates the growth implication of dispersion of population distribution in terms of educational attainment levels. Based on a pooled 5-year interval time-series data set of 94 developed and developing countries for 1960 to 1995, the study finds that dispersion index as well as average index of human capital positively influences productivity growth. Given limited social resources for human...

  16. Characterising refractive index dispersion in chalcogenide glasses

    DEFF Research Database (Denmark)

    Fang, Y.; Sojka, L.; Jayasuriya, D.

    2016-01-01

    Much effort has been devoted to the study of glasses that contain the chalcogen elements (sulfur, selenium and tellurium) for photonics' applications out to MIR wavelengths. In this paper we describe some techniques for determining the refractive index dispersion characteristics of these glasses....... Knowledge of material dispersion is critical in delivering step-index fibres including with high numerical aperture for mid-infrared supercontinuum generation....

  17. Calculations of precursor propagation in dispersive dielectrics.

    Energy Technology Data Exchange (ETDEWEB)

    Bacon, Larry Donald

    2003-08-01

    The present study is a numerical investigation of the propagation of electromagnetic transients in dispersive media. It considers propagation in water using Debye and composite Rocard-Powles-Lorentz models for the complex permittivity. The study addresses this question: For practical transmitted spectra, does precursor propagation provide any features that can be used to advantage over conventional signal propagation in models of dispersive media of interest? A companion experimental study is currently in progress that will attempt to measure the effects studied here.

  18. Study of LPG Release & Dispersion Model

    Institute of Scientific and Technical Information of China (English)

    Mu Shanjun; Peng Xiangwei

    2003-01-01

    The current applicable release & dispersion models are reviewed. A typical model is developed on the basis of LPG storage conditions in China and the authors' research. The study is focused on the relationship between LPG composition and release rate, and on the influence of buildings or structures located in the surrounding area on the dispersion of gas plume. The established model is compared with existing models by the use of published field test data.

  19. Dispersive Approach to the Trace Anomaly

    OpenAIRE

    Kawka, N.; Teryaev, O. V.; Veretin, O.L.

    1997-01-01

    In the scalar $\\phi^4$ field model the dispersive approach to the trace anomaly is proposed. It is shown that it is impossible to get dispersion representation for all formfactors so that preserve both the translation and dilatation Ward identities. Subtractions which preserve energy-momentum conservation violate the classical trace Ward--Takahashi identity and give rise to an anomalous contribution to the matrix element of stress tensor $\\theta_\\mu^\

  20. Casein Micelle Dispersions under Osmotic Stress

    OpenAIRE

    Bouchoux, Antoine; Cayemitte, Pierre-Emerson; Jardin, Julien; Gésan-Guiziou, Geneviève; Cabane, Bernard

    2009-01-01

    Casein micelles dispersions have been concentrated and equilibrated at different osmotic pressures using equilibrium dialysis. This technique measured an equation of state of the dispersions over a wide range of pressures and concentrations and at different ionic strengths. Three regimes were found. i), A dilute regime in which the osmotic pressure is proportional to the casein concentration. In this regime, the casein micelles are well separated and rarely interact, whereas the osmotic press...