Note: This page contains sample records for the topic activated combustion synthesis from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Electric Current Activated Combustion Synthesis and Chemical Ovens Under Terrestrial and Reduced Gravity Conditions.  

National Technical Information Service (NTIS)

Combustion synthesis (CS) generally involves mixing reactants together (e.g., metal powders) and igniting the mixture. Typically, a reaction wave will pass through the sample. In field activated combustion synthesis (FACS), the addition of an electric fie...

C. Unuvar D. Fredrick U. Anselmi-Tamburini A. Manerbino J. Y. Guigne Z. A. Munir B. D. Shaw

2004-01-01

2

Pulsed current activated combustion synthesis and consolidation of nanostructured ReSi1.75  

NASA Astrophysics Data System (ADS)

Dense nanostructured ReSi1.75 was synthesized by the pulsed current activated combustion synthesis (PCACS) method within 2 min in one step from mechanically activated powders of Re and 1.75 Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense ReSi1.75 was produced under simultaneous application of 80 MPa of pressure and a pulsed current. The average grain size and mechanical properties (hardness and fracture toughness) of the compound were investigated.

Shon, In-Jin; Kim, Su-Chul; Lee, Byung-Soo; Kim, Byung-Ryang

2009-03-01

3

Electric Current Activated Combustion Synthesis and Chemical Ovens Under Terrestrial and Reduced Gravity Conditions  

NASA Technical Reports Server (NTRS)

Combustion synthesis (CS) generally involves mixing reactants together (e.g., metal powders) and igniting the mixture. Typically, a reaction wave will pass through the sample. In field activated combustion synthesis (FACS), the addition of an electric field has a marked effect on the dynamics of wave propagation and on the nature, composition, and homogeneity of the product as well as capillary flow, mass-transport in porous media, and Marangoni flows, which are influenced by gravity. The objective is to understand the role of an electric field in CS reactions under conditions where gravity-related effects are suppressed or altered. The systems being studied are Ti+Al and Ti+3Al. Two different ignition orientations have been used to observe effects of gravity when one of the reactants becomes molten. This consequentially influences the position and concentration of the electric current, which in turn influences the entire process. Experiments have also been performed in microgravity conditions. This process has been named Microgravity Field Activated Combustion Synthesis (MFACS). Effects of gravity have been demonstrated, where the reaction wave temperature and velocity demonstrate considerable differences besides the changes of combustion mechanisms with the different high currents applied. Also the threshold for the formation of a stable reaction wave is increased under zero gravity conditions. Electric current was also utilized with a chemical oven technique, where inserts of aluminum with minute amounts of tungsten and tantalum were used to allow observation of effects of settling of the higher density solid particles in liquid aluminum at the present temperature profile and wave velocity of the reaction.

Unuvar, C.; Fredrick, D.; Anselmi-Tamburini, U.; Manerbino, A.; Guigne, J. Y.; Munir, Z. A.; Shaw, B. D.

2004-01-01

4

Combustion synthesized TiO{sub 2} for enhanced photocatalytic activity under the direct sunlight-optimization of titanylnitrate synthesis  

SciTech Connect

Graphical abstract: Effect of oxidant on the combustion synthesis of TiO{sub 2} has been studied by preparing titanylnitrate in four different ways from Ti(IV) iso-propoxide. It is observed that oxidant preparation method has a significant effect on physico-chemical as well as photocatalytic properties of TiO{sub 2}. All the catalysts showed excellent photocatalytic activity than Degussa P-25 under direct sunlight for the degradation of a textile dye (methylene blue), without the need of external light sources, oxygen supply and reactor systems. Highlights: ? Optimized synthesis of titanylnitrate. ? Influence of titanylnitrate synthesis on the physico-chemical properties of TiO{sub 2} prepared by combustion synthesis. ? Development of highly efficient TiO{sub 2} photocatalysts those are active under the direct sunlight in open atmosphere. ? Degradation of the textile dye (methylene blue) under direct sunlight. -- Abstract: Optimized synthesis of Ti-precursor ‘titanylnitrate’ for one step combustion synthesis of N- and C-doped TiO{sub 2} catalysts were reported and characterized by using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), diffused reflectance UV–vis spectroscopy, N{sub 2} adsorption and X-ray photoelectron spectroscopy (XPS). XRD confirmed the formation of TiO{sub 2} anatase and nano-crystallite size which was further confirmed by TEM. UV-DRS confirmed the decrease in the band gap to less than 3.0 eV, which was assigned due to the presence of C and N in the framework of TiO{sub 2} as confirmed by X-ray photoelectron spectroscopy. Degradation of methylene blue in aqueous solution under the direct sunlight was carried out and typical results indicated the better performance of the synthesized catalysts than Degussa P-25.

Daya Mani, A. [Department of Chemistry, IIT Hyderabad, Yeddumailaram 502 205 (India)] [Department of Chemistry, IIT Hyderabad, Yeddumailaram 502 205 (India); Laporte, V. [Ecole Polytechnique Federale de Lausanne (EPFL), Interdisciplinary Centre for Electron Microscopy – Surface Analysis Facility, CH-Lausanne (Switzerland)] [Ecole Polytechnique Federale de Lausanne (EPFL), Interdisciplinary Centre for Electron Microscopy – Surface Analysis Facility, CH-Lausanne (Switzerland); Ghosal, P. [Defence Metallurgical Research Laboratory (DMRL), Kanchanbagh, Hyderabad 500 058 (India)] [Defence Metallurgical Research Laboratory (DMRL), Kanchanbagh, Hyderabad 500 058 (India); Subrahmanyam, Ch., E-mail: csubbu@iith.ac.in [Department of Chemistry, IIT Hyderabad, Yeddumailaram 502 205 (India)

2012-09-15

5

Combustion synthesis of complex oxides  

Microsoft Academic Search

Advanced ceramic materials have numerous applications in electronic engineering, chemical engineering, and semiconductor industry. The synthesis of these materials at an economical cost is the bottleneck in the application of these materials. Self-propagating High-temperature Synthesis (SHS) is a new technique for producing these materials for exothermic systems by a combustion wave that propagates and produces high purity products. The full

Qimin Ming

1999-01-01

6

Combustion synthesis method and products  

DOEpatents

Disclosed is a method of producing dense refractory products, comprising: (a) obtaining a quantity of exoergic material in powder form capable of sustaining a combustion synthesis reaction; (b) removing absorbed water vapor therefrom; (c) cold-pressing said material into a formed body; (d) plasma spraying said formed body with a molten exoergic material to form a coat thereon; and (e) igniting said exoergic coated formed body under an inert gas atmosphere and pressure to produce self-sustained combustion synthesis. Also disclosed are products produced by the method.

Holt, J. Birch (San Jose, CA) [San Jose, CA; Kelly, Michael (West Alexandria, OH) [West Alexandria, OH

1993-01-01

7

Combustion synthesis method and products  

DOEpatents

Disclosed is a method of producing dense refractory products, comprising: (a) obtaining a quantity of exoergic material in powder form capable of sustaining a combustion synthesis reaction; (b) removing absorbed water vapor therefrom; (c) cold-pressing said material into a formed body; (d) plasma spraying said formed body with a molten exoergic material to form a coat thereon; and (e) igniting said exoergic coated formed body under an inert gas atmosphere and pressure to produce self-sustained combustion synthesis. Also disclosed are products produced by the method.

Holt, J.B.; Kelly, M.

1993-03-30

8

Combustion synthesis of thermoelectric oxides  

NASA Astrophysics Data System (ADS)

Thermoelectric materials can be used to convert temperature difference applied across them to a electrical energy. They can be used to recover waste heat and reuse it. Two thermoelectric materials, calcium cobaltate (Ca 1.24Co1.62O3.86) and yttrium cuprate (YCuO 2) were synthesized by two different types of combustion synthesis, Self-propagating High-temperature Synthesis (SHS) and thermal explosion. Combustion synthesis is more time and energy efficient than conventional methods of preparation of thermoelectric oxides. This work shows that combustion synthesis is a viable alternative for synthesis of thermoelectric oxides with comparable characteristics and thermoelectric performance to compounds prepared by traditional syntheses. Thermoelectric properties of calcium cobaltate were evaluated and compared to data published in recent literature. A finite element model of SHS is also developed. It can be used to study the reaction process of the synthesis in detail and can predict results of experiments. The model was validated by comparison with experimental observations.

Selig, Jiri

9

Gravity Effects on Combustion Synthesis of Glasses.  

National Technical Information Service (NTIS)

The Combustion Synthesis technique has been used to produce glasses based on B2O3-Al2O3-MgO and CaO-Al2O3. The combustion characteristics of these combustion synthesis reactions using both small cylindrical pellets (SCP) and large spherical pellets (LSP) ...

H. C. Yi J. Y. Guigne J. J. Moore L. A. Robinson A. R. Manerbino F. D. Schowengerdt

2000-01-01

10

Combustion synthesis of calcium aluminates  

SciTech Connect

Commercial calcium aluminate cements for refractory use are known to contain various phases, the hydration behavior of which is interdependent and not fully understood. Hydration studies normally require that pure oxides be synthesized. Solid-state synthesis of single aluminates requires high temperatures and full conversion is not guaranteed. Moreover, it is difficult to obtain a compositionally homogeneous product with this method. The present work discusses a straightforward combustion synthesis technique to prepare submicron calcium aluminates using the corresponding metal nitrates-urea mixtures, at low temperature and short reaction times. The effect of the ratio oxidizer/fuel in the redox mixture was investigated, namely, to find out if urea contents below stoichiometry were enough to trigger the explosive combustion of the fuel and the subsequent decomposition of the salts, and how that ratio affected the phase formation and the characteristics, e.g., morphology and grain size, of the powder produced.

Fumo, D.A.; Segadaes, A.M. [Univ. of Aveiro (Portugal). Dept. Ceramics and Glass Engineering] [Univ. of Aveiro (Portugal). Dept. Ceramics and Glass Engineering; Morelli, M.R. [Federal Univ. Sao Carlos, Sao Paulo (Brazil). Dept. of Materials Engineering] [Federal Univ. Sao Carlos, Sao Paulo (Brazil). Dept. of Materials Engineering

1996-10-01

11

Microwave-assisted combustion synthesis of nano iron oxide/iron-coated activated carbon, anthracite, cellulose fiber, and silica, with arsenic adsorption studies  

EPA Science Inventory

Combustion synthesis of iron oxide/iron coated carbons such as activated carbon, anthracite, cellulose fiber and silica is described. The reactions were carried out in alumina crucibles using a Panasonic kitchen microwave with inverter technology, and the reaction process was com...

12

Combustion synthesis continuous flow reactor  

DOEpatents

The present invention is a reactor for combustion synthesis of inorganic powders. The reactor includes a reaction vessel having a length and a first end and a second end. The reaction vessel further has a solution inlet and a carrier gas inlet. The reactor further has a heater for heating both the solution and the carrier gas. In a preferred embodiment, the reaction vessel is heated and the solution is in contact with the heated reaction vessel. It is further preferred that the reaction vessel be cylindrical and that the carrier gas is introduced tangentially into the reaction vessel so that the solution flows helically along the interior wall of the reaction vessel. As the solution evaporates and combustion produces inorganic material powder, the carrier gas entrains the powder and carries it out of the reactor. 10 figs.

Maupin, G.D.; Chick, L.A.; Kurosky, R.P.

1998-01-06

13

Combustion synthesis continuous flow reactor  

DOEpatents

The present invention is a reactor for combustion synthesis of inorganic powders. The reactor includes a reaction vessel having a length and a first end and a second end. The reaction vessel further has a solution inlet and a carrier gas inlet. The reactor further has a heater for heating both the solution and the carrier gas. In a preferred embodiment, the reaction vessel is heated and the solution is in contact with the heated reaction vessel. It is further preferred that the reaction vessel be cylindrical and that the carrier gas is introduced tangentially into the reaction vessel so that the solution flows helically along the interior wall of the reaction vessel. As the solution evaporates and combustion produces inorganic material powder, the carrier gas entrains the powder and carries it out of the reactor.

Maupin, Gary D. (Richland, WA); Chick, Lawrence A. (West Richland, WA); Kurosky, Randal P. (Maple Valley, WA)

1998-01-01

14

Combustion Synthesis of Magnesium Aluminate  

NASA Astrophysics Data System (ADS)

In the system MgO-Al2O3, three compounds MgAl2O4, MgAl6O10 (also expressed as- Mg0.4Al2.4O4) and MgAl26O40 are well known. Importance of the first two is well established. Magnesium aluminate (MgAl2O4) spinel is a technologically important material due to its interesting thermal properties. The MgAl2O4 ceramics also find application as humidity sensors. Apart from the luminescence studies, the interest in MgAl2O4 is due to various applications such as humidity-sensing and PEM fuel cells, TL/OSL dosimetry of the ionizing radiations, white light source. Interest in the MgAl6O10 has aroused due to possible use as a substrate for GaN growth. Attempt was made to synthesize these compounds by the combustion synthesis using metal nitrates as oxidizer and urea as a fuel. Compounds MgAl2O4 and MgAl6O10 were formed in a single step, while MgAl26O40 was not formed by this procedure. Activation of MgAl6O10 by rare earth ions like Ce3+, Eu3+ and Tb3+ and ns2 ion Pb2+ could be achieved. Excitation bands for MgAl6O10 are at slightly shorter wavelengths compared to those reported for MgAl2O4.

Kale, M. A.; Joshi, C. P.; Moharil, S. V.

2011-10-01

15

Combustion synthesis of advanced composite materials  

NASA Technical Reports Server (NTRS)

Self-propagating high temperature (combustion) synthesis (SHS), has been investigated as a means of producing both dense and expanded (foamed) ceramic and ceramic-metal composites, ceramic powders and whiskers. Several model exothermic combustion synthesis reactions were used to establish the importance of certain reaction parameters, e.g., stoichiometry, green density, combustion mode, particle size, etc. on the control of the synthesis reaction, product morphology and properties. The use of an in situ liquid infiltration technique and the effect of varying the reactants and their stoichiometry to provide a range of reactant and product species i.e., solids, liquids and gases, with varying physical properties e.g., volatility and thermal conductivity, on the microstructure and morphology of synthesized composite materials is discussed. Conducting the combustion synthesis reaction in a reactive gas environment to take advantage of the synergistic effects of combustion synthesis and vapor phase transport is also examined.

Moore, John J.

1993-01-01

16

Gravity Effects on Combustion Synthesis of Glasses  

NASA Technical Reports Server (NTRS)

The Combustion Synthesis technique has been used to produce glasses based on B2O3-Al2O3-MgO and CaO-Al2O3. The combustion characteristics of these combustion synthesis reactions using both small cylindrical pellets (SCP) and large spherical pellets (LSP) are presented. Low density pellets (approx. 35% of their theoretical density) were used, which made synthesis of low exothermic combustion reactions possible. Microstructural analysis of reacted samples was carried out to identify the glass-forming compositions. The effects of gravity on the glass formation were studied aboard the KC-135 using SCP samples. Gravity seemed to have such obvious effects on the combustion characteristics that the wave velocity was lower and the Width of the combustion wave was larger under reduced gravity conditions. Samples produced under low gravity also had more enhanced vitrification than those on ground, while some systems also exhibited lower combustion temperatures. It was also found that the container significantly affects both the combustion characteristics and microstructure. Substantially more divitrification occurred at the area which was in contact with the support (container).

Yi, H. C.; Guigne, J. Y.; Moore, J. J.; Robinson, L. A.; Manerbino, A. R.; Schowengerdt, F. D.; Gokoglu, S. (Technical Monitor)

2000-01-01

17

Combustion and Plasma Synthesis of High-Temperature Materials  

NASA Astrophysics Data System (ADS)

KEYNOTE ADDRESS. Self-Propagating High-Temperature Synthesis: Twenty Years of Search and Findings (A. Merzhanov). SOLID-STATE COMBUSTION SYNTHESIS. Recent Progress in Combustion Synthesis of High-Performance Materials in Japan (M. Koizumi & Y. Miyamoto). Modeling and Numerical Computation of a Nonsteady SHS Process (A. Bayliss & B. Matkowsky). New Models of Quasiperiodic Burning in Combustion Synthesis (S. Margolis, et al.). Modeling of SHS Operations (V. Hlavacek, et al.). Combustion Theory for Sandwiches of Alloyable Materials (R. Armstrong & M. Koszykowski). Observations on the Combustion Reaction Between Thin Foils of Ni and Al (U. Anselmi-Tamburini & Z. Munir). Combustion Synthesis of Intermetallic Compounds (Y. Kaieda, et al.). Combustion Synthesis of Nickel Aluminides (B. Rabin, et al.). Self-Propagating High-Temperature Synthesis of NiTi Intermetallics (H. Yi & J. Moore). Shock-Induced Chemical Synthesis of Intermetallic Compounds (S. Work, et al.). Advanced Ceramics Via SHS (T. DeAngelis & D. Weiss). In-Situ Formation of SiC and SiC-C Blocked Solids by Self-Combustion Synthesis (S. Ikeda, et al.). Powder Purity and Morphology Effects in Combustion-Synthesis Reactions (L. Kecskes, et al.). Simultaneous Synthesis and Densification of Ceramic Components Under Gas Pressure by SHS (Y. Miyamoto & M. Koizumi). The Use of Self-Propagating High-Temperature Synthesis of High-Density Titanium Diboride (P. Zavitsanos, et al.). Metal--Ceramic Composite Pipes Produced by a Centrifugal-Thermit Process (O. Odawara). Simultaneous Combustion Synthesis and Densification of AIN (S. Dunmead, et al.). Fabrication of a Functionally Gradient Material by Using a Self-Propagating Reaction Process (N. Sata, et al.). Combustion Synthesis of Oxide-Carbide Composites (L. Wang, et al.). Heterogeneous Reaction Mechanisms in the Si-C System Under Conditions of Solid Combustion (R. Pampuch, et al.). Experimental Modeling of Particle-Particle Interactions During SHS of TiB2 -Al2O3 (K. Logan, et al.). Combustion Synthesis in the Ti-C-Ni-Al System (S. Dunmead, et al.). Combustion Synthesis Dynamics Modeling (T. Kottke, et al.). Elementary Processes in SiO2-Al Thermite-Type Reactions Activated or Induced by Mechanochemical Treatment (G. Hida & I. Lin). Combustion Synthesis of Ceramic Preforms for Molten-Metal Infiltration (D. Halverson, et al.). Combustion Characteristics of Solid-Solid Systems: Experiments and Modeling (S. Kumar, et al.). Microstructure of TiB2 Sintered by the Self-Combustion Method (K. Urabe, et al..). A Laser-Ignition Study of Gasless Reactions Using Thermography (C. Chow & J. Mohler). Shock-Induced Reaction Synthesis-Assisted Processing of Ceramics (R. Ward, et al.). Summary Assessment of the Application of SPS and Related Reaction Processing to Produce Dense Ceramics (R. Rice). Shock Consolidation of Combustion-Synthesized Ceramics (A. Niiler, et al.). High-Pressure Burning Rate of Silicon in Nitrogen (M. Costantino & J. Holt). Preparation of a TiC Single Crystal by the Floating-Zone Method from a Self-Combustion Rod (S. Otani, et al.). PLASMA AND GAS-PHASE SYNTHESIS. Thermal Plasma Synthesis of Ceramic Powders and Coatings (T. Yoshida). A Theoretical Comparison of Conventional and Hybrid RF-Plasma Reactors (J. McKelliget & N. El-Kaddah). Homogeneous Nucleation and Particle Growth in Thermal Plasma Synthesis (S. Girshick & C.-P. Chiu). Formation of Refractory Aerosol Particles (R. Flagan, et al.). Ceramic-Powder Synthesis in an Aerosol Reactor (M. Alam, et al.). Silica-Particle Formation Using the Counter-Flow Diffusion Flame Burner (J. Katz, et al.). Synthesis and Properties of Low-Carbon Boron Carbides (C. Adkins, et al.). Synthesis of Si, SiC, and Si3N4 Powders Under High Number Density Conditions (J. Haggerty & J. Flint). Rapid Preparation of Titanium and Other Transition-Metal Nitride- and Carbide Powders by a Carbo-Reduction Method Using Arc-Image Heating (M. Yoshimura, et al.). Microwave Plasma Densification of Aluminum Nitride (S. Knittel & S. Risbud). Plasma Synth

Munir, Z. A.; Holt, J. B.

1997-04-01

18

Reaction engineering principles of combustion synthesis of advanced materials  

NASA Astrophysics Data System (ADS)

A mathematical model of solid-solid combustion synthesis and gas-solid combustion synthesis is formulated and the governing equations are numerically solved. The stability of solid-solid combustion is briefly discussed. Results of numerical simulations of the two types of combustion are summarized.

Gatica, Jorge E.; Dandekar, Hemant W.; Viljoen, Hendrik J.; Hlavacek, Vladimir

19

Combustion and Plasma Synthesis of High-Temperature Materials  

Microsoft Academic Search

KEYNOTE ADDRESS. Self-Propagating High-Temperature Synthesis: Twenty Years of Search and Findings (A. Merzhanov). SOLID-STATE COMBUSTION SYNTHESIS. Recent Progress in Combustion Synthesis of High-Performance Materials in Japan (M. Koizumi & Y. Miyamoto). Modeling and Numerical Computation of a Nonsteady SHS Process (A. Bayliss & B. Matkowsky). New Models of Quasiperiodic Burning in Combustion Synthesis (S. Margolis, et al.). Modeling of SHS

Z. A. Munir; J. B. Holt

1997-01-01

20

Combustion synthesis of calcium aluminates  

Microsoft Academic Search

Commercial calcium aluminate cements for refractory use are known to contain various phases, the hydration behavior of which is interdependent and not fully understood. Hydration studies normally require that pure oxides be synthesized. Solid-state synthesis of single aluminates requires high temperatures and full conversion is not guaranteed. Moreover, it is difficult to obtain a compositionally homogeneous product with this method.

D. A. Fumo; M. R. Morelli; A. M. Segadães

1996-01-01

21

Combustion synthesis of boride and other composites  

Microsoft Academic Search

A self-sustaining combustion synthesis process for producing hard, tough, lightweight BâC\\/TiBâ composites is described. It is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the BâC and TiBâ reactants. For lightweight products the composition must be relatively rich in the BâC component. BâC-rich composites are obtained by varying the initial temperature of the

D. C. Halverson; B. Y. Lum; Z. A. Munir

1988-01-01

22

Combustion synthesis of boride and other composites  

Microsoft Academic Search

This patent describes a self-sustaining combustion synthesis process for producing hard, tough, lightweight BâC\\/TiBâ composites. It is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the BâC and TiBâ reactants. For lightweight products the composition must be relatively rich in the BâC component. BâC-rich composites are obtained by varying the initial temperature of

D. C. Halverson; B. Y. Lum; Z. A. Munir

1989-01-01

23

Combustion synthesis of boride and other composites  

Microsoft Academic Search

A self-sustaining combustion synthesis process for producing hard, tough, lightweight B.sub.4 C\\/TiB.sub.2 composites is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the B.sub.4 C and TiB.sub.2 reactants. For lightweight products the composition must be relatively rich in the B.sub.4 C component. B.sub.4 C-rich composites are obtained by varying the initial temperature of

Danny C. Halverson; Beverly Y. Lum; Zuhair A. Munir

1989-01-01

24

Combustion synthesis of boride and other composites  

DOEpatents

A self-sustaining combustion synthesis process for producing hard, tough, lightweight B/sub 4/C/TiB/sub 2/ composites is described. It is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the B/sub 4/C and TiB/sub 2/ reactants. For lightweight products the composition must be relatively rich in the B/sub 4/C component. B/sub 4/C-rich composites are obtained by varying the initial temperature of the reactants. The product is hard, porous material whose toughness can be enhanced by filling the pores with aluminum or other metal phases using a liquid metal infiltration process. The process can be extended to the formation of other composites having a low exothermic component. 9 figs., 4 tabs.

Halverson, D.C.; Lum, B.Y.; Munir, Z.A.

1988-07-28

25

Combustion Synthesis of Transition Metal Carbosulfides  

NASA Astrophysics Data System (ADS)

The combustion synthesis of ternary and quaternary carbosulfides of the transition metals was investigated to obtain high-purity materials to be tested as solid lubricants in high-temperature environments. The main carbosulfide formation mechanisms have been clarified in the case of the technologically interesting tantalum carbosulfide, enabling the preparation of reaction products with controlled purity. The formation of molten tantalum sulfide as an intermediate product was found to play a key role for obtaining a homogeneous reaction product, and the presence of excess carbon reduced the oxygen content of the carbosulfide. However, the higher the overall carbon contents, the higher is the amount of carbide impurities in the reaction products. Use of iodine or hexachlorobenzene as a catalyzer minimized the need of excess sulfur in the raw powder mixture, reduced the amount of carbide impurities, and contributed to the homogenization of the reaction products.

Wally, Pablo; Ueki, Masanori

1998-07-01

26

Reverse microemulsion synthesis of nanostructured complex oxides for catalytic combustion  

NASA Astrophysics Data System (ADS)

Catalysts play an important role in many industrial processes, but their use in high-temperature applications-such as energy generation through natural gas combustion, steam reforming and the partial oxidation of hydrocarbons to produce feedstock chemicals-is problematic. The need for catalytic materials that remain stable and active over long periods at high operation temperatures, often in the presence of deactivating or even poisoning compounds, presents a challenge. For example, catalytic methane combustion, which generates power with reduced greenhouse-gas and nitrogen-oxide emissions, is limited by the availability of catalysts that are sufficiently active at low temperatures for start-up and are then able to sustain activity and mechanical integrity at flame temperatures as high as 1,300°C. Here we use sol-gel processing in reverse microemulsions to produce discrete barium hexaaluminate nanoparticles that display excellent methane combustion activity, owing to their high surface area, high thermal stability and the ultrahigh dispersion of cerium oxide on the their surfaces. Our synthesis method provides a general route to the production of a wide range of thermally stable nanostructured composite materials with large surface-to-volume ratios and an ultrahigh component dispersion that gives rise to synergistic chemical and electronic effects, thus paving the way to the development of catalysts suitable for high-temperature industrial applications.

Zarur, Andrey J.; Ying, Jackie Y.

2000-01-01

27

Reverse microemulsion synthesis of nanostructured complex oxides for catalytic combustion  

PubMed

Catalysts play an important role in many industrial processes, but their use in high-temperature applications-such as energy generation through natural gas combustion, steam reforming and the partial oxidation of hydrocarbons to produce feedstock chemicals--is problematic. The need for catalytic materials that remain stable and active over long periods at high operation temperatures, often in the presence of deactivating or even poisoning compounds, presents a challenge. For example, catalytic methane combustion, which generates power with reduced greenhouse-gas and nitrogen-oxide emissions, is limited by the availability of catalysts that are sufficiently active at low temperatures for start-up and are then able to sustain activity and mechanical integrity at flame temperatures as high as 1,300 degrees C. Here we use sol-gel processing in reverse microemulsions to produce discrete barium hexa-aluminate nanoparticles that display excellent methane combustion activity, owing to their high surface area, high thermal stability and the ultrahigh dispersion of cerium oxide on the their surfaces. Our synthesis method provides a general route to the production of a wide range of thermally stable nanostructured composite materials with large surface-to-volume ratios and an ultrahigh component dispersion that gives rise to synergistic chemical and electronic effects, thus paving the way to the development of catalysts suitable for high-temperature industrial applications. PMID:10638751

Zarur; Ying

2000-01-01

28

The combustion synthesis of Ni-Ti shape memory alloys  

SciTech Connect

Combustion synthesis of Ni-Ti-series shape-memory alloys yields both time and energy savings over conventional production methods. The solidified combustion synthesis process products have been cold-rolled into plates which exhibit the shape-memory effect, and it was noted that shape-memory transition temperatures may be tailored over a -78 to 460 C temperature range through the substitution of a third element for Ni; this element may be Pd or Fe. Accounts are given of the experimental combustion syntheses of Ni-Ti-Fe and Ti-Ni-Pd. 24 refs.

Moore, J.J.; Yi, H.C. (Colorado School of Mines, Golden (USA))

1990-08-01

29

Preparation of calcium aluminate matrix composites by combustion synthesis  

Microsoft Academic Search

CaO–Al2O3–TiB2 composites have been produced by the Combustion Synthesis technique. These materials have matrices based on binary calcium-aluminate compounds, i.e., Ca3Al2O6 (C3A), Ca12Al14O33 (C12A7), CaAl2O4 (CA), CaAl4O7 (CA2) and CaAl12O19 (CA6). Except for samples with the matrix composition of C3A, the combustion synthesis reactions can be characterized as stable self-propagating waves with combustion temperatures ranging from 2125 K to 2717

H. C. Yi; J. Y. Guigné; J. J. Moore; F. D. Schowengerdt; L. A. Robinson; A. R. Manerbino

2002-01-01

30

The solution combustion synthesis of nanophosphors  

SciTech Connect

Nanophosphors are defined as nano-sized (1-100mn), insulating, inorganic materials that emit light under particle or electromagnetic excitation. Their unique luminescence properties provide an excellent potential for applications in radiation detection and imaging. Herein, solution combustion synthesis (SCS) is presented as a method to prepare nanophosphor powders, while X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL), photoluminescence excitation (PLE), and other techniques were used to characterize their structural and optical properties. The goal of this work is to synthesize bright, high-quality powders of nanophosphors, consolidate them into bulk materials and study their structural and optical properties using XRD, TEM, PL, and PLE. SCS is of interest because it is a robust, inexpensive, and facile technique, which yields a significant amount of a wide variety of oxide materials, in a short amount of time. Several practical nanophosphors were synthesized and investigated in this work, including simple oxides such as Y{sub 2}O{sub 3}:Bi, Y{sub 2}O{sub 3}:Tb, Y{sub 2}O{sub 3}:Eu and Gd{sub 2}O{sub 3}:Eu, complex oxides such as Gd{sub 2}SiO{sub 5}:Ce, Y{sub 2}SiO{sub 5}:Ce, Lu{sub 2}SiO{sub 5}:Ce, Zn{sub 2}SiO{sub 4}:Mn, and Y{sub 3}Al{sub 5}O{sub 12}:Ce. Results demonstrate that altering the processing parameters such as water content of the precursor solution, ignition temperature, fuel type and amount, and post-synthesis annealing can significantly improve light output, and that it is possible to optimize the luminescence output of oxyorthosilicates by reducing the amount of silica in the precursor mixture.

Tornga, Stephanie C [Los Alamos National Laboratory

2009-01-01

31

Combustion synthesis of boride and other composites  

SciTech Connect

This patent describes a self-sustaining combustion synthesis process for producing hard, tough, lightweight B{sub 4}C/TiB{sub 2} composites. It is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the B{sub 4}C and TiB{sub 2} reactants. For lightweight products the composition must be relatively rich in the B{sub 4}C component. B{sub 4}C-rich composites are obtained by varying the initial temperature of the reactants. The product is hard, porous material whose toughness can be enhanced by filling the pores with aluminum or other metal phases using a liquid metal infiltration process. The process can be extended to the formation of other composites having a low exothermic component.0:008360his patent describes a neutron reactivity control system for a LWBR incorporating a stationary seed-blanket core arrangement. The core arrangement includes a plurality of contiguous hexagonal shaped regions. Each region has a central and a peripheral blanket area juxapositioned an annular seed area. The blanket areas contain thoria fuel rods while the annular seed area includes seed fuel rods and movable thoria shim control rods.

Halverson, D.C.; Lum, B.Y.; Munir, Z.A.

1989-11-07

32

Joining NiAl using simultaneous combustion synthesis and pressure  

SciTech Connect

Nickel aluminide-based intermetallics are attractive in applications requiring high thermal stability, corrosion and oxidation resistance, and high-temperature mechanical properties. However, if components are to be produced using these intermetallics, efficient joining techniques need to be developed. This paper provides an initial investigation of the application of combustion (self propagating, high temperature) synthesis (SHS) as a means of joining NiAl intermetallic materials. Combustion synthesis is a technique whereby an exothermic reaction mixture is used to synthesize the required product(s). If the reaction is sufficiently exothermic, it can be self sustaining once initiated at the ignition temperature, Tig. The heat generated by the reaction results in an increase in temperature to a maximum combustion temperature, Tc, which is usually less than the calculated adiabatic temperature, Tad, on account of heat losses from the reaction. Combustion synthesis reactions can be operated in two different modes of ignition, i.e. propagating and simultaneous combustion modes. In each case, the exothermic reactant mix, typically in powder form, is pressed in the required reaction stoichiometry and at a certain green density. In reaction mixtures which are less exothermic, such as the synthesis of an intermetallic compound from its elements, e.g. reaction, the simultaneous combustion mode is often used.

Torres, R.D.; Strohaecker, T.R. (PPGEMM/UFRGS, Porto Alegre (Brazil)); Moore, J.J.; Edwards, G.R. (Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering)

1994-02-15

33

Kinetic analysis of the combustion synthesis of molybdenum and titanium silicides  

NASA Astrophysics Data System (ADS)

The temperature profiles associated with the passage of self-propagating combustion waves during the synthesis of MoSi2 and Ti5Si3 were determined. From these profiles, kinetic analyses of the combustion synthesis process for these two silicides were made. The synthesis is associated with high heating rates: 1.3 × 104 and 4.9 × 104 K·s-1 for MoSi2 and Ti5Si3, respectively. The width of the combustion zone was determined as 1.3 and 1.8 mm for the silicides of Mo and Ti, respectively. The degree of conversion, ?, and its spatial distribution and the conversion rate, ??/?t, were determined. However, because of the inherent characteristics of wave propagation in MoSi2, only in the case of Ti5Si3 could the activation energy be calculated. An average value of 190 kJ µ mol-1 was determined for titanium suicide.

Wang, Lily L.; Munir, Z. A.

1995-05-01

34

Centrifugally-assisted combustion synthesis of functionally-graded materials  

SciTech Connect

Functionally graded materials (FGM`s) have been prepared by a variety of techniques, including combustion synthesis, and the use of a centrifugal force in this method of synthesis has been demonstrated previously. However, in the earlier work, a centrifugal force was applied to investigate the changes in the dynamics of self-propagating combustion waves or to deposit coatings on the inside surfaces of pipes. The use of a centrifugal force to investigate the formation of FGM`s has not been reported previously and is the focus of this communication. In this work, the authors have chosen thermite reactions to investigate the feasibility of FGM formation by centrifugally-assisted combustion synthesis.

Lai, W.; Munir, Z.A.; McCoy, B.J.; Risbud, S.H. [Univ. of California, Davis, CA (United States)] [Univ. of California, Davis, CA (United States)

1997-02-01

35

Solution combustion synthesis of {gamma}(L)-Bi{sub 2}MoO{sub 6} and photocatalytic activity under solar radiation  

SciTech Connect

Highlights: {yields} Solution combustion technique was used to synthesize {gamma}(L)-Bi{sub 2}MoO{sub 6}. {yields} The material was in crystalline orthorhombic phase. {yields} High photocatalytic activity under solar radiation was observed. -- Abstract: The facile method of solution combustion was used to synthesize {gamma}(L)-Bi{sub 2}MoO{sub 6}. The material was crystallized in a purely crystalline orthorhombic phase with sizes varying from 300 to 500 nm. Because the band gap was 2.51 eV, the degradation of wide variety of cationic and anionic dyes was investigated under solar radiation. Despite the low surface area (<1 m{sup 2}/g) of the synthesized material, {gamma}(L)-Bi{sub 2}MoO{sub 6} showed high photocatalytic activity under solar radiation due to its electronic and morphological properties.

Saha, Dipankar; Madras, Giridhar [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (India)] [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (India); Guru Row, T.N., E-mail: ssctng@sscu.iisc.ernet.in [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (India)

2011-08-15

36

Solution combustion synthesis and visible light-induced photocatalytic activity of mixed amorphous and crystalline MgAl 2O 4 nanopowders  

Microsoft Academic Search

Mixed amorphous and crystalline MgAl2O4 nanopowders with visible light-induced photocatalytic activity were prepared via a simple solution combustion method using glycine and urea as fuel mixtures. The obtained samples were characterized by X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, Brunauer–Emmett–Teller (BET) surface area, thermogravimetry, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV–Vis diffuse reflection

Fa-tang Li; Ye Zhao; Ying Liu; Ying-juan Hao; Rui-hong Liu; Di-shun Zhao

2011-01-01

37

Combustion Synthesis Of Ultralow-density Nanoporous Gold Foams  

SciTech Connect

A new synthetic pathway for producing nanoporous gold monoliths through combustion synthesis from Au bistetrazoJeamine complexes has been demonstrated. Applications of interest for Au nanofoams include new substrates for nanoparticle-mediated catalysis, embedded antennas, and spectroscopy. Integrated support-and-catalystin-one nanocomposites prepared through combustion synthesis of mixed AuBTA/metal oxide pellets would also be an interesting technology approach for low-cost in-line catalytic conversion media. Furthermore, we envision preparation of ultrahigh surface area gold electrodes for application in electrochemical devices through this method.

Tappan, Bruce C [Los Alamos National Laboratory; Mueller, Alex H [Los Alamos National Laboratory; Steiner, Stephen A [Los Alamos National Laboratory; Luther, Erik P [Los Alamos National Laboratory

2008-01-01

38

Combustion synthesis and characterization of uranium and thorium tellurides  

Microsoft Academic Search

This report describes an investigation of the chemical systems uranium-tellurium and thorium-tellurium. A novel synthesis technique, combustion synthesis, which uses the exothermic heat of reaction rather than externally supplied heat, was utilized to form the phases UTe, U3Te4, and UTe2 in the U-Te system and the phases ThTe, Th2Te3, and ThTe2 in the Th-Te system from reactions of the type

Czechowicz

1985-01-01

39

Combustion synthesis of low exothermic component rich composites  

Microsoft Academic Search

A self-sustaining combustion synthesis process for producing hard, tough, lightweight, low exothermic potential product (LEPP)\\/high exothermic potential product (HEPP) composites is based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the LEPP and HEPP reactants. For lightweight products the composition must be relatively rich in the LEPP component. LEPP rich composites are obtained by

Danny C. Halverson; Beverly Y. Lum; Zuhair A. Munir

1991-01-01

40

Combustion synthesis of low exothermic component rich composites  

Microsoft Academic Search

This patent describes a self-sustaining combustion synthesis process for producing hard, tough, lightweight, low exothermic potential product (LEPP)\\/high exothermic potential product (HEPP) composites based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the LEPP and HEPP reactants. For lightweight products the composition must be relatively rich in the LEPP component. LEPP rich composites are

D. C. Halverson; B. Y. Lum; Z. A. Munir

1991-01-01

41

Combustion Synthesis of Niobium Intermetallics and Composites.  

National Technical Information Service (NTIS)

This report describes studies carried out on the various aspects of micropyretic synthesis on Ni and Nb aluminides. The effect of process parameters like compaction pressure, diluents, preheat temperature, and particle size on the process and on the synth...

J. A. Sekhar G. K. Dey D. Carr V. Gupta

1997-01-01

42

Synthesis and characterization of sintering-resistant silica-encapsulated Fe3O4 magnetic nanoparticles active for oxidation and chemical looping combustion.  

PubMed

A nanocomposite catalyst composed of ferromagnetic magnetite cores (15.5 +/- 2.0 nm) and silica shells with a thickness of 4.5 +/- 1.0 nm (Fe(3)O(4)@SiO(2)) was prepared by a two-step microemulsion-based synthesis. X-ray photoelectron spectroscopy and Raman spectroscopy after oxidation support the presence of a stable Fe(3)O(4) core and a surface phase of gamma-Fe(2)O(3). The nanocomposite structure exhibited 100% conversion of CO in oxygen at a residence time of 0.1 s at 310 degrees C. When pre-oxidized, the Fe(3)O(4)@SiO(2) catalyst is shown to be a suitable solid oxygen carrier for chemical looping combustion of methane at 700 degrees C. The nanocomposites retain their magnetism following the reaction which provides the potential for use of magnetic separation and capture in moving bed reactor applications. The core magnetite within the silica shell is resistant to sintering and a bulk phase transition to temperatures as high as 700 degrees C. These catalysts can be of use in applications of high temperature applications where catalyst recovery by magnetic separation may be required. PMID:20453272

Park, Jung-Nam; Zhang, Peng; Hu, Yong-Sheng; McFarland, Eric W

2010-06-01

43

Combustion synthesis of ceramic and metal-matrix composites  

NASA Technical Reports Server (NTRS)

Combustion synthesis or self-propagating high temperature synthesis (SHS) is effected by heating a reactant mixture, to above the ignition temperature (Tig) whereupon an exothermic reaction is initiated which produces a maximum or combustion temperature, Tc. These SHS reactions are being used to produce ceramics, intermetallics, and composite materials. One of the major limitations of this process is that relatively high levels of porosity, e.g., 50 percent, remain in the product. Conducting these SHS reactions under adiabatic conditions, the maximum temperature is the adiabatic temperature, Tad, and delta H (Tad) = 0, Tad = Tc. If the reactants or products go through a phase change, the latent heat of transformation needs to be taken into account.

Moore, John J.; Feng, Heng J.; Hunter, Kevin J.; Wirth, David G.

1993-01-01

44

Combustion synthesis and characterization of uranium and thorium tellurides  

SciTech Connect

This report describes an investigation of the chemical systems uranium-tellurium and thorium-tellurium. A novel synthesis technique, combustion synthesis, which uses the exothermic heat of reaction rather than externally supplied heat, was utilized to form the phases UTe, U3Te4, and UTe2 in the U-Te system and the phases ThTe, Th2Te3, and ThTe2 in the Th-Te system from reactions of the type U/sub x/ + Te/sub y/ = U/sub x/Te/sub y/. With this synthetic method, U-Te and Th-Te products could be formed in a matter of seconds, and the purity of the products was often greater than that of the starting materials used. Control over final product stoichiometry was found to be very difficult. The product phase distribution observed in combustion products, as determined by x-ray diffraction, electron microprobe, and optical metallographic methods, was found to be spatially complex. Lattice constants were calculated from x-ray diffraction patterns for the compounds UTe, U3Te4, and ThTe. SOLGASMIX thermodynamic equilibrium calculations were performed using available and estimated thermodynamic data on the system U-Te-O in an attempt to understand the products formed by combustion. Adiabatic combustion reaction temperatures for specific U-Te and Th-Te reactions were also calculated utilizing available and estimated thermodynamic data. 71 refs., 31 figs., 15 tabs.

Czechowicz, D.G.

1985-10-01

45

Cermet materials prepared by combustion synthesis and metal infiltration  

DOEpatents

Ceramic-metal composites (cermets) are made by a combination of self-propagating high temperature combustion synthesis and molten metal infiltration. Solid-gas, solid-solid and solid-liquid reactions of a powder compact produce a porous ceramic body which is infiltrated by molten metal to produce a composite body of higher density. AlN-Al and many other materials can be produced. 6 figures.

Holt, J.B.; Dunmead, S.D.; Halverson, D.C.; Landingham, R.L.

1991-01-29

46

Cermet materials prepared by combustion synthesis and metal infiltration  

DOEpatents

Ceramic-metal composites (cermets) are made by a combination of self-propagating high temperature combustion synthesis and molten metal infiltration. Solid-gas, solid-solid and solid-liquid reactions of a powder compact produce a porous ceramic body which is infiltrated by molten metal to produce a composite body of higher density. AlN-Al and many other materials can be produced.

Holt, Joseph B. (San Jose, CA) [San Jose, CA; Dunmead, Stephen D. (Davis, CA) [Davis, CA; Halverson, Danny C. (Modesto, CA) [Modesto, CA; Landingham, Richard L. (Livermore, CA) [Livermore, CA

1991-01-01

47

Grained composite materials prepared by combustion synthesis under mechanical pressure  

DOEpatents

Dense, finely grained composite materials comprising one or more ceramic phase or phase and one or more metallic and/or intermetallic phase or phases are produced by combustion synthesis. Spherical ceramic grains are homogeneously dispersed within the matrix. Methods are provided, which include the step of applying mechanical pressure during or immediately after ignition, by which the microstructures in the resulting composites can be controllably selected.

Dunmead, Stephen D. (Davis, CA); Holt, Joseph B. (San Jose, CA); Kingman, Donald D. (Danville, CA); Munir, Zuhair A. (Davis, CA)

1990-01-01

48

Gas-Phase Combustion Synthesis of Nonoxide Nanoparticles in Microgravity  

NASA Technical Reports Server (NTRS)

Gas-phase combustion synthesis is a promising process for creating nanoparticles for the growing nanostructure materials industry. The challenges that must be addressed are controlling particle size, preventing hard agglomerates, maintaining purity, and, if nonoxides are synthesized, protecting the particles from oxidation and/or hydrolysis during post-processing. Sodium-halide Flame Encapsulation (SFE) is a unique methodology for producing nonoxide nanoparticles that addresses these challenges. This flame synthesis process incorporates sodium and metal-halide chemistry, resulting in nanoparticles that are encapsulated in salt during the early stages of their growth in the flame. Salt encapsulation has been shown to allow control of particle size and morphology, while serving as an effective protective coating for preserving the purity of the core particles. Metals and compounds that have been produced using this technology include Al, W, Ti, TiB2, AlN, and composites of W-Ti and Al-AlN. Oxygen content in SFE synthesized nano- AlN has been measured by neutron activation analysis to be as low as 0.54wt.%, as compared to over 5wt.% for unprotected AlN of comparable size. The overall objective of this work is to study the SFE process and nano-encapsulation so that they can be used to produce novel and superior materials. SFE experiments in microgravity allow the study of flame and particle dynamics without the influence of buoyancy forces. Spherical sodium-halide flames are produced in microgravity by ejecting the halide from a spherical porous burner into a quiescent atmosphere of sodium vapor and argon. Experiments are performed in the 2.2 sec Drop Tower at the NASA-Glenn Research Center. Numerical models of the flame and particle dynamics were developed and are compared with the experimental results.

Axelbaum, R. L.; Kumfer, B. M.; Sun, Z.; Chao, B. H.

2001-01-01

49

Ultra-high speed neutron diffraction studies of combustion synthesis  

NASA Astrophysics Data System (ADS)

In-situ neutron diffraction at time resolutions in the range 380-900 ms recorded on the instrument D20 at the Institut Laue-Langevin have been used to capture the reaction mechanisms during the furnace ignited combustion synthesis of a range of M nAX n-1 phases (M-early transition metal, A-group IIIA or IVA element, X-either C or N), intermetallic compounds (Ti 5Si 3) and intermetallic compound-refractory carbide composites (Ni-Al-Ti-C). The sequence of diffraction patterns reveals great complexity. Some reactions occur completely in the solid state and others involve a transient liquid phase(s). In all but binary mixtures, transient solid phases that may persist for as little as a few seconds were observed. Data analysis methods are illustrated which allow the determination of: (i) the sequence of phases and reaction mechanism, (ii) the crystal structure, atomic substitutions etc of the phases present, (iii) the ‘trigger’ mechanism for the self-sustaining reaction, (iv) the reaction kinetics and activation energy for growth of the product phase (via quantitative phase analysis using Rietveld refinement scale factors and a non-isothermal Avrami kinetic equation), (v) the average sample temperature (via thermal expansion/contraction of known phases) and the formation enthalpy of the product phase (via excursions in the sample temperature).

Kisi, Erich H.; Riley, Daniel P.; Curfs, Caroline C.

2006-11-01

50

Synthesis and characterization of iron orthophosphate by solution combustion method  

SciTech Connect

Graphical abstract: Display Omitted Highlights: ? Solution combustion synthesis was firstly employed to prepare FePO{sub 4}. ? Pure, well-crystallized and porous FePO{sub 4} was obtained and characterized. ? The results proved SCS a time saving and practically applicable method. -- Abstract: The present work applies solution combustion synthesis (SCS) by employing glycine as organic fuel to stimulate the synthesis of pure iron orthophosphate with well-defined reaction parameters. The structural and morphological properties of the products were characterized and confirmed by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and surface analyzer, respectively. Thermal behaviors were also investigated by TG/DT analyses. The optimal condition was set at 500 °C in a few minutes, giving pure iron orthophosphate with a good level of crystallinity and 11,769 m{sup 2}/g surface area. The results proved SCS a time saving and practically applicable method.

Baykan, Demet [Department of Chemistry, Faculty of Science, Hacettepe University, Ankara (Turkey)] [Department of Chemistry, Faculty of Science, Hacettepe University, Ankara (Turkey); Oztas, Nursen Altuntas, E-mail: nursen@hacettepe.edu.tr [Department of Chemistry, Faculty of Science, Hacettepe University, Ankara (Turkey)

2012-12-15

51

Solution combustion synthesis and characterization of nanosized bismuth ferrite  

NASA Astrophysics Data System (ADS)

The present paper describes a simple method of nanosized BiFeO3 by the solution combustion synthesis using bismuth and iron nitrates as oxidizers and the combination fuel of citric acid and ammonium hydroxide, with fuel to oxidizer ratio (? = 1) one. The X-ray Diffraction results indicated rhombohedral phase (R3m) with JCPDS data card no: 72-2035. The ferroelectric transition of the sample at 8310C was detected by differential thermal analysis. Thermal analysis was done by Thermal gravimetric-Differential thermal analyzer and obtained results were presented in this paper.

Sai Kumar, V. Sesha; Rao, K. Venkateswara; Krishnaveni, T.; Kishore Goud, A. Shiva; Reddy, P. Ranjith

2012-06-01

52

Synthesis and characterization of pure Cu and CuO nano particles by solution combustion synthesis  

NASA Astrophysics Data System (ADS)

The Cu and CuO nano particles were prepared by using solution combustion technique with copper nitrate as an oxidizer and citric acid as the fuel. The solution combustion synthesis (SCS) method provides the advanced ceramics, nano-composites and catalyst materials and also produces homogeneous, crystalline and un-agglomerated multi-component oxides. The pure CuO nano particles were prepared for rich oxidant to fuel ratio. As prepared powder were further calcined at 600 °C for 2 hrs. The powder was characterized by different techniques such as XRD, TG-DTA, and SEM etc.

Patil, Sarika P.; Patil, Shital P.; Puri, V. R.; Jadhav, L. D.

2013-06-01

53

Active Combustion Control for Aircraft Gas Turbine Engines  

NASA Technical Reports Server (NTRS)

Lean-burning combustors are susceptible to combustion instabilities. Additionally, due to non-uniformities in the fuel-air mixing and in the combustion process, there typically exist hot areas in the combustor exit plane. These hot areas limit the operating temperature at the turbine inlet and thus constrain performance and efficiency. Finally, it is necessary to optimize the fuel-air ratio and flame temperature throughout the combustor to minimize the production of pollutants. In recent years, there has been considerable activity addressing Active Combustion Control. NASA Glenn Research Center's Active Combustion Control Technology effort aims to demonstrate active control in a realistic environment relevant to aircraft engines. Analysis and experiments are tied to aircraft gas turbine combustors. Considerable progress has been shown in demonstrating technologies for Combustion Instability Control, Pattern Factor Control, and Emissions Minimizing Control. Future plans are to advance the maturity of active combustion control technology to eventual demonstration in an engine environment.

DeLaat, John C.; Breisacher, Kevin J.; Saus, Joseph R.; Paxson, Daniel E.

2000-01-01

54

Combustion synthesis of low exothermic component rich composites  

SciTech Connect

This patent describes a self-sustaining combustion synthesis process for producing hard, tough, lightweight, low exothermic potential product (LEPP)/high exothermic potential product (HEPP) composites based on the thermodynamic dependence of adiabatic temperature and product composition on the stoichiometry of the LEPP and HEPP reactants. For lightweight products the composition must be relatively rich in the LEPP component. LEPP rich composites are obtained by varying the initial temperature of the reactants. The product is hard, porous material whose toughness can be enhanced by filling the pores with aluminum or other metal phases using a liquid metal infiltration process. The process can be extended to the formation of other composites having a low exothermic component.

Halverson, D.C.; Lum, B.Y.; Munir, Z.A.

1991-02-05

55

Gravitational Effects on Combustion Synthesis of Advanced Porous Materials  

NASA Technical Reports Server (NTRS)

Combustion Synthesis (self-Propagating high-temperature synthesis-(SHS)) of porous Ti-TiB(x), composite materials has been studied with respect to the sensitivity to the SHS reaction parameters of stoichiometry, green density, gasifying agents, ambient pressure, diluents and gravity. The main objective of this research program is to engineer the required porosity and mechanical properties into the composite materials to meet the requirements of a consumer, such as for the application of bone replacement materials. Gravity serves to restrict the gas expansion and the liquid movement during SHS reaction. As a result, gravitational forces affect the microstructure and properties of the SHS products. Reacting these SHS systems in low gravity in the KC-135 aircraft has extended the ability to form porous products. This paper will emphasize the effects of gravity (low g, 1g and 2g) on the SHS reaction process, and the microstructure and properties of the porous composite. Some of biomedical results are also discussed.

Zhang, X.; Moore, J. J.; Schowengerdt, F. D.; Thorne, K.

2000-01-01

56

Design and Operation of the Synthesis Gas Generator System for Reformed Propane and Glycerin Combustion  

NASA Astrophysics Data System (ADS)

Due to an increased interest in sustainable energy, biodiesel has become much more widely used in the last several years. Glycerin, one major waste component in biodiesel production, can be converted into a hydrogen rich synthesis gas to be used in an engine generator to recover energy from the biodiesel production process. This thesis contains information detailing the production, testing, and analysis of a unique synthesis generator rig at the University of Kansas. Chapter 2 gives a complete background of all major components, as well as how they are operated. In addition to component descriptions, methods for operating the system on pure propane, reformed propane, reformed glycerin along with the methodology of data acquisition is described. This chapter will serve as a complete operating manual for future students to continue research on the project. Chapter 3 details the literature review that was completed to better understand fuel reforming of propane and glycerin. This chapter also describes the numerical model produced to estimate the species produced during reformation activities. The model was applied to propane reformation in a proof of concept and calibration test before moving to glycerin reformation and its subsequent combustion. Chapter 4 first describes the efforts to apply the numerical model to glycerin using the calibration tools from propane reformation. It then discusses catalytic material preparation and glycerin reformation tests. Gas chromatography analysis of the reformer effluent was completed to compare to theoretical values from the numerical model. Finally, combustion of reformed glycerin was completed for power generation. Tests were completed to compare emissions from syngas combustion and propane combustion.

Pickett, Derek Kyle

57

Combustion based technique for synthesis and joining of refractory materials  

NASA Astrophysics Data System (ADS)

Gasless combustion systems offer features that make them attractive tools for a variety of potential applications. Among them are rapid heating rates, high exothermicity, and high maximum temperatures. These characteristics were exploited to accomplish three separate concepts including the joining of refractory materials, synthesis of a pore-free composite, and the study of thermal explosion in mechanically activated powders. Honeywell Aerospace is a leading producer of carbon brakes for commercial aircraft. The manufacturing process involves chemical vapor infiltration (CVI) to form a carbon matrix around a carbon fiber preform. A major disadvantage of this approach is the time required to form a fully dense preform, which is on the order of 140 days. In addition, after the brakes are in service, they have to be discarded while there is a relatively thick amount of friction material still available. There is a profit motive for reusing these discs which are out of spec. One such example would be to perform a refurbishment by bonding a new thin C/C element onto a used "core" to produce a brake that meets performance specifications. Unfortunately, joining C/C composites is not a simple task, as carbon does not lend itself to welding, and other means (e.g. mechanical or adhesives) would not hold up to the harsh operational conditions. A novel apparatus was designed, built, and proven to join C/C using so-called reactive resistance welding (RRW). It is shown that a joint stronger than the original material can be achieved using moderate electrical current and mechanical force. Additionally, joining layers of similar thickness and microstructure were obtained with different reactive media, ranging from pellets of pressed powders (˜1-2 mm) to thin metal foils (˜25 micron). By modifying the schematic of the RRW apparatus, porous C/C was infiltrated with liquid silicon in order to form a new pore-free C/C-SiC composite. It is shown that using such a process, the silicon rapidly fills the open pore structure with only a thin layer of silicon carbide forming around the periphery of the pores. As the high-temperature treatment time is extended, carbon from the composite diffuses through this layer and reacts with the silicon subsequently crystallizing a bulk silicon carbide phase and forming an essentially pore-free composite. The utility of the apparatus was further demonstrated for the study of electrical initiation of an exothermic reactive system, Ni-Al. The effect of short-term high-energy milling on this system was investigated and it was found to significantly decrease the ignition temperature and activation energy without formation of any new phases. Scanning electron microscopy, electron dispersive x-ray spectroscopy, x-ray diffraction, infrared thermal imaging, and mechanical testing were used to study the process dynamics and properties of these materials.

White, Jeremiah David Edward

58

Characteristics of the combustion synthesis of TiC and Fe-TiC composites  

Microsoft Academic Search

The combustion synthesis of TiC, using the thermal explosion mode, was investigated by varying some of the process parameters including the reactant particle size, the pre-compaction pressure, and the heating rate. Based on these observations, a combustion model for the reaction was developed. When iron was added to titanium and carbon black powders, the ignition temperature was dictated by the

A. Saidi; A. Chrysanthou; J. V. Wood; J. L. F. Kellie

1994-01-01

59

Kinetics of combustion synthesis in the TiC and TiC-Ni systems  

Microsoft Academic Search

The self-propagating reactions, termed self-propagating high-temperature synthesis (SHS), or more simply, combustion synthesis, have received increasing attention especially for the preparation of refractory ceramic and intermetallic compounds. The kinetics and mechanisms of combustion reactions in the Ti-C and Ti-C-Ni systems were studied. Samples were produced by igniting compacts of elemental Ti, C, and Ni powders with a tungsten heating coil

Stephen D. Dunmead; J. B. Holt; D. W. Readey; C. E. Semier

1989-01-01

60

Microwave-assisted combustion synthesis of nanocrystalline MgAl 2O 4 spinel powder  

Microsoft Academic Search

A stoichiometric MgAl2O4 spinel powder was synthesized by a microwave-assisted combustion synthesis (MWCS) route. For the purpose of comparison, another stoichiometric MgAl2O4 spinel powder was also prepared following the conventional combustion synthesis (CCS) method. The batch size had a strong influence on the specific surface area of the material, which in turn is highly dependent on the preparation method adopted.

I. Ganesh; R. Johnson; G. V. N. Rao; Y. R. Mahajan; S. S. Madavendra; B. M. Reddy

2005-01-01

61

Technology Awareness Workshop on Active Combustion Control (ACC) in Propulsion Systems: JANNAF Combustion Subcommittee Workshop  

NASA Technical Reports Server (NTRS)

A JANNAF Combustion Subcommittee Technology Awareness Seminar on Active Combustion Control (ACC) in Propulsion Systems' was held 12 November 1997 at the NASA Lewis Research Center (LeRC), Cleveland, Ohio. The objectives of the seminar were: 1) Define the need and potential of ACC to meet future requirements for gas turbines and ramjets; 2) Explain general principles of ACC and discuss recent successes to suppress combustion instabilities, increase combustion efficiency, reduce emission, and extend flammability limits; 3) Identify R&D barriers/needs for practical implementation of ACC; 4) Explore potential for improving coordination of future R&D activities funded by various government agencies. Over 40 individuals representing senior management from over 20 industry and government organizations participated. This document summarizes the presentations and findings of this seminar.

Fry, Ronald S. (Editor); Gannaway, Mary T. (Editor)

1997-01-01

62

Combustion synthesis of a nanoceramic and its transparent properties  

NASA Astrophysics Data System (ADS)

La0.1Nd0.1Y1.8O3 transparent ceramics nanopowders were prepared using the combustion synthesis. To achieve such transparent ceramics, Y2O3 were used as matrix materials and La3+ and Nd3+ were used as dopants, polyethyleneglycol (PEG) as dispersants for the sintering under vacuum 10-3 Pa and 1600 °C for 6 h. The precursor and powders calcined at different temperatures were characterized using TG-DTA, XRD, BET and FESEM. The transmittance of the transparent ceramics was measured using the sub-photometer. Results showed that La3+ and Nd3+ were completely dissolved into the cubic lattice of Y2O3. The sizes of Y1.8La0.1Nd0.1O3 powders were uniform and spherical-like. The particle sizes of powders gradually increased with increasing the calcination temperature. The dispersant can effectively prevent the powders from the agglomeration, and the particle sizes of powders gradually increased with increasing citric acid. The transmittance of the Y1.8La0.1Nd0.1O3 transparent ceramics was close to its theoretical value (80%).

Luo, Junming; Li, Wen; Xu, Jilin; Deng, Liping

2012-07-01

63

Using Combustion Synthesis to Reinforce Berms and Other Regolith Structures  

NASA Technical Reports Server (NTRS)

The Moonraker Excavator and other tools under development for use on the Moon, Mars, and asteroids will be employed to construct a number of civil engineering projects and to mine the soil. Mounds of loose soil will be subject to the local transport mechanisms plus artificial mechanisms such as blast effects from landers and erosion from surface vehicles. Some of these structures will require some permanence, with a minimum of maintenance and upkeep. Combustion Synthesis (CS) is a family of processes and techniques whereby chemistry is used to transform materials, often creating flame in a hard vacuum. CS can be used to stabilize civil engineering works such as berms, habitat shielding, ramps, pads, roadways, and the like. The method is to unroll thin sheets of CS fabric between layers of regolith and then fire the fabric, creating a continuous sheet of crusty material to be interposed among layers of loose regolith. The combination of low-energy processes, ISRU (in situ resource utilization) excavator, and CS fabrics, seems compelling as a general method for establishing structures of some permanence and utility, especially in the role of robotic missions as precursors to manned exploration and settlement. In robotic precursory missions, excavator/ mobility ensembles mine the Lunar surface, erect constructions of soil, and dispense sheets of CS fabrics that are covered with layers of soil, fired, and then again covered with layers of soil, iterating until the desired dimensions and forms are achieved. At the base of each berm, for example, is a shallow trench lined with CS fabric, fired and filled, mounded, and then covered and fired, iteratively to provide a footing against lateral shear. A larger trench is host to a habitat module, backfilled, covered with fabric, covered with soil, and fired. Covering the applied CS fabric with layers of soil before firing allows the resulting matrix to incorporate soil both above and below the fabric ply into the fused layer, developing a very irregular surface which, like sandpaper, can provide an anchor for loose soil. CS fabrics employ a coarse fiberglass weave that persists as reinforcement for the fired material. The fiberglass softens at a temperature that exceeds the combustion temperature by factors of two to three, and withstands the installation process. This type of structure should be more resistant to rocket blast effects from Lunar landers.

Rodriquez, Gary

2013-01-01

64

The Effects of Gravity on Combustion and Structure Formation During Synthesis of Advanced Materials  

NASA Technical Reports Server (NTRS)

Combustion in a variety of heterogeneous systems, leading to the synthesis of advanced materials, is characterized by high temperatures (2000-3500 K) and heating rates (up to 10(exp 6) K/s) at and ahead of the reaction front. These high temperatures generate liquids and gases which are subject to gravity-driven flow. The removal of such gravitational effects is likely to provide increased control of the reaction front, with a consequent improvement in control of the microstructure of the synthesized products. Thus, microgravity experiments can lead to major advances in the understanding of fundamental aspects of combustion and structure formation under the extreme conditions of the combustion synthesis wave. In addition, the specific features of microgravity environment allow one to produce unique materials, which cannot be obtained under terrestrial conditions. The general goals of the current research are: 1) to improve the understanding of fundamental phenomena taking place during combustion of heterogeneous systems, 2) to use low-gravity experiments for insight into the physics and chemistry of materials synthesis processes, and 3) based on the obtained knowledge, to optimize processing conditions for synthesis of advanced materials with desired microstructures and properties. This research follows logically from the results of investigations we have conducted in the framework of our previous grant on gravity influence on combustion synthesis (CS) of gasless systems. Prior work, by others and by us, has clearly demonstrated that gravity plays an important role during combustion synthesis of materials. The immediate tasks for the future are to quantitatively identify the nature of observed effects, and to create accurate local kinetic models of the processes, which can lead to a control of the microstructure and properties of the synthesized materials. In summary, this is the value of the proposed research. Based on our prior work, we focus on the fundamental aspects of combustion and structure formation under the unique condition of microgravity.

Varma, A.; Pelekh, A.; Mukasyan, A.

1999-01-01

65

Gas-Phase Combustion Synthesis of Aluminum Nitride Powder  

NASA Technical Reports Server (NTRS)

Due to its combined properties of high electrical resistivity and high thermal conductivity aluminum nitride (AlN) is a highly desirable material for electronics applications. Methods are being sought for synthesis of unagglomerated, nanometer-sized powders of this material, prepared in such a way that they can be consolidated into solid compacts having minimal oxygen content. A procedure for synthesizing these powders through gas-phase combustion is described. This novel approach involves reacting AlCl3, NH3, and Na vapors. Equilibrium thermodynamic calculations show that 100% yields can be obtained for these reactants with the products being AlN, NaCl, and H2. The NaCl by-product is used to coat the AlN particles in situ. The coating allows for control of AlN agglomeration and protects the powders from hydrolysis during post-flame handling. On the basis of thermodynamic and kinetic considerations, two different approaches were employed to produce the powder, in co-flow diffusion flame configurations. In the first approach, the three reactants were supplied in separate streams. In the second, the AlCl3 and NH3 were premixed with HCl and then reacted with Na vapor. X-ray diffraction (XRD) spectra of as-produced powders show only NaCl for the first case and NaCl and AlN for the second. After annealing at 775 C tinder dynamic vacuum, the salt was removed and XRD spectra of powders from both approaches show only AlN. Aluminum metal was also produced in the co-flow flame by reacting AlCl3 with Na. XRD spectra of as-produced powders show the products to be only NaCl and elemental aluminum.

Axelbaum, R. L.; Lottes, C. R.; Huertas, J. I.; Rosen, L. J.

1996-01-01

66

Structural and electrochemical properties of LiCoO 2 prepared by combustion synthesis  

Microsoft Academic Search

LiCoO2 powders were prepared by combustion synthesis, using metallic nitrates as the oxidant and metal sources and urea as fuel. A small amount of the LiCoO2 phase was obtained directly from the combustion reaction, however, a heat treatment was necessary for the phase crystallization. The heat treatment was performed at the temperature range from 400 up to 700 °C for

E. I. Santiago; A. V. C. Andrade; C. O. Paiva-Santos; L. O. S. Bulhoes

2003-01-01

67

Carbon combustion synthesis of lithium cobalt oxide as cathode material for lithium ion battery  

Microsoft Academic Search

Lithium cobalt oxide (LiCoO2) was synthesized by carbon combustion synthesis (CCS) using carbon as fuel. X-ray diffraction (XRD) and scanning electron microscope (SEM) measurements showed that carbon combustion led to the formation of layered structure of LiCoO2 and the particle size could be controlled by carbon content. For the LiCoO2 sample prepared at 800°C for 2h, at molar ratio of

Yongle Gan; Li Zhang; Yanxuan Wen; Fan Wang; Haifeng Su

2008-01-01

68

Combustion synthesis of advanced materials. [using in-situ infiltration technique  

NASA Technical Reports Server (NTRS)

The combustion synthesis of ceramic-metal composites using an in-situ liquid infiltration technique is described. The effect of varying the reactants and their stoichiometry to provide a range of reactant and product species i.e. solids, liquids and gases, with varying physical properties e.g. thermal conductivity, on the microstructure and morphology of synthesized products is also described. Alternatively, conducting the combustion synthesis reaction in a reactive gas environment is also discussed, in which advantages can be gained from the synergistic effects of combustion synthesis and vapor phase transport. In each case, the effect of the presence or absence of gravity (density) driven fluid flow and vapor transport is discussed as is the potential for producing new and perhaps unique materials by conducting these SHS reactions under microgravity conditions.

Moore, J. J.; Feng, H. J.; Perkins, N.; Readey, D. W.

1992-01-01

69

Synthesis of fine-grained .alpha.-silicon nitride by a combustion process  

DOEpatents

A combustion synthesis process for the preparation of .alpha.-silicon nitride and composites thereof is disclosed. Preparation of the .alpha.-silicon nitride comprises the steps of dry mixing silicon powder with an alkali metal azide, such as sodium azide, cold-pressing the mixture into any desired shape, or loading the mixture into a fused, quartz crucible, loading the crucible into a combustion chamber, pressurizing the chamber with nitrogen and igniting the mixture using an igniter pellet. The method for the preparation of the composites comprises dry mixing silicon powder (Si) or SiO.sub.2, with a metal or metal oxide, adding a small amount of an alkali metal azide such as sodium azide, introducing the mixture into a suitable combustion chamber, pressurizing the combustion chamber with nitrogen, igniting the mixture within the combustion chamber, and isolating the .alpha.-silicon nitride formed as a reaction product.

Holt, J. Birch (San Jose, CA); Kingman, Donald D. (Danville, CA); Bianchini, Gregory M. (Livermore, CA)

1990-01-01

70

Solid-state combustion synthesis of ceramics and alloys in reduced gravity  

NASA Technical Reports Server (NTRS)

Possible microgravity effects are explored in the combustion synthesis of ceramics and alloys from their constituent elements. Molten intermediates are typically present during the combustion process, thereby offering the chance for natural convection to take place. Numerical simulations suggest that the combustion front in concert with gravity may act as a partial zone-refinement mechanism which is attempting to sweep out porosity in the sample. Contrary to suggestions by dimensional analysis, no effects on the combustion rate are seen. An analytical model of the combustion velocity as a function of the gravitational field and the spreading rate of molten material gives the correct order of magnitude of the gravity effect as measured by centrifuge experiments.

Valone, S. M.; Behrens, R. G.

1988-01-01

71

Combustion synthesis and optical properties of ceria doped gadolinium-oxide nanopowder  

NASA Astrophysics Data System (ADS)

The Ceria doped Gadolinium (Gd2O3) nanopowder was synthesized by combustion synthesis by using urea as a fuel. The combustion synthesis method which is reported here is advantageous from the perspectives of small size of the nanoparticle. The structural and photoluminescence (PL) property of sample was studies. Gd2O3:Ce3+ nanoparticles exhibit green emission around 543 nm. The result of XRD show that synthesized sample has cubic structure. The average size of particle is found to be 45 nm. The surface morphology of the films is also presented.

Tamrakar, Raunak Kumar; Bisen, D. P.

2013-06-01

72

Microstructure and mechanical properties of gamma TiAl based alloys produced by combustion synthesis + compaction route  

Microsoft Academic Search

Microstructure and mechanical properties of ?-TiAl alloy with the chemical composition Ti–48Al–2Cr–2Nb (at.%) have been investigated. The alloy was prepared in one step using a combustion synthesis+compaction process, where the synthesis and the shaping take place at the same time. Two different combustion routes were used: forced self-propagating high-temperature synthesis+compaction (FSHS+C) and thermal explosion+compaction (TE+C).Fully lamellar microstructure was obtained in

I. Agote; J. Coleto; M. Gutiérrez; A. Sargsyan; M. García de Cortazar; M. A. Lagos; I. P. Borovinskaya; A. E. Sytschev; V. L. Kvanin; N. T. Balikhina; S. G. Vadchenko; K. Lucas; A. Wisbey; L. Pambaguian

2008-01-01

73

DEXTROSE-TEMPLATED MICROWAVE-ASSISTED COMBUSTION SYNTHESIS OF SPONGY METAL OXIDES  

EPA Science Inventory

Microwave-assisted combustion synthesis of porous nanocrystalline titania and carbon coated titania is reported using dextrose as template and the product was compared with the one obtained using conventional heating furnace. Out of three compositions viz., 1:1, 1:3, and 1:5 (met...

74

Combustion synthesis of advanced ceramic and ceramic-metal composites. Ph.D. Thesis  

SciTech Connect

The combustion synthesis of ceramic-metal composites using an in-situ liquid infiltration technique is described and used to produce various ceramic and ceramic-metal composites. The structure and properties of the synthesized composites are strongly dependent upon the reaction parameters of the combustion reaction, and the effect of varying the reactants and their stoichiometry to provide a range of reactant and product species i.e. solids, liquids and gases, with varying physical properties, e.g., thermal conductivity, on the microstructure and morphology of synthesized products is discussed with reference to this effect on the fundamental thermochemistry of these exothermic reactions, and different mechanisms are proposed to explain the results. A model exothermic reaction is used to demonstrate the application of simultaneous combustion synthesis, conducted under a consolidating pressure, as an affordable (low cost), in-situ synthesis technique for the production of dense, interpenetrating phase ceramic and ceramic-metal composites. The effects of the important process parameters, e. g., reaction stoichiometry and diluents, green density, pressure and temperature, on microstructure and mechanical properties of these high performance composites are discussed. An examination and critical application of the important processing parameters in combustion synthesis reactions have been used to produce a model ceramic-metal-intermetallic functionally graded material (FGM). Although the FGM produced is, essentially, a model system, the investigation has demonstrated how the combustion synthesis reaction and processing parameters can be controlled to produce a dense FGM composite with a required microstructure in a simple one-step, affordable process.

Feng, H.

1994-01-01

75

Apparatus and method for gas turbine active combustion control system  

NASA Technical Reports Server (NTRS)

An Active Combustion Control System and method provides for monitoring combustor pressure and modulating fuel to a gas turbine combustor to prevent combustion dynamics and/or flame extinguishments. The system includes an actuator, wherein the actuator periodically injects pulsed fuel into the combustor. The apparatus also includes a sensor connected to the combustion chamber down stream from an inlet, where the sensor generates a signal detecting the pressure oscillations in the combustor. The apparatus controls the actuator in response to the sensor. The apparatus prompts the actuator to periodically inject pulsed fuel into the combustor at a predetermined sympathetic frequency and magnitude, thereby controlling the amplitude of the pressure oscillations in the combustor by modulating the natural oscillations.

Umeh, Chukwueloka (Inventor); Kammer, Leonardo C. (Inventor); Shah, Minesh (Inventor); Fortin, Jeffrey B. (Inventor); Knobloch, Aaron (Inventor); Myers, William J. (Inventor); Mancini, Alfred Albert (Inventor)

2011-01-01

76

Carbothermal synthesis of Si3N4 powders using a combustion synthesis precursor  

NASA Astrophysics Data System (ADS)

Si3N4 powders were synthesized by a carbothermal reduction method using a SiO2 + C combustion synthesis precursor derived from a mixed solution consisting of silicic acid (Si source), polyacrylamide (additive), nitric acid (oxidizer), urea (fuel), and glucose (C source). Scanning electron microscopy (SEM) micrographs showed that the obtained precursor exhibited a uniform mixture of SiO2 + C composed of porous blocky particles up to ˜20 ?m. The precursor was subsequently calcined under nitrogen at 1200-1550°C for 2 h. X-ray diffraction (XRD) analysis revealed that the initial reduction reaction started at about 1300°C, and the complete transition of SiO2 into Si3N4 was found at 1550°C. The Si3N4 powders, synthesized at 1550°C, exhibit a mixture phase of ?- and ?-Si3N4 and consist of mainly agglomerates of fine particles of 100-300 nm, needle-like crystals and whiskers with a diameter of about 100 nm and a length up to several micrometers, and a minor amount of irregular-shaped growths.

Chu, Ai-min; Qin, Ming-li; Jia, Bao-rui; Lu, Hui-feng; Qu, Xuan-hui

2013-01-01

77

Combustion synthesis of TiB2-Al2O3-Al composite materials  

NASA Technical Reports Server (NTRS)

The oxide-aluminum exothermic reduction reaction is presently used in the combustion-synthesis of ceramic/metal composites. An excess of Al is used in the reacting materials, which rapidly generate enough heat to exceed Al's melting point. The molten Al thus evolved is allowed to infiltrate the porous ceramic matrix as the exothermic reaction proceeds; this feature of the process turns the disadvantage of high porosity levels in combustion-synthesized materials into an advantage. Attention is given to the system obtained with 3TiO2 + 3B2O3 + (10-x)Al starting materials.

Feng, H. J.; Moore, J. J.; Wirth, D. G.

1991-01-01

78

Solution combustion synthesis and optimization of phosphors for plasma display panels  

NASA Astrophysics Data System (ADS)

The optimization of primary phosphors required for display panels were carried out. Phosphors were synthesized by simple solution combustion technique. The synthesis is based on the exothermic reaction between the fuel (urea) and oxidizer (ammonium nitrate).The heat generated in the reaction is used for auto combustion of precursors. The crystal structures of the prepared samples were confirmed by powder XRD technique and particle morphology by FE-SEM. The Photoluminescence properties were investigated under ultraviolet (UV) and vacuum ultraviolet (VUV) radiations respectively. Prepared phosphors were found to have the best luminous performance with respect to intensity and color purity under 254 nm and 147 nm wavelength radiations.

Ingle, J. T.; Sonekar, R. P.; Omanwar, S. K.; Wang, Yuhua; Zhao, Lei

2014-06-01

79

40 CFR 62.15310 - What records must I keep for municipal waste combustion units that use activated carbon?  

Code of Federal Regulations, 2010 CFR

...waste combustion units that use activated carbon? 62.15310 Section 62...waste combustion units that use activated carbon? For municipal waste combustion units that use activated carbon to control...

2009-07-01

80

40 CFR 62.15310 - What records must I keep for municipal waste combustion units that use activated carbon?  

Code of Federal Regulations, 2010 CFR

...waste combustion units that use activated carbon? 62.15310 Section 62...waste combustion units that use activated carbon? For municipal waste combustion units that use activated carbon to control...

2010-07-01

81

40 CFR 60.1855 - What records must I keep for municipal waste combustion units that use activated carbon?  

Code of Federal Regulations, 2010 CFR

...waste combustion units that use activated carbon? 60.1855 Section 60...waste combustion units that use activated carbon? For municipal waste combustion units that use activated carbon to control...

2010-07-01

82

40 CFR 60.1370 - What records must I keep for municipal waste combustion units that use activated carbon?  

Code of Federal Regulations, 2010 CFR

...waste combustion units that use activated carbon? 60.1370 Section 60...waste combustion units that use activated carbon? For municipal waste combustion units that use activated carbon to control...

2010-07-01

83

Low-reactive circulating fluidized bed combustion (CFBC) fly ashes as source material for geopolymer synthesis.  

PubMed

In this contribution, low-reactive circulating fluidized bed combustion (CFBC) fly ashes (CFAs) have firstly been utilized as a source material for geopolymer synthesis. An alkali fusion process was employed to promote the dissolution of Si and Al species from the CFAs, and thus to enhance the reactivity of the ashes. A high-reactive metakaolin (MK) was also used to consume the excess alkali needed for the fusion. Reactivities of the CFAs and MK were examined by a series of dissolution tests in sodium hydroxide solutions. Geopolymer samples were prepared by alkali activation of the source materials using a sodium silicate solution as the activator. The synthesized products were characterized by mechanical testing, scanning electron microscopy (SEM), X-ray diffractography (XRD), as well as Fourier transform infrared spectroscopy (FTIR). The results of this study indicate that, via enhancing the reactivity by alkali fusion and balancing the Na/Al ratio by additional aluminosilicate source, low-reactive CFAs could also be recycled as an alternative source material for geopolymer production. PMID:19853434

Xu, Hui; Li, Qin; Shen, Lifeng; Zhang, Mengqun; Zhai, Jianping

2010-01-01

84

Low-reactive circulating fluidized bed combustion (CFBC) fly ashes as source material for geopolymer synthesis  

SciTech Connect

In this contribution, low-reactive circulating fluidized bed combustion (CFBC) fly ashes (CFAs) have firstly been utilized as a source material for geopolymer synthesis. An alkali fusion process was employed to promote the dissolution of Si and Al species from the CFAs, and thus to enhance the reactivity of the ashes. A high-reactive metakaolin (MK) was also used to consume the excess alkali needed for the fusion. Reactivities of the CFAs and MK were examined by a series of dissolution tests in sodium hydroxide solutions. Geopolymer samples were prepared by alkali activation of the source materials using a sodium silicate solution as the activator. The synthesized products were characterized by mechanical testing, scanning electron microscopy (SEM), X-ray diffractography (XRD), as well as Fourier transform infrared spectroscopy (FTIR). The results of this study indicate that, via enhancing the reactivity by alkali fusion and balancing the Na/Al ratio by additional aluminosilicate source, low-reactive CFAs could also be recycled as an alternative source material for geopolymer production.

Xu Hui; Li Qin; Shen Lifeng [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093 (China); Zhang Mengqun [Center of Modern Analysis, Nanjing University, Nanjing 210093 (China); Zhai Jianping, E-mail: jpzhai@nju.edu.c [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093 (China)

2010-01-15

85

Combustion  

NASA Astrophysics Data System (ADS)

The process whereby a substance is combined with oxygen with the production of heat. Burning is a familiar example of this process. The energy required to propel chemical rockets is provided by the combustion of fuel with an oxidant at very high temperatures. A common oxidant is liquid oxygen (often denoted by LOX). Others include hydrogen peroxide and nitrogen tetroxide....

Murdin, P.

2000-11-01

86

Flash synthesis of Li2TiO3 powder by microwave-induced solution combustion  

NASA Astrophysics Data System (ADS)

Nano-crystalline Li2TiO3 powder was prepared by a microwave-induced solution combustion synthesis (MSCS) route using urea as fuel. It is observed that combustion reaction, which did not occur by conventional heating, happened when microwave heating was induced. The as-synthesized Li2TiO3 powder exhibits a narrow size distribution. In MSCS, the total metal ion concentration (Cm) in the starting solution plays an important role. By changing Cm values in starting solution, SCS process including ignition time, combustion period and reaction rate can be controlled. The as-prepared powder could be sintered up to 92.6% of the theoretical density at 1223 K.

Zhou, Qilai; Tao, Liyao; Gao, Yue; Xue, Lihong; Yan, Youwei

2014-12-01

87

A combustion process for the instant synthesis of ?-iron oxide  

Microsoft Academic Search

The preparation of y-Fe203, a technologically important recording material, involves precipitation of o~-FeOOH, dehydration-reduction of oI-FeOOH to F%O4 and the controlled oxidation of Fe30 4 to y-Fe203. The oxygen partial pressure, moisture content and temperature at which oxidation occurs are critical. Earlier, we reported the single-step preparation of 7-Fe203 and Co-doped 7-Fe203 [1-3] by the thermal decomposition\\/combustion of the iron(II)

K. Suresh; K. C. Patil

1993-01-01

88

The Effect of Gravity on the Combustion Synthesis of Porous Biomaterials  

NASA Technical Reports Server (NTRS)

Production of highly porous composite materials by traditional materials processing is limited by difficult processing techniques. This work investigates the use of self propagating high temperature (combustion) synthesis (SHS) to create porous tricalcium phosphate (Ca3(PO4)2), TiB-Ti, and NiTi in low and microgravity. Combustion synthesis provides the ability to use set processing parameters to engineer the required porous structure suitable for bone repair or replacement. The processing parameters include green density, particle size, gasifying agents, composition, and gravity. The advantage of the TiB-Ti system is the high level of porosity achieved together with a modulus that can be controlled by both composition (TiB-Ti) and porosity. At the same time, NiTi exhibits shape memory properties. SHS of biomaterials allows the engineering of required porosity coupled with resorbtion properties and specific mechanical properties into the composite materials to allow for a better biomaterial.

Castillo, M.; Zhang, X.; Moore, J. J.; Schowengerdt, F. D.; Ayers, R. A.

2003-01-01

89

Effect of Gravity on the Combustion Synthesis of NI-AL and Ni3AL-TiB2 Composites from Elements.  

National Technical Information Service (NTIS)

Previous studies on the combustion synthesis of advanced materials indicate that combustion and structure formation mechanisms involve several stages including melting of reactants and products, spreading of the melt, droplet coalescence, diffusion and co...

A. Varma H. C. Yi P. J. Mcginn

1995-01-01

90

The combustion synthesis of boride composites. [BâC\\/TiBâ infiltrated with Al  

Microsoft Academic Search

We have investigated the combustion synthesis process as a means of producing hard, tough, lightweight Bâc\\/TiBâ composites. We based our experimental program on thermodynamic calculations. Adiabatic temperatures and product compositions were determined on the basis of the stoichiometry and initial temperature of the reactants. For lightweight products the composition must be relatively rich in the BâC component. We found that

D. C. Halverson; B. Y. Lum; Z. A. Munir

1987-01-01

91

A novel microwave combustion approach for single step synthesis of ?-Al 2O 3 nanopowders  

Microsoft Academic Search

A novel method for synthesis of nano-sized ?-Al2O3 particles in a single step using microwave is being reported for the first time. The sol of aluminum nitrate with urea mixed in the stoichiometric ratios in accordance with jet propellant chemistry, when combusted in a microwave oven gave fine single phase ?-Al2O3 nanoparticles. The resultant oxide powder was characterized by TGA

Kiranmala Laishram; Rekha Mann; Neelam Malhan

92

Combustion synthesis, characterization and sintering behavior of magnesium aluminate (MgAl 2O 4) powders  

Microsoft Academic Search

Nanocrystalline magnesium aluminate powders with different specific surface area, morphology and crystallite size were obtained by combustion synthesis using triethylenetetramine and a mixture of urea and triethylenetetramine, respectively. Triethylenetetramine yields after annealing at 700°C a spinel powder with a BET surface area of 175.8m2g?1 and an average crystallite size of 4.9nm. Urea and triethylenetetramine fuel mixture lead after annealing at

Robert Iano?; Radu Laz?u

2009-01-01

93

Emulsion Combustion and Flame Spray Synthesis of Zinc Oxide\\/Silica Particles  

Microsoft Academic Search

Two flame spray methods, emulsion combustion method (ECM) and flame spray pyrolysis (FSP), were compared for synthesis of pure and mixed SiO2 and ZnO nanoparticles. The effect of silicon precursor was investigated using liquid hexamethyldisiloxane (HMDSO) or SiO2 sol, while for ZnO zinc acetate (ZA) was used. Gas phase reaction took place when using HMDSO as Si precursor, forming nanoparticles,

Takao Tani; Naoyoshi Watanabe; Kazumasa Takatori

2003-01-01

94

Modified Combustion Synthesis of ZnO Nanoparticles Using Renewable Fuel  

NASA Astrophysics Data System (ADS)

Zinc oxide nanoparticles were successfully synthesized using cost effective modified combustion synthesis route employing zinc nitrate hexahydrate as oxidant and palm oil derived C8 fatty alcohol as fuel in various ratios. The calcined zinc oxide exhibited hexagonal phase with wurtzite structure. The crystallite sizes of the samples were ranging from ca. 28 to 40 nm. Therefore, palm oil derived C8 fatty alcohol successfully played the role as low-cost and renewable fuel to synthesize zinc oxide nanoparticles.

Shah, N. N. H.; >H Misran, N. A. A.; Salim, M. A.; Othman, S. Z.; >A Manap,

2013-06-01

95

Combustion synthesis of CoCrMo orthopedic implant alloys: microstructure and properties  

Microsoft Academic Search

Because of their excellent properties, such as corrosion resistance, fatigue strength and biocompatibility, cobalt-based alloys are widely used in total hip and knee replacements, dental devices and support structures for heart valves. In this work, CoCrMo alloys were synthesized using a novel method based on combustion synthesis (CS), an advanced technique to produce a wide variety of materials including alloys

Bingyun Li; Alexander Mukasyan; Arvind Varma

2003-01-01

96

Combustion synthesis of titanium aluminides via co-reduction of oxides  

Microsoft Academic Search

In this study, Ti-50Al and Ti-48Al-2Cr powders were produced via reduction of TiO2\\/Al2O3 and TiO2\\/Al2O3\\/Cr2O3 mixtures with Ca. Upon addition of KClO4 to the above mixtures, a combustion synthesis process was initiated in the systems. In the presence of KClO4, the reduction temperature decreased from 1000 to 550°C.

A. R. Kamali; M. R. Farhang

2008-01-01

97

Combustion synthesis and properties of fine particle fluorescent aluminous oxides  

Microsoft Academic Search

Fine particle fluorescent aluminous oxide materials like Cr3+-doped ?-Al2O3 (ruby), MgAl2O4, LaAlO3, Y3Al5O12 and Ce3+-doped Y3Al5O12, LaMgAl11O19, CaAl12O19 and CeMgAl11O19 have been prepared by the combustion of the corresponding metal nitrate-aluminium nitrate-urea\\/carbohydrazide mixtures at\\u000a 500°C in less than 5 min. Formation of these Cr3+- and Ce3+-doped aluminous oxides has been confirmed by their characteristic XRD, colour, UV-visible and fluorescence spectra

J J Kingsley; N Manickam; K C Patil

1990-01-01

98

Effect of combustion condition on cytotoxic and inflammatory activity of residential wood combustion particles  

NASA Astrophysics Data System (ADS)

Residential heating is an important local source of fine particles and may cause significant exposure and health effects in populations. We investigated the cytotoxic and inflammatory activity of particulate emissions from normal (NC) and smouldering (SC) combustion in one masonry heater. The PM 1-0.2 and PM 0.2 samples were collected from the dilution tunnel with a high-volume cascade impactor (HVCI). Mouse RAW 264.7 macrophages were exposed to the PM-samples for 24 h. Inflammatory mediators, (IL-6, TNF? and MIP-2), and cytotoxicity (MTT-test), were measured. Furthermore, apoptosis and cell cycle of macrophages were analyzed. The HVCI particulate samples were characterized for ions, elements and PAH compounds. Assays of elemental and organic carbon were conducted from parallel low volume samples. All the samples displayed mostly dose-dependent inflammatory and cytotoxic activity. SC samples were more potent than NC samples at inducing cytotoxicity and MIP-2 production, while the order of potency was reversed in TNF? production. SC-PM 1-0.2 sample was a significantly more potent inducer of apoptosis than the respective NC sample. After adjustment for the relative toxicity with emission factor (mg MJ -1), the SC-PM emissions had clearly higher inflammatory and cytotoxic potential than the NC-PM emissions. Thus, operational practice in batch burning of wood and the resultant combustion condition clearly affect the toxic potential of particulate emissions.

Jalava, Pasi I.; Salonen, Raimo O.; Nuutinen, Kati; Pennanen, Arto S.; Happo, Mikko S.; Tissari, Jarkko; Frey, Anna; Hillamo, Risto; Jokiniemi, Jorma; Hirvonen, Maija-Riitta

2010-05-01

99

Synthesis and Characterization of Nano CoFe2O4 by Low-Temperature Combustion Synthesis Using Different Fuels  

NASA Astrophysics Data System (ADS)

The combustion synthesis has been utilized to prepare nanophased powders of cobalt spinel ferrite using ODH and glycine fuels. The product was characterized by X-ray diffraction; Fourier transformed spectroscopy, scanning electron microscopy, UV-Vis absorption etc. The XRD patterns reveal spinal cubic structure. SEM profiles show the product is porous, agglomeration, irregular in shape. The crystallite size was estimated using Scherer's formula and W-H plots and show nano in size (13 nm: ODH & 36 nm: Glycine). The UV-Vis absorption shows at ~430 nm in both the samples.

Jnaneshwara, D. M.; Krishna, R. Gopala; Nagabhushana, H.; Nagabhushana, B. M.; Shivakumara, C.; Chakradhar, R. P. S.

2011-07-01

100

Reduced-order modeling and active control of dry-low-emission combustion  

Microsoft Academic Search

This dissertation is a complementary experimental and theoretical investigation of combustion instability and lean blowout (LBO) in dry-low-emission (DLE) gas turbine engines, aiming to understand the fundamental mechanisms and shed light on active combustion control. Combustion instability involves complicated physicochemical processes, and many of the underlying mechanisms remain unknown, despite extensive research in the past several decades. A practical control

Tongxun Yi

2007-01-01

101

Role of fuel/oxidizer ratio on the synthesis conditions of Cu–Al{sub 2}O{sub 3} nanocomposite prepared through solution combustion synthesis  

SciTech Connect

Highlights: ? With increasing the fuel to oxidizer ratio synthesis products changed from CuO to Cu{sub 2}O. ? With increasing the fuel to oxidizer ratio the combustion temperature decreased. ? Maximum ratio that synthesis could occur was achieved. ? The stoichiometric ratio had the maximum combustion temperature. ? Solution with graphite had lower combustion temperature. -- Abstract: The role of fuel/oxidizer ratio in the synthesis conditions of Cu–Al{sub 2}O{sub 3} nanocomposite, which was prepared through solution combustion synthesis, method was investigated. For this purpose, copper and aluminum nitrates as well as urea were used as oxidizer and fuel, respectively. The fuel/oxidizer (F/O) ratios were selected from the range of 0.9–1.75. The products were analyzed using X-ray diffraction, SEM and TEM techniques. During the process the temperature was recorded as a function of time. The results showed that by increasing the F/O ratio up to the stoichiometric amount, the combustion temperature increases. Further increment of F/O ratio resulted in a decrease in the combustion temperature. Microscopic evaluations, using SEM and TEM, proved feasibility of the production of Cu–Al{sub 2}O{sub 3} through this method.

Nasiri, H., E-mail: h.nasiri85@yahoo.com [Department of Material Science and Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, P.O. Box: 91775-1111, Mashhad (Iran, Islamic Republic of); Bahrami Motlagh, E.; Vahdati Khaki, J.; Zebarjad, S.M. [Department of Material Science and Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, P.O. Box: 91775-1111, Mashhad (Iran, Islamic Republic of)] [Department of Material Science and Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, P.O. Box: 91775-1111, Mashhad (Iran, Islamic Republic of)

2012-11-15

102

Combustion Synthesis Reactions in Cold-Rolled Ni/Al and Ti/Al Multilayers  

NASA Astrophysics Data System (ADS)

In this article, a cold rolling method was developed to fabricate Ni/Al and Ti/Al multilayer foils, and the combustion synthesis reactions in the cold-rolled foils were investigated. Combustion synthesis reactions were initiated by heating one end of the cold-rolled foil in a flame for several seconds. The Ni/Al foils went through three reaction stages. The first reaction stage was a displacement of reaction zone with Al3Ni as the reaction product. During the second stage, the part of the foil in the flame underwent thermal explosion. In the last stage, the heat released by thermal explosion triggered a self-propagating high-temperature synthesis (SHS) reaction across the foil that resulted in the formation of AlNi. In contrast, the Ti/Al foils experienced only two reaction stages. First, a displacement of the reaction zone propagated across the foil with formation of Al3Ti at the Ti/Al interface. Then a thermal explosion reaction occurred in the part of foil that was heated in the flame, resulting in many different phases in the reacted foil.

Qiu, Xiaotun; Liu, Ranran; Guo, Shengmin; Graeter, Jesse Harris; Kecskes, Laszlo; Wang, Jiaping

2009-07-01

103

Polyvinyl chloride plastics in municipal solid waste combustion. Impact upon dioxin emissions: A synthesis of views  

SciTech Connect

This report examines the issue of whether the polyvinyl chloride (PVC) plastics content of municipal solid waste (MSW) is a significant contributor to emissions of chlorinated dibenzo-p-dioxins (dioxins) that are associated with MSW combustion. Indications based on a consideration of this issue are developed through a synthesis of available information. While there is convincing experimental evidence that various conditions can cause production of dioxins when PVC is thermally treated, a fundamental issue that remains to be solved is how these findings relate to operating conditions that are characteristic of well designed, maintained and operated MSW combustion facilities, equipped with modern air pollution controls. These findings largely have been derived from laboratory or pilot scale experimentation and from full-scale studies that have carried out at facilities of varying design and purpose.

Not Available

1993-04-01

104

Synthesis of the Nanocrystalline Nickel Ferrite by a Novel Mechano Sol-Gel Auto-Combustion Method  

NASA Astrophysics Data System (ADS)

In this work, a novel method of mechano sol-gel auto-combustion has been developed for production of single phase nickel ferrite nanocrystalline powder, consisting of a sol-gel auto-combustion synthesis followed by a high energy milling process before calcination. Sol-gel auto-combustion was carried out using a gel including citric acid as a reductant and metal nitrates as oxidants. This gel exhibited a self-propagating behavior after ignition in air. The effects of the intermediate high energy milling on the physical properties of the final product after calcination were investigated. The results showed that with a high energy milling of the sol-gel auto-combusted powders with a ball-to-powder mass ratio of 20 for 20 h, the temperature of calcination for synthesis of the single phase ferrite reduced from 1000°C to 700°C and the size of the ferrite crystallites decreased from 72 nm to 15 nm.

Shahmirzaei, M.; Seyyed Ebrahimi, S. A.; Dehghan, R.

105

Red photoluminescence in NdAlO 3 crystalline ceramic powders prepared by combustion synthesis  

NASA Astrophysics Data System (ADS)

Red light (two bands peaked at ? ˜680 and ˜697 nm), visible by naked eye, is emitted by crystalline ceramic powders of NdAlO 3 prepared by direct combustion synthesis when the sample is irradiated by unfocused ultraviolet pulsed laser light ( ? = 337 nm). This is the first observation of luminescence at the visible from NdAlO 3 structure. The red emission can be explained by assuming that the quantum cutting process 4D 3/2 ? 4F 9/2 ? 4I 9/2 is the relevant relaxation mechanism involved in the down-conversion process.

Maciel, Glauco S.; Rakov, Nikifor; Zanon, R. A. de S.; Fellows, C. E.; Guimarães, R. B.; Rodrigues, J. J., Jr.

2008-11-01

106

Development of a novel combustion synthesis method for synthesizing of ceramic oxide powders  

Microsoft Academic Search

A novel combustion synthesis method has been developed to prepare electronic ceramic oxide powders—Ni0.5Zn0.5Fe2O4, ZnO, LiCoO2, BaFe12O19 and YBa2Cu3O7?x (x?0.25). Organic compounds (e.g., glycine, urea, citric acid, alanine, or carbohydrazide) to be mixed directly with metal nitrates without adding water, is the key technique of this method. Metal nitrates acting as oxidants were also used as cation sources, whereas an

Chyi-Ching Hwang; Tsung-Yung Wu; Jun Wan; Jih-Sheng Tsai

2004-01-01

107

Synthesis and sintering of nanocrystalline hydroxyapatite powders by citric acid sol-gel combustion method  

SciTech Connect

The citric acid sol-gel combustion method has been used for the synthesis of nanocrystalline hydroxyapatite (HAP) powder from calcium nitrate, diammonium hydrogen phosphate and citric acid. The phase composition of HAP powder was characterized by X-ray powder diffraction analysis (XRD). The morphology of HAP powder was observed by transmission electron microscope (TEM). The HAP powder has been sintered into microporous ceramic in air at 1200 deg. C with 3 h soaking time. The microstructure and phase composition of the resulting HAP ceramic were characterized by scanning electron microscope (SEM) and XRD, respectively. The physical characterization of open porosity and flexural strength have also been carried out.

Han Yingchao; Li Shipu; Wang Xinyu; Chen Xiaoming

2004-01-03

108

Solution combustion synthesis of MgAl 2O 4 using fuel mixtures  

Microsoft Academic Search

The paper reveals a new perspective concerning the rational fuel selection and the logical elaboration of the recipes for the MgAl2O4 solution combustion synthesis. It was shown that Mg(NO3)2·6H2O and Al(NO3)3·9H2O exhibit different behavior with respect to urea, glycine and ?-alanine. Urea proved to be the most adequate fuel for Al(NO3)3·9H2O, while ?-alanine proved to be the most appropriate fuel

Robert Iano?; Ioan Laz?u; Cornelia P?curariu; Paul Barvinschi

2008-01-01

109

Synthesis of Mg 1? x Co x Al 2O 4 blue pigments via combustion route  

Microsoft Academic Search

MgAl2O4 was successfully used as crystalline host network for the synthesis of cobalt-based blue ceramic pigments. Different compositions of Mg1?xCoxAl2O4 (x=0.1–0.3) powders have been prepared by the combustion reaction of corresponding metal nitrates with mixtures of urea and ?-alanine. The resultant powders were characterized by means of XRD, TG-DTA, EDAX, SEM, BET surface area, diffuse reflectance spectrometry and CIEL?a?b? color

Robert Iano?; Radu Laz?u; Paul Barvinschi

2011-01-01

110

Combustion synthesis and effects of processing parameters on physical properties of {alpha}-alumina  

SciTech Connect

Fine particle porous {alpha}-alumina has been prepared by a wet chemical method of combustion synthesis using an aqueous precursor containing aluminum nitrate (oxidizer) and carbohydrazide, an organic fuel as starting materials. The aluminum nitrate and carbohydrazide were reacted exothermically at 400--600 C. The synthesis of {alpha}-alumina ({alpha}-Al{sub 2}O{sub 3}) was used as a model for understanding the effects of processing parameters on physical properties such as surface area, average pore size, and residual carbon content. The porous powders were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface area analysis and elemental analysis. The decomposition of the starting materials was investigated using differential thermal and thermogravimetric analyses (DTA/TGA). It has been shown that the furnace temperature, fuel/oxidizer ratio, and precursor water content can be tailored to produce powders with different physical properties.

Collins, M.V.; Hirschfeld, D.A.; Shea, L.E.

2000-01-04

111

Al 2O 3–TiC–ZrO 2 nanocomposites fabricated by combustion synthesis followed by hot pressing  

Microsoft Academic Search

Al2O3–TiC–ZrO2 nanocomposites were prepared by combustion synthesis followed by hot pressing with TiO2, Al, C and ZrO2 as raw materials. Combustion synthesis is favorable to obtain in situ formed powder with TiC and ZrO2 nanoparticles distributed in Al2O3 matrix. The effects of varying amount of ZrO2 nano-scale additives on the mechanical properties and microstructure of Al2O3–TiC composite were studied. An

Qian Dong; Qing Tang; Wenchao Li

2008-01-01

112

MINIMIZATION OF TOXIC COMBUSTION BYPRODUCTS: REVIEW OF CURRENT ACTIVITIES  

EPA Science Inventory

In general, toxic combustion byproducts (TCBS) are the unwanted residues remaining in flue gases, combustion ashes, and wastewaters from the operation of an incineration or combustion facility. f a combustor is not well designed and operated, it may emit too high a level of TCBS....

113

A synthesis of carbon dioxide emissions from fossil-fuel combustion  

SciTech Connect

This synthesis discusses the emissions of carbon dioxide from fossil-fuel combustion and cement production. While much is known about these emissions, there is still much that is unknown about the details surrounding these emissions. This synthesis explores 5 our knowledge of these emissions in terms of why there is concern about them; how they are calculated; the major global efforts on inventorying them; their global, regional, and national totals at different spatial and temporal scales; how they are distributed on global grids (i.e. maps); how they are transported in models; and the uncertainties associated with these different aspects of the emissions. The magnitude of emissions 10 from the combustion of fossil fuels has been almost continuously increasing with time since fossil fuels were first used by humans. Despite events in some nations specifically designed to reduce emissions, or which have had emissions reduction as a byproduct of other events, global total emissions continue their general increase with time. Global total fossil-fuel carbon dioxide emissions are known to within 10% uncertainty (95% 15 confidence interval). Uncertainty on individual national total fossil-fuel carbon dioxide emissions range from a few percent to more than 50 %. The information discussed in this manuscript synthesizes global, regional and national fossil-fuel carbon dioxide emissions, their distributions, their transport, and the associated uncertainties.

Andres, Robert Joseph [ORNL; Boden, Thomas A [ORNL; Breon, F.-M. [CEA/DSM/LSCE, Gif sur Yvette, France; Ciais, P. [LSCE/CEA, Gif-sur-Yvette, France; Davis, S. [Carnegie Institution of Washington; Erickson, D [Oak Ridge National Laboratory (ORNL); Gregg, J. S. [Riso National Laboratory, Roskilde, Denmark; Jacobson, Andrew [NOAA ESRL and CIRES; Marland, Gregg [Appalachian State University; Miller, J. [NOAA ESRL and CIRES; Oda, T [NOAA ESRL/Boulder, CO/Cooperative Institute for Research in the Atmosphere, Colorado State Univ.; Oliver, J. G. J. [PBL Netherlands Environmental Assessment Agency, Bilthoven, The Netherlands; Raupach, Michael [CSIRO Marine and Atmospheric Research; Rayner, P [University of Melbourne, Australia; Treanton, K. [Energy Statistics Division, International Energy Agency, Paris, France

2012-01-01

114

Joining of Ni-TiC FGM and Ni-Al Intermetallics by Centrifugal Combustion Synthesis  

SciTech Connect

A centrifugal combustion synthesis (CCS) process has been investigated to join a Ni-Al intermetallic compound and a Ni-TiC cermet. The cermet, a tubular graphite mold, and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. When the combustion synthesis reaction was induced in the centrifugal force field, a synthesized molten Ni-Al alloy flowed into the graphite mold and joined to the cermet. The soundness of the joint interface depended on the volume percentage of TiC phase in the cermet. A lot of defects were formed near the interface between the Ni-TiC cermet and the cast Ni-Al alloy when the volume percentage of TiC was 50% or higher. For this kind of cermet system, using a functionally graded cermet such as Ni-10 vol.%TiC/Ni-25 vol.%TiC/Ni-50 vol.%TiC overcame this difficulty. The four-point bending strength of the joined specimen consisting of the three-layered FGM cermet and cast Ni-29 mol%Al alloy was 1010 MPa which is close to the result for a Ni-29 mol%Al alloy specimen.

Ohmi, Tatsuya; Matsuura, Kiyotaka; Iguchi, Manabu [Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo, Hokkaido, 060-8628 (Japan); Mizuma, Kiminori [Graduate Student of Hokkaido University (Japan)

2008-02-15

115

Synthesis of nano-crystalline TaC-TaB by microwave-assisted combustion synthesis  

NASA Astrophysics Data System (ADS)

In present study, TaC-TaB nanocrystalline powder was produced by microwave synthesis. 3Ta and BC Al as starting materials were milled for 1, 3, 6 and 9 h then pressed to form pellets. Green compacts were placed in a microwave oven with powder equal 1100W and argon atmosphere, for synthesis. The final products were studied by XRD and SEM analytical techniques. The results showed increasing of the milling time to 9 h the synthesis of desired phases (TaC and TaB) was associated with greater success and the amount of the side products and intermediate compounds reach to minimum in the product. Also, with increasing of milling time from 1 to 9 h the required time for synthesis of samples reduces from 3 min to 35 sec. This method is an economical method for the preparation TaC-TaB powder with respect to energy, time and simplicity.

Aminikia, Behzad

2013-12-01

116

Synthesis of yttrium iron garnet (YIG) by citrate–nitrate gel combustion and precursor plasma spray processes  

Microsoft Academic Search

The influence of synthesis conditions on the formation of yttrium iron garnet (YIG) powders starting from the same precursor solution was investigated by employing a citrate–nitrate (C–N) gel combustion process and a precursor plasma spraying technique. Two different C–N ratios were used in the synthesis and their influences on phase formation were studied by thermal analysis (DTA\\/TGA) and X-ray powder

X. Z. Guo; B. G. Ravi; P. S. Devi; J. C. Hanson; J. Margolies; R. J. Gambino; J. B. Parise; S. Sampath

2005-01-01

117

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

SciTech Connect

The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization. However, unburned carbon is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, the principal objective of this work was to characterize and utilize the unburned carbon in fly ash for the production of activated carbons. The unburned carbon samples were collected from different combustion systems, including pulverized utility boilers, a utility cyclone, a stoker, and a fluidized bed combustor. LOI (loss-on-ignition), proximate, ultimate, and petrographic analyses were conducted, and the surface areas of the samples were characterized by N2 adsorption isotherms at 77K. The LOIs of the unburned carbon samples varied between 21.79-84.52%. The proximate analyses showed that all the samples had very low moisture contents (0.17 to 3.39 wt %), while the volatile matter contents varied between 0.45 to 24.82 wt%. The elemental analyses show that all the unburned carbon samples consist mainly of carbon with very little hydrogen, nitrogen, sulfur and oxygen In addition, the potential use of unburned carbon as precursor for activated carbon (AC) was investigated. Activated carbons with specific surface area up to 1075m{sup 2}/g were produced from the unburned carbon. The porosity of the resultant activated carbons was related to the properties of the unburned carbon feedstock and the activation conditions used. It was found that not all the unburned carbon samples are equally suited for activation, and furthermore, their potential as activated carbons precursors could be inferred from their physical and chemical properties. The developed porosity of the activated carbon was a function of the oxygen content, porosity and H/C ratio of the parent unburned carbon feedstock. It was observed that extended activation times and high activation temperatures increased the porosity of the produced activated carbon at the expense of the solid yield. The development of activated carbon from unburned carbon in fly ash has been proven to be a success by this study in terms of the higher surface areas of the resultant activated carbons, which are comparable with commercial activated carbons. However, unburned carbon samples obtained from coal-fired power plants as by-product have high ash content, which is unwanted for the production of activated carbons. Therefore, the separation of unburned carbon from the fly ash is expected to be beneficial for the utilization of unburned carbon to produce activated carbons with low ash content.

Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

2003-09-30

118

Combustion synthesis of lanthanum chromite starting from water solutions: Investigation of process mechanism by DTA–TGA–MS  

Microsoft Academic Search

The mechanism of combustion synthesis of lanthanum chromite was investigated by carrying out simultaneous differential thermal analysis (DTA), thermal-gravimetric analysis (TGA) and quadrupole mass spectrometry measurements (MS). The whole process was found to involve several phenomena: urea and nitrates thermal decomposition, exothermal reactions occurring directly between nitrates and urea as well as between their decomposition products, final reaction between solid

S. Biamino; C. Badini

2004-01-01

119

Dynamical Processes in Active Control of Combustion Instabilities  

Microsoft Academic Search

Summary Strong coupling of combustion with pressure waves gives rise to oscillations and instabilities. Such dynamical phenomena raise difficult practical issues and their understanding and control constitute challenging scientific and technological problems. These topics have received considerable attention during the last period in relation with incidents encountered in gas turbines operating in the premixed mode. Combustion dynamics is also to

S. Candel; S. Ducruix; T. Schuller; D. Durox; F. Lacas

120

Dextrose-templated microwave-assisted combustion synthesis of spongy metal oxides  

NASA Astrophysics Data System (ADS)

We report microwave-assisted combustion synthesis of porous nanocrystalline titania and carbon coated titania using dextrose as a template and compare the product with that obtained using a conventional heating furnace. Out of three compositions, namely, 1:1, 1:3, and 1:5 (metal:dextrose), 1:3 favors formation of consistent porous structures. The samples were then characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray analysis (EDX), x-ray diffraction (XRD) and x-ray mapping. This general and eco-friendly method uses a benign natural polymer, dextrose, to create spongy porous structures and can be extended to other transition metal oxides such as ZrO2, Al2O3 and SiO2.

Nadagouda, Mallikarjuna N.; Varma, Rajender S.

2006-10-01

121

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

SciTech Connect

The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization. However, unburned carbon is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, this report evaluates and compares several routes for the production of activated carbons from unburned carbon in fly ash, including physical and chemical activation methods. During the present reporting period (June 30, 2001-June 29, 2002), additional characterization work was conducted under Task 1 ''Procurement and characterization of CCBPs''. The suite collected includes samples from pulverized utility boilers, a utility cyclone unit equipped with a beneficiation technology, a stoker, and a fluidized bed combustor. Proximate, ultimate, and petrographic analyses of the fly ash samples previously collected were measured. Furthermore, the surface areas of the samples assembled were characterized by N{sub 2} adsorption isotherms at 77 K. The proximate analyses showed that all the samples had very low moisture contents (0.17 to 3.39 wt%), while volatile matter contents of the samples varied between 0.45 to 24.8 wt%. The ultimate analyses of all the fly ash samples showed that they contained primarily carbon, while the hydrogen contents of all the samples were very low. In addition, during the current reporting period, also Task 2 ''Development of activated carbons'' and Task 3 ''Characterization of activated carbons'' were continued.

Prof. Harold H. Schobert; Dr. M. Mercedes Maroto-Valer; Ms. Zhe Lu

2002-09-27

122

Solution combustion synthesis of calcium zirconate, CaZrO{sub 3}, powders  

SciTech Connect

Single-phase CaZrO{sub 3} powder was prepared by heating at 300 deg. C an aqueous solution of Ca(NO{sub 3}){sub 2}, ZrO(NO{sub 3}){sub 2} and beta-C{sub 3}H{sub 7}NO{sub 2} (molar ratio=3:3:4). TG-DTA analysis indicated that an intense exothermic reaction occurred at 255 deg. C, which lead to the formation of a voluminous white powder. No additional annealing was required, as pure crystalline CaZrO{sub 3} resulted directly from the combustion reaction. Although no advanced milling was performed, the specific surface area of the powder was 21.5 m{sup 2}/g. The average crystallite size of CaZrO{sub 3} was 23.9 nm. After sintering in air at 1400 deg. C for 2 h, the pellets - shaped by uniaxial pressing at 200 MPa - reached 95% of the theoretical density, had no open pores and were slightly translucent. - Graphical abstract: Single-phase CaZrO{sub 3} powder was prepared by low-temperature combustion synthesis. The resulting powder had a BET area of 21.5 m{sup 2}/g. After sintering at 1400 deg. C for 2 h 95% of the theoretical density was reached.

Ianos, Robert, E-mail: robert_ianos@yahoo.co ['Politehnica' University of Timisoara, Faculty of Industrial Chemistry and Environmental Engineering, P-ta Victoriei No. 2, Timisoara 300006 (Romania); Barvinschi, Paul [West University of Timisoara, Faculty of Physics, Bd. Vasile Parvan No. 4, Timisoara 300223 (Romania)

2010-03-15

123

Sol-gel auto-combustion synthesis of totally immiscible NiAg alloy  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Chemically synthesized immiscible NiAg alloy nanoparticles without protecting matrix. Black-Right-Pointing-Pointer A chemical method providing both a nonequilibrium thermal process and a good mixing of precursors. Black-Right-Pointing-Pointer Observation of extinction planes in NiAg alloy. -- Abstract: Immiscible crystalline NiAg alloy was successfully synthesized by the newly developed sol-gel auto-combustion method. The structure and composition were examined by X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM). All evidence supports that homogeneous NiAg alloy with FCC structure was synthesized. The differential thermal analysis and thermogravimetry (DTA-TG) measurement shows that the alloy has a good thermal stability until 315 Degree-Sign C. Unusually some extinction planes are observed in the XRD pattern and HRTEM images. The random distribution of atoms and the large difference between Ni and Ag atom form factors should be regarded as the main reasons for the observation of the extinction planes. The quenching like nonequilibrium thermal process in the combustion is taken as the key factor in the synthesis of immiscible alloy. And the addition of ethylene glycol in the precursors is found to benefit the formation of NiAg alloy.

Jiang, Yuwen [National Laboratory of Microstructure and Department of Physics, Nanjing University, Nanjing 210093 (China)] [National Laboratory of Microstructure and Department of Physics, Nanjing University, Nanjing 210093 (China); Yang, Shaoguang, E-mail: sgyang@nju.edu.cn [National Laboratory of Microstructure and Department of Physics, Nanjing University, Nanjing 210093 (China)] [National Laboratory of Microstructure and Department of Physics, Nanjing University, Nanjing 210093 (China); Hua, Zhenghe; Gong, Jiangfeng; Zhao, Xiaoning [National Laboratory of Microstructure and Department of Physics, Nanjing University, Nanjing 210093 (China)] [National Laboratory of Microstructure and Department of Physics, Nanjing University, Nanjing 210093 (China)

2011-12-15

124

Different toxic mechanisms are activated by emission PM depending on combustion efficiency  

NASA Astrophysics Data System (ADS)

Ambient air levels of fine particulate matter (PM ? 2.5 ?m) are associated with mortality and morbidity. In addition to traffic, large quantities of fine and ultrafine particles (UFPs ? 100 nm) are emitted by residential wood combustion. Polycyclic aromatic hydrocarbon (PAH) and soot-rich emissions from small scale heating appliances have been linked with a plethora of toxicological effects. Recently, new technology appliances have been introduced into use although there are several uncertainties related to the toxicological properties of those emissions. In this study, PM1 (PM ? 1 ?m) emissions from three different biomass combustion situations were compared. PM samples were produced in a novel adjustable biomass combustion reactor to avoid the problems encountered if one uses different appliances to generate the desired combustion conditions. The combustion conditions represented efficient, intermediate and smoldering situations. The concentration related effects of the particles (15, 50,150 and 300 ?g ml-1) were investigated in a RAW264.7 macrophage cell line after 24 h' exposure. We analyzed cellular metabolic activity, cell cycle, and indicators of genotoxicty, oxidative stress and proinflammatory responses. Interestingly, the particles collected from smoldering and intermediate combustion conditions decreased cellular metabolic activity less than those from efficient combustion (10-fold difference). However, the samples from intermediate and smoldering combustion evoked greater DNA damage in the comet assay (2.5-fold difference). In contrast, only the particulate samples from efficient combustion triggered G2-cell cycle arrest and oxidative stress in the macrophages. These results indicate that ash rich PM emissions from appliances with almost complete combustion may still exert health impacts. However, particulate emissions from efficient combustion were small when compared to the two other situations. Thus, even with their faults and the obvious need for development, consumers should be encouraged to purchase efficient combustion devices in order to reduce exposure to PM induced adverse health effects.

Uski, O.; Jalava, P. I.; Happo, M. S.; Leskinen, J.; Sippula, O.; Tissari, J.; Mäki-Paakkanen, J.; Jokiniemi, J.; Hirvonen, M.-R.

2014-06-01

125

Retention of mercury in activated carbons in coal combustion and gasification flue gases  

Microsoft Academic Search

To avoid the emission of toxic mercury compounds from coal combustion and gasification, efficient gas cleaning systems need to be developed. In this work, the effectiveness of activated carbons for retaining mercury in gases from coal gasification was evaluated and contrasted with the results obtained in a coal combustion atmosphere. The performance of a sulphur-loaded carbon (RBHG3) was compared with

M. Antonia Lopez-Antón; Juan M. D Tascón; M. Rosa Mart??nez-Tarazona

2002-01-01

126

Modeling and simulation of combustion chamber and propellant dynamics and issues in active control of combustion instabilities  

NASA Astrophysics Data System (ADS)

A method for a comprehensive approach to analysis of the dynamics of an actively controlled combustion chamber, with detailed analysis of the combustion models for the case of a solid rocket propellant, is presented here. The objective is to model the system as interconnected blocks describing the dynamics of the chamber, combustion and control. The analytical framework for the analysis of the dynamics of a combustion chamber is based on spatial averaging, as introduced by Culick. Combustion dynamics are analyzed for the case of a solid propellant. Quasi-steady theory is extended to include the dynamics of the gas-phase and also of a surface layer. The models are constructed so that they produce a combustion response function for the solid propellant that can be immediately introduced in the our analytical framework. The principal objective mechanisms responsible for the large sensitivity, observed experimentally, of propellant response to small variations. We show that velocity coupling, and not pressure coupling, has the potential to be the mechanism responsible for that high sensitivity. We also discuss the effect of particulate modeling on the global dynamics of the chamber and revisit the interpretation of the intrinsic stability limit for burning of solid propellants. Active control is also considered. Particular attention is devoted to the effect of time delay (between sensing and actuation); several methods to compensate for it are discussed, with numerical examples based on the approximate analysis produced by our framework. Experimental results are presented for the case of a Dump Combustor. The combustor exhibits an unstable burning mode, defined through the measurement of the pressure trace and shadowgraph imaging. The transition between stable and unstable modes of operation is characterized by the presence of hysteresis, also observed in other experimental works, and hence not a special characteristic of this combustor. Control is introduced in the form of pulsed secondary fuel. We show the capability of forcing the transition from unstable to stable burning, hence extending the stable operating regime of the combustor. The transition, characterized by the use of a shadowgraph movie sequence, is attributed to a combined fluid-mechanic and combustion mechanism.

Isella, Giorgio Carlo

127

Characterization of Mg 1? x Ni x Al 2O 4 solid solutions prepared by combustion synthesis  

Microsoft Academic Search

Mg1?xNixAl2O4 (x=0, 0.25, 0.5, 0.75 and 1) solid solutions have been prepared by combustion synthesis. After annealing the combustion synthesized powders at 1000°C for 3h single-phase Mg1?xNixAl2O4 was obtained over the entire range of compositions. The lattice parameter of Mg1?xNixAl2O4 gradually increased from 8.049Å (NiAl2O4) to 8.085Å (MgAl2O4), which certified the formation of the spinel solid solutions. All samples prepared

Robert Iano?; Paul Barvinschi

2011-01-01

128

Microwave-induced combustion synthesis of aluminum oxide-titanium carbide powder  

NASA Astrophysics Data System (ADS)

Microwave heating offers many potential advantages, including synthesizing of material. This advantage results from the unique features of microwave heating which include its internal volumetric heating and subsequent inverted temperature profile. Fundamental knowledge of how reaction parameters influence microwave-ignition behavior is needed in order to provide information required for synthesizing the desired products. This study was performed to synthesize Al2O3-TiC powders by using microwave heating. The important reaction parameters were identified using the Plackett-Burman design including amount of excess Al and Al2O3, particle size of C and Al2O 3, and heating method. The effect of these reaction parameters on the ignition behavior and characteristics of the resulting powders was then evaluated by the central composite design. The combustion synthesis of Al2O3-TiC powders using microwave heating (MH) and microwave hybrid heating (MHH) was successfully achieved. The MHH-ignited sample required a longer time to reach ignition temperature and thus resulted in a lower combustion temperature. The results showed no significant difference in characteristics of powders ignition time and temperature, while decreasing the combustion temperature. An increased particle size of Al2O3 lowered the ignition time and temperature. The density of product decreased with increasing amounts of Al. Addition of excess Al2O3 to reactants resulted in decreasing the agglomeration size. The empirical models relating these important parameters and their interactions to the responses were then developed. The mechanism governing the combustion reaction of Al2O 3-TiC powders under microwave and conventional heating was also investigated. The results suggested that reaction mechanisms using these two methods were similar. The reaction proceeded in a three-stage process where the aluminum melted, then the melting Al reacted with the titania, and finally the titanium reacted with the carbon to produce the Al2O3-TiC. The only difference was the way the reactants were heated. In conventional heating, material was heated by heat transfer process depending on its thermal conductivity. Heating by microwaves is a function of dielectric properties of the material. Depending on the microwave absorption of the materials in question, heat generation by microwave heating occurs internally.

Atong, Duangduen

2000-11-01

129

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

SciTech Connect

The implementation of increasingly stringent Clean Air Act Regulations by the coal utility industry has resulted in an increase in the concentration of unburned carbon in coal combustion fly ash. In 1999, around 6 million tons of unburned carbon were disposed in the US, due to the present lack of efficient routes for its utilization. However, unburned carbon is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, this report evaluates and compares several routes for the production of activated carbons from unburned carbon, including physical activation with steam or CO{sub 2}, and chemical activation using KOH pretreatment. During the present reporting period (June 30, 2000--June 29, 2001), Task 1 ''Procurement and characterization of CCBPs'' was concluded, including samples from pulverized utility boilers, a utility cyclone unit equipped with a beneficiation technology, a suspension-fired research boiler, and a class C fly ash. The characterization studies showed that the samples collected have significantly different carbon contents, as determined by the ASTM C114 procedure, with the sample from the cyclone unit containing the highest carbon content (LOI of {approx} 80%), since this unit has been retrofitted with a technology to separate the unburned carbon from the fly ash. The porosity of the samples assembled was characterized by N{sub 2} adsorption isotherms at 77K. The surface areas of the class F fly ash samples from pulverized coal combustors are between 30-40 m{sup 2}/g, while the samples from the suspension-fired research boiler had surface area around 115 m{sup 2}/g. As expected, the surface areas of the class C ash is much higher than that of the class F ashes, with values up to 390 m{sup 2}/g. In addition, during the current reporting period, also Task 2 ''Development of activated carbons'' and Task 3 ''Characterization of activated carbons'' were continued.

Prof. Harold H. Schobert; Dr. M. Mercedes Maroto-Valer; Ms. Zhe Lu

2001-09-29

130

Performance Evaluation of a High Bandwidth Liquid Fuel Modulation Valve for Active Combustion Control.  

National Technical Information Service (NTIS)

At the NASA Glenn Research Center, a characterization rig was designed and constructed for the purpose of evaluating high bandwidth liquid fuel modulation devices to determine their suitability for active combustion control research. Incorporated into the...

C. T. Chang D. R. Vrnak J. C. DeLaat J. R. Saus

2012-01-01

131

Combustion synthesis of ceramic-metal composite materials - The TiC-Al2O3-Al system  

NASA Technical Reports Server (NTRS)

Combustion synthesis was applied for producing ceramic-metal composites with reduced levels of porosity, by allowing an excess amount of liquid metal, generated by the exothermic reaction during synthesis, to infiltrate the pores. It is shown that this method, when applied to TiC-Al2O3 system, led to a decreased level of porosity in the resulting TiC-Al2O3-Al product, as compared with that of TiC-Al2O3 system. This in situ procedure is more efficient than the two-stage conventional processes (i.e., sintering followed by liquid metal infiltration), although there are limitations with respect to total penetration of the liquid metal and maintaining a stable propagation of the combustion reaction.

Feng, H. J.; Moore, John J.; Wirth, D. G.

1992-01-01

132

Studies on combustion catalytic activity of some pure and doped lanthanum cobaltites  

Microsoft Academic Search

The aim of this work is to compare the catalytic activity of some pure and doped lanthanum cobaltites, prepared by solution combustion technique, with a Pt\\/Al2O3 commercial catalyst. As test reaction we used the combustion of lean methane mixtures. The experimental data evidenced a significantly better catalytic activity of a cerium-doped lanthanum cobaltite, prepared by using ?-alanine as fuel. The

Magdalena Bosomoiu; Grigore Bozga; Daniela Berger; Cristian Matei

2008-01-01

133

Multifunction Gd2O3:Eu nanocrystals produced by solution combustion synthesis: Structural, luminescent, and magnetic characterization  

Microsoft Academic Search

The synthesis, structural, luminescent, and magnetic properties of multifunction 8 at. % Eu-doped Gd2O3 nanocrystals were investigated. The material was synthesized by the solution combustion technique and characterized by x-ray diffraction (XRD), transmission electron microscopy, and photoluminescence and magnetization measurements. The as-prepared material presents predominant base-centered monoclinic structure with average crystallite size of 35 nm. Isothermal annealing at 1000 °C

L. G. Jacobsohn; B. L. Bennett; R. E. Muenchausen; S. C. Tornga; J. D. Thompson; O. Ugurlu; D. W. Cooke; A. L. Lima Sharma

2008-01-01

134

Inverse peptide synthesis via activated ?-aminoesters.  

PubMed

A mild, practical, and simple procedure for peptide-bond formation is reported. Instead of activation of the carboxylic acid functionality, the reaction involves an unprecedented use of activated ?-aminoesters. The method provides a straightforward entry to dipeptides and was effective when a sensitive cysteine residue was used, as no epimerization was detected in this case. The applicability of this method to iterative peptide synthesis was illustrated by the synthesis of a model tetrapeptide in the challenging reverse N?C direction. PMID:24757099

Suppo, Jean-Simon; Subra, Gilles; Bergès, Matthieu; Marcia de Figueiredo, Renata; Campagne, Jean-Marc

2014-05-19

135

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

Microsoft Academic Search

The implementation of increasingly stringent Clean Air Act Regulations by the coal utility industry has resulted in an increase in the concentration of unburned carbon in coal combustion fly ash. In 1999, around 6 million tons of unburned carbon were disposed in the US, due to the present lack of efficient routes for its utilization. However, unburned carbon is a

Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

2001-01-01

136

Synthesis and characterization of X-ray nanophosphors using solution-combustion  

NASA Astrophysics Data System (ADS)

We investigated nanophosphor materials that exhibit high resolution and emission efficiency for use in X-ray medical imaging. Rare-earth phosphor material has long been used due to its high atomic number and emission efficiency, but these materials tend to exhibit lower resolution and emission efficiency when manufactured in bulk. In this study, we synthesized nanometer-scale phosphors of Gd2O3:Eu and Y2O3:Eu using the solution-combustion method, and we evaluated the dependence of the optical properties of these nanophosphors on europium concentration and synthesis atmosphere. The nanophosphors were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) spectroscopy. Characterization of the optical properties revealed that both Gd2O3:Eu and Y2O3:Eu exhibited peak emission intensity at 611 nm, which corresponded to that for commercial bulk phosphors. These results imply that manufacturing nanophosphors can achieve thin and compact displays that have enhanced performance, and that improvements in emission efficiency of nanophosphors could reduce the required patient dose for medical imaging.

Park, H. J.; Shin, J. W.; Oh, K. M.; Jeon, S. P.; Kim, S. H.; Lee, Y. K.; Nam, S. H.

2011-12-01

137

Highly aluminium doped barium and strontium ferrite nanoparticles prepared by citrate auto-combustion synthesis  

SciTech Connect

Aluminium doped barium and strontium hexaferrite nanoparticles BaAl {sub x}Fe{sub (12-x)}O{sub 19} and SrAl {sub x}Fe{sub (12-x)}O{sub 19} were synthesised via a sol-gel route using citric acid to complex the ions followed by an auto-combustion reaction. This method shows promise for the synthesis of complex ferrite powders with small particle size. It was found that around half of the iron could be substituted for aluminium in the barium ferrite with structure retention, whereas strontium aluminium ferrites could be produced with any aluminium content including total substitution of the iron. All synthesised materials consisted of particles smaller than 1 {mu}m, which is the size of a single magnetic domain, and various doping levels were achieved with the final elemental composition being within the bounds of experimental error. The materials show structural and morphological changes as they move from iron to aluminium ferrites. Such materials may be promising for imaging applications.

Shirtcliffe, Neil J. [Nottingham Trent University, Clifton Lane, Clifton, Nottingham NG11 8NS (United Kingdom)]. E-mail: neil.shirtcliffe@ntu.ac.uk; Thompson, Simon [Nottingham Trent University, Clifton Lane, Clifton, Nottingham NG11 8NS (United Kingdom); O'Keefe, Eoin S. [QinetiQ, Farnborough, Hampshire (United Kingdom); Appleton, Steve [QinetiQ, Farnborough, Hampshire (United Kingdom); Perry, Carole C. [Nottingham Trent University, Clifton Lane, Clifton, Nottingham NG11 8NS (United Kingdom)]. E-mail: carole.perry@ntu.ac.uk

2007-02-15

138

Structural and spectroscopic analyses of europium doped yttrium oxyfluoride powders prepared by combustion synthesis  

SciTech Connect

A facile widely spread technique employed to produce low-cost high-yield oxide powders, combustion synthesis, was used to prepare yttrium oxyfluoride crystalline ceramic powders. The structure of the powders was analyzed by X-ray powder diffraction and Rietveld refinement. Samples heat treated at 700 °C had a predominance of vernier orthorhombic Y{sub 6}O{sub 5}F{sub 8} phase, while samples heat treated at 800 °C crystallized in stoichiometric rhombohedral YOF phase. The samples were doped with luminescent europium trivalent ions (Eu{sup 3+}) in different concentrations (1–15 wt.%) and Judd-Ofelt theory was used to probe the distortion from the inversion symmetry of the local crystal field and the degree of covalency between the rare-earth ion and the surrounding ligands. The luminescence lifetime was measured and the luminescence quantum efficiency (LQE) was estimated. We observed that Eu{sup 3+}:Y{sub 6}O{sub 5}F{sub 8} samples presented higher LQE in spite of the larger local crystal field anisotropy found for Eu{sup 3+}:YOF samples.

Rakov, Nikifor [PG-Ciência dos Materiais, Universidade Federal do Vale do São Francisco, 48902-300 Juazeiro, BA (Brazil)] [PG-Ciência dos Materiais, Universidade Federal do Vale do São Francisco, 48902-300 Juazeiro, BA (Brazil); Guimarães, R. B.; Maciel, Glauco S. [Instituto de Física, Universidade Federal Fluminense, 24210-346 Niterói, RJ (Brazil)] [Instituto de Física, Universidade Federal Fluminense, 24210-346 Niterói, RJ (Brazil); Lozano B, W. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil)] [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil)

2013-07-28

139

Structural and spectroscopic analyses of europium doped yttrium oxyfluoride powders prepared by combustion synthesis  

NASA Astrophysics Data System (ADS)

A facile widely spread technique employed to produce low-cost high-yield oxide powders, combustion synthesis, was used to prepare yttrium oxyfluoride crystalline ceramic powders. The structure of the powders was analyzed by X-ray powder diffraction and Rietveld refinement. Samples heat treated at 700 °C had a predominance of vernier orthorhombic Y6O5F8 phase, while samples heat treated at 800 °C crystallized in stoichiometric rhombohedral YOF phase. The samples were doped with luminescent europium trivalent ions (Eu3+) in different concentrations (1-15 wt.%) and Judd-Ofelt theory was used to probe the distortion from the inversion symmetry of the local crystal field and the degree of covalency between the rare-earth ion and the surrounding ligands. The luminescence lifetime was measured and the luminescence quantum efficiency (LQE) was estimated. We observed that Eu3+:Y6O5F8 samples presented higher LQE in spite of the larger local crystal field anisotropy found for Eu3+:YOF samples.

Rakov, Nikifor; Guimara~es, R. B.; Lozano B., W.; Maciel, Glauco S.

2013-07-01

140

Mechanism of combustion in a nitrogen-oxygen atmosphere of the char produced by the pyrolysis of surface activated sludge  

Microsoft Academic Search

The rate of combustion of char produced by the pyrolysis of surplus activated sludge was measured in a nitrogen-oxygen atmosphere by thermogravimetric analysis. The effects on the rate of combustion of the temperature of combustion, the concentration of oxygen, the temperature of pyrolysis, and the size of the char particle were investigated. At temperatures of combustion below 550°C, the overall

N. Arai; M. Hasatani; S. Sugiyama

1983-01-01

141

Optimization of the low temperature combustion synthesis of Er3+ doped lead-natrium-yttrium-fluoride phosphor  

NASA Astrophysics Data System (ADS)

The low-temperature combustion synthesis (LCS) method is the most popular method for the synthesis of ultrafine oxides and compound oxides. A kind of Er-Y-Pb-Na quaternary fluoride sensitive to 1.55 ?m was synthesized by the LCS method and the synthesis conditions were optimized with orthogonal experiments. Intense upconversion emissions at 522 nm, 541.4 nm and 654.7 nm corresponding to the 2H11/2, 4S3/2 and 4F9/2 transitions to the 4I15/2 ground state were observed when excited by CW laser radiation at 1.55 ?m. The effect of the carbamide amount on the phase formation and the luminescence intensity was analyzed. The product is of uniform particle size of ca. 40 nm, which is very outstanding for its reutilization in the infrared detection field.

Lu, Liping; Zhang, Xiyan

2014-12-01

142

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

Microsoft Academic Search

The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization.

Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

2003-01-01

143

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

Microsoft Academic Search

The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly fly ash containing unburned carbon. However, the carbonaceous residue in fly ash, unburned carbon (UC), is a potential precursor for the production of adsorbent carbons, since it has gone through a

Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

2000-01-01

144

Impact initiated combustion of aluminum exposed to mechanical pre-activation  

NASA Astrophysics Data System (ADS)

The impact initiation of as-received and mechanically activated aluminum powder compacts is investigated through uniaxial stress rod-on-anvil impact experiments. The compacts reveal light emission due to combustion reaction at velocities greater than 165 m/s. Mechanical pre-activation, such as that achieved via high-energy ball milling (HEBM) or high strain machining, strain hardens the starting materials, affecting their combustion initiation behavior. The starting materials are characterized by their lattice strain, size, and surface area to volume ratio. High speed imaging reveals that the threshold velocity (minimum velocity necessary for reaction initiation) changes as a function of the mechanical pre-activation.

Breidenich, J. L.; Turner, J.; Kennedy, G.; Thadhani, N. N.

2014-05-01

145

Differential behaviour of combustion and gasification fly ash from Puertollano Power Plants (Spain) for the synthesis of zeolites and silica extraction.  

PubMed

Coal gasification (IGCC) and pulverised coal combustion (PCC) fly ashes (FAs), obtained from two power plants fed with the carboniferous bituminous coal from Puertollano (Spain), were characterised and used as raw materials for zeolite synthesis by direct conversion (DC) and by alkaline fusion (Fu), and SiO2 extraction (Si-Ex) at laboratory scale. The Puertollano FAs are characterised by a high SiO2 content (59%) with respect to EU coal FAs. High zeolite synthesis yields were obtained from both FAs by using conventional alkaline activation. However, the Si extraction yields were very different. The results of the zeolite synthesis from the Si-bearing extracts from both FAs demonstrated that high purity zeolites with high cation exchange capacity (CEC, between 4.3 and 5.3meq/g) can be produced. The solid residue arising from Si-Ex is also a relatively high NaP1 zeolite product (CEC 2.4-2.7 meq/g) equivalent to the DC products. The zeolitic materials synthesised from both FAs by Fu showed an intermediate (between the high purity zeolites and the DC products) zeolite content with CEC values from 3.4 to 3.7 meq/g. Low leachable metal contents were obtained from high purity A and X zeolites and zeolite material synthesised by Fu for PCC FA. PMID:19097700

Font, O; Moreno, N; Díez, S; Querol, X; López-Soler, A; Coca, P; Peña, F García

2009-07-15

146

Microstructure of the Ti{sub 3}Al(Nb)/TiB composite produced by combustion synthesis  

SciTech Connect

The combustion synthesis technique was used to produce the intermetallic composite {alpha}{sub 2}-Ti{sub 3}Al(Nb) reinforced with TiB fibers. The microstructure was examined by scanning electron microscopy (SEM), X-ray diffraction analysis, and transmission electron microscopy (TEM). Neither the {beta} nor the {beta}{sub 0} phase was found in the intermetallic matrix. The TiB phase with B27 structure existed in the form of polycrystalline faceted whiskers growing in the <010> direction of the unit cell. No defined crystallographic relationship between the TiB whiskers and the matrix was found in the investigation.

Yang, W.Y. [Univ. of Science and Technology, Beijing (China); Yi, H.C. [Guingne International, Paradise, Newfoundland (Canada); Petric, A. [McMaster Univ., Hamilton, Ontario (Canada). Dept. of Materials Science and Engineering

1995-11-01

147

Melt-Casting of Translucent MgAl2O4 Ceramics by Combustion Synthesis Under High Gravity  

Microsoft Academic Search

Translucent MgAl2O4 was prepared by combustion synthesis melt-casting under high gravity. Compared with common gravitational condition, under high-gravity condition the separation between ceramic and metal melts was accelerated, and thus the content of residual Ni in MgAl2O4 ingot was reduced. By the incorporation of SiO2 or Si-Na-Ca-Mg-O glass additives, residual Ni was eliminated and single-phase MgAl2O4 was obtained. On the

Guanghua Liu; Jiangtao Li; Zengchao Yang

2012-01-01

148

Synthesis and characterization of Ni x Mg 1? x Al 2O 4 nano ceramic pigments via a combustion route  

Microsoft Academic Search

MgAl2O4 was successfully used as a crystalline host network for the synthesis of nickel-based nano cyan refractory ceramic pigments. Different compositions of NixMg1?xAl2O4 (0.1?x?0.8) powders have been prepared by using a low temperature combustion reaction (LTCR) of the corresponding metal nitrates with urea (U) as a fuel at 300°C in an open air furnace. The as-synthesized samples were characterized by

I. S. Ahmed; H. A. Dessouki; A. A. Ali

2011-01-01

149

Melt-Casting of Translucent MgAl2O4 Ceramics by Combustion Synthesis Under High Gravity  

Microsoft Academic Search

Translucent MgAl2O4 was prepared by combustion synthesis melt-casting under high gravity. Compared with common gravitational condition, under high-gravity condition the separation between ceramic and metal melts was accelerated, and thus the content of residual Ni in MgAl2O4 ingot was reduced. By the incorporation of SiO2 or Si-Na-Ca-Mg-O glass additives, residual Ni was eliminated and single-phase MgAl2O4 was obtained. On the

Guanghua Liu; Jiangtao Li; Zengchao Yang

2011-01-01

150

Eco-friendly combustion-based synthesis of metal aluminates MAl 2 O 4 (M = Ni, Co)  

Microsoft Academic Search

Nanosized metal aluminates, MAl2O4 (M = Ni, Co), have been prepared following a nonpolluting, low temperature, and self-sustaining starch single-fuel combustion\\u000a synthesis. The mixed fuel-coordinating actions of starch have given rise to an intermediary precursor which afforded monodisperse\\u000a metal aluminate nanoparticles. The thermal analysis of the [M(II), Al(III)]-starch precursors indicates a similar thermochemical\\u000a reactivity for the two compounds, displaying a sequence of

Alina Tirsoaga; Diana Visinescu; Bogdan Jurca; Adelina Ianculescu; Oana Carp

151

Combustion Synthesis of Nanoparticulate LiMgxMn1-xPO4 (x=0, 0.1, 0.2) Carbon Composites  

SciTech Connect

A combustion synthesis technique was used to prepare nanoparticulate LiMgxMn1-xPO4 (x=0, 0.1,0.2)/carbon composites. Powders consisted of carbon-coated particles about 30 nm in diameter, which were partly agglomerated into larger secondary particles. The utilization of the active materials in lithium cells depended most strongly upon the post-treatment and the Mg content, and was not influenced by the amount of carbon. Best results were achieved with a hydrothermally treated LiMg0.2Mn0.8PO4/C composite, which exhibited close to 50percent utilization of the theoretical capacity at a C/2 discharge rate.

Doeff, Marca M; Chen, Jiajun; Conry, Thomas E.; Wang, Ruigang; Wilcox, James; Aumentado, Albert

2009-12-14

152

Synthesis of Monolithic ?-Sialon Powders (Si6-zAlzOzN8-z, Z = 2-4) through Controlling the Combustion Reaction Temperature  

NASA Astrophysics Data System (ADS)

Pure ?-sialon powders with the controlled z values (z = 2- 4) were successfully prepared from stoichiometric mixtures of constituent elements (Si, Al and SiO2) under a nitrogen pressure of 1 MPa by the combustion synthesis (CS) method. The raw materials were combusted with different ratios of a commercial sialon powder of z = 1 as a diluent (0, 10, 20, 30, 40, 50 wt %). Without diluent, the reactions temperatures were very high (> 2000 °C) and the product contained metal Si residue besides Sialon products. The combustion temperatures of nitridation reactions were controlled by using Sialon (z = 1) as a diluent. The combustion reactions completed at 50 wt% dilution, and pure ?-sialon phases were synthesized. However, the individual peaks of ?-Sialon (z = 1) diluent were also detected. Single-phase ?-sialon powders were obtained by using the products as diluents and repeating the combustion for few times.

Shahien, Mohammed; Radwan, Mohamed; Kirihara, Soshu; Miyamoto, Yoshinari; Sakurai, Toshitaka

2011-05-01

153

Combustion synthesis, structure and transformation characteristics of titanium carbide-nickel titanium composites  

NASA Astrophysics Data System (ADS)

An investigation into the production of TiC-NiTi composites by a technique combining self-propagating high temperature synthesis (SHS) of elemental powders with densification by quasi-isostatic pressing (QIP) has been performed. Composites with volume fractions of NiTi between 0.1 and 0.8 were produced and the resulting structures and transformation characteristics were studied. Powder mixtures prepared anticipating the formation of stoichiometric TiC resulted in the formation of composites with a eutectic-based mixture of Ni3Ti and NiTi. This titanium impoverishment of the matrix is consistent with the formation of nonstoichiometric TiCx during the combustion reaction. The Ni3Ti phase was suppressed by anticipating the formation of TiC0.7 and adjusting the chemical content of the reactant mixture to include additional titanium. In order to help optimize densification parameters, the QIP process was modeled by analytical methods. A solution to the problem of uniaxial upsetting of a porous cylinder was developed and combined with indentation experiments on SHS produced TiC0.7-30NiTi to determine constitutive properties. Transmission electron microscopy (TEM) showed that the individual B19' variants were internally twinned by either [011] Type II twinning or (111¯) Type I twinning. Wavy bands of B19' martensite, internally twinned by the (001)B19', compound twinning mode, were also observed in the 40NiTi composite. Occasionally, localized twinning appeared at the interface with the carbide particles. In-situ TEM showed that the parent B2 transformed first to the R-phase during cooling. As the temperature was further reduced, the B19' martensite nucleated at the TiCx interfaces and grew away from the particles. The growth of individual B19' variants was limited by impingement with other martensite variants. Thermal cycling appeared to change the transformation path. After 30 thermal cycles, the cubic B2 phase was observed coexisting with the monoclinic B19' phase. The R-phase transformation was suppressed. The mechanical performance of the 30NiTi composite was also evaluated. The compressive strength was 2.8 GPa and the Young's modulus was 300 GPa. Ballistic depth of penetration tests showed that the mass efficiency of the 30NiTi composite was 6.7.

Strutt, Elizabeth R.

154

Combustion synthesis and luminescent properties of metal yttrium borates M3Y2 (BO3)4:Eu3+ (M = Ba, Sr) for PDPs applications  

NASA Astrophysics Data System (ADS)

The polycrystalline powder samples of Eu3+ activated; mixed metal yttrium borate phosphors M3Y2(BO3)4 (M = Ba, Sr) with improved color purity of red emission for plasma display panels (PDPs) were prepared by solution combustion technique. The synthesis is based up on the exothermic reaction between the fuel (Urea) and oxidizer (Ammonium nitrate) .The heat generated in the reaction is utilized for auto combustion of ingredients. The formation of desired product and crystal structure was confirmed by powder XRD technique; while particle morphology was studied using FE-SEM. Samples under 254 and 147 nm excitation showed intense and pure red emission around 613 nm corresponding to the electric dipole 5D0 ? 7F2 transition of Eu3+, CIE chromaticity coordinates of synthesized phosphors was found to be (x = 0.67, y = 0.32) close to National Television Standard Committee (NTSC) for red color; found suitable to employ in plasma display panels (PDPs) applications.

Ingle, J. T.; Sonekar, R. P.; Omanwar, S. K.; Wang, Yuhua; Zhao, Lei

2014-07-01

155

Problems with determining oxygen deficiencies for use in ratios used for assessing spontaneous combustion activity  

Microsoft Academic Search

Several common ratios used for determining spontaneous combustion activity rely on comparing the amount of various products of oxidation with the amount of oxygen consumed to produce these products. As coal gets hotter, oxidation reactions become more efficient meaning more products produced for less oxygen consumed. There are many problems associated with accurately determining the true amount of oxygen used.

D. M. Brady

156

Application of active combustion instability control to a heavy duty gas turbine  

SciTech Connect

During the prototype shop tests, the Model V84.3A ring combustor gas turbine unexpectedly exhibited a noticeable humming caused by self-excited flame vibrations in the combustion chamber for certain operating conditions. The amplitudes of the pressure fluctuations in the combustor were unusually high when compared to the previous experience with silo combustor machines. As part of the optimization program, the humming was investigated and analyzed. To date, combustion instabilities in real, complex combustors cannot be predicted analytically during the design phase. Therefore, and as a preventive measure against future surprises by humming, a feedback system was developed which counteracts combustion instabilities by modulation of the fuel flow rate with rapid valves (active instability control, AIC). The AIC achieved a reduction of combustion-induced pressure amplitudes by 86%. The combustion instability in the Model V84.3A gas turbine was eliminated by changes of the combustor design. Therefore, the AIC is not required for the operation of customer gas turbines.

Seume, J.R.; Vortmeyer, N.; Krause, W. [Siemens Power Generation, Berlin (Germany); Hermann, J.; Hantschk, C.C.; Zangl, P.; Gleis, S.; Vortmeyer, D. [Technical Univ. of Munich (Germany). Lehrstruhl B. Fuer Thermodynamik; Orthmann, A. [pad Software, Haar-Salmdorf (Germany)

1998-10-01

157

Synthesis and Anticancer Activity of Epipolythiodiketopiperazine Alkaloids  

PubMed Central

The epipolythiodiketopiperazine (ETP) alkaloids are a highly complex class of natural products with potent anticancer activity. Herein, we report the application of a flexible and scalable synthesis, allowing the construction of dozens of ETP derivatives. The evaluation of these compounds against cancer cell lines in culture allows for the first expansive structure–activity relationship (SAR) to be defined for monomeric and dimeric ETP-containing natural products and their synthetic cognates. Many ETP derivatives demonstrate potent anticancer activity across a broad range of cancer cell lines, and kill cancer cellsviainduction of apoptosis. Several traits thatbode well for the translational potential of the ETP class of natural products includeconcise and efficient synthetic access, potent induction of apoptotic cell death, activity against a wide range of cancer types, and a broad tolerance for modifications at multiple sitesthat should facilitate small-molecule drug development, mechanistic studies, and evaluation in vivo.

Boyer, Nicolas; Morrison, Karen C.; Kim, Justin; Hergenrother, Paul J.; Movassaghi, Mohammad

2013-01-01

158

Measurement of in vivo cholesterol synthesis from 2H2O: a rapid procedure for the isolation, combustion, and isotopic assay of erythrocyte cholesterol.  

PubMed

A rapid preparative scale purification of erythrocyte free cholesterol has been developed for measurements of in vivo cholesterol synthesis from 2H2O. The quantity and purity of cholesterol obtained is suitable for combustion, zinc reduction of the water formed, and determination of deuterium isotopic content by gas isotope ratio mass spectrometry. The ability to detect and to quantitate a range of cholesterol synthesis rates is illustrated by measurements on young pigs receiving diets without and with added dietary cholesterol. PMID:1940619

Wong, W W; Hachey, D L; Feste, A; Leggitt, J; Clarke, L L; Pond, W G; Klein, P D

1991-06-01

159

The study of combustion synthesis of fine-particle ?-lithium aluminate  

Microsoft Academic Search

Fine-particle ?-lithium aluminate has been prepared by the combustion of mixtures of the metal nitrates, M(NO3)x(M = Li, Al) as oxidizers and urea and citric acid as fuels, at low temperature and short reaction time. The combustion products were identified from X-ray powder diffraction (XRD) patterns, scanning electron microscopy (SEM), and pore size distribution measurements. As the total composition of

Wei Lin; Xinde Bai; Yunhan Ling; Jinlong Yang; Wenjun Ma

2003-01-01

160

Magneto-thermal and dielectric properties of biferroic YCrO{sub 3} prepared by combustion synthesis  

SciTech Connect

Microstructural, magnetothermal and dielectric properties of YCrO{sub 3} powders prepared by combustion and solid state methods have been studied by a combination of XRD, specific heat, magnetization and permittivity measurements. The TEM and XRD characterization confirm that the combustion powders are amorphous plate-like agglomerates of nano-sized crystalline particles. A more uniform grain size along with an increase of the relative density is observed by SEM in the sintered samples prepared by combustion route with respect to those produced by solid state reaction. Similar to the material obtained through solid state synthesis, the material prepared by the combustion method also shows spin canted antiferromagnetic ordering of Cr{sup +3} (S=3/2) at {approx}140 K, which is shown by magnetization as well as {lambda}-type anomaly in the total specific heat. Furthermore, the magnetic contribution to the total specific heat reveals spin fluctuations above T{sub N} and a spin reorientation transition at about 60 K. Both YCrO{sub 3} compounds show a diffuse phase transition at about 450 K, typical of a relaxor ferroelectric, which is characterized by a broad peak in the real part of the dielectric permittivity as a function of temperature, with the peak decreasing in magnitude and shifting to higher temperature as the frequency increases. The relaxor dipoles are due to the local non-centrosymmetric structure. Furthermore, the high loss tangent in a broad range of temperature as well as conductivity analysis indicates a hopping mechanism for the electronic conductivity as we believe it is a consequence of the outer d{sup 3}-shell, which have detrimental effects on the polarization and the pooling process in the YCrO{sub 3} bulk material. The more uniform particle size and higher density material synthesized through the combustion process leads to an improvement in the dielectric Properties. - Graphical abstract: Combustion method: An alternative route for synthesized a new family of multiferroics. Amorphous agglomerates of nano-sized particles of YCrO{sub 3} compounds.

Duran, A., E-mail: dural@cnyn.unam.m [Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia, Apartado Postal 2681, C.P. 22800, Ensenada, B.C. (Mexico); Arevalo-Lopez, A.M.; Castillo-Martinez, E. [Departamento de Quimica Inorganica y Laboratorio Complutense de Altas Presiones, Facultad de Quimica, Universidad Complutense de Madrid, E.U., 28040 Madrid (Spain); Garcia-Guaderrama, M. [Centro de Investigacion en Materiales DIP-CUCEI, Universidad de Guadalajara. Av. Revolucion 1500, Col. Olimpica, Guadalajara (Mexico); Moran, E. [Departamento de Quimica Inorganica y Laboratorio Complutense de Altas Presiones, Facultad de Quimica, Universidad Complutense de Madrid, E.U., 28040 Madrid (Spain); Cruz, M.P. [Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia, Apartado Postal 2681, C.P. 22800, Ensenada, B.C. (Mexico); Fernandez, F. [Universidad Politecnica de Madrid, E.U. Ingenieria Tecnica Industrial, Ronda de Valencia, 3, E-28012 Madrid (Spain); Alario-Franco, M.A. [Departamento de Quimica Inorganica y Laboratorio Complutense de Altas Presiones, Facultad de Quimica, Universidad Complutense de Madrid, E.U., 28040 Madrid (Spain)

2010-08-15

161

The effect of pressure on the combustion synthesis of a functionally-graded material: TiB[sub 2]-Al[sub 2]O[sub 3]-Al ceramic-metal composite system  

SciTech Connect

This article describes some recent research on the synthesis of functionally-graded materials (FGM) using combustion synthesis or self-propagating high-temperature synthesis (SHS). A model ceramic-metal SHS system was investigated. The effects of combustion mode, reactant stoichiometry (xAl), green density, and applied loads on the stability of the SHS reaction and density of the FGM product are described.

Feng, H.J.; Moore, J.J. (Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering)

1993-10-01

162

Highly Selective Synthesis of Catalytically Active Monodisperse Rhodium Nanocubes  

SciTech Connect

Synthesis of monodisperse and shape-controlled colloidal inorganic nanocrystals (NCs) is of increasing scientific interest and technological significance. Recently, shape control of Pt, Pd, Ag, Au, and Rh NCs has been obtained by tuning growth kinetics in various solution-phase approaches, including modified polyol methods, seeded growth by polyol reduction, thermolysis of organometallics, and micelle techniques. Control of reduction kinetics of the noble metal precursors and regulation of the relative growth rates of low-index planes (i.e. {l_brace}100{r_brace} and {l_brace}111{r_brace}) via selective adsorption of selected chemical species are two keys for achieving shape modification of noble metal NCs. One application for noble metal NCs of well-defined shape is in understanding how NC faceting (determines which crystallographic planes are exposed) affects catalytic performance. Rh NCs are used in many catalytic reactions, including hydrogenation, hydroformylation, hydrocarbonylation, and combustion reactions. Shape manipulation of Rh NCs may be important in understanding how faceting on the nanoscale affects catalytic properties, but such control is challenging and there are fewer reports on the shape control of Rh NCs compared to other noble metals. Xia and coworkers obtained Rh multipods exhibiting interesting surface plasmonic properties by a polyol approach. The Somorjai and Tilley groups synthesized crystalline Rh multipods, cubes, horns and cuboctahedra, via polyol seeded growth. Son and colleagues prepared catalytically active monodisperse oleylamine-capped tetrahedral Rh NCs for the hydrogenation of arenes via an organometallic route. More recently, the Somorjai group synthesized sizetunable monodisperse Rh NCs using a one-step polyol technique. In this Communication, we report the highly selective synthesis of catalytically active, monodisperse Rh nanocubes of < 10 nm by a seedless polyol method. In this approach, Br{sup -} ions from trimethyl(tetradecyl)ammonium bromide (TTAB) effectively stabilize the {l_brace}100{r_brace} faces of Rh NCs, and induce the evolution of nanocubes (Scheme 1). For a typical synthesis, 0.2 mmol RhCl{sub 3} hydrate, 1 mmol TTAB, and 4 mmol poly(vinylpyrrolidone) (PVP, Mw = 24,000), were added to 20 ml ethylene glycol at room temperature. The stock solution was heated to 80 C and purged for 20 min while stirring, producing a dark brown solution. The flask was then heated to 185 C and maintained at this temperature for 1.5 h under an Ar atmosphere. When the reaction was complete, an excess of acetone was added to the solution at room temperature to precipitate the nanocubes. The Rh nanocubes were separated by centrifugation and washed twice by precipitation/dissolution with ethanol/hexanes.

Zhang, Y.; Grass, M.E.; Kuhn, J.N.; Tao, F.; Habas, S.E.; Huang, W.; Yang, P.; Somorjai, G.A.

2009-02-21

163

Combustion synthesis of metal-matrix composites. Part 1: The Ti-TiC-Al{sub 2}O{sub 3} system  

SciTech Connect

Combustion synthesis or Self-propagating High-temperature Synthesis (SHS) is a process that involves a reaction which is sufficiently exothermic to sustain itself, and, as such, provides considerable potential for the development of an affordable (low cost), energetically efficient means of producing advanced materials. In the combustion synthesis process, a mix of the reactant powders, pressed into a pellet, is heated to the ignition temperature, Tig, when the exothermic reaction takes place, transforming reactants into products. The heat generated by the reaction raises the temperature of the products to a maximum recorded combustion temperature, Tc, which, under adiabatic conditions, would be the adiabatic temperature, Tad. However, in most combustion reactions, Tc is less than Tad, since heat losses occur from the reaction front. Materials synthesized with each of these combustion modes are typically associated with high levels of porosity, e.g., 50%, which is manifested as both macroporosity and microporosity. Previous work demonstrated that it was possible to decrease the porosity of a TiC-Al{sub 2}O{sub 3}-Ti composite by incorporating an excess liquid metal into the combustion synthesis reaction system. This reaction utilizes aluminothermic reduction of TiO{sub 2} to generate the exothermic condition, and at the same time, uses the required TiO{sub 2}/Al stoichiometry to provide the excess Ti to generate an excess Ti in a matrix of TiC and Al{sub 2}O{sub 3}, each of which are synthesized, in-situ within the overall reaction system.

Kunrath, A.O.; Strohaecker, T.R. [UFRGS, Porto Alegre, Rio Grande do Sul (Brazil). Dept. de Metalurgia] [UFRGS, Porto Alegre, Rio Grande do Sul (Brazil). Dept. de Metalurgia; Moore, J.J. [Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering] [Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering

1996-01-15

164

The Effects of Gravity on the Combustion Synthesis of B2O3-Al2O3-MgO Glass Ceramic Composites  

NASA Technical Reports Server (NTRS)

Glass ceramic composites based on B2O3-Al2O3-MgO have been produced by combustion synthesis in a Self-propagating mode. The gravitational effects on the combustion characteristics such as combustion wave velocity (V), and combustion temperature (T(sub c)) were studied. The results showed that the gravitational effects on these parameters were inconclusive. The microstructure of this system has also been analyzed with X-ray Diffraction and light microscopy. These results showed a higher amount of divitrification occurs under both reduced gravity and high gravity conditions. The gravitational effects on formation of pores, overall porosity and apparent porosity for this family of glass-ceramics also shows to be inconclusive. Possible reasons for these results are discussed.

Manerbino, A. R.; Yi, H. C.; Guigne, J. Y.; Moore, J. J.; Schowengerdt, F. D.

2000-01-01

165

Powder synthesis and characterization of nanocrystalline CeO{sub 2} via the combustion processes  

SciTech Connect

Nanocrystalline CeO{sub 2} powders were synthesized by the combustion reactions using citric acid and glycol as fuels and nitrate as an oxidant. The adiabatic flame temperatures in the auto ignition processes of the precursors were calculated theoretically. XRD measurements indicated that the powders produced in the combustion processes were cubic fluorite CeO{sub 2} phase. The size and morphology of the particles and extent of agglomeration in the powders were studied using transmission electron microscopy (TEM) and the particle size analyzer respectively. Blue shifts of the absorption peak of the as-prepared powders were observed.

Gu Lina [Department of Material Science and Engineering, University of Science and Technology of China, 230026 Hefei (China) and School of Chemistry and Chemical Engineering, Anhui University, 230039 Hefei (China)]. E-mail: gln@mail.ustc.edu.cn; Meng Guangyao [Department of Material Science and Engineering, University of Science and Technology of China, 230026 Hefei (China)

2007-07-03

166

The combustion synthesis of boride composites. [B/sub 4/C/TiB/sub 2/ infiltrated with Al  

SciTech Connect

We have investigated the combustion synthesis process as a means of producing hard, tough, lightweight B/sub 4/c/TiB/sub 2/ composites. We based our experimental program on thermodynamic calculations. Adiabatic temperatures and product compositions were determined on the basis of the stoichiometry and initial temperature of the reactants. For lightweight products the composition must be relatively rich in the B/sub 4/C component. We found that B/sub 4/C-rich composites could only be obtained by increasing the initial temperature of the reactants. The product is a hard, porous material whose toughness should be enhanced by filling the pores with aluminum using a liquid-metal infiltration process. 9 figs., 3 tabs.

Halverson, D.C.; Lum, B.Y.; Munir, Z.A.

1987-10-01

167

Synthesis of thermostable geopolymer from circulating fluidized bed combustion (CFBC) bottom ashes  

Microsoft Academic Search

Circulating fluidized bed combustion (CFBC) bottom ashes (CBAs) are a class of calcined aluminosilicate wastes with a unique thermal history. While landfill disposal of hazardous element-containing CBAs poses serious challenge, these wastes have long been neglected as source materials for geopolymer production. In this paper, geopolymerization of ground CBAs was investigated. Reactivity of the CBAs was analyzed by respective dissolution

Hui Xu; Qin Li; Lifeng Shen; Wei Wang; Jianping Zhai

2010-01-01

168

Sol-gel auto-combustion synthesis of zinc ferrite for moderate temperature desulfurization  

SciTech Connect

Zinc ferrite as a desulfurization sorbent with an average crystallite size of about 36 nm was synthesized by a sol-gel auto-combustion method. The precursor for the sorbent was a gel obtained from metal nitrates and citric acid by a sol process. The nitrate-citrate gel exhibits a self-propagating combustion behavior, and after combustion, it can transform into a nanosized spinel structured zinc ferrite directly. The prepared sorbent has a larger specific surface area and higher reactivity when compared with the sorbent achieved by a solid mixing method, and it could efficiently reduce the H{sub 2}S concentration from 6000 ppm to less than 2 ppm at a moderate temperature range. The sulfur capacity at 400{sup o}C reaches about 38.5 g of sulfur/100 g of sorbent, which corresponds to 96.4% of the theoretical value. The temperature programmed oxidation test for the sulfided sorbent shows that the most sulfur is desorbed before 500{sup o}C. XRD results confirm that the sulfided sample after exposure to a 5% O{sub 2}/N{sub 2} gas mixture at 500{sup o}C can be regenerated completely, which indicates that the regeneration temperature of the sorbent prepared by the sol-gel auto-combustion method could be greatly reduced. 40 refs., 10 figs., 2 tabs.

Rongjun Zhang; Jiejie Huang; Jiantao Zhao; Zhiqiang Sun; Yang Wang [Chinese Academy of Sciences, Taiyuan (China). Institute of Coal Chemistry

2007-09-15

169

Utilization of Coal Combustion Ashes for the Synthesis of Ordinary and Special Cements  

Microsoft Academic Search

Raw mixes containing pulverized coal fly ash (with limestone and silica sand) or fluidized bed coal combustion ash (fly and bottom, with added limestone, anodization mud, and, when necessary, flue gas desulfurization gypsum), aimed at generating ordinary Portland or calcium sulfoaluminate clinkers, respectively, were heated in a laboratory electric oven at temperatures ranging from 1150° to 1500°C and submitted to

Milena Marroccoli; Maria Lucia Pace; Antonio Telesca; Gian Lorenzo Valenti; Fabio Montagnaro

2010-01-01

170

Total synthesis and antiplasmodial activity of pohlianin C and analogues.  

PubMed

The first synthesis of the glycine-rich cyclic octapeptide pohlianin C is reported, confirming the structure of this natural product. Screening against Plasmodium falciparum reveals moderate antiplasmodial activity, consistent with data obtained from the natural sample. In addition, the synthesis of three analogues reveals that the antiplasmodial activity of pohlianin C can be preserved or increased with simplified structures. PMID:24813731

Lawer, Aggie; Tai, Jonathan; Jolliffe, Katrina A; Fletcher, Sabine; Avery, Vicky M; Hunter, Luke

2014-06-15

171

Synthesis of La{sup 3+} doped nanocrystalline ceria powder by urea-formaldehyde gel combustion route  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Nano LC synthesized by gel combustion, using urea-formaldehyde fuel for first time. Black-Right-Pointing-Pointer Largely single crystals were produced in average range of 20-30 nm. Black-Right-Pointing-Pointer La{sup 3+} doping increases cell dimension linearly. Black-Right-Pointing-Pointer La{sup 3+} doping introduces ionic point defects but does not change electronic band gap. Black-Right-Pointing-Pointer Presence of Ce{sup 3+} indicates that this synthesis route produces reactive powders. -- Abstract: Nanocrystalline ceria powders doped with various concentrations of lanthanum oxide have been prepared following gel combustion route using for the first time urea-formaldehyde as fuel. The synthesized products were characterized by XRD, FESEM, TEM, PL and UV-vis spectroscopy. Peak positions of XRD were refined and the lattice parameters were obtained by applying Cohen's method. Unit cell parameter increases with concentration of La{sup 3+} ion and the variation is consistently linear. XRD calculations showed the dependence of crystallite size on dopant concentrations at lower level. TEM observation revealed unagglomerated particles to be single crystals in the average range of 20-30 nm. Band gap of the La{sup 3+} doped ceria materials does not change with doping. Spectroscopic experiments proved the existence of Ce{sup 3+} in the formed powder.

Biswas, M. [Central Glass and Ceramic Research Institute, Kolkata 700 032 (India)] [Central Glass and Ceramic Research Institute, Kolkata 700 032 (India); Bandyopadhyay, S., E-mail: sbando@cgcri.res.in [Central Glass and Ceramic Research Institute, Kolkata 700 032 (India)

2012-03-15

172

Comparative sinterability of combustion synthesized and commercial titanium carbides  

SciTech Connect

The influence of various parameters on the sinterability of combustion synthesized titanium carbide was investigaged. Titanium carbide powders, prepared by the combustion synthesis process, were sintered in the temperature range 1150 to 1600/sup 0/C. Incomplete combustion and high oxygen contents were found to be the cause of reduced shrinkage during sintering of the combustion syntheized powders when compared to the shrinkage of commercial TiC. Free carbon was shown to inhibit shrinkage. The activation energy for sintering was found to depend on stoichiometry (C/Ti). With decreasing C/Ti, the rate of sintering increased. 29 references, 16 figures, 13 tables.

Manley, B.W.

1984-11-01

173

Synthesis of nanoparticles of barium lanthanum hafnium oxide by a modified combustion process.  

PubMed

Barium lanthanum hafnium oxide, a complex perovskite ceramic, has been synthesized as nanoparticles by a modified combustion process for the first time. The Ba, La, and Hf ions required for the formation of Ba2LaHfO5.5 were obtained in solution by dissolving in boiling nitric acid a stoichiometric mixture of BaCO3, La2O3, and HfO2 that had been heated at 1200 degrees C for 4 h. By complexing the ions with citric acid and using ammonia as fuel, it was possible to get Ba2LaHfO5.5 as nanoparticles in a single-step combustion process. The powder obtained by the present combustion process was characterized by X-ray diffraction, BET surface area analysis, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and scanning and high-resolution transmission electron microscopy. According to the results of X-ray and electron diffraction, the powder synthesized through the combustion process showed single-phase barium lanthanum hafnium oxide. The transmission electron microscopic investigations showed a grain size of 42 nm, with a standard deviation of 8 nm. The nanoparticles of Ba2LaHfO5.5 synthesized by the present combustion technique could be sintered to > 97% of the theoretical density at a relatively low temperature of 1425 degrees C. Scanning electron microscopic studies on the sintered Ba2LaHfO5.5 samples showed that the final grain size of the sintered specimen was < 500 nm. PMID:12908329

John, Asha M; Jose, R; Divakar, R; Koshy, J

2002-02-01

174

Active RC Synthesis Techniques for Significant Reactance Reduction.  

National Technical Information Service (NTIS)

Many developments in the field of active RC synthesis have been motivated exclusively by the desire to eliminate the necessity of inductance (by utilization of the active element). Recently, and to an increasing extent with the advent of molecular electro...

I. M. Horowitz G. R. Branner

1968-01-01

175

Coal combustion science  

SciTech Connect

The objective of this activity is to support the Office of Fossil Energy in executing research on coal combustion science. This activity consists of basic research on coal combustion that supports both the Pittsburgh Energy Technology Center (PETC) Direct Utilization Advanced Research and Technology Development Program, and the International Energy Agency (IEA) Coal Combustion Science Project. Specific tasks include: coal devolatilization, coal char combustion, and fate of mineral matter during coal combustion. 91 refs., 40 figs., 9 tabs.

Hardesty, D.R. (ed.); Baxter, L.L.; Fletcher, T.H.; Mitchell, R.E.

1990-11-01

176

Synthesis of Nanoscale Nd-Doped Ceria Via Urea-Formaldehyde Combustion Method  

NASA Astrophysics Data System (ADS)

Nanocrystalline neodymium-doped ceria solid solutions with Nd3+ concentrations varying from 4 to 20 mol pct have been synthesized by gel combustion method, using urea-formaldehyde as fuel for Nd doping. The combustion reaction is explained through differential scanning calorimetry (DSC)-differential thermogravimetric analysis (TGA), whereas the synthesized materials are characterized through X-ray diffractometry (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The phase obtained from the exothermic reaction contains Nd-substituted CeO2. The deviation of the lattice parameter from Vegard's law and the decrease in crystallite size with dopant concentration has been explained. The as-synthesized particles are largely nanoporous single crystallites, existing in loosely held spherical-shaped agglomerates. The size of the agglomerates increases with increasing dopant content. High-resolution TEM (HRTEM) reveals the fact that the unit cells are strained.

Biswas, M.; Bandyopadhyay, S.

2013-11-01

177

Synthesis of antimony-doped tin oxide (ATO) nanoparticles by the nitrate-citrate combustion method  

SciTech Connect

Antimony-doped tin oxide (ATO) nanoparticles having rutile structure have been synthesized by the combustion method using citric acid (CA) as fuel and nitrate as an oxidant, the metal sources were granulated tin and Sb{sub 2}O{sub 3}. The influence of citric acid (fuel) to metal ratio on the average crystallite size, specific surface area and morphology of the nanoparticles has been investigated. X-ray diffraction showed the tin ions were reduced to elemental tin during combustion reaction. The average ATO crystallite size increased with the increase of citric acid (fuel). Powder morphology and the comparison of crystallite size and grain size shows that the degree of agglomeration of the powder decreased with an increase of the ratio. The highest specific surface area was 37.5 m{sup 2}/g when the citric acid to tin ratio was about 6.

Zhang Jianrong [State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Gao Lian [State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)]. E-mail: Liangaoc@online.sh.cn

2004-12-02

178

Synthesis of YAG powder by the modified sol–gel combustion method  

Microsoft Academic Search

Yttrium aluminum garnet (YAG) precursor was prepared by sol–gel combustion method using ethanol as solvent. Nano-sized YAG powders were obtained by precalcining the precursor at 500°C, and then calcining at different temperatures. The phase formation and characteristics of YAG powders were investigated by means of XRD, TG\\/DSC and TEM. Pure crystalline YAG phase was obtained at 800°C, without any intermediate

Lin Yang; Tiecheng Lu; Hui Xu; Nian Wei

2009-01-01

179

Synthesis of lutetium aluminum garnet powders by nitrate–citrate sol–gel combustion process  

Microsoft Academic Search

Polycrystalline lutetium aluminum garnet (Lu3Al5O12) powders were prepared by a simple sol–gel combustion method using aluminum nitrate, lutetium oxide and citric acid as the starting materials. The XRD results showed that the amorphous precursor converted directly to pure LuAG at 900°C. The TEM investigations revealed that the synthesized LuAG powders are nano-sized with an average particle size 20–30nm.

Huili Li; Xuejian Liu; Liping Huang

2007-01-01

180

Synthesis and luminescence properties of nanocrystalline Gd 2O 3:Eu 3+ by combustion process  

Microsoft Academic Search

The nanocrystalline Gd2O3:Eu3+ powders with cubic phase were prepared by a combustion method in the presence of urea and glycol. The effects of the annealing temperature on the crystallization and luminescence properties were studied. The results of XRD show pure phase can be obtained, the average crystallite size could be calculated as 7, 8, 15, and 23nm for the precursor

Yanhong Li; Guangyan Hong

2007-01-01

181

Combustion synthesis and characterization of substituted lithium cobalt oxides in lithium batteries  

Microsoft Academic Search

Substituted lithium cobaltates LiCo0.5M0.5O2 (where M=Ni, Mg, Mn, Zn) have been synthesized by the combustion of mixtures obtained from aqueous solutions containing the respective metal nitrates, LiNO3, and urea in stoichiometric amounts. The mixtures, when dried and fired at 700°C, ignite and yield submicron-sized powders. Physical properties of the synthesized products are discussed in the light of structural (XRD, SEM)

C Julien; M. A Camacho-Lopez; T Mohan; S Chitra; P Kalyani; S Gopukumar

2000-01-01

182

Chemical synthesis of nanocrystalline magnesium aluminate spinel via nitrate–citrate combustion route  

Microsoft Academic Search

Nanocrystalline magnesium aluminate spinel (MgAl2O4) was synthesized using metal nitrates, citric acid and ammonium solutions. The precursor and the calcined powders at different temperatures were characterized by X-ray diffraction (XRD), simultaneous thermal analysis (STA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The combustion mechanism was also studied by a quadrupole mass spectrometer (QMS)

Ali Saberi; Farhad Golestani-Fard; Hosein Sarpoolaky; Monika Willert-Porada; Thorsten Gerdes; Reinhard Simon

2008-01-01

183

WC-based catalyst for isopropyl alcohol dehydration as prepared by combustion synthesis  

Microsoft Academic Search

WC-based catalyst was prepared by SHS method using highly exothermic WO3 + Mg + C mixtures. Two kinds of tungsten oxide—commercially available and obtained by decomposition of the peroxo complex\\u000a of tungsten oxide—were used as tungsten sources. To soften violent conditions of combustion, the well-known salt dilution\\u000a method was applied. Tuning the reaction temperature by added NaCl and carbon afforded

Kh. V. Manukyan; A. R. Zurnachyan; S. L. Kharatyan; R. A. Mnatsakanyan

2011-01-01

184

Combustion synthesis of Ni-Zn ferrite powder-influence of oxygen balance value  

SciTech Connect

In this study, Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} powder was synthesized via an exothermic reaction between nitrates [Ni(NO{sub 3}){sub 2}.6H{sub 2}O, Zn(NO{sub 3}){sub 2}.6H{sub 2}O, Fe(NO{sub 3}){sub 3}.9H{sub 2}O, and NH{sub 4}NO{sub 3}] and glycine [NH{sub 2}CH{sub 2}COOH]. By adjusting the glycine-to-nitrates ratio, the oxygen balance (OB) values of the reactant mixtures can be varied in which the combustion phenomena is altered and thereby the as-synthesized products with different characteristics are obtained. An interpretation based on the measurement of maximum combustion temperature (T{sub c}) and the amounts of gas evolved during reaction for various OB values has been proposed regarding the nature of combustion and its correlation with the characteristics of as-synthesized products. After instrumental analyses, it is shown that the as-synthesized powders are nanoscale crystallites with a large specific surface area and they inherit a superparamagnetic behavior.

Hwang, C.-C. [Department of Applied Chemistry, Chung Cheng Institute of Technology, National Defence University, Number 190, Sanyuan First Street, Tashi Jen, Taoyuan 33509, Taiwan (China)]. E-mail: cchwang1@ccit.edu.tw; Tsai, J.-S. [Department of Applied Chemistry, Chung Cheng Institute of Technology, National Defence University, Number 190, Sanyuan First Street, Tashi Jen, Taoyuan 33509, Taiwan (China); Huang, T.-H. [Department of Applied Chemistry, Chung Cheng Institute of Technology, National Defence University, Number 190, Sanyuan First Street, Tashi Jen, Taoyuan 33509, Taiwan (China); Peng, C.-H. [Department of Materials Science and Engineering, National Chao Tung University, Hsinchu 300, Taiwan (China); Chen, S.-Y. [Department of Materials Science and Engineering, National Chao Tung University, Hsinchu 300, Taiwan (China)

2005-01-15

185

Combustion-Characteristic-Based Active Thrust Modulation of a Solid Rocket Motor  

NASA Astrophysics Data System (ADS)

A new concept of thrust modulation of solid propellant rocket motor is proposed. Some propellants cannot burn at intermediate pressure, while they can burn at lower and higher pressures. When one applies such a propellant to a motor, two combustion modes or two thrust levels are attainable without any change of the nozzle configuration. In the experiments different ignition conditions brought independent two combustion modes (low mode and high mode) in the same motor geometry. Some motors showed a natural transition from low mode to high mode. As an example, the alternative thrust levels were 50 N and 180 N. The natural transition was restricted with use of the partitioned grain. An active transition method was explored by exerting pressure perturbation through a vent hole with a ball valve. The valve system worked for the transition from high mode to low mode, but the reverse transition was not achieved well.

Tanaka, Masafumi; Gaspard, Guillaume; Urakawa, Katsuya

186

Synthesis and antioxidant activity of new tetraarylpyrroles.  

PubMed

The synthesis and in vitro antioxidant activity of 17 new tetraarylpyrroles are investigated by 2 tests highly documented in the literature: capability to prevent Fe(2+)-induced lipid peroxidation on microsomes, which is a membrane preparation rich in polyunsaturated fatty acids, and direct scavenging effect on a stable free radical, 1,l-diphenyl-2-picryl-hydrazyl (DPPH). For the Fe(2+)-induced microsomal lipid peroxidation system, the results show that molecules which possess 2-pyrazinyl or 2-pyridyl in the 3- and 4-positions on the pyrrole ring are the most efficient. Introduction of methoxy groups on the phenyl ring in the 2- and 5-positions increases the effects but the higher activity is obtained with 2-furyl or 2-thienyl. The only compounds which possess a direct scavenger effect on trapping the stable free radical DPPH are those which have 2-pyridyl in the 3- and 4-positions and 2-furyl or 2-thienyl in the 2- and 5-positions. PMID:10889322

Lehuédé; Fauconneau; Barrier; Ourakow; Piriou; Vierfond

1999-11-01

187

[Spectrum and synthesis of rare earth activated nanoparticle].  

PubMed

La2O3: Eu(3+) nanoparticles were prepared by Gly assistant combustion synthesis with the sizes from 12-28 nm, and a characterization of XRD was done. Spectral properties of the nanoparticles were compared with the bulk. High resolution spectra were measured. Site selective excitation was employed to probe the local environments of Eu(3+) ions in La2O3 nanoparticles. The luminescent centers on the surface and the center of the nanoparticles were excited respectively. The spectra were related to surface information. The luminescence from C3v site and the site with lower symmetry on the surface was distinguished. PMID:16826894

Chang, Jian-Jun; Huang, Shi-Hua; Peng, Hong-Shang; Meng, Chun-Xia; You, Fang-Tian; Lü, Shao-Zhe; Sun, Ling-Dong

2006-02-01

188

Combustion synthesis of Y2O2S:Eu3+ phosphors  

NASA Astrophysics Data System (ADS)

The red phosphors of Y2O2S:Eu3+ were synthesized by combustion reactions from mixed metal nitrate reactants and a fuel CH4N2S with ignition temperatures of 450°C. Sulfur was produced by CH4N2S decomposed at high temperature. Y2O3 decomposed by Y(NO3) 3 reacted in Sulfur atmosphere to synthesize Y2O2S host. From altering the ratio of CH4N2S and metal nitrate, the pure phase Y2O2S:Eu3+ red phosphor was obtained. The conclusion was proved by XRD patterns and emission spectrum.

Yang, Zhiping; Yang, Yong; Li, Xu; Li, Xingmin

2006-01-01

189

Low temperature combustion synthesis of Co x Mg 1? x Al 2O 4 nano pigments using oxalyldihydrazide as a fuel  

Microsoft Academic Search

Oxalyldihydrazide as a fuel was used to prepare new nano size blue refractory ceramic pigments MgAl2O4: xCo2+ (0.00?x?0.10) using low temperature combustion synthesis (LCS) method. The synthesized and calcined powders were characterized by Fourier transform infra red (FTIR) spectrometry, electronic spectra, thermogravimetry, differential thermogravimetry, differential thermal analysis, X-ray diffraction (XRD) analysis, and transmission electron microscopy (TEM). Also, the color measurements

I. S. Ahmed; S. A. Shama; H. A. Dessouki; A. A. Ali

2011-01-01

190

Synthesis and biological activity of chloroethyl pyrimidine nucleosides.  

PubMed

The synthesis and biological activity of chloroethyl pyrimidine nucleosides is presented. One of these new nucleosides analogues significantly inhibited cell proliferation, migration and invasion as tested in vitro on the A431 vulvar epidermal carcinoma cell line. PMID:18205066

Colombeau, Ludovic; Teste, Karine; Hadj-Bouazza, Amel; Chaleix, Vincent; Zerrouki, Rachida; Kraemer, Michel; Catherine, Odile Sainte

2008-02-01

191

Combustion Synthesis and Optical Properties of Eu3+-Doped BaGd2ZnO5 f- f Transition Nanophosphor for White LED  

NASA Astrophysics Data System (ADS)

An Eu3+-doped BaGd2(1- x)ZnO5 nanophosphor has been synthesized by means of a single-step, urea-assisted, solution-combustion process. The structural, morphological, and optical properties of the nanophosphor were studied by x-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy. The XRD results showed that the pure orthorhombic BaGd2ZnO5 structure with space group Pbnm was obtained at 900°C. The intense red luminescence at 628 nm on near-UV (396 nm) excitation is because of the hypersensitive 5D0 ? 7F2 transition of luminescent activator Eu3+ ions, located at a site with no inversion symmetry in the BaGd2ZnO5 crystal lattice. The optimum doping concentration and decay time of Eu3+-doped BaGd2(1- x)ZnO5 nanophosphor were also determined. The emission could be effectively tuned from blue to the white and red regions by varying the concentration of europium ions. Decay curve analysis revealed that cross-relaxation is primarily responsible for the concentration quenching. High luminescent intensity, low-cost, easy synthesis, uniform shape, and controlled color tunability suggest use of BaGd2ZnO5:Eu3+ as an efficient red-emitting nanophosphor for near-UV-based LED solid-state lighting applications.

Singh, Sonika; Khatkar, Satyender Pal; Arora, Rajni; Sangwan, Dayawati; Khatkar, Avni; Taxak, Vinod Bala

2014-04-01

192

Combustion synthesis and engineering of nanoparticles for electronic, structural and superconductor applications  

SciTech Connect

Fully dense, nanocrystalline ceramic articles were prepared by the new nanofabrication process. The process consists of two steps: synthesis of ceramic nanoparticles and fabrication of dense, nanocrystalline ceramic parts. The synthesis step produced 10-nanometer-diameter crystallites, and is capable of being scaled up to kilogram/hour production rates. The fabrication step produced dense parts at significantly reduced sintering temperatures and times -- representing a factor of 10--100 reduction in process energy requirements. The process was demonstrated by producing ultrafine-grained yttria-stabilized ZrO[sub 2], an important material with a variety of energy-related applications (solid electrolytes, oxygen sensors, electrode materials, thermal barrier coatings, etc.). Results from this period clearly illustrate the capabilities of this energy-efficient and directly commercializable process for producing dense, nanocrystalline, multicomponent oxide ceramics.

Stangle, G.C.; Amarakoon, V.R.W.; Schulze, W.A.

1993-05-28

193

A generalized method of active RC network synthesis.  

NASA Technical Reports Server (NTRS)

A completely general active RC network synthesis technique using a grounded gyrator and a summing amplifier is described. The technique overcomes serious limitations of previous RC-gyrator realizations and offers advantages o ver other general active RC synthesis methods. The technique is well suited for construction using thin-film RC networks and integrated circuit operational amplifiers, and provides a configuration which is quite insensitive to element variations.

Leach, D. P.; Chan, S.-P.

1971-01-01

194

Exploratory combustion synthesis: amorphous indium yttrium oxide for thin-film transistors.  

PubMed

We report the implementation of amorphous indium yttrium oxide (a-IYO) as a thin-film transistor (TFT) semiconductor. Amorphous and polycrystalline IYO films were grown via a low-temperature solution process utilizing exothermic "combustion" precursors. Precursor transformation and the IYO films were analyzed by differential thermal analysis, thermogravimetric analysis, X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, and optical transmission, which reveal efficient conversion to the metal oxide lattice and smooth, transparent films. a-IYO TFTs fabricated with a hybrid nanodielectric exhibit electron mobilities of 7.3 cm(2) V(-1) s(-1) (T(anneal) = 300 °C) and 5.0 cm(2) V(-1) s(-1) (T(anneal) = 250 °C) for 2 V operation. PMID:22625409

Hennek, Jonathan W; Kim, Myung-Gil; Kanatzidis, Mercouri G; Facchetti, Antonio; Marks, Tobin J

2012-06-13

195

Low temperature combustion synthesis and magnetostructural properties of Co-Mn nanoferrites  

NASA Astrophysics Data System (ADS)

In the present work, Co1-xMnxFe2O4 nanoparticles were synthesized by the low-temperature auto-combustion method. The thermal decomposition process was investigated by means of differential and thermal gravimetric analysis (TG-DTA) that showed the precursor yield the final product above 450 °C. The phase purity and crystal lattice symmetry were estimated from X-ray diffraction (XRD). Microstructural features observed by scanning electron microscopy (SEM) demonstrates that the fine clustered particles were formed with an increase in average grain size with Mn2+ content. Fourier transform infrared spectroscopy (FTIR) study confirms the formation of spinel ferrite. Room temperature magnetization measurements showed that the magnetization Ms increases from 29 to 60 emu/g and Hc increases from 13 to 28 Oe with increase in Mn2+ content, which implies that these materials may be applicable for magnetic data storage and recording media.

Salunkhe, A. B.; Khot, V. M.; Phadatare, M. R.; Thorat, N. D.; Joshi, R. S.; Yadav, H. M.; Pawar, S. H.

2014-02-01

196

Synthesis of ultrafine YAG:Tb phosphor by nitrate-citrate sol-gel combustion process  

SciTech Connect

Ultrafine terbium-doped yttrium aluminum garnet (YAG:Tb) phosphor powders are prepared by a nitrate-citrate sol-gel combustion process using 1:1 ratio of citrate/nitrate. Phase evolution of the synthesized powder is determined by X-ray diffraction (XRD) techniques. Single-phase cubic YAG:Tb crystalline powder is obtained by calcinating the amorphous materials at 900 deg. C and no intermediate phase is observed. Transmission electronic microscope (TEM) morphology shows that the resultant YAG:Tb powders have uniform size and good homogeneity. The particle size of the product is investigated as a function of the calcination temperature. The photoluminescence (PL) spectrum of Tb{sup 3+} substituted for Y{sup 3+} in YAG with 5.0% content has been measured on samples calcined at different temperatures.

Zhang Junji; Ning Jinwei; Liu Xuejian; Pan Yubai; Huang Liping

2003-06-19

197

Microwave-assisted solution combustion synthesis of nanostructured Zn2SnO4  

NASA Astrophysics Data System (ADS)

Nanoparticle powders of zinc stannate indate spinel (Zn2SnO4) were prepared with a single step process. First nano-oxides of ZnO and SnO2 were obtained by microwave-assisted combustion of aqueous solution of metal nitrates (as the oxidizer) and glycine (as fuel). This method is rapid, effective, cheap and convenient. In this paper, different combinations of fuel to oxidant ratio was used to prepare Zn2SnO4 nanoparticle and its effect on structural, morphologica and optical characteristics were investigated using powder x-ray diffractometer, scanning electron microscope, Fourier transform infrared spectra meter and UV-Vis absorbance spectroscopy respectively. The structural parameters were calculated from PXRD pattern which confirmed the spinel structure of Zn2SnO4. The SEM investigations evidenced the presence of homogeneous distribution of spherical nanoparticles.

Nehru, L. C.; Sanjeeviraja, C.

2013-06-01

198

Combustion synthesis in the Ti-C-Ni-Mo system: Part I. Micromechanisms  

NASA Astrophysics Data System (ADS)

Combustion-wave arresting experiments were conducted on Ti-C-Ni and Ti-C-Ni-Mo powder mixtures. The reactant powder mixtures were placed within a conical hole machined in a Cu block. The reaction was initiated at the base of the cone and proceeded down the cone axis, toward the apex, until the heat loss to the Cu block was sufficient to arrest the reaction. This enabled the postreaction characterization of the three distinct regions of the combustion wave: unreacted, partially reacted, and fully reacted. The unreacted region is characterized by removal of a surface scale on the Ti particles and Ti ? ? ? solid-state phase transformation. The partially reacted region is characterized by a number of physical processes and a distinct interface with the unreacted region. These processes include the formation of Ti-Ni phases, Ti-Ni melt, TiC, layer on the C particles, and TiCx spherules. The TiCx layer is composed of coarsening TiCx precipitates which are ejected into the progressively Ni-rich Ti-Ni melt. These TiCx spherules vary in size with apparent diameters of approximately 0.2 to 1 ?m. No distinct interface exists between the partially and fully reacted regions. Final consumption of C is followed by TiCx spherule growth by combined Ostwald ripening and grain coalescence mechanisms resulting in an apparent diameter of 2.5 ?m. The addition of Mo does not significantly affect the processes occurring within the partially reacted region. It is apparent that Mo enters into solution with the Ti-Ni melt at a rate much slower than that characteristic of the other processes (i.e., Ti-Ni melt mixing or Ti-C reaction).

Lasalvia, J. C.; Kim, D. K.; Lipsett, R. A.; Meyers, M. A.

1995-11-01

199

Combustion front dynamics in the combustion synthesis of refractory metal carbides and di-borides using time-resolved X-ray diffraction.  

PubMed

A compact diffraction-reaction chamber, using a 2-inch photodiode array detector, has been employed to investigate the chemical dynamics at the combustion front of a selected series of refractory metal carbides and di-borides from their constituent element reactants as well as binary products from B4C as a reactant. These systems are denoted as (i) M + C --> MC; (ii) M + 2B --> MB2; and (iii) 3M + B4C --> 2MB2 + MC, where M = Ti, Zr, Nb, Hf or Ta. Time-resolved X-ray diffraction using intense synchrotron radiation at frame rates up to 10 frames s(-1) (or 100 ms frame(-1)) was employed. The combustion reactions were found to complete within 200-400 ms. In contrast to the Ta + C --> TaC combustion system studied earlier, in which a discernible intermediate sub-carbide phase was first formed, reacted further and disappeared to yield the final TaC product, no intermediate sub-carbide or sub-boride was detected in the current systems. Combustion for the Ti, Zr and Hf systems involved a liquid phase, in which the adiabatic temperatures Tad are well above the melting points of the respective reactant metals and have a typical combustion front velocity of 5-6 mm s(-1). The Nb and Ta systems have lower Tad, involving no liquid phase. These are truly solid combustion systems and have a lower combustion front velocity of 1-2 mm s(-1). The current study opens up a new avenue to chemical dynamics and macrokinetic investigations of high-temperature solid-state reactions. PMID:16799224

Wong, Joe; Larson, E M; Waide, P A; Frahm, R

2006-07-01

200

Multifunction Gd2O3:Eu nanocrystals produced by solution combustion synthesis: Structural, luminescent, and magnetic characterization  

NASA Astrophysics Data System (ADS)

The synthesis, structural, luminescent, and magnetic properties of multifunction 8 at. % Eu-doped Gd2O3 nanocrystals were investigated. The material was synthesized by the solution combustion technique and characterized by x-ray diffraction (XRD), transmission electron microscopy, and photoluminescence and magnetization measurements. The as-prepared material presents predominant base-centered monoclinic structure with average crystallite size of 35 nm. Isothermal annealing at 1000 °C for up to 152 h induced gradual structural transition toward the body-centered cubic structure. Debye-Scherrer analysis of XRD results showed that annealing did not induce grain growth of monoclinic nanocrystals, while cubic nanocrystals reached 47 nm after annealing for 152 h. The luminescent behavior was monitored as a function of annealing time and related to the structural transformation. In particular, an inversion of the predominant photoluminescence emission line from 621.4 to 609.5 nm was observed and related to changes in the crystalline field resultant to phase transformation from cubic to monoclinic. Magnetic measurements revealed the paramagnetic nature of the material, much insensitive to the crystallographic structure.

Jacobsohn, L. G.; Bennett, B. L.; Muenchausen, R. E.; Tornga, S. C.; Thompson, J. D.; Ugurlu, O.; Cooke, D. W.; Lima Sharma, A. L.

2008-05-01

201

Model-Based, Multiscale Self-Tuning Controller Developed for Active Combustion Control  

NASA Technical Reports Server (NTRS)

New challenges concerning system health-monitoring and life-extending robust controls for the Ultra-Efficient Engine Technology Project, as well as other advanced engine and power system concepts at NASA and elsewhere, have renewed the control community s interest in smart, model-based methods. In particular, these challenges have further motivated efforts at the NASA Glenn Research Center to exploit the versatility and superiority of the dynamic features extraction of multiscale analysis for controls--such as with "wavelets" and "wavelet filter-banks.' The accomplishments reported herein pertain to the active suppression of combustion instabilities in liquid-fuel combustors via fuel modulation. The fundamentals and initial success of this innovation were reported for a unique demonstration of active combustion control (a research collaboration of NASA Glenn with Pratt & Whitney and the United Technologies Research Center, UTRC). This demonstration, conducted in 2002 at UTRC on the NASA single nozzle rig (SNR) combustor, was the first known suppression of high-frequency instability with a liquid-fueled combustor. The SNR is based on a high-powered military engine combustor that exhibited well-known instabilities.

Le, Dzu K.

2005-01-01

202

Microwave assisted combustion synthesis of CdFe2O4: Magnetic and electrical properties  

NASA Astrophysics Data System (ADS)

CdFe2O4 particles were synthesized by the microwave assisted combustion method using two different fuels—glycine and urea. Microwave heating provides higher chemical yield within a minute. The synthesized particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), ac impedance spectroscopy, vibrating sample magnetometry (VSM) and electron spin resonance (ESR) methods. XRD analysis shows the cubic structure of CdFe2O4. The high and low frequency absorption bands of CdFe2O4 were found using FTIR analysis. Spherical morphology was revealed from the SEM images. ESR and VSM measurements reveal the antiferromagnetic behavior of CdFe2O4. The electrical conductivities of CdFe2O4 synthesized using glycine and urea are 6.5×10-7 S cm-1 and 4.7×10-8 S cm-1 respectively at 240 oC. At elevated temperatures an occurrence of increase in conductivity was observed, which indicates the semiconducting behavior of CdFe2O4. The dielectric spectral analysis reveals that dielectric constant of CdFe2O4 decreases with frequency and increases with temperature.

Vasanthi, V.; Shanmugavani, A.; Sanjeeviraja, C.; Kalai Selvan, R.

2012-07-01

203

Solution-combustion synthesis and photoluminescence properties of YBO3:Tb3+ phosphor powders  

NASA Astrophysics Data System (ADS)

YBO3:Tb3+ nanocrystalline phosphors were successfully deposited by a solution-combustion method, using rare-earth nitrates, urea and boric acid as starting materials. The crystal structure, morphology, chemical composition and photoluminescence properties of the films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The results of SEM and XRD revealed that the powders were composed of spherical YBO3:Tb3+ nanocrystals with average grain size of between 50 and 100 nm. The electron diffraction spectroscopy (EDS) confirmed the presence of the Y, B, O, and C. The XRD measurements revealed YBO3:Tb3+ (JCPDS:83-1205) structure when annealed at 1000 °C for 2 h. The YBO3:Tb3+ powders exhibited emissions at 490, 545 and 585 nm, which were assigned to the 5D4-7F6, 5D4-7F5 and 5D4-7F4 transitions of Tb3+, respectively. Among them, the green emission at 545 nm (5D4-7F5) was dominant.

Onani, Martin O.; Okil, Joseph O.; Dejene, Francis B.

2014-04-01

204

Triggered instabilities in rocket motors and active combustion control for an incinerator afterburner  

Microsoft Academic Search

Two branches of research are conducted in this thesis. The first deals with nonlinear combustion response as a mechanism for triggering combustion instabilities in solid rocket motors. A nonlinear wave equation is developed to study a wide class of combustion response functions to second-order in fluctuation amplitude. Conditions for triggering are derived from analysis of limit cycles, and regions of

Josef M. Wicker

1999-01-01

205

In vitro immunotoxic and genotoxic activities of particles emitted from two different small-scale wood combustion appliances  

NASA Astrophysics Data System (ADS)

Residential wood combustion appliances emit large quantities of fine particles which are suspected to cause a substantial health burden worldwide. Wood combustion particles contain several potential health-damaging metals and carbon compounds such as polycyclic aromatic hydrocarbons (PAH), which may determine the toxic properties of the emitted particles. The aim of the present study was to characterize in vitro immunotoxicological and chemical properties of PM 1 ( Dp ? 1 ?m) emitted from a pellet boiler and a conventional masonry heater. Mouse RAW264.7 macrophages were exposed for 24 h to different doses of the emission particles. Cytotoxicity, production of the proinflammatory cytokine TNF-? and the chemokine MIP-2, apoptosis and phases of the cell cycle as well as genotoxic activity were measured after the exposure. The type of wood combustion appliance had a significant effect on emissions and chemical composition of the particles. All the studied PM 1 samples induced cytotoxic, genotoxic and inflammatory responses in a dose-dependent manner. The particles emitted from the conventional masonry heater were 3-fold more potent inducers of programmed cell death and DNA damage than those emitted from the pellet boiler. Furthermore, the particulate samples that induced extensive DNA damage contained also large amounts of PAH compounds. Instead, significant differences between the studied appliances were not detected in measurements of inflammatory mediators, although the chemical composition of the combustion particles differed considerably from each other. In conclusion, the present results show that appliances representing different combustion technology have remarkable effects on physicochemical and associated toxicological and properties of wood combustion particles. The present data indicate that the particles emitted from incomplete combustion are toxicologically more potent than those emitted from more complete combustion processes.

Tapanainen, Maija; Jalava, Pasi I.; Mäki-Paakkanen, Jorma; Hakulinen, Pasi; Happo, Mikko S.; Lamberg, Heikki; Ruusunen, Jarno; Tissari, Jarkko; Nuutinen, Kati; Yli-Pirilä, Pasi; Hillamo, Risto; Salonen, Raimo O.; Jokiniemi, Jorma; Hirvonen, Maija-Riitta

2011-12-01

206

Effect of KCl, NaCl and CaCl{sub 2} mixture on volume combustion synthesis of TiB{sub 2} nanoparticles  

SciTech Connect

Highlights: {yields} A low melting diluent lowers the ignition temperature in combustion synthesis. {yields} Deagglomerated synthesized products are formed as the result of diluent addition. {yields} Addition of 45% salt mixture resulted in formation of 70 nm TiB{sub 2} nanoparticles. {yields} Thermodynamically unstable Mg{sub 2}TiO{sub 4} and Mg{sub 3}B{sub 2}O{sub 6} by-products were formed. {yields} Small change in particle size was observed with addition of salt mixture. -- Abstract: Preparation of titanium diboride (TiB{sub 2}) nanoparticles was carried out by volume combustion synthesis. TiO{sub 2}, B{sub 2}O{sub 3} and elemental Mg were mixed with 0-60% salt mixture of KCl, NaCl and CaCl{sub 2} with increment of 15% as a low melting temperature diluent. Compressed samples were synthesized in a tubular furnace at a constant heating rate under argon atmosphere. Thermal analysis of the process showed that the addition of the low melting temperature salts mixture led to a significant decrease in ignition and combustion temperatures. Synthesized samples were then leached by nitric and hydrochloric acids to remove impurities. The samples were examined by XRD, SEM and DLS analysis. The results showed the formation of fine deagglomerated particles with the addition of the salts mixture. The results revealed that 45% salts mixture had the smallest average particle size of about 90 nm.

Nekahi, Atiye [Mining and Metallurgical Engineering Department, Amirkabir University of Technology, 424 Hafez Ave., Tehran 15875-4413 (Iran, Islamic Republic of)] [Mining and Metallurgical Engineering Department, Amirkabir University of Technology, 424 Hafez Ave., Tehran 15875-4413 (Iran, Islamic Republic of); Firoozi, Sadegh, E-mail: s.firoozi@aut.ac.ir [Mining and Metallurgical Engineering Department, Amirkabir University of Technology, 424 Hafez Ave., Tehran 15875-4413 (Iran, Islamic Republic of)] [Mining and Metallurgical Engineering Department, Amirkabir University of Technology, 424 Hafez Ave., Tehran 15875-4413 (Iran, Islamic Republic of)

2011-09-15

207

Active Control of High Frequency Combustion Instability in Aircraft Gas-Turbine Engines  

NASA Technical Reports Server (NTRS)

Active control of high-frequency (greater than 500 Hz) combustion instability has been demonstrated in the NASA single-nozzle combustor rig at United Technologies Research Center. The combustor rig emulates an actual engine instability and has many of the complexities of a real engine combustor (i.e. actual fuel nozzle and swirler, dilution cooling, etc.) In order to demonstrate control, a high-frequency fuel valve capable of modulating the fuel flow at up to 1kHz was developed. Characterization of the fuel delivery system was accomplished in a custom dynamic flow rig developed for that purpose. Two instability control methods, one model-based and one based on adaptive phase-shifting, were developed and evaluated against reduced order models and a Sectored-1-dimensional model of the combustor rig. Open-loop fuel modulation testing in the rig demonstrated sufficient fuel modulation authority to proceed with closed-loop testing. During closed-loop testing, both control methods were able to identify the instability from the background noise and were shown to reduce the pressure oscillations at the instability frequency by 30%. This is the first known successful demonstration of high-frequency combustion instability suppression in a realistic aero-engine environment. Future plans are to carry these technologies forward to demonstration on an advanced low-emission combustor.

Corrigan, Bob (Technical Monitor); DeLaat, John C.; Chang, Clarence T.

2003-01-01

208

Synthesis and antimicrobial activity of some anthranilic acid derivatives.  

PubMed

The synthesis of eight derivatives of anthranilic acid is described. Investigation of their antimicrobial activity showed that four of the compounds, viz; anthranilohydrazide, 3,4-dihydro-4-oxo-1,2,3-benzotriazine, triazine-beta-naphthol adduct and N-phenyl anthranilic acid showed significant antibacterial activity. None of the compounds showed any noticeable antifungal effect. PMID:7433494

Kar, A; Gugnani, H C; Madumere, U A

1980-08-01

209

Structural, morphological and optical investigations on BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} elaborated by a microwave induced solution combustion synthesis  

SciTech Connect

Graphical abstract: Graphical abstract (with Research highlights). This is a paragraph for graphical abstract. Research highlights: {yields} Synthesis of BAM:Eu{sup 2+} by MISCS using different fuel to oxidizer molar ratios. {yields} Both blue and red phosphors were obtained. {yields} Majority of blue phosphors was obtained for fuel-rich synthesis. {yields} A specific morphology was observed for each contribution. -- Abstract: Blue-emitting Eu{sup 2+}-doped barium magnesium aluminate (BaMgAl{sub 10}O{sub 17}:Eu{sup 2+}) for advanced displays and lighting devices was prepared by a microwave induced solution combustion synthesis using urea as combustion fuel and nitrates as oxidizer. Purity control of as-synthesized blue phosphor particles was undertaken by modifying the fuel to oxidizer molar ratio. X-ray diffraction, scanning electron microscopy and photoluminescence were used to investigate powders crystallinity, particles size, morphology and luminescent properties, respectively. Fuel-rich urea reactions preferentially lead to pure phases compared to the powders synthesized with a stoichiometric fuel to oxidizer ratio. In both cases, we produce a nearly pure well-crystallized and nanostructured BaMgAl{sub 10}O{sub 17}:Eu{sup 2+}. Photoluminescence measurements exhibit the characteristic blue emission of Eu{sup 2+} under UV light excitation however a weak red emission associated to Eu{sup 3+} is also detected.

Pradal, Nathalie [Clermont Universite, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France) [Clermont Universite, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, LMI, F-63177 Aubiere (France); Potdevin, Audrey, E-mail: Audrey.Potdevin@univ-bpclermont.fr [Clermont Universite, ENSCCF, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France) [Clermont Universite, ENSCCF, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, LMI, F-63177 Aubiere (France); Chadeyron, Genevieve [Clermont Universite, ENSCCF, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France) [Clermont Universite, ENSCCF, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, LMI, F-63177 Aubiere (France); Mahiou, Rachid [Clermont Universite, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France) [Clermont Universite, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, LMI, F-63177 Aubiere (France)

2011-04-15

210

Combustion synthesis of Co-doped zinc oxide nanoparticles using mixture of citric acid–glycine fuels  

Microsoft Academic Search

In this study, cobalt-doped ZnO nanoparticles were synthesized by combustion method. Mixtures of citric acid and glycine were used as fuel. As-prepared powders were characterized by XRD, XPS, SEM-EDX, TEM and spectrophotometer. XRD patterns indicated that combustion reaction by different fuel mixture resulted in the formation of pure ZnO phase. However, citric acid combustion alone led to amorphous powder. Scherrer's

Sousan Rasouli; Shirin Jebeli Moeen

2011-01-01

211

Combustion oscillation control  

SciTech Connect

Premixing of fuel and air can avoid high temperatures which produce thermal NOx, but oscillating combustion must be eliminated. Combustion oscillations can also occur in Integrated Gasification Combined Cycle turbines. As an alternative to design or operating modifications, METC is investigating active combustion control (ACC) to eliminate oscillations; ACC uses repeated adjustment of some combustion parameter to control the variation in heat release that drives oscillations.

Richards, G.A.; Janus, M.C.

1996-12-31

212

Optimal cooperative control synthesis of active displays  

NASA Technical Reports Server (NTRS)

The utility of augmenting displays to aid the human operator in controlling high order complex systems is well known. Analytical evaluations of various display designs for a simple k/s-squared plant in a compensatory tracking task using an Optimal Control Model (OCM) of human behavior is carried out. This analysis reveals that significant improvement in performance should be obtained by skillful integration of key information into the display dynamics. The cooperative control synthesis technique previously developed to design pilot-optimal control augmentation is extended to incorporate the simultaneous design of performance enhancing augmented displays. The application of the cooperative control synthesis technique to the design of augmented displays is discussed for the simple k/s-squared plant. This technique is intended to provide a systematic approach to design optimally augmented displays tailored for specific tasks.

Garg, S.; Schmidt, D. K.

1985-01-01

213

Advanced bioreactor concepts for gaseous substrates: Conversion of synthesis gas to liquid fuels and removal of SO{sub x} and NO{sub x} from coal combustion gases. CRADA final report  

SciTech Connect

The purpose of the proposed research program was the development and demonstration of a new generation of gaseous substrate-based bioreactors for the production of liquid fuels from coal synthesis gas and the removal of NO{sub x} and SO{sub x} species from coal combustion flue gas. This study addressed the further investigation of optimal bacterial strains, growth media and kinetics for the biocatalytic conversion of coal synthesis gas to liquid fuel such as ethanol and the reduction of gaseous flue gas constituents. The primary emphasis was on the development of advanced bioreactor systems coupled with innovative biocatalytic systems that will provide increased productivity under controlled conditions. It was hoped that this would result in bioprocessing options that have both technical and economic feasibility, thus, ensuring early industrial use. Predictive mathematical models were formulated to accommodate hydrodynamics, mass transport, and conversion kinetics, and provide the data base for design and scale-up. The program was separated into four tasks: (1) Optimization of Biocatalytic Kinetics; (2) Development of Well-mixed and Columnar Reactors; (3) Development of Predictive Mathematical Models; and (4) Industrial Demonstration. Research activities addressing both synthesis gas conversion and flue gas removal were conducted in parallel by BRI and ORNL respectively.

Kaufman, E.N.; Selvaraj, P.T.

1997-10-01

214

Interaction of pulsating and spinning waves in condensed phase combustion  

SciTech Connect

The authors employ a nonlinear stability analysis in the neighborhood of a multiple bifurcation point to describe the interaction of pulsating and spinning modes of condensed phase combustion. Such phenomena occur in the synthesis of refractory materials. In particular, they consider the propagation of combustion waves in a long thermally insulated cylindrical sample and show that steady, planar combustion is stable for a modified activation energy/melting parameter less than a critical value. Above this critical value primary bifurcation states, corresponding to time-periodic pulsating and spinning modes of combustion, emanate from the steadily propagating solution. By varying the sample radius, the authors split a multiple bifurcation point to obtain bifurcation diagrams which exhibit secondary, tertiary, and quarternary branching to various types of quasi-periodic combustion waves.

Booty, M.R.; Margolis, S.B.; Matkowsky, B.J.

1986-10-01

215

The Synthesis and Antimicrobial Activity of Heterocyclic Derivatives of Totarol  

PubMed Central

The synthesis and antimicrobial activity heterocyclic analogs of the diterpenoid totarol are described. An advanced synthetic intermediate with a ketone on the A-ring is used to attach fused heterocycles and a carbon-to-nitrogen atom replacement is made on the B-ring by de novo synthesis. A-ring analogs with an indole attached exhibit, for the first time, enhanced antimicrobial activity relative to the parent natural product. Preliminary experiments demonstrate that the indole analogs do not target the bacterial cell division protein FtsZ as had been hypothesized for totarol.

Kim, Michelle B.; O'Brien, Terrence E.; Moore, Jared T.; Anderson, David E.; Foss, Marie H.; Weibel, Doug-las B.; Ames, James B.; Shaw, Jared T.

2012-01-01

216

Active Combustion Control for Aircraft Gas-Turbine Engines-Experimental Results for an Advanced, Low-Emissions Combustor Prototype  

NASA Technical Reports Server (NTRS)

Lean combustion concepts for aircraft engine combustors are prone to combustion instabilities. Mitigation of instabilities is an enabling technology for these low-emissions combustors. NASA Glenn Research Center s prior activity has demonstrated active control to suppress a high-frequency combustion instability in a combustor rig designed to emulate an actual aircraft engine instability experience with a conventional, rich-front-end combustor. The current effort is developing further understanding of the problem specifically as applied to future lean-burning, very low-emissions combustors. A prototype advanced, low-emissions aircraft engine combustor with a combustion instability has been identified and previous work has characterized the dynamic behavior of that combustor prototype. The combustor exhibits thermoacoustic instabilities that are related to increasing fuel flow and that potentially prevent full-power operation. A simplified, non-linear oscillator model and a more physics-based sectored 1-D dynamic model have been developed to capture the combustor prototype s instability behavior. Utilizing these models, the NASA Adaptive Sliding Phasor Average Control (ASPAC) instability control method has been updated for the low-emissions combustor prototype. Active combustion instability suppression using the ASPAC control method has been demonstrated experimentally with this combustor prototype in a NASA combustion test cell operating at engine pressures, temperatures, and flows. A high-frequency fuel valve was utilized to perturb the combustor fuel flow. Successful instability suppression was shown using a dynamic pressure sensor in the combustor for controller feedback. Instability control was also shown with a pressure feedback sensor in the lower temperature region upstream of the combustor. It was also demonstrated that the controller can prevent the instability from occurring while combustor operation was transitioning from a stable, low-power condition to a normally unstable high-power condition, thus enabling the high-power condition.

DeLaat, John C.; Kopasakis, George; Saus, Joseph R.; Chang, Clarence T.; Wey, Changlie

2012-01-01

217

Active Combustion Control in a Ramjet Using Large-eddy Simulations  

Microsoft Academic Search

A large-eddy simulation model has been developed to study combustion instability in a ramjet combustor. A thin-flame model for premixed combustion is employed in the numerical scheme, which explicitly uses the local turbulent flame speed in the governing equation. Combustion instability in the ramjet has been numerically simulated. Two types of instability arc observed: a small-amplitude, high-frequency instability and a

SURESH MENON

1992-01-01

218

Ultralow concentrations of ibuprofen activate cell prostaglandin synthesis.  

PubMed

The interest in the prostaglandin (PG) synthesis by animal cells today grows steadily because of the difficulties in obtaining them by any other way. Murine peritoneal macrophages can under certain conditions synthesize large amounts of PGs. The effect of well-known nonsteroidal anti-inflammatory drug ibuprofen on PG synthesis by the cells using a high-performance liquid chromatography (HPLC) method with fluorescence detection of 4-bromomethyl-7-methoxy-coumarin (BrMMC) derivatives was studied. In our case, the main metabolites were PGE2 and PGF2a. The PG synthesis activation effect was shown by ibuprofen concentrations in the 10(-10)-10(-14) M range with the maximum effect of 10(-12)M. In this case, the ibuprofen effect was comparable in value with the effect of well-known cell PG synthesis activator--calcium ionophore A23187. Although the exact mechanism of such an effect is not clear at the moment, at low concentration, ibuprofen itself is able to activate PG synthesis in murine peritoneal macrophages. PMID:9100354

Sergeeva, M G; Gonchar, M V; Chistyakov, V V; Mevkh, A T

1996-01-01

219

Presence of estrogenic activity from emission of fossil fuel combustion as detected by a recombinant yeast bioassay  

NASA Astrophysics Data System (ADS)

Estrogenic activities of emission samples generated by fossil fuel combustion were investigated with human estrogen receptor (ER) recombinant yeast bioassay. The results showed that there were weak but clear estrogenic activities in combustion emissions of fossil fuels including coal, petroleum, and diesel. The estrogenic relative potency (RP) of fossil fuel combustion was the highest in petroleum-fired car, followed by coal-fired stove, diesel-fired agrimotor, coal-fired electric power station. On the other hand, the estrogenic relative inductive efficiency (RIE) was the highest in coal-fired stove and coal-fired electric power station, followed by petroleum-fired car and diesel-fired agrimotor. The estrogenic activities in the sub-fractions from chromatographic separation of emitted materials were also determined. The results indicated that different chemical fractions in these complex systems have different estrogenic potencies. The GC/MS analysis of the emission showed that there were many aromatic carbonyls, big molecular alcohol, PAHs and derivatives, and substituted phenolic compounds and derivatives which have been reported as environmental estrogens. The existence of estrogenic substances in fossil fuel combustion demands further investigation of their potential adverse effects on human and on the ecosystem. The magnitude of pollution due to global usage of fossil fuels makes it imperative to understand the issue of fossil fuel-derived endocrine activities and the associated health risks, particularly the aggregated risks stemmed from exposure to toxicants of multiple sources.

Wang, Jingxian; Wu, Wenzhong; Henkelmann, Bernhard; You, Li; Kettrup, Antonius; Schramm, Karl-Werner

220

Cholera toxin induces synthesis of phospholipase A2-activating protein.  

PubMed

The mechanism of cholera toxin (CT)-stimulated arachidonate metabolism was evaluated. CT caused rapid in vitro synthesis of prostaglandin E2 (PGE2) in murine smooth muscle-like cells (BC3H1), reaching maximal levels within 3 to 4 min. In comparison, cyclic AMP (cAMP) levels were unchanged, and addition of dibutyryl cAMP did not affect PGE2 synthesis. CT-induced PGE2 synthesis was prevented by actinomycin D or cycloheximide, indicating a need for de novo protein synthesis. Northern blot analysis of total RNA from BC3H1 cells revealed that exposure to CT resulted in an increase in abundance of mRNA encoding phospholipase A2 (PLA2)-activating protein (PLAP). PLAP is a regulatory protein that increases the enzymatic activity of cellular PLA(2), which in turn causes increased hydrolysis of arachidonate from membrane phospholipids. Furthermore, CT evoked the accumulation of PLAP mRNA in J774 (murine monocyte/macrophage) and Caco-2 (human intestinal epithelial) cells in vitro, but the responses were more delayed than that of BC3H1 cells. A protein band of approximately 35 kDa, which corresponded to the size of PLAP, was observed in sodium dodecyl sulfate extracts of Caco-2 cells by Western blot (immunoblot) analysis using affinity-purified antibodies to PLAP synthetic peptides. Synthesis of PLAP protein was increased after 2 h of exposure to CT. Exposure of mouse intestinal loops to either CT or live Salmonella typhimurium for 3 h increased mucosal PLAP mRNA levels. The role of PLAP in CT-induced PGE2 synthesis provides an attractive explanation for the reported suppression of CT-induced intestinal secretion by inhibitors of protein synthesis. PMID:8675318

Peterson, J W; Saini, S S; Dickey, W D; Klimpel, G R; Bomalaski, J S; Clark, M A; Xu, X J; Chopra, A K

1996-06-01

221

Synthesis and anticonvulsant activity of enaminones  

Microsoft Academic Search

Further investigation of the potential anticonvulsant activity of the enaminones was attempted to discern the possible role of metabolites as the active\\/co-active entities of the esters of the enaminones. A series of 5-methyl-2-cyclohexene enaminones, the hypothesised metabolites corresponding to a sequence of active and inactive esters were synthesised and evaluated for anticonvulsant activity. With two exceptions, ethyl 4-[(4-cyanophenyl)amino]-6-methyl-2-oxocyclohex-3-ene-1-carboxylate (1k), and

Natalie D Eddington; Donna S Cox; Manoj Khurana; Noha N Salama; James P Stables; Sylvia J Harrison; Abraham Negussie; Robert S Taylor; Uy Q Tran; Jacqueline A Moore; Judith C Barrow; K. R Scott

2003-01-01

222

Combustion devices technology team - An overview and status of STME-related activities  

Microsoft Academic Search

The Consortium for CFD applications in propulsion technology has been formed at NASA\\/Marshall Space Flight Center. The combustion devices technology team is one of the three teams that constitute the Consortium. While generally aiming to advance combustion devices technology for rocket propulsion, the team's efforts for the last 1 and 1\\/2 years have been focused on issues relating to the

P. K. Tucker; Margie Croteau-Gillespie

1992-01-01

223

Synthesis and biological activity of mustard derivatives of thymine.  

PubMed

The synthesis and biological activity of a novel DNA cross-linking antitumor agent is presented. The new alkylating agent significantly inhibited cell proliferation, migration and invasion as tested in vitro on the A431 vulvar epidermal carcinoma cell line. PMID:18569783

Hadj-Bouazza, Amel; Teste, Karine; Colombeau, Ludovic; Chaleix, Vincent; Zerrouki, Rachida; Kraemer, Michel; Sainte Catherine, Odile

2008-05-01

224

Synthesis of optically active vomifoliol and roseoside stereoisomers.  

PubMed

A synthesis of optically active vomifoliol stereoisomers 1-4 and their glucosides, roseoside stereoisomers 5-8, was accomplished via alpha-acetylenic alcohol 11a or 11b effectively prepared by an asymmetric transfer hydrogenation of alpha,beta-acetylenic ketone 10. Simultaneous separation of these stereoisomers by HPLC was also performed. PMID:15863927

Yamano, Yumiko; Ito, Masayoshi

2005-05-01

225

Synthesis of (-)-arctigenin derivatives and their anticancer activity.  

PubMed

The natural dibenzylbutyrolactone type lignanolide (-)-arctigenin, which was prepared from fructus arctii, showed obvious anticancer activity. The synthesis of four new (-)-arctigenin derivatives and their anticancer bioactivities were examined. The structures of the four new synthetic derivatives were elucidated. PMID:21867457

Gui-Rong, Chen; Li-Ping, Cai; De-Qiang, Dou; Ting-Guo, Kang; Hong-Fu, Li; Fu-Rui, Li; Ning, Jiang

2012-01-01

226

Optimal cooperative control synthesis of active displays  

NASA Technical Reports Server (NTRS)

A technique is developed that is intended to provide a systematic approach to synthesizing display augmentation for optimal manual control in complex, closed-loop tasks. A cooperative control synthesis technique, previously developed to design pilot-optimal control augmentation for the plant, is extended to incorporate the simultaneous design of performance enhancing displays. The technique utilizes an optimal control model of the man in the loop. It is applied to the design of a quickening control law for a display and a simple K/s(2) plant, and then to an F-15 type aircraft in a multi-channel task. Utilizing the closed loop modeling and analysis procedures, the results from the display design algorithm are evaluated and an analytical validation is performed. Experimental validation is recommended for future efforts.

Garg, S.; Schmidt, D. K.

1985-01-01

227

Optimal cooperative control synthesis of active displays  

NASA Technical Reports Server (NTRS)

A technique is developed that is intended to provide a systematic approach to synthesizing display augmentation for optimal manual control in complex, closed-loop tasks. A cooperative control synthesis technique, previously developed to design pilot-optimal control augmentation for the plant, is extended to incorporate the simultaneous design of performance enhancing displays. The technique utilizes an optimal control model of the man in the loop. It is applied to the design of a quickening control law for a display and a simple K/(s squared) plant, and then to an F-15 type aircraft in a multichannel task. Utilizing the closed-loop modeling and analysis procedures, the results from the display design algorithm are evaluated and an analytical validation is performed. Experimental validation is recommended for future efforts.

Gary, Sanjay; Schmidt, David K.

1987-01-01

228

Fuel mixture approach for solution combustion synthesis of Ca{sub 3}Al{sub 2}O{sub 6} powders  

SciTech Connect

Single-phase 3CaO.Al{sub 2}O{sub 3} powders were prepared via solution combustion synthesis using a fuel mixture of urea and {beta}-alanine. The concept of using this fuel mixture comes from the individual reactivity of calcium nitrate and aluminum nitrate with respect to urea and {beta}-alanine. It was proved that urea is the optimum fuel for Al(NO{sub 3}){sub 3} whereas {beta}-alanine is the most suitable fuel for Ca(NO{sub 3}){sub 2}. X-ray diffraction and thermal analysis investigations revealed that heating at 300 deg. C the precursor mixture containing the desired metal nitrates, urea and {beta}-alanine triggers a vigorous combustion reaction, which yields single-phase nanocrystalline 3CaO.Al{sub 2}O{sub 3} powder (33.3 nm). In this case additional annealing was no longer required. The use of a single fuel failed to ensure the formation of 3CaO.Al{sub 2}O{sub 3} directly from the combustion reaction. After annealing at 900 deg. C for 1 h, the powders obtained by using a single fuel (urea or {beta}-alanine) developed a phase composition comprising of 3CaO.Al{sub 2}O{sub 3}, 12CaO.7Al{sub 2}O{sub 3} and CaO.

Ianos, Robert ['Politehnica' University of Timisoara, Faculty of Industrial Chemistry and Environmental Engineering, P-ta Victoriei No. 2, Timisoara 300006 (Romania)], E-mail: robert_ianos@yahoo.com; Lazau, Ioan; Pacurariu, Cornelia ['Politehnica' University of Timisoara, Faculty of Industrial Chemistry and Environmental Engineering, P-ta Victoriei No. 2, Timisoara 300006 (Romania); Barvinschi, Paul [West University of Timisoara, Faculty of Physics, Bd. V. Parvan No. 4, Timisoara 300223 (Romania)

2009-07-15

229

Solution combustion synthesis of CeO{sub 2}-CeAlO{sub 3} nano-composites by mixture-of-fuels approach  

SciTech Connect

Nano-composites of CeO{sub 2}-CeAlO{sub 3} are synthesised by solution combustion method employing (a) urea and (b) a mixture of urea and glycine as fuels with corresponding metal nitrates. The as-prepared powders are all nano-sized (5-30 nm) and the same is confirmed by broadening of the X-ray diffraction peaks and transmission electron microscopy. A starting composition of Ce:Al in the atomic ratio 4:6 gives rise to different phases depending on the fuel being used for combustion. When urea alone is used as fuel, nano-crystalline CeO{sub 2} phase is formed with Al{sub 2}O{sub 3} being in the amorphous state. When the mixture of fuels is used, a mixture of nano-sized CeO{sub 2} and CeAlO{sub 3} phases is obtained. However, upon sintering at 1400 deg. C in air, the stable phases CeO{sub 2} and {alpha}-Al{sub 2}O{sub 3} are formed in both the cases. Combustion synthesis using mixture-of-fuels is proposed to be a route to stabilise low oxidation compounds such as CeAlO{sub 3}.

Aruna, S.T. [Surface Engineering Division, National Aerospace Laboratories, Post Bag No. 1779, Bangalore 560017 (India); Kini, N.S. [Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India)], E-mail: nagesh.kini@gmail.com; Rajam, K.S. [Surface Engineering Division, National Aerospace Laboratories, Post Bag No. 1779, Bangalore 560017 (India)

2009-04-02

230

Effect of support on the catalytic activity of manganese oxide catalyts for toluene combustion.  

PubMed

The aim of this work was to study combustion of toluene (1000ppm) over MnO(2) modified with different supports. ?-Al(2)O(3) and ?-Al(2)O(3) obtained from Boehmite, ?-Al(2)O(3) (commercial), SiO(2), TiO(2) and ZrO(2) were used as commercial support materials. In view of potential interest of this process, the influence of support material on the catalytic performance was discussed. The deposition of 9.5MnO(2) was performed by impregnation over support. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction and oxidation (TPR/TPO) and thermogravimetric analysis (TGA). The catalytic tests were carried out at atmospheric pressure in a fixed-bed flow reactor. 9.5MnO(2)/?-Al(2)O(3)(B) (synthesized from Boehmite) catalyst exhibits the highest catalytic activity, over which the toluene conversion was up to 90% at a temperature of 289°C. Considering all the characterization and reaction data reported in this study, it was concluded that the manganese state and oxygen species played an important role in the catalytic activity. PMID:22579460

Pozan, Gulin Selda

2012-06-30

231

Synthesis, structural investigation and magnetic properties of Zn2+ substituted cobalt ferrite nanoparticles prepared by the sol-gel auto-combustion technique  

NASA Astrophysics Data System (ADS)

Structural morphology and magnetic properties of the Co1-xZnxFe2O4 (0.0?x?1.0) spinel ferrite system synthesized by the sol-gel auto-combustion technique using nitrates of respective metal ions have been studied. The ratio of metal nitrates to citric acid was taken at 1:3. The as prepared powder of cobalt zinc ferrite was sintered at 600 °C for 12 h after TG/DTA thermal studies. Compositional stoichiometry was confirmed by energy dispersive analysis of the X-ray (EDAX) technique. Single phase cubic spinel structure of Co-Zn nanoparticles was confirmed by XRD data. The average crystallite size (t), lattice constant (a) and other structural parameters of zinc substituted cobalt ferrite nanoparticles were calculated from XRD followed by SEM and FTIR. It is observed that the sol-gel auto-combustion technique has many advantages for the synthesis of technologically applicable Co-Zn ferrite nanoparticles. The present investigation clearly shows the effect of the synthesis method and possible relation between magnetic properties and microstructure of the prepared samples. Increase in nonmagnetic Zn2+ content in cobalt ferrite nanoparticles is followed by decrease in nB, Ms and other magnetic parameters. Squareness ratio for the Co-ferrite was 1.096 at room temperature.

Raut, A. V.; Barkule, R. S.; Shengule, D. R.; Jadhav, K. M.

2014-05-01

232

Synthesis of actively adjustable springs by antagonistic redundant actuation  

NASA Technical Reports Server (NTRS)

A methodology for active spring generation is presented based on antagonistic redundant actuation. Antagonistic properties are characterized using an effective system stiffness. 'Antagonistic stiffness' is generated by preloading a closed-chain (parallel) linkage system. Internal load distribution is investigated along with the necessary conditions for spring synthesis. The performance and stability of a proposed active spring are shown by simulation, and applications are discussed.

Yi, Byung-Ju; Freeman, Robert A.

1992-01-01

233

Cyclobutane-Containing Alkaloids: Origin, Synthesis, and Biological Activities  

PubMed Central

Present review describes research on novel natural cyclobutane-containing alkaloids isolated from terrestrial and marine species. More than 60 biological active compounds have been confirmed to have antimicrobial, antibacterial, antitumor, and other activities. The structures, synthesis, origins, and biological activities of a selection of cyclobutane-containing alkaloids are reviewed. With the computer program PASS some additional biological activities are also predicted, which point toward new possible applications of these compounds. This review emphasizes the role of cyclobutane-containing alkaloids as an important source of leads for drug discovery.

Sergeiko, Anastasia; Poroikov, Vladimir V; Hanus, Lumir O; Dembitsky, Valery M

2008-01-01

234

Tormentic acid derivatives: synthesis and apoptotic activity.  

PubMed

Several derivatives of tormentic acid have been prepared and tested for their antitumor activity. The dichloroacetate 14 is an excellent antitumor active agent acting by an apoptose inducing pathway as demonstrated by OA/PI staining, DNA laddering experiments as well as by an annexin V binding assay. PMID:22995818

Csuk, René; Siewert, Bianka; Dressel, Christian; Schäfer, Renate

2012-10-01

235

Lightweight, Actively Cooled Ceramic Matrix Composite Thrustcells Successfully Tested in Rocket Combustion Lab.  

National Technical Information Service (NTIS)

In a joint effort between the NASA Glenn Research Center and the NASA Marshall Space Flight Center, regeneratively cooled ceramic matrix composite (CMC) thrustcells were developed and successfully tested in Glenn's Rocket Combustion Lab. Cooled CMC's offe...

M. H. Jaskowiak S. K. Elam M. R. Effinger

2002-01-01

236

Synthesis and antitumour activity of ?-hydroxyisovalerylshikonin analogues  

Microsoft Academic Search

A series of novel ?-hydroxyisovalerylshikonin analogues bearing oxygen-containing substituents at the side-chain hydroxyl of shikonin were designed and synthesized. The cytotoxicities of these compounds were evaluated in vitro against multi-drug resistant (MDR) cell lines DU-145 and HeLa. Most compounds exhibited significant inhibitory activity on both cell lines. The structure–activity relationship showed the analogues with ether substituents displayed the most potent antitumour

Zhen Rao; Xin Liu; Wen Zhou; Jing Yi; Shao-Shun Li

2011-01-01

237

Preparation and characterization of 80 s ribosomes of ascites tumor cells active in polypeptide synthesis  

Microsoft Academic Search

SUMMARY The preparation of tumor ribosomes that are essentially free of polyribosomes and active in polypeptide synthesis is described. Most active preparations were obtained by incubating ribosomal suspensions 20 min under conditions of protein synthesis. After this time, all polysomes had been converted to 80 S particles which could be stimulated to polypeptide synthesis by polyuridylic acid or liver mRNA.

Karl Letnansky

1972-01-01

238

Combustion joining of refractory materials  

Microsoft Academic Search

This paper overviews heterogeneous exothermic reactive systems as they apply to the joining of materials. Techniques that\\u000a are investigated fall under two general schemes: so-called Volume Combustion Synthesis (VCS) and Self-Propagating High-Temperature\\u000a Synthesis (SHS). Within the VCS scheme, applications that are considered include Reactive Joining (RJ), Reactive Resistance\\u000a Welding (RRW), and Spark Plasma Sintering (SPS). Under the SHS scheme, Combustion

A. S. Mukasyan; J. D. E. White

2007-01-01

239

Synthesis and antimalarial activity of prodigiosenes.  

PubMed

Several analogues of the natural compound prodigiosin with modified A- and C-rings were synthesised as were some of their tin, cobalt, boron and zinc complexes. The antimalarial activity of these prodigiosenes was evaluated in vitro using the 3D7 Plasmodium falciparum strain. The presence of a nitrogen atom in the A-ring is needed for antimalarial activity but the presence of an alkyl group at the ?'-position of the C-ring seems detrimental. Dibutyl tin complexes exhibit IC50 values mostly in the nanomolar range with equal or improved activity compared to the free-base prodigiosene ligand, despite the fact that the general toxicity of such tin complexes is demonstrably lower than that of the free-bases. PMID:24834447

Marchal, Estelle; Smithen, Deborah A; Uddin, Md Imam; Robertson, Andrew W; Jakeman, David L; Mollard, Vanessa; Goodman, Christopher D; MacDougall, Kristopher S; McFarland, Sherri A; McFadden, Geoffrey I; Thompson, Alison

2014-06-28

240

Synthesis and activity of biomimetic biofilm disruptors.  

PubMed

Biofilms are often associated with human bacterial infections, and the natural tolerance of biofilms to antibiotics challenges treatment. Compounds with antibiofilm activity could become useful adjuncts to antibiotic therapy. We used norspermidine, a natural trigger for biofilm disassembly in the developmental cycle of Bacillus subtilis , to develop guanidine and biguanide compounds with up to 20-fold increased potency in preventing biofilm formation and breaking down existing biofilms. These compounds also were active against pathogenic Staphylococcus aureus . An integrated approach involving structure-activity relationships, protonation constants, and crystal structure data on a focused synthetic library revealed that precise spacing of positively charged groups and the total charge at physiological pH distinguish potent biofilm inhibitors. PMID:23406351

Böttcher, Thomas; Kolodkin-Gal, Ilana; Kolter, Roberto; Losick, Richard; Clardy, Jon

2013-02-27

241

Synthesis and Activity of Biomimetic Biofilm Disruptors  

PubMed Central

Biofilms are often associated with human bacterial infections, and the natural tolerance of biofilms to antibiotics challenges treatment. Compounds with antibiofilm activity could become useful adjuncts to antibiotic therapy. We used norspermidine, a natural trigger for biofilm disassembly in the developmental cycle of Bacillus subtilis, to develop guanidine and biguanide compounds with up to 20-fold increased potency in preventing biofilm formation and breaking down existing biofilms. These compounds also were active against pathogenic Staphylococcus aureus. An integrated approach involving structure–activity relationships, protonation constants, and crystal structure data on a focused synthetic library revealed that precise spacing of positively charged groups and the total charge at physiological pH distinguish potent biofilm inhibitors.

2013-01-01

242

Active control of combustion oscillations in a lean premixed combustor by secondary fuel injection coupling with chemiluminescence imaging technique  

Microsoft Academic Search

An active control of combustion driven oscillations occurring in a lean premixed model combustor is demonstrated by means of a secondary fuel injection. An unstable condition, which leads to self-excited pressure oscillations beyond 170dB, is chosen as control target. Keeping the inlet air temperature, the air mass flow rate and the overall equivalence ratio, respectively at 700K, 78g\\/s and 0.50,

Shigeru Tachibana; Laurent Zimmer; Yoji Kurosawa; Kazuo Suzuki

2007-01-01

243

Synthesis of nanocrystalline yttria doped ceria powder by urea-formaldehyde polymer gel auto-combustion process  

SciTech Connect

Nanocrystalline yttria doped ceria powder has been prepared by auto-combustion of a transparent gel formed by heating an aqueous acidic solution containing methylol urea, urea, cerium(III) nitrate and yttrium(III) nitrate. The TGA and DSC studies showed the combustion reaction of the gel initiated at 225 deg. C and completed within a short period of time. XRD spectrum of the combustion product reveals the formation of phase pure cubic yttria doped ceria during the combustion process. Loose agglomerate of yttria doped ceria particle obtained by the combustion reaction could be easily deagglomerated by planetary ball milling and the powder obtained contains particles in the size range of 0.05-3.3 {mu}m with D {sub 50} value of 0.13 {mu}m. The powder particles are aggregate of nanocrystallites with a wide size range of 14-105 nm. Pellets prepared by pressing the yttria doped ceria powder sintered to 95.2% TD at 1400 deg. C.

Biswas, M. [Ceramic Division, Naval Materials Research Laboratory, Defence Research and Development Organization, Shil Badlapur Road, Anandnagar P.O., Addl. Ambernath, Thane 421 506 (India); Prabhakaran, K. [Ceramic Division, Naval Materials Research Laboratory, Defence Research and Development Organization, Shil Badlapur Road, Anandnagar P.O., Addl. Ambernath, Thane 421 506 (India)]. E-mail: kp2952002@yahoo.co.uk; Gokhale, N.M. [Ceramic Division, Naval Materials Research Laboratory, Defence Research and Development Organization, Shil Badlapur Road, Anandnagar P.O., Addl. Ambernath, Thane 421 506 (India); Sharma, S.C. [Ceramic Division, Naval Materials Research Laboratory, Defence Research and Development Organization, Shil Badlapur Road, Anandnagar P.O., Addl. Ambernath, Thane 421 506 (India)

2007-04-12

244

Synthesis of biologically active bridged diazabicycloheptanes.  

PubMed

The chemistry underlying how diazabicycloheptanes are assembled is described, subdivided according to chemical structure of two types, the 3,6 diazabicyclo[3.1.1]heptane and the 2,5-diazabicyclo[2.2.1]heptane ring system. Detailed information on myriad of activities of compounds derived from the two scaffolds are reported. PMID:22830336

Murineddu, G; Asproni, B; Pinna, G; Curzu, M M; Dore, A; Pau, A; Deligia, F; Pinna, G A

2012-01-01

245

Effect of nitrogen-containing impurities on the activity of perovskitic catalysts for the catalytic combustion of methane.  

PubMed

LaMnO(3), either pure or doped with 10 mol % Sr, has been prepared by flame pyrolysis in nanostructured form. Such catalysts have been tested for the catalytic flameless combustion of methane, achieving very high catalytic activity. The resistance toward poisoning by some model N-containing impurities has been checked in order to assess the possibility of operating the flameless catalytic combustion with biogas, possibly contaminated by S- or N-based compounds. This would be a significant improvement from the environmental point of view because the application of catalytic combustion to gas turbines would couple improved energy conversion efficiency and negligible noxious emissions, while the use of biogas would open the way to energy production from a renewable source by means of very efficient technologies. A different behavior has been observed for the two catalysts; namely, the undoped sample was more or less heavily poisoned, whereas the Sr-doped sample showed slightly increasing activity upon dosage of N-containing compounds. A possible reaction mechanism has been suggested, based on the initial oxidation of the organic backbone, with the formation of NO. The latter may adsorb more or less strongly depending on the availability of surface oxygen vacancies (i.e., depending on doping). Decomposition of NO may leave additional activated oxygen species on the surface, available for low-temperature methane oxidation and so improving the catalytic performance. PMID:23039114

Buchneva, Olga; Gallo, Alessandro; Rossetti, Ilenia

2012-11-01

246

Synthesis of azathia analogues of platelet activating factor with polyheterosidechains.  

PubMed

The synthesis of azathia analogues of the platelet activating factor with oxygen and sulphur-containing sidechains is reported. The starting point is 1-acetylthio-3-hydroxy-2-propaneamine-HCl, which permits the formation of the thioether and the acetamido linkage in one step. The phosphocholine part is introduced via 2-chloro-2-oxo-1,3,2-dioxaphospholane and subsequent ring opening with trimethylamine under pressure. PMID:2090358

Zeidler, J M; Zimmermann, W; Roth, H J

1990-08-01

247

Efficient synthesis of fluorothiosparfosic acid analogues with potential antitumoral activity.  

PubMed

In this paper, we describe a short synthesis of N-(phosphonoacetyl)-L-aspartate (PALA) analogues. The mono- and difluorinated thioacetamide precursors were prepared in one step from methyl (diethoxyphosphono)di- and monofluoromethyldithioacetates 8 and 11 as starting materials. Antiproliferating properties on a L1210 strain and ATCase inhibition of these new compounds are disclosed. ThioPALA(FF) 5c showed a remarkable cytotoxic activity towards murine leukemia L1210, when used as tetraester. PMID:15975800

Pfund, Emmanuel; Lequeux, Thierry; Masson, Serge; Vazeux, Michel; Cordi, Alex; Pierre, Alain; Serre, Valérie; Hervé, Guy

2005-08-15

248

Synthesis and preliminary antihyperlipidaemic activities evaluation of andrographolide derivatives.  

PubMed

Recent studies indicated that andrographolide was a potential antihyperlipidaemic therapeutic agent. In the paper, the synthesis of a series of andrographolide derivatives was described and their antihyperlipidaemic activities were evaluated in vivo. As compared with TG, TC, HDL-C and LDL-C concentrations, some of the derivatives exhibited better antihyperlipidaemic effects than positive control atromide. Therein, compound 6i, which was the most potent compound, could serve as a new lead for further development of antihyperlipidaemic agents. PMID:22385174

Wang, Bin; Tang, Chunlei; Han, Yaodan; Guo, Ruzhou; Qian, Hai; Huang, Wenlong

2012-03-01

249

Synthesis and pharmacological activity of diterpenylnaphthoquinone derivatives.  

PubMed

New diterpenylquinones, combining a diterpene diacid and a naphthoquinone, were prepared from junicedric acid and lapachol. The new derivatives were assessed as gastroprotective agents by the HCl-EtOH-induced gastric lesions model in mice as well as for basal cytotoxicity on the following human cell lines: Normal lung fibroblasts (MRC-5), gastric epithelial adenocarcinoma (AGS), and hepatocellular carcinoma (Hep G2). Several of the new compounds were significantly active as antiulcer agents and showed selective cytotoxicity against AGS cells. PMID:21996716

Pertino, Mariano Walter; Theoduloz, Cristina; Palenzuela, Jose Antonio; Afonso, Maria del Mar; Yesilada, Erdem; Monsalve, Francisco; González, Paulo; Droguett, Daniel; Schmeda-Hirschmann, Guillermo

2011-01-01

250

SSAF – A Tool for Active Filter Synthesis  

Microsoft Academic Search

\\u000a In this paper a software tool used to determine the topological elements of active analog continuous-time filters is presented.\\u000a The filter is described by an arbitrary transfer functions expressed as t(s) = p(s)\\/e(s)t({\\\\rm s}) = p({\\\\rm s})\\/e({\\\\rm s}), where e(s) is the natural mode (pole) polynomial and p(s) is the transmission zero polynomial. The goal is to obtain filters having

Elena Doicaru; Lucian B?rbulescu; Claudius Dan

251

Constitutive Somatostatin Receptor Subtype 2 Activity Attenuates GH Synthesis  

PubMed Central

Somatostatin signals predominantly through somatostatin receptor (SSTR) subtype 2 to attenuate GH release. However, the independent role of the receptor in regulating GH synthesis is unclear. Because we had previously demonstrated constitutive SSTR2 activity in mouse corticotrophs, we now analyzed GH regulation in rat pituitary somatotroph (GC) tumor cells, which express SSTR2 exclusively and are devoid of endogenous somatostatin ligand. We demonstrate that moderately stable SSTR2 overexpression (GpSSTR2WT cells) was associated with decreased GH promoter activity, GH mRNA, and hormone levels compared with those of control transfectants (GpCon cells). In contrast, levels of GH mRNA and peptide and GH promoter activity were unchanged in GpSSTR2DRY stable transfectants moderately expressing DRY motif mutated SSTR2 (R140A). GpSSTR2DRY did not exhibit an enhanced octreotide response as did GpSSTR2WT cells; however, both SSTR2WT-enhanced yellow fluorescent protein (eYFP) and SSTR2DRY-eYFP internalized on octreotide treatment. Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, increased GH synthesis in wild-type GC cells and primary pituitary cultures. GpSSTR2WT cells induced GH synthesis more strongly on SAHA treatment, evident by both higher GH peptide and mRNA levels compared with the moderate but similar GH increase observed in GpCon and GpSSTR2DRY cells. In vivo SAHA also increased GH release from GpSSTR2WT but not from control xenografts. Endogenous rat GH promoter chromatin immunoprecipitation showed decreased baseline acetylation of the GH promoter with exacerbated acetylation after SAHA treatment in GpSSTR2WT compared with that of either GpSSTR2DRY or control cells, the latter 2 transfectants exhibiting similar GH promoter acetylation levels. In conclusion, modestly increased SSTR2 expression constitutively decreases GH synthesis, an effect partially mediated by GH promoter histone deacetylation.

Ben-Shlomo, Anat; Pichurin, Oxana; Khalafi, Ramtin; Zhou, Cuiqi; Chesnokova, Vera; Ren, Song-Guang; Liu, Ning-Ai

2013-01-01

252

Constitutive somatostatin receptor subtype 2 activity attenuates GH synthesis.  

PubMed

Somatostatin signals predominantly through somatostatin receptor (SSTR) subtype 2 to attenuate GH release. However, the independent role of the receptor in regulating GH synthesis is unclear. Because we had previously demonstrated constitutive SSTR2 activity in mouse corticotrophs, we now analyzed GH regulation in rat pituitary somatotroph (GC) tumor cells, which express SSTR2 exclusively and are devoid of endogenous somatostatin ligand. We demonstrate that moderately stable SSTR2 overexpression (GpSSTR2(WT) cells) was associated with decreased GH promoter activity, GH mRNA, and hormone levels compared with those of control transfectants (GpCon cells). In contrast, levels of GH mRNA and peptide and GH promoter activity were unchanged in GpSSTR2(DRY) stable transfectants moderately expressing DRY motif mutated SSTR2 (R140A). GpSSTR(2DRY) did not exhibit an enhanced octreotide response as did GpSSTR2(WT) cells; however, both SSTR2(WT)-enhanced yellow fluorescent protein (eYFP) and SSTR2(DRY)-eYFP internalized on octreotide treatment. Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, increased GH synthesis in wild-type GC cells and primary pituitary cultures. GpSSTR2(WT) cells induced GH synthesis more strongly on SAHA treatment, evident by both higher GH peptide and mRNA levels compared with the moderate but similar GH increase observed in GpCon and GpSSTR2(DRY) cells. In vivo SAHA also increased GH release from GpSSTR2(WT) but not from control xenografts. Endogenous rat GH promoter chromatin immunoprecipitation showed decreased baseline acetylation of the GH promoter with exacerbated acetylation after SAHA treatment in GpSSTR2(WT) compared with that of either GpSSTR(2DRY) or control cells, the latter 2 transfectants exhibiting similar GH promoter acetylation levels. In conclusion, modestly increased SSTR2 expression constitutively decreases GH synthesis, an effect partially mediated by GH promoter histone deacetylation. PMID:23696564

Ben-Shlomo, Anat; Pichurin, Oxana; Khalafi, Ramtin; Zhou, Cuiqi; Chesnokova, Vera; Ren, Song-Guang; Liu, Ning-Ai; Melmed, Shlomo

2013-07-01

253

Europium luminescence enhancement in Al{sub 2}O{sub 3}:Eu{sup 3+} powders prepared by direct combustion synthesis  

SciTech Connect

The luminescence properties of Eu{sup 3+}:Al{sub 2}O{sub 3} powders prepared via low temperature direct combustion synthesis was investigated. It was observed that the heat treatment of the powders modifies the dynamics of the radiative transition {sup 5}D{sub 0}{yields}{sup 7}F{sub 2} of Eu{sup 3+} (1.0 mol %) and produces an enhancement of the luminescence intensity by nearly one order of magnitude. The luminescence enhancement is attributed to the presence of Eu{sup 3+} in {alpha}-Al{sub 2}O{sub 3} crystalline phase as the heat treatment drastically reduces the amount of amorphous Al{sub 2}O{sub 3} phases present in the powder.

Rakov, Nikifor; Maciel, Glauco S.; Lozano B, W.; Araujo, Cid B. de [Universidade Federal do Vale do Sao Francisco, 56306-410 Petrolina, Pernambuco (Brazil); Departamento de Fisica, Universidade Federal de Pernambuco, 50670-901 Recife, Pernambuco (Brazil)

2007-02-01

254

Synthesis and antibacterial activity of doxycycline neoglycosides.  

PubMed

A set of 37 doxycycline neoglycosides were prepared, mediated via a C-9 alkoxyamino-glycyl-based spacer reminiscent of that of tigecycline. Subsequent in vitro antibacterial assays against representative drug-resistant Gram negative and Gram positive strains revealed a sugar-dependent activity profile and one doxycycline neoglycoside, the 2'-amino-?-D-glucoside conjugate, to rival that of the parent pharmacophore. In contrast, the representative tetracycline-susceptible strain E. coli 25922 was found to be relatively responsive to a range of doxycycline neoglycosides. This study also extends the use of aminosugars in the context of neoglycosylation via a simple two-step strategy anticipated to be broadly applicable for neoglycorandomization. PMID:23987662

Zhang, Jianjun; Ponomareva, Larissa V; Marchillo, Karen; Zhou, Maoquan; Andes, David R; Thorson, Jon S

2013-09-27

255

Synthesis of methylenebisamides using CC- or DCMT-activated DMSO.  

PubMed

Bisamides are key fragments for the introduction of gem-diaminoalkyl residues into retroinverso pseudopeptide derivatives and in the synthesis of peptidomimetic compounds. The literature methods for these types of compounds have certain drawbacks. In particular, when amides react with electrophile-activated DMSO, the yields are rather low. We have found new electrophiles, 2,4,6-trichloro[1,3,5]triazine (CC) and 2,4-dichloro-6-methoxy[1,3,5]triazine (DCMT), which activate DMSO in the presence of amides to yield methylenebisamides in good to fair yields. The amides can be aromatic or aliphatic. The operation is simple and the reagents are inexpensive. PMID:19190739

Wang, Qiang; Sun, Lili; Jiang, Yu; Li, Chunbao

2008-01-01

256

Synthesis of protopanaxadiol derivatives and evaluation of their anticancer activities  

PubMed Central

Protopanaxadiol (PPD), an aglycon of ginseng saponins, has shown anticancer activity in previous studies. Here we report the semi-synthesis of 9 PPD derivatives with acetyl substitutions. Subsequently, the antiproliferative effects of these 9 analogs on different human cancer cell lines were investigated. Compounds 1 and 3 showed more significant and more potent antiproliferative activity compared to PPD and other derivatives. A flow cytometric assay indicated that Compounds 1 and 3 arrested cell cycle progression in the G1 phase and significantly induced apoptosis of cancer cells.

Du, Guang-Jian; Dai, Qing; Williams, Stainley; Wang, Chong-Zhi; Yuan, Chun-Su

2010-01-01

257

Lightweight, Actively Cooled Ceramic Matrix Composite Thrustcells Successfully Tested in Rocket Combustion Lab  

NASA Technical Reports Server (NTRS)

In a joint effort between the NASA Glenn Research Center and the NASA Marshall Space Flight Center, regeneratively cooled ceramic matrix composite (CMC) thrustcells were developed and successfully tested in Glenn's Rocket Combustion Lab. Cooled CMC's offer the potential for substantial weight savings over more traditional metallic parts. Two CMC concepts were investigated. In the first of these concepts, an innovative processing approach utilized by Hyper-Therm, Inc., allowed woven CMC coolant containment tubes to be incorporated into the complex thruster design. In this unique design, the coolant passages had varying cross-sectional shapes but maintained a constant cross-sectional area along the length of the thruster. These thrusters were silicon carbide matrix composites reinforced with silicon carbide fibers. The second concept, which was supplied by Ceramic Composites, Inc., utilized copper cooling coils surrounding a carbon-fiber-reinforced carbon matrix composite. In this design, a protective gradient coating was applied to the inner thruster wall. Ceramic Composites, Inc.'s, method of incorporating the coating into the fiber and matrix eliminated the spallation problem often observed with thermal barrier coatings during hotfire testing. The focus of the testing effort was on screening the CMC material's capabilities as well as evaluating the performance of the thermal barrier or fiber-matrix interfacial coatings. Both concepts were hot-fire tested in gaseous O2/H2 environments. The test matrix included oxygen-to-fuel ratios ranging from 1.5 to 7 with chamber pressures to 400 psi. Steady-state internal wall temperatures in excess of 4300 F were measured in situ for successful 30-sec test runs. Photograph of actively cooled composite thrustcell fabricated by Hyper-Therm is shown. The thrustcell is a silicon-carbide-fiber-reinforced silicon carbide matrix composite with woven cooling channels. The matrix is formed via chemical vapor infiltration. Photograph of hot-fire test of an actively cooled carbon-fiber-reinforced carbon matrix composite thrustcell is also shown. This composite thrustcell, which was fabricated by CCI, Inc., was wound with copper cooling coils to contain the water coolant. The tests were run with oxygen fuel ratios up to seven with chamber pressures of 200 psia.

Jaskowiak, Martha H.; Elam, Sandra K.; Effinger, Michael R.

2002-01-01

258

A status of the activities of the NASA. Marshall Space Flight Center Combustion Devices Technology Team  

Microsoft Academic Search

The Consortium for Computational Fluid Dynamics (CFD) Applications in Propulsion Technology was established to focus on computational fluid dynamics applications in propulsion. Specific areas of effort include developing the CFD technology required to address rocket propulsion issues, validating the technology, and applying the validated technology to design problems. The Combustion Devices Technology Team was formed to implement the above objectives

Kevin Tucker

1992-01-01

259

Synthesis of Passive and Active Bracing in Active Structures.  

National Technical Information Service (NTIS)

The seismic resistance achieved by optimizing the design of the conventional members of a structure equipped with structural control is evaluated. Viscoelastic (VE) dampers and active bracing system (ABS) are studied individually, as well as combined as a...

C. P. Pantelides S. R. Tzan

1996-01-01

260

Observation of nonuniform shrinkage and activation of highly porous chars during combustion in an improved electrodynamic chamber  

SciTech Connect

Combustion of single particles of highly porous synthetic char has been investigated in an electrodynamic chamber (EDC). The main reasons for using the EDC for studying high temperature kinetics of single particles are to (1) sustain the particle without moving at all times at a known point, (2) eliminate heat and mass transfer limitations, (3) observe particle-to-particle differences, (4) fully characterize the particle prior to combustion, and (5) monitor the important properties of the single particle through its entire combustion history. In this device the particle is heated radiatively by a focused laser beam to the desired temperature. During the heating the particle should not move by more than 1% of its diameter since the waist of the beam is comparable to the particle diameter. A strong proportional-integral-derivative (PID) position controller was developed to maintain the particle at the center of the EDC, with position stability better than 0.6% of its diameter. Further development of the EDC included (1) real time measurement of the particle shape and diameter with a temporal resolution of 0.1 ms and (2) infrared optical pyrometry with wide spectral bands to determine the particle temperature to within {+-} 10 K. Oxidation of synthetic char particles (Spherocarb) was studied in the EDC at temperatures around 900 K. Transients of the particle weight, size, shape, temperature, and position of the particle were measured in real-time. Using the present EDC two new phenomena were observed when highly porous chars were heated (in the range 800--900 K): (1) prior to conversion there was a stage in which mass loss or size change did not occur, this is attributed to activation of the char and was found to depend on the particle temperature; (2) nonuniform shrinkage during combustion--the initially spherical particles were consumed nonuniformly in all the numerous experiments. Quantitative results are presented for both phenomena.

Weiss, Y. [Ben-Gurion Univ. of the Negev, Beer-Sheva (Israel). Dept. of Mechanical Engineering] [Ben-Gurion Univ. of the Negev, Beer-Sheva (Israel). Dept. of Mechanical Engineering; Bar-Ziv, E. [Ben-Gurion Univ. of the Negev, Beer-Sheva (Israel). Dept. of Mechanical Engineering] [Ben-Gurion Univ. of the Negev, Beer-Sheva (Israel). Dept. of Mechanical Engineering; [Nuclear Research Center, Beer-Sheva (Israel)

1995-06-01

261

Global emissions of hydrogen chloride and chloromethane from coal combustion, incineration and industrial activities: Reactive Chlorine Emissions Inventory  

NASA Astrophysics Data System (ADS)

Much if not all of the chlorine present in fossil fuels is released into the atmosphere as hydrogen chloride (HCl) and chloromethane (CH3Cl, methyl chloride). The chlorine content of oil-based fuels is so low that these sources can be neglected, but coal combustion provides significant releases. On the basis of national statistics for the quantity and quality of coal burned during 1990 in power and heat generation, industrial conversion and residential and commercial heating, coupled with information on the chlorine contents of coals, a global inventory of national HCl emissions from this source has been constructed. This was combined with an estimate of the national emissions of HCl from waste combustion (both large-scale incineration and trash burning) which was based on an estimate of the global quantity released from this source expressed per head of population. Account was taken of reduced emissions where flue gases were processed, for example to remove sulphur dioxide. The HCl emitted in 1990, comprising 4.6 ± 4.3 Tg Cl from fossil fuel and 2 ± 1.9 Tg Cl from waste burning, was spatially distributed using available information on point sources such as power generation utilities and population density by default. Also associated with these combustion sources are chloromethane emissions, calculated to be 0.075 ± 0.07 Tg as Cl (equivalent) from fossil fuels and 0.032 ± 0.023 Tg Cl (equivalent) from waste combustion. These were distributed spatially exactly as the HCl emissions, and a further 0.007 Tg Cl in chloromethane from industrial process activity was distributed by point sources.

McCulloch, Archie; Aucott, Michael L.; Benkovitz, Carmen M.; Graedel, Thomas E.; Kleiman, Gary; Midgley, Pauline M.; Li, Yi-Fan

1999-04-01

262

Activation of serum complement inhibits collagen synthesis in fetal rat bone in organ culture  

Microsoft Academic Search

Summary  Activation of rabbit serum complement caused a marked reduction in collagen synthesis but a much smaller change in noncollagen\\u000a protein synthesis in fetal rat calvaria maintained in organ culture. In the periosteum of the fetal rat calvarium, both collagen\\u000a and noncollagen protein synthesis were reduced, whereas in the central bone, presumably enriched in osteoblasts, only collagen\\u000a synthesis was inhibited. This

Barbara E. Kream; Lawrence G. Raisz; Ann L. Sandberg

1982-01-01

263

Comparative investigation on chemical looping combustion of coal-derived synthesis gas containing H2S over supported NiO oxygen carriers  

SciTech Connect

Chemical looping combustion (CLC) of simulated coal-derived synthesis gas was conducted with NiO oxygen carriers supported on SiO2, ZrO2, TiO2, and sepiolite. The effect of H2S on the performance of these samples for the CLC process was also evaluated. Five-cycle thermogravimetric analysis (TGA) tests at 800 #1;C indicated that all oxygen carriers had a stable performance at 800 #1;C, except NiO/SiO2. Full reduction/oxidation reactions of the oxygen carrier were obtained during the five-cycle test. It was found that support had a significant effect on reaction performance of NiO both in reduction and oxidation rates. The reduction reaction was significantly faster than the oxidation reaction for all oxygen carriers, while the oxidation reaction is fairly slow due to oxygen diffusion on NiO layers. The reaction profile was greatly affected by the presence of H2S, but there was no effect on the capacity due to the presence of H2S in synthesis gas. The presence of H2S decreased reduction reaction rates significantly, but oxidation rates of reduced samples increased. X-ray diffraction (XRD) data of the oxidized samples after a five-cycle test showed stable crystalline phases without any formation of sulfides or sulfites/sulfates. Increase in reaction temperature to 900 #1;C had a positive effect on the performance.

Ksepko, E.; Siriwardane, R.; Tian, H.; Simonyi, T.; Sciazko, M.

2010-01-01

264

Synthesis, characterization and performance of single-component CO2-binding organic liquids (CO2BOL) for post combustion CO2 capture  

SciTech Connect

Carbon dioxide (CO2) emission to the atmosphere will increase significantly with the shift to coal powered plants for energy generation. This increase in CO2 emission will contribute to climate change. There is need to capture and sequester large amounts of CO2 emitted from these coal power plants in order to mitigate the environmental effects. Here we report the synthesis, characterization and system performance of multiple third generation CO2 binding organic liquids (CO2BOLs) as a solvent system for post combustion gas capture. Alkanolguanidines and alkanolamidines are single component CO2BOLs that reversibly bind CO2 chemically as liquid zwitterionic amidinium / guanidinium alkylcarbonates. Three different alkanolguanidines and alkanolamidines were synthesized and studied for CO2 capacity and binding energetics. Solvent performance of these three CO2BOLs was evaluated by batch-wise CO2 uptake and release over multiple cycles. Synthesis of CO2BOLs, characterization, CO2 uptake, selectivity towards CO2 as well as solvent tolerance to water will be discussed.

Koech, Phillip K.; Heldebrant, David J.; Rainbolt, James E.; Zheng, Feng; Smurthwaite, Tricia D.

2010-03-31

265

Synthesis and characterization of MoO 3 nanostructures by solution combustion method employing morphology and size control  

Microsoft Academic Search

Molybdenum oxide nanostructures were synthesized utilizing the solution combustion method where the ammonium molybdate powder\\u000a and an organic additive were used as precursors. Different organic additives including ethylene diamine tetra-acetic acid\\u000a (EDTA), polyethylene glycol 200 (PEG 200), sorbitol and urea were used as surfactants in order to investigate the effect of\\u000a additive structure on morphology and particle size of products.

D. Parviz; M. Kazemeini; A. M. Rashidi; Kh. Jafari Jozani

2010-01-01

266

Combustion synthesis and photoluminescence of Eu 3+, Dy 3+-doped La 2Zr 2O 7 nanocrystals  

Microsoft Academic Search

A facile and energy saving sol–gel combustion method has been used to prepare La2Zr2O7 nanocrystallines. The pyrochlore La2Zr2O7 nanocrystals have been obtained at a relatively low temperature with the grain size ranging from 45 to 70nm. Eu3+ and Dy3+ have been introduced into the La2Zr2O7 crystal structure, respectively, and the intense photoluminescence was observed. The relative intensity of electric dipole

Aiyu Zhang; Mengkai Lü; Guangjun Zhou; Shumei Wang; Yuanyuan Zhou

2006-01-01

267

Synthesis of high thermal conductivity nano-scale aluminum nitride by a new carbothermal reduction method from combustion precursor  

Microsoft Academic Search

AlN nano-scale powder was obtained through a new carbothermal reduction from combustion precursor at 1500°C for 2h in graphite furnace. The resultant product was a white solid powder, characterized by XRD, TEM, SAD and FIIR spectra. The results indicated that the product consisted of wurtzite AlN with an average size of about 80nm. Through presureless and free-additive sintering at 1850°C

JiaCai Kuang; ChangRui Zhang; XinGui Zhou; SiQing Wang

2003-01-01

268

Combustion synthesis and characterisation of Ni-MO-YSZ (M = Mg, Ca, Al 2\\/3) cermet anodes for SOFCs  

Microsoft Academic Search

The performance of Ni-yttria-stabilised zirconia (YSZ) cermet anodes can deteriorate with time and on redox and thermal cycling due to coarsening and\\/or oxidation of the Ni particles. Small additions of a second oxide phase may arrest degradation. In this work, Ni-YSZ-MO compositions (M=Mg, Ca, Al2\\/3, respectively, NZM, NZC, NZA) were prepared by combustion. Phase composition and microstructural characteristics were assessed

E. Chinarro; F. M. Figueiredo; G. C. Mather; J. R. Jurado; J. R. Frade

2007-01-01

269

Endothelin stimulates platelet-activating factor synthesis by cultured rat kupffer cells  

Microsoft Academic Search

Endothelins are potent peptide mediators that elicit glycogenolytic and vasoconstrictor actions in the liver. Endothelins were found to stimulate the synthesis and release of the lipid mediator platelet-activating factor in cultured rat Kupffer cells. Endothelin-mediated synthesis of platelet-activating factor required extracellular calcium in that the calcium chelator, EGTA and nifedipine, a calcium ion channel blocker, inhibited platelet-activating factor synthesis. The

Shamimunisa B. Mustafa; Chandrashekhar R. Gandhi; Stephen A. K. Harvey; Merle S. Olson

1995-01-01

270

Combustion synthesis, characterization and catalytic application of MoO 3–ZrO 2 nanocomposite oxide towards one pot synthesis of octahydroquinazolinones  

Microsoft Academic Search

Pure ZrO2 and MoO3 (10mol%)-ZrO2 nanocomposite oxides were prepared by solution combustion method using glycine as fuel. The synthesized materials were characterized by X-ray diffraction (XRD), Scanning Electron microscopy (SEM), Transmission electron microscopy (TEM) and UV–vis spectroscopic technique. XRD study revealed selective stabilization of the tetragonal phase of zirconia in presence of MoO3. The crystallite size was calculated from the

Satish Samantaray; B. G. Mishra

2011-01-01

271

Studies on the redox properties of chromite perovskite catalysts for soot combustion  

Microsoft Academic Search

This paper deals with the preparation (by combustion synthesis), the characterization (by XRD, AAS, BET, SEM, TEM, TPD\\/R, and XPS analyses), the catalytic activity testing (in a temperature-programmed combustion microreactor and in a DSC analyzer), and the assessment of the reaction mechanism of a series of nanostructured soot combustion catalysts based on La–Cr substoichiometric or alkali-metal-substituted perovskites (La0.9CrO3, La0.8CrO3, La0.9Na0.1CrO3,

Nunzio Russo; Debora Fino; Guido Saracco; Vito Specchia

2005-01-01

272

Synthesis and Antimicrobial Activity of Silver-Doped Hydroxyapatite Nanoparticles  

PubMed Central

The synthesis of nanosized particles of Ag-doped hydroxyapatite with antibacterial properties is of great interest for the development of new biomedical applications. The aim of this study was the evaluation of Ca10?xAgx(PO4)6(OH)2 nanoparticles (Ag:HAp-NPs) for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years and became a major health problem. Here, we report a method for synthesizing Ag doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionised water. Also, in this paper Ag:HAp-NPs are evaluated for their antimicrobial activity against Gram-positive and Gram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our compounds are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures.

Ciobanu, Carmen Steluta; Iconaru, Simona Liliana; Chifiriuc, Mariana Carmen; Costescu, Adrian; Le Coustumer, Philippe; Predoi, Daniela

2013-01-01

273

Coal Combustion Science  

SciTech Connect

The objective of this activity is to support the Office of Fossil Energy in executing research on coal combustion science. This activity consists of basic research on coal combustion that supports both the Pittsburgh Energy Technology Center Direct Utilization Advanced Research and Technology Development Program, and the International Energy Agency Coal Combustion Science Project. Specific tasks for this activity include: (1) coal devolatilization - the objective of this risk is to characterize the physical and chemical processes that constitute the early devolatilization phase of coal combustion as a function of coal type, heating rate, particle size and temperature, and gas phase temperature and oxidizer concentration; (2) coal char combustion -the objective of this task is to characterize the physical and chemical processes involved during coal char combustion as a function of coal type, particle size and temperature, and gas phase temperature and oxygen concentration; (3) fate of mineral matter during coal combustion - the objective of this task is to establish a quantitative understanding of the mechanisms and rates of transformation, fragmentation, and deposition of mineral matter in coal combustion environments as a function of coal type, particle size and temperature, the initial forms and distribution of mineral species in the unreacted coal, and the local gas temperature and composition.

Hardesty, D.R. (ed.); Fletcher, T.H.; Hurt, R.H.; Baxter, L.L. (Sandia National Labs., Livermore, CA (United States))

1991-08-01

274

Triggered instabilities in rocket motors and active combustion control for an incinerator afterburner  

NASA Astrophysics Data System (ADS)

Two branches of research are conducted in this thesis. The first deals with nonlinear combustion response as a mechanism for triggering combustion instabilities in solid rocket motors. A nonlinear wave equation is developed to study a wide class of combustion response functions to second-order in fluctuation amplitude. Conditions for triggering are derived from analysis of limit cycles, and regions of triggering are found in parametric space. Introduction of linear cross-coupling and quadratic self-coupling among the acoustic modes appears to be how the nonlinear combustion response produces triggering to a stable limit cycle. Regions of initial conditions corresponding to stable pulses were found, suggesting that stability depends on initial phase angle and harmonic content, as well as the composite amplitude, of the pulse. Also, dependence of nonlinear stability upon system parameters is considered. The second part of this thesis presents research for a controller to improve the emissions of an incinerator afterburner. The developed controller was experimentally tested at the Naval Air Warfare Center (NAWC), on a 50kW-scale model of an afterburner for Naval shipboard incinerator applications. Acoustic forcing of the combustor's reacting shear layer is used to control the formation of coherent vortical structures, within which favorable fuel-air mixing and efficient combustion can occur. Laser-based measurements of CO emissions are used as the performance indicator for the combustor. The controller algorithm is based on the downhill simplex method and adjusts the shear layer forcing parameters in order to minimize the CO emissions. The downhill simplex method was analyzed with respect to its behavior in the face of time-variation of the plant and noise in the sensor signal, and was modified to account for these difficulties. The control system has experimentally demonstrated the ability (1) to find optimal control action for single- and multi-variable control, (2) to maintain optimal control for time-varying operating states, and (3) to automatically adjust auxiliary fuel in response to changing stoichiometry of the incoming waste pyrolysis gas. Also presented but not tested in the experiments are an expert-type model-guidance feature to aid convergence of the controller to optimum control, and methodology for maintaining flammability.

Wicker, Josef M.

1999-11-01

275

Synthesis of high thermal conductivity nano-scale aluminum nitride by a new carbothermal reduction method from combustion precursor  

NASA Astrophysics Data System (ADS)

AlN nano-scale powder was obtained through a new carbothermal reduction from combustion precursor at 1500°C for 2 h in graphite furnace. The resultant product was a white solid powder, characterized by XRD, TEM, SAD and FIIR spectra. The results indicated that the product consisted of wurtzite AlN with an average size of about 80 nm. Through presureless and free-additive sintering at 1850°C for 6 h, it showed that AlN nano-scale powders possess excellent sintering property, whose thermal conductivity was measured to be 120 W/m K. High thermal conductivity mechanism was proposed.

Kuang, JiaCai; Zhang, ChangRui; Zhou, XinGui; Wang, SiQing

2003-09-01

276

Combustion noise  

NASA Technical Reports Server (NTRS)

A review of the subject of combustion generated noise is presented. Combustion noise is an important noise source in industrial furnaces and process heaters, turbopropulsion and gas turbine systems, flaring operations, Diesel engines, and rocket engines. The state-of-the-art in combustion noise importance, understanding, prediction and scaling is presented for these systems. The fundamentals and available theories of combustion noise are given. Controversies in the field are discussed and recommendations for future research are made.

Strahle, W. C.

1977-01-01

277

Synthesis of luminescent SnO2:Eu3+ nanorods via a salt-assisted solution combustion process.  

PubMed

SnO2:Eu3+ nanorods have been successfully synthesized by annealing products from microwave-induced KCl-assisted solution combustion reaction, which uses tin (IV) chloride pentahydrate and europium nitrate as cationic source, ethyl glycol as fuel and ammonium nitrate as combustion-supporting agent. The structural and photoluminescent properties of SnO2:Eu3+ nanorods were investigated by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), selected area electron diffractometry (SAED), X-ray diffractometry (XRD) and photoluminescence spectroscopy. The phase transformation in the synthetic process was observed by X-ray diffraction pattern. Accordingly, the growth mechanism of SnO2:Eu3+ nanorods was discussed. The results showed that the SnO2:Eu3+ nanorods were rutile-structured single crystals with 10-15 nm in diameter and 200-250 nm in length. Proper addition of KCl into redox mixture solution is critical to the formation of SnO2:Eu3+ nanorods. The doped Eu3+ concentration has obvious effect on the photoluminescence of SnO2:Eu3+ nanorods. The approach is convenient, inexpensive and efficient for the high yield preparation of SnO2:Eu3+ nanorods. PMID:24758061

Chen, Weifan; Liu, Ming; Liu, Yue; Lin, Yucui; Yu, Lixing; Hong, Jianming

2014-07-01

278

Synthesis, characterization and photoluminescence properties of Gd 2O 3:Eu 3+ nanophosphors prepared by solution combustion method  

NASA Astrophysics Data System (ADS)

Gd 2O 3:Eu 3+ (0.5-8.0 mol%) nanophosphors have been prepared by low temperature solution combustion method using metal nitrates as oxidizers and oxalyl dihydrazide (ODH) as a fuel. The phosphors are well characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and photoluminescence (PL) techniques. PXRD patterns of as-formed and calcined (800 °C, 3 h) Gd 2O 3 powders exhibit monoclinic phase with mean crystallite sizes ranging from 20 to 50 nm. Eu 3+ doping changes the structure from monoclinic to mixed phase of monoclinic and cubic. SEM micrographs shows the products are foamy, agglomerated and fluffy in nature due to the large amount of gases liberated during combustion reaction. Upon 254 nm excitation the photoluminescence of the Gd 2O 3:Eu 3+ particles show red emission at 611 nm corresponding to 5D 0? 7F 2 transition. It is observed that PL intensity increases with calcination temperature. This might be attributed to better crystallization and eliminates the defects, which serve as centers of non-radiative relaxation for nanomaterials. It is observed that the optical energy gap ( Eg) is widened with increase Eu 3+ content.

Dhananjaya, N.; Nagabhushana, H.; Nagabhushana, B. M.; Chakradhar, R. P. S.; Shivakumara, C.; Rudraswamy, B.

2010-09-01

279

Mild Combustion  

Microsoft Academic Search

The Mild Combustion is characterized by both an elevated temperature of reactants and low temperature increase in the combustion process. These features are the results of several technological demands coming from different application fields. This review paper aims to collect information which could be useful in understanding the fundamentals and applications of Mild Combustion. The information in this field are

Antonio Cavaliere; Mara de Joannon

2004-01-01

280

Role of SO{sub 2} for elemental mercury removal from coal combustion flue gas by activated carbon  

SciTech Connect

In order to clarify the role of SO{sub 2} in the removal of mercury from coal combustion flue gas by activated carbon, the removal of Hg{sup 0} vapor from simulated coal combustion flue gas containing SO{sub 2} by a commercial activated carbon (AC) was studied. The Hg{sup 0} removal experiments were carried out in a conventional flow type packed bed reactor system with simulated flue gases having a composition of Hg{sup 0} (4.9 ppb), SO{sub 2} (0 or 500 ppm), CO{sub 2} (10%), H{sub 2}O (0 or 15%), O{sub 2} (0 or 5%), and N{sub 2} (balance gas) at a space velocity (SV) of 6.0 x 104 h{sup -1} in a temperature rang 60-100 {sup o}C. It was found that, for SO{sub 2} containing flue gas, the presence of both O{sub 2} and H{sub 2}O was necessary for the removal of Hg{sup 0} and the Hg{sup 0} removal was favored by lowering the reaction temperature in the order of 60 > 80 > 100{sup o}C. The presence of SO{sub 2} in the flue was essential for the removal of Hg{sup 0} by untreated activated carbon. The activated carbons pretreated with SO{sub 2} or H{sub 2}SO{sub 4} prior to the Hg{sup 0} removal also showed Hg{sup 0} removal activities even in the absence of SO{sub 2}; however, the presence of SO{sub 2} also suppressed the Hg{sup 0} removal of the SO{sub 2}-pretreated AC or H{sub 2}SO{sub 4} preadded AC. 19 refs., 11 figs.

M. Azhar Uddin; Toru Yamada; Ryota Ochiai; Eiji Sasaoka [Okayama University, Okayama (Japan). Department of Material and Energy Science

2008-07-15

281

Synthesis of szentiamide, a depsipeptide from entomopathogenic Xenorhabdus szentirmaii with activity against Plasmodium falciparum  

PubMed Central

Summary The synthesis of the recently characterized depsipeptide szentiamide (1), which is produced by the entomopathogenic bacterium Xenorhabdus szentirmaii, is described. Whereas no biological activity was previously identified for 1, the material derived from the efficient synthesis enabled additional bioactivity tests leading to the identification of a notable activity against insect cells and Plasmodium falciparum, the causative agent of malaria.

Nollmann, Friederike I; Dowling, Andrea; Kaiser, Marcel; Deckmann, Klaus; Grosch, Sabine; ffrench-Constant, Richard

2012-01-01

282

Polymer synthesis via activated esters: A new dimension of creativity in macromolecular chemistry  

Microsoft Academic Search

The polymerization and chemistry of activated acrylates have been elaborated in recent years to provide a uniquely versatile method of polymer synthesis. The new method is simple, generally applicable, and is ideally suitable for the synthesis of specialty polymers of interest in the emerging technologies in chemistry, engineering, biotechnology and medicine. This article discusses the polymerization and copolymerization of activated

Reza Arshady

283

Protein synthesis inhibition and memory for pole jump active avoidance and extinction. [Mice  

Microsoft Academic Search

This study utilizes a pole jump active avoidance task to investigate the effects of protein synthesis on memory formation. An extinction training procedure for this task is also described. Amnesia for extinction is produced by inhibition of protein synthesis and is also demonstrated by active responding, so it is clear that there is no general impairment sufficient to disrupt motor

J. F. Flood; M. E. Jarvik; E. L. Bennett; A. E. Orme; M. R. Rosenzweig

1977-01-01

284

Third millenium ideal gas and condensed phase thermochemical database for combustion (with update from active thermochemical tables).  

SciTech Connect

The thermochemical database of species involved in combustion processes is and has been available for free use for over 25 years. It was first published in print in 1984, approximately 8 years after it was first assembled, and contained 215 species at the time. This is the 7th printed edition and most likely will be the last one in print in the present format, which involves substantial manual labor. The database currently contains more than 1300 species, specifically organic molecules and radicals, but also inorganic species connected to combustion and air pollution. Since 1991 this database is freely available on the internet, at the Technion-IIT ftp server, and it is continuously expanded and corrected. The database is mirrored daily at an official mirror site, and at random at about a dozen unofficial mirror and 'finger' sites. The present edition contains numerous corrections and many recalculations of data of provisory type by the G3//B3LYP method, a high-accuracy composite ab initio calculation. About 300 species are newly calculated and are not yet published elsewhere. In anticipation of the full coupling, which is under development, the database started incorporating the available (as yet unpublished) values from Active Thermochemical Tables. The electronic version now also contains an XML file of the main database to allow transfer to other formats and ease finding specific information of interest. The database is used by scientists, educators, engineers and students at all levels, dealing primarily with combustion and air pollution, jet engines, rocket propulsion, fireworks, but also by researchers involved in upper atmosphere kinetics, astrophysics, abrasion metallurgy, etc. This introductory article contains explanations of the database and the means to use it, its sources, ways of calculation, and assessments of the accuracy of data.

Burcat, A.; Ruscic, B.; Chemistry; Technion - Israel Inst. of Tech.

2005-07-29

285

Photocatalytically active titanium dioxide nanopowders: Synthesis, photoactivity and magnetic separation  

NASA Astrophysics Data System (ADS)

Two approaches were used to obtain nanocrystalline titanium dioxide (TiO2) photocatalyst powders. Firstly, low-temperature synthesis method and secondly liquid flame spraying. The structural properties of the produced powders were determined with X-ray diffraction, transmission electron microscopy and nitrogen adsorption tests. The photocatalytic properties of the powders were studied with methylene blue (MB) discoloration tests. After discolorations tests, TiO2 was coagulated with magnetite particles using FeCl3·6 H2O at a fixed pH value. Magnetic separation of coagulated TiO2 and magnetite was carried out by a permanent magnet. The obtained results showed that the particle size of the powders synthesized at low-temperature was very small and the specific surface area high. The phase content of the powder was also shown to depend greatly on the acidity of the synthesis solution. Powder synthesized by liquid flame spraying was mixture of anatase and rutile phases with essentially larger particle size and lower specific surface area than those of low-temperature synthesized powders. The MB discoloration test showed that photocatalytic activity depends on the phase structure as well as the specific surface area of the synthesized TiO2 powder. The magnetic separation of TiO2-magnetite coagulate from solution proved to be efficient around pH:8.

Nikkanen, J.-P.; Heinonen, S.; Huttunen Saarivirta, E.; Honkanen, M.; Levänen, E.

2013-12-01

286

Importance of activity data for improving the residential wood combustion emission inventory at regional level  

NASA Astrophysics Data System (ADS)

The contribution of residential wood combustion (RWC) to emission inventory at local level was estimated using a bottom-up approach for the Lombardy Region of North Italy. A survey, based on the CATI (Computer Assisted Telephone Interviewing) method, has been undertaken through 18,000 interviews. The interviews had the objective to characterize the RWC use in this region, in term of both total and municipal wood consumption. Details on the type of appliances used in RWC were also gathered. The results of the survey were then statistically analyzed in order to allow an estimate of RWC with high spatial resolution (i.e., at municipal level) in relation to the size and altitude of the territory. The work provides new evidence of the importance of wood combustion as a key source for PM and NMVOC emissions at local level, and thus highlights the importance of technological improvements and new policies aimed at emission reduction in this sector. Considering the great differences in average PM emission factors between low efficiency appliances (fireplaces, old stoves) and high efficiency ones (new stoves, pellet burners), this work emphasizes the importance of obtaining more detailed information on the types of wood appliances used for arriving at a reliable PM emission inventory for RWC.

Pastorello, Cinzia; Caserini, Stefano; Galante, Silvia; Dilara, Panagiota; Galletti, Fabio

2011-06-01

287

Combustion synthesis and photoluminescence of Eu3+, Dy3+-doped La2Zr2O7 nanocrystals  

NASA Astrophysics Data System (ADS)

A facile and energy saving sol gel combustion method has been used to prepare La2Zr2O7 nanocrystallines. The pyrochlore La2Zr2O7 nanocrystals have been obtained at a relatively low temperature with the grain size ranging from 45 to 70 nm. Eu3+ and Dy3+ have been introduced into the La2Zr2O7 crystal structure, respectively, and the intense photoluminescence was observed. The relative intensity of electric dipole transition and magnetic dipole transition is considered for luminescence emission both of Eu3+ and Dy3+. The dependence of luminescence intensity on dopant concentration and the effect of Dy3+ co-doping on Eu3+ luminescence are also discussed.

Zhang, Aiyu; Lü, Mengkai; Zhou, Guangjun; Wang, Shumei; Zhou, Yuanyuan

2006-11-01

288

Synthesis and characterization of nano crystalline BaFe{sub 12}O{sub 19} powders by low temperature combustion  

SciTech Connect

Nano crystalline BaFe{sub 12}O{sub 19} powders have been prepared at a relatively low calcination temperature by a gel combustion technique using citric acid as a fuel/reductant and nitrates as oxidants. The effects of processing parameters, such as Ba/Fe ratio, citric acid/nitrates ratio, reaction temperature on the powder characteristics and magnetic properties of the resultant barium ferrites were investigated. By controlling the molar ratio of citric acid to metal nitrates, nano crystalline BaFe{sub 12}O{sub 19} powders with different particle sizes have been obtained. Phase attributes, microstructures and magnetic properties of the powders were characterized using X-ray diffraction analysis, X-ray line-broadening technique, Fourier transform infrared spectroscopy measurements, transmission electron microscopy and vibrating sample magnetometer. The maximum saturation magnetization value and intrinsic coercivity value for the obtained barium hexaferrites are 59.36 emu/g and 5540 Oe.

Huang Jianguo; Zhuang Hanrui; Li Wenlan

2003-01-01

289

Chemically Adjusting Plasma Temperature, Energy and Reactivity (CAPTEAR) Method Using NOx and Combustion for Selective Synthesis of Sc3N@C80 Metallic Nitride Fullerenes  

PubMed Central

Goals are (1) to selectively synthesize MNFs in lieu of empty-cage fullerenes (e.g., C60, C70) without compromising MNF yield and (2) to test our hypothesis that MNFs possess a different set of optimal formation parameters than empty-cage fullerenes. In this work, we introduce a novel approach for the selective synthesis of metallic nitride fullerenes (MNFs). This new method is “Chemically Adjusting Plasma Temperature, Energy and Reactivity” (CAPTEAR). The CAPTEAR approach with copper nitrate hydrate uses NOx vapor from NOx generating solid reagents, air and combustion to “tune” the temperature, energy and reactivity of the plasma environment. The extent of temperature, energy and reactive environment is stoichiometrically varied until optimal conditions for selective MNF synthesis are achieved. Analysis of soot extracts indicate that percentages of C60 and Sc3N@C80 are inversely related, whereas the percentages of C70 and higher empty-cage C2n fullerenes are largely unaffected. Hence, there may be a “competitive link” in the formation and mechanism of C60 and Sc3N@C80. Using this CAPTEAR method, purified MNFs (96% Sc3N@C80, 12 mg) have been obtained in soot extracts without a significant penalty in milligram yield when compared to control soot extracts (4% Sc3N@C80, 13 mg Sc3N@C80). The CAPTEAR process with Cu(NO3)2·2.5 H2O uses an exothermic nitrate moiety to suppress empty-cage fullerene formation, whereas Cu functions as a catalyst additive to offset the reactive plasma environment and boost the Sc3N@C80 MNF production.

Stevenson, Steven; Thompson, M. Corey; Coumbe, H. Louie; Mackey, Mary A.; Coumbe, Curtis E.; Phillips, J. Paige

2008-01-01

290

Synthesis and anti-prion activity evaluation of aminoquinoline analogues.  

PubMed

Transmissible spongiform encephalopathies form a group of neurodegenerative diseases that affect humans and other mammals. They occur when the native prion protein is converted into an infectious isoform, the scrapie PrP, which aggregates, leading to neurodegeneration. Although several compounds were evaluated for their ability to inhibit this conversion, there is no effective therapy for such diseases. Previous studies have shown that antimalarial compounds, such as quinolines, possess anti-scrapie activity. Here, we report the synthesis and evaluate the effect of aminoquinoline derivatives on the aggregation of a prion peptide. Our results show that 4-amino-7-chloroquinoline and N-(7-chloro-4-quinolinyl)-1,2-ethanediamine inhibit the aggregation significantly. Therefore, such aminoquinolines might be considered as candidates for the further development of therapeutics to prevent the development of prion diseases. PMID:20797807

Macedo, Bruno; Kaschula, Catherine H; Hunter, Roger; Chaves, Juliana A P; van der Merwe, Johannes D; Silva, Jerson L; Egan, Timothy J; Cordeiro, Yraima

2010-11-01

291

Synthesis of nanocrystalline magnesium aluminate (MgAl 2O 4) spinel powder by the urea–formaldehyde polymer gel combustion route  

Microsoft Academic Search

Nanocrystalline MgAl2O4 spinel powder was synthesized by the urea–formaldehyde (UF) polymer gel combustion route. A transparent gel formed from magnesium nitrate, aluminium nitrate and UF after drying underwet self-sustained combustion when initiated with a burning splinter. The combustion product on calcinations at 850°C formed MgAl2O4 spinel. Calcination of the combustion product resulted in particle coarsening. The powder obtained by planetary

K. Prabhakaran; D. S. Patil; R. Dayal; N. M. Gokhale; S. C. Sharma

2009-01-01

292

Transition metal bimetallic oxycarbides: Synthesis, characterization, and activity studies  

SciTech Connect

A new family of bimetallic oxycarbide compounds M{sup I}-M{sup II}-O-C (M{sup I} = Mo, W; M{sup II} = V, Nb, Cr, Fe, Co, Ni) has been synthesized by carburizing bimetallic oxide precursors using a temperature-programmed method. The oxide precursors are prepared by conventional solid-state reaction between two appropriate monometallic oxides. The synthesis involves passing a 20 mol% CH{sub 4} in H{sub 2} mixture over the oxide precursors while raising the temperature at a linear rate of 8.3 {times} 10{sup {minus}2} K/s (5 K/min) to a final temperature (T{sub max}) which is held for a period of time (t{sub hold}). The synthesis, chemisorption properties, and reactivation of the materials indicate that the compounds can be divided into two groups of different reducibility (high and low). Their surface activity and surface area are evaluated based on CO chemisorption and N{sub 2} physisorption measurements. It is found that the CO number density correlates with the reducibility of the compounds. The catalysts were evaluated for hydroprocessing in a three-phase trickle-bed reactor operated at 3.1 MPa and 643 K. The feed was a model liquid mixture containing 3000 ppm sulfur (dibenzothiophene), 2000 ppm nitrogen (quinoline), 500 ppm oxygen (benzofuran), 20 wt% aromatics (tetralin), and balance aliphatics (tetradecane). The bimetallic oxycarbides had moderate activity for HDN of quinoline, with Nb-Mo-O-C showing higher HDN than a commercial sulfided Ni-Mo/Al{sub 2}O{sub 3} catalyst tested at the same conditions. X-ray diffraction of the spent catalysts indicated that the oxycarbides of the early transition metals were tolerant of sulfur, while those involving the late transition metals showed bulk sulfide phases.

Oyama, S.T.; Yu, C.C.; Ramanathan, S. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Environmental Catalysis and Materials Lab.] [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Environmental Catalysis and Materials Lab.

1999-06-10

293

Layered Composite of TiC-TiB2 to Ti-6Al-4V in Graded Composition by Combustion Synthesis in High-gravity Field  

NASA Astrophysics Data System (ADS)

By taking combustion synthesis to prepare solidified TiB2 matrix ceramic in high-gravity field, the layered composite of TiC-TiB2 ceramic to Ti-6Al-4V substrate in graded composition was achieved. XRD, FESEM and EDS results showed that the bulk full-density solidified TiC-TiB2 composite was composed of fine TiB2 platelets, TiC irregular grains, a few of ?-Al2O3 inclusions and Cr alloy phases, and ?'-Ti phases alternating with Ti-enriched carbides constituted the matrix of the joint in which fine TiB platelets were embedded, whereas some C, B atoms were also detected at the heat-affected zone of Ti-6A1-4V substrate. The layered composite of the solidified ceramic to Ti-6Al-4V substrate in graded composition with continuous microstructure was considered a result of fused joint and inter-diffusion between liquid ceramic and surface-molten Ti alloy, followed by TiB2-Ti peritectic reaction and subsequent eutectic reaction in TiC-TiB-Ti ternary system.

Huang, Xuegang; Zhao, Zhongmin; Zhang, Long

2013-03-01

294

Sol-gel auto-combustion synthesis, structural and enhanced magnetic properties of Ni2+ substituted nanocrystalline Mg-Zn spinel ferrite  

NASA Astrophysics Data System (ADS)

Nanocrystalline arrays of Ni2+ substituted Mg-Zn spinel ferrite having a generic formula Mg0.7-xNixZn0.3Fe2O4 (x=0.0, 0.2, 0.4 and 0.6) were successfully synthesized by sol-gel auto-combustion technique. The fuel used in the synthesis process was citric acid and the metal nitrate-to-citric acid ratio was taken as 1:3. The phase, crystal structure and morphology of Mg-Ni-Zn ferrites were investigated by X-ray diffraction, scanning electron microscopy, and Fourier transformer infrared spectroscopy techniques. The lattice constant, crystallite size, porosity and cation distribution were determined from the X-ray diffraction data method. The FTIR spectroscopy is used to deduce the structural investigation and redistribution of cations between octahedral and tetrahedral sites of Mg-Ni-Zn spinel structured material. Morphological investigation suggests the formation of grain growth as the Ni2+ content x increases. The saturation magnetization and magneton number were determined from hysteresis loop technique. The saturation magnetization increases with increasing Ni2+ concentration ‘x’ in Mg-Zn ferrite.

Bobade, D. H.; Rathod, S. M.; Mane, Maheshkumar L.

2012-09-01

295

Fabrication of Cu-riched W-Cu composites by combustion synthesis and melt-infiltration in ultrahigh-gravity field  

NASA Astrophysics Data System (ADS)

Unadulterated Cu-riched W-Cu composites of W27-Cu73, W34-Cu66, W40-Cu60, W49-Cu51 and W56-Cu44 have been prepared by a novel method called combustion synthesis and melt-infiltration in ultrahigh-gravity field, of which W27-Cu73 and W34-Cu66 showed good ductility and W40-Cu60, W49-Cu51 and W56-Cu44 were brittle. In this technique, Cu melt accompanied with a great amount of heat was produced by thermit reaction and infiltrated into W-Cu powder bed. When the powder bed was Cu-riched powder bed such as W50-Cu50 or W60-Cu40, Cu melt would go through the powder bed, reach the bottom of the graphite crucible and then form a heat dissipation channel. Thus the cooling rate was so fast that the product was mixed up with impurity. The problem can be solved by putting some W powders under W50-Cu50 or W60-Cu40 powder bed to prevent the formation of heat dissipation channel.

Zhao, Pei; Guo, Shibin; Liu, Guanghua; Chen, Yixiang; Li, Jiangtao

2013-10-01

296

Fabrication of (Nd(0.01)La(x)Y(0.99-x))2O3 nanoparticles and transparent ceramics by combustion synthesis.  

PubMed

Y2O3 acts as the matrix material when doped with different content of La2O3 for reducing sintering temperature and refining grains. The (Nd(0.01)La(x)Y(0.99-x))2O3 nanoparticles and transparent ceramics are fabricated by a combustion synthesis. The powder feature is characterized by TEM. The microstructure, mechanical properties and transmittance of the samples are examined by SEM, HV-1000 hardness tester and fluorescence analyzer respectively. The results show that the (Nd(0.01)La(x)Y(0.99-x))2O3 nanoparticles are homogeneous in size and nearly spherical with average diameter in the range of 40-60 nm. There are no other phases except the Y2O3 cubic phase in the (Nd(0.01)La(x)Y(0.99-x))2O3 nanoparticles. The grains of the samples significantly reduce with increasing La2O3 content. The hardness and fracture toughness increase rapidly first and then gradually tend to plateau with increasing La2O3 content. The transmittance of sample also increases gradually with increasing La2O3, the largest transmittance exceeds 77% when the La2O3 content is x = 0.12. PMID:22413276

Luo, Jun-Ming; Deng, Li-Ping; Xu, Ji-Lin

2011-11-01

297

Rapid synthesis of room temperature ferromagnetic Ag-doped LaMnO{sub 3} perovskite phases by the solution combustion method  

SciTech Connect

We report the rapid solution combustion synthesis and characterization of Ag-substituted LaMnO{sub 3} phases at relatively low temperature using oxalyl dihydrazide, as fuel. Structural parameters were refined by the Rietveld method using powder X-ray diffraction data. While the parent LaMnO{sub 3} crystallizes in the orthorhombic structure, the Ag-substituted compounds crystallize in the rhombohedral symmetry. On increasing Ag-content, unit cell volume and Mn-O-Mn bond angle decreases. The Fourier transform infra red spectrum shows two absorption bands corresponding to Mn-O stretching vibration ({nu}{sub s} mode) and Mn-O-Mn deformation vibration ({nu}{sub b} mode) around 600 cm{sup -1} and 400 cm{sup -1} for the compositions, x = 0.0, 0.05 and 0.10, respectively. Electrical resistivity measurements reveal that composition-controlled metal to insulator transition, with the maximum metal to insulator being 280 K for the composition La{sub 0.75}Ag{sub 0.25}MnO{sub 3}. Increase in magnetic moment was observed with increase in Ag-content. The maximum magnetic moment of 35 emu/g was observed for the composition La{sub 0.80}Ag{sub 0.20}MnO{sub 3}.

Bellakki, Manjunath B. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012 (India)] [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012 (India); Shivakumara, C., E-mail: shiva@sscu.iisc.ernet.in [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012 (India); Vasanthacharya, N.Y. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012 (India)] [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012 (India); Prakash, A.S. [Central Electrochemical Research Institute-Chennai Unit, CSIR-Madras Complex, Chennai 600 113 (India)] [Central Electrochemical Research Institute-Chennai Unit, CSIR-Madras Complex, Chennai 600 113 (India)

2010-11-15

298

Reaction synthesis of intermetallics.  

National Technical Information Service (NTIS)

Exothermicity associated with the synthesis of aluminides was utilized to obtain nickel, iron, and cobalt aluminides. Combustion synthesis, extrusion, and hot pressing were utilized to obtain intermetallics and their composites. Extrusion conditions, redu...

S. C. Deevi V. K. Sikka

1994-01-01

299

A novel microbial synthesis of catalytically active Ag-alginate biohydrogel and its antimicrobial activity.  

PubMed

The green synthesis of supported noble metal nanoparticles is now the most exciting field for various catalytic applications as well as biomedical applications. In this paper we report a novel synthesis method of a polymer consisting of silver nanoparticles (AgNPs) using immobilized microorganisms in alginate beads. Microorganisms present in the polymer reduce aqueous AgNO3 to AgNPs which get trapped in the polymer to form Ag-Alginate (Ag-Alg) biohydrogel. The formed biohydrogel was characterized by UV-visible (UV-Vis) spectroscopy, dynamic light scattering (DLS) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDS), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) analysis. TEM analysis showed that less than 15 nm AgNPs formed in the polymer. The Ag-Alg biohydrogel exhibited efficient heterogeneous catalytic activity in the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4 in aqueous solution with durable reusability. Also this biohydrogel showed excellent antimicrobial activity against pathogenic bacteria (antibiotic resistant) and fungi. The described synthesis method of Ag-Alg biohydrogel can be considered robust, cost effective and eco-friendly. The formed highly catalytic active biohydrogel can be used as catalyst in industries and drinking water purification. PMID:23698554

Otari, S V; Patil, R M; Waghmare, S R; Ghosh, S J; Pawar, S H

2013-07-21

300

Catalytic activity of oxidized (combusted) oil shale for removal of nitrogen oxides with ammonia as a reductant in combustion gas streams, Part 1  

SciTech Connect

Oxidized oil shale from the combustor in the LLNL hot recycle solids oil shale retorting process has been studied as a catalyst for removing nitrogen oxides from laboratory gas streams using NH{sub 3} as areductant. Combusted Green River oil shale heated at 10{degrees}C/min in an Ar/O{sub 2}/NO/NH{sub 3} mixture ({approximately}93%/6%/2000 ppm/4000 ppm) with a gas residence time of {approximately}0.6 sec exhibited NO removal between 250 and 500{degrees}C, with maximum removal of 70% at {approximately}400{degrees}C. Under isothermal conditions with the same gas mixture, the maximum NO removal was found to be {approximately}64%. When CO{sub 2} was added to the gas mixture at {approximately}8%, the NO removal dropped to {approximately}50%. However, increasing the gas residence time to {approximately}1.2 sec, increased NO removal to 63%. These results are not based on optimized process conditions, but indicate oxidized (combusted) oil shale is an effective catalyst for NO removal from combustion gas streams using NH{sub 3} as the reductant.

Reynolds, J.G.; Taylor, R.W.; Morris, C.J.

1992-06-10

301

[Synthesis of pyronaridine related compounds and comparison of antimalarial activities].  

PubMed

The paper reports the synthesis of pyronaridine (I) related compounds II-V for exploring whether the antimalarial activity of pyronaridine is by virtue of a nitrogen atom at position 1 in the ring and a pair of pyrrolidinyl Mannich base side chains in its structure. The condensation of 2-methoxy-6,9-dichloroacridine or 4,7-dichloro-1,5-naphthyridine with 4-hydroxy-3,5-bis-(pyrrolidinyl-1'-methyl) aniline yielded the related compound II, 1-deazapyronaridine, or V, 5-azabispyroquine, respectively. 2-Methoxy-7,10-dichlorobenzo (b) 1,5-naphthyridine or 4,7-dichloro-1,5-naphthyridine was condensed with 4-diethylamino-1-methylbutylamine to obtain the related compound III, azacrin, or IV, 5-azachloroquine, respectively. The results of in vivo tests against Plasmodium berghei chloroquine-resistant ANKA strain, drug-sensitive P. berghei N line and drug-resistant P. yoelii nigeriensis line showed that all the related compounds II-V were less effective than pyronaridine (I). It suggests that the nitrogen atom at position 1 and pyrrolidinyl Mannich base side chains on the structure of pyronaridine play an important and indispensable role for antimalarial activity of pyronaridine. The pyrrolidinyl Mannich bases impart increased activity to the corresponding compounds. PMID:8285067

Chen, C; Zheng, X Y; Guo, H Z

1993-01-01

302

Combustion synthesis and engineering nanoparticles for electronic, structural and superconductor applications. Final report, May 31, 1992--May 30, 1996  

SciTech Connect

Dense, nanocrystalline ceramic articles of doped ZrO{sub 2} (for use in solid electrolytes, oxygen sensors, electrode materials, thermal barrier coatings, etc.), BaTiO{sub 3} (for capacitor applications), and YBa{sub 2}Cu{sub 3}O{sub 7-x} (a high-temperature superconductor with uses, e.g., in magnetic flux trapping and high-speed capacitor applications) were prepared by the new nanofabrication process that has been developed in this research program. The process consists of two steps: synthesis of ceramic nanoparticles, and fabrication of dense ceramic articles that possess nanocrystalline features. The synthesis step is capable of producing 10-nanometer-diameter crystallites of doped ZrO{sub 2}, and of being scaled up to kilogram/hour production rates. The fabrication step produced dense, ultrafine-grained articles at significantly reduced sintering temperatures and times--representing a factor of 10-100 reduction in process energy requirements. The process has thus been shown to be technically feasible, while a preliminary engineering cost analysis of a pilot plant-scale version of the process indicates that it is both a cost- and an energy-efficient method of producing nanoparticles and nanocrystalline ceramics from those nanoparticles. One U.S. patent for this process has been allowed, and an additional five (continuation-in-part) applications have been filed. Technology transfer efforts have begun, through ongoing discussions with representatives from three manufacturing concerns.

Stangle, G.C.; Schulze, W.A.; Amarakoon, V.R.W.

1996-05-30

303

Filtration combustion: Smoldering and SHS  

NASA Technical Reports Server (NTRS)

Smolder waves and SHS (self-propagating high-temperature synthesis) waves are both examples of combustion waves propagating in porous media. When delivery of reactants through the pores to the reaction site is an important aspect of the process, it is referred to as filtration combustion. The two types of filtration combustion have a similar mathematical formulation, describing the ignition, propagation and extinction of combustion waves in porous media. The goal in each case, however, is different. In smoldering the desired goal is to prevent propagation, whereas in SHS the goal is to insure propagation of the combustion wave, leading to the synthesis of desired products. In addition, the scales in the two areas of application may well differ. For example, smoldering generally occurs at a relatively low temperature and with a smaller propagation velocity than SHS filtration combustion waves. Nevertheless, the two areas of application have much in common, so that mechanisms learned about in one application can be used to advantage in the other. In this paper we discuss recent results in the areas of filtration combustion.

Matkowsky, Bernard J.

1995-01-01

304

Synthesis of nanocrystalline magnesium titanate by an auto-igniting combustion technique and its structural, spectroscopic and dielectric properties  

SciTech Connect

Nanocrystalline magnesium titanate was synthesized through an auto-ignited combustion method. The phase purity of the powder was examined using X-ray diffraction, thermo gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy and Raman spectroscopy. The transmission electron microscopy study showed that the particle size of the as-prepared powder was in between 20 and 40 nm. The nanopowder could be sintered to 98% of the theoretical density at 1200 {sup o}C for 3 h. The microstructure of the sintered surface was examined using scanning electron microscopy. The dielectric constant ({epsilon}{sub r}) of 16.7 and loss factor (tan {delta}) of the order of 10{sup -4} were obtained at 5 MHz when measured using LCR meter. The quality factor (Q{sub u} x f) 73,700 and temperature coefficient of resonant frequency ({tau}{sub f}) -44.3 ppm/{sup o}C, at 6.5 GHz are the best reported values for sintered pellets obtained from phase pure nanocrystalline MgTiO{sub 3} powder.

Suresh, M.K. [Electronic Materials Research Laboratory, DST-FIST Sponsored Postgraduate and Research Department of Physics, Mar Ivanios College, Nalanchira, Thiruvananthapuram 695015, Kerala (India)] [Electronic Materials Research Laboratory, DST-FIST Sponsored Postgraduate and Research Department of Physics, Mar Ivanios College, Nalanchira, Thiruvananthapuram 695015, Kerala (India); Thomas, J.K., E-mail: jkthomasemrl@yahoo.com [Electronic Materials Research Laboratory, DST-FIST Sponsored Postgraduate and Research Department of Physics, Mar Ivanios College, Nalanchira, Thiruvananthapuram 695015, Kerala (India); Sreemoolanadhan, H. [Vikram Sarabai Space Centre, Indian Space Research Organization, Department of Space, Thiruvananthapuram (India)] [Vikram Sarabai Space Centre, Indian Space Research Organization, Department of Space, Thiruvananthapuram (India); George, C.N. [Department of Physics, Bishop Moore College, Mavelikkara (India)] [Department of Physics, Bishop Moore College, Mavelikkara (India); John, Annamma; Solomon, Sam [Dielectric Materials Research Laboratory, Department of Physics, St. John's College, Anchal 691306, Kerala (India)] [Dielectric Materials Research Laboratory, Department of Physics, St. John's College, Anchal 691306, Kerala (India); Wariar, P.R.S. [Department of Physics, University College, Thiruvananthapuram, Kerala (India)] [Department of Physics, University College, Thiruvananthapuram, Kerala (India); Koshy, J. [Electronic Materials Research Laboratory, DST-FIST Sponsored Postgraduate and Research Department of Physics, Mar Ivanios College, Nalanchira, Thiruvananthapuram 695015, Kerala (India)] [Electronic Materials Research Laboratory, DST-FIST Sponsored Postgraduate and Research Department of Physics, Mar Ivanios College, Nalanchira, Thiruvananthapuram 695015, Kerala (India)

2010-07-15

305

Preparation of ?-Si6-zAlzOzN8-z (z = 1-3) by combustion synthesis  

NASA Astrophysics Data System (ADS)

?-Si6-zAlzOzN8-z (z = 1, 2, and 3) powders were combustion synthesized under a low nitrogen pressure of 1 MPa. Si, Al and SiO2 were used as the starting materials, and ?-SiAlON (z = 1) was added as diluent. The CSed powders then were sintered by spark plasma sintering at 1600 °C for 12 min. The products were analyzed by X-Ray Diffraction (XRD) and FE-SEM. The Vickers hardness was measured by a Vickers microhardness tester at room temperature. The purity of the CSed products reached above 86% for z = 1, 2, and 3. Pure and dense ?-SiAlONs (z = 1, 2 and 3) were obtained by SPS of CSed powders without any sintering additives, and the relative densities reached greater than 98% in theoretical. The Vickers hardness showed decreasing with the increase of z value, and the data ranges between 14.7 and 17.6 GPa due to different z values.

Yi, Xuemei; Watanabe, Kotaro; Akiyama, Tomohiro

2011-05-01

306

Fast Solution-Combustion Synthesis of Nitrogen-Modified Li4Ti5O12 Nanomaterials with Improved Electrochemical Performance.  

PubMed

A series of nitrogen-modified Li4Ti5O12 (N-LTO) nanomaterials with hierarchical micro/nanoporous structures are first synthesized via a facile one-step combustion process using thermal decomposition of urea. Successful deposition of a TiN thin layer onto the LTO surface was confirmed by transmission electron microscopy with energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric measurements. The electrochemical performances of the N-LTO nanomaterials are also investigated in this work. Compared with pristine LTO, the N-LTO nanomaterial with 1.1 wt % nitrogen exhibits a higher rate capability and better reversibility. At charge/discharge rates of 1, 2, 8, and 15 C, the discharge capacities of the N-LTO electrode were 159, 150, 128, and 108 mAh g(-1), respectively. After 200 cycles at 1 C, its capacity retention was 98.5% with almost no capacity fading. PMID:24779672

Li, Xue; Lin, Huang-Chang; Cui, Wang-Jun; Xiao, Qian; Zhao, Jin-Bao

2014-05-28

307

Synthesis, characterization and antimicrobial activity of some novel benzimidazole derivatives  

PubMed Central

A series of novel N-((1H-benzoimidazol-1-yl) methyl)-4-(1-phenyl-5-substituted-4, 5-dihydro-1-benzoimidazol-1-yl) methyl)-4-(1-phenyl-5-substituted-4, 5-dihydro-1H-pyrazol-3-yl) benzenamine were synthesized by treating various 1-(4-((1H-benzoimidazol-1-yl) methylamino) phenyl)-3-substitutedprop-2-en-1-one with phenyl hydrazine in the presence of sodium acetate through a simple ring closure reaction. The starting material, 1-(4-((1H-benzoimidazol-1-yl) methylamino) phenyl)-3-substitutedprop-2-en-1-one,-benzoimidazol-1-yl) methylamino) phenyl)-3-substitutedprop-2-en-1-one, was synthesized from o-phenylenediamine by a multistep synthesis. All the synthesized compounds were characterized by spectroscopic means and elemental analyses. The title compounds were investigated for in vitro antibacterial and antifungal properties against some human pathogenic microorganisms by employing the agar streak dilution method using Ciprofloxacin and Ketoconazole as standard drugs. All title compounds showed activity against the entire strains of microorganism. Structural activity relationship studies reveal that compounds possessing an electron-withdrawing group display better activity than the compounds containing electron-donating groups, whereas the unsubstituted derivatives display moderate activity. Based on the results obtained, N-((1H-benzoimidazol-1-yl) methyl)-4-(1-phenyl-5-(4-(trifluoromethyl) phenyl)-4,5-dihydro-1H-pyrazol-3-yl) benzenamine 5i was found to be very active compared with the rest of the compounds and standard drugs that were subjected to antimicrobial assay.

Krishnanjaneyulu, Immadisetty Sri; Saravanan, Govindaraj; Vamsi, Janga; Supriya, Pamidipamula; Bhavana, Jarugula Udaya; Sunil Kumar, Mittineni Venkata

2014-01-01

308

Synthesis and antimalarial activities of optically active labdane-type diterpenes.  

PubMed

An efficient method for the synthesis of optically active labdane-type diterpenes from (+)-manool 8 is described. We prepared the natural labdane-type diterpene 5 via key intermediate peroxide 9, and synthetic hydroxybutenolides 6 and 7 via a furan photosensitised oxygenation reaction of labdafuran (14). Compounds 5, 6, 7 and 9 were evaluated as inhibitors of the beta-haematin formation and globin proteolysis, and then were assayed in a malarial murine model. Compound 9 was the most promising compound, showing a positive correlation between in vitro and in vivo activities. PMID:19521902

Villamizar, José; Pittelaud, Jean P; Rodrigues, Juan R; Gamboa, Neira; Canudas, Nieves; Tropper, Eleonora; Salazar, Franklin; Fuentes, Juan

2009-01-01

309

Expeditious oligosaccharide synthesis via selective, semi-orthogonal, and orthogonal activation  

PubMed Central

Traditional strategies for oligosaccharide synthesis often require extensive protecting and/or leaving group manipulations between each glycosylation step, thereby increasing the total number of synthetic steps while decreasing the efficiency of the synthesis. In contrast, expeditious strategies allow for the rapid chemical synthesis of complex carbohydrates by minimizing extraneous chemical manipulations. Oligosaccharide synthesis by selective activation of one leaving group over another is one such expeditious strategy. Herein, the significant improvements that have recently emerged in the area of the selective activation are discussed. The development of orthogonal strategy further expands the scope of the selective activation methodology. Surveyed in this article, are representative examples wherein these excellent innovations have been applied to the synthesis of various oligosaccharide sequences.

Kaeothip, Sophon; Demchenko, Alexei V.

2011-01-01

310

Relationship of lipogenic enzyme activities to the rate of rat liver fatty acid synthesis  

SciTech Connect

The mechanism by which diet regulates liver lipogenesis is unclear. Here the authors report how dietary alterations effect the activities of key enzymes of fatty acid (FA) synthesis. Male Sprague-Dawley rats, 400-500 g, were fasted for 48h and then refed a fat-free, high carbohydrate (HC) diet (75% cal. from sucrose) for 0,3,9,24 and 48h, or refed a HC diet for 48h, then fed a high-fat (HF) diet (44% cal. from corn oil) for 3,9,24 and 48h. The FA synthesis rate and the activities of acetyl CoA carboxylase (AC), fatty acid synthase (FAS), ATP citrate lyase (CL), and glucose 6-phosphate dehydrogenase (G6PDH) were determined in the livers. FA synthesis was assayed with /sup 3/H/sub 2/O, enzyme activities were measured spectrophotometrically except for AC which was assayed with /sup 14/C-bicarbonate. There was no change in the activity of AC during fasting or on the HC diet. Fasting decreased the rate of FA synthesis by 25% and the activities of FAS and CL by 50%; refeeding the HC diet induced parallel changes in FA synthesis and the activities of FAS, CL, and G6PDH. After 9h on the HF diet, FA synthesis had decreased sharply, AC activity increased significantly while no changes were detected in the other activities. Subsequently FA synthesis did not change while the activities of the enzymes decreased slowly. These enzymes did not appear to regulate FA synthesis during inhibition of lipogenesis, but FAS, CL or G6PDH may be rate limiting in the induction phase. Other key factors may regulate FA synthesis during dietary alterations.

Nelson, G.; Kelley, D.; Schmidt, P.; Virk, S.; Serrato, C.

1986-05-01

311

Synthesis and antiproliferative activity of unnatural enantiomers of 7-epi-goniofufurone and crassalactone C.  

PubMed

A facile synthesis of 7-epi-(-)-goniofufurone as well as the first synthesis of (-)-crassalactone C was achieved starting from D-xylose. A comparison of their in vitro antitumour activities with those observed for the corresponding naturally occurring enantiomers was provided. PMID:18783950

Popsavin, Velimir; Benedekovi?, Goran; Sre?o, Bojana; Popsavin, Mirjana; Francuz, Jovana; Koji?, Vesna; Bogdanovi?, Gordana

2008-10-01

312

Synthesis and antiproliferative activity of unnatural enantiomers of 7- epi-goniofufurone and crassalactone C  

Microsoft Academic Search

A facile synthesis of 7-epi-(?)-goniofufurone as well as the first synthesis of (?)-crassalactone C was achieved starting from d-xylose. A comparison of their in vitro antitumour activities with those observed for the corresponding naturally occurring enantiomers was provided.

Velimir Popsavin; Goran Benedekovi?; Bojana Sre?o; Mirjana Popsavin; Jovana Francuz; Vesna Koji?; Gordana Bogdanovi?

2008-01-01

313

Synthesis and Antiangiogenic Activity of N-Alkylated Levamisole Derivatives  

PubMed Central

Inhibition of angiogenesis is a promising addition to current cancer treatment strategies. Neutralization of vascular endothelial growth factor by monoclonal antibodies is clinically effective but may cause side effects due to thrombosis. Low molecular weight angiogenesis inhibitors are currently less effective than antibody treatment and are also associated with serious side effects. The discovery of new chemotypes with efficient antiangiogenic activity is therefore of pertinent interest. (S)-Levamisole hydrochloride, an anthelminthic drug approved for human use and with a known clinical profile, was recently shown to be an inhibitor of angiogenesis in vitro and exhibited tumor growth inhibition in mice. Here we describe the synthesis and in vitro evaluation of a series of N-alkylated analogues of levamisole with the aim of characterizing structure–activity relationships with regard to inhibition of angiogenesis. N-Methyllevamisole and p-bromolevamisole proved more effective than the parent compound, (S)-levamisole hydrochloride, with respect to inhibition of angiogenesis and induction of undifferentiated cluster morphology in human umbilical vein endothelial cells grown in co-culture with normal human dermal fibroblasts. Interestingly, the cluster morphology caused by N-methyllevamisole was different than the clusters observed for levamisole, and a third “cord-like” morphology resembling that of the known drug suramin was observed for an aniline-containing derivative. New chemotypes exhibiting antiangiogenic effects in vitro are thus described, and further investigation of their underlying mechanism of action is warranted.

Sylvest, Lene; Friis, Tina; Staerk, Dan; J?rgensen, Flemming Steen; Olsen, Christian A.; Houen, Gunnar

2012-01-01

314

Synthesis and antitumor activity of lapathoside D and its analogs.  

PubMed

Phenylpropanoid sucrose esters are important class of plant-derived natural products and have greater potential to be leads for new drugs because of their structural diversity and broad-array of pharmacological and biological activities. Regio- and chemo-selective acylation of 2,1':4,6-O-di-isopropylidene sucrose 4 with cinnamoyl chloride 5 and p-acetoxycinnamoyl chloride 6 afforded mono-, di-, tri- and tetra- variant PSEs in moderate yields. The first total synthesis of di-substituted PSE, lapathoside D 1' has been achieved successfully in short and simple synthetic steps from sucrose 3 as an inexpensive starting material. Lapathoside D 1 and a set of selected synthesized PSEs were tested for in vitro cytotoxicity against human cervical epithelioid carcinoma (HeLa) cell lines. Most of the compounds exhibited significant antitumor activity with their IC(50) values ranging from 0.05 to 7.63 ?M. The primary screening results indicated that PSEs might be valuable source for new potent anticancer drug candidates. PMID:22542106

Panda, Parthasarathi; Appalashetti, Manjuvani; Natarajan, Meenubharathi; Chan-Park, Mary B; Venkatraman, Subbu S; Judeh, Zaher M A

2012-07-01

315

Synthesis, characterization and biological activities of curcumin nanospheres.  

PubMed

Curcumin is one of the most versatile compounds obtained from Curcuma longa. The major obstacle in the therapeutic use of curcumin is its aqueous solubility. To enhance its aqueous solubility and biological activities, we prepared curcumin nanospheres (CNSs) by wet milling-solvent evaporation technique without any surfactants. In this study, we have focused on the synthesis, characterization and biological effects of CNSs. DLS and SEM analyses showed 50-80 nm spherical shaped CNSs with a zeta potential of -31.65 mV. FTIR revealed that there were no structural changes to CNSs. Antibacterial and antifungal studies proved that CNSs were much more effective than curcumin against Escherichia coil, Staphylococcus aureus and Candida albicans. Antioxidant activity of CNSs showed promising result for therapeutic applications. The in vitro anti-inflammatory studies proved that CNSs possessed enhanced anti-inflammatory effect against protein denaturation. Cytotoxicity and uptake of CNSs showed more toxicity on cancer cells (T47D, MG63, A375) sparing normal HDF and IEC cell lines. Skin permeation studies showed CNSs retained at different layers of pig skin. These results give clear evidence for their use against microbial and fungal skin infections as well as cancer treatment. PMID:24738332

Arunraj, T R; Sanoj Rejinold, N; Mangalathillam, Sabitha; Saroj, Soumya; Biswas, Raja; Jayakumar, R

2014-02-01

316

Computational combustion  

Microsoft Academic Search

Progress in the field of computational combustion over the past 50 years is reviewed. Particular attention is given to those classes of models that are common to most system modeling efforts, including fluid dynamics, chemical kinetics, liquid sprays, and turbulent flame models. The developments in combustion modeling are placed into the time-dependent context of the accompanying exponential growth in computer

Charles K. Westbrook; Yasuhiro Mizobuchi; Thierry J. Poinsot; Phillip J. Smith; Jürgen Warnatz

2005-01-01

317

Computational Combustion  

Microsoft Academic Search

Progress in the field of computational combustion over the past 50 years is reviewed. Particular attention is given to those classes of models that are common to most system modeling efforts, including fluid dynamics, chemical kinetics, liquid sprays, and turbulent flame models. The developments in combustion modeling are placed into the time-dependent context of the accompanying exponential growth in computer

C K Westbrook; Y Mizobuchi; T J Poinsot; P J Smith; J Warnatz

2004-01-01

318

Combustion Technology Outreach  

NASA Technical Reports Server (NTRS)

Lewis' High Speed Research (HSR) Propulsion Project Office initiated a targeted outreach effort to market combustion-related technologies developed at Lewis for the next generation of supersonic civil transport vehicles. These combustion-related innovations range from emissions measurement and reduction technologies, to diagnostics, spray technologies, NOx and SOx reduction of burners, noise reduction, sensors, and fuel-injection technologies. The Ohio Aerospace Institute and the Great Lakes Industrial Technology Center joined forces to assist Lewis' HSR Office in this outreach activity. From a database of thousands of nonaerospace firms considered likely to be interested in Lewis' combustion and emission-related technologies, the outreach team selected 41 companies to contact. The selected companies represent oil-gas refineries, vehicle/parts suppliers, and manufacturers of residential furnaces, power turbines, nonautomobile engines, and diesel internal combustion engines.

1995-01-01

319

A concise synthesis of tetrabenazine: an intramolecular aza-Prins-type cyclization via oxidative C-H activation.  

PubMed

A concise synthesis of tetrabenazine and dihydrotetrabenazine is described. The key feature of this synthesis is the intramolecular aza-Prins-type cyclization of an amino allylsilane via oxidative C-H activation. PMID:22103629

Son, Young Wook; Kwon, Tae Hui; Lee, Jae Kyun; Pae, Ae Nim; Lee, Jae Yeol; Cho, Yong Seo; Min, Sun-Joon

2011-12-16

320

Interaction of pulsating and spinning waves in condensed phase combustion  

Microsoft Academic Search

The authors employ a nonlinear stability analysis in the neighborhood of a multiple bifurcation point to describe the interaction of pulsating and spinning modes of condensed phase combustion. Such phenomena occur in the synthesis of refractory materials. In particular, they consider the propagation of combustion waves in a long thermally insulated cylindrical sample and show that steady, planar combustion is

Michael R. Booty; Stephen B. Margolis; Bernard J. Matkowsky

1986-01-01

321

Synthesis, characterization and antibacterial activity of new fluorescent chitosan derivatives.  

PubMed

The present work aims to the development of innovative new derivatives of chitosan that can be used for medical applications. This innovation is based on the synthesis and characterization of chitosan-g-aminoanthracene derivatives. Thus, N-(anthracen-9-yl)-4,6-dichloro-[1,3,5]-triazin-2-amine (AT) reacted with chitosan by the following steps: at first, cyanuric chloride reacted with 9-aminoanthracene to obtain N-(anthracen-9-yl)-4,6-dichloro-[1,3,5]-triazin-2-amine (AT), then the AT reacted with chitosan to obtain (CH-g-AT). The final product of CH-g-AT was separated, purified and re-crystallized by dioxane. The structure of the prepared chitosan derivatives was confirmed by FTIR-ATR, solid-NMR, TGA, X-RD, and DSC. The new chitosan derivatives showed fluorescence spectra in liquid and in solid state as well. CH-g-AT showed also high antibacterial activity against gram -ve species (Escherichia coli). PMID:24472505

P?ichystalová, Hana; Almonasy, Numan; Abdel-Mohsen, A M; Abdel-Rahman, Rasha M; Fouda, Moustafa M G; Vojtova, L; Kobera, Libor; Spotz, Zdenek; Burgert, Ladislav; Jancar, J

2014-04-01

322

The Synthesis of Active Metabolites and Analogues of Vitamin D3  

Microsoft Academic Search

The literature date on the synthesis of the active metabolites and analogues of vitamin D3 (cholecalciferol), which play an important role in regulating the homeostatis of calcium in the organism, are reviewed. The bibliography includes 150 references.

R. I. Yakhimovich

1980-01-01

323

Self-tuning regulators for combustion oscillations  

Microsoft Academic Search

Self-excited combustion oscillations arise from a coupling between unsteady combustion and acoustic waves, and can cause structural damage to many combustion systems. Active control provides a way of extending the systems' stable operating range by interrupting the damaging thermoacoustic interaction. The active controller considered injects some fuel unsteadily into the burning region, thereby altering the heat-release rate, in response to

Stéphanie Evesque; Ann P. Dowling; Anuradha M. Annaswamy

2003-01-01

324

Photoluminescence properties of Ba 2ZnSi 2O 7:Eu 2+, Re 3+ (Re = Dy, Nd) long lasting phosphors prepared by the combustion-assisted synthesis method  

Microsoft Academic Search

Long lasting alkaline earth silicates, Ba2ZnSi2O7:Eu, Dy, Ba2ZnSi2O7:Eu, Nd and Ba2ZnsSi2O7:Eu, Dy, Nd were prepared by the combustion-assisted synthesis (CAS) method. The obtained phosphors were characterized by means of X-ray diffraction (XRD) and their photoluminescence spectrum (PSL). The emission spectrum shows a single band centered at 503nm, which corresponds to the 4f65d1?4f7 transition of Eu2+. The Ba2ZnSi2O7:Eu phosphors showed blue-green

Shanshan Yao; Yuanyuan Li; Lihong Xue; Youwei Yan

2010-01-01

325

Synthesis, thermal and spectral characterization of nanosized Ni x Mg 1? x Al 2O 4 powders as new ceramic pigments via combustion route using 3-methylpyrozole-5-one as fuel  

Microsoft Academic Search

New NixMg1?xAl2O4 nanosized in different composition (0.1?x?0.8) powders have been synthesized successively for first time by using low temperature combustion reaction (LTCR) of corresponding metal chlorides, carbonates and nitrates as salts with 3-methylpyrozole-5-one (3MP5O) as fuel at 300°C in open air furnace. Magnesium aluminate spinel (MgAl2O4) was used as crystalline host network for the synthesis of nickel-based nano ceramic pigments.

Ibrahim S. Ahmed; Sayed A. Shama; Hassan A. Dessouki; Ayman A. Ali

2011-01-01

326

Autocrine activities of basic fibroblast growth factor: regulation of endothelial cell movement, plasminogen activator synthesis, and DNA synthesis  

PubMed Central

We have found that the spontaneous migration of bovine aortic endothelial cells from the edge of a denuded area in a confluent monolayer is dependent upon the release of endogenous basic fibroblast growth factor (bFGF). Cell movement is blocked by purified polyclonal rabbit IgG to bFGF as well as affinity purified anti-bFGF IgG and anti- bFGF F(ab')2 fragments. The inhibitory effect of the immunoglobulins is dependent upon antibody concentration, is reversible, is overcome by the addition of recombinant bFGF, and is removed by affinity chromatography of the antiserum through a column of bFGF-Sepharose. Cell movement is also reversibly inhibited by the addition of protamine sulfate and suramin; two agents reported to block bFGF binding to its receptor. The addition of recombinant bFGF to wounded monolayers accelerates the movement of cells into the denuded area. Transforming growth factor beta which has been shown to antagonize several other effects of bFGF also inhibits cell movement. The anti-bFGF IgG prevents the movement of bovine capillary endothelial cells, BHK-21, NIH 3T3, and human skin fibroblasts into a denuded area. Antibodies to bFGF, as well as suramin and protamine sulfate also suppress the basal levels of plasminogen activator and DNA synthesis in bovine aortic endothelial cells.

1988-01-01

327

Antitumor Platinum Compounds: Synthesis, Structure and Biological Activity.  

National Technical Information Service (NTIS)

Contents: General introduction--(Survey of the development of platinum coordination compounds in the chemotherapy of cancer; and introduction to the work described in this thesis.); Synthesis and characterization of platinum and palladium compounds with n...

C. G. van Kralingen

1979-01-01

328

Removal of volatile organic compounds from activated carbon by thermal desorption and catalytic combustion  

Microsoft Academic Search

The thermal desorption of saturated activated carbon discharged from an industrial adsorber and catalytic oxidation of desorbed\\u000a products over a Pt\\/Al2O3 catalyst were investigated. The activated carbon is almost completely regenerated by flushing with air at 200?C for 30 min.\\u000a Desorbed products are fully oxidized over the Pt\\/Al2O3 catalyst above 275?C.

D. Rankovic; Z. Arsenijevic; N. Radic; B. Grbic; Ž. Grbav?i?

2007-01-01

329

Combustion of dried animal dung as biofuel results in the generation of highly redox active fine particulates  

PubMed Central

Background The burning of biomass in the developing world for heating and cooking results in high indoor particle concentrations. Long-term exposure to airborne particulate matter (PM) has been associated with increased rates of acute respiratory infections, chronic obstructive lung disease and cancer. In this study we determined the oxidative activity of combustion particles derived from the biomass fuel dung cake by examining their capacity to deplete antioxidants from a model human respiratory tract lining fluid (RTLF). For comparison, the observed oxidative activity was compared with that of particles derived from industrial and vehicular sources. Results Incubation of the dung cake particle suspensions in the RTLF for 4 h resulted in a mean loss of ascorbate of 72.1 ± 0.7 and 89.7 ± 2.5% at 50 and 100 ?g/ml, respectively. Reduced glutathione was depleted by 49.6 ± 4.3 and 63.5 ± 22.4% under the same conditions. The capacity of these samples to deplete ascorbate was in excess of that observed with diesel or gasoline particles, but comparable to that seen with residual oil fly ash and considerably in excess of all three control particles in terms of glutathione depletion. Co-incubation with the metal chelator diethylenetriaminepentaacetate inhibited these losses, whilst minimal inhibition was seen with superoxide dismutase and catalase treatment. The majority of the activity observed appeared to be contained within aqueous particle extracts. Conclusion These data demonstrate that biomass derived particles have considerable oxidative activity, largely attributable to their transition metal content.

Mudway, Ian S; Duggan, Sean T; Venkataraman, Chandra; Habib, Gazala; Kelly, Frank J; Grigg, Jonathan

2005-01-01

330

Combustion detector  

NASA Technical Reports Server (NTRS)

A device has been developed for generating a rapid response signal upon the radiation-emitting combustion reaction of certain gases in order to provide a means for the detection and identification of such reaction and concurrently discriminate against spurious signals. This combustion might be the first stage of a coal mine explosion process, and thereby this device could provide a warning of the impending explosion in time to initiate quenching action. This device has the capability of distinguishing between the light emitted from a combustion reaction and the light emitted by miners' lamps, electric lamps, welding sparks or other spurious events so that the quenching mechanism is triggered only when an explosion-initiating combustion occurs.

Trimpi, R. L.; Nealy, J. E.; Grose, W. L. (inventor)

1973-01-01

331

Combustion Physics.  

ERIC Educational Resources Information Center

Discusses how physics is used to improve the efficiency of combustion, pointing out that the interdisciplinary topic has applications to problems of real industrial relevance and practical value. (JN)

Jones, A. R.

1985-01-01

332

Design, synthesis and antibacterial activity of 3-methylenepyrrolidine formyl hydroxyamino derivatives as novel peptide deformylase inhibitors.  

PubMed

The synthesis and antibacterial activity of 3-methylenepyrrolidine formyl hydroxyamino derivatives are reported. The antibacterial activities of these derivatives were evaluated to discover SAR at P(1') and P(3') positions, and most of these derivatives exhibit better in vitro antibacterial activity than existing drugs against drug-resistant clinical isolates including MRSA, PRSP, and Haemophilus influenzae. PMID:21185180

Shi, Wei; Ma, Haikun; Duan, Yuejiao; Aubart, Kelly; Fang, Yuhong; Zonis, Rimma; Yang, Liping; Hu, Wenhao

2011-02-01

333

Rare earth activated nanosized oxide phosphors: synthesis and optical properties  

Microsoft Academic Search

Gd2O3:Eu and (Gd,Y)2O3:Eu nanocrystals were prepared by the glycine assist combustion method. The as-prepared products are porous networks from the HTEM and isolated nanoparticles can be observed after further annealing. From the luminescence spectra and XRD patterns, the prepared Gd2O3:Eu nanocrystals were found to be monoclinic. While Y3+ doped into the Gd2O3 to form the complex host, the structure changed

Lingdong Sun; Jiang Yao; Changhui Liu; Chunsheng Liao; Chunhua Yan

2000-01-01

334

Laccase Catalyzed Synthesis of Iodinated Phenolic Compounds with Antifungal Activity  

PubMed Central

Iodine is a well known antimicrobial compound. Laccase, an oxidoreductase which couples the one electron oxidation of diverse phenolic and non-phenolic substrates to the reduction of oxygen to water, is capable of oxidizing unreactive iodide to reactive iodine. We have shown previously that laccase-iodide treatment of spruce wood results in a wash-out resistant antimicrobial surface. In this study, we investigated whether phenolic compounds such as vanillin, which resembles sub-structures of softwood lignin, can be directly iodinated by reacting with laccase and iodide, resulting in compounds with antifungal activity. HPLC-MS analysis showed that vanillin was converted to iodovanillin by laccase catalysis at an excess of potassium iodide. No conversion of vanillin occurred in the absence of enzyme. The addition of redox mediators in catalytic concentrations increased the rate of iodide oxidation ten-fold and the yield of iodovanillin by 50%. Iodinated phenolic products were also detected when o-vanillin, ethyl vanillin, acetovanillone and methyl vanillate were incubated with laccase and iodide. At an increased educt concentration of 0.1 M an almost one to one molar ratio of iodide to vanillin could be used without compromising conversion rate, and the insoluble iodovanillin product could be recovered by simple centrifugation. The novel enzymatic synthesis procedure fulfills key criteria of green chemistry. Biocatalytically produced iodovanillin and iodo-ethyl vanillin had significant growth inhibitory effects on several wood degrading fungal species. For Trametes versicolor, a species causing white rot of wood, almost complete growth inhibition and a partial biocidal effect was observed on agar plates. Enzymatic tests indicated that the iodinated compounds acted as enzyme responsive, antimicrobial materials.

Ihssen, Julian; Schubert, Mark; Thony-Meyer, Linda; Richter, Michael

2014-01-01

335

The synthesis and photocatalytic activity of ZnSe microspheres  

NASA Astrophysics Data System (ADS)

This paper reports the synthesis of semiconductor ZnSe microspheres composed of nanoparticles via a solvothermal route between the organic molecule selenophene (C4H4 Se) and ZnCl2 without adding any surfactant. The ZnSe microspheres were characterized by x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), specific surface area measurement, and photoluminescence (PL) spectra. A strong and broad blue PL emission at 443 nm in wavelength (~2.79 eV in photon energy) is attributed to the near-band-edge (NBE) emission of ZnSe, while the 530 nm peak is a defect-related (DL) emission. The photocatalytic activity of the as-prepared ZnSe microspheres was evaluated by photodegradation of methyl orange (MO) dye under ultraviolet (UV) light and visible light irradiation. The degradations of MO reach 94% or 95.1%, close to 100%, in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 7 or 10 h under UV irradiation, respectively. Meanwhile the degradations of MO reach 94.3% or 60.6% in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 12 h, respectively. The degradation rate of ZnSe microspheres is twice that of ZnSe commercial powder under UV light irradiation, and three times under visible light irradiation. The degradation process of MO dye on ZnSe microspheres under UV or visible light is also discussed.

Cao, Huaqiang; Xiao, Yujiang; Zhang, Sichun

2011-01-01

336

Laccase catalyzed synthesis of iodinated phenolic compounds with antifungal activity.  

PubMed

Iodine is a well known antimicrobial compound. Laccase, an oxidoreductase which couples the one electron oxidation of diverse phenolic and non-phenolic substrates to the reduction of oxygen to water, is capable of oxidizing unreactive iodide to reactive iodine. We have shown previously that laccase-iodide treatment of spruce wood results in a wash-out resistant antimicrobial surface. In this study, we investigated whether phenolic compounds such as vanillin, which resembles sub-structures of softwood lignin, can be directly iodinated by reacting with laccase and iodide, resulting in compounds with antifungal activity. HPLC-MS analysis showed that vanillin was converted to iodovanillin by laccase catalysis at an excess of potassium iodide. No conversion of vanillin occurred in the absence of enzyme. The addition of redox mediators in catalytic concentrations increased the rate of iodide oxidation ten-fold and the yield of iodovanillin by 50%. Iodinated phenolic products were also detected when o-vanillin, ethyl vanillin, acetovanillone and methyl vanillate were incubated with laccase and iodide. At an increased educt concentration of 0.1 M an almost one to one molar ratio of iodide to vanillin could be used without compromising conversion rate, and the insoluble iodovanillin product could be recovered by simple centrifugation. The novel enzymatic synthesis procedure fulfills key criteria of green chemistry. Biocatalytically produced iodovanillin and iodo-ethyl vanillin had significant growth inhibitory effects on several wood degrading fungal species. For Trametes versicolor, a species causing white rot of wood, almost complete growth inhibition and a partial biocidal effect was observed on agar plates. Enzymatic tests indicated that the iodinated compounds acted as enzyme responsive, antimicrobial materials. PMID:24594755

Ihssen, Julian; Schubert, Mark; Thöny-Meyer, Linda; Richter, Michael

2014-01-01

337

First quarterly report of the DARPA dynamic synthesis and consolidation program  

SciTech Connect

The report covers activities of national laboratories, universities, and research institutes. The program activities include dynamic compaction, shock activation, and combustion and plasma synthesis. The primary materials under study are AlN, Al/sub 2/O/sub 3/, TiC, and TiB/sub 2/. (DLC)

Cline, C.F. (ed.)

1982-08-01

338

DETECTION OF ANDROGENIC ACTIVITY IN EMISSIONS FROM DIESEL FUEL AND BIOMASS COMBUSTION  

EPA Science Inventory

The present study evaluated both diesel fuel exhaust and biomass (wood) burn extracts for androgen receptor¿mediated activity using MDA-kb2 cells, which contain an androgen-responsive promoter-luciferase reporter gene construct. This assay and analytical fractionization of the sa...

339

Measurement of Microbial Activity and Growth in the Ocean by Rates of Stable Ribonucleic Acid Synthesis  

PubMed Central

A relatively simple and extremely sensitive technique for measuring rates of stable ribonucleic acid (RNA) synthesis was devised and applied to bacterial cultures and seawater samples. The procedure is based upon the uptake and incorporation of exogenous radiolabeled adenine into cellular RNA. To calculate absolute rates of synthesis, measurements of the specific radioactivity of the intracellular adenosine 5?-triphosphate pools (precursor to RNA) and of the total amount of radioactivity incorporated into stable cellular RNA per unit time are required. Since the rate of RNA synthesis is positively correlated with growth rate, measurements of RNA synthesis should be extremely useful for estimating and comparing the productivities of microbial assemblages in nature. Adenosine 5?-triphosphate, adenylate energy charge, and rates of stable RNA synthesis have been measured at a station located in the Columbian Basin of the Caribbean Sea. A subsurface peak in RNA synthesis (and therefore growth) was located within the dissolved oxygen minimum zone (450 m), suggesting in situ microbiological utilization of dissolved molecular oxygen. Calculations of the specific rates of RNA synthesis (i.e., RNA synthesis per unit of biomass) revealed that the middepth maximum corresponded to the highest specific rate of growth (420 pmol of adenine incorporated into RNA·day?1) of all depths sampled, including the euphotic zone. The existence of an intermediate depth zone of active microbial growth may be an important site for nutrient regeneration and may serve as a source of reduced carbon for mesopelagic and deep sea environments.

Karl, David M.

1979-01-01

340

Catalytic activity of oxidized (combusted) oil shale for removal of nitrogen oxides with ammonia as a reductant in combustion gas streams, Part 2  

SciTech Connect

Oxidized oil shale from the combustor in the LLNL Hot-Recycled-Solids (HRS) oil shale retorting process has been found to be a catalyst for removing nitrogen oxides from laboratory gas streams using NH{sub 3} as a reductant. Oxidized Green River oil shale heated at 10{degree}C/min in an Ar/O{sub 2}/NO/NH{sub 3} mixture ({approximately}93%/6%/2000 ppM/4000 ppM) with a gas residence time of {approximately}0.6 sec removed NO between 250 and 500{degree}C, with maximum removal of 70% at {approximately}400{degree}C. Under isothermal conditions with the same gas mixture, the maximum NO removal was {approximately}64%. When CO{sub 2} was added to the gas mixture at {approximately}8%, the NO removal dropped to {approximately}50%. However, increasing the gas residence time to {approximately}1.2 sec, increased NO removal to 63%. Nitrogen balances of these experiments suggest selective catalytic reduction of NO is occurring using NH{sub 3} as the reductant. These results are not based on completely optimized process conditions, but indicate oxidized oil shale is an effective catalyst for NO removal from combustion gas streams using NH{sub 3} as the reductant. Parameters calculated for implementing oxidized oil shale for NO{sub x} remediation on the current HRS retort indicate an abatement device is practical to construct.

Reynolds, J.G.; Taylor, R.W.; Morris, C.J.

1993-01-04

341

Catalytic activity of oxidized (combusted) oil shale for removal of nitrogen oxides with ammonia as a reductant in combustion gas streams, Part 2  

SciTech Connect

Oxidized oil shale from the combustor in the LLNL Hot-Recycled-Solids (HRS) oil shale retorting process has been found to be a catalyst for removing nitrogen oxides from laboratory gas streams using NH[sub 3] as a reductant. Oxidized Green River oil shale heated at 10[degree]C/min in an Ar/O[sub 2]/NO/NH[sub 3] mixture ([approximately]93%/6%/2000 ppM/4000 ppM) with a gas residence time of [approximately]0.6 sec removed NO between 250 and 500[degree]C, with maximum removal of 70% at [approximately]400[degree]C. Under isothermal conditions with the same gas mixture, the maximum NO removal was [approximately]64%. When CO[sub 2] was added to the gas mixture at [approximately]8%, the NO removal dropped to [approximately]50%. However, increasing the gas residence time to [approximately]1.2 sec, increased NO removal to 63%. Nitrogen balances of these experiments suggest selective catalytic reduction of NO is occurring using NH[sub 3] as the reductant. These results are not based on completely optimized process conditions, but indicate oxidized oil shale is an effective catalyst for NO removal from combustion gas streams using NH[sub 3] as the reductant. Parameters calculated for implementing oxidized oil shale for NO[sub x] remediation on the current HRS retort indicate an abatement device is practical to construct.

Reynolds, J.G.; Taylor, R.W.; Morris, C.J.

1993-01-04

342

Preparation, luminescence and defect studies of Eu{sup 2+}-activated strontium hexa-aluminate phosphor prepared via combustion method  

SciTech Connect

Preparation of Eu{sup 2+} ions activated strontium hexa-aluminate phosphor using the combustion method is described. An efficient phosphor can be prepared by this method at reaction temperatures as low as 500 deg. C in a few minutes. Powder X-ray diffraction (XRD), transmission electron microscopy, scanning electron microscope analysis were used to characterize the as prepared product and the optical properties were studied by photoluminescence (PL) spectra. Thermally stimulated luminescence studies also have been carried out on SrAl{sub 12}O{sub 19}:Eu{sup 2+} phosphor. The TSL glow curve is broad and indicates two dominant peaks at 206 and 345 deg. C. Defect centres formed in irradiated phosphor have been studied using the technique of electron spin resonance. One of the centres is characterized by an isotropic g-value of 2.0055 and is assigned to a F{sup +} centre. The two annealing stages of F{sup +} centre in the region 125-230 and 340-390 deg. C appear to correlate with the release of carriers resulting in TSL peaks at 206 and 345 deg. C, respectively. - Graphical abstract: SEM image of SrAl{sub 12}O{sub 19}:Eu.

Singh, Vijay [Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Gundu Rao, T.K. [R.S.I.C., Indian Institute of Technology, Powai, Mumbai 400 076 (India); Zhu Junjie [Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China)]. E-mail: jjzhu@nju.edu.cn

2006-08-15

343

Nucleic acid and protein synthesis associated with the induction of nitrate reductase activity in radish cotyledons  

PubMed Central

1. RNA and protein synthesis was studied during the incubation of excised radish cotyledons in nitrate, conditions that induced nitrate reductase activity in the tissue. 2. Synthesis of total RNA and protein, as measured by the incorporation of radioactive precursor, was significantly stimulated in the presence of nitrate (compared with chloride control), but was decreased in the presence of ammonium nitrate, which induced higher enzyme activity. 3. Synthesis of RNA and protein was required for induction of enzyme activity, as determined by using the inhibitors actinomycin D, puromycin and cycloheximide. 4. On the basis of 5-fluorouracil inhibition, the synthesis of only DNA-like RNA was required for induction, but no differences, either quantitative or qualitative, were observed in DNA-like RNA synthesis in the presence or absence of induction. 5. A 100-fold purification of the nitrate reductase activity showed no increase in nitrate reductase protein, nor any increased incorporation of radioactive precursor into nitrate reductase protein in the induced versus the control system. Such results suggested that the protein synthesis required for induction may be for a protein other than nitrate reductase.

Ingle, J.

1968-01-01

344

Modelling catalytic combustion of carbon monoxide and hydrocarbons over catalytically active wire meshes  

Microsoft Academic Search

A new way of preparing catalytically active wire meshes through a thermal-spray technique is described. A metal substrate (e.g. Kanthal AF) was plasma-sprayed with a composite ceramic\\/polymer-powder. The polymer content of the sprayed layer was burnt off whereupon a well-defined macro-porosity was created. By treating the so obtained material with an alumina-sol the specific surface area could be increased by

Anders Fredrik Ahlström-Silversand; Claes Ulf Ingemar Odenbrand

1999-01-01

345

Combustion synthesis and engineering of nanoparticles for electronic, structural and superconductor applications. Annual progress report, December 1, 1992--August 19, 1993.  

National Technical Information Service (NTIS)

Fully dense, nanocrystalline ceramic articles were prepared by a new nanofabrication process. The process consists of two steps: synthesis of ceramic nanoparticles and fabrication of dense, nanocrystalline ceramic parts. The synthesis step produced 10-nan...

G. C. Stangle V. R. W. Amarakoon W. A. Schulze

1993-01-01

346

Combustion synthesis and engineering of nanoparticles for electronic, structural and superconductor applications. Annual progress report, December 1, 1992--May 31, 1993.  

National Technical Information Service (NTIS)

Fully dense, nanocrystalline ceramic articles were prepared by the new nanofabrication process. The process consists of two steps: synthesis of ceramic nanoparticles and fabrication of dense, nanocrystalline ceramic parts. The synthesis step produced 10-n...

G. C. Stangle V. R. W. Amarakoon W. A. Schulze

1993-01-01

347

Influence of dopamine synthesis on methamphetamine-induced changes in striatal and adrenal tyrosine hydroxylase activity  

Microsoft Academic Search

Methamphetamine in large doses decreases striatal tyrosine hydroxylase activity. This effect is prevented by neuroleptic agents such as chlorpromazine and haloperidol which would suggest that released dopamine may be involved in the response. To test this hypothesis, we have altered dopamine synthesis with a-methyl-p-tyrosine and l-Dopa and found that dopamine synthesis is necessary for the observed depression of striatal TH

J. W. Gibb; F. J. Kogan

1979-01-01

348

The rate of synthesis and decomposition of tissue proteins in hypokinesia and increased muscular activity  

NASA Technical Reports Server (NTRS)

During hypokinesia and physical loading (swimming) of rats, the radioactivity of skeletal muscle, liver, kidney, heart, and blood proteins was determined after administration of radioactive amino acids. Tissue protein synthesis decreased during hypokinesia, and decomposition increased. Both synthesis and decomposition increased during physical loading, but anabolic processes predominated in the total tissue balance. The weights of the animals decreased in hypokinesia and increased during increased muscle activity.

Fedorov, I. V.; Chernyy, A. V.; Fedorov, A. I.

1978-01-01

349

New Synthetic Routes to More Active Cu\\/ZnO Catalysts Used for Methanol Synthesis  

Microsoft Academic Search

New preparation routes are applied to synthesize novel Cu\\/ZnO catalysts exhibiting high catalytic activity in methanol synthesis. In particular, the deposition–precipitation of copper onto high specific surface area (SSA) zinc oxide particles and the chemical vapor deposition of diethyl zinc turned out to be effective techniques, leading to promising methanol synthesis catalysts due to the enlargement of the Cu-ZnO interface.

Melanie Kurtz; Natalia Bauer; Christoph Büscher; Hagen Wilmer; Olaf Hinrichsen; Ralf Becker; Stefan Rabe; Klaus Merz; Matthias Driess; Roland A. Fischer; Martin Muhler

2004-01-01

350

The Activation of Hydrocarbon CH Bonds over Transition Metal Oxide Catalysts: A FTIR Study of Hydrocarbon Catalytic Combustion over MgCr 2O 4  

Microsoft Academic Search

The interaction of light hydrocarbons (methane, ethane, propane, propene, n-butane, isobutane, 1-butene, benzene, and toluene) with the oxidized surface of the spinel MgCr2O4 (an active hydrocarbon combustion catalyst) has been investigated by FTIR spectroscopy in the temperature range 300-773 K. This interaction results in the reduction of the catalyst and the production of oxygen-containing adsorbed species. These species have been

E. Finnocchio; G. Busca; V. Lorenzelli; R. J. Willey

1995-01-01

351

New acyclonucleosides: synthesis and anti-HIV activity.  

PubMed

The synthesis of new acyclic nucleosides is described. These syntheses were accomplished by various methods: glycosylation, selective or total deprotection, oxidation/reduction, chlorination or azidation of hydroxyl groups. The compounds were characterized with NMR, mass and IR spectroscopy. Antiviral properties of these compounds were evaluated on HIV-1 infected cell lines. PMID:16270666

Hadj-Bouazza, Amel; Zerrouki, Rachida; Krausz, Pierre; Laumond, Géraldine; Aubertin, Anne Marie; Champavier, Yves

2005-01-01

352

Synthesis of diamond on WC-Co substrates using a KrF excimer laser in combination with a combustion flame  

Microsoft Academic Search

A KrF excimer laser was used in combination with a combustion flame to deposit diamond films on cemented tungsten carbide (WC-Co) substrates. The laser has a wavelength of 248 nm, a pulse width of 23 ns, a pulse energy range of 84~450 mJ, and a repetition rate up to 50 Hz. Using the combustion flame method, diamond films were deposited

Y. X. Han; H. Ling; Y. F. Lu

2007-01-01

353

Bubble Combustion  

NASA Technical Reports Server (NTRS)

A method of energy production that is capable of low pollutant emissions is fundamental to one of the four pillars of NASA s Aeronautics Blueprint: Revolutionary Vehicles. Bubble combustion, a new engine technology currently being developed at Glenn Research Center promises to provide low emissions combustion in support of NASA s vision under the Emissions Element because it generates power, while minimizing the production of carbon dioxide (CO2) and nitrous oxides (NOx), both known to be Greenhouse gases. and allows the use of alternative fuels such as corn oil, low-grade fuels, and even used motor oil. Bubble combustion is analogous to the inverse of spray combustion: the difference between bubble and spray combustion is that spray combustion is spraying a liquid in to a gas to form droplets, whereas bubble combustion involves injecting a gas into a liquid to form gaseous bubbles. In bubble combustion, the process for the ignition of the bubbles takes place on a time scale of less than a nanosecond and begins with acoustic waves perturbing each bubble. This perturbation causes the local pressure to drop below the vapor pressure of the liquid thus producing cavitation in which the bubble diameter grows, and upon reversal of the oscillating pressure field, the bubble then collapses rapidly with the aid of the high surface tension forces acting on the wall of the bubble. The rapid and violent collapse causes the temperatures inside the bubbles to soar as a result of adiabatic heating. As the temperatures rise, the gaseous contents of the bubble ignite with the bubble itself serving as its own combustion chamber. After ignition, this is the time in the bubble s life cycle where power is generated, and CO2, and NOx among other species, are produced. However, the pollutants CO2 and NOx are absorbed into the surrounding liquid. The importance of bubble combustion is that it generates power using a simple and compact device. We conducted a parametric study using CAVCHEM, a computational model developed at Glenn, that simulates the cavitational collapse of a single bubble in a liquid (water) and the subsequent combustion of the gaseous contents inside the bubble. The model solves the time-dependent, compressible Navier-Stokes equations in one-dimension with finite-rate chemical kinetics using the CHEMKIN package. Specifically, parameters such as frequency, pressure, bubble radius, and the equivalence ratio were varied while examining their effect on the maximum temperature, radius, and chemical species. These studies indicate that the radius of the bubble is perhaps the most critical parameter governing bubble combustion dynamics and its efficiency. Based on the results of the parametric studies, we plan on conducting experiments to study the effect of ultrasonic perturbations on the bubble generation process with respect to the bubble radius and size distribution.

Corrigan, Jackie

2004-01-01

354

Biofuels combustion.  

PubMed

This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acids and used primarily to replace or supplement conventional diesel fuels. Research efforts on so-called second- and third-generation biofuels are discussed briefly. PMID:23298249

Westbrook, Charles K

2013-01-01

355

Synthesis and structure--activity relationships of aroylpyrrole alkylamide bradykinin (B2) antagonists.  

PubMed

The synthesis and structure-activity relationships of a novel series of aroylpyrrole alkylamides as potent selective bradykinin B(2) receptor antagonists are described. Several members of this series display nanomolar affinity at the B(2) receptor and show activity in an animal model of antinociception. PMID:12657278

Youngman, Mark A; Carson, John R; Lee, Jung S; Dax, Scott L; Zhang, Sui-Po; Colburn, Ray W; Stone, Dennis J; Codd, Ellen E; Jetter, Michele C

2003-04-01

356

Synthesis of New Hydrophilic and Hydrophobic Cobinamides as NO-Independent sGC Activators  

PubMed Central

Herein, the synthesis of novel hydrophobic and hydrophilic cobinamides via aminolysis of vitamin B12 derivatives that activate soluble guanyl cyclase (sGC) is presented. Unlike other sGC regulators, they target the catalytic domain of sGC and show higher activity than (CN)2Cbi.

2012-01-01

357

Synthesis of Various Water-Soluble C60 Derivatives and Their Superoxide-Quenching Activity  

Microsoft Academic Search

In order to examine the utility of fullerene as a medicinal application, we evaluated the reaction between fullerene derivatives and active oxygen species in vitro. This paper describes the synthesis of various water-soluble C60 derivatives (cationic and anionic) and evaluation of their superoxide (O2 ) quenching activity. Cationic C60 derivatives showed fairly high efficiency.

Kensuke Okuda; Takashi Hirota; Masaaki Hirobe; Tetsuo Nagano; Masataka Mochizuki; Tadahiko Mashino

2000-01-01

358

Compliant Walled Combustion Devices.  

National Technical Information Service (NTIS)

Combustion devices described herein comprise a compliant combustion chamber wall or segment. The compliant segment deforms during combustion in the combustion chamber. Some devices may include a compliant wall configured to stretch responsive to pressure ...

H. Prahlad J. Helm R. E. Pelrine S. Oh S. E. Stanford

2005-01-01

359

Synthesis and anti-microbial activities of choline-like quaternary ammonium chlorides.  

PubMed

New choline-like quaternary ammonium chlorides were obtained. The work-up procedure of synthesis was quick and efficient. The obtained chlorides showed anti-microbial activities. Quaternary ammonium chlorides derivatives of deanol esters exhibited strong activity and wide anti-bacterial spectra, similar to the activity of benzalkonium chloride. The relationship between chemical structure and anti-microbial activity was analyzed by the QSAR method. PMID:14642336

Pernak, Juliusz; Chwa?a, Przemys?aw

2003-01-01

360

Fluidized-bed combustion  

SciTech Connect

This report describes the activities of the Morgantown Energy Technology Center's research and development program in fluidized-bed combustion from October 1, 1987, to September 30, 1989. The Department of Energy program involves atmospheric and pressurized systems. Demonstrations of industrial-scale atmospheric systems are being completed, and smaller boilers are being explored. These systems include vortex, multi-solid, spouted, dual-sided, air-cooled, pulsed, and waste-fired fluidized-beds. Combustion of low-rank coal, components, and erosion are being studied. In pressurized combustion, first-generation, combined-cycle power plants are being tested, and second-generation, advanced-cycle systems are being designed and cost evaluated. Research in coal devolatilization, metal wastage, tube corrosion, and fluidization also supports this area. 52 refs., 24 figs., 3 tabs.

Botros, P E

1990-04-01

361

Synthesis and characterization of Gd{sup 3+} and Nd{sup 3+} co-doped ceria by using citric acid-nitrate combustion method  

SciTech Connect

A series of Ce{sub 0.8}Gd{sub 0.2-x}Nd{sub x}O{sub 2-{delta}} (x = 0-0.20) compositions have been synthesized by citric acid-nitrate combustion method. XRD measurements indicate that all the obtained materials crystallized in cubic fluorite-type structure. Lattice parameters were calculated by Rietveld method and the parameter a values in Ce{sub 0.8}Gd{sub 0.2-x}Nd{sub x}O{sub 2-{delta}} system obey Vegard's law, a (A) = 5.4224 + 0.1208x. The obtained powders have good sinterability and the relative density could reach above 95% after being sintered at 1400 {sup o}C. Impedance spectroscopy measurements indicated that the conductivity of Ce{sub 0.8}Gd{sub 0.2-x}Nd{sub x}O{sub 2-{delta}} first increased and then decreased with Nd dopant content x. The maximum conductivity, {sigma}{sub 700{sup o}C} = 6.26 x 10{sup -2} S/cm, was found in Ce{sub 0.8}Gd{sub 0.12}Nd{sub 0.08}O{sub 1.9} when sintered at 1300 {sup o}C. The corresponding activation energies of conduction had a minimum value E{sub a} = 0.676 eV. The results tested experimentally the validity of the effective atomic number concept of recent density functional theory, which had suggested that co-dopant with effective atomic number between 61 (Pm) and 62 (Sm) was the ideal dopant exhibiting high ionic conductivity and low activation energy.

Yao, Hong-Chang, E-mail: yaohongchang@zzu.edu.cn [Department of Chemistry, Zhengzhou University, Zhengzhou 450052 (China)] [Department of Chemistry, Zhengzhou University, Zhengzhou 450052 (China); Zhang, Yu-Xin [Department of Chemistry, Zhengzhou University, Zhengzhou 450052 (China) [Department of Chemistry, Zhengzhou University, Zhengzhou 450052 (China); Henan Vocational College of Chemical Technology, Zhengzhou 450052 (China); Liu, Jia-Jia; Li, Yue-Li; Wang, Jian-She; Li, Zhong-Jun [Department of Chemistry, Zhengzhou University, Zhengzhou 450052 (China)] [Department of Chemistry, Zhengzhou University, Zhengzhou 450052 (China)

2011-01-15

362

The effect of silicon powder characteristics on the combustion of silicon/Teflon/Viton nanoenergetics  

NASA Astrophysics Data System (ADS)

Due to its thin passivation layer, potentially good aging characteristics, and ease of surface functionalization nanoscale silicon (nSi) may offer some advantages over nanoaluminum as a reactive fuel in nanoenergetic compositions, particularly with fluorine-based oxidizers. Currently, Si nanopowder can be quite expensive and the quality of commercial powders has been found to vary drastically. As a result limited efforts have focused on the role specific surface area, active content, morphology, and dominant particle size of the powder have on the combustion performance. This work investigates the effect of such characteristics on the combustion of silicon (Si)/polytetrafluoroethylene (Teflon)/FC-2175 (Viton) (SiTV) nanoenergetics. A cost effective combustion synthesis route, salt assisted combustion synthesis, was used to produce several Si powders and these were directly compared to commercial nanoscale Si powders. Reactive mixtures of SiTV were burned at atmospheric conditions and burning rates, combustion temperatures, spectral intensities, and effective plume emissivities were measured. Measured combustion temperatures ranged from 1664 to 2380 K and were limited by Si powder active content. This was found to drive plume emissivity and maximum spectral intensity, which had values ranging from 0.10 to 0.55 for effective plume emissivity and 17.6 to 48.1 kW m -2-sr-1-mum-1 for maximum spectral intensity. Burning rates ranged from 0.7 to 3.4 mm s-1 and were found to be dependent on the dominant particle size of the powder. Powders synthesized with salt assisted combustion resulted in comparable burning rate, plume emissivity and maximum spectral intensity to commercial porous Si powder (Vesta Ceramics).

Terry, Brandon C.

363

Combustion Synthesis of Magnesium Aluminate  

Microsoft Academic Search

In the system MgO-Al2O3, three compounds MgAl2O4,MgAl6O10 (also expressed as- Mg0.4Al2.4O4) and MgAl26O40 are well known. Importance of the first two is well established. Magnesium aluminate (MgAl2O4) spinel is a technologically important material due to its interesting thermal properties. The MgAl2O4 ceramics also find application as humidity sensors. Apart from the luminescence studies, the interest in MgAl2O4 is due to

M. A. Kale; C. P. Joshi; S. V. Moharil

2011-01-01

364

Combustion Synthesis of Magnesium Aluminate  

Microsoft Academic Search

In the system MgO-Al2O3, three compounds MgAl2O4, MgAl6O10 (also expressed as- Mg0.4Al2.4O4) and MgAl26O40 are well known. Importance of the first two is well established. Magnesium aluminate (MgAl2O4) spinel is a technologically important material due to its interesting thermal properties. The MgAl2O4 ceramics also find application as humidity sensors. Apart from the luminescence studies, the interest in MgAl2O4 is due

M. A. Kale; C. P. Joshi; S. V. Moharil

2011-01-01

365

Synthesis and biological activity of enantiomers of antitumor irofulven.  

PubMed

Stereoselective synthesis of (-)-irofulven has been achieved by cycloaddition of (R)-5-chloro-5-methyl-2-cyclopentenone to the 1,3-dipolar intermediate from 1-acetyl-1-(diazoacetyl)cyclopropane. The enantiomer, (+)-irofulven, was prepared in a similar way starting with (S)-5-chloro-5-methyl-2-cyclopentenone. (+)-Irofulven was 5 to 6 times less toxic than (-)-irofulven to adenocarcinoma (MV 522) cells. PMID:14750783

McMorris, Trevor C; Staake, Michael D; Kelner, Michael J

2004-02-01

366

Silver nanoparticles: Green synthesis and their antimicrobial activities  

Microsoft Academic Search

This review presents an overview of silver nanoparticles (Ag NPs) preparation by green synthesis approaches that have advantages over conventional methods involving chemical agents associated with environmental toxicity. Green synthetic methods include mixed-valence polyoxometallates, polysaccharide, Tollens, irradiation, and biological. The mixed-valence polyoxometallates method was carried out in water, an environmentally-friendly solvent. Solutions of AgNO3 containing glucose and starch in water

Virender K. Sharma; Ria A. Yngard; Yekaterina Lin

2009-01-01

367

Second progress report of the DARPA dynamic synthesis and consolidation program  

SciTech Connect

The program activities include dynamic compaction, shock activation and combustion and plasma synthesis. The primary materials under study are the compounds AlN, Al/sub 2/O/sub 3/, TiC and TiB/sub 2/.

Cline, C.F. (ed.)

1983-03-01

368

Sodium tungstate activates glycogen synthesis through a non-canonical mechanism involving G-proteins.  

PubMed

Tungstate treatment ameliorates experimental diabetes by increasing liver glycogen deposition through an as yet unidentified mechanism. The signalling mechanism of tungstate was studied in CHOIR cells and primary cultured hepatocytes. This compound exerted its pro-glycogenic effects through a new G-protein-dependent and Tyr-Kinase Receptor-independent mechanism. Chemical or genetic disruption of G-protein signalling prevented the activation of the Ras/ERK cascade and the downstream induction of glycogen synthesis caused by tungstate. Thus, these findings unveil a novel non-canonical signalling pathway that leads to the activation of glycogen synthesis and that could be exploited as an approach to treat diabetes. PMID:23260418

Zafra, Delia; Nocito, Laura; Domínguez, Jorge; Guinovart, Joan J

2013-01-31

369

Design, diversity-oriented synthesis and structure activity relationship studies of quinolinyl heterocycles as antimycobacterial agents.  

PubMed

The current study reports design and diversity oriented synthesis of novel bis heterocycles with a common 2-methyl, C-4 unsubstituted quinoline moiety as the central key heterocycle. Employing reagent based skeletal diversity approach; a facile synthesis of bis heterocycles with different heterocyclic rings at C-3 position of the quinoline moiety has been accomplished. A broad range of heterocyclic frameworks thus obtained were evaluated for their antimycobacterial activity. The active scaffolds were further explored by a parallel library generation in order to establish SAR. Further, low cytotoxicity against A549 cell line enhances the potential of the synthesized molecules as promising antimycobacterial agents. PMID:24189497

Rachakonda, Venkatesham; Alla, Manjula; Kotipalli, Sudha Sravanti; Ummani, Ramesh

2013-12-01

370

Cobalt Molybdenum Oxynitrides: Synthesis, Structural, Characterization, and Catalytic Activity for the Oxygen Reduction Reaction  

SciTech Connect

Here, we report the synthesis and characterization of CoxMo1 xOyNz compounds supported on carbon black as potential cathode catalysts for ORR. They were prepared by a conventional impregnation method. Their ORR activities in both acid and alkaline electrolytes were evaluated via half-cell measurements. The synthesis temperature and sample composition both strongly impacted their physical and chemical properties. Factors influencing their crystal structures, morphologies and ORR activities will be discussed based on the results of structural and spectroscopic studies.

Cao, Bingfei [ORNL; Veith, Gabriel M [ORNL; Diaz, Rosa [Brookhaven National Laboratory (BNL); Liu, Jue [State University of New York, Stony Brook; Stach, Eric [Brookhaven National Laboratory (BNL); Adzic, Radoslav R. [Brookhaven National Laboratory (BNL); Khalifah, P. [Stony Brook University (SUNY)

2013-01-01

371

Altered cytokine activities are related to the suppression of synthesis of normal immunoglobulin in multiple myeloma.  

PubMed

The content of peripheral blood B cells (B1+) was reduced in patients of multiple myeloma (MM) and not in those with benign monoclonal gammopathy (BMG) compared to normal donors (P less than 0.01). This observation correlated with the suppression of synthesis of normal immunoglobulin (Ig) in MM. Thus, cytokine activities regulating the proliferation of normal mature B cells, such as B cell stimulatory factor 1 (BSF-1)/interleukin 4 (IL-4), B cell growth inhibitory factor (BIF) and IL-2 in peripheral blood T cells, and IL-1 in peripheral blood adherent cells, were investigated in patients with BMG (n = 7) and MM (n = 28). All patients of MM having a marked suppression of synthesis of all other normal Ig, had significantly lower levels of BSF-1 activity and inversely higher levels of BIF activity than those of normal donors. However, patients with BMG having no suppression of synthesis of normal Ig had BSF-1 and BIF activities similar to normal donors. There was no significant difference in IL-1 and IL-2 activities between both normal donors and BMG versus MM patients. These data show that in MM altered cytokine activities correlate with suppression of synthesis of normal Ig. PMID:2643860

Kawano, M; Iwato, K; Asaoku, H; Tanabe, O; Tanaka, H; Ishikawa, H; Kuramoto, A

1989-02-01

372

Smoldering Combustion Experiments in Microgravity  

NASA Technical Reports Server (NTRS)

The Microgravity Smoldering Combustion (MSC) experiment is part of a study of the smolder characteristics of porous combustible materials in a microgravity environment. Smoldering is a non-flaming form of combustion that takes place in the interior of porous materials and takes place in a number of processes ranging from smoldering of porous insulation materials to high temperature synthesis of metals. The objective of the study is to provide a better understanding of the controlling mechanisms of smolder, both in microgravity and normal-gravity. As with many forms of combustion, gravity affects the availability of oxidizer and transport of heat, and therefore the rate of combustion. Microgravity smolder experiments, in both a quiescent oxidizing environment, and in a forced oxidizing flow have been conducted aboard the NASA Space Shuttle (STS-69 and STS-77 missions) to determine the effect of the ambient oxygen concentration and oxidizer forced flow velocity on smolder combustion in microgravity. The experimental apparatus is contained within the NASA Get Away Special Canister (GAS-CAN) Payload. These two sets of experiments investigate the propagation of smolder along the polyurethane foam sample under both diffusion driven and forced flow driven smoldering. The results of the microgravity experiments are compared with identical ones carried out in normal gravity, and are used to verify present theories of smolder combustion. The results of this study will provide new insights into the smoldering combustion process. Thermocouple histories show that the microgravity smolder reaction temperatures (Ts) and propagation velocities (Us) lie between those of identical normal-gravity upward and downward tests. These observations indicate the effect of buoyancy on the transport of oxidizer to the reaction front.

Walther, David C.; Fernandez-Pello, A. Carlos; Urban, David L.

1997-01-01

373

Bimetallic Fe-Ni Oxygen Carriers for Chemical Looping Combustion  

SciTech Connect

The relative abundance, low cost, and low toxicity of iron make Fe-based oxygen carriers of great interest for chemical looping combustion (CLC), an emerging technology for clean and efficient combustion of fossil and renewable fuels. However, Fe also shows much lower reactivity than other metals (such as Ni and Cu). Here, we demonstrate strong improvement of Fe-based carriers by alloying the metal phase with Ni. Through a combination of carrier synthesis and characterization with thermogravimetric and fixed-bed reactor studies, we demonstrate that the addition of Ni results in a significant enhancement in activity as well as an increase in selectivity for total oxidation. Furthermore, comparing alumina and ceria as support materials highlights the fact that reducible supports can result in a strong increase in oxygen carrier utilization.

Bhavsar, Saurabh; Veser, Goetz

2013-11-06

374

Solidphase synthesis of kojic acid-tripeptides and their tyrosinase inhibitory activity, storage stability, and toxicity  

Microsoft Academic Search

A small library of kojic acid-tripeptides (Ko-X1X2X3) was prepared by solid-phase parallel synthesis and assayed to evaluate their tyrosinase inhibitory activity. Most of the kojic acid-tripeptides showed better activities than kojic acid. Kojic acid-FWY was the best compound, and it exhibited 100-fold tyrosinase inhibitory activity compared with kojic acid. In addition, their storage stabilities were approximately 15 times higher and

Hanyoung Kim; Jaehui Choi; Jin Ku Cho; Sun Yeou Kim; Yoon-Sik Lee

2004-01-01

375

Observation of nonuniform shrinkage and activation of highly porous chars during combustion in an improved electrodynamic chamber  

Microsoft Academic Search

Combustion of single particles of highly porous synthetic char has been investigated in an electrodynamic chamber (EDC). The main reasons for using the EDC for studying high temperature kinetics of single particles are to (1) sustain the particle without moving at all times at a known point, (2) eliminate heat and mass transfer limitations, (3) observe particle-to-particle differences, (4) fully

Yony Weiss; Ezra Bar-Ziv

1995-01-01

376

Global emissions of hydrogen chloride and chloromethane from coal combustion, incineration and industrial activities: Reactive Chlorine Emissions Inventory  

Microsoft Academic Search

Much if not all of the chlorine present in fossil fuels is released into the atmosphere as hydrogen chloride (HCl) and chloromethane (CH3Cl, methyl chloride). The chlorine content of oil-based fuels is so low that these sources can be neglected, but coal combustion provides significant releases. On the basis of national statistics for the quantity and quality of coal burned

Archie McCulloch; Michael L. Aucott; Carmen M. Benkovitz; Thomas E. Graedel; Gary Kleiman; Pauline M. Midgley; Yi-Fan Li

1999-01-01

377

Method for the production of synthesis gas  

SciTech Connect

A method is claimed for the continuous production of synthesis gas comprising of carbon monoxide and hydrogen through the autothermal gasification of solid combustibles in a pressure reactor. The method involves the following: introducing into a screw machine containing two parallely ordered shafts, a finely divided solid combustible; moistening and intimately mixing the solid combustible with 2 to 30% by weight of water, degasing and compressing the moist solid combustible to a pressure higher than that of the reactor; adding the gas-tight compressed and moist solid combustible to a reaction chamber-through a burner where the combustible is brought into contact with the gasification medium; evaporating the water in the compressed and moist solid combustible and producing a comminuted dispersion of the solid combustible in the mixture of the gasification medium and water vapor; reacting the combustible dispersion to give a raw synthesis gas; and removing the raw synthesis gas from the reactor.

Escher, G.; Harjung, J.; Wenning, H.P.

1981-11-24

378

Microwave-induced combustion synthesis and electrical conductivity of Ce 1? x Gd x O 2?1\\/2 x ceramics  

Microsoft Academic Search

Ce1?xGdxO2?1\\/2x nanopowder were successfully synthesized by microwave-induced combustion process. For the preparation, cerium nitrate, gadolinium nitrate hexahydrate, and urea were used for the microwave-induced combustion process. The process took only 30min to obtain Ce1?xGdxO2?1\\/2x powders. The exo-endo temperature, phase identification, and morphology of resultant powders were investigated by TG\\/DTA, XRD, and SEM. The as-received Ce1?xGdxO2?1\\/2x powders showed that the average

Yen-Pei Fu; Yen-Shao Chang; Shaw-Bing Wen

2006-01-01

379

Microwave-induced combustion synthesis and electrical conductivity of Ce{sub 1-x}Gd âOâââ2x} ceramics  

Microsoft Academic Search

Ce{sub 1-x}Gd âOâââ2x} nanopowder were successfully synthesized by microwave-induced combustion process. For the preparation, cerium nitrate, gadolinium nitrate hexahydrate, and urea were used for the microwave-induced combustion process. The process took only 30 min to obtain Ce{sub 1-x}Gd âOâââ2x} powders. The exo-endo temperature, phase identification, and morphology of resultant powders were investigated by TG\\/DTA, XRD, and SEM. The as-received Ce{sub

Y.-P.. Fu; Y.-S. Chang; S.-B. Wen

2006-01-01

380

Synthesis and removal of phenylalanine ammonia-lyase activity in illuminated discs of potato tuber parenchyme.  

PubMed

(1) The synthesis and removal of phenylalanine ammonia-lyase (EC 4.3.1.5) in illuminated discs of potato (Solanum tuberosum cv King Edward) tuber tissue has been investigated by density labelling with deuterium (2H) from deuterium oxide (2H2O) followed by centrifugation to equilibrium in a CsC1 density gradient. (2) Temporal changes in enzyme level have been described in terms of the equation (dE/dt) = ks-kdE where (dE/dt) is the rate of change of enzyme level per unit of tissue (E) with respect to time (t), ks is the rate constant for synthesis of the enzyme and kd is the rate constant for the removal of active enzyme. (3) The optimal concentration of 2H2O was determined by analysis of the relationship between 2H2O concentration, development of enzyme activity and the magnitude of the increase in buoyant density of phenylalanine ammonia-lyase. A concentration of 2H2O of about 40% (v/v) was found to be optimal, allowing achievement of maximal or near maximal increases in the buoyant density of the enzyme without inhibition of the development of enzyme activity, thereby circumventing the major drawback of 2H2O as a source of density label. (4) The overlapping distribution profiles of enzyme activity after density gradient centrifugation were resolved by an iterative method of best fit which allows estimation of the proportions of pre-existing, unlabelled enzyme and newly synthesised, labelled enzyme at the end of the labelling period. This technique has been developed to obtain the rate constants for enzyme synthesis and for removal of active enzyme throughout the period of rapid change in enzyme level. (5) It is demonstrated that the initial rapid increase in phenylalanine ammonia-lyase activity in illuminated discs reflects an increase in the rate constant for enzyme synthesis in the absence of activation of pre-existing enzyme and in the absence of removal of active enzyme. The abrupt transition to a phase of decline in enzyme activity is caused by (a) a reduction in the rate constant for enzyme synthesis and (b) a dramatic increase in the rate constant for removal of active enzyme. The subsequent stabilisation of the enzyme is caused by decay of both rate constants to relatively low levels. (6) The results are consistent with hypothesis that rapid modulation of enzyme levels during tissue differentiation is achieved by simultaneous changesin the rate constants for both enzyme synthesis and for removal of active enzyme. PMID:760822

Lamb, C J; Merritt, T K; Butt, V S

1979-01-18

381

Salt-assistant combustion synthesis of nanocrystalline Nd{sub 2}(Zr{sub 1-x}Sn{sub x}){sub 2}O{sub 7} (0 {<=} x {<=} 1) solid solutions  

SciTech Connect

Nanocrystalline Nd{sub 2}(Zr{sub 1-x}Sn{sub x}){sub 2}O{sub 7} series solid solutions were prepared by a convenient salt-assisted combustion process using glycine as fuel. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The results showed the Zr ion can be partially replaced by Sn ion. The partial substituted products were still single-phase solid solutions and the crystal form remained unchanged. TEM images reveal that the products are composed of well-dispersed square-shaped nanocrystals. The method provides a convenient and low-cost route for the synthesis of nanostructures of oxide materials.

Tong Yuping, E-mail: huabeitong@yahoo.cn [School of Civil Engineering and Communication, North China Institute of Water Conservancy and Hydroelectric Power, Zhengzhou 450011 (China); Wang Yanping [College of Mechanical Engineering and Automation, Zhejiang Sci-Tech University, Hangzhou 310018 (China)

2009-11-15

382

Design, synthesis and antiproliferative activity of styryl lactones related to (+)-goniofufurone  

Microsoft Academic Search

This paper describes a straightforward divergent synthesis of (+)-goniofufurone mimics (4, 5 and 6) starting from d-xylose. In a preliminary bioassay, analogues 4 and 5 exhibited a submicromolar antiproliferative activity towards HL-60 cells, while the corresponding parent compound 1 was completely inactive against this cell line. At the same time, these molecules showed approximately 10-fold stronger cytotoxicity in the same

Velimir Popsavin; Bojana Sre?o; Goran Benedekovi?; Jovana Francuz; Mirjana Popsavin; Vesna Koji?; Gordana Bogdanovi?

2010-01-01

383

Total synthesis and antihypertensive activity of (±)7,8-dihydroxy-3-methyl-isochromanone-4  

Microsoft Academic Search

This letter describes the total synthesis, preliminary biological evaluation and mechanism studies of a novel and structurally unique isochromanone, (±)7,8-dihydroxy-3-methyl-isochromanone-4 (1), a nature product contained in banana (Musa sapientum L.) peel. The bioassay showed that compound 1 displays potent antihypertensive activity in renal hypertensive rats and further mechanism studies revealed that it is an ACE inhibitor.

Jie Liu; Hao Ren; Jinyi Xu; Renren Bai; Qi Yan; Wenlong Huang; Xiaoming Wu; Jihua Fu; Qiujuan Wang; Qian Wu; Rong Fu

2009-01-01

384

The Respiratory Syncytial Virus Polymerase Has Multiple RNA Synthesis Activities at the Promoter  

PubMed Central

Respiratory syncytial virus (RSV) is an RNA virus in the Family Paramyxoviridae. Here, the activities performed by the RSV polymerase when it encounters the viral antigenomic promoter were examined. RSV RNA synthesis was reconstituted in vitro using recombinant, isolated polymerase and an RNA oligonucleotide template representing nucleotides 1–25 of the trailer complement (TrC) promoter. The RSV polymerase was found to have two RNA synthesis activities, initiating RNA synthesis from the +3 site on the promoter, and adding a specific sequence of nucleotides to the 3? end of the TrC RNA using a back-priming mechanism. Examination of viral RNA isolated from RSV infected cells identified RNAs initiated at the +3 site on the TrC promoter, in addition to the expected +1 site, and showed that a significant proportion of antigenome RNAs contained specific nucleotide additions at the 3? end, demonstrating that the observations made in vitro reflected events that occur during RSV infection. Analysis of the impact of the 3? terminal extension on promoter activity indicated that it can inhibit RNA synthesis initiation. These findings indicate that RSV polymerase-promoter interactions are more complex than previously thought and suggest that there might be sophisticated mechanisms for regulating promoter activity during infection.

Tremaglio, Chadene Z.; Fearns, Rachel

2012-01-01

385

Synthesis of conformationally locked carbocyclic nucleoside phosphonates to probe the active site of HIV-1 RT  

PubMed Central

The conformationally locked carbocyclic nucleoside phosphonates 2 and 2? and key intermediates for the synthesis of 3 and 3? were prepared from a chiral cyclopentene derivative and epicholorohydrine, respectively. The structure of the nucleoside precursor 6 was confirmed by X-ray crystallography. These carbocyclic nucleoside phosphonates were designed to probe their binding interactions at the active site of HIV-1-RT.

Saneyoshi, Hisao; Vu, B. Christie; Hughes, Stephen H.; Boyer, Paul L.; Sarafianos, Stefan G.; Marquez, Victor E.

2009-01-01

386

Localization of epidermal sphingolipid synthesis and serine palmitoyl transferase activity: alterations imposed by permeability barrier requirements  

Microsoft Academic Search

Sphingolipids, the predominant lipid species in mammalian stratum corneum play, a central role in permeability barrier homeostatis. Prior studies have shown that the epidermis synthesizes abundant sphingolipids, a process regulated by barrier requirements, and that inhibition of sphingolipid synthesis interferes with barrier homeostasis. To investigate further the relationship between epidermal sphingolipid metabolism and barrier function, we localized sphingolipid synthetic activity

W. M. Holleran; W. N. Gao; K. R. Feingold; P. M. Elias

1995-01-01

387

Synthesis of Ureido-Muraymycidine Derivatives for Structure Activity Relationship Studies of Muraymycins  

PubMed Central

One of the key constituents of the muraymycins is the 6-membered cyclic guanidine, (2S,3S)-muraymycidine (or epi-capreomycidine). In order to diversify the structure of the oligo-peptide moiety of the muraymycins for thorough structure activity relationship studies, we have developed a highly stereoselective synthesis of ureido-muraymycidine derivatives with the lactone 4a.

Aleiwi, Bilal A.; Schneider, Christopher M.

2012-01-01

388

Synthesis and structure-activity relationship of benzetimide derivatives as human CXCR3 antagonists.  

PubMed

The synthesis and evaluation of benzetimide derivatives showing potent CXCR3 antagonism are described. Optimization of the screening hits led to the identification of more potent CXCR3 antagonists devoid of anti-cholinergic activity and identification of the key pharmacophore moieties of the series. PMID:18922694

Bongartz, Jean-Pierre; Buntinx, Mieke; Coesemans, Erwin; Hermans, Bart; Lommen, Guy Van; Wauwe, Jean Van

2008-11-01

389

Synthesis and structure–activity relationship of benzetimide derivatives as human CXCR3 antagonists  

Microsoft Academic Search

The synthesis and evaluation of benzetimide derivatives showing potent CXCR3 antagonism are described. Optimization of the screening hits led to the identification of more potent CXCR3 antagonists devoid of anti-cholinergic activity and identification of the key pharmacophore moieties of the series.

Jean-Pierre Bongartz; Mieke Buntinx; Erwin Coesemans; Bart Hermans; Guy Van Lommen; Jean Van Wauwe

2008-01-01

390

Total Synthesis and Absolute Configuration of Laurenditerpenol: A Hypoxia Inducible Factor-1 Activation Inhibitor  

PubMed Central

The absolute stereo structure of the natural product laurenditerpenol (1S, 6R, 7S, 10R, 11R, 14S, 15R) has been accomplished from eight plausible stereoisomers by its first asymmetric total synthesis in a highly convergent and flexible synthetic pathway. Six stereoisomers of laurenditerpenol were synthesized and evaluated for their biological activity.

Chittiboyina, Amar G.; Kumar, Gundluru Mahesh; Carvalho, Paulo B.; Liu, Yang; Zhou, Yu-Dong; Nagle, Dale G.

2010-01-01

391

Peptide deformylase inhibitors with non-peptide scaffold: synthesis and structure-activity relationships.  

PubMed

Peptide deformylase (PDF), which removes the formyl group at the N-terminal methionine residue of nascent protein, has been recognized as a potent target for antibacterial therapy. We report herein the synthesis and structure-activity relationship studies of non-peptide PDF inhibitors. PMID:21146987

Lee, Seung Kyu; Choi, Kwang Hyun; Lee, Sang Jae; Lee, Jong Sun; Park, Ji Yun; Kim, B Moon; Lee, Bong Jin

2011-01-01

392

Total Synthesis and Structure-Activity Relationship of Glycoglycerolipids from Marine Organisms  

PubMed Central

Glycoglycerolipids occur widely in natural products, especially in the marine species. Glycoglycerolipids have been shown to possess a variety of bioactivities. This paper will review the different methodologies and strategies for the synthesis of biological glycoglycerolipids and their analogs for bioactivity assay. In addition, the bioactivities and structure-activity relationship of the glycoglycerolipids are also briefly outlined.

Zhang, Jun; Li, Chunxia; Yu, Guangli; Guan, Huashi

2014-01-01

393

Total synthesis of the cyanobacterial metabolite nostodione A: discovery of its antiparasitic activity against Toxoplasma gondii.  

PubMed

A total synthesis of the cyanobacterial natural product nostodione A is reported involving a convergent, diversity-oriented route. A small assemblage of structural analogues were prepared and their cytotoxicity and anti-invasion activity against the protozoal parasite Toxoplasma gondii is reported for the first time. PMID:24970332

McNulty, J; Keskar, K; Bordón, C; Yolken, R; Jones-Brando, L

2014-07-15

394

Synthesis of andrographolide derivatives and their TNF-? and IL6 expression inhibitory activities  

Microsoft Academic Search

The synthesis of a series of andrographolide derivatives was described and their inhibitory effects on TNF-? and IL-6 secretion in mouse macrophages were also evaluated. Most of the tested compounds showed inhibitory effects, and the compounds with the structure of 12-hydroxy-14-dehydroandrographolide showed better inhibitory activity than the compounds with the structure of isoandrographolide.

Jing Li; Wenlong Huang; Huibin Zhang; Xinyang Wang; Huiping Zhou

2007-01-01

395

Catalyst Activity Maintenance for the Liquid Phase Synthesis Gas-to-Dimethyl Ether Process.  

National Technical Information Service (NTIS)

At the heart of the single-step liquid phase syngas-to-DME process (LPDME) is a catalyst system that can be active as well as stable. In the Alternative Fuels I program, a dual-catalyst system containing a Cu-based commercial methanol synthesis catalyst (...

X. D. Peng

2002-01-01

396

Synthesis, receptor binding and activity of iso and azakainoids  

PubMed Central

Two syntheses for the production of an unsubstituted azakainoid are described. The 1,3-dipolar cycloaddition of diazomethane with trans-dibenzyl glutaconate yields a 1-pyrazoline, which may be reduced directly to the pyrazolidine. An unexpected trans-cis isomerization is observed during Hg/Al reduction of the 1-pyrazoline N=N bond. Alternatively, when TMS diazomethane is used as the dipole, the resulting 2-pyrazoline obtained after desilylation may be reduced with NaCNBH3 to provide the trans azakainate analog exclusively. The synthesis of an unsubstituted isokainoid via Michael addition is also described. Glutamate receptor binding assays revealed that the azakaniod has a moderate affinity for unspecified glutamate receptors. Membrane depolarization of Aplysia neurons upon application of the azakainoid demonstrates that it is an ionotropic glutamate receptor agonist.

Wang, Wentian; Simovic, Dragan D.; Di, Mingping; Fieber, Lynne; Rein, Kathleen S.

2013-01-01

397

Plant oligoadenylates: enzymatic synthesis, isolation, and biological activities.  

PubMed

An enzyme that converts [3H, 32P]ATP, with a 3H:32P ratio of 1:1, to oligoadenylates with the same 3H:32P ratio was increased in plants following treatment with human leukocyte interferon or plant antiviral factor or inoculation with tobacco mosaic virus. The enzyme was extracted from tobacco leaves, callus tissue cultures, or cell suspension cultures. The enzyme, a putative plant oligoadenylate synthetase, was immobilized on poly(rI) . poly(rC)-agarose columns and converted ATP into plant oligoadenylates. These oligoadenylates were displaced from DEAE-cellulose columns with 350 mM KCl buffer, dialyzed, and further purified by high-performance liquid chromatography (HPLC) and DEAE-cellulose gradient chromatography. In all steps of purification, the ratio of 3H:32P in the oligoadenylates remained 1:1. The plant oligoadenylates isolated by displacement with 350 mM KCl had a molecular weight greater than 1000. The plant oligoadenylates had charges of 5- and 6-. HPLC resolved five peaks, three of which inhibited protein synthesis in reticulocyte and wheat germ systems. Partial structural elucidation of the plant oligoadenylates has been determined by enzymatic and chemical treatments. An adenylate with a 3',5'-phosphodiester and/or a pyrophosphoryl linkage with either 3'- or 5'-terminal phosphates is postulated on the basis of treatment of the oligoadenylates with T2 RNase, snake venom phosphodiesterase, and bacterial alkaline phosphatase and acid and alkaline hydrolyses. The plant oligoadenylates at 8 X 10(-7) M inhibit protein synthesis by 75% in lysates from rabbit reticulocytes and 45% in wheat germ cell-free systems.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3994978

Devash, Y; Reichman, M; Sela, I; Reichenbach, N L; Suhadolnik, R J

1985-01-29

398

Developing novel organocatalyzed aldol reactions for the enantioselective synthesis of biologically active molecules  

PubMed Central

Aldol reaction is one of the most important methods for the formation of carbon-carbon bonds. Because of its significance and usefulness, asymmetric versions of this reaction have been realized with different approaches in the past. Over the last decade, the area of organocatalysis has made significant progresses. As one of most studied reactions in organocatalyses, organocatalyzed aldol reaction has emerged as a powerful tool for the synthesis of a large number of useful products in optically enriched forms. In this review, we summarize our efforts on the development of novel organocatalyzed aldol reactions for the enantioselective synthesis of biological active molecules. Literatures closely related to our studies are also covered.

Bhanushali, Mayur; Zhao, Cong-Gui

2011-01-01

399

Studies on the synthesis of terbium-activated gadolinium oxysulphide phosphors  

NASA Astrophysics Data System (ADS)

Terbium activated gadolinium oxysulphide phosphor (Gd2O2S: Tb) shows bright green luminescence and high efficiency under X-ray excitation. Phosphor utilization depends on powder characteristics and luminescent properties that are regulated during the synthesis stage. The paper prsents some of our results referring to the synthesis of Gd2O2S: Tb phosphor by solid state reaction route, from oxide precursors. The influence of flux composition and amount as well as the sulphide supplier concentration on phosphor properties was investigated in order to prepare efficient luminescent powders for the manufacture of X-ray intensifying screens for medical diagnosis.

Muresan, Laura; Popovici, Elisabeth-Jeanne; Hristea, Amalia; Indrea, Emil; Vasilescu, Marilena

2004-10-01

400

Synthesis of a Benzodiazepine-derived Rhodium NHC Complex by C-H Bond Activation  

SciTech Connect

The synthesis and characterization of a Rh(I)-NHC complex generated by C-H activation of 1,4-benzodiazepine heterocycle are reported. This complex constitutes a rare example of a carbene tautomer of a 1,4-benzodiazepine aldimine stabilized by transition metal coordination and demonstrates the ability of the catalytically relevant RhCl(PCy{sub 3}){sub 2} fragment to induce NHC-forming tautomerization of heterocycles possessing a single carbene-stabilizing heteroatom. Implications for the synthesis of benzodiazepines and related pharmacophores via C-H functionalization are discussed.

Bergman, Roberg G.; Gribble, Jr., Michael W.; Ellman, Jonathan A.

2008-01-30

401

Green synthesis, characterization and catalytic activity of palladium nanoparticles by xanthan gum  

NASA Astrophysics Data System (ADS)

Here, we report the synthesis, characterization and catalytic evaluation of palladium nanoparticles (PdNPs) using xanthan gum, acting as both reducing and stabilizing agent without using any synthetic reagent. The uniqueness of our method lies in its fast synthesis rates using hydrothermal method in autoclave at a pressure of 15 psi and at 120 °C temperature by 10 min time. The formation and size of the PdNPs were characterized by UV-visible spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. The catalytic activity of PdNPs was evaluated on the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride using spectrophotometry.

Santoshi kumari, Amrutham; Venkatesham, Maragoni; Ayodhya, Dasari; Veerabhadram, Guttena

2014-05-01

402

Microwave-assisted synthesis of new benzimidazole derivatives with lipase inhibition activity.  

PubMed

A practical protocol has been used for the synthesis of benzimidazoles. The reaction of iminoester hydrochlorides of phenylacetic with 4,5-dichloro-1,2-phenylenediamine under microwave irradiation leads to the benzimidazole derivatives with good yields and in short reaction times. After the synthesis of benzimidazoles, we synthesized ester and hydrazide derivatives under microwave irradiation with good yields. All compounds were evaluated with regard to pancreatic lipase activity and 3b, 3c, 5a and 6a showed lipase inhibition at various concentrations. PMID:23327641

Mente?e, Emre; Bekta?, Hakan; Ülker, Serdar; Bekircan, Olcay; Kahveci, Bahittin

2014-02-01

403

Synthesis and diuretic activity of bicyclic fused heterocycles containing oxime-O-sulfonic acid moiety.  

PubMed

In order to investigate the origin of the loop-type diuretic activity of M17055 (1), several variants (3-9) were designed and synthesized by modifying the quinolinone skeleton, and their diuretic activities were compared with the lead 1 and furosemide in dogs. It was found that the negative charge distribution pattern afforded by the dispositional arrangement of the 4-oxime-O-sulfonic acid and 1-N-acyl carbonyl moiety attached to the tetrahydropyridine ring system is inevitable for the development of the activity, which strongly supports the previously proposed model for the active site of the Na(+)-K(+)-2Cl(-) cotransporter. Also reported is the first synthesis of the dihydrothieno[3,2-b]pyridine-7(4H)-one ring system required in the synthesis of compound 9. PMID:10758284

Nishijima, K; Nishida, H; Yamashita, Y; Ito, M; Onuki, Y; Mizota, M; Miyano, S

2000-02-01

404

Total synthesis of syringolin?a and improvement of its biological activity.  

PubMed

The development process for syringolin?A analogues having improved proteasome inhibitory and antitumor activity is described. The strategy was to first establish a convergent synthesis of syringolin?A using a rare intramolecular Ugi three-component reaction in the last stage of the synthesis, so as to gain access toa set of structure-based analogues. The inhibitory activity of chymotrypsin-like activity of 20S proteasome was largely improved by targeting the S3?subsite of the ?5 subunit. Cytotoxic activity was also improved by installing the membrane-permeable substituent. These biological properties are comparable to those of bortezomib, a clinically used first-line proteasome inhibitor. PMID:24668894

Chiba, Takuya; Hosono, Hidetaka; Nakagawa, Koji; Asaka, Masahiro; Takeda, Hiroshi; Matsuda, Akira; Ichikawa, Satoshi

2014-05-01

405

Synthesis and antibacterial activity of 9-substituted minocycline derivatives.  

PubMed

A number of 9-acylamino and 9-sulfonylamino derivatives of minocycline have been synthesized for structure-activity relationship studies. These compounds showed activity against both tetracycline-susceptible and tetracycline-resistant strains. Many of the 9-sulfonylamino derivatives exhibited improved antibacterial activity against a number of tetracycline- and minocycline-resistant Gram-positive pathogens. PMID:16246559

Sum, Phaik-Eng; Ross, Adma T; Petersen, Peter J; Testa, Raymond T

2006-01-15

406

Synthesis and hydroxyl radicals scavenging activity of quaternized carboxymethyl chitosan  

Microsoft Academic Search

In order to determine the effect of the forms of the amido groups of chitosan on antioxidant activity, quaternized carboxymethyl chitosan (QCMC) derivatives were prepared with a degree of quaternization ranging from 34.3% to 59.5%. The antioxidant activity of QCMCs against hydroxyl radicals was assessed. The results indicated that QCMCs have better hydroxyl radicals scavenging activity than that of carboxymethyl

Zhanyong Guo; Ronge Xing; Song Liu; Zhimei Zhong; Pengcheng Li

2008-01-01

407

Synthesis and antimicrobial activity of ?-aminoboronic-containing peptidomimetics.  

PubMed

A library of 175 dipeptidomimetics and tripeptidomimetics containing an ?-amino boronic acid or boronate has been synthesized, and the activity toward Mycobacterium tuberculosis, Candida albicans, Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli and Pseudomonas aeruginosa has been screened. Although there is no clear structure-activity relationship, several compounds exhibit promising activity against different pathogens. PMID:24222512

Gozhina, Olga V; Svendsen, John Sigurd; Lejon, Tore

2014-01-01

408

Total Synthesis of GEX1Q1, Assignment of C-5 Stereoconfiguration and Evaluation of Spliceosome Inhibitory Activity.  

PubMed

An enantioselective total synthesis of GEX1Q1 has been accomplished in a convergent manner. The C-5 asymmetric center has now been assigned through synthesis. GEX1Q1 displayed slightly better spliceosome inhibitory activity over its C-5 epimer. The salient features of this synthesis include an asymmetric hetero-Diels-Alder reaction to construct the tetrahydropyran ring and a Suzuki cross-coupling to assemble the key segments. PMID:24869489

Ghosh, Arun K; Ma, Nianchun; Effenberger, Kerstin A; Jurica, Melissa S

2014-06-01

409

Study of the kinetic parameters for synthesis and hydrolysis of pharmacologically active salicin isomer catalyzed by baker's yeast maltase  

NASA Astrophysics Data System (ADS)

One of the key elements for understanding enzyme reactions is determination of its kinetic parameters. Since transglucosylation is kinetically controlled reaction, besides the reaction of synthesis, very important is the reaction of enzymatic hydrolysis of created product. Therefore, in this study, kinetic parameters for synthesis and secondary hydrolysis of pharmacologically active ? isosalicin by baker's yeast maltase were calculated, and it was shown that specifity of maltase for hydrolysis is approximately 150 times higher then for synthesis.

Veli?kovi?, D. V.; Dimitrijevi?, A. S.; Bihelovi?, F. J.; Jankov, R. M.; Milosavi?, N.

2011-12-01

410

Synthesis, antimicrobial and anticancer activity of new thiosemicarbazone derivatives.  

PubMed

Thiosemicarbazones of p-aminobenzoic acid (PABA) were synthesized and tested for their antimicrobial and anticancer activity. Hydroxamate derivatives 4a-4l were found to have better antimicrobial and anticancer activity than their acid counterpart. Compound 4d was found to have good antimicrobial activity against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Vibrio cholerae, and Bacillus subtilis with IC(50) value of about 1 µM. Compound 4f showed potent antifungal activity against Candida albicans (IC(50) ?= 1.29 µM) and compound 4h showed potent anticancer activity (IC(50) ?= 0.07 µM). PMID:21290424

Kulandaivelu, Umasankar; Padmini, Valisakka Gari; Suneetha, Kyatham; Shireesha, Boyapati; Vidyasagar, Jannu Vincent; Rao, Tadikonda Rama; K N, Jayaveera; Basu, Arijit; Jayaprakash, Venkatesan

2011-02-01

411

Potassium effects on activated-carbon-supported iron catalysts for Fischer-Tropsch synthesis  

Microsoft Academic Search

The effect of potassium on the activity, selectivity, and distribution of products (hydrocarbons and oxygenates) was studied over iron catalysts supported on activated carbon (AC) for Fischer-Tropsch synthesis (FTS). This is part of a wider study on the incremental effects of components (including the support) of a multicomponent (Fe-Cu-Mo-K\\/AC) FTS catalyst. The range of potassium loading used was 0-2 wt%.

Wenping Ma; Edwin L. Kugler; Dady B. Dadyburjor

2007-01-01

412

Synthesis and acetylcholinesterase inhibitory activity of huperzine A—E2020 combined compound  

Microsoft Academic Search

The synthesis of huperzine-E2020 combined compound (3) has been accomplished and the activities of 3 and the intermediates 12 and 13 to inhibit the activity of acetylcholinesterase have been measured. Conformation analyses and molecular docking studies of E2020 and the eight isomers of 12 were carried out. The results indicated that binding energies of all isomers of 12 with AChE

Fanxing Zeng; Hualiang Jiang; Yufeng Zhai; Haiyan Zhang; Kaixian Chen; Ruyun Ji

1999-01-01

413

(+)-agelasine D: improved synthesis and evaluation of antibacterial and cytotoxic activities.  

PubMed

An improved synthesis of (+)-agelasine D (10) from (+)-manool is reported together with cytotoxic and antibacterial data for agelasine D and structurally close synthetic analogues. These compounds display a broad spectrum of antibacterial activities including effects on M. tuberculosis and Gram-positive and Gram-negative bacteria (both aerobes and anaerobes). They exhibit profound cytotoxic activity against several cancer cells, including a multidrug-resistant cell line. (+)-Agelasine D (10) has been isolated earlier from a marine sponge (Agelas sp.). PMID:16562840

Vik, Anders; Hedner, Erik; Charnock, Colin; Samuelsen, Orjan; Larsson, Rolf; Gundersen, Lise-Lotte; Bohlin, Lars

2006-03-01

414

Omaezallene from red alga Laurencia sp.: structure elucidation, total synthesis, and antifouling activity.  

PubMed

Natural antifouling products have been the subject of considerable attention. We screened marine algae for antifouling activity and discovered omaezallenes, the new bromoallene-containing natural products isolated from the red alga Laurencia?sp. Described is the isolation, structure elucidation, and total syntheses of omaezallenes. The relative and absolute configurations of natural omaezallenes were unambiguously established through total synthesis. The antifouling activities and ecotoxicity of omaezallenes were also evaluated. PMID:24616156

Umezawa, Taiki; Oguri, Yuko; Matsuura, Hiroshi; Yamazaki, Shohei; Suzuki, Masahiro; Yoshimura, Erina; Furuta, Takeshi; Nogata, Yasuyuki; Serisawa, Yukihiko; Matsuyama-Serisawa, Kazuyo; Abe, Tsuyoshi; Matsuda, Fuyuhiko; Suzuki, Minoru; Okino, Tatsufumi

2014-04-01

415

Synthesis and antioxygenic activities of seabuckthorn flavone-3-ols and analogs.  

PubMed

A practical synthesis of polyhydroxy- and regiospecifically methylated flavone-3-ols which are components of commercial 'seabuckthorn flavone' has been achieved by modified Algar-Flynn-Oyamada method. Antioxidant activities of seabuckthorn extracts, isolated products and a number of flavone-3-ols have been determined. Structure-activity relationships have been discussed. Amongst the compounds tested, gallic acid, which is also present in seabuckthorn, was found to be the most effective antioxidant and radioprotectant. PMID:21821414

Pandurangan, N; Bose, Chinchu; Banerji, A

2011-09-15

416

Support Effect and Active Sites on Promoted Ruthenium Catalysts for Ammonia Synthesis  

Microsoft Academic Search

The catalytic activities of three supported, barium-promoted ruthenium catalysts for ammonia synthesis are reported. The three supports are silicon nitride (Si3N4), magnesium aluminum spinel (MgAl2O4), and graphitized carbon (C). The effect of the promoter on the activity is strongly dependent on the choice of support material in accordance with several previous observations. Here, this dependence is ascribed to a difference

Thomas W. Hansen; Poul L. Hansen; Søren Dahl; Claus J. H. Jacobsen

2002-01-01

417

Respiratory syncytial virus infection of human mononuclear phagocytes stimulates synthesis of platelet-activating factor.  

PubMed

Production of platelet-activating factor 1-O-alkyl-2-acetyl-sn-glycero-3- phosphocholine (PAF), a potent mediator of inflammation, by mononuclear phagocytes varies with their stage of cellular differentiation and the nature of the eliciting stimulus. The human monocytic cell line U937 can be induced to differentiate to a macrophage-like cell following phorbol myristate acetate exposure, and after differentiation, these cells efficiently support replication of respiratory syncytial virus (RSV). U937 cells induced to differentiate with phorbol myristate acetate demonstrated a time-dependent decrease in PAF synthesis. RSV infection of these differentiated U937 cells caused a sustained stimulation of PAF synthesis that paralleled viral replication and was dependent on infectious virus. Virus increased the activity of lyso-PAF:acetyl-CoA acetyl-transferase (PAF acetyltransferase) in cell lysates, thus enhancing the anabolic pathway of PAF synthesis without altering the activity of PAF acetylhydrolase, which regulates PAF catabolism. RSV infection of human monocytes also caused a marked increase in [3H] monocytes also caused to uninfected monocytes. Thus, virus infection serves as a novel stimulus to induce PAF synthesis in human mononuclear phagocytes and suggests that increased PAF production may have a critical role in the inflammatory response to RSV. PMID:2005091

Villani, A; Cirino, N M; Baldi, E; Kester, M; McFadden, E R; Panuska, J R

1991-03-25

418

Analyses of isoamylase gene activity in wild-type barley indicate its involvement in starch synthesis.  

PubMed

The notion of debranching enzyme activity as a participant in starch synthesis is gaining acceptance. Inconsistent reports from mutant analyses implicate either isoamylase or pullulanase as a determinant in amylopectin formation and whether wild-type plants utilize one or the other, or both, of these debranching enzymes in starch synthesis is unclear. Recent results on the sul mutant in maize suggest that both forms of debranching enzymes might be involved in amylopectin formation. We wished to find out if isoamylase takes part in starch synthesis by comparing isoamylase gene activity under three conditions: (1) during starch accumulation in developing sink tissues; (2) during starch degradation in germinating seeds; (3) in ectopic expression after applying sucrose, a starch precursor. We isolated the gene for barley isoamylase, isol, and analysed its expression and regulation in germinating seeds, developing endosperm and vegetative tissues, and compared the isoamylase gene expression in sink tissues from three different species. Our results indicate that isoamylase gene activity is involved in starch synthesis in wild-type plants and is modulated by sucrose. PMID:10437827

Sun, C; Sathish, P; Ahlandsberg, S; Jansson, C

1999-06-01

419

Neurosilence: profound suppression of neural activity following intracerebral administration of the protein synthesis inhibitor anisomycin.  

PubMed

Early in their formation, memories are thought to be labile, requiring a process called consolidation to give them near-permanent stability. Evidence for consolidation as an active and biologically separate mnemonic process has been established through posttraining manipulations of the brain that promote or disrupt subsequent retrieval. Consolidation is thought to be ultimately mediated via protein synthesis since translational inhibitors such as anisomycin disrupt subsequent memory when administered in a critical time window just following initial learning. However, when applied intracerebrally, they may induce additional neural disturbances. Here, we report that intrahippocampal microinfusions of anisomycin in urethane-anesthetized rats at dosages previously used in memory consolidation studies strongly suppressed (and in some cases abolished) spontaneous and evoked local field potentials (and associated extracellular current flow) as well as multiunit activity. These effects were not coupled to the production of pathological electrographic activity nor were they due to cell death. However, the amount of suppression was correlated with the degree of protein synthesis inhibition as measured by autoradiography and was also observed with cycloheximide, another translational inhibitor. Our results suggest that (1) the amnestic effects of protein synthesis inhibitors are confounded by neural silencing and that (2) intact protein synthesis is crucial for neural signaling itself. PMID:22396412

Sharma, Arjun V; Nargang, Frank E; Dickson, Clayton T

2012-02-15

420

Activation of Aluminum as an Effective Reducing Agent by Pitting Corrosion for Wet-chemical Synthesis  

PubMed Central

Metallic aluminum (Al) is of interest as a reducing agent because of its low standard reduction potential. However, its surface is invariably covered with a dense aluminum oxide film, which prevents its effective use as a reducing agent in wet-chemical synthesis. Pitting corrosion, known as an undesired reaction destroying Al and is enhanced by anions such as F?, Cl?, and Br? in aqueous solutions, is applied here for the first time to activate Al as a reducing agent for wet-chemical synthesis of a diverse array of metals and alloys. Specifically, we demonstrate the synthesis of highly dispersed palladium nanoparticles on carbon black with stabilizers and the intermetallic Cu2Sb/C, which are promising candidates, respectively, for fuel cell catalysts and lithium-ion battery anodes. Atomic hydrogen, an intermediate during the pitting corrosion of Al in protonic solvents (e.g., water and ethylene glycol), is validated as the actual reducing agent.

Li, Wei; Cochell, Thomas; Manthiram, Arumugam

2013-01-01

421

Activation of aluminum as an effective reducing agent by pitting corrosion for wet-chemical synthesis.  

PubMed

Metallic aluminum (Al) is of interest as a reducing agent because of its low standard reduction potential. However, its surface is invariably covered with a dense aluminum oxide film, which prevents its effective use as a reducing agent in wet-chemical synthesis. Pitting corrosion, known as an undesired reaction destroying Al and is enhanced by anions such as F?, Cl?, and Br? in aqueous solutions, is applied here for the first time to activate Al as a reducing agent for wet-chemical synthesis of a diverse array of metals and alloys. Specifically, we demonstrate the synthesis of highly dispersed palladium nanoparticles on carbon black with stabilizers and the intermetallic Cu?Sb/C, which are promising candidates, respectively, for fuel cell catalysts and lithium-ion battery anodes. Atomic hydrogen, an intermediate during the pitting corrosion of Al in protonic solvents (e.g., water and ethylene glycol), is validated as the actual reducing agent. PMID:23390579

Li, Wei; Cochell, Thomas; Manthiram, Arumugam

2013-01-01

422

Enhanced synthesis and antimicrobial activities of bacteriocins produced by Mexican strains of Bacillus thuringiensis.  

PubMed

Recently, we reported the synthesis of five bacteriocin-like inhibitor substances (Bt-BLIS: morricin 269, kurstacin 287, kenyacin 404, entomocin 420, and tolworthcin 524) by Mexican strains of Bacillus thuringiensis. Here we show that, collectively, these Bt-BLIS have a moderate to broad spectrum of antibacterial activity, being toxic to clinically significant against Gram-positive and Gram-negative bacteria, including common etiological agents of human diseases, such as strep throat and scarlet fever, septicemia, pneumonia, urinary tract infection, and emetic and gastrointestinal syndromes. Although synthesis of the five Bt-BLIS was independent of the presence of a target inducing bacterium, we demonstrated for the first time that a proteinaceous component(s) secreted by, or liberated by proteolytic cleavage of Bacillus cereus 183 following treatment with proteinase K, enhanced Bt-BLIS synthesis. PMID:18654760

de la Fuente-Salcido, N; Guadalupe Alanís-Guzmán, Ma; Bideshi, D K; Salcedo-Hernández, R; Bautista-Justo, M; Barboza-Corona, J E

2008-12-01

423

Synthesis and biological evaluation of a unique heparin mimetic hexasaccharide for structure-activity relationship studies.  

PubMed

To date, the structure-activity relationship studies of heparin/heparan sulfate with their diverse binding partners such as growth factors, cytokines, chemokines, and extracellular matrix proteins have been limited yet provide early insight that specific sequences contribute to this manifold biological role. This has led to an impetus for the chemical synthesis of oligosaccharide fragments of these complex polysaccharides, which can provide an effective tool for this goal. The synthesis of three heparin mimetic hexasaccharides with distinct structural patterns is described herein, and the influence of the targeted substitution on their bioactivity profiles is studied using in vitro affinity and/or inhibition toward different growth factors and proteins. Additionally, the particularly challenging synthesis of an irregular hexasaccharide is reported, which, interestingly, in spite of being considerably structurally similar with its two counterparts, displayed a unique and remarkably distinct profile in the test assays. PMID:24786387

Roy, Sucharita; El Hadri, Ahmed; Richard, Sebastien; Denis, Fanny; Holte, Kimberly; Duffner, Jay; Yu, Fei; Galcheva-Gargova, Zoya; Capila, Ishan; Schultes, Birgit; Petitou, Maurice; Kaundinya, Ganesh V

2014-06-12

424

Fundamental combustion and diagnostics research at Sandia. Progress report, April-June 1980  

SciTech Connect

The combustion research emphasizes basic research into fundamental problems associated with combustion. The overall program addresses detailed chemistry of combustion, fundamental processes associated with laminar and turbulent flames, development of research techniques specifically applicable to combustion environments, and operation of the user-oriented Combustion Research Facility. The first section of this report contains activities in Combustion Research, the second section contains activities in Molecular Physics and Spectroscopy, and the third section contains activities in Diagnostics Research.

Gusinow, M.A. (ed.)

1980-09-01

425

Combustion synthesis and engineering of nanoparticles for electronic, structural and superconductor applications. Annual progress report, August 20, 1993--May 30, 1994.  

National Technical Information Service (NTIS)

Fully dense, nanocrystalline ceramic articles were prepared by the new nanofabrication process developed in this research program. The process consists of two steps: synthesis of ceramic nanoparticles and fabrication of dense, nanocrystalline ceramic part...

G. C. Stangle V. R. W. Amarakoon W. A. Schulze

1994-01-01

426

Syndecan-2 regulates melanin synthesis via protein kinase C ?II-mediated tyrosinase activation.  

PubMed

Syndecan-2, a transmembrane heparan sulfate proteoglycan that is highly expressed in melanoma cells, regulates melanoma cell functions (e.g. migration). Since melanoma is a malignant tumor of melanocytes, which largely function to synthesize melanin, we investigated the possible involvement of syndecan-2 in melanogenesis. Syndecan-2 expression was increased in human skin melanoma tissues compared with normal skin. In both mouse and human melanoma cells, siRNA-mediated knockdown of syndecan-2 was associated with reduced melanin synthesis, whereas overexpression of syndecan-2 increased melanin synthesis. Similar effects were also detected in human primary epidermal melanocytes. Syndecan-2 expression did not affect the expression of tyrosinase, a key enzyme in melanin synthesis, but instead enhanced the enzymatic activity of tyrosinase by increasing the membrane and melanosome localization of its regulator, protein kinase C?II. Furthermore, UVB caused increased syndecan-2 expression, and this up-regulation of syndecan-2 was required for UVB-induced melanin synthesis. Taken together, these data suggest that syndecan-2 regulates melanin synthesis and could be a potential therapeutic target for treating melanin-associated diseases. PMID:24472179

Jung, Hyejung; Chung, Heesung; Chang, Sung Eun; Choi, Sora; Han, Inn-Oc; Kang, Duk-Hee; Oh, Eok-Soo

2014-05-01

427

RNA and protein synthesis is required for Ancylostoma caninum larval activation  

PubMed Central

The developmentally arrested infective larva of hookworms encounters a host-specific signal during invasion that initiates the resumption of suspended developmental pathways. The resumption of development during infection is analogous to recovery from the facultative arrested dauer stage in the free-living nematode Caenorhabditis elegans. Infective larvae of the canine hookworm Ancylostoma caninum resume feeding and secrete molecules important for infection when exposed to a host mimicking signal in vitro. This activation process is a model for the initial steps of the infective process. Dauer recovery requires protein synthesis, but not RNA synthesis in C. elegans. To determine the role of RNA and protein synthesis in hookworm infection, inhibitors of RNA and protein synthesis were tested for their effect on feeding and secretion by A. caninum infective larvae. The RNA synthesis inhibitors ?-amanitin and actinomycin D inhibit feeding dose-dependently, with IC50 values of 30 and 8 µM, respectively. The protein synthesis inhibitors puromycin (IC50 =110 µM), cycloheximide (IC50 =50 µM), and anisomycin (IC50 =200 µM) also displayed dose-dependent inhibition of larval feeding. Significant inhibition of feeding by ?-amanitin and anisomycin occurred when the inhibitors were added before 12 h of the activation process, but not if the inhibitors were added after 12 h. None of the RNA or protein synthesis inhibitors prevented secretion of the activation-associated protein ASP-1, despite nearly complete inhibition of feeding. The results indicate that unlike dauer recovery in C. elegans, de novo gene expression is required for hookworm larval activation, and the critical genes are expressed within 12 h of exposure to activating stimuli. However, secretion of infection-associated proteins is independent of gene expression, indicating that the proteins are pre-synthesized and stored for rapid release during the initial stages of infection. The genes that are inhibited represent a subset of those required for the transition to parasitism, and therefore represent interesting targets for further investigation. Furthermore, while dauer recovery provides a useful model for hookworm infection, the differences identified here highlight the importance of exercising caution before making generalizations about parasitic nematodes based on C. elegans biology.

Dryanovski, Dilyan I.; Dowling, Camille; Gelmedin, Verena; Hawdon, John M.

2011-01-01

428

Synthesis and antimycobacterial activity of pyrazine and quinoxaline derivatives.  

PubMed

A series of pyrazine and quinoxaline derivatives have been synthesized, and their activity against M. tuberculosis (Mtb) and Mycobacterium avium (MAC) are reported. The 4-acetoxybenzyl ester of pyrazinoic acid and 4'-acetoxybenzyl 2-quinoxalinecarboxylate showed excellent activity against Mtb (MIC ranges of less than 1-6.25 microg/mL) but only modest activity against MAC (MICs of 4-32 microg/mL). PMID:12459027

Seitz, Lainne E; Suling, William J; Reynolds, Robert C

2002-12-01

429

Synthesis and antibacterial activity of aminosugar-functionalized intercalating agents.  

PubMed

A series of previously reported amino sugar-functionalized intercalating agents, 3-14, were evaluated in two antibacterial assays (paper disk diffusion and 96-well microdilution) against Bacillus atrophaeus, ATCC 9372 and Escherichia coli, ATCC 47076. Although none of the compounds were active against this E. coli strain, several showed activity against B. atrophaeus. In anticipation of the need for larger amounts of these compounds for future structure-activity relationship studies, improved routes to 11-14 were developed. PMID:19926076

Shi, Wei; Marcus, Sandra L; Lowary, Todd L

2010-01-11

430

Synthesis and hypoglycemic activity of some new theophylline derivatives.  

PubMed

Thirty-one new theophylline derivatives have been synthesized and evaluated for their hypoglycemic activity. Compounds 24 (56% reduction) and 31 (57% reduction) showed better hypoglycemic activity than the standard drug glibenclamide which showed 52% reduction in serum glucose level. Compound 27 remarkably reduced serum glucose level by 53%. Ten compounds showed varying degrees of hypoglycemic activity ranging from 20 to 37% reduction in serum glucose level compared to the standard drug. The aromatic amide functionality is the common feature of these theophylline hypoglycemic derivatives. However, anthranilamide and or aliphatic amides proved to be the least active compounds in the present series. PMID:23701264

Alafeefy, Ahmed M; Alqasoumi, Saleh I; Abdel Hamid, Sami G; El-Tahir, Kamal E H; Mohamed, Menshawy; Zain, Mohamed E; Awaad, Amani S

2014-06-01

431

Space Station Freedom combustion research  

NASA Technical Reports Server (NTRS)

Extended operations in microgravity, on board spacecraft like Space Station Freedom, provide both unusual opportunities and unusual challenges for combustion science. On the one hand, eliminating the intrusion of buoyancy provides a valuable new perspective for fundamental studies of combustion phenomena. On the other hand, however, the absence of buoyancy creates new hazards of fires and explosions that must be understood to assure safe manned space activities. These considerations - and the relevance of combustion science to problems of pollutants, energy utilization, waste incineration, power and propulsion systems, and fire and explosion hazards, among others - provide strong motivation for microgravity combustion research. The intrusion of buoyancy is a greater impediment to fundamental combustion studies than to most other areas of science. Combustion intrinsically heats gases with the resulting buoyant motion at normal gravity either preventing or vastly complicating measurements. Perversely, this limitation is most evident for fundamental laboratory experiments; few practical combustion phenomena are significantly affected by buoyancy. Thus, we have never observed the most fundamental combustion phenomena - laminar premixed and diffusion flames, heterogeneous flames of particles and surfaces, low-speed turbulent flames, etc. - without substantial buoyant disturbances. This precludes rational merging of theory, where buoyancy is of little interest, and experiments, that always are contaminated by buoyancy, which is the traditional path for developing most areas of science. The current microgravity combustion program seeks to rectify this deficiency using both ground-based and space-based facilities, with experiments involving space-based facilities including: laminar premixed flames, soot processes in laminar jet diffusion flames, structure of laminar and turbulent jet diffusion flames, solid surface combustion, one-dimensional smoldering, ignition and flame spread of liquids, drop combustion, and quenching of panicle-air flames. Unfortunately, the same features that make microgravity attractive for fundamental combustion experiments, introduce new fire and explosion hazards that have no counterpart on earth. For example, microgravity can cause broader flammability limits, novel regimes of flame spread, enhanced effects of flame radiation, slower fire detector response, and enhanced combustion upon injecting fire extinguishing agents, among others. On the other hand, spacecraft provide an opportunity to use 'fire-safe' atmospheres due to their controlled environment. Investigation of these problems is just beginning, with specific fire safety experiments supplementing the space based fundamental experiments listed earlier; thus, much remains to be done to develop an adequate technology base for fire and explosion safety considerations for spacecraft.

Faeth, G. M.

1992-01-01

432

Peptide deformylase inhibitors with retro-amide scaffold: synthesis and structure-activity relationships.  

PubMed

Peptide deformylase (PDF) is a metalloprotease catalyzing the removal of a formyl group from newly synthesized proteins. Thus inhibition of PDF activity is considered to be one of the most effective antibiotic strategies. Reported herein are the synthesis and structure-activity relationship studies of retro-amide inhibitors based on actinonin, a naturally occurring PDF inhibitor. Analysis of the structure-activity relationships led to the discovery of 7a, which exhibits potent enzyme inhibition and antibacterial activity against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. PMID:20615695

Lee, Seung Kyu; Choi, Kwang Hyun; Lee, Sang Jae; Suh, Se Won; Kim, B Moon; Lee, Bong Jin

2010-08-01

433

The Application of Self-Propagating High-Temperature Synthesis of Engineered Porous Composite Biomedical Materials  

Microsoft Academic Search

The term “self-propagating high-temperature synthesis” (SHS), or “combustion synthesis”, refers to an exothermic chemical reaction process that utilizes the heat generated by the exothermic reaction to ignite and sustain a propagating combustion wave through the reactants to produce the desired product(s). The products of combustion synthesis normally are extremely porous: Typically 50 percent of theoretical density. Advantages of combustion synthesis

R. Ayers; D. Burkes; G. Gottoli; H. C. Yi; J. J. Moore

2007-01-01

434

Novel convenient synthesis of biologically active esters of hydroxylamine.  

PubMed

Alkylation of ethyl N-hydroxyacetimidate with readily available methanesulfonates of functionally substituted alcohols and subsequent deprotection of aminooxy group is a novel and convenient method to prepare functionally substituted esters of hydroxylamine with high overall yield. This approach is a good alternative to well-known reaction of N-hydroxyphthalimide with alcohols under the Mitsunobu conditions. The properties of ethoxyethylidene protection of aminooxy group on the contrary to that of N-alkoxyphthalimide group allow to perform a wide spectra of the transformations in the radical of N-protected hydroxylamine derivatives. This is essential for synthetic strategies consisting in the introduction of N-protected aminooxy group at one of the first steps of synthesis and subsequent transformations of the radical.The inhibitory effect of one of the newly synthesized compound, 1-guanidinooxy-3-aminopropane (GAPA), was compared with that of well-known inhibitors of ornithine decarboxylase namely, alpha-difluoromethylornithine (DFMO) and 1-aminooxy-3-aminopropane (APA) on Leishmania donovani, a protozoan parasite that causes visceral leishmaniasis. GAPA, on the contrary with APA and DFMO, in micromolar concentrations, inhibited the growth of both amastigotes and promastigotes of sodium antimony gluconate-resistant forms of L. donovani. PMID:19997759

Khomutov, Maxim A; Mandal, Swati; Weisell, Janne; Saxena, Neiha; Simonian, Alina R; Vepsalainen, Jouko; Madhubala, Rentala; Kochetkov, Sergey N

2010-02-01

435

Combustibility of titanium powders  

NASA Technical Reports Server (NTRS)

The combustion of compact samples was studied; the mechanism of autoignition is defined. Several studies are made of the combustibility of titanium using 50 samples. The data provide a clear idea of the combustibility of titanium powders.

Popov, Ye. I.; Poyarkov, V. G.; Finayev, Yu. A.

1989-01-01

436

Coal Combustion and Utilization.  

National Technical Information Service (NTIS)

Information on the following subjects is included within the scope of the publication, but all subjects may not appear in each issue: coal combustion, power plant fuel, MHD generators, fuel cells, combustion chemistry, combustion systems.

1986-01-01

437

Synthesis and biological activity of new arenediyne-linked isoxazolidines.  

PubMed

Arenediyne-isoxazolidine conjugates have been synthesized as a new scaffold for the development of bioactive mimics. Some of the synthesized compounds are endowed with antiproliferative activity against three human cancer cell lines. Their thermal reactivity suggests that the biological activity probably could not be linked to the Bergman cyclization. PMID:24835789

Romeo, Roberto; Navarra, Michele; Giofrè, Salvatore V; Carnovale, Caterina; Cirmi, Santa; Lanza, Giuseppe; Chiacchio, Maria A

2014-07-01

438

Synthesis, reactivity and biological activity of 5-alkoxymethyluracil analogues  

PubMed Central

Summary This review article summarizes the results of a long-term investigation of 5-alkoxymethyluracil analogues and is aimed, in particular, at methods of syntheses. Most of the presented compounds were synthesized in order to evaluate their biological activity, therefore, a brief survey of biological activity, especially antiviral, cytotoxic and antibacterial, is also reported.

Brulikova, Lucie

2011-01-01

439

Synthesis and Photocatalytic Activity of Doped Zinc Oxide Nanoparticles  

Microsoft Academic Search

In this study, we have investigated the effect of doping with cobalt and manganese oxide on the photocatalytic activity of nanoparticulate zinc oxide. Zinc oxide powders with controlled particle size, minimal agglomeration, and controlled chemical composition were manufactured by mechanochemical processing. The photocatalytic activity of the powders was measured using the spin trapping technique with electron paramagnetic resonance spectroscopy. It

Aaron Dodd; Allan McKinley; Martin Saunders; Takuya Tsuzuki

2006-01-01

440

Synthesis and evaluation of antibacterial activities of andrographolide analogues  

Microsoft Academic Search

Andrographolide (Andro), the main active component of the herb Andrographis paniculata, has been used for many years to treat a variety of diseases including bacterial and viral infections. Andro was recently reported to act by inhibiting the bacterial quorum sensing system. We ha