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1

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

2

Combustion synthesis method and products  

DOEpatents

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

Holt, J.B.; Kelly, M.

1993-03-30

3

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

E-print Network

, including unique pigments and catalysts, materials for SOFC and lithium batteries, oxygen sensors solution (aqueous) combustion synthesis (SCS) method.[1­3] Typically SCS involves a self-sustained reaction

Mukasyan, Alexander

4

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

5

COMBUSTION SYNTHESIS OF ADVANCED MATERIALS: PRINCIPLESAND APPLICATIONS  

E-print Network

. Gasless Combustion SynthesisFrom Elements B. Combustion Synthesis in Gas-Solid Systems C. Products Density for Gasless Systems D. Green Mixture Density and Initial Gas Pressure for Gas-Solid Systems E). This review article summarizes the state of the art in combustion syn- thesis,from both the scientijc

Mukasyan, Alexander

6

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

EPA Science Inventory

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

7

Combustion synthesis continuous flow reactor  

DOEpatents

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

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

1998-01-01

8

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

9

Gravity Effects on Combustion Synthesis of Glasses  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

10

Combustion synthesis of ZnO and Ag-doped ZnO and their bactericidal and photocatalytic activities  

NASA Astrophysics Data System (ADS)

The combustion synthesized ZnO and 0.9 at.% Ag-doped ZnO have been characterized by powder X-ray diffraction and energy dispersive X-ray, UV-visible diffuse reflectance, photoluminescence and impedance spectroscopies. Doping sharpens the band gap absorption, displays surface plasmon resonance, suppresses the blue emission, enhances the near band gap emission and increases the charge transfer resistance and capacitance. Ag-doping by combustion method improves significantly the bactericidal activity but not the photocatalytic activity.

Karunakaran, C.; Rajeswari, V.; Gomathisankar, P.

2011-09-01

11

Solution Combustion Synthesis Impregnated Layer Combustion Synthesis is a Novel  

E-print Network

) · Short reaction time (~ sec) · High temperature gradient (up to 106 K/s) Two modes of CS ·Heterogeneous products on combustion temperature profile Effect of gas phase product;Conventional Combustion System: Characteristics: · Exothermic nature of reaction · High temperature (2000 °C

Mukasyan, Alexander

12

Candle filter fabrication using combustion synthesis method  

SciTech Connect

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

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

1996-12-31

13

Methane-assisted combustion synthesis of nanocomposite tin dioxide materials  

E-print Network

Methane-assisted combustion synthesis of nanocomposite tin dioxide materials S.D. Bakrania *, C., Ann Arbor, MI 48109-2125, USA Abstract Combustion synthesis of tin dioxide (SnO2) was studied using: Combustion synthesis; Nanoparticles; Tin dioxide; Metals 1. Introduction Tin dioxide (SnO2) is the most

Wooldridge, Margaret S.

14

Nanocrystalline pirochromite spinel through solution combustion synthesis  

Microsoft Academic Search

The production of magnesiumchromium oxides by solution combustion synthesis was investigated using glycine and urea for the first time. Ammonium dichromate, urea\\/glycine and ammonium nitrate aqueous solutions were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and

M. J. de Andrade; M. D. Lima; R. Bonadiman; C. P. Bergmann

2006-01-01

15

Combustion synthesis of thoria a feasibility study  

Microsoft Academic Search

In an effort to prepare a thoria powder feed that can be compacted and sintered at lower temperatures, the feasibility of the combustion synthesis was studied. Here, preparations using thorium nitrate as oxidant and urea or citric acid as fuel were studied. The powders thus prepared were characterized for surface area and crystallite size and were compacted into pellets and

V. Chandramouli; S. Anthonysamy; P. R. Vasudeva Rao

1999-01-01

16

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

17

Soft-combustion synthesis of a new cathode-active material, LiVWO 6, for lithium-ion batteries  

NASA Astrophysics Data System (ADS)

Brannerite-LiVWO 6, has been synthesized by employing a wet-chemical soft-combustion (low temperature) technique and its battery-active character as candidate cathode material in lithium-containing batteries is reported in the light of electrochemical means. Structural and thermal properties have also been studied by means of classical techniques such as XRD and thermal analysis. The structural features are found to be similar to its analogous counterpart, brannerite-LiVMoO 6 previously reported. Quasi-layered type LiVWO 6 crystallizes in brannerite structure of AB 2O 6 type, having a general formula LiM 2'O 6 (M'=transition metal) with lattice parameters a=9.347 , b=3.670 , c=6.593 and ?=11150'. The thermochemical reactions that occur during the soft-combustion of the precursor mass facilitate the formation of the above compound at 434C as deduced from TG-DTA scan. The product (LiVWO 6) thus prepared (calcined at 700C) exhibits the submicrometer grains (<1 ?m) whose specific surface area is found to be 4.97 m 2/g as deduced from BET analysis. The redox behavior of the above compound has been examined for LiVWO 6/Li +/Li under the wet electrolyte (1 M LiPF 6: EC+DMC) environment in the voltage regime 4.0 and 1.5 V using constant current technique at a current density of 0.8 mA/cm 2. It has been found that the test cell containing LiVWO 6/Li couple demonstrates excellent charge-discharge behavior in the voltage regime 3.0-1.5 V and the specific capacity of 240 mAh/g has been deduced from the first charge-discharge cycle in the voltage regime 4.0-1.5 V.

Prabaharan, S. R. S.; Yong, Tou T.; Fauzi, Ahmad; Michael, M. S.

18

Combustion synthesis and quasi-isostatic densication of powder cermets  

E-print Network

Combustion synthesis and quasi-isostatic densi®cation of powder cermets E.A. Olevskya,* , E; Combustion synthesis; Constitutive modeling; Cermets 1. Introduction Self-propagating high In order for the bene®ts of SHS to be realized for the production of structural cermets, the process must

Meyers, Marc A.

19

Combustion synthesis of porous glasses and ceramics for bone repair.  

PubMed

Porous bioactive materials with constituents such as CaO, P2O5, SiO2, MgO, K2O, Na2O implanted in bone can activate a biologic response to enhance bone healing. These biomaterials are currently formed utilizing wet chemistry, plasma spray, D-gun, sintering, and diffusion bond techniques. This work investigates the use of self propagating high temperature combustion synthesis (SHS) in the creation of porous bioactive glasses for bone repair. The use of combustion synthesis has many advantages over the methods mentioned previously. The primary advantages are the ability to control the process to provide specified porosity (% porosity, pore size distribution, interconnected pores, functionally grading of porosity), structural mechanical properties, together with rapid production of the material. The focus of this project is the investigation of combustion synthesis reactions based on the reaction system 3CaO + P2O5==>Ca3(PO4)2 and incorporating other known biocompatible constituents into the reaction. PMID:11347436

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

2001-01-01

20

The Effects of Gravity on Combustion and Structure Formation During Combustion Synthesis in Gasless Systems  

NASA Technical Reports Server (NTRS)

There have been relatively few publications examining the role of gravity during combustion synthesis (CS), mostly involving thermite systems. The main goal of this research was to study the influence of gravity on the combustion characteristics of heterogeneous gasless systems. In addition, some aspects of microstructure formation processes which occur during gasless CS were also studied. Four directions for experimental investigation have been explored: (1) the influence of gravity force on the characteristic features of heterogeneous combustion wave propagation (average velocity, instantaneous velocities, shape of combustion front); (2) the combustion of highly porous mixtures (with porosity greater than that for loose powders), which cannot be obtained in normal gravity; (3) the effect of gravity on sample expansion during combustion, in order to produce highly porous materials under microgravity conditions; and (4) the effect of gravity on the structure formation mechanism during the combustion synthesis of poreless composite materials.

Varma, Arvind; Mukasyan, Alexander; Pelekh, Aleksey

1997-01-01

21

Combustion synthesis of boride and other composites  

DOEpatents

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

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

1988-07-28

22

Combustion synthesis of boride and other composites  

DOEpatents

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

Halverson, Danny C. (Modesto, CA); Lum, Beverly Y. (Livermore, CA); Munir, Zuhair A. (Davis, CA)

1989-01-01

23

Fuel mediated solution combustion synthesis of ZnO supported gold clusters and nanoparticles and their catalytic activity and in vitro cytotoxicity.  

PubMed

Nanocomposites of gold nanoparticles and semiconductor ZnO with wurtzite structure, made by solution combustion synthesis (SCS), as a function of the Zn/fuel ratio with polyethylene glycol (PEG) as fuel exhibit the presence of both nanoparticles and clusters. Atomic gold clusters present on the surface of ZnO nanorods which can be identified by XPS and SEM are easily monitored and characterized by positive ion MALDI experiments as mostly odd numbered clusters, Au3 to Au11 in decreasing amounts. Low concentrations of the fuel produce AuClO and nanoparticles (NPs), with no clusters. Au-ZnO nanocomposites at all [Au] exhibit single blue shifted plasmon absorption and corresponding photoluminescence (PL). Increasing particle size prefers surface plasmon resonance (SPR) scattering of metal that could lead to PL enhancement; however, available ZnO surface in the Au-ZnO composite becomes more important than the particle size of the composite with higher [Au]. The catalytic activity of these Au-ZnO nanocomposites tested on 4-nitrophenol clearly revealed the presence of an intermediate with both NPs and clusters playing different roles. An in vitro study of cytotoxicity on MCF-7 cell lines revealed that these gold nanostructures have turned out to be powerful nanoagents for destruction of cancer cells even with small amounts of gold particles/clusters. The nanorods of ZnO, known to be nontoxic to normal cells, play a lesser role in the anticancer activity of these Au-ZnO nanocomposites. PMID:25271812

Chanu, T Inakhunbi; Muthukumar, Thangavelu; Manoharan, Periakaruppan T

2014-11-21

24

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

25

Synthesis of zeolite phases from combustion by-products.  

PubMed

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

Pimraksa, Kedsarin; Chindaprasirt, Prinya; Setthaya, Naruemon

2010-12-01

26

Combustion synthesis of tin dioxide nanocomposites for gas sensing applications  

NASA Astrophysics Data System (ADS)

The current work focuses on understanding the mechanisms controlling tin dioxide (SnO2) nanoparticle morphology in combustion synthesis systems and how nanoarchitecture affects performance of solid-state gas sensors. A range of analytical methods (including transmission and scanning electron microscopy, x-ray diffraction, nitrogen absorption, and XEDS) were used to characterize the materials properties as a function of the combustion synthesis conditions. A novel method of generating tin dioxide materials was developed which provides a new degree of control over SnO2 morphology; including spherical, nanorod and encapsulated particle architectures. A simplified model for particle formation based on characteristic times was developed to identify the physical and chemical processes affecting the morphologies observed using transmission electron microscope imaging. The SnO2 nanoparticles evolve from primary particles sizes of 7 nm to 14 nm through the synthesis region, and the results indicate interparticle collision and sintering are the dominant mechanisms in determining particle size and morphology for the flame conditions studied. Metal acetates were used to create metal/SnO 2 nanocomposite materials, and the processes controlling gold acetate decomposition in particular were explored. The results of the studies suggest a relationship between the precursor crystallite size and the product nanoparticles. The well-characterized SnO2 particles were evaluated as the active materials for gas-sensing. Sensor sensitivity and time response to carbon monoxide in dry air was used to investigate microstructure-performance links. Excellent sensitivity (3 7, based on the ratio of the resistance of the sensor in air to the resistance in the target gas) and time response (4--20 seconds) were demonstrated for the thin film gas sensors. Fabrication studies demonstrated the sensor performance was a strong function of the film deposition method. A novel method for manufacturing sensors with outstanding consistency and performance was developed. This method was used to explore the effects of microstructure and composition on sensor performance. Gold and palladium doped SnO2 gas sensors indicated the introduction of dopants has potential to improve sensor performance; however, the effects are dependent on the additive distribution and location. The combustion synthesis and sensor fabrication methods that are the results of these studies will dramatically accelerate the design of new sensors and sensor optimization.

Bakrania, Smitesh Dhirajlal

27

Synthesis gas use in internal combustion engines.  

E-print Network

??The objective of this dissertation was to investigate the combustion characteristics of a compression ignition, spark ignition, and homogeneous charge compression ignition engine operating on (more)

Bika, Anil Singh

2010-01-01

28

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

29

Combustion synthesis and characterization of uranium and thorium tellurides  

Microsoft Academic Search

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

Czechowicz

1985-01-01

30

Combustion Synthesis and Characterization of CeO2 Nanopowder  

Microsoft Academic Search

Modified combustion procedure, named as polymer complex solution method (PCS), was used for synthesis of CeO2 nanopowder. As fuel was employed polyethylene glycol (PEG) with average molecular weight 200. Post-synthesis ther- mal treatments were done at 800 C for 2 hours. X-ray powder diffraction, electron microscopy (SEM and TEM), laser light scattering, infrared spectroscopy, UV-VIS diffuse reflectance spectroscopy and luminescence

Miodrag Mitri; Miroslav D. Drami anina

31

Combustion synthesis of uraniathoria solid solutions  

Microsoft Academic Search

The feasibility of the combustion synthesis using citric acid as the fuel was studied in order to prepare a homogeneous mixture of uranium dioxidethorium dioxide feed powder that could be cold compacted without binder or lubricant and sintered to a high density (?95% theoretical density) at relatively low temperatures (?1573 K). Systematic studies were carried out to optimize various process

S Anthonysamy; K Ananthasivan; V Chandramouli; I Kaliappan; P. R Vasudeva Rao

2000-01-01

32

Synthesis and characterization of iron orthophosphate by solution combustion method  

SciTech Connect

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

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

2012-12-15

33

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.

34

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

35

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

36

Combustion synthesis of low exothermic component rich composites  

DOEpatents

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

Halverson, Danny C. (Modesto, CA); Lum, Beverly Y. (Livermore, CA); Munir, Zuhair A. (Davis, CA)

1991-01-01

37

Active Combustion Control for Aircraft Gas Turbine Engines  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

38

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

39

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.

2014-01-28

40

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

E-print Network

Combustion synthesis/quasi-isostatic pressing of TiC­NiTi cermets: processing and mechanical the chemical content of the reactant mixture to include addi- tional titanium. These cermets combine the high

Meyers, Marc A.

41

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

NASA Astrophysics Data System (ADS)

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

Pickett, Derek Kyle

42

An overview of European activities on microgravity combustion  

NASA Technical Reports Server (NTRS)

The global objective of the European efforts in microgravity combustion is to combine theoretical and experimental work, both under normal and reduced gravity, to progress in the basic understanding of gravity dependent phenomena in various combustion situations. The first phase of the European activities on microgravity combustion has been summarized in refs. 1, 2, and 3. This overview will summarize the more recent developments. The focus will be on new experimental facilities, new research topics, and new collaborative efforts.

Goekalp, Iskender

1993-01-01

43

A synthesis of carbon dioxide emissions from fossil-fuel combustion  

Microsoft Academic Search

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

Robert Joseph Andres; Thomas A Boden; F.-M. Breon; P. Ciais; S. Davis; D Erickson; J. S. Gregg; Andrew Jacobson; Gregg Marland; J. Miller; T Oda; J. G. J. Oliver; Michael Raupach; P Rayner; K. Treanton

2012-01-01

44

Active combustion control : modeling, design and implementation  

E-print Network

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

Park, Sungbae, 1973-

2004-01-01

45

Structural and electrochemical properties of LiCoO 2 prepared by combustion synthesis  

Microsoft Academic Search

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

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

2003-01-01

46

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

E-print Network

synthesis technique (hydrazine/metal-nitrate method). The process starts with aque- ous solutions of Eu(NO3)3 and Ga(NO3)3 as the precursors and hydrazine as (non-carbonaceous) fuel. A spontaneous combustion, the ignition temperature and the volume of precursors. Combustion synthesis using hydrazine (N2H4) with metal

McKittrick, Joanna

47

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

48

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

NASA Astrophysics Data System (ADS)

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

Tamrakar, Raunak Kumar; Bisen, D. P.

2013-06-01

49

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

50

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

51

Synthesis of tungsten carbidecarbon nanomaterials by combustion reaction  

Microsoft Academic Search

It has been studied the possibility to synthesize the new catalytic systems, based on a carbon carrier precipitated tungsten carbides, under the self-propagating combustion regime. For this purpose the tungsten (VI) oxide deposited on a surface of the fine-grained carbon black was reduced by magnesium under the combustion mode. Uniform structures of WC or W2C nanosized phases were observed, depending

Kh. G. Kirakosyan; Kh. V. Manukyan; S. L. Kharatyan; R. A. Mnatsakanyan

2008-01-01

52

Synthesis of red-emitting, small particle size luminescent oxides using an optimized combustion process  

Microsoft Academic Search

A novel ceramic synthesis technique, combustion synthesis, was explored to produce red-emitting Cr{sup 3+}-doped YAlO and Eu{sup 3+}-doped YO phosphors with improved physical and luminescent properties. This technique involves the reaction of metal nitrates (oxidizers) and an organic fuel (urea, carbohydrazide, glycine) at 500 C. Resulting powders are well-crystallized, with a large surface area and small particle size. The spectral

Lauren E. Shea; Joanna McKittrick; Olivia A. Lopez; Esther Sluzky

1996-01-01

53

Nanocrystalline Cr 2O 3 and amorphous CrO 3 produced by solution combustion synthesis  

Microsoft Academic Search

The synthesis of chromium oxides by solution combustion synthesis was investigated. Ammonium dichromate, glycine, urea and ammonium nitrate dissolved in aqueous solution were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and the fuel\\/oxidant ratio. Amorphous CrO3

M. D. Lima; R. Bonadimann; M. J. de Andrade; J. C. Toniolo; C. P. Bergmann

2006-01-01

54

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...

55

Combustion synthesis of SiO2 on the aluminum plate  

NASA Astrophysics Data System (ADS)

The approach of utilizing combustion synthesis to make fine particles of SiO2, Al2O3 and TiO2 is a quite modern technology. Through the chemical reaction in post-flame region, fine SiO2 particles can be formed with high purity on plate surface. Therefore, the combustion synthesis of SiO2 powders is an important area for further research and development, especially for the application of SiO2 in the semiconductor industry. This investigation proposes an experimental approach (i.e., a gas-phase combustion synthesis) using two different kinds of organic compounds, Hexamethyldisilazane (HMDSA) and Hexamethyldisioxane (HMDSO), as the silicon precursors. A premixed gas burner is chosen with C3H8 as fuel, air as oxidant and part of the air was used as the carrying gas to entrain HMDSA/HMDSO vapor into the combustible mixture. Observations show that the C3H8/air flame changed color from a pale-blue flame to light yellow and then orange when different amounts of precursors were introduced. Through the chemical reaction in the post-flame region, fine SiO2 particles were formed in the gas phase and then quenched and collected on an aluminum flat plate. The objective of this paper is to study the effects of HMDSO and HMDSA concentrations and flame temperatures on the synthesis of SiO2 particles.

Yeh, C. L.; Zhao, E.; Ma, H. K.

2001-03-01

56

Electrical properties of Ni\\/YSZ cermets obtained through combustion synthesis  

Microsoft Academic Search

The synthesis of Ni\\/YSZ cermet with controlled microstructural characteristics presents a lot of interest for many solid-state electrochemical applications. These materials are generally obtained by reducing poorly sintered mixtures of YSZ with nickel oxide by hydrogen. We recently proposed an alternative route based on a thermite reaction performed in a combustion regime. This method makes it possible, in one step,

U Anselmi-Tamburini; G Chiodelli; M Arimondi; F Maglia; G Spinolo; Z. A Munir

1998-01-01

57

Carbothermal synthesis of Si3N4 powders using a combustion synthesis precursor  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

58

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

59

Solution combustion synthesis and optimization of phosphors for plasma display panels  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

60

Apparatus and method for gas turbine active combustion control system  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

61

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

PubMed

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

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

2010-01-01

62

Synthesis of WC and dense WC5 vol.% Co hard materials by high-frequency induction heated combustion  

Microsoft Academic Search

Tungsten carbide (WC) and dense WC5vol.% Co materials, with grain size of ?1?m, were synthesized by high-frequency induction heated combustion synthesis (HFIHCS) method in one step from elemental powders of W, C, and cobalt (Co) within several minutes. Simultaneous combustion synthesis and densification were accomplished under the combined effects of an induced current and mechanical pressure. In the absence of

Hwan-Cheol Kim; Dong-Young Oh; Jiang Guojian; In-Jin Shon

2004-01-01

63

Synthesis and characterization of IR up-conversion material CaS:Eu, Sm by low-temperature combustion synthesis method  

Microsoft Academic Search

Infrared up-conversion material CaS:Eu, Sm was synthesized by the low-temperature combustion synthesis (LCS) method, which has expanded the application range of the LCS method which is always used in the synthesis of oxides and compound oxides. The combustion process was discussed and the effect of the amount of carbamide on the up-conversion luminescence properties was analyzed. XRD patterns show that

Liping Lu; Xiyan Zhang; Zhaohui Bai; Xiaoyun Mi

2009-01-01

64

Flash synthesis of Li2TiO3 powder by microwave-induced solution combustion  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

65

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

NASA Astrophysics Data System (ADS)

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

Jo, Ilguk

66

Combustion synthesis of CoCrMo orthopedic implant alloys: microstructure and properties  

Microsoft Academic Search

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

Bingyun Li; Alexander Mukasyan; Arvind Varma

2003-01-01

67

Parametric study of the gel-combustion synthesis of nanocrystalline ZrO 2-based powders  

Microsoft Academic Search

In this paper, we report a study of the effect on the powder morphology of zirconia based solid solutions of several parameters of the synthesis by gel-combustion routes, such as fuel, metal\\/fuel ratio, composition of the nanopowder, pH of the precursor solution, etc. We evaluated the average crystallite size, BET specific surface area and the degree of agglomeration of the

I. O. Fbregas; D. G. Lamas

2011-01-01

68

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

Microsoft Academic Search

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

Takao Tani; Naoyoshi Watanabe; Kazumasa Takatori

2003-01-01

69

Gel-Combustion synthesis to obtain Co3O4 nanopowders for solar selective surfaces  

Microsoft Academic Search

Selective solar paints based on Co3O4 solid particles were prepared. In this study, two combustion routes for synthesis of Co3O4 using lysine and EDTA, as fuels, were used. Co3O4 nanopowders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and BET specific surface area. The Co3O4 particles showed different SBET, with dimensions ranging from a

M. C. Gardey Merino; G. E. Lascalea; P. Vzquez

70

Combustion synthesis of nano-sized tungsten carbide powder and effects of sodium halides  

Microsoft Academic Search

The synthesis of nano-size tungsten carbide powder has been investigated with a WO3+Mg+C+ carbonate system using alkali halides. The effects of different types of alkali halides on combustion temperature\\u000a and tungsten carbide formation were discussed. Sodium fluoride had a notable effect on the particle size of the product and\\u000a the degree of transformation from the initial mixture. A small amount

H. I. Won; H. H. Nersisyan; C. W. Won

2010-01-01

71

A combustion synthesis method to obtain alternative cermet materials for SOFC anodes  

Microsoft Academic Search

Homogeneous mixtures of nanocrystalline powders of NiYSZ, (Ni,Co)YSZ, (Ni,Fe)YSZ, and (Ni,Cu)YSZ were obtained by combustion synthesis from mixtures of molten nitrates and urea. Electrolyte\\/anode bilayers were then prepared by pressing a cermet layer onto a previously pressed yttria-stabilised zirconia (YSZ) electrolyte layer, at room temperatures, and then co-firing; this yields a porous cermet anode, and a dense YSZ layer with

A Ringued; J. A Labrincha; J. R Frade

2001-01-01

72

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

PubMed Central

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

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

2014-01-01

73

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

74

Combustion  

NASA Technical Reports Server (NTRS)

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

Bulzan, Dan

2007-01-01

75

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

SciTech Connect

Highlights: ? With increasing the fuel to oxidizer ratio synthesis products changed from CuO to Cu{sub 2}O. ? With increasing the fuel to oxidizer ratio the combustion temperature decreased. ? Maximum ratio that synthesis could occur was achieved. ? The stoichiometric ratio had the maximum combustion temperature. ? Solution with graphite had lower combustion temperature. -- Abstract: The role of fuel/oxidizer ratio in the synthesis conditions of CuAl{sub 2}O{sub 3} nanocomposite, which was prepared through solution combustion synthesis, method was investigated. For this purpose, copper and aluminum nitrates as well as urea were used as oxidizer and fuel, respectively. The fuel/oxidizer (F/O) ratios were selected from the range of 0.91.75. The products were analyzed using X-ray diffraction, SEM and TEM techniques. During the process the temperature was recorded as a function of time. The results showed that by increasing the F/O ratio up to the stoichiometric amount, the combustion temperature increases. Further increment of F/O ratio resulted in a decrease in the combustion temperature. Microscopic evaluations, using SEM and TEM, proved feasibility of the production of CuAl{sub 2}O{sub 3} through this method.

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

2012-11-15

76

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

77

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

78

Combustion of Na 2B 4O 7 + Mg + C to synthesis B 4C powders  

NASA Astrophysics Data System (ADS)

Boron carbide powder was fabricated by combustion synthesis (CS) method directly from mixed powders of borax (Na 2B 4O 7), magnesium (Mg) and carbon. The adiabatic temperature of the combustion reaction of Na 2B 4O 7 + 6 Mg + C was calculated. The control of the reactions was achieved by selecting reactant composition, relative density of powder compact and gas pressure in CS reactor. The effects of these different influential factors on the composition and morphologies of combustion products were investigated. The results show that, it is advantageous for more Mg/Na 2B 4O 7 than stoichiometric ratio in Na 2B 4O 7 + Mg + C system and high atmosphere pressure in the CS reactor to increase the conversion degree of reactants to end product. The final product with the minimal impurities' content could be fabricated at appropriate relative density of powder compact. At last, boron carbide without impurities could be obtained after the acid enrichment and distilled water washing.

Guojian, Jiang; Jiayue, Xu; Hanrui, Zhuang; Wenlan, Li

2009-09-01

79

Glycerol-assisted solution combustion synthesis of improved LiMn2O4  

NASA Astrophysics Data System (ADS)

Spinel LiMn2O4 has been synthesized by a glycerol-assisted combustion synthesis method. The phase composition and morphologies of the compound were ascertained by X-ray diffraction (XRD) and scanning electron microscope (SEM). The electrochemical characterization was performed by using CR2032 coin-type cell. XRD analysis indicates that single phase spinel LiMn2O4 with good crystallinity has been obtained as a result of 5 h treatment at 600 C. SEM investigation indicates that the average particle size of the sample is 200 nm. The initial discharge specific capacity of the LiMn2O4 is 123 mAh/g at a current density of 30 mA/g. When the current density increased to 300 mA/g, the LiMn2O4 offered a discharge specific capacity of 86 mAh/g. Compared with the LiMn2O4 prepared by a conventional solution combustion synthesis method at the same temperature, the prepared LiMn2O4 possesses higher purity, better crystallinity and more uniformly dispersed particles. Moreover, the initial discharge specific capacity, rate capability and cycling performance of the prepared LiMn2O4 are significantly improved.

Liu, Guiyang; Xin, Kong; Zhang, Lili; Wang, Baosen; He, Ying

2013-08-01

80

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

81

Synthesis of yttrium iron garnet (YIG) by citratenitrate 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 citratenitrate (CN) gel combustion process and a precursor plasma spraying technique. Two different CN 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

82

AN EXPERIMENTAL INVESTIGATION OF COMBUSTION SYNTHESIS OF SILICON DIOXIDE (SiO2) PARTICLES IN PREMIXED FLAMES  

Microsoft Academic Search

An experimental study of gas-phase combustion synthesis of silicon dioxide (SiO2) particles was conducted in C3H8\\/air and H2\\/air premixed flames. Two types of organosilicon compounds, HMDSO and HMDSA. were used as the silicon precursors of synthesis processes. The objective of this investigation was to study the effects of HMDSO and HMDSA concentration, flame temperature, water vapor, and oxygen mole fraction

C. L. YEH; E. ZHAO; H. K. MA

2001-01-01

83

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

84

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

SciTech Connect

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

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

2003-09-30

85

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

86

Dynamical Processes in Active Control of Combustion Instabilities  

Microsoft Academic Search

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

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

87

Effect of nanocomposite synthesis on the combustion performance of a ternary thermite.  

PubMed

Nanocomposite thermites are attractive materials for their diverse applications from metallurgy to ordnance technologies. While there are a plethora of combinations of fuel and oxidizers, this work shows that the composite's overall performance is intimately tied to how the fuel and oxidizer are prepared and combined. Comparison of the combustion velocities of two separate ternary mixtures of Al-Fe(2)O(3)-SiO(2), one prepared in situ using sol-gel processing and the other prepared by physically mixing discrete nanoscale particles, demonstrated different burning behaviors as a result of preparation technique. The stoichiometry of the two sets of thermite was varied to examine the influence of SiO(2) on combustion velocity as a means to control the reaction behavior. For pure Fe(2)O(3) + Al reactions, results show that the sol-gel synthesized materials (40 m/s) exhibit increased velocities over the physically mixed materials (9 m/s) by approximately 4 times. This trend is not observed, however, upon addition of SiO(2) to the thermite mixture; ternary thermites with 40 wt % SiO(2) showed decreased burn velocities of 0.02 m/s for sol-gel prepared thermites compared to 0.2 m/s for their physically mixed counterparts. The observed trends are believed to be caused by the unique mixing between the Fe(2)O(3) and SiO(2) phases resulting from the two synthesis techniques. PMID:16853608

Prentice, Daniel; Pantoya, Michelle L; Clapsaddle, Brady J

2005-11-01

88

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

SciTech Connect

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

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

2011-12-15

89

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

90

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

NASA Astrophysics Data System (ADS)

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

Isella, Giorgio Carlo

91

One step synthesis of dense MoSi 2SiC composite by high-frequency induction heated combustion and its mechanical properties  

Microsoft Academic Search

Dense MoSi2SiC composite was synthesized by high-frequency induction heated combustion synthesis method within 2min in one step from elemental powders of Mo, Si and C. Simultaneous combustion synthesis and densification were carried out under the combined effect of an induced current and mechanical pressure. Highly dense MoSi2SiC with relative density of up to 98% was produced under simultaneous application of

Dong Young Oh; Hwan Cheol Kim; Jin Kook Yoon; In Jin Shon

2005-01-01

92

Visible and NIR luminescence of nanocrystalline ?-Ga 2O 3:Er 3+ prepared by solution combustion synthesis  

Microsoft Academic Search

In this paper we report on facile solution combustion synthesis of erbium doped ?-Ga2O3 with urea as fuel. The product was characterized using powder X-ray diffraction and transmission electron microscopy (TEM). X-ray diffraction and TEM showed that the material is nanostructured. Luminescence properties of ?-Ga2O3:Er are studied with excitation in near infrared (Nd:YAG laser at 1064nm) and visible (argon laser

Tomislav Biljan; Andreja Gajovi?; Zlatko Mei?

2008-01-01

93

Spectroscopic analysis of Eu3+ -and Eu3+:Yb3+-doped yttrium silicate crystalline powders prepared by combustion synthesis  

Microsoft Academic Search

Yttrium silicate powders doped with Eu3+ and codoped with Eu3+ and Yb3+ were prepared by combustion synthesis. The x-ray powder diffraction data showed the presence of Y2SiO5 and Y2Si2O7 crystalline phases. Singly doped (1 wt %) sample illuminated with ultraviolet light (lambda=256 nm) showed the characteristic red luminescence corresponding to 5D0-->7FJ transitions of Eu3+. The Judd-Ofelt intensity parameters were calculated

Nikifor Rakov; Dayanne F. Amaral; Glauco S. Maciel

2010-01-01

94

Spectroscopic analysis of Eu3+ -and Eu3+:Yb3+-doped yttrium silicate crystalline powders prepared by combustion synthesis  

Microsoft Academic Search

Yttrium silicate powders doped with Eu3+ and codoped with Eu3+ and Yb3+ were prepared by combustion synthesis. The x-ray powder diffraction data showed the presence of Y2SiO5 and Y2Si2O7 crystalline phases. Singly doped (1 wt %) sample illuminated with ultraviolet light (?=256 nm) showed the characteristic red luminescence corresponding to 5D0?7FJ transitions of Eu3+. The JuddOfelt intensity parameters were calculated

Nikifor Rakov; Dayanne F. Amaral; Renato B. Guimares; Glauco S. Maciel

2010-01-01

95

Synthesis of WC and dense WC xvol.%Co hard materials by high-frequency induction heated combustion method  

Microsoft Academic Search

WC and dense WCxvol.%Co materials, with grain size of <1 ?m, were synthesized by high-frequency induction heated combustion synthesis (HFIHCS) method in one step from elemental powders of W, C and Co within several minutes. In the absence of cobalt additive, WC can be formed, but its relative density was low (about 70%) under simultaneous application of a 60 MPa

Hwan-Cheol Kim; Dong-Young Oh; In-Jin Shon

2004-01-01

96

Preparation of Nano Y 2O 2S:Eu Phosphor by Ethanol Assisted Combustion Synthesis Method  

Microsoft Academic Search

Y2O2S:Eu nano crystallines were prepared by a new ethanol assisted combustion synthesis method using sulfurcontained organic fuel in an ethanol-aqueous solution. The as-prepared nanocrystallines were characterized by X-ray diffraction, transmission electron microscope, photoluminescence spectra and X-ray luminescence spectra. It is shown that the assistant fuel ethanol has the effect of decreasing the water needed, simplifying the experiment procedure by dissolving

Xixian Luo; Wanghe Cao; Mingming Xing

2006-01-01

97

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

NASA Astrophysics Data System (ADS)

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

Rakov, Nikifor; Guimares, R. B.; Lozano B., W.; Maciel, Glauco S.

2013-07-01

98

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

SciTech Connect

A facile widely spread technique employed to produce low-cost high-yield oxide powders, combustion synthesis, was used to prepare yttrium oxyfluoride crystalline ceramic powders. The structure of the powders was analyzed by X-ray powder diffraction and Rietveld refinement. Samples heat treated at 700 C had a predominance of vernier orthorhombic Y{sub 6}O{sub 5}F{sub 8} phase, while samples heat treated at 800 C crystallized in stoichiometric rhombohedral YOF phase. The samples were doped with luminescent europium trivalent ions (Eu{sup 3+}) in different concentrations (115 wt.%) and Judd-Ofelt theory was used to probe the distortion from the inversion symmetry of the local crystal field and the degree of covalency between the rare-earth ion and the surrounding ligands. The luminescence lifetime was measured and the luminescence quantum efficiency (LQE) was estimated. We observed that Eu{sup 3+}:Y{sub 6}O{sub 5}F{sub 8} samples presented higher LQE in spite of the larger local crystal field anisotropy found for Eu{sup 3+}:YOF samples.

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

2013-07-28

99

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

NASA Astrophysics Data System (ADS)

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

Lu, Liping; Zhang, Xiyan

2014-12-01

100

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

Code of Federal Regulations, 2013 CFR

...municipal waste combustion units that use activated carbon...of average carbon feed rate. Document five items...municipal waste combustion unit basis, record the required...municipal waste combustion unit at your plant. Include...Records of low carbon feed rates. Document three...

2013-07-01

101

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

Code of Federal Regulations, 2011 CFR

...municipal waste combustion units that use activated carbon...of average carbon feed rate. Document five items...municipal waste combustion unit basis, record the required...municipal waste combustion unit at your plant. Include...Records of low carbon feed rates. Document three...

2011-07-01

102

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

Code of Federal Regulations, 2013 CFR

...municipal waste combustion units that use activated carbon...of average carbon feed rate. Document five items...municipal waste combustion unit basis, record the required...municipal waste combustion unit at your plant. Include...Records of low carbon feed rates. Document three...

2013-07-01

103

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

Code of Federal Regulations, 2011 CFR

...municipal waste combustion units that use activated carbon...of average carbon feed rate. Document five items...municipal waste combustion unit basis, record the required...municipal waste combustion unit at your plant. Include...Records of low carbon feed rates. Document three...

2011-07-01

104

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

Code of Federal Regulations, 2013 CFR

...municipal waste combustion units that use activated carbon...of average carbon feed rate. Document five items...municipal waste combustion unit basis, record the required...municipal waste combustion unit at your plant. Include...Records of low carbon feed rates. Document three...

2013-07-01

105

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

Code of Federal Regulations, 2011 CFR

...municipal waste combustion units that use activated carbon...of average carbon feed rate. Document five items...municipal waste combustion unit basis, record the required...municipal waste combustion unit at your plant. Include...Records of low carbon feed rates. Document three...

2011-07-01

106

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

Code of Federal Regulations, 2010 CFR

...municipal waste combustion units that use activated carbon...of average carbon feed rate. Document five items...municipal waste combustion unit basis, record the required...municipal waste combustion unit at your plant. Include...Records of low carbon feed rates. Document three...

2010-07-01

107

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

Code of Federal Regulations, 2012 CFR

...municipal waste combustion units that use activated carbon...of average carbon feed rate. Document five items...municipal waste combustion unit basis, record the required...municipal waste combustion unit at your plant. Include...Records of low carbon feed rates. Document three...

2012-07-01

108

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

Code of Federal Regulations, 2012 CFR

...municipal waste combustion units that use activated carbon...of average carbon feed rate. Document five items...municipal waste combustion unit basis, record the required...municipal waste combustion unit at your plant. Include...Records of low carbon feed rates. Document three...

2012-07-01

109

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

Code of Federal Regulations, 2010 CFR

...municipal waste combustion units that use activated carbon...of average carbon feed rate. Document five items...municipal waste combustion unit basis, record the required...municipal waste combustion unit at your plant. Include...Records of low carbon feed rates. Document three...

2010-07-01

110

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

Code of Federal Regulations, 2012 CFR

...municipal waste combustion units that use activated carbon...of average carbon feed rate. Document five items...municipal waste combustion unit basis, record the required...municipal waste combustion unit at your plant. Include...Records of low carbon feed rates. Document three...

2012-07-01

111

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

Microsoft Academic Search

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

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

2002-01-01

112

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

Microsoft Academic Search

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

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

2000-01-01

113

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

Microsoft Academic Search

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

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

2003-01-01

114

Marine Natural Meroterpenes: Synthesis and Antiproliferative Activity  

PubMed Central

Meroterpenes are compounds of mixed biogenesis, isolated from plants, microorganisms and marine invertebrates. We have previously isolated and determined the structure for a series of meroterpenes extracted from the ascidian Aplidium aff. densum. Here, we demonstrate the chemical synthesis of three of them and their derivatives, and evaluate their biological activity on two bacterial strains, on sea urchin eggs, and on cancerous and healthy human cells. PMID:20390109

Simon-Levert, Annabel; Menniti, Christophe; Soulere, Laurent; Geneviere, Anne-Marie; Barthomeuf, Chantal; Banaigs, Bernard; Witczak, Anne

2010-01-01

115

Auto-combustion synthesis of nanocrystalline LaFeO 3  

Microsoft Academic Search

Nanocrystalline LaFeO3 with particle size of about 30nm was directly synthesized by solgel auto-combustion method at room temperature. The overall process involves three steps: formation of homogeneous sol; formation of dried gel; and combustion of the dried gel. Experiments revealed that LaFeO3 dried gel derived from citrate and nitrate sol exhibits self-propagating combustion at room temperature once it is ignited

Xiwei Qi; Ji Zhou; Zhenxing Yue; Zhilun Gui; Longtu Li

2003-01-01

116

Perylenequinones: Isolation, Synthesis, and Biological Activity  

PubMed Central

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

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

2013-01-01

117

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

118

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

119

Biosynthesis, Synthesis and Biological Activities of Pyrrolobenzodiazepines  

PubMed Central

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

Gerratana, Barbara

2014-01-01

120

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

121

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

2010-03-15

122

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

123

Non-interpenetrated IRMOF-8: synthesis, activation, and gas sorption.  

PubMed

The synthesis and successful activation of IRMOF-8 (Zn(4)O(ndc)(3), ndc = naphthalene-2,6-dicarboxylate) is presented. Room temperature synthesis effectively suppresses interpenetration. Although conventional activation under reduced pressure leads to structural collapse, activation by flowing supercritical CO(2) yields a guest-free material with a BET surface area of 4461 m(2) g(-1). PMID:22930156

Feldblyum, Jeremy I; Wong-Foy, Antek G; Matzger, Adam J

2012-10-11

124

Optical properties of nanocrystalline-coated Y 2O 3:Er 3+, Yb 3+ obtained by mechano-chemical and combustion synthesis  

Microsoft Academic Search

Y2O3:Er3+, Yb3+ nanocrystals have been obtained by ball milling and using a combustion synthesis procedure. In both cases the nanocrystals have been successfully coated with SiO2 following the Stber method. The average size of the as-synthesized nanoparticles has been estimated from X-ray diffraction patterns and transmission electron microscopy images. The dependence of the optical properties of these samples on synthesis

R. Martn-Rodrguez; R. Valiente; C. Pesquera; F. Gonzlez; C. Blanco; V. Potin; M. C. Marco de Lucas

2009-01-01

125

Combustion synthesis/quasi-isostatic pressing of TiC0.7NiTi cermets: microstructure and transformation characteristics  

E-print Network

Combustion synthesis/quasi-isostatic pressing of TiC0.7­NiTi cermets: microstructure Abstract TiC0.7­NiTi cermets were produced by com- bustion synthesis followed by quasi-isostatic consolidation while the reaction products were still hot and ductile. The TiC0.7­NiTi cermets were characterized

Meyers, Marc A.

126

Predicting Spontaneous Ignition and Combustion in Fixed Beds of Activated Carbon  

Microsoft Academic Search

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

S. BIGG

1989-01-01

127

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

128

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

SciTech Connect

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

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

2010-08-15

129

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

130

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

SciTech Connect

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

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

1993-10-01

131

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

E-print Network

/metal nitrate method R. Garci´a and G.A. Hirata Programa de Posgrado en Fi´sica de Materiales CICESE by a more typical combustion synthesis reaction between nitrates and a carbonaceous fuel at a higher exothermic reaction occurs between metal nitrates and a carbonaceous reductive fuel, resulting in a porous

McKittrick, Joanna

132

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

PubMed

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

Zhao, Zelun; Zhu, Yunfeng; Li, Liquan

2012-06-01

133

Effect of heating conditions during combustion synthesis on the characteristics of Ni 0.5 Zn 0.5 Fe 2 O 4 nanopowders  

Microsoft Academic Search

Ni-Zn ferrite powders were synthesized by combustion reaction. The effect of external conditions of heating on the characteristics of the resulting powders was evaluated. Two synthesis routes were studied. The first involved preheating on a hot plate at 300C and subsequently heating in a muffle furnace at 700C (RCPM). In the second route the powders (RCP) were heated directly to

A. C. F. M. Costa; E. Tortella; M. R. Morelli; M. Kaufman; R. H. G. A. Kiminami

2002-01-01

134

Total synthesis and antiplasmodial activity of pohlianin C and analogues.  

PubMed

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

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

2014-06-15

135

Fast and slow active control of combustion instabilities in liquid-fueled combustors  

NASA Astrophysics Data System (ADS)

This thesis describes an experimental investigation of two different novel active control approaches that are employed to suppress combustion instabilities in liquid-fueled combustors. A "fast" active controller requires continuous modulation of the fuel injection rate at the frequency of the instability with proper phase and gain. Use of developed optical tools reveals that the "fast" active control system suppresses the instability by changing the nearly flat distribution of the phase between pressure and heat release oscillations to a gradually varying phase distribution, thus dividing the combustion zone into regions that alternately damp and drive combustor oscillations. The effects of these driving/damping regions tend to counter one another, which result in significant damping of the unstable oscillations. In contrast, a "slow" active controller operates at a rate commensurate with that at which operating conditions change during combustor operation. Consequently, "slow" controllers need infrequent activation in response to changes in engine operating conditions to assure stable operation at all times. Using two types of fuel injectors that can produce large controllable variation of fuel spray properties, it is shown that by changing the spray characteristics it is possible to significantly damp combustion instabilities. Similar to the aforementioned result of the "fast" active control study, "slow" change of the fuel spray properties also modifies the nearly flat phase distribution during unstable operation to a gradually varying phase distribution, resulting in combustor "stabilization". Furthermore, deconvolutions of CH*-chemiluminescence images reveal the presence of vortex-flame interaction during unstable operation. Strong driving of instabilities occurs where the mean axial velocity of the flow is approximately zero, a short distance downstream of the flame holder where a significant fraction of the fuel burns in phase with the pressure oscillations. It is shown that the "fast" and "slow" active control approaches suppress combustion instabilities in a different manner. Nevertheless, the both control approaches successfully suppress combustion instabilities by modifying the temporal and spatial behavior of the combustion process heat release that is responsible for driving the instability.

Lee, Jae-Yeon

136

Synthesis of nanocrystalline NiAl by mechanically activated self-propagating high-temperature synthesis and mechanically activated annealing process  

NASA Astrophysics Data System (ADS)

The mechanically activated self-propagating high-temperature synthesis (MASHS) technique and the mechanically activated annealing process (M2AP) were used to produce NiAl intermetallic compound. Rietveld analysis of X-ray diffraction data was used to characterize the mechanically activated powders, MASHS and M2AP end-products. Two-phase (B2+L12) nickel aluminide intermetallic compounds were synthesized by the mechanically activated volume combustion synthesis (MASHS). A single phase B2 NiAl was formed when mechanically activated annealing process (M2AP) was performed. Starting from a mixture of elemental pure powders, both M2AP and MASHS milling processes lead to nanostructured powders. Structural analysis deduced from the Rietveld refinement of X-ray diffraction patterns of NiAl compounds synthesized by SHS after a milling of 6 h show the formation of ?-NiAl phase with a cell parameter a = (0.2885 1.2618 10-4) nm. The average crystallite size is D = (44.6421 2.4263) nm and the microstrains values are close to those of metallic alloys ? = (0.2142 1.6186 10-2)%. Finally, scanning electron microscopy (SEM) was carried out to characterize the microstructure of end-products.

Arroussi, Soumia; Ali-Rachedi, Mahieddine; Chemam, Abdelbaki; Benaldjia, Abdelaziz; Amara, Abdelaziz; Gasmi, Brahim; Andasmas, Mohamed; Guerioune, Mohamed

2013-12-01

137

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

NASA Astrophysics Data System (ADS)

W-Cu functionally graded material (FGM, 75 wt% W + 25 wt% Cu40 wt% W + 60 wt% Cu) has been prepared by a method of high-gravity combustion synthesis and melt-infiltration in a short time (5 min). The infiltration mechanism in the high-gravity field was investigated. The W-Cu FGM showed an overall relative density of 97% and gradually-varying properties in terms of density, micro hardness, coefficient of thermal expansion. Especially, the W-Cu FGM exhibited a coefficient of thermal expansion between those of W and Cu, and thus could be used as a transition layer between W and Cu to relax the thermal stresses.

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

2014-02-01

138

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

E-print Network

components indicated. 8 Figure 5 - Air dryer (left) and custom flow separator (right) in line before air controller. 9 Figure 6 Image of transformer powering igniter 10 Figure 7 - General Motors... rig 20 Figure 16 - Air control system with important features indicated. 21 Figure 17 - Omega gas flow controller for propane (or other combustible gasses) 22 Figure 18 - Glycerin control...

Pickett, Derek

2013-12-31

139

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

Microsoft Academic Search

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

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

2010-01-01

140

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

SciTech Connect

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

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

2007-09-15

141

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

142

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

143

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

Microsoft Academic Search

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

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

2000-01-01

144

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

145

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

NASA Astrophysics Data System (ADS)

Lanthanum and niobium doped PZT with composition (Pb0.93La0.07)[(Zr0.60Ti0.40)]0.9825Nb0.0175O3 (PZTLN) was prepared by the gel-combustion method. A precursor sol was obtained from lead nitrate, zirconyl nitrate, lanthanum oxide, peroxo-citrato-niobium and a peroxo-citrate complex of titanium isopropoxide as starting precursors. Various molar ratios of citrate/nitrate (CA/NO3- = 1.3, 0.36 and 0.09) were used to prepare very fine powders of PZTLN. The gels resulting from these sols were transformed into powders by an auto-combustion process at <=400 C. The powders consisted of rhombohedral PZT (PbZr0.60Ti0.40O3), pyrochlore (Pb2Ti2O6) and lead carbonate (Pb2OCO3) phases. The pure rhombohedral phase is found in PZTLN pellets sintered at 1100 C for all citrate/nitrate ratios. Titanium and niobium precursors were modified with peroxo radicals. During the gel-combustion reaction, the temperature of the gel increases, leading to lead evaporation. The loss of lead as well as the particle size increases as the CA/NO3- ratio decreases. The smallest grained powder (about 50 nm) was obtained with the ratio CA/NO3- equal to 0.09.

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

2006-03-01

146

Effect of chemical composition of isomorphous metavanadates on their catalytic activity toward carbon combustion  

SciTech Connect

Metal vanadates of K, Rb, and Cs and their solid solutions were prepared by reaction between carbonates and vanadium(V) oxide, characterized by X-ray diffraction and tested as catalysts for carbon combustion. These vanadates are all orthorhombic but show different lattice parameters depending on the ionic radius of alkali metals. A complete solubility in the solid state was found to exist for the systems KVO{sub 3}-RbVO{sub 3} and RbVO{sub 3}-CsVO{sub 3}, while only terminal solid solutions were found in the KVO{sub 3}-CsVO{sub 3} system. The lattice parameters (mainly b{sub 0}) of the orthorhombic cell increased with the increase of the ionic radius of the alkali metal. This increase was found to be closely linked to the substitution of a larger metal for a smaller one when a complete solubility occurs. The catalytic activity, investigated by temperature programmed oxidation (TPO) experiments, improves progressively along with the introduction of a more electropositive and larger alkaline metal in the vanadate crystal structure. The catalytic performance, however, does not seem to be dependent on the crystal structure because, due to polymorphic transformations, not all these vanadates keep the orthorhombic structure in the temperature range suitable for the catalytic carbon combustion (350--600 C). The catalytic activity of these vanadates towards carbon combustion thus seems to be strictly related to their chemical composition only.

Badini, C.; Mazza, D.; Ronchetti, S.; Saracco, G. [Politecnico di Torino (Italy). Dipt di Scienza dei Materiali e Ingegneria Chimica] [Politecnico di Torino (Italy). Dipt di Scienza dei Materiali e Ingegneria Chimica

1999-04-01

147

NiYSZ cermet anodes prepared by citrate\\/nitrate combustion synthesis  

Microsoft Academic Search

The synthesis of NiYSZ cermets with tailored particle package, shape and microstructural characteristics is essential when preparing anodes for solid oxide fuel cells (SOFC). These materials are generally prepared by sintering and subsequent reduction of the mixture of metal oxides. In order to obtain cermets with an adequate contact area between electrocatalyst (Ni) and ionic conductor (YSZ), an alternative route

Marjan Marinek; Klementina Zupan; Jadran Maek

2002-01-01

148

Synthesis of optically active phosphonamino acids esters at microwave assistance  

Microsoft Academic Search

A preparative synthesis was developed for phosphonamino acids esters proceeding from natural amino acids with the use of microwave\\u000a assistance. A series of phosphonamino acids esters was prepared from optically active natural ?-amino acids.

M. M. Kabachnik; E. V. Villemson; I. P. Beletskaya

2008-01-01

149

Combustion synthesis and photoluminescence of Tb3+ doped LaAlO3 nanophosphors  

NASA Astrophysics Data System (ADS)

Terbium doped lanthanum aluminate (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), Rietveld refinement, 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 green emission is reported at 542 nm, from the 5D level, which intensity depends on Tb concentration.

Dhahri, A.; Horchani-Naifer, K.; Benedetti, A.; Enrichi, F.; Frid, M.; Riello, P.

2013-04-01

150

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

151

On the effects of organic matter 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. The 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. Based on this extensive data set, the role of sulphuric acid coating and of the organic fraction of the combustion particles for the CCN activation was investigated. Modelling of CCN activation was conducted using microphysical and chemical properties obtained from the measurements as input data. Coating the combustion particles with water-soluble sulphuric acid, increases the potential CCN activation, or lowers the activation diameter, respectively. The adaptation of a Khler model to the experimental data yielded coatings from 0.1 to 3 vol-% of water-soluble matter, which corresponds to an increase in the fraction of CCN-activated combustion particles from ?10-4 to ?10-2 at a water vapour saturation ratio Sw=1.006. Additional particle coating by coagulation of combustion particles and aqueous sulphuric acid particles formed by nucleation further reduces the CCN activation diameter. In contrast, 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. The resulting reduction in the potential CCN activation with an increasing fraction of non-volatile OC becomes visible as a trend in the experimental data. 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.

2005-12-01

152

Amplifier insensitive integrator design for active RC filter synthesis  

E-print Network

AM?LIFIER INSENSITIVE INTEGRATOR DESIGN FOR ACTIVE RC FILTER SYNTHESIS A Thesis by GLENN ROGER BAILEY Submitted to the Graduate College of Texas A&M University in partial fulfillment of the'requirement for the degree of MASTER OF SCIENCE... May 1980 Major Subject: Electrical Engineering AMPLIFIER INSENSITIVE INTEGRATOR DESIGN FOR ACTIVE RC FILTER SYNTHESIS A Thesis by GLENN ROGER BAILEY Approved as to style and content by: (Chairman of Comit ee) (Member) ( ember) (Member) (Hea...

Bailey, Glenn Roger

2012-06-07

153

Combustion synthesis, structural characterization, thermo and photoluminescence studies of CdSiO?:Dy? nanophosphor.  

PubMed

CdSiO(3):Dy(3+) (1-9mol%) nanophosphors were prepared for the first time using the solution combustion method. The process of monoclinic phase formation was investigated by PXRD, TG-DTA and FTIR. The results show that the phase formation temperature of combustion-derived monoclinic CdSiO(3) is found to be lower as compared to the powders prepared by solid-state and sol-gel methods. It was observed that the average crystallite size calculated by Debye-Scherrer's formula and Williamson-Hall (W-H) plot are well comparable and was found to be in the range of 35-70 nm. Scanning electron micrographs indicate that there exist circular microcrystalline particles. It is observed that the optical energy gap is widened with the increase of Dy(3+) ion dopant. The photoluminescence (PL) spectra exhibit characteristic transitions of Dy(3+) due to (4)F(9/2)?(6)H(15/2) (blue) and (4)F(9/2)?(6)H(13/2) (yellow) regions. The thermoluminescence (TL) glow curve of CdSiO(3):Dy(3+) nano powder exposed to UV irradiation exhibited one main peak centered at 170C. The intensity of the main peak increases up to the dose of 20 min then it decreases. The glow curves were analyzed by the glow peak shape method and the estimated trap parameters are discussed. PMID:22481172

Manjunatha, C; Sunitha, D V; Nagabhushana, H; Nagabhushana, B M; Sharma, S C; Chakradhar, R P S

2012-07-01

154

Near-infrared quantum cutting in Ce3+, Er3+, and Yb3+ doped yttrium silicate powders prepared by combustion synthesis  

Microsoft Academic Search

Yttrium silicate (YS) powders doped with Ce3+, Er3+, and Yb3+ were prepared by combustion synthesis. The material was investigated for use as energy downconverters to reduce thermalization losses in crystalline Si solar cells. The powders were excited by UV light (355 nm), and near-infrared emission around 1 ?m was observed corresponding to a quantum cutting (QC) effect. The QC process

Nikifor Rakov; Glauco S. Maciel

2011-01-01

155

The influence of Yb 3+ doping on the upconversion luminescence of Pr 3+ in aluminum oxide based powders prepared by combustion synthesis  

Microsoft Academic Search

The effect of ytterbium (Yb3+) doping on the upconversion (UC) emission of praseodymium (Pr3+) doped in aluminum oxide based powders prepared by combustion synthesis is reported for near-infrared excitation (?=980nm). Our experimental results show that the crystalline structure and the UC emission changes with the Yb3+ concentration. The sample containing only Pr3+ (1.0wt.%) did not show any UC signal and

G. S. Maciel; R. B. Guimares; P. G. Barreto; I. C. S. Carvalho; N. Rakov

2009-01-01

156

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

Microsoft Academic Search

Yttrium silicate powders doped with Eu{sup 3+} and codoped with Eu{sup 3+} and Yb{sup 3+} were prepared by combustion synthesis. The x-ray powder diffraction data showed the presence of YSiO and YSiO crystalline phases. Singly doped (1 wt %) sample illuminated with ultraviolet light (=256 nm) showed the characteristic red luminescence corresponding to DF{sub J} transitions of Eu{sup 3+}. The

Nikifor Rakov; Dayanne F. Amaral; Renato B. Guimaraes; Glauco S. Maciel

2010-01-01

157

Effect of Mo on microstructure and mechanical properties of TiCNi-based cermets produced by combustion synthesisimpact forging technique  

Microsoft Academic Search

The effect of Mo additions on the microstructure and mechanical properties of TiC-30 wt.% Ni cermets produced by the combustion synthesis-impact forging technique was investigated. The Mo content was varied between 0 and 10 wt.%, in 2 wt.% increments. Cylindrical tiles 6.35 cm in diameter and 1.27 cm thick were produced with apparent densities above 99%. Microscopically, the addition of

J. C. LaSalvia; D. K. Kim; M. A. Meyers

1996-01-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

159

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

160

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

161

Synthesis of alumina powder by the urea-glycine-nitrate combustion process: a mixed fuel approach to nanoscale metal oxides  

NASA Astrophysics Data System (ADS)

Main objective of present work is to study the efficiency of mixed fuel towards solution combustion synthesis of alumina powder, which otherwise prepared by single fuel and study of properties of final product with mixed fuel approach. Two different fuels, glycine and urea, along with aluminium nitrates have been used to prepare nanophase alumina powder. Different fuel to oxidizer ratios and different percentage combination of two fuels were used to prepare six samples. In all samples, nanoscale particle size obtained. Parameter which continuously changes the results of various characterisations is percentage combination of two fuels. In case where percentage of urea is higher than glycine reaction takes place with high exothermicity and hence crystallinity in product phase, whereas glycine promotes amorphous character. With mixed fuel approach, crystallinity can be enhanced easily, by calcinations of powder product at low temperature, because due to mixed urea and glycine, there is already some fraction of crystallinity observed. Overall mixed fuel approach has ability to produce nanophase alumina powder with wide range of particles size.

Sharma, Amit; Rani, Amita; Singh, Ajay; Modi, O. P.; Gupta, Gaurav K.

2014-03-01

162

Synthesis and characterization of Y2O3:Eu3+ phosphors using the Sol-Combustion method  

NASA Astrophysics Data System (ADS)

Y2O3:Eu3+phosphor powders were prepared by the Sol-Combustion synthesis method using a sulfur-contained organic fuel in an ethanol-aqueous solution. The structural, morphological and optical properties of the as-prepared Y2O3:Eu3+phosphors were obtained for different fuel to host ratios (S/Y molar ratios). The estimated grain sizes were calculated using the X-ray diffraction patterns were found to vary between 158-180 nm. The grain sizes were found to slightly decrease with the increase of the S/Y molar ratios. From photo luminescent spectra, the main emission peak arising from the 5D0?7F2 transition was observed at 626 nm, while the weaker emissions at shorter wavelength values were ascribed to the 5D1, 5D2?7DJ (J=1, 2, 3, ) transitions of Eu3+. From these emission spectra it was clear that the S/Y molar ratios have significant effects on the maximum intensities and phosphorescence time of these phosphors.

Ali, A. G.; Dejene, B. F.; Swart, H. C.

2014-04-01

163

Aqueous Combustion Synthesis of Aluminum Oxide Thin Films and Application as Gate Dielectric in GZTO Solution-Based TFTs.  

PubMed

Solution processing has been recently considered as an option when trying to reduce the costs associated with deposition under vacuum. In this context, most of the research efforts have been centered in the development of the semiconductors processes nevertheless the development of the most suitable dielectrics for oxide based transistors is as relevant as the semiconductor layer itself. In this work we explore the solution combustion synthesis and report on a completely new and green route for the preparation of amorphous aluminum oxide thin films; introducing water as solvent. Optimized dielectric layers were obtained for a water based precursor solution with 0.1 M concentration and demonstrated high capacitance, 625 nF cm(-2) at 10 kHz, and a permittivity of 7.1. These thin films were successfully applied as gate dielectric in solution processed gallium-zinc-tin oxide (GZTO) thin film transistors (TFTs) yielding good electrical performance such as subthreshold slope of about 0.3 V dec(-1) and mobility above 1.3 cm(2) V(-1) s(-1). PMID:25354332

Branquinho, Rita; Salgueiro, Daniela; Santos, Ldia; Barquinha, Pedro; Pereira, Lus; Martins, Rodrigo; Fortunato, Elvira

2014-11-26

164

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

165

Effect of fuel ratio on combustion synthesis and properties of magnetic nanostructures  

NASA Astrophysics Data System (ADS)

We report a simple one-step solution combustion method for the preparation of ultrafine Ni, NiO and Ni/NiO nanostructures. The fuel-to-oxidizer ratio can be tuned to control the formation of either nanoparticles (Ni or NiO) or nanocomposites (Ni/NiO). The resultant nanostructures are characterized by x-ray diffraction, scanning electron microscopy, Raman spectroscopy and vibrating sample magnetometer. Processing under fuel rich conditions leads to the formation of Ni/NiO nanocomposite while fuel lean environment results in primarily NiO. The processing conditions influence the stoichiometry and the size (6.8 to 39.5 nm) of NiO nanoparticles. The intensity of one- phonon Raman longitudinal optical mode is found to be higher than two-phonon optical mode for non-stoichiometric NiO. The saturation magnetization and coercivity of the as-synthesized powders are influenced by the ratio of Ni to NiO, stoichiometry of NiO and pore size.

Arunkumar, P.; Aadhavan, R.; Bhanuchandar, S.; Babu, K. Suresh

2014-09-01

166

Synthesis, structure and electromagnetic properties of Mn-Zn ferrite by sol-gel combustion technique  

NASA Astrophysics Data System (ADS)

The electromagnetic absorbing behaviors of a thin coating fabricated by mixing Mn-Zn ferrite with epoxy resin (EP) were studied. The spinel ferrites Mn1-xZnxFe2O4 (x=0.2, 0.5 and 0.8) were synthesized with citrate acid as complex agent by sol-gel combustion method. The microstructure and surface morphology of Mn-Zn ferrite powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The complex permittivity and complex permeability of the fabricated ferrite/EP composites were investigated in terms of their contributions to the absorbing properties in the low frequency (10 MHz to 1 GHz). The microwave absorption of the prepared ferrite/EP composites could be tailored by matching the dielectric loss and magnetic loss and by controlling the doped metal ratio. The composites with the ferrite composition x=0.2 are found to show higher reflection loss compared with the composites with other compositions. It is proposed that the prepared composites can potentially be applied in electromagnetic microwave absorbing field.

Wang, Wenjie; Zang, Chongguang; Jiao, Qingjie

2014-01-01

167

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

168

Synthesis of Eu3+ doped yttrium orthosilicate phosphor by sol-combustion method  

NASA Astrophysics Data System (ADS)

Eu3+ doped yttrium orthosilicate (Y2SiO5) phosphor was prepared by the sol-combustion method using citric acid as complexing agent in this experiment. The X-ray diffraction (XRD) pattern, excitation and emission spectra were used to investigate the crystal structure and luminescent properties of the phosphor. XRD pattern showed that pure Y2SiO5:Eu3+ phosphor was obtained. The excitation spectrum was composed of a broad band from 200-350 nm and a series of narrow bands from 350-500 nm, in which the excitation peaks at 400 nm and 470 nm were stronger. The emission spectrum showed the most intense emission peak was located at 613 nm, which corresponded to the 5D0-->7F2 transition of Eu3+. The results showed that this phosphor could be excited by UV or blue light and emit red light. The luminescent intensity depends on the concentration of Eu3+ and it reached the maximum when the molar concentration of Eu3+ was 4 mol%. In this study, we found that the emission intensity reached maximum when the ratio of citric acid and Y3+ was 1.5:1. The results indicated that Y2SiO5:Eu3+ is a potential red-emitting candidate phosphor for white light-emitting diodes.

Guan, Li; Jin, Litao; Jia, Guoqi; Li, Xu; Yang, Zhiping; Guo, Qinglin; Fu, Guangsheng

2010-11-01

169

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

170

Oxygen tension limits nitric oxide synthesis by activated macrophages.  

PubMed Central

Previous studies have established that constitutive calcium-dependent ('low-output') nitric oxide synthase (NOS) is regulated by oxygen tension. We have investigated the role of oxygen tension in the synthesis of NO by the 'high-output' calcium-independent NOS in activated macrophages. Hypoxia increased macrophage NOS gene expression in the presence of one additional activator, such as lipopolysaccharide or interferon-gamma, but not in the presence of both. Hypoxia markedly reduced the synthesis of NO by activated macrophages (as measured by accumulation of nitrite and citrulline), such that, at 1% oxygen tension, NO accumulation was reduced by 80-90%. The apparent K(m) for oxygen calculated from cells exposed to a range of oxygen tensions was found to be 10.8%, or 137 microM, O(2) This value is considerably higher than the oxygen tension in tissues, and is virtually identical to that reported recently for purified recombinant macrophage NOS. The decrease in NO synthesis did not appear to be due to diminished arginine or cofactor availability, since arginine transport and NO synthesis during recovery in normoxia were normal. Analysis of NO synthesis during hypoxia as a function of extracellular arginine indicated that an altered V(max), but not K(m)(Arg), accounted for the observed decrease in NO synthesis. We conclude that oxygen tension regulates the synthesis of NO in macrophages by a mechanism similar to that described previously for the calcium-dependent low-output NOS. Our data suggest that oxygen tension may be an important physiological regulator of macrophage NO synthesis in vivo. PMID:10970783

McCormick, C C; Li, W P; Calero, M

2000-01-01

171

Turbulent combustion  

SciTech Connect

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

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

1993-12-01

172

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

173

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

SciTech Connect

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

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

2011-09-15

174

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

175

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

NASA Astrophysics Data System (ADS)

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

Agilandeswari, K.; Ruban Kumar, A.

2014-09-01

176

COMBUSTION SYNTHESIS AND CHARACTERIZATION OF NANOCRYSTALLINE ALKALINE EARTH ALUMINATE Sr4Al14O25:RE(RE = Eu, Dy, Sm)  

NASA Astrophysics Data System (ADS)

Nanoscale phosphors have superior performance characteristics than the bulk phosphors. This paper explains the synthesis and characterization like XRD, FTIR, SEM and photoluminescence properties of nanocrystalline Sr4Al14O25 doped with rare earth elements like europium, dysprosium and samarium by combustion method. XRD showed the nanoscale crystalline nature of as-prepared samples. SEM confirmed size of the particle less than 100 nm. Photoluminescent emission spectra showed strong orange red emission at 593 nm for Sr4Al14O25:Sm3+. The green emission of Eu2+ was observed at around 490 nm for Sr4Al14O25:Eu2+.

Hedaoo, V. P.; Bhatkar, V. B.; Omanwar, S. K.

2013-08-01

177

Synthesis of a Microcystis aeruginosa predicted metabolite with antimalarial activity.  

PubMed

The synthesis of a Microcystis aeruginosa predicted metabolite analog of aerucyclamide B was performed. This hexacyclopeptide was obtained from three heterocyclic building blocks by a convergent macrocycle-assembly methodology. The compound exhibited good in vitro antiplasmodial activity (IC(50): 0.18 ?M, K1, cholorquine resistant strain). PMID:22765903

Pea, Stella; Scarone, Laura; Manta, Eduardo; Stewart, Lindsay; Yardley, Vanessa; Croft, Simon; Serra, Gloria

2012-08-01

178

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

PubMed

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

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

2012-01-01

179

Optimal cooperative control synthesis of active displays  

NASA Technical Reports Server (NTRS)

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

Gary, Sanjay; Schmidt, David K.

1987-01-01

180

Optimal cooperative control synthesis of active displays  

NASA Technical Reports Server (NTRS)

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

Garg, S.; Schmidt, D. K.

1985-01-01

181

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

182

Practical synthesis of hydroxychromenes and evaluation of their biological activity.  

PubMed

A simple and efficient seven steps synthesis of brodifacoum and difethialone from phenylacetyl chloride is described. The key synthetic strategies involve Friedel-Crafts acylation, intramolecular ring cyclization and condensation reaction in the presence of Brnsted-Lowry acids. It was found that brodifacoum showed favorable inhibiting activities on LPS-stimulated nitrite production in BV-2 microglia cells. Brodifacoum exhibited superior anti-inflammatory effects than difethialone. We expect that an efficient linear synthesis of 4-hydroxycoumarin derivatives and key fragments that are useful agents for the modulation of inflammation as well as inhibition of coagulation will be of practical use. PMID:22205090

Jung, Jae-Chul; Oh, Seikwan

2011-01-01

183

Synthesis of Nano-Sized Li2MnO3 Powders by Citrate-Ntrate Gel Combustion Process and Their Electrochemical Properties  

NASA Astrophysics Data System (ADS)

Pure Li2MnO3 powders with naon-sized were synthesized by low-temperature combustion synthesis. The synthesis, structure, morphology, electrochemical characterizations of Li2MnO3 was characterized by means of XRD, SEM, TEM and charge-discharge test. The particle properties of the Li2MnO3 powders varied according to the calcinations temperatures and time. The first discharge capacities of Li2MnO3 powders decreased with temperatures increasing. The discharge capacity of Li2MnO3 obtained at 600C with 12 hours had the largest discharge capacity of 173mAh/g at first discharge, with a particle size of 1040nm.

Yao, Lan; Yu, Zhiyong; Qian, Jun; Liu, Hanxing

2013-07-01

184

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

NASA Astrophysics Data System (ADS)

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

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

185

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

PubMed Central

Present review describes research on novel natural cyclobutane-containing alkaloids isolated from terrestrial and marine species. More than 60 biological active compounds have been confirmed to have antimicrobial, antibacterial, antitumor, and other activities. The structures, synthesis, origins, and biological activities of a selection of cyclobutane-containing alkaloids are reviewed. With the computer program PASS some additional biological activities are also predicted, which point toward new possible applications of these compounds. This review emphasizes the role of cyclobutane-containing alkaloids as an important source of leads for drug discovery. PMID:19696873

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

2008-01-01

186

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

Microsoft Academic Search

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

T. Murayama; T. Chikahisa; Y. Fujiwara

1998-01-01

187

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

Microsoft Academic Search

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

P. K. Tucker; Margie Croteau-Gillespie

1992-01-01

188

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

SciTech Connect

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

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

2009-04-02

189

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

PubMed

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

Pozan, Gulin Selda

2012-06-30

190

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

NASA Astrophysics Data System (ADS)

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 crystallization of as-combusted Gd2O3: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 Y2O3:Eu phosphor, even without further thermal annealing. This direct solution combustion method can be used to prepare a variety of high quality oxide nanocrystals.

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

2010-08-01

191

Synthesis of La 1? x Sr x MO 3 (M = Mn, Fe, Co, Ni) nanopowders by alanine-combustion technique  

Microsoft Academic Search

La1?xSrxMO3 (M=Mn, Fe, Co, Ni, x=00.3) powders were obtained by solution combustion technique using metal nitrates and ?-alanine. The as-prepared powders, resulted by the combustion reaction, were annealed at different temperatures to investigate the evolution of crystalline phases. For the strontium-doped lanthanum-based perovskites, higher annealing temperatures than for the corresponding pure lanthanum-based perovskites are needed to obtain single-phase compounds depending

D. Berger; C. Matei; G. Voicu; A. Bobaru

2010-01-01

192

Activation of renin synthesis is dependent on intact nitric oxide production  

Microsoft Academic Search

Activation of renin synthesis is dependent on intact nitric oxide production. The present study investigated whether or not nitric oxide (NO) synthesis mediates mechanisms regulating activation of renin formation. Studies were performed on afferent arterioles freshly isolated from the rat kidney. We have shown previously that this preparation is a useful model to study regulation of renin synthesis and secretion.

Pierre-Louis Tharaux; Jean-Claude Dussaule; Marie-Dominique Pauti; Yves Vassitch; Raymond Ardaillou; Christos Chatziantoniou

1997-01-01

193

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

194

Synthesis And Biological Activity of Borane Phosphonate DNA  

Microsoft Academic Search

Borane phosphonate oligodeoxyribonucleotides are synthesized from 5?-O-[benzhydroxybis(trimethylsilyloxy)silyl]-2?-deoxyribonucleoside-3?-O-methylphosphoramidites. The exocyclic amine functions of adenine, guanine, and cytosine are protected with trimethoxytrityl, and thymine is unprotected. Using these synthons and under standard conditions via activation with S-ethylthiotetrazole, condensations on a highly crosslinked polystyrene support are in excess of 99%. Following the complete synthesis of the oligodeoxyribonucleotide phosphite triester, oxidation with THFBH3 yields

Magdalena Olesiak; Angelika Krivenko; Heera Krishna; Marvin H. Caruthers

2011-01-01

195

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

196

Constitutive Somatostatin Receptor Subtype 2 Activity Attenuates GH Synthesis  

PubMed Central

Somatostatin signals predominantly through somatostatin receptor (SSTR) subtype 2 to attenuate GH release. However, the independent role of the receptor in regulating GH synthesis is unclear. Because we had previously demonstrated constitutive SSTR2 activity in mouse corticotrophs, we now analyzed GH regulation in rat pituitary somatotroph (GC) tumor cells, which express SSTR2 exclusively and are devoid of endogenous somatostatin ligand. We demonstrate that moderately stable SSTR2 overexpression (GpSSTR2WT cells) was associated with decreased GH promoter activity, GH mRNA, and hormone levels compared with those of control transfectants (GpCon cells). In contrast, levels of GH mRNA and peptide and GH promoter activity were unchanged in GpSSTR2DRY stable transfectants moderately expressing DRY motif mutated SSTR2 (R140A). GpSSTR2DRY did not exhibit an enhanced octreotide response as did GpSSTR2WT cells; however, both SSTR2WT-enhanced yellow fluorescent protein (eYFP) and SSTR2DRY-eYFP internalized on octreotide treatment. Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, increased GH synthesis in wild-type GC cells and primary pituitary cultures. GpSSTR2WT cells induced GH synthesis more strongly on SAHA treatment, evident by both higher GH peptide and mRNA levels compared with the moderate but similar GH increase observed in GpCon and GpSSTR2DRY cells. In vivo SAHA also increased GH release from GpSSTR2WT but not from control xenografts. Endogenous rat GH promoter chromatin immunoprecipitation showed decreased baseline acetylation of the GH promoter with exacerbated acetylation after SAHA treatment in GpSSTR2WT compared with that of either GpSSTR2DRY or control cells, the latter 2 transfectants exhibiting similar GH promoter acetylation levels. In conclusion, modestly increased SSTR2 expression constitutively decreases GH synthesis, an effect partially mediated by GH promoter histone deacetylation. PMID:23696564

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

2013-01-01

197

Activation and de novo synthesis of hydrogenase in Chlamydomonas  

SciTech Connect

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

Roessler, P.G.; Lien, S.

1984-12-01

198

Advanced Combustion  

SciTech Connect

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

Holcomb, Gordon R. [NETL

2013-03-11

199

Synthesis and antifungal activities of miltefosine analogs  

PubMed Central

Miltefosine is an alkylphosphocholine that shows broad-spectrum in vitro antifungal activities and limited in vivo efficacy in mouse models of cryptococcosis. To further explore the potential of this class of compounds for the treatment of systemic mycoses, nine analogs (3a3i) were synthesized by modifying the choline structural moiety and the alkyl chain length of miltefosine. In vitro testing of these compounds against the opportunistic fungal pathogens Candida albicans, Candida glabrata, Candida krusei, Aspergillus fumigatus, and Cryptococcus neoformans revealed that N-benzyl-N,N-dimethyl-2-{[(hexadecyloxy)hydroxyphosphinyl]oxy}ethanaminium inner salt (3a), N,N-dimethyl-N-(4-nitrobenzyl)-2-{[(hexadecyloxy)hydroxyphosphinyl]oxy}ethanaminium inner salt (3d), and N-(4-methoxybenzyl)-N,N-dimethyl-2-{[(hexadecyloxy)hydroxyphosphinyl]oxy}ethanaminium inner salt (3e) exhibited minimum inhibitory concentrations (MIC) of 2.55.0 ?g/mL against all tested pathogens, when compared to miltefosine with MICs of 2.53.3 ?g/mL. Compound 3a showed low in vitro cytotoxicity against three mammalian cell lines similar to miltefosine. In vivo testing of 3a and miltefosine against C. albicans in a mouse model of systemic infection did not demonstrate efficacy. The results of this study indicate that further investigation will be required to determine the potential usefulness of the alkylphosphocholines in the treatment of invasive fungal infections. PMID:23891181

Ravu, Ranga Rao; Chen, Ying-Lien; Jacob, Melissa R.; Pan, Xuewen; Agarwal, Ameeta K.; Khan, Shabana I.; Heitman, Joseph; Clark, Alice M.; Li, Xing-Cong

2013-01-01

200

Influence of thermally induced structural changes of 2 wt% Pd\\/LaFeO 3 on methane combustion activity  

Microsoft Academic Search

The influence of the calcination temperature on the structure and catalytic activity of 2wt% Pd\\/LaFeO3 for methane combustion has been investigated. LaFeO3 (calcined at 700C) was impregnated with Pd(NO3)2 and subsequently calcined at temperatures between 300C and 1000C. Characterization using TPR, XPS, DRIFTS and XAS revealed the presence of Pd in at least two different coordination environments. A fraction of

Arnim Eyssler; Alexander Winkler; Peter Mandaliev; Paul Hug; Anke Weidenkaff; Davide Ferri

2011-01-01

201

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

E-print Network

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

Shawabkeh, Reyad A.

202

Upconversion emission from Tm 3+:Yb 3+ and Tm 3+:Er 3+:Yb 3+ doped Y 2SiO 5 powders prepared by combustion synthesis  

Microsoft Academic Search

Tm3+:Er3+:Yb3+ doped Y2SiO5 powders were prepared by combustion synthesis with estimated as-prepared weight (wt.) % concentrations of 0.25:0.0:2.0, 0.25:0.5:2.0 and 0.25:1.0:2.0, respectively. Blue (Tm3+: 1G4?3H6), green (Er3+: 4S3\\/2, 2H11\\/2?4I15\\/2) and red (Er3+: 4F9\\/2?4I15\\/2) upconversion (UC) emissions were observed under 975nm infrared diode laser excitation. The UC process took place via energy transfer from Yb3+ to Er3+ and Tm3+ ions. The

Nikifor Rakov; Glauco S. Maciel; R. B. Guimares; I. C. S. Carvalho

2010-01-01

203

Combustion synthesis and luminescent properties of a blue-green emitting phosphor: (Ba1.95, Eu0.05)ZnSi2O7:B3+  

NASA Astrophysics Data System (ADS)

A blue-green emitting phosphor (Ba1.95, Eu0.05)ZnSi2O7: B{/x 3+} was prepared by combustion synthesis and an efficient blue-green emission under near-ultraviolet was observed. The luminescence, crystallinity and particle sizes were investigated by using luminescence spectrometry, X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The emission spectrum shows a single band centered at 503 nm, which corresponds to the 4 f 65 d 1 ?4 f 7 transition of Eu2+. The excitation spectrum is a broad band extending from 260 to 465 nm, which matches the emission of ultraviolet light-emitting diodes. The optical absorption spectra of the (Ba1.95, Eu0.05)ZnSi2O7: B{/0.06 3+} exhibited band-gap energies of 3.9 eV. The results showed that boric acid was effective in improving the luminescence intensity of (Ba1.95, Eu0.05)ZnSi2O7, and the optimum molar ratio of boric acid to zinc nitrate was about 0.06. The phosphor (Ba1.95, Eu0.05)ZnSi2O7: B{0.06/3+} synthesized by combustion method showed 1.5 times improved emission intensity compared with that of the Ba1.95ZnSi2O7: Eu{0.05/2+} phosphor under ? ex = 353 nm.

Yao, Shan-Shan; Li, Yuan-Yuan; Xue, Li-Hong; You, Yan; Yan, You-Wei

2009-12-01

204

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

205

Synthesis, characterization and electrocatalytic activity of fused gold nanoparticles.  

PubMed

This paper describes the synthesis of fused spherical gold nanoparticles (AuNPs) and their electrocatalytic activity towards the oxidation of hydroxylamine (HA). Fused AuNPs were prepared by one-pot synthesis using 2-mercapto-4-methyl-5-thiazoleacetic acid (TAA) as a stabilizing agent and sodium borohydride (NaBH4) as a reducing agent. The HR-TEM images showed that two individual AuNP were joined via on its surface with a size range of approximately 7 nm and a length of approximately 15 nm diameter. The pH studies showed that the synthesized fused AuNPs was stable at pH > 8. This indicated that the carboxylate ion present on the TAA molecule stabilized the AuNPs from aggregation. Further, the fused AuNPs were utilized for the electrocatalytic oxidation of hydroxylamine (HA) after immobilized them on (3-mercaptopropyl)-trimethoxysilane (MPTS) sol-gel film modified Au electrode. The AuNPs modified electrode showed an excellent electrocatalytic activity towards the oxidation of HA in 0.2 M phosphate buffer solution (pH 7.2) by shifting its oxidation potential to 100 mV less positive and enhancing its oxidation current for more than three times when compared to bare Au electrode. Further, it was found that the fused AuNPs modified electrode showed greater electrocatalytic activity towards HA than the spherical AuNPs modified electrodes. PMID:21449361

Kannan, P; John, S Abraham

2011-03-01

206

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 100C in deionised water. Also, in this paper Ag:HAp-NPs are evaluated for their antimicrobial activity against gram-positive and gram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our compounds are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures. PMID:23509801

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

2013-01-01

207

Efficient discovery of bioactive scaffolds by activity-directed synthesis.  

PubMed

The structures and biological activities of natural products have often provided inspiration in drug discovery. The functional benefits of natural products to the host organism steers the evolution of their biosynthetic pathways. Here, we describe a discovery approach-which we term activity-directed synthesis-in which reactions with alternative outcomes are steered towards functional products. Arrays of catalysed reactions of ?-diazo amides, whose outcome was critically dependent on the specific conditions used, were performed. The products were assayed at increasingly low concentration, with the results informing the design of a subsequent reaction array. Finally, promising reactions were scaled up and, after purification, submicromolar ligands based on two scaffolds with no previous annotated activity against the androgen receptor were discovered. The approach enables the discovery, in tandem, of both bioactive small molecules and associated synthetic routes, analogous to the evolution of biosynthetic pathways to yield natural products. PMID:25242481

Karageorgis, George; Warriner, Stuart; Nelson, Adam

2014-10-01

208

Efficient discovery of bioactive scaffolds by activity-directed synthesis  

NASA Astrophysics Data System (ADS)

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

Karageorgis, George; Warriner, Stuart; Nelson, Adam

2014-10-01

209

Effect of chemical composition of isomorphous metavanadates on their catalytic activity toward carbon combustion  

Microsoft Academic Search

Metal vanadates of K, Rb, and Cs and their solid solutions were prepared by reaction between carbonates and vanadium(V) oxide, characterized by X-ray diffraction and tested as catalysts for carbon combustion. These vanadates are all orthorhombic but show different lattice parameters depending on the ionic radius of alkali metals. A complete solubility in the solid state was found to exist

C. Badini; D. Mazza; S. Ronchetti; G. Saracco

1999-01-01

210

In search for active non-precious metal catalyst for VOC combustion  

Microsoft Academic Search

The study is devoted to the evaluation of the cobalt and copper doped cobalt catalysts deposited on the structured carriers for VOC combustion. The catalysts have been tested in n-hexane oxidation in the jet-stirred gradientless reactor at various temperatures. As the reactor has occurred not to provide sufficient mixing conditions a model has been proposed which allowed to discriminate between

Joanna Lojewska; Andrzej Kolodziej; Ryszard Kapica; Arkadiusz Knapik; Jacek Tyczkowski

2009-01-01

211

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

SciTech Connect

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

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

1997-10-01

212

Emissions from syngas combustion  

SciTech Connect

Gasification technology has matured to the point that previously-held hesitations regarding performance and availability have given way to acceptance of the technology for energy generation. Indeed, the past few years have seen a significant increase in the number of gasifiers installed for generation of power and heat, and the number of installations is expected to increase dramatically over the next several decades as demand for efficient and environmentally sound energy generation increases. It is valuable to consider the environmental impact of this new generation of energy production systems, specifically release of gaseous emissions from combustion of the synthesis gas produced by gasification. Emissions from syngas combustion in turbines, engines and boilers are discussed in this review. The types of emissions considered include the unburned fuel components and partially oxidized species, nitrogen and sulfur-containing gases, volatile organic compounds, and other trace elements. Combustion of synthesis gas, in general, produces lower emissions for heat and power generation than conventional liquid and solid fuels. The composition of the syngas strongly influences the level of emissions. Hydrogen and carbon monoxide in synthesis gases results in elevated combustion temperature that facilitates the thermal formation of NO and NO{sub 2}. In contrast, higher temperatures promote complete combustion and reduce the emission of organic volatiles, which are formed mainly from minor fractions of hydrocarbons in synthesis gases. Particulate matter, metallic compounds and other undesired pollutants are usually removed before firing synthesis gases for heat and power production. Therefore, integrated gasification and combined cycle systems are more environmentally friendly than conventional power generation systems.

Whitty, K.J.; Zhang, H.R.; Eddings, E.G. [University of Utah, Salt Lake City, UT (United States). Inst. for Clean & Secure Energy

2008-07-01

213

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

SciTech Connect

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

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

2010-03-31

214

Low-temperature synthesis of nanocrystalline NiOYSZ powders by succinic acid-assisted combustion  

Microsoft Academic Search

Nanocrystalline composite powders, NiOYSZ were prepared by the succinic acid-containing gel-combustion method at a temperature as low as 310C. FT-IR, XRD, DTA\\/TGA, SEM and TEM were employed to characterize the thermal decomposition of the precursor and the phase evolution and morphology of the calcined powders. The results of FT-IR and thermal analysis showed that the pyrolysis of the precursor began

Fu-Yun Shih; Kuan-Zong Fung; Hung-Cheng Lin; Guo-Ju Chen

2006-01-01

215

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

Microsoft Academic Search

Gd2O3:Eu3+ (0.58.0mol%) 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 (800C, 3h) Gd2O3 powders exhibit monoclinic phase

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

2010-01-01

216

Combustion synthesis and effect of LaMnO 3 and LaOCl powder mixture on HMX thermal decomposition  

Microsoft Academic Search

LaOCl powder mixture and perovskite-type LaMnO3 were prepared by stearic acid gel combustion method. The obtained powders were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques. LaOCl powder mixture was a mixture of LaOCl and significant amounts of amorphous materials. When heated at 973.15K, the mixture was found

Zhi-Xian Wei; Yan Wang; Xue-Jun Zhang; Chang-Wen Hu

2010-01-01

217

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

NASA Astrophysics Data System (ADS)

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

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

1999-04-01

218

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

219

Synthesis and biological activity of new 2-nitroimidazole derivatives.  

PubMed

In an earlier paper we described the synthesis and the antitrichomonas activity of 2-nitro-alpha,alpha,1-trimethyl-1H-imidazole-5-methanol (2). Starting from this compound, several derivatives have been synthesized. Among these, the phenyl carbonate 8 has been shown to possess activity equal to that of 2 and to be less toxic. This compound therefore is interesting in comparison with some antitrichomonas agents currently in use clinically. Before undertaking an in-depth investigation, compound 8 was subjected to some studies to see whether it has any effects on the central nervous system (CNS). Preliminary results show that, at therapeutic doses, it might induce unwanted CNS effects to a lesser degree than metronidazole. PMID:211235

Cavalleri, B; Volpe, G; Arioli, V; Pizzocheri, F; Diena, A

1978-08-01

220

The Synthesis and Antimicrobial Activity of Heterocyclic Derivatives Michelle B. Kim,  

E-print Network

natural product. Preliminary experiments demonstrate that the indole analogues do not target the bacterialThe Synthesis and Antimicrobial Activity of Heterocyclic Derivatives of Totarol Michelle B. Kim: The synthesis and antimicrobial activity of hetero- cyclic analogues of the diterpenoid totarol are described

Weibel, Douglas B.

221

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

NASA Astrophysics Data System (ADS)

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

Wicker, Josef M.

1999-11-01

222

Digital active control law synthesis for aeroservoelastic systems  

NASA Technical Reports Server (NTRS)

This paper presents a formulation for synthesis of digital active control laws for aeroservoelastic systems, which are typically modeled by large order equations in order to accurately represent the rigid and flexible body modes, unsteady aerodynamic forces, actuator dynamics, and gust spectra. The control law is expected to satisfy multiple design requirements on the dynamic loads, responses, actuator deflection and rate limitations, as well as maintain certain stability margins, yet should be simple enough to be implemented by an onboard digital microprocessor. The synthesis procedure minimizes a linear quadratic Gaussian type cost function, by updating selected free parameters of the control law, while satisfying a set of inequality constraints on the design loads, responses and stability margins. A stable classical control law or an estimator based full or reduced order control law can be used as an initial design starting point. The gradients of the cost function and the constraints, with respect to the digital control law design variables are derived analytically, to facilitate rapid convergence. Selected design responses can be treated as constraints instead of lumping them into the cost function, in order to satisfy individual root-mean-square load and response limitations. Constraints are also imposed on the minimum singular value requirements for stability robustness improvement.

Mukhopadhyay, Vivekananda

1988-01-01

223

Synthesis of highly ordered 30 nm NiFe2O4 particles by the microwave-combustion method  

NASA Astrophysics Data System (ADS)

NiFe2O4 of 30 nm average size was synthesized by microwave combustion and subsequent solid state reaction at 1273 K. The materials were characterized by X-ray diffraction, TEM, vibrating sample magnetometery and Mssbauer spectroscopy. The microwave combustion produced materials were comprised chemically of ferrites and a smaller amount of hematite. The NiFe2O4 particles have the cubic spinel structure with crystallites of sizes less than 10 nm, and were found to have low magnetization, and essentially no hysteresis loop; characteristics of superparamagnetism. Upon annealing at temperatures 973 K and below, crystallite growth was accompanied by increase in both coercive field and magnetization. The coercive field was a maximum for the sample annealed at 973 K. On the other hand, crystallite growth at higher annealing temperatures yielded mainly ferrites and improvement in soft magnetic properties. Mssbauer and magnetization measurements indicate that the fine NiFe2O4 particles produced at the annealing temperature of 1273 K are in good chemical and magnetic order, excluding the spins arrangement at the surface of the particles which show spin glass-like behavior.

Mahmoud, M. H.; Elshahawy, A. M.; Makhlouf, Salah A.; Hamdeh, H. H.

2014-11-01

224

Synthesis of Li2TiO3 by sol-gel combustion method and its gel-casting formation  

NASA Astrophysics Data System (ADS)

Lithium metatitanate (Li2TiO3) has been recognized as a candidate of ceramic tritium breeder materials for its excellent performance. In this paper, Li2TiO3 powder was synthetized by a modified sol-gel combustion process, and the ratio of fuel to oxidizer was optimized. DTA-TG analysis indicated that an intense exothermic reaction occurred at 539 K, which led to the formation of a voluminous white powder. No additional annealing process was required, as pure crystalline ?-Li2TiO3 was directly obtained from the combustion reaction. The powder had nano-scale structure and large specific surface area of 9.6 m2/g. Li2TiO3 pebbles with desired size and shape were prepared by gel-casting technique using the as-prepared powder. The pebbles reached a high density (81-86% T.D) after sintered at a relatively low temperature (?1373 K) for 2 h. The sintering pebbles had a smooth surface, homogeneous microstructure and small grain size.

Hong, Ming; Zhang, Yingchun; Mi, Yingying; Jiang, Yuanyuan; Xiang, Maoqiao

2014-12-01

225

Combustion synthesis and effect of LaMnO 3 and La 0.8Sr 0.2MnO 3 on RDX thermal decomposition  

Microsoft Academic Search

Perovskite-type LaMnO3 and La0.8Sr0.2MnO3 with high specific surface areas were prepared by stearic acid gel combustion method. The obtained powders were characterized by XRD, FT-IR, SEM and XPS techniques. Their catalytic activities were investigated on thermal decomposition of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by TG-DSC techniques. The experimental results show that LaMnO3 is a more effective catalyst than La0.8Sr0.2MnO3 for the sublimation and

Zhi-Xian Wei; Lin Wei; Lin Gong; Yan Wang; Chang-Wen Hu

2010-01-01

226

Combustion noise  

NASA Technical Reports Server (NTRS)

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

Strahle, W. C.

1977-01-01

227

Low-temperature metal-oxide thin-film transistors formed by directly photopatternable and combustible solution synthesis.  

PubMed

We investigated the formation of ultraviolet (UV)-assisted directly patternable solution-processed oxide semiconductor films and successfully fabricated thin-film transistors (TFTs) based on these films. An InGaZnO (IGZO) solution that was modified chemically with benzoylacetone (BzAc), whose chelate rings decomposed via a ?-?* transition as result of UV irradiation, was used for the direct patterning. A TFT was fabricated using the directly patterned IGZO film, and it had better electrical characteristics than those of conventional photoresist (PR)-patterned TFTs. In addition, the nitric acid (HNO3) and acetylacetone (AcAc) modified In2O3 (NAc-In2O3) solution exhibited both strong UV absorption and high exothermic reaction. This method not only resulted in the formation of a low-energy path because of the combustion of the chemically modified metal-oxide solution but also allowed for photoreaction-induced direct patterning at low temperatures. PMID:23534400

Rim, You Seung; Lim, Hyun Soo; Kim, Hyun Jae

2013-05-01

228

Efficient synthesis of anacardic acid analogues and their antibacterial activities.  

PubMed

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

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

2013-03-15

229

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

230

Synthesis, characterization and antimicrobial activity of some novel benzimidazole derivatives  

PubMed Central

A series of novel N-((1H-benzoimidazol-1-yl) methyl)-4-(1-phenyl-5-substituted-4, 5-dihydro-1-benzoimidazol-1-yl) methyl)-4-(1-phenyl-5-substituted-4, 5-dihydro-1H-pyrazol-3-yl) benzenamine were synthesized by treating various 1-(4-((1H-benzoimidazol-1-yl) methylamino) phenyl)-3-substitutedprop-2-en-1-one with phenyl hydrazine in the presence of sodium acetate through a simple ring closure reaction. The starting material, 1-(4-((1H-benzoimidazol-1-yl) methylamino) phenyl)-3-substitutedprop-2-en-1-one,-benzoimidazol-1-yl) methylamino) phenyl)-3-substitutedprop-2-en-1-one, was synthesized from o-phenylenediamine by a multistep synthesis. All the synthesized compounds were characterized by spectroscopic means and elemental analyses. The title compounds were investigated for in vitro antibacterial and antifungal properties against some human pathogenic microorganisms by employing the agar streak dilution method using Ciprofloxacin and Ketoconazole as standard drugs. All title compounds showed activity against the entire strains of microorganism. Structural activity relationship studies reveal that compounds possessing an electron-withdrawing group display better activity than the compounds containing electron-donating groups, whereas the unsubstituted derivatives display moderate activity. Based on the results obtained, N-((1H-benzoimidazol-1-yl) methyl)-4-(1-phenyl-5-(4-(trifluoromethyl) phenyl)-4,5-dihydro-1H-pyrazol-3-yl) benzenamine 5i was found to be very active compared with the rest of the compounds and standard drugs that were subjected to antimicrobial assay. PMID:24696814

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

2014-01-01

231

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

SciTech Connect

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

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

2010-11-15

232

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

233

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

PubMed Central

Traditional strategies for oligosaccharide synthesis often require extensive protecting and/or leaving group manipulations between each glycosylation step, thereby increasing the total number of synthetic steps while decreasing the efficiency of the synthesis. In contrast, expeditious strategies allow for the rapid chemical synthesis of complex carbohydrates by minimizing extraneous chemical manipulations. Oligosaccharide synthesis by selective activation of one leaving group over another is one such expeditious strategy. Herein, the significant improvements that have recently emerged in the area of the selective activation are discussed. The development of orthogonal strategy further expands the scope of the selective activation methodology. Surveyed in this article, are representative examples wherein these excellent innovations have been applied to the synthesis of various oligosaccharide sequences. PMID:21663897

Kaeothip, Sophon; Demchenko, Alexei V.

2011-01-01

234

Synthesis and biological evaluation of orally active prodrugs of indomethacin.  

PubMed

Synthesis and biological evaluation of orally active prodrugs (1a-d) of indomethacin are described. Prodrugs 1a-c showed a similar degree of anti-inflammatory activity, and prodrug 1d was found to be less potent than the parent drug indomethacin (1). Ulcer index (UI) data indicated that 1a (UI = 19), 1c (UI = 0), and 1d (UI = 0) were substantially less ulcerogenic and 1b (UI = 62) was more ulcerogenic than parent drug 1 (UI = 47). These prodrugs demonstrated good stability at acidic and basic pH and found to be more lipophilic than parent drug compound 1, indicated by partition coefficients measured in octanol-buffer system at pH 7.4 and 3.0. On the basis of in vivo studies, 1a and 1c compounds were selected for metabolic stability in rat liver microsome (RLM) and rat plasma (RP), and both were found to be enzymatically labile. Prodrugs 1a and 1c emerged as potent anti-inflammatory agents with a lesser potential for ulcer than the parent drug indomethacin. PMID:21284386

Bandgar, Babasaheb P; Sarangdhar, Rajendra Janardan; Viswakarma, Santosh; Ahamed, Fakrudeen Ali

2011-03-10

235

Synthesis of novel bisindolylmethane Schiff bases and their antibacterial activity.  

PubMed

In an effort to develop new antibacterial drugs, some novel bisindolylmethane derivatives containing Schiff base moieties were prepared and screened for their antibacterial activity. The synthesis of the bisindolylmethane Schiff base derivatives 3-26 was carried out in three steps. First, the nitro group of 3,3'-((4-nitrophenyl)-methylene)bis(1H-indole) (1) was reduced to give the amino substituted bisindolylmethane 2 without affecting the unsaturation of the bisindolylmethane moiety using nickel boride in situ generated. Reduction of compound 1 using various catalysts showed that combination of sodium borohydride and nickel acetate provides the highest yield for compound 2. Bisindolylmethane Schiff base derivatives were synthesized by coupling various benzaldehydes with amino substituted bisindolylmethane 2. All synthesized compounds were characterized by various spectroscopic methods. The bisindolylmethane Schiff base derivatives were evaluated against selected Gram-positive and Gram-negative bacterial strains. Derivatives having halogen and nitro substituent display weak to moderate antibacterial activity against Salmonella typhi, S. paratyphi A and S. paratyphi B. PMID:25102118

Imran, Syahrul; Taha, Muhammad; Ismail, Nor Hadiani; Khan, Khalid Mohammed; Naz, Farzana; Hussain, Memona; Tauseef, Saima

2014-01-01

236

Synthesis, characterization and biological activities of curcumin nanospheres.  

PubMed

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

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

2014-02-01

237

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

238

Cholesterol synthesis inhibitors protect against platelet-activating factor-induced neuronal damage  

Microsoft Academic Search

BACKGROUND: Platelet-activating factor (PAF) is implicated in the neuronal damage that accompanies ischemia, prion disease and Alzheimer's disease (AD). Since some epidemiological studies demonstrate that statins, drugs that reduce cholesterol synthesis, have a beneficial effect on mild AD, we examined the effects of two cholesterol synthesis inhibitors on neuronal responses to PAF. METHODS: Primary cortical neurons were treated with cholesterol

Clive Bate; Louis Rumbold; Alun Williams

2007-01-01

239

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

2012-01-01

240

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

241

Rapid room temperature synthesis of electrocatalytically active Au nanostructures.  

PubMed

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 absorption spectrum of colloidal nanoparticles displays two bands ~580 and ~930 nm, corresponding to the dipole and quadrupole plasmon resonance, respectively. TEM measurements show that the Au nanostructures have penta-twined polyhedral shape with an average size of 52 nm. X-ray and selected area electron diffraction patterns reveal the existence of face centered cubic nanocrystalline Au. The concentration of Au(III) controls the stability of the nanoparticles. The nanoparticles were immobilized on 3-D silicate network pre-assembled on a conducting support to examine their electrocatalytic activity. The nanoparticle-based electrochemical interface was characterized by spectral, voltammetric and impedance measurements. The nanoparticle shows high catalytic activity in the oxidation of NADH and reduction of oxygen. Unique inverted 'V' shape voltammogram was obtained for the oxidation of NADH at less positive potential. The nanoparticle-based interface favors two-step four-electron reduction of oxygen to water in neutral pH. Significant decrease in the overpotential for the oxidation of NADH and reduction of oxygen with respect to the polycrystalline Au electrode was observed. The electrocatalytic performance of the polyhedral nanoparticle is compared with the conventional citrate stabilized spherical nanoparticles. PMID:20970809

Das, Ashok Kumar; Raj, C Retna

2011-01-15

242

Filtration combustion: Smoldering and SHS  

NASA Technical Reports Server (NTRS)

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

Matkowsky, Bernard J.

1995-01-01

243

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 ...

244

The Synthesis of Active Metabolites and Analogues of Vitamin D3  

NASA Astrophysics Data System (ADS)

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

Yakhimovich, R. I.

1980-04-01

245

Combustion Synthesis of La 0.8Sr 0.2MnO 3 and Its Effect on HMX Thermal Decomposition  

Microsoft Academic Search

Perovskite-type La0.8Sr0.2MnO3 was prepared by stearic acid gel combustion method. The obtained powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scaning electron micrograph (SEM) and X-ray photoelectron spectroscopy (XPS) techniques. The catalytic activity of La0.8Sr0.2MnO3 was investigated on thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by thermal gravity-differential scanning calorimetry (TG-DSC) techniques. The experimental results show that La0.8Sr0.2MnO3

Yan WANG; Lei GONG; Yanbin LI; Zhixian WEI

2010-01-01

246

Bonding characteristics of the Al2O3-metal composite coating fabricated onto carbon steel by combustion synthesis  

NASA Astrophysics Data System (ADS)

The fabrication of an alumina-metal composite coating onto a carbon steel substrate by using a self-propagating high-temperature synthesis technique was demonstrated. The effects of the type and thickness of the pre-coated layer on the binding structure and surface quality of the coating were systematically investigated. The macrostructure, phase composition, and bonding interface between the coating and the substrate were investigated by scanning electronic microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectrometry (EDS). The diffraction patterns indicated that the coating essentially consisted of ?-Al2O3, Fe(Cr), and FeOAl2O3. With an increase in the thickness of the pre-coated working layer, the coating became more smooth and compact. The transition layer played an important role in enhancing the binding between the coating and the substrate. When the pre-coated working layer was 10 mm and the pre-coated transition layer was 1 mm, a compact structure and metallurgical bonding with the substrate were obtained. Thermal shock test results indicated that the ceramic coating exhibited good thermal shock resistance when the sample was rapidly quenched from 800C to room temperature by plunging into water.

Xue, Xiao-feng; Wang, Ze-hua; Zhou, Ze-hua; Jiang, Shao-qun; Cheng, Jiang-bo; Wang, Chang-hao; Shao, Jia

2014-09-01

247

Internal combustion engine  

Microsoft Academic Search

An internal combustion engine is disclosed which includes active cylinders being always active and inactive cylinders being inactive when the engine load is below a predetermined value. The engine has an intake passage divided into first and second branches connected to active and inactive cylinders, respectively. The second branch is provided near its inlet with a stop valve and is

Y. Etoh; T. Tanaka

1982-01-01

248

Polyamine stimulation of ribosomal synthesis and activity in a polyamine-dependent mutant of Escherichia coli.  

PubMed

A polyamine-dependent mutant of Escherichia coli KK101 was isolated by treatment of E. coli MA261 with N-methyl-N'-nitro-N-nitrosoguanidine. In the absence of putrescine, doubling time of the mutant was 496 min. The mutation was accompanied by a change in the nature of the 30 S ribosomal subunits. Addition of putrescine to the mutant stimulated the synthesis of proteins and subsequently, this led to stimulation of RNA and DNA synthesis. Under these conditions, we determined which proteins were preferentially synthesized. Putrescine stimulated the synthesis of ribosomal protein S1 markedly, but stimulated ribosomal proteins S4, L20, and X1, and RNA polymerase slightly. The amounts of initiation factors 2 and 3 synthesized were not influenced significantly by putrescine. The preferential stimulation of the synthesis of ribosomal protein S1 occurred as early as 20 min after the addition of putrescine, while stimulation of the synthesis of the other ribosomal proteins and RNA polymerase appeared at 40 min. The stimulation of the synthesis of ribosomal RNA also occurred at 40 min after addition of putrescine. Our results indicate that putrescine can stimulate both the synthesis and the activity of ribosomes. The increase in the activity of ribosomes was achieved by the association of S1 protein to S1-depleted ribosomes. The early stimulation of ribosomal protein S1 synthesis after addition of putrescine may be important for stimulation of cell growth by polyamines. PMID:2643387

Kashiwagi, K; Sakai, Y; Igarashi, K

1989-01-01

249

Laccase catalyzed synthesis of iodinated phenolic compounds with antifungal activity.  

PubMed

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

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

2014-01-01

250

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

251

Combustion Technology Outreach  

NASA Technical Reports Server (NTRS)

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

1995-01-01

252

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

NASA Astrophysics Data System (ADS)

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

Rankovi?, D.; Arsenijevi?, Z.; Radi?, N.; Grbi?, B.; Grbav?i?, .

2007-09-01

253

Investigation of the active state of supported palladium catalysts in the combustion of methane  

Microsoft Academic Search

Possible relationships between the structure and activity of supported palladium catalysts for the oxidation of methane have been explored. Samples have been exposed to a wide range of oxidation and reduction pretreatments and the activity for methane oxidation has been determined as a function of time-on-stream, both for pre-oxidised and for pre-reduced samples. Parallel experiments on the rate and extent

R. Burch; F. J. Urbano

1995-01-01

254

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

2013-09-01

255

Synthesis and cytotoxic activity of some derivatives of alkyl piperidine.  

PubMed

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

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

2013-05-01

256

Synthesis of Pro-Xylane TM: A new biologically active C-glycoside in aqueous media  

Microsoft Academic Search

The scope and limitation of Lubineaus reaction were evaluated for the synthesis of C-glycosides (compounds 113). Further transformation of side chain carbonyl was also achieved (compounds 1623). Optimization of these two steps was investigated in xylose case. Some of the compounds were shown to stimulate sulfated glycosaminoglycans (GAGs) synthesis. Compound 20 (called Pro-XylaneTM) was identified as the best activator of

Alexandre Cavezza; Christophe Boulle; Amlie Guguiniat; Patrick Pichaud; Simon Trouille; Louis Ricard; Maria Dalko-Csiba

2009-01-01

257

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

258

Internal combustion engine using premixed combustion of stratified charges  

DOEpatents

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

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

2003-12-30

259

Activation of AMP-Activated Protein Kinase Leads to the Phosphorylation of Elongation Factor 2 and an Inhibition of Protein Synthesis  

Microsoft Academic Search

Protein synthesis, in particular peptide-chain elongation, consumes cellular energy. Anoxia activates AMP-activated protein kinase (AMPK, see [1]), resulting in the inhibition of biosynthetic pathways to conserve ATP. In anoxic rat hepatocytes or in hepatocytes treated with 5-aminoimidazole-4-carboxamide (AICA) riboside, AMPK was activated and protein synthesis was inhibited. The inhibition of protein synthesis could not be explained by changes in the

Sandrine Horman; Gareth J. Browne; Ulrike Krause; Jigna V. Patel; Didier Vertommen; Luc Bertrand; Alain Lavoinne; Louis Hue; Christopher G. Proud; Mark H. Rider

2002-01-01

260

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

261

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

262

Studies in combustion dynamics  

SciTech Connect

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

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

1993-12-01

263

Dual ionic controls for the activation of protein synthesis at fertilization.  

PubMed

The general metabolic activation of the sea urchin egg at fertilization is dependent on a release of intracellular stores of calcium and the subsequent transient elevation of intracellular Ca2+ (refs 1--3). However, this elevation does not by itself lead to increased macromolecular synthesis and development but initiates steps which result in a long-term elevation of intracellular pH (refs 4--6). Among the developmental processes dependent on the elevation of intracellular pH is the large acceleration in the rate of protein synthesis at fertilization. Weak penetrating bases such as ammonia can be used to mimic the processes resulting in an increase in intracellular pH and so show the corresponding increases in protein synthesis rate. Conversely, it is possible to demonstrate a gradual but complete shut down of protein synthesis if the intracellular pH is reduced to the unfertilized level with penetrating weak acids. However, the rate of protein synthesis in ammonia-activated eggs lags behind that of fertilized controls even though ammonia activation can result in an intracellular pH increase greater than occurs in the fertilized egg. This result has led to the suggestion that factors other than intracellular pH may be regulating protein synthesis following fertilization. To investigate the possibility that the Ca2+ transient may have such a role, we measured the rate of amino acid incorporation in eggs that were activated in various ionic conditions which enabled the effects of Ca2+ and pH changes to be studied separately. Our results, reported here, show that if intracellular pH is elevated, increases in intracellular Ca2+ play an additional part in the activation of protein synthesis at fertilization. PMID:7422008

Winkler, M M; Steinhardt, R A; Grainger, J L; Minning, L

1980-10-01

264

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

2012-01-01

265

FGF19 as a Postprandial, Insulin-Independent Activator of Hepatic Protein and Glycogen Synthesis  

Microsoft Academic Search

Fibroblast growth factor (FGF) 19 is an enterokine synthesized and released when bile acids are taken up into the ileum. We show that FGF19 stimulates hepatic protein and glycogen synthesis but does not induce lipogenesis. The effects of FGF19 are independent of the activity of either insulin or the protein kinase Akt and, instead, are mediated through a mitogen-activated protein

Serkan Kir; Sara A. Beddow; Varman T. Samuel; Paul Miller; Stephen F. Previs; Kelly Suino-Powell; H. Eric Xu; Gerald I. Shulman; Steven A. Kliewer; David J. Mangelsdorf

2011-01-01

266

700, 100, and 20 hp combustion test facility yearly activity report for the period April 1, 1979 to April 1, 1980  

SciTech Connect

Management and Technical Services Co./ General Electric was awarded the contract to operate, modify and maintain the DOE/PETC 700 hp, 100 hp, and 20 hp Combustion Test Facility. These facilities were designed and built by the Department of Energy at Pittsburgh Energy Technology Center and its ultimate success is the responsibility of DOE/PETC. MATSCO/GE will provide support to assist in the goal of successful operation of this pilot plant facility. The primary objective of the DOE/PETC 700 hp and 100 hp CTF is to establish the practicality of coal oil slurry combustion as a technically, economically and environmentally feasible retrofit technology. The 20 hp CTF is to provide a test bed to evaluate synthetic fuels for its technical feasibility and its effect on the environment. Four series of combustion tests were completed. Coal-oil mixes for all tests were number 6 fuel oil and Pittsburgh Seam Coal. The tests were executed successfully. Operational problems were handled as required without excessive delay of the testing program. Additional studies performed concurrently with the combustion testing included flame studies, stack emissions studies during all tests, standard measurements of equipment wear after each test series and extensive erosion and corrosion analyses of boiler test coupons and the burner section of the fuel train after the 500 h endurance test. Testing activity and required facility modifications were coordinated through Department of Energy personnel.

Not Available

1980-01-01

267

Comprehensive analysis of combustion enhancement mechanisms in a supersonic flow of CH4-O2 mixture with electric-discharge-activated oxygen molecules  

NASA Astrophysics Data System (ADS)

Mechanisms of ignition and combustion enhancement in a supersonic CH4-O2 reactive flow behind an inclined shock wave front are analyzed numerically when chemically active species are produced by electric discharges with different values of reduced electric field. The analysis is carried out based on thermally nonequilibrium kinetic models both for the discharge and for the shock-induced combustion, taking into account the disruption of thermodynamic equilibrium between vibrational and translational degrees of freedom of the reacting molecules and treating the vibrational-electronic-chemistry coupling. It is demonstrated that the presence of electronically excited O2 molecules O2(a 1?g) and O_2(b\\,^1\\!\\Sigma_g^+) as well as O atoms in oxygen plasma allows one to intensify the chain mechanism of CH4-O2 combustion even if the energy put to O2 molecules in the discharge is sufficiently low. The excitation of O2 molecules to the singlet states O2(a 1?g) and O_2(b\\,^1\\!\\Sigma_g^+) is more preferable in shortening the induction zone length than the production of O atoms in the course of dissociation of O2 molecules due to electron impact. However, both excitation of O2 molecules to the singlet delta and singlet sigma states and production of O atoms in an electric discharge are much more effective in combustion enhancement than merely heating the mixture.

Starik, A. M.; Loukhovitski, B. I.; Chernukho, A. P.

2012-06-01

268

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

PubMed

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

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

2014-08-11

269

Highly bacterial resistant silver nanoparticles: synthesis and antibacterial activities  

Microsoft Academic Search

In this article, we describe a simple one-pot rapid synthesis route to produce uniform silver nanoparticles by thermal reduction\\u000a of AgNO3 using oleylamine as reducing and capping agent. To enhance the dispersal ability of as-synthesized hydrophobic silver nanoparticles\\u000a in water, while maintaining their unique properties, a facile phase transfer mechanism has been developed using biocompatible\\u000a block co-polymer pluronic F-127. Formation

Bhupendra ChudasamaAnjana; Anjana K. Vala; Nidhi Andhariya; R. V. Mehta; R. V. Upadhyay

2010-01-01

270

Synthesis of Starch - Stabilized Silver Nanoparticles and Their Antimicrobial Activity  

Microsoft Academic Search

In this study silver nanoparticles were prepared using silver nitrate as the metal precursor, starch as protecting agent and sodium borohydride (NaBH4) as a reducing agent by chemical reduction method. The formation of the silver nanoparticles was monitored using UV-Vis absorption spectroscopy, cyclic voltammetry and particle size analyzer and characterized by Transmission Electron microscopy (TEM) and X-Ray Diffraction (XRD).Synthesis of

V. RAJI; M. CHAKRABORTY; P. A. PARIKH

2012-01-01

271

Synthesis, characterization, and antibacterial activities of novel N -halamine copolymers  

Microsoft Academic Search

The synthesis and antibacterial properties of N-halamine copolymers are reported in this paper. 3-(4?-vinylbenzyl)-5,5-dimethylhydantoin (VBDMH) monomer and its copolymers\\u000a with n-butyl methacrylate (BMA) were prepared under mild conditions. The effects of monomer feeds on the composition of the final\\u000a copolymers and reaction conversion were investigated. It was found that VBDMH had higher reactivities than BMA in the copolymerization\\u000a reactions and

Ying Chen; Li Wang; Haojie Yu; Quan Shi; Xiaochen Dong

2007-01-01

272

Total synthesis, antiprotozoal and cytotoxicity activities of rhuschalcone VI and analogs.  

PubMed

The total synthesis of a potent antiplasmodial natural bichalcone, rhuschalcone VI, is described starting from simple and available resorcinol and 4-hydroxybenzaldehyde. Key steps include the solvent-free Aldol syntheses of chalcones, and the successful application of the Suzuki-Miyaura coupling reaction in the synthesis of bichalcones. The present work constitutes a general method for the rapid syntheses of a number of bichalcones related to rhuschalcone VI. Some of the bichalcones showed moderate antiprotozoal activities against Bodo caudatus, a preliminary screening system for antitrypanosomal activities, most of them with little or no cytotoxicity. PMID:20304658

Mihigo, Shetonde O; Mammo, Wendimagegn; Bezabih, Merhatibeb; Andrae-Marobela, Kerstin; Abegaz, Berhanu M

2010-04-01

273

Inhibition of ongoing myeloma IgE synthesis in vitro by activated human T cells.  

PubMed

The ability of activated T cells to suppress ongoing IgE synthesis in vitro was assessed using U266--a human myeloma cell line spontaneously producing IgE. T cells were able to inhibit U266 IgE synthesis in the presence of 10 micrograms/ml of Con A by 41.8% (p less than 0.01). T cells preincubated with 10 or 50 micrograms/ml of Con A and washed extensively were still able to inhibit U266 IgE synthesis in the absence of Con A by 41 and 46% (p less than 0.05 and p less than 0.02, respectively). The decrease in IgE measured was due to inhibition of newly formed IgE by U266, as shown by control experiments with cycloheximide. The inhibition was not due to the simple depletion of nutrient growth factors by the activated T cells, as it did not occur with MOLT-4, T cells that are very active metabolically; nor could it be reversed with medium containing IL 2 and B cell growth factors. Culture supernatants of Con A-activated T cells were also able to suppress IgE synthesis by U266 (21%; p less than 0.01), which suggests that upon appropriate activation, T cells secrete material(s) with inhibitory properties for IgE synthesis. Activation of T cells by mixed lymphocyte culture using puromycin-treated lymphoblastoid cell lines as stimulators also generated T cells that had suppressive activity for IgE synthesis. T cells activated with Con A and subsequently incubated with IgE demonstrated a diminished ability to suppress IgE synthesis. This observation is in agreement with the finding that patients with high levels of IgE may lack isotype-specific suppressor T cells for spontaneous IgE secretion. However, T cells from such patients have so far shown variable loss of IgE suppressive function. These results suggest that human IgE synthesis is susceptible to inhibition at a very differentiated stage, and this may be important in expression of allergic diseases. PMID:6220058

Hassner, A; Saxon, A

1983-04-01

274

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

275

Biofuels Combustion  

NASA Astrophysics Data System (ADS)

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.

Westbrook, Charles K.

2013-04-01

276

Biofuels combustion.  

PubMed

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

Westbrook, Charles K

2013-01-01

277

Spray combustion stability project  

NASA Technical Reports Server (NTRS)

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

Jeng, San-Mou; Litchford, Ron J.

1992-01-01

278

Synthesis, antioxidant evaluation, and quantitative structureactivity relationship studies of chalcones  

Microsoft Academic Search

Synthesis, antioxidant activity, and quantitative structureactivity relationship (QSAR) of 25 of chalcone derivatives is\\u000a reported here. They were synthesized by ClaisenSchmidt reaction and were characterized by FTIR, NMR, and mass spectroscopy.\\u000a Antioxidant activity is evaluated through four different methods namely, superoxide radical-scavenging, hydrogen peroxide\\u000a scavenging, reducing power, and DPPH radical-scavenging assays. Generally, compounds with SCH3 and OCH3 in the para

P. M. Sivakumar; P. K. Prabhakar; M. Doble

2011-01-01

279

Biologically Active Chorionic Gonadotropin: Synthesis by the Human Fetus  

NASA Astrophysics Data System (ADS)

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

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

1983-04-01

280

Formal synthesis of optically active ingenol via ring-closing olefin metathesis.  

PubMed

The construction of strained carbon skeletons by ring-closing olefin metathesis (RCM) was investigated. With well-designed diene 4, RCM was found to be applicable to the formation of a highly strained inside-outside bicyclo[4.4.1]undecane skeleton of ingenol, a bioactive diterpenoid, and formal total synthesis of optically active ingenol (1) was achieved. The key features of this synthesis are construction of an A-ring by spirocyclization of the ketone with an allylic chloride unit, 26, and ring closure of a B-ring by olefin metathesis. Starting from Funk's keto ester 6, the key intermediate aldehyde 9 in Winkler's total synthesis was synthesized in eight steps in 12.5% overall yield. This strategy of direct cyclization of a strained inside-outside skeleton provided the first easy access to optically active ingenol. PMID:15527254

Watanabe, Kazushi; Suzuki, Yuto; Aoki, Kenta; Sakakura, Akira; Suenaga, Kiyotake; Kigoshi, Hideo

2004-11-12

281

Synthesis and antitumor activity of 10-alkyl-10-deazaminopterins. A convenient synthesis of 10-deazaminopterin.  

PubMed

Requirements for large-scale synthesis of the potent antitumor drug 10-deazaminopterin have led to development of a facile synthesis of this compound and its 10-alkyl analogues. The lithium diisopropyl amide generated dianions of appropriate p-alkylbenzoic acids were alkylated with 3-methoxyallyl chloride. The resulting 4-(p-carboxyphenyl)-1-methoxy-1-butenes were brominated at pH 7-8 to afford the 2-bromo-4-(p-carboxyphenyl)butyraldehydes. Condensation with 2,4,5,6-tetraminopyrimidine and subsequent in situ oxidation of the resulting dihydropteridines yielded crystalline 10-alkyl-10-deaza-4-amino-4-deoxypteroic acids. The pteroic acids were coupled with diethyl glutamate via the mixed anhydride method, followed by saponification at room temperature, to give the target 10-deazaminopterins. The 10-alkyl compounds were approximately equipotent to 10-deazaminopterin as growth inhibitors of folate-dependent bacteria. Their abilities to inhibit Lactobacillus casei and L1210 derived dihydrofolate reductases were also similar. Transport properties in vitro were suggestive of an improved therapeutic index for the 10-alkyl analogues. Against L1210 in mice, the percent increase in life span at the LD10 dosage was +151% (methotrexate), +178% (10-deazaminopterin), +235% (10-methyl analogue), and +211% (10-ethyl analogue). 10,10-Dimethyl-10-deazaminopterin was less effective at an equimolar dosage, but the ILS at the maximum dose tested (72 mg/kg) was +135%. It was far less toxic than the other analogues possibly because of enhanced clearance. PMID:7143361

DeGraw, J I; Brown, V H; Tagawa, H; Kisliuk, R L; Gaumont, Y; Sirotnak, F M

1982-10-01

282

The effect of silicon powder characteristics on the combustion of silicon/Teflon/Viton nanoenergetics  

NASA Astrophysics Data System (ADS)

Due to its thin passivation layer, potentially good aging characteristics, and ease of surface functionalization nanoscale silicon (nSi) may offer some advantages over nanoaluminum as a reactive fuel in nanoenergetic compositions, particularly with fluorine-based oxidizers. Currently, Si nanopowder can be quite expensive and the quality of commercial powders has been found to vary drastically. As a result limited efforts have focused on the role specific surface area, active content, morphology, and dominant particle size of the powder have on the combustion performance. This work investigates the effect of such characteristics on the combustion of silicon (Si)/polytetrafluoroethylene (Teflon)/FC-2175 (Viton) (SiTV) nanoenergetics. A cost effective combustion synthesis route, salt assisted combustion synthesis, was used to produce several Si powders and these were directly compared to commercial nanoscale Si powders. Reactive mixtures of SiTV were burned at atmospheric conditions and burning rates, combustion temperatures, spectral intensities, and effective plume emissivities were measured. Measured combustion temperatures ranged from 1664 to 2380 K and were limited by Si powder active content. This was found to drive plume emissivity and maximum spectral intensity, which had values ranging from 0.10 to 0.55 for effective plume emissivity and 17.6 to 48.1 kW m -2-sr-1-mum-1 for maximum spectral intensity. Burning rates ranged from 0.7 to 3.4 mm s-1 and were found to be dependent on the dominant particle size of the powder. Powders synthesized with salt assisted combustion resulted in comparable burning rate, plume emissivity and maximum spectral intensity to commercial porous Si powder (Vesta Ceramics).

Terry, Brandon C.

283

Activation of the membrane glucolipid synthesis in Acholeplasma laidlawii by phosphatidylglycerol and other anionic lipids.  

PubMed

In membrane lipids of the prokaryote Acholeplasma laidlawii similar phase equilibria and a nearly constant spontaneous curvature are maintained by an extensive metabolic regulation of especially the major polar lipids monoglucosyldiacylglycerol (MGlcDAG) and diglucosyldiacylglycerol (DGlcDAG), forming nonlamellar and lamellar phases, respectively. A constant surface charge density is maintained by the anionic phospholipid fraction. These lipids are synthesized from phosphatidic acid in two competing pathways. The in vitro synthesis of MGlcDAG and DGlcDAG were totally lost upon delipidation of the membrane proteins by detergent solubilization or solvent extraction of lyophilized cells. Activities were restored by critical concentrations of anionic lipids, but not by bilayer or nonbilayer zwitterionic phospholipids or glucolipids. Phosphatidylglycerol (PG), and to a lesser extent certain other anionic lipids, could activate the synthesis of MGlcDAG in lipid bilayers, whereas the synthesis of DGlcDAG was similarly dependent upon PG only. Two endogenous phosphoglucolipids with no activating potency could partially replace the PG activator for the MGlcDAG synthesis but less so for DGlcDAG formation. A change of inert matrix from phosphatidylcholine to DGlcDAG lowered the apparent cooperativity, but enhanced the efficiency, of activation by PG for both glucolipid synthesizing enzymes, most strongly the synthesis of DGlcDAG. These results indicate that the enzymatic formation of MGlcDAG is regulated by the lipid surface charge density, whereas the consecutive step to DGlcDAG is more dependent upon the specific properties of PG. The modulating effect of the surrounding matrix on the activator efficiencies and cooperativity may constitute part of the bilayer-nonbilayer lipid regulation mechanism. PMID:8089114

Karlsson, O P; Dahlqvist, A; Wieslander, A

1994-09-23

284

Combustion & Health  

E-print Network

FFCOMBUSTION & HEALTH Winifred J. Hamilton, PhD, SM Clear Air Through Energy Efficiency (CATEE) Galveston, TX October 9?11, 2012 FFCOMBUSTION & HEALTH FFCOMBUSTION: THE THREAT ? Biggest threat to world ecosystems (and to human health...) ? Combustion of fossil fuels for ? Electricity ? Industrial processes ? Vehicle propulsion ? Cooking and heat ? Other ? Munitions ? Fireworks ? Light ? Cigarettes, hookahs? FFCOMBUSTION & HEALTH FFCOMBUSTION: THE THREAT ? SCALE (think health...

Hamilton, W.

2012-01-01

285

Synthesis and biological activities of thioether derivatives related to the antiestrogens tamoxifen and ICI 164384  

Microsoft Academic Search

The catalyzed coupling reaction of activated alcohol and mercaptan was used for the short and efficient synthesis of 14 thioether compounds. Two types of side chains, the methyl butyl alkylamide related to the pure steroidal antiestrogen ICI 164384 and the dimethylamino ethyloxy phenyl related to the clinically used nonsteroidal antiestrogen tamoxifen, were introduced by a thioether link on two types

Serge Auger; Yves Mrand; Jolle D. Pelletier; Donald Poirier; Fernand Labrie

1995-01-01

286

The Respiratory Syncytial Virus Polymerase Has Multiple RNA Synthesis Activities at the Promoter  

PubMed Central

Respiratory syncytial virus (RSV) is an RNA virus in the Family Paramyxoviridae. Here, the activities performed by the RSV polymerase when it encounters the viral antigenomic promoter were examined. RSV RNA synthesis was reconstituted in vitro using recombinant, isolated polymerase and an RNA oligonucleotide template representing nucleotides 125 of the trailer complement (TrC) promoter. The RSV polymerase was found to have two RNA synthesis activities, initiating RNA synthesis from the +3 site on the promoter, and adding a specific sequence of nucleotides to the 3? end of the TrC RNA using a back-priming mechanism. Examination of viral RNA isolated from RSV infected cells identified RNAs initiated at the +3 site on the TrC promoter, in addition to the expected +1 site, and showed that a significant proportion of antigenome RNAs contained specific nucleotide additions at the 3? end, demonstrating that the observations made in vitro reflected events that occur during RSV infection. Analysis of the impact of the 3? terminal extension on promoter activity indicated that it can inhibit RNA synthesis initiation. These findings indicate that RSV polymerase-promoter interactions are more complex than previously thought and suggest that there might be sophisticated mechanisms for regulating promoter activity during infection. PMID:23093940

Tremaglio, Chadene Z.; Fearns, Rachel

2012-01-01

287

Concise synthesis of Valerena-4,7(11)-diene, a highly active sedative, from valerenic acid.  

PubMed

A concise synthesis of valerena-4,7(11)-diene with potent sedative activity was achieved in three steps involving, reduction of carboxylic acid, bromination of the resulting alcohol, and reduction of the bromide from valerenic acid in a 63% total yield. This synthetic method makes it possible to provide further materials for biological testing to realize comprehensive SAR studies. PMID:20834146

Kitayama, Takashi; Kawabata, Genki; Ito, Michiho

2010-01-01

288

Synthesis and HIV1 integrase inhibitory activities of caffeic acid dimers derived from Salvia officinalis  

Microsoft Academic Search

The synthesis of two caffeoyl-coumarin conjugates, derived from sagecoumarin, has been accomplished, starting from ferulic acid, isoferulic acid and sesamol. Both compounds exhibited potent inhibitory activities at micromolar concentrations against HIV-1 integrase in 3?-end processing reaction but were less effective against HIV-1 replication in a single-round infection assay of HeLa-?-gal-CD4+ cells.

Fabrice Bailly; Clmence Queffelec; Gladys Mbemba; Jean-Franois Mouscadet; Philippe Cotelle

2005-01-01

289

A simple and efficient synthesis of fused morpholine pyrrolidines/piperdines with potential insecticidal activities.  

PubMed

A simple and efficient synthesis of fused morpholine pyrrolidine/piperdine core structures was accomplished via a Petasis-borono Mannich reaction of cyclic amino alcohols, glyoxal and arylboronic acids with moderate to good yields. The bioassay data showed that the synthesized compounds displayed selective insecticidal activities against armyworm and root-knot nematode. PMID:24927942

Wang, Jiayi; Xu, Beiling; Si, Shanyu; Li, Hui; Song, Gonghua

2014-11-01

290

Facile synthesis of three bidesmosidic oleanolic acid saponins with strong inhibitory activity on pancreatic lipase.  

PubMed

The first synthesis of scabiosaponins E (1), F (2), and G (3), three new oleanolic acid saponins with strong inhibitory activity on pancreatic lipase isolated from the Chinese traditional medicinal herb Scabiosa tschiliensis, was efficiently achieved in an one-pot strategy under the combined use of glycosyl trichloroacetimidates and p-toluene 1-thioglycosides (STol) as donors. PMID:19463989

Guo, Tiantian; Liu, Qingchao; Wang, Peng; Zhang, Lei; Zhang, Wei; Li, Yingxia

2009-07-01

291

Synthesis of indoles using visible light: photoredox catalysis for palladium-catalyzed c?h activation.  

PubMed

A combined palladium- and photoredox-catalyzed C?H olefination enables the synthesis of indoles. By using visible light, the direct C?H activation of aromatic enamines can be achieved and a variety of indole derivatives can be obtained in good yields under mild reaction conditions. PMID:25284332

Zoller, Jochen; Fabry, David C; Ronge, Meria A; Rueping, Magnus

2014-11-24

292

Synthesis and in vitro antitumor activity of phthalimide-based polymers containing camptothecin  

E-print Network

Synthesis and in vitro antitumor activity of phthalimide-based polymers containing camptothecin 2004 Abstract To improve the therapeutic efficacy of 20(s)-camptothecin (CPT) polymeric drugs,2,3,6-tetrahydrophthalimidoacetamidoglycine camptothecin ester (ETPA-gly-CPT), was synthesized by linking its hydroxyl group

Theodorakis, Emmanuel

293

Synthesis and biological activity of medium molecular weight polymers of camptothecin  

E-print Network

Synthesis and biological activity of medium molecular weight polymers of camptothecin Neung-Ju Lee. Keywords: 3,6-Endo-methylene-1,2,3,6-tetrahydrophthalimidohaxanoylcamptothecin; Camptothecin; Poly,10], neocarzinostatin [11], podophyllotoxin [12] and camptothecin (CPT) [13­16]. Among these compounds the CPT

Theodorakis, Emmanuel

294

Synthesis of conformationally locked carbocyclic nucleoside phosphonates to probe the active site of HIV-1 RT  

PubMed Central

The conformationally locked carbocyclic nucleoside phosphonates 2 and 2? and key intermediates for the synthesis of 3 and 3? were prepared from a chiral cyclopentene derivative and epicholorohydrine, respectively. The structure of the nucleoside precursor 6 was confirmed by X-ray crystallography. These carbocyclic nucleoside phosphonates were designed to probe their binding interactions at the active site of HIV-1-RT. PMID:18776534

Saneyoshi, Hisao; Vu, B. Christie; Hughes, Stephen H.; Boyer, Paul L.; Sarafianos, Stefan G.; Marquez, Victor E.

2009-01-01

295

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-Vzquez, Gabriel; Ypez, Lilin; Hernndez-Campos, Alicia; Tapia, Amparo; Hernndez-Luis, Francisco; Cedillo, Roberto; Gonzlez, Jos; Martnez-Fernndez, Antonio; Martnez-Grueiro, Mercedes; Castillo, Rafael

2003-10-15

296

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

Microsoft Academic Search

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

Alexander Burcat; Branko Ruscic

2005-01-01

297

Synthesis and antimicrobial activity of novel quinazolone derivatives.  

PubMed

Three novel series of 4-oxoquinazoline derivatives were prepared and evaluated as potential antimicrobial agents. Evaluation of the antimicrobial activity of a variety of 4-substituted-1-thiosemicarbazides, 3,4-disubstituted thiazolines, and 3-substituted-5-thiazolidones reveals that the majority possess significant in vitro activity against Gram-positive organisms. Some derivatives also exhibited antifungal activity. PMID:6381690

Habib, N S; Khalil, M A

1984-07-01

298

Green synthesis, characterization and catalytic activity of palladium nanoparticles by xanthan gum  

NASA Astrophysics Data System (ADS)

Here, we report the synthesis, characterization and catalytic evaluation of palladium nanoparticles (PdNPs) using xanthan gum, acting as both reducing and stabilizing agent without using any synthetic reagent. The uniqueness of our method lies in its fast synthesis rates using hydrothermal method in autoclave at a pressure of 15 psi and at 120 C temperature by 10 min time. The formation and size of the PdNPs were characterized by UV-visible spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. The catalytic activity of PdNPs was evaluated on the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride using spectrophotometry.

Santoshi kumari, Amrutham; Venkatesham, Maragoni; Ayodhya, Dasari; Veerabhadram, Guttena

2014-05-01

299

Synthesis of a Benzodiazepine-derived Rhodium NHC Complex by C-H Bond Activation  

SciTech Connect

The synthesis and characterization of a Rh(I)-NHC complex generated by C-H activation of 1,4-benzodiazepine heterocycle are reported. This complex constitutes a rare example of a carbene tautomer of a 1,4-benzodiazepine aldimine stabilized by transition metal coordination and demonstrates the ability of the catalytically relevant RhCl(PCy{sub 3}){sub 2} fragment to induce NHC-forming tautomerization of heterocycles possessing a single carbene-stabilizing heteroatom. Implications for the synthesis of benzodiazepines and related pharmacophores via C-H functionalization are discussed.

Bergman, Roberg G.; Gribble, Jr., Michael W.; Ellman, Jonathan A.

2008-01-30

300

Clofibrate-induced increases in peroxisomal proteins: effect on synthesis, degradation, and mRNA activity  

SciTech Connect

The effect of clofibrate on the polypeptide composition of peroxisomes was determined. A simple method was developed for the isolation of peroxisomes with a purity of 90-95% using sedimentation in a metrizamide gradient. The specific activities of HD did not change with clofibrate treatment so that the increases in enzyme activities are solely due to increases in protein amounts. The hepatic concentration of HD increased 63 times. The HD synthesis rate, as measured by the incorporation of (/sup 3/H)leucine, increased 74 times, so that the increase in the synthesis was sufficient to account for the increase in protein. Clofibrate caused no discernible change in the degradation rate of HD labeled with (/sup 14/C)bicarbonate. The half-life of HD was approximately 2 days. The translatable mRBA coding for HD increased 55 times. This value is not significantly different from the increase in HD protein or in HD synthesis. This observation was also true for several other peroxisomal proteins. Therefore, clofibrate causes an increase in the mRNA activity, which increases the synthesis of HD leading to an accumulation of protein and enzyme activity. The kinetics of the clofibrate-induced changes in HD synthesis rate, protein level, and enzymatic activity was analyzed using a simple model which included the half-lives of the drug, mRNA, and protein. The best fit of the model to the data gave an mRNA half-life of 10 hours and a protein half-life of 1.8 days, with no significant change by clofibrate.

Mortensen, R.M.

1983-01-01

301

Operation and maintenance of DOE/PETC Combustion Test Facilities. Final activity report, December 20, 1982-January 18, 1985  

SciTech Connect

On December 20, 1982, Management and Technical Services Company/General Electric (MATSCO/GE) began to operate, modify and maintain the Combustion Test Facilities at the Pittsburgh Energy Technology Center (PETC). The work is divided into three main programs: Alternate Fuels/In-House Research, Flue Gas Cleanup Research and Development, and Advanced Research and Technology Development. The objectives of the initial programs were to (1) retrofit the boilers with minimum modifications; (2) prepare CWM with coal concentrations that result in acceptable mixing, handling, and transport characteristics; (3) achieve stable CWM flames in boilers without supplemental fuel assistance; and (4) establish CWM combustion characteristics. In the 700-HP CTF, investigations into the effects on combustion of methanol addition, coal particle size, and oxygen enrichment of the combustion air were pursued, as well as evaluation of various burners, reduction of NO/sub x/ emissions through the introduction of staged air, and evaluation of anthracite CWM combustion. Work at the 100-HP CTF focused on investigation of coal particle size, use of various coal and petroleum by-products, the effects of long-term ash deposition in the boiler, and new burner nozzle adaptations. In December, 1983, MATSCO/GE assumed responsibilities of operation, modification, and maintenance of the Coal-Fired Flue Gas Cleanup Test Facility. The Dry Combined Flue Gas Cleanup PDU was completely built and shaken down, and formal testing of lime slurry injection into the flue gas for SO/sub 2//NO/sub x/ reduction was initiated. In the Copper Oxide Continuous Life Cycle PDU, construction of the furnace was completed and construction of the absorber and regenerator units was begun. 15 figs., 10 tabs.

Not Available

1985-01-01

302

Bimetallic Fe-Ni Oxygen Carriers for Chemical Looping Combustion  

SciTech Connect

The relative abundance, low cost, and low toxicity of iron make Fe-based oxygen carriers of great interest for chemical looping combustion (CLC), an emerging technology for clean and efficient combustion of fossil and renewable fuels. However, Fe also shows much lower reactivity than other metals (such as Ni and Cu). Here, we demonstrate strong improvement of Fe-based carriers by alloying the metal phase with Ni. Through a combination of carrier synthesis and characterization with thermogravimetric and fixed-bed reactor studies, we demonstrate that the addition of Ni results in a significant enhancement in activity as well as an increase in selectivity for total oxidation. Furthermore, comparing alumina and ceria as support materials highlights the fact that reducible supports can result in a strong increase in oxygen carrier utilization.

Bhavsar, Saurabh; Veser, Goetz

2013-11-06

303

Omaezallene from red alga Laurencia sp.: structure elucidation, total synthesis, and antifouling activity.  

PubMed

Natural antifouling products have been the subject of considerable attention. We screened marine algae for antifouling activity and discovered omaezallenes, the new bromoallene-containing natural products isolated from the red alga Laurencia?sp. Described is the isolation, structure elucidation, and total syntheses of omaezallenes. The relative and absolute configurations of natural omaezallenes were unambiguously established through total synthesis. The antifouling activities and ecotoxicity of omaezallenes were also evaluated. PMID:24616156

Umezawa, Taiki; Oguri, Yuko; Matsuura, Hiroshi; Yamazaki, Shohei; Suzuki, Masahiro; Yoshimura, Erina; Furuta, Takeshi; Nogata, Yasuyuki; Serisawa, Yukihiko; Matsuyama-Serisawa, Kazuyo; Abe, Tsuyoshi; Matsuda, Fuyuhiko; Suzuki, Minoru; Okino, Tatsufumi

2014-04-01

304

Stress protein synthesis and peroxidase activity in a submersed aquatic macrophyte exposed to cadmium  

Microsoft Academic Search

Sago pondweed (Potamogeton pectinatus L.) was exposed to CdCl to evaluate peroxidase (POD) activity and stress protein (SP) synthesis as potential biomarkers of contaminant stress in an aquatic plant. Peroxidase activity did not increase in sago pondweed incubated for 24 h in a liquid culture medium containing 0.5, 0.75, or 1 mM CdCl. By contrast, at each of these CdCl

Melanie M. Siesko; R. M. Grossfeld; W. J. Fleming

1997-01-01

305

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

PubMed

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

Pandurangan, N; Bose, Chinchu; Banerji, A

2011-09-15

306

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 AlgarFlynnOyamada method. Antioxidant activities of seabuckthorn extracts, isolated products and a number of flavone-3-ols have been determined. Structureactivity 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

307

Self-enhanced catalytic activities of functionalized graphene sheets in the combustion of nitromethane: molecular dynamic simulations by molecular reactive force field.  

PubMed

Functionalized graphene sheet (FGS) is a promising additive that enhances fuel/propellant combustion, and the determination of its mechanism has attracted much interest. In the present study, a series of molecular dynamic simulations based on a reactive force field (ReaxFF) are performed to explore the catalytic activity (CA) of FGS in the thermal decay of nitromethane (NM, CH3NO2). FGSs and pristine graphene sheets (GSs) are oxidized in hot NM liquid to increase their functionalities and subsequently show self-enhanced CAs during the decay. The CAs result from the interatomic exchanges between the functional groups on the sheets and the NM liquid, i.e., mainly between H and O atoms. CA is dependent on the density of NM, functionalities of sheets, and temperature. The GSs and FGSs that originally exhibit different functionalities tend to possess similar functionalities and consequently similar CAs as temperature increases. Other carbon materials and their oxides can accelerate combustion of other fuels/propellants similar to NM, provided that they can be dispersed and their key reaction steps in combustion are similar to NM. PMID:25055727

Zhang, Chaoyang; Wen, Yushi; Xue, Xianggui

2014-08-13

308

Activation of aluminum as an effective reducing agent by pitting corrosion for wet-chemical synthesis.  

PubMed

Metallic aluminum (Al) is of interest as a reducing agent because of its low standard reduction potential. However, its surface is invariably covered with a dense aluminum oxide film, which prevents its effective use as a reducing agent in wet-chemical synthesis. Pitting corrosion, known as an undesired reaction destroying Al and is enhanced by anions such as F?, Cl?, and Br? in aqueous solutions, is applied here for the first time to activate Al as a reducing agent for wet-chemical synthesis of a diverse array of metals and alloys. Specifically, we demonstrate the synthesis of highly dispersed palladium nanoparticles on carbon black with stabilizers and the intermetallic Cu?Sb/C, which are promising candidates, respectively, for fuel cell catalysts and lithium-ion battery anodes. Atomic hydrogen, an intermediate during the pitting corrosion of Al in protonic solvents (e.g., water and ethylene glycol), is validated as the actual reducing agent. PMID:23390579

Li, Wei; Cochell, Thomas; Manthiram, Arumugam

2013-01-01

309

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.

310

[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

311

Synthesis of cerium-activated strontium-magnesium orthophosphate phosphors  

Microsoft Academic Search

Cerium activated strontium-magnesium orthophosphate phosphors could be used in the manufacture of erithermal or copy machine lamps. Under short wave UV radiation, cerium activated strontium-magnesium orthophosphate exhibits strong UV luminescence with emission maximum at 370-380 nm. The luminescent emission depends on both host matrix composition and activator amount. Samples of (SrxMgy)3(PO4)2:Ce phosphors with variable composition, i.e., different Mg\\/Sr ratio and

Maria Vadan; Elisabeth-Jeanne Popovici; Laura Ungur; Cristina Ciocan; Ligia Pascu; D. Macarovici

2001-01-01

312

Derivatives of benzothiadiazole-7-carboxylates: synthesis and biological activity  

Microsoft Academic Search

Salicylic acid (SA) and methyl jasmonate (MJ) are important plant signal molecules to cause systemic acquired resistance (SAR), while its reported that they also have wide spectrum antitumor activities. Benzothiadiazole-7-carboxylates are plant activators\\u000a which can cause SAR just like SA and MJ. To investigate whether the benzothiadiazole-7-carboxylate family is endowed with anticancer activities, several benzothiadiazole-7-carboxylate\\u000a derivatives are synthesized and their

Weiping Zhu; Zhenjiang Zhao; Yufang Xu

2008-01-01

313

Synthesis and antibacterial activity of aminosugar-functionalized intercalating agents.  

PubMed

A series of previously reported amino sugar-functionalized intercalating agents, 3-14, were evaluated in two antibacterial assays (paper disk diffusion and 96-well microdilution) against Bacillus atrophaeus, ATCC 9372 and Escherichia coli, ATCC 47076. Although none of the compounds were active against this E. coli strain, several showed activity against B. atrophaeus. In anticipation of the need for larger amounts of these compounds for future structure-activity relationship studies, improved routes to 11-14 were developed. PMID:19926076

Shi, Wei; Marcus, Sandra L; Lowary, Todd L

2010-01-11

314

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

PubMed Central

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

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

1991-01-01

315

Synthesis and hypoglycemic activity of some new theophylline derivatives.  

PubMed

Thirty-one new theophylline derivatives have been synthesized and evaluated for their hypoglycemic activity. Compounds 24 (56% reduction) and 31 (57% reduction) showed better hypoglycemic activity than the standard drug glibenclamide which showed 52% reduction in serum glucose level. Compound 27 remarkably reduced serum glucose level by 53%. Ten compounds showed varying degrees of hypoglycemic activity ranging from 20 to 37% reduction in serum glucose level compared to the standard drug. The aromatic amide functionality is the common feature of these theophylline hypoglycemic derivatives. However, anthranilamide and or aliphatic amides proved to be the least active compounds in the present series. PMID:23701264

Alafeefy, Ahmed M; Alqasoumi, Saleh I; Abdel Hamid, Sami G; El-Tahir, Kamal E H; Mohamed, Menshawy; Zain, Mohamed E; Awaad, Amani S

2014-06-01

316

Synthesis and antiviral activity of certain second generation methylenecyclopropane nucleosides  

PubMed Central

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

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

2012-01-01

317

Emission phenomena in a SHS combustion wave  

Microsoft Academic Search

There are numerous experimental data indicating that the action of electromagnetic and magnetic fields on the combustion wave\\u000a of self-propagating high-temperature synthesis (SHS) changes the process kinetics and the structure and properties of the\\u000a reaction products. Emission phenomena in the combustion wave have received less attention. High rates of chemical energy dissipation\\u000a in SHS (1012 W\\/m3) are accompanied by physical

Yu. M. Maksimov; A. I. Kirdyashkin; R. M. Gabbasov; V. G. Salamatov

2009-01-01

318

Synthesis, magnetic properties and catalytic activity of hierarchical cobalt microflowers.  

PubMed

A simple one pot synthesis method for the silver catalyzed growth of pure hexagonal close packed cobalt by the reduction of cobalt salt using hydrazine hydrate in the presence of triethanolamine (TEA), diethanolamine (DEA) and ethylene glycol (EG) as capping agents at 90 degrees C within 10 min has been reported. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the product prepared in the presence of capping agents show the formation of the well defined porous flowery architecture originating from the interlinked 2D wavy nanoflakes. When the same reaction is performed in the absence of any capping agent, the agglomeration of the flakes of cobalt with irregular spherical morphology is observed. The effect of the reaction conditions on the size and the shape of the products have also been studied. Vibration sample magnetometer (VSM) shows, that the products are ferromagnetic in nature irrespective of the capping agents used and possess high value of coercivity, when prepared in the absence of any capping agent. These cobalt microflowers have also been proved as an alternative to the other available expensive catalysts (Au, Ag, Pt) in the room temperature production of p-aminophenol for its applications in pharmaceutical, photographic and plastic industries. PMID:22849064

Senapati, Samarpita; Srivastava, Suneel Kumar; Singh, Shiv Brat

2012-04-01

319

Combustion control  

Microsoft Academic Search

This patent describes an improved method of operating in a combustion process which is regulated by maintaining a preselected feed forward relationship of fuel input and air input. It comprises: establishing a fuel\\/air input peak relationship for the approximately stoichiometric condition which produces the maximum infrared radiation; selecting a desired operating fuel\\/air ratio based on a result of the fuel\\/air

Zabielski

1990-01-01

320

Synthesis, reactivity and biological activity of 5-alkoxymethyluracil analogues  

PubMed Central

Summary This review article summarizes the results of a long-term investigation of 5-alkoxymethyluracil analogues and is aimed, in particular, at methods of syntheses. Most of the presented compounds were synthesized in order to evaluate their biological activity, therefore, a brief survey of biological activity, especially antiviral, cytotoxic and antibacterial, is also reported. PMID:21804865

Brulikova, Lucie

2011-01-01

321

Synthesis and biological activities of thio-avarol derivatives.  

PubMed

Eleven new thio-avarol derivatives (3-13) were synthesized. Their antimicrobial, brine shrimp lethality, and free-radical scavenging activities and acetylcholinesterase inhibition, together with 12 already reported semisynthetic thio-avarol derivatives (14-25), were evaluated. Structure-activity relationships among these thio derivatives were determined. PMID:19007183

Pejin, Boris; Iodice, Carmine; Tommonaro, Giuseppina; De Rosa, Salvatore

2008-11-01

322

[Synthesis of analogues of acetohydroxam lacetic acid with phytotoxic activity].  

PubMed

Syntheses, spectroscopic data and phytotoxic activities of some N-acyl-O-alkylhydroxylamines, similar in structure to the natural compoud, methyl acetohydroxamyl acetate, are reported. Many of synthesized compounds show strong growth-inhibiting activity on both roots and coleoptiles of Triticum vulgare seedlings. PMID:1253963

Bellando, M; Frattini, C; Nano, G M

1976-03-01

323

Synthesis and antimicrobial activity of novel 5-aminoimidazole-4-carboxamidrazones.  

PubMed

A mild and simple method was developed to prepare a series of fifteen 5-aminoimidazole 4-carboxamidrazones, starting from the easily accessible 5-amino-4-cyanoformimidoyl imidazoles. The antimicrobial activity of these novel amidrazones was screened against Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli, Pseudomonas aeruginosa) bacteria and Candida sp. (Candida albicans, Candida krusei, Candida parapsilosis). Only a subset of compounds displayed fair-moderate activity against S. aureus and E. coli but all exhibited activity against Candida sp. The three most potent antifungal compounds were further tested against Cryptococcus neoformans, Aspergillus fumigatus and three dermatophytes (Trichophyton rubrum, Trichophyton mentagrophytes, Microsporum gypseum). These three hit compounds strongly inhibited C. krusei and C. neoformans growth, although their activity on filamentous fungi was very weak when compared to the activity on yeasts. PMID:25193230

Ribeiro, Ana I; Gabriel, Carla; Cerqueira, Ftima; Maia, Marta; Pinto, Eugnia; Sousa, Joo Carlos; Medeiros, Rui; Proena, M Fernanda; Dias, Alice M

2014-10-01

324

Synthesis and antimicrobial activity of 3-alkoxyjatrorrhizine derivatives.  

PubMed

The compounds 3-ethoxy- ( 2), 3-butoxy- ( 3), 3-hexyloxy- ( 4), 3-octyloxy- ( 5), 3-decyloxy- ( 6) and 3-dodecyloxyjatrorrhizine chlorides ( 7) were synthesized and tested for their antimicrobial activity in vitro to evaluate structure-activity relationships. Substitution of the H with alkyl groups at C-3-OH led to significant changes in the antimicrobial activity. The antimicrobial activity of the substituted derivatives was 32 - 1000 times higher than that of jatorrhizine ( 1), which increased as the aliphatic chain was elongated and then decreased slightly when the alkyl chain exceeded eight carbon atoms. 3-Octyloxyjatrorrhizine ( 5) displayed the highest antimicrobial activity of all compounds. The LD (50) values of compounds 1 - 7 were more than 6000 mg/kg body weight, showing a low toxicity. The toxicities of compounds 2 - 7 were slightly lower than that of ( 1). PMID:18300191

Wang, Li-jun; Ye, Xiao-li; Li, Xue-gang; Sun, Qing-lei; Yu, Gang; Cao, Xiao-gang; Liang, Yan-ting; Zhang, Hua-san; Zhou, Jia-zhou

2008-02-01

325

Design, Synthesis and Antiviral Activity Studies of Schizonepetin Derivatives  

PubMed Central

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

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

2013-01-01

326

Thermal solvent-free synthesis of chromonyl chalcones, pyrazolines and their in vitro antibacterial, antifungal activities.  

PubMed

A facile and ecofriendly synthesis of new chromonyl chalcones 3a-b from 3-formylchromone 1 and active methyl compounds 2a-b is reported under thermal solvent-free heating condition in good yields. The chromonyl chalcones 3a-b were used as intermediates under green condition for the synthesis of new bioactive pyrazoline derivatives 4a-f. The compounds were tested for antimicrobial activity by disk diffusion assay with slight modifications against Gram-positive, Gram-negative strains of bacteria as well as fungal strains. The investigation of antimicrobial screening revealed that compounds 3a-b and 4a-f showed antibacterial and antifungal activities. PMID:21612378

Siddiqui, Zeba N; Praveen, Shagufta; Musthafa, T N Mohammed; Ahmad, Anis; Khan, Asad U

2012-02-01

327

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

NASA Astrophysics Data System (ADS)

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

Gonzlez, C. P.; Montao, A. M.; Gonzlez, A. K.; Ros, C. A.

2014-06-01

328

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, Vnia L; Diniz, Cladio G; Le Hyaric, Mireille

2013-05-15

329

Synthesis and Biological Activity of a Gemcitabine Phosphoramidate Prodrug  

PubMed Central

A gemcitabine (2,2-difluorodeoxycytidine, dFdC) phosphoramidate prodrug designed for the intracellular delivery of gemcitabine 5-monophosphate was synthesized. The prodrug was about an order of magnitude less active than gemcitabine against wild-type cells, and the nucleoside transport inhibitor dipyridamole reduced prodrug activity. The prodrug was more active than gemcitabine against two deoxycytidine kinase-deficient cell lines. The results suggest that the prodrug is a potent growth inhibitor that can bypass dCK deficiency at higher drug concentrations. PMID:17602464

Wu, Weidong; Sigmond, Jennifer; Peters, Godefridus J.; Borch, Richard F.

2008-01-01

330

Synthesis and biological activities of diflunisal hydrazidehydrazones  

Microsoft Academic Search

Several diflunisal hydrazidehydrazone derivatives namely 2?,4?-difluoro-4-hydroxybiphenyl-3-carboxylic acid [(5-nitro-2-furyl\\/substitutedphenyl)methylene] hydrazide (3ao) 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. Gniz Kkgzel; Adil Mazi; Fikrettin Sahin; Suzan ztrk; James Stables

2003-01-01

331

Long Lasting Protein Synthesis- and Activity-Dependent Spine Shrinkage and Elimination after Synaptic Depression  

PubMed Central

Neuronal circuits modify their response to synaptic inputs in an experience-dependent fashion. Increases in synaptic weights are accompanied by structural modifications, and activity dependent, long lasting growth of dendritic spines requires new protein synthesis. When multiple spines are potentiated within a dendritic domain, they show dynamic structural plasticity changes, indicating that spines can undergo bidirectional physical modifications. However, it is unclear whether protein synthesis dependent synaptic depression leads to long lasting structural changes. Here, we investigate the structural correlates of protein synthesis dependent long-term depression (LTD) mediated by metabotropic glutamate receptors (mGluRs) through two-photon imaging of dendritic spines on hippocampal pyramidal neurons. We find that induction of mGluR-LTD leads to robust and long lasting spine shrinkage and elimination that lasts for up to 24 hours. These effects depend on signaling through group I mGluRs, require protein synthesis, and activity. These data reveal a mechanism for long lasting remodeling of synaptic inputs, and offer potential insights into mental retardation. PMID:23951097

Ramiro-Corts, Yazmn; Israely, Inbal

2013-01-01

332

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

PubMed Central

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

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

2013-01-01

333

Synthesis, topoisomerase I inhibitory and cytotoxic activities of chromone derivatives.  

PubMed

A series of chromone derivatives were designed as potential topoisomerase I (Top I) inhibitors based on the docking simulation study. Sixteen synthesized compounds were evaluated for Top I inhibitory activity and some compounds were further tested for in vitro cytotoxic activity. The most potent inhibitor, chromone 11b showed greater inhibitory activity (IC50 = 1.46 ?M) than the known Top I inhibitors, i.e., camptothecin, fisetin and morin, but inactive against breast cancer cell (MCF-7), oral cavity cancer cell (KB) and small cell lung cancer (NCI-H187). Chromone 11c, another potent inhibitor (IC50 = 6.16 ?M), exhibited cytotoxic activity against KB (IC50 = 73.32 ?M) and NCI-H187 (IC50 = 36.79 ?M). PMID:23030699

Maicheen, Chirattikan; Jittikoon, Jiraphun; Vajragupta, Opa; Ungwitayatorn, Jiraporn

2013-05-01

334

Heavy metal-activated synthesis of peptides in Chlamydomonas reinhardtii  

SciTech Connect

In this study, the authors have addressed the capacity of the green alga Chlamydomonas reinhardtii to produce metal-binding peptides in response to stress induced by the heavy metals Cd{sup 2+}, Hg{sup 2+}, and Ag{sup +}. Cells cultured in the presence of sublethal concentrations of Cd{sup 2+} synthesized and accumulated oligopeptides consisting solely of glutamic acid, cysteine, and glycine in an average ratio of 3:3:1. Cadmium-induced peptides were isolated in their native form as higher molecular weight peptide-metal complexes with an apparent molecular weight of approximately 6.5 {times} 10{sup 3}. The isolated complex bound cadmium (as evidenced by absorption spectroscopy) and sequestered (with a stoichiometry of 0.7 moles of cadmium per mole of cysteine) up to 70% of the total cadmium found in extracts of cadmium-treated cells. In Hg{sup 2+}-treated cells, the principal thiol-containing compound induced by Hg{sup 2+} ion was glutathione. It is possible that glutathione functions in plant cells (as it does in animal cells) to detoxify heavy metals. Cells treated with Ag{sup +} ions also synthesized a sulfur-containing component with a charge to mass ratio similar to Cd{sup 2+}-induced peptides. But, in contrast to the results obtained using Cd{sup 2+} as an inducer, these molecules did not accumulate to significant levels in Ag{sup +}-treated cells. The presence of physiological concentrations of Cu{sup 2+} in the growth medium blocked the synthesis of the Ag{sup +}-inducible component(s) and rendered cells resistant to the toxic effects of Ag{sup +}, suggesting competition between Cu{sup 2+} and Ag{sup +} ions, possibly at the level of metal uptake.

Howe, G.; Merchant, S. (Univ. of California, Los Angeles (United States))

1992-01-01

335

Synthesis and anti-inflammatory activity of indole glucosinolates.  

PubMed

The nitronate and nitrovinyl methods to synthesize indole glucosinolates (GLs) have been investigated. The results were applied to generally the most prevalent natural indole glucosinolates to synthesize 4-methoxyglucobrassicin (MGB) and neo-glucobrassicin (NGB) in moderate overall yield for the first time. The anti-inflammatory activity of the synthetic indole GLs was determined by inhibition of TNF-? secretion in LPS-stimulated THP-1 cells. The data showed that glucobrassicin (GB) exhibited higher activity than other synthetic indolyl GLs. PMID:24360830

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

2014-01-15

336

The synthesis and surface active properties of certain amphoteric compounds  

Microsoft Academic Search

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

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

1963-01-01

337

Synthesis and antibacterial activity of nitroaryl thiadiazole-levofloxacin hybrids.  

PubMed

Novel levofloxacin-containing hybrids carrying a 5-(nitroaryl)-1,3,4-thiadiazol-2-yl group were synthesized and evaluated in vitro against Gram-positive and Gram-negative bacteria. Preliminary data indicated that levofloxacin-nitrofuran and levofloxacin-nitroimidazole hybrids have a potent activity against Gram-positive organisms with enhanced anti-staphylococcal activity compared with the parent quinolone (N-desmethyl levofloxacin). PMID:17036368

Foroumadi, Alireza; Mansouri, Shahla; Emami, Saeed; Mirzaei, Javad; Sorkhi, Maedeh; Saeid-Adeli, Nosratollah; Shafiee, Abbas

2006-11-01

338

Synthesis, characterization and optical properties of Ce3+ activated CaMgAl10O17 phosphor  

NASA Astrophysics Data System (ADS)

Phosphor material CaMgAl10O17 with varying concentration of rare earth Ce3+ synthesis by combustion method at 500C. The synthesized phosphor material characterized for their crystallinity and nature by XRD measurements. The photoluminescence measurements of phosphor exhibit mainly two PL spectra 382nm and 575 nm in blue and red region, respectively, this is due to crystal field and covalence effect. These results show that concentration quenching occur at 5mol of Ce dopant. The results suggest the possibility of utilizing as a phosphor may be in solid state lighting.

Selot, Anupam; Aynyas, Mahendra; Tiwari, Manoj; Dev, Kapil

2014-04-01

339

Origami-inspired active structures: a synthesis and review  

NASA Astrophysics Data System (ADS)

Origami, the ancient art of paper folding, has inspired the design of engineering devices and structures for decades. The underlying principles of origami are very general, which has led to applications ranging from cardboard containers to deployable space structures. More recently, researchers have become interested in the use of active materials (i.e., those that convert various forms of energy into mechanical work) to effect the desired folding behavior. When used in a suitable geometry, active materials allow engineers to create self-folding structures. Such structures are capable of performing folding and/or unfolding operations without being kinematically manipulated by external forces or moments. This is advantageous for many applications including space systems, underwater robotics, small scale devices, and self-assembling systems. This article is a survey and analysis of prior work on active self-folding structures as well as methods and tools available for the design of folding structures in general and self-folding structures in particular. The goal is to provide researchers and practitioners with a systematic view of the state-of-the-art in this important and evolving area. Unifying structural principles for active self-folding structures are identified and used as a basis for a quantitative and qualitative comparison of numerous classes of active materials. Design considerations specific to folded structures are examined, including the issues of crease pattern identification and fold kinematics. Although few tools have been created with active materials in mind, many of them are useful in the overall design process for active self-folding structures. Finally, the article concludes with a discussion of open questions for the field of origami-inspired engineering.

Peraza-Hernandez, Edwin A.; Hartl, Darren J.; Malak, Richard J., Jr.; Lagoudas, Dimitris C.

2014-09-01

340

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

PubMed

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

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

2014-01-01

341

Synthesis and characterization of Fe doped mesoporous Al 2 O 3 by solgel method and its use in trichloroethylene combustion  

Microsoft Academic Search

Two mesoporous alumina samples were synthesized using the solgel method, and these samples were tested as catalysts in trichloroethylene\\u000a combustion reaction. One alumina sample was doped with Fe to study the influence of a small amount of this agent on the characteristics\\u000a and properties of alumina as a catalyst. Both catalysts (pure alumina and alumina doped with Fe) were thoroughly

Carlos J. Lucio-Ortiz; Javier Rivera De la Rosa; Aracely Hernandez Ramirez; Jose A. De los Reyes Heredia; Paz del Angel; Severino Muoz-Aguirre; Lina M. De Len-Covin

2011-01-01

342

Synthesis and antibacterial activity of nitroaryl thiadiazole-gatifloxacin hybrids.  

PubMed

A number of gatifloxacin analogues containing a nitroaryl-1,3,4-thiadiazole moiety attached to the piperazine ring at C-7 position were prepared and evaluated as antibacterial agents against a panel of gram-positive and gram-negative bacteria. Among synthesized compounds, nitrofuran analog 6a exhibited more potent inhibitory activity against gram-positive bacteria including Staphylococcus epidermidis (MIC=0.0078 microg/mL), Bacillus subtilis (MIC=0.0039 microg/mL), Enterococcus faecalis (MIC=0.125 microg/mL) and Micrococcus luteus (MIC=0.125 microg/mL), with respect to other synthesized compounds and reference drug gatifloxacin. The target compounds were also assessed for their cytotoxic activity against normal mouse fibroblast (NIH/3T3) cells using MTT assay. The results indicated that these compounds exhibit antibacterial activity at non-cytotoxic concentrations. PMID:18950903

Jazayeri, Seyyedehsamira; Moshafi, Mohammad Hassan; Firoozpour, Loghman; Emami, Saeed; Rajabalian, Saeed; Haddad, Mitra; Pahlavanzadeh, Farahnaz; Esnaashari, Manzarbanoo; Shafiee, Abbas; Foroumadi, Alireza

2009-03-01

343

Synthesis and anticonvulsant activity of novel purine derivatives.  

PubMed

A series of new purines containing triazole and other heterocycle substituents was synthesized and evaluated for their preliminary anticonvulsant activity and neurotoxicity by using the maximal electroshock (MES), subcutaneous pentylenetetrazole (scPTZ) and rotarod neurotoxicity (TOX) tests. Among the compounds studied, 9-decyl-6-(1H-1,2,4-triazol-1-yl)-9H-purine (5e) was the most potent compound, with a median effective dose of 23.4 mg/kg and a high protective index of more than 25.6 after intraperitoneal administration in mice. Compound 5e showed significant oral activity against MES-induced seizures in mice, with an ED50 of 39.4 mg/kg and a PI above 31.6. These results demonstrate that compound 5e possesses better anticonvulsant activity and is safer than the commercially available drugs carbamazepine and valproate in MES, scPTZ and TOX models. PMID:25062008

Wang, Shi-Ben; Jin, Peng; Li, Fu-Nan; Quan, Zhe-Shan

2014-09-12

344

Synthesis and Antiinflammatory Activity of Newer Pyrazolinylbenzidines and Isoxazolinylbenzidines  

PubMed Central

In an effort to search for more active antiinflammatory agent, a series of pyrazolinylbenzidines and isoxazolylbenzidines was designed, synthesized, and screened for their potential as novel orally inflammation inhibitors. Compounds 4,4-bis-(1-acetyl-5-substitutedaryl-2-pyrazolin-3-yl)benzidines (8-13) and 4,4-bis-(2-substitutedaryl-isoxazolin-4-yl)benzidines (14-19) have been synthesized from 4,4-bis-(substituted benzylidenyl-acetyl)benzidines (2-7). The structures of the products have been delineated by spectral and elemental analysis. Compounds 2-19 evaluated for antiinflammatory activity and acute toxicity and results are reported. The compound 4,4-bis-[1-acetyl-5-(p-methoxyphenyl)-2-pyrazolin-3-yl)benzidine (9) showed more potent and dose-dependent antiinflammatory activity in comparison to reference drug.

Sharma, S.; Saxena, K. K.

2014-01-01

345

Antituberculosis: Synthesis and Antimycobacterial Activity of Novel Benzimidazole Derivatives  

PubMed Central

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

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

2013-01-01

346

Synthesis and evaluation of antibacterial activities of andrographolide analogues.  

PubMed

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 found to be much more potent than the parent Andro in inhibiting bacterial growth and quorum sensing system. Compounds 5 and 7 significantly reduced virulence factor production. Compound 7 completely inhibited Pseudomonas aeruginosa (P. aeruginosa) biofilm formation, and exhibited synergistic activity with conventional antibiotics. These findings suggest that compound 7 may be the basis for future drug development to combat the unmet needs of virulence factor production, biofilm formation and antibiotic resistance. PMID:19152987

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

2009-07-01

347

Synthesis and antiproliferative activity of thiazolidine analogs for melanoma.  

PubMed

We have previously described 2-aryl-thiazolidine-4-carboxylic acid amides as a novel class of antiproliferative agents for prostate cancer. Screening these compounds with melanoma cell lines revealed that several of them have potent antiproliferative activity and selectivity against melanoma. To further improve the potency and selectivity, we synthesized a new series of analogs and tested them in two melanoma cell lines and fibroblast cells (negative controls). Comparison of anticancer effects of these compounds with a standard chemotherapeutic agent, sorafenib, showed that they are very effective in killing melanoma cells with low micromolar to nanomolar antiproliferative activity and provide us a new lead for developing potential drugs for melanoma. PMID:17561392

Li, Wei; Lu, Yan; Wang, Zhao; Dalton, James T; Miller, Duane D

2007-08-01

348

Synthesis, tautomeric structures, and antitumor activity of new perimidines.  

PubMed

New series of perimidine derivatives and fused perimidines were derived from the reaction of ketene aminals 1 and 2 with diazotized anilines or hydrazonoyl chlorides. In addition, 8,10-disubstituted-[1,2,4]triazolo[4,3-a]perimidines (20a-m) were prepared through the reaction of perimidine-2-thione (15) with hydrazonoyl chlorides. The structures of the newly synthesized compounds were established on the basis of spectral data and elemental analyses. Some products were investigated for their antitumor activities against the human breast cancer cell line MCF-7 and the liver carcinoma cell line HEPG-2, and the results of some derivatives showed promising activity. PMID:23553920

Farghaly, Thoraya A; Mahmoud, Huda K

2013-05-01

349

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; Hernndez-Campos, Alicia; Ypez, Lilin; Hernndez-Luis, Francisco; Navarrete-Vzquez, Gabriel; Tapia, Amparo; Corts, Rafael; Hernndez, Manuel; Castillo, Rafael

2002-08-19

350

Synthesis and anti-microbial activity of hydroxylammonium ionic liquids.  

PubMed

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

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

2011-06-01

351

Synthesis and Antimycobacterial Activity of 2,1?-Dihydropyridomycins  

PubMed Central

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

2012-01-01

352

Synthesis and biological activity of some derivatives of rifamycin P.  

PubMed

A series of derivatives of rifamycin P, an antibiotic produced by fermentation of a mutant strain of Nocardia mediterranea or by chemical modification of rifamycin S, have been prepared. The structures of these compounds were determined by 1H NMR, IR, UV, and LC/MS. Their in vitro and in vivo antibacterial activities in comparison with rifampicin and two other rifamycins under investigation were evaluated. The derivatives were more active than rifamycin P against Mycobacterium avium complex and other slowly and rapidly growing nontuberculous mycobacteria which frequently cause systemic infection in patients with AIDS. 2'-(Diethylamino)rifamycin P (P/DEA) appears suitable for further investigation. PMID:2329569

Cavalleri, B; Turconi, M; Tamborini, G; Occelli, E; Cietto, G; Pallanza, R; Scotti, R; Berti, M; Roman, G; Parenti, F

1990-05-01

353

Synthesis of Y3Ba5Cu8O18 superconductor powder by auto-combustion reaction: Effects of citrate-nitrate ratio  

NASA Astrophysics Data System (ADS)

In this experiment, nanocrystalline Y3Ba5Cu8O18 superconductor powder was prepared by citrate-nitrate auto-combustion reaction. A series of Y3Ba5Cu8O18 precursor gels with different citrate-nitrate ratio ranged from 0.3 to 1.0 have been prepared by varying the amount of citric acid added. The auto-combustion reaction during drying process transformed the precursor gels into ashes powder that upon calcinations at 900 C yield Y3Ba5Cu8O18 nanocrystalline powders. The TG/DTA analysis reveals that the precursor gels with 0.3 ? c/n < 1.0 decomposed in a single-step reaction combusted at temperature of around 230 C. Established from XRD and SEM characterization, the Y3Ba5Cu8O18 calcined powder prepared from c/n = 0.7 precursor gels has got the orthorhombic structure with smallest particle size (?10 nm) compared to the rest of the batches. Samples with c/n = 0.5 and 0.7 appeared in this work to be electrically superconducting at temperature above 100 K as measured using standard four-probe technique. This emphasized on maintaining a stoichiometric or near stoichiometric reaction for the analysis.

Suan, Mohd Shahadan Mohd; Johan, Mohd Rafie; Chua Siang, Tat

2012-10-01

354

Synthesis and Antibacterial Activity of Pentacyclines: A Novel Class of Tetracycline Analogs  

PubMed Central

Employing a highly efficient total synthesis approach, we synthesized and evaluated for antibacterial activity diverse and novel pentacycline analogs with systematic variations at C7, C8, C9, and C10. Certain substitution groups, as well as substitution patterns at various positions, were found to be preferred for increased antibacterial activity. A number of pentacycline analogs displayed potent activity in vitro and in vivo, especially against Gram-positive organisms. Several analogs have also shown promising oral bioavailability in rats and cynomolgus monkey. PMID:21500832

2011-01-01

355

Synthesis and SAR study of modulators inhibiting tRXR?-dependent AKT activation  

PubMed Central

RXR? represents an intriguing and unique target for pharmacologic interventions. We recently showed that Sulindac and a designed analog could bind to RXR? and modulate its biological activity, including inhibition of the interaction of an N-terminally truncated RXR? (tRXR?) with the p85? regulatory subunit of phosphatidylinositol-3-OH kinase (PI3K). Here we report the synthesis, testing and SAR of a series of novel analogs of Sulindac as potential modulators for inhibiting tRXR?-dependent AKT activation. A new compound 30 was identified to have improved biological activity. PMID:23434637

Wang, Zhi-Gang; Chen, Liqun; Chen, Jiebo; Zheng, Jian-Feng; Gao, Weiwei; Zeng, Zhiping; Zhou, Hu; Zhang, Xiao-kun; Huang, Pei-Qiang; Su, Ying

2013-01-01

356

Analysis and synthesis of distributed-lumped-active networks by digital computer  

NASA Technical Reports Server (NTRS)

The use of digital computational techniques in the analysis and synthesis of DLA (distributed lumped active) networks is considered. This class of networks consists of three distinct types of elements, namely, distributed elements (modeled by partial differential equations), lumped elements (modeled by algebraic relations and ordinary differential equations), and active elements (modeled by algebraic relations). Such a characterization is applicable to a broad class of circuits, especially including those usually referred to as linear integrated circuits, since the fabrication techniques for such circuits readily produce elements which may be modeled as distributed, as well as the more conventional lumped and active ones.

1973-01-01

357

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. PMID:22373086

2011-01-01

358

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

359

Ageing mechanisms on PdO x-based catalysts for natural gas combustion in premixed burners  

Microsoft Academic Search

The ageing effect induced by S-compounds over 2%Pd\\/CeO22ZrO2, 2%Pd\\/LaMnO32ZrO2 and 2%Pd\\/BaCeO32ZrO2 catalysts for CH4 combustion was investigated; S-compounds are in fact added as odorants in the natural gas network for safety purposes. Pd-based catalysts were prepared by solution combustion synthesis (SCS), starting from metal nitrates\\/glycine mixtures. Basic characterization (XRD, BET, FESEM analysis), FTIR studies and catalytic activity tests were performed

Stefania Specchia; Pietro Palmisano; Elisabetta Finocchio; Guido Busca

2010-01-01

360

N-Deoxyribosides of ergot alkaloids: Synthesis and biological activity  

Microsoft Academic Search

N-Deoxyribosides of agroclavine (1), lysergol (2), and 9,10-dihydrolysergol (3) were prepared by SnCl4 -catalyzed N-glycosylation of their TMS derivatives with 1-chloro-3,5-di-O-toluoyl-2-deoxy-D-ribofuranose. None of the new compounds exhibited activity against HIV.

Vladimr K?en; Petr Olovsk; Vladimr Havl?ek; Petr Sedmera; Myriam Witvrouw; Erik De Clecq

1997-01-01

361

Heteroatom Analogues of Hydrocodone: Synthesis and Biological Activity  

PubMed Central

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

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

2013-01-01

362

Synthesis and anticancer activity of a series of norcantharidin analogues.  

PubMed

Cantharidin (1) and norcantharidin (2) display high levels of anticancer activity against a broad range of tumour cell lines. Synthetic manipulation of norcantharidin yields (3S,3aR,4S,7R,7aS)-3-hydroxyhexahydro-4,7-epoxyisobenzofuran-1(3H)-one (3), which also displays a high level of anticancer activity against tumour cells but interestingly, shows selectivity towards HT29 (colon; GI(50) = 14 ?M) and SJ-G2 (glioblastoma; GI(50) = 15 ?M) cell lines. Substitution at the hydroxyl group of the cyclic lactone within (3) produces a diasteromeric pair of products that have no difference in cytotoxicity over the cell lines tested. Incorporation of an isopropyl tail at this position (16) produced the most promising compound of this series to date, with strong selectivity towards HT29 (colon; GI(50) = 19 ?M) and SJ-G2 (glioblastoma; GI(50) = 21 ?M) cell lines but completely void of any activity against the remaining tumour cell lines (GI(50) > 100 ?M), as per the parent molecule. We also discovered that the introduction of a terminal phosphate moiety (28) at the same position produced a different trend in cytotoxicity with strong activity in BE2-C (neuroblastoma; GI(50) = 9 ?M) cells; suggestive of an alternate mode of action. PMID:22796041

Tarleton, Mark; Gilbert, Jayne; Sakoff, Jennette A; McCluskey, Adam

2012-08-01

363

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

PubMed

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

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

2007-06-01

364

Synthesis of novel substituted tetrazoles having antifungal activity  

Microsoft Academic Search

In an effort to find potent antifungal agents, a variety of triazole derivatives with a 5-substituted tetrazole structure 6, 7, 12 and 14 were prepared and evaluated for antifungal activity against Candida spp., Cryptococcus neoformans, and Aspergillus spp. in vitro. The location of the methyl group at the C-3 of compounds 12 and 14 has been demonstrated to be a

Ram Shankar Upadhayaya; Sanjay Jain; Neelima Sinha; Nawal Kishore; Ramesh Chandra; Sudershan K Arora

2004-01-01

365

Synthesis and Vasorelaxant Activity of New Coumarin and Furocoumarin Derivatives  

Microsoft Academic Search

We have synthesized a new series of coumarins and furocoumarins and evaluated their vasorelaxant activity in rat aorta rings pre-contracted with noradrenaline or by depolarisation with high KCl. The new furocoumarins relax smooth vascular muscle with a profile similar to that of khellin (a furochromone that directly relaxes smooth muscle) and at a greater potency, suggesting that these compounds have

Manuel Campos-Toimil; Francisco Orallo; Lourdes Santana; Eugenio Uriarte

2002-01-01

366

Synthesis and Biological Activity of Bimorpholine and its Carbanucleoside  

Microsoft Academic Search

A new enantiomerically pure carbacyclic nucleoside analogue with bimorpholine as a nonaromatic nucleobase was synthesized. The nucleoside analogue and bimorpholine were tested for cytotoxicity using an MTT assay and the xCELLigence System. Both assays revealed that compound 3 was highly cytotoxic at a 50 ?M concentration while the cytotoxic effect of compound 1 was much less prominent. No antiretroviral activity

Kerti Ausmees; Anastasia Selyutina; Kristel Ktt; Kristin Lippur; Tnis Pehk; Margus Lopp; Eva usinaite; Andres Merits; Tnis Kanger

2011-01-01

367

Starburst99: Synthesis Models for Galaxies with Active Star Formation  

Microsoft Academic Search

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

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

1999-01-01

368

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

369

Synthesis, anticancer activity and structure-activity relationship of some anticancer agents based on cyclopenta (b) thiophene scaffold.  

PubMed

Methods for the synthesis of new heterocyclic systems of thieno (3,2-d)- (1,2,3)-triazine derivatives and N-(3-cyano-5,6-dihydro-4H-cyclopenta (b) thiophene derivatives have been developed. The newly synthesized compounds were tested in vitro against human breast carcinoma cell line (MCF-7). Compounds 7 and 9 have shown the highest activity among the two synthesized series. The results of this study have led to the identification of two lead compounds with good inhibitory activities that can confirm the design of the next generation inhibitors of tyrosine kinase with fewer side effects such as hepatotoxicity and resistance. PMID:25015456

Said, Mohamed; Elshihawy, Hosam

2014-07-01

370

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

PubMed Central

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

Bukowska-Faniband, Ewa; Hederstedt, Lars

2013-01-01

371

Synthesis of silver nanoparticles with antibacterial activity using the lichen Parmotrema praesorediosum.  

PubMed

Development of a green chemistry process for the synthesis of silver nanoparticles has become a focus of interest. This would offer numerous benefits, including ecofriendliness and compatibility for biomedical applications. Here we report the synthesis of silver nanoparticles from the reduction of silver nitrate and an aqueous extract of the lichen Parmotrema praesorediosum as a reductant as well as a stabilizer. The physical appearance of these silver nanoparticles was characterized using ultraviolet-visible spectroscopy, electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction techniques. The results show that silver nanoparticles synthesized using P. praesorediosum have an average particle size of 19 nm with a cubic structure. The antibacterial activity of the synthesized silver nanoparticles was tested against eight micro-organisms using the disk diffusion method. The results reveal that silver nanoparticles synthesized using P. praesorediosum have potential antibacterial activity against Gram-negative bacteria. PMID:24379670

Mie, Ropisah; Samsudin, Mohd Wahid; Din, Laily B; Ahmad, Azizan; Ibrahim, Nazlina; Adnan, Siti Noor Adnalizawati

2014-01-01

372

Total synthesis of racemic and (R) and (S)-4-methoxyalkanoic acids and their antifungal activity.  

PubMed

The total synthesis of 4-methoxydecanoic acid and 4-methoxyundecanoic acid in racemic and stereoselective [(R) and (S)] forms has been accomplished. For stereoselective synthesis of the compounds (S) and (R)-BINOL complexes have been used to generate the required chiral centres. The antifungal activity of these compounds has been studied against different organisms and the results were found to be impressive. The activity of the compounds in racemic and in stereoselective forms was compared. (R)-4-Methoxydecanoic acid was found to be most potent (MIC: 0.019 mg/mL against Candida albicans MTCC 227, C. albicans MTCC 4748, Aspergillus brasiliensis (niger) MTCC 281 and Issatchenkia orientalis MTCC 3020). PMID:21555164

Das, Biswanath; Shinde, Digambar Balaji; Kanth, Boddu Shashi; Kamle, Avijeet; Kumar, C Ganesh

2011-07-01

373

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

PubMed

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

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

2012-02-01

374

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

E-print Network

Zi and A. aerogenes. Inhibition by CTP and a sigmoidal velocity- substrate plot were demonstrated when aspartate concentration was varied. The effects of heat-treatment of ATCase resulted in in- f creased inhibition by CIP, a phenomenon unlike that seen... CONTROL OF ENZYME SYNTHESIS. DISCUSSION. . ~ ~ LITERATURE CITED. VITA. 11 20 26 32 34 vii LIST OF TABLES Tab le l. Inhibition of ATCase. Page 19 2. Levels of ATCase specific activity of wild type strain PRLR3 and mutant strain HA14...

Deutsch, Walter Andrew

2012-06-07

375

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

E-print Network

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

Falkinham, Joseph

376

Solvent-Free Synthesis of Some 1,5-Benzothiazepines and Benzodiazepines and Their Antibacterial Activity  

Microsoft Academic Search

An efficient and convenient synthesis of 1, 5-benzothiazepines (3a-3f) and 1, 5-benzodiazepines (4a-4f) from chalcones (2a-2f) by the action of o-amino thiophenol and o-phenylenediamine in the presence of inorganic support is reported. These compounds are characterized by elemental analysis and spectral studies viz: IR, H NMR, and C NMR. Newly synthesized compounds were screened for their antibacterial activity against ?

R. K. Saini; Y. C. Joshi; P. Joshi

2008-01-01

377

Synthesis of optically active bisdifluorocyclopropanes through a chemo-enzymatic reaction strategy  

Microsoft Academic Search

The first synthesis of bisdifluorocyclopropane derivatives has been accomplished via a chemo-enzymatic reaction strategy; (E)- or (Z)-3-tributylstannyl-2-propenols were prepared and their conversion led to the (trans,trans)- and (cis,cis)-bisdifluorocyclopropanes. The subsequent lipase-catalyzed reaction efficiently afforded optically active (trans,trans)-2,2,5,5-tetrafluoro-1,6-bis(hydroxymethyl)bicyclopropane.

Koichi Mitsukura; Satoshi Korekiyo; Toshiyuki Itoh

1999-01-01

378

Cross-linked crystals of hydroxynitrile lyase as catalyst for the synthesis of optically active cyanohydrins  

Microsoft Academic Search

Purified hydroxynitrile lyase (HNL) from Manihot esculenta was crystallized by the sitting-drop vapour-diffusion method. The bipyramidal crystals formed (1020 ?m) were cross-linked with different amounts of glutaraldehyde and used as biocatalyst for the synthesis of optically active cyanohydrins. The cross-linked crystals were more stable than Celite-immobilized enzymes when incubated in organic solvents, especially in polar solvents. After six consecutive batch

David Costes; Ernst Wehtje; Patrick Adlercreutz

2001-01-01

379

Easy access to Evans' oxazolidinones. Stereoselective synthesis and antibacterial activity of a new 2-oxazolidinone derivative.  

PubMed

An interesting new approach was developed for the synthesis of Evans' chiral auxiliaries with excellent yields. In turn, another new stereoselective and efficient strategy has also allowed for the preparation of a 2-oxazolidinone derivative in 34% overall yield from the Morita-Baylis-Hillman adduct. The antibacterial activity of this oxazolidinone was tested against Staphylococcus aureus strains isolated from animals with mastitis infections. PMID:24914892

Diaz, Gaspar; de Freitas, Michelle A A; Ricci-Silva, Maria E; Diaz, Marisa A N

2014-01-01

380

Synthesis and HIV-1 integrase inhibitory activities of caffeic acid dimers derived from Salvia officinalis.  

PubMed

The synthesis of two caffeoyl-coumarin conjugates, derived from sagecoumarin, has been accomplished, starting from ferulic acid, isoferulic acid and sesamol. Both compounds exhibited potent inhibitory activities at micromolar concentrations against HIV-1 integrase in 3'-end processing reaction but were less effective against HIV-1 replication in a single-round infection assay of HeLa-beta-gal-CD4+ cells. PMID:16183277

Bailly, Fabrice; Queffelec, Clmence; Mbemba, Gladys; Mouscadet, Jean-Franois; Cotelle, Philippe

2005-11-15

381

Total synthesis and antihypertensive activity of (+/-)7,8-dihydroxy-3-methyl-isochromanone-4.  

PubMed

This letter describes the total synthesis, preliminary biological evaluation and mechanism studies of a novel and structurally unique isochromanone, (+/-)7,8-dihydroxy-3-methyl-isochromanone-4 (1), a nature product contained in banana (Musa sapientum L.) peel. The bioassay showed that compound 1 displays potent antihypertensive activity in renal hypertensive rats and further mechanism studies revealed that it is an ACE inhibitor. PMID:19233642

Liu, Jie; Ren, Hao; Xu, Jinyi; Bai, Renren; Yan, Qi; Huang, Wenlong; Wu, Xiaoming; Fu, Jihua; Wang, Qiujuan; Wu, Qian; Fu, Rong

2009-03-15

382

Synthesis of Pyrimidine Incorporated Piperazine Derivatives and their Antimicrobial Activity  

PubMed Central

Thiophene substituted chalcones (1a-e) were cyclised with thiourea in presence of potassium hydroxide to get 4-substituted-6-(thiophen-2-yl)pyrimidine-2-thiols (2a-e) which were then stirred with methyl iodide to obtain 4-substituted-2-(methylsulfanyl)-6-(thiophen-2-yl)pyrimidines (3a-e). Compounds (3a-e) were refluxed with different N-methylpiperazine and N-phenylpiperazine to afford 4-substituted-2-(4-methylpiperazin-1-yl)-6-(thiophen-2-yl)pyrimidines (4a-e) and 4-substituted-2-(4-phenylpiperazin-1-yl)-6-(thiophen-2-yl)pyrimidines (5a-e). The structures of all the newly synthesised compounds 4b, 4d, 5a and 5b showed good antibacterial activity at 40?g/mlconcentration. Compounds 4a, 4d, 4e, 5c and 5e showed significant antifungal activity at 40 ?g/ml concentration compared with standard drugs.

Thriveni, K. S.; Padmashali, B.; Siddesh, M. B.; Sandeep, C.

2014-01-01

383

Synthesis and antioxidant activities of Coenzyme Q analogues.  

PubMed

A series of 2,3-dimethoxy-5-methyl-1,4-benzoquinones (Coenzyme Q) substituted at the C-6 position with various groups were designed and synthesized based on the Coenzyme Q10 as potent antioxidant. Invitro antioxidant activities of these compounds were evaluated and compared with commercial antioxidant Coenzyme Q10 employing DPPH assay. All these synthesized Coenzyme Q analogues are found to exhibit good antioxidant activities. Of which Compound 8b bearing a N-benzoylpiperazine group at the C-6 position showed more potent inhibition of DPPH radical than Coenzyme Q10. All these results suggested the applicability of the Coenzyme Q analogues as potent antioxidants for combating oxidative stress. PMID:25232967

Wang, Jin; Li, Shuo; Yang, Tao; Yang, Jian

2014-10-30

384

Synthesis and herbicidal activity of substituted pyrazole isothiocyanates.  

PubMed

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

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

2012-01-01

385

Design, synthesis, and vasorelaxation activity of novel imperatorin derivatives.  

PubMed

In this study, a series of novel imperatorin derivatives 7a-7e were designed and synthesized. Their vasorelaxation activities were evaluated by the pharmacological experiments in vitro. Most of the tested compounds exhibited better water solubility and vasorelaxation activity in different degrees, especially 7b and 7c with EC50 values of 2.29 and 2.63?M, respectively on mesenteric artery, 7d and 7e with EC50 values of 1.04 and 2.65?M, respectively on brain artery. The results indicated that these novel compounds have a potential interest for the development of novel and potent vasorelaxant agents for different kinds of arteries. PMID:23659576

Zhou, Nan; He, Jian-Yu; Wang, Tao; Zhang, Jie; He, Huai-Zhen

2013-01-01

386

Natural tetraponerines: a general synthesis and antiproliferative activity.  

PubMed

A stereocontrolled general methodology to access all natural tetraponerines from (+)-T1 to (+)-T8 is detailed. Two consecutive indium-mediated aminoallylations with the appropriate enantiomer of chiral N-tert-butylsulfinamide and a thermodynamic control at the aminal stereocenter allow the formation of each natural tetraponerine with excellent stereoselectivity. The use of 4-bromobutanal in the first aminoallylation leads to the formation of 5-6-5 tetraponerines, while 5-bromopentanal is required to build the scaffold of 6-6-5 tetraponerines. A cross-metathesis reaction of the second aminoallylation product with cis-3-hexene is used to elongate the side chain up to 5 carbons so as to prepare the tetraponerines T5 to T8. The anticancer activity of these heavier tetraponerines against four different carcinoma human cell lines is examined, observing a promising cytotoxic activity of (+)-T7 against breast carcinoma cell line MCF-7. PMID:24731136

Bosque, Irene; Gonzalez-Gomez, Jose C; Loza, Mara Isabel; Brea, Jos

2014-05-01

387

Synthesis and antiprotozoal activity of nitazoxanide-N-methylbenzimidazole hybrids.  

PubMed

A series of a novel hybrid compounds between nitazoxanide and N-methylbenzimidazole were synthesized starting from the corresponding N-methyl-2-nitroanilines. The new hybrid compounds (1-13) were evaluated in vitro against Giardia intestinalis, Entamoeba histolytica, Trichomonas vaginalis. NTZ, MTZ and ABZ were used as drug standards. Experimental evaluations revealed all of the new compounds (1-13) were active and showed strong activity against the three protozoa, particularly with E. histolytica where the IC50 values ranged between 3 and 69 nM. Overall, compounds 2, 5, 7, 8, 9, 11 and 12 stood out with values lower than 87 nM for all three protozoa, comparatively better than the reference drugs. PMID:24183540

Soria-Arteche, Olivia; Hernndez-Campos, Alicia; Ypez-Mulia, Lilin; Trejo-Soto, Pedro Josu; Hernndez-Luis, Francisco; Gres-Molina, Jorge; Maldonado, Luis A; Castillo, Rafael

2013-12-15

388

Synthesis and cytotoxic activity of novel curcumin analogues  

Microsoft Academic Search

Five novel curcumin analogues bearing different substituents at 4-position of phenyl group were synthesized. Their structures were confirmed by NMR and HRMS spectrum. Their cytotoxic activities against six tumor cell lines were tested by the standard MTT assay in vitro. The results indicated that four analogues (1A1C, 1E) with solubilizing moieties showed selective potent cytotoxicity against HepG2, HeLa and CT26

Qin Zhang; Yao Fu; Hao Wei Wang; Tao Gong; Yong Qin; Zhi Rong Zhang

2008-01-01

389

Synthesis and biological activity of amide derivatives of nimbolide  

Microsoft Academic Search

Nimbolide (1), a limonoid isolated from Azadirachta indica, is the chief cytotoxic principle in Neem leaves extract. Using nimbolide as a lead compound for anti-cancer analogue design, a series of nimbolide derivatives have been synthesized and evaluated for in vitro cytotoxic activity against a panel of human cancer cell lines. Out of 10 compounds screened 2g, 2h and 2i showed

B. S. Sastry; K. Suresh Babu; T. Hari Babu; S. Chandrasekhar; P. V. Srinivas; A. K. Saxena; J. Madhusudana Rao

2006-01-01

390

The Structural Basis of Ribosome Activity in Peptide Bond Synthesis  

Microsoft Academic Search

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

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

2000-01-01

391

Synthesis of some heterocycles of potential biological activity  

Microsoft Academic Search

A convenient method for the preparation of imidazobenzimidazole3, imidazoimidazole5, imidazotriazole6 and pyrano [2, 3-c] oxazole7 derivatives is described. This depends on interaction of 2-methyl-4-arylidene-2-oxazolin-5-ones1 with o-diamines, thiosemicarbazide and\\/or ethylcyanoacetate. The effect of alcoholic potassium cyanide on oxazolinone1 was studied. Antibacterial activity of the obtained products was studied.

Abd Elfattah Ali Harb; Fatma H. Mostafa; Saoud A. Metwally

1990-01-01

392

Synthesis and Radioprotective Activity of New Organosilicon and Germanium Compounds  

PubMed Central

Silathiazolidine and metalladithioacetals (M = Si, Ge) have been prepared by the interaction of dialkyldichloro- or bis(diethylamino)dialkylsilanes and -germanes with 3-[N-(2- thioethyl)]amino-propanamide (WR-2529) and [1-thioethyl-2-(1-naphtylmethyl)]-2- imidazoline. The study of these compounds in the field of chemical radioprotection has shown a notable decrease in the toxicity and a rather large increase in the radioprotective activity of these new derivatives in comparison with the starting organic compounds. PMID:18475835

Rima, Ghassoub; Dagiral, Rodolphe; Lion, Claude; Fatome, Marc; Roman, Vincent; Laval, Jean-Denis

1998-01-01

393

Influence of Mechanical Activation on Synthesis of Zinc Metatitanate  

Microsoft Academic Search

Investigations of a ZnO-TiO2 binary oxide mixture during mechanical treatment were mainly focused on obtaining orthotitanate Zn2TiO4 with a spinel structure. Due to the specific way of energy transfer during mechanical treatment using a high-energy ball mill, the system passes through low temperature ZnTiO3 metatitanate phase formation. Mechanical activation was performed on an equimolar ratio mixture of ZnO and TiO2.

N. Labus; N. Obradovi?; T. Sre?kovi?; V. Miti?; M. M. Risti?

394

Carbocyclic Analogues of Inosine-5'-Monophosphate: Synthesis and Biological Activity  

PubMed Central

9-(4-Phosphonomethoxy-2-cyclopenten-1-yl)hypoxanthine and 9-(4-phosphonomethoxy-2,3-dihydroxycyclopenten-1-yl)hypoxanthine were synthesized as isosteric carbocyclic analogues of inosine-5-monophosphate. The synthesized compounds were shown to be capable of inhibiting the activity of human type II inosine-5?-monophosphate dehydrogenase (IMPDH II) (IC50 = 500 M) and to have no significant effects on the growth ofMycobacterium tuberculosis. PMID:23346382

Matyugina, E.S.; Andreevskaya, S.N.; Smirnova, T.G.; Khandazhinskaya, A.L.

2012-01-01

395

On the active sites for higher oxygenate synthesis over Rh  

SciTech Connect

A knowledge of the reactivity of adsorbed species and activity of sites in essential for the elucidation of the mechanism of a catalytic reaction on supported metal. Transient infrared study reveals that linear CO adsorbed on single Rh sites is involved in CO insertion leading to the formation of higher oxygenates. This mechanistic information suggests that the selectivity to higher oxygenates can be enhanced by blocking bridged CO sites and increasing the concentration of single Rh sites.

Chuang, S.S.C.; Balakos, M.W.; Brundage, M.A.; Krishnamurthy, R. [Univ. of Akron, OH (United States). Dept. of Chemical Engineering

1994-12-31

396

Synthesis, characterization and antibacterial activity of salicyloyl chitosan  

Microsoft Academic Search

Salicyloyl chitosan (SCS) with different degrees of substitution (DS) and molecular weight (MW) were synthesized from chitosan and salicylic acid. Their structures were characterized by UV, FTIR, 1H NMR and XRD, which showed that the acylate reaction took place at the N-position of chitosan. The DS value of SCS ranged from 0.10 to 0.71. The antibacterial activities were assessed according

Guanghua He; Xu Chen; Yihua Yin; Hua Zheng; Xiong Xiong; Yumin Du

2011-01-01

397

Design and Synthesis of a Novel Triptycene-Based Ligand for Modeling Carboxylate-Bridged Diiron Enzyme Active Sites  

E-print Network

A novel triptycene-based ligand with a preorganized framework was designed to model carboxylate-bridged diiron active sites in bacterial multicomponent monooxygenase (BMM) hydroxylase enzymes. The synthesis of the ...

Li, Yang

398

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

PubMed Central

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

Jeon, Woo Hyung

2014-01-01

399

Synthesis and anticonvulsant activity of N-(2-hydroxyethyl) cinnamamide derivatives.  

PubMed

A series of novel N-(2-hydroxyethyl) cinnamamide derivatives were synthesized and screened for their anticonvulsant activities by the maximal electroshock (MES) test and their neurotoxicity was evaluated by the rotarod neurotoxicity test (Tox). The MES test showed that compounds I(N-(2-hydroxyethyl) cinnamamide) and 1d ((E)-3-(3-fluorophenyl)-N-(2-hydroxyethyl)acrylamide) were found to possess better anticonvulsant activity but also had lower toxicity. In the anti-MES potency test, these compounds exhibited median effective dose (ED(50)) of 17.7 and 17.0 mg/kg, respectively, and median toxicity dose (TD(50)) of 154.9 and 211.1, respectively, resulting in a protective index (PI) of 8.8 and 12.4, respectively, which is much greater than the PI of the marked antiepileptic drug carbamazepine. To further investigate the effects of the anticonvulsant activity in several different models, compounds I and 1d were tested against convulsions induced by chemical substances, including pentylenetetrazole (PTZ), isoniazid, 3-mercaptopropionic acid, and thiosemicarbazide. PMID:19272675

Guan, Li-Ping; Wei, Cheng-Xi; Deng, Xian-Qing; Sui, Xin; Piao, Hu-Ri; Quan, Zhe-Shan

2009-09-01

400

Plumbagin analogs-synthesis, characterization, and antitubercular activity  

PubMed Central

Considering the emerging problem of drug resistance in tuberculosis, there is an urgent need of development of new analogs that are useful in curing drug resistant tuberculosis. In India, tuberculosis continues to remain one of the most pressing health problems. India is the highest tuberculosis burden country in the world, accounting one fifth of global incidence - estimated 2.0-2.5 million cases annually. In 2011, approximately 8.7 million new cases of tuberculosis and 1.4 million people die from tuberculosis each year worldwide. Current antitubercular therapies are successful against normal tuberculosis but it is not suitable for drug resistant tuberculosis. In this study Plumbagin analogs, obtained from Plumbago zeylanica (Family-Plumbaginaceae), have been synthesized. Out of the various synthesized analogs, the antitubercular activity of compound a and b was evaluated using standard H37Rv and S, H, R, and E sensitive M tuberculosis strains using LRF assay method. Compound a showed strong activity against both standard H37Rv and S, H, R and E sensitive M. tuberculosis strains as compared to standard Rifampicin. The other compounds are proved to be more active against standard H37Rv and S, H, R and E sensitive M. tuberculosis strain as compared to Rifampicin. PMID:24696815

Nayak, Nishi; Bajpai, Meenakshi; Razdan, Balkishen

2014-01-01

401

PPAR?: energy combustion, hypolipidemia, inflammation and cancer  

PubMed Central

The peroxisome proliferator-activated receptor ? (PPAR?, or NR1C1) is a nuclear hormone receptor activated by a structurally diverse array of synthetic chemicals known as peroxisome proliferators. Endogenous activation of PPAR? in liver has also been observed in certain gene knockout mouse models of lipid metabolism, implying the existence of enzymes that either generate (synthesize) or degrade endogenous PPAR? agonists. For example, substrates involved in fatty acid oxidation can function as PPAR? ligands. PPAR? serves as a xenobiotic and lipid sensor to regulate energy combustion, hepatic steatosis, lipoprotein synthesis, inflammation and liver cancer. Mainly, PPAR? modulates the activities of all three fatty acid oxidation systems, namely mitochondrial and peroxisomal ?-oxidation and microsomal ?-oxidation, and thus plays a key role in energy expenditure. Sustained activation of PPAR? by either exogenous or endogenous agonists leads to the development of hepatocellular carcinoma resulting from sustained oxidative and possibly endoplasmic reticulum stress and liver cell proliferation. PPAR? requires transcription coactivator PPAR-binding protein (PBP)/mediator subunit 1(MED1) for its transcriptional activity. PMID:20414453

Pyper, Sean R.; Viswakarma, Navin; Yu, Songtao; Reddy, Janardan K.

2010-01-01

402

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

PubMed Central

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

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

2013-01-01

403

Signaling regulates activity of DHCR24, the final enzyme in cholesterol synthesis.  

PubMed

The role of signaling in regulating cholesterol homeostasis is gradually becoming more widely recognized. Here, we explored how kinases and phosphorylation sites regulate the activity of the enzyme involved in the final step of cholesterol synthesis, 3?-hydroxysterol ?24-reductase (DHCR24). Many factors are known to regulate DHCR24 transcriptionally, but little is known about its posttranslational regulation. We developed a system to specifically test human ectopic DHCR24 activity in a model cell-line (Chinese hamster ovary-7) using siRNA targeted only to hamster DHCR24, thus ensuring that all activity could be attributed to the human enzyme. We determined the effect of known phosphorylation sites and found that mutating certain residues (T110, Y299, and Y507) inhibited DHCR24 activity. In addition, inhibitors of protein kinase C ablated DHCR24 activity, although not through a known phosphorylation site. Our data indicate a novel mechanism whereby DHCR24 activity is regulated by signaling. PMID:24363437

Luu, Winnie; Zerenturk, Eser J; Kristiana, Ika; Bucknall, Martin P; Sharpe, Laura J; Brown, Andrew J

2014-03-01

404

Synthesis, anticandidal activity and cytotoxicity of some tetrazole derivatives.  

PubMed

In this study, 14 different 2-[(1-methyl-1H-tetrazole-5-yl)thio]-1-(phenyl)ethanone derivatives (1-14) were synthesized. The structures of the obtained compounds were elucidated using IR, (1)H-NMR, (13)C-NMR and FAB(+)-MS spectral data and elemental analyses results. The compounds were screened for their anticandidal activity using the microbroth dilution method and for their cytotoxic effects using the MTT assay against NIH/3T3 cells. Some of the compounds were found to be potent anticandidal agents with weak cytotoxicities. PMID:23323990

Kaplancikli, Zafer Asim; Yurtta?, Leyla; zdemir, Ahmet; Turan-Zitouni, Glhan; I?can, Gkalp; Akal?n, Gl?en; Abu Mohsen, Usama

2014-02-01

405

Design, synthesis and anticancer activity of oxoaporphine alkaloid derivatives.  

PubMed

A series of new oxoaporphine derivatives were synthesized and their inhibitory activity of topoisomerase I, cytotoxicity and DNA-binding properties were studied. Oxoaporphine can strongly inhibit topoisomerase I at concentrations of 5-50?M and the cytotoxicity of the derivatives are more potent than their lead compound. Hypochromism, broadening and red shift in the absorption spectra were observed when these compounds bind to calf thymus DNA (CT DNA). These spectral characteristics were consistent with the intercalative binding of these compounds. PMID:24964344

Wei, Yong-Biao; Li, Ying-Xin; Song, Hui; Feng, Xian-Jin

2014-10-01

406

Synthesis and biological activity of bimorpholine and its carbanucleoside.  

PubMed

A new enantiomerically pure carbacyclic nucleoside analogue with bimorpholine as a nonaromatic nucleobase was synthesized. The nucleoside analogue and bimorpholine were tested for cytotoxicity using an MTT assay and the xCELLigence System. Both assays revealed that compound 3 was highly cytotoxic at a 50 ?M concentration while the cytotoxic effect of compound 1 was much less prominent. No antiretroviral activity was detected for this compound. In contrast, it acted as a potent inhibitor of hepatitis C virus (HCV) replication. Most likely this effect originates largely from the cytotoxicity of the compound; however, it is possible that a specific mechanism of HCV inhibition also exists. PMID:22060554

Ausmees, Kerti; Selyutina, Anastasia; Ktt, Kristel; Lippur, Kristin; Pehk, Tnis; Lopp, Margus; Zusinaite, Eva; Merits, Andres; Kanger, Tnis

2011-11-01

407

Synthesis and psychotropic activity of functionally substituted diaziridines and bisdiaziridines  

SciTech Connect

The authors examine the psychotropic activity of diaziridines which differ considerable in their structures and the C- and N-substituents. Diaziridines are monoamine oxidase inhibitors in the brain and, thus, are potential antidepressants. The acute toxicities and some pharmacological effects of diaziridines are shown. Mice were used in the experiments. The bisdiaziridines obtained differ in their /sup 1/H and /sup 13/C NMR spectra. The effect is presented of functionally substituted diaziridines on the effects of reserpine, 5-hydroxytryptophan, tryptamine, corazole, and apomorphine hypothermia.

Kostyanovskii, R.G.; Shustov, G.V.; Nabiev, O.G.; Denisenko, S.N.; Sukhanova, S.A.; Lavretskaya, E.F.

1987-04-01

408

Synthesis and catalytic activity of polysaccharide templated nanocrystalline sulfated zirconia  

NASA Astrophysics Data System (ADS)

Nanoscaled materials are of great interest due to their unique enhanced optical, electrical and magnetic properties. Sulfate-promoted zirconia has been shown to exhibit super acidic behavior and high activity for acid catalyzed reactions. Nanocrystalline zirconia was prepared in the presence of polysaccharide template by interaction between ZrOCl2?8H2O and chitosan template. The interaction was carried out in aqueous phase, followed by the removal of templates by calcination at optimum temperature and sulfation. The structural and textural features were characterized by powder XRD, TG, SEM and TEM. XRD patterns showed the peaks of the diffractogram were in agreement with the theoretical data of zirconia with the catalytically active tetragonal phase and average crystalline size of the particles was found to be 9 nm, which was confirmed by TEM. TPD using ammonia as probe, FTIR and BET surface area analysis were used for analyzing surface features like acidity and porosity. The BET surface area analysis showed the sample had moderately high surface area. FTIR was used to find the type species attached to the surface of zirconia. UV-DRS found the band gap of the zirconia was found to be 2.8 eV. The benzylation of o-xylene was carried out batchwise in atmospheric pressure and 433K temperature using sulfated zirconia as catalyst.

Sherly, K. B.; Rakesh, K.

2014-01-01

409

2-Phenylaminonaphthoquinones and related compounds: Synthesis, trypanocidal and cytotoxic activities.  

PubMed

A series of new 2-aminonaphthoquinones and related compounds were synthesized and evaluated in vitro as trypanocidal and cytotoxic agents. Some tested compounds inhibited epimastigote growth and trypomastigote viability. Several compounds showed similar or higher activity and selectivity as compared with current trypanocidal drug, nifurtimox. Compound 4l exhibit higher selectivity than nifurtimox against Trypanosoma cruzi in comparison with Vero cells. Some of the synthesized quinones were tested against cancer cells and normal fibroblasts, showing that certain chemical modifications on the naphthoquinone moiety induce and excellent increase the selectivity index of the cytotoxicity (4g and 10). The results presented here show that the anti-T. cruzi activity of 2-aminonaphthoquinones derivatives can be improved by the replacement of the benzene ring by a pyridine moiety. Interestingly, the presence of a chlorine atom at C-3 and a highly lipophilic alkyl group or aromatic ring are newly observed elements that should lead to the discovery of more selective cytotoxic and trypanocidal compounds. PMID:25127463

Sieveking, Ivan; Thomas, Pablo; Estvez, Juan C; Quiones, Natalia; Cullar, Mauricio A; Villena, Juan; Espinosa-Bustos, Christian; Fierro, Anglica; Tapia, Ricardo A; Maya, Juan D; Lpez-Muoz, Rodrigo; Cassels, Bruce K; Estvez, Ramon J; Salas, Cristian O

2014-09-01

410

Utilization of blended fluidized bed combustion (FBC) ash and pulverized coal combustion (PCC) fly ash in geopolymer  

Microsoft Academic Search

In this paper, synthesis of geopolymer from fluidized bed combustion (FBC) ash and pulverized coal combustion (PCC) fly ash was studied in order to effectively utilize both ashes. FBC-fly ash and bottom ash were inter-ground to three different finenesses. The ashes were mixed with as-received PCC-fly ash in various proportions and used as source material for synthesis of geopolymer. Sodium

Prinya Chindaprasirt; Ubolluk Rattanasak

2010-01-01

411

Combustion synthesis and luminescence properties of yellow-emitting phosphors Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+}  

SciTech Connect

Graphical abstract: A yellow-emitting phosphor Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} was firstly synthesized by the solution-combustion method. The photoluminescence excitation and emission spectra, temperature dependence of luminescence intensity, and luminescence lifetime of the phosphor were investigated. Highlights: Black-Right-Pointing-Pointer Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} phosphor was synthesized by a solution-combustion method. Black-Right-Pointing-Pointer Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} showed an intense yellow emission band centered at 569 nm with the CIE coordinate of (0.453, 0.526). Black-Right-Pointing-Pointer The temperature dependent luminescence property and mechanism of Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} were studied. -- Abstract: Yellow-emitting phosphor Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} was synthesized by a solution-combustion method. The phase structure and microstructure were determined by the X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis, respectively. The as-prepared Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} phosphor absorbed near ultraviolet and blue light of 320-500 nm, and showed an intense yellow emission band centered at 569 nm with the CIE coordinate of (0.453, 0.526). The lifetime of Eu{sup 2+} ions in Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} phosphor was measured, furthermore the temperature dependent luminescence property and mechanism were studied, which also testified that the present phosphor had a promising potential for white light-emitting diodes.

Xia, Zhiguo, E-mail: xiazg426@yahoo.com.cn [School of Materials Sciences and Technology, China University of Geosciences, Beijing 100083 (China)] [School of Materials Sciences and Technology, China University of Geosciences, Beijing 100083 (China); Liao, Libing, E-mail: lbliao@cugb.edu.cn [School of Materials Sciences and Technology, China University of Geosciences, Beijing 100083 (China)] [School of Materials Sciences and Technology, China University of Geosciences, Beijing 100083 (China); Zhang, Zepeng; Wang, Yafang [School of Materials Sciences and Technology, China University of Geosciences, Beijing 100083 (China)] [School of Materials Sciences and Technology, China University of Geosciences, Beijing 100083 (China)

2012-02-15

412

Synthesis and pharmacological activity of 1-aryl-s-alkylaminopropanes  

SciTech Connect

In a search for novel antiarrhythmic drugs, some compounds of general formula ArCR/sup 1/R/sup 2/CHR/sup 3/NR/sub 2/ x HCl have been synthesized in which the structures of the aromatic and aliphatic moieties of the molecule have been varied. The elemental analyses of the compounds obtained are given, as are the spectral properties of the stereoisomers. The studies show that in this series of compounds the highest antiarrhythmic activity is possessed by the erythro-isomers of arylalkylaminopropanols bearing a tetralin ring in the aromatic moiety of the molecule and an isopropylamino-group attached to the aromatic moiety of the branched chain.

Anichkov, S.V.; Dumpis, M.A.; Krasnova, E.I.

1987-03-01

413

Synthesis and Activity of Novel Acylthiourea with Hydantoin  

PubMed Central

The 41 novel acylthiourea derivatives with hydantoin were synthesized in moderate to excellent yields by using 5-(4-aminophenyl)- and 5-(4-aminobenzyl)- hydantoin or 5-(4-aminobenzyl)-thiohydantoin as raw materials and characterized by IR, 1H NMR spectra and elementary analysis. The preliminary bioassay showed that these compounds exhibit certain selectively herbicidal activities with the 91%, 94% and 87% inhibition rates of 7l, 8o and 8p against B. campestris, 100%, 100% and 95% efficacy against B. campestris in a greenhouse test, respectively. 7a, 7b, 7c and 7d exhibited 74%, 79%, 79% and 71% inhibition rates against F. oxysporum, respectively. PMID:24077124

Han, Jintao; Dong, Hongbo; Xu, Zhihong; Wang, Jinmin; Wang, Mingan

2013-01-01

414

Design, synthesis, antinociceptive and anti-inflammatory activities of novel piroxicam analogues.  

PubMed

In this paper we report the design, synthesis, antinociceptive and anti-inflammatory activities of a series of benzothiazine N-acylhydrazones 14ah, planned by structural modification of piroxicam (1), a non steroidal anti-inflammatory drug. Among the synthesized analogues, compounds 14f (LASSBio-1637) and 14g (LASSBio-1639) were identified as novel antinociceptive and anti-inflammatory prototypes, active by oral administration, acting by a mechanism of action that seems to be different from that of piroxicam, since they were inactive as an inhibitor of cyclooxygenase (COX-1 and COX-2) at concentrations of 10 mM. PMID:23192189

de Miranda, Amanda Silva; Bispo Jnior, Walfrido; da Silva, Yolanda Karla Cupertino; Alexandre-Moreira, Magna Suzana; Castro, Rosane de Paula; Sabino, Jos Ricardo; Lio, Luciano Morais; Lima, Ldia Moreira; Barreiro, Eliezer J

2012-01-01

415

Synthesis of highly active visible-light-driven colloidal silver orthophosphate  

NASA Astrophysics Data System (ADS)

The present study deals with the synthesis of highly uniform and spherical visible-light-driven colloidal silver phosphate (Ag 3PO 4) with the size of 200 nm. These colloidal particles showed excellent photocatalytic activity for the removal of different dyes and pesticide under sunlight-type excitation. The photocatalytic activity of these particles, obtained by colloidal method, was found to be much higher than silver phosphate obtained by precipitation method, or titanium dioxide, or zinc oxide under identical conditions. The effect of catalyst amount and recyclability on the photocatalytic response of Ag 3PO 4 was also investigated.

Khan, A.; Qamar, M.; Muneer, M.

2012-01-01

416

Synthesis and anticonvulsant activities of N-benzyl (2R)-2-acetamido-3-oxysubstituted propionamide derivatives  

PubMed Central

Lacosamide has been submitted for regulatory approval in the United States and Europe for the treatment of epilepsy. Previous synthetic methods did not permit the elaboration of the structureactivity relationship (SAR) for the 3-oxy site in lacosamide. We report an expedient five-step stereospecific synthesis for N-benzyl (2R)-2-acetamido-3-oxysubstituted propionamide analogs beginning with d-serine methyl ester. The procedure incorporated alkyl (e.g. methyl, primary, secondary, and tertiary) and aryl groups at this position. The SAR for the 3-oxy site showed maximal activity in animal seizure models for small 3-alkoxy substituents. PMID:18789868

Morieux, Pierre; Stables, James P.; Kohn, Harold

2009-01-01

417

Synthesis and polymorphic control for visible light active titania nanoparticles  

NASA Astrophysics Data System (ADS)

Titania (TiO2) is useful for many applications in photocatalysis, antimicrobials, pigment, deodorization, and decomposition of harmful organics and undesirable compounds in the air and waste water under UV irradiation. Among the three phases of TiO2, Rutile, Anatase, and Brookite, studies have been more focused on the anatase and rutile phases. Pure brookite is the most difficult phase to prepare, even under hydrothermal conditions. Predominantly brookite phase TiO2 nanoparticles were prepared by the Water-based Ambient Condition Sol (WACS) process in our laboratory. The objectives of this research were to enhance visible light active (VLA) photocatalytic properties of polymorphic brookite TiO2 by minimizing the lattice defects and narrowing band gap of titania by nitrogen and/or carbon chromophone, and to investigate the deactivation, reusability, and regeneration of the VLA titania in order to design better titania catalysts for organic compound degradation applications. In order to study the influence of hydroxyl content on photocatalytic activities (PCAs) of polymorphic titania nanoparticles, the WACS samples were post-treated by a Solvent-based Ambient Condition Sol (SACS) process in sec-butanol (sec-BuOH). All samples were characterized for phase composition, surface area, hydroxyl contamination, and particle morphology by x-ray diffraction, N2 physisorption, FT-IR, solid state 1H NMR and scanning electron microscopy, and then compared to a commercial titania, Degussa P25. Evaluation of methyl orange (MO) degradation under UV irradiation results showed that the lower lattice hydroxyl content in SACS titania enhanced the PCA. As-prepared titania and SACS samples, which have similar surface areas and crystallinity, were compared in order to prove that the superior PCA came from the reduction in the lattice hydroxyl content. To enhance PCA and VLA properties of WACS, an alternative high boiling point polar solvent, N-methylpyrrolidone (NMP), was utilized in the SACS process at a higher treatment temperature to modify polymorphic titania nanoparticles. This SACS sample was called "SACS-NMP". SACS, using NMP as the solvent, could also extract lattice hydroxyls, and decorate nitrogen on the titania surface. The PCA of SACS-NMP was superior to that of SACS-sec-BuOH. Nitrogen incorporation of SACS-NMP titania was investigated by CHN analysis and x-ray photoelectron spectroscopy (XPS). VL absorbance for all samples was characterized by UV-Vis absorption spectrophotometry. PCA of MO degradation under UV and VL showed that SACS-NMP is a powerful treatment to enhance PCA by minimizing lattice hydroxyls and doping the titania surface with nitrogen. The effect of calcination conditions on SACS-NMP samples was also studied. The calcination conditions, especially the temperature and calcination atmosphere, have an influence on the BET surface area, crystallite size, titania phase content, and PCA under VL irradiation. SACS-NMP samples calcined in air at 200C for 2 hours showed the best VL activated photocatalytic performance in this research. Additionally, the SACS-NMP sample exhibited superior VL properties to several available reference anatase titania samples. This could be explained as the effective charge separation by the intercrystalline electron transport from brookite to anatase grains complemented by strong VL absorption by the nitrogen species in NMP. The deactivation and regeneration of the VLA titania were investigated and compared to a commercial titania, Kronos VLP7000. PCA of the titania under VL for MO decolorization gradually decreased with increasing testing time and the number of runs. The cause of the deactivation was identified as the deposition of the decomposed MO or the carbonaceous deposit. Among the possible regeneration procedures for used SACS-NMP samples, methanol washing was shown to be the most effective up to 80% of the PCA recovery. Accordingly, the SACS-NMP samples could not be completely recovered since a regeneration process would possibly remove some of nitrogen species responsib

Kaewgun, Sujaree

418

Rhodium mediated bond activation: from synthesis to catalysis  

SciTech Connect

Recently, our lab has developed monoanionic tridentate ligand, To{sup R}, showing the corresponding coordination chemistry and catalyst reactivity of magnesium, zirconium, zinc and iridium complexes. This thesis details synthetic chemistry, structural study and catalytic reactivity of the To{sup R}-supported rhodium compounds. Tl[To{sup R}] has been proved to be a superior ligand transfer agent for synthesizing rhodium complexes. The salt metathesis route of Tl[To{sup M}] with [Rh({mu}-Cl)(CO)]{sub 2} and [Rh({mu}- Cl)(COE)]{sub 2} gives To{sup M}Rh(CO){sub 2} (2.2) and To{sup M}RhH({eta}{sup 3}-C{sub 8}H{sub 13}) (3.1) respectively while Tl[To{sup P}] with [Rh({mu}-Cl)(CO)]{sub 2} affords To{sup P}Rh(CO){sub 2} (2.3). 2.2 reacts with both strong and weak electrophiles, resulting in the oxazoline N-attacked and the metal center-attacked compounds correspondingly. Using one of the metal center-attacked electrophiles, 2.3 was demonstrated to give high diastereoselectivity. Parallel to COE allylic C-H activation complex 3.1, the propene and allylbenzene allylic C-H activation products have also been synthesized. The subsequent functionalization attempts have been examined by treating with Brnsted acids, Lewis acids, electrophiles, nucleophiles, 1,3-dipolar reagents and reagents containing multiple bonds able to be inserted. Various related complexes have been obtained under these conditions, in which one of the azide insertion compounds reductively eliminates to give an allylic functionalization product stoichiometrically. 3.1 reacts with various primary alcohols to give the decarbonylation dihydride complex To{sup M}Rh(H){sub 2}CO (4.1). 4.1 shows catalytic reactivity for primary alcohol decarbonylation under a photolytic condition. Meanwhile, 2.2 has been found to be more reactive than 4.1 for catalytic alcohol decarbonylation under the same condition. Various complexes and primary alcohols have been investigated as well. The proposed mechanism is based on the stochiometric reactions of the possible metal and organic intermediates. Primary amines, hypothesized to undergo a similar reaction pathway, have been verified to give dehydrogenative coupling product, imines. In the end, the well-developed neutral tridentate Tpm coordinates to the rhodium bis(ethylene) dimer in the presence of TlPF{sub 6} to give the cationic complex, [TpmRh(C{sub 2}H{sub 4}){sub 2}][PF{sub 6}] (5.1). 5.1 serves as the first example of explicit determination of the solid state hapticity, evidenced by X-ray structure, among all the cationic Tpm{sup R}M(C{sub 2}H{sub 4}){sub 2}{sup +} (Tpm{sup R} = Tpm, Tpm*, M = Rh, Ir) derivatives. The substitution chemistry of this compound has been studied by treating with soft and hard donors. The trimethylphosphine-sbustituted complex activates molecular hydrogen to give the dihydride compound.

Ho, Hung-An

2012-03-06

419

Phosphorylated troglitazone activates PPARgamma and inhibits vascular smooth muscle cell proliferation and proteoglycan synthesis.  

PubMed

Phosphorylation of alpha-tocopherol produces an entity with enhanced antiatherogenic properties. Troglitazone, an alpha-tocopherol derivative of a 2,4-thiazolidinedione nucleus, is an antidiabetic agent that shows fatal idiosyncratic hepatotoxicity, a property not shared by later agents. We investigated the effects of phosphorylation of troglitazone (to yield "phosphoglitazone") on the biochemical pharmacologic properties of troglitazone. We investigated its ability to act as a PPARgamma agonist and to inhibit 2 atherogenic properties of vascular smooth muscle cells (vSMC)-proliferation and proteoglycan synthesis. PPARgamma activity was assessed in a transfection assay. Proliferation was assessed by [H]-thymidine incorporation and cell counting and proteoglycan synthesis by [S]-sulfate incorporation using human vSMCs stimulated with platelet-derived growth factor (PDGF; 50 ng/mL) and transforming growth factor (TGF)-beta (2 ng/mL). Phosphoglitazone was a full agonist for PPARgamma with a potency and efficacy similar to troglitazone. Phosphoglitazone also inhibited cell proliferation and proteoglycan synthesis with potency similar to troglitazone. We conclude that phosphorylation retains the pharmacologic activity of troglitazone while decreasing its lipophilicity and therefore potentially its toxicity. A phosphorylated derivative of a 2,4-thiazolidinedione warrants further investigation as a potential new therapeutic agent for the treatment of insulin resistance and Type 2 diabetes. PMID:18356692

Little, Peter J; Ballinger, Mandy L; Survase, Soniya; Osman, Narin; Ogru, Esra; Geytenbeek, Stephen; Bruemmer, Dennis; Nigro, Julie

2008-03-01

420

Synthesis, reactions and antimicrobial activities of 8-ethoxycoumarin derivatives.  

PubMed

Condensation of 3-acetyl-8-ethoxycoumarin (3) with thiosemicarbazide gave ethylidenehydrazinecarbothioamide 5, which was transformed into the thiazolidin-4-one derivatives 6,7. Interaction of 3 with DMF/POCl(3) gave b-chloroacroline derivative 8. Treatment of 3 with malononitrile gave benzo[c]chromone and 2-aminobenzonitrile derivatives 9 and 10, respectively with respect to the reaction conditions. Condensation of 3-(2-bromoacetyl)-8-ethoxycoumarin (4) with o-phenylenediamine gave 3-(quioxaline-2-yl)-8-ethoxycoumarin hydrobromide (11), while 4 reacted with 2-aminopyridine to give chromenopyridopyrimidine derivative 12. Condensation of 4 with potassium thio-cyanate/methanol gave an unexpected derivative, 2H-chromeno-3-carboxy(methyl-carbonimidic)thioanhydride 16, which upon treatment with (NH(2))(2)H(2)O gave 3-ethoxy-2-hydroxybenzaldehyde azine 19. Interaction of 4 with thiourea derivatives gave thiazole derivatives 20a-c. The structures of the newly synthesized compounds were confirmed by their spectra data. The newly synthesized compounds were also screened for their antimicrobial activity. PMID:22258342

Mohamed, Hany M; Abd El-Wahab, Ashraf H F; Ahmed, Kamal A; El-Agrody, Ahmed M; Bedair, Ahmed H; Eid, Fathy A; Khafagy, Mostafa M

2012-01-01

421

Combustion chemistry  

SciTech Connect

This research is concerned with the development and use of sensitivity analysis tools to probe the response of dependent variables to model input variables. Sensitivity analysis is important at all levels of combustion modeling. This group`s research continues to be focused on elucidating the interrelationship between features in the underlying potential energy surface (obtained from ab initio quantum chemistry calculations) and their responses in the quantum dynamics, e.g., reactive transition probabilities, cross sections, and thermal rate coefficients. The goals of this research are: (i) to provide feedback information to quantum chemists in their potential surface refinement efforts, and (ii) to gain a better understanding of how various regions in the potential influence the dynamics. These investigations are carried out with the methodology of quantum functional sensitivity analysis (QFSA).

Brown, N.J. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01

422

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

PubMed

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. PMID:21918584

Bhanushali, Mayur; Zhao, Cong-Gui

2011-06-01

423

Synthesis of monodispersed silver nanoparticles using Hibiscus cannabinus leaf extract and its antimicrobial activity  

NASA Astrophysics Data System (ADS)

Synthesis of silver nanoparticles using leaf extract of Hibiscus cannabinus has been investigated. The influences of different concentration of H. cannabinus leaf extract, different metal ion concentration and different reaction time on the above cases on the synthesis of nanoparticles were evaluated. The synthesized nanoparticles were characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The prepared silver nanoparticles were monodispersed, spherical in shape with the average particle size of 9 nm and shows surface plasmon peak at 446 nm. The study also reveals that the ascorbic acid present in H. cannabinus leaf extract has been used as reducing agent. The prepared silver nanoparticle shows good antimicrobial activity against Escherichia coli, Proteus mirabilis and Shigella flexneri.

Bindhu, M. R.; Umadevi, M.

2013-01-01

424

Total synthesis of 10-isocyano-4-cadinene and its stereoisomers and evaluations of antifouling activities.  

PubMed

The first enantioselective total synthesis of 10-isocyano-4-cadinene, a marine sesquiterpene isolated from nudibranchs of the family Phyllidiidae, and determination of its absolute stereochemistry were achieved. 10-Isocyano-4-cadinene is expected to be a novel nontoxic antifouling agent. In the synthesis, intermolecular Diels-Alder reaction and samarium diiodide induced Barbier-type cyclization were employed as key steps. The absolute configuration of 10-isocyano-4-cadinene was determined as (1S,6S,7R,10S) by comparison of the optical rotations between natural and synthetic samples. In addition, the authors successfully synthesized 10-epi- and di-1,6-epi-10-isocyano-4-cadinene through the same synthetic pathway. Antifouling activities against Balanus amphitrite with the cadinenes were also evaluated. PMID:21755975

Nishikawa, Keisuke; Nakahara, Hiroshi; Shirokura, Yousuke; Nogata, Yasuyuki; Yoshimura, Erina; Umezawa, Taiki; Okino, Tatsufumi; Matsuda, Fuyuhiko

2011-08-19

425

Activation of 5' adenosine monophosphate-activated protein kinase blocks cumulus cell expansion through inhibition of protein synthesis during in vitro maturation in Swine.  

PubMed

The serine/threonine kinase 5' adenosine monophosphate-activated protein kinase (AMPK), a heterotrimeric protein known as a metabolic switch, is involved in oocyte nuclear maturation in mice, cattle, and swine. The present study analyzed AMPK activation in cumulus cell expansion during in vitro maturation (IVM) of porcine cumulus-oocyte complexes (COC). 5-Aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR) is a well-known activator of AMPK. It inhibited oocyte meiotic resumption in COC. Moreover, cumulus cell expansion did not occur in the presence of AICAR, demonstrating its marked impact on cumulus cells. Activation of AMPK was supported by AICAR-mediated phosphorylation of alpha AMPK subunits. Furthermore, the presence of AICAR increased glucose uptake, a classical response to activation of this metabolic switch in response to depleted cellular energy levels. Neither nuclear maturation nor cumulus expansion was reversed by glucosamine, an alternative substrate in hyaluronic acid synthesis, through the hexosamine biosynthetic pathway, which ruled out possible depletion of substrates. Both increased gap junction communication and phosphodiesterase activity in COC are dependent on protein synthesis during the initial hours of IVM; however, both were inhibited in the presence of AICAR, which supports the finding that activation of AMPK by AICAR mediated inhibition of protein synthesis. Moreover, this protein synthesis inhibition was equivalent to that of the well-known protein synthesis inhibitor cycloheximide, as observed on cumulus expansion and protein concentration. Finally, the phosphorylation level of selected kinases was investigated. The pattern of raptor phosphorylation is supportive of activation of AMPK-mediated inhibition of protein synthesis. In conclusion, AICAR-mediated AMPK activation in porcine COC inhibited cumulus cell expansion and protein synthesis. These results bring new considerations to the importance of this kinase in ovarian physiology and to the development of new oocyte culture medium. PMID:25031357

Santiquet, Nicolas; Sasseville, Maxime; Laforest, Martin; Guillemette, Christine; Gilchrist, Robert B; Richard, Franois J

2014-08-01

426

Synthesis, biological evaluation and structure-activity relationships of new quinoxaline derivatives as anti-Plasmodium falciparum agents.  

PubMed

We report the synthesis and antimalarial activities of eighteen quinoxaline and quinoxaline 1,4-di-N-oxide derivatives, eight of which are completely novel. Compounds 1a and 2a were the most active against Plasmodium falciparum strains. Structure-activity relationships demonstrated the importance of an enone moiety linked to the quinoxaline ring. PMID:24552985

Gil, Ana; Pabn, Adriana; Galiano, Silvia; Burguete, Asuncin; Prez-Silanes, Silvia; Deharo, Eric; Monge, Antonio; Aldana, Ignacio

2014-01-01

427

Synthesis, biological activities and bioavailability of moschamine, a safflomide-type phenylpropenoic acid amide found in Centaurea cyanus  

Microsoft Academic Search

Moschamine is a phenylpropenoic acid amide found in plants. In this article, the synthesis and two biological activities (serotoninergic and cyclooxygenase (COX) inhibitory activities) and bioavailability of moschamine were described. Moschamine was synthesised and confirmed using NMR spectroscopic methods. Using the moschamine synthesised, serotoninergic and COX inhibitory activities were investigated. At the concentration of 10??mol?L, moschamine was able to inhibit

Jae B. Park

2011-01-01

428

Synthesis, biological activities and bioavailability of moschamine, a safflomide-type phenylpropenoic acid amide found in Centaurea cyanus  

Microsoft Academic Search

Moschamine is a phenylpropenoic acid amide found in plants. In this article, the synthesis and two biological activities (serotoninergic and cyclooxygenase (COX) inhibitory activities) and bioavailability of moschamine were described. Moschamine was synthesised and confirmed using NMR spectroscopic methods. Using the moschamine synthesised, serotoninergic and COX inhibitory activities were investigated. At the concentration of 10??mol?L, moschamine was able to inhibit

Jae B. Park

2012-01-01

429

Synthesis, conformation, and activity of human insulin-like peptide 5 (INSL5).  

PubMed

Insulin-like peptide 5 (INSL5) was first identified through searches of the expressed sequence tags (EST) databases. Primary sequence analysis showed it to be a prepropeptide that was predicted to be processed in vivo to yield a two-chain sequence (A and B) that contained the insulin-like disulfide cross-links. The high affinity interaction between INSL5 and the receptor RXFP4 (GPCR142) coupled with their apparent coevolution and partially overlapping tissue expression patterns strongly suggest that INSL5 is an endogenous ligand for RXFP4. Given that the primary function of the INSL5-RXFP4 pair remains unknown, an effective means of producing sufficient quantities of this peptide and its analogues is needed to systematically investigate its structural and biological properties. A combination of solid-phase peptide synthesis methods together with regioselective disulfide bond formation were used to obtain INSL5. Both chains were unusually resistant to standard synthesis protocols and required highly optimized conditions for their acquisition. In particular, the use of a strong tertiary amidine, DBU, as N(alpha)-deprotection base was required for the successful assembly of the B chain; this highlights the need to consider incomplete deprotection rather than acylation as a cause of failed synthesis. Following sequential disulfide bond formation and chain combination, the resulting synthetic INSL5, which was obtained in good overall yield, was shown to possess a similar secondary structure to human relaxin-3 (H3 relaxin). The peptide was able to inhibit cAMP activity in SK-N-MC cells that expressed the human RXFP4 receptor with a similar activity to H3 relaxin. In contrast, it had no activity on the human RXFP3 receptor. Synthetic INSL5 demonstrates equivalent activity to the recombinant-derived peptide, and will be an important tool for the determination of its biological function. PMID:18576448

Akhter Hossain, Mohammed; Bathgate, Ross A D; Kong, Chze K; Shabanpoor, Fazel; Zhang, Suode; Haugaard-Jnsson, Linda M; Rosengren, K Johan; Tregear, Geoffrey W; Wade, John D

2008-07-21

430

Cytotoxic T-cell activation by polyribonucleotides: DNA synthesis is not required  

PubMed Central

We have shown that cytotoxic T cells can be polyclonally activated by a short exposure to complexes of polyadenylic:polyuridylic acid (poly A:U). Activation is optimal at a dose of 100 microgram/ml poly A:U and occurs during a 2 h incubation period in the absence of antigen. Killing of allogeneic, but not syngeneic, target cells can be observed after 12 h in culture and peaks after 21-24 h in the absence of any nonspecific binding ligand. The observed cytotoxicity is mediated by T lymphocytes and dose not require accessory macrophages or DNA synthesis for the activation or expression of effector functions. These results suggest that few requirements exist for the activation of cytotoxic T cells. PMID:197193

1977-01-01

431

Humans Transforming the Water Cycle: Community-Based Activities in Hydrologic Synthesis  

NASA Astrophysics Data System (ADS)

This paper describes a newly convened effort to design and execute synthesis studies in hydrology. We focus on an emerging view that human activities are affecting strongly the basic character of the water cycle, through a myriad of processes including water abstraction and flow diversion, land cover change, pollution, destruction of aquatic biodiversity, and climate change. A major scientific challenge is to understand how these changes manifest themselves and if they generate synergistic impacts across the different scales. Our primary synthesis goal is to quantify widespread alteration of hydrologic systems over local-to-regional domains focusing on the Northeast corridor of the United States over a 500-yr period (1600 to 2100). This is a region bearing sharp gradients in climate, land and water management and emblematic of pressures on water resources across the nation. This science agenda will be advanced through the activities of a consolidated Working Group (WG), which will study Regional Watersheds, Hydromorphology, and Continental Processes. The effort expands activities first consolidated under CUAHSI, and welcomes several new members who have led major CUAHSI, NSF, National Academy, regional, national, and international community activities. Our WG maintains cross-linked sub-groups framework to provide focus and unity of purpose. A project implementation design will be presented, including research, education, and outreach efforts.

Vorosmarty, C. J.; Frolking, S.; Green, M.

2007-12-01

432

Pyridoxine-derived bicyclic amido-, ureido-, and carbamato-pyridinols: synthesis and antiangiogenic activities.  

PubMed

We recently developed an efficient and practical synthesis for a novel series of pyridoxine-derived 6-amido-2,4,5-trimethylpyridin-3-ols and found that this novel scaffold has outstanding activity to inhibit angiogenesis measured by the quantitative chick embryo chorioallantoic membrane (CAM) assay. As an effort to extend the scope of the amidopyridinol scaffold, we here report the synthesis and antiangiogenic activities of a series of bicyclic versions of the amidopyridinol including five- and six-membered cyclic amide-, cyclic urea-, and cyclic carbamate-fused pyridinols. The six membered bicyclic derivatives were prepared by the reported procedures, and the five-membered ring-fused ones were synthesized by new synthetic methods developed in this study. CAM assays showed that both six- and five-membered lactam-fused pyridinols have activities comparable to sunitinib malate, the positive control, in inhibition of vascular endothelial growth factor-induced angiogenesis. On the other hand, the urea and the carbamate derivatives showed modest to moderate antiangiogenic activities. In summary, some bicyclic aminopyridinols can provide a good platform for structural exploitation in future medicinal chemistry work. PMID:25255328

Lee, Hyunji; Kim, Dong-Guk; Banskota, Suhrid; Lee, You Kyoung; Nam, Tae-Gyu; Kim, Jung-Ae; Jeong, Byeong-Seon

2014-10-15

433

Enantioselective synthesis of tatanans A-C and reinvestigation of their glucokinase-activating properties  

PubMed Central

The tatanans are members of a novel class of complex sesquilignan natural products recently isolated from the rhizomes of Acorus tatarinowii Schott plants. Tatanans A, B and C have previously been reported to have potent glucokinase-activating properties that exceed the in vitro activity of known synthetic antidiabetic agents. Here, using a series of sequential [3,3]-sigmatropic rearrangements, we report the total synthesis of tatanan A in 13 steps and 13% overall yield. We also complete a concise enantioselective total synthesis of more complex, atropisomeric tatanans B and C via a distinct convergent strategy based on a palladium-catalysed diastereotopic aromatic group differentiation (12 steps, 4% and 8% overall yield, respectively). A plausible biosynthetic relationship between acyclic tatanan A and spirocyclic tatanans B and C is proposed and probed experimentally. With sufficient quantities of the natural products in hand, we undertake a detailed functional characterization of the biological activities of tatanans AC. Contrary to previous reports, our assays utilizing pure recombinant human enzyme demonstrate that tatanans do not function as allosteric activators of glucokinase. PMID:23609092

Xiao, Qing; Jackson, Jeffrey J.; Basak, Ashok; Bowler, Joseph M.; Miller, Brian G.; Zakarian, Armen

2014-01-01

434

Perovskites with cotton-like morphology consisting of nanoparticles and nanorods: Their synthesis by the combustion method and their NO x adsorption behavior  

Microsoft Academic Search

The perovskites La0.8A0.2MnO3 (A=Cs) and La0.8A0.2Mn0.8B0.2O3 (A=Cs and B=Ga) have been synthesized by a solution-combustion method using metal nitrates, urea and glucose as the fuel materials. The structures of the synthesized products were studied by XRD, FT-IR, SEM, and BET analyses. The morphology of La0.8Cs0.2MnO3 (LCM) was cotton-like whereas the product of La0.8Cs0.2Mn0.8Ga0.2O3 (LCMG) was comprised of rather voluminous cotton-like

Toshio Suzuki; Yoshinobu Fujishiro; Masanobu Awano

2009-01-01

435

One-step combustion synthesis of NiFe2O4-reduced graphene oxide hybrid materials for photodegradation of methylene blue  

NASA Astrophysics Data System (ADS)

NiFe2O4-reduced graphene oxide (RGO) hybrid materials (NFRGs) were synthesized by a simple one-step combustion method. The structures, morphologies and magnetic properties were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and vibrating sample magnetometer analysis. The results show that graphene oxide sheets are not oxidized, but reduced to RGO. The superparamagnetic behavior of NFRGs was observed. The as-synthesized magnetically separable NFRGs show improved photodegradation performance when compared to neat NiFe2O4, attributed to the narrowing band gap, the efficient transfer of photo-generated electron from NiFe2O4 to RGO sheets, and the improved adsorptive property of photocatalyst due to the high specific surface area of RGO sheets.

Zhang, Dafeng; Ding, Qi; Pu, Xipeng; Su, Changhua; Shao, Xin; Ding, Guqiao; Zhang, Zheng Gang; Fang, Qiannan

2014-10-01

436

Distribution of SO 2, NO x and CO 2 emissions from fuel combustion and industrial activities in Asia with 1 1 resolution  

NASA Astrophysics Data System (ADS)

Spatial distribution of SO 2, NO x and CO 2 emissions from fuel combustion and industrial activities in Asia has been obtained with 1 1 latitude-longitude resolution for 1975, 1980 and 1987 covering the geographical area of 60E-150E and 10S-55N. Locations of major power plants, iron and steel industry, chemical and petrochemical industry, oil refineries, airports and harbors have been identified for improving accuracy of the allocation of emissions to each grid. Intensive emissions are observed in the Pacific rim region of Asia including Japan, North and South Korea, the coastal area of China and Taiwan where several grids have annual emissions exceeding 100 GgS, 50 GgN and 10 TgC for SO 2, NO x and CO 2, respectively. High emission of SO 2 is also observed for several grids in the inland area of China.

Akimoto, Hajime; Narita, Hirohito

437

Enantioselective synthesis of 2-methyl indolines by palladium catalysed asymmetric C(sp3)-H activation/cyclisation.  

PubMed

The first example of the enantioselective methyl C-H activation by an intramolecular ArPdX species and subsequent cyclisation was developed. Palladium catalysts using commercially available chiral diphosphines yield good ee's (up to 93% ee) in the synthesis of 2-methyl indolines from 2-halo N-isopropyl anilides. This approach was also employed for the synthesis of enantioenriched cyclohexyl fused indolines with moderate enantioselectivities. PMID:21927738

Anas, Saithalavi; Cordi, Alex; Kagan, Henri B

2011-11-01

438

Study of the carburization of an iron catalyst during the Fischer-Tropsch synthesis: influence on its catalytic activity  

Microsoft Academic Search

The fast transformation of an ironalumina catalyst into Fe\\/sub 2+x\\/C during the H + CO reaction was followed by in situ Moessbauer spectroscopy at 523 K and the behavior was compared with changes in catalytic activity for Fischer-Tropsch synthesis. After a few hours of synthesis, no metallic iron could be detected by either Moessbauer or IR spectroscopy, whereas the CO

M. Pijolat; V. Perrichon; P. Bussiere

1987-01-01

439

Combustion Fundamentals Research  

NASA Technical Reports Server (NTRS)

Increased emphasis is placed on fundamental and generic research at Lewis Research Center with less systems development efforts. This is especially true in combustion research, where the study of combustion fundamentals has grown significantly in order to better address the perceived long term technical needs of the aerospace industry. The main thrusts for this combustion fundamentals program area are as follows: analytical models of combustion processes, model verification experiments, fundamental combustion experiments, and advanced numeric techniques.

1983-01-01

440

Total synthesis and structure-activity investigation of the marine natural product neopeltolide.  

PubMed

The total synthesis and biological evaluation of neopeltolide and analogs are reported. The key bond-forming step utilizes a Lewis acid-catalyzed intramolecular macrocyclization that installs the tetrahydropyran ring and macrocycle simultaneously. Independent of each other, neither the macrolide nor the oxazole side chain substituents of neopeltolide can inhibit the growth of cancer cell lines. The biological data of the analogs indicate that alterations to either the ester side chain or the stereochemistry of the macrolide result in a loss of biological activity. PMID:19663512

Custar, Daniel W; Zabawa, Thomas P; Hines, John; Crews, Craig M; Scheidt, Karl A

2009-09-01

441

The design, synthesis and structure-activity relationships of novel isoindoline-based histone deacetylase inhibitors.  

PubMed

The design, synthesis and biological evaluation of a novel series of isoindoline-based hydroxamates is described. Several analogs were shown to inhibit HDAC1 with IC(50) values in the low nanomolar range and inhibit cellular proliferation of HCT116 human colon cancer cells in the sub-micromolar range. The cellular potency of compound 17e was found to have greater in vitro anti-proliferative activity than several compounds in late stage clinical trials for the treatment of cancer. The in vitro safety profiles of selected compounds were assessed and shown to be suitable for further lead optimization. PMID:21742496

Shultz, Michael; Fan, Jianmei; Chen, Christine; Cho, Young Shin; Davis, Nicole; Bickford, Sheri; Buteau, Kristen; Cao, Xueying; Holmqvist, Mats; Hsu, Meier; Jiang, Lei; Liu, Gang; Lu, Qiang; Patel, Chetan; Suresh, Joghee Raju; Selvaraj, Mannangatti; Urban, Laszlo; Wang, Ping; Yan-Neale, Yan; Whitehead, Lewis; Zhang, Haiyan; Zhou, Liping; Atadja, Peter

2011-08-15

442

Synthesis and biological activity of N-substituted-tetrahydro-?-carbolines containing peptide residues  

PubMed Central

Summary The synthesis of novel peptide conjugates of N-substituted-tetrahydro-?-carbolines has been performed using the sequence of the Ugi multicomponent reaction and Cu(I)-catalyzed click chemistry. The effect of obtained ?-carbolinepeptide conjugates on the rat liver mitochondria was evaluated. It was found that all compounds in the concentration of 30 M did onot induce depolarization of mitochondria but possessed some inhibitory effect on the mitochondria permeability transition. The original N-substituted-tetrahydro-?-carbolines containing an terminal alkyne group demonstrated a high prooxidant activity, whereas their conjugates with peptide fragments slightly inhibited both autooxidation and the t-BHP-induced lipid peroxidation. PMID:24454569

Sokolova, Nadezhda V; Sokolov, Vladimir B; Vinogradova, Daria V; Shevtsova, Elena F; Dubova, Ludmila G

2014-01-01