WorldWideScience

Sample records for fo hafnia silica

  1. Submicrometric gratings fabrication from photosensitive organo-silica-hafnia thin films elaborated by sol-gel processing

    Energy Technology Data Exchange (ETDEWEB)

    Franc, Janyce [Universite de Lyon, F-42023 Saint-Etienne (France); CNRS, UMR 5516, Laboratoire Hubert Curien, 42023 Saint-Etienne (France); Universite de Saint-Etienne, Jean-Monnet, F-42023 Saint-Etienne (France); Barnier, Vincent, E-mail: barnier@emse.fr [Ecole Nationale Superieure des Mines, SMS-EMSE, CNRS:UMR 5146, LCG, F-42023 Saint-Etienne (France); Vocanson, Francis, E-mail: francis.vocanson@univ-st-etienne.fr [Universite de Lyon, F-42023 Saint-Etienne (France); CNRS, UMR 5516, Laboratoire Hubert Curien, 42023 Saint-Etienne (France); Universite de Saint-Etienne, Jean-Monnet, F-42023 Saint-Etienne (France); Gamet, Emilie; Lesage, Maryline [Universite de Lyon, F-42023 Saint-Etienne (France); CNRS, UMR 5516, Laboratoire Hubert Curien, 42023 Saint-Etienne (France); Universite de Saint-Etienne, Jean-Monnet, F-42023 Saint-Etienne (France); Jamon, Damien [Universite de Lyon, F-42023 Saint-Etienne (France); Laboratoire Claude Chappe, Telecom Saint-Etienne, 42000 Saint-Etienne Cedex 2 (France); Universite de Saint-Etienne, Jean-Monnet, F-42023 Saint-Etienne (France); Jourlin, Yves [Universite de Lyon, F-42023 Saint-Etienne (France); CNRS, UMR 5516, Laboratoire Hubert Curien, 42023 Saint-Etienne (France); Universite de Saint-Etienne, Jean-Monnet, F-42023 Saint-Etienne (France)

    2012-07-31

    The aim of this study is the elaboration of a high index sol-gel material in order to prepare submicrometric grating. The gratings were obtained after few seconds of UV exposure in one step using an organically modified silica-hafnia matrix. The chemical composition of thin films after UV and annealing treatments were studied using Fourier Transform Infrared Spectroscopy and X-Ray Photoelectron Spectroscopy. The study of optical properties revealed that the annealed films are transparent from 200 to 1000 nm and have a refractive index from 1.550 to 1.701 depending on the hafnium concentration. - Highlights: Black-Right-Pointing-Pointer Silica-hafnia matrix with high refractive index was prepared using sol-gel process. Black-Right-Pointing-Pointer Organic and inorganic networks formation of thin films was investigated. Black-Right-Pointing-Pointer Optical properties are influenced by annealing treatment and initial hafnium amount. Black-Right-Pointing-Pointer The use of high Si:Hf molar ratio can lead to a loss transmittance below 300 nm. Black-Right-Pointing-Pointer Submicrometric grating period can be prepared using a holographic method.

  2. Effect of electric field distribution on the morphologies of laser-induced damage in hafnia-silica multilayer polarizers

    International Nuclear Information System (INIS)

    Genin, F.Y.; Stolz, C.J.; Reitter, T.; Kozlowski, M.R.; Bevis, R.P.; vonGunten, M.K.

    1997-01-01

    Hafnia-silica multilayer polarizers were deposited by e-beam evaporation onto BK7 glass substrates. The polarizers were designed to operate at 1064 nm at Brewster's angle (56 degree). They were tested with a 3-ns laser pulse at 45, 56, and 65 degree incidence angle in order to vary the electric field distribution in the multilayer, study their effects on damage morphology, and investigate possible advantages of off-use angle laser conditioning. Morphology of the laser-induced damage was characterized by optical and scanning electron microscopy. Four distinct damage morphologies (pit, flat bottom pit, scald, outer layer delamination) were observed; they depend strongly on incident angle of the laser beam. Massive delamination observed at 45 and 56 degree incidence, did not occur at 65 degree; instead, large and deep pits were found at 65 degree. Electric field distribution, temperature rise, and change in stress in the multilayer were calculated to attempt to better understand the relation between damage morphology, electric field peak locations, and maximum thermal stress gradients. The calculations showed a twofold increase in stress change in the hafnia top layers depending on incident angle. Stress gradient in the first hafnia-silica interface was found to be highest for 45, 56, and 65 degree, respectively. Finally, the maximum stress was deeper in the multilayer at 65 degree. Although the limitations of such simple thermal mechanical model are obvious, the results can explain that outer layer delamination is more likely at 45 and 56 degree than 65 degree and that damage sites are expected to be deeper at 65 degree

  3. Sol-Gel Derived Hafnia Coatings

    Science.gov (United States)

    Feldman, Jay D.; Stackpoole, Mairead; Blum, Yigal; Sacks, Michael; Ellerby, Don; Johnson, Sylvia M.; Venkatapathy, Ethiras (Technical Monitor)

    2002-01-01

    Sol-gel derived hafnia coatings are being developed to provide an oxidation protection layer on ultra-high temperature ceramics for potential use in turbine engines (ultra-efficient engine technology being developed by NASA). Coatings using hafnia sol hafnia filler particles will be discussed along with sol synthesis and characterization.

  4. Structure, thermodynamics, and crystallization of amorphous hafnia

    International Nuclear Information System (INIS)

    Luo, Xuhui; Demkov, Alexander A.

    2015-01-01

    We investigate theoretically amorphous hafnia using the first principles melt and quench method. We identify two types of amorphous structures of hafnia. Type I and type II are related to tetragonal and monoclinic hafnia, respectively. We find type II structure to show stronger disorder than type I. Using the phonon density of states, we calculate the specific heat capacity for type II amorphous hafnia. Using the nudged elastic band method, we show that the averaged transition barrier between the type II amorphous hafnia and monoclinic phase is approximately 0.09 eV/HfO 2 . The crystallization temperature is estimated to be 421 K. The calculations suggest an explanation for the low thermal stability of amorphous hafnia

  5. Reactive evaporation of low-defect density hafnia

    International Nuclear Information System (INIS)

    Chow, R.; Falabella, S.; Loomis, G.E.; Rainer, F.; Stolz, C.J.; Kozlowski, M.R.

    1993-01-01

    Motivation for this work includes observations at Lawrence Livermore National Laboratory of a correlation between laser damage thresholds and both the absorption and the nodular-defect density of coatings. Activated oxygen is used to increase the metal-oxidation kinetics at the coated surface during electron-beam deposition. A series of hafnia layers are made with various conditions: two μ-wave configuations, two sources (hafnium and hafnia), and two reactive oxygen pressures. Laser damage thresholds (1064-nm, 10-ns pulses), absorption (at 511 nm), and nodular-defect densities from these coatings are reported. The damage thresholds are observed to increase as the absorption of the coatings decreases. However, no significant increase in damage thresholds are observed with the coatings made from a low nodular-defect density source material (hafnium). Hafnia coatings can be made from hafnium sources that have lower nodular-defect densities, lower absorption, and damage thresholds that are comparable with coatings made from a conventional hafnia source

  6. Assessing hafnium on hafnia as an oxygen getter

    International Nuclear Information System (INIS)

    O'Hara, Andrew; Demkov, Alexander A.; Bersuker, Gennadi

    2014-01-01

    Hafnium dioxide or hafnia is a wide band gap dielectric used in a range of electronic applications from field effect transistors to resistive memory. In many of these applications, it is important to maintain control over oxygen stoichiometry, which can be realized in practice by using a metal layer, specifically hafnium, to getter oxygen from the adjacent dielectric. In this paper, we employ density functional theory to study the thermodynamic stability of an interface between (100)-oriented monoclinic hafnia and hafnium metal. The nudged elastic band method is used to calculate the energy barrier for migration of oxygen from the oxide to the metal. Our investigation shows that the presence of hafnium lowers the formation energy of oxygen vacancies in hafnia, but more importantly the oxidation of hafnium through the migration of oxygen from hafnia is favored energetically

  7. 40 CFR 264.259 - Special requirements for hazardous wastes FO20, FO21, FO22, FO23, FO26, and FO27.

    Science.gov (United States)

    2010-07-01

    ... HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES Waste Piles § 264.259 Special requirements for hazardous wastes FO20, FO21, FO22, FO23, FO26, and FO27. (a) Hazardous Wastes FO20, FO21, FO22, FO23, FO26... requirements are necessary for piles managing hazardous wastes FO20, FO21, FO22, FO23, FO26, and FO27 in order...

  8. 40 CFR 264.231 - Special requirements for hazardous wastes FO20, FO21, FO22, FO23, FO26, and FO27.

    Science.gov (United States)

    2010-07-01

    ... HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES Surface Impoundments § 264.231 Special requirements for hazardous wastes FO20, FO21, FO22, FO23, FO26, and FO27. (a) Hazardous Wastes FO20, FO21, FO22... surface impoundments managing hazardous wastes FO20, FO21, FO22, FO23, FO26, and FO27 in order to reduce...

  9. Oxygen vacancy chain and conductive filament formation in hafnia

    Science.gov (United States)

    Xue, Kan-Hao; Miao, Xiang-Shui

    2018-04-01

    The stability and aggregation mechanisms of oxygen vacancy chains are studied for hafnia using self-energy corrected density functional theory. While oxygen vacancies tend not to align along the c-axis of monoclinic HfO2, oxygen vacancy chains along a-axis and b-axis are energetically favorable, with cohesive energies of 0.05 eV and 0.03 eV per vacancy, respectively. Nevertheless, with an increase of the cross section area, intensive oxygen vacancy chains become much more stable in hafnia, which yields phase separation into Hf-clusters and HfO2. Compared with disperse single vacancy chains, intensive oxygen vacancy chains made of 4, 6, and 8 single vacancy chains are energetically more favorable by 0.17, 0.20, and 0.30 eV per oxygen vacancy, respectively. On the other hand, while a single oxygen vacancy chain exhibits a tiny electronic energy gap of around 0.5 eV, metallic conduction emerges for the intensive vacancy chain made of 8 single vacancy chains, which possesses a filament cross section area of ˜0.4 nm2. This sets a lower area limit for Hf-cluster filaments from metallic conduction point of view, but in real hafnia resistive RAM devices the cross section area of the filaments can generally be much larger (>5 nm2) for the sake of energy minimization. Our work sets up a bridge between oxygen vacancy ordering and phase separation in hafnia, and shows a clear trend of filament stabilization with larger dimensions. The results could explain the threshold switching phenomenon in hafnia when a small AFM tip was used as the top electrode, as well as the undesired multimode operation in resistive RAM cells with 3 nm-thick hafnia.

  10. 40 CFR 264.317 - Special requirements for hazardous wastes FO20, FO21, FO22, FO23, FO26, and FO27.

    Science.gov (United States)

    2010-07-01

    ... HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES Landfills § 264.317 Special requirements for... 40 Protection of Environment 25 2010-07-01 2010-07-01 false Special requirements for hazardous wastes FO20, FO21, FO22, FO23, FO26, and FO27. 264.317 Section 264.317 Protection of Environment...

  11. 40 CFR 264.283 - Special requirements for hazardous wastes FO20, FO21, FO22, FO23, FO26, and FO27.

    Science.gov (United States)

    2010-07-01

    ... HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES Land Treatment § 264.283 Special requirements... 40 Protection of Environment 25 2010-07-01 2010-07-01 false Special requirements for hazardous wastes FO20, FO21, FO22, FO23, FO26, and FO27. 264.283 Section 264.283 Protection of Environment...

  12. Laser damage resistance of hafnia thin films deposited by electron beam deposition, reactive low voltage ion plating, and dual ion beam sputtering

    International Nuclear Information System (INIS)

    Gallais, Laurent; Capoulade, Jeremie; Natoli, Jean-Yves; Commandre, Mireille; Cathelinaud, Michel; Koc, Cian; Lequime, Michel

    2008-01-01

    A comparative study is made of the laser damage resistance of hafnia coatings deposited on fused silica substrates with different technologies: electron beam deposition (from Hf or HfO2 starting material), reactive low voltage ion plating, and dual ion beam sputtering.The laser damage thresholds of these coatings are determined at 1064 and 355 nm using a nanosecond pulsed YAG laser and a one-on-one test procedure. The results are associated with a complete characterization of the samples: refractive index n measured by spectrophotometry, extinction coefficient k measured by photothermal deflection, and roughness measured by atomic force microscopy

  13. Physical property improvement of IZTO thin films using a hafnia buffer layer

    Science.gov (United States)

    Park, Jong-Chan; Kang, Seong-Jun; Choi, Byeong-Gyun; Yoon, Yung-Sup

    2018-01-01

    Hafnia (HfO2) has excellent mechanical and chemical stability, good transmittance, high dielectric constant, and radiation resistance property; thus, it can prevent impurities from permeating into the depositing films. So, we deposited hafnia films with various thicknesses in the range of 0-60 nm on polyethylene naphthalate (PEN) substrates before depositing indium-zinc-tin oxide (IZTO) thin films on them using RF magnetron sputtering, and their structural, morphological, optical, and electrical properties were evaluated. All IZTO thin films were successfully deposited without cracks or pinholes and had amorphous structures. As the thickness of the hafnia film increased to 30 nm, the overall properties improved; a surface roughness of 2.216 nm, transmittance of 82.59% at 550 nm, resistivity of 5.66 × 10-4 Ω cm, sheet resistance of 23.60 Ω/sq, and figure of merit of 6.26 × 10-3 Ω-1 were realized. These results indicate that the structure and materials studied in this research are suitable for application in flexible transparent electronic devices such as organic light emitting diodes, liquid crystal displays, touch panels, and solar cells.

  14. Stabilization of ferroelectric properties in Hafnia and Zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Kersch, Alfred [Univ. of Applied Sciences Munich (Germany). Modeling and Simulation Lab

    2016-11-01

    Experiments by our collaborators show that not only earth alkaline metals but also lanthanides and boron group metals are capable of inducing ferroelectric behavior in Hafnia. These dopants are known to form more complex defect structures due to their 3-valent nature. This requires further simulation. In some cases computationally more expensive density functionals will be required.

  15. XSL-FO

    CERN Document Server

    Pawson, Dave

    2002-01-01

    No matter how flexible and convenient digital information has become, we haven't done away with the need to see information in print. Extensible Style Language-Formatting Objects, or XSL-FO, is a set of tools developers and web designers use to describe page printouts of their XML (including XHTML) documents. If you need to produce high quality printed material from your XML documents, then XSL-FO provides the bridge. XSL-FO is one of the few books to go beyond a basic introduction to the technology. While many books touch on XSL-FO in their treatment of XSLT, this book offers in-depth co

  16. Characterization of electron beam deposited thin films of HfO2 and binary thin films of (HfO2:SiO2) by XRD and EXAFS measurements

    International Nuclear Information System (INIS)

    Das, N.C.; Sahoo, N.K.; Bhattacharyya, D.; Thakur, S.; Kamble, N.M.; Nanda, D.; Hazra, S.; Bal, J.K.; Lee, J.F.; Tai, Y.L.; Hsieh, C.A.

    2009-10-01

    In this report, we have discussed the microstructure and the local structure of composite thin films having varying hafnia and silica compositions and prepared by reactive electron beam evaporation. XRD and EXAFS studies have confirmed that the pure hafnium oxide thin film has crystalline microstructure whereas the films with finite hafnia and silica composition are amorphous. The result of EXAFS analysis has shown that the bond lengths as well as coordination numbers around hafnium atom change with the variation of hafnia and silica compositions in the thin film. Finally, change of bond lengths has been correlated with change of refractive index and band gap of the composite thin films. (author)

  17. Biofilm formation in Hafnia alvei HUMV-5920, a human isolate

    Directory of Open Access Journals (Sweden)

    Itziar Chapartegui-González

    2016-11-01

    Full Text Available Hafnia alvei is a Gram-negative, rodshaped, facultative anaerobic bacterium of the family Enterobacteriaceae that has been isolated from various mammals, fish, insects and birds. In humans, case reports of Hafnia-associated enteric infections have been chiefly reported in Spain. Although H. alvei shares some virulence mechanisms with other Gram-negative enteropathogens little is known about the factors that contribute to its pathogenesis or virulence factors and regulatory circuits that may enhance the establishment and survival of H. alvei in the environment. The goal of the present study was to analyze the capacity of a H. alvei clinical isolate (strain HUMV-5920 to form biofilms. Biofilm formation by this strain increases during growth at 28 °C compared to 37 °C. Investigation of multicellular behavior by confocal microscopy, crystal violet and calcofluor staining in this strain showed biofilm formation associated with the production of cellulose. Importantly, several genes related to cellulose production including bcsABZC and yhjQ are present in the H. alvei HUMV-5920 chromosome. The ability of H. alvei to adhere to abiotic surfaces and to form biofilms likely contributes to its persistence in the hospital environment or food processing environments, increasing the probability of causing infections. Therefore, a better understanding of the adherence properties of this species will provide greater insights into the diseases it causes.

  18. Synthesis of dense yttrium-stabilised hafnia pellets for nuclear applications by spark plasma sintering

    International Nuclear Information System (INIS)

    Tyrpekl, Vaclav; Holzhäuser, Michael; Hein, Herwin; Vigier, Jean-Francois; Somers, Joseph; Svora, Petr

    2014-01-01

    Graphical abstract: Densification of HfO 2 –Y 2 O 3 micro-beads by Spark Plasma Sintering High density pellets with homogenous distribution of Hf and Y serve as neutron absorbers. - Abstract: Dense yttrium–stabilised hafnia pellets (91.35 wt.% HfO 2 and 8.65 wt.% Y 2 O 3 ) were prepared by spark plasma sintering consolidation of micro-beads synthesised by the “external gelation” sol–gel technique. This technique allows a preparation of HfO 2 –Y 2 O 3 beads with homogenous yttria–hafnia solid solution. A sintering time of 5 min at 1600 °C was sufficient to produce high density pellets (over 90% of the theoretical density) with significant reproducibility. The pellets have been machined in a lathe to the correct dimensions for use as neutron absorbers in an experimental test irradiation in the High Flux Reactor (HFR) in Petten, Holland, in order to investigate the safety of americium based nuclear fuels

  19. Recovery of Hafnia alvei from diseased brown trout, Salmo trutta L., and healthy noble crayfish, Astacus astacus (L.), in Bulgaria.

    Science.gov (United States)

    Orozova, P; Sirakov, I; Chikova, V; Popova, R; Al-Harbi, A H; Crumlish, M; Austin, B

    2014-10-01

    Hafnia alvei was isolated in Bulgaria from healthy noble crayfish, Astacus astacus (L.), and then from farmed diseased brown trout, Salmo trutta L., with signs of haemorrhagic septicaemia. The isolates were identified initially with conventional phenotyping and commercial Merlin Micronaut and API 20E rapid identification systems, followed by sequencing of the 16S rRNA gene. Hafnia alvei Bt1, Bt2 and Aa4 were of low virulence to rainbow trout and brown trout, although cytotoxicity was demonstrated by Bt1 and Bt2, but not by Aa4. © 2014 John Wiley & Sons Ltd.

  20. FoAM Kernow Activity Report 2016

    OpenAIRE

    Griffiths, Amber; Griffiths, David

    2016-01-01

    This review shows selected projects from the FoAM Kernow studio in 2016. FoAM is a network of transdisciplinary labs at the intersection of art, science, nature and everyday life. FoAM’s members are generalists - people who work across disparate fields in an entangled, speculative culture. Research and creative projects at FoAM combine elements of futurecrafting, citizen science, prototyping, experience design and process facilitation to re-imagine possible futures, and artistic experime...

  1. FoAM Kernow Activity Report 2017

    OpenAIRE

    Griffiths, Amber; Weatherill, Aidan; Griffiths, David

    2017-01-01

    This review shows selected projects from the FoAM Kernow studio in 2017. FoAM is a network of transdisciplinary labs at the intersection of art, science, nature and everyday life. FoAM’s members are generalists - people who work across disparate fields in an entangled, speculative culture. Research and creative projects at FoAM combine elements of futurecrafting, citizen science, prototyping, experience design and process facilitation to re-imagine possible futures.

  2. Fudecalone, a new anticoccidial agent produced by Penicillium sp. FO-2030.

    Science.gov (United States)

    Tabata, N; Tomoda, H; Masuma, R; Iwai, Y; Omura, S

    1995-01-01

    Penicillium sp. FO-2030, a soil isolate, was found to produce a new anticoccidial compound. The active compound, designated fudecalone, was isolated from the fermentation broth of the producing strain by solvent extraction, silica gel column chromatography and preparative HPLC. The structure of fudecalone was elucidated to be 3,3a,6,6a,7,8,9,10-octahydro-1-hydroxy-4,7,7-trimethyl-1H-naphtho[1,8a- c]furan-6-one mainly by spectroscopic studies including various NMR measurements. The anticoccidial activity using cell systems indicated that schizont formation of monensin-resistant Eimeria tenella was completely inhibited by fudecalone at concentrations more than 16 microM.

  3. FoTotoro

    OpenAIRE

    Valenzuela Bandín, Fernando de

    2014-01-01

    FoTotoro es una obra gráfica de integración, en la que se mezcla la fotografía y las imágenes CG (Computer Graphics) para reconstruir uno de los momentos más icónicos de la película de animación "Mi vecino Totoro". Con este proyecto se pretende lograr una obra de calidad mezclando estos dos recursos multimedia y crear una visión personal del autor de la obra de Hayao Miyazaki "Mi vecino Totoro". FoTotoro és una obra gràfica d'integració, en la qual es barreja la fotografia i les imatges CG...

  4. Andrastins A-C, new protein farnesyltransferase inhibitors produced by Penicillium sp. FO-3929. I. Producing strain, fermentation, isolation, and biological activities.

    Science.gov (United States)

    Omura, S; Inokoshi, J; Uchida, R; Shiomi, K; Masuma, R; Kawakubo, T; Tanaka, H; Iwai, Y; Kosemura, S; Yamamura, S

    1996-05-01

    New protein farnesyltransferase inhibitors, andrastins A-C, have been discovered in the cultured broth of Penicillium sp. FO-3929. Andrastins extracted from broth supernatant were purified by silica gel chromatography, ODS chromatography and HPLC. The IC50 of andrastins A, B, and C against protein farnesyltransferase were 24.9, 47.1, and 13.3 microM, respectively.

  5. Membrane fouling of forward osmosis (FO) membrane for municipal wastewater treatment: A comparison between direct FO and OMBR.

    Science.gov (United States)

    Sun, Yan; Tian, Jiayu; Zhao, Zhiwei; Shi, Wenxin; Liu, Dongmei; Cui, Fuyi

    2016-11-01

    In this work, membrane fouling behavior in a direct forward osmosis (FO) and an osmotic membrane bioreactor (OMBR) for municipal wastewater treatment was systematically investigated and compared. During the long-term operation, much severer flux decline was observed for the direct FO than that for the OMBR. The cake layer was found to be much thicker, together with large amounts of microorganisms growing on the membrane surface in direct FO. Interestingly, no obvious attachment of microorganisms on the membrane surface was observed in the OMBR. The fourier transform infrared spectroscopy (FTIR) and excitation emission matrices (EEM) analyses showed the polysaccharides and proteins were the dominant organic foulants in the fouling layer, and the quantity of the organic substances was also higher in direct FO than that in OMBR. Energy-dispersive X-ray (EDX) results indicated the main inorganic elements in the fouling layer were Ca, Mg, Fe and P, all of which exhibited higher relative percentages in direct FO than that in OMBR. The occurrence of higher contents of microorganisms, organic foulants and inorganic elements in the cake layer caused a higher filtration resistance for the FO membrane in the direct FO. Although more severe membrane fouling was identified in direct FO, the hydraulic and chemical cleaning was more effective on recovering the water permeability of the membrane in direct FO than that in OMBR. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. The Danish FoU Programme

    DEFF Research Database (Denmark)

    Magnussen, Lisbeth; Gottlieb, Susanne; Maaløe, Inger

    I 1999 modtog det danske erhvervsuddannelsessystem Bertelsmann Prisen for dets innovative kapacitet. En af de vigtigste faktorer for den kontinuerlige fornyelse af det danske erhvervsuddannelsessystem er det danske Forsøgs- og Udviklingsprogram (FoU). Publikationen beskriver det danske FoU progra...

  7. Mechanism of the monoclinic-to-tetragonal phase transition induced in zirconia and hafnia by swift heavy ions

    International Nuclear Information System (INIS)

    Benyagoub, Abdenacer

    2005-01-01

    Recent results demonstrated that defect formation or amorphization are not the only structural changes induced by swift heavy ions in crystalline materials and that under certain circumstances crystalline-to-crystalline phase transitions can also occur. For instance, it was found that both zirconia and hafnia transform from the monoclinic to the tetragonal phase with a kinetics involving a double ion impact process. In order to understand the origin of this ion-beam induced phase transition, the behavior of these twin oxides was analyzed and compared. In fact, the likeness of these materials offered the unique opportunity to impose drastic constraints on the possible models proposed to explain the creation of atomic displacements in the wake of swift heavy ions. This comparison clearly suggests that the thermal spike is the most appropriate process which governs the transition from the monoclinic to the tetragonal phase in zirconia and hafnia

  8. Phase evolution and thermal properties of yttria-stabilized hafnia nano-coatings deposited on alumina

    Science.gov (United States)

    Rubio, Ernesto Javier

    High-temperature coatings are critical to the future power-generation systems and industries. Thermal barrier coatings (TBCs), which are usually the ceramic materials applied as thin coatings, protect engine components and allow further increase in engine temperatures for higher efficiency. Thus, the durability and reliability of the coating systems have to be more robust compared to current natural gas based engines. While a near and mid-term target is to develop TBC architecture with a 1300 °C surface temperature tolerance, a deeper understanding of the structure evolution and thermal behavior of the TBC-bond coat interface, specifically the thermally grown oxide (TGO), is of primary importance. In the present work, attention is directed towards yttria-stabilized hafnia (YSH) coatings on alumina (α-Al2O 3) to simulate the TBC-TGO interface and understand the phase evolution, microstructure and thermal oxidation of the coatings. YSH coatings were grown on α-Al2O3 substrates by sputter deposition by varying coating thickness in a wide range ˜30-1000 nm. The effect of coating thickness on the structure, morphology and the residual stress has been investigated using X-ray diffraction (XRD) and high resolution scanning electron microscopy (SEM). Thermal oxidation behavior of the coatings has been evaluated using the isothermal oxidation measurements under static conditions. X-ray diffraction analyses revealed the existence of monoclinic hafnia phase for relatively thin coatings indicating that the interfacial phenomena are dominant in phase stabilization. The evolution towards pure stabilized cubic phase of hafnia with the increasing coating thickness is observed. The SEM results indicate the changes in morphology of the coatings; the average grain size increases from 15 to 500 nm with increasing thickness. Residual stress was calculated employing XRD using the variable ψ-angle. Relation between residual stress and structural change is also studied. The results

  9. Morphologies of laser-induced damage in hafnia-silica multilayer mirror and polarizer coatings

    International Nuclear Information System (INIS)

    Genin, F.Y.; Stolz, C.J.

    1996-08-01

    Hafnium-silica multilayer mirrors and polarizers were deposited by e-beam evaporation onto BK7 glass substrates. The mirrors and polarizers were coated for operation at 1053 nm at 45 degree and at Brewster's angle (56 degree), respectively. They were tested with a single 3-ns laser pulse. Morphology of the laser-induced damage was characterized by optical and scanning electron microscopy. Four distinct damage morphologies were found: pits, flatbottom pits, scalds, and delaminates. The pits and flat bottom pits ( 2 ). The pits seemed to result from ejection of nodular defects by causing local enhancement of the electric field. Scalds and delaminates could be observed at higher fluences (above 13 J/cm 2 ) and seemed to result from the formation of plasmas on the surface. These damage types often originated at pits and were less than 300 μm diameter; their size increased almost linearly with fluence. Finally, effects of the damage on the beam (reflectivity degradation and phase modulations) were measured

  10. Long-term trends of foE and geomagnetic activity variations

    Directory of Open Access Journals (Sweden)

    A. V. Mikhailov

    2003-03-01

    Full Text Available A relationship between foE trends and geomagnetic activity long-term variations has been revealed for the first time. By analogy with earlier obtained results on the foF2 trends it is possible to speak about the geomagnetic control of the foE long-term trends as well. Periods of increasing geomagnetic activity correspond to negative foE trends, while these trends are positive for the decreasing phase of geomagnetic activity. This "natural" relationship breaks down around 1970 (on some stations later when pronounced positive foE trends have appeared on most of the stations considered. The dependence of foE trends on geomagnetic activity can be related with nitric oxide variations at the E-layer heights. The positive foE trends that appeared after the "break down" effect may also be explained by the [NO] decrease which is not related to geomagnetic activity variations. But negative trends or irregular foE variations on some stations for the same time period require some different mechanism. Chemical pollution of the lower thermosphere due to the anthropogenic activity may be responsible for such abnormal foE behavior after the end of the 1960s.Key words. Ionosphere (ionosphere-atmosphere interactions; ionospheric disturbances

  11. First-principles modeling of hafnia-based nanotubes.

    Science.gov (United States)

    Evarestov, Robert A; Bandura, Andrei V; Porsev, Vitaly V; Kovalenko, Alexey V

    2017-09-15

    Hybrid density functional theory calculations were performed for the first time on structure, stability, phonon frequencies, and thermodynamic functions of hafnia-based single-wall nanotubes. The nanotubes were rolled up from the thin free layers of cubic and tetragonal phases of HfO 2 . It was shown that the most stable HfO 2 single-wall nanotubes can be obtained from hexagonal (111) layer of the cubic phase. Phonon frequencies have been calculated for different HfO 2 nanolayers and nanotubes to prove the local stability and to find the thermal contributions to their thermodynamic functions. The role of phonons in stability of nanotubes seems to be negligible for the internal energy and noticeable for the Helmholtz free energy. Zone folding approach has been applied to estimate the connection between phonon modes of the layer and nanotubes and to approximate the nanotube thermodynamic properties. It is found that the zone-folding approximation is sufficiently accurate for heat capacity, but less accurate for entropy. The comparison has been done between the properties of TiO 2 , ZrO 2 , and HfO 2 . © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  12. The Structure of Liquid and Amorphous Hafnia

    Directory of Open Access Journals (Sweden)

    Leighanne C. Gallington

    2017-11-01

    Full Text Available Understanding the atomic structure of amorphous solids is important in predicting and tuning their macroscopic behavior. Here, we use a combination of high-energy X-ray diffraction, neutron diffraction, and molecular dynamics simulations to benchmark the atomic interactions in the high temperature stable liquid and low-density amorphous solid states of hafnia. The diffraction results reveal an average Hf–O coordination number of ~7 exists in both the liquid and amorphous nanoparticle forms studied. The measured pair distribution functions are compared to those generated from several simulation models in the literature. We have also performed ab initio and classical molecular dynamics simulations that show density has a strong effect on the polyhedral connectivity. The liquid shows a broad distribution of Hf–Hf interactions, while the formation of low-density amorphous nanoclusters can reproduce the sharp split peak in the Hf–Hf partial pair distribution function observed in experiment. The agglomeration of amorphous nanoparticles condensed from the gas phase is associated with the formation of both edge-sharing and corner-sharing HfO6,7 polyhedra resembling that observed in the monoclinic phase.

  13. Research on AO/FO batch management technology in aircraft production

    Directory of Open Access Journals (Sweden)

    Yin Haijun

    2018-01-01

    Full Text Available Based on the analysis of the characteristics and significance of AO/FO in the process of aircraft production, this paper analyzes the format rules of AO/FO batch management from the perspective of technology realization, and details the AO/FO The change of the query and the change status tracking, introduces the AO/FO single-stand status display in the batch management, increases the structure definition of the attribute table in the batch management, and designs the relevant algorithm to store and calculate the batch information. Finally, based on the above theory support AO/FO batch management system successfully used in the production of a machine.

  14. Space Weathering of Silicates Simulated by Successive Laser Irradiation: In Situ Reflectance Measurements of Fo90, Fo99+, and Sio2

    Science.gov (United States)

    Loeffler, M. J.; Dukes, C. A.; Christoffersen, R.; Baragiola, R. A.

    2016-01-01

    Pulsed-laser irradiation causes the visible-near-infrared spectral slope of olivine (Fo90 and Fo99+) and SiO2 to increase (redden), while the olivine samples darken and the SiO2 samples brighten slightly. XPS analysis shows that irradiation of Fo90 produces metallic Fe. Analytical SEM and TEM measurements confirm that reddening in the Fo90 olivine samples correlates with the production of nanophase metallic Fe (npFe0) grains, 2050 nm in size. The reddening observed in the SiO2 sample is consistent with the formation of SiO or other SiOx species that absorb in the visible. The weak spectral brightening induced by laser irradiation of SiO2 is consistent with a change in surface topography of the sample. The darkening observed in the olivine samples is likely caused by the formation of larger npFe0 particles, such as the 100400 nm diameter npFe0 identified during our TEM analysis of Fo90 samples. The Fo90 reflectance spectra are qualitatively similar to those in previous experiments suggesting that in all cases formation of npFe0 is causing the spectral alteration. Finally, we find that the accumulation of successive laserpulses cause continued sample darkening in the Vis-NIR, which suggests that repeated surface impacts are an efficient way to darken airless body surfaces.

  15. Properties of fluorosulfate-based ionic liquids and geometries of (FO2SOH)OSO2F- and (FO2SOH)2O2SOF-.

    Science.gov (United States)

    Enomoto, Takeshi; Matsumoto, Kazuhiko; Hagiwara, Rika

    2011-12-14

    A room temperature ionic liquid (IL) based on the fluorosulfate anion (SO(3)F(-)) has been synthesized by the reaction of 1-ethyl-3-methylimidazolium (EMIm(+)) chloride and fluorosulfuric acid (HOSO(2)F). The viscosity, ionic conductivity, and electrochemical window of EMImSO(3)F at 25 °C are 46.6 mPa s, 10.8 mS cm(-1), and 4.3 V, respectively. According to a solvatochromic measurement using ILs, there is a trend in the donor ability of fluoro- and oxofluoroanions, PF(6)(-) OSO(2)F and EMIm(FO(2)SOH)(2)O(2)SOF, respectively. Both the salts are liquid at room temperature without a HOSO(2)F dissociation pressure (OSO(2)F and 5.1 mPa s and 43.2 mS cm(-1) for EMIm(FO(2)SOH)(2)O(2)SOF). The vibrational modes and bonding properties of these anionic species are discussed with the aid of quantum mechanical calculations. The (FO(2)SOH)OSO(2)F(-) anion in EMIm(FO(2)SOH)OSO(2)F does not have an inversion centre, which stands in contrast to the one with an inversion centre (e.g. observed in solid Cs(FO(2)SOH)OSO(2)F). The (FO(2)SOH)(2)O(2)SOF(-) anion in EMIm(FO(2)SOH)(2)O(2)SOF is characterized by vibrational spectroscopy under C(s) symmetry.

  16. Complete genome sequence of a commensal bacterium, Hafnia alvei CBA7124, isolated from human feces.

    Science.gov (United States)

    Song, Hye Seon; Kim, Joon Yong; Kim, Yeon Bee; Jeong, Myeong Seon; Kang, Jisu; Rhee, Jin-Kyu; Kwon, Joseph; Kim, Ju Suk; Choi, Jong-Soon; Choi, Hak-Jong; Nam, Young-Do; Roh, Seong Woon

    2017-01-01

    Members of the genus Hafnia have been isolated from the feces of mammals, birds, reptiles, and fish, as well as from soil, water, sewage, and foods. Hafnia alvei is an opportunistic pathogen that has been implicated in intestinal and extraintestinal infections in humans. However, its pathogenicity is still unclear. In this study, we isolated H. alvei from human feces and performed sequencing as well as comparative genomic analysis to better understand its pathogenicity. The genome of H. alvei CBA7124 comprised a single circular chromosome with 4,585,298 bp and a GC content of 48.8%. The genome contained 25 rRNA genes (9 5S rRNA genes, 8 16S rRNA genes, and 8 23S rRNA genes), 88 tRNA genes, and 4043 protein-coding genes. Using comparative genomic analysis, the genome of this strain was found to have 72 strain-specific singletons. The genome also contained genes for antibiotic and antimicrobial resistance, as well as toxin-antitoxin systems. We revealed the complete genome sequence of the opportunistic gut pathogen, H. alvei CBA7124. We also performed comparative genomic analysis of the sequences in the genome of H. alvei CBA7124, and found that it contained strain-specific singletons, antibiotic resistance genes, and toxin-antitoxin systems. These results could improve our understanding of the pathogenicity and the mechanism behind the antibiotic resistance of H. alvei strains.

  17. High historical values of foEs—Reality or artefact?

    Science.gov (United States)

    Laštovička, J.; Boška, J.; Burešová, D.; Kouba, D.

    2012-01-01

    Very high values of foEs had sometimes been reported in the past. These values, as well as all other ionogram-scaled values, had been derived from ionograms under the assumption of the vertical reflection of ordinary mode of sounding radio waves. In the past it was impossible to check the validity of this assumption. However, modern digisondes determine clearly the oblique or extraordinary mode reflections. To test the assumption of the vertical reflection of ordinary mode for high values of foEs, seven summers (June 2004-August 2010) from a midlatitude station Pruhonice are chosen. All hourly values of foEs≥6.0 MHz are selected from this data set, altogether 282 values. In 90% of cases the “classical” way of evaluation of foEs provides values higher than “true” values from modern digisonde (average difference about 1 MHz). 38% of “classical” foEs are oblique reflections, which however do not occur in direction perpendicular to geomagnetic field. The occurrence of high values of foEs varies very much from year to year between 0 and 130 events per year. As for diurnal variation, a pronounced maximum occurs at ˜10:00LT and 16:00LT (secondary), and a minimum after midnight.

  18. Introducing the concept of critical Fo in batch heat processing Introduzindo o conceito de Fo crítico no processamento térmico em batelada

    Directory of Open Access Journals (Sweden)

    Homero Ferracini Gumerato

    2009-12-01

    Full Text Available The determination of the sterilization value for low acid foods in retorts includes a critical evaluation of the factory's facilities and utilities, validation of the heat processing equipment (by heat distribution assays, and finally heat penetration assays with the product. The intensity of the heat process applied to the food can be expressed by the Fo value (sterilization value, in minutes, at a reference temperature of 121.1 °C, and a thermal index, z, of 10 °C, for Clostridium botulinum spores. For safety reasons, the lowest value for Fo is frequently adopted, being obtained in heat penetration assays as indicative of the minimum process intensity applied. This lowest Fo value should always be higher than the minimum Fo recommended for the food in question. However, the use of the Fo value for the coldest can fail to statistically explain all the practical occurrences in food heat treatment processes. Thus, as a result of intense experimental work, we aimed to develop a new focus to determine the lowest Fo value, which we renamed the critical Fo. The critical Fo is based on a statistical model for the interpretation of the results of heat penetration assays in packages, and it depends not only on the Fo values found at the coldest point of the package and the coldest point of the equipment, but also on the size of the batch of packages processed in the retort, the total processing time in the retort, and the time between CIPs of the retort. In the present study, we tried to explore the results of physical measurements used in the validation of food heat processes. Three examples of calculations were prepared to illustrate the methodology developed and to introduce the concept of critical Fo for the processing of canned food.A determinação do valor de esterilização de alimentos de baixa acidez em autoclaves compreende uma minuciosa avaliação das instalações e utilidades da fábrica, uma validação do equipamento de processo t

  19. Torque-coupled thermodynamic model for FoF1 -ATPase

    Science.gov (United States)

    Ai, Guangkuo; Liu, Pengfei; Ge, Hao

    2017-05-01

    FoF1 -ATPase is a motor protein complex that utilizes transmembrane ion flow to drive the synthesis of adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and phosphate (Pi). While many theoretical models have been proposed to account for its rotary activity, most of them focus on the Fo or F1 portions separately rather than the complex as a whole. Here, we propose a simple but new torque-coupled thermodynamic model of FoF1 -ATPase. Solving this model at steady state, we find that the monotonic variation of each portion's efficiency becomes much more robust over a wide range of parameters when the Fo and F1 portions are coupled together, as compared to cases when they are considered separately. Furthermore, the coupled model predicts the dependence of each portion's kinetic behavior on the parameters of the other. Specifically, the power and efficiency of the F1 portion are quite sensitive to the proton gradient across the membrane, while those of the Fo portion as well as the related Michaelis constants for proton concentrations respond insensitively to concentration changes in the reactants of ATP synthesis. The physiological proton gradient across the membrane in the Fo portion is also shown to be optimal for the Michaelis constants of ADP and phosphate in the F1 portion during ATP synthesis. Together, our coupled model is able to predict key dynamic and thermodynamic features of the FoF1 -ATPase in vivo semiquantitatively, and suggests that such coupling approach could be further applied to other biophysical systems.

  20. Young-infant Sepsis Combined with Urinary Tract Infection Due to Hafnia alvei

    Directory of Open Access Journals (Sweden)

    Chia-Hung Liu

    2007-01-01

    Full Text Available Hafnia alvei infections are uncommon and occur mainly in adult patients featuring underlying illnesses. Its isolation in pediatric cases is even more unusual. We report a rare case of sepsis combined with urinary tract infection caused by H. alvei in a 39-day-old infant who did not appear to feature any underlying disease. The infant was successfully treated with ceftriaxone over a 14-day period. In this case, we want to remind clinicians that the possibility of an extraintestinal invasive infection such as bacteremia or urinary tract infection caused by H. alvei should be taken into account in young infants who feature no apparent underlying disease. [J Formos Med Assoc 2007;106(3 Suppl:S39-S43

  1. Treatment of Medical Radioactive Liquid Waste Using Forward Osmosis (FO) Membrane Process

    KAUST Repository

    Lee, Songbok

    2018-04-07

    The use of forward osmosis (FO) for concentrating radioactive liquid waste from radiation therapy rooms in hospitals was systematically investigated in this study. The removal of natural and radioactive iodine using FO was first investigated with varying pHs and draw solutions (DSs) to identify the optimal conditions for FO concentration. Results showed that FO had a successful rejection rate for both natural and radioactive iodine (125I) of up to 99.3%. This high rejection rate was achieved at a high pH, mainly due to electric repulsion between iodine and membrane. Higher iodine removal by FO was also attained with a DS that exhibits a reverse salt flux (RSF) adequate to hinder iodine transport. Following this, actual radioactive medical liquid waste was collected and concentrated using FO under these optimal conditions. The radionuclides in the medical waste (131I) were removed effectively, but the water recovery rate was limited due to severe membrane fouling. To enhance the recovery rate, hydraulic washing was applied, but this had only limited success due to combined organic-inorganic fouling of the FO membrane. Finally, the effect of FO concentration on the reduction of septic tank volume was simulated as a function of recovery rate. To our knowledge, this study is the first attempt to explore the potential of FO technology for treating radioactive waste, and thus could be expanded to the dewatering of the radioactive liquid wastes from a variety of sources, such as nuclear power plants.

  2. NiO and Fe/Mn in Fo-rich olivines from OIB, MORB, and mantle peridotites

    Science.gov (United States)

    Li, H.; Baker, M.; Hofmann, A. E.; Clague, D.; Stolper, E.

    2006-12-01

    Olivines from mantle peridotites have a narrow range of NiO (0.36±0.03 [1σ] wt%), but NiO of olivines in basalts suggest NiO in mantle olivines is actually more variable: e.g., Hawaiian phenocrysts (Fo>90) have NiO >0.55%, and olivines from continental flood basalts can have >0.5% NiO. At the other end of the spectrum, some basaltic suites (e.g., Iceland, MORBs) have Fo>90 olivines with NiO >0.2%. Partial melting calculations on peridotites show it is difficult to generate liquids that crystallize Fo>90 olivines with >0.4% NiO without resorting to complex processes. Hypotheses to explain the variability of NiO in mantle-derived olivines include (1) reaction of peridotite with silica-rich melts of eclogite results in decreasing modal abundance of olivine and increasing NiO in olivine [1,2]; (2) magmas with NiO-rich olivines come from sources enriched in NiO due to a core-derived component [3]. [4] proposed that high Fe/Mn of Hawaiian vs. Icelandic and MORB lavas reflect a core-derived component in their sources. Possible core incorporation is poorly constrained but FeO and NiO are expected to increase by such processes, leading to correlations between NiO and Fe/Mn in mantle rocks with significant core-derived components. We present high-precision analyses of Fo-rich olivines from OIBs, MORBs, komatiites, and mantle peridotites, focusing on NiO contents and Fe/Mn ratios. Our goal is to test hypotheses to explain elevated NiO of Fo-rich olivines in basalts. Olivines are Fo85.1-93.4; more were analyzed, but we focused on this range to avoid complications due to decreasing NiO in olivine with crystallization. Errors (1σ) are 0.01 wt% in NiO and 1.5 in Fe/Mn (wt). Our data show several features: (1) NiO contents and Fe/Mn ratios of Fo>88 olivines are positively correlated, with the low end of the trend (NiO ~0.23%, Fe/Mn ~61) defined by MORB and Iceland and the high end of the trend (NiO ~0.55%, Fe/Mn ~80) by Reunion and Hawaii. Between these end points, there is a

  3. Osmotically and thermally isolated forward osmosis-membrane distillation (fo-md) integrated module for water treatment applications

    KAUST Repository

    Ghaffour, Noreddine

    2016-09-01

    An integrated forward osmosis-membrane distillation (FO-MD) module and systems and methods incorporating the module is disclosed providing higher efficiencies and using less energy. The FO-MD module is osmotically and thermally isolated. The isolation can prevent mixing of FO draw solution/FO permeate and MD feed, and minimize dilution of FO draw solution and cooling of MD feed. The module provides MD feed solution and FO draw solution streams that flow in the same module but are separated by an isolation barrier. The osmotically and thermally isolated FO-MD integrated module, systems and methods offer higher driving forces of both FO and MD processes, higher recovery, and wider application than previously proposed hybrid FO- MD systems.

  4. Osmotically and thermally isolated forward osmosis-membrane distillation (fo-md) integrated module for water treatment applications

    KAUST Repository

    Ghaffour, NorEddine; Francis, Lijo; Li, Zhenyu; Valladares, Rodrigo; Alsaadi, Ahmad S.; Ghdaib, Muhannad Abu; Amy, Gary L.

    2016-01-01

    An integrated forward osmosis-membrane distillation (FO-MD) module and systems and methods incorporating the module is disclosed providing higher efficiencies and using less energy. The FO-MD module is osmotically and thermally isolated. The isolation can prevent mixing of FO draw solution/FO permeate and MD feed, and minimize dilution of FO draw solution and cooling of MD feed. The module provides MD feed solution and FO draw solution streams that flow in the same module but are separated by an isolation barrier. The osmotically and thermally isolated FO-MD integrated module, systems and methods offer higher driving forces of both FO and MD processes, higher recovery, and wider application than previously proposed hybrid FO- MD systems.

  5. Day-to-day variability of foEs in the equatorial ionosphere

    Science.gov (United States)

    Somoye, E. O.; Akala, A. O.; Adeniji-Adele, R. A.; Onori, E. O.; Ogwala, A.; Karimu, A. O.

    2013-09-01

    seasonal, and solar cycle effects of the variability (VR) of the critical frequency of sporadic E layer (foEsq) are investigated at Ibadan (7.4°N, 3.9°E, 6°S dip) in the African sector during high solar activity (HSA) year of 1958 (Rz = 181), moderate solar activity (MSA) year of 1973 (Rz = 30), and low solar activity (LSA) year of 1965 (Rz = 17). The diurnal variation of foEsq VR is characterized by post-midnight (32%-78%) and pre-midnight (20%-84%) peaks during high solar activity (HSA), the only epoch of the three showing these peaks and a diurnal trend. While the daytime foEsq VRs of the three epochs show no seasonal trend, pre-midnight and post-midnight, the foEsq VRs during HSA and LSA show seasonal trends. Similarity is observed in the curve of reciprocal of percentage occurrence of Esq and that of foEsq VR, indicating inverse variation of percentage occurrence and foEsq VR. Longitudinal influence is observed in the diurnal variation of HSA and MSA July foEsq VR of Ibadan (7.4°N, 3.9°E, 6°S dip) in the African sector, which is in the neighborhood of the Greenwich Meridian (GM); Singapore (1.3°N, 108.3°E, 17.6°S dip) in the Asian sector, east of GM; and Huancayo (12°S, 284.7°E, 1.90 dip) in the American sector, west of GM.

  6. Lorenzo Foà (1937 - 2014)

    CERN Multimedia

    2014-01-01

    Lorenzo Foà, a protagonist of Experimental High Energy Physics for five decades and mentor of dozens of students, passed away peacefully and unexpectedly in Pisa on 13 January 2014. He was a professor at the Scuola Normale Superiore in Pisa and spent most of his scientific career at CERN.   Lorenzo Foà (left) in front of the ALEPH detector, 2001. He is photographed with Jack Steinberger (centre) and Pierre Lazeyras (right). In the early 1960s Lorenzo was among the proponents of two experiments that allowed the first measurements of π0 and η lifetimes via the Primakoff effect at Frascati and then at DESY. Later he joined the CERN-Orsay-Pisa Collaboration, studying polarisation in hadron scattering, and then the Pisa-Stony Brook Collaboration at the CERN ISR. This experiment discovered that the total proton-proton cross section starts increasing at ISR energies, a departure from what had previously appeared to be a flat “asymptotic” beha...

  7. Investigation of the relationship between ionospheric foF2 and earthquakes

    Science.gov (United States)

    Karaboga, Tuba; Canyilmaz, Murat; Ozcan, Osman

    2018-04-01

    Variations of the ionospheric F2 region critical frequency (foF2) have been investigated statistically before earthquakes during 1980-2008 periods in Japan area. Ionosonde data was taken from Kokubunji station which is in the earthquake preparation zone for all earthquakes. Standard Deviations and Inter-Quartile Range methods are applied to the foF2 data. It is observed that there are anomalous variations in foF2 before earthquakes. These variations can be regarded as ionospheric precursors and may be used for earthquake prediction.

  8. Removal of organic micro-pollutants (phenol, aniline and nitrobenzene) via forward osmosis (FO) process: Evaluation of FO as an alternative method to reverse osmosis (RO)

    KAUST Repository

    Cui, Yue

    2016-01-05

    In this study, we have explored and compared the effectiveness of using (1) lab-fabricated forward osmosis (FO) membranes under both FO and reverse osmosis (RO) modes and (2) commercially available RO membranes under the RO mode for the removal of organic micro-pollutants. The lab-fabricated FO membranes are thin film composite (TFC) membranes consisting of a polyamide layer and a porous substrate cast from three different materials; namely, Matrimid, polyethersulfone (PESU) and sulfonated polyphenylene sulfone (sPPSU). The results show that the FO mode is superior to the RO mode in the removal of phenol, aniline and nitrobenzene from wastewater. The rejections of all three TFC membranes to all the three organic micro-pollutants under the FO processes are higher than 72% and can be even higher than 90% for aniline when a 1000 ppm aromatic aqueous solution and 1 M NaCl are employed as feeds. These performances outperform the results obtained from themselves and commercially available RO membranes under the RO mode. In addition, the rejection can be maintained even when treating a more concentrated feed solution (2000 ppm). The removal performance can be further enhanced by using a more concentrated draw solution (2 M). The water flux is almost doubled, and the rejection increment can reach up to 17%. Moreover, it was observed that annealing as a post-treatment would help compact the membrane selective layer and further enhance the separating efficiency. The obtained organic micro-pollutant rejections and water fluxes under various feasible operating conditions indicate that the FO process has potential to be a viable treatment for wastewater containing organic micro-pollutants.

  9. Removal of organic micro-pollutants (phenol, aniline and nitrobenzene) via forward osmosis (FO) process: Evaluation of FO as an alternative method to reverse osmosis (RO).

    Science.gov (United States)

    Cui, Yue; Liu, Xiang-Yang; Chung, Tai-Shung; Weber, Martin; Staudt, Claudia; Maletzko, Christian

    2016-03-15

    In this study, we have explored and compared the effectiveness of using (1) lab-fabricated forward osmosis (FO) membranes under both FO and reverse osmosis (RO) modes and (2) commercially available RO membranes under the RO mode for the removal of organic micro-pollutants. The lab-fabricated FO membranes are thin film composite (TFC) membranes consisting of a polyamide layer and a porous substrate cast from three different materials; namely, Matrimid, polyethersulfone (PESU) and sulfonated polyphenylene sulfone (sPPSU). The results show that the FO mode is superior to the RO mode in the removal of phenol, aniline and nitrobenzene from wastewater. The rejections of all three TFC membranes to all the three organic micro-pollutants under the FO processes are higher than 72% and can be even higher than 90% for aniline when a 1000 ppm aromatic aqueous solution and 1 M NaCl are employed as feeds. These performances outperform the results obtained from themselves and commercially available RO membranes under the RO mode. In addition, the rejection can be maintained even when treating a more concentrated feed solution (2000 ppm). The removal performance can be further enhanced by using a more concentrated draw solution (2 M). The water flux is almost doubled, and the rejection increment can reach up to 17%. Moreover, it was observed that annealing as a post-treatment would help compact the membrane selective layer and further enhance the separating efficiency. The obtained organic micro-pollutant rejections and water fluxes under various feasible operating conditions indicate that the FO process has potential to be a viable treatment for wastewater containing organic micro-pollutants. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Sustainable water recovery from oily wastewater via forward osmosis-membrane distillation (FO-MD).

    Science.gov (United States)

    Zhang, Sui; Wang, Peng; Fu, Xiuzhu; Chung, Tai-Shung

    2014-04-01

    This study proposed and investigated a hybrid forward osmosis - membrane distillation (FO-MD) system for sustainable water recovery from oily wastewater by employing lab-fabricated FO and MD hollow fiber membranes. Stable oil-in-water emulsions of different concentrations with small droplet sizes (oil droplets and partial permeation of acetic acid could be achieved. Finally, an integrated FO-MD system was developed to treat the oily wastewater containing petroleum, surfactant, NaCl and acetic acid at 60 °C in the batch mode. The water flux in FO undergoes three-stage decline due to fouling and reduction in osmotic driving force, but is quite stable in MD regardless of salt concentration. Oily wastewater with relatively high salinity could be effectively recovered by the FO-MD hybrid system while maintaining large water flux, at least 90% feed water recovery could be readily attained with only trace amounts of oil and salts, and the draw solution was re-generated for the next rounds of FO-MD run. Interestingly, significant amount of acetic acid was also retained in the permeate for further reuse as a chemical additive during the production of crude oil. The work has demonstrated that not only water but also organic additives in the wastewater could be effectively recovered by FO-MD systems for reuse or other utilizations. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. Role of Vertical Larynx Movement and Cervical Lordosis in FO Control.

    Science.gov (United States)

    Honda, Kiyoshi; Hirai, Hiroyuki; Masaki, Shinobu; Shimada, Yasuhiro

    1999-01-01

    Functional characteristics of the cervical structures of the larynx are investigated in search of physiological mechanisms of extralaryngeal FO control. Mean Response Time experiments were performed to record the positions of the articulators and the larynx during vowel production with different FO values. (Author/VWL)

  12. Long-term trends in foF2: their estimating and origin

    Directory of Open Access Journals (Sweden)

    W. Wan

    2008-03-01

    Full Text Available This paper deals with two problems, methods of foF2 trend determination and origin of trends in foF2, both being controversial in current literature. We found that various regression-based methods and artificial neural network-based method of Yue et al. (2006 provided comparable results within uncertainties caused mainly by various ways of removing/suppressing the dominant solar cycle effect. The role of geomagnetic activity in the observed trends in foF2 was probably substantial and might be still even rather dominant in the last quarter of the 20th century.

  13. What is next for forward osmosis (FO) and pressure retarded osmosis (PRO)

    KAUST Repository

    Chung, Neal Tai-Shung

    2015-10-29

    This short review summarizes our understanding and perspectives on FO and PRO processes and meaningful R & D in order to develop effective and sustainable FO and PRO technologies for water reuse and osmotic power generation.

  14. What is next for forward osmosis (FO) and pressure retarded osmosis (PRO)

    KAUST Repository

    Chung, Neal Tai-Shung; Luo, Lin; Wan, Chun Feng; Cui, Yue; Amy, Gary L.

    2015-01-01

    This short review summarizes our understanding and perspectives on FO and PRO processes and meaningful R & D in order to develop effective and sustainable FO and PRO technologies for water reuse and osmotic power generation.

  15. A mechanism of midlatitude noontime foE long-term variations inferred from European observations

    Science.gov (United States)

    Mikhailov, A. V.; Perrone, L.; Nusinov, A. A.

    2017-04-01

    Manually scaled June noontime monthly median foE values at three European stations Rome, Juliusruh, and Slough/Chilton were used to understand the mechanism of foE long-term variations. The 11 year running mean smoothed foE manifests long-term (for some solar cycles) variations with the rising phase at the end of 1960-1985 and the falling phase after 1985. A close relationship (even in details) between (foEave)11y and (R12)11y variations with the correlation coefficient of 0.996 (absolutely significant according to Fisher F criterion) suggests that the Sun is the source of these (foEave)11y long-term variations. After removing solar activity long-term variations the residual (foEave)11y trend is very small ( 0.029% per decade) being absolutely insignificant. This means that all (foEave)11y variations are removed with one solar activity index, (R12)11y, i.e., this means that long-term variations are fully controlled by solar activity. Theory of midlatitude daytime E region tells us that long-term variations of solar EUV in two lines λ = 977 Å (CIII) and λ = 1025.7 Å (HLyβ) and X-ray radiation with λ foE long-term variations have a natural (not anthropogenic) origin related to long-term variations of solar activity. No peculiarities in relation with the last deep solar minimum in 2008-2009 have been revealed.

  16. Treatment of Medical Radioactive Liquid Waste Using Forward Osmosis (FO) Membrane Process

    KAUST Repository

    Lee, Songbok; Kim, Youngjin; Park, Jungmi; Shon, Ho Kyong; Hong, Seungkwan

    2018-01-01

    , hydraulic washing was applied, but this had only limited success due to combined organic-inorganic fouling of the FO membrane. Finally, the effect of FO concentration on the reduction of septic tank volume was simulated as a function of recovery rate. To our

  17. Cyclophilin D Promotes Brain Mitochondrial F1FO ATP Synthase Dysfunction in Aging Mice.

    Science.gov (United States)

    Gauba, Esha; Guo, Lan; Du, Heng

    2017-01-01

    Brain aging is the known strongest risk factor for Alzheimer's disease (AD). In recent years, mitochondrial deficits have been proposed to be a common mechanism linking brain aging to AD. Therefore, to elucidate the causative mechanisms of mitochondrial dysfunction in aging brains is of paramount importance for our understanding of the pathogenesis of AD, in particular its sporadic form. Cyclophilin D (CypD) is a specific mitochondrial protein. Recent studies have shown that F1FO ATP synthase oligomycin sensitivity conferring protein (OSCP) is a binding partner of CypD. The interaction of CypD with OSCP modulates F1FO ATP synthase function and mediates mitochondrial permeability transition pore (mPTP) opening. Here, we have found that increased CypD expression, enhanced CypD/OSCP interaction, and selective loss of OSCP are prominent brain mitochondrial changes in aging mice. Along with these changes, brain mitochondria from the aging mice demonstrated decreased F1FO ATP synthase activity and defective F1FO complex coupling. In contrast, CypD deficient mice exhibited substantially mitigated brain mitochondrial F1FO ATP synthase dysfunction with relatively preserved mitochondrial function during aging. Interestingly, the aging-related OSCP loss was also dramatically attenuated by CypD depletion. Therefore, the simplest interpretation of this study is that CypD promotes F1FO ATP synthase dysfunction and the resultant mitochondrial deficits in aging brains. In addition, in view of CypD and F1FO ATP synthase alterations seen in AD brains, the results further suggest that CypD-mediated F1FO ATP synthase deregulation is a shared mechanism linking mitochondrial deficits in brain aging and AD.

  18. Inhibition of the early stage of Salmonella enterica serovar Enteritidis biofilm development on stainless steel by cell-free supernatant of a Hafnia alvei culture.

    Science.gov (United States)

    Chorianopoulos, Nikos G; Giaouris, Efstathios D; Kourkoutas, Yiannis; Nychas, George-John E

    2010-03-01

    Compounds present in Hafnia alvei cell-free culture supernatant cumulatively negatively influence the early stage of biofilm development by Salmonella enterica serovar Enteritidis on stainless steel while they also reduce the overall metabolic activity of S. Enteritidis planktonic cells. Although acylhomoserine lactones (AHLs) were detected among these compounds, the use of several synthetic AHLs was not able to affect the initial stage of biofilm formation by this pathogen.

  19. Variability study of foF2 for an equatorial station

    International Nuclear Information System (INIS)

    Adeniyi, J.O.; Radicella, S.M.; Adimula, I.A.

    1994-08-01

    The deviation of hourly values of foF 2 from the monthly median values was used to study the variability of foF 2 . The study was done for the period of high and low solar activity. Generally the range of variation of the deviation is not dependent on solar activity. There is a tendency for positive deviation to occur on magnetically disturbed days and for negative deviation to occur on quiet days. The magnitude of the deviation does not depend on whether the day is disturbed or quiet. The correlation between Ap index and deviation of foF 2 from the median value is generally poor. THe range of deviation at night is usually higher than that of the daytime for the period of high solar activity. Some seasonal effect were also observed on the deviation. (author). 4 refs, 5 figs, 3 tabs

  20. Jordanian silica sand and cement as a reinforcement material for polystyrene matrix composites

    International Nuclear Information System (INIS)

    Jalham, S. I.

    1999-01-01

    The behaviour of polystyrene matrix composites with different percentages of Jordaanian Silica Sand as a Reinforcement Materials (0, 5, 25, 50, and 75 wt%) and different mean grain sizes of sand particles (60, 75, 85, and 300μ m) and with cement as a boning materials in the amount fo 1/6 wt% of the wt% of silica sand were manufactured and tested under compression loading in the Industrial Engineering Department as the Uninersity of Jordan as a part of large study on local materials. The main conclusions of this investigation are: a long-term, durable structure of the polystyrene composite reinforced by silica sand and cement was achieved by mixing the constituents with water; the higher the volume fraction of the reinforcement, the higher the volume fraction of reinforcement, the higher the strength while for 75% of reinforcement, the strength dropped to an amount less than that of the matrix; the higher the grain size, the higher the strength; longitudinal brittle fracture was observed for the composites, and a homogeneous distribution of the sand particles helped in increasing the strength of the composite by playing an important role in distributing the applied load. (author). 11 refs., 6 tabs, 2 figs

  1. Hybrid SBR–FO system for wastewater treatment and reuse: Operation, fouling and cleaning

    KAUST Repository

    Valladares Linares, Rodrigo

    2016-04-05

    Forward osmosis (FO) is a novel membrane separation process that potentially can be used as an energy-saving alternative to conventional membrane processes. A hybrid sequential batch reactor (SBR)–FO process was explored. In this system, a plate and frame FO cell including two flat-sheet FO membranes was submerged in a bioreactor treating synthetic domestic wastewater. The dissolved organic carbon (DOC) removal efficiency of the system was 98.55%. Total nitrogen removal was 62.4%, with nitrate, nitrite and ammonium removals of 58.4%, 96.2% and 88.4%, respectively. Phosphate removal was almost 100%. The 15-hour cycle average water flux of a virgin membrane with air scouring was 2.95 L/m2·h− 1. Air scouring can help to remove loose foulants from the membrane active layer, thus helping to recover up to 89.5% of the original flux. Chemical cleaning of the fouled active layer of the FO membrane was not as effective as air scouring. Natural organic matter (NOM) characterization methods (liquid chromatography–organic carbon detection (LC–OCD) and 3-D fluorescence excitation emission matrix (FEEM)) show that the FO membrane has a very good performance in rejecting biopolymers, humics and building blocks, but a limited ability in rejecting low molecular weight neutrals. Transparent exopolymer particles (TEP) and other biopolymers might be associated with fouling of the membrane on the support layer. A 1% sodium hypochlorite (NaOCl) cleaning solution was proved to be effective for removing the foulants from the support layer and recovering the original flux.

  2. Efficiently Combining Water Reuse and Desalination through Forward Osmosis-Reverse Osmosis (FO-RO) Hybrids: A Critical Review.

    Science.gov (United States)

    Blandin, Gaetan; Verliefde, Arne R D; Comas, Joaquim; Rodriguez-Roda, Ignasi; Le-Clech, Pierre

    2016-07-01

    Forward osmosis (FO) is a promising membrane technology to combine seawater desalination and water reuse. More specifically, in a FO-reverse osmosis (RO) hybrid process, high quality water recovered from the wastewater stream is used to dilute seawater before RO treatment. As such, lower desalination energy needs and/or water augmentation can be obtained while delivering safe water for direct potable reuse thanks to the double dense membrane barrier protection. Typically, FO-RO hybrid can be a credible alternative to new desalination facilities or to implementation of stand-alone water reuse schemes. However, apart from the societal (public perception of water reuse for potable application) and water management challenges (proximity of wastewater and desalination plants), FO-RO hybrid has to overcome technical limitation such as low FO permeation flux to become economically attractive. Recent developments (i.e., improved FO membranes, use of pressure assisted osmosis, PAO) demonstrated significant improvement in water flux. However, flux improvement is associated with drawbacks, such as increased fouling behaviour, lower rejection of trace organic compounds (TrOCs) in PAO operation, and limitation in FO membrane mechanical resistance, which need to be better considered. To support successful implementation of FO-RO hybrid in the industry, further work is required regarding up-scaling to apprehend full-scale challenges in term of mass transfer limitation, pressure drop, fouling and cleaning strategies on a module scale. In addition, refined economics assessment is expected to integrate fouling and other maintenance costs/savings of the FO/PAO-RO hybrid systems, as well as cost savings from any treatment step avoided in the water recycling.

  3. Efficiently Combining Water Reuse and Desalination through Forward Osmosis—Reverse Osmosis (FO-RO Hybrids: A Critical Review

    Directory of Open Access Journals (Sweden)

    Gaetan Blandin

    2016-07-01

    Full Text Available Forward osmosis (FO is a promising membrane technology to combine seawater desalination and water reuse. More specifically, in a FO-reverse osmosis (RO hybrid process, high quality water recovered from the wastewater stream is used to dilute seawater before RO treatment. As such, lower desalination energy needs and/or water augmentation can be obtained while delivering safe water for direct potable reuse thanks to the double dense membrane barrier protection. Typically, FO-RO hybrid can be a credible alternative to new desalination facilities or to implementation of stand-alone water reuse schemes. However, apart from the societal (public perception of water reuse for potable application and water management challenges (proximity of wastewater and desalination plants, FO-RO hybrid has to overcome technical limitation such as low FO permeation flux to become economically attractive. Recent developments (i.e., improved FO membranes, use of pressure assisted osmosis, PAO demonstrated significant improvement in water flux. However, flux improvement is associated with drawbacks, such as increased fouling behaviour, lower rejection of trace organic compounds (TrOCs in PAO operation, and limitation in FO membrane mechanical resistance, which need to be better considered. To support successful implementation of FO-RO hybrid in the industry, further work is required regarding up-scaling to apprehend full-scale challenges in term of mass transfer limitation, pressure drop, fouling and cleaning strategies on a module scale. In addition, refined economics assessment is expected to integrate fouling and other maintenance costs/savings of the FO/PAO-RO hybrid systems, as well as cost savings from any treatment step avoided in the water recycling.

  4. Efficiently Combining Water Reuse and Desalination through Forward Osmosis—Reverse Osmosis (FO-RO) Hybrids: A Critical Review

    Science.gov (United States)

    Blandin, Gaetan; Verliefde, Arne R.D.; Comas, Joaquim; Rodriguez-Roda, Ignasi; Le-Clech, Pierre

    2016-01-01

    Forward osmosis (FO) is a promising membrane technology to combine seawater desalination and water reuse. More specifically, in a FO-reverse osmosis (RO) hybrid process, high quality water recovered from the wastewater stream is used to dilute seawater before RO treatment. As such, lower desalination energy needs and/or water augmentation can be obtained while delivering safe water for direct potable reuse thanks to the double dense membrane barrier protection. Typically, FO-RO hybrid can be a credible alternative to new desalination facilities or to implementation of stand-alone water reuse schemes. However, apart from the societal (public perception of water reuse for potable application) and water management challenges (proximity of wastewater and desalination plants), FO-RO hybrid has to overcome technical limitation such as low FO permeation flux to become economically attractive. Recent developments (i.e., improved FO membranes, use of pressure assisted osmosis, PAO) demonstrated significant improvement in water flux. However, flux improvement is associated with drawbacks, such as increased fouling behaviour, lower rejection of trace organic compounds (TrOCs) in PAO operation, and limitation in FO membrane mechanical resistance, which need to be better considered. To support successful implementation of FO-RO hybrid in the industry, further work is required regarding up-scaling to apprehend full-scale challenges in term of mass transfer limitation, pressure drop, fouling and cleaning strategies on a module scale. In addition, refined economics assessment is expected to integrate fouling and other maintenance costs/savings of the FO/PAO-RO hybrid systems, as well as cost savings from any treatment step avoided in the water recycling. PMID:27376337

  5. Mesoporous Silica Gel-Based Mixed Matrix Membranes for Improving Mass Transfer in Forward Osmosis: Effect of Pore Size of Filler.

    Science.gov (United States)

    Lee, Jian-Yuan; Wang, Yining; Tang, Chuyang Y; Huo, Fengwei

    2015-11-23

    The efficiency of forward osmosis (FO) process is generally limited by the internal concentration polarization (ICP) of solutes inside its porous substrate. In this study, mesoporous silica gel (SG) with nominal pore size ranging from 4-30 nm was used as fillers to prepare SG-based mixed matrix substrates. The resulting mixed matrix membranes had significantly reduced structural parameter and enhanced membrane water permeability as a result of the improved surface porosity of the substrates. An optimal filler pore size of ~9 nm was observed. This is in direct contrast to the case of thin film nanocomposite membranes, where microporous nanoparticle fillers are loaded to the membrane rejection layer and are designed in such a way that these fillers are able to retain solutes while allowing water to permeate through them. In the current study, the mesoporous fillers are designed as channels to both water and solute molecules. FO performance was enhanced at increasing filler pore size up to 9 nm due to the lower hydraulic resistance of the fillers. Nevertheless, further increasing filler pore size to 30 nm was accompanied with reduced FO efficiency, which can be attributed to the intrusion of polymer dope into the filler pores.

  6. Mesoporous Silica Gel–Based Mixed Matrix Membranes for Improving Mass Transfer in Forward Osmosis: Effect of Pore Size of Filler

    Science.gov (United States)

    Lee, Jian-Yuan; Wang, Yining; Tang, Chuyang Y.; Huo, Fengwei

    2015-01-01

    The efficiency of forward osmosis (FO) process is generally limited by the internal concentration polarization (ICP) of solutes inside its porous substrate. In this study, mesoporous silica gel (SG) with nominal pore size ranging from 4–30 nm was used as fillers to prepare SG-based mixed matrix substrates. The resulting mixed matrix membranes had significantly reduced structural parameter and enhanced membrane water permeability as a result of the improved surface porosity of the substrates. An optimal filler pore size of ~9 nm was observed. This is in direct contrast to the case of thin film nanocomposite membranes, where microporous nanoparticle fillers are loaded to the membrane rejection layer and are designed in such a way that these fillers are able to retain solutes while allowing water to permeate through them. In the current study, the mesoporous fillers are designed as channels to both water and solute molecules. FO performance was enhanced at increasing filler pore size up to 9 nm due to the lower hydraulic resistance of the fillers. Nevertheless, further increasing filler pore size to 30 nm was accompanied with reduced FO efficiency, which can be attributed to the intrusion of polymer dope into the filler pores. PMID:26592565

  7. Combination of forward osmosis (FO) process with coagulation/flocculation (CF) for potential treatment of textile wastewater.

    Science.gov (United States)

    Han, Gang; Liang, Can-Zeng; Chung, Tai-Shung; Weber, Martin; Staudt, Claudia; Maletzko, Christian

    2016-03-15

    A novel combination of forward osmosis (FO) process with coagulation/flocculation (CF) (FO-CF) has been experimentally conceived for the treatment and reuse of textile wastewater. FO is employed to spontaneously recover water from the wastewater via osmosis and thus effectively reduces its volume with a dramatically enhanced dye concentration. CF is then applied to precipitate and remove dyes from the FO concentrated stream with much improved efficiency and reduced chemical dosage. The FO-CF hybrid system exhibits unique advantages of high water flux and recovery rate, well controlled membrane fouling, high efficiency, and minimal environmental impact. Using a lab-made thin-film composite (TFC) FO membrane, an initial water flux (Jw) of 36.0 L m(-2) h(-1) with a dye rejection of 99.9% has been demonstrated by using 2 M NaCl as the draw solution and synthetic textile wastewater containing multiple textile dyes, inorganic salts and organic additives as the feed under the FO mode. The Jw could be maintained at a high value of 12.0 L m(-2) h(-1) even when the recovery rate of the wastewater reaches 90%. Remarkable reverse fouling behavior has also been observed where the Jw of the fouled membrane can be almost fully restored to the initial value by physical flushing without using any chemicals. Due to the great dye concentration in the FO concentrated wastewater stream, the CF process could achieve more than 95% dye removal with a small dosage of coagulants and flocculants at 500-1000 ppm. The newly developed FO-CF hybrid process may open up new exploration of alternative technologies for the effective treatment and reuse of textile effluents. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Comparison of foE and M(3000)F2 variability at Ibadan, Singapore and Slough

    Science.gov (United States)

    Somoye, E. O.; Onori, E. O.; Akala, A. O.

    2013-01-01

    The variability, VR, of critical frequency of E-layer, foE, and ionospheric propagation factor, M(3000)F2 at Ibadan (7.4°N, 3.9°E, 6°S dip) is investigated for local time, seasonal and solar cycle variations. Latitudinal influence of these characteristics is sought by comparison with foE VR and M(3000)F2 VR of Slough ( 51.5°N, 359.4°E, 66.5°N dip) in the European sector, and Singapore (1.3°N,103.8°E, 17.6°S dip) in the Asian sector. While the pattern of foE VR is similar to those of other F2 characteristics with characteristic peaks around dawn and dusk, M(3000)F2 VR shows no clear diurnal trend.A lower bound of foE VR is usually 3% while the maximum VR ranges between 8% and13% at post-sunrise and pre-sunset hours at all the epochs, M(3000)F2 VR is however lower during MSA (about 9%) than during LSA and HSA when it is 4% to about 12-14%. Generally, daytime M(3000)F2 VR is greater than that of foE VR by between 5% and 10%. Furthermore, no latitudinal difference is observed in both characteristics during both HSA and MSA. While nighttime M(3000)F2 VR is about half that of nighttime foF2 VR (the critical frequency of F2-layer ) VR, daytime VR of both characteristics are about equal during the three epochs at Ibadan. For Slough, nighttime M(3000)F2 VR and nighttime foF2 VR as well as the daytime VR of both characteristics are about equal. This difference is most likely due to latitudinal effect.

  9. Produced Water Treatment Using the Switchable Polarity Solvent Forward Osmosis (SPS FO) Desalination Process: Preliminary Engineering Design Basis

    Energy Technology Data Exchange (ETDEWEB)

    Wendt, Daniel; Adhikari, Birendra; Orme, Christopher; Wilson, Aaron

    2016-05-01

    Switchable Polarity Solvent Forward Osmosis (SPS FO) is a semi-permeable membrane-based water treatment technology. INL is currently advancing SPS FO technology such that a prototype unit can be designed and demonstrated for the purification of produced water from oil and gas production operations. The SPS FO prototype unit will used the thermal energy in the produced water as a source of process heat, thereby reducing the external process energy demands. Treatment of the produced water stream will reduce the volume of saline wastewater requiring disposal via injection, an activity that is correlated with undesirable seismic events, as well as generate a purified product water stream with potential beneficial uses. This paper summarizes experimental data that has been collected in support of the SPS FO scale-up effort, and describes how this data will be used in the sizing of SPS FO process equipment. An estimate of produced water treatment costs using the SPS FO process is also provided.

  10. Long-term trend of foE in European higher middle latitudes

    Science.gov (United States)

    Laštovička, Jan

    2016-04-01

    Long-term changes and trends have been observed in the whole ionosphere below its maximum. As concerns the E region, historical global data (Bremer, 2008) provide predominantly slightly positive trend, even though some stations provide a negative trend. Here we use data of two European stations with the best long data series of parameters of the ionospheric E layer, Slough/Chilton and Juliusruh over 1975-2014 (40 years). Noon-time medians (10-14 LT) are analyzed. The trend pattern after removing solar influence is complex. For yearly average values for Chilton first foE is decreasing in 1975-1990 by about 0.1 MHz, then the trend levels off or a little increase occurs in 1990-2004, and finally in 2004-2014 again a decrease is observed (again by about 0.1 MHz but over shorter period). Juliusruh yields a similar pattern. Similar analysis is also done for some months to check seasonal dependence of trends. The stability of relation between solar activity and foE is tested to clarify potential role of this factor in apparent trend of foE.

  11. Real-time ligation chain reaction for DNA quantification and identification on the FO-SPR.

    Science.gov (United States)

    Knez, Karel; Spasic, Dragana; Delport, Filip; Lammertyn, Jeroen

    2015-05-15

    Different assays have been developed in the past years to meet point-of-care diagnostic tests requirements for fast and sensitive quantification and identification of targets. In this paper, we developed the ligation chain reaction (LCR) assay on the Fiber Optic Surface Plasmon Resonance (FO-SPR) platform, which enabled simultaneous quantification and cycle-to-cycle identification of DNA during amplification. The newly developed assay incorporated FO-SPR DNA melting assay, previously developed by our group. This required establishment of several assay parameters, including buffer ionic strength and thermal ramping speed as these parameters both influence the ligation enzyme performance and the hybridization yield of the gold nanoparticles (Au NPs) on the FO-SPR sensor. Quantification and identification of DNA targets was achieved over a wide concentration range with a calibration curve spanning 7 orders of magnitude and LOD of 13.75 fM. Moreover, the FO-SPR LCR assay could discriminate single nucleotide polymorphism (SNPs) without any post reaction analysis, featuring thus all the essential requirements of POC tests. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. KORELASI PENGGUNAAN BAHASA INGGRIS DALAM PENAMAAN FACTORY OUTLET (FO DI BANDUNG TERHADAP KEPUTUSAN PEMBELIAN

    Directory of Open Access Journals (Sweden)

    Gartika Rahmasari

    2016-03-01

        Abstrak - Bahasa Inggris merupakan bahasa yang memiliki prestise atau kedudukan yang tinggi, bahkan di Indonesia yang memiliki bahasa Indonesia sebagai bahasa nasional. Bahasa Inggris sebagai bahasa internasional mendapatkan apresiasi lebih tinggi dibandingkan dengan bahasa Indonesia, khususnya di bidang pariwisata. Bandung sebagai salah satu tujuan pariwisata, khususnya wisata kuliner dan tujuan belanja, tidak terkecuali mendapat pengaruh yang besar dalam hal penggunaan bahasa Inggris. Hal ini dapat dilihat dari penggunaan sejumlah nama Factory Outlet yang ada di Bandung, yang hampir sebagian besar menggunakan bahasa Ingris atau serapan bahasa Inggris sebagai “brand” atau nama yang digunakan oleh Factory Outlet yang tersebar di seluruh Bandung. Jurnal ini merupakan study literatur yang meneliti tentang hubungan penggunaan bahasa Asing dalam nama Factory Outlet  (FO terhadap keputusan pembelian. Yang menjadi responden yang diteliti dalam penelitian ini adalah mahasiswa Ilmu Komunikasi, Universitas Telkom sebanyak 55 responden, dengan rentang usia 17-20 tahun. Dari hasil penelitian, diketahui bahwa secara umum, penggunaan bahasa Inggris dalam penamaan Factory Outlet (FO mempengaruhi keputusan responden untuk berbelanja ke FO tersebut.   Kata Kunci: Keputusan Pembelian, Factory Outlet, FO, Bahasa Inggris.

  13. Hydrothermal stability of silica, hybrid silica and Zr-doped hybrid silica membranes

    NARCIS (Netherlands)

    ten Hove, Marcel; Luiten-Olieman, Mieke W.J.; Huiskes, Cindy; Nijmeijer, Arian; Winnubst, Louis

    2017-01-01

    Hybrid silica membranes have demonstrated to possess a remarkable hydrothermal stability in pervaporation and gas separation processes allowing them to be used in industrial applications. In several publications the hydrothermal stability of pure silica or that of hybrid silica membranes are

  14. Fumed silica. Fumed silica

    Energy Technology Data Exchange (ETDEWEB)

    Sukawa, T.; Shirono, H. (Nippon Aerosil Co. Ltd., Tokyo (Japan))

    1991-10-18

    The fumed silica is explained in particulate superfineness, high purity, high dispersiveness and other remarkable characteristics, and wide application. The fumed silica, being presently produced, is 7 to 40nm in average primary particulate diameter and 50 to 380m{sup 2}/g in specific surface area. On the surface, there coexist hydrophilic silanol group (Si-OH) and hydrophobic siloxane group (Si-O-Si). There are many characteristics, mutually different between the fumed silica, made hydrophobic by the surface treatment, and untreated hydrophilic silica. The treated silica, if added to the liquid product, serves as agent to heighten the viscosity, prevent the sedimentation and disperse the particles. The highest effect is given to heighten the viscosity in a region of 4 to 9 in pH in water and alcohol. As filling agent to strengthen the elastomer and polymer, and powder product, it gives an effect to prevent the consolidation and improve the fluidity. As for its other applications, utilization is made of particulate superfineness, high purity, thermal insulation properties and adsorption characteristics. 2 to 3 patents are published for it as raw material of quartz glass. 38 refs., 16 figs., 4 tabs.

  15. Emerging forward osmosis (FO) technologies and challenges ahead for clean water and clean energy applications

    KAUST Repository

    Chung, Tai-Shung; Li, Xue; Ong, Rui Chin; Ge, Qingchun; Wang, Honglei; Han, Gang

    2012-01-01

    The purpose of this short review is to share our understanding and perspectives with the chemical, environmental, water and osmotic power communities on FO processes in order to conduct meaningful R & D and develop effective and sustainable FO technologies for clean water and clean energy. © 2012 Elsevier Ltd. All rights reserved.

  16. Emerging forward osmosis (FO) technologies and challenges ahead for clean water and clean energy applications

    KAUST Repository

    Chung, Tai-Shung

    2012-08-01

    The purpose of this short review is to share our understanding and perspectives with the chemical, environmental, water and osmotic power communities on FO processes in order to conduct meaningful R & D and develop effective and sustainable FO technologies for clean water and clean energy. © 2012 Elsevier Ltd. All rights reserved.

  17. Ferric and cobaltous hydroacid complexes for forward osmosis (FO) processes

    KAUST Repository

    Ge, Qingchun; Fu, Fengjiang; Chung, Neal Tai-Shung

    2014-01-01

    Cupric and ferric hydroacid complexes have proven their advantages as draw solutes in forward osmosis in terms of high water fluxes, negligible reverse solute fluxes and easy recovery (Ge and Chung, 2013. Hydroacid complexes: A new class of draw solutes to promote forward osmosis (FO) processes. Chemical Communications 49, 8471-8473.). In this study, cobaltous hydroacid complexes were explored as draw solutes and compared with the ferric hydroacid complex to study the factors influencing their FO performance. The solutions of the cobaltous complexes produce high osmotic pressures due to the presence of abundant hydrophilic groups. These solutes are able to dissociate and form a multi-charged anion and Na+ cations in water. In addition, these complexes have expanded structures which lead to negligible reverse solute fluxes and provide relatively easy approaches in regeneration. These characteristics make the newly synthesized cobaltous complexes appropriate as draw solutes. The FO performance of the cobaltous and ferric-citric acid (Fe-CA) complexes were evaluated respectively through cellulose acetate membranes, thin-film composite membranes fabricated on polyethersulfone supports (referred as TFC-PES), and polybenzimidazole and PES dual-layer (referred as PBI/PES) hollow fiber membranes. Under the conditions of DI water as the feed and facing the support layer of TFC-PES FO membranes (PRO mode), draw solutions at 2.0M produced relatively high water fluxes of 39-48 LMH (Lm-2hr-1) with negligible reverse solute fluxes. A water flux of 17.4 LMH was achieved when model seawater of 3.5wt.% NaCl replaced DI water as the feed and 2.0M Fe-CA as the draw solution under the same conditions. The performance of these hydroacid complexes surpasses those of the synthetic draw solutes developed in recent years. This observation, along with the relatively easy regeneration, makes these complexes very promising as a novel class of draw solutes. © 2014 Elsevier Ltd.

  18. Ferric and cobaltous hydroacid complexes for forward osmosis (FO) processes

    KAUST Repository

    Ge, Qingchun

    2014-07-01

    Cupric and ferric hydroacid complexes have proven their advantages as draw solutes in forward osmosis in terms of high water fluxes, negligible reverse solute fluxes and easy recovery (Ge and Chung, 2013. Hydroacid complexes: A new class of draw solutes to promote forward osmosis (FO) processes. Chemical Communications 49, 8471-8473.). In this study, cobaltous hydroacid complexes were explored as draw solutes and compared with the ferric hydroacid complex to study the factors influencing their FO performance. The solutions of the cobaltous complexes produce high osmotic pressures due to the presence of abundant hydrophilic groups. These solutes are able to dissociate and form a multi-charged anion and Na+ cations in water. In addition, these complexes have expanded structures which lead to negligible reverse solute fluxes and provide relatively easy approaches in regeneration. These characteristics make the newly synthesized cobaltous complexes appropriate as draw solutes. The FO performance of the cobaltous and ferric-citric acid (Fe-CA) complexes were evaluated respectively through cellulose acetate membranes, thin-film composite membranes fabricated on polyethersulfone supports (referred as TFC-PES), and polybenzimidazole and PES dual-layer (referred as PBI/PES) hollow fiber membranes. Under the conditions of DI water as the feed and facing the support layer of TFC-PES FO membranes (PRO mode), draw solutions at 2.0M produced relatively high water fluxes of 39-48 LMH (Lm-2hr-1) with negligible reverse solute fluxes. A water flux of 17.4 LMH was achieved when model seawater of 3.5wt.% NaCl replaced DI water as the feed and 2.0M Fe-CA as the draw solution under the same conditions. The performance of these hydroacid complexes surpasses those of the synthetic draw solutes developed in recent years. This observation, along with the relatively easy regeneration, makes these complexes very promising as a novel class of draw solutes. © 2014 Elsevier Ltd.

  19. Cleaning protocol for a FO membrane fouled in wastewater reuse

    KAUST Repository

    Valladares Linares, Rodrigo; Li, Zhenyu; Yangali-Quintanilla, Victor; Li, Qingyu; Amy, Gary L.

    2013-01-01

    Forward osmosis (FO) is an emerging technology which can be applied in water reuse applications. Osmosis is a natural process that involves less energy consumption than reverse osmosis (RO), and therefore can be applied as a dilution process before low-pressure RO; it is expected to compete favourably against current advanced water reuse technologies that use microfiltration/ultrafiltration and RO. The focus of this research was to assess the efficiency of different cleaning procedures to remove fouling from the surface of a FO membrane during the operation of a submerged system working in FO-mode (active layer (AL) facing feed solution) intended for secondary wastewater effluent (SWWE) recovery, using seawater as draw solution (DS), which will be diluted and can further be fed to a low-pressure RO unit to produce fresh water. Natural organic matter (NOM) fouling was expected to affect the AL, while for the support layer (SL), transparent exopolymer particles (TEP) were used as indicators of fouling due to their stickiness and propensity to enhance the attachment of other foulants in seawater on the membrane surface. The composition of the NOM fouling layer was determined after proper characterisation with a liquid chromatograph coupled with organic carbon detection (LC-OCD), showing biopolymers and protein-like substances as the main constituents. NOM fouling showed high hydraulic reversibility after a 25% flux decline was observed, up to 89.5% when in situ air scouring for 15 min was used as a cleaning technique. Chemical cleaning with a mixture of Alconox, an industrial detergent containing phosphates, and sodium EDTA showed to increase the reversibility (93.6%). Osmotic backwash using a 4% NaCl solution and DI water proved to be ineffective to recover flux due to the salt diffusion phenomena occurring at the AL. Part of the flux that could not be recovered is attributable to TEP fouling on the SL, which forms clusters clearly identifiable with an optical

  20. Cleaning protocol for a FO membrane fouled in wastewater reuse

    KAUST Repository

    Valladares Linares, Rodrigo

    2013-05-30

    Forward osmosis (FO) is an emerging technology which can be applied in water reuse applications. Osmosis is a natural process that involves less energy consumption than reverse osmosis (RO), and therefore can be applied as a dilution process before low-pressure RO; it is expected to compete favourably against current advanced water reuse technologies that use microfiltration/ultrafiltration and RO. The focus of this research was to assess the efficiency of different cleaning procedures to remove fouling from the surface of a FO membrane during the operation of a submerged system working in FO-mode (active layer (AL) facing feed solution) intended for secondary wastewater effluent (SWWE) recovery, using seawater as draw solution (DS), which will be diluted and can further be fed to a low-pressure RO unit to produce fresh water. Natural organic matter (NOM) fouling was expected to affect the AL, while for the support layer (SL), transparent exopolymer particles (TEP) were used as indicators of fouling due to their stickiness and propensity to enhance the attachment of other foulants in seawater on the membrane surface. The composition of the NOM fouling layer was determined after proper characterisation with a liquid chromatograph coupled with organic carbon detection (LC-OCD), showing biopolymers and protein-like substances as the main constituents. NOM fouling showed high hydraulic reversibility after a 25% flux decline was observed, up to 89.5% when in situ air scouring for 15 min was used as a cleaning technique. Chemical cleaning with a mixture of Alconox, an industrial detergent containing phosphates, and sodium EDTA showed to increase the reversibility (93.6%). Osmotic backwash using a 4% NaCl solution and DI water proved to be ineffective to recover flux due to the salt diffusion phenomena occurring at the AL. Part of the flux that could not be recovered is attributable to TEP fouling on the SL, which forms clusters clearly identifiable with an optical

  1. Controlling the morphology and performance of FO membrane via adjusting the atmosphere humidity during casting procedure

    Science.gov (United States)

    Zuo, Hao-Ran; Cao, Gui-Ping; Wang, Meng; Zhang, Huan-Huan; Song, Chen-Chen; Fang, Xu; Wang, Tao

    2018-03-01

    Forward osmosis (FO) has received great interest for its considerable potential in a wide range of fields. In this work, the morphology and performance of FO membrane were regulated by adjusting the atmosphere humidity (HC) of casting procedure. The polysulfone support layer was casted under various atmosphere humidity levels ranging from 40% to 80%. By multi-techniques such as SEM, AFM, and XPS, it was proved that the atmosphere humidity had modified the surface morphology and thickness of the skin layer in support layer, which contributed up to 90% of the structure parameter, resulting in distinct morphology, thickness, and cross-linking degree of active layer. The active layer with sparse bead-like wrinkles on the smooth surface of support layer casted at HC = 65% showed the highest water permeability [26.9 (L/m2 h MPa)] and considerable low salt permeability [0.0390 (L/m2 h)]. It was found that the water flux of FO-65 was 27% and 46% higher than that of FO-80 in AL-DS and AL-FS mode, respectively, and the salt rejection was as high as 98%. Our work highlighted the importance of considering the effect of atmosphere humidity during casting when design an FO membrane for appropriate performance.

  2. A prediction model of short-term ionospheric foF2 based on AdaBoost

    Science.gov (United States)

    Zhao, Xiukuan; Ning, Baiqi; Liu, Libo; Song, Gangbing

    2014-02-01

    In this paper, the AdaBoost-BP algorithm is used to construct a new model to predict the critical frequency of the ionospheric F2-layer (foF2) one hour ahead. Different indices were used to characterize ionospheric diurnal and seasonal variations and their dependence on solar and geomagnetic activity. These indices, together with the current observed foF2 value, were input into the prediction model and the foF2 value at one hour ahead was output. We analyzed twenty-two years' foF2 data from nine ionosonde stations in the East-Asian sector in this work. The first eleven years' data were used as a training dataset and the second eleven years' data were used as a testing dataset. The results show that the performance of AdaBoost-BP is better than those of BP Neural Network (BPNN), Support Vector Regression (SVR) and the IRI model. For example, the AdaBoost-BP prediction absolute error of foF2 at Irkutsk station (a middle latitude station) is 0.32 MHz, which is better than 0.34 MHz from BPNN, 0.35 MHz from SVR and also significantly outperforms the IRI model whose absolute error is 0.64 MHz. Meanwhile, AdaBoost-BP prediction absolute error at Taipei station from the low latitude is 0.78 MHz, which is better than 0.81 MHz from BPNN, 0.81 MHz from SVR and 1.37 MHz from the IRI model. Finally, the variety characteristics of the AdaBoost-BP prediction error along with seasonal variation, solar activity and latitude variation were also discussed in the paper.

  3. Creep Behavior of Hafnia and Ytterbium Silicate Environmental Barrier Coating Systems on SiC/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Zhu, Dongming; Fox, Dennis S.; Ghosn, Louis J.; Harder, Bryan

    2011-01-01

    Environmental barrier coatings will play a crucial role in future advanced gas turbine engines because of their ability to significantly extend the temperature capability and stability of SiC/SiC ceramic matrix composite (CMC) engine components, thus improving the engine performance. In order to develop high performance, robust coating systems for engine components, appropriate test approaches simulating operating temperature gradient and stress environments for evaluating the critical coating properties must be established. In this paper, thermal gradient mechanical testing approaches for evaluating creep and fatigue behavior of environmental barrier coated SiC/SiC CMC systems will be described. The creep and fatigue behavior of Hafnia and ytterbium silicate environmental barrier coatings on SiC/SiC CMC systems will be reported in simulated environmental exposure conditions. The coating failure mechanisms will also be discussed under the heat flux and stress conditions.

  4. Environmental and economic assessment of hybrid FO-RO/NF system with selected inorganic draw solutes for the treatment of mine impaired water

    KAUST Repository

    Kim, Jung Eun

    2018-01-01

    A hybrid forward osmosis (FO) and reverse osmosis (RO)/nanofiltration (NF) system in a closed-loop operation with selected draw solutes was evaluated to treat coal mine impaired water. This study provides an insight of selecting the most suitable draw solution (DS) by conducting environmental and economic life cycle assessment (LCA). Baseline environmental LCA showed that the dominant components to energy use and global warming are the DS recovery processes (i.e. RO or NF processes) and FO membrane materials, respectively. When considering the DS replenishment in FO, the contribution of chemical use to the overall global warming impact was significant for all hybrid systems. Furthermore, from an environmental perspective, the FO-NF hybrid system with Na2SO4 shows the lowest energy consumption and global warming with additional considerations of final product water quality and FO brine disposal. From an economic perspective, the FO-NF with Na2SO4 showed the lowest total operating cost due to its lower DS loss and relatively low solute cost. In a closed-loop system, FO-NF with NaCl and Na2SO4 had the lowest total water cost at optimum NF recovery rates of 90 and 95%, respectively. FO-NF with Na2SO4 had the lowest environmental and economic impacts. Overall, draw solute performances and cost in FO and recovery rate in RO/NF play a crucial role in determining the total water cost and environmental impact of FO hybrid systems in a closed-loop operation.

  5. SoFoCles: feature filtering for microarray classification based on gene ontology.

    Science.gov (United States)

    Papachristoudis, Georgios; Diplaris, Sotiris; Mitkas, Pericles A

    2010-02-01

    Marker gene selection has been an important research topic in the classification analysis of gene expression data. Current methods try to reduce the "curse of dimensionality" by using statistical intra-feature set calculations, or classifiers that are based on the given dataset. In this paper, we present SoFoCles, an interactive tool that enables semantic feature filtering in microarray classification problems with the use of external, well-defined knowledge retrieved from the Gene Ontology. The notion of semantic similarity is used to derive genes that are involved in the same biological path during the microarray experiment, by enriching a feature set that has been initially produced with legacy methods. Among its other functionalities, SoFoCles offers a large repository of semantic similarity methods that are used in order to derive feature sets and marker genes. The structure and functionality of the tool are discussed in detail, as well as its ability to improve classification accuracy. Through experimental evaluation, SoFoCles is shown to outperform other classification schemes in terms of classification accuracy in two real datasets using different semantic similarity computation approaches.

  6. Oxygen Buffering in High Pressure Solid Media Assemblies: New Approach Enabling Study of fO2 from IW-4 to IW+4.5

    Science.gov (United States)

    Righter, K.; Pando, K. M.; Ross, D. K.; Butterworth, A. L.; Gainsforth, Z.; Jilly-Rehak, C. E.; Westphal, A. J.

    2017-01-01

    Oxygen fugacity is an intensive parameter that controls some fundamental chemical and physical properties in planetary materials. In terrestrial magmas high fO2 promotes magnetite stability and low fO2 causes Fe-enrichment due to magnetite suppression. In lunar and asteroidal basalts, low fO2 can allow metal to be stable. Experimental studies will therefore be most useful if they are done at a specific and relevant fO2 for the samples under consideration. Control of fO2 in the solid media apparatus (piston cylinder multi-anvil) has relied on either sliding sensors or graphite capsule buffering, which are of limited application to the wide range of fO2 recorded in planetary or astromaterials. Here we describe a new approach that allows fO2 to be specified across a wide range of values relevant to natural samples.

  7. Parametric decadal climate forecast recalibration (DeFoReSt 1.0

    Directory of Open Access Journals (Sweden)

    A. Pasternack

    2018-01-01

    Full Text Available Near-term climate predictions such as decadal climate forecasts are increasingly being used to guide adaptation measures. For near-term probabilistic predictions to be useful, systematic errors of the forecasting systems have to be corrected. While methods for the calibration of probabilistic forecasts are readily available, these have to be adapted to the specifics of decadal climate forecasts including the long time horizon of decadal climate forecasts, lead-time-dependent systematic errors (drift and the errors in the representation of long-term changes and variability. These features are compounded by small ensemble sizes to describe forecast uncertainty and a relatively short period for which typically pairs of reforecasts and observations are available to estimate calibration parameters. We introduce the Decadal Climate Forecast Recalibration Strategy (DeFoReSt, a parametric approach to recalibrate decadal ensemble forecasts that takes the above specifics into account. DeFoReSt optimizes forecast quality as measured by the continuous ranked probability score (CRPS. Using a toy model to generate synthetic forecast observation pairs, we demonstrate the positive effect on forecast quality in situations with pronounced and limited predictability. Finally, we apply DeFoReSt to decadal surface temperature forecasts from the MiKlip prototype system and find consistent, and sometimes considerable, improvements in forecast quality compared with a simple calibration of the lead-time-dependent systematic errors.

  8. Parametric decadal climate forecast recalibration (DeFoReSt 1.0)

    Science.gov (United States)

    Pasternack, Alexander; Bhend, Jonas; Liniger, Mark A.; Rust, Henning W.; Müller, Wolfgang A.; Ulbrich, Uwe

    2018-01-01

    Near-term climate predictions such as decadal climate forecasts are increasingly being used to guide adaptation measures. For near-term probabilistic predictions to be useful, systematic errors of the forecasting systems have to be corrected. While methods for the calibration of probabilistic forecasts are readily available, these have to be adapted to the specifics of decadal climate forecasts including the long time horizon of decadal climate forecasts, lead-time-dependent systematic errors (drift) and the errors in the representation of long-term changes and variability. These features are compounded by small ensemble sizes to describe forecast uncertainty and a relatively short period for which typically pairs of reforecasts and observations are available to estimate calibration parameters. We introduce the Decadal Climate Forecast Recalibration Strategy (DeFoReSt), a parametric approach to recalibrate decadal ensemble forecasts that takes the above specifics into account. DeFoReSt optimizes forecast quality as measured by the continuous ranked probability score (CRPS). Using a toy model to generate synthetic forecast observation pairs, we demonstrate the positive effect on forecast quality in situations with pronounced and limited predictability. Finally, we apply DeFoReSt to decadal surface temperature forecasts from the MiKlip prototype system and find consistent, and sometimes considerable, improvements in forecast quality compared with a simple calibration of the lead-time-dependent systematic errors.

  9. Hysterosalpingo-foam sonography (HyFoSy): Tolerability, safety and the occurrence of pregnancy post-procedure.

    Science.gov (United States)

    Tanaka, Keisuke; Chua, Jackie; Cincotta, Robert; Ballard, Emma L; Duncombe, Gregory

    2018-02-01

    Fallopian tube patency testing is an essential part of infertility evaluation. Hysterosalpingo-contrast sonography (HyCoSy) has been described as reliable, well tolerated and safe compared to other modalities such as laparoscopy and a dye test or hysterosalpingography. Limited availability of the previously used contrast has led to the introduction of a foam contrast agent as an alternative. To assess the tolerability, safety and occurrence of pregnancy post-procedure of hysterosalpingo-foam sonography (HyFoSy). A retrospective cohort study of women who had a HyFoSy at Queensland Ultrasound for Women from March 2013 to February 2015. A questionnaire was sent to their referring doctor to identify any complications or subsequent pregnancies with or without artificial reproductive technology (ART) within six months of the HyFoSy. Of 200 women, four cases were abandoned due to difficulty introducing the intracervical catheter, severe discomfort or a vasovagal episode. Response from referring doctors for 155 women reported no post-procedural complication. One hundred and eleven women were followed up for at least six months. Twenty-four out of 59 women (40.7%) who had ART and 24 out of 52 women (46.2%) who did not have ART conceived. Fifty percent of women who were nulligravida at the time of investigation, found to have at least one patent fallopian tube, whose partner had a normal semen analysis, spontaneously conceived within the time of follow up. HyFoSy is well tolerated and safe. A preponderance of pregnancies in the first month after HyFoSy suggests that a therapeutic effect may exist. © 2017 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists.

  10. Silica Nephropathy

    Directory of Open Access Journals (Sweden)

    N Ghahramani

    2010-06-01

    Full Text Available Occupational exposure to heavy metals, organic solvents and silica is associated with a variety of renal manifestations. Improved understanding of occupational renal disease provides insight into environmental renal disease, improving knowledge of disease pathogenesis. Silica (SiO2 is an abundant mineral found in sand, rock, and soil. Workers exposed to silica include sandblasters, miners, quarry workers, masons, ceramic workers and glass manufacturers. New cases of silicosis per year have been estimated in the US to be 3600–7300. Exposure to silica has been associated with tubulointerstitial disease, immune-mediated multisystem disease, chronic kidney disease and end-stage renal disease. A rare syndrome of painful, nodular skin lesions has been described in dialysis patients with excessive levels of silicon. Balkan endemic nephropathy is postulated to be due to chronic intoxication with drinking water polluted by silicates released during soil erosion. The mechanism of silica nephrotoxicity is thought to be through direct nephrotoxicity, as well as silica-induced autoimmune diseases such as scleroderma and systemic lupus erythematosus. The renal histopathology varies from focal to crescentic and necrotizing glomerulonephritis with aneurysm formation suggestive of polyarteritis nodosa. The treatment for silica nephrotoxicity is non-specific and depends on the mechanism and stage of the disease. It is quite clear that further research is needed, particularly to elucidate the pathogenesis of silica nephropathy. Considering the importance of diagnosing exposure-related renal disease at early stages, it is imperative to obtain a thorough occupational history in all patients with renal disease, with particular emphasis on exposure to silica, heavy metals, and solvents.

  11. Effective As(III) Removal by A Multi-Charged Hydroacid Complex Draw Solute Facilitated Forward Osmosis-Membrane Distillation (FO-MD) Processes.

    Science.gov (United States)

    Ge, Qingchun; Han, Gang; Chung, Tai-Shung

    2016-03-01

    Effective removal of As(III) from water by an oxalic acid complex with the formula of Na3[Cr(C2O4)3] (Na-Cr-OA) is demonstrated via an forward osmosis-membrane distillation (FO-MD) hybrid system in this study. Na-Cr-OA first proved its superiority as a draw solute with high water fluxes and negligible reverse fluxes in FO, then a systematic investigation of the Na-Cr-OA promoted FO process was conducted to ascertain the factors in As(III) removal. Relatively high water fluxes of 28 LMH under the FO mode and 74 LMH under the pressure retarded osmosis (PRO) mode were achieved when using a 1000 ppm As(III) solution as the feed and 1.0 M Na-Cr-OA as the draw solution at 60 °C. As(III) removal with a water recovery up to 21.6% (FO mode) and 48.3% (PRO mode) were also achieved in 2 h. An outstanding As(III) rejection with 30-3000 μg/L As(III) in the permeate was accomplished when As(III) feed solutions varied from 5 × 10(4) to 1 × 10(6) μg/L, superior to the best FO performance reported for As(III) removal. Incorporating MD into FO not only makes As(III) removal sustainable by reconcentrating the Na-Cr-OA solution simultaneously, but also reduces the As(III) concentration below 10 μg/L in the product water, meeting the WHO standard.

  12. Novel cellulose ester substrates for high performance flat-sheet thin-film composite (TFC) forward osmosis (FO) membranes

    KAUST Repository

    Ong, Rui Chin

    2015-01-01

    A novel hydrophilic cellulose ester with a high intrinsic water permeability and a water partition coefficient was discovered to construct membrane supports for flat-sheet thin film composite (TFC) forward osmosis (FO) membranes for water reuse and seawater desalination with high performance. The performance of TFC-FO membranes prepared from the hydrophilic cellulose ester containing a high degree of OH and a moderate degree of Pr substitutions clearly surpasses those prepared from cellulose esters and other polymers with moderate hydrophilicity. Post-treatments of TFC-FO membranes using sodium dodecyl sulfate (SDS) and glycerol followed by heat treatment further enhance the water flux without compromising the selectivity. Positron annihilation lifetime analyses have confirmed that the SDS/glycerol post-treatment increases the free volume size and fractional free volume of the polyamide selective layer. The newly developed post-treated TFC-FO membranes exhibit a remarkably high water flux up to 90 LMH when the selective layer is oriented towards the draw solution (i.e., PRO mode) using 1. M NaCl as the draw solution and DI water as the feed. For seawater desalination, the membranes display a high water flux up to 35 LMH using a 2. M NaCl draw solution. These water fluxes exceeded the water fluxes achieved by other types of FO membranes reported in literatures. © 2014 Elsevier B.V.

  13. A novel TFC forward osmosis (FO) membrane supported by polyimide (PI) microporous nanofiber membrane

    Science.gov (United States)

    Chi, Xiang-Yu; Zhang, Ping-Yun; Guo, Xue-Jiao; Xu, Zhen-Liang

    2018-01-01

    A novel interfacial polymerization (IP) procedure on polyimide (PI) microporous nanofiber membrane support with mean pore size 1.27 μm was reported. Using m-phenylenediamine (MPD) as aqueous phase monomer, trimesoyl chloride (TMC) as organic phase monomer, ethanol as aqueous phase co-solvent, thin-film composite (TFC) forward osmosis (FO) membrane was fabricated by two IP procedures. The first IP procedure with the unconventional order (ie, the membrane was immersed in the TMC organic phase first, then in the co-solvent ethanol-water MPD aqueous phase) was used to diminish the pore size of PI microporous nanofiber membrane support for the formation of the polyamide layer. The secondary IP procedure was employed to form the relatively dense polyamide layer with conventional order (ie, the membrane was immersed in the co-solvent ethanol-water MPD aqueous phase first, then in the TMC organic phase). The experimental results showed that higher ethanol concentration led to the relatively higher pure water permeability in RO process and osmotic water flux in FO process, whereas NaCl rejection in RO process decreased and reverse salt flux increased. The specific salt flux (Js/Jv) of TFC FO PI nanofiber membrane (PIN-2-4) could be as low as 0.095 g/L in FO mode. These results could be attributed to influence of the addition of ethanol into aqueous phase on the surface morphology, hydrophilicity and polyamide layer structure.

  14. Some Durability Characteristics of Micro Silica and Nano Silica Contained Concrete

    Directory of Open Access Journals (Sweden)

    Mohammed Salah Nasr

    2016-12-01

    Full Text Available This paper aims to investigate the influence of replacement of cement with nano and micro silica admixtures on some durability properties of concrete such as water absorption, chloride content and pH tests. Three replacement ratios (5%,10%,15% of micro silica and four replacement proportions (0.5%,1.5%,3%,5% for nano silica were used in this study. Two exposure conditions were considered for chloride content test: wetting-drying and full immersing exposure in 6% of chloride ions solution, NaCl type. Results showed that mixes of %5 micro silica and 5% nano silica had lower content of chloride (about 0.19% and 0.18% for wetting-drying and full immersing exposure respectively. For water absorption test, all mixes incorporated micro and nano silica, except for %5 micro silica mix, showed lower absorption than control mixes. For pH test, results indicated that the adding of nano and micro silica didn’t affect adversely the alkalinity of concrete.

  15. Effect of salinity and temperature on treatment of concentrated wastewater from RO by FO-MD

    Science.gov (United States)

    Zhou, Yingru; Huang, Manhong; Deng, Qian

    2018-02-01

    In this study the appropriate temperature of the membrane distillation (MD) hot side (the permeation flux of MD was controlled by adjusting the hot side temperature) was selected according to the water flux of FO process so that the water transfer rate on both sides of FO and MD was consistent and the FO-MD process could be stable operation. When the salt concentration of feed solution was 30, 55, 80 and 100 g/L, the desalination rates changed little, which were 99.1%, 98.4%, 98.9% and 98.7%, respectively. The removal rate of COD was 93.8%, 94.2%, 91.6% and 92.7% which also changed little like the desalination rates. The removal rate of chromaticity increased with the increase of salinity, which attained 96.6%, 97.0%, 97.2% and 97.9%, respectively. This study proved that salinity of the feed solution affected little on the removal rate of contaminants but great on the water flux, with the increase of salinity from 30 to 100 g/L, the water flux was 6.05, 4.81, 4.33 and 3.87 LMH with the appropriate temperature (67.5±0.5, 64.5±0.5, 62.5±0.5 and 60.5±0.5 °C) of MD hot side. In a word, FO-MD was first used to treat the high salinity RO water with over 30 g/L total dissolved solids (TDS), FO-MD was a promising new process for high salinity wastewater treatment, and the hybrid system can solve the problem of lower draw solution concentration, and the high-quality production water will be obtained directly by this hybrid system with low membrane fouling tendency.

  16. A prediction model of short-term ionospheric foF2 Based on AdaBoost

    Science.gov (United States)

    Zhao, Xiukuan; Liu, Libo; Ning, Baiqi

    Accurate specifications of spatial and temporal variations of the ionosphere during geomagnetic quiet and disturbed conditions are critical for applications, such as HF communications, satellite positioning and navigation, power grids, pipelines, etc. Therefore, developing empirical models to forecast the ionospheric perturbations is of high priority in real applications. The critical frequency of the F2 layer, foF2, is an important ionospheric parameter, especially for radio wave propagation applications. In this paper, the AdaBoost-BP algorithm is used to construct a new model to predict the critical frequency of the ionospheric F2-layer one hour ahead. Different indices were used to characterize ionospheric diurnal and seasonal variations and their dependence on solar and geomagnetic activity. These indices, together with the current observed foF2 value, were input into the prediction model and the foF2 value at one hour ahead was output. We analyzed twenty-two years’ foF2 data from nine ionosonde stations in the East-Asian sector in this work. The first eleven years’ data were used as a training dataset and the second eleven years’ data were used as a testing dataset. The results show that the performance of AdaBoost-BP is better than those of BP Neural Network (BPNN), Support Vector Regression (SVR) and the IRI model. For example, the AdaBoost-BP prediction absolute error of foF2 at Irkutsk station (a middle latitude station) is 0.32 MHz, which is better than 0.34 MHz from BPNN, 0.35 MHz from SVR and also significantly outperforms the IRI model whose absolute error is 0.64 MHz. Meanwhile, AdaBoost-BP prediction absolute error at Taipei station from the low latitude is 0.78 MHz, which is better than 0.81 MHz from BPNN, 0.81 MHz from SVR and 1.37 MHz from the IRI model. Finally, the variety characteristics of the AdaBoost-BP prediction error along with seasonal variation, solar activity and latitude variation were also discussed in the paper.

  17. Effective As(III) Removal by A Multi-Charged Hydroacid Complex Draw Solute Facilitated Forward Osmosis-Membrane Distillation (FO-MD) Processes

    KAUST Repository

    Ge, Qingchun

    2016-01-29

    © 2016 American Chemical Society. Effective removal of As(III) from water by an oxalic acid complex with the formula of Na3[Cr(C2O4)3] (Na-Cr-OA) is demonstrated via an forward osmosis-membrane distillation (FO-MD) hybrid system in this study. Na-Cr-OA first proved its superiority as a draw solute with high water fluxes and negligible reverse fluxes in FO, then a systematic investigation of the Na-Cr-OA promoted FO process was conducted to ascertain the factors in As(III) removal. Relatively high water fluxes of 28 LMH under the FO mode and 74 LMH under the pressure retarded osmosis (PRO) mode were achieved when using a 1000 ppm As(III) solution as the feed and 1.0 M Na-Cr-OA as the draw solution at 60 °C. As(III) removal with a water recovery up to 21.6% (FO mode) and 48.3% (PRO mode) were also achieved in 2 h. An outstanding As(III) rejection with 30-3000 μg/L As(III) in the permeate was accomplished when As(III) feed solutions varied from 5 × 104 to 1 × 106 μg/L, superior to the best FO performance reported for As(III) removal. Incorporating MD into FO not only makes As(III) removal sustainable by reconcentrating the Na-Cr-OA solution simultaneously, but also reduces the As(III) concentration below 10 μg/L in the product water, meeting the WHO standard.

  18. Effective As(III) Removal by A Multi-Charged Hydroacid Complex Draw Solute Facilitated Forward Osmosis-Membrane Distillation (FO-MD) Processes

    KAUST Repository

    Ge, Qingchun; Han, Gang; Chung, Neal Tai-Shung

    2016-01-01

    © 2016 American Chemical Society. Effective removal of As(III) from water by an oxalic acid complex with the formula of Na3[Cr(C2O4)3] (Na-Cr-OA) is demonstrated via an forward osmosis-membrane distillation (FO-MD) hybrid system in this study. Na-Cr-OA first proved its superiority as a draw solute with high water fluxes and negligible reverse fluxes in FO, then a systematic investigation of the Na-Cr-OA promoted FO process was conducted to ascertain the factors in As(III) removal. Relatively high water fluxes of 28 LMH under the FO mode and 74 LMH under the pressure retarded osmosis (PRO) mode were achieved when using a 1000 ppm As(III) solution as the feed and 1.0 M Na-Cr-OA as the draw solution at 60 °C. As(III) removal with a water recovery up to 21.6% (FO mode) and 48.3% (PRO mode) were also achieved in 2 h. An outstanding As(III) rejection with 30-3000 μg/L As(III) in the permeate was accomplished when As(III) feed solutions varied from 5 × 104 to 1 × 106 μg/L, superior to the best FO performance reported for As(III) removal. Incorporating MD into FO not only makes As(III) removal sustainable by reconcentrating the Na-Cr-OA solution simultaneously, but also reduces the As(III) concentration below 10 μg/L in the product water, meeting the WHO standard.

  19. Degradation of phytate by the 6-phytase from Hafnia alvei: a combined structural and solution study.

    Science.gov (United States)

    Ariza, Antonio; Moroz, Olga V; Blagova, Elena V; Turkenburg, Johan P; Waterman, Jitka; Roberts, Shirley M; Vind, Jesper; Sjøholm, Carsten; Lassen, Søren F; De Maria, Leonardo; Glitsoe, Vibe; Skov, Lars K; Wilson, Keith S

    2013-01-01

    Phytases hydrolyse phytate (myo-inositol hexakisphosphate), the principal form of phosphate stored in plant seeds to produce phosphate and lower phosphorylated myo-inositols. They are used extensively in the feed industry, and have been characterised biochemically and structurally with a number of structures in the PDB. They are divided into four distinct families: histidine acid phosphatases (HAP), β-propeller phytases, cysteine phosphatases and purple acid phosphatases and also split into three enzyme classes, the 3-, 5- and 6-phytases, depending on the position of the first phosphate in the inositol ring to be removed. We report identification, cloning, purification and 3D structures of 6-phytases from two bacteria, Hafnia alvei and Yersinia kristensenii, together with their pH optima, thermal stability, and degradation profiles for phytate. An important result is the structure of the H. alvei enzyme in complex with the substrate analogue myo-inositol hexakissulphate. In contrast to the only previous structure of a ligand-bound 6-phytase, where the 3-phosphate was unexpectedly in the catalytic site, in the H. alvei complex the expected scissile 6-phosphate (sulphate in the inhibitor) is placed in the catalytic site.

  20. Step size of the rotary proton motor in single FoF1-ATP synthase from a thermoalkaliphilic bacterium by DCO-ALEX FRET

    Science.gov (United States)

    Hammann, Eva; Zappe, Andrea; Keis, Stefanie; Ernst, Stefan; Matthies, Doreen; Meier, Thomas; Cook, Gregory M.; Börsch, Michael

    2012-02-01

    Thermophilic enzymes operate at high temperatures but show reduced activities at room temperature. They are in general more stable during preparation and, accordingly, are considered to be more rigid in structure. Crystallization is often easier compared to proteins from bacteria growing at ambient temperatures, especially for membrane proteins. The ATP-producing enzyme FoF1-ATP synthase from thermoalkaliphilic Caldalkalibacillus thermarum strain TA2.A1 is driven by a Fo motor consisting of a ring of 13 c-subunits. We applied a single-molecule Förster resonance energy transfer (FRET) approach using duty cycle-optimized alternating laser excitation (DCO-ALEX) to monitor the expected 13-stepped rotary Fo motor at work. New FRET transition histograms were developed to identify the smaller step sizes compared to the 10-stepped Fo motor of the Escherichia coli enzyme. Dwell time analysis revealed the temperature and the LDAO dependence of the Fo motor activity on the single molecule level. Back-and-forth stepping of the Fo motor occurs fast indicating a high flexibility in the membrane part of this thermophilic enzyme.

  1. Modeling ionospheric foF2 by using empirical orthogonal function analysis

    Directory of Open Access Journals (Sweden)

    E. A

    2011-08-01

    Full Text Available A similar-parameters interpolation method and an empirical orthogonal function analysis are used to construct empirical models for the ionospheric foF2 by using the observational data from three ground-based ionosonde stations in Japan which are Wakkanai (Geographic 45.4° N, 141.7° E, Kokubunji (Geographic 35.7° N, 140.1° E and Yamagawa (Geographic 31.2° N, 130.6° E during the years of 1971–1987. The impact of different drivers towards ionospheric foF2 can be well indicated by choosing appropriate proxies. It is shown that the missing data of original foF2 can be optimal refilled using similar-parameters method. The characteristics of base functions and associated coefficients of EOF model are analyzed. The diurnal variation of base functions can reflect the essential nature of ionospheric foF2 while the coefficients represent the long-term alteration tendency. The 1st order EOF coefficient A1 can reflect the feature of the components with solar cycle variation. A1 also contains an evident semi-annual variation component as well as a relatively weak annual fluctuation component. Both of which are not so obvious as the solar cycle variation. The 2nd order coefficient A2 contains mainly annual variation components. The 3rd order coefficient A3 and 4th order coefficient A4 contain both annual and semi-annual variation components. The seasonal variation, solar rotation oscillation and the small-scale irregularities are also included in the 4th order coefficient A4. The amplitude range and developing tendency of all these coefficients depend on the level of solar activity and geomagnetic activity. The reliability and validity of EOF model are verified by comparison with observational data and with International Reference Ionosphere (IRI. The agreement between observations and EOF model is quite well, indicating that the EOF model can reflect the major changes and the temporal distribution characteristics of the mid-latitude ionosphere of the

  2. Microporous silica membranes

    DEFF Research Database (Denmark)

    Boffa, Vittorio; Yue, Yuanzheng

    2012-01-01

    Hydrothermal stability is a crucial factor for the application of microporous silica-based membranes in industrial processes. Indeed, it is well established that steam exposure may cause densification and defect formation in microporous silica membranes, which are detrimental to both membrane...... permeability and selectivity. Numerous previous studies show that microporous transition metal doped-silica membranes are hydrothermally more stable than pure silica membranes, but less permeable. Here we present a quantitative study on the impact of type and concentration of transition metal ions...... on the microporous structure, stability and permeability of amorphous silica-based membranes, providing information on how to design chemical compositions and synthetic paths for the fabrication of silica-based membranes with a well accessible and highly stabile microporous structure....

  3. The Mineralogy, Geochemistry, and Redox State of Multivalent Cations During the Crystallization of Primitive Shergottitic Liquids at Various (f)O2. Insights into the (f)O2 Fugacity of the Martian Mantle and Crustal Influences on Redox Conditions of Martian Magmas.

    Science.gov (United States)

    Shearer, C. K.; Bell, A. S.; Burger, P. V.; Papike, J. J.; Jones, J.; Le, L.; Muttik, N.

    2016-01-01

    The (f)O2 [oxygen fugacity] of crystallization for martian basalts has been estimated in various studies to range from IW-1 to QFM+4 [1-3]. A striking geochemical feature of the shergottites is the large range in initial Sr isotopic ratios and initial epsilon(sup Nd) values. Studies by observed that within the shergottite group the (f)O2 [oxygen fugacity] of crystallization is highly correlated with these chemical and isotopic characteristics with depleted shergottites generally crystallizing at reduced conditions and enriched shergottites crystallizing under more oxidizing conditions. More recent work has shown that (f)O2 [oxygen fugacity] changed during the crystallization of these magmas from one order of magnitude in Y980459 (Y98) to several orders of magnitude in Larkman Nunatak 06319. These real or apparent variations within single shergottitic magmas have been attributed to mixing of a xenocrystic olivine component, volatile loss-water disassociation, auto-oxidation during crystallization of mafic phases, and assimilation of an oxidizing crustal component (e.g. sulfate). In contrast to the shergottites, augite basalts such as NWA 8159 are highly depleted yet appear to be highly oxidized (e.g. QFM+4). As a first step in attempting to unravel petrologic complexities that influence (f)O2 [oxygen fugacity] in martian magmas, this study explores the effect of (f)O2 [oxygen fugacity] on the liquid line of descent (LLD) for a primitive shergottite liquid composition (Y98). The results of this study will provide a fundamental basis for reconstructing the record of (f)O2 [oxygen fugacity] in shergottites and other martian basalts, its effect on both mineral chemistries and valence state partitioning, and a means for examining the role of crystallization (and other more complex processes) on the petrologic linkages between olivine-phyric and pyroxene-plagioclase shergottites.

  4. Upgrading CCIR's fo F 2 maps using available ionosondes and genetic algorithms

    Science.gov (United States)

    Gularte, Erika; Carpintero, Daniel D.; Jaen, Juliana

    2018-04-01

    We have developed a new approach towards a new database of the ionospheric parameter fo F 2 . This parameter, being the frequency of the maximum of the ionospheric electronic density profile and its main modeller, is of great interest not only in atmospheric studies but also in the realm of radio propagation. The current databases, generated by CCIR (Committee Consultative for Ionospheric Radiowave propagation) and URSI (International Union of Radio Science), and used by the IRI (International Reference Ionosphere) model, are based on Fourier expansions and have been built in the 60s from the available ionosondes at that time. The main goal of this work is to upgrade the databases by using new available ionosonde data. To this end we used the IRI diurnal/spherical expansions to represent the fo F 2 variability, and computed its coefficients by means of a genetic algorithm (GA). In order to test the performance of the proposed methodology, we applied it to the South American region with data obtained by RAPEAS (Red Argentina para el Estudio de la Atmósfera Superior, i.e. Argentine Network for the Study of the Upper Atmosphere) during the years 1958-2009. The new GA coefficients provide a global better fit of the IRI model to the observed fo F 2 than the CCIR coefficients. Since the same formulae and the same number of coefficients were used, the overall integrity of IRI's typical ionospheric feature representation was preserved. The best improvements with respect to CCIR are obtained at low solar activities, at large (in absolute value) modip latitudes, and at night-time. The new method is flexible in the sense that can be applied either globally or regionally. It is also very easy to recompute the coefficients when new data is available. The computation of a third set of coefficients corresponding to days of medium solar activity in order to avoid the interpolation between low and high activities is suggested. The same procedure as for fo F 2 can be perfomed to

  5. Development and Release of a GRACE-FO "Grand Simulation" Data Set by JPL

    Science.gov (United States)

    Fahnestock, E.; Yuan, D. N.; Wiese, D. N.; McCullough, C. M.; Harvey, N.; Sakumura, C.; Paik, M.; Bertiger, W. I.; Wen, H. Y.; Kruizinga, G. L. H.

    2017-12-01

    The GRACE-FO mission, to be launched early in 2018, will require several stages of data processing to be performed within its Science Data System (SDS). In an effort to demonstrate effective implementation and inter-operation of this level 1, 2, and 3 data processing, and to verify its combined ability to recover a truth Earth gravity field to within top-level requirements, the SDS team has performed a system test which it has termed the "Grand Simulation". This process starts with iteration to converge on a mutually consistent integrated truth orbit, non-gravitational acceleration time history, and spacecraft attitude time history, generated with the truth models for all elements of the integrated system (geopotential, both GRACE-FO spacecraft, constellation of GPS spacecraft, etc.). Level 1A data products are generated and then the GPS time to onboard receiver time clock error is introduced into those products according to a realistic truth clock offset model. The various data products are noised according to current best estimate noise models, and then some are used within a precision orbit determination and clock offset estimation/recovery process. Processing from level 1A to level 1B data products uses the recovered clock offset to correct back to GPS time, and performs gap-filling, compression, etc. This exercises nearly all software pathways intended for processing actual GRACE-FO science data. Finally, a monthly gravity field is recovered and compared against the truth background field. In this talk we briefly summarize the resulting performance vs. requirements, and lessons learned in the system test process. Finally, we provide information for use of the level 1B data set by the general community for gravity solution studies and software trials in anticipation of operational GRACE-FO data. ©2016 California Institute of Technology. Government sponsorship acknowledged.

  6. BioFoV - An open platform for forensic video analysis and biometric data extraction

    DEFF Research Database (Denmark)

    Almeida, Miguel; Correia, Paulo Lobato; Larsen, Peter Kastmand

    2016-01-01

    to tailor-made software, based on state of art knowledge in fields such as soft biometrics, gait recognition, photogrammetry, etc. This paper proposes an open and extensible platform, BioFoV (Biometric Forensic Video tool), for forensic video analysis and biometric data extraction, aiming to host some...... of the developments that researchers come up with for solving specific problems, but that are often not shared with the community. BioFoV includes a simple to use Graphical User Interface (GUI), is implemented with open software that can run in multiple software platforms, and its implementation is publicly available....

  7. Chemical treatment of commercial reverse osmosis membranes for use in FO

    Science.gov (United States)

    Commercially available reverse osmosis (RO) membranes – SW30HR, BW30, and AG – were chemically treated for use in forward osmosis (FO). Nitric acid, phosphoric acid, sulfuric acid, ethanol, and ethanol–acid–water ternary solutions were employed for the treatment. All three membra...

  8. The c-Ring of the F1FO-ATP Synthase: Facts and Perspectives.

    Science.gov (United States)

    Nesci, Salvatore; Trombetti, Fabiana; Ventrella, Vittoria; Pagliarani, Alessandra

    2016-04-01

    The F1FO-ATP synthase is the only enzyme in nature endowed with bi-functional catalytic mechanism of synthesis and hydrolysis of ATP. The enzyme functions, not only confined to energy transduction, are tied to three intrinsic features of the annular arrangement of c subunits which constitutes the so-called c-ring, the core of the membrane-embedded FO domain: (i) the c-ring constitution is linked to the number of ions (H(+) or Na(+)) channeled across the membrane during the dissipation of the transmembrane electrochemical gradient, which in turn determines the species-specific bioenergetic cost of ATP, the "molecular currency unit" of energy transfer in all living beings; (ii) the c-ring is increasingly involved in the mitochondrial permeability transition, an event linked to cell death and to most mitochondrial dysfunctions; (iii) the c subunit species-specific amino acid sequence and susceptibility to post-translational modifications can address antibacterial drug design according to the model of enzyme inhibitors which target the c subunits. Therefore, the simple c-ring structure not only allows the F1FO-ATP synthase to perform the two opposite tasks of molecular machine of cell life and death, but it also amplifies the enzyme's potential role as a drug target.

  9. Crystalline Silica Primer

    Science.gov (United States)

    ,

    1992-01-01

    Crystalline silica is the scientific name for a group of minerals composed of silicon and oxygen. The term crystalline refers to the fact that the oxygen and silicon atoms are arranged in a threedimensional repeating pattern. This group of minerals has shaped human history since the beginning of civilization. From the sand used for making glass to the piezoelectric quartz crystals used in advanced communication systems, crystalline silica has been a part of our technological development. Crystalline silica's pervasiveness in our technology is matched only by its abundance in nature. It's found in samples from every geologic era and from every location around the globe. Scientists have known for decades that prolonged and excessive exposure to crystalline silica dust in mining environments can cause silicosis, a noncancerous lung disease. During the 1980's, studies were conducted that suggested that crystalline silica also was a carcinogen. As a result of these findings, crystalline silica has been regulated under the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard (HCS). Under HCS, OSHAregulated businesses that use materials containing 0.1% or more crystalline silica must follow Federal guidelines concerning hazard communication and worker training. Although the HCS does not require that samples be analyzed for crystalline silica, mineral suppliers or OSHAregulated

  10. Validation of foF2 and TEC Modeling During Geomagnetic Disturbed Times: Preliminary Outcomes of International Forum for Space Weather Modeling Capabilities Assessment

    Science.gov (United States)

    Shim, J. S.; Tsagouri, I.; Goncharenko, L. P.; Kuznetsova, M. M.

    2017-12-01

    To address challenges of assessment of space weather modeling capabilities, the CCMC (Community Coordinated Modeling Center) is leading the newly established "International Forum for Space Weather Modeling Capabilities Assessment." This presentation will focus on preliminary outcomes of the International Forum on validation of modeled foF2 and TEC during geomagnetic storms. We investigate the ionospheric response to 2013 Mar. geomagnetic storm event using ionosonde and GPS TEC observations in North American and European sectors. To quantify storm impacts on foF2 and TEC, we first quantify quiet-time variations of foF2 and TEC (e.g., the median and the average of the five quietest days for the 30 days during quiet conditions). It appears that the quiet time variation of foF2 and TEC are about 10% and 20-30%, respectively. Therefore, to quantify storm impact, we focus on foF2 and TEC changes during the storm main phase larger than 20% and 50%, respectively, compared to 30-day median. We find that in European sector, both foF2 and TEC response to the storm are mainly positive phase with foF2 increase of up to 100% and TEC increase of 150%. In North America sector, however, foF2 shows negative effects (up to about 50% decrease), while TEC shows positive response (the largest increase is about 200%). To assess modeling capability of reproducing the changes of foF2 and TEC due to the storm, we use various model simulations, which are obtained from empirical, physics-based, and data assimilation models. The performance of each model depends on the selected metrics, therefore, only one metrics is not enough to evaluate the models' predictive capabilities in capturing the storm impact. The performance of the model also varies with latitude and longitude.

  11. The Effect of fO2 on Partition Coefficients of U and Th between Garnet and Silicate Melt

    Science.gov (United States)

    Huang, F.; He, Z.; Schmidt, M. W.; Li, Q.

    2014-12-01

    Garnet is one of the most important minerals controlling partitioning of U and Th in the upper mantle. U is redox sensitive, while Th is tetra-valent at redox conditions of the silicate Earth. U-series disequilibria have provided a unique tool to constrain the time-scales and processes of magmatism at convergent margins. Variation of garnet/meltDU/Th with fO2 is critical to understand U-series disequilibria in arc lavas. However, there is still no systematic experimental study about the effect of fO2 on partitioning of U and Th between garnet and melt. Here we present experiments on partitioning of U, Th, Zr, Hf, Nb, Ta, and REE between garnet and silicate melts at various fO2. The starting material was hydrous haplo-basalt. The piston cylinder experiments were performed with Pt double capsules with C-CO, MnO-Mn3O4 (MM), and hematite-magnetite (HM) buffers at 3 GPa and 1185-1230 oC. The experiments produced garnets with diameters > 50μm and quenched melt. Major elements were measured by EMPA at ETH Zurich. Trace elements were determined using LA-ICP-MS at Northwestern University (Xi'an, China) and SIMS (Cameca1280 at the Institute of Geology and Geophysics, Beijing, China), producing consistent partition coefficient data for U and Th. With fO2 increasing from CCO to MM and HM, garnet/meltDU decreases from 0.041 to 0.005, while garnet/meltDTh ranges from 0.003 to 0.007 without correlation with fO2. Notably, garnet/meltDTh/U increases from 0.136 at CCO to 0.41 at HM. Our results indicate that U is still more compatible than Th in garnet even at the highest fO2 considered for the subarc mantle wedge (~NNO). Therefore, we predict that if garnet is the dominant phase controlling U-Th partitioning during melting of the mantle wedge, melts would still have 230Th excess over 238U. This explains why most young continental arc lavas have 230Th excess. If clinopyroxene is the dominant residual phase during mantle melting, U could be more incompatible than Th at high fO2

  12. FO hydrophone with hydrostatic pressure compensation: comparative experiment with a conventional piezo hydrophone

    NARCIS (Netherlands)

    Cheng, L.K.; Bruijn, D. de

    1998-01-01

    This paper presents the performance of a TPD FO hydrophone with hydrostatic pressure compensation. In particularly a comparison with a conventional piezo hydrophone system is discussed. ©2003 Copyright SPIE

  13. The inhibition of the mitochondrial F1FO-ATPase activity when activated by Ca2+ opens new regulatory roles for NAD.

    Science.gov (United States)

    Nesci, Salvatore; Trombetti, Fabiana; Ventrella, Vittoria; Pirini, Maurizio; Pagliarani, Alessandra

    2018-01-26

    The mitochondrial F1FO-ATPase is uncompetitively inhibited by NAD+ only when the natural cofactor Mg2+ is replaced by Ca2+, a mode putatively involved in cell death. The Ca2+-dependent F1FO-ATPase is also inhibited when NAD+ concentration in mitochondria is raised by acetoacetate. The enzyme inhibition by NAD+ cannot be ascribed to any de-ac(et)ylation or ADP-ribosylation by sirtuines, as it is not reversed by nicotinamide. Moreover, the addition of acetyl-CoA or palmitate, which would favor the enzyme ac(et)ylation, does not affect the F1FO-ATPase activity. Consistently, NAD+ may play a new role, not associated with redox and non-redox enzymatic reactions, in the Ca2+-dependent regulation of the F1FO-ATPase activity.

  14. FirefOx Design Reference fO2 Sensor for Hot, Deep Atmospheres

    Science.gov (United States)

    Izenberg, N.; Papadakis, S.; Deglau, D.; Francomacaro, A. S.

    2016-12-01

    Understanding the composition of the lowest portion of Venus' atmosphere is critical to knowing the stable mineralogy of the rocks there. Oxygen gas is a critical trace component, with fugacity, or partial pressure, estimated in the range of 10-19 to 10-22 from early probe measurements down to 22km altitude (Pioneer Venus, Venera), chemical equilibrium measurements, and other modeling. "FirefOx" is a simple oxygen fugacity sensor with the express purpose of determining the partial pressure of oxygen in the lowest scale heights of the Venus atmosphere, and especially the lowest hundreds of meters; the surface atmosphere interface, where the atmosphere and surface move to thermodynamic equilibrium. Knowledge of the fO2 at the surface atmosphere interface is crucial to determining the stable mineralogy of surface materials (e.g. magnetite vs. hematite) and gas chemistry in the near-surface atmosphere FirefOx is a Metal/Metal Oxide oxygen fugacity sensor intended to be mounted on the outside of a Venus descent probe, with electronics housed inside a thermally controlled environment. The sole sensor capability is the precise, accurate detection of the partial pressure of oxygen gas (fO2) in the near-surface environment of Venus, at up to 95-bar pressure (predominantly CO2. Surface temperatures at mean planetary elevation are near 735 K, thus a required operational temperature range of 710-740 K covers a range of near-surface elevations. FirefOx system requirements are low ( 100-200 grams, mass, milliwatt power, several kilobytes total science data). A design reference sensor, composed of custom, Yittria-ZrO ceramic electrolyte, with an encapsulated Pd/PdO standard and patterned Pt electrodes has demonstrated scientifically useful signal-to-noise millivolt level potential at temperatures as low as 620 K, relatable to fO2 by a Nernst equation E = RT/4F ln(PO2/PrefO2) where E = open circuit potential across the sensor electrolyte, R = universal gas constant, T

  15. Silica coated ionic liquid templated mesoporous silica nanoparticles ...

    African Journals Online (AJOL)

    A series of long chain pyridinium based ionic liquids 1-tetradecylpyridinium bromide, 1-hexadecylpyridinium bromide and 1-1-octadecylpyridinium bromide were used as templates to prepare silica coated mesoporous silica nanoparticles via condensation method under basic condition. The effects of alkyl chain length on ...

  16. Long-term trends in foF2: A comparison of various methods

    Czech Academy of Sciences Publication Activity Database

    Laštovička, Jan; Mikhailov, A. V.; Ulich, T.; Bremer, J.; Elias, A. G.; Ortiz de Adler, N.; Jara, V.; Abarca del Rio, R.; Foppiano, A. J.; Ovalle, E.; Danilov, A. D.

    2006-01-01

    Roč. 68, č. 17 (2006), s. 1854-1870 ISSN 1364-6826 Institutional research plan: CEZ:AV0Z30420517 Keywords : Ionosphere * foF2 * Long-term trends * Anthropogenic effects Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.448, year: 2006

  17. Crystallization and preliminary X-ray crystallographic characterization of TrmFO, a folate-dependent tRNA methyltransferase from Thermotoga maritima

    International Nuclear Information System (INIS)

    Cicmil, Nenad

    2008-01-01

    T. maritima TrmFO was overexpressed, purified and crystallized. A diffraction data set was collected to a resolution of 2.6 Å. TrmFO, previously classified as GID, is a methyltransferase that catalyzes the formation of 5-methyluridine or ribothymidine (T) at position 54 in tRNA in some Gram-positive bacteria. To date, TrmFO is the only characterized tRNA methyltransferase that does not use S-adenosylmethionine as the methyl-group donor. Instead, the donor of the methyl group is N 5 ,N 10 -methylenetetrahydrofolate. The crystallization and preliminary X-ray crystallographic studies of TrmFO are reported here. The recombinant protein, cloned from Thermotoga maritima genomic DNA, was overproduced in Esherichia coli and crystallized in 25%(v/v) PEG 4000, 100 mM NaCl and sodium citrate buffer pH 5.0 at 291 K using the hanging-drop vapor-diffusion method. The plate-shaped crystals diffracted to 2.6 Å and belong to the orthorhombic space group P2 1 2 1 2 1 , with unit-cell parameters a = 79.94, b = 92.46, c = 127.20 Å

  18. Advanced oxidation of biorefractory organics in aqueous solution together with bioelectricity generation by microbial fuel cells with composite FO/GPEs

    Science.gov (United States)

    Fu, Bao-rong; Shen, Chao; Ren, Jing; Chen, Jia-yi; Zhao, Lin

    2018-03-01

    In this study, ferric oxide loading graphite particle electrodes (FO/GPEs) were prepared as cathode of a three-dimensional electrode MFC-Fenton system. The properties of the composite cathode were examined with higher surface area and more mesopores. FO/GPEs could work as both cathode and Fenton iron reagents, contributing to high oxidation activity and better performance of electricity generation. The application of FO/GPEs MFC-Fenton system on degrading p-nitrophenol presented high catalytic efficiency in a wide range of pH value. The removal of p-nitrophenol and TOC attained to about 85 % within 8 and 64 h at neutral pH, respectively. A neutral FO/GPEs MFC-Fenton oxidation mechanism was also proposed. Specifically, both the surface iron sites and dissolved iron ions catalyzed the decomposition of H2O2. As results, the generated hydroxyl radicals were used for p-nitrophenol degradation and the iron oxide was recycled.

  19. NOM and TEP fouling of a forward osmosis (FO) membrane: Foulant identification and cleaning

    KAUST Repository

    Valladares Linares, Rodrigo

    2012-12-01

    The study of forward osmosis (FO) membranes has increased due to the already demonstrated advantages compared to high-energy membrane processes such as reverse osmosis (RO). This research focuses on characterization of the natural organic matter (NOM) fraction causing fouling on the active layer (AL) of a FO membrane in a novel plate and frame module configuration, facing secondary wastewater effluent as a feed solution (FS) and seawater used as a draw solution (DS). In addition, transparent exopolymer particles (TEP) were observed on the support layer (SL) of the membrane in contact with the DS. The NOM fouling layer, after characterizing the water samples and membranes used, was found to be composed of biopolymers and protein-like substances, which adversely affect the flux of water through the FO membrane. However, NOM fouling showed high reversibility, up to 90% when air scouring for 15. min is used as a cleaning technique. The irreversible fouling in this work was found to be 8.2% after chemical cleaning. On the support layer of the membrane, TEP formed clusters clearly identifiable with an optical microscope and a TEP-specific dye. Chemical cleaning with 1% NaOCl for 10. min proved to be the most effective method to remove TEP. © 2012.

  20. NOM and TEP fouling of a forward osmosis (FO) membrane: Foulant identification and cleaning

    KAUST Repository

    Valladares Linares, Rodrigo; Yangali-Quintanilla, Victor; Li, Zhenyu; Amy, Gary L.

    2012-01-01

    The study of forward osmosis (FO) membranes has increased due to the already demonstrated advantages compared to high-energy membrane processes such as reverse osmosis (RO). This research focuses on characterization of the natural organic matter (NOM) fraction causing fouling on the active layer (AL) of a FO membrane in a novel plate and frame module configuration, facing secondary wastewater effluent as a feed solution (FS) and seawater used as a draw solution (DS). In addition, transparent exopolymer particles (TEP) were observed on the support layer (SL) of the membrane in contact with the DS. The NOM fouling layer, after characterizing the water samples and membranes used, was found to be composed of biopolymers and protein-like substances, which adversely affect the flux of water through the FO membrane. However, NOM fouling showed high reversibility, up to 90% when air scouring for 15. min is used as a cleaning technique. The irreversible fouling in this work was found to be 8.2% after chemical cleaning. On the support layer of the membrane, TEP formed clusters clearly identifiable with an optical microscope and a TEP-specific dye. Chemical cleaning with 1% NaOCl for 10. min proved to be the most effective method to remove TEP. © 2012.

  1. Sensitization of erbium in silicon-rich silica : the effect of annealing temperature and hydrogen passivation

    International Nuclear Information System (INIS)

    Wilkinson, A.R.; Forcales, M.; Elliman, R.G.

    2005-01-01

    This paper reports on the effect of annealing temperature and hydrogen passivation on the excitation cross-section and photoluminescence of erbium in silicon-rich silica. Samples were prepared by co-implantation of Si and Er into SiO 2 followed by a single thermal anneal at temperatures ranging from 800 to 1100 degrees C, and with or without hydrogen passivation performed at 500 degrees C. Using time-resolved photoluminescence, the effective erbium excitation cross-section is shown to increase by a factor 3, while the number of optically active erbium ions decreases by a factor of 4 with increasing annealing temperature. Hydrogen passivation is shown to increase the luminescence intensity and to shorten the luminescence lifetime at 1.54 μm only in the presence of Si nanocrystals. The implications fo these results for realizing a silicon-based optical amplifier are also discussed. (author). 19 refs., 3 figs

  2. Silica-Immobilized Enzyme Reactors

    Science.gov (United States)

    2007-08-01

    Silica-IMERs 14 implicated in neurological disorders such as Schizophrenia and Parkinson’s disease.[86] Drug discovery for targets that can alter the...primarily the activation of prodrugs and proantibiotics for cancer treatments or antibiotic therapy , respectively.[87] Nitrobenzene nitroreductase was...BuChE) Monolith disks* Packed Silica Biosilica Epoxide- Silica Silica-gel Enzyme Human AChE Human AChE Human AChE Equine BuChE Human

  3. Nitrogen diffusion in hafnia and the impact of nitridation on oxygen and hydrogen diffusion: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Sathiyanarayanan, Rajesh, E-mail: rajessat@in.ibm.com, E-mail: rajesh.sathiyanarayanan@gmail.com; Pandey, R. K.; Murali, K. V. R. M. [IBM Semiconductor Research and Development Center, Bangalore 560045 (India)

    2015-01-21

    Using first-principles simulations, we have computed incorporation energies and diffusion barriers of ammonia, the nitrogen molecule and atomic nitrogen in monoclinic hafnia (m-HfO{sub 2}). Our calculations show that ammonia is likely to dissociate into an NH{sub 2} molecular unit, whereas the nitrogen molecule remains as a molecule either in the interstitial space or at an oxygen lattice site. The lowest energy pathway for the diffusion of atomic nitrogen interstitials consists of the hopping of the nitrogen interstitial between neighboring three-coordinated lattice oxygen atoms that share a single Hf atom, and the barrier for such hops is determined by a switching mechanism. The substitutional nitrogen atom shows a preference for diffusion through the doubly positive oxygen vacancy-mediated mechanism. Furthermore, we have investigated the impact of nitrogen atoms on the diffusion barriers of oxygen and hydrogen interstitials in m-HfO{sub 2}. Our results show that nitrogen incorporation has a significant impact on the barriers for oxygen and hydrogen diffusion: nitrogen atoms attract oxygen and hydrogen interstitials diffusing in the vicinity, thereby slowing down (reducing) their diffusion (diffusion length)

  4. MASS BALANCE OF SILICA IN STRAW FROM THE PERSPECTIVE OF SILICA REDUCTION IN STRAW PULP

    Directory of Open Access Journals (Sweden)

    Celil Atik,

    2012-06-01

    Full Text Available The high silica content of wheat straw is an important limiting factor for straw pulping. High silica content complicates processing and black liquor recovery, wears out factory installations, and lowers paper quality. Each section of wheat straw has different cells and chemical compositions and thus different silica content. In this work, the silica content of balled straw samples were examined according to their physical components, including internodes, nodes, leaves (sheath and blade, rachis, grain, other plant bodies, and other plant spikes. Mass distribution of silica was determined by a dry ashing method. Half (50.90% of the silica comes from leaves, and its mechanical separation will reduce the silica content in wheat straw pulp significantly. Destroying silica bodies by sonication will increase the strength properties of straw pulp.

  5. Liquid Phase Deposition of Silica on the Hexagonally Close-Packed Monolayer of Silica Spheres

    Directory of Open Access Journals (Sweden)

    Seo Young Yoon

    2013-01-01

    Full Text Available Liquid phase deposition is a method used for the nonelectrochemical production of polycrystalline ceramic films at low temperatures, most commonly silicon dioxide films. Herein, we report that silica spheres are organized in a hexagonal close-packed array using a patterned substrate. On this monolayer of silica spheres, we could fabricate new nanostructures in which deposition and etching compete through a modified LPD reaction. In the early stage, silica spheres began to undergo etching, and then, silica bridges between the silica spheres appeared by the local deposition reaction. Finally, the silica spheres and bridges disappeared completely. We propose the mechanism for the formation of nanostructure.

  6. Crystallization and preliminary X-ray crystallographic characterization of TrmFO, a folate-dependent tRNA methyltransferase from Thermotoga maritima

    Energy Technology Data Exchange (ETDEWEB)

    Cicmil, Nenad, E-mail: cicmil@uiuc.edu [Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States)

    2008-03-01

    T. maritima TrmFO was overexpressed, purified and crystallized. A diffraction data set was collected to a resolution of 2.6 Å. TrmFO, previously classified as GID, is a methyltransferase that catalyzes the formation of 5-methyluridine or ribothymidine (T) at position 54 in tRNA in some Gram-positive bacteria. To date, TrmFO is the only characterized tRNA methyltransferase that does not use S-adenosylmethionine as the methyl-group donor. Instead, the donor of the methyl group is N{sup 5},N{sup 10}-methylenetetrahydrofolate. The crystallization and preliminary X-ray crystallographic studies of TrmFO are reported here. The recombinant protein, cloned from Thermotoga maritima genomic DNA, was overproduced in Esherichia coli and crystallized in 25%(v/v) PEG 4000, 100 mM NaCl and sodium citrate buffer pH 5.0 at 291 K using the hanging-drop vapor-diffusion method. The plate-shaped crystals diffracted to 2.6 Å and belong to the orthorhombic space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 79.94, b = 92.46, c = 127.20 Å.

  7. New Evidence That Nonlinear Source-Filter Coupling Affects Harmonic Intensity and fo Stability During Instances of Harmonics Crossing Formants.

    Science.gov (United States)

    Maxfield, Lynn; Palaparthi, Anil; Titze, Ingo

    2017-03-01

    The traditional source-filter theory of voice production describes a linear relationship between the source (glottal flow pulse) and the filter (vocal tract). Such a linear relationship does not allow for nor explain how changes in the filter may impact the stability and regularity of the source. The objective of this experiment was to examine what effect unpredictable changes to vocal tract dimensions could have on fo stability and individual harmonic intensities in situations in which low frequency harmonics cross formants in a fundamental frequency glide. To determine these effects, eight human subjects (five male, three female) were recorded producing fo glides while their vocal tracts were artificially lengthened by a section of vinyl tubing inserted into the mouth. It was hypothesized that if the source and filter operated as a purely linear system, harmonic intensities would increase and decrease at nearly the same rates as they passed through a formant bandwidth, resulting in a relatively symmetric peak on an intensity-time contour. Additionally, fo stability should not be predictably perturbed by formant/harmonic crossings in a linear system. Acoustic analysis of these recordings, however, revealed that harmonic intensity peaks were asymmetric in 76% of cases, and that 85% of fo instabilities aligned with a crossing of one of the first four harmonics with the first three formants. These results provide further evidence that nonlinear dynamics in the source-filter relationship can impact fo stability as well as harmonic intensities as harmonics cross through formant bandwidths. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  8. A natural driven membrane process for brackish and wastewater treatment: photovoltaic powered ED and FO hybrid system.

    Science.gov (United States)

    Zhang, Yang; Pinoy, Luc; Meesschaert, Boudewijn; Van der Bruggen, Bart

    2013-09-17

    In isolated locations, remote areas, or islands, potable water is precious because of the lack of drinking water treatment facilities and energy supply. Thus, a robust and reliable water treatment system based on natural energy is needed to reuse wastewater or to desalinate groundwater/seawater for provision of drinking water. In this work, a hybrid membrane system combining electrodialysis (ED) and forward osmosis (FO), driven by renewable energy (solar energy), denoted as EDFORD (ED-FO Renewable energy Desalination), is proposed to produce high-quality water (potable) from secondary wastewater effluent or brackish water. In this hybrid membrane system, feedwater (secondary wastewater effluent or synthetic brackish water) was drawn to the FO draw solution while the organic and inorganic substances (ions, compounds, colloids and particles) were rejected. The diluted draw solution was then pumped to the solar energy driven ED. In the ED unit, the diluted draw solution was desalted and high-quality water was produced; the concentrate was recycled to the FO unit and reused as the draw solution. Results show that the water produced from this system contains a low concentration of total organic carbon (TOC), carbonate, and cations derived from the feedwater; had a low conductivity; and meets potable water standards. The water production cost considering the investment for membranes and solar panel is 3.32 to 4.92 EUR m(-3) (for 300 days of production per year) for a small size potable water production system.

  9. Grafting of polymer onto silica surface in the presence of γ-ray irradiated silica

    International Nuclear Information System (INIS)

    Tsuchida, A.; Yokoyama, R.; Takami, M.; Chen, J.; Ohta, M.; Tsubokawa, N.

    2002-01-01

    Complete text of publication follows. We have reported the graft polymerization of vinyl monomers initiated by surface radicals formed by the decomposition of azo and peroxide groups previously introduced onto the surface. In addition, the grafting of polymers onto carbon black has been reported by the reaction of polymer radicals with the surface. On the other hand, it is well known that the relatively stable radicals are generated on the surface by the γ-ray irradiation. In this paper, the grafting of polystyrene onto silica surface during the thermal polymerization of styrene in the presence of γ-ray irradiated silica, grafting mechanism and thermal stability of grafted polymer will be discussed. The grafting of polymers onto silica surface by irradiation of polymer-adsorbed silica was also investigated. Silica obtained from Mitsubishi Chemical Co., Japan was used after pulverization: the particle size was 0.037-0.088 mm. Irradiation was performed in Cs-137 source at room temperature. The silica was irradiated at 50 Gy with dose rate of 3.463 Gy/min. Into a polymerization tube, styrene and irradiated silica was charged and the polymerization was carried out under argon under stirring. The percentage of polystyrene grafting was determined from weight loss when polystyrene-grafted silica was heated at 600 deg C by a thermal analyzer. Untreated silica did not affect the thermal polymerization of styrene. On the contrary, the thermal polymerization of styrene was remarkably retarded in the presence of the irradiated silica at 60 deg C. Similar tendency was reported during the polymerization of vinyl monomers in the presence of carbon black. In the initial stage of the polymerization in the presence of the irradiated silica below 50 deg C, the polymerization was accelerated. During the polymerization in the presence of irradiated silica, polystyrene was grafted onto the surface: the percentage of grafting was 5-11%. The amount of polystyrene grafted onto silica

  10. Hydrothermal stability of microporous silica and niobia-silica membranes

    NARCIS (Netherlands)

    Boffa, V.; Blank, David H.A.; ten Elshof, Johan E.

    2008-01-01

    The hydrothermal stability of microporous niobia–silica membranes was investigated and compared with silica membranes. The membranes were exposed to hydrothermal conditions at 150 and 200 °C for 70 h. The change of pore structure before and after exposure to steam was probed by single-gas permeation

  11. Serpentinization processes: Influence of silica

    Science.gov (United States)

    Huang, R.; Sun, W.; Ding, X.; Song, M.; Zhan, W.

    2016-12-01

    Serpentinization systems are highly enriched in molecular hydrogen (H2) and hydrocarbons (e.g. methane, ethane and propane). The production of hydrocarbons results from reactions between H2 and oxidized carbon (carbon dioxide and carbon monoxide), which possibly contribute to climate changes during early history of the Earth. However, the influence of silica on the production of H2 and hydrocarbons was poorly constrained. We performed experiments at 311-500 °C and 3.0 kbar using mechanical mixtures of silica and olivine in ratios ranging from 0 to 40%. Molecular hydrogen (H2), methane, ethane and propane were formed, which were analyzed by gas chromatography. It was found that silica largely decreased H2 production. Without any silica, olivine serpentinization produced 94.5 mmol/kg H2 after 20 days of reaction time. By contrast, with the presence of 20% silica, H2 concentrations decreased largely, 8.5 mmol/kg. However, the influence of silica on the production of hydrocarbons is negligible. Moreover, with the addition of 20%-40% silica, the major hydrous minerals are talc, which was quantified according to an established standard curve calibrated by infrared spectroscopy analyses. It shows that silica greatly enhances olivine hydration, especially at 500 °C. Without any addition of silica, reaction extents were serpentinization at 500 °C and 3.0 kbar. By contrast, with the presence of 50% silica, olivine was completely transformed to talc within 9 days. This study indicates that silica impedes the oxidation of ferrous iron into ferric iron, and that rates of olivine hydration in natural geological settings are much faster with silica supply.

  12. Long-term trends of foF2 independent of geomagnetic activity

    Directory of Open Access Journals (Sweden)

    A. D. Danilov

    Full Text Available A detailed analysis of the foF2 data at a series of ionospheric stations is performed to reveal long-term trends independent of the long-term changes in geomagnetic activity during the recent decades (nongeomagnetic trends. The method developed by the author and published earlier is used. It is found that the results for 21 out of 23 stations considered agree well and give a relative nongeomagnetic trend of -0.0012 per year (or an absolute nongeomagnetic trend of about -0.012 MHz per year for the period between 1958 and the mid-nineties. The trends derived show no dependence on geomagnetic latitude or local time, a fact confirming their independence of geomagnetic activity. The consideration of the earlier period (1948–1985 for a few stations for which the corresponding data are available provides significantly lower foF2 trends, the difference between the later and earlier periods being a factor of 1.6. This is a strong argument in favor of an anthropogenic nature of the trends derived.Key words. Ionosphere (ionosphere-atmosphere interactions; ionospheric disturbances; mid-latitude ionosphere

  13. Interfacial interaction between the epoxidized natural rubber and silica in natural rubber/silica composites

    Science.gov (United States)

    Xu, Tiwen; Jia, Zhixin; Luo, Yuanfang; Jia, Demin; Peng, Zheng

    2015-02-01

    The epoxidized natural rubber (ENR) as an interfacial modifier was used to improve the mechanical and dynamical mechanical properties of NR/silica composites. In order to reveal the interaction mechanism between ENR and silica, the ENR/Silica model compound was prepared by using an open mill and the interfacial interaction of ENR with silica was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and stress-strain testing. The results indicated that the ring-opening reaction occurs between the epoxy groups of ENR chains and Si-OH groups on the silica surfaces and the covalent bonds are formed between two phases, which can improve the dispersion of silica in the rubber matrix and enhance the interfacial combination between rubber and silica. The ring-opening reaction occurs not only in vulcanization process but also in mixing process, meanwhile, the latter seems to be more important due to the simultaneous effects of mechanical force and temperature.

  14. Interfacial interaction between the epoxidized natural rubber and silica in natural rubber/silica composites

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tiwen [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Jia, Zhixin, E-mail: zxjia@scut.edu.cn [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Luo, Yuanfang; Jia, Demin [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Peng, Zheng [Agricultural Product Processing Research Institute, Chinese Academy of Tropical Agriculture Sciences, Zhanjiang 524001 (China)

    2015-02-15

    Highlights: • Substantiate the ring open reaction between Si-OH of silica and epoxy groups of ENR. • ENR can act as a bridge between NR and silica to enhance the interfacial interaction. • As a modifier, ENR gets the potential to be used in the tread of green tire for improving the wet skid resistance apparently. - Abstract: The epoxidized natural rubber (ENR) as an interfacial modifier was used to improve the mechanical and dynamical mechanical properties of NR/silica composites. In order to reveal the interaction mechanism between ENR and silica, the ENR/Silica model compound was prepared by using an open mill and the interfacial interaction of ENR with silica was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and stress–strain testing. The results indicated that the ring-opening reaction occurs between the epoxy groups of ENR chains and Si-OH groups on the silica surfaces and the covalent bonds are formed between two phases, which can improve the dispersion of silica in the rubber matrix and enhance the interfacial combination between rubber and silica. The ring-opening reaction occurs not only in vulcanization process but also in mixing process, meanwhile, the latter seems to be more important due to the simultaneous effects of mechanical force and temperature.

  15. Monitoring transient elastic energy storage within the rotary motors of single FoF1-ATP synthase by DCO-ALEX FRET

    Science.gov (United States)

    Ernst, Stefan; Düser, Monika G.; Zarrabi, Nawid; Börsch, Michael

    2012-03-01

    The enzyme FoF1-ATP synthase provides the 'chemical energy currency' adenosine triphosphate (ATP) for living cells. Catalysis is driven by mechanochemical coupling of subunit rotation within the enzyme with conformational changes in the three ATP binding sites. Proton translocation through the membrane-bound Fo part of ATP synthase powers a 10-step rotary motion of the ring of c subunits. This rotation is transmitted to the γ and ɛ subunits of the F1 part. Because γ and ɛ subunits rotate in 120° steps, we aim to unravel this symmetry mismatch by real time monitoring subunit rotation using single-molecule Förster resonance energy transfer (FRET). One fluorophore is attached specifically to the F1 motor, another one to the Fo motor of the liposome-reconstituted enzyme. Photophysical artifacts due to spectral fluctuations of the single fluorophores are minimized by a previously developed duty cycle-optimized alternating laser excitation scheme (DCO-ALEX). We report the detection of reversible elastic deformations between the rotor parts of Fo and F1 and estimate the maximum angular displacement during the load-free rotation using Monte Carlo simulations.

  16. Subunit rotation in a single FoF1-ATP synthase in a living bacterium monitored by FRET

    Science.gov (United States)

    Seyfert, K.; Oosaka, T.; Yaginuma, H.; Ernst, S.; Noji, H.; Iino, R.; Börsch, M.

    2011-03-01

    FoF1-ATP synthase is the ubiquitous membrane-bound enzyme in mitochondria, chloroplasts and bacteria which provides the 'chemical energy currency' adenosine triphosphate (ATP) for cellular processes. In Escherichia coli ATP synthesis is driven by a proton motive force (PMF) comprising a proton concentration difference ΔpH plus an electric potential ΔΨ across the lipid membrane. Single-molecule in vitro experiments have confirmed that proton-driven subunit rotation within FoF1-ATP synthase is associated with ATP synthesis. Based on intramolecular distance measurements by single-molecule fluorescence resonance energy transfer (FRET) the kinetics of subunit rotation and the step sizes of the different rotor parts have been unraveled. However, these experiments were accomplished in the presence of a PMF consisting of a maximum ΔpH ~ 4 and an unknown ΔΨ. In contrast, in living bacteria the maximum ΔpH across the plasma membrane is likely 0.75, and ΔΨ has been measured between -80 and -140 mV. Thus the problem of in vivo catalytic turnover rates, or the in vivo rotational speed in single FoF1-ATP synthases, respectively, has to be solved. In addition, the absolute number of functional enzymes in a single bacterium required to maintain the high ATP levels has to be determined. We report our progress of measuring subunit rotation in single FoF1-ATP synthases in vitro and in vivo, which was enabled by a new labeling approach for single-molecule FRET measurements.

  17. Gas Separation through Bilayer Silica, the Thinnest Possible Silica Membrane.

    Science.gov (United States)

    Yao, Bowen; Mandrà, Salvatore; Curry, John O; Shaikhutdinov, Shamil; Freund, Hans-Joachim; Schrier, Joshua

    2017-12-13

    Membrane-based gas separation processes can address key challenges in energy and environment, but for many applications the permeance and selectivity of bulk membranes is insufficient for economical use. Theory and experiment indicate that permeance and selectivity can be increased by using two-dimensional materials with subnanometer pores as membranes. Motivated by experiments showing selective permeation of H 2 /CO mixtures through amorphous silica bilayers, here we perform a theoretical study of gas separation through silica bilayers. Using density functional theory calculations, we obtain geometries of crystalline free-standing silica bilayers (comprised of six-membered rings), as well as the seven-, eight-, and nine-membered rings that are observed in glassy silica bilayers, which arise due to Stone-Wales defects and vacancies. We then compute the potential energy barriers for gas passage through these various pore types for He, Ne, Ar, Kr, H 2 , N 2 , CO, and CO 2 gases, and use the data to assess their capability for selective gas separation. Our calculations indicate that crystalline bilayer silica, which is less than a nanometer thick, can be a high-selectivity and high-permeance membrane material for 3 He/ 4 He, He/natural gas, and H 2 /CO separations.

  18. Functional characterization of the gene FoOCH1 encoding a putative α-1,6-mannosyltransferase in Fusarium oxysporum f. sp. cubense.

    Science.gov (United States)

    Li, Min-Hui; Xie, Xiao-Ling; Lin, Xian-Feng; Shi, Jin-Xiu; Ding, Zhao-Jian; Ling, Jin-Feng; Xi, Ping-Gen; Zhou, Jia-Nuan; Leng, Yueqiang; Zhong, Shaobin; Jiang, Zi-De

    2014-04-01

    Fusarium oxysporum f. sp. cubense (FOC) is the causal agent of banana Fusarium wilt and has become one of the most destructive pathogens threatening the banana production worldwide. However, few genes related to morphogenesis and pathogenicity of this fungal pathogen have been functionally characterized. In this study, we identified and characterized the disrupted gene in a T-DNA insertional mutant (L953) of FOC with significantly reduced virulence on banana plants. The gene disrupted by T-DNA insertion in L953 harbors an open reading frame, which encodes a protein with homology to α-1,6-mannosyltransferase (OCH1) in fungi. The deletion mutants (ΔFoOCH1) of the OCH1 orthologue (FoOCH1) in FOC were impaired in fungal growth, exhibited brighter staining with fluorescein isothiocyanate (FITC)-Concanavalin A, had less cell wall proteins and secreted more proteins into liquid media than the wild type. Furthermore, the mutation or deletion of FoOCH1 led to loss of ability to penetrate cellophane membrane and decline in hyphal attachment and colonization as well as virulence to the banana host. The mutant phenotypes were fully restored by complementation with the wild type FoOCH1 gene. Our data provide a first evidence for the critical role of FoOCH1 in maintenance of cell wall integrity and virulence of F. oxysporum f. sp. cubense. Copyright © 2014 Elsevier Inc. All rights reserved.

  19. Effect of fO2 on phase relationship in basaltic andesites during magmatic differentiation: Control of fO2 and sulphur speciation in piston cylinder experiments.

    Science.gov (United States)

    Matjuschkin, Vladimir; Tattitch, Brian; Blundy, Jonathan D.; Skora, Susanne

    2014-05-01

    Within the mantle wedge above subduction zones, oxidation reaction take place by interaction of reduced mantle rocks with more oxidized, hydrous fluids, which can cause a local drop of the solidus, resulting in partial melting (2,6,7). The resultant melts are more oxidized that their ocean floor counterparts, which has implications for their subsequent differentiation paths, the speciation of multivalent elements and the solubility and transport of chemical compounds in magmatic systems (1,4,5). We present a series of sulphur-doped high-pressure experiments conducted to investigate the effect of oxygen fugacity on phase relationships and the behaviour of sulphur in silicate melts. Natural aphyric andesite (FM37) erupted from Laguna del Maule volcano, Chile (3) was selected as a starting composition. Experiments were carried out at 5kbar, 950-1150° C and variable oxygen fugacity conditions. New experiments buffered at Co-CoO and Ni-NiO buffer conditions have been performed using a new "MTB capsule design" developed in order to accurately control fO2 by means of a double capsule containing metal-oxide buffers and a pyrex sleeve to minimise H2 diffusion. This new design constrains oxygen fugacity to within ±0.1-0.2logfO2 units of the target value. Before conducting these experiments, the assemblage was tested multiple times at 10kbar, 1000° C over 24-48 hours and demonstrated consistent, accurate fO2 control. Analyses of the preliminary experimental run products, from a related Chilean basaltic andesite starting composition, demonstrate a clear effect of fO2 on phase relationships and the proportion of melt generated during experiments. Under oxidized conditions, as temperature decreased from 1150° C to 1050° C, the amount of melt decreased from 100% to ~80%, due to the formation of orthopyroxene, anhydrite and plagioclase. In contrast, in reduced runs the system remains nearly liquid (~5% crystals) down to 950° C due to the change in sulphur speciation and

  20. Synthesis of uniform carbon at silica nanocables and luminescent silica nanotubes with well controlled inner diameters

    International Nuclear Information System (INIS)

    Qian Haisheng; Yu Shuhong; Ren Lei; Yang Yipeng; Zhang Wei

    2006-01-01

    Uniform carbon at silica nanocables and silica nanotubes with well-controlled inner diameters can be synthesized in an easy way by a sacrificial templating method. This was performed using carbon nanofibres as hard templates that were synthesized previously by a hydrothermal carbonization process. Silica nanotubes with well-controlled inner diameters were synthesized from carbon at silica core-shell nanostructures by removal of the core carbon component. The inner diameters of the as-prepared silica nanotubes can be well controlled from several nanometres to hundreds of nanometres by adjusting the diameters of the carbon nanofibres. The silica nanotubes synthesized by this method display strong photoluminescence in ultraviolet at room temperature. Such uniform silica nanotubes might find potential applications in many fields such as encapsulation, catalysis, chemical/biological separation, and sensing

  1. Silica/Perfluoropolymer nanocomposites fabricated by direct melt-compounding: a novel method without surface modification on nano-silica.

    Science.gov (United States)

    Tanahashi, Mitsuru; Hirose, Masaki; Watanabe, Yusuke; Lee, Jeong-Chang; Takeda, Kunihiko

    2007-07-01

    A novel method for the fabrication of silica/perfluoropolymer nanocomposites was investigated, whereby nano-sized silica particles without surface modification were dispersed uniformly through mechanical breakdown of loosely packed agglomerates of silica nanoparticles with low fracture strength in a polymer melt during direct melt-compounding. The method consists of two stages. The first stage involves preparation of the loose silica agglomerate, and the second stage involves melt-compounding of a completely hydrophobic perfluoropolymer, poly(tetrafluoroethyleneco-perfluoropropylvinylether), with the loose silica agglomerates prepared in the first stage. In the first stage, the packing structure and the fracture strength of the silica agglomerate were controlled by destabilizing an aqueous colloidal silica solution with a mean primary diameter of 190 nm via pH control and salt addition. In the next stage, the silica/perfluoropolymer nanocomposite was fabricated by breaking down the prepared loose silica agglomerates with low fracture strength by means of a shear force inside the polymer melt during melt-compounding.

  2. Pico-second laser materials interactions: mechanisms, material lifetime and performance optimization Ted Laurence(14-ERD-014)

    Energy Technology Data Exchange (ETDEWEB)

    Laurence, Ted A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-12-14

    Laser-induced damage with ps pulse widths straddles the transition from intrinsic, multiphoton ionization- and avalanche ionization-based ablation with fs pulses to defectdominated, thermal-based damage with ns pulses. We investigated the morphology and scaling of damage for commonly used silica and hafnia coatings as well as fused silica. Using carefully calibrated laser-induced damage experiments, in situ imaging, and high-resolution optical microscopy, atomic force microscopy, and scanning electron microscopy, we showed that defects play an important role in laser-induced damage for pulse durations as short as 1 ps. Three damage morphologies were observed: standard material ablation, ultra-high density pits, and isolated absorbers. For 10 ps and longer, the isolated absorbers limited the damage performance of the coating materials. We showed that damage resulting from the isolated absorbers grows dramatically with subsequent pulses for sufficient fluences. For hafnia coatings, we used electric field modeling and experiments to show that isolated absorbers near the surface were affected by the chemical environment (vacuum vs. air) for pulses as short as 10 ps. Coupled with the silica results, these results suggested that improvements in the performance in the 10 -60 ps range have not reached fundamental limits. These findings motivate new efforts, including a new SI LDRD in improving the laser-damage performance of multi-layer dielectric coatings. A damage test facility for ps pulses was developed and automated, and was used for testing production optics for ARC. The resulting software was transferred to other laser test facilities for fs pulses and multiple wavelengths with 30 ps pulses. Additionally, the LDRD supported the retention and promotion of an important staff scientist in high-resolution dynamic microscopy and laser-damage testing.

  3. A comparison of neural network-based predictions of foF2 with the IRI-2012 model at conjugate points in Southeast Asia

    Science.gov (United States)

    Wichaipanich, Noraset; Hozumi, Kornyanat; Supnithi, Pornchai; Tsugawa, Takuya

    2017-06-01

    This paper presents the development of Neural Network (NN) model for the prediction of the F2 layer critical frequency (foF2) at three ionosonde stations near the magnetic equator of Southeast Asia. Two of these stations including Chiang Mai (18.76°N, 98.93°E, dip angle 12.7°N) and Kototabang (0.2°S, 100.3°E, dip angle 10.1°S) are at the conjugate points while Chumphon (10.72°N, 99.37°E, dip angle 3.0°N) station is near the equator. To produce the model, the feed forward network with backpropagation algorithm is applied. The NN is trained with the daily hourly values of foF2 during 2004-2012, except 2009, and the selected input parameters, which affect the foF2 variability, include day number (DN), hour number (HR), solar zenith angle (C), geographic latitude (θ), magnetic inclination (I), magnetic declination (D) and angle of meridian (M) relative to the sub-solar point, the 7-day mean of F10.7 (F10.7_7), the 81-day mean of SSN (SSN_81) and the 2-day mean of Ap (Ap_2). The foF2 data of 2009 and 2013 are then used for testing the NN model during the foF2 interpolation and extrapolation, respectively. To examine the performance of the proposed NN, the root mean square error (RMSE) of the observed foF2, the proposed NN model and the IRI-2012 (CCIR and URSI options) model are compared. In general, the results show the same trends in foF2 variation between the models (NN and IRI-2012) and the observations in that they are higher during the day and lower at night. Besides, the results demonstrate that the proposed NN model can predict the foF2 values more closely during daytime than during nighttime as supported by the lower RMSE values during daytime (0.5 ≤ RMSE ≤ 1.0 for Chumphon and Kototabang, 0.7 ≤ RMSE ≤ 1.2 at Chiang Mai) and with the highest levels during nighttime (0.8 ≤ RMSE ≤ 1.5 for Chumphon and Kototabang, 1.2 ≤ RMSE ≤ 2.0 at Chiang Mai). Furthermore, the NN model predicts the foF2 values more accurately than the IRI model at the

  4. Sonochemical coating of magnetite nanoparticles with silica.

    Science.gov (United States)

    Dang, Feng; Enomoto, Naoya; Hojo, Junichi; Enpuku, Keiji

    2010-01-01

    Magnetite nanoparticles were coated with silica through the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under ultrasonic irradiation. The ultrasonic irradiation was used to prevent the agglomeration of the magnetite particles and accelerate the hydrolysis and condensation of TEOS. TEM, DLS, XRF, VSM, TG and sedimentation test were used to characterize the silica-coated magnetite particles. The dispersibility of silica-coated magnetite particles in aqueous solution was improved significantly and the agglomerate particle size was decreased to 110 nm. It was found that the agglomerate particle size of silica-coated magnetite particles was mainly decided by the coating temperature and the pH value in the silica-coating process. The weight ratio of silica in silica-coated magnetite particles was mainly decided by the pH value in the silica-coating process. The dispersibility of silica-coated magnetite particles was mainly decided by the agglomerate particle size of the suspension. The oxidation of magnetite particles in air was limited through the coated silica. The magnetism of silica-coated magnetite particles decreased slightly after silica-coating.

  5. Oxalic acid complexes: Promising draw solutes for forward osmosis (FO) in protein enrichment

    KAUST Repository

    Ge, Qingchun; Chung, Neal Tai-Shung

    2015-01-01

    Highly soluble oxalic acid complexes (OACs) were synthesized through a one-pot reaction. The OACs exhibit excellent performance as draw solutes in FO processes with high water fluxes and negligible reverse solute fluxes. Efficient protein enrichment was achieved. The diluted OACs can be recycled via nanofiltration and are promising as draw solutes.

  6. Silica reinforced triblock copolymer gels

    DEFF Research Database (Denmark)

    Theunissen, E.; Overbergh, N.; Reynaers, H.

    2004-01-01

    The effect of silica and polymer coated silica particles as reinforcing agents on the structural and mechanical properties of polystyrene-poly(ethylene/butylene)-polystyrene (PS-PEB-PS) triblock gel has been investigated. Different types of chemically modified silica have been compared in order...

  7. Effect of silica concentration on electrical conductivity of epoxy resin-carbon black-silica nanocomposites

    International Nuclear Information System (INIS)

    Zhang Wei; Blackburn, Richard S.; Dehghani-Sanij, Abbas A.

    2007-01-01

    Electrical properties of nanocomposites are determined by the conductive paths of carbon black and influenced by a 'network' of silica. With increasing content of silica, carbon black (CB) particles are optimally dispersed, contributing to the generation of a conductive network between CB particles via direct particle contact and a tunneling effect; maximum conductivity for the epoxy resin-CB-silica nanocomposite described herein occurs at a ratio of 0.6:1.0 (SiO 2 :CB). As a non-conductive component, excessive silica will prevent electron flow, giving rise to low conductivity

  8. The Cr Redox Record of fO2 Variation in Angrites. Evidence for Redox Conditions of Angrite Petrogenesis and Parent Body

    Science.gov (United States)

    Shearer, Charles K.; Bell, Aaron S.; Burger, Paul V.; Papike, James J.; Jones, John; Le, Loan

    2016-01-01

    Angrites represent some of the earliest stages of planetesimal differentiation. Not surprisingly, there is no simple petrogenetic model for their origin. Petrogenesis has been linked to both magmatic and impact processes. Studies demonstrated that melting of chondritic material (e.g. CM, CV) at redox conditions where pure iron metal is unstable (e.g., IW+1 to IW+2) produced angrite-like melts. Alternatively, angrites were produced at more reducing conditions (redox conditions during crystallization (e.g., Fe metal and a Fe-Ti oxide with potential Fe3+. There have been several estimates of fO2 for angrites. Most notably, experiments examined the variation of DEu/DGd with fO2, between plagioclase and fassaitic pyroxene in equilibrium with an angrite melt composition. They used their observations to estimate the fO2 of crystallization to be approximately IW+0.6 for angrite LEW 86010. This estimate is only a "snapshot" of fO2 conditions during co-crystallization of plagioclase and pyroxene. Preliminary XANES analyses of V redox state in pyroxenes from D'Orbigny reported changes in fO2 from IW-0.7 during early pyroxene crystallization to IW+0.5 during latter episodes of pyroxene crystallization [15]. As this was a preliminary report, it presented limited information concerning the effects of pyroxene orientation and composition on the V valence measurements, and the effect of melt composition on valence and partitioning behavior of V. A closer examination of fO2 as recorded by Cr valence state in olivine will allow us to test models for primordial melting of chondritic material to produce the angrite parent melts. Here, we report the our initial stages of examining the origin and conditions of primordial melting on the angrite parent body and test some of the above models by integrating an experimental study of Cr and V valence partitioning between olivine [OL] and an angrite melt, with micro-scale determinations of Cr and V oxidation state in OL in selected "volcanic

  9. FoCal – A high granularity electromagnetic calorimeter for forward direct photon measurements

    NARCIS (Netherlands)

    Zhang, C.

    2017-01-01

    The measurement of direct photon production at forward rapidity (y∼3−5) at the LHC provides access to the structure of protons and nuclei at very small values of fractional momentum (x∼10−5). FoCal, an extremely-high-granularity Forward Calorimeter covering 3.3<η<5.3 is proposed as a detector

  10. Silica particles and method of preparation thereof

    NARCIS (Netherlands)

    2015-01-01

    The invention is in the field of silica products. More in particular, the invention is in the field of amorphous silica particles. The invention is directed to amorphous silica particles and related products including clusters of said silica particles, a suspension of said silica particles, and an

  11. FoCa: a modular treatment planning system for proton radiotherapy with research and educational purposes.

    Science.gov (United States)

    Sánchez-Parcerisa, D; Kondrla, M; Shaindlin, A; Carabe, A

    2014-12-07

    FoCa is an in-house modular treatment planning system, developed entirely in MATLAB, which includes forward dose calculation of proton radiotherapy plans in both active and passive modalities as well as a generic optimization suite for inverse treatment planning. The software has a dual education and research purpose. From the educational point of view, it can be an invaluable teaching tool for educating medical physicists, showing the insights of a treatment planning system from a well-known and widely accessible software platform. From the research point of view, its current and potential uses range from the fast calculation of any physical, radiobiological or clinical quantity in a patient CT geometry, to the development of new treatment modalities not yet available in commercial treatment planning systems. The physical models in FoCa were compared with the commissioning data from our institution and show an excellent agreement in depth dose distributions and longitudinal and transversal fluence profiles for both passive scattering and active scanning modalities. 3D dose distributions in phantom and patient geometries were compared with a commercial treatment planning system, yielding a gamma-index pass rate of above 94% (using FoCa's most accurate algorithm) for all cases considered. Finally, the inverse treatment planning suite was used to produce the first prototype of intensity-modulated, passive-scattered proton therapy, using 13 passive scattering proton fields and multi-leaf modulation to produce a concave dose distribution on a cylindrical solid water phantom without any field-specific compensator.

  12. Metal-dielectric-CNT nanowires for surface-enhanced Raman spectroscopy

    Science.gov (United States)

    Bond, Tiziana C.; Altun, Ali; Park, Hyung Gyu

    2017-10-03

    A sensor with a substrate includes nanowires extending vertically from the substrate, a hafnia coating on the nanowires that provides hafnia coated nanowires, and a noble metal coating on the hafnia coated nanowires. The top of the hafnia and noble metal coated nanowires bent onto one another to create a canopy forest structure. There are numerous randomly arranged holes that let through scattered light. The many points of contact, hot spots, amplify signals. The methods include the steps of providing a Raman spectroscopy substrate, introducing nano crystals to the Raman spectroscopy substrate, growing a forest of nanowires from the nano crystals on the Raman spectroscopy substrate, coating the nanowires with hafnia providing hafnia coated nanowires, and coating the hafnia coated nanowires with a noble metal or other metal.

  13. COOH-functionalisation of silica particles

    Energy Technology Data Exchange (ETDEWEB)

    Majewski, Peter, E-mail: peter.majewski@unisa.edu.au [School of Advanced Manufacturing and Mechanical Engineering, Mawson Institute, University of South Australia, Adelaide (Australia); Albrecht, Trent [Ian Wark Research Institute, University of South Australia, Adelaide (Australia); Weber, Siegfried [Department of Biotechnology, University of Applied Sciences, Mannheim (Germany)

    2011-09-01

    In this study COOH-functionalised silica is synthesised using phosphonateN-(phosphonomethyl)iminodiacetic acid (PMIDA) in an aqueous solution. The presence of PMIDA on the silica particles was verified using Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy and titration. Experimentally, surface concentrations of COOH functional groups of up to about 3 mmol/g{sub silica} were achieved, whereas theoretical calculation of the maximum COOH functional group concentration gave about 1 mmol/g{sub silica}. The discrepancy may be caused by PMIDA multilayer formation on the particle.

  14. Ionospheric foF2 at EIA region: comparison between observations and IRI model

    Science.gov (United States)

    Chuo, Y. J.; Lee, C. C.

    We have used data from an equatorial ionization anomaly area station in the western Pacific region to study the monthly variability of foF2 Diurnal seasonal and solar activity effects were investigated The data established by this study are proposed as valid input values for the development of URSI and CCIR options for the International Reference Ionosphere

  15. Modeling ionospheric foF 2 response during geomagnetic storms using neural network and linear regression techniques

    Science.gov (United States)

    Tshisaphungo, Mpho; Habarulema, John Bosco; McKinnell, Lee-Anne

    2018-06-01

    In this paper, the modeling of the ionospheric foF 2 changes during geomagnetic storms by means of neural network (NN) and linear regression (LR) techniques is presented. The results will lead to a valuable tool to model the complex ionospheric changes during disturbed days in an operational space weather monitoring and forecasting environment. The storm-time foF 2 data during 1996-2014 from Grahamstown (33.3°S, 26.5°E), South Africa ionosonde station was used in modeling. In this paper, six storms were reserved to validate the models and hence not used in the modeling process. We found that the performance of both NN and LR models is comparable during selected storms which fell within the data period (1996-2014) used in modeling. However, when validated on storm periods beyond 1996-2014, the NN model gives a better performance (R = 0.62) compared to LR model (R = 0.56) for a storm that reached a minimum Dst index of -155 nT during 19-23 December 2015. We also found that both NN and LR models are capable of capturing the ionospheric foF 2 responses during two great geomagnetic storms (28 October-1 November 2003 and 6-12 November 2004) which have been demonstrated to be difficult storms to model in previous studies.

  16. Metal-silica sol-gel materials

    Science.gov (United States)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  17. Silica aerogel Cerenkov counter

    International Nuclear Information System (INIS)

    Yasumi, S.; Masaike, A.; Yamamoto, A.; Yoshimura, Y.; Kawai, H.

    1984-03-01

    In order to obtain silica aerogel radiators of good quality, the prescription used by Saclay group has been developed. We have done several experiments using beams from KEK.PS to test the performance of a Cerenkov counter with aerogel modules produced in KEK. It turned out that these modules had excellent quality. The production rate of silica aerogel in KEK is 15 -- 20 litres a week. Silica aerogel modules of 20 x 10 x 3 cm 3 having the refractive index of 1.058 are successfully being used by Kyoto University group in the KEK experiment E92 (Σ). Methodes to produce silica aerogel with higher refractive index than 1.06 has been investigated both by heating an module with the refractive index of 1.06 and by hydrolyzing tetraethyl silicate. (author)

  18. Melt flow and mechanical properties of silica/perfluoropolymer nanocomposites Fabricated by direct melt-compounding without surface modification on nano-silica.

    Science.gov (United States)

    Tanahashi, Mitsuru; Watanabe, Yusuke; Lee, Jeong-Chang; Takeda, Kunihiko; Fujisawa, Toshiharu

    2009-01-01

    The authors have previously developed a novel method for the fabrication of silica/perfluoropolymer nanocomposites, wherein nano-sized silica particles without surface modification were dispersed uniformly through breakdown of loosely packed agglomerates of silica nanoparticles with low fracture strength in a polymer melt during direct melt-compounding. The method consists of two stages; the first stage involves preparation of the loose silica agglomerate, and the second stage involves melt-compounding of a completely hydrophobic perfluoropolymer, PFA (poly(tetrafluoroethylene-co-perfluoropropylvinylether)), with the loose silica agglomerates. By using this simple method without any lipophilic treatment of the silica surfaces, silica nanoparticles with a primary diameter of 190 nm could be dispersed uniformly into the PFA matrix. The main purpose of the present study is to evaluate the melt flow and tensile properties of silica/PFA nanocomposites fabricated by the above method. In order to elucidate the effects of the size of the dispersed silica in the PFA matrix on the properties of the composites, silica/PFA composite samples exhibiting the dispersion of larger-sized silica particle-clusters were fabricated as negative controls of the silica dispersion state. The results obtained under the present experimental conditions showed that the size of the dispersed silica in the PFA matrix exerts a strong influence on the ultimate tensile properties, such as tensile strength and elongation at break, and the melt flow rate (MFR) of the composite materials. The MFR of the silica/PFA nanocomposite became higher than that of the pure PFA without silica addition, although the MFR of the PFA composites containing larger silica particle-clusters became much lower than that of the pure PFA. Furthermore, uniform dispersion of isolated silica nanoparticles was found to improve not only the Young's modulus but also the ultimate tensile properties of the composite.

  19. Multifunctional nanomedicine with silica: Role of silica in nanoparticles for theranostic, imaging, and drug monitoring.

    Science.gov (United States)

    Chen, Fang; Hableel, Ghanim; Zhao, Eric Ruike; Jokerst, Jesse V

    2018-07-01

    The idea of multifunctional nanomedicine that enters the human body to diagnose and treat disease without major surgery is a long-standing dream of nanomaterials scientists. Nanomaterials show incredible properties that are not found in bulk materials, but achieving multi-functionality on a single material remains challenging. Integrating several types of materials at the nano-scale is critical to the success of multifunctional nanomedicine device. Here, we describe the advantages of silica nanoparticles as a tool for multifunctional nano-devices. Silica nanoparticles have been intensively studied in drug delivery due to their biocompatibility, degradability, tunable morphology, and ease of modification. Moreover, silica nanoparticles can be integrated with other materials to obtain more features and achieve theranostic capabilities and multimodality for imaging applications. In this review, we will first compare the properties of silica nanoparticles with other well-known nanomaterials for bio-applications and describe typical routes to synthesize and integrate silica nanoparticles. We will then highlight theranostic and multimodal imaging application that use silica-based nanoparticles with a particular interest in real-time monitoring of therapeutic molecules. Finally, we will present the challenges and perspective on future work with silica-based nanoparticles in medicine. Copyright © 2018 Elsevier Inc. All rights reserved.

  20. Interpretation of monoclinic hafnia valence electron energy-loss spectra by time-dependent density functional theory

    Science.gov (United States)

    Hung, L.; Guedj, C.; Bernier, N.; Blaise, P.; Olevano, V.; Sottile, F.

    2016-04-01

    We present the valence electron energy-loss spectrum and the dielectric function of monoclinic hafnia (m -HfO2) obtained from time-dependent density-functional theory (TDDFT) predictions and compared to energy-filtered spectroscopic imaging measurements in a high-resolution transmission-electron microscope. Fermi's golden rule density-functional theory (DFT) calculations can capture the qualitative features of the energy-loss spectrum, but we find that TDDFT, which accounts for local-field effects, provides nearly quantitative agreement with experiment. Using the DFT density of states and TDDFT dielectric functions, we characterize the excitations that result in the m -HfO2 energy-loss spectrum. The sole plasmon occurs between 13 and 16 eV, although the peaks ˜28 and above 40 eV are also due to collective excitations. We furthermore elaborate on the first-principles techniques used, their accuracy, and remaining discrepancies among spectra. More specifically, we assess the influence of Hf semicore electrons (5 p and 4 f ) on the energy-loss spectrum, and find that the inclusion of transitions from the 4 f band damps the energy-loss intensity in the region above 13 eV. We study the impact of many-body effects in a DFT framework using the adiabatic local-density approximation (ALDA) exchange-correlation kernel, as well as from a many-body perspective using "scissors operators" matched to an ab initio G W calculation to account for self-energy corrections. These results demonstrate some cancellation of errors between self-energy and excitonic effects, even for excitations from the Hf 4 f shell. We also simulate the dispersion with increasing momentum transfer for plasmon and collective excitation peaks.

  1. One-step transvaginal three-dimensional hysterosalpingo-foam sonography (3D-HyFoSy) confirmation test for Essure® follow-up: a multicenter study.

    Science.gov (United States)

    Zizolfi, B; Lazzeri, L; Franchini, M; Di Spiezio Sardo, A; Nappi, C; Piccione, E; Exacoustos, C

    2018-01-01

    To evaluate, in patients who underwent Fallopian-tube sterilization by hysteroscopic insertion of an Essure® device, the feasibility and accuracy of three-dimensional (3D) transvaginal sonography (TVS) to check the position of the device and 3D hysterosalpingo-foam sonography (3D-HyFoSy) using contrast-enhanced gel foam to assess consequent tubal occlusion. This was a prospective multicenter study conducted from June 2012 to July 2014 in four Italian centers, which included 50 women who underwent hysteroscopic Essure microinsert placement in a total of 95 Fallopian tubes. Placement of the microinserts was performed in an outpatient setting following standard procedure recommendations. All patients underwent transvaginal 3D-HyFoSy and hysterosalpingography (HSG) approximately 12-14 weeks after the procedure. The position of the devices was first checked on 3D-TVS and classified according to specific criteria (Positions A, B, C and D). Then, 3D-HyFoSy with ExEm® gel foam as the ultrasound contrast agent was performed to confirm tubal occlusion by the absence of contrast agent within the tubes and/or around the ovaries. To evaluate the feasibility of 3D-HyFoSy, consecutive volume acquisitions were performed while injecting the gel foam. After sonographic evaluation, women underwent HSG to assess the success of sterilization, as standard methodology. Side effects and pain evoked during and after 3D-HyFoSy and HSG were evaluated using a numeric pain rating scale. On 3D-TVS, 10 devices (10.5%) were in Position A, two (2.1%) in Position B, 59 (62.1%) in Position C and 24 (25.3%) in Position D. During 3D-HyFoSy, tubal occlusion was observed in 89 of 95 tubes (93.7%). In the six cases in which the passage of the contrast was observed, one device (16.7%) was in Position B, one device (16.7%) in Position D and four devices (66.7%) were found to lie in Position C. Tubal patency was confirmed at HSG with a concordance rate of 100%. The mean pain score associated with 3D-HyFo

  2. Kinetics of the reaction of F atoms with O2 and UV spectrum of FO2 radicals in the gas phase at 295 K

    DEFF Research Database (Denmark)

    Ellermann, T.; Sehested, J.; Nielsen, O.J.

    1994-01-01

    The ultraviolet absorption spectrum of FO2 radicals and the kinetics of the reaction of F atoms with O2 have been studied in the gas phase at 295 K using pulse radiolysis combined with kinetic UV spectroscopy. At 230 nm, sigma(FO2) = (5.08 +/- 0.70) X 10(-18) cm2 molecule-1. The kinetics of the r......The ultraviolet absorption spectrum of FO2 radicals and the kinetics of the reaction of F atoms with O2 have been studied in the gas phase at 295 K using pulse radiolysis combined with kinetic UV spectroscopy. At 230 nm, sigma(FO2) = (5.08 +/- 0.70) X 10(-18) cm2 molecule-1. The kinetics...

  3. Study of the pluronic-silica interaction in synthesis of mesoporous silica under mild acidic conditions.

    Science.gov (United States)

    Sundblom, Andreas; Palmqvist, Anders E C; Holmberg, Krister

    2010-02-02

    The interaction between silica and poly(ethylene oxide) (PEO) in water may appear trivial and it is generally stated that hydrogen bonding is responsible for the attraction. However, a literature search shows that there is not a consensus with respect to the mechanism behind the attractive interaction. Several papers claim that only hydrogen bonding is not sufficient to explain the binding. The silica-PEO interaction is interesting from an academic perspective and it is also exploited in the preparation of mesoporous silica, a material of considerable current interest. This study concerns the very early stage of synthesis of mesoporous silica under mild acidic conditions, pH 2-5, and the aim is to shed light on the interaction between silica and the PEO-containing structure directing agent. The synthesis comprises two steps. An organic silica source, tetraethylorthosilicate (TEOS), is first hydrolyzed and Pluronic P123, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymer, is subsequently added at different time periods following the hydrolysis of TEOS. It is shown that the interaction between the silica and the Pluronic is dependent both on the temperature and on the time between onset of TEOS hydrolysis and addition of the copolymer. The results show that the interaction is mainly driven by entropy. The effect of the synthesis temperature and of the time between hydrolysis and addition of the copolymer on the final material is also studied. The material with the highest degree of mesoorder was obtained when the reaction was performed at 20 degrees C and the copolymer was added 40 h after the start of TEOS hydrolysis. It is claimed that the reason for the good ordering of the silica is that whereas particle formation under these conditions is fast, the rate of silica condensation is relatively low.

  4. Silica coatings on clarithromycin.

    Science.gov (United States)

    Bele, Marjan; Dmitrasinovic, Dorde; Planinsek, Odon; Salobir, Mateja; Srcic, Stane; Gaberscek, Miran; Jamnik, Janko

    2005-03-03

    Pre-crystallized clarithromycin (6-O-methylerythromycin A) particles were coated with silica from the tetraethyl orthosilicate (TEOS)-ethanol-aqueous ammonia system. The coatings had a typical thickness of 100-150 nm and presented about 15 wt.% of the silica-drug composite material. The properties of the coatings depended on reactant concentration, temperature and mixing rate and, in particular, on the presence of a cationic surfactant (cetylpyridinium chloride). In the presence of cetylpyridinium chloride the silica coatings slightly decreased the rate of pure clarithromycin dissolution.

  5. Oxygen configurations in silica

    International Nuclear Information System (INIS)

    Chelikowsky, James R.; Chadi, D. J.; Binggeli, N.

    2000-01-01

    We propose a transition state for oxygen in silica. This state is produced by the insertion of an oxygen molecule into the Si-O-Si bond, i.e., it consists of producing a Si-O-O-O-Si bond. This state allows molecular oxygen diffusion in silica without breaking the molecular O 2 bond and it is energetically more stable than a peroxy configuration. This configuration may allow for exchange of molecular oxygen with the oxygen in the silica framework. (c) 2000 The American Physical Society

  6. The Effect of Various Acids to the Gelation Process to the Silica Gel Characteristic Using Organic Silica

    Science.gov (United States)

    Rahman, NA; Widiyastuti, W.; Sigit, D.; Ajiza, M.; Sujana, W.

    2018-01-01

    Bagasse ash is solid waste of cane sugar industry which contain of silica more than 51%. Some previous study of silica gel from bagasse ash have been conducted often and been applied. This study concerns about the effect of various acid used in the process of gelation to the characteristic of silica gel produced. Then, this silica gel will be used as adsorbent. As that, the silica gel must fulfill the requirements of adsorbent, as have good pores characteristics, fit in mesoporous size so that adsorbent diffusion process is not disturbed. A fitted pores size of silica gel can be prepared by managing acid concentration used. The effect of acid, organic acid (tartaric acid) and inorganic acid (hydrochloric acid), is investigated in detail. The acid is added into sodium silicate solution in that the gel is formed, the pores structures can be investigated with BET, the crystal form is analyzed with XRD and the pore structure is analyzed visually with SEM. By managing the acid concentration added, it gets the effect of acid to the pore structure of silica gel. The bigger concentration is, the bigger the pore’s size of silica gel produced.

  7. Gene clusters of Hafnia alvei strain FB1 important in survival and pathogenesis: a draft genome perspective.

    Science.gov (United States)

    Tan, Jia-Yi; Yin, Wai-Fong; Chan, Kok-Gan

    2014-01-01

    Hafnia alvei is an opportunistic pathogen involved in various types of nosocomical infections. The species has been found to inhabit food and mammalian guts. However, its status as an enteropathogen, and whether the food-inhabiting strains could be a source of gastrointestinal infection remains obscure. In this report we present a draft genome of H. alvei strain FB1 isolated from fish paste meatball, a food popular among Malaysian and Chinese populations. The data was generated on the Illumina MiSeq platform. A comparative study was carried out on FB1 against two other previously sequenced H. alvei genomes. Several gene clusters putatively involved in survival and pathogenesis of H. alvei FB1 in food and gut environment were characterised in this study. These include the widespread colonisation island (WCI), the tad locus that is known to play an essential role in biofilm formation, a eut operon that might contribute to advantage in nutrient acquisition in gut environment, and genes responsible for siderophore production This features enable the bacteria to successful colonise in the host gut environment. With the whole genome data of H. alvei FB1 presented in this study, we hope to provide an insight into future studies on this candidate of enteropathogen by looking into the possible mechanisms employed to survive stresses and gain advantage in competitions, which eventually leads to successful colonisation and pathogenesis. This is to serve as the basis for more effective clinical diagnosis and treatment.

  8. Preparation and characterization of hybrid Nafion/silica and Nafion/silica/PTA membranes for redox flow batteries

    Energy Technology Data Exchange (ETDEWEB)

    Glibin, V.; Pupkevich, V.; Svirko, L.; Karamanev, D. [Western Ontario Univ., London, ON (Canada). Dept. of Biochemical and Chemical Engineering

    2008-07-01

    Redox flow batteries are both efficient and cost-effective. However, the long-term stability of most ion-exchange membranes is limited as a result of the high oxidation rates of ions with high redox potentials. A method of synthesizing multi-component Nafion-silica and Nafion-silica-PTA membranes was presented in this study, which also investigated the electrochemical and ion transport properties of the membranes. Membranes were cast from dimethylformamide (DMFA) solution. The iron ion diffusion kinetics of the Nafion-silica and Nafion-silica PTA membranes were studied by dialysis. Results of the investigation demonstrated that the introduction of silica and phosphotungstic acid (PTA) into the Nafion membrane composition resulted in a significant decrease of ion transfer through the membrane. The addition of PTA also increased membrane permeability to ferric ions. The low iron diffusion coefficient and high ionic conductivity of the Nafion-silica membrane makes it a promising material for use in redox flow batteries. 4 refs., 1 tab., 1 fig.

  9. Silica-Coated Liposomes for Insulin Delivery

    Directory of Open Access Journals (Sweden)

    Neelam Dwivedi

    2010-01-01

    Full Text Available Liposomes coated with silica were explored as protein delivery vehicles for their enhanced stability and improved encapsulation efficiency. Insulin was encapsulated within the fluidic phosphatidylcholine lipid vesicles by thin film hydration at pH 2.5, and layer of silica was formed above lipid bilayer by acid catalysis. The presence of silica coating and encapsulated insulin was identified using confocal and electron microscopy. The native state of insulin present in the formulation was evident from Confocal Micro-Raman spectroscopy. Silica coat enhances the stability of insulin-loaded delivery vehicles. In vivo study shows that these silica coated formulations were biologically active in reducing glucose levels.

  10. Silica artificial opal incorporated with silver nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Li Wenjiang, E-mail: wjli@zju.edu.cn [Center for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Zhejiang University, Joint Research Center of Photonics of the Royal Institute of Technology and Zhejiang University, Zijingang Campus, Room 210, East Building 5, Hangzhou 310058 (China); Sun Tan [Center for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Zhejiang University, Joint Research Center of Photonics of the Royal Institute of Technology and Zhejiang University, Zijingang Campus, Room 210, East Building 5, Hangzhou 310058 (China)

    2009-07-15

    The silica artificial opal with a three-dimensional (3D) periodic structure was prepared using highly monodispersed silica microspheres by a force packing method in ITO glass cell. The silica artificial opal incorporated with silver nanoparticles was fabricated by the electroplating technique. The optical microscope images of the synthetic sample and the corresponding optical properties were measured after each treatment of electroplating-washing-drying circle. The transmission and reflection spectra presented a red shift, showing that the effective refractive index of the complex silver/silica opal increased after each electroplating. Combining the SEM images, it was seen that the silver nanoparticles could be directly deposited on the surface of silica spheres in the opaline structure. The silver/silica complex opal film could provide a simple way to tune the opal properties by controlling silver nanoparticles in the silica opal. The silver/silica opal crystal structures could be used for nano-photonic circuits, white-light LEDs or as photocatalysts.

  11. Silica artificial opal incorporated with silver nanoparticles

    International Nuclear Information System (INIS)

    Li Wenjiang; Sun Tan

    2009-01-01

    The silica artificial opal with a three-dimensional (3D) periodic structure was prepared using highly monodispersed silica microspheres by a force packing method in ITO glass cell. The silica artificial opal incorporated with silver nanoparticles was fabricated by the electroplating technique. The optical microscope images of the synthetic sample and the corresponding optical properties were measured after each treatment of electroplating-washing-drying circle. The transmission and reflection spectra presented a red shift, showing that the effective refractive index of the complex silver/silica opal increased after each electroplating. Combining the SEM images, it was seen that the silver nanoparticles could be directly deposited on the surface of silica spheres in the opaline structure. The silver/silica complex opal film could provide a simple way to tune the opal properties by controlling silver nanoparticles in the silica opal. The silver/silica opal crystal structures could be used for nano-photonic circuits, white-light LEDs or as photocatalysts.

  12. Silica nanoparticle stability in biological media revisited.

    Science.gov (United States)

    Yang, Seon-Ah; Choi, Sungmoon; Jeon, Seon Mi; Yu, Junhua

    2018-01-09

    The stability of silica nanostructure in the core-silica shell nanomaterials is critical to understanding the activity of these nanomaterials since the exposure of core materials due to the poor stability of silica may cause misinterpretation of experiments, but unfortunately reports on the stability of silica have been inconsistent. Here, we show that luminescent silver nanodots (AgNDs) can be used to monitor the stability of silica nanostructures. Though relatively stable in water and phosphate buffered saline, silica nanoparticles are eroded by biological media, leading to the exposure of AgNDs from AgND@SiO 2 nanoparticles and the quenching of nanodot luminescence. Our results reveal that a synergistic effect of organic compounds, particularly the amino groups, accelerates the erosion. Our work indicates that silica nanostructures are vulnerable to cellular medium and it may be possible to tune the release of drug molecules from silica-based drug delivery vehicles through controlled erosion.

  13. Thermally stable silica-coated hydrophobic gold nanoparticles.

    Science.gov (United States)

    Kanehara, Masayuki; Watanabe, Yuka; Teranishi, Toshiharu

    2009-01-01

    We have successfully developed a method for silica coating on hydrophobic dodecanethiol-protected Au nanoparticles with coating thickness ranging from 10 to 40 nm. The formation of silica-coated Au nanoparticles could be accomplished via the preparation of hydrophilic Au nanoparticle micelles by cationic surfactant encapsulation in aqueous phase, followed by hydrolysis of tetraethylorthosilicate on the hydrophilic surface of gold nanoparticle micelles. Silica-coated Au nanoparticles exhibited quite high thermal stability, that is, no agglomeration of the Au cores could be observed after annealing at 600 degrees C for 30 min. Silica-coated Au nanoparticles could serve as a template to derive hollow nanoparticles. An addition of NaCN solution to silica-coated Au nanoparticles led the formation of hollow silica nanoparticles, which were redispersible in deionized water. The formation of the hollow silica nanoparticles results from the mesoporous structures of the silica shell and such a mesoporous structure is applicable to both catalyst support and drug delivery.

  14. Variations of the critical foE-frequency of the ionosphere connected with earthquakes. Evaluation of observations of the vertical sounding station "Tokyo"

    Science.gov (United States)

    Liperovskaya, Elena V.; Meister, Claudia-Veronika; Hoffmann, Dieter H. H.; Silina, Alexandra S.

    2016-04-01

    In the present work the critical frequencies foE and foF2 of the ionosphere are considered as possible earthquake precursors. The statistical analysis of the critical frequencies is carried out based on the data of the vertical sounding station (VSS) "Kokubunji" ("Tokyo") (ϕ = 35.7o N, λ = 139.5o E, 1957-1988) obtained every hour. Disturbances are considered on the background of seasonal, geomagnetic as well as 11-years and 27-days Solar variations. Special normalized parameters E and F are introduced, which represent the almost seasonal-independent parts of foE and foF2. Days with high Solar (Wolf number > 100) and geomagnetic (ΣKp > 25) activities are excluded from the analysis. For all data (observed every hour) analysed, no correlations of the normalized parameters E and F are found. One day before the seismic shock, a positive correlation is observed. The superimposed epochs method is used to determine the temporal behaviour of E and F. It is found that E and F decrease one day before the earthquakes provided that the seismic shocks occur at distances 600 5.5 is situated at depths smaller than 60 km. The reliability of the effect is larger than 98 %. Possible physical mechanisms of the phenomenon are discussed.

  15. Chitosan-silica complex membranes from sulfonic acid functionalized silica nanoparticles for pervaporation dehydration of ethanol-water solutions.

    Science.gov (United States)

    Liu, Ying-Ling; Hsu, Chih-Yuan; Su, Yu-Huei; Lai, Juin-Yih

    2005-01-01

    Nanosized silica particles with sulfonic acid groups (ST-GPE-S) were utilized as a cross-linker for chitosan to form a chitosan-silica complex membranes, which were applied to pervaporation dehydration of ethanol-water solutions. ST-GPE-S was obtained from reacting nanoscale silica particles with glycidyl phenyl ether, and subsequent sulfonation onto the attached phenyl groups. The chemical structure of the functionalized silica was characterized with FTIR, (1)H NMR, and energy-dispersive X-ray. Homogeneous dispersion of the silica particles in chitosan was observed with electronic microscopies, and the membranes obtained were considered as nanocomposites. The silica nanoparticles in the membranes served as spacers for polymer chains to provide extra space for water permeation, so as to bring high permeation rates to the complex membranes. With addition of 5 parts per hundred of functionalized silica into chitosan, the resulting membrane exhibited a separation factor of 919 and permeation flux of 410 g/(m(2) h) in pervaporation dehydration of 90 wt % ethanol aqueous solution at 70 degrees C.

  16. Amorphous silica from rice husk at various temperatures

    International Nuclear Information System (INIS)

    Javed, S.J.; Feroze, N.; Tajwar, S.

    2008-01-01

    Rice husk is being used as a source of energy in many heat generating system because of its high calorific value and its availability in many rice producing areas. Rice husk contains approximately 20% silica which is presented in hydrated form. This hydrated silica can be retrieved as amorphous silica under controlled thermal conditions. Uncontrolled burning of rice husk produces crystalline silica which is not reactive silica but can be used as filler in many applications. Amorphous silica is reactive silica which has better market value due to its reactive nature in process industry. The present study deals with the production of amorphous silica at various temperatures from rice husk. Various ashes were prepared in tube furnace by changing the burning temperatures for fixed time intervals and analyzed by XRD. It has been observed that for two hours calculation's of rice husk renders mostly amorphous silica at 650 degree C where as at higher temperatures crystalline silica was obtained. (author)

  17. Cellular membrane trafficking of mesoporous silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Fang, I-Ju [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    This dissertation mainly focuses on the investigation of the cellular membrane trafficking of mesoporous silica nanoparticles. We are interested in the study of endocytosis and exocytosis behaviors of mesoporous silica nanoparticles with desired surface functionality. The relationship between mesoporous silica nanoparticles and membrane trafficking of cells, either cancerous cells or normal cells was examined. Since mesoporous silica nanoparticles were applied in many drug delivery cases, the endocytotic efficiency of mesoporous silica nanoparticles needs to be investigated in more details in order to design the cellular drug delivery system in the controlled way. It is well known that cells can engulf some molecules outside of the cells through a receptor-ligand associated endocytosis. We are interested to determine if those biomolecules binding to cell surface receptors can be utilized on mesoporous silica nanoparticle materials to improve the uptake efficiency or govern the mechanism of endocytosis of mesoporous silica nanoparticles. Arginine-glycine-aspartate (RGD) is a small peptide recognized by cell integrin receptors and it was reported that avidin internalization was highly promoted by tumor lectin. Both RGD and avidin were linked to the surface of mesoporous silica nanoparticle materials to investigate the effect of receptor-associated biomolecule on cellular endocytosis efficiency. The effect of ligand types, ligand conformation and ligand density were discussed in Chapter 2 and 3. Furthermore, the exocytosis of mesoporous silica nanoparticles is very attractive for biological applications. The cellular protein sequestration study of mesoporous silica nanoparticles was examined for further information of the intracellular pathway of endocytosed mesoporous silica nanoparticle materials. The surface functionality of mesoporous silica nanoparticle materials demonstrated selectivity among the materials and cancer and normal cell lines. We aimed to determine

  18. Synthesis of Various Silica Nanoparticles for Foam Stability

    International Nuclear Information System (INIS)

    Yoon, Suk Bon; Yoon, Inho; Jung, Chonghun; Kim, Chorong; Choi, Wangkyu; Moon, Jeikwon

    2013-01-01

    The synthesis of the non-porous silica nanoparticles with uniform sizes has been reported through the Sto ber method, the synthesis of meso porous silica nanoparticles with a specific morphology such as core-shell, rod-like, and hexagonal shapes is not so common. As a synthetic strategy for controlling the particle size, shape, and porosity, the synthesis of core-shell silicas with meso porous shells formed on silica particle cores through the self-assembly of silica precursor and organic templates or spherical meso porous silicas using modified Sto ber method was also reported. Recently, in an effort to reduce the amount of radioactive waste and enhance the decontamination efficiency during the decontamination process of nuclear facilities contaminated with radionuclides, a few research for the preparation of the decontamination foam containing solid nanoparticles has been reported. In this work, the silica nanoparticles with various sizes, shapes, and structures were synthesized based on the previous literatures. The resulting silica nanoparticles were used to investigate the effect of the nanoparticles on the foam stability. In a study on the foam stability using various silica nanoparticles, the results showed that the foam volume and liquid volume in foam was enhanced when using a smaller size and lower density of the silica nanoparticles. Silica nanoparticles with various sizes, shapes, and structures such as a non-porous, meso porous core-shell, and meso porous silica were synthesized to investigate the effect of the foam stability. The sizes and structural properties of the silica nanoparticles were easily controlled by varying the amount of silica precursor, surfactant, and ammonia solution as a basic catalyst. The foam prepared using various silica nanoparticles showed that foam the volume and liquid volume in the foam were enhanced when using a smaller size and lower density of the silica nanoparticles

  19. Silica removal in industrial effluents with high silica content and low hardness.

    Science.gov (United States)

    Latour, Isabel; Miranda, Ruben; Blanco, Angeles

    2014-01-01

    High silica content of de-inked paper mill effluents is limiting their regeneration and reuse after membrane treatments such as reverse osmosis (RO). Silica removal during softening processes is a common treatment; however, the effluent from the paper mill studied has a low hardness content, which makes the addition of magnesium compounds necessary to increase silica removal. Two soluble magnesium compounds (MgCl₂∙6H₂O and MgSO₄∙7H₂O) were tested at five dosages (250-1,500 mg/L) and different initial pH values. High removal rates (80-90%) were obtained with both products at the highest pH tested (11.5). With these removal efficiencies, it is possible to work at high RO recoveries (75-85%) without silica scaling. Although pH regulation significantly increased the conductivity of the waters (at pH 11.5 from 2.1 to 3.7-4.0 mS/cm), this could be partially solved by using Ca(OH)₂ instead of NaOH as pH regulator (final conductivity around 3.0 mS/cm). Maximum chemical oxygen demand (COD) removal obtained with caustic soda was lower than with lime (15 vs. 30%). Additionally, the combined use of a polyaluminum coagulant during the softening process was studied; the coagulant, however, did not significantly improve silica removal, obtaining a maximum increase of only 10%.

  20. Social Media Use and the Fear of Missing out (FoMO) While Studying Abroad

    Science.gov (United States)

    Hetz, Patricia R.; Dawson, Christi L.; Cullen, Theresa A.

    2015-01-01

    Fear of Missing Out (FoMO) is a social construct that examines whether students are concerned that they are missing out on experiences that others are having, and we examined this relation to their concerns over missing activities in their home culture. This mixed-methods pilot study sought to determine how social media affects the study abroad…

  1. FoCuS-point: software for STED fluorescence correlation and time-gated single photon counting

    DEFF Research Database (Denmark)

    Waithe, Dominic; Clausen, Mathias P; Sezgin, Erdinc

    2016-01-01

    to be established quickly and efficiently. AVAILABILITY AND IMPLEMENTATION: FoCuS-point is written in python and is available through the github repository: https://github.com/dwaithe/FCS_point_correlator. Furthermore, compiled versions of the code are available as executables which can be run directly in Linux...

  2. F.O. Schechtel’s house on bolshaya sadovaya street as an object of cultural heritage

    Directory of Open Access Journals (Sweden)

    Gatsunaev Konstantin Nikolaevich

    2016-10-01

    Full Text Available F.O. Schechtel’s private house on Bolshaya Sadovaya Street in Moscow built in 1910 became a peculiar result of creative activity of the most famous architect of an era of “Silver age” of the Russian culture. The highest professionalism of the architect was expressed not only in composite decisions and the system of decor of the building, but also in organizational and technical aspects of his construction. The former F.O. Schechtel’s mansion for several decades has been one of the centers of Moscow’s cultural life. The memorial value of the house consists not only of its architectural advantages. The building keeps the memory of F.O. Schechtel - a first-class architect, stenographer, illustrator and graphic artist, a master of applied art, a public figure and a teacher. He personified the best qualities of Russian intellectuals: high ethical standards and active living position. The activity of the architect Schechtel was exclusively fruitful both in quantitative, and in qualitative sense. There are about fifty buildings in Moscow which were constructed according to his projects. Each of them comprised opening and generating of a new direction or introduction of new methods of construction. Schechtel gave other architects an opportunity to further develop these methods. The structures built upon Schechtel’s projects in many respects have defined unique lines of Moscow city landscape of the end of 19th - the beginning of the 20th centuries. Numerous relatives of Schechtel lived in the mansion and in its wings in addition to the head of the family. The contribution of each of them to the development of the Russian culture is significant.

  3. The Pozzolanic reaction of silica fume

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede

    2012-01-01

    Silica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone. In the ......Silica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone....... In the present paper different aspects of the pozzolanic reaction of silica fume are investigated. These include chemical shrinkage, isothermal heat development and strength development. Key data for these are given and compared with theoretical calculations, and based on presented measurements the energy...

  4. 21 CFR 584.700 - Hydrophobic silicas.

    Science.gov (United States)

    2010-04-01

    ...) Product. Amorphous fumed hydrophobic silica or precipitated hydrophobic silica (CAS Reg. No. 68611-0944... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Hydrophobic silicas. 584.700 Section 584.700 Food... DRUGS, FEEDS, AND RELATED PRODUCTS FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE IN FEED AND...

  5. Biomimetic silica encapsultation of living cells

    Science.gov (United States)

    Jaroch, David Benjamin

    Living cells perform complex chemical processes on size and time scales that artificial systems cannot match. Cells respond dynamically to their environment, acting as biological sensors, factories, and drug delivery devices. To facilitate the use of living systems in engineered constructs, we have developed several new approaches to create stable protective microenvironments by forming bioinspired cell-membrane-specific silica-based encapsulants. These include vapor phase deposition of silica gels, use of endogenous membrane proteins and polysaccharides as a site for silica nucleation and polycondensation in a saturated environment, and protein templated ordered silica shell formation. We demonstrate silica layer formation at the surface of pluripotent stem-like cells, bacterial biofilms, and primary murine and human pancreatic islets. Materials are characterized by AFM, SEM and EDS. Viability assays confirm cell survival, and metabolite flux measurements demonstrate normal function and no major diffusion limitations. Real time PCR mRNA analysis indicates encapsulated islets express normal levels of genetic markers for β-cells and insulin production. The silica glass encapsulant produces a secondary bone like calcium phosphate mineral layer upon exposure to media. Such bioactive materials can improve device integration with surrounding tissue upon implantation. Given the favorable insulin response, bioactivity, and long-term viability observed in silica-coated islets, we are currently testing the encapsulant's ability to prevent immune system recognition of foreign transplants for the treatment of diabetes. Such hybrid silica-cellular constructs have a wide range of industrial, environmental, and medical applications.

  6. A new parameter-free soft-core potential for silica and its application to simulation of silica anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Izvekov, Sergei, E-mail: sergiy.izvyekov.civ@mail.mil; Rice, Betsy M. [Weapons and Materials Research Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States)

    2015-12-28

    A core-softening of the effective interaction between oxygen atoms in water and silica systems and its role in developing anomalous thermodynamic, transport, and structural properties have been extensively debated. For silica, the progress with addressing these issues has been hampered by a lack of effective interaction models with explicit core-softening. In this work, we present an extension of a two-body soft-core interatomic force field for silica recently reported by us [S. Izvekov and B. M. Rice, J. Chem. Phys. 136(13), 134508 (2012)] to include three-body forces. Similar to two-body interaction terms, the three-body terms are derived using parameter-free force-matching of the interactions from ab initio MD simulations of liquid silica. The derived shape of the O–Si–O three-body potential term affirms the existence of repulsion softening between oxygen atoms at short separations. The new model shows a good performance in simulating liquid, amorphous, and crystalline silica. By comparing the soft-core model and a similar model with the soft-core suppressed, we demonstrate that the topology reorganization within the local tetrahedral network and the O–O core-softening are two competitive mechanisms responsible for anomalous thermodynamic and kinetic behaviors observed in liquid and amorphous silica. The studied anomalies include the temperature of density maximum locus and anomalous diffusivity in liquid silica, and irreversible densification of amorphous silica. We show that the O–O core-softened interaction enhances the observed anomalies primarily through two mechanisms: facilitating the defect driven structural rearrangements of the silica tetrahedral network and modifying the tetrahedral ordering induced interactions toward multiple characteristic scales, the feature which underlies the thermodynamic anomalies.

  7. Microporous Silica Based Membranes for Desalination

    Directory of Open Access Journals (Sweden)

    João C. Diniz da Costa

    2012-09-01

    Full Text Available This review provides a global overview of microporous silica based membranes for desalination via pervaporation with a focus on membrane synthesis and processing, transport mechanisms and current state of the art membrane performance. Most importantly, the recent development and novel concepts for improving the hydro-stability and separating performance of silica membranes for desalination are critically examined. Research into silica based membranes for desalination has focussed on three primary methods for improving the hydro-stability. These include incorporating carbon templates into the microporous silica both as surfactants and hybrid organic-inorganic structures and incorporation of metal oxide nanoparticles into the silica matrix. The literature examined identified that only metal oxide silica membranes have demonstrated high salt rejections under a variety of feed concentrations, reasonable fluxes and unaltered performance over long-term operation. As this is an embryonic field of research several target areas for researchers were discussed including further improvement of the membrane materials, but also regarding the necessity of integrating waste or solar heat sources into the final process design to ensure cost competitiveness with conventional reverse osmosis processes.

  8. Study of the effect of some of the experimental parameters on the x-ray fluorescence determination of traces of hafnia in high purity zirconia

    International Nuclear Information System (INIS)

    Qurbani, J.M.; Khanna, P.P.; Agrawal, R.M.

    1974-01-01

    The effect of the following parameters : (i) analytical lines HfLsub(αsub(1)) or HfLsub(βsub(1,6)) or HfLsub(βsub(2)) (ii) detectors - scintillation or gas flow proportional (iii) collimators - fine or coarse (iv) x-ray tube voltage, current and power (v) order of diffraction : I or II of analysing crystal LiF (200), on the precision of the results and the sensitivity of the method in the x-ray fluorescence determination of traces of hafnia in high purity zirconia, has been studied. Philips semiautomatic x-ray spectrometer PW 1220 with associated equipment has been used. Synthetic standards containing HfO 2 in the range 20 ppm to 1 % in ZrO 2 , presented as double layer pellets have been used. LiF (200) analysing crystal, tungsten target x-ray tube, automatic pulse height selection and pulse height discrimination were used in all the cases. The set - 'HfLsub(βsub(1,6)) analytical line, fine collimator and gas flow proportional counter detector' - gave the best performance. (author)

  9. FoCaLiZe: Inside an F-IDE

    Directory of Open Access Journals (Sweden)

    François Pessaux

    2014-04-01

    Full Text Available For years, Integrated Development Environments have demonstrated their usefulness in order to ease the development of software. High-level security or safety systems require proofs of compliance to standards, based on analyses such as code review and, increasingly nowadays, formal proofs of conformance to specifications. This implies mixing computational and logical aspects all along the development, which naturally raises the need for a notion of Formal IDE. This paper examines the FoCaLiZe environment and explores the implementation issues raised by the decision to provide a single language to express specification properties, source code and machine-checked proofs while allowing incremental development and code reusability. Such features create strong dependencies between functions, properties and proofs, and impose an particular compilation scheme, which is described here. The compilation results are runnable OCaml code and a checkable Coq term. All these points are illustrated through a running example.

  10. Variability in foF2 at an equatorial station and the influence of magnetic activity

    International Nuclear Information System (INIS)

    Adeniyi, J.O.; Radicella, S.M.

    2003-01-01

    Variability in foF2 is investigated for an equatorial station in the African region. Variability during the day time at high solar activity varies between 10 and 30 percent. It varies between 10 and 20 percent at high solar activity. Magnetic storms increase the variability at both solar activity periods. (author)

  11. Synthesis and application of silica gel modified with alkoxyalcohols. Alkoxyalcohol shushoku silica gel no gosei to riyo

    Energy Technology Data Exchange (ETDEWEB)

    Moriguchi, T.; Ishiguro, H.; Matsubara, Y.; Yoshihara, M.; Maeshima, T.; Ito, S. (Kinki University, Osaka (Japan). Faculty of Science and Engineering)

    1991-08-20

    Several kinds of silica gel modified by alkoxyalcohols were synthesized by refluxing and dehyration and the organic reactions were studied when these silica gels were used as the catalyst. It could be confirmed by FT-IR spectra, DTA and elementary analysis that alkoxylalcohols adhere to the surface of silica gels without any decomposition. The acetate was produced by using alkyl halides. It was found that the modified silica gels had clearly the catalytic action for the reaction with n-hexyl bromide and dibromoethane although unmodified silica gels did not show the catalytic action. The reducing reaction of carbonyl compounds was carried out. The reaction proceeded at 25 centigrade for acetophenone, cyclohexanone, 1-indanone and 2-octanone to produce the corresponding reduction products. 11 refs., 5 figs., 4 tabs.

  12. Facile route of biopolymer mediated ferrocene (FO) nanoparticles in aqueous dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Kaus, Noor Haida Mohd., E-mail: noorhaida@usm.my [School of Chemical Sciences, Universiti Sains Malaysia, 11800, Penang, Malaysia and Centre for Organized Matter Chemistry, School of Chemistry, Cantock' s Close, BS8 1TS, Bristol (United Kingdom); Collins, A. M.; Mann, S. [Centre for Organized Matter Chemistry, School of Chemistry, Cantock' s Close, BS8 1TS, Bristol (United Kingdom)

    2014-10-24

    In this paper, we present a facile method for production stable aqueous dispersion of ferrocene (FO) nanoparticles. Ferrocene compounds were employed to achieve stable nanodispersions, stabilized with three different biopolymers namely, alginate, CM-dextran and chitosan. The nanoparticles produce are spherical, less than 10 nm in mean diameter and highly stable without any sedimentation. Fourier infrared transform (FTIR) and X-ray diffraction (XRD) studies confirmed the purity of ferrocene nanoparticles there is no modifications occur during the preparation route. FTIR spectra results were consistent with the presence of absorption band of cyclopentadienyl ring (C{sub 5}H{sub 5}{sup −} ion) which assigned to ν(C-C) vibrations (1409 cm-1), δ(C-H) stretching at 1001 cm{sup −1} and π(C-H) vibrations at 812 cm{sup −1}. Furthermore, all functional group for biopolymers such as CO from carboxyl group of CM-dextran and sodium alginate appears at 1712 cm{sup −1} and 1709 cm{sup −1} respectively, indicating there are steric repulsion interactions for particles stabilization. Powder X-ray diffraction patterns of sedimented samples of the biopolymers-stabilized ferrocene (FO) showed all reflections which were indexed respectively to the (−110), (001), (−201), (−111), (200), (−211), (210), (120) and (111) according to the monoclinic phase ferrocene. This confirmed that the products obtained were of high purity of Fe and EDAX analysis also suggests that the presence of the Fe element in the colloidal dispersion.

  13. Novel cellulose ester substrates for high performance flat-sheet thin-film composite (TFC) forward osmosis (FO) membranes

    KAUST Repository

    Ong, Rui Chin; Chung, Neal Tai-Shung; de Wit, Jos S.; Helmer, Bradley J.

    2015-01-01

    and seawater desalination with high performance. The performance of TFC-FO membranes prepared from the hydrophilic cellulose ester containing a high degree of OH and a moderate degree of Pr substitutions clearly surpasses those prepared from cellulose esters

  14. SCC modification by use of amorphous nano-silica

    NARCIS (Netherlands)

    Quercia Bianchi, G.; Spiesz, P.R.; Hüsken, G.; Brouwers, H.J.H.

    2014-01-01

    In this study two different types of nano-silica (nS) were applied in self-compacting concrete (SCC), both having similar particle size distributions (PSD), but produced through two different processes: fumed powder silica and precipitated silica in colloidal suspension. The influence of nano-silica

  15. Agmatine attenuates silica-induced pulmonary fibrosis.

    Science.gov (United States)

    El-Agamy, D S; Sharawy, M H; Ammar, E M

    2014-06-01

    There is a large body of evidence that nitric oxide (NO) formation is implicated in mediating silica-induced pulmonary fibrosis. As a reactive free radical, NO may not only contribute to lung parenchymal tissue injury but also has the ability to combine with superoxide and form a highly reactive toxic species peroxynitrite that can induce extensive cellular toxicity in the lung tissues. This study aimed to explore the effect of agmatine, a known NO synthase inhibitor, on silica-induced pulmonary fibrosis in rats. Male Sprague Dawley rats were treated with agmatine for 60 days following a single intranasal instillation of silica suspension (50 mg in 0.1 ml saline/rat). The results revealed that agmatine attenuated silica-induced lung inflammation as it decreased the lung wet/dry weight ratio, protein concentration, and the accumulation of the inflammatory cells in the bronchoalveolar lavage fluid. Agmatine showed antifibrotic activity as it decreased total hydroxyproline content of the lung and reduced silica-mediated lung inflammation and fibrosis in lung histopathological specimen. In addition, agmatine significantly increased superoxide dismutase (p Agmatine also reduced silica-induced overproduction of pulmonary nitrite/nitrate as well as tumor necrosis factor α. Collectively, these results demonstrate the protective effects of agmatine against the silica-induced lung fibrosis that may be attributed to its ability to counteract the NO production, lipid peroxidation, and regulate cytokine effects. © The Author(s) 2014.

  16. All-silica nanofluidic devices for DNA-analysis fabricated by imprint of sol-gel silica with silicon stamp

    DEFF Research Database (Denmark)

    Mikkelsen, Morten Bo Lindholm; Letailleur, Alban A; Søndergård, Elin

    2011-01-01

    We present a simple and cheap method for fabrication of silica nanofluidic devices for single-molecule studies. By imprinting sol-gel materials with a multi-level stamp comprising micro- and nanofeatures, channels of different depth are produced in a single process step. Calcination of the imprin......We present a simple and cheap method for fabrication of silica nanofluidic devices for single-molecule studies. By imprinting sol-gel materials with a multi-level stamp comprising micro- and nanofeatures, channels of different depth are produced in a single process step. Calcination...... of the imprinted hybrid sol-gel material produces purely inorganic silica, which has very low autofluorescence and can be fusion bonded to a glass lid. Compared to top-down processing of fused silica or silicon substrates, imprint of sol-gel silica enables fabrication of high-quality nanofluidic devices without...

  17. Degradability and Clearance of Silicon, Organosilica, Silsesquioxane, Silica Mixed Oxide, and Mesoporous Silica Nanoparticles

    KAUST Repository

    Croissant, Jonas G.

    2017-01-13

    The biorelated degradability and clearance of siliceous nanomaterials have been questioned worldwide, since they are crucial prerequisites for the successful translation in clinics. Typically, the degradability and biocompatibility of mesoporous silica nanoparticles (MSNs) have been an ongoing discussion in research circles. The reason for such a concern is that approved pharmaceutical products must not accumulate in the human body, to prevent severe and unpredictable side-effects. Here, the biorelated degradability and clearance of silicon and silica nanoparticles (NPs) are comprehensively summarized. The influence of the size, morphology, surface area, pore size, and surface functional groups, to name a few, on the degradability of silicon and silica NPs is described. The noncovalent organic doping of silica and the covalent incorporation of either hydrolytically stable or redox- and enzymatically cleavable silsesquioxanes is then described for organosilica, bridged silsesquioxane (BS), and periodic mesoporous organosilica (PMO) NPs. Inorganically doped silica particles such as calcium-, iron-, manganese-, and zirconium-doped NPs, also have radically different hydrolytic stabilities. To conclude, the degradability and clearance timelines of various siliceous nanomaterials are compared and it is highlighted that researchers can select a specific nanomaterial in this large family according to the targeted applications and the required clearance kinetics.

  18. Functionalization of silica nanoparticles for polypropylene nanocomposites applications

    International Nuclear Information System (INIS)

    Bracho, Diego; Palza, Humberto; Quijada, Raul; Dougnac, Vivianne

    2011-01-01

    Synthetic silica nanospheres of different diameters produced via the sol-gel method were used in order to enhance the barrier properties of the polypropylene-silica nanocomposites. Modification of the silica surface by reaction with organic chlorosilanes was performed in order to improve the particles interaction with the polypropylene matrix and its dispersion. Unmodified and modified silica nanoparticles were characterized using electronic microscopy (TEM), elemental analysis, thermo gravimetric analysis (TGA), and solid state nuclear magnetic resonance (NMR) spectroscopy. Preliminary permeability tests of the polymer-silica nanocomposite films showed no significant change at low particles load (3 wt%) regardless its size or surface functionality, mainly because of the low aspect ratio of the silica nanospheres. However, it is expected that at a higher concentration of silica particles differences will be observed. (author)

  19. Toughening Mechanisms in Silica-Filled Epoxy Nanocomposites

    Science.gov (United States)

    Patel, Binay S.

    Epoxies are widely used as underfill resins throughout the microelectronics industry to mechanically couple and protect various components of flip-chip assemblies. Generally rigid materials largely surround underfill resins. Improving the mechanical and thermal properties of epoxy resins to better match those of their rigid counterparts can help extend the service lifetime of flip-chip assemblies. Recently, researchers have demonstrated that silica nanoparticles are effective toughening agents for lightly-crosslinked epoxies. Improvements in the fracture toughness of silica-filled epoxy nanocomposites have primarily been attributed to two toughening mechanisms: particle debonding with subsequent void growth and matrix shear banding. Various attempts have been made to model the contribution of these toughening mechanisms to the overall fracture energy observed in silica-filled epoxy nanocomposites. However, disparities still exist between experimental and modeled fracture energy results. In this dissertation, the thermal, rheological and mechanical behavior of eight different types of silica-filled epoxy nanocomposites was investigated. Each nanocomposite consisted of up to 10 vol% of silica nanoparticles with particle sizes ranging from 20 nm to 200 nm, with a variety of surface treatments and particle structures. Fractographical analysis was conducted with new experimental approaches in order to accurately identify morphological evidence for each proposed toughening mechanism. Overall, three major insights into the fracture behavior of real world silica-filled epoxy nanocomposites were established. First, microcracking was observed as an essential toughening mechanism in silica-filled epoxy nanocomposites. Microcracking was observed on the surface and subsurface of fractured samples in each type of silica-filled epoxy nanocomposite. The additional toughening contribution of microcracking to overall fracture energy yielded excellent agreement between experimental

  20. Simultaneous monitoring of the two coupled motors of a single FoF1-ATP synthase by three-color FRET using duty cycle-optimized triple-ALEX

    Science.gov (United States)

    Zarrabi, N.; Ernst, S.; Düser, M. G.; Golovina-Leiker, A.; Becker, W.; Erdmann, R.; Dunn, S. D.; Börsch, M.

    2009-02-01

    FoF1-ATP synthase is the enzyme that provides the 'chemical energy currency' adenosine triphosphate, ATP, for living cells. The formation of ATP is accomplished by a stepwise internal rotation of subunits within the enzyme. Briefly, proton translocation through the membrane-bound Fo part of ATP synthase drives a 10-step rotary motion of the ring of c subunits with respect to the non-rotating subunits a and b. This rotation is transmitted to the γ and ɛ subunits of the F1 sector resulting in 120° steps. In order to unravel this symmetry mismatch we monitor subunit rotation by a single-molecule fluorescence resonance energy transfer (FRET) approach using three fluorophores specifically attached to the enzyme: one attached to the F1 motor, another one to the Fo motor, and the third one to a non-rotating subunit. To reduce photophysical artifacts due to spectral fluctuations of the single fluorophores, a duty cycle-optimized alternating three-laser scheme (DCO-ALEX) has been developed. Simultaneous observation of the stepsizes for both motors allows the detection of reversible elastic deformations between the rotor parts of Fo and F1.

  1. Polar silica-based stationary phases. Part II- Neutral silica stationary phases with surface bound maltose and sorbitol for hydrophilic interaction liquid chromatography.

    Science.gov (United States)

    Rathnasekara, Renuka; El Rassi, Ziad

    2017-07-28

    Two neutral polyhydroxylated silica bonded stationary phases, namely maltose-silica (MALT-silica) and sorbitol-silica (SOR-silica), have been introduced and chromatographically characterized in hydrophilic interaction liquid chromatography (HILIC) for a wide range of polar compounds. The bonding of the maltose and sorbitol to the silica surface was brought about by first converting bare silica to an epoxy-activated silica surface via reaction with γ-glycidoxypropyltrimethoxysilane (GPTMS) followed by attaching maltose and sorbitol to the epoxy surface in the presence of the Lewis acid catalyst BF 3 .ethereate. Both silica based columns offered the expected retention characteristics usually encountered for neutral polar surface. The retention mechanism is majorly based on solute' differential partitioning between an organic rich hydro-organic mobile phase (e.g., ACN rich mobile phase) and an adsorbed water layer on the surface of the stationary phase although additional hydrogen bonding was also responsible in some cases for solute retention. The MALT-silica column proved to be more hydrophilic and offered higher retention, separation efficiency and resolution than the SOR-silica column among the tested polar solutes such as derivatized mono- and oligosaccharides, weak phenolic acids, cyclic nucleotide monophosphate and nucleotide-5'-monophosphates, and weak bases, e.g., nucleobases and nucleosides. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Magnetic core-shell silica particles

    NARCIS (Netherlands)

    Claesson, E.M.

    2007-01-01

    This thesis deals with magnetic silica core-shell colloids and related functionalized silica structures. Synthesis routes have been developed and optimized. The physical properties of these colloids have been investigated, such as the magnetic dipole moment, dipolar structure formation and

  3. Anomalous enthalpy relaxation in vitreous silica

    DEFF Research Database (Denmark)

    Yue, Yuanzheng

    2015-01-01

    scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling) has impact on enthalpy relaxation in glass. Here, we find that vitreous silica (as a strong system) exhibits striking anomalies in both glass transition and enthalpy...... relaxation compared to fragile oxide systems. The anomalous enthalpy relaxation of vitreous silica is discovered by performing the hyperquenching-annealing-calorimetry experiments. We argue that the strong systems like vitreous silica and vitreous Germania relax in a structurally cooperative manner, whereas...... the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica....

  4. Mesoporous Silica from Rice Husk Ash

    Directory of Open Access Journals (Sweden)

    S.A. Mandavgane

    2010-12-01

    Full Text Available Mesoporous silica is used as a raw material in several areas: in preparation of catalysts, in inks, as aconcrete hardening accelerator, as a component of detergents and soaps, as a refractory constituent etc.Sodium silicate is produced by reacting rice hull ash (RHA with aqueous NaOH and silica is precipitatedfrom the sodium silicate by acidification. In the present work, conversion of about 90% of silica containedin RHA into sodium silicate was achieved in an open system at temperatures of about 100 °C. The resultsshowed that silica obtained from RHA is mesoporous, has a large surface area and small particle size.Rice Husk is usually mixed with coal and this mixture is used for firing boilers. The RHA therefore, usuallycontains carbon particles. Activated carbon embedded on silica has been prepared using the carbon alreadypresent in RHA. This carbon shows good adsorption capacity. ©2010 BCREC UNDIP. All rights reserved(Received: 25th April 2010, Revised: 17th June 2010, Accepted: 24th June 2010[How to Cite: V.R. Shelke, S.S. Bhagade, S.A. Mandavgane. (2010. Mesoporous Silica from Rice Husk Ash. Bulletin of Chemical Reaction Engineering and Catalysis, 5 (2: 63-67. doi:10.9767/bcrec.5.2.793.63-67

  5. Practical Hydrogen Loading of Air Silica Fibres

    DEFF Research Database (Denmark)

    Sørensen, Henrik Rokkjær; Jensen, Jesper Bevensee; Jensen, Jesper Bo Damm

    2005-01-01

    A method for hydrogen-loading air-silica optical fibres has been developed allowing out-diffusion times comparable to standard step-index fibres. Examples of the first grating written in Ge-doped air-silica fibres using a 266nm UV-laser are shown.......A method for hydrogen-loading air-silica optical fibres has been developed allowing out-diffusion times comparable to standard step-index fibres. Examples of the first grating written in Ge-doped air-silica fibres using a 266nm UV-laser are shown....

  6. Effect of support on hydro-metathesis of propene: A comparative study of W(CH 3 ) 6 anchored to silica vs. silica-alumina

    KAUST Repository

    Tretiakov, Mykyta; Samantaray, Manoja; Saidi, Aya; Basset, Jean-Marie

    2018-01-01

    Hydro-metathesis of propene was carried out by using well-defined W(CH3)6 supported on silica and silica-alumina. It was observed that W(CH3)6 supported silica-alumina catalyst is much better (TON 4577) than the silica supported catalyst (TON 2104

  7. Altering the concentration of silica tunes the functional properties of collagen-silica composite scaffolds to suit various clinical requirements.

    Science.gov (United States)

    Perumal, Sathiamurthi; Ramadass, Satiesh Kumar; Gopinath, Arun; Madhan, Balaraman; Shanmugam, Ganesh; Rajadas, Jayakumar; Mandal, Asit Baran

    2015-12-01

    The success of a tissue engineering scaffold depends on a fine balance being achieved between the physicochemical and biological properties. This study attempts to understand the influence of silica concentration on the functional properties of collagen-silica (CS) composite scaffolds for soft tissue engineering applications. Increasing the ratio of silica to collagen (0.25, 0.5, 0.75, 1.0, 1.25, 1.5 and 2.0 w/w) gave a marked advantage in terms of improving the water uptake and compressive modulus of the CS scaffolds, while also enhancing the biological stability and the turnover time. With increase in silica concentration the water uptake and compressive modulus increased concurrently, whereas it was not so for surface porous architecture and biocompatibility which are crucial for cell adhesion and infiltration. Silica:collagen ratio of ≤1 exhibits favourable surface biocompatibility, and any further increase in silica concentration has a detrimental effect. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Double-lock ratchet mechanism revealing the role of  SER-344 in FoF1 ATP synthase

    KAUST Repository

    Beke-Somfai, T.; Lincoln, P.; Norden, B.

    2011-01-01

    In a majority of living organisms, FoF1 ATP synthase performs the fundamental process of ATP synthesis. Despite the simple net reaction formula, ADP+Pi→ATP+H2O, the detailed step-by-step mechanism of the reaction yet remains to be resolved owing

  9. Silica-Coated Liposomes for Insulin Delivery

    OpenAIRE

    Neelam Dwivedi; M. A. Arunagirinathan; Somesh Sharma; Jayesh Bellare

    2010-01-01

    Liposomes coated with silica were explored as protein delivery vehicles for their enhanced stability and improved encapsulation efficiency. Insulin was encapsulated within the fluidic phosphatidylcholine lipid vesicles by thin film hydration at pH 2.5, and layer of silica was formed above lipid bilayer by acid catalysis. The presence of silica coating and encapsulated insulin was identified using confocal and electron microscopy. The native state of insulin present in the formulation was evid...

  10. Spectroscopy of FO Aquarii - Evidence for reprocessing in a hot wind

    International Nuclear Information System (INIS)

    Martell, P.J.; Kaitchuck, R.H.

    1991-01-01

    Results are presented on spectroscopic observations of FO Aqr, carried out on the nights of September 4-7, 1986 with the 1.8-m Perkins Telescope at Lowell Observatory. It is shown that the observed 21-min modulation of the He II 4686-A line is driven by two emission components which vary in flux and have large negative radial velocities. Arguments are presented to the effect that the modulated portion of the He II 4686-A emission originates from the reprocessing of X-rays in hot winds at these two sites. It is suggested that all other 21-min modulations are due to reprocessing. 32 refs

  11. Kinetics of silica-phase transitions

    International Nuclear Information System (INIS)

    Duffy, C.J.

    1993-07-01

    In addition to the stable silica polymorph quartz, several metastable silica phases are present in Yucca Mountain. The conversion of these phases to quartz is accompanied by volume reduction and a decrease in the aqueous silica activity, which may destabilize clinoptilolite and mordenite. The primary reaction sequence for the silica phases is from opal or glass to disordered opal-CT, followed by ordering of the opal-CT and finally by the crystallization of quartz. The ordering of opal-CT takes place in the solid state, whereas the conversion of opal-CT takes place through dissolution-reprecipitation involving the aqueous phase. It is proposed that the rate of conversion of opal-CT to quartz is controlled by diffusion of defects out of a disordered surface layer formed on the crystallizing quartz. The reaction rates are observed to be dependent on temperature, pressure, degree of supersaturation, and pH. Rate equations selected from the literature appear to be consistent with observations at Yucca Mountain

  12. Health hazards due to the inhalation of amorphous silica

    Energy Technology Data Exchange (ETDEWEB)

    Merget, R.; Bruening, T. [Research Institute for Occupational Medicine (BGFA), Bochum (Germany); Bauer, T. [Bergmannsheil, University Hospital, Department of Internal Medicine, Division of Pneumonology, Allergology and Sleep Medicine, Bochum (Germany); Kuepper, H.U.; Breitstadt, R. [Degussa-Huels Corp., Wesseling (Germany); Philippou, S. [Department of Pathology, Augusta Krankenanstalten, Bochum (Germany); Bauer, H.D. [Research Institute for Hazardous Substances (IGF), Bochum (Germany)

    2002-01-01

    Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic (''thermal'' or ''fumed'') silica, and (3) chemically or physically modified silica. According to the different physico-chemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or

  13. Health hazards due to the inhalation of amorphous silica

    International Nuclear Information System (INIS)

    Merget, R.; Bruening, T.; Bauer, T.; Kuepper, H.U.; Breitstadt, R.; Philippou, S.; Bauer, H.D.

    2002-01-01

    Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic (''thermal'' or ''fumed'') silica, and (3) chemically or physically modified silica. According to the different physico-chemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or emphysema cannot be excluded. There is no

  14. Identification and comparative quantification of bio-active phthalides in essential oils from si-wu-tang, fo-shou-san, radix angelica and rhizoma chuanxiong.

    Science.gov (United States)

    Tang, Yuping; Zhu, Min; Yu, Sheng; Hua, Yongqing; Duan, Jin-Ao; Su, Shulan; Zhang, Xu; Lu, Yin; Ding, Anwei

    2010-01-15

    Phthalides are important bio-active constituents in Si-Wu-Tang and Fo-Shou-San, two commonly used Traditional Chinese Medicine (TCM) combined prescriptions mainly derived from Radix Angelica and Rhizoma Chuanxiong. In this paper, the contents of eight phthalides, including Z-ligustilide, E-ligustilide, Z-butylenephthalide, E-butylene-phthalide, 3-butylphthalide, neocnidilide and senkyunolide A were determined or estimated by gas chromatography-mass spectrometry (GC-MS). The results showed GC-MS was a simple, rapid, and high sensitive method for analyzing phthalides in Si-Wu-Tang, Fo-Shou-San, Radix Angelica and Rhizoma Chuanxiong, and the extractable contents of each phthalides including Z-ligustilide, E-ligustilide, Z-butylenephthalide, etc. varied after Radix Angelica, Rhizoma Chuanxiong were combined into a formulation, such as Si-Wu-Tang and Fo-Shou-San. Furthermore, inhibition activity of essential oils from Si-Wu-Tang, Fo-Shou-San, Radix Angelica and Rhizoma Chuanxiong on uterine contraction was tested in an in vitro assay, and the results showed that the activity of the essential oil is higher as the content of the phthalides increase, which demonstrated that phthalides are possibly main active components inhibiting mice uterine contraction in vitro. All of the results suggested that comparative analysis of chemical components and pharmacological activities of each herb and formula is possibly helpful to elucidate the active components in traditional Chinese medicine, and to reveal the compatibility mechanism of TCM formulae.

  15. Grassy Silica Nanoribbons and Strong Blue Luminescence

    Science.gov (United States)

    Wang, Shengping; Xie, Shuang; Huang, Guowei; Guo, Hongxuan; Cho, Yujin; Chen, Jun; Fujita, Daisuke; Xu, Mingsheng

    2016-09-01

    Silicon dioxide (SiO2) is one of the key materials in many modern technological applications such as in metal oxide semiconductor transistors, photovoltaic solar cells, pollution removal, and biomedicine. We report the accidental discovery of free-standing grassy silica nanoribbons directly grown on SiO2/Si platform which is commonly used for field-effect transistors fabrication without other precursor. We investigate the formation mechanism of this novel silica nanostructure that has not been previously documented. The silica nanoribbons are flexible and can be manipulated by electron-beam. The silica nanoribbons exhibit strong blue emission at about 467 nm, together with UV and red emissions as investigated by cathodoluminescence technique. The origins of the luminescence are attributed to various defects in the silica nanoribbons; and the intensity change of the blue emission and green emission at about 550 nm is discussed in the frame of the defect density. Our study may lead to rational design of the new silica-based materials for a wide range of applications.

  16. Characterization of silica particles prepared via urease-catalyzed urea hydrolysis and activity of urease in sol–gel silica matrix

    International Nuclear Information System (INIS)

    Kato, Katsuya; Nishida, Masakazu; Ito, Kimiyasu; Tomita, Masahiro

    2012-01-01

    Highlights: ► Silica precipitation occurred via urease-catalytic reactions. ► Higher urease activity for silica synthesis enables mesostructure of silica–urease composites. ► Urease encapsulating in silica matrix retained high activity. - Abstract: Urease templated precipitation of silica synthesized by sol–gel chemistry produces a composite material allowing high urease activity. This study investigates the structural properties of the composite material that allow for the retention of the urease hydrolysis activity. Scanning (SEM) and transmission (TEM) electron microscopy reveal that the composite has a mesoporous structure composed of closely packed spherical structures ∼20–50 nm in diameter. Brunauer–Emmett–Teller (BET) analysis revealed that the surface area and pore volume of the composite prepared under the conditions of 50 mM urea and 25 °C is relatively high (324 m 2 /g and 1.0 cm 3 /g). These values are equivalent to those of usual mesoporous silica materials synthesized from the self-assembly of triblock copolymers as organic templates. In addition, after encapsulating in a sol–gel silica matrix, urease retained high activity (∼90% of the activity compared with native urease). Our results suggest a new method for synthesizing mesoporous silica materials with highly tunable pore sizes and shapes under mild conditions.

  17. Winter climate change and fine root biogenic silica in sugar maple trees (Acer saccharum): Implications for silica in the Anthropocene

    Science.gov (United States)

    Maguire, Timothy J.; Templer, Pamela H.; Battles, John J.; Fulweiler, Robinson W.

    2017-03-01

    Winter temperatures are projected to increase over the next century, leading to reductions in winter snowpack and increased frequency of soil freezing in many northern forest ecosystems. Here we examine biogenic silica (BSi) concentrations in sugar maple (Acer saccharum) fine roots collected from a snow manipulation experiment at Hubbard Brook Experimental Forest (New Hampshire, USA). Increased soil freezing significantly lowered the BSi content of sugar maple fine roots potentially decreasing their capacity to take up water and dissolved nutrients. The reduced silica uptake (8 ± 1 kmol silica km-2) by sugar maple fine roots is comparable to silica export from temperate forest watersheds. We estimate that fine roots account for 29% of sugar maple BSi, despite accounting for only 4% of their biomass. These results suggest that increased frequency of soil freezing will reduce silica uptake by temperate tree roots, thereby changing silica availability in downstream receiving waters.

  18. Mesoporous Silica from Rice Husk Ash

    Directory of Open Access Journals (Sweden)

    V.R. Shelke

    2011-01-01

    Full Text Available Mesoporous silica is used as a raw material in several areas: in preparation of catalysts, in inks, as a concrete hardening accelerator, as a component of detergents and soaps, as a refractory constituent etc. Sodium silicate is produced by reacting rice hull ash (RHA with aqueous NaOH and silica is precipitated from the sodium silicate by acidification. In the present work, conversion of about 90% of silica contained in RHA into sodium silicate was achieved in an open system at temperatures of about 100 °C. The results showed that silica obtained from RHA is mesoporous, has a large surface area and small particle size. Rice Husk is usually mixed with coal and this mixture is used for firing boilers. The RHA therefore, usually contains carbon particles. Activated carbon embedded on silica has been prepared using the carbon already present in RHA. This carbon shows good adsorption capacity. ©2010 BCREC UNDIP. All rights reserved(Received: 25th April 2010, Revised: 17th June 2010, Accepted: 24th June 2010[How to Cite: V.R. Shelke, S.S. Bhagade, S.A. Mandavgane. (2010. Mesoporous Silica from Rice Husk Ash. Bulletin of Chemical Reaction Engineering and Catalysis, 5 (2: 63-67. doi:10.9767/bcrec.5.2.793.63-67][DOI: http://dx.doi.org/10.9767/bcrec.5.2.793.63-67

  19. Production and Application of Olivine Nano-Silica in Concrete

    Science.gov (United States)

    Mardiana, Oesman; Haryadi

    2017-05-01

    The aim of this research was to produce nano silica by synthesis of nano silica through extraction and dissolution of ground olivine rock, and applied the nano silica in the design concrete mix. The producing process of amorphous silica used sulfuric acid as the dissolution reagent. The separation of ground olivine rock occurred when the rock was heated in a batch reactor containing sulfuric acid. The results showed that the optimum mole ratio of olivine- acid was 1: 8 wherein the weight ratio of the highest nano silica generated. The heating temperature and acid concentration influenced the mass of silica produced, that was at temperature of 90 °C and 3 M acid giving the highest yield of 44.90%. Characterization using Fourier Transform Infrared (FTIR ) concluded that amorphous silica at a wavenumber of 1089 cm-1 indicated the presence of siloxane, Si-O-Si, stretching bond. Characterization using Scanning Electron Microscope - Energy Dispersive Spectroscopy (SEM-EDS) showed the surface and the size of the silica particles. The average size of silica particles was between 1-10 μm due to the rapid aggregation of the growing particles of nano silica into microparticles, caused of the pH control was not fully achieved.

  20. Pumping Iron and Silica Bodybuilding

    Science.gov (United States)

    Mcnair, H.; Brzezinski, M. A.; Krause, J. W.; Parker, C.; Brown, M.; Coale, T.; Bruland, K. W.

    2016-02-01

    The availability of dissolved iron influences the stoichiometry of nutrient uptake by diatoms. Under nutrient replete conditions diatoms consume silicic acid and nitrate in a 1:1 ratio, this ratio increases under iron stress. Using the tracers 32Si and PDMPO, the total community and group-specific silica production rates were measured along a gradient of dissolved iron in an upwelling plume off the California coast. At each station, a control (ambient silicic acid) and +20 µM silicic acid treatment were conducted with each tracer to determine whether silicic acid limitation controlled the rate of silica production. Dissolved iron was 1.3 nmol kg-1 nearshore and decreased to 0.15 nmol kg-1 offshore. Silicic acid decreased more rapidly than nitrate, it was nearly 9 µM higher in the nearshore and 7 µM lower than nitrate in the middle of the transect where the iron concentration had decreased. The rate of diatom silica production decreased in tandem with silicic acid concentration, and silica production limitation by low silicic acid was most pronounced when iron concentrations were >0.4 nmol kg-1. The composition of the diatom assemblage shifted from Chaetoceros spp. dominated nearshore to a more sparse pennate-dominated assemblage offshore. Changes in taxa-specific silica production rates will be reported based on examination of PDMPO labeled cells using confocal microscopy.

  1. Effect of silica particle size on macrophage inflammatory responses.

    Directory of Open Access Journals (Sweden)

    Toshimasa Kusaka

    Full Text Available Amorphous silica particles, such as nanoparticles (<100 nm diameter particles, are used in a wide variety of products, including pharmaceuticals, paints, cosmetics, and food. Nevertheless, the immunotoxicity of these particles and the relationship between silica particle size and pro-inflammatory activity are not fully understood. In this study, we addressed the relationship between the size of amorphous silica (particle dose, diameter, number, and surface area and the inflammatory activity (macrophage phagocytosis, inflammasome activation, IL-1β secretion, cell death and lung inflammation. Irrespective of diameter size, silica particles were efficiently internalized by mouse bone marrow-derived macrophages via an actin cytoskeleton-dependent pathway, and induced caspase-1, but not caspase-11, activation. Of note, 30 nm-1000 nm diameter silica particles induced lysosomal destabilization, cell death, and IL-1β secretion at markedly higher levels than did 3000 nm-10000 nm silica particles. Consistent with in vitro results, intra-tracheal administration of 30 nm silica particles into mice caused more severe lung inflammation than that of 3000 nm silica particles, as assessed by measurement of pro-inflammatory cytokines and neutrophil infiltration in bronchoalveolar lavage fluid of mice, and by the micro-computed tomography analysis. Taken together, these results suggest that silica particle size impacts immune responses, with submicron amorphous silica particles inducing higher inflammatory responses than silica particles over 1000 nm in size, which is ascribed not only to their ability to induce caspase-1 activation but also to their cytotoxicity.

  2. Pecan drying with silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Ghate, S.R.; Chhinnan, M.S.

    1983-07-01

    High moisture in-shell pecans were dried by keeping them in direct and indirect contact with silica gel to investigate their drying characteristics. In-shell pecans were also dried with ambient air from a controlled environment chamber and with air dehumidified by silica gel. Direct contact and dehumidified air drying seemed feasible approaches.

  3. Influence of organic solvents on interfacial water at surfaces of silica gel and partially silylated fumed silica

    International Nuclear Information System (INIS)

    Turov, V.V.; Gun'ko, V.M.; Tsapko, M.D.; Bogatyrev, V.M.; Skubiszewska-Zieba, J.; Leboda, R.; Ryczkowski, J.

    2004-01-01

    The effects of organic solvents (dimethylsulfoxide-d 6 (DMSO-d 6 ), chloroform-d, acetone-d 6 , and acetonitrile-d 3 ) on the properties of interfacial water at surfaces of silica gel Si-40 and partially silylated fumed silica A-380 were studied by means of the 1 H NMR spectroscopy with freezing-out of adsorbed water at 180 1 H NMR investigations were also analysed on the basis of the structural characteristics of silicas and quantum chemical calculations of the chemical shifts δ H and solvent effects. DMSO-d 6 and acetonitrile-d 3 are poorly miscible with water in silica gel pores in contrast to the bulk liquids. DMSO-d 6 and chloroform-d affect the structure of the interfacial water weaker than acetone-d 6 and acetonitrile-d 3 at amounts of liquids greater than the pore volume. Acetone-d 6 and acetonitrile-d 3 can displace water from pores under this condition. The chemical shift of protons in water adsorbed on silica gel is 3.5-6.5 ppm, which corresponds to the formation of two to four hydrogen bonds per molecule. Water adsorbed on partially silylated fumed silica has two 1 H NMR signals at 5 and 1.1-1.7 ppm related to different structures (droplets and small clusters) of the interfacial water

  4. Silica and lung cancer: a controversial issue.

    Science.gov (United States)

    Pairon, J C; Brochard, P; Jaurand, M C; Bignon, J

    1991-06-01

    The role of crystalline silica in lung cancer has long been the subject of controversy. In this article, we review the main experimental and epidemiological studies dealing with this problem. Some evidence for a genotoxic potential of crystalline silica has been obtained in the rare in vitro studies published to date. In vivo studies have shown that crystalline silica is carcinogenic in the rat; the tumour types appear to vary according to the route of administration. In addition, an association between carcinogenic and fibrogenic potency has been observed in various animal species exposed to crystalline silica. An excess of lung cancer related to occupational exposure to crystalline silica is reported in many epidemiological studies, regardless of the presence of silicosis. However, most of these studies are difficult to interpret because they do not correctly take into account associated carcinogens such as tobacco smoke and other occupational carcinogens. An excess of lung cancer is generally reported in studies based on silicosis registers. Overall, experimental and human studies suggest an association between exposure to crystalline silica and an excess of pulmonary malignancies. Although the data available are not sufficient to establish a clear-cut causal relationship in humans, an association between the onset of pneumoconiosis and pulmonary malignancies is probable. In contrast, experimental observations have given rise to a pathophysiological mechanism that might account for a putative carcinogenic potency of crystalline silica.

  5. New Silica Magnetite Sorbent: The Influence of Variations of Sodium Silicate Concentrations on Silica Magnetite Character

    Science.gov (United States)

    Azmiyawati, C.; Pratiwi, P. I.; Darmawan, A.

    2018-04-01

    The adsorption capacity of an adsorbent is determined by the adsorbent and the adsorbate properties. The character of the adsorbent will play a major role in its ability to adsorb the corresponding adsorbate. Therefore, in this study we looked at the effects of variations of sodium silicate concentrations on the resulting magnetite silica adsorbent properties. The application of silica coating on the magnetite was carried out through a sol-gel process with sodium silicate and HCl precursors. Based on the characterization data obtained, it was found that the silica coating on magnetite can increase the resistance to acid leaching, increase the particle size, but decrease the magnetic properties of the magnetite. Based on Gas Sorption Analyzer (GSA) and X-ray Difraction (XRD) data it can successively be determined that increase in concentration of sodium silicate will increase the surface area and amorphous structure of the Silica Magnetie.

  6. Dispersibility of silica fume in mortar and its effect on properties of mortar. Silica fume no bunsan to mortar no shotokusei

    Energy Technology Data Exchange (ETDEWEB)

    Oga, H; Uomoto, T [The University of Tokyo, Tokyo (Japan). Institute of Industrial Science

    1992-08-01

    Effect of silica fume dispersibility on concrete characteristics was discussed. Properties of mortar mixed with silica fume to exhibit compression strength varied with displacement rates, patterns, and mixing time of silica fume. In submerged curing age of 28 days, the compression strength in a mortar mixed with silica fume at 10% was affected only very little by the mixing time for both pelletizing and non-pelletizing types for up to 180 seconds. The strength increased thereafter with the mixing time. The compression strength at 1020 seconds showed higher value by about 150 kgf/cm [sup 2] than when no silica fume is added, with a difference because of patterns disappearing. In the case of a mixing time of 1020 seconds, neutralization depth receives very little effect from a pattern difference, and decreases with increasing displacement rate. Neutralization coefficient of the mortar mixed with silica fume at 10% decreased with the mixing time, and it was possible to suppress the neutralization coefficient to 25% of the case without silica fume addition in a 1020-second mixing. 7 refs., 8 figs., 1 tab.

  7. Synthesis of Silica Nanoparticles by Sol-Gel: Size-Dependent Properties, Surface Modification, and Applications in Silica-Polymer Nano composites-A Review

    International Nuclear Information System (INIS)

    Ismail, A.R.; Vejayakumaran, P.

    2012-01-01

    Application of silica nanoparticles as fillers in the preparation of nano composite of polymers has drawn much attention, due to the increased demand for new materials with improved thermal, mechanical, physical, and chemical properties. Recent developments in the synthesis of monodispersed, narrow-size distribution of nanoparticles by sol-gel method provide significant boost to development of silica-polymer nano composites. This paper is written by emphasizing on the synthesis of silica nanoparticles, characterization on size-dependent properties, and surface modification for the preparation of homogeneous nano composites, generally by sol-gel technique. The effect of nano silica on the properties of various types of silica-polymer composites is also summarized.

  8. Silica sol as grouting material: a physio-chemical analysis.

    Science.gov (United States)

    Sögaard, Christian; Funehag, Johan; Abbas, Zareen

    2018-01-01

    At present there is a pressing need to find an environmentally friendly grouting material for the construction of tunnels. Silica nanoparticles hold great potential of replacing the organic molecule based grouting materials currently used for this purpose. Chemically, silica nanoparticles are similar to natural silicates which are essential components of rocks and soil. Moreover, suspensions of silica nanoparticles of different sizes and desired reactivity are commercially available. However, the use of silica nanoparticles as grouting material is at an early stage of its technological development. There are some critical parameters such as long term stability and functionality of grouted silica that need to be investigated in detail before silica nanoparticles can be considered as a reliable grouting material. In this review article we present the state of the art regarding the chemical properties of silica nanoparticles commercially available, as well as experience gained from the use of silica as grouting material. We give a detailed description of the mechanisms underlying the gelling of silica by different salt solutions such as NaCl and KCl and how factors such as particle size, pH, and temperature affect the gelling and gel strength development. Our focus in this review is on linking the chemical properties of silica nanoparticles to the mechanical properties to better understand their functionality and stability as grouting material. Along the way we point out areas which need further research.

  9. Preparation of thick silica coatings on carbon fibers with fine-structured silica nanotubes induced by a self-assembly process

    Directory of Open Access Journals (Sweden)

    Benjamin Baumgärtner

    2017-05-01

    Full Text Available A facile method to coat carbon fibers with a silica shell is presented in this work. By immobilizing linear polyamines on the carbon fiber surface, the high catalytic activity of polyamines in the sol–gel-processing of silica precursors is used to deposit a silica coating directly on the fiber’s surface. The surface localization of the catalyst is achieved either by attaching short-chain polyamines (e.g., tetraethylenepentamine via covalent bonds to the carbon fiber surface or by depositing long-chain polyamines (e.g., linear poly(ethylenimine on the carbon fiber by weak non-covalent bonding. The long-chain polyamine self-assembles onto the carbon fiber substrate in the form of nanoscopic crystallites, which serve as a template for the subsequent silica deposition. The silicification at close to neutral pH is spatially restricted to the localized polyamine and consequently to the fiber surface. In case of the linear poly(ethylenimine, silica shells of several micrometers in thickness can be obtained and their morphology is easily controlled by a considerable number of synthesis parameters. A unique feature is the hierarchical biomimetic structure of the silica coating which surrounds the embedded carbon fiber by fibrillar and interconnected silica fine-structures. The high surface area of the nanostructured composite fiber may be exploited for catalytic applications and adsorption purposes.

  10. Ordered nanoporous silica as carriers for improved delivery of water insoluble drugs: a comparative study between three dimensional and two dimensional macroporous silica

    Directory of Open Access Journals (Sweden)

    Wang Y

    2013-10-01

    Full Text Available Ying Wang, Qinfu Zhao, Yanchen Hu, Lizhang Sun, Ling Bai, Tongying Jiang, Siling WangDepartment of Pharmaceutics, Shenyang Pharmaceutical University, Liaoning Province, People’s Republic of ChinaAbstract: The goal of the present study was to compare the drug release properties and stability of the nanoporous silica with different pore architectures as a matrix for improved delivery of poorly soluble drugs. For this purpose, three dimensional ordered macroporous (3DOM silica with 3D continuous and interconnected macropores of different sizes (200 nm and 500 nm and classic mesoporous silica (ie, Mobil Composition of Matter [MCM]-41 and Santa Barbara Amorphous [SBA]-15 with well-ordered two dimensional (2D cylindrical mesopores were successfully fabricated and then loaded with the model drug indomethacin (IMC via the solvent deposition method. Scanning electron microscopy (SEM, N2 adsorption, differential scanning calorimetry (DSC, and X-ray diffraction (XRD were applied to systematically characterize all IMC-loaded nanoporous silica formulations, evidencing the successful inclusion of IMC into nanopores, the reduced crystallinity, and finally accelerated dissolution of IMC. It was worth mentioning that, in comparison to 2D mesoporous silica, 3DOM silica displayed a more rapid release profile, which may be ascribed to the 3D interconnected pore networks and the highly accessible surface areas. The results obtained from the stability test indicated that the amorphous state of IMC entrapped in the 2D mesoporous silica (SBA-15 and MCM-41 has a better physical stability than in that of 3DOM silica. Moreover, the dissolution rate and stability of IMC loaded in 3DOM silica was closely related to the pore size of macroporous silica. The colorimetric 3-(4,5-Dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT and Cell Counting Kit (CCK-8 assays in combination with direct morphology observations demonstrated the good biocompatibility of nanoporous

  11. Measurement and modelization of silica opal optical properties

    OpenAIRE

    Avoine , Amaury; Ngoc Hong , Phan; Frederich , Hugo; Aregahegn , Kifle; Bénalloul , Paul; Coolen , Laurent; Schwob , Catherine; Thu Nga , Pham; Gallas , Bruno; Maître , Agnès

    2014-01-01

    International audience; We present the synthesis process and optical characterization of artificial silica opals. The specular reflection spectra are analyzed and compared to band structure calculations and finite difference time domain (FDTD) simulations. The silica optical index is a key parameter to correctly describe an opal and is usually not known and treated as a free parameter. Here we propose a method to infer the silica index, as well as the silica spheres diameter, from the reflect...

  12. Functionalized mesoporous silica materials for molsidomine adsorption: Thermodynamic study

    International Nuclear Information System (INIS)

    Alyoshina, Nonna A.; Parfenyuk, Elena V.

    2013-01-01

    A series of unmodified and organically modified mesoporous silica materials was prepared. The unmodified mesoporous silica was synthesized via sol–gel synthesis in the presence of D-glucose as pore-forming agent. The functionalized by phenyl, aminopropyl and mercaptopropyl groups silica materials were prepared via grafting. The fabricated adsorbent materials were characterized by Fourier transform infrared spectroscopy (FTIR) analysis, N 2 adsorption/desorption and elemental analysis methods. Then their adsorption properties for mesoionic dug molsidomine were investigated at 290–313 K and physiological pH value. Thermodynamic parameters of molsidomine adsorption on the synthesized materials have been calculated. The obtained results showed that the adsorption process of molsidomine on the phenyl modified silica is the most quantitatively and energetically favorable. The unmodified and mercaptopropyl modified silica materials exhibit significantly higher adsorption capacities and energies for molsidomine than the aminopropyl modified sample. The effects are discussed from the viewpoint of nature of specific interactions responsible for the adsorption. - Graphical abstract: Comparative analysis of the thermodynamic characteristics of molsidomine adsorption showed that the adsorption process on mesoporous silica materials is controlled by chemical nature of surface functional groups. Molsidomine adsorption on the phenyl modified silica is the most quantitatively and energetically favorable. Taking into account ambiguous nature of mesoionic compounds, it was found that molsidomine is rather aromatic than dipolar. Display Omitted - Highlights: • Unmodified and organically modified mesoporous silica materials were prepared. • Molsidomine adsorption on the silica materials was studied. • Phenyl modified silica shows the highest adsorption capacity and favorable energy. • Molsidomine exhibits the lowest affinity to aminopropyl modified silica

  13. A new ionospheric storm scale based on TEC and foF2 statistics

    Science.gov (United States)

    Nishioka, Michi; Tsugawa, Takuya; Jin, Hidekatsu; Ishii, Mamoru

    2017-01-01

    In this paper, we propose the I-scale, a new ionospheric storm scale for general users in various regions in the world. With the I-scale, ionospheric storms can be classified at any season, local time, and location. Since the ionospheric condition largely depends on many factors such as solar irradiance, energy input from the magnetosphere, and lower atmospheric activity, it had been difficult to scale ionospheric storms, which are mainly caused by solar and geomagnetic activities. In this study, statistical analysis was carried out for total electron content (TEC) and F2 layer critical frequency (foF2) in Japan for 18 years from 1997 to 2014. Seasonal, local time, and latitudinal dependences of TEC and foF2 variabilities are excluded by normalizing each percentage variation using their statistical standard deviations. The I-scale is defined by setting thresholds to the normalized numbers to seven categories: I0, IP1, IP2, IP3, IN1, IN2, and IN3. I0 represents a quiet state, and IP1 (IN1), IP2 (IN2), and IP3 (IN3) represent moderate, strong, and severe positive (negative) storms, respectively. The proposed I-scale can be used for other locations, such as polar and equatorial regions. It is considered that the proposed I-scale can be a standardized scale to help the users to assess the impact of space weather on their systems.

  14. Synthesis and Gas Transport Properties of Hyperbranched Polyimide–Silica Hybrid/Composite Membranes

    Directory of Open Access Journals (Sweden)

    Masako Miki

    2013-12-01

    Full Text Available Hyperbranched polyimide–silica hybrids (HBPI–silica HBDs and hyperbranched polyimide–silica composites (HBPI–silica CPTs were prepared, and their general and gas transport properties were investigated to clarify the effect of silica sources and preparation methods. HBPI–silica HBDs and HBPI–silica CPTs were synthesized by two-step polymerization of A2 + B3 monomer system via polyamic acid as precursor, followed by hybridizing or blending silica sources. Silica components were incorporated by the sol-gel reaction with tetramethoxysilane (TMOS or the addition of colloidal silica. In HBPI-silica HBDs, the aggregation of silica components is controlled because of the high affinity of HBPI and silica caused by the formation of covalent bonds between HBPI and silica. Consequently, HBPI-silica HBDs had good film formability, transparency, and mechanical properties compared with HBPI-silica CPTs. HBPI-silica HBD and CPT membranes prepared via the sol-gel reaction with TMOS showed specific gas permeabilities and permselectivities for CO2/CH4 separation, that is, both CO2 permeability and CO2/CH4 selectivity increased with increasing silica content. This result suggests that gas transport can occur through a molecular sieving effect of the porous silica network derived from the sol-gel reaction and/or through the narrow interfacial region between the silica networks and the organic matrix.

  15. Functionalized Mesoporous Silica Membranes for CO2 Separation Applications

    Directory of Open Access Journals (Sweden)

    Hyung-Ju Kim

    2015-01-01

    Full Text Available Mesoporous silica molecular sieves are emerging candidates for a number of potential applications involving adsorption and molecular transport due to their large surface areas, high pore volumes, and tunable pore sizes. Recently, several research groups have investigated the potential of functionalized mesoporous silica molecular sieves as advanced materials in separation devices, such as membranes. In particular, mesoporous silica with a two- or three-dimensional pore structure is one of the most promising types of molecular sieve materials for gas separation membranes. However, several important challenges must first be addressed regarding the successful fabrication of mesoporous silica membranes. First, a novel, high throughput process for the fabrication of continuous and defect-free mesoporous silica membranes is required. Second, functionalization of mesopores on membranes is desirable in order to impart selective properties. Finally, the separation characteristics and performance of functionalized mesoporous silica membranes must be further investigated. Herein, the synthesis, characterization, and applications of mesoporous silica membranes and functionalized mesoporous silica membranes are reviewed with a focus on CO2 separation.

  16. Development of silica RO membranes

    International Nuclear Information System (INIS)

    Ikeda, Ayumi; Kawamoto, Takashi; Matsuyama, Emi; Utsumi, Keisuke; Nomura, Mikihiro; Sugimoto, Masaki; Yoshikawa, Masato

    2012-01-01

    Silica based membranes have been developed by using a counter diffusion CVD method. Effects of alkyl groups in the silica precursors and deposition temperatures had investigated in order to control pore sizes of the silica membranes. In this study, this type of a silica membrane was applied for RO separation. Effects of silica sources, deposition temperatures and post treatments had been investigated. Tetramethoxysilane (TMOS), Ethyltrimethoxysilane (ETMOS) and Phenyltrimethoxysilane (PhTMOS) were used as silica precursors. A counter diffusion CVD method was carried out for 90 min at 270 - 600degC on γ-alumina capillary substrates (effective length: 50 mm, φ: 4 nm: NOK Co.). O 3 or O 2 was introduced into the inside of the substrate at the O 2 rate of 0.2 L min -1 . Ion beam irradiation was carried out for a post treatment using Os at 490 MeV for 1.0 x 10 10 ions cm -2 or 3.0 x 10 10 ions cm -2 . Single gas permeance was measured by using H 2 , N 2 and SF 6 . RO tests were employed at 3.0 or 5.4 MPa for 100 mg L -1 of feed NaCl solution. First, effects of the silica sources were investigated. The total fluxes increased by increasing N 2 permeance through the silica membrane deposited by ETMOS. The maximum NaCl rejection was 28.2% at 12.2 kg m -2 h -1 of the total flux through the membrane deposited at 270degC. N 2 permeance was 9.6 x 10 -9 mol m -2 s -1 Pa -1 . While, total fluxes through the membrane deposited by using PhTMOS were smaller than those through the ETMOS membranes. The phenyl groups for the PhTMOS membrane must be important for the hydrophobic properties through the membrane. Next, effects of ion beam irradiation were tested for the TMOS membranes. Water is difficult to permeate through the TMOS membranes due to the low N 2 permeance through the membrane (3.1 x 10 -11 mol m -2 s -1 Pa -1 ). N 2 permeance increased to 7.3 x 10 -9 mol m -2 s -1 Pa -1 by the irradiation. Irradiation amounts had little effects on N 2 permeance. However, NaCl rejections

  17. Molecular Dynamics Simulations of Water Droplets On Hydrophilic Silica Surfaces

    DEFF Research Database (Denmark)

    Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard L.

    2009-01-01

    and DNA microarrays technologies.Although extensive experimental, theoretical and computational work has been devoted to study the nature of the interaction between silica and water, at the molecular level a complete understanding of silica-water systems has not been reached. Contact angle computations...... dynamics (MD) simulations of a hydrophilic air-water-silica system using the MD package FASTTUBE. We employ quantum chemistry calculation to obtain air-silica interaction parameters for the simulations. Our simulations are based in the following force fields: i) The silica-silica interaction is based...... of water droplets on silica surfaces offers a useful fundamental and quantitative measurement in order to study chemical and physical properties of water-silica systems. For hydrophobic systems the static and dynamic properties of the fluid-solid interface are influenced by the presence of air. Hence...

  18. Silica scintillating materials prepared by sol-gel methods

    International Nuclear Information System (INIS)

    Werst, D.W.; Sauer, M.C. Jr.; Cromack, K.R.; Lin, Y.; Tartakovsky, E.A.; Trifunac, A.D.

    1993-01-01

    Silica was investigated as a rad-hard alternative to organic polymer hosts for organic scintillators. Silica sol-gels were prepared by hydrolysis of tetramethoxysilane in alcohol solutions. organic dyes were incorporated into the gels by dissolving in methanol at the sol stage of gel formation. The silica sol-gel matrix is very rad-hard. The radiation stability of silica scintillators prepared by this method is dye-limited. Transient radioluminescence was measured following excitation with 30 ps pulses of 20 MeV electrons

  19. Influence of organic solvents on interfacial water at surfaces of silica gel and partially silylated fumed silica

    Energy Technology Data Exchange (ETDEWEB)

    Turov, V.V.; Gun' ko, V.M.; Tsapko, M.D.; Bogatyrev, V.M.; Skubiszewska-Zieba, J.; Leboda, R.; Ryczkowski, J

    2004-05-15

    The effects of organic solvents (dimethylsulfoxide-d{sub 6} (DMSO-d{sub 6}), chloroform-d, acetone-d{sub 6}, and acetonitrile-d{sub 3}) on the properties of interfacial water at surfaces of silica gel Si-40 and partially silylated fumed silica A-380 were studied by means of the {sup 1}H NMR spectroscopy with freezing-out of adsorbed water at 180silicas and quantum chemical calculations of the chemical shifts {delta}{sub H} and solvent effects. DMSO-d{sub 6} and acetonitrile-d{sub 3} are poorly miscible with water in silica gel pores in contrast to the bulk liquids. DMSO-d{sub 6} and chloroform-d affect the structure of the interfacial water weaker than acetone-d{sub 6} and acetonitrile-d{sub 3} at amounts of liquids greater than the pore volume. Acetone-d{sub 6} and acetonitrile-d{sub 3} can displace water from pores under this condition. The chemical shift of protons in water adsorbed on silica gel is 3.5-6.5 ppm, which corresponds to the formation of two to four hydrogen bonds per molecule. Water adsorbed on partially silylated fumed silica has two {sup 1}H NMR signals at 5 and 1.1-1.7 ppm related to different structures (droplets and small clusters) of the interfacial water.

  20. Surface characterization of polyethylene terephthalate/silica nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Parvinzadeh, Mazeyar, E-mail: mparvinzadeh@gmail.com [Department of Textile, Islamic Azad University, Science and Research Branch, Tehran (Iran, Islamic Republic of); Moradian, Siamak [Department of Polymer and Color Engineering, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of); Rashidi, Abosaeed [Department of Textile, Islamic Azad University, Science and Research Branch, Tehran (Iran, Islamic Republic of); Yazdanshenas, Mohamad-Esmail [Department of Textile, Islamic Azad University, Yazd Branch, Yazd (Iran, Islamic Republic of)

    2010-02-15

    Poly(ethylene terephthalate) (PET) based nanocomposites containing hydrophilic (i.e. Aerosil 200 or Aerosil TT 600) or hydrophobic (i.e. Aerosil R 972) nano-silica were prepared by melt compounding. Influence of nano-silica type on surface properties of the resultant nanocomposites was investigated by the use of Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), contact angle measurement (CAM), scanning electron microscopy (SEM) and reflectance spectroscopy (RS). The possible interaction between nano-silica particles and PET functional groups at bulk and surface were elucidated by transmission FTIR and FTIR-ATR spectroscopy, respectively. AFM studies of the resultant nanocomposites showed increased surface roughness compared to pure PET. Contact angle measurements of the resultant PET composites demonstrated that the wettability of such composites depends on surface treatment of the particular nano-silica particles used. SEM images illustrated that hydrophilic nano-silica particles tended to migrate to the surface of the PET matrix.

  1. New insight into silica deposition in horsetail (Equisetum arvense

    Directory of Open Access Journals (Sweden)

    Exley Christopher

    2011-07-01

    Full Text Available Abstract Background The horsetails (Equisetum sp are known biosilicifiers though the mechanism underlying silica deposition in these plants remains largely unknown. Tissue extracts from horsetails grown hydroponically and also collected from the wild were acid-digested in a microwave oven and their silica 'skeletons' visualised using the fluor, PDMPO, and fluorescence microscopy. Results Silica deposits were observed in all plant regions from the rhizome through to the stem, leaf and spores. Numerous structures were silicified including cell walls, cell plates, plasmodesmata, and guard cells and stomata at varying stages of differentiation. All of the major sites of silica deposition in horsetail mimicked sites and structures where the hemicellulose, callose is known to be found and these serendipitous observations of the coincidence of silica and callose raised the possibility that callose might be templating silica deposition in horsetail. Hydroponic culture of horsetail in the absence of silicic acid resulted in normal healthy plants which, following acid digestion, showed no deposition of silica anywhere in their tissues. To test the hypothesis that callose might be templating silica deposition in horsetail commercially available callose was mixed with undersaturated and saturated solutions of silicic acid and the formation of silica was demonstrated by fluorimetry and fluorescence microscopy. Conclusions The initiation of silica formation by callose is the first example whereby any biomolecule has been shown to induce, as compared to catalyse, the formation of silica in an undersaturated solution of silicic acid. This novel discovery allowed us to speculate that callose and its associated biochemical machinery could be a missing link in our understanding of biosilicification.

  2. Functionalized mesoporous silica materials for molsidomine adsorption: Thermodynamic study

    Energy Technology Data Exchange (ETDEWEB)

    Alyoshina, Nonna A.; Parfenyuk, Elena V., E-mail: evp@iscras.ru

    2013-09-15

    A series of unmodified and organically modified mesoporous silica materials was prepared. The unmodified mesoporous silica was synthesized via sol–gel synthesis in the presence of D-glucose as pore-forming agent. The functionalized by phenyl, aminopropyl and mercaptopropyl groups silica materials were prepared via grafting. The fabricated adsorbent materials were characterized by Fourier transform infrared spectroscopy (FTIR) analysis, N{sub 2} adsorption/desorption and elemental analysis methods. Then their adsorption properties for mesoionic dug molsidomine were investigated at 290–313 K and physiological pH value. Thermodynamic parameters of molsidomine adsorption on the synthesized materials have been calculated. The obtained results showed that the adsorption process of molsidomine on the phenyl modified silica is the most quantitatively and energetically favorable. The unmodified and mercaptopropyl modified silica materials exhibit significantly higher adsorption capacities and energies for molsidomine than the aminopropyl modified sample. The effects are discussed from the viewpoint of nature of specific interactions responsible for the adsorption. - Graphical abstract: Comparative analysis of the thermodynamic characteristics of molsidomine adsorption showed that the adsorption process on mesoporous silica materials is controlled by chemical nature of surface functional groups. Molsidomine adsorption on the phenyl modified silica is the most quantitatively and energetically favorable. Taking into account ambiguous nature of mesoionic compounds, it was found that molsidomine is rather aromatic than dipolar. Display Omitted - Highlights: • Unmodified and organically modified mesoporous silica materials were prepared. • Molsidomine adsorption on the silica materials was studied. • Phenyl modified silica shows the highest adsorption capacity and favorable energy. • Molsidomine exhibits the lowest affinity to aminopropyl modified silica.

  3. Reinforcement of natural rubber hybrid composites based on marble sludge/Silica and marble sludge/rice husk derived silica

    Directory of Open Access Journals (Sweden)

    Khalil Ahmed

    2014-03-01

    Full Text Available A research has been carried out to develop natural rubber (NR hybrid composites reinforced with marble sludge (MS/Silica and MS/rice husk derived silica (RHS. The primary aim of this development is to scrutinize the cure characteristics, mechanical and swelling properties of such hybrid composite. The use of both industrial and agricultural waste such as marble sludge and rice husk derived silica has the primary advantage of being eco-friendly, low cost and easily available as compared to other expensive fillers. The results from this study showed that the performance of NR hybrid composites with MS/Silica and MS/RHS as fillers is extremely better in mechanical and swelling properties as compared with the case where MS used as single filler. The study suggests that the use of recently developed silica and marble sludge as industrial and agricultural waste is accomplished to provide a probable cost effective, industrially prospective, and attractive replacement to the in general purpose used fillers like china clay, calcium carbonate, and talc.

  4. Physiology, Biochemistry, and Applications of F420- and Fo-Dependent Redox Reactions.

    Science.gov (United States)

    Greening, Chris; Ahmed, F Hafna; Mohamed, A Elaaf; Lee, Brendon M; Pandey, Gunjan; Warden, Andrew C; Scott, Colin; Oakeshott, John G; Taylor, Matthew C; Jackson, Colin J

    2016-06-01

    5-Deazaflavin cofactors enhance the metabolic flexibility of microorganisms by catalyzing a wide range of challenging enzymatic redox reactions. While structurally similar to riboflavin, 5-deazaflavins have distinctive and biologically useful electrochemical and photochemical properties as a result of the substitution of N-5 of the isoalloxazine ring for a carbon. 8-Hydroxy-5-deazaflavin (Fo) appears to be used for a single function: as a light-harvesting chromophore for DNA photolyases across the three domains of life. In contrast, its oligoglutamyl derivative F420 is a taxonomically restricted but functionally versatile cofactor that facilitates many low-potential two-electron redox reactions. It serves as an essential catabolic cofactor in methanogenic, sulfate-reducing, and likely methanotrophic archaea. It also transforms a wide range of exogenous substrates and endogenous metabolites in aerobic actinobacteria, for example mycobacteria and streptomycetes. In this review, we discuss the physiological roles of F420 in microorganisms and the biochemistry of the various oxidoreductases that mediate these roles. Particular focus is placed on the central roles of F420 in methanogenic archaea in processes such as substrate oxidation, C1 pathways, respiration, and oxygen detoxification. We also describe how two F420-dependent oxidoreductase superfamilies mediate many environmentally and medically important reactions in bacteria, including biosynthesis of tetracycline and pyrrolobenzodiazepine antibiotics by streptomycetes, activation of the prodrugs pretomanid and delamanid by Mycobacterium tuberculosis, and degradation of environmental contaminants such as picrate, aflatoxin, and malachite green. The biosynthesis pathways of Fo and F420 are also detailed. We conclude by considering opportunities to exploit deazaflavin-dependent processes in tuberculosis treatment, methane mitigation, bioremediation, and industrial biocatalysis. Copyright © 2016, American Society for

  5. Modified silica sol coatings for surface enhancement of leather.

    Science.gov (United States)

    Mahltig, Boris; Vossebein, Lutz; Ehrmann, Andrea; Cheval, Nicolas; Fahmi, Amir

    2012-06-01

    The presented study reports on differently modified silica sols for coating applications on leather. Silica sols are prepared by acidic hydrolysis of tetraethoxysilane and modified by silane compounds with fluorinated and non-fluorinated alkylgroups. In contrast to many earlier investigations regarding sol-gel applications on leather, no acrylic resin is used together with the silica sols when applying on leather. The modified silica particles are supposed to aggregate after application, forming thus a modified silica coating on the leather substrate. Scanning electron microscopy investigation shows that the applied silica coatings do not fill up or close the pores of the leather substrate. However, even if the pores of the leather are not sealed by this sol-gel coating, an improvement of the water repellent and oil repellent properties of the leather substrates are observed. These improved properties of leather by application of modified silica sols can provide the opportunity to develop sol-gel products for leather materials present in daily life.

  6. Synthesis and Characterizations of Fine Silica Powder from Rice Husk Ash

    International Nuclear Information System (INIS)

    Khin Muyar Latt

    2011-12-01

    The silica content of rice husk ash obtained from the uncontrolled burning temperature of gasifier was 90.4%. The obtained rice husk ash was an amorphous form of silica with low crystallization by XRD. The sodium hydroxide solution, 1.5N, 2N, 2.5N and 3N, respectively was used to prepare sodium silicate solution by extraction method. The product silica was produced by acid precipitation method used 4.5N, 5.5N and 6.5N sulphuric acid solution. The highest yield percent of product silica extraced by 2.5N sodium hydroxide solution at 5N sulphuric acid solution was 88.84%. The crystallize size of product silica containing silicalite as a source of silica was 86nm at this condition. The fine silica powder was produced by acid refluxing mothod used 5.5N, 6N and 6.5N hydrochloric acid solution. 98% of pure fine silica powder can be produced from the product silica by refluxing method. The crystallize size of fine silica powder was 54nm. The distribution of the crystallize size of product silica powder could be found uniform in size and agglomeration. The Fourier Transform Infrared Spectra indicate the hydrogen bonded silinol groups and siloxane groups in product silica and fine silica powder.

  7. Niobia-silica and silica membranes for gas separation

    NARCIS (Netherlands)

    Boffa, V.

    2008-01-01

    This thesis describes the development of ceramic membranes suitable for hydrogen separation and CO2 recovery from gaseous streams. The research work was focused on the three different parts of which gas selective ceramic membranes are composed, i.e., the microporous gas selective silica layer, the

  8. Sonochemical synthesis of silica particles and their size control

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hwa-Min [Advanced Materials and Chemical Engineering, Catholic University of Daegu, Gyeongbuk 38430 (Korea, Republic of); Lee, Chang-Hyun [Electronic and Electrical Engineering, Catholic University of Daegu, Gyeongbuk 38430 (Korea, Republic of); Kim, Bonghwan, E-mail: bhkim@cu.ac.kr [Electronic and Electrical Engineering, Catholic University of Daegu, Gyeongbuk 38430 (Korea, Republic of)

    2016-09-01

    Graphical abstract: - Highlights: • Silica particles were easily prepared by an ultrasound-assisted sol–gel method. • The particle size was controlled by the ammonium hydroxide/water molar ratio. • The size-controlled diameter of silica particles ranged from 40 to 400 nm. • The particles were formed in a relatively short reaction time. - Abstract: Using an ultrasound-assisted sol–gel method, we successfully synthesized very uniformly shaped, monodisperse, and size-controlled spherical silica particles from a mixture of ethanol, water, and tetraethyl orthosilicate in the presence of ammonia as catalyst, at room temperature. The diameters of the silica particles were distributed in the range from 40 to 400 nm; their morphology was well characterized by scanning electron microscopy. The silica particle size could be adjusted by choosing suitable concentrations of ammonium hydroxide and water, which in turn determined the nucleation and growth rates of the particles during the reaction. This sonochemical-based silica synthesis offers an alternative way to produce spherical silica particles in a relatively short reaction time. Thus, we suggest that this simple, low-cost, and efficient method of preparing uniform silica particles of various sizes will have practical and wide-ranging industrial applicability.

  9. Effect of the Silica Content of Diatoms on Protozoan Grazing

    Directory of Open Access Journals (Sweden)

    Shuwen Zhang

    2017-06-01

    Full Text Available This study examined the effect that silica content in diatom cells has on the behavior of protists. The diatoms Thalassiosira weissflogii and T. pseudonana were cultured in high or low light conditions to achieve low and high silica contents, respectively. These cells were then fed to a heterotrophic dinoflagellate Noctiluca scintillans and a ciliate Euplotes sp. in single and mixed diet experiments. Our results showed that in general, N. scintillans and Euplotes sp. both preferentially ingested the diatoms with a low silica content rather than those with a high silica content. However, Euplotes sp. seemed to be less influenced by the silica content than was N. scintillans. In the latter case, the clearance and ingestion rate of the low silica diatoms were significantly higher, both in the short (6-h and long (1-d duration grazing experiments. Our results also showed that N. scintillans required more time to digest the high silica-containing cells. As the high silica diatoms are harder to digest, this might explain why N. scintillans exhibits a strong preference for the low silica prey. Thus, the presence of high silica diatoms might limit the ability of the dinoflagellate to feed. Our findings suggest that the silica content of diatoms affects their palatability and digestibility and, consequently, the grazing activity and selectivity of protozoan grazers.

  10. Stimulated resonant scattering at stressed fused silica surface

    International Nuclear Information System (INIS)

    Bouchut, Philippe; Reymermier, Maryse

    2015-01-01

    The radiative emission in CO 2 laser heated stressed fused silica is radically modified when gold microspheres are on the surface. At high heating rates, the emission dynamics changes from thermoluminescence to stimulated resonant scattering with an emission rate that is increased tenfold and the near infrared (NIR) spectrum is red-shifted. We show that the dynamic tensile stress that rises in heated silica is coupled with a fluctuating electromagnetic field that enables electromagnetic friction between moving OH emitters from silica bulk and NIR resonant scatterers at the silica surface. (paper)

  11. Arachidonic acid metabolism in silica-stimulated bovine alveolar macrophages

    International Nuclear Information System (INIS)

    Englen, M.D.

    1989-01-01

    The in vitro production of arachidonic acid (AA) metabolites in adherent bovine alveolar macrophages (BAM) incubated with silica was investigated. BAM were pre-labelled with 3 H-AA, and lipid metabolites released into the culture medium were analyzed by high performance liquid chromatography (HPLC). Lactate dehydrogenase (LDH) release was simultaneously assayed to provide an indication of cell injury. Increasing doses of silica selectively stimulated the 5-lipoxygenase pathway of AA metabolism, while cyclooxygenase metabolite output was suppressed. LDH release increased in a linear, dose-dependent fashion over the range of silica doses used. Moreover, within 15 min following addition of a high silica dose, a shift to the production of 5-lipoxygenase metabolites occurred, accompanied by a reduction in cyclooxygenase products. This rapid alteration in AA metabolism preceded cell injury. To examine the relationship between cytotoxicity and AA metabolite release by BAM exposed to silicas with different cytotoxic and fibrogenic activities, BAM were exposed to different doses of DQ-12, Minusil-5, and Sigma silicas, and carbonyl iron beads. The median effective dose (ED 50 ) of each particulate to stimulate the release of AA metabolites and LDH was calculated. The ED 50 values for DQ-12, Minusil-5, and Sigma silica showed that the relative cytotoxicities of the different silicas for BAM corresponded to the relative potencies of the silicas to elicit 5-lipoxygenase metabolites from BAM. These results indicate that the cytotoxic, and presumed fibrogenic potential, of a silica is correlated with the potency to stimulate the release of leukotrienes from AM

  12. Three-dimensional printing of transparent fused silica glass

    Science.gov (United States)

    Kotz, Frederik; Arnold, Karl; Bauer, Werner; Schild, Dieter; Keller, Nico; Sachsenheimer, Kai; Nargang, Tobias M.; Richter, Christiane; Helmer, Dorothea; Rapp, Bastian E.

    2017-04-01

    Glass is one of the most important high-performance materials used for scientific research, in industry and in society, mainly owing to its unmatched optical transparency, outstanding mechanical, chemical and thermal resistance as well as its thermal and electrical insulating properties. However, glasses and especially high-purity glasses such as fused silica glass are notoriously difficult to shape, requiring high-temperature melting and casting processes for macroscopic objects or hazardous chemicals for microscopic features. These drawbacks have made glasses inaccessible to modern manufacturing technologies such as three-dimensional printing (3D printing). Using a casting nanocomposite, here we create transparent fused silica glass components using stereolithography 3D printers at resolutions of a few tens of micrometres. The process uses a photocurable silica nanocomposite that is 3D printed and converted to high-quality fused silica glass via heat treatment. The printed fused silica glass is non-porous, with the optical transparency of commercial fused silica glass, and has a smooth surface with a roughness of a few nanometres. By doping with metal salts, coloured glasses can be created. This work widens the choice of materials for 3D printing, enabling the creation of arbitrary macro- and microstructures in fused silica glass for many applications in both industry and academia.

  13. Similarity and differences in morphology and mechanisms of the foF2 and TEC disturbances during the geomagnetic storms on 26–30 September 2011

    Directory of Open Access Journals (Sweden)

    M. V. Klimenko

    2017-08-01

    Full Text Available This study presents an analysis of the ground-based observations and model simulations of ionospheric electron density disturbances at three longitudinal sectors (eastern European, Siberian and American during geomagnetic storms that occurred on 26–30 September 2011. We use the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP to reveal the main mechanisms influencing the storm-time behavior of the total electron content (TEC and the ionospheric F2 peak critical frequency (foF2 during different phases of geomagnetic storms. During the storm's main phase the long-lasting positive disturbances in TEC and foF2 at sunlit mid-latitudes are mainly explained by the storm-time equatorward neutral wind. The effects of eastward electric field can only explain the positive ionospheric storm in the first few hours of the initial storm phase. During the main phase the ionosphere was more changeable than the plasmasphere. The positive disturbances in the electron content at the plasmaspheric heights (800–20 000 km at high latitudes can appear simultaneously with the negative disturbances in TEC and foF2. The daytime positive disturbances in foF2 and TEC occurred at middle and low latitudes and at the Equator due to n(O ∕ n(N2 enhancement during later stage of the main phase and during the recovery phase of the geomagnetic storm. The plasma tube diffusional depletion and negative disturbances in electron and neutral temperature were the main formation mechanisms of the simultaneous formation of the positive disturbances in foF2 and negative disturbances in TEC at low latitudes during the storm's recovery phase.

  14. Modification of silica surface by gamma ray induced Ad micellar Polymerization

    International Nuclear Information System (INIS)

    Buathong, Salukjit; Pongprayoon, Thirawudh; Suwanmala, Phiriyatorn

    2005-10-01

    Precipitated silica is often added to natural rubber compounds in order to improve performance in commercial application. A problem with using silica as filler is the poor compatibility between silica and natural rubber. In this research, polyisoprene was coated on silica surface by gamma ray induced ad micellar polymerization in order to achieve the better compatibility between silica and natural rubber. The modified silica was characterized by FT-IR, and SEM. The results show that polyisoprene was successfully coated on silica surface via gamma ray induced ad micellar polymerization

  15. Spread-F occurrences and relationships with foF2 and h'F at low- and mid-latitudes in China

    Science.gov (United States)

    Wang, Ning; Guo, Lixin; Zhao, Zhenwei; Ding, Zonghua; Lin, Leke

    2018-04-01

    Ionospheric irregularities are an important phenomenon in scientific studies and applications of radio-wave propagation. Spread-F echoes in ionograms are a type of high-frequency band irregularities that include frequency spread-F (FSF), range spread-F (RSF), and mixed spread-F (MSF) events. In this study, we obtained spread-F data from four ionosondes at low- and mid-latitudes near the 120°E chain in China during the 23rd solar cycle. We used these data to investigate spread-F occurrence percentages and variations with local time, season, latitude, and solar activity. The four ionosondes were located at Haikou (HK) (20°N, 110.34°E), Guangzhou (GZ) (23.14°N, 113.36°E), Beijing (BJ) (40.11°N, 116.28°E), and Changchun (CC) (43.84°N, 125.28°E). We also present possible correlations between spread-Fs and other ionospheric parameters, such as the critical frequency of the F2-layer (foF2) and the virtual height of the bottom-side F-layer (h'F). In particular, we investigated the possible threshold of the foF2 affecting the FSF and the relationship between the h'F and the RSF. The main conclusions are as follows: (a) the FSF occurrence percentages were anti-correlated with solar activity at all four sites; meanwhile, RSF occurrence rates increased with the increase in solar activity at HK, but not at the other three sites; (b) FSF occurrence rates were larger at the mid-latitudes than expected, while FSFs occurred more often after midnight; (c) the highest FSF occurrence rates mostly appeared during the summer months, while RSFs occurred mostly in the equinoctial months of 2000-2002 at HK and GZ; (d) a lower foF2 was suitable for FSF events; nevertheless, h'F and RSF occurrences satisfied the parabolic relationship; (e) the foF2 thresholds for FSFs were 15, 14, 7.6, and 7.8 MHz at HK, GZ, BJ, and CC, respectively. The h'Fs occurring between 240 and 290 km were more favorable for RSF occurrences. These results are important for understanding ionospheric

  16. Investigation of fused silica dynamic behaviour

    International Nuclear Information System (INIS)

    Malaise, F.; Chevalier, J.M.; Bertron, I.; Malka, F.

    2006-01-01

    The survivability of the fused silica shields to shrapnel impacts is a key factor for the affordable operation of the intense laser irradiation future facility Laser Mega Joule (LMJ). This paper presents experimental data and computational modelling for LMJ fused silica upon shock wave loading and unloading. Gas-gun flyer plate impact and explosively driven tests have been conducted to investigate the dynamic behaviour of this material. Hugoniot states and the Hugoniot Elastic Limit of LMJ fused silica have been obtained. These experimental data are useful for determining some constitutive model constants of the 'Crack-Model', a continuum tensile and compressive failure model with friction based. This model has been improved by taking into account nonlinear elasticity. The numerical results obtained by performing computations of the previous tests and some ballistic impact tests are discussed. The numerical comparisons with the experimental data show good agreement. Further developments to simulate the permanent densification and the solid-to-solid phase transformation of fused silica are required. (authors)

  17. Silica uptake in aquatic and wetland macrophytes: a strategic choice between silica, lignin and cellulose?

    Science.gov (United States)

    Schoelynck, Jonas; Bal, Kris; Backx, Hans; Okruszko, Tomasz; Meire, Patrick; Struyf, Eric

    2010-04-01

    *Although silica (Si) is not an essential element for plant growth in the classical sense, evidence points towards its functionality for a better resistance against (a)biotic stress. Recently, it was shown that wetland vegetation has a considerable impact on silica biogeochemistry. However, detailed information on Si uptake in aquatic macrophytes is lacking. *We investigated the biogenic silica (BSi), cellulose and lignin content of 16 aquatic/wetland species along the Biebrza river (Poland) in June 2006 and 2007. The BSi data were correlated with cellulose and lignin concentrations. *Our results show that macrophytes contain significant amounts of BSi: between 2 and 28 mg BSi g(-1). This is in the same order of magnitude as wetland species (especially grasses). Significant antagonistic correlations were found between lignin, cellulose and BSi content. Interestingly, observed patterns were opposite for wetland macrophytes and true aquatic macrophytes. *We conclude that macrophytes have an overlooked but potentially vast storage capacity for Si. Study of their role as temporal silica sinks along the land-ocean continuum is needed. This will further understanding of the role of ecosystems on land ocean transport of this essential nutrient.

  18. Mesoporous Silica: A Suitable Adsorbent for Amines

    Directory of Open Access Journals (Sweden)

    Abdollahzadeh-Ghom Sara

    2009-01-01

    Full Text Available Abstract Mesoporous silica with KIT-6 structure was investigated as a preconcentrating material in chromatographic systems for ammonia and trimethylamine. Its adsorption capacity was compared to that of existing commercial materials, showing its increased adsorption power. In addition, KIT-6 mesoporous silica efficiently adsorbs both gases, while none of the employed commercial adsorbents did. This means that KIT-6 Mesoporous silica may be a good choice for integrated chromatography/gas sensing micro-devices.

  19. Pedogenic silica accumulation in chronosequence soils, southern California

    Science.gov (United States)

    Kendrick, K.J.; Graham, R.C.

    2004-01-01

    Chronosequential analysis of soil properties has proven to be a valuable approach for estimating ages of geomorphic surfaces where no independent age control exists. In this study we examined pedogenic silica as an indicator of relative ages of soils and geomorphic surfaces, and assessed potential sources of the silica. Pedogenic opaline silica was quantified by tiron (4,5-dihydroxy-1,3-benzene-disulfonic acid [disodium salt], C6H 4Na2O8S2) extraction for pedons in two different chromosequences in southern California, one in the San Timoteo Badlands and one in Cajon Pass. The soils of hoth of these chronosequences are developed in arkosic sediments and span 11.5 to 500 ka. The amount of pedogenic silica increases with increasing duration of pedogenesis, and the depth of the maximum silica accumulation generally coincides with the maximum expression of the argillic horizon. Pedogenic silica has accumulated in all of the soils, ranging from 1.2% tiron-extractable Si (Sitn) in the youngest soil to 4.6% in the oldest. Primary Si decreases with increasing duration of weathering, particularly in the upper horizons, where weathering conditions are most intense. The loss of Si coincides with the loss of Na and K, implicating the weathering of feld-spars as the likely source of Si loss. The quantity of Si lost in the upper horizons is adequate to account for the pedogenic silica accumulation in the subsoil. Pedogenic silica was equally effective as pedogenic Fe oxides as an indicator of relative soil age in these soils.

  20. A novel method to characterize silica bodies in grasses.

    Science.gov (United States)

    Dabney, Clemon; Ostergaard, Jason; Watkins, Eric; Chen, Changbin

    2016-01-01

    The deposition of silicon into epidermal cells of grass species is thought to be an important mechanism that plants use as a defense against pests and environmental stresses. There are a number of techniques available to study the size, density and distribution pattern of silica bodies in grass leaves. However, none of those techniques can provide a high-throughput analysis, especially for a great number of samples. We developed a method utilizing the autofluorescence of silica bodies to investigate their size and distribution, along with the number of carbon inclusions within the silica bodies of perennial grass species Koeleria macrantha. Fluorescence images were analyzed by image software Adobe Photoshop CS5 or ImageJ that remarkably facilitated the quantification of silica bodies in the dry ash. We observed three types of silica bodies or silica body related mineral structures. Silica bodies were detected on both abaxial and adaxial epidermis of K. macrantha leaves, although their sizes, density, and distribution patterns were different. No auto-fluorescence was detected from carbon inclusions. The combination of fluorescence microscopy and image processing software displayed efficient utilization in the identification and quantification of silica bodies in K. macrantha leaf tissues, which should applicable to biological, ecological and geological studies of grasses including forage, turf grasses and cereal crops.

  1. Gas-phase acylation of aminopropyl-silica gel in the synthesis of some chemically bonded silica materials for analytical applications

    International Nuclear Information System (INIS)

    Basiuk, Vladimir; Khil'chevskaya, E.G.

    1991-01-01

    Gas-phase acylation of aminopropyl-silica gel with aliphatic dicarboxylic (succinic, adipic and sebacic) and 4-aminobenzoic acids is proposed as a rapid and efficient one-step method for the synthesis of carboxyalkyl- and 4-aminophenylamidopropyl-silica gels, usually used as zwitterion exchangers for liquid chromatography and matrices for multi-step syntheses of silica-bound aromatic azo reagents for the sorption and chromatographic separation of metal ions. Acylation degrees of 59-90% are achieved after 0.5 h. IR spectra of the acylation products and near-UV-visible spectra for bonded aromatic azo compounds, based on 4-aminobenzamidopropyl-silica gel, are presented. Some positive and negative aspects of the gas-phase acylation are discussed. (author). 34 refs.; 2 figs.; 2 tabs

  2. Measurement and modelization of silica opal reflection properties: Optical determination of the silica index

    Science.gov (United States)

    Avoine, Amaury; Hong, Phan Ngoc; Frederich, Hugo; Frigerio, Jean-Marc; Coolen, Laurent; Schwob, Catherine; Nga, Pham Thu; Gallas, Bruno; Maître, Agnès

    2012-10-01

    Self-assembled artificial opals (in particular silica opals) constitute a model system to study the optical properties of three-dimensional photonic crystals. The silica optical index is a key parameter to correctly describe an opal but is difficult to measure at the submicrometer scale and usually treated as a free parameter. Here, we propose a method to extract the silica index from the opal reflection spectra and we validate it by comparison with two independent methods based on infrared measurements. We show that this index gives a correct description of the opal reflection spectra, either by a band structure or by a Bragg approximation. In particular, we are able to provide explanations in quantitative agreement with the measurements for two features : the observation of a second reflection peak in specular direction, and the quasicollapse of the p-polarized main reflection peak at a typical angle of 54∘.

  3. Porous silica nanoparticles as carrier for curcumin delivery

    Science.gov (United States)

    Hartono, Sandy Budi; Hadisoewignyo, Lannie; Irawaty, Wenny; Trisna, Luciana; Wijaya, Robby

    2018-04-01

    Mesoporous silica nanoparticles (MSN) with large surface areas and pore volumes show great potential as drug and gene carriers. However, there are still some challenging issues hinders their clinical application. Many types of research in the use of mesoporous silica material for drug and gene delivery involving complex and rigorous procedures. A facile and reproducible procedure to prepare combined drug carrier is required. We investigated the effect of physiochemical parameters of mesoporous silica, including structural symmetry (cubic and hexagonal), particles size (micro size: 1-2 µm and nano size: 100 -300 nm), on the solubility and release profile of curcumin. Transmission Electron Microscopy, X-Ray Powder Diffraction, and Nitrogen sorption were used to confirm the synthesis of the mesoporous silica materials. Mesoporous silica materials with different mesostructures and size have been synthesized successfully. Curcumin has anti-oxidant, anti-inflammation and anti-virus properties which are beneficial to fight various diseases such as diabetic, cancer, allergic, arthritis and Alzheimer. Curcumin has low solubility which minimizes its therapeutic effect. The use of nanoporous material to carry and release the loaded molecules is expected to enhance curcumin solubility. Mesoporous silica materials with a cubic mesostructure had a higher release profile and curcumin solubility, while mesoporous silica materials with a particle size in the range of nano meter (100-300) nm also show better release profile and solubility.

  4. Mesoporous silica formulation strategies for drug dissolution enhancement: a review.

    Science.gov (United States)

    McCarthy, Carol A; Ahern, Robert J; Dontireddy, Rakesh; Ryan, Katie B; Crean, Abina M

    2016-01-01

    Silica materials, in particular mesoporous silicas, have demonstrated excellent properties to enhance the oral bioavailability of poorly water-soluble drugs. Current research in this area is focused on investigating the kinetic profile of drug release from these carriers and manufacturing approaches to scale-up production for commercial manufacture. This review provides an overview of different methods utilized to load drugs onto mesoporous silica carriers. The influence of silica properties and silica pore architecture on drug loading and release are discussed. The kinetics of drug release from mesoporous silica systems is examined and the manufacturability and stability of these formulations are reviewed. Finally, the future prospects of mesoporous silica drug delivery systems are considered. Substantial progress has been made in the characterization and development of mesoporous drug delivery systems for drug dissolution enhancement. However, more research is required to fully understand the drug release kinetic profile from mesoporous silica materials. Incomplete drug release from the carrier and the possibility of drug re-adsorption onto the silica surface need to be investigated. Issues to be addressed include the manufacturability and regulation status of formulation approaches employing mesoporous silica to enhance drug dissolution. While more research is needed to support the move of this technology from the bench to a commercial medicinal product, it is a realistic prospect for the near future.

  5. Cathodoluminescence microcharacterization of ballen silica in impactites

    International Nuclear Information System (INIS)

    Okumura, T.; Ninagawa, K.; Toyoda, S.; Gucsik, A.; Nishido, H.

    2009-01-01

    The ballen silica shows fairly weak (faint) CL with homogeneous feature in its grain exhibiting almost same spectral pattern with two broad band peaks at around 390 and 650 nm, which might be assigned to self-trapped excitons (STE) or an intrinsic and nonbridging oxygen hole centers (NBOHC), respectively, recognized in amorphous and crystalline silica. In addition, ballen silica from Lappajaervi crater shows bright and heterogeneous CL with a broad band centered at around 410 nm, presumably attributed to [AlO 4 /M + ] 0 centers or self-trapped excitons (STE). Micro-Raman and micro-XRD analyses show that fairly homogeneous CL part is α-quartz and heterogeneous CL part is composed of α-cristobalite and α-quartz. These indicate that ballen silica could be formed in the quenching process from relatively high temperature.

  6. Grazing incidence angle based sensing approach integrated with fiber-optic Fourier transform infrared (FO-FTIR) spectroscopy for remote and label-free detection of medical device contaminations

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, Moinuddin, E-mail: moinuddin.hassan@fda.hhs.gov; Ilev, Ilko [Optical Therapeutics and Medical Nanophotonics Laboratory, Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, Maryland 20993 (United States)

    2014-10-15

    Contamination of medical devices has become a critical and prevalent public health safety concern since medical devices are being increasingly used in clinical practices for diagnostics, therapeutics and medical implants. The development of effective sensing methods for real-time detection of pathogenic contamination is needed to prevent and reduce the spread of infections to patients and the healthcare community. In this study, a hollow-core fiber-optic Fourier transform infrared spectroscopy methodology employing a grazing incidence angle based sensing approach (FO-FTIR-GIA) was developed for detection of various biochemical contaminants on medical device surfaces. We demonstrated the sensitivity of FO-FTIR-GIA sensing approach for non-contact and label-free detection of contaminants such as lipopolysaccharide from various surface materials relevant to medical device. The proposed sensing system can detect at a minimum loading concentration of approximately 0.7 μg/cm{sup 2}. The FO-FTIR-GIA has the potential for the detection of unwanted pathogen in real time.

  7. Effect of silica and water content on the glass transition of poly(ethylene glycol) monomethylether-silica gel-lithium perchlorate ormolytes

    International Nuclear Information System (INIS)

    Korwin, Rebecca S.; Masui, Hitoshi

    2005-01-01

    The effect of silica and water content on the glass transition temperature, T g , of MPEG2000-silica-LiClO 4 ormolytes was assessed by differential scanning calorimetry (DSC). The sol-gel synthesized ormolytes consisted of various amounts of poly(ethylene glycol) monomethylether (M.W. 2000 g/mol; i.e., MPEG2000) tethered to silica gel through the hydroxyl terminus via a urethane linkage. DSC features corresponding to physisorbed and hydrogen-bonded water, as well as the glass transition of the polyether, were identified. Both silica and LiClO 4 raise the T g and suppress crystallization of the polyether component. Water plasticizes the polyether and stoichiometrically solvates and sequesters Li + , thereby, lowering T g

  8. H2 uptake in the Li-dispersed silica nano-tubes

    International Nuclear Information System (INIS)

    Jin Bae Lee; Soon Chang Lee; Sang Moon Lee; Hae Jin Kim

    2006-01-01

    Highly ordered Li-dispersed silica nano-tubes were prepared by sol-gel template method for hydrogen storage. Isolated Li-dispersed silica nano-tubes can be easily obtained by removing the AAO template with 2M NaOH. From the XRD study, the Li-dispersed silica nano-tubes showed the amorphous phase with silica frameworks. The uniform length and diameter of Li-dispersed silica nano-tubes could be examined with the electron microscopy studies. The wall thickness and diameter of nano-tubes are about 50-60 nm and 200-400 nm, respectively. The obtained Li-dispersed silica nano-tubes have the hydrogen adsorption capacity 2.25 wt% at 77 K under 47 atm. (authors)

  9. Hafnium in peralkaline and peraluminous boro-aluminosilicate glass, and glass subcomponents: a solubility study

    International Nuclear Information System (INIS)

    Davis, Linda L.; Darab, John G.; Qian, Maoxu; Zhao, Donggao; Palenik, Christopher S.; Li, Hong; Strachan, Denis M.; Li, Liyu

    2003-01-01

    A relationship between the solubility of hafnia (HfO2) and the host glass composition was explored by determining the solubility limits of HfO2 in peralkaline and peraluminous borosilicate glasses in the system SiO2-Al2O3-B2O3-Na2O, and in glasses in the system SiO2-Na2O-Al2O3 in air at 1450 C. The only Hf-bearing phase to crystallize in the peralkaline borosilicate melts is hafnia, while in the boron-free melts sodium-hafnium silicates crystallize. All peraluminous borosilicate melts crystallize hafnia, but the slightly peraluminous glasses also have sector-zoned hafnia crystals that contain Al and Si. The more peraluminous borosilicate glasses also crystallize a B-containing mullite. The general morphology of the hafnia crystals changes as peralkalinity (Na2O/(Na2O+Al2O3)) decreases, as expected in melts with increasing viscosity. In all of the glasses with Na2O > Al2O3, the solubility of hafnia is linearly and positively correlated with Na2O/(Na2O + Al2O3) or Na2O - Al2O3 (excess sodium), despite the presence of 5 to 16 mol% B2O3. The solubility of hafnia is higher in the sodium-aluminum borosilicate glasses than in the sodium-aluminosilicate glasses, suggesting that the boron is enhancing the effect that excess sodium has on the incorporation of Hf into the glass structure. The results of this solubility study are compared to other studies of high-valence cation solubility in B-free silicate melts. From this, for peralkaline B-bearing glasses, it is shown that, although the solubility limits are higher, the solution behavior of hafnia is the same as in B-free silicate melts previously studied. By comparison, also, it is shown that in peraluminous melts, there must be a different solution mechanism for hafnia: different than for peralkaline sodium-aluminum borosilicate glasses and different than for B-free silicate melts studied by others

  10. Measurement and modelization of silica opal optical properties

    Science.gov (United States)

    Avoine, Amaury; Hong, Phan Ngoc; Frederich, Hugo; Aregahegn, Kifle; Bénalloul, Paul; Coolen, Laurent; Schwob, Catherine; Thu Nga, Pham; Gallas, Bruno; Maître, Agnès

    2014-03-01

    We present the synthesis process and optical characterization of artificial silica opals. The specular reflection spectra are analyzed and compared to band structure calculations and finite difference time domain (FDTD) simulations. The silica optical index is a key parameter to correctly describe an opal and is usually not known and treated as a free parameter. Here we propose a method to infer the silica index, as well as the silica spheres diameter, from the reflection spectra and we validate it by comparison with two independent infrared methods for the index and, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements for the spheres diameter.

  11. Measurement and modelization of silica opal optical properties

    International Nuclear Information System (INIS)

    Avoine, Amaury; Ngoc Hong, Phan; Frederich, Hugo; Aregahegn, Kifle; Bénalloul, Paul; Coolen, Laurent; Schwob, Catherine; Gallas, Bruno; Maître, Agnès; Thu Nga, Pham

    2014-01-01

    We present the synthesis process and optical characterization of artificial silica opals. The specular reflection spectra are analyzed and compared to band structure calculations and finite difference time domain (FDTD) simulations. The silica optical index is a key parameter to correctly describe an opal and is usually not known and treated as a free parameter. Here we propose a method to infer the silica index, as well as the silica spheres diameter, from the reflection spectra and we validate it by comparison with two independent infrared methods for the index and, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements for the spheres diameter. (paper)

  12. Distribution of silica species in cooling water system in nuclear power station

    International Nuclear Information System (INIS)

    Akiba, Kenichi; Onozuka, Teruo; Shindo, Manabu.

    1995-01-01

    Distribution of silica species was examined by spectrophotometric method based on the formation of molybdosilicic acid species. Ultra-microamounts of ionic (reactive) silica were determined by collection of silicomolybdenum blue compound on a nitrocellulose membrane filter. Total concentrations of silica including nonionic (polymer and colloidal) species were also determined after decomposition of unreactive silica in alkali solutions. Water in the nuclear reactor (Onagawa BWR No.1) contained high concentration of silica (∼600 ppb) and ionic silica was found to be predominant (∼90%). In condensate system, silica contents were of a lower level (2-6 ppb), but the ionic silica contents were comparable to others (20-60%). The silica species appear to be brought and accumulated in the reactor from the condensate system, and then the silica species change to ionic species under high pressure and high temperature. (author)

  13. Distribution of silica species in cooling water system in nuclear power station

    Energy Technology Data Exchange (ETDEWEB)

    Akiba, Kenichi [Tohoku Univ., Sendai (Japan). Inst. for Advanced Materials Processing; Onozuka, Teruo; Shindo, Manabu

    1995-12-01

    Distribution of silica species was examined by spectrophotometric method based on the formation of molybdosilicic acid species. Ultra-microamounts of ionic (reactive) silica were determined by collection of silicomolybdenum blue compound on a nitrocellulose membrane filter. Total concentrations of silica including nonionic (polymer and colloidal) species were also determined after decomposition of unreactive silica in alkali solutions. Water in the nuclear reactor (Onagawa BWR No.1) contained high concentration of silica ({approx}600 ppb) and ionic silica was found to be predominant ({approx}90%). In condensate system, silica contents were of a lower level (2-6 ppb), but the ionic silica contents were comparable to others (20-60%). The silica species appear to be brought and accumulated in the reactor from the condensate system, and then the silica species change to ionic species under high pressure and high temperature. (author).

  14. Thermodynamics of the silica-steam system

    Energy Technology Data Exchange (ETDEWEB)

    Krikorian, Oscar H [Lawrence Radiation Laboratory, University of California, Livermore, CA (United States)

    1970-05-01

    In most nuclear cratering and cavity formation applications, the working fluid in the expanding cavity consists primarily of vaporized silica and steam. The chemical reaction products of silica and steam under these conditions are not known, although it is known that silica is very volatile in the presence of high-pressure steam under certain geologic conditions and in steam turbines. A review is made of work on the silica-steam system in an attempt to determine the vapor species that exist, and to establish the associated thermo-dynamic data. The review indicates that at 600-900 deg K and 1-100 atm steam pressure, Si(OH){sub 4} is the most likely silicon-containing gaseous species. At 600-900 deg. K and 100-1000 atm steam, Si{sub 2}O(OH){sub 6} is believed to predominate, whereas at 1350 deg K and 2000-9000 atm, a mixture of Si(OH){sub 4} and Si{sub 2}O(OH){sub 6} is consistent with the observed volatilities. In work at 1760 deg. K in which silica was reacted either with steam at 0.5 and 1 atm, or with gaseous mixtures of H{sub 2}/H{sub 2}O and O{sub 2}/H{sub 2}O at 1 atm total pressure, only part of the volatility could be accounted for by Si(OH){sub 4}. Hydrogen was found to greatly enhance the volatility of silica, and oxygen to suppress it. The species most likely to explain this behavior is believed to be SiO(OH). A number of other species may also be significant under these conditions. Thermodynamic data have been estimated for all species considered. The Si-OH bond dissociation energy is found to be {approx}117 kcal/mole in both Si(OH){sub 4} and Si{sub 2}O(OH){sub 6}. (author)

  15. Supramolecular structures on silica surfaces and their adsorptive properties.

    Science.gov (United States)

    Belyakov, Vladimir N; Belyakova, Lyudmila A; Varvarin, Anatoly M; Khora, Olexandra V; Vasilyuk, Sergei L; Kazdobin, Konstantin A; Maltseva, Tetyana V; Kotvitskyy, Alexey G; Danil de Namor, Angela F

    2005-05-01

    The study of adsorptive and chemical immobilization of beta-cyclodextrin on a surface of hydroxylated silicas with various porous structure is described. Using IR spectroscopy, thermal gravimetrical analysis with a programmed heating, and chemical analysis of the silica surface, it is shown that the process of adsorption-desorption of beta-cyclodextrin depends on the porous structure of the silica. The reaction of esterification was used for chemical grafting of beta-cyclodextrin on the surface of hydroxylated silicas. Hydrolytic stability of silicas chemically modified by beta-cyclodextrin apparently is explained by simultaneous formation of chemical and hydrogen bonds between surface silanol groups and hydroxyl groups of beta-cyclodextrin. The uptake of the cations Cu(II), Cd(II), and Pb(II) and the anions Cr(VI) and As(V) by silicas modified with beta-cyclodextrin is investigated as a function of equilibrium ion concentrations. The increase of ion uptake and selectivity of ion extraction in comparison with starting silicas is established. It is due to the formation of surface inclusion complexes of the "host-guest" type in which one molecule of beta-cyclodextrin interacts simultaneously with several ions.

  16. Photooxidation of ethylene over Cu-modified and unmodified silica

    OpenAIRE

    Ichihashi, Yuichi; Matsumura, Yasuyuki

    2003-01-01

    Silica catalyzes photooxidation of ethylene to carbon dioxide and modification of copper on silica results in the lower reaction rate and partial production of ethylene oxide. The reaction does not proceed by the light irradiation through a color filter (λ>280 nm). ESR measurement indicates that radical oxygen species assignable T-shape Si − O3− can be produced on silica by UV irradiation at 77 K. The same species are also found on silica modified with copper by UV irradiation whi...

  17. Silica scale prevention technology using organic additive, Geogard SX

    Energy Technology Data Exchange (ETDEWEB)

    Baltazar, Almario; Garcia, Serafin; Solis, Ramonito; Fragata, Jimmy; Ellseworth, Lucero; Llenarizas, Leonardo; Tabuena, Joseph Erwin (PNOC Energy Development Corporation, Makati City (Philippines))

    1998-09-15

    A field trial on the application of an organic additive, phosphino carboxylic acid copolymer, was conducted in a geothermal system to evaluate its effectiveness in preventing silica deposition from brine containing ultra high silica concentration (1000-1300 ppm). Low polymer concentration was applied for about five months, and treatment efficiency based on silica concentrations in various sampling points ranged from 64 to 98%. Treatment efficiency improved as a function of time. Massive silica scaling in the fluid collection and disposal system was minimized.

  18. Acid-base equilibria inside amine-functionalized mesoporous silica.

    Science.gov (United States)

    Yamaguchi, Akira; Namekawa, Manato; Kamijo, Toshio; Itoh, Tetsuji; Teramae, Norio

    2011-04-15

    Acid-base equilibria and effective proton concentration inside a silica mesopore modified with a trimethyl ammonium (TMAP) layer were studied by steady-state fluorescence experiments. The mesoporous silica with a dense TMAP layer (1.4 molecules/nm(2)) was prepared by a post grafting of N-trimethoxysilylpropyl-N,N,N-trimethylammonium at surfactant-templated mesoporous silica (diameter of silica framework =3.1 nm). The resulting TMAP-modified mesoporous silica strongly adsorbed of anionic fluorescence indicator dyes (8-hydroxypyrene-1,3,6-trisulfonate (pyranine), 8-aminopyrene-1,3,6-trisulfonate (APTS), 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid disulfuric acid (TPPS), 2-naphthol-3,6-disulfonate (2NT)) and fluorescence excitation spectra of these dyes within TMAP-modified mesoporous silica were measured by varying the solution pH. The fluorescence experiments revealed that the acid-base equilibrium reactions of all pH indicator dyes within the TMAP-modified silica mesopore were quite different from those in bulk water. From the analysis of the acid-base equilibrium of pyranine, the following relationships between solution pH (pH(bulk)) and the effective proton concentration inside the pore (pH(pore)) were obtained: (1) shift of pH(pore) was 1.8 (ΔpH(pore)=1.8) for the pH(bulk) change from 2.1 to 9.1 (ΔpH(bulk)=7.0); (2) pH(pore) was not simply proportional to pH(bulk); (3) the inside of the TMAP-modified silica mesopore was suggested to be in a weak acidic or neutral condition when pH(bulk) was changed from 2.0 to 9.1. Since these relationships between pH(bulk) and pH(pore) could explain the acid-base equilibria of other pH indicator dyes (APTS, TPPS, 2NT), these relationships were inferred to describe the effective proton concentration inside the TMAP-modified silica mesopore. © 2011 American Chemical Society

  19. Physical and chemical controls (fO2, T, pH) of the opposite behaviour of U and Sn-W as examplified by hydrothermal deposits in France and Great-Britain, and solubility data

    International Nuclear Information System (INIS)

    Dubessy, J.; Nguyen-Trung, C.; Cathelineau, M.; Cuney, M.; Leroy, J.; Poty, B.; Ramboz, C.; Charoy, B.; Weisbrod, A.

    1987-01-01

    In uranium deposits, fO 2 and fS 2 of mineralizing fluids are higher than values fixed by the pyrite-hematite-magnetite triple point, as shown by uraninite-hematite and/or pyrite mineral association. The stability of quartz-K feldspar-muscovite paragenesis in the wall-rocks of hydrothermal U deposits indicates weakly acid pH. By contrast, in the Sn-W occurrences from the French Southern Massif Central, the fO 2 of mineralizing fluids is between Ni-NiO and Q-F-M buffers as shown by fluid inclusions. The pH of these fluids is weakly acid to weakly basic. Sn-W mineralizing fluids from Cornwall are by contrast purely aqueous and acid. Experimental data on UO 2 , SnO 2 , FeWO 4 , CaWO 4 solubility and metal species in fluids show that fO 2 > H-M are required for uranium transport whereas fO 2 ≤ Ni-NiO favours Sn transport. The fluid oxidation state has no direct influence on the transport and deposition of tungsten. The fO 2 control on the hydrothermal transport properties of these three metals is related on the one hand to the fluid and rock composition, and on the other hand to the minimal 320 0 C temperature required for homogeneous equilibria in the C-O-H system to control the oxidation state at low values. At high temperatures, Sn, Fe and Ca chloride complexes are more stable than carbonate and phosphate uranium complexes. All these results show that temperature and fO 2 account for the opposite behaviour of uranium and tin-tungsten in hydrothermal systems between 300 0 to 500 0 C

  20. Sílica solúvel em solos Soluble silica in soils

    Directory of Open Access Journals (Sweden)

    Bernardo van Raij

    1973-01-01

    Full Text Available Determinou-se a silica solúvel nos horizontes superficial e B2 de 44 perfis de solos do Estado de São Paulo. A extração da silica com solução 0,0025M de cloreto de cálcio evitou a dispersão dos solos e forneceu resultados em média apenas 8% menores do que a silica solúvel em água. Os resultados variaram de 2,2 a 92,2 ppm de SiO2. Verificou-se que, para solos com teores semelhantes de argila, os teores de silica solúvel foram maiores para solos com horizonte B textural, quando comparados com solos de horizonte B latossólico. Dentro dos agrupamentos de solos com horizonte B textural e horizonte B latossólico, os teores de silica solúvel foram maiores para os solos mais argilosos. Não foi observada relação entre silica solúvel e o pH dos solos.The extraction of soluble silica of soils with 0.0025M calcium chloride solution avoided dispersion of clay and results were on the average only 8% lower than water soluble silica. The results for surface and B2 horizons of 44 soil profiles of the State of São Paulo varied between 2.2 and 92.9 ppm of SiO2. For soils with similar clay contents, soluble silica was higher for soil with argillic B horizons as compared with soils with oxic B horizons. Within each group of soils, higher soluble silica results were associated with higher clay contents. Soluble silica apparently was not related to soil pH.

  1. Structure and Properties of LENRA/ Silica Composite

    International Nuclear Information System (INIS)

    Mahathir Mohamed; Dahlan Mohd

    2010-01-01

    The sol-gel reaction using tetra ethoxysilane (TEOS) was conducted for modified natural rubber (NR) matrix to obtain in situ generated NR/ silica composite. The present of acrylate group in the modified NR chain turns the composite into radiation-curable. The maximum amount of silica generated in the matrix was 50 p hr by weight. During the sol-gel process the inorganic mineral was deposited in the rubber matrix forming hydrogen bonding between organic and inorganic phases. The composites obtained were characterized by various techniques including thermogravimetric analysis and infrared spectrometry to study their molecular structure. The increase in mechanical properties was observed for low silica contents ( 30 p hr) where more silica were generated, agglomerations were observed at the expense of the mechanical properties. From the DMTA data, it shows an increase of the interaction between the rubber and silica phases up to 30 p hr TEOS. Structure and morphology of the heterogeneous system were analyzed by transmission electron microscopy. The average particle sizes of between 150 nm to 300 nm were achieved for the composites that contain less than 20 p hr of TEOS. (author)

  2. Silica promoted self-assembled mesoporous aluminas. Impact of the silica precursor on the structural, textural and acidic properties

    NARCIS (Netherlands)

    Perez, Lidia Lopez; Zarubina, Valeriya; Mayoral, Alvaro; Melian-Cabrera, Ignacio

    2015-01-01

    This paper investigates the effect of silica addition on the structural, textural and acidic properties of an evaporation induced self-assembled (EISA) mesoporous alumina. Two silica addition protocols were applied while maintaining the EISA synthesis route. The first route is based on the addition

  3. Face-specific Replacement of Calcite by Amorphous Silica Nanoparticles

    Science.gov (United States)

    Liesegang, M.; Milke, R.; Neusser, G.; Mizaikoff, B.

    2016-12-01

    Amorphous silica, composed of nanoscale spheres, is an important biomineral, alteration product of silicate rocks on the Earth's surface, and precursor material for stable silicate minerals. Despite constant progress in silica sphere synthesis, fundamental knowledge of natural silica particle interaction and ordering processes leading to colloidal crystals is absent so far. To understand the formation pathways of silica spheres in a geologic environment, we investigated silicified Cretaceous mollusk shell pseudomorphs from Coober Pedy (South Australia) using focused ion beam (FIB)-SEM tomography, petrographic microscopy, µ-XRD, and EMPA. The shells consist of replaced calcite crystals (ionic strength remain constant throughout the replacement process, permitting continuous silica nanoparticle formation and diffusion-limited colloid aggregation. Our study provides a natural example of the transformation of an atomic crystal to an amorphous, mesoscale ordered material; thus, links the research fields of natural colloidal crystal formation, carbonate-silica replacement, and crystallization by oriented particle aggregation (CPA).

  4. Phase behavior of methane hydrate in silica sand

    International Nuclear Information System (INIS)

    Sun, Shi-Cai; Liu, Chang-Ling; Ye, Yu-Guang; Liu, Yu-Feng

    2014-01-01

    Highlights: • Hydrate p-T trace in coarse-grained sediment is consistent with that in bulk water. • Fine-grained sediment affects hydrate equilibrium for the depressed water activity. • Hydrate equilibrium in sediment is related to the pore size distribution. • The application of hydrate equilibrium in sediment depends on the actual condition. -- Abstract: Two kinds of silica sand powder with different particle size were used to investigate the phase behavior of methane hydrate bearing sediment. In coarse-grained silica sand, the measured temperature and pressure range was (281.1 to 284.2) K and (5.9 to 7.8) MPa, respectively. In fine-grained silica sand, the measured temperature and pressure range was (281.5 to 289.5) K and (7.3 to 16.0) MPa, respectively. The results show that the effect of coarse-grained silica sand on methane hydrate phase equilibrium can be ignored; however, the effect of fine-grained silica sand on methane hydrate phase equilibrium is significant, which is attributed to the depression of water activity caused by the hydrophilicity and negatively charged characteristic of silica particle as well as the pore capillary pressure. Besides, the analysis of experimental results using the Gibbs–Thomson equation shows that methane hydrate phase equilibrium is related to the pore size distribution of silica sand. Consequently, for the correct application of phase equilibrium data of hydrate bearing sediment, the geological condition and engineering requirement should be taken into consideration in gas production, resource evaluation, etc

  5. Synthesis and characterization of mesoporous silica core-shell particles

    Directory of Open Access Journals (Sweden)

    Milan Nikolić

    2010-06-01

    Full Text Available Core-shell particles were formed by deposition of primary silica particles synthesized from sodium silicate solution on functionalized silica core particles (having size of ~0.5 µm prepared by hydrolysis and condensation of tetraethylortosilicate. The obtained mesoporous shell has thickness of about 60 nm and consists of primary silica particles with average size of ~21 nm. Scanning electron microscopy and zeta potential measurements showed that continuous silica shell exists around functionalized core particles which was additionally proved by FTIR and TEM results.

  6. Fabrication of keratin-silica hydrogel for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Kakkar, Prachi; Madhan, Balaraman, E-mail: bmadhan76@yahoo.co.in

    2016-09-01

    In the recent past, keratin has been fabricated into different forms of biomaterials like scaffold, gel, sponge, film etc. In lieu of the myriad advantages of the hydrogels for biomedical applications, a keratin-silica hydrogel was fabricated using tetraethyl orthosilicate (TEOS). Textural analysis shed light on the physical properties of the fabricated hydrogel, inturn enabling the optimization of the hydrogel. The optimized keratin-silica hydrogel was found to exhibit instant springiness, optimum hardness, with ease of spreadability. Moreover, the hydrogel showed excellent swelling with highly porous microarchitecture. MTT assay and DAPI staining revealed that keratin-silica hydrogel was biocompatible with fibroblast cells. Collectively, these properties make the fabricated keratin-silica hydrogel, a suitable dressing material for biomedical applications. - Highlights: • Keratin-silica hydrogel has been fabricated using sol–gel technique. • The hydrogel shows appropriate textural properties. • The hydrogel promotes fibroblast cells proliferation. • The hydrogel has potential soft tissue engineering applications like wound healing.

  7. Supercritical carbon dioxide versus toluene as reaction media in silica functionalisation: Synthesis and characterisation of bonded aminopropyl silica intermediate.

    Science.gov (United States)

    Ashu-Arrah, Benjamin A; Glennon, Jeremy D

    2017-06-09

    This research reports supercritical carbon dioxide versus toluene as reaction media in silica functionalisation for use in liquid chromatography. Bonded aminopropyl silica (APS) intermediates were prepared when porous silica particles (Exsil-pure, 3μm) were reacted with 3-aminopropyltriethoxysilane (3-APTES) or N,N-dimethylaminopropyltrimethoxysilane (DMAPTMS) using supercritical carbon dioxide (sc-CO 2 ) and toluene as reaction media. Covalent bonding to silica was confirmed using elemental microanalysis (CHN), thermogravimetric analysis (TGA), zeta potential (ξ), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, scanning electron microscopy (SEM) and solid-state nuclear magnetic resonance (CP/MAS NMR) spectroscopy. The results demonstrate that under sc-CO 2 conditions of 100°C/414bar in a substantial reduced time of 3h, the surface coverage of APS (evaluated from%C obtained from elemental analysis) prepared with APTES (%C: 8.03, 5.26μmol/m -2 ) or DMAPTES (%C: 5.12, 4.58μmol/m 2 ) is somewhat higher when compared to organic based reactions under reflux in toluene at a temperature of 110°C in 24h with APTES (%C: 7.33, 4.71μmol/m 2 ) and DMAPTMS (%C: 4.93, 4.38μmol/m 2 ). Zeta potential measurements revealed a change in electrostatic surface charge from negative values for bare Exsil-pure silica to positive for functionalised APS materials indicating successful immobilization of the aminosilane onto the surface of silica. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Variability of biological effects of silicas: Different degrees of activation of the fifth component of complement by amorphous silicas

    International Nuclear Information System (INIS)

    Governa, Mario; Amati, Monica; Fenoglio, Ivana; Valentino, Matteo; Coloccini, Sabrina; Bolognini, Lucia; Carlo Botta, Gian; Emanuelli, Monica; Pierella, Francesca; Volpe, Anna Rita; Astolfi, Paola; Carmignani, Marco; Fubini, Bice

    2005-01-01

    A biogenic and a pyrogenic amorphous silica were incubated in normal human plasma and compared on a per unit surface basis for their ability to split C5 molecules and yield small C5a peptides. Since C5a peptides induce selective chemotactic attraction of polymorphonuclear leukocytes (PMN), measurement of PMN-induced chemotaxis was used as an index of C5 activation. Though to a lesser extent than the crystalline forms, amorphous silicas can promote the cleavage of C5 protein and generation of C5a-like fragment. The biogenic silica, which differs from the pyrogenic variety in particle shape, level of contaminants, and degree of surface hydrophilicity, besides specific surface, induced a greater response. Both silicas activated C5 through a process which seems to involve multiple events similar to those induced by crystalline silica. C5 molecules are adsorbed and hydroxyl radicals are generated through Haber Weiss cycles catalyzed by the redox-active iron present at the particle surface either as trace impurities or chelated from plasma by silanol groups. In turn, these radicals convert native C5 to an oxidized C5-like form C5(H 2 O 2 ). Finally, C5(H 2 O 2 ) is cleaved by protease enzymatic action of plasma kallikrein activated by the same silica dusts, yielding a product, C5a(H 2 O 2 ), having the same functional characteristic as C5a

  9. Effect of occupational silica exposure on pulmonary function.

    Science.gov (United States)

    Hertzberg, Vicki Stover; Rosenman, Kenneth D; Reilly, Mary Jo; Rice, Carol H

    2002-08-01

    To assess the effect of occupational silica exposure on pulmonary function. Epidemiologic evaluation based on employee interview, plant walk-through, and information abstracted from company medical records, employment records, and industrial hygiene measurements. Drawn from 1,072 current and former hourly wage workers employed before January 1, 1986. Thirty-six individuals with radiographic evidence of parenchymal changes consistent with asbestosis or silicosis were excluded. In addition, eight individuals whose race was listed as other than white or black were excluded. Analysis of spirometry data (FVC, FEV1, FEV1/FVC) only using the test results that met American Thoracic Society criteria for reproducibility and acceptability shows decreasing percent-predicted FVC and FEV1 and decreasing FEV1/FVC in relationship to increasing silica exposure among smokers. Logistic regression analyses of abnormal FVC and abnormal FEV1 values (where abnormal is defined as OSHA)-allowable level of 0.1 mg/m3. Longitudinal analyses of FVC and FEV1 measurements show a 1.6 mL/yr and 1.1 mL/yr, respectively, decline per milligram/cubic meter mean silica exposure (p = 0.011 and p = 0.001, respectively). All analyses were adjusted for weight, height, age, ethnicity, smoking status, and other silica exposures. Systematic problems leading to measurement error were possible, but would have been nondifferential in effect and not related to silica measurements. There is a consistent association between increased pulmonary function abnormalities and estimated measures of cumulative silica exposure within the current allowable OSHA regulatory level. Despite concerns about the quality control of the pulmonary function measurements use in these analyses, our results support the need to lower allowable air levels of silica and increase efforts to encourage cessation of cigarette smoking among silica-exposed workers.

  10. IMPROVEMENT OF EXPANSIVE SOIL BY USING SILICA FUME

    Directory of Open Access Journals (Sweden)

    Kawther Y. AL-Soudany

    2018-01-01

    Full Text Available Expansive soils are characterized by their considerable volumetric deformations representing a serious challenge for the stability of the engineering structures such as foundations. Consequently, the measurements of swelling properties, involving swelling and swell pressure, become extremely important in spite of their determination needs a lot of time with costly particular equipment. Thus, serious researches attempts have been tried to remedy such soils by means of additives such as cement, lime, steel fibers, stone dust, fly ash and silica fume. In this research the study of silica fume has studied to treatment expansion soil, the clay soil was brought from Al-Nahrawan in Baghdad. The soil selected for the present investigation prepared in laboratory by mixing natural soil with different percentages of bentonite (30, 50 and 70% by soil dry weight. The test program included the effect of bentonite on natural soil then study the effect of silica fume (SF on prepared soil by adding different percentage of silica fume (3, 5, and 7 by weight to the prepared soils and the influence of these admixtures was observed by comparing their results with those of untreated soils (prepared soils. The results show that both liquid limit and plasticity index decreased with the addition of silica fume, while the plastic limit is increase with its addition. As well as, a decrease in the maximum dry unit weight with an increase in the optimum water contents have been obtained with increasing the percentage of addition of the silica fume. It is also observed an improvement in the free swell, swelling pressure by using silica fume. It can be concluded that the silica fume stabilization may be used as a successful way for the treatment of expansive clay.

  11. Poly(2-aminothiazole)-silica nanocomposite particles: Synthesis and morphology control

    Science.gov (United States)

    Zou, Hua; Wu, Di; Sun, Hao; Chen, Suwu; Wang, Xia

    2018-04-01

    Synthesis of conducting polymer-silica colloidal nanocomposites has been recognized as an effective method to overcome the poor processability of heterocyclic conducting polymers prepared by chemical oxidative method. However, the morphology control of such conducting polymer-silica nanocomposites was seldomly reported in the literature. Novel poly(2-aminothiazole)(PAT)-silica nanocomposite particles can be conveniently prepared by chemical oxidative polymerization of 2-aminothiazole using CuCl2 oxidant in the presence of ∼20 nm silica nanoparticles. The effects of varying the oxidant/monomer ratio and silica sol concentration on the morphology and size of the resulting PAT-silica nanocmposites have been studied. Optimization of the oxidant/monomer molar ratio and initial silica sol concentration allows relatively round spherical particles of 150-350 nm in diameter to be achieved. The nanocomposite particles have a well-defined raspberry-like morphology with a silica-rich surface, but a significant fraction of PAT component still exists on the surface and, which is beneficial for its applications. Furthermore, the surface compositions of the colloidal nanocomposites could be regulated to some extent. Based on the above results, a possible formation mechanism of the spherical nanocomposite particles is proposed.

  12. Study of silica sol-gel materials for sensor development

    Science.gov (United States)

    Lei, Qiong

    Silica sol-gel is a transparent, highly porous silicon oxide glass made at room temperature by sol-gel process. The name of silica sol-gel comes from the observable physical phase transition from liquid sol to solid gel during its preparation. Silica sol-gel is chemically inert, thermally stable, and photostable, it can be fabricated into different desired shapes during or after gelation, and its porous structure allows encapsulation of guest molecules either before or after gelation while still retaining their functions and sensitivities to surrounding environments. All those distinctive features make silica sol-gel ideal for sensor development. Study of guest-host interactions in silica sol-gel is important for silica-based sensor development, because it helps to tailor local environments inside sol-gel matrix so that higher guest loading, longer shelf-life, higher sensitivity and faster response of silica gel based sensors could be achieved. We focused on pore surface modification of two different types of silica sol-gel by post-grafting method, and construction of stable silica hydrogel-like thin films for sensor development. By monitoring the mobility and photostability of rhodamine 6G (R6G) molecules in silica alcogel thin films through single molecule spectroscopy (SMS), the guest-host interactions altered by post-synthesis grafting were examined. While physical confinement remains the major factor that controls mobility in modified alcogels, both R6G mobility and photostability register discernable changes after surface charges are respectively reversed and neutralized by aminopropyltriethoxysilane (APTS) and methyltriethoxysilane (MTES) grafting. The change in R6G photostability was found to be more sensitive to surface grafting than that of mobility. In addition, silica film modification by 0.4% APTS is as efficient as that by pure MTES in lowering R6G photostability, which suggests that surface charge reversal is more effective than charge neutralization

  13. Characterization for Post-treatment Effect of Bagasse Ash for Silica Extraction

    OpenAIRE

    Patcharin Worathanakul; Wisaroot Payubnop; Akhapon Muangpet

    2009-01-01

    Utilization of bagasse ash for silica sources is one of the most common application for agricultural wastes and valuable biomass byproducts in sugar milling. The high percentage silica content from bagasse ash was used as silica source for sodium silicate solution. Different heating temperature, time and acid treatment were studies for silica extraction. The silica was characterized using various techniques including X-ray fluorescence, X-ray diffraction, Scanning electro...

  14. Synthesis and characterization of titanium oxide supported silica materials

    Science.gov (United States)

    Schrijnemakers, Koen

    2002-01-01

    Titania-silica materials are interesting materials for use in catalysis, both as a catalyst support as well as a catalyst itself. Titania-silica materials combine the excellent support and photocatalytic properties of titania with the high thermal and mechanical stability of silica. Moreover, the interaction of titania with silica leads to new active sites, such as acid and redox sites, that are not found on the single oxides. In this Ph.D. two recently developed deposition methods were studied and evaluated for their use to create titanium oxide supported silica materials, the Chemical Surface Coating (CSC) and the Molecular Designed Dispersion (MDD). These methods were applied to two structurally different silica supports, an amorphous silica gel and the highly ordered MCM-48. Both methods are based on the specific interaction between a titanium source and the functional groups on the silica surface. With the CSC method high amounts of titanium can be obtained. However, clustering of the titania phase is observed in most cases. The MDD method allows much lower titanium amounts to be deposited without the formation of crystallites. Only at the highest Ti loading very small crystallites are formed after calcination. MCM-48 and silica gel are both pure SiO2 materials and therefore chemically similar to each other. However, they possess a different morphology and are synthesized in a different way. As such, some authors have reported that the MCM-48 surface would be more reactive than the surface of silica gel. In our experiments however no differences could be observed that confirmed this hypothesis. In the CSC method, the same reactions were observed and similar amounts of Ti and Cl were deposited. In the case of the MDD method, no difference in the reaction mechanism was observed. However, due to the lower thermal and hydrothermal stability of the MCM-48 structure compared to silica gel, partial incorporation of Ti atoms in the pore walls of MCM-48 took place

  15. Silica coating of nanoparticles by the sonogel process.

    Science.gov (United States)

    Chen, Quan; Boothroyd, Chris; Tan, Gim Hong; Sutanto, Nelvi; Soutar, Andrew McIntosh; Zeng, Xian Ting

    2008-02-05

    A modified aqueous sol-gel route was developed using ultrasonic power for the silica coating of indium tin oxide (ITO) nanoparticles. In this approach, organosilane with an amino functional group was first used to cover the surface of as-received nanoparticles. Subsequent silica coating was initiated and sustained under power ultrasound irradiation in an aqueous mixture of surface-treated particles and epoxy silane. This process resulted in a thin but homogeneous coverage of silica on the particle surface. Particles coated with a layer of silica show better dispersability in aqueous and organic media compared with the untreated powder. Samples were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and the zeta potential.

  16. Effect of support on hydro-metathesis of propene: A comparative study of W(CH 3 ) 6 anchored to silica vs. silica-alumina

    KAUST Repository

    Tretiakov, Mykyta

    2018-03-27

    Hydro-metathesis of propene was carried out by using well-defined W(CH3)6 supported on silica and silica-alumina. It was observed that W(CH3)6 supported silica-alumina catalyst is much better (TON 4577) than the silica supported catalyst (TON 2104). We demonstrated that the present catalysts are much better than the previously reported (tantalum hydride/KCC-1, TON 786) catalyst. For the first time, we observed the formation of n-decane from propene, which enables us to think of using cheaper raw materials and converting them to petroleum range alkanes using hydro-metathesis reaction.

  17. Silica biomineralization via the self-assembly of helical biomolecules.

    Science.gov (United States)

    Liu, Ben; Cao, Yuanyuan; Huang, Zhehao; Duan, Yingying; Che, Shunai

    2015-01-21

    The biomimetic synthesis of relevant silica materials using biological macromolecules as templates via silica biomineralization processes attract rapidly rising attention toward natural and artificial materials. Biomimetic synthesis studies are useful for improving the understanding of the formation mechanism of the hierarchical structures found in living organisms (such as diatoms and sponges) and for promoting significant developments in the biotechnology, nanotechnology and materials chemistry fields. Chirality is a ubiquitous phenomenon in nature and is an inherent feature of biomolecular components in organisms. Helical biomolecules, one of the most important types of chiral macromolecules, can self-assemble into multiple liquid-crystal structures and be used as biotemplates for silica biomineralization, which renders them particularly useful for fabricating complex silica materials under ambient conditions. Over the past two decades, many new silica materials with hierarchical structures and complex morphologies have been created using helical biomolecules. In this review, the developments in this field are described and the recent progress in silica biomineralization templating using several classes of helical biomolecules, including DNA, polypeptides, cellulose and rod-like viruses is summarized. Particular focus is placed on the formation mechanism of biomolecule-silica materials (BSMs) with hierarchical structures. Finally, current research challenges and future developments are discussed in the conclusion. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Novel bioactive materials: silica aerogel and hybrid silica aerogel/pseudowollastonite

    Directory of Open Access Journals (Sweden)

    Reséndiz-Hernández, P. J.

    2014-10-01

    Full Text Available Silica aerogel and hybrid silica aerogel/pseudowollastonite materials were synthesized by controlled hydrolysis of tetraethoxysilane (TEOS using also methanol (MeOH and pseudowollastonite particles. The gels obtained were dried using a novel process based on an ambient pressure drying. Hexane and hexamethyl-disilazane (HMDZ were the solvents used to chemically modify the surface. In order to assess bioactivity, aerogels, without and with pseudowollastonite particles, were immersed in simulated body fluid (SBF for 7 and 14 days. The hybrid silica aerogel/pseudowollastonite showed a higher bioactivity than that observed for the single silica aerogel. However, as in both cases a lower bioactivity was observed, a biomimetic method was also used to improve it. In this particular method, samples of both materials were immersed in SBF for 7 days followed by their immersion in a more concentrated solution (1.5 SBF for 14 days. A thick and homogeneous bonelike apatite layer was formed on the biomimetically treated materials. Thus, bioactivity was successfully improved even on the aerogel with no pseudowollastonite particles. As expected, the hybrid silica aerogel/pseudowollastonite particles showed a higher bioactivity.Se sintetizaron aerogel de sílice y aerogel híbrido de sílice/partículas de pseudowollastonita por hidrólisis controlada de tetraetoxisilano (TEOS usando metanol (MeOH y partículas de pseudowollastonita. Los geles obtenidos se secaron utilizando un novedoso proceso basado en una presión de secado ambiental. Hexano y hexametil-disilazano fueron los solventes usados para modificar químicamente la superficie. Para evaluar la bioactividad, los aerogeles con y sin partículas de pseudowollastonita se sumergieron en un fluido fisiológico simulado (SBF por 7 y 14 días. El aerogel híbrido de sílice/partículas de pseudowollastonita mostró más alta bioactividad que la observada por el aerogel solo. Sin embargo, en ambos casos, se

  19. Synthesis, characterisation and functionalisation of luminescent silica nanoparticles

    International Nuclear Information System (INIS)

    Labéguerie-Egéa, Jessica; McEvoy, Helen M.; McDonagh, Colette

    2011-01-01

    The synthesis of highly monodispersed, homogeneous and stable luminescent silica nanoparticles, synthesized using a process based on the Stöber method is reported here. These particles have been functionalised with the ruthenium and europium complexes: bis (2,2′-bipyridine)-(5-aminophenanthroline) Ru bis (hexafluorophosphate), abbreviated to (Ru(bpy) 2 (phen-5-NH 2 )(PF 6 )), and tris (dibenzoylmethane)-mono (5-aminophenanthroline) europium(III), abbreviated to (Eu:TDMAP). Both dyes have a free amino group available, facilitating the covalent conjugation of the dyes inside the silica matrix. Due to the covalent bond between the dyes and the silica, no dye leaching or nanoparticle diameter modification was observed. The generic and versatile nature of the synthesis process was demonstrated via the synthesis of both europium and ruthenium-functionalised nanoparticles. Following this, the main emphasis of the study was the characterisation of the luminescence of the ruthenium-functionalised silica nanoparticles, in particular, as a function of surface carboxyl or amino group functionalisation. It was demonstrated that the luminescence of the ruthenium dye is highly affected by the ionic environment at the surface of the nanoparticle, and that these effects can be counteracted by encapsulating the ruthenium-functionalised nanoparticles in a plain 15 nm silica layer. Moreover, the ruthenium-functionalised silica nanoparticles showed high relative brightness compared to the free dye in solution and efficient functionalisation with amino or carboxyl groups. Due to their ease of fabrication and attractive characteristics, the ruthenium-functionalised silica nanoparticles described here have the potential to be highly desirable fluorescent labels, particularly, for biological applications.

  20. High-average-power laser medium based on silica glass

    Science.gov (United States)

    Fujimoto, Yasushi; Nakatsuka, Masahiro

    2000-01-01

    Silica glass is one of the most attractive materials for a high-average-power laser. We have developed a new laser material base don silica glass with zeolite method which is effective for uniform dispersion of rare earth ions in silica glass. High quality medium, which is bubbleless and quite low refractive index distortion, must be required for realization of laser action. As the main reason of bubbling is due to hydroxy species remained in the gelation same, we carefully choose colloidal silica particles, pH value of hydrochloric acid for hydrolysis of tetraethylorthosilicate on sol-gel process, and temperature and atmosphere control during sintering process, and then we get a bubble less transparent rare earth doped silica glass. The refractive index distortion of the sample also discussed.

  1. Nanoporous silica membranes with high hydrothermal stability

    DEFF Research Database (Denmark)

    Boffa, Vittorio; Magnacca, Giualiana; Yue, Yuanzheng

    to improve the stability of nanoporous silica structure. This work is a quantitative study on the impact of type and concentration of transition metal ions on the microporous structure and stability of amorphous silica-based membranes, which provides information on how to design chemical compositions...

  2. Bragg gratings in air-silica structured fibers

    NARCIS (Netherlands)

    Groothoff, N.; Canning, J.; Buckley, E.; Lyttikainen, K.; Zagari, J.

    2003-01-01

    We report on grating writing in air-silica structured optical fibers with pure silica cores by use of two-photon absorption at 193 nm. A decrease in propagation loss with irradiation was observed. The characteristic growth curves were obtained. © 2003 Optical Society of America.

  3. Regional impact assessment of land use scenarios in developing countries using the FoPIA approach: Findings from five case studies

    NARCIS (Netherlands)

    König, H.J.; Uthes, S.; Schuler, J.; Zhen, L.; Purushothaman, S.; Suarma, U.; Sghaier, M.; Makokha, S.; Helming, K.; Sieber, S.; Chen, L.; Brouwer, F.M.; Morris, J.; Wiggering, H.

    2013-01-01

    The impact of land use changes on sustainable development is of increasing interest in many regions of the world. This study aimed to test the transferability of the Framework for Participatory Impact Assessment (FoPIA), which was originally developed in the European context, to developing

  4. Preparation of silica nanoparticles through microwave-assisted acid-catalysis.

    Science.gov (United States)

    Lovingood, Derek D; Owens, Jeffrey R; Seeber, Michael; Kornev, Konstantin G; Luzinov, Igor

    2013-12-16

    Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan δ solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials' morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by Stöber's methods, which have smooth surfaces.

  5. 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

  6. Colloidal titania-silica-iron oxide nanocomposites and the effect from silica thickness on the photocatalytic and bactericidal activities

    Energy Technology Data Exchange (ETDEWEB)

    Chanhom, Padtaraporn [Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Charoenlap, Nisanart [Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok 10210 (Thailand); Tomapatanaget, Boosayarat [Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Insin, Numpon, E-mail: Numpon.I@chula.ac.th [Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand)

    2017-04-01

    New types of colloidal multifunctional nanocomposites that combine superparamagnetic character and high photocatalytic activity were synthesized and investigated. The superparamagnetic nanocomposites composed of anatase titania, silica, and iron oxide nanoparticles (TSI) were synthesized using thermal decomposition method followed by microemulsion method, without calcination at high temperature. Different techniques including X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to characterize and confirm the structure of the nanocomposites. These nanocomposites showed high photocatalytic activity when used in the photodegradation of methylene blue under irradiation with a black light lamp. Moreover, the nanocomposites exhibited high antibacterial properties. From our study, the nanocomposites can be useful in various applications such as removal of pollutants with readily separation from the environment using an external magnetic field. These composites could effectively photo-degrade the dye at least three cycles without regeneration. The effects of silica shell thickness on the photocatalytic activity was investigated, and the thickness of 6 nm of the silica interlayer is enough for the inhibition of electron translocation between titania and iron oxide nanoparticles and maintaining the efficiency of photocatalytic activity of titania nanoparticles. - Highlights: • New colloidal nanocomposites of iron oxide-silica-titania were prepared. • The nanocomposites exhibited high photocatalytic activity with magnetic response. • The effects of silica thickness on photocatalytic activity were investigated. • Bactericidal activity of the nanocomposites was demonstrated.

  7. Investigations on the homogeneity of silica glass and on the order of X-amorphous silica by luminescence measurements

    International Nuclear Information System (INIS)

    Boden, G.

    1982-08-01

    Silica glasses melted from crystalline SiO 2 were exposed to ionizing radiation. At room temperature the spatial intensity distribution of the emitted luminescent radiation has been recorded by means of photographic or autoradiographic materials. Thereby schlieren and inhomogeneities are made visible and information is obtained on the melting process of the crystalline SiO 2 . Synthetic fused silica made from SiCl 4 shows no luminescent radiation. Depending on the penetration depth of the ionizing radiation the bulk or the surface of the sample can be studied. The decay curves of the integral luminescence intensity yield data on inhomogeneities in the silica glass leading to conclusions on order state and structure. The luminescence intensity and its half-life are a measure for the inhomogeneity of the silica glass and the existence of so-called 'preordered states'. This connection between luminescence intensity and the order state is found also with other X-amorphous SiO 2 modifications: silica gel, precipitated silicic acids, porous SiO 2 glasses, aerosil, thin SiO 2 layers, mechanically activated quartz: whereas no luminescence phenomena occur in disordered nearly ideally amorphous SiO 2 species, the luminescence increases with increasing order degree of the SiO 2 network and attains a high intensity in the case of the crystalline SiO 2 modifications quartz and cristobalite

  8. Silicosis and Silica-Induced Autoimmunity in the Diversity Outbred Mouse

    Directory of Open Access Journals (Sweden)

    Jessica M. Mayeux

    2018-04-01

    Full Text Available Epidemiological studies have confidently linked occupational crystalline silica exposure to autoimmunity, but pathogenic mechanisms and role of genetic predisposition remain poorly defined. Although studies of single inbred strains have yielded insights, understanding the relationships between lung pathology, silica-induced autoimmunity, and genetic predisposition will require examination of a broad spectrum of responses and susceptibilities. We defined the characteristics of silicosis and autoimmunity and their relationships using the genetically heterogeneous diversity outbred (DO mouse population and determined the suitability of this model for investigating silica-induced autoimmunity. Clinically relevant lung and autoimmune phenotypes were assessed 12 weeks after a transoral dose of 0, 5, or 10 mg crystalline silica in large cohorts of DO mice. Data were further analyzed for correlations, hierarchical clustering, and sex effects. DO mice exhibited a wide range of responses to silica, including mild to severe silicosis and importantly silica-induced systemic autoimmunity. Strikingly, about half of PBS controls were anti-nuclear antibodies (ANA positive, however, few had disease-associated specificities, whereas most ANAs in silica-exposed mice showed anti-ENA5 reactivity. Correlation and hierarchical clustering showed close association of silicosis, lung biomarkers, and anti-ENA5, while other autoimmune characteristics, such as ANA and glomerulonephritis, clustered separately. Silica-exposed males had more lung inflammation, bronchoalveolar lavage fluid cells, IL-6, and autoantibodies. DO mice are susceptible to both silicosis and silica-induced autoimmunity and show substantial individual variations reflecting their genetic diverseness and the importance of predisposition particularly for autoimmunity. This model provides a new tool for deciphering the relationship between silica exposure, genes, and disease.

  9. Triconstituent co-assembly to ordered mesostructured polymer-silica and carbon-silica nanocomposites and large-pore mesoporous carbons with high surface areas.

    Science.gov (United States)

    Liu, Ruili; Shi, Yifeng; Wan, Ying; Meng, Yan; Zhang, Fuqiang; Gu, Dong; Chen, Zhenxia; Tu, Bo; Zhao, Dongyuan

    2006-09-06

    Highly ordered mesoporous polymer-silica and carbon-silica nanocomposites with interpenetrating networks have been successfully synthesized by the evaporation-induced triconstituent co-assembly method, wherein soluble resol polymer is used as an organic precursor, prehydrolyzed TEOS is used as an inorganic precursor, and triblock copolymer F127 is used as a template. It is proposed for the first time that ordered mesoporous nanocomposites have "reinforced concrete"-structured frameworks. By adjusting the initial mass ratios of TEOS to resol, we determined the obtained nanocomposites possess continuous composition with the ratios ranging from zero to infinity for the two constituents that are "homogeneously" dispersed inside the pore walls. The presence of silicates in nanocomposites dramatically inhibits framework shrinkage during the calcination, resulting in highly ordered large-pore mesoporous carbon-silica nanocomposites. Combustion in air or etching in HF solution can remove carbon or silica from the carbon-silica nanocomposites and yield ordered mesoporous pure silica or carbon frameworks. The process generates plenty of small pores in carbon or/and silica pore walls. Ordered mesoporous carbons can then be obtained with large pore sizes of approximately 6.7 nm, pore volumes of approximately 2.0 cm(3)/g, and high surface areas of approximately 2470 m(2)/g. The pore structures and textures can be controlled by varying the sizes and polymerization degrees of two constituent precursors. Accordingly, by simply tuning the aging time of TEOS, ordered mesoporous carbons with evident bimodal pores at 2.6 and 5.8 nm can be synthesized.

  10. In situ-growth of silica nanowires in ceramic carbon composites

    Directory of Open Access Journals (Sweden)

    Rahul Kumar

    2017-09-01

    Full Text Available An understanding of the processing and microstructure of ceramic–carbon composites is critical to development of these composites for applications needing electrically conducting, thermal shock resistant ceramic materials. In the present study green compacts of carbon ceramic composites were prepared either by slurry processing or dry powder blending of one or more of the three — clay, glass, alumina and carbon black or graphite. The dried green compacts were sintered at 1400 °C in flowing argon. The ceramic carbon composites except the ones without clay addition showed formation of silica nanowires. The silica nanowire formation was observed in both samples prepared by slip casting and dry powder compaction containing either carbon black or graphite. TEM micrographs showed presence of carbon at the core of the silica nanowires indicating that carbon served the role of a catalyst. Selected area electron diffraction (SAED suggested that the silica nanowires are amorphous. Prior studies have reported formation of silica nanowires from silicon, silica, silicon carbide but this is the first report ever on formation of silica nanowires from clay.

  11. Spectrophotometric determination of silica in water. Low range

    International Nuclear Information System (INIS)

    Acosta L, E.

    1992-07-01

    The spectrophotometric method for the determination of the silica element in water, demineralized water, raw waters, laundry waters, waters treated with ion exchange resins and sea waters is described. This method covers the determination of the silica element in the interval from 20 to 1000 μg/l on 50 ml. of base sample. These limits its can be variable if the size of the used aliquot one is changed for the final determination of the silica element. (Author)

  12. Chemical immobilisation of humic acid on silica

    NARCIS (Netherlands)

    Koopal, L.K.; Yang, Y.; Minnaard, A.J.; Theunissen, P.L.M.; Riemsdijk, W.H. van

    1998-01-01

    Immobilisation of purified Aldrich humic acid (PAHA) on aminopropyl silica and glutaraldehyde-activated aminopropyl silica has been investigated. In general the humic acid is bound to the solid by both physical and chemical bonds. The physically adsorbed HA can be released to a large extent at high

  13. Moessbauer spectroscopic characterisation of catalysts obtained by interaction between tetra-n-butyl-tin and silica or silica supported rhodium

    International Nuclear Information System (INIS)

    Millet, J.M.M.; Toyir, J.; Didillon, B.; Candy, J.P.; Nedez, C.; Basset, J.M.

    1997-01-01

    Moessbauer spectroscopy at 78 K was used to study the interaction between tetra-n-butyl-tin and the surfaces of silica or silica supported rhodium. At room temperature, the tetra-n-butyl-tin was physically adsorbed on the surfaces. After reaction under hydrogen at 373 K, the formation of grafted organometallic fragments on the Rh surface was confirmed whereas with pure silica, ≡SiO-Sn(n-C 4 H 9 ) 3 moieties were observed. After treatment at 523 K, the rhodium grafted organometallic species was completely decomposed and there was formation of a defined bimetallic RhSn compound

  14. Examining the role of shrub expansion and fire in Arctic plant silica cycling

    Science.gov (United States)

    Carey, J.; Fetcher, N.; Parker, T.; Rocha, A. V.; Tang, J.

    2017-12-01

    All terrestrial plants accumulate silica (SiO2) to some degree, although the amount varies by species type, functional group, and environmental conditions. Silica improves overall plant fitness, providing protection from a variety of biotic and abiotic stressors. Plant silica uptake serves to retain silica in terrestrial landscapes, influencing silica export rates from terrestrial to marine systems. These export rates are important because silica is often the limiting nutrient for primary production by phytoplankton in coastal waters. Understanding how terrestrial plant processes influence silica export rates to oceanic systems is of interest on the global scale, but nowhere is this issue more important than in the Arctic, where marine diatoms rely on silica for production in large numbers and terrestrial runoff largely influences marine biogeochemistry. Moreover, the rapid rate of change occurring in the Arctic makes understanding plant silica dynamics timely, although knowledge of plant silica cycling in the region is in its infancy. This work specifically examines how shrub expansion, permafrost thaw, and fire regimes influence plant silica behavior in the Alaskan Arctic. We quantified silica accumulation in above and belowground portions of three main tundra types found in the Arctic (wet sedge, moist acidic, moist non-acidic tundra) and scaled these values to estimate how shrub expansion alters plant silica accumulation rates. Results indicate that shrub expansion via warming will increase silica storage in Arctic land plants due to the higher biomass associated with shrub tundra, whereas conversion of tussock to wet sedge tundra via permafrost thaw would produce the opposite effect in the terrestrial plant BSi pool. We also examined silica behavior in plants exposed to fire, finding that post-fire growth results in elevated plant silica uptake. Such changes in the size of the terrestrial vegetation silica reservoir could have direct consequences for the rates

  15. Molecular Dynamics Simulations of Water Nanodroplets on Silica Surfaces

    DEFF Research Database (Denmark)

    Zambrano, Harvey A; Walther, Jens Honore; Jaffe, Richard L.

    2009-01-01

    and DNA microarrays technologies.4,5,6,7,8 Although extensive experimental, theoretical and computational work has been devoted to study the nature of the interaction between silica and water,2,9-16 at the molecular level a complete understanding of silica-water systems has not been reached. Contact angle...... computations of water droplets on silica surfaces offers a useful fundamental and quantitative measurement in order to study chemical and physical properties of water-silica systems.3,16,17,18 For hydrophobic systems the static and dynamic properties of the fluid-solid interface are influenced by the presence...

  16. Mesoporous silica nanotubes hybrid membranes for functional nanofiltration

    International Nuclear Information System (INIS)

    El-Safty, Sherif A; Shahat, Ahmed; Mekawy, Moataz; Nguyen, Hoa; Warkocki, Wojciech; Ohnuma, Masato

    2010-01-01

    The development of nanofiltration systems would greatly assist in the production of well-defined particles and biomolecules with unique properties. We report a direct, simple synthesis of hexagonal silica nanotubes (NTs), which vertically aligned inside anodic alumina membranes (AAM) by means of a direct templating method of microemulsion phases with cationic surfactants. The direct approach was used as soft templates for predicting ordered assemblies of surfactant/silica composites through strong interactions within AAM pockets. Thus, densely packed NTs were successfully formed in the entirety of the AAM channels. These silica NTs were coated with layers of organic moieties to create a powerful technique for the ultrafine filtration. The resulting modified-silica NTs were chemically robust and showed affinity toward the transport of small molecular particles. The rigid silica NTs inside AAM channels had a pore diameter of ≤ 4 nm and were used as ultrafine filtration systems for noble metal nanoparticles (NM NPs) and semiconductor nanocrystals (SC NCs) fabricated with a wide range of sizes (1.0-50 nm) and spherical/pyramidal morphologies. Moreover, the silica NTs hybrid membranes were also found to be suitable for separation of biomolecules such as cytochrome c (CytC). Importantly, this nanofilter design retains high nanofiltration efficiency of NM NPs, SC NCs and biomolecules after a number of reuse cycles. Such retention is crucial in industrial applications.

  17. Enhanced microcontact printing of proteins on nanoporous silica surface

    Energy Technology Data Exchange (ETDEWEB)

    Blinka, Ellen; Hu Ye; Gopal, Ashwini; Hoshino, Kazunori; Lin, Kevin; Zhang, John X J [Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78758 (United States); Loeffler, Kathryn; Liu Xuewu; Ferrari, Mauro, E-mail: John.Zhang@engr.utexas.edu [Department of Nanomedicine and Biomedical Engineering, University of Texas Health Science Service, Houston, TX 77031 (United States)

    2010-10-15

    We demonstrate porous silica surface modification, combined with microcontact printing, as an effective method for enhanced protein patterning and adsorption on arbitrary surfaces. Compared to conventional chemical treatments, this approach offers scalability and long-term device stability without requiring complex chemical activation. Two chemical surface treatments using functionalization with the commonly used 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA) were compared with the nanoporous silica surface on the basis of protein adsorption. The deposited thickness and uniformity of porous silica films were evaluated for fluorescein isothiocyanate (FITC)-labeled rabbit immunoglobulin G (R-IgG) protein printed onto the substrates via patterned polydimethlysiloxane (PDMS) stamps. A more complete transfer of proteins was observed on porous silica substrates compared to chemically functionalized substrates. A comparison of different pore sizes (4-6 nm) and porous silica thicknesses (96-200 nm) indicates that porous silica with 4 nm diameter, 57% porosity and a thickness of 96 nm provided a suitable environment for complete transfer of R-IgG proteins. Both fluorescence microscopy and atomic force microscopy (AFM) were used for protein layer characterizations. A porous silica layer is biocompatible, providing a favorable transfer medium with minimal damage to the proteins. A patterned immunoassay microchip was developed to demonstrate the retained protein function after printing on nanoporous surfaces, which enables printable and robust immunoassay detection for point-of-care applications.

  18. Molecular Regulation of the Mitochondrial F1Fo-ATPsynthase: Physiological and Pathological Significance of the Inhibitory Factor 1 (IF 1

    Directory of Open Access Journals (Sweden)

    Danilo Faccenda

    2012-01-01

    Full Text Available In mammals, the mitochondrial F1Fo-ATPsynthase sets out the energy homeostasis by producing the bulk of cellular ATP. As for every enzyme, the laws of thermodynamics command it; however, it is privileged to have a dedicated molecular regulator that controls its rotation. This is the so-called ATPase Inhibitory Factor 1 (IF1 that blocks its reversal to avoid the consumption of cellular ATP when the enzyme acts as an ATP hydrolase. Recent evidence has also demonstrated that IF1 may control the alignment of the enzyme along the mitochondrial inner membrane, thus increasing the interest for the molecule. We conceived this review to outline the fundamental knowledge of the F1Fo-ATPsynthase and link it to the molecular mechanisms by which IF1 regulates its way of function, with the ultimate goal to highlight this as an important and possibly unique means to control this indispensable enzyme in both physiological and pathological settings.

  19. Silica fractionation and reactivity in soils

    Science.gov (United States)

    Unzué Belmonte, Dácil; Barão, Lúcia; Vandevenne, Floor; Schoelynck, Jonas; Struyf, Eric; Meire, Patrick

    2014-05-01

    The Si cycle is a globally important biogeochemical cycle, with strong connections to other biogeochemical cycles, including C. Silica is taken up by plants to form protective structures called phytoliths, which become a part of the soil and contribute strongly to soil Si cycling upon litter burial. Different silica fractions are found in soils, with phytoliths among the most easily soluble, especially compared to silicate minerals. A whole set of secondary non-biogenic fractions exist, that also have a high reactivity (adsorbed Si, reactive secondary minerals…). A good characterization of the different fractions of reactive silica is crucial to move forward knowledge on ecosystem Si cycling, which has been recognized in the last decade as crucial for terrestrial Si fluxes. A new method to analyze the different fractions of silica in soils has been described by Koning et al. (2002) and adapted by our research team (Barão et al. 2013). Using a continuous extraction of Si and aluminum in 0.5M NaOH, biogenic and non-biogenic reactive fractions are separated based on their Si/Al ratios and their reactivity in NaOH. Applying this new method I will investigate three emerging ideas on how humans can affect directly terrestrial Si fluxes. -Land use. I expect strong silica fractionation and reactivity differences in different land uses. These effects due to agricultural and forestry management have already been shown earlier in temperate soils (Vandevenne et al. 2012). Now we will test this hypothesis in recently deforested soils, in the south of Brazil. 'Pristine' forest, managed forest and tobacco field soils (with and without rotation crops) will be studied. This research belongs to an interdisciplinary project on soils and global change. -Fire. According to the IPCC report, extreme events such as fires (number and intensity) would increase due to climate change. We analyzed litter from spruce forest, beech forest and peat soils at two burning levels, after 350°C and

  20. Preparation and characterization of rice hull silica products

    International Nuclear Information System (INIS)

    Quirit, Leni L.; Llaguno, Elma C.; Pagdanganan, Fernando C.; Hernandez, Karen N.

    2008-01-01

    Rice hull is an abundant agricultural waste material which could be a renewable energy source when combusted. The combustion residue (called rice hull ash or RHA) contains a significant amount (20% of the hull) of potentially high grade silica. Silica gels prepared from rice hull were found to have properties comparable to two commercial desiccant silica gels (Blue Merck and FNG-A) in terms of chemical and amorphous structure, surface area, desiccant characteristics, microstructure and heats of adsorption. These properties were determined from water vapor adsorption measurements, electron microscopy, and from infrared and x-ray diffraction spectra. The acid treated rice hull gels were found to have fewer elemental impurities detected by qualitative x-ray fluorescence, compared to the commercial gels. Thermogravimetric analysis (TGA) data showed that this technique can also be used to indirectly compare impurity levels in the samples, in terms of the amorphous to crystalline phase transition. Using an improved acid treatment method, a silica gel sample was prepared from rice hull and compared to three commercial chromatographic silica gels using quantitative elemental x-ray fluorescence analysis. Elemental levels in the rice hull gel were within the range of levels or close to the detection limits of corresponding elements in the chromatographic gels. Water vapor adsorption, x-ray diffraction, infrared spectroscopy and scanning electron microscopy showed that the rice hull gel was similar to the commercial chromatographic silica gel Davison 12. Zeolites are crystalline aluminosilicates used as molecular sieves for purification and catalytic purposes. Zeolites X and Y were synthesized from rice hull silica gel and aluminum hydroxide. For comparison, controls were synthesized from commercial silica gel. The samples and controls exhibited characteristics infrared peaks corresponding to the vibrations of the TO 4 (T=Si, Al) of the zeolite framework. The x

  1. Characteristics of N-Acylhomoserine Lactones Produced by Hafnia alvei H4 Isolated from Spoiled Instant Sea Cucumber

    Directory of Open Access Journals (Sweden)

    Hong-Man Hou

    2017-04-01

    Full Text Available This study aimed to identify N-acylhomoserine lactone (AHL produced by Hafnia alvei H4, which was isolated from spoiled instant sea cucumber, and to investigate the effect of AHLs on biofilm formation. Two biosensor strains, Chromobacterium violaceum CV026 and Agrobacterium tumefaciens KYC55, were used to detect the quorum sensing (QS activity of H. alvei H4 and to confirm the existence of AHL-mediated QS system. Thin layer chromatography (TLC and high resolution triple quadrupole liquid chromatography/mass spectrometry (LC/MS analysis of the AHLs extracted from the culture supernatant of H. alvei H4 revealed the existence of at least three AHLs: N-hexanoyl-l-homoserine lactone (C6-HSL, N-(3-oxo-octanoyl-l-homoserine lactone (3-oxo-C8-HSL, and N-butyryl-l-homoserine lactone (C4-HSL. This is the first report of the production of C4-HSL by H. alvei. In order to determine the relationship between the production of AHL by H. alvei H4 and bacterial growth, the β-galactosidase assay was employed to monitor AHL activity during a 48-h growth phase. AHLs production reached a maximum level of 134.6 Miller unites at late log phase (after 18 h and then decreased to a stable level of about 100 Miller unites. AHL production and bacterial growth displayed a similar trend, suggesting that growth of H. alvei H4 might be regulated by QS. The effect of AHLs on biofilm formation of H. alvei H4 was investigated by adding exogenous AHLs (C4-HSL, C6-HSL and 3-oxo-C8-HSL to H. alvei H4 culture. Biofilm formation was significantly promoted (p < 0.05 by 5 and 10 µM C6-HSL, inhibited (p < 0.05 by C4-HSL (5 and 10 µM and 5 µM 3-oxo-C8-HSL, suggesting that QS may have a regulatory role in the biofilm formation of H. alvei H4.

  2. The potential use of silica sand as nanomaterials for mortar

    Science.gov (United States)

    Setiati, N. Retno

    2017-11-01

    The development of nanotechnology is currently experiencing rapid growth. The use of the term nanotechnology is widely applied in areas such as healthcare, industrial, pharmaceutical, informatics, or construction. By the nanotechnology in the field of concrete construction, especially the mechanical properties of concrete are expected to be better than conventional concrete. This study aims to determine the effect of the potential of silica sand as a nanomaterial that is added into the concrete mix The methodology used consist of nanomaterial synthesis process of silica sand using Liquid Polishing Milling Technology (PLMT). The XRF and XRD testing were conducted to determine the composition of silica contained in the silica sand and the level of reactivity of the compound when added into the concrete mix. To determine the effect of nano silica on mortar, then made the specimen with size 50 mm x 50 mm x 50 mm. The composition of mortar is made in two variations, ie by the addition of 3% nano silica and without the addition of nanosilica. To know the mechanical properties of mortar, it is done testing of mortar compressive strength at the age of 28 days. Based on the analysis and evaluation, it is shown that compounds of silica sand in Indonesia, especially Papua reached more than 99% SiO2 and so that the amorphous character of silica sand can be used as a nanomaterial for concrete construction. The results of mechanical tests show that there is an increase of 12% compressive strength of mortar that is added with 3% nano silica.

  3. Adsorption of benzyldimethylhexadecylammonium chloride at the hydrophobic silica-water interface studied by total internal reflection Raman spectroscopy: effects of silica surface properties and metal salt addition.

    Science.gov (United States)

    Grenoble, Zlata; Baldelli, Steven

    2013-08-29

    The adsorption of the cationic surfactant benzyldimethylhexadecylammonium (BDMHA(+)) chloride was studied at an octadecyltrichlorosilane (OTS)-monolayer-modified silica-water interface by Raman spectroscopy in total internal reflection (TIR) geometry. The present study demonstrates the capabilities of this spectroscopic technique to evaluate thermodynamic and kinetic BDMHA(+)Cl(-) adsorption properties at the hydrophobic silica surface. The surface coverage of BDMHA(+) decreased by 50% at the hydrophobic OTS-silica surface relative to the surface coverage on bare silica; the dominating driving mechanisms for surfactant adsorption were identified as hydrophobic effects and head group charge screening by the electrolyte counterions. Addition of magnesium metal salt (MgCl2) to the aqueous solution (∼ neutral pH) lowered the surface coverage and moderately increased the Langmuir adsorption constants relative to those of the pure surfactant. These trends were previously observed at the hydrophilic, negatively charged silica surface but with a smaller change in the Gibbs free energy of adsorption at the hydrophobic silica surface. The hydrophobic OTS-silica surface properties resulted in shorter times for the surfactant to reach steady-state adsorption conditions compared to the slow adsorption kinetics previously seen with the surfactant at the hydrophilic surface. Adsorption isotherms, based on Raman signal intensities from spectral analysis, were developed according to the Langmuir adsorption model for the pure surfactant at the OTS-silica-water interface; the modified Langmuir model was applied to the surfactant adsorption in the presence of 5, 10, 50, and 100 mM magnesium chloride. Spectral analysis of the Raman scattering intensities and geometric considerations suggests a hemimicelle-type surface aggregate as the most likely surfactant structure at the OTS-silica surface. The different kinetics observed at the hydrophilic versus the hydrophobic silica surface

  4. Preparation and Characterization of Silica/Polyamide-imide Nanocomposite Thin Films

    Directory of Open Access Journals (Sweden)

    Hwang Jong-Sun

    2010-01-01

    Full Text Available Abstract The functional silica/polyamide-imide composite films were prepared via simple ultrasonic blending, after the silica nanoparticles were modified by cationic surfactant—cetyltrimethyl ammonium bromide (CTAB. The composite films were characterized by scanning electron microscope (SEM, thermo gravimetric analysis (TGA and thermomechanical analysis (TMA. CTAB-modified silica nanoparticles were well dispersed in the polyamide-imide matrix, and the amount of silica nanoparticles to PAI was investigated to be from 2 to 10 wt%. Especially, the coefficients of thermal expansion (CET continuously decreased with the amount of silica particles increasing. The high thermal stability and low coefficient of thermal expansion showed that the nanocomposite films can be widely used in the enamel wire industry.

  5. Obtaining high purity silica from rice hulls

    Directory of Open Access Journals (Sweden)

    José da Silva Júnior

    2010-01-01

    Full Text Available Many routes for extracting silica from rice hulls are based on direct calcining. These methods, though, often produce silica contaminated with inorganic impurities. This work presents the study of a strategy for obtaining silica from rice hulls with a purity level adequate for applications in electronics. The technique is based on two leaching steps, using respectively aqua regia and Piranha solutions, which extract the organic matrix and inorganic impurities. The material was characterized by Fourier-transform infrared spectroscopy (FTIR, powder x-ray diffraction (XRD, x-ray fluorescence (XRF, scanning electron microscopy (SEM, particle size analysis by laser diffraction (LPSA and thermal analysis.

  6. Formation of Silica-Lysozyme Composites Through Co-Precipitation and Adsorption

    Science.gov (United States)

    van den Heuvel, Daniela B.; Stawski, Tomasz M.; Tobler, Dominique J.; Wirth, Richard; Peacock, Caroline L.; Benning, Liane G.

    2018-04-01

    Interactions between silica and proteins are crucial for the formation of biosilica and the production of novel functional hybrid materials for a range of industrial applications. The proteins control both precipitation pathway and the properties of the resulting silica-organic composites. Here we present data on the formation of silica-lysozyme composites through two different synthesis approaches (co-precipitation vs. adsorption) and show that the chemical and structural properties of these composites, when analyzed using a combination of synchrotron-based scattering (total scattering and SAXS), spectroscopic, electron microscopy and potentiometric methods vary dramatically. We document that while lysozyme was not incorporated into nor did its presence alter the molecular structure of silica, it strongly enhanced the aggregation of silica particles due to electrostatic and potentially hydrophobic interactions, leading to the formation of composites with characteristics differing from pure silica. The differences increased with increasing lysozyme content for both synthesis approaches. Yet, the absolute changes differ substantially between the two sets of composites, as lysozyme did not just affect aggregation during co-precipitation but also particle growth and likely polymerization during co-precipitation. Our results improve the fundamental understanding of how organic macromolecules interact with dissolved and nanoparticulate silica and how these interactions control the formation pathway of silica-organic composites from sodium silicate solutions, a widely available and cheap starting material.

  7. Optical constants of quartz, vitreous silica and neutron-irradiated vitreous silica. II. Analysis of the infrared spectrum of vitreous silica

    Energy Technology Data Exchange (ETDEWEB)

    Gaskell, P H [Cambridge Univ. (UK). Cavendish Lab.; Johnson, D W [Pilkington Research and Development Laboratories, Lathom, nr. Ormskirk, Lancashire, UK

    1976-03-01

    Optical constant data for vitreous silica and neutron-irradiated vitreous silica, given in part I are examined in an attempt to gain further knowledge of the structure of the glass. Strong features of the spectrum can be described by band broadening parameters, which are calculated using an extension of the Wilson GF matrix method, and are shown to be quantitatively related to the distribution of Si-O distances and oxygen bond angles obtained from X-ray scattering data. The approximation commonly used to generate the optically active vibrational spectra of glasses, namely to form the product of the vibrational density of states function and a weakly frequency-dependent intensity factor gives a relatively poor representation of the experimental spectrum. The magnitude of 'disorder-induced' absorption in regions well away from the major bands is semi-quantitatively estimated by subtracting the contributions of the major bands. Interpretation of some of the features of this difference spectrum is possible in terms of vibrations of nonbridging oxygen atoms, but if this interpretation is correct, it is necessary to postulate clustering of 'dangling' oxygen atoms, which would not be consistent with a random network model for the structure. An alternative explanation, that the vibrations are framework modes, leads to the conclusion that the preferred configuration in vitreous silica resembles the arrangement of silicon-oxygen tetrahedra in cristobalite.

  8. Silica gel matrix immobilized Chlorophyta hydrodictyon africanum ...

    African Journals Online (AJOL)

    Chlorophyta hydrodictyon africanum was immobilized on a silica gel matrix to improve its mechanical properties. The algae-silica gel adsorbent was used for batch sorption studies of a cationic dye, methylene blue (MB). Optimum adsorption was obtained with a dosage of 0.8 g bio sorbent. Results from sorption studies ...

  9. What Is Crystalline Silica?

    Science.gov (United States)

    ... and ceramic manufacturing and the tool and die, steel and foundry industries. Crystalline silica is used in manufacturing, household abrasives, adhesives, paints, soaps, and glass. Additionally, ...

  10. Chronic obstructive pulmonary disease and occupational exposure to silica.

    Science.gov (United States)

    Rushton, Lesley

    2007-01-01

    Prolonged exposure to high levels of silica has long been known to cause silicosis This paper evaluates the evidence for an increased risk of chronic obstructive pulmonary disease (COPD) in occupations and industries in which exposure to crystalline silica is the primary exposure, with a focus on the magnitude of risks and levels of exposure causing disabling health effects. The literature suggests consistently elevated risks of developing COPD associated with silica exposure in several occupations, including the construction industry; tunneling; cement industry; brick manufacturing; pottery and ceramic work; silica sand, granite and diatomaceous earth industries; gold mining; and iron and steel founding, with risk estimates being high in some, even after taking into account the effect of confounders like smoking. Average dust levels vary from about 0.5 mg.m3 to over 10 mg.m3 and average silica levels from 0.04 to over 5 mg.m3, often well above occupational standards. Factors influencing the variation from industry to industry in risks associated with exposure to silica-containing dusts include (a) the presence of other minerals in the dust, particularly when associated with clay minerals; (b) the size of the particles and percentage of quartz; (c) the physicochemical characteristics, such as whether the dust is freshly fractured. Longitudinal studies suggest that loss of lung function occurs with exposure to silica dust at concentrations of between 0.1 and 0.2 mg.m3, and that the effect of cumulative silica dust exposure on airflow obstruction is independent of silicosis. Nevertheless, a disabling loss of lung function in the absence of silicosis would not occur until between 30 and 40 years exposure.

  11. Solid-state 29Si NMR and FTIR analyses of lignin-silica coprecipitates

    DEFF Research Database (Denmark)

    Cabrera Orozco, Yohanna; Cabrera, Andrés; Larsen, Flemming Hofmann

    2016-01-01

    When agricultural residues are processed to ethanol, lignin and silica are some of the main byproducts. Separation of these two products is difficult and the chemical interactions between lignin and silica are not well described. In the present study, the effect of lignin-silica complexing has been...... investigated by characterizing lignin and silica coprecipitates by FTIR and solid state NMR. Silica particles were coprecipitated with three different lignins, three lignin model compounds, and two silanes representing silica-in-lignin model compounds. Comparison of 29Si SP/MAS NMR spectra revealed differences...

  12. Characterization of the adsorption of water vapor and chlorine on microcrystalline silica

    Science.gov (United States)

    Skiles, J. A.; Wightman, J. P.

    1979-01-01

    The characterization of water adsorption on silica is necessary to an understanding of how hydrogen chloride interacts with silica. The adsorption as a function of outgas temperatures of silica and as a function of the isotherm temperature was studied. Characterization of the silica structure by infrared analysis, X-ray diffraction and differential scanning calorimetry, surface area determinations, characterization of the sample surface by electron spectroscopy for chemical analysis (ESCA), and determinations of the heat of immersion in water of silica were investigated. The silica with a scanning electron microscope was examined.

  13. Uniform silica nanoparticles encapsulating two-photon absorbing fluorescent dye

    International Nuclear Information System (INIS)

    Wu Weibing; Liu Chang; Wang Mingliang; Huang Wei; Zhou Shengrui; Jiang Wei; Sun Yueming; Cui Yiping; Xu Chunxinag

    2009-01-01

    We have prepared uniform silica nanoparticles (NPs) doped with a two-photon absorbing zwitterionic hemicyanine dye by reverse microemulsion method. Obvious solvatochromism on the absorption spectra of dye-doped NPs indicates that solvents can partly penetrate into the silica matrix and then affect the ground and excited state of dye molecules. For dye-doped NP suspensions, both one-photon and two-photon excited fluorescence are much stronger and recorded at shorter wavelength compared to those of free dye solutions with comparative overall dye concentration. This behavior is possibly attributed to the restricted twisted intramolecular charge transfer (TICT), which reduces fluorescence quenching when dye molecules are trapped in the silica matrix. Images from two-photon laser scanning fluorescence microscopy demonstrate that the dye-doped silica NPs can be actively uptaken by Hela cells with low cytotoxicity. - Graphical abstract: Water-soluble silica NPs doped with a two-photon absorbing zwitterionic hemicyanine dye were prepared. They were found of enhanced one-photon and two-photon excited fluorescence compared to free dye solutions. Images from two-photon laser scanning fluorescence microscopy demonstrate that the dye-doped silica NPs can be actively uptaken by Hela cells.

  14. One-step synthesis of dye-incorporated porous silica particles

    Energy Technology Data Exchange (ETDEWEB)

    Liu Qing; DeShong, Philip; Zachariah, Michael R., E-mail: mrz@umd.edu [University of Maryland, Department of Chemistry and Biochemistry (United States)

    2012-07-15

    Fluorescent nanoparticles have a variety of biomedical applications as diagnostics and traceable drug delivery agents. Highly fluorescent porous silica nanoparticles were synthesized in a water/oil phase by a microemulsion method. What is unique about the resulting porous silica nanoparticles is the combination of a single-step, efficient synthesis and the high stability of its fluorescence emission in the resulting materials. The key of the success of this approach is the choice of a lipid dye that functions as a surrogate surfactant in the preparation. The surfactant dye was incorporated at the interface of the inorganic silica matrix and organic environment (pore template), and thus insures the stability of the dye-silica hybrid structure. The resulting fluorescent silica materials have a number of properties that make them attractive for biomedical applications: the availability of various color of the resulting nanoparticle from among a broad spectrum of commercially dyes, the controllablity of pore size (diameters of {approx}5 nm) and particle size (diameters of {approx}40 nm) by adjusting template monomer concentration and the water/oil ratio, and the stability and durability of particle fluorescence because of the deep insertion of surfactant's tail into the silica matrix.

  15. Feasibility Study for Monitoring Actinide Elements in Process Materials Using FO-LIBS at Advanced spent fuel Conditioning Process Facility

    Energy Technology Data Exchange (ETDEWEB)

    Han, Bo-Young; Choi, Daewoong; Park, Se Hwan; Kim, Ho-Dong [Nonproliferation System Research Division, Korea Atomic Energy Research Institute, Daejeon, 305-353 (Korea, Republic of); Dae, Dongsun [Department of Chemistry, Mokpo National University, Jeonnam 534-729 (Korea, Republic of); Whitehouse, Andrew I. [Applied Photonics Ltd., Unit 8 Carleton Business Park, Skipton, North Yorkshire BD23 2DE (United Kingdom)

    2015-07-01

    Korea Atomic Energy Research Institute (KAERI) have been developing the design and deployment methodology of Laser- Induced Breakdown Spectroscopy (LIBS) instrument for safeguards application within the argon hot cell environment at Advanced spent fuel Conditioning Process Facility (ACPF), where ACPF is a facility being refurbished for the laboratory-scaled demonstration of advanced spent fuel conditioning process. LIBS is an analysis technology used to measure the emission spectra of excited elements in the local plasma of a target material induced by a laser. The spectra measured by LIBS are analyzed to verify the quality and quantity of the specific element in the target matrix. Recently LIBS has been recognized as a promising technology for safeguards purposes in terms of several advantages including a simple sample preparation and in-situ analysis capability. In particular, a feasibility study of LIBS to remotely monitor the nuclear material in a high radiation environment has been carried out for supporting the IAEA safeguards implementation. Fiber-Optic LIBS (FO-LIBS) deployment was proposed by Applied Photonics Ltd because the use of fiber optics had benefited applications of LIBS by delivering the laser energy to the target and by collecting the plasma light. The design of FO-LIBS instrument for the measurement of actinides in the spent fuel and high temperature molten salt at ACPF had been developed in cooperation with Applied Photonics Ltd. FO-LIBS has some advantages as followings: the detectable plasma light wavelength range is not limited by the optical properties of the thick lead-glass shield window and the potential risk of laser damage to the lead-glass shield window is not considered. The remote LIBS instrument had been installed at ACPF and then the feasibility study for monitoring actinide elements such as uranium, plutonium, and curium in process materials has been carried out. (authors)

  16. Feasibility Study for Monitoring Actinide Elements in Process Materials Using FO-LIBS at Advanced spent fuel Conditioning Process Facility

    International Nuclear Information System (INIS)

    Han, Bo-Young; Choi, Daewoong; Park, Se Hwan; Kim, Ho-Dong; Dae, Dongsun; Whitehouse, Andrew I.

    2015-01-01

    Korea Atomic Energy Research Institute (KAERI) have been developing the design and deployment methodology of Laser- Induced Breakdown Spectroscopy (LIBS) instrument for safeguards application within the argon hot cell environment at Advanced spent fuel Conditioning Process Facility (ACPF), where ACPF is a facility being refurbished for the laboratory-scaled demonstration of advanced spent fuel conditioning process. LIBS is an analysis technology used to measure the emission spectra of excited elements in the local plasma of a target material induced by a laser. The spectra measured by LIBS are analyzed to verify the quality and quantity of the specific element in the target matrix. Recently LIBS has been recognized as a promising technology for safeguards purposes in terms of several advantages including a simple sample preparation and in-situ analysis capability. In particular, a feasibility study of LIBS to remotely monitor the nuclear material in a high radiation environment has been carried out for supporting the IAEA safeguards implementation. Fiber-Optic LIBS (FO-LIBS) deployment was proposed by Applied Photonics Ltd because the use of fiber optics had benefited applications of LIBS by delivering the laser energy to the target and by collecting the plasma light. The design of FO-LIBS instrument for the measurement of actinides in the spent fuel and high temperature molten salt at ACPF had been developed in cooperation with Applied Photonics Ltd. FO-LIBS has some advantages as followings: the detectable plasma light wavelength range is not limited by the optical properties of the thick lead-glass shield window and the potential risk of laser damage to the lead-glass shield window is not considered. The remote LIBS instrument had been installed at ACPF and then the feasibility study for monitoring actinide elements such as uranium, plutonium, and curium in process materials has been carried out. (authors)

  17. Molecular Organization Induced Anisotropic Properties of Perylene - Silica Hybrid Nanoparticles.

    Science.gov (United States)

    Sriramulu, Deepa; Turaga, Shuvan Prashant; Bettiol, Andrew Anthony; Valiyaveettil, Suresh

    2017-08-10

    Optically active silica nanoparticles are interesting owing to high stability and easy accessibility. Unlike previous reports on dye loaded silica particles, here we address an important question on how optical properties are dependent on the aggregation-induced segregation of perylene molecules inside and outside the silica nanoparticles. Three differentially functionalized fluorescent perylene - silica hybrid nanoparticles are prepared from appropriate ratios of perylene derivatives and tetraethyl orthosilicate (TEOS) and investigated the structure property correlation (P-ST, P-NP and P-SF). The particles differ from each other on the distribution, organization and intermolecular interaction of perylene inside or outside the silica matrix. Structure and morphology of all hybrid nanoparticles were characterized using a range of techniques such as electron microscope, optical spectroscopic measurements and thermal analysis. The organizations of perylene in three different silica nanoparticles were explored using steady-state fluorescence, fluorescence anisotropy, lifetime measurements and solid state polarized spectroscopic studies. The interactions and changes in optical properties of the silica nanoparticles in presence of different amines were tested and quantified both in solution and in vapor phase using fluorescence quenching studies. The synthesized materials can be regenerated after washing with water and reused for sensing of amines.

  18. Tailoring silver nanoparticle construction using dendrimer templated silica networks

    International Nuclear Information System (INIS)

    Liu Xiaojun; Kakkar, Ashok

    2008-01-01

    We have examined the role of the internal environment of dendrimer templated silica networks in tailoring the construction of silver nanoparticle assemblies. Silica networks from which 3,5-dihydroxybenzyl alcohol based dendrimer templates have been completely removed, slowly wet with an aqueous solution of silver acetate. The latter then reacts with internal silica silanol groups, leading to chemisorption of silver ions, followed by the growth of silver oxide nanoparticles. Silica network constructed using generation 4 dendrimer contains residual dendrimer template, and mixes with aqueous silver acetate solution easily. Upon chemisorption, silver ions get photolytically reduced to silver metal under a stabilizing dendrimer environment, leading to the formation of silver metal nanoparticles

  19. Distinct metamorphic evolution of alternating silica-saturated and silica-deficient microdomains within garnet in ultrahigh-temperature granulites: An example from Sri Lanka

    Directory of Open Access Journals (Sweden)

    P.L. Dharmapriya

    2017-09-01

    Full Text Available Here we report the occurrence of garnet porphyroblasts that have overgrown alternating silica-saturated and silica deficient microdomains via different mineral reactions. The samples were collected from ultrahigh-temperature (UHT metapelites in the Highland Complex, Sri Lanka. In some of the metapelites, garnet crystals have cores formed via a dehydration reaction, which had taken place at silica-saturated microdomains and mantle to rim areas formed via a dehydration reaction at silica-deficient microdomains. In contrast, some other garnets in the same rock cores had formed via a dehydration reaction which occurred at silica-deficient microdomains while mantle to rim areas formed via a dehydration reaction at silica-saturated microdomains. Based on the textural observations, we conclude that the studied garnets have grown across different effective bulk compositional microdomains during the prograde evolution. These microdomains could represent heterogeneous compositional layers (paleobedding/laminations in the precursor sediments or differentiated crenulation cleavages that existed during prograde metamorphism. UHT metamorphism associated with strong ductile deformation, metamorphic differentiation and crystallization of locally produced melt may have obliterated the evidence for such microdomains in the matrix. The lack of significant compositional zoning in garnet probably due to self-diffusion during UHT metamorphism had left mineral inclusions as the sole evidence for earlier microdomains with contrasting chemistry.

  20. The flavoprotein Mcap0476 (RlmFO) catalyzes m5U1939 modification in Mycoplasma capricolum 23S rRNA

    DEFF Research Database (Denmark)

    Lartigue, Carole; Lebaudy, Anne; Blanchard, Alain

    2014-01-01

    Efficient protein synthesis in all organisms requires the post-transcriptional methylation of specific ribosomal ribonucleic acid (rRNA) and transfer RNA (tRNA) nucleotides. The methylation reactions are almost invariably catalyzed by enzymes that use S-adenosylmethionine (AdoMet) as the methyl g...... specifically modifies m5U1939 in 23S rRNA, a conserved methylation catalyzed by AdoMet-dependent enzymes in all other characterized bacteria. The Mcap0476 methyltransferase (renamed RlmFO) represents the first folate-dependent flavoprotein seen to modify ribosomal RNA.......Efficient protein synthesis in all organisms requires the post-transcriptional methylation of specific ribosomal ribonucleic acid (rRNA) and transfer RNA (tRNA) nucleotides. The methylation reactions are almost invariably catalyzed by enzymes that use S-adenosylmethionine (AdoMet) as the methyl...... group donor. One noteworthy exception is seen in some bacteria, where the conserved tRNA methylation at m5U54 is added by the enzyme TrmFO using flavin adenine dinucleotide together with N5,N10-methylenetetrahydrofolate as the one-carbon donor. The minimalist bacterium Mycoplasma capricolum possesses...

  1. Multifunctional Silica Nanoparticles Modified via Silylated-Decaborate Precursors

    Directory of Open Access Journals (Sweden)

    Fatima Abi-Ghaida

    2015-01-01

    Full Text Available A new class of multifunctional silica nanoparticles carrying boron clusters (10-vertex closo-decaborate and incorporating luminescent centers (fluorescein has been developed as potential probes/carriers for potential application in boron neutron capture therapy (BNCT. These silica nanoparticles were charged in situ with silylated-fluorescein fluorophores via the Stöber method and their surface was further functionalized with decaborate-triethoxysilane precursors. The resulting decaborate dye-doped silica nanoparticles were characterized by TEM, solid state NMR, DLS, nitrogen sorption, elemental analysis, and fluorescence spectroscopy.

  2. Electrodeposition of zinc–silica composite coatings: challenges in incorporating functionalized silica particles into a zinc matrix

    Directory of Open Access Journals (Sweden)

    Tabrisur Rahman Khan, Andreas Erbe, Michael Auinger, Frank Marlow and Michael Rohwerder

    2011-01-01

    Full Text Available Zinc is a well-known sacrificial coating material for iron and co-deposition of suitable particles is of interest for further improving its corrosion protection performance. However, incorporation of particles that are well dispersible in aqueous electrolytes, such as silica particles, is extremely difficult. Here, we report a detailed study of Zn–SiO2 nanocomposite coatings deposited from a zinc sulfate solution at pH 3. The effect of functionalization of the silica particles on the electro-codeposition was investigated. The best incorporation was achieved for particles modified with SiO2–SH, dithiooxamide or cysteamine; these particles have functional groups that can strongly interact with zinc and therefore incorporate well into the metal matrix. Other modifications (SiO2–NH3+, SiO2–Cl and N,N-dimethyldodecylamine of the silica particles lead to adsorption and entrapment only.

  3. Cr3+ and Cr4+ luminescence in glass ceramic silica

    International Nuclear Information System (INIS)

    Martines, Marco A.U.; Davolos, Marian R.; Jafelicci, Miguel Junior; Souza, Dione F. de; Nunes, Luiz A.O.

    2008-01-01

    This paper reports on the effect of glass ceramic silica matrix on [CrO 4 ] 4- and Cr 2 O 3 NIR and visible luminescence. Chromium-containing silica was obtained by precipitation from water-glass and chromium nitrate acid solution with thermal treatment at 1000 deg. C. From XRD results silica and silica-chromium samples are crystalline. The chromium emission spectrum presents two main broad bands: one in the NIR region (1.1-1.7μm) and other in the visible region (0.6-0.7μm) assigned to Cr 4+ and to Cr 3+ , respectively. This thermal treated glass ceramic silica-chromium sample stabilizes the [CrO 4 ] 4- where Cr 4+ substitutes for Si 4+ and also hexacoordinated Cr 3+ group probably as segregated phase in the system. It can be pointed out that luminescence spectroscopy is a powerful tool for detecting the two chromium optical centers in the glass ceramic silica

  4. Exposure to respirable crystalline silica in South African farm workers

    International Nuclear Information System (INIS)

    Swanepoel, Andrew; Rees, David; Renton, Kevin; Kromhout, Hans

    2009-01-01

    Although listed in some publications as an activity associated with silica (quartz) exposure, agriculture is not widely recognized as an industry with a potential for silica associated diseases. Because so many people work in agriculture; and because silica exposure and silicosis are associated with serious diseases such as tuberculosis (TB), particular in those immunological compromised by the Human immunodeficiency virus (HIV), silica exposure in agriculture is potentially very important. But in South Africa (SA) very little is known about silica exposure in this industry. The objectives of this project are: (a) to measure inhalable and respirable dust and its quartz content on two typical sandy soil farms in the Free State province of SA for all major tasks done on the farms; and (b) to characterise the mineralogy soil type of these farms. Two typical farms in the sandy soil region of the Free State province were studied. The potential health effects faced by these farm workers from exposure to respirable crystalline silica are discussed.

  5. Reactive processing of silica-reinforced tire rubber : new insight into the time- and temperature-dependence of silica rubber interaction

    NARCIS (Netherlands)

    Mihara, S.

    2009-01-01

    In recent years, silica has become one of the most important fillers used in tire tread compounds due to its contribution to a better environment. Silica is capable of not only reducing the rolling resistance but also improving the wet skid resistance of tires, compared to carbon black as a filler.

  6. Amorphous silica in ultra-high performance concrete: First hour of hydration

    Energy Technology Data Exchange (ETDEWEB)

    Oertel, Tina, E-mail: tina.oertel@isc.fraunhofer.de [Fraunhofer-Institute for Silicate Research ISC, Neunerplatz 2, 97082 Würzburg (Germany); Chair for Inorganic Chemistry I, Universität Bayreuth, Universitätsstr. 30, 95440 Bayreuth (Germany); Hutter, Frank [Fraunhofer-Institute for Silicate Research ISC, Neunerplatz 2, 97082 Würzburg (Germany); Helbig, Uta, E-mail: uta.helbig@th-nuernberg.de [Chair for Crystallography and X-ray Methods, Technische Hochschule Nürnberg Georg Simon Ohm, Wassertorstraße 10, 90489 Nürnberg (Germany); Sextl, Gerhard [Fraunhofer-Institute for Silicate Research ISC, Neunerplatz 2, 97082 Würzburg (Germany); Chair for Chemical Technology of Advanced Materials, Julius Maximilian Universität, Röntgenring 11, 97070 Würzburg (Germany)

    2014-04-01

    Amorphous silica in the sub-micrometer size range is widely used to accelerate cement hydration. Investigations including properties of silica which differ from the specific surface area are rare. In this study, the reactivity of varying types of silica was evaluated based on their specific surface area, surface silanol group density, content of silanol groups and solubility in an alkaline suspension. Pyrogenic silica, silica fume and silica synthesized by hydrolysis and condensation of alkoxy silanes, so-called Stoeber particles, were employed. Influences of the silica within the first hour were further examined in pastes with water/cement ratios of 0.23 using in-situ X-ray diffraction, cryo scanning electron microscopy and pore solution analysis. It was shown that Stoeber particles change the composition of the pore solution. Na{sup +}, K{sup +}, Ca{sup 2+} and silicate ions seem to react to oligomers. The extent of this reaction might be highest for Stoeber particles due to their high reactivity.

  7. Fluorescent Silica Nanoparticles in the Detection and Control of the Growth of Pathogen

    International Nuclear Information System (INIS)

    Chitra, K.; Annadurai, G.

    2013-01-01

    In this present study the bio conjugated fluorescent silica nanoparticles give an efficient fluorescent-based immunoassay for the detection of pathogen. The synthesized silica nanoparticles were poly dispersed and the size of the silica nanoparticles was in the range of 114-164 nm. The energy dispersive X-ray spectrophotometer showed the presence of silica at 1.8 keV and the selected area diffractometer showed amorphous nature of silica nanoparticles. The FTIR spectrum confirmed the attachment of dye and carboxyl group onto the silica nanoparticles surface. The fluorescent silica nanoparticles showed highly efficient fluorescence and the fluorescent emission of silica nanoparticles occurred at 536 nm. The SEM image showed the aggregation of nanoparticles and bacteria. The growth of the pathogenic E. coli was controlled using silica nanoparticles; therefore silica nanoparticles could be used in food packaging material, biomedical material, and so forth. This work provides a rapid, simple, and accurate method for the detection of pathogen using fluorescent-based immunoassay.

  8. Microwave-assisted silica coating and photocatalytic activities of ZnO nanoparticles

    International Nuclear Information System (INIS)

    Siddiquey, Iqbal Ahmed; Furusawa, Takeshi; Sato, Masahide; Suzuki, Noboru

    2008-01-01

    A new and rapid method for silica coating of ZnO nanoparticles by the simple microwave irradiation technique is reported. Silica-coated ZnO nanoparticles were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HR-TEM), CHN elemental analysis and zeta potential measurements. The FT-IR spectra and XPS clearly confirmed the silica coating on ZnO nanoparticles. The results of XPS analysis showed that the elements in the coating at the surface of the ZnO nanoparticles were Zn, O and Si. HR-TEM micrographs revealed a continuous and uniform dense silica coating layer of about 3 nm in thickness on the surface of ZnO nanoparticles. In addition, the silica coating on the ZnO nanoparticles was confirmed by the agreement in the zeta potential of the silica-coated ZnO nanoparticles with that of SiO 2 . The results of the photocatalytic degradation of methylene blue (MB) in aqueous solution showed that silica coating effectively reduced the photocatalytic activity of ZnO nanoparticles. Silica-coated ZnO nanoparticles showed excellent UV shielding ability and visible light transparency

  9. Method of synthesizing silica nanofibers using sound waves

    Science.gov (United States)

    Sharma, Jaswinder K.; Datskos, Panos G.

    2015-09-15

    A method for synthesizing silica nanofibers using sound waves is provided. The method includes providing a solution of polyvinyl pyrrolidone, adding sodium citrate and ammonium hydroxide to form a first mixture, adding a silica-based compound to the solution to form a second mixture, and sonicating the second mixture to synthesize a plurality of silica nanofibers having an average cross-sectional diameter of less than 70 nm and having a length on the order of at least several hundred microns. The method can be performed without heating or electrospinning, and instead includes less energy intensive strategies that can be scaled up to an industrial scale. The resulting nanofibers can achieve a decreased mean diameter over conventional fibers. The decreased diameter generally increases the tensile strength of the silica nanofibers, as defects and contaminations decrease with the decreasing diameter.

  10. Plasma Polymerization of Acetylene onto silica: and Approach to control the distribution of silica in single elastomers and immiscible blends

    NARCIS (Netherlands)

    Tiwari, M.; Noordermeer, Jacobus W.M.; Ooij, W.J.; Dierkes, Wilma K.

    2008-01-01

    Surface modification of silica by acetylene plasma polymerization is applied in order to improve the dispersion in and compatibility with single rubbers and their blends. Silica, used as a reinforcing filler for elastomers, is coated with a polyacetylene (PA) film under vacuum conditions. Water

  11. Study of radon transport through concrete modified with silica fume

    International Nuclear Information System (INIS)

    Chauhan, R.P.; Kumar, Amit

    2013-01-01

    The concentration of radon in soil usually varies between a few kBq/m 3 and tens or hundreds of kBq/m 3 depending upon the geographical region. This causes the transport of radon from the soil to indoor environments by diffusion and advection through the pore space of concrete. To reduce indoor radon levels, the use of concrete with low porosity and a low radon diffusion coefficient is recommended. A method of reducing the radon diffusion coefficient through concrete and hence the indoor radon concentration by using silica fume to replace an optimum level of cement was studied. The diffusion coefficient of the concrete was reduced from (1.63 ± 0.3) × 10 −7 to (0.65 ± 0.01) × 10 −8 m 2 /s using 30% substitution of cement with silica fume. The compressive strength of the concrete increased as the silica-fume content increased, while radon exhalation rate and porosity of the concrete decreased. This study suggests a cost-effective method of reducing indoor radon levels. -- Highlights: • Radon diffusion study through silica fume modified concrete was carried out. • Radon diffusion coefficient of concrete decreased with increase of silica fume contents. • Compressive strength increased with increase of silica fume. • Radon exhalation rates and porosity of samples decreased with addition of silica fume. • Radon diffusion coefficient decreased to 2.6% by 30% silica fume substitution

  12. Extraction of metal ions using chemically modified silica gel: a PIXE analysis.

    Science.gov (United States)

    Jal, P K; Dutta, R K; Sudarshan, M; Saha, A; Bhattacharyya, S N; Chintalapudi, S N; K Mishra, B

    2001-08-30

    Organic ligand with carboxyhydrazide functional group was immobilised on the surface of silica gel and the metal binding capacity of the ligand-embedded silica was investigated. The functional group was covalently bonded to the silica matrix through a spacer of methylene groups by sequential reactions of silica gel with dibromobutane, malonic ester and hydrazine in different media. Surface area value of the modified silica was determined. The changes in surface area were correlated with the structural change of the silica surface due to chemical modifications. A mixture solution of metal ions [K(I),Cr(III),Co(II),Ni(II),Cu(II),Zn(II),Hg(II) and U(VI)] was treated with the ligand-embedded silica in 10(-3) M aqueous solution. The measurement of metal extraction capacity of the silica based ligand was done by multielemental analysis of the metal complexes thus formed by using Proton Induced X-ray Emission (PIXE) technique.

  13. On the problem of silica solubility at high pH

    International Nuclear Information System (INIS)

    Eikenberg, J.

    1990-07-01

    The aqueous system Na 2 O-H 2 O-SiO 2 is considered to play an important role when strong alkaline pore waters of a cement based intermediate level radioactive waste repository intrude into the rock formations surrounding the near field. Under such conditions unknown quantities of silica may dissolve. Therefore the pH-dependence of the solubility of amorphous silica and quartz is investigated by a parameter variation study using the geochemical speciation code MINEQL/EIR. Published silica solubility data obtained in sodium hydroxide solutions at 25 and 90 o C are compared with the results of four models which use different proposed values of the rather uncertain equilibrium constants. Of main interest is the question of whether, in a high pH region, the silica solubility can be explained with different monomeric species only, or to what extent additional polymeric silica species have to be considered as well. The solubility of amorphous silica at 25 o C is well understood up to a pH of about 10.5, where it is determined by the solubility product and the first dissociation constant of monomeric silic acid. The most probable cause of the increased solubility of amorphous silica in the region between pH 10.5 and 11.3 is the formation of dimers, trimers and tetramers. Below a total silica concentration of 0.001 M and pH ≤ 10.0, however, polymerisation proves to be insignificant. Besides low temperature studies using amorphous silica, the solubility of quartz has also been measured in NaOH solutions at 90 o C. As is the case at lower temperatures, the reported values for the second dissociation constant at 90 o C scatter widely. It can be shown that in a NaOH medium up to 0.1 M only mononuclear silica species are stable. Therefore it is concluded that the trend of monomers to form polymers decreases strongly with temperature. In strong NaOH solutions at elevated temperatures, silica-sodium ion pairing seems to gain importance. (author) 12 figs., 9 tabs., 65 refs

  14. Hydroxylated crystalline edingtonite silica faces as models for the amorphous silica surface

    Energy Technology Data Exchange (ETDEWEB)

    Tosoni, S; Civalleri, B; Ugliengo, P [Dipartimento di Chimica IFM and NIS (Centre of Excellence), Universita di Torino, Via P. Giuria 7, 10125 Torino - ITALY (Italy); Pascale, F [Laboratoire de Cristallographie ed Modelisation des Materiaux Mineraux et Biologiques, UMR-CNRS-7036. Universite Henri Poincare - Nancy I, B.P. 239, 54506 Vandoeuvre-les-Nancy Cedex 05 - FRANCE (France)], E-mail: piero.ugliengo@unito.it

    2008-06-01

    Fully hydroxylated surfaces derived from crystalline edingtonite were adopted to model the variety of sites known to exist at the amorphous silica surface, namely isolated, geminal and interacting silanols. Structures, energetics and vibrational features of the surfaces either bare or in contact with water were modelled at DFT level using the B3LYP functional with a GTO basis set of double-zeta polarized quality using the periodic ab-initio CRYSTAL06 code. Simulated infrared spectra of both dry and water wet edingtonite surfaces were in excellent agreement with the experimental ones recorded on amorphous silica. Water interaction energies were compared with microcalorimetric differential heats of adsorption data showing good agreement, albeit computed ones being slightly underestimated due to the lack of dispersive forces in the B3LYP functional.

  15. Environmental and economic assessment of hybrid FO-RO/NF system with selected inorganic draw solutes for the treatment of mine impaired water

    KAUST Repository

    Kim, Jung Eun; Phuntsho, Sherub; Chekli, Laura; Choi, Joon Yong; Shon, Ho Kyong

    2018-01-01

    draw solution (DS) by conducting environmental and economic life cycle assessment (LCA). Baseline environmental LCA showed that the dominant components to energy use and global warming are the DS recovery processes (i.e. RO or NF processes) and FO

  16. Preparation and flow cytometry of uniform silica-fluorescent dye microspheres.

    Science.gov (United States)

    Bele, Marjan; Siiman, Olavi; Matijević, Egon

    2002-10-15

    Uniform fluorescent silica-dye microspheres have been prepared by coating preformed monodispersed silica particles with silica layers containing rhodamine 6G or acridine orange. The resulting dispersions exhibit intense fluorescent emission between 500 and 600 nm, over a broad excitation wavelength range of 460 to 550 nm, even with exceedingly small amounts of dyes incorporated into the silica particles (10-30 ppm, expressed as weight of dye relative to weight of dry particles). The fluorescent particles can be prepared in micrometer diameters suitable for analyses using flow cytometry with 488-nm laser excitation.

  17. Radiation effect on polystyrene deposited and grafted on silica gel

    International Nuclear Information System (INIS)

    Kusama, Y.; Udagawa, A.; Takehisa, M.

    1978-01-01

    The effect of radiation on polystyrene was studied in the presence and absence of silica gel by molecular weight measurement with gel permeation chromatography (GPC). Polystyrene crosslinked under vacuum in the absence of silica gel, but it either crosslinked or degraded by radiation, depending on the molecular weight of the polymer in the presence of silica gel. part of the deposited polymer bonded to silica gel by radiation; the G value for graft-chain formation is in the range of 0.01 to 0.1. Irradiation of polystyrene grafted on silica gel resulted in degradation of the graft chain because of the transfer of energy from silica gel. The G value for main chain scission was about 2 when graft polymer was irradiated in the absence of homopolymer. The degradation of graft polymer was suppressed when the polymer was irradiated in the presence of homopolymer, and the amount of unextractable polymer from silica gel increased with increasing irradiation. This adds evidence to the estimation that an increase in grafting percent coupled with a slight decrease in molecular weight at a later stage of radiation-induced polymerization of styrene adsorbed on slica gel is due to a secondary effect of radiation on the polymer

  18. In vitro effects of cisplatin-functionalized silica nanoparticles on chondrocytes

    Energy Technology Data Exchange (ETDEWEB)

    Bhowmick, Tridib Kumar; Yoon, Diana [University of Maryland, Department of Chemical and Biomolecular Engineering (United States); Patel, Minal; Fisher, John [University of Maryland, Fischell Department of Bioengineering (United States); Ehrman, Sheryl, E-mail: sehrman@umd.ed [University of Maryland, Department of Chemical and Biomolecular Engineering (United States)

    2010-10-15

    In this study, we evaluated the combined effect of a known toxic molecule, cisplatin, in combination with relatively nontoxic nanoparticles, amorphous fumed silica, on chondrocyte cells. Cisplatin was attached to silica nanoparticles using aminopropyltriethoxy silane as a linker molecule, and characterized in terms of size, shape, specific surface area, as well as the dissolution of cisplatin from the silica surface. The primary particle diameter of the as-received silica nanoparticles ranged from 7.1 to 61 nm, estimated from measurements of specific surface area, and the primary particles were aggregated. The effects of cisplatin-functionalized silica particles with different specific surface areas (41, 85, 202, 237, and 297 m{sup 2}/g) were compared in vitro on chondrocytes, the parenchymal cell of hyaline cartilage. The results show that adverse effects on cell function, as evidenced by reduced metabolic activity measured by the MTT assay and increased membrane permeability observed using the Live/Dead stain, can be correlated with specific surface area of the silica. Cisplatin-functionalized silica nanoparticles with the highest specific surface area incited the greatest response, which was almost equivalent to that induced by free cisplatin. This result suggests the importance of particle specific surface area in interactions between cells and surface-functionalized nanomaterials.

  19. In vitro effects of cisplatin-functionalized silica nanoparticles on chondrocytes

    Science.gov (United States)

    Bhowmick, Tridib Kumar; Yoon, Diana; Patel, Minal; Fisher, John; Ehrman, Sheryl

    2010-10-01

    In this study, we evaluated the combined effect of a known toxic molecule, cisplatin, in combination with relatively nontoxic nanoparticles, amorphous fumed silica, on chondrocyte cells. Cisplatin was attached to silica nanoparticles using aminopropyltriethoxy silane as a linker molecule, and characterized in terms of size, shape, specific surface area, as well as the dissolution of cisplatin from the silica surface. The primary particle diameter of the as-received silica nanoparticles ranged from 7.1 to 61 nm, estimated from measurements of specific surface area, and the primary particles were aggregated. The effects of cisplatin-functionalized silica particles with different specific surface areas (41, 85, 202, 237, and 297 m2/g) were compared in vitro on chondrocytes, the parenchymal cell of hyaline cartilage. The results show that adverse effects on cell function, as evidenced by reduced metabolic activity measured by the MTT assay and increased membrane permeability observed using the Live/Dead stain, can be correlated with specific surface area of the silica. Cisplatin-functionalized silica nanoparticles with the highest specific surface area incited the greatest response, which was almost equivalent to that induced by free cisplatin. This result suggests the importance of particle specific surface area in interactions between cells and surface-functionalized nanomaterials.

  20. Extracting silica from rice husk treated with potassium permanganate

    International Nuclear Information System (INIS)

    Javed, S.H.; Naveed, S.

    2008-01-01

    As an agro-waste material the rice husk is abundantly available is rice growing areas. In many areas rice husk after burning involves disposal problems because of higher quantities of silica present in it. Rice husk contains about 20 per cent silica, which is present in hydrated amorphous form. On thermal treatment the silica converts into crystobalite, which is a crystalline form of silica. However amorphous silica can be produced under controlled conditions ensuring high reactivity and large surface area. Leaching the rice husk with organic acids and alkalies removes the metallic impurities from its surface. How a dilute solution of potassium permanganate affects the rice husk is the subject of this research paper. The rice husk was treated with the dilute solution of potassium permanganate at room temperature and then analyzed by SEM, TGA and the ash by analytical treatment after burning under controlled temperature. The SEM results revealed that the protuberances of the rice husk were eaten away by the solution of potassium permanganate. Pyrolysis of rice husks showed that the thermal degradation of the treated rice husk was faster than the untreated rice husk where as analytical results confirmed the presence of more amorphous silica than untreated rice husk. (author)

  1. Preparation of Mesoporous Silica-Supported Palladium Catalysts for Biofuel Upgrade

    Directory of Open Access Journals (Sweden)

    Ling Fei

    2012-01-01

    Full Text Available We report the preparation of two hydrocracking catalysts Pd/CoMoO4/silica and Pd/CNTs/CoMoO4/silica (CNTs, carbon nanotubes. The structure, morphologies, composition, and thermal stability of catalysts were studied by X-ray diffraction (XRD, scanning electron microscopy (SEM, Raman spectroscopy, transmission electron microscopy (TEM, energy-dispersive X-ray (EDX, and thermogravimetric analysis (TGA. The catalyst activity was measured in a Parr reactor with camelina fatty acid methyl esters (FAMEs as the feed. The analysis shows that the palladium nanoparticles have been incorporated onto mesoporous silica in Pd/CoMoO4/silica or on the CNTs surface in Pd/CNTs/CoMoO4/silica catalysts. The different combinations of metals and supports have selective control cracking on heavy hydrocarbons.

  2. Two-dimensional silica opens new perspectives

    Science.gov (United States)

    Büchner, Christin; Heyde, Markus

    2017-12-01

    In recent years, silica films have emerged as a novel class of two-dimensional (2D) materials. Several groups succeeded in epitaxial growth of ultrathin SiO2 layers using different growth methods and various substrates. The structures consist of tetrahedral [SiO4] building blocks in two mirror symmetrical planes, connected via oxygen bridges. This arrangement is called a silica bilayer as it is the thinnest 2D arrangement with the stoichiometry SiO2 known today. With all bonds saturated within the nano-sheet, the interaction with the substrate is based on van der Waals forces. Complex ring networks are observed, including hexagonal honeycomb lattices, point defects and domain boundaries, as well as amorphous domains. The network structures are highly tuneable through variation of the substrate, deposition parameters, cooling procedure, introducing dopants or intercalating small species. The amorphous networks and structural defects were resolved with atomic resolution microscopy and modeled with density functional theory and molecular dynamics. Such data contribute to our understanding of the formation and characteristic motifs of glassy systems. Growth studies and doping with other chemical elements reveal ways to tune ring sizes and defects as well as chemical reactivities. The pristine films have been utilized as molecular sieves and for confining molecules in nanocatalysis. Post growth hydroxylation can be used to tweak the reactivity as well. The electronic properties of silica bilayers are favourable for using silica as insulators in 2D material stacks. Due to the fully saturated atomic structure, the bilayer interacts weakly with the substrate and can be described as quasi-freestanding. Recently, a mm-scale film transfer under structure retention has been demonstrated. The chemical and mechanical stability of silica bilayers is very promising for technological applications in 2D heterostacks. Due to the impact of this bilayer system for glass science

  3. Synthesis of Novel Mesoporous Silica Materials with Hierarchical Pore Structures

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Suk Bon; Choi, Wang Kyu; Choi, Byung Seon; Moon, Jei Kwon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    Porous materials with various pore sizes in the range of micropore (< 2 nm), mesopore (2-50 nm), and macropore (> 50 nm) are attractive due to their many emerging applications such as catalysts, separation systems, and low dielectric constant materials. The discovery of new M41S mesoporous silica families with pore sizes larger than 2 nm in diameter in 1992 extended the applications into much wider pore ranges, bringing in a new prosperous era in porous material research. The synthesis of these silica materials has been mainly accomplished through a self-assembly between surfactant molecules and inorganic species under various pH conditions. Recently, core-shell nanoparticles with a silica core and mesoporous shell under basic conditions were synthesized using the silica nanoparticles as a core, and a silica precursor (TEOS) and cationic surfactant (CTABr) as a material for the formation of the mesoporous shell. The resultant materials were very monodispersive in size and showed a narrow pore size distribution in the range of ca 2-3 nm in diameter, depending on the alkyl-chain length of the surfactants used. In this work, the mesoporous shell coated-fumed silicas (denoted as MS M-5s) were synthesized by using fumed silica instead of the silica nanoparticle as a core based on previous reports. Also, the structural properties of the MS M-5s such as the specific surface area and pore volume were easily controlled by varying the amount of the silica precursor and surfactant. The resultant materials exhibited a BET surface area of ca 279-446 m{sup 2}/g and total pore volume of ca 0.64-0.74 cm{sup 3}/g and showed a narrow pore size distribution (PSD) due to the removal of the organic surfactant molecules

  4. Removing Dissolved Silica from Waste Water with Catechol and Active Carbon

    Energy Technology Data Exchange (ETDEWEB)

    Sasan, Koroush [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Nanoscale Sciences Dept.; Brady, Patrick [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Nuclear Energy Program; Krumhansl, James L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Geosciences Dept.; Nenoff, Tina M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Physical Chemical and Nano Sciences Center

    2017-01-01

    Fresh water scarcity is going to be a global great challenge in the near future because of the increasing population. Our water resources are limited and, hence, water treatment and recycling methods are the only alternatives for fresh water procurement in the upcoming decades. Water treatment and recycling methods serve to remove harmful or problematic constituents from ground, surface and waste waters prior to its consumption, industrial supply, or other uses. Scale formation in industrial and domestic installations is still an important problem during water treatment. In water treatment, silica scaling is a real and constant concern for plant operations. The focus of this study is on the viability of using a combination of catechol and active carbon to remove dissolved silica from concentrated cooling tower water (CCTW). Various analytical methods, such as ICP-MS and UV-vis, were used to understand the structure-property relationship between the material and the silica removal results. UV-Vis indicates that catechol can react with silica ions and form a silica-catecholate complex. The speciation calculation of catechol and silica shows that catechol and silica bind in the pH range of 8 – 10; there is no evidence of linkage between them in neutral and acidic pHs. The silica removal results indicate that using ~4g/L of catechol and 10g/L active carbon removes up to 50% of the dissolved silica from the CCTW.

  5. Preparation of Silica Nanoparticles and Its Beneficial Role in Cementitious Materials

    Directory of Open Access Journals (Sweden)

    S. Ahalawat

    2011-07-01

    Full Text Available Spherical silica nanoparticles (n‐SiO2 with controllable size have been synthesized using tetraethoxysilane as starting material and ethanol as solvent by sol‐gel method. Morphology and size of the particles was controlled through surfactants. Sorbitan monolaurate, sorbitain monopalmitate and sorbitain monostearate produced silica nanoparticles of varying sizes (80‐150 nm, indicating the effect of chain length of the surfactant. Increase in chain length of non‐ionic surfactant resulted in decreasing particle size of silica nanoparticles. Further, the size of silica particles was also controlled using NH3 as base catalyst. These silica nanoparticles were incorporated into cement paste and their role in accelerating the cementitious reactions was investigated. Addition of silica nanoparticles into cement paste improved the microstructure of the paste and calcium leaching is significantly reduced as n‐SiO2 reacts with calcium hydroxide and form additional calcium‐ silicate‐hydrate (C‐S‐H gel. It was found that calcium hydroxide content in silica nanoparticles incorporated cement paste reduced ~89% at 1 day and up to ~60% at 28 days of hydration process. Synthesized silica particles and cement paste samples were characterized using scanning electron microscopy (SEM, powder X‐ray diffraction (XRD, infrared spectroscopy (IR and thermogravimetric analysis (TGA.

  6. A novel synthesis of micrometer silica hollow sphere

    International Nuclear Information System (INIS)

    Pan Wen; Ye Junwei; Ning Guiling; Lin Yuan; Wang Jing

    2009-01-01

    Silica microcapsules (hollow spheres) were synthesized successfully by a novel CTAB-stabilized water/oil emulsion system mediated hydrothermal method. The addition of urea to a solution of aqueous phase was an essential step of the simple synthetic procedure of silica hollow spheres, which leads to the formation of silica hollow spheres with smooth shell during hydrothermal process. The intact hollow spheres were obtained by washing the as-synthesized solid products with distilled water to remove the organic components. A large amount of silanol groups were retained in the hollow spheres by this facile route without calcination. The morphologies and optical properties of the product were characterized by transmission electron microscopy, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Furthermore, on the basis of a series of SEM observations, phenomenological elucidation of a mechanism for the growth of the silica hollow spheres has been presented

  7. Utilization of rice husk ash as silica source for the synthesis of mesoporous silicas and their application to CO2 adsorption through TREN/TEPA grafting

    International Nuclear Information System (INIS)

    Bhagiyalakshmi, Margandan; Yun, Lee Ji; Anuradha, Ramani; Jang, Hyun Tae

    2010-01-01

    Mesoporous MCM-41, MCM-48 and SBA-15 were synthesized using Rice husk ash (RHA) as the silica source and their defective Si-OH sites were functionalized by 3-cholropropyltrimethoxysilane (CPTMS) which was subsequently grafted with amine compounds, Tris(2-aminoethyl)amine (TREN) and Tetraethylenepentamine (TEPA). X-ray powder diffraction (XRD) and BET results of the parent mesoporous silica suggested their closeness of structural properties to those obtained from conventional silica sources. CO 2 adsorption of branched amine TREN and straight chain amine TEPA at 25, 50 and 75 deg. C was obtained by Thermogravimetric Analyser (TGA) at atmospheric pressure. TREN grafted mesoporous silica showed 7% of CO 2 adsorption while TEPA grafted mesoporous silicas showed less CO 2 adsorption, which is due to the presence of isolated amine groups in TREN. TREN grafted mesoporous silicas were also observed to be selective towards CO 2 , thermally stable and recyclable. The order of CO 2 adsorption with respect to amount of amine grafting was observed to be MCM-48/TREN > MCM-41/TREN > SBA-15/TREN.

  8. Refractive index dispersion law of silica aerogel

    International Nuclear Information System (INIS)

    Bellunato, T.; Calvi, M.; Matteuzzi, C.; Musy, M.; Perego, D.L.; Storaci, B.

    2007-01-01

    This paper presents measurements of the refractive index of a hygroscopic silica aerogel block at several wavelengths. The measurements, performed with a monochromator, have been compared with different parameterisations for n(λ), in order to determine the best chromaticity law for the aerogel. This is an important input for design and operation of RICH detectors with silica aerogel radiator. (orig.)

  9. Silica colloids and their effect on radionuclide sorption. A literature review

    International Nuclear Information System (INIS)

    Hoelttae, P.; Hakanen, M.

    2008-05-01

    Silica sol, commercial colloidal silica manufactured by Eka Chemicals in Bohus, Sweden is a promising inorganic grout material for sealing small fractures in low permeable rock. This literature review collects information about the use of silica sol as an injection grout material, the properties of inorganic, especially silica colloids, colloid contents in granitic groundwater conditions, essential characterization methods and colloid-mediated transport of radionuclides. Objective was to evaluate the release and mobility of silica sol colloids, the effect of the groundwater conditions, the amount of colloids compared with natural colloids in Olkiluoto conditions, radionuclide sorption on colloids and their contribution to radionuclide transport. Silica sol seems to be a feasible material to seal fractures with an aperture as small as 10 μm in low permeable rock. The silica sol gel is sufficiently stable to limit to water ingress during the operational phase, the requirement that the pH should be below 11 is fulfilled and the compatibility with Engineered Barrier System (EBS) materials is expected to be good. No significant influence on the bentonite properties caused by the silica sol is expected when calcium chloride is used as an accelerator but the influence of sodium chloride has not been examined. No significant release of colloids is expected under prevailing groundwater conditions. The long-term (100 y) stability of silica sol gel has not yet been clearly demonstrated and a long-term release of silica colloids cannot be excluded. The question is the amount of colloids, how mobile they are and the influence of possible glacial melt waters. The bentonite buffer used in the EBS system is assumed to be a potential source of colloids. In a study in Olkiluoto, bentonite colloids were found only in low salinity groundwater. In general, low salinity water (total dissolved solids -1 ) favours colloid stability and bentonite colloids can remain stable over long

  10. Control of silicification by genetically engineered fusion proteins: Silk–silica binding peptides

    Science.gov (United States)

    Zhou, Shun; Huang, Wenwen; Belton, David J.; Simmons, Leo O.; Perry, Carole C.; Wang, Xiaoqin; Kaplan, David L.

    2014-01-01

    In the present study, an artificial spider silk gene, 6mer, derived from the consensus sequence of Nephila clavipes dragline silk gene, was fused with different silica-binding peptides (SiBPs), A1, A3 and R5, to study the impact of the fusion protein sequence chemistry on silica formation and the ability to generate a silk–silica composite in two different bioinspired silicification systems: solution–solution and solution– solid. Condensed silica nanoscale particles (600–800 nm) were formed in the presence of the recombinant silk and chimeras, which were smaller than those formed by 15mer-SiBP chimeras [1], revealing that the molecular weight of the silk domain correlated to the sizes of the condensed silica particles in the solution system. In addition, the chimeras (6mer-A1/A3/R5) produced smaller condensed silica particles than the control (6mer), revealing that the silica particle size formed in the solution system is controlled by the size of protein assemblies in solution. In the solution–solid interface system, silicification reactions were performed on the surface of films fabricated from the recombinant silk proteins and chimeras and then treated to induce β-sheet formation. A higher density of condensed silica formed on the films containing the lowest β-sheet content while the films with the highest β-sheet content precipitated the lowest density of silica, revealing an inverse correlation between the β-sheet secondary structure and the silica content formed on the films. Intriguingly, the 6mer-A3 showed the highest rate of silica condensation but the lowest density of silica deposition on the films, compared with 6mer-A1 and -R5, revealing antagonistic crosstalk between the silk and the SiBP domains in terms of protein assembly. These findings offer a path forward in the tailoring of biopolymer–silica composites for biomaterial related needs. PMID:25462851

  11. Control of silicification by genetically engineered fusion proteins: silk-silica binding peptides.

    Science.gov (United States)

    Zhou, Shun; Huang, Wenwen; Belton, David J; Simmons, Leo O; Perry, Carole C; Wang, Xiaoqin; Kaplan, David L

    2015-03-01

    In the present study, an artificial spider silk gene, 6mer, derived from the consensus sequence of Nephila clavipes dragline silk gene, was fused with different silica-binding peptides (SiBPs), A1, A3 and R5, to study the impact of the fusion protein sequence chemistry on silica formation and the ability to generate a silk-silica composite in two different bioinspired silicification systems: solution-solution and solution-solid. Condensed silica nanoscale particles (600-800 nm) were formed in the presence of the recombinant silk and chimeras, which were smaller than those formed by 15mer-SiBP chimeras, revealing that the molecular weight of the silk domain correlated to the sizes of the condensed silica particles in the solution system. In addition, the chimeras (6mer-A1/A3/R5) produced smaller condensed silica particles than the control (6mer), revealing that the silica particle size formed in the solution system is controlled by the size of protein assemblies in solution. In the solution-solid interface system, silicification reactions were performed on the surface of films fabricated from the recombinant silk proteins and chimeras and then treated to induce β-sheet formation. A higher density of condensed silica formed on the films containing the lowest β-sheet content while the films with the highest β-sheet content precipitated the lowest density of silica, revealing an inverse correlation between the β-sheet secondary structure and the silica content formed on the films. Intriguingly, the 6mer-A3 showed the highest rate of silica condensation but the lowest density of silica deposition on the films, compared with 6mer-A1 and -R5, revealing antagonistic crosstalk between the silk and the SiBP domains in terms of protein assembly. These findings offer a path forward in the tailoring of biopolymer-silica composites for biomaterial related needs. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  12. Thiol-functionalized silica colloids, grains, and membranes for irreversible adsorption of metal(oxide) nanoparticles

    NARCIS (Netherlands)

    Claesson, E.M.; Philipse, A.P.

    2007-01-01

    Thiol-functionalization is described for silica surfaces from diverging origin, including commercial silica nanoparticles and St¨ober silica as well as silica structures provided by porous glasses and novel polymer-templated silica membranes. The functionalization allows in all cases for the

  13. Thermal and Mechanical Properties of Poly(butylene succinate Films Reinforced with Silica

    Directory of Open Access Journals (Sweden)

    Sangviroon Nanthaporn

    2015-01-01

    Full Text Available In recent year, bioplastics have become more popular resulting from the growing concerns on environmental issues and the rising fossil fuel price. However, their applications were limited by its mechanical and thermal properties. The aim of this research is thus to improve mechanical and thermal properties of PBS bioplastic films by reinforcing with silica. Due to the poor interfacial interaction between the PBS matrix and silica, glycidyl methacrylate grafted poly(butylene succinate (PBS-g-GMA was used as a compatibilizer in order to improve the interaction between bioplastic films and filler. PBS-g-GMA was prepared in a twin-screw extruder and analyzed by the FTIR spectrometer. PBS and silica were then mixed in a twin-screw extruder and processed into films by a chill-roll cast extruder. The effects of silica loading on thermal and mechanical properties of the prepared bioplastic films were investigated. It was found that the mechanical properties of PBS/silica composite films were improved when 1%wt of silica was added. However, the mechanical properties decreased with increasing silica loading due to the agglomeration of silica particles. The results also show that the silica/PBS films with PBS-g-GMA possessed improved mechanical properties over the films without the compatibilizer.

  14. Treatment of oil sands mature fine tailings with silica

    Energy Technology Data Exchange (ETDEWEB)

    Moffett, R.H. [DuPont Canada Inc., Mississauga, ON (Canada)

    2010-07-01

    This PowerPoint presentation discussed a method of treating mature fine tailings (MFT) with silica. Rheology modifications with silica treatments were examined. Experimental studies demonstrated a significant slump at 30 minutes after mixing. Flow properties were studied at a 2 degree angle. The MFT thin lift evaporative drying procedure was used to determine the effects of the silica treatments. Methods of using pressure to dewater MFTs were reviewed. The results of a field test conducted to determine the flow behaviour of MFTs treated with low dose silica were presented. Drying characteristics and strength gains were also evaluated. Results of the study showed that the MFTs had a tendency to channel at discharge points. After a 15 day period that included a freeze-thaw the MFTs had cracks that continued to enlarge, full depth cracking, and fine cracking. The field tests demonstrated that in-situ polymerization of silica within the water phase of fluid fine tails provides significant modifications to rheological properties, and that the onset of rheological modification can be controlled over a range of conditions and times. tabs., figs.

  15. Silver nanoprisms self-assembly on differently functionalized silica surface

    International Nuclear Information System (INIS)

    Pilipavicius, J; Chodosovskaja, A; Beganskiene, A; Kareiva, A

    2015-01-01

    In this work colloidal silica/silver nanoprisms (NPRs) composite coatings were made. Firstly colloidal silica sols were synthesized by sol-gel method and produced coatings on glass by dip-coating technique. Next coatings were silanized by (3-Aminopropyl)triethoxysilane (APTES), N-[3-(Trimethoxysilyl)propyl]ethylenediamine (AEAPTMS), (3- Mercaptopropyl)trimethoxysilane (MPTMS). Silver NPRs where synthesized via seed-mediated method and high yield of 94±15 nm average edge length silver NPRs were obtained with surface plasmon resonance peak at 921 nm. Silica-Silver NPRs composite coatings obtained by selfassembly on silica coated-functionalized surface. In order to find the most appropriate silanization way for Silver NPRs self-assembly, the composite coatings were characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), water contact angle (CA) and surface free energy (SFE) methods. Results have showed that surface functionalization is necessary to achieve self-assembled Ag NPRs layer. MPTMS silanized coatings resulted sparse distribution of Ag NPRs. Most homogeneous, even distribution composite coatings obtained on APTES functionalized silica coatings, while AEAPTMS induced strong aggregation of Silver NPRs

  16. Diagenetic silica enrichment and late-stage groundwater activity in Gale crater, Mars

    Science.gov (United States)

    Frydenvang, Jens; Gasda, Patrick J.; Hurowitz, Joel A.; Grotzinger, John P.; Wiens, Roger C.; Newsom, Horton E.; Edgett, Ken S.; Watkins, Jessica; Bridges, John C.; Maurice, Sylvestre; Fisk, Martin R.; Johnson, Jeffrey R.; Rapin, William; Stein, Nathan; Clegg, Sam M.; Schwenzer, S. P.; Bedford, C.; Edwards, P.; Mangold, Nicolas; Cousin, Agnes; Anderson, Ryan; Payre, Valerie; Vaniman, David; Blake, David; Lanza, Nina L.; Gupta, Sanjeev; Van Beek, Jason; Sautter, Violaine; Meslin, Pierre-Yves; Rice, Melissa; Milliken, Ralf; Gellert, Ralf; Thompson, Lucy; Clark, Ben C.; Sumner, Dawn Y.; Fraeman, Abigail A.; Kinch, Kjartan M; Madsen, Morten B.; Mitofranov, Igor; Jun, Insoo; Calef, Fred J.; Vasavada, Ashwin R.

    2017-01-01

    Diagenetic silica enrichment in fracture-associated halos that crosscut lacustrine and unconformably overlying aeolian sedimentary bedrock is observed on the lower north slope of Aeolis Mons in Gale crater, Mars. The diagenetic silica enrichment is colocated with detrital silica enrichment observed in the lacustrine bedrock yet extends into a considerably younger, unconformably draping aeolian sandstone, implying that diagenetic silica enrichment postdates the detrital silica enrichment. A causal connection between the detrital and diagenetic silica enrichment implies that water was present in the subsurface of Gale crater long after deposition of the lacustrine sediments and that it mobilized detrital amorphous silica and precipitated it along fractures in the overlying bedrock. Although absolute timing is uncertain, the observed diagenesis likely represents some of the most recent groundwater activity in Gale crater and suggests that the timescale of potential habitability extended considerably beyond the time that the lacustrine sediments of Aeolis Mons were deposited.

  17. Selective porous gates made from colloidal silica nanoparticles

    Directory of Open Access Journals (Sweden)

    Roberto Nisticò

    2015-11-01

    Full Text Available Highly selective porous films were prepared by spin-coating deposition of colloidal silica nanoparticles on an appropriate macroporous substrate. Silica nanoparticles very homogenous in size were obtained by sol–gel reaction of a metal oxide silica precursor, tetraethyl orthosilicate (TEOS, and using polystyrene-block-poly(ethylene oxide (PS-b-PEO copolymers as soft-templating agents. Nanoparticles synthesis was carried out in a mixed solvent system. After spin-coating onto a macroporous silicon nitride support, silica nanoparticles were calcined under controlled conditions. An organized nanoporous layer was obtained characterized by a depth filter-like structure with internal porosity due to interparticle voids. Permeability and size-selectivity were studied by monitoring the diffusion of probe molecules under standard conditions and under the application of an external stimulus (i.e., electric field. Promising results were obtained, suggesting possible applications of these nanoporous films as selective gates for controlled transport of chemical species in solution.

  18. Effect of silica nanoparticles on polyurethane foaming process and foam properties

    International Nuclear Information System (INIS)

    Francés, A B; Bañón, M V Navarro

    2014-01-01

    Flexible polyurethane foams (FPUF) are commonly used as cushioning material in upholstered products made on several industrial sectors: furniture, automotive seating, bedding, etc. Polyurethane is a high molecular weight polymer based on the reaction between a hydroxyl group (polyol) and isocyanate. The density, flowability, compressive, tensile or shearing strength, the thermal and dimensional stability, combustibility, and other properties can be adjusted by the addition of several additives. Nanomaterials offer a wide range of possibilities to obtain nanocomposites with specific properties. The combination of FPUF with silica nanoparticles could develop nanocomposite materials with unique properties: improved mechanical and thermal properties, gas permeability, and fire retardancy. However, as silica particles are at least partially surface-terminated with Si-OH groups, it was suspected that the silica could interfere in the reaction of poyurethane formation.The objective of this study was to investigate the enhancement of thermal and mechanical properties of FPUF by the incorporation of different types of silica and determining the influence thereof during the foaming process. Flexible polyurethane foams with different loading mass fraction of silica nanoparticles (0-1% wt) and different types of silica (non treated and modified silica) were synthesized. PU/SiO 2 nanocomposites were characterized by FTIR spectroscopy, TGA, and measurements of apparent density, resilience and determination of compression set. Addition of silica nanoparticles influences negatively in the density and compression set of the foams. However, resilience and thermal stability of the foams are improved. Silica nanoparticles do not affect to the chemical structure of the foams although they interfere in the blowing reaction

  19. Silica nanoparticles with a substrate switchable luminescence

    International Nuclear Information System (INIS)

    Bochkova, O D; Mustafina, A R; Fedorenko, S V; Konovalov, A I

    2011-01-01

    Silica nanoparticles with visible (Tb and Ru doped), near IR (Yb doped) and dual visible-near IR luminescence (Ru-Yb doped) were obtained by reverse w/o microemulsion procedure. Plenty of luminescent complexes (from 4900 to 10000) encapsulated into each nanoparticle ensures the intensive luminescence of nanoparticles and their applicability as biomarkers. The silica surface decoration by definite anchor groups is the required step for the gaining to these nanoparticles marking and sensing functions. Thus covalent and non-covalent surface modification of these nanoparticles was developed to provide the binding with biotargets and sensing of anions. The dicationic surfactant coating of negatively charged Tb(III)-TCAS doped silica nanoparticles was chosen as the basis for the anion responsible system. The reversible insertion of the quenching anions (namely phenol red) into the surfactant based layer at the surface of luminescent nanoparticles switches off the Tb-centered luminescence. In turn the reversible reestablishment of the luminescence results from the competitive insertion of the non-quenching anions into the surfactant layer at the silica/water interface. The hydrophobic anions exemplified by dodecylsulfates versus hydrophilic ones (hydrophosphates) are preferable in the competition with phenol red anions.

  20. Silica incorporated membrane for wastewater based filtration

    Science.gov (United States)

    Fernandes, C. S.; Bilad, M. R.; Nordin, N. A. H. M.

    2017-10-01

    Membrane technology has long been applied for waste water treatment industries due to its numerous advantages compared to other conventional processes. However, the biggest challenge in pressure driven membrane process is membrane fouling. Fouling decreases the productivity and efficiency of the filtration, reduces the lifespan of the membrane and reduces the overall efficiency of water treatment processes. In this study, a novel membrane material is developed for water filtration. The developed membrane incorporates silica nanoparticles mainly to improve its structural properties. Membranes with different loadings of silica nanoparticles were applied in this study. The result shows an increase in clean water permeability and filterability of the membrane for treating activated sludge, microalgae solution, secondary effluent and raw sewage as feed. Adding silica into the membrane matrix does not significantly alter contact angle and membrane pore size. We believe that silica acts as an effective pore forming agent that increases the number of pores without significantly altering the pore sizes. A higher number of small pores on the surface of the membrane could reduce membrane fouling because of a low specific loading imposed to individual pores.

  1. Fractal dimensions of silica gels generated using reactive molecular dynamics simulations

    International Nuclear Information System (INIS)

    Bhattacharya, Sudin; Kieffer, John

    2005-01-01

    We have used molecular dynamics simulations based on a three-body potential with charge transfer to generate nanoporous silica aerogels. Care was taken to reproduce the sol-gel condensation reaction that forms the gel backbone as realistically as possible and to thereby produce credible gel structures. The self-similarity of aerogel structures was investigated by evaluating their fractal dimension from geometric correlations. For comparison, we have also generated porous silica glasses by rupturing dense silica and computed their fractal dimension. The fractal dimension of the porous silica structures was found to be process dependent. Finally, we have determined that the effect of supercritical drying on the fractal nature of condensed silica gels is not appreciable

  2. Analýza dopadu tzv. daňové reformy na podnikatele FO

    OpenAIRE

    Tydlačková, Pavlína

    2008-01-01

    Bakalářská práce pojednává o daňových změnách týkající se podnikatelů FO, které souvisí s reformou veřejných financí. Obsahuje návody, postupy, praktické příklady a potřebné informace k pochopení změn a sestavení správného daňového přiznání. This bachelor’s thesis deals with the tax changes concerning a sole trader associated with a reform of public finance. It includes directions, procedures, practical examples and necessary informations to understanding changes and process correct declar...

  3. Micro-XANES Determination Fe Speciation in Natural Basalts at Mantle-Relevant fO2

    Science.gov (United States)

    Fischer, R.; Cottrell, E.; Lanzirotti, A.; Kelley, K. A.

    2007-12-01

    We demonstrate that the oxidation state of iron (Fe3+/ΣFe) can be determined with a precision of ±0.02 (10% relative) on natural basalt glasses at mantle-relevant fO2 using Fe K-edge X-ray absorption near edge structure (XANES) spectroscopy. This is equivalent to ±0.25 log unit resolution relative to the QFM buffer. Precise determination of the oxidation state over this narrow range (Fe3+/ΣFe=0.06-0.30) and at low fO2 (down to QFM-2) relies on appropriate standards, high spectral resolution, and highly reproducible methods for extracting the pre-edge centroid position. We equilibrated natural tholeiite powder in a CO/CO2 gas mixing furnace at 1350°C from QFM-3 to QFM+2 to create six glasses of known Fe3+/ΣFe, independently determined by Mössbauer spectroscopy. XANES spectra were collected at station X26A at NSLS, Brookhaven Natl. Lab, in fluorescence mode (9 element Ge array detector) using both Si(111) and Si(311) monochromators. Generally, the energy position of the 1s→3d (pre-edge) transition centroid is the most sensitive monitor of Fe oxidation state using XANES. For the mixture of Fe oxidation states in these glasses and the resulting coordination geometries, the pre-edge spectra are best defined by two multiple 3d crystal field transitions. The Si(311) monochromator, with higher energy resolution, substantially improved spectral resolution for the 1s→3d transition. Dwell times of 5s at 0.1eV intervals across the pre-edge region yielded spectra with the 1s→3d transition peaks clearly resolved. The pre-edge centroid position is highly sensitive to the background subtraction and peak fitting procedures. Differences in fitting models result in small but significant differences in the calculated peak area of each pre-edge multiplet, and the relative contribution of each peak to the calculated centroid. We assessed several schemes and obtained robust centroid positions by simultaneously fitting the background with a damped harmonic oscillator (DHO

  4. Exploring encapsulation mechanism of DNA and mononucleotides in sol-gel derived silica.

    Science.gov (United States)

    Kapusuz, Derya; Durucan, Caner

    2017-07-01

    The encapsulation mechanism of DNA in sol-gel derived silica has been explored in order to elucidate the effect of DNA conformation on encapsulation and to identify the nature of chemical/physical interaction of DNA with silica during and after sol-gel transition. In this respect, double stranded DNA and dAMP (2'-deoxyadenosine 5'-monophosphate) were encapsulated in silica using an alkoxide-based sol-gel route. Biomolecule-encapsulating gels have been characterized using UV-Vis, 29 Si NMR, FTIR spectroscopy and gas adsorption (BET) to investigate chemical interactions of biomolecules with the porous silica network and to examine the extent of sol-gel reactions upon encapsulation. Ethidium bromide intercalation and leach out tests showed that helix conformation of DNA was preserved after encapsulation. For both biomolecules, high water-to-alkoxide ratio promoted water-producing condensation and prevented alcoholic denaturation. NMR and FTIR analyses confirmed high hydraulic reactivity (water adsorption) for more silanol groups-containing DNA and dAMP encapsulated gels than plain silica gel. No chemical binding/interaction occurred between biomolecules and silica network. DNA and dAMP encapsulated silica gelled faster than plain silica due to basic nature of DNA or dAMP containing buffer solutions. DNA was not released from silica gels to aqueous environment up to 9 days. The chemical association between DNA/dAMP and silica host was through phosphate groups and molecular water attached to silanols, acting as a barrier around biomolecules. The helix morphology was found not to be essential for such interaction. BET analyses showed that interconnected, inkbottle-shaped mesoporous silica network was condensed around DNA and dAMP molecules.

  5. Silica-Immobilized Enzyme Reactors; Application to Cholinesterase-Inhibition Studies

    National Research Council Canada - National Science Library

    Luckarift, Heather R; Johnson, Glenn R; Spain, Jim C

    2006-01-01

    ...) using silica-encapsulated equine butyrycholinestearse (BuChE) as a model system. Peptide-mediated silica formation was used to encapsulate BuChE, directly immobilizing the enzyme within a commercial pre-packed column...

  6. Crosslinkable fumed silica-based nanocomposite electrolytes for rechargeable lithium batteries

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yangxing; Yerian, Jeffrey A.; Khan, Saad A.; Fedkiw, Peter S. [Department of Chemical & amp; Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695-7905 (United States)

    2006-10-27

    Electrochemical and rheological properties are reported of composite polymer electrolytes (CPEs) consisting of dual-functionalized fumed silica with methacrylate and octyl groups+low-molecular weight poly(ethylene glycol) dimethyl ether (PEGdm)+lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, lithium imide)+butyl methacrylate (BMA). The role of butyl methacrylate, which aids in formation of a crosslinked network by tethering adjacent fumed silica particles, on rheology and electrochemistry is examined together with the effects of fumed silica surface group, fumed silica weight percent, salt concentration, and solvent molecular weight. Chemical crosslinking of the fumed silica with 20% BMA shows a substantial increase in the elastic modulus of the system and a transition from a liquid-like/flocculated state to an elastic network. In contrast, no change in lithium transference number and only a modest decrease (factor of 2) on conductivity of the CPE are observed, indicating that a crosslinked silica network has minimal effect on the mechanism of ionic transport. These trends suggest that the chemical crosslinks occur on a microscopic scale, as opposed to a molecular scale, between adjacent silica particles and therefore do not impede the segmental mobility of the PEGdm. The relative proportion of the methacrylate and octyl groups on the silica surface displays a nominal effect on both rheology and conductivity following crosslinking although the pre-cure rheology is a function of the surface groups. Chemical crosslinked nanocomposite polymer electrolytes offer significant higher elastic modulus and yield stress than the physical nanocomposite counterpart with a small/negligible penalty of transport properties. The crosslinked CPEs exhibit good interfacial stability with lithium metal at open circuit, however, they perform poorly in cycling of lithium-lithium cells. (author)

  7. Structure and dynamics of a silica melt in neutral confinement

    Science.gov (United States)

    Geske, Julian; Drossel, Barbara; Vogel, Michael

    2017-04-01

    We analyze the effects of spatial confinement on viscous silica using molecular dynamics simulations. For this purpose, we prepare a silica melt in a cylindrical pore, which is produced by pinning appropriate fractions of silicon and oxygen atoms in a bulk system after an equilibration period. In this way, the structure of the confined silica melt remains unaffected, while the confinement has a strong impact on the dynamics. We find that the structural relaxation of viscous silica is slowed down according to a double exponential law when approaching the pore wall. Moreover, we observe that static density correlations exist in the vicinity of the pore wall. Based on these effects, we determine dynamical and structural length scales of the silica melt. Both length scales show a similar increase upon cooling, with values on the order of the next-neighbor distances in the studied temperature range. Interestingly, we find no evidence that the growth of the length scales is affected by a fragile-to-strong transition of the silica melt. This observation casts serious doubts on the relevance of these length scales for the structural relaxation, at least for the studied glass former.

  8. XAFS study on silica glasses irradiated in a nuclear reactor

    International Nuclear Information System (INIS)

    Yoshida, Tomoko; Yoshida, Hisao; Hara, Takanobu; Ii, Tatsuya; Okada, Tomohisa; Tanabe, Tetsuo

    2000-01-01

    X-ray absorption technique (XANES and EXAFS) was applied to study the local structures of silica glasses before and after the irradiation in a nuclear reactor. Although our separate photoluminescence (PL) measurements clearly showed the different aspects about oxygen vacancies in these samples, i.e., at least the B 2β type oxygen-deficient center exists as an intrinsic defect in the fused silica glass while another type B 2α center is formed in the synthesized silica glass, such differences did not directly reflect on the X-ray absorption spectra (XANES and EXAFS). However, the curve-fitting analysis of EXAFS showed that the number of oxygen atoms coordinated to Si relatively increased after the irradiation. This result may indicate the occurrence of the structural relaxation in the irradiated samples, that is, a slightly distorted SiO 4 tetrahedra in silica glasses relaxed to the regular SiO 4 tetrahedra due to the break of some connections between SiO 4 units in the silica glasses. Thus, the X-ray absorption technique gave the important information of the in-reactor irradiated silica glasses which complements the results obtained from PL measurements

  9. On the PEEK composites reinforced by surface-modified nano-silica

    International Nuclear Information System (INIS)

    Lai, Y.H.; Kuo, M.C.; Huang, J.C.; Chen, M.

    2007-01-01

    The nano-sized silica fillers reinforced poly(ether ether ketone) (PEEK) composites were fabricated by means of compression molding technique. The nano-sized silica, measuring 30 nm in size, was firstly modified by surface pretreatment with stearic acid. The performances and properties of the resulting PEEK/SiO 2 nanocomposites were examined in terms of tensile loading, hardness, dynamic mechanical analysis (DMA), thermomechanical analysis (TMA), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The modified nano-silica was seen to disperse more uniformly than the unmodified counterpart. The XRD patterns of the modified silica reinforced PEEK composites reveal a systematic shift toward higher angles, suggesting the smaller d-spacing of the PEEK crystallites. The coefficient of thermal expansion (CTE) becomes lowered when the content of the nano-silica increases. Furthermore, the CTE of the modified silica filled PEEK nanocomposites shows the higher CTE values. A logic model is proposed. The increment of the dynamic modulus for the PEEK nanocomposites is up to 40% at elevated temperatures from 100 to 250 deg. C, indicating the apparent improvement of elevated temperature mechanical properties

  10. Fabrication and optical characterization of gold-infiltrated silica opals

    International Nuclear Information System (INIS)

    Li Wenjiang; Sun Gang; Tang Fangqiong; Tam, W.Y.; Li Jensen; Chan, C T; Sheng Ping

    2005-01-01

    We report the fabrication of metal-infiltrated silica opals for optical studies. Highly mono-dispersed silica microspheres are fabricated and assembled by a force packing method to form opals with large domain sizes. The opals are then infiltrated with gold by an electroplating technique. The optical properties of the infiltrated opals in the visible range are studied and model calculations based on a multiple-scattering formalism are used to interpret the experimental results. The calculated position of the directional gap of the silica opal agrees very well with experimental observation. We found that the optical properties of the infiltrated sample can be explained using a model system in which the voids in the silica opal are partially filled with Au and the surface of the slab is covered with a thin layer of Au

  11. Silica from triethylammonium tris (oxalato) silicate (IV) thermal decomposition

    International Nuclear Information System (INIS)

    Ferracin, L.C.; Ionashiro, M.; Davolos, M.R.

    1990-01-01

    Silica can be obtained from differents precursors by differents methods. In this paper it has been investigated the thermal decomposition of triethylammonium tris (oxalato) silicate (IV) to render silica. Among the trisoxalato-complexes of silicon preparation methods reviewed it has been used the Bessler's one with the reflux adaptaded in microwave oven. Thermal decomposition analysis of the compound has been made by TG-DTG and DTA curves. Silica powders obtained and heated between 300 to 900 0 C in a oven were characterized by infrared vibrational spectroscopy, X-ray powder difraction and nitrogen adsorption isotherm (BET). The triethylammonium tris (oxalato) silicate (IV) thermal decomposition takes place at 300 0 C and the silica powder obtained is non cristalline with impurities that are eliminated with heating at 400 0 C. (author) [pt

  12. SR-B1 Is a Silica Receptor that Mediates Canonical Inflammasome Activation

    Directory of Open Access Journals (Sweden)

    Misato Tsugita

    2017-01-01

    Full Text Available The inhalation of silica dust is associated with fibrosis and lung cancer, which are triggered by macrophage inflammatory responses; however, how macrophages recognize silica remains largely unknown. Here, we identify by functional expression cloning the class B scavenger receptor SR-B1 as a silica receptor. Through an extracellular α-helix, both mouse and human SR-B1 specifically recognized amorphous and crystalline silica, but not titanium dioxide nanoparticles, latex nanoparticles, or monosodium urate crystals, although all particles exhibited negative surface potentials. Genetic deletion of SR-B1 and masking of SR-B1 by monoclonal antibodies showed that SR-B1-mediated recognition of silica is associated with caspase-1-mediated inflammatory responses in mouse macrophages and human peripheral blood monocytes. Furthermore, SR-B1 was involved in silica-induced pulmonary inflammation in mice. These results indicate that SR-B1 is a silica receptor associated with canonical inflammasome activation.

  13. Agricultural waste as a source for the production of silica nanoparticles.

    Science.gov (United States)

    Vaibhav, Vineet; Vijayalakshmi, U; Roopan, S Mohana

    2015-03-15

    The major interest of the paper deals with the extraction of silica from four natural sources such as rice husk, bamboo leaves, sugarcane bagasse and groundnut shell. These waste materials in large quantities can create a serious environmental problem. Hence, there is a need to adopt proper strategy to reduce the waste. In the present investigation, all the waste materials are subjected to moisture removal in a hot plate and sintered at 900°C for 7 h. The sintered powder was treated with 1 M NaOH to form sodium silicate and then with 6M H2SO4 to precipitate silica. The prepared silica powders were characterized by FT-IR, XRD and SEM-EDAX analysis. The silica recovered from different sources was found to vary between 52% and 78%. Magnesium substituted silica was formed from the groundnut waste and further treatment is required to precipitate silica. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Studies on silica sol-clay particle interactions by small-angle neutron scattering

    International Nuclear Information System (INIS)

    Moini, A.; Pinnavaia, T.J.; Michigan State Univ., East Lansing; Thiyagarajan, P.; White, J.W.

    1988-01-01

    SANS data were collected on a series of hydrolyzed silica and silica-clay complexes prepared from a 40 A silica sol and aqueous suspensions of Na + montmorillonite. The hydrolyzed silica product showed a peak centered at Q=0.0856 A -1 corresponding to a distance of 73 A between the sol particles. For such an evaporated gel in which the particles are in close contact, this distance is expected to be very close to the particle diameter indicating partial aggregation of the original spheres. A similar feature was observed in the SANS data for silica-clay products indicating the presence of some unintercalated silica. The intensity of this scattering was found to be dependent on the silica:clay ratio and the reaction time. The SANS data in the region from Q=0.006 to 0.025 A -1 were characteristic of clay scattering and exhibited a power-law behavior. The change in the slope of this curve upon reaction of the clay with the silica sol was interpreted in terms of a separation of clay platelets caused by a binding interaction with the sol particles. (orig.)

  15. Synthesis and Properties of Carbon Nanotube-Grafted Silica Nanoarchitecture-Reinforced Poly(Lactic Acid

    Directory of Open Access Journals (Sweden)

    Yao-Wen Hsu

    2017-07-01

    Full Text Available A novel nanoarchitecture-reinforced poly(lactic acid (PLA nanocomposite was prepared using multi-walled carbon nanotube (MWCNT-grafted silica nanohybrids as reinforcements. MWCNT-grafted silica nanohybrids were synthesized by the generation of silica nanoparticles on the MWCNT surface through the sol-gel technique. This synthetic method involves organo-modified MWCNTs that are dispersed in tetrahydrofuran, which incorporates tetraethoxysilane that undergoes an ultrasonic sol-gel process. Gelation yielded highly dispersed silica on the organo-modified MWCNTs. The structure and properties of the nanohybrids were established using 29Si nuclear magnetic resonance, Raman spectroscopy, wide-angle X-ray diffraction, thermogravimetric analysis, and transmission electron microscopy. The resulting MWCNT nanoarchitectures were covalently assembled into silica nanoparticles, which exhibited specific and controllable morphologies and were used to reinforce biodegradable PLA. The tensile strength and the heat deflection temperature (HDT of the PLA/MWCNT-grafted silica nanocomposites increased when the MWCNT-grafted silica was applied to the PLA matrix; by contrast, the surface resistivity of the PLA/MWCNT-grafted silica nanocomposites appeared to decline as the amount of MWCNT-grafted silica in the PLA matrix increased. Overall, the reinforcement of PLA using MWCNT-grafted silica nanoarchitectures was efficient and improved its mechanical properties, heat resistance, and electrical resistivity.

  16. In situ polymerization of L-Lactide in the presence of fumed silica

    International Nuclear Information System (INIS)

    Prebe, A.; Alcouffe, P.; Cassagnau, Ph.; Gerard, J.F.

    2010-01-01

    Chemiorheology, i.e. rheological changes during the polymerization, of a biosourced monomer, i.e. L-Lactide, containing fumed silica have been studied. For that purpose, the reaction was proceeded in situ between the plates of a dynamic rheometer. The polymerization kinetics was followed from the variation of the complex shear modulus versus reaction time. Moreover, at temperatures lower than the crystallization temperature, it was possible to follow the crystallization process while the polymerization takes place. Adding fumed silica particles into the monomer leads to the formation of a physical (percolated) network from particle-particle interactions, i.e. silica, in the L-Lactide probably hydrophilic interactions. The gel-like structure was kept while the polymerization as long as the strain remains low indicating that the silica particle network remains weak. Furthermore, the mechanism of the break down of the gel structure under large deformation as well as the recovery was discussed. It seems that the non-linearity effect of the nanocomposites stems in the silica inter-particle interactions. It was found that silica particles do not have any effect on the temperature of crystallization - molar mass relation but could act as nucleating agent. In situ polymerization of L-Lactide in the presence of 5 wt.% of modified fumed silica was carried out in a reactor. It was found that fumed hydrophilic silica leaded to a microcomposite with highly dense agglomerates in the polymer matrix whereas with a less hydrophilic silica it was possible to decrease the size of the agglomerates increasing the dispersion. The finest dispersion state was achieved with the 'initiating' functionalized silica leading to a 'grafting from' polymerization of the L-Lactide. Such functionalized silica leads to a nanoscale dispersion in a one-step bulk polymerization with only a few small agglomerates.

  17. Retention of U(VI) onto silica in presence of model organic molecules

    International Nuclear Information System (INIS)

    Pham, T.T.H.; Mercier-Bion, F.; Drot, R.; Lagarde, G.; Simoni, E.; Lambert, J.

    2008-01-01

    It is well-known that the organic matter influences the retention of ions onto mineral surfaces. However, the major part of concerned studies implies humic substances and complex solids. Another approach for identifying the sorption mechanisms is possible by studying simpler solids than those present in natural medium. So, silica is chosen as mineral surface because of its abundance in soils and of the presence of Si-O groups in clayey minerals. Uranium (VI) is selected as cation. Simple organic molecules like acetic (one carboxylic group) and oxalic (two carboxylic functions) acids are considered as models of the natural organic matter for understanding their role in the retention of U(VI) onto powders and slides of silica. Binary (organics/silica, U(VI)/silica) and ternary systems (organics/silica/U(VI)) are studied by complementary approaches. Sorption edges as function of pH are obtained by liquid scintillation methods and capillary electrophoresis. Different spectroscopic techniques are used to deduce the interactions between the organic matter and U(VI) sorbed onto the silica whose: Time-Resolved Laser induced Fluorescence Spectroscopy (TRLFS), X-ray Photoelectron Spectroscopy (XPS), Nuclear Microprobe Analysis (NMA). The results of the effect of these model organic molecules onto the U(VI) retention showed a good agreement between the different techniques. Concerning the acetic acid, there are not differences in the sorption percentages of uranyl (see the figure). All these results indicate that the uranyl-acetate complexes stay in the aqueous solution rather than sorbing onto the silica. On the contrary, oxalic acid influences the sorption of U(VI) onto the silica surface. The sorption percentage of U(VI) in the ternary system (oxalic acid/silica/U(VI)) is lower than the binary system (U(VI)/silica) (see the figure). So, the presence of oxalic acid decreases the sorption of U(VI) onto the silica surface. (authors)

  18. In situ polymerization of L-Lactide in the presence of fumed silica

    Energy Technology Data Exchange (ETDEWEB)

    Prebe, A. [Universite de Lyon, F-69361, Lyon (France); CNRS, UMR 5223, Ingenierie des Materiaux Polymeres, F-69622, Villeurbanne (France); Universite Claude Bernard Lyon 1, F-69622, Villeurbanne (France); INSA Lyon, F-69621, Villeurbanne (France); Alcouffe, P. [Universite de Lyon, F-69361, Lyon (France); CNRS, UMR 5223, Ingenierie des Materiaux Polymeres, F-69622, Villeurbanne (France); Universite Claude Bernard Lyon 1, F-69622, Villeurbanne (France); Cassagnau, Ph., E-mail: philippe.cassagnau@univ-lyon1.fr [Universite de Lyon, F-69361, Lyon (France); CNRS, UMR 5223, Ingenierie des Materiaux Polymeres, F-69622, Villeurbanne (France); Universite Claude Bernard Lyon 1, F-69622, Villeurbanne (France); Gerard, J.F. [Universite de Lyon, F-69361, Lyon (France); CNRS, UMR 5223, Ingenierie des Materiaux Polymeres, F-69622, Villeurbanne (France); INSA Lyon, F-69621, Villeurbanne (France)

    2010-11-01

    Chemiorheology, i.e. rheological changes during the polymerization, of a biosourced monomer, i.e. L-Lactide, containing fumed silica have been studied. For that purpose, the reaction was proceeded in situ between the plates of a dynamic rheometer. The polymerization kinetics was followed from the variation of the complex shear modulus versus reaction time. Moreover, at temperatures lower than the crystallization temperature, it was possible to follow the crystallization process while the polymerization takes place. Adding fumed silica particles into the monomer leads to the formation of a physical (percolated) network from particle-particle interactions, i.e. silica, in the L-Lactide probably hydrophilic interactions. The gel-like structure was kept while the polymerization as long as the strain remains low indicating that the silica particle network remains weak. Furthermore, the mechanism of the break down of the gel structure under large deformation as well as the recovery was discussed. It seems that the non-linearity effect of the nanocomposites stems in the silica inter-particle interactions. It was found that silica particles do not have any effect on the temperature of crystallization - molar mass relation but could act as nucleating agent. In situ polymerization of L-Lactide in the presence of 5 wt.% of modified fumed silica was carried out in a reactor. It was found that fumed hydrophilic silica leaded to a microcomposite with highly dense agglomerates in the polymer matrix whereas with a less hydrophilic silica it was possible to decrease the size of the agglomerates increasing the dispersion. The finest dispersion state was achieved with the 'initiating' functionalized silica leading to a 'grafting from' polymerization of the L-Lactide. Such functionalized silica leads to a nanoscale dispersion in a one-step bulk polymerization with only a few small agglomerates.

  19. Comparison of Effect of Metakaolin and silica Fume on Fly Ash Concrete Performance

    Directory of Open Access Journals (Sweden)

    Hou Yunfen

    2016-01-01

    Full Text Available Silica fume is a common mineral admixture used in HSC and HPC, but being its high price and shrinkage in concrete, its usage is under restrictions. As a new mineral admixture, metakaolin gets more and more attention. In order to compare the difference between silica fume and metakaolin, the effects of metakaolin and silica fume on concrete workability, compressive strength, and chloride penetration resistance are studied. It shows that incorporating with fly ash together, silica fume reduces the slump extension, but metakaolin can increases it; silica fume can increases early strength more than metakaolin can, but it isn’t useful for later and long-time strength; metakaolin not only can increase early strength, but also can improve long-time strength. Silica fume and metakaolin can increase the chloride penetration resistance. As a new mineral additive, metakaolin can play a role in concrete which silica fume does, even much better than silica fume.

  20. Amorphous silica maturation in chemically weathered clastic sediments

    Science.gov (United States)

    Liesegang, Moritz; Milke, Ralf; Berthold, Christoph

    2018-03-01

    A detailed understanding of silica postdepositional transformation mechanisms is fundamental for its use as a palaeobiologic and palaeoenvironmental archive. Amorphous silica (opal-A) is an important biomineral, an alteration product of silicate rocks on the surface of Earth and Mars, and a precursor material for stable silica phases. During diagenesis, amorphous silica gradually and gradationally transforms to opal-CT, opal-C, and eventually quartz. Here we demonstrate the early-stage maturation of several million year old opal-A from deeply weathered Early Cretaceous and Ordovician sedimentary rocks of the Great Artesian Basin (central Australia). X-ray diffraction, scanning electron microscopy, and electron probe microanalyses show that the mineralogical maturation of the nanosphere material is decoupled from its chemical properties and begins significantly earlier than micromorphology suggests. Non-destructive and locally highly resolved X-ray microdiffraction (μ-XRD2) reveals an almost linear positive correlation between the main peak position (3.97 to 4.06 Å) and a new asymmetry parameter, AP. Heating experiments and calculated diffractograms indicate that nucleation and growth of tridymite-rich nanodomains induce systematic peak shifts and symmetry variations in diffraction patterns of morphologically juvenile opal-A. Our results show that the asymmetry parameter traces the early-stage maturation of amorphous silica, and that the mineralogical opal-A/CT stage extends to smaller d-spacings and larger FWHM values than previously suggested.

  1. Silica from Ash

    Indian Academy of Sciences (India)

    management, polymer composites and chemical process design. Figure 1 Difference in color of the ash ... The selection of ash is important as the quality of ash determines the total amount as well as quality of silica recoverable Ash which has undergone maximum extent of combustion is highly desirable as it contains ...

  2. Waste Water for Power Generation via Energy Efficient Selective Silica Separations

    Energy Technology Data Exchange (ETDEWEB)

    Nenoff, Tina M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brady, Patrick Vane [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sasan, Koroush [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Paap, Scott M. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Heimer, Brandon Walter [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Krumhansl, James L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Howe, Kerry [Univ. of New Mexico, Albuquerque, NM (United States); Stoll, Zachary [Univ. of New Mexico, Albuquerque, NM (United States); Stomp, James [Univ. of New Mexico, Albuquerque, NM (United States)

    2017-09-01

    Silica is ubiquitous in produced and industrial waters, and plays a major disruptive role in water recycle. Herein we have investigated the use of mixed oxides for the removal of silica from these waters, and their incorporation into a low cost and low energy water purification process. High selectivity hydrotalcite (HTC, (Mg6Al2(OH)16(CO3)•4H2O)), is combined in series with high surface area active alumina (AA, (Al2O3)) as the dissolved silica removal media. Batch test results indicated that combined HTC/AA is a more effective method for removing silica from industrial cooling tower wasters (CTW) than using HTC or AA separately. The silica uptake via ion exchange on the mixed oxides was confirmed by Fourier transform infrared (FTIR), and Energy dispersive spectroscopy (EDS). Furthermore, HTC/AA effectively removes silica from CTW even in the presence of large concentrations of competing anions, such as Cl-, NO3- HCO3-, CO32- and SO42-. Similar to batch tests, Single Path Flow Through (SPFT) tests with sequential HTC/AA column filtration has very high silica removal too. Technoeconomic Analysis (TEA) was simultaneously performed for cost comparisons to existing silica removal technologies.

  3. Interactions between Food Additive Silica Nanoparticles and Food Matrices

    Directory of Open Access Journals (Sweden)

    Mi-Ran Go

    2017-06-01

    Full Text Available Nanoparticles (NPs have been widely utilized in the food industry as additives with their beneficial characteristics, such as improving sensory property and processing suitability, enhancing functional and nutritional values, and extending shelf-life of foods. Silica is used as an anti-caking agent to improve flow property of powered ingredients and as a carrier for flavors or active compounds in food. Along with the rapid development of nanotechnology, the sizes of silica fall into nanoscale, thereby raising concerns about the potential toxicity of nano-sized silica materials. There have been a number of studies carried out to investigate possible adverse effects of NPs on the gastrointestinal tract. The interactions between NPs and surrounding food matrices should be also taken into account since the interactions can affect their bioavailability, efficacy, and toxicity. In the present study, we investigated the interactions between food additive silica NPs and food matrices, such as saccharides, proteins, lipids, and minerals. Quantitative analysis was performed to determine food component-NP corona using HPLC, fluorescence quenching, GC-MS, and ICP-AES. The results demonstrate that zeta potential and hydrodynamic radius of silica NPs changed in the presence of all food matrices, but their solubility was not affected. However, quantitative analysis on the interactions revealed that a small portion of food matrices interacted with silica NPs and the interactions were highly dependent on the type of food component. Moreover, minor nutrients could also affect the interactions, as evidenced by higher NP interaction with honey rather than with a simple sugar mixture containing an equivalent amount of fructose, glucose, sucrose, and maltose. These findings provide fundamental information to extend our understanding about the interactions between silica NPs and food components and to predict the interaction effect on the safety aspects of food

  4. Quantification of Residual Stress from Photonic Signatures of Fused Silica

    Science.gov (United States)

    Cramer, K. Elliott; Hayward, Maurice; Yost, William E.

    2013-01-01

    A commercially available grey-field polariscope (GFP) instrument for photoelastic examination is used to assess impact damage inflicted upon the outer-most pane of Space Shuttle windows made from fused silica. A method and apparatus for calibration of the stress-optic coefficient using four-point bending is discussed. The results are validated on known material (acrylic) and are found to agree with literature values to within 6%. The calibration procedure is then applied to fused-silica specimens and the stress-optic coefficient is determined to be 2.43 +/- 0.54 x 10(exp -12)/Pa. Fused silica specimens containing impacts artificially made at NASA's Hypervelocity Impact Technology Facility (HIT-F), to simulate damage typical during space flight, are examined. The damage sites are cored from fused silica window carcasses and examined with the GFP. The calibrated GFP measurements of residual stress patterns surrounding the damage sites are presented. Keywords: Glass, fused silica, photoelasticity, residual stress

  5. Toxicity of silica nanoparticles and the effect of protein corona

    DEFF Research Database (Denmark)

    Foldbjerg, Rasmus; Jespersen, Lars Vesterby; Wang, Jing

    2010-01-01

      The cytotoxicity of silica nanoparticles (NPs) was investigated in the human lung cell line, A549. Silica NPs of different sizes (DLS size; 16-42 nm) were used to determine appropriate dose metrics whereas the effect of the NP corona was tested by coating the NPs with bovine serum albumin (BSA......). The NPs were characterized by TEM and DLS as monodisperse and non-aggregated in solution and the NP suspensions were free of metal and endotoxin impurities as tested by ICP-MS and the LAL test. Cellular uptake and binding of the silica NPs was indirectly assessed by flow cytometry side scatter and SEM...... upon silica NP exposure. The silica NP surface area was found to be the best dose metric for predicting cytotoxicity and IL-8 release. Generally, the NPs were only cytotoxic at high concentrations and BSA-coating of the NPs significantly decreased the cytotoxicity and cellular IL-8 secretion. All...

  6. Decomposition of silica-alumina ores of Afghanistan by sulfuric acid

    International Nuclear Information System (INIS)

    Khomidi, A.K.; Mamatov, E.D.

    2016-01-01

    Present article is devoted to decomposition of silica-alumina ores of Afghanistan by sulfuric acid. Physicochemical properties of initial silica-alumina ores were studied by means of X-ray phase, differential thermal and silicate analysis. The influence of temperature, process duration and acid concentration on extraction rate of valuable components was considered. The optimal conditions of decomposition of silica-alumina ores of Afghanistan by sulfuric acid were proposed.

  7. Characteristics of waste automotive glasses as silica resource in ferrosilicon synthesis.

    Science.gov (United States)

    Farzana, Rifat; Rajarao, Ravindra; Sahajwalla, Veena

    2016-02-01

    This fundamental research on end-of-life automotive glasses, which are difficult to recycle, is aimed at understanding the chemical and physical characteristics of waste glasses as a resource of silica to produce ferrosilicon. Laboratory experiments at 1550°C were carried out using different automotive glasses and the results compared with those obtained with pure silica. In situ images of slag-metal separation showed similar behaviour for waste glasses and silica-bearing pellets. Though X-ray diffraction (XRD) showed different slag compositions for glass and silica-bearing pellets, formation of ferrosilicon was confirmed. Synthesized ferrosilicon alloy from waste glasses and silica were compared by Raman, X-ray photoelectron spectroscopy and scanning electron microscopy (SEM) analysis. Silicon concentration in the synthesized alloys showed almost 92% silicon recovery from the silica-bearing pellet and 74-92% silicon recoveries from various waste glass pellets. The polyvinyl butyral (PVB) plastic layer in the windshield glass decomposed at low temperature and did not show any detrimental effect on ferrosilicon synthesis. This innovative approach of using waste automotive glasses as a silica source for ferrosilicon production has the potential to create sustainable pathways, which will reduce specialty glass waste in landfill. © The Author(s) 2015.

  8. Radiation resistance of GeO2-doped silica core optical fibers

    International Nuclear Information System (INIS)

    Shibata, Shuichi; Nakahara, Motohiro; Omori, Yasuharu

    1985-01-01

    Effects of hlogen addition to silica glass on the loss in optical fibers are examined by using halogen-free, chlorine-containing and fluorine-containing GeO 2 -doped silica core optical fibers. Measurements are made for dependence of induced loss in these optical fibers on various factors such as wavelength and total dose of gamma radiation as well as GeO 2 content. Ultraviolet absorption spectra are also observed. In addition, effects of halogens added to pure silica fibers are considered on the basis of Raman spectra of three different optical fibers (pure, F-doped, and F- and GeO 2 -codoped silica core). Thus, it is concluded that (1) addition of halogens (F and Cl) serves to decrease GeO defects and Ge(3) defects in GeO 2 -doped silica optical fibers ; (2) addition of halogens suppresses the increase in loss in GeO 2 -doped silica optical fibers induced by gamma radiation ; and (3) there are close relations between the increase in loss induced by gamma radiation and defects originally existing in the fibers. Effects of halogens added to GeO 2 -doped and pure silica optical fibers can be explained on the basis of the latter relations. (Nogami, K.)

  9. Spectrophotometric determination of silica in water with Hach equipment

    International Nuclear Information System (INIS)

    Acosta L, E.

    1992-06-01

    The method for the determination of the silica element in water, demineralized water, raw waters, laundry waters, waters treated with ion exchange resins and sea waters using the indicated technique in the operation manual of the Hach equipment with a DR/3 spectrophotometer is described. This method covers the determination of the silica element in the interval from 0 to 1.5 mg/l on 50 ml. of base sample. These limits its can be variable if the size of the used aliquot one is changed for the final determination of the silica element. (Author)

  10. Respiratory health effects of exposure to crystalline silica epidemiology.

    CSIR Research Space (South Africa)

    Hnzido, E

    1999-01-01

    Full Text Available The present report describes two additional studies of exposure-response relationship between respiratory disease and silica dust in gold mines. Section 3 describes a study of pulmonary tuberculosis in relation to silica dust, and section 4...

  11. Proton Conductivity of Nafion/Ex-Situ Sulfonic Acid-Modified Stöber Silica Nanocomposite Membranes As a Function of Temperature, Silica Particles Size and Surface Modification

    Science.gov (United States)

    Muriithi, Beatrice; Loy, Douglas A.

    2016-01-01

    The introduction of sulfonic acid modified silica in Nafion nanocomposite membranes is a good method of improving the Nafion performance at high temperature and low relative humidity. Sulfonic acid-modified silica is bifunctional, with silica phase expected to offer an improvement in membranes hydration while sulfonic groups enhance proton conductivity. However, as discussed in this paper, this may not always be the case. Proton conductivity enhancement of Nafion nanocomposite membranes is very dependent on silica particle size, sometimes depending on experimental conditions, and by surface modification. In this study, Sulfonated Preconcentrated Nafion Stober Silica composites (SPNSS) were prepared by modification of Stober silica particles with mercaptopropyltriethoxysilane, dispersing the particles into a preconcentrated solution of Nafion, then casting the membranes. The mercapto groups were oxidized to sulfonic acids by heating the membranes in 10 wt % hydrogen peroxide for 1 h. At 80 °C and 100% relative humidity, a 20%–30% enhancement of proton conductivity was only observed when sulfonic acid modified particle less than 50 nm in diameter were used. At 120 °C, and 100% humidity, proton conductivity increased by 22%–42% with sulfonated particles with small particles showing the greatest enhancement. At 120 °C and 50% humidity, the sulfonated particles are less efficient at keeping the membranes hydrated, and the composites underperform Nafion and silica-Nafion nanocomposite membranes. PMID:26828525

  12. Nanostructured Mesoporous Silicas for Bone Tissue Regeneration

    Directory of Open Access Journals (Sweden)

    Isabel Izquierdo-Barba

    2008-01-01

    Full Text Available The research on the development of new biomaterials that promote bone tissue regeneration is receiving great interest by the biomedical scientific community. Recent advances in nanotechnology have allowed the design of materials with nanostructure similar to that of natural bone. These materials can promote new bone formation by inducing the formation of nanocrystalline apatites analogous to the mineral phase of natural bone onto their surfaces, i.e. they are bioactive. They also stimulate osteoblast proliferation and differentiation and, therefore, accelerate the healing processes. Silica-based ordered mesoporous materials are excellent candidates to be used as third generation bioceramics that enable the adsorption and local control release of biological active agents that promote bone regeneration. This local delivery capability together with the bioactive behavior of mesoporous silicas opens up promising expectations in the bioclinical field. In this review, the last advances in nanochemistry aimed at designing and tailoring the chemical and textural properties of mesoporous silicas for biomedical applications are described. The recent developed strategies to synthesize bioactive glasses with ordered mesopore arrangements are also summarized. Finally, a deep discussion about the influence of the textural parameters and organic modification of mesoporous silicas on molecules adsorption and controlled release is performed.

  13. Crystallization of biogenic hydrous amorphous silica

    Science.gov (United States)

    Kyono, A.; Yokooji, M.; Chiba, T.; Tamura, T.; Tuji, A.

    2017-12-01

    Diatom, Nitzschia cf. frustulum, collected from Lake Yogo, Siga prefecture, Japan was cultured in laboratory. Organic components of the diatom cell were removed by washing with acetone and sodium hypochlorite. The remaining frustules were studied by SEM-EDX, FTIR spectroscopy, and synchrotron X-ray diffraction. The results showed that the spindle-shaped morphology of diatom frustule was composed of hydrous amorphous silica. Pressure induced phase transformation of the diatom frustule was investigated by in situ Raman spectroscopic analysis. With exposure to 0.3 GPa at 100 oC, Raman band corresponding to quartz occurred at ν = 465 cm-1. In addition, Raman bands known as a characteristic Raman pattern of moganite was also observed at 501 cm-1. From the integral ratio of Raman bands, the moganite content in the probed area was estimated to be approximately 50 wt%. With the pressure and temperature effect, the initial morphology of diatom frustule was completely lost and totally changed to a characteristic spherical particle with a diameter of about 2 mm. With keeping the compression of 5.7 GPa at 100 oC, a Raman band assignable to coesite appeared at 538 cm-1. That is, with the compression and heating, the hydrous amorphous silica can be readily crystallized into quartz, moganite, and coesite. The first-principles calculations revealed that a disiloxane molecule stabilized in a trans configuration is twisted 60o and changed into the cis configuration with a close approach of water molecule. It is therefore a reasonable assumption that during crystallization of hydrous amorphous silica, the Si-O-Si bridging unit with the cis configuration would survive as a structural defect and then crystallized into moganite by keeping the geometry. This hypothesis is adaptable to the phase transformation from hydrous amorphous silica to coesite as well, because coesite has the four-membered rings and easily formed from the hydrous amorphous silica under high pressure and high

  14. Controlling the synthesis conditions for silica nanosphere from semi-burned rice straw

    International Nuclear Information System (INIS)

    Hessien, M.M.; Rashad, M.M.; Zaky, R.R.; Abdel-Aal, E.A.; El-Barawy, K.A.

    2009-01-01

    Silica nanoparticles have been prepared through dissolution-precipitation process from rice straw ash (RSA) for different electronic applications. The dissolution of silica from RSA was carried out using alkali leaching process by sodium hydroxide. The precipitation of silica from the produced sodium silicate solution was carried out using sulphuric acid at pH 7. The factors affecting the precipitation process of the sodium silicate solution of dissociated RSA; such as; sodium silicate concentration, sulfuric acid concentration and addition of anionic surfactant (sodium dodecyl sulfate, SDS) on the particle size of the precipitated silica were studied. X-ray diffraction (XRD), X-ray fluorescence (XRF), specific surface area S BET and transmission electron microscope (TEM) have been used for the characterization of the produced nano-silica. The results showed that the optimum conditions of the dissolution efficiency of the silica of about 99% was achieved at 100 deg. C for 4 h, and NaOH/SiO 2 molar ratio three. The particle size of the precipitated silica gel was decreased with increasing Na 2 SiO 3 and SDS concentrations, while H 2 SO 4 concentration had insignificant effect. Particle size of about 16 nm can be achieved at 30% Na 2 SiO 3 , 4% H 2 SO 4 and 200 ppm SDS. The produced silica had 99.93% purity, amorphous and nanosphere particles with narrow size distribution. The produced silica can be used in many applications especially for chemical mechanical polishing (CMP) slurries for semiconductors industries.

  15. On the improvement of mechanical properties of monolithic silica aerogels (for transparent insulating material); Silica aerogel (tomei dannetsu zairyo) kyodo no kaizen ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Tajiri, K; Igarashi, K; Tanemura, S [National Industrial Research Institute of Nagoya, Nagoya (Japan)

    1997-11-25

    Study was made on improvement of the strength of silica aerogel as transparent insulating material. Silica aerogel is a low-density porous material with high heat insulation and transparency. To develop a insulating material with high transparency, monolithic silica aerogel was studied. For direct use of it for windows, its strength improvement was attempted. The aerogel was prepared by supercritical drying (alcohol or CO2) of silica wet gel obtained by hydrolysis and condensation of silicon alkoxide solution. To prepare the aerogel bonded on plate glass for strength improvement, the aerogel was bonded to alkoxide by exposing active silanol radical through F-etching of plate glass surface. However, to obtain the practical large-area bonded aerogel, shrinkage control of the aerogel in supercritical drying was necessary. Addition of Laponite into a silica network for strength improvement by polymer increased the bending strength by 50%. Although some reduction of its transparency was observed because of clouding, its heat insulation was stable. Further strength improvement is necessary for its practical use. 5 figs., 1 tab.

  16. Silica micro- and nanoparticles reduce the toxicity of surfactant solutions.

    Science.gov (United States)

    Ríos, Francisco; Fernández-Arteaga, Alejandro; Fernández-Serrano, Mercedes; Jurado, Encarnación; Lechuga, Manuela

    2018-04-20

    In this work, the toxicity of hydrophilic fumed silica micro- and nanoparticles of various sizes (7 nm, 12 nm, and 50 μm) was evaluated using the luminescent bacteria Vibrio fischeri. In addition, the toxicity of an anionic surfactant solution (ether carboxylic acid), a nonionic surfactant solution (alkyl polyglucoside), and a binary (1:1) mixture of these solutions all containing these silica particles was evaluated. Furthermore, this work discusses the adsorption of surfactants onto particle surfaces and evaluates the effects of silica particles on the surface tension and critical micellar concentration (CMC) of these anionic and nonionic surfactants. It was determined that silica particles can be considered as non-toxic and that silica particles reduce the toxicity of surfactant solutions. Nevertheless, the toxicity reduction depends on the ionic character of the surfactants. Differences can be explained by the different adsorption behavior of surfactants onto the particle surface, which is weaker for nonionic surfactants than for anionic surfactants. Regarding the effects on surface tension, it was found that silica particles increased the surface activity of anionic surfactants and considerably reduced their CMC, whereas in the case of nonionic surfactants, the effects were reversed. Copyright © 2018 Elsevier B.V. All rights reserved.

  17. Hydrophobic silica nanoparticles as reinforcing filler for poly (lactic acid polymer matrix

    Directory of Open Access Journals (Sweden)

    Pilić Branka M.

    2016-01-01

    Full Text Available Properties of poly (lactic acid (PLA and its nanocomposites, with silica nanoparticles (SiO2, as filler were investigated. Neat PLA films and PLA films with different percentage of hydrophobic fumed silica nanoparticles (0.2, 0.5, 1, 2, 3 and 5 wt. % were prepared by solution casting method. Several tools were used to characterize the influence of different silica content on crystalline behavior, and thermal, mechanical and barrier properties of PLA/SiO2 nanocomposites. Results from scanning electron microscope (SEM showed that the nanocomposite preparation and selection of specific hydrophobic spherical nano filler provide a good dispersion of the silica nanoparticles in the PLA matrix. Addition of silica nanoparticles improved mechanical properties, the most significant improvement being observed for lowest silica content (0.2wt.%. Barrier properties were improved for all measured gases at all loadings of silica nanoparticles. The degree of crystallinity for PLA slightly increased by adding 0.2 and 0.5 wt. % of nano filler. [Projekat Ministarstva nauke Republike Srbije, br. III46001

  18. AMINO AND MERCAPTO-SILICA HYBRID FOR Cd(II ADSORPTION IN AQUEOUS SOLUTION

    Directory of Open Access Journals (Sweden)

    Buhani Buhani

    2010-06-01

    Full Text Available Modification of silica gel with 3-aminopropyltrimethoxysilane and 3-mercaptopropyltrimethoxysilane through sol-gel technique producing amino-silica hybrid (HAS and mercapto-silica hybrid (HMS, respectively, has been carried out using tetraethylorthosilicate (TEOS as silica source. The adsorbents were characterized using infrared spectroscopy (IR, and X-ray energy dispersion spectroscopy (EDX. Adsorption of Cd(II individually as well as its binary mixture with Ni(II, Cu(II, and Zn(II in solution was performed in a batch system. Adsorption capacities of Cd(II ion on adsorbent of silica gel (SG, HAS, and HMS are 86.7, 256.4 and 319.5 μmol/g with the adsorption energies are 24.60, 22.61 and 23.15 kJ/mol, respectively. Selectivity coefficient (α of Cd(II ion toward combination of Cd(II/Ni(II, Cd(II/Cu(II, and Cd(II/Zn(II ions on HAS adsorbent is relatively smaller than those on HMS adsorbent which has α > 1.   Keywords: adsorption, amino-silica hybrid, mercapto-silica

  19. Influence of Nano Silica on Alkyd Films

    DEFF Research Database (Denmark)

    Nikolic, Miroslav

    . The present work centers on the reinforcement of alkyd binders emulsified in water and used in exterior wood coatings with nano silica. Raman spectroscopy was used throughout the study to maintain the reproducibility of results as it was found that colloidal nano silica can increase or decrease the speed...... of alkyd curing affecting the tested mechanical properties. Hydrophilic, colloidal nano silica was seen to have limited effect in improving the mechanical properties due to problems in properly dispersing and attaining good surface interactions with the hydrophobic alkyd polymer. Efforts in increasing...... the interactions with the alkyd polymer while keeping the nano filler stable in the water phase did not show further improvements of mechanical properties. The best results in respect to mechanical properties, as measured under static and dynamic loading, were obtained with the use of hexamethyldisilazane treated...

  20. Mesoporous Structure Control of Silica in Room-Temperature Synthesis under Basic Conditions

    Directory of Open Access Journals (Sweden)

    Jeong Wook Seo

    2015-01-01

    Full Text Available Various types of mesoporous silica, such as continuous cubic-phase MCM-48, hexagonal-phase MCM-41, and layer-phase spherical silica particles, have been synthesized at room temperature using cetyltrimethylammonium bromide as a surfactant, ethanol as a cosurfactant, tetraethyl orthosilicate as a silica precursor, and ammonia as a condensation agent. Special care must be taken both in the filtering of the resultant solid products and in the drying process. In the drying process, further condensation of the silica after filtering was induced. As the surfactant and cosurfactant concentrations in the reaction mixture increased and the NH3 concentration decreased, under given conditions, continuous cubic MCM-48 and layered silica became the dominant phases. A cooperative synthesis mechanism, in which both the surfactant and silica were involved in the formation of mesoporous structures, provided a good explanation of the experimental results.

  1. Silica aerogel and space astrophysics

    International Nuclear Information System (INIS)

    Koch-Miramond, L.

    1985-09-01

    Silica aerogels have been produced in large and transparent blocks for space astrophysics experiments since the beginning of the 1970's. They were used in cosmic ray experiments on board balloons by the Saclay group. A new space venture where aerogel Cerenkov radiators will play a decisive role is currently being prepared by a large collaboration of European and US Institutes. It will be part of the so-called International Solar Polar Mission (ISPM) which will explore the heliosphere over the full range of solar latitudes from the ecliptic (equatorial) plane to the magnetic poles of the sun. Comments on properties and long term behaviour of silica aerogel cerenkov radiators in space environment are given

  2. Evaluation of silica nanoparticle toxicity after topical exposure for 90 days

    Directory of Open Access Journals (Sweden)

    Ryu HJ

    2014-12-01

    Full Text Available Hwa Jung Ryu,1,* Nak-won Seong,2,* Byoung Joon So,1 Heung-sik Seo,2 Jun-ho Kim,2 Jeong-Sup Hong,2 Myeong-kyu Park,2 Min-Seok Kim,2 Yu-Ri Kim,3 Kyu-Bong Cho,4 Mu yeb Seo,2 Meyoung-Kon Kim,3 Eun Ho Maeng,2 Sang Wook Son1 1Department of Dermatology, Korea University College of Medicine, Seoul, South Korea; 2Korea Testing and Research Institute, Gyunggi-Do, South Korea; 3Department of Biochemistry and Molecular Biology, Korea University College of Medicine, Seoul, South Korea; 4Department of Clinical Laboratory Science, Shinheung College, Uijeongbu, South Korea *These authors contributed equally to this work Abstract: Silica is a very common material that can be found in both crystalline and amorphous forms. Well-known toxicities of the lung can occur after exposure to the crystalline form of silica. However, the toxicities of the amorphous form of silica have not been thoroughly studied. The majority of in vivo studies of amorphous silica nanoparticles (NPs were performed using an inhalation exposure method. Since silica NPs can be commonly administered through the skin, a study of dermal silica toxicity was necessary to determine any harmful effects from dermal exposures. The present study focused on the results of systemic toxicity after applying 20 nm colloidal silica NPs on rat skin for 90 days, in accordance with the Organization for Economic Cooperation and Development test guideline 411 with a good laboratory practice system. Unlike the inhalation route or gastrointestinal route, the contact of silica NPs through skin did not result in any toxicity or any change in internal organs up to a dose of 2,000 mg/kg in rats. Keywords: silica nanoparticles, toxicity, dermal route

  3. In situ synthesis of copper nanoparticles on SBA-16 silica spheres

    Directory of Open Access Journals (Sweden)

    Asma Tufail Shah

    2016-07-01

    Full Text Available A chemical method for in situ synthesis of copper nanoparticles on SBA-16 silica spheres under ambient conditions has been reported. The silica support has been introduced into copper precursor solution before chemical reduction. Metal ions diffuse into mesopores (pore diameter 5–7 nm of silica where in situ reduction by hydrazine leads to formation of nanoparticles. These mesopores act as nanoreactor and their walls prevent metal particle’s agglomeration by providing a physical barrier. The obtained copper nanoparticles have been investigated by electron microscopy, X-ray diffraction, UV–Visible spectroscopy, Fourier transform Infra-red spectroscopy and thermogravimetric analyzer. SEM, TEM and UV–Visible spectroscopic images revealed that nanosized particles have been successfully synthesized by this method. Thermogravimetric investigations revealed that copper nanoparticles impregnated on silica were thermally more stable compared to unsupported nanoparticles. Silica not only helps in maintaining the particle size but also makes nanoparticles stable at high temperatures due to its thick pore walls. Macro sized silica support also makes separation/handling of nanoparticles easy and simple.

  4. Nanoscale assembly of lanthanum silica with dense and porous interfacial structures.

    Science.gov (United States)

    Ballinger, Benjamin; Motuzas, Julius; Miller, Christopher R; Smart, Simon; Diniz da Costa, João C

    2015-02-03

    This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)3) suggests the formation of La2O3 surrounded by lanthanum silicate.

  5. Radiation hardening in sol-gel derived Er3+-doped silica glasses

    International Nuclear Information System (INIS)

    Hari Babu, B.; León Pichel, Mónica; Ollier, Nadège; El Hamzaoui, Hicham; Bigot, Laurent; Savelii, Inna; Bouazaoui, Mohamed; Poumellec, Bertrand; Lancry, Matthieu; Ibarra, Angel

    2015-01-01

    The aim of the present paper is to report the effect of radiation on the Er 3+ -doped sol-gel silica glasses. A possible application of these sol-gel glasses could be their use in harsh radiation environments. The sol-gel glasses are fabricated by densification of erbium salt-soaked nanoporous silica xerogels through polymeric sol-gel technique. The radiation-induced attenuation of Er 3+ -doped sol-gel silica is found to increase with erbium content. Electron paramagnetic resonance studies reveal the presence of E′ δ point defects. This happens in the sol-gel aluminum-silica glass after an exposure to γ-rays (kGy) and in sol-gel silica glass after an exposure to electrons (MGy). The concentration levels of these point defects are much lower in γ-ray irradiated sol-gel silica glasses. When the samples are co-doped with Al, the exposure to γ-ray radiation causes a possible reduction of the erbium valence from Er 3+ to Er 2+ ions. This process occurs in association with the formation of aluminum oxygen hole centers and different intrinsic point defects

  6. The increase in pH during aging of porous sol-gel silica spheres

    NARCIS (Netherlands)

    Titulaer, M.K.; Kegel, W.K.; Jansen, J.B.H.; Geus, John W.

    1994-01-01

    The increase in pH in the hydrothermal fluid is studied after hydrothermal aging of porous silica gel spheres of 1–3 mm diameter. The porous silica spheres are formed by the sol-gel process from a supersaturated silica solution. The increase of the pH of the hydrothermal solution affects the silica

  7. Reactive silica fractions in coastal lagoon sediments from the northern Gulf of Mexico

    Science.gov (United States)

    Krause, Jeffrey W.; Darrow, Elizabeth S.; Pickering, Rebecca A.; Carmichael, Ruth H.; Larson, Ashley M.; Basaldua, Jose L.

    2017-12-01

    Continental-margin sediments account for 50% of the oceanic biogenic silica burial despite covering Gulf of Mexico (nGoM), we measured sediment biogenic silica at sites removed from major freshwater discharge sources using the traditional method and a method that has been modified for deltaic systems to quantify other reactive silica pools, specifically those involved in the process of reverse weathering. The magnitude of authigenically-altered biogenic silica during our study was significant and represented, on average, 33% of the total sediment biogenic silica among core depths and sites. Additionally, there was a significant relationship between the degree to which the biogenic silica pool was authigenically altered and the source of the sediment organic matter, with lower modification in sediments corresponding with higher terrestrial organic matter. We observed no positive correlation between the magnitude of authigenic modification and sediment clay content. Thus, our findings suggest that these processes may occur within a variety of sediment compositions and add to a growing body of evidence suggesting that reverse weathering of silica in coastal systems is a significant pathway in the global silica budget.

  8. Aminopropyl-Silica Hybrid Particles as Supports for Humic Acids Immobilization

    Directory of Open Access Journals (Sweden)

    Mónika Sándor

    2016-01-01

    Full Text Available A series of aminopropyl-functionalized silica nanoparticles were prepared through a basic two step sol-gel process in water. Prior to being aminopropyl-functionalized, silica particles with an average diameter of 549 nm were prepared from tetraethyl orthosilicate (TEOS, using a Stöber method. In a second step, aminopropyl-silica particles were prepared by silanization with 3-aminopropyltriethoxysilane (APTES, added drop by drop to the sol-gel mixture. The synthesized amino-functionalized silica particles are intended to be used as supports for immobilization of humic acids (HA, through electrostatic bonds. Furthermore, by inserting beside APTES, unhydrolysable mono-, di- or trifunctional alkylsilanes (methyltriethoxy silane (MeTES, trimethylethoxysilane (Me3ES, diethoxydimethylsilane (Me2DES and 1,2-bis(triethoxysilylethane (BETES onto silica particles surface, the spacing of the free amino groups was intended in order to facilitate their interaction with HA large molecules. Two sorts of HA were used for evaluating the immobilization capacity of the novel aminosilane supports. The results proved the efficient functionalization of silica nanoparticles with amino groups and showed that the immobilization of the two tested types of humic acid substances was well achieved for all the TEOS/APTES = 20/1 (molar ratio silica hybrids having or not having the amino functions spaced by alkyl groups. It was shown that the density of aminopropyl functions is low enough at this low APTES fraction and do not require a further spacing by alkyl groups. Moreover, all the hybrids having negative zeta potential values exhibited low interaction with HA molecules.

  9. Fused silica thermal conductivity dispersion at high temperature

    International Nuclear Information System (INIS)

    Bouchut, P.; Decruppe, D.; Delrive, L.

    2004-01-01

    A continuous CO 2 laser is focused to locally anneal small fused silica spots. A noncontact radiometry diagnostic enables us to follow surface temperature variation that occurs from site to site. A 'steady state' dispersion of surface temperature is observed across our sample. We show that nonhomogeneous silica thermal conductivity, above 1000 K is responsible for this temperature dispersion

  10. Bioinspired silica as drug delivery systems and their biocompatibility

    DEFF Research Database (Denmark)

    Steven, Christopher R.; Busby, Grahame A.; Mather, Craig

    2014-01-01

    Silica nanoparticles have been shown to have great potential as drug delivery systems (DDS), however, their fabrication often involves harsh chemicals and energy intensive laborious methods. This work details the employment of a bioinspired "green" method for the controlled synthesis of silica, use...

  11. Sonochemical synthesis of (3-aminopropyl)triethoxysilane-modified monodispersed silica nanoparticles for protein immobilization

    International Nuclear Information System (INIS)

    Shen, Shou-Cang; Ng, Wai Kiong; Chia, Leonard; Dong, Yuan-Cai; Tan, Reginald B.H.

    2011-01-01

    Graphical abstract: 3-Aminopropyltriethoxysilane modified monodispersed silica nanoparticles were synthesized by rapid sonochemical co-condensation to achieve high capability for protein immobilization. Highlights: → Amino-modified monodispersed silica nanoparticles were synthesized by rapid co-condensation. → Strong positive charge was created by aminopropyl-modification. → Capability for immobilization of negatively charged protein was enhanced. → Electrostatic interaction between proteins and surface contributed to the enhanced adsorption. -- Abstract: 3-Aminopropyltriethoxysilane modified monodispersed silica nanoparticles were synthesized by a rapid sonochemical co-condensation synthesis procedure. The chemical nature of surface organic modifier on the obtained modified silica nanoparticle was characterized by 13 C and 29 Si MAS Nuclear Magnetic Resonance (NMR) spectroscopies, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA)- differential scanning calorimetry (DSC). Due to the strengthened positive surface charge of the silica nanoparticles by the modification with aminopropyl groups, the capability for bovine serum albumin (BSA) adsorption was significantly increased as compared with bare silica nanoparticles. 80 mg/g BSA was adsorbed on modified silica nanoparticles, whereas only 20 mg/g BSA could be loaded on pure silica nanoparticles. The enhanced positive surface charge repelled proteins with net positive charge and the modified silica nanoparticles exhibited negligible adsorption of lysozyme, thus a selective adsorption of proteins could be achieved.

  12. Sonochemical synthesis of (3-aminopropyl)triethoxysilane-modified monodispersed silica nanoparticles for protein immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Shou-Cang, E-mail: shen_shoucang@ices.a-star.edu.sg [Institute of Chemical and Engineering Sciences, A-STAR (Agency for Science, Technology and Research), 1 Pesek Road, Jurong Island, Singapore 627833 (Singapore); Ng, Wai Kiong; Chia, Leonard; Dong, Yuan-Cai [Institute of Chemical and Engineering Sciences, A-STAR (Agency for Science, Technology and Research), 1 Pesek Road, Jurong Island, Singapore 627833 (Singapore); Tan, Reginald B.H., E-mail: reginald_tan@ices.a-star.edu.sg [Institute of Chemical and Engineering Sciences, A-STAR (Agency for Science, Technology and Research), 1 Pesek Road, Jurong Island, Singapore 627833 (Singapore); Department of Chemical and Biomolecular Engineering, The National University of Singapore, 4 Engineering Drive 4, Singapore 117576 (Singapore)

    2011-10-15

    Graphical abstract: 3-Aminopropyltriethoxysilane modified monodispersed silica nanoparticles were synthesized by rapid sonochemical co-condensation to achieve high capability for protein immobilization. Highlights: {yields} Amino-modified monodispersed silica nanoparticles were synthesized by rapid co-condensation. {yields} Strong positive charge was created by aminopropyl-modification. {yields} Capability for immobilization of negatively charged protein was enhanced. {yields} Electrostatic interaction between proteins and surface contributed to the enhanced adsorption. -- Abstract: 3-Aminopropyltriethoxysilane modified monodispersed silica nanoparticles were synthesized by a rapid sonochemical co-condensation synthesis procedure. The chemical nature of surface organic modifier on the obtained modified silica nanoparticle was characterized by {sup 13}C and {sup 29}Si MAS Nuclear Magnetic Resonance (NMR) spectroscopies, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA)- differential scanning calorimetry (DSC). Due to the strengthened positive surface charge of the silica nanoparticles by the modification with aminopropyl groups, the capability for bovine serum albumin (BSA) adsorption was significantly increased as compared with bare silica nanoparticles. 80 mg/g BSA was adsorbed on modified silica nanoparticles, whereas only 20 mg/g BSA could be loaded on pure silica nanoparticles. The enhanced positive surface charge repelled proteins with net positive charge and the modified silica nanoparticles exhibited negligible adsorption of lysozyme, thus a selective adsorption of proteins could be achieved.

  13. Ultrasonic electrodeposition of silver nanoparticles on dielectric silica spheres

    International Nuclear Information System (INIS)

    Tang Shaochun; Tang Yuefeng; Gao Feng; Liu Zhiguo; Meng Xiangkang

    2007-01-01

    In the present study, a facile and one-step ultrasonic electrodeposition method is first applied to controllably coat colloidal silica spheres with silver nanoparticles. This method is additive-free and very direct, because processes necessary in many other approaches, such as pretreatment of the silica sphere surface and pre-preparation of silver nanoparticles, are not involved in it. Furthermore, it makes possible the coating of dielectric substrates with metal through an electrodeposition route. Under appropriate conditions, silver nanoparticles with sizes of 8-10 nm in diameter can be relatively homogeneously deposited onto the surface of preformed colloidal silica spheres. Silver particles with different sizes and dispersive uniformity on silica sphere surfaces can also be obtained by adjusting the current density (I), the concentration of electrolyte (C) and the electrolysis time (t). The possible ultrasonic electrodeposition mechanism is also suggested according to the experimental results

  14. The opinions of residents towards economic, social, cultural and environmental impacts of tourism in Foça

    OpenAIRE

    Nevzat Gümüş; Salman Özüpekçe

    2009-01-01

    The purpose of this study is, to determine the peoples’ ideas on the economic, social, cultural and environmental effects of tourism; investigate the altering of these ideas in terms of urban-rural, sex, occupation and level of education. A survey consisting of factual questions and Likert-type was carried out with 76 people who live in Foça district center, Yeni Foca town, New Bağarası and Gerenköy. In the light of the data obtained, the attitudes towards tourism activities...

  15. Electrochemical lithium migration to mitigate alkali-silica reaction in existing concrete structures

    NARCIS (Netherlands)

    Silva De Souza, L.M.

    2016-01-01

    Alkali-silica reaction (ASR) is a deterioration process that affects the durability of concrete structures worldwide. During the reaction, hydroxyl and alkali ions present in the pore solution react with reactive silica from the aggregate, forming a hygroscopic ASR gel. Alternatively, the silica

  16. Formation of monodisperse mesoporous silica microparticles via spray-drying.

    Science.gov (United States)

    Waldron, Kathryn; Wu, Winston Duo; Wu, Zhangxiong; Liu, Wenjie; Selomulya, Cordelia; Zhao, Dongyuan; Chen, Xiao Dong

    2014-03-15

    In this work, a protocol to synthesize monodisperse mesoporous silica microparticles via a unique microfluidic jet spray-drying route is reported for the first time. The microparticles demonstrated highly ordered hexagonal mesostructures with surface areas ranging from ~900 up to 1500 m(2)/g and pore volumes from ~0.6 to 0.8 cm(3)/g. The particle size could be easily controlled from ~50 to 100 μm from the same diameter nozzle via changing the initial solute content, or changing the drying temperature. The ratio of the surfactant (CTAB) and silica (TEOS), and the amount of water in the precursor were found to affect the degree of ordering of mesopores by promoting either the self-assembly of the surfactant-silica micelles or the condensation of the silica as two competing processes in evaporation induced self-assembly. The drying rate and the curvature of particles also affected the self-assembly of the mesostructure. The particle mesostructure is not influenced by the inlet drying temperature in the range of 92-160 °C, with even a relatively low temperature of 92 °C producing highly ordered mesoporous microparticles. The spray-drying derived mesoporous silica microparticles, while of larger sizes and more rapidly synthesized, showed a comparable performance with the conventional mesoporous silica MCM-41 in controlled release of a dye, Rhodamine B, indicating that these spray dried microparticles could be used for the immobilisation and controlled release of small molecules. Copyright © 2013 Elsevier Inc. All rights reserved.

  17. Pore fabrication in various silica-based nanoparticles by controlled etching

    KAUST Repository

    Zhao, Lan

    2010-07-20

    A novel method based on controlled etching was developed to fabricate nanopores on preformed silica nanoparticles (<100 nm in diameter). The obtained monodisperse nanoporous particles could form highly stable homogeneous colloidal solution. Fluorescent silica nanoparticles and magnetic silica-coated γ-Fe 2O 3 nanoparticles were investigated as examples to illustrate that this strategy could be generally applied to various silica-based functional nanoparticles. The results indicated that this method was effective for generating pores on these nanoparticles without altering their original functionalities. The obtained multifunctional nanoparticles would be useful for many biological and biomedical applications. These porous nanoparticles could also serve as building blocks to fabricate three-dimensionally periodic structures that have the potential to be used as photonic crystals. © 2010 American Chemical Society.

  18. Investigation of adsorption performance deterioration in silica gel–water adsorption refrigeration

    International Nuclear Information System (INIS)

    Wang Dechang; Zhang Jipeng; Xia Yanzhi; Han Yanpei; Wang Shuwei

    2012-01-01

    Highlights: ► Adsorption deterioration of silica gel in refrigeration systems is verified. ► Possible factors to cause such deterioration are analyzed. ► Specific surface area, silanol content and adsorption capacity are tested. ► The pollution is the primary factor to decline the adsorption capacity. ► Deteriorated samples are partly restored after being processed by acid solution. - Abstract: Silica gel acts as a key role in adsorption refrigeration systems. The adsorption deterioration must greatly impact the performance of the silica gel–water adsorption refrigeration system. In order to investigate the adsorption deterioration of silica gel, many different silica gel samples were prepared according to the application surroundings of silica gel in adsorption refrigeration systems after the likely factors to cause such deterioration were analyzed. The specific surface area, silanol content, adsorption capacity and pore size distribution of those samples were tested and the corresponding adsorption isotherms were achieved. In terms of the experimental data comparisons, it could be found that there are many factors to affect the adsorption performance of silica gel, but the pollution was the primary one to decline the adsorption capacity. In addition, the adsorption performance of the deteriorated samples after being processed by acid solution was explored in order to find the possible methods to restore its adsorption performance.

  19. Precipitate coarsening and self organization in erbium-doped silica

    DEFF Research Database (Denmark)

    Sckerl, Mads W.; Guldberg-Kjær, Søren Andreas; Poulsen, Mogens Rysholt

    1999-01-01

    The influence of heat treatment at and above 1100 degrees C on thin erbium-rich silica layers embedded in silica has been studied experimentally by secondary ion-mass spectrometry and cross-sectional transmission electron microscopy. Redistribution of erbium atoms is observed at these temperature...

  20. Thermal and Hydrothermal Treatment of Silica Gels as Solid Stationary Phases in Gas Chromatography

    Directory of Open Access Journals (Sweden)

    Ashraf Yehia El-Naggar

    2013-01-01

    Full Text Available Silica gel was prepared and treated thermally and hydrothermally and was characterized as solid stationary phase in gas chromatography. The characteristics have been evaluated in terms of polarity, selectivity, and separation efficiencies. These parameters were used to assess the outer silica surface contributions and the degree of surface deactivation brought about by different treatment techniques. The parent silica elutes the paraffinic hydrocarbons with high efficiency of separation and elutes aromatic hydrocarbons with nearly good separation and has bad separation of alcohols. The calcined silica at 500°C and 1000°C has a pronounced effect on the separation of aromatic hydrocarbons compared with the parent silica and hydrothermal treatment of silica. With respect to alcohols separation, the obtained bad separations using treated and untreated silica reflect the little effect of the thermal and hydrothermal treatment on the silica surface deactivation.

  1. Plasmonic properties and enhanced fluorescence of gold and dye-doped silica nanoparticle aggregates

    Science.gov (United States)

    Green, Nathaniel Scott

    The development of metal-enhanced fluorescence has prompted a great interest in augmenting the photophysical properties of fluorescent molecules with noble metal nanostructures. Our research efforts, outlined in this dissertation, focus on augmenting properties of fluorophores by conjugation with gold nanostructures. The project goals are split into two separate efforts; the enhancement in brightness of fluorophores and long distance non-radiative energy transfer between fluorophores. We believe that interacting dye-doped silica nanoparticles with gold nanoparticles can facilitate both of these phenomena. Our primary research interest is focused on optimizing brightness, as this goal should open a path to studying the second goal of non-radiative energy transfer. The two major challenges to this are constructing suitable nanomaterials and functionalizing them to promote plasmonically active complexes. The synthesis of dye-doped layered silica nanoparticles allows for control over the discrete location of the dye and a substrate that can be surface functionalized. Controlling the exact location of the dye is important to create a silica spacer, which promotes productive interactions with metal nanostructures. Furthermore, the synthesis of silica nanoparticles allows for various fluorophores to be studied in similar environments (removing solvent and other chemo-sensitive issues). Functionalizing the surface of silica nanoparticles allows control over the degree of silica and gold nanoparticle aggregation in solution. Heteroaggregation in solution is useful for producing well-aggregated clusters of many gold around a single silica nanoparticle. The dye-doped surface functionalized silica nanoparticles can than be mixed efficiently with gold nanomaterials. Aggregating multiple gold nanospheres around a single dye-doped silica nanoparticle can dramatically increase the fluorescent brightness of the sample via metal-enhanced fluorescence due to increase plasmonic

  2. Reaction products of densified silica fume agglomerates in concrete

    International Nuclear Information System (INIS)

    Diamond, Sidney; Sahu, Sadananda; Thaulow, Niels

    2004-01-01

    Most silica fume currently used in concrete is in the dry densified form and consists of agglomerates of sizes between 10 μm and several millimeters. Many of these agglomerates may break down only partially in normal concrete mixing. Examination of various mature silica-fume-bearing concretes using backscatter mode scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis shows that such agglomerates have reacted in situ and given rise to recognizable types of reaction products filling the space within the original outline of the agglomerate. One type is 'quiescent', and usually shows no evidence of volume instability. EDX spectra indicate that the product formed within such grains is C-S-H of very low Ca/Si ratio, with modest alkali contents. Other silica fume agglomerates may undergo a distinct alkali-silica-type reaction (ASR), with the reaction product found within the original outline of the agglomerate having significantly less calcium and usually much higher alkali contents than the quiescent type. Such reacted agglomerates show evidence of local expansion, shrinkage cracking (on drying), and other features common to ASR. Both types may be found within the same concrete, sometimes in close proximity. It further appears that exposure to seawater may convert previously formed reaction products of silica fume agglomerates to magnesium silicate hydrates

  3. Interferences of Silica Nanoparticles in Green Fluorescent Protein Folding Processes.

    Science.gov (United States)

    Klein, Géraldine; Devineau, Stéphanie; Aude, Jean Christophe; Boulard, Yves; Pasquier, Hélène; Labarre, Jean; Pin, Serge; Renault, Jean Philippe

    2016-01-12

    We investigated the relationship between unfolded proteins, silica nanoparticles and chaperonin to determine whether unfolded proteins could stick to silica surfaces and how this process could impair heat shock protein activity. The HSP60 catalyzed green fluorescent protein (GFP) folding was used as a model system. The adsorption isotherms and adsorption kinetics of denatured GFP were measured, showing that denaturation increases GFP affinity for silica surfaces. This affinity is maintained even if the surfaces are covered by a protein corona and allows silica NPs to interfere directly with GFP folding by trapping it in its unstructured state. We determined also the adsorption isotherms of HSP60 and its chaperonin activity once adsorbed, showing that SiO2 NP can interfere also indirectly with protein folding through chaperonin trapping and inhibition. This inhibition is specifically efficient when NPs are covered first with a layer of unfolded proteins. These results highlight for the first time the antichaperonin activity of silica NPs and ask new questions about the toxicity of such misfolded proteins/nanoparticles assembly toward cells.

  4. Persistent superhydrophilicity of sol-gel derived nanoporous silica thin films

    International Nuclear Information System (INIS)

    Ganjoo, S; Azimirad, R; Akhavan, O; Moshfegh, A Z

    2009-01-01

    In this investigation, sol-gel synthesized nanoporous silica thin films, annealed at different temperatures, with long time superhydrophilic property have been studied. Two kinds of sol-gel silica thin films were fabricated by dip-coating of glass substrates in two different solutions; with low and high water. The transparent coated films were dried at 100 deg. C and then annealed in a temperature range of 200-500 deg. C. The average water contact angle of the silica films prepared with low water content and annealed at 300 deg. C measured about 5 deg. for a long time (6 months) without any UV irradiation. Instead, adding water into the sol resulted in silica films with an average water contact angle greater than 60 deg. Atomic force microscopic analysis revealed that the silica films prepared with low water had a rough surface (∼30 nm), while the films prepared with high water had a smoother surface (∼2 nm). Using x-ray photoelectron spectroscopy, we have shown that with a decrease in the surface water on the film, its hydrophilicity increases logarithmically.

  5. The comparative immunotoxicity of mesoporous silica nanoparticles and colloidal silica nanoparticles in mice

    Directory of Open Access Journals (Sweden)

    Lee S

    2013-01-01

    Full Text Available Soyoung Lee,1,* Mi-Sun Kim,1,* Dakeun Lee,2 Taeg Kyu Kwon,3 Dongwoo Khang,4 Hui-Suk Yun,5 Sang-Hyun Kim11CMRI, Laboratory of Immunotoxicology, Department of Pharmacology,School of Medicine, Kyungpook National University, Daegu, Republic of Korea; 2Department of Pathology, School of Medicine, Kyungpook National University, Daegu, Republic of Korea; 3Department of Immunology, School of Medicine, Keimyung University, Daegu, Republic of Korea; 4School of Nano and Advanced Materials Science and Engineering, Gyeongsang National University, Jinju, Republic of Korea; 5Engineering Ceramics Department, Powder and Ceramics Division, Korea Institute of Materials Science, Changwon, Republic of Korea*These authors contributed equally to this workBackground: Mesoporous silica (MPS nanoparticles (NPs, which have a unique pore structure and extremely large surface area and pore volume, have received much attention because of their biomedical application potential. Using MPS NPs for biomedical devices requires the verification of their biocompatibility because the surface area of NPs is one of the most important determinants of toxicity, including the cellular uptake and immune response. We have previously reported that the cytotoxicity and inflammation potential of MPS NPs have been shown to be lower than those of general amorphous colloidal silica (Col NPs in macrophages, but the low cytotoxicity does not guarantee high biocompatibility in vivo. In this study, we compared the in vivo immunotoxicity of MPS and Col NPs in the mouse model to define the effects of pore structural conditions of silica NPs.Materials and methods: Both MPS and Col NPs (2, 20, and 50 mg/kg/day were intraperitoneally administered in female BALB/c mice for 4 weeks, and clinical toxicity, lymphocyte population, serum IgG/IgM levels, and histological changes were examined.Results: There was no overt sign of clinical toxicity in either MPS- or Col-treated mice. However, MPS NPs led to

  6. Knowledge Brokerage for Impact Assessment of Land Use Scenarios in Inner Mongolia, China: Extending and Testing the FoPIA Approach

    Directory of Open Access Journals (Sweden)

    Hannes J. König

    2015-04-01

    Full Text Available While land serves numerous societal functions and contributes to sustainable development, it is often unclear how these functions are affected by political decisions and common drivers of land use change, such as economic development, climate change and demographic change. This study evaluates alternative land use scenarios in reference to a rural region of Inner Mongolia Autonomous Region (China, where various processes and decisions have historically triggered unsustainable development. The scientifically tested “Framework for Participatory Impact Assessment (FoPIA” method is developed further to address specific features of the case study region, and its function as a knowledge-brokerage (KB tool is evaluated. Three scenarios are developed and analysed in expert workshops. “Land intensification: Agriculture” and “Land intensification: Mining” scenarios are found to have mainly negative environmental and social effects and positive economic impacts, while the “Environmental conservation and tourism” scenario is found to more positively affect all three sustainability dimensions. Assessments of methodological phases show that the FoPIA primarily serves to establish the KB process and that the framework particularly benefits from early examinations of scientific results by policy makers.

  7. A protecting group approach toward synthesis of Au–silica Janus nanostars

    OpenAIRE

    D. Rodríguez-Fernández; T. Altantzis; H. Heidari; S. Bals; L.M. Liz-Marzán

    2013-01-01

    Abstract: The concept of protecting groups, widely used in organic chemistry, has been applied for the synthesis of Au-silica Janus stars, in which gold branches protrude from one half of Au-silica Janus spheres. This configuration opens up new possibilities to apply the plasmonic properties of gold nanostars, as well as a variety of chemical functionalizations on the silica component.

  8. A protecting group approach toward synthesis of Au-silica Janus nanostars.

    Science.gov (United States)

    Rodríguez-Fernández, Denis; Altantzis, Thomas; Heidari, Hamed; Bals, Sara; Liz-Marzán, Luis M

    2014-01-04

    The concept of protecting groups, widely used in organic chemistry, has been applied for the synthesis of Au-silica Janus stars, in which gold branches protrude from one half of Au-silica Janus spheres. This configuration opens up new possibilities to apply the plasmonic properties of gold nanostars, as well as a variety of chemical functionalizations on the silica component.

  9. Silica-scaled chrysophytes of Lake Baikal

    Directory of Open Access Journals (Sweden)

    A. Yu. Bessudova

    2017-12-01

    Full Text Available The list of silica-scaled chrysophytes of Lake Baikal has been enlarged using electron microscopy. It has been supplemented with 12 species and 2 forms. Spiniferomonas takahashii has been observed for the first time in the water bodies of Russia. According to our data, the list of silica-scaled chrysophytes of Lake Baikal includes 25 species and intra-species taxa: Chrysosphaerella – 3, Paraphysomonas – 2, Clathromonas – 1, Spiniferomonas – 7, Mallomonas – 8 and Synura – 4. We have also analyzed their seasonal dynamics and observed algal species that are dominant in spring, summer and autumn.

  10. Formation of Uniform Hollow Silica microcapsules

    Science.gov (United States)

    Yan, Huan; Kim, Chanjoong

    2013-03-01

    Microcapsules are small containers with diameters in the range of 0.1 - 100 μm. Mesoporous microcapsules with hollow morphologies possess unique properties such as low-density and high encapsulation capacity, while allowing controlled release by permeating substances with a specific size and chemistry. Our process is a one-step fabrication of monodisperse hollow silica capsules with a hierarchical pore structure and high size uniformity using double emulsion templates obtained by the glass-capillary microfluidic technique to encapsulate various active ingredients. These hollow silica microcapsules can be used as biomedical applications such as drug delivery and controlled release.

  11. A novel method for the synthesis of monodisperse gold-coated silica nanoparticles

    International Nuclear Information System (INIS)

    English, Michael D.; Waclawik, Eric R.

    2012-01-01

    Monodisperse silica nanoparticles were synthesised by the well-known Stober protocol, then dispersed in acetonitrile (ACN) and subsequently added to a bisacetonitrile gold(I) coordination complex ([Au(MeCN) 2 ] + ) in ACN. The silica hydroxyl groups were deprotonated in the presence of ACN, generating a formal negative charge on the siloxy groups. This allowed the [Au(MeCN) 2 ] + complex to undergo ligand exchange with the silica nanoparticles and form a surface coordination complex with reduction to metallic gold (Au 0 ) proceeding by an inner sphere mechanism. The residual [Au(MeCN) 2 ] + complex was allowed to react with water, disproportionating into Au 0 and Au(III), respectively, with the Au 0 adding to the reduced gold already bound on the silica surface. The so-formed metallic gold seed surface was found to be suitable for the conventional reduction of Au(III) to Au 0 by ascorbic acid (ASC). This process generated a thin and uniform gold coating on the silica nanoparticles. The silica NPs batches synthesised were in a size range from 45 to 460 nm. Of these silica NP batches, the size range from 400 to 480 nm were used for the gold-coating experiments.

  12. Fluorescent proteins as efficient tools for evaluating the surface PEGylation of silica nanoparticles

    Science.gov (United States)

    Zhang, Wei; Ma, Minyan; Zhang, Xiao-ai; Zhang, Ze-yu; Saleh, Sayed M.; Wang, Xu-dong

    2017-06-01

    Surface PEGylation is essential for preventing non-specific binding of biomolecules when silica nanoparticles are utilized for in vivo applications. Methods for installing poly(ethylene glycol) on a silica surface have been widely explored but varies from study to study. Because there is a lack of a satisfactory method for evaluating the properties of silica surface after PEGylation, the prepared nanoparticles are not fully characterized before use. In some cases, even non-PEGylated silica nanoparticles were produced, which is unfortunately not recognized by the end-user. In this work, a fluorescent protein was employed, which acts as a sensitive material for evaluating the surface protein adsorption properties of silica nanoparticles. Eleven different methods were systematically investigated for their reaction efficiency towards surface PEGylation. Results showed that both reaction conditions (including pH, catalyst) and surface functional groups of parent silica nanoparticles play critical roles in producing fully PEGylated silica nanoparticles. Great care needs to be taken in choosing the proper coupling chemistry for surface PEGylation. The data and method shown here will guarantee high-quality PEGylated silica nanoparticles to be produced and guide their applications in biology, chemistry, industry and medicine.

  13. Kinetics Study of Gas Pollutant Adsorption and Thermal Desorption on Silica Gel

    Directory of Open Access Journals (Sweden)

    Rong A

    2017-06-01

    Full Text Available Silica gel is a typical porous desiccant material. Its adsorption performance for gaseous air pollutants was investigated to determine its potential contribution to reducing such pollutants. Three gaseous air pollutants, toluene, carbon dioxide, and methane, were investigated in this paper. A thermogravimetric analyzer was used to obtain the equilibrium adsorption capacity of gases on single silica gel particles. The silica gel adsorption capacity for toluene is much higher than that for carbon dioxide and methane. To understand gas pollutant thermal desorption from silica gel, the thermogravimetric analysis of toluene desorption was conducted with 609 ppm toluene vapor at 313 K, 323 K, and 333 K. The overall regeneration rate of silica gel was strongly dependent on temperature and the enthalpy of desorption. The gas pollutant adsorption performance and thermal desorption on silica gel material may be used to estimate the operating and design parameters for gas pollutant adsorption by desiccant wheels.

  14. Synthesis of porous carbon/silica nanostructured microfiber with ultrahigh surface area

    Science.gov (United States)

    Zhou, Dan; Dong, Yan; Cui, Liru; Lin, Huiming; Qu, Fengyu

    2014-12-01

    Carbon/silica-nanostructured microfibers were synthesized via electrospinning method using phenol-formaldehyde resin and tetraethyl orthosilicate as carbon and silica precursor with triblock copolymer Pluronic P123 as soft template. The prepared samples show uniform microfiber structure with 1 μm in diameter and dozens of microns in length. Additionally, the mesopores in the material is about 2-6 nm. When the silica component was removed by HF, the porous carbon microfibers (PCMFs) were obtained. In addition, after the carbon/silica composites were calcined in air, the porous silica microfibers (PSiMFs) were obtained, revealing the converse porous nanostructure as PCMFs. It is a simple way to prepare PCMFs and PSiMFs with silica and carbon as the template to each other. Additionally, PCMFs possess an ultrahigh specific surface area (2,092 m2 g-1) and large pore volume. The electrochemical performance of the prepared PCMF material was investigated in 6.0 M KOH electrolyte. The PCMF electrode exhibits a high specific capacitance (252 F g-1 at 0.5 A g-1). Then, superior cycling stability (97 % retention after 4,000 cycles) mainly is due to its unique nanostructure.

  15. Sol-gel preparation of Ag-silica nanocomposite with high electrical conductivity

    Science.gov (United States)

    Ma, Zhijun; Jiang, Yuwei; Xiao, Huisi; Jiang, Bofan; Zhang, Hao; Peng, Mingying; Dong, Guoping; Yu, Xiang; Yang, Jian

    2018-04-01

    Sol-gel derived noble-metal-silica nanocomposites are very useful in many applications. Due to relatively low price, higher conductivity, and higher chemical stability of silver (Ag) compared with copper (Cu), Ag-silica has gained much more research interest. However, it remains a significant challenge to realize high loading of Ag content in sol-gel Ag-silica composite with high structural controllability and nanoparticles' dispersity. Different from previous works by using multifunctional silicon alkoxide to anchor metal ions, here we report the synthesis of Ag-silica nanocomposite with high loading of Ag nanoparticles by employing acetonitrile bi-functionally as solvent and metal ions stabilizer. The electrical conductivity of the Ag-silica nanocomposite reached higher than 6800 S/cm. In addition, the Ag-silica nanocomposite could simultaneously possess high electrical conductivity and positive conductivity-temperature coefficient by properly controlling the loading content of Ag. Such behavior is potentially advantageous for high-temperature devices (like phosphoric acid fuel cells) and inhibiting the thermal-induced increase of devices' internal resistance. The strategy proposed here is also compatible with block-copolymer directed self-assembly of mesoporous material, spin-coating of film and electrospinning of nanofiber, making it more charming in various practical applications.

  16. Reactive Diazonium-Modified Silica Fillers for High-Performance Polymers.

    Science.gov (United States)

    Sandomierski, Mariusz; Strzemiecka, Beata; Chehimi, Mohamed M; Voelkel, Adam

    2016-11-08

    We describe a simple way of modification of three silica-based fillers with in situ generated 4-hydroxymethylbenzenediazonium salt ( + N 2 -C 6 H 4 -CH 2 OH). The rationale for using a hydroxyl-functionalized diazonium salt is that it provides surface-functionalized fillers that can react with phenolic resins. The modification of silica by diazonium salts was assessed using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). FTIR spectroscopy permitted the tracking of benzene ring breathing and C-C. The absence of the characteristic N≡N stretching vibration in the 2200-2300 cm -1 range indicates the loss of the diazonium group. XPS results indicate a higher C/Si atomic ratio after the diazonium modification of fillers and the presence of π-π* C1s satellite peaks characteristic of the surface-tethered aromatic species. Adhesion of aryl layers to the silicas is excellent because they withstand harsh thermal and organic solvent treatments. Phenolic resins (used, for example, as binders in abrasive products) were filled with diazonium-modified silicas at 10-25 wt %. The reactivity of the fillers toward phenolic resins was evaluated by the determination of the flow distance. After annealing at 180 °C, the diazonium-modified silica/phenolic resin composites were mechanically tested using the three-point flexural method. The flexural strength was found to be up to 35% higher than that of the composites prepared without any diazonium salts. Diazonium-modified silica with surface-bound -CH 2 -OH groups is thus ideal reactive filler for phenolic resins. Such filler ensures interfacial chemical reactions with the matrix and imparts robust mechanical properties to the final composites. This specialty diazonium-modified silica will find potential application as fillers in the composites for the abrasive industry. More generally, aryl diazonium salts are a unique new series of compounds for tailoring the surface properties of fillers

  17. Peculiarities of hydration of Portland cement with synthetic nano-silica

    Science.gov (United States)

    Kotsay, Galyna

    2017-12-01

    Application of nano-materials in cement products significantly, improves their properties. Of course, the effectiveness of the materials depends on their quantity and the way they are introduced into the system. So far, amongst nano-materials used in construction, the most preferred was nano-silica. This research investigated the effect of synthetic precipitated nano-silica on the cement hydration as well as, on the physical and mechanical properties of pastes and mortars. Obtained results showed that admixture of nano-silica enhanced flexural and compressive strength of cement after 2 and 28 days, however, only when admixture made up 0.5% and 1.0%. On the other hand, the use of nano-silica in the amount 2% had some limitations, due to its ability to agglomerate, which resulted in deterioration of the rheological and mechanical properties.

  18. Behaviour of Epoxy Silica Nanocomposites Under Static and Creep Loading

    Science.gov (United States)

    Constantinescu, Dan Mihai; Picu, Radu Catalin; Sandu, Marin; Apostol, Dragos Alexandru; Sandu, Adriana; Baciu, Florin

    2017-12-01

    Specific manufacturing technologies were applied for the fabrication of epoxy-based nanocomposites with silica nanoparticles. For dispersing the fillers in the epoxy resin special equipment such as a shear mixer and a high energy sonicator with temperature control were used. Both functionalized and unfunctionalized silica nanoparticles were added in three epoxy resins. The considered filling fraction was in most cases 0.1, 0.3 and 0.5 wt%.. The obtained nanocomposites were subjected to monotonic uniaxial and creep loading at room temperature. The static mechanical properties were not significantly improved regardless the filler percentage and type of epoxy resin. Under creep loading, by increasing the stress level, the nanocomposite with 0.1 wt% silica creeps less than all other materials. Also the creep rate is reduced by adding silica nanofillers.

  19. Ordered silica particles made by nonionic surfactant for VOCs sorption

    Energy Technology Data Exchange (ETDEWEB)

    Difallah, Oumaima; Hamaizi, Hadj, E-mail: hamaizimizou@yahoo.fr [University of Oran, OranMenaouer (Algeria); Amate, Maria Dolores Urena; Socias-Viciana, Maria Del Mar [University of Almeria (Spain)

    2017-07-15

    Adsorption of light organic compounds such acetone, 1-propanol and carbon dioxide was tested by using mesoporous silica materials made from non ionic surfactant with long chain and silica sources as tetraethyl orthosilicate TEOS and modified Na-X and Li-A Zeolites. X-ray powder diffraction (XRD), nitrogen adsorption-desorption analysis and scanning electron microscopy (SEM) were applied to characterize the silica particles of a variety prepared samples. Acetone, 1-propanol and CO{sub 2} adsorption at 298K was evaluated by a volumetric method and indicate a high sorption capacity of organic compounds depending essentially on the porous texture of adsorbents. An adsorption kinetic model was proposed to describe the adsorption of VOCs over template-free mesoporous silica materials. A good agreement with experimental data was found. (author)

  20. Formation mechanisms of colloidal silica via sodium silicate

    International Nuclear Information System (INIS)

    Tsai, M.-S.; Huang, P.Y.; Yang, C.-H.

    2006-01-01

    Colloidal silica is formed by titrating active silicic acid into a heated KOH with seed solution. The colloidal silica formation mechanisms are investigated by sampling the heated solution during titration. In the initial stage, the added seeds were dissolved. This might due to the dilution of seed concentration, the addition of potassium hydroxide (KOH) and the heating at 100 deg. C. Homogenous nucleation and surface growth occur simultaneously in the second stage of colloidal silica formation. Homogenous nucleation is more important when the seed concentration is relatively low. On the other hand, surface growth plays an important role when the seed concentration is increased. In the middle seed concentration, the seed particles grow up and some new small particles are born by the homogenous nucleation process to form a bimodal size distribution product. As the titrating volume of active silicic acid exceeds a specific value in the last stage the particle size increases rapidly and the particle number decreases, which may be caused by the aggregation of particles. The intervals between each stage were varied with the seed concentration. Increasing the seed concentration led to the formation of uniform particle size colloidal silica

  1. Granulated Silica Method for the Fiber Preform Production

    Directory of Open Access Journals (Sweden)

    Sönke Pilz

    2017-07-01

    Full Text Available During the past few years, we have studied the granulated silica method as a versatile and cost effective way of fiber preform production and the sol-gel method. Until now, we have used the sol-gel technology together with an iterative re-melting and milling step in order to produce rare earth or transition metal doped granular material for the granulated silica method. Here, we present that the iterative re-melting (laser-assisted and milling step is no longer needed to reach a high homogeneity. The sol-gel method also offers a high degree of compositional flexibility with respect to dopants; it further facilitates achieving high concentrations, even in cases when several dopants are used. We employed optical active doped sol-gel derived granulate for the fiber core, whereas pure or index-raised granulated silica has been employed for the cladding. Based on the powder-in-tube technique, where silica glass tubes are appropriately filled with these granular materials, fibers has been directly drawn (“fiber rapid prototyping”, or eventually after an additional optional quality enhancing vitrification step. The powder-in-tube technique is also ideally suited for the preparation of microstructured optical fibers.

  2. Fabrication of semi-transparent super-hydrophobic surface based on silica hierarchical structures

    KAUST Repository

    Chen, Ping-Hei

    2011-01-01

    This study successfully develops a versatile method of producing superhydrophobic surfaces with micro/nano-silica hierarchical structures on glass surfaces. Optically transparent super hydrophobic silica thin films were prepared by spin-coating silica particles suspended in a precursor solution of silane, ethanol, and H2O with molar ratio of 1:4:4. The resulting super hydrophobic films were characterized by scanning electron microscopy (SEM), optical transmission, and contact angle measurements. The glass substrates in this study were modified with different particles: micro-silica particles, nano-silica particles, and hierarchical structures. This study includes SEM micrographs of the modified glass surfaces with hierarchical structures at different magnifications. © 2011 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

  3. Improving Fracture Toughness of Epoxy Nanocomposites by Silica Nanoparticles

    Directory of Open Access Journals (Sweden)

    Seyed Reza Akherati Sany

    2017-04-01

    Full Text Available An epoxy resin was modified by silica nanoparticles and cured with an anhydride. The particles with different batches of 12, 20, and 40 nm sizes were each distributed into the epoxy resin ultrasonically. Electron microscopy images showed that the silica particles were well dispersed throughout the resin. Tensile test results showed that Young’s modulus and tensile strength increased with the volume fraction and surface area of the silica particles. The simultaneous use of two average sizes of 20 and 40 nm diameter silica particles still increased these mechanical properties but other combinations of silica particles were unsuccessful. A three-point bending test on each pre-cracked specimen was performed to measure the mode I fracture toughness energy. The fracture energy increased from 283 J/m2 for the unmodified epoxy to about 740 J/m2 for the epoxy with 4.5 wt% of 12 nm diameter silica nanoparticles. The fracture energy of smaller particles was greater because of their higher surface to volume ratio. The fracture energy results showed also that the combined nanoparticles has a synergic effect on the fracture toughness of nanocomposites. Simultaneous use of 10 and 20 nm particles increased the fracture energy to about 770 J/m2. Finally, crack-opening displacement was calculated and found to be in the range of several micrometers which was much larger than the sizes of particles studied. Thus, the toughening mechanisms of crack pinning and crack deflection have a negligible effect on improvement of toughness, nevertheless, the plastic deformation and plastic void growth are dominant mechanisms in epoxy toughening by nanoparticles.

  4. Reducing ZnO nanoparticles toxicity through silica coating

    Directory of Open Access Journals (Sweden)

    Sing Ling Chia

    2016-10-01

    Full Text Available ZnO NPs have good antimicrobial activity that can be utilized as agents to prevent harmful microorganism growth in food. However, the use of ZnO NPs as food additive is limited by the perceived high toxicity of ZnO NPs in many earlier toxicity studies. In this study, surface modification by silica coating was used to reduce the toxicity of ZnO NPs by significantly reducing the dissolution of the core ZnO NPs. To more accurately recapitulate the scenario of ingested ZnO NPs, we tested our as synthesized ZnO NPs in ingestion fluids (synthetic saliva and synthetic gastric juice to determine the possible forms of ZnO NPs in digestive system before exposing the products to colorectal cell lines. The results showed that silica coating is highly effective in reducing toxicity of ZnO NPs through prevention of the dissociation of ZnO NPs to zinc ions in both neutral and acidic condition. The silica coating however did not alter the desired antimicrobial activity of ZnO NPs to E. coli and S. aureus. Thus, silica coating offered a potential solution to improve the biocompatibility of ZnO NPs for applications such as antimicrobial agent in foods or food related products like food packaging. Nevertheless, caution remains that high concentration of silica coated ZnO NPs can still induce undesirable cytotoxicity to mammalian gut cells. This study indicated that upstream safer-by-design philosophy in nanotechnology can be very helpful in a product development.

  5. Cooperative catalysis by silica-supported organic functional groups

    OpenAIRE

    Margelefsky, Eric L.; Zeidan, Ryan K.; Davis, Mark E.

    2008-01-01

    Hybrid inorganic–organic materials comprising organic functional groups tethered from silica surfaces are versatile, heterogeneous catalysts. Recent advances have led to the preparation of silica materials containing multiple, different functional groups that can show cooperative catalysis; that is, these functional groups can act together to provide catalytic activity and selectivity superior to what can be obtained from either monofunctional materials or homogeneous catalysts. This tutorial...

  6. Synthesis of internally functionalized silica nanoparticles for theranostic applications

    Science.gov (United States)

    Walton, Nathan Isaac

    This thesis addresses the synthesis and characterization of novel inorganic silica nanoparticle hybrids. It focuses in large part on their potential applications in the medical field. Silica acts as a useful carrier for a variety of compounds and this thesis silica will demonstrate its use as a carrier for boron or gadolinium. Boron-10 and gadolinium-157 have been suggested for the radiological treatment of tumor cells through the process called neutron capture therapy (NCT). Gadolinium is also commonly used as a Magnetic Resonance Imaging (MRI) contrast agent. Particles that carry it have potential theranostic applications of both imaging and treating tumors. Chapter 1 presents a background on synthetic strategies and usages of silica nanoparticles, and NCT theory. Chapter 2 describes a procedure to create mesoporous metal chelating silica nanoparticles, mDTTA. This is achieved via a co-condensation of tetraethoxysilane (TEOS) and 3-trimethoxysilyl-propyl diethylenetriamine (SiDETA) followed by a post-synthesis modification step with bromoacetic acid (BrAA). These particles have a large surface area and well-defined pores of ~2 nm. The mDTTA nanoparticles were used to chelate the copper(II), cobalt(II) and gadolinium(III). The chelating of gadolinium is the most interesting since it can be used as a MRI contrast agent and a neutron capture therapeutic. The synthetic procedure developed also allows for the attachment of a fluorophore that gives the gadolinium chelating mDTTA nanoparticles a dual imaging modality. Chapter 3 presents the synthetic method used to produce two classes of large surface area organically modified silica (ORMOSIL) nanoparticles. Condensating the organosilane vinyltrimethoxysilane in a micellar solution results in nanoparticles that are either surface rough (raspberry-like) or mesoporous nanoparticles, which prior to this thesis has not been demonstrated in ORMOSIL chemistry. Furthermore, the vinyl functionalities are modified, using

  7. Community Geothermal Technology Program: Silica bronze project. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Bianchini, H.

    1989-10-01

    Objective was to incorporate waste silica from the HGP-A geothermal well in Pohoiki with other refractory materials for investment casting of bronze sculpture. The best composition for casting is about 50% silica, 25% red cinders, and 25% brick dust; remaining ingredient is a binder, such as plaster and water.

  8. Enhanced photocatalytic activity of titania-silica mixed oxide prepared via basic hydrolyzation

    International Nuclear Information System (INIS)

    Xie Chao; Xu Zili; Yang Qiujing; Xue Baoyong; Du Yaoguo; Zhang Jiahua

    2004-01-01

    Two different synthesis routes were applied to prepare TiO 2 -XSiO 2 (X denotes mol% of silica in titania-silica mixed oxides) with different silica concentrations by using ammonia water as hydrolysis catalyst. Through comparing the photocatalytic performance of two sets of mixed oxides, we found that the photocatalytic activity of mixed oxides prepared via the route which can promote homogeneity, was significantly enhanced as compared with that of counterparts prepared via the another route, and the highest photocatalytic activity obtained by adding about 9.1 mol% silica into titania was much higher than that of pure TiO 2 . The mixed oxides were investigated by means of XRD, thermal analysis, UV-vis, FT-IR and XPS. The characterization results suggest that, in comparison with pure TiO 2 , the mixed oxides exhibit smaller crystallite size and higher thermal stability which can elevate the temperature of anatase to rutile phase transformation due to the addition of silica. Furthermore, Broensted acidity, which is associated with the formation of Ti-O-Si hetero linkages where tetrahedrally coordinated silica is chemically mixed with the octahedral titania matrix, may be a very important contribution to the enhanced photocatalytic activity of titania-silica mixed oxides as well

  9. Aqueous Dispersions of Silica Stabilized with Oleic Acid Obtained by Green Chemistry.

    Science.gov (United States)

    Nistor, Cristina Lavinia; Ianchis, Raluca; Ghiurea, Marius; Nicolae, Cristian-Andi; Spataru, Catalin-Ilie; Culita, Daniela Cristina; Pandele Cusu, Jeanina; Fruth, Victor; Oancea, Florin; Donescu, Dan

    2016-01-05

    The present study describes for the first time the synthesis of silica nanoparticles starting from sodium silicate and oleic acid (OLA). The interactions between OLA and sodium silicate require an optimal OLA/OLANa molar ratio able to generate vesicles that can stabilize silica particles obtained by the sol-gel process of sodium silicate. The optimal molar ratio of OLA/OLANa can be ensured by a proper selection of OLA and respectively of sodium silicate concentration. The titration of sodium silicate with OLA revealed a stabilization phenomenon of silica/OLA vesicles and the dependence between their average size and reagent's molar ratio. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) measurements emphasized the successful synthesis of silica nanoparticles starting from renewable materials, in mild condition of green chemistry. By grafting octadecyltrimethoxysilane on the initial silica particles, an increased interaction between silica particles and the OLA/OLANa complex was achieved. This interaction between the oleyl and octadecyl chains resulted in the formation of stable gel-like aqueous systems. Subsequently, olive oil and an oleophylic red dye were solubilized in these stable aqueous systems. This great dispersing capacity of oleosoluble compounds opens new perspectives for future green chemistry applications. After the removal of water and of the organic chains by thermal treatment, mesoporous silica was obtained.

  10. Soft template synthesis of yolk/silica shell particles.

    Science.gov (United States)

    Wu, Xue-Jun; Xu, Dongsheng

    2010-04-06

    Yolk/shell particles possess a unique structure that is composed of hollow shells that encapsulate other particles but with an interstitial space between them. These structures are different from core/shell particles in that the core particles are freely movable in the shell. Yolk/shell particles combine the properties of each component, and can find potential applications in catalysis, lithium ion batteries, and biosensors. In this Research News article, a soft-template-assisted method for the preparation of yolk/silica shell particles is presented. The demonstrated method is simple and general, and can produce hollow silica spheres incorporated with different particles independent of their diameters, geometry, and composition. Furthermore, yolk/mesoporous silica shell particles and multishelled particles are also prepared through optimization of the experimental conditions. Finally, potential applications of these particles are discussed.

  11. An investigation of laser processing of silica surfaces

    International Nuclear Information System (INIS)

    Weber, A.J.; Stewart, A.F.; Exarhos, G.J.; Stowell, W.K.

    1988-01-01

    An initial set of experiments has been conducted to determine the practicality of laser processing of optical substrates. In contrast to earlier work, a high average power CO 2 laser was used to flood load the entire surface of each test sample. Fused silica substrates were laser polished on both surfaces at power densities ranging from 150 to 350 W/cm 2 . During each test sequence sample surface temperatures were recorded using a thermal imaging system. Extensive pre- and post-test characterization revealed that surface roughness and scattering of bare silica surfaces were reduced while internal stress increased. Laser damage thresholds were found to increase only for certain conditions. Changes in the microstructure were observed. These preliminary experiments demonstrate that laser processing can dramatically improve the optical properties of fused silica substrates

  12. Effect of Synthesis Time on Morphology of Hollow Porous Silica Microspheres

    Directory of Open Access Journals (Sweden)

    Qian CHEN

    2012-03-01

    Full Text Available Hollow porous silica microspheres may be applicable as containers for the controlled release in drug delivery systems (DDS, foods, cosmetics, agrochemical, textile industry, and in other technological encapsulation use. In order to control the surface morphological properties of the silica microspheres, the effect of synthesis time on their formation was studied by a method of water-in-oil (W/O emulsion mediated sol-gel techniques. An aqueous phase of water, ammonium hydroxide and a surfactant Tween 20 was emulsified in an oil phase of 1-octanol with a stabilizer, hydroxypropyl cellulose (HPC, and a surfactant, sorbitan monooleate (Span 80 with low hydrophile-lipophile balance (HLB value. Tetraethyl orthosilicate (TEOS as a silica precursor was added to the emulsion. The resulting silica particles at different synthesis time 24, 48, and 72 hours were air-dried at room temperature and calcinated at 773 K for 3 hours. The morphology of the particles was characterized by scanning electron microscopy and the particle size distribution was measured by laser diffraction. The specific surface areas were studied by 1-point BET method, and pore sizes were measured by Image Tool Software. Both dense and porous silica microspheres were observed after all three syntheses. Hollow porous silica microspheres were formed at 24 and 48 hours synthesis time. Under base catalyzed sol-gel solution, the size of silica particles was in the range of 5.4 μm to 8.2 μm, and the particles had surface area of 111 m2/g – 380 m2/g. The longer synthesis time produced denser silica spheres with decreased pore sizes.DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1344

  13. Pulmonary hypertension and vascular remodeling in mice exposed to crystalline silica.

    Science.gov (United States)

    Zelko, Igor N; Zhu, Jianxin; Ritzenthaler, Jeffrey D; Roman, Jesse

    2016-11-28

    Occupational and environmental exposure to crystalline silica may lead to the development of silicosis, which is characterized by inflammation and progressive fibrosis. A substantial number of patients diagnosed with silicosis develop pulmonary hypertension. Pulmonary hypertension associated with silicosis and with related restrictive lung diseases significantly reduces survival in affected subjects. An animal model of silicosis has been described previously however, the magnitude of vascular remodeling and hemodynamic effects of inhaled silica are largely unknown. Considering the importance of such information, this study investigated whether mice exposed to silica develop pulmonary hypertension and vascular remodeling. C57BL6 mice were intratracheally injected with either saline or crystalline silica at doses 0.2 g/kg, 0.3 g/kg and 0.4 g/kg and then studied at day 28 post-exposure. Pulmonary hypertension was characterized by changes in right ventricular systolic pressure and lung histopathology. Mice exposed to saline showed normal lung histology and hemodynamic parameters while mice exposed to silica showed increased right ventricular systolic pressure and marked lung pathology characterized by a granulomatous inflammatory reaction and increased collagen deposition. Silica-exposed mice also showed signs of vascular remodeling with pulmonary artery muscularization, vascular occlusion, and medial thickening. The expression of pro-inflammatory genes such as TNF-α and MCP-1 was significantly upregulated as well as the expression of the pro-remodeling genes collagen type I, fibronectin and the metalloproteinases MMP-2 and TIMP-1. On the other hand, the expression of several vasculature specific genes involved in the regulation of endothelial function was significantly attenuated. We characterized a new animal model of pulmonary hypertension secondary to pulmonary fibrosis induced by crystalline silica. Our data suggest that silica promotes the damage of the

  14. Assessment of Methods to Consolidate Iodine-Loaded Silver-Functionalized Silica Aerogel

    Energy Technology Data Exchange (ETDEWEB)

    Matyas, Josef; Engler, Robert K.

    2013-09-01

    The U.S. Department of Energy is currently investigating alternative sorbents for the removal and immobilization of radioiodine from the gas streams in a nuclear fuel reprocessing plant. One of these new sorbents, Ag0-functionalized silica aerogels, shows great promise as a potential replacement for Ag-bearing mordenites because of its high selectivity and sorption capacity for iodine. Moreover, a feasible consolidation of iodine-loaded Ag0-functionalized silica aerogels to a durable SiO2-based waste form makes this aerogel an attractive choice for sequestering radioiodine. This report provides a preliminary assessment of the methods that can be used to consolidate iodine-loaded Ag0-functionalized silica aerogels into a final waste form. In particular, it focuses on experimental investigation of densification of as prepared Ag0-functionalized silica aerogels powders, with or without organic moiety and with or without sintering additive (colloidal silica), with three commercially available techniques: 1) hot uniaxial pressing (HUP), 2) hot isostatic pressing (HIP), and 3) spark plasma sintering (SPS). The densified products were evaluated with helium gas pycnometer for apparent density, with the Archimedes method for apparent density and open porosity, and with high-resolution scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) for the extent of densification and distribution of individual elements. The preliminary investigation of HUP, HIP, and SPS showed that these sintering methods can effectively consolidate powders of Ag0-functionalized silica aerogel into products of near-theoretical density. Also, removal of organic moiety and adding 5.6 mass% of colloidal silica to Ag0-functionalized silica aerogel powders before processing provided denser products. Furthermore, the ram travel data for SPS indicated that rapid consolidation of powders can be performed at temperatures below 950°C.

  15. Functionalized mesoporous silica nanoparticles for oral delivery of budesonide

    Energy Technology Data Exchange (ETDEWEB)

    Yoncheva, K., E-mail: krassi.yoncheva@gmail.com [Department of Pharmaceutical Technology, Faculty of Pharmacy, Medical University of Sofia, 2 Dunav Str., 1000 Sofia (Bulgaria); Popova, M. [Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Sofia (Bulgaria); Szegedi, A.; Mihaly, J. [Institute of Nanochemistry and Catalysis, Chemical Research Center, Hungarian Academy of Sciences, Pusztaszeri út. 59-67, 1025 Budapest (Hungary); Tzankov, B.; Lambov, N.; Konstantinov, S.; Tzankova, V. [Department of Pharmaceutical Technology, Faculty of Pharmacy, Medical University of Sofia, 2 Dunav Str., 1000 Sofia (Bulgaria); Pessina, F.; Valoti, M. [Dipartimento di Scienze della Vita, Universita di Siena, via Aldo Moro 2, Siena (Italy)

    2014-03-15

    Non-functionalized and amino-functionalized mesoporous silica nanoparticle were loaded with anti-inflammatory drug budesonide and additionally post-coated with bioadhesive polymer (carbopol). TEM images showed spherical shape of the nanoparticles and slightly higher polydispersity after coating with carbopol. Nitrogen physisorption and thermogravimetic analysis revealed that more efficient loading and incorporation into the pores of nanoparticles was achieved with the amino-functionalized silica carrier. Infrared spectra indicated that the post-coating of these nanoparticles with carbopol led to the formation of bond between amino groups of the functionalized carrier and carboxyl groups of carbopol. The combination of amino-functionalization of the carrier with the post-coating of the nanoparticles sustained budesonide release. Further, an in vitro model of inflammatory bowel disease showed that the cytoprotective effect of budesonide loaded in the post-coated silica nanoparticles on damaged HT-29 cells was more pronounced compared to the cytoprotection obtained with pure budesonide. -- Graphical abstract: Silica mesoporous MCM-41 particles were amino-functionalized, loaded with budesonide and post-coated with bioadhesive polymer (carbopol) in order to achieve prolonged residence of anti-inflammatory drug in GIT. Highlights: • Higher drug loading in amino-functionalized mesoporous silica. • Amino-functionalization and post-coating of the nanoparticles sustained drug release. • Achievement of higher cytoprotective effect with drug loaded into the nanoparticles.

  16. Sol-gel Derived Warfarin - Silica Composites for Controlled Drug Release.

    Science.gov (United States)

    Dolinina, Ekaterina S; Parfenyuk, Elena V

    2017-01-01

    Warfarin, commonly used anticoagulant in clinic, has serious shortcomings due to its unsatisfactory pharmacodynamics. One of the efficient ways for the improvement of pharmacological and consumer properties of drugs is the development of optimal drug delivery systems. The aim of this work is to synthesize novel warfarin - silica composites and to study in vitro the drug release kinetics to obtain the composites with controlled release. The composites of warfarin with unmodified (UMS) and mercaptopropyl modified silica (MPMS) were synthesized by sol-gel method. The composite formation was confirmed by FTIR spectra. The concentrations of warfarin released to media with pH 1.6, 6.8 and 7.4 were measured using UV spectroscopy. The drug release profiles from the solid composites were described by a series of kinetic models which includes zero order kinetics, first order kinetics, the modified Korsmeyer-Peppas model and Hixson-Crowell model. The synthesized sol-gel composites have different kinetic behavior in the studied media. In contrast to the warfarin composite with unmodified silica, the drug release from the composite with mercaptopropyl modified silica follows zero order kinetics for 24 h irrespective to the release medium pH due to mixed mechanism (duffusion + degradation and/or disintegration of silica matrix). The obtained results showed that warfarin - silica sol-gel composites have a potential application for the development of novel oral formulation of the drug with controlled delivery. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  17. Thermo-physical properties of silica gel for adsorption desalination cycle

    KAUST Repository

    Thu, Kyaw; Chakraborty, Anutosh; Saha, Bidyut Baran; Ng, Kim Choon

    2013-01-01

    Thermo-physical properties, surface characteristics and water vapor uptake capacity are key parameters in the selection of adsorbent for an adsorption desalination (AD) cycle. In the AD cycles, silica gel is used as adsorbent due to their high water vapor uptake capacity, reliability, repeatability and inexpensiveness as compared to other adsorbents. Three types of commercially available silica gels (Type-RD 2560,Type-A5BW and Type-A++) are investigated using a surface characteristic analyzer and their thermo-physical properties are evaluated using several analysis methods. The instrument used in this investigation employs the static volumetric method with liquid Nitrogen at 77 K as the filing fluid. The surface area of each adsorbent is studied using Brunauer-Emmett-Teller (BET) method whilst the pore size distribution (PSD) analysis is conducted with the Non-Local Density Functional Theory (NLDFT). It is observed that the Type-A++ silica gel (granular type) possesses the highest surface area of 863.6 m2/g amongst the three parent silica gels studied. It has a two-maxima or bimodal distribution pattern where the pore diameters are distributed mostly between 10 Å and 30 Å. Water vapor uptake capacity of silica gels are studied with water vapor dosage apparatus and the results show that the Type-A++ silica gel exhibits a highest equilibrium uptake at 537 cm3/g. These thermo-physical properties are essential for the design and the numerical simulation of AD cycles. © 2012 Published by Elsevier Ltd.

  18. Thermo-physical properties of silica gel for adsorption desalination cycle

    KAUST Repository

    Thu, Kyaw

    2013-02-01

    Thermo-physical properties, surface characteristics and water vapor uptake capacity are key parameters in the selection of adsorbent for an adsorption desalination (AD) cycle. In the AD cycles, silica gel is used as adsorbent due to their high water vapor uptake capacity, reliability, repeatability and inexpensiveness as compared to other adsorbents. Three types of commercially available silica gels (Type-RD 2560,Type-A5BW and Type-A++) are investigated using a surface characteristic analyzer and their thermo-physical properties are evaluated using several analysis methods. The instrument used in this investigation employs the static volumetric method with liquid Nitrogen at 77 K as the filing fluid. The surface area of each adsorbent is studied using Brunauer-Emmett-Teller (BET) method whilst the pore size distribution (PSD) analysis is conducted with the Non-Local Density Functional Theory (NLDFT). It is observed that the Type-A++ silica gel (granular type) possesses the highest surface area of 863.6 m2/g amongst the three parent silica gels studied. It has a two-maxima or bimodal distribution pattern where the pore diameters are distributed mostly between 10 Å and 30 Å. Water vapor uptake capacity of silica gels are studied with water vapor dosage apparatus and the results show that the Type-A++ silica gel exhibits a highest equilibrium uptake at 537 cm3/g. These thermo-physical properties are essential for the design and the numerical simulation of AD cycles. © 2012 Published by Elsevier Ltd.

  19. Magnetic polymer-silica composites as bioluminescent sensors for bilirubin detection

    Energy Technology Data Exchange (ETDEWEB)

    Timin, Alexander S., E-mail: a_timin@mail.ru [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000, Ivanovo (Russian Federation); RASA Center in Tomsk, Tomsk Polytechnic University, pros. Lenina, 30, Tomsk (Russian Federation); Solomonov, Alexey V. [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000, Ivanovo (Russian Federation); Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, 7610001 (Israel); Kumagai, Akiko; Miyawaki, Atsushi [Cell Function Dynamics, Brain Science Institute RIKEN, 2-1 Hirosawa, Wako-city, Saitama, 351-0198 (Japan); Khashirova, Svetlana Yu; Zhansitov, Azamat [Kabardino-Balkar State University, 173 Chernyshevskogo St., Nal' chik, 360004, Kabardino-Balkaria (Russian Federation); Rumyantsev, Evgeniy V. [Inorganic Chemistry Department, Ivanovo State University of Chemistry and Technology (ISUCT), 7, Sheremetevsky prosp., 153000, Ivanovo (Russian Federation)

    2016-11-01

    The synthesis of multifunctional nano-sized materials is leading to the rapid development of key application, including improved drug delivery, bioimaging and protein separation. In this work, magnetic silica particles modified with novel guanidine containing co-polymers were manufactured via sol-gel method. To evaluate the chemical composition of our prepared samples, FT-IR spectroscopy and thermogravimetry were conducted. Scanning electron microscopy was used in order to investigate the morphology of final products after modification by guanidine containing co-polymers and iron nanoparticles. In addition, the surface of polymer-silica composites was functionalized by the novel bilirubin-inducible fluorescent protein UnaG. In an aqueous bilirubin solution, the silica particles decorated with the polymer-UnaG have showed bright fluorescence. Synthesis and characterization of these hybrid materials allow developing of new multifunctional nano-sized materials, which will be used for detection and separation of bilirubin, a lipophilic heme catabolite that is a clinical diagnostic for liver function. - Highlights: • Novel magnetic silicas grafted by guanidine containing co-polymers were prepared. • Unag protein was effectively loaded into polymer coated silicas. • The fluorescent properties depend on content of bilirubin.

  20. Magnetic polymer-silica composites as bioluminescent sensors for bilirubin detection

    International Nuclear Information System (INIS)

    Timin, Alexander S.; Solomonov, Alexey V.; Kumagai, Akiko; Miyawaki, Atsushi; Khashirova, Svetlana Yu; Zhansitov, Azamat; Rumyantsev, Evgeniy V.

    2016-01-01

    The synthesis of multifunctional nano-sized materials is leading to the rapid development of key application, including improved drug delivery, bioimaging and protein separation. In this work, magnetic silica particles modified with novel guanidine containing co-polymers were manufactured via sol-gel method. To evaluate the chemical composition of our prepared samples, FT-IR spectroscopy and thermogravimetry were conducted. Scanning electron microscopy was used in order to investigate the morphology of final products after modification by guanidine containing co-polymers and iron nanoparticles. In addition, the surface of polymer-silica composites was functionalized by the novel bilirubin-inducible fluorescent protein UnaG. In an aqueous bilirubin solution, the silica particles decorated with the polymer-UnaG have showed bright fluorescence. Synthesis and characterization of these hybrid materials allow developing of new multifunctional nano-sized materials, which will be used for detection and separation of bilirubin, a lipophilic heme catabolite that is a clinical diagnostic for liver function. - Highlights: • Novel magnetic silicas grafted by guanidine containing co-polymers were prepared. • Unag protein was effectively loaded into polymer coated silicas. • The fluorescent properties depend on content of bilirubin.

  1. Interphases, gelation, vitrification, porous glasses and the generalized Cauchy relation: epoxy/silica nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Philipp, M; Mueller, U; Jimenez Rioboo, R J; Baller, J; Sanctuary, R; Krueger, J K [Laboratoire de Physique des Materiaux, University of Luxembourg, 162A avenue de la Faiencerie, L-1511 Luxembourg (Luxembourg); Possart, W [Fachbereich Werkstoffwissenschaften, Universitaet des Saarlandes, D-66123 Saarbruecken (Germany)], E-mail: martine.philipp@uni.lu

    2009-02-15

    The generalized Cauchy relation (gCR) of epoxy/silica nano-composites does not show either the chemically induced sol-gel transition or the chemically induced glass transition in the course of polymerization. Astonishingly, by varying the silica nanoparticles' concentration between 0 and 25 vol% in the composites, the Cauchy parameter A of the gCR remains universal and can be determined from the pure epoxy's elastic moduli. Air-filled porous silica glasses are considered as models for percolated silica particles. A longitudinal modulus versus density representation evidences the aforementioned transition phenomena during polymerization of the epoxy/silica nanocomposites. The existence of optically and mechanically relevant interphases is discussed.

  2. Interphases, gelation, vitrification, porous glasses and the generalized Cauchy relation: epoxy/silica nanocomposites

    International Nuclear Information System (INIS)

    Philipp, M; Mueller, U; Jimenez Rioboo, R J; Baller, J; Sanctuary, R; Krueger, J K; Possart, W

    2009-01-01

    The generalized Cauchy relation (gCR) of epoxy/silica nano-composites does not show either the chemically induced sol-gel transition or the chemically induced glass transition in the course of polymerization. Astonishingly, by varying the silica nanoparticles' concentration between 0 and 25 vol% in the composites, the Cauchy parameter A of the gCR remains universal and can be determined from the pure epoxy's elastic moduli. Air-filled porous silica glasses are considered as models for percolated silica particles. A longitudinal modulus versus density representation evidences the aforementioned transition phenomena during polymerization of the epoxy/silica nanocomposites. The existence of optically and mechanically relevant interphases is discussed.

  3. Silica exposure and silicosis among Ontario hardrock miners: II. Exposure estimates.

    Science.gov (United States)

    Verma, D K; Sebestyen, A; Julian, J A; Muir, D C; Schmidt, H; Bernholz, C D; Shannon, H S

    1989-01-01

    An epidemiological investigation was carried out to determine the relationship between silicosis in hardrock miners in Ontario and cumulative exposure to silica (free crystalline silica--alpha quartz) dust. This second report describes a side-by-side air-sampling program used to derive a konimeter/gravimetric silica conversion curve. A total of 2,360 filter samples and 90,000 konimeter samples were taken over 2 years in two mines representing the ore types gold and uranium, both in existing conditions as well as in an experimental stope in which dry drilling was used to simulate the high dust conditions of the past. The method of calculating cumulative respirable silica exposure indices for each miner is reported.

  4. Controlled growth of silica-titania hybrid functional nanoparticles through a multistep microfluidic approach.

    Science.gov (United States)

    Shiba, K; Sugiyama, T; Takei, T; Yoshikawa, G

    2015-11-11

    Silica/titania-based functional nanoparticles were prepared through controlled nucleation of titania and subsequent encapsulation by silica through a multistep microfluidic approach, which was successfully applied to obtaining aminopropyl-functionalized silica/titania nanoparticles for a highly sensitive humidity sensor.

  5. Styrene grafted natural rubber reinforced by in situ silica generated via sol–gel technique

    Energy Technology Data Exchange (ETDEWEB)

    Sittiphan, Torpong [Program of Petrochemistry and Polymer Sciences, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Prasassarakich, Pattarapan [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Poompradub, Sirilux, E-mail: sirilux.p@chula.ac.th [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand)

    2014-02-15

    Highlights: • Sol–gel reaction by NR latex was the absence of use of organic solvent and base catalyst. • Well dispersed in situ formed silica particles in the rubber matrix were obtained. • In situ silica was better to improve mechanical properties of rubber vulcanizates. -- Abstract: The filling of styrene graft natural rubber (ST-GNR) with in situ formed silica was performed using the sol–gel reaction via the latex solution method. The mechanical properties of ST-GNR/NR vulcanizate were improved when using the in situ formed silica to levels higher than those obtained with the commercial ex situ formed silica filled ST-GNR/NR vulcanizates at a comparable silica content of 12 parts by weight per hundred parts of rubber. Transmission electron microscopy analysis revealed that the in situ silica particles were small (∼40 nm diameter) and well dispersed, while the commercial silica particles were larger (∼60 nm diameter) and markedly agglomerated in the rubbery matrix. The mechanical properties of the composites prepared via both the solid rubber and latex solution methods were comparable.

  6. Surface-Enhanced Raman Scattering Using Silica Whispering-Gallery Mode Resonators

    Science.gov (United States)

    Anderson, Mark S.

    2013-01-01

    The motivation of this work was to have robust spectroscopic sensors for sensitive detection and chemical analysis of organic and molecular compounds. The solution is to use silica sphere optical resonators to provide surface-enhanced spectroscopic signal. Whispering-gallery mode (WGM) resonators made from silica microspheres were used for surface-enhanced Raman scattering (SERS) without coupling to a plasmonic mechanism. Large Raman signal enhancement is observed by exclusively using 5.08-micron silica spheres with 785-nm laser excitation. The advantage of this non-plasmonic approach is that the active substrate is chemically inert silica, thermally stable, and relatively simple to fabricate. The Raman signal enhancement is broadly applicable to a wide range of molecular functional groups including aliphatic hydrocarbons, siloxanes, and esters. Applications include trace organic analysis, particularly for in situ planetary instruments that require robust sensors with consistent response.

  7. Solvent free amorphisation for pediatric formulations (minitablets) using mesoporous silica

    DEFF Research Database (Denmark)

    Monsuur, Fred; Choudhari, Yogesh; Reddy, Upendra

    2016-01-01

    Introduction: Most silica based amorphisation strategies are using organic solvent loading methods. Towards pediatric formulations this is creating concerns. With this in mind the development of a dry amorphisation strategy was the focus of this study. The high internal surface area of mesoporous...... silica gel is densely crowded with silanol groups, which can provide hydrogen-bonding possibilities with a drug, potentially resulting in amorphisation. Purpose: Amorphous drugs provide an advantage in solubility; however, their low physical stability always remained concern. Additional there was a need...... to understand the mechanism and variables of dry amorphisation. Method: Ibuprofen (IBU) and Syloid® silica at different ratios were co-milled at variable milling times between 1 and 90 min. The interaction with; and amorphisation of IBU; on Syloid® silica was analyzed using SEM, FTIR, DSC and XRD. The co...

  8. Enhancement of nonlinear optical properties of compounds of silica

    Indian Academy of Sciences (India)

    The aim of this paper is to introduce a method for enhancing the nonlinear optical properties in silica glass by using metallic nanoparticles. First, the T-matrix method is developed to calculate the effective dielectric constant for the compound of silica glass and metallic nanoparticles, both of which possess nonlinear dielectric ...

  9. Dependence of thermal conductivity in micro to nano silica

    Indian Academy of Sciences (India)

    This work presents the measurement of thermal conductivity of nano-silica particles using needle probe method. The validation test of thermal probe was conducted on ice and THF hydrates using our experimental set up and the results are satisfactory when compared with the literature data. The nano silica used in this ...

  10. Synthesis of porous carbon/silica nanostructured microfiber with ultrahigh surface area

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Dan; Dong, Yan; Cui, Liru; Lin, Huiming, E-mail: hiuminglin@gmail.com; Qu, Fengyu, E-mail: qufengyu2012@yahoo.cn, E-mail: qufengyu@hrbnu.edu.cn [Harbin Normal University, College of Chemistry and Chemical Engineering (China)

    2014-12-15

    Carbon/silica-nanostructured microfibers were synthesized via electrospinning method using phenol-formaldehyde resin and tetraethyl orthosilicate as carbon and silica precursor with triblock copolymer Pluronic P123 as soft template. The prepared samples show uniform microfiber structure with ∼1 μm in diameter and dozens of microns in length. Additionally, the mesopores in the material is about 2–6 nm. When the silica component was removed by HF, the porous carbon microfibers (PCMFs) were obtained. In addition, after the carbon/silica composites were calcined in air, the porous silica microfibers (PSiMFs) were obtained, revealing the converse porous nanostructure as PCMFs. It is a simple way to prepare PCMFs and PSiMFs with silica and carbon as the template to each other. Additionally, PCMFs possess an ultrahigh specific surface area (2,092 m{sup 2} g{sup −1}) and large pore volume. The electrochemical performance of the prepared PCMF material was investigated in 6.0 M KOH electrolyte. The PCMF electrode exhibits a high specific capacitance (252 F g{sup −1} at 0.5 A g{sup −1}). Then, superior cycling stability (97 % retention after 4,000 cycles) mainly is due to its unique nanostructure.

  11. Effect of Dissolved Silica on Immobilization of Boron by Magnesium Oxide

    Directory of Open Access Journals (Sweden)

    Shoko Nozawa

    2018-02-01

    Full Text Available The effect of silica on the immobilization reaction of boron by magnesium oxide was investigated by laboratory experiments. In the absence of silica, due to dissolution of the magnesium oxide, boron was removed from solutions by the precipitation of multiple magnesium borates. In the presence of silica, magnesium silica hydrate (M-S-H was formed as a secondary mineral, which takes up boron. Here 11B magic-angle spinning nuclear magnetic resonance (MAS-NMR and Fourier transform infrared spectrometer (FT-IR data show that a part of the boron would be incorporated into M-S-H structures by isomorphic substitution of silicon. Another experiment where magnesium oxide and amorphous silica were reacted beforehand and boron was added later showed that the shorter the reaction time of the preceding reaction, the higher the sorption ratio of boron. That is, boron was incorporated into the M-S-H mainly by coprecipitation. The experiments in the study here show that the sorption of boron in the presence of silica is mainly due to the incorporation of boron during the formation of the M-S-H structure, which suggests that boron would not readily leach out, and that stable immobilization of boron can be expected.

  12. A Pervaporation Study of Ammonia Solutions Using Molecular Sieve Silica Membranes

    Directory of Open Access Journals (Sweden)

    Xing Yang

    2014-02-01

    Full Text Available An innovative concept is proposed to recover ammonia from industrial wastewater using a molecular sieve silica membrane in pervaporation (PV, benchmarked against vacuum membrane distillation (VMD. Cobalt and iron doped molecular sieve silica-based ceramic membranes were evaluated based on the ammonia concentration factor downstream and long-term performance. A modified low-temperature membrane evaluation system was utilized, featuring the ability to capture and measure ammonia in the permeate. It was found that the silica membrane with confirmed molecular sieving features had higher water selectivity over ammonia. This was due to a size selectivity mechanism that favoured water, but blocked ammonia. However, a cobalt doped silica membrane previously treated with high temperature water solutions demonstrated extraordinary preference towards ammonia by achieving up to a 50,000 mg/L ammonia concentration (a reusable concentration level measured in the permeate when fed with 800 mg/L of ammonia solution. This exceeded the concentration factor expected by the benchmark VMD process by four-fold, suspected to be due to the competitive adsorption of ammonia over water into the silica structure with pores now large enough to accommodate ammonia. However, this membrane showed a gradual decline in selectivity, suspected to be due to the degradation of the silica material/pore structure after several hours of operation.

  13. Comparison of ionospheric F2 peak parameters foF2 and hmF2 with IRI2001 at Hainan

    Science.gov (United States)

    Wang, X.; Shi, J. K.; Wang, G. J.; Gong, Y.

    2009-06-01

    Monthly median values of foF2, hmF2 and M(3000)F2 parameters, with quarter-hourly time interval resolution for the diurnal variation, obtained with DPS4 digisonde at Hainan (19.5°N, 109.1°E; Geomagnetic coordinates: 178.95°E, 8.1°N) are used to investigate the low-latitude ionospheric variations and comparisons with the International Reference Ionosphere (IRI) model predictions. The data used for the present study covers the period from February 2002 to April 2007, which is characterized by a wide range of solar activity, ranging from high solar activity (2002) to low solar activity (2007). The results show that (1) Generally, IRI predictions follow well the diurnal and seasonal variation patterns of the experimental values of foF2, especially in the summer of 2002. However, there are systematic deviation between experimental values and IRI predictions with either CCIR or URSI coefficients. Generally IRI model greatly underestimate the values of foF2 from about noon to sunrise of next day, especially in the afternoon, and slightly overestimate them from sunrise to about noon. It seems that there are bigger deviations between IRI Model predictions and the experimental observations for the moderate solar activity. (2) Generally the IRI-predicted hmF2 values using CCIR M(3000)F2 option shows a poor agreement with the experimental results, but there is a relatively good agreement in summer at low solar activity. The deviation between the IRI-predicted hmF2 using CCIR M(3000)F2 and observed hmF2 is bigger from noon to sunset and around sunrise especially at high solar activity. The occurrence time of hmF2 peak (about 1200 LT) of the IRI model predictions is earlier than that of observations (around 1500 LT). The agreement between the IRI hmF2 obtained with the measured M(3000)F2 and the observed hmF2 is very good except that IRI overestimates slightly hmF2 in the daytime in summer at high solar activity and underestimates it in the nighttime with lower values near

  14. Preparation of Silica Modified with 2-Mercaptoimidazole and its SorptionProperties of Chromium(III

    Directory of Open Access Journals (Sweden)

    Harry Budiman

    2009-01-01

    Full Text Available Modified silica gel was prepared to remove the heavy metal of chromium(III from water sample. Silica gel was used as supporting material and the 2-mercaptoimidazole was immobilized onto surface silica so that the silica would have selective properties to adsorb the heavy metal chromium(III through the formation of coordination compound between the 2-mercaptoimidazole and chromium(III. The characterization of modified silica gel was carried out by analyzing the Fourier Transform Infrared Spectrum of this material in order to ensure the immobilization of 2-mercaptoimidazole onto the surface. The effect of pH solution, initial concentration of chromium(III, and interaction time were investigated in batch mode to find the adsorption properties of chromium(III onto modified silica. The condition optimum of these parameters was applied to determine the removal percentage of chromium(III in water sample using the modified silica gel

  15. Selectivity of silica species in ocean observed from seasonal and local changes

    Science.gov (United States)

    Tanaka, Miho; Takahashi, Kazuya; Nemoto, Masao; Horimoto, Naho

    2013-03-01

    Silicic acids, derived from SiO2 (silica), have several chemical forms in solution. Silica is a nutrient for diatoms, which are phytoplankton in oceans. Silica species can be used as a tracer to examine the behavior of silica in nature. The speciation for silica by FAB-MS (fast atom bombardment mass spectrometry) has been carried out for seawater samples from Tokyo Bay and Sagami Bay to investigate the seasonal and locational changes of the depth profiles of silica species. The species, [Si(OH)2O2Na+]-, [Si2(OH)5O2]- ([dimer]-), [Si2(OH)4O3Na+]-, [Si(OH)7O5-] ([cyclic tetramer]-), [Si4(OH)6O6Na+]-, [Si(OH)9O]- ([linear tetramer]-) and [Si4(OH)8O5Na+]- were mainly identified by FAB-MS. The seasonal and locational changes and the reproducibility of depth profiles of silica species were determined from October 2001 to July 2002. The depth profile of the ratio of linear tetramer to cyclic tetramer reflects the activity of diatoms, implying that the linear tetramer is the preferred "food" for diatoms. In particular, the depth profile for the ratio of linear tetramer to cyclic tetramer exhibits a critical changes that depend on the season. Furthermore, the depth profiles for the samples from Sagami Bay (open ocean) indicate that seawater is easily exchanged by ocean currents (the Japan Current). Thus, silica speciation by FAB-MS can give us a new tracer indicating the characteristics of the seawater budget, which change with depth, season and ocean locality.

  16. The Effect of Hydrothermal Treatment on Olivine Nano-Silica

    NARCIS (Netherlands)

    Griend, van de M.C; Lazaro, A.; Brouwers, H.J.H.

    2012-01-01

    This paper provides an overview of the effects of ripening the olivine nano-silica to form particles with a lower specific surface area for optimal use in high performance concrete. The nano-silica was ripened using a hydrothermal treatment in a mixed batch reactor at 90 C, pH ranging from 8 to 10

  17. Upgrading offshore pipelines concrete coated by silica fume additive against aggressive mechanical laying

    OpenAIRE

    M.I. Abdou; Hesham Abuseda

    2016-01-01

    Studies have been carried out to investigate the possibility of utilizing a broad range of micro-silica partial additions with cement in the production of concrete coating. This study investigated the strength properties and permeability of micro-silica concrete to achieve resistance toward concrete cracking and damage during laying. The chemical composition of micro-silica (silica fume) was determined, and has been conducted on concrete mixes with additions of 3 up to 25% by weight of cement...

  18. Erabulenols, inhibitors of cholesteryl ester transfer protein produced by Penicillium sp. FO-5637. I.Production, isolation and biological properties.

    Science.gov (United States)

    Tomoda, H; Tabata, N; Masuma, R; Si, S Y; Omura, S

    1998-07-01

    Penicillium sp. FO-5637, a soil isolate, was found to produce a series of inhibitors of cholesteryl ester transfer protein (CETP). Novel active compounds, designated erabulenols A and B, were isolated from the fermentation broth of the producing strain by solvent extraction, ODS column chromatography and HPLC. Erabulenols A and B inhibit human CETP activity with IC50 values of 47.7 and 58.2 microM in an in vitro assay system containing 200 microM BSA, respectively.

  19. Fabrication of transparent superhydrophobic glass with fibered-silica network

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Feng [College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006 (China); Shi, Zhenwu, E-mail: zwshi@suda.edu.cn [College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006 (China); Jiang, Yingjie; Xu, Chengyun; Wu, Zhuhui; Wang, Yanyan [College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006 (China); Peng, Changsi, E-mail: changsipeng@suda.edu.cn [College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province & Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006 (China)

    2017-06-15

    Highlights: • Superhydrophobic fibred-silica film with water contact angle of 166° and sliding angle of 1° was efficiently prepared using soot as template by CVD. • The film showed transmittance of 88% in visible range. • The superhydrophobic film possesses excellent mechanical robustness, chemical corrosion resistance, and thermal stability. • The superhydrophobic film showed outstanding self-cleaning behavior. - Abstract: In this paper, silica was deposited on the soot film pre-coated glass via chemical vapor deposition. Through calcination at 500 °C with the assistance of O{sub 2} airflow, the soot film was removed and a novel robust fibered-silica network film was then decorated onto the glass substrate. After modification with fluorosilane, the surface water contact angle (WCA) was 166° and sliding angle (SA) was 1° which behaves a good self-cleaning for the as-prepared glass. And its average transmittance was still over 88% in visible wavelength. Moreover, this fibered-silica coating showed a strong tolerance for heavy water droplets, acid/alkali corrosion, salt solution immersion and thermal treatment.

  20. Surge-Resistant Nanocomposite Enameled Wire Using Silica Nanoparticles with Binary Chemical Compositions on the Surface

    Directory of Open Access Journals (Sweden)

    Jeseung Yoo

    2015-01-01

    Full Text Available We developed polyesterimide (PEI nanocomposite enameled wires using surface-modified silica nanoparticles with binary chemical compositions on the surface. The modification was done using silanes assisted by ultrasound, which facilitated high density modification. Two different trimethoxysilanes were chosen for the modification on the basis of resemblance of chemical compositions on the silica surface to PEI varnish. The surface-modified silica was well dispersed in PEI varnish, which was confirmed by optical observation and viscosity measurement. The glass transition temperature of the silica-PEI nanocomposite increased with the silica content. The silica-dispersed PEI varnish was then used for enameled wire fabrication. The silica-PEI nanocomposite enameled wire exhibited a much longer lifetime compared to that of neat PEI enameled wire in partial discharge conditions.