An Analysis Of Pole/zero Cancellation In LTR-based Feedback Design

DEFF Research Database (Denmark)

Niemann, Hans Henrik; Jannerup, Ole Erik

1990-01-01

The pole/zero cancellation in LTR-based feedback design will be analyzed for both full-order as well as minimal-order observers. The asymptotic behaviour of the sensitivity function from the LTR-procedure are given in explicit expressions in the case when a zero is not cancelled by an equivalent...... pole. It will be shown that the non-minimum phase case is included as a special case. The results are not based on any specific LTR-method....

Fabrication and Characterization of Linear and Nonlinear Photonic Devices in Fused Silica by Femtosecond Laser Writing

Science.gov (United States)

Ng, Jason Clement

Femtosecond laser processing is a flexible, three-dimensional (3D) fabrication technique used to make integrated low-loss photonic devices in fused silica. My work expanded the suite of available optical devices through the design and optimization of linear optical components such as low-loss (70-nm spectral window. My work further complemented femtosecond laser processing with the development of nonlinear device capabilities. While thermal poling is a well known process, significant challenges had restricted the development of nonlinear devices in fused silica. The laser writing process would erase the induced nonlinearity (erasing) while a written waveguide core acted as a barrier to the thermal poling process (blocking). Using second harmonic (SH) microscopy, the effectiveness of thermal poling on laser-written waveguides was systematically analyzed leading to the technique of "double poling", which effectively overcomes the two challenges of erasing and blocking. In this new process the substrate is poled before and after waveguide writing to restore the induced nonlinearity within the vicinity of the waveguide to enable effective poling for inducing a second-order nonlinearity (SON) in fused silica. A new flexible, femtosecond laser based erasure process was also developed to enable quasi-phase matching and to form arbitrarily chirped gratings. Following this result, second harmonic generation (SHG) in a quasiphase-matched (QPM) femtosecond laser written waveguide device was demonstrated. SHG in a chirped QPM structure was also demonstrated to illustrate the flexibility of the femtosecond laser writing technique. These are the first demonstration of frequency doubling in an all-femtosecond-laser-written structure. A maximum SHG conversion efficiency of 1.3 +/- 0.1x10 -11/W-cm-2 was achieved for the fundamental wavelength of 1552.8 nm with a phase-matching bandwidth of 4.4 nm for a 10.0-mm-long waveguide. For a shorter sample, an effective SON of chi(2) = 0

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.

Force interaction and 3D pole movement in double poling.

Science.gov (United States)

Stöggl, T; Holmberg, H-C

2011-12-01

The aim of this study was to analyze double poling using combined kinetic and 3D kinematic analysis at high skiing speeds as regards pole force components, pole angles and pole behavior during the poling and swing phase. The hypothesis was that a horizontal pole force is more predictive for maximal skiing speed (V(max)) than the resultant pole force. Sixteen elite skiers performed a double-poling V(max) test while treadmill roller skiing. Pole forces and 3D kinematics of pole movement at a speed of 30 km/h were analyzed and related to V(max). The duration of the "preparation phase" showed the strongest relationship with V(max) (r=0.87, Pmax) compared with the resultant pole force. Impact force was not related to V(max). At high skiing speeds, skiers should aim to combine high pole forces with appropriate timing of pole forces and appropriate pole and body positions during the swing and poling phase. The emphasis in training should be on the development of specific strength capacities for pole force production and the utilization of these capacities in double-poling training sessions. © 2011 John Wiley & Sons A/S.

Acoustic wave filter based on periodically poled lithium niobate.

Science.gov (United States)

Courjon, Emilie; Bassignot, Florent; Ulliac, Gwenn; Benchabane, Sarah; Ballandras, Sylvain

2012-09-01

Solutions for the development of compact RF passive transducers as an alternative to standard surface or bulk acoustic wave devices are receiving increasing interest. This article presents results on the development of an acoustic band-pass filter based on periodically poled ferroelectric domains in lithium niobate. The fabrication of periodically poled transducers (PPTs) operating in the range of 20 to 650 MHz has been achieved on 3-in (76.2-mm) 500-μm-thick wafers. This kind of transducer is able to excite elliptical as well as longitudinal modes, yielding phase velocities of about 3800 and 6500 ms(-1), respectively. A new type of acoustic band-pass filter is proposed, based on the use of PPTs instead of the SAWs excited by classical interdigital transducers. The design and the fabrication of such a filter are presented, as well as experimental measurements of its electrical response and transfer function. The feasibility of such a PPT-based filter is thereby demonstrated and the limitations of this method are discussed.

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.

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.

Novel silica-based ion exchange resin

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-11-01

Eichrom`s highly successful Diphonixo resin resembles a conventional ion exchange resin in its use of sulfonic acid ligands on a styrene- divinylbenzene matrix. Diphonix resin exhibits rapid exchange kinetics that allow economical operation of ion exchange systems. Unlike conventional resins, Diphonix resin contains chelating ligands that are diphosphonic acid groups that recognize and remove the targeted metals and reject the more common elements such as sodium, calcium and magnesium. This latter property makes Diphonix ideal for many industrial scale applications, including those involving waste treatment. For treatment of low-level, transuranic (TRU) and high- level radioactive wastes, Diphonix`s polystyrene backbone hinders its application due to radiolytic stability of the carbon-hydrogen bonds and lack of compatibility with expected vitrification schemes. Polystyrene-based Diphonix is approximately 60% carbon- hydrogen. In response to an identified need within the Department of Energy for a resin with the positive attributes of Diphonix that also exhibits greater radiolytic stability and final waste form compatibility, Eichrom has successfully developed a new, silica-based resin version of Diphonix. Target application for this new resin is for use in environmental restoration and waste management situations involving the processing of low-level, transuranic and high-level radioactive wastes. The resin can also be used for processing liquid mixed waste (waste that contains low level radioactivity and hazardous constituents) including mixed wastes contaminated with organic compounds. Silica-based Diphonix is only 10% carbon-hydrogen, with the bulk of the matrix silica.

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....

Nanoporous Silica-Based Protocells at Multiple Scales for Designs of Life and Nanomedicine

Directory of Open Access Journals (Sweden)

Jie Sun

2015-01-01

Full Text Available Various protocell models have been constructed de novo with the bottom-up approach. Here we describe a silica-based protocell composed of a nanoporous amorphous silica core encapsulated within a lipid bilayer built by self-assembly that provides for independent definition of cell interior and the surface membrane. In this review, we will first describe the essential features of this architecture and then summarize the current development of silica-based protocells at both micro- and nanoscale with diverse functionalities. As the structure of the silica is relatively static, silica-core protocells do not have the ability to change shape, but their interior structure provides a highly crowded and, in some cases, authentic scaffold upon which biomolecular components and systems could be reconstituted. In basic research, the larger protocells based on precise silica replicas of cells could be developed into geometrically realistic bioreactor platforms to enable cellular functions like coupled biochemical reactions, while in translational research smaller protocells based on mesoporous silica nanoparticles are being developed for targeted nanomedicine. Ultimately we see two different motivations for protocell research and development: (1 to emulate life in order to understand it; and (2 to use biomimicry to engineer desired cellular interactions.

Super-Hydrophobic/Icephobic Coatings Based on Silica Nanoparticles Modified by Self-Assembled Monolayers

Directory of Open Access Journals (Sweden)

Junpeng Liu

2016-12-01

Full Text Available A super-hydrophobic surface has been obtained from nanocomposite materials based on silica nanoparticles and self-assembled monolayers of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS using spin coating and chemical vapor deposition methods. Scanning electron microscope images reveal the porous structure of the silica nanoparticles, which can trap small-scale air pockets. An average water contact angle of 163° and bouncing off of incoming water droplets suggest that a super-hydrophobic surface has been obtained based on the silica nanoparticles and POTS coating. The monitored water droplet icing test results show that icing is significantly delayed by silica-based nano-coatings compared with bare substrates and commercial icephobic products. Ice adhesion test results show that the ice adhesion strength is reduced remarkably by silica-based nano-coatings. The bouncing phenomenon of water droplets, the icing delay performance and the lower ice adhesion strength suggest that the super-hydrophobic coatings based on a combination of silica and POTS also show icephobicity. An erosion test rig based on pressurized pneumatic water impinging impact was used to evaluate the durability of the super-hydrophobic/icephobic coatings. The results show that durable coatings have been obtained, although improvement will be needed in future work aiming for applications in aerospace.

Construction of Silica-Based Micro/Nanoplatforms for Ultrasound Theranostic Biomedicine.

Science.gov (United States)

Zhou, Yang; Han, Xiaoxia; Jing, Xiangxiang; Chen, Yu

2017-09-01

Ultrasound (US)-based biomedicine has been extensively explored for its applications in both diagnostic imaging and disease therapy. The fast development of theranostic nanomedicine significantly promotes the development of US-based biomedicine. This progress report summarizes and discusses the recent developments of rational design and fabrication of silica-based micro/nanoparticles for versatile US-based biomedical applications. The synthetic strategies and surface-engineering approaches of silica-based micro/nanoparticles are initially discussed, followed by detailed introduction on their US-based theranostic applications. They have been extensively explored in contrast-enhanced US imaging, US-based multi-modality imaging, synergistic high-intensity focused US (HIFU) ablation, sonosensitizer-enhanced sonodynamic therapy (SDT), as well as US-triggered chemotherapy. Their biological effects and biosafety have been briefly discussed to guarantee further clinical translation. Based on the high biocompatibility, versatile composition/structure and high performance in US-based theranostic biomedicine, these silica-based theranostic agents are expected to pave a new way for achieving efficient US-based theranostics of disease by taking the specific advantages of material science, nanotechnology and US-based biomedicine. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnet pole tips

Science.gov (United States)

Thorn, Craig E.; Chasman, Chellis; Baltz, Anthony J.

1984-04-24

An improved magnet which more easily provides a radially increasing magnetic field, as well as reduced fringe field and requires less power for a given field intensity. The subject invention comprises a pair of spaced, opposed magnetic poles which further comprise a pair of pole roots, each having a pole tip attached to its center. The pole tips define the gap between the magnetic poles and at least a portion of each pole tip is separated from its associated pole root. The separation begins at a predetermined distance from the center of the pole root and increases with increasing radial distance while being constant with azimuth within that portion. Magnets in accordance with the subject invention have been found to be particularly advantageous for use in large isochronous cyclotrons.

Method and apparatus for assembling a permanent magnet pole assembly

Science.gov (United States)

Carl, Jr., Ralph James; Bagepalli, Bharat Sampathkumaran [Niskayuna, NY; Jansen, Patrick Lee [Scotia, NY; Dawson, Richard Nils [Voorheesville, NY; Qu, Ronghai [Clifton Park, NY; Avanesov, Mikhail Avramovich [Moscow, RU

2009-08-11

A pole assembly for a rotor, the pole assembly includes a permanent magnet pole including at least one permanent magnet block, a plurality of laminations including a pole cap mechanically coupled to the pole, and a plurality of laminations including a base plate mechanically coupled to the pole.

Simplified Analytic Approach of Pole-to-Pole Faults in MMC-HVDC for AC System Backup Protection Setting Calculation

Directory of Open Access Journals (Sweden)

Tongkun Lan

2018-01-01

Full Text Available AC (alternating current system backup protection setting calculation is an important basis for ensuring the safe operation of power grids. With the increasing integration of modular multilevel converter based high voltage direct current (MMC-HVDC into power grids, it has been a big challenge for the AC system backup protection setting calculation, as the MMC-HVDC lacks the fault self-clearance capability under pole-to-pole faults. This paper focused on the pole-to-pole faults analysis for the AC system backup protection setting calculation. The principles of pole-to-pole faults analysis were discussed first according to the standard of the AC system protection setting calculation. Then, the influence of fault resistance on the fault process was investigated. A simplified analytic approach of pole-to-pole faults in MMC-HVDC for the AC system backup protection setting calculation was proposed. In the proposed approach, the derived expressions of fundamental frequency current are applicable under arbitrary fault resistance. The accuracy of the proposed approach was demonstrated by PSCAD/EMTDC (Power Systems Computer-Aided Design/Electromagnetic Transients including DC simulations.

Rare Earth-Activated Silica-Based Nanocomposites

Directory of Open Access Journals (Sweden)

C. Armellini

2007-01-01

Full Text Available Two different kinds of rare earth-activated glass-based nanocomposite photonic materials, which allow to tailor the spectroscopic properties of rare-earth ions: (i Er3+-activated SiO2-HfO2 waveguide glass ceramic, and (ii core-shell-like structures of Er3+-activated silica spheres obtained by a seed growth method, are presented.

Differently-catalyzed silica-based precursors as functional additives for the epoxy-based hybrid materials

Czech Academy of Sciences Publication Activity Database

Perchacz, Magdalena; Beneš, Hynek; Zhigunov, Alexander; Serkis, Magdalena; Pavlova, Ewa

2016-01-01

Roč. 99, 2 September (2016), s. 434-446 ISSN 0032-3861 R&D Projects: GA ČR(CZ) GA14-05146S; GA MŠk(CZ) LO1507 Institutional support: RVO:61389013 Keywords : epoxy-silica hybrid material * solvent-free sol-gel process * silica-based precursor Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.684, year: 2016

Multimodality Imaging with Silica-Based Targeted Nanoparticle Platforms

International Nuclear Information System (INIS)

Lewis, Jason S.

2012-01-01

Objectives: To synthesize and characterize a C-Dot silica-based nanoparticle containing 'clickable' groups for the subsequent attachment of targeting moieties (e.g., peptides) and multiple contrast agents (e.g., radionuclides with high specific activity) (1,2). These new constructs will be tested in suitable tumor models in vitro and in vivo to ensure maintenance of target-specificity and high specific activity. Methods: Cy5 dye molecules are cross-linked to a silica precursor which is reacted to form a dye-rich core particle. This core is then encapsulated in a layer of pure silica to create the core-shell C-Dot (Figure 1) (2). A 'click' chemistry approach has been used to functionalize the silica shell with radionuclides conferring high contrast and specific activity (e.g. 64Cu and 89Zr) and peptides for tumor targeting (e.g. cRGD and octreotate) (3). Based on the selective Diels-Alder reaction between tetrazine and norbornene, the reaction is bioorthogonal, highyielding, rapid, and water-compatible. This radiolabeling approach has already been employed successfully with both short peptides (e.g. octreotate) and antibodies (e.g. trastuzumab) as model systems for the ultimate labeling of the nanoparticles (1). Results: PEGylated C-Dots with a Cy5 core and labeled with tetrazine have been synthesized (d = 55 nm, zeta potential = -3 mV) reliably and reproducibly and have been shown to be stable under physiological conditions for up to 1 month. Characterization of the nanoparticles revealed that the immobilized Cy5 dye within the C-Dots exhibited fluorescence intensities over twice that of the fluorophore alone. The nanoparticles were successfully radiolabeled with Cu-64. Efforts toward the conjugation of targeting peptides (e.g. cRGD) are underway. In vitro stability, specificity, and uptake studies as well as in vivo imaging and biodistribution investigations will be presented. Conclusions: C-Dot silica-based nanoparticles offer a robust, versatile, and multi

Quantitative analysis of silica aerogel-based thermal insulation coatings

DEFF Research Database (Denmark)

Kiil, Søren

2015-01-01

containing intact hollow glass or polymer spheres showed that silica aerogel particles are more efficient in an insulation coating than hollow spheres. In a practical (non-ideal) comparison, the ranking most likely cannot be generalized. A parameter study demonstrates how the model can be used, qualitatively......A mathematical heat transfer model for a silica aerogel-based thermal insulation coating was developed. The model can estimate the thermal conductivity of a two-component (binder-aerogel) coating with potential binder intrusion into the nano-porous aerogel structure. The latter is modelled using...... a so-called core–shell structure representation. Data from several previous experimental investigations with silica aerogels in various binder matrices were used for model validation. For some relevant cases with binder intrusion, it was possible to obtain a very good agreement between simulations...

Mesoporous Silica Molecular Sieve based Nanocarriers: Transpiring Drug Dissolution Research.

Science.gov (United States)

Pattnaik, Satyanarayan; Pathak, Kamla

2017-01-01

Improvement of oral bioavailability through enhancement of dissolution for poorly soluble drugs has been a very promising approach. Recently, mesoporous silica based molecular sieves have demonstrated excellent properties to enhance the dissolution velocity of poorly water-soluble drugs. Current research in this area is focused on investigating the factors influencing the drug release from these carriers, the kinetics of drug release and manufacturing approaches to scale-up production for commercial manufacture. This comprehensive review provides an overview of different methods adopted for synthesis of mesoporous materials, influence of processing factors on properties of these materials and drug loading methods. The drug release kinetics from mesoporous silica systems, the manufacturability and stability of these formulations are reviewed. Finally, the safety and biocompatibility issues related to these silica based materials are discussed. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Polymer-filler interactions in polyether based thermoplastic polyureathane/silica nanocomposites

OpenAIRE

Heinz, Özge; Heinz, Ozge

2013-01-01

Thermoplastic polyurethaneureas (TPU) are a unique class of materials that are used in a broad range of applications due to their tailorable chemistry and morphology that allow engineering materials with targeted properties. The central theme of this dissertation is to develop an understanding on polymer-filler interfacial interactions and related reinforcing mechanism of silica nanoparticles in polyether based TPU/silica nanocomposites. Prior to our investigation on nanocomposite materials, ...

Multimodality Imaging with Silica-Based Targeted Nanoparticle Platforms

Energy Technology Data Exchange (ETDEWEB)

Jason S. Lewis

2012-04-09

Objectives: To synthesize and characterize a C-Dot silica-based nanoparticle containing 'clickable' groups for the subsequent attachment of targeting moieties (e.g., peptides) and multiple contrast agents (e.g., radionuclides with high specific activity) [1,2]. These new constructs will be tested in suitable tumor models in vitro and in vivo to ensure maintenance of target-specificity and high specific activity. Methods: Cy5 dye molecules are cross-linked to a silica precursor which is reacted to form a dye-rich core particle. This core is then encapsulated in a layer of pure silica to create the core-shell C-Dot (Figure 1) [2]. A 'click' chemistry approach has been used to functionalize the silica shell with radionuclides conferring high contrast and specific activity (e.g. 64Cu and 89Zr) and peptides for tumor targeting (e.g. cRGD and octreotate) [3]. Based on the selective Diels-Alder reaction between tetrazine and norbornene, the reaction is bioorthogonal, highyielding, rapid, and water-compatible. This radiolabeling approach has already been employed successfully with both short peptides (e.g. octreotate) and antibodies (e.g. trastuzumab) as model systems for the ultimate labeling of the nanoparticles [1]. Results: PEGylated C-Dots with a Cy5 core and labeled with tetrazine have been synthesized (d = 55 nm, zeta potential = -3 mV) reliably and reproducibly and have been shown to be stable under physiological conditions for up to 1 month. Characterization of the nanoparticles revealed that the immobilized Cy5 dye within the C-Dots exhibited fluorescence intensities over twice that of the fluorophore alone. The nanoparticles were successfully radiolabeled with Cu-64. Efforts toward the conjugation of targeting peptides (e.g. cRGD) are underway. In vitro stability, specificity, and uptake studies as well as in vivo imaging and biodistribution investigations will be presented. Conclusions: C-Dot silica-based nanoparticles offer a robust

Development of high-average-power-laser medium based on silica glass

International Nuclear Information System (INIS)

Fujimoto, Yasushi; Nakatsuka, Masahiro

2000-01-01

We have developed a high-average-power laser material based on silica glass. A new method using Zeolite X is effective for homogeneously dispersing rare earth ions in silica glass to get a high quantum yield. High quality medium, which is bubbleless and quite low refractive index distortion, must be required for realization of laser action, and therefore, we have carefully to treat the gelation and sintering processes, such as, selection of colloidal silica, pH value of for hydrolysis of tetraethylorthosilicate, and sintering history. The quality of the sintered sample and the applications are discussed. (author)

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 ...

Nitridated fibrous silica (KCC-1) as a sustainable solid base nanocatalyst

KAUST Repository

Bouhrara, Mohamed; Ranga, Chanakya; Fihri, Aziz; Shaikh, Rafik; Sarawade, Pradip; Emwas, Abdul-Hamid M.; Hedhili, Mohamed N.; Polshettiwar, Vivek

2013-01-01

We observed that support morphology has dramatic effects on the performance of nitridated silica as a base. By simply replacing conventional silica supports (such as SBA-15 and MCM-41) with fibrous nanosilica (KCC-1), we observed multifold enhancement in the catalytic activity of the nitridated solid base for Knoevenagel condensations and transesterification reactions. This enhancement of the activity can be explained by amine accessibility, which is excellent in KCC-1 due to its open and flexible fibrous structure, that facilitates penetration and interaction with basic amine sites. © 2013 American Chemical Society.

Nitridated fibrous silica (KCC-1) as a sustainable solid base nanocatalyst

KAUST Repository

Bouhrara, Mohamed

2013-09-03

We observed that support morphology has dramatic effects on the performance of nitridated silica as a base. By simply replacing conventional silica supports (such as SBA-15 and MCM-41) with fibrous nanosilica (KCC-1), we observed multifold enhancement in the catalytic activity of the nitridated solid base for Knoevenagel condensations and transesterification reactions. This enhancement of the activity can be explained by amine accessibility, which is excellent in KCC-1 due to its open and flexible fibrous structure, that facilitates penetration and interaction with basic amine sites. © 2013 American Chemical Society.

Physical Characteristics of Chitosan Based Film Modified With Silica and Polyethylene Glycol

Directory of Open Access Journals (Sweden)

F. Widhi Mahatmanti

2014-07-01

Full Text Available Recently, development of film materials is focused on finding the films with high chemical and physical stabilities. Organic based material such as chitosan produces films with low physical stability, and hence addition of inorganic materials necessary. In this research, the effect of silica and polyethylene glycol (PEG addition on the properties of chitosan based films has been investigated. Precursors used to produce films included chitosan with the deacetylation degree of 83% and sodium silicate solution as the silica source. A simple synthesis in a one-pot process was carried out by mixing 1%(w of chitosan solution in 2%(v/v acetate acid and sodium silicate solution (27% SiO2 in various composition ratios and casting the solution on a glass dish. The tensile strength and percentage of elongation decrease with increasing the silica content. The tensile strength tends to decline with addition of PEG, but the elongation percentage of the film increases. Hydrophilicity of the film decreases with the addition of silica and increases with the addition of PEG. The addition of silica and PEG does not change significantly the morphology of the film and functional groups indicating the domination of physical interaction among active sites in the film components.

Reliability assessment of power pole infrastructure incorporating deterioration and network maintenance

International Nuclear Information System (INIS)

Ryan, Paraic C.; Stewart, Mark G.; Spencer, Nathan; Li, Yue

2014-01-01

There is considerable investment in timber utility poles worldwide, and there is a need to examine the structural reliability and probability based management optimisation of these power distribution infrastructure elements. The work presented in this paper builds on the existing studies in this area through assessment of both treated and untreated timber power poles, with the effects of deterioration and network maintenance incorporated in the analysis. This more realistic assessment approach, with deterioration and maintenance considered, was achieved using event-based Monte Carlo simulation. The output from the probabilistic model is used to illustrate the importance of considering network maintenance in the time-dependent structural reliability assessment of timber power poles. Under wind load, treated and untreated poles designed and maintained in accordance with existing Australian standards were found to have similar failure rates. However, untreated pole networks required approximately twice as many maintenance based pole replacements to sustain the same level of reliability. The effect of four different network maintenance strategies on infrastructure performance was also investigated herein. This assessment highlighted the fact that slight alterations to network maintenance practices can lead to significant changes in performance of timber power pole networks. - Highlights: • A time-dependent structural reliability model was developed for timber power poles. • Deterioration and network maintenance were incorporated into this event based model. • Network maintenance had a significant impact on power pole wind vulnerability. • Treated and untreated poles designed to Australian standards had similar reliability. • Minor alterations to maintenance strategies had large effects on network performance

Geometric Modelling of Octagonal Lamp Poles

Science.gov (United States)

Chan, T. O.; Lichti, D. D.

2014-06-01

Lamp poles are one of the most abundant highway and community components in modern cities. Their supporting parts are primarily tapered octagonal cones specifically designed for wind resistance. The geometry and the positions of the lamp poles are important information for various applications. For example, they are important to monitoring deformation of aged lamp poles, maintaining an efficient highway GIS system, and also facilitating possible feature-based calibration of mobile LiDAR systems. In this paper, we present a novel geometric model for octagonal lamp poles. The model consists of seven parameters in which a rotation about the z-axis is included, and points are constrained by the trigonometric property of 2D octagons after applying the rotations. For the geometric fitting of the lamp pole point cloud captured by a terrestrial LiDAR, accurate initial parameter values are essential. They can be estimated by first fitting the points to a circular cone model and this is followed by some basic point cloud processing techniques. The model was verified by fitting both simulated and real data. The real data includes several lamp pole point clouds captured by: (1) Faro Focus 3D and (2) Velodyne HDL-32E. The fitting results using the proposed model are promising, and up to 2.9 mm improvement in fitting accuracy was realized for the real lamp pole point clouds compared to using the conventional circular cone model. The overall result suggests that the proposed model is appropriate and rigorous.

Influence of polyolefin fibers on the engineering properties of cement-based composites containing silica fume

International Nuclear Information System (INIS)

Han, Ta-Yuan; Lin, Wei-Ting; Cheng, An; Huang, Ran; Huang, Chin-Cheng

2012-01-01

Highlights: ► Experimental study is focus on the engineering properties of cement-based composites. ► Different mixes containing fiber and silica fume proportions have been tested. ► The influence of different mixes on the engineering properties has been discussed. ► The properties are included strength, ductility, permeability and microstructure. -- Abstract: This study evaluated the mechanical properties of cement-based composites produced with added polyolefin fibers and silica fume. Material variables included the water-cementitious ratio, the dosage of silica fume, and the length and dosage of polyolefin fiber. Researchers conducted tests on compressive strength, splitting tensile strength, direct tensile strength, resistivity, rapid chloride penetration, and initial surface absorption, and performed microscopic observation. Test results indicate that the specimens containing silica fume have higher compressive strength than the control and specimen made with fibers. The specimens with polyolefin fiber and silica fume have considerably higher tensile strength and ductility than the control and specimens made with silica fume. The specimens containing silica fume and polyolefin fiber demonstrated better resistance to chloride penetration than composites with polyolefin fiber or silica fume. For a given volume fraction, short polyolefin fiber performs better than its long counterpart in improving the properties of concrete. Specimens containing silica fume demonstrated a significant increase in resistivity and decrease in the total charge passed and absorption. Scanning electron microscopy illustrates that the polyolefin fiber acts to arrest the propagation of internal cracks.

Silica-scavenging effects in ceria-based solid electrolytes

Directory of Open Access Journals (Sweden)

Ivanova, D.

2008-08-01

Full Text Available Composite materials based on gadolinium doped ceria (CGO with additions of silica, with both silica and lanthanum oxide, and with lanthanum silicate, were prepared by the conventional ceramic route, to assess the silica scavenging role of lanthanum oxide additions. Structural, microstructural and electrical characterization of these samples confirmed the formation of one apatite type lanthanum silicate-based phase from reaction of silica with lanthanum oxide. The formation of this phase occurred in parallel with a significant enhancement of the grain boundary conductivity of these composite materials. Further interaction between constituents, involving diffusion of La to CGO, and Ce and Gd to the apatite phase, had no significant consequences on the electrical performance of these materials. Overall, lanthanum oxide was shown to remove the siliceous phases from the grain boundaries of CGO.

Se prepararon materiales compuestos basados en óxido de cerio dopado con gadolinio (TGO con adicciones de sílice, con sílice y óxido de lantano y silicato del lantano, mediante procesamiento cerámico convencional con objeto de confirmar el papel secuestrante de sílice de las adicciones. La caracterización estructural, microestructural y eléctrica de las muestras confirmó la formación de una fase tipo apatito basada en silicato de lantano a partir de la reacción de la sílice con el óxido de lantano. La formación de esta fase ocurre en paralelo con un incremento significativo de la conductividad a través del borde de grano de estos materiales. La interacción entre los constituyentes, incluyendo la difusión del La al CGO, y el Ce y el Gd a la fase apatito, no tiene consecuencias significativas sobre el comportamiento eléctrico de estos materiales. Resumiendo, el óxido de lantano es capaz de eliminar las fases silicias del borde de grano del CGO.

Thermal poling of multi-wire array optical fiber

DEFF Research Database (Denmark)

Huang, Lin; An, Honglin; Hayashi, Juliano G.

2018-01-01

We demonstrate in this paper thermal poling of multi-wire array fibers, which extends poling of fibers with two anodes to similar to 50 and similar to 500 wire array anodes. The second harmonic microscopy observations show that second order nonlinearity (SON) layers are developed surrounding all...... the rings of wires in the similar to 50 anode array fiber with poling of 1.8kV, 250 degrees C and 30min duration, and the outer rings of the similar to 500 anode array fiber at lower poling temperature. Our simulations based on a two-dimensional charge dynamics model confirm this can be explained...

Silica Based Superhydrophobic Nanocoatings for Natural Rubber Surfaces

Directory of Open Access Journals (Sweden)

Veromee Kalpana Wimalasiri

2017-01-01

Full Text Available Silica based nonfluorinated superhydrophobic coatings for natural rubber surfaces have been developed. The coating was synthesized using nanosilica dispersion and a polychloroprene type binder as a compatibilizer. This nanocoating of silica was applied on to the surface of finished natural rubber gloves, by spray coating or dipped coating methods. The nanocoating demonstrates a water contact angle of more than 150° and sliding angle of 7°. The morphological features of the coating have been studied using scanning electron microscopy and atomic force microscopy while Fourier transform infrared spectroscopy was used to understand the nature of surface functional groups. Both imaging techniques provided evidence for the presence of nanosized particles in the coating. Coated gloves demonstrated comparable mechanical properties and significantly better alcohol resistivity when compared to those of the uncoated gloves.

Optimal pole shifting controller for interconnected power system

International Nuclear Information System (INIS)

Yousef, Ali M.; Kassem, Ahmed M.

2011-01-01

Research highlights: → Mathematical model represents a power system which consists of synchronous machine connected to infinite bus through transmission line. → Power system stabilizer was designed based on optimal pole shifting controller. → The system performances was tested through load disturbances at different operating conditions. → The system performance with the proposed optimal pole shifting controller is compared with the conventional pole placement controller. → The digital simulation results indicated that the proposed controller has a superior performance. -- Abstract: Power system stabilizer based on optimal pole shifting is proposed. An approach for shifting the real parts of the open-loop poles to any desired positions while preserving the imaginary parts is presented. In each step of this approach, it is required to solve a first-order or a second-order linear matrix Lyapunov equation for shifting one real pole or two complex conjugate poles, respectively. This presented method yields a solution, which is optimal with respect to a quadratic performance index. The attractive feature of this method is that it enables solutions of the complex problem to be easily found without solving any non-linear algebraic Riccati equation. The present power system stabilizer is based on Riccati equation approach. The control law depends on finding the feedback gain matrix, and then the control signal is synthesized by multiplying the state variables of the power system with determined gain matrix. The gain matrix is calculated one time only, and it works over wide range of operating conditions. To validate the power of the proposed PSS, a linearized model of a simple power system consisted of a single synchronous machine connected to infinite bus bar through transmission line is simulated. The studied power system is subjected to various operating points and power system parameters changes.

Optimal pole shifting controller for interconnected power system

Energy Technology Data Exchange (ETDEWEB)

Yousef, Ali M., E-mail: drali_yousef@yahoo.co [Electrical Eng. Dept., Faculty of Engineering, Assiut University (Egypt); Kassem, Ahmed M., E-mail: kassem_ahmed53@hotmail.co [Control Technology Dep., Industrial Education College, Beni-Suef University (Egypt)

2011-05-15

Research highlights: {yields} Mathematical model represents a power system which consists of synchronous machine connected to infinite bus through transmission line. {yields} Power system stabilizer was designed based on optimal pole shifting controller. {yields} The system performances was tested through load disturbances at different operating conditions. {yields} The system performance with the proposed optimal pole shifting controller is compared with the conventional pole placement controller. {yields} The digital simulation results indicated that the proposed controller has a superior performance. -- Abstract: Power system stabilizer based on optimal pole shifting is proposed. An approach for shifting the real parts of the open-loop poles to any desired positions while preserving the imaginary parts is presented. In each step of this approach, it is required to solve a first-order or a second-order linear matrix Lyapunov equation for shifting one real pole or two complex conjugate poles, respectively. This presented method yields a solution, which is optimal with respect to a quadratic performance index. The attractive feature of this method is that it enables solutions of the complex problem to be easily found without solving any non-linear algebraic Riccati equation. The present power system stabilizer is based on Riccati equation approach. The control law depends on finding the feedback gain matrix, and then the control signal is synthesized by multiplying the state variables of the power system with determined gain matrix. The gain matrix is calculated one time only, and it works over wide range of operating conditions. To validate the power of the proposed PSS, a linearized model of a simple power system consisted of a single synchronous machine connected to infinite bus bar through transmission line is simulated. The studied power system is subjected to various operating points and power system parameters changes.

Derivation of nominal strength for wood utility poles

Science.gov (United States)

Ronald W. Wolfe; Jozsef Bodig; Patricia Lebow

2001-01-01

The designated fiber stress values published in the American National Standards Institute Standard for Poles, ANSI 05.1, no longer reflect the state of the knowledge. These values are based on a combination of test data from small clear wood samples and small poles (

The Pole Orientation, Pole Precession, and Moment of Inertia Factor of Saturn

Science.gov (United States)

Jacobson, R. A.; French, R. G.; Nicholson, P. D.; Hedman, M.; Colwell, J. E.; Marouf, E.; Rappaport, N.; McGhee, C.; Sepersky, T.; Lonergan, K.

2011-01-01

This paper discusses our determination of the Saturn's pole orientation and precession using a combination of Earthbased and spacecraft based observational data. From our model of the polar motion and the observed precession rate we obtain a value for Saturn's polar moment of inertia

Instrument for analysis of electric motors based on slip-poles component

Science.gov (United States)

Haynes, Howard D.; Ayers, Curtis W.; Casada, Donald A.

1996-01-01

A new instrument for monitoring the condition and speed of an operating electric motor from a remote location. The slip-poles component is derived from a motor current signal. The magnitude of the slip-poles component provides the basis for a motor condition monitor, while the frequency of the slip-poles component provides the basis for a motor speed monitor. The result is a simple-to-understand motor health monitor in an easy-to-use package. Straightforward indications of motor speed, motor running current, motor condition (e.g., rotor bar condition) and synthesized motor sound (audible indication of motor condition) are provided. With the device, a relatively untrained worker can diagnose electric motors in the field without requiring the presence of a trained engineer or technician.

The use of carrier RNA to enhance DNA extraction from microfluidic-based silica monoliths.

Science.gov (United States)

Shaw, Kirsty J; Thain, Lauren; Docker, Peter T; Dyer, Charlotte E; Greenman, John; Greenway, Gillian M; Haswell, Stephen J

2009-10-12

DNA extraction was carried out on silica-based monoliths within a microfluidic device. Solid-phase DNA extraction methodology was applied in which the DNA binds to silica in the presence of a chaotropic salt, such as guanidine hydrochloride, and is eluted in a low ionic strength solution, such as water. The addition of poly-A carrier RNA to the chaotropic salt solution resulted in a marked increase in the effective amount of DNA that could be recovered (25ng) compared to the absence of RNA (5ng) using the silica-based monolith. These findings confirm that techniques utilising nucleic acid carrier molecules can enhance DNA extraction methodologies in microfluidic applications.

Effects of Silica Nanostructures in Poly(ethylene oxide)-Based Composite Polymer Electrolytes.

Science.gov (United States)

Mohanta, Jagdeep; Anwar, Shahid; Si, Satyabrata

2016-06-01

The present work describes the synthesis of some poly(ethylene oxide)-based nanocomposite polymer electrolyte films using various silica nanostructures as the inorganic filler by simple solution mixing technique, in which the nature of the silica nanostructures play a vital role in modulating their electrochemical performances at room temperature. The silica nanostructures are prepared by ammonical hydrolysis of tetraethyl orthosilicate following the modified St6ber method. The resulting films are characterized by X-ray diffraction and differential scanning calorimeter to study their crystallinity. Room temperature AC impedance spectroscopy is utilized to determine the Li+ ion conductivity of the resulting films. The observed conductivity values of various NCPE films depend on the nature of silica filling as well as on their surface characteristics and also on the varying PEO-Li+ ratio, which is observed to be in the order of 10(-7)-10(-6) S cm(-1).

Testing Silica Fume-Based Concrete Composites under Chemical and Microbiological Sulfate Attacks

Directory of Open Access Journals (Sweden)

Adriana Estokova

2016-04-01

Full Text Available Current design practices based on descriptive approaches to concrete specification may not be appropriate for the management of aggressive environments. In this study, the durability of cement-based materials with and without the addition of silica fume, subjected to conditions that leach calcium and silicon, were investigated. Chemical corrosion was simulated by employing various H2SO4 and MgSO4 solutions, and biological corrosion was simulated using Acidithiobacillus sp. bacterial inoculation, leading to disrupted and damaged surfaces; the samples’ mass changes were studied following both chemical and biological attacks. Different leaching trends were observed via X-ray fluorescence when comparing chemical with biological leaching. Lower leaching rates were found for concrete samples fortified with silica fume than those without silica fume. X-ray diffraction and scanning electron microscopy confirmed a massive sulfate precipitate formation on the concrete surface due to bacterial exposure.

Pole Dancing Auto-ethnography – Practice, Pedagogy, Performance

Directory of Open Access Journals (Sweden)

Amy Patricia Cadwallader

2017-02-01

Full Text Available In this research paper, the author addresses the following four questions: 1 What are the implications of bringing pole dancing into concert dance, not as a caricature or theatrical version of what is performed in strip clubs, but as its own, free-standing art form? 2 In what ways will years of ballet and modern dance training influence the type of dancing that emerges from dancers when poles and other apparatuses are introduced? 3 How can the author create an original pole dancing style and pedagogical methods for teaching it? 4 Who participates in pole fitness classes and how does the demographic change based on location? What about when pole fitness classes are offered in an academic setting? The author shares first-hand experiences of investigating pole dancing in fitness classes, attending performances, engaging in a rehearsal process with highly trained dancers, and teaching pole dancing to movers with a wide range of abilities. The author addresses how research plans changed as she encountered limitations of budget and time constraints. The author also elaborates on the creative process that she engaged in with her thesis cast, collaborators, and supporting designers in the making of Super-beneath, a theatrical dance work that uses five, free-standing poles. She outline the vignettes, overall structure, and narrative of the work. The author then discusses where this research fits into the larger field of pole dancing, and the even larger field of dance. In the final sections of this paper, the author describes her pedagogical practices relating to pole classes, what “practice as research” means to her, and how she would like to continue on this research trajectory in the future.

Bone tissue engineering using silica-based mesoporous nanobiomaterials:Recent progress.

Science.gov (United States)

Shadjou, Nasrin; Hasanzadeh, Mohammad

2015-10-01

Bone disorders are of significant concern due to increase in the median age of our population. It is in this context that tissue engineering has been emerging as a valid approach to the current therapies for bone regeneration/substitution. Tissue-engineered bone constructs have the potential to alleviate the demand arising from the shortage of suitable autograft and allograft materials for augmenting bone healing. Silica based mesostructured nanomaterials possessing pore sizes in the range 2-50 nm and surface reactive functionalities have elicited immense interest due to their exciting prospects in bone tissue engineering. In this review we describe application of silica-based mesoporous nanomaterials for bone tissue engineering. We summarize the preparation methods, the effect of mesopore templates and composition on the mesopore-structure characteristics, and different forms of these materials, including particles, fibers, spheres, scaffolds and composites. Also, the effect of structural and textural properties of mesoporous materials on development of new biomaterials for production of bone implants and bone cements was discussed. Also, application of different mesoporous materials on construction of manufacture 3-dimensional scaffolds for bone tissue engineering was discussed. It begins by giving the reader a brief background on tissue engineering, followed by a comprehensive description of all the relevant components of silica-based mesoporous biomaterials on bone tissue engineering, going from materials to scaffolds and from cells to tissue engineering strategies that will lead to "engineered" bone. Copyright © 2015 Elsevier B.V. All rights reserved.

Location selection and layout for LB10, a lunar base at the Lunar North Pole with a liquid mirror observatory

Science.gov (United States)

Detsis, Emmanouil; Doule, Ondrej; Ebrahimi, Aliakbar

2013-04-01

We present the site selection process and urban planning of a Lunar Base for a crew of 10 (LB10), with an infrared astronomical telescope, based on the concept of the Lunar LIquid Mirror Telescope. LB10 is a base designated for permanent human presence on the Moon. The base architecture is based on utilization of inflatable, rigid and regolith structures for different purposes. The location for the settlement is identified through a detailed analysis of surface conditions and terrain parameters around the Lunar North and South Poles. A number of selection criteria were defined regarding construction, astronomical observations, landing and illumination conditions. The location suggested for the settlement is in the vicinity of the North Pole, utilizing the geographical morphology of the area. The base habitat is on a highly illuminated and relatively flat plateau. The observatory in the vicinity of the base, approximately 3.5 kilometers from the Lunar North Pole, inside a crater to shield it from Sunlight. An illustration of the final form of the habitat is also depicted, inspired by the baroque architectural form.

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.

Nanostructural Organization of Naturally Occurring Composites—Part I: Silica-Collagen-Based Biocomposites

Directory of Open Access Journals (Sweden)

Hermann Ehrlich

2008-01-01

Full Text Available Glass sponges, as examples of natural biocomposites, inspire investigations aiming at both a better understanding of biomineralization mechanisms and novel developments in the synthesis of nanostructured biomimetic materials. Different representatives of marine glass sponges of the class Hexactinellida (Porifera are remarkable because of their highly flexible basal anchoring spicules. Therefore, investigations of the biochemical compositions and the micro- and nanostructure of the spicules as examples of naturally structured biomaterials are of fundamental scientific relevance. Here we present a detailed study of the structural and biochemical properties of the basal spicules of the marine glass sponge Monorhaphis chuni. The results show unambiguously that in this glass sponge a fibrillar protein of collagenous nature is the template for the silica mineralization in all silica-containing structural layers of the spicule. The structural similarity and homology of collagens derived from M. chuni spicules to other sponge and vertebrate collagens have been confirmed by us using FTIR, amino acid analysis and mass spectrometric sequencing techniques. We suggest that nanomorphology of silica formed on proteinous structures could be determined as an example of biodirected epitaxial nanodistribution of amorphous silica phase on oriented fibrillar collagen templates. Finally, the present work includes a discussion relating to silica-collagen-based hybrid materials for practical applications as biomaterials.

Pole lengths influence O2-cost during double poling in highly trained cross-country skiers.

Science.gov (United States)

Carlsen, Camilla Høivik; Rud, Bjarne; Myklebust, Håvard; Losnegard, Thomas

2018-02-01

In elite cross-country skiing, double poling is used in different terrain. This study compared O 2 -cost and kinematics during double poling with four different pole lengths [self-selected (SS), SS - 5 cm, SS + 5 cm, SS + 10 cm] at Low versus Moderate incline. Thirteen highly trained male cross-country skiers (mean ± SD 23 ± 3 years; 182 ± 4 cm; 77 ± 6 kg) completed eight submaximal trials with roller skis on a treadmill at two conditions: "Low incline" (1.7°; 4.5 m s -1 ) and "Moderate incline" (4.5°; 2.5 m s -1 ) with each of the four pole lengths. O 2 -cost and 3D body kinematics were assessed in each trial. In Low incline, SS + 10 cm induced a lower O 2 -cost than all the other pole lengths [P size (ES) 0.5-0.8], whereas no differences were found between the remaining pole lengths (P > 0.05; ES 0.2-0.4). In Moderate incline, significant differences between all pole lengths were found for O 2 -cost, with SS - 5 cm > SS > SS + 5 cm > SS + 10 cm (P differences in O 2 -cost between SS and the other pole lengths were greater in Moderate incline than Low incline (SS - 5 cm; 1.5%, ES 0.8, SS + 5 cm; 1.3%, ES 1.0, and SS + 10 cm; 1.9%, ES 1.0, all P difference was found in cycle, poling or reposition times between pole lengths. However, at both conditions a smaller total vertical displacement of center of mass was observed with SS + 10 cm compared to the other pole lengths. Increasing pole length from SS - 5 cm to SS + 10 cm during double poling induced lower O 2 -cost and this advantage was greater in Moderate compared to Low incline.

Influence of silica fume and fly ash on hydration, microstructure and strength of cement based mixtures

Energy Technology Data Exchange (ETDEWEB)

Weng, Kaimao

1992-10-01

The influence of fly ash and silica fume on the hydration, microstructure and strength of cement-based mixtures was investigated. A literature review of the hydration processes, compressive strength development, and microstructure of Portland cement is presented, followed by description of materials and specimens preparation and experimental methodology. It was found that silica fume retards cement hydration at low water/concrete ratios. It reduces calcium hydroxide significantly and increases the amount of hydrates at early ages. Fly ash retards hydration more significantly at high water/concrete ratios than at low ratios. The combination of silica fume and fly ash further retards hydration at one day. Silica fume dominates the reaction with calcium hydroxide. Silica fume significantly increases early strength of mortars and concrete, while fly ash reduces early strength. Silica fume can substantially increase strength of fly ash mortar and concrete after 7 days. Silica fume refines pores in the range 100-500 A, while fly ash mortars exhibit gradual pore refinement as hydration proceeds. Silica fume dominates the pore refinement if used with fly ash. 89 refs., 74 figs., 16 tabs.

Second harmonic generation from corona-poled polymer thin films ...

Indian Academy of Sciences (India)

2014-02-09

Feb 9, 2014 ... We characterize thermal stability of second harmonic generation (SHG) properties of four different Y-type polymers poled using corona poling method. These polymers are based on donor–acceptor–donor-type repeating unit with different aromatic moieties acting as donors and dicyanomethylene acting as ...

Structural behaviour of concrete poles used in electric's power distribution network

Directory of Open Access Journals (Sweden)

Mehran Zeynalian

2017-12-01

Full Text Available Based on a preliminary study on regional electric companies, it is shown that there is no precise structural design on the concrete poles. This leads to uneconomical and overestimated networks’ components. Therefore, this study was aimed to investigate the lateral performance of the concrete poles which are employed in electric’s power distribution network. This paper presents a numerical study on structural performance of 12 m concrete poles used in electric’s power distribution network using Abaqus software. A sensitivity study for mesh size is carried out and concrete damaged plasticity has been employed. The results show that relatively coarse mesh (average in damaged concrete method gives more reliable result. Some experimental tests based on the Iranian standards were performed in order to make a bench mark for numerical output. Comparison between numerical and experimental results indicates a good agreement between the results. The outcomes also suggest that while the applied lateral load is less than around 400 kg which is assumed as the nominal resistance of the pole, no transverse crack occurs. Based on both experimental and numerical results, one or two transverse cracks are reported when the applied force reaches up to 600 kg. The rate of cracks is amplified by increasing the applied force; and finally, the pole would lose its capacity when the load rises much more than 1200 kg. The study also shows that the poles are very weak when the load direction changes. Also, it can be concluded that the final strength of the pole is higher than what the standards recommend. Finally, seismic behavior factor of the poles around both main axes are evaluated. The estimated seismic resistance factor for the concrete poles indicates that the prescribed R factor for such structure is relatively low; and can be improved at least 20%.

Radiolabeling Silica-Based Nanoparticles via Coordination Chemistry: Basic Principles, Strategies, and Applications.

Science.gov (United States)

Ni, Dalong; Jiang, Dawei; Ehlerding, Emily B; Huang, Peng; Cai, Weibo

2018-03-20

As one of the most biocompatible and well-tolerated inorganic nanomaterials, silica-based nanoparticles (SiNPs) have received extensive attention over the last several decades. Recently, positron emission tomography (PET) imaging of radiolabeled SiNPs has provided a highly sensitive, noninvasive, and quantitative readout of the organ/tissue distribution, pharmacokinetics, and tumor targeting efficiency in vivo, which can greatly expedite the clinical translation of these promising NPs. Encouraged by the successful PET imaging of patients with metastatic melanoma using 124 I-labeled ultrasmall SiNPs (known as Cornell dots or C dots) and their approval as an Investigational New Drug (IND) by the United States Food and Drug Administration, different radioisotopes ( 64 Cu, 89 Zr, 18 F, 68 Ga, 124 I, etc.) have been reported to radiolabel a wide variety of SiNPs-based nanostructures, including dense silica (dSiO 2 ), mesoporous silica (MSN), biodegradable mesoporous silica (bMSN), and hollow mesoporous silica nanoparticles (HMSN). With in-depth knowledge of coordination chemistry, abundant silanol groups (-Si-O-) on the silica surface or inside mesoporous channels not only can be directly used for chelator-free radiolabeling but also can be readily modified with the right chelators for chelator-based labeling. However, integrating these labeling strategies for constructing stably radiolabeled SiNPs with high efficiency has proven difficult because of the complexity of the involved key parameters, such as the choice of radioisotopes and chelators, nanostructures, and radiolabeling strategy. In this Account, we present an overview of recent progress in the development of radiolabeled SiNPs for cancer theranostics in the hope of speeding up their biomedical applications and potential translation into the clinic. We first introduce the basic principles and mechanisms for radiolabeling SiNPs via coordination chemistry, including general rules of selecting proper

2D Stabilised analytic signal method in DC pole-pole potential data ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

synthetic error prone secondary pole-pole potential data. 1. Introduction. Analytical signal .... The meaning of the rest of the parameters is self- evident. The three ..... interpretation using 3-D analytic signal; Geophysics 57. 116–125. Starostenko ...

Periodically poled silicon

Science.gov (United States)

Hon, Nick K.; Tsia, Kevin K.; Solli, Daniel R.; Khurgin, Jacob B.; Jalali, Bahram

2010-02-01

Bulk centrosymmetric silicon lacks second-order optical nonlinearity χ(2) - a foundational component of nonlinear optics. Here, we propose a new class of photonic device which enables χ(2) as well as quasi-phase matching based on periodic stress fields in silicon - periodically-poled silicon (PePSi). This concept adds the periodic poling capability to silicon photonics, and allows the excellent crystal quality and advanced manufacturing capabilities of silicon to be harnessed for devices based on χ(2)) effects. The concept can also be simply achieved by having periodic arrangement of stressed thin films along a silicon waveguide. As an example of the utility, we present simulations showing that mid-wave infrared radiation can be efficiently generated through difference frequency generation from near-infrared with a conversion efficiency of 50% based on χ(2) values measurements for strained silicon reported in the literature [Jacobson et al. Nature 441, 199 (2006)]. The use of PePSi for frequency conversion can also be extended to terahertz generation. With integrated piezoelectric material, dynamically control of χ(2)nonlinearity in PePSi waveguide may also be achieved. The successful realization of PePSi based devices depends on the strength of the stress induced χ(2) in silicon. Presently, there exists a significant discrepancy in the literature between the theoretical and experimentally measured values. We present a simple theoretical model that produces result consistent with prior theoretical works and use this model to identify possible reasons for this discrepancy.

Permanent magnet machine and method with reluctance poles and non-identical PM poles for high density operation

Science.gov (United States)

Hsu, John S.

2010-05-18

A method and apparatus in which a stator (11) and a rotor (12) define a primary air gap (20) for receiving AC flux and at least one source (23, 40), and preferably two sources (23, 24, 40) of DC excitation are positioned for inducing DC flux at opposite ends of the rotor (12). Portions of PM material (17, 17a) are provided as boundaries separating PM rotor pole portions from each other and from reluctance poles. The PM poles (18) and the reluctance poles (19) can be formed with poles of one polarity having enlarged flux paths in relation to flux paths for pole portions of an opposite polarity, the enlarged flux paths communicating with a core of the rotor (12) so as to increase reluctance torque produced by the electric machine. Reluctance torque is increased by providing asymmetrical pole faces. The DC excitation can also use asymmetric poles and asymmetric excitation sources. Several embodiments are disclosed with additional variations.

Comparative DNA isolation behaviours of silica and polymer based sorbents in batch fashion: monodisperse silica microspheres with bimodal pore size distribution as a new sorbent for DNA isolation.

Science.gov (United States)

Günal, Gülçin; Kip, Çiğdem; Eda Öğüt, S; İlhan, Hasan; Kibar, Güneş; Tuncel, Ali

2018-02-01

Monodisperse silica microspheres with bimodal pore-size distribution were proposed as a high performance sorbent for DNA isolation in batch fashion under equilibrium conditions. The proposed sorbent including both macroporous and mesoporous compartments was synthesized 5.1 μm in-size, by a "staged shape templated hydrolysis and condensation method". Hydrophilic polymer based sorbents were also obtained in the form of monodisperse-macroporous microspheres ca 5.5 μm in size, with different functionalities, by a developed "multi-stage microsuspension copolymerization" technique. The batch DNA isolation performance of proposed material was comparatively investigated using polymer based sorbents with similar morphologies. Among all sorbents tried, the best DNA isolation performance was achieved with the monodisperse silica microspheres with bimodal pore size distribution. The collocation of interconnected mesoporous and macroporous compartments within the monodisperse silica microspheres provided a high surface area and reduced the intraparticular mass transfer resistance and made easier both the adsorption and desorption of DNA. Among the polymer based sorbents, higher DNA isolation yields were achieved with the monodisperse-macroporous polymer microspheres carrying trimethoxysilyl and quaternary ammonium functionalities. However, batch DNA isolation performances of polymer based sorbents were significantly lower with respect to the silica microspheres.

POLE-LIKE STREET FURNITURE DECOMPOSTION IN MOBILE LASER SCANNING DATA

Directory of Open Access Journals (Sweden)

F. Li

2016-06-01

Full Text Available Automatic semantic interpretation of street furniture has become a popular topic in recent years. Current studies detect street furniture as connected components of points above the street level. Street furniture classification based on properties of such components suffers from large intra class variability of shapes and cannot deal with mixed classes like traffic signs attached to light poles. In this paper, we focus on the decomposition of point clouds of pole-like street furniture. A novel street furniture decomposition method is proposed, which consists of three steps: (i acquirement of prior-knowledge, (ii pole extraction, (iii components separation. For the pole extraction, a novel global pole extraction approach is proposed to handle 3 different cases of street furniture. In the evaluation of results, which involves the decomposition of 27 different instances of street furniture, we demonstrate that our method decomposes mixed classes street furniture into poles and different components with respect to different functionalities.

Pole-Like Street Furniture Decompostion in Mobile Laser Scanning Data

Science.gov (United States)

Li, F.; Oude Elberink, S.; Vosselman, G.

2016-06-01

Automatic semantic interpretation of street furniture has become a popular topic in recent years. Current studies detect street furniture as connected components of points above the street level. Street furniture classification based on properties of such components suffers from large intra class variability of shapes and cannot deal with mixed classes like traffic signs attached to light poles. In this paper, we focus on the decomposition of point clouds of pole-like street furniture. A novel street furniture decomposition method is proposed, which consists of three steps: (i) acquirement of prior-knowledge, (ii) pole extraction, (iii) components separation. For the pole extraction, a novel global pole extraction approach is proposed to handle 3 different cases of street furniture. In the evaluation of results, which involves the decomposition of 27 different instances of street furniture, we demonstrate that our method decomposes mixed classes street furniture into poles and different components with respect to different functionalities.

An ultrasensitive hollow-silica-based biosensor for pathogenic Escherichia coli DNA detection.

Science.gov (United States)

Ariffin, Eda Yuhana; Lee, Yook Heng; Futra, Dedi; Tan, Ling Ling; Karim, Nurul Huda Abd; Ibrahim, Nik Nuraznida Nik; Ahmad, Asmat

2018-03-01

A novel electrochemical DNA biosensor for ultrasensitive and selective quantitation of Escherichia coli DNA based on aminated hollow silica spheres (HSiSs) has been successfully developed. The HSiSs were synthesized with facile sonication and heating techniques. The HSiSs have an inner and an outer surface for DNA immobilization sites after they have been functionalized with 3-aminopropyltriethoxysilane. From field emission scanning electron microscopy images, the presence of pores was confirmed in the functionalized HSiSs. Furthermore, Brunauer-Emmett-Teller (BET) analysis indicated that the HSiSs have four times more surface area than silica spheres that have no pores. These aminated HSiSs were deposited onto a screen-printed carbon paste electrode containing a layer of gold nanoparticles (AuNPs) to form a AuNP/HSiS hybrid sensor membrane matrix. Aminated DNA probes were grafted onto the AuNP/HSiS-modified screen-printed electrode via imine covalent bonds with use of glutaraldehyde cross-linker. The DNA hybridization reaction was studied by differential pulse voltammetry using an anthraquinone redox intercalator as the electroactive DNA hybridization label. The DNA biosensor demonstrated a linear response over a wide target sequence concentration range of 1.0×10 -12 -1.0×10 -2 μM, with a low detection limit of 8.17×10 -14 μM (R 2 = 0.99). The improved performance of the DNA biosensor appeared to be due to the hollow structure and rough surface morphology of the hollow silica particles, which greatly increased the total binding surface area for high DNA loading capacity. The HSiSs also facilitated molecule diffusion through the silica hollow structure, and substantially improved the overall DNA hybridization assay. Graphical abstract Step-by-step DNA biosensor fabrication based on aminated hollow silica spheres.

DETECTION AND CLASSIFICATION OF POLE-LIKE OBJECTS FROM MOBILE MAPPING DATA

Directory of Open Access Journals (Sweden)

K. Fukano

2015-08-01

Full Text Available Laser scanners on a vehicle-based mobile mapping system can capture 3D point-clouds of roads and roadside objects. Since roadside objects have to be maintained periodically, their 3D models are useful for planning maintenance tasks. In our previous work, we proposed a method for detecting cylindrical poles and planar plates in a point-cloud. However, it is often required to further classify pole-like objects into utility poles, streetlights, traffic signals and signs, which are managed by different organizations. In addition, our previous method may fail to extract low pole-like objects, which are often observed in urban residential areas. In this paper, we propose new methods for extracting and classifying pole-like objects. In our method, we robustly extract a wide variety of poles by converting point-clouds into wireframe models and calculating cross-sections between wireframe models and horizontal cutting planes. For classifying pole-like objects, we subdivide a pole-like object into five subsets by extracting poles and planes, and calculate feature values of each subset. Then we apply a supervised machine learning method using feature variables of subsets. In our experiments, our method could achieve excellent results for detection and classification of pole-like objects.

Compact high-field superconducting quadrupole magnet with holmium poles

Energy Technology Data Exchange (ETDEWEB)

Barlow, D.B.; Kraus, R.H. Jr.; Lobb, C.T.; Menzel, M.T. (Los Alamos National Lab., NM (United States)); Walstrom, P.L. (Grumman Space Systems, Los Alamos, NM (United States))

1992-03-15

A compact high-field superconducting quadrupole magnet was designed and built with poles made of the rare-earth metal holmium. The magnet is intended for use in superconducting coupled-cavity linear accelerators where compact high-field quadrupoles are needed, but where the use of permanent magnets is ruled out because of trapped-flux losses. The magnet has a clear bore diameter of 1.8 cm, outside diameter of 11 cm, length of 11 cm, and pole tip length of 6 cm. The effect of using holmium, a material with a higher saturation field than iron, was investigated by replacing poles made of iron with identical poles made of holmium. The magnet was operated at a temperature of 4.2 K and reached a peak quadrupole field gradient of 355 T/m, a 10% increase over the same magnet with iron poles. This increase in performance is consistent with calculations based on B-H curves that were measured for holmium at 4.2 K. (orig.).

Synthetic focused array of electrical prospecting using pole-pole array potential data; Sanjigen denki tansaho ni okeru nikyokuho den`i data wo mochiita denryu shusoku haichi no goseiho

Energy Technology Data Exchange (ETDEWEB)

Suzuki, K [Central Research Institute of Electric Power Industry, Tokyo (Japan)

1997-10-22

Various methods have been put into practice for the conventional two-dimensional pole configuration using a single line in three-dimensional electrical prospecting. Pole configuration effective for the three-dimensional exploration has not been investigated. This paper describes synthetic focused array using four pairs of guarded poles based on pole-pole array potential data in the case of arrangement of measuring points on a grid. Results of the numerical simulation are also described. For the focused array, laterolog of electrical logging is applied to the surface prospecting. Directivity can be given to the current from the main pole by controlling the current from guarded pole. It was found from the simulation that the resistivity anomaly is concentrated directly on the embedded ball for the focused array rather than for the pole-pole array. It was also found that two conductive balls can be clearly separated for the focused array rather than for the dipole-dipole array. Accordingly, it was considered that results approximating the original structures can be obtained by analyzing using the both arrays. 5 refs., 6 figs.

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.

Least 1-Norm Pole-Zero Modeling with Sparse Deconvolution for Speech Analysis

DEFF Research Database (Denmark)

Shi, Liming; Jensen, Jesper Rindom; Christensen, Mads Græsbøll

2017-01-01

In this paper, we present a speech analysis method based on sparse pole-zero modeling of speech. Instead of using the all-pole model to approximate the speech production filter, a pole-zero model is used for the combined effect of the vocal tract; radiation at the lips and the glottal pulse shape...

Tree-loop duality relation beyond single poles

Energy Technology Data Exchange (ETDEWEB)

Bierenbaum, Isabella [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Buchta, Sebastian; Draggiotis, Petros; Malamos, Ioannis; Rodrigo, German [Valencia Univ. Paterna (Spain). Inst. de Fisica Corpuscular

2012-11-15

We develop the Tree-Loop Duality Relation for two- and three-loop integrals with multiple identical propagators (multiple poles). This is the extension of the Duality Relation for single poles and multi-loop integrals derived in previous publications. We prove a generalization of the formula for single poles to multiple poles and we develop a strategy for dealing with higher-order pole integrals by reducing them to single pole integrals using Integration By Parts.

Polymer poling characterization using second harmonic generation (SHG)

Science.gov (United States)

Tellier, Gildas; Averty, Dominique; Blart, Errol; Boisrobert, Christian; Gundel, Hartmut; Le Tacon, Sylvain; Monnereau, Cyrille; Odobel, Fabrice; Seveno, Raynald

2006-04-01

Several polymer molecules have structures which are suitable for the non-linear optic applications. We report on the design and fabrication of a high performance electro-optic modulator made of polymer thin films. The polymer we study contains a chromophore based on Disperse Red One covalently grafted to a host-matrix. The polymer materials are deposited in thin layers on a glass substrate by chemical solution deposition, either by spin-coating or by dip-coating. The thickness of the films is ranging from a hundred nanometers to several micrometers. Initially, the polymer molecules are randomly oriented and the films are isotropic, hence no electro-optic effect can be observed. In order to break the symmetry and align the chromophores, the films are submitted to the so-called corona poling process. As a result, their structure become non-centrosymmetric and the second-order susceptibility is no longer zero. The corona poling method consists of applying a high electric field to the polymer by means of a needle electrode, placed above the polymer film which is posed on a grounded sample support electrode. Thermal regulation of the support electrode allows to control the temperature during the poling of the films. Once the poling process has been established, a chemical cross-linking function is thermally activated in order to fix the orientation of the chromophores in the polymer matrix. The orientation and its stability in time is evaluated with a Second Harmonic Generation measurement set-up using the Makers Fringes configuration. We studied the influence of the poling temperature, the distance between the corona needle electrode and the sample, the high voltage applied, and the duration of the poling process on the efficiency of chromophore orientation in order to optimize the poling procedure. Finally, aging of poled polymer samples has been investigated at elevated temperatures, confirming the stability of the cross-linking process.

POLE somatic mutations in advanced colorectal cancer.

Science.gov (United States)

Guerra, Joana; Pinto, Carla; Pinto, Diana; Pinheiro, Manuela; Silva, Romina; Peixoto, Ana; Rocha, Patrícia; Veiga, Isabel; Santos, Catarina; Santos, Rui; Cabreira, Verónica; Lopes, Paula; Henrique, Rui; Teixeira, Manuel R

2017-12-01

Despite all the knowledge already gathered, the picture of somatic genetic changes in colorectal tumorigenesis is far from complete. Recently, germline and somatic mutations in the exonuclease domain of polymerase epsilon, catalytic subunit (POLE) gene have been reported in a small subset of microsatellite-stable and hypermutated colorectal carcinomas (CRCs), affecting the proofreading activity of the enzyme and leading to misincorporation of bases during DNA replication. To evaluate the role of POLE mutations in colorectal carcinogenesis, namely in advanced CRC, we searched for somatic mutations by Sanger sequencing in tumor DNA samples from 307 cases. Microsatellite instability and mutation analyses of a panel of oncogenes were performed in the tumors harboring POLE mutations. Three heterozygous mutations were found in two tumors, the c.857C>G, p.Pro286Arg, the c.901G>A, p.Asp301Asn, and the c.1376C>T, p.Ser459Phe. Of the POLE-mutated CRCs, one tumor was microsatellite-stable and the other had low microsatellite instability, whereas KRAS and PIK3CA mutations were found in one tumor each. We conclude that POLE somatic mutations exist but are rare in advanced CRC, with further larger studies being necessary to evaluate its biological and clinical implications. © 2017 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

Silica functionalized Cu(II) acetylacetonate Schiff base complex: An efficient catalyst for the oxidative condensation reaction of benzyl alcohol with amines

Science.gov (United States)

Anbarasu, G.; Malathy, M.; Karthikeyan, P.; Rajavel, R.

2017-09-01

Silica functionalized Cu(II) acetylacetonate Schiff base complex via the one pot reaction of silica functionalized 3-aminopropyltriethoxysilane with acetyl acetone and copper acetate has been reported. The synthesized material was well characterized by analytical techniques such as FT-IR, UV-DRS, XRD, SEM-EDX, HR-TEM, EPR, ICP-AES and BET analysis. The characterization results confirmed the grafting of Cu(II) Schiff base complex on the silica surface. The catalytic activity of synthesized silica functionalized Cu(II) acetylacetonate Schiff base complex was evaluated through the oxidative condensation reaction of benzyl alcohol to imine.

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)

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.

Hybrid silica luminescent materials based on lanthanide-containing lyotropic liquid crystal with polarized emission

Energy Technology Data Exchange (ETDEWEB)

Selivanova, N.M., E-mail: natsel@mail.ru [Kazan National Research Technological University, 68 Karl Marx Str., Kazan 420015 (Russian Federation); Vandyukov, A.E.; Gubaidullin, A.T. [A.E. Arbuzov Institute of Organic and Physical Chemistry of the Kazan Scientific Center of the Russian Academy of Sciences, 8 Acad. Arbuzov Str., Kazan 420088 (Russian Federation); Galyametdinov, Y.G. [Kazan National Research Technological University, 68 Karl Marx Str., Kazan 420015 (Russian Federation)

2014-11-14

This paper represents the template method for synthesis of hybrid silica films based on Ln-containing lyotropic liquid crystal and characterized by efficient luminescence. Luminescence films were prepared in situ by the sol–gel processes. Lyotropic liquid crystal (LLC) mesophases C{sub 12}H{sub 25}O(CH{sub 2}CH{sub 2}O){sub 10}H/Ln(NO{sub 3}){sub 3}·6H{sub 2}O/H{sub 2}O containing Ln (III) ions (Dy, Tb, Eu) were used as template. Polarized optical microscopy, X-ray powder diffraction, and FT-IR-spectroscopy were used for characterization of liquid crystal mesophases and hybrid films. The morphology of composite films was studied by the atomic force microscopy method (AFM). The optical properties of the resulting materials were evaluated. It was found that hybrid silica films demonstrate significant increase of their lifetime in comparison with an LLC system. New effects of linearly polarized emission revealed for Ln-containing hybrid silica films. Polarization in lanthanide-containing hybrid composites indicates that silica precursor causes orientation of emitting ions. - Highlights: • We suggest a new simple approach for creating luminescence hybrid silica films. • Ln-containing hybrid silica films demonstrate yellow, green and red emissions. • Tb(III)-containing hybrid film have a high lifetime. • We report effects of linearly polarized emission in hybrid film.

Carrier Phase GPS Navigation to the North Pole

Science.gov (United States)

Moore, T.; Roberts, G. W.

Over the last few years, on-the-fly integer ambiguity resolution for GPS has proven to be successful over short baselines (500 km. New techniques have been developed at the University of Nottingham to allow very long baseline integer ambiguity resolution, on-the-fly. A major problem with the use of carrier phase data is that posed by cycle slips. A technique for detecting and correcting cycle slips has been developed, and its use is discussed in this paper. The new technique has been proven through a series of trials, one of which included two flights to the North Pole, performing centimetric level positioning all the way to the pole. For many years, the GD Aero-Systems Course of the Air Warfare Centre based at RAF Cranwell executed a series of equipment flight trials to the North Pole, called the ARIES Flights. In May 1996, the authors were fortunate to take part in both flights, via Iceland and Greenland, to the North Pole. Based on reference stations at Thule Air Base, integer ambiguity resolution was accomplished, on-the-fly, and centimetric level navigation maintained throughout the flights. Earlier trials detailed in the paper demonstrate that the technique can resolve integer ambiguities on-the-fly within a few seconds over a baseline length of approximately 134 km, resulting in an accuracy of 12 cm. The majority of the residual error source for this being the ionosphere.

Fibreglass as an alternative to wood poles : Transmission and distribution poles and crossarms : use of fiber reinforced composite materials for overhead electric utility lines

Energy Technology Data Exchange (ETDEWEB)

Wiles, J.R. [Shakespeare Composites and Electronics, Newberry, SC (United States)

2002-07-01

For over thirty years, Shakespeare Composites and Electronics has manufactured fiberglass composite lighting and utility poles, as well as being the number one maker of composite crossarms. Composite poles have a few advantages, such as being lightweight, they do no rust, are woodpecker and termite resistant, use no harmful chemicals, and have long life. A chart displaying the comparative pole weights is presented. The key design factors of fiberglass composite utility poles are: pole diameter, fiberglass type and wind angle, layers (thickness) of fiberglass, resin type and formulation, resin mix consistency, cure cycle and maximum curing temperature, and others. Two charts were also displayed presenting 40 feet class 4 pole bending strengths and 40 feet class 2 pole bending strengths. The author indicated that composite poles have a better strength consistency than wood, while being as consistent as steel and prestressed concrete. The design is based on an overload factor of safety of 2.5 for numerous installations. Some of the analytical methods used include mechanical testing, finite element modeling, and thermal analysis. The author describes in detail the concerns associated with attachments. Coating consists of a system of ultra violet blockers in the resin followed by an added resin rich polyester veil outer surface. In addition, there is a proprietary coating process with additional ultra violet blockers. Quality control is effected at the plant. The weathering system lasts 80 years. figs.

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

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.

Soft-Templating Synthesis of Mesoporous Silica-Based Materials for Environmental Applications

Science.gov (United States)

Gunathilake, Chamila Asanka

Dissertation research is mainly focus on: 1) the development of mesoporous silica materials with organic pendant and bridging groups (isocyanurate, amidoxime, benzene) and incorporated metal (aluminum, zirconium, calcium, and magnesium) species for high temperature carbon dioxide (CO2) sorption, 2) phosphorous-hydroxy functionalized mesoporous silica materials for water treatment, and 3) amidoxime-modified ordered mesoporous silica materials for uranium sorption under seawater conditions. The goal is to design composite materials for environmental applications with desired porosity, surface area, and functionality by selecting proper metal oxide precursors, organosilanes, tetraethylorthosilicate, (TEOS), and block copolymer templates and by adjusting synthesis conditions. The first part of dissertation presents experimental studies on the merge of aluminum, zirconium, calcium, and magnesium oxides with mesoporous silica materials containing organic pendant (amidoxime) and bridging groups (isocyanurate, benzene) to obtain composite sorbents for CO2 sorption at ambient (0-25 °C) and elevated (60-120 °C) temperatures. These studies indicate that the aforementioned composite sorbents are fairly good for CO2 capture at 25 °C via physisorption mechanism and show a remarkably high affinity toward CO2 chemisorption at 60-120 °C. The second part of dissertation is devoted to silica-based materials with organic functionalities for removal of heavy metal ions such as lead from contaminated water and for recovery of metal ions such as uranium from seawater. First, ordered mesoporous organosilica (OMO) materials with diethylphosphatoethyl and hydroxyphosphatoethyl surface groups were examined for Pb2+ adsorption and showed unprecedented adsorption capacities up to 272 mg/g and 202 mg/g, respectively However, the amidoxime-modified OMO materials were explored for uranium extraction under seawater conditions and showed remarkable capacities reaching 57 mg of uranium per gram

Comparison of two silica-based extraction methods for DNA isolation from bones.

Science.gov (United States)

Rothe, Jessica; Nagy, Marion

2016-09-01

One of the most demanding DNA extractions is from bones and teeth due to the robustness of the material and the relatively low DNA content. The greatest challenge is due to the manifold nature of the material, which is defined by various factors, including age, storage, environmental conditions, and contamination with inhibitors. However, most published protocols do not distinguish between different types or qualities of bone material, but are described as being generally applicable. Our laboratory works with two different extraction methods based on silica membranes or the use of silica beads. We compared the amplification success of the two methods from bone samples with different qualities and in the presence of inhibitors. We found that the DNA extraction using the silica membrane method results an in higher DNA yield but also in a higher risk of co-extracting impurities, which can act as inhibitors. In contrast the silica beads method shows decreased co-extraction of inhibitors but also less DNA yield. Related to our own experiences it has to be considered that each bone material should be reviewed independently regarding the analysis and extraction method. Therefore, the most ambitious task is determining the quality of the bone material, which requires substantial experience. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

A review on chemical methodologies for preparation of mesoporous silica and alumina based materials.

Science.gov (United States)

Naik, Bhanudas; Ghosh, Narendra Nath

2009-01-01

The discovery of novel family of molecular sieves called M41S aroused a worldwide resurgence in the field of porous materials. According to IUPAC definition inorganic solids that contain pores with diameter in the size range of 20-500 A are considered mesoporous materials. Mesoporous silica and alumina based materials find applications in catalysis, adsorption, host- guest encapsulation etc. This article reviews the current state of art and outline the recent patents in mesoporous materials research in three general areas: Synthesis, various mechanisms involved for porous structure formation and applications of silica and alumina based mesoporous materials.

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.

The Effect of Aging and Silanization on the Mechanical Properties of Fumed Silica-based Dental Composite

Directory of Open Access Journals (Sweden)

Khaje S

2015-12-01

Full Text Available Statement of Problem: Mechanical strength and durability of dental composites are the main topics studied in this field of science today. This study examined fumed silica-based composite as a strong and durable restorative material through flexural and cycling test methods. Objectives: The purpose of this study was to evaluate the effect of silanization, ageing, cycling and hybridizing on mechanical properties of fumed silica-based resin composite. Materials and Methods: Composites were made of light-cured copolymer based on Bisphenol A glycolmethacrylate (Bis-GMA and Triethylene glycoldimethacrylate (TEGDMA at proportion of 50:50 which reinforced by fumed silica filler. For each composite sample, 5 specimen bars were made using Teflon mould (2 x 2 x 25 mm3. The samples with 12 wt% fumed silica (FS were considered as a base line group. The samples were exposed to cyclic cold water (FS-CCW and hot water (FS-CHW. The effect of silanization and adding more filler was studied together with samples containing 12 wt% (FS-S (12, 16 wt% (FS-S (16 and 20 wt% (FS-S (20 fumed silica filler. The filler was silanized with (γ-MPS. The degree of conversion was assessed with Fourier Transform Infra-Red spectroscopy. Flexural properties were evaluated with the Three-Point Bending test. Flexural data were analyzed with Excel software. Hardness was measured with an Atomic Force Microscope (AFM. Results: The degree of conversion of the resin reached 74% within 24 hrs. Salinization allowed more filler to be wetted by resin. Addition of silanized particles from sample FS-S (12 to sample FS-S (20 improved the mechanical strength. Hybridizing fumed silica with nano-silica (FS-N had no significant effect on the strength, but nano-hardness improved greatly. Ageing and cycling had adverse effects on the strength of the sample FS. The flexural strength of FS-CHW was 72% less than FS sample. Conclusions: Sample FS-N with low diluent and filler percentage complied with the

Solid Silica-based Sulphonic Acid as an Efficient Green Catalyst for ...

African Journals Online (AJOL)

NJD

Solid Silica-based Sulphonic Acid as an Efficient Green. Catalyst for the Selective Oxidation of Sulphides to. Sulphoxides using NaCIO in Aqueous Media. Ali Amoozadeh* and Firouzeh Nemati. Department of Chemistry, Faculty of Science, Semnan University, Semnan, Iran. Received 21 October 2008, revised 6 December ...

Optimisation and characterisation of silica-based reversed-phase liquid chromatographic systems for the analysis of basic pharmaceuticals

NARCIS (Netherlands)

Vervoort, R.J.M.; Debets, A.J.J.; Claessens, H.A.; Cramers, C.A.M.G.; Jong, de G.J.

2000-01-01

Reversed-phase liquid chromatography using silica-based columns is successfully applied in many separations. However, also some drawbacks exist, i.e. the analysis of basic compounds is often hampered by ionic interaction of the basic analytes with residual silanols present on the silica surface,

Recent advances in poled optical fibres

DEFF Research Database (Denmark)

Pruneri, V.; Margulis, W.; Myrén, N.

2005-01-01

A second-order nonlinearity can be induced in optical fibres through poling. We describe accomplishments of the EU project GLAMOROUS in making low-cost high performance electrooptic and nonlinear optical fibre- and waveguide-based components. In particular a comparison with more traditional...

Electric poling-assisted additive manufacturing process for PVDF polymer-based piezoelectric device applications

International Nuclear Information System (INIS)

Lee, ChaBum; Tarbutton, Joshua A

2014-01-01

This paper presents a new additive manufacturing (AM) process to directly and continuously print piezoelectric devices from polyvinylidene fluoride (PVDF) polymeric filament rods under a strong electric field. This process, called ‘electric poling-assisted additive manufacturing or EPAM, combines AM and electric poling processes and is able to fabricate free-form shape piezoelectric devices continuously. In this process, the PVDF polymer dipoles remain well-aligned and uniform over a large area in a single design, production and fabrication step. During EPAM process, molten PVDF polymer is simultaneously mechanically stresses in-situ by the leading nozzle and electrically poled by applying high electric field under high temperature. The EPAM system was constructed to directly print piezoelectric structures from PVDF polymeric filament while applying high electric field between nozzle tip and printing bed in AM machine. Piezoelectric devices were successfully fabricated using the EPAM process. The crystalline phase transitions that occurred from the process were identified by using the Fourier transform infrared spectroscope. The results indicate that devices printed under a strong electric field become piezoelectric during the EPAM process and that stronger electric fields result in greater piezoelectricity as marked by the electrical response and the formation of sharper peaks at the polar β crystalline wavenumber of the PVDF polymer. Performing this process in the absence of an electric field does not result in dipole alignment of PVDF polymer. The EPAM process is expected to lead to the widespread use of AM to fabricate a variety of piezoelectric PVDF polymer-based devices for sensing, actuation and energy harvesting applications with simple, low cost, single processing and fabrication step. (paper)

A silica long base tiltmeter with high stability and resolution.

Science.gov (United States)

Boudin, F; Bernard, P; Longuevergne, L; Florsch, N; Larmat, C; Courteille, C; Blum, P-A; Vincent, T; Kammentaler, M

2008-03-01

In order to be able to provide valuable data in multiparameter measurement field operations, tiltmeters need to have a noise level better or equal than 10(-9) rad for a period range from a few minutes to a few years and a long term stability ranging from 10(-7) to 10(-8) rad/yr. Tiltmeter measurements should also be as much as possible insensitive to thermal disturbances, by taking great care of the horizontality of the base line tube first. Secondly, thermal responses have been assessed. We also took great care of the coupling of our tiltmeters with the bedrock. We've designed a long base tiltmeter with sensors in silica which has a low dilatation coefficient. The linear variable displacement transducer is based on coil coupling (powered by an alternative voltage). Finally we show the results of two 100 m silica water tube tiltmeters which were installed in a mine in the French Vosges massif in the framework of a hydrology research project. These instruments show a remarkably good stability (6.5x10(-9) rad/month) and a low noise level (of the order of 10(-11) rad). Toroidal and spheroidal free modes of the Earth were observed after the two last major earthquakes on Sumatra.

Hydrogen peroxide biosensor based on microperoxidase-11 immobilized in a silica cavity array electrode.

Science.gov (United States)

Tian, Shu; Zhou, Qun; Gu, Zhuomin; Gu, Xuefang; Zhao, Lili; Li, Yan; Zheng, Junwei

2013-03-30

Hydrogen peroxide biosensor based on the silica cavity array modified indium-doped tin oxide (ITO) electrode was constructed. An array of silica microcavities was fabricated by electrodeposition using the assembled polystyrene particles as template. Due to the resistance gradient of the silica cavity structure, the silica cavity exhibits a confinement effect on the electrochemical reactions, making the electrode function as an array of "soft" microelectrodes. The covalently immobilized microperoxidase-11(MP-11) inside these SiO2 cavities can keep its physiological activities, the electron transfer between the MP-11 and electrode was investigated through electrochemical method. The cyclic voltammetric curve shows a quasi-reversible electrochemical redox behavior with a pair of well-defined redox peaks, the cathodic and anodic peaks are located at -0.26 and -0.15V. Furthermore, the modified electrode exhibits high electrocatalytic activity toward the reduction of hydrogen peroxide and also shows good analytical performance for the amperometric detection of H2O2 with a linear range from 2×10(-6) to 6×10(-4)M. The good reproducibility and long-term stability of this novel electrode not only offer an opportunity for the detection of H2O2 in low concentration, but also provide a platform to construct various biosensors based on many other enzymes. Copyright © 2013 Elsevier B.V. All rights reserved.

Formation of Micro and Mesoporous Amorphous Silica-Based Materials from Single Source Precursors

Directory of Open Access Journals (Sweden)

Mohd Nazri Mohd Sokri

2016-03-01

Full Text Available Polysilazanes functionalized with alkoxy groups were designed and synthesized as single source precursors for fabrication of micro and mesoporous amorphous silica-based materials. The pyrolytic behaviors during the polymer to ceramic conversion were studied by the simultaneous thermogravimetry-mass spectrometry (TG-MS analysis. The porosity of the resulting ceramics was characterized by the N2 adsorption/desorption isotherm measurements. The Fourier transform infrared spectroscopy (FT-IR and Raman spectroscopic analyses as well as elemental composition analysis were performed on the polymer-derived amorphous silica-based materials, and the role of the alkoxy group as a sacrificial template for the micro and mesopore formations was discussed from a viewpoint to establish novel micro and mesoporous structure controlling technologies through the polymer-derived ceramics (PDCs route.

Composite hydrogel based on surface modified mesoporous silica and poly[(2-acryloyloxy)ethyl trimethylammonium chloride

International Nuclear Information System (INIS)

Torres, Cecilia C.; Urbano, Bruno F.; Campos, Cristian H.; Rivas, Bernabé L.; Reyes, Patricio

2015-01-01

This work focused on the synthesis, characterization and water absorbency of a composite hydrogel based on poly[(2-acryloyloxy)ethyl trimethylammonium chloride] and mesoporous silica, MCM-41. The MCM-41 was synthesized and later surface functionalized with triethoxyvinylsilane (VTES) and 3-trimethoxysilylpropylmethacrylate (TMSPM) by a post-grafting procedure. The composite hydrogels were obtained by in-situ polymerization using a mixture of monomer, crosslinker and initiator in the presence of functionalized MCM-41. Diverse characterization techniques were used at the different stages of synthesis, namely, FT-IR, TEM, SEM, DRX, 29 Si and 13 C solid state NMR, and N 2 adsorption isotherms at 77 K. Finally, the water uptake performance of the composites was tested as a function of time, mesoporous silica loading and coupling agent used at the functionalization. The composites using non-functionalized MCM-41 reached the highest water uptake, whereas those composite with MCM-41 TMSPM exhibited the lowest sorption. - Highlights: • Hydrophilic crosslinked polymer-mesoporous silica was obtained. • Mesoporous silica MCM-41 was synthesized and functionalized with organosilane. • Functionalization of MCM-41 affects the water uptake of composite. • Mesoporous silica is covalently bound to the polymer acting as crosslinked point

Controlled release of phenytoin for epilepsy treatment from titania and silica based materials

International Nuclear Information System (INIS)

Lopez, Tessy; Ortiz, Emma; Meza, Doraliz; Basaldella, Elena; Bokhimi, Xim; Magana, Carlos; Sepulveda, Antonio; Rodriguez, Francisco; Ruiz, Javier

2011-01-01

Research highlights: → Template technique was used to obtain well ordered nanostructured materials: SBA-15 and titania tubes. → Phenytoin (PH), a drug used in epilepsy treatment, was loaded in these materials to used como PH release. → Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. → The load-release PH are faster in nanostructured TiO2 tubes than in mesoporous silica matrix. → There is an inverse effect of the surface area of the structured materials on the amount of released PH. - Abstract: Template technique was used to obtain well ordered nanostructured materials: mesoporous silica and nanostructured titania tubes. This technique permits the synthesis of solids with controlled mesoporosity, where a large variety of molecules that have therapeutic activity can be hosted and further released to specific sites. In this work phenytoin (PH), a drug used in epilepsy treatment, was loaded in ordered mesoporous silica (SBA 15) and nanostructured titania tubes (TiO 2 ). The pure materials and those containing PH were characterized by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N 2 adsorption-desorption at 77 K. In order to determine the loading capacity of the antiepileptic drug on these silica- and titania-based materials, the loading and release of PH was investigated using UV-vis spectroscopy. Tubular structures were found for the titania samples, for which the X-ray diffractograms showed to be formed by anatase and rutile phases. On the other hand, an amorphous phase was found in the silica sample. A highly ordered hexagonal structure of 1D cylindrical channels was also observed for this material. Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. The adsorption and desorption of PH are faster in nanostructured TiO 2 tubes than in mesoporous silica matrix.

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

surface at 50 deg C was more than that at 80 deg C, indicating the difference of molecular weight of polystyrene and polymerization mechanism. It is concluded that at lower temperature, the grafting based on the propagation of polystyrene from surface radical preferentially proceeded, but at higher temperature, the coupling reaction of propagating polymer radical with surface radical was determinating. Unextractable polymer remained on the silica surface by the γ-ray irradiation of polymer-adsorbed silica

Advanced three dimensional characterization of silica-based ultraporous materials

OpenAIRE

Foray , Genevieve; Roiban , L.; Rong , Q.; Perret , A.; Ihiawakrim , D.; Masenelli-Varlot , K.; Maire , E.; Yrieix , B.

2016-01-01

International audience; Whatever the field of application (building, transportation, packaging, etc.) energy losses must be reduced to meet the government target of a 40% cut in CO 2 emissions. This leads to a challenge for materials scientists: designing materials with thermal conductivities lower than 0.015 W m À1 K À1 under ambient conditions. Such a low value requires reducing air molecule mobility in highly porous materials, and silica-based superinsulation materials (SIM) made of packed...

A variable-mode stator consequent pole memory machine

Science.gov (United States)

Yang, Hui; Lyu, Shukang; Lin, Heyun; Zhu, Z. Q.

2018-05-01

In this paper, a variable-mode concept is proposed for the speed range extension of a stator-consequent-pole memory machine (SCPMM). An integrated permanent magnet (PM) and electrically excited control scheme is utilized to simplify the flux-weakening control instead of relatively complicated continuous PM magnetization control. Due to the nature of memory machine, the magnetization state of low coercive force (LCF) magnets can be easily changed by applying either a positive or negative current pulse. Therefore, the number of PM poles may be changed to satisfy the specific performance requirement under different speed ranges, i.e. the machine with all PM poles can offer high torque output while that with half PM poles provides wide constant power range. In addition, the SCPMM with non-magnetized PMs can be considered as a dual-three phase electrically excited reluctance machine, which can be fed by an open-winding based dual inverters that provide direct current (DC) bias excitation to further extend the speed range. The effectiveness of the proposed variable-mode operation for extending its operating region and improving the system reliability is verified by both finite element analysis (FEA) and experiments.

Development of novel biocompatible hybrid nanocomposites based on polyurethane-silica prepared by sol gel process

Energy Technology Data Exchange (ETDEWEB)

Rashti, Ali [Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Yahyaei, Hossein [Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Firoozi, Saman [Department of Tissue Engineering & Regenerative Medicine, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Ramezani, Sara [Department of Neuroscience, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Rahiminejad, Ali [Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Karimi, Roya [Department of Tissue Engineering and Applied Cell Science, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Farzaneh, Khadijeh [Tehran Heart Center, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Mohseni, Mohsen [Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Ghanbari, Hossein, E-mail: hghanbari@tums.ac.ir [Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Tehran Heart Center, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Medical Biomaterials Research Center, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of)

2016-12-01

Due to high biocompatibility, polyurethane has found many applications, particularly in development of biomedical devices. A new nanocomposite based on thermoset polyurethane and silica nanoparticles was synthesized using sol-gel method. Sol-gel process was fulfilled in two acidic and basic conditions by using tetraethylorthosilicate (TEOS) and trimethoxyisocyanatesilane as precursors. The hybrid films characterized for mechanical and surface properties using tensile strength, contact angle, ATR-FTIR and scanning electron microscopy. Biocompatibility and cytotoxicity of the hybrids were assessed using standard MTT, LDH and TUNEL assays. The results revealed that incorporation of silica nanoparticles was significantly improved tensile strength and mechanical properties of the hybrids. Based on the contact angle results, silica nanoparticles increased hydrophilicity of the hybrids. Biocompatibility by using human lung epithelial cell line (MRC-5) demonstrated that the hybrids were significantly less cytotoxic compared to pristine polymer as tested by MTT and LDH assays. TUNEL assay revealed no signs of apoptosis in all tested samples. The results of this study demonstrated that incorporation of silica nanoparticles into polyurethane lead to the enhancement of biocompatibility, indicating that these hybrids could potentially be used in biomedical field in particular as a new coating for medical implants. - Highlights: • Nanocomposites based on polyurethane and nanosilica prepared by sol-gel method fabricated • Addition of inorganic phase improved mechanical properties. • Nanosilica prepared by sol-gel method increased hydrophilicity. • By adding nanosilica to polyurethane biocompatibility increased significantly.

Don't trust equivalency presumptions when choosing distribution poles

Energy Technology Data Exchange (ETDEWEB)

Rollins, M.

2003-08-01

The variety of electric power distribution poles are described (wood, steel, prestressed concrete) in an effort to alert utilities that simple substitution of one type of pole for another based on presumed equivalency entails the risk that the replacement poles are unfit for the load conditions and do not comply with National Electrical Safety Code (NESC) requirements. A thorough evaluation of all design loads and the proper application of the appropriate overload and strength factors must take place prior to selecting the type of replacement to avoid misapplication of a product in situations for which it was not designed. Relevant provisions of NESC are described.

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...

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.

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...

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.

Analytical transmissibility based transfer path analysis for multi-energy-domain systems using four-pole parameter theory

Science.gov (United States)

Mashayekhi, Mohammad Jalali; Behdinan, Kamran

2017-10-01

The increasing demand to minimize undesired vibration and noise levels in several high-tech industries has generated a renewed interest in vibration transfer path analysis. Analyzing vibration transfer paths within a system is of crucial importance in designing an effective vibration isolation strategy. Most of the existing vibration transfer path analysis techniques are empirical which are suitable for diagnosis and troubleshooting purpose. The lack of an analytical transfer path analysis to be used in the design stage is the main motivation behind this research. In this paper an analytical transfer path analysis based on the four-pole theory is proposed for multi-energy-domain systems. Bond graph modeling technique which is an effective approach to model multi-energy-domain systems is used to develop the system model. In this paper an electro-mechanical system is used as a benchmark example to elucidate the effectiveness of the proposed technique. An algorithm to obtain the equivalent four-pole representation of a dynamical systems based on the corresponding bond graph model is also presented in this paper.

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.

Composite hydrogel based on surface modified mesoporous silica and poly[(2-acryloyloxy)ethyl trimethylammonium chloride

Energy Technology Data Exchange (ETDEWEB)

Torres, Cecilia C. [Department of Organic Chemistry, Faculty of Chemical Science, University of Concepción (Chile); Urbano, Bruno F., E-mail: burbano@udec.cl [Department of Polymer Chemistry, Faculty of Chemical Science, University of Concepción (Chile); Campos, Cristian H. [Department of Organic Chemistry, Faculty of Chemical Science, University of Concepción (Chile); Rivas, Bernabé L. [Department of Polymer Chemistry, Faculty of Chemical Science, University of Concepción (Chile); Reyes, Patricio [Department of Physical Chemistry, Faculty of Chemical Science, University of Concepción (Chile)

2015-02-15

This work focused on the synthesis, characterization and water absorbency of a composite hydrogel based on poly[(2-acryloyloxy)ethyl trimethylammonium chloride] and mesoporous silica, MCM-41. The MCM-41 was synthesized and later surface functionalized with triethoxyvinylsilane (VTES) and 3-trimethoxysilylpropylmethacrylate (TMSPM) by a post-grafting procedure. The composite hydrogels were obtained by in-situ polymerization using a mixture of monomer, crosslinker and initiator in the presence of functionalized MCM-41. Diverse characterization techniques were used at the different stages of synthesis, namely, FT-IR, TEM, SEM, DRX, {sup 29}Si and {sup 13}C solid state NMR, and N{sub 2} adsorption isotherms at 77 K. Finally, the water uptake performance of the composites was tested as a function of time, mesoporous silica loading and coupling agent used at the functionalization. The composites using non-functionalized MCM-41 reached the highest water uptake, whereas those composite with MCM-41 TMSPM exhibited the lowest sorption. - Highlights: • Hydrophilic crosslinked polymer-mesoporous silica was obtained. • Mesoporous silica MCM-41 was synthesized and functionalized with organosilane. • Functionalization of MCM-41 affects the water uptake of composite. • Mesoporous silica is covalently bound to the polymer acting as crosslinked point.

Mesoporous Silica Thin Membranes with Large Vertical Mesochannels for Nanosize-Based Separation.

Science.gov (United States)

Liu, Yupu; Shen, Dengke; Chen, Gang; Elzatahry, Ahmed A; Pal, Manas; Zhu, Hongwei; Wu, Longlong; Lin, Jianjian; Al-Dahyan, Daifallah; Li, Wei; Zhao, Dongyuan

2017-09-01

Membrane separation technologies are of great interest in industrial processes such as water purification, gas separation, and materials synthesis. However, commercial filtration membranes have broad pore size distributions, leading to poor size cutoff properties. In this work, mesoporous silica thin membranes with uniform and large vertical mesochannels are synthesized via a simple biphase stratification growth method, which possess an intact structure over centimeter size, ultrathin thickness (≤50 nm), high surface areas (up to 1420 m 2 g -1 ), and tunable pore sizes from ≈2.8 to 11.8 nm by adjusting the micelle parameters. The nanofilter devices based on the free-standing mesoporous silica thin membranes show excellent performances in separating differently sized gold nanoparticles (>91.8%) and proteins (>93.1%) due to the uniform pore channels. This work paves a promising way to develop new membranes with well-defined pore diameters for highly efficient nanosize-based separation at the macroscale. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Double-Layer Surface Modification of Polyamide Denture Base Material by Functionalized Sol-Gel Based Silica for Adhesion Improvement.

Science.gov (United States)

Hafezeqoran, Ali; Koodaryan, Roodabeh

2017-09-21

Limited surface treatments have been proposed to improve the bond strength between autopolymerizing resin and polyamide denture base materials. Still, the bond strength of autopolymerizing resins to nylon polymer is not strong enough to repair the fractured denture effectively. This study aimed to introduce a novel method to improve the adhesion of autopolymerizing resin to polyamide polymer by a double layer deposition of sol-gel silica and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AE-APTMS). The silica sol was synthesized by acid-catalyzed hydrolysis of tetraethylorthosilicate (TEOS) as silica precursors. Polyamide specimens were dipped in TEOS-derived sol (TS group, n = 28), and exposed to ultraviolet (UV) light under O 2 flow for 30 minutes. UV-treated specimens were immersed in AE-APTMS solution and left for 24 hours at room temperature. The other specimens were either immersed in AE-APTMS solution (AP group, n = 28) or left untreated (NT group, n = 28). Surface characterization was investigated by fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Two autopolymerizing resins (subgroups G and T, n = 14) were bonded to the specimens, thermocycled, and then tested for shear bond strength with a universal testing machine. Data were analyzed with one-way ANOVA followed by Tukey's HSD (α = 0.05). FTIR spectra of treated surfaces confirmed the chemical modification and appearance of functional groups on the polymer. One-way ANOVA revealed significant differences in shear bond strength among the study groups. Tukey's HSD showed that TS T and TS G groups had significantly higher shear bond strength than control groups (p = 0.001 and p < 0.001, respectively). Moreover, bond strength values of AP T were statistically significant compared to controls (p = 0.017). Amino functionalized TEOS-derived silica coating is a simple and cost-effective method for improving the bond strength between the autopolymerizing resin and polyamide

A new nanocomposite polymer electrolyte based on poly(vinyl alcohol) incorporating hypergrafted nano-silica

KAUST Repository

Hu, Xian-Lei

2012-01-01

Solid-state nanocomposite polymer electrolytes based on poly(vinyl alcohol)(PVA) incorporating hyperbranched poly(amine-ester) (HBPAE) grafted nano-silica (denoted as SiO2-g-HBPAE) have been prepared and investigated. Through surface pretreatment of nanoparticles, followed by Michael-addition and a self-condensation process, hyperbranched poly(amine-ester) was directly polymerized from the surface of nano-silica. Then the hypergrafted nanoparticles were added to PVA matrix, and blended with lithium perchlorate via mold casting method to fabricate nanocomposite polymer electrolytes. By introducing hypergrafted nanoparticles, ionic conductivity of solid composite is improved significantly at the testing temperature. Hypergrafted nano-silica may act as solid plasticizer, promoting lithium salt dissociation in the matrix as well as improving segmental motion of matrix. In addition, tensile testing shows that such materials are soft and tough even at room temperature. From the dielectric spectra of nanocomposite polymer electrolyte as the function of temperature, it can be deduced that Arrhenius behavior appears depending on the content of hypergrafted nano-silica and concentration of lithium perchlorate. At a loading of 15 wt% hypergrafted nano-silica and 54 wt% lithium perchlorate, promising ionic conductivities of PVA nanocomposite polymer electrolyte are achieved, about 1.51 × 10 ^-4 S cm^-1 at 25 °C and 1.36 × 10^-3 S cm^-1 at 100 °C. © The Royal Society of Chemistry.

Highly porous flame-retardant and sustainable biofoams based on wheat gluten and in situ polymerized silica

DEFF Research Database (Denmark)

Wu, Qiong; Andersson, Richard L.; Holgate, Tim

2014-01-01

This article presents a novel type of flame-retardant biohybrid foam with good insulation properties based on wheat gluten and silica, the latter polymerized in situ from hydrolysed tetraethyl orthosilicate (TEOS). This led to the formation of intimately mixed wheat gluten and silica phases, wher...... with a vacuum treatment to remove the largest air bubbles. X-ray photoelectron and infrared spectroscopy showed that silicon was present mainly as SiO2....

The effect of poling conditions on the performance of piezoelectric energy harvesters fabricated by wet chemistry

KAUST Repository

Fuentes-Fernandez, Erika Maria-Anai

2015-03-25

The effect of poling conditions on the power output of piezoelectric energy harvesters using sol-gel based Pb(Zr0.53,Ti0.47)O3-Pb(Zn1/3,Nb2/3)O3 piezoelectric thin-films has been investigated. A strong correlation was established between the poling efficiency and harvester output. A method based on simple capacitance-voltage measurements is shown to be an effective approach to estimate the power output of harvesters poled under different conditions. The poling process was found to be thermally activated with an activation energy of 0.12 eV, and the optimum poling conditions were identified (200 kV cm-1, 250 °C for 50 min). The voltage output and power density obtained under optimum poling conditions were measured to be 558 V cm-2 and 325 μW cm-2, respectively. © The Royal Society of Chemistry.2015.

Controlled release of phenytoin for epilepsy treatment from titania and silica based materials

Energy Technology Data Exchange (ETDEWEB)

Lopez, Tessy, E-mail: tessy3@prodigy.net.mx [Universidad Autonoma Metropolitana-Xochimilco. Departamento de Microbiologia. Calzada del Hueso 1100, Col. Villa Quietud, Coyoacan, C.P. 04960, Mexico D.F. Mexico (Mexico); Instituto Nacional de Neurologia y Neurocirugia ' MVS' . Laboratorio de Nanotecnologia. Av. Insurgentes Sur 3877, Col. La Fama, Tlalpan, 14269, Mexico, D.F. Mexico (Mexico); Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118 (United States); Ortiz, Emma [Instituto Nacional de Neurologia y Neurocirugia ' MVS' . Laboratorio de Nanotecnologia. Av. Insurgentes Sur 3877, Col. La Fama, Tlalpan, 14269, Mexico, D.F. Mexico (Mexico); Meza, Doraliz [Universidad Autonoma Metropolitana-Iztapalapa, Departamento de Quimica, Av. San Rafael Atlixco 186, A.P. 55-534, Mexico D.F., C.P. 09340 (Mexico); Basaldella, Elena [CIC-CINDECA - Universidad Nacional de La Plata - Calle 47 No 257 - La Plata (Argentina); Bokhimi, Xim; Magana, Carlos [Instituto de fisica, UNAM. Circuito de la Investigacion s/n. C.U. Mexico D.F. 01000 (Mexico); Sepulveda, Antonio; Rodriguez, Francisco; Ruiz, Javier [Departamento de Quimica Inorganica, Universidad de Alicante. Apartado 99, E-03080 Alicante, Espana Spain (Spain)

2011-04-15

Research highlights: {yields} Template technique was used to obtain well ordered nanostructured materials: SBA-15 and titania tubes. {yields} Phenytoin (PH), a drug used in epilepsy treatment, was loaded in these materials to used como PH release. {yields} Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. {yields} The load-release PH are faster in nanostructured TiO2 tubes than in mesoporous silica matrix. {yields} There is an inverse effect of the surface area of the structured materials on the amount of released PH. - Abstract: Template technique was used to obtain well ordered nanostructured materials: mesoporous silica and nanostructured titania tubes. This technique permits the synthesis of solids with controlled mesoporosity, where a large variety of molecules that have therapeutic activity can be hosted and further released to specific sites. In this work phenytoin (PH), a drug used in epilepsy treatment, was loaded in ordered mesoporous silica (SBA 15) and nanostructured titania tubes (TiO{sub 2}). The pure materials and those containing PH were characterized by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N{sub 2} adsorption-desorption at 77 K. In order to determine the loading capacity of the antiepileptic drug on these silica- and titania-based materials, the loading and release of PH was investigated using UV-vis spectroscopy. Tubular structures were found for the titania samples, for which the X-ray diffractograms showed to be formed by anatase and rutile phases. On the other hand, an amorphous phase was found in the silica sample. A highly ordered hexagonal structure of 1D cylindrical channels was also observed for this material. Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. The adsorption and desorption of PH are faster in nanostructured TiO{sub 2} tubes than in mesoporous silica

Blue-Emitting Small Silica Particles Incorporating ZnSe-Based Nanocrystals Prepared by Reverse Micelle Method

Directory of Open Access Journals (Sweden)

Masanori Ando

2007-01-01

Full Text Available ZnSe-based nanocrystals (ca. 4-5 nm in diameter emitting in blue region (ca. 445 nm were incorporated in spherical small silica particles (20–40 nm in diameter by a reverse micelle method. During the preparation, alkaline solution was used to deposit the hydrolyzed alkoxide on the surface of nanocrystals. It was crucially important for this solution to include Zn2+ ions and surfactant molecules (thioglycolic acid to preserve the spectral properties of the final silica particles. This is because these substances in the solution prevent the surface of nanocrystals from deterioration by dissolution during processing. The resultant silica particles have an emission efficiency of 16% with maintaining the photoluminescent spectral width and peak wavelength of the initial colloidal solution.

Evaluation of the pole figure

International Nuclear Information System (INIS)

Cabrera B, E.; Macias B, L.R.

1984-01-01

In the present work it's shown the possibility of obtaining a pole-figure from the data generated in a conventional X-ray equipment, with a commercial goniometer and no electronic device to process the data. The way to plot the pole-figure on-line is by means of measuring the diffractogram and plot manually the stereographic projections. The atainable precision is very low in such a cumbersome process. In this paper we substitute such method by storing the data in a punched tape from a conventional teletype. The data is processed in a computer and the pole-figure is recorded by a plotter attached to the computer. (author)

Manganese–Schiff base complex immobilized silica materials

Indian Academy of Sciences (India)

III)]+ and [Mn(salophen)]+: [N,N′-bis(salicylaldehyde)-1,2-phenylenediimino manganese(III)]+ were introduced into/onto the MCM-41 type silica spheres and used for the electrocatalytic reduction of oxygen. Synthesized materials were ...

Pole shifting with constrained output feedback

International Nuclear Information System (INIS)

Hamel, D.; Mensah, S.; Boisvert, J.

1984-03-01

The concept of pole placement plays an important role in linear, multi-variable, control theory. It has received much attention since its introduction, and several pole shifting algorithms are now available. This work presents a new method which allows practical and engineering constraints such as gain limitation and controller structure to be introduced right into the pole shifting design strategy. This is achieved by formulating the pole placement problem as a constrained optimization problem. Explicit constraints (controller structure and gain limits) are defined to identify an admissible region for the feedback gain matrix. The desired pole configuration is translated into an appropriate cost function which must be closed-loop minimized. The resulting constrained optimization problem can thus be solved with optimization algorithms. The method has been implemented as an algorithmic interactive module in a computer-aided control system design package, MVPACK. The application of the method is illustrated to design controllers for an aircraft and an evaporator. The results illustrate the importance of controller structure on overall performance of a control system

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.

Comparison of the surface ion density of silica gel evaluated via spectral induced polarization versus acid-base titration

Science.gov (United States)

Hao, Na; Moysey, Stephen M. J.; Powell, Brian A.; Ntarlagiannis, Dimitrios

2016-12-01

Surface complexation models are widely used with batch adsorption experiments to characterize and predict surface geochemical processes in porous media. In contrast, the spectral induced polarization (SIP) method has recently been used to non-invasively monitor in situ subsurface chemical reactions in porous media, such as ion adsorption processes on mineral surfaces. Here we compare these tools for investigating surface site density changes during pH-dependent sodium adsorption on a silica gel. Continuous SIP measurements were conducted using a lab scale column packed with silica gel. A constant inflow of 0.05 M NaCl solution was introduced to the column while the influent pH was changed from 7.0 to 10.0 over the course of the experiment. The SIP measurements indicate that the pH change caused a 38.49 ± 0.30 μS cm- 1 increase in the imaginary conductivity of the silica gel. This increase is thought to result from deprotonation of silanol groups on the silica gel surface caused by the rise in pH, followed by sorption of Na+ cations. Fitting the SIP data using the mechanistic model of Leroy et al. (Leroyet al., 2008), which is based on the triple layer model of a mineral surface, we estimated an increase in the silica gel surface site density of 26.9 × 1016 sites m- 2. We independently used a potentiometric acid-base titration data for the silica gel to calibrate the triple layer model using the software FITEQL and observed a total increase in the surface site density for sodium sorption of 11.2 × 1016 sites m- 2, which is approximately 2.4 times smaller than the value estimated using the SIP model. By simulating the SIP response based on the calibrated surface complexation model, we found a moderate association between the measured and estimated imaginary conductivity (R2 = 0.65). These results suggest that the surface complexation model used here does not capture all mechanisms contributing to polarization of the silica gel captured by the SIP data.

Properties and shaping of lightweight ceramics based on phosphate-bonded hollow silica microspheres

NARCIS (Netherlands)

With, de G.; Verweij, H.

1986-01-01

The values for the Young's modulus, strength, fracture toughness and thermal conductivity of lightweight ceramics based on phosphate-bonded hollow silica microspheres are reported as a function of the processing conditions. They are compared with the relevant data for other lightweight ceramic

Utility poles not affected by CCA decision

Energy Technology Data Exchange (ETDEWEB)

De Venzio, H. [Arch Wood Protection Canada, Mississauga, ON (Canada)

2002-08-01

A voluntary decision by industry to move non-industrial use of treated lumber products away from pressure-treated wood containing chromated copper arsenate (CCA) preservative was announced by the Environmental Protection Agency on February 12, 2002. Although new alternative wood preservatives would be used, this decision does not affect utility poles, which will continue to be sold and installed. The author provides a brief historical outline concerning the creation of CCA in 1933 and its subsequent uses. CCA has many advantages, including clean surface of the poles, ground line treatment that is not required thus eliminating the requirement to rotate the poles during extended storage periods. Conductivity is low, as is corrosivity without affecting the bending characteristics of the wood. The injection of a refined hydrocarbon oil emulsion in the outer layer of the pole after the treatment with CCA is offered by some pole producers to facilitate gaff penetration. Sawing, drilling and nailing are also made easier. Water repellents can be added to the treating solution to improve climbability, slowing down the absorption and release of moisture. Warranties, extending for 50-year periods, are offered by some companies against wood-destroying organisms. The North American Wood Pole Coalition (NAWPC) was formed in 1998 to promote the use of wood poles, and publishes brochures and technical bulletins to that effect.

Influence of geometry on mechanical properties of bio-inspired silica-based hierarchical materials

International Nuclear Information System (INIS)

Dimas, Leon S; Buehler, Markus J

2012-01-01

Diatoms, bone, nacre and deep-sea sponges are mineralized natural structures found abundantly in nature. They exhibit mechanical properties on par with advanced engineering materials, yet their fundamental building blocks are brittle and weak. An intriguing characteristic of these structures is their heterogeneous distribution of mechanical properties. Specifically, diatoms exhibit nanoscale porosity in specific geometrical configurations to create regions with distinct stress strain responses, notably based on a single and simple building block, silica. The study reported here, using models derived from first principles based full atomistic studies with the ReaxFF reactive force field, focuses on the mechanics and deformation mechanisms of silica-based nanocomposites inspired by mineralized structures. We examine single edged notched tensile specimens and analyze stress and strain fields under varied sample size in order to gain fundamental insights into the deformation mechanisms of structures with distinct ordered arrangements of soft and stiff phases. We find that hierarchical arrangements of silica nanostructures markedly change the stress and strain transfer in the samples. The combined action of strain transfer in the deformable phase, and stress transfer in the strong phase, acts synergistically to reduce the intensity of stress concentrations around a crack tip, and renders the resulting composites less sensitive to the presence of flaws, for certain geometrical configurations it even leads to stable crack propagation. A systematic study allows us to identify composite structures with superior fracture mechanical properties relative to their constituents, akin to many natural biomineralized materials that turn the weaknesses of building blocks into a strength of the overall system. (paper)

POLE-LIKE STREET FURNITURE DECOMPOSTION IN MOBILE LASER SCANNING DATA

OpenAIRE

Li, F.; Oude Elberink, S.; Vosselman, G.

2016-01-01

Automatic semantic interpretation of street furniture has become a popular topic in recent years. Current studies detect street furniture as connected components of points above the street level. Street furniture classification based on properties of such components suffers from large intra class variability of shapes and cannot deal with mixed classes like traffic signs attached to light poles. In this paper, we focus on the decomposition of point clouds of pole-like street furniture. A nove...

Alkali Metal Modification of Silica Gel-Based Stationary Phase in Gas Chromatography

Directory of Open Access Journals (Sweden)

Ashraf Yehia El-Naggar

2013-01-01

Full Text Available Modification of the precipitated silica gel was done by treatment with alkali metal (NaCl before and after calcination. The silica surfaces before and after modification were confirmed by infrared spectroscopy in order to observe the strength and abundance of the acidic surface OH group bands which play an important role in the adsorption properties of polar and nonpolar solutes. The surface-modified silica gels were tested as GC solid stationary phases in terms of the separation efficiency for various groups of non-polar and polar solutes. Also, thermodynamic parameters (ΔH, ΔG, and ΔS were determined using n-hexane as a probe in order to show the adsorbate-adsorbent interaction. It was observed that the non-polar solutes could be separated Independent on the reactivity and porosity of the silica surfaces. The efficiency of the surface-modified silica gels to separate the aromatic hydrocarbons seemed to be strongly influenced by the density of the surface hydroxyls.

l-Cysteine-modified silver-functionalized silica-based material as an efficient solid-phase extraction adsorbent for the determination of bisphenol A.

Science.gov (United States)

Li, Yuanyuan; Zhu, Nan; Li, Bingxiang; Chen, Tong; Ma, Yulong; Li, Qiang

2018-02-01

A new silver-functionalized silica-based material with a core-shell structure based on silver nanoparticle-coated silica spheres was synthesized, and silver nanoparticles were modified using strongly bound l-cysteine. l-Cysteine-silver@silica was characterized by scanning electron microscopy and FTIR spectroscopy. Then, a solid-phase extraction method based on l-cysteine-silver@silica was developed and successfully used for bisphenol A determination prior to HPLC analysis. The results showed that the l-cysteine-silver@silica as an adsorbent exhibited good enrichment capability for bisphenol A, and the maximum adsorption saturation was 20.93 mg/g. Moreover, a short adsorption equilibrium time was obtained due to the presence of silver nanoparticles on the surface of the silica. The extraction efficiencies were then optimized by varying the eluents and pH. Under the optimized conditions, good linearity for bisphenol A was obtained in the range from 0.4 to 4.0 μM (R 2  > 0.99) with a low limit of detection (1.15 ng/mL). The spiked recoveries from tap water and milk samples were satisfactory (85-102%) with relative standard deviations below 5.2% (n = 3), which indicated that the method was suitable for the analysis of bisphenol A in complex samples. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study on Pole Arrangement of the CEDM Coils

International Nuclear Information System (INIS)

Park, Jin Seok; Lee, Myoung Goo; Kim, Hyun Min; Cho, Yeon Ho; Choi, Taek Sang

2013-01-01

The coil stack assembly is important for reliable operation of the CEDM, there have been efforts to improve the design by optimizing the design parameters such as dimensions and winding turns. However, magnetic forces of the CEDM can also change by different pole arrangement even if their design parameters are the same. Since the latch coil and lift coil are installed connected to each other, they produce magnetically coupled field when they are energized at the same time. This coupling field can affect the magnetic force of the CEDM significantly. In this paper, coil pole arrangement effects are studied. Electro-magnetic analysis is performed for the different pole arrangements of the CEDM coils to calculate the magnetic forces. Pole arrangement effects on magnetic forces were studied by static analysis of the CEDM magnetic field. Magnetic forces were calculated and compared for the two different pole arrangements of the coils. The results show that the magnetic poles of the lift coil and latch coil shall be arranged to have the same magnetic pole direction to achieve higher magnetic force

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.

A conformal mapping based fractional order approach for sub-optimal tuning of PID controllers with guaranteed dominant pole placement

Science.gov (United States)

Saha, Suman; Das, Saptarshi; Das, Shantanu; Gupta, Amitava

2012-09-01

A novel conformal mapping based fractional order (FO) methodology is developed in this paper for tuning existing classical (Integer Order) Proportional Integral Derivative (PID) controllers especially for sluggish and oscillatory second order systems. The conventional pole placement tuning via Linear Quadratic Regulator (LQR) method is extended for open loop oscillatory systems as well. The locations of the open loop zeros of a fractional order PID (FOPID or PIλDμ) controller have been approximated in this paper vis-à-vis a LQR tuned conventional integer order PID controller, to achieve equivalent integer order PID control system. This approach eases the implementation of analog/digital realization of a FOPID controller with its integer order counterpart along with the advantages of fractional order controller preserved. It is shown here in the paper that decrease in the integro-differential operators of the FOPID/PIλDμ controller pushes the open loop zeros of the equivalent PID controller towards greater damping regions which gives a trajectory of the controller zeros and dominant closed loop poles. This trajectory is termed as "M-curve". This phenomena is used to design a two-stage tuning algorithm which reduces the existing PID controller's effort in a significant manner compared to that with a single stage LQR based pole placement method at a desired closed loop damping and frequency.

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

Efficacy of the lithotripsy in treating lower pole renal stones.

Science.gov (United States)

Cui, Helen; Thomee, Eeke; Noble, Jeremy G; Reynard, John M; Turney, Benjamin W

2013-06-01

Use of extracorporeal lithotripsy is declining in North America and many European countries despite international guidelines advocating it as a first-line therapy. Traditionally, lithotripsy is thought to have poor efficacy at treating lower pole renal stones. We evaluated the success rates of lithotripsy for lower pole renal stones in our unit. 50 patients with lower pole kidney stones ≤15 mm treated between 3/5/11 and 19/4/12 were included in the study. Patients received lithotripsy on a fixed-site Storz Modulith SLX F2 lithotripter according to a standard protocol. Clinical success was defined as stone-free status or asymptomatic clinically insignificant residual fragments (CIRFs) ≤3 mm at radiological follow-up. The mean stone size was 7.8 mm. The majority of stones (66 %) were between 5 and 10 mm. 28 % of stones were between 10 and 15 mm. For solitary lower pole stones complete stone clearance was achieved in 63 %. Total stone clearance including those with CIRFs was achieved in 81 % of patients. As expected, for those with multiple lower pole stones the success rates were lower: complete clearance was observed in 39 % and combined clearance including those with CIRFs was 56 %. Overall, complete stone clearance was observed in 54 % of patients and clearance with CIRFs was achieved in 72 % of patients. Success rate could not be attributed to age, stone size or gender. Our outcome data for the treatment of lower pole renal stones (≤15 mm) compare favourably with the literature. With this level of stone clearance, a non-invasive, outpatient-based treatment like lithotripsy should remain the first-line treatment option for lower pole stones. Ureteroscopy must prove that it is significantly better either in terms of clinical outcome or patient satisfaction to justify replacing lithotripsy.

Diagnosis of excessive vibration signals of two-pole generator rotors in balancing

International Nuclear Information System (INIS)

Park, Jong Po

2000-01-01

Cause of excessive vibration with twice the rotational speed of a two-pole generator rotor for the fossil power plants was investigated. The two-pole generator rotor, treated as a typically asymmetric rotor in vibration analysis, produces asynchronous vibration with twice the rotational speed, sub-harmonic critical speeds, and potentially unstable operating zones due to its own inertia and/or stiffness asymmetry. This paper introduces a practical balancing procedure, and presents the results of the investigation on sources of the excessive vibration based on the experimental vibration data of the asymmetric two-pole rotor in balancing

Rotor pole refurbishment for hydrogenerators: insulation problems and solutions

International Nuclear Information System (INIS)

Reynolds, R.R.; Rux, L.

2005-01-01

Rotor poles for Unit 1 at Lower Granite Powerhouse were removed from the rotor and shipped to a repair facility for refurbishment. Upon inspection, it was found that all of the pole bodies exhibited a distinct bow, center to end, on the pole mounting surface. In some cases, the deflection was as much as 0.106 inch. Concerns were raised about how this condition might affect the ability to properly insulate and/or re-seat the poles. This paper presents details of the rotor pole and field winding evaluation, the problems encountered, and the solutions implemented to successfully refurbish the rotor poles and field winding. (author)

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.

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.

Adsorption of Cr(VI) using silica-based adsorbent prepared by radiation-induced grafting

International Nuclear Information System (INIS)

Qiu Jingyi; Wang Ziyue; Li Huibo; Xu Ling; Peng Jing; Zhai Maolin; Yang Chao; Li Jiuqiang; Wei Genshuan

2009-01-01

Silica-based adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto the silanized silica followed by a protonation process. The FTIR spectra and XPS analysis proved that DMAEMA was grafted successfully onto the silica surface. The resultant adsorbent manifested a high ion exchange capacity (IEC) of ca. 1.30 mmol/g and the Cr(VI) adsorption behavior of the adsorbent was further investigated, revealing the recovery of Cr(VI) increased with the adsorbent feed and the equilibrium adsorption could be achieved within 40 min. The adsorption capacity, strongly depended on the pH of the solution, reached a maximum Cr(VI) uptake (ca. 68 mg/g) as the pH was in the range of 2.5-5.0. Furthermore, even in strong acidic (4.0 mol/L HNO 3 ) or alkaline media (pH 11.0), the adsorbent had a sound Cr(VI) uptake capacity (ca. 22 and 30 mg/g, respectively), and the adsorption followed Langmuir mode. The results indicated that this adsorbent, prepared via a convenient approach, is applicable for removing heavy-metal-ion pollutants (e.g. Cr(VI)) from waste waters.

Fault Current Distribution and Pole Earth Potential Rise (EPR) Under Substation Fault

Science.gov (United States)

Nnassereddine, M.; Rizk, J.; Hellany, A.; Nagrial, M.

2013-09-01

New high-voltage (HV) substations are fed by transmission lines. The position of these lines necessitates earthing design to ensure safety compliance of the system. Conductive structures such as steel or concrete poles are widely used in HV transmission mains. The earth potential rise (EPR) generated by a fault at the substation could result in an unsafe condition. This article discusses EPR based on substation fault. The pole EPR assessment under substation fault is assessed with and without mutual impedance consideration. Split factor determination with and without the mutual impedance of the line is also discussed. Furthermore, a simplified formula to compute the pole grid current under substation fault is included. Also, it includes the introduction of the n factor which determines the number of poles that required earthing assessments under substation fault. A case study is shown.

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

Avoidance of a Landau pole by flat contributions in QED

Energy Technology Data Exchange (ETDEWEB)

Klaczynski, Lutz, E-mail: lutz.klaczynski@gmx.de [Department of Physics, Humboldt University Berlin, 12489 Berlin (Germany); Kreimer, Dirk, E-mail: kreimer@mathematik.hu-berlin.de [Alexander von Humboldt Chair in Mathematical Physics, Humboldt University, Berlin 12489 (Germany)

2014-05-15

We consider massless Quantum Electrodynamics in the momentum scheme and carry forward an approach based on Dyson–Schwinger equations to approximate both the β-function and the renormalized photon self-energy (Yeats, 2011). Starting from the Callan–Symanzik equation, we derive a renormalization group (RG) recursion identity which implies a non-linear ODE for the anomalous dimension and extract a sufficient but not necessary criterion for the existence of a Landau pole. This criterion implies a necessary condition for QED to have no such pole. Solving the differential equation exactly for a toy model case, we integrate the corresponding RG equation for the running coupling and find that even though the β-function entails a Landau pole it exhibits a flat contribution capable of decreasing its growth, in other cases possibly to the extent that such a pole is avoided altogether. Finally, by applying the recursion identity, we compute the photon propagator and investigate the effect of flat contributions on both spacelike and timelike photons. -- Highlights: •We present an approach to approximate both the β-function and the photon self-energy. •We find a sufficient criterion for the self-energy to entail the existence of a Landau pole. •We study non-perturbative ‘flat’ contributions that emerge within the context of our approach. •We discuss a toy model and how it is affected by flat contributions.

Solar Open Flux Migration from Pole to Pole: Magnetic Field Reversal.

Science.gov (United States)

Huang, G-H; Lin, C-H; Lee, L C

2017-08-25

Coronal holes are solar regions with low soft X-ray or low extreme ultraviolet intensities. The magnetic fields from coronal holes extend far away from the Sun, and thus they are identified as regions with open magnetic field lines. Coronal holes are concentrated in the polar regions during the sunspot minimum phase, and spread to lower latitude during the rising phase of solar activity. In this work, we identify coronal holes with outward and inward open magnetic fluxes being in the opposite poles during solar quiet period. We find that during the sunspot rising phase, the outward and inward open fluxes perform pole-to-pole trans-equatorial migrations in opposite directions. The migration of the open fluxes consists of three parts: open flux areas migrating across the equator, new open flux areas generated in the low latitude and migrating poleward, and new open flux areas locally generated in the polar region. All three components contribute to the reversal of magnetic polarity. The percentage of contribution from each component is different for different solar cycle. Our results also show that the sunspot number is positively correlated with the lower-latitude open magnetic flux area, but negatively correlated with the total open flux area.

Semiclassical approach to Regge poles trajectories calculations for nonsingular potentials: Thomas-Fermi type

International Nuclear Information System (INIS)

Belov, S M; Avdonina, N B; Felfli, Z; Marletta, M; Msezane, A Z; Naboko, S N

2004-01-01

A simple semiclassical approach, based on the investigation of anti-Stokes line topology, is presented for calculating Regge poles for nonsingular (Thomas-Fermi type) potentials, namely potentials with singularities at the origin weaker than order -2. The anti-Stokes lines for Thomas-Fermi potentials have a more complicated structure than those of singular potentials and require careful application of complex analysis. The explicit solution of the Bohr-Sommerfeld quantization condition is used to obtain approximate Regge poles. We introduce and employ three hypotheses to obtain several terms of the Regge pole approximation

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...

Cross-poling textures in a lead zirconate titanate piezoelectric material

International Nuclear Information System (INIS)

Wan, Shan; Bowman, Keith J.

2000-01-01

Tetragonal ferroelectric materials are polarized to induce the anisotropy necessary for the piezoelectric effect. This poling of the material is inherently an orientation process. Pole figure texture measurements of poling and cross-poling in a lead zirconate titanate Navy VI material show domain motion. The resulting axisymmetric and three-dimensional textures demonstrate the contribution of 90 degree sign domain motion to piezoelectricity. Cross-poling results in strong orientations with lower applied fields than in the initial poling steps. (c) 2000 Materials Research Society

South Pole rockets, (1)

International Nuclear Information System (INIS)

Kimura, Iwane

1977-01-01

Wave-particle interaction was observed, using three rockets, S-210 JA-20, -21 and S-310 JA-2, launched from the South Pole into aurora. Electron density and temperature were measured with these rockets. Simultaneous observations of waves were also made from a satellite (ISIS-II) and at two ground bases (Showa base and Mizuho base). Observed data are presented in this paper. These include electron density and temperature in relation to altitude; variation of electron (60 - 80 keV) count rate with altitude; VLF spectra measured by the PWL of S-210 JA-20 and -21 rockets and the corresponding VLF spectra at the ground bases; low-energy (<10 keV) electron flux measured by S-310 JA-2 rocket; and VLF spectrum measured with S-310 JA-2 rocket. Scheduled measurements for the next project are also briefly described. (Aoki, K.)

Reuse of poles treated with CCA; CCA-kyllaestettyjen puupylvaeiden uudelleenkaeyttoe

Energy Technology Data Exchange (ETDEWEB)

Lehmus, E. [Vtt Building and Transport, Espoo (Finland)

2005-07-01

This study investigated the feasibility of re-using utility poles or parts of poles for structural use in construction. There are more than 10 million poles in Finland and about 200 000 poles will be removed from service yearly during the next few years. The directive 2003/2/EY will restrict the use of poles treated with CCA. This will change the practice that the energy and telecommunication companies have given the removed poles to the land owners. The present study launched by the Technical Research Centre of Finland (VTT) was carried out to determine the technical condition of CCA impregnated poles removed from service and the concentration levels and leaching of remaining preservatives. To summarize the results of the tests, it is safe to say that re-use of recovered poles of 30 to 50 years of age is possible. Both the preservative concentrations and strength/load-bearing capacity are high enough to allow the use of the poles as load-bearing structures. (orig.)

Optical Fibre NO2 Sensor Based on Lutetium Bisphthalocyanine in a Mesoporous Silica Matrix

Directory of Open Access Journals (Sweden)

Marc Debliquy

2018-03-01

Full Text Available In this article, we describe a NO2 sensor consisting of a coating based on lutetium bisphthalocyanine (LuPc2 in mesoporous silica. The sensor exploits the absorption spectrum change of this material which strongly and reversibly decreases in contact with NO2. NO2 is measured by following the amplitude change in the reflected spectrum of the coating deposited on the tip of a silica fibre. As diffusion of NO2 in LuPc2 is slow, the response time could be slow. To reduce it, the active molecules are dispersed in a mesoporous silica matrix deposited by a sol-gel process (Evaporation Induced Self Assembly avoiding the formation of large crystals. Doing so, the response is fairly fast. As the recovery is slow at room temperature, the recovery time is reduced by exposure to UV light at 365 nm. This UV light is directly introduced in the fibre yielding a practical sensor sensitive to NO2 in the ppm range suitable for pollution monitoring.

A new surface catalytic model for silica-based thermal protection material for hypersonic vehicles

Directory of Open Access Journals (Sweden)

Li Kai

2015-10-01

Full Text Available Silica-based materials are widely employed in the thermal protection system for hypersonic vehicles, and the investigation of their catalytic characteristics is crucially important for accurate aerothermal heating prediction. By analyzing the disadvantages of Norman’s high and low temperature models, this paper combines the two models and proposes an eight-reaction combined surface catalytic model to describe the catalysis between oxygen and silica surface. Given proper evaluation of the parameters according to many references, the recombination coefficient obtained shows good agreement with experimental data. The catalytic mechanisms between oxygen and silica surface are then analyzed. Results show that with the increase of the wall temperature, the dominant reaction contributing to catalytic coefficient varies from Langmuir–Hinshelwood (LH recombination (TW  1350 K. The surface coverage of chemisorption areas varies evidently with the dominant reactions in the high temperature (HT range, while the surface coverage of physisorption areas varies within quite low temperature (LT range (TW < 250 K. Recommended evaluation of partial parameters is also given.

The pole tide in deep oceans

Science.gov (United States)

Dickman, S. R.

1990-01-01

The fluid-dynamical theory of the pole tide is examined by describing the oceanic response to the Chandler wobble and assessing its implications for mantle anelasticity and low-frequency ocean dynamics. The Laplace tide equations accounting for bottom friction are given, and a spherical harmonic approach is delineated in which the time-independent portion of the tide height is expanded. Pole-tide height and related inertia products are linearly proportional to wobble amplitude, and the final equations are modified to account for mantle elasticity and oceanic loading. Results for pole tide effects are given for various earth models with attention to the role of boundary constraints. A dynamic effect is identified which lengthens the Chandler period by about 1 day more than static lengthening, a contribution that suggests a vigorous low-frequency response. The values derived are shown to agree with previous models that do not incorporate the effects of the pole tide.

POLE mutations in families predisposed to cutaneous melanoma

DEFF Research Database (Denmark)

Aoude, Lauren G; Heitzer, Ellen; Johansson, Peter

2015-01-01

Germline mutations in the exonuclease domain of POLE have been shown to predispose to colorectal cancers and adenomas. POLE is an enzyme involved in DNA repair and chromosomal DNA replication. In order to assess whether such mutations might also predispose to cutaneous melanoma, we interrogated...... variants in the exonuclease domain of POLE. Although this frequency is not significantly higher than that in unselected Caucasian controls, we observed multiple cancer types in the melanoma families, suggesting that some germline POLE mutations may predispose to a broad spectrum of cancers, including...

Plotter of pole figure using data from x-ray diffraction

International Nuclear Information System (INIS)

Lima, A.F.

1990-01-01

Any polycrystalline aggregate normally has a preferred crystallographic orientation, or texture which depends on its thermal and or mechanical history. Preferred orientation is best described by means of a pole figure. A pole figure is a stereographic projection which shows the variation in pole density with pole orientation, for a selected set of crystal planes. In this work, computer programs was developed to plot pole figures. The corrected intensities are calculated and directly transmitted to the plotter. The different intensities levels are represented by different colors in the pole figure. (author)

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

Characterization of Electret Based on Inorganic-organic Nanocomposite Using Fluoropolymer and Silica Nanoparticles

International Nuclear Information System (INIS)

Suzuki, M; Shimokizaki, M; Takahashi, T; Aoyagi, S; Yoshikawa, Y

2015-01-01

An A novel electret based on inorganic-organic nano composite using fluoropolymer and silica nanoparticles was developed in this study. CYTOP® is used to fabricate the nanocomposite electret, which is one of fluoropolymer. Three kinds of silica nanoparticles dispersed in methyl ethyl ketone were employed. Each type of nanoparticles was mixed in the CYTOP or stuck between three layers of CYTOP. Then, negative charge was implanted by corona discharge method. The initial surface potential of the nanocomposite electret was higher than that of a control electret made of pure CYTOP. Additionally, time stability of those was also better than that of control electret. However, above mentioned properties of the mix-typed electret was worse than that of stuck-typed electret, because of discharging through aggregates composed of the nanoparticles. (paper)

Effects of slotting and unipolar flux on magnetic pull in a two-pole induction motor with an extra four-pole stator winding

Energy Technology Data Exchange (ETDEWEB)

Sinervo, A.

2013-06-01

This thesis is about the radial magnetic forces between the rotor and stator in twopole induction machines. The magnetic forces arise from rotor eccentricity. The asymmetric air-gap makes the flux density on one side of the rotor stronger than on the opposite side. This produces magnetic pull. The magnetic flux density distribution in the air-gap can be expressed with spatial harmonics, i.e. flux densities with different pole-pair numbers. In two-pole machines, the main part of the magnetic force is produced by the interaction of two- and fourpole flux unless the four-pole flux is damped by parallel paths in the stator winding or an extra four-pole stator winding. The rest of the force comes from the interaction of two-pole and unipolar flux and from the higher harmonics of the air-gap flux of which the slot harmonics are a major part. The force caused by the higher harmonics and the unipolar flux is studied in the case where a four-pole stator winding is used to reduce the four-pole flux. The higher harmonics are found to produce, in addition to the traditional unbalanced magnetic pull, a force similar to the effect of the unipolar flux and the two can be distinguished only by measuring the unipolar flux. In measurements at various operation points, the higher harmonics are found to produce much more force than the unipolar flux and two-pole flux but the unipolar flux is still significant. The four-pole winding also is used to actively control the four-pole flux and the magnetic forces. Designing the controller requires a low order model of the system. Such a model is derived and the effect of the slot harmonics and the unipolar flux are included in the model. Different measurements techniques and methods are presented to identify and validate the control model. The operation point dependence of the system dynamics is studied via measurements. All results are obtained from a 30 kW test motor. The rotor of the test machine has a long flexible shaft on external

Deep glass etched microring resonators based on silica-on-silicon technology

DEFF Research Database (Denmark)

Ou, Haiyan; Rottwitt, Karsten; Philipp, Hugh Taylor

2006-01-01

Microring resonators fabricated on silica-on-silicon technology using deep glass etching are demonstrated. The fabrication procedures are introduced and the transmission spectrum of a resonator is presented.......Microring resonators fabricated on silica-on-silicon technology using deep glass etching are demonstrated. The fabrication procedures are introduced and the transmission spectrum of a resonator is presented....

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.

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.

Enhancement of Hybrid SPEEK Based Polymer–Cyclodextrin-Silica Inorganic Membrane for Direct Methanol Fuel Cell Application

Directory of Open Access Journals (Sweden)

Tutuk Djoko Kusworo

2017-06-01

  Keywords: Direct Methanol Fuel Cell, Poly(ether ether ketone, cyclodextrin-silica, sulfonation, ionic conductivity. Article History: Received January 18th 2017; Received in revised form April 21st 2017; Accepted June 22nd 2017; Available online How to Cite This Article: Kusworo, T.D., Hakim, M.F. and Hadiyanto, H. (2017 Enhancement of Hybrid SPEEK Based Polymer–Cyclodextrin-Silica Inorganic Membrane for Direct Methanol Fuel Cell Application. International Journal of Renewable Energy Development, 6(2, 165-170. https://doi.org/10.14710/ijred.6.2.165-170

From Beale Number to Pole Placement Design of a Free Piston Stirling Engine

Directory of Open Access Journals (Sweden)

Zare Shahryar

2017-12-01

Full Text Available In this paper, pole placement-based design and analysis of a free piston Stirling engine (FPSE is presented and compared to the well-defined Beale number design technique. First, dynamic and thermodynamic equations governing the engine system are extracted. Then, linear dynamics of the free piston Stirling engine are studied using dynamic systems theory tools such as root locus. Accordingly, the effects of variations of design parameters such as mass of pistons, stiffness of springs, and frictional damping on the locations of dominant closed-loop poles are investigated. The design procedure is thus conducted to place the dominant poles of the dynamic system at desired locations on the s-plane so that the unstable dynamics, which is the required criterion for energy generation, is achieved. Next, the closed-loop poles are selected based on a desired frequency so that a periodical system is found. Consequently, the design parameters, including mass and spring stiffness for both power and displacer pistons, are obtained. Finally, the engine power is calculated through the proposed control-based analysis and the result is compared to those of the experimental work and the Beale number approach. The outcomes of this work clearly reveal the effectiveness of the control-based design technique of FPSEs compared to the well-known approaches such as Beale number.

Repair and rehabilitation of wood utility poles with fibre-reinforced polymers

Energy Technology Data Exchange (ETDEWEB)

Polyzois, D.; Kell, J.A. [Manitoba Univ., Winnipeg, MB (Canada). Dept. of Civil Engineering

2007-01-15

In order to ensure safe and reliable service, all wood utility poles need an effective maintenance program. The service life of a wood utility pole depends on several factors, such as decay, mechanical damage, weathering, and changing design requirements. An effective preservative treatment and maintenance program can effectively extend the service life of the wood pole. However, all poles will attain a point when they are no longer suitable for their intended use. New innovative methods are therefore required to restore and maintain the structural integrity of existing wood poles, especially in light of the increasing cost of quality wood for use in poles as well as a result of environmental concerns regarding pole disposal and chemical treatment of existing poles. This article presented results from a research program carried out at the University of Manitoba to develop a repair and rehabilitation technique for wood poles using fibre-reinforced polymers (FRP). It also provided a brief overview of current standards for wood utility poles and reinforcing stubs and discussed the experimental program where long, air-dried jack pine poles were tested in order to evaluate the effectiveness of a proposed rehabilitation system consisting of FRP splines and FRP jackets. The ultimate capacity of the poles was determined using the CSA standard for wood poles. The capacity of the rehabilitated poles was nearly 93 per cent of the average ultimate capacity of the average ultimate capacity of poles tested during the first phase of the study, and 23 per cent higher than the capacity required by CSA standards. 7 refs., 2 figs., 4 tabs.

Design of a portable CAT scanner for utility pole inspection

International Nuclear Information System (INIS)

Miller, W.H.

1986-01-01

Work is under way at the University of Missouri, Columbia (UMC) to design, build, and test a portable computerized axial tomography (CAT) device for the nondestructive, field imaging of wooden utility poles. CAT is a well-established medical technology that has recently been applied to a number of industrial applications. Wooden utility poles are prone to rot and decay at ground level; current techniques to assess this loss of strength are relatively primitive, i.e., tapping the pole (hitting the pole with a hammer) or boring into the pole for samples and then testing inside the bore hole with an electrical pulse device. The accuracy in identifying poles needing replacement using these techniques is ∼ 70%. Since the cost of replacing a pole ranges from hundreds to thousands of dollars, an accurate, nondestructive method is needed. CAT can accurately image a wooden utility pole (since the size, density, and atomic elements of a pole are similar to the human head to torso), as was confirmed by imaging poles using the UMC nuclear engineering EMI-1010 medical scanner. Detailed images have been produced showing the ring structure of the wood and voids due to rot or decay. Images approaching this quality have also been produced on living trees using semiportable systems by other researchers

Spontaneous Temporal Pole Encephalocele Presenting with Epilepsy: Report of Two Cases.

Science.gov (United States)

Shimada, Seijiro; Kunii, Naoto; Kawai, Kensuke; Usami, Kenichi; Matsuo, Takeshi; Uno, Takeshi; Koizumi, Tomoyuki; Saito, Nobuhito

2015-09-01

Refractory temporal lobe epilepsy due to spontaneous temporal pole encephalocele is a rare but increasingly recognized condition. Optimal surgical management is complicated by the lack of knowledge regarding both the extent of the epileptogenic area and the need for repair of the encephalocele. We report two cases that add significant information to these issues. In Case 1, with a 5-year history of refractory seizures, implantation of diagnostic subdural electrodes into the anterior temporal base happened to abolish the seizures completely. No structural changes were evident on postoperative magnetic resonance imaging. In Case 2, with a large encephalocele and a 5-year history of refractory seizures, surgical disconnection of the temporal pole successfully abolished seizures without any need for encephalocele repair. These two cases support the view that the epileptogenic area is confined to within the temporal pole for spontaneous temporal pole encephalocele. Temporopolar disconnection represents one surgical option for this entity that achieves seizure cessation without requiring extra repair procedures. Copyright © 2015 Elsevier Inc. All rights reserved.

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

the specific organelle that mesoporous silica nanoparticles could approach via the identification of harvested proteins from exocytosis process. Based on the study of endo- and exocytosis behavior of mesoporous silica nanoparticle materials, we can design smarter drug delivery vehicles for cancer therapy that can be effectively controlled. The destination, uptake efficiency and the cellular distribution of mesoporous silica nanoparticle materials can be programmable. As a result, release mechanism and release rate of drug delivery systems can be a well-controlled process. The deep investigation of an endo- and exocytosis study of mesoporous silica nanoparticle materials promotes the development of drug delivery applications.

In Situ Poling and Imidization of Amorphous Piezoelectric Polyimides

Science.gov (United States)

Park, Cheol; Ounaies, Zoubeida; Wise, Kristopher E.; Harrison, Joycelyn S.; Bushnell, Dennis M. (Technical Monitor)

2002-01-01

An amorphous piezoelectric polyimide containing polar functional groups has been developed using a combination of experimental and molecular modeling for potential use in high temperature applications. This amorphous polyimide, (Beta-CN)APB/ODPA, has exhibited good thermal stability and piezoelectric response at temperatures up to 150C. Density functional calculations predicted that a partially cured amic acid (open imide ring) possesses a dipole moment four times larger than the fully imidized closed ring. In situ poling and imidization of the partially cured (Beta-CN)APB/ODPA, was studied in an attempt to maximize the degree of dipolar orientation and the resultant piezoelectric response. A positive corona poling was used to minimize localized arcing during poling and to allow use of higher poling fields without dielectric breakdown. The dielectric relaxation strength, remanent polarization, and piezoelectric response were evaluated as a function of the poling profile. The partially cured, corona poled polymers exhibited higher dielectric relaxation strength (delta varepsilon), remanent polarization (Pr) and piezoelectric strain coefficient (d33) than the fully cured, conventionally poled ones.

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.

Patchy micelles based on coassembly of block copolymer chains and block copolymer brushes on silica particles.

Science.gov (United States)

Zhu, Shuzhe; Li, Zhan-Wei; Zhao, Hanying

2015-04-14

Patchy particles are a type of colloidal particles with one or more well-defined patches on the surfaces. The patchy particles with multiple compositions and functionalities have found wide applications from the fundamental studies to practical uses. In this research patchy micelles with thiol groups in the patches were prepared based on coassembly of free block copolymer chains and block copolymer brushes on silica particles. Thiol-terminated and cyanoisopropyl-capped polystyrene-block-poly(N-isopropylacrylamide) block copolymers (PS-b-PNIPAM-SH and PS-b-PNIPAM-CIP) were synthesized by reversible addition-fragmentation chain transfer polymerization and chemical modifications. Pyridyl disulfide-functionalized silica particles (SiO2-SS-Py) were prepared by four-step surface chemical reactions. PS-b-PNIPAM brushes on silica particles were prepared by thiol-disulfide exchange reaction between PS-b-PNIPAM-SH and SiO2-SS-Py. Surface micelles on silica particles were prepared by coassembly of PS-b-PNIPAM-CIP and block copolymer brushes. Upon cleavage of the surface micelles from silica particles, patchy micelles with thiol groups in the patches were obtained. Dynamic light scattering, transmission electron microscopy, and zeta-potential measurements demonstrate the preparation of patchy micelles. Gold nanoparticles can be anchored onto the patchy micelles through S-Au bonds, and asymmetric hybrid structures are formed. The thiol groups can be oxidized to disulfides, which results in directional assembly of the patchy micelles. The self-assembly behavior of the patchy micelles was studied experimentally and by computer simulation.

Carbon dots based dual-emission silica nanoparticles as ratiometric fluorescent probe for nitrite determination in food samples.

Science.gov (United States)

Xiang, Guoqiang; Wang, Yule; Zhang, Heng; Fan, Huanhuan; Fan, Lu; He, Lijun; Jiang, Xiuming; Zhao, Wenjie

2018-09-15

In this work, a simple and effective strategy for designing a ratiometric fluorescent nanosensor was described. A carbon dots (CDs) based dual-emission nanosensor for nitrite was prepared by coating the CDs on to dye-doped silica nanoparticles. Dual-emission silica nanoparticles fluorescence was quenched in sulfuric acid using potassium bromate (KBrO 3 ). The nitrite present catalyzed the KBrO 3 oxidation, resulting in ratiometric fluorescence response of the dual-emission silica nanoparticles. Several important parameters affecting the performance of the nanosensor were investigated. Under optimized conditions, the limit of detection was 1.0 ng mL -1 and the linear range 10-160 ng mL -1 . Furthermore, the sensor was suitable for nitrite determination in different food samples. Copyright © 2018 Elsevier Ltd. All rights reserved.

Biomechanical characteristics and speed adaptation during kick double poling on roller skis in elite cross-country skiers.

Science.gov (United States)

Göpfert, Caroline; Holmberg, Hans-Christer; Stöggl, Thomas; Müller, Erich; Lindinger, Stefan Josef

2013-06-01

Recent developments in cross-country ski racing should promote the use of kick double poling. This technique, however, has not been the focus in athletes' training and has barely been investigated. The aims of the present study were to develop a function-based phase definition and to analyse speed adaptation mechanisms for kick double poling in elite cross-country skiers. Joint kinematics and pole/plantar forces were recorded in 10 athletes while performing kick double poling at three submaximal roller skiing speeds. A speed increase was associated with increases in cycle length and rate, while absolute poling and leg push-off durations shortened. Despite maintained impulses of force, the peak and average pole/leg forces increased. During double poling and leg push-off, ranges of motion of elbow flexion and extension increased (p push-off showed high variability among elite skiers, thus illustrating important aspects for technique training.

A poling study on lead zirconate titanate composition

International Nuclear Information System (INIS)

Bryant, P.J.

1992-01-01

Ceramics produced by the conventional mixed oxide route are dual phased. Because the titania and zirconia are not perfectly homogenized, some parts of the ceramic are more tetragonal (titanium rich) and other parts more rhombohedral (zirconium rich). This inhomogeneity means that some domains can be more easily poled than others. Lastly, the density and porosity can affect the poling process if the flaw density becomes such that the breakdown voltage is exceeded by the required poling voltage. The phase boundary determined by most dielectric and piezoelectric measurements is significantly removed from the 44% titanium content determined by neutron diffraction. The indicators that are most consistent with this value are the minimum in the poling efficiency curve and the shape of the dissipative factor curve. The reason for the discrepancy appears to be related to the broad coexistence region of the two phases and the differing poling efficiencies of each phase. It has been established that different poling temperature profiles can substantially modify the observed properties. Such behaviour is again related to the inhomogeneity of the ceramic and the presence of the two phases. 4 refs., 5 figs

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

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.

All-Pole Recursive Digital Filters Design Based on Ultraspherical Polynomials

OpenAIRE

N. Stojanovic; N. Stamenkovic; V. Stojanovic

2014-01-01

A simple method for approximation of all-pole recursive digital filters, directly in digital domain, is described. Transfer function of these filters, referred to as Ultraspherical filters, is controlled by order of the Ultraspherical polynomial, nu. Parameter nu, restricted to be a nonnegative real number (nu ≥ 0), controls ripple peaks in the passband of the magnitude response and enables a trade-off between the passband loss and the group delay response of the resulting filter. Chebyshev f...

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)

Tent-Poles of the Bestseller

DEFF Research Database (Denmark)

Jensen, Thessa; Vistisen, Peter

2013-01-01

This article proposes a framework for understanding and analysing how the passive audience of a media event turns into active stakeholders. The starting point is the cross-media content quadrant (Jensen and Vistisen, 2012), which shows how the producer’s control is distributed on social media...... platforms, while storytelling evolves around a tent-pole, for example, a bestseller or blockbuster. To further explain how the audience engages, a three-step rhetoric model largely based on Bitzer (1998) and Tolkien (1971) is developed and explained....

Self-Poling of BiFeO3 Thick Films.

Science.gov (United States)

Khomyakova, Evgeniya; Sadl, Matej; Ursic, Hana; Daniels, John; Malic, Barbara; Bencan, Andreja; Damjanovic, Dragan; Rojac, Tadej

2016-08-03

Bismuth ferrite (BiFeO3) is difficult to pole because of the combination of its high coercive field and high electrical conductivity. This problem is particularly pronounced in thick films. The poling, however, must be performed to achieve a large macroscopic piezoelectric response. This study presents evidence of a prominent and reproducible self-poling effect in few-tens-of-micrometer-thick BiFeO3 films. Direct and converse piezoelectric measurements confirmed that the as-sintered BiFeO3 thick films yield d33 values of up to ∼20 pC/N. It was observed that a significant self-poling effect only appears in cases when the films are heated and cooled through the ferroelectric-paraelectric phase transition (Curie temperature TC ∼ 820 °C). These self-poled films exhibit a microstructure with randomly oriented columnar grains. The presence of a compressive strain gradient across the film thickness cooled from above the TC was experimentally confirmed and is suggested to be responsible for the self-poling effect. Finally, the macroscopic d33 response of the self-poled BiFeO3 film was characterized as a function of the driving-field frequency and amplitude.

Temperature effect on the physico-chemical properties of silica based bio-hybrid composite for uranium uptake

International Nuclear Information System (INIS)

Mishra, Archana; Melo, Jose Savio

2013-01-01

In the present work, silica based bio-hybrid composite has been prepared using Streptococcus lactis cells and silica nanoparticles through one step single process of spray drying. Bio-hybrids have many desired characteristics, and are thus used in a wide range of applications for example environmental cleanup which is of increasing importance. Thermogravimetric and thermodynamic analysis have been employed to understand the binding of uranium to the synthesized bio-hybrid material. Analysis of the thermodynamic parameters (ΔG 0 , ΔS 0 and ΔH 0 ) provides information regarding the inherent energy and feasibility of the sorption process. (author)

Shock wave lithotripsy outcomes for lower pole and non-lower pole stones from a university teaching hospital: Parallel group comparison during the same time period

Science.gov (United States)

Geraghty, Robert; Burr, Jacob; Simmonds, Nick; Somani, Bhaskar K.

2015-01-01

Introduction: Shock wave lithotripsy (SWL) is a treatment option for all locations of renal and ureteric stones. We compared the results of SWL for lower pole renal stones with all other non-lower pole renal and ureteric stones during the same time period. Material and Methods: All SWL procedures were carried out as day case procedures by a mobile lithotripter from January 2012 to August 2013. The follow-up imaging was a combination of KUB X-ray or USS. Following SWL treatment, the stone free rate (SFR) was defined as ≤3 mm fragments. Results: A total of 148 patients with a mean age of 62 years underwent 201 procedures. Of the 201 procedures, 93 (46%) were for lower pole stones. The non-lower pole stones included upper pole (n = 36), mid pole (n = 40), renal pelvis (n = 10), PUJ (n = 8), mid ureter (n = 3), upper ureter (n = 5) and a combination of upper, middle and/or lower pole (n = 6). The mean stone size for lower pole stones (7.4 mm; range: 4-16 mm) was slightly smaller than non-lower pole stones (8 mm; range: 4-17 mm). The stone fragmentation was successful in 124 (62%) of patients. However, the SFR was statistically significantly better (P = 0.023) for non-lower pole stones 43 (40%) compared to lower pole stones 23 (25%). There were 9 (4%) minor complications and this was not significantly different in the two groups. Conclusions: Although SWL achieves a moderately high stone fragmentation rate with a low complication rate, the SFR is variable depending on the location of stone and the definition of SFR, with lower pole stones fairing significantly worse than stones in all other locations. PMID:25657543

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.

Effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete

Science.gov (United States)

Memon, Fareed Ahmed; Nuruddin, Muhd Fadhil; Shafiq, Nasir

2013-02-01

The effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete (SCGC) was investigated in this paper. The work focused on the concrete mixes with a fixed water-to-geopolymer solid (W/Gs) ratio of 0.33 by mass and a constant total binder content of 400 kg/m3. The mass fractions of silica fume that replaced fly ash in this research were 0wt%, 5wt%, 10wt%, and 15wt%. The workability-related fresh properties of SCGC were assessed through slump flow, V-funnel, and L-box test methods. Hardened concrete tests were limited to compressive, splitting tensile and flexural strengths, all of which were measured at the age of 1, 7, and 28 d after 48-h oven curing. The results indicate that the addition of silica fume as a partial replacement of fly ash results in the loss of workability; nevertheless, the mechanical properties of hardened SCGC are significantly improved by incorporating silica fume, especially up to 10wt%. Applying this percentage of silica fume results in 4.3% reduction in the slump flow; however, it increases the compressive strength by 6.9%, tensile strength by 12.8% and flexural strength by 11.5%.

PNRA. South-pole directory listing

OpenAIRE

Biagioni, Stefania; Carlesi, Carlo; Carpen?, Andrea; Ramorino, Chiara; Rossi, Lucio

1992-01-01

In the following all DATA-SET descriptors (DSD) contained in the "South-Pole Directory" (vers. 1992) are listed. The "South-Pole Directory" was a joint project between ENEA and CNR. The IEI/CNR took care of the data digitalization and check and of the english translation (where necessary). The ARF/CNR and the Progetto Antartide/ENEA joined the IEI/CNR in defining the acronyms of the Sensor_Names and of the Source_Names, together with the short and long names for the Data_Centers. Finally, the...

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)

Silica-Based and Borate-Based, Titania-Containing Bioactive Coatings Characterization: Critical Strain Energy Release Rate, Residual Stresses, Hardness, and Thermal Expansion

Directory of Open Access Journals (Sweden)

Omar Rodriguez

2016-12-01

Full Text Available Silica-based and borate-based glass series, with increasing amounts of TiO2 incorporated, are characterized in terms of their mechanical properties relevant to their use as metallic coating materials. It is observed that borate-based glasses exhibit CTE (Coefficient of Thermal Expansion closer to the substrate’s (Ti6Al4V CTE, translating into higher mode I critical strain energy release rates of glasses and compressive residual stresses and strains at the coating/substrate interface, outperforming the silica-based glasses counterparts. An increase in the content of TiO2 in the glasses results in an increase in the mode I critical strain energy release rate for both the bulk glass and for the coating/substrate system, proving that the addition of TiO2 to the glass structure enhances its toughness, while decreasing its bulk hardness. Borate-based glass BRT3, with 15 mol % TiO2 incorporated, exhibits superior properties overall compared to the other proposed glasses in this work, as well as 45S5 Bioglass® and Pyrex.

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.

Pressure transmitter surveillance: the dominant real pole case

International Nuclear Information System (INIS)

Blazquez, J.; Ballestrin, J.

1995-01-01

There are about 500 pressure transmitters in a nuclear power plant. Due to Safety requirements, some of them must be specially surveilled. Sensor response time to a pressure ramp is the usual quantity to be measured. Response time, τ r , reflects the dynamics of the sensor and the sensing line. A real pole is due to the inner sensor structure, but the complex pole stands for the sensing line too. The real pole usually is the dominant in most sensors. On line monitoring noise analysis regards simultaneously both, the sensor and the sensing line, but the noise signal contains not only the sensor poles, but many others coming from the plant, so must be conditioned previously and the determination of τ r is not free of systematic errors. That is the price to be paid for non disturbing the plant. When the real pole is dominant, the sensing line contribution is negligible, so the on line noise monitoring methods are supported by the laboratory experiments and the real pole border in the PSD is properly identified. The mean square frequency results proportional to τ r -1 , so manual techniques are designed for response time surveillance made by non noise plant's maintenance technicians. (author)

A Short Overview on the Biomedical Applications of Silica, Alumina and Calcium Phosphate-based Nanostructured Materials.

Science.gov (United States)

Ellahioui, Younes; Prashar, Sanjiv; Gómez-Ruiz, Santiago

2016-01-01

This article reviews the use of silica, alumina and calcium phosphate-based nanostructured materials with biomedical applications. A short introduction on the use of the materials in Science, Nanotechnology and Health is included followed by a revision of each of the selected materials. A description of the principal synthetic methods used in the preparation of the materials in nanostructured form is included. The most widely used applications in biomedicine are reviewed including, for example drug-delivery, bone regeneration, imaging, sensoring amongst others. Finally, a short description of the toxicity and cytotoxicity associated with each of the materials of this revision is presented. This short literature revision serves to demonstrate the very promising future ahead of nanosystems based on silica, alumina and calcium phosphate for biological and biomedical applications.

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∘.

Silica-based PLC with heterogeneously-integrated PDs for one-chip DP-QPSK receiver.

Science.gov (United States)

Kurata, Yu; Nasu, Yusuke; Tamura, Munehisa; Kasahara, Ryoichi; Aozasa, Shinichi; Mizuno, Takayuki; Yokoyama, Haruki; Tsunashima, Satoshi; Muramoto, Yoshifumi

2012-12-10

To realize a DP-QPSK receiver PLC, we heterogeneously integrated eight high-speed PDs on a silica-based PLC platform with a PBS, 90-degree optical hybrids and a VOA. The use of a 2.5%-Δ waveguide reduced the receiver PLC size to 11 mm x 11 mm. We successfully demonstrated 32 Gbaud DP-QPSK signal demodulation with the receiver PLC.

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.

Jupiter's interior and deep atmosphere: The initial pole-to-pole passes with the Juno spacecraft

DEFF Research Database (Denmark)

Bolton, S. J.; Adriani, Alberto; Adumitroaie, V.

2017-01-01

On 27 August 2016, the Juno spacecraft acquired science observations of Jupiter, passing less than 5000 kilometers above the equatorial cloud tops. Images of Jupiter's poles show a chaotic scene, unlike Saturn's poles. Microwave sounding reveals weather features at pressures deeper than 100 bars,...... of magnitude more precise. This has implications for the distribution of heavy elements in the interior, including the existence and mass of Jupiter's core. The observed magnetic field exhibits smaller spatial variations than expected, indicative of a rich harmonic content....

SOL-GEL SILICA-BASED Ag–Ca–P COATINGS WITH AGRESSIVE PRETREATMENT OF TITANIUM SUBSTRATE

Directory of Open Access Journals (Sweden)

ELENA BORSHCHEVA

2011-12-01

Full Text Available The aim of the experiment was the obtaining of thin silica coatings on titanium by sol-gel method, using mechanical (SiC - paper No.180 and chemical (leaching in HF pretreatments of the titanium substrates. The solutions were based on TEOS. For the sol-gel dipping process 4 different solutions were prepared: silica, silica with AgNO3 and silica + AgNO3 with brushite (CaHPO4·2H2O or monetite (CaHPO4 powders. The solutions were aged for 7 and 14 days at laboratory temperature. After sol-gel dip-coating process the samples were dried and fired. The adhesion of fired coatings was measured by tape test according to ASTM procedure and the bioactivity of the coatings was tested using in vitro test. The surfaces of the samples after firing, tape test and in vitro test were observed with the optical and electron microscopes. The firing results showed that silica-silver coatings did not change, brushite sol-gel coatings have cracked and the monetite sol-gel coatings have cracked also, but less than brushite ones. In spite of coating´s crackings, the square’s frames made on the surfaces were without any breakdowns after tape tests and the adhesion of all coatings was very good, classified by the highest grade 5. The results of in vitro tests showed that all coatings interacted with simulated body fluid (SBF. After exposition in SBF the new layer formed on substrates. In case of 7 days aged coatings containing brushite the new layer was uniform and compact. In case of 7 days aged coatings containing monetite the new layer was formed by crystals aggregated tightly together. The monetite and brushite coatings prepared from 14 days aged sol were the same as previous ones, but they were thicker. X-ray analyses after in vitro test confirmed dellaite, titanate and hydroxyapatite phases.

Particles as S-matrix poles: hadron democracy

International Nuclear Information System (INIS)

Chew, G.F.

1989-01-01

The connection between two theoretical ideas of the 1950s is traced in this article, namely that hadrons are nonfundamental, ''composite'' particles and that all physically observable particles correspond to singularities of an analytic scattering matrix. The S matrix theory developed by Werner Heisenberg in the early forties now incorporated the concepts of unitarity, invariance, analyticity and causality. The meson-exchange force meant that poles must be present in nucleon-nuclear and pion-nucleon scattering as predicted by dispersion relations. Experimental work in accessible regions determined pole residues. Pole residue became associated with force strength and pole position with particle mass. In 1959, the author discovered the so-called ''bootstrap'' theory the rho meson as a force generates a rho particle. By the end of the 1950s it was clear that all hadrons had equal status, each being bound states of other hadrons, sustained by hadron exchange forces and that hadrons are self-generated by an S-matrix bootstrap mechanism that determines all their properties. (UK)

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.

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)

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).

Synthesis of Polyurethane/Silica Modified Epoxy Polymer Based on 1,3-Propanediol for Coating Application

Directory of Open Access Journals (Sweden)

Lutviasari Nuraini

2017-11-01

Full Text Available Studies on the synthesis of polyurethane/silica modified epoxy polymer using 1,3-propanediol has been conducted. Synthesis of polymers made by reaction of tolonate and 1,3-propanediol (ratio NCO/OH=2.5 as the building blocks of polyurethane with diglycidyl ether bisphenol A (DGEBA epoxy and catalyst dibutyltin dilaurate (DBTL.The total weight of the polyurethane used was 20% (w/w of the total epoxy. Based on Fourier Transform Infrared (FTIR and 1H-Nuclear Magnetic Resonance (1H-NMR spectra indicated the existence of a new bond that is formed from the reaction of isocyanate group and hydroxyl group, where the hydroxyl groups derived from epoxy and 1,3-propanediol. The addition of silica (5, 10, and 15% w/w to epoxy into the epoxy-modified polyurethane has been carried out through sol-gel reaction of tetraethyl orthosilicate (TEOS. The isocyanate conversion rate for the addition of silica 5, 10, and 15% are 95.69; 100, and 100%, respectively. The morphology and element identification by Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis (SEM/EDX, showed that Si element has been successfully added in the polymer. From the tensile strength and elongation analysis, also thermal stability analysis using Thermal Gravimetric Analyzer (TGA, the increase of silica amount into the polyurethane modified epoxy did not significantly affect to thermal properties, but decrease the tensile strength of the polymer.

The practice of pole dance as a leisure activity in Denmark

DEFF Research Database (Denmark)

Jensen, Andorra Lynn

2015-01-01

The aim of this study is to explore the how pole dance is practiced as a form of leisure activity in Denmark. The methodical approach is qualitative and inspired by ethnography. I have conducted a field study where I have observed and participated in the pole dance culture in Copenhagen from May ...... addresses the difference between a focus on dance and a focus on tricks in pole dancing as well as it examines the different opinions pole studio owners have concerning ‘sexiness’ in pole dance and how this affects the way pole dance is practiced....

Condition Assessment of Foundation Piles and Utility Poles Based on Guided Wave Propagation Using a Network of Tactile Transducers and Support Vector Machines

Directory of Open Access Journals (Sweden)

Ulrike Dackermann

2017-12-01

Full Text Available This paper presents a novel non-destructive testing and health monitoring system using a network of tactile transducers and accelerometers for the condition assessment and damage classification of foundation piles and utility poles. While in traditional pile integrity testing an impact hammer with broadband frequency excitation is typically used, the proposed testing system utilizes an innovative excitation system based on a network of tactile transducers to induce controlled narrow-band frequency stress waves. Thereby, the simultaneous excitation of multiple stress wave types and modes is avoided (or at least reduced, and targeted wave forms can be generated. The new testing system enables the testing and monitoring of foundation piles and utility poles where the top is inaccessible, making the new testing system suitable, for example, for the condition assessment of pile structures with obstructed heads and of poles with live wires. For system validation, the new system was experimentally tested on nine timber and concrete poles that were inflicted with several types of damage. The tactile transducers were excited with continuous sine wave signals of 1 kHz frequency. Support vector machines were employed together with advanced signal processing algorithms to distinguish recorded stress wave signals from pole structures with different types of damage. The results show that using fast Fourier transform signals, combined with principal component analysis as the input feature vector for support vector machine (SVM classifiers with different kernel functions, can achieve damage classification with accuracies of 92.5% ± 7.5%.

A decomposable silica-based antibacterial coating for percutaneous titanium implant

Directory of Open Access Journals (Sweden)

Wang J

2017-01-01

Full Text Available Jia Wang,1,* Guofeng Wu,2,* Xiangwei Liu,3,* Guanyang Sun,1 Dehua Li,3 Hongbo Wei3 1State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi’an, 2Department of Prosthodontics, Nanjing Stomatological Hospital, Medical School of Nanjing University, Nanjing, 3State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Diseases & Shaanxi Engineering Research Center for Dental Materials and Advanced Manufacture, Department of Oral Implants, School of Stomatology, The Fourth Military Medical University, Xi’an, People’s Republic of China *These authors contributed equally to this work Abstract: Although percutaneous titanium implants have become one of the best choices as retainers in the facial defects, peri-implantitis still occurs at a significant rate. This unwanted complication occurs due to adhesion of bacteria and subsequent biofilm formation. To solve this problem, we have developed a novel antibiotic nanodelivery system based on self-decomposable silica nanoparticles. In this study, silica-gentamycin (SG nanoparticles were successfully fabricated using an innovative one-pot solution. The nanoparticles were incorporated within a gelatin matrix and cross-linked on microarc-oxidized titanium. To characterize the SG nanoparticles, their particle size, zeta potential, surface morphology, in vitro drug release, and decomposition process were sequentially evaluated. The antibacterial properties against the gram-positive Staphylococcus aureus, including bacterial viability, antibacterial rate, and bacteria morphology, were analyzed using SG-loaded titanium specimens. Any possible influence of released gentamycin on the viability of human fibroblasts, which are the main component of soft tissues, was investigated. SG nanoparticles from the

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

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.

Pole orientation of 16 Psyche by two independent methods

Science.gov (United States)

Tedesco, E. F.; Taylor, R. C.

1985-01-01

Nineteen new lightcurves of 16 Psyche are presented along with a pole orientation derived using two independent methods, namely, photometric astrometry and magnitude-amplitude-shape-aspect. The pole orientations found using these two methods agree to within 4 deg. The results from applying photometric astrometry were prograde rotation, a sidereal period of 0.1748143 days + or - 0.0000003 days, and a pole at longitude 223 deg and latitude +37 deg, with an uncertainty of 10 deg, and, from applying magnitude-amplitude-shape-aspect a pole at 220 + or - 1 deg, +40 + or - 4 deg, and a modeled triaxial ellipsoid shape (a greater than b greater than c) and a/b = 1.33 + or - 0.07. The discrepancy between the high-pole latitude found here and the low latitudes reported by Lupishko et al. (1982) and Zhou and Yang (1982) is discussed.

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.

Current superimposition variable flux reluctance motor with 8 salient poles

Science.gov (United States)

Takahara, Kazuaki; Hirata, Katsuhiro; Niguchi, Noboru; Kohara, Akira

2017-12-01

We propose a current superimposition variable flux reluctance motor for a traction motor of electric vehicles and hybrid electric vehicles, which consists of 10 salient poles in the rotor and 12 slots in the stator. However, iron losses of this motor in high rotation speed ranges is large because the number of salient poles is large. In this paper, we propose a current superimposition variable flux reluctance motor that consists of 8 salient poles and 12 slots. The characteristics of the 10-pole-12-slot and 8-pole-12-slot current superimposition variable flux reluctance motors are compared using finite element analysis under vector control.

Current superimposition variable flux reluctance motor with 8 salient poles

Directory of Open Access Journals (Sweden)

Takahara Kazuaki

2017-12-01

Full Text Available We propose a current superimposition variable flux reluctance motor for a traction motor of electric vehicles and hybrid electric vehicles, which consists of 10 salient poles in the rotor and 12 slots in the stator. However, iron losses of this motor in high rotation speed ranges is large because the number of salient poles is large. In this paper, we propose a current superimposition variable flux reluctance motor that consists of 8 salient poles and 12 slots. The characteristics of the 10-pole-12-slot and 8-pole-12-slot current superimposition variable flux reluctance motors are compared using finite element analysis under vector control.

Recent progress of ordered mesoporous silica-supported chiral metallic catalysts

Directory of Open Access Journals (Sweden)

LIU Rui

2013-02-01

Full Text Available Recently,ordered silica-based mesoporous chiral organometallics-functionalized heterogeneous catalysts have attracted extensive research interest due to their excellent properties,such as easy preparation,high activity and convenient recycle.This review mainly summarizesthe generally prepared strategy and the silica-based organometallics-functionalized heterogeneous catalysts reported in the literatures.

Development of a multi-pole magnetorheological brake

International Nuclear Information System (INIS)

Shiao, Yaojung; Nguyen, Quang-Anh

2013-01-01

This paper presents a new approach in the design and optimization of a novel multi-pole magnetorheological (MR) brake that employs magnetic flux more effectively on the surface of the rotor. MR brakes with conventional single ring-type electromagnetic poles have reached the limits of torque enhancement. One major reason is the limitation of the magnetic field strength within the active area of the MR fluid due to the geometric constraints of the coil. The multi-pole MR brake design features multiple electromagnetic poles surrounded by several coils. As a result, the active chaining areas for the MR fluid are greatly increased, and significant brake torque improvement is achieved. The coil structure, as a part of the stator, becomes flexible and customizable in terms of space usage for the winding and bobbin design. In addition, this brake offers extra options in its dimensions for torque enhancement because either the radial or the axial dimensions of the rotor can be increased. Magnetic circuit analysis was conducted to analyze the effects of the design parameters on the field torque. After that, simulations were done to find the optimal design under all major geometric constraints with a given power supply. The results show that the multi-pole MR brake provides a considerable braking torque increase while maintaining a compact and solid design. This is confirmation of its feasibility in actual braking applications. (paper)

Effectiveness of silica based sol-gel microencapsulation method for odorants and flavors leading to sustainable environment.

Science.gov (United States)

Ashraf, Muhammad Aqeel; Khan, Aysha Masood; Ahmad, Mushtaq; Sarfraz, Maliha

2015-01-01

Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits.

Study of the National Science Foundation's South Pole Station as an analogous data base for the logistical support of a Moon laboratory

Science.gov (United States)

Hickam, H. H., Jr.

1993-01-01

The day will come when the United States will want to return to the Earth's Moon. When that occurs, NASA may look to the Apollo program for technical and inspirational guidance. The Apollo program, however, was designed to be an end to itself--the landing of a man on the Moon and his return safely within the decade of the 1960's. When that was accomplished, the program folded because it was not self-sustaining. The next time we return to the Moon, we should base our planning on a program that is designed to be a sustained effort for an indefinite period. It is the thrust of this report that the South Pole Station of the National Science Foundation can be used to develop analogs for the construction, funding, and logistical support of a lunar base. Other analogs include transportation and national efforts versus international cooperation. A recommended lunar base using the South Pole Station as inspiration is provided, as well as details concerning economical construction of the base over a 22-year period.

Fatigue failure and cracking in high mast poles.

Science.gov (United States)

2012-03-01

This report presents the findings of a comprehensive research project to investigate the fatigue : cracking and failure of galvanized high mast illumination poles (HMIP). Ultrasonic inspection of : poles throughout the state has revealed the presence...

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

Optically transparent, superhydrophobic methyltrimethoxysilane based silica coatings without silylating reagent

International Nuclear Information System (INIS)

Kavale, Mahendra S.; Mahadik, D.B.; Parale, V.G.; Wagh, P.B.; Gupta, Satish C.; Rao, A.Venkateswara; Barshilia, Harish C.

2011-01-01

The superhydrophobic surfaces have drawn lot of interest, in both academic and industries because of optically transparent, adherent and self-cleaning behavior. Surface chemical composition and morphology plays an important role in determining the superhydrophobic nature of coating surface. Such concert of non-wettability can be achieved, using surface modifying reagents or co-precursor method in sol-gel process. Attempts have been made to increase the hydrophobicity and optical transparency of methyltrimethoxysilane (MTMS) based silica coatings using polymethylmethacrylate (PMMA) instead of formal routes like surface modification using silylating reagents. The optically transparent, superhydrophobic uniform coatings were obtained by simple dip coating method. The molar ratio of MTMS:MeOH:H 2 O was kept constant at 1:5.63:1.58, respectively with 0.5 M NH 4 F as a catalyst and the weight percent of PMMA varied from 1 to 8. The hydrophobicity of silica coatings was analyzed by FTIR and contact angle measurements. These substrates exhibited 91% optical transmittance as compared to glass and water drop contact angle as high as 171 ± 1 deg. The effect of humidity on hydrophobic nature of coating has been studied by exposing these films at relative humidity of 90% at constant temperature of 30 deg. C for a period of 45 days. The micro-structural studies carried out by transmission electron microscopy (TEM).

Efficient CO2 sorbents based on silica foam with ultra-large mesopores

KAUST Repository

Qi, Genggeng; Fu, Liling; Choi, Brian Hyun; Giannelis, Emmanuel P.

2012-01-01

A series of high-capacity, amine impregnated sorbents based on a cost-effective silica foam with ultra-large mesopores is reported. The sorbents exhibit fast CO2 capture kinetics, high adsorption capacity (of up to 5.8 mmol g^-1 under 1 atm of dry CO2), as well as good stability over multiple adsorption-desorption cycles. A simple theoretical analysis is provided relating the support structure to sorbent performance. © 2012 The Royal Society of Chemistry.

Biodiesel production by using lipase immobilized onto novel silica-based hybrid foams

Energy Technology Data Exchange (ETDEWEB)

Brun, Nicolas [Centre de Recherche Paul Pascal, Pessac (France); Institut des Sciences Moleculaires, Talence (France); Garcia, Annick Babeau; Oestreicher, Victor; Durand, Fabien; Backov, Renal [Centre de Recherche Paul Pascal, Pessac (France); Deleuze, Herve [Institut des Sciences Moleculaires, Talence (France); Laurent, Guillaume; Sanchez, Clement [Laboratoire de Chimie de la Matiere Condensee, Paris (France)

2010-07-01

The covalent immobilization of crude lipases within silica-based macroporous frameworks have been performed by combining sol-gel process, concentrated direct emulsion, lyotropic mesophase and post-synthesis functionalizations. The assynthesized open cell hybrid monoliths exhibit high macroscopic porosity, around 90%, providing interconnected scaffold while reducing the diffusion low kinetic issue. The entrapment of enzymes in such foams deals with a high stability over esterification of fatty acids, hydrolysis of triglycerides (not shown herein) and biodiesel production by transesterification. (orig.)

CURRENT STATUS OF THE POLE-AND-LINE FISHERY IN EASTERN PART OF INDONESIA

Directory of Open Access Journals (Sweden)

Agustinus Anung Widodo

2016-12-01

Full Text Available The promotion of pole-and-line fishery for a selective gear operating in the Indonesian tuna management area is considered as the proper policy in response to the increasing market demand with tuna eco-labeled. Appropriate information in addressing the current status of the pole-and-line fishery in Indonesia is an important step in order to support the promotion. Data used to describe the fishery were obtained through scientific port sampling program in collaboration between RCFMC and WCPFC in 2010 to 2014 and also scientific observer onboard program collaboration RCFMC and CRAC Co. Ltd. in 2013. The results show that presently the number of pole and line fleets was decreased significantly and remain about 232 fleetsin Sorong, Bitung and Kendari and Larantuka. The national annual total catch of pole-and line during 1980 – 2013 was recorded between 24,000 and 160,000 tons per year (average 98,117 tons per year. This value is estimated to contribute about 20% of Indonesia annual total catch of tuna in FMAs713-717. The pole-andline catch rates based at Bitung, Kendari and Sorong were fluctuated in each year with the range respective between 8.79 and 17.93 tons/trip/vessel, 4.78 and 5.36 ton/trip/vessel and about 7,99 ton ton/trip/vessel. Pole-and-line fishery operated in Indonesian FMAs 713-717 is considered as selective fishery, with > 80 % catches of skipjack in matured stage. The tuna-live bait fish ratio in Indonesian pole-and-line was 4.41 :1, then an improvement of live bait ratio as well as its management is required.

A Direct Algorithm for Pole Placement by State-derivative Feedback for Single-input Linear Systems

Directory of Open Access Journals (Sweden)

Taha H. S. Abdelaziz

2003-01-01

Full Text Available This paper deals with the direct solution of the pole placement problem for single-input linear systems using state-derivative feedback. This pole placement problem is always solvable for any controllable systems if all eigenvalues of the original system are nonzero. Then any arbitrary closed-loop poles can be placed in order to achieve the desired system performance. The solving procedure results in a formula similar to the Ackermann formula. Its derivation is based on the transformation of a linear single-input system into Frobenius canonical form by a special coordinate transformation, then solving the pole placement problem by state derivative feedback. Finally the solution is extended also for single-input time-varying control systems. The simulation results are included to show the effectiveness of the proposed approach.

Generalized pole inflation: Hilltop, natural, and chaotic inflationary attractors

Energy Technology Data Exchange (ETDEWEB)

Terada, Takahiro, E-mail: takahiro.terada@apctp.org [Department of Physics, The University of Tokyo, Tokyo 113-0033 (Japan); Asia Pacific Center for Theoretical Physics, Pohang 37673 (Korea, Republic of)

2016-09-10

A reformulation of inflationary model analyses appeared recently, in which inflationary observables are determined by the structure of a pole in the inflaton kinetic term rather than the shape of the inflaton potential. We comprehensively study this framework with an arbitrary order of the pole taking into account possible additional poles in the kinetic term or in the potential. Depending on the setup, the canonical potential becomes the form of hilltop or plateau models, variants of natural inflation, power-law inflation, or monomial/polynomial chaotic inflation. We demonstrate attractor behaviors of these models and compute corrections from the additional poles to the inflationary observables.

Development of a field pole of 1 MW-class HTS motor

International Nuclear Information System (INIS)

Yuan, S; Kimura, Y; Miki, M; Felder, B; Tsuzuki, K; Izumi, M; Ida, T; Umemoto, K; Aizawa, K; Yokoyama, M

2010-01-01

We report a field-pole high-temperature superconductor (HTS) magnet designed for 1 MW-class motor for propulsion. The field pole is assembled to the rotor of the radial-type motor. Each field pole is composed of HTS-Bi2223 tape wound into coils which have been piled up as a double pancake coils. In the design concept of the motor, we employ field poles without iron core. We prepared the test field-pole coil, whose dimension is smaller than the designed one for 1 MW, and tested its performances after cooling under self-field and external magnetic field. We verified the operation with the minimum bend radius of the coils required in the motor design, while keeping an optimal current which is lower than the critical current of the field-pole coil. The test HTS field poles were successfully cooled down and operated under a magnetic field ranging up to 5 T. We report the results of the test field-pole coil and the manufacture of a practical racetrack coil with Bi2223 and discuss the adaptability to 1 MW-class motors.

Development of a field pole of 1 MW-class HTS motor

Science.gov (United States)

Yuan, S.; Kimura, Y.; Miki, M.; Felder, B.; Tsuzuki, K.; Ida, T.; Izumi, M.; Umemoto, K.; Aizawa, K.; Yokoyama, M.

2010-06-01

We report a field-pole high-temperature superconductor (HTS) magnet designed for 1 MW-class motor for propulsion. The field pole is assembled to the rotor of the radial-type motor. Each field pole is composed of HTS-Bi2223 tape wound into coils which have been piled up as a double pancake coils. In the design concept of the motor, we employ field poles without iron core. We prepared the test field-pole coil, whose dimension is smaller than the designed one for 1 MW, and tested its performances after cooling under self-field and external magnetic field. We verified the operation with the minimum bend radius of the coils required in the motor design, while keeping an optimal current which is lower than the critical current of the field-pole coil. The test HTS field poles were successfully cooled down and operated under a magnetic field ranging up to 5 T. We report the results of the test field-pole coil and the manufacture of a practical racetrack coil with Bi2223 and discuss the adaptability to 1 MW-class motors.

The effect of poling conditions on the performance of piezoelectric energy harvesters fabricated by wet chemistry

KAUST Repository

Fuentes-Fernandez, Erika Maria-Anai; Gnade, Bruce E; Quevedo-Ló pez, Manuel Angel; Shah, Pradeep; Alshareef, Husam N.

2015-01-01

The effect of poling conditions on the power output of piezoelectric energy harvesters using sol-gel based Pb(Zr0.53,Ti0.47)O3-Pb(Zn1/3,Nb2/3)O3 piezoelectric thin-films has been investigated. A strong correlation was established between the poling

Multiple pole in the electron--hydrogen-atom scattering amplitude

International Nuclear Information System (INIS)

Amusia, M.Y.; Kuchiev, M.Y.

1982-01-01

It is demonstrated that the amplitude for electron--hydrogen-atom forward scattering has the third-order pole at the point E = -13.6 eV, E being the energy of the incident electron. The coefficients which characterize the pole are calculated exactly. The invalidity of the Born approximation is proved. The contribution of the pole singularity to the dispersion relation for the scattering amplitude is discussed

The cos2φ azimuthal asymmetry of unpolarized dilepton production at the Z pole

International Nuclear Information System (INIS)

Lu Zhun; Schmidt, Ivan

2011-01-01

We calculate the Boer-Mulders effect contribution to the cos2φ azimuthal asymmetry of unpolarized dilepton production near the Z-pole. Based on the tree-level expression in the transverse momentum dependent factorization framework, we show that the corresponding asymmetry near the Z-pole is negative, which is opposite to the asymmetry in the low Q 2 region, dominated by the production via a virtual photon. We calculate the asymmetry generated by the Boer-Mulders effect near the Z-pole at the Relativistic Heavy Ion Collider (RHIC), with √(s)=500 GeV. We find that the magnitude of the asymmetry is several percent, and therefore it is measurable. The experimental confirmation of this sign change of the asymmetry from the low Q 2 region to the Z-pole provides direct evidence of the chiral-odd structure of quarks inside an unpolarized nucleon.

The polarization modulation and fabrication method of two dimensional silica photonic crystals based on UV nanoimprint lithography and hot imprint.

Science.gov (United States)

Guo, Shuai; Niu, Chunhui; Liang, Liang; Chai, Ke; Jia, Yaqing; Zhao, Fangyin; Li, Ya; Zou, Bingsuo; Liu, Ruibin

2016-10-04

Based on a silica sol-gel technique, highly-structurally ordered silica photonic structures were fabricated by UV lithography and hot manual nanoimprint efforts, which makes large-scale fabrication of silica photonic crystals easy and results in low-cost. These photonic structures show perfect periodicity, smooth and flat surfaces and consistent aspect ratios, which are checked by scanning electron microscopy (SEM) and atomic force microscopy (AFM). In addition, glass substrates with imprinted photonic nanostructures show good diffraction performance in both transmission and reflection mode. Furthermore, the reflection efficiency can be enhanced by 5 nm Au nanoparticle coating, which does not affect the original imprint structure. Also the refractive index and dielectric constant of the imprinted silica is close to that of the dielectric layer in nanodevices. In addition, the polarization characteristics of the reflected light can be modulated by stripe nanostructures through changing the incident light angle. The experimental findings match with theoretical results, making silica photonic nanostructures functional integration layers in many optical or optoelectronic devices, such as LED and microlasers to enhance the optical performance and modulate polarization properties in an economical and large-scale way.

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

Live imaging of spindle pole disorganization in docetaxel-treated multicolor cells

International Nuclear Information System (INIS)

Sakaushi, Shinji; Nishida, Kumi; Minamikawa, Harumi; Fukada, Takashi; Oka, Shigenori; Sugimoto, Kenji

2007-01-01

Treatment of cells with docetaxel at low concentrations induces aberrant bipolar spindles of which two centrosomes stay at only one pole, and also induces multipolar spindles. To gain insight into the relations between centrosome impairment and structural defects of the spindle, live-cell imaging was performed on a human MDA Auro/imp/H3 cell line in which centrosomes/mitotic spindles, nuclear membrane and chromatin were simultaneously visualized by fluorescent proteins. In the presence of docetaxel at IC 50 concentration, the centrosomes did not segregate, and multiple aster-like structures ectopically arose around the disappearing nuclear membrane. Those ectopic structures formed an acentrosomal pole opposing to the two-centrosomes-containing pole. In late metaphase, one pole often fragmented into multiple spindle poles, leading multipolar division. These results suggest that spindle pole fragility may be induced by centrosome impairment, and collapse of the pole may contribute to induction of aneuploid daughter cells

Transformer-assisted PWM zero-voltage switching pole inverter with high output bandwidth applied to linear motor drives

NARCIS (Netherlands)

Myrzik, J.M.A.; Duarte, J.L.; Haardt, de P.; Vissers, J.

2002-01-01

An application of the transformer-assisted PWM zero-voltage switching pole inverter (TRAP) is described in this paper. The TRAP is based on the auxiliary resonant commutated pole inverter (ARCP), but avoids its disadvantages. This paper describes the converter functionality and its applicability

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.

A comprehensive study of soft magnetic materials based on FeSi spheres and polymeric resin modified by silica nanorods

International Nuclear Information System (INIS)

Strečková, M.; Füzer, J.; Kobera, L.; Brus, J.; Fáberová, M.; Bureš, R.; Kollár, P.; Lauda, M.; Medvecký, Ĺ.; Girman, V.; Hadraba, H.; Bat'ková, M.; Bat'ko, I.

2014-01-01

A novel soft magnetic composite (SMC) based on spherical FeSi particles precisely covered by hybrid phenolic resin was designed. The hybrid resin including silica nano-rods chemically incorporated into the phenolic polymer matrix was prepared by the modified sol–gel method. A chemical bridge connecting silica nano-rods with the base polymeric net was verified by FTIR, 13 C and 29 Si NMR spectroscopy, whereas the shape and size of silica nano-rods were determined by TEM. It is shown that the modification of polymeric resin by silica nano-rods generally leads to the improved thermal and mechanical properties of the final samples. The hybrid resin serves as a perfect insulating coating deposited on FeSi particles and the core–shell particles can be further compacted by standard powder metallurgy methods in order to prepare final samples for mechanical, electric and magnetic testing. SEM images evidence negligible porosity, uniform distribution of the hybrid resin around FeSi particles, as well as, dimensional shape stability of the final samples after thermal treatment. The hardness, flexural strength and density of the final samples are comparable to the sintered SMCs, but they simultaneously exhibit much higher specific resistivity along with only slightly lower coercivity and permeability. - Highlights: • Soft magnetic composites are designed for electrotechnical applications. • Electroinsulating layer consists of phenolic resin modified with silica nano-rods. • NMR, FTIR and DSC analysis is used to characterize hybrid resin. • Spherical Fe–Si particles covered by hybrid resin form a core–shell composite. • Mechanical, electrical and magnetic properties are described in detail

Biomimetic Cationic Nanoparticles Based on Silica: Optimizing Bilayer Deposition from Lipid Films

Directory of Open Access Journals (Sweden)

Rodrigo T. Ribeiro

2017-10-01

Full Text Available The optimization of bilayer coverage on particles is important for a variety of biomedical applications, such as drug, vaccine, and genetic material delivery. This work aims at optimizing the deposition of cationic bilayers on silica over a range of experimental conditions for the intervening medium and two different assemblies for the cationic lipid, namely, lipid films or pre-formed lipid bilayer fragments. The lipid adsorption on silica in situ over a range of added lipid concentrations was determined from elemental analysis of carbon, hydrogen, and nitrogen and related to the colloidal stability, sizing, zeta potential, and polydispersity of the silica/lipid nanoparticles. Superior bilayer deposition took place from lipid films, whereas adsorption from pre-formed bilayer fragments yielded limiting adsorption below the levels expected for bilayer adsorption.

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.

Direct synthesis of acid-base bifunctionalized hexagonal mesoporous silica and its catalytic activity in cascade reactions.

Science.gov (United States)

Shang, Fanpeng; Sun, Jianrui; Wu, Shujie; Liu, Heng; Guan, Jingqi; Kan, Qiubin

2011-03-01

A series of efficient acid-base bifunctionalized hexagonal mesoporous silica (HMS) catalysts contained aminopropyl and propanesulfonic acid have been synthesized through a simple co-condensation by protection of amino group. The results of small-angle XRD, TEM, and N(2) adsorption-desorption measurements show that the resultant materials have mesoscopic structures. X-ray photoelectron spectroscopies, elemental analysis (EA), back titration, (29)Si NMR and (13)C NMR confirm that the organosiloxanes were condensed as a part of the silica framework. The resultant catalysts exhibit excellent acid-basic properties, which make them possess high activity for one-pot deacetalization-Knoevenagel and deacetalization-nitroaldol (Henry) reactions. Copyright © 2010 Elsevier Inc. All rights reserved.

Effectiveness of silica based sol-gel microencapsulation method for odorants and flavors leading to sustainable environment

Science.gov (United States)

Ashraf, Muhammad Aqeel; Khan, Aysha Masood; Ahmad, Mushtaq; Sarfraz, Maliha

2015-01-01

Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits. PMID:26322304

Effectiveness of silica based Sol-gel microencapsulation Method for odorants and flavours leading to sustainable Environment

Directory of Open Access Journals (Sweden)

Muhammad Aqeel eAshraf

2015-08-01

Full Text Available Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol–gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol–gel SiO2 is non-toxic and safe, whereas the sol–gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped actives, thereby broadening the practical utilization of chemically unstable essential oils. Reviewing progress in the fabrication of diverse odorant and flavoured sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits.

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.

Effect of materials and manufacturing on the bending stiffness of vaulting poles

Science.gov (United States)

Davis, C. L.; Kukureka, S. N.

2012-09-01

The increase in the world record height achieved in pole vaulting can be related to the improved ability of the athletes, in terms of their fitness and technique, and to the change in materials used to construct the pole. For example in 1960 there was a change in vaulting pole construction from bamboo to glass fibre reinforced polymer (GFRP) composites. The lighter GFRP pole enabled the athletes to have a faster run-up, resulting in a greater take-off speed, giving them more kinetic energy to convert into potential energy and hence height. GFRP poles also have a much higher failure stress than bamboo, so the poles were engineered to bend under the load of the athlete, thereby storing elastic strain energy that can be released as the pole straightens, resulting in greater energy efficiency. The bending also allowed athletes to change their vaulting technique from a style that involved the body remaining almost upright during the vault to one where the athlete goes over the bar with their feet upwards. Modern vaulting poles can be made from GFRP and/or carbon fibre reinforced polymer (CFRP) composites. The addition of carbon fibres maintains the mechanical properties of the pole, but allows a reduction in the weight. The number and arrangement of the fibres determines the mechanical properties, in particular the bending stiffness. Vaulting poles are also designed for an individual athlete to take into account each athlete’s ability and physical characteristics. The poles are rated by ‘weight’ to allow athletes to select an appropriate pole for their ability. This paper will review the development of vaulting poles and the requirements to maximize performance. The properties (bending stiffness and pre-bend) and microstructure (fibre volume fraction and lay-up) of typical vaulting poles will be discussed. Originally published as Davis C L and Kukureka S N (2004) Effect of materials and manufacturing on the bending stiffness of vaulting poles The Engineering of

The Effect of Using Sewage Sludge Ash with and without Nano Silica Particles on Properties of Self-compacting Cement Based Materials

Directory of Open Access Journals (Sweden)

Amin Khoshravesh

2014-10-01

Full Text Available Nowadays using pozzolanic materials is crucial as a replacement of needed cement, improving properties of cement based materials and saving costs. On the other hand sewage sludge is harmful to the environment and human health. So in this research the sewage sludge ash has been used as an artificial pozzolan to produce self compacting cement based materials which could be evaluated as a revolution in the concrete industry. The objective of this research was to accelerate the performance of sewage sludge ash by utilizing nano silica particles. This research includes 10 mix designs for self compacting mortar and concrete made up of binary and ternary cementitious blends of sewage sludge ash (0%,5%,10%,15%,20% and nano silica (0%,1%. The results showed that by adding the sewage sludge ash, rheological and mechanical properties of the samples were reduced and for small percentages of sewage sludge ash, the durability characteristics were improved. The results also showed that adding nano silica improved the mechanical and durability properties of self compacting mortar and concrete. Finally in presence of nano silica, the reactivity of the sewage sludge ash was increased and its performance was improved.

Study of association of Eu(III) β-diketonato-1,10-phenanthroline complexes in silica-based hybrid materials

Energy Technology Data Exchange (ETDEWEB)

Fadieiev, Yevhen M.; Smola, Sergii S. [A.V. Bogatsky Physico-chemical Institute, National Academy of Sciences of Ukraine, 86, Lustdorfskaya doroga, 65080 Odessa (Ukraine); Malinka, Elena V. [Odessa National Academy of Food Technology, 112, Kanatna Street, 65039 Odessa (Ukraine); Rusakova, Nataliia V., E-mail: lanthachem@ukr.net [A.V. Bogatsky Physico-chemical Institute, National Academy of Sciences of Ukraine, 86, Lustdorfskaya doroga, 65080 Odessa (Ukraine)

2017-03-15

Hybrid organic-inorganic materials based on silica and mixed-ligand complexes of Eu(III) with β-diketones and 1,10-phenanthroline with covalent and non-covalent attachment to matrix were obtained by a sol-gel route. Luminescent study of obtained systems allowed to propose spectral criteria for estimation of the uniformity of complex distribution in amorphous silica matrix. Thus, such criteria are the broadening of Eu(III) 4f-luminescence bands, emission decay and the shape of plot of the emission intensity vs. concentration of complex in the materials. Full width of {sup 5}D{sub 0}→{sup 7}F{sub 2} band at its half maximum and the ratio of the {sup 5}D{sub 0}→{sup 7}F{sub 2} and {sup 5}D{sub 0}→{sup 7}F{sub 1} bands intensities were used as quantitative measures of spectral changes and the bands broadening in Eu(III) emission spectra. - Highlights: • Modification of Eu(III) β-diketonates by an anchor fragments was carried out. • The degree of association of molecules was estimated based on emission spectra. • Covalent anchoring of complexes promotes their uniform distribution in matrix. • Non-covalently grafted complexes are prone to association in amorphous silica.

X-ray analysis of phase coexistence and electric poling processing in alkaline niobate-based compositions

International Nuclear Information System (INIS)

Fu Jian; Zuo Ruzhong; Liu Yi

2010-01-01

The characteristic and origin of two-phase coexistence and the content of each phase in typical alkaline niobate-based lead-free compositions were investigated through the refinement of X-ray diffraction peaks and the measurement of dielectric constant versus temperature curves. The diffuse nature of polymorphic phase transition has resulted in the coexistence of two ferroelectric phases within a wide composition and temperature range. As a result, the optimum piezoelectric properties appear in the composition rich in tetragonal phases and there is a remarkable poling temperature effect. Discussions on the difference between morphotropic phase boundary and polymorphic phase boundary were made in combination with the variation of electrical properties.

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.

PolyPole-1: An accurate numerical algorithm for intra-granular fission gas release

International Nuclear Information System (INIS)

Pizzocri, D.; Rabiti, C.; Luzzi, L.; Barani, T.; Van Uffelen, P.; Pastore, G.

2016-01-01

The transport of fission gas from within the fuel grains to the grain boundaries (intra-granular fission gas release) is a fundamental controlling mechanism of fission gas release and gaseous swelling in nuclear fuel. Hence, accurate numerical solution of the corresponding mathematical problem needs to be included in fission gas behaviour models used in fuel performance codes. Under the assumption of equilibrium between trapping and resolution, the process can be described mathematically by a single diffusion equation for the gas atom concentration in a grain. In this paper, we propose a new numerical algorithm (PolyPole-1) to efficiently solve the fission gas diffusion equation in time-varying conditions. The PolyPole-1 algorithm is based on the analytic modal solution of the diffusion equation for constant conditions, combined with polynomial corrective terms that embody the information on the deviation from constant conditions. The new algorithm is verified by comparing the results to a finite difference solution over a large number of randomly generated operation histories. Furthermore, comparison to state-of-the-art algorithms used in fuel performance codes demonstrates that the accuracy of PolyPole-1 is superior to other algorithms, with similar computational effort. Finally, the concept of PolyPole-1 may be extended to the solution of the general problem of intra-granular fission gas diffusion during non-equilibrium trapping and resolution, which will be the subject of future work. - Highlights: • A new numerical algorithm (PolyPole-1) for intra-granular fission gas release in time-varying conditions is developed. • The concept combines the modal analytic solution for constant conditions and a polynomial correction. • PolyPole-1 is extensively verified and compared to other state-of-the-art algorithms. • PolyPole-1 exhibits a superior accuracy and a similar computational time relative to other algorithms. • The PolyPole-1 algorithm can be

PolyPole-1: An accurate numerical algorithm for intra-granular fission gas release

Energy Technology Data Exchange (ETDEWEB)

Pizzocri, D. [Politecnico di Milano, Department of Energy, Nuclear Engineering Division, Via La Masa 34, 20156 Milano (Italy); Rabiti, C. [Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Luzzi, L.; Barani, T. [Politecnico di Milano, Department of Energy, Nuclear Engineering Division, Via La Masa 34, 20156 Milano (Italy); Van Uffelen, P. [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, 76125 Karlsruhe (Germany); Pastore, G., E-mail: giovanni.pastore@inl.gov [Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States)

2016-09-15

The transport of fission gas from within the fuel grains to the grain boundaries (intra-granular fission gas release) is a fundamental controlling mechanism of fission gas release and gaseous swelling in nuclear fuel. Hence, accurate numerical solution of the corresponding mathematical problem needs to be included in fission gas behaviour models used in fuel performance codes. Under the assumption of equilibrium between trapping and resolution, the process can be described mathematically by a single diffusion equation for the gas atom concentration in a grain. In this paper, we propose a new numerical algorithm (PolyPole-1) to efficiently solve the fission gas diffusion equation in time-varying conditions. The PolyPole-1 algorithm is based on the analytic modal solution of the diffusion equation for constant conditions, combined with polynomial corrective terms that embody the information on the deviation from constant conditions. The new algorithm is verified by comparing the results to a finite difference solution over a large number of randomly generated operation histories. Furthermore, comparison to state-of-the-art algorithms used in fuel performance codes demonstrates that the accuracy of PolyPole-1 is superior to other algorithms, with similar computational effort. Finally, the concept of PolyPole-1 may be extended to the solution of the general problem of intra-granular fission gas diffusion during non-equilibrium trapping and resolution, which will be the subject of future work. - Highlights: • A new numerical algorithm (PolyPole-1) for intra-granular fission gas release in time-varying conditions is developed. • The concept combines the modal analytic solution for constant conditions and a polynomial correction. • PolyPole-1 is extensively verified and compared to other state-of-the-art algorithms. • PolyPole-1 exhibits a superior accuracy and a similar computational time relative to other algorithms. • The PolyPole-1 algorithm can be

Modern methods of experimental construction of texture complete direct pole figures by using X-ray data

Science.gov (United States)

Isaenkova, M.; Perlovich, Yu; Fesenko, V.

2016-04-01

Currently used methods for constructing texture complete direct pole figure (CDPF) based on the results of X-ray diffractometric measurements were considered with respect to the products of Zr-based alloys and, in particular, used in a nuclear reactor cladding tubes, for which the accuracy of determination of integral texture parameters is of the especial importance. The main attention was devoted to technical issues which are solved by means of computer processing of large arrays of obtained experimental data. Among considered questions there are amendments of the defocusing, techniques for constructing of complete direct pole figures and determination of integral textural parameters. The methods of reconstruction of complete direct pole figures by partial direct pole figures recorded up to tilt angles of sample ψ=70-80°: the method of extrapolation of data to an uninvestigated region of the stereographic projection, and the method of "sewing" of partial pole figures measured for three mutually perpendicular plane sections of the product. The limits of applicability of these methods, depending on the shape of the test product and the degree of inhomogeneity of the layer-by-layer texture, were revealed. On the basis of a large number of experimental data, the accuracy of the integral parameters used for calculation of the physical and mechanical properties of metals with a hexagonal crystal structure was found to be equal to 0.02, when taking into account the texture heterogeneity of regular products from Zr-based alloys.

Zwitterionic silica-based monolithic capillary columns for isocratic and gradient hydrophilic interaction liquid chromatography

Czech Academy of Sciences Publication Activity Database

Moravcová, Dana; Planeta, Josef; Kahle, Vladislav; Roth, Michal

2012-01-01

Roč. 1270, DEC 28 (2012), s. 178-185 ISSN 0021-9673 R&D Projects: GA MV VG20112015021; GA ČR(CZ) GAP206/11/0138; GA ČR(CZ) GAP106/12/0522 Institutional support: RVO:68081715 Keywords : HILIC * Monolithic silica column * Nucleoside separation * Nucleic acid base Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.612, year: 2012

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.

Determination of the crystallite orientation distribution from direct pole figures

International Nuclear Information System (INIS)

Araujo Gomes, P.A.M. de.

1977-01-01

A method is described which allows to calculate the crystallite orientation distribution in polycrystalline material, from direct pole figures data of its crystallographic planes (Roe's Method). The programme was applied to (1010), (0002), (1011) and (1120) complete pole figures data for a commercial, thin sheet Zircaloy-4 tubing specimen. A semi-automatic Rigaku-Denki texture goniometer, which scans the reciprocal lattice sphere pointwise outputting the data in a punched tape, was used to obtain the pole figures. This is consistent with the results obtained through direct conclusion from the pole figures. (author)

Theoretical modeling and experimental analyses of laminated wood composite poles

Science.gov (United States)

Cheng Piao; Todd F. Shupe; Vijaya Gopu; Chung Y. Hse

2005-01-01

Wood laminated composite poles consist of trapezoid-shaped wood strips bonded with synthetic resin. The thick-walled hollow poles had adequate strength and stiffness properties and were a promising substitute for solid wood poles. It was necessary to develop theoretical models to facilitate the manufacture and future installation and maintenance of this novel...

Comparative Investigation on the Performance of Modified System Poles and Traditional System Poles Obtained from PDC Data for Diagnosing the Ageing Condition of Transformer Polymer Insulation Materials

Directory of Open Access Journals (Sweden)

Jiefeng Liu

2018-02-01

Full Text Available The life expectancy of a transformer is largely depended on the service life of transformer polymer insulation materials. Nowadays, several papers have reported that the traditional system poles obtained from polarization and depolarization current (PDC data can be used to assess the condition of transformer insulation systems. However, the traditional system poles technique only provides limited ageing information for transformer polymer insulation. In this paper, the modified system poles obtained from PDC data are proposed to assess the ageing condition of transformer polymer insulation. The aim of the work is to focus on reporting a comparative investigation on the performance of modified system poles and traditional system poles for assessing the ageing condition of a transformer polymer insulation system. In the present work, a series of experiments have been performed under controlled laboratory conditions. The PDC measurement data, degree of polymerization (DP and moisture content of the oil-immersed polymer pressboard specimens were carefully monitored. It is observed that, compared to the relationships between traditional system poles and DP values, there are better correlations between the modified system poles and DP values, because the modified system poles can obtain much more ageing information on transformer polymer insulation. Therefore, the modified system poles proposed in the paper are more suitable for the diagnosis of the ageing condition of transformer polymer insulation.

Choice of wood poles can reduce greenhouse gases

Energy Technology Data Exchange (ETDEWEB)

Sedjo, R. A.

2002-07-01

The first, second and third assessment reports on climate change of the Intergovernmental Panel on Climate Change (IPCC) are reviewed in an effort to highlight results of past studies on the total life cycle energy utilization of wood products compared with the use of substitute materials such as steel, concrete, bricks and aluminum. Without exception, all studies found that the total energy requirements associated with wood materials are substantially lower than those of other commonly substituted materials. For example, it has been clearly demonstrated that wooden poles are more environmentally benign than concrete or steel poles with regard to their energy utilization and their potential to contribute to atmospheric carbon dioxide emissions. An estimate to convert wood poles to steel poles showed that while the greenhouse gas emissions associated with pole conversion were modest compared to the national total, they were nevertheless a significant percentage of US annual emission (approximately 2.8 per cent of annual US total of 5.28 billion tons of carbon dioxide). These studies provide empirical confirmation of the concept that substitution of high energy-intensive materials for low-energy-using wood materials contributes substantially to the overall increase of carbon dioxide emissions through their overall higher energy requirements.

Analysis of car’s frontal collision against pole

Science.gov (United States)

Ispas, N.; Nastasoiu, M.

2017-10-01

Reducing the effects of traffic accidents over the occupants is a major objective of collision attempts. Impacts between the car and the pole are very dangerous for the physical integrity of the car’s occupants. To minimalize the effects of such events on the passengers of a vehicle, a whole series of efforts by both designers and experienced engineers led to increasingly the vehicles safety. The main aim of these paper is to quantify the influences over the car passengers of loads involved by car against pole collisions using the same car model at different speeds. Also, this kind on occupant influences were study using a small car model. Other goal of the paper was the study of the cars stiffness in frontal collision against the pole. The paper’s experimental results were obtained by support of DSD, Dr. Steffan Datentechnik GmbH - Linz, Austria. The described tests were performed in full test facility of DSD Linz, in “Easter 2016 PC-Crash Seminar”. Cars accelerations, velocities, rotations angles after pole impact were registered and discussed. The novelty of the paper consists in studies referred for the same car model involved in car against pole collisions at different impact speeds. Paper’s conclusions can be future used for car safety improvement.

Effects of Cu over Pd based catalysts supported on silica or niobia

Directory of Open Access Journals (Sweden)

Roma M.N.S.C.

2000-01-01

Full Text Available Palladium and palladium-copper catalysts supported on silica and niobia were characterized by H2 chemisorption and H2-O2 titration. Systems over silica were also analyzed by transmission electron microscopy and EXAFS. The metallic dispersion decreased from 20% to 7% when the content of Pd was increased from 0.5wt.-% to 3wt.-% in monometallic catalysts. The addition of 3 wt.-% Cu to obtain Pd-Cu catalysts caused a remarkable capacity loss of hydrogen chemisorption. TPR analysis suggested an interaction between the two metals and EXAFS characterization of the catalyst supported on silica confirmed the formation of Pd-Cu alloy. Pd/Nb2O5 catalysts showed turnover numbers higher than those obtained with the Pd/SiO2 systems in the cyclohexane dehydrogenation. However, the bimetallic catalysts showed very low turnover numbers.

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.

Ambient pressure dried tetrapropoxysilane-based silica aerogels with high specific surface area

Science.gov (United States)

Parale, Vinayak G.; Han, Wooje; Jung, Hae-Noo-Ree; Lee, Kyu-Yeon; Park, Hyung-Ho

2018-01-01

In the present paper, we report the synthesis of tetrapropoxysilane (TPOS)-based silica aerogels with high surface area and large pore volume. The silica aerogels were prepared by a two-step sol-gel process followed by surface modification via a simple ambient pressure drying approach. In order to minimize drying shrinkage and obtain hydrophobic aerogels, the surface of the alcogels was modified using trichloromethylsilane as a silylating agent. The effect of the sol-gel compositional parameters on the polymerization of aerogels prepared by TPOS, one of the precursors belonging to the Si(OR)4 family, was reported for the first time. The oxalic acid and NH4OH concentrations were adjusted to achieve good-quality aerogels with high surface area, low density, and high transparency. Controlling the hydrolysis and condensation reactions of the TPOS precursor turned out to be the most important factor to determine the pore characteristics of the aerogel. Highly transparent aerogels with high specific surface area (938 m2/g) and low density (0.047 g/cm3) could be obtained using an optimized TPOS/MeOH molar ratio with appropriate concentrations of oxalic acid and NH4OH.

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)

Effect of silica-based fillers on structure and properties of epoxy-based composites; Efeito das cargas a base de silica na estrutura e propriedades de compositos a base de resina epoxidica

Energy Technology Data Exchange (ETDEWEB)

Solymossy, Ana Paula F.; Dahmouche, Karim; Soares, Bluma G. [Instituto de Macromoleculas (IMA), Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Rocha, L. Alonso; Ribeiro, Sidney J.L, E-mail: apfiuza@ima.ufrj.br [Instituto de Quimica, Universidade Estadual Paulista (UNESP), Araraquara-SP (Brazil)

2011-07-01

In the present work, the incorporation effect of nanoparticles of commercial silica (Aerosil R200 - R200), polysilsesquioxane (POSS) and in-situ synthesized mesoporous silica (MP) on the structure, curing and thermal properties of epoxy resin. SAXS analysis of R200 and MP composites showed a tendency to Guinier plateau, while the POSS composite showed larger particle size. By the rheological analysis it was possible to measure the gel time of the composites, of which the greater value obtained was for MP, followed by POSS and then by R200, due to their affinity with the matrix and particle sizes. DMA showed that R200 composite has the lowest modulus, when compared with the other composites. The MP composite has higher Tg than POSS composite and lower than R200 composite. (author)

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

South Pole Region of the Moon as Seen by Clementine

Science.gov (United States)

1994-01-01

Lunar mosaic of 1500 Clementine images of the south polar region of the moon. The projection is orthographic, centered on the south pole. The Schrodinger Basin (320 km in diameter) is located in the lower right of the mosaic. Amundsen-Ganswindt is the more subdued circular basin between Schrodinger and the pole. The polar regions of the moon are of special interest because of the postulated occurrence of ice in permanently shadowed areas. The south pole is of greater interest because the area that remains in shadow is much larger than that at the north pole.

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.

Construction of proton exchange membranes under ultrasonic irradiation based on novel fluorine functionalizing sulfonated polybenzimidazole/cellulose/silica bionanocomposite.

Science.gov (United States)

Esmaielzadeh, Sheida; Ahmadizadegan, Hashem

2018-03-01

Novel sulfonated polybenzimidazole (s-PBI)/cellulose/silica bionanocomposite membranes were prepared from fluorine-containing s-PBI copolymer with a cellulose/silica precursor and a bonding agent. The introduction of the bonding agent results in the reinforcing interfacial interaction between s-PBI chains and the cellulose/silica nanoparticles. Commercially available silica nanoparticles were modified with biodegradable nanocellolose through ultrasonic irradiation technique. Transmission electron microscopy (TEM) analyses showed that the cellulose/silica composites were well dispersed in the s-PBI matrix on a nanometer scale. The mechanical properties and the methanol barrier ability of the s-PBI films were improved by the addition of cellulose/silica. The modulus of the s-PBI/10 wt% cellulose/silica nanocomposite membranes had a 45% increase compared to the pure s-PBI films, and the methanol permeability decreased by 62% with respect to the pure s-PBI membranes. The conductivities of the s-PBI/cellulose/silica nanocomposites were slightly lower than the pure s-PBI. The antibacterial activity of (s-PBI)/cellulose/silica was investigated against Gram-positive bacteria, ie, Staphylococcus aureus and methicillin-resistant S. aureus and Gram-negative bacteria, ie, Escherichia coli, E. coli O157:H7 and Pseudomonas aeruginosa by the disc diffusion method using Mueller Hinton agar at different sizes of cellulose/silica. All of the synthesized (s-PBI)/cellulose/silica were found to have high antibacterial activity. Copyright © 2017 Elsevier B.V. All rights reserved.

Silica- and silylated europium-based luminescent hybrids: new analysis tools for biological environments

International Nuclear Information System (INIS)

Pereira Duarte, Adriana

2012-01-01

The association of the very interesting luminescence properties of the lanthanide chelates with the physicochemical properties of inorganic matrix such as silica is a promising way to obtain new probes or luminescent markers for biology analyses. In this idea, this work focuses on the preparation of new hybrid materials based on the grafting of new europium(III) complexes on silica nanoparticles. These europium complexes were developed in our group using bifunctional ligands containing both complexing and grafting sites. Intrinsic characteristic of the ligands gives us the ability to make a covalent bond between the material surface and the complex. Two different methodologies were used; the first one is the direct grafting reaction involving the complex and silica nanoparticles (i.e. dense or meso-porous particles). The second one is the Stoeber reaction, where the SiO 2 nanoparticles were prepared in presence of the europium complex. The last methodology has an additional difficult, because of the presence of silylated europium complex, it needs a closer control of the physicochemical conditions. The new organic-inorganic hybrid materials, obtained in this work, present an interesting luminescence behavior and this one is depending on the localization of the europium complex, i.e. on the surface or within the nanoparticles. In addition, the obtained hybrids present the nano-metric dimension and the complex is not leachable. Analyses were realized to describe the luminescence properties, beyond surface and structural characteristics. Initial results show that the new hybrids are promising candidates for luminescent bio-markers, particularly for the time-resolved analysis. (author) [fr

REGION NORTH OF TEACHER EDUCATION POLICY AND EVALUATION OF POLES OPEN UNIVERSITY SYSTEM OF BRAZIL

Directory of Open Access Journals (Sweden)

Celso José da Costa

2013-03-01

Full Text Available This text aims to present, in general, the north region and policies for teacher training implemented in the last 5 years, locating in this context the importance of the Brazil Open University system and its supporting poles face as methodology research linked to the project "Institutionalization of Distance Education in Brazil." Greater emphasis will be given to data from the states of Pará and Acre, given that two authors of this text act as coordinators of the poles supporting attendance System Open University of Brazil in these states. We design the text, based on testimony of poles coordinators who participated in participatory research, conducted by the Research Group "Teacher education and information and communication technologies", LANTE / UFF. We aim also to identify the structure and functioning of the Poles face Supporting UAB in the North as well as the assessment tool applied in this region.

State-PID Feedback for Pole Placement of LTI Systems

Directory of Open Access Journals (Sweden)

Sarawut Sujitjorn

2011-01-01

Full Text Available Pole placement problems are especially important for disturbance rejection and stabilization of dynamical systems and regarded as algebraic inverse eigenvalue problems. In this paper, we propose gain formulae of state feedback through PID-elements to achieve desired pole placement for a delay-free LTI system with single input. Real and complex stable poles can be assigned with the proposed compact gain formulae. Numerical examples show that our proposed gain formulae can be used effectively resulting in very satisfactory responses.

Pole solutions for flame front propagation

CERN Document Server

Kupervasser, Oleg

2015-01-01

This book deals with solving mathematically the unsteady flame propagation equations. New original mathematical methods for solving complex non-linear equations and investigating their properties are presented. Pole solutions for flame front propagation are developed. Premixed flames and filtration combustion have remarkable properties: the complex nonlinear integro-differential equations for these problems have exact analytical solutions described by the motion of poles in a complex plane. Instead of complex equations, a finite set of ordinary differential equations is applied. These solutions help to investigate analytically and numerically properties of the flame front propagation equations.

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.

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

Ordered mesoporous silica-based inorganic nanocomposites

International Nuclear Information System (INIS)

Wang Qingqing; Shantz, Daniel F.

2008-01-01

This article reviews the synthesis and characterization of nanoparticles and nanowires grown in ordered mesoporous silicas (OMS). Summarizing work performed over the last 4 years, this article highlights the material properties of the final nanocomposite in the context of the synthesis methodology employed. While certain metal-OMS systems (e.g. gold in MCM-41) have been extensively studied this article highlights that there is a rich set of chemistries that have yet to be explored. The article concludes with some thoughts on future developments and challenges in this area. - Graphical abstract: HAADF TEM image of gold nanoparticles in amine-functionalized MCM-41 (from Ref. [22])

On pole structure assignment in linear systems

Czech Academy of Sciences Publication Activity Database

Loiseau, J.-J.; Zagalak, Petr

2009-01-01

Roč. 82, č. 7 (2009), s. 1179-1192 ISSN 0020-7179 R&D Projects: GA ČR(CZ) GA102/07/1596 Institutional research plan: CEZ:AV0Z10750506 Keywords : linear systems * linear state feedback * pole structure assignment Subject RIV: BC - Control Systems Theory Impact factor: 1.124, year: 2009 http://library.utia.cas.cz/separaty/2009/AS/zagalak-on pole structure assignment in linear systems.pdf

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.

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.

Fluorescence lifetime studies of MeV erbium implanted silica glass

International Nuclear Information System (INIS)

Lidgard, A.; Polman, A.; Jacobsen, D.C.; Blonder, G.E.; Kistler, R.; Poate, J.M.; Becker, P.C.

1991-01-01

MeV erbium ion implantation into various SiO 2 glasses has been studied with the aim of incorporating the rare-earth dopant as an optically active ion in the silica network. The lifetime of the excited state ranges from 1.6 to 12.8 ms, depending on base material and implantation fluence. These results have positive implications for silica-based integrated optical technology. (Author)

Fluorescence lifetime studies of MeV erbium implanted silica glass

Energy Technology Data Exchange (ETDEWEB)

Lidgard, A.; Polman, A.; Jacobsen, D.C.; Blonder, G.E.; Kistler, R.; Poate, J.M.; Becker, P.C. (AT and T Bell Labs., Murray Hill, NJ (USA))

1991-05-23

MeV erbium ion implantation into various SiO{sub 2} glasses has been studied with the aim of incorporating the rare-earth dopant as an optically active ion in the silica network. The lifetime of the excited state ranges from 1.6 to 12.8 ms, depending on base material and implantation fluence. These results have positive implications for silica-based integrated optical technology. (Author).

High pH mobile phase effects on silica-based reversed-phase high-performance liquid chromatographic columns

NARCIS (Netherlands)

Kirkland, J.J.; Straten, van M.A.; Claessens, H.A.

1995-01-01

Aqueous mobile phases above pH 8 often cause premature column failure, limiting the utility of silica-based columns for applications requiring high pH. Previous studies suggest that covalently bound silane ligands are hydrolyzed and removed by high-pH mobile phases. However, we found that the

Effect of nanosized silica in poly(methyl methacrylate)-lithium bis(trifluoromethanesulfonyl)imide based polymer electrolytes

Energy Technology Data Exchange (ETDEWEB)

Ramesh, S.; Lu, Soon-Chien [Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Setapak, 53300 Kuala Lumpur (Malaysia)

2008-12-01

The effect of nanosized silica when incorporated in polymer electrolytes is analyzed by means of Fourier transform infrared (FTIR) spectroscopy, conductivity and thermal properties. Nanocomposite polymer electrolytes are synthesized by the dispersion of nanosized silica (SiO{sub 2}), up to 10 wt.% maximum, into a matrix formed by poly(methyl methacrylate) (PMMA) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The highest conductivity is 2.44 x 10{sup -6} S cm{sup -1} at room temperature, with 4 wt.% of silica added. The FTIR spectra show evidence of complexation between PMMA, LiTFSI and SiO{sub 2}. The addition of silica to the polymer electrolytes also improves the thermal stability and the ability to retain conductivity over time. (author)

A novel enzyme-mimic nanosensor based on quantum dot-Au nanoparticle@silica mesoporous microsphere for the detection of glucose

Energy Technology Data Exchange (ETDEWEB)

Li, Yang; Ma, Qiang; Liu, Ziping [Department of Analytical Chemistry, College of Chemistry, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Wang, Xinyan [Changchun Institute of Applied Chemistry Chinese Academy of Sciences, Changchun 130022 (China); Su, Xingguang, E-mail: suxg@jlu.edu.cn [Department of Analytical Chemistry, College of Chemistry, Jilin University, Qianjin Street 2699, Changchun 130012 (China)

2014-08-20

Highlights: • Design QD-Au NP@silica mesoporous microspheres as a novel enzyme-mimic nanosensor. • Composition of two kinds of nanoparticle can be controlled through silica layers coating. • Our nanosensor for glucose detection has high sensitivity and selectivity. - Abstract: QD-Au NP@silica mesoporous microspheres have been fabricated as a novel enzyme-mimic nanosensor. CdTe quantum dots (QDs) were loaded into the core, and Au nanoparticles (NPs) were encapsulated in the outer mesoporous shell. QDs and Au NPs were separated in the different space of the nanosensor, which prevent the potential energy or electron transfer process between QDs and Au NPs. As biomimetic catalyst, Au NPs in the mesoporous silica shell can catalytically oxidize glucose as glucose oxidase (GOx)-mimicking. The resultant hydrogen peroxide can quench the photoluminescence (PL) signal of QDs in the microsphere core. Therefore the nanosensor based on the decrease of the PL intensity of QDs was established for the glucose detection. The linear range for glucose was in the range of 5–200 μM with a detection limit (3σ) of 1.32 μM.

Silica hollow bottle resonators for use as whispering gallery mode based chemical sensors

Science.gov (United States)

Stoian, Razvan-Ionut; Bui, Khoa V.; Rosenberger, A. T.

2015-12-01

A simple three-step method for making silica hollow bottle resonators (HBRs) was developed. This procedure is advantageous because it uses commercially available materials, is cost effective, and is easy to implement. Additionally, the use of these HBRs as whispering gallery mode based chemical sensors is demonstrated by preliminary absorption sensing results in the near infrared (1580-1660 nm) using a trace gas (CH4) in air at atmospheric pressure and a dye (SDA2072) in methanol solution.

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

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.

Silica-sol-based spin-coating barrier layer against phosphorous diffusion for crystalline silicon solar cells.

Science.gov (United States)

Uzum, Abdullah; Fukatsu, Ken; Kanda, Hiroyuki; Kimura, Yutaka; Tanimoto, Kenji; Yoshinaga, Seiya; Jiang, Yunjian; Ishikawa, Yasuaki; Uraoka, Yukiharu; Ito, Seigo

2014-01-01

The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n(+) emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion.

Design, production, and characterization of artificial protein- and silica-based biomaterials

Science.gov (United States)

Marner, Wesley Darrell, II

This work focused on a specific protein polymer, poly(EAK) n, denoting a protein with n repeats of the amino acid monomer sequence AEAEAKAKAEAEAKAK (where A=alanine, E=glutamic acid, and K=lysine). Previous work has focused on lower molecular weight versions of these proteins, where n=1 and n=9. Those studies showed that while poly(EAK)9 an order of magnitude increase in hydrogel strength over EAK1, even the higher molecular weight version forms a relatively weak hydrogel. The first part of this dissertation describes efforts to improve the mechanical properties of poly(EAK)n hydrogels by investigating the self-assembly of higher molecular weight versions of the protein, where n = 24 and n = 63. Genes encoding these proteins were constructed and expressed in the bacterium Escherichia coli, and the proteins can be purified from cell culture by affinity chromatography. The solubility of these proteins, however, is significantly lower than the lower molecular weight versions of poly(EAK)n previously explored. Interestingly, despite decreased solubility, these proteins quickly form a stable gel-like matrix while in the milieu of the homogenized cell lysate. Congo Red binding assays and circular dichroism studies also indicate that poly(EAK)24 and poly(EAK)63 each self-assemble into stacked beta-sheet structures. While poor solubility prevents their use as a stand-alone biomaterial, these higher molecular weight protein polymers may prove useful as virtual crosslinking agents for hydrogels formed from lower molecular weight poly(EAK)n molecules. The second portion of this dissertation describes the generation of new biosilica matrices. Silica is one of the most abundant biominerals on Earth and is produced by a variety of organisms. One such organism is the diatom Cylindrotheca fusiformis. From dilute aqueous solutions of silica and using relatively mild processing conditions, these unicellular organisms create silica frustules with exquisite microstructures having

Integrated 3D printing and corona poling process of PVDF piezoelectric films for pressure sensor application

Science.gov (United States)

Kim, Hoejin; Torres, Fernando; Wu, Yanyu; Villagran, Dino; Lin, Yirong; Tseng, Tzu-Liang(Bill

2017-08-01

This paper presents a novel process to fabricate piezoelectric films from polyvinylidene fluoride (PVDF) polymer using integrated fused deposition modeling (FDM) 3D printing and corona poling technique. Corona poling is one of many effective poling processes that has received attention to activate PVDF as a piezoelectric responsive material. The corona poling process occurs when a PVDF polymer is exposed to a high electric field created and controlled through an electrically charged needle and a grid electrode under heating environment. FDM 3D printing has seen extensive progress in fabricating thermoplastic materials and structures, including PVDF. However, post processing techniques such as poling is needed to align the dipoles in order to gain piezoelectric properties. To further simplify the piezoelectric sensors and structures fabrication process, this paper proposes an integrated 3D printing process with corona poling to fabricate piezoelectric PVDF sensors without post poling process. This proposed process, named ‘Integrated 3D Printing and Corona poling process’ (IPC), uses the 3D printer’s nozzle and heating bed as anode and cathode, respectively, to create poling electric fields in a controlled heating environment. The nozzle travels along the programmed path with fixed distance between nozzle tip and sample’s top surface. Simultaneously, the electric field between the nozzle and bottom heating pad promotes the alignment of dipole moment of PVDF molecular chains. The crystalline phase transformation and output current generated by printed samples under different electric fields in this process were characterized by a Fourier transform infrared spectroscopy and through fatigue load frame. It is demonstrated that piezoelectric PVDF films with enhanced β-phase percentage can be fabricated using the IPC process. In addition, mechanical properties of printed PVDF was investigated by tensile testing. It is expected to expand the use of additive

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

Measurement and calculation of cosmic radiation exposure during a pole-to-pole flight sequence

International Nuclear Information System (INIS)

Taylor, Graeme C.; Ojjeh, Captain Aziz

2010-01-01

Cosmic ray dosimetry measurements were carried out on board a Global Express business jet operated by TAG Aviation (UK) during a pole-to-pole flight sequence that took place in November 2008. One Hawk TEPC and two EPDN2s were flown, and the TEPC measurements compared to calculated values from the route dose codes AVIDOS, CARI 6M, EPCARD versions 3.2 and 3.34, QARM and SIEVERT (online version). The largest difference between measured and calculated doses for the total flight sequence was found to be 13%. Agreement between the readings of the TEPC and the EPDN2s (once a calibration factor from the CERN High Energy Reference Field had been applied) was reasonably good given the relatively large uncertainties associated with the EPDN2 measurements.

Relation between Statistics of Radiowave Reception at South Pole Station and Auroral Oval Characteristics: Data and Monte Carlo Simulations

Science.gov (United States)

Labelle, J.; Noonan, K.

2006-12-01

Despite their remote location, radio receivers at South Pole Station regularly detect AM broadcast band signals propagating from transmitters thousands of kilometers away. Statistical analysis of received radiowave power at South Pole during 2004 and 2005, integrated over the frequency range of AM broadcast stations, reveals a distinctive time-of-day (UT) dependence: a broad maximum in received power centered at 1500 UT corresponds to magnetic daytime; signal levels are lower during magnetic nighttime except for a calculated based on two contributions: daytime D-region absorption and auroral absorption. The latter varies with day of year and magnetic local time in a complex fashion due to the asymmetric shape and varying size of the auroral oval and the offset of South Pole from the geomagnetic pole. The Monte Carlo simulations confirm that the enhanced absorption of AM broadcast signals during magnetic nighttime results from auroral absorption. Furthermore, the simulations predict that a weak (<0.5 dB) peak near magnetic midnight, similar to that observed in the data, arises from including in the statistical data base intervals when the auroral oval is contracted. These results suggest that ground based radio observations at a sufficiently remote high-latitude site such as South Pole may effectively monitor auroral oval characteristics on a statistical basis at least.

Direct localization of poles of a meromorphic function from measurements on an incomplete boundary

Science.gov (United States)

Nara, Takaaki; Ando, Shigeru

2010-01-01

This paper proposes an algebraic method to reconstruct the positions of multiple poles in a meromorphic function field from measurements on an arbitrary simple arc in it. A novel issue is the exactness of the algorithm depending on whether the arc is open or closed, and whether it encloses or does not enclose the poles. We first obtain a differential equation that can equivalently determine the meromorphic function field. From it, we derive linear equations that relate the elementary symmetric polynomials of the pole positions to weighted integrals of the field along the simple arc and end-point terms of the arc when it is an open one. Eliminating the end-point terms based on an appropriate choice of weighting functions and a combination of the linear equations, we obtain a simple system of linear equations for solving the elementary symmetric polynomials. We also show that our algorithm can be applied to a 2D electric impedance tomography problem. The effects of the proximity of the poles, the number of measurements and noise on the localization accuracy are numerically examined.

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.

A discussion on leading renormalon in the pole mass

Science.gov (United States)

Komijani, J.

2017-08-01

Perturbative series of some quantities in quantum field theories, such as the pole mass of a quark, suffer from a kind of divergence called renormalon divergence. In this paper, the leading renormalon in the pole mass is investigated, and a map is introduced to suppress this renormalon. The inverse of the map is then used to generate the leading renormalon and obtain an expression to calculate its overall normalization. Finally, the overall normalization of the leading renormalon of the pole mass is calculated for several values of quark flavors.

Effect of nano silica based modifying agent for hydrophobic coating application

International Nuclear Information System (INIS)

Nurul Huda Mudri; Nik Ghazali Nik Salleh; Mek Zah Salleh

2016-01-01

Hydrophobic coatings find wide application in industry due to their unique features such as water repellent and self-cleaning properties. In this study, modifying agent was synthesized by way of nano silica particles dispersion in polydimethyl siloxane with addition of surfactant, catalyst and stabilizer using high speed distemper. The modifying agent was added into coating formulation and cured under UV exposure. Scanning Electron Microscopy image of the film found that the nano silica particles were distributed well on substrate. Contact angle measurement gave the highest reading of 116 degree for 20 % wt of the modifying agent. The optical properties of the film were evaluated via transmission and haze test. (author)

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...

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

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.

Physics on the Z-pole

International Nuclear Information System (INIS)

Omori, Tsunehiko; Kurihara, Yoshimasa; Sugimoto, Yasuhiro; Fujii, Yoshiaki; Fujii, Keisuke

1994-01-01

JLC will provide a high luminosity of 2.0 x 10 33 cm -2 s -1 on the Z-pole. To realize the Z-pole running we need to add a transport line to bypass unnecessary part of the main linac. With this high luminosity, the third angle of the unitality triangle (sin 2φ 3 ) can be measured in B s (B s ) → pK s channel with 3σ sensitivity in 1 year when sin 2φ 3 = -0.5, Xs = 10, and the branching ratio of the channel is 2 x 10 -5 . Also sin 2 θw can be measured with accuracy of Δsin 2 θw/sin 2 θw = 0.1%. (J.P.N.)

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.

Functionalization of mesoporous silica membrane with a Schiff base fluorophore for Cu(II) ion sensing

Energy Technology Data Exchange (ETDEWEB)

Chen Xiaotong [Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku 980-8578, Sendai, Miyagi Prefecture (Japan); Department of Chemistry, Tsinghua University, Beijing 100084 (China); Yamaguchi, Akira [College of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512 (Japan); Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Tokai, Ibaraki 319-1106 (Japan); Namekawa, Manato [Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku 980-8578, Sendai, Miyagi Prefecture (Japan); Kamijo, Toshio [Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku 980-8578, Sendai, Miyagi Prefecture (Japan); Tsuruoka National College of Technology, Aza-Sawada, Tsuruoka 997-8511 (Japan); Teramae, Norio, E-mail: teramae@m.tohoku.ac.jp [Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku 980-8578, Sendai, Miyagi Prefecture (Japan); Tong, Aijun, E-mail: tongaj@mail.tsinghua.edu.cn [Department of Chemistry, Tsinghua University, Beijing 100084 (China)

2011-06-24

Graphical abstract: Highlights: > A hybrid mesoporous membrane (SB-HMM) functionalized by Schiff base fluorophores was fabricated. > SB-HMM showed strong fluorescence with aggregation-induced emission enhancement properties. > SB-HMM was applicable for the detection of Cu(II) in an aqueous solution with good reversibility and reproducibility. - Abstract: A Schiff base (SB) immobilized hybrid mesoporous silica membrane (SB-HMM) was prepared by immobilizing a Schiff base onto the pore surface of mesoporous silica (pore size = 3.1 nm) embedded in the pores of a porous anodic alumina membrane. In contrast to the non-fluorescent analogous SB molecule in homogeneous solutions, SB-HMM exhibited intense fluorescence due to emission enhancement caused by aggregation of SB groups on the pore surface. The high quantum efficiency of the surface SB groups allows SB-HMM to function as a fluorescent sensor for Cu(II) ions in an aqueous solution with good sensitivity, selectivity and reproducibility. Under the optimal conditions described, the linear ranges of fluorescence intensity for Cu(II) are 1.2-13.8 (M (R{sup 2} = 0.993) and 19.4-60 (R{sup 2} = 0.992) (M. The limit of detection for Cu(II) is 0.8 {mu}M on basis of the definition by IUPAC (C{sub LOD} = 3.3S{sub b}/m).

Sugar and pH dual-responsive mesoporous silica nanocontainers based on competitive binding mechanisms

Science.gov (United States)

Yilmaz, M. Deniz; Xue, Min; Ambrogio, Michael W.; Buyukcakir, Onur; Wu, Yilei; Frasconi, Marco; Chen, Xinqi; Nassar, Majed S.; Stoddart, J. Fraser; Zink, Jeffrey I.

2014-12-01

A sugar and pH dual-responsive controlled release system, which is highly specific towards molecular stimuli, has been developed based on the binding between catechol and boronic acid on a platform of mesoporous silica nanoparticles (MSNs). By grafting phenylboronic acid stalks onto the silica surface, catechol-containing β-cyclodextrins can be attached to the orifices of the MSNs' nanopores through formation of boronate esters which block access to the nanopores. These esters are stable enough to prevent cargo molecules from escaping. The boronate esters disassociate in the presence of sugars, enabling the molecule-specific controlled-release feature of this hybrid system. The rate of release has been found to be tunable by varying both the structures and the concentrations of sugars, as a result of the competitive binding nature associated with the mechanism of its operation. Acidification also induces the release of cargo molecules. Further investigations show that the presence of both a low pH and sugar molecules provides cooperative effects which together control the rate of release.A sugar and pH dual-responsive controlled release system, which is highly specific towards molecular stimuli, has been developed based on the binding between catechol and boronic acid on a platform of mesoporous silica nanoparticles (MSNs). By grafting phenylboronic acid stalks onto the silica surface, catechol-containing β-cyclodextrins can be attached to the orifices of the MSNs' nanopores through formation of boronate esters which block access to the nanopores. These esters are stable enough to prevent cargo molecules from escaping. The boronate esters disassociate in the presence of sugars, enabling the molecule-specific controlled-release feature of this hybrid system. The rate of release has been found to be tunable by varying both the structures and the concentrations of sugars, as a result of the competitive binding nature associated with the mechanism of its operation

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.

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.

Silica hollow bottle resonators for use as whispering gallery mode based chemical sensors

International Nuclear Information System (INIS)

Stoian, Razvan-Ionut; Bui, Khoa V; Rosenberger, A T

2015-01-01

A simple three-step method for making silica hollow bottle resonators (HBRs) was developed. This procedure is advantageous because it uses commercially available materials, is cost effective, and is easy to implement. Additionally, the use of these HBRs as whispering gallery mode based chemical sensors is demonstrated by preliminary absorption sensing results in the near infrared (1580–1660 nm) using a trace gas (CH 4 ) in air at atmospheric pressure and a dye (SDA2072) in methanol solution. (paper)

Silica nanoparticle-based dual imaging colloidal hybrids: cancer cell imaging and biodistribution

Directory of Open Access Journals (Sweden)

Lee H

2015-08-01

Full Text Available Haisung Lee,1 Dongkyung Sung,2 Jinhoon Kim,3 Byung-Tae Kim,3 Tuntun Wang,4 Seong Soo A An,5 Soo-Won Seo,6 Dong Kee Yi4 1Molecular Diagnostics, In Vitro Diagnostics Unit, New Business Division, SK Telecom, 2Department of Life Sciences, Graduate School of Korea University, 3Interdisciplinary Graduate Program of Biomedical Engineering, School of Medicine, Sungkyunkwan University, Samsung Medical Center, 4Department of Chemistry, Myongji University, Seoul, 5Department of Bionanotechnology, Gachon Medical Research Institute, Gachon University, Seongnam, 6Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu, Republic of Korea Abstract: In this study, fluorescent dye-conjugated magnetic resonance (MR imaging agents were investigated in T mode. Gadolinium-conjugated silica nanoparticles were successfully synthesized for both MR imaging and fluorescence diagnostics. Polyamine and polycarboxyl functional groups were modified chemically on the surface of the silica nanoparticles for efficient conjugation of gadolinium ions. The derived gadolinium-conjugated silica nanoparticles were investigated by zeta potential analysis, transmission electron microscopy, inductively coupled plasma mass spectrometry, and energy dispersive x-ray spectroscopy. MR equipment was used to investigate their use as contrast-enhancing agents in T1 mode under a 9.4 T magnetic field. In addition, we tracked the distribution of the gadolinium-conjugated nanoparticles in both lung cancer cells and organs in mice. Keywords: dual bioimaging, MR imaging, silica colloid, T1 contrast imaging, nanohybrid

Sequential Vapor Infiltration Treatment Enhances the Ionic Current Rectification Performance of Composite Membranes Based on Mesoporous Silica Confined in Anodic Alumina.

Science.gov (United States)

Liang, Yanyan; Liu, Zhengping

2016-12-20

Ionic current rectification of nanofluidic diode membranes has been studied widely in recent years because it is analogous to the functionality of biological ion channels in principle. We report a new method to fabricate ionic current rectification membranes based on mesoporous silica confined in anodic aluminum oxide (AAO) membranes. Two types of mesostructured silica nanocomposites, hexagonal structure and nanoparticle stacked structure, were used to asymmetrically fill nanochannels of AAO membranes by a vapor-phase synthesis (VPS) method with aspiration approach and were further modified via sequence vapor infiltration (SVI) treatment. The ionic current measurements indicated that SVI treatment can modulate the asymmetric ionic transport in prepared membranes, which exhibited clear ionic current rectification phenomenon under optimal conditions. The ionic current rectifying behavior is derived from the asymmetry of surface conformations, silica species components, and hydrophobic wettability, which are created by the asymmetrical filling type, silica depositions on the heterogeneous membranes, and the condensation of silanol groups. This article provides a considerable strategy to fabricate composite membranes with obvious ionic current rectification performance via the cooperation of the VPS method and SVI treatment and opens up the potential of mesoporous silica confined in AAO membranes to mimic fluid transport in biological processes.

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

Poles of the S matrix for a complex potential

International Nuclear Information System (INIS)

Dabrowski, J.

1996-01-01

Trajectories of S matrix poles in complex k plane are presented for a complex square well potential. A simple rule is given for predicting the effect of an absorptive potential on the location of these poles. copyright 1996 The American Physical Society

Institutional Evaluation in Poles of the Open University System of Brazil

Directory of Open Access Journals (Sweden)

Alexciano de Sousa Martins

2018-03-01

Full Text Available The study wanted to know the institutional evaluation in poles of distance education, of the Open University of Brazil (UAB system, analyzing the poles of the State of Ceará. The UAB system of the Brazilian Ministry of Education makes it possible to offer courses of higher level agreements with public universities. Ceará counts on UAB poles, since 2006, that form teachers and other professionals, even in regions lacking public higher education. The objective of this study was to discuss the importance of the institutional evaluation in the poles of the Open University of Brazil program through an exploratory and descriptive field research, showing that the institutional evaluation at the poles is minimal and out of line with the legislation in force. Suggestions on how to develop the evaluative practice.

A variational EM method for pole-zero modeling of speech with mixed block sparse and Gaussian excitation

DEFF Research Database (Denmark)

Shi, Liming; Nielsen, Jesper Kjær; Jensen, Jesper Rindom

2017-01-01

The modeling of speech can be used for speech synthesis and speech recognition. We present a speech analysis method based on pole-zero modeling of speech with mixed block sparse and Gaussian excitation. By using a pole-zero model, instead of the all-pole model, a better spectral fitting can...... be expected. Moreover, motivated by the block sparse glottal flow excitation during voiced speech and the white noise excitation for unvoiced speech, we model the excitation sequence as a combination of block sparse signals and white noise. A variational EM (VEM) method is proposed for estimating...... in reconstructing of the block sparse excitation....

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

Carbon-dot-based dual-emission silica nanoparticles as a ratiometric fluorescent probe for vanadium(V) detection in mineral water samples

Science.gov (United States)

He, Lijun; Zhang, Heng; Fan, Huanhuan; Jiang, Xiuming; Zhao, Wenjie; Xiang, Guo Qiang

2018-01-01

Herein, we propose a simple and effective strategy for designing a ratiometric fluorescent nanosensor. We designed and developed a carbon dots (CDs) based dual-emission nanosensor for vanadium(V) by coating the surface of dye-doped silica nanoparticles with CDs. The fluorescence of dual-emission silica nanoparticles was quenched in acetic acid through potassium bromate (KBrO3) oxidation. V(V) could catalyze KBrO3 oxidation reaction process, resulting in the ratiometric fluorescence quenching of dual-emission silica nanoparticles. We investigated several important parameters affecting the performance of the nanosensor. Under the optimized conditions, the detection limit of this nanosensor reached 1.1 ng mL- 1 and the linear range from 10 to 800 ng mL- 1. Furthermore, we found that the sensor was suitable for determination of V(V) in different mineral water samples with satisfactory results.

Catalytic Activity and Photophysical Properties of Biomolecules Immobilized on Mesoporous Silica

DEFF Research Database (Denmark)

Ikemoto, Hideki

Mesoporous silicas, based on Santa Barbara Amorphous-15 (SBA-15), with different morphology, structure, pore size and functional groups have been synthesized. Two metalloenzymes and a photosynthetic membrane protein were immobilized on or confined in the pores of the mesoporous silicas to prepare...

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.

Double-Layer Magnetic Nanoparticle-Embedded Silica Particles for Efficient Bio-Separation.

Directory of Open Access Journals (Sweden)

San Kyeong

Full Text Available Superparamagnetic Fe3O4 nanoparticles (NPs based nanomaterials have been exploited in various biotechnology fields including biomolecule separation. However, slow accumulation of Fe3O4 NPs by magnets may limit broad applications of Fe3O4 NP-based nanomaterials. In this study, we report fabrication of Fe3O4 NPs double-layered silica nanoparticles (DL MNPs with a silica core and highly packed Fe3O4 NPs layers. The DL MNPs had a superparamagnetic property and efficient accumulation kinetics under an external magnetic field. Moreover, the magnetic field-exposed DL MNPs show quantitative accumulation, whereas Fe3O4 NPs single-layered silica nanoparticles (SL MNPs and silica-coated Fe3O4 NPs produced a saturated plateau under full recovery of the NPs. DL MNPs are promising nanomaterials with great potential to separate and analyze biomolecules.

Pluronic-Functionalized Silica-Lipid Hybrid Microparticles: Improving the Oral Delivery of Poorly Water-Soluble Weak Bases.

Science.gov (United States)

Rao, Shasha; Richter, Katharina; Nguyen, Tri-Hung; Boyd, Ben J; Porter, Christopher J H; Tan, Angel; Prestidge, Clive A

2015-12-07

A Pluronic-functionalized silica-lipid hybrid (Plu-SLH) microparticle system for the oral delivery of poorly water-soluble, weak base drugs is reported for the first time. A highly effective Plu-SLH microparticle system was composed of Labrasol as the lipid phase, Pluronic F127 as the polymeric precipitation inhibitor (PPI), and silica nanoparticles as the solid carrier. For the model drug cinnarizine (CIN), the Plu-SLH delivery system was shown to offer significant biopharmaceutical advantages in comparison with unformulated drug and drug in the silica-lipid hybrid (SLH) system. In vitro two-phase dissolution studies illustrated significantly reduced pH provoked CIN precipitation and an 8- to 14-fold improvement in the extent of dissolution in intestinal conditions. In addition, under simulated intestinal digesting conditions, the Plu-SLH provided approximately three times more drug solubilization than the SLH. Oral administration in rats resulted in superior bioavailability for Plu-SLH microparticles, i.e., 1.6- and 2.1-fold greater than the SLH and the unformulated CIN, respectively. A physical mixture of Pluronic and SLH (Plu&SLH), having the same composition as Plu-SLH, was also evaluated, but showed no significant increase in CIN absorption when compared to unmodified CIN or SLH. This work represents the first study where different methods of incorporating PPI to formulate solid-state lipid-based formulations were compared for the impact on the biopharmaceutical performance. The data suggest that the novel physicochemical properties and structure of the fabricated Plu-SLH microparticle delivery system play an important role in facilitating the synergistic advantage of Labrasol and Pluronic F127 in preventing drug precipitation, and the Plu-SLH provides efficient oral delivery of poorly water-soluble weak bases.

The self-consistent dynamic pole tide in global oceans

Science.gov (United States)

Dickman, S. R.

1985-01-01

The dynamic pole tide is characterized in a self-consistent manner by means of introducing a single nondifferential matrix equation compatible with the Liouville equation, modelling the ocean as global and of uniform depth. The deviations of the theory from the realistic ocean, associated with the nonglobality of the latter, are also given consideration, with an inference that in realistic oceans long-period modes of resonances would be increasingly likely to exist. The analysis of the nature of the pole tide and its effects on the Chandler wobble indicate that departures of the pole tide from the equilibrium may indeed be minimal.

Moisture sensor based on evanescent wave light scattering by porous sol-gel silica coating

Science.gov (United States)

Tao, Shiquan; Singh, Jagdish P.; Winstead, Christopher B.

2006-05-02

An optical fiber moisture sensor that can be used to sense moisture present in gas phase in a wide range of concentrations is provided, as well techniques for making the same. The present invention includes a method that utilizes the light scattering phenomenon which occurs in a porous sol-gel silica by coating an optical fiber core with such silica. Thus, a porous sol-gel silica polymer coated on an optical fiber core forms the transducer of an optical fiber moisture sensor according to an embodiment. The resulting optical fiber sensor of the present invention can be used in various applications, including to sense moisture content in indoor/outdoor air, soil, concrete, and low/high temperature gas streams.

A brilliant sandwich type fluorescent nanostructure incorporating a compact quantum dot layer and versatile silica substrates.

Science.gov (United States)

Huang, Liang; Wu, Qiong; Wang, Jing; Foda, Mohamed; Liu, Jiawei; Cai, Kai; Han, Heyou

2014-03-18

A "hydrophobic layer in silica" structure was designed to integrate a compact quantum dot (QD) layer with high quantum yield into scalable silica hosts containing desired functionality. This was based on metal affinity driven assembly of hydrophobic QDs with versatile silica substrates and homogeneous encapsulation of organosilica/silica layers.

A new route for preparation of sodium-silicate-based hydrophobic silica aerogels via ambient-pressure drying

International Nuclear Information System (INIS)

Bangi, Uzma K H; Rao, A Venkateswara; Rao, A Parvathy

2008-01-01

An in-depth investigation into the synthesis of hydrophobic silica aerogels prepared by the surface derivatization of wet gels followed by subsequent drying at ambient pressure is reported. The following sol-gel parameters were examined for their effect on the physical properties of the derived aerogels: number of gel washings with water, percentage of hexane or methanol in silylating mixture, molar ratio of tartaric acid: Na 2 SiO 3 , gel aging period, weight% of silica, trimethylchlorosilane (TMCS) percentage, and silylation period. These parameters were varied from 1 to 4, 0 to 100%, 0.27 to 1.2, 0 to 4 h, 1.5 to 8 wt.%, 20 to 40% and 6 to 24 h, respectively. The properties of hydrophobic silica aerogels synthesized by this new route were investigated in terms of bulk density, percentage volume shrinkage, percentage porosity, thermal conductivity and contact angle with water, and by Fourier transform infrared spectroscopy (FTIR). The as-prepared hydrophobic silica aerogels exhibited high temperature stability (up to approximately 435 0 C) as measured by thermogravimetric/differential thermal analysis (TGA-DTA). The optimal sol-gel parameters were found to be a molar ratio of Na 2 SiO 3 :H 2 O : tartaric acid : TMCS of 1 : 146.67 : 0.86 : 9.46, an aging period of 3 h, four washings with water in 24 h and the use of a 50% hexane- or methanol-based silylating mixture. Aerogels prepared with these optimal parameters were found to exhibit 50% optical transparency in the visible range, 84 kg m -3 density, 0.090 W mK -1 thermal conductivity, 95% porosity and a contact angle of 146 0 with water

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.

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.

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.

Hybrid Mesoporous Silica-Based Drug Carrier Nanostructures with Improved Degradability by Hydroxyapatite.

Science.gov (United States)

Hao, Xiaohong; Hu, Xixue; Zhang, Cuimiao; Chen, Shizhu; Li, Zhenhua; Yang, Xinjian; Liu, Huifang; Jia, Guang; Liu, Dandan; Ge, Kun; Liang, Xing-Jie; Zhang, Jinchao

2015-10-27

Potential bioaccumulation is one of the biggest limitations for silica nanodrug delivery systems in cancer therapy. In this study, a mesoporous silica nanoparticles/hydroxyapatite (MSNs/HAP) hybrid drug carrier, which enhanced the biodegradability of silica, was developed by a one-step method. The morphology and structure of the nanoparticles were characterized by TEM, DLS, FT-IR, XRD, N2 adsorption-desorption isotherms, and XPS, and the drug loading and release behaviors were tested. TEM and ICP-OES results indicate that the degradability of the nanoparticles has been significantly improved by Ca(2+) escape from the skeleton in an acid environment. The MSNs/HAP sample exhibits a higher drug loading content of about 5 times that of MSNs. The biological experiment results show that the MSNs/HAP not only exhibits good biocompatibility and antitumor effect but also greatly reduces the side effects of free DOX. The as-synthesized hybrid nanoparticles may act as a promising drug delivery system due to their good biocompatibility, high drug loading efficiency, pH sensitivity, and excellent biodegradability.

Preparation of sponge-reinforced silica aerogels from tetraethoxysilane and methyltrimethoxysilane for oil/water separation

Science.gov (United States)

Li, Ming; Jiang, Hongyi; Xu, Dong

2018-04-01

Polyurethane sponge-reinforced silica aerogels based on tetraethoxysilane (TEOS) and methyltrimethoxysilane (MTMS) were fabricated by a facile method through sol-gel reaction followed by ambient pressure drying. In sponge-reinforced silica aerogels, nanoporous aerogel aggregates fill in the pores of polyurethane sponge. The sponge-reinforced aerogels are hydrophobic and oleophilic and show extremely high absorption for machine oil (10.6 g g‑1 for TEOS-based aerogel and 9.2 g g‑1 for MTMS-based aerogel). In addition, the sponge-reinforced aerogel composites exhibit notable improvements with regards to mechanical properties. The compressive strength was enhanced obviously up to about 349 KPa for TEOS-based aerogel and 60 KPa for MTMS-based aerogel. Specially, sponge-reinforced silica aerogels based on MTMS drastically shrank upon loading and then recovered to the original size when unloaded. The property differences of the sponge-reinforced silica aerogels caused by the two precursors were discussed in terms of morphologies, pore size distributions and chemical structure.

Novel titration method for surface-functionalised silica

Energy Technology Data Exchange (ETDEWEB)

Hofen, Kai; Weber, Siegfried [Department of Biotechnology, University of Applied Sciences, Mannheim (Germany); Chan, Chiu Ping Candace [School of Advanced Manufacturing and Mechanical Engineering, Mawson Institute, University of South Australia, Mawson Lakes Blvd, Mawson Lakes 5095 (Australia); Majewski, Peter, E-mail: peter.majewski@unisa.edu.au [School of Advanced Manufacturing and Mechanical Engineering, Mawson Institute, University of South Australia, Mawson Lakes Blvd, Mawson Lakes 5095 (Australia)

2011-01-15

This paper describes three inexpensive and fast analytical methods to characterise grafted particle surfaces. The reaction of silica with (3-aminopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane and N-(phosphonomethyl)iminodiacetic acid hydrate, respectively, leads to NH{sub 2}-, SO{sub 3}H- or COOH-functionalised silica, which were characterised by X-ray photoelectron spectrometry and titration in nonaqueous media as well as with two titration methods in a water-based environment. In the work presented, factors influencing the titrations are pointed out and solutions are presented to overcome these limiting factors are shown.

Novel titration method for surface-functionalised silica

International Nuclear Information System (INIS)

Hofen, Kai; Weber, Siegfried; Chan, Chiu Ping Candace; Majewski, Peter

2011-01-01

This paper describes three inexpensive and fast analytical methods to characterise grafted particle surfaces. The reaction of silica with (3-aminopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane and N-(phosphonomethyl)iminodiacetic acid hydrate, respectively, leads to NH 2 -, SO 3 H- or COOH-functionalised silica, which were characterised by X-ray photoelectron spectrometry and titration in nonaqueous media as well as with two titration methods in a water-based environment. In the work presented, factors influencing the titrations are pointed out and solutions are presented to overcome these limiting factors are shown.

The change of electric field and of some other insulating properties during isochronal annealing in thermally poled Ge-doped silica films

DEFF Research Database (Denmark)

Liu, Q.M.; Poumellec, B.; Braga, D.

2005-01-01

induced electric field and other insulating properties like electron traps population and conductivity in high field. Concerning the change of the contrast at low dose arising from the poling electric field, we show that this field begins to disappear at around 450 degrees C and is erased completely...... at 650 degrees C. Using a larger dose allows measuring the change in conductivity contrast. We find a stability similar to the electric field with a disappearance around 450 similar to 650 degrees C. On the contrary, for intermediate dose, the contrast remains for larger annealing temperature. It allows...

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.

The Written-Pole{sup TM} motor: high efficiency - low start current

Energy Technology Data Exchange (ETDEWEB)

Beck, B. [C.Eng. Precise Power Corp., Bradenton, FL (United States); Friesen, D. [P.E. Manitoba Hydro, Winnipeg (Canada)

2000-07-01

Written-Pole{sup TM} technology is a patented machine technology, which changes the magnetic polarity of the rotor field in a rotating machine, while the machine is operating. The number of poles is thereby changed, resulting in a constant frequency - variable speed machine. When operating as a motor, a Written-Pole machine has inherently low starting current and high operating efficiency. (orig.)

Silica-on-silicon optical couplers and coupler based optical filters

DEFF Research Database (Denmark)

Leick, Lasse

2002-01-01

is not an adequate description of the waveguides. A simple application for an optical couplers is as a 980/1550 nm mulitmplexer for erbium doped wavguide amplifiers. A numerical analysis shows that a directional coupler has acceptable specifications, whereas a mulit mode interference coupler does not. The wavelength......This work concerns modeling and chracterization of non ampligying silica-on-silicon optical components for wavelength division mulitplexed networks. Emphasis is placed on optical couplers and how they can be used as building blocks for devices with a larger complexity. It has been investigated how...... to construct wavelength flattened and process tolerant couplers. A thorough comparison between directional couplers, multi mode interference couplers and interferometer-based couplers has been performed. Numerically all these architectures have the ability to obtain similar wavelength-flatness, but the multi...

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)

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.

Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials.

Science.gov (United States)

Hesemann, Peter; Nguyen, Thy Phung; Hankari, Samir El

2014-04-11

The synthesis of nanostructured anionic-surfactant-templated mesoporous silica (AMS) recently appeared as a new strategy for the formation of nanostructured silica based materials. This method is based on the use of anionic surfactants together with a co-structure-directing agent (CSDA), mostly a silylated ammonium precursor. The presence of this CSDA is necessary in order to create ionic interactions between template and silica forming phases and to ensure sufficient affinity between the two phases. This synthetic strategy was for the first time applied in view of the synthesis of surface functionalized silica bearing ammonium groups and was then extended on the formation of materials functionalized with anionic carboxylate and bifunctional amine-carboxylate groups. In the field of silica hybrid materials, the "anionic templating" strategy has recently been applied for the synthesis of silica hybrid materials from cationic precursors. Starting from di- or oligosilylated imidazolium and ammonium precursors, only template directed hydrolysis-polycondensation reactions involving complementary anionic surfactants allowed accessing structured ionosilica hybrid materials. The mechanistic particularity of this approach resides in the formation of precursor-surfactant ion pairs in the hydrolysis-polycondensation mixture. This review gives a systematic overview over the various types of materials accessed from this cooperative ionic templating approach and highlights the high potential of this original strategy for the formation of nanostructured silica based materials which appears as a complementary strategy to conventional soft templating approaches.

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.

Densification of Silica Spheres: A New Pathway to Nano-Dimensioned Zeolite-Based Catalysts.

Science.gov (United States)

Machoke, Albert Gonche Fortunatus; Apeleo Zubiri, Benjamin; Leonhardt, Rainer; Marthala, Venkata Ramana Reddy; Schmiele, Martin; Unruh, Tobias; Hartmann, Martin; Spiecker, Erdman; Schwieger, Wilhelm

2017-08-16

Nanosized materials are expected to play a unique role in the development of future catalytic processes. Herein, pre-prepared and geometrically well-defined amorphous silica spheres are densified into silica-rich zeolites with nanosized dimensions. After the densification, the obtained nanosized zeolites exhibit the same spherical morphology like the starting precursor but characterized by a drastically reduced size, higher density, and high crystallinity. The phase transformation into crystalline zeolite material and the densification effect are achieved through a well-controlled steam-assisted treatment of the larger precursor particles so that the transformation process proceeds always towards the center of the spheres, just like a shrinking process. Furthermore, this procedure is applicable also to commercially available silica particles, as well as aluminum-containing systems (precursors) leading to acidic nano-catalysts with improved catalytic performance. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study of recursive model for pole-zero cancellation circuit

International Nuclear Information System (INIS)

Zhou Jianbin; Zhou Wei; Hong Xu; Hu Yunchuan; Wan Xinfeng; Du Xin; Wang Renbo

2014-01-01

The output of charge sensitive amplifier (CSA) is a negative exponential signal with long decay time which will result in undershoot after C-R differentiator. Pole-zero cancellation (PZC) circuit is often applied to eliminate undershoot in many radiation detectors. However, it is difficult to use a zero created by PZC circuit to cancel a pole in CSA output signal accurately because of the influences of electronic components inherent error and environmental factors. A novel recursive model for PZC circuit is presented based on Kirchhoff's Current Law (KCL) in this paper. The model is established by numerical differentiation algorithm between the input and the output signal. Some simulation experiments for a negative exponential signal are carried out using Visual Basic for Application (VBA) program and a real x-ray signal is also tested. Simulated results show that the recursive model can reduce the time constant of input signal and eliminate undershoot. (authors)

[Poles of American tegumentary leishmaniasis production in northern Paraná State, Brazil].

Science.gov (United States)

Monteiro, Wuelton Marcelo; Neitzke, Herintha Coeto; Silveira, Thaís Gomes Verzignassi; Lonardoni, Maria Valdrinez Campana; Teodoro, Ueslei; Ferreira, Maria Eugênia Moreira Costa

2009-05-01

American tegumentary leishmaniasis is endemic in the State of Paraná, with 99.3% of the cases reported in the South of Brazil. Spatial distribution of the disease in northern Paraná was verified, identifying the most relevant geographic areas in epidemiological terms. The study used data recorded on epidemiological forms from the Teaching and Research Clinical Test Laboratory of the State University in Maringá, from 1987 to 2004. The study only included individuals that were infected in the municipalities (counties) in northern Paraná. Identification of the epidemiological units (poles and circuits) was based on spatial density of cases, according to the model proposed by the National Health Foundation, considering the most likely infection sites. Considering 1,933 reported cases, 1,611 were infected in northern Paraná. American tegumentary leishmaniasis distribution in Paraná State suggests two circuits for production of the disease: Paraná-Paranapanema, highlighting the Cinzas-Laranjinha, Tibagi, Ivaí-Pirapó, Piquiri, and Baixo Iguaçu poles, and Ribeira, highlighting the Alto Ribeira pole.

A rapid silica spin column-based method of RNA extraction from fruit trees for RT-PCR detection of viruses.

Science.gov (United States)

Yang, Fan; Wang, Guoping; Xu, Wenxing; Hong, Ni

2017-09-01

Efficient recovery of high quality RNA is very important for successful RT-PCR detection of plant RNA viruses. High levels of polyphenols and polysaccharides in plant tissues can irreversibly bind to and/or co-precipitate with RNA, which influences RNA isolation. In this study, a silica spin column-based RNA isolation method was developed by using commercially available silica columns combined with the application of a tissue lysis solution, and binding and washing buffers with high concentration guanidinium thiocyanate (GuSCN, 50% w/v), which helps remove plant proteins, polysaccharides and polyphenolic compounds. The method was successfully used to extract high quality RNA from citrus (Citrus aurantifolia), grapevine (Vitis vinifera), peach (Prunus persica), pear (Pyrus spp.), taro (Colocosia esculenta) and tobacco (Nicotiana benthamiana) samples. The method was comparable to conventional CTAB method in RNA isolation efficiency, but it was more sample-adaptable and cost-effective than commercial kits. High quality RNA isolated using silica spin column-based method was successfully used for the RT-PCR and/or multiplex RT-PCR amplification of woody fruit tree viruses and a viroid. The study provided a useful tool for the detection and characterization of plant viruses. Copyright © 2017 Elsevier B.V. All rights reserved.

Regge poles and alpha scattering

International Nuclear Information System (INIS)

Ceuleneer, R.

1974-01-01

The direct Regge pole model as a means of describing resonances in elastic particle scattering has been used for the analysis of the so-called ''anormalous large angle scattering'' of alpha particles by spinless nuclei. (Z.M.)

Designer silica layers for advanced applications: Processing and properties

Science.gov (United States)

Anderson, Adam

Recently, as scientists have investigated the application of conventional MEMS devices to biological systems, the exciting fields of bio-MEMS and microfluidics have emerged. Due to their small size, bio-MEMS and microfluidics devices offer the advantage of requiring only small sample and reagent volumes, in a potentially low-cost, integrated package. Such devices have the potential to significantly advance point-of-care diagnostics devices and improve overall patient care. However, due to the extremely small feature size, the large surface area-to-volume ratio in these devices makes controlling surface interactions of critical importance. Recently, there has been a shift to polymeric materials for fabrication of microfluidics devices due to their lower cost, ease of device fabrication by various processes, varied and favorable material properties, and, in some cases, pre-existing regulatory agency approvals. As a result, various surface modification strategies for polymeric surfaces have been proposed, but with only limited success. The proven success of organosilicon-based precursors in a wide variety of surface modification strategies has been demonstrated, with a body of knowledge on the general subject dating back nearly fifty years. However, these proven methodologies cannot be transferred to many important polymeric materials due to a lack of sufficient reactive groups on the surface. If any polymer surface could be made reactive by some intermediate treatment, the wide body of knowledge of organosilicon-based surface modification chemistries could be leveraged to advance the state-of-the-art in surface modification for microfluidics applications, where polymeric substrates are commonly encountered. This thesis reports on the processing properties and chemical properties of a vapor deposited silica layer, which is formed from the vapor phase hydrolysis of silicon tetrachloride. This layer can be deposited at low temperatures to a wide variety of substrates

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

Effect of surface hydroxyl groups on heat capacity of mesoporous silica

Science.gov (United States)

Marszewski, Michal; Butts, Danielle; Lan, Esther; Yan, Yan; King, Sophia C.; McNeil, Patricia E.; Galy, Tiphaine; Dunn, Bruce; Tolbert, Sarah H.; Hu, Yongjie; Pilon, Laurent

2018-05-01

This paper quantifies the effect of surface hydroxyl groups on the effective specific and volumetric heat capacities of mesoporous silica. To achieve a wide range of structural diversity, mesoporous silica samples were synthesized by various methods, including (i) polymer-templated nanoparticle-based powders, (ii) polymer-templated sol-gel powders, and (iii) ambigel silica samples dried by solvent exchange at room temperature. Their effective specific heat capacity, specific surface area, and porosity were measured using differential scanning calorimetry and low-temperature nitrogen adsorption-desorption measurements. The experimentally measured specific heat capacity was larger than the conventional weight-fraction-weighted specific heat capacity of the air and silica constituents. The difference was attributed to the presence of OH groups in the large internal surface area. A thermodynamic model was developed based on surface energy considerations to account for the effect of surface OH groups on the specific and volumetric heat capacity. The model predictions fell within the experimental uncertainty.

All-Pole Recursive Digital Filters Design Based on Ultraspherical Polynomials

Directory of Open Access Journals (Sweden)

N. Stojanovic

2014-09-01

Full Text Available A simple method for approximation of all-pole recursive digital filters, directly in digital domain, is described. Transfer function of these filters, referred to as Ultraspherical filters, is controlled by order of the Ultraspherical polynomial, nu. Parameter nu, restricted to be a nonnegative real number (nu ≥ 0, controls ripple peaks in the passband of the magnitude response and enables a trade-off between the passband loss and the group delay response of the resulting filter. Chebyshev filters of the first and of the second kind, and also Legendre and Butterworth filters are shown to be special cases of these allpole recursive digital filters. Closed form equations for the computation of the filter coefficients are provided. The design technique is illustrated with examples.

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.

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.

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

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.

A Nanoscale Plasma Etching Process for Pole Tip Recession of Perpendicular Recording Magnetic Head

OpenAIRE

LIU, Shoubin; HE, Dayao

2017-01-01

The pole tip of perpendicular recording head is constructed in a stacked structure with materials of NiCoFe, NiFe, Al2O3 and AlTiC. The surfaces of different materials are set at different heights below the air-bearing surface of slider. This paper presented a plasma dry etching process for Pole Tip Recession (PTR) based on an ion beam etching system. Ar and O2 mixed plasma at small incident angles have a high removal rate to the nonmagnetic material. It was utilised to etch the reference sur...

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.

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

The Achievements of the GLAMOROUS Project on Poling

DEFF Research Database (Denmark)

Margulis, Walter; Myrén, N.; Fage-Pedersen, Jacob

2005-01-01

The GLAMOROUS project had as objective to demonstrate the feasibility of fibre and waveguide components with a second order nonlinearity induced by poling. The accomplishments of this nine-partners European Research Project are described.......The GLAMOROUS project had as objective to demonstrate the feasibility of fibre and waveguide components with a second order nonlinearity induced by poling. The accomplishments of this nine-partners European Research Project are described....

Converting point-wise nuclear cross sections to pole representation using regularized vector fitting

Science.gov (United States)

Peng, Xingjie; Ducru, Pablo; Liu, Shichang; Forget, Benoit; Liang, Jingang; Smith, Kord

2018-03-01

Direct Doppler broadening of nuclear cross sections in Monte Carlo codes has been widely sought for coupled reactor simulations. One recent approach proposed analytical broadening using a pole representation of the commonly used resonance models and the introduction of a local windowing scheme to improve performance (Hwang, 1987; Forget et al., 2014; Josey et al., 2015, 2016). This pole representation has been achieved in the past by converting resonance parameters in the evaluation nuclear data library into poles and residues. However, cross sections of some isotopes are only provided as point-wise data in ENDF/B-VII.1 library. To convert these isotopes to pole representation, a recent approach has been proposed using the relaxed vector fitting (RVF) algorithm (Gustavsen and Semlyen, 1999; Gustavsen, 2006; Liu et al., 2018). This approach however needs to specify ahead of time the number of poles. This article addresses this issue by adding a poles and residues filtering step to the RVF procedure. This regularized VF (ReV-Fit) algorithm is shown to efficiently converge the poles close to the physical ones, eliminating most of the superfluous poles, and thus enabling the conversion of point-wise nuclear cross sections.

Long-Term Bending Creep Behavior of Thin-Walled CFRP Tendon Pretensioned Spun Concrete Poles

Directory of Open Access Journals (Sweden)

Giovanni P. Terrasi

2014-07-01

Full Text Available This paper discusses the long-term behavior of a series of highly-loaded, spun concrete pole specimens prestressed with carbon fiber-reinforced polymer (CFRP tendons, which were subjected to outdoor four-point bending creep tests since 1996 in the frame of collaboration with the Swiss precast concrete producer, SACAC (Società Anonima Cementi Armati Centrifugati. The 2 m span cylindrical beams studied are models for lighting poles produced for the last 10 years and sold on the European market. Five thin-walled pole specimens were investigated (diameter: 100 mm; wall-thickness: 25–27 mm. All specimens were produced in a pretensioning and spinning technique and were prestressed by pultruded CFRP tendons. Initially, two reference pole specimens were tested in quasi-static four-point bending to determine the short-term failure moment and to model the short-term flexural behavior. Then, three pole specimens were loaded to different bending creep moments: while the lowest loaded specimen was initially uncracked, the second specimen was loaded with 50% of the short-term bending failure moment and exhibited cracking immediately after load introduction. The highest loaded pole specimen sustained a bending moment of 72% of the short-term bending failure moment for 16.5 years before failing in July 2013, due to the bond failure of the tendons, which led to local crushing of the high-performance spun concrete (HPSC. Besides this, long-term monitoring of the creep tests has shown a limited time- and temperature-dependent increase of the deflections over the years, mainly due to the creep of the concrete. A concrete creep-based model allowed for the calculation of the long-term bending curvatures with reasonable accuracy. Furthermore, the pole specimens showed crack patterns that were stable over time and minimal slippage of the tendons with respect to the pole’s end-faces for the two lower load levels. The latter proves the successful and durable

Anti-Biofilm Efficacy of Nitric Oxide-Releasing Silica Nanoparticles

OpenAIRE

Hetrick, Evan M.; Shin, Jae Ho; Paul, Heather S.; Schoenfisch, Mark H.

2009-01-01

The ability of nitric oxide (NO)-releasing silica nanoparticles to kill biofilm-based microbial cells is reported. Biofilms of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, and Candida albicans were formed in vitro and exposed to NO-releasing silica nanoparticles. Replicative viability experiments revealed that ≥ 99% of cells from each type of biofilm were killed via NO release, with the greatest efficacy (≥ 99.999% killing) against gram-negative...

Water-Dependent Photonic Bandgap in Silica Artificial Opals

OpenAIRE

Gallego-Gomez, Francisco; Blanco, Alvaro; Canalejas-Tejero, Victor; Lopez, Cefe

2011-01-01

Some characteristics of silica-based structuresa-like the photonic properties of artificial opals formed by silica spheresa-can be greatly affected by the presence of adsorbed water. The reversible modification of the water content of an opal is investigated here by moderate heating (below 300 °C) and measuring in situ the changes in the photonic bandgap. Due to reversible removal of interstitial water, large blueshifts of 30 nm and a bandgap narrowing of 7% are observed. The latter is partic...

Pole Shape Optimization of Permanent Magnet Synchronous Motors Using the Reduced Basis Technique

Directory of Open Access Journals (Sweden)

A. Jabbari

2010-03-01

Full Text Available In the present work, an integrated method of pole shape design optimization for reduction of torque pulsation components in permanent magnet synchronous motors is developed. A progressive design process is presented to find feasible optimal shapes. This method is applied on the pole shape optimization of two prototype permanent magnet synchronous motors, i.e., 4-poles/6-slots and 4-poles-12slots.

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.

Silica-Coated Liposomes for Insulin Delivery

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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.

A Study on Silica Sand Quality in Yazaram and Mugulbu Deposits ...

African Journals Online (AJOL)

The suitability of silica sand deposits of Yazaram and Mugulbu in Mubi South Local Government Area of Adamawa State, Nigeria for commercial glass production were assessed based on the chemical and physical properties of the silica sand samples collected along the river side's. Test was carried out at the National ...

Fabrication and evaluation of hybrid silica/polymer optical fiber sensors for large strain measurement

Science.gov (United States)

Huang, Haiying

2007-04-01

Silica-based optical fiber sensors are widely used in structural health monitoring systems for strain and deflection measurement. One drawback of silica-based optical fiber sensors is their low strain toughness. In general, silica-based optical fiber sensors can only reliably measure strains up to 2%. Recently, polymer optical fiber sensors have been employed to measure large strain and deflection. Due to their high optical losses, the length of the polymer optical fibers is limited to 100 meters. In this paper, we present a novel economical technique to fabricate hybrid silica/polymer optical fiber strain sensors for large strain measurement. First, stress analysis of a surface-mounted optical fiber sensor is performed to understand the load distribution between the host structure and the optical fiber in relation to their mechanical properties. Next, the procedure of fabricating a polymer sensing element between two optical fibers is explained. The experimental set-up and the components used in the fabrication process are described in details. Mechanical testing results of the fabricated silica/polymer optical fiber strain sensor are presented.

Detection and classification of pole-like road objects from mobile LiDAR data in motorway environment

Science.gov (United States)

Yan, Li; Li, Zan; Liu, Hua; Tan, Junxiang; Zhao, Sainan; Chen, Changjun

2017-12-01

Mobile LiDAR Scanning (MLS) can collect 3-dimensional (3D) road and road-related geospatial information accurately and efficiently. Pole-like objects located in road environment are important street furniture and they are necessary information in road inventory and road mapping. The automatic detection and classification of pole-like road objects from mobile LiDAR data can greatly reduce the cost and improve the efficiency. This paper provides a complete workflow for the detection and classification of pole-like road objects from mobile LiDAR data in motorway environment. The major workflow includes three steps: data preprocessing, pole-like road objects detection and pole-like road objects classification. In data preprocessing step, ground points are removed by an automatic ground filtering algorithm, and then off-ground points are clustered into segments and the overlapped segments containing pole-like road objects are further separated through an iterative min-cut based segmentation approach. In detection step, filters utilizing both prior and shape information are used to detect the target objects. In classification step, features of objects are calculated and classified using Random Forest classifier. Our method was tested on two datasets scanned in motorway environment, and the results showed that the Matthews correlation coefficient of the two datasets in detection step was 93.7% and 95.9% respectively and the overall accuracy of the two datasets in classification step was 96.5% and 97.9% respectively.

Separable pole expansions in four-nucleon bound state calculations

International Nuclear Information System (INIS)

Sofianos, S.A.; Fiedeldey, H.; Haberzettl, H.; Sandhas, W.

1982-04-01

We compare the utility of the Generalized Unitary Pole Expansion (GUPE) and the Energy-Dependent Pole Expansion (EDPE) for the three-body subsystem amplitudes in four-body state calculations for a variety of separable and local nucleon-nucleon interactions. It is found that, with the EDPE, the four-body binding energy is well reproduced with only two terms each for the (2+2)- and the (3+1)-subsystem, respectively, while the GUPE requires three terms for the (3+1)-channel and four terms for the (2+2)-channel. We thus conclude that pole dominance is of greater importance for the GUPE than for EDPE, which works equally well for both types of subsystems. It is found that both methods, in particular the EDPE, converge more rapidly with increasing repulsion in the two-body interaction, i.e. the more realistic the interaction becomes. Both expansions require similar computing times for a converged calculation and are about 15-20 times faster than the widely used Hilbert-Schmidt Expansion (HSE). The respective merits of the two pole expansions are discussed and compared with the HSE. (orig.)

Evidence of highly oxidizing environment over the South Pole

International Nuclear Information System (INIS)

Davis, D.

2001-01-01

Researchers at the Georgia Institute of Technology have discovered high levels of an air purifying chemical or oxidizing agent in the near-surface atmosphere over the South Pole. This research, funded by the National Science Foundation, has implications for interpreting historical global climate records stored in Antarctic ice cores. The hydroxyl (OH) radical is higher at the South Pole than that estimated from OH measurements recorded at the equator. The OH radical is vital to scrubbing pollution and naturally occurring chemicals from the air and prevents a buildup of toxic levels of chemicals. The near surface atmospheric zone is a highly oxidizing environment at the South Pole. There is evidence that oxidizing chemistry continues to occur in the buried snow. This active chemistry could modify chemical species before they are trapped in the ice in their final chemical forms. Therefore, glaciochemists who study climate change based on analysis of trace chemicals trapped in polar ice will have to be more careful in their interpretations of Antarctic ice cores. Any significant increase of nitric oxide levels in any snow-covered area should result in high OH levels. Scientists used the selected-ion chemical ionization mass spectrometer technique to measure OH. To measure nitric oxide (NO), they used chemiluminescence with modifications to improve its sensitivity. Nitric oxide is also a radical and is a by-product of internal combustion engines. At the South Pole, it is formed when ultraviolet radiation interacts with nitrate ions. The source of NO is not clear, but it may originate from stratospheric denitrification and the long-range transport of nitric acid formed at low latitude during electrical storms. Scientists are also working to better understand the oxidation of dimethyl sulfide (DMS) under the cold conditions and high latitudes of Antarctica. This information will help glaciochemists to better interpret sulfate and methane sulfonate concentrations

New generation all-silica based optical elements for high power laser systems

Science.gov (United States)

Tolenis, T.; GrinevičiÅ«tÄ--, L.; Melninkaitis, A.; Selskis, A.; Buzelis, R.; MažulÄ--, L.; Drazdys, R.

2017-08-01

Laser resistance of optical elements is one of the major topics in photonics. Various routes have been taken to improve optical coatings, including, but not limited by, materials engineering and optimisation of electric field distribution in multilayers. During the decades of research, it was found, that high band-gap materials, such as silica, are highly resistant to laser light. Unfortunately, only the production of anti-reflection coatings of all-silica materials are presented to this day. A novel route will be presented in materials engineering, capable to manufacture high reflection optical elements using only SiO2 material and GLancing Angle Deposition (GLAD) method. The technique involves the deposition of columnar structure and tailoring the refractive index of silica material throughout the coating thickness. A numerous analysis indicate the superior properties of GLAD coatings when compared with standard methods for Bragg mirrors production. Several groups of optical components are presented including anti-reflection coatings and Bragg mirrors. Structural and optical characterisation of the method have been performed and compared with standard methods. All researches indicate the possibility of new generation coatings for high power laser systems.

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.

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.

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.

Development and characterization of silica and titania based nano structured materials for the removal of indoor and outdoor air pollutants

Science.gov (United States)

Peiris, Thelge Manindu Nirasha

Solar energy driven catalytic systems have gained popularity in environmental remediation recently. Various photocatalytic systems have been reported in this regard and most of the photocatalysts are based on well-known semiconducting material, Titanium Dioxide, while some are based on other materials such as Silicon Dioxide and various Zeolites. However, in titania based photocatalysts, titania is actively involved in the catalytic mechanism by absorbing light and generating exitons. Because of this vast popularity of titania in the field of photocatalysis it is believed that photocatalysis mainly occurs via non-localized mechanisms and semiconductors are extremely important. Even though it is still rare, photocatalysis could be localized and possible without use of a semiconductor as well. Thus, to support localized photocatalytic systems, and to compare the activity to titania based systems, degradation of organic air pollutants by nanostructured silica, titania and mixed silica titania systems were studied. New materials were prepared using two different approaches, precipitation technique (xerogel) and aerogel preparation technique. The prepared xerogel samples were doped with both metal (silver) and non-metals (carbon and sulfur) and aerogel samples were loaded with Chromium, Cobalt and Vanadium separately, in order to achieve visible light photocatalytic activity. Characterization studies of the materials were carried out using Nova BET analysis, DR UV-vis spectrometry, powder X-ray diffraction, X-ray photoelectron Spectroscopy, FT-IR spectroscopy, Transmission Electron Microscopy, etc. Kinetics of the catalytic activities was studied using a Shimadzu GCMS-QP 5000 instrument using a closed glass reactor. All the experiments were carried out in gaseous phase using acetaldehyde as the model pollutant. Kinetic results suggest that chromium doped silica systems are good UV and visible light active photocatalysts. This is a good example for a localized

Domain wall width of lithium niobate poled during growth

CERN Document Server

Brooks, R; Hole, D E; Callejo, D; Bermudez, V; Diéguez, E

2003-01-01

Good quality crystals of periodically poled lithium niobate can be generated directly during growth. However, the temperature gradients at the zone boundaries define the width of the regions where the polarity is reversed. Hence, the region influenced the domain transition may be a significant fraction of the overall poling period for material poled during growth. Evidence for the scale of this feature is reported both by chemical etching and by the less common method of ion beam luminescence and the 'domain wall' width approximately 1 mu m for these analyses. The influence of the reversal region may differ for alternative techniques but the relevance to device design for second harmonic generation is noted.

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.

Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials

Directory of Open Access Journals (Sweden)

Peter Hesemann

2014-04-01

Full Text Available The synthesis of nanostructured anionic-surfactant-templated mesoporous silica (AMS recently appeared as a new strategy for the formation of nanostructured silica based materials. This method is based on the use of anionic surfactants together with a co-structure-directing agent (CSDA, mostly a silylated ammonium precursor. The presence of this CSDA is necessary in order to create ionic interactions between template and silica forming phases and to ensure sufficient affinity between the two phases. This synthetic strategy was for the first time applied in view of the synthesis of surface functionalized silica bearing ammonium groups and was then extended on the formation of materials functionalized with anionic carboxylate and bifunctional amine-carboxylate groups. In the field of silica hybrid materials, the “anionic templating” strategy has recently been applied for the synthesis of silica hybrid materials from cationic precursors. Starting from di- or oligosilylated imidazolium and ammonium precursors, only template directed hydrolysis-polycondensation reactions involving complementary anionic surfactants allowed accessing structured ionosilica hybrid materials. The mechanistic particularity of this approach resides in the formation of precursor-surfactant ion pairs in the hydrolysis-polycondensation mixture. This review gives a systematic overview over the various types of materials accessed from this cooperative ionic templating approach and highlights the high potential of this original strategy for the formation of nanostructured silica based materials which appears as a complementary strategy to conventional soft templating approaches.

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...

Characterization polyethylene terephthalate nanocomposites mixing with nano-silica and titanium oxide

Directory of Open Access Journals (Sweden)

Rusu Mircea A.

2017-01-01

Full Text Available Polyethylene terephthalate (PET based nanocomposites containing nano-silica (Aerosil (Degusa and titanium oxide (TiO2 (Merk were prepared by melt compounding. Influence of nano-silica and titanium oxide on properties of the resulting nanocomposites was investigated by scanning electron microscopy (SEM, Fourier transform infrared spectroscopy (FTIR and atomic force microscopy (AFM. The possible interaction between nano-silica and titanium oxide particles with PET functional groups at bulk and surface was elucidated by transmission of FTIR-ATR spectroscopy. AFM studies of the resulting nanocomposites showed an increased surface roughness compared to pure PET. SEM images illustrated that nano-silica particles have tendency to migrate to the surface of the PET matrix much more than titanium oxide powder.

Mechanical and thermomechanical properties of polycarbonate-based polyurethane-silica nanocomposites

Directory of Open Access Journals (Sweden)

Rafał Poręba

2011-09-01

Full Text Available In this work aliphatic polycarbonate-based polyurethane-silica nanocomposites were synthesized and characterized. The influence of the type and of the concentration of nanofiller differing in average particle size (7 nm for Aerosil 380 and 40 nm for Nanosilica 999 on mechanical and thermomechanical properties was investigated. DMTA measurements showed that Nanosilica 999, irrespective of its concentration, slightly increased the value of the storage shear modulus G’ but Aerosil 380 brings about a nearly opposite effect, the shear modulus in the rubber region decreases with increasing filler content. Very high elongations at break ranging from 800% to more than 1000%, as well as high tensile strengths illustrate excellent ultimate tensile properties of the prepared samples. The best mechanical and thermomechanical properties were found for the sample filled with 0.5 wt.% of Nanosilica 999.

effect of number of rotor poles on ac losses of permanent magnet

African Journals Online (AJOL)

HOD

A study on permanent magnet (PM) eddy current and core losses of dual-stator PM machines is investigated in this paper. ... material in the retaining sleeves of surface-mounted ... rotor-pole numbers (13-poleand 14-pole in particular) ... Table 2: Optimized Machine Parameters. Number of rotor poles. 4. 5. 7. 8. 10. 11. 13. 14.

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)

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.

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

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

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%.

Influence of the absorptive part of the complex potential on the S-Matrix poles

International Nuclear Information System (INIS)

Grama, C.; Grama, N.; Zamfirescu, I

2001-01-01

Although the polology of the S-matrix has been extensively studied, it occurred that some aspects remained disputable in the case of complex central potential V(r)=gV(r), g in C . These aspects are related to the origin of the observed narrow Σ-hypernuclear states that have been interpreted by Gal, Toker and Alexander as states which correspond to S-matrix poles situated in the second k-plane quadrant. From the analytical properties of the S-matrix for a real potential it results that there is no pole in the first and second k-plane quadrants, except for the imaginary k-axis. By switching on the absorption the S-matrix poles for real potential can evolve into the second quadrant of the k-plane. A critical study of the Σ-hypernuclear states needs the analysis of the motion of the S-matrix poles in the k-plane for variable complex coupling strength g. Recently contradictory opinions relative to the S-matrix poles trajectories in the complex k-plane for a complex square potential occurred. According to some authors the poles in the second quadrant can occur either from bound state poles moving anticlockwise, or from virtual state poles and capture resonant state poles moving clockwise as the absorption is switched on. Dabrowski argues that the statement made by Gal et al, Bonetti et al and Oset et al concerning the movement of the virtual poles with increasing absorptive potential is in general not correct. Dabrowski relates the direction in which the pole moves when the potential absorption increases to the direction in which the pole moves with increasing the real part of the potential, without clarifying this last question. For example, two poles moving in opposite directions along the imaginary k-axis are associated by Dabrowski to the same state. This is a wrong result, because one should associate a single pole to each quantum state. The aim of our work is to study the influence of the absorptive part of the potential on the S-matrix poles for the non

VT Green Mountain Power Pole Data

Data.gov (United States)

Vermont Center for Geographic Information — (Link to Metadata) Green Mountain Power (GMP) pole and OVERHEAD linear distribution/sub-transmission model data. THE LINEAR DISTRIBUTION LAYER ONLY INCLUDES OVERHEAD...

Low equation, pion-nucleon scattering, and Castillejo-Dalitz-Dyson pole

International Nuclear Information System (INIS)

Nakano, K.; Nogami, Y.

1986-01-01

We examine the p-wave πN scattering at medium energies by means of the Low equation with a view to determining the form factor of the πN interaction. Solutions of the equation with and without a Castillejo-Dalitz-Dyson (CDD) pole are used. The solution with no CDD pole corresponds to the old Chew-Low model, whereas the one with a CDD pole corresponds to the quark version of the Chew-Low model. The πN interaction form factor is determined so that the Δ resonance is well reproduced. We find that the solution with a CDD pole leads to a softer form factor but is not as soft as those expected from the nucleon size in the quark model. Using the solutions and form factors thus determined, we also examine the pionic contributions to the nucleon magnetic moment and the nucleon mass

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

Double Trouble: A Rare Case of Bilateral Upper Pole Ureteropelvic Junction Obstruction

Directory of Open Access Journals (Sweden)

Craig A. Peters

2014-09-01

Full Text Available A 16-year-old girl presented with bilateral back pain caused by bilateral upper pole ureteropelvic junction obstructions; an extremely rare phenomenon. Bilateral robotically assisted upper pole pyeloplasties were preformed at the same setting with an excellent clinical response. Although rare, upper pole ureteropelvic junction obstruction is a defined entity that urologists should be aware of.

Poles near the thresholds in the coupled ΛN - ΣN system

International Nuclear Information System (INIS)

Yamamura, H.; Miyagawa, K.

1999-01-01

We find t-matrix poles near the ΣN threshold for the meson theoretical Nijmegen YN interactions including hard-core models. These poles are connected with the strength of the ΛN - ΣN coupling. We also observe antibound-state poles below the ΛN threshold which correlate with scattering lengths. Refs. 4, tabs. 2 (author)

Design of an adaptive pole assignment controller for steam generators and its experimental study

International Nuclear Information System (INIS)

Na, Man Gyun; No, Hee Cheon

1992-01-01

An adaptive observer is designed that both parameters and state variables of the steam generator are estimated simultaneously. A pole assignment controller is derived on the basis of the adaptive observer. The characteristics of the overall closed-loop control system can be expressed in terms of its poles, assigned poles. The troublesome tuning procedure of the P-I controller is reduced to the determination of the desired poles only. The proposed algorithm is compared with the conventional P-I controller through numerical simulation. Also, the adaptive pole assignment controller is studied experimentally by implementing it to the mock-up of the nuclear steam generator. The adaptive pole assignment controller shows better responses than the P-l controller does. (Author)

Field analysis and enhancement of multi-pole magnetic components fabricated on printed circuit board

International Nuclear Information System (INIS)

Chiu, K.-C.; Chen, C.-S.

2007-01-01

A multi-pole magnetic component magnetized with a fine magnetic pole pitch of less than 1 mm is very difficult to achieve by using traditional methods. Moreover, it requires a precise mechanical process and a complicated magnetization system. Different fine magnetic pole pitches of 300, 350 and 400 μm have been accomplished on 9-pole magnetic components through the printed circuit board (PCB) manufacturing technology. Additionally, another fine magnetic pole pitch of 500 μm was also fabricated on a dual-layered (DL) wire circuit structure to investigate the field enhancement. After measurements, a gain factor of 1.37 was obtained in the field strength. The field variations among different magnetic pole pitches were analyzed in this paper

The ionic conductivity, mechanical performance and morphology of two-phase structural electrolytes based on polyethylene glycol, epoxy resin and nano-silica

Energy Technology Data Exchange (ETDEWEB)

Feng, Qihang; Yang, Jiping, E-mail: jyang08@163.com; Yu, Yalin; Tian, Fangyu; Zhang, Boming; Feng, Mengjie; Wang, Shubin

2017-05-15

Highlights: • Structural electrolytes based on PEG-epoxy resins were prepared. • Factors of influencing ionic conductivity and mechanical properties were studied. • Co-continuous morphology was benefit for improved structural electrolyte property. • Efficiently optimized multifunctional electrolyte performance was achieved. - Abstract: As one of significant parts of structural power composites, structural electrolytes have desirable mechanical properties like structural resins while integrating enough ionic conductivity to work as electrolytes. Here, a series of polyethylene glycol (PEG)-epoxy-based electrolytes filled with nano-silica were prepared. The ionic conductivity and mechanical performance were studied as functions of PEG content, lithium salt concentration, nano-silica content and different curing agents. It was found that, PEG-600 and PEG-2000 content in the epoxy electrolyte system had a significant effect on their ionic conductivity. Furthermore, increasing the nano-silica content in the system induced increased ionic conductivity, decreased glass transition temperature and mechanical properties, and more interconnected irregular network in the cured systems. The introduction of rigid m-xylylenediamine resulted in enhanced mechanical properties and reasonably decreased ionic conductivity. As a result, these two-phase epoxy structural electrolytes have great potential to be used in the multifunctional energy storage devices.

Fabrication of amorphous silica nanowires via oxygen plasma treatment of polymers on silicon

Science.gov (United States)

Chen, Zhuojie; She, Didi; Chen, Qinghua; Li, Yanmei; Wu, Wengang

2018-02-01

We demonstrate a facile non-catalytic method of fabricating silica nanowires at room temperature. Different polymers including photoresists, parylene C and polystyrene are patterned into pedestals on the silicon substrates. The silica nanowires are obtained via the oxygen plasma treatment on those pedestals. Compared to traditional strategies of silica nanowire fabrication, this method is much simpler and low-cost. Through designing the proper initial patterns and plasma process parameters, the method can be used to fabricate various regiment nano-scale silica structure arrays in any laboratory with a regular oxygen-plasma-based cleaner or reactive-ion-etching equipment.

The self-consistent dynamic pole tide in non-global oceans

Science.gov (United States)

Dickman, S. R.

1988-01-01

The dynamic pole tide is determined by solving Laplace tide equations which take into account the presence of continents in oceans, oceanic self-gravitation and loading, and mantle elasticity. Dynamical effects are found to be only mild. It is shown that the dynamical pole tide contributes about one day more to the Chandler period than a static pole tide would, and dissipates wobble energy at a very weak rate. It is noted that, depending on the wobble period predicted for an oceanless elastic earth, mantle anelasticity at low frequencies may nevertheless contribute negligibly to the Chandler period.

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.

Duty cycle dependence of a periodically poled LiNbO3-based electro-optic Solc filter.

Science.gov (United States)

Rabia, Eyal; Arie, Ady

2006-01-20

We demonstrate that the performance of a periodically poled LiNbO3- (PPLN-) based electro-optic Solc filter is dependent on the duty cycle of the crystal. This may limit the performance of the device for applications such as add-drop filtering and switching, owing to the deterioration of the extinction ratio. It is shown that by adding a retarder to the Solc filter it is possible to improve the extinction ratio; thus the dependence of the filter on the duty cycle can be reduced. Using Jones calculus, we analyzed the effect of a variable retarder that can also be rotated on the extinction ratio. We experimentally observed a 6 dB increase in the extinction ratio when we used a half-wavelength retarder.

Fabrication of poly(o-anisidine) coated silica core-shell microspheres and their electrorheological response

Science.gov (United States)

Lee, Chul Joo; Choi, Hyoung Jin

2017-11-01

In this work, silica/poly(o-anisidine) (POA) core-shell structured microspheres were synthesized by coating the silica core surface with POA with a help of a chemical grafting agent, N-[(3-trimethoxylsilyl)-propyl] aniline. The synthesized silica microspheres were then applied as a polymer/inorganic composite particle-based electrorheological (ER) fluid. The morphology of the silica/POA microspheres was examined by using both transmission electron microscopy and scanning electron microscopy, while their thermal properties and chemical structure were checked by thermogravimetric analysis and Fourier-transform infrared spectroscopy, respectively. The ER properties of the silica/POA particle-based ER fluid were examined by using a Couette-type rotational rheometer equipped with a high-voltage power supplier and analyzed by the Bingham model and modified Mason number. In order to obtain additional information about the electrical polarization properties, the dielectric spectra were measured by an LCR meter and fitted by using the Cole-Cole equation. Furthermore, suspension stability of the ER fluid was tested using Turbiscan.

Real-time digital signal recovery for a multi-pole low-pass transfer function system.

Science.gov (United States)

Lee, Jhinhwan

2017-08-01

In order to solve the problems of waveform distortion and signal delay by many physical and electrical systems with multi-pole linear low-pass transfer characteristics, a simple digital-signal-processing (DSP)-based method of real-time recovery of the original source waveform from the distorted output waveform is proposed. A mathematical analysis on the convolution kernel representation of the single-pole low-pass transfer function shows that the original source waveform can be accurately recovered in real time using a particular moving average algorithm applied on the input stream of the distorted waveform, which can also significantly reduce the overall delay time constant. This method is generalized for multi-pole low-pass systems and has noise characteristics of the inverse of the low-pass filter characteristics. This method can be applied to most sensors and amplifiers operating close to their frequency response limits to improve the overall performance of data acquisition systems and digital feedback control systems.

Polymer/silica hybrid waveguide temperature sensor based on asymmetric Mach-Zehnder interferometer

Science.gov (United States)

Niu, Donghai; Wang, Xibin; Sun, Shiqi; Jiang, Minghui; Xu, Qiang; Wang, Fei; Wu, Yuanda; Zhang, Daming

2018-04-01

A highly sensitive waveguide temperature sensor based on asymmetric Mach-Zehnder interferometer was designed and experimentally demonstrated. The interferometer is based on the polymer/silica hybrid waveguide structure, and Norland Optical Adhesive 73 (NOA 73) was employed as the waveguide core to enhance the temperature sensitivity. The influence of the different length differences between the two interferometer arms on the sensitivity of the sensor was systemically studied. It is shown that the maximum temperature sensitivity of -431 pm °C-1 can be obtained in the range of 25 °C-75 °C, while the length difference is 92 μm. Moreover, the temperature sensitivity contributions from different core materials were also investigated experimentally. It is shown that the waveguide material and microstructure of the device have significant influences on the sensitivity of the waveguide temperature sensor.

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

Dual soft-template system based on colloidal chemistry for the synthesis of hollow mesoporous silica nanoparticles.

Science.gov (United States)

Li, Yunqi; Bastakoti, Bishnu Prasad; Imura, Masataka; Tang, Jing; Aldalbahi, Ali; Torad, Nagy L; Yamauchi, Yusuke

2015-04-20

A new dual soft-template system comprising the asymmetric triblock copolymer poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) is used to synthesize hollow mesoporous silica (HMS) nanoparticles with a center void of around 17 nm. The stable PS-b-P2VP-b-PEO polymeric micelle serves as a template to form the hollow interior, while the CTAB surfactant serves as a template to form mesopores in the shells. The P2VP blocks on the polymeric micelles can interact with positively charged CTA(+) ions via negatively charged hydrolyzed silica species. Thus, dual soft-templates clearly have different roles for the preparation of the HMS nanoparticles. Interestingly, the thicknesses of the mesoporous shell are tunable by varying the amounts of TEOS and CTAB. This study provides new insight on the preparation of mesoporous materials based on colloidal chemistry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Cytotoxic evaluation of hydroxyapatite-filled and silica/hydroxyapatite-filled acrylate-based restorative composite resins: An in vitro study.

Science.gov (United States)

Chadda, Harshita; Naveen, Sangeetha Vasudevaraj; Mohan, Saktiswaren; Satapathy, Bhabani K; Ray, Alok R; Kamarul, Tunku

2016-07-01

Although the physical and mechanical properties of hydroxyapatite-filled dental restorative composite resins have been examined, the biocompatibility of these materials has not been studied in detail. The purpose of this in vitro study was to analyze the toxicity of acrylate-based restorative composite resins filled with hydroxyapatite and a silica/hydroxyapatite combination. Five different restorative materials based on bisphenol A-glycidyl methacrylate (bis-GMA) and tri-ethylene glycol dimethacrylate (TEGDMA) were developed: unfilled (H0), hydroxyapatite-filled (H30, H50), and silica/hydroxyapatite-filled (SH30, SH50) composite resins. These were tested for in vitro cytotoxicity by using human bone marrow mesenchymal stromal cells. Surface morphology, elemental composition, and functional groups were determined by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), and Fourier-transformed infrared spectroscopy (FTIR). The spectra normalization, baseline corrections, and peak integration were carried out by OPUS v4.0 software. Both in vitro cytotoxicity results and SEM analysis indicated that the composite resins developed were nontoxic and supported cell adherence. Elemental analysis with EDX revealed the presence of carbon, oxygen, calcium, silicon, and gold, while the presence of methacrylate, hydroxyl, and methylene functional groups was confirmed through FTIR analysis. The characterization and compatibility studies showed that these hydroxyapatite-filled and silica/hydroxyapatite-filled bis-GMA/TEGDMA-based restorative composite resins are nontoxic to human bone marrow mesenchymal stromal cells and show a favorable biologic response, making them potential biomaterials. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

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...

Iron Pole Shape Optimization of IPM Motors Using an Integrated Method

Directory of Open Access Journals (Sweden)

JABBARI, A.

2010-02-01

Full Text Available An iron pole shape optimization method to reduce cogging torque in Interior Permanent Magnet (IPM motors is developed by using the reduced basis technique coupled by finite element and design of experiments methods. Objective function is defined as the minimum cogging torque. The experimental design of Taguchi method is used to build the approximation model and to perform optimization. This method is demonstrated on the rotor pole shape optimization of a 4-poles/24-slots IPM motor.

Sun's pole-equator flux differences

Energy Technology Data Exchange (ETDEWEB)

Belvedere, G [Istituto di Astronomia dell' Universita di Catania, Italy; Paterno, L [Osservatorio Astrofisico di Catania, Italy

1977-04-01

The possibility that large flux differences between the poles and the equator at the bottom of the solar convective zone are compatible with the small differences observed at the surface is studied. The consequences of increasing the depth of the convective zone due to overshooting are explored. A Boussinesq model is used for the convective zone and it is assumed that the interaction of the global convection with rotation is modelled through a convective flux coefficient whose perturbed part is proportional to the local Taylor number. The numerical integration of the equations of motion and energy shows that coexistence between large pole-equator flux differences at the bottom and small ones at the surface is possible if the solar convective zone extends to a depth of 0.4 R(Sun). The angular velocity distribution inside the convective zone is in agreement with the ..cap alpha omega..-dynamo theories of the solar cycle.

INNOVATIVE CLUSTER OR COMPETITIVENESS POLE?

Directory of Open Access Journals (Sweden)

Liliana Scutaru

2015-02-01

Full Text Available The paper analyzes the situation of clusters in Romania and their areas of activity and innovation in entrepreneurship Romanian state. It is made also a territorial distribution of clusters on the eight regions. The findings lead to the conclusion that there are some clusters that have the vocation to become poles of competitiveness in areas such as renewable energy, automotive, electronics, health, biotechnology, mechatronics or ICT (Information and Communication Technology which represent the resources for future of the Romanian economy. Regarding the degree of innovation of Romanian Small and Medium Enterprises (SMEs, the level is relatively modest, 30.8% of all enterprises being innovative. If we were to answer the question the title suggests, we would say "yes" to both since the innovative cluster as well as the competitiveness pole promotes par excellence, innovation through study, research and stimulation of creativity. And this is more than enough to support economic growth of Romania and maintain the competitiveness worldwide.

Circularly photostimulated electrogyration in europium- and terbium-doped GaN nanocrystals embedded in a silica xerogel matrix

International Nuclear Information System (INIS)

Kityk, I V; Nyk, M; Strek, W; Jablonski, J M; Misiewicz, J

2005-01-01

Circularly polarized optical poling was proposed and discovered for GaN nanocrystallites embedded in a silica xerogel matrix. The method consists of the creation of screw-like polarization of the medium during the interaction of two circularly polarized coherent bicolour beams. It was shown that doping of the GaN nanocrystallites by Tb 3+ and Eu 3+ ions leads to substantial enhancement of the electrogyration. The effect observed is a consequence of the superposition of nanoconfined effects and the contribution of the localized rare-earth 4f levels. The role of the anharmonic electron-phonon interaction is discussed. The photoluminescence and cathodoluminescence spectra of the GaN composites were investigated. It was demonstrated that the Eu-doped nanocrystallites give a substantially higher effect of the electrogyration compared to the Tb-doped and non-doped ones

POLE proofreading mutations elicit an anti-tumor immune response in endometrial cancer

Science.gov (United States)

van Gool, Inge C; Eggink, Florine A; Freeman-Mills, Luke; Stelloo, Ellen; Marchi, Emanuele; de Bruyn, Marco; Palles, Claire; Nout, Remi A; de Kroon, Cor D; Osse, Elisabeth M; Klenerman, Paul; Creutzberg, Carien L; Tomlinson, Ian PM; Smit, Vincent THBM; Nijman, Hans W

2015-01-01

Purpose Recent studies have shown that 7-12% of endometrial cancers (ECs) are ultramutated due to somatic mutation in the proofreading exonuclease domain of the DNA replicase POLE. Interestingly, these tumors have an excellent prognosis. In view of the emerging data linking mutation burden, immune response and clinical outcome in cancer, we investigated whether POLE-mutant ECs showed evidence of increased immunogenicity. Experimental design We examined immune infiltration and activation according to tumor POLE proofreading mutation in a molecularly defined EC cohort including 47 POLE-mutant tumors. We sought to confirm our results by analysis of RNAseq data from the TCGA EC series and used the same series to examine whether differences in immune infiltration could be explained by an enrichment of immunogenic neoepitopes in POLE-mutant ECs. Results Compared to other ECs, POLE-mutants displayed an enhanced cytotoxic T cell response, evidenced by increased numbers of CD8+ tumor infiltrating lymphocytes and CD8A expression, enrichment for a tumor-infiltrating T cell gene signature, and strong upregulation of the T cell cytotoxic differentiation and effector markers T-bet, Eomes, IFNG, PRF and granzyme B. This was accompanied by upregulation of T cell exhaustion markers, consistent with chronic antigen exposure. In-silico analysis confirmed that POLE-mutant cancers are predicted to display more antigenic neo-epitopes than other ECs, providing a potential explanation for our findings. Conclusions Ultramutated POLE proofreading-mutant ECs are characterized by a robust intratumoral T cell response, which correlates with, and may be caused by an enrichment of antigenic neo-peptides. Our study provides a plausible mechanism for the excellent prognosis of these cancers. PMID:25878334

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.

Personaliotsinguteenust tasub kasutada siis, kui rahaline kokkuhoid pole esmane / Merike Lees

Index Scriptorium Estoniae

Lees, Merike, 1976-

2006-01-01

Ilmunud ka: Delovõje Vedomosti 1. veebr. lk. 13. Personaliotsinguteenuse kasutamine on õigustatud siis, kui ettevõttes pole personalispetsialisti ning rahaline kokkuhoid pole esmatähtis. Kommenteerivad: Eero Erastus, Madis Sander ja Marti Rehemaa

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.

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

Real-time power angle determination of salient-pole synchronous machine based on air gap measurements

Energy Technology Data Exchange (ETDEWEB)

Despalatovic, Marin; Jadric, Martin; Terzic, Bozo [FESB University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, R. Boskovica bb, 21000 Split (Croatia)

2008-11-15

This paper presents a new method for the real-time power angle determination of the salient-pole synchronous machines. This method is based on the terminal voltage and air gap measurements, which are the common features of the hydroturbine generator monitoring system. The raw signal of the air gap sensor is used to detect the rotor displacement with reference to the fundamental component of the terminal voltage. First, the algorithm developed for the real-time power angle determination is tested using the synthetic data obtained by the standard machine model simulation. Thereafter, the experimental investigation is carried out on the 26 MVA utility generator. The validity of the method is verified by comparing with another method, which is based on a tooth gear mounted on the rotor shaft. The proposed real-time algorithm has an adequate accuracy and needs a very short processing time. For applications that do not require real-time processing, such as the estimation of the synchronous machine parameters, the accuracy is additionally increased by applying an off-line data-processing algorithm. (author)

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

KAUST Repository

Fernandes, Nikhil J; Akbarzadeh, Johanna; Peterlik, Herwig; Giannelis, Emmanuel P

2013-01-01

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

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

KAUST Repository

Fernandes, Nikhil J

2013-02-04

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

Effect of Dangling Bonds on De-Poling Time for Polymeric Electric Field Optical Sensors

Directory of Open Access Journals (Sweden)

Amir R. Ali

2018-01-01

Full Text Available This paper investigates the possible chemical changes in polydimethylsiloxane (PDMS caused by two different techniques of fabrication for ultra-sensitive electric field optical sensors. The sensing element is a micro-sphere made from 60:1 PDMS (60 parts base silicon elastomer to one part polymer curing agent by volume. The measurement principle is based on the morphology dependent resonances (MDR shifts of the micro-sphere. We present the effects of curing and poling of polymer micro-spheres used as optical sensors. The degree of curing leads to changes in the de-poling time which results from dangling bonds in the polymeric chains. Consequently, the longevity of the sensitivity of the sensor can extended by two orders of magnitude. An analysis is carried out along with preliminary experiments to investigate that behavior.

Clusters of cyclones encircling Jupiter’s poles

Science.gov (United States)

Adriani, A.; Mura, A.; Orton, G.; Hansen, C.; Altieri, F.; Moriconi, M. L.; Rogers, J.; Eichstädt, G.; Momary, T.; Ingersoll, A. P.; Filacchione, G.; Sindoni, G.; Tabataba-Vakili, F.; Dinelli, B. M.; Fabiano, F.; Bolton, S. J.; Connerney, J. E. P.; Atreya, S. K.; Lunine, J. I.; Tosi, F.; Migliorini, A.; Grassi, D.; Piccioni, G.; Noschese, R.; Cicchetti, A.; Plainaki, C.; Olivieri, A.; O’Neill, M. E.; Turrini, D.; Stefani, S.; Sordini, R.; Amoroso, M.

2018-03-01

The familiar axisymmetric zones and belts that characterize Jupiter’s weather system at lower latitudes give way to pervasive cyclonic activity at higher latitudes. Two-dimensional turbulence in combination with the Coriolis β-effect (that is, the large meridionally varying Coriolis force on the giant planets of the Solar System) produces alternating zonal flows. The zonal flows weaken with rising latitude so that a transition between equatorial jets and polar turbulence on Jupiter can occur. Simulations with shallow-water models of giant planets support this transition by producing both alternating flows near the equator and circumpolar cyclones near the poles. Jovian polar regions are not visible from Earth owing to Jupiter’s low axial tilt, and were poorly characterized by previous missions because the trajectories of these missions did not venture far from Jupiter’s equatorial plane. Here we report that visible and infrared images obtained from above each pole by the Juno spacecraft during its first five orbits reveal persistent polygonal patterns of large cyclones. In the north, eight circumpolar cyclones are observed about a single polar cyclone; in the south, one polar cyclone is encircled by five circumpolar cyclones. Cyclonic circulation is established via time-lapse imagery obtained over intervals ranging from 20 minutes to 4 hours. Although migration of cyclones towards the pole might be expected as a consequence of the Coriolis β-effect, by which cyclonic vortices naturally drift towards the rotational pole, the configuration of the cyclones is without precedent on other planets (including Saturn’s polar hexagonal features). The manner in which the cyclones persist without merging and the process by which they evolve to their current configuration are unknown.

TERRITORIAL COHESION AND LOCAL DEVELOPMENT USING EUROPEAN STRUCTURAL AND COHESION FUNDS AT THE LEVEL OF GROWTH POLES – CASE STUDY GROWTH POLE BRASOV

Directory of Open Access Journals (Sweden)

Aida Petronela CATANA

2015-08-01

Full Text Available The growth poles were established in Romania in 2008 as centers for urban development in compliance with European and national policies and they include an urban nucleus and its rural surroundings.  According to the legal framework, for each of the growth poles an Integrated Development Plan should be adopted as basis for European Structural and Cohesion Funds investments. This is a new document in addition to local development plans/strategies of the local communities or counties and regional development plans. From another point of view, the growth poles are representing teritorial units which have to assure territorial cohesion for its urban and rural administrative units. Into this respect, there are different spatial planning documents which have to be followed by the territorial and administrative units, according to the Romanian legislation. Beyond these, there are rules and compulsory criterias for accessing European Structural and Cohesion funds the problems being faced by the associations established by local communities in order to manage the growth poles’s areas. Taking into account all these, we may say that growth poles are the crossing points for different policies translated into plans and operational programmes’s criterias for getting ESC Funds.

Immobilization of Lactobacillus rhamnosus in mesoporous silica-based material: An efficiency continuous cell-recycle fermentation system for lactic acid production.

Science.gov (United States)

Zhao, Zijian; Xie, Xiaona; Wang, Zhi; Tao, Yanchun; Niu, Xuedun; Huang, Xuri; Liu, Li; Li, Zhengqiang

2016-06-01

Lactic acid bacteria immobilization methods have been widely used for lactic acid production. Until now, the most common immobilization matrix used is calcium alginate. However, Ca-alginate gel disintegrated during lactic acid fermentation. To overcome this deficiency, we developed an immobilization method in which Lactobacillus rhamnosus cells were successfully encapsulated into an ordered mesoporous silica-based material under mild conditions with a high immobilization efficiency of 78.77% by using elemental analysis. We also optimized the cultivation conditions of the immobilized L. rhamnosus and obtained a high glucose conversion yield of 92.4%. Furthermore, L. rhamnosus encapsulated in mesoporous silica-based material exhibited operational stability during repeated fermentation processes and no decrease in lactic acid production up to 8 repeated batches. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

The pH-dependant attachment of ceria nanoparticles to silica using surface analytical techniques

International Nuclear Information System (INIS)

Dawkins, K.; Rudyk, B.W.; Xu, Z.; Cadien, K.

2015-01-01

Graphical abstract: - Highlights: • A model for interaction between ceria nanoparticles and silica surfaces is proposed. • Proposed model investigated using zeta potential measurements and XPS. • Surface contamination is minimized at higher slurry pH levels. • High-resolution Ce 3d XPS and surface composition measured at different pH levels. • Variations in ceria contamination on silica surfaces via SEM and AES are studied. - Abstract: The adhesion and removal of ceria particles to a silica surface was investigated with the use of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and auger electron spectroscopy (AES) measurements. A model is presented based on electrophoretic mobility measurements of ceria slurry and silica particles at different pH's. XPS results show that at acidic pH values, ceria is present on silica surfaces, but at alkaline pH values, far less ceria is present, or no ceria is present in the extreme case. SEM results corroborated the XPS results showing uniform distribution of ceria particles on silica surface at pH 6 while a clean silica surface is observed at pH 12. However, SEM images show agglomeration of ceria particles occurring at the isoelectric point of ceria at ∼pH 9.6. High resolution Ce 3d XPS analysis indicates that ceria present on the surface is composed ∼31% Ce(III) and ∼69% Ce(IV). AES mapping done at specific points on the silica surface validated both XPS and SEM results. Based on XPS, SEM and AES analyses, it is clear that an alkaline pH is necessary to minimize particulate contamination of silica surface by ceria

Russians, Jews, and Poles: Russification and Antisemitism 1881-1914

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Theodor R. Weeks

2012-07-01

Full Text Available Relations between Poles and Jews deteriorated significantly in the three decades leading up to World War I. Many reasons for this phenomenon can be given, for example: economic competition, a general atmosphere of acute nationalism, increased migration, perceived threats to traditional forms of life and religion. Exacerbating all of these factors, however, was the fact of Polish statelessness and the extreme sensitivity of Poles to perceived threats to their culture and nation. In particular within the Russian Empire, Poles perceived the very future of their nation at risk. In such circumstances the continued existence of Jewish cultural difference combined with the development of specifically Jewish forms of national awakening (e.g., the Bund and Zionism were understood by many in Polish society as ingratitude and collaboration with the Russian occupier

Investigation of experimental pole-figure errors by simulation of individual spectra

International Nuclear Information System (INIS)

Lychagina, T. A.; Nikolaev, D. I.

2007-01-01

The errors in measuring the crystallographic texture described by pole figures are studied. A set of diffraction spectra for a sample of the MA2-1 alloy (Mg + 4.5% Al + 1% Zn) are measured, simulation of individual spectra on the basis of which the pole figures were obtained is performed, and their errors are determined. The conclusion about the possibility of determining the effect of errors of the diffraction peak half-width on the pole figure errors that was drawn in our previous studies is confirmed

Adsorption and Desorption of Chemical Warfare Agent Simulants on Silica Surfaces with Hydrophobic Coating

International Nuclear Information System (INIS)

Park, Eun Ji; Kim, Young Dok

2013-01-01

Aim of our study is finding adsorbents suitable for pre-concentration of chemical warfare agents (CWAs). We considered Tenax, bare silica and polydimethylsiloxane (PDMS)-coated silica as adsorbents for dimethyl methylphosphonate (DMMP) and dipropylene glycol methyl ether (DPGME). Tenax showed lower thermal stability, and therefore, desorption of CWA simulants and decomposition of Tenax took place simultaneously. Silica-based adsorbents showed higher thermal stabilities than Tenax. A drawback of silica was that adsorption of CWA simulant (DMMP) was significantly reduced by pre-treatment of the adsorbents with humid air. In the case of PDMS-coated silica, influence of humidity for CWA simulant adsorption was less pronounced due to the hydrophobic nature of PDMS-coating. We propose that PDMS-coated silica can be of potential importance as adsorbent of CWAs for their pre-concentration, which can facilitate detection of these CWAs

Adsorption and Desorption of Chemical Warfare Agent Simulants on Silica Surfaces with Hydrophobic Coating

Energy Technology Data Exchange (ETDEWEB)

Park, Eun Ji; Kim, Young Dok [Sungkyunkwan Univ., Suwon (Korea, Republic of)

2013-07-15

Aim of our study is finding adsorbents suitable for pre-concentration of chemical warfare agents (CWAs). We considered Tenax, bare silica and polydimethylsiloxane (PDMS)-coated silica as adsorbents for dimethyl methylphosphonate (DMMP) and dipropylene glycol methyl ether (DPGME). Tenax showed lower thermal stability, and therefore, desorption of CWA simulants and decomposition of Tenax took place simultaneously. Silica-based adsorbents showed higher thermal stabilities than Tenax. A drawback of silica was that adsorption of CWA simulant (DMMP) was significantly reduced by pre-treatment of the adsorbents with humid air. In the case of PDMS-coated silica, influence of humidity for CWA simulant adsorption was less pronounced due to the hydrophobic nature of PDMS-coating. We propose that PDMS-coated silica can be of potential importance as adsorbent of CWAs for their pre-concentration, which can facilitate detection of these CWAs.

Investigation Effects of Narrowing Rotor Pole Embrace to Efficiency and Cogging Torque at PM BLDC Motor

Directory of Open Access Journals (Sweden)

Cemil Ocak

2016-02-01

Full Text Available Engineers think that pole embrace size of a PM BLDC motor affects directly the efficiency and the torque. Dealing with theexperimental research, in the studywe have investigated the effects of narrowing rotor pole embrace step by step by changing sizes parametrically. By doing so, high efficiency and low cogging torque would have been obtained for a 20 W PM BLDC motor. In order to do this,pole arc to pole pitch ratio of magnets at the rotor poles has been changed parametrically (0.5 to 1 by genetic algorithm methodfirst. Then the electromagnetic field dispersions, output parameters of the motor, new rotor constructions have been obtained; and new pole embrace has been derived from the variation of pole arc to pole pitch ratio. We have also calculatedthe magnetic flux distribution, output power, torque, cogging torque and efficiency values analytically and the effects of new pole embrace to motor efficiency and torque have been simulated. The developed 18 slots, 6 poles, surface mounted inner runner configuration rotor machine is proposed as to be used insmall dentistry apparatus.

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.

Perhydropolysilazane derived silica coating protecting Kapton from atomic oxygen attack

Energy Technology Data Exchange (ETDEWEB)

Hu Longfei [China Academy of Aerospace Aerodynamics, Beijing 100074 (China); Li Meishuan, E-mail: mshli@imr.ac.cn [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Xu Caihong; Luo Yongming [Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China)

2011-11-30

By using surface sol-gel method with perhydropolysilazane (PHPS) as a precursor, a silica coating was prepared on a Kapton substrate as an atomic oxygen (AO) protective coating. The AO exposure tests were conducted in a ground-based simulator. It is found that the erosion yield of Kapton decreases by about three orders of magnitude after the superficial application of the coating. After AO exposure, the surface of the coating is smooth and uniform, no surface shrinkage induced cracks or undercutting erosion are observed. This is because that during AO exposure the PHPS is oxidized directly to form SiO{sub 2} without through intermediate reaction processes, the surface shrinkage and cracking tendency are prohibited. Meanwhile, this PHPS derived silica coating also presents self-healing effect due to the oxidation of free Si. Compared with other kinds of silica or organic polymer coatings, this PHPS derived silica coating exhibits a superior AO erosion resistance.

Perhydropolysilazane derived silica coating protecting Kapton from atomic oxygen attack

International Nuclear Information System (INIS)

Hu Longfei; Li Meishuan; Xu Caihong; Luo Yongming

2011-01-01

By using surface sol–gel method with perhydropolysilazane (PHPS) as a precursor, a silica coating was prepared on a Kapton substrate as an atomic oxygen (AO) protective coating. The AO exposure tests were conducted in a ground-based simulator. It is found that the erosion yield of Kapton decreases by about three orders of magnitude after the superficial application of the coating. After AO exposure, the surface of the coating is smooth and uniform, no surface shrinkage induced cracks or undercutting erosion are observed. This is because that during AO exposure the PHPS is oxidized directly to form SiO 2 without through intermediate reaction processes, the surface shrinkage and cracking tendency are prohibited. Meanwhile, this PHPS derived silica coating also presents self-healing effect due to the oxidation of free Si. Compared with other kinds of silica or organic polymer coatings, this PHPS derived silica coating exhibits a superior AO erosion resistance.

Study of interaction in silica glass via model potential approach

Science.gov (United States)

Mann, Sarita; Rani, Pooja

2016-05-01

Silica is one of the most commonly encountered substances in daily life and in electronics industry. Crystalline SiO2 (in several forms: quartz, cristobalite, tridymite) is an important constituent of many minerals and gemstones, both in pure form and mixed with related oxides. Cohesive energy of amorphous SiO2 has been investigated via intermolecular potentials i.e weak Van der Waals interaction and Morse type short-range interaction. We suggest a simple atom-atom based Van der Waals as well as Morse potential to find cohesive energy of glass. It has been found that the study of silica structure using two different model potentials is significantly different. Van der Waals potential is too weak (P.E =0.142eV/molecule) to describe the interaction between silica molecules. Morse potential is a strong potential, earlier given for intramolecular bonding, but if applied for intermolecular bonding, it gives a value of P.E (=-21.92eV/molecule) to appropriately describe the structure of silica.

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

Synthesis and characterization of a new material based on porous silica-Chemically immobilized C,N-pyridylpyrazole for heavy metals adsorption

Energy Technology Data Exchange (ETDEWEB)

Radi, Smaail [Laboratoire de Chimie Organique, Macromoleculaire et Produits Naturels, Departement de Chimie, Faculte des Sciences, Universite Mohamed 1er, BP 524, 60 000 Oujda (Morocco)], E-mail: radi_smaail@yahoo.fr; Attayibat, Ahmed [Laboratoire de Chimie Organique, Macromoleculaire et Produits Naturels, Departement de Chimie, Faculte des Sciences, Universite Mohamed 1er, BP 524, 60 000 Oujda (Morocco); Lekchiri, Yahya [Laboratoire de Biochimie, Departement de Biologie, Faculte des Sciences, Universite Mohamed 1er, BP 524, 60 000 Oujda (Morocco); Ramdani, Abdelkrim [Laboratoire de Chimie Organique, Macromoleculaire et Produits Naturels, Departement de Chimie, Faculte des Sciences, Universite Mohamed 1er, BP 524, 60 000 Oujda (Morocco); Bacquet, Maryse [Laboratoire de Chimie Macromoleculaire, Universite des Sciences et Technologies de Lille, 59655 Villeneuve d' Ascq (France)

2008-10-15

The immobilization of C,N-pyridylpyrazole on the surface of epoxy group containing silica gel phase for the formation of a newly synthesized material based on porous silica-bound C,N-pyridylpyrazole (SGPP) is described. The surface modification was characterized by {sup 13}C NMR of solid sample, elemental analysis and infrared spectra and was studied and evaluated by determination of the surface area using the BET equation, the adsorption and desorption capability using the isotherm of nitrogen and BJH pore sizes, respectively. The new material exhibits good thermal stability determined by thermogravimetry curves. The synthesized material was utilised in column and batch methods for separation and trace extraction of (Hg{sup 2+}, Cd{sup 2+}, Pb{sup 2+}, Cu{sup 2+}, Zn{sup 2+}, K{sup +}, Na{sup +} and Li{sup +}) and compared to results of classical liquid-liquid extraction with the unbound C,N-pyridylpyrazole compound. The grafting at the surface of silica does not affect complexing properties of the ligand and the material exhibits a high selectivity toward Hg(II)

Hydrophilic nano-silica coating agents with platinum and diamond nanoparticles for denture base materials.

Science.gov (United States)

Yoshizaki, Taro; Akiba, Norihisa; Inokoshi, Masanao; Shimada, Masayuki; Minakuchi, Shunsuke

2017-05-31

Preventing microorganisms from adhering to the denture surface is important for ensuring the systemic health of elderly denture wearers. Silica coating agents provide high hydrophilicity but lack durability. This study investigated solutions to improve the durability of the coating layer, determine an appropriate solid content concentration of SiO 2 in the silica coating agent, and evaluate the effect of adding platinum (Pt) and diamond nanoparticles (ND) to the agent. Five coating agents were prepared with different SiO 2 concentrations with/without Pt and ND additives. The contact angle was measured, and the brush-wear test was performed. Scanning electron microscopy was used to investigate the silica coating layer. The appropriate concentration of SiO 2 was found to be 0.5-0.75 wt%. The coating agents with additives showed significantly high hydrophilicity immediately after coating and after the brush-wear test. The coating agents with/without additives formed a durable coating layer even after the brush-wear test.

Cellular effects and gene expression after exposure to amorphous silica nanoparticles in vitro

DEFF Research Database (Denmark)

Foldbjerg, Rasmus; Beer, Christiane; Wang, Jing

Much of the concerns regarding engineered NP toxicity are based on knowledge from previous studies on ambient and environmental particles. E.g., the effects of exposure to silica dust particles have been studied intensively due to the carcinogenicity of crystalline silica. However, the increasing...

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

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.

Optimizing detection of road furniture (pole-like object in Mobile Laser Scanner data

Directory of Open Access Journals (Sweden)

D. Li

2013-10-01

Full Text Available Due to the road safety problem is becoming more and more serious recent years, existing road safety assessment by using automatic method is necessary. Meanwhile, since the pole-like objects have large effect on road safety and are in high demand as facilities to be managed, the automatic pole-like objects extraction is becoming a hot issue. As a result, a robust, quick and automatic pole-like object detection algorithm in MLS data is proposed in this paper. Two datasets are tested to show performance of the proposed algorithm, it demonstrates that it is feasible to detect tree with an overall accuracy of over 92% and other pole-like object of 72% in dataset A and 82% of tree points and 75% of other pole points in dataset B.

A disposable biosensor based on immobilization of laccase with silica spheres on the MWCNTs-doped screen-printed electrode

Directory of Open Access Journals (Sweden)

Li Yuanting

2012-09-01

Full Text Available Abstract Background Biosensors have attracted increasing attention as reliable analytical instruments in in situ monitoring of public health and environmental pollution. For enzyme-based biosensors, the stabilization of enzymatic activity on the biological recognition element is of great importance. It is generally acknowledged that an effective immobilization technique is a key step to achieve the construction quality of biosensors. Results A novel disposable biosensor was constructed by immobilizing laccase (Lac with silica spheres on the surface of multi-walled carbon nanotubes (MWCNTs-doped screen-printed electrode (SPE. Then, it was characterized in morphology and electrochemical properties by scanning electron microscopy (SEM and cyclic voltammetry (CV. The characterization results indicated that a high loading of Lac and a good electrocatalytic activity could be obtained, attributing to the porous structure, large specific area and good biocompatibility of silica spheres and MWCNTs. Furthermore, the electrochemical sensing properties of the constructed biosensor were investigated by choosing dopamine (DA as the typical model of phenolic compounds. It was shown that the biosensor displays a good linearity in the range from 1.3 to 85.5 μM with a detection limit of 0.42 μM (S/N = 3, and the Michaelis-Menten constant (Kmapp was calculated to be 3.78 μM. Conclusion The immobilization of Lac was successfully achieved with silica spheres to construct a disposable biosensor on the MWCNTs-doped SPE (MWCNTs/SPE. This biosensor could determine DA based on a non-oxidative mechanism in a rapid, selective and sensitive way. Besides, the developed biosensor could retain high enzymatic activity and possess good stability without cross-linking reagents. The proposed immobilization approach and the constructed biosensor offer a great potential for the fabrication of the enzyme-based biosensors and the analysis of phenolic compounds.

Inorganic-organic hybrids based on poly (ε-Caprolactone and silica oxide and characterization by relaxometry applying low-field NMR

Directory of Open Access Journals (Sweden)

Mariana Sato de Souza de Bustamante Monteiro

2012-12-01

Full Text Available Poly (ε-caprolactone (PCL based hybrids containing different amounts of modified (Aerosil® R972 and unmodified (Aerosil® A200 silica oxide were prepared employing the solution method, using chloroform. The relationships of the amount of nanofillers, organic coating, molecular structure and intermolecular interaction of the hybrid materials were investigated mainly using low-field nuclear magnetic resonance (NMR. The NMR analyses involved the hydrogen spin-lattice relaxation time (T1H and hydrogen spin-lattice relaxation time in the rotating frame (T1ρH. The spin-lattice relaxation time measurements revealed that the PCL/silica oxide hybrids were heterogeneous, meaning their components were well dispersed. X-ray diffraction (XRD, differential scanning calorimetry (DSC and thermogravimetric analysis (TGA were also employed. The DSC data showed that all the materials had lower crystallization temperature (Tc and melting temperature (Tm, so the crystallinity degree of the PCL decreased in the hybrids. The TGA analysis demonstrated that the addition of modified and unmodified silica oxide does not cause considerable changes to PCL's thermal stability, since no significant variations in the maximum temperature (Tmax were observed in relation to the neat polymer.

Optical absorption of neutron-irradiated silica fibers

International Nuclear Information System (INIS)

Cooke, D.W.; Farnum, E.H.; Bennett, B.L.

1996-01-01

Induced-loss spectra of silica-based optical fibers exposed to high (10 23 n-m -2 ) and low (10 21 n-m -2 ) fluences of neutrons at the Los Alamos Spallation Radiation Effects Facility (LASREF) have been measured. Two types of fibers consisting of a pure fused silica core with fluorine-doped (∼4 mole %) cladding were obtained from Fiberguide Industries and used in the as-received condition. Anhydroguide trademark and superguide trademark fibers contained less than 1 ppm, and 600 to 800 ppm of OH, respectively. The data suggest that presently available silica fibers can be used in plasma diagnostics, but the choice and suitability depends upon the spectral region of interest. Low-OH content fibers can be used for diagnostic purposes in the interval ∼800 to 1400 mn if the exposure is to high-fluence neutrons. For low-fluence neutron exposures, the low-OH content fibers are best suited for use in the interval ∼800 to 2000 nm, and the high-OH content fibers are the choice for the interval ∼400 to 800 nm

Effect of Nano Silica on the Physical Property of Porous Concrete Pavement

Science.gov (United States)

Yusak, Mohd Ibrahim Mohd; Ezree Abdullah, Mohd; Putra Jaya, Ramadhansyah; Rosli Hainin, Mohd; Ibrahim, Mohd Haziman Wan

2017-08-01

Rice husk can be categorized as an organic waste material from paddy industries. Silica is a major inorganic element of the rice husk. The aim of present study is to evaluate the effect of Nano silica on the physical properties of porous concrete pavement. Rice husk has been burned in the furnace (650°C for 6 hours) and ground for four different grinding times (33, 48, 63 and 81 hours). Five types of mixes were prepared to evaluate the different Nano silica grinding time. A Nano silica dosage of 10% by weight of binder was used throughout the experiments. The physical properties were examined through compressive strength, transmission electron microscopy and x-ray fluorescence. The experimental results indicate that the different Nano size gives a different effect to porous concrete strength. Based on the results obtained, Nano silica ground for 63 hours (65.84nm) gives the best result and performance to porous concrete pavement specimens.

In-situ poling and structurization of piezoelectric particulate composites.

Science.gov (United States)

Khanbareh, H; van der Zwaag, S; Groen, W A

2017-11-01

Composites of lead zirconate titanate particles in an epoxy matrix are prepared in the form of 0-3 and quasi 1-3 with different ceramic volume contents from 10% to 50%. Two different processing routes are tested. Firstly a conventional dielectrophoretic structuring is used to induce a chain-like particle configuration, followed by curing the matrix and poling at a high temperature and under a high voltage. Secondly a simultaneous combination of dielectrophoresis and poling is applied at room temperature while the polymer is in the liquid state followed by subsequent curing. This new processing route is practiced in an uncured thermoset system while the polymer matrix still possess a relatively high electrical conductivity. Composites with different degrees of alignment are produced by altering the magnitude of the applied electric field. A significant improvement in piezoelectric properties of quasi 1-3 composites can be achieved by a combination of dielectrophoretic alignment of the ceramic particles and poling process. It has been observed that the degree of structuring as well as the functional properties of the in-situ structured and poled composites enhance significantly compared to those of the conventionally manufactured structured composites. Improving the alignment quality enhances the piezoelectric properties of the particulate composites.

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...

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.

Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction.

Science.gov (United States)

Ma, Hao; Zheng, Xiaoyang; Luo, Xuan; Yi, Yong; Yang, Fan

2018-01-30

Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM) method to calculate the mechanical properties of silica aerogels with different geometric properties such as particle size, pore size, ligament diameter, etc. The FVM simulation results show that a power law correlation existing between relative density and mechanical properties (elastic modulus and yield stress) of silica aerogels, which are consistent with experimental and literature studies. In addition, depending on the relative densities, different strategies are proposed in order to synthesize silica aerogels with better mechanical performance by adjusting the distribution of pore size and ligament diameter of aerogels. Finally, the results suggest that it is possible to synthesize silica aerogels with ultra-low density as well as high strength and stiffness as long as the textural features are well controlled. It is believed that the FVM simulation methodology could be a valuable tool to study mechanical performance of silica aerogel based materials in the future.

Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction

Directory of Open Access Journals (Sweden)

Hao Ma

2018-01-01

Full Text Available Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM method to calculate the mechanical properties of silica aerogels with different geometric properties such as particle size, pore size, ligament diameter, etc. The FVM simulation results show that a power law correlation existing between relative density and mechanical properties (elastic modulus and yield stress of silica aerogels, which are consistent with experimental and literature studies. In addition, depending on the relative densities, different strategies are proposed in order to synthesize silica aerogels with better mechanical performance by adjusting the distribution of pore size and ligament diameter of aerogels. Finally, the results suggest that it is possible to synthesize silica aerogels with ultra-low density as well as high strength and stiffness as long as the textural features are well controlled. It is believed that the FVM simulation methodology could be a valuable tool to study mechanical performance of silica aerogel based materials in the future.

Potentiometric urea biosensor based on multi-walled carbon nanotubes (MWCNTs)/silica composite material

International Nuclear Information System (INIS)

Ahuja, Tarushee; Kumar, D.; Singh, Nahar; Biradar, A.M.; Rajesh

2011-01-01

A novel potentiometric urea biosensor has been fabricated with urease (Urs) immobilized multi-walled carbon nanotubes (MWCNTs) embedded in silica matrix deposited on the surface of indium tin oxide (ITO) coated glass plate. The enzyme Urs was covalently linked with the exposed free -COOH groups of functionalized MWCNTs (F-MWCNTs), which are subsequently incorporated within the silica matrix by sol-gel method. The Urs/MWCNTs/SiO 2 /ITO composite modified electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA) and UV-visible spectroscopy. The morphologies and electrochemical performance of the modified Urs/MWCNTs/SiO 2 /ITO electrode have been investigated by scanning electron microscopy (SEM) and potentiometric method, respectively. The synergistic effect of silica matrix, F-MWCNTs and biocompatibility of Urs/MWCNTs/SiO 2 made the biosensor to have the excellent electro catalytic activity and high stability. The resulting biosensor exhibits a good response performance to urea detection with a wide linear range from 2.18 x 10 -5 to 1.07 x 10 -3 M urea. The biosensor shows a short response time of 10-25 s and a high sensitivity of 23 mV/decade/cm 2 .

Functionalization of silica nanoparticles for polypropylene nanocomposites applications