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1

Microwave activated combustion synthesis of titanium aluminides  

Microsoft Academic Search

TiAl and Ti3Al titanium aluminide intermetallic compounds were synthesized using a microwave activated combustion synthesis (MACS) method and compared to thermal activation (TACS) and conventional combustion (CS) methods. MACS represents an example of our “synergistic processing” philosophy, wherein the useful attributes of microwave processing and combustion synthesis are used synergistically. Thermodynamic calculations indicated activation was required for combustion synthesis to

J. R. Jokisaari; S. Bhaduri

2005-01-01

2

Pulsed current activated combustion synthesis and consolidation of nanostructured ReSi 1.75  

Microsoft Academic Search

Dense nanostructured ReSi1.75 was synthesized by the pulsed current activated combustion synthesis (PCACS) method within 2 min in one step from mechanically\\u000a activated powders of Re and 1.75 Si. Simultaneous combustion synthesis and densification were accomplished under the combined\\u000a effects of a pulsed current and mechanical pressure. Highly dense ReSi1.75 was produced under simultaneous application of 80 MPa of pressure

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

2009-01-01

3

Pulsed current activated combustion synthesis and consolidation of ultrafine NbSi 2 from mechanically activated powders  

Microsoft Academic Search

Dense ultrafine NbSi2 was synthesized using the pulsed current activated combustion synthesis (PCACS) method within 2 min and in one step from\\u000a mechanically activated powders of Nb and 2Si. Simultaneous combustion synthesis and densification were accomplished under\\u000a the combined effects of a pulsed current and mechanical pressure. Highly dense NbSi2 with a relative density of up to 98 % was

In-Yong Ko; Byung-Ryang Kim; Kee-Seok Nam; Byung-Moon Moon; Byung-Soo Lee; In-Jin Shon

2009-01-01

4

Combustion synthesis and nanomaterials  

Microsoft Academic Search

The recent developments and trends in combustion science towards the synthesis of nanomaterials are discussed. Different modifications made to conventional combustion approaches for preparation of nanomaterials are critically analyzed. Special attention is paid to various applications of combustion synthesized nanosized products.

Singanahally T. Aruna; Alexander S. Mukasyan

2008-01-01

5

Simultaneous pulsed current activated combustion synthesis and densification of NbSi 2–SiC composite  

Microsoft Academic Search

Dense ultrafine NbSi2–SiC composite was synthesized by the pulsed current activated combustion synthesis (PCACS) method within 3min in one step from mechanically activated powders of NbC and 3Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense NbSi2–SiC composite with relative density of up to 97% was produced under

In-Jin Shon; Hyun-Kuk Park; Hwan-Cheol Kim; Jin-Kook Yoon; In-Yong Ko

2008-01-01

6

Simultaneous synthesis and consolidation of nanostructured TaSi 2–Si 3N 4 composite by pulsed current activated combustion  

Microsoft Academic Search

Dense nanostructured 4TaSi2–Si3N4 composite was synthesized by pulsed current activated combustion synthesis (PCACS) method within 3min in one step from mechanically activated powders of TaN and Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense 4TaSi2–Si3N4 composite with relative density of up to 98% was produced under simultaneous

Hyun-Kuk Park; Jeong-Hwan Park; Jin-Kook Yoon; In-Yong Ko; Jung-Mann Doh; In-Jin Shon

2009-01-01

7

Combustion synthesis of fullerenes  

SciTech Connect

This paper reports the isolation of C{sub 60} and C{sub 70} from combustion soot that is produced in high-temperature, low-pressure premixed flat flames. A critical parameter for high fullerene yields in combustion appears to be a very high flame temperature. Equilibrium calculations indicate that low pressures are important, but the experimental evidence is not clear at this time. Combustion synthesis yields fullerenes with a C{sub 70}/C{sub 60} ratio of about 40%, as compared with the 12% reported for electric-arc-generated fullerenes. The overall yields from carbon are very low (ca. 0.03%) but the soot studied had been produced in flames that were in no way optimized for fullerene production.

Mckinnon, J.T.; Bell, W.L. (TDA Research, Inc., Wheat Ridge, CO (US)); Barkley, R.M. (Cooperative Inst. for Research on Environmental Sciences, Boulder, CO (US))

1992-01-01

8

Rapid consolidation of nanocrystalline NbSi 2 Si 3 N 4 composites by pulsed current activated combustion synthesis  

Microsoft Academic Search

A dense nanostructured 4NbSi2-Si3N4 composite was synthesized by a Pulsed Current Activated Combustion Synthesis (PCACS) method within 3 minutes in one step\\u000a from mechanically activated powders of NbN and Si. Simultaneous combustion synthesis and densification were accomplished under\\u000a the combined effects of a pulsed current and mechanical pressure. A highly dense 4NbSi2-Si3N4 composite with a relative density of up to

In-Yong Ko; Jeong-Hwan Park; Kee-Seok Nam; In-Jin Shon

2010-01-01

9

Properties and consolidation of nanocrystalline WSi 2–SiC composite from mechanically activated powders by pulsed current activated combustion synthesis  

Microsoft Academic Search

Dense nanostructured WSi2–SiC composite was synthesized by pulsed current activated combustion synthesis method within 2min in one step from mechanically activated powders of WC and 3Si. Simultaneous combustion synthesis and consolidation were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense WSi2–SiC with relative density of up to 99.8% was produced under simultaneous application of

In-Jin Shon; Jeong-Hwan Park; In-Yong Ko; Jung-Mann Doh; Jin-Kook Yoon; Kee-Seok Nam

2011-01-01

10

Cost effective combustion synthesis of silicon nitride  

Microsoft Academic Search

The feasibility of mechanical activation (MA)-assisted combustion synthesis (CS) of Si3N4 was demonstrated by using Si\\/NH4Cl as reactants under a nitrogen pressure of 2MPa. MA treatment significantly enhances the reactivity of Si powders, which effectively promotes the nitridation of silicon. The NH4Cl had the same effect as Si3N4 diluent in preventing extensive melting of Si within the combustion wave zone.

Yi-Xiang Chen; Jiang-Tao Li; Ji-Sheng Du

2008-01-01

11

Combustion synthesis method and products  

DOEpatents

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

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

1993-01-01

12

ZrSi 2–SiC composite obtained from mechanically activated ZrC + 3Si powders by pulsed current activated combustion synthesis  

Microsoft Academic Search

Dense nanostructured ZrSi2–SiC composite was simultaneously synthesized and consolidated by pulsed current activated combustion synthesis (PCACS) within 2min in one step from mechanically activated powders of ZrC and 3Si. Highly dense ZrSi2–SiC with relative density of up to 97% was produced under simultaneous application of a pressure of 60MPa and the pulsed current. The average grain size and mechanical properties

In-Yong Ko; Jeong-Hwan Park; Jin-Kook Yoon; Kee-Seok Nam; In-Jin Shon

2010-01-01

13

Combustion Synthesis of Nanostructures  

NASA Astrophysics Data System (ADS)

Novel carbon and inorganic 1D nanostructures were prepared by combustion of metal-polytetrafluoroethylene (PTFE) systems in a calorimetric bomb. The high carbon yield from silicon-containing PTFE starting materials is due to the production and volatility of SiF4.

Huczko, A.; Lange, H.; Chojecki, G.; Cudzi??o, S.; Zhu, Y. Q.; Walton, D. R. M.; Kroto, H. W.; Presz, A.; Diduszko, R.

2002-10-01

14

Gravity Effects on Combustion Synthesis of Glasses.  

National Technical Information Service (NTIS)

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

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

2000-01-01

15

Novel approaches to solution-combustion synthesis of nanomaterials  

Microsoft Academic Search

Solution-combustion is an attractive approach to synthesis of nanomaterials for a variety of applications, including catalysts,\\u000a fuel cells, and biotechnology. In this paper, several novel methods based on the combustion of a reactive solution are presented.\\u000a These methods include self-propagating sol-gel combustion and combustion of impregnated inert and active supports. It was\\u000a demonstrated that, based on the fundamental understanding of

A. S. Mukasyan; P. Dinka

2007-01-01

16

Study of Impurities in Combustion Synthesis Systems.  

National Technical Information Service (NTIS)

This investigation is directed toward a detailed understanding of the nature of the evolution of solid and gaseous impurities during the Combustion Synthesis (Self-Propagating High Temperature Synthesis) of ceramic materials. The identities and amounts of...

L. J. Kecskes A. Niiler

1988-01-01

17

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

18

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

19

Combustion synthesis of Dy3+, Eu3+ activated Na2X(PO4)F (X = Mg, Ca, Sr) phosphors for lamp industry  

NASA Astrophysics Data System (ADS)

In this paper we have reported synthesis and characterization of Dy3+ and Eu3+ activated Na2Mg(PO4)F, Na2Ca(PO4)F and Na2Sr(PO4)F phosphors. These phosphors were prepared by combustion synthesis and characterized by XRD and photoluminescence techniques. Dy3+ ion gives PL emission in blue and yellow region of the visible spectrum by 385 nm excitation of the LED excitation and Eu3+ ion gives PL emission in the red region of visible spectrum under 251 nm UV-excitation (Hg excitation), respectively. Therefore, above prepared Dy3+ activated phosphors are more applicable for white LED and Eu3+ activated phosphors are more applicable for Hg excitation lamp. Hence prepared, Dy3+ and Eu3+ activated Na2X(PO4)F (X = Ca, Sr, Mg) phosphors by combustion method are very potential application in the field of lamp industry.

Dhoble, S. J.; Pawade, V. B.; Shinde, K. N.

2010-10-01

20

Combustion and plasma synthesis of high-temperature materials  

SciTech Connect

Various papers on combustion and plasmas synthesis of high-temperature materials are presented. Individual topics addressed include: self-propagation high-temperature synthesis, modeling and numerical computation of a nonsteady SHS process, new modes of quasi-periodic burning in combustion synthesis, combustion synthesis of intermetallic compounds, combustion synthesis of nickel aluminides, advanced ceramics via SHS, simultaneous combustion synthesis and densification of AlN, combustion synthesis of oxide-carbide composites. Also discussed are: combustion synthesis in the Ti-C-Ni-Al systems, combustion synthesis dynamics modeling, shock-induced reaction synthesis-assisted processing of ceramics, shock consolidation of combustion-synthesized ceramics, thermal plasma synthesis ceramic powders and coatings, formation of refractory aerosol particles, silica particle formation using the counterflow diffusion flame burner, synthesis of Si, SiC, and Si3N4 powders under high number density conditions.

Munir, Z.A.; Holt, J.B. (California, University, Davis (United States) Lawrence Livermore National Laboratory, Livermore, CA (United States))

1990-01-01

21

Combustion synthesis of YAG:Ce and related phosphors  

NASA Astrophysics Data System (ADS)

YAG:Ce is an important phosphor having applications in various fields ranging from solid state lighting to scintillation detectors. YAG phosphors doped with activators are mainly synthesized by solid state reaction techniques that require high sintering temperatures (above 1500°C) to eliminate YAM and YAP phases. Though several soft chemical routes have been explored for synthesis of YAG, most of these methods are complex and phase pure materials are not obtained in one step, but prolonged annealing at temperatures around 1000°C or above become necessary. One step combustion synthesis of YAG:Ce3+ and related phosphors carried out at 500°C furnace temperature is reported here. Activation with Ce3+ could be achieved during the synthesis without taking recourse to any post-combustion thermal treatment. LEDs prepared from the combustion synthesized YAG:Ce3+, exhibited properties comparable to those produced from the commercial phosphor.

Gupta, K. V. K.; Muley, A.; Yadav, P.; Joshi, C. P.; Moharil, S. V.

2011-11-01

22

The combustion synthesis of iron group metal fine powders  

NASA Astrophysics Data System (ADS)

The new approach has been developed for the synthesis of nickel (Ni), cobalt (Co) and iron (Fe) powders from the appropriate oxides by the solid combustion method. The reduction was made by sodium azide (NaN3) at the presence of carbon in the argon atmosphere. The variation of combustion temperature and velocity was performed by using alkali metal salt as an inert diluent. The values of combustion parameters were measured and also the temperature distribution in a combustion wave are obtained. The geometric sizes of reactionary zones and the activation energy of the process were estimated. The optimum conditions for single-phase metal powder synthesis were found. Powders fabricated in this way had cubic structure and particles size about 0.5-2.0?m for Ni, Co and 1-3?m for Fe. In a number of cases the formation of spherical particles with the average size about 5-15?m were observed.

Lee, J. H.; Nersisyan, H. H.; Won, C. W.

2004-01-01

23

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

24

Combustion Synthesis in a Mechanically Activated Mg-C-TiO2-H3BO3 System  

NASA Astrophysics Data System (ADS)

TiC-TiB2 nanocomposite was fabricated by self-propagating high-temperature synthesis (SHS) of mechanically milled powders. H3BO3, TiO2, Mg, and C as starting materials were milled for 0.5, 1, and 3 h then pressed to form pellets. Green compacts were placed in a tube furnace which had been preheated to three different temperatures of 900, 1000, and 1100 °C with argon atmosphere, for the synthesis. The prepared samples were studied by XRD, SEM, and TEM analytical technique. TiC and TiB2 were not formed during milling process. According to the XRD patterns of synthesized samples, ball milling for 0.5 h is the optimum time for mechanical activation of the mixed powders. Further investigation indicated that 900 °C is the best temperature for the synthesis of this mixture. By using Williamson-Hall method, the average crystallite sizes of TiB2 and TiC were calculated 40.7 and 75.6 nm, respectively, which were confirmed by TEM images.

Aminikia, B.; Tayebifard, S. A.; Youzbashi, A. A.

2012-06-01

25

Activated combustion features in the Mo-Si-C-promoter system and synthesis of MoSi{sub 2}-SiC composite powders  

SciTech Connect

Opportunities on combustion synthesizing the MoSi{sub 2}-SiC ceramic composites in a wide range of compositions under the chemical activated mode were studied. Molybdenum, silicon powders and carbon black were used as initial reagents, and Teflon was used as an activating additive. It was established that Teflon displays a dual (kinetic and thermal) impact on the interaction between reagents. The phasic character of the combustion process evolution, being characterized by low- and high-temperature regimes, was revealed. The end-products were subjected to SEM, XRD and chemical analyses.

Hambartsumyan, A.A. [Laboratory of Kinetics of SHS Processes, A.B. Nalbandyan Institute of Chemical Physics, National Academy of Sciences, P. Sevak str. 5/2, Yerevan 0014 (Armenia); Khachatryan, H.L. [Department of Chemical Physics, Yerevan State University, A. Manukyan str. 1, Yerevan 0025 (Armenia)], E-mail: hayk@ichph.sci.am; Harutyunyan, A.B. [Laboratory of Kinetics of SHS Processes, A.B. Nalbandyan Institute of Chemical Physics, National Academy of Sciences, P. Sevak str. 5/2, Yerevan 0014 (Armenia); Kharatyan, S.L. [Laboratory of Kinetics of SHS Processes, A.B. Nalbandyan Institute of Chemical Physics, National Academy of Sciences, P. Sevak str. 5/2, Yerevan 0014 (Armenia); Department of Chemical Physics, Yerevan State University, A. Manukyan str. 1, Yerevan 0025 (Armenia)

2007-12-04

26

Combustion synthesis of novel boron carbide  

NASA Astrophysics Data System (ADS)

The solid-state boron carbide is one of the hardest materials known, ranking third behind diamond and cubic boron nitride. Boron carbide (BxCx) enriched in the 10B isotope is used as a control rod material in the nuclear industry due to its high neutron absorption cross section and other favorable physico-chemical properties. Conventional methods of preparation of boron carbide are energy intensive processes accompanied by huge loss of boron. Attempts were made at IGCAR Kalpakkam to develop energy efficient and cost effective methods to prepare boron carbide. The products of the gel combustion and microwave synthesis experiments were characterized for phase purity by XRD. The carbide formation was ascertained using finger-print spectroscopy of FTIR. Samples of pyrolized/microwave heated powder were characterized for surface morphology using SEM. The present work shows the recent advances in understanding of structural and chemical variations in boron carbide and their influence on morphology, optical and vibrational property results discussed in details.

Harini, R. Saai; Manikandan, E.; Anthonysamy, S.; Chandramouli, V.; Eswaramoorthy, D.

2013-02-01

27

Combustion synthesis of transition-metal nitrides  

SciTech Connect

A new process, using sodium azide (NaN/sub 3/) as a solid source of nitrogen, for the production of transition-metal nitride materials is presented. For example, a -325 mesh Ti powder with average particle size of 22..mu.. was mixed with NaN/sub 3/ powder in a glass jar on a vibratory mill for 5 minutes. The powder was cold-pressed into cylinders or poured into quartz crucibles. The quartz crucible containing the powder was placed in a glove box which was pumped down to approx. 200 ..mu... After back-filling with nitrogen to one atmosphere the powder was ignited by a tungsten coil which was in contact with the surface of the powder. The combustion temperature was estimated to be at least 2200/sup 0/C at the maximum point. A thick cloud of smoke, consisting of Na vapor and other volatile gases from the initial powders, evolved during reaction. The reaction product is a loose, friable powder that is easily removed from the quartz crucible. The average grain size of the TiN powder is 10..mu.. as shown in a SEM micrograph. X-ray-diffraction analysis verified the powder to be TiN with no trace of Ti metal. The advantages of this process are high-purity products, high rates of synthesis, and energy efficient since no furnaces are required.

Holt, J.B.; Kingman, D.D.

1983-02-14

28

Combustion synthesis of TiO 2 nanoparticles as photocatalyst  

Microsoft Academic Search

This paper describes a new type of combustion synthesis of metal oxide nanoparticles, in which the adiabatic flame temperature of the solid phase reaction is beyond the boiling point of the product, and its implementation for the synthesis of titanium dioxide as photocatalyst. In this study, raw materials comprising titanium particles of different sizes and sodium perchlorate were intensively mixed

Yasuaki Kitamura; Noriyuki Okinaka; Tamaki Shibayama; Orlando Omar Prieto Mahaney; Daisuke Kusano; Bunsho Ohtani; Tomohiro Akiyama

2007-01-01

29

Gravitational Effects on Combustion Synthesis of Advanced Porous Materials.  

National Technical Information Service (NTIS)

Combustion Synthesis (self-Propagating high-temperature synthesis-(SHS)) of porous Ti-TiB(x), composite materials has been studied with respect to the sensitivity to the SHS reaction parameters of stoichiometry, green density, gasifying agents, ambient pr...

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

2000-01-01

30

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

2010-04-26

31

Effects of gravity and electric current in combustion synthesis  

NASA Astrophysics Data System (ADS)

Combustion synthesis (CS) has been a popular research topic in the last 3 decades. Interest in the process was motivated by the attractive properties and possibilities of CS, compared to conventional materials processing and synthesis techniques. Although, CS is a fairly simple process, it involves quite complex mechanisms that occur simultaneously at rapidly changing high temperatures in the short duration (several seconds) of the combustion reaction. Along with other parameters, gravity plays an important role in CS. Therefore, various investigations have been performed in the last decade with the aim of understanding the effects of gravity in several reduced gravity platforms. However, a deeper fundamental comprehension of the effects of gravity on non-equilibrium mechanisms of CS is needed. Similarly, electric current activation has been introduced and investigated as a processing parameter to CS for more than ten years. It presents several advantages to CS, by overcoming kinetic and thermodynamic limitations as well as providing control over the properties of the combustion reaction and of the final product. Effects of an electric current have not been previously investigated under reduced gravity conditions. The present investigation utilized a chemical oven technique, in which the system under investigation is embedded in a mixture of potentially exothermic powder mixture. It focused on answering essential questions by separating different mechanisms and understanding fundamental aspects of gravity and electric current in CS. The phenomena investigated included reactive settling, dissolution and precipitation, and reactive liquid metal flow. Eventually, this knowledge could contribute towards synthesizing materials that cannot be formed in terrestrial gravity.

Unuvar, Cosan

32

One Step Combustion Synthesis Of YAG:Ce Phosphor For Solid State Lighting  

NASA Astrophysics Data System (ADS)

YAG:Ce is an important phosphor having applications in various fields ranging from solid state lighting to scintillation detectors. YAG phosphors doped with activators are mainly synthesized by solid state reaction techniques that require high sintering temperatures (above 1500°C) to eliminate YAM and YAP phases. Though several soft chemical routes have been explored for synthesis of YAG, most of these methods are complex and phase pure materials are not obtained in one step, but prolonged annealing at temperatures around 1000 C or above becomes necessary. One step combustion synthesis of YAG:Ce3+ and related phosphors carried out at 500 C furnace temperature is reported here. Activation with Ce3+ could be achieved during the synthesis without taking recourse to any post-combustion thermal treatment. LEDs prepared from the combustion synthesized YAG:Ce3+, exhibited properties comparable to those produced from the commercial phosphor.

Yadav, Pooja; Gupta, K. Vijay Kumar; Muley, Aarti; Joshi, C. P.; Moharil, S. V.

2011-10-01

33

Active control of combustion instabilities  

NASA Astrophysics Data System (ADS)

A theoretical analysis of active control of combustion thermo-acoustic instabilities is developed in this dissertation. The theoretical combustion model is based on the dynamics of a two-phase flow in a liquid-fueled propulsion system. The formulation is based on a generalized wave equation with pressure as the dependent variable, and accommodates all influences of combustion, mean flow, unsteady motions and control inputs. The governing partial differential equations are converted to an equivalent set of ordinary differential equations using Galerkin's method by expressing the unsteady pressure and velocity fields as functions of normal mode shapes of the chamber. This procedure yields a representation of the unsteady flow field as a system of coupled nonlinear oscillators that is used as a basis for controllers design. Major research attention is focused on the control of longitudinal oscillations with both linear and nonlinear processes being considered. Starting with a linear model using point actuators, the optimal locations of actuators and sensors are developed. The approach relies on the quantitative measures of the degree of controllability and component cost. These criterion are arrived at by considering the energies of the system's inputs and outputs. The optimality criteria for sensor and actuator locations provide a balance between the importance of the lower order (controlled) and the higher (residual) order modes. To address the issue of uncertainties in system's parameter, the minimax principles based controller is used. The minimax corresponds to finding the best controller for the worst parameter deviation. In other words, choosing controller parameters to minimize, and parameter deviation to maximize some quadratic performance metric. Using the minimax-based controller, a remarkable improvement in the control system's ability to handle parameter uncertainties is achieved when compared to the robustness of the regular control schemes such as LQR and LQG. Since the observed instabilities are harmonic, the concept of "harmonic input" is successfully implemented using a parametric controller to eliminate the thermo-acoustic instability. This control scheme relies on the determination of a phase-shift to maximize the energy dissipation and a controller gain to assure stability and minimize a pre-specified performance index. The closed loop control law design is based on finding an optimal phase angle such that the heat release produced by secondary oscillatory fuel injection is out of phase with the mode's pressure oscillations, thus maximizing energy dissipation, and on finding the limits on the controller gain that ensures system stability. The optimal gains are determined using ITA, ISE, ITAE performance indices. Simulations show successful implementation of the proposed technique.

Al-Masoud, Nidal A.

34

Combustion Synthesis Of Ultralow-density Nanoporous Gold Foams  

SciTech Connect

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

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

2008-01-01

35

Combustion synthesis of gadolinia doped ceria powder  

Microsoft Academic Search

Gadolinia doped ceria (GDC) powders with different gadolinia content in the range 0–15mol% were prepared by solution combustion route using a solution of cerium nitrate, gadolinium nitrate and citric acid. In the experiments citric acid to metal nitrate molar ratio was taken as 5:6. The solution on heating formed gel before combustion. Thermal analysis of the gel precursors containing different

T. Mahata; G. Das; R. K. Mishra; B. P. Sharma

2005-01-01

36

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

PubMed

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

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

2010-05-07

37

Combustion synthesis of advanced materials: Studies of the influence of gravity and reaction kinetics  

NASA Astrophysics Data System (ADS)

Combustion synthesis is an attractive technique to synthesize a wide variety of advanced materials that include powders and near-net shape products of ceramics, intermetallics, composites and functionally gradient materials. It is also considered to be a valuable method for space applications, because of low energy requirements and simple equipment. However, it is necessary to understand how microgravity influences the combustion mechanism and properties of the synthesized materials. In this work, combustion synthesis experiments were conducted both in normal and in low-gravity conditions, using a unique setup designed and developed for this purpose. Microgravity experiments were done in NASA Lewis Research Center using Drop Tower which provided 2.2 s of 10-5 g level, as well as on-board DC-9 aircraft (20 s of 10-2 g). It was clearly demonstrated that gravity plays an important role during combustion synthesis. It significantly influences both the combustion and structure formation processes. It was also shown that microgravity conditions allow the synthesis of materials with improved micro- and macrostructures. The study of chemical reaction kinetics in combustion synthesis systems is of critical importance. The measurement of kinetic parameters (especially activation energy) and a comparison with known elementary processes provides an insight into the controlling step of the mechanism. In this work, a computer-assisted electrothermography method was developed to determine the intrinsic kinetics of reactions under conditions similar to those realized during combustion synthesis of materials. This technique was applied to investigate the kinetics and other features associated with the reaction of titanium with nitrogen at 1 atm pressure. It was shown that at temperatures below the melting point of titanium, the reaction follows parabolic rate law. The obtained activation energy value is in good agreement with literature data. At higher temperatures, however, the reaction mechanism is different due to faster diffusion of nitrogen in molten titanium. Mathematical treatment of experimentally obtained heat generation curves allowed to estimate the diffusion coefficient of nitrogen in molten titanium. In addition, the reaction rate was shown to depend strongly on the heating rate.

Pelekh, Aleksey Yevgeuyevich

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. 6 figures.

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

1991-01-29

39

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

40

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. 5 figs.

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

1988-12-12

41

Combustion synthesis of Ga 2 O 3 nanoparticles  

Microsoft Academic Search

Nanophase of Ga2O3 has potentially important applications in photocatalysis. We report the synthesis of nanophase of the metastable ?- and stable\\u000a ?-Ga2O3 and demonstrate that it is possible to prepare a continuously varying mixture starting from the pure metastable ?- to the\\u000a pure ?-phase. This is achieved by employing a facile and reliable combustion route, using urea as a fuel.

V. Srihari; V. Sridharan; H. K. Sahu; G. Raghavan; V. S. Sastry; C. S. Sundar

2009-01-01

42

Ultra-high speed neutron diffraction studies of combustion synthesis  

NASA Astrophysics Data System (ADS)

In-situ neutron diffraction at time resolutions in the range 380 900 ms recorded on the instrument D20 at the Institut Laue-Langevin have been used to capture the reaction mechanisms during the furnace ignited combustion synthesis of a range of MnAXn-1 phases (M—early transition metal, A—group IIIA or IVA element, X—either C or N), intermetallic compounds (Ti5Si3) and intermetallic compound-refractory carbide composites (Ni Al Ti C). The sequence of diffraction patterns reveals great complexity. Some reactions occur completely in the solid state and others involve a transient liquid phase(s). In all but binary mixtures, transient solid phases that may persist for as little as a few seconds were observed. Data analysis methods are illustrated which allow the determination of: (i) the sequence of phases and reaction mechanism, (ii) the crystal structure, atomic substitutions etc of the phases present, (iii) the ‘trigger’ mechanism for the self-sustaining reaction, (iv) the reaction kinetics and activation energy for growth of the product phase (via quantitative phase analysis using Rietveld refinement scale factors and a non-isothermal Avrami kinetic equation), (v) the average sample temperature (via thermal expansion/contraction of known phases) and the formation enthalpy of the product phase (via excursions in the sample temperature).

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

2006-11-01

43

Combustion synthesis of silicon carbide assisted by a magnesium plus polytetrafluoroethylene mixture  

SciTech Connect

In this study, the use of SiC combustion synthesis for immobilization of {sup 14}C was considered. Due to the low exothermicity of the reaction between silicon and graphite, a highly exothermic mixture (magnesium and polytetrafluoroethylene) was used both as a chemical oven and activate additive in the mixture. With this configuration the reaction between graphite and silicon was initiated and propagated on the whole sample. The self-propagating high temperature synthesis samples were characterized by using scanning electron microscopy and X-ray diffraction.

Ayral, R.M. [Institut Charles Gerhardt Montpellier, PMOF-UM2-CNRS Pl. E. Bataillon, 34095 Montpellier Cedex 5 (France); Rouessac, F., E-mail: florence.rouessac@univ-montp2.fr [Institut Charles Gerhardt Montpellier, PMOF-UM2-CNRS Pl. E. Bataillon, 34095 Montpellier Cedex 5 (France); Massoni, N. [CEA, DEN, DTCD, 30207 Bagnols-sur-Ceze (France)

2009-11-15

44

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

45

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.

46

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

47

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

48

The laser-induced combustion synthesis of iron-oxide nanocomposite coatings on aluminum  

NASA Astrophysics Data System (ADS)

The potential of synthesizing nano-structure coatings on aluminum cast alloys during laser surface engineering has been explored based on combustion synthesis and underlying rapid-solidification principles. The roles of cooling rate, heterogeneous nucleation site density, and grain multiplication in structure refinements are well known. By combining combustion synthesis and laser surface engineering, refinement to nanostructure is envisioned.

Nayak, S.; Dahotre, Narendra B.

2002-09-01

49

Combustion synthesis of porous materials for bone replacement.  

PubMed

Production of highly porous composite materials by traditional materials processing is limited by difficult processing techniques. However, combustion or self-propagating high-temperature synthesis (SHS) allows many porous ceramic, intermetallic, glass, and metallic systems to be formed with relative ease. Examination of the SHS reaction parameters that control the extent of porosity further increases the feasibility of producing novel composites for such uses as bone implant applications. Combustion Synthesis of porous Ti-TiBx and NiTi composite materials have been studied with respect to the sensitivity to the SHS reaction parameters of stoichiometry, green density, gasifying agents, and gravity. The main objective of this research program is to engineer the required porosity and mechanical properties into the composite materials to meet the requirements of a consumer, such as for the application of bone replacement materials. Biomedical results indicated strongly that there is natural bone ingrowth with no apparent immune response in the composite materials produced by this process. PMID:11347435

Zhang, X; Ayers, R A; Thorne, K; Moore, J J; Schowengerdt, F

2001-01-01

50

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

Microsoft Academic Search

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

Ngoc Nhiem Dao; Minh Dai Luu

2012-01-01

51

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.

House, The S.

2013-05-15

52

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

53

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

54

In situ combustion synthesis of dense ceramic and ceramic-metal interpenetrating phase composites  

Microsoft Academic Search

A model exothermic reaction is used to demonstrate the application of simultaneous combustion synthesis, conducted under a\\u000a consolidating pressure, as a one-stepin situ synthesis technique for the production of dense ceramic and ceramic-metal interpenetrating phase composites (IPC). The addition\\u000a of an excess amount of metal,e.g., Al, and\\/or a diluent,e.g., Al2O3, lowers the combustion temperature and aids in the refinement of

H. J. Feng; J. J. Moore

1995-01-01

55

Diesel soot combustion activity of ceria promoted with alkali metals  

Microsoft Academic Search

Catalytic oxidation technique for reducing particulate emissions from diesel engines is based on the use of a catalyst in order to decrease the combustion temperature of soot down to the same range of temperature of exhaust gases. The main objective of this work was to investigate the promotional effect of alkali metals in the soot combustion activity of ceria-based catalysts.

Eleonora Aneggi; Carla de Leitenburg; Giuliano Dolcetti; Alessandro Trovarelli

2008-01-01

56

Microstructure of wave propagation during combustion synthesis of advanced materials: Experiments and theory  

NASA Astrophysics Data System (ADS)

Combustion synthesis (CS) is an attractive method for producing advanced materials, including ceramics, intermetallics, and composites. In this process, after initiation by an external heat source, a highly exothermic reaction propagates through the sample in a self-sustained combustion wave. The process offers the possibility of producing materials with novel structures and properties. At conventional magnifications and imaging rates, the combustion wave appears to propagate in a planar, steady manner. However, using higher magnifications (>400X) and imaging rates (1000 frames/sec), fluctuations in the shape and propagation of the combustion front were observed. These variations in local conditions (i.e., the microstructure of the combustion wave) can influence the microstructure and properties of materials produced by combustion synthesis. In this work, the microstructure of wave propagation during combustion synthesis is investigated experimentally and theoretically. Using microscopic high-speed imaging, the spatial and temporal fluctuations of the combustion front shape and propagation were investigated. New image analysis methods were developed to characterize the heterogeneity of the combustion front quantitatively. The initial organization of the reaction medium was found to affect the heterogeneity of the combustion wave. Moreover, at the microscopic level, two different regimes of combustion propagation were observed. In the quasihomogeneous mechanism, the microstructure of the combustion wave resembles what is viewed macroscopically, and steady, planar propagation is observed. In the relay-race mechanism, while planar at the macroscopic level, the combustion front profiles are irregularly shaped, with arc-shaped convexities and concavities at the microscopic level. Also, the reaction front propagates as a series of rapid jumps and hesitations. Based on the combustion wave microstructure, new criteria were developed to determine the boundaries between quasihomogeneous and relay-race mechanisms, as functions of the initial organization of the reaction medium (i.e. particle size and porosity). In conjunction with the experiments, a microheterogeneous cell model was developed that simulates the local propagation of the combustion wave. Accounting for the stochastically organized medium with non-uniform properties, calculated results for the microstructural parameters of the combustion wave, and their dependence on density and reactant particle size, were in good qualitative agreement with experimental data.

Hwang, Stephen

57

Combustion synthesis of LiGa and LiAl intermetallic alloys  

NASA Astrophysics Data System (ADS)

LiAl and LiGa intermetallic alloys have been synthesized using the simultaneous combustion mode of combustion synthesis. LiAl intermetallic is potentially suitable as a temper alloy for producing aluminum-lithium alloys and as an anodic material for high-energy batteries. LiGa can be used as a reduction alloy to recover valuable reactive metals from molten salt effluent in actinide recovery technology. The effects of particle size, preignition heating rate, and theoretical green density on the ignition and combustion temperatures have been studied in an effort to more precisely control the synthesis reaction of these intermetallics. A lithium particle size of -20 /xm was found to be suitable when the combustion synthesis reaction was conducted at a high heating rate (>1.0 cC/s) and a moderate green density (55 to 65 pct theoretical). Preignition diffusion is suggested as the cause for low exothermic heat release at high green densities. A combustion temperature above the melting point of the LiGa intermetallic compound can be achieved under optimized conditions. However, the exothermicity and, therefore, the adiabatic temperature is too low for either LiAl or LiGa to be produced by the propagating mode of combustion synthesis.

Pritchett, S. R.; Mishra, B.; Moore, J. J.

1995-02-01

58

Effect of milling time on TiB2-Al2O3 composite produced by combustion synthesis  

NASA Astrophysics Data System (ADS)

In this present research, TiB2-Al2O3 composite was fabricated by self-propagating hightemperature synthesis (SHS) of mechanically activated powders. H3BO3, TiO2 and Al as starting materials were mechanically activated for 1, 3, 6 and 9 h then pressed to form pellets. Green compacts were placed in a tube furnace with argon atmosphere, for synthesis. According to the XRD patterns showed that the TiB2-Al2O3 composite has been successfully fabricated by thermal explosion mode of combustion synthesis. Also, it was found that, 6 h is the optimum time for mechanical activation. That increasing milling time up to 9 h had no significant effect other than refining the crystallite sizes of the components specially TiB2.

Aminikia, Behzad

2012-09-01

59

PTFE, an effective additive on the combustion synthesis of silicon nitride  

Microsoft Academic Search

Combustion synthesis (CS) of Si3N4 with the addition of polytetrafluoroethylene (PTFE) was carried out at a relatively low N2 pressure of 2MPa. It was found that the additive PTFE promoted the nitridation of Si. The ?-Si3N4 contents in the periphery of the combustion-synthesized products showed great dependence on the contents of PTFE added in the reactants, which reached 77.7wt.% with

Yixiang Chen; Zhiming Lin; Jiangtao Li; Jisheng Du; Shuliang Yang

2008-01-01

60

The effect of gravity on the combustion synthesis of metal-ceramic composites  

Microsoft Academic Search

The effects of gravity on the combustion characteristics and microstructure of metal-ceramic composites (HfB2\\/Al and Ni3Ti\\/TiB2 systems) were studied under both normal and low gravity conditions. Under normal gravity conditions, pellets were ignited in three orientations relative to the gravity vector. Low gravity combustion synthesis (SHS) was carried out on a DC-9 aircraft at the NASA-Lewis Research Center. It was

H. C. Yi; J. Y. Guigné; T. C. Woodger; J. J. Moore

1998-01-01

61

The effect of gravity on the combustion synthesis of metal-ceramic composites  

Microsoft Academic Search

The effects of gravity on the combustion characteristics and microstructure of metal-ceramic composites (HfB2\\/Al and Ni3Ti\\/TiB2 systems) were studied under both normal and low gravity conditions. Under normal gravity conditions, pellets were ignited\\u000a in three orientations relative to the gravity vector. Low gravity combustion synthesis (SHS) was carried out on a DC-9 aircraft\\u000a at the NASA-Lewis Research Center. It was

H. C. Yi; J. Y. Guigné; T. C. Woodger; J. J. Moore

1998-01-01

62

Combustion synthesis and characterization of phosphor KSr4 (BO3)3:Dy3+  

NASA Astrophysics Data System (ADS)

The polycrystalline sample of KSr4 (BO3)3:Dy [KSBD] was successfully synthesized by novel solution combustion synthesis and has been studied for its thermoluminescence (TL) characteristics. The TL glow curve of the compound was composed of two peaks around 183 °C and 314 °C. The peaks are deconvoluted to determine kinetic parameters i.e. trap depth or activation energy and frequency factor from the glow curve by using peak shape method. Though the Zeff of KSBD material is very high, TL sensitivity of the phosphor was found to be as responsive as commercial phosphor TLD-100. Fading effect, variation of TL glow peak intensity with dose also been studied. The emission spectra monitored for 350 nm excitation shows the characteristic emission of Dy3+ ions.

Bajaj, N. S.; Omanwar, S. K.

2013-04-01

63

Sol-gel auto-combustion synthesis of spinel-type ferrite nanomaterials  

NASA Astrophysics Data System (ADS)

Recent developments and trends of sol-gel auto-combustion method for spinel ferrite nanomaterial synthesis are briefly discussed and critically analyzed. The analysis of various parameters of reaction which could be used for better understanding of synthesis process and control of microstructure and property of spinel ferrite nanopowder products was the main objective of this review article. Special attention was paid to variety of particle size and phase purity. For these purposes the correlation between complexant, oxygen balance and combustion process chemical additives, as well as heating mechanism and atmosphere, was established. These results are relevant from standpoints of both application and processing of ferrites.

Sutka, Andris; Mezinskis, Gundars

2012-06-01

64

Lean Premixed Combustion/Active Control  

SciTech Connect

An experimental comparison between two contrasting fuel-air swirlers for industrial gas turbine applications was undertaken at the United Technologies Research Center. The first, termed an Aerodynamic nozzle, relied on the prevailing aerodynamic forces to stabilize the downstream combustion zone. The second configuration relied on a conventional bluff plate for combustion stability and was hence named a Bluff-Body nozzle. Performance mapping over the power curve revealed the acoustic superiority of the Bluff-Body nozzle. Two dimensional Rayleigh indices calculated from CCD images identified larger acoustic driving zones associated with the Aerodynamic nozzle relative to its bluff counterpart. The Bluff-Body's success is due to increased flame stabilization (superior anchoring ability) which reduced flame motion and thermal/acoustic coupling.

D. J. Seery

2000-02-01

65

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...

66

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

Microsoft Academic Search

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

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

2010-01-01

67

Fabrication and simultaneous bonding of metal matrix composite by combustion synthesis reaction  

Microsoft Academic Search

The combustion synthesis and bonding of TiB2\\/Cu composite were simultaneously performed in a single process. The heat of reaction of TiB2 formation was high enough to form the bonded interface between the composite and an aluminum rod. Intermetallic compounds consisting of copper and aluminum were observed at the interface.

Y. J. Kwon; M. Kobashi; T. Choh; N. Kanetake

2004-01-01

68

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

69

Combustion synthesis of intermetallides of the iron-titanium system  

SciTech Connect

The paper investigates the laws of combustion of titanium-iron powder mixtures. The authors try to obtain the intermetallic compounds of the Fe-Ti system. The minimum initial temperature of the process was estimated, and the adiabatic combustion temperatures, were calculated for various initial temperatures by the method described in the paper. An analysis of the results showed that it is possible to distinguish regions of dependence of the maximum combustion temperature T /SUB max/ on T /SUB i/ , the burning rate increasing monotonically with increase in T /SUB i/ . It is proposed to solve the problem of the limiting stage in a subsequent study by means of a structural investigation of the reaction zone.

Pribytkov, G.A.; Itin, V.I.; Semenova, A.A.

1985-03-01

70

Optimization of Active Control Systems for Suppressing Combustion Dynamics.  

National Technical Information Service (NTIS)

Results from an experimental study of active combustion control using modulated secondary fuel on a laboratory-scale, lean premixed dump combustors are presented. A simple phase-delay, closed-loop controller was used for these tests operating at the 4th s...

D. A. Santavicca J. Lee J. Stenzler K. Kim

2001-01-01

71

Synthesis and characterization of actinide metal compounds formed by combustion  

SciTech Connect

This paper briefly describes the results of attempts to synthesize arsenides, phosphides, and antimonides of uranium and thorium using Self-Propagating High-Temperature Synthesis (SHS) techniques. This paper first summarizes the chemistry and thermodynamics of these chemical systems, describes SHS synthesis techniques, and then describes the results of the syntheses using data from powder x-ray diffraction, metallographic, and electron microprobe analyses.

Behrens, R.G.; King, M.A.

1985-01-01

72

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

Code of Federal Regulations, 2010 CFR

...combustion units that use activated carbon? 60.1855 Section...AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED...combustion units that use activated carbon? For municipal waste...combustion units that use activated carbon to control...

2010-07-01

73

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

Code of Federal Regulations, 2010 CFR

...combustion units that use activated carbon? 60.1370 Section...AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED...combustion units that use activated carbon? For municipal waste...combustion units that use activated carbon to control...

2010-07-01

74

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

Code of Federal Regulations, 2010 CFR

...combustion units that use activated carbon? 62.15310 Section...AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED...combustion units that use activated carbon? For municipal waste...combustion units that use activated carbon to control...

2010-07-01

75

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

Code of Federal Regulations, 2010 CFR

...combustion units that use activated carbon? 62.15310 Section...AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED...combustion units that use activated carbon? For municipal waste...combustion units that use activated carbon to control...

2009-07-01

76

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

Code of Federal Regulations, 2013 CFR

...waste combustion units that use activated carbon? 60.1370 Section 60.1370 Protection...waste combustion units that use activated carbon? For municipal waste combustion units that use activated carbon to control dioxins/furans or...

2013-07-01

77

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

Code of Federal Regulations, 2013 CFR

...waste combustion units that use activated carbon? 62.15310 Section 62.15310 ...waste combustion units that use activated carbon? For municipal waste combustion units that use activated carbon to control dioxins/furans or...

2013-07-01

78

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

Code of Federal Regulations, 2013 CFR

...waste combustion units that use activated carbon? 60.1855 Section 60.1855 Protection...waste combustion units that use activated carbon? For municipal waste combustion units that use activated carbon to control dioxins/furans or...

2013-07-01

79

Fabrication of SiC, Si sub 3 N sub 4 and AlN by Combustion Synthesis.  

National Technical Information Service (NTIS)

Combustion synthesis is a process, which takes advantage of the high exothermic heat of many chemical reactions to form refractory compounds. Borides, carbides, and nitrides are a technologically important group of refractory materials. The new process is...

J. B. Holt Z. A. Munir

1983-01-01

80

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

81

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

PubMed

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

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

2009-10-22

82

Microemulsions in the preparation of highly active combustion catalysts  

Microsoft Academic Search

Catalytic activity in combustion of toluene in toluene–air mixtures and physical–chemical properties of platinum catalysts prepared from reverse microemulsions (water-in-oil) and by classical impregnation from water solutions of H2PtCl6 were studied. Microemulsion catalysts were more active than those prepared classically from water solutions. Size of Pt in classically impregnated catalysts was three times higher than that of catalysts prepared from

J Rymeš; G Ehret; L Hilaire; M Boutonnet; Kv?ta Jirátová

2002-01-01

83

Combustion Synthesis of BaCaP207:Eu2+ Pyrophosphate Blue Phosphor For Solid State Lighting  

NASA Astrophysics Data System (ADS)

In this paper, synthesis of Eu2+ activated BaCaP207 pyrophosphate based phosphor by using modified combustion synthesis has been reported and studied for its X-ray diffraction pattern (XRD).Photoluminescence (PL) properties under near ultraviolet (n-UV) excitation . The BaCaP207:Eu2+ exhibits unique color: a blue band centered at 455 nm originating from Eu2+ when excited at 354 nm, which is suitable for solid state lighting and near ultra violet light emitting diodes (n-UV LED).Surface morphology has been also studied by scanning electron microscope and the room temperature FTIR spectrum for studying the nature of the chemical bonds, and their molecular environment was investigated.CIE(Commission Internationalede L'Eclairage) chromaticity coordinates values are estimated from emission spectra of BaCaP207:Eu2+ for the prepared sample

Kohale, R. L.; Dhoble, S. J.

2011-10-01

84

Sol–gel combustion synthesis of BNBT powders  

Microsoft Academic Search

Ba-modified bismuth sodium titanate with composition 0.94[(Bi0.5Na0.5)TiO3]-0.06BaTiO3 (BNBT) was prepared by a citrate nitrate sol–gel combustion method. The sol was obtained using barium acetate, bismuth nitrate,\\u000a sodium nitrate and a peroxo-citrate complex of titanium isopropoxide as starting precursors. Various molar ratios of citrate\\/nitrate\\u000a (C\\/N) were considered for the sol production. The corresponding gels were fired at different temperatures (300, 400,

Elisa Mercadelli; Carmen Galassi; Anna Luisa Costa; Stefania Albonetti; Alessandra Sanson

2008-01-01

85

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

86

In situ combustion synthesis of dense ceramic and ceramic-metal interpenetrating phase composites  

SciTech Connect

A model exothermic reaction is used to demonstrate the application of simultaneous combustion synthesis, conducted under a consolidating pressure, as a one-step in situ synthesis technique for the production of dense ceramic and ceramic-metal interpenetrating phase composites (IPC). The addition of an excess amount of metal, e.g., Al, and/or a diluent, e.g., Al{sub 2}O{sub 3}, lowers the combustion temperature and aids in the refinement of the microstructure, facilitating an increase in compressive strength and elastic modulus. The effects of the important process parameters, e.g., reaction stoichiometry and diluents, green density, pressure, and temperature, on micro-structure and properties of these high-performance composites are discussed.

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

1995-04-01

87

The effect of an electric field on self-sustaining combustion synthesis: Part I. modeling studies  

NASA Astrophysics Data System (ADS)

An analysis of the effect of an electric field on self-propagating high-temperature synthesis (SHS) reactions is presented. Using the synthesis of SiC as a model, the analysis showed that the imposition of a field results in a highly localized distribution of the current density. It was shown that the current is primarily restricted to the region just ahead of the combustion zone. Thus, in addition to the chemical heat release, this zone also includes heat release from an electric source, a value equivalent to ?E2 where ? is the conductivity and E is the field. From the dependence of the degree of conversion to the product on the applied voltage, it is shown that the velocity of the combustion wave is linearly proportional to the field.

Feng, A.; Munir, Z. A.

1995-05-01

88

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

Microsoft Academic Search

We report microwave-assisted combustion synthesis of porous nanocrystalline titania and carbon coated titania using dextrose as a template and compare the product with that obtained using a conventional heating furnace. Out of three compositions, namely, 1:1, 1:3, and 1:5 (metal:dextrose), 1:3 favors formation of consistent porous structures. The samples were then characterized using scanning electron microscopy (SEM), transmission electron microscopy

Mallikarjuna N Nadagouda; Rajender S Varma

2006-01-01

89

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

Microsoft Academic Search

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

Kiranmala Laishram; Rekha Mann; Neelam Malhan

90

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

Microsoft Academic Search

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

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

2006-01-01

91

Modified Combustion Synthesis of ZnO Nanoparticles Using Renewable Fuel  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

92

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

Microsoft Academic Search

Aluminium doped barium and strontium hexaferrite nanoparticles BaAlxFe(12?x)O19 and SrAlxFe(12?x)O19 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

Neil J.. Shirtcliffe; Simon Thompson; Eoin S. O’Keefe; Steve Appleton; Carole C.. Perry

2007-01-01

93

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

94

Combustion Synthesis and Properties of Fine Particle Spinel Manganites  

NASA Astrophysics Data System (ADS)

Fine particle spinel manganites have been prepared by thermal decomposition of the precursors N2H5M1/3Mn2/3(N2H3COO)3 . H2O (M = Co and Ni) and M1/3 Mn2/3(N2H3COO)2 . 2H2O (M = Mg and Zn), as well as by the combustion of redox mixtures containing M(II) nitrate (M = Mg, Co, Ni, Cu, and Zn), Mn(II) nitrate, and maleic hydrazide (MH) in the required molar ratio. Both the precursor and redox mixtures undergo self-propagating, gas-producing, exothermic reactions once ignited at 250-375°C to yield corresponding manganites in less than 5 min. Formation of single phase products was confirmed by X-ray powder diffraction patterns. The manganites are of submicrometer size and have surface area in the range 20-76 m2/g.

Dhas, N. Arul; Patil, K. C.

1993-02-01

95

Active suppression of vortex-driven combustion instability using controlled liquid-fuel injection  

Microsoft Academic Search

Combustion instabilities remain one of the most challenging problems encountered in developing propulsion and power systems. Large amplitude pressure oscillations, driven by unsteady heat release, can produce numerous detrimental effects. Most previous active control studies utilized gaseous fuels to suppress combustion instabilities. However, using liquid fuel to suppress combustion instabilities is more realistic for propulsion applications. Active instability suppression in

Bin Pang

2005-01-01

96

Preparation of Nickel Thin Sheets with Nanosized Ferrites by Combustion Synthesis and Electroforming  

NASA Astrophysics Data System (ADS)

Composite nickel sheets with nanosized nickel--zinc ferrite particles were prepared as electromagnetic shielding materials by electroforming in a modified nickel--sulfate bath with nickel--zinc ferrite particles. The nanosized nickel--zinc ferrites were prepared by combustion synthesis and mechanical milling. The combustion temperature and propagation rate were about 1150 °C and 8.9 mm/s, respectively. Neutron diffractometry revealed that the final nickel--zinc ferrites formed by combustion synthesis followed by mechanical milling were Ni0.42Zn0.58Fe2O4 with the crystal structure and lattice parameter of Fd3m and 0.84124 nm, respectively. Microstructure observation and chemical analysis by transmission electron microscopy and energy-dispersive spectroscopy respectively showed that nanosized nickel--zinc ferrite particles with a diameter of about 20 nm exist in the thin composite nickel sheet. Maximum magnetization (Ms), residual magnetization (Mr), and coercive force (i) were 7.75 Wb/m2/kg, 0.88 m3/kg, and 1297 A/m, respectively. The complex permeability decreases with an increase in frequency, and its real value (?\\text{r{}') has an maximum at about 0.65 GHz.

Choi, Yong

2011-01-01

97

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

SciTech Connect

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

Not Available

1993-04-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

99

Combustion and Plasma Synthesis of High Temperature Materials.  

National Technical Information Service (NTIS)

The preparation and processing of well characterized materials, including ceramic and composite phases continue to be the focus of widespread research and development activities in the United States and elsewhere. As in other sub-disciplines of Materials ...

Z. A. Munir

1989-01-01

100

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

NASA Astrophysics Data System (ADS)

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

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

101

Microstructural evolution of the titanium particles in the in-situ composition of TiC–Fe by the combustion synthesis  

Microsoft Academic Search

Coarse titanium powder was mixed with iron and carbon black powders, and the mixture was used for a combustion front quenching test. The quenched sample was analysed by scanning electron microscope and energy dispersive X-ray analyses to study the microstructural evolution of the titanium particles in the combustion synthesis. Also, the combustion temperature was measured, and the phase constituent of

Quncheng Fan; Huifen Chai; Zhihao Jin

1999-01-01

102

Combustion synthesis of heterogeneous calcium phosphate bioceramics from calcium oxide and phosphate precursors  

Microsoft Academic Search

The solid-state reaction of combustion synthesis has been demonstrated to be capable of rapidly producing materials for biomedical\\u000a applications. Reactant powders of CaO and P2O5 were pressed into cylinders and reacted by heating a tungsten filament in either an argon, CO2 or N2 atmosphere. Reaction systems examined were: (1) 3CaO + P2O5 ? Ca3(PO4)2 (TCP) and (2) 4CaO + P2O5

R. Ayers; N. Hannigan; N. Vollmer; C. Unuvar

2011-01-01

103

Starch – A suitable fuel in new low-temperature combustion-based synthesis of zinc aluminate oxides  

Microsoft Academic Search

Starch has been tested as single-fuel and in a two-fuel mixture, together with N-methylurea, in a new combustion-based synthesis of zinc aluminate oxides, using different fuel compositions and equivalence ratios ?e (?e=fuel\\/oxidant). The combustion process has been analyzed by simultaneous thermal analysis. The corresponding oxides were characterized by X-ray diffraction analysis, UV–Vis spectroscopy, scanning electron microscopy and BET investigations. Crystal

Diana Visinescu; Bogdan Jurca; Adelina Ianculescu; Oana Carp

2011-01-01

104

Combustion synthesis: a new route for repair of gas turbine components—principles and metallurgical structure in the NiAl\\/RBD61\\/superalloy junction  

Microsoft Academic Search

A new technique for repairing turbine blade materials based on combustion synthesis is described in this article. This process uses a local internal generation of heat provided by the NiAl combustion synthesis in order to rebuild damaged turbine components. In this study, a nickel base braze was inserted between a substrate of nickel base superalloy and a powders compact (Ni+Al).

C Pascal; R. M Marin-Ayral; J. C Tédenac; C Merlet

2003-01-01

105

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

SciTech Connect

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

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

2000-01-04

106

Effects of TiC and Al 4C 3 addition on combustion synthesis of Ti 2AlC  

Microsoft Academic Search

Preparation of the ternary carbide Ti2AlC was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) from the elemental powder compacts of Ti:Al:C=2:1:1, TiC-containing samples with TiC of 6.67–14.3mol%, and Al4C3-containing samples with Al4C3 of 1.96–10mol%. Effects of TiC and Al4C3 addition were studied on combustion characteristics and the degree of phase conversion. Due to the growth

C. L. Yeh; Y. G. Shen

2009-01-01

107

Effect of precursors on the combustion synthesis of TiC-Al2O3 composite  

NASA Astrophysics Data System (ADS)

In the combustion synthesis of TiC-Al2O3 composites from TiO2, Al, and C, different types of precursors, i.e., anatase and rutile TiO2 and graphite and carbon black were used. The measurements of combustion wave velocity showed that the reactivity was higher with graphite as a carbon source and anatase as a TiO2 source. This was also confirmed by analyzing the degree of conversion of reactants to products. For the precursors investigated, the wave propagation of the 3TiO2-4Al-3C system diluted by Al2O3 showed that the limit of wave propagation was more dependent on carbon source than on TiO2. The wave front of all the samples proceeded in unstable combustion mode. Temperature profiles in the reaction zone suggested that the heat-affected zone was broader in the case of graphite carbon source than carbon black. The microstructures and chemical composition of the products were also studied.

Choi, Yoon; Rhee, Shi-Woo

1994-07-01

108

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

109

Combustion characteristics and influential factors of isooctane active-thermal atmosphere combustion assisted by two-stage reaction of n-heptane  

SciTech Connect

This paper presents an experimental study on the isooctane active-thermal atmosphere combustion (ATAC) which is assisted by two-stage reaction of n-heptane. The active-thermal atmosphere is created by low- and high-temperature reactions of n-heptane which is injected at intake port, and isooctane is directly injected into combustion chamber near the top dead center. The effects of isooctane injection timing, active-thermal atmosphere intensity, overall equivalence ratio, and premixed ratio on combustion characteristics and emissions are investigated. The experimental results reveal that, the isooctane ignition and combustion can be classified to thermal atmosphere combustion, active atmosphere combustion, and active-thermal atmosphere combustion respectively according to the extent of n-heptane oxidation as well as effects of isooctane quenching and charge cooling. n-Heptane equivalence ratio, isooctane equivalence ratio and isooctane delivery advance angle are major control parameters. In one combustion cycle, the isooctane ignited and burned after those of n-heptane, and then this combustion phenomenon can also be named as dual-fuel sequential combustion (DFSC). The ignition timing of the overall combustion event is mainly determined by n-heptane equivalence ratio and can be controlled in flexibility by simultaneously adjusting isooctane equivalence ratio. The isooctane ignition regime, overall thermal efficiency, and NO{sub x} emissions show strong sensitivity to the fuel delivery advance angle between 20 CA BTDC and 25 CA BTDC. (author)

Lu, Xingcai; Ji, Libin; Ma, Junjun; Zhou, Xiaoxin; Huang, Zhen [Key Lab. for Power Machinery and Engineering of MOE, Shanghai Jiao Tong University, 200240 Shanghai (China)

2011-02-15

110

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

Microsoft Academic Search

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

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

2005-01-01

111

Historical perspective and contribution of US researchers into the field of self-propagating high-temperature synthesis (SHS)\\/combustion synthesis (CS): Personal reflections  

Microsoft Academic Search

In 1967, Merzhanov, Skhiro, and Borovinskaya published the first comprehensive paper describing self-sustaining character of reactions in a condensed phase, which could be utilized for synthesis of many ceramic and intermetallic materials [1]. In this paper, the authors demonstrated the principle of the so called “solid flame” using reactions between transition metals and boron, carbon or nitrogen. The world-wide combustion

J. W. McCauley; J. A. Puszynski

2008-01-01

112

Simulation study of wave propagation instabilities for the combustion synthesis of transition metals aluminides.  

PubMed

Interest in the mode of propagation of self-sustaining reactions has been motivated by the influence of the mode on the microstructure and composition of the final product. However, comprehensive studies relating the onset of the various propagation modes to the chemical and phase transformations taking place in the sample are still lacking. In the present work propagation instabilities in self-propagating high-temperature synthesis (SHS) of transition metal aluminides are studied using a computer simulation approach. The results are presented for the SHS of NiAl, CoAl, TiAl, and NbAl(3). Particular emphasis is made with respect to the influence of process variables and system parameters on the onset of propagation instabilities, in relation to the physicochemical processes taking place during the propagation of the combustion front. PMID:16599478

Gennari, Silvia; Anselmi-Tamburini, Umberto; Maglia, Filippo; Spinolo, Giorgio; Munir, Zuhair A

2006-04-13

113

Microwave Ignited Combustion Synthesis as a Joining Technique for Dissimilar Materials  

NASA Astrophysics Data System (ADS)

Microwave energy has been exploited to ignite combustion synthesis (CS) reactions of properly designed powders mixtures, in order to rapidly reach the joining between different kinds of materials, including metals (Titanium and Inconel) and ceramics (SiC). Beside the great advantage offered by CS itself, i.e., rapid and highly localized heat generation, the microwaves selectivity in being absorbed by micrometric metallic powders and not by bulk metallic components represents a further intriguing aspect in advanced materials joining applications, namely the possibility to avoid the exposition to high temperatures of the entire substrates to be joined. Moreover, in case of microwaves absorbing substrates, the competitive microwaves absorption by both substrates and powdered joining material, leads to the possibility of adhesion, interdiffusion and chemical bonding enhancements. In this study, both experimental and numerical simulation results are used to highlight the great potentialities of microwave ignited CS in the joining of advanced materials.

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

2012-05-01

114

Screen-printing of ferrite magnetic nanoparticles produced by carbon combustion synthesis of oxides  

NASA Astrophysics Data System (ADS)

The feasibility of screen-printing process of hard ferrite magnetic nanoparticles produced by carbon combustion synthesis of oxides (CCSO) is investigated. In CCSO, the exothermic oxidation of carbon generates a smolder thermal reaction wave that propagates through the solid reactant mixture converting it to the desired oxides. The complete conversion of hexaferrites occurs using reactant mixtures containing 11 wt. % of carbon. The BaFe12O19 and SrFe12O19 hexaferrites had hard magnetic properties with coercivity of 3 and 4.5 kOe, respectively. It was shown that the synthesized nanoparticles could be used to fabricate permanent magnet structures by consolidating them using screen-printing techniques.

Martirosyan, Karen S.; Dannangoda, Chamath; Galstyan, Eduard; Litvinov, Dmitri

2012-05-01

115

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

NASA Astrophysics Data System (ADS)

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

Nadagouda, Mallikarjuna N.; Varma, Rajender S.

2006-10-01

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

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.

118

Effect of Preparation Conditions on Visible Photocatalytic Activity of Titania Synthesized by Solution Combustion Method * * Supported by the Key Laboratory of Material-Oriented Chemical Engineering of Jiangsu Province and Ministry of Education  

Microsoft Academic Search

Titania catalysts were synthesized by a solution combustion method (SCM). Photodegradation of 4-chlorophenol (4-CP) using the synthesized catalysts was studied under both visible light (? ? 420nm) and sunlight irradiation. The effect of preparation conditions on photocatalytic activities of the synthesized catalysts was investigated. The optimal photocatalytic activity of the catalyst (denoted as A1) was obtained under the following synthesis

Youping CHENG; Hongqi SUN; Wanqin JIN; Nanping XU

2007-01-01

119

Feedback Control of Combustion Instabilities: A Case Study in Active Adaptive Control of Complex Physical Systems.  

National Technical Information Service (NTIS)

The technical objectives of the program are: Study active control of combustion instability in a laboratory scale combustor based on fuel flow modulation or an alternative practical means of actuation. Develop a model of the plant taking into account the ...

A. Gulati G. C. Goodman

1989-01-01

120

Effects of Si 3N 4 addition on formation of aluminum nitride by self-propagating combustion synthesis  

Microsoft Academic Search

An experimental study on the preparation of aluminum nitride (AlN) by self-propagating high-temperature synthesis (SHS) was conducted with powder compacts under nitrogen pressures of 0.79–4.24MPa. Reactant compacts were diluted by 30–50wt% of AlN to avoid the melting of aluminum during combustion. In addition, silicon nitride (Si3N4) was adopted as a solid source of nitrogen in the reactant compacts and its

C. L. Yeh; E. W. Liu

2007-01-01

121

Combustion Synthesis of BaCO3 and Its Application for Eu(III) Adsorption From Aqueous Solution  

Microsoft Academic Search

A combustion method using urea as fuel and barium nitrate as oxidant was applied for the synthesis of barium carbonate, which was characterized by XRD, IR, SEM and BET. A batch technique was employed to study the Eu(III) adsorption from an aqueous solution using BaCO3. It was found that the adsorption process attains equilibrium within 3 hours and depends upon

F. Granados-Correa; M. Jiménez-Reyes

2011-01-01

122

An overview of synthetic fuel combustion issues and research activities  

SciTech Connect

With the reduction in the availability of conventional hydrocarbons for fuels in the transportation, utility and industrial sectors, there is need to include fuels produced from low hydrogento-carbon ratio sources, such as coal, shale oil and tar sands. Various processes are being developed to produce coal-derived liquids, solids and gases, oil from shale and heavy oils from tar sands. It has been established that the cost and energy intensive requirements to refine these syncrudes to a hydrogen-carbon ratio and boiling range more typical of conventional fuels is very large. Therefore, there is a large economic driving force for the design, development and implementation of combustion equipment capable of burning synthetic fuels of widely varying properties in a thermally efficient and environmentally acceptable manner. Concurrently, the need to conserve energy and to control pollutant emissions is also forcing improvements in combustion efficiency and reductions in pollutant emissions of existing energy-conversion devices using present-day fuels including heavy and residual oils. The requirements on the design of combustion equipment to meet these objectives will be severe and will demand substantial improvements in our ability to understand the combustion process and its controlling parameters. Many recent studies have considered the combustion of synthetic fuels. The problem is that current combustor technology has evolved slowly, is based upon empirical methods, and contains little consideration for fuel flexibility. The situation is particularly acute now because of the present uncertainties in fuel supplies and the corresponding uncertainties in design for fuel flexibility.

Boni, A.A.; Bienstock, D.; Edelman, R.B.; Fischer, J.

1982-03-01

123

Combustion-aided suspension plasma spraying of Y{sub 2}O{sub 3} nanoparticles: Synthesis and modeling  

SciTech Connect

Combustion-aided suspension plasma spraying (SPS) was developed for the synthesis of Y{sub 2}O{sub 3} nanoparticles. Numerical models for Ar, Ar/O{sub 2}, and combustion-aided plasma fields were built using FLUENT V6.3.2(c) to compare their different plasma thermophysical properties. Modeling and experimental results both indicate that the plasma field was substantially altered by combustion-aided SPS. The plasma exhibited an elevated volume average temperature and reduced velocity as well as a broadened plasma plume, which resulted in an enhanced vapor supersaturation degree and a faster quenching rate in the radial direction. These can be attributed to the dual effects of oxygen dissociation/recombination and acetone solvent combustion. Consequently, productivity of the obtained nanoparticles increased remarkably and the particles' morphology was improved, with a smaller mean particle size and a narrower size distribution in comparison with those of powder feeding spraying. Furthermore, plasma-induced cubic{yields}monoclinic phase transformation in the as-sprayed Y{sub 2}O{sub 3} particles was restrained by combustion-aided SPS to some extent.

Sun, X. L.; Tok, A. I. Y.; Lim, S. L.; Boey, F. Y. C. [School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Kang, C. W. [Institute of High Performance Computing, 1 Science Park Road, No. 01-01, The Capricorn, Singapore Science Park II, Singapore 117528 (Singapore); Ng, H. W. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

2008-02-01

124

Novel Salt-Assisted Combustion Synthesis of High Surface Area Ceria Nanopowders by An Ethylene Glycol-Nitrate Combustion Process  

Microsoft Academic Search

A novel salt-assisted combustion process with ethylene glycol as a fuel and nitrate as an oxidant to synthesize high surface area ceria nanopowders was reported. The effects of various tunable conditions, such as fuel-to-oxidant ratio, type of salts, and amount of added salts, on the characteristics of the as-prepared powders were investigated by X-ray diffraction, transmission electron microscopy and BET

Weifan Chen; Fengsheng Li; Jiyi Yu; Yongxiu Li

2006-01-01

125

Development of Activated Carbons from Coal Combustion By-Products.  

National Technical Information Service (NTIS)

The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly fly ash containing unburned carbon. However, the carbonaceous residue ...

H. H. Schobert M. M. Maroto-Valer Z. Lu

2000-01-01

126

Mechanical activation of titanium powder ignition and combustion  

SciTech Connect

This article discusses the possible intensification of metal powder ignition and combustion processes during their mechanical treatment. The defectivity of the structure and diffusion permeability is examined. Tests were conducted on electrolytic titanium powders of mark TP-6 and TU 48-0561-4/0-80. Powder samples were selected after specific time intervals and their ignition and combustion characteristics were determined. The titanium powder was placed in a 16-mm-diameter capsule from brass mesh which does not obstruct gas supply to the specimen, and was then inserted in a metal module heated to a definite temperature in a muffle furnace. It is shown that treatment of the powder results in significant facilitation of its flammability. The electron exoemission was measured on the primary and treated titanium powders. The data on titanium powder ignition and combustion and the results of studying the exoemission indicate that the intensification observed for combustion and ignition is related to the origin of defects on the powder grain surface during its mechanical treatment.

Voyuev, S.I.; Barzykin, V.V.; Chernenko, E.V.; Maslov, V.M.; Poletaev, S.V.; Rozenband, V.I.; Smurak, S.Z.

1983-11-01

127

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

128

Combustion synthesis as a novel method for production of 1-D SiC nanostructures.  

PubMed

1-D nanostructures of cubic phase silicon carbide (beta-SiC) were efficiently produced by combustion synthesis of mixtures containing Si-containing compounds and halocarbons in a calorimetric bomb. The influence of the operating parameters on 1-D SiC formation yield was studied. The heat release, the heating rate, and the chamber pressure increase were monitored during the process. The composition and structural features of the products were characterized by elemental analysis, X-ray diffraction, differential thermal analysis/ thermogravimetric technique, Raman spectroscopy, scanning and transmission electron microscopy, and energy-dispersive X-ray spectrometry. This self-induced growth process can produce SiC nanofibers and nanotubes ca. 20-100 nm in diameter with the aspect ratio higher than 1000. Bulk scale Raman studies showed the product to be comprised of mostly cubic polytype of SiC and that finite size effects are present. We believe that the nucleation mechanism involving radical gaseous species is responsible for 1-D nanostructures growth. The present study has enlarged the family of nanofibers and nanotubes available and offers a possible, new general route to 1-D crystalline materials. PMID:16853065

Huczko, Andrzej; Bystrzejewski, Micha?; Lange, Hubert; Fabianowska, Agnieszka; Cudzi?o, Stanis?aw; Panas, Andrzej; Szala, Mateusz

2005-09-01

129

Synthesis of high-purity polycrystalline MAX phases in Ti–Al–C system through Mechanically Activated Self-propagating High-temperature Synthesis  

Microsoft Academic Search

Ternary MAX phase compounds were synthesized using an alternative route called MASHS (Mechanically Activated Self-propagating High-temperature Synthesis). This original process combines a short duration ball milling (MA) of reactants (Ti, Al, C) with a self-sustaining combustion (SHS). The particle size evolution of the powder mixture during Mechanical Activation was monitored using XRD profile analysis. The effect of Al-excess was also

A. Hendaoui; D. Vrel; A. Amara; P. Langlois; M. Andasmas; M. Guerioune

2010-01-01

130

Rapid synthesis of ultrahigh adsorption capacity zirconia by a solution combustion technique.  

PubMed

Tetragonal ZrO(2) was synthesized by the solution combustion technique using glycine as the fuel. The compound was characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, and BET surface area analysis. The ability of this compound to adsorb dyes was investigated, and the compound had a higher adsorption capacity than commercially activated carbon. Infrared spectroscopic observations were used to determine the various interactions and the groups responsible for the adsorption activity of the compound. The effects of the initial concentration of the dye, temperature, adsorbent concentration, and pH of the solution were studied. The kinetics of adsorption was described as a first-order process, and the relative magnitudes of internal and external mass transfer processes were determined. The equilibrium adsorption was also determined and modeled by a composite Langmuir-Freundlich isotherm. PMID:21355572

Deshpande, Parag A; Polisetti, Sneha; Madras, Giridhar

2011-02-28

131

Synthesis of tribromoacetanilides and their photochemical activity  

SciTech Connect

The synthesis of tribromoacetanilides was accomplished by the carbodimide method using dicyclohexylcarbodiimide and tribomoacetates of the corresponding anilines. The photochemical activity of the prepared tribromoacetanilides was studied, and it was shown that some of these compounds can be used for the development of light-sensitive systems.

Grishina, A.D.; Degutis, Y.A.; Myadyakshene, G.S.; Vannikov, A.V.

1985-10-01

132

Personalized implant for high tibial opening wedge: combination of solid freeform fabrication with combustion synthesis process.  

PubMed

In this work a new generation of bioceramic personalized implants were developed. This technique combines the processes of solid freeform fabrication (SFF) and combustion synthesis (CS) to create personalized bioceramic implants with tricalcium phosphate (TCP) and hydroxyapatite (HA). These porous bioceramics will be used to fill the tibial bone gap created by the opening wedge high tibial osteotomy (OWHTO). A freeform fabrication with three-dimensional printing (3DP) technique was used to fabricate a metallic mold with the same shape required to fill the gap in the opening wedge osteotomy. The mold was subsequently used in a CS process to fabricate the personalized ceramic implants with TCP and HA compositions. The mold geometry was designed on commercial 3D CAD software. The final personalized bioceramic implant was produced using a CS process. This technique was chosen because it exploits the exothermic reaction between P?O? and CaO. Also, chemical composition and distribution of pores in the implant could be controlled. To determine the chemical composition, the microstructure, and the mechanical properties of the implant, cylindrical shapes were also fabricated using different fabrication parameters. Chemical composition was performed by X-ray diffraction. Pore size and pore interconnectivity was measured and analyzed using an electronic microscope system. Mechanical properties were determined by a mechanical testing system. The porous TCP and HA obtained have an open porous structure with an average 400?µm channel size. The mechanical behavior shows great stiffness and higher load to failure for both ceramics. Finally, this personalized ceramic implant facilitated the regeneration of new bone in the gap created by OWHTO and provides additional strength to allow accelerated rehabilitation. PMID:21750185

Zhim, Fouad; Ayers, Reed A; Moore, John J; Moufarrège, Richard; Yahia, L'Hocine

2011-07-12

133

Al2O3\\/ZrO2 (Y2O3) Prepared by Combustion Synthesis Under High Gravity  

Microsoft Academic Search

By introducing ZrO2 (4Y) powder into the thermit, Al2O3\\/ZrO2 (4Y) composite ceramics of different composition and microstructures were prepared through combustion synthesis under high gravity, and the correlations of composition, microstructures and mechanical properties of composite ceramics were investigated. The results of XRD, SEM and EDS showed that Al2O3\\/33%ZrO2 (4Y) were composed of random-orientated rod-shaped colonies consisting of a triangular

Long Zhang; Zhongmin Zhao; Yigang Song; Weiguo Wang; Hongbo Liu

2009-01-01

134

Strong upconversion from Er3Al5O12 ceramic powders prepared by low temperature direct combustion synthesis  

NASA Astrophysics Data System (ADS)

Crystalline ceramic powders of Er3Al5O12 were obtained by low temperature direct combustion synthesis. Irradiating the sample with a low-power continuous-wave infrared (1.48 ?m) diode laser led to ultraviolet, violet, blue, green, and red (380, 410, 456, 495, 525, 550, and 660 nm) emissions. The strong upconversion luminescence appeared to the eyes as an intense green color. The presence of efficient four- and three-photon frequency upconversion processes makes this material an excellent candidate for use in photonic devices based on upconverter phosphors.

Maciel, Glauco S.; Rakov, Nikifor; Fokine, Michael; Carvalho, Isabel C. S.; Pinheiro, Carlos B.

2006-08-01

135

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

136

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

SciTech Connect

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

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

1995-11-01

137

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

138

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

139

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

PubMed

Circulating fluidized bed combustion (CFBC) bottom ashes (CBAs) are a class of calcined aluminosilicate wastes with a unique thermal history. While landfill disposal of hazardous element-containing CBAs poses serious challenge, these wastes have long been neglected as source materials for geopolymer production. In this paper, geopolymerization of ground CBAs was investigated. Reactivity of the CBAs was analyzed by respective dissolution of the ashes in 2, 5, and 10N NaOH and KOH solutions. Geopolymer pastes were prepared by activating the CBAs by a series of alkalis hydroxides and/or sodium silicate solutions. Samples were cured at 40 degrees C for 168 h, giving a highest compressive strength of 52.9 MPa. Of the optimal specimen, characterization was conducted by TG-DTA, SEM, XRD, as well as FTIR analyses, and thermal stability was determined in terms of compressive strength evolution via exposure to 800 or 1050 degrees C followed by three cooling regimes, i.e. cooling in air, cooling in the furnace, and immerging in water. The results show that CBAs could serve as favorable source materials for thermostable geopolymers, which hold a promise to replace ordinary Portland cement (OPC) and organic polymers in a variety of applications, especially where fire hazards are of great concern. PMID:19879690

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

2009-10-06

140

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

Microsoft Academic Search

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

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

2003-01-01

141

Combustion synthesis of Cobalt ferrite Nanoparticles–Influence of fuel to oxidizer ratio  

Microsoft Academic Search

The effect of fuel characteristics on the processing of nano-sized Cobalt ferrite fine powders by the combustion technique is reported. By using different combinations of glycine fuel and metal nitrates, the adiabatic flame temperature (Tad) of the process as well as product characteristics could be controlled easily. Thermodynamic modelling of the combustion reaction shows that as the fuel-to-oxidant ratio increases,

A. B. Salunkhe; V. M. Khot; M. R. Phadatare; S. H. Pawar

142

Methane combustion over palladium catalysts: The effect of carbon dioxide and water on activity  

Microsoft Academic Search

The influence of water and carbon dioxide on the activity of a series of palladium catalysts for the combustion of methane has been studied. It has been found that both compounds have an inhibitory effect but the extent of this depends on the experimental conditions. When both are present in the feedstream, the effect of carbon dioxide is negligible, the

R. Burch; F. J. Urbano; P. K. Loader

1995-01-01

143

Effect of hydrogen sulfide on chemical looping combustion of coal-derived synthesis gas over bentonite-supported metal-oxide oxygen carriers  

Microsoft Academic Search

The effect of hydrogen sulfide (HS) on the chemical looping combustion of coal-derived synthesis gas with bentonite-supported metal oxides - such as iron oxide, nickel oxide, manganese oxide, and copper oxide - was investigated by thermogravimetric analysis, mass spectrometry, and X-ray photoelectron spectroscopy (XPS). During the reaction with synthesis gas containing HS, metal-oxide oxygen carriers were first reduced by carbon

Hanjing Tian; Thomas Simonyi; James Poston; Ranjani Siriwardane

2009-01-01

144

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.

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

2013-01-01

145

Synthesis and biological activity of olomoucine II.  

PubMed

Based on our previous experiences with synthesis of purines, novel 2,6,9-trisubstituted purine derivatives were prepared and assayed for the ability to inhibit CDK1/cyclin B kinase. One of newly synthesized compounds designated as olomoucine II, 6-[(2-hydroxybenzyl)amino]-2-[[1-(hydroxymethyl)propyl]amino]-9-isopropylpurine, displays 10 times higher inhibitory activity than roscovitine, potent and specific CDK1 inhibitor. Olomoucine II in vitro cytotoxic activity exceeds purvalanol A, the most potent CDK inhibitor, as it kills the CEM cells with IC(50) value of 3.0 microM. PMID:12392733

Krystof, Vladimír; Lenobel, René; Havlícek, Libor; Kuzma, Marek; Strnad, Miroslav

2002-11-18

146

Removal of elemental mercury from coal combustion flue gas by chloride-impregnated activated carbon  

Microsoft Academic Search

In this work, adsorption of vapour-phase elemental mercury (Hg0) from pulverised-coal combustion flue gas by commercially available granular activated carbons treated with zinc chloride (ZnCl2) impregnation was investigated. The experiment results showed that ZnCl2 impregnation significantly enhanced the adsorptive capacity for mercury vapour, but decreased the specific surface area of the activated carbon. This could be explained by the occurrence

Hancai Zeng; Feng Jin; Jia Guo

2004-01-01

147

Simple synthesis of nano-sized refractory metal carbides by combustion process  

Microsoft Academic Search

Combustion reactions of transition metal oxides (WO3, MoO3, Ta2O5, Nb2O5, ZrO2, and TiO2), magnesium, carbon, and sodium fluoride produce a range of nanostructured transition metal carbides (W2C, Mo2C, TaC, NbC, ZrC, and TiC) with low amounts of free carbon. Sodium fluoride improves unfavorable combustion regimes and facilitates\\u000a the carburization of metal carbides. The average particle size of carbides prepared in

Hyung Il Won; Nersisyan Hayk; Chang Whan Won; Hyuk Hee Lee

2011-01-01

148

Active suppression of vortex-driven combustion instability using controlled liquid-fuel injection  

NASA Astrophysics Data System (ADS)

Combustion instabilities remain one of the most challenging problems encountered in developing propulsion and power systems. Large amplitude pressure oscillations, driven by unsteady heat release, can produce numerous detrimental effects. Most previous active control studies utilized gaseous fuels to suppress combustion instabilities. However, using liquid fuel to suppress combustion instabilities is more realistic for propulsion applications. Active instability suppression in vortex-driven combustors using a direct liquid fuel injection strategy was theoretically established and experimentally demonstrated in this dissertation work. Droplet size measurements revealed that with pulsed fuel injection management, fuel droplet size could be modulated periodically. Consequently, desired heat release fluctuation could be created. If this oscillatory heat release is coupled with the natural pressure oscillation in an out of phase manner, combustion instabilities can be suppressed. To identify proper locations of supplying additional liquid fuel for the purpose of achieving control, the natural heat release pattern in a vortex-driven combustor was characterized in this study. It was found that at high Damkohler number oscillatory heat release pattern closely followed the evolving vortex front. However, when Damkohler number became close to unity, heat release fluctuation wave no longer coincided with the coherent structures. A heat release deficit area was found near the dump plane when combustor was operated in lean premixed conditions. Active combustion instability suppression experiments were performed in a dump combustor using a controlled liquid fuel injection strategy. High-speed Schlieren results illustrated that vortex shedding plays an important role in maintaining self-sustained combustion instabilities. Complete combustion instability control requires total suppression of these large-scale coherent structures. The sound pressure level at the excited dominant frequency was reduced by more than 20 dB with controlled liquid fuel injection method. Scaling issues were also investigated in this dump combustor to test the effectiveness of using pulsed liquid fuel injection strategies to suppress instabilities at higher power output conditions. With the liquid fuel injection control method, it was possible to suppress strong instabilities with initial amplitude of +/-5 psi down to the background noise level. The stable combustor operating range was also expanded from equivalence ratio of 0.75 to beyond 0.9.

Pang, Bin

149

Investigation of Adaptive Signal Processing Approaches to Active Combustion Control.  

National Technical Information Service (NTIS)

There has been significant progress made in understanding dynamic models and control system designs for active control of thermoacoustic instabilities. During the past several years, there has been an increasing trend away from mostly empirical or experim...

M. A. Vaudrey W. R. Saunders W. T. Baumann

2001-01-01

150

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

151

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

Microsoft Academic Search

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

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

2010-01-01

152

Iron-stabilized nanocrystalline ZrO{sub 2} solid solutions: Synthesis by combustion and thermal stability  

SciTech Connect

The synthesis of Fe{sup 3+}-stabilized zirconia by the nitrate/urea combustion route was investigated. Using several characterization techniques, including X-ray diffraction, field-emission-gun scanning electron microscopy and notably Moessbauer spectroscopy, it was possible to determine the appropriate amount of urea that allows to obtain a totally stabilized Zr{sub 0.9}Fe{sub 0.1}O{sub 1.95} solid solution. The nanocrystalline zirconia solid solution is mostly tetragonal, but the presence of the cubic phase could not be ruled out. An in-depth study of the thermal stability in air showed that the Fe{sup 3+} solubility in the stabilized solid solution starts to decrease at about 875 deg. C which results in the formation of hematite (possibly containing some Zr{sup 4+}) at the surface of the zirconia grains and further provokes the progressive transformation into the monoclinic zirconia phase.

Legorreta Garcia, Felipe [Universite de Toulouse, CIRIMAT, CNRS-UPS-INP, Universite Paul-Sabatier, 31062 Toulouse cedex 9 (France); Resende, Valdirene Gonzaga de; De Grave, Eddy [NUMAT, Department of Subatomic and Radiation Physics, University of Ghent, Proeftuinstraat 86, B-9000 Gent (Belgium); Peigney, Alain; Barnabe, Antoine [Universite de Toulouse, CIRIMAT, CNRS-UPS-INP, Universite Paul-Sabatier, 31062 Toulouse cedex 9 (France); Laurent, Christophe, E-mail: laurent@chimie.ups-tlse.fr [Universite de Toulouse, CIRIMAT, CNRS-UPS-INP, Universite Paul-Sabatier, 31062 Toulouse cedex 9 (France)

2009-06-03

153

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

PubMed

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

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

2002-02-01

154

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

155

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

156

Photo- and radioluminescence characteristics of bismuth germanate nanoparticles by sol-gel and pressure-assisted combustion synthesis  

NASA Astrophysics Data System (ADS)

Bismuth germanate (Bi4Ge3O12, BGO) nanophosphors have been synthesized by sol-gel and pressure-assisted combustion synthesis techniques. Sol-gel or combustion synthesized precursors for BGO were post-annealed by a fast or slow thermal treatment, both in ambient air. The microstructure of synthesized samples under fast annealing consists of spherical shape nanoparticles with an average diameter size of 4 nm, whereas those prepared by the slow thermal treatment have faceted surface with diameter in the range of 2-6 nm. Both samples yield strong bluish-white luminescence under UV excitation of 4.3 eV (288 nm). The luminescence band is composed of a double-peak suggesting a contribution from two fundamental emissions at 2.83 eV (440 nm) and 2.43 eV (510 nm). The powders excited by X-ray of 7 keV from a synchrotron source showed the typical radioluminescence of BGO. These nanophosphors yield similar scintillating properties as BGO single crystal.

Oviedo, M. J.; Contreras, O.; Rodriguez, C. E.; Macedo, Z. S.; Hirata, G. A.; McKittrick, J.

2012-05-01

157

Comparative sinterability of combustion synthesized and commercial titanium carbides  

SciTech Connect

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

Manley, B.W.

1984-11-01

158

Ignition and Combustion Properties of Activated Carbon Containing Adsorbed Hydrocarbons.  

National Technical Information Service (NTIS)

Activated carbon contained in large filter beds is used in nuclear submarines for removal of odors and trace contaminants. Because organic vapors are concentrated in this way in the carbon, a study was made to get information for assessing the fire hazard...

F. J. Woods J. E. Johnson

1964-01-01

159

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

160

Characterization and Activity of Supported Palladium Combustion Catalysts  

Microsoft Academic Search

The catalytic activity of Pd supported on ?-Al2O3, Ba-Al2O3, and La–Al2O3 has been examined in complete oxidation of methane when operating in excess of oxygen. Two different sizes of Pd particles have been considered. Foreign ions have a strong influence with respect to the stabilization of alumina when submitted to a temperature as high as 1000°C. In contrast, no specific

P. O. Thevenin; E. Pocoroba; L. J. Pettersson; H. Karhu; I. J. Väyrynen; S. G. Järås

2002-01-01

161

Active control of combustion instability in a liquid-fueled los-NOx combustor  

Microsoft Academic Search

A practical active control system for the mitigation of combustion instability has been designed and demonstrated in a lean, premixed, single-nozzle combustor at realistic engine operating conditions. A full-scale engine fuel nozzle was modified to incorporate a simple fuel flow actuator. Results indicate that the system was capable of reducing pressure fluctuations by 82% (15 dB or 5.6x) while maintaining

J. M. Cohen; N. M. Rey; C. A. Jacobson; T. J. Anderson

1999-01-01

162

Effect of Gravity on Porous Tricalcium Phosphate and Nonstoichiometric Titanium Carbide Produced via Combustion Synthesis.  

National Technical Information Service (NTIS)

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 ne...

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

2004-01-01

163

Influence of thermal conditions on the combustion synthesis of Si 2N 2O phase  

Microsoft Academic Search

This work is a contribution to the study of Si2N2O synthesis via Self-Propagating High-temperature Synthesis (SHS).The elaboration of Si2N2O was carried out using two kinds of experimental equipments and differences both in reaction temperatures and in products compositions were evidenced.In order to determine the reaction mechanisms, several compositions and thermal conditions of the reactant mixture were studied.Considering our results, two

N. Pradeilles; M. C. Record; R. M. Marin-Ayral; A. V. Linde; I. A. Studenikin; V. V. Grachev

2008-01-01

164

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

NASA Astrophysics Data System (ADS)

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

Biswas, M.; Bandyopadhyay, S.

2013-11-01

165

The influence of combustion synthesis conditions on the ?-Al 2 O 3 powder preparation  

Microsoft Academic Search

Fuel type and fuel\\/aluminium nitrate molar ratio proved to be of great importance during the preparation of ?-Al2O3 powders. A stoichiometric amount of urea (U) enabled the formation of ?-Al2O3 with a surface area of 24 m2\\/g directly from the combustion reaction. Monoethanolamine, triethylenetetramine, trishydroxymethylaminomethane, and triethanolamine\\u000a yield amorphous powders. This behaviour was explained by the reaction mechanism, which requires the

Robert Ianos; Ioan Lazau; Cornelia Pacurariu

2009-01-01

166

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

Microsoft Academic Search

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

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

2011-01-01

167

Combustion Synthesis of Al3Ni Foam Filled in Hollow Pipe Component and Cell Morphology Analysis  

Microsoft Academic Search

Al3Ni foam was synthesized by a combustion reaction in a hollow steel pipe. Aluminum powder and nickel powder were blended by Al\\/Ni molar bending ratio of 4.5, and titanium and boron carbide (B4C) powders were added to increase the heat of reaction. Al3Ni matrix was synthesized by the reaction between Al and Ni, and TiC and TiB2 particles were formed

Makoto Kobashi; Naoyuki Kanetake

2009-01-01

168

Influence of fuel ratios on auto combustion synthesis of barium ferrite nano particles  

Microsoft Academic Search

Single-domain barium ferrite nano particles have been synthesized with narrow particle-size distribution using an auto combustion\\u000a technique. In this process, citric acid was used as a fuel. Ratios of cation to fuel were maintained variously at 1:1, 1:2\\u000a and 1:3. The pH was 7 in all cases. Of all three cases, a cation to citric acid ratio of 1:2 gives

D. Bahadur; S. Rajakumar; Ankit Kumar

2006-01-01

169

Microstructural aspects of gasless combustion of mechanically activated mixtures. I. High-speed microvideorecording of the NiAl composition  

Microsoft Academic Search

Gasless combustion of a mechanically activated Ni-Al mixture is experimentally studied; the process is compared with the characteristics\\u000a of combustion of a nonactivated Ni-Al mixture. Mechanical activation of the Ni-Al mixture is shown to form layered conglomerates\\u000a consisting of numerous layers of the initial components. As a result, the structure of the medium becomes very similar to\\u000a a cellular structure,

A. S. Rogachev; N. A. Kochetov; V. V. Kurbatkina; E. A. Levashov; P. S. Grinchuk; O. S. Rabinovich; N. V. Sachkova; F. Bernard

2006-01-01

170

Convective combustion in porous media: singular limit of high activation energy  

NASA Astrophysics Data System (ADS)

In this paper, we consider a system of degenerate reaction diffusion equations which describes a convective (pressure driven) regime of combustion in porous media. The goal of this paper is to study the behaviour of this system in the limit of high activation energy. We show that the limit solution for this problem in arbitrary spatial dimension solves a parabolic equation with memory term similar to one arising in solid combustion. Moreover, under the additional assumption of the solution being time increasing, we prove that the limit problem coincides with Stefan problem for supercooled water with spatially inhomogeneous coefficients. We also obtain the precise limit problem for (not necessarily planar) travelling waves in any dimension.

Gordon, Peter V.; Weiss, Georg S.

2013-01-01

171

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

172

Combustion synthesis and photoluminescence of Eu3+ doped LaAlO3 nanophosphors  

NASA Astrophysics Data System (ADS)

Eu3+ doped LaAlO3 nanophosphors were successfully synthesized by a combustion process using concentrated solution of lanthanum nitrates and aluminate as oxidiser, and glycine acid as fuel. The powders were characterized by infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fluorescence spectroscopy. Pure LaAlO3 phase was obtained at 800 °C heated for 4 h, without formation of any intermediate phase, with an average crystal size, as determined by TEM, of 60 nm. Intense photoluminescence emission is reported at 616 nm, allowing the use of this material as red phosphor.

Dhahri, A.; Horchani-Naifer, K.; Benedetti, A.; Enrichi, F.; Ferid, M.

2012-09-01

173

Effect of the physical state of activators on the combustion of composite rocket propellants. II. Colloidal inhibitors  

Microsoft Academic Search

The effect of inhibitors added as powders and colloidal solutions to propellants on the combustion of ammonium perchlorate\\u000a composite rocket propellants is investigated. Transformation of chemical governors of the composite-propellant burning rate\\u000a into the ultradisperse state (<0.05 ?m) increases the effectiveness of the inhibitors and decreases their concentration in\\u000a the propellant provided that particle aggregation is prevented both in synthesis

A. I. Lesnikovich; G. F. Levchik; S. A. Vorobéeva

1998-01-01

174

Use of combustion and thermal explosion for the synthesis of intermetallic compounds and their alloys  

Microsoft Academic Search

Methods of utilizing the heat evolving during reactions between components for the synthesis of intermetallic compounds and their alloys may vary depending on the character of the exothermic processes occurring in the metal powder mixtures employed. During the initiation of a reaction in some local volume of a substance heat is liberated in the reaction zone. This raises the temperature

V. I. Itin; A. D. Bratchikov; L. N. Postnikova

1980-01-01

175

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

Microsoft Academic Search

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

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

2011-01-01

176

Synthesis of nanoparticles of CoxFe(3-x)O4 by combustion reaction method  

NASA Astrophysics Data System (ADS)

Nanocrystalline magnetic particles of CoxFe(3-x)O4, with x ranging from 0.79 to 1.15, has been synthesised by combustion reaction method using iron nitrate Fe(NO3)3.9H2O, cobalt nitrate Co(NO3)2·6H2O, and urea CO(NH2)2 as fuel without template and subsequent heat treatment. The process is quite simple and inexpensive since it does not involve intermediate decomposition and/or calcining steps. The maximum reaction temperature ranged from 850 to 1010 °C and combustion lasted less then 30 s for all systems. X-ray diffraction patterns of all systems showed broad peaks consistent with cubic inverse spinel structure of CoFe2O4. The absence of extra reflections in the diffraction patterns of as-prepared materials ensures phase purity. The average crystallite sizes determined from the prominent (3 1 1) peak of the diffraction using Scherre's equation and TEM micrographs consisted of ca. 27 nm in spherical morphology. FTIR spectra of the as-prepared material showed traces of organic and metallic salts byproducts. However, when the same material was washed with deionised water the byproducts were rinsed off, resulting in pure materials. Magnetic properties such as saturation magnetisation, remanence magnetisation and coercivity field measured at room temperature were 48 emu/g, 15 emu/g and 900 Oe, respectively.

Franco, Adolfo; Celma de Oliveira Lima, Emília; Novak, Miguel A.; Wells, Paulo R.

2007-01-01

177

Preparation and characterization of SiAlON matrix composites reinforced with combustion synthesis rod-like SiAlON particles  

Microsoft Academic Search

SiAlON matrix composites were prepared from a precursor reaction mixture of ?-Si3N4, AlN, Al2O3 and Y2O3 powders and reinforced with different proportions of elongated SiAlON particles obtained by combustion synthesis. Green cylindrical specimens were consolidated by slip casting from well dispersed suspensions. The dried samples were densified by hot pressing at 1650 and 1700°C and then characterized for density, phase

V. X. Lima Filho; J. P. Davim; C. A. Cairo; J. M. F. Ferreira

2009-01-01

178

Use of BN as a reactant in combustion synthesis of TiN TiB 2 composites under nitrogen pressure  

Microsoft Academic Search

An experimental study on direct formation of TiNTiB2 composites by self-propagating high-temperature synthesis (SHS) was conducted using compacted samples of titanium (Ti) and boron nitride (BN) powders ignited in gaseous nitrogen. Effects of sample green density, nitrogen pressure, starting stoichiometry of reactant compacts, and diluent content on the degree of conversion and combustion characteristics were investigated. With the addition of

C. L. Yeh; G. S. Teng

2006-01-01

179

Effect of urea and glycine fuels on the combustion reaction synthesis of Mn–Zn ferrites: Evaluation of morphology and magnetic properties  

Microsoft Academic Search

The goal of this study is to evaluate the influence of the urea and glycine fuels on the synthesis of Mn–Zn ferrite by combustion reaction. The morphology and magnetic properties of the resulting powders were investigated. The powders were characterized by X-ray diffraction (XRD), nitrogen adsorption (BET), scanning and transmission electron microscopy (SEM and TEM), and magnetic measurement of M×H

A. C. F. M. Costa; V. J. Silva; C. C. Xin; D. A. Vieira; D. R. Cornejo; R. H. G. A. Kiminami

2010-01-01

180

[Spectrum and synthesis of rare earth activated nanoparticle].  

PubMed

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

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

2006-02-01

181

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

SciTech Connect

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

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

1993-05-28

182

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

Microsoft Academic Search

CuO\\/bentonite and CuO-BHA nanocomposites were studied as oxygen carriers in chemical-looping;\\u000acombustion (CLC) of simulated synthesis gas. Global reaction rates of reduction and oxidation, as the function;\\u000aof reaction conversion, were calculated from 10-cycle oxidation\\/reduction tests utilizing thermogravimetric;\\u000aanalysis at atmospheric pressure between 700 and 900 °C. It was found that the reduction reactions are always;\\u000afaster than oxidation reactions;

Hanjing Tian; Karuna Chaudhari; Thomas Simonyi; James Poston; Tengfei Liu; Tom Sanders; Go?tz Veser; Ranjani Siriwardane

2008-01-01

183

Synthesis and Characterisation of Bimetallic Pd–Rh\\/Alumina Combustion Catalysts  

Microsoft Academic Search

This paper reports the possibility of associating Pd with another noble metal (rhodium) which is able to form a thermally stable oxide to extend toward higher temperatures the stability range of PdO. Bimetallic Pd–Rh\\/alumina catalysts were prepared and compared to reference Pd\\/alumina and Rh\\/alumina solids. The synthesis of the bimetallic catalysts was carried out by either co-impregnation or stepwise impregnation

Mohamed Rassoul; François Gaillard; Edouard Garbowski; Michel Primet

2001-01-01

184

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

185

Studies on Eu doped Ba and Zn aluminate phosphors prepared by combustion synthesis  

NASA Astrophysics Data System (ADS)

BaAl2O4:Eu2+ and ZnAl2O4:Eu3+ phosphors were prepared by urea combustion route. The formation of crystalline aluminates was confirmed by X-ray diffraction. The X-band EPR spectra of BaAl2O4:Eu2+ showed the presence of Eu2+ ions, while in the case of ZnAl2O4:Eu3+, no signal attributable to Eu2+ was observed. The broad band UV excited luminescence of BaAl2O4:Eu2+ was observed at the blue region (?max = 439 nm) due to transitions from the 4f65d1 to the 4f7 configuration of the Eu2+ ion, whereas ZnAl2O4:Eu3+ gave an emission at 613 nm attributed to 5D0 7F2 transition of Eu3+ ions.

Singh, Vijay; Natarajan, V.; Zhu, Jun-Jie

2007-07-01

186

Combustion Front Dynamics in the Combustion Synthesis of Refractory Metal Carbides and Di-borides using Time-Resolved X-ray Diffraction  

SciTech Connect

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 {yields} MC; (ii) M + 2B {yields} MB{sub 2}; and (iii) 3M + B{sub 4}C {yields} 2MB{sub 2} + 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{sup -1} (or 100 ms frame{sup -1}) was employed. The combustion reactions were found to complete within 200-400 ms. In contrast to the Ta + C {yields} 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 T{sub ad} are well above the melting points of the respective reactant metals and have a typical combustion front velocity of 5-6 mm s{sup -1}. The Nb and Ta systems have lower T{sub ad}, involving no liquid phase. These are truly solid combustion systems and have a lower combustion front velocity of 1-2 mm s{sup -1}. The current study opens up a new avenue to chemical dynamics and macrokinetic investigations of high-temperature solid-state reactions.

Wong,J.; Larson, E.; Waide, P.; Frahm, R.

2006-01-01

187

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

188

On the effects of hydrocarbon and sulphur-containing compounds on the CCN activation of combustion particles  

NASA Astrophysics Data System (ADS)

The European PartEmis project (''Measurement and prediction of emissions of aerosols and gaseous precursors from gas turbine engines'') was focussed on the characterisation and quantification of exhaust emissions from a gas turbine engine. A comprehensive suite of aerosol, gas and chemi-ion measurements were conducted under different combustor operating conditions and fuel sulphur concentrations. Combustion aerosol characterisation included on-line measurements of mass and number concentration, size distribution, mixing state, thermal stability of internally mixed particles, hygroscopicity, cloud condensation nuclei (CCN) activation potential, and off-line analysis of chemical composition. Modelling of CCN activation of combustion particles was conducted using microphysical and chemical properties obtained from the measurements as input data. Based on this unique data set, the role of sulphuric acid coatings on the combustion particles, formed in the cooling exhaust plume through either direct condensation of gaseous sulphuric acid or coagulation with volatile condensation particles nucleating from gaseous sulphuric acid, and the role of the organic fraction for the CCN activation of combustion particles was investigated. It was found that particles containing a large fraction of non-volatile organic compounds grow significantly less at high relative humidity than particles with a lower content of non-volatile OC. Also the effect of the non-volatile OC fraction on the potential CCN activation is significant. While a coating of water-soluble sulphuric acid increases the potential CCN activation, or lowers the activation diameter, respectively, the non-volatile organic compounds, mainly found at lower combustion temperatures, can partially compensate this sulphuric acid-related enhancement of CCN activation of carbonaceous combustion aerosol particles.

Petzold, A.; Gysel, M.; Vancassel, X.; Hitzenberger, R.; Puxbaum, H.; Vrochticky, S.; Weingartner, E.; Baltensperger, U.; Mirabel, P.

2005-05-01

189

Structural and luminescence investigation on gadolinium gallium garnet nanocrystalline powders prepared by solution combustion synthesis  

NASA Astrophysics Data System (ADS)

Nanocrystalline powders of undoped and lanthanide (Pr3+, Tm3+)-doped gadolinium gallium garnet, Gd3Ga5O12 (GGG), were prepared by propellant synthesis and studied by x-ray powder diffraction (XRD), electron diffraction (ED), high-resolution electron microscopy (HREM) and luminescence spectroscopy. The x-ray diffraction patterns of the GGG samples were analysed using the Rietveld method. The Rietveld refinement reveals the existence of two garnet-type phases: both are cubic (space group Ia\\bar {3}d ) with a slightly different lattice parameter and probably a slightly different composition. Electron diffraction and electron microscopy measurements confirm the x-ray diffraction results. EDX measurements for lanthanide-doped samples show that stable solid solutions with composition Gd3-xLnxGa5O12, xap0.3 (Ln = Pr; Tm) have been obtained. The luminescence properties of the Tm3+-doped nanocrystalline GGG samples were measured and analysed.

Krsmanovi?, R.; Morozov, V. A.; Lebedev, O. I.; Polizzi, S.; Speghini, A.; Bettinelli, M.; Van Tendeloo, G.

2007-08-01

190

Modeling of combustion instabilities and their active control in a gas fueled combustor  

NASA Astrophysics Data System (ADS)

This study deals with the development of simplified models for simulation of combustion instabilities and their active control. Modulation of a part of the fuel supply is used to damp instabilities by generating heat release oscillations that are out of phase with the existing pressure oscillations. A model that accounts for mixing using a heuristic source term has been developed, and used for simulation of combustion instabilities and their control in a premixed gaseous rocket motor. For validation with experimental data, the model is used to investigate the combustor's response to open loop excitation by pulsation of the secondary fuel injection rate. The numerical model's prediction that (a) the pressure oscillation amplitude decreases, and (b) the phase shift between the fuel injection rate and heat-release oscillations increases linearly, as the frequency of fuel injection rate increases, are in good agreement with experimental data from a gas rocket. Subsequently, the heuristic model is used to study the performances of an observer based control system and an adaptive control system. A modular model that is oriented towards application in a lean premixed gas turbine combustor has been developed. A dump combustor geometry has been used to demonstrate cases of stable and unstable combustion. The two modules of the model are the recirculation zone, which is modeled as either a quasi steady or unsteady well stirred reactor, and the separation-free core flow region which is modeled as a quasi one dimensional flow with source terms. The observed cases of unstable combustion involve fluctuations in local equivalence ratio, and in the mass and energy exchange between the recirculation zone and the core flow. Roe scheme, the numerical scheme used for the solution of the heuristic and the modular models, has been extended to appropriately account for various source terms that occur in a generalized quasi one dimensional flow. The effect of the source terms is accounted by the use of relevant compatibility relations from the theory of characteristics. This approach is demonstrated with examples for not only Roe scheme but also for characteristics-based boundary conditions.

Mohanraj, Rajendran

191

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

2012-01-19

192

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

Microsoft Academic Search

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°C and completed within a short period of time. XRD spectrum of the combustion product reveals

M. Biswas; K.. Prabhakaran; N. M. Gokhale; S. C. Sharma

2007-01-01

193

The Combustion Synthesis Zns Doped Materials to Create Ultra-Electroluminscent Materials in Microgravity  

NASA Astrophysics Data System (ADS)

Self-propagating high temperature synthesis (SHS) utilises a rapid exothermic process involving high energy and nonlinearity coupled with a high cooling rate to produce materials formed outside of normal equilibrium boundaries thus possessing unique properties. The elimination of gravity during this process allows capillary forces to dominate mixing of the reactants which results in a superior and enhanced homogeneity in the product materials. ZnS type materials have been previously conducted in reduced gravity and normal gravity. It has been claimed in literature that a near perfect phases of ZnS wurtzite was produced. Although, the SHS of this material is possible at high pressures, there have been no advancements in refining this structure to create ultra-electroluminescent materials. Utilising this process with ZnS doped with Cu, Mn, or rare earth metals such as Eu and Pr leads to electroluminescence properties, thus making this an attractive electroluminescent material. The work described here will revisit the SHS of ZnS and will re-examine the work performed in both normal gravity and in reduced gravity within the Queensland University of Technology Drop Tower Facility. Quantifications in the lattice parameters, crystal structures, and phases produced are presented to further explore the unique structure-property performance relationships produced from the SHS of ZnS materials.

Castillo, Martin; Steinberg, Theodore

2012-07-01

194

ACTIVE TEXTURE SYNTHESIS BASED ON MULTI-AGENT  

Microsoft Academic Search

In this paper, we propose a novel active texture synthesis al- gorithm based on multi-agent, aiming at overcoming some drawbacks of existing popular patch-based methods. By defining agents' attributes and behaviors, we dexterously convert the texture synthesis issue to an optimization prob- lem. It can quickly achieve high-quality results for a wide variety of textures without any extra overhead for

Fei Wu; Changshui Zhang

195

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

SciTech Connect

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

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

1997-10-01

196

Managing creative projects: An empirical synthesis of activities  

Microsoft Academic Search

This paper proposes a radical empirical look on the concrete activities of project managers involved in creative projects, with a specific focus on “non-administrative” issues. Through four case studies in the video-game industry, multimedia, advertising and a circus, we propose an integrated synthesis of what creative project managers actually do. Beyond analytical, cognitive, psychological, symbolic and discursive activities, we identify

Laurent Simon

2006-01-01

197

Active Combustion Control in a Ramjet Using Large-eddy Simulations  

Microsoft Academic Search

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

SURESH MENON

1992-01-01

198

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

199

Synthesis and antibacterial activity evaluation of metronidazole–triazole conjugates  

Microsoft Academic Search

Synthesis and antibacterial activity of metronidazole–triazole conjugates are reported. Total 21 hybrid compounds have been synthesized with different substitution pattern on the triazole ring in order to study their influence on the antibacterial activity. These compounds demonstrated potent to weak antibacterial activity against Gram-positive, and Gram-negative bacteria. Six compounds have shown equal or better antibacterial activity against Gram-negative strains than

Beena; Nitin Kumar; Rajesh K. Rohilla; N. Roy; Diwan S. Rawat

2009-01-01

200

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

201

Biocatalytic synthesis of optically active tertiary alcohols  

Microsoft Academic Search

The enzymatic preparation of optically pure tertiary alcohols under sustainable conditions has received much attention. The\\u000a conventional chemical synthesis of these valuable building blocks is still hampered by the use of harmful reagents such as\\u000a heavy metal catalysts. Successful examples in biocatalysis used esterases, lipases, epoxide hydrolases, halohydrin dehalogenases,\\u000a thiamine diphosphate-dependent enzymes, terpene cyclases, -acetylases, and -dehydratases. This mini-review provides

Robert Kourist; Uwe T. Bornscheuer

2011-01-01

202

Study of size-fractionated coal-combustion aerosols using instrumental neutron activation analysis  

Microsoft Academic Search

The chemical composition of aerosols emitted during coal combustion was studied as a function of particle size down to 0.01 m. The aerosol collections were carried out in a 81 MW capacity boiler that burned Venezuelan coal in a circulating fluidized bed combustion chamber. The samples were analyzed with upstream of the electrostatic precipitator using a Berner low-pressure impactor, which

W. Maenhaut; E. I. Kauppinen; T. M. Lind

1993-01-01

203

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

204

Chemical synthesis of biologically active monoglycosylated GM2-activator protein analogue using N-sulfanylethylanilide peptide.  

PubMed

Going to SEA(lide): Total chemical synthesis of a 162-residue glycoprotein analogue of the monoglycosylated human GM2-activator protein (GM2AP) was achieved. Key steps were the use of N-sulfanylethylanilide (SEAlide) peptides in the kinetic chemical ligation synthesis of a large peptide fragment, and a convergent native chemical ligation for final fragment assembly. PMID:23765733

Sato, Kohei; Shigenaga, Akira; Kitakaze, Keisuke; Sakamoto, Ken; Tsuji, Daisuke; Itoh, Kohji; Otaka, Akira

2013-06-13

205

Pyrophosphate-condensing activity linked to nucleic acid synthesis.  

PubMed Central

In some preparations of DNA dependent RNA polymerase a new enzymatic activity has been found which catalyzes the condensation of two pyrophosphate molecules, liberated in the process of RNA synthesis, to one molecule of orthophosphate and one molecule of Mg (or Mn) - chelate complex with trimetaphosphate. This activity can also cooperate with DNA-polymerase, on condition that both enzymes originate from the same cells. These results point to two general conclusions. First, energy is conserved in the overall process of nucleic acid synthesis and turnover, so that the process does not require an energy influx from the cell's general resources. Second, the synthesis of nucleic acids is catalyzed by a complex enzyme system which contains at least two separate enzymes, one responsible for nucleic acid polymerization and the other for energy conservation via pyrophosphate condensation. Images

Volloch, V Z; Rits, S; Tumerman, L

1979-01-01

206

The effect of water on the activity of supported palladium catalysts in the catalytic combustion of methane  

Microsoft Academic Search

Supported palladium catalysts are very active in the combustion of methane, but still little is known about the kinetic parameters. In this paper a rate expression is presented for an alumina-supported palladium oxide catalyst in the temperature range 180–515°C. Special care was taken to ensure differential conditions during the experiments. In this way, an apparent activation energy of 151±15kJ\\/mol was

J. C. van Giezen; F. R. van den Berg; J. L. Kleinen; A. J. van Dillen; J. W. Geus

1999-01-01

207

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

208

Selective phase synthesis of a high luminescence Gd2O3:Eu nanocrystal phosphor through direct solution combustion.  

PubMed

A Gd(2)O(3):Eu nanocrystal phosphor has been directly synthesized by a mild solution combustion method with a single step approach while avoiding further thermal annealing. The as-combusted Gd(2)O(3):Eu powders have been characterized by x-ray diffraction, infrared spectroscopy, transmission electron microscopy and photoluminescence spectra. The ratio of citric acid to metal nitrate (C/M) has a critical impact on the phase composition and crystallization of as-combusted Gd(2)O(3):Eu. An optimal C/M ratio of 0.7 gave highly crystalline powders with a single cubic phase, and a high luminescence intensity comparable with that of a commercial Y(2)O(3):Eu phosphor, even without further thermal annealing. This direct solution combustion method can be used to prepare a variety of high quality oxide nanocrystals. PMID:20671360

Xia, Guodong; Wang, Sumei; Zhou, Shengming; Xu, Jun

2010-07-30

209

Selective phase synthesis of a high luminescence Gd2O3:Eu nanocrystal phosphor through direct solution combustion  

Microsoft Academic Search

A Gd2O3:Eu nanocrystal phosphor has been directly synthesized by a mild solution combustion method with a single step approach while avoiding further thermal annealing. The as-combusted Gd2O3:Eu powders have been characterized by x-ray diffraction, infrared spectroscopy, transmission electron microscopy and photoluminescence spectra. The ratio of citric acid to metal nitrate (C\\/M) has a critical impact on the phase composition and

Guodong Xia; Sumei Wang; Shengming Zhou; Jun Xu

2010-01-01

210

One-step synthesis of barium hexaferrite nano-powders via microwave-assisted sol–gel auto-combustion  

Microsoft Academic Search

Single phase barium hexaferrite nano-powders have been innovatively one-step synthesized via a microwave-assisted sol–gel auto-combustion in a specially designed quartz vessel using citric acid and ethylene diamine tetraacetic acid as composite chelating agents and freeze-drying technique to remove sols’ moisture. The auto-combustion product powder is characterized by fluffy particle aggregates with the crystallites ranging from 50 to 100nm in diameter

Liu Junliang; Zeng Yanwei; Guo Cuijing; Zhang Wei; Yang Xiaowei

2010-01-01

211

Cholera toxin induces synthesis of phospholipase A2-activating protein.  

PubMed Central

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

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

1996-01-01

212

Synthesis of novel chiral macrolides and their antifungal activity  

Microsoft Academic Search

Nineteen chiral macrocyclic diamide–diester ligands were synthesized using a three step reaction. The synthesis utilized the condensation of dicarbonyl dichlorides with chiral 2-aminoethanol derivatives. The reaction was catalyzed in a dual catalyst system. Some of the compounds were found to display antifungal activity.

Ming Zhang Gao; Jian Gao; Zun Le Xu; Ralph A. Zingaro

2002-01-01

213

Synthesis and analgetic activity of nicotinic esters of morphine derivatives.  

PubMed

The synthesis of morphine nicotinates is described using nicotinyl chloride in the presence of pyridine. Isomorphine and isocodeine nicotinates were prepared from the corresponding morphine and codeine derivatives with nicotinic acid in the presence of triphenylphosphine and diethyl azodicarboxylate. Unexpectedly the reaction of 14-hydroxy-dihydromorphinone derivatives was anomalous, enolesters were formed. The analgetic activity of selected compounds was determined. PMID:7904819

Hosztafi, S; Köhegyi, I; Simon, C; Fürst, Z

1993-11-01

214

Synthesis and Biological Activity of Phosphatidylinositol 3, 4, 5-Trisphosphorothioate  

PubMed Central

Metabolically-stabilized analogues of PtdIns(3,4,5)P3 have shown long-lived agonist activity for cellular events mediated by this phosphoinositide. We describe an efficient method for the total asymmetric synthesis of the trisphosphorothioate (PT) analogue of PtdIns(3,4,5)P3. Intracellular delivery of dipalmitoyl PtdIns(3,4,5)PT3 mimicked insulin in activating sodium transport in A6 cells.

Zhang, Honglu; Xu, Yong; Markadieu, Nicolas; Beauwens, Renaud; Erneux, Christophe; Prestwich, Glenn D.

2008-01-01

215

Synthesis and anti-inflammatory activity of aromatic glucosinolates.  

PubMed

Aromatic GLs are important members of the glucosinolate family of compounds because of their potential biological activity and medicinal properties. This study has shown success in the high yielding synthesis of some important aromatic GLs as well as the results of testing for anti-inflammatory properties of the synthetic GLs. 3,4-Dimethoxyphenylglucosinolate was found to be the most active anti-inflammatory of the seven glucosinolates assayed. PMID:23978357

Vo, Quan V; Trenerry, Craige; Rochfort, Simone; Wadeson, Jenny; Leyton, Carolina; Hughes, Andrew B

2013-08-09

216

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

217

Synthesis and biological activity of flavanone derivatives  

Microsoft Academic Search

A series of new flavanone derivatives of farrerol was synthesized by a convenient method. The in vitro anti-tumor activity of these compounds was evaluated against human Bel-7402, HL-60, BGC-823 and KB cell lines, the protein tyrosine kinase (PTK) inhibitor activity was also tested. Their cytoprotective activity was tested using hydrogen peroxide (H2O2)-induced injury in human umbilical vein endothelial cells. Their

Lei Shi; Xiu E Feng; Jing Rong Cui; Lian Hua Fang; Guan Hua Du; Qing Shan Li

2010-01-01

218

Synthesis, antifungal and antimicrobial activity of alkylphospholipids.  

PubMed

The antifungal, antibacterial and haemolytic activity of a series of alkylphosphocholines (e.g., miltefosine) and alkylglycerophosphocholines (e.g., edelfosine) has been investigated. These compound classes exhibit significant antifungal and moderate antibacterial activities. Several new alkylphosphocholine derivatives with amide or ester bonds in the alkyl chain have been synthesised. These compounds show much lower haemolytic activity than miltefosine. Alkylphosphocholines and alkylglycerophosphocholines show significant promise as novel orally available antifungal and antibacterial therapeutics. PMID:17532639

Obando, Daniel; Widmer, Fred; Wright, Lesley C; Sorrell, Tania C; Jolliffe, Katrina A

2007-05-17

219

Combustion joining of refractory materials  

Microsoft Academic Search

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

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

2007-01-01

220

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

PubMed

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

Buchneva, Olga; Gallo, Alessandro; Rossetti, Ilenia

2012-10-05

221

Surface chemical activation in synthesis of high-temperature superconductors  

SciTech Connect

Solid-state synthesis of YBa{sub 2}Cu{sub 3}O{sub 7-x} (1-2-3) high-temperature superconductor from yttria, copper oxide, and barium carbonate is the most widely employed method in laboratory studies and sometimes in pilot-scale production because of the availability of reagents and simplicity. The disadvantage of this technique is a low rate of reaction between the components, mainly between CuO and BaCO{sub 3}, below 810-830{degrees}C. Low activity of the mixture is caused by the chemical nature of the reagents and, in particular, by the state of the particle surface. In some cases, the surface can be mechanically activated by thoroughly milling the initial charge. Formation of the product in the activated sample was found to be complete at 850-900{degrees}C. Prolonged heating largely affects the structural perfection of the resultant YBa{sub 2}Cu{sub 3}O{sub 7-x} material. Substantial decrease in the synthesis temperature and duration is caused, along with other factors, by the formation of a new surface in the ground materials. On the other hand, milling of the material results in contamination with isomorphous substituents, in particular with iron originating from mill parts. Such contamination leads to the degradation of the physical properties of the product. In this work, the authors report a method for chemical activation of oxide-carbonate starting mixtures for the synthesis of yttrium barium cuprate.

Spitsyna, N.P.; Fotiev, A.A. [Institute of Solid-State Chemistry, Ekaterinburg (Russian Federation); Spitsyn, P.K. [Uralredmet Joint-Stock Company, Verkhnyaya Pyshma (Russian Federation)

1995-02-01

222

Combustion leftovers  

Microsoft Academic Search

Combustion processes almost never completely exhaust all of the available fuel. In this paper, we will consider three combustion scenarios (back-to-back premixed flames in stagnation point flow, travelling combustion waves, and microgravity spherical flame balls) and show how to calculate the amount of fuel which will be left over no matter how long we allow the combustion processes to continue.

R. O Weber; G. N Mercer; H. S Sidhu

2002-01-01

223

Synthesis and fungicidal activity of a series of novel aryloxylepidines.  

PubMed

A series of novel (hetero) aryloxylepidine derivatives was devised as hybrid structures of the phenoxyquinoline and phenethoxyquin(az)oline fungicides. Synthesis of these targets required the development of several new routes to derivatised 4-hydroxymethylquinolines, and subsequent coupling with phenols or haloarenes. The aryloxylepidines generally showed moderate broad-spectrum fungicidal activity across several diseases of cereals. Substitution of the quinoline ring with chlorine at the 7- and/or 5-positions gave molecules with high levels of protectant activity against Erysiphe graminis f sp tritici (powdery mildew of wheat), but this did not improve the level of fungicidal activity against other diseases. In vitro activity against mitochondrial electron transport complex I (MET) derived from Ustilago maydis showed that 8-fluorolepidine analogues were moderately active at this target site, while the more fungicidally active 7- and 5,7-substituted compounds were inactive. This indicates that MET is not the primary target of these highly active powdery mildewicides. PMID:11561412

Kirby, N V; Daeuble, J F; Davis, L N; Hannum, A C; Hellwig, K; Lawler, L K; Parker, M H; Pieczko, M E

2001-09-01

224

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

225

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

226

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

227

Synthesis and pharmacological activity of diterpenylnaphthoquinone derivatives.  

PubMed

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

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

2011-10-13

228

Synthesis, Antiinflammatory and Analgesic Activity of 4Antipyrine Derivatives  

Microsoft Academic Search

Previously [1 – 3], we have reported on the derivatives of 4-aryl-2,4-dioxobutanoic (aroylpyruvic) acids (Ia – Ie, see scheme) possessing analgesic, antiinflammatory, anticonvulsant, and other pharmacological activities. In continuation of these investigations, we have attempted the synthesis of compounds combining the structures of pyruvic acid and 4-aminoantipyrine, the latter representing a base heterocycle in the series of non-narcotic analgesics [4].

A. E. Rubtsov; R. R. Makhmudov; N. V. Kovylyaeva; N. I. Prosyanik; A. V. Bobrov; V. V. Zalesov

2002-01-01

229

Surface chemical activation in synthesis of high-temperature superconductors  

Microsoft Academic Search

Solid-state synthesis of YBaâCuâO{sub 7-x} (1-2-3) high-temperature superconductor from yttria, copper oxide, and barium carbonate is the most widely employed method in laboratory studies and sometimes in pilot-scale production because of the availability of reagents and simplicity. The disadvantage of this technique is a low rate of reaction between the components, mainly between CuO and BaCOâ, below 810-830°C. Low activity

N. P. Spitsyna; A. A. Fotiev; P. K. Spitsyn

1995-01-01

230

Rapid room temperature synthesis of electrocatalytically active Au nanostructures  

Microsoft Academic Search

We describe a facile route for the one-pot room temperature synthesis of anisotropic Au nanostructures in aqueous solution in the absence of seeds or surfactants and their electrocatalytic activity. The Au nanostructures were synthesized using piperazine derivatives 1-(2-hydroxyethyl)piperazine and 1,4-Bis(2-hydroxyethyl)piperazine as reducing agents. The Au nanostructures were characterized by spectral, transmission electron microscopic (TEM), X-ray diffraction and electrochemical measurements. The

Ashok Kumar Das; C. Retna Raj

2011-01-01

231

Synthesis and antioxidative activity of 6-hydroxypyridoxine.  

PubMed

An attempt to synthesize 6-hydroxypyridoxine (OPN), hydroxylation on C-6 of pyridoxine (PN) by hydroxyl radical (OH*). was conducted. Application of two well-known OH* generating reactions, i.e. the Fenton reaction and the Fe2+-EDTA/ascorbate reaction, were unsuccessful, as large amounts of by-products were formed. Although generation of OH* by autoxidation of ascorbic acid in the absence of metal ions was slow, by-products were formed in small quantities, and OPN was easily obtained in colorless crystals. Its structure was confirmed by spectral analyses. OPN was comparable to polyphenols such as (+)-catechin, rutin and gallic acid in the antioxidative activity against linoleic acid peroxidation, and was an effective DPPH radical scavenger, though the DPPH radical-scavenging activity of OPN was somewhat lower than that of the polyphenols. PN was relatively inactive under the conditions used here, indicating that the introduction of a hydroxyl group on C-6 of PN greatly enhanced both activities. PMID:14974735

Tadera, Kenjiro; Minami, Yuji; Fukushima, Nozomi; Chohchi, Miki

2003-12-01

232

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...

233

Synthesis and biological activity of 5-fluorotubercidin.  

PubMed

The electrophilic fluorination of 4-chloropyrrolo[2,3-d]pyrimidine (1) was studied culminating a 59% conversion of compound 1 to 4-chloro-5-fluoropyrrolo[2,3-d]pyrimidine (2) using Selectfluor. This transformation proceeded via the 4-chloro-5,6-dihydro-5-fluoro-6-hydroxypyrrolo[2,3-d]pyrimidine (3) in a 9:1 trans:cis ratio. The trans isomer of compound 3 was studied by 1H NMR and 19F NMR, and the 5-H tautomer (4) was observed as another intermediate. A modified Vorbruggen procedure of compound 2 and tetra-O-acetylribose gave 4-chloro-5-fluoro-7-(2,3,5,-tri-O-benzoyl-beta-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine (6) in a 65% yield. Treatment of compound 6 with ammonia (l) in dioxane gave 5-fluorotubercidin (7). No antibacterial activity was observed. An MTT assay (Promega) against Huh-7 liver cells, normal mouse spleen cells stimulated with Con A (a T-cell mitogen), and normal mouse spleen stimulated with LPS (a B-cell mitogen) showed no significant toxicity. Increased activity of 7 over tubercidin was observed against L-1210 cells and toxicity in fibroblast cells was reduced. PMID:15043144

Wang, Xiaojing; Seth, Punit P; Ranken, Ray; Swayze, Eric E; Migawa, Michael T

2004-01-01

234

Total synthesis and cytotoxic activity of stellatin.  

PubMed

Stellatin (3,4-dihydro-8-hydroxy-7-hydroxymethyl-6-methoxyisocoumarin) (8), an extrolite of fungal genera Emericella and Aspergillus, was synthesized. Thus, Vilsmeier-Haack formylation of methyl ester of 3,5-dimethoxy-4-methylphenylacetic acid (1) to afford the formyl ester (2) followed sulfamic acid-sodium chlorite oxidation of the aldehydic function to yield the carboxy ester (3). Chemoselective reduction of ester function in the latter using NaBH(4)/THF/MeOH furnished the corresponding hydroxy acid (4) that on cyclodehydration afforded the 3,4-dihydro-6,8-dimethoxy-7-methylisocoumarin (5). Benzylic bromination of the C-7 methyl in 5 using NBS/benzoyl peroxide to give the 7-bromomethyldihydroisocoumarin (6) followed the nucleophilic substitution using aqueous acetone to provide 7-hydroxymethyl-dihydroisocoumarin (7). Finally, the regioselective demethylation of 8-methoxyl group using anhydrous magnesium iodide furnished the stellatin (8). The dihydroisocoumarins (5-8) were screened for cytotoxic activity against human keratinocyte cell line and were found to exhibit moderate to good activity. PMID:21279872

Saeed, Aamer; Ashraf, Zaman; Rafique, Hummera

2011-02-01

235

Synthesis and paroxonase activities of novel bromophenols.  

PubMed

Three novel bromophenols 10-12 were synthesized. Acylation of veratrole (4) with 2,3-dimethoxy benzoic acid (5) gave a kown diarylmethanone 6. Bromination of 6 with different equivalents of molecular bromine afforded new di and tribrominated compounds 7-9 which were converted to their corresponding bromophenols 10-12 via O-demethylation with BBr3. Paraoxonase-1 (PON1) was purified from human serum with approximately 42% and 3584?U × mg(-1) specific activity. The synthesized compounds 6-12 showed inhibitory effects on paraoxonase-1 (PON1) which is an organophosphate (OP) hydrolyser and an antioxidant bioscavenger enzyme. IC50 values were determined in the range of 0.123-1.212?mM. Graphical abstract [Formula: see text]. PMID:22994801

Akbaba, Yusuf; Türke?, Cüneyt; Polat, Leyla; Söyüt, Hakan; Sahin, Ertan; Menzek, Abdullah; Göksu, Süleyman; Beydemir, Sükrü

2012-09-20

236

Synthesis and antibacterial activity of doxycycline neoglycosides.  

PubMed

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

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

2013-08-29

237

Double ignitions of Ni?Al combustion reactions  

Microsoft Academic Search

Double ignitions of Ni?Al combustion reactions have been numerically studied in this research. Due to the lower exothermic heat of the metallic reactions, the propagation of Ni?Al combustion front during combustion synthesis is found to extinguish half way for some reactions. To allow the combustion front to propagate completely, the reaction is always ignited again during the experimental demonstration. In

2003-01-01

238

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 Ni0.25Cu0.25Zn0.50Fe2O4 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 degC. The sintered body possesses fine-grained microstructure, good frequency stability and high-quality factor compared to the sample prepared by conventional ceramic route.

Yue, Z.; Zhou, J.; Li, L.; Zhang, H.; Gui, Z.

2000-01-01

239

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

Microsoft Academic Search

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

Masafumi Tanaka; Guillaume Gaspard; Katsuya Urakawa

2010-01-01

240

Development of Activated Carbons from Coal Combustion By-Products. Annual Technical Progress Report, June 2002.  

National Technical Information Service (NTIS)

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 ...

H. H. Schobert M. M. Maroto-Valer Z. Lu

2002-01-01

241

Method of activating limestone for enhanced capture of sulfur from post combustion gases.  

National Technical Information Service (NTIS)

Calcium based sulfur sorbent is prepared in a highly reactive form for use in removing gaseous sulfur species from coal combustion gases by heating finely divided limestone particles at a temperature of at least 2,000 K for a period of 5 to 50 millisecond...

J. S. Abichandan N. T. Holcombe A. F. Litka J. A. Woodroffe

1991-01-01

242

Catalytic synthesis of enantiopure mixed diacylglycerols - synthesis of a major M. tuberculosis phospholipid and platelet activating factor.  

PubMed

An efficient catalytic one-pot synthesis of TBDMS-protected diacylglycerols has been developed, starting from enantiopure glycidol. Subsequent migration-free deprotection leads to stereo- and regiochemically pure diacylglycerols. This novel strategy has been applied to the synthesis of a major Mycobacterium tuberculosis phospholipid, its desmethyl analogue, and platelet activating factor. PMID:24057355

Fodran, Peter; Minnaard, Adriaan J

2013-09-12

243

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

Microsoft Academic Search

Nanocrystalline magnesium titanate was synthesized through an auto-ignited combustion method. The phase purity of the powder was examined using X-ray diffraction, thermo gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy and Raman spectroscopy. The transmission electron microscopy study showed that the particle size of the as-prepared powder was in between 20 and 40nm. The nanopowder could be sintered to

M. K. Suresh; J. K. Thomas; H. Sreemoolanadhan; C. N. George; Annamma John; Sam Solomon; P. R. S. Wariar; J. Koshy

2010-01-01

244

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

245

Synthesis and characterization of LiMn 2O 4\\/Ag composite by citrate gel and combustion method  

Microsoft Academic Search

The powder of LiMn2O4\\/Ag composite was prepared by citrate gel and combustion technique using lithium acetate, manganese acetate and silver nitrate as starting materials. Phase identification, surface morphology and electrochemical properties were studied by X-ray diffraction, scanning electron microscopy, galvanostatic charge–discharge experiments, and electrochemical impedance spectroscopy. The results show that the powder is the composite of LiMn2O4 and Ag metal,

Xian Ming Wu; Shang Chen; Ze Qiang He; Zhuo Bing Xiao; Ming You Ma; Jian Ben Liu

2008-01-01

246

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

247

Rapid synthesis of mesoporous ceria–zirconia solid solutions via a novel salt-assisted combustion process  

Microsoft Academic Search

Mesoporous ceria–zirconia solid solutions were prepared by a novel salt-assisted combustion process using ethylene glycol as a fuel and nitrate as an oxidant. The effects of various operating conditions such as the fuel-to-oxidant ratio and the nature and amount of added salt on the characteristics of the products were investigated by X-ray diffraction (XRD) and nitrogen adsorption analysis. Results from

Weifan Chen; Fengsheng Li; Jiyi Yu; Leili Liu; Hailian Gao

2006-01-01

248

Sol gel auto-combustion synthesis of SiO2-doped NiZn ferrite by using various fuels  

Microsoft Academic Search

A nitrate chelate silica gel was prepared from metallic nitrates, citric acid and tetraethoxysilane (TEOS) by sol gel process with different complexing agents such as glycine, hydrazine and citric acid, and it was further used to synthesize Ni0.5Zn0.5Fe2O4\\/20 wt% SiO2 nanocomposites by auto-combustion. The effect of varying complexing agent on the structural and magnetic properties of the composites was studied

K. H. Wu; T. H. Ting; M. C. Li; W. D. Ho

2006-01-01

249

Synthesis of protopanaxadiol derivatives and evaluation of their anticancer activities  

PubMed Central

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

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

2010-01-01

250

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.

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

2008-01-01

251

Aqua mediated synthesis of bio-active compounds.  

PubMed

Recently the aqueous medium has attracted the interest of organic chemists, and many. Moreover, in the past 20 years, the drug-discovery process has undergone extraordinary changes, and high-throughput biological screening of potential drug candidates has led to an ever-increasing demand for novel drug-like compounds. Noteworthy advantages were observed during the course of study on aqua mediated synthesis of compounds of medicinal importance. The established advantages of water as a solvent for reactions are, water is the most abundant and available resource on the planet and many biochemical processes occur in aqueous medium. This review will focus on describing new developments in the application of water in medicinal chemistry for the synthesis of bio-active compounds possessing various biological properties. PMID:23544463

Panda, Siva S

2013-05-01

252

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

253

Study of flame quenching and near-wall combustion of lean burn fuel-air mixture in a catalytically activated spark-ignited lean burn engine  

SciTech Connect

A study of the catalytic activation of charge near the combustion chamber wall and of the flame quenching phenomenon was carried out to identify whether flame quenches due to catalytic activation or due to thermal quenching. It was found that (1) the diffusion rate of fuel into the boundary sublayer limits the catalytic surface reaction rate during combustion; (2) the results of the present flame quench model indicate that the flame quenches due to the heat loss to walls, and the depletion of fuel due to the catalyst coated on the combustion chamber walls does not affect flame quenching; (3) the catalysts coated on the combustion chamber surface do not contribute increased hydrocarbon emissions, but actually reduce them; (4) each catalyst has a specific surface temperature, at which the Damkoehler number for surface reaction is unity.

Nedunchezhian, N. [Department of Automobile Engineering, IRTT, Erode 638 316 (India); Dhandapani, S. [Department of Mechanical Engineering, CIT, Coimbatore 641 014 (India)

2006-01-01

254

Synthesis and pharmacological activities of amine-boranes.  

PubMed

A number of amine-boranes and related derivatives possess a wide range of biological activities including antineoplastic, antiviral, hypolipidemic, anti-inflammatory activities, anti-osteoporotic and dopamine receptor antagonist activities. The compounds include borane complexes of alpha-amino acids, aromatic, aliphatic and heterocyclic amines, and nucleosides. The syntheses of amine-borane derivatives are generally carried out by first preparing a tertiary amine- or phosphine-cyano- or carboxyborane to serve as a borane donor for a subsequent Lewis acid exchange reaction. Borane adducts of simple aliphatic amines, heterocyclic amines and nucleic acids demonstrated potent cytotoxic activity in vitro and in vivo against murine and human tumor models. These boron-containing compounds were shown to inhibit DNA synthesis; such inhibition was caused primarily by reducing de novo purine biosynthesis via inhibition of PRPP amidotransferase, IMP dehydrogenase and dihydrofolate reductase activities. Aliphatic, heterocyclic and nucleoside amine-boranes have also been shown to possess hypolipidemic activity in mice and rats. Many boron derivatives from different chemical classes demonstrated both cytotoxic and hypolipidemic activities. They decreased low-density lipoprotein (LDL) cholesterol while increasing high-density lipoprotein (HDL) cholesterol levels. The mode of action of these compounds in the 50-100 microM concentration range appeared to be by increasing lipid excretion from the body and by inhibiting rate-limiting enzyme activities for the de novo synthesis of lipids and cholesterol (e.g., phosphatidylate phosphohydrolase, ATP-dependent citrate lyase, cytoplasmic acetyl coenzyme A [CoA] synthetase, HMG CoA reductase, and acetyl CoA carboxylase). Selected amine-boranes (e.g., trimethylamine-cyanoborane, N-methylmorpholine-cyanoborane, and the base-boronated 2'-deoxynucleosides) have anti-inflammatory, analgesic, anti-arthritic and anti-osteoporotic activities. PMID:16101500

Burnham, Bruce S

2005-01-01

255

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

256

Comparative Sinterability of Combustion Synthesized and Commercial Titanium Carbides.  

National Technical Information Service (NTIS)

The influence of various parameters on the sinterability of combustion synthesized titanium carbide was investigaged. Titanium carbide powders, prepared by the combustion synthesis process, were sintered in the temperature range 1150 to 1600 exp 0 C. Inco...

B. W. Manley

1984-01-01

257

Synthesis and antiarrhythmic activity of new biologically active potassium and magnesium donors  

Microsoft Academic Search

A series of new biologically active substances have been synthesized on the basis of glutamic acid, pyridoxalphosphate, and\\u000a glycerophosphate to serve as ligands for potassium, calcium, and magnesium donors. General procedures for the synthesis and\\u000a physicochemical characterization of the synthesized compounds are described. The synthesized compounds showed high antiarrhythmic\\u000a activity in tests on rats and rabbits. The most active compounds

A. S. Berlyand; A. A. Prokopov; A. G. Mulyar; M. T. Gasanov

2007-01-01

258

Transition metal mixed oxides as combustion catalysts: preparation, characterization and activity mechanisms  

Microsoft Academic Search

A number of transition metal mixed oxides with spinel-type, corundum-type and perovskite-type structures have been prepared and characterized. Attempts have been made to improve their morphological properties and their stability. Some of them have been tested in the catalytic combustion of methane, CO and H2 (perovskites), of propane and of phenantrene. FT-IR experiments allowed to obtain a quite complete picture

G. Busca; M. Daturi; E. Finocchio; V. Lorenzelli; G. Ramis; R. J. Willey

1997-01-01

259

Synthesis of nanocrystalline NiO\\/doped CeO 2 compound powders through combustion of citrate\\/nitrate gel  

Microsoft Academic Search

The ultrafine NiO\\/doped CeO2 (Ce0.8Gd0.2O1.9) compound powders were synthesized through the combustion of a citrate\\/nitrate gel. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that this method is effective to prepare uniform NiO\\/Ce0.8Gd0.2O1.9 double phase compound powders. Moreover, the appropriate molar ratio of citric acid to rare earth metal ions (MRCM) in the precursors has a strong influence

J. S Lian; X. Y Zhang; H. P Zhang; Z. H Jiang; J Zhang

2004-01-01

260

Combustion engineering  

SciTech Connect

This book is an introduction to combustion science. It discusses general aspects of combustion processes and deals with combustion of premixed mixtures and covers basic concepts of flame propagation, including the flame structure, burning velocity, flame stability, and the Rankine-Hugoniot equations. The book also deals with diffusive combustion, covering laminar and turbulent diffusion flames. Explosions and detonations, including ideal and nonideal explosions, and detonation wave structure are addressed. The determination of the burned gas states is discussed.

Ohtake, K.; Fujiwara, T.

1985-01-01

261

Mild Combustion  

Microsoft Academic Search

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

Antonio Cavaliere; Mara de Joannon

2004-01-01

262

Synthesis, characterization and photoluminescence properties of Gd2O3:Eu3+ nanophosphors prepared by solution combustion method  

NASA Astrophysics Data System (ADS)

Gd2O3:Eu3+ (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) Gd2O3 powders exhibit monoclinic phase with mean crystallite sizes ranging from 20 to 50 nm. Eu3+ 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 Gd2O3:Eu3+ particles show red emission at 611 nm corresponding to 5D0?7F2 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 Eu3+ content.

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

2010-09-01

263

Synthesis and antimicrobial activity of silver-doped hydroxyapatite nanoparticles.  

PubMed

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 Ca(10-x)Ag(x)(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

2012-12-30

264

Synthesis and SAR studies of praziquantel derivatives with activity against Schistosoma japonicum.  

PubMed

The synthesis and structure-activity relationship (SAR) studies of praziquantel derivatives with activity against adult Schistosoma japonicum are described. Several of them showed better worm killing activity than praziquantel and could serve as leads for further optimization. PMID:23912271

Wang, Wen-Long; Song, Li-Jun; Chen, Xia; Yin, Xu-Ren; Fan, Wen-Hua; Wang, Gu-Ping; Yu, Chuan-Xin; Feng, Bainian

2013-07-31

265

Cyclic aza-peptide integrin ligand synthesis and biological activity.  

PubMed

Aza-peptides are obtained by replacement of the ?-C-atom of one or more amino acids by a nitrogen atom in a peptide sequence. Introduction of aza-residues into peptide sequences may result in unique structural and pharmacological properties, such that aza-scanning may be used to probe structure-activity relationships. In this study, a general approach for the synthesis of cyclic aza-peptides was developed by modification of strategies for linear aza-peptide synthesis and applied in the preparation of cyclic aza-pentapeptides containing the RGD (Arg-Gly-Asp) sequence. Aza-amino acid scanning was performed on the cyclic RGD-peptide Cilengitide, cyclo[R-G-D-f-N(Me)V] 1, and its parent peptide cyclo(R-G-D-f-V) 2, potent antagonists of the ?v?3, ?v?5, and ?5?1 integrin receptors, which play important roles in human tumor metastasis and tumor-induced angiogenesis. Although incorporation of the aza-residues resulted generally in a loss of binding affinity, cyclic aza-peptides containing aza-glycine retained nanomolar activity toward the ?v?3 receptor. PMID:22582818

Spiegel, Jochen; Mas-Moruno, Carlos; Kessler, Horst; Lubell, William D

2012-06-04

266

Microstructural Evolution of Titanium Carbide-Chromium Carbide (TiC-Cr3C2) Composites Produced via Combustion Synthesis  

Microsoft Academic Search

A microstructural analysis of compounds produced by com- bustion synthesis coupled with hot pressing, for reactions between titanium, chromium, and carbon, was conducted. The reactions were aimed to produce composites of Cr3C2 and TiC at three different volume fractions of each carbide (25\\/75, 50\\/50, and 75\\/25). Large amounts of chromium and carbon were found to be in solution in the

Augusto O. Kunrath; Ivar E. Reimanis; John J. Moore

2004-01-01

267

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

268

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

269

Co-combustion of coal and biomass in pulverized fuel and fluidized bed systems -- Activities and research in Europe  

Microsoft Academic Search

Biomass or sewage sludge utilized as additional fuel in coal combustion systems has consequences on combustion behavior, emissions, corrosion, and residual matter. Therefore, at the beginning of 1993 the European Union within the frame of the APAS program launched a project called ``Combined Combustion of Biomass\\/Sewage Sludge and Coal''. Within this project, the effects of burning sewage sludge and agricultural

K. R. G. Hein; H. Spliethoff

1999-01-01

270

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

271

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

272

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

273

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

274

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

275

Synthesis, structure characterization and catalytic activity of nickel tungstate nanoparticles  

NASA Astrophysics Data System (ADS)

Taguchi robust design was applied to optimize experimental parameters for controllable, simple and fast synthesis of nickel tungstate nanoparticles. NiWO4 nanoparticles were synthesized by precipitation reaction involving addition of nickel ion solution to the tungstate aqueous reagent and then formation of nickel tungstate nucleolus which are insoluble in aqueous media. Effects of various parameters such as nickel and tungstate concentrations, flow rate of reagent addition and reactor temperature on diameter of synthesized nickel tungstate nanoparticles were investigated experimentally by the aid of orthogonal array design. The results for analysis of variance (ANOVA) showed that particle size of nickel tungstate can be effectively tuned by controlling significant variables involving nickel and tungstate concentrations and flow rate; while, temperature of the reactor has a no considerable effect on the size of NiWO4 particles. The ANOVA results proposed the optimum conditions for synthesis of nickel tungstate nanoparticles via this technique. Also, under optimum condition nanoparticles of NiWO4 were prepared and their structure and chemical composition were characterized by means of EDAX, XRD, SEM, FT-IR spectroscopy, UV-vis spectroscopy, and photoluminescence. Finally, catalytic activity of the nanoparticles in a cycloaddition reaction was examined.

Pourmortazavi, Seied Mahdi; Rahimi-Nasrabadi, Mehdi; Khalilian-Shalamzari, Morteza; Zahedi, Mir Mahdi; Hajimirsadeghi, Seiedeh Somayyeh; Omrani, Ismail

2012-12-01

276

Computational Combustion  

SciTech Connect

Progress in the field of computational combustion over the past 50 years is reviewed. Particular attention is given to those classes of models that are common to most system modeling efforts, including fluid dynamics, chemical kinetics, liquid sprays, and turbulent flame models. The developments in combustion modeling are placed into the time-dependent context of the accompanying exponential growth in computer capabilities and Moore's Law. Superimposed on this steady growth, the occasional sudden advances in modeling capabilities are identified and their impacts are discussed. Integration of submodels into system models for spark ignition, diesel and homogeneous charge, compression ignition engines, surface and catalytic combustion, pulse combustion, and detonations are described. Finally, the current state of combustion modeling is illustrated by descriptions of a very large jet lifted 3D turbulent hydrogen flame with direct numerical simulation and 3D large eddy simulations of practical gas burner combustion devices.

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

2004-08-26

277

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

278

Combustion heater  

Microsoft Academic Search

A wood burning combustion heater comprises a combustion chamber for long logs arranged to burn down from one end to the other in cigar-like fashion, an after-burner tube arrayed above and essentially parallel to the elongated logs with the air and burned gasses following an S-shaped path through the combustion chamber and out through the exhaust tube, an after-burner within

Kalenian

1980-01-01

279

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

280

Rapid synthesis of mesoporous ceria-zirconia solid solutions via a novel salt-assisted combustion process  

SciTech Connect

Mesoporous ceria-zirconia solid solutions were prepared by a novel salt-assisted combustion process using ethylene glycol as a fuel and nitrate as an oxidant. The effects of various operating conditions such as the fuel-to-oxidant ratio and the nature and amount of added salt on the characteristics of the products were investigated by X-ray diffraction (XRD) and nitrogen adsorption analysis. Results from transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) showed that the introduction of leachable inert inorganic salt as a hard agglomeration inhibitor into the redox mixture precursor led to the breakup of fractal nanocrystallite agglomerates and the mesoporous structure formed by the loose agglomeration of monodispersed nanoparticles, which was also confirmed by small-angle XRD and nitrogen adsorption analysis. The presence of salt was found to result in a more than 10-fold increase in the specific surface area of the products from 17.34 to 208.17 m{sup 2}/g at a given molar ratio of ethylene glycol-nitrate. A mechanism scheme was proposed to illustrate the possible formation processes and discuss the role of the salt additives.

Chen Weifan [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing, Jiangsu 210094 (China)]. E-mail: weifan-chen@163.com; Li Fengsheng [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing, Jiangsu 210094 (China); Yu Jiyi [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing, Jiangsu 210094 (China); Liu Leili [College of Chemical Engineering, Shandong Institute of Light Industry, Jinan 250100 (China); Gao Hailian [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing, Jiangsu 210094 (China)

2006-12-14

281

Combustion synthesis of blue-emitting submicron CaAl4O7:Eu2+, Dy3+ persistence phosphor.  

PubMed

Long persistence phosphor CaAl4O7:Eu(2+), Dy(3+) were prepared by a combustion method. The phosphors were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), decay time measurement techniques and photoluminescence spectra (PL). The CaAl4O7:Eu(2+), Dy(3+) phosphor showed a broad blue emission, peaking at 445?nm when excited at 341?nm. Such a blue emission can be attributed to the intrinsic 4f???5d transitions of Eu(2+) in the host lattices. The lifetime decay curve of the Dy(3+) co-doped CaAl4O7:Eu(2+) phosphor contains a fast decay component and another slow decay one. Surface morphology also has been studied by SEM. The calculated CIE colour chromaticity coordinates was (0.227, 043). We have also discussed a possible long-persistent mechanism of CaAl4O7:Eu(2+), Dy(3+) phosphor. All the results indicate that this phosphor has promising potential for practical applications in the field of long-lasting phosphors for the purposes of sign boards and defence. PMID:22162513

Yerpude, A N; Dhoble, S J

2011-12-12

282

Synthesis and anticonvulsant activities of some triazolothiadiazole derivatives.  

PubMed

The present study describes the synthesis and anticonvulsant activity evaluation of 6-substituted-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives (4a-4x) and their partially dehydrogenated products 5,6-dihydro-6-substituted-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives (5a-5n). The bioevaluation demonstrated that most compounds in the series of 4a-4x exhibited potent anticonvulsant activity in the maximal electroshock test. Among which, 6-(4-chlorophenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole (4h) emerged as the most promising candidate on the basis of its favorable ED(50) value of 23.7 mg/kg and PI value of 10.8. In addition, the potency of compound 4h against seizures induced by pentylenetetrazole, 3-mercaptopropionic acid, and bicuculline in the chemical-induced seizure tests suggested that compound 4h displayed broad-spectrum activity in several models, and it may exert its anticonvulsant activity through affecting the GABAergic system. PMID:22532235

Deng, Xian-Qing; Dong, Zheng-Qi; Song, Ming-Xia; Shu, Bing; Wang, Shi-Ben; Quan, Zhe-Shan

2012-04-25

283

Characterization of platelet-activating factor synthesis in glomerular endothelial cell lines.  

PubMed

Platelet-activating factor synthesis in two transformed lines of glomerular endothelial cells was characterized and contrasted with platelet-activating factor production in macrovascular-derived endothelial cells as well as with glomerular cells of mesenchymal origin. Platelet-activating factor synthesis was assessed in intact cells and in cell-free preparations. Glomerular endothelial cells constitutively synthesize bio-active alkyl-PAF, and this basal activity can be chronically augmented by various inflammatory and thrombotic agents. In contrast, thrombin-mediated platelet-activating factor formation in bovine pulmonary aortic endothelial cells as well as in glomerular mesangial cells is acute and transient. The potential role of anti-inflammatory prostanoids to function as negative feedback modulators of thrombin- or endothelin-mediated platelet-activating factor synthesis was also investigated, as the synthesis of platelet-activating factor is often associated with the formation of these prostanoids. Indomethacin augmented receptor-mediated platelet-activating factor synthesis while prostanoids of the E and I series reduced agonist-stimulated PAF synthesis. In summary, the unique capacity of glomerular endothelial cells to respond to inflammatory stimuli with sustained platelet-activating factor synthesis is a clear indication of this cell's pivotal role in augmenting the inflammatory response in the limited environment of the glomerulus. PMID:7853801

Kester, M; Nowinski, R J; Holthöfer, H; Marsden, P A; Dunn, M J

1994-11-01

284

Investigations of high specific activity solid-phase peptide synthesis  

SciTech Connect

There is increasing interest in biological and pharmaceutical research in biotechnology, and drugs based on endogenous peptides. As a result, the demand for high specific activity radiolabeled peptides will continue to increase. It therefore becomes important that there be a variety of effective methods available for the preparation of these compounds, labeled in specific sites. Investigations to date have shown that in the coupling of labeled amino acids in solid-phase peptide synthesis, the efficiency of incorporation into the solid phase increases with decreasing proportions of labeled amino acid, but the fraction of bound radioactivity recoverable as labeled peptide decreases correspondingly. Increasing the reaction time in the coupling compensates to some extent for the low amino acid to resin ratios and the more dilute reaction conditions.

Landvatter, S.W.; Heys, J.R.; Bryan, W.M.; Garnes, K.T.; Blackburn, D.W.

1985-11-01

285

Synthesis and immunosuppressive activity of L-rhamnopyranosyl flavonoids.  

PubMed

Astilbin, a flavonoid isolated from different plants, shows diverse biological activities. This paper reports the synthesis and immunosuppressive activity of seven analogues of astilbin, which may shed light on the structure-activity relationship of the compounds. The following glycosyl flavonoids, 6-alpha-L-rhamnopyranosyloxyflavanone (20), 3-alpha-L-rhamnopyranosyloxyflavone (22), 3-alpha-L-rhamnopyranosyloxyflavanone (24), 3-alpha-L-rhamnopyranosyloxychromanone (26), 4-alpha-L-rhamnopyranosyloxychromanol (27), 7-hydroxy-3-alpha-L-rhamnopyranosyloxyflavanone (30) and 4'-hydroxy-3-alpha-L-rhamnopyranosyloxyflavanone (32) were prepared respectively by glycosylation of 6-hydroxyflavanone (1), 3-hydroxyflavone (2), 3-hydroxyflavanone (5), 3-hydroxychromanone (8), 4-chromanol (9), 7-benzyloxy-3-hydroxyflavanone (12), 4'-benzyloxy-3-hydroxyflavanone (15). Among them, compounds 5, 8, 12 and 15 were synthesized from flavanone (3), 4-chromanone (6), 7-hydroxyflavanone (10) and 4'-hydroxyflavanone (13) respectively. Similar to astilbin (4), compounds 22, 24, 26, 30 and 32 significantly inhibited the single mixed lymphocytes reaction (sMLR) and enhanced the apoptosis of spleen cells isolated from mice with sheep red blood cell-induced delayed-type hypersensitivity respectively. However, compound 20 only showed a slight tendency to inhibit sMLR at higher concentration. Both compounds 20 and 27 did not influence the cell apoptosis. These data suggest that the following factors play essential roles in determining the biological activity of the flavonoids: the position at which the sugar is linked to the flavone, the presence of carbonyl on C-4 and phenol hydroxyl group in A or B ring. However, the presence of a B ring is unfavorable for the biological activity and the double bond at C2-C3 in C-ring shows little effect on the activity. PMID:16763696

Yang, Xiaoliang; Sun, Yang; Xu, Qiang; Guo, Zijian

2006-06-08

286

Regulation of choline sulphatase synthesis and activity in Aspergillus nidulans  

PubMed Central

1. Choline O-sulphate is taken up from the growth medium to the same extent by sulphur-deficient and sulphur-sufficient mycelia of Aspergillus nidulans, but hydrolysis of the transported sulphate ester in vivo only occurs in the sulphur-deficient mycelia. 2. Choline sulphatase activity could not be detected in vitro in sulphur-sufficient mycelia of wild-type and sulphur mutants of A. nidulans, but after sulphur starvation all strains showed appreciable activity of this enzyme. 3. Optimum activity of choline sulphatase in an ultrasonically treated preparation of sulphur-deficient mycelia was at pH7·5. The optimum substrate concentration was in excess of 25mm and Km was 0·035m. The enzyme was completely inhibited by 10mm-SO32?, PO43?, CN? and cysteine. 4. Growth of sulphur-deficient mycelia on various sulphur sources resulted in a decrease of choline sulphatase activity in vitro. The decrease appeared to be due to a repression of choline sulphatase synthesis rather than to inhibition of activity. De-repression by growth on a sulphur-deficient medium was prevented by cycloheximide. Unlike the choline sulphatase of bacteria the fungal enzyme did not need to be substrate-induced. 5. By using sulphur mutants the identity of the co-repressor was limited to S2O32?, cysteine-S-sulphonate, cysteine or compounds derived directly from them. Circumstantial evidence suggests that the co-repressor is cysteine. 6. Inhibition of choline sulphatase activity in vivo was demonstrated with cysteine as the sulphur source for growth.

Scott, J. M.; Spencer, B.

1968-01-01

287

Combustion process  

SciTech Connect

A combustion catalyst containing both manganese and antimony in a temperature range of above about 1260/sup 0/ F. has been found to result in unexpactedly high CO/sub 2//CO ratios in the regenerator off-gas when CO is combusted.

McKay, D.L.

1984-07-03

288

Synthesis and Antiangiogenic Activity of N-Alkylated Levamisole Derivatives  

PubMed Central

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

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

2012-01-01

289

Synthesis and antitumor activity of lapathoside D and its analogs.  

PubMed

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

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

2012-03-28

290

Autotrophic synthesis of activated acetic acid from two CO 2 in Methanobacterium thermoautotrophicum  

Microsoft Academic Search

An in vitro system of autotropic synthesis of activated acetic acid from14CO2 inMethanobacterium thermoautotrophicum was developed.(1)A recognized14CO2-fixation product in vitro was activated [14C] acetic acid. It could be trapped enzymatically into citrate and released again as [14C] acetate by citrate synthase and citrate lyase, respectively.(2)The synthesis of both activated acetic acid and methane from CO2 proceeded in parallel under a

Erhard Stupperich; Georg Fuchs

1984-01-01

291

Some aspects of hydrocarbon activation on platinum group metal combustion catalysts  

Microsoft Academic Search

The activation of different hydrocarbons on Pt and Pd catalysts has been investigated. The role of different forms of surface oxygen, and an explanation for the unusual order of activity (methane > ethane) is presented.

R. Burch; P. K. Loader; F. J. Urbano

1996-01-01

292

Analyses of isoamylase gene activity in wild-type barley indicate its involvement in starch synthesis  

Microsoft Academic Search

The notion of debranching enzyme activity as a participant in starch synthesis is gaining acceptance. Inconsistent reports from mutant analyses implicate either isoamylase or pullulanase as a determinant in amylopectin formation and whether wild-type plants utilize one or the other, or both, of these debranching enzymes in starch synthesis is unclear. Recent results on the su1 mutant in maize suggest

Chuanxin Sun; P. Sathish; Staffan Ahlandsberg; Christer Jansson

1999-01-01

293

Synthesis of glaucogenin d, a structurally unique disecopregnane steroid with potential antiviral activity.  

PubMed

The first chemical synthesis of glaucogenin D, a 13,14:14,15-disecopregnane steroid with potential antiviral activity, has been accomplished in 12 steps from a hirundigenin-type intermediate. The present route would also be amenable to the synthesis of natural and unnatural glaucogenin derivatives for SAR studies. PMID:24011079

Gui, Jinghan; Tian, Hailong; Tian, Weisheng

2013-09-06

294

Isolation, structural determination, and total synthesis of a new biologically active ?-lactone produced by Seiridium unicorne  

Microsoft Academic Search

The structure of a new biologically active ?-lactone, produced by Seiridium unicome, was determined to be (2S,3R,5S)-(?)-2,3-dihydroxytetradecan-5-olide. The relative configuration was elucidated from NMR experiments. The synthesis of the enantiomer from D-glucose revealed the absolute configuration. The total synthesis of the natural form was also achieved from (R)-malic acid.

Hiroaki Toshima; Ayako Watanabe; Hiroji Sato; Akitami Ichihara

1998-01-01

295

Glucose released by hydrolytic activity of amylase influences the pigment synthesis in Penicillium sp NIOM-02.  

PubMed

Carbon catabolite repression is generally considered as a regulatory mechanism to ensure sequential synthesis of secondary metabolites. In this study we made an attempt to understand the influence of amylase activity on pigment synthesis in Penicillium sp NIOM-02. The amylase activity is inversely proportional to pigment production. The high performance liquid chromatography analysis of amylase reaction revealed glucose as the major product of starch hydrolysis. The fungus grown in acarbose (inhibitor of amylase) incorporated media produced higher quantities of pigments. Apparently, glucose released due to amylase activity influenced the pigment synthesis by cAMP signaling pathway. PMID:22581402

Puttananjaiah, Mohan-Kumari H; Dhale, Mohan A

2012-05-14

296

Evaluation of coal combustion byproducts as soil liming materials: their influence on soil pH and enzyme activities  

Microsoft Academic Search

There is considerable interest in the use of coal combustion byproducts as soil liming materials in agricultural production, but there is concern that such use may be detrimental to the quality of agricultural soils. To evaluate these byproducts as liming materials and address issues related to soil quality, we compared the influence of different amounts of four combustion byproducts [fly

R. Siddaramappa; R. J. Wright; E. E. Codling; G. Gao; Gregory W. McCarty

1994-01-01

297

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

Microsoft Academic Search

Residential wood combustion appliances emit large quantities of fine particles which are suspected to cause a substantial health burden worldwide. Wood combustion particles contain several potential health-damaging metals and carbon compounds such as polycyclic aromatic hydrocarbons (PAH), which may determine the toxic properties of the emitted particles. The aim of the present study was to characterize in vitro immunotoxicological and

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

298

Composition, microstructures and properties of Al2O3\\/ZrO2 (Y2O3) self-growing ceramic composites prepared by combustion synthesis under high gravity  

Microsoft Academic Search

By introducing ZrO2 (4Y) powder into the thermit, Al2O3\\/ZrO2 (4Y) composite ceramics were prepared through combustion synthesis under high gravity, and the correlations of composition, microstructures and mechanical properties of composite ceramics were investigated. The results of XRD, SEM and EDS showed that Al2O3\\/33%ZrO2 (4Y) were composed of random-orientated rod-shaped colonies consisting of a triangular dispersion of orderly submicron-nanometer t-ZrO2

Z M Zhao; L Zhang; Y G Song; W G Wang; H B Liu

2009-01-01

299

Microstructures and mechanical properties of large-scale Al2O3\\/ZrO2(Y2O3) self-growing ceramic plates prepared by combustion synthesis under high gravity  

Microsoft Academic Search

By introducing ZrO2 and Y2O3 mixed powder into the thermit, the large-scale Al2O3\\/ZrO2 (Y2O3) self-growing ceramic plates were prepared from the melts through combustion synthesis under high gravity. The materials were mainly formed by randomly-orientated rod-shaped colonies with faceted structures consisting of a triangular dispersion of orderly nanosubmicron ZrO2 fibers in the Al2O3 matrix, surrounded by the boundary regions that

Zhongmin Zhao; Long Zhang; Shiyue Zhang; Chuanzeng Pan; Jing Zhang; Yalin Song; Hao Zhu

2007-01-01

300

Unsaturated and carbocyclic nucleoside analogues: synthesis, antitumor, and antiviral activity.  

PubMed

A series of unsaturated analogues of nucleosides were prepared and their cytotoxic, antitumor, and antiviral activities were investigated. Alkylation of cytosine with (E)-1,4-dichloro-2-butene gave chloro derivative 2f, which was hydrolyzed to alcohol 2h. Cytosine, adenine, 2-amino-6-chloropurine, thymine, and (Z)-1,4-chloro-2-butene gave compounds 4c-f, which, after hydrolysis, afforded alcohols 4a, 4b, 4g, and 4h. Alkenes 4d and 4e were cyclized to heterocycles 12 and 13. Alkylation of 2,6-diaminopurine with 1,4-dichloro-2-butyne led to chloro derivative 6a, which was hydrolyzed to alcohol 6b. Allenic isomerization of 6b gave compound 5c. Chloro derivatives 2e-g, 4c-f, 5d, and 6c-e as well as pyrimidine oxacyclopentenes 9c and 9d are slow-acting inhibitors of murine leukemia L1210 of IC50 10-100 microM. The most active were analogues 4c, 4d, 4e, and 6e (IC50 10-20 microM). The corresponding hydroxy derivatives were less active of inactive. Inhibition of macromolecular synthesis with compounds 4c, 4d, 6e, 9c, and 9d follows the order: DNA greater than RNA greater than or equal to protein. Cytotoxic effects of 4c, 6e, and 9d are not reversed with any of the four basic ribonucleosides or 2'-deoxyribonucleosides. Inhibitory activity of cytosine derivative 9c is reversed with uridine and 2'-deoxyuridine but not with the corresponding cytosine nucleosides. Zone assays in several tumor cell lines show that active compounds are cytotoxic agents with little selectivity for tumor cells. Analogue 6c showed 16.7% ILS in leukemia P388/o implanted ip in mice at 510 and 1020 mg/kg, respectively. Cytallene (5b) and 6'beta-hydroxyaristeromycin (10) exhibited significant activity against Friend and Rauscher murine leukemia viruses. The rest of the hydroxy derivatives, with the exception of 4a, were moderately effective or inactive as antiviral agents. None of the chloro derivatives or oxacyclopentenes exhibited an antiviral effect at noncytotoxic concentrations. Z-Olefin 4b and 2-aminoadenallene (5c) are substrates for adenosine deaminase. PMID:1992143

Phadtare, S; Kessel, D; Corbett, T H; Renis, H E; Court, B A; Zimlicka, J

1991-01-01

301

Detection of androgenic activity in emissions from diesel fuel and biomass combustion.  

PubMed

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 samples were used as tools to separate active from inactive fractions, with the goal of identifying the specific compounds responsible for the activity. A significant androgenic response was detected from the diesel emission. High-performance liquid chromatographic fractionation of the sample indicated that significant androgenic activity was retained in three fractions. 4-Hydroxybiphenyl was identified from the most active fraction using gas chromatography/mass spectroscopy. This purified compound was then tested at doses from 1 nM to 100 microM. 4-Hydroxybiphenol exhibited antagonist activity at low concentrations and agonist activity at high concentrations. A competitive-binding assay confirmed binding to the androgen receptor, with a median inhibitory concentration for radioligand binding of approximately 370 nM. Significant androgenic activity also was detected in the wood burn samples, but we were unable to identify the specific chemicals responsible for this endocrine activity. The present study demonstrates that in vitro bioassays can serve as sensitive bioanalytical tools to aid in characterization of complex environmental mixtures. PMID:16916032

Owens, Clyde V; Lambright, Christy; Cardon, Mary; Gray, L Earl; Gullett, Brian K; Wilson, Vickie S

2006-08-01

302

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

2011-01-07

303

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:21218408

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

2011-01-01

304

Calculating Low Pressure Chemical Activation Atmospheric Hydrocarbon Synthesis Rates  

NASA Astrophysics Data System (ADS)

The formation of larger hydrocarbons, polyacetylenes, aromatics, and nitriles in the reducing atmospheres of the outer planets and moons occurs by recombination and addition reactions of smaller fragments at low temperatures and pressures, difficult to reach in the laboratory. However, because C-C bonds are usually weaker than C-H bonds, cleavage reactions can occur which interrupt this synthesis. The competing dissociation and recombination channels in these chemical activation reactions will be energy and pressure dependent. (Similar competition can occur during photolysis.) The rate constants can be determined computationally using statistical rate theory with parameters available from experiments and quantum calculations. We have applied this approach to generate temperature and pressure dependent rate constant expressions for several reactions that help determine atmospheric concentrations of larger hydrocarbon species in jovian atmospheres. Attention must be paid to isomers and H tunneling. Examples include: H + C3H7 -> CH3 + C2H5 C2H3 + C2H5 -> C4H8, H + C4H7, or CH3 + C3H5 (allyl isomer) H + C3H5 -> C3H6 or CH3 + C2H3 CH3 + CN -> H + CH2CN In addition, if photolysis is followed by internal conversion of electronic energy to vibrationally excited ground state molecules, the same approach may apply to computing C-C scission product yields. Product experiments to test this are underway. Research supported by grants from the NASA Outer Planets Research Program and Planetary Atmospheres Program.

Smith, Gregory P.

2008-09-01

305

Chemical synthesis and immunosuppressive activity of dipalmitoyl phosphatidylinositol hexamannoside.  

PubMed

Phosphatidylinositol mannosides (PIMs) isolated from mycobacteria have been identified as an important class of phosphoglycolipids with significant immune-modulating properties. We present here the synthesis of dipalmitoyl phosphatidylinositol hexamannoside (PIM(6)) 1 and the first reported functional biology of a synthetic PIM(6). Key steps in the synthetic protocol included the selective glycosylation of an inositol 2,6-diol with a suitably protected mannosyl donor and construction of the glycan core utilizing a [3 + 4] thio-glycosylation strategy. The target 1 was purified by reverse phase chromatography and characterized by standard spectroscopic methods, HPLC, and chemical modification by deacylation to dPIM(6). The (1)H NMR spectrum of synthetic dPIM(6) obtained from 1 matched that of dPIM(6) obtained from nature. PIM(6) (1) exhibited dendritic cell-dependent suppression of CD8(+) T cell expansion in a human mixed lymphocyte reaction consistent with the well established immunosuppressive activity of whole mycobacteria. PMID:21574597

Ainge, Gary D; Compton, Benjamin J; Hayman, Colin M; Martin, William John; Toms, Steven M; Larsen, David S; Harper, Jacquie L; Painter, Gavin F

2011-05-24

306

Combustion systems  

SciTech Connect

This patent describes an external combustion engine such as a Stirling engine and the like, having an external heat system housing in which is defined a heater space, a hollow liner formed of a ceramic material disposed in the heater space and defining a combustion chamber. Biasing means are coupled to a first end of the liner and coupled with the housing so as to maintain the liner in the heater space while dampening transmission of vibration in the housing to the liner.

Kralick, J.

1986-03-04

307

Studies on the Development of New Methods of Synthesis of Biologically Active Substances Using Biochemical Systems.  

National Technical Information Service (NTIS)

4 R-Faranal and its four homologues were synthesized by applications of the stereospecific method using pig liver farnesyl pyrophosphate synthetase as a catalyzer for chiral synthesis. The homologues were assayed for trail pheromone activity with Pharaoh'...

K. Ogura T. Koyama M. Kobayashi M. Ito

1984-01-01

308

Brønsted acid assisted activation of imide carbonyl group: regioselective synthesis of isoindoloisoquinolinone alkaloid (±)-nuevamine.  

PubMed

Activation of imide carbonyl group with trifluoromethanesulfonic acid facilitates the intramolecular cyclization of phenethylphthalimides to give a fused isoindoloisoquinolinone skeleton. The first one pot regioselective synthesis of isoindoloisoquinolinone alkaloid (±)-nuevamine has been successfully executed using this methodology. PMID:21938306

Selvakumar, Jayaraman; Ramanathan, Chinnasamy Ramaraj

2011-09-22

309

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 ...

310

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

PubMed Central

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

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

2005-01-01

311

Iron single crystals as ammonia synthesis catalysts: effect of surface structure on catalyst activity  

Microsoft Academic Search

The activity of three iron single-crystal faces with respect to their ability to catalyze ammonia synthesis was investigated. At 798 K and a total pressure of 20 atm of a stoichiometric mixture of hydrogen and nitrogen, the relative rates of ammonia formation were found to be 418:25:1 for Fe(111), Fe(100), and Fe(110) samples, respectively. The activation energy for ammonia synthesis

N. D. Spencer; R. C. Schoonmaker; G. A. Somorjai

1982-01-01

312

C-H activation: a complementary tool in the total synthesis of complex natural products.  

PubMed

The recent advent of transition-metal mediated C-H activation is revolutionizing the synthetic field and gradually infusing a "C-H activation mind-set" in both students and practitioners of organic synthesis. As a powerful testament of this emerging synthetic tool, applications of C-H activation in the context of total synthesis of complex natural products are beginning to blossom. Herein, recently completed total syntheses showcasing creative and ingenious incorporation of C-H activation as a strategic manoeuver are compared with their "non-C-H activation" counterparts, illuminating a new paradigm in strategic synthetic design. PMID:22736530

Chen, David Y-K; Youn, So Won

2012-06-26

313

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

314

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

315

Effect of particle- and specimen-level transport on product state in compacted-powder combustion synthesis and thermal debinding of polymers from molded powders  

NASA Astrophysics Data System (ADS)

The existence of large gradients within particles and fast temporal variations in the temperature and species concentration prevents the use of asymptotic approximations for the closure of the volume-averaged, specimen-level formulations. In this case a solution of the particle-level transport problem is needed to complement the specimen-level volume-averaged equations. Here, the use of combined specimen-level and particle-level models for transport in reactive porous media is demonstrated with two examples. For the gasless compacted-powder combustion synthesis, a three-scale model is developed. The specimen-level model is based on the volume-averaged equations for species and temperature. Local thermal equilibrium is assumed and the macroscopic mass diffusion and convection fluxes are neglected. The particle-level model accounts for the interparticle diffusion (i.e., the liquid migration from liquid-rich to liquid-lean regions) and the intraparticle diffusion (i.e., the species mass diffusion within the product layer formed at the surface of the high melting temperature component). It is found that the interparticle diffusion controls the extent of conversion to the final product, the maximum temperature, and to a smaller degree the propagation velocity. The intraparticle diffusion controls the propagation velocity and to a smaller degree the maximum temperature. The initial stages of thermal degradation of EVA from molded specimens is modeled using volume-averaged equations for the species and empirical models for the kinetics of the thermal degradation, the vapor-liquid equilibrium, and the diffusion coefficient of acetic acid in the molten polymer. It is assumed that a bubble forms when the partial pressure of acetic acid exceeds the external ambient pressure. It is found that the removal of acetic acid is characterized by two regimes, a pre-charge dominated regime and a generation dominated regime. For the development of an optimum debinding schedule, the heating rate is modulated to avoid bubbling, while the concentration and temperature follow the bubble-point line for the mixture. The results show a strong dependence on the presence of a pre-charge. It is shown that isolation of the pre-charge effect by using temporary lower heating rates results in an optimum schedule for which the process time is reduced by over 70% when compared to a constant heating rate schedule.

Oliveira, Amir Antonio Martins

316

The synthesis and photocatalytic activity of ZnSe microspheres  

NASA Astrophysics Data System (ADS)

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

Cao, Huaqiang; Xiao, Yujiang; Zhang, Sichun

2011-01-01

317

The synthesis and photocatalytic activity of ZnSe microspheres.  

PubMed

This paper reports the synthesis of semiconductor ZnSe microspheres composed of nanoparticles via a solvothermal route between the organic molecule selenophene (C(4)H(4) Se) and ZnCl(2) without adding any surfactant. The ZnSe microspheres were characterized by x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), specific surface area measurement, and photoluminescence (PL) spectra. A strong and broad blue PL emission at 443 nm in wavelength (?2.79 eV in photon energy) is attributed to the near-band-edge (NBE) emission of ZnSe, while the 530 nm peak is a defect-related (DL) emission. The photocatalytic activity of the as-prepared ZnSe microspheres was evaluated by photodegradation of methyl orange (MO) dye under ultraviolet (UV) light and visible light irradiation. The degradations of MO reach 94% or 95.1%, close to 100%, in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 7 or 10 h under UV irradiation, respectively. Meanwhile the degradations of MO reach 94.3% or 60.6% in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 12 h, respectively. The degradation rate of ZnSe microspheres is twice that of ZnSe commercial powder under UV light irradiation, and three times under visible light irradiation. The degradation process of MO dye on ZnSe microspheres under UV or visible light is also discussed. PMID:21135462

Cao, Huaqiang; Xiao, Yujiang; Zhang, Sichun

2010-12-06

318

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

319

Synthesis of nanocrystalline yttrium iron garnets by sol–gel combustion process: The influence of pH of precursor solution  

Microsoft Academic Search

The nitrate–citrate gels exhibit auto-catalytic behavior, which can be used to synthesize the nanocrystalline YIG powders. In this study yttrium iron garnet (Y3Fe5O12) nanocrystalline powders were prepared by a sol–gel auto-combustion process. The influence of pH value of the precursor solution on the combustion behavior and the garnet phase formation of synthesized powders were investigated by scanning electron microscopy (SEM),

S. Hosseini Vajargah; H. R. Madaah Hosseini; Z. A. Nemati

2006-01-01

320

Effects of addition of Pt to PdO\\/Al 2O 3 catalyst on catalytic activity for methane combustion and TEM observations of supported particles  

Microsoft Academic Search

Effects of addition of Pt to PdO\\/?-Al2O3 catalyst on the catalytic activity for methane combustion have been investigated. The size distributions and the shapes of supported particles in catalysts and their behavior at high temperature were measured. The results were discussed in relation with the heat resistance of supported particles. Supported particles were characterized by transmission electron microscopy (TEM) and

Kohji Narui; Hirohide Yata; Keiichi Furuta; Akio Nishida; Yasuhiko Kohtoku; Tokuo Matsuzaki

1999-01-01

321

Biofuels combustion.  

PubMed

This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acids and used primarily to replace or supplement conventional diesel fuels. Research efforts on so-called second- and third-generation biofuels are discussed briefly. PMID:23298249

Westbrook, Charles K

2013-01-04

322

A p(v)-N activation strategy for the synthesis of nucleoside polyphosphates.  

PubMed

A general and high-yielding synthesis of nucleoside 5'-triphosphates (NTPs) and nucleoside 5'-diphosphates (NDPs) from protected nucleoside 5'-phosphoropiperidates promoted by 4,5-dicyanoimidazole (DCI) has been developed. (31)P NMR tracing experiments showed that the sequential deprotection and coupling reactions were exceptionally clean. The phosphoropiperidate exhibited superior reactivity to the conventional phosphoromorpholidate toward DCI-promoted NTP/NDP synthesis. The experimental results suggested that the mechanism of DCI activation could be distinctive for NTP and NDP synthesis, depending on the different nucleophilicity of pyrophosphate and phosphate. PMID:23915427

Sun, Qi; Gong, Shanshan; Sun, Jian; Liu, Si; Xiao, Qiang; Pu, Shouzhi

2013-08-22

323

Stratified combustion type engine  

Microsoft Academic Search

The present invention relates to a stratified combustion type engine comprising an engine cylinder, a main combustion chamber located above the cylinder, an injection nozzle for injecting auxiliary fuel towards the combustion chamber, and an open pre-combustion chamber provided within the combustion chamber for locally holding and vaporizing the flow of auxiliary fuel from the injection nozzle. The pre-combustion chamber

Kamiya

1977-01-01

324

Stratified combustion type engine  

Microsoft Academic Search

A stratified combustion type engine is described that is comprised of an engine cylinder, a main combustion chamber located above the cylinder, an injection nozzle for injecting auxiliary fuel towards the combustion chamber, and an open pre-combustion chamber provided within the combustion chamber for locally holding and vaporizing the flow of auxiliary fuel from the injection nozzle. The pre-combustion chamber

Kamiya

1978-01-01

325

Factors influencing synthesis and activity of ?-galactosidase in Lactobacillus acidophilus  

Microsoft Academic Search

Summary In the type-strainLactobacillus acidophilus ATCC 4356 ß-galactosidase (ß-gal) was inducible; lactose, galactose, melibiose and probably maltose, but not glucose, fructose, mannose, sucrose and cellobiose, induced ß-gal synthesis. Glucose partially inhibited ß-gal-induction by lactose but not by isopropyl-ß-D-thiogalactoside. ß-gal synthesis during cell growth was maximal at 0.4% lactose, stimulated by Ca2+ but inhibited by Mg2+ and Mn2+. ß-gal in the

Tarun Bhowmik; M. C. Johnson; Bibek Ray

1987-01-01

326

Yeast protein synthesis. Preparation and analysis of a highly active cell-free system  

PubMed Central

A detailed description is given of the techniques for preparing, handling and assaying a cell-free protein-synthesizing system from yeast, analogous to crude (S-30) Escherichia coli extracts. Its basic characteristics are described. The rate of poly(U)-directed polyphenylalanine synthesis was at least fivefold higher than in previously reported yeast cell-free systems, approaching that of crude mammalian cell-free systems. Fractionation of the S-30 extracts lowered activity. Organelles and their fragments present in the S-30 extract neither contributed to nor inhibited cytoplasmic protein synthesis. There was a component localized in the high-speed supernatant that caused an inhibition of polyphenylalanine synthesis. Poly(U) programmed the synthesis of long-chain polyphenylalanine, in contrast with the only other yeast system in which this has been examined (Bretthauer & Golichowski, 1968). Preincubation techniques inactivated the system and probably a small proportion only of the ribosomes was active.

Sissons, Christopher H.

1974-01-01

327

Synthesis of optimal pendulum control in the presence of active interference  

NASA Astrophysics Data System (ADS)

The problem of optimal control synthesis for a pendulum in the presence of active interference is formulated as a positional linear differential second-order game. By using a combination of numerical and analytical approaches, optimal control synthesis is performed over the entire phase position space. A version of the differential game problem in which the moment of the game end is not fixed is also analyzed.

Sokolov, B. N.; Turova, V. L.

1988-10-01

328

Synthesis of copper-activated zinc sulphide phosphors sensitive to beta radiation  

Microsoft Academic Search

Attempts were made to synthesize copper activated zinc sulphide phosphors sensitive to (beta) -radiation. In this purpose, homogeneous synthesis mixtures were prepared from luminescent grade zinc sulphide - thiosulfate route -, copper nitrate and alkaline and\\/or alkaline-earth chloride and were fired at 800-900 degrees C, in nitrogen atmosphere. ZnS:Cu,Cl phosphors prepared in various synthesis conditions were characterized by crystalline structure,

Elisabeth-Jeanne Popovici; Flavia Forgaciu; Cristina Ciocan; Ligia Pascu; D. Angelescu; C. Postolache

2000-01-01

329

Activation of ribosomal and messenger RNA synthesis in excised Jerusalem artichoke tuber slices  

Microsoft Academic Search

RNA synthesis was studied in Jerusalem artichoke (Helianthus tuberosus L.) tuber slices immediately following excision and during the early period of aging in water. Incorporation of [3H]adenosine into RNA was detected as early as 20 min after excision. Measurement of the specific activities of RNA (cpm\\/µg) and of ATP showed that RNA synthesis proceeded at a constant rate for the

Henry Byrne; George Setterfield

1977-01-01

330

Inhibition of human placental progesterone synthesis by estranes: a novel relationship of structure to activity.  

PubMed

The inhibition of human placental progesterone synthesis by estranes was investigated in vitro. Inhibition tended to increase with structural changes such as unsaturation of ring B, increased planarity and oxidation of the 17-hydroxyl to a ketone while biological "estrogenic" activity decreased. The finding that weak estrogens inhibit progesterone synthesis indicates a natural mechanism for control of hormonogenesis in the human placenta and a new approach to pharmacologic control of fertility. PMID:916672

Edwards, D P; Bransome, E D; O'Conner, J L; Braselton, W E

1977-09-01

331

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

332

Design and synthesis of orally active inhibitors of TNF synthesis as anti-rheumatoid arthritis drugs.  

PubMed

A novel series of TNF inhibitors was identified based on the screening of existing MMP inhibitor libraries. Further SAR optimization led to the discovery of a novel lead compound. Its synthesis, efficacy in experimental animal models, and pharmacokinetic data are discussed. PMID:14592482

Chen, Jian Jeffrey; Dewdney, Nolan; Lin, Xiaohong; Martin, Robert L; Walker, Keith A M; Huang, Jane; Chu, Frances; Eugui, Elsie; Mirkovich, Anna; Kim, Yong; Sarma, Keshab; Arzeno, Humberto; Van Wart, Harold E

2003-11-17

333

Asymmetric oxidation of sulfides catalyzed by titanium and vanadium complexes in the synthesis of biologically active sulfoxides  

NASA Astrophysics Data System (ADS)

Published data on the asymmetric synthesis of chiral biologically active sulfoxides by oxidation of appropriate sulfides catalyzed by titanium and vanadium complexes are generalized. Bibliography — 87 references.

Volcho, Konstantin P.; Salakhutdinov, Nariman F.

2009-05-01

334

Tobacco Mg protoporphyrin IX methyltransferase is involved in inverse activation of Mg porphyrin and protoheme synthesis.  

PubMed

Protoporphyrin, a metabolic intermediate of tetrapyrrole biosynthesis, is metabolized by Mg chelatase and ferrochelatase and is directed into the Mg-branch for chlorophyll synthesis and in the Fe-branch for protoheme synthesis respectively. Regulation of the enzyme activities at the beginning of this branchpoint ensures accurate partition of protoporphyrin, but is still not entirely understood. Transgenic tobacco plants were generated that express antisense or sense RNA for inhibited and excessive expression of Mg protoporphyrin methyltransferase (MgPMT) respectively. This enzyme accepts Mg protoporphyrin from Mg chelatase and catalyses the transfer of a methyl group to the carboxyl group of the C13-propionate side chain. Low MgPMT activity is correlated with reduced Mg chelatase activity and a low synthesis rate of 5-aminolevulinate, but with enhanced ferrochelatase activity. In contrast, high MgPMT activity leads to inverse activity profiles: high activities of Mg chelatase and for 5-aminolevulinate synthesis, but reduced activity of ferrochelatase, indicating a direct influence of MgPMT in combination with Mg chelatase on the metabolic flux of ALA and the distribution of protoporphyrin into the branched pathway. The modified enzyme activities in tetrapyrrole biosynthesis in the transgenic plants can be explained with changes of certain corresponding mRNA contents: increased 5-aminolevulinate synthesis and Mg chelatase activity correlate with enhanced transcript levels of the HemA, Gsa, and CHLH gene encoding glutamyl-tRNA reductase, glutamate-1-semialdehyde aminotransferase and a Mg chelatase subunit respectively. It is proposed that reduced and increased MgPMT activity in chloroplasts is communicated to the cytoplasm for modulating transcriptional activities of regulatory enzymes of the pathway. PMID:15634204

Alawady, Ali E; Grimm, Bernhard

2005-01-01

335

Variation in 3?-hydroxysteroid dehydrogenase activity and in pregnenolone supply rate can paradoxically alter androstenedione synthesis.  

PubMed

The 3?-hydroxysteroid dehydrogenase/?(5)-?(4) isomerase (3?-HSD) and 17?-hydroxylase/17,20-lyase cytochrome P450 (P450c17) enzymes are important in determining the balance of the synthesis of different steroids such as progesterone (P4), glucocorticoids, androgens, and estrogens. How this is achieved is not a simple matter because each of the two enzymes utilizes more than one substrate and some substrates are shared in common between the two enzymes. The two synthetic pathways, ?(4) and ?(5), are interlinked such that it is difficult to predict how the synthesis of each steroid changes when any of the enzyme activities is varied. In addition, the P450c17 enzyme exhibits different substrate specificities among species, particularly with respect to the 17,20-lyase activity. The mathematical model developed in this study simulates the network of reactions catalyzed by 3?-HSD and P450c17 that characterizes steroid synthesis in human, non-human primate, ovine, and bovine species. In these species, P450c17 has negligible 17,20-lyase activity with the ?(4)-steroid 17?-hydroxy-progesterone (17OH-P4); therefore androstenedione (A4) is synthesized efficiently only from dehydroepiandrosterone (DHEA) through the ?(5) pathway. The model helps to understand the interplay between fluxes through the ?(4) and ?(5) pathways in this network, and how this determines the response of steroid synthesis to the variation in 3?-HSD activity or in the supply of the precursor substrate, pregnenolone (P5). The model simulations show that A4 synthesis can change paradoxically when 3?-HSD activity is varied. A decrease in 3?-HSD activity to a certain point can increase A4 synthesis by favouring metabolism through the ?(5) pathway, though further decrease in 3?-HSD activity beyond that point eventually limits A4 synthesis. The model also showed that due to the competitive inhibition of the enzymes' activities by substrates and products, increasing the rate of P5 supply above a certain point can suppress the synthesis of A4, DHEA, and 17OH-P4, and consequently drive more P5 towards P4 synthesis. PMID:22024430

Nguyen, Phuong T T; Lee, Rita S F; Conley, Alan J; Sneyd, James; Soboleva, Tanya K

2011-10-17

336

Activation of PPAR? lowers synthesis and concentration of cholesterol by reduction of nuclear SREBP-2  

Microsoft Academic Search

To elucidate the mechanisms underlying the cholesterol lowering effects of PPAR? agonists we investigated key regulators of cholesterol synthesis and uptake in rats and in the rat hepatoma cell line Fao after treatment with the PPAR? agonists clofibrate and WY 14,643, respectively. In rat liver as well as in Fao cells, PPAR? activation led to a decrease of transcriptionally active

Bettina König; Alexander Koch; Julia Spielmann; Christian Hilgenfeld; Gabriele I. Stangl; Klaus Eder

2007-01-01

337

Synthesis of novel HIV protease inhibitors (PI) with activity against PI-resistant virus.  

PubMed

A series of HIV protease inhibitors with modifications on the P3 position have been designed and synthesized. These compounds exhibit excellent antiviral activity against both the wild type enzyme and PI-resistant clinical viral isolates. The synthesis and biological activity of the compounds are described. PMID:17692518

Raghavan, Subharekha; Lu, Zhijian; Beeson, Teresa; Chapman, Kevin T; Schleif, William A; Olsen, David B; Stahlhut, Mark; Rutkowski, Carrie A; Gabryelski, Lori; Emini, Emilio; Tata, James R

2007-07-31

338

Design and synthesis of highly potent HIV protease inhibitors with activity against resistant virus.  

PubMed

A series of highly potent HIV protease inhibitors have been designed and synthesized. These compounds are active against various clinical viral isolates as well as wild-type virus. The synthesis and biological activity of these HIV protease inhibitors are discussed. PMID:12729673

Lu, Zhijian; Raghavan, Subharekha; Bohn, Joann; Charest, Mark; Stahlhut, Mark W; Rutkowski, Carrie A; Simcoe, Amy L; Olsen, David B; Schleif, William A; Carella, Anthony; Gabryelski, Lori; Jin, Lixia; Lin, Jiunn H; Emini, Emilio; Chapman, Kevin; Tata, James R

2003-05-19

339

Design, synthesis, and structure-activity relationship studies of ATP analogues as DNA gyrase inhibitors.  

PubMed

We report herein the design and synthesis of ATP-analogues, namely 4-amino-pyrazolo[3,4-d]pyrimidines and 4-amino-pyrazolo[1,5-a][1,3,5]triazines, with DNA gyrase inhibitory activity. Among these series, some compounds exhibited promising antibacterial activity. PMID:10782694

Lübbers, T; Angehrn, P; Gmünder, H; Herzig, S; Kulhanek, J

2000-04-17

340

An active RC synthesis and design of filters using voltage-to-current transducers  

Microsoft Academic Search

This paper presents an active RC synthesis and design of filters on the basis of nodal admittance matrix. The method implies the construction of equivalent (2 × 2) nodal admittance matrices satisfying the voltage transfer-functions of Type 1 and Type 2. Each of the matrices so obtained is found to be realized by positive resistances, capacitances and an active element VCT. The

S. K. Saha

1970-01-01

341

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

342

Effect of Pd or Ag additive on the activity and stability of monolithic LaCoO 3 perovskites for catalytic combustion of methane  

Microsoft Academic Search

The LaCoO3 perovskite-type catalysts in this study were monoliths resting on supports made of heat-resisting foil and washcoated with Al2O3. The La0.9Ag0.1CoO3 or La0.92Pd0.08CoO3 perovskite was used as the active phase. Partial substitution of lanthanum in the LaCoO3 perovskite with palladium or silver enhances the activity of the monolithic catalysts in the combustion of methane. XPS and XRD analyses show

Barbara Kucharczyk; W?odzimierz Tylus

2004-01-01

343

Design of low-temperature Pt-carbon combustion catalysts for VOC's treatments  

Microsoft Academic Search

Two series of Pt\\/C-catalysts were prepared using pure carbon aerogels as supports. The influence of porosity, surface chemistry and Pt dispersion on the activity of Pt\\/C combustion catalysts was analyzed. The synthesis of the supports was fitted to have a monomodal pore size distribution in the meso and macropore range respectively. Both supports were functionalized by oxidation treatment with H2O2

S. Morales-Torres; F. J. Maldonado-Hódar; A. F. Pérez-Cadenas; F. Carrasco-Marín

2010-01-01

344

Sound Synthesis by Flexible Activation Function Recurrent Neural Networks  

Microsoft Academic Search

In this paper we investigate on the use of adaptive spline neural networks, to define a new general class of physical-like\\u000a sound synthesis models, based on a learning from examples strategy (in particular in this paper we study single-reed woodwind\\u000a instruments). It is well known that one of the main problems in physical modeling concerns the difficulty of parameter identification

Aurelio Uncini

2002-01-01

345

RNA-targeted activators, but not DNA-targeted activators, repress the synthesis of short transcripts at the human immunodeficiency virus type 1 long terminal repeat.  

PubMed Central

The human immunodeficiency virus type 1 (HIV-1) promoter directs the synthesis of two types of RNA molecules: full-length transcripts, whose synthesis is activated by the viral activator Tat, and short transcripts, whose synthesis is dependent on the inducer of short transcripts (IST), a bipartite DNA element located in large part downstream of the HIV-1 transcriptional start site. In the absence of Tat, short transcripts constitute the large majority of the RNA molecules synthesized from the HIV-1 promoter. In the presence of Tat, synthesis of the short transcripts is repressed and synthesis of the full-length transcripts is activated. Tat is unique among transcriptional activators in acting through an RNA target, the TAR element. However, Tat has been shown to activate transcription from a DNA target when fused to the appropriate DNA binding domain, raising the question of why Tat has been directed to the RNA. Here we have compared the abilities of Tat and other RNA- and DNA-bound activators to stimulate transcription from the HIV-1 promoter. We show that DNA-targeted activators, including DNA-targeted Tat, activate the synthesis of both short and long transcripts, while RNA-targeted Tat and another RNA-targeted activator activate the synthesis of full-length transcripts but specifically repress that of short transcripts. The unique ability of RNA-targeted activators to down-regulate short transcript synthesis suggests that Tat is directed to the RNA specifically for the purpose of repressing short transcripts.

Pendergrast, P S; Hernandez, N

1997-01-01

346

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

Microsoft Academic Search

Much if not all of the chlorine present in fossil fuels is released into the atmosphere as hydrogen chloride (HCl) and chloromethane (CH3Cl, methyl chloride). The chlorine content of oil-based fuels is so low that these sources can be neglected, but coal combustion provides significant releases. On the basis of national statistics for the quantity and quality of coal burned

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

1999-01-01

347

Cobalt Molybdenum Oxynitrides: Synthesis, Structural, Characterization, and Catalytic Activity for the Oxygen Reduction Reaction  

SciTech Connect

Here, we report the synthesis and characterization of CoxMo1 xOyNz compounds supported on carbon black as potential cathode catalysts for ORR. They were prepared by a conventional impregnation method. Their ORR activities in both acid and alkaline electrolytes were evaluated via half-cell measurements. The synthesis temperature and sample composition both strongly impacted their physical and chemical properties. Factors influencing their crystal structures, morphologies and ORR activities will be discussed based on the results of structural and spectroscopic studies.

Cao, Bingfei [ORNL; Veith, Gabriel M [ORNL; Diaz, Rosa [Brookhaven National Laboratory (BNL); Liu, Jue [State University of New York, Stony Brook; Stach, Eric [Brookhaven National Laboratory (BNL); Adzic, Radoslav R. [Brookhaven National Laboratory (BNL); Khalifah, P. [Stony Brook University (SUNY)

2013-01-01

348

Liquid fuel combustion apparatus  

Microsoft Academic Search

This patent describes a vaporized liquid fuel combustion apparatus of the type including: a cylinder defining a combustion chamber, the cylinder having an inlet end for receipt of combustion air and an outlet end for exhausting gaseous combustion products; an end plate covering the inlet end of the cylinder; a blower, including a rotor and a casing, for supplying combustion

K. Sawada; Y. Kimijima; H. Umehara

1986-01-01

349

Gas turbine combustion  

Microsoft Academic Search

This text focuses on the fundamentals of gas turbine combustion, emphasizing combustor design and performance. The material presented is based on the latest research results. Aerodynamic and heat transfer processes in gas turbine combustors as well as the combustion performance parameters of ignition, combustion efficiency, and stability are described. Some of the topics covered are combustion fundamentals; diffusers; aerodynamics; combustion

1983-01-01

350

Synthesis of aminoquinazoline derivatives and their antiproliferative activities against melanoma cell line.  

PubMed

The synthesis of a novel series of aminoquinazoline derivatives 1a-r and their antiproliferative activities against A375 human melanoma cell line were described. Among them, six compounds showed superior antiproliferative activities to Sorafenib as a reference compound. In particular, the representative compound 1q bearing chromen-4-one moiety exhibited excellent antiproliferative activity (IC(50)=0.006 ?M) and good selectivity over HS27 fibroblast cell line. PMID:20797858

Lee, Junsang; Nam, Bong Soo; Kim, Hwan; Oh, Chang-Hyun; Lee, So Ha; Cho, Seung Joo; Sim, Tae Bo; Hah, Jung-Mi; Kim, Dong Jin; Tae, Jinsung; Yoo, Kyung Ho

2010-08-06

351

Fundamental combustion and diagnostics research at Sandia. Progress report, April-June 1980  

SciTech Connect

The combustion research emphasizes basic research into fundamental problems associated with combustion. The overall program addresses detailed chemistry of combustion, fundamental processes associated with laminar and turbulent flames, development of research techniques specifically applicable to combustion environments, and operation of the user-oriented Combustion Research Facility. The first section of this report contains activities in Combustion Research, the second section contains activities in Molecular Physics and Spectroscopy, and the third section contains activities in Diagnostics Research.

Gusinow, M.A. (ed.)

1980-09-01

352

[Synthesis and expression of transforming growth factor-beta in activated macrophages].  

PubMed

It has been established that once macrophages become activated, they pass through different stages of functional activity. Mouse macrophages activated by BCG "exerted" pronounced cytotoxic effects for 2-5 days to be followed later by growth-stimulating ones. However, in other experiments, the cytotoxic effect was either absent or occurred at later stages which was probably due to a certain functional state of macrophages before activation. The synthesis of TGF-beta increased 1-2 days after activation with BCG vaccine, lipopolysacharide and gamma radiation. An increase in mRNA TGF-beta i expression was observed only 5 days after activation of macrophages. PMID:9064911

Zubova, S G; Danilov, A O; Okulov, V B; Kiagulov, D F; Stiuf, I I; Zaritski?, A I

1996-01-01

353

Serum factors affect Na+ pump activity and DNA synthesis in cultured cerebellar neural cells.  

PubMed

In neurone-enriched cultures derived from early postnatal rat cerebellum and maintained in serum-free medium, addition of serum (10% FCS) evoked a rapid increase in Na+ pump activity (as measured by ouabain-sensitive 86Rb accumulation) by activation of a Na+/H+ exchanger. This effect did not occur with cultured cerebellar astrocytes. In contrast, exposure to serum increased DNA synthesis ([3H]thymidine incorporation) in both cultured cerebellar astrocytes and in the neurone-enriched cultures. However, in the latter cultures this effect was shown by autoradiography to be due to contaminating astrocytes. Thus, in cultured cerebellar neural cells an enhancement of intracellular Na+ accumulation by serum factors may not be linked to initiation of DNA synthesis. Furthermore, raising intracellular Na+ by ouabain exposure actually decreased neural cellular DNA synthesis. PMID:4065424

Atterwill, C K; Atkinson, D J

1985-11-01

354

Lymphocyte activation induced by Trichinella spiralis infection reflected as spontaneous DNA synthesis in vitro.  

PubMed Central

Spleen cells from mice, infected with Trichinella spiralis, were cultured in micro and macrocultures without stimulatory agents. As controls, various polyclonal T and B cell activators were used. During the course of the infection the cells exhibited an increased spontaneous DNA synthesis compared to the cells from uninfected controls. It was also found that the relative proportion of theta and Ig-positive cells and macrophages was not significantly affected by the infection. To characterize the in vivo stimulated cells one week after infection various techniques were used. Autoradiography combined with immunofluorescence revealed that virtually all labelled cells were Ig-negative. Removal of macrophages by silica powder decreased the spontaneous DNA synthesis but not to the level of the controls. Spleen cells from infected nude mice did not show any increased spontaneous DNA synthesis, whereas the effluent cells obtained after separation on Ig-complexed columns still showed an enhanced spontaneous DNA synthesis. These results indicate that T. spiralis infection causes a macrophage dependent activation of T cells which in vitro is detectable as spontaneous DNA synthesis.

Ljungstrom, I; Sundqvist, K G

1979-01-01

355

Pulsating Combustion Device Miniaturization.  

National Technical Information Service (NTIS)

The phenomenon of pulsating combustion remains one of the least understood forms of combustion. In this thesis, combustion oscillations are classified into the categories of chamber oscillations, system oscillations, and intrinsic oscillations. Two pulsat...

R. K. Crowe

1976-01-01

356

Synthesis, properties, sintering and microstructure of sphene, CaTiSiO{sub 5}: A comparative study of coprecipitation, sol-gel and combustion processes  

SciTech Connect

Sphene (CaTiSiO{sub 5}), a titanosilicate ceramic considered as a host material for the immobilization of radioactive waste from nuclear power reactors, has been prepared using coprecipitation, sol-gel, and solution combustion methods. All these processes initially yielded amorphous powders, which on further calcination, crystallized to yield sphere along with perovskite, titania, and cristobalite. The coprecipitation-derived powder calcined at 1,000 C for 2 h showed the formation of single phase sphere; whereas, the sol-gel-derived and combustion-derived powders required higher temperature (1,200 C for 2 h) for single phase sphene to form. Coprecipitation-derived sphene powder achieved 96% theoretical density when sintered at 1,300 C for 2 h, and the microstructure of the sintered body showed a uniform grain size of {approx} 1 {micro}m.

Muthuraman, M.; Patil, K.C. [Indian Inst. of Science, Bangalore (India). Dept. of Inorganic and Physical Chemistry

1998-04-01

357

Synthesis of the long-persistence phosphor CaAl2O4:Eu2+, Dy3+, Nd3+ by combustion method and its luminescent properties.  

PubMed

Calcium aluminate phosphor co-doped Eu(2+), Dy(3+), Nd(3+) is prepared by the combustion method. We study systemically the influences of the quantity of mixed Dy(3+) ion, the quantity of flux H(3)BO(3), the differences in dispersing methods between magnetic stirring and ultrasonic dispersing and the combustion temperature on the long-persistence phosphor. The analytical results indicate that Dy(3+) ion improves the properties of the phosphors CaAl(2)O(4):Eu(2+), Nd(3+). The appropriate quantity of flux H(3)BO(3 )to( )reduce the forming temperature of the sample was determined. The monoclinic single phase of CaAl(2)O(4) formed at 500 degrees C and remained steady. The calcium aluminate co-doped Eu(2+), Dy(3+), Nd(3+) was synthesized by dispersal of the raw material using the ultrasonic method, and it had better optical properties. PMID:19572382

Zhang, Bo; Zhao, Changliang; Chen, Donghua

358

Synthesis and antiparasitic activity of albendazole and mebendazole analogues.  

PubMed

Albendazole (Abz) and Mebendazole (Mbz) analogues have been synthesized and in vitro tested against the protozoa Giardia lamblia, Trichomonas vaginalis and the helminths Trichinella spiralis and Caenorhabditis elegans. Results indicate that compounds 4a, 4b (Abz analogues), 12b and 20 (Mbz analogues) are as active as antiprotozoal agents as Metronidazole against G. lamblia. Compound 9 was 58 times more active than Abz against T. vaginalis. Compounds 8 and 4a also shown high activity against this protozoan. Compounds 4b and 5a were as active as Abz. None of the Mbz analogues showed activity against T. vaginalis. The anthelmintic activity presented by these compounds was poor. PMID:14527558

Navarrete-Vázquez, Gabriel; Yépez, Lilián; Hernández-Campos, Alicia; Tapia, Amparo; Hernández-Luis, Francisco; Cedillo, Roberto; González, José; Martínez-Fernández, Antonio; Martínez-Grueiro, Mercedes; Castillo, Rafael

2003-10-15

359

Localization of epidermal sphingolipid synthesis and serine palmitoyl transferase activity: alterations imposed by permeability barrier requirements  

Microsoft Academic Search

Sphingolipids, the predominant lipid species in mammalian stratum corneum play, a central role in permeability barrier homeostatis. Prior studies have shown that the epidermis synthesizes abundant sphingolipids, a process regulated by barrier requirements, and that inhibition of sphingolipid synthesis interferes with barrier homeostasis. To investigate further the relationship between epidermal sphingolipid metabolism and barrier function, we localized sphingolipid synthetic activity

W. M. Holleran; W. N. Gao; K. R. Feingold; P. M. Elias

1995-01-01

360

Synthesis and HDAC inhibitory activity of isosteric thiazoline-oxazole largazole analogs.  

PubMed

The synthesis of an isosteric analog of the natural product and HDAC inhibitor largazole is described. The sulfur atom in the thizaole ring of the natural product has been replaced with an oxygen atom, constituting an oxazole ring. The biochemical activity and cytotoxicity of this species is described. PMID:24035339

Guerra-Bubb, Jennifer M; Bowers, Albert A; Smith, William B; Paranal, Ronald; Estiu, Guillermina; Wiest, Olaf; Bradner, James E; Williams, Robert M

2013-06-18

361

Antimelanogenic activity of hydrocoumarins in cultured normal human melanocytes by stimulating intracellular glutathione synthesis  

Microsoft Academic Search

The antimelanogenic activity of six hydrocoumarins and !-tocopherol (!-Toc) in normal human melanocytes was evaluated in both cell culture systems and cell homogenates. The inhibitory effects of hydrocoumarins depended upon their substituent groups. !-Toc and some of the hydrocoumarins inhibited melanogenesis in cultured normal human melanocytes, although they did not influence melanin synthesis in enzyme solution prepared as cell homogenates.

Tatsuo Yamamura; Junichi Onishi; Tomihiro Nishiyama

2002-01-01

362

Direct organic functionalization of Ti–MCM-41: Synthesis condition, organic content, and catalytic activity  

Microsoft Academic Search

The conditions for the direct synthesis of organically functionalized Ti-substituted MCM-41 materials have been investigated to improve the catalytic efficiency in epoxidation reactions. The 29Si MAS NMR measurements indicate that there is a strong correlation between the catalytic activity and the surface hydrophobicity estimated by means of water adsorption capacity regardless of the kind of modifying organic groups. In the

Naoko Igarashi; Satoshi Kidani; Rizwan Ahemaito; Kazuhito Hashimoto; Takashi Tatsumi

2005-01-01

363

Synthesis of 4-trifluoromethylpyrido[1,2- a]pyrimidin-2-ones utilizing activated alkynoates  

Microsoft Academic Search

The synthesis of the biologically relevant, 4-trifluoromethylpyrido[1,2-a]pyrimidin-2-one 7, is reported. Addition of substituted 2-aminopyridines 5 to activated alkynoates leads to the facile formation of a series of metabolically stable trifluoromethyl substituted pyrido[1,2-a]pyrimidines under mild conditions.

Geraldine C. B Harriman; Shannon Chi; Min Zhang; Andrea Crowe; Robert A Bennett; Ian Parsons

2003-01-01

364

Synthesis and structure-activity relationship (SAR) study of 4-azabenzoxazole analogues as H3 antagonists.  

PubMed

The synthesis and SAR of a novel series of 4-azabenzoxazole histamine H(3) antagonists is described. Introduction of substituted phenyl, pyridyl and fused heterocyclic groups to the 6-position of the 4-azabenzoxazole core gave a series of compounds with good H(3) antagonist activity in both ex vivo and in vivo assays. PMID:22326166

Shao, Ning; Aslanian, Robert; West, Robert E; Williams, Shirley M; Wu, Ren-Long; Hwa, Joyce; Sondey, Christopher; Lachowicz, Jean; Palani, Anandan

2012-01-24

365

Synthesis and antibacterial activity of some new heterocycles incorporating phthalazine.  

PubMed

3-(1,4-Dioxo-3,4,4e,5,10,10a-hexahydro-1H-5,10-benzeno-benzo[g]phthalazin-2-yl)-3-oxo-propiononitrile (1) was utilized as key intermediate for the synthesis of some new iminocoumarin 2, chromenone 3, aminothiazole 4, triazepine 5a, b and 6, hydrazono-propiononitrile 7, pyridopyrazotriazine 8, monobromo 9, dibromo 10 quinoxaline 11, ketene N,S-acetal 13, ketene S,S-diacetal 17 and 18a, b and methyl dithioate 20 derivatives, respectively. The newly synthesized compounds were characterized by IR, (1)H NMR, (13)C NMR and mass spectral studies. Representative compounds of the synthesized product were tested and evaluated as antibacterial agent. PMID:19570595

Khalil, A M; Berghot, M A; Gouda, M A

2009-06-13

366

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

367

Synthesis and Antifungal Activity of Musa Phytoalexins and Structural Analogs  

Microsoft Academic Search

Several perinaphthenone\\/phenylphenalenone compounds were synthesized to e s- tablish a relationship between structure and antifungal activity against Mycosphaerella fijien- sis. Substitutions on the unsaturated carbonyl system or addition of a phenyl group reduced antibiotic activity.

Winston Quiñones; Gustavo Escobar; Fernando Echeverri; Fernando Torres; Yoni Rosero; Victor Arango; Gloria Cardona; Adriana Gallego

2000-01-01

368

The Application of Self-Propagating High-Temperature Synthesis of Engineered Porous Composite Biomedical Materials  

Microsoft Academic Search

The term “self-propagating high-temperature synthesis” (SHS), or “combustion synthesis”, refers to an exothermic chemical reaction process that utilizes the heat generated by the exothermic reaction to ignite and sustain a propagating combustion wave through the reactants to produce the desired product(s). The products of combustion synthesis normally are extremely porous: Typically 50 percent of theoretical density. Advantages of combustion synthesis

R. Ayers; D. Burkes; G. Gottoli; H. C. Yi; J. J. Moore

2007-01-01

369

Effects of activation methods on DNA synthesis and development of parthenogenetic porcine embryos.  

PubMed

This study investigated the timing of DNA synthesis and patterns of pronuclear (PN) formation during the first cell cycle, and its influence on developmental competence, velocity and proliferation index of porcine parthenote blastocysts produced by different activation treatments. Oocytes were activated as follows: electrical stimulation (EST), EST combined with 7.5 ?g/ml cytochalasin B (EST + CCB), 10 ?g/ml cycloheximide (EST + CHX) and 1.9 mm 6-dimethylaminopurine (EST + 6-DMAP) for 3 h. DNA synthesis and PN formation were evaluated using 1 mm 5'bromo-2'deoxy-uridne (BrdU) at 2 h intervals from 1 to 13 h or 5 to 13 h of post-activation (hpa), respectively. In EST, DNA synthesis started at 3 hpa, reached the peak at 11 hpa and decreased at 13 hpa. Treatment with 6-DMAP resulted in an early increase of DNA synthesis at 3 hpa, whereas CCB delayed DNA synthesis for 2 h. In EST and EST + 6-DMAP, most of the eggs showed 1PN, whereas, incidence of 2PN in EST + CCB was higher than 1PN. EST + CHX was observed with 1PN, 2PN and multiple PN. Blastocyst rate in EST + CCB and EST + 6-DMAP were significantly (p<0.05) higher than EST + CHX. But, the developmental velocity was not different among groups. Proliferation index of blastocysts, as indicated the number of blastomere at S-phase of the cell cycle was low in all groups. In conclusion, CCB, CHX and 6-DMAP used for producing porcine parthenogenetic embryos induced different onset of DNA synthesis and PN, but they did not affect the subsequent embryo development. PMID:21492262

Ock, S A; Kwack, D O; Mohana Kumar, B; Han, J; Kim, S W; Rho, G J

2011-04-15

370

Tryptophan analogues. 1. Synthesis and antihypertensive activity of positional isomers.  

PubMed

A series of tryptophan analogues having the carboxyl function at the beta-position was synthesized and tested for antihypertensive activity. The 5-methoxy analogue 46 exhibited antihypertensive activity in the rat via the oral route and was much more potent than the normal tryptophan analogue. The methyl ester was found to be a critical structural feature for activity. PMID:7097726

Safdy, M E; Kurchacova, E; Schut, R N; Vidrio, H; Hong, E

1982-06-01

371

Synthesis and anti-platelet activity of obovatol derivatives  

Microsoft Academic Search

Obovatol derivatives were synthesized and evaluated for anti-platelet activity. Three derivatives (1, 2, 4i) displayed equipotent activity to obovatol in arachidonic acid-induced platelet aggregation. An initial SAR study revealed\\u000a that the introduction of alkoxy group in B ring could enhance inhibitory activity.

Jae-Hwan Kwak; Seul Lee; Eun-Seok Park; Jin-Kyung In; Jiho Song; Young Jin Kim; Nam Song Choi; Heesoon Lee; Yeo-Pyo Yun; Jin Tae Hong; Young-Shin Kwak; Kyung Hoon Min; Jae-Kyung Jung

2011-01-01

372

c-Fos Activates Glucosylceramide Synthase and Glycolipid Synthesis in PC12 Cells*  

PubMed Central

It has been demonstrated that c-Fos has, in addition to its well recognized AP-1 transcription factor activity, the capacity to associate to the endoplasmic reticulum and activate key enzymes involved in the synthesis of phospholipids required for membrane biogenesis during cell growth and neurite formation. Because membrane genesis requires the coordinated supply of all its integral membrane components, the question emerges as to whether c-Fos also activates the synthesis of glycolipids, another ubiquitous membrane component. We show that c-Fos activates the metabolic labeling of glycolipids in differentiating PC12 cells. Specifically, c-Fos activates the enzyme glucosylceramide synthase (GlcCerS), the product of which, GlcCer, is the first glycosylated intermediate in the pathway of synthesis of glycolipids. By contrast, the activities of GlcCer galactosyltransferase 1 and lactosylceramide sialyltransferase 1 are essentially unaffected by c-Fos. Co-immunoprecipitation experiments in cells co-transfected with c-Fos and a V5-tagged version of GlcCerS evidenced that both proteins participate in a physical association. c-Fos expression is tightly regulated by specific environmental cues. This strict regulation assures that lipid metabolism activation will occur as a response to cell requirements thus pointing to c-Fos as an important regulator of key membrane metabolisms in membrane biogenesis-demanding processes.

Crespo, Pilar M.; Silvestre, David C.; Gil, German A.; Maccioni, Hugo J. F.; Daniotti, Jose L.; Caputto, Beatriz L.

2008-01-01

373

Developing novel organocatalyzed aldol reactions for the enantioselective synthesis of biologically active molecules  

PubMed Central

Aldol reaction is one of the most important methods for the formation of carbon-carbon bonds. Because of its significance and usefulness, asymmetric versions of this reaction have been realized with different approaches in the past. Over the last decade, the area of organocatalysis has made significant progresses. As one of most studied reactions in organocatalyses, organocatalyzed aldol reaction has emerged as a powerful tool for the synthesis of a large number of useful products in optically enriched forms. In this review, we summarize our efforts on the development of novel organocatalyzed aldol reactions for the enantioselective synthesis of biological active molecules. Literatures closely related to our studies are also covered.

Bhanushali, Mayur; Zhao, Cong-Gui

2011-01-01

374

Synthesis, antimicrobial and anticancer activity of new thiosemicarbazone derivatives.  

PubMed

Thiosemicarbazones of p-aminobenzoic acid (PABA) were synthesized and tested for their antimicrobial and anticancer activity. Hydroxamate derivatives 4a-4l were found to have better antimicrobial and anticancer activity than their acid counterpart. Compound 4d was found to have good antimicrobial activity against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Vibrio cholerae, and Bacillus subtilis with IC(50) value of about 1 µM. Compound 4f showed potent antifungal activity against Candida albicans (IC(50) ?= 1.29 µM) and compound 4h showed potent anticancer activity (IC(50) ?= 0.07 µM). PMID:21290424

Kulandaivelu, Umasankar; Padmini, Valisakka Gari; Suneetha, Kyatham; Shireesha, Boyapati; Vidyasagar, Jannu Vincent; Rao, Tadikonda Rama; K N, Jayaveera; Basu, Arijit; Jayaprakash, Venkatesan

2010-11-25

375

Synthesis and AChE inhibitory activity of new chiral tetrahydroacridine analogues from terpenic cyclanones.  

PubMed

This work describes the enantioselective synthesis of a new series of terpenic chiral 9-aminotetrahydroacridine analogues. Several chiral ketones were synthesized from natural monoterpenes in an optically active form and subjected to the cyclodehydration reactions with anthranilonitrile in the presence of BF(3).Et(2)O as catalyst. The 9-aminotetrahydroacridine analogues were tested as acetylcholinesterase (AChE) inhibitors. Based on qualitative structure-activity relationship some trends are suggested. PMID:19954865

dos Santos Pisoni, Diego; Sobieski da Costa, Jessé; Gamba, Douglas; Petzhold, Cesar Liberato; de Amorim Borges, Antonio César; Ceschi, Marco Antonio; Lunardi, Paula; Saraiva Gonçalves, Carlos Alberto

2009-11-10

376

Structure and Chemical Synthesis of a Biologically Active Form of Renilla (Sea Pansy) Luciferin  

Microsoft Academic Search

The structure of a biologically active form of Renilla (sea pansy) luciferin has been elucidated; this structure, confirmed by total chemical synthesis, is 3,7-dihydro-2-methyl-6-(p-hydroxyphenyl)-8-benzylimidazo [1,2-a] pyrazin-3-one. In the natural compound the methyl group at the 2 position is replaced by an unknown, more complex group. For this reason the synthetic compound is 10% as active as the natural compound in

Kazuo Hori; Milton J. Cormier

1973-01-01

377

Activation of PAF receptors results in enhanced synthesis of 2-arachidonoylglycerol (2AG) in immune cells  

Microsoft Academic Search

The endocannabinoid signaling system is believed to play a down-regulatory role in the control of cell functions. However, little is known about the factors activating endocannabinoid synthesis and which of two known endocannabinoids, 2-arachidonoylglyc- erol (2-AG) or N-arachidonoylethanolamine (20:4n-6 NAE, anandamide), is of physiological importance. We approached these questions by studying a possible link between cell activation with 1-O-alkyl-2-acetyl-sn-glycero- 3-phosphocholine

EVGUENI V. BERDYSHEV; PATRICIA C. SCHMID; RANDY J. KREBSBACH; HARALD H. O. SCHMID

2001-01-01

378

Oriented synthesis and in vitro anticancer activity of biquinazoline-2,2'-diones.  

PubMed

The synthesis of a series of biquinazoline-2,2'-diones starting from o-nitrobenzaldehydes, anilines, and triphosgene is presented. This general approach features a novel and easy way for access to the target products. The mechanistic course of the reaction suggests the involvement of reduction, coupling, and cyclization by one-pot. These compounds were also investigated in vitro for anticancer activity, and some were found to have good anticancer activity. PMID:20028094

Dou, Guolan; Shi, Daqing; Li, Yonghai

379

Synthesis and antioxygenic activities of seabuckthorn flavone-3-ols and analogs.  

PubMed

A practical synthesis of polyhydroxy- and regiospecifically methylated flavone-3-ols which are components of commercial 'seabuckthorn flavone' has been achieved by modified Algar-Flynn-Oyamada method. Antioxidant activities of seabuckthorn extracts, isolated products and a number of flavone-3-ols have been determined. Structure-activity relationships have been discussed. Amongst the compounds tested, gallic acid, which is also present in seabuckthorn, was found to be the most effective antioxidant and radioprotectant. PMID:21821414

Pandurangan, N; Bose, Chinchu; Banerji, A

2011-07-14

380

Synthesis and antioxygenic activities of seabuckthorn flavone-3-ols and analogs  

Microsoft Academic Search

A practical synthesis of polyhydroxy- and regiospecifically methylated flavone-3-ols which are components of commercial ‘seabuckthorn flavone’ has been achieved by modified Algar–Flynn–Oyamada method. Antioxidant activities of seabuckthorn extracts, isolated products and a number of flavone-3-ols have been determined. Structure–activity relationships have been discussed. Amongst the compounds tested, gallic acid, which is also present in seabuckthorn, was found to be the

N. Pandurangan; Chinchu Bose; A. Banerji

2011-01-01

381

Simplified dynemicin analogues: diastereoselective synthesis and evaluation of their activity against plasmid DNA.  

PubMed

The total synthesis of two diastereoisomeric simplified dynemicin analogues is reported. The key steps involved are: the regio- and diastereoselective functionalisation of an appropriate racemic quinoline precursor and the ring closure to give the 10-membered enediyne moiety through a Pd(0)-catalysed Stille reaction. After the successful conversion of one of these derivatives into a compound more readily activable under nearly physiological conditions, the activity against plasmid DNA was evaluated. PMID:14664386

Guanti, Giuseppe; Riva, Renta

2003-11-21

382

Synthesis and antibacterial activity of novel 4-pyrrolidinylthio carbapenems. Part III  

Microsoft Academic Search

The synthesis and biological activity of a novel series of 2-alkyl-4-pyrrolidinylthio-?-methylcarbapenems containing a variety of cationic heteroaromatic substituents is described. As a result of these studies, we uncovered a relationship between in vitro antibacterial activity and the length of the alkyl spacer part, and discovered FR20950 (1c), containing a two methylene spacer moiety and an imidazolio group, which possesses a

Hidenori Azami; David Barrett; Keiji Matsuda; Hideo Tsutsumi; Kenichi Washizuka; Minoru Sakurai; Satoru Kuroda; Fumiyuki Shirai; Toshiyuki Chiba; Toshiaki Kamimura; Masayoshi Murata

1999-01-01

383

Study of the kinetic parameters for synthesis and hydrolysis of pharmacologically active salicin isomer catalyzed by baker's yeast maltase  

NASA Astrophysics Data System (ADS)

One of the key elements for understanding enzyme reactions is determination of its kinetic parameters. Since transglucosylation is kinetically controlled reaction, besides the reaction of synthesis, very important is the reaction of enzymatic hydrolysis of created product. Therefore, in this study, kinetic parameters for synthesis and secondary hydrolysis of pharmacologically active ? isosalicin by baker's yeast maltase were calculated, and it was shown that specifity of maltase for hydrolysis is approximately 150 times higher then for synthesis.

Veli?kovi?, D. V.; Dimitrijevi?, A. S.; Bihelovi?, F. J.; Jankov, R. M.; Milosavi?, N.

2011-12-01

384

Ionizing Radiation Causes Active Degradation and Reduces Matrix Synthesis in Articular Cartilage  

PubMed Central

Purpose Little is known regarding radiation effects on adult articular (joint) cartilage, though joint damage has been reported following cancer treatment or occupational exposures. The goal of this study was to determine if radiation can reduce cartilage matrix production; induce cartilage degradation; or interfere with the anabolic effects of IGF-1. Materials and Methods Isolated chondrocytes cultured in monolayers and whole explants harvested from ankles of human donors and knees of pigs were irradiated with 2 or 10 Gy ?-rays, with or without IGF-1 stimulation. Proteoglycan synthesis and IGF-1 signaling were examined at Day 1; cartilage degradation throughout the first 96 hours. Results Human and pig cartilage responded similarly to radiation. Cell viability was unchanged. Basal and IGF-1 stimulated proteoglycan synthesis was reduced following exposure, particularly following 10 Gy. Both doses decreased IGF-induced Akt activation and IGF-1 receptor phosphorylation. Matrix metalloproteinases (ADAMTS5, MMP-1, and MMP-13) and proteoglycans were released into media after 2 and 10 Gy. Conclusions Radiation induced an active degradation of cartilage, reduced proteoglycan synthesis, and impaired IGF-1 signaling in human and pig chondrocytes. Lowered Akt activation could account for decreased matrix synthesis. Radiation may cause a functional decline of cartilage health in joints after exposure, contributing to arthropathy.

Willey, J.S.; Long, D.L.; Vanderman, K.S.; Loeser, R.F.

2013-01-01

385

Approaches to the synthesis of a novel, anti-HIV active integrase inhibitor.  

PubMed

The novel HIV-1 integrase inhibitor 1, discovered in our laboratory, exhibits potent anti-HIV activity against a diverse set of HIV-1 isolates and also against HIV-2 and SIV. In addition, this compound displays low cellular cytotoxicity and possesses a favorable in vitro drug interaction profile with respect to isozymes of cytochrome P450 (CYP) and uridine 5'-diphospho-glucuronosyltransferase (UGT). However, the total synthesis of this significant HIV integrase inhibitor has not been reported. This contribution describes an optimized, reproducible, multi-step, synthetic route to inhibitor 1. The yield for the separate steps averaged about 80%. The methodologies utilized in the synthesis were, among others, a palladium-catalyzed cross-coupling reaction, a crossed-Claisen condensation, and a hydrazino amide synthesis step. Successful alternative synthetic methodologies for some of the steps are also described. PMID:24100441

Okello, Maurice; Nishonov, Malik; Singh, Pankaj; Mishra, Sanjay; Mangu, Naveen; Seo, Byung; Gund, Machhindra; Nair, Vasu

2013-10-07

386

Enhanced synthesis and antimicrobial activities of bacteriocins produced by Mexican strains of Bacillus thuringiensis.  

PubMed

Recently, we reported the synthesis of five bacteriocin-like inhibitor substances (Bt-BLIS: morricin 269, kurstacin 287, kenyacin 404, entomocin 420, and tolworthcin 524) by Mexican strains of Bacillus thuringiensis. Here we show that, collectively, these Bt-BLIS have a moderate to broad spectrum of antibacterial activity, being toxic to clinically significant against Gram-positive and Gram-negative bacteria, including common etiological agents of human diseases, such as strep throat and scarlet fever, septicemia, pneumonia, urinary tract infection, and emetic and gastrointestinal syndromes. Although synthesis of the five Bt-BLIS was independent of the presence of a target inducing bacterium, we demonstrated for the first time that a proteinaceous component(s) secreted by, or liberated by proteolytic cleavage of Bacillus cereus 183 following treatment with proteinase K, enhanced Bt-BLIS synthesis. PMID:18654760

de la Fuente-Salcido, N; Guadalupe Alanís-Guzmán, Ma; Bideshi, D K; Salcedo-Hernández, R; Bautista-Justo, M; Barboza-Corona, J E

2008-07-25

387

Fluidized bed combustion method  

SciTech Connect

A process is described for fluidized bed combustion of particulate combustible material in a furnace comprising feeding the particulate combustible material to the furnace and imparting a turbulent fluidized bed motion to the particulate combustible material within the furnace through the use of a vibrating screen. The screen is connected to means for vibrating the screen as the principal source of energy for imparting the turbulent fluidizing motion to the combustible material. This feeds combustion air to the fluidized bed of combustible material, discharging products of combustion from the furnace, and causing the fluidized bed to move in substantially horizontal direction so that combustible material is conveyed from the location of feed to the furnace through a combustion stage in the furnace to the location of discharge as combustible products.

Love, R.E.

1986-12-16

388

[Design, synthesis and biological activity evaluation of adenosine analogues].  

PubMed

N6-(2-Hydroxyethyl) adenosine, HEA (1), an active ingredient isolated from cultured mycelia of cordyceps species which is a famous traditional tonic in China, showed brain protective, sedative hypnotic activity in pharmacological tests. In order to explore novel non-benzodiazepine sedative-hypnotic agents, HEA was treated as the lead compound. Twenty three target compounds were designed and synthesized. Their chemical structures were characterized by 1H NMR, MS and elemental analysis. Pharmacological test in vivo showed that target compounds 8, 4, 13 were more active than HEA on locomotor and gasping activities of mice. Structure-activity relationships showed that the ribose moiety at N-9 position of adenine base was critical for activity. PMID:23984522

Wang, Dong-Mei; Liu, Xiao-Hui; Guo, Hui; Huang, Jun-Hua; Wang, Lin

2013-06-01

389

The synthesis and photolarvicidal activity of 2,5-diarylethynylthiophenes.  

PubMed

The photoactivatable insecticides have photoactive features and broad applications. The derivatives of the alpha-terthienyl analogues were synthesized for evaluating their photolarvicidal activities and 13 2,5-diarylethynylthiophenes were investigated to determine their effect on the second-instar larvae of Plutella xylostella L. Based on their photolarvicidal activities, the 2,5-Dithienylethynylthiophene, 2,5-Diphenylethynylthiophene, 2,5-Di-4-Methoxylphenylethynylthiophene and 2,5-Di-3,4-Methylenedioxyphenylethynylthiophene were found to be the most potent compounds, and their LC(50) values were 34.1 mg l(-1), 48.4 mg l(-1), 60.8 mg l(-1) and 42.7 mg l(-1), respectively. The relationship analysis between structure and activity showed that the middle thiophene ring played an important role on the activities. The electron donor substituents increased the photolarvicidal activities and the length of the alkyl chain had negative influence on the activities. PMID:17703944

Wu, Ren-Hai; Hu, Shan; Xu, Han-Hong; Wei, Xiao-Yi; Hu, Lin

2007-07-17

390

Synthesis of Dihydropyridine Analogues for Sperm Immobilizing Activity  

NASA Astrophysics Data System (ADS)

In the present study, the activity of seven newly synthesized dihydropyridine analogues on the motility of sperm were determined and compared to nifedipine activity that was used as standard. Sperm motility reduced value for test compounds 6a-g shows a gradual increase proportional to the size elongation of alkyl ester groups. Consequently the size of alkyl is important in the activity of test compounds and finally increase in the lipophil size of hydrocarbon`s ester (R1) is inversely related to the activity of the synthetic compounds. As a result, the methyl ester of the test compounds with 50% of nifedipine activity (in two hours group) is the most active test compound.

Sadeghipour Roodsari, H. R.; Amini, M.; Naghibi Harat, Z.; Daneshgar, P.; Vosooghi, M.; Shafiee, A.

391

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

392

Modified solution combustion route for the preparation of plasma sprayable ceria powder  

Microsoft Academic Search

Plasma sprayable grade ceria powder was prepared by the solution combustion method. This is the first report on the application of solution combustion for the synthesis of plasma sprayable grade oxide powders. The fuels and fuel ratios used in the solution combustion were modified to achieve adequate flowability. It was found that when a mixture of fuels like glycine and

S. T. Aruna; K. S. Rajam

2009-01-01

393

Synthesis and antimicrobial activities of new pyridinium and benzimidazolium chlorides  

Microsoft Academic Search

A novel class of pyridinium and benzimidazolium chloride has been obtained in high yield. The antimicrobial activities of three homologous series of pyridinium and benzimidazolium chlorides against cocci, rods, fungi and bacillus have been measured. The antimicrobial activities of N,N?-bis[3-(1-alkoxymethyl)pyridinium chloride]methylenediamines, 1-undecyloxymethyl-3-(1-benzimidazolmethylamino)pyridinium, 1-undecyloxymethyl- and 1-dodecyloxymethyl-3-[1(benzotriazol-1-yl)methylamino]pyridinium chlorides exhibited strong activity and wide antibacterial spectra similar to the activity of benzalkonium chloride.

Juliusz Pernak; Jarostaw Rogo?a; Ilona Mirska

2001-01-01

394

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.

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

1991-01-01

395

Activation of protein synthesis in cardiomyocytes by the hypertrophic agent phenylephrine requires the activation of ERK and involves phosphorylation of tuberous sclerosis complex 2 (TSC2).  

PubMed

The hypertrophic Gq-protein-coupled receptor agonist PE (phenylephrine) activates protein synthesis. We showed previously that activation of protein synthesis by PE requires MEK [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase] and mTOR (mammalian target of rapamycin). However, it remained unclear whether ERK activation was required and which downstream components were involved in activating mTOR and protein synthesis. Using an adenovirus encoding the MKP3 (MAPK phosphatase 3) to inhibit ERK activity, we demonstrate that ERK is essential for the activation of protein synthesis by PE. Activation and phosphorylation of S6K1 (ribosomal protein S6 kinase 1) and phosphorylation of eIF4E (eukaryotic initiation factor 4E)-binding protein (both are mTOR targets) were also inhibited by MKP3, suggesting that ERK is also required for the activation of mTOR signalling. PE stimulation of cardiomyocytes induced the phosphorylation of TSC2 (tuberous sclerosis complex 2), a negative regulator of mTOR activity. TSC2 was phosphorylated only weakly at Thr1462, but phosphorylated at additional sites within the sequence RXRXX(S/T). This differs from the phosphorylation induced by insulin, indicating that MEK/ERK signalling targets distinct sites in TSC2. This phosphorylation may be mediated by p90RSK (90 kDa ribosomal protein S6K), which is activated by ERK, and appears to involve phosphorylation at Ser1798. Activation of protein synthesis by PE is partially insensitive to the mTOR inhibitor rapamycin. Inhibition of the MAPK-interacting kinases by CGP57380 decreases the phosphorylation of eIF4E and PE-induced protein synthesis. Moreover, CGP57380+rapamycin inhibited protein synthesis to the same extent as blocking ERK activation, suggesting that MAPK-interacting kinases and regulation of mTOR each contribute to the activation of protein synthesis by PE in cardiomyocytes. PMID:15757502

Rolfe, Mark; McLeod, Laura E; Pratt, Phillip F; Proud, Christopher G

2005-06-15

396

Stability of supported metal and supported metal oxide combustion catalysts  

Microsoft Academic Search

Catalysts used for high-temperature combustion of light hydrocarbons must maintain high activity over long time intervals by avoiding excessive sintering and deactivation in the hot and corrosive combustion environment. The sintering resistance and chemical stability of catalytically active phases is a key technical problem that must be solved for the development of commercially viable combustion catalysts. All noble metals and

Jon G. McCarty; M. Gusman; D. M. Lowe; D. L. Hildenbrand; K. N. Lau

1999-01-01

397

Acyclic analogues of lipid A: synthesis and biological activities.  

PubMed

The synthesis of a series of novel acyclic analogues of lipid A, the lipophilic terminal of lipopolysaccharide (LPS), is reported. In these compounds, the reducing glucose unit of lipid A has been replaced by an acyclic analogue unit (abbreviated as AAU) consisting of a spacer (of varying length), an (R)-3-hydroxytetradecanamido moiety (of varying configuration at the carbon of attachment), and a CO2H group. The AAU has been attached to the anomeric carbon of the nonreducing glucose unit of lipid A, either through glycosidic linkage or through an acyl linkage. Further, amide isosteres of these acyclic analogues have been prepared using suitably protected 2,3-diamino-2,3-dideoxyglucose instead of 2-amino-2-deoxyglucose. All the compounds were well characterized and were tested for their ability to induce TNF-alpha in mouse bone marrow-derived macrophages, to enhance nonspecific resistance to infection in mice and to induce endotoxic shock in mice. The results showed a dramatic dependence, for the first time, on the length of the spacer and on the configuration of the carbon bearing the amido group in the AAU part of the analogues. PMID:1404227

Bulusu, M A; Waldstätten, P; Hildebrandt, J; Schütze, E; Schulz, G

1992-09-18

398

Drug Development of the Antimalarial Agent Artemisinin: Total Synthesis, Analog Synthesis, and Structure-Activity Relationship Studies.  

National Technical Information Service (NTIS)

The enantioselective total synthesis of (+)-artemisinin has been optimized and carried out at multigram scale. An alternate approach to the total synthesis afforded racemic 6, 9-desmethylartemisinin 79 and a related analog 80. A synthetic intermediate fro...

M. A. Avery

1990-01-01

399

Immobilization of lysozyme on cotton fabrics; synthesis, characterication, and activity  

Technology Transfer Automated Retrieval System (TEKTRAN)

The antimicrobial activity of lysozyme derives from the hydrolysis of the bacterial cell wall polysaccharide at the glycosidic bond that links N-acetyl-glucosamine and N-acetyl-muramic acid. Maintaining the activity of lysozyme while bound to a cellulose substrate is a goal toward developing enzyme...

400

Synthesis of quinoline-Mannich bases of possible antimalarial activity.  

PubMed

For possible antimalarial activity, a series of some 4-substituted aminoquinoline Mannich bases (5a-e) was synthesized. The antimalarial evaluation showed that compound 5b was active against Plasmodium berghei in mice at a dose of 100 mg/kg. PMID:3906678

Kamel, M M; Nabih, I; Nasr, M E; Abbasi, M M

1985-09-01

401

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

402

Synthesis and evaluation of antibacterial activities of andrographolide analogues  

Microsoft Academic Search

Andrographolide (Andro), the main active component of the herb Andrographis paniculata, has been used for many years to treat a variety of diseases including bacterial and viral infections. Andro was recently reported to act by inhibiting the bacterial quorum sensing system. We have synthesized several Andro analogues and investigated their antibacterial activity and mechanism of action. The new compounds were

Xiaojian Jiang; Pei Yu; Jie Jiang; Zaijun Zhang; Zhongli Wang; Zhaoqi Yang; Zhiming Tian; Susan C. Wright; James W. Larrick; Yuqiang Wang

2009-01-01

403

Synthesis and antiparasitic activity of albendazole and mebendazole analogues  

Microsoft Academic Search

Albendazole (Abz) and Mebendazole (Mbz) analogues have been synthesized and in vitro tested against the protozoa Giardia lamblia, Trichomonas vaginalis and the helminths Trichinella spiralis and Caenorhabditis elegans. Results indicate that compounds 4a, 4b (Abz analogues), 12b and 20 (Mbz analogues) are as active as antiprotozoal agents as Metronidazole against G. lamblia. Compound 9 was 58 times more active than

Gabriel Navarrete-Vázquez; Lilián Yépez; Alicia Hernández-Campos; Amparo Tapia; Francisco Hernández-Luis; Roberto Cedillo; José González; Antonio Mart??nez-Fernández; Mercedes Mart??nez-Grueiro; Rafael Castillo

2003-01-01

404

Synthesis and antifungal activity of coumarins and angular furanocoumarins  

Microsoft Academic Search

Angelicin, a naturally occurring furanocoumarin, that showed antifungal activity, was considered as a lead structure for a group of synthetic coumarins. Antifungal activities of the synthesized coumarins and angelicin derivatives were reported against Candida albicans, Cryptococcus neoformans, Saccharomyces cerevisiae and Aspergillus niger. Human cell line cytotoxicity of several coumarins was evaluated against KB cells. Angelicin and several potent antifungals showed

Soroush Sardari; Yoki Mori; Kiyoshi Horita; Ronald G Micetich; Sansei Nishibe; Mohsen Daneshtalab

1999-01-01

405

Synthesis and antiinflammatory activity of N,N?-substituted succinodiamides  

Microsoft Academic Search

Earlier [1 -3] we studied the dependence of the biological activity of substituted diamides of succinic and glutaric acids with the pyrazolone rings on the character of amide group substituents. The maximum antiinflammatory activity was observed for substituted diamides with ethanol- and methylethanolamine residues. It was reported that substitution of an alkyl group for one hydrogen atom in the amino

D. Burdulene; Z. Stumbryavichyute; Z. Talaikite; V. Zlatkuvene; L. Leonavichene; V. Astrauskas

1996-01-01

406

Combustion apparatus  

US Patent & Trademark Office Database

A combustion apparatus 2 has a fuel spraying nozzle 12, a feed canal 16 and a return canal 17, both the canals connected to the nozzle, with the former canal 16 feeding a fuel to the nozzle and with the latter canal 17 allowing an unsprayed portion of the fuel to flow back. An electromagnetic pump 18 disposed in the feed canal 16 serves to compress the fuel towards the nozzle 12, and an injector valve 25 is disposed in the return canal 17. A controller 40 regulates the operation of the injector valve 25 in the manner of duty-ratio control so as to adjust the flow rate of the fuel being sprayed out of the nozzle 12.

2005-06-21

407

Synthesis, local anaesthetic and antiarrhythmic activities of N-alkyl derivatives of proline anilides.  

PubMed

We describe here the design, synthesis and evaluation of in vivo local anaesthetic and antiarrhythmic activities of a series of N-alkylproline anilides. Most of the compounds demonstrated surface anaesthetic activity higher than that of lidocaine, ropivacaine and bupivacaine. We established that the local anaesthetic activity was sensitive to structural variations in the substitution pattern at the aromatic ring and the type of alkyl group at the proline nitrogen atom. Some of the prepared N-alkylproline anilides possessed significant antiarrhythmic activity with higher therapeutic indexes than the reference drugs. PMID:23474900

Kalinin, Dmitrii V; Pantsurkin, Vladimir I; Syropyatov, Boris Ya; Kalinina, Svetlana A; Rudakova, Irina P; Vakhrin, Mikhail I; Dolzhenko, Anton V

2013-02-16

408

Design, synthesis and antiviral activity studies of schizonepetin derivatives.  

PubMed

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

2013-08-20

409

Synthesis and antimicrobial activities of 4-purpuromycin derivatives.  

PubMed

Purpuromycin (1) is a natural antibiotic with a broad spectrum of activity encompassing bacteria, fungi and protozoa. A new series of derivatives of 1 was prepared by the modification or replacement of the C-4 hydroxyl group. The physico-chemical characteristics and the in vitro antimicrobial activity of these new semisynthetic purpuromycin derivatives are reported. Attachment of a variety of bulky groups to the C-4 hydroxyl group as well as acylation or mesylation of 1 gave derivatives with significantly reduced antifungal activity, while the antimicrobial activity of these derivatives against Gram-positive and Gram-negative bacteria was only slightly decreased. All compounds were inactive against Escherichia coli. The C-4 epimers showed different in vitro activity as compared with those having the natural configuration, particularly against fungi. PMID:8765673

Trani, A; Dallanoce, C; Ferrari, P; Goldstein, B; Ripamonti, F; Ciabatti, R

1996-07-01

410

Synthesis and antimicrobial activity of novel amphiphilic aromatic amino alcohols.  

PubMed

We report in this work the preparation and in vitro antimicrobial evaluation of novel amphiphilic aromatic amino alcohols synthesized by reductive amination of 4-alkyloxybenzaldehyde with 2-amino-2-hydroxymethyl-propane-1,3-diol. The antibacterial activity was determined against four standard strains (Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa) and 21 clinical isolates of methicillin-resistant Staphylococcus aureus. The antifungal activity was evaluated against four yeast (Candida albicans, Candida tropicalis, Candida glabrata and Candida parapsilosis). The results obtained showed a strong positive correlation between the lipophilicity and the antibiotic activity of the tested compounds. The best activities were obtained against the Gram-positive bacteria (MIC=2-16?gml(-1)) for the five compounds bearing longer alkyl chains (4c-g; 8-14 carbons), which were also the most active against Candida (MIC=2-64?gml(-1)). Compound 4e exhibited the highest levels of inhibitory activity (MIC=2-16?gml(-1)) against clinical isolates of MRSA. A concentration of twice the MIC resulted in bactericidal activity of 4d against 19 of the 21 clinical isolates. PMID:23587426

de Almeida, Angelina M; Nascimento, Thiago; Ferreira, Bianca S; de Castro, Pedro P; Silva, Vânia L; Diniz, Claúdio G; Le Hyaric, Mireille

2013-03-28

411

Combustion synthesis of nano-crystalline Nd-doped ceria and Nd 2O 3 and their fractal behavior as studied by small angle X-ray scattering  

Microsoft Academic Search

Nano-crystalline Nd2O3 and Ce0.50Nd0.50O1.75 were synthesized by the gel combustion technique, using glycine as the fuel and the corresponding metal nitrates as oxidants. The products were characterized by XRD to ascertain the phase purity. The crystallite sizes as calculated by X-ray line broadening were found to be about 10 and 35nm for Nd2O3, obtained from the fuel-deficient and propellant ratios,

S. V. Chavan; P. U. M. Sastry; A. K. Tyagi

2008-01-01

412

Surfactant-Assisted Sol-Gel Auto-Combustion Synthesis of Sr-Hexaferrite Nano-Crystalline Powder Using Different Fuels and Basic Agents  

NASA Astrophysics Data System (ADS)

In this research Sr-hexaferrite powder was synthesized by a sol-gel auto-combustion route using two different fuels (glycine and citric acid) and two different basic agents (ammonia and trimethylamine). N-decyltrimethylammonium bromide (C13H30BrN) was also employed as a cationic surfactant. The results showed the finest crystallite size and the lowest calcination temperature have been obtained as 27.2 nm and 800° C respectively, in the presence of citric acid, trimethylamine and surfactant.

Ebrahimi, S. A. S.; Hasab, M. G.; Badiei, A.

2010-03-01

413

Surfactant-Assisted Sol-Gel Auto-Combustion Synthesis of SR-HEXAFERRITE Nanopowder Using Different Fuels and Basic Agents  

NASA Astrophysics Data System (ADS)

In this research Sr-hexaferrite powder was synthesized by a sol-gel auto-combustion route using two different fuels (glycine and citric acid) and two different basic agents (ammonia and trimethylamine). N-decyltrimethylammonium bromide (C13H30BrN) was also employed as a cationic surfactant. The results showed the finest crystallite size and the lowest calcination temperature have been obtained as 27.2 nm and 800 °C respectively, in the presence of citric acid, trimethylamine and surfactant.

Ghobeiti Hassab, M.; Seyyed Ebrahimi, S. A.; Dehghan, R.

414

Sol–gel auto-combustion synthesis of SiO 2-doped NiZn ferrite by using various fuels  

Microsoft Academic Search

A nitrate–chelate–silica gel was prepared from metallic nitrates, citric acid and tetraethoxysilane (TEOS) by sol–gel process with different complexing agents such as glycine, hydrazine and citric acid, and it was further used to synthesize Ni0.5Zn0.5Fe2O4\\/20wt% SiO2 nanocomposites by auto-combustion. The effect of varying complexing agent on the structural and magnetic properties of the composites was studied by FTIR, 29Si CP\\/MAS

K. H. Wu; T. H. Ting; M. C. Li; W. D. Ho

2006-01-01

415

Leptin stimulates protein synthesis-activating translation machinery in human trophoblastic cells.  

PubMed

Leptin was originally considered as an adipocyte-derived signaling molecule for the central control of metabolism. However, pleiotropic effects of leptin have been identified in reproduction and pregnancy, particularly in placenta, where it may work as an autocrine hormone, mediating angiogenesis, growth, and immunomodulation. Leptin receptor (LEPR, also known as Ob-R) shows sequence homology to members of the class I cytokine receptor (gp130) superfamily. In fact, leptin may function as a proinflammatory cytokine. We have previously found that leptin is a trophic and mitogenic factor for trophoblastic cells. In order to further investigate the mechanism by which leptin stimulates cell growth in JEG-3 cells and trophoblastic cells, we studied the phosphorylation state of different proteins of the initiation stage of translation and the total protein synthesis by [(3)H]leucine incorporation in JEG-3 cells. We have found that leptin dose-dependently stimulates the phosphorylation and activation of the translation initiation factor EIF4E as well as the phosphorylation of the EIF4E binding protein EIF4EBP1 (PHAS-I), which releases EIF4E to form active complexes. Moreover, leptin dose-dependently stimulates protein synthesis, and this effect can be partially prevented by blocking mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3 kinase (PIK3) pathways. In conclusion, leptin stimulates protein synthesis, at least in part activating the translation machinery, via the activation of MAPK and PIK3 pathways. PMID:19553602

Pérez-Pérez, Antonio; Maymó, Julieta; Gambino, Yésica; Dueñas, José L; Goberna, Raimundo; Varone, Cecilia; Sánchez-Margalet, Víctor

2009-06-24

416

Control of protein synthesis in yeast mitochondria: the concept of translational activators.  

PubMed

Mitochondria contain their own genome which codes for a small number of proteins. Most mitochondrial translation products are part of the membrane-embedded reaction centers of the respiratory chain complexes. In the yeast Saccharomyces cerevisiae, the expression of these proteins is regulated by translational activators that bind mitochondrial mRNAs, in most cases to their 5'-untranslated regions, and each mitochondrial mRNA appears to have its own translational activator(s). Recent studies showed that these translational activators can be part of feedback control loops which only permit translation if the downstream assembly of nascent translation products can occur. In several cases, the accumulation of a non-assembled protein prevents further synthesis of this protein but not translation in general. These control loops prevent the synthesis of potentially harmful assembly intermediates of the reaction centers of mitochondrial enzymes. Since such regulatory feedback loops only work if translation occurs in the compartment in which the complexes of the respiratory chain are assembled, these control mechanisms require the presence of a translation machinery in mitochondria. This might explain why eukaryotic cells maintained DNA in mitochondria during the last two billion years of evolution. This review gives an overview of the mitochondrial translation system and summarizes the current knowledge on translational activators and their role in the regulation of mitochondrial protein synthesis. This article is part of a Special Issue entitled: Protein import and quality control in mitochondria and plastids. PMID:22450032

Herrmann, Johannes M; Woellhaf, Michael W; Bonnefoy, Nathalie

2012-03-16

417

Synthesis and biological activities of diflunisal hydrazide–hydrazones  

Microsoft Academic Search

Several diflunisal hydrazide–hydrazone derivatives namely 2?,4?-difluoro-4-hydroxybiphenyl-3-carboxylic acid [(5-nitro-2-furyl\\/substitutedphenyl)methylene] hydrazide (3a–o) have been synthesised. Methyl 2?,4?-difluoro-4-hydroxybiphenyl-3-carboxylate (1) and 2?,4?-difluoro-4-hydroxybiphenyl-3-carboxylic acid hydrazide (2) were also synthesised and used as intermediate compounds. All synthesised compounds were screened for their antimycobacterial activity against Mycobacterium tuberculosis H37 Rv, antimicrobial activities against various bacteria, fungi and yeast species. Compound 3a have shown activity against Staphylococcus epidermis

S. Güniz Küçükgüzel; Adil Mazi; Fikrettin Sahin; Suzan Öztürk; James Stables

2003-01-01

418

Bismuth-based oxide semiconductors: Mild synthesis and practical applications  

NASA Astrophysics Data System (ADS)

In this dissertation study, bismuth based oxide semiconductors were prepared using 'mild' synthesis techniques---electrodeposition and solution combustion synthesis. Potential environmental remediation and solar energy applications of the prepared oxides were evaluated. Bismuth vanadate (BiVO4) was prepared by electrodeposition and solution combustion synthesis. A two step electrosynthesis strategy was developed and demonstrated for the first time. In the first step, a Bi film was first electrodeposited on a Pt substrate from an acidic BiCl3 medium. Then, this film was anodically stripped in a medium containing hydrolyzed vanadium precursor, to generate Bi3+, and subsequent BiVO4 formation by in situ precipitation. The photoelectrochemical data were consistent with the in situ formation of n-type semiconductor films. In the solution combustion synthesis procedure, BiVO4 powders were prepared using bismuth nitrate pentahydrate as the bismuth precursor and either vanadium chloride or vanadium oxysulfate as the vanadium precursor. Urea, glycine, or citric acid was used as the fuel. The effect of the vanadium precursor on the photocatalytic activity of combustion synthesized BiVO 4 was evaluated in this study. Methyl orange was used as a probe to test the photocatalytic attributes of the combustion synthesized (CS) samples, and benchmarked against a commercial bismuth vanadate sample. The CS samples showed superior activity to the commercial benchmark sample, and samples derived from vanadium chloride were superior to vanadium oxysulfate counterparts. The photoelectrochemical properties of the various CS samples were also studied and these samples were shown to be useful both for environmental photocatalytic remediation and water photooxidation applications. Silver bismuth tungstate (AgBiW2O8) nanoparticles were prepared for the first time by solution combustion synthesis by using silver nitrate, bismuth nitrate, sodium tungstate as precursors for Ag, Bi, and W respectively and urea as the fuel. The photocatalytic activity of these nanoparticles was superior to a sample prepared by solid-state synthesis. The combustion-synthesized particles were subsequently modified with Pt catalyst islands using a photodeposition technique and then used for the photo-generation of syngas (CO + H2). Formic acid was used in these experiments for in situ generation of CO2 and its subsequent reduction to CO. In the absence of Pt modification, H2 was not obtained. These results were compared with those obtained with acetic acid in place of formic acid, and finally the mechanistic pathways for syngas and methane photogeneration are presented.

Timmaji, Hari Krishna

419

Synthesis of CDP-Activated Ribitol for Teichoic Acid Precursors in Streptococcus pneumoniae?  

PubMed Central

Streptococcus pneumoniae has unusually complex cell wall teichoic acid and lipoteichoic acid, both of which contain a ribitol phosphate moiety. The lic region of the pneumococcal genome contains genes for the uptake and activation of choline, the attachment of phosphorylcholine to teichoic acid precursors, and the transport of these precursors across the cytoplasmic membrane. The role of two other, so far uncharacterized, genes, spr1148 and spr1149, in the lic region was determined. TarJ (spr1148) encodes an NADPH-dependent alcohol dehydrogenase for the synthesis of ribitol 5-phosphate from ribulose 5-phosphate. TarI (spr1149) encodes a cytidylyl transferase for the synthesis of cytidine 5?-diphosphate (CDP)-ribitol from ribitol 5-phosphate and cytidine 5?-triphosphate. We also present the crystal structure of TarI with and without bound CDP, and the structures present a rationale for the substrate specificity of this key enzyme. No transformants were obtained with insertion plasmids designed to interrupt the tarIJ genes, indicating that their function could be essential for cell growth. CDP-activated ribitol is a precursor for the synthesis of pneumococcal teichoic acids and some of the capsular polysaccharides. Thus, all eight genes in the lic region have a role in teichoic acid synthesis.

Baur, Stefanie; Marles-Wright, Jon; Buckenmaier, Stephan; Lewis, Richard J.; Vollmer, Waldemar

2009-01-01

420

Synthesis and antiangiogenic activity of exo-olefinated deoxoartemisinin derivatives.  

PubMed

10-exo-Bromoalkylidene and benzylidene deoxoartemisinin derivatives with antiangiogenic activity were synthesized from corresponding 10-alkanesulfonyl dihydroartemisinin and 10-phenylmethanesulfonyl dihydroartemisinin using a highly efficient, mild, and simple Ramberg-Bäcklund rearrangement. PMID:15203143

Oh, Sangtae; Jeong, In Howa; Shin, Woon-Seob; Lee, Seokjoon

2004-07-16

421

Synthesis and evaluation of dioleoyl glyceric acids showing antitrypsin activity.  

PubMed

Previously, Lešová et al. reported the isolation and identification of metabolite OR-1, showing antitrypsin activity, produced during fermentation by Penicillium funiculosum. The structure of OR-1 was a mixture of glyceric acid (GA), esterified with C(14)-C(18) fatty acids, and oleic acid (C18:1) as the most predominant fatty acid (Folia Microbiol. 46, 21-23, 2001). In this study, dioleoyl D-GA and dioleoyl L-GA were synthesized via diesterification with oleoyl chloride, and their antitrypsin activities were evaluated using both a disk diffusion method and spectral absorption measurements. The results show that both compounds and their equivalent mixtures possess antitrypsin activities; however, their IC(50) values (approximately 2 mM) are much higher than that of OR-1 (4.25 µM), suggesting that dioleoyl GA does not play a major role in the OR-1 antitrypsin activity. PMID:21606621

Habe, Hiroshi; Fukuoka, Tokuma; Sato, Shun; Kitamoto, Dai; Sakaki, Keiji

2011-01-01

422

Liquid fuel combustion apparatus  

Microsoft Academic Search

A liquid fuel combustion apparatus is described comprising: wall means defining a cylindrical combustion chamber; a cylindrical portion of the wall means having a first port therein for receiving an ignition device and a first nipple integral with the wall means and surrounding the first port; means for introducing fuel and combustion air into the combustion chamber and for removing

K. Sawada; K. Kikuchi

1987-01-01

423

Thermal Pulse Combustion  

Microsoft Academic Search

This paper describes theoretical and experimental observations of combustion oscillations produced in a continuously mixed, jet-stirred combustion system. This work is distinct from other investigations of pulse combustion, because it is shown both theoretically and experimentally that combustion oscillations can be produced with a steady supply of fuel and air, requiring no mechanical or aerodynamic valves. The theory is a

G. A. RICHARDS; G. J. MORRIS; D. W. SHAW; S. A. KEELEY; M. J. WELTER

1993-01-01

424

Rotary internal combustion engine  

SciTech Connect

This patent describes an internal combustion engine comprising; a rotary compressor mechanism; a rotary expander mechanism; and combustion chamber means disposed between the compressor mechanism and the expander mechanism, whereby compressed air is delivered to the combustion chamber through the compressor discharge port, and pressurized gas is delivered from the combustion chamber into the expander mechanism through the pressurized gas intake port.

Le, L.K.

1990-11-20

425

Pulse combustion apparatus  

Microsoft Academic Search

A pulse combustion apparatus is described which includes: a combustion chamber; an exhaust system including an exhaust pipe forming a resonant system with the combustion chamber and a generally cylindrical exhaust cushion chamber downstream of the exhaust pipe for receiving combustion gases from the pipe and communicating with an exhaust outlet form the apparatus; means for delivering successive fuel charges

Kitchen

1986-01-01

426

Synthesis and antitumor activity of simplified ecteinascidin–saframycin analogs  

Microsoft Academic Search

Two series of simplified analogs of the ecteinascidin–saframycin type alkaloids were prepared from l-DOPA. Their in vitro antitumor activity was tested against three human cancer cell lines (HCT-8 colon carcinoma, Bel-7402 liver carcinoma, and BGC-823 gastric carcinoma). Among these compounds, the ester analogs have stronger activities than those of amide analogs in general. Among them, 1-naphthalene carboxylate ester analog 31

Zhan-Zhu Liu; Ye Wang; Ye-Feng Tang; Shi-Zhi Chen; Xiao-Guang Chen; Hong-Yan Li

2006-01-01

427

Total Chemical Synthesis of Biologically Active Vascular Endothelial Growth Factor  

PubMed Central

A 204 residue covalent-dimer vascular endothelial growth factor, with full mitogenic activity, was made by one-pot native chemical ligation from three unprotected peptide segments. The covalent structure of synthetic VEGF was confirmed by precise mass measurement, and the three dimensional structure of the synthetic protein molecule was determined by high resolution X-ray crystallography. Robust, practical synthetic access to biologically active VEGF will aid in the development of novel anti-angiogenic therapeutics.

Mandal, Kalyaneswar; Kent, Stephen B. H.

2012-01-01

428

Synthesis, Isolation of Phenazine Derivatives and Their Antimicrobial Activities  

Microsoft Academic Search

Antimicrobial activity of natural phenazine-1-carboxylic acid (PCA) from Pseudomonas aeruginosa TISTR 781 and synthetic phenazine-5,10- dioxide (PDO), prepared by oxidation of the phenazine, were evaluated by in vitro disc diffusion and minimal inhibitory concentration (MIC) methods. The results indicated that both phenazine derivatives differed clearly in their antimicrobial activity. PCA showed better efficacy against growth of Acidovorax avenae subsp. citrulli,

Aunchalee NANSATHIT; Sukanya APIPATTARAKUL; Chanokporn PHAOSIRI; Paweena PONGDONTRI; Saksit CHANTHAI; Chalerm RUANGVIRIYACHAI

2009-01-01

429

Synthesis and antiparasitic activity of 2-(trifluoromethyl)-benzimidazole derivatives.  

PubMed

2-(Trifluoromethyl)benzimidazole derivatives substituted at the 1-, 5-, and 6-positions have been synthesized and in vitro tested against the protozoa Giardia lamblia, Entamnoeha histolytica. and the helminth Trichinella spiralis. Results indicate that all the compounds tested are more active as antiprotozoal agents than Albendazole and Metronidazole. One compound (20) was as active as Albendazole against T. spiralis. These compounds were also tested for their effect on tubulin polymerization and none inhibited tubulin polymerization. PMID:11206455

Navarrete-Vázquez, G; Cedillo, R; Hernández-Campos, A; Yépez, L; Hernädez-Luis, F; Valdez, J; Morales, R; Cortés, R; Hernández, M; Castillo, R

2001-01-22

430

Synthesis and anti-inflammatory activity of celecoxib like compounds.  

PubMed

Nine novel 4-[3-(4-Dimethylamino-phenyl)-5-aryl-4,5-dihydro-pyrazol-1-yl]-benzenesulfonamides (2a-i) were synthesized and evaluated for their anti-inflammatory and antiproliferative activities. These compounds (2a-i) showed moderate to strong anti-inflammatory activity in carrageenan rat paw oedema test. Compounds 2b, 2d and 2g showing comparable anti-inflammatory activity to that of reference drug celecoxib were evaluated for their ulcerogenic and analgesic activities. The effect of 2b, 2d and 2g on the content of NO, TNF-? and PGE2 in exudates from rat paw stimulated by carrageenan was also evaluated. The compound 2c showed considerable antitumor activities against all 60 human tumor cell lines with effective GI50 (MG-MID) value of 3.63 µM. It exhibited maximum activity against melanoma (LOX IMVI and SK-MEL-5) cancer cell lines with GI50 value less than 2 ?M. PMID:22957719

Ovais, Syed; Yaseen, Shafiya; Bashir, Rafia; Rathore, Pooja; Samim, Mohammed; Singh, Surender; Nair, Vinod; Javed, Kalim

2012-09-07

431

Synthesis and in vitro anticancer activities of some selenadiazole derivatives.  

PubMed

A novel series of fourteen substituted selenadiazoles has been synthesized and the compounds tested for their in vitro antiproliferative and cytotoxic activities. The tests were carried out against leukemia (CCRF-CEM), colon (HT-29), lung (HTB-54), and breast (MCF-7) cancer cells. In order to assess the selectivity of the compounds under investigation the assays were also carried out on two non-tumoral lines - one mammary (184B5) and one bronchial epithelium (BEAS-2B) cell line. Assay-based antiproliferative activity studies revealed that seven derivatives (2a, 2c, 2e, 2f, 2g, 3a, and 3b) exhibited good activity against MCF-7 cells: for instance, 2c and 2f inhibited cell growth with nanomolar GI?? values. Compound 2f had a better antitumoral profile than vinorelbine and paclitaxel, two drugs that are used as first-line treatments in advanced, recurrent, and/or metastatic cancer. In the other cell lines the compounds showed moderate activity or were inactive - with the exception of 2a, which was also found to have antiproliferative activity. Modulation of the cell cycle and apoptotic effects of active compounds were further evaluated in MCF-7 cells. Of these, 6-bromo[1,2,5]selenadiazolo[3,4-b]pyridine (2a) was the most active, with an apoptogenic effect 3.9 times higher than that of camptothecin, which was used as a positive control. Compound 2a also provoked cell cycle arrest with a significant decrease in the G?/G? phase cell population and an increase in S and G?/M cells, thus suggesting mitotic arrest prior to metaphase. PMID:21110339

Plano, Daniel; Moreno, Esther; Font, María; Encío, Ignacio; Palop, Juan Antonio; Sanmartín, Carmen

2010-11-01

432

Effect of calcination temperature on the H2O2 decomposition activity of nano-crystalline Co3O4 prepared by combustion method  

NASA Astrophysics Data System (ADS)

Cobalt oxide nano-particles were prepared by combustion method using urea as a combustion fuel. The effects of calcination temperature, 350-1000 °C, on the physicochemical, surface and catalytic properties of the prepared Co3O4 nano-particles were studied. The products were characterized by thermal analyses (TGA & DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. Textural features of the obtained catalysts were investigated using nitrogen adsorption at -196 °C. X-ray diffraction confirmed that the resulting oxide was pure single-crystalline Co3O4 nano-particles. Transmission electron microscopy indicating that, the crystallite size of Co3O4 nano-crystals was in the range of 8-34 nm. The catalytic activities of prepared nano-crystalline Co3O4 catalysts were tested for H2O2 decomposition at 35-50 °C temperature range. Experimental results revealed that, the catalytic decomposition of H2O2 decreases with increasing the calcination temperature. This was correlated with the observed particle size increase accompanying the calcination temperature rise.

Makhlouf, M. Th.; Abu-Zied, B. M.; Mansoure, T. H.

2013-06-01

433

Synthesis and antioxidant activity of peptide-based ebselen analogues.  

PubMed

A series of di- and tripeptide-based ebselen analogues has been synthesized. The compounds were characterized by (1)H, (13)C, and (77)Se NMR spectroscopy and mass spectral techniques. The glutathione peroxidase (GPx)-like antioxidant activity has been studied by using H(2)O(2) , tert-butyl hydroperoxide (tBuOOH), and cumene hydroperoxide (Cum-OOH) as substrates, and glutathione (GSH) as a cosubstrate. Although all the peptide-based compounds have a selenazole ring similar to that of ebselen, the GPx activity of these compounds highly depends on the nature of the peptide moiety attached to the nitrogen atom of the selenazole ring. It was observed that the introduction of a phenylalanine (Phe) amino acid residue in the N-terminal reduces the activity in all three peroxide systems. On the other hand, the introduction of aliphatic amino acid residues such as valine (Val) significantly enhances the GPx activity of the ebselen analogues. The difference in the catalytic activity of dipeptide-based ebselen derivatives can be ascribed mainly to the change in the reactivity of these compounds toward GSH and peroxide. Although the presence of the Val-Ala-CO(2) Me moiety facilitates the formation of a catalytically active selenol species, the reaction of ebselen analogues that has a Phe-Ile-CO(2) Me residue with GSH does not generate the corresponding selenol. To understand the antioxidant activity of the peptide-based ebselen analogues in the absence of GSH, these compounds were studied for their ability to inhibit peroxynitrite (PN)-mediated nitration of bovine serum albumin (BSA) and oxidation of dihydrorhodamine 123. In contrast to the GPx activity, the PN-scavenging activity of the Phe-based peptide analogues was found to be comparable to that of the Val-based compounds. However, the introduction of an additional Phe residue to the ebselen analogue that had a Val-Ala dipeptide significantly reduced the potency of the parent compound in PN-mediated nitration. PMID:21400619

Satheeshkumar, Kandhan; Mugesh, Govindasamy

2011-03-11

434

Combustion of Alternative Fuel Study (CAFS).  

National Technical Information Service (NTIS)

Results of a study intended to provide ERDA with a guide to future activities in waste-based fuel combustion hardware research, development and demonstration are reported. Four study activities were undertaken: the identification of the types, quantities ...

R. B. Saunders

1977-01-01

435

Design, synthesis, and fungicidal activity of novel analogues of pyrrolnitrin.  

PubMed

A series of novel analogues of pyrrolnitrin containing a thiophene moiety were designed and synthesized by a facile method, and their structures were characterized by (1)H nuclear magnetic resonance (NMR) and high-resolution mass spectrometry. The isomers IV-h and V-h were isolated, and their structures were identified by 2D NMR, including heteronuclear multiple-quantum coherence (HMQC), heteronuclear multiple-bond correlation (HMBC), and nuclear Overhauser effect spectrometry (NOESY) spectra. Their fungicidal activities against five fungi were evaluated, and the results indicated that some of the title compounds showed excellent fungicidal activities in vitro against Alternaria solani , Gibberella zeae , Physalospora piricola , Fusarium omysporum , and Cercospora arachidicola at the dosage of 50 microg mL(-1). Some compounds shown moderate activity at low dosage. Compound V-h could be considered as a leading structure for further design of agricultural fungicides. PMID:19681615

Wang, Ming-Zhong; Xu, Han; Feng, Qi; Wang, Li-Zhong; Wang, Su-Hua; Li, Zheng-Ming

2009-09-01

436

Design, synthesis and antifungal activities of novel pyrrole alkaloid analogs.  

PubMed

A series of novel analogs of pyrrole alkaloid were designed and synthesized by a facile method and their structures were characterized by 1H NMR, 13C NMR and high-resolution mass spectrometry (HRMS). The structure of compound 2a was identified by 2D NMR including heteronuclear multiple-quantum coherence (HMQC), heteronuclear multiple-bond correlation (HMBC) and H-H correlation spectrometry (H-H COSY) spectra. Their antifungal activities against five fungi were evaluated, and the results indicated that some of the title compounds showed moderate fungicidal activities in vitro against Alternaria solani, Cercospora arachidicola, Fusarium omysporum, Gibberella zeae and Physalospora piricola at the dosage of 50 ?g mL(-1). Compound 2a and 3a exhibited good activities against P. piricola at low dosage. PMID:21356570

Wang, Ming-Zhong; Xu, Han; Liu, Tuan-Wei; Feng, Qi; Yu, Shu-Jing; Wang, Su-Hua; Li, Zheng-Ming

2011-01-28

437

Design, synthesis and potent cytotoxic activity of novel podophyllotoxin derivatives.  

PubMed

Twenty new acyl thiourea derivatives of podophyllotoxin and 4'-demethylepipodophyllotoxin were prepared and screened for their cytotoxicity against four human tumor cell lines, A-549, DU-145, KB, and KBvin. With IC50 values of 0.098-1.13 ?M, compounds 13b, 13c, and 13o displayed much better cytotoxic activity than the control etoposide. Most importantly, 13b and 13o exhibited promising cytotoxicity against the drug resistant tumor cell line KBvin with IC50 values of 0.098 and 0.13 ?M, respectively, while etoposide lost activity completely. Structure-activity relationship (SAR) correlations of the new derivatives have been established. Compounds 13b and 13o merit further development as a new generation of epipodophyllotoxin-derived antitumor clinical trial candidates. PMID:23490151

Li, Wen-Qun; Wang, Xu-Li; Qian, Keduo; Liu, Ying-Qian; Wang, Chih-Ya; Yang, Liu; Tian, Jin; Morris-Natschke, Susan L; Zhou, Xing-Wen; Lee, Kuo-Hsiung

2013-02-17

438

Synthesis and antiprotozoal activity of original porphyrin precursors and derivatives.  

PubMed

Importance of heme in African trypanosomes, Leishmania sp. and Plasmodium sp. metabolisms justifies considering the potential of porphyrins and their precursors and derivatives as potential antiparasitic agents by interfering with heme metabolism. Consequently, twenty-four porphyrin precursors and derivatives were evaluated against Leishmania donovani, Trypanosoma brucei and Plasmodium sp. The best active compound against Trypanosoma brucei brucei was a new porphyrin derivative; compound 4i, with a MEC value of 6.25 ?M justifying further in vivo evaluation. Whereas these compounds were not active against intramacrophage amastigotes of L. donovani, another new porphyrin derivative, compound 4f was active in vitro against Plasmodium falciparum at 20 nM and a slight delay of mice survival was observed on the Plasmodium berghei/Swiss mice model at 50 ?mol/kg/day × 4. Pharmacomodulations should be further developed relying on a better knowledge on the porphyrin behaviour into the parasites comparatively to host cells. PMID:23851117

Abada, Zahra; Cojean, Sandrine; Pomel, Sébastien; Ferrié, Laurent; Akagah, Bernardin; Lormier, Anh Tuan; Loiseau, Philippe M; Figadère, Bruno

2013-06-12

439

Synthesis and biological evaluation of an electronically activated isooxacephem.  

PubMed

New isooxacephem (+/-)-3-ethyl 2-hydrogen (6RS,7RS)-8-oxo-7-(phenylacetamido)-4-oxa-1-azabicyclo [4.2.0]oct-2-ene-2, 3-dicarboxylate (8) was synthesized from (+/-)-dibenzyl 2-[cis-2-oxo-3-(phenylacetamido)-4-styryl-1-azetidinyl]-2-[t- butyldimethylsiloxy(methoxycarbonyl)methyl]malonate (1) in six steps. This bicyclic beta-lactam was found to possess notable biological activities against several pathogenic microorganisms in vitro, including Staphylococcus aureus 95, S. aureus FDA 209P, Escherichia coli ATCC 39188, Salmonella typhi O-901, Pseudomonas aeruginosa 18S-H, P. aeruginosa 1101-75, and Klebsiella pneumoniae NCTC 418. The electronic activation of the beta-lactam moiety by an ester group plays a prominent role in the biological activity of this novel isooxacephem. PMID:8879559

Hakimelahi, G H; Tsay, S C; Tso, H H; Ramezani, Z; Hwu, J R

1996-08-01

440

HBTU activation for automated Fmoc solid-phase peptide synthesis.  

PubMed

Excellent results have been obtained for the Fmoc solid-phase syntheses of peptides using the activating reagent 2-(1H-benzotriazol-1-yl)-1,1,3,3,-tetramethyluronium hexafluorophosphate (HBTU). Activation occurs very rapidly in N,N-dimethylformamide and N-methyl-pyrrolidone, optimal solvents for peptide-resin solvation. It has been observed that complete coupling reactions occur in only 10-30 min. Residues such as Arg, Ile, Leu and Val, which often require double coupling by other activation methods, react with high efficiency by single coupling when HBTU is used. The Fmoc/HBTU chemistry has recently been applied to the peptide synthesizers. The incorporation of trityl side-chain protection for Fmoc-Asn and Fmoc-Gln further enhances coupling efficiencies in difficult sequences. PMID:1815783

Fields, C G; Lloyd, D H; Macdonald, R L; Otteson, K M; Noble, R L

441

Synthesis of 4-hydroxysphinganine and characterization of sphinganine hydroxylase activity in corn.  

PubMed

Sphinganine and 4-hydroxysphinganine (phytosphingosine) are the predominant free long-chain bases in lipid extracts of plant tissues. While the synthesis of sphinganine in plants has been investigated, the metabolic origin of 4-hydroxysphinganine is not known. Three different approaches utilizing fumonisin B(1), an inhibitor of sphinganine acylation, alone or in combination with beta-chloroalanine, an inhibitor of sphinganine synthesis, were used to establish that free 4-hydroxysphinganine is produced in excised corn shoots by the direct hydroxylation of sphinganine and not from the breakdown of complex sphingolipids. Sphinganine hydroxylase activity was characterized in microsomes isolated from corn. The enzyme was found to utilize D-erythro-sphinganine (with half-maximal activity observed at a substrate concentration of approximately 60 microM) and either NADPH (K(m)=33 microM) or NADH (K(m)=58 microM) as substrates. Ceramide hydroxylation was also demonstrated in corn microsomes, and the lack of competition between ceramide and sphinganine suggests the presence of distinct enzymes responsible for hydroxylating these two substrates. Using marker assays, sphinganine hydroxylase activity was localized to the endoplasmic reticulum. Sphinganine hydroxylase activity in microsomes isolated from corn shoots treated with fumonisin B(1) increased more than 3-fold compared to controls. The results of this study shed light on sphingolipid long-chain base synthesis and modification in plant tissues and suggest a possible contribution of sphinganine hydroxylase in manifesting the effects of fumonisin in plants. PMID:12831841

Wright, Brooke S; Snow, Jonathan W; O'Brien, Theresa C; Lynch, Daniel V

2003-07-15

442

Synthesis and anti-inflammatory activity of three nitro chalcones.  

PubMed

The aim of this study was to synthesize three nitro substituted chalcones and to evaluate their anti-inflammatory activity in the model of carrageenan induced edema in rats. The nitro chalcone were prepared by aldol condensation using of mechanical agitation and environmentally friendly solvents with 72-73% yields in approximately 2h. The three structures were evaluated on biological activity at dose of 200mg/kg and they showed anti-inflammatory protective effect by both oral and intraperitoneal administration, this effect was time dependent. PMID:24012185

Gómez-Rivera, Abraham; Aguilar-Mariscal, Hidemí; Romero-Ceronio, Nancy; Roa-de la Fuente, Luis F; Lobato-García, Carlos E

2013-08-19

443

Graphene-CdS composite, synthesis and enhanced photocatalytic activity  

NASA Astrophysics Data System (ADS)

Graphene-CdS (G-CdS) composites were synthesized through a simple solvothermal method. The formed CdS nanospheres were homogeneously scattered on the surface of graphene sheets. Fluorescence quenching effect of the G-CdS composites indicated effective transfer of photo-excited electrons from CdS to graphene, suppressed the recombination of photo-generated electron-hole pairs, so that the enhanced visible light induced photodegradation activity for Rhodamine B (RhB) was achieved. Based on the high photocatalytic activity and well stability, the G-CdS composite containing 70% CdS can be expected to be a practical visible light photocatalyst.

Gao, Zhiyong; Liu, Ning; Wu, Dapeng; Tao, Wenguang; Xu, Fang; Jiang, Kai

2012-01-01

444

Synthesis and antiparasitic activity of 1H-benzimidazole derivatives.  

PubMed

Compounds 1-18 have been synthesized and tested in vitro against the protozoa Giardia lamblia, Entamoeba histolytica and the helminth Trichinella spiralis. Inhibition of rat brain tubulin polymerization was also measured and compared for each compound. Results indicate that most of the compounds tested were more active as antiprotozoal agents than Metronidazole and Albendazole. None of the compounds was as active as Albendazole against T. spiralis. Although only compounds 3, 9 and 15 (2-methoxycarbonylamino derivatives) inhibited tubulin polymerization, these were not the most potent antiparasitic compounds. PMID:12127542

Valdez, Juan; Cedillo, Roberto; Hernández-Campos, Alicia; Yépez, Lilián; Hernández-Luis, Francisco; Navarrete-Vázquez, Gabriel; Tapia, Amparo; Cortés, Rafael; Hernández, Manuel; Castillo, Rafael

2002-08-19

445

Synthesis and cytotoxic activity of trisubstituted-1,3,5-triazines.  

PubMed

1,3,5-Triazine derivatives were screened for phototoxicity as well as the cytotoxic activities against leukemia and adenocarcinoma derived cell lines in comparison to the normal human keratinocytes. A simple and environmentally friendly procedure has been developed for the synthesis of 1,3,5-triazine derivatives under microwave irradiation in the presence of a HY zeolite. The catalyst can be recovered and reused. Thus, the procedure provides a simple and green synthetic methodology under environmentally friendly conditions. Structure-activity relationships between the chemical structures and antimycobacterial and photosynthesis-inhibiting activity of the evaluated compounds are also discussed. PMID:17449247

Arya, Kapil; Dandia, Anshu

2007-04-10

446

Silver triflate catalyzed synthesis of 3-aminoalkylated indoles and evaluation of their antibacterial activities.  

PubMed

An efficient, one-pot synthesis was developed for 3-aminoalkylated indoles by three-component coupling reaction of aldehydes, N-methylanilines, and indoles using AgOTf as a catalyst. A series of twenty 3-aminoalkylated indoles was evaluated for their antibacterial activities against both Gram negative and Gram positive bacteria. Compounds 4b and 4r showed good antibacterial activity against both Gram positive and Gram negative strains. However, inversing the property of substituent (from 4r to 4q) resulted in the significant fall in the magnitude of antibacterial activity against Escherichia coli. PMID:22373086

Rao, Vagicherla Kameshwara; Rao, Madharam Sudershan; Jain, Navin; Panwar, Jitendra; Kumar, Anil

2011-09-27

447

Silver triflate catalyzed synthesis of 3-aminoalkylated indoles and evaluation of their antibacterial activities  

PubMed Central

An efficient, one-pot synthesis was developed for 3-aminoalkylated indoles by three-component coupling reaction of aldehydes, N-methylanilines, and indoles using AgOTf as a catalyst. A series of twenty 3-aminoalkylated indoles was evaluated for their antibacterial activities against both Gram negative and Gram positive bacteria. Compounds 4b and 4r showed good antibacterial activity against both Gram positive and Gram negative strains. However, inversing the property of substituent (from 4r to 4q) resulted in the significant fall in the magnitude of antibacterial activity against Escherichia coli.

2011-01-01

448

Synthesis of essramycin and comparison of its antibacterial activity.  

PubMed

The triazolopyrimidine natural product essramycin (1) was synthesized without the use of protecting groups via a two-step reaction scheme involving a 3-amino-1,2,4-triazole intermediate, and its structure was unequivocally determined. However, in contrast to the natural product, the synthetic essramycin (1) did not display any antibacterial activity. PMID:21049974

Tee, Ernest H L; Karoli, Tomislav; Ramu, Soumya; Huang, Johnny X; Butler, Mark S; Cooper, Matthew A

2010-11-04

449

Synthesis and antitubercular activity of heterocycle substituted diphenyl ether derivatives.  

PubMed

Despite being an ancient disease, tuberculosis (TB) remains the leading single-agent infectious disease killer in the world. The emerging serious problem of TB control and clinical management prompted us to synthesize a novel series of heterocyclic substituted diphenyl ether derivatives and determine their activity against the H37Rv strain of Mycobacterium. All ten compounds inhibited the growth of the H37Rv strain of Mycobacterium at concentrations of 1 microg/mL. This activity was found to be comparable to the reference drugs rifampicin and isoniazid at the same concentration. While the antimicrobial activity of other diphenyl ether analogues, such as triclosan, is associated with the inhibition of enoyl-ACP reductase (ENR), the synthesised substituted diphenyl ether derivatives did not affect this enzyme activity in spite of their structural similarity with triclosan. Therefore, these compounds appear to have a novel mechanism of action against M. tuberculosis, and their structural features should be studied further for their potential as new antitubercular drugs. PMID:20443682

Kini, Suvarna G; Bhat, Anilchandra; Pan, Zhiqiang; Dayan, Franck E

2010-10-01

450

Natural aliphatic oxygenated unsaturated acids. Synthesis and biological activity  

Microsoft Academic Search

The review is devoted to natural unsaturated acyclic acids containing oxygen functions. Compounds of the aceto-genin and propiogenin types containing hydroxy, oxo, and epoxy groups as well as ether, hydrofuran, and hydropyran fragments are considered. Data are given on the biological activities of the acids themselves or of natural compounds whose structural elements are unsaturated acids. The methodology and strategy

Alexander G. Tolstikov; Genrikh A. Tolstikov

1996-01-01

451

Synthesis and biological activity of heterocycles from chalcone  

Microsoft Academic Search

The chalcone 3 was synthesized from 3-acetyl-4-hydroxy coumarin and 3-formylchromone by refluxing in ethanol in the presence of a catalytic\\u000a amount of pyridine. 3 was converted to bipyrazoles 4a-b by treatment with hydrazine and phenylhydrazine. The compounds were screened for their antibacterial activity.

Zeba N. Siddiqui; Mohammad Asad; Shagufta Praveen

2008-01-01

452

Synthesis and antimicrobial activities of some sulphur containing chromene derivatives.  

PubMed

A series of 3,3-dimethyl-3Hbenzothieno[3,2-f][1]-benzopyran analogues modified at the pyran 1,2-double bond were synthesized. The corresponding dihydro and (+/-)-cis-diol derivatives were converted into diacetate and cyclic carbonate upon acylation. The title compounds were characterized by spectroscopic analysis and screened for their antimicrobial activity in vitro. PMID:22908574

Serbetçi, Tuba; Birteksöz, Seher; Prado, Soizic; Michel, Sylvie; Tillequin, François

2012-07-01

453

Total synthesis and antiangiogenic activity of cyclopentane analogues of fumagillol  

Microsoft Academic Search

Novel cyclopentane analogues of fumagillol were synthesized and their endothelial cell proliferation inhibitory activities were evaluated. The cyclopentane-fumagillol derivatives were synthesized from (?)-2,3-O-isopropylidene-d-erythronolactone via stereoselective glycolate Claisen rearrangement and intramolecular ester enolate alkylation as key steps.

Byeong-Seon Jeong; Nam Song Choi; Soon Kil Ahn; Hoon Bae; Hak Sung Kim; Deukjoon Kim

2005-01-01

454

Synthesis and antifungal activity of benzimidazole, benzotriazole and aminothiazole derivatives.  

PubMed

In recent years, the use of antifungal drugs in human medicine has increased, especially with the advent of AIDS epidemic. Efforts have focused on the development of new, less toxic and more efficacious antifungal drugs with novel mechanism of action. The purpose of this study was to synthesize of some new benzimidazole, benzotriazole and aminothiazole derivatives and to evaluate their activity against some species of Candida, Aspergillus and dermatophytes. The desired compounds were synthesized by the reaction of benzimidazole and benzotriazole with bromoalkanes and also by the reaction of an amide derivative of aminothiazole with 2-piperazino-1-ethanol in an efficient solvent in the presence of tetraethyl ammounim bromide or triethylamine) as catalyst. Chemical structures of all the new compounds were confirmed by spectrophotometric methods. Antifungal activities of the new compounds were evaluated by broth micro dilution method as recommended by CLSI. Among the tested compounds, 1-nonyl-1H-benzo[d]imidazole and 1-decyl-1H-benzo[d]imidazole exhibited the best antifungal activities. Of the examined synthetic compounds in different categories, benzimidazole derivatives established better antifungal activities than benzotriazole derivatives, and the piperazine analogue had no significant antifungal effect. PMID:23181082

Khabnadideh, S; Rezaei, Z; Pakshir, K; Zomorodian, K; Ghafari, N

2012-04-01

455

Convergent synthesis and cytotoxic activities of 26-thio- and selenodioscin.  

PubMed

Convergent block syntheses of 26-thio- and selenodioscin have been achieved by developing the highly stereoselective 1,2-trans glycosylations of chacotriosyl imidate without recourse to neighboring group assistance. Both thiodioscin and selenodioscin possess cytotoxic activities similar to dioscin, a natural spirostanol glycoside. PMID:23751199

Chen, Pengwei; Wang, Peng; Song, Ni; Li, Ming

2013-06-07

456

Synthesis, antifungal, and antiviral activity of hydrophosphoryl derivatives of mycoheptin  

Microsoft Academic Search

Reactions of the polyene macrolide antibiotic mycoheptin with aldehydes and hypophosphorous acid yielded its hydrophosphoryl\\u000a derivatives. The physicochemical and biological properties the resulting mycoheptin derivatives were studied. Biological investigations\\u000a showed that hydrophosphoryl derivatives of mycoheptin were less toxic than the initial antibiotic and had antifungal and antiviral\\u000a activity.

V. V. Belakhov; Yu. L. Shenin

2007-01-01

457

Synthesis, Properties and Biological Activity of Organotitanium Substituted Heteropolytungstates  

PubMed Central

Six new compounds [(CpTi)X, Cp=??-c?H?, X=Ge, Ga, B) have been prepared and their Keggin structures determined by elementary analysis, IR, UV, ?H NMR and ???WNMR spectrometry. The results show that the complexes retain Keggin structure. The complexes exhibit antitumoral activity in vitro as shown by MTT experiment.

Wang, Xiaohong; Li, Jianxin; He, Jianghua

2001-01-01

458

Synthesis, cytotoxicity and in vitro antileishmanial activity of naphthothiazoles.  

PubMed

The leishmaniasis is a spectral disease caused by the protozoan Leishmania spp., which threatens millions of people worldwide. Current treatments exhibit high toxicity, and there is no vaccine available. The need for new lead compounds with leishmanicidal activity is urgent. Considering that many lead leishmanicidal compounds contain a quinoidal scaffold and the thiazole heterocyclic ring is found in a number of antimicrobial drugs, we proposed a hybridization approach to generate a diverse set of semi-synthetic heterocycles with antileishmanial activity. We found that almost all synthesized compounds demonstrated potent activity against promastigotes of Leishmania (Viannia) braziliensis and reduced the survival index of Leishmania amastigotes in mammalian macrophages. Furthermore, the compounds were not cytotoxic to macrophages at fivefold higher concentrations than the EC50 for promastigotes. All molecules fulfilled Lipinski's Rule of Five, which predicts efficient orally absorption and permeation through biological membranes, the in silico pharmacokinetic profile confirmed these characteristics. The potent and selective activity of semi-synthetic naphthothiazoles against promastigotes and amastigotes reveals that the 2-amino-naphthothiazole ring may represent a scaffold for the design of compounds with leishmanicidal properties and encourage the development of drug formulation and new compounds for further studies in vivo. PMID:23421616

de Toledo, Juliano S; Junior, Paulo E S; Manfrim, Viviane; Pinzan, Camila F; de Araujo, Alexandre S; Cruz, Angela K; Emery, Flavio S

2013-06-01

459

Total Chemical Synthesis of Biologically Active Vascular Endothelial Growth Factor  

SciTech Connect

The 204-residue covalent-dimer vascular endothelial growth factor (VEGF, see picture) with full mitogenic activity was prepared from three unprotected peptide segments by one-pot native chemical ligations. The covalent structure of the synthetic VEGF was confirmed by precise mass measurement, and the three-dimensional structure of the synthetic protein was determined by high-resolution X-ray crystallography.

Mandal, Kalyaneswar; Kent, Stephen B.H. (UC)

2011-09-15

460

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

2013-03-21

461

Synthesis and biological activity of cinnamaldehydes as angiogenesis inhibitors  

Microsoft Academic Search

A series of 2-hydroxycinnamaldehyde derivatives was synthesized for examing a structure-acti