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1

DOI: 10.1002/adem.200700076 Novel Method for Synthesis of Nano-Materials: Combustion of Active  

E-print Network

DOI: 10.1002/adem.200700076 Novel Method for Synthesis of Nano-Materials: Combustion of Active- and combustion synthesis. A combination of combustion and reactive solution approaches leads to so- called solution (aqueous) combustion synthesis (SCS) method.[1­3] Typically SCS involves a self-sustained reaction

Mukasyan, Alexander

2

Solution Combustion Synthesis Impregnated Layer Combustion Synthesis is a Novel  

E-print Network

Solution Combustion Synthesis Impregnated Layer Combustion Synthesis is a Novel Methodology Engineering University of Notre Dame University of Notre Dame #12;Outline: Overview of combustion synthesis Reaction system Combustion front analaysis Theoretical model results Conclusions Acknowledgements #12

Mukasyan, Alexander

3

Photocatalytic activity of BiVO 4 nanospheres obtained by solution combustion synthesis using sodium carboxymethylcellulose  

Microsoft Academic Search

BiVO4 nanospheres were obtained through solution combustion synthesis (SCS) in presence of sodium carboxymethylcellulose (CMC). The CMC polymer had a double function, as a fuel and as a protecting agent in the particles growth process. The formation and characterization of oxide was carried out by simultaneous thermal analysis (TGA\\/DTA), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared

U. M. García Pérez; S. Sepúlveda-Guzmán; A. Martínez-de la Cruz; U. Ortiz Méndez

2011-01-01

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

Synthesis of Highly Active Mg-BASED Hydrides Using Hydriding Combustion Synthesis and NbF5 Additives  

NASA Astrophysics Data System (ADS)

Superiority of the hydriding combustion (HC) technique over conventional metallurgical approach to the synthesis of cost-effective Mg based hydrides, which show promise as hydrogen storage materials, is well known. In the present research, we report further improvements in HC prepared Mg-based materials, achieved by optimizing the preparative parameters of HC and by catalytic addition. Mg90-Ni60-C40 composites prepared using optimized processing parameters were ball-milled with NbF5 (10 h) and characterized for their micro-structural and hydriding properties. The ball-milled/catalyzed powder showed decreased crystallinity with CNTs on its surfaces. Surface area of the ball-milled powder decreased to almost half of the as-HC powder, while TG analysis revealed a four-fold decrease in the desorption temperature of the milled powder compared to that of the as-HC prepared powder. Activated samples achieved the maximum absorption/desorption limits (5.3 wt.%) at as low as 100°C, underlining the possibility of the use of these materials in portable hydrogen storage devices.

Chourashiya, M. G.; Park, C. N.; Park, C. J.

2012-09-01

6

COMBUSTION SYNTHESIS OF ADVANCED MATERIALS: PRINCIPLESAND APPLICATIONS  

E-print Network

COMBUSTION SYNTHESIS OF ADVANCED MATERIALS: PRINCIPLESAND APPLICATIONS Arvind Varma, Alexander S. Gasless Combustion SynthesisFrom Elements B. Combustion Synthesis in Gas-Solid Systems C. Products of Thermite-vpe SHS D. Commercial Aspects IV. Theoretical Considerations A. Combustion Wave Propagation Theory

Mukasyan, Alexander

7

Combustion Synthesis of Silicon Carbide 389 Combustion Synthesis of Silicon Carbide  

E-print Network

Combustion Synthesis of Silicon Carbide 389 X Combustion Synthesis of Silicon Carbide Alexander S. Mukasyan University of Notre Dame USA 1. Introduction Combustion synthesis (CS) is an effective technique by which combustion synthesis can occur: self - propagating high-temperature synthesis (SHS) and volume

Mukasyan, Alexander

8

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

9

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...

10

Combustion Synthesis of Magnesium Aluminate  

SciTech Connect

In the system MgO-Al{sub 2}O{sub 3}, three compounds MgAl{sub 2}O{sub 4}, MgAl{sub 6}O{sub 10}(also expressed as-Mg{sub 0.4}Al{sub 2.4}O{sub 4}) and MgAl{sub 26}O{sub 40} are well known. Importance of the first two is well established. Magnesium aluminate (MgAl{sub 2}O{sub 4}) spinel is a technologically important material due to its interesting thermal properties. The MgAl{sub 2}O{sub 4} ceramics also find application as humidity sensors. Apart from the luminescence studies, the interest in MgAl{sub 2}O{sub 4} 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 MgAl{sub 6}O{sub 10} 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 MgAl{sub 2}O{sub 4} and MgAl{sub 6}O{sub 10} were formed in a single step, while MgAl{sub 26}O{sub 40} was not formed by this procedure. Activation of MgAl{sub 6}O{sub 10} by rare earth ions like Ce{sup 3+}, Eu{sup 3+} and Tb{sup 3+} and ns{sup 2} ion Pb{sup 2+} could be achieved. Excitation bands for MgAl{sub 6}O{sub 10} are at slightly shorter wavelengths compared to those reported for MgAl{sub 2}O{sub 4}.

Kale, M. A. [Physics Department, S.V.S.S. College of Engineering and Research, Nagpur 4411 10 (India); Joshi, C. P. [Physics Department, Ramdeobaba Engineering College, Katol Road, Nagpur 440 013 (India); Moharil, S. V. [Physics Department, RTM Nagpur University, Nagpur, 440033 (India)

2011-10-20

11

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

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 and quasi-isostatic densication of powder cermets  

E-print Network

Combustion synthesis and quasi-isostatic densi®cation of powder cermets E.A. Olevskya,* , E-propagating High-temperature synthesis (also known as SHS or combustion synthesis) presents a bright potential equation parameters. The distortion undergone by the combustion synthesis products during QIP densi

Meyers, Marc A.

14

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

15

Candle filter fabrication using combustion synthesis method  

SciTech Connect

Using self-propagating, high-temperature synthesis fabrication techniques, unique combinations of materials were studied for use in candle filter development. Materials suitable for corrosive atmospheres with improved filtration and mechanical properties were identified within the context of manufacturing simplicity, versatility and cost-effectiveness. Material combinations suitable for combustion synthesis were identified which match the temperature, strength and corrosion resistance requirements of operation in pressurized, fluidized-bed combustion environments. Tests on porosity, permeability and strength indicated the ability of the method to process porous filter material which matches or surpasses the performance levels of current, production candle filter material samples.

Hanus, G.J.; Uznanski, K.T.; DeCoursin, D.G.; Hickel, S.D. [Phoenix Solutions Co., Minneapolis, MN (United States); Shtessel, E. [Exotherm Corp., Camden, NJ (United States)

1996-12-31

16

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

17

Novel Active Combustion Control Valve  

NASA Technical Reports Server (NTRS)

This project presents an innovative solution for active combustion control. Relative to the state of the art, this concept provides frequency modulation (greater than 1,000 Hz) in combination with high-amplitude modulation (in excess of 30 percent flow) and can be adapted to a large range of fuel injector sizes. Existing valves often have low flow modulation strength. To achieve higher flow modulation requires excessively large valves or too much electrical power to be practical. This active combustion control valve (ACCV) has high-frequency and -amplitude modulation, consumes low electrical power, is closely coupled with the fuel injector for modulation strength, and is practical in size and weight. By mitigating combustion instabilities at higher frequencies than have been previously achieved (approximately 1,000 Hz), this new technology enables gas turbines to run at operating points that produce lower emissions and higher performance.

Caspermeyer, Matt

2014-01-01

18

Combustion synthesis of titanium carbide: Theory and experiment  

Microsoft Academic Search

The combustion synthesis of titanium carbide from elemental powders has been theoretically and experimentally studied as a model system for self -propagating high temperature synthesis (SHS) of refractory compounds. Calculations of the adiabatic temperature of combustion of graphite and titanium powders to form TiCx have been made to show the effects of stoichiometry, dilution and the initial temperature of the

J. B. Holt; Z. A. Munir

1986-01-01

19

Demonstration of Active Combustion Control  

NASA Technical Reports Server (NTRS)

The primary objective of this effort was to demonstrate active control of combustion instabilities in a direct-injection gas turbine combustor that accurately simulates engine operating conditions and reproduces an engine-type instability. This report documents the second phase of a two-phase effort. The first phase involved the analysis of an instability observed in a developmental aeroengine and the design of a single-nozzle test rig to replicate that phenomenon. This was successfully completed in 2001 and is documented in the Phase I report. This second phase was directed toward demonstration of active control strategies to mitigate this instability and thereby demonstrate the viability of active control for aircraft engine combustors. This involved development of high-speed actuator technology, testing and analysis of how the actuation system was integrated with the combustion system, control algorithm development, and demonstration testing in the single-nozzle test rig. A 30 percent reduction in the amplitude of the high-frequency (570 Hz) instability was achieved using actuation systems and control algorithms developed within this effort. Even larger reductions were shown with a low-frequency (270 Hz) instability. This represents a unique achievement in the development and practical demonstration of active combustion control systems for gas turbine applications.

Lovett, Jeffrey A.; Teerlinck, Karen A.; Cohen, Jeffrey M.

2008-01-01

20

Active control in combustion systems with vortices  

Microsoft Academic Search

The paper reviews active vortex combustion control studies and focuses on practical applications. The vortex combustion control method requires that the fuel and other reactants are injected periodically into air vortices at timing and location which ensure optimal mixing and combustion. Advanced laser diagnostics were employed to study the interaction between the turbulent vortical mixing and the combustion process. Subsequently,

E. J. Gutmark; T. P. Parr; K. J. Wilson; K. C. Schadow

1995-01-01

21

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

22

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

23

Synthesis of zeolite phases from combustion by-products.  

PubMed

Synthesis of zeolites from combustion by-products, including fly ash, bottom ash and rice husk ash, was studied. A molar ratio of SiO2/Al2O3 of 1.5 was used for the syntheses. Refluxing and hydrothermal methods were also used for synthesis for comparison. The reaction temperatures of refluxing and hydrothermal methods were 100 degrees C and 130 degrees C, respectively. Sodalite, phillipsite-K, and zeolite P1 with analcime were obtained when fly ash, bottom ash and rice husk ash were used as starting materials, respectively. With rice husk ash as a starting material, zeolite P1 was produced. This result had advantages over previous studies as there was no prior activation required for the synthesis. The concentrations and types of alkaline used in the synthesis also determined the zeolite type. The different zeolites obtained from three systems were measured for specific surface area and pore size by using BET and Hg-porosimetry, respectively. Ammonium exchange capacities of the synthesised powders containing zeolites, sodalite, zeolite P1 and phillipsite-K were 38.5, 65.0 and 154.7 meq 100 g(-1), respectively. PMID:20421244

Pimraksa, Kedsarin; Chindaprasirt, Prinya; Setthaya, Naruemon

2010-12-01

24

Combustion synthesis of advanced materials: Part I. Reaction parameters  

Microsoft Academic Search

An explanation of combustion (self propagating high temperature) synthesis (SHS) is given together with a historical perspective of the examination of such exothermic reactions. The application of thermochemical functions has been used to predict theoretically the maximum adiabatic temperature, Tad. This, combined with a knowledge of the ignition temperature, Tig, and the actual combustion temperature, Tc, has been used to

John J. Moore; H. J. Feng

1995-01-01

25

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

26

Burning Velocities in Catalytically Assisted Self-Propagating High-Temperature Combustion Synthesis Systems  

E-print Network

Burning Velocities in Catalytically Assisted Self-Propagating High-Temperature Combustion Synthesis-phase transport agents clearly augment the combustion synthesis process. The burning velocities. © 2001 by The Combustion Institute INTRODUCTION Self-propagating high-temperature combustion synthesis

Wooldridge, Margaret S.

27

Active control of combustion instability  

SciTech Connect

The principle of 'antisound' is used to construct a method for the suppression of combustion instabilities. This active instability control (AIC) method uses external acoustic excitation by a loudspeaker to suppress the oscillations of a flame. The excitation signal is provided by a microphone located upstream of the flame. This signal is filtered, processed, amplified, and sent to the loudspeaker. The AIC method is validated on a laboratory combustor. It allows the suppression of all unstable modes of the burner for any operating ratio. The influence of the microphone and loudspeaker locations on the performance of the AIC system is described. For a given configuration, domains of stability, i.e., domains where the AIC system parameters provide suppression of the oscillation, are investigated. Measurements of the electric input of the loudspeaker show that the energy consumption of the AIC system is almost negligible and suggest that this method could be used for industrial combustor stabilization. Finally, a simple model describing the effects of the AIC system is developed and its results compared to the experiment.

Lang, W.; Poinsot, T.; Candel, S.

1987-12-01

28

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

29

Microwave assisted combustion synthesis of non-equilibrium intermetallic compounds.  

PubMed

A simplified model of the microwave-assisted combustion synthesis of Ni and Al metal powders to form the NiAl intermetallic on titanium and steel substrates is presented. The simulation couples an electro-thermal model with a chemical model, accounting for local heat generation due to the highly exothermic nature of the reactions between the powders. Numerical results, validated by experimental values, show that the capability of microwaves to convey energy, and not heat, can be used to alter the temperature profiles during and after the combustion synthesis, leading to unique intermetallic microstructures. This phenomenon is ascribed to the extended existence of high temperature liquid intermetallic phases, which react with the metallic substrates at the interface. Moreover, microwave heating selectivity allows to maintain the bulk of the substrate metallic materials to a much lower temperature, compared to combustion synthesis in conventionally heated furnaces, thus reducing possible unwanted transformations like phase change or oxidation. PMID:21721328

Veronesi, Paolo; Rosa, Roberto; Colombini, Elena; Leonelli, Cristina; Poli, Giorgio; Casagrande, Angelo

2010-01-01

30

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

31

Combustion Synthesis of Advanced Porous Materials in Microgravity Environment  

NASA Technical Reports Server (NTRS)

Combustion synthesis, otherwise known as self-propagating high temperature synthesis (SHS), can be used to produce engineered advanced porous material implants which offer the possibility for bone ingrowth as well as a permanent structure framework for the long-term replacement of bone defects. The primary advantage of SHS is based on its rapid kinetics and favorable energetics. The structure and properties of materials produced by SHS are strongly dependent on the combustion reaction conditions. Combustion reaction conditions such as reaction stoichiometry, particle size, green density, the presence and use of diluents or inert reactants, and pre-heating of the reactants, will affect the exothermicity of the reaction. A number of conditions must be satisfied in order to obtain high porosity materials: an optimal amount of liquid, gas and solid phases must be present in the combustion front. Therefore, a balance among these phases at the combustion front must be created by the SHS reaction to successfully engineer a bone replacement material system. Microgravity testing has extended the ability to form porous products. The convective heat transfer mechanisms which operate in normal gravity, 1 g, constrain the combustion synthesis reactions. Gravity also acts to limit the porosity which may be formed as the force of gravity serves to restrict the gas expansion and the liquid movement during reaction. Infiltration of the porous product with other phases can modify both the extent of porosity and the mechanical properties.

Zhang, X.; Moore, J. J.; Schowengerdt, F. D.; Johnson, D. P.

1999-01-01

32

Combustion synthesis and nanomaterials Singanahally T. Aruna a,*, Alexander S. Mukasyan b,1  

E-print Network

Combustion synthesis and nanomaterials Singanahally T. Aruna a,*, Alexander S. Mukasyan b,1 October 2008 Accepted 2 December 2008 Keywords: Combustion synthesis Self-propagating high-temperature synthesis Solution combustion Nanomaterials Catalysts Phosphors a b s t r a c t The recent developments

Mukasyan, Alexander

33

Combustion synthesis of calcium phosphate bioceramic powders A. Cu neyt Tas *,1  

E-print Network

Combustion synthesis of calcium phosphate bioceramic powders A. CuÃ? neyt Tas *,1 Department)2; Combustion synthesis; Hydroxyapatite 1. Introduction Calcium hydroxyapatite (HA: Ca10(PO4)6(OH)2), the major), instead of water, as the precipitation medium. Self-propagating combustion synthesis (SPCS

Tas, A. Cuneyt

34

Separation and Purification Technology 25 (2001) 117126 Perovskite membranes by aqueous combustion synthesis  

E-print Network

Separation and Purification Technology 25 (2001) 117­126 Perovskite membranes by aqueous combustion. The aqueous combustion synthesis of LSC powders was investigated over a wide range of synthesis conditions, , the reaction can proceed in three different modes: Smoldering Combustion Synthesis (SCS), B0.7, with maximum

Mukasyan, Alexander

35

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

36

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

37

Overview of IEA biomass combustion activities  

NASA Astrophysics Data System (ADS)

The objectives of the International Energy Agency (IEA) bioenergy program are: (1) to encourage cooperative research, development and use of energy and the increased utilization of alternatives to oil; and (2) to establish increased program and project cooperation between participants in the whole field of bioenergy. There are four Task Annexes to the Implementing Agreement during the period 1992-1994: Efficient and Environmentally Sound Biomass Production Systems; Harvesting and Supply of Woody Biomass for Energy; Biomass Utilization; and Conversion of Municipal Solid Waste Feedstock to Energy. The report describes the following biomass combustion activities during the period 1992-1994: Round robin test of a wood stove; Emissions from biomass combustion; A pilot project cofiring biomass with oil to reduce SO2 emissions; Small scale biomass chip handling; Energy from contaminated wood waste combustion; Modeling of biomass combustion; Wood chip cogeneration; Combustion of wet biomass feedstocks, ash reinjection and carbon burnout; Oxidation of wet biomass; Catalytic combustion in small wood burning appliances; Characterization of biomass fuels and ashes; Measurement techniques (FTIR).

Hustad, J. E.

1994-07-01

38

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); Dunmead, Stephen D. (Davis, CA); Halverson, Danny C. (Modesto, CA); Landingham, Richard L. (Livermore, CA)

1991-01-01

39

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

40

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

41

Combustion Synthesis of Doped Thermoelectric Oxides  

SciTech Connect

Self-propagating high-temperature synthesis (SHS) was used to prepare silver doped calcium cobaltates (Ca1.24- xAgxCo1.62O3.86, x = 0.03 - 0.12) powders. SHS is a simple and economic process to synthesize ceramic materials with minimum energy requirements. The heat generated by the SHS reaction can sustain the propagation of the reaction front and convert reactants to desired products. The effect of doping level on thermoelectric properties was investigated in this study. Results show the substitution of calcium by silver decreases the thermal conductivity significantly. XRD and surface area measurements show synthesized powders are phase pure and have large specific surface areas.

Selig, Jiri [Lamar University; Lin, Sidney [Lamar University; Lin, Hua-Tay [ORNL; Johnson, D Ray [ORNL

2012-01-01

42

Synthesis and investigations on CO catalytic oxidation activity of nanostructured Ce0.5Zr0.5O2 prepared by combustion method using polyvinyl alcohol  

NASA Astrophysics Data System (ADS)

Nanostructured Ce0.5Zr0.5O2 samples were synthesized by the combustion of the gel obtained from a mixture of polyvinyl alcohol (PVA) and metal nitrates at a temperature as low as 600?°C. The prepared samples were investigated by x-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Their specific surface areas were determined from N2 adsorption measurement at 77?K by Brunauer–Emmet–Teller (BET) method and their CO catalytic oxidation activities were investigated using a Landcom II instrument. The XRD and FE-SEM results revealed that Ce0.5Zr0.5O2 nanocrystallines began to grow isotropically at 600?°C with the nanostructure found in all prepared samples. Further thermal treatment at 600?°C for 2?h yields the single crystalline phase Ce0.5Zr0.5O2 nanostructured samples with average crystalline size < 50?nm and specific surface area of about 73?m2?g?1. Besides, the effects of a number of factors such as calcination temperature and Ce/Zr molar ratio on the formation of prepared samples as well as the oxidative conversion of carbon monoxide over nanostructured Ce0.5Zr0.5O2 catalyst were also studied.

Nhiem Dao, Ngoc; Luu, Minh Dai

2012-03-01

43

Effects of gravity on combustion synthesis of functionally graded biomaterials  

NASA Astrophysics Data System (ADS)

Combustion synthesis, or self-propagating, high temperature synthesis is currently being used at the Colorado School of Mines to produce advanced materials for biomedical applications. These biomaterials include ceramic, intermetallic, and metal-matrix composites for applications ranging from structural to oxidation- and wear-resistant materials, e.g., TiC-Ti, TiC-Cr 3C 2, MOSi 2-SiC, NiAl-TiB 2, to engineered porous composites, e.g., B 4C-Al 2O 3, Ti-TiB x, Ni-Ti, Ca 3(P0 4) 2 and glass-ceramic composites, e.g., CaO-SiO 2-BaO-Al 2O 3-TiB 2. The goal of the functionally graded biomaterials project is to develop new materials, graded in porosity and composition, which will combine the desirable mechanical properties of implant, e.g., NiTi, with the bone-growth enhancement properties of porous biodegradable ceramics, e.g., Ca 3(PO 4) 2. Recent experiments on the NASA parabolic flight (KC-135) aircraft have shown that gravity plays an important role in controlling the structure and properties of materials produced by combustion synthesis. The results of these studies, which will be presented at the conference, will provide valuable input to the design of experiments to be done in Space-DRUMS TM, a containerless materials processing facility scheduled to be placed on the International Space Station in 2003.

Castillo, M.; Moore, J. J.; Schowengerdt, F. D.; Ayers, R. A.; Zhang, X.; Umakoshi, M.; Yi, H. C.; Guigne, J. Y.

2003-07-01

44

Effects of gravity on combustion synthesis of functionally graded biomaterials  

NASA Astrophysics Data System (ADS)

Combustion synthesis, or self-propagating, high temperature synthesis (SHS) is currently being used at the Colorado School of Mines to produce advanced materials for biomedical applications. These biomaterials include ceramic, intermetallic, and metal-matrix composites for applications ranging from structural to oxidation- and wear-resistant materials, e.g., TiC-Ti, TiC-Cr3 C2 , MoSi2 - SiC, NiAl-TiB2 , to engineered porous composites, e.g., B4 C-A l2 O3 , Ti-TiBx , Ni-Ti, Ca 3 (PO4 )2 and glass- ceramic composites, e.g., CaO-SiO2 - B a O-A l2 O3 -T i B2 . The goal of the functionally graded biomaterials project is to develop new materials, graded in porosity and composition, which will combine the desirable mechanical properties of implant, e.g., NiTi, with the bone-growth enhancement properties of porous biodegradable ceramics, e.g., Ca 3 (PO4 )2 . Recent experiments on the NASA parabolic flight (KC- 135) aircraft have shown that gravity plays an important role in controlling the structure and properties of materials produced by combustion synthesis. The results of these studies, which will be presented at the conference, will provide valuable input to the design of experiments to be done in Space-DRUMSTM, a containerless materials processing facility scheduled to be placed on the International Space Station in 2003.

Moore, J.; Schowengerdt, F.; Ayers, R.; Castillo, M.; Zhang, X.; Umakoshi, U.; Yi, C.; Guigne, J.

45

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

46

Mechanochemical and volume combustion synthesis of ZrB 2  

Microsoft Academic Search

Formation of ZrB2 by volume combustion synthesis (VCS) and mechanochemical process (MCP) from ZrO2–Mg–B2O3 was studied. Production of ZrB2 by VCS in air occurred with the formation of side products, Zr2ON2 and Mg3B2O6 in addition to MgO and ZrB2. Zr2ON2 formation was prevented by conducting VCS experiments under argon. Wet ball milling was applied to the VCS products before leaching

Bar?? Akgün; H. Erdem Çamurlu; Yavuz Topkaya; Naci Sevinç

2011-01-01

47

Combustion synthesis/quasi-isostatic pressing of TiCNiTi cermets: processing and mechanical response  

E-print Network

Combustion synthesis/quasi-isostatic pressing of TiC­NiTi cermets: processing and mechanical and alumina particulate before initiation of the combustion reaction. The sample was ignited within the particulate and subjected to a uniaxial load immediately after passage of the combustion wave

Meyers, Marc A.

48

A density functional theory study of hydrocarbon combustion and synthesis on Ni surfaces.  

PubMed

Combustion and synthesis of hydrocarbons may occur directly (CH ? C + H and CO ? C + O) or via a formyl (CHO) intermediate. Density functional theory (DFT) calculations were performed to calculate the activation and reaction energies of these reactions on Ni(111), Ni(110), and Ni(100) surfaces. The results show that the energies are sensitive to the surface structure. The dissociation barrier for methylidyne (CH ? C + H: catalytic hydrocarbon combustion) is lower than that for its oxidation reaction (CH + O ? CHO) on the Ni(110) and Ni(100) surfaces. However the oxidation barrier is lower than that for dissociation on the Ni(111) surface. The dissociation barrier for methylidyne dissociation decreases in the order Ni(111) > Ni(100) > Ni(110). The barrier of formyl dissociation to CO and H is almost the same on the Ni(111) and Ni(110) surfaces and is lower compared to the Ni(100) surface. The energy barrier for carbon monoxide dissociation (CO ? C + O: catalytic hydrocarbon synthesis) is higher than that of for its hydrogenation reaction (CO + H ? CHO) on all three surfaces. This means that the hydrogenation to CHO is favored on these nickel surfaces. The energy barrier for both reactions decreases in the order Ni(111) > Ni(100) > Ni(110). The barrier for formyl dissociation to CH + O decreases in the order Ni(100) > Ni(111) > Ni(110). Based on these DFT calculations, the Ni(110) surface shows a better catalytic activity for hydrocarbon combustion compared to the other surfaces, and Ni is a better catalyst for the combustion reaction than for hydrocarbon synthesis, where the reaction rate constants are small. The reactions studied here support the BEP principles with R(2) values equal to 0.85 for C-H bond breaking/forming and 0.72 for C-O bond breaking /forming reactions. PMID:25690364

Mohsenzadeh, Abas; Richards, Tobias; Bolton, Kim

2015-03-01

49

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

50

Combustion diagnostic for active engine feedback control  

DOEpatents

This invention detects the crank angle location where combustion switches from premixed to diffusion, referred to as the transition index, and uses that location to define integration limits that measure the portions of heat released during the combustion process that occur during the premixed and diffusion phases. Those integrated premixed and diffusion values are used to develop a metric referred to as the combustion index. The combustion index is defined as the integrated diffusion contribution divided by the integrated premixed contribution. As the EGR rate is increased enough to enter the low temperature combustion regime, PM emissions decrease because more of the combustion process is occurring over the premixed portion of the heat release rate profile and the diffusion portion has been significantly reduced. This information is used to detect when the engine is or is not operating in a low temperature combustion mode and provides that feedback to an engine control algorithm.

Green, Jr., Johney Boyd (Knoxville, TN); Daw, Charles Stuart (Knoxville, TN); Wagner, Robert Milton (Knoxville, TN)

2007-10-02

51

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

52

Combustion  

NSDL National Science Digital Library

In this chemistry activity, learners discover that the weight of the product of combustion is greater than that of the starting material. Learners will compare the weight of steel wool before and after it is heated. Learners are asked to consider why the steel wool weighs more (oxidation) as well as write the balanced chemical equation for the burning of steel. This activity uses an open flame; adult supervision is recommended. The resource includes notes for educators and extension ideas.

2014-01-28

53

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

54

Active combustion control : modeling, design and implementation  

E-print Network

Continuous combustion systems common in propulsion and power generation applications are susceptible to thermoacoustic instability, which occurs under lean burn conditions close to the flammability where most emissions and ...

Park, Sungbae, 1973-

2004-01-01

55

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

56

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

57

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

58

Processing and characterization of functionally graded titanium/titanium boride/titanium diboride composites by combustion synthesis/compaction and microwaves  

NASA Astrophysics Data System (ADS)

The use of functionally graded materials (FGMs) in aircraft, armor, medical and electronics industries is becoming more common as their performances exceed the capabilities of homogeneous materials. The concept of functionally graded materials (FGMs) was initially proposed to minimize problems such as poor mechanical integrity and interfacial adhesion associated with the presence of abrupt interfaces in metal-ceramic bonded structures. In this thesis, the combustion synthesis (CS) method was explored in fabricating FGMs in the Ti-B binary system. Among other methods CS has shown potential in terms of process economics and simplicity. Compositionally graded trilayered and five layered composites were produced by using three combustion methods: conventional combustion synthesis, combustion synthesis/compaction and microwave activated combustion synthesis. The porosity formation during CS has precluded the widespread use of this method. Therefore, a strategy was proposed to reduce the porosity, first, through control of vigorous combustion reactions and second, by applying pressure on the ignited samples. The control of the reactions was done by selecting compositions away from the stoichiometry without resorting to adding a third element into the system. These initiatives resulted in net shaped graded composites with improved density and hardness. As another processing method, microwave activated combustion synthesis was utilized by using SiC as a susceptor. When compared to conventional CS, microwave processed FGMs exhibited better microstructural homogeneity. All three methods resulted in Ti-TiB-TiB2 graded composite materials with continuous and crack free interfaces. Moire Interferometry tests were conducted to compare the deformation behavior of conventional combustion synthesized FGMs with that of microwave activated FGMs. The comparison was based on their in-plane displacements under compression loading. It was found that microwave produced FGMs exhibit a more compliant behavior. Under loads as low as 0.37 kN, the composites strained plastically. Also higher boron content layers exhibited a more compliant behavior compared to pure titanium layers.

Cirakoglu, Menderes

59

A Novel Combustion Synthesis Preparation of CuO/ZnO/ZrO2/Pd for Oxidative Hydrogen Production from Methanol  

E-print Network

A Novel Combustion Synthesis Preparation of CuO/ZnO/ZrO2/Pd for Oxidative Hydrogen Production from pre- pared via three combustion synthesis routes including volume combustion, impregnated substrate combustion, and so-called second wave impregnation combustion methods. These catalysts were characterized via

Mukasyan, Alexander

60

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

61

Combustion synthesis, sintering and magnetical properties of nanocristalline Ni-Zn ferrites doped with samarium  

Microsoft Academic Search

An investigation was made of combustion synthesis to uniformly incorporate small amounts of samarium additive into nanocrystalline Ni0.5Zn0.5Fe2 - xSmxO4 (0.0 = x = 0.1) nanopowders (˜26–20 nm particle size). The effect of the addition of the rare-earth ion samarium on the microstructure, relative density and magnetic properties of the Ni-Zn ferrite obtained by combustion reaction was studied. The samples

Ana Cristina F. M. Costa; Márcio R. Morelli; Ruth H. G. A. Kiminami

2004-01-01

62

Combustion synthesis and photoluminescence of nanocrystalline Y 2O 3:Eu phosphors  

Microsoft Academic Search

Nanoscale Y2O3:Eu phosphors have been prepared by glycine-nitrate solution combustion synthesis. The particle size of resultant powders is much related to the combustion flame temperature, which can be controlled by adjusting the glycine-to-nitrate ratio. The IR spectra, the excitation and the diffuse reflection spectra show the particle-size dependence of optical properties. The quenching concentration of nanostructured phosphors is increased greatly,

Tao Ye; Zhao Guiwen; Zhang Weiping; Xia Shangda

1997-01-01

63

Combustion of Powder Mixtures Forming Reaction Products - Synthesis of NiAl  

Microsoft Academic Search

Combustion of powder mixtures under adiabatic conditions -Self-propagating High-temperature Synthesis (SHS)-is an efficient and attractive technique to synthesize a host of materials for high technology applications, namely, ceramics, intermetallics, composites and functionally graded materials. Conditions necessary for and general features of this technique are briefly reviewed.Experimental investigations on synthesis of nickel monoaluminide from stoichiometric mixtures of component powders by this

S. K. ROY; A. BISWAS

2001-01-01

64

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

65

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

66

Combustion of Powder Mixtures Forming Reaction Products – Synthesis of NiAl  

Microsoft Academic Search

Combustion of powder mixtures under adiabatic conditions–Self-propagating High-temperature Synthesis (SHS)-is an efficient and attractive technique to synthesize a host of materials for high technology applications, namely, ceramics, intermetallics, composites and functionally graded materials. Conditions necessary for and general features of this technique are briefly reviewed.

S. K. ROY; A. BISWAS

2002-01-01

67

Effect of heating rate on the combustion synthesis of Ti-Al intermetallic compounds  

Microsoft Academic Search

Titanium aluminide compounds were synthesized by the thermal explosion mode of self-propagating high-temperature synthesis (SHS). The effects of heating rate on the combustion characteristics and the microstructures of the products were studied. It was found that the low density of the reacted sample was due to the outgassing of water vapour and other gases, which were released by dissociation of

H. C. Yi; A. Petric; J. J. Moore

1992-01-01

68

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...

69

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

70

Mechanistic Studies Of Combustion And Structure Formation During Combustion Synthesis Of Advanced Materials: Phase Separation Mechanism For Bio-Alloys  

NASA Technical Reports Server (NTRS)

Among all implant materials, Co-Cr-Mo alloys demonstrate perhaps the most useful balance of resistance to corrosion, fatigue and wear, along with strength and biocompatibility [1]. Currently, these widely used alloys are produced by conventional furnace technology. Owing to high melting points of the main alloy elements (e.g. Tm.p.(Co) 1768 K), high-temperature furnaces and long process times (several hours) are required. Therefore, attempts to develop more efficient and flexible methods for production of such alloys with superior properties are of great interest. The synthesis of materials using combustion phenomena is an advanced approach in powder metallurgy [2]. The process is characterized by unique conditions involving extremely fast heating rates (up to 10(exp 6 K/s), high temperatures (up to 3500 K), and short reaction times (on the order of seconds). As a result, combustion synthesis (CS) offers several attractive advantages over conventional metallurgical processing and alloy development technologies. The foremost is that solely the heat of chemical reaction (instead of an external source) supplies the energy for the synthesis. Also, simple equipment, rather than energy-intensive high-temperature furnaces, is sufficient. This work was devoted to experiments on CS of Co-based alloys by utilizing thermite (metal oxide-reducing metal) reactions, where phase separation subsequently produces materials with tailored compositions and properties. Owing to high reaction exothermicity, the CS process results in a significant increase of temperature (up to 3000 C), which is higher than melting points of all products. Since the products differ in density, phase separation may be a gravitydriven process: the heavy (metallic phase) settles while the light (slag) phase floats. The goal was to determine if buoyancy is indeed the major mechanism that controls phase segregation.

Varma, A.; Lau, C.; Mukasyan, A.

2003-01-01

71

Mechanistic Studies of 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 (mu-g) experiments lead to major advances in the understanding of fundamental aspects of combustion and structure formation under the extreme conditions of the combustion synthesis (CS) wave. In addition, the specific features of microgravity environment allow one to produce unique materials, which cannot be obtained under terrestrial conditions. The current research is a logic continuation of our previous work on investigations of the fundamental phenomena of combustion and structure formation that occur at the high temperatures achieved in a CS wave. Our research is being conducted in three main directions: 1) Microstructural Transformations during Combustion Synthesis of Metal-Ceramic Composites. The studies are devoted to the investigation of particle growth during CS of intermetallic-ceramic composites, synthesized from nickel, aluminum, titanium, and boron metal reactants. To determine the mechanisms of particle growth, the investigation varies the relative amount of components in the initial mixture to yield combustion wave products with different ratios of solid and liquid phases, under 1g and mu-g conditions; 2) Mechanisms of Heat Transfer during Reactions in Heterogeneous Media. Specifically, new phenomena of gasless combustion wave propagation in heterogeneous media with porosity higher than that achievable in normal gravity conditions, are being studied. Two types of mixtures are investigated: clad powders, where contact between reactants occurs within each particle, and mixtures of elemental powders, where interparticle contacts are important for the reaction; and 3) Mechanistic Studies of Phase Separation in Combustion of Thermite Systems. Studies are devoted to experiments on thermite systems (metal oxide-reducing metal) where phase separation processes occur to produce alloys with tailored compositions and properties. The separation may be either gravity-driven or due to surface forces, and systematic studies to elucidate the true mechanism are being conducted. The knowledge obtained will be used to find the most promising ways of controlling the microstructure and properties of combustion-synthesized materials. Low-gravity experiments are essential to create idealized an environment for insights into the physics and chemistry of advanced material synthesis processes.

Varma, A.; Lau, C.; Mukasyan, A. S.

2001-01-01

72

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

73

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

74

Processing of porous TiB2-ZrO2 composites by combustion synthesis  

SciTech Connect

Porous titanium diboride (TiB2) - zirconia (ZrO2) composites were produced by the combustion-synthesis process. The starting materials contained various ratios of Ti, B, and partially stabilized ZrO2 (Y2O3) powders. Compacted pellets could be ignited and the exothermic reactions were self-sustaining. With the increase in ZrO2 content, the reaction was more controlled. The as-processed materials were characterized by X-ray and scanning electron microscopy. ZrO2 remained as the tetragonal phase in the microstructure. These preliminary results indicate that it is possible to produce transformation-toughened TiB2-matrix composites by the combustion-synthesis process. 14 refs.

Bhaduri, S.B.; Radhakrishnan, R.

1992-08-01

75

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

76

Lightweight Mg-based composites with thermodynamically stable interfaces by in-situ combustion synthesis  

NASA Astrophysics Data System (ADS)

Lightweight Mg-based composites have been produced by in-situ combustion synthesis of the Al-Ti-C reaction system. The characteristics of the in-situ composites were investigated in terms of phase evolution and interfacial stability using various analysis techniques. The structural analysis results showed that full conversion of the Al-Ti-C reactants into spherical TiC reinforcements with sizes around 1mum was achieved by the combustion reaction. In-situ formed TiC had less oxygen and higher Al contents at the interface than ex-situ formed TiC; these clean interfaces with an Al layer on the reinforcements were shown to yield interfacial stability. For these reasons, the in-situ composites exhibited higher theoretical densities and also good mechanical properties compared with ex-situ produced composites. The interfacial characteristics of molten Mg with the Al-Ti-C reactants and the commercial TiC+Al substrates were evaluated using an infiltration technique under an argon atmosphere. Infiltration length increased with time at temperature, yielding activation energies (Ea) for each system. The value of Ea for the Al-Ti-C system (307.31kJ/mol) is lower than that for the other system (350.84kJ/mol); the high Ea value indicates that the infiltration is not a simple viscosity-controlled phenomenon but involves a chemical reaction. Formation of the Al3Ti phase was observed from the crystal structural analysis of the infiltrated area; thus, existence of reaction promoting the wetting of Mg. The phase evolution, reaction mechanism and kinetics of the Al-Ti-C reaction were studied using DSC and HT-XRD. It was confirmed that, along with the melting of Al, there was formation of Al3Ti by reaction between Al and Ti. A detailed structural analysis indicates that, the reaction mechanism involves melting of Al followed by formation and growth of Al 3Ti, which then contacts the graphite powder and initiates the combustion reaction. The effect of important process parameters, such as the Al content and the reactant sizes, on the microstructure of the resulting in-situ composites is discussed. Feasibility and castability of the composites were investigated by high pressure die casting the composite preforms into automotive parts and durability tests were conducted on the cast parts.

Jo, Ilguk

77

Combustion synthesis and EIS characterization of TiO 2–SnO 2 system  

Microsoft Academic Search

TiO2 is an insulator, but using specific dopants, can modify sharply its electronic structure towards semiconducting behavior. This type of response is widely applied in many electrochemical and electrocatalytical devices, namely chlorine production, hydrocarbon oxidation, CO and CO2 hydrogenation and as electroactive substrata for biological cell growth.Combustion synthesis is a very simple, rapid and clean method for material preparation, which

E. Chinarro; B. Moreno; J. R. Jurado

2007-01-01

78

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

79

Self-propagating high-temperature synthesis for compound thermoelectrics and new criterion for combustion processing  

PubMed Central

The existing methods of synthesis of thermoelectric (TE) materials remain constrained to multi-step processes that are time and energy intensive. Here we demonstrate that essentially all compound thermoelectrics can be synthesized in a single-phase form at a minimal cost and on the timescale of seconds using a combustion process called self-propagating high-temperature synthesis. We illustrate this method on Cu2Se and summarize key reaction parameters for other materials. We propose a new empirically based criterion for sustainability of the combustion reaction, where the adiabatic temperature that represents the maximum temperature to which the reacting compact is raised as the combustion wave passes through, must be high enough to melt the lower melting point component. Our work opens a new avenue for ultra-fast, low-cost, large-scale production of TE materials, and provides new insights into combustion process, which greatly broaden the scope of materials that can be successfully synthesized by this technique. PMID:25223333

Su, Xianli; Fu, Fan; Yan, Yonggao; Zheng, Gang; Liang, Tao; Zhang, Qiang; Cheng, Xin; Yang, Dongwang; Chi, Hang; Tang, Xinfeng; Zhang, Qingjie; Uher, Ctirad

2014-01-01

80

New combustion synthesis technique for the production of (InxGa1-x)2O3 powders: Hydrazine/metal nitrate method  

E-print Network

New combustion synthesis technique for the production of (InxGa1-x)2O3 powders: Hydrazine. The combustion reaction occurred when heating the precursors between 150 and 200 °C in a closed vessel filled by a more typical combustion synthesis reaction between nitrates and a carbonaceous fuel at a higher

McKittrick, Joanna

81

A New Combustion Synthesis Method for GaN:Eu3+ and Ga2O3 :Eu3+  

E-print Network

A New Combustion Synthesis Method for GaN:Eu3+ and Ga2O3 :Eu3+ Luminescent Powders G. A. Hirata1 between the precursors. The preparation of Eu-doped Ga2O3 powders was achieved using a new combustion)3 and Ga(NO3)3 as the precursors and hydrazine as (non-carbonaceous) fuel. A spontaneous combustion

McKittrick, Joanna

82

Combustion  

NASA Technical Reports Server (NTRS)

An overview of the emissions related research being conducted as part of the Fundamental Aeronautics Subsonics Fixed Wing Project is presented. The overview includes project metrics, milestones, and descriptions of major research areas. The overview also includes information on some of the emissions research being conducted under NASA Research Announcements. Objective: Development of comprehensive detailed and reduced kinetic mechanisms of jet fuels for chemically-reacting flow modeling. Scientific Challenges: 1) Developing experimental facilities capable of handling higher hydrocarbons and providing benchmark combustion data. 2) Determining and understanding ignition and combustion characteristics, such as laminar flame speeds, extinction stretch rates, and autoignition delays, of jet fuels and hydrocarbons relevant to jet surrogates. 3) Developing comprehensive kinetic models for jet fuels.

Bulzan, Dan

2007-01-01

83

Facile microwave-combustion synthesis of wurtzite CdS nanoparticles.  

PubMed

In this study we first report microwave-combustion synthesis of faceted CdS nanoparticles by using cadmium thiocyanate complex as a single source precursor. This is the first example of a metal-thiocyanate (M-SCN) complex being used as a source for metal sulfides (M-S) preparation in a microwave-combustion process. The synthesized CdS was characterized using X-ray diffraction (XRD), field mission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). The by-product assisted combustion synthesis yields CdS nanoparticles with the mixtures of octahedral geometries, hexagonal, and triangle plate morphologies and the sizes were found to be 100 nm to 5 microm. The XRD patterns imply the formation of well crystallized wurtzite CdS. The influence of cadmium and sulfur precursors and microwave irradiation time on the morphology of CdS nanoparticle was also investigated. The cadmium and sulfur precursors strongly influenced the CdS morphology and increasing the microwave irradiation time and intensity has no effect on the CdS morphology. In addition, a plausible mechanism of CdS nanoparticle formation has been proposed in this research. PMID:22097510

Amutha, R; Muruganandham, M; Lee, G J; Wu, J J

2011-09-01

84

Synthesis, droplet combustion, and sooting characteristics of biodiesel produced from waste vegetable oils  

SciTech Connect

In light of the potential of fatty acid methyl ester (FAME, i.e. biodiesel) as a renewable energy source, an innovative acid catalyzed process was developed for the synthesis of biodiesel from waste vegetable oils. The synthesized biodiesels were analytically characterized for their major components, molar fraction and molecular weight of each component, the average molecular weight, and the heat of combustion. Their droplet combustion characteristics in terms of the burning rate, flame size, and sooting tendency were subsequently determined in a high-temperature, freely-falling droplet apparatus. Results show that the biodiesel droplet has higher burning rate, and that biodiesel in general has a lower propensity to soot because its molecular oxygen content promotes the oxidation of the soot precursors.

Li, T. X.; Zhu, D. L.; Akafuah, N.; Saito, K.; Law, C. K.

2011-01-01

85

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

Code of Federal Regulations, 2012 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Compliance Times for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

2012-07-01

86

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

Code of Federal Regulations, 2010 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Performance for Small Municipal Waste Combustion Units for Which Construction is Commenced...records must I keep for municipal waste combustion units that use activated carbon?...

2010-07-01

87

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

Code of Federal Regulations, 2014 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Compliance Times for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

2014-07-01

88

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

Code of Federal Regulations, 2010 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Compliance Times for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

2010-07-01

89

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

Code of Federal Regulations, 2013 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Requirements for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

2013-07-01

90

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

Code of Federal Regulations, 2011 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Requirements for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

2011-07-01

91

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

Code of Federal Regulations, 2010 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Requirements for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

2010-07-01

92

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

Code of Federal Regulations, 2014 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Requirements for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

2014-07-01

93

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

Code of Federal Regulations, 2011 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Performance for Small Municipal Waste Combustion Units for Which Construction is Commenced...records must I keep for municipal waste combustion units that use activated carbon?...

2011-07-01

94

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

Code of Federal Regulations, 2013 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Performance for Small Municipal Waste Combustion Units for Which Construction is Commenced...records must I keep for municipal waste combustion units that use activated carbon?...

2013-07-01

95

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

Code of Federal Regulations, 2014 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Performance for Small Municipal Waste Combustion Units for Which Construction is Commenced...records must I keep for municipal waste combustion units that use activated carbon?...

2014-07-01

96

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

Code of Federal Regulations, 2011 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Compliance Times for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

2011-07-01

97

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

Code of Federal Regulations, 2012 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Performance for Small Municipal Waste Combustion Units for Which Construction is Commenced...records must I keep for municipal waste combustion units that use activated carbon?...

2012-07-01

98

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

Code of Federal Regulations, 2013 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Compliance Times for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

2013-07-01

99

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

Code of Federal Regulations, 2012 CFR

...records must I keep for municipal waste combustion units that use activated carbon? ...Requirements for Small Municipal Waste Combustion Units Constructed on or Before August...records must I keep for municipal waste combustion units that use activated carbon?...

2012-07-01

100

Combustion synthesis: A suitable method to prepare Al 2 O 3 doped materials for thermoluminescent dosimetry  

Microsoft Academic Search

In this work we present an alternative route to synthesize rare-earth doped aluminum oxide materials for thermoluminescent (TL) dosimetry using the combustion synthesis (CS) technique. The samples were prepared by mixing aluminum nitrate (Al(NO3)3·9H2O), urea (CO(NH2)2), and europium nitrate (Eu(NO3)3), terbium nitrate (Tb(NO3)3) and tetra-ethyl-ortho-silicate (TEOS, C8H20O4Si) in appropriate amounts as dopants in an aqueous solution. The excess water was

Vinícius S. M. de Barros; Walter M. de Azevedo; Helen J. Khoury; Pedro Linhares Filho

2008-01-01

101

Synthesis and anticancer activity of epipolythiodiketopiperazine alkaloids  

E-print Network

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 ...

Boyer, Nicolas

102

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

103

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

104

Spray-combustion synthesis: Efficient solution route to high-performance oxide transistors.  

PubMed

Metal-oxide (MO) semiconductors have emerged as enabling materials for next generation thin-film electronics owing to their high carrier mobilities, even in the amorphous state, large-area uniformity, low cost, and optical transparency, which are applicable to flat-panel displays, flexible circuitry, and photovoltaic cells. Impressive progress in solution-processed MO electronics has been achieved using methodologies such as sol gel, deep-UV irradiation, preformed nanostructures, and combustion synthesis. Nevertheless, because of incomplete lattice condensation and film densification, high-quality solution-processed MO films having technologically relevant thicknesses achievable in a single step have yet to be shown. Here, we report a low-temperature, thickness-controlled coating process to create high-performance, solution-processed MO electronics: spray-combustion synthesis (SCS). We also report for the first time, to our knowledge, indium-gallium-zinc-oxide (IGZO) transistors having densification, nanoporosity, electron mobility, trap densities, bias stability, and film transport approaching those of sputtered films and compatible with conventional fabrication (FAB) operations. PMID:25733848

Yu, Xinge; Smith, Jeremy; Zhou, Nanjia; Zeng, Li; Guo, Peijun; Xia, Yu; Alvarez, Ana; Aghion, Stefano; Lin, Hui; Yu, Junsheng; Chang, Robert P H; Bedzyk, Michael J; Ferragut, Rafael; Marks, Tobin J; Facchetti, Antonio

2015-03-17

105

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

NASA Astrophysics Data System (ADS)

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; Mizuma, Kiminori; Matsuura, Kiyotaka; Iguchi, Manabu

2008-02-01

106

The effect of hydrostatic pressure on the combustion synthesis of Y 2O 3:Bi nanophosphor  

NASA Astrophysics Data System (ADS)

The effects of pressurized Ar environments during the solution combustion synthesis (SCS) of Y 2O 3:Bi nanophosphor were investigated. Three fuels were used urea, glycine and hexamethylenetetramine (HMT) and the nanopowders were characterized by X-ray diffraction, scanning electron microscopy, photoluminescence, fluorescence lifetime, and thermoluminescence measurements. The dominant crystallographic phase was cubic, with crystallite size being insensitive to the hydrostatic pressure but increasing for fuels with higher heat of combustion. At least for nanopowders obtained using fuels with higher heats of combustion, higher Ar hydrostatic pressures lead to lower photoluminescence output. Fluorescence lifetime measurements on HMT-prepared samples yielded lifetimes of 330 and 900 ns for Bi 3+ ions in S 6 and C 2 sites, respectively, and no variation in these values was observed for hydrostatic pressures from 0.1 to 9.7 MPa. Shorter lifetime values than reported for conventional SCS are likely related to higher concentration of quenching defects. In agreement with these results, thermoluminescence measurements showed that higher concentrations of electronic traps are present in samples synthesized under higher pressures.

Jacobsohn, L. G.; Tappan, B. C.; Tornga, S. C.; Blair, M. W.; Luther, E. P.; Mason, B. A.; Bennett, B. L.; Muenchausen, R. E.

2010-03-01

107

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....

108

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

109

Effect Of Gravity On Porous Tricalcium Phosphate And Nonstoichiometric Titanium Carbide Produced Via Combustion Synthesis  

NASA Technical Reports Server (NTRS)

Novel processing techniques, such as self-propagating high temperature synthesis (SHS), have the capability to rapidly produce advanced porous materials that are difficult to fabricate by other methods. This processing technique is also capable of near net shape synthesis, while variable gravity allows the manipulation of the structure and composition of the material. The creation of porous tricalcium phosphate (TCP) is advantageous in the biomaterials field, since it is both a biocompatible material and an osteoconductive material. Porous tricalcium phosphate produced via SHS is an excellent candidate for bone scaffold material in the bone regeneration process. The porosity allows for great vascularization and ingrowth of tissue. Titanium Carbide is a nonstoichiometric biocompatible material that can be incorporated into a TiC-Ti composite system using combustion synthesis. The TiC-Ti composite exhibits a wide range of mechanical and chemical properties. Both of these material systems (TCP and TiC-Ti) can be used to advantage in designing novel bone replacement materials. Gravity plays an important role in both the pore structure and the chemical uniformity of these composite systems and offers considerable potential in advanced bone engineering.

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

2003-01-01

110

Combustion synthesis of MoSi{sub 2} - SiC oxidation resistant coatings  

SciTech Connect

Several high-temperature, oxidation resistant materials were investigated as possible coatings for molybdenum furnace elements. Molybdenum disilicide (MoSi{sub 2}) composites are potential candidates for these high temperature coating applications. Composite materials were selected based on several factors, including oxidation resistance, coefficients of thermal expansion, compatibility at the coating/substrate interface, thermodynamic stability over a large temperature range and adhesion. The synthesis of dense MoSi{sub 2}-SiC composites through simultaneous combustion and hot-pressing is currently being investigated. Functionally graded materials (FGM`s) are being studied to overcome some of the property differences between a coating and a substrate. Oxidation testing was used to determine the protective qualities of the FGM`s.

Monroe, K.A.; Govindarajan, S.; Moore, J.J. [Colorado School of Mines, Golden, CO (United States)] [and others

1994-12-31

111

Oxygen carrier development for chemical looping combustion of coal derived synthesis gas  

SciTech Connect

In the present work, NETL researchers have studied chemical looping combustion (CLC) with an oxygen carrier NiO/bentonite (60 wt.% NiO) for the IGCC systems utilizing simulated synthesis gas. Multi cycle CLC was conducted with NiO/Bentonite in TGA at atmospheric pressure and in a high pressure reactor in a temperature range between 700-900°C. Global reaction rates of reduction and oxidation as a function of conversion were calculated for all oxidation-reduction cycles utilizing the TGA data. The effect of particle size of the oxygen carrier on CLC was studied for the size between 20-200 mesh. The multi cycle CLC tests conducted in a high pressure packed bed flow reactor indicated constant total production of CO2 from fuel gas at 800°C and 900°C and full consumption of hydrogen during the reaction.

Siriwardane, R.V.; Chaudhari, K.; Zinn, A.N.; Simonyi, T.; Robinson, Clark; Poston, J.A.

2006-09-01

112

Combustion synthesis of CuFe{sub 2}O{sub 4}  

SciTech Connect

Metallic ferrites are investigated as prospective materials for different applications especially as anodes in extractive metallurgy. CuFe{sub 2}O{sub 4}, one of the important ferrites, is envisaged for substituting the carbon anode in Hall-Heroult cells. A single step combustion process has been used for the synthesis of CuFe{sub 2}O{sub 4} powder from cupric nitrate, ferric nitrate and urea. The experimental conditions for maximum conversion efficiency of the precursor powders have been optimized. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) have confirmed the formation, structure and homogeneity of the as-prepared powders. The detailed physical, electrical and structural characterization of the materials have been carried out for the specimens obtained on sintering at different temperatures up to 1000 deg. C.

Selvan, R. Kalai; Augustin, C.O.; Berchmans, L. John; Saraswathi, R

2003-01-01

113

Optical filtering and luminescence property of some molybdates prepared by combustion synthesis  

SciTech Connect

As an important class of lanthanide inorganic compounds, rare earth ions doped molybdates have gained much attention due to their attractive luminescence and structural properties, supporting various promising applications as phosphor materials in the fields such as white light-emitting diodes, optical fibers, biolabel, lasers, and so on. The molybdate family has promising trivalent cation conducting properties and most of the optical properties result from electron transitions of the 4f shell, which are greatly affected by the composition and structures of rare-earth compounds. In this paper we report the molybdate CaMoO{sub 4}:Eu{sup 3+} for red SSL and Bi{sub 1.4}Y{sub 0.6}MoO{sub 6}, Y{sub 6}MoO{sub 12} for optical filtering, prepared by one step combustion synthesis.

Yadav, P. J., E-mail: yadav.pooja75@yahoo.in [Department of Electronics, RTM Nagpur University, Nagpur (India); Joshi, C. P. [Physics Department, RCOEM, Nagpur (India); Moharil, S. V., E-mail: svmoharil@yahoo.com [Physics Department, RTM Nagpur University, Nagpur (India)

2014-10-15

114

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

115

a New Combustion Synthesis Technique for Rare Earth-Doped Iii-Nitride Luminescent Powders  

NASA Astrophysics Data System (ADS)

A new low temperature method to produce ((RE)xGa1-x)2O3(1?x?0 and RE=Eu, Yb, Pr and Tm) powders with high purity, high chemical homogeneity and improved crystallinity has been developed. This procedure produces finely divided powders through an exothermic reaction between the precursors. The process starts with aqueous solutions of RE(NO3)3 and Ga(NO3)3 as the precursors and hydrazine as the (non-carbonaceous) fuel. The combustion reaction occurs when heating the precursors between 150 and 200°C in a closed vessel filled with an inert gas (Ar), which yields (RExGa1-x)2O3 directly. The preparation of RE-doped Ga2O3 powders was using a new combustion synthesis technique (Hydrazine / metal nitrate method). The preparation of Eu-doped GaN was using the ammonium hexafluoro-metal method. The powders were crystalline and high-purity as determined by XPS, EDS, SEM and XRD measurements.

Ramos, F. E.; Garcia, R.; Hirata, G. A.; Bosze, E. J.; McKittrick, J.

116

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

117

Active control of combustion instabilities via hybrid resetting controllers  

Microsoft Academic Search

We propose an energy flow resetting control architecture as a means for achieving enhanced energy dissipation in combustion systems. The overall framework is based on a hybrid controller architecture wherein the closed-loop dynamical system is characterized by impulsive differential equations. The proposed framework is used to design high-performance hybrid controllers for suppressing thermoacoustic oscillations in combustion chambers by efficiently dissipating

Wassim M. Haddad; V. Chellabsina; NataSa A. Kablar

2000-01-01

118

Influence of the addition of hydrogen and of a synthesis gas on the characteristics of the process of combustion of gasoline-air mixtures under conditions typical of internal combustion engines  

Microsoft Academic Search

The influence of the addition of hydrogen and of a synthesis gas on the basic parameters of combustion of gasoline-air fuel mixtures is investigated theoretically. The possibility of feeding gasoline internal combustion engines with lean fuel mixtures with a concentration of 5 10 vol.% hydrogen is shown; this will greatly improve their ecological purity.

A. N. Migun; A. P. Chernukho; S. A. Zhdanok

2006-01-01

119

Method and apparatus for active control of combustion rate through modulation of heat transfer from the combustion chamber wall  

DOEpatents

The flame propagation rate resulting from a combustion event in the combustion chamber of an internal combustion engine is controlled by modulation of the heat transfer from the combustion flame to the combustion chamber walls. In one embodiment, heat transfer from the combustion flame to the combustion chamber walls is mechanically modulated by a movable member that is inserted into, or withdrawn from, the combustion chamber thereby changing the shape of the combustion chamber and the combustion chamber wall surface area. In another embodiment, heat transfer from the combustion flame to the combustion chamber walls is modulated by cooling the surface of a portion of the combustion chamber wall that is in close proximity to the area of the combustion chamber where flame speed control is desired.

Roberts Jr., Charles E.; Chadwell, Christopher J.

2004-09-21

120

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

121

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

122

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

123

Chemical-looping combustion of coal-derived synthesis gas over copper oxide oxygen carriers  

SciTech Connect

CuO/bentonite and CuO-BHA nanocomposites were studied as oxygen carriers in chemical-looping combustion (CLC) of simulated synthesis gas. Global reaction rates of reduction and oxidation, as the function of reaction conversion, were calculated from 10-cycle oxidation/reduction tests utilizing thermogravimetric analysis at atmospheric pressure between 700 and 900 °C. It was found that the reduction reactions are always faster than oxidation reactions; reaction temperature and particle size do not significantly affect the reaction performance of CuO/bentonite. Multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivity for production of CO2 from fuel gas at 800 and 900 °C and full consumption of hydrogen during the reaction. Results of the tapered element oscillating microbalance showed a negative effect of pressure on the global rates of reduction-oxidation reactions at higher fractional conversions. X-ray diffraction patterns confirmed the presence of CuO in the bulk phase of the oxidized sample. Electron microanalysis showed significant morphology changes of reacted CuO/bentonite samples after the 10 oxidation-reduction cycles above 700 °C in an atmospheric thermogravimetric analyzer. The nanostructured CuO-BHA carrier also showed excellent stability and, in comparison to the CuO/bentonite system, slightly accelerated redox kinetics albeit at the expense of significantly increased complexity of manufacturing. Overall, both types of CuO carriers exhibited excellent reaction performance and thermal stability for the CLC process at 700-900 °C.

Tian, H.; Chaudhari, K.; Simonyi, T.; Poston, J.; Liu, T.; Sanders, T.; Veser, G.; Siriwardane, R.

2008-01-01

124

Chemical-looping combustion of coal-derived synthesis gas over copper oxide oxygen carriers  

SciTech Connect

CuO/bentonite and CuO?BHA nanocomposites were studied as oxygen carriers in chemical-looping combustion (CLC) of simulated synthesis gas. Global reaction rates of reduction and oxidation, as the function of reaction conversion, were calculated from 10-cycle oxidation/reduction tests utilizing thermogravimetric analysis at atmospheric pressure between 700 and 900 °C. It was found that the reduction reactions are always faster than oxidation reactions; reaction temperature and particle size do not significantly affect the reaction performance of CuO/bentonite. Multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivity for production of CO2 from fuel gas at 800 and 900 °C and full consumption of hydrogen during the reaction. Results of the tapered element oscillating microbalance showed a negative effect of pressure on the global rates of reduction?oxidation reactions at higher fractional conversions. X-ray diffraction patterns confirmed the presence of CuO in the bulk phase of the oxidized sample. Electron microanalysis showed significant morphology changes of reacted CuO/bentonite samples after the 10 oxidation?reduction cycles above 700 °C in an atmospheric thermogravimetric analyzer. The nanostructured CuO?BHA carrier also showed excellent stability and, in comparison to the CuO/bentonite system, slightly accelerated redox kinetics albeit at the expense of significantly increased complexity of manufacturing. Overall, both types of CuO carriers exhibited excellent reaction performance and thermal stability for the CLC process at 700?900 °C.

Tian, Hanjing; Chaudhari, K.P.; Simonyi, Thomas; Poston, J.A.; Liu, Tengfei; Sanders, Tom; Veser, Goetz; Siriwardane, R.V.

2008-11-01

125

Perylenequinones: Isolation, Synthesis, and Biological Activity  

PubMed Central

The perylenequinones are a novel class of natural products characterized by pentacyclic conjugated chromophore giving rise to photoactivity. Potentially useful light-activated biological activity, targeting protein kinase C (PKC), has been identified for several of the natural products. Recently discovered new members of this class of compound, as well as several related phenanthroperylenequinones, are reviewed. Natural product modifications that improve biological profiles, and avenues for the total synthesis of analogs, which are not available from the natural product series, are outlined. An overview of structure/function relationships is provided. PMID:24039544

Mulrooey, Carol A.; O'Brien, Erin M.; Morgan, Barbara J.

2013-01-01

126

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

127

Biosynthesis, Synthesis and Biological Activities of Pyrrolobenzodiazepines  

PubMed Central

Pyrrolobenzodiazepines (PBDs) are sequence selective DNA alkylating agents with remarkable antineoplastic activity. They are either naturally produced by actinomycetes or synthetically produced. The remarkable broad spectrum of activities of the naturally produced PBDs encouraged the synthesis of several PBDs, including dimeric and hybrid PBDs yielding to an improvement in the DNA binding sequence specificity and in the potency of this class of compounds. However, limitation in the chemical synthesis prevented the testing of one of the most potent PBDs, sibiromycin, a naturally produced glycosylated PBDs. Only recently the biosynthetic gene clusters for PBDs have been identified opening the doors to the production of glycosylated PBDs by mutasynthesis and biosynthetic engineering. The present review describes the recent studies on the biosynthesis of naturally produced pyrrolobenzodiazepines. In addition, it provides an overview on the isolation and characterization of naturally produced PBDs, on the chemical synthesis of PBDs, on the mechanism of DNA alkylation, and on the DNA binding affinity and cytotoxic properties of both naturally produced and synthetic pyrrolobenzodiazepines. PMID:20544978

Gerratana, Barbara

2014-01-01

128

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. PMID:23914293

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

2013-01-01

129

Chemical-looping combustion of coal-derived synthesis gas over copper oxide oxygen carriers  

SciTech Connect

CuO/bentonite and CuO-BHA nanocomposites were studied as oxygen carriers in chemical-looping combustion (CLC) of simulated synthesis gas. Global reaction rates of reduction and oxidation, as the function of reaction conversion, were calculated from 10-cycle oxidation/reduction tests utilizing thermogravimetric analysis at atmospheric pressure between 700 and 900{degree}C. It was found that the reduction reactions are always faster than oxidation reactions; reaction temperature and particle size do not significantly affect the reaction performance of CuO/bentonite. Multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivity for production of CO{sub 2} from fuel gas at 800 and 900{degree}C and full consumption of hydrogen during the reaction. Results of the tapered element oscillating microbalance showed a negative effect of pressure on the global rates of reduction-oxidation reactions at higher fractional conversions. X-ray diffraction patterns confirmed the presence of CuO in the bulk phase of the oxidized sample. Electron microanalysis showed significant morphology changes of reacted CuO/bentonite samples after the 10 oxidation-reduction cycles above 700{degree}C in an atmospheric thermogravimetric analyzer. The nanostructured CuO-BHA carrier also showed excellent stability and, in comparison to the CuO/bentonite system, slightly accelerated redox kinetics albeit at the expense of significantly increased complexity of manufacturing. Overall, both types of CuO carriers exhibited excellent reaction performance and thermal stability for the CLC process at 700-900{degree}C. 48 refs., 12 figs., 8 tabs.

Hanjing Tian; Karuna Chaudhari; Thomas Simonyi; James Poston; Tengfei Liu; Tom Sanders; Goetz Veser; Ranjani Siriwardane [U.S. Department of Energy, Morgantown, WV (United States). National Energy Technology Laboratory

2008-11-15

130

Cloud-active particles from African savanna combustion experiments  

NASA Astrophysics Data System (ADS)

In order to study the behaviour of the combustion aerosols and to quantify the emission of particles, especially of CCN, various burning experiments on Guinean savanna species as commonly growing in Ivory Coast and throughout Africa were carried out in a large test chamber (160 m 3) or in a combustion chamber capable of separating the flaming phase from the smoldering one. The total particulate matter, as dominated by the smoldering process, ranges from 0.005 to 0.019 g per g of dry matter (d.m.), while the number of Aitken nuclei is of the same order of magnitude for both processes, averaging ? 2.5 × 10 12 g -1 d.m. A large part of the particles are hygroscopic even at relative humidity (RH) quite below water saturation. Such a behaviour may be explained by the chemical composition of resolved-size particle samples. Ion chromatography reveals that most particles with diameter ?0.5 ?m contain the larger mass fraction of chloride, nitrate and sulfate, so that the combustion particles can deliquesce as salt particles or as salt-coated particles at critical RH related to NH 4NO 3, NaNO 3, NH 4Cl, (NH 4) 2SO 4, etc. The CCN emission factor (EF) is 2 to 6 times higher for the smoldering than for the flaming, probably due to the larger particle size range. For all experiments, the EF averages ? 2 × 10 11 g -1 d.m. at 0.1% supersaturation (SS), leading to a flux of 300 to 600 CCN s -1 cm -2 and thus to an overall production rate of 3 × 10 19 to 6 × 10 19 CCN s -1 at 0.1% SS for the African savannas, that is a source of the same order of magnitude as the other ones, natural or anthropogenic.

Pham-Van-Dinh; Lacaux, Jean-Pierre; Serpolay, Roger

131

Influence of the addition of hydrogen and of a synthesis gas on the characteristics of the process of combustion of gasoline-air mixtures under conditions typical of internal combustion engines  

Microsoft Academic Search

The influence of the addition of hydrogen and of a synthesis gas on the basic parameters of combustion of gasoline-air fuel\\u000a mixtures is investigated theoretically. The possibility of feeding gasoline internal combustion engines with lean fuel mixtures\\u000a with a concentration of 5–10 vol.% hydrogen is shown; this will greatly improve their ecological purity.

A. N. Migun; A. P. Chernukho; S. A. Zhdanok

2006-01-01

132

Processing and characterization of functionally graded TiB{sub 2}/NiAl produced by the combustion synthesis process  

SciTech Connect

NiAl/TiB{sub 2} functionally graded composites were produced by the combustion synthesis process. X-ray diffraction and optical microscopy were used to characterize the microstructure. Hardness measurement at room temperature and 900{degrees}C were used to probe the mechanical properties. The Vickers hardness at room temperature varies linearly with TiB{sub 2} content. However, the high temperature hardness varies non-linearly with TiB{sub 2} content and is sensitive to microstructure. In particular, plastic flow in NiAl at high temperature depends on TiB{sub 2} particle size.

Torres, R.D.; Reimanis, I.E.; Mustoe, G.G.W.; Moore, J.J. [Colorado School of Mines, Golden, CO (United States)

1997-12-31

133

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

134

Modeling Reaction Front Propagation and Porosity in Pressure-Assisted Combustion Synthesis of Porous NiTi Intermetallics  

NASA Astrophysics Data System (ADS)

A mathematical model is developed to investigate the effect of various processing parameters on pressure-assisted combustion synthesis of NiTi intermetallics. Specifically, preheat and ambient temperature, particle size, initial porosity, and pressure differential are studied to determine their influence on propagation behavior and final porosity. The governing equations are solved using a high-order-implicit numerical scheme capable of accommodating the steep spatial and temporal gradients of properties. The predicted results appear plausible and consistent with the trends presented in the available literature.

Ballas, Matthew; Li, Zhiliang; Ilegbusi, Olusegun J.

2012-03-01

135

Catalytic charge activation in a lean-burn internal combustion engine  

Microsoft Academic Search

Catalytic surface ignition commonly begins at temperatures several hundred degrees Celsius lower than the gas phase ignition temperature for the same combustible mixture. Heterogeneous catalysis therefore can be used to modify homogeneous chemical activity under otherwise non-reacting conditions. Theoretical analysis of flame propagation through catalytically activated mixtures and fundamental experiments with a catalytic plug-flow reactor have shown that catalytic prereaction

Beyerlein

1987-01-01

136

Experimental Investigation of Active Noise Controller for Internal Combustion Engine Exhaust System  

Microsoft Academic Search

Two active noise control (ANC) algorithms for internal combustion engine exhaust systems are developed and their performances are compared in various experiments. The first controller is based on the filtered-x least mean square (FXLMS) algorithm with feedback neutralization, while the second is a fixed controller with a gain-scheduled active control technique for broadband attenuation with thermal effects. Both control algorithms

Jian-Da Wu; Chih-Keng Chen; Chun-Ying Lee; Tian-Hua Lee

2002-01-01

137

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.

138

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

139

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

140

: Synthesis, Characterization, and Enhanced Photocatalytic Activity  

NASA Astrophysics Data System (ADS)

3D hierarchical microspheres of Cu-loaded Bi2WO6 are successfully prepared by the hydrothermal synthesis method on a large scale. The as-prepared samples are characterized by UV-Vis DRS, BET, XRD, XPS, and SEM. The results reveal that the light absorption of Cu-loaded Bi2WO6 has higher intensity in the visible range and a bathochromic shift of the absorption edge compared to that of pure Bi2WO6. The photocatalytic activity is evaluated by phenol removal from aqueous solution under visible-light irradiation. The results demonstrate that loaded Cu significantly enhances the photocatalytic activity of Bi2WO6, for the loaded Cu acts as the electron receptor on the surface of Bi2WO6, and inhibits the recombination of photogenerated electron-hole. The content of loaded Cu has an impact on the catalytic activity, and the 1.0 wt.% Cu-loaded Bi2WO6 exhibits the best photocatalytic activity in the degradation of phenol. Furthermore, the reaction kinetics of phenol removal from aqueous solution over the Cu-loaded Bi2WO6 is established by the way of the Langmuir-Hinshelwood model. The results indicate that the process of photodegradation of phenol on Cu-loaded Bi2WO6 match the Langmuir-Hinshelwood kinetic model.

Gao, Xiaoming; Fu, Feng; Li, Wenhong

2014-12-01

141

Synthesis by the solution combustion process and magnetic properties of iron oxide (Fe 3 O 4 and ?-Fe 2 O 3 ) particles  

Microsoft Academic Search

This article describes the solution combustion synthesis technique as applicable to iron oxide powder production using urea\\u000a as fuel and ferric nitrate as an oxidizer. It focuses on the thermodynamic modeling of the combustion reaction under different\\u000a fuel-to-oxidant ratios. X-ray diffraction showed magnetite (Fe3O4) and hematite (?-Fe2O3) phase formations for the as-synthesized powders. The smallest crystallite size was obtained by

Juliano Toniolo; Antonio S. Takimi; Mônica J. Andrade; Renato Bonadiman; Carlos P. Bergmann

2007-01-01

142

The influence of Nd3+ in CaAl2O4:Eu2+,Nd3+ phosphor fabricated by combustion synthesis  

NASA Astrophysics Data System (ADS)

Eu2+, Nd3+ co-doped calcium aluminate (CaAl2O4) phosphor with high brightness and long afterglow were fabricated by urea-nitrate solution combustion synthesis at 600°C. The phosphor powder of combustion synthesis were generally more homogeneous and had fewer impurity than phosphor fabricated by conventional solid-state methods, the character could conduce to obtain more exact data. The excitation and emission spectrum indicated that there waxs only one luminescence center Eu2+, both of the characteristic spectrums of Eu3+ and Nd3+ weren't discovered. As a secondary activator, Nd3+ could make remarkable influence on the afterglow of phosphor. From altering the moral ratio of Eu2+ and Nd3+, the lasting time of afterglow and thermoluminescence were studied respectively, when Nd3+ wasn't appended, the intensity of initial brightness could compared with other materials which had different ratio of Eu2+ and Nd3+, however the brightness of afterglow decayed rapidly, the lasting time and brightness of afterglow were improved with reduce the radio of Eu2+ and Nd3+, while the ratio achieved some value, the lasting time of afterglow become shorten with the reduce of ratio of Eu2+ and Nd3+. Moreover the depth of trap was calculated from the parameter of thermoluminescence. However, the emission spectrum and XRD patterns didn't change obviously with the altering ratio of Eu2+ and Nd3+. It showed that the little amount of doped rear earth ions (Eu2+ and Nd3+) had almost no effect on the CaAl2O4 phase composition. Based on these conclusions, the model of the luminescence process of CaAl2O4:Eu2+, Nd3+ was built.

Yang, Zhiping; Yang, Yong; Li, Xingmin; Li, Xu; Liu, Chong; Feng, Jianwei

2005-01-01

143

Predicting Spontaneous Ignition and Combustion in Fixed Beds of Activated Carbon  

Microsoft Academic Search

A mathematical model is presented which gives good agreement with experimental results for the spontaneous ignition and combustion of a bed of activated carbon granules through which heated air is passed. The model simulates the temporal development of temperature and gas species concentration profiles along the axis of the bed. Previously reported empirical relationships between the spontaneous ignition temperature (SIT)

S. BIGG

1989-01-01

144

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

145

Synthesis and Anticancer Activity of All Known (-)-Agelastatin Sunkyu Han,  

E-print Network

Synthesis and Anticancer Activity of All Known (-)-Agelastatin Alkaloids Sunkyu Han, Dustin S-by-side evaluation of all known (-)-agelastatin alkaloids against nine human cancer cell lines are described. Our concise synthesis of these alkaloids exploits the intrinsic chemistry of plausible biosynthetic precursors

Hergenrother, Paul J.

146

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

147

The Effect of Pressure on the Combustion Synthesis of a Functionally-Graded Material: TiB 2 Al 2 O 3 Al Ceramic Metal Composite System  

Microsoft Academic Search

This article describes some recent research on the synthesis of functionally-graded materials (FGM using combustion synthesis\\u000a or self- propagating high-temperature synthesis (SHS). A model ceramic-metal SHS system was investigated based on the reaction\\u000a system: 3TiO2 + 3B2O3 + (10 + x)Al = 3TiB2 + 5Al2O2 + xAl in which x was varied between 0 and 17 to achieve the required

H. J. Feng; J. J. Moore

1993-01-01

148

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

149

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  

Microsoft Academic Search

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.

H. J. Feng; J. J. Moore

1993-01-01

150

Measurement of in vivo cholesterol synthesis from 2H20: a rapid procedure for the isolation, combustion, and isotopic assay of erythrocyte cholesterol  

Microsoft Academic Search

A rapid preparative scale purification of erythrocyte free cholesterol has been developed for measurements of in vivo cholesterol synthesis from 2H20. The quantity and purity of cholesterol obtained is suitable for combustion, zinc reduction of the water formed, and determination of deuterium isotopic con- tent by gas isotope ratio mass spectrometry. The ability to detect and to quantitate a range

William W. Wong; David L. Hachey; Andrew Feste; Jeffrey Leggitt; Lucinda L. Clarke; Wilson G. Pond; Peter D. Klein

151

Efficient catalysis by MgCl2 in hydrogen generation via hydrolysis of Mg-based hydride prepared by hydriding combustion synthesis.  

PubMed

Magnesium chloride efficiently catalyzed the hydrolysis of Mg-based hydride prepared by hydriding combustion synthesis. Hydrogen yield of 1635 mL g(-1) was obtained (MgH(2)), i.e. with 96% conversion in 30 min at 303 K. PMID:22538836

Zhao, Zelun; Zhu, Yunfeng; Li, Liquan

2012-06-01

152

Active metal template synthesis of rotaxanes, catenanes and knots   

E-print Network

The use of a chemical template to control the spatial arrangement of reactants revolutionized the synthesis of mechanically interlocked molecules. The recently developed ‘active metal template’ strategy, in which transition ...

McGonigal, Paul R.

2011-01-01

153

Fast fabrication of W-Cu functionally graded material by high-gravity combustion synthesis and melt-infiltration  

NASA Astrophysics Data System (ADS)

W-Cu functionally graded material (FGM, 75 wt% W + 25 wt% Cu—40 wt% W + 60 wt% Cu) has been prepared by a method of high-gravity combustion synthesis and melt-infiltration in a short time (˜5 min). The infiltration mechanism in the high-gravity field was investigated. The W-Cu FGM showed an overall relative density of ˜97% and gradually-varying properties in terms of density, micro hardness, coefficient of thermal expansion. Especially, the W-Cu FGM exhibited a coefficient of thermal expansion between those of W and Cu, and thus could be used as a transition layer between W and Cu to relax the thermal stresses.

Zhao, P.; Guo, S. B.; Liu, G. H.; Chen, Y. X.; Li, J. T.

2014-02-01

154

Stereoselective heterocycle synthesis through oxidative carbon-hydrogen bond activation.  

PubMed

Heterocycles are ubiquitous structures in both drugs and natural products, and efficient methods for their construction are being pursued constantly. Carbon-hydrogen bond activation offers numerous advantages for the synthesis of heterocycles with respect to minimizing the length of synthetic routes and reducing waste. As interest in chiral medicinal leads increases, stereoselective methods for heterocycle synthesis must be developed. The use of carbon-hydrogen bond activation reactions for stereoselective heterocycle synthesis has produced a range of creative transformations that provide a wide array of structural motifs, selected examples of which are described in this review. PMID:21061234

Liu, Lei; Floreancig, Paul E

2010-01-01

155

Synthesis and anticancer activity of novel deoxoartemisinin-glycolipid hybrids.  

PubMed

The practical synthesis and anticancer activity of novel deoxoartemisinin-glycolipid hybrids, which incorporate two drugs into a single molecule and can impact multiple targets simultaneously are presented. These hybrids exhibited potent in vitro anticancer activity against several human cancer cell lines. The deoxoartemisinin-glycolipid hybrids generally demonstrated better anticancer activity than either artemisinin or daumone alone and cisplatin. PMID:24614158

Min, Dongguk; Kim, Minkyu; Ricci, Jérémy; Jung, Sora; Kim, Kirim; Chung, Won-Yoon; Park, Kwang-Kyun; Jung, Mankil

2014-01-01

156

Combustion synthesis of fine particle rare earth orthoaluminates and yttrium aluminum garnet  

NASA Astrophysics Data System (ADS)

Fine particle rare earth orthoaluminates, LnAlO 3, where Ln = La, Pr, Nd, Sm, Gd, Tb, and Dy, and yttrium aluminum garnet, Y 3Al 5O 12 (YAG), have been prepared by a novel combustion process using corresponding rare earth nitrate, aluminum nitrate, and urea/carbohydrazide mixtures. A saturated aqueous solution of the mixture when rapidly heated at 500°C foams and ignites to yield voluminous, crystalline single phase rare earth orthoaluminates in less than 5 min. The solid combustion products were characterized by XRD, SEM, TEM, particle size analysis, and surface area measurements. Rare earth orthoaluminates obtained have 3-4 m 2/g surface area, with particle size in the range of 0.1-0.6 ?m and an average agglomerate size of 4-5 ?m.

Kingsley, J. J.; Suresh, K.; Patil, K. C.

1990-10-01

157

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

NASA Technical Reports Server (NTRS)

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 rig s design are features that approximate conditions similar to those that would be encountered by a candidate device if it were installed on an actual combustion research rig. The characterized dynamic performance measures obtained through testing in the rig are planned to be accurate indicators of expected performance in an actual combustion testing environment. To evaluate how well the characterization rig predicts fuel modulator dynamic performance, characterization rig data was compared with performance data for a fuel modulator candidate when the candidate was in operation during combustion testing. Specifically, the nominal and off-nominal performance data for a magnetostrictive-actuated proportional fuel modulation valve is described. Valve performance data were collected with the characterization rig configured to emulate two different combustion rig fuel feed systems. Fuel mass flows and pressures, fuel feed line lengths, and fuel injector orifice size was approximated in the characterization rig. Valve performance data were also collected with the valve modulating the fuel into the two combustor rigs. Comparison of the predicted and actual valve performance data show that when the valve is operated near its design condition the characterization rig can appropriately predict the installed performance of the valve. Improvements to the characterization rig and accompanying modeling activities are underway to more accurately predict performance, especially for the devices under development to modulate fuel into the much smaller fuel injectors anticipated in future lean-burning low-emissions aircraft engine combustors.

Saus, Joseph R.; DeLaat, John C.; Chang, Clarence T.; Vrnak, Daniel R.

2012-01-01

158

Synthesis of La and Nb doped PZT powder by the gel-combustion method  

NASA Astrophysics Data System (ADS)

Lanthanum and niobium doped PZT with composition (Pb0.93La0.07)[(Zr0.60Ti0.40)]0.9825Nb0.0175O3 (PZTLN) was prepared by the gel-combustion method. A precursor sol was obtained from lead nitrate, zirconyl nitrate, lanthanum oxide, peroxo-citrato-niobium and a peroxo-citrate complex of titanium isopropoxide as starting precursors. Various molar ratios of citrate/nitrate (CA/NO3- = 1.3, 0.36 and 0.09) were used to prepare very fine powders of PZTLN. The gels resulting from these sols were transformed into powders by an auto-combustion process at <=400 °C. The powders consisted of rhombohedral PZT (PbZr0.60Ti0.40O3), pyrochlore (Pb2Ti2O6) and lead carbonate (Pb2O·CO3) phases. The pure rhombohedral phase is found in PZTLN pellets sintered at 1100 °C for all citrate/nitrate ratios. Titanium and niobium precursors were modified with peroxo radicals. During the gel-combustion reaction, the temperature of the gel increases, leading to lead evaporation. The loss of lead as well as the particle size increases as the CA/NO3- ratio decreases. The smallest grained powder (about 50 nm) was obtained with the ratio CA/NO3- equal to 0.09.

Cernea, M.; Montanari, G.; Galassi, C.; Costa, A. L.

2006-03-01

159

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

NASA Astrophysics Data System (ADS)

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 system must be able to achieve satisfactory control performances in the presence of large uncertainties, large variations, and even unknown system dynamics. Toward this goal, an observer-based controller, capable of attenuating multiple unstable modes with unknown characteristics, is developed. A mechanism suitable for online prediction of the safety margin to the onset of combustion instability is presented, which does not require knowing the unstable frequencies. The shortage of a reliable, high-frequency, proportional fuel actuator is a major technical challenge for active combustion control. A complementary theoretical and experimental study is performed on a pump-style, high-frequency, magnetostrictive fuel actuator. Improvements to the fuel setup have been made according to the model predictions, which have been experimentally shown to be beneficial to combustion instability control. The second part of this dissertation is about modeling, prediction, and control of lean blowout. The experimentally observed, "intensified", low frequency, near-LBO combustion oscillations have been used as incipient LBO precursors, and are characterized as low-dimension chaotic behavior in the present study. The normalized chemiluminescence RMS and the normalized cumulative duration of LBO precursor events are recommended for LBO prediction in generic gas turbine engines. Linear stability analysis shows that, with decreasing equivalence ratios, a complex conjugate pair of eigenvalues emerges from three negative real ones, moves left toward the right half phase plane, and finally crosses the imaginary axis. Model predictions qualitatively and even quantitatively match the experiments. Simulation of the nonlinear WSR models shows the "triggered instability" which is similar to that in rocket motors. It is numerically demonstrated that zero-mean small-amplitude fuel modulations based on modern feedback control principles, can be very effective in strengthening the flame's robustness to external disturbances without exacerbating the overall emissions. Experimental demonstrations are suggested for future research.

Yi, Tongxun

160

Test Plan for Measuring Ventilation Rates and Combustible Gas Levels in TWRS Active Catch Tanks  

SciTech Connect

The purpose of this data collection activity is to obtain data for a screening of combustible gases in catch tanks that are currently operated by the River Protection Project (RPP). The results will be used to support closure of the flammable gas unreviewed safety question for these facilities. The data collection will be conducted in accordance with the ''Tank Safety Screening Data Quality Objective'' (Dukelow et al. 1995). Combustible gas, ammonia, and organic vapor levels in the headspace of the catch tanks will be field-measured using hand-held instruments. If a combustible gas level measurement in a tank exceeds an established threshold, vapor grab samples (i.e., Hoke and SUMMA) will be collected for laboratory analysis. In addition, ventilation rates of some catch tanks will be determine using the tracer gas injection method to evaluate removal of flammable gas by air flowing through the tanks. This test plan identifies the field tests, sample collection, laboratory analysis, quality assurance, and reporting objectives for this data collection effort. The plan also provides step-by-step direction for field measurement of combustible gas concentrations and determination of ventilation rates.

NGUYEN, D.M.

2000-03-01

161

Test Plan for Measuring Ventilation Rates and Combustible Gas Levels in TWRS Active Catch Tanks  

SciTech Connect

The purpose of this sampling activity is to obtain data to support an initial evaluation of potential hazards due to the presence of combustible gas in catch tanks that are currently operated by the River Protection Project (RPP). Results of the hazard analysis will be used to support closure of the flammable gas unreviewed safety question for these facilities. The data collection will be conducted in accordance with the Tank Safety Screening Data Quality Objective (Dukelow et al. 1995). Combustible gas, ammonia, and organic vapor levels in the headspace of the catch tanks will be field-measured using hand-held instruments. If a combustible gas level measurement in a tank exceeds an established threshold, gas samples will he collected in SUMMA' canisters for more extensive laboratory analysis. In addition, ventilation rates of some catch tanks will be measured to evaluate removal of flammable gas by air flowing through the tanks. This test plan identifies the sample collection, laboratory analysis, quality assurance, and reporting objectives for this data collection effort. The plan also provides the procedures for field measurement of combustible gas concentrations and ventilation rates.

NGUYEN, D.M.

1999-10-25

162

Test Plan for Measuring Ventilation Rates and Combustible Gas Levels in TWRS Active Catch Tanks  

SciTech Connect

The purpose of this data collection activity is to obtain data for a screening of combustible gases in catch tanks that are currently operated by the River Protection Project (RPP). The results will be used to support closure of the flammable gas unreviewed safety question for these facilities. The data collection will be conducted in accordance with the ''Tank Safety Screening Data Quality Objective'' (Dukelow et a1 1995). Combustible gas, ammonia, and organic vapor levels in the headspace of the catch tanks will be field-measured using hand-held instruments. If a combustible gas level measurement in a tank exceeds an established threshold, vapor grab samples will be collected for laboratory analysis. In addition, ventilation rates of some catch tanks will be determined using the tracer gas injection method to evaluate removal of flammable gas by air flowing through the tanks. This test plan identifies the field tests, sample collection, laboratory analysis, quality assurance, and reporting objectives for this data collection effort. The plan also provides step by-step direction for field measurement of combustible gas concentrations and determination of ventilation rates.

NGUYEN, D.M.

2000-02-01

163

Synthesis of silicon nitride by a combustion reaction under high nitrogen pressure  

SciTech Connect

Fine Si3N4 powders were prepared by the combustion reaction of an Si powder compact under 10 MPa nitrogen pressure. Addition of Si3N4 powder to the starting Si promoted conversion of the reactants to homogeneous Si3N4 particles. Submicrometer Si3N4 powders with a uniform size distribution around 0.5 microns were obtained from a 1.8 Si-0.4 Si3N4 mixture (molar ratio); they were free of residual Si. 8 references.

Hirao, K.; Miyamoto, Y.; Koizumi, M.

1986-04-01

164

REM sleep dreams and the activation-synthesis hypothesis.  

PubMed

The authors studied 104 dreams obtained from 14 subjects and quantified the formal aspects of the subjects' dream experiences by the following categories: movement in dreams, sensation, affect, dream bizarreness, and dream lucidity. Their results are compared with the predictions of the activation-synthesis hypothesis, which postulates that the characteristic formal aspects of dreams correspond to characteristic aspects of physiological activation during REM sleep. Although further experimental work is needed, the authors show that their results are consistent with and supportive of the activation-synthesis hypothesis. PMID:7258349

McCarley, R W; Hoffman, E

1981-07-01

165

Proceedings of the Combustion Institute. Volume 30  

SciTech Connect

Papers discussed combustion theory and modelling, turbulent combustion, laser diagnostics and control, chemical kinetics, computational combustion, flames, detonations, droplet combustion, catalysis/materials synthesis, pulse detonations engines, diagnosis, engine combustion, heterogeneous combustion, pollutants (PAH and soot), kinetics, flame diagnosis, propulsion, laminar diffusion flames, lifted turbulent flames, nanoparticles, premixed turbulent flames, solid oxide fuel cells, laminar flames, stationary power systems, and plasma supported flames.

NONE

2005-01-15

166

Causes of Combustion Instabilities with Passive and Active Methods of Control for practical application to Gas Turbine Engines  

NASA Astrophysics Data System (ADS)

Combustion at high pressure in applications such as rocket engines and gas turbine engines commonly experience destructive combustion instabilities. These instabilities results from interactions between combustion heat release, fluid mechanics and acoustics. This research explores the significant affect of unstable fluid mechanics processes in augmenting unstable periodic combustion heat release. The frequency of the unstable heat release may shift to match one of the combustors natural acoustic frequencies which then can result in significant energy exchange from chemical to acoustic energy resulting in thermoacoustic instability. The mechanisms of the fluid mechanics in coupling combustion to acoustics are very broad with many varying mechanisms explained in detail in the first chapter. Significant effort is made in understanding these mechanisms in this research in order to find commonalities, useful for mitigating multiple instability mechanisms. The complexity of combustion instabilities makes mitigation of combustion instabilities very difficult as few mitigation methods have historically proven to be very effective for broad ranges of combustion instabilities. This research identifies turbulence intensity near the forward stagnation point and movement of the forward stagnation point as a common link in what would otherwise appear to be very different instabilities. The most common method of stabilization of both premixed and diffusion flame combustion is through the introduction of swirl. Reverse flow along the centerline is introduced to transport heat and chemically active combustion products back upstream to sustain combustion. This research develops methods to suppress the movement of the forward stagnation point without suppressing the development of the vortex breakdown process which is critical to the transport of heat and reactive species necessary for flame stabilization. These methods are useful in suppressing the local turbulence at the forward stagnation point, limiting dissipation of heat and reactive species significantly improving stability. Combustion hardware is developed and tested to demonstrate the stability principles developed as part of this research. In order to more completely understand combustion instability a very unique method of combustion was researched where there are no discrete points of combustion initiation such as the forward stagnation point typical in many combustion systems including swirl and jet wake stabilized combustion. This class of combustion which has empirical evidence of great stability and efficient combustion with low CO, NOx and UHC emissions is described as high oxidization temperature distributed combustion. This mechanism of combustion is shown to be stable largely because there are no stagnations points susceptible to fluid mechanic perturbations. The final topic of research is active combustion control by fuel modulation. This may be the only practical method of controlling most instabilities with a single technique. As there are many papers reporting active combustion control algorithms this research focused on the complexities of the physics of fuel modulation at frequencies up to 1000 Hz with proportionally controlled flow amplitude. This research into the physics of high speed fluid movement, oscillation mechanical mechanisms and electromagnetics are demonstrated by development and testing of a High Speed Latching Oscillator Valve.

Cornwell, Michael D.

167

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

168

Activation of catalysts for synthesizing methanol from synthesis gas  

DOEpatents

A method for activating a methanol synthesis catalyst is disclosed. In this method, the catalyst is slurried in an inert liquid and is activated by a reducing gas stream. The activation step occurs in-situ. That is, it is conducted in the same reactor as is the subsequent step of synthesizing methanol from a methanol gas stream catalyzed by the activated catalyst still dispersed in a slurry.

Blum, David B. (108 Tall Oaks Dr., Wayne, NJ 07470); Gelbein, Abraham P. (45 Headley Rd., Morristown, NJ 07960)

1985-01-01

169

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

170

Nuclear-grade zirconium prepared by combining combustion synthesis with molten-salt electrorefining technique  

NASA Astrophysics Data System (ADS)

Zirconium has a low absorption cross-section for neutrons, which makes it an ideal material for use in nuclear reactor applications. However, hafnium typically contained in zirconium causes it to be far less useful for nuclear reactor materials because of its high neutron-absorbing properties. In the present study, a novel effective method has been developed for the production of hafnium-free zirconium. The process includes two main stages: magnesio-thermic reduction of ZrSiO 4 under a combustion mode, to produce zirconium silicide (ZrSi), and recovery of hafnium-free zirconium by molten-salt electrorefining. It was found that, depending on the electrorefining procedure, it is possible to produce zirconium powder with a low hafnium content: 70 ppm, determined by ICP-AES analysis.

Li, Hui; Nersisyan, Hayk H.; Park, Kyung-Tae; Park, Sung-Bin; Kim, Jeong-Guk; Lee, Jeong-Min; Lee, Jong-Hyeon

2011-06-01

171

Solution combustion method for synthesis of nanostructured hydroxyapatite, fluorapatite and chlorapatite  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HAP), fluorapatite (Fap) and chlorapatite (Clap) were prepared by solution combustion method with further annealing at 800 °C. The characterization and structural features of the synthesized powders were evaluated by the powder X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and transmission electron microscopy (TEM) techniques. Characterization results from XRD and Rietveld analysis revealed that OH- in the HAP lattice were gradually substituted with the increase of F- and Cl- content and totally substituted at the molar concentration of 0.28 and 0.6, respectively. The results from FI-IR have also confirmed the incorporation of substituted anions in the apatite structure.

Zhao, Junjie; Dong, Xiaochen; Bian, Mengmeng; Zhao, Junfeng; Zhang, Yao; Sun, Yue; Chen, JianHua; Wang, XuHong

2014-09-01

172

USE OF COMBUSTION SYNTHESIS IN PREPARING CERAMIC-MATRIX AND METAL-MATRIX COMPOSITE POWDERS  

SciTech Connect

A standard combustion-based approach typically used to synthesize nanosize oxide powders has been modified to prepare composite oxide-metal powders for subsequent densification via sintering or hot-pressing into ceramic- or metal-matrix composites. Copper and cerium nitrate salts were dissolved in the appropriate ratio in water and combined with glycine, then heated to cause autoignition. The ratio of glycine-to-total nitrate concentration was found to have the largest effect on the composition, agglomerate size, crystallite size, and dispersivity of phases in the powder product. After consolidation and sintering under reducing conditions, the resulting composite compact consists of a well-dispersed mixture of sub-micron size reinforcement particles in a fine-grained matrix.

Weil, K. Scott; Hardy, John S.

2005-03-01

173

Solution combustion synthesis of calcium phosphate particles for controlled release of bovine serum albumin.  

PubMed

Four different phase compositions of calcium phosphate (CaP) particles were prepared via a solution combustion method. X-ray diffraction (XRD) and Rietveld analysis results revealed that the variations in the nominal Ca/P (molar) ratios were found to provide a favorable control in the different proportions of CaP materials. Bovine serum albumin (BSA) was used as a model protein to study the loading and release behavior. The release profile indicated that the BSA release rates depended on the phase compositions of the CaP particles, and showed an order of TCP-BSA>BCP-1-BSA>BCP-2-BSA>HA-BSA. The results suggested that the BSA protein release rate can be controlled by varying the phase compositions of CaP carriers. Moreover, the release process involved two stages: firstly surface diffusion via ion exchange and secondly intraparticle diffusion. PMID:25746262

Zhao, Junfeng; Zhao, Junjie; Qian, Yu; Zhang, Xiali; Zhou, Feifei; Zhang, Hong; Lu, Hongbin; Chen, JianHua; Wang, XuHong; Yu, Wencong

2015-05-01

174

The Synthesis and Antimicrobial Activity of Heterocyclic Derivatives of Totarol  

PubMed Central

The synthesis and antimicrobial activity of heterocyclic analogues 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 analogues with an indole attached exhibit, for the first time, enhanced antimicrobial activity relative to the parent natural product. Preliminary experiments demonstrate that the indole analogues do not target the bacterial cell division protein FtsZ as had been hypothesized for totarol. PMID:23119123

2012-01-01

175

EPR investigation on synthesis of Lithium zinc vanadate using sol-gel-combustion route and its optical properties  

NASA Astrophysics Data System (ADS)

The present work describes the synthesis of Lithium zinc vanadate (LiZnVO4) nanophosphor prepared by sol-gel-combustion method and its optical properties. The prepared sample was characterized by X-ray diffraction, SEM, electron paramagnetic resonance and photoluminescence spectroscopy. X-ray diffraction study showed the formation of pure LiZnVO4 at 600 °C with distorted phenacite structure. SEM investigation revealed that the phosphor powder has spherical morphology with particle size of about 100-200 nm. EPR study showed the change of coordination sphere around vanadium from axially distorted octahedral symmetry to tetrahedral geometry along with the change in oxidation state of vanadium ion from +4 to +5. The emission spectrum showed a broad emission at 543 nm with ?ex = 375 nm. The decay time obtained on mono-exponential fitting was 8.3 ?s. The colour coordinates of the system were evaluated using CIE index diagram to be 0.31 and 0.41, which suggest that the prepared material is a potential green emitting phosphor. A bright green colour emission was also observed directly from this phosphor upon excitation with an UV source.

Pathak, Nimai; Gupta, Santosh K.; Prince, Angelina; Kadam, R. M.; Natarajan, V.

2014-01-01

176

Phytochrome activation of two nuclear genes requires cytoplasmic protein synthesis.  

PubMed Central

We have investigated the effects of protein synthesis inhibitors on light-induced expression of two plant nuclear genes, Cab and rbcS, in wheat, pea and transgenic tobacco. Light activation of these two genes is very sensitive to cycloheximide, an inhibitor of cytoplasmic protein synthesis but not to chloramphenicol, an inhibitor of organellar protein synthesis. Studies with chimeric gene constructs in transgenic tobacco seedlings show that cycloheximide exerts its effect at the transcriptional level. As a control, we show that the expression of the cauliflower mosaic virus (CaMV) 35S promoter is enhanced by cycloheximide treatment, irrespective of the coding sequence used. Escape-time analyses with green wheat seedlings show that the cycloheximide block for Cab gene expression is after the primary signal transduction step linked to phytochrome photoconversion. Our results suggest that phytochrome activation of Cab and rbcS is mediated by a labile protein factor(s) synthesized on cytoplasmic ribosomes. Images PMID:2583082

Lam, E; Green, P J; Wong, M; Chua, N H

1989-01-01

177

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

178

Robust active combustion control for the optimization of environmental performance and energy efficiency  

NASA Astrophysics Data System (ADS)

Criteria pollutant regulations, climate change concerns, and energy conservation efforts are placing strict constraints in the design and operation of advanced, stationary combustion systems. To ensure minimal pollutant emissions and maximal efficiency at every instant of operation while preventing reaction blowout, combustion systems need to react and adapt in real-time to external changes. This study describes the development, demonstration, and evaluation of a multivariable feedback control system, designed to maximize the performance of natural gas-fired combustion systems. A feedback sensor array was developed to monitor reaction stability and measure combustion performance as a function of NOx, CO, and O, emissions. Acoustic and UV chemiluminescent emissions were investigated for use as stability indicators. Modulated signals of CH* and CO2* chemiluminescence were found to correlate well with the onset of lean blowout. A variety of emissions sensors were tested and evaluated, including conventional CEMS', micro-fuel cells, a zirconia NOx transducer, and a rapid response predictive NOx sensor based on UV flame chemiluminescence. A dual time-scale controller was designed to actively optimize operating conditions by maximizing a multivariable performance function J using a linear direction set search algorithm. The controller evaluated J under slow, quasi steady-state conditions, while dynamically monitoring the reaction zone at high speed for pre-blowout instabilities or boundary condition violations. To establish the input control parameters, two burner systems were selected: a 30 kW air-swirl, generic research burner, and a 120 kW scaled, fuel-staged, industrial boiler burner. The parameters, chosen to most affect burner performance, consisted of air swirl intensity and excess air for the generic burner, and fuel-staging and excess air for the boiler burner. A set of optimization parameters was also established to ensure efficient and deterministic optimization. The active control system was demonstrated and evaluated by optimizing the burners under practical conditions. In most cases, the controller was able to locate, within 10--15 min, a global performance peak that simultaneously minimized emissions and maximized system efficiency within specified stability limits. The active controller demonstrated flexibility and robustness by (a) successfully optimizing different burners for different J functions, initial conditions, and sensor combinations, and (b) successfully reoptimizing a burner under the effect of simulated window fouling and following sudden inlet perturbations, including load cycling and a misaligned fuel injector.

Demayo, Trevor Nat

179

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

180

Synthesis and biological activity of some antitumor benzophenanthridinium salts.  

PubMed

A facil synthesis of benzophenanthridinium salts has been developed and used for preparing a number of these compounds. The antitumor activities in mouse leukemia L1210 (LE) and P388 (PS) were determined as well as some selected antimicrobial activities. Although antitumor activity was exhibited by several of the derivatives, none was as active as the naturally occurring alkaloid fagaronine. Fagaronine was made available as a synthetic by an improved procedure. Some structure-activity relationships among antitumor benzophenanthridinium salts are discussed. PMID:1097692

Stermitz, F R; Gillespie, J P; Amoros, L G; Romero, R; Stermitz, T A; Larson, K A; Earl, S; Ogg, J E

1975-07-01

181

Synthesis and anticancer activity studies of cyclopamine derivatives  

Technology Transfer Automated Retrieval System (TEKTRAN)

A diversity-oriented synthesis has been developed for facile construction of a library of carbohydrate-cyclopamine conjugates. The synthetic protocol is suitable for generating cyclopamine derivatives with various structural motifs for exploring the desired activity. From this initial library, we ...

182

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

183

Synthesis of cobalt ferrite (CoFe2O4) nanoparticles using combustion, coprecipitation, and precipitation methods: A comparison study of size, structural, and magnetic properties  

NASA Astrophysics Data System (ADS)

In this work the cobalt ferrite (CoFe2O4) nanoparticles are synthesized using three different methods; combustion, coprecipitation, and precipitation. Size, structural, and magnetic properties were determined and compared using X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). XRD data analysis showed an average size of 69.5 nm for combustion, 49.5 nm for coprecipitation, and 34.7 nm for precipitation samples which concorded with SEM images. XRD data further revealed a reverse cubic spinel structure with the space group Fd-3m in all three samples. VSM data of samples showed a saturation point in the magnetic field of less than 15 kOe. Magnetization saturation (Ms) was 56.7 emu/g for combustion synthestized samples, 55.8 emu/g for coprecipitation samples, and 47.2 emu/g for precipitation samples. Coercivity (Hc) was 2002 Oe for combustion synthestized samples, 850 Oe for coprecipitation samples, and 233 Oe for precipitation samples. These results show that various methods of nanoparticle synthesis can lead to different particle sizes and magnetic properties. Hc and Ms are greatest in the combustion method and least in precipitation method.

Houshiar, Mahboubeh; Zebhi, Fatemeh; Razi, Zahra Jafari; Alidoust, Ali; Askari, Zohreh

2014-12-01

184

A superstructure-based optimal synthesis of PSA cycles for post-combustion CO2 capture  

SciTech Connect

Recent developments have shown pressure/vacuum swing adsorption (PSA/VSA) to be a promising option to effectively capture CO2 from flue gas streams. In most commercial PSA cycles, the weakly adsorbed component in the mixture is the desired product, and enriching the strongly adsorbed CO2 is not a concern. On the other hand, it is necessary to concentrate CO2 to high purity to reduce CO2 sequestration costs and minimize safety and environmental risks. Thus, it is necessary to develop PSA processes specifically targeted to obtain pure strongly adsorbed component. A multitude of PSA/VSA cycles have been developed in the literature for CO2 capture from feedstocks low in CO2 concentration. However, no systematic methodology has been suggested to develop, evaluate, and optimize PSA cycles for high purity CO2 capture. This study presents a systematic optimization-based formulation to synthesize novel PSA cycles for a given application. In particular, a novel PSA superstructure is presented to design optimal PSA cycle configurations and evaluate CO2 capture strategies. The superstructure is rich enough to predict a number of different PSA operating steps. The bed connections in the superstructure are governed by time-dependent control variables, which can be varied to realize most PSA operating steps. An optimal sequence of operating steps is achieved through the formulation of an optimal control problem with the partial differential and algebraic equations of the PSA system and the cyclic steady state condition. Large-scale optimization capabilities have enabled us to adopt a complete discretization methodology to solve the optimal control problem as a largescale nonlinear program, using the nonlinear optimization solver IPOPT. The superstructure approach is demonstrated for case studies related to post-combustion CO2 capture. In particular, optimal PSA cycles were synthesized, which maximize CO2 recovery for a given purity, and minimize overall power consumption. The results show the potential of the superstructure to predict PSA cycles with up to 98% purity and recovery of CO2. Moreover, for recovery of around 85% and purity of over 90%, these cycles can recover CO2 from atmospheric flue gas with a low power consumption of 465 kWh tonne#1;1 CO2. The approach presented is, therefore, very promising and quite useful for evaluating the suitability of different adsorbents, feedstocks, and operating strategies for PSA, and assessing its usefulness for CO2 capture.

Agarwal, A.; Biegler, L.; Zitney, S.

2010-07-01

185

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

186

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

187

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. PMID:19696873

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

2008-01-01

188

Synthesis of multifunctional nanostructured zinc-iron mixed oxide photocatalyst by a simple solution-combustion technique.  

PubMed

A series of nanostructure zinc-iron mixed oxide photocatalysts have been fabricated by solution-combustion method using urea as the fuel, and nitrate salts of both iron and zinc as the metal source. Different characterization tools, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV-visible spectra (DRUV-vis), electron microscopy, and photoelectrochemical measurement were employed to establish the structural, electronic, and optical properties of the material. Electron microscopy confirmed the nanostructure of the photocatalyst. The synthesized photocatalysts were examined towards photodegradation of 4-chloro-2-nitro phenol (CNP), rhodamine 6G (R6G), and photocatalytic hydrogen production under visible light (? ? 400 nm). The photocatalyst having zinc to iron ratio of 50:50 showed best photocatalytic activity among all the synthesized photocatalysts. PMID:22201304

Pradhan, Gajendra Kumar; Martha, Satyabadi; Parida, K M

2012-02-01

189

Synthesis and antiplasmodial activity of lycorine derivatives.  

PubMed

Twenty seven lycorine derivatives were prepared and evaluated for their in vitro antimalarial activity against chloroquine-sensitive strains of Plasmodium falciparum. The best antiplasmodial activities were achieved with lycorine derivatives that present free hydroxyl groups at C-1 and C-2 or esterified as acetates or isobutyrates. The double bond C-2-C-3 is also important for the activity. Concerning to the antiplasmodial activity of the secolycorines, the higher values were obtained with the replacement of the methylenedioxy moiety by hydroxyl or acetate groups and with methyl substituent attached to the nitrogen atom. PMID:20627737

Cedrón, Juan C; Gutiérrez, David; Flores, Ninoska; Ravelo, Angel G; Estévez-Braun, Ana

2010-07-01

190

Study of wear between piston ring and cylinder housing of an internal combustion engine by thin layer activation technique  

Microsoft Academic Search

The wear analysis of a compression ring and cylinder housing of an Internal Combustion Engine by thin layer activation (TLA) with 40 MeV alpha-particles from the Variable Energy Cyclotron at Calcutta is reported. The calibration curves have been obtained for Fe and Ni using stacked foil activation technique for determining the absolute wear in these machine parts. It has been

D. P. Chowdhury; Jayanta Chaudhuri; V. S. Raju; S. K. Das; B. B. Bhattacharjee; S. Gangadharan

1989-01-01

191

Synthesis and biological activities of 2-oxocycloalkylsulfonamides.  

PubMed

A series of novel 2-oxocycloalkylsulfonamides (4) were synthesized and their structures confirmed by IR, (1)H NMR, and elemental analysis. The bioassay showed that they have fair to excellent fungicidal activities against Botrytis cinerea Pers and Sclerotinia sclerotiorum. Among them, compounds 4A(10), 4A(11), 4A(12), 4B(2), and 4B(3), the EC(50) values of which were 2.12, 3.66, 3.96, 2.38, and 2.43 microg/mL, respectively, displayed excellent fungicidal activity against B. cinerea Pers, and are comparable with commercial fungicide procymidone (the EC(50) value is 2.45 microg/mL). 3D QSAR against B. cinerea Pers was studied, a statistically significant and chemically meaningful CoMFA model was developed and some compounds which have a high predicted activity were forecasted. In addition, the bioassay also showed that the compounds have good inhibitory activities against human tumor cells HL-60, BGC-823, Bel-7402 and KB. It is interesting to point out that the antitumor activities of compounds 4 are in accordance with their fungicidal activity to a great extent: compounds having relatively best antitumor activities (4A(10), 4A(11), 4A(12), and 4B(3)) also displayed excellent fungicidal activity. PMID:18331796

Li, Xinghai; Yang, Xinling; Liang, Xiaomei; Kai, Zhenpeng; Yuan, Huizu; Yuan, Dekai; Zhang, Jianjun; Wang, Ruiqing; Ran, Fuxiang; Qi, Shuhua; Ling, Yun; Chen, Fuheng; Wang, Daoquan

2008-04-15

192

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

193

Turbulent combustion  

SciTech Connect

Turbulent combustion is the dominant process in heat and power generating systems. Its most significant aspect is to enhance the burning rate and volumetric power density. Turbulent mixing, however, also influences the chemical rates and has a direct effect on the formation of pollutants, flame ignition and extinction. Therefore, research and development of modern combustion systems for power generation, waste incineration and material synthesis must rely on a fundamental understanding of the physical effect of turbulence on combustion to develop theoretical models that can be used as design tools. The overall objective of this program is to investigate, primarily experimentally, the interaction and coupling between turbulence and combustion. These processes are complex and are characterized by scalar and velocity fluctuations with time and length scales spanning several orders of magnitude. They are also influenced by the so-called {open_quotes}field{close_quotes} effects associated with the characteristics of the flow and burner geometries. The authors` approach is to gain a fundamental understanding by investigating idealized laboratory flames. Laboratory flames are amenable to detailed interrogation by laser diagnostics and their flow geometries are chosen to simplify numerical modeling and simulations and to facilitate comparison between experiments and theory.

Talbot, L.; Cheng, R.K. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01

194

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

195

Design, synthesis and glucose uptake activity of some novel glitazones.  

PubMed

Herein, we report a library consisting of some novel glitazones containing thiazolidinedione and its bioisosteres, rhodanine and oxadiazolidine ring structures as their basic scaffold for their antidiabetic activity. Twelve novel glitazones with diverse chemical structures were designed and synthesized by adopting appropriate synthetic schemes and analyzed. Later, subjected to in vitro glucose uptake assay in the absence and presence of insulin to confirm their antidiabetic activity using rat hemi-diaphragm. The titled compounds exhibited glucose uptake activity ranging weak to significant activity. Compounds 4, 5, 9, 11, 15, 16, 19 and 20 showed considerable glucose uptake activity apart from rosiglitazone, a standard drug. Compound 16 happens to be the candidate compound from this study to investigate further. The illustration about their design, synthesis, analysis and glucose uptake activity is reported here along with the in vitro and in silico study based structure-activity relationships. PMID:24927033

Kar, Koyel; Krithika, Uma; Mithuna; Basu, Prabhuddha; Santhosh Kumar, S; Reji, Anu; Prashantha Kumar, B R

2014-10-01

196

Passive active neutron radioassay measurement uncertainty for combustible and glass waste matrices  

SciTech Connect

Using a modified statistical sampling and verification approach, total uncertainty of INEL`s Passive Active Neutron (PAN) radioassay system was evaluated for combustible and glass content codes. Waste structure and content of 100 randomly selected drums in each the waste categories were computer modeled based on review of real-time radiography video tapes. Specific quantities of Pu were added to the drum models according to an experimental design. These drum models were then submitted to the Monte Carlo Neutron Photon code processing and subsequent calculations to produce simulated PAN system measurements. The reported Pu masses from the simulation runs were compared with the corresponding input masses. Analysis of the measurement errors produced uncertainty estimates. This paper presents results of the uncertainty calculations and compares them to previous reported results obtained for graphite waste.

Blackwood, L.G.; Harker, Y.D.; Meachum, T.R.; Yoon, Woo Y.

1997-01-01

197

Phenytoin-based bivalent ligands: design, synthesis and anticonvulsant activity.  

PubMed

Synthesis, characterization and anticonvulsant properties of new bivalent ligands derived from phenytoin were described. Initial anticonvulsant screening was performed using maximal electroshock (MES) and pentylenetetrazole (PTZ) screens in mice. The neurotoxicity for compounds that showed significant anticonvulsant activity was determined applying the rotorod test. Most of the test compounds were found to be effective in at least one seizure model in a dose of 100 mg/kg. Compound 5e exhibited marked anticonvulsant activity in both MES and PTZ screens. The computer-aided prediction of biological activity was carried out. PMID:23263804

Botros, Samir; Khalil, Nadia A; Naguib, Bassem H; El-Dash, Yara

2012-12-01

198

Synthesis, characterization, temperature dependent electrical and magnetic properties of Ca3Co4O9 by a starch assisted sol-gel combustion method  

NASA Astrophysics Data System (ADS)

In this present work we discussed the synthesis of pure Ca3Co4O9 ceramic powder by a starch assisted sol-gel combustion method. The products were characterized by powder X-ray diffraction (XRD), thermogravimetric and differential thermal analyses (TGA-DTA), Fourier transformation infrared spectroscopy (FTIR), scanning electron microscope (SEM) and UV-visible diffuse reflectance spectroscopy (DRS). X-ray diffraction pattern confirmed the formation of single phase Ca3Co4O9 at a sintering temperature of 1073 K, and it is also confirmed in the thermal analysis. SEM images indicate the presence of diffused microporous sphere like morphology and the grain sizes are in the range of 150-300 nm. Optical properties of Ca3Co4O9 ceramic show a band gap at an energy level of 2.10 eV. A maximum electrical resistivity of 0.002 m? cm was exhibited by Ca3Co4O9 that was decreased to 0.0012 m? cm, when the temperature increased from 300 K to 473 K. Dielectric studies were conducted at various temperatures from room temperature to 673 K and the results indicate that the space charge polarization contributes to the conduction mechanism. It also shows that the dielectric relaxation with activation energy is 0.96 eV. The magnetic properties as a function of temperature represent the ferri-paramagnetic phase transition at above 50 K. M-H curve shows the hysteresis loop with saturation magnetization (Ms) and confirms the presence of soft magnetic materials.

Agilandeswari, K.; Ruban Kumar, A.

2014-09-01

199

EGCG assisted green synthesis of ZnO nanopowders: Photodegradative, antimicrobial and antioxidant activities.  

PubMed

Zinc oxide nanopowders were synthesized by solution combustion method using Epigallocatechin gallate (EGCG) a tea catechin as fuel. The structure and morphology of the product was characterized by Powder X-ray Diffraction, Scanning Electron Microscopy, photoluminescence and UV-Visible spectroscopy. The nanopowders (Nps) were subjected to photocatalytic and biological activities such as antimicrobial and antioxidant studies. PXRD patterns demonstrate that the formed product belongs to hexagonal wurtzite system. SEM images show that the particles are agglomerated to form sponge like structure and the average crystallite sizes were found to be ?10-20nm. PL spectra exhibit broad and strong peak at 590nm due to the Zn-vacancies, and O-vacancies. The prepared ZnO Nps exhibit excellent photocatalytic activity for the photodegradation of malachite green (MG) and methylene blue (MB) indicating that the ZnO NPs are potential photocatalytic semiconductor materials. ZnO NPs exhibit significant bactericidal activity against Klebsiella aerogenes, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus using the agar well diffusion method. Furthermore, the ZnO nano powders show good antioxidant activity by potentially scavenging DPPH radicals. The study successfully demonstrates synthesis of ZnO NPs by simple ecofriendly route employing EGCG as fuel that exhibit superior photodegradative, antibacterial and antioxidant activities. PMID:25459708

Suresh, D; Udayabhanu; Nethravathi, P C; Lingaraju, K; Rajanaika, H; Sharma, S C; Nagabhushana, H

2014-11-01

200

EGCG assisted green synthesis of ZnO nanopowders: Photodegradative, antimicrobial and antioxidant activities  

NASA Astrophysics Data System (ADS)

Zinc oxide nanopowders were synthesized by solution combustion method using Epigallocatechin gallate (EGCG) a tea catechin as fuel. The structure and morphology of the product was characterized by Powder X-ray Diffraction, Scanning Electron Microscopy, photoluminescence and UV-Visible spectroscopy. The nanopowders (Nps) were subjected to photocatalytic and biological activities such as antimicrobial and antioxidant studies. PXRD patterns demonstrate that the formed product belongs to hexagonal wurtzite system. SEM images show that the particles are agglomerated to form sponge like structure and the average crystallite sizes were found to be ?10-20 nm. PL spectra exhibit broad and strong peak at 590 nm due to the Zn-vacancies, and O-vacancies. The prepared ZnO Nps exhibit excellent photocatalytic activity for the photodegradation of malachite green (MG) and methylene blue (MB) indicating that the ZnO NPs are potential photocatalytic semiconductor materials. ZnO NPs exhibit significant bactericidal activity against Klebsiella aerogenes, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus using the agar well diffusion method. Furthermore, the ZnO nano powders show good antioxidant activity by potentially scavenging DPPH radicals. The study successfully demonstrates synthesis of ZnO NPs by simple ecofriendly route employing EGCG as fuel that exhibit superior photodegradative, antibacterial and antioxidant activities.

Suresh, D.; Udayabhanu; Nethravathi, P. C.; Lingaraju, K.; Rajanaika, H.; Sharma, S. C.; Nagabhushana, H.

2015-02-01

201

Oxindole-3-spiropyrrolidines and -piperidines. Synthesis and local anesthetic activity.  

PubMed

The synthesis and local anesthetic properties of five 1-dealkyloxindole-3-spiropyrrolidines and six 1-dealkyloxindole-3-spiropiperidines are described. The compounds studied include members of all five possible positional isomers of the two classes of spirooxindoles; all showed local anesthetic activity by the rat sciatic nerve block method. The coincidence of the least variability in the relative positions of basic nitrogen, amide carbonyl, and aromatic ring (compounds 1 and 6) with lowest normalized toxicity is noteworthy. PMID:940109

Kornet, M J; Thio, A P

1976-07-01

202

Synthesis and enzymatic degradation of optically active depsipeptide copolymers  

Microsoft Academic Search

This paper describes the synthesis and biodegradation of copolymers of cyclic depsipeptide with ?-caprolactone (CL) or lactide (LA). Optically active cyclic depsipeptides, 3,6-dimethyl-2,5-morpholinediones (DMOs), were prepared by the reaction of an amino acid (D-, L-, or DL-alanine) with a hydroxy acid derivative (DL-2-bromopropionyl bromide). These isomers are abbreviated as D-DMO, L-DMO and DL-DMO respectively, according to the names of alanine

Hiroyuki Shirahama; Kouichi Umemoto; Hajime Yasuda

1999-01-01

203

Measurement of chloroplast ATP synthesis activity in Arabidopsis.  

PubMed

There are numerous options for monitoring ATP synthesis in chloroplasts using isolated thylakoid membranes, intact chloroplasts, and even whole leaves. Currently, the most commonly used method employs isolated thylakoids coupling the synthesis of ATP to light emission from luciferin in a reaction catalyzed by luciferase. The luciferin-luciferase assay can be highly sensitive and is a direct measure of ATP. Another direct measurement of ATP is the incorporation of 32P into ATP, which, while more technically difficult, has the advantage over the luciferin-luciferase assay of being able to distinguish newly synthesized from total ATP. The phosphorylation of ADP results in a net decrease in pKa (acid disassociation constant) between the reactants and the product ATP, resulting in an increase in the pH of the assay media, which can be used as a convenient, continuous measurement of ATP synthesis. The formation of ??H+ across the thylakoid membrane and its concomitant dissipation as ATP is synthesized can be measured by an electrochromic absorption band shift (ECS) of thylakoid pigments measured at 518 nm (Witt, Biochim. Biophys. Acta 505:355-427, 1979; Petty and Jackson, Biochim. Biophys. Acta: Bioenergetics 547:463-473, 1979). The first-order decay time of the ESC can be used to estimate the rate of ATP synthesis providing a noninvasive, indirect method for measuring ATP synthase activity that can be used with intact leaves. PMID:21863453

Grennan, Aleel K; Ort, Donald R

2011-01-01

204

Combustion synthesis\\/quasi-isostatic pressing of TiC 0.7 –NiTi cermets: microstructure and transformation characteristics  

Microsoft Academic Search

TiC0.7–NiTi cermets were produced by combustion synthesis followed by quasi-isostatic consolidation while the reaction products\\u000a were still hot and ductile. The TiC0.7–NiTi cermets were characterized by differential scanning calorimetry, room temperature transmission electron microscopy (TEM),\\u000a and in-situ TEM (temperature varied during observation). The matrix of the as-synthesized 20NiTi, 40NiTi, and 60NiTi composites\\u000a contains both R and B19? martensites at room

E. R. Strutt; T. Radetic; E. A. Olevsky; M. A. Meyers

2008-01-01

205

Combustion synthesis, characterization and metal–insulator transition studies of nanocrystalline La 1? x Ca x MnO 3 (0.0 ? x ? 0.5)  

Microsoft Academic Search

Nanocrystalline CMR materials La1?xCaxMnO3 (0.0?x?0.5) are prepared by a low temperature, self-propagating combustion synthesis. As-formed and heat treated calcium doped lanthanum manganites are crystalline, showing cubic symmetry. However, as-formed cubic LaMnO3 on calcination at 900°C for 6h, transformed into rhombohedral phase. The microstructure and morphology of the compounds show that the particles are nearly spherical in shape and are agglomerated.

B. M. Nagabhushana; R. P. Sreekanth Chakradhar; K. P. Ramesh; C. Shivakumara; G. T. Chandrappa

2007-01-01

206

Activation and de novo synthesis of hydrogenase in Chlamydomonas  

SciTech Connect

Two distinct processes are involved in the formation of active hydrogenase during anaerobic adaptation of Chlamydomonas reinhardtii cells. In the first 30 minutes of anaerobiosis, nearly all of the hydrogenase activity can be attributed to activation of constituitive polypeptide precursor, based on the insensitivity of the process to treatment with cycloheximide (15 micrograms per milliliter). This concentration of cycloheximide inhibits protein synthesis by greater than 98%. After the initial activation period, de novo protein synthesis plays a critical role in the adaptation process since cycloheximide inhibits the expression of hydrogenase in maximally adapted cells by 70%. Chloramphenicol (500 micrograms per milliliter) has a much lesser effect on the adaptation process. Incubation of cell-free extracts under anaerobic conditions in the presence of dithionite, dithiothreitol, NADH, NADP, ferredoxin, ATP, Mg/sup 2 +/, Ca/sup 2 +/, and iron does not lead to active hydrogenase formation. Furthermore, in vivo reactivation of oxygen-inactivated hydrogenase does not appear to take place. The adaptation process is very sensitive to the availability of iron. Iron-deficient cultures lose the ability to form active hydrogenase before growth, photosynthesis, and respiration are significantly affected. Preincubation of iron-deficient cells with iron 2 hours prior to the adaptation period fully restores the capacity of the cells to synthesize functional hydrogenase.

Roessler, P.G.; Lien, S.

1984-12-01

207

ChemTeacher: Combustion  

NSDL National Science Digital Library

ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Combustion page includes resources for teaching students about the chemistry behind combustion.

2012-07-23

208

Synthesis and antitumor activities of glucan derivatives  

Microsoft Academic Search

A highly efficient and practical method for the preparation of ?-d-Glc-(1?6)-[?-d-Glc-(1?3)]-?-d-Glc-(1?6)-?-d-Glc-(1?6)-[?-d-Glc-(1?3)]-d-Glc-OMe was described. A dendritic nonasaccharide was also synthesized. The antitumor activities of hexasaccharide, the dendrimer, their sulfated derivatives, together with the natural glucan–protein and the corresponding polysaccharide isolated from barmy mycelium of Grifola frondosa, were preliminarily investigated based on Sarcoma-180 studies in mice tests. Our results suggest that the

Yuguo Du; Guofeng Gu; Yuxia Hua; Guohua Wei; Xinshan Ye; Guangli Yu

2004-01-01

209

Synthesis and biological activities of 2-oxocycloalkylsulfonamides  

Microsoft Academic Search

A series of novel 2-oxocycloalkylsulfonamides (4) were synthesized and their structures confirmed by IR, 1H NMR, and elemental analysis. The bioassay showed that they have fair to excellent fungicidal activities against Botrytis cinerea Pers and Sclerotinia sclerotiorum. Among them, compounds 4A10, 4A11, 4A12, 4B2, and 4B3, the EC50 values of which were 2.12, 3.66, 3.96, 2.38, and 2.43?g\\/mL, respectively, displayed

Xinghai Li; Xinling Yang; Xiaomei Liang; Zhenpeng Kai; Huizu Yuan; Dekai Yuan; Jianjun Zhang; Ruiqing Wang; Fuxiang Ran; Shuhua Qi; Yun Ling; Fuheng Chen; Daoquan Wang

2008-01-01

210

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. PMID:20926945

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

2010-01-01

211

Design, Synthesis, and Trypanocidal Activity of New Aminoadamantane Derivatives  

PubMed Central

To develop functionalized adamantanes for treating African trypanosomiasis, we report on the synthesis of new 1-alkyl-2-aminoadamantanes 1a-i, 1-alkyltricyclo[3.3.1.13,7]decan-2-guanylhydrazones 2a-g, and their congeneric thiosemicarbazones 3a,b. The potency of these compounds against Trypanosoma brucei was compared to that of amantadine and rimantadine and found to be substantially higher. The most active analogues, 1c, 1d, 2c, 2g, and 3b, illustrate the synergistic effect of the lipophilic character of the C1 side chain and the C2 functionality on trypanocidal activity. PMID:18281929

Papanastasiou, Ioannis; Tsotinis, Andrew; Kolocouris, Nicolas; Prathalingam, S. Radhika; Kelly, John M.

2008-01-01

212

Synthesis and characterization of activated carbo-aluminosilicate material from oil shale  

E-print Network

Synthesis and characterization of activated carbo-aluminosilicate material from oil shale Reyad activated carbo-aluminosilicate materials were prepared from oil shale by chemical activation. The chemical Published by Elsevier Inc. Keywords: Synthesis; Activated carbo-aluminosilicate; Adsorption; Oil shale

Shawabkeh, Reyad A.

213

Impact of oxy-fuel combustion gases on mercury retention in activated carbons from a macroalgae waste: Effect of water.  

PubMed

The aim of this study is to understand the different sorption behaviors of mercury species on activated carbons in the oxy-fuel combustion of coal and the effect of high quantities of water vapor on the retention process. The work evaluates the interactions between the mercury species and a series of activated carbons prepared from a macroalgae waste (algae meal) from the agar-agar industry in oxy-combustion atmospheres, focussing on the role that the high concentration of water in the flue gases plays in mercury retention. Two novel aspects are considered in this work (i) the impact of oxy-combustion gases on the retention of mercury by activated carbons and (ii) the performance of activated carbons prepared from biomass algae wastes for this application. The results obtained at laboratory scale indicate that the effect of the chemical and textural characteristics of the activated carbons on mercury capture is not as important as that of reactive gases, such as the SOx and water vapor present in the flue gas. Mercury retention was found to be much lower in the oxy-combustion atmosphere than in the O2+N2 (12.6% O2) atmosphere. However, the oxidation of elemental mercury (Hg(0)) to form oxidized mercury (Hg(2+)) amounted to 60%, resulting in an enhancement of mercury retention in the flue gas desulfurization units and a reduction in the amalgamation of Hg(0) in the CO2 compression unit. This result is of considerable importance for the development of technologies based on activated carbon sorbents for mercury control in oxy-combustion processes. PMID:25585865

Lopez-Anton, M A; Ferrera-Lorenzo, N; Fuente, E; Díaz-Somoano, M; Suarez-Ruíz, I; Martínez-Tarazona, M R; Ruiz, B

2015-04-01

214

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

Microsoft Academic Search

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

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

2005-01-01

215

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

216

Synthesis and Anticancer Activity of all known (?)-Agelastatin Alkaloids  

PubMed Central

The full details for our enantioselective total syntheses of (?)-agelastatins A–F (1–6), the evolution of a new methodology for synthesis of substituted azaheterocycles, and the first side-by-side evaluation of all known (?)-agelastatin alkaloids against nine human cancer cell lines are described. Our concise synthesis of these alkaloids exploits the intrinsic chemistry of plausible biosynthetic precursors and capitalizes on a late-stage synthesis of the C-ring. The critical copper-mediated cross-coupling reaction was expanded to include guanidine-based systems, offering a versatile preparation of substituted imidazoles. The direct comparison of the anticancer activity of all naturally occurring (?)-agelastatins in addition to eight advanced synthetic intermediates enabled a systematic analysis of the structure activity relationship within the natural series. Significantly, (?)-agelastatin A (1) is highly potent against six blood cancer cell lines (20–190 nM) without affecting normal red blood cells (>333 ?M). (?)-Agelastatin A (1) and (?)-agelastatin D (4), the two most potent members of this family, induce dose dependent apoptosis and arrest cells in the G2/M-phase of the cell cycle; however, using confocal microscopy we have determined that neither alkaloid affects tubulin dynamics within cells. PMID:24152243

Han, Sunkyu; Siegel, Dustin S.; Morrison, Karen C.; Hergenrother, Paul J.

2014-01-01

217

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

218

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

219

mTOR coordinates protein synthesis, mitochondrial activity and proliferation.  

PubMed

Protein synthesis is one of the most energy consuming processes in the cell. The mammalian/mechanistic target of rapamycin (mTOR) is a serine/threonine kinase that integrates a multitude of extracellular signals and intracellular cues to drive growth and proliferation. mTOR activity is altered in numerous pathological conditions, including metabolic syndrome and cancer. In addition to its well-established role in regulating mRNA translation, emerging studies indicate that mTOR modulates mitochondrial functions. In mammals, mTOR coordinates energy consumption by the mRNA translation machinery and mitochondrial energy production by stimulating synthesis of nucleus-encoded mitochondria-related proteins including TFAM, mitochondrial ribosomal proteins and components of complexes I and V. In this review, we highlight findings that link mTOR, mRNA translation and mitochondrial functions. PMID:25590164

Morita, Masahiro; Gravel, Simon-Pierre; Hulea, Laura; Larsson, Ola; Pollak, Michael; St-Pierre, Julie; Topisirovic, Ivan

2015-02-16

220

Self-propagating combustion synthesis of CdSiO3 nano powder: structural and dosimetric applications  

NASA Astrophysics Data System (ADS)

Un-doped CdSiO3 nano phosphor has been synthesized by a low temperature solution combustion technique using cadmium nitrate as a cadmium source, oxalyldihydrazide (ODH) as a fuel and tetraethyl orthosilicate (TEOS) as a silica source. Powder x-ray diffraction (PXRD) patterns of CdSiO3 sample calcined at 800 °C for 2 h show monoclinic phase. The average crystallite sizes were estimated using Debye–Scherrer’s formula and Williamson–Hall (W–H) plots and are found to be 23–32 nm, respectively. SEM and TEM images of CdSiO3 reveal that they are foamy products with large agglomerates of very fine particles and the particles are in nano size. The optical energy band gap (Eg) of un-doped sample was estimated from Tauc relation as 5.6 eV. Thermoluminescence (TL) spectrum of the samples irradiated with UV source in the dose range 5–40 min was recorded at a heating rate of 5 °C s?1. The phosphor shows a well resolved glow peak at ˜166 °C. It is observed that TL intensity increased almost linearly with increase of dose, which is highly useful in radiation dosimetry. The kinetic parameters such as activation energy (E), frequency factor (s) and order of kinetics was estimated by three different methods.

Manohara, B. M.; Nagabhushana, H.; Thyagarajan, K.; Prashantha, S. C.; Nagabhushana, B. M.; Shivakumara, C.; Sharma, S. C.

2015-02-01

221

The combustion synthesis of the ferroelectric material, BaTiO{sub 3}, studied by time-resolved X-ray diffraction  

SciTech Connect

The combustion synthesis of the common ferroelectric material, BaTiO{sub 3}, was developed using the stoichiometry: BaO{sub 2}+0.2thinspTi+0.8thinspTiO{sub 2}{r_arrow}BaTiO{sub 3}+0.3thinspO{sub 2}. An adiabatic temperature, T{sub ad}, of the reaction was calculated from known thermodynamic data to be 1917thinsp{degree}C. Real time chemical changes in the formation of BaTiO{sub 3} during the reaction have been monitored using time-resolved X-ray diffraction with synchrotron radiation as the X-ray source. A time resolution of 250 ms was achieved. The combustion synthesis of BaTiO{sub 3} was followed by observing the intensities of reactant and product Bragg diffraction peaks in order to qualitatively identify the phases present. Because BaTiO{sub 3} forms initially as a cubic phase, X-ray diffraction of the product was monitored for a period of 20 min after the reaction to observe the phase transformation to the tetragonal form. This transformation is evident in these post-reaction scans as the cubic 110 and 220 peaks are split to the tetragonal 101/110 and 202/220 ones, respectively. {copyright} {ital 1999 International Centre for Diffraction Data.}

Larson, E.M. [College of Science and Allied Health, Grand Canyon University, Phoenix, Arizona 85017 (United States); Wong, J.; Holt, J.B.; Waide, P.A.; Rupp, B. [Lawrence Livermore National Laboratory, University of California, PO Box 808, Livermore, California 94551 (United States)

1999-06-01

222

Chemical synthesis and tyrosinase inhibitory activity of rhododendrol glycosides.  

PubMed

The concise synthesis of rhododendrol glycosides 3-8, which are novel derivatives of (+)-epirhododendrin (1) and (-)-rhododendrin (2), has been achieved in six steps from benzaldehyde 9. The key reactions include aldol condensation and trichloroacetimidate glycosylation. From biological studies, it has been determined that synthetic derivatives of 1 and 2 possess potent tyrosinase inhibitory activity. Particularly, the inhibitory activity of cellobioside 8 (IC50=1.51?M) is six times higher than that of kojic acid. The R-epimers (4, 6, and 8) possessed more potent activity than the corresponding S-epimers (3, 5, and 7), indicating that tyrosinase inhibitory activity is significantly governed by stereochemistry of rhododendrol glycosides. PMID:24332496

Iwadate, Takehiro; Kashiwakura, Yutaka; Masuoka, Noriyoshi; Yamada, Yoichi; Nihei, Ken-Ichi

2014-01-01

223

Synthesis and antifungal activity of novel streptochlorin analogues.  

PubMed

Streptochlorin, first isolated as a new antibiotic in 1988 from the lipophilic extracts of the mycelium of a Streptomyces sp, is an indole natural products with a variety of biological activities. Based on the methods developed for the synthesis of pimprinine in our laboratory, we have synthesized a series of indole-modified streptochlorin analogues and measured their activities against seven phytopathogenic fungi. Some of the analogues displayed good activity in the primary assays, and the seven compounds 10b, 10c, 11e, 13e, 21, 22c and 22e (shown in Figure 1) were identified as the most promising candidates for further study. Structural optimization is still ongoing with the aim of discovering synthetic analogues with improved antifungal activity. PMID:25633493

Zhang, Ming-Zhi; Chen, Qiong; Xie, Cai-Hong; Mulholland, Nick; Turner, Sarah; Irwin, Dianne; Gu, Yu-Cheng; Yang, Guang-Fu; Clough, John

2015-03-01

224

Biological activity of a leached chernozem contaminated with the products of combustion of petroleum gas and its restoration upon phytoremediation  

NASA Astrophysics Data System (ADS)

It is shown that contamination of leached chernozems by combustion products of petroleum gas favors changes in the biological activity of the soil: the number of hydrocarbon-oxidizing bacteria and micromycetes has increased, as well as the activity of catalase and lipase and phytotoxicity. Bromopsis inermis Leys used as a phytoameliorant has accelerated the destruction of hydrocarbons in the rhizosphere. The benzpyrene concentration in plants on contaminated soils considerably exceeds its background concentration.

Kireeva, N. A.; Novoselova, E. I.; Shamaeva, A. A.; Grigoriadi, A. S.

2009-04-01

225

Experimental and numerical investigations of jet active control for combustion applications  

NASA Astrophysics Data System (ADS)

Controlling the mixing of a gas (usually fuel) issuing from a tube into surrounding air is a basic problem in multiple combustion systems. The purpose of the present work is to develop an actuator device to control the mixing enhancement of an axisymmetric non-reactive jet. The actuators consist of four small jets feeding the primary jet flow. These four jets are oriented to add an azimuthal component to the velocity field. The influence of the jets' deflection and position along the main jet duct is discussed. Schlieren photographs and planar laser-induced fluorescence measurements are used to compare the efficiency of the three configurations of interest. The effect of 'control-to-main' mass flow rates' ratio is quantified through hot wire anemometry results. Large eddy simulations (LES) of both forced and unforced configurations are also performed. The objectives of the numerical part of this work are to understand the actuator effect and to validate LES as a tool to study active control. This paper was presented at the Third International Symposium on Turbulence and Shear Flow Phenomena (Sendai, Japan, 24-27 June 2003).

Faivre, Vincent; Poinsot, Thierry

2004-08-01

226

Combustion of Syngas in Internal Combustion Engines  

Microsoft Academic Search

The combustion of synthesis gas will play an important role in advanced power systems based on the gasification of fuel feedstocks and combined cycle power production. While the most commonly discussed option is to burn syngas in gas turbine engines, another possibility is to burn the syngas in stationary reciprocating engines. Whether spark ignited or compression ignited, syngas could serve

André L. Boehman; Olivier Le Corre

2008-01-01

227

Synthesis, characterization of double perovskite Ca{sub 2}MSbO{sub 6} (M = Dy, Fe, Cr, Al) materials via sol–gel auto-combustion and their catalytic properties  

SciTech Connect

Double perovskite-type oxide Ca{sub 2}MSbO{sub 6} materials, where M = Dy, Fe, Cr, and Al, were prepared by using the sol–gel auto-combustion method. The role of different B-site cations on their synthesis, structures, morphologies and catalytic properties was investigated. The progress of double-perovskite type structure formation and the disappearance of the organic phases were monitored by infrared absorption spectroscopy (FTIR). Double perovskite oxide structures were evaluated using X-ray diffraction (XRD), while the microstructure of obtained compounds was studied using scanning electron microscopy (SEM). Also, BET surface areas were measured at the liquid nitrogen temperature by nitrogen adsorption. Catalytic properties of the obtained compounds were evaluated by test reaction of hydrogen peroxide decomposition. - Highlights: • Ca{sub 2}MSbO{sub 6} double perovskites were obtained by sol–gel auto-combustion method. • Ca{sub 2}MSbO{sub 6} (M = Dy, Fe, Cr and Al) as catalysts in H{sub 2}O{sub 2} decomposition • Strong relationship between particles' shape, BET area and catalytic performance • Ca{sub 2}FeSbO{sub 6} spherical grains show superior catalytic activity.

Feraru, S. [“Alexandru Ioan Cuza” University, Faculty of Chemistry, Bv. Carol I no. 11, Iasi 700506 (Romania); Samoila, P. [“Petru Poni” Institute of Macromolecular Chemistry, 41A, Gr. Ghica Voda Alley, 700487 Iasi (Romania); Borhan, A.I. [“Alexandru Ioan Cuza” University, Faculty of Chemistry, Bv. Carol I no. 11, Iasi 700506 (Romania); Ignat, M. [“Alexandru Ioan Cuza” University, Faculty of Chemistry, Bv. Carol I no. 11, Iasi 700506 (Romania); “Petru Poni” Institute of Macromolecular Chemistry, 41A, Gr. Ghica Voda Alley, 700487 Iasi (Romania); Iordan, A.R. [“Alexandru Ioan Cuza” University, Faculty of Chemistry, Bv. Carol I no. 11, Iasi 700506 (Romania); Palamaru, M.N., E-mail: palamaru@uaic.ro [“Alexandru Ioan Cuza” University, Faculty of Chemistry, Bv. Carol I no. 11, Iasi 700506 (Romania)

2013-10-15

228

Synthesis, characterization and antiproliferative activity of ?-aryl-?-iodo-?-lactones  

NASA Astrophysics Data System (ADS)

A convenient pathway for the synthesis of new of ?-aryl-?-iodo-?-lactones is described. The synthetic route led to both cis and trans isomers which were separated by column chromatography or crystallization. The structures of synthesized compounds were confirmed by spectroscopic methods: IR, NMR and HR-MS. For lactones with naphthyl ring (6e and 7e) the crystal structures were also obtained. The lactones were screened for biological evaluation against cancer line HL-60 (human promyelocytic leukemia). The tests showed that the presence of substituent at the benzene ring does not significantly affect the antiproliferative activity of the compound.

Wzorek, Alicja; Gawdzik, Barbara; G?adkowski, Witold; Urbaniak, Mariusz; Bara?ska, Anita; Mali?ska, Maura; Wo?niak, Krzysztof; Kempi?ska, Katarzyna; Wietrzyk, Joanna

2013-09-01

229

Synthesis and biological activity of fluorescent neonicotinoid insecticide thiamethoxam.  

PubMed

Here, we describe the synthesis of two new fluorescent derivatives of thiamethoxam and compared their toxicity on aphid Acyrthosiphon pisum and their mode of action on insect nicotinic acetylcholine receptors expressed on the sixth abdominal ganglion. The compound 3 with two 2-chlorothiazole moieties was found to be more toxic using toxicological bioassays 24 h and 48 h after exposure while compound 4 appeared more active using cockroach ganglionic depolarization. Interestingly, thiamethoxam appeared more effective than component 3 and 4, respectively. Our results demonstrated that component 3 and 4 act as agonists of insect nicotinic acetylcholine receptors. PMID:24915877

Taillebois, Emiliane; Langlois, Paul; Cunha, Thomas; Seraphin, Denis; Thany, Steeve H

2014-08-01

230

Efficient discovery of bioactive scaffolds by activity-directed synthesis  

NASA Astrophysics Data System (ADS)

The structures and biological activities of natural products have often provided inspiration in drug discovery. The functional benefits of natural products to the host organism steers the evolution of their biosynthetic pathways. Here, we describe a discovery approach—which we term activity-directed synthesis—in which reactions with alternative outcomes are steered towards functional products. Arrays of catalysed reactions of ?-diazo amides, whose outcome was critically dependent on the specific conditions used, were performed. The products were assayed at increasingly low concentration, with the results informing the design of a subsequent reaction array. Finally, promising reactions were scaled up and, after purification, submicromolar ligands based on two scaffolds with no previous annotated activity against the androgen receptor were discovered. The approach enables the discovery, in tandem, of both bioactive small molecules and associated synthetic routes, analogous to the evolution of biosynthetic pathways to yield natural products.

Karageorgis, George; Warriner, Stuart; Nelson, Adam

2014-10-01

231

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. PMID:23509801

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

2013-01-01

232

Synthesis of nanocrystilline ferrites by sol-gel combustion process: the influence of pH value of solution  

NASA Astrophysics Data System (ADS)

The dried nitrate-citrate gels exhibit auto-catalytic combustion behavior, which can be used to synthesize the nanocrystalline ferrite powders. In this study, NiCuZn ferrite nanocrystalline powders with composition of (Ni 0.25Cu 0.25Zn 0.5)O(Fe 2O 3) 0.98 were synthesized by a sol-gel auto-catalytic combustion process. The influences of pH value of the precursor solution on the gel morphology, combustion behavior and crystallite size of synthesized powders were investigated with the help of scanning electron microscopy observation, thermal analysis, infrared (IR) spectra and X-ray diffraction technique. The experiments showed that the pH value of the mixed precursor solutions has a significant influence on the morphology of dried gels. The high porous precursors with network structure can be formed at high pH values after the solutions were dried at 135°C. With increasing pH value, the combustion rate is increased significantly. The as-burnt powders become uniform in size and the crystallites size is increased from 26 to 48 nm with pH value increasing from 2 to 7. The combustion reaction mechanisms were put forward with the help of IR spectra and differential thermal analysis techniques.

Yue, Zhenxing; Guo, Wenyu; Zhou, Ji; Gui, Zhilun; Li, Longtu

2004-03-01

233

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

234

Synthesis, characteristics and antimicrobial activity of ZnO nanoparticles.  

PubMed

The utilization of various plant resources for the bio synthesis of metallic nano particles is called green technology and it does not utilize any harmful protocols. Present study focuses on the green synthesis of ZnO nano particles by Zinc Carbonate and utilizing the bio-components of powder extract of dry ginger rhizome (Zingiber officinale). The ZnO nano crystallites of average size range of 23-26nm have been synthesized by rapid, simple and eco friendly method. Zinc oxide nano particles were characterized by using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX). FTIR spectra confirmed the adsorption of surfactant molecules at the surface of ZnO nanoparticles and the presence of ZnO bonding. Antimicrobial activity of ZnO nano particles was done by well diffusion method against pathogenic organisms like Klebsiella pneumonia, Staphylococcus aureus and Candida albicans and Penicillium notatum. It is observed that the ZnO synthesized in the process has the efficient antimicrobial activity. PMID:25748589

Janaki, A Chinnammal; Sailatha, E; Gunasekaran, S

2015-06-01

235

The effect of gravity on the combustion synthesis of Ni-Al and Ni3Al-TiB2 composites from elements  

NASA Technical Reports Server (NTRS)

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 convection, buoyancy of solid particles, and densification of the liquid product. Most of these processes are affected by gravity. Conducting the combustion synthesis under microgravity conditions is expected to help elucidate the reaction mechanisms. Two systems were examined. The first involves Ni/AI cladded particles, which is an ideal system to examine the individual particle and liquid flow before combustion occurs. For comparison, elemental Ni and Al powders with the same stoichiometry as that of the cladded particles were also used in some experiments. The second system was the Ni3AITiB2 composite in which the Ni3AI (-delta H(sub f) = 153.1 kJ/mol) phase melts during reaction enabling us to examine settling of the liquid phase. The amount of liquid phase was controlled by varying the TiB2 (-delta H(sub f) = 323.8 kJ/mol) content which generates the additional heat. The overall reactions for the two systems can be expressed as follows. System 1: 4Ni + 2AI yields Ni3AI + NiA and System 2: 3Ni + Al + x (Ti + 2B) yields Ni3Al + x(TiB2). For the first system, pellets were pressed directly from the cladded particles, at green densities about 77 +/- 3% of theoretical value. For the second, the pellets were prepared by mixing the elemental reactant powders in the required stoichiometry by ball-milling and then pressing uniaxially at green densities about 70 +/- 3 percent of theoretical. The pellets were cylindrical in shape, 10 mm in diameter and length typically 20-30 mm. The pellet samples were reacted in UHP Argon (1 atm) using the experimental setup and procedure described previously. After reaction, the samples were sectioned axially in order to conduct the microstructural analysis in the longitudinal direction. The phase composition of the reacted product was determined by X-ray diffraction (XRD) and the microstructure was analyzed using scanning electron microscopy (SEM) along with energy dispersive X-ray spectrometry (EDX).

Varma, Arvind; Yi, Hu Chun; Mcginn, Paul J.

1995-01-01

236

Synthesis and Antiproliferative Activities of Quebecol and Its Analogs  

PubMed Central

Simple and efficient synthesis of quebecol and a number of its analogs was accomplished in five steps. The synthesized compounds were evaluated for antiproliferative activities against human cervix adenocarcinoma (HeLa), human ovarian carcinoma (SKOV-3), human colon carcinoma (HT-29), and human breast adenocarcinoma (MCF-7) cancer cell lines. Among all the compounds, 7c, 7d, 7f, and 8f exhibited antiproliferative activities against four tested cell lines with inhibition over 80% at 75 ?M after 72 h, whereas, compound 7b and 7g were more selective towards MCF-7 cell line. The IC50 values for compounds 7c, 7d, and 7f were 85.1 ?M, 78.7 ?M, and 80.6 ?M against MCF-7 cell line, respectively, showing slightly higher antiproliferactive activtiy than the synthesized and isolated quebecol with an IC50 value of 104.2 ?M against MCF-7. PMID:23953195

Pericherla, Kasiviswanadharaju; Shirazi, Amir Nasrolahi; Rao, V. Kameshwara; Tiwari, Rakesh K.; DaSilva, Nicholas; McCaffrey, Kellen T.; Beni, Yousef A.; González-Sarrías, Antonio; Seeram, Navindra P.; Parang, Keykavous; Kumar, Anil

2013-01-01

237

Synthesis and antibacterial activity of of silver nanoparticles  

NASA Astrophysics Data System (ADS)

Silver nanoparticles have been known to have inhibitory and bactericidal effects but the antimicrobial mechanism have not been clearly revealed. Here, we report on the synthesis of metallic nanoparticles of silver using wild strains of Penicillium isolated from environment. Kinetics of the formation of nanosilver was monitored using the UV-Vis. TEM micrographs showed the formation of silver nanoparticles in the range 10-100 nm. Obtained Ag nanoparticles were evaluated for their antimicrobial activity against the gram-positive and gram-negative bacteria. As results, Bacillus cereus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were effectively inhibited. Nanosilver is a promising candidate for development of future antibacterial therapies because of its wide spectrum of activity.

Maliszewska, I.; Sadowski, Z.

2009-01-01

238

Advanced Combustion  

SciTech Connect

The activity reported in this presentation is to provide the mechanical and physical property information needed to allow rational design, development and/or choice of alloys, manufacturing approaches, and environmental exposure and component life models to enable oxy-fuel combustion boilers to operate at Ultra-Supercritical (up to 650{degrees}C & between 22-30 MPa) and/or Advanced Ultra-Supercritical conditions (760{degrees}C & 35 MPa).

Holcomb, Gordon R. [NETL

2013-03-11

239

Dipeptide Synthesis by an Aminopeptidase from Streptomyces septatus TH-2 and Its Application to Synthesis of Biologically Active Peptides  

Microsoft Academic Search

Dipeptide synthesis by aminopeptidase from Streptomyces septatus TH-2 (SSAP) was demonstrated using free amino acid as an acyl donor and aminoacyl methyl ester as an acyl acceptor in 98% methanol (MeOH). SSAP retained its activity after more than 100 h in 98% MeOH, and in the case of phenylalanyl-phenylalanine methyl ester synthesis, the enzyme reaction reached equilibrium when more than

Jiro Arima; Yoshiko Uesugi; Misugi Uraji; Masaki Iwabuchi; Tadashi Hatanaka

2006-01-01

240

Ultrasound-enhanced lipase activity in the synthesis of sugar ester using ionic liquids  

Microsoft Academic Search

Ionic liquids (ILs) which can dissolve high concentration of sugars and retain enzyme activity have been reported as good reaction media for the synthesis of sugar esters. However, the activities of lipases in ILs are usually lower than those in conventional organic solvents used for sugar ester synthesis. In this work, therefore, the ultrasound irradiation was used to increase enzyme

Sang Hyun Lee; Hiep Minh Nguyen; Yoon-Mo Koo; Sung Ho Ha

2008-01-01

241

[Up-conversion luminescent materials of Y2O3: RE(RE=Er or Er/Yb) prepared by sol-gel combustion synthesis].  

PubMed

Y2O3 powders doped with rare-earth ions were synthesized by sol-gel combustion synthesis. Effects of different calcinating temperatures, Er+ doping concentration and Yb3+ doping concentration were investigated. It was shown that the single well crystallized Y2O3 powders could be obtained at 800 degrees C; as the calcinating temperature increased, the crystallinity and upconversion luminescence intensity were higher; the particle size was uniform around 1 microm at 900 degrees C; when Er3+ doping concentration was 1 mol%, the green upconversion luminescence intensity reached the maximum, but for red upconversion luminescence, when Er3+ doping concentration was 4 mol%, its luminescence intensity reached the maximum; as the ratio of Yb3+ to Er3+ was 4:1, the green emission intensity reached the maximum, while the red emission intensity was always increasing as Yb3+ doping concentration increased. PMID:21284150

Han, Peng-de; Zhang, Le; Huang, Xiao-gu; Wang, Li-xi; Zhang, Qi-tu

2010-11-01

242

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

243

Diesel engine smoke reduction by controlling early thermal cracking process and activation later stage combustion  

SciTech Connect

In this investigation, extensive soot reduction was attempted with two parallel approaches: blending of oxygenated fuel and generation of strong turbulence during the combustion process. In the early stage of usual diesel combustion, the droplets in the spray are thermally cracked to low boiling point components as C2 to C5 due to the shortage of oxygen, and these components result in the formation of soot. To control the thermal cracking process, the addition of oxygenated additives to the fuel was attempted. As a result, remarkable soot reduction was obtained by adding small amounts of oxygen to the fuel. To generate strong turbulence, a small chamber connected to the main combustion chamber was added and small amount of fuel were injected into the chamber, resulting in significant soot reduction. Additionally, a clearly apparent NO{sub x}reduction was obtained by the mixing control.

Murayama, T. [Hokkaido Automotive Engineering Coll., Sapporo (Japan); Chikahisa, T. [Hokkaido Univ., Sapporo (Japan); Fujiwara, Y. [Hokkaido Inst. of Tech., Sapporo (Japan)

1998-07-01

244

Diesel engine smoke reduction by controlling early thermal cracking process and activating later stage combustion  

SciTech Connect

In this investigation, extensive soot reduction was attempted with two parallel approaches: blending of oxygenated fuel and generation of strong turbulence during the combustion process. In the early stage of usual diesel combustion, the droplets in the spray are thermally cracked to low boiling point components as C{sub 2} to C{sub 5} due to the shortage of oxygen, and these components result in the formation of soot. To control the thermal cracking process, the addition of oxygenated additives to the fuel was attempted. As a result, remarkable soot reduction was obtained by adding small amounts of oxygen to the fuel. To generate strong turbulence, a small chamber connected to the main combustion chamber was added and small amounts of fuel were injected into the chamber, resulting in significant soot reduction. Additionally, a clearly apparent NOx reduction was obtained by the mixing control.

Murayama, Tadashi [Hokkaido Automotive Engineering Coll., Sapporo (Japan); Chikahisa, Takemi [Hokkaido Univ., Sapporo (Japan); Fujiwara, Yasuhiro [Hokkaido Inst. of Tech., Sapporo (Japan)

1996-12-31

245

Test plan for measuring ventilation rates and combustible gas levels in TWRS active catch tanks  

SciTech Connect

The purpose of this test is to provide an initial screening of combustible gas concentrations in catch tanks that currently are operated by Tank Waste Remediation System (TWRS). The data will be used to determine whether or not additional data will be needed for closure of the flammable gas unreviewed safety question for these facilities. This test will involve field measurements of ammonia, organic vapor, and total combustible gas levels in the headspace of the catch tanks. If combustible gas level in a tank exceeds an established threshold, gas samples will be collected in SUMMA canisters for more extensive laboratory analysis. In addition, ventilation rates of some catch tanks will be measured to evaluate removal of flammable gas by air flow through the tanks.

NGUYEN, D.M.

1999-05-20

246

Test plan for measuring ventilation rates and combustible gas levels in RPP active catch tanks  

SciTech Connect

The purpose of this test is to provide an initial screening of combustible gas concentrations in catch tanks that currently are operated by River Protection Project (RPP). The data will be used to determine whether or not additional data will be needed for closure of the flammable gas unreviewed safety question for these facilities. This test will involve field measurements of ammonia, organic vapor, and total combustible gas levels in the headspace of the catch tanks. If combustible gas level in a tank exceeds an established threshold, gas samples will be collected in SUMMA canisters for more extensive laboratory analysis. In addition, ventilation rates of some catch tanks will be measured to evaluate removal of flammable gas by air flow through the tanks.

NGUYEN, D.M.

1999-06-03

247

Activated platelets signal chemokine synthesis by human monocytes.  

PubMed Central

Human blood monocytes adhere rapidly and for prolonged periods to activated platelets that display P-selectin, an adhesion protein that recognizes a specific ligand on leukocytes, P-selectin glycoprotein-1. We previously demonstrated that P-selectin regulates expression and secretion of cytokines by stimulated monocytes when it is presented in a purified, immobilized form or by transfected cells. Here we show that thrombin-activated platelets induce the expression and secretion of monocyte chemotactic protein-1 and IL-8 by monocytes. Enhanced monokine synthesis requires engagement of P-selectin glycoprotein-1 on the leukocyte by P-selectin on the platelet. Secretion of the chemokines is not, however, directly signaled by P-selectin; instead, tethering of the monocytes by P-selectin is required for their activation by RANTES (regulated upon activation normal T cell expressed presumed secreted), a platelet chemokine not previously known to induce immediate-early gene products in monocytes. Adhesion of monocytes to activated platelets results in nuclear translocation of p65 (RelA), a component of the NF-kappaB family of transcription factors that binds kappaB sequences in the regulatory regions of monocyte chemotactic protein-1, IL-8, and other immediate-early genes. However, expression of tissue factor, a coagulation protein that also has a kappaB sequence in the 5' regulatory region of its gene, is not induced in monocytes adherent to activated platelets. Thus, contact of monocytes with activated platelets differentially affects the expression of monocyte products. These experiments suggest that activated platelets regulate chemokine secretion by monocytes in inflammatory lesions in vivo and provide a model for the study of gene regulation in cell-cell interactions. PMID:8617886

Weyrich, A S; Elstad, M R; McEver, R P; McIntyre, T M; Moore, K L; Morrissey, J H; Prescott, S M; Zimmerman, G A

1996-01-01

248

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

249

Commercial investments in Combustion research aboard ISS  

NASA Astrophysics Data System (ADS)

The Center for Commercial Applications of Combustion in Space (CCACS) at the Colorado School of Mines is working with a number of companies planning commercial combustion research to be done aboard the International Space Station (ISS). This research will be conducted in two major ISS facilities, SpaceDRUMS™ and the Fluids and Combustion Facility. SpaceDRUMS™, under development by Guigne Technologies, Ltd., of St. John's Newfoundland, is a containerless processing facility employing active acoustic sample positioning. It is capable of processing the large samples needed in commercial research and development with virtually complete vibration isolation from the space station. The Fluids and Combustion Facility (FCF), being developed by NASA-Glenn Research Center in Cleveland, is a general-purpose combustion furnace designed to accommodate a wide range of scientific experiments. SpaceDRUMS™ will be the first commercial hardware to be launched to ISS. Launch is currently scheduled for UF-1 in 2001. The CCACS research to be done in SpaceDRUMS™ includes combustion synthesis of glass-ceramics and porous materials. The FCF is currently scheduled to be launched to ISS aboard UF-3 in 2002. The CCACS research to be done in the FCF includes water mist fire suppression, catalytic combustion and flame synthesis of ceramic powders. The companies currently planning to be involved in the research include Guigne International, Ltd., Technology International, Inc., Coors Ceramics Company, TDA Research, Advanced Refractory Technologies, Inc., ADA Technologies, Inc., ITN Energy Systems, Inc., Innovative Scientific Solutions, Inc., Princeton Instruments, Inc., Environmental Engineering Concepts, Inc., and Solar Turbines, Inc. Together, these companies are currently investing almost $2 million in cash and in-kind annually toward the seven commercial projects within CCACS. Total private investment in CCACS research to date is over $7 million. .

Schowengerdt, F. D.

2000-01-01

250

SYNTHESIS AND BIOLOGICAL ACTIVITY OF NITRO-SUBSTITUTED CYCLOPENTA-FUSED PAH  

EPA Science Inventory

PAH containing a peripherally fused cyclopenta ring are genotoxically active in Salmonella and mammalian cells and have been identified in combustion emissions. Since the cyclopenta ring is predicted to be susceptible to electrophilic attack, nitrosubstituted cyclopenta-fused PAH...

251

Synthesis and biological activity of salinomycin conjugates with floxuridine.  

PubMed

As part of our program to develop anticancer agents, we have synthesized new compounds, which are conjugates between well-known anticancer drug, floxuridine and salinomycin which is able to selectivity kill cancer stem cells. The conjugates were obtained in two ways i.e. by copper(I) catalysed click Huisgen cycloaddition reaction performed between 3'-azido-2',3'-dideoxy-5-fluorouridine and salinomycin propargyl amide, and by the ester synthesis starting from salinomycin and floxuridine under mild condition. The compounds obtained were characterized by spectroscopic methods and evaluated for their in vitro cytotoxicity against seven human cancer cell lines as well as antibacterial activity against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MRSE). The conjugate obtained by esterification reaction showed a significantly higher antiproliferative activity against the drug-resistant cancer cells and lower toxicity than those of salinomycin and floxuridine towards normal cells, as well as standard anticancer drugs, such as cisplatin and doxorubicin. The conjugate compound revealed also moderate activity against MRSA and MRSE bacterial strains. Very high activity of floxuridine and 5-fluorouracil against MRSA and MRSE has been also observed. PMID:25644674

Huczy?ski, Adam; Antoszczak, Micha?; Kleczewska, Natalia; Lewandowska, Marta; Maj, Ewa; Stefa?ska, Joanna; Wietrzyk, Joanna; Janczak, Jan; Celewicz, Lech

2015-03-26

252

Study of wear between piston ring and cylinder housing of an internal combustion engine by thin layer activation technique  

NASA Astrophysics Data System (ADS)

The wear analysis of a compression ring and cylinder housing of an Internal Combustion Engine by thin layer activation (TLA) with 40 MeV ?-particles from the Variable Energy Cyclotron at Calcutta is reported. The calibration curves have been obtained for Fe and Ni using stacked foil activation technique for determining the absolute wear in these machine parts. It has been possible to determine the pattern of wear on the points along the surface of machine components. The minimum detectable depth in this wear study has been estimated at 0.11 ± 0.04 ?m.

Chowdhury, D. P.; Chaudhuri, Jayanta; Raju, V. S.; Das, S. K.; Bhattacharjee, B. B.; Gangadharan, S.

1989-07-01

253

Low temperature synthesis of ultrafine Pb(Zr,Ti)O{sub 3} powder by sol-gel combustion  

SciTech Connect

Lead zirconate titanate powders are derived from a novel aqueous-based citrate-nitrate/oxynitrate sol-gel combustion process. Aqueous solutions of metal nitrates or oxynitrates are transformed into gels with citric acid under heating. The received gels undergo a self-propagating combustion reaction on heating to 180{degree}C and subsequently yield voluminous ashes. These ashes form single phase perovskite Pb(Zr{sub 0.53}Ti{sub 0.47})O{sub 3} powder with a specific surface area of 8m{sup 2}/g upon calcination at 550{degree}C. The ashes show a homogeneous distribution of lead, zirconium, and titanium ions which guarantees short diffusion paths in solid state formation of PZT perovskite. The redox behavior of the gels was studied with the help of DTA experiments. Powders are characterized in terms of XRD, SEM, and EDX analysis. {copyright} {ital 1997 Materials Research Society.}

Schaefer, J.; Sigmund, W.; Roy, S.; Aldinger, F. [Max-Planck-Institut fuer Metallforschung, Pulvermetallurgisches Laboratorium und Institut fuer Nichtmetallische Anorganische Materialien, Universitaet Stuttgart, Heisenbergstrasse 5, 70569 Stuttgart (Germany)

1997-10-01

254

Synthesis of nanocrystalline NiCuZn ferrite powders by sol-gel auto-combustion method  

NASA Astrophysics Data System (ADS)

A nitrate-citrate gel was prepared from metal nitrates and citric acid by sol-gel process, in order to synthesize Ni 0.25Cu 0.25Zn 0.50Fe 2O 4 ferrite. The thermal decomposition process was investigated by DTA-TG, IR and XRD techniques. The results revealed that the nitrate-citrate gel exhibits self-propagating combustion behavior. After combustion, the gel directly transformed into single-phase, nano-sized NiCuZn ferrite particles with spinel crystal structure. The synthesized powder can be densified at a temperature lower than 900°C. The sintered body possesses fine-grained microstructure, good frequency stability and high-quality factor compared to the sample prepared by conventional ceramic route.

Yue, Zhenxing; Zhou, Ji; Li, Longtu; Zhang, Hongguo; Gui, Zhilun

2000-01-01

255

Synthesis and Structural Activity Relationship Study of Antitubercular Carboxamides  

PubMed Central

The unusual structure and chemical composition of the mycobacterial cell wall, the tedious duration of therapy, and resistance developed by the microorganism have made the recurrence of the disease multidrug resistance and extensive or extreme drug resistance. The prevalence of tuberculosis in synergy with HIV/AIDS epidemic augments the risk of developing the disease by 100-fold. The need to synthesize new drugs that will shorten the total duration of effective treatment and/or significantly reduce the dosage taken under DOTS supervision, improve on the treatment of multidrug-resistant tuberculosis which defies the treatment with isoniazid and rifampicin, and provide effective treatment for latent TB infections which is essential for eliminating tuberculosis prompted this review. In this review, we considered the synthesis and structure activity relationship study of carboxamide derivatives with antitubercular potential. PMID:25610646

Ugwu, D. I.; Ezema, B. E.; Eze, F. U.; Ugwuja, D. I.

2014-01-01

256

Synthesis and biological activities of novel dexibuprofen tetraacetylriboflavin conjugates.  

PubMed

A series of novel dexibuprofen derivatives covalently linked via alkylene spacers of variable length to tetraacetylated riboflavin have been developed. The target compounds became accessible by reaction of the chloromethyl ester of dexibuprofen with tetraacetylriboflavin (compound 7) or by synthesis of the appropriate N3-(omega-iodoalkyl)-2',3',4',5'-Tetraacetylriboflavin followed by treatment with dexibuprofen (derivatives 8-11), respectively. Biological screening revealed that the target compounds exhibit antiproliferative effects on MCF-7 breast cancer and HT-29 colon carcinoma cells with IC50 values in the range of 8-15 microM. Enzymatic studies on human platelets indicated significant COX-1 inhibitory activities of the target compounds. PMID:17110105

Banekovich, Christian; Ott, Ingo; Koch, Thao; Matuszczak, Barbara; Gust, Ronald

2007-02-01

257

Experimental and numerical investigations of jet active control for combustion applications  

Microsoft Academic Search

Controlling the mixing of a gas (usually fuel) issuing from a tube into surrounding air is a basic problem in multiple combustion systems. The purpose of the present work is to develop an actuator device to control the mixing enhancement of an axisymmetric non-reactive jet. The actuators consist of four small jets feeding the primary jet flow. These four jets

Vincent Faivre; Thierry Poinsot

2004-01-01

258

Energy efficiency analyses of active flow aftertreatment systems for lean burn internal combustion engines  

Microsoft Academic Search

The use of three way catalytic converters in stoichiometric burn reciprocating internal combustion engine systems has proved to be an effective and efficient method for reducing the level of criteria pollutants. However, such passive systems have not been as successful in emission amelioration when combined with lean burn engines. This is because of the thermochemical nature of the exhaust gases

Ming Zheng; Graham T. Reader

2004-01-01

259

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

NASA Technical Reports Server (NTRS)

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 Space Transportation Main Engine (STME) nozzle. The nozzle design uses hydrogen-rich turbine exhaust to cool the wall in a film/dump scheme. This method of cooling presents challenges and associated risks for the nozzle designers and the engine/vehicle integrators. Within the nozzle itself, a key concern is the ability to effectively and efficiently film cool the wall. From the National Launch System vehicle base standpoint, there are concerns with dumping combustible gases at the nozzle exit and their potential adverse effects on the base thermal environment. The Combustion Team has developed and is implementing plans to use validated CFD tools to aid in risk mitigation for both areas.

Tucker, P. K.; Croteau-Gillespie, Margie

1992-01-01

260

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

261

Synthesis of nanocrystalline ytterbium-doped yttria by citrate-gel combustion method and fabrication of ceramic materials  

Microsoft Academic Search

Nanosized ytterbium doped yttria powders were prepared by citrate-gel combustion techniques. As-synthesized precursor and calcined powders were characterized for their crystalline structure, particle size and morphologies. Nanocrystalline Yb3+:Y2O3 powders with pure cubic yttria crystal structure were obtained by calcination of as-prepared precursors at 1100°C for 3h. Powders obtained were well dispersed with an average particle size of 60nm. By using

Nengli Wang; Xiyan Zhang; Zhaohui Bai; Haiying Sun; Quansheng Liu; Liping Lu; Xiaoyun Mi; Xiaochun Wang

2011-01-01

262

Self-propagating high temperature combustion synthesis of TiC\\/TiB 2 ceramic–matrix composites  

Microsoft Academic Search

TiC\\/TiB2 ceramic–matrix composites were produced by self-propagating high temperature combustion syntheses combined with pseudo hot isostatic pressing using Ti, B4C and carbon powder. The results of XRD and SEM analysis showed that the final product was pure and no unreacted B4C, Ti or carbon appeared. The microstructure of synthesized products consisted of the clubbed TiB2 grains and equiaxed or irregular

Zhang Xinghong; Zhu Chuncheng; Qu Wei; He Xiaodong; V. L Kvanin

2002-01-01

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

Efficient synthesis of anacardic acid analogues and their antibacterial activities.  

PubMed

Anacardic acid derivatives exhibit a broad range of biological activities. In this report, an efficient method for the synthesis of anacardic acid derivatives was explored, and a small set of salicylic acid variants synthesised retaining a constant hydrophobic element (a naphthyl tail). The naphthyl side chain was introduced via Wittig reaction and the aldehyde installed using directed ortho-metalation reaction of the substituted o-anisic acids. The failure of ortho-metalation using unprotected carboxylic acid group compelled us to use directed ortho-metalation in which a tertiary amide was used as a strong ortho-directing group. In the initial route, tertiary amide cleavage during final step was challenging, but cleaving the tertiary amide before Wittig reaction was beneficial. The Wittig reaction with protected carboxylic group (methyl ester) resulted in side-products whereas using sodium salt resulted in higher yields. The novel compounds were screened for antibacterial activity and cytotoxicity. Although substitution on the salicylic head group enhanced antibacterial activities they also enhanced cytotoxicity. PMID:23416004

Mamidyala, Sreeman K; Ramu, Soumya; Huang, Johnny X; Robertson, Avril A B; Cooper, Matthew A

2013-03-15

265

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. PMID:24696814

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

2014-01-01

266

The role of microstructure refinement on the impact ignition and combustion behavior of mechanically activated Ni/Al reactive composites  

NASA Astrophysics Data System (ADS)

Metal-based reactive composites have great potential as energetic materials due to their high energy densities and potential uses as structural energetic materials and enhanced blast materials however these materials can be difficult to ignite with typical particle size ranges. Recent work has shown that mechanical activation of reactive powders increases their ignition sensitivity, yet it is not fully understood how the role of microstructure refinement due to the duration of mechanical activation will influence the impact ignition and combustion behavior of these materials. In this work, impact ignition and combustion behavior of compacted mechanically activated Ni/Al reactive powder were studied using a modified Asay shear impact experiment where properties such as the impact ignition threshold, ignition delay time, and combustion velocity were identified as a function of milling time. It was found that the mechanical impact ignition threshold decreases from an impact energy of greater than 500 J to an impact energy of ˜50 J as the dry milling time increases. The largest jump in sensitivity was between the dry milling times of 25% of critical reaction milling time (tcr) (4.25 min) and 50% tcr (8.5 min) corresponding to the time at which nanolaminate structures begin to form during the mechanical activation process. Differential scanning calorimetry analysis indicates that this jump in the sensitivity to thermal and mechanical impact is dictated by the formation of nanolaminate structures, which reduce the temperature needed to begin the dissolution of nickel into aluminum. It was shown that a milling time of 50%-75% tcr may be near optimal when taking into account both the increased ignition sensitivity of mechanical activated Ni/Al and potential loss in reaction energy for longer milling times. Ignition delays due to the formation of hotspots ranged from 1.2 to 6.5 ms and were observed to be in the same range for all milling times considered less than tcr. Combustion velocities ranged from 20-23 cm/s for thermally ignited samples and from 25-31 cm/s for impacted samples at an impact energy of 200-250 J.

Mason, B. A.; Groven, L. J.; Son, S. F.

2013-09-01

267

Combustion synthesis of SrAl4O7:Eu2+, Dy3+, Gd3+ long lasting phosphor  

NASA Astrophysics Data System (ADS)

Long afterglow strontium aluminates SrAl4O7:Eu2+,Dy3+,Gd3+ phosphor was prepared by combustion method. The X-ray diffraction (XRD), Scanning electron microscope (SEM) and photoluminescence (PL) spectrum as well as the luminescence decay were used to characterize the long lasting phosphor. The emission spectrum of the phosphor shows broadened band at 495 nm assigned to the 4f65d?4f7(8S7/2) transition of Eu2+. The present phosphor shows green persistent luminescence after removal of the UV light.

Yerpude, A. N.; Dhoble, S. J.

2015-02-01

268

Synthesis and photocatalytic activity of titania microspheres with hierarchical structures  

SciTech Connect

Research highlights: {yields} Lauryl alcohol directs the formation of titania with hierarchical structures. {yields} Hierarchical structures endow the higher specific area to titania. {yields} Titania had a higher photocatalytic activity than commercial Degussa P25. {yields} The synthesis process of the target product is low-cost. -- Abstract: A combined sol-gel and solvothermal process was introduced to fabricate the titania microspheres with hierarchical structures by using lauryl alcohol as the structure-directing agent. Scanning electron microscope, high-resolution transmission electron microscope, Fourier transform infrared spectrograph and powder X-ray powder diffraction indicated that the molar ratio of lauryl alcohol, water and tetra-n-butyl titanate was the key factor for the formation of the mono-dispersed titania with anatase phase and the optimal ratio was 1.2:4:1. The diameter of the end-product was 523 {+-} 74 nm and it was composed of smaller nanoparticles with about 6.8 nm size in diameter. Photocatalytic activity of the end-product was investigated by employing Rhodamine B and Methylene blue as the model compounds. The target microspheres exhibited the higher photocatalytic efficiency compared with commercial Degussa P25 titania and this result might be due to the hierarchical structures of microspheres according to the analysis of Brunauer-Emmett-Teller specific surface areas.

Cheng, Qian-Qian; Cao, Ying [College of Chemistry and Environmental Science, Henan Normal University, 46 East of Construction Road, Xinxiang 453007 (China)] [College of Chemistry and Environmental Science, Henan Normal University, 46 East of Construction Road, Xinxiang 453007 (China); Yang, Lin, E-mail: yanglin1819@163.com [College of Chemistry and Environmental Science, Henan Normal University, 46 East of Construction Road, Xinxiang 453007 (China)] [College of Chemistry and Environmental Science, Henan Normal University, 46 East of Construction Road, Xinxiang 453007 (China); Zhang, Pei-Pei; Wang, Kui; Wang, Hua-Jie [College of Chemistry and Environmental Science, Henan Normal University, 46 East of Construction Road, Xinxiang 453007 (China)] [College of Chemistry and Environmental Science, Henan Normal University, 46 East of Construction Road, Xinxiang 453007 (China)

2011-03-15

269

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. PMID:23024819

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

2012-01-01

270

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

271

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

272

One-step solution-combustion synthesis of complex spinel titanate flake particles with enhanced lithium-storage properties  

NASA Astrophysics Data System (ADS)

In this work, we report the formation of porous Li2MTi3O8 (M = Zn, Co) flakes (hereafter referred to as f-Li2MTi3O8) via a facile one-step solution-combustion in less than 10 min. As anodes for rechargeable lithium-ion batteries, the synthesized f-Li2MTi3O8 exhibits high reversible charge-discharge capacity, great cycling stability and high rate performance. These results can be attributed to the intrinsic characteristics of spinel Li2MTi3O8 flakes, in which a porous framework could provide a diffusion space for lithium ion insertion into and extraction from the anode material, resulting in excellent cycle performance, even cycling at high rate of 2000 mA g-1.

Li, Xue; Xiao, Qian; Liu, Bo; Lin, Huangchang; Zhao, Jinbao

2015-01-01

273

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

274

MICROWAVE-ASSISTED GREENER SYNTHESIS OF PHARMACEUTICALLY ACTIVE HETEROCYCLES UNDER BENIGN CONDITIONS  

EPA Science Inventory

Green chemistry is a rapidly developing new field that provides us a proactive avenue for the sustainable development of future science and technologies. Environmentally benign protocols have been developed for the synthesis of various pharmaceutically active heterocycles namely ...

275

Synthesis of oolongtheanins and their inhibitory activity on micellar cholesterol solubility in vitro.  

PubMed

The synthesis of oolongtheanins (1a-d) was accomplished from EGC and/or EGCg in three steps. Oolongtheanin-3'-O-gallate (1b) showed more potent inhibitory activity on micellar cholesterol solubility than did EGCg. PMID:25619638

Ogawa, Kazuki; Hirose, Sayumi; Yamamoto, Hitomi; Shimada, Masaya; Nagaoka, Satoshi; Yanase, Emiko

2015-02-15

276

Plant polyphenols: chemical properties, biological activities, and synthesis.  

PubMed

Eating five servings of fruits and vegetables per day! This is what is highly recommended and heavily advertised nowadays to the general public to stay fit and healthy! Drinking green tea on a regular basis, eating chocolate from time to time, as well as savoring a couple of glasses of red wine per day have been claimed to increase life expectancy even further! Why? The answer is in fact still under scientific scrutiny, but a particular class of compounds naturally occurring in fruits and vegetables is considered to be crucial for the expression of such human health benefits: the polyphenols! What are these plant products really? What are their physicochemical properties? How do they express their biological activity? Are they really valuable for disease prevention? Can they be used to develop new pharmaceutical drugs? What recent progress has been made toward their preparation by organic synthesis? This Review gives answers from a chemical perspective, summarizes the state of the art, and highlights the most significant advances in the field of polyphenol research. PMID:21226137

Quideau, Stéphane; Deffieux, Denis; Douat-Casassus, Céline; Pouységu, Laurent

2011-01-17

277

Indenopyrazole oxime ethers: synthesis and ?1-adrenergic blocking activity.  

PubMed

This paper reports the synthesis and cardiac activity of new ?-blockers derived from (Z/E)-indeno[1,2-c]pyrazol-4(1H)-one oximes (5a,b). The latter compounds were allowed to react with epichlorohydrin, followed by reacting the oxiranyl derivatives formed (6a,b) with some aliphatic amines to give the target compounds (Z/E)-1-phenyl-1H-indeno[1,2-c]pyrazol-4-one O-((2-hydroxy-3-(substituted amino)propyl)oxime (7a-c) and (Z/E)-1-methyl-1H-indeno[1,2-c]pyrazol-4-one O-((2-hydroxy-3-(substituted amino)propyl)oxime (8a-c). These final products 7a-c and 8a-c were evaluated for their ability to modulate the cardiac performance of a prototype mammalian heart. The results showed that, out of these molecules tested, 7b elicits a more potent depressant effect on contractility and relaxation, and competitively antagonizes ?1-adrenergic receptors. PMID:25618014

Angelone, Tommaso; Caruso, Anna; Rochais, Christophe; Caputo, Angela Maria; Cerra, Maria Carmela; Dallemagne, Patrick; Filice, Elisabetta; Genest, David; Pasqua, Teresa; Puoci, Francesco; Saturnino, Carmela; Sinicropi, Maria Stefania; El-Kashef, Hussein

2015-03-01

278

Synthesis and antifungal activities of novel polyheterocyclic spirooxindole derivatives.  

PubMed

A series of spirooxindole tetrahydrofuran derivatives were obtained in moderate to good yields via oxindole derivatives and ?-arylacrylonitrile derivatives via base-mediated cascade [3 + 2] double Michael reactions under mild conditions and the application of this method in the synthesis of bioactive analogues, such as functionalized spirooxindole octahydrofuro[3,4-c]pyridine derivatives which contain two new heterocyclic rings and two quaternary carbon centers, has also been developed. Subsequently, antifungal activities of all of the synthesized compounds were evaluated against five phytopathogenic fungi (Rhizoctonia solani, Fusarium semitectum, Alternaria solani, Valsa mali and Fusarium graminearum) using the mycelium growth rate method. The preliminary results showed that the spirooxindole octahydrofuro[3,4-c]pyridine derivative showed higher growth inhibition of Valsa mali and Fusarium graminearum, than spirooxindole tetrahydrofuran derivatives . For example, spirooxindole octahydrofuro[3,4-c]pyridine derivative , having a bromine atom at the meta position of the benzene ring, was the best compound in inhibiting F. g. with an IC50 value of 3.31, in particular with inhibition of on F. g. being similar to that of the control cycloheximide (IC50 = 3.3 ?g mL(-1)). PMID:25820179

Wu, Jia-Shou; Zhang, Xue; Zhang, Ying-Lao; Xie, Jian-Wu

2015-04-22

279

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

280

Synthesis and characterization of vanadium nanoparticles on activated carbon and their catalytic activity in thiophene hydrodesulphurization  

NASA Astrophysics Data System (ADS)

Vanadium nanoparticles (˜7 nm) stabilized on activated carbon were synthesized by the reduction of VCl 3·3THF with K[BEt 3H]. This material was characterized by inductive coupled plasma-atomic emission spectroscopy (ICP-AES), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analyses. The catalytic performance of the carbon-supported vanadium was studied using thiophene hydrodesulfurization (HDS) as model reaction at 300 °C and P = 1 atm. The catalytic activity of the vanadium carbide phase on the activated carbon carrier was more significant than that of the reference catalysts, alumina supported NiMoS. The method proposed for the synthesis of such a catalyst led to an excellent performance of the HDS process.

Pinto, Susana; D'Ornelas, Lindora; Betancourt, Paulino

2008-06-01

281

Synthesis and antifungal activity of novel triazole compounds containing piperazine moiety.  

PubMed

Design and synthesis of triazole library antifungal agents having piperazine side chains, analogues to fluconazole were documented. The synthesis highlighted utilization of the click chemistry on the basis of the active site of the cytochrome P450 14?-demethylase (CYP51). Their structures were characterized by (1)H-NMR, (13)C-NMR, MS and IR. The influences of piperazine moiety on in vitro antifungal activities of all the target compounds were evaluated against eight human pathogenic fungi. PMID:25090121

Wang, Yanwei; Xu, Kehan; Bai, Guojing; Huang, Lei; Wu, Qiuye; Pan, Weihua; Yu, Shichong

2014-01-01

282

Upconversion fluorescence and its thermometric sensitivity of Er3+:Yb3+ co-doped SrF2 powders prepared by combustion synthesis  

NASA Astrophysics Data System (ADS)

Upconversion fluorescence of co-doped Er3+:Yb3+:SrF2 powders prepared by combustion synthesis was investigated under near-infrared ( ? = 980 nm) continuous wave laser excitation. Surface morphology of the samples and structures of the Er3+:Yb3+:SrF2 powders were studied with scanning electronic microscopy, energy dispersive x-ray, and x-ray powder diffraction. The spectrum of the fluorescence contains bands centered at ~410, ~522, ~545 and ~660 nm, corresponding respectively to transitions from upper levels 2H9/2, 2H11/2, 4S3/2 and 4F9/2 to the ground state 4I15/2, which can be identified as 4 f-4 f transitions from Er3+ excited states. In addition, the fluorescence is found sensitive to the temperature, which suggests that an optical temperature sensor would be feasible. The maximum sensitivity of the proposed sensor was found 0.00396 K-1.

Rakov, Nikifor; Maciel, Glauco S.; Xiao, Mufei

2014-09-01

283

Spectroscopic analysis of Eu{sup 3+} -and Eu{sup 3+}:Yb{sup 3+}-doped yttrium silicate crystalline powders prepared by combustion synthesis  

SciTech Connect

Yttrium silicate powders doped with Eu{sup 3+} and codoped with Eu{sup 3+} and Yb{sup 3+} were prepared by combustion synthesis. The x-ray powder diffraction data showed the presence of Y{sub 2}SiO{sub 5} and Y{sub 2}Si{sub 2}O{sub 7} crystalline phases. Singly doped (1 wt %) sample illuminated with ultraviolet light ({lambda}=256 nm) showed the characteristic red luminescence corresponding to {sup 5}D{sub 0}{yields}{sup 7}F{sub J} transitions of Eu{sup 3+}. The Judd-Ofelt intensity parameters were calculated from experimental data and the radiative and nonradiative relaxation rates were estimated. The results showed that the nonradiative relaxation rate is smaller in yttrium silicate compared to yttrium oxide powder, a reference material, prepared under similar conditions. Codoped samples were exposed to near-infrared laser excitation ({lambda}=975 nm) and the red luminescence of Eu{sup 3+} was also observed. In this case, the luminescence is achieved due to a cooperative upconversion (CUC) process involving energy transfer (ET) from pairs of ytterbium ions to europium ions. The ET rate was estimated by fitting a rate equation model with the dynamics of CUC red emission.

Rakov, Nikifor [PG-Ciencia dos Materiais, Universidade Federal do Vale do Sao Francisco, 48902-300 Juazeiro, BA (Brazil); Amaral, Dayanne F.; Guimaraes, Renato B.; Maciel, Glauco S. [Instituto de Fisica, Universidade Federal Fluminense, 24210-346 Niteroi, RJ (Brazil)

2010-10-15

284

Cooperative upconversion luminescence in Tb3+:Yb3+ co-doped Y2SiO5 powders prepared by combustion synthesis  

NASA Astrophysics Data System (ADS)

Frequency upconversion (UC) luminescence via cooperative energy transfer (CET) process between pairs of Yb3+ and Tb3+ ions was investigated in Tb3+:Yb3+:Y2SiO5 crystalline ceramic powders prepared by combustion synthesis. Surface morphology and structure of the powders were investigated by scanning electronic microscopy and X-ray powder diffraction. Photoluminescence experiments were performed in Tb3+-singly doped samples using ultraviolet light (?=255 nm) and in Tb3+:Yb3+ co-doped samples using a near-infrared (NIR) diode laser (?=975 nm). Upon excitation with the NIR diode laser, UC luminescence with an intense emission band centered at ~549 nm, corresponding to the 4f intraband 5D4?7F5 transition of Tb3+, along with less intense emission bands at ~490, ~590 and ~620 nm, corresponding to other 5D4?7FJ transitions, was detected. The CET rate was estimated by analyzing the dynamics of UC luminescence with rate equations model of the electronic populations.

Rakov, Nikifor; Vieira, Simone A.; Guimarães, Renato B.; Maciel, Glauco S.

2014-03-01

285

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

286

Synthesis and Anticancer Activity of All Known (?)-Agelastatin Alkaloids  

E-print Network

The full details of our enantioselective total syntheses of (?)-agelastatins A–F (1–6), the evolution of a new methodology for synthesis of substituted azaheterocycles, and the first side-by-side evaluation of all known ...

Han, Sunkyu

287

Synthesis and anti-melanogenic activity of hydroxyphenyl benzyl ether analogues  

Microsoft Academic Search

In order to develop potent skin whitening agents, we have synthesized 17 hydroxyphenyl benzyl ether compounds and tested their melanin synthesis inhibitory activity, DPPH free radical scavenging activity and tyrosinase inhibitory activity. Compounds 32, 35 and 36 possessing 4-hydroxyphenyl benzyl ether structure showed excellent inhibitory capacity with almost 50-fold than arbutin used as a reference in the inhibition test of

Kiran Sapkota; Eunmiri Roh; Eunyoung Lee; Eun-Mi Ha; Jae-Ho Yang; Eung-Seok Lee; Youngjoo Kwon; Youngsoo Kim; Younghwa Na

2011-01-01

288

Synthesis and antibacterial property of quinolines with potent DNA gyrase activity  

Microsoft Academic Search

Synthesis of a series of novel tetrahydroquinoline annulated heterocycles has been accomplished by intramolecular imino and bisimino Diels–Alder reaction. These compounds were evaluated for their antibacterial activity. All the synthetic compounds, exhibited good antibacterial activity against microorganisms of which one of them 7 was found to be as active as the antibiotic ciplofloxacin and is found to have MIC value

Ekambaram Ramesh; Rathna Durga R. S. Manian; Ragavachary Raghunathan; Shilpakala Sainath; Malathi Raghunathan

2009-01-01

289

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

290

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

291

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

292

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

293

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. PMID:24594755

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

2014-01-01

294

Eu3+-activated SrMoO4 phosphors for white LEDs applications: Synthesis and structural characterization  

NASA Astrophysics Data System (ADS)

We report the synthesis of Eu3+-activated SrMoO4 phosphors by the facile nitrate-citrate gel combustion method. Powder XRD and Rietveld refinement data confirmed that these phosphors have a monophasic scheelite-type tetragonal structure with space group I41/a (No. 88). FESEM micrographs indicate the agglomerated spherical particles. FTIR spectra showed four stretching and bending vibrational modes (2Au and 2Eu). UV-Visible absorption spectroscopy illustrated that the optical band gap energy (Eg) values increase with increase in Eu3+ concentration. The host SrMoO4 phosphor exhibited an intense blue emission under UV excitation (368 nm). The Eu3+-activated SrMoO4 phosphors revealed characteristic luminescence due to Eu3+ ion corresponding to 5D1 ? 7FJ (J = 1, 2) and 5D0 ? 7FJ (J = 1, 2, 3, 4) transitions upon 465 nm excitation. The electric dipole transition located at 615 nm (5D0 ? 7F2) was stronger than the magnetic dipole transition located at 592 nm (5D0 ? 7F1). Intensity parameters (?2, ?4) and radiative properties such as transition probabilities (AT), radiative lifetime (?rad) and branching ratio (?) of Eu3+-activated SrMoO4 phosphors were calculated using the Judd-Ofelt theory. Based on the CIE chromaticity diagram, these phosphors can be promising materials for the development of blue and orange-red component in white LEDs.

Shivakumara, C.; Saraf, Rohit

2015-04-01

295

Thermoelectric and magnetic properties of perovskite-type manganate phases synthesised by ultrasonic spray combustion (USC)  

Microsoft Academic Search

Electron-doped manganate phases were synthesised by ultrasonic spray combustion (USC) to investigate the magnetic and transport properties related to their morphology. The nanocrystallite microstructure obtained from the USC synthesis is characterized by the presence of twinned domains coexisting with ordered crystalline material. Classical solid state reaction (SSR) methods were applied to compare their thermoelectric activities with the USC compounds. Magnetic

Laura Bocher; Rosa Robert; Myriam H. Aguirre; Sylvie Malo; Sylvie Hébert; Antoine Maignan; Anke Weidenkaff

2008-01-01

296

Combustion monitoring  

SciTech Connect

This article describes application analysis system to lean-burn engines, engines that feature EGR, or other engines in which unfavorable combustion occurs, to control engine roughness, lower fuel consumption, and reduce NOx emission and combustion inconsistencies among cylinders. The idea of monitoring combustion of an internal combustion engine, and using the obtained data to control combustion, is not new. Two well-known methods have been developed: one involves combustion-pressure analysis, and the other measures ionic currents in combustion gas. Although highly precise analysis can be achieved by the former, there are problems in the installation of combustion pressure sensors, and their durability and cost. There are also problems in installing ionic-current sensors, and the reliability of data obtained from such sensors is questionable. Researchers at Honda R and D Co. and NGK Spark Plug Co. have developed a method which uses spark-plug-voltage analysis for monitoring combustion. Voltage is measured by noncontact sensors in the high-voltage zone near the spark plugs. Monitoring is done in real time by processing waveform data and measuring the ion density. This monitoring system can control combustion during fluctuations of the air/fuel ratio (A/F), exhaust gas recirculation (EGR), and ignition timing for lean-burn or other conventional engines. By controlling combustion near the lean, EGR, and timing limits, it is possible to reduce fuel consumption and exhaust emissions, while maintaining driveability.

Not Available

1993-07-01

297

Preparation and evaluation of coal-derived activated carbons for removal of mercury vapor from simulated coal combustion flue fases  

USGS Publications Warehouse

Coal-derived activated carbons (CDACs) were tested for their suitability in removing trace amounts of vapor-phase mercury from simulated flue gases generated by coal combustion. CDACs were prepared in bench-scale and pilot-scale fluidized-bed reactors with a three-step process, including coal preoxidation, carbonization, and then steam activation. CDACs from high-organicsulfur Illinois coals had a greater equilibrium Hg0 adsorption capacity than activated carbons prepared from a low-organic-sulfur Illinois coal. When a low-organic-sulfur CDAC was impregnated with elemental sulfur at 600 ??C, its equilibrium Hg0 adsorption capacity was comparable to the adsorption capacity of the activated carbon prepared from the high-organicsulfur coal. X-ray diffraction and sulfur K-edge X-ray absorption near-edge structure examinations showed that the sulfur in the CDACs was mainly in organic forms. These results suggested that a portion of the inherent organic sulfur in the starting coal, which remained in the CDACs, played an important role in adsorption of Hg0. Besides organic sulfur, the BET surface area and micropore area of the CDACs also influenced Hg0 adsorption capacity. The HgCl2 adsorption capacity was not as dependent on the surface area and concentration of sulfur in the CDACs as was adsorption of Hg0. The properties and mercury adsorption capacities of the CDACs were compared with those obtained for commercial Darco FGD carbon.

Hsi, H.-C.; Chen, S.; Rostam-Abadi, M.; Rood, M.J.; Richardson, C.F.; Carey, T.R.; Chang, R.

1998-01-01

298

Synthesis of a Tristearoyl Lipomannan via Pre-activation-based Iterative One-pot Glycosylation  

PubMed Central

A convergent and efficient strategy was developed for the synthesis of lipomannan (LM), useful for vaccine development. Thioglycosides were employed as glycosyl donors to construct two key pseudotrisaccharide and tetramannose intermediates through pre-activation-based glycosylation strategy. These building blocks were then successfully coupled to form the LM core, which was lapidated, phospholipidated, and finally globally deprotected to afford the target molecule. The intermediate LM core involved in this synthesis contained orthogonal protections, which would facilitate its variable modifications for the preparation of other complex LM derivatives and for the synthesis of LM conjugates as LM-based vaccines. PMID:24266397

Gao, Jian; Guo, Zhongwu

2014-01-01

299

Activation of nuclear polypeptide synthesis in rat liver cells in the case of inhibition of template synthesis of proteins. Contribution of nuclear polypeptide synthesis to the change in the chromatin structure  

SciTech Connect

The correlation between the activity of nuclear polypeptide synthesis (NPS) and template synthesis of proteins in rat liver cells was investigated. It was established that the NPS is activated under conditions of inhibition of protein synthesis in the cytoplasm. It was shown on model experiments that the systems of NPS and ADP-ribosylation of nuclear proteins compete in determining the general structure of chromatin: ADP-ribosylation promotes condensation, while NPS promotes decondensation of the chromatin.

Gutnikova, M.N.; Shevchenko, N.A.; Boikov, P.Ya.; Mitrokhin, Yu.I.; Todorov, I.N.

1986-06-10

300

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

301

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

302

Microwave assisted solvent-free synthesis and biological activities of novel imines (Schiff bases)  

Microsoft Academic Search

Twelve new ortho-Hydroxyketimines were synthesized by conventional as well as microwave method and evaluated for their antinemic activity against Meloidogyne incognita [(Kofoid and White) Chitwood]. Conventional methods for synthesis of Schiff bases require refluxing at 140°C of the reactants in different solvents for at least 24 h or more, where as the microwave-assisted synthesis has brought down the reaction time

Aditi Kundu; Najam Akhtar Shakil; Dinesh B. Saxena; Pankaj; Jitendra Kumar; Suresh Walia

2009-01-01

303

Synthesis and cytotoxic activity of some derivatives of alkyl piperidine.  

PubMed

Synthesis of novel phenacyl derivatives of alkyl piperidine as cytotoxic agents via simple and single step reaction procedure is going to be reported here. Twelve new compounds were successfully synthesized in moderate yield and in solid form. Their synthesis was confirmed by TLC, melting point, CHN analysis and through different spectral studies such as UV, IR, Mass and proton NMR. The advantages of this synthetic route are simple operation, mild reaction conditions and good yields. These newly synthesized derivatives were extensively explored for their cytotoxicity by brine shrimp lethality assay. PMID:23625425

Jahan, Sarwat; Akhtar, Shamim; Saify, Zafar Saied; Mushtaq, Nousheen; Sial, Ali Akbar; Kamil, Arfa; Arif, Muhammed

2013-05-01

304

Investigating the performance of CoxOy/activated carbon catalysts for ethyl acetate catalytic combustion  

NASA Astrophysics Data System (ADS)

The catalytic properties of Co-supported activated carbon (AC) catalysts for ethyl acetate catalytic elimination in air were investigated. Results showed that air atmosphere promoted the generation of high-valence state cobalt oxides, and promote the production of reactive oxygen species (ROS) in the Co3O4/AC catalyst. ROS crucially functioned in improving the catalytic activity of Co3O4/AC catalysts. Therefore, CoACA catalyst prepared in air exhibited higher catalytic activity than CoACN catalyst prepared in nitrogen, and CoACA catalyst led to high ethyl acetate conversion (>93%) and stability at a low reaction temperature (210 °C).

Xie, Hongmei; Zhao, Xiaoping; Zhou, Guilin; He, Xiaoling; Lan, Hai; Jiang, Zongxuan

2015-01-01

305

Upscaling Self-Sustaining Treatment for Active Remediation (STAR): Experimental Study of Scaling Relationships for Smouldering Combustion to Remediate Soil  

NASA Astrophysics Data System (ADS)

Self-sustaining Treatment for Active Remediation (STAR) is a relatively new remediation approach for soil contaminated with organic industrial liquids. This technology uses smouldering combustion, a controlled, self-sustaining burning reaction, to destroy nonaqueous phase liquids (NAPLs) and thereby render soil clean. While STAR has been proven at the bench scale, success at industrial scales requires the process to be scaled-up significantly. The objective of this study was to conduct an experimental investigation into how liquid smouldering combustion phenomena scale. A suite of detailed forward smouldering experiments were conducted in short (16 cm dia. x 22 cm high), intermediate (16 cm dia. x 127 cm high), and large (97 cm dia. x 300 cm high; a prototype ex-situ reactor) columns; this represents scaling of up to 530 times based on the volume treated. A range of fuels were investigated, with the majority of experiments conducted using crude oil sludge as well as canola oil as a non-toxic surrogate for hazardous contaminants. To provide directly comparable data sets and to isolate changes in the smouldering reaction which occurred solely due to scaling effects, sand grain size, contaminant type, contaminant concentration and air injection rates were controlled between the experimental scales. Several processes could not be controlled and were identified to be susceptible to changes in scale, including: mobility of the contaminant, heat losses, and buoyant flow effects. For each experiment, the propagation of the smouldering front was recorded using thermocouples and analyzed by way of temperature-time and temperature-distance plots. In combination with the measurement of continuous mass loss and gaseous emissions, these results were used to evaluate the fundamental differences in the way the reaction front propagates through the mixture of sand and fuel across the various scales. Key governing parameters were compared between the small, intermediate, and large scale experiments, including: peak temperatures, velocities and thicknesses of the smouldering front, rates of mass destruction of the contaminant, and rates of gaseous emissions during combustion. Additionally, upward and downward smouldering experiments were compared at the column scale to assess the significance of buoyant flow effects. An understanding of these scaling relationships will provide important information to aid in the design of field-scale applications of STAR.

Kinsman, L.; Gerhard, J.; Torero, J.; Scholes, G.; Murray, C.

2013-12-01

306

Postpolymerization modification using less cytotoxic activated ester polymers for the synthesis of biological active polymers.  

PubMed

Activated ester polymers, pioneered by Ferruti and Ringsdorf in the 1970s, are attractive polymeric materials because they can easily be converted into functional polymers by reacting with amine nucleophiles. In the present study, methyl salicylate acrylate, salicyl acrylate, and tert-butyl salicylate acrylate monomers were polymerized yielding three novel reactive precursors suitable for the postpolymerization modification with primary and secondary amines. The reactivities of poly(pentafluorophenyl acrylate), poly(methyl salicylate acrylic ester), and poly(salicyl acrylate) toward amines were compared by kinetic studies and revealed the practical applicability of salicylic acid based derivatives for efficient postpolymerization modifications. In addition, in vitro cytotoxicity of water-soluble leaving groups, pentafluorophenol and salicylic acid, as well as water-soluble polymers containing the respective activated ester groups were investigated using HeLa cells. In short, compared to the frequently used poly(pentafluorophenyl acrylate), poly(salicyl acrylate) activated ester feature a lower reactivity, but exhibit less cytotoxicity. In this respect, poly(salicyl acrylate) as reactive precursor polymers may become alternative routes for the synthesis of functional polyacrylamides when it comes to advanced applications in vivo. PMID:25019415

He, Lirong; Szameit, Kristina; Zhao, Hui; Hahn, Ulrich; Theato, Patrick

2014-08-11

307

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...

308

Memory retrieval requires ongoing protein synthesis and NMDA receptor activity-mediated AMPA receptor trafficking.  

PubMed

Whereas consolidation and reconsolidation are considered dynamic processes requiring protein synthesis, memory retrieval has long been considered a passive readout of previously established plasticity. However, previous findings suggest that memory retrieval may be more dynamic than previously thought. This study therefore aimed at investigating the molecular mechanisms underlying memory retrieval in the rat. Infusion of protein synthesis inhibitors (rapamycin or anisomycin) in the amygdala 10 min before memory retrieval transiently impaired auditory fear memory expression, suggesting ongoing protein synthesis is required to enable memory retrieval. We then investigated the role of protein synthesis in NMDA receptor activity-mediated AMPA receptor trafficking. Coinfusion of an NMDA receptor antagonist (ifenprodil) or infusion of an AMPA receptor endocytosis inhibitor (GluA23Y) before rapamycin prevented this memory impairment. Furthermore, rapamycin transiently decreased GluA1 levels at the postsynaptic density (PSD), but did not affect extrasynaptic sites. This effect at the PSD was prevented by an infusion of GluA23Y before rapamycin. Together, these data show that ongoing protein synthesis is required before memory retrieval is engaged, and suggest that this protein synthesis may be involved in the NMDAR activity-mediated trafficking of AMPA receptors that takes place during memory retrieval. PMID:25673841

Lopez, Joëlle; Gamache, Karine; Schneider, Rilla; Nader, Karim

2015-02-11

309

A simple aloe vera plant-extracted microwave and conventional combustion synthesis: Morphological, optical, magnetic and catalytic properties of CoFe2O4 nanostructures  

NASA Astrophysics Data System (ADS)

Nanocrystalline magnetic spinel CoFe2O4 was synthesized by a simple microwave combustion method (MCM) using ferric nitrate, cobalt nitrate and Aloe vera plant extracted solution. For the comparative study, it was also prepared by a conventional combustion method (CCM). Powder X-ray diffraction, energy dispersive X-ray and selected-area electron diffraction results indicate that the as-synthesized samples have only single-phase spinel structure with high crystallinity and without the presence of other phase impurities. The crystal structure and morphology of the powders were revealed by high resolution scanning electron microscopy and transmission electron microscopy, show that the MCM products of CoFe2O4 samples contain sphere-like nanoparticles (SNPs), whereas the CCM method of samples consist of flake-like nanoplatelets (FNPs). The band gap of the samples was determined by UV-Visible diffuse reflectance and photoluminescence spectroscopy. The magnetization (Ms) results showed a ferromagnetic behavior of the CoFe2O4 nanostructures. The Ms value of CoFe2O4-SNPs is higher i.e. 77.62 emu/g than CoFe2O4-FNPs (25.46 emu/g). The higher Ms value of the sample suggest that the MCM technique is suitable for preparing high quality nanostructures for magnetic applications. Both the samples were successfully tested as catalysts for the conversion of benzyl alcohol. The resulting spinel ferrites were highly selective for the oxidation of benzyl alcohol and exhibit important difference among their activities. It was found that CoFe2O4-SNPs catalyst show the best performance, whereby 99.5% selectivity of benzaldehyde was achieved at close to 93.2% conversion.

Manikandan, A.; Sridhar, R.; Arul Antony, S.; Ramakrishna, Seeram

2014-11-01

310

Veratridine-induced phosphorylation and activation of tyrosine hydroxylase, and synthesis of catecholamines in cultured bovine adrenal medullary cells  

Microsoft Academic Search

The mechanism of the synthesis of catecholamines by veratridine was studied in cultured bovine adrenal medullary cells. (1) Veratridine increased the phosphorylation and activity of tyrosine hydroxylase as well as the synthesis of [14C]catecholamines from [14C]tyrosine, all of which were inhibited by tetrodotoxin. Veratridine-induced activation of tyrosine hydroxylase and synthesis of [14C]catecholamines were reduced in 20 mmol\\/l extracellular Na+ or

Yasuhito Uezono; Nobuyuki Yanagihara; Akihiko Wada; Yoshiro Koda; Kenji Yokota; Hideyuki Kobayashi; Futoshi Izumi

1989-01-01

311

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. PMID:16202154

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

2005-01-01

312

Synthesis of pure, active, and fine NiFe?O? by aerosolization  

E-print Network

SYNTHESIS OF PURE, ACTIVE, AND FINE NiFezO& BY AEROSOLIZATION A Thesis by HSUAN-FU YU Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE... December 1989 Major Subject: Chemical Engineering SYNTHESIS OF PURE, ACTIVE, AND FINE NiFe&O& BY AEROSOLIZATION A Thesis by HSUAN-FU YU Approved as to style and content by: Ahmed M. Gadalla (Chair of Committee) Philip T. Eubank (Member) William H...

Yu, Hsuan-Fu

1989-01-01

313

Calotropis procera mediated combustion synthesis of ZnAl2O4:Cr(3+) nanophosphors: structural and luminescence studies.  

PubMed

ZnAl2O4:Cr(3+) nanophosphors were synthesized for the first time by a simple and environment friendly route using Calotropis procera milk latex as fuel. The structural and surface morphological studies were carried out using powder X-ray diffraction (PXRD), scanning electron microscopy and transmission electron microscopy techniques. The photoluminescence (PL) properties of ZnAl2O4:Cr(3+) as a function of dopant concentration and calcination temperature was studied in detail. The PXRD patterns and Rietveld confinement confirmed the cubic crystal system with space group Fd-3m. The crystallite size estimated from Scherrer's and W-H plots was found to be in the range of 16-26 nm. The PL spectrum shows an intense peak at ?688 and ?699 nm assigned to spin-forbidden (2)Eg?(4)A2g transition of Cr(3+) ions. The PL measurements for two excitations (?410 and 527 nm) and with respect to calcination temperature indicated no significant change in the shape and position of emission peak except PL intensity. The CIE chromaticity coordinates lies well within the white region. Thermoluminescence (TL) studies revealed well resolved glow peak at ?212°C with a small shoulder at 188 and 233°C. The glow peak intensity at ?212°C increases linearly with ?-dose which suggest ZnAl2O4:Cr(3+) is suitable candidate for radiation dosimetric applications. The activation energy (E in eV), order of kinetics (b) and Frequency factor (s) were estimated using glow peak shape method. PMID:25459629

Ravikumar, B S; Nagabhushana, H; Sharma, S C; Vidya, Y S; Anantharaju, K S

2015-02-01

314

Calotropis procera mediated combustion synthesis of ZnAl2O4:Cr3+ nanophosphors: Structural and luminescence studies  

NASA Astrophysics Data System (ADS)

ZnAl2O4:Cr3+ nanophosphors were synthesized for the first time by a simple and environment friendly route using Calotropis procera milk latex as fuel. The structural and surface morphological studies were carried out using powder X-ray diffraction (PXRD), scanning electron microscopy and transmission electron microscopy techniques. The photoluminescence (PL) properties of ZnAl2O4:Cr3+ as a function of dopant concentration and calcination temperature was studied in detail. The PXRD patterns and Rietveld confinement confirmed the cubic crystal system with space group Fd-3m. The crystallite size estimated from Scherrer's and W-H plots was found to be in the range of 16-26 nm. The PL spectrum shows an intense peak at ?688 and ?699 nm assigned to spin - forbidden 2Eg ? 4A2g transition of Cr3+ ions. The PL measurements for two excitations (?410 and 527 nm) and with respect to calcination temperature indicated no significant change in the shape and position of emission peak except PL intensity. The CIE chromaticity coordinates lies well within the white region. Thermoluminescence (TL) studies revealed well resolved glow peak at ?212 °C with a small shoulder at 188 and 233 °C. The glow peak intensity at ?212 °C increases linearly with ?-dose which suggest ZnAl2O4:Cr3+ is suitable candidate for radiation dosimetric applications. The activation energy (E in eV), order of kinetics (b) and Frequency factor (s) were estimated using glow peak shape method.

Ravikumar, B. S.; Nagabhushana, H.; Sharma, S. C.; Vidya, Y. S.; Anantharaju, K. S.

2015-02-01

315

Transgalactosylation and hydrolytic activities of commercial preparations of ?-galactosidase for the synthesis of prebiotic carbohydrates.  

PubMed

?-Galactosidases exhibit both hydrolytic and transgalactosylation activities; the former has been used traditionally for the production of delactosed milk and dairies, while the latter is being increasingly used for the synthesis of lactose-derived oligosaccharides: balance between both activities was highly dependent on the enzyme origin: ?-galactosidases from Aspegillus oryzae and Bacillus circulans exhibited high transgalactosylation activity, while those from one from Kluyveromyces exhibited high hydrolytic activity but quite low transgalactosylation activity. Also the affinity for the donors (lactose or lactulose) and the acceptors (lactose, lactulose or fructose) of transgalactosylated galactose was dependent on the enzyme origin, as reflected by the Michaelis constants obtained in the synthesis of galacto-oligosaccharides, fructosyl-galacto-oligosaccharides and lactulose. Finally, the balance between transgalactosylation and hydrolytic activities of ?-galactosidases could be tuned by changing the concentration of galactose donor. PMID:25659627

Guerrero, Cecilia; Vera, Carlos; Conejeros, Raúl; Illanes, Andrés

2015-03-01

316

Cooperative upconversion luminescence in Tb{sup 3+}:Yb{sup 3+} co-doped Y{sub 2}SiO{sub 5} powders prepared by combustion synthesis  

SciTech Connect

Frequency upconversion (UC) luminescence via cooperative energy transfer (CET) process between pairs of Yb{sup 3+} and Tb{sup 3+} ions was investigated in Tb{sup 3+}:Yb{sup 3+}:Y{sub 2}SiO{sub 5} crystalline ceramic powders prepared by combustion synthesis. Surface morphology and structure of the powders were investigated by scanning electronic microscopy and X-ray powder diffraction. Photoluminescence experiments were performed in Tb{sup 3+}-singly doped samples using ultraviolet light (?=255 nm) and in Tb{sup 3+}:Yb{sup 3+} co-doped samples using a near-infrared (NIR) diode laser (?=975 nm). Upon excitation with the NIR diode laser, UC luminescence with an intense emission band centered at ?549 nm, corresponding to the 4f intraband {sup 5}D{sub 4}?{sup 7}F{sub 5} transition of Tb{sup 3+}, along with less intense emission bands at ?490, ?590 and ?620 nm, corresponding to other {sup 5}D{sub 4}?{sup 7}F{sub J} transitions, was detected. The CET rate was estimated by analyzing the dynamics of UC luminescence with rate equations model of the electronic populations. -- Graphical Abstract: Left: Cooperative upconversion luminescence spectra of three powder samples prepared by combustion synthesis. Right: The SEM image of the powder showing that it consists of agglomerated flake-like shaped particles of various sizes. Full scale bar is 20 ?m. Highlights: • Yttrium orthosilicate (Y{sub 2}SiO{sub 5}) powders were prepared by combustion synthesis. • Cooperative upconversion is observed for the first time in Tb{sup 3+}–Yb{sup 3+} doped Y{sub 2}SiO{sub 5}. • Energy transfer and back-transfer rates between Tb{sup 3+} and Yb{sup 3+} pairs were estimated.

Rakov, Nikifor, E-mail: nikifor.gomez@univasf.edu.br [PG - Ciência dos Materiais, Universidade Federal do Vale do São Francisco, 48902-300 Juazeiro, BA (Brazil); Vieira, Simone A. [PG - Ciência dos Materiais, Universidade Federal do Vale do São Francisco, 48902-300 Juazeiro, BA (Brazil); Guimarães, Renato B. [Instituto de Física, Universidade Federal Fluminense, 24210-346 Niterói, RJ (Brazil); Maciel, Glauco S., E-mail: glauco@if.uff.br [Instituto de Física, Universidade Federal Fluminense, 24210-346 Niterói, RJ (Brazil)

2014-03-15

317

Synthesis and Structure-Activity Relationship Studies of Furan-ring Fused Chalcones as Antiproliferative Agents.  

PubMed

As part of our continuing investigation of flavonoid derivatives as potential anticancer substances, the synthesis of 25 cinnamoyl derivatives of benzofuran as furan-fused chalcones was carried-out and these compounds were further evaluated for their antiproliferative activity towards HL60 promyelocytic leukemia cells. In comparison with 2',4'-dihydroxychalcone, attachment of a furan moiety on the A-ring enhanced activity by more than twofold. Benzofurans may be useful in the design of biologically active flavonoids. PMID:25667461

Saito, Yusuke; Kishimoto, Maho; Yoshizawa, Yuko; Kawaii, Satoru

2015-02-01

318

Synthesis and antibacterial property of quinolines with potent DNA gyrase activity.  

PubMed

Synthesis of a series of novel tetrahydroquinoline annulated heterocycles has been accomplished by intramolecular imino and bisimino Diels-Alder reaction. These compounds were evaluated for their antibacterial activity. All the synthetic compounds, exhibited good antibacterial activity against microorganisms of which one of them 7 was found to be as active as the antibiotic ciplofloxacin and is found to have MIC value of 2.5 mg/mL against Escherichia coli. PMID:19097914

Ramesh, Ekambaram; Manian, Rathna Durga R S; Raghunathan, Ragavachary; Sainath, Shilpakala; Raghunathan, Malathi

2009-01-15

319

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

320

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

321

Synthesis, antioxidant and radical scavenging activities of novel benzimidazoles.  

PubMed

The synthesis and antioxidant evaluation of some novel benzimidazole derivatives (10-24) are described. Antioxidant properties of the compounds were investigated employing various in vitro systems viz., microsomal NADPH-dependent inhibition of lipid peroxidation (LP), interaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and scavenging of superoxide anion radical. Compounds 12 and 13 showed very good antioxidant capacity and were 17-18-fold more potent than BHT (IC50 2.3 x 10(-4) M) with 1.3 x 10(-5) M and 1.2 x 10(-5) M IC50 values, respectively, by interaction of the stable DPPH free radical. PMID:16335060

Ayhan-Kilcigil, Gülgün; Ku?, Canan; Coban, Tülay; Can-Eke, Benay; Ozbey, Süheyla; Iscan, Mümtaz

2005-10-01

322

Biologically Active Chorionic Gonadotropin: Synthesis by the Human Fetus  

NASA Astrophysics Data System (ADS)

The kidney, and to a slight extent the liver, of human fetuses were found to synthesize and secrete the ? subunit common to glycoprotein hormones. Fetal lung and muscle did not synthesize this protein. Since fetal kidney and liver were previously found to synthesize ? chorionic gonadotropin, their ability to synthesize bioactive chorionic gonadotropin was also determined. The newly synthesized hormone bound to mouse Leydig cells and elicited a biological response: namely, the synthesis of testosterone. These results suggest that the human fetus may participate in metabolic homeostasis during its development.

McGregor, W. G.; Kuhn, R. W.; Jaffe, R. B.

1983-04-01

323

Activation of protein kinase C inhibits synthesis and release of decidual prolactin  

SciTech Connect

Activation of calcium-activated, phospholipid-dependent protein kinase C by diacylglycerol and phorbol esters has been shown to mediate release of hormones in many systems. To determine whether protein kinase C activation is also involved in the regulation of prolactin release from human decidual, the authors have examined the effects of various acylglycerols and phorbol esters on the synthesis and release of prolactin from cultured human decidual cells. sn-1,2-Dioctanolyglycerol (diC8), which is known to stimulate protein kinase C in other systems, inhibited prolactin release in a dose-dependent manner with maximal inhibition of 53.1% at 100 M. Diolein (100 M), which also stimulates protein kinase C activity in some systems, inhibited prolactin release by 21.3%. Phorbol 12-myristate 13-acetate (PMA), phorbol 12,13-didecanoate, and 4US -phorbol 12,13-dibutyrate, which activate protein kinase C in other systems, also inhibited the release of prolactin, which the protein kinase C inactivate 4 -phorbol-12,13-didecanoate was without effect. The inhibition of prolactin release was secondary to a decrease in prolactin synthesis. Although diC8 and PMA inhibited the synthesis and release of prolactin, these agents had no effect on the synthesis or release of trichloroacetic acid-precipitable (TVS)methionine-labeled decidual proteins and did not cause the release of the cytosolic enzymes lactic dehydrogenase and alkaline phosphatase. DiC8 and PMA stimulates the specific activity of protein kinase C in decidual tissue by 14.6 and 14.0-fold, respectively. The inhibition of the synthesis and release of prolactin by diC8 and phorbol esters strongly implicates protein kinase C in the regulation of the production and release of prolactin from the decidua.

Harman, I.; Costello, A.; Ganong, B.; Bell, R.M.; Handwerger, S.

1986-08-01

324

Correlation of guanosine triphosphate cyclohydrolase activity and the synthesis of pterins in Drosophila melanogaster  

Microsoft Academic Search

The enzyme guanosine triphosphate cyclohydrolase (GTP cyclohydrolase), which in bacteria is known to be the first enzyme in the biosynthetic pathway for the synthesis of pteridines, has been discovered in extracts of Drosophila melanogaster. Most of the enzyme (80%) is located in the head of the adult fly. An analysis of enzyme activity during development in Drosophila has revealed the

C. L. Fan; L. M. Hall; A. J. Skrinska; G. M. Brown

1976-01-01

325

Synthesis and biological activity of medium range molecular weight polymers containing  

E-print Network

Synthesis and biological activity of medium range molecular weight polymers containing exo-3®ed by FTIR, 1 H NMR and 13 C NMR spectroscopies. The apparent average molecular weights and polydispersity acid (ETCA); medium molecular weight; photopolymerization; in vitro cytotoxicity; in vivo antitumour

Theodorakis, Emmanuel

326

Synthesis and activity of 2-oxoamides containing long chain ?-amino acids  

Microsoft Academic Search

Oxoamides based on long chain ?-amino acids were synthesized. 1-Benzyl substituted long chain amines, needed for such synthesis, were synthesized starting from Boc-phenylalaninol. The oxidative conversion of a phenyl group to a carboxyl group was used as the key transformation synthetic step. The compounds synthesized were studied for their activity against GIVA PLA2, and were proven to be weak inhibitors.

Violetta Constantinou-Kokotou; Anna Peristeraki; Christoforos G. Kokotos; David A. Six; EDWARD A. DENNISb

2005-01-01

327

One-Pot Synthesis of Protein-Embedded Metal-Organic Frameworks with Enhanced Biological Activities  

E-print Network

One-Pot Synthesis of Protein-Embedded Metal-Organic Frameworks with Enhanced Biological Activities Information ABSTRACT: Protein molecules were directly embedded in metal-organic frameworks (MOFs) by a coprecipitation method. The protein molecules majorly embedded on the surface region of MOFs display high

Zare, Richard N.

328

Recyclable synthesis, characterization, and antimicrobial activity of chitosan-based polysaccharide composite materials  

E-print Network

Recyclable synthesis, characterization, and antimicrobial activity of chitosan-based polysaccharide.1002/jbm.a.34520 Abstract: We have successfully developed a simple and totally recyclable method, and recov- ered by distilling the washed solution, the method is totally recyclable. Spectroscopic

Reid, Scott A.

329

Pyrazinoic Acid Decreases the Proton Motive Force, Respiratory ATP Synthesis Activity, and Cellular ATP Levels?†  

PubMed Central

Pyrazinoic acid, the active form of the first-line antituberculosis drug pyrazinamide, decreased the proton motive force and respiratory ATP synthesis rates in subcellular mycobacterial membrane assays. Pyrazinoic acid also significantly lowered cellular ATP levels in Mycobacterium bovis BCG. These results indicate that the predominant mechanism of killing by this drug may operate by depletion of cellular ATP reserves. PMID:21876062

Lu, Ping; Haagsma, Anna C.; Pham, Hoang; Maaskant, Janneke J.; Mol, Selena; Lill, Holger; Bald, Dirk

2011-01-01

330

Synthesis and insecticidal activity of chromanone and chromone analogues of diacylhydrazines  

Microsoft Academic Search

Diacylhydrazine derivatives have been identified as one of the most important insect growth regulators. A variety of diacylhydrazine derivatives were designed and synthesized in recent years due to their unique action mechanism, simple structure, and environmental benign character. This paper describes the molecular design, synthesis, and insecticidal activities of a series of chromanone and chromone analogues of diacylhydrazine derivatives. The

Pei-Liang Zhao; Jing Li; Guang-Fu Yang

2007-01-01

331

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

332

Ionic liquid self-combustion synthesis of BiOBr/Bi24O31Br10 heterojunctions with exceptional visible-light photocatalytic performances.  

PubMed

Heterostructured BiOBr/Bi24O31Br10 nanocomposites with surface oxygen vacancies are constructed by a facile in situ route of one-step self-combustion of ionic liquids. The compositions can be easily controlled by simply adjusting the fuel ratio of urea and 2-bromoethylamine hydrobromide (BTH). BTH serves not only as a fuel, but also as a complexing agent for ionic liquids and a reactant to supply the Br element. The heterojunctions show remarkable adsorptive ability for both the cationic dye of rhodamine B (RhB) and the anionic dye of methylene orange (MO) at high concentrations, which is attributed to the abundant surface oxygen vacancies. The sample containing 75.2% BiOBr and 24.8% Bi24O31Br10 exhibits the highest photocatalytic activity. Its reaction rate constant is 4.0 and 9.0 times that of pure BiOBr in degrading 50 mg L(-1) of RhB and 30 mg L(-1) of MO under visible-light (? > 400 nm) irradiation, respectively, which is attributed to the narrow band gap and highly efficient transfer efficiency of charge carriers. Different photocatalytic reaction processes and mechanisms over pure BiOBr and heterojunctions are proposed. PMID:25482071

Li, Fa-tang; Wang, Qing; Ran, Jingrun; Hao, Ying-juan; Wang, Xiao-jing; Zhao, Dishun; Qiao, Shi Zhang

2015-01-21

333

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

334

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

335

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

336

Intracellular synthesis of silver nanoparticle by actinobacteria and its antimicrobial activity  

NASA Astrophysics Data System (ADS)

Intracellular synthesis of silver nanoparticles (AgNPs) using Rhodococcus spp. is demonstrated. The synthesized nanoparticles were characterized by UV-Vis spectroscopy, X-ray diffraction, energy dispersive spectroscopy, Fourier trans-form infrared spectroscopy, and transmission electron microscopy. Transmission electron microscopy study of microorganisms' revealed synthesis of nanoparticle was occurring inside the cell, in the cytoplasm. AgNPs ranged from 5 to 50 nm. Formed nanoparticles were stable in the colloidal solution due to presence of proteins on the surface. AgNPs showed excellent bactericidal and bacteriostatic activity against pathogenic microorganisms.

Otari, S. V.; Patil, R. M.; Ghosh, S. J.; Thorat, N. D.; Pawar, S. H.

2015-02-01

337

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

2015-03-01

338

Combustion & Health  

E-print Network

) ? Combustion of fossil fuels for ? Electricity ? Industrial processes ? Vehicle propulsion ? Cooking and heat ? Other ? Munitions ? Fireworks ? Light ? Cigarettes, hookahs? FFCOMBUSTION & HEALTH FFCOMBUSTION: THE THREAT ? SCALE (think health... for public health and strategies to reduce GHG ? Reduce CO2 emissions by 50% by 2030 ? Reduction in PM2.5 deaths greatly offset costs in all models FFCOMBUSTION & HEALTH FFCOMBUSTION: PM EXPOSURE ? Combustion is source of most concern ? Health...

Hamilton, W.

2012-01-01

339

DNA gyrase (GyrB)\\/topoisomerase IV (ParE) inhibitors: Synthesis and antibacterial activity  

Microsoft Academic Search

The synthesis and antibacterial activities of three chemotypes of DNA supercoiling inhibitors based on imidazolo[1,2-a]pyridine and [1,2,4]triazolo[1,5-a]pyridine scaffolds that target the ATPase subunits of DNA gyrase and topoisomerase IV (GyrB\\/ParE) is reported. The most potent scaffold was selected for optimization leading to a series with potent Gram-positive antibacterial activity and a low resistance frequency.

Stephen P. East; Clara Bantry White; Oliver Barker; Stephanie Barker; James Bennett; David Brown; E. Andrew Boyd; Christopher Brennan; Chandana Chowdhury; Ian Collins; Emmanuelle Convers-Reignier; Brian W. Dymock; Rowena Fletcher; David J. Haydon; Mihaly Gardiner; Stuart Hatcher; Peter Ingram; Paul Lancett; Paul Mortenson; Konstantinos Papadopoulos; Carol Smee; Helena B. Thomaides-Brears; Heather Tye; James Workman; Lloyd G. Czaplewski

2009-01-01

340

Synthesis of novel substituted 1,3-diaryl propenone derivatives and their antimalarial activity in vitro  

Microsoft Academic Search

The synthesis of novel 1,3-diaryl propenone derivatives and their antimalarial activity in vitro against asexual blood stages of human malaria parasite, Plasmodium falciparum, are described. Chalcone derivatives were prepared via Claisen–Schmidt condensation of substituted aldehydes with substituted methyl ketones. Antiplasmodial IC50 (half maximal inhibitory concentration) activity of these compounds ranged between 1.5 and 12.3?g\\/ml. The chloro-series, 1,2,4-triazole substituted chalcone was

Nidhi Mishra; Preeti Arora; Brajesh Kumar; Lokesh C. Mishra; Amit Bhattacharya; Satish K. Awasthi; Virendra K. Bhasin

2008-01-01

341

Effect of ruthenium precursor on hydrogen-treated active carbon supported ruthenium catalysts for ammonia synthesis  

Microsoft Academic Search

Active carbon (A.C.), after treatment at 1123 K with hydrogen for more than 24 h, was found to be very effective as a support for ruthenium catalysis in ammonia synthesis. The activity of barium promoted Ru catalysts supported on this treated A.C. is affected remarkably by the Ru precursor. Ru3(CO)12 was found previously to be the most effective Ru precursor

Zhi-hua Zhong; Ken-ichi Aika

1998-01-01

342

Plant oligoadenylates: enzymatic synthesis, isolation, and biological activities  

SciTech Connect

An enzyme that converts (/sup 3/H, /sup 32/P)ATP, with a /sup 3/H:/sup 32/P ratio of 1:1, to oligoadenylates with the same /sup 3/H:/sup 32/P 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 /sup 3/H:/sup 32/P 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.

Devash, Y.; Reichman, M.; Sela, I.; Reichenbach, N.L.; Suhadolnik, R.J.

1985-01-29

343

Aziridinyldinitrobenzamides: synthesis and structure-activity relationships for activation by E. coli nitroreductase.  

PubMed

The 5-aziridinyl-2,4-dinitrobenzamide CB 1954 is a substrate for the oxygen-insensitive nitroreductase (NTR) from E. coli and is in clinical trial in combination with NTR-armed adenoviral vectors in a GDEPT protocol; CB 1954 is also of interest for selective deletion of NTR-marked cells in normal tissues. Since little further drug development has been carried out around this lead, we report here the synthesis of more soluble variants and regioisomers and structure-activity relationship (SAR) studies. The compounds were primarily prepared from the corresponding chloro(di)nitroacids through amide side chain elaboration and subsequent aziridine formation. One-electron reduction potentials [E(1)], determined by pulse radiolysis, were around -400 mV, varying little for aziridinyldinitrobenzamide regioisomers. Cytotoxicity in a panel of NTR-transfected cell lines showed that in the CB 1954 series there was considerable tolerance of substituted CONHR side chains. The isomeric 2-aziridinyl-3,5-dinitrobenzamide was also selective toward NTR+ve lines but was approximately 10-fold less potent than CB 1954. Other regioisomers were too insoluble to evaluate. While CB 1954 gave both 2- and 4-hydroxylamine metabolites in NTR+ve cells, related analogues with substituted carboxamides gave only a single hydroxylamine metabolite possibly because the steric bulk in the side chain constrains binding within the active site. CB 1954 is also a substrate for the two-electron reductase DT-diaphorase, but all of the other aziridines (regioisomers and close analogues) were poorer substrates with resulting improved specificity for NTR. Bystander effects were determined in multicellular layer cocultures and showed that the more hydrophilic side chains resulted in a modest reduction in bystander killing efficiency. A limited number of analogues were tested for in vivo activity, using a single ip dose to CD-1 nude mice bearing WiDr-NTR(neo) tumors. The most active of the CB 1954 analogues was a diol derivative, which showed a substantial median tumor growth delay (59 days compared with >85 days for CB 1954) in WiDr xenografts comprising 50% NTR+ve cells. The diol is much more soluble and can be formulated in saline for administration. The results suggest there may be advantages with carefully selected analogues of CB 1954; the weaker bystander effect of its diol derivative may be an advantage in the selective cell ablation of NTR-tagged cells in normal tissues. PMID:15163209

Helsby, Nuala A; Atwell, Graham J; Yang, Shangjin; Palmer, Brian D; Anderson, Robert F; Pullen, Susan M; Ferry, Dianne M; Hogg, Alison; Wilson, William R; Denny, William A

2004-06-01

344

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. PMID:23390579

Li, Wei; Cochell, Thomas; Manthiram, Arumugam

2013-01-01

345

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

346

Design, synthesis, and preliminary activity evaluation of novel pyrimidine derivatives as Acid pump antagonists.  

PubMed

Acid-related diseases of the upper gastrointestinal tract, especially gastroesophageal reflux disease (GERD), remain a widespread problem worldwide. In this paper, we reported the design, synthesis, and preliminary gastric antisecretory activity evaluation of novel pyrimidine derivatives as acid pump antagonists. The gastric antisecretory activity assay results showed that all compounds displayed potent gastric antisecretory activity when gastric secretion was stimulated by histamine. The most potent compound 5g exhibited even similar gastric antisecretory activity compared with the control revaprazan, and the relative inhibition rate was 93.0%, which was worthy of further investigation. PMID:24995399

Song, Weiguo; Zhang, Xiaopan; Li, Shutao; Xu, Wenfang

2015-03-01

347

Synthesis, antifungal activity, and QSAR study of novel trichodermin derivatives.  

PubMed

In an attempt to discover more potential antifungal agents, in this study, 21 novel trichodermin derivatives containing conjugated oxime ester (5a-5u) were designed and synthesized and were screened for in vitro antifungal activity. The bioassay tests showed that some of them exhibited good inhibitory activity against the tested pathogenic fungi. Compound 5a exhibited better activity against Pyricularia oryzae and Sclerotonia sclerotiorum than trichodermin, and compound 5j showed particular activity against P.oryzae and Botrytis cinerea. The quantitative structure-activity relationship (QSAR) indicated that log P and hardness were two critical parameters for the biological activities. The result suggested that these would be potential lead compounds for the development of fungicides with further structure modification. PMID:25290081

Cheng, Jing-Li; Zheng, Min; Yao, Ting-Ting; Li, Xiao-Liang; Zhao, Jin-Hao; Xia, Min; Zhu, Guo-Nian

2015-01-01

348

Synthesis of indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) nano-powder by sol–gel combustion hybrid method  

Microsoft Academic Search

ITO and FTO nano-powders were synthesized employing a new route sol–gel combustion hybrid method using acetylene black as a fuel. The dried gels exhibited an auto-catalytic combustion behavior. ITO and FTO nano-powders with narrow size distribution were obtained at 750 °C. Crystal structures were examined by powder X-ray diffraction (XRD) and particle morphology as well as crystal size was investigated by

Chi-Hwan Han; Sang-Do Han; Jihye Gwak; S. P. Khatkar

2007-01-01

349

Peroxidase synthesis and activity in the interaction of soybean with Phytophthora megasperma f. sp. glycinea (Pmg)  

SciTech Connect

Changes, in peroxidase (EC1.11.1.7) have been reported following infection. However, determinations of biosynthesis of quantities of the peroxidase protein molecule have not been madeexclamation In this study hypocotyl of soybean seedlings (Glycine max; cv Harosoy, susceptible; cv Harosoy 63, resistant) were inoculated with zoospores of Pmg. Incorporation of /sup 35/S-methionine (supplied with inoculum) in TCA precipitates was measured. Peroxidase synthesis was measured by immuno precipitation using antibodies against a cationic and an anionic peroxidase derived from peanut cells. Specific peroxidase activity increased rapidly from 5 to 9 h following infection in the resistant reaction but not in the susceptible reaction or the water controls. There was increased synthesis of the anionic peroxidase but not of the cationic peroxidase in the resistant reaction. The anionic peroxidase did not increase in the susceptible until 15 h. The ratio of peroxidase synthesis to total protein synthesis decreased in inoculated tissues compared to control. Peroxidase synthesis is, therefore, a relative minor host response to infection.

Chibbar, R.N.; Esnault, R.; Lee, D.; van Huystee, R.B.; Ward, E.W.B.

1986-04-01

350

Activity-dependent rapid local RhoA synthesis is required for hippocampal synaptic plasticity.  

PubMed

Dendritic protein synthesis and actin cytoskeleton reorganization are important events required for the consolidation of hippocampal LTP and memory. However, the temporal and spatial relationships between these two processes remain unclear. Here, we report that treatment of adult rat hippocampal slices with BDNF or with tetraethylammonium (TEA), which induces a chemical form of LTP, produces a rapid and transient increase in RhoA protein levels. Changes in RhoA were restricted to dendritic spines of CA3 and CA1 and require de novo protein synthesis regulated by mammalian target of rapamycin (mTOR). BDNF-mediated stimulation of RhoA activity, cofilin phosphorylation, and actin polymerization were completely suppressed by protein synthesis inhibitors. Furthermore, intrahippocampal injections of RhoA antisense oligodeoxynucleotides inhibited theta burst stimulation (TBS)-induced RhoA upregulation in dendritic spines and prevented LTP consolidation. Addition of calpain inhibitors after BDNF or TEA treatment maintained RhoA levels elevated and prolonged the effects of BDNF and TEA on actin polymerization. Finally, the use of isoform-selective calpain inhibitors revealed that calpain-2 was involved in RhoA synthesis, whereas calpain-1 mediated RhoA degradation. Overall, this mechanism provides a novel link between dendritic protein synthesis and reorganization of the actin cytoskeleton in hippocampal dendritic spines during LTP consolidation. PMID:25653381

Briz, Victor; Zhu, Guoqi; Wang, Yubin; Liu, Yan; Avetisyan, Mariam; Bi, Xiaoning; Baudry, Michel

2015-02-01

351

Synthesis and antiviral activity of certain second generation methylenecyclopropane nucleosides  

PubMed Central

A second-generation series of substituted methylenecyclopropane nucleosides (MCPNs) has been synthesized and evaluated for antiviral activity against a panel of human herpesviruses, and for cytotoxicity. Although alkylated 2,6-diaminopurine analogs showed little antiviral activity, the compounds containing ether and thioether substituents at the 6-position of the purine did demonstrate potent and selective antiviral activity against several different human herpesviruses. In the 6-alkoxy series, antiviral activity depended on the length of the ether carbon chain, with the optimum chain length being about four carbon units long. For the corresponding thioethers, compounds containing secondary thioethers were more potent than those with primary thioethers. PMID:22607883

Williams, John D.; Khan, Atiyya R.; Harden, Emma A.; Hartline, Caroll B.; Jefferson, Geraldine M.; Keith, Kathy A.; Prichard, Mark N.; Zemlicka, Jiri; Peet, Norton P.; Bowlin, Terry L.

2012-01-01

352

Stimulation of phosphatidylcholine synthesis by activators of protein kinase C is dissociable from increased phospholipid hydrolysis.  

PubMed Central

The aim of this study was to clarify the relationship between the stimulatory effects of protein kinase C activators, including phorbol 12-myristate 13-acetate (PMA) and bryostatin, on the hydrolysis of phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn) and on PtdCho synthesis. The cell lines used were selected because of their differential responses to protein kinase C activators and included rat-1 fibroblasts, untransformed and A-raf-transformed NIH 3T3 fibroblasts and human HL60 leukaemia cells. Exposure of rat-1 and NIH 3T3 fibroblasts to 100 nM-PMA stimulated phospholipase D-mediated hydrolysis of phospholipids about 2- and 6-fold respectively. In contrast, 100 nM-PMA had similar (2.5-3.0-fold) stimulatory effects on PtdCho synthesis in these cell lines. In the untransformed NIH 3T3 cells, both PMA and bryostatin stimulated both phospholipid hydrolysis and PtdCho synthesis, with 100 nM-bryostatin being somewhat less potent than 100 nM-TPA. In contrast, in A-raf-transformed NIH 3T3 cells or in HL60 cells, only TPA, but not bryostatin, stimulated PtdCho synthesis. In these transformed cells, bryostatin had 3-fold, or higher, stimulatory effects on phospholipid hydrolysis. Addition of ionomycin, a Ca2(+)-elevating agent, partially restored the stimulatory effect of bryostatin on PtdCho synthesis, but it failed to modify the effect of bryostatin on phospholipid hydrolysis. These data indicate that increased phospholipid hydrolysis is not necessarily associated with increased PtdCho synthesis. PMID:1989580

Kiss, Z; Chattopadhyay, J; Pettit, G R

1991-01-01

353

Activation and inhibition of ATP synthesis in cell envelope vesicles of Halobacterium halobium.  

PubMed

The characteristics of ATP synthesis in cell envelope vesicles of Halobacterium halobium were further studied. The results confirmed the previous conclusion (Mukohata et al. (1986) J. Biochem. 99, 1-8) that the ATP synthase in this extremely halophilic archaebacterium can not be an ordinary type of F0F1-ATPase, which has been thought to be ubiquitous among all the aerobic organisms on our biosphere. The ATP synthesis was activated most in 1 M NaCl and/or KCl, and at 40 degrees C, and at 80 mM MgCl2 where F0F1-ATPase loses its activity completely. The synthesis was negligible at 10 degrees C, and at 5 mM MgCl2. The Km for ADP was about 0.3 mM in the presence of 20 mM Pi, 1 M NaCl, 80 mM MgCl2, and 10 mM PIPES at pH 6.8 and 20 degrees C. The ATP synthesis was not inhibited by NaN3 and quercetin (specific inhibitors for F0F1-ATPase) or vanadate (for E1E2-ATPase) or ouabain (for Na+,K+-ATPase) or P1,P5-di(adenosine-5')pentaphosphate (AP5A, for adenylate kinase). The ATP synthesis was not inhibited by modification (pretreatment) with NaN3 or 5'-p-fluorosulfonylbenzoyladenosine (FSBA). On the contrary, the ATP synthesis was rather non-specifically inhibited by N-ethylmaleimide (NEM), trinitrobenzenesulfonate (TNBS), phenylglyoxal, and pyridoxal phosphate. 7-Chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl) as well as N,N'-dicyclohexylcarbodiimide (DCCD) was found to be a specific inhibitor at least partly, because the NBD-Cl inhibition was partly prevented by ADP added to the modification mixture. PMID:3584088

Mukohata, Y; Yoshida, M

1987-02-01

354

Studies in combustion dynamics  

SciTech Connect

The goal of this program is to develop a fundamental understanding and a quantitative predictive capability in combustion modeling. A large part of the understanding of the chemistry of combustion processes comes from {open_quotes}chemical kinetic modeling.{close_quotes} However, successful modeling is not an isolated activity. It necessarily involves the integration of methods and results from several diverse disciplines and activities including theoretical chemistry, elementary reaction kinetics, fluid mechanics and computational science. Recently the authors have developed and utilized new tools for parallel processing to implement the first numerical model of a turbulent diffusion flame including a {open_quotes}full{close_quotes} chemical mechanism.

Koszykowski, M.L. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01

355

Combustion 2000  

SciTech Connect

This report presents work carried out under contract DE-AC22-95PC95144 ''Combustion 2000 - Phase II.'' The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: {lg_bullet} thermal efficiency (HHV) {ge} 47% {lg_bullet} NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard) {lg_bullet} coal providing {ge} 65% of heat input {lg_bullet} all solid wastes benign {lg_bullet} cost of electricity {le} 90% of present plants Phase I, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase I also included preliminary R&D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. Phase II, had as its initial objective the development of a complete design base for the construction and operation of a HIPPS prototype plant to be constructed in Phase III. As part of a descoping initiative, the Phase III program has been eliminated and work related to the commercial plant design has been ended. The rescoped program retained a program of engineering research and development focusing on high temperature heat exchangers, e.g. HITAF development (Task 2); a rescoped Task 6 that is pertinent to Vision 21 objectives and focuses on advanced cycle analysis and optimization, integration of gas turbines into complex cycles, and repowering designs; and preparation of the Phase II Technical Report (Task 8). This rescoped program deleted all subsystem testing (Tasks 3, 4, and 5) and the development of a site specific engineering design and test plan for the HIPPS prototype plant (Task 7). Work reported herein is from: {lg_bullet} Task 2.2.4 Pilot Scale Testing {lg_bullet} Task 2.2.5.2 Laboratory and Bench Scale Activities

None

2000-06-30

356

Synthesis and characterization of inorganic polymers from the alkali activation of an aluminosilicate  

NASA Astrophysics Data System (ADS)

This paper presents the results of the synthesis and characterization of inorganic polymers (IP) from aluminosilicates: bentonite (BT) and pumice (PP). The synthesis of IP, was carried out by two methods involving alkaline activation, at room temperature and 80 ± 5 °C, using as activating agent sodium silicate both commercial and analytical (Na2SiO3). Sodium hydroxide (NaOH) at 3 M, 7 M and 12 M was added. A lower degree of polymerization was obtained by using analytical precursors subjected to room temperature and 80 ± 5°C. Replacement of heating by the use of the commercial activating agent with greater alkalinity allows the formation of a 3D network. The materials were structurally characterized by FTIR spectroscopy with Attenuated Reflectance (ATR), Scanning Electron Microscope (SEM) and X -ray diffraction (DRX).

González, C. P.; Montaño, A. M.; González, A. K.; Ríos, C. A.

2014-06-01

357

Ovicidal activity of chitin synthesis inhibitors when fed to adult German cockroaches (Dictyoptera: Blattellidae).  

PubMed

Ovicidal activity was observed in four adult groups (virgin males; virgin females; newly gravid females; and inseminated, reproducing females) of the German cockroach, Blattella germanica (L.), fed the chitin synthesis inhibitors triflumuron, chlorfluazuron, hexafluron, and UC 84572 (structure not disclosed) at the LC50's and LC95's determined from fifth-stage nymphs. All compounds were active only when fed to reproducing females (including the feeding period in which the ootheca is developing). Hexafluron and triflumuron at the LC50 caused 100% inhibition of hatch in reproducing females. Chlorfluazuron and UC 84572 at the LC50 had similar ovicidal activity (45.8 and 50.0% hatch, respectively). Female German cockroaches fed the chitin synthesis inhibitors before mating and after the ootheca had protruded from the abdomen were not affected. Reproductive capabilities of males were not affected, and males did not effectively transfer the compounds to untreated females during mating. PMID:2388230

DeMark, J J; Bennett, G W

1990-07-01

358

Study Abroad Learning Activities: A Synthesis and Comparison  

Microsoft Academic Search

Learning activities are described for study abroad tours with appropriateness discussed in terms of study tour characteristics of location, integration with academic credit, and time spent on the tour. Journal writing is the most versatile activity. Company visits are the most impressive to students. Simulations engage students but require computer technology. Projects require sufficient research resources. Lecture\\/testing and treasure hunts

Charles R. Duke

2000-01-01

359

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. PMID:21804865

Brulikova, Lucie

2011-01-01

360

Design, synthesis and cytotoxic activity evaluation of new aminosubstituted benzofurans.  

PubMed

A number of new aminosubstituted benzofuran analogues have been prepared and their cytotoxic/cytostatic activity was investigated against five human tumor cell lines (MCF-7, SKBR3, SKOV3, HCT-116 and HeLa). Certain compounds showed noticeable tumor cell growth inhibition, indicative of possible structure-activity relationships. PMID:24047215

Daniilides, Konstantinos; Lougiakis, Nikolaos; Pouli, Nicole; Marakos, Panagiotis; Samara, Pinelopi; Tsitsilonis, Ourania

2014-01-01

361

Synthesis, antiproliferative and antibacterial activity of new amides of salinomycin.  

PubMed

A series of 11 novel amides of salinomycin were synthesized for the first time. All the obtained compounds were found to show potent antiproliferative activity against human cancer cell lines including the drug-resistant cancer cells. Four new salinomycin derivatives revealed good antibacterial activity against clinical isolates of methicillin-resistant Staphylococcus epidermidis (MRSE). PMID:24631190

Antoszczak, Micha?; Maj, Ewa; Stefa?ska, Joanna; Wietrzyk, Joanna; Janczak, Jan; Brzezinski, Bogumil; Huczy?ski, Adam

2014-04-01

362

Synthesis and anticancer activity of quinopimaric and maleopimaric acids’ derivatives.  

PubMed

A series of quinopimaric and maleopimaric acids’ derivatives modified in the E-ring, at the carbonyl- and carboxyl-groups were synthesized and their in vitro cytotoxic activity was evaluated at the National Cancer Institute, USA. Methyl esters of dihydroquinopimaric, 1a,4a-dehydroquinopimaric, 2,3-epoxyquinopimaric, 1-ethylenketal-dihydroquinopimaric, 1-ethylenketal-4-hydroxyiminodihydroquinopimaric acids displayed an activity on renal cancer, leukemia, colon cancer and breast cancer cell lines in concentration 10(?5) M. Methyl 1,4-dihydroxyiminodihydroquinopimarate showed both a potent and broad spectrum of cytotoxic activity against NSC lung cancer, colon cancer, breast cancer, renal cancer and leukemia and revealed in vivo antineoplastic activity towards mouse solid transplantable mammary carcinoma Ca755 and colon adenocarcinoma AKATOL. The information about antineoplastic activity of the studied quinopimaric and maleopimaric acids’ derivatives will be used for hit to lead optimization in these chemical series. PMID:25440729

Tretyakova, Elena V; Smirnova, Irina E; Kazakova, Oxana B; Tolstikov, Genrikh A; Yavorskaya, Nadejda P; Golubeva, Irina S; Pugacheva, Rujena B; Apryshko, Galina N; Poroikov, Vladimir V

2014-11-15

363

Synthesis and antimalarial activity of new haemanthamine-type derivatives.  

PubMed

Thirty one derivatives were prepared from the natural alkaloids haemanthamine (1), haemanthidine (2) and 11-hydroxyvittatine (3). They were evaluated for their in vitro antimalarial activity against chloroquine-sensitive strains of Plasmodium falciparum and some structure-activity relationships were outlined. For haemanthamine derivatives having a methoxy group at C-3, the presence of a free hydroxyl group at C-11 is important for the activity. The double bond at C-1-C-2 plays also an important role to achieve good inhibitory activity. Compound 35 with two nicotinate groups at C-3 and at C-11 was the most active compound with a IC(50) = 0.8 ± 0.06 ?M. PMID:22910226

Cedrón, Juan C; Gutiérrez, David; Flores, Ninoska; Ravelo, Ángel G; Estévez-Braun, Ana

2012-09-15

364

Design, Synthesis and Antiviral Activity Studies of Schizonepetin Derivatives  

PubMed Central

A series of schizonepetin derivatives have been designed and synthesized in order to obtain potent antivirus agents. The antiviral activity against HSV-1 and influenza virus H3N2 as well as the cytotoxicity of these derivatives was evaluated by using cytopathic effect (CPE) inhibition assay in vitro. Compounds M2, M4, M5 and M34 showed higher inhibitory activity against HSV-1 virus with the TC50 values being in micromole. Compounds M28, M33, and M35 showed higher inhibitory activity against influenza virus H3N2 with their TC50 values being 96.4, 71.0 and 75.4 ?M, respectively. Preliminary biological activity evaluation indicated that the anti-H3N2 and anti-HSV-1 activities improved obviously through the introduction of halogen into the structure of schizonepetin. PMID:23965980

Bao, Beihua; Meng, Zheng; Li, Nianguang; Meng, Zhengjie; Zhang, Li; Cao, Yudan; Yao, Weifeng; Shan, Mingqiu; Ding, Anwei

2013-01-01

365

Sandia Combustion Research Program  

SciTech Connect

During the late 1970s, in response to a national energy crisis, Sandia proposed to the US Department of Energy (DOE) a new, ambitious program in combustion research. Shortly thereafter, the Combustion Research Facility (CRF) was established at Sandia's Livermore location. Designated a ''user facility,'' the charter of the CRF was to develop and maintain special-purpose resources to support a nationwide initiative-involving US inventories, industry, and national laboratories--to improve our understanding and control of combustion. This report includes descriptions several research projects which have been simulated by working groups and involve the on-site participation of industry scientists. DOE's Industry Technology Fellowship program, supported through the Office of Energy Research, has been instrumental in the success of some of these joint efforts. The remainder of this report presents results of calendar year 1988, separated thematically into eleven categories. Referred journal articles appearing in print during 1988 and selected other publications are included at the end of Section 11. Our traditional'' research activities--combustion chemistry, reacting flows, diagnostics, engine and coal combustion--have been supplemented by a new effort aimed at understanding combustion-related issues in the management of toxic and hazardous materials.

Johnston, S.C.; Palmer, R.E.; Montana, C.A. (eds.)

1988-01-01

366

Ionic liquid self-combustion synthesis of BiOBr/Bi24O31Br10 heterojunctions with exceptional visible-light photocatalytic performances  

NASA Astrophysics Data System (ADS)

Heterostructured BiOBr/Bi24O31Br10 nanocomposites with surface oxygen vacancies are constructed by a facile in situ route of one-step self-combustion of ionic liquids. The compositions can be easily controlled by simply adjusting the fuel ratio of urea and 2-bromoethylamine hydrobromide (BTH). BTH serves not only as a fuel, but also as a complexing agent for ionic liquids and a reactant to supply the Br element. The heterojunctions show remarkable adsorptive ability for both the cationic dye of rhodamine B (RhB) and the anionic dye of methylene orange (MO) at high concentrations, which is attributed to the abundant surface oxygen vacancies. The sample containing 75.2% BiOBr and 24.8% Bi24O31Br10 exhibits the highest photocatalytic activity. Its reaction rate constant is 4.0 and 9.0 times that of pure BiOBr in degrading 50 mg L-1 of RhB and 30 mg L-1 of MO under visible-light (? > 400 nm) irradiation, respectively, which is attributed to the narrow band gap and highly efficient transfer efficiency of charge carriers. Different photocatalytic reaction processes and mechanisms over pure BiOBr and heterojunctions are proposed.Heterostructured BiOBr/Bi24O31Br10 nanocomposites with surface oxygen vacancies are constructed by a facile in situ route of one-step self-combustion of ionic liquids. The compositions can be easily controlled by simply adjusting the fuel ratio of urea and 2-bromoethylamine hydrobromide (BTH). BTH serves not only as a fuel, but also as a complexing agent for ionic liquids and a reactant to supply the Br element. The heterojunctions show remarkable adsorptive ability for both the cationic dye of rhodamine B (RhB) and the anionic dye of methylene orange (MO) at high concentrations, which is attributed to the abundant surface oxygen vacancies. The sample containing 75.2% BiOBr and 24.8% Bi24O31Br10 exhibits the highest photocatalytic activity. Its reaction rate constant is 4.0 and 9.0 times that of pure BiOBr in degrading 50 mg L-1 of RhB and 30 mg L-1 of MO under visible-light (? > 400 nm) irradiation, respectively, which is attributed to the narrow band gap and highly efficient transfer efficiency of charge carriers. Different photocatalytic reaction processes and mechanisms over pure BiOBr and heterojunctions are proposed. Electronic supplementary information (ESI) available: XRD pattern for composition calculation (Fig. S1), SEM photographs (Fig. S2), N2 absorption-desorption isotherms (Fig. S3), STEM images (Fig. S4), time-course variation of ln(C0/C) of dyes (Fig. S5), Appearance photographs for adsorption of dyes (Fig. S6), UV-Vis absorption spectra of NBT (Fig. S7), pseudo-first order rate constants for RhB and MO degradation (Tables S1 and S2), electronegativity, calculated CB and VB edge positions (Table S3). See DOI: 10.1039/c4nr05451b

Li, Fa-Tang; Wang, Qing; Ran, Jingrun; Hao, Ying-Juan; Wang, Xiao-Jing; Zhao, Dishun; Qiao, Shi Zhang

2014-12-01

367

Synthesis and insecticidal activity of heptafluoroisopropyl-containing benzoylphenylurea structures.  

PubMed

Fourteen novel heptafluoroisopropyl-containing benzoylphenylureas were designed and synthesized. Their insecticidal activities against armyworm ( Pseudaletia separata Walker) were examined and compared with the commercial product diflubenzuron. Three compounds (IIi, IIj, and IIk) showed excellent insecticidal effect, and their activity resembled that of diflubenzuron. Compound IIi also showed nearly the same insecticidal activity as novaluron on African cotton leafworm ( Spodoptera littoralis ). Furthermore, results from a field trial indicated that 5% EC IIi exhibited similar efficacy in comparison with chlorfluazuron and hexaflumuron against imported cabbage worm ( Pieris rapae L.) and diamondback moth ( Plutella xylostella ), respectively. PMID:20014763

Zhang, Jian; Tang, Xiuhong; Ishaaya, Isaac; Cao, Song; Wu, Jingjing; Yu, Jinlong; Li, Hui; Qian, Xuhong

2010-03-10

368

Ribosome Synthesis and MAPK Activity Modulate Ionizing Radiation-Induced Germ Cell Apoptosis in Caenorhabditis elegans  

PubMed Central

Synthesis of ribosomal RNA by RNA polymerase I (RNA pol I) is an elemental biological process and is key for cellular homeostasis. In a forward genetic screen in C. elegans designed to identify DNA damage-response factors, we isolated a point mutation of RNA pol I, rpoa-2(op259), that leads to altered rRNA synthesis and a concomitant resistance to ionizing radiation (IR)-induced germ cell apoptosis. This weak apoptotic IR response could be phenocopied when interfering with other factors of ribosome synthesis. Surprisingly, despite their resistance to DNA damage, rpoa-2(op259) mutants present a normal CEP-1/p53 response to IR and increased basal CEP-1 activity under normal growth conditions. In parallel, rpoa-2(op259) leads to reduced Ras/MAPK pathway activity, which is required for germ cell progression and physiological germ cell death. Ras/MAPK gain-of-function conditions could rescue the IR response defect in rpoa-2(op259), pointing to a function for Ras/MAPK in modulating DNA damage-induced apoptosis downstream of CEP-1. Our data demonstrate that a single point mutation in an RNA pol I subunit can interfere with multiple key signalling pathways. Ribosome synthesis and growth-factor signalling are perturbed in many cancer cells; such an interplay between basic cellular processes and signalling might be critical for how tumours evolve or respond to treatment. PMID:24278030

Eberhard, Ralf; Stergiou, Lilli; Hofmann, E. Randal; Hofmann, Jen; Haenni, Simon; Teo, Youjin; Furger, André; Hengartner, Michael O.

2013-01-01

369

Synthesis and antibacterial activity of monocyclic 3-carboxamide tetramic acids  

PubMed Central

Summary A chemical library of carboxamide-substituted tetramates designed by analogy with antibacterial natural products, a method for their rapid construction, and the evaluation of their antibacterial activity is reported. PMID:24204399

Jeong, Yong-Chul

2013-01-01

370

Synthesis, characterisation and antitumour activity of some quercetin analogues.  

PubMed

Quercetin is one of the most abundant naturally occurring flavonoid and is associated with a wide range of biological activities, such as antioxidant, antiinflammatory and anticancer activities. However, there are multiple problems associated with the bioavailability of quercetin, thereby restricting its use. Taking this into consideration, the structure of quercetin was modified by removal of multiple hydroxyl groups and introduction of substituents such as Cl, OCH3 and N (CH3)2 on the p-position of the B-ring. The effect of structural modification on the anticancer activity was studied using four different cell lines, including MCF-7, HepG2, HCT-15 and PC-3. Compound 1a has shown an activity better than quercetin in HepG2 cell lines, whereas 1c and 1e showed significant growth inhibition of the HCT-15 cell lines. PMID:24019576

Gadhwal, M K; Patil, Swati; D'Mello, Priscilla; Joshi, Urmila; Sinha, Ragini; Govil, G

2013-03-01

371

Synthesis and evaluation of antimycobacterial activity of new benzimidazole aminoesters.  

PubMed

A total of 51 novel benzimidazoles were synthesized by a 4-step reaction starting from basic compound 4-fluoro-3-nitrobenzoic acid under relatively mild reaction conditions. The structure of the novel benzimidazoles was confirmed by mass spectra as well as (1)H NMR spectroscopic data. Out of the 51 novel synthesized compounds, 42 of them were screened for their antimycobacterial activity against Mycobacterium tuberculosis H37Rv strain using BacTiter-Glo™ Microbial Cell Viability (BTG) method. Results of activity screened using Alamar Blue method was also provided for comparison purposes. Two of the novel benzimidazoles synthesized showed moderately good activity with IC50 of less than 15 ?M. Compound 5g, ethyl 2-(4-(trifluoromethyl)phenyl)-1-(2-morpholinoethyl)-1H-benzo[d]imidazole-5-carboxylate, was found to be the most active with IC50 of 11.52 ?M. PMID:24996257

Yoon, Yeong Keng; Ali, Mohamed Ashraf; Wei, Ang Chee; Choon, Tan Soo; Ismail, Rusli

2015-03-26

372

The synthesis and surface active properties of certain amphoteric compounds  

Microsoft Academic Search

In order to gain some insight into the correlation between chemical structure and surface active properties, a number of amphoteric\\u000a surface active agents were synthesized. All of these compounds possessed both a quaternary ammonium group and an anionic functional\\u000a group. The anionic functional group was either a carboxylate, sulfonate, or a sulfate group. The molecules possessed either\\u000a one or two

W. M. Linfield; P. G. Abend; G. A. Davis

1963-01-01

373

Synthesis and radioprotective activity of new cysteamine and cystamine derivatives  

SciTech Connect

A variety of N-(aminoalkanoyl)-S-acylcysteamine and N,N'-bis(aminoalkanoyl)cystamine salt derivatives were synthesized. Toxicity and radioprotective activity (as the dose reduction factor DRF) were determined in vivo on mice and compared to WR 2721 and S-acetylcysteamine hydrochloride. One of the most interesting compounds of this series was N-glycyl-S-acetylcysteamine trifluoroacetate (16, I 102). Structure-activity relationships are discussed.

Oiry, J.; Pue, J.Y.; Imbach, J.L.; Fatome, M.; Sentenac-Roumanou, H.; Lion, C.

1986-11-01

374

Synthesis and opioid activity of new fentanyl analogs  

Microsoft Academic Search

Three new fentanyl analogs (compounds 3-4-5) have been synthesized and evaluated for antinociceptive properties using the writhing test. The analgesic property of the active compound, N-[1-phenylpyrazol-3-yl]-N-[1-(2-phenethyl)-4-piperidyl)] propenamide (compound 4), was tested using the hot plate test in mice. Its opioid agonistic activity was characterized using three isolated tissues: guinea pig ileum, mouse vas deferens, and rabbit vas deferens. Compound 4

Roc??o Girón; Raquel Abalo; Carlos Goicoechea; Ma Isabel Mart??n; Luis F Callado; Carolina Cano; Pilar Goya; Nadine Jagerovic

2002-01-01

375

NASA Microgravity Combustion Science Program  

NASA Technical Reports Server (NTRS)

Combustion is a key element of many critical technologies used by contemporary society. For example, electric power production, home heating, surface and air transportation, space propulsion, and materials synthesis all utilize combustion as a source of energy. Yet, although combustion technology is vital to our standard of living, it poses great challenges to maintaining a habitable environment. For example, pollutants, atmospheric change and global warming, unwanted fires and explosions, and the incineration of hazardous wastes are major problem areas which would benefit from improved understanding of combustion. Effects of gravitational forces impede combustion studies more than most other areas of science since combustion involves production of high-temperature gases whose low density results in buoyant motion, vastly complicating the execution and interpretation of experiments. Effects of buoyancy are so ubiquitous that their enormous negative impact on the rational development of combustion science is generally not recognized. Buoyant motion also triggers the onset of turbulence, yielding complicating unsteady effects. Finally, gravity forces cause particles and drops to settle, inhibiting deconvoluted studies of heterogeneous flames important to furnace, incineration and power generation technologies. Thus, effects of buoyancy have seriously limited our capabilities to carry out 'clean' experiments needed for fundamental understanding of flame phenomena. Combustion scientists can use microgravity to simplify the study of many combustion processes, allowing fresh insights into important problems via a deeper understanding of elemental phenomena also found in Earth-based combustion processes and to additionally provide valuable information concerning how fires behave in microgravity and how fire safety on spacecraft can be enhanced.

King, Merrill K.

1997-01-01

376

Internal combustion engine using premixed combustion of stratified charges  

DOEpatents

During a combustion cycle, a first stoichiometrically lean fuel charge is injected well prior to top dead center, preferably during the intake stroke. This first fuel charge is substantially mixed with the combustion chamber air during subsequent motion of the piston towards top dead center. A subsequent fuel charge is then injected prior to top dead center to create a stratified, locally richer mixture (but still leaner than stoichiometric) within the combustion chamber. The locally rich region within the combustion chamber has sufficient fuel density to autoignite, and its self-ignition serves to activate ignition for the lean mixture existing within the remainder of the combustion chamber. Because the mixture within the combustion chamber is overall premixed and relatively lean, NO.sub.x and soot production are significantly diminished.

Marriott, Craig D. (Rochester Hills, MI); Reitz, Rolf D. (Madison, WI

2003-12-30

377

A role for PPAR? in the control of SREBP activity and lipid synthesis in the liver  

PubMed Central

Inclusion of the PPAR? (peroxisome-proliferator-activated receptor ?) activator WY 14,643 in the diet of normal mice stimulated the hepatic expression of not only genes of the fatty acid oxidation pathway, but also those of the de novo lipid synthetic pathways. Induction of fatty acid synthase mRNA by WY 14,643 was greater during the light phase of the diurnal cycle, when food intake was low and PPAR? expression was high. Hepatic fatty acid pathway flux in vivo showed a similar pattern of increases. The abundance of mRNAs for genes involved in hepatic cholesterol synthesis was also increased by WY 14,643, but was associated with a decrease in cholesterogenic carbon flux. None of these changes were apparent in PPAR?-null mice. Mice of both genotypes showed the expected decreases in 3-hydroxy-3-methylglutaryl-CoA reductase mRNA levels and cholesterol synthesis in response to an increase in dietary cholesterol. The increase in fatty acid synthesis due to WY 14,643 was not mediated by increased expression of SREBP-1c (sterol regulatory element binding protein-1c) mRNA, but by an increase in cleavage of the protein to the active form. An accompanying rise in stearoyl-CoA desaturase mRNA expression suggested that the increase in lipogenesis could have resulted from an alteration in membrane fatty acid composition that influenced SREBP activation. PMID:15777286

2005-01-01

378

Simple synthesis of novel diphenylsulfapyrimidine acetates from chalcones and their antimicrobial activity.  

PubMed

Given the significant low yield (19-43%) in reported results on the cyclocondensation of sulfaguanidine acetate with chalcones, a careful reinvestigation was carried out. A new series of chalcones, bearing electron-attracting groups in the aromatic moiety, have been used as precursors in the synthesis of diphenylsulfapyrimidine acetates with good yield. All synthesized compounds were active against G(+)- and G(-)-bacteria, and fungi. Combination of substituents (Cl, OMe, NO2, etc.) enhanced antimicrobial activity. Derivative with two NO2 groups exhibits an activity comparable with sulfadiazine. PMID:12744076

Wasfy, A A F; Aly, A A

2003-01-01

379

Hypoxic neuronal necrosis: Protein synthesis-independent activation of a cell death program  

PubMed Central

Hypoxic necrosis of dentate gyrus neurons in primary culture required the activation of an orderly cell death program independent of protein synthesis. Early mitochondrial swelling and loss of the mitochondrial membrane potential were accompanied by release of cytochrome c and followed by caspase-9-dependent activation of caspase-3. Caspase-3 and -9 inhibitors reduced neuronal necrosis. Calcium directly induced cytochrome c release from isolated mitochondria. Hypoxic neuronal necrosis may be an active process in which the direct effect of hypoxia on mitochondria may lead to the final common pathway of caspase-3-mediated neuronal death. PMID:12606726

Niquet, Jerome; Baldwin, Roger A.; Allen, Suni G.; Fujikawa, Denson G.; Wasterlain, Claude G.

2003-01-01

380

Activation of cholesterol synthesis in preference to fatty acid synthesis in liver and adipose tissue of transgenic mice overproducing sterol regulatory element-binding protein-2.  

PubMed Central

We produced transgenic mice that express a dominant-positive truncated form of sterol regulatory element-binding protein-2 (SREBP-2) in liver and adipose tissue. The encoded protein lacks the membrane-binding and COOH-terminal regulatory domains, and it is therefore not susceptible to negative regulation by cholesterol. Livers from the transgenic mice showed increases in mRNAs encoding multiple enzymes of cholesterol biosynthesis, the LDL receptor, and fatty acid biosynthesis. The elevations in mRNA for 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) synthase and HMG CoA reductase were especially marked (13-fold and 75-fold, respectively). As a result, the transgenic livers showed a 28-fold increase in the rate of cholesterol synthesis and a lesser fourfold increase in fatty acid synthesis, as measured by intraperitoneal injection of [3H]water. These results contrast with previously reported effects of dominant-positive SREBP-1a, which activated fatty acid synthesis more than cholesterol synthesis. In adipose tissue of the SREBP-2 transgenics, the mRNAs for cholesterol biosynthetic enzymes were elevated, but the mRNAs for fatty acid biosynthetic enzymes were not. We conclude that SREBP-2 is a relatively selective activator of cholesterol synthesis, as opposed to fatty acid synthesis, in liver and adipose tissue of mice. PMID:9616204

Horton, J D; Shimomura, I; Brown, M S; Hammer, R E; Goldstein, J L; Shimano, H

1998-01-01

381

[Evaluation of micromycetes potential concerning synthesis of biologically active substances].  

PubMed

Screening of 41 cultures of some researched strains of micromycetes by their antibiotic and phytotoxic activities in relation to different test-organisms--Gram-positive, Gram-negative, phytopathogenic bacteria, yeasts and green algae was conducted. The wide spectrum of antibiotic action was characterized for the cultures of Gliocladium catenulatum 2709, 3942 Penicillium vulpinum 3957, Ulocladium atrum 1889, U.consortiale 960, Trithirachium album 2673. A fungistatic activity was shown by only two strains U. consortiale 960 and Nectria inventa 3949. A small group consisted of cultures with high phytotoxic activity: P. vulpimum 3957, U. atrum 1889, U. consortiale 960, N. inventa 3949, Eupenicillium parvum 3128, Bipolaris sorokinia 4080, Paecilomyces lilacinus 1428, 1492, T. album 2673. They showed the activity in relation to the majority of test-cultures of the green algae. We consider two cultures: U. consortiale 960 and P. vulpinum 3957 to be the most promising for further researches, they differ by a wide spectrum of antibiotic and phytotoxic activity and were not studied before. The paper is presented in Ukrainian. PMID:20455437

Savchuk, Ia I; Za?chenko, O M

2010-01-01

382

Antitumour indolequinones: synthesis and activity against human pancreatic cancer cells.  

PubMed

An important determinant of the growth inhibitory activity of indolequinones against pancreatic cancer cells is substitution on the 2-position with 2-unsubstituted derivatives being markedly more potent. A series of indolequinones bearing a range of substituents on nitrogen and at the indolylcarbinyl position was prepared by copper(II)-mediated reaction of bromoquinones and enamines, followed by functional group interconversions. The compounds were then assayed for their ability to inhibit the growth of pancreatic cancer cells. The pKa of the leaving group at the 3-position was shown to influence growth inhibitory activity that is consistent with the proposed mechanism of action of reduction, loss of leaving group and formation of a reactive iminium species. Substitutions on the indole nitrogen were well tolerated with little influence on growth inhibitory activity while substitutions at the 5- and 6-positions larger than methoxy led to decreased activity. The studies presented define the range of substitutions of 2-unsubstituted indolequinones required for optimal growth inhibitory activity. PMID:24848343

Inman, Martyn; Visconti, Andrea; Yan, Chao; Siegel, David; Ross, David; Moody, Christopher J

2014-07-21

383

Design, synthesis and fungicidal activities of some novel pyrazole derivatives.  

PubMed

In order to discover new compounds with good fungicidal activities, 32 pyrazole derivatives were designed and synthesized. The structures of the target compounds were confirmed by 1H-NMR, 13C-NMR, and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), and their fungicidal activities against Botrytis cinerea, Rhizoctonia solani Kuhn, Valsa mali Miyabe et Yamada, Thanatephorus cucumeris (Frank) Donk, Fusarium oxysporum (S-chl) f.sp. cucumerinum Owen, and Fusarium graminearum Schw were tested. The bioassay results indicated that most of the derivatives exhibited considerable antifungal activities, especially compound 26 containing a p-trifluoromethyl- phenyl moiety showed the highest activity, with EC50 values of 2.432, 2.182, 1.787, 1.638, 6.986, and 6.043 ?g/mL against B. cinerea, R. solani, V. mali, T. cucumeris, F. oxysporum, and F. graminearum, respectively. Moreover, the activities of compounds such as compounds 27-32 were enhanced by introducing isothiocyanate and carboxamide moieties to the 5-position of the pyrazole ring. PMID:25203055

Liu, Xue-Ru; Wu, Hua; He, Ze-Yu; Ma, Zhi-Qing; Feng, Jun-Tao; Zhang, Xing

2014-01-01

384

Antituberculosis: Synthesis and Antimycobacterial Activity of Novel Benzimidazole Derivatives  

PubMed Central

A total of seven novel benzimidazoles were synthesized by a 4-step reaction starting from 4-fluoro-3-nitrobenzoic acid under relatively mild reaction conditions. The synthesized compounds were screened for their antimycobacterial activity against M. tuberculosis H37Rv (MTB-H37Rv) and INH-resistant M. tuberculosis (INHR-MTB) strains using agar dilution method. Three of them displayed good activity with MIC of less than 0.2??M. Compound ethyl 1-(2-(4-(4-(ethoxycarbonyl)-2-aminophenyl)piperazin-1-yl)ethyl)-2-(4-(5-(4-fluorophenyl)pyridin-3-ylphenyl-1H-benzo[d]imidazole-5-carboxylate (5g) was found to be the most active with MIC of 0.112??M against MTB-H37Rv and 6.12??M against INHR-MTB, respectively. PMID:24381946

Keng Yoon, Yeong; Ashraf Ali, Mohamed; Choon, Tan Soo; Ismail, Rusli; Chee Wei, Ang; Suresh Kumar, Raju; Beevi, Farzana

2013-01-01

385

Antituberculosis: synthesis and antimycobacterial activity of novel benzimidazole derivatives.  

PubMed

A total of seven novel benzimidazoles were synthesized by a 4-step reaction starting from 4-fluoro-3-nitrobenzoic acid under relatively mild reaction conditions. The synthesized compounds were screened for their antimycobacterial activity against M. tuberculosis H??Rv (MTB-H??Rv) and INH-resistant M. tuberculosis (INHR-MTB) strains using agar dilution method. Three of them displayed good activity with MIC of less than 0.2??M. Compound ethyl 1-(2-(4-(4-(ethoxycarbonyl)-2-aminophenyl)piperazin-1-yl)ethyl)-2-(4-(5-(4-fluorophenyl)pyridin-3-ylphenyl-1H-benzo[d]imidazole-5-carboxylate (5 g) was found to be the most active with MIC of 0.112 ?M against MTB-H??Rv and 6.12 ?M against INHR-MTB, respectively. PMID:24381946

Keng Yoon, Yeong; Ashraf Ali, Mohamed; Choon, Tan Soo; Ismail, Rusli; Chee Wei, Ang; Suresh Kumar, Raju; Osman, Hasnah; Beevi, Farzana

2013-01-01

386

Synthesis and antitumor activity of natural compound aloe emodin derivatives.  

PubMed

In this study, we have synthesized novel water soluble derivatives of natural compound aloe emodin 4(a-j) by coupling with various amino acid esters and substituted aromatic amines, in an attempt to improve the anticancer activity and to explore the structure-activity relationships. The structures of the compounds were determined by (1) H NMR and mass spectroscopy. Cell growth inhibition assays revealed that the aloe emodin derivatives 4d, 4f, and 4i effectively decreased the growth of HepG2 (human liver cancer cells) and NCI-H460 (human lung cancer cells) and some of the derivatives exhibited comparable antitumor activity against HeLa (Human epithelial carcinoma cells) and PC3 (prostate cancer cells) cell lines compared to that of the parent aloe emodin at low micromolar concentrations. PMID:25323822

Thimmegowda, Naraganahalli R; Park, Chanmi; Shwetha, Bettaswamigowda; Sakchaisri, Krisada; Liu, Kangdong; Hwang, Joonsung; Lee, Sangku; Jeong, Sook J; Soung, Nak K; Jang, Jae H; Ryoo, In-Ja; Ahn, Jong S; Erikson, Raymond L; Kim, Bo Y

2015-05-01

387

Synthesis and antibacterial activity of sulfonamides. SAR and DFT studies  

NASA Astrophysics Data System (ADS)

A series of substituted sulfonamide derivatives were synthesized from chlorosulfonyl isocyanate (CSI) in tree steps (carbamoylation, sulfamoylation and deprotection). Antibacterial activity in vitro of some newly formed compounds investigated against clinical strains Gram-positive and Gram-negative: Escherichia coli and Staphylococcus aureus applying the method of dilution and minimal inhibition concentration (MIC) methods. These compounds have significant bacteriostatic activity with totalities of bacterial strains used. DFT calculations with B3LYP/6-31G(d) level have been used to analyze the electronic and geometric characteristics deduced for the stable structure of three compounds presenting conjugation between a nitrogen atom N through its lone pair and an aromatic ring next to it. The principal quantum chemical descriptors have been correlated with the antibacterial activity.

Boufas, Wahida; Dupont, Nathalie; Berredjem, Malika; Berrezag, Kamel; Becheker, Imène; Berredjem, Hajira; Aouf, Nour-Eddine

2014-09-01

388

Synthesis and herbicidal activity of phenyl-substituted benzoylpyrazoles.  

PubMed

A novel series of substituted 3-phenyl benzoylpyrazoles were prepared and tested as potential grass herbicides. The targeted materials were prepared by three newly developed synthetic routes, which allowed a comprehensive study of the SAR (structure-activity relationships) of this series. The best combination of grass weed activity (Avena fatua L, Setaria viridis (L) Beauv and Alopecurus myosuroides Huds) and wheat selectivity was obtained with an alkoxy group in the 4-position of the phenyl ring. Activity was further enhanced by the presence of tert-butyl on the pyrazole and a methyl group at the C-2 position of the benzoyl moiety. The alkoxy-substituted 3-phenylbenzoylpyrazoles are a novel class of herbicides with potential utility for control of important grass weeds in cereals. PMID:12476990

Siddall, Thomas L; Ouse, David G; Benko, Zoltan L; Garvin, Gail M; Jackson, Johnny L; McQuiston, Jeffrey M; Ricks, Michael J; Thibault, Thomas D; Turner, James A; Vanheertum, John C; Weimer, Monte R

2002-12-01

389

Synthesis and anti-microbial activity of hydroxylammonium ionic liquids.  

PubMed

Eight hydroxylammonium-based room temperature ionic liquids (ILs) have been synthesized by acid-base neutralization of ethanolamines with organic acids. The ILs were characterized by infrared and nuclear magnetic resonance spectroscopies and elemental analysis. Their anti-microbial activities were determined using the well-diffusion method. All eight ILs were toxic to Staphylococcus aureus, while 2-hydroxyethylammonium lactate and 2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium acetate showed high anti-microbial activity against a wide range of human pathogens. PMID:21421256

Ismail Hossain, M; El-Harbawi, Mohanad; Noaman, Yousr Abdulhadi; Bustam, Mohd Azmi B; Alitheen, Noorjahan Banu Mohamed; Affandi, Nor Azrin; Hefter, Glenn; Yin, Chun-Yang

2011-06-01

390

Synthesis and Antimycobacterial Activity of 2,1?-Dihydropyridomycins  

PubMed Central

Dihydropyridomycins 2 and 3, which lack the characteristic enol ester moiety of the potent antimycobacterial natural product pyridomycin (1), have been prepared from l-Thr, R- and S-hydroxy isovaleric acid, and 3-pyridinecarboxaldehyde. The 2R isomer 2 shows only 4-fold lower anti-Mtb activity than 1, indicating that the enol ester moiety in the natural product is not critical for its biological activity. This finding establishes 2 as a potent and more practical lead for anti-TB drug discovery. PMID:24900646

2012-01-01

391

Antioxidant status and Na(+), K (+)-ATPase activity in freshwater fish Carassius auratus exposed to different combustion products of Nafion 117 membrane: an integrated biomarker approach.  

PubMed

Nafion 117 membrane (N117), an important polymer electrolyte membrane (PEM), has been widely applied in numerous chemical technologies. Its increasing production and utilization will inevitably lead to the problem of waste disposal, with incineration as an important method. However, toxicity data of its combustion products on aquatic organisms have been seldom reported. The present study was therefore conducted to investigate the antioxidant response and Na(+), K(+)-ATPase activity in liver of Carassius auratus exposed to different combustion products of N117 for 5, 15, and 30 days. The concentrations of fluorine ion (F(-)) in the aquaria among the exposure durations were analyzed using the ion chromatography system. The results showed that these treatments have the capability to induce oxidative stress and suppress Na(+), K(+)-ATPase activity, as indicated by some significant alterations on these measured toxicity end-points in fish liver. According to the integrated biomarker response (IBR) index, the toxicity intensity of these experimental treatments was tentatively ranked. Taken together, these observations provided some preliminary data on the potential toxicity of the combustion products of N117 on aquatic organisms and could fill the information gaps in the toxicity database of the current-use PEM. PMID:25398218

Feng, Mingbao; Wang, Xinghao; Wang, Chao; Qin, Li; Wei, Zhongbo; Wang, Zunyao

2015-03-01

392

DGK1-encoded Diacylglycerol Kinase Activity Is Required for Phospholipid Synthesis during Growth Resumption from Stationary Phase in Saccharomyces cerevisiae*  

PubMed Central

In the yeast Saccharomyces cerevisiae, triacylglycerol mobilization for phospholipid synthesis occurs during growth resumption from stationary phase, and this metabolism is essential in the absence of de novo fatty acid synthesis. In this work, we provide evidence that DGK1-encoded diacylglycerol kinase activity is required to convert triacylglycerol-derived diacylglycerol to phosphatidate for phospholipid synthesis. Cells lacking diacylglycerol kinase activity (e.g. dgk1? mutation) failed to resume growth in the presence of the fatty acid synthesis inhibitor cerulenin. Lipid analysis data showed that dgk1? mutant cells did not mobilize triacylglycerol for membrane phospholipid synthesis and accumulated diacylglycerol. The dgk1? phenotypes were partially complemented by preventing the formation of diacylglycerol by the PAH1-encoded phosphatidate phosphatase and by channeling diacylglycerol to phosphatidylcholine via the Kennedy pathway. These observations, coupled to an inhibitory effect of dioctanoyl-diacylglycerol on the growth of wild type cells, indicated that diacylglycerol kinase also functions to alleviate diacylglycerol toxicity. PMID:21071438

Fakas, Stylianos; Konstantinou, Chrysanthos; Carman, George M.

2011-01-01

393

Choline Transport Activity Regulates Phosphatidylcholine Synthesis through Choline Transporter Hnm1 Stability*  

PubMed Central

Choline is a precursor for the synthesis of phosphatidylcholine through the CDP-choline pathway. Saccharomyces cerevisiae expresses a single high affinity choline transporter at the plasma membrane, encoded by the HNM1 gene. We show that exposing cells to increasing levels of choline results in two different regulatory mechanisms impacting Hnm1 activity. Initial exposure to choline results in a rapid decrease in Hnm1-mediated transport at the level of transporter activity, whereas chronic exposure results in Hnm1 degradation through an endocytic mechanism that depends on the ubiquitin ligase Rsp5 and the casein kinase 1 redundant pair Yck1/Yck2. We present details of how the choline transporter is a major regulator of phosphatidylcholine synthesis. PMID:24187140

Fernández-Murray, J. Pedro; Ngo, Michael H.; McMaster, Christopher R.

2013-01-01

394

Metal organic framework-mediated synthesis of highly active and stable Fischer-Tropsch catalysts.  

PubMed

Depletion of crude oil resources and environmental concerns have driven a worldwide research on alternative processes for the production of commodity chemicals. Fischer-Tropsch synthesis is a process for flexible production of key chemicals from synthesis gas originating from non-petroleum-based sources. Although the use of iron-based catalysts would be preferred over the widely used cobalt, manufacturing methods that prevent their fast deactivation because of sintering, carbon deposition and phase changes have proven challenging. Here we present a strategy to produce highly dispersed iron carbides embedded in a matrix of porous carbon. Very high iron loadings (>40?wt %) are achieved while maintaining an optimal dispersion of the active iron carbide phase when a metal organic framework is used as catalyst precursor. The unique iron spatial confinement and the absence of large iron particles in the obtained solids minimize catalyst deactivation, resulting in high active and stable operation. PMID:25740709

Santos, Vera P; Wezendonk, Tim A; Jaén, Juan José Delgado; Dugulan, A Iulian; Nasalevich, Maxim A; Islam, Husn-Ubayda; Chojecki, Adam; Sartipi, Sina; Sun, Xiaohui; Hakeem, Abrar A; Koeken, Ard C J; Ruitenbeek, Matthijs; Davidian, Thomas; Meima, Garry R; Sankar, Gopinathan; Kapteijn, Freek; Makkee, Michiel; Gascon, Jorge

2015-01-01

395

Synthesis of high specific activity (1- sup 3 H) farnesyl pyrophosphate  

SciTech Connect

The synthesis of tritiated farnesyl pyrophosphate with high specific activity is reported. trans-trans Farnesol was oxidized to the corresponding aldehyde followed by reduction with lithium aluminium tritide (5%-{sup 3}H) to give trans-trans (1-{sup 3}H)farnesol. The specific radioactivity of the alcohol was determined from its triphenylsilane derivative, prepared under very mild conditions. The tritiated alcohol was phosphorylated by initial conversion to an allylic halide, and subsequent treatment of the halide with tris-tetra-n-butylammonium hydrogen pyrophosphate. The hydride procedure followed in this work has advantages over existing methods for the synthesis of tritiated farnesyl pyrophosphate, with the possibility of higher specific activity and a much higher yield obtained. 10 refs., 3 figs.

Saljoughian, M.; Morimoto, H.; Williams, P.G.

1991-08-01

396

Metal organic framework-mediated synthesis of highly active and stable Fischer-Tropsch catalysts  

NASA Astrophysics Data System (ADS)

Depletion of crude oil resources and environmental concerns have driven a worldwide research on alternative processes for the production of commodity chemicals. Fischer–Tropsch synthesis is a process for flexible production of key chemicals from synthesis gas originating from non-petroleum-based sources. Although the use of iron-based catalysts would be preferred over the widely used cobalt, manufacturing methods that prevent their fast deactivation because of sintering, carbon deposition and phase changes have proven challenging. Here we present a strategy to produce highly dispersed iron carbides embedded in a matrix of porous carbon. Very high iron loadings (>40?wt %) are achieved while maintaining an optimal dispersion of the active iron carbide phase when a metal organic framework is used as catalyst precursor. The unique iron spatial confinement and the absence of large iron particles in the obtained solids minimize catalyst deactivation, resulting in high active and stable operation.

Santos, Vera P.; Wezendonk, Tim A.; Jaén, Juan José Delgado; Dugulan, A. Iulian; Nasalevich, Maxim A.; Islam, Husn-Ubayda; Chojecki, Adam; Sartipi, Sina; Sun, Xiaohui; Hakeem, Abrar A.; Koeken, Ard C. J.; Ruitenbeek, Matthijs; Davidian, Thomas; Meima, Garry R.; Sankar, Gopinathan; Kapteijn, Freek; Makkee, Michiel; Gascon, Jorge

2015-03-01

397

Cortex synthesis during Bacillus subtilis sporulation depends on the transpeptidase activity of SpoVD  

PubMed Central

The nonessential process of peptidoglycan synthesis during Bacillus subtilis sporulation is one model to study bacterial cell wall biogenesis. SpoVD is a class B high-molecular-weight penicillin-binding protein that is specific for sporulation. Strains lacking this protein produce spores without the peptidoglycan cortex layer and are heat sensitive. The detailed functions of the four different protein domains of SpoVD are unknown, and the observed phenotype of strains lacking the entire protein could be an indirect defect. We therefore inactivated the transpeptidase domain by substitution of the active-site serine residue. Our results demonstrate that endospore cortex synthesis depends on the transpeptidase activity of SpoVD specifically. PMID:23789716

Bukowska-Faniband, Ewa; Hederstedt, Lars

2013-01-01

398

Electrochemical synthesis of tetrahexahedral rhodium nanocrystals with extraordinarily high surface energy and high electrocatalytic activity.  

PubMed

Noble metal nanocrystals (NCs) enclosed with high-index facets hold a high catalytic activity thanks to the high density of low-coordinated step atoms that they exposed on their surface. Shape-control synthesis of the metal NCs with high-index facets presents a big challenge owing to the high surface energy of the NCs, and the shape control for metal Rh is even more difficult because of its extraordinarily high surface energy in comparison with Pt, Pd, and Au. The successful synthesis is presented of tetrahexahedral Rh NCs (THH Rh NCs) enclosed by {830} high-index facets through the dynamic oxygen adsorption/desorption mediated by square-wave potential. The results demonstrate that the THH Rh NCs exhibit greatly enhanced catalytic activity over commercial Rh black catalyst for the electrooxidation of ethanol and CO. PMID:24692362

Yu, Neng-Fei; Tian, Na; Zhou, Zhi-You; Huang, Long; Xiao, Jing; Wen, Yu-Hua; Sun, Shi-Gang

2014-05-12

399

Synthesis and biological activity of ?-glucosyl C24:0 and C20:2 ceramides  

PubMed Central

?-Glucosyl ceramides 4 and 5 have been synthesised and evaluated for their ability to stimulate the activation and expansion of human iNKT cells. The key challenge in the synthesis of both target molecules was the stereoselective synthesis of the ?-glycosidic linkage. Of the methods examined, glycosylation using per-TMS-protected glucosyl iodide 16 was completely ?-selective and provided gram quantities of amine 11, from which ?-glucosyl ceramides 4 and 5 were obtained by N-acylation. ?-GlcCer 4, containing a C24 saturated acyl chain, stimulated a marked proliferation and expansion of human circulating iNKT cells in short-term cultures. ?-GlcCer 5, which contains a C20 11,14-cis-diene acyl chain (C20:2), induced extremely similar levels of iNKT cell activation and expansion. PMID:20529677

Jervis, Peter J.; Veerapen, Natacha; Bricard, Gabriel; Cox, Liam R.; Porcelli, Steven A.; Besra, Gurdyal S.

2010-01-01

400

Cortex synthesis during Bacillus subtilis sporulation depends on the transpeptidase activity of SpoVD.  

PubMed

The nonessential process of peptidoglycan synthesis during Bacillus subtilis sporulation is one model to study bacterial cell wall biogenesis. SpoVD is a class B high-molecular-weight penicillin-binding protein that is specific for sporulation. Strains lacking this protein produce spores without the peptidoglycan cortex layer and are heat sensitive. The detailed functions of the four different protein domains of SpoVD are unknown, and the observed phenotype of strains lacking the entire protein could be an indirect defect. We therefore inactivated the transpeptidase domain by substitution of the active-site serine residue. Our results demonstrate that endospore cortex synthesis depends on the transpeptidase activity of SpoVD specifically. PMID:23789716

Bukowska-Faniband, Ewa; Hederstedt, Lars

2013-09-01

401

Starburst99: Synthesis Models for Galaxies with Active Star Formation  

Microsoft Academic Search

Starburst99 is a comprehensive set of model predictions for spectrophotometric and related properties of galaxies with active star formation. The models are an improved and extended version of the data set previously published by Leitherer & Heckman. We have upgraded our code by implementing the latest set of stellar evolution models of the Geneva group and the model atmosphere grid

Claus Leitherer; Daniel Schaerer; Jeffrey D. Goldader; Rosa M. González Delgado; Carmelle Robert; Denis Foo Kune; Duília F. de Mello; Daniel Devost; Timothy M. Heckman

1999-01-01

402

Heteroatom Analogues of Hydrocodone: Synthesis and Biological Activity  

PubMed Central

Heteroatom analogues of hydrocodone, in which the N-methyl functionality was replaced with oxygen, sulfur, sulfoxide, and sulfone, were prepared by a short sequence from the ethylene glycol ketal of hydrocodone; a carbocyclic analogue of bisnorhydrocodone was also prepared. The compounds were tested for receptor binding and revealed moderate levels of activity for the sulfone analogue of hydrocodone. PMID:23397939

Giacometti, Robert D.; Duchek, Jan; Werner, Lukas; Husni, Afeef S.; McCurdy, Christopher R.; Cutler, Stephen J.; Cox, D. Phillip; Hudlicky, Tomas

2013-01-01

403

Synthesis and Antimalarial Activities of Cyclen 4-Aminoquinoline Analogs  

Technology Transfer Automated Retrieval System (TEKTRAN)

In an attempt to augment the efficacy of 7-chloro 4-aminoquinoline analogs and also to overcome resistance to anti-malarial agents we synthesized three cyclen analogs of chloroquine (4,6,7). Compound 4 displays the most potent in vitro and in vivo antimalarial activities. It displays an IC50 of 7.5 ...

404

Synthesis and antifungal activity of thiadiazole-functionalized chitosan derivatives.  

PubMed

A groups of novel water soluble chitosan derivatives containing 1,3,4-thiadiazole group were synthesized including 1,3,4-thiadiazole (TPCTS), 2-methyl-1,3,4-thiadiazole (MTPCTS), and 2-phenyl-1,3,4-thiadiazole (PTPCTS). Their antifungal activity against three kinds of phytopathogens was estimated by hypha measurement in vitro, and the fungicidal assessment shows that the synthesized chitosan derivatives have excellent activity against tested fungi. Of all the synthesized chitosan derivatives, MTPCTS inhibited the growth of the tested phytopathogens most effectively with inhibitory indices of 75.3%, 82.5%, and 65.8% against Colletotrichum lagenarium (Pass) Ell.et halst, Phomopsis asparagi (Sacc.) Bubak, and Monilinia fructicola (Wint.) Honey respectively at 1.0 mg/mL. These indices are higher than those of chitosan. These data also demonstrate that the hydrophobic moiety (alkyl and phenyl) and the length of alkyl substituent in thiadiazole tend to affect the antifungal activity of chitosan derivatives. It is hypothesized that thiadiazole groups enable the synthesized chitosan to possess obviously better antifungal activity and good solubility in water. PMID:23624516

Li, Qing; Ren, Jianming; Dong, Fang; Feng, Yan; Gu, Guodong; Guo, Zhanyong

2013-05-24

405

Synthesis of isoquinuclidine analogs of chloroquine: antimalarial and antileishmanial activity.  

PubMed

The isoquinuclidine (2-azabicyclo[2.2.2]octane) ring system may be viewed as a semi-rigid boat form of the piperidine ring and, when properly substituted, a scaffold for rigid analogs of biologically active ethanolamines and propanolamines. It is present in natural products (such as ibogaine and dioscorine) that display interesting pharmacological properties. In this study, we have expanded our continuing efforts to incorporate this ring system in numerous pharmacophores, by designing and synthesizing semirigid analogs of the antimalarial drug chloroquine. The analogs were tested in vitro against Plasmodium falciparum strains and Leishmania donovani promastigote cultures. Compounds 6 and 13 displayed potent antimalarial activity against both chloroquine-susceptible D6 and the -resistant W2 strains of P. falciparum. All analogs also demonstrated significant antileishmanial activity with compounds 6 and 13 again being the most potent. The fact that these compounds are active against both chloroquine-resistant and chloroquine-sensitive strains as well as leishmanial cells makes them promising candidates for drug development. PMID:17400457

Khan, M O Faruk; Levi, Mark S; Tekwani, Babu L; Wilson, Norman H; Borne, Ronald F

2007-06-01

406

Spray combustion stability project  

NASA Technical Reports Server (NTRS)

This report summarizes research activity on the Spray Combustion Stability Project, characterizes accomplishments and current status, and discusses projected future work. The purpose is to provide a concise conceptual overview of the research effort to date so the reader can quickly assimilate the gist of the research results and place them within the context of their potential impact on liquid rocket engine design technology.

Jeng, San-Mou; Litchford, Ron J.

1992-01-01

407

STRUCTURE-ACTIVITY STUDY OF PARACETAMOL ANALOGUES: INHIBITION OF REPLICATIVE DNA SYNTHESIS IN V79 CHINESE HAMSTER CELLS  

EPA Science Inventory

Experimental and theoretical evidence pertaining to cytotoxic and genotoxic activity of paracetamol in biological systems was used to formulate a simple mechanistic hypothesis to explain the relative inhibition of replicative DNA synthesis by a series of 19 structurally similar p...

408

Synthesis of ethoxy dibenzooxaphosphorin oxides through palladium-catalyzed C(sp2)–H activation/C–O formation  

PubMed Central

Summary We report an efficient Pd-catalyzed C(sp2)–H activation/C–O bond formation for the synthesis of ethoxy dibenzooxaphosphorin oxides from 2-(aryl)arylphosphonic acid monoethyl esters under aerobic conditions. PMID:24991271

Jeon, Woo Hyung

2014-01-01

409

Combustion synthesis and thermal expansion measurements of the rare earth-uranium ternary oxides RE 6UO 12 (RE=La, Nd and Sm)  

NASA Astrophysics Data System (ADS)

Rare earth-uranium ternary oxides were synthesized by a solution combustion route. The starting materials were the corresponding metal nitrates and urea. In these preparations, the metal nitrates act as oxidizer and urea as fuel. Highly exothermic decomposition of the metal nitrate-urea complexes on heating at about 500 K leads to a combustion process yielding RE 6UO 12 fine powders. Thermal expansion measurements of these compounds were carried out in the temperature range of 298-1173 K by high temperature X-ray powder diffractometry. The observed axial thermal expansion behaviour is explained on the basis of the crystal chemistry of the compounds.

Jena, Hrudananda; Asuvathraman, R.; Govindan Kutty, K. V.

2000-08-01

410

Combustion Control  

E-print Network

. There are many opportunities to improve combustion system efficiency. However, there is no single correct way to maximize efficiency. Each technique must be evaluated and compared before a final selection is made. You have a choice of many energy saving systems...

Riccardi, R. C.

1984-01-01

411

Conjugates of methyl 6-aminopenicillanate with biscatechol-hydroxamate chelators: synthesis and siderophoric activity  

Microsoft Academic Search

A synthesis of biscatechol-hydroxamate and triscatechol chelators and of conjugates of the former with methyl 6-aminopenicillanate is described. It is based on the multiple use of the ylide Ph3PCCO as a C2 building block in one-pot coupling reactions between aldehydes and alcohols or amines. These conjugates were actively internalized into siderophore-deficient Escherichia coli mutant H5596.

Rainer Schobert; Andreas Stangl; Kerstin Hannemann

2006-01-01

412

Total Chemical Synthesis of Enzymatically Active Human Type II Secretory Phospholipase A2  

Microsoft Academic Search

Human group II secretory phospholipase A2 (sPLA2) is an enzyme found in the alpha granules of platelets and at inflammatory sites. Although its physiological function is unclear, sPLA2 can inhibit blood coagulation reactions independent of its lipolytic action. To study the molecular basis of PLA2 activities, we developed a total chemical synthesis of sPLA2 by chemical ligation of large unprotected

Tilman M. Hackeng; Carine M. Mounier; Cassian Bon; Philip E. Dawson; John H. Griffin; Stephen B. H. Kent

1997-01-01

413

Synthesis and activity of 2-oxoamides containing long chain beta-amino acids.  

PubMed

2-Oxoamides based on long chain beta-amino acids were synthesized. 1-Benzyl substituted long chain amines, needed for such synthesis, were synthesized starting from Boc-phenylalaninol. The oxidative conversion of a phenyl group to a carboxyl group was used as the key transformation synthetic step. The compounds synthesized were studied for their activity against GIVA PLA(2), and were proven to be weak inhibitors. PMID:15635664

Constantinou-Kokotou, Violetta; Peristeraki, Anna; Kokotos, Christoforos G; Six, David A; Dennis, Edward A

2005-07-01

414

A novel toxic alkaloid from poison hemlock ( Conium maculatum L., Apiaceae): Identification, synthesis and antinociceptive activity  

Microsoft Academic Search

2-Pentylpiperidine, named conmaculatin, a novel volatile alkaloid related to coniine was identified from the renowned toxic weed Conium maculatum L. (Apiaceae). The structure of conmaculatin was corroborated by synthesis (8 steps starting from cyclohexanol, overall yield 12%). Conmaculatin’s strong peripheral and central antinociceptive activity in mice was observed in a narrow dose range (10–20mg\\/kg). It was found to be lethal

Niko Radulovi?; Nevenka ?or?evi?; Marija Deni?; Mariana Martins Gomes Pinheiro; Patricia Dias Fernandes; Fabio Boylan

415

A novel toxic alkaloid from poison hemlock (Conium maculatum L., Apiaceae): identification, synthesis and antinociceptive activity.  

PubMed

2-Pentylpiperidine, named conmaculatin, a novel volatile alkaloid related to coniine was identified from the renowned toxic weed Conium maculatum L. (Apiaceae). The structure of conmaculatin was corroborated by synthesis (8 steps starting from cyclohexanol, overall yield 12%). Conmaculatin's strong peripheral and central antinociceptive activity in mice was observed in a narrow dose range (10-20mg/kg). It was found to be lethal in doses higher than 20mg/kg. PMID:22063758

Radulovi?, Niko; Dor?evi?, Nevenka; Deni?, Marija; Pinheiro, Mariana Martins Gomes; Fernandes, Patricia Dias; Boylan, Fabio

2012-02-01

416

Synthesis and structure-activity relationship of trisubstituted thiazoles as Cdc7 kinase inhibitors.  

PubMed

The Cell division cycle 7 (Cdc7) protein kinase is essential for DNA replication and maintenance of genome stability. We systematically explored thiazole-based compounds as inhibitors of Cdc7 kinase activity in cancer cells. Our studies resulted in the identification of a potent, selective Cdc7 inhibitor that decreased phosphorylation of the direct substrate MCM2 in vitro and in vivo, and inhibited DNA synthesis and cell viability in vitro. PMID:24793884

Reichelt, Andreas; Bailis, Julie M; Bartberger, Michael D; Yao, Guomin; Shu, Hong; Kaller, Matthew R; Allen, John G; Weidner, Margaret F; Keegan, Kathleen S; Dao, Jennifer H

2014-06-10

417

Protein synthesis is required for caspase activation and induction of apoptosis by bisphosphonate drugs.  

PubMed

The exact mechanisms of action of antiresorptive bisphosphonate drugs remain unclear, although they may inhibit bone resorption by mechanisms that can lead to osteoclast apoptosis. These drugs also cause apoptosis in J774 macrophages, probably as a consequence of inhibition of protein prenylation. However, the molecular pathways that lead to apoptosis are not known. In some cells, apoptosis induced by statins (other inhibitors of protein prenylation) is dependent on protein synthesis. The aim of this study was to further characterize the kinetics and biochemical features of bisphosphonate-induced apoptosis, including the dependence on protein synthesis. Alendronate-induced apoptosis in J774 cells occurred after approximately 16 hr of treatment, although shorter exposures to the drug followed by incubation in bisphosphonate-free medium also committed cells to apoptosis. The appearance of apoptotic cells was associated with the appearance of caspase-3-like activity. Apoptosis induced by bisphosphonate or mevastatin was found to be dependent on protein synthesis because cycloheximide inhibited chromatin condensation, DNA fragmentation and activation of caspase-3-like protease or proteases. Protein synthesis was required for events that lead to commitment to apoptosis but not for the execution phase because cycloheximide did not prevent apoptosis when added >/=15 hr after the start of alendronate treatment. Furthermore, staurosporine-induced caspase-3-like activity and apoptosis in J774 cells could not be prevented by cycloheximide. These observations demonstrate that activation of caspase-3-like proteases and inhibition of commitment to apoptosis by cycloheximide are common features of apoptotic cell death induced by inhibitors of protein prenylation such as bisphosphonates. PMID:9765505

Coxon, F P; Benford, H L; Russell, R G; Rogers, M J

1998-10-01

418

Synthesis and antimicrobial activity of symmetrical two-tailed dendritic tricarboxylato amphiphiles  

E-print Network

Synthesis and antimicrobial activity of symmetrical two-tailed dendritic tricarboxylato amphiphiles dendritic amphiphiles--R2NCONHC((CH2)2COOH)3, 2(n,n), and R2CHNHCONHC((CH2)2COOH)3, 3(n,n), where R = n-CnH2 moiety of an amphiphile, highly hydrophobic headgroups are needed to enable solubility in water. Our

Falkinham, Joseph

419

Stimulation of dopamine synthesis and activation of tyrosine hydroxylase by phorbol diesters in rat striatum  

SciTech Connect

In rat striatal synaptosomes, 4..beta..-phorbol 12-myristate 13-acetate (PMA) and 4 ..beta..-phorbol 12,13-dibutyrate (PDBu), two activators of Ca/sup 2 +/-phospholipid-dependent protein kinase (protein kinase C) increased dopamine (DA) synthesis measured by following the release of /sup 14/CO/sub 2/ from L-(1-/sup 14/C) tyrosine. Maximal stimulation (21-28% increase of basal rate) was produced by 0.5 ..mu..M PMA and 1 ..mu..M PDBu. 4 ..beta..-Phorbol and 4 ..beta..-phorbol 13-acetate, which are not activators of protein kinase C, were ineffective at 1 ..mu..M. PMA did not change the release of /sup 14/CO/sub 2/ from L-(1-/sup 14/C)DOPA. Addition of 1 mM EGTA to a Ca/sup 2 +/-free incubation medium failed to affect PMA stimulation. KCl (60 mM) enhanced DA synthesis by 25%. Exposure of synaptosomes to either PMA or PDBu prior to KCl addition resulted in a more than additive increase (80-100%) of DA synthesis. A similar synergistic effect was observed when the phorbol diesters were combined with either veratridine or d-amphetamine but not with forskolin and dibutyryl cyclic AMP. Pretreatment of striatal synaptosomes with phorbol diesters produced an activation of tyrosine hydroxylase (TH) associated with a 60% increase of the Vmax and a decrease of the Km for the pterine cofactor 6-methyl-5,6,7,8-tetrahydropterin. These results indicate that protein kinase C participates in the regulation of striatal TH in situ and that its activation may act synergistically with DA releasing agents in stimulating DA synthesis. 37 references, 3 figures, 3 tables.

Onali, P.; Olianas, M.C.

1987-03-23

420

Facile Synthesis and Preliminary Structure-Activity Analysis of New Sulfonamides Against Trypanosoma brucei.  

PubMed

The high throughput screening of a library of over 87,000 drug-like compounds against the African sleeping sickness parasite resulted in the discovery of hits with a wide range of molecular diversity. We report here the medicinal chemistry development of one such hit, a tetrahydroisoquinoline disulfonamide, with the synthesis and testing of 26 derivatives against the trypanosome subspecies. Activities in the 2-4 ?M range were revealed with a selectivity index suitable for further development. PMID:24900868

Rashad, Adel A; Jones, Amy J; Avery, Vicky M; Baell, Jonathan; Keller, Paul A

2014-05-01

421

Control of the activity and synthesis of aspartate transcarbamylase in Aerobacter aerogenes  

E-print Network

: (a) Is this organism excreting uracil, uridine, or some pyrimidine intermediate? (b) In isolating a 5-fluorouracil resistant mutant, did the organism become resistant to 5-fluorouridine? (c) Is the mutant feedback modified? It was believed... of MASTER OF SCIENCE December, l97l - Ma)or Sub)ect: Genetics CONTROL OF THE ACTIVITY AND SYNTHESIS OF ASPARTATE TRANSCARBAMYLASE IN AEROBAGTER AEBOGENES A Thesis by Walter Andrew Deutsch Approved as to style and content by: (Chairman of Committee...

Deutsch, Walter Andrew

1971-01-01

422

Combustion 2000  

SciTech Connect

This report presents work carried out under contract DE-AC22-95PC95144 ''Combustion 2000 - Phase II.'' The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: {lg_bullet} thermal efficiency (HHV) {ge} 47% {lg_bullet} NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard) {lg_bullet} coal providing {ge} 65% of heat input {lg_bullet} all solid wastes benign {lg_bullet} cost of electricity {le} 90% of present plants Phase I, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase I also included preliminary R&D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. Phase II, had as its initial objective the development of a complete design base for the construction and operation of a HIPPS prototype plant to be constructed in Phase III. As part of a descoping initiative, the Phase III program has been eliminated and work related to the commercial plant design has been ended. The rescoped program retained a program of engineering research and development focusing on high temperature heat exchangers, e.g. HITAF development (Task 2); a rescoped Task 6 that is pertinent to Vision 21 objectives and focuses on advanced cycle analysis and optimization, integration of gas turbines into complex cycles, and repowering designs; and preparation of the Phase II Technical Report (Task 8). This rescoped program deleted all subsystem testing (Tasks 3, 4, and 5) and the development of a site-specific engineering design and test plan for the HIPPS prototype plant (Task 7). Work reported herein is from: {lg_bullet} Task 2.2.4 Pilot Scale Testing {lg_bullet} Task 2.2.5.2 Laboratory and Bench Scale Activities

None

1999-12-31

423

Lopinavir Impairs Protein Synthesis and Induces eEF2 Phosphorylation via the Activation of AMP-Activated Protein Kinase  

PubMed Central

HIV anti-retroviral drugs decrease protein synthesis, although the underlying regulatory mechanisms of this process are not fully established. Therefore, we investigated the effects of the HIV protease inhibitor lopinavir (LPV) on protein metabolism. We also characterized the mechanisms that mediate the effects of this drug on elongation factor-2 (eEF2), a key component of the translational machinery. Treatment of C2C12 myocytes with LPV produced a dose-dependent inhibitory effect on protein synthesis. This effect was observed at 15 min and was maintained for at least 4 h. Mechanistically, LPV increased the phosphorylation of eEF2 and thereby decreased the activity of this protein. Increased phosphorylation of eEF2 was associated with increased activity of its upstream regulators AMP-activated protein kinase (AMPK) and eEF2 kinase (eEF2K). Both AMPK and eEF2K directly phosphorylated eEF2 in an in vitro kinase assay suggesting two distinct paths lead to eEF2 phosphorylation. To verify this connection, myocytes were treated with the AMPK inhibitor compound C. Compound C blocked eEF2K and eEF2 phosphorylation, demonstrating that LPV affects eEF2 activity via an AMPK-eEF2K dependent pathway. In contrast, incubation of myocytes with rottlerin suppressed eEF2K, but not eEF2 phosphorylation, suggesting that eEF2 can be regulated independent of eEF2K. Finally, LPV did not affect PP2A activity when either eEF2 or peptide was used as the substrate. Collectively, these results indicate that LPV decreases protein synthesis, at least in part, via inhibition of eEF2. This appears regulated by AMPK which can act directly on eEF2 or indirectly via the action of eEF2K. PMID:18712774

Hong-Brown, Ly Q.; Brown, C. Randell; Huber, Danuta S.; Lang, Charles H.

2008-01-01

424

Recombinant Neuregulin 1 Does Not Activate Cardiomyocyte DNA Synthesis in Normal or Infarcted Adult Mice  

PubMed Central

Objectives Neuregulin 1 signaling plays an important role in cardiac trabecular development, and in sustaining functional integrity in adult hearts. Treatment with neuregulin 1 enhances adult cardiomyocyte differentiation, survival and/or function in vitro and in vivo. It has also been suggested that recombinant neuregulin 1?1 (NRG1?1) induces cardiomyocyte proliferation in normal and injured adult hearts. Here we further explore the impact of neuregulin 1 signaling on adult cardiomyocyte cell cycle activity. Methods and Results Adult mice were subjected to 9 consecutive daily injections of recombinant NRG1?1 or vehicle, and cardiomyocyte DNA synthesis was quantitated via bromodeoxyuridine (BrdU) incorporation, which was delivered using mini-osmotic pumps over the entire duration of NRG1?1 treatment. NRG1?1 treatment inhibited baseline rates of cardiomyocyte DNA synthesis in normal mice (cardiomyocyte labelling index: 0.019±0.005% vs. 0.003±0.001%, saline vs. NRG1?1, P<0.05). Acute NRG1?1 treatment did result in activation of Erk1/2 and cardiac myosin regulatory light chain (down-stream mediators of neuregulin signalling), as well as activation of DNA synthesis in non-cardiomyocytes, validating the biological activity of the recombinant protein. In other studies, mice were subjected to permanent coronary artery occlusion, and cardiomyocyte DNA synthesis was monitored via tritiated thymidine incorporation which was delivered as a single injection 7 days post-infarction. Daily NRG1?1 treatment had no impact on cardiomyocyte DNA synthesis in the infarcted myocardium (cardiomyocyte labelling index: 0.039±0.011% vs. 0.027±0.021%, saline vs. NRG1?1, P>0.05). Summary These data indicate that NRG1?1 treatment does not increase cardiomyocyte DNA synthesis (and consequently does not increase the rate of cardiomyocyte renewal) in normal or infarcted adult mouse hearts. Thus, any improvement in cardiac structure and function observed following neuregulin treatment of injured hearts likely occurs independently of overt myocardial regeneration. PMID:25545368

Reuter, Sean; Soonpaa, Mark H.; Firulli, Anthony B.; Chang, Audrey N.; Field, Loren J.

2014-01-01

425

Synthesis and Antimycobacterial Activity of Symmetric Thiocarbohydrazone Derivatives against Mycobacterium bovis BCG  

PubMed Central

In this work, we reported the synthesis and evaluation of antimycobacterial and antifungal activity of a series of thiocarbohydrazone derivatives which are thiacetazone congeners. The target compounds were synthesized in superior yields by reacting thiocarbohydrazide with different aromatic aldehydes and methyl ketones. Compounds 8, 19 and 25 were found to be the most potent derivatives, exhibiting acceptable activity against Mycobacterium bovis BCG compared to thiacetazone and ethambutol as reference substances. Compounds 8, 15 and 25 exhibited the highest activity against Candida albicans. The most active compounds had a completely different aromatic ring system with various electronic, steric and lipophilic natures. This is understandable in light of the fact that carbohydrazone derivatives must undergo a metabolic activation step before exerting their anti-TB activity and different SAR rules govern each one of these two processes. PMID:24250608

Haj Mohammad Ebrahim Tehrani, Kamaleddin; Kobarfard, Farzad; Azerang, Parisa; Mehravar, Maryam; Soleimani, Zohreh; Ghavami, Ghazaleh; Sardari, Soroush

2013-01-01

426

Estrogen receptor ? inhibitor activates the unfolded protein response, blocks protein synthesis, and induces tumor regression.  

PubMed

Recurrent estrogen receptor ? (ER?)-positive breast and ovarian cancers are often therapy resistant. Using screening and functional validation, we identified BHPI, a potent noncompetitive small molecule ER? biomodulator that selectively blocks proliferation of drug-resistant ER?-positive breast and ovarian cancer cells. In a mouse xenograft model of breast cancer, BHPI induced rapid and substantial tumor regression. Whereas BHPI potently inhibits nuclear estrogen-ER?-regulated gene expression, BHPI is effective because it elicits sustained ER?-dependent activation of the endoplasmic reticulum (EnR) stress sensor, the unfolded protein response (UPR), and persistent inhibition of protein synthesis. BHPI distorts a newly described action of estrogen-ER?: mild and transient UPR activation. In contrast, BHPI elicits massive and sustained UPR activation, converting the UPR from protective to toxic. In ER?(+) cancer cells, BHPI rapidly hyperactivates plasma membrane PLC?, generating inositol 1,4,5-triphosphate (IP3), which opens EnR IP3R calcium channels, rapidly depleting EnR Ca(2+) stores. This leads to activation of all three arms of the UPR. Activation of the PERK arm stimulates phosphorylation of eukaryotic initiation factor 2? (eIF2?), resulting in rapid inhibition of protein synthesis. The cell attempts to restore EnR Ca(2+) levels, but the open EnR IP3R calcium channel leads to an ATP-depleting futile cycle, resulting in activation of the energy sensor AMP-activated protein kinase and phosphorylation of eukaryotic elongation factor 2 (eEF2). eEF2 phosphorylation inhibits protein synthesis at a second site. BHPI's novel mode of action, high potency, and effectiveness in therapy-resistant tumor cells make it an exceptional candidate for further mechanistic and therapeutic exploration. PMID:25825714

Andruska, Neal D; Zheng, Xiaobin; Yang, Xujuan; Mao, Chengjian; Cherian, Mathew M; Mahapatra, Lily; Helferich, William G; Shapiro, David J

2015-04-14

427

Synthesis and biological activity of polyalthenol and pentacyclindole analogues.  

PubMed

A series of indole sesquiterpenes analogues of polyalthenol and pentacyclindole have been synthesized starting from ent-halimic acid in order to test their biological activity. These analogues include diverse oxidation levels at the sesquiterpenyl moiety and different functionalization on the indole ring. All synthetic derivatives were tested against a representative panel of Gram positive and Gram negative bacterial strains, and the human solid tumour cell lines A549 (non-small cell lung), HBL-100 (breast), HeLa (cervix), SW1573 (non-small cell lung), T-47D (breast) and WiDr (colon). Overall, the compounds presented activity against the cancer cell lines. The resulting lead, displaying a polyalthenol scaffold, showed GI50 values in the range 1.2-5.7 ?M against all cell lines tested. PMID:24412720

Marcos, Isidro S; Moro, Rosalina F; Costales, Isabel; Basabe, Pilar; Díez, David; Gil, Ana; Mollinedo, Faustino; Pérez-de la Rosa, Fátima; Pérez-Roth, Eduardo; Padrón, José M

2014-02-12

428

Synthesis and Analgesic Activity of Novel Hydrazide and Hydrazine Derivatives  

PubMed Central

The uses of non-steroidal anti-inflammatory drugs (NSAIDs) are limited by a variety of side effects. So research on preparing new analgesic agents is important. According to some reports about the analgesic activity of hydrazide and hydrazine derivatives a new series of these compounds were synthesized in order to obtain new analgesic compounds. The final compounds 10a-10e and 15a-15d were prepared by condensation of corresponding hydrazides 7,8 and 11-14 with different aldehydes 9a-9e. The structures of all synthesized compounds were confirmed by means of FT-IR, 1H-NMR and Mass spectra. All compounds were evaluated for their analgesic activities by abdominal constriction test (writhing test). Most of the synthesized compounds induced significant reduction in the writhing response when compared to control and compound 15 was more potent than mefenamic acid in the writhing test. PMID:24523751

Nassiri Koopaei, Mansur; Assarzadeh, Mohammad Javad; Almasirad, Ali; Ghasemi-Niri, Seyedeh Farnaz; Amini, Mohsen; Kebriaeezadeh, Abbas; Nassiri Koopaei, Nasser; Ghadimi, Maryam; Tabei, Arash

2013-01-01

429

Synthesis and herbicidal activity of substituted pyrazole isothiocyanates.  

PubMed

Isothiocyanates and substituted pyrazoles were combined to form a series of novel isothiocyanates with highly effective herbicidal activity. The target compounds were analyzed by elemental analysis, 1H-NMR, EI-MS and IR spectroscopy. The synthesized compounds, particularly compounds 3-1 and 3-7, exhibited good herbicidal activities against four weeds. The EC(50) values of compound 3-1 against Echinochloa crusgalli L., Cyperus iria L., Dactylis glomerata L., and Trifolium repens L. were 64.32, 65.83, 62.42, and 67.72 µg/mL, respectively. The EC(50) values of compound 3-7 against E. crusgalli L., C. iria L., D. glomerata L., T. repens L. were 65.33, 64.90, 59.41 and 67.41 µg/mL, respectively. Compounds 3-1 and 3-7 may be further optimized as lead compounds for new herbicides. PMID:23075815

Wu, Hua; Feng, Jun-Tao; Lin, Kai-Chun; Zhang, Xing

2012-01-01

430

Synthesis and cytotoxic activity of latentiated derivatives of 3-methyleneoxindole.  

PubMed

Several latentiated derivatives of 3-methyleneoxindole were synthesized and examined for cytotoxic activity. The latentiated forms are represented by three general types which differ in leaving and cleaved groups. All are expected to be converted into 3-methyleneoxindole by bioactivation processes normally occurring in the cell. Two compounds were tested against L-1210 lymphoid leukemia, and six were tested against P-388 lymphocytic leukemia; all were inactive. PMID:560471

Kornet, M J; Thio, A P; Thorstenson, J H

1977-07-01

431

The Structural Basis of Ribosome Activity in Peptide Bond Synthesis  

Microsoft Academic Search

Using the atomic structures of the large ribosomal subunit from Haloarcula marismortui and its complexes with two substrate analogs, we establish that the ribosome is a ribozyme and address the catalytic properties of its all-RNA active site. Both substrate analogs are contacted exclusively by conserved ribosomal RNA (rRNA) residues from domain V of 23S rRNA; there are no protein side-chain

Poul Nissen; Jeffrey Hansen; Nenad Ban; Peter B. Moore; Thomas A. Steitz

2000-01-01

432

Synthesis and anti-norovirus activity of pyranobenzopyrone compounds.  

PubMed

During the last decade, noroviruses have gained media attention as the cause of large scale outbreaks of gastroenteritis on cruise ships, dormitories, nursing homes, etc. Although noroviruses do not multiply in food or water, they can cause large outbreaks because approximately 10-100 virions are sufficient to cause illness in a healthy adult. Recently, it was shown that the activity of acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT1) enzyme may be important in norovirus infection. In search of anti-noroviral agents based on the inhibition of ACAT1, we synthesized and evaluated the inhibitory activities of a class of pyranobenzopyrone molecules containing amino, pyridine, substituted quinolines, or 7,8-benzoquinoline nucleus. Three of the sixteen evaluated compounds possess ED(50) values in the low micrometer range. 2-Quinolylmethyl derivative 3A and 4-quinolylmethyl derivative 4A showed ED(50) values of 3.4 and 2.4 ?M and TD(50) values of >200 and 96.4 ?M, respectively. The identified active compounds are suitable for further modification for the development of anti-norovirus agents. PMID:22513282

Pokhrel, Laxman; Kim, Yunjeong; Nguyen, Thi D T; Prior, Allan M; Lu, Jianyu; Chang, Kyeong-Ok; Hua, Duy H

2012-05-15

433

Synthesis, antioxidant and anticholinesterase activities of novel coumarylthiazole derivatives.  

PubMed

A newly series of coumarylthiazole derivatives containing aryl urea/thiourea groups were synthesized and their inhibitory effects on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) were evaluated. The result showed that all the synthesized compounds exhibited inhibitory activity to both cholinesterases. Among them, 1-(4-(8-methoxy-2-oxo-2H-chromen-3-yl)thiazol-2-yl)-3-(4-chlorophenyl)thiourea (f8, IC50=4.58?M) was found to be the most active compound against AChE, and 1-(4-fluorophenyl)-3-(4-(6-nitro-2-oxo-2H-chromen-3-yl)thiazol-2-yl)urea (e31) exhibited the strongest inhibition against BuChE with IC50 value of 4.93?M, which was 3.5-fold more potent than that of galantamine. The selectivity of f8 and e31 were 2.64 and 0.04, respectively. In addition, the cupric reducing antioxidant capacities (CUPRAC) and ABTS cation radical scavenging abilities of the synthesized compounds were investigated for antioxidant activity. Among them, f8, f4 and f6 (IC50=1.64, 1.82 and 2.69?M, respectively) showed significantly better ABTS cation radical scavenging ability than standard quercetin (IC50=15.49?M). PMID:25706320

Kurt, Belma Zengin; Gazioglu, Isil; Sonmez, Fatih; Kucukislamoglu, Mustafa

2015-04-01

434

Synthesis and anti-influenza activities of novel baicalein analogs.  

PubMed

A series of novel flavones derivatives were synthesized based on modification of the active ingredients of a traditional Chinese medicine Scutellaria baicalensis GEORGI and screened for anti-influenza activity. The synthetic baicalein (flavone) analogs, especially with the B-rings substituted with bromine atoms, were much more potent than oseltamivir or ribavirin against H1N1 Tamiflu-resistant (H1N1 TR) virus and usually with more favorable selectivity. The most promising were 5b, 5c, 6b and 6c, all displaying an 50% effective concentration (EC50) at around 4.0-4.5?µM, and a selective index (SI=50% cytotoxic concentration (CC50)/EC50)>70. For seasonal H3N2-infected influenza virus, both 5a and 5b with SI >17.3 indicated superior to ribavirin. The flavonoids having both not-naturally-occurring bromo-substituted B-rings and appropriate hydroxyls positioning on the A-rings might be critical in determining the activity and selectivity against H1N1-Tamiflu-resistant infected influenza viruses. PMID:24572377

Chung, Shu-Ting; Chien, Pei-Yu; Huang, Wen-Hsin; Yao, Chen-Wen; Lee, An-Rong

2014-01-01

435

Synthesis and anticoagulant activity of polyureas containing sulfated carbohydrates.  

PubMed

Polyurea-based synthetic glycopolymers containing sulfated glucose, mannose, glucosamine, or lactose as pendant groups have been synthesized by step-growth polymerization of hexamethylene diisocyanate and corresponding secondary diamines. The obtained polymers were characterized by gel permeation chromatography, nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. The nonsulfated polymers showed similar results to the commercially available biomaterial polyurethane TECOFLEX in a platelet adhesion assay. The average degree of sulfation after reaction with SO3 was calculated from elemental analysis and found to be between three and four -OSO3 groups per saccharide. The blood-compatibility of the synthetic polymers was measured using activated partial thromboplastin time, prothrombin time, thrombin time, anti-IIa, and anti-Xa assays. Activated partial thromboplastin time, prothrombin time, and thrombin time results indicated that the mannose and lactose based polymers had the highest anticoagulant activities among all the sulfated polymers. The mechanism of action of the polymers appears to be mediated via an anti-IIa pathway rather than an anti-Xa pathway. PMID:25329742

Huang, Yongshun; Shaw, Maureen A; Mullins, Eric S; Kirley, Terence L; Ayres, Neil

2014-12-01

436

Synthesis and anticoagulant activity of the quaternary ammonium chitosan sulfates.  

PubMed

Quaternary ammonium chitosan sulfates with diverse degrees of substitution (DS) ascribed to sulfate groups between 0.52 and 1.55 were synthesized by reacting quaternary ammonium chitosan with an uncommon sulfating agent (N(SO(3)Na)(3)) that was prepared from sodium bisulfite (NaHSO(3)) through reaction with sodium nitrite (NaNO(2)) in the aqueous system homogeneous. The structures of the derivatives were characterized by FTIR, (1)H NMR and (13)C NMR. The factors affecting DS of quaternary ammonium chitosan sulfates which included the molar ratio of NaNO(2) to quaternary ammonium chitosan, sulfated temperature, sulfated time and pH of sulfated reaction solution were investigated in detail. Its anticoagulation activity in vitro was determined by an activated partial thromboplastin time (APTT) assay, a thrombin time (TT) assay and a prothrombin time (PT) assay. Results of anticoagulation assays showed quaternary ammonium chitosan sulfates significantly prolonged APTT and TT, but not PT, and demonstrated that the introduction of sulfate groups into the quaternary ammonium chitosan structure improved its anticoagulant activity obviously. The study showed its anticoagulant properties strongly depended on its DS, concentration and molecular weight. PMID:21996571

Fan, Lihong; Wu, Penghui; Zhang, Jinrong; Gao, Song; Wang, Libo; Li, Mingjia; Sha, Mingming; Xie, Weiguo; Nie, Min

2012-01-01

437

Synthesis and evaluation of antiproliferative activity of a novel series of hydroxychavicol analogs.  

PubMed

We have recently demonstrated that hydroxychavicol is a major constituent and the most active biophenolic of Piper betel leaves with significant antiproliferative activity in the micro molar range. Herein we present the design, synthesis and evaluation of fifteen novel hydroxychavicol analogs with varying antiproliferative activities in cancer cell lines from two representative tissue types, namely, the prostate and cervix that show very encouraging results compared to the parent compounds. Our long range goal is to develop a structure-activity guided relationship to gain mechanistic insights into novel molecular targets of this class of bioactive molecules for rational drug development. Cytotoxicity-guided experimentation on these novel analogs yielded the following structural factors as the key activity regulators: 1) unlike the hydroxyl substituent at position-4, the position-3 hydroxyl is vital for enhanced activity 2) acetoxyl groups are dispensable for activity as corroborated earlier by others 3) allylic double bonds at 2'C-3'C serve to positively influence antiproliferative activity 4) long saturated side chains at 1'-position negatively regulate antiproliferative activity and 5) maneuvering position-4 with a benzyl group positively impacted the biological activity profile. Most amphiphilic compounds showed moderate to good therapeutic potential as expected on the basis of medicinal chemistry principles. Intriguingly, the most active compound with ten-fold higher activity than the parent molecule was realized by sheer serendipity to employ a silica gel based rearrangement that was further explored using nuclear magnetic resonance spectroscopy and density functional theory calculations. This is the first report to describe strategies for optimal synthesis of a novel series of 15 analogs based upon hydroxychavicol, a simple phytochemical of immense anticancer potential. PMID:24508612

Yadav, Yogesh; Owens, Eric A; Sharma, Vibhuti; Aneja, Ritu; Henary, Maged

2014-03-21

438

Synthesis and photocatalytic activity of electrospun niobium oxide nanofibers  

SciTech Connect

Graphical abstract: Different morphologies are obtained for the electrospun niobium oxide nanofibers with different phase structures. The nanofibers of the two phase structures present different band gap value and the light absorption. Hexagonal phase nanofibers show better photocatalytic activity compared with the orthorhombic nanofibers. Highlights: ? Niobium oxide nanofibers of two phase structures were fabricated by electrospinning. ? Photocatalytic properties of the niobium oxide nanofibers were first explored. ? Nanofibers of different phase structures showed different photocatalytic activities. ? Reasons for the differences in the photocatalysis were carefully discussed. - Abstract: Niobium oxide (Nb{sub 2}O{sub 5}) nanofibers have been synthesized by sol–gel based electrospinning technique. Pure hexagonal phase (H-Nb{sub 2}O{sub 5}) and orthorhombic phase (O-Nb{sub 2}O{sub 5}) nanofibers were obtained by thermally annealing the electrospun Nb{sub 2}O{sub 5}/polyvinylpyrrolidone composite fibers in air at 500 °C and 700 °C, respectively. The fibers were characterized using the X-ray diffraction, scanning electron microscopy, specific surface area analyzer and UV–vis diffuse reflectance spectroscopy. Photocatalytic activities of the obtained nanofibers were evaluated depending on the degradation of methyl orange. The results indicate that the heat-treatment temperature, the crystalline structure and the morphology affected the physical and chemical properties of the as-prepared Nb{sub 2}O{sub 5} nanofibers. The H-Nb{sub 2}O{sub 5} nanofibers obtained at lower temperature showed better potential for the application as a promising photocatalyst.

Qi, Shishun [Institute of Electro Ceramics and Devices, School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Zuo, Ruzhong, E-mail: piezolab@hfut.edu.cn [Institute of Electro Ceramics and Devices, School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Liu, Yi [Institute of Electro Ceramics and Devices, School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Wang, Yu [Department of Applied Physics and Materials Research Center, The Hong Kong Polytechnic University, Hong Kong (China)

2013-03-15

439

Multisite phosphorylation of oxysterol-binding protein regulates sterol binding and activation of sphingomyelin synthesis  

PubMed Central

The endoplasmic reticulum (ER)-Golgi sterol transfer activity of oxysterol-binding protein (OSBP) regulates sphingomyelin (SM) synthesis, as well as post-Golgi cholesterol efflux pathways. The phosphorylation and ER-Golgi localization of OSBP are correlated, suggesting this modification regulates the directionality and/or specificity of transfer activity. In this paper, we report that phosphorylation on two serine-rich motifs, S381-S391 (site 1) and S192, S195, S200 (site 2), specifically controls OSBP activity at the ER. A phosphomimetic of the SM/cholesterol-sensitive phosphorylation site 1 (OSBP-S5E) had increased in vitro cholesterol and 25-hydroxycholesterol–binding capacity, and cholesterol extraction from liposomes, but reduced transfer activity. Phosphatidylinositol 4-phosphate (PI(4)P) and cholesterol competed for a common binding site on OSBP; however, direct binding of PI(4)P was not affected by site 1 phosphorylation. Individual site 1 and site 2 phosphomutants supported oxysterol activation of SM synthesis in OSBP-deficient CHO cells. However, a double site1/2 mutant (OSBP-S381A/S3D) was deficient in this activity and was constitutively colocalized with vesicle-associated membrane protein–associated protein A (VAP-A) in a collapsed ER network. This study identifies phosphorylation regulation of sterol and VAP-A binding by OSBP in the ER, and PI(4)P as an alternate ligand that could be exchanged for sterol in