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1

OXYGEN ENHANCED COMBUSTION FOR NOx CONTROL  

SciTech Connect

This quarterly technical progress report will summarize work accomplished for the Program through the fourth quarter January-March 2001 in the following task areas: Task 1 - Oxygen Enhanced Combustion, Task 2 - Oxygen Transport Membranes and Task 4 - Program Management. This report will also recap the results of the past year. The program is proceeding in accordance with the objectives for the first year. OTM material characterization was completed. 100% of commercial target flux was demonstrated with OTM disks. The design and assembly of Praxair's single tube high-pressure test facility was completed. The production of oxygen with a purity of better than 99.5% was demonstrated. Coal combustion testing was conducted at the University of Arizona. Modest oxygen enhancement resulted in NOx emissions reduction. The injector for oxygen enhanced coal based reburning was conducted at Praxair. Combustion modeling with Keystone boiler was completed. Pilot-scale combustion test furnace simulations continued this quarter.

David R. Thompson; Lawrence E. Bool; Jack C. Chen

2001-04-01

2

OXYGEN ENHANCED COMBUSTION FOR NOx CONTROL  

Microsoft Academic Search

Conventional wisdom says adding oxygen to a combustion system enhances product throughput, system efficiency, and, unless special care is taken, increases NOx emissions. This increase in NOx emissions is typically due to elevated flame temperatures associated with oxygen use leading to added thermal NOx formation. Innovative low flame temperature oxy-fuel burner designs have been developed and commercialized to minimize both

David R. Thompson; Lawrence E. Bool; Jack C. Chen

2004-01-01

3

OXYGEN ENHANCED COMBUSTION FOR NOx CONTROL  

SciTech Connect

This quarterly technical progress report will summarize work accomplished for the Program through the fourth quarter January-March 2002 in the following task areas: Task 1--Oxygen Enhanced Combustion, Task 2--Oxygen Transport Membranes, Task 3--Economic Evaluation and Task 4--Program Management. This report will also recap the results of the past year. The program is proceeding in accordance with the objectives for the second year. The first round of pilot scale testing with 3 bituminous coals was completed at the University of Utah. Full-scale testing equipment is in place and experiments are underway. Coal combustion lab-scale testing was completed at the University of Arizona. Modest oxygen enhancement resulted in NOx emissions reduction. Combustion modeling activities continued with pilot-scale combustion test furnace simulations. 75% of target oxygen flux was demonstrated with small PSO1 tube in Praxair's single tube high-pressure test facility. The production of oxygen with a purity of better than 99.999% was demonstrated. Economic evaluation has confirmed the advantage of oxygen-enhanced combustion. Two potential host sites have been identified.

David R. Thompson; Lawrence E. Bool; Jack C. Chen

2002-04-01

4

OXYGEN ENHANCED COMBUSTION FOR NOx CONTROL  

SciTech Connect

Conventional wisdom says adding oxygen to a combustion system enhances product throughput, system efficiency, and, unless special care is taken, increases NOx emissions. This increase in NOx emissions is typically due to elevated flame temperatures associated with oxygen use leading to added thermal NOx formation. Innovative low flame temperature oxy-fuel burner designs have been developed and commercialized to minimize both thermal and fuel NOx formation for gas and oil fired industrial furnaces. To be effective these systems require close to 100% oxy-fuel combustion and the cost of oxygen is paid for by fuel savings and other benefits. For applications to coal-fired utility boilers at the current cost of oxygen, however, it is not economically feasible to use 100% oxygen for NOx control. In spite of this conventional wisdom, Praxair and its team members, in partnership with the US Department of Energy National Energy Technology Laboratory, have developed a novel way to use oxygen to reduce NOx emissions without resorting to complete oxy-fuel conversion. In this concept oxygen is added to the combustion process to enhance operation of a low NOx combustion system. Only a small fraction of combustion air is replaced with oxygen in the process. By selectively adding oxygen to a low NOx combustion system it is possible to reduce NOx emissions from nitrogen-containing fuels, including pulverized coal, while improving combustion characteristics such as unburned carbon. A combination of experimental work and modeling was used to define how well oxygen enhanced combustion could reduce NOx emissions. The results of this work suggest that small amounts of oxygen replacement can reduce the NOx emissions as compared to the air-alone system. NOx emissions significantly below 0.15 lbs/MMBtu were measured. Oxygen addition was also shown to reduce carbon in ash. Comparison of the costs of using oxygen for NOx control against competing technologies, such as SCR, show that this concept offers substantial savings over SCR and is an economically attractive alternative to purchasing NOx credits or installing other conventional technologies. In conjunction with the development of oxygen based low NOx technology, Praxair also worked on developing the economically enhancing oxygen transport membrane (OTM) technology which is ideally suited for integration with combustion systems to achieve further significant cost reductions and efficiency improvements. This OTM oxygen production technology is based on ceramic mixed conductor membranes that operate at high temperatures and can be operated in a pressure driven mode to separate oxygen with infinite selectivity and high flux. An OTM material was selected and characterized. OTM elements were successfully fabricated. A single tube OTM reactor was designed and assembled. Testing of dense OTM elements was conducted with promising oxygen flux results of 100% of target flux. However, based on current natural gas prices and stand-alone air separation processes, ceramic membranes do not offer an economic advantage for this application. Under a different DOE-NETL Cooperative Agreement, Praxair is continuing to develop oxygen transport membranes for the Advanced Boiler where the economics appear more attractive.

David R. Thompson; Lawrence E. Bool; Jack C. Chen

2004-04-01

5

OXYGEN ENHANCED COMBUSTION FOR NOx CONTROL  

SciTech Connect

This quarterly technical progress report will summarize work accomplished for the Program through the eleventh quarter, October-December 2002, in the following task areas: Task 1 - Oxygen Enhanced Combustion, Task 2 - Oxygen Transport Membranes, Task 3 - Economic Evaluation and Task 4 - Program Management. The program is proceeding in accordance with the objectives for the third year. Pilot scale experiments conducted at the University of Utah were aimed at confirming the importance of oxygen injection strategy for different types of burners. CFD modeling at REI was used to better understand the potential for increased corrosion under oxygen enhanced combustion conditions. Data from a full-scale demonstration test in Springfield, MO were analyzed. OTM element development continued with preliminary investigation of an alternative method of fabrication of PSO1d elements. OTM process development continued with long-term testing of a PSO1d element. Economic evaluation has confirmed the advantage of oxygen-enhanced combustion. Proposals have been submitted for two additional beta test sites. A first commercial proposal has been submitted. Economic analysis of a beta site test performance was conducted.

David R. Thompson; Lawrence E. Bool; Jack C. Chen

2003-02-01

6

OXYGEN ENHANCED COMBUSTION FOR NOx CONTROL  

SciTech Connect

This quarterly technical progress report will summarize work accomplished for the Program through the second quarter July--September 2000 in the following task areas: Task 1-Oxygen Enhanced Combustion, Task 2-Oxygen Transport Membranes and Task 4-Program Management. The program is proceeding in accordance with the objectives for the first year. OTM tube characterization is well underway, the design and assembly of the high pressure permeation test facility is complete and the facility will be in full operation during the next quarter. Combustion testing has been initiated at both the University of Arizona and Praxair. Testing at the University of Arizona has experienced some delays; steps have been take to get the test work back on schedule. Completion of the first phase of the testing is expected in next quarter. Combustion modeling has been started at both REI and Praxair, preliminary results are expected in the next quarter.

Lawrence E. Bool; Jack C. Chen; David R. Thompson

2000-10-01

7

OXYGEN ENHANCED COMBUSTION FOR NOx CONTROL  

SciTech Connect

Increased environmental regulations will require utility boilers to reduce NO{sub x} emissions to less than 0.15lb/MMBtu in the near term. Conventional technologies such as Selective Catalytic Reduction (SCR) and Selective Non-Catalytic Reduction (SNCR) are unable to achieve these lowered emission levels without substantially higher costs and major operating problems. Oxygen enhanced combustion is a novel technology that allows utilities to meet the NO{sub x} emission requirements without the operational problems that occur with SCR and SNCR. Furthermore, oxygen enhanced combustion can achieve these NO{sub x} limits at costs lower than conventional technologies. The objective of this program is to demonstrate the use of oxygen enhanced combustion as a technical and economical method of meeting the EPA State Implementation Plan for NO{sub x} reduction to less than 0.15lb/MMBtu for a wide range of boilers and coal. The oxygen enhanced coal combustion program (Task 1) focused this quarter on the specific objective of exploration of the impact of oxygen enrichment on NO{sub x} formation utilizing small-scale combustors for parametric testing. Research efforts toward understanding any limitations to the applicability of the technology to different burners and fuels such as different types of coal are underway. The objective of the oxygen transport membrane (OTM) materials development program (Task 2.1) is to ascertain a suitable material composition that can be fabricated into dense tubes capable of producing the target oxygen flux under the operating conditions. This requires that the material have sufficient oxygen permeation resulting from high oxygen ion conductivity, high electronic conductivity and high oxygen surface exchange rate. The OTM element development program (Task 2.2) objective is to develop, fabricate and characterize OTM elements for laboratory and pilot reactors utilizing quality control parameters to ensure reproducibility and superior performance. A specific goal is to achieve a material that will sinter to desired density without compromising other variables such as reaction to binder systems or phase purity. Oxygen-enhanced combustion requires a facility which is capable of supplying high purity oxygen (>99.5%) at low costs. This goal can be achieved through the thermal integration of high temperature air separation with ceramic OTM. The objective of the OTM process development program (Task 2.3) is to demonstrate successfully the program objectives on a lab-scale single OTM tube reactor under process conditions comparable to those of an optimum large-scale oxygen facility. This quarterly technical progress report will summarize work accomplished for the Program through the first quarter April--June 2000 in the following task areas: Task 1 Oxygen Enhanced Coal Combustion; Task 2 Oxygen Transport Membranes; and Task 4 Program Management.

Lawrence E. Bool; Jack C. Chen; David R. Thompson

2000-07-01

8

OXYGEN ENHANCED COMBUSTION FOR NOx CONTROL  

SciTech Connect

This quarterly technical progress report will summarize work accomplished for the Program through the ninth quarter April-June 2002 in the following task areas: Task 1--Oxygen Enhanced Combustion, Task 2--Oxygen Transport Membranes, Task 3--Economic Evaluation and Task 4--Program Management. The program is proceeding in accordance with the objectives for the third year. Full-scale testing using the Industrial Boiler Simulation Facility (ISBF) at Alstom Power was completed. The pilot scale experiments to evaluate the effect of air preheat and transport air stoichiometric ratio (SR) on NOx emissions were conducted at the University of Utah. Combustion modeling activities continued with full-scale combustion test furnace simulations. An OTM element was tested in Praxair's single tube high-pressure test facility and two thermal cycles were completed. PSO1d elements of new dimension were tested resulting in a lower flux than previous PSO1d elements of different dimensions, however, no element deformation was observed. Economic evaluation has confirmed the advantage of oxygen-enhanced combustion. Two potential host beta sites have been identified and proposals submitted.

David R. Thompson; Lawrence E. Bool; Jack C. Chen

2002-08-01

9

OXYGEN ENHANCED COMBUSTION FOR NOx CONTROL  

SciTech Connect

This quarterly technical progress report will summarize work accomplished for the Program through the twelfth quarter, January-March 2003, in the following task areas: Task 1--Oxygen Enhanced Combustion, Task 2--Oxygen Transport Membranes, Task 3--Economic Evaluation and Task 4--Program Management. The program is proceeding in accordance with the objectives for the third year. Pilot scale experiments conducted at the University of Utah explored both the effectiveness of oxygen addition and the best way to add oxygen with a scaled version of Riley Power's newest low NOx burner design. CFD modeling was done to compare the REI's modeling results for James River Unit 3 with the NOx and LOI results obtained during the demonstration program at that facility. Investigation of an alternative method of fabrication of PSO1d elements was conducted. OTM process development work has concluded with the completion of a long-term test of a PSO1d element Economic evaluation has confirmed the advantage of oxygen-enhanced combustion. Proposals have been submitted for two additional beta test sites. Commercial proposals have been submitted. Economic analysis of a beta site test performance was conducted.

David R. Thompson; Lawrence E. Bool; Jack C. Chen

2003-04-01

10

High-Efficiency, High-Capacity, Low-NOx Aluminum Melting Using Oxygen-Enhanced Combustion  

SciTech Connect

This report describes the development and application of a novel oxygen enhanced combustion system with an integrated vacuum swing adsorption (VSA) oxygen supply providing efficient, low NOx melting in secondary aluminum furnaces. The mainstay of the combustion system is a novel air-oxy-natural gas burner that achieves high productivity and energy efficiency with low NOx emissions through advanced mixing concepts and the use of separate high- and low-purity oxidizer streams. The technology was installed on a reverberatory, secondary aluminum melting plant at the Wabash Aluminum Alloy's Syracuse, N.Y. plant, where it is currently in operation. Field testing gave evidence that the new burner technology meets the stringent NOx emissions target of 0.323 lb NO2/ton aluminum, thus complying with regulations promulgated by Southern California's South Coast Air Quality Management District (SCAQMD). Test results also indicated that the burner technology exceeded fuel efficiency and melting capacity goals. Economic modeling showed that the novel air-oxy-fuel (ADF) combustion technology provides a substantial increase in furnace profitability relative to air-fuel operation. Model results also suggest favorable economics for the air-oxy-fuel technology relative to a full oxy-fuel conversion of the furnace.

D'Agostini, M.D.

2000-06-02

11

Numerical study of the enhancement of combustion performance in a scramjet combustor due to injection of electric-discharge-activated oxygen molecules  

NASA Astrophysics Data System (ADS)

A comprehensive analysis of the efficiency of an approach based on the injection of a thin oxygen stream, subjected to a tailored electric discharge, into a supersonic H2-air flow to enhance the combustion performance in the mixing layer and in the scramjet combustor is conducted. It is shown that for such an approach there exist optimal values of reduced electric field E/N and transversal dimension d of the injected oxygen stream, which provide the minimal length of induction zone in the mixing layer. The optimal values of E/N and d depend on air flow parameters and the specific energy put into the oxygen. The injection of a thin oxygen stream (d = 1 mm) subjected to an electric discharge with E/N = 50-100 Td, which produces mostly singlet oxygen O2(a 1?g) and O_{2}(b\\,^{1}\\Sigma_{g}^{+} ) molecules and atomic oxygen, allows one to arrange stable combustion in a scramjet duct at an extremely low air temperature Tair = 900 K and pressure Pair = 0.3 bar even at a small specific energy put into the oxygen Es = 0.2 J ncm-3, and to provide rather high combustion completeness ? = 0.73. The advance in the energy released during combustion is much higher (hundred times), in this case, than the energy supplied to the oxygen stream in the electric discharge. This approach also makes it possible to ensure the rather high combustion completeness in the scramjet combustor with reduced length. The main reason for the combustion enhancement of the H2-air mixture in the scramjet duct is the intensification of chain-branching reactions due to the injection of a small amount of cold non-equilibrium oxygen plasma comprising highly reactive species, O2(a 1?g) and O_{2}(b\\,^{1}\\Sigma_{g}^{+} ) molecules and O atoms, into the H2-air supersonic flow.

Starik, A. M.; Bezgin, L. V.; Kopchenov, V. I.; Loukhovitski, B. I.; Sharipov, A. S.; Titova, N. S.

2013-12-01

12

Characteristics of non-premixed oxygen-enhanced combustion: I. The presence of appreciable oxygen at the location of maximum temperature  

SciTech Connect

The presence of appreciable molecular oxygen at the location of maximum temperature has been observed in non-premixed oxygen-enhanced combustion (OEC) processes, specifically in flames having a high stoichiometric mixture fraction (Z{sub st}) produced with diluted fuel and oxygen-enrichment. For conventional fuel-air flames, key features of the flame are consistent with the flame sheet approximation (FSA). In particular, the depletion of O{sub 2} at the location of maximum temperature predicted by the FSA correlates well with the near-zero O{sub 2} concentration measured at this location for conventional fuel-air flames. In contradistinction, computational analysis with detailed kinetics demonstrates that for OEC flames at high Z{sub st}: (1) there is an appreciable concentration of O{sub 2} at the location of maximum temperature and (2) the maximum temperature is not coincident with the location of global stoichiometry, O{sub 2} depletion, or maximum heat release. We investigate these phenomena computationally in three non-premixed ethylene flames at low, moderate, and high Z{sub st}, but with equivalent adiabatic flame temperatures. Results demonstrate that the location of O{sub 2} depletion occurs in the vicinity of global stoichiometry for flames of any Z{sub st} and that the presence of appreciable O{sub 2} at the location of maximum temperature for high Z{sub st} flames is caused by a shift in the location of maximum temperature relative to the location of O{sub 2} depletion. This shifting is attributed to: (1) finite-rate multi-step chemistry resulting in exothermic heat release that is displaced from the location of O{sub 2} depletion and (2) the relative location of the heat release region with respect to the fuel and oxidizer boundaries in mixture fraction space. A method of superposition involving a variation of the flame sheet approximation with two heat sources is shown to be sufficient in explaining this phenomenon. (author)

Skeen, S.A.; Axelbaum, R.L. [Department of Energy, Environmental, and Chemical Engineering, Washington University in St. Louis, One Brookings Drive, Box 1180, St. Louis, MO 63130 (United States); Yablonsky, G. [Department of Energy, Environmental, and Chemical Engineering, Washington University in St. Louis, One Brookings Drive, Box 1180, St. Louis, MO 63130 (United States); Parks College, Saint Louis University, St. Louis, MO 63103 (United States)

2009-11-15

13

Dilute Oxygen Combustion, Phase 2 Final Report.  

National Technical Information Service (NTIS)

A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) ...

Y. Wang H. Kobayashi

2005-01-01

14

Dilute Oxygen Combustion. Phase 3 Report.  

National Technical Information Service (NTIS)

Dilute Oxygen Combustion (DOC) burners have been successfully installed and operated in the reheat furnace at Auburn Steel Co., Inc., Auburn, NY, under Phase 3 of the Dilute Oxygen Combustion project. Two new preheat zones were created employing a total o...

M. F. Riley

2000-01-01

15

Dilute Oxygen Combustion - Phase 3 Report  

Microsoft Academic Search

Dilute Oxygen Combustion (DOC) burners have been successfully installed and operated in the reheat furnace at Auburn Steel Co., Inc., Auburn, NY, under Phase 3 of the Dilute Oxygen Combustion project. Two new preheat zones were created employing a total of eight 6.5 MMBtu\\/hr capacity burners. The preheat zones provide a 30 percent increase in maximum furnace production rate, from

Riley; Michael F

2000-01-01

16

Dilute Oxygen Combustion; Phase I Final Report  

Microsoft Academic Search

A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting

H. M. Ryan; M. F. Riley; H. Kobayashi

1997-01-01

17

Dilute Oxygen Combustion; Phase 3 Final Report  

Microsoft Academic Search

Dilute Oxygen Combustion (DOC) burners have been successfully installed and operated in the reheat furnace at Auburn Steel Co., Inc., Auburn, NY, under Phase 3 of the Dilute Oxygen Combustion project. Two new preheat zones were created employing a total of eight 6.5 MMBtu\\/hr capacity burners. The preheat zones provide a 30 percent increase in maximum furnace production rate, from

M. F. Riley; H. M. Ryan

2000-01-01

18

Dilute Oxygen Combustion; Phase 2 Final Report  

Microsoft Academic Search

A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting

H. M. Ryan; M. F. Riley; H. Kobayashi

2005-01-01

19

Dilute Oxygen Combustion; Phase IV Final Report  

Microsoft Academic Search

Novel furnace designs based on Dilute Oxygen Combustion (DOC) technology were developed under subcontract by Techint Technologies, Coraopolis, PA, to fully exploit the energy and environmental capabilities of DOC technology and to provide a competitive offering for new furnace construction opportunities. Capital cost, fuel, oxygen and utility costs, NOx emissions, oxide scaling performance, and maintenance requirements were compared for five

Riley

2003-01-01

20

Oxygen Compatibility Screening Tests in Oxygen-Rich Combustion Environment  

NASA Technical Reports Server (NTRS)

The identification and characterization of oxygen-rich compatible materials enables full-flow, staged combustion designs. Although these oxygen-rich designs offer significant cost, performance, and reliability benefits over existing systems, they have never been used operationally by the United States. If these systems are to be realized, it is critical to understand the long-term oxidative stability in high-temperature, high-pressure, oxygen-rich combustion environments. A unique facility has been constructed at the NASA Lewis Research Center to conduct tests of small-scale rocket engine materials and subcomponents in an oxygen-rich combustion environment that closely approximates a full-scale rocket engine. Thus, a broad range of advanced materials and concepts can be screened in a timely manner and at a relatively low cost.

Eckel, Anerew J.

1997-01-01

21

SITE PROGRAM APPLICATIONS ANALYSIS ASSESSMENT OF SUPERFUND APPLICATIONS FOR THE AMERICAN COMBUSTION INC. PYRETRON OXYGEN ENHANCED BURNER  

EPA Science Inventory

Incineration is widely used to clean up Superfund sites. Modifications which improve the efficiency with which waste can be incinerated are therefore of interest to EPA. Oxygen/air burners are of interest because their installation on conventional incinerators can allow for signi...

22

ENHANCED COMBUSTION WOODSTOVE (ECW) TECHNOLOGY  

EPA Science Inventory

The paper discusses Enhanced Combustion Woodstove (ECW) technology, developed by EPA in response to the field observation that woodstoves certified by EPA as being clean burning were not achieving the level of emission control "seen" in laboratory tests. ts development was also i...

23

Combustion of bulk titanium in oxygen  

NASA Technical Reports Server (NTRS)

The combustion of bulk titanium in one atmosphere oxygen is studied using laser ignition and several analytical techniques. These were high-speed color cinematography, time and space resolved spectra in the visible region, metallography (including SEM) of specimens quenched in argon gas, X-ray and chemical product analyses, and a new optical technique, the Hilbert transform method. The cinematographic application of this technique for visualizing phase objects in the combustion zone is described. The results indicate an initial vapor phase reaction immediately adjacent to the molten surface but as the oxygen uptake progresses the evaporation approaches the point of congruency and a much reduced evaporation rate. This and the accumulation of the various soluble oxides soon drive the reaction zone below the surface where gas formation causes boiling and ejection of particles. The buildup of rutile cuts off the oxygen supply and the reaction ceases.

Clark, A. F.; Moulder, J. C.; Runyan, C. C.

1975-01-01

24

Quantitative measurement of oxygen in microgravity combustion  

NASA Technical Reports Server (NTRS)

This research combines two innovations in an experimental system which should result in a new capability for quantitative, nonintrusive measurement of major combustion species. Using a newly available vertical cavity surface-emitting diode laser (VCSEL) and an improved spatial scanning method, we plan to measure the temporal and spatial profiles of the concentrations and temperatures of molecular oxygen in a candle flame and in a solid fuel (cellulose sheet) system. The required sensitivity for detecting oxygen is achieved by the use of high frequency wavelength modulation spectroscopy (WMS). Measurements will be performed in the NASA Lewis 2.2-second Drop Tower Facility. The objective of this research is twofold. First, we want to develop a better understanding of the relative roles of diffusion and reaction of oxygen in microgravity combustion. As the primary oxidizer species, oxygen plays a major role in controlling the observed properties of flames, including flame front speed (in solid or liquid flames), extinguishment characteristics, flame size, and flame temperature. The second objective is to develop better diagnostics based on diode laser absorption which can be of real value in microgravity combustion research. We will also demonstrate diode lasers' potential usefulness for compact, intrinsically-safe monitoring sensors aboard spacecraft. Such sensors could be used to monitor any of the major cabin gases as well as important pollutants.

Silver, Joel A.

1995-01-01

25

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

26

Quantitative Measurement of Oxygen in Microgravity Combustion  

NASA Technical Reports Server (NTRS)

A low-gravity environment, in space or in ground-based facilities such as drop towers, provides a unique setting for studying combustion mechanisms. Understanding the physical phenomena controlling the ignition and spread of flames in microgravity has importance for space safety as well as for better characterization of dynamical and chemical combustion processes which are normally masked by buoyancy and other gravity-related effects. Due to restrictions associated with performing measurements in reduced gravity, diagnostic methods which have been applied to microgravity combustion studies have generally been limited to capture of flame emissions on film or video, laser Schlieren imaging and (intrusive) temperature measurements using thermocouples. Given the development of detailed theoretical models, more sophisticated diagnostic methods are needed to provide the kind of quantitative data necessary to characterize the properties of microgravity combustion processes as well as provide accurate feedback to improve the predictive capabilities of the models. When the demands of space flight are considered, the need for improved diagnostic systems which are rugged, compact, reliable, and operate at low power becomes apparent. The objective of this research is twofold. First, we want to develop a better understanding of the relative roles of diffusion and reaction of oxygen in microgravity combustion. As the primary oxidizer species, oxygen plays a major role in controlling the observed properties of flames, including flame front speed (in solid or liquid flames), extinguishment characteristics, flame size and flame temperature. The second objective is to develop better diagnostics based on diode laser absorption which can be of real value in both microgravity combustion research and as a sensor on-board Spacelab as either an air quality monitor or as part of a fire detection system. In our prior microgravity work, an eight line-of-sight fiber optic system measured water vapor mole fractions in the NASA Lewis 2.2-sec Drop Tower. In that system, the laser and all electronics resided at the top of the drop tower and was connected via a fiber optic cable to the rig, on which a 'pitch and catch' set of fiber collimating lenses were used to transmit the laser beam across a jet diffusion flame. This system required eight independent detection/demodulation units and had poor spatial resolution. This research builds on this earlier work, resulting in an improved capability for quantitative, nonintrusive measurement of major combustion species. A vertical cavity surface-emitting diode laser (VCSEL) and a continuous spatial scanning method permit the measurement of temporal and spatial profiles of the concentrations and temperatures of molecular oxygen. High detection sensitivity is achieved with wavelength modulation spectroscopy (WMS). One-g experiments are performed using a slot diffusion flame. Microgravity measurements on a solid fuel (cellulose sheet) system are planned for the NASA Lewis 2.2-second Drop Tower Facility.

Silver, Joel A.

1997-01-01

27

Detailed chemical kinetic mechanisms for combustion of oxygenated fuels  

Microsoft Academic Search

Thermodynamic properties and detailed chemical kinetic models have been developed for the combustion of two oxygenates: methyl butanoate, a model compound for biodiesel fuels, and methyl formate, a related simpler molecule. Bond additivity methods and rules for estimating kinetic parameters were adopted from hydrocarbon combustion and extended. The resulting mechanisms have been tested against the limited combustion data available in

E. M. Fisher; W. J. Pitz; H. J. Curran; C. K. Westbrook

2000-01-01

28

Low NOx combustion using cogenerated oxygen and nitrogen streams  

DOEpatents

Combustion of hydrocarbon fuel is achieved with less formation of NOx by feeding the fuel into a slightly oxygen-enriched atmosphere, and separating air into oxygen-rich and nitrogen-rich streams which are fed separately into the combustion device.

Kobayashi, Hisashi (Putnam Valley, NY) [Putnam Valley, NY; Bool, Lawrence E. (East Aurora, NY) [East Aurora, NY; Snyder, William J. (Ossining, NY) [Ossining, NY

2009-02-03

29

Dilute Oxygen Combustion Phase 2 Final Report  

SciTech Connect

A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NOx production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature (~1366 K) oxidant (7-27% O2 vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d+ scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d+ scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW (~0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NOx emissions increased with increasing furnace nitrogen content and furnace temperature, but remained relatively insensitive to variations in fuel injection velocity and firing rate. NOx emissions below 5-10-3 g/MJ (10 ppm-air equivalent at 3% O2 dry) were obtained for furnace temperatures below 1533 K (2300?F) and furnace nitrogen levels between 1 and 40%. CO emissions were typically low (<35 ppm). Detailed in-furnace species measurements revealed the importance of the interior furnace circulation patterns, as influenced by fuel and oxidant injection schemes, on pollutant emissions. The combustion stability traits of several DOC burner arrangements were ascertained through furnace pressure measurements, wit6h increased stability occurring as furnace temperature increased and as the separation distance between fuel and oxidant inputs decreased. Based on current market conditions, oxy-fuel conversion of batch steel reheat furnaces with a DOC burner is justified on the basis of lower utility costs alone. However, conversion of continuous steel reheat furnaces, which are responsible for most steel production, required additional economic incentives, such as further fuel savings, increased furnace productivity, or emission credits.

Ryan, H.M.; Riley, M.F.; Kobayashi, H.

2005-09-30

30

Dilute oxygen combustion. Phase I report  

SciTech Connect

A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NO{sub x}) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NO{sub x} through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NO{sub x} production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature ({approximately}1366 K) oxidant (7-27% O{sub 2} vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d{sup +} scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d{sup +} scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW ({approximately}0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NO{sub x} emissions increased with increasing furnace nitrogen content and furnace temperature, but remained relatively insensitive to variations in fuel injection velocity and firing rate. NO{sub x} emissions below 5{times}10{sup -3} g/MJ (10 ppm-air equivalent at 3% O{sub 2} dry) were obtained for furnace temperatures below 1533 K (2300{degree}F) and furnace nitrogen levels between 1 and 40%. CO emissions were typically low (<35 ppm). Detailed in- furnace species measurements revealed the importance of the interior furnace circulation patterns, as influenced by fuel and oxidant injection schemes, on pollutant emissions. The combustion stability traits of several DOC burner arrangements were ascertained through furnace pressure measurements, with increased stability occurring as furnace temperature increased and as the separation distance between fuel and oxidant inputs decreased. Based on current market conditions, oxy-fuel conversion of batch steel reheat furnaces with a DOC burner is justified on the basis of utility costs alone. However, conversion of continuous steel reheat furnaces, which are responsible for most steel production, requires additional economic incentives, such as further fuel savings, increased furnace productivity, or emission credits.

NONE

1997-10-01

31

Dilute Oxygen Combustion Phase I Final Report  

SciTech Connect

A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NOx production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature (~1366 K) oxidant (7-27% O2 vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d+ scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d+ scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW (~0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NOx emissions increased with increasing furnace nitrogen content and furnace temperature, but remained relatively insensitive to variations in fuel injection velocity and firing rate. NOx emissions below 5-10-3 g/MJ (10 ppm-air equivalent at 3% O2 dry) were obtained for furnace temperatures below 1533 K (2300°F) and furnace nitrogen levels between 1 and 40%. CO emissions were typically low (<35 ppm). Detailed in-furnace species measurements revealed the importance of the interior furnace circulation patterns, as influenced by fuel and oxidant injection schemes, on pollutant emissions. The combustion stability traits of several DOC burner arrangements were ascertained through furnace pressure measurements, wit6h increased stability occurring as furnace temperature increased and as the separation distance between fuel and oxidant inputs decreased. Based on current market conditions, oxy-fuel conversion of batch steel reheat furnaces with a DOC burner is justified on the basis of lower utility costs alone. However, conversion of continuous steel reheat furnaces, which are responsible for most steel production, required additional economic incentives, such as further fuel savings, increased furnace productivity, or emission credits.

Ryan, H.M.; Riley, M.F.; Kobayashi, H.

1997-10-31

32

Praxair's dilute oxygen combustion technology for pyrometallurgical applications  

Microsoft Academic Search

Dilute oxygen combustion (DOC) technology uses separate high-velocity fuel and oxygen jets to generate strong in-furnace gas recirculation, producing combustion between the fuel and a highly diluted oxygen and furnace-gas mixture. These very low NOx oxy-fuel burners have been developed and commercially demonstrated in steel reheating furnaces. The burner design meets industry needs for increased productivity and lower operating costs

M. F. Riley; H. Kobayashi; A. C. Deneys

2001-01-01

33

Praxair’s dilute oxygen combustion technology for pyrometallurgical applications  

Microsoft Academic Search

Dilute oxygen combustion (DOC) technology uses separate high-velocity fuel and oxygen jets to generate strong in-furnace gas\\u000a recirculation, producing combustion between the fuel and a highly diluted oxygen and furnace-gas mixture. These very low NOx\\u000a oxy-fuel burners have been developed and commercially demonstrated in steel reheating furnaces. The burner design meets industry\\u000a needs for increased productivity and lower operating costs

M. F. Riley; H. Kobayashi; A. C. Deneys

2001-01-01

34

Dilute Oxygen Combustion Phase IV Final Report  

SciTech Connect

Novel furnace designs based on Dilute Oxygen Combustion (DOC) technology were developed under subcontract by Techint Technologies, Coraopolis, PA, to fully exploit the energy and environmental capabilities of DOC technology and to provide a competitive offering for new furnace construction opportunities. Capital cost, fuel, oxygen and utility costs, NOx emissions, oxide scaling performance, and maintenance requirements were compared for five DOC-based designs and three conventional air5-fired designs using a 10-year net present value calculation. A furnace direct completely with DOC burners offers low capital cost, low fuel rate, and minimal NOx emissions. However, these benefits do not offset the cost of oxygen and a full DOC-fired furnace is projected to cost $1.30 per ton more to operate than a conventional air-fired furnace. The incremental cost of the improved NOx performance is roughly $6/lb NOx, compared with an estimated $3/lb. NOx for equ8pping a conventional furnace with selective catalytic reduction (SCCR) technology. A furnace fired with DOC burners in the heating zone and ambient temperature (cold) air-fired burners in the soak zone offers low capital cost with less oxygen consumption. However, the improvement in fuel rate is not as great as the full DOC-fired design, and the DOC-cold soak design is also projected to cost $1.30 per ton more to operate than a conventional air-fired furnace. The NOx improvement with the DOC-cold soak design is also not as great as the full DOC fired design, and the incremental cost of the improved NOx performance is nearly $9/lb NOx. These results indicate that a DOC-based furnace design will not be generally competitive with conventional technology for new furnace construction under current market conditions. Fuel prices of $7/MMBtu or oxygen prices of $23/ton are needed to make the DOC furnace economics favorable. Niche applications may exist, particularly where access to capital is limited or floor space limitations are critical. DOC technology will continue to have a highly competitive role in retrofit applications requiring increases in furnace productivity.

Riley, M.F.

2003-04-30

35

ENHANCED SO3 EMISSIONS FROM STAGED COMBUSTION  

EPA Science Inventory

The report gives results of an experimental study to determine if staged combustion can increase (enhance) the SO3 level in a combustion gas, relative to that observed in a similar single-stage process. Methane flames doped with H2S were used to examine the staging effects, emplo...

36

Engine Valve Actuation For Combustion Enhancement  

DOEpatents

A combustion chamber valve, such as an intake valve or an exhaust valve, is briefly opened during the compression and/or power strokes of a 4-stroke combustion cycle in an internal combustion engine (in particular, a diesel or CI engine). The brief opening may (1) enhance mixing withing the combustion chamber, allowing more complete oxidation of particulates to decrease engine emissions; and/or may (2) delay ignition until a more desirable time, potentially allowing a means of timing ignition in otherwise difficult-to-control conditions, e.g., in HCCI (Homogeneous Charge Compression Ignition) conditions.

Reitz, Rolf Deneys (Madison, WI); Rutland, Christopher J. (Madison, WI); Jhavar, Rahul (Madison, WI)

2004-05-18

37

Engine valve actuation for combustion enhancement  

DOEpatents

A combustion chamber valve, such as an intake valve or an exhaust valve, is briefly opened during the compression and/or power strokes of a 4-strokes combustion cycle in an internal combustion engine (in particular, a diesel or CI engine). The brief opening may (1) enhance mixing withing the combustion chamber, allowing more complete oxidation of particulates to decrease engine emissions; and/or may (2) delay ignition until a more desirable time, potentially allowing a means of timing ignition in otherwise difficult-to-control conditions, e.g., in HCCI (Homogeneous Charge Compression Ignition) conditions.

Reitz, Rolf Deneys (Madison, WI); Rutland, Christopher J. (Madison, WI); Jhavar, Rahul (Madison, WI)

2008-03-04

38

DEMONSTRATION BULLETIN: THE PYRETRON OXYGEN BURNER, AMERICAN COMBUSTION TECHNOLOGIES, INC.  

EPA Science Inventory

The Pyretron is a burner which is designed to allow for the injection of oxygen into the combustion air stream for the purpose of increasing the efficiency of a hazardous waste incinerator. The SITE demonstration of the Pyretron took place at the U.S. EPA's Combustion Re...

39

Ignition and combustion of boron particles in hydrogen\\/oxygen combustion products at 30 to 150 atmospheres  

Microsoft Academic Search

The ignition and combustion of crystalline boron particles is studied at high pressures and temperatures in the combustion products of nitrogen diluted premixed hydrogen\\/oxygen mixtures at nearly constant pressure conditions. Particle ignition and combustion are monitored optically by measuring combusting particle emissions. The methodology is used to measure the ignition delay and combustion times of ˜24 micron boron particles over

Robert Oliver Foelsche

1998-01-01

40

Combustion Enhancement with a Silent Discharge Plasma  

NASA Astrophysics Data System (ADS)

It is well known that the application of an external electric field to a flame can affect its propagation speed, stability, and combustion chemistry (Lawton & Weinberg 1969). External electrodes, arc discharges, and plasma jets have been employed to allow combustible gas mixtures to operate outside their flammability limits by gas heating, injection of free radicals, and field-promoted flame stabilization (Yagodnikov & Voronetskii 1994). Other investigators have carried out experiments with silent electrical discharges applied to propagating flames (Inomata et al 1983, Kim et al 2003). These have demonstrated that the flame propagation velocity is actually decreased (combustion retarded) when a silent discharge is applied directly to the flame region, but that the flame propagation velocity is increased (combustion promoted) when a silent discharge is applied to the unburned gas mixture upstream of a flame. Two other recent works have considered the possibility of combustion enhancement in aircraft gas turbine engine combustor mixers by using a plasma-generating fuel nozzle, that employs an electric-arc or microwave plasma generator, to produce dissociated fuel or ionized fuel (Johnson et al 2001); and pulsed corona-enhanced detonation of fuel-air mixtures in jet engines (Wang et al 2003). In contrast to these prior works, we have employed a silent discharge plasma (SDP) reactor to break up large fuel molecules into smaller molecules and create free radicals or other active species in a gas stream before the fuel is mixed with an oxidizer and combusted. In experiments reported here, a cylindrical SDP reactor was used to 'activate' propane before mixing it with air and igniting the combustible gas mixture. With the plasma, the physical appearance of the flame changes and substantial changes in mass spectrometer fragmentation peaks are observed (e.g., propane fragments decrease and water and carbon dioxide increase). This indicates that the combustion process is enhanced with the application of the plasma. Results of changes in the degree of combustion will be discussed in terms of variations in the plasma specific energy.

Rosocha, Louis

2003-10-01

41

Ignition and combustion of metals in oxygen  

NASA Technical Reports Server (NTRS)

Tests in which metals were rubbed against themselves in oxygen have revealed that increasing oxygen pressure does not always increase the potential for ignition. It is believed that there exists a specific pressure above which convective heat loss due to higher oxygen density will overcome the potential increase in the oxidation rate afforded by the increase in oxygen pressure. Test results have shown that, once a specific oxygen pressure is exceeded, greater rates of frictional energy were required for ignition of metals as pressure is increased. Other test results have indicated that as oxygen pressure is increased during the rubbing process, the bulk sample equilibrium temperatures decrease. These results support the belief that increases in convective heat loss as pressure is increased can raise the energy requirements for ignition of metals or lower their ignition potentials. Testing has also indicated that, when metals were exposed to a rubbing process and oxygen pressure was increased, metals such as carbon steel exhibited a decrease in their bulk ignition temperatures, whereas metals such as Monel showed bulk ignition temperatures independent of pressure.

Benz, Frank J.; Zhu, S.

1987-01-01

42

Effects of oxygen dissociation on hypervelocity combustion experiments  

NASA Technical Reports Server (NTRS)

Results are presented of a comparative experimental study conducted to measure the effects of the test gas oxygen dissociation produced in reflected shock tunnels on hypervelocity combustion. An identical combustor model was tested in a reflected shock tunnel with test gas containing about 50 pct by mass of oxygen in dissociated form, as either nitric oxide or atomic oxygen, and in an expansion tube with test gas having negligible dissociated oxygen. Comparisons are made at two test conditions that are energy equivalent to flight conditions at Mach 13.5 and 17.

Bakos, R. J.; Morgan, R. G.; Tamagno, J.

1992-01-01

43

Natural Ores as Oxygen Carriers in Chemical Looping Combustion  

SciTech Connect

Chemical looping combustion (CLC) is a combustion technology that utilizes oxygen from oxygen carriers (OC), such as metal oxides, instead of air to combust fuels. The use of natural minerals as oxygen carriers has advantages, such as lower cost and availability. Eight materials, based on copper or iron oxides, were selected for screening tests of CLC processes using coal and methane as fuels. Thermogravimetric experiments and bench-scale fixed-bed reactor tests were conducted to investigate the oxygen transfer capacity, reaction kinetics, and stability during cyclic reduction/oxidation reaction. Most natural minerals showed lower combustion capacity than pure CuO/Fe{sub 2}O{sub 3} due to low-concentrations of active oxide species in minerals. In coal CLC, chryscolla (Cu-based), magnetite, and limonite (Fe-based) demonstrated better reaction performances than other materials. The addition of steam improved the coal CLC performance when using natural ores because of the steam gasification of coal and the subsequent reaction of gaseous fuels with active oxide species in the natural ores. In methane CLC, chryscolla, hematite, and limonite demonstrated excellent reactivity and stability in 50-cycle thermogravimetric analysis tests. Fe{sub 2}O{sub 3}-based ores possess greater oxygen utilization but require an activation period before achieving full performance in methane CLC. Particle agglomeration issues associated with the application of natural ores in CLC processes were also studied by scanning electron microscopy (SEM).

Tian, Hanjing; Siriwardane, Ranjani; Simonyi, Thomas; Poston, James

2013-08-01

44

Combustion Chemistry of Vibrationally Excited Oxygen.  

National Technical Information Service (NTIS)

We are investigating the use of stimulated resonance Raman pumping to prepare oxygen in selected vibrational states of the ground electronic manifold. This necessitates the development of a laser source capable of producing radiation in the region of the ...

R. B. Miles J. Gelfand H. Rabitz

1984-01-01

45

Research on ignition and combustion in oxygen systems  

NASA Technical Reports Server (NTRS)

The work on ignition and combustion research in oxygen systems under the sponsorship of NASA's Aerospace Safety Research and Data Institute is described. Preliminary results of ignition of nonmetallic materials by electric arc and mechanical impact are presented. Ignition by a resonant process involving repeated shock waves has been demonstrated and some of the results included. In addition, results of studies concerned with ignition due to the rapid rupture of metal films and diaphragms are reviewed. Burning rate studies of three nonmetallic materials in oxygen enriched environments were completed and the results presented. A brief description of these combustion studies under zero gravity is also included. These results are compared to combustion under one gravity.

Ordin, P. M.

1973-01-01

46

International cooperation on hydrogen/oxygen high pressure combustion  

NASA Astrophysics Data System (ADS)

DLR and DASA of Germany as well as CNES and SEP of France have decided to collaborate on oxygen/hydrogen highpressure combustion. In order to promote and intensify a common program the novel research and test facility P8 for LO 2/GH 2 high-pressure rocket combustors is presently being built at the DLR in Lampoldshausen. It provides for combustion chamber pressures up to 30 MPa at a maximum total propellant mass flow rate of 9.5 kg/s. The P8 test bench will be jointly financed, operated and utilized. The paper describes the design of P8, its instrumentation and combustion diagnostics as well as the organization of this international cooperation. Finally, the currently planned research program on highpressure combustion will be discussed.

Sternfeld, Hans J.; Haidn, Oskar J.; Potier, Bruno; Vuillermoz, Patrick; Popp, Michael

1995-10-01

47

Ignition and combustion of boron particles in hydrogen/oxygen combustion products at 30 to 150 atmospheres  

NASA Astrophysics Data System (ADS)

The ignition and combustion of crystalline boron particles is studied at high pressures and temperatures in the combustion products of nitrogen diluted premixed hydrogen/oxygen mixtures at nearly constant pressure conditions. Particle ignition and combustion are monitored optically by measuring combusting particle emissions. The methodology is used to measure the ignition delay and combustion times of ˜24 micron boron particles over a range of pressures (30-150 atm), temperatures (2440, 2630, 2830 K), excess Osb2 concentrations (5, 11, 20%), and with two proposed ignition enhancers (COsb2, HF). Several particles sizes are investigated at one condition (˜12, ˜24, ˜48 mum) to determine particle scaling laws. Although boron has been observed previously to exhibit a two-stage ignition process at lower pressures and temperatures, only a single continuously increasing luminous stage is observed here. Boron particle ignition delays for ˜24 mum are of the order of 1-2 milliseconds, and are reduced with increased pressure, decreased particle size, and increased temperature but increase with increasing ambient oxygen concentrations. Combustion times for ˜24 mum particles are between 1-5 msec, but drop significantly between 2440 K and 2600 K, decreasing by a factor of at least two, and are reduced with increased pressure. Both ignition delays and combustion times obey a dsp1-scaling law (linear) as particle diameter increases, suggesting processes are kinetics-controlled. The two tested ignition-enhancing agents show no signs of accelerated ignition and 5% HF was found to increase ignition delays. Measured ignition delays are compared to predictions from two ignition models showing generally good agreement in the average sense when convective heating is handled appropriately; however, the models under-predict the measured decrease in boron particle ignition delays with increasing pressure and do not predict the sharp decrease in ignition and combustion times as temperature is increased between 2440 K and 2600 K. The results of this study demonstrate that boron particle lifetimes at elevated pressures are sufficiently short to make these particles suitable for additives to propellants and that smaller 1-10 mum sized particles, which have still shorter lifetimes, may be appropriate for addition to explosives.

Foelsche, Robert Oliver

48

Oxygen enriched combustion system performance study: Volume 3, Burner tests and combustion modeling: Final report, Phase 1  

Microsoft Academic Search

Oxygen enriched combustion (OEC) has been shown to have significant energy savings potential in industrial furnace applications. High temperature industrial furnaces, such as glass melting furnaces, appear to be the most promising applications for oxygen enriched combustion. In these applications, the principal energy savings result from minimizing the fuel energy required to heat the diluent nitrogen in air. The results

Y. Kwan; A. R. Abele; W. Richter; S. L. Chen; R. Payne; H. Kobayashi; S. L. Silver

1988-01-01

49

Oxygen Index: An Approximate Value for the Evaluation of Combustion Characteristics.  

National Technical Information Service (NTIS)

The oxygen index has gained international recognition for the determination of combustion characteristics of plastic material. The amounts of oxygen and nitrogen were more accurately determined for existing test equipment in order to specify the oxygen in...

I. Zartmann D. Reinwardt A. Franke

1986-01-01

50

Powdered aluminum and oxygen rocket propellants: Subscale combustion experiments  

NASA Technical Reports Server (NTRS)

Aluminum combined with oxygen has been proposed as a potential lunar in situ propellant for ascent/descent and return missions for future lunar exploration. Engine concepts proposed to use this propellant have not previously been demonstrated, and the impact on performance from combustion and two-phase flow losses could only be estimated. Therefore, combustion tests were performed for aluminum and aluminum/magnesium alloy powders with oxygen in subscale heat-sink rocket engine hardware. The metal powder was pneumatically injected, with a small amount of nitrogen, through the center orifice of a single element O-F-O triplet injector. Gaseous oxygen impinged on the fuel stream. Hot-fire tests of aluminum/oxygen were performed over a mixture ratio range of 0.5 to 3.0, and at a chamber pressure of approximately 480 kPa (70 psia). The theoretical performance of the propellants was analyzed over a mixture ratio range of 0.5 to 5.0. In the theoretical predictions the ideal one-dimensional equilibrium rocket performance was reduced by loss mechanisms including finite rate kinetics, two-dimensional divergence losses, and boundary layer losses. Lower than predicted characteristic velocity and specific impulse performance efficiencies were achieved in the hot-fire tests, and this was attributed to poor mixing of the propellants and two-phase flow effects. Several tests with aluminum/9.8 percent magnesium alloy powder did not indicate any advantage over the pure aluminum fuel.

Meyer, Mike L.

1993-01-01

51

Kinetics of Coal Char Combustion in Oxygen-Enriched Environment  

NASA Astrophysics Data System (ADS)

The influence of oxygen-enriched gaseous atmosphere on coal char combustion was studied. Two different coals, i.e. lignite and bituminous coal, were used as a basic fuel and the reacting gases of oxygen & CO2 were used to simulate flue gas recirculation. Moreover, a broad range of in-furnace conditions, i.e. five temperatures of 873, 973, 1073, 1173, 1273K and five oxygen concentrations of 20, 40, 60, 80, 100%vol., was investigated. Thermogravimetric method of measurement was employed to obtain the processing data on fuel conversion rate under foregoing investigated conditions. For further calculations, simplified Shrinking-Core Model was introduced. Finally, fundamental kinetic parameters, i.e. pre-exponential factor, activation energy and reaction order, were established and then on the basis of their values reaction-controlling regime for coal char combustion in oxygen-enriched environment was predicted. The investigations, financially supported by Polish Government, are a part of Framework Project "Supercritical Coal-fired Power Units".

Czakiert, T.; Nowak, W.

52

Enhanced Combustion Low NOx Pulverized Coal Burner  

SciTech Connect

For more than two decades, ALSTOM Power Inc. (ALSTOM) has developed a range of low cost, in-furnace technologies for NOx emissions control for the domestic U.S. pulverized coal fired boiler market. This includes ALSTOM's internally developed TFS 2000 firing system, and various enhancements to it developed in concert with the U.S. Department of Energy (DOE). As of 2004, more than 200 units representing approximately 75,000 MWe of domestic coal fired capacity have been retrofit with ALSTOM low NOx technology. Best of class emissions range from 0.18 lb/MMBtu for bituminous coals to 0.10 lb/MMBtu for subbituminous coals, with typical levels at 0.24 lb/MMBtu and 0.13 lb/MMBtu, respectively. Despite these gains, NOx emissions limits in the U.S. continue to ratchet down for new and existing (retrofit) boiler equipment. If enacted, proposed Clear Skies legislation will, by 2008, require an average, effective, domestic NOx emissions rate of 0.16 lb/MMBtu, which number will be reduced to 0.13 lb/MMBtu by 2018. Such levels represent a 60% and 67% reduction, respectively, from the effective 2000 level of 0.40 lb/MMBtu. Low cost solutions to meet such regulations, and in particular those that can avoid the need for a costly selective catalytic reduction system (SCR), provide a strong incentive to continue to improve low NOx firing system technology to meet current and anticipated NOx control regulations. In light of these needs, ALSTOM, in cooperation with the DOE, is developing an enhanced combustion, low NOx pulverized coal burner which, when integrated with ALSTOM's state-of-the-art, globally air staged low NOx firing systems, will provide a means to achieve less than 0.15 lb/MMBtu NOx at less than 3/4 the cost of an SCR with low to no impact on balance of plant issues when firing a high volatile bituminous coal. Such coals can be more economic to fire than subbituminous or Powder River Basin (PRB) coals, but are more problematic from a NOx control standpoint as existing firing system technologies do not provide a means to meet current or anticipated regulations absent the use of an SCR. The DOE/ALSTOM program performed large pilot scale combustion testing in ALSTOM's Industrial Scale Burner Facility (ISBF) at its U.S. Power Plant Laboratories facility in Windsor, Connecticut. During this work, the near-field combustion environment was optimized to maximize NOx reduction while minimizing the impact on unburned carbon in ash, slagging and fouling, corrosion, and flame stability/turn-down under globally reducing conditions. Initially, ALSTOM utilized computational fluid dynamic modeling to evaluate a series of burner and/or near field stoichiometry controls in order to screen promising design concepts in advance of the large pilot scale testing. The third and final test, to be executed, will utilize several variants of the best nozzle tip configuration and compare performance with 3 different coals. The fuels to be tested will cover a wide range of coals commonly fired at US utilities. The completion of this work will provide sufficient data to allow ALSTOM to design, construct, and demonstrate a commercial version of an enhanced combustion low NOx pulverized coal burner. A preliminary cost/performance analysis of the developed enhanced combustion low NOx burner applied to ALSTOM's state-of-the-art TFS 2000 firing system was performed to show that the burner enhancements is a cost effective means to reduce NOx.

Ray Chamberland; Aku Raino; David Towle

2006-09-30

53

Polymer-Oxygen Compatibility Testing: Effect of Oxygen Aging on Ignition and Combustion Properties  

NASA Technical Reports Server (NTRS)

The oxygen compatibility of six polymers used in oxygen service was evaluated after exposure for 48 hours to oxygen pressures ranging from 350 to 6200 kPa (50 to 900 psia), and temperatures ranging from 50 to 250 C (122 to 302 F). Three elastomers were tested: CR rubber (C873-70), FKM fluorocarbon rubber (Viton A), and MPQ silicone rubber (MIL-ZZ-765, Class 2); and three thermoplastics were tested: polyhexamethylene adipamide (Zytel 42), polytetrafluoroethylene (Teflon TFE), and polychlorotrifluoroethylene (Neoflon CTFE M400H). Post-aging changes in mass, dimensions, tensile strength, elongation at break, and durometer hardness were determined. Also, the compression set was determined for the three elastomers. Results show that the properties under investigation were more sensitive to oxygen pressure at low to moderate temperatures, and more sensitive to temperature at low to moderate oxygen pressures. Inspection of the results also suggested that both chain scissioning and cross-linking processes were operative, consistent with heterogeneous oxidation. Attempts are underway to verify conclusively the occurrence of heterogeneous oxidation using a simple modulus profiling technique. Finally, the effect of aging at 620 kpa (90 psia) and 121 C (250 F) on ignition and combustion resistance was determined. As expected, aged polymers were less ignitable and combustible (had higher AlTs and lower heats of combustion). Special attention was given to Neoflon CTFE. More specifically, the effect of process history (compression versus extrusion molding) and percent crystallinity (quick- versus slow-quenched) on the AIT, heat of combustion, and impact sensitivity of Neoflon CTFE was investigated. Results show the AIT, heat of combustion, and impact sensitivity to be essentially independent of Neoflon CTFE process history and structure.

Waller, Jess M.; Haas, Jon P.; Wilson, D. Bruce; Fries, Joseph (Technical Monitor)

2000-01-01

54

Detailed Chemical Kinetic Modeling of Diesel Combustion with Oxygenated Fuels  

SciTech Connect

Emission standards for diesel engines in vehicles have been steadily reduced in recent years, and a great deal of research and development effort has been focused on reducing particulate and nitrogen oxide emissions. One promising approach to reducing emissions involves the addition of oxygen to the fuel, generally by adding an oxygenated compound to the normal diesel fuel. Miyamoto et al. [1] showed experimentally that particulate levels can be significantly reduced by adding oxygenated species to the fuel. They found the Bosch smoke number (a measure of the particulate or soot levels in diesel exhaust) falls from about 55% for conventional diesel fuel to less than 1% when the oxygen content of the fuel is above about 25% by mass, as shown in Figure 1. It has been well established that addition of oxygenates to automotive fuel, including both diesel fuel as well as gasoline, reduces NOx and CO emissions by reducing flame temperatures. This is the basis for addition of oxygenates to produce reformulated gasoline in selected portions of the country. Of course, this is also accompanied by a slight reduction in fuel economy. A new overall picture of diesel combustion has been developed by Dec [2], in which laser diagnostic studies identified stages in diesel combustion that had not previously been recognized. These stages are summarized in Figure 2. The evolution of the diesel spray is shown, starting as a liquid jet that vaporizes and entrains hot air from the combustion chamber. This relatively steady process continues as long as fuel is being injected. In particular, Dec showed that the fuel spray vaporizes and mixes with air and products of earlier combustion to provide a region in which a gas phase, premixed fuel-rich ignition and burn occurs. The products of this ignition are then observed experimentally to lead rapidly to formation of soot particles, which subsequently are consumed in a diffusion flame. Recently, Flynn et al. [3] used a chemical kinetic and mixing model to study the premixed, rich ignition process. Using n-heptane as a representative diesel fuel, they showed that addition of an oxygenated additive, methanol, to the fuel reduced the concentrations of a number of hydrocarbon species in the products of the rich ignition. Specifically, methanol addition reduced the total concentrations of acetylene, ethylene and 1,3-butadiene, as well as propargyl and vinyl radicals, in the ignition products. These are the same species shown in a number of studies [4-6] to be responsible for formation of aromatic and polycyclic aromatic species in flames, species which lead eventually to production of soot. Flynn et al. did not, however, examine the kinetic processes responsible for the computed reduction in production of soot precursor species. At least two hypotheses have been advanced to explain the role that oxygenated species play in diesel ignition and the reduction in the concentrations of these species. The first is that the additive, methanol in the case of Flynn et al., does not contain any C-C bonds and cannot then produce significant levels of the species such as acetylene, ethylene or the unsaturated radicals which are known to lead to aromatic species. The second hypothesis is that the product distribution changes very naturally as oxygen is added and the overall equivalence ratio is reduced. In the present study, we repeat the ignition calculations of Flynn et al. and include a number of other oxygenated species to determine which of these theories is more applicable to this model.

Curran, H J; Fisher, E M; Glaude, P-A; Marinov, N M; Pitz, W J; Westbrook, C K; Flynn, P F; Durrett, R P; zur Loye, A O; Akinyemi, O C; Dryer, F L

2000-01-11

55

Methanol Droplet Combustion in Oxygen-Inert Environments in Microgravity  

NASA Technical Reports Server (NTRS)

The Flame Extinguishment (FLEX) experiment that is currently underway in the Combustion Integrated Rack facility onboard the International Space Station is aimed at understanding the effects of inert diluents on the flammability of condensed phase fuels. To this end, droplets of various fuels, including alkanes and alcohols, are burned in a quiescent microgravity environment with varying amounts of oxygen and inert diluents to determine the limiting oxygen index (LOI) for these fuels. In this study we report experimental observations of methanol droplets burning in oxygen-nitrogen-carbon dioxide and oxygen-nitrogen-helium gas mixtures at 0.7 and 1 atmospheric pressures. The initial droplet size varied between approximately 1.5 mm and 4 mm to capture both diffusive extinction brought about by insufficient residence time at the flame and radiative extinction caused by excessive heat loss from the flame zone. The ambient oxygen concentration varied from a high value of 30% by volume to as low as 12%, approaching the limiting oxygen index for the fuel. The inert dilution by carbon dioxide and helium varied over a range of 0% to 70% by volume. In these experiments, both freely floated and tethered droplets were ignited using symmetrically opposed hot-wire igniters and the burning histories were recorded onboard using digital cameras, downlinked later to the ground for analysis. The digital images yielded droplet and flame diameters as functions of time and subsequently droplet burning rate, flame standoff ratio, and initial and extinction droplet diameters. Simplified theoretical models correlate the measured burning rate constant and the flame standoff ratio reasonably well. An activation energy asymptotic theory accounting for time-dependent water dissolution or evaporation from the droplet is shown to predict the measured diffusive extinction conditions well. The experiments also show that the limiting oxygen index for methanol in these diluent gases is around 12% to 13% oxygen by volume.

Nayagam, Vedha; Dietrich, Daniel L.; Hicks, Michael C.; Williams, Forman A.

2013-01-01

56

Kinetic mechanism of combustion of hydrogen-oxygen mixtures  

NASA Astrophysics Data System (ADS)

Based on the analysis of the databases published in the scientific literature and concerned with the reaction rate constants in the H2/O2 system, a new kinetic mechanism is suggested for describing the processes of ignition, combustion, and detonation in hydrogen-oxygen gaseous mixtures. Attention is mainly focused on consideration of a low-temperature region ( T < 1000 K) where a chain of reactions of the formation and subsequent decomposition of hydrogen peroxide plays the major role in the system ignition. The proposed mechanism has been tested by comparing computational results with available data on measurement of the ignition-delay time in shock tubes.

Gerasimov, G. Ya.; Shatalov, O. P.

2013-09-01

57

Enhanced Combustion Low NOx Pulverized Coal Burner  

SciTech Connect

For more than two decades, Alstom Power Inc. (Alstom) has developed a range of low cost, infurnace technologies for NOx emissions control for the domestic U.S. pulverized coal fired boiler market. This includes Alstom's internally developed TFS 2000{trademark} firing system, and various enhancements to it developed in concert with the U.S. Department of Energy. As of the date of this report, more than 270 units representing approximately 80,000 MWe of domestic coal fired capacity have been retrofit with Alstom low NOx technology. Best of class emissions range from 0.18 lb/MMBtu for bituminous coal to 0.10 lb/MMBtu for subbituminous coal, with typical levels at 0.24 lb/MMBtu and 0.13 lb/MMBtu, respectively. Despite these gains, NOx emissions limits in the U.S. continue to ratchet down for new and existing boiler equipment. On March 10, 2005, the Environmental Protection Agency (EPA) announced the Clean Air Interstate Rule (CAIR). CAIR requires 25 Eastern states to reduce NOx emissions from the power generation sector by 1.7 million tons in 2009 and 2.0 million tons by 2015. Low cost solutions to meet such regulations, and in particular those that can avoid the need for a costly selective catalytic reduction system (SCR), provide a strong incentive to continue to improve low NOx firing system technology to meet current and anticipated NOx control regulations. The overall objective of the work is to develop an enhanced combustion, low NOx pulverized coal burner, which, when integrated with Alstom's state-of-the-art, globally air staged low NOx firing systems will provide a means to achieve: Less than 0.15 lb/MMBtu NOx emissions when firing a high volatile Eastern or Western bituminous coal, Less than 0.10 lb/MMBtu NOx emissions when firing a subbituminous coal, NOx reduction costs at least 25% lower than the costs of an SCR, Validation of the NOx control technology developed through large (15 MWt) pilot scale demonstration, and Documentation required for economic evaluation and commercial application. During the project performance period, Alstom performed computational fluid dynamics (CFD) modeling and large pilot scale combustion testing in its Industrial Scale Burner Facility (ISBF) at its U.S. Power Plant Laboratories facility in Windsor, Connecticut in support of these objectives. The NOx reduction approach was to optimize near-field combustion to ensure that minimum NOx emissions are achieved with minimal impact on unburned carbon in ash, slagging and fouling, corrosion, and flame stability/turn-down. Several iterations of CFD and combustion testing on a Midwest coal led to an optimized design, which was extensively combustion tested on a range of coals. The data from these tests were then used to validate system costs and benefits versus SCR. Three coals were evaluated during the bench-scale and large pilot-scale testing tasks. The three coals ranged from a very reactive subbituminous coal to a moderately reactive Western bituminous coal to a much less reactive Midwest bituminous coal. Bench-scale testing was comprised of standard ASTM properties evaluation, plus more detailed characterization of fuel properties through drop tube furnace testing and thermogravimetric analysis. Bench-scale characterization of the three test coals showed that both NOx emissions and combustion performance are a strong function of coal properties. The more reactive coals evolved more of their fuel bound nitrogen in the substoichiometric main burner zone than less reactive coal, resulting in the potential for lower NOx emissions. From a combustion point of view, the more reactive coals also showed lower carbon in ash and CO values than the less reactive coal at any given main burner zone stoichiometry. According to bench-scale results, the subbituminous coal was found to be the most amenable to both low NOx, and acceptably low combustibles in the flue gas, in an air staged low NOx system. The Midwest bituminous coal, by contrast, was predicted to be the most challenging of the three coals, with the Western bituminous coal predicted to beh

David Towle; Richard Donais; Todd Hellewell; Robert Lewis; Robert Schrecengost

2007-06-30

58

Detailed Chemical Kinetic Mechanisms for Combustion of Oxygenated Fuels  

SciTech Connect

Thermodynamic properties and detailed chemical kinetic models have been developed for the combustion of two oxygenates: methyl butanoate, a model compound for biodiesel fuels, and methyl formate, a related simpler molecule. Bond additivity methods and rules for estimating kinetic parameters were adopted from hydrocarbon combustion and extended. The resulting mechanisms have been tested against the limited combustion data available in the literature, which was obtained at low temperature, subatmospheric conditions in closed vessels, using pressure measurements as the main diagnostic. Some qualitative agreement was obtained, but the experimental data consistently indicated lower overall reactivities than the model, differing by factors of 10 to 50. This discrepancy, which occurs for species with well-established kinetic mechanisms as well as for methyl esters, is tentatively ascribed to the presence of wall reactions in the experiments. The model predicts a region of weak or negative dependence of overall reaction rate on temperature for each methyl ester. Examination of the reaction fluxes provides an explanation of this behavior, involving a temperature-dependent competition between chain-propagating unimolecular decomposition processes and chain-branching processes, similar to that accepted for hydrocarbons. There is an urgent need to obtain more complete experimental data under well-characterized conditions for thorough testing of the model.

Fisher, E.M.; Pitz, W.J.; Curran, H.J.; Westbrook, C.K.

2000-01-11

59

Thermodynamic, transport, and flow properties of gaseous products resulting from combustion of methane-air-oxygen  

NASA Technical Reports Server (NTRS)

Results of calculations to determine thermodynamic, transport, and flow properties of combustion product gases are presented. The product gases are those resulting from combustion of methane-air-oxygen and methane-oxygen mixtures. The oxygen content of products resulting from the combustion of methane-air-oxygen mixtures was similiar to that of air; however, the oxygen contained in products of methane-oxygen combustion ranged from 20 percent by volume to zero for stoichiometric combustion. Calculations were made for products of reactant mixtures with fuel percentages, by mass, of 7.5 to 20. Results are presented for specific mixtures for a range of pressures varying from 0.0001 to 1,000 atm and for temperatures ranging from 200 to 3,800 K.

Klich, G. F.

1976-01-01

60

Alarming Oxygen Depletion Caused by Hydrogen Combustion and Fuel Cells and their Resolution by Magnegas$^{TM}$  

Microsoft Academic Search

We recall that hydrogen combustion does resolve the environmental problems of fossil fuels due to excessive emission of carcinogenic substances and carbon dioxide. However, hydrogen combustion implies the permanent removal from our atmosphere of directly usable oxygen, a serious environmental problem called oxygen depletion, since the combustion turns oxygen into water whose separation to restore the original oxygen is prohibitive

R. M. Santilli

2000-01-01

61

RECENT ADVANCES IN CaSO4 OXYGEN CARRIER FOR CHEMICAL-LOOPING COMBUSTION (CLC) PROCESS  

Microsoft Academic Search

Chemical-looping combustion (CLC) is a novel combustion technology with inherent separation of the greenhouse gas CO2 and low NOx (NO, NO2, N2O) emissions. In CLC, the solid oxygen carrier supplies the stoichiometric oxygen needed for CO2 and water formation, resulting in a free nitrogen mixture. The performance of oxygen carrier is the key to CLC's application. A good oxygen carrier

Qingjie Guo; Jianshe Zhang; Hongjing Tian

2012-01-01

62

Modeling of laser-induced combustion of iron in oxygen during gas-laser cutting  

Microsoft Academic Search

A physical and mathematical model is proposed for cyclic combustion of iron in an oxygen stream during oxygen gas-laser cutting\\u000a of sheet metal. The combustion front is driven by focused laser radiation and heterogeneous iron oxidation in oxygen. The\\u000a burning rate is limited by the rate of oxygen supply from the gas phase to the metal surface, and the motion

G. V. Ermolaev; O. B. Kovalev

2010-01-01

63

Experimental Conditions Determination for Constant Volume Combustion Calorimetry in Oxygen Calorimetrie de Combustion a Volume Constant dans l'Oxygene: Definition des Conditions Experimentales.  

National Technical Information Service (NTIS)

The initial and final state of constant volume combustion calorimeters in an oxygen atmosphere are discussed. Sampling techniques such as powdering and sealing in polyethylene bags are dealt with. The merits of a rotating bomb calorimeter are reviewed. Th...

M. Ducros

1973-01-01

64

Combustion Enhancement with a Silent Discharge Plasma  

Microsoft Academic Search

It is well known that the application of an external electric field to a flame can affect its propagation speed, stability, and combustion chemistry (Lawton & Weinberg 1969). External electrodes, arc discharges, and plasma jets have been employed to allow combustible gas mixtures to operate outside their flammability limits by gas heating, injection of free radicals, and field-promoted flame stabilization

Louis Rosocha

2003-01-01

65

An investigation of plasma enhanced combustion  

NASA Astrophysics Data System (ADS)

This study examines the use of plasma discharges in flame stabilization. Three different types of plasma discharges are applied to a lifted jet diffusion flame in coflow, and evaluated for their abilities to enhance flame stabilization. A single electrode corona discharge (SECD) is found to maintain the flame at a 20 % higher coflow speed than that without the discharge. A dielectric barrier discharge (DBD) results in flame stabilization at up to 50 % higher coflow speed. Finally, an ultra short-pulsed repetitive discharge (USRD) is found to increase the stability limit by nearly ten-fold. The stabilization process is sensitive to the positioning of the discharge in the flow field, and the optimal position of the discharge is mapped into mixture fraction space. The result shows that the local mixture fraction at the optimal position is much leaner than that of a conventional lifted jet flame. Parametric studies are conducted in a plasma-assisted methane/air premixed flame system using USRD. Criteria for optimal electrode selection are suggested. Platinum provides the best result at low frequency operation (< 20 kHz) but tungsten shows better performance at high frequency operation (> 20 kHz). The increase in the flame stability limit is also investigated. The flame stability limit extends from an equivalence ratio of 0.7 to 0.47. Nitric oxide (NO) concentration in the premixed flame is measured. The discharge is a potential source of NO. Under certain conditions, we observed the presence of a cold pre-flame, located between the discharge and the main flame. It is found that the pre-flame partially consumes some NO. The flame kernel structure and ignition mechanism of plasma-assisted premixed combustion are discussed. It is observed that the pre-flame has an abundance of OH radicals. The key physics of the flame ignition is the diffusion of an OH stream (from the pre-flame) into the surrounding combustible mixture to form the main flame. Lastly, the proposed flame kernel structure is numerically validated using the OPPDIF code. The simulation shows that possibly three reaction zones, one pre-flame and two main flames, exist in this flame configuration.

Kim, Woo Kyung

66

Combustion  

NASA Astrophysics Data System (ADS)

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

Murdin, P.

2000-11-01

67

Koon sainetsu nenshoki kenkyu kaihatsu yo tei sanso nensho shiken sochi. (Low oxygen combustion tester for high temperature reheat combustors).  

National Technical Information Service (NTIS)

As a part of the development of high efficiency reheat cycle gas turbines, the combustion tester capable of testing under various oxygen content conditions at a combuster inlet was developed, to examine the flame holding, combustion and emission character...

1989-01-01

68

Synergetic effects of mixed copper-iron oxides oxygen carriers in chemical looping combustion  

SciTech Connect

Chemical looping combustion (CLC) is an emerging technology for clean energy production from fuels. CLC produces sequestration-ready CO{sub 2}-streams without a significant energy penalty. Development of efficient oxygen carriers is essential to successfully operate a CLC system. Copper and iron oxides are promising candidates for CLC. Copper oxide possesses high reactivity but it has issues with particle agglomeration due to its low melting point. Even though iron oxide is an inexpensive oxygen carrier it has a slower reactivity. In this study, mixed metal oxide carriers containing iron and copper oxides were evaluated for coal and methane CLC. The components of CuO and Fe{sub 2}O{sub 3} were optimized to obtain good reactivity while maintaining physical and chemical stability during cyclic reactions for methane-CLC and solid-fuel CLC. Compared with single metal oxygen carriers, the optimized Cu–Fe mixed oxide oxygen carriers demonstrated high reaction rate, better combustion conversion, greater oxygen usage and improved physical stability. Thermodynamic calculations, XRD, TGA, flow reactor studies and TPR experiments suggested that there is a strong interaction between CuO and Fe{sub 2}O{sub 3} contributing to a synergistic effect during CLC reactions. The amount of oxygen release of the mixed oxide carrier in the absence of a fuel was similar to that of the single metal oxides. However, in the presence of fuels, the oxygen consumption and the reaction profiles of the mixed oxide carriers were significantly better than that of the single metal oxides. The nature of the fuel not only influenced the reactivity, but also the final reduction status of the oxygen carriers during chemical looping combustion. Cu oxide of the mixed oxide was fully reduced metallic copper with both coal and methane. Fe oxide of the mixed oxide was fully reduced Fe metal with methane but it was reduced to only FeO with coal. Possible mechanisms of how the presence of CuO enhances the reduction of Fe{sub 2}O{sub 3} are discussed.

Siriwardane, Ranjani; Tian, Hanjing; Simonyi, Thomas; Poston, James

2013-06-01

69

National Combustion Code Parallel Performance Enhancements  

NASA Technical Reports Server (NTRS)

The National Combustion Code (NCC) is being developed by an industry-government team for the design and analysis of combustion systems. The unstructured grid, reacting flow code uses a distributed memory, message passing model for its parallel implementation. The focus of the present effort has been to improve the performance of the NCC code to meet combustor designer requirements for model accuracy and analysis turnaround time. Improving the performance of this code contributes significantly to the overall reduction in time and cost of the combustor design cycle. This report describes recent parallel processing modifications to NCC that have improved the parallel scalability of the code, enabling a two hour turnaround for a 1.3 million element fully reacting combustion simulation on an SGI Origin 2000.

Quealy, Angela; Benyo, Theresa (Technical Monitor)

2002-01-01

70

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

Microsoft Academic Search

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

D. M. Brady

71

Microwave enhanced combustion of laminar hydrocarbon flame fronts  

Microsoft Academic Search

The X-43 missions in 2005 demonstrated the feasibility of a hydrogen fueled scramjet. Since that time, the cost, performance, and safety concerns surrounding the use of hydrogen have motivated researchers to investigate methods of enhancing the performance of easily stored hydrocarbon based fuels by improving their ignition, flammability, and flameholding characteristics. The microwave enhanced combustion testbed has demonstrated a significant

Emanuel Solomon Stockman

2009-01-01

72

Carbon deposition model for oxygen-hydrocarbon combustion, volume 1  

NASA Technical Reports Server (NTRS)

Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at pressures of 1000 to 1500 psia. No carbon deposition on the chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational consequences of carbon deposition on preburner/gas generator performance. The report is in two volumes, of which this is Volume 1 covering the main body of the report plus Appendixes A through D.

Hernandez, R.; Ito, J. I.; Niiya, K. Y.

1987-01-01

73

Metallized gelled propellants: Oxygen/RP-1/aluminum combustion experiments  

NASA Technical Reports Server (NTRS)

A series of combustion experiments using metallized gelled liquid propellants were conducted. These experiments used a small 30- to 40-lb(sub f) thrust engine composed of a modular injector, igniter, chamber and nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-wt percent, 5-wt percent, and 44-wt percent loadings of aluminum and gaseous oxygen and the oxidizer. Ten different injectors were used during the testing: 6 were for the baseline O2/RP-1 tests and 4 for the gelled fuels. Relatively high C-star efficiencies were obtained with gelled RP-1 (0-wt% RP-1/Al) and metallized 5-wt% RP-1/Al over the O/F range tested: 90-98%. A peak of 98 percent efficiency was reached with ungelled O2/RP-1 and up to 95% efficiency was obtained with gelled RP-1/Al (55-wt% Al). Injector erosion was evident with the 55-wt% testing, while there was little or no erosion seen with the gelled RP-1 with 0 and 5-wt% Al. A protective layer of gelled fuel formed in the firings that minimized the damage to the rocket injector face. This effect may provide a useful technique for engine cooling.

Palaszewski, Bryan

1994-01-01

74

Carbon Deposition Model for Oxygen-Hydrocarbon Combustion, Volume 2  

NASA Technical Reports Server (NTRS)

Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at chamber pressures of 1000 to 1500 psia. No carbon deposition on chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational concequences of carbon deposition on preburner/gas generator performance. This is Volume 2 of the report, which contains data plots of all the test programs.

Hernandez, R.; Ito, J. I.; Niiya, K. Y.

1987-01-01

75

Plasma enhancement of combustion of solid fuels  

SciTech Connect

Plasma fuel systems that increase the coal burning efficiency are discussed. The systems were tested for fuel oil-free startup of boilers and stabilizating a pulverized-coal flame in power-generating boilers equipped with different types of burner and burning all types of power-generating coal. Plasma ignition, thermochemical treatment of an air-fuel mixture prior to combustion, and its burning in a power-generating boiler were numerically simulated. Environmental friendliness of the plasma technology was demonstrated.

Askarova, A.S.; Karpenko, E.I.; Messerle, V.E.; Ustimenko, A.B. [Institute of Combustion Problems, Alma Ata (Kazakhstan)

2006-03-15

76

Coal-water mixture combustion using oxygen-enriched air and staged firing  

Microsoft Academic Search

Coal-water mixture (CWM) combustion experiments using oxygen-enriched air were conducted in an oil-designed 700-hp watertube boiler using a bituminous CWM. The results indicated that the use of oxygen-enriched air increased carbon burnout, reduced uncontrolled fly ash emissions, and reduced combustion air preheating requirements. The boiler efficiency increased because of reduced flue gas heat losses. The improvement in boiler performance compared

Y. C. Fu; G. T. Bellas; J. I. Joubert

1987-01-01

77

Oxygen enriched combustion system performance study: Phase 1, Interim\\/final report: Volume 1, Technical and economic analysis  

Microsoft Academic Search

Technical and economic feasibility of using oxygen enriched combustion (OEC) and preheated oxygen enriched combustion (POEC) for industrial furnace applications was evaluated. The potential for fuel savings and productivity improvements with OEC\\/POEC systems was parametrically analyzed for a broad range of furnace conditions including those for steel heating, glass melting and aluminum melting. The changes in combustion characteristics with OEC

Kobayashi; Hisashi

1987-01-01

78

Pulse Combustion: Impinging Jet Heat Transfer Enhancement  

Microsoft Academic Search

A new method for convective heat transfer enhancement is described. The technique involves the use of a pulse combustor to generate a transient jet that impinges on a flat plate. Enhancements in convective heat transfer of a factor of up to 2.5, compared to a steady impinging jet at approximately the same Reynolds number, have been obtained. Heat transfer data

R A. EIBECK; J. O. KELLER; T. T. BRAMLETTE; D. J. SAILOR

1993-01-01

79

Enhancement of pulverized coal combustion by plasma technology  

SciTech Connect

Plasma-assisted pulverized coal combustion is a promising technology for thermal power plants (TPP). This article reports one- and three- dimensional numerical simulations, as well as laboratory and industrial measurements of coal combustion using a plasma-fuel system (PFS). The chemical kinetic and fluid mechanics involved in this technology are analysed. The results show that a PFS, can be used to promote early ignition and enhanced stabilization of a pulverized coal flame. It is shown that this technology, in addition to enhancing the combustion efficiency of the flame, reduces harmful emissions from power coals of all ranks (brown, bituminous, anthracite and their mixtures). Data summarising the experience of 27 pulverized coal boilers in 16 thermal power plants in several countries (Russia, Kazakhstan, Korea, Ukraine, Slovakia, Mongolia and China), embracing steam productivities from 75 to 670 tons per hour (TPH), are presented. Finally, the practical computation of the characteristics of the PFS, as function of coal properties, is discussed.

Gorokhovski, M.A.; Jankoski, Z.; Lockwood, F.C.; Karpenko, E.I.; Messerle, V.E.; Ustimenko, A.B. [University of Rouen, Rouen (France)

2007-07-01

80

Rocket combustion chamber life-enhancing design concepts  

NASA Technical Reports Server (NTRS)

NASA continues to pursue technologies which can lead to an increase in life and reduce the costs of fabrication of the Space Shuttle Main Engine. The joint NASA/Air Force Advanced Launch System Program has set its prime objectives to be high reliability and low cost for their new advanced booster engine. In order to meet these objectives, NASA will utilize the results of several ongoing programs to provide the required technologies. An overview is presented of those programs which address life enhancing design concepts for the combustion chamber. Seven different design concepts, which reduce the thermal strain and/or increase the material strength of the combustion chamber liner wall are discussed. Subscale rocket test results are presented, where available, for life enhancing design concepts. Two techniques for reducing chamber fabrication costs are discussed, as well as issues relating to hydrocarbon fuels/combustion chamber liner materials compatibility.

Quentmeyer, Richard J.

1990-01-01

81

Combustion of 316 stainless steel in high-pressure gaseous oxygen  

NASA Technical Reports Server (NTRS)

Upward combustion of 316 stainless steel (SS) rods is discussed and a combustion model is presented. The effects of varying oxygen pressure and rod diameter on the rate limiting processes for combustion of 316 SS are evaluated. The rate-limiting steps for combustion up 316 SS rods are shown to be dependent on the incorporation and mass transport of oxygen in the molten mass, and heat transfer between the molten mass and rod. Both these rate-limiting steps are shown to be dependent on rod diameter. Small (d/r/ = 0.051 cm) 316 SS rods are shown to be dependent on convective heat transfer, and larger rods (d/r/ not less than 0.32 cm) are shown to be dependent on oxygen incorporation and mass transport in the molten mass.

Benz, Frank; Steinberg, Theodore A.; Janoff, Dwight

1989-01-01

82

Sonically Enhanced Combustion of Coal Water Slurry Fuel.  

NASA Astrophysics Data System (ADS)

An investigation was performed to demonstrate that a high intensity acoustic field can enhance the convective transfer processes occurring during CWSF (coal water slurry fuel) combustion. It was carried out in a 300,000 Btu/h sonic combustor. For the runs conducted, SPLs of 156 dB and 145 dB, respectively, were measured below the fuel injection point and before the exit to the combustor. Frequency was held at 1400 Hz. Combustion efficiency was improved when the extent of burnout was well below 100% and when the droplet size distribution was relatively coarse. The maximum improvement in burnout was 7.9%, under the coarsest atomization conditions investigated. Results from modelling show that sonically enhanced heat transfer plays a negligible role in improving the rate of combustion of CWSF. However, such enhancement may well be important for other applications (e.g. spray drying) involving longer drying times and/or small steady slip velocities. The application of a sonic field improves the rate of combustion of CWSF mainly through increased mass transfer rates, the enhancement being greatest for relatively coarse atomization. It is commonly accepted that the largest particles of fuel are the most likely to avoid full burnout in a practical combustor and thus contribute to erosion, slagging, and fouling via inertial mechanisms. By acting preferentially on these particles, operational difficulties can be minimized.

Ramachandran, Prakash

1990-01-01

83

Combustion Enhancement in Scramjet-Operation of a RBCC Engine  

NASA Astrophysics Data System (ADS)

Combination of a scramjet (supersonic combustion ramjet) flow-pass with embedded rocket engines (the combined system termed as Rocket Based Combined Cycle engine) are expected to be the most effective propulsion system for Booster stage of space launch vehicles. At hypersonic regime, it will be operated at rather high rocket engine output for final acceleration with some Isp gains due to air-breathing effects. In this regime, attaining thrust at this high-speed regime becomes very difficult, so that parallel injection of the fuel for scramjet combustion is favorable as the momentum of the injection can contribute to the thrust production. Thus, embedded rocket chamber was supposed to the operated as fuel rich gas generator at very high output. This configuration was tested at simulated flight Mach number of 7-11 at High Enthalpy Shock Tunnel (HIEST) with detonation tube as the source of the simulated rocket exhaust. However, combustion of the residual fuel in the rocket exhaust with airflow could not be attained. Direct-connect combustor tests were performed to evaluate effectiveness of a combustion enhancement technique termed auxiliary injection, i.e., a portion of fuel to be directly injected into airflow to provide ignition source for the residual fuel. Results of both the engine model tests at HIEST and the direct-connect tests are summarized and presented, and modification to the engine model for combustion enhancement was proposed.

Sadatake Tomioka, By; Ryohei Kobayashi; Murakami, Atsuo; Shuichi Ueda; Komuro, Tomoyuki; Katsuhiro Itoh, And

84

Experimental Research of the Oxygen-Enriched Combustion of Sewage Sludge and Coal in CFB  

NASA Astrophysics Data System (ADS)

Sewage sludge is the by-products of sewage treatment, and it is a fuel of high moisture, high ash and low caloric. Oxygen-enriched combustion technology is one of the new and clean coal combustion technologies that can control pollutant emission, which makes CO2 separation, SO2 treatment become easier, and NOx emission reduced. In this paper, we carried out the experimental research on the advantages of oxygen-enriched combustion and the characteristics of sewage sludge in a CFB incinerator that the diameter of the furnace is 100 mm, It is an important foundation for the industrialized application of the oxygen-enriched combustion of sewage sludge and coal in CFB. Experimental analyzed on the combustion characteristics of three conditions in the oxygen concentration of 21%˜35%, which were the weight ratio of coal and sludge were 1?1, 1?2 and also the coal was given. Furthermore, the change of gas composition along with the change of oxygen content and the temperature of dense phase region was analyzed. The results showed that the combustion characteristics differ from the different mixing rate between coal and sludge in different oxygen atmosphere, when the fluidized air velocity was 1.56 m/s˜1.88 m/s, the combustion stability; When the amount of the fuel was constant, as the increase of the oxygen contents in the experimental atmosphere, the total air volume decreased, the furnace temperature increased gradually, the concentration of SO2 and NOx showed increasing trend, which is beneficial to the removal of SO2; The concentration of NOx was increased gradually as temperature of the fluidized bed increased.

Xin, S. W.; Lu, X. F.; Liu, H. Z.

85

Esperson Dome oxygen combustion pilot test: Postburn coring results  

SciTech Connect

Postburn corehole data from an O[sub 2] combustion pilot test in Esperson Dome field, Liberty County, TX, show that the combustion temperature was 930 to 1,020 F. Final oil saturation was 0% in the burned zone and 11% to 34% in the sand adjacent to the burned zone. Roughly 49,000 bbl of incremental oil was produced at an injected O[sub 2]/produced-oil ratio of 4.1 Mscf/bbl.

Choquette, S.P.; Sampath, K.; Northrop, P.S.; Edwards, J.T.; Laali, H. (Mobil Research and Development Corp., Dallas, TX (United States)); Rowland, B. (Mobil Exploration and Producing Services Inc., Dallas, TX (United States)); Morrow, D.

1993-05-01

86

International cooperation on hydrogen oxygen high pressure combustion  

Microsoft Academic Search

DLR and DASA of Germany as well as CNES and SEP of France have decided to collaborate on oxygenhydrogen highpressure combustion. In order to promote and intensify a common program the novel research and test facility P8 for LO2GH2 high-pressure rocket combustors is presently being built at the DLR in Lampoldshausen. It provides for combustion chamber pressures up to 30

M. Popp; O. J. Haidn; B. Potier; P. Vuillermoz

1995-01-01

87

Reactive oxygen species enhance insulin sensitivity  

PubMed Central

SUMMARY Chronic reactive oxygen species (ROS) production by mitochondria may contribute to the development of insulin resistance, a primary feature of type 2 diabetes. In recent years it has become apparent that ROS generation in response to physiological stimuli such as insulin may also facilitate signaling by reversibly oxidizing and inhibiting protein tyrosine phosphatases (PTPs). Here we report that mice lacking one of the key enzymes involved in the elimination of physiological ROS, glutathione peroxidase 1 (Gpx1), were protected from high fat diet-induced insulin resistance. The increased insulin sensitivity in Gpx1?/? mice was attributed to insulin-induced phosphatidylinositol-3-kinase/Akt signaling and glucose uptake in muscle and could be reversed by the anti-oxidant N-acetylcysteine. Increased insulin signaling correlated with enhanced oxidation of the PTP family member PTEN, which terminates signals generated by phosphatidylinositol-3-kinase. These studies provide causal evidence for the enhancement of insulin signaling by ROS in vivo.

Loh, Kim; Deng, Haiyang; Fukushima, Atsushi; Cai, Xiaochu; Boivin, Benoit; Galic, Sandra; Bruce, Clinton; Shields, Benjamin J.; Skiba, Beata; Ooms, Lisa M.; Stepto, Nigel; Wu, Ben; Mitchell, Christina A.; Tonks, Nicholas K.; Watt, Matthew J.; Febbraio, Mark A.; Crack, Peter J.; Andrikopoulos, Sofianos; Tiganis, Tony

2010-01-01

88

Microwave enhanced combustion of laminar hydrocarbon flame fronts  

NASA Astrophysics Data System (ADS)

The X-43 missions in 2005 demonstrated the feasibility of a hydrogen fueled scramjet. Since that time, the cost, performance, and safety concerns surrounding the use of hydrogen have motivated researchers to investigate methods of enhancing the performance of easily stored hydrocarbon based fuels by improving their ignition, flammability, and flameholding characteristics. The microwave enhanced combustion testbed has demonstrated a significant increase in the laminar flame speed of a premixed CH4/air flame when 1.3 kW continuous wave (CW) microwave radiation is directed at the flame front in a high-Q resonant cavity. The main aspect of the research aimed to accurately quantify key combustion parameters in the microwave enhanced flame using laser diagnostics for improved spatial resolution and accuracy over invasive probe devices. Particle image velocimetry (PIV), filtered Rayleigh scattering (FRS), and planar laser induced fluorescence (PLIF) were used to measured flame speed, temperature, and OH radical concentrations, respectively. The PIV and FRS laser experiments measured increases in flame speed up to 20% and a deposition of only 30 W of microwave power into the flame. The temperature measurements show an increase of temperature within the flame front as well as in the post flame region that are not of large enough magnitude to account for the flame speed increase via simple joule heating. Alongside PLIF measurements of an enhanced concentration of OH in the flame zone, these results imply that the microwave enhanced combustion was a combined thermal joule heating and non-equilibrium interaction. By replacing the CW microwave source with a pulsed magnetron that is capable of generating 1 mus wide, 30 kW peak power pulses at 1000 pulses per second, similar flame speed enhancements were achieved with 40 times less power. This effort provides the first realistic approach towards incorporating the microwave enhanced combustion concept into a scramjet combustor.

Stockman, Emanuel Solomon

89

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

Microsoft Academic Search

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

N. Arai; M. Hasatani; S. Sugiyama

1983-01-01

90

Enhanced Combustion Low NOx Pulverized Coal Burner  

Microsoft Academic Search

For more than two decades, Alstom Power Inc. (Alstom) has developed a range of low cost, infurnace technologies for NOx emissions control for the domestic U.S. pulverized coal fired boiler market. This includes Alstom's internally developed TFS 2000{trademark} firing system, and various enhancements to it developed in concert with the U.S. Department of Energy. As of the date of this

David Towle; Richard Donais; Todd Hellewell; Robert Lewis; Robert Schrecengost

2007-01-01

91

Alarming Oxygen Depletion Caused by Hydrogen Combustion and Fuel Cells and their Resolution by Magnegas$^{TM}$  

Microsoft Academic Search

We recall that hydrogen combustion does resolve the environmental problems of\\u000afossil fuels due to excessive emission of carcinogenic substances and carbon\\u000adioxide. However, hydrogen combustion implies the permanent removal from our\\u000aatmosphere of directly usable oxygen, a serious environmental problem called\\u000aoxygen depletion, since the combustion turns oxygen into water whose separation\\u000ato restore the original oxygen is prohibitive

Ruggero Maria Santilli

2000-01-01

92

BIOLOGICALLY ENHANCED OXYGEN TRANSFER IN THE ACTIVATED SLUDGE PROCESS (JOURNAL)  

EPA Science Inventory

Biologically enhanced oxgyen transfer has been a hypothesis to explain observed oxygen transfer rates in activated sludge systems that were well above that predicted from aerator clean-water testing. The enhanced oxygen transfer rates were based on tests using BOD bottle oxygen ...

93

Detailed chemical kinetic modeling of diesel combustion with oxygenated fuels  

SciTech Connect

The influence of oxygenated hydrocarbons as additives to diesel fuels on ignition, NOx emissions and soot production has been examined using a detailed chemical kinetic reaction mechanism. N-heptane was used as a representative diesel fuel, and methanol, ethanol, dimethyl ether and dimethoxymethane were used as oxygenated fuel additives. It was found that addition of oxygenated hydrocarbons reduced NOx levels and reduced the production of soot precursors. When the overall oxygen content in the fuel reached approximately 25% by mass, production of soot precursors fell effectively to zero, in agreement with experimental studies. The kinetic factors responsible for these observations are discussed.

Pitz, W J; Curran, H J; Fisher, E; Glaude, P A; Marinov, N M; Westbrook, C K

1999-10-28

94

Sensor for measuring the oxygen content in the exhaust gas of combustion engines and method thereof  

SciTech Connect

An improved lambda sensor is disclosed for the measurement of the oxygen content in the exhaust gas of internal combustion engines in which the sensor element is provided with a gas permeable wrapping coated with a catalyst. The sensor delivers a clear well defined signal in the so-called rich exhaust gas, which makes possible a more precise adjustment of the fuel-air mixture fed to the internal combustion engine.

Bozon, A.; Koberstein, E.; Pletka, H.; Voelker, H.

1982-12-07

95

Combustion Dynamics of Plasma-Enhanced Premixed and Nonpremixed Flames  

Microsoft Academic Search

Combustion dynamics are investigated for plasma-enhanced methane-air flames in premixed and nonpremixed configurations using a transient arc dc plasmatron. Planar laser-induced fluorescence images of hydroxyl (OH) and carbon monoxide (CO) radicals are obtained over a range of equivalence ratios (? = 0.7 - 1.3), flow rates (6-18 LPM), and plasma powers (100-900 mA) to monitor radical propagation and in situ

Xing Rao; Steve Hammack; Tonghun Lee; Campbell Carter; Igor B. Matveev

2010-01-01

96

Oxygen index: An approximate value for the evaluation of combustion characteristics  

NASA Technical Reports Server (NTRS)

The oxygen index has gained international recognition for the determination of combustion characteristics of plastic material. The amounts of oxygen and nitrogen were more accurately determined for existing test equipment in order to specify the oxygen index as precisely and as reproducible as possible. Parameters are outlined such as the size of the ignition flame, ignition of test pieces, test piece sizes and test temperature. The minimum oxygen index was determined by the dimension and duration of the fire. The results are sufficiently accurate for factory operating conditions and are also reproducible.

Zartmann, I.; Reinwardt, D.; Franke, A.

1986-01-01

97

Powdered Aluminum and Oxygen Rocket Propellants: Subscale Combustion Experiments.  

National Technical Information Service (NTIS)

Aluminum combined with oxygen has been proposed as a potential lunar in situ propellant for ascent/descent and return missions for future lunar exploration. Engine concepts proposed to use this propellant have not previously been demonstrated, and the imp...

M. L. Meyer

1993-01-01

98

Numerical simulation of operation processes in the combustion chamber and gas generator of oxygen-methane liquid rocket engine  

NASA Astrophysics Data System (ADS)

The results of numerical simulations of processes in gas generators and combustion chambers operating on oxygen and methane are presented. Specific features of mixing, evaporation, and combustion of propellants have been investigated. The degree of combustion completeness in chambers with three types of injectors - coaxial-jet gas-liquid, liquid-liquid monopropellant, and bipropellant impinging-jets injectors - has been estimated.

Kalmykov, G. P.; Larionov, A. A.; Sidlerov, D. A.; Yanchilin, L. A.

2009-09-01

99

Chemical looping combustion of biomass-derived syngas using ceria-supported oxygen carriers.  

PubMed

Cu, Ni and Fe oxides supported on ceria were investigated for their performance as oxygen carriers during the chemical looping combustion of biomass-derived syngas. A complex gas mixture containing CO, H2, CO2, CH4 and other hydrocarbons was used to simulate the complex fuel gas environment derived from biomass gasification. Results show that the transfer of the stored oxygen into oxidants for the supported Cu and Ni oxides at 800°C for the combustion of syngas was effective (>85%). The unsupported Cu oxide showed high oxygen carrying capacity but particle sintering was observed at 800°C. A reaction temperature of 950°C was required for the supported Fe oxides to transfer the stored oxygen into oxidants effectively. Also, for the complex fuel gas environment, the supported Ni oxide was somewhat effective in reforming CH4 and other light hydrocarbons into CO, which may have benefits for the reduction of tar produced during biomass pyrolysis. PMID:23711944

Huang, H B; Aisyah, L; Ashman, P J; Leung, Y C; Kwong, C W

2013-07-01

100

Potentiometric microdetermination of aluminium in organic compounds after combustion in a modified oxygen flask  

Microsoft Academic Search

The microdetermination of aluminium in organic compounds by oxygen flask combustion, a simultaneous fusioncombustion procedure was developed, in which the sample in a mixture with KHSO4 is burnt in a modified oxygen flask under suitable conditions so that the alumina formed is immediately converted into the corresponding water-soluble sulfate. 2.4 ml of 6M HCl are used as absorption solution, in

Antonio Campiglio

1986-01-01

101

Laser-induced breakdown spectroscopy for measurement of fuel\\/oxygen mixing in combustion  

Microsoft Academic Search

Laser-induced breakdown spectroscopy (LIBS) is applied for measurement of C-O equivalence ratios and mixing in a methane\\/oxygen flame. A nominal 10-nanosecond Q-switched Nd:YAG laser is used to effect a cascade-type optical breakdown in the flame, which is projected above a pre-mixed McKenna burner. Atomic and ionic carbon and oxygen spectra are used to verify the combustion equivalence ratios in the

Matthew Dackman; J. W. L. Lewis; Ying-Ling Chen; Lei Shi

2007-01-01

102

PROGRESS IN DETAILED KINETIC MODELING OF THE COMBUSTION OF OXYGENATED COMPONENTS OF BIOFUELS.  

PubMed

Due to growing environmental concerns and diminishing petroleum reserves, a wide range of oxygenated species has been proposed as possible substitutes to fossil fuels: alcohols, methyl esters, acyclic and cyclic ethers. After a short review the major detailed kinetic models already proposed in the literature for the combustion of these molecules, the specific classes of reactions considered for modeling the oxidation of acyclic and cyclic oxygenated molecules respectively, are detailed. PMID:23700355

Sy Tran, Luc; Sirjean, Baptiste; Glaude, Pierre-Alexandre; Fournet, René; Battin-Leclerc, Frédérique

2012-07-01

103

Hydrocarbon combustion enhancement by applied electric field and plasma kinetics  

NASA Astrophysics Data System (ADS)

Hydrocarbon flame speed and flame structure modifications have been studied using a low dc applied electric field opposing the gas flow directions. Our electrode configuration leads to a relatively high conduction current with a low applied voltage drop in the flame that permits to collect ~1011 cm-3 chemi-ion density at the pre-heat flame zone, which seems to simulate DBDs and other plasma assisted combustion enhancement conditions. The dissociative recombination of major positive chemi-ions H3O+ and HCO+ produces 1011 cm-3 H, O and OH radicals modifying both combustion kinetics and fluidics. Also, flame electrical conductivity measurement was found to correlate very well with the CH, OH and C2 chemiluminescence intensity fluctuations.

Ganguly, B. N.

2007-12-01

104

OXYGEN-ENRICHED COAL COMBUSTION WITH CARBON DIOXIDE RECYCLE AND RECOVERY: SIMULATION AND EXPERIMENTAL STUDY  

SciTech Connect

This report examines coal combustion using oxygen feed with carbon dioxide recycle to control the adiabatic flame temperature. Computer simulations using an existing state-of-the-art 3-dimensional computer code for turbulent reacting flows with reacting particles were employed to study the effects of increased carbon dioxide mole fraction on the char burnout, radiant heat transfer, metal partitioning, and NOx formation.

John M. Veranth; Gautham Krishnamoorthy

2001-04-01

105

Sensor for measuring the oxygen content in the exhaust gas of combustion engines and method thereof  

Microsoft Academic Search

An improved lambda sensor is disclosed for the measurement of the oxygen content in the exhaust gas of internal combustion engines in which the sensor element is provided with a gas permeable wrapping coated with a catalyst. The sensor delivers a clear well defined signal in the so-called rich exhaust gas, which makes possible a more precise adjustment of the

A. Bozon; E. Koberstein; H. Pletka; H. Voelker

1982-01-01

106

Mathematical analysis of potentiometric oxygen sensors for combustion-gas streams  

Microsoft Academic Search

The mathematical tools necessary to describe quantitatively the chemical processes that dictate the performance of exhaust oxygen sensors are developed. Such sensor are used commonly to monitor exhaust streams generated by internal-combustion processes. Calculated results compared will with available experimental results, although several open questions are identified that require more experimental data. The mathematical formalism for describing the transport of

Daniel R. Baker; Mark W. Verbrugge

1994-01-01

107

Promoted Combustion of Metals in a High-Pressure, Flowing Oxygen Environment  

NASA Technical Reports Server (NTRS)

Traditional promoted combustion testing has used 0.125 inch diameter samples that are ignited in a pressurized, oxygen-enriched environment. Many years of testing this sample size have yielded useful data regarding threshold pressure, or the minimum oxygen pressure required to support self-sustained combustion. However, when a material is tested in a flowing system, the threshold pressure changes. White Sands Test Facility has developed a test system to burn samples in flowing gaseous oxygen. Current sample configurations are 0.5 inch diameter rods and 1.25 inch diameter pipes with pressures ranging up to 2000 psi and gas velocities reaching 200 ft/s. This paper describes the test apparatus, modifications made as the result of a fire, and a description of the tests currently being performed.

Maes, M. J.; Stoltzfus, J. M.

2001-01-01

108

Determining the Source of Oxygen in Post-Detonation Combustion of Aluminum  

NASA Astrophysics Data System (ADS)

Aluminum is often added to explosive formulations in the form of micron-sized particles to increase the energy released. Aluminum particles combust by reacting with oxidizers from the detonation products (such as CO) and the surrounding atmosphere (O2). Quantifying the oxygen contribution from these sources is important for improved modeling and formulation. This work will determine the ratio of oxygen from detonation products to oxygen from the atmosphere using isotopic labeling. We detonated a 10-20 g aluminum-containing explosive formulation in a simulated air atmosphere where the oxygen was ^18O2. We collected the solid detonation products after detonation and analyzed them using secondary ion mass spectrometry (SIMS) to measure the ratio of ^18O to ^16O and thus the percentage of oxygen of aluminum combustion from the detonation products versus from the atmosphere. Preliminary results of detonations performed in a rigid chamber showed ˜60% of the oxygen came from the atmosphere. In further experiments, we will create a free-field condition by performing detonations in flexible, thin-walled plastic spheres of known radius containing an ^18O2-enriched air atmosphere. We will then isolate the post-detonation aluminum oxide and determine the oxygen isotope ratio using SIMS analysis.

Monat, Jeremy; Carney, Joel; Lightstone, James; Shimizu, Nobumichi

2011-06-01

109

Effect of support on reactivity and selectivity of Ni-based oxygen carriers for chemical-looping combustion  

Microsoft Academic Search

Different Ni-based oxygen carriers were prepared by dry impregnation using ?-Al2O3 as support. The reactivity, selectivity during methane combustion, attrition rate and agglomeration behavior of the oxygen carriers were measured and analyzed in a thermogravimetric analyzer and in a batch fluidized bed during multi-cycle reduction–oxidation tests.Ni-based oxygen carriers prepared on ?-Al2O3 showed low reactivity and low methane combustion selectivity to

Pilar Gayán; Luis F. de Diego; Francisco García-Labiano; Juan Adánez; Alberto Abad; Cristina Dueso

2008-01-01

110

Two-wavelength pyrometry study of the combustion of sulfide minerals: Part III. The influence of oxygen concentration on pyrite combustion  

NASA Astrophysics Data System (ADS)

The strong influence of oxygen concentration on the combustion of pyrite at a furnace temperature of 1130 K has been investigated by pyrometer measurements of the temperature of individual particles and by morphological examination of the reaction products. Three distinct types of behavior were identified depending on the oxygen concentration. With oxygen levels between 10 and 40 pct, the maximum temperature of the pyrite particles increased linearly from about 2000 to over 3000 K while heating rates also climbed. The characteristics of the combustion pulses from the pyrometer revealed that cenosphere inflation occurred at the maximum particle temperature and that the freezing of a magnetite shell is subsequent to, not associated with, sudden expansion of the particles. For oxygen concentrations between 40 and 80 pct, the maximum particle temperature was independent of oxygen concentration, remaining constant at 3000 to 3400 K; however, heating rates were some-what variable. The combustion pulse characteristics again suggested that particles inflate into cenospheres but there was an increased tendency for them to rupture. At oxygen concentrations of 80 pct and greater, higher heating rates were measured but the maximum particle temperatures were limited to 3200 to 3500 K. The combustion pulse characteristics in oxygen suggested that the termination of reactions is consistent with material ejection or particle disintegration as opposed to cenosphere inflation. The results generally were consistent with the reaction rate being governed by oxygen transport in the gas phase, although at higher oxygen concentrations evaporation of the iron species and other physical phenomena limited the particle temperature.

Tuffrey, N. E.; Richards, G. G.; Brimacombe, J. K.

1995-10-01

111

A System for Controlling the Oxygen Content of a Gas Produced by Combustion  

NASA Technical Reports Server (NTRS)

A mixture of air, CH4 and OH(2) is burned in a combustion chamber to produce a product gas in the test section. The OH(2) content of the product gas is compared with the OH(2) content of reference air in an OH(2) sensor. If there is a difference an error signal is produced at the output of a control circuit which by the means of a solenoid valve, regulates the flow of OH(2) into the combustion chamber to make the error signal zero. The product gas in the test section has the same oxygen content as air.

Singh, J. J.; Davis, W. T.; Puster, R. L. (inventors)

1984-01-01

112

Carbon dioxide remediation via oxygen-enriched combustion using dense ceramic membranes  

DOEpatents

A method of combusting pulverized coal by mixing the pulverized coal and an oxidant gas to provide a pulverized coal-oxidant gas mixture and contacting the pulverized coal-oxidant gas mixture with a flame sufficiently hot to combust the mixture. An oxygen-containing gas is passed in contact with a dense ceramic membrane of metal oxide material having electron conductivity and oxygen ion conductivity that is gas-impervious until the oxygen concentration on one side of the membrane is not less than about 30% by volume. An oxidant gas with an oxygen concentration of not less than about 30% by volume and a CO.sub.2 concentration of not less than about 30% by volume and pulverized coal is contacted with a flame sufficiently hot to combust the mixture to produce heat and a flue gas. One dense ceramic membrane disclosed is selected from the group consisting of materials having formulae SrCo.sub.0.8 Fe.sub.0.2 O.sub.x, SrCo.sub.0.5 FeO.sub.x and La.sub.0.2 Sr.sub.0.8 Co.sub.0.4 Fe.sub.0.6 O.sub.x.

Balachandran, Uthamalingam (Hinsdale, IL); Bose, Arun C. (Pittsburgh, PA); McIlvried, Howard G. (Pittsburgh, PA)

2001-01-01

113

Enhanced oxygen precipitation in electron irradiated silicon  

Microsoft Academic Search

The precipitation of oxygen has been investigated for 2 MeV electron irradiated silicon samples, with irradiation doses 1015–1018 cm?2, at an annealing temperature of 900 °C for up to 444 h. The samples initially contained either different concentrations of the vacancy-oxygen (VO) center created at the irradiation, or the vacancy-dioxygen (VO2) center created by annealing at 350 °C after the

Tomas Hallberg; J. Lennart Lindström

1992-01-01

114

Enhanced Glow Discharge Production of Oxygen  

NASA Technical Reports Server (NTRS)

Studies starting in late seventies have shown Mars atmosphere can be used as a feedstock for oxygen production using simple chemical processing systems during early phases of the Mars exploration program. This approach has been recognized as one of the most important in-situ resource utilization (ISRU) concepts for enabling future round trip Mars missions. It was determined a decade ago that separation of oxygen can be accomplished efficiently by permeation through a silver membrane at temperatures well below 1000 K. This process involves adsorption of atomic oxygen on the surface and its subsequent diffusion through a silver lattice via an oxygen concentration gradient. We have determined recently that glow discharge can be used to liberate atomic oxygen from Mars atmosphere and that the oxygen can be collected through a silver permeation membrane. Recently, we demonstrated a substantial increase in energy efficiency of the process by applying a radio frequency discharge in combination with a silver permeation membrane. The experiments were performed using pure carbon dioxide in the pressure range equal to Mars surface conditions. Energy efficiency was defined as the ratio of the energy required to dissociate a unit mass of oxygen from carbon dioxide to the (electrical) energy consumed by the overall system during the dissociation and collection process. The research effort, started at NASA Langley Research Center, continued with this project. Oxygen production apparatus, built and operated under the research grant NAG1-1140 was relocated to the Atomic Beams Laboratory at ODU in July 1996, being since then in fall operation.

Ash, Robert; Zhong, Shi

1998-01-01

115

A Preliminary Study on the Toxic Combustion Products Testing of Polymers Used in High-Pressure Oxygen Systems  

NASA Technical Reports Server (NTRS)

One likely cause of polymer ignition in a high-pressure oxygen system is adiabatic-compression heating of polymers caused by pneumatic impact. Oxidative _ pyrolysis or combustion of polymers in a high-pressure oxygen system could generate toxic gases. This paper reports the preliminary results of toxic combustion product testing of selected polymers in a pneumatic-impact test system. Five polymers commonly used in high-pressure oxygen systems, Nylon 6/6, polychlorotrifluoroethylene (CTFE), polytetrafluoroethylene (PTFE), fluoroelastomer (Viton(TradeMark) A), and nitrile rubber (Buna N), were tested in a pneumatic-impact test system at 2500- or 3500-psia oxygen pressure. The polymers were ignited and burned, then combustion products were collected in a stainless-steel sample bottle and analyzed by GC/MS/IRD, GC/FID, and GC/Methanizer/FID. The results of adiabatic-compression tests show that combustion of hydrocarbon polymers, nitrogen-containing polymers, and halogenated polymers in high-pressure oxygen systems are relatively complete. Toxicity of the combustion product gas is presumably much lower than the combustion product gas generated from ambient-pressure oxygen (or air) environments. The NASA-Lewis equilibrium code was used to determine the composition of combustion product gas generated from a simulated, adiabatic-compression test of nine polymers. The results are presented and discussed.

Hshieh, Fu-Yu; Beeson, Harold D.

2004-01-01

116

Chemicl-looping combustion of coal with metal oxide oxygen carriers  

SciTech Connect

The combustion and reoxidation properties of direct coal chemical-looping combustion (CLC) over CuO, Fe2O3, Co3O4, NiO, and Mn2O3 were investigated using thermogravimetric analysis (TGA) and bench-scale fixed-bed flow reactor studies. When coal is heated in either nitrogen or carbon dioxide (CO2), 50% of weight loss was observed because of partial pyrolysis, consistent with the proximate analysis. Among various metal oxides evaluated, CuO showed the best reaction properties: CuO can initiate the reduction reaction as low as 500 °C and complete the full combustion at 700 °C. In addition, the reduced copper can be fully reoxidized by air at 700 °C. The combustion products formed during the CLC reaction of the coal/metal oxide mixture are CO2 and water, while no carbon monoxide was observed. Multicycle TGA tests and bench-scale fixed-bed flow reactor tests strongly supported the feasibility of CLC of coal by using CuO as an oxygen carrier. Scanning electron microscopy (SEM) images of solid reaction products indicated some changes in the surface morphology of a CuO-coal sample after reduction/oxidation reactions at 800 °C. However, significant surface sintering was not observed. The interactions of fly ash with metal oxides were investigated by X-ray diffraction and thermodynamic analysis. Overall, the results indicated that it is feasible to develop CLC with coal by metal oxides as oxygen carriers.

Siriwardane, R.; Tian, H.; Richards, G.; Simonyi, T.; Poston, J.

2009-01-01

117

The use of NiO as an oxygen carrier in chemical-looping combustion  

Microsoft Academic Search

The feasibility of using NiO as an oxygen carrier during chemical-looping combustion has been investigated. A thermodynamic analysis with CH4 as fuel showed that the yield of CH4 to CO2 and H2O was between 97.7 and 99.8% in the temperature range 700–1200°C, with the yield decreasing as the temperature increases. Carbon deposition is not expected as long as sufficient metal

Tobias Mattisson; Marcus Johansson; Anders Lyngfelt

2006-01-01

118

Dynamic Oxygen-Enhanced MRI of Cerebrospinal Fluid  

PubMed Central

Oxygen causes an increase in the longitudinal relaxation rate of tissues through its T1-shortening effect owing to its paramagnetic properties. Due to such effects, MRI has been used to study oxygen-related signal intensity changes in various body parts including cerebrospinal fluid (CSF) space. Oxygen enhancement of CSF has been mainly studied using MRI sequences with relatively longer time resolution such as FLAIR, and T1 value calculation. In this study, fifteen healthy volunteers were scanned using fast advanced spin echo MRI sequence with and without inversion recovery pulse in order to dynamically track oxygen enhancement of CSF. We also focused on the differences of oxygen enhancement at sulcal and ventricular CSF. Our results revealed that CSF signal after administration of oxygen shows rapid signal increase in both sulcal CSF and ventricular CSF on both sequences, with statistically significant predominant increase in sulcal CSF compared with ventricular CSF. CSF is traditionally thought to mainly form from the choroid plexus in the ventricles and is absorbed at the arachnoid villi, however, it is also believed that cerebral arterioles contribute to the production and absorption of CSF, and controversy remains in terms of the precise mechanism. Our results demonstrated rapid oxygen enhancement in sulcal CSF, which may suggest inhaled oxygen may diffuse into sulcal CSF space rapidly probably due to the abundance of pial arterioles on the brain sulci.

Mehemed, Taha M.; Fushimi, Yasutaka; Okada, Tomohisa; Yamamoto, Akira; Kanagaki, Mitsunori; Kido, Aki; Fujimoto, Koji; Sakashita, Naotaka; Togashi, Kaori

2014-01-01

119

Dynamic oxygen-enhanced MRI of cerebrospinal fluid.  

PubMed

Oxygen causes an increase in the longitudinal relaxation rate of tissues through its T1-shortening effect owing to its paramagnetic properties. Due to such effects, MRI has been used to study oxygen-related signal intensity changes in various body parts including cerebrospinal fluid (CSF) space. Oxygen enhancement of CSF has been mainly studied using MRI sequences with relatively longer time resolution such as FLAIR, and T1 value calculation. In this study, fifteen healthy volunteers were scanned using fast advanced spin echo MRI sequence with and without inversion recovery pulse in order to dynamically track oxygen enhancement of CSF. We also focused on the differences of oxygen enhancement at sulcal and ventricular CSF. Our results revealed that CSF signal after administration of oxygen shows rapid signal increase in both sulcal CSF and ventricular CSF on both sequences, with statistically significant predominant increase in sulcal CSF compared with ventricular CSF. CSF is traditionally thought to mainly form from the choroid plexus in the ventricles and is absorbed at the arachnoid villi, however, it is also believed that cerebral arterioles contribute to the production and absorption of CSF, and controversy remains in terms of the precise mechanism. Our results demonstrated rapid oxygen enhancement in sulcal CSF, which may suggest inhaled oxygen may diffuse into sulcal CSF space rapidly probably due to the abundance of pial arterioles on the brain sulci. PMID:24956198

Mehemed, Taha M; Fushimi, Yasutaka; Okada, Tomohisa; Yamamoto, Akira; Kanagaki, Mitsunori; Kido, Aki; Fujimoto, Koji; Sakashita, Naotaka; Togashi, Kaori

2014-01-01

120

EFFECT OF OXYGEN - ENHANCEMENT ON HAZARDOUS WASTE INCINERATION  

EPA Science Inventory

How does the addition of oxygen improve the applicability of incineration? his paper addresses that question by evaluating the performance of oxygen enhanced hazardous waste incineration in three different applications. he cases studied include a laboratory study of the use of ox...

121

Molecular Gas Dynamical Analysis of Initial Combustion Enhancement Due to a Plasma Torch in Supersonic Shear Flow  

NASA Astrophysics Data System (ADS)

The 1st report clarified the superiority of the atomic oxygen injected from a plasma torch with the diffusive mode operation for initiating supersonic combustion. In this paper the features of combustion enhancement by various combinations of plasma mole flux and heat flux are investigated. The effectiveness of each combination is evaluated by H2O production efficiency. A molecular dynamical numerical simulation technique with the reactional molecular collision model is applied for the analysis of multi-species reaction system. The results of parametric study show that the effect of atomic oxygen plasma is attributed to the mole flux, whilst the strong dependence on the heat flux is observed for the atomic hydrogen plasma.

Obata, Shigeo; Nagashima, Toshio

122

Alterations of bitumen produced by the in-situ combustion process at the oxygen Wolf Lake Project, Alberta  

Microsoft Academic Search

The Oxygen Wolf Lake Project, operated by BP Resources Canada Limited, recovers bitumen by an in-situ combustion process. Bitumen samples produced from this process were analyzed and compared with analyses of unaltered bitumen from the same formation. The naphtha and middle distillate fractions were greater in the samples produced by the in-situ combustion process, which indicates thermal cracking has occurred.

C. Riechert; B. Fuhr; G. Williams; H. Sawatzky; K. Jha; R. Lafleur

1989-01-01

123

COâ emission abatement in IGCC power plants by semiclosed cycles: Part A -- With oxygen-blown combustion  

Microsoft Academic Search

This paper analyzes the fundamentals of IGCC power plants where carbon dioxide produced by syngas combustion can be removed, liquefied and eventually disposed, to limit the environmental problems due to the greenhouse effect. To achieve this goal, a semiclosed-loop gas turbine cycle using an highly-enriched COâ mixture as working fluid was adopted. As the oxidizer, the syngas combustion utilizes oxygen

P. Chiesa; G. Lozza

1999-01-01

124

Emission of oxygenated polycyclic aromatic hydrocarbons from indoor solid fuel combustion.  

PubMed

Indoor solid fuel combustion is a dominant source of polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs) and the latter are believed to be more toxic than the former. However, there is limited quantitative information on the emissions of OPAHs from solid fuel combustion. In this study, emission factors of OPAHs (EF(OPAH)) for nine commonly used crop residues and five coals burnt in typical residential stoves widely used in rural China were measured under simulated kitchen conditions. The total EF(OPAH) ranged from 2.8 ± 0.2 to 8.1 ± 2.2 mg/kg for tested crop residues and from 0.043 to 71 mg/kg for various coals and 9-fluorenone was the most abundant specie. The EF(OPAH) for indoor crop residue burning were 1-2 orders of magnitude higher than those from open burning, and they were affected by fuel properties and combustion conditions, like moisture and combustion efficiency. For both crop residues and coals, significantly positive correlations were found between EFs for the individual OPAHs and the parent PAHs. An oxygenation rate, R(o), was defined as the ratio of the EFs between the oxygenated and parent PAH species to describe the formation potential of OPAHs. For the studied OPAH/PAH pairs, mean R(o) values were 0.16-0.89 for crop residues and 0.03-0.25 for coals. R(o) for crop residues burned in the cooking stove were much higher than those for open burning and much lower than those in ambient air, indicating the influence of secondary formation of OPAH and loss of PAHs. In comparison with parent PAHs, OPAHs showed a higher tendency to be associated with particulate matter (PM), especially fine PM, and the dominate size ranges were 0.7-2.1 ?m for crop residues and high caking coals and <0.7 ?m for the tested low caking briquettes. PMID:21375317

Shen, Guofeng; Tao, Shu; Wang, Wei; Yang, Yifeng; Ding, Junnan; Xue, Miao; Min, Yujia; Zhu, Chen; Shen, Huizhong; Li, Wei; Wang, Bin; Wang, Rong; Wang, Wentao; Wang, Xilong; Russell, Armistead G

2011-04-15

125

Combustion Stability Analyses of Coaxial Element Injectors with Liquid Oxygen/Liquid Methane Propellants  

NASA Technical Reports Server (NTRS)

Liquid rocket engines using oxygen and methane propellants are being considered by the National Aeronautics and Space Administration (NASA) for in-space vehicles. This propellant combination has not been previously used in a flight-qualified engine system, so limited test data and analysis results are available at this stage of early development. NASA has funded several hardware-oriented activities with oxygen and methane propellants over the past several years with the Propulsion and Cryogenic Advanced Development (PCAD) project, under the Exploration Technology Development Program. As part of this effort, the NASA Marshall Space Flight Center has conducted combustion stability analyses of several of the configurations. This paper presents test data and analyses of combustion stability from the recent PCAD-funded test programs at the NASA MSFC. These test programs used swirl coaxial element injectors with liquid oxygen and liquid methane propellants. Oxygen was injected conventionally in the center of the coaxial element, and swirl was provided by tangential entry slots. Injectors with 28-element and 40-element patterns were tested with several configurations of combustion chambers, including ablative and calorimeter spool sections, and several configurations of fuel injection design. Low frequency combustion instability (chug) occurred with both injectors, and high-frequency combustion instability occurred at the first tangential (1T) transverse mode with the 40-element injector. In most tests, a transition between high-amplitude chug with gaseous methane flow and low-amplitude chug with liquid methane flow was readily observed. Chug analyses of both conditions were conducted using techniques from Wenzel and Szuch and from the Rocket Combustor Interactive Design and Analysis (ROCCID) code. The 1T mode instability occurred in several tests and was apparent by high-frequency pressure measurements as well as dramatic increases in calorimeter-measured heat flux throughout the chamber. Analyses of the transverse mode were conducted with ROCCID and empirical methods such as Hewitt d/V. This paper describes the test hardware configurations, test data, analysis methods, and presents results of the various analyses.

Hulka, J. R.

2010-01-01

126

A Brief Study on Toxic Combustion Products of the Polymers Used in High-Pressure Oxygen Systems  

NASA Technical Reports Server (NTRS)

One likely cause of polymer ignition in a high-pressure oxygen system is the adiabatic-compression heating of polymers caused by pneumatic impact. Oxidative pyrolysis or combustion of polymers in a high-pressure oxygen system could generate toxic gases. This paper investigates the feasibility of using the NASA pneumatic-impact system to conduct adiabatic-compression combustion tests and determines the toxic combustion products produced from the burning of five selected polymers. Five polymers commonly used in high-pressure oxygen systems, Zytel(Registered TradeMark) 42 (Nylon 6/6), Buna N (nitrile rubber), Witon(Registered TradeMark) A (copolymer of vinylidene fluoride and hexafluoropropylene), Neoflon(Registered TradeMark) (polychlorotrifluoroethylene), and Teflon(Registered TradeMark) (polytetrafluoroethylene), were tested in the NASA pneumatic-impact test system at 17.2-MPa oxygen pressure. The polymers were ignited and burned; combustion products were collected in a stainless-steel sample bottle and analyzed using various methods. The results show that the NASA pneumatic-impact system is an appropriate test system to conduct adiabatic-compression combustion tests and to collect combustion products for further chemical analysis. The composition of the combustion product gas generated from burning the five selected polymers are presented and discussed.

Hshieh, Fu-Yu; Beeson, Harold D.

2005-01-01

127

Reduction Kinetics of a CasO4 Based Oxygen Carrier for Chemical-Looping Combustion  

NASA Astrophysics Data System (ADS)

The CaSO4 based oxygen carrier has been proposed as an alternative low cost oxygen carrier for Chemical-looping combustion (CLC) of coal. The reduction of CaSO4 to CaS is an important step for the cyclic process of reduction/oxidation in CLC of coal with CaSO4 based oxygen carrier. Thermodynamic analysis of CaSO4 oxygen carrier with CO based on the principle of Gibbs free energy minimization show that the essentially high purity of CO2 can be obtained, while the solid product is CaS instead of CaO. The intrinsic reduction kinetics of a CaSO4 based oxygen carrier with CO was investigated in a differential fixed bed reactor. The effects of gas partial pressure (20%-70%) and temperature (880-950°C) on the reduction were investigated. The reduction was described with shrinking unreacted core model. Experimental results of CO partial pressure on the solid conversion show that the reduction of fresh oxygen carriers is of first order with respect to the CO partial pressure. Both chemical reaction control and product layer diffusion control determine the reduction rate. The dependences of reaction rate constant and effective diffusivity with temperature were both obtained. The kinetic equation well predicted the experimental data.

Xiao, R.; Song, Q. L.; Zheng, W. G.; Deng, Z. Y.; Shen, L. H.; Zhang, M. Y.

128

Oxygen bomb combustion of biological samples for inductively coupled plasma optical emission spectrometry  

NASA Astrophysics Data System (ADS)

A rapid sample preparation method is proposed for decomposition of milk powder, corn bran, bovine and fish tissues, containing certified contents of the analytes. The procedure involves sample combustion in a commercial stainless steel oxygen bomb operating at 25 bar. Most of the samples were decomposed within 5 min. Diluted nitric acid or water-soluble tertiary amines 10% v/v were used as absorption solutions. Calcium, Cu, K, Mg, Na, P, S and Zn were recovered with the bomb washings and determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Ethanol mixed with paraffin was used as a combustion aid to allow complete combustion. A cooling step prior releasing of the bomb valve was employed to increase the efficiency of sample combustion. Iodine was also determined in milk samples spiked with potassium iodide to evaluate the volatilization and collection of iodine in amine CFA-C medium and the feasibility of its determination by ICP-OES with axial view configuration. Most of the element recoveries in the samples were between 91 and 105% and the certified and found contents exhibited a fair agreement at a 95% confidence level.

Souza, Gilberto B.; Carrilho, Elma Neide V. M.; Oliveira, Camila V.; Nogueira, Ana Rita A.; Nóbrega, Joaquim A.

2002-12-01

129

Photographic study of combustion in a rocket engine I : variation in combustion of liquid oxygen and gasoline with seven methods of propellant injection  

NASA Technical Reports Server (NTRS)

Motion pictures at camera speeds up to 3000 frames per second were taken of the combustion of liquid oxygen and gasoline in a 100-pound-thrust rocket engine. The engine consisted of thin contour and injection plates clamped between two clear plastic sheets forming a two-dimensional engine with a view of the entire combustion chamber and nozzle. A photographic investigation was made of the effect of seven methods of propellant injection on the uniformity of combustion. From the photographs, it was found that the flame front extended almost to the faces of the injectors with most of the injection methods, all the injection systems resulted in a considerable nonuniformity of combustion, and luminosity rapidly decreased in the divergent part of the nozzle. Pressure vibration records indicated combustion vibrations that approximately corresponded to the resonant frequencies of the length and the thickness of the chamber. The combustion temperature divided by the molecular weight of the combustion gases as determined from the combustion photographs was about 50 to 70 percent of the theoretical value.

Bellman, Donald R; Humphrey, Jack C

1948-01-01

130

Chemical-looping combustion of coal with metal oxide oxygen carriers  

SciTech Connect

The combustion and reoxidation properties of direct coal chemical-looping combustion (CLC) over CuO, Fe{sub 2}O{sub 3}, CO{sub 3}O{sub 4}, NiO, and Mn{sub 2}O{sub 3} were investigated using thermogravimetric analysis (TGA) and bench-scale fixed-bed flow reactor studies. When coal is heated in either nitrogen or carbon dioxide (CO{sub 2}), 50% of weight loss was observed because of partial pyrolysis, consistent with the proximate analysis. Among various metal oxides evaluated, CuO showed the best reaction properties: CuO can initiate the reduction reaction as low as 500{sup o}C and complete the full combustion at 700{sup o}C. In addition, the reduced copper can be fully reoxidized by air at 700{sup o}C. The combustion products formed during the CLC reaction of the coal/metal oxide mixture are CO{sub 2} and water, while no carbon monoxide was observed. Multicycle TGA tests and bench-scale fixed-bed flow reactor tests strongly supported the feasibility of CLC of coal by using CuO as an oxygen carrier. Scanning electron microscopy (SEM) images of solid reaction products indicated some changes in the surface morphology of a CuO-coal sample after reduction/oxidation reactions at 800 {sup o}C. However, significant surface sintering was not observed. The interactions of fly ash with metal oxides were investigated by X-ray diffraction and thermodynamic analysis. Overall, the results indicated that it is feasible to develop CLC with coal by metal oxides as oxygen carriers. 22 refs., 12 figs., 2 tabs.

Ranjani Siriwardane; Hanjing Tian; George Richards; Thomas Simonyi; James Poston [United States Department of Energy, Morgantown, WN (United States). National Energy Technology Laboratory

2009-08-15

131

Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis.  

PubMed

The oxygen evolution reaction is a key reaction in water splitting. The common approach in the development of oxygen evolution catalysts is to search for catalytic materials with new and optimized chemical compositions and structures. Here we report an orthogonal approach to improve the activity of catalysts without alternating their compositions or structures. Specifically, liquid phase exfoliation is applied to enhance the oxygen evolution activity of layered double hydroxides. The exfoliated single-layer nanosheets exhibit significantly higher oxygen evolution activity than the corresponding bulk layered double hydroxides in alkaline conditions. The nanosheets from nickel iron and nickel cobalt layered double hydroxides outperform a commercial iridium dioxide catalyst in both activity and stability. The exfoliation creates more active sites and improves the electronic conductivity. This work demonstrates the promising catalytic activity of single-layered double hydroxides for the oxygen evolution reaction. PMID:25030209

Song, Fang; Hu, Xile

2014-01-01

132

Variable oxygen/nitrogen enriched intake air system for internal combustion engine applications  

DOEpatents

An air supply control system for selectively supplying ambient air, oxygen enriched air and nitrogen enriched air to an intake of an internal combustion engine includes an air mixing chamber that is in fluid communication with the air intake. At least a portion of the ambient air flowing to the mixing chamber is selectively diverted through a secondary path that includes a selectively permeable air separating membrane device due a differential pressure established across the air separating membrane. The permeable membrane device separates a portion of the nitrogen in the ambient air so that oxygen enriched air (permeate) and nitrogen enriched air (retentate) are produced. The oxygen enriched air and the nitrogen enriched air can be selectively supplied to the mixing chamber or expelled to atmosphere. Alternatively, a portion of the nitrogen enriched air can be supplied through another control valve to a monatomic-nitrogen plasma generator device so that atomic nitrogen produced from the nitrogen enriched air can be then injected into the exhaust of the engine. The oxygen enriched air or the nitrogen enriched air becomes mixed with the ambient air in the mixing chamber and then the mixed air is supplied to the intake of the engine. As a result, the air being supplied to the intake of the engine can be regulated with respect to the concentration of oxygen and/or nitrogen.

Poola, Ramesh B. (Woodridge, IL); Sekar, Ramanujam R. (Naperville, IL); Cole, Roger L. (Elmhurst, IL)

1997-01-01

133

Systematic Reduction of Combustion Reaction Mechanisms of common Hydrocarbons and Oxygenated Fuels  

NASA Astrophysics Data System (ADS)

The aim of this work is the development of a numerical technique for the reduction of reaction mechanisms of common hydrocarbon and oxygenated fuels, such as methane, ethylene, propane, methanol and ethanol, using steady-state and partial equilibrium assumptions. Numerical tests are carried to establish the basic chain for each fuel as well as to determine the amount of small products of combustion, whose concentration depends on the turbulent mixing and needs to be controlled due to environmental restrictions. The results are in agreement with data in the literature.

de Bortoli, A. L.; Vaz, F. A.; Lorenzzetti, G. S.; Martins, I.

2010-09-01

134

Corrosion prevention in copper combustion chamber liners of liquid oxygen/methane booster engines  

NASA Technical Reports Server (NTRS)

The use of a protective gold coating for preventing the corrosion of copper combustion chamber liners in liquid oxygen/methane booster engines is discussed with reference to experimental results. Gold-plated and unplated copper alloy specimens were tested in a carbothermal test facility providing realistic simulations of booster engine cooling channel conditions, such as temperature, pressure, flow velocity, and heat flux. Metallographic examinations of the unplated specimens showed severe corrosion as a result of the reaction with the sulfur-containing contaminant in the fuel. In contrast, gold-plated specimens showed no corrosion under similar operating conditions.

Rosenberg, S. D.; Gage, M. L.

1990-01-01

135

Carbon monoxide and oxygen combustion experiments: A demonstration of Mars in situ propellants  

NASA Technical Reports Server (NTRS)

The feasibility of using carbon monoxide and oxygen as rocket propellants was examined both experimentally and theoretically. The steady-state combustion of carbon monoxide and oxygen was demonstrated for the first time in a subscale rocket engine. Measurements of experimental characteristic velocity, vacuum specific impulse, and thrust coefficient efficiency were obtained over a mixture ratio range of 0.30 to 2.0 and a chamber pressures of 1070 and 530 kPa. The theoretical performance of the propellant combination was studied parametrically over the same mixture ratio range. In addition to one dimensional ideal performance predictions, various performance reduction mechanisms were also modeled, including finite-rate kinetic reactions, two-dimensional divergence effects and viscous boundary layer effects.

Linne, Diane L.

1991-01-01

136

Combustion Stability Characteristics of the Project Morpheus Liquid Oxygen/Liquid Methane Main Engine  

NASA Technical Reports Server (NTRS)

The Project Morpheus liquid oxygen (LOX) / liquid methane rocket engines demonstrated acousticcoupled combustion instabilities during sea-level ground-based testing at the NASA Johnson Space Center (JSC) and Stennis Space Center (SSC). High-amplitude, 1T, 1R, 1T1R (and higher order) modes appear to be triggered by injector conditions. The instability occurred during the Morpheus-specific engine ignition/start sequence, and did demonstrate the capability to propagate into mainstage. However, the instability was never observed to initiate during mainstage, even at low power levels. The Morpheus main engine is a JSC-designed 5,000 lbf-thrust, 4:1 throttling, pressure-fed cryogenic engine using an impinging element injector design. Two different engine designs, named HD4 and HD5, and two different builds of the HD4 engine all demonstrated similar instability characteristics. Through the analysis of more than 200 hot fire tests on the Morpheus vehicle and SSC test stand, a relationship between ignition stability and injector/chamber pressure was developed. The instability has the distinct characteristic of initiating at high relative injection pressure drop (dP) at low chamber pressure (Pc); i.e., instabilities initiated at high dP/Pc at low Pc during the start sequence. The high dP/Pc during start results during the injector /chamber chill-in, and is enhanced by hydraulic flip in the injector orifice elements. Because of the fixed mixture ratio of the existing engine design (the main valves share a common actuator), it is not currently possible to determine if LOX or methane injector dP/Pc were individual contributors (i.e., LOX and methane dP/Pc typically trend in the same direction within a given test). The instability demonstrated initiation characteristic of starting at or shortly after methane injector chillin. Colder methane (e.g., sub-cooled) at the injector inlet prior to engine start was much more likely to result in an instability. A secondary effect of LOX sub-cooling was also possibly observed; greater LOX sub- cooling improved stability. Some tests demonstrated a low-amplitude 1L-1T instability prior to LOX injector chill-in. The Morpheus main engine also demonstrated chug instabilities during some engine shutdown sequences on the flight vehicle and SSC test stand. The chug instability was also infrequently observed during the startup sequence. The chug instabilities predictably initiated at low dP/Pc at low Pc. The chug instabilities were always self-limiting; startup chug instabilities terminated during throttle-up and shutdown chug instabilities decayed by shutdown termination.

Melcher, J. C.; Morehead, Robert L.

2014-01-01

137

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

SciTech Connect

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

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

2005-01-15

138

Laser-induced breakdown spectroscopy for measurement of fuel/oxygen mixing in combustion  

NASA Astrophysics Data System (ADS)

Laser-induced breakdown spectroscopy (LIBS) is applied for measurement of C-O equivalence ratios and mixing in a methane/oxygen flame. A nominal 10-nanosecond Q-switched Nd:YAG laser is used to effect a cascade-type optical breakdown in the flame, which is projected above a pre-mixed McKenna burner. Atomic and ionic carbon and oxygen spectra are used to verify the combustion equivalence ratios in the range of 0.5 to 2.0. Emission spectra are obtained separately from the near ultraviolet (vicinity of 250nm) and from the visible (vicinity of 430nm) using gated array detectors. Emission data are obtained over a range of sub-microsecond delay times following the laser pulse. The ultraviolet lines exhibit significantly larger signal-to-noise/background ratios, but the visible lines possess greater relative intensity. Implications of these results are discussed for local measurements of fuel-oxidizer ratios for both atmospheric pressure and high pressure combustion.

Dackman, Matthew; Lewis, J. W. L.; Chen, Ying-Ling; Shi, Lei

2007-11-01

139

An experimental study on shock-induced combustion of isolated regions of hydrogen-oxygen mixtures  

NASA Astrophysics Data System (ADS)

The interaction of a strong plane shock wave with isolated regions of gaseous mixtures was examined through a series of shock tube experiments. Specifically, the non-uniform mixtures examined consisted of a spherical bubble of pure hydrogen or hydrogen-oxygen mixtures surrounded by either an oxygen, nitrogen or air atmosphere. Shocks in the range of Mach 1.7 to 3.7 were studied. The interaction events where recorded with high speed shadowgraphs and pressure trace recordings. No chemical reactions were observed in the interactions of shocks with strengths up to Mach 3.7 with pure hydrogen spheres due to inadequate mixing of the reactants. In addition no reaction was observed for shocks up to Mach 3.0 for premixed spheres of equivalence ratios of 1.0, 0.7, and 0.5. However, shock induced combustion was observed for incident shock strengths above Mach 3.0. This demarcation between reaction and non-reaction corresponds to the classical third explosion limit for a hydrogen-oxygen mixture. Measurements of the induction period for hydrogen-oxygen mixtures for pressure and temperature conditions near the third explosion limit are also reported. This data will aid the study of the initiation and propagation of detonation waves and provide a useful set of test data for computational fluid dynamics codes involving reactive flows.

Valentino, Michael Anthony

140

Longevity, oxygen toxicity and radiation-enhanced resistance to oxygen in tribolium confusum  

SciTech Connect

Sublethal doses of ionizing radiation increase longevity in a variety of insects suggesting that irradiation may retard the age-dependent decline of physiological functions. There have been no systematic investigations of the response of irradiated populations to stress, however. The authors have demonstrated that resistance of adult flour beetles, Tribolium confusum, to oxygen poisoning declines progressively with age. They have examined oxygen resistance of irradiated populations of T. confusum as a function of age at irradiation, of time after irradiation, and of radiation dose and of dose-modifying factors. Shortly after gamma-irradiation, flour beetles exhibited a decline in resistance to oxygen toxicity. Then, about two weeks after irradiation, the LD/sub 50/ exposure time in pure oxygen was much greater than that of nonirradiated beetles, and this enhanced resistance persisted for about 6 months. The magnitude of the enhancement was a function of dose, decreased with increasing age at irradiation, and was modified by radiation factors. Sublethal irradiation under anoxia, at low dose rate, or with dose fractionation reduced the development of oxygen resistance to approximately the same degree that it reduced acute radiation lethality . Radiation-enhanced resistance to stress may be an important factor in the increased longevity of irradiated insects.

Lee, Y.J.

1985-01-01

141

Emissions of parent, nitro, and oxygenated polycyclic aromatic hydrocarbons from residential wood combustion in rural China.  

PubMed

Residential wood combustion is one of the important sources of air pollution in developing countries. Among the pollutants emitted, parent polycyclic aromatic hydrocarbons (pPAHs) and their derivatives, including nitrated and oxygenated PAHs (nPAHs and oPAHs), are of concern because of their mutagenic and carcinogenic effects. In order to evaluate their impacts on regional air quality and human health, emission inventories, based on realistic emission factors (EFs), are needed. In this study, the EFs of 28 pPAHs (EF(PAH28)), 9 nPAHs (EF(PAHn9)), and 4 oPAHs (EF(PAHo4)) were measured for residential combustion of 27 wood fuels in rural China. The measured EF(PAH28), EF(PAHn9), and EF(PAHo4) for brushwood were 86.7 ± 67.6, 3.22 ± 1.95 × 10(-2), and 5.56 ± 4.32 mg/kg, which were significantly higher than 12.7 ± 7.0, 8.27 ± 5.51 × 10(-3), and 1.19 ± 1.87 mg/kg for fuel wood combustion (p < 0.05). Sixteen U.S. EPA priority pPAHs contributed approximately 95% of the total of the 28 pPAHs measured. EFs of pPAHs, nPAHs, and oPAHs were positively correlated with one another. Measured EFs varied obviously depending on fuel properties and combustion conditions. The EFs of pPAHs, nPAHs, and oPAHs were significantly correlated with modified combustion efficiency and fuel moisture. Nitro-naphthalene and 9-fluorenone were the most abundant nPAHs and oPAHs identified. Both nPAHs and oPAHs showed relatively high tendencies to be present in the particulate phase than pPAHs due to their lower vapor pressures. The gas-particle partitioning of freshly emitted pPAHs, nPAHs, and oPAHs was primarily controlled by organic carbon absorption. PMID:22765266

Shen, Guofeng; Tao, Shu; Wei, Siye; Zhang, Yanyan; Wang, Rong; Wang, Bin; Li, Wei; Shen, Huizhong; Huang, Ye; Chen, Yuanchen; Chen, Han; Yang, Yifeng; Wang, Wei; Wang, Xilong; Liu, Wenxin; Simonich, Staci L M

2012-08-01

142

Does oxygen enhance the radiation-induced inactivation of penicillinase  

SciTech Connect

The radiation-induced inactivation of penicillinase (..beta..-lactamase, EC 3.5.2.6) in dilute aqueous solutions buffered with phosphate was studied by examining enzyme radiosensitivity in the presence of various gases (He, O/sub 2/, H/sub 2/, N/sub 2/O and N/sub 2/O + O/sub 2/). The introduction of either N/sub 2/O or O/sub 2/ was found to reduce the radiodamage. On the other hand, H/sub 2/ or N/sub 2/O + O/sub 2/ gas mixture enhanced the radiosensitivity. In the presence of formate and oxygen no enzyme inactivation was detected. The results indicated that the specific damaging efficiency of H atoms is more than twofold higher than that of OH radicals; therefore, in 50 mM phosphate buffer, where more than half the free radicals are H atoms, the H radicals are responsible for the majority of the damage. The superoxide radicals appeared to be completely inactive and did not contribute to enzyme inactivation. Oxygen affected the radiosensitivity in two ways: (1) it protected by converting e/sub aq//sup -/ and H into harmless O/sub 2/-radicals; and (2) it increased inactivation by enhancing the damage brought about by OH radicals (OER = 2.6). In oxygenated buffer the protection effect of oxygen exceeded that of sensitization, thus giving rise to a moderate overall protection effect.

Samuni, A.; Kalkstein, A.; Czapski, G.

1980-04-01

143

Kinetic mechanism for low-pressure oxygen/methane ignition and combustion  

NASA Astrophysics Data System (ADS)

It is known that during a launch of a rocket, the interaction of the exhaust gases of rocket engines with the atmosphere causes a local depletion of the ozone layer. In order to study these chemical processes in detail, a chemical reaction mechanism of the methane oxidation appropriate for high- and low-pressure conditions and a chemical reactor network to reproduce operating conditions in rocket engines and in the environment have been developed. An earlier developed detailed chemical kinetic model for the high-pressure CH4/O2 combustion has been improved for the low pressure and low temperature methane combustion and augmented with a submodel for NOx formation. The main model improvements are related to the pressure depending reactions. The model has been validated for operating conditions of 0.02 < p < 100 atm, 300 < T < 1800 K and 0.5 < ? < 3.0. The network of chemical reactors available in CHEMICAL WORKBENCH software has been successfully developed to simulate chemical processes in the convergent divergent rocket nozzle and in the exhaust-jet. Simulations performed have shown that the exhaust gases of a methane/oxygen propelled liquid rocket engine contain high amounts of active radicals, which can influence the formation of nitrogen compounds and consume ozone in the atmosphere.

Slavinskaya, N. A.; Wiegand, M.; Starcke, J. H.; Riedel, U.; Haidn, O. J.; Suslov, D.

2013-03-01

144

Fate of hazardous air pollutants in oxygen-fired coal combustion with different flue gas recycling.  

PubMed

Experiments were performed to characterize transformation and speciation of hazardous air pollutants (HAPs), including SO(2)/SO(3), NO(x), HCl, particulate matter, mercury, and other trace elements in oxygen-firing bituminous coal with recirculation flue gas (RFG) from 1) an electrostatic precipitator outlet or 2) a wet scrubber outlet. The experimental results showed that oxycombustion with RFG generated a flue gas with less volume and containing HAPs at higher levels, while the actual emissions of HAPs per unit of energy produced were much less than that of air-blown combustion. NO(x) reduction was achieved in oxycombustion because of the elimination of nitrogen and the destruction of NO in the RFG. The elevated SO(2)/SO(3) in flue gas improved sulfur self-retention. SO(3) vapor could reach its dew point in the flue gas with high moisture, which limits the amount of SO(3) vapor in flue gas and possibly induces material corrosion. Most nonvolatile trace elements were less enriched in fly ash in oxycombustion than air-firing because of lower oxycombustion temperatures occurring in the present study. Meanwhile, Hg and Se were found to be enriched on submicrometer fly ash at higher levels in oxy-firing than in air-blown combustion. PMID:22439940

Zhuang, Ye; Pavlish, John H

2012-04-17

145

Enhancement by platelets of oxygen radical responses of human neutrophils  

SciTech Connect

When human blood neutrophils were incubated with immune complexes (consisting of IgG antibody) in the presence of platelets, there was a 2 to 10 fold enhancement in the generation of O-/sub 2/ and H/sub 2/O/sub 2/. This enhancement phenomenon was proportional to the dose of immune complex added and the number of platelets present. The response was not agonist specific since similar enhancement also occurred with the following agonists: phorbol myristate acetate, opsonized zymosan particles and the chemotactic peptide N-formyl-met-leu-phe. The platelet related phenomenon of enhanced O-/sub 2/ generation could not be reproduced by the addition of serotonin, histamine or platelet-derived growth factor and was not affected by prior treatment of platelets with cyclooxygenase inhibitors (indomethacin, piroxicam) or lipoxygenase inhibitors (nafazatrom, BW755C or nordihydroguaiaretic acid). However, activation of platelets by thrombin caused release into the platelet supernatant fluid of a factor that, only in the presence of immune complexes, caused enhanced O-/sub 2/ responses to neutrophils. These data indicate that platelets potentiate oxygen radical responses of human neutrophils and suggest a mechanisms by which platelets may participate in tissue injury which is mediated by oxygen radical products from activated neutrophils.

McCulloch, K.K.; Powell, J.; Johnson, K.J.; Ward, P.A.

1986-03-01

146

Embryonic oxygen enhances learning ability in hatchling lizards  

PubMed Central

Introduction Producing smart offspring is an important fitness trait; individuals with enhanced cognitive ability should be more adept at responding to complex environmental demands. Cognitive ability can be influenced by conditions experienced during embryonic development. Although oxygen is necessary for embryonic development, availability can be limited within the nest environment because of substrate type, hydric conditions, and temperature. We do not yet understand, however, whether oxygen availability during embryonic development influences offspring fitness, especially cognitive ability. To address this question we incubated Mongolian Racerunner lizard (Eremias argus) eggs under hypoxic (12% O2), normoxic (21% O2), and hyperoxic conditions (30% O2). Results Hypoxia not only slowed hatching time, but also resulted in constrained cognitive ability relative to hatchlings experiencing normoxic or hyperoxic incubation conditions. Oxygen did not influence hatching success, body size or sprint speed of hatchlings. Conclusions Oxygen availability during embryonic development has important influences on incubation duration and cognitive ability of hatchling lizards. This study provides the first evidence that oxygen availability during embryonic development can modify cognitive ability of oviparous reptiles.

2014-01-01

147

Lignocellulosic fiber charge enhancement by catalytic oxidation during oxygen delignification.  

PubMed

A series of one-stage oxygen delignification treatments with a softwood (SW) kraft pulp were studied employing 0.0-0.5% of a bismuth ruthenium pyrochlore oxide catalyst. The results demonstrated that a 0.09-0.18% charge of catalyst in an oxygen stage provided a 52.2-116.0% increase of carboxylic acid groups in the cellulosic component of kraft pulps without a significant decrease in fiber viscosity. A 3-factor at 3-level (L(9)3(3)) orthogonal experimental design was used to identify the main factors influencing acid group formation in pulp carbohydrates. The relative significance of experimental parameters for polysaccharide acid group formation was the molar equivalent NaOH, oxygen pressure, and finally, reaction temperature under the experimental conditions studied. The optimized reaction parameters for fiber charge development were shown to be 85-100 degrees C, 2.5% NaOH, and 800-960 kPa oxygen pressure. Pulps with higher fiber carboxylic acid content introduced by catalytic oxidation during oxygen delignification yielded a 10.9-33.7% increase in fiber charge after elemental chlorine free (ECF) pulp bleaching. The enhanced fiber charge resulted in 6.7-17.1% increase in paper sheet tensile index at comparable pulp viscosity. PMID:17107682

Zhang, Dongcheng; Chai, Xin-Sheng; Pu, Yunqiao; Ragauskas, Arthur J

2007-02-15

148

Effect of fuel gas composition in chemical-looping combustion with Ni-based oxygen carriers. 1. Fate of sulfur  

SciTech Connect

Chemical-looping combustion (CLC) has been suggested among the best alternatives to reduce the economic cost of CO{sub 2} capture using fuel gas because CO{sub 2} is inherently separated in the process. For gaseous fuels, natural gas, refinery gas, or syngas from coal gasification can be used. These fuels may contain different amounts of sulfur compounds, such as H{sub 2}S and COS. An experimental investigation of the fate of sulfur during CH{sub 4} combustion in a 500 W{sub th} CLC prototype using a Ni-based oxygen carrier has been carried out. The effect on the oxygen carrier behavior and combustion efficiency of several operating conditions such as temperature and H{sub 2}S concentration has been analyzed. Nickel sulfide, Ni3S{sub 2}, was formed at all operating conditions in the fuel reactor, which produced an oxygen carrier deactivation and lower combustion efficiencies. However, the oxygen carrier recovered their initial reactivity after certain time without sulfur addition. The sulfides were transported to the air reactor where SO{sub 2} was produced as final gas product. Agglomeration problems derived from the sulfides formation were never detected during continuous operation. Considering both operational and environmental aspects, fuels with sulfur contents below 100 vppm H{sub 2}S seem to be adequate to be used in an industrial CLC plant.

Garcia-Labiano, F.; de Diego, L.F.; Gayan, P.; Adanez, J.; Abad, A.; Dueso, C. [CSIC, Zaragoza (Spain)

2009-03-15

149

Some observations on plasma-assisted combustion enhancement using dielectric barrier discharges  

NASA Astrophysics Data System (ADS)

We explore an effective way to promote propane combustion by applying a plasma discharge for efficiency enhancement. A coaxial-cylinder, dielectric barrier discharge is used to activate propane and air before they are mixed with each other and ignited for combustion. The characteristics of the combustion flame are well studied and evaluated by varying various operational parameters. It is found that the combustion process can be enhanced by applying a plasma on either the propane or air stream, and the combustion stability is found to be somewhat sensitive to the lean burning conditions and confined to a relatively narrow operating window. The temperature and spectrum of the flame in the main combustion zone are investigated with a 4 W plasma in the on or off state. The main components are identified, and the possible physical and chemical reaction mechanisms are discussed. A comparative analysis of these spectra and temperatures obtained in the main flame suggests that the energy generated from the 4 W plasma is partially used to heat the reaction gases in the flame, and another part of the energy is used to increase the luminosity, especially for activation of air. We also observe that combustion of high flow rate propane and/or air requires more discharge energy density under certain conditions. A comparison of combustion enhancement through different activation methods in flame blowout tests shows that reactive species derived from activation of air play a more critical role in the blowout limit of propane combustion flame than those generated by activation of propane at low equivalence ratio and propane flow.

Tang, Jie; Zhao, Wei; Duan, Yixiang

2011-08-01

150

Experiments on chemical looping combustion of coal with a NiO based oxygen carrier  

SciTech Connect

A chemical looping combustion process for coal using interconnected fluidized beds with inherent separation of CO{sub 2} is proposed in this paper. The configuration comprises a high velocity fluidized bed as an air reactor, a cyclone, and a spout-fluid bed as a fuel reactor. The high velocity fluidized bed is directly connected to the spout-fluid bed through the cyclone. Gas composition of both fuel reactor and air reactor, carbon content of fly ash in the fuel reactor, carbon conversion efficiency and CO{sub 2} capture efficiency were investigated experimentally. The results showed that coal gasification was the main factor which controlled the contents of CO and CH{sub 4} concentrations in the flue gas of the fuel reactor, carbon conversion efficiency in the process of chemical looping combustion of coal with NiO-based oxygen carrier in the interconnected fluidized beds. Carbon conversion efficiency reached only 92.8% even when the fuel reactor temperature was high up to 970 C. There was an inherent carbon loss in the process of chemical looping combustion of coal in the interconnected fluidized beds. The inherent carbon loss was due to an easy elutriation of fine char particles from the freeboard of the spout-fluid bed, which was inevitable in this kind of fluidized bed reactor. Further improvement of carbon conversion efficiency could be achieved by means of a circulation of fine particles elutriation into the spout-fluid bed or the high velocity fluidized bed. CO{sub 2} capture efficiency reached to its equilibrium of 80% at the fuel reactor temperature of 960 C. The inherent loss of CO{sub 2} capture efficiency was due to bypassing of gases from the fuel reactor to the air reactor, and the product of residual char burnt with air in the air reactor. Further experiments should be performed for a relatively long-time period to investigate the effects of ash and sulfur in coal on the reactivity of nickel-based oxygen carrier in the continuous CLC reactor. (author)

Shen, Laihong; Wu, Jiahua; Xiao, Jun [Thermoenergy Engineering Research Institute, Southeast University, 2 Sipailou, Nanjing 210096 (China)

2009-03-15

151

Combustion, Respiration and Intermittent Exercise: A Theoretical Perspective on Oxygen Uptake and Energy Expenditure  

PubMed Central

While no doubt thought about for thousands of years, it was Antoine Lavoisier in the late 18th century who is largely credited with the first “modern” investigations of biological energy exchanges. From Lavoisier’s work with combustion and respiration a scientific trend emerges that extends to the present day: the world gains a credible working hypothesis but validity goes missing, often for some time, until later confirmed using proper measures. This theme is applied to glucose/glycogen metabolism where energy exchanges are depicted as conversion from one form to another and, transfer from one place to another made by both the anaerobic and aerobic biochemical pathways within working skeletal muscle, and the hypothetical quantification of these components as part of an oxygen (O2) uptake measurement. The anaerobic and aerobic energy exchange components of metabolism are represented by two different interpretations of O2 uptake: one that contains a glycolytic component (1 L O2 = 21.1 kJ) and one that does not (1 L O2 = 19.6 kJ). When energy exchange transfer and oxygen-related expenditures are applied separately to exercise and recovery periods, an increased energy cost for intermittent as compared to continuous exercise is hypothesized to be a direct result.

Scott, Christopher B.

2014-01-01

152

160 h of chemical-looping combustion in a 10 kW reactor system with a NiO-based oxygen carrier  

Microsoft Academic Search

Chemical-looping combustion, CLC, is a technology with inherent separation of the greenhouse gas CO2. The technique uses an oxygen carrier made up of particulate metal oxide to transfer oxygen from combustion air to fuel. In this work, an oxygen carrier consisting of 60% NiO and 40% NiAl2O4 was used in a 10kW CLC reactor system for 160h of operation with

Carl Linderholm; Alberto Abad; Tobias Mattisson; Anders Lyngfelt

2008-01-01

153

Enhancement of in-situ combustion by steam stimulation of production wells  

SciTech Connect

Steam stimulation of individual wells was used to improve the performance of an in-situ combustion project operated by BP Resources Canada Ltd. in the Cold Lake oil-sand deposits of northeastern Alberta. In addition, steam was used to protect production wells that were threatened by the combustion front or had experienced oxygen breakthrough. The effectiveness of these steam uses varied. This paper describes the strategy developed for the use of steam injection and case histories and draws conclusions on how to use steam injection for maximum effect.

Galas, C.M.F.; Ejiogu, G.C.

1993-11-01

154

Combustion of solid fuel slabs with gaseous oxygen in a hybrid motor analog  

NASA Technical Reports Server (NTRS)

Using a high-pressure, two-dimensional hybrid motor, an experimental investigation was conducted on fundamental processes involved in hybrid rocket combustion. HTPB (Hydroxyl-terminated Polybutadiene) fuel cross-linked with diisocyanate was burned with gaseous oxygen (GOX) under various operating conditions. Large-amplitude pressure oscillations were encountered in earlier test runs. After identifying the source of instability and decoupling the GOX feed-line system and combustion chamber, the pressure oscillations were drastically reduced from plus or minus 20% of the localized mean pressure to an acceptable range of plus or minus 1.5%. Embedded fine--wire thermocouples indicated that the surface temperature of the burning fuel was around 1000 K depending upon axial locations and operating conditions. Also, except near the leading edge region, the subsurface thermal wave profiles in the upstream locations are thicker than those in the downstream locations since the solid-fuel regression rate, in general, increases with distance along the fuel slab. The recovered solid fuel slabs in the laminar portion of the boundary layer exhibited smooth surfaces, indicating the existence of a liquid melt layer on the burning fuel surface in the upstream region. After the transition section, which displayed distinct transverse striations, the surface roughness pattern became quite random and very pronounced in the downstream turbulent boundary-layer region. Both real-time X-ray radiography and ultrasonic pulse echo techniques were used to determine the instantaneous web thicknesses and instantaneous solid-fuel regression rates over certain portions of the fuel slabs. Globally averaged and axially dependent but time-averaged regression rates were also obtained and presented. Several tests were conducted using, simultaneously, one translucent fuel slab and one fuel slab processed with carbon black powder. The addition of carbon black did not affect the measured regression rates or surface temperatures in comparison to the translucent fuel slabs.

Chiaverini, Martin J.; Harting, George C.; Lu, Yeu-Cherng; Kuo, Kenneth K.; Serin, Nadir; Johnson, David K.

1995-01-01

155

An experimental study on high temperature and low oxygen air combustion  

Microsoft Academic Search

High temperature preheated and diluted air combustion has been confirmed as the technology, mainly applied to industrial furnaces and kilns, to realize higher thermal efficiency and lower emissions. The purpose of this study was to investigate fundamental aspects of the above-mentioned combustion experimentally and to compare with those in ordinary hydrocarbon combustion with room temperature air. The test items were

W. B. Kim; D. H. Chung; J. B. Yang; D. S. Noh

2000-01-01

156

Solid waste management of a chemical-looping combustion plant using Cu-based oxygen carriers.  

PubMed

Waste management generated from a Chemical-Looping Combustion (CLC) plant using copper-based materials is analyzed by two ways: the recovery and recycling of the used material and the disposal of the waste. A copper recovery process coupled to the CLC plant is proposed to avoid the loss of active material generated by elutriation from the system. Solid residues obtained from a 10 kWth CLC prototype operated during 100 h with a CuO-Al2O3 oxygen carrier prepared by impregnation were used as raw material in the recovery process. Recovering efficiencies of approximately 80% were obtained in the process, where the final products were an eluate of Cu(NO3)2 and a solid. The eluate was used for preparation of new oxygen carriers by impregnation, which exhibited high reactivity for reduction and oxidation reactions as well as adequate physical and chemical properties to be used in a CLC plant. The proposed recovery process largely decreases the amount of natural resources (Cu and Al203) employed in a CLC power plant as well as the waste generated in the process. To determine the stability of the different solid streams during deposition in a landfill, these were characterized with respect to their leaching behavior according to the European Union normative. The solid residue finally obtained in the CLC plant coupled to the recovery process (composed by Al2O3 and CuAl2O4) can be classified as a stable nonreactive hazardous waste acceptable at landfills for nonhazardous wastes. PMID:17874801

García-Labiano, Francisco; Gayán, Pilar; Adánez, Juan; De Diego, Luis F; Forero, Carmen R

2007-08-15

157

Alterations of bitumen produced by the in-situ combustion process at the oxygen Wolf Lake Project, Alberta  

SciTech Connect

The Oxygen Wolf Lake Project, operated by BP Resources Canada Limited, recovers bitumen by an in-situ combustion process. Bitumen samples produced from this process were analyzed and compared with analyses of unaltered bitumen from the same formation. The naphtha and middle distillate fractions were greater in the samples produced by the in-situ combustion process, which indicates thermal cracking has occurred. Gas chromatograph and Mass Spectral analyses of these samples have been used to further describe the changes to the oil. The compositional changes found in the study have been related to reductions in viscosity and density. Implications of bitumen alterations to the performance of the combustion process and production problems are discussed.

Riechert, C.; Fuhr, B. (Alberta Research Council, Edmonton (Canada)); Williams, G. (British Petroleum Canada Ltd., Calgary, Alberta (Canada)); Sawatzky, H.; Jha, K.; Lafleur, R. (Canmet, Energy Mines and Resources Canada, Ottawa, Ontario (Canada))

1989-04-01

158

Contrasting reactive oxygen species and transition metal concentrations in combustion aerosols.  

PubMed

The presence of reactive oxygen species (ROS) and 10 transition metals (Ag, Cd, Co, Cu, Fe, Mn, Ni, Ti, V and Zn) in both the acid-soluble and water-soluble fractions of fine particles of combustion origin were determined. ROS was analyzed using the dichlorofluorescin fluorescence technique. Particles emitted from on-road vehicles, gas cooking, incense burning, and cigarette smoke were characterized along with those in the background air of outdoor and indoor environments. In addition, this study evaluated the possible relationships between ROS and individual transition metals. It is found that cigarette smoke which had the highest concentration of metals also contained the highest concentration of ROS. Regression analysis performed showed that water-soluble metals including Cd, Co, Cu, Fe, Mn, and Ni showed better correlation with ROS concentration as compared to acid-soluble (total) metals. The findings demonstrated that water-soluble metals could be one of the species influencing ROS formation in ambient air. PMID:17011545

See, S W; Wang, Y H; Balasubramanian, R

2007-03-01

159

Reference concepts for a space-based hydrogen-oxygen combustion, turboalternator, burst power system  

SciTech Connect

This report describes reference concepts for a hydrogen-oxygen combustion, turboalternator power system that supplies power during battle engagement to a space-based, ballistic missile defense platform. All of the concepts are open''; that is, they exhaust hydrogen or a mixture of hydrogen and water vapor into space. We considered the situation where hydrogen is presumed to be free to the power system because it is also needed to cool the platform's weapon and the situation where hydrogen is not free and its mass must be added to that of the power system. We also considered the situation where water vapor is an acceptable exhaust and the situation where it is not. The combination of these two sets of situations required four different power generation systems, and this report describes each, suggests parameter values, and estimates masses for each of the four. These reference concepts are expected to serve as a baseline'' to which other types of power systems can be compared, and they are expected to help guide technology development efforts in that they suggest parameter value ranges that will lead to optimum system designs. 7 refs., 18 figs., 5 tabs.

Edenburn, M.W.

1990-07-01

160

OXYGEN-ENRICHED COAL COMBUSTION WITH CARBON DIOXIDE RECYCLE AND RECOVERY: SIMULATION AND EXPERIMENTAL STUDY  

SciTech Connect

Two computational problems were worked on for this study. The first chapter examines the option of coal combustion using oxygen feed with carbon dioxide recycle to control the adiabatic flame temperature. Computer simulations using an existing state-of-the-art 3-dimensional computer code for turbulent reacting flows with reacting particles were employed to study the effects of increased carbon dioxide mole fraction on the char burnout, radiant heat transfer, metal partitioning, and NOx formation. The second chapter compares assumptions for the CO/CO{sub 2} ratio at the surface of mineral inclusions made in previous studies to predictions obtained from a pseudo-steady state kinetic model (SKIPPY) for a single porous particle. The detailed kinetic simulations from SKIPPY for varying particle sizes and bulk gas compositions were used to develop algebraic expressions for the CO/CO{sub 2} ratio that can be incorporated into metal vaporization sub-models run as a post processor to detailed furnace simulations. Vaporization rate controls the formation of metal-enriched sub-micron particles in pulverized coal fired power plants.

John M. Veranth; Gautham Krishnamoorthy

2002-02-28

161

Plasma torch for ignition, flameholding and enhancement of combustion in high speed flows  

NASA Technical Reports Server (NTRS)

Preheating of fuel and injection into a plasma torch plume fro adjacent the plasma torch plume provides for only ignition with reduced delay but improved fuel-air mixing and fuel atomization as well as combustion reaction enhancement. Heat exchange also reduced erosion of the anode of the plasma torch. Fuel mixing atomization, fuel mixture distribution enhancement and combustion reaction enhancement are improved by unsteady plasma torch energization, integral formation of the heat exchanger, fuel injection nozzle and plasma torch anode in a more compact, low-profile arrangement which is not intrusive on a highspeed air flow with which the invention is particularly effective and further enhanced by use of nitrogen as a feedstock material and inclusion of high pressure gases in the fuel to cause effervescence during injection.

O'Brien, Walter F. (Inventor); Billingsley, Matthew C. (Inventor); Sanders, Darius D. (Inventor); Schetz, Joseph A. (Inventor)

2009-01-01

162

Metallized Gelled Propellants: Oxygen/RP-1/Aluminum Rocket Heat Transfer and Combustion Measurements  

NASA Technical Reports Server (NTRS)

A series of rocket engine heat transfer experiments using metallized gelled liquid propellants was conducted. These experiments used a small 20- to 40-lb/f thrust engine composed of a modular injector, igniter, chamber and nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-percentage by weight loadings of aluminum particles. Gaseous oxygen was used as the oxidizer. Three different injectors were used during the testing: one for the baseline O(2)/RP-1 tests and two for the gelled and metallized gelled fuel firings. Heat transfer measurements were made with a rocket engine calorimeter chamber and nozzle with a total of 31 cooling channels. Each chamber used a water flow to carry heat away from the chamber and the attached thermocouples and flow meters allowed heat flux estimates at each of the 31 stations. The rocket engine Cstar efficiency for the RP-1 fuel was in the 65-69 percent range, while the gelled 0 percent by weight RP-1 and the 5-percent by weight RP-1 exhibited a Cstar efficiency range of 60 to 62% and 65 to 67%, respectively. The 55-percent by weight RP-1 fuel delivered a 42-47% Cstar efficiency. Comparisons of the heat flux and temperature profiles of the RP-1 and the metallized gelled RP-1/A1 fuels show that the peak nozzle heat fluxes with the metallized gelled O2/RP-1/A1 propellants are substantially higher than the baseline O2/RP-1: up to double the flux for the 55 percent by weight RP-1/A1 over the RP-1 fuel. Analyses showed that the heat transfer to the wall was significantly different for the RP-1/A1 at 55-percent by weight versus the RP-1 fuel. Also, a gellant and an aluminum combustion delay was inferred in the 0 percent and 5-percent by weight RP-1/A1 cases from the decrease in heat flux in the first part of the chamber. A large decrease in heat flux in the last half of the chamber was caused by fuel deposition in the chamber and nozzle. The engine combustion occurred well downstream of the injector face based on the heat flux estimates from the temperature measurements.

Palaszewski, Bryan; Zakany, James S.

1996-01-01

163

NiO particles with Ca and Mg based additives produced by spray- drying as oxygen carriers for chemical-looping combustion  

Microsoft Academic Search

Chemical-looping combustion is a two-step combustion process where CO2 is obtained in a separate stream, ready for compression and sequestration. The technique involves two interconnected fluidized bed reactors, with a solid oxygen carrier circulating between them. Results of reactivity experiments with 24 different oxygen carriers, based on NiO with NiAl2O4 and\\/or MgAl2O4 and produced with spray-drying, are presented. The investigation

Erik Jerndal; Tobias Mattisson; Ivo Thijs; Frans Snijkers; Anders Lyngfelt

2009-01-01

164

An experimental study on high temperature and low oxygen air combustion  

Microsoft Academic Search

High temperature preheated and diluted air combustion has been confirmed as the technology, mainly applied to industrial furnaces\\u000a and kilns, for realizing higher thermal efficiency and lower emissions. The purpose of this study was to investigate fundamental\\u000a aspects of the above-mentioned combustion experimentally and to compare with those in ordinary hydrocarbon combustion with\\u000a room temperature air. The test items were

Dae Hun Chung; Jae Bok Yang; Dong Sun Noh; Won Bae Kim

1999-01-01

165

An experimental study on high temperature and low oxygen air combustion  

Microsoft Academic Search

High temperature preheated and diluted air combustion has been confirmed as the technology, mainly applied to industrial furnaces\\u000a and kilns, to realize higher thermal efficiency and lower emissions. The purpose of this study was to investigate fundamental\\u000a aspects of the above-mentioned combustion experimentally and to compare with those in ordinary hydrocarbon combustion with\\u000a room temperature air. The test items were

W. B. Kim; D. H. Chung; J. B. Yang; D. S. Noh

2000-01-01

166

Oxygen enhancement ratio of fractionated regimens in vitro  

SciTech Connect

The oxygen enhancement ratio (OER) of proliferating and nonproliferating cells grown in vitro was measured using accelerated fractionated regimens. Irradiations were performed either twice daily or three times per day, with a minimum of 6 h between the consecutive fractions. The dose delivered was 2.3 Gy per fraction. Two significant observations were made: (i) the OER of accelerated fractionation regimens for proliferating cells is lower than that obtained from single-exposure experiments at 2.3 Gy (approximately 1.4 vs 2.4, respectively), while for nonproliferating cells it is approximately the same (2.3); (ii) the fractionated regimen does not spare proliferating cells irradiated under hypoxic conditions, and thus the fractionated survival curve lies below the single-exposure curve. For cells irradiated under aerobic conditions or for nonproliferating cells, irradiated under either hypoxic or aerobic conditions, the fractionated survival curve lies above the single-exposure curves as expected.

Palcic, B.; Korbelik, M.; Trotter, M.; Revesz, L.

1989-03-01

167

Resonant enhanced multiphoton ionization studies of atomic oxygen  

NASA Technical Reports Server (NTRS)

In resonant enhanced multiphoton ionization (REMPI), an atom absorbs several photons making a transition to a resonant intermediate state and subsequently ionizing out of it. With currently available tunable narrow-band lasers, the extreme sensitivity of REMPI to the specific arrangement of levels can be used to selectively probe minute amounts of a single species (atom) in a host of background material. Determination of the number density of atoms from the observed REMPI signal requires a knowledge of the multiphoton ionization cross sections. The REMPI of atomic oxygen was investigated through various excitation schemes that are feasible with available light sources. Using quantum defect theory (QDT) to estimate the various atomic parameters, the REMPI dynamics in atomic oxygen were studied incorporating the effects of saturation and a.c. Stark shifts. Results are presented for REMPI probabilities for excitation through various 2p(3) (4S sup o) np(3)P and 2p(3) (4S sup o) nf(3)F levels.

Dixit, S. N.; Levin, D.; Mckoy, V.

1987-01-01

168

Metallized gelled propellants: Oxygen/RP-1/aluminum rocket combustion experiments  

NASA Technical Reports Server (NTRS)

A series of combustion experiments were conducted to measure the specific impulse, Cstar-, and specific-impulse efficiencies of a rocket engine using metallized gelled liquid propellants. These experiments used a small 20- to 40-1bf (89- to 178-N) thrust, modular engine consisting of an injector, igniter, chamber and nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-wt% loadings of aluminum and gaseous oxygen was the oxidizer. Ten different injectors were used during the testing: 6 for the baseline 02/RP-1 tests and 4 for the gelled fuel tests which covered a wide range of mixture ratios. At the peak of the Isp versus oxidizer-to-fuel ratio (O/F) data, a range of 93 to 99% Cstar efficiency was reached with ungelled 02/RP-1. A Cstar efficiency range of 75 to 99% was obtained with gelled RP-l (0-wt% RP-1/Al) while the metallized 5-wt% RP-1/Al delivered a Cstar efficiency of 94 to 99% at the peak Isp in the O/F range tested. An 88 to 99% Cstar efficiency was obtained at the peak Isp of the gelled RP1/Al with 55-wt% Al. Specific impulse efficiencies for the 55-wt% RP-1/Al of 67%-83% were obtained at a 2.4:1 expansion ratio. Injector erosion was evident with the 55-wt% testing, while there was little or no erosion seen with the gelled RP-1 with 0- and 5-wt% Al. A protective layer of gelled fuel formed in the firings that minimized the damage to the rocket injector face. This effect may provide a useful technique for engine cooling. These experiments represent a first step in characterizing the performance of and operational issues with gelled RP-1 fuels.

Palaszewski, Bryan; Zakany, James S.

1995-01-01

169

DEVELOPMENT OF AN ENHANCED COMBUSTION LOW NOx PULVERIZED COAL BURNER  

Microsoft Academic Search

For more than two decades, ALSTOM Power Inc. (ALSTOM) has developed a range of low cost, in-furnace technologies for NOx emissions control for the domestic U.S. pulverized coal fired boiler market. This includes the internally developed TFS 2000TM firing system, and various enhancements to it developed in concert with the U.S. Department of Energy (DOE). As of the date of

Galen Richards; David Towle; Robert Lewis; Kevin Connolly; Richard Donais; Todd Hellewell

170

Intramolecular distribution of stable nitrogen and oxygen isotopes of nitrous oxide emitted during coal combustion  

Microsoft Academic Search

The intramolecular distribution of stable isotopes in nitrous oxide that is emitted during coal combustion was analyzed using an isotopic ratio mass spectrometer equipped with a modified ion collector system (IRMS). The coal was combusted in a test furnace fitted with a single burner and the flue gases were collected at the furnace exit following removal of SOx, NOx, and

Mitsuteru Ogawa; Naohiro Yoshida

2005-01-01

171

Demonstration of oxygen-enriched combustion system on a light-duty vehicle to reduce cold-start emissions  

SciTech Connect

The oxygen content in the ambient air drawn by combustion engines can be increased by polymer membranes. The authors have previously demonstrated that 23 to 25% (concentration by volume) oxygen-enriched intake air can reduce hydrocarbons (HC), carbon monoxide (CO), air toxics, and ozone-forming potential (OFP) from flexible-fueled vehicles (FFVs) that use gasoline or M85. When oxygen-enriched air was used only during the initial start-up and warm-up periods, the emission levels of all three regulated pollutants [CO, nonmethane hydrocarbons (NMHC), and NO{sub x}] were lower than the U.S. EPA Tier II (year 2004) standards (without adjusting for catalyst deterioration factors). In the present work, an air separation membrane module was installed on the intake of a 2.5-L FFV and tested at idle and free acceleration to demonstrate the oxygen-enrichment concept for initial start-up and warm-up periods. A bench-scale, test set-up was developed to evaluate the air separation membrane characteristics for engine applications. On the basis of prototype bench tests and from vehicle tests, the additional power requirements and module size for operation of the membrane during the initial period of the cold-phase, FTP-75 cycle were evaluated. A prototype membrane module (27 in. long, 3 in. in diameter) supplying about 23% oxygen-enriched air in the engine intake only during the initial start-up and warm-up periods of a 2.5-L FFV requires additional power (blower) of less than one horsepower. With advances in air separation membranes to develop compact modules, oxygen enrichment of combustion air has the potential of becoming a more practical technique for controlling exhaust emissions from light-duty vehicles.

Sekar, R.; Poola, R.B.

1997-08-01

172

Analytical chemical kinetic investigation of the effects of oxygen, hydrogen, and hydroxyl radicals on hydrogen-air combustion  

NASA Technical Reports Server (NTRS)

Quantitative values were computed which show the effects of the presence of small amounts of oxygen, hydrogen, and hydroxyl radicals on the finite-rate chemical kinetics of premixed hydrogen-air mixtures undergoing isobaric autoignition and combustion. The free radicals were considered to be initially present in hydrogen-air mixtures at equivalence ratios of 0.2, 0.6, 1.0, and 1.2. Initial mixture temperatures were 1100 K, 1200 K, and 1500 K, and pressures were 0.5, 1.0, 2.0, and 4.0 atm. Of the radicals investigated, atomic oxygen was found to be the most effective for reducing induction time, defined as the time to 5 percent of the total combustion temperature rise. The reaction time, the time between 5 percent and 95 percent of the temperature rise, is not decreased by the presence of free radicals in the initial hydrogen-air mixture. Fuel additives which yield free radicals might be used to effect a compact supersonic combustor design for efficient operation in an otherwise reaction-limited combustion regime.

Carson, G. T., Jr.

1974-01-01

173

Laser Diagnostics of Combustion Enhancement on a CH4/Air Bunsen Flame by Dielectric Barrier Discharge  

NASA Astrophysics Data System (ADS)

We investigate plasma-assisted combustion for premixed CH4/air Bunsen flames. Dielectric barrier discharge (DBD) is employed to produce non-equilibrium plasma for combustion enhancement. The transient planar laser induced fluorescence (PLIF) technique of CH and OH radicals is used to image reaction zones for enhancement measurement, and the emission spectra of the Bunsen flame are monitored to explore the kinetics mechanism. From the drift of radicals in PLIF images, the quantitative enhancement of plasma on the flame velocities of premixed methane/air flames is experimentally measured, and the data show that the flame velocities are increased by at least 15% in the presented equivalence ratio range. Furthermore, the well analyzed emission spectra of the Bunsen flame (300-800 nm) with/without DBD reveal that the emissions as well as the concentrations of the crucial radicals (like C2, CH, OH etc.) in combustion all are intensified greatly by the discharge. In addition, the appearance of excited spectral bands of N2 and N+2 during discharge indicates that the premixed gas is also heated and ionized partially by the DBD.

Zhang, Shao-Hua; Yu, Xi-Long; Chen, Li-Hong; Zhang, Xin-Yu

2013-08-01

174

Combustion conditions discrimination properties of Pt-doped TiO 2 thin film oxygen sensor  

Microsoft Academic Search

Present work focuses on evaluation of microfabricated Pt-doped titanium oxide thin film sensors capability to discriminate different combustion conditions of a real gasoline engine; actually, zirconia-based lambda probes are a well-established technology in the field of combustion control for fuel injection engines, but these devices suffer high production cost. A cheap mass fabrication method to produce thin film platinum-doped titania

L. Francioso; D. S. Presicce; P. Siciliano; A. Ficarella

2007-01-01

175

Deciphering mechanisms of enhanced-retarded oxygen diffusion in doped Si  

NASA Astrophysics Data System (ADS)

We study enhanced/retarded diffusion of oxygen in doped silicon by means of first principle calculations. We evidence that the migration energy of oxygen dimers cannot be significantly affected by strain, doping type, or concentration. We attribute the enhanced oxygen diffusion in p-doped silicon to reduced monomer migration energy and the retarded oxygen diffusion in Sb-doped to monomer trapping close to a dopant site. These two mechanisms can appear simultaneously for a given dopant leading to contradictory experimental results. More generally, our findings cast a new light on phenomena involving oxygen diffusion: precipitation, thermal donors formation, and light induced degradation.

Timerkaeva, Dilyara; Caliste, Damien; Pochet, Pascal

2013-12-01

176

Phosphate enhances reactive oxygen species production and suppresses osteoblastic differentiation.  

PubMed

Phosphate has been shown to work as a signaling molecule in several cells including endothelial cells and chondrocytes. However, it is largely unknown how phosphate affects osteoblastic cells. In the present study, we investigated the effects of phosphate on reactive oxygen species (ROS) production and osteoblastic differentiation in murine osteoblastic MC3T3-E1 cells. Phosphate increased production of ROS in MC3T3-E1 cells and the inhibitors of sodium-phosphate cotransporter and NADPH oxidase suppressed ROS production by phosphate. Silencing Nox1 and Nox4 also inhibited the increase of ROS by phosphate. Phosphate also decreased alkaline phosphatase activity induced by bone morphogenetic protein 2 and this inhibition was abrogated by an inhibitor of NADPH oxidase. Furthermore, phosphate decreased the expression of osteoblastic marker genes in MC3T3-E1 cells. These results indicate that phosphate suppresses osteoblastic differentiation at least in part by enhancing ROS production in MC3T3-E1 cells. PMID:24052209

Okamoto, Takaaki; Taguchi, Manabu; Osaki, Tomoko; Fukumoto, Seiji; Fujita, Toshiro

2014-07-01

177

Modeling of the chemical-looping combustion of methane using a Cu-based oxygen-carrier  

SciTech Connect

A mathematical model for a bubbling fluidized bed has been developed to simulate the performance of the fuel-reactor in chemical-looping combustion (CLC) systems. This model considers both the fluid dynamic of the fluidized bed and freeboard and the kinetics of reduction of the oxygen-carrier, here CuO impregnated on alumina. The main outputs of the model are the conversion of the carrier and the gas composition at the reactor exit, the axial profiles of gas concentrations and the fluid dynamical structure of the reactor. The model was validated using measurements when burning CH{sub 4} in a 10 kW{sub th} prototype using a Cu-based oxygen-carrier. The influence of the circulation rate of solids, the load of fuel gas, the reactor temperature and size of the oxygen-carrier particles were analyzed. Combustion efficiencies predicted by the model showed a good agreement with measurements. Having validated the model, the implications for designing and optimizing a fuel-reactor were as follows. The inventory of solids for a high conversion of the fuel was sensitive to the reactor's temperature, the solids' circulation rate and the extent to which the solids entering to the reactor had been regenerated. The optimal ratio of oxygen-carrier to fuel was found to be 1.7-4 for the Cu-based oxygen-carrier used here. In this range, the inventory of solids to obtain a combustion efficiency of 99.9% at 1073 K was less than 130 kg/MW{sub th}. In addition, the model's results were very sensitive to the resistance to gas diffusing between the emulsion and bubble phases in the bed, to the decay of solids' concentration in the freeboard and to the efficiency contact between gas and solids in the freeboard. Thus, a simplified model, ignoring any restriction to gas and solids contacting each other, will under-predict the inventory of solids by a factor of 2-10. (author)

Abad, Alberto; Adanez, Juan; Garcia-Labiano, Francisco; de Diego, Luis F.; Gayan, Pilar [Instituto de Carboquimica (CSIC), Department of Energy and Environment, Miguel Luesma Castan 4, 50018 Zaragoza (Spain)

2010-03-15

178

TECHNOLOGY EVALUATION REPORT SITE PROGRAM DEMONSTRATION TEST, THE AMERICAN COMBUSTION PYRETRON THERMAL DESTRUCTION SYSTEM AT THE U.S. EPA'S COMBUSTION  

EPA Science Inventory

A series of demonstration tests of the American Combustion, Inc. Thermal Destruction System was performed under the SITE program. his oxygen-enhanced combustion system was retrofit to the rotary kiln incinerator at EPA's Combustion Research Facility. his system's performeance was...

179

Early Gaseous Oxygen Enrichment to Enhance Magnetite Pellet Oxidation  

NASA Astrophysics Data System (ADS)

It is suggested that oxygen enrichment in the gas atmosphere, during continuous heating of magnetite pellets, can cause pellets to be oxidized throughout their volumes, eliminating unoxidized cores. The peculiarities of the oxidation kinetics of magnetite concentrate imply that such oxygen enrichment might be particularly effective at lower temperatures. This suggestion was tested by developing and testing a mixed-control model for pellet oxidation (to allow the sizes of unreacted cores to be predicted), and by experimentally testing the effects of oxygen enrichment at relatively low temperatures ("early oxygen enrichment"). The results confirmed that the extents (depth) of oxidation and pellet strength were both improved significantly by applying oxygen enrichment up to 873 K (600 °C), as part of a heating cycle up to 1073 K (800 °C).

Tang, Ming; Cho, Hyeon Jeong; Pistorius, Petrus Christiaan

2014-04-01

180

CO{sub 2} emission abatement in IGCC power plants by semiclosed cycles: Part A -- With oxygen-blown combustion  

SciTech Connect

This paper analyzes the fundamentals of IGCC power plants where carbon dioxide produced by syngas combustion can be removed, liquefied and eventually disposed, to limit the environmental problems due to the greenhouse effect. To achieve this goal, a semiclosed-loop gas turbine cycle using an highly-enriched CO{sub 2} mixture as working fluid was adopted. As the oxidizer, the syngas combustion utilizes oxygen produced by an air separation unit. Combustion gases mainly consist of CO{sub 2} and H{sub 2}O: after expansion, heat recovery and water condensation, a part of the exhausts, highly concentrated in CO{sub 2}, can be easily extracted, compressed and liquefied for storage or disposal. A detailed discussion about the configuration and the thermodynamic performance of these plants is the aim of the paper. Proper attention was paid to: (i) the modelization of the gasification section and of its integration with the power cycle, (ii) the optimization of pressure ratio due the change of the cycle working fluid, (iii) the calculation of the power consumption of the auxiliary equipment, including the compression train of the separated CO{sub 2} and the air separation unit. The resulting overall efficiency is in the 38--39% range, with status-of-the-art gas turbine technology, but resorting to a substantially higher pressure ratio. The extent of modifications to the gas turbine engine, with respect to commercial units, was therefore discussed. Relevant modifications are needed, but not involving changes in the technology. A second plant scheme will be considered in the second part of the paper, using air for syngas combustion and a physical absorption process to separate CO{sub 2} from nitrogen-rich exhausts. A comparison between the two options will be addressed there.

Chiesa, P.; Lozza, G.

1999-10-01

181

Review of the PDWA Concept for Combustion Enhancement in a Supersonic Air-Breathing Combustor Environment  

NASA Technical Reports Server (NTRS)

This paper reviews the design of the Pulsed Detonation Wave Augmentor (PDWA) concept and the preliminary computational fluid dynamics studies that supported it. The PDWA relies on the rapid generation of detonation waves in a small tube, which are then injected into the supersonic stream of the main combustor. The blast waves thus generated are used to stimulate the mixing and combustion inside the main combustor. The mixing enhancement relies on various forms of the baroclinic interaction, where misaligned pressure and density gradients combine to produce vortical flow. By using unsteady shock waves, the concept also uses the Richtmyer-Meshkov effect to further increase the rate of mixing. By carefully designing the respective configurations of the combustor and the detonation tubes, one can also increase the penetration of the fuel into the supersonic air stream. The unsteady shocks produce lower stagnation pressure losses than steady shocks. Combustion enhancement can also be obtained through the transient shock-heating of the fuel-air interface, and the lowering of the ignition delay in these regions. The numerical simulations identify these processes, and show which configurations give the best results. Engineering considerations are also presented, and discuss the feasibility of the concept. Of primary importance are the enhancements in performance, the design simplicity, the minimization of the power, cost, and weight, and the methods to achieve very rapid cycling.

Canbier, Jean-Luc; Edwards, Thomas A. (Technical Monitor)

1995-01-01

182

Solid Fuel - Oxygen Fired Combustion for Production of Nodular Reduced Iron to Reduce CO2 Emissions and Improve Energy Efficiencies  

SciTech Connect

The current trend in the steel industry is an increase in iron and steel produced in electric arc furnaces (EAF) and a gradual decline in conventional steelmaking from taconite pellets in blast furnaces. In order to expand the opportunities for the existing iron ore mines beyond their blast furnace customer base, a new material is needed to satisfy the market demands of the emerging steel industry while utilizing the existing infrastructure and materials handling capabilities. This demand creates opportunity to convert iron ore or other iron bearing materials to Nodular Reduced Iron (NRI) in a recently designed Linear Hearth Furnace (LHF). NRI is a metallized iron product containing 98.5 to 96.0% iron and 2.5 to 4% C. It is essentially a scrap substitute with little impurity that can be utilized in a variety of steelmaking processes, especially the electric arc furnace. The objective of this project was to focus on reducing the greenhouse gas emissions (GHG) through reducing the energy intensity using specialized combustion systems, increasing production and the use of biomass derived carbon sources in this process. This research examined the use of a solid fuel-oxygen fired combustion system and compared the results from this system with both oxygen-fuel and air-fuel combustion systems. The solid pulverized fuels tested included various coals and a bio-coal produced from woody biomass in a specially constructed pilot scale torrefaction reactor at the Coleraine Minerals Research Laboratory (CMRL). In addition to combustion, the application of bio-coal was also tested as a means to produce a reducing atmosphere during key points in the fusion process, and as a reducing agent for ore conversion to metallic iron to capture the advantage of its inherent reduced carbon footprint. The results from this study indicate that the approaches taken can reduce both greenhouse gas emissions and the associated energy intensity with the Linear Hearth Furnace process for converting iron ore to metallic iron nodules. Various types of coals including a bio-coal produced though torrefaction can result in production of NRI at reduced GHG levels. The process results coupled with earlier already reported developments indicate that this process technique should be evaluated at the next level in order to develop parameter information for full scale process design. Implementation of the process to full commercialization will require a full cost production analysis and comparison to other reduction technologies and iron production alternatives. The technical results verify that high quality NRI can be produced under various operating conditions at the pilot level.

Donald R. Fosnacht; Richard F. Kiesel; David W. Hendrickson; David J. Englund; Iwao Iwasaki; Rodney L. Bleifuss; Mathew A. Mlinar

2011-12-22

183

Enhancement of hybrid rocket combustion performance using nano-sized energetic particles  

NASA Astrophysics Data System (ADS)

Until now, the regression rate of classical hybrid rocket engines have typically been an order of magnitude lower than solid propellant motors; thus, hybrids require a relatively large fuel surface area for a given thrust level. In addition to low linear regression rates, relatively low combustion efficiency (87 to 92%), low mass burning rates, varying oxidizer-to-fuel ratio during operation, and lack of scaling laws have been reported. These disadvantages can be ameliorated by introducing nano-sized energetic powder additives into the solid fuel. The addition of nano-sized energetic particles into the solid fuel enhances performance as measured by parameters such as: density specific impulse, mass and linear burning rates, and thrust. Thermophysical properties of the solid fuel such as density, heat of combustion, thermal diffusivity, and thermal conductivity are also enhanced. The types of nano-sized energetic particles used in this study include aluminum, boron, boron carbide, and some Viton-A coated particles. Since the combustion process of solid fuels in a hybrid rocket engine is governed by the mass flux of the oxidizer entering the combustion chamber, the rate-limiting process is the mixing and reacting of the pyrolysis products of the fuel grain with the incoming oxidizer. The overall goal of this research was to determine the relative propulsive and combustion behavior for a family of newly-developed HTPB-based solid-fuel formulations containing various nano-sized energetic particles. Seventeen formulations contained 13% additive by weight, one formulation (SF4) contained 6.5% additive by weight, and one formulation (SF19) contained 5.65% boron by weight. The two hybrid rocket engines which were used in this investigation were the Long Grain Center-Perforated (LGCP) rocket engine and the X-Ray Transparent Casing (XTC) rocket engine. The smaller scale LGCP rocket engine was used to evaluate all of the formulations because conducting experiments using the LGCP required much less preparation and materials. (Abstract shortened by UMI.)

Risha, Grant Alexander

184

NO X removal in excess oxygen by plasma-enhanced selective catalytic reduction  

Microsoft Academic Search

In the off-gases of internal combustion engines running with oxygen excess, non-thermal plasmas (NTPs) have an oxidative potential, which results in an effective conversion of NO to NO2. In combination with appropriate catalysts and ammonia (NH3-SCR) or hydrocarbons (HC-SCR) as a reducing agent, this can be utilized to reduce nitric oxides (NO and NO2) synergistically to molecular nitrogen.The combination of

H Miessner; K.-P Francke; R Rudolph; Th Hammer

2002-01-01

185

The influence of oxygen concentration on the combustion of a fuel/oxidizer mixture  

SciTech Connect

The aim of the present study is to investigate the influence of the O{sub 2} concentration on the combustion behaviour of a fuel/oxidizer mixture. The material tested is a ternary mixture of lactose, starch, and potassium nitrate, which has already been used in an attempt to estimate heat release rate using the FM-Global Fire Propagation Apparatus. It provides a well-controlled combustion chamber to study the evolution of the combustion products when varying the O{sub 2} concentration, between air and low oxidizer conditions. Different chemical behaviours have been exhibited. When the O{sub 2} concentration was reduced beyond 18%, large variations were observed in the CO{sub 2} and CO concentrations. This critical O{sub 2} concentration seems to be the limit before which the material only uses its own oxidizer to react. On the other hand, mass loss did not highlight this change in chemical reactions and remained similar whatever the test conditions. This presumes that the oxidation of CO into CO{sub 2} are due to reactions occurring in the gas phase especially for large O{sub 2} concentrations. This actual behaviour can be verified using a simplified flammability limit model adapted for the current work. Finally, a sensitivity analysis has been carried out to underline the influence of CO concentration in the evaluation of heat release rate using typical calorimetric methods. The results of this study provide a critical basis for the investigation of the combustion of a fuel/oxidizer mixture and for the validation of future numerical models. (author)

Biteau, H. [School of Engineering and Electronics, BRE Centre for Fire Safety Engineering, The University of Edinburgh, Edinburgh EH9 3JL (United Kingdom); Institut National de l'Environnement Industriel et des Risques, Parc Technologique Alata, Verneuil en Halatte (France); Fuentes, A. [Institut Universitaire des Systemes Thermiques Industriels (CNRS UMR 6595), Universite de Provence, 13453 Marseille Cedex 13 (France); Marlair, G. [Institut National de l'Environnement Industriel et des Risques, Parc Technologique Alata, Verneuil en Halatte (France); Torero, J.L. [School of Engineering and Electronics, BRE Centre for Fire Safety Engineering, The University of Edinburgh, Edinburgh EH9 3JL (United Kingdom)

2010-04-15

186

Experiments on chemical looping combustion of coal with a NiO based oxygen carrier  

Microsoft Academic Search

A chemical looping combustion process for coal using interconnected fluidized beds with inherent separation of CO2 is proposed in this paper. The configuration comprises a high velocity fluidized bed as an air reactor, a cyclone, and a spout-fluid bed as a fuel reactor. The high velocity fluidized bed is directly connected to the spout-fluid bed through the cyclone. Gas composition

Laihong Shen; Jiahua Wu; Jun Xiao

2009-01-01

187

Development of Sewage Sludge Direct Melting System Using Oxygen Enriched Combustion.  

National Technical Information Service (NTIS)

Based on strict requirements for a smaller volume and more sludge stability than incinceration, Mitsubishi Heavy Industries (MHI) has developed a new sewage sludge direct melting system. The features of this system are that by using oxygen enriched combus...

S. Nishikawa H. Honda K. Tokuda M. Irino S. Okuno

1989-01-01

188

Fibronectin coating of oxygenator membranes enhances endothelial cell attachment  

PubMed Central

Background Extracorporeal membrane oxygenation (ECMO) can replace the lungs’ gas exchange capacity in refractory lung failure. However, its limited hemocompatibility, the activation of the coagulation and complement system as well as plasma leakage and protein deposition hamper mid- to long-term use and have constrained the development of an implantable lung assist device. In a tissue engineering approach, lining the blood contact surfaces of the ECMO device with endothelial cells might overcome these limitations. As a first step towards this aim, we hypothesized that coating the oxygenator’s gas exchange membrane with proteins might positively influence the attachment and proliferation of arterial endothelial cells. Methods Sheets of polypropylene (PP), polyoxymethylpentene (TPX) and polydimethylsiloxane (PDMS), typical material used for oxygenator gas exchange membranes, were coated with collagen, fibrinogen, gelatin or fibronectin. Tissue culture treated well plates served as controls. Endothelial cell attachment and proliferation were analyzed for a period of 4 days by microscopic examination and computer assisted cell counting. Results Endothelial cell seeding efficiency is within range of tissue culture treated controls for fibronectin treated surfaces only. Uncoated membranes as well as all other coatings lead to lower cell attachment. A confluent endothelial cell layer develops on fibronectin coated PDMS and the control surface only. Conclusions Fibronectin increases endothelial cells’ seeding efficiency on different oxygenator membrane material. PDMS coated with fibronectin shows sustained cell attachment for a period of four days in static culture conditions.

2013-01-01

189

Oxygen enhancement induced by ionic implantation in scandium diphthalocyanine thin films  

Microsoft Academic Search

Secondary ion mass spectrometry correlated with ionic implantations has allowed us to determine oxygen bulk concentration in scandium diphthalocyanine thin films. This concentration, around 2×1020 atom cm?3, increases by a factor 20–25 in implanted areas. This oxygen enhancement is observed for oxygen implantation but as well for xenon, caesium, or iodine implantation, and therefore is not dependent on the nature

S. Robinet; M. Gauneau; M. Salvi; C. Clarisse; R. Chaplain

1990-01-01

190

Reduction of NO{sub x} and particulate emissions by using oxygen-enriched combustion air in a locomotive diesel engine.  

SciTech Connect

This paper discusses operational and emissions results obtained with a locomotive (two-cylinder, EMD 567B) research diesel engine when oxygen-enriched combustion air is used. An operating regime was identified in which particulates and NO{sub x} could be reduced simultaneously when the concentration of intake air oxygen, fueling rate, and injection timing were optimized. Using oxygen from an external source, particulates were reduced by approximately 60% and NO{sub x} emissions were reduced by 15--20% with the optimal operating strategy. Higher gross power, lower peak cylinder pressures, and lower brake-specific fuel consumption were also observed. Gross power was increased by about 15--20% at base peak combustion pressure, and gross brake-specific fuel consumption was decreased by 2--10% with load. The effect of achieving oxygen enrichment by means of an air separation membrane is beyond the scope of the current study.

Poola, R. B.; Sekar, R. R.; Energy Systems; Electro-Motive Div., General Motors Corp.

2003-04-01

191

EXPERIMENTAL AND NUMERICAL STUDIES OF OPPOSED JET OXYGEN-ENHANCED METHANE DIFFUSION FLAMES  

Microsoft Academic Search

Planar oxygen-enhanced methane counterflow flames are investigated by optical diagnostics and numerical simulation. The major species concentrations and temperature measured from Raman scattering are compared to the detailed simulations of the flame formed between two opposed jets. The effect of stretch and the influence of oxygen concentration in the oxidizer on the flame structure are studied for nitrogen-diluted methane fuel

ZHONGXIAN CHENG; JOSEPH A. WEHRMEYER; ROBERT W. PITZ

2006-01-01

192

Investigation of asphalt (bitumen)-fuelled chemical looping combustion using durable copper-based oxygen carrier  

Microsoft Academic Search

Bitumen is a liquid fuel recovered from Alberta oil sands by mining or enhanced oil recovery methods, depending on the depth of the deposits. Steam is a typical in-situ enhanced oil recovery agent used to extract bitumen from underground oil reservoirs with minor surface disturbance. The CO2 emissions from natural gas steam boilers for enhanced oil recovery have been steadily

Yan Cao; Bin Li; Hou-Yin Zhao; Chia-Wei Lin; Song P Sit; Wei-Ping Pan

2011-01-01

193

Plasmon-enhanced luminescence from ultrathin hybrid polymer nanoassemblies for microscopic oxygen sensor application.  

PubMed

Plasmon-enhanced luminescence was developed for luminescent oxygen sensor application. Luminescent polymer Langmuir-Blodgett films containing platinum-porphyrin were assembled plane-to-plane with a silver nanoparticle array. The hybrid polymer nanoassemblies allow more than 10-fold luminescence enhancement in air. The luminescence intensity and lifetime measurements as functions of the number of layers revealed that some platinum-porphyrin, which is close to silver nanoparticles, is effectively enhanced. The enhancement enables us to monitor 2D oxygen distribution mapping on the micrometer scale. PMID:20822112

Mitsuishi, Masaya; Tanaka, Hiroyuki; Obata, Makoto; Miyashita, Tokuji

2010-10-01

194

Improved Regional Analysis of Oxygen-Enhanced Lung MR Imaging Using Image Registration  

Microsoft Academic Search

\\u000a Oxygen enhanced MR imaging of the lung is a promising technique for monitoring a range of pulmonary diseases but regional\\u000a analysis is hampered by lung motion and volume changes due to breathing. We have developed an image registration method to\\u000a improve the quantitative regional analysis of both static and dynamic oxygen-enhanced pulmonary MRI. Images were acquired\\u000a using a HASTE sequence

Josephine H. Naish; Geoffrey J. M. Parker; Paul C. Beatty; Alan Jackson; John C. Waterton; Simon S. Young; Christopher J. Taylor

2004-01-01

195

Determination of Local Experimental Heat-Transfer Coefficients on Combustion Side of an Ammonia-Oxygen Rocket  

NASA Technical Reports Server (NTRS)

Local experimental heat-transfer coefficients were measured in the chamber and throat of a 2400-pound-thrust ammonia-oxygen rocket engine with a nominal chamber pressure of 600 pounds per square inch absolute. Three injector configurations were used. The rocket engine was run over a range of oxidant-fuel ratio and chamber pressure. The injector that achieved the best performance also produced the highest rates of heat flux at design conditions. The heat-transfer data from the best-performing injector agreed well with the simplified equation developed by Bartz at the throat region. A large spread of data was observed for the chamber. This spread was attributed generally to the variations of combustion processes. The spread was least evident, however, with the best-performing injector.

Liebert, Curt H.; Ehlers, Robert C.

1961-01-01

196

Carbon deposition model for oxygen-hydrocarbon combustion. Task 6: Data analysis and formulation of an empirical model  

NASA Technical Reports Server (NTRS)

The formation and deposition of carbon (soot) was studied in the Carbon Deposition Model for Oxygen-Hydrocarbon Combustion Program. An empirical, 1-D model for predicting soot formation and deposition in LO2/hydrocarbon gas generators/preburners was derived. The experimental data required to anchor the model were identified and a test program to obtain the data was defined. In support of the model development, cold flow mixing experiments using a high injection density injector were performed. The purpose of this investigation was to advance the state-of-the-art in LO2/hydrocarbon gas generator design by developing a reliable engineering model of gas generator operation. The model was formulated to account for the influences of fluid dynamics, chemical kinetics, and gas generator hardware design on soot formation and deposition.

Makel, Darby B.; Rosenberg, Sanders D.

1990-01-01

197

Performance and Stability Characteristics of a Uni-Element Swirl Injector for Oxygen-Rich Stage Combustion Cycles  

NASA Technical Reports Server (NTRS)

A uni-element liquid propellant combustion performance and instability study for liquid RP-1 and hot oxygen-rich pre-burner products was conducted, at a chamber pressure of about 1000 psi. using flush and recessed swirl injectors. High-frequency pressure transducer measurements were analyzed to yield the characteristic frequencies which were compared to expected frequencies of the chamber. Modes, which were discovered to be present within the main chamber included, the first longitudinal, detected at approximately 1950 Hz, and the second longitudinal mode at approximately 3800 Hz. An additional first longitudinal quarter wave mode was measured at a frequency of approximately 23000 Hz for the recessed swirl injector configuration. The characteristic instabilities resulting from these experiments were relatively weak averaging 0.2% to 0.3% of the chamber pressure.

Pal, S.; Kalitan, D.; Woodward, R. D.; Santoro, R. J.

2004-01-01

198

Ignition delays, heats of combustion, and reaction rates of aluminum alkyl derivatives used as ignition and combustion enhancers for supersonic combustors  

NASA Technical Reports Server (NTRS)

The work was based on adapting an apparatus and procedure developed at Southwest Research Institute for rating the ignition quality of fuels for diesel engines. Aluminum alkyls and various Lewis-base adducts of these materials, both neat and mixed 50/50 with pure JP-10 hydrocarbon, were injected into the combustion bomb using a high-pressure injection system. The bomb was pre-charged with air that was set at various initial temperatures and pressures for constant oxygen density. The ignition delay times were determined for the test materials at these different initial conditions. The data are presented in absolute terms as well as comparisons with the parent alkyls. The relative heats of reaction of the various test materials were estimated based on a computation of the heat release, using the pressure data recorded during combustion in the bomb. In addition, the global reaction rates for each material were compared at a selected tmperature and pressure.

Ryan, T. W., III; Harlowe, W. W.; Schwab, S.

1992-01-01

199

Transition from Branching-Chain Kinetics to Partial Equilibrium in the Combustion of Lean Hydrogen-Oxygen Mixtures in Shock Waves.  

National Technical Information Service (NTIS)

Concentration profiles of the OH radical in the shock-initiated combustion of lean hydrogen-oxygen-argon mixtures at low pressures and temperatures are found to exhibit pronounced spikes prior to attainment of partial equilibrium. It is shown that this ef...

W. C. Gardiner K. Moringa D. L. Ripley T. Takeyama

1967-01-01

200

Combustion of polymers in a low pressure and low oxygen environment  

NASA Astrophysics Data System (ADS)

The effect of low pressure on the behavior of fires is very important to the study of fire safety in the aviation industry. This thesis explores the effect of low pressure on different components of flammability at low pressures, like those encountered at high altitude. An experiment was setup to measure the time to ignition, the mass flux at ignition, as well as the steady burning mass flux for different pressures and oxygen concentrations. The test measured the mass loss, oxygen consumption, soot production and average flame temperature. A square sample of PMMA was burned under different external heat fluxes, total pressures and oxygen concentrations. The experiments were compared to analytical expressions, to try to understand how pressure and oxygen concentration affect the behavior of a fire. Low pressure environment reduced the ignition delay time, indicating a sample is more prone to ignition at lower pressure. On the other hand the sample showed a reduction of steady burning mass flux, indicating the fire is less intense at lower pressure. The results show a good agreement with the analytical analysis

Zarzecki, Mariusz

201

Principles of solid state oxygen sensors for lean combustion gas control  

Microsoft Academic Search

This paper gives an overview about oxygen sensors for automotive applications to control the air–fuel ratio in order to reduce emissions and fuel consumption. The three-way catalyst system (TWC) using the potentiometric sensors based on zirconia represents the most effective system for the emission control at this time. New control strategies with linear lambda control at ?=1, for direct injection

E. Ivers-Tiffée; K. H. Härdtl; W. Menesklou; J. Riegel

2001-01-01

202

Erythropoiesis-stimulating agents and other methods to enhance oxygen transport.  

PubMed

Oxygen is essential for life, and the body has developed an exquisite method to collect oxygen in the lungs and transport it to the tissues. Hb contained within red blood cells (RBCs), is the key oxygen-carrying component in blood, and levels of RBCs are tightly controlled according to demand for oxygen. The availability of oxygen plays a critical role in athletic performance, and agents that enhance oxygen delivery to tissues increase aerobic power. Early methods to increase oxygen delivery included training at altitude, and later, transfusion of packed RBCs. A breakthrough in understanding how RBC formation is controlled included the discovery of erythropoietin (Epo) and cloning of the EPO gene. Cloning of the EPO gene was followed by commercial development of recombinant human Epo (rHuEpo). Legitimate use of this and other agents that affect oxygen delivery is important in the treatment of anaemia (low Hb levels) in patients with chronic kidney disease or in cancer patients with chemotherapy-induced anaemia. However, competitive sports was affected by illicit use of rHuEpo to enhance performance. Testing methods for these agents resulted in a cat-and-mouse game, with testing labs attempting to detect the use of a drug or blood product to improve athletic performance (doping) and certain athletes developing methods to use the agents without being detected. This article examines the current methods to enhance aerobic performance and the methods to detect illicit use. PMID:18362898

Elliott, S

2008-06-01

203

Strong Photoluminescence Enhancement of MoS2 through Defect Engineering and Oxygen Bonding.  

PubMed

We report on a strong photoluminescence (PL) enhancement of monolayer MoS2 through defect engineering and oxygen bonding. Micro-PL and Raman images clearly reveal that the PL enhancement occurs at cracks/defects formed during high-temperature annealing. The PL enhancement at crack/defect sites could be as high as thousands of times after considering the laser spot size. The main reasons of such huge PL enhancement include the following: (1) the oxygen chemical adsorption induced heavy p doping and the conversion from trion to exciton; (2) the suppression of nonradiative recombination of excitons at defect sites, which was verified by low-temperature PL measurements. First-principle calculations reveal a strong binding energy of ?2.395 eV for an oxygen molecule adsorbed on a S vacancy of MoS2. The chemically adsorbed oxygen also provides a much more effective charge transfer (0.997 electrons per O2) compared to physically adsorbed oxygen on an ideal MoS2 surface. We also demonstrate that the defect engineering and oxygen bonding could be easily realized by mild oxygen plasma irradiation. X-ray photoelectron spectroscopy further confirms the formation of Mo-O bonding. Our results provide a new route for modulating the optical properties of two-dimensional semiconductors. The strong and stable PL from defects sites of MoS2 may have promising applications in optoelectronic devices. PMID:24836121

Nan, Haiyan; Wang, Zilu; Wang, Wenhui; Liang, Zheng; Lu, Yan; Chen, Qian; He, Daowei; Tan, Pingheng; Miao, Feng; Wang, Xinran; Wang, Jinlan; Ni, Zhenhua

2014-06-24

204

Catalytic enhancement of singlet oxygen production and optical gain in electric discharge oxygen-iodine laser systems  

NASA Astrophysics Data System (ADS)

We are investigating catalytically enhanced production of singlet oxygen, O2(a1?g), observed by reaction of O2/He discharge effluents over an iodine oxide film surface in a microwave discharge-flow reactor at 320 K. We have previously reported a two-fold increase in the O2(a) yields by this process, and corresponding enhancement of I(2P1/2) excitation and small-signal gain upon injection of I2 and NO2. In this paper we review observed I* excitation behavior and correlations of the catalytically generated O2(a) with atomic oxygen over a large range of discharge-flow conditions to develop a conceptual reaction mechanism for the phenomena. We describe a first-generation catalytic module for the PSI supersonic MIDJet/EOIL reactor, and tests with this module for catalyst coating deposition and enhancement of the small-signal gain observed in the supersonic flow. The results present compelling evidence for catalytic production of vibrationally excited O2(X,v) and its participation in the I* excitation process. The observed catalytic effects could significantly benefit the development of high-power electrically driven oxygen-iodine laser systems.

Lee, Seonkyung; Rawlins, Wilson T.; Hicks, Adam J.; Konen, Ian M.; Plumb, Emily P.; Davis, Steven J.

2011-02-01

205

Conversion of Methane to Hydrogen in a Reversible Flow Reactor in the Process of Filtration Combustion of Fuel Mixtures Enriched with Oxygen  

NASA Astrophysics Data System (ADS)

This paper considers the process of partial oxidation of methane to syngas in a reversible flow reactor in the process of filtration combustion of fuel mixtures enriched with oxygen in an inert porous medium. Experimental studies have been made of the influence of the volume concentration of oxygen in the initial fuel mixture on the basic parameters of the conversion process — the maximum temperature in the combustion wave and the composition of reaction products. Investigations have been carried out for fuel mixtures having different calorific values under the same filtration conditions. It has been shown that the addition of oxygen to the initial methane-air mixture permits increasing considerably the efficiency of the conversion process.

Dmitrenko, Yu. M.; Klyovan, R. A.

2013-11-01

206

Kinetic modeling of electronically enhanced reaction pathways in Plasma Assisted Combustion  

NASA Astrophysics Data System (ADS)

The use of plasma energy to enhance and control the chemical reactions during combustion, a technology referred to as ``plasma assisted combustion'' (PAC), can result in a variety of beneficial effects: e.g. stable lean operation, pollution reduction, and wider range of p-T operating conditions. While experimental evidence abounds, theoretical understanding of PAC is at best incomplete, and numerical tools still lack in reliable predictive capabilities. In the context of a joint experimental-numerical effort at Michigan State University, we present here a modular Python framework dedicated to the dynamic optimization of non-equilibrium PAC systems. We first describe a novel kinetic global model, which aims at exploring scaling laws in parameter space, as well as the effect of a non-Maxwellian electron energy distribution function (EEDF). With such a model, we reproduce literature results and we critically review the effect of data uncertainty and limiting assumptions. Then, we explore means of measuring a non-Maxwellian EEDF through the use of a detailed collisional-radiative model, coupled to optical emission spectroscopy. Finally, we investigate the effect of different numerical integrators, as well as customized routines specifically designed to solve stiff sparse ODE systems.

Parsey, Guy; Gü?lü, Yaman; Verboncoeur, John; Christlieb, Andrew

2012-10-01

207

Mathematical modeling of MSW combustion and SNCR in a full-scale municipal incinerator and effects of grate speed and oxygen-enriched atmospheres on operating conditions.  

PubMed

The rising popularity of incineration of municipal solid waste (MSW) calls for detailed mathematical modeling and accurate prediction of pollutant emissions. In this paper, mathematical modeling methods for both solid and gaseous phases were employed to simulate the operation of a 450 t/d MSW-burning incinerator to obtain detailed information on the flow and combustion characteristics in the furnace and to predict the amount of pollutant emissions. The predicted data were compared to on-site measurements of gas temperature, gas composition and SNCR de-NO(X) system. The major operating conditions considered in this paper were grate speed and oxygen concentration. A suitable grate speed ensures complete waste combustion. The predictions are as follows: volatile release increases with increasing grate speed, and the maximal value is within the range of 700-800 kg/m(2)h; slow grate speeds result in incomplete combustion of fixed carbon; the gas temperature at slow grate speeds is higher due to adequate oxygenation for fixed carbon combustion, and the deviation reaches 200K; NO(X) emission decreases, but CO emission and O(2) concentrations increase, and the deviation is 63%, 34% and 35%, respectively. Oxygen-enriched atmospheres promote the destruction of most pollutants due to the high oxygen partial pressure and temperature. The furnace temperature, NO production and CO emission increase as the oxygen concentration increases, and the deviation of furnace exit temperature, NO and CO concentration is 38.26%, 58.43% and 86.67%, respectively. Finally, oxygen concentration is limited to below 35% to prevent excessive CO and NO(X) emission without compromising plant performance. The current work greatly helps to understand the operating characteristics of large-scale MSW-burning plants. PMID:20627508

Liang, Zengying; Ma, Xiaoqian

2010-12-01

208

The effect of O 2 enrichment on NO x formation in biomass co-fired pulverised coal combustion  

Microsoft Academic Search

Oxygen enrichment of the combustion air in pulverised coal combustion for power plant is seen as a possible retrofit measure to improve CO2 scrubbing and capture. This technique produces a reduced volume of flue gas with higher CO2 concentration than normal air combustion that will contributes to the enhancement of amine scrubbing plant efficiencies. We report in this article the

W. Nimmo; S. S. Daood; B. M. Gibbs

2010-01-01

209

The upper airway response to pollen is enhanced by exposure to combustion particulates: a pilot human experimental challenge study.  

PubMed Central

Although human experimental studies have shown that gaseous pollutants enhance the inflammatory response to allergens, human data on whether combustion particulates enhance the inflammatory response to allergen are limited. Therefore, we conducted a human experimental study to investigate whether combustion particulates enhance the inflammatory response to aeroallergens. "Enhancement" refers to a greater-than-additive response when combustion particulates are delivered with allergen, compared with the responses when particulates and allergen are delivered alone. Eight subjects, five atopic and three nonatopic, participated in three randomized exposure-challenge sessions at least 2 weeks apart (i.e., clean air followed by allergen, particles followed by no allergen, or particles followed by allergen). Each session consisted of nasal exposure to combustion particles (target concentration of 1.0 mg/m3) or clean air for 1 hr, followed 3 hr later by challenge with whole pollen grains or placebo. Nasal lavage was performed immediately before particle or clean air exposure, immediately after exposure, and 4, 18 and 42 hr after pollen challenge. Cell counts, differentials, and measurement of cytokines were performed on each nasal lavage. In atopic but not in nonatopic subjects, when allergen was preceded by particulates, there was a significant enhancement immediately after pollen challenge in nasal lavage leukocytes and neutrophils (29.7 X 10(3) cells/mL and 25.4 X 10(3) cells/mL, respectively). This represents a 143% and 130% enhancement, respectively. The enhanced response for interleukin-4 was 3.23 pg/mL (p = 0.06), a 395% enhancement. In atopic subjects there was evidence of an enhanced response when particulates, as compared to clean air, preceded the allergen challenge.

Hauser, Russ; Rice, Timothy M; Krishna Murthy, G G; Wand, Matt P; Lewis, Daniel; Bledsoe, Toni; Paulauskis, Joseph

2003-01-01

210

Low temperature complete combustion of dilute methane over Mn-doped ZrO 2 catalysts: factors influencing the reactivity of lattice oxygen and methane combustion activity of the catalyst  

Microsoft Academic Search

Complete combustion of methane (1.0 vol.% in air) over Mn-doped ZrO2 catalysts with different Mn\\/Zr mole ratios (0–1.0) at different temperatures (400–600°C) and space velocities (51,000–150,000cm3g?1h?1) and also over Mn-impregnated ZrO2 have been thoroughly investigated. Reactivity of the lattice oxygen of the catalysts was studied by temperature-programmed reduction (TPR) with H2 and also by the temperature-programmed reaction of lattice oxygen

Vasant R. Choudhary; Balu S. Uphade; Suryakant G. Pataskar

2002-01-01

211

Enhanced water electrolysis: Electrocatalytic generation of oxygen gas at manganese oxide nanorods modified electrodes  

Microsoft Academic Search

This study is concerned with the electrocatalytic evolution of oxygen gas at manganese oxide nanorods modified Pt, Au and GC electrodes in 0.5M KOH solution. The electrochemical measurements revealed a significant enhancement of the electrocatalytic activity of the Pt, Au and GC electrodes towards the oxygen evolution reaction (OER) upon the electrodeposition of manganese oxide nanoparticles (nano-MnOx), that is, the

Mohamed S. El-Deab; Mohamed I. Awad; Ahmad M. Mohammad; Takeo Ohsaka

2007-01-01

212

Method for automatically initiating in situ combustion for enhanced thermal recovery of hydrocarbons from a well  

Microsoft Academic Search

A method for initiating an in situ combustion operation for heating a well to recover petroleum from a subterranean reservoir in the well comprises lowering an elongated combustion chamber suspended from a hollow electrical cable with an air supply tube therearound which supplies electricity, fuel gas, and air to the combusion chamber, mixing an air-fuel mixture in the combustion chamber,

C. E. Howard; D. G. Calvin; R. W. Jr. Pitts

1979-01-01

213

Light enhanced calcification in Stylophora pistillata: effects of glucose, glycerol and oxygen  

PubMed Central

Zooxanthellate corals have long been known to calcify faster in the light than in the dark, however the mechanism underlying this process has been uncertain. Here we tested the effects of oxygen under controlled pCO2 conditions and fixed carbon sources on calcification in zooxanthellate and bleached microcolonies of the branching coral Stylophora pistillata. In zooxanthellate microcolonies, oxygen increased dark calcification rates to levels comparable to those measured in the light. However in bleached microcolonies oxygen alone did not enhance calcification, but when combined with a fixed carbon source (glucose or glycerol), calcification increased. Respiration rates increased in response to oxygen with greater increases when oxygen is combined with fixed carbon. ATP content was largely unaffected by treatments, with the exception of glycerol which decreased ATP levels.

Tambutte, Eric; Allemand, Denis; Tambutte, Sylvie

2014-01-01

214

Light enhanced calcification in Stylophora pistillata: effects of glucose, glycerol and oxygen.  

PubMed

Zooxanthellate corals have long been known to calcify faster in the light than in the dark, however the mechanism underlying this process has been uncertain. Here we tested the effects of oxygen under controlled pCO2 conditions and fixed carbon sources on calcification in zooxanthellate and bleached microcolonies of the branching coral Stylophora pistillata. In zooxanthellate microcolonies, oxygen increased dark calcification rates to levels comparable to those measured in the light. However in bleached microcolonies oxygen alone did not enhance calcification, but when combined with a fixed carbon source (glucose or glycerol), calcification increased. Respiration rates increased in response to oxygen with greater increases when oxygen is combined with fixed carbon. ATP content was largely unaffected by treatments, with the exception of glycerol which decreased ATP levels. PMID:24883242

Holcomb, Michael; Tambutté, Eric; Allemand, Denis; Tambutté, Sylvie

2014-01-01

215

A laboratory model of a hydrogen/oxygen engine for combustion and nozzle studies  

NASA Astrophysics Data System (ADS)

A small laboratory diagnostic thruster was developed in order to evaluate approaches for the use of temperature and pressure sensors for the investigation of low thrust rocket flowfields. Tests were performed at chamber pressures of about 255 kPa, 370 kPa, and 500 kPa with oxidizer/fuel mixture ratios between 4.0 and 8.0. Two gaseous hydrogen/gaseous oxygen injector designs were tested with 60 and 75 fuel film cooling. The results of hot-wire tests showed the thruster and instrumentation designs to be effective. Azimuthal temperature distributions were found to be a function of operating conditions and hardware configuration. Results indicated that small differences in injector design can result in dramatically different thruster performance and wall temperature behavior. However, the importance of these injector effects may be decreased by operating at a high fuel film cooling rate.

Morren, Sybil H.; Myers, Roger M.; Benko, Stephen E.; Arrington, Lynn A.; Reed, Brian D.

1993-06-01

216

Rat surfactant protein D enhances the production of oxygen radicals by rat alveolar macrophages.  

PubMed Central

Rat surfactant protein D (SP-D) was shown to enhance the production of oxygen radicals by rat alveolar macrophages. This enhancement, which was determined by a lucigenin-dependent chemiluminescence assay, was maximal after 18 min at an SP-D concentration of 0.2 micrograms/ml. Surfactant lipids did not influence the stimulation of alveolar macrophages by SP-D, whereas the oxygen-radical production of these cells induced by surfactant protein A was inhibited by the lipids in a concentration-dependent manner.

Van Iwaarden, J F; Shimizu, H; Van Golde, P H; Voelker, D R; Van Golde, L M

1992-01-01

217

The enhancing effects of hyperbaric oxygen on mouse skin carcinogenesis.  

PubMed

The effects of hyperbaric oxygen (HBO) on mouse skin two-stage chemical carcinogenesis were examined. Six-week-old inbred CD-1 female mice were divided into the following five groups: group 1, normoxia and application of 25 nmol 7,12-dimethylbenz[a]anthracene (DMBA) and 8.5 nmol 12-O-tetradecanoylphorbol-13-acetate (TPA) (n=19); group 2, HBO and DMBA/TPA (n=21); group 3, HBO and DMBA/acetone (n=3); group 4, normoxia and acetone (n=3); and group 5, non-treatment group (n=5). HBO was started at the same time as DMBA. Mice were euthanized at 23 weeks after the start of the experiment. Mice in group 2 showed the occurrence of tumors at 8 weeks after the beginning of the experiment, while the occurrence of tumors in mice in group 1 was observed beginning at 9 weeks. There was a difference in occurrence among low-grade papillomas, high-grade papillomas and SCCs in both groups 1 and 2 by the ? (2)-test at end of the experiment (p<0.05). The Ki-67 labeling indices of tumors revealed that the percentages of positive cells in low-grade papillomas in groups 1 and 2 were 15.27 ± 2.54% and 29.67 ± 2.82%, respectively (p<0.01). The results suggested that the tumors in group 2, which was treated with HBO, were more progressive than those in group 1, which was not treated with HBO. In this study, HBO accelerated tumor cell proliferation and advanced tumor progression in skin carcinogenesis by DMBA/TPA. PMID:24791069

Doguchi, Hiroshi; Saio, Masanao; Kuniyoshi, Shimpei; Matsuzaki, Akiko; Yoshimi, Naoki

2014-04-01

218

The Enhancing Effects of Hyperbaric Oxygen on Mouse Skin Carcinogenesis  

PubMed Central

The effects of hyperbaric oxygen (HBO) on mouse skin two-stage chemical carcinogenesis were examined. Six-week-old inbred CD-1 female mice were divided into the following five groups: group 1, normoxia and application of 25 nmol 7,12-dimethylbenz[a]anthracene (DMBA) and 8.5 nmol 12-O-tetradecanoylphorbol-13-acetate (TPA) (n=19); group 2, HBO and DMBA/TPA (n=21); group 3, HBO and DMBA/acetone (n=3); group 4, normoxia and acetone (n=3); and group 5, non-treatment group (n=5). HBO was started at the same time as DMBA. Mice were euthanized at 23 weeks after the start of the experiment. Mice in group 2 showed the occurrence of tumors at 8 weeks after the beginning of the experiment, while the occurrence of tumors in mice in group 1 was observed beginning at 9 weeks. There was a difference in occurrence among low-grade papillomas, high-grade papillomas and SCCs in both groups 1 and 2 by the ?2-test at end of the experiment (p<0.05). The Ki-67 labeling indices of tumors revealed that the percentages of positive cells in low-grade papillomas in groups 1 and 2 were 15.27 ± 2.54% and 29.67 ± 2.82%, respectively (p<0.01). The results suggested that the tumors in group 2, which was treated with HBO, were more progressive than those in group 1, which was not treated with HBO. In this study, HBO accelerated tumor cell proliferation and advanced tumor progression in skin carcinogenesis by DMBA/TPA.

Doguchi, Hiroshi; Saio, Masanao; Kuniyoshi, Shimpei; Matsuzaki, Akiko; Yoshimi, Naoki

2014-01-01

219

A laboratory model of a hydrogen/oxygen engine for combustion and nozzle studies  

NASA Astrophysics Data System (ADS)

A small laboratory diagnostic thruster was developed to augment present low thrust chemical rocket optical and heat flux diagnostics at the NASA Lewis Research Center. The objective of this work was to evaluate approaches for the use of temperature and pressure sensors for the investigation of low thrust rocket flow fields. The nominal engine thrust was 110 N. Tests were performed at chamber pressures of about 255 kPa, 370 kPa, and 500 kPa with oxidizer to fuel mixture ratios between 4.0 and 8.0. Two gaseous hydrogen/gaseous oxygen injector designs were tested with 60 percent and 75 percent fuel film cooling. The thruster and instrumentation designs were proven to be effective via hot fire testing. The thruster diagnostics provided inner wall temperature and static pressure measurements which were compared to the thruster global performance data. For several operating conditions, the performance data exhibited unexpected trends which were correlated with changes in the axial wall temperature distribution. Azimuthal temperature distributions were found to be a function of operating conditions and hardware configuration. The static pressure profiles showed that no severe pressure gradients were present in the rocket. The results indicated that small differences in injector design can result in dramatically different thruster performance and wall temperature behavior, but that these injector effects may be overshadowed by operating at a high fuel film cooling rate.

Morren, Sybil Huang; Myers, Roger M.; Benko, Stephen E.; Arrington, Lynn A.; Reed, Brian D.

1993-06-01

220

A Laboratory Model of a Hydrogen/Oxygen Engine for Combustion and Nozzle Studies  

NASA Technical Reports Server (NTRS)

A small laboratory diagnostic thruster was developed to augment present low thrust chemical rocket optical and heat flux diagnostics at the NASA Lewis Research Center. The objective of this work was to evaluate approaches for the use of temperature and pressure sensors for the investigation of low thrust rocket flow fields. The nominal engine thrust was 110 N. Tests were performed at chamber pressures of about 255 kPa, 370 kPa, and 500 kPa with oxidizer to fuel mixture ratios between 4.0 and 8.0. Two gaseous hydrogen/gaseous oxygen injector designs were tested with 60 percent and 75 percent fuel film cooling. The thruster and instrumentation designs were proven to be effective via hot fire testing. The thruster diagnostics provided inner wall temperature and static pressure measurements which were compared to the thruster global performance data. For several operating conditions, the performance data exhibited unexpected trends which were correlated with changes in the axial wall temperature distribution. Azimuthal temperature distributions were found to be a function of operating conditions and hardware configuration. The static pressure profiles showed that no severe pressure gradients were present in the rocket. The results indicated that small differences in injector design can result in dramatically different thruster performance and wall temperature behavior, but that these injector effects may be overshadowed by operating at a high fuel film cooling rate.

Morren, Sybil Huang; Myers, Roger M.; Benko, Stephen E.; Arrington, Lynn A.; Reed, Brian D.

1993-01-01

221

Oxygen-enhanced biodegradation of phenoxy acids in ground water at contaminated sites.  

PubMed

The effects of adding oxygen to anaerobic aquifer materials on biodegradation of phenoxy acid herbicides were studied by laboratory experiments with aquifer material from two contaminated sites (a former agricultural machinery service and an old landfill). At both sites, the primary pollutants were phenoxy acids and related chlorophenols. It was found that addition of oxygen enhanced degradation of the six original phenoxy acids and six original chlorophenols. Inverse modeling on 14C 4-chloro-2-methylphenoxypropanoic acid (MCPP) degradation curves revealed that increasing the oxygen concentrations from <0.3 mg/L up to 7 to 8 mg/L shortened the lag phases (from approximately 150 d to 5 to 25 d) and increased first-order degradation rate constants by 1 order of magnitude (from approximately 5 x 10(-2) d(-1) to up to 30 x 10(-2) d(-1)). Additionally, the degree of MCPP mineralization was increased (30% to 50% mineralized at low oxygen concentrations and 50% to 70% mineralized at high oxygen concentrations, based on 14CO2 recovery). These positive effects on degradation were observed even at relatively low oxygen concentrations (2 mg/L). Furthermore, effects related to the addition of oxygen on the general geochemistry were studied. An oxygen consumption of 2.2 to 2.6 mg O2/g dw was observed due to oxidation of solid organic matter and, to some extent (0.5% to 11% of the total oxygen consumption), water-soluble compounds such as Fe2+, dissolved Mn, nonvolatile organic carbon, and NH4+. Overall, the results suggest that stimulated biodegradation by addition of oxygen might be a feasible remediation technology at herbicide-contaminated sites, although oxygen consumption by the sediment could limit the applicability. PMID:16556207

Tuxen, Nina; Reitzel, Lotte A; Albrechtsen, Hans-Jørgen; Bjerg, Poul L

2006-01-01

222

Lithium Combustion: A Review.  

National Technical Information Service (NTIS)

This review deals with the chemical reactions, ignition, and combustion of lithium combustion in air and in the components of air, including oxygen, nitrogen, water, and carbon dioxide. It was found that lithium reacts vigorously with these substances. In...

R. A. Rhein

1990-01-01

223

Removing aromatic and oxygenated VOCs from polluted air stream using Pt-carbon aerogels: assessment of their performance as adsorbents and combustion catalysts.  

PubMed

Two series of Pt-catalysts were prepared by impregnation or doping of carbon aerogels and different porous textures and Pt-dispersion were obtained. The performance of the samples in the elimination of organic compounds (VOCs) by adsorption and catalytic combustion was studied and compared with the characteristics of both the VOCs and the catalysts and the interactions between them. Toluene, xylenes and acetone were selected as representative aromatic or oxygenated VOCs. The adsorption of VOCs is favoured at room temperature in the case of meso/microporous materials, but at the higher catalytic reaction temperature, the micropores volume is more important. Adsorption and catalytic combustion occur simultaneously, and are both dependent on temperature, albeit in opposite directions. The combustion of aromatic compounds takes place at a lower temperature than that required for acetone combustion, so favouring the accumulation of adsorbed VOC, something that should be avoided to minimize risks. Catalytic performance improves with the contact time and is independent of oxygen content above 5% v/v, but declines significantly below this limit. PMID:21872395

Maldonado-Hódar, Francisco José

2011-10-30

224

NiO\\/NiAl 2O 4 oxygen carriers prepared by sol-gel for chemical-looping combustion fueled by gas  

Microsoft Academic Search

Chemical-looping combustion with inherent CO2 enrichment depends on the high-powered oxygen carriers. Ni(NO3)2 and Al(OC3H7)3 are selected as the main raw materials to prepare sol-gel-derived NiO\\/NiAl2O4, by matching the appropriate experimental parameters. The oxygen carrier with a mass content of 60% NiO, a sintering temperature of 1300°C, and a sintering time of 6 h performs comparatively good physicochemical properties. The

Hai-bo ZHAO; Li-ming LIU; Di XU; Chu-guang ZHENG; Guo-jun LIU; Lin-lin JIANG

2008-01-01

225

NiO\\/Al 2O 3 oxygen carriers for chemical-looping combustion prepared by impregnation and deposition–precipitation methods  

Microsoft Academic Search

Ni-based oxygen carriers (OC) with different NiO content were prepared by incipient wet impregnation, at ambient (AI), and hot conditions (HI) and by deposition–precipitation (DP) methods using ?-Al2O3 and ?-Al2O3 as supports. The OC were characterized by BET, Hg porosimetry, mechanical strength, TPR, XRD and SEM\\/EDX techniques. Reactivity of the OC was measured in a thermogravimetric analyzer and methane combustion

Pilar Gayán; Cristina Dueso; Alberto Abad; Juan Adanez; Luis F. de Diego; Francisco García-Labiano

2009-01-01

226

The effect of pulmonary blood flow changes on oxygen-enhanced lung magnetic resonance imaging.  

PubMed

In this study, we investigated the effects of changes in pulmonary blood flow on oxygen-enhanced lung magnetic resonance imaging. Increased pulmonary blood flow was produced by intravenous infusion of sildenafil (0.2 mg/kg) in 10 New Zealand white rabbits. Decreased pulmonary blood flow was produced by single subcutaneous injection of monocrotaline (60 mg/kg). A velocity-encoded cine magnetic resonance imaging for pulmonary blood flow and an oxygen-enhanced lung magnetic resonance imaging were performed at baseline, during sildenafil infusion, and after monocrotaline injection. We compared the baseline data to those obtained during sildenafil infusion and after monocrotaline injection for pulmonary blood flow changes and signal intensity enhancement ratios of oxygen-enhanced lung magnetic resonance imaging. Wilcoxon's signed rank test was used for statistical analysis. There was a significant difference between pulmonary blood flow at baseline (418.6±108.9 mL/min) and after sildenafil (491.9±118.0 mL/min; P=0.005) or between pulmonary blood flow at baseline and after monocrotaline administration (356.3±85.8 mL/min; P=0.017). However, there was no significant difference between the signal intensity enhancement ratios at baseline (23.8±11.4%) and after sildenafil (24.0±7.9%; P=0.953) or the signal intensity enhancement ratios at baseline and after monocrotaline administration (22.7±10.3%; P=0.374). Changes in pulmonary blood flow had little effect on the signal intensity enhancement ratio of oxygen-enhanced lung magnetic resonance imaging. PMID:22760954

Lee, Hye-Jeong; Park, Jaeseok; Hur, Jin; Kim, Young Jin; Nam, Ji Eun; Choi, Byoung Wook; Choe, Kyu Ok

2013-06-01

227

Enhancement of NADP-malic enzyme in transgenic rice induced the accumulation of reactive oxygen species  

Microsoft Academic Search

It had been demonstrated that the photosynthetic photodamage, such as photoinhibition and photooxidation, was enhanced in\\u000a transgenic rice plants overexpressing NADP-malic enzyme (ME). However, its physiological base has not been investigated. In\\u000a order to elucidate the physiological elements contributed to the enhancement of photodamage in NADP-ME transgenic rice plants,\\u000a some physiological indices related to reactive oxygen species (ROS) accumulation were

Wei Chi

2006-01-01

228

New insights into enriched-air in-situ combustion  

SciTech Connect

This paper presents the results of 10 enriched-air in-situ combustion-tube tests performed on core from the Athabasca oil sands deposit. The tests show that at high pressures, the use of oxygen-enriched air results in increased low-temperature reactions between the oxygen and the oil, resulting in an increased fuel load and decreased burn stability. Although water injection may enhance the performance of oxygen combustion, it may also lead to increased oxygen storage in the swept zone.

Moore, R.G.; Bennion, D.W.; Belgrave, J.D.M.; Gle, D.N.; Ursenbach, M.G. (Calgary Univ., AB (Canada))

1990-07-01

229

Thermofluid analysis of the SSME preburner using a gas-gas diffusion model for oxygen and hydrogen combustion at supercritical pressures  

NASA Technical Reports Server (NTRS)

The paper discusses the thermofluid analysis of the Space Shuttle Main Engine (SSME) fuelside preburner. The governing equations have been solved numerically to predict flow, heat transfer, mixing, and combustion. A two-fluid approach is adopted in which oxygen is regarded as one fluid and hydrogen is regarded as the other fluid. The chemical kinetics is assumed to be very fast so that combustion is primarily controlled by the rate of mixing between oxygen and hydrogen. The preburner pressure is much greater than the critical pressures of oxygen and hydrogen; hence, a gas-gas diffusion model (rather than an evaporation model) has been developed to compute the rate of interphase mixing. Empirical correlations have been incorporated to account for the effect of slip on the interphase exchange. A sensitivity study has been performed with various model parameters. It is observed that the model can predict possibility of incomplete combustion and local regions of high temperatures under steady operating conditions. Some of these anomalies have been observed in actual tests, and the numerical model is useful for understanding possible causes and remedies. At least some measurements are needed for quantitative verification of the model.

Prakash, C.; Singhal, A. K.; Shafer, C.

1986-01-01

230

Hemoglobin-based oxygen carrier and convection enhanced oxygen transport in a hollow fiber bioreactor.  

PubMed

A mathematical model was developed to study O(2) transport in a convection enhanced hepatic hollow fiber (HF) bioreactor, with hemoglobin-based O(2) carriers (HBOCs) present in the flowing cell culture media stream of the HF lumen. In this study, four HBOCs were evaluated: PEG-conjugated human hemoglobin (MP4), human hemoglobin (hHb), bovine hemoglobin (BvHb) and polymerized bovine hemoglobin (PolyBvHb). In addition, two types of convective flow in the HF extra capillary space (ECS) were considered in this study. Starling flow naturally occurs when both of the ECS ports are closed. If one of the ECS ports is open, forced convective flow through the ECS will occur due to the imposed pressure difference between the lumen and ECS. This type of flow is referred to as cross-flow in this work, since some of the fluid entering the HF lumen will pass across the HF membrane and exit via the open ECS port. In this work, we can predict the dissolved O(2) concentration profile as well as the O(2) transport flux in an individual HF of the bioreactor by solving the coupled momentum and mass transport equations. Our results show that supplementation of the cell culture media with HBOCs can dramatically enhance O(2) transport to the ECS (containing hepatocytes) and lead to the formation of an in vivo-like O(2) spectrum for the optimal culture of hepatocytes. However, both Starling flow and cross-flow have a very limited effect on O(2) transport in the ECS. Taken together, this work represents a novel predictive tool that can be used to design or analyze HF bioreactors that expose cultured cells to defined overall concentrations and gradients of O(2). PMID:19072844

Chen, Guo; Palmer, Andre F

2009-04-15

231

An interpretation of the observed oxygen and nitrogen enhancements in low energy cosmic rays  

NASA Technical Reports Server (NTRS)

It is proposed that the enhancements of cosmic ray oxygen and nitrogen observed at approximately 10 MeV/nucleon could result from neutral interstellar particles which are swept into the solar cavity. This is caused by motion of the sun through the interstellar medium, and the particles are subsequently ionized and accelerated.

Fisk, L. A.; Kozlovsky, B.; Ramaty, R.

1973-01-01

232

New insights into factors influencing the clinically relevant oxygen enhancement ratio  

Microsoft Academic Search

Background and purpose: This paper deals with the variations in the oxygen enhancement ratios that could be observed (OER?) when comparing oxic and hypoxic cells in different types of fractionated experiments as a consequence of the non-linearity of the underlying cell survival curves. Calculations have been made of the OER? that would be obtained for fractionated irradiations with a series

Alexandru Da?u; Juliana Denekamp

1998-01-01

233

Reducible Supports for Ni-based Oxygen Carriers in Chemical Looping Combustion  

SciTech Connect

Nuclear spin relaxation, small-angle X-ray scattering (SAXS), and electrospray ionization mass spectrometry (ESI-MS) techniques are used to determine supramolecular arrangement of 3-methyl-1-octyl-4-phenyl-1H-triazol-1,2,3-ium bis(trifluoromethanesulfonyl)imide [OMPhTz][Tf{sub 2}N], an example of a triazolium-based ionic liquid. The results obtained showed first-order thermodynamic dependence for nuclear spin relaxation of the anion. First-order relaxation dependence is interpreted as through-bond dipolar relaxation. Greater than first-order dependence was found in the aliphatic protons, aromatic carbons (including nearest neighbors), and carbons at the end of the aliphatic tail. Greater than first order thermodynamic dependence of spin relaxation rates is interpreted as relaxation resulting from at least one mechanism additional to through-bond dipolar relaxation. In rigid portions of the cation, an additional spin relaxation mechanism is attributed to anisotropic effects, while greater than first order thermodynamic dependence of the octyl side chain’s spin relaxation rates is attributed to cation–cation interactions. Little interaction between the anion and the cation was observed by spin relaxation studies or by ESI-MS. No extended supramolecular structure was observed in this study, which was further supported by MS and SAXS. nuclear Overhauser enhancement (NOE) factors are used in conjunction with spin–lattice relaxation time (T{sub 1}) measurements to calculate rotational correlation times for C–H bonds (the time it takes for the vector represented by the bond between the two atoms to rotate by one radian). The rotational correlation times are used to represent segmental reorientation dynamics of the cation. A combination of techniques is used to determine the segmental interactions and dynamics of this example of a triazolium-based ionic liquid.

Bhavsar, Saurabh; Veser, Goetz

2013-04-01

234

Enhancement of fine-scale mixing for fuel-rich plume combustion  

NASA Astrophysics Data System (ADS)

The effect of enhancing small-scale turbulent structures on the combustion intensity and flame stability was studied in nonreacting and reacting flows. Hot-wire anemometry was used to map the mean and turbulent flow fields of the nonreacting flows. Reacting flows were studied in a free flame and in a ducted gas-generator fuel-rich plume using Planar Laser Induced Fluorescence, a rake of thermocouples and high speed photography. A modified circular nozzle having several backward facing steps upstream of its exit was used to introduce numerous inflection points in the initial mean velocity profiles, thus producing multiple corresponding sources of small-scale turbulence generators. Cold flow tests showed turbulence increases of up to six times the initial turbulence level relative to a circular nozzle. The ensuing result was that the flame of this nozzle was more intense with a homogeneous heat release. The fuel-rich plume was stable even in supersonic speeds, and secondary ignition was obtained under conditions that prevented sustained afterburning using the circular nozzle.

Schadow, K. C.; Gutmark, E.; Parr, T. P.; Parr, D. M.; Wilson, K. J.; Ferrell, G. B.

1987-01-01

235

The enhancement of the mixing and combustion processes in supersonic flow applied to scramjet engine  

SciTech Connect

The Reynolds averaged parabolized Navier-Stokes equations are employed for the numerical study of turbulent mixing and combustion of a supersonic hydrogen jet in a supersonic airflow. A one-equation differential turbulence model is utilized. The simplified flame sheet model is employed for the numerical simulation of the supersonic combustion. 24 refs.

Kopchenov, V.I.; Lomkov, K.E. (Tsentral'nyi NII Aviatsionnogo Motorostroeniia, Moscow (Russian Federation))

1992-07-01

236

Detection of Molecular Oxygen at Low Concentrations Using Quartz Enhanced Photoacoustic Spectroscopy  

PubMed Central

Molecular oxygen is detected at low concentrations using photoacoustic spectroscopy despite its unfavorable photoacoustic properties. The system consists of a seed laser diode, a tapered amplifier and a quartz tuning fork based spectrophone, thus employing quartz enhanced photoacoustic spectroscopy (QEPAS). With this system a detection limit of 13 ppm is reached with a compact and long term stable setup. Further improvement of the detection limit is possible by adding suitable gases to the sample gas that promote the radiationless de-excitation of the oxygen molecules.

Pohlkotter, Andreas; Kohring, Michael; Willer, Ulrike; Schade, Wolfgang

2010-01-01

237

Imaging lung function using rapid dynamic acquisition of T1-maps during oxygen enhancement.  

PubMed

This paper describes imaging of lung function with oxygen-enhanced MRI using dynamically acquired T1 parameter maps, which allows an accurate, quantitative assessment of time constants of T1-enhancement and therefore lung function. Eight healthy volunteers were examined on a 1.5-T whole-body scanner. Lung T1-maps based on an IR Snapshot FLASH technique (TE = 1.4 ms, TR = 3.5 ms, FA = 7 (composite function )) were dynamically acquired from each subject. Without waiting for full relaxation between subsequent acquisition of T1-maps, one T1-map was acquired every 6.7 s. For comparison, all subjects underwent a standard pulmonary function test (PFT). Oxygen wash-in and wash-out time course curves of T1 relaxation rate (R1)-enhancement were obtained and time constants of oxygen wash-in (w(in)) and wash-out (w(out)) were calculated. Averaged over the whole right lung, the mean w(out) was 43.90 +/- 10.47 s and the mean (w(in)) was 51.20 +/- 15.53 s, thus about 17% higher in magnitude. Wash-in time constants correlated strongly with forced expired volume in one second in percentage of the vital capacity (FEV1 % VC) and with maximum expiratory flow at 25% vital capacity (MEF25), whereas wash-out time constants showed only weak correlation. Using oxygen-enhanced rapid dynamic acquisition of T1-maps, time course curves of R1-enhancement can be obtained. With w(in) and w(out) two new parameters for assessing lung function are available. Therefore, the proposed method has the potential to provide regional information of pulmonary function in various lung diseases. PMID:15042464

Arnold, J F T; Fidler, F; Wang, T; Pracht, E D; Schmidt, M; Jakob, P M

2004-04-01

238

Metal-enhanced fluorescence based excitation volumetric effect of plasmon-enhanced singlet oxygen and super oxide generation.  

PubMed

In this contribution we show that the Metal-Enhanced Fluorescence (MEF) Excitation Volumetric Effect (EVE), has a profound effect on the formation of Reactive Oxygen Species (ROS), such as singlet oxygen ((1)O2) and superoxide anion radical (O2(-)*), when sensitizers are placed in close proximity to plasmon supporting nanoparticulate substrates. In particular, when the singlet oxygen sensitizer rose bengal is placed on a SiFs surface, i.e. on a silver island film, the (1)O2 response to power is non-linear, and at 100 mW excitation power (535 nm) it is about 5 times higher, as compared to glass control samples, measured with the commercially available (1)O2 probe Sensor Green™. We also report a similar power dependence of superoxide generation for acridine on SiFs surfaces, but using the dihydroethidium O2(-)* probe (DHE). Our findings are consistent with our previously postulated Metal-Enhanced Fluorescence (MEF) and EVE models. PMID:23873175

Karolin, Jan; Geddes, Chris D

2013-10-14

239

Ignition delays, heats of combustion, and reaction rates of aluminum alkyl derivatives used as ignition and combustion enhancers for supersonic combustion  

NASA Technical Reports Server (NTRS)

The subject of this paper is the design of supersonic combustors which will be required in order to achieve the needed reaction rates in a reasonable sized combustor. A fuel additive approach, which is the focus of this research, is the use of pyrophorics to shorten the ignition delay time and to increase the energy density of the fuel. Pyrophoric organometallic compounds may also provide an ignition source and flame stabilization mechanism within the combustor, thus permitting use of hydrocarbon fuels in supersonic combustion systems. Triethylaluminum (TEA) and trimethylaluminum (TMA) were suggested for this application due to their high energy density and reactivity. The objective here is to provide comparative data for the ignition quality, the energy content, and the reaction rates of several different adducts of both TEA and TMA. The results of the experiments indicate the aluminum alkyls and their more stable derivatives reduce the ignition delay and total reaction time to JP-10 jet fuel. Furthermore, the temperature dependence of ignition delay and total reaction time of the blends of the adducts are significantly lower than in neat JP-10.

Ryan, Thomas W., III; Schwab, S. T.; Harlowe, W. W.

1992-01-01

240

Origin of enhanced activity in palladium alloy electrocatalysts for oxygen reduction reaction.  

PubMed

We explored the origin of the enhanced activity of Pd-alloy electrocatalysts for the O2 reduction reaction by correlating the electrocatalytic activity of intrinsic Pd and Pt surfaces and Pd and Pt overlayers on several substrates with their electronic properties, and established the volcano-type dependence of O2 reduction activity on the binding energy of oxygen and the d-band center of the top metal layer. Intrinsic Pd and Pt surfaces bind oxygen too firmly to allow efficient removal of the adsorbed reaction intermediates. Therefore, they do not have the highest activity and are not on the top of the volcano plot. A Pd overlayer on a Pd3Fe(111) alloy, was predicted to lie on top of the volcano plot, and thus, it appears to be the most active catalyst among investigated ones because of its moderate interaction with oxygen. The results can help in designing better electrocatalysts for fuel cells and other applications. PMID:17441757

Shao, Minhua; Liu, Ping; Zhang, Junliang; Adzic, Radoslav

2007-06-21

241

Enhanced conductivity of reduced graphene oxide decorated with aluminium oxide nanoparticles by oxygen annealing  

NASA Astrophysics Data System (ADS)

A process involving the filtration of graphene oxide (GO) dispersion through an alumina membrane, followed by oxygen annealing to synthesize alumina nanoparticles exclusively at the edges of holes or vacancies in the reduced graphene oxide (rGO) plane, is used to prepare paper-like composites with a 21% enhanced electrical conductivity. Moreover, the rGO/alumina nanocomposites have a smaller band gap and hydrophilic properties.A process involving the filtration of graphene oxide (GO) dispersion through an alumina membrane, followed by oxygen annealing to synthesize alumina nanoparticles exclusively at the edges of holes or vacancies in the reduced graphene oxide (rGO) plane, is used to prepare paper-like composites with a 21% enhanced electrical conductivity. Moreover, the rGO/alumina nanocomposites have a smaller band gap and hydrophilic properties. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00362k

Liu, Hao; Choy, Kwang-Leong; Roe, Martin

2013-06-01

242

Root effect hemoglobin may have evolved to enhance general tissue oxygen delivery.  

PubMed

The Root effect is a pH-dependent reduction in hemoglobin-O2 carrying capacity. Specific to ray-finned fishes, the Root effect has been ascribed specialized roles in retinal oxygenation and swimbladder inflation. We report that when rainbow trout are exposed to elevated water carbon dioxide (CO2), red muscle partial pressure of oxygen (PO2) increases by 65%--evidence that Root hemoglobins enhance general tissue O2 delivery during acidotic stress. Inhibiting carbonic anhydrase (CA) in the plasma abolished this effect. We argue that CA activity in muscle capillaries short-circuits red blood cell (RBC) pH regulation. This acidifies RBCs, unloads O2 from hemoglobin, and elevates tissue PO2, which could double O2 delivery with no change in perfusion. This previously undescribed mechanism to enhance O2 delivery during stress may represent the incipient function of Root hemoglobins in fishes. PMID:23766325

Rummer, Jodie L; McKenzie, David J; Innocenti, Alessio; Supuran, Claudiu T; Brauner, Colin J

2013-06-14

243

A detailed chemical analysis of changes to bitumen produced by the in situ combustion process at the oxygen Wolf Lake Project, Alberta. Part 11; Whole oil samples  

SciTech Connect

The detailed chemical changes in bitumen brought about over a one year period by a in situ combustion process in an oil sands reservoir have been investigated. Relative to a core sample, the fireflood-produced oils exhibited a significant reduction in density and viscosity which began early in the production cycle. This behavior was correlated with a marked increase in material boiling in the naphtha and middle distillate ranges and a concomitant decrease in the residue cut. The sulfur and nitrogen contents in the produced oils decreased relative to the core sample. A reduction in the acid number of the produced oil samples was coupled with an increase in the oxygen content as the fireflood proceeded. In this paper the relationship between these changes and the dynamics of the in situ combustion process are discussed.

Alex, R.F.; Fuhr, B.; Reichert, C. (Alberta Research Council, Oil Sands and Hydrocarbon Recovery, Edmonton, Alberta T6H 5X2 (CA))

1992-01-01

244

Diamagnetic levitation enhances growth of liquid bacterial cultures by increasing oxygen availability  

PubMed Central

Diamagnetic levitation is a technique that uses a strong, spatially varying magnetic field to reproduce aspects of weightlessness, on the Earth. We used a superconducting magnet to levitate growing bacterial cultures for up to 18 h, to determine the effect of diamagnetic levitation on all phases of the bacterial growth cycle. We find that diamagnetic levitation increases the rate of population growth in a liquid culture and reduces the sedimentation rate of the cells. Further experiments and microarray gene analysis show that the increase in growth rate is owing to enhanced oxygen availability. We also demonstrate that the magnetic field that levitates the cells also induces convective stirring in the liquid. We present a simple theoretical model, showing how the paramagnetic force on dissolved oxygen can cause convection during the aerobic phases of bacterial growth. We propose that this convection enhances oxygen availability by transporting oxygen around the liquid culture. Since this process results from the strong magnetic field, it is not present in other weightless environments, e.g. in Earth orbit. Hence, these results are of significance and timely to researchers considering the use of diamagnetic levitation to explore effects of weightlessness on living organisms and on physical phenomena.

Dijkstra, Camelia E.; Larkin, Oliver J.; Anthony, Paul; Davey, Michael R.; Eaves, Laurence; Rees, Catherine E. D.; Hill, Richard J. A.

2011-01-01

245

Diamagnetic levitation enhances growth of liquid bacterial cultures by increasing oxygen availability.  

PubMed

Diamagnetic levitation is a technique that uses a strong, spatially varying magnetic field to reproduce aspects of weightlessness, on the Earth. We used a superconducting magnet to levitate growing bacterial cultures for up to 18 h, to determine the effect of diamagnetic levitation on all phases of the bacterial growth cycle. We find that diamagnetic levitation increases the rate of population growth in a liquid culture and reduces the sedimentation rate of the cells. Further experiments and microarray gene analysis show that the increase in growth rate is owing to enhanced oxygen availability. We also demonstrate that the magnetic field that levitates the cells also induces convective stirring in the liquid. We present a simple theoretical model, showing how the paramagnetic force on dissolved oxygen can cause convection during the aerobic phases of bacterial growth. We propose that this convection enhances oxygen availability by transporting oxygen around the liquid culture. Since this process results from the strong magnetic field, it is not present in other weightless environments, e.g. in Earth orbit. Hence, these results are of significance and timely to researchers considering the use of diamagnetic levitation to explore effects of weightlessness on living organisms and on physical phenomena. PMID:20667843

Dijkstra, Camelia E; Larkin, Oliver J; Anthony, Paul; Davey, Michael R; Eaves, Laurence; Rees, Catherine E D; Hill, Richard J A

2011-03-01

246

ENHANCED FORMATION OF DIOXINS AND FURANS FROM COMBUSTION DEVICES BY ADDITION OF TRACE QUANTITIES OF BROMINE  

EPA Science Inventory

Past pilot-scale experimental studies have shown a dramatic increase in the formation of certain chlorinated products of incomplete combustion (PICs) caused by the addition of trace amounts of bromine (Br). Emissions of trichloroethylene and tetrachloorethylene, generated as PICs...

247

Super-mixing combustion enhanced by resonance between micro-shear layer and acoustic excitation  

Microsoft Academic Search

In terms of the application of high-speed and high-load combustion to isothermal-expansion combustion proposed by the authors, flow and reaction control of relatively small diffusion flames ejected from nozzles 0.5 and 1 mm in width are investigated using acoustic resonance; this study is the first step for the mixing control of a micro-diffusion flame which is considered to be a

H Yoshida; M Koda; Y Ooishi; K. P Kobayashi; M Saito

2001-01-01

248

Enhancement of oxidative vaporization of chromium (III) oxide and chromium by oxygen atoms  

NASA Technical Reports Server (NTRS)

Rates of oxidative vaporization of Cr2O3 were found to be markedly enhanced in the presence of O atoms. Investigations were conducted over the temperature range 470 to 1520 K. For Cr2O3 the enhancement was about 10 to the 9th power at 820 K in oxygen containing 2.5 percent atoms. Rapid oxidative vaporization of bare chromium was observed below 1070 K, the rate being about one-half that of Cr2O3. Results are interpreted in terms of thermochemical analysis.

Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.

1974-01-01

249

Icariin enhances neuronal survival after oxygen and glucose deprivation by increasing SIRT1  

Microsoft Academic Search

It has been reported that icariin protects neurons against ischemia\\/reperfusion injury. In this study, we found that icariin could enhance neuronal viability and suppress neuronal death after oxygen and glucose deprivation (OGD). Further study showed that neuroprotection by icariin was through the induction of Sirtuin type 1 (SIRT1), an effect that was reversed by SIRT1 inhibitor III and P38 inhibitor

Lin Wang; Ling Zhang; Zhi-Bin Chen; Jia-Yong Wu; Xin Zhang; Yun Xu

2009-01-01

250

Long term analysis of the biomass content in the feed of a waste-to-energy plant with oxygen-enriched combustion air.  

PubMed

Thermal utilization of municipal solid waste and commercial wastes has become of increasing importance in European waste management. As waste materials are generally composed of fossil and biogenic materials, a part of the energy generated can be considered as renewable and is thus subsidized in some European countries. Analogously, CO(2) emissions of waste incinerators are only partly accounted for in greenhouse gas inventories. A novel approach for determining these fractions is the so-called balance method. In the present study, the implementation of the balance method on a waste-to-energy plant using oxygen-enriched combustion air was investigated. The findings of the 4-year application indicate on the one hand the general applicability and robustness of the method, and on the other hand the importance of reliable monitoring data. In particular, measured volume flows of the flue gas and the oxygen-enriched combustion air as well as corresponding O(2) and CO(2) contents should regularly be validated. The fraction of renewable (biogenic) energy generated throughout the investigated period amounted to between 27 and 66% for weekly averages, thereby denoting the variation in waste composition over time. The average emission factor of the plant was approximately 45 g CO(2) MJ(-1) energy input or 450 g CO(2) kg(-1) waste incinerated. The maximum error of the final result was about 16% (relative error), which was well above the error (<8%) of the balance method for plants with conventional oxygen supply. PMID:21382872

Fellner, Johann; Cencic, Oliver; Zellinger, Günter; Rechberger, Helmut

2011-10-01

251

Ultraviolet Irradiation-Dependent Fluorescence Enhancement of Hemoglobin Catalyzed by Reactive Oxygen Species  

PubMed Central

Ultraviolet (UV) light has a potent effect on biological organisms. Hemoglobin, an oxygen-transport protein, plays an irreplaceable role in sustaining life of all vertebrates. In this study we scrutinize the effects of ultraviolet irradiation (UVI) as well as visible irradiation on the fluorescence characteristics of bovine hemoglobin (BHb) in vitro. Data show that UVI results in fluorescence enhancement of BHb in a dose-dependant manner. Furthermore, UVI-induced fluorescence enhancement is significantly increased when BHb is pretreated with hydrogen peroxide (H2O2), a type of reactive oxygen species (ROS). Meanwhile, The water-soluble antioxidant vitamin C suppresses this UVI-induced fluorescence enhancement. In contrast, green light irradiation does not lead to fluorescence enhancement of BHb no matter whether H2O2 is acting on the BHb solution or not. Taken together, these results indicate that catalysis of ROS and UVI-dependent irradiation play two key roles in the process of UVI-induced fluorescence enhancement of BHb.

Pan, Leiting; Wang, Xiaoxu; Yang, Shuying; Wu, Xian; Lee, Imshik; Zhang, Xinzheng; Rupp, Romano A.; Xu, Jingjun

2012-01-01

252

Ultraviolet irradiation-dependent fluorescence enhancement of hemoglobin catalyzed by reactive oxygen species.  

PubMed

Ultraviolet (UV) light has a potent effect on biological organisms. Hemoglobin, an oxygen-transport protein, plays an irreplaceable role in sustaining life of all vertebrates. In this study we scrutinize the effects of ultraviolet irradiation (UVI) as well as visible irradiation on the fluorescence characteristics of bovine hemoglobin (BHb) in vitro. Data show that UVI results in fluorescence enhancement of BHb in a dose-dependent manner. Furthermore, UVI-induced fluorescence enhancement is significantly increased when BHb is pretreated with hydrogen peroxide (H(2)O(2)), a type of reactive oxygen species (ROS). Meanwhile, The water-soluble antioxidant vitamin C suppresses this UVI-induced fluorescence enhancement. In contrast, green light irradiation does not lead to fluorescence enhancement of BHb no matter whether H(2)O(2) is acting on the BHb solution or not. Taken together, these results indicate that catalysis of ROS and UVI-dependent irradiation play two key roles in the process of UVI-induced fluorescence enhancement of BHb. PMID:22952902

Pan, Leiting; Wang, Xiaoxu; Yang, Shuying; Wu, Xian; Lee, Imshik; Zhang, Xinzheng; Rupp, Romano A; Xu, Jingjun

2012-01-01

253

Pyrolysis combustion flow calorimetry  

Microsoft Academic Search

A method for evaluating the combustibility of milligram samples is described. Pyrolysis-combustion flow calorimetry (PCFC) separately reproduces the solid state and gas phase processes of flaming combustion in a nonflaming test by controlled pyrolysis of the sample in an inert gas stream followed by high temperature oxidation of the volatile pyrolysis products. Oxygen consumption calorimetry is used to measure the

Richard E Lyon; Richard N Walters

2004-01-01

254

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

SciTech Connect

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

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

2010-01-01

255

Communication: Enhanced oxygen reduction reaction and its underlying mechanism in Pd-Ir-Co trimetallic alloys  

SciTech Connect

Based on a combined density functional theory and experimental study, we present that the electrochemical activity of Pd{sub 3}Co alloy catalysts toward oxygen reduction reaction (ORR) can be enhanced by adding a small amount of Ir. While Ir tends to favorably exist in the subsurface layers, the underlying Ir atoms are found to cause a substantial modification in the surface electronic structure. As a consequence, we find that the activation barriers of O/OH hydrogenation reactions are noticeably lowered, which would be mainly responsible for the enhanced ORR activity. Furthermore, our study suggests that the presence of Ir in the near-surface region can suppress Co out-diffusion from the Pd{sub 3}Co substrate, thereby improving the durability of Pd-Ir-Co catalysts. We also discuss the relative roles played by Ir and Co in enhancing the ORR activity relative to monometallic Pd catalysts.

Ham, Hyung Chul; Hwang, Gyeong S., E-mail: gshwang@che.utexas.edu [Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Manogaran, Dhivya [Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712 (United States)] [Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712 (United States); Lee, Kang Hee; Jin, Seon-ah; You, Dae Jong; Pak, Chanho [Energy Lab, Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd., Suwon (Korea, Republic of)] [Energy Lab, Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd., Suwon (Korea, Republic of); Kwon, Kyungjung [Department of Energy and Mineral Resources Engineering, Sejong University, Seoul 143-747 (Korea, Republic of)] [Department of Energy and Mineral Resources Engineering, Sejong University, Seoul 143-747 (Korea, Republic of)

2013-11-28

256

EFFECTS OF HYBRID REBURNING\\/SNCR STRATEGY ON NOX\\/CO REDUCTION AND THERMAL CHARACTERISTICS IN OXYGEN-ENRICHED LPG FLAME  

Microsoft Academic Search

From the view of the environmental protection against the usage of fossil fuels, a great amount of effort has been exerted to find an effective method that is not only for pollutant reduction, but also for higher thermal efficiency. In order to enhance combustion efficiency, oxygen-enriched combustion is used by increasing the oxygen ratio in the oxidizer. However, since the

CHANG YEOP LEE; SEUNG WOOK BAEK

2007-01-01

257

Enhanced in-situ biodegradation of petroleum hydrocarbons using passive addition of oxygen to groundwater  

SciTech Connect

A field trial incorporating the addition of oxygen to ground water through a passive interception system to ground water in a shallow sand aquifer beneath a former gasoline station in southwestern Ontario (Canada) has been initiated. The purpose of the trial is to evaluate the degree of remediation by oxygen-enhanced biodegradation. Based on the results of preliminary tests, the selected oxygen source is an oxygen-releasing compound (ORC), a proprietary metal peroxide powder. The ORC is mixed with sand, wrapped in a permeable filter sock and lowered down an unpumped well to the ground water zone in a retrievable plastic harness. In the design configuration adopted for the test, seven source wells constructed of 20 cm diameter PVC plastic were installed across a segment of a plume containing elevated concentrations of BTEX. The wells were screened (No. 8 slot) across the water table from 3 m below ground surface to their terminal depths at 6 m. The source wells were installed at 0.8 m centers in staggered fashion in two adjacent rows separated by 0.8 m. The experiment was designed with the intent of inducing convergent flow of ground water through the source wells to ensure interception of the plume across the trial segment by maintaining hydraulic conductivity of the ORC-filled chambers within the wells above that of the surrounding aquifer materials.

Smyth, D.J.A. [Univ. of Waterloo, Ontario (Canada); Wilson, R.D.; Byerley, B.T.; Chapman, S.W.; Mackay, D.M.

1995-09-01

258

Biologically enhanced cathode design for improved capacity and cycle life for lithium-oxygen batteries  

NASA Astrophysics Data System (ADS)

Lithium-oxygen batteries have a great potential to enhance the gravimetric energy density of fully packaged batteries by two to three times that of lithium ion cells. Recent studies have focused on finding stable electrolytes to address poor cycling capability and improve practical limitations of current lithium-oxygen batteries. In this study, the catalyst electrode, where discharge products are deposited and decomposed, was investigated as it has a critical role in the operation of rechargeable lithium-oxygen batteries. Here we report the electrode design principle to improve specific capacity and cycling performance of lithium-oxygen batteries by utilizing high-efficiency nanocatalysts assembled by M13 virus with earth-abundant elements such as manganese oxides. By incorporating only 3-5?wt% of palladium nanoparticles in the electrode, this hybrid nanocatalyst achieves 13,350?mAh?g-1c (7,340?mAh?g-1c+catalyst) of specific capacity at 0.4?A?g-1c and a stable cycle life up to 50 cycles (4,000?mAh?g-1c, 400?mAh?g-1c+catalyst) at 1?A?g-1c.

Oh, Dahyun; Qi, Jifa; Lu, Yi-Chun; Zhang, Yong; Shao-Horn, Yang; Belcher, Angela M.

2013-11-01

259

Biologically enhanced cathode design for improved capacity and cycle life for lithium-oxygen batteries.  

PubMed

Lithium-oxygen batteries have a great potential to enhance the gravimetric energy density of fully packaged batteries by two to three times that of lithium ion cells. Recent studies have focused on finding stable electrolytes to address poor cycling capability and improve practical limitations of current lithium-oxygen batteries. In this study, the catalyst electrode, where discharge products are deposited and decomposed, was investigated as it has a critical role in the operation of rechargeable lithium-oxygen batteries. Here we report the electrode design principle to improve specific capacity and cycling performance of lithium-oxygen batteries by utilizing high-efficiency nanocatalysts assembled by M13 virus with earth-abundant elements such as manganese oxides. By incorporating only 3-5 wt% of palladium nanoparticles in the electrode, this hybrid nanocatalyst achieves 13,350 mAh g(-1)(c) (7,340 mAh g(-1)(c+catalyst)) of specific capacity at 0.4 A g(-1)(c) and a stable cycle life up to 50 cycles (4,000 mAh g(-1)(c), 400 mAh g(-1)(c+catalyst)) at 1 A g(-1)(c). PMID:24220635

Oh, Dahyun; Qi, Jifa; Lu, Yi-Chun; Zhang, Yong; Shao-Horn, Yang; Belcher, Angela M

2013-01-01

260

Coating Hydrostatic Bearings To Resist Ignition In Oxygen  

NASA Technical Reports Server (NTRS)

Coats of superalloy MA754 plasma-sprayed onto occasionally rubbing surfaces of hydrostatic journal bearings operating in liquid and/or gaseous oxygen, according to proposal. Prevents ignition and combustion occurring when components made of stainless steels or other conventional bearing alloys rub against each other in oxygen. Eliminates need for runner and enhances control over critical bearing clearance.

Funkhouser, Merle E.

1993-01-01

261

Enhanced proliferation of human skeletal muscle precursor cells derived from elderly donors cultured in estimated physiological (5%) oxygen  

Microsoft Academic Search

Human skeletal muscle precursor cells (myoblasts) have significant therapeutic potential and are a valuable research tool\\u000a to study muscle cell biology. Oxygen is a critical factor in the successful culture of myoblasts with low (1–6%) oxygen culture\\u000a conditions enhancing the proliferation, differentiation, and\\/or viability of mouse, rat, and bovine myoblasts. The specific\\u000a effects of low oxygen depend on the myoblast

Sheree D. Martin; Fiona M. Collier; Mark A. Kirkland; Ken Walder; Nicole Stupka

2009-01-01

262

Chilling-enhanced photooxidation: The production, action and study of reactive oxygen species produced during chilling in the light  

Microsoft Academic Search

Chilling-enhanced photooxidation is the light- and oxygen-dependent bleaching of photosynthetic pigments that occurs upon the exposure of chilling-sensitive plants to temperatures below approximately 10 °C. The oxidants responsible for the bleaching are the reactive oxygen species (ROS) singlet oxygen (1O2), superoxide anion radical (O2?,hydrogen peroxide (H2O2), the hydroxyl radical (OH·), and the monodehydroascorbate radical (MDA) which are generated by a

Robert R. Wise

1995-01-01

263

Exploring few-layer graphene and graphene oxide as fillers to enhance the oxygen-atom corrosion resistance of composites.  

PubMed

Few-layer graphene (FLG) and graphene oxide (GO) were explored to enhance the oxygen-atom corrosion resistance of composites. FLG flakes of two different average lateral sizes (large: ?1.3 ?m(2) and small: ?0.23 ?m(2)) were prepared by a centrifugation-based size selection route. After exposure to oxygen atoms, although all fillers could enhance the oxygen-atom corrosion resistance of the composites, we found a much greater enhancement using large FLG, i.e. adding 1 wt% large FLG can achieve a 42% decrease in the composites' mass loss. Bonding and barrier effects of the flaked fillers are responsible for the enhanced resistance. These preliminary yet intriguing results pave a novel way for resisting oxygen-atom corrosion. PMID:24776931

Yi, Min; Shen, Zhigang; Zhao, Xiaohu; Liu, Lei; Liang, Shuaishuai; Zhang, Xiaojing

2014-06-21

264

Characterization of mercury-enriched coal combustion residues from electric utilities using enhanced sorbents for mercury control  

SciTech Connect

This report evaluates changes that may occur to coal-fired power plant air pollution control residues from the use of activated carbon and other enhanced sorbents for reducing air emissions of mercury and evaluates the potential for captured pollutants leaching during the disposal or use of these residues. Leaching of mercury, arsenic, and selenium during land disposal or beneficial use of coal combustion residues (CCRs) is the environmental impact pathway evaluated in this report. Coal combustion residues refer collectively to fly ash and other air pollution control solid residues generated during the combustion of coal collected through the associated air pollution control system. This research is part of an on-going effort by US Environmental protection Agency (EPA) to use a holistic approach to account for the fate of mercury and other metals in coal throughout the life-cycle stages of CCR management. This report focuses on facilities that use injected sorbents for mercury control. It includes four facilities with activated carbon injection (ACI) and two facilities using brominated ACI. Fly ash has been obtained from each facility with and without operation of the sorbent injection technology for mercury control. Each fly ash sampled was evaluated in the laboratory for leaching as a function of pH and liquid-to-solid ratio. Mercury, arsenic and selenium were the primary constituent of interest; results for these elements are presented here. 30 refs., 30 figs., 14 tabs., 10 apps.

Sanchez, F.; Keeney, R.; Kosson, D.; Delapp, R. [Vanderbilt University, Nashville, TN (United States). Dept. of Civil and Environmental Engineering

2006-02-15

265

Saturated nucleate pool boiling of oxygen under magnetically-enhanced effective gravity  

NASA Astrophysics Data System (ADS)

We investigate the effect of enhancing gravity on saturated nucleate pool boiling of oxygen for effective gravities (geff) of 1g, 6g, and 16g (g=9.8;m s-2) at a saturation pressure of 760;torr and for heat fluxes of 10˜3000;W m-2. The effective gravity on the oxygen is increased by applying a magnetic body force generated by a superconducting solenoid. We measure the heater temperature (expressed as a reduced superheat) as a function of heat flux and fit this data to a piecewise power-law/linear boiling curve. At low heat flux (400;W m-2) the superheat is proportional to the cube root of the heat flux. At higher heat fluxes, the superheat is a linear function of the heat flux. The value of the transition heat flux separating these two regions is proportional to geff^0.25, indicating a possible link to the critical heat flux.

Corcovilos, T. A.; Turk, M. E.; Strayer, D. M.; Asplund, N. N.; Yeh, N.-C.

2008-03-01

266

The impact of chlorine disinfection on biochemical oxygen demand levels in chemically enhanced primary treatment effluent.  

PubMed

The response trends of biochemical oxygen demand (BOD) and organic strength after the chlorination/dechlorination process were explored through a 2-year, 5-month chemically enhanced primary treatment (CEPT) effluent onsite monitoring program and a 2-month laboratory-scale study. The monitoring results showed that better instantaneous mixing at the chlorine injection point reduced the effect of chlorination/dechlorination on the 5-day BOD levels. The laboratory study results demonstrated that chlorination did not change the particle size distribution, dissolved organic carbon, or chemical oxygen demand of the organic content of the effluent. Nevertheless, chlorination/dechlorination strongly affected the BOD measurement when nitrification was inhibited by changing bioactivity/biodegradation rates. PMID:23863431

Dai, Ji; Jiang, Feng; Shang, Chii; Chau, Kwok-ming; Tse, Yuet-kar; Lee, Chi-fai; Chen, Guang-Hao; Fang, Jingyun; Zhai, Liming

2013-01-01

267

FEASIBILITY STUDY OF ENHANCED COMBUSTION VIA IMPROVED WOOD STOVE FIREBOX DESIGN  

EPA Science Inventory

The paper gives results of an examination of materials that might be used within the firebox of a wood-burning stove to produce more uniform and complete combustion. Although many materials were initially considered, refractory materials appear to possess the qualities desired re...

268

Enhancement of hybrid rocket combustion performance using nano-sized energetic particles  

Microsoft Academic Search

Until now, the regression rate of classical hybrid rocket engines have typically been an order of magnitude lower than solid propellant motors; thus, hybrids require a relatively large fuel surface area for a given thrust level. In addition to low linear regression rates, relatively low combustion efficiency (87 to 92%), low mass burning rates, varying oxidizer-to-fuel ratio during operation, and

Grant Alexander Risha

2003-01-01

269

Enhanced Formation of Oxidants from Bimetallic Nickel-Iron Nanoparticles in the Presence of Oxygen  

PubMed Central

Nanoparticulate zero-valent iron (nZVI) rapidly reacts with oxygen to produce strong oxidants, capable of transforming organic contaminants in water. However, the low yield of oxidants with respect to the iron added normally limits the application of this system. Bimetallic nickel-iron nanoparticles (nNi-Fe; i.e., Ni-Fe alloy and Ni-coated Fe nanoparticles) exhibited enhanced yields of oxidants compared to nZVI. nNi-Fe (Ni-Fe alloy nanoparticles with [Ni]/[Fe] = 0.28 and Ni-coated Fe nanoparticles with [Ni]/[Fe] = 0.035) produced approximately 40% and 85% higher yields of formaldehyde from the oxidation of methanol relative to nZVI at pH 4 and 7, respectively. Ni-coated Fe nanoparticles showed a higher efficiency for oxidant production relative to Ni-Fe alloy nanoparticles based on Ni content. Addition of Ni did not enhance the oxidation of 2-propanol or benzoic acid, indicating that Ni addition did not enhance hydroxyl radical formation. The enhancement in oxidant yield was observed over a pH range of 4 – 9. The enhanced production of oxidant by nNi-Fe appears to be attributable to two factors. First, the nNi-Fe surface is less reactive toward hydrogen peroxide (H2O2) than the nZVI surface, which favors the reaction of H2O2 with dissolved Fe(II) (the Fenton reaction). Second, the nNi-Fe surface promotes oxidant production from the oxidation of ferrous ion by oxygen at neutral pH values.

Lee, Changha; Sedlak, David L.

2009-01-01

270

Phototherapy and malignancy: possible enhancement by iron administration and hyperbaric oxygen.  

PubMed

Photodynamic therapy (PDT) is a new therapeutic approach for the treatment of malignant tumors. Hyperbaric oxygen (HBO(2)) shows beneficial effects in various modalities of cancer interventions. Tumor cells tend to accumulate large amount of iron. There is interaction between tissue content of oxygen, iron, free radical production and tissue damage. Accumulation of intracellular iron is necessary for the production of oxygen radicals. HBO(2) increases tissue oxygen and hydrogen peroxide production in the cells. Malignant cells require iron, and exhibit more transferrin receptors. The photodynamic sensitization of human leukemic cells is achieved with accumulation of porphyrins stimulated by 5-aminolaevulanic acid (ALA) plus hemin. Further, a significant improvement in tumor response is obtained when PDT is delivered during hyperoxygenation. When PDT is combined with hyperoxygenation, the hypoxic condition is improved and the cell killing rate at various time points after PDT is significantly enhanced. Photosensitization with use of porphyrins is used with HBO(2) and PDT for treatment of certain tumors. PDT with ALA is used for treatment of actinic keratosis (AK). The combination of iron administration (by injection or oral rout), hemin, or transferrin, as a source for iron, HBO(2) as a source of oxygen under pressure and PDT as a source of generating free-radical tissue damage may be useful in the treatment of tumors. The possibility of combining HBO(2), iron, light and local photosensitizers to overcome skin tumors deserve extensive laboratory and clinical research work. Conclusively, iron, HBO(2), and PDT may have synergistic effect to hamper tumor cells. PMID:16860490

Al-Waili, Noori S; Butler, Glenn J

2006-01-01

271

Influence of oxygen content in the fuel mixture on the thermo- and electrophysical combustion properties in laminar hydrocarbon flames  

Microsoft Academic Search

While investigating the effects of the excess oxidizer coefficient on combustion, it was endeavored to undertake a many-slded analysis of the processes involved. In particular~ the following have been investigated: the distributions of the electric potential and of temperature [i], of the positive ions [2], of the hydrogen radical [3], of the excited particles CH* and C'2 [4], and of

B. S. Fialkov; N. D. Shcherbakov; N. K. Akst; M. D. Ostrovskii

1984-01-01

272

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

SciTech Connect

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

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

2012-09-15

273

Sensitivity enhancement of carbon nanotube based ammonium ion sensors through surface modification by using oxygen plasma treatment  

SciTech Connect

We have shown that the sensitivity of carbon nanotube (CNT) based sensors can be enhanced as high as 74 times through surface modification by using the inductively coupled plasma chemical vapor deposition method with oxygen. The plasma treatment power was maintained as low as 10 W within 20 s, and the oxygen plasma was generated far away from the sensors to minimize the plasma damage. From X-ray photoelectron spectroscopy analysis, we found that the concentration of oxygen increased with the plasma treatment time, which implies that oxygen functional groups or defect sites were generated on the CNT surface.

Yeo, Sanghak; Woong Jang, Chi; Lee, Seok; Min Jhon, Young [Sensor System Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of)] [Sensor System Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Choi, Changrok [Center for Nano-Bio Convergence, Korea Research Institute of Standards and Science, Daejeon 305-340, North Korea (Korea, Republic of)] [Center for Nano-Bio Convergence, Korea Research Institute of Standards and Science, Daejeon 305-340, North Korea (Korea, Republic of)

2013-02-18

274

Imaging lung function using rapid dynamic acquisition of T 1 -maps during oxygen enhancement  

Microsoft Academic Search

This paper describes imaging of lung function with oxygen-enhanced MRI using dynamically acquired T\\u000a \\u0009\\u0009\\u0009\\u0009\\u0009\\u0009\\u0009\\u00091 parameter maps, which allows an accurate, quantitative assessment of time constants of T\\u000a \\u0009\\u0009\\u0009\\u0009\\u0009\\u0009\\u0009\\u00091-enhancement and therefore lung function. Eight healthy volunteers were examined on a 1.5-T whole-body scanner. Lung T\\u000a \\u0009\\u0009\\u0009\\u0009\\u0009\\u0009\\u0009\\u00091-maps based on an IR Snapshot FLASH technique (TE = 1.4 ms, TR = 3.5

J. F. T. Arnold; F. Fidler; T. Wang; E. D. Pracht; M. Schmidt; P. M. Jakob

2004-01-01

275

Directly Imprinted Surface-Emitting Distributed Feedback Structure Polymer Sensor Laser Devices for Enhanced Oxygen Sensitivity  

NASA Astrophysics Data System (ADS)

We report on a gas detection enhancement by means of amplified spontaneous emission (ASE) as well as laser emission from the conjugated polymer poly[(2-methoxy-5(2-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV). Upon photo-pumping of spin-cast films, ASE was achieved. Periodic distributed feedback (DFB) structures were fabricated directly in the active polymer layer using the soft-lithographic technique of liquid imprinting. When the structured DFB grating was photo-pumped, laser emission was observed perpendicular to the substrate surface. For both, ASE as well as lasing, we monitored the output emission intensities under the influence of argon and ambient atmosphere resulting in a change in their threshold behavior. We clearly show that these changes are by virtue of a sensitivity enhancement resulting from oxygen acting as reversible quenching defect.

Gaal, Martin; Sax, Stefan; Plank, Harald; Teuchtmann, Michael; Rinnerbauer, Veronika; Hasenfu{ß}, Christine; Schmidt, Holger; Hingerl, Kurt; List, Emil J. W.

2008-01-01

276

Enhanced formation of oxidants from bimetallic nickel-iron nanoparticles in the presence of oxygen.  

PubMed

Nanoparticulate zero-valent iron (nZVI) rapidly reacts with oxygen to produce strong oxidants capable of transforming organic contaminants in water. However,the low yield of oxidants with respect to the iron added normally limits the application of this system. Bimetallic nickel-iron nanoparticles (nNi-Fe; i.e., Ni-Fe alloy and Ni-coated Fe nanoparticles) exhibited enhanced yields of oxidants compared to nZVI. nNi-Fe (Ni-Fe alloy nanoparticles with [Ni]/[Fe] = 0.28 and Ni-coated Fe nanoparticles with [Ni]/[Fe] = 0.035) produced approximately 40% and 85% higher yields of formaldehyde from the oxidation of methanol relative to nZVI at pH 4 and 7, respectively. Ni-coated Fe nanoparticles showed a higher efficiency for oxidant production relative to Ni-Fe alloy nanoparticles based on Ni content. Addition of Ni did not increase the oxidation of 2-propanol or benzoic acid, indicating that Ni addition did not enhance hydroxyl radical formation. The enhancement in oxidant yield was observed over a pH range of 4-9. The enhanced production of oxidant by nNi-Fe appears to be attributable to two factors. First, the nNi-Fe surface is less reactive toward hydrogen peroxide (H2O2) than the nZVI surface, which favors the reaction of H2O2 with dissolved Fe(II) (the Fenton reaction). Second, the nNi-Fe surface promotes oxidant production from the oxidation of ferrous ion by oxygen at neutral pH values. PMID:19068843

Lee, Changha; Sedlak, David L

2008-11-15

277

Electron-beam-induced acoustic-wave enhancement of gaseous combustion  

Microsoft Academic Search

The combustion rate of premixed gases in a closed vessel was increased by injecting a high-current electron beam into the gas mixture within about 20 ms of spark ignition. This effect was observed with the fuels ethylene, methane, ethane, propane, and n-butane. Experimental results provide strong evidence that e-beam excitation of the fundamental longitudinal-acoustic mode of the cylindrical chamber is

S. W. Bidwell; R. A. Bosch; R. M. Gilgenbach

1989-01-01

278

Two-photon antenna-core oxygen probe with enhanced performance.  

PubMed

Recent development of two-photon phosphorescence lifetime microscopy (2PLM) of oxygen enabled first noninvasive high-resolution measurements of tissue oxygenation in vivo in 3D, providing valuable physiological information. The so far developed two-photon-enhanced phosphorescent probes comprise antenna-core constructs, in which two-photon absorbing chromophores (antenna) capture and channel excitation energy to a phosphorescent core (metalloporphyrin) via intramolecular excitation energy transfer (EET). These probes allowed demonstration of the methods' potential; however, they suffer from a number of limitations, such as partial loss of emissivity to competing triplet state deactivation pathways (e.g., electron transfer) and suboptimal sensitivity to oxygen, thereby limiting spatial and temporal resolution of the method. Here we present a new probe, PtTCHP-C307, designed to overcome these limitations. The key improvements include significant increase in the phosphorescence quantum yield, higher efficiency of the antenna-core energy transfer, minimized quenching of the phosphorescence by electron transfer and increased signal dynamic range. For the same excitation flux, the new probe is able to produce up to 6-fold higher signal output than previously reported molecules. Performance of PtTCHP-C307 was demonstrated in vivo in pO2 measurements through the intact mouse skull into the bone marrow, where all blood cells are made from hematopoietic stem cells. PMID:24848643

Roussakis, Emmanuel; Spencer, Joel A; Lin, Charles P; Vinogradov, Sergei A

2014-06-17

279

Enhancement of ammonia dehydrogenation by introduction of oxygen onto cobalt and iron cluster cations.  

PubMed

Reactions of oxygen-chemisorbed cobalt and iron cluster cations (Co(n)O(m)(+) and Fe(n)O(m)(+); n = 3-6, m = 1-3) with an NH(3) molecule have been investigated in comparison with their bare metal cluster cations at a collision energy of 0.2 eV by use of a guided ion beam tandem mass spectrometer. We have observed three kinds of reaction products, which come from NH(3) chemisorption with and without release of a metal atom from the cluster and dehydrogenation of the chemisorbed NH(3). Reaction cross sections and branching fractions are strongly influenced by the number of oxygen atoms introduced onto the metal clusters. Oxygen-chemisorbed metal clusters with particular compositions such as Co(4)O(+), Co(5)O(2)(+), and Fe(5)O(2)(+) are extremely reactive for NH(3) dehydrogenation, whereas Co(4)O(2)(+) and Fe(4)O(2)(+) exhibit high reactivity for NH(3) chemisorption with metal release. The enhancement of dehydrogenation for specific compositions can be interpreted in terms of competition between O-H and neighboring Co-H (or Fe-H) formation. PMID:21090639

Hirabayashi, Shinichi; Ichihashi, Masahiko; Kondow, Tamotsu

2010-12-23

280

Characterization of chemical looping combustion of coal in a 1 kW{sub th} reactor with a nickel-based oxygen carrier  

SciTech Connect

Chemical looping combustion is a novel technology that can be used to meet the demand on energy production without CO{sub 2} emission. To improve CO{sub 2} capture efficiency in the process of chemical looping combustion of coal, a prototype configuration for chemical looping combustion of coal is made in this study. It comprises a fast fluidized bed as an air reactor, a cyclone, a spout-fluid bed as a fuel reactor and a loop-seal. The loop-seal connects the spout-fluid bed with the fast fluidized bed and is fluidized by steam to prevent the contamination of the flue gas between the two reactors. The performance of chemical looping combustion of coal is experimentally investigated with a NiO/Al{sub 2}O{sub 3} oxygen carrier in a 1 kW{sub th} prototype. The experimental results show that the configuration can minimize the amount of residual char entering into the air reactor from the fuel reactor with the external circulation of oxygen carrier particles giving up to 95% of CO{sub 2} capture efficiency at a fuel reactor temperature of 985 C. The effect of the fuel reactor temperature on the release of gaseous products of sulfur species in the air and fuel reactors is carried out. The fraction of gaseous sulfur product released in the fuel reactor increases with the fuel reactor temperature, whereas the one in the air reactor decreases correspondingly. The high fuel reactor temperature results in more SO{sub 2} formation, and H{sub 2}S abatement in the fuel reactor. The increase of SO{sub 2} in the fuel reactor accelerates the reaction of SO{sub 2} with CO to form COS, and COS concentration in the fuel reactor exit gas increases with the fuel reactor temperature. The SO{sub 2} in the air reactor exit gas is composed of the product of sulfur in residual char burnt with air and that of nickel sulfide oxidization with air in the air reactor. Due to the evident decrease of residual char in the fuel reactor with increasing fuel reactor temperature, it results in the decrease of residual char entering the air reactor from the fuel reactor, and the decrease of SO{sub 2} from sulfur in the residual char burnt with air in the air reactor. (author)

Shen, Laihong; Wu, Jiahua; Gao, Zhengping; Xiao, Jun [Thermoenergy Engineering Research Institute, Southeast University, Nanjing 210096 (China)

2010-05-15

281

Motorcycle exhaust particulates enhance vasoconstriction in organ culture of rat aortas and involve reactive oxygen species.  

PubMed

The effects of motorcycle exhaust particulate on vasoconstriction were determined using rat thoracic aortas under organ culture conditions treated with organic extracts of motorcycle exhaust particulate from a two-stroke engine. The motorcycle exhaust particulate extract (MEPE) induced a concentration-dependent enhancement of vasoconstriction elicited by phenylephrine in the organ cultures of both intact and endothelium-denuded aortas for 18 h. Nifedipine (an L-type Ca2+ channel blocker), manganese acetate (an inorganic Ca2+ channel blocker), and staurosporine (a nonselective protein kinase C inhibitor), but not the selective protein kinase C inhibitor chelerythrine, inhibited the enhancement of vasoconstriction by MEPE. Staurosporine has also been reported as a myosin light chain kinase (MLCK) inhibitor, so we tested whether the MLCK pathway was involved in the effect of MEPE. The results showed that ML-9 (a selective MLCK inhibitor) could inhibit the enhancement of vasoconstriction by MEPE. The phosphorylation of a 20-kDa myosin light chain in a primary culture of rat vascular smooth muscle cells was also enhanced by MEPE. Moreover, we also examined the role of reactive oxygen species (ROS) in the stimulatory effect of MEPE on vasoconstriction. The antioxidant N-acetylcysteine significantly inhibited the enhancement of vasoconstriction by MEPE. A time-dependent increase in ROS production by MEPE was also detected in primary cultures of vascular smooth muscle cells. These results indicate that MEPE induces a marked enhancement of vasoconstriction in aortas under organ culture conditions and imply that a ROS-Ca2+-MLCK pathway may be involved in this MEPE-induced response. PMID:12805640

Tzeng, Hui-Ping; Yang, Rong-Sen; Ueng, Tzuu-Huei; Lin-Shiau, Shoei-Yn; Liu, Shing-Hwa

2003-09-01

282

Erythropoiesis-stimulating agents and other methods to enhance oxygen transport  

Microsoft Academic Search

Oxygen is essential for life, and the body has developed an exquisite method to collect oxygen in the lungs and transport it to the tissues. Hb contained within red blood cells (RBCs), is the key oxygen-carrying component in blood, and levels of RBCs are tightly controlled according to demand for oxygen. The availability of oxygen plays a critical role in

S Elliott

2008-01-01

283

Enhanced proliferation and dopaminergic differentiation of ventral mesencephalic precursor cells by synergistic effect of FGF2 and reduced oxygen tension  

SciTech Connect

Effective numerical expansion of dopaminergic precursors might overcome the limited availability of transplantable cells in replacement strategies for Parkinson's disease. Here we investigated the effect of fibroblast growth factor-2 (FGF2) and FGF8 on expansion and dopaminergic differentiation of rat embryonic ventral mesencephalic neuroblasts cultured at high (20%) and low (3%) oxygen tension. More cells incorporated bromodeoxyuridine in cultures expanded at low as compared to high oxygen tension, and after 6 days of differentiation there were significantly more neuronal cells in low than in high oxygen cultures. Low oxygen during FGF2-mediated expansion resulted also in a significant increase in tyrosine hydroxylase-immunoreactive (TH-ir) dopaminergic neurons as compared to high oxygen tension, but no corresponding effect was observed for dopamine release into the culture medium. However, switching FGF2-expanded cultures from low to high oxygen tension during the last two days of differentiation significantly enhanced dopamine release and intracellular dopamine levels as compared to all other treatment groups. In addition, the short-term exposure to high oxygen enhanced in situ assessed TH enzyme activity, which may explain the elevated dopamine levels. Our findings demonstrate that modulation of oxygen tension is a recognizable factor for in vitro expansion and dopaminergic differentiation of rat embryonic midbrain precursor cells.

Jensen, Pia [Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Winslowparken 21, DK-5000 Odense C (Denmark) [Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Winslowparken 21, DK-5000 Odense C (Denmark); Department of Neurosurgery, University of Bern, CH-3010 Bern (Switzerland); Gramsbergen, Jan-Bert; Zimmer, Jens [Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Winslowparken 21, DK-5000 Odense C (Denmark)] [Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Winslowparken 21, DK-5000 Odense C (Denmark); Widmer, Hans R. [Department of Neurosurgery, University of Bern, CH-3010 Bern (Switzerland)] [Department of Neurosurgery, University of Bern, CH-3010 Bern (Switzerland); Meyer, Morten, E-mail: MMeyer@health.sdu.dk [Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Winslowparken 21, DK-5000 Odense C (Denmark)] [Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Winslowparken 21, DK-5000 Odense C (Denmark)

2011-07-15

284

Oxygen Reduction Kinetics Enhancement on a 2 Heterostructured Oxide Surface for Solid Oxide Fuel Cells  

SciTech Connect

Heterostructured interfaces of oxides, which can exhibit transport and reactivity characteristics remarkably different from those of bulk oxides, are interesting systems to explore in search of highly active cathodes for the oxygen reduction reaction (ORR). Here, we show that the ORR of {approx}85 nm thick La{sub 0.8}Sr{sub 0.2}CoO{sub 3-{delta}} (LSC{sub 113}) films prepared by pulsed laser deposition on (001)-oriented yttria-stabilized zirconia (YSZ) substrates is dramatically enhanced ({approx} 3-4 orders of magnitude above bulk LSC{sub 113}) by surface decorations of (La{sub 0.5}Sr{sub 0.5}){sub 2}CoO{sub 4{+-}{delta}} (LSC{sub 214}) with coverage in the range from {approx}0.1 to {approx}15 nm. Their surface and atomic structures were characterized by atomic force, scanning electron, and scanning transmission electron microscopy, and the ORR kinetics were determined by electrochemical impedance spectroscopy. Although the mechanism for ORR enhancement is not yet fully understood, our results to date show that the observed ORR enhancement can be attributed to highly active interfacial LSC{sub 113}/LSC{sub 214} regions, which were shown to be atomically sharp.

Crumlin, Ethan [Massachusetts Institute of Technology (MIT); Mutoro, Eva [ORNL; Ahn, Sung Jin [Massachusetts Institute of Technology (MIT); Jose la O', Gerardo [Massachusetts Institute of Technology (MIT); Leonard, Donovan N [ORNL; Borisevich, Albina Y [ORNL; Biegalski, Michael D [ORNL; Christen, Hans M [ORNL; Shao-Horn, Yang [Massachusetts Institute of Technology (MIT)

2010-01-01

285

Oxygen Ion Implantation Enhanced Silicon-Vacancy Photoluminescence and n-Type Conductivity of Ultrananocrystalline Diamond Films  

NASA Astrophysics Data System (ADS)

We report the enhanced silicon-vacancy (Si-V) photoluminescence (PL) intensity and n-type conductivity of ultrananocrystalline diamond (UNCD) films by oxygen ion (O+) implantation. With O+ dose increasing from 1014 to 1015 cm-2, the PL intensity and n-type conductivity significantly increase by 6 and 45 times, respectively, after 1000°C annealing. The secondary ion mass spectroscopy mapping measurements show that the content of oxygen is larger in the zone, which has larger content of silicon, indicating that oxygen tends to adhere to silicon. It is suggested that oxygen related Si-V defects are formed, which will enhance the PL intensity and n-type conductivity of UNCD films.

Hu, Xiao-Jun; Li, Nian

2013-08-01

286

Enhanced heme protein expression by ammonia-oxidizing communities acclimated to low dissolved oxygen conditions.  

PubMed

This study has investigated the acclimation of ammonia-oxidizing communities (AOC) to low dissolved oxygen (DO) concentrations. Under controlled laboratory conditions, two sequencing batch reactors seeded with activated sludge from the same source were operated at high DO (near saturation) and low DO (0.1 mg O?/L) concentrations for a period of 220 days. The results demonstrated stable and complete nitrification at low DO conditions after an acclimation period of approximately 140 days. Acclimation brought about increased specific oxygen uptake rates and enhanced expression of a particular heme protein in the soluble fraction of the cells in the low DO reactor as compared to the high DO reactor. The induced protein was determined not to be any of the enzymes or electron carriers present in the conventional account of ammonia oxidation in ammonia-oxidizing bacteria (AOB). Further research is required to determine the specific nature of the heme protein detected; a preliminary assessment suggests either a type of hemoglobin protein or a lesser-known component of the energy-transducing pathways of AOB. The effect of DO on AOC dynamics was evaluated using the 16S rRNA gene as the basis for phylogenetic comparisons and organism quantification. Ammonium consumption by ammonia-oxidizing archaea and anaerobic ammonia-oxidizing bacteria was ruled out by fluorescent in situ hybridization in both reactors. Even though Nitrosomonas europaea was the dominant AOB lineage in both high and low DO sequencing batch reactors at the end of operation, this enrichment could not be linked in the low DO reactor to acclimation to oxygen-limited conditions. PMID:23435900

Arnaldos, Marina; Kunkel, Stephanie A; Stark, Benjamin C; Pagilla, Krishna R

2013-12-01

287

Including oxygen enhancement ratio in ion beam treatment planning: model implementation and experimental verification.  

PubMed

We present a method for adapting a biologically optimized treatment planning for particle beams to a spatially inhomogeneous tumor sensitivity due to hypoxia, and detected e.g., by PET functional imaging. The TRiP98 code, established treatment planning system for particles, has been extended for including explicitly the oxygen enhancement ratio (OER) in the biological effect calculation, providing the first set up of a dedicated ion beam treatment planning approach directed to hypoxic tumors, TRiP-OER, here reported together with experimental tests. A simple semi-empirical model for calculating the OER as a function of oxygen concentration and dose averaged linear energy transfer, generating input tables for the program is introduced. The code is then extended in order to import such tables coming from the present or alternative models, accordingly and to perform forward and inverse planning, i.e., predicting the survival response of differently oxygenated areas as well as optimizing the required dose for restoring a uniform survival effect in the whole irradiated target. The multiple field optimization results show how the program selects the best beam components for treating the hypoxic regions. The calculations performed for different ions, provide indications for the possible clinical advantages of a multi-ion treatment. Finally the predictivity of the code is tested through dedicated cell culture experiments on extended targets irradiation using specially designed hypoxic chambers, providing a qualitative agreement, despite some limits in full survival calculations arising from the RBE assessment. The comparison of the predictions resulting by using different model tables are also reported. PMID:23681217

Scifoni, E; Tinganelli, W; Weyrather, W K; Durante, M; Maier, A; Krämer, M

2013-06-01

288

Catalytic Activity Enhancement for Oxygen Reduction on Epitaxial Perovskite Thin Films for Solid-Oxide Fuel Cells  

SciTech Connect

The active ingredient: La{sub 0.8}Sr{sub 0.2}CoO{sub 3-{delta}} (LSC) epitaxial thin films are prepared on (001)-oriented yttria-stabilized zirconia (YSZ) single crystals with a gadolinium-doped ceria (GDC) buffer layer. The LSC epitaxial films exhibit better oxygen reduction kinetics than bulk LSC. The enhanced activity is attributed in part to higher oxygen nonstoichiometry.

La O', Gerardo Jose [Massachusetts Institute of Technology (MIT); Ahn, Sung Jin [Massachusetts Institute of Technology (MIT); Crumlin, Ethan [Massachusetts Institute of Technology (MIT); Orikasa, Yuki [Massachusetts Institute of Technology (MIT); Biegalski, Michael D [ORNL; Christen, Hans M [ORNL; Shao-Horn, Yang [Massachusetts Institute of Technology (MIT)

2010-01-01

289

On the mechanism of enhanced oxygen reduction reaction in nitrogen-doped graphene nanoribbons.  

PubMed

Nitrogen (N)-doped carbon materials were shown in recent studies to have promising catalytic activity for oxygen reduction reaction (ORR) as a metal-free alternative to platinum, but the underlying molecular mechanism or even the active sites for high catalytic efficiency are still missing or controversial both experimentally and theoretically. We report here the results of periodic density functional theory (DFT) calculations about the ORR at the edge of a graphene nanoribbon (GNR). The edge structure and doped-N near the edge are shown to enhance the oxygen adsorption, the first electron transfer, and also the selectivity toward the four-electron, rather than the two-electron, reduction pathway. We find that the outermost graphitic nitrogen site in particular gives the most desirable characteristics for improved ORR activity, and hence the active site. However, the latter graphitic nitrogen becomes pyridinic-like in the next electron and proton transfer reaction via the ring-opening of a cyclic C-N bond. This inter-conversion between the graphitic and pyridinic sites within a catalytic cycle may reconcile the controversy whether the pyridinic, graphitic, or both nitrogens are active sites. PMID:21946759

Kim, Heejin; Lee, Kirak; Woo, Seong Ihl; Jung, Yousung

2011-10-21

290

Hyperbaric oxygen treatment of tissue-engineered mucosa enhances secretion of angiogenic factors in vitro.  

PubMed

The survival of tissue-engineered mucosa (TEM) after implantation is mostly dependent on the presence of blood vessels for continuous oxygen supply. Therefore the stimulation of vascularization of TEM is essential to improve survival in vivo. Hyperbaric oxygen (HBO) treatment, used to improve wound healing, stimulates the secretion of angiogenic factors. In this study we evaluated the effect of daily HBO treatments on TEM for 1, 3, or 5 consecutive days. Overall histology with hematoxylin-eosin staining showed no apparent changes after one treatment. After three and five HBO treatments, the basal layer became irregular and pyknotic cells were observed. Measurements of the viable epithelium showed significant thinning after one and five treatments, however, proliferation was not affected. The angiogenic factors keratinocyte growth factor (KGF), hepatocyte growth factor (HGF), basic fibroblast growth factor (FGFbasic), and placental growth factor (PlGF) were significantly increased after one HBO treatment, whereas after three treatments a significant decrease of FGFbasic and PlGF was seen. After five treatments KGF, PlGF, and vascular endothelial growth factor (VEGF) were significantly increased. One HBO treatment of TEM enhances the secretion of important angiogenic factors, hereby potentially improving the survival rate after in vivo implantation. PMID:24320751

Tra, Wendy Maria Wilhelmina; Spiegelberg, Linda; Tuk, Bastiaan; Hovius, Steven Eric Ruden; Perez-Amodio, Soledad

2014-05-01

291

Spatially resolved measurement of singlet delta oxygen by radar resonance-enhanced multiphoton ionization.  

PubMed

Coherent microwave Rayleigh scattering (Radar) from resonance-enhanced multiphoton ionization (REMPI) was demonstrated to directly and nonintrusively measure singlet delta oxygen, O(2)(a(1)?(g)), with high spatial resolution. Two different approaches, photodissociation of ozone and microwave discharge plasma in an argon and oxygen flow, were utilized for O(2)(a(1)?(g)) generation. The d(1)?(g)?a(1)?(g) (3-0) and d(1)?(g)?a(1)?(g) (1-0) bands of O(2)(a(1)?(g)) were detected by Radar REMPI for two different flow conditions. Quantitative absorption measurements using sensitive off-axis integrated cavity output spectroscopy (ICOS) was used simultaneously to evaluate the accuracy and sensitivity of the Radar REMPI technique. The detection limit of Radar REMPI was found to be comparable to the ICOS technique with a detection threshold of approximately 10(14) molecules/cm(3) but with a spatial resolution that was 8 orders of magnitude smaller than the ICOS technique. PMID:23811904

Wu, Yue; Zhang, Zhili; Ombrello, Timothy M

2013-07-01

292

Enhancing Electrocatalytic Oxygen Reduction on Nitrogen-Doped Graphene by Active Sites Implantation  

NASA Astrophysics Data System (ADS)

The shortage of nitrogen active sites and relatively low nitrogen content result in unsatisfying eletrocatalytic activity and durability of nitrogen-doped graphene (NG) for oxygen reduction reaction (ORR). Here we report a novel approach to substantially enhance electrocatalytic oxygen reduction on NG electrode by the implantation of nitrogen active sites with mesoporous graphitic carbon nitride (mpg-C3N4). Electrochemical characterization revealed that in neutral electrolyte the resulting NG (I-NG) exhibited super electrocatalytic activity (completely 100% of four-electron ORR pathway) and durability (nearly no activity change after 100000 potential cyclings). When I-NG was used as cathode catalyst in microbial fuel cells (MFCs), power density and its drop percentage were also much better than the NG and Pt/C ones, demonstrating that the current I-NG was a perfect alternative to Pt/C and offered a new potential for constructing high-performance and less expensive cathode which is crucial for large-scale application of MFC technology.

Feng, Leiyu; Yang, Lanqin; Huang, Zujing; Luo, Jingyang; Li, Mu; Wang, Dongbo; Chen, Yinguang

2013-11-01

293

Enhancing electrocatalytic oxygen reduction on nitrogen-doped graphene by active sites implantation.  

PubMed

The shortage of nitrogen active sites and relatively low nitrogen content result in unsatisfying eletrocatalytic activity and durability of nitrogen-doped graphene (NG) for oxygen reduction reaction (ORR). Here we report a novel approach to substantially enhance electrocatalytic oxygen reduction on NG electrode by the implantation of nitrogen active sites with mesoporous graphitic carbon nitride (mpg-C3N4). Electrochemical characterization revealed that in neutral electrolyte the resulting NG (I-NG) exhibited super electrocatalytic activity (completely 100% of four-electron ORR pathway) and durability (nearly no activity change after 100,000 potential cyclings). When I-NG was used as cathode catalyst in microbial fuel cells (MFCs), power density and its drop percentage were also much better than the NG and Pt/C ones, demonstrating that the current I-NG was a perfect alternative to Pt/C and offered a new potential for constructing high-performance and less expensive cathode which is crucial for large-scale application of MFC technology. PMID:24264379

Feng, Leiyu; Yang, Lanqin; Huang, Zujing; Luo, Jingyang; Li, Mu; Wang, Dongbo; Chen, Yinguang

2013-01-01

294

IGF-I enhances cellular senescence via the reactive oxygen species-p53 pathway  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Cellular senescence plays an important role in tumorigenesis and aging process. Black-Right-Pointing-Pointer We demonstrated IGF-I enhanced cellular senescence in primary confluent cells. Black-Right-Pointing-Pointer IGF-I enhanced cellular senescence in the ROS and p53-dependent manner. Black-Right-Pointing-Pointer These results may explain the underlying mechanisms of IGF-I involvement in tumorigenesis and in regulation of aging. -- Abstract: Cellular senescence is characterized by growth arrest, enlarged and flattened cell morphology, the expression of senescence-associated {beta}-galactosidase (SA-{beta}-gal), and by activation of tumor suppressor networks. Insulin-like growth factor-I (IGF-I) plays a critical role in cellular growth, proliferation, tumorigenesis, and regulation of aging. In the present study, we show that IGF-I enhances cellular senescence in mouse, rat, and human primary cells in the confluent state. IGF-I induced expression of a DNA damage marker, {gamma}H2AX, the increased levels of p53 and p21 proteins, and activated SA-{beta}-gal. In the confluent state, an altered downstream signaling of IGF-I receptor was observed. Treatment with a reactive oxygen species (ROS) scavenger, N-acetylcystein (NAC) significantly suppressed induction of these markers, indicating that ROS are involved in the induction of cellular senescence by IGF-I. In p53-null mouse embryonic fibroblasts, the IGF-I-induced augmentation of SA-{beta}-gal and p21 was inhibited, demonstrating that p53 is required for cellular senescence induced by IGF-I. Thus, these data reveal a novel pathway whereby IGF-I enhances cellular senescence in the ROS and p53-dependent manner and may explain the underlying mechanisms of IGF-I involvement in tumorigenesis and in regulation of aging.

Handayaningsih, Anastasia-Evi; Takahashi, Michiko; Fukuoka, Hidenori; Iguchi, Genzo; Nishizawa, Hitoshi; Yamamoto, Masaaki; Suda, Kentaro [Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe (Japan)] [Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe (Japan); Takahashi, Yutaka, E-mail: takahash@med.kobe-u.ac.jp [Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe (Japan)] [Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe (Japan)

2012-08-24

295

Vertical migration of aggregated aerobic and anaerobic ammonium oxidizers enhances oxygen uptake in a stagnant water layer.  

PubMed

Ammonium can be removed as dinitrogen gas by cooperating aerobic and anaerobic ammonium-oxidizing bacteria (AerAOB and AnAOB). The goal of this study was to verify putative mutual benefits for aggregated AerAOB and AnAOB in a stagnant freshwater environment. In an ammonium fed water column, the biological oxygen consumption rate was, on average, 76 kg O(2) ha(-1) day(-1). As the oxygen transfer rate of an abiotic control column was only 17 kg O(2) ha(-1) day(-1), biomass activity enhanced the oxygen transfer. Increasing the AnAOB gas production increased the oxygen consumption rate with more than 50% as a result of enhanced vertical movement of the biomass. The coupled decrease in dissolved oxygen concentration increased the diffusional oxygen transfer from the atmosphere in the water. Physically preventing the biomass from rising to the upper water layer instantaneously decreased oxygen and ammonium consumption and even led to the occurrence of some sulfate reduction. Floating of the biomass was further confirmed to be beneficial, as this allowed for the development of a higher AerAOB and AnAOB activity, compared to settled biomass. Overall, the results support mutual benefits for aggregated AerAOB and AnAOB, derived from the biomass uplifting effect of AnAOB gas production. PMID:17401560

Vlaeminck, Siegfried E; Dierick, Katleen; Boon, Nico; Verstraete, Willy

2007-07-01

296

Oxygen-enhanced IrMn spin valves deposited by ion-beam and magnetron sputtering  

SciTech Connect

Enhancement of giant magnetoresistance properties of single (bottom) and dual IrMn-based spin valves through exposure of part of the CoFe pinned layer to O{sub 2} is reported. Under optimal conditions, a {Delta}R/R of 10.4% [H{sub ua}=460Oe, H{sub f}=5.1Oe, and H{sub c}=4.7Oe for a free and pinned layer thickness (permalloy equivalent) of 50 Aa each] for an ion beam sputtered single spin valve, and a {Delta}R/R of as high as 20.5% for a magnetron sputtered dual spin valve having a 30 Aa thick CoFe free layer are observed, compared to a value of 6.5% and 10.6% for the corresponding spin valve without O{sub 2} exposure, respectively. Transmission electron microscopy results reveal the presence of a thin (10 Aa) crystalline oxygen-containing layer near the IrMn{endash}CoFe pinned layer interface as a result of O{sub 2} exposure. X-ray reflectivity data show smoother interfaces for the spin valves subjected to O{sub 2} exposure, consistent with the lower H{sub f} and smaller sheet resistance observed for these samples. The enhanced {Delta}R/R thus can be attributed to improved growth after O{sub 2} exposure. {copyright} 2001 American Institute of Physics.

Lee, W. Y.; Carey, M.; Toney, M. F.; Rice, P.; Gurney, B.; Chang, H.-C.; Allen, E.; Mauri, D.

2001-06-01

297

Mechanism of enhanced superoxide production in the cytochrome b(6)f complex of oxygenic photosynthesis.  

PubMed

The specific rate of superoxide (O2(•-)) production in the purified active crystallizable cytochrome b6f complex, normalized to the rate of electron transport, has been found to be more than an order of magnitude greater than that measured in isolated yeast respiratory bc1 complex. The biochemical and structural basis for the enhanced production of O2(•-) in the cytochrome b6f complex compared to that in the bc1 complex is discussed. The higher rate of superoxide production in the b6f complex could be a consequence of an increased residence time of plastosemiquinone/plastoquinol in its binding niche near the Rieske protein iron-sulfur cluster, resulting from (i) occlusion of the quinone portal by the phytyl chain of the unique bound chlorophyll, (ii) an altered environment of the proton-accepting glutamate believed to be a proton acceptor from semiquinone, or (iii) a more negative redox potential of the heme bp on the electrochemically positive side of the complex. The enhanced rate of superoxide production in the b6f complex is physiologically significant as the chloroplast-generated reactive oxygen species (ROS) functions in the regulation of excess excitation energy, is a source of oxidative damage inflicted during photosynthetic reactions, and is a major source of ROS in plant cells. Altered levels of ROS production are believed to convey redox signaling from the organelle to the cytosol and nucleus. PMID:24298890

Baniulis, Danas; Hasan, S Saif; Stofleth, Jason T; Cramer, William A

2013-12-17

298

Intrinsic Relationship between Enhanced Oxygen Reduction Reaction Activity and Nanoscale Work Function of Doped Carbons.  

PubMed

Nanostructured carbon materials doped with a variety of heteroatoms have shown promising electrocatalytic activity in the oxygen reduction reaction (ORR). However, understanding of the working principles that underpin the superior ORR activity observed with doped nanocarbons is still limited to predictions based on theoretical calculations. Herein, we demonstrate, for the first time, that the enhanced ORR activity in doped nanocarbons can be correlated with the variation in their nanoscale work function. A series of doped ordered mesoporous carbons (OMCs) were prepared using N, S, and O as dopants; the triple-doped, N,S,O-OMC displayed superior ORR activity and four-electron selectivity compared to the dual-doped (N,O-OMC and S,O-OMC) and the monodoped (O-OMC) OMCs. Significantly, the work functions of these heteroatom-doped OMCs, measured by Kelvin probe force microscopy, display a strong correlation with the activity and reaction kinetics for the ORR. This unprecedented experimental insight can be used to provide an explanation for the enhanced ORR activity of heteroatom-doped carbon materials. PMID:24911055

Cheon, Jae Yeong; Kim, Jong Hun; Kim, Jae Hyung; Goddeti, Kalyan C; Park, Jeong Young; Joo, Sang Hoon

2014-06-25

299

Colloidal gold nanorings for improved photodynamic therapy through field-enhanced generation of reactive oxygen species  

NASA Astrophysics Data System (ADS)

Au nanostructures that exhibit strong localized surface plasmon resonance (SPR) have excellent potential for photo-medicine, among a host of other applications. Here, we report the synthesis and use of colloidal gold nanorings (GNRs) with potential for enhanced photodynamic therapy of cancer. The GNRs were fabricated via galvanic replacement reaction of sacrificial Co nanoparticles in gold salt solution with low molecular weight (Mw = 2,500) poly(vinylpyrrolidone) (PVP) as a stabilizing agent. The size and the opening of the GNRs were controlled by the size of the starting Co particles and the concentration of the gold salt. UV-Vis absorption measurements indicated the tunability of the SPR of the GNRs from 560 nm to 780 nm. MTT assay showed that GNRs were non-toxic and biocompatible when incubated with breast cancer cells as well as the healthy counterpart cells. GNRs conjugated with 5-aminolevulinic acid (5-ALA) photosensitizer precursor led to elevated formation of reactive oxygen species and improved efficacy of photodynamic therapy of breast cancer cells under light irradiation compared to 5-ALA alone. These results can be attributed to significantly enhance localized electromagnetic field of the GNRs.

Hu, Yue; Yang, Yamin; Wang, Hongjun; Du, Henry

2013-02-01

300

Final report on the project entitled: Highly Preheated Combustion Air System with/without Oxygen Enrichment for Metal Processing Furnaces  

SciTech Connect

This work develops and demonstrates a laboratory-scale high temperature natural gas furnace that can operate with/without oxygen enrichment to significantly improve energy efficiency and reduce emissions. The laboratory-scale is 5ft in diameter & 8ft tall. This furnace was constructed and tested. This report demonstrates the efficiency and pollutant prevention capabilities of this test furnace. The project also developed optical detection technology to control the furnace output.

Arvind Atreya

2007-02-16

301

Reactivity of a NiO\\/Al 2O 3 oxygen carrier prepared by impregnation for chemical-looping combustion  

Microsoft Academic Search

The reactivity of a Ni-based oxygen carrier prepared by hot incipient wetness impregnation (HIWI) on ?-Al2O3 with a NiO content of 18wt% was studied in this work. Pulse experiments with the reduction period divided into 4-s pulses were performed in a fluidized bed reactor at 1223K using CH4 as fuel. The number of pulses was between 2 and 12. Information

Cristina Dueso; Alberto Abad; Francisco García-Labiano; Luis F. de Diego; Pilar Gayán; Juan Adánez; Anders Lyngfelt

2010-01-01

302

High-Pressure Promoted-Combustion Chamber  

NASA Technical Reports Server (NTRS)

Proposed combustion-testing chamber burns specimens of materials in fully contained, high-pressure oxygen atmosphere. Test operator uses handles on threaded retaining rings to attach or remove top or bottom plates sealing combustion chamber. Tests conducted in static or flowing oxygen. Oxygen inlet and outlet far enough above burning specimen, little danger of entrainment of burning fragments in oxygen flowing out.

Rucker, Michelle A.; Stoltzfus, Joel M.

1990-01-01

303

Reactive Oxygen Species Prevent Imiquimod-Induced Psoriatic Dermatitis through Enhancing Regulatory T Cell Function  

PubMed Central

Psoriasis is a chronic inflammatory skin disease resulting from immune dysregulation. Regulatory T cells (Tregs) are important in the prevention of psoriasis. Traditionally, reactive oxygen species (ROS) are known to be implicated in the progression of inflammatory diseases, including psoriasis, but many recent studies suggested the protective role of ROS in immune-mediated diseases. In particular, severe cases of psoriasis vulgaris have been reported to be successfully treated by hyperbaric oxygen therapy (HBOT), which raises tissue level of ROS. Also it was reported that Treg function was closely associated with ROS level. However, it has been only investigated in lowered levels of ROS so far. Thus, in this study, to clarify the relationship between ROS level and Treg function, as well as their role in the pathogenesis of psoriasis, we investigated imiquimod-induced psoriatic dermatitis (PD) in association with Treg function both in elevated and lowered levels of ROS by using knockout mice, such as glutathione peroxidase-1?/? and neutrophil cytosolic factor-1?/? mice, as well as by using HBOT or chemicals, such as 2,3-dimethoxy-1,4-naphthoquinone and N-acetylcysteine. The results consistently showed Tregs were hyperfunctional in elevated levels of ROS, whereas hypofunctional in lowered levels of ROS. In addition, imiquimod-induced PD was attenuated in elevated levels of ROS, whereas aggravated in lowered levels of ROS. For the molecular mechanism that may link ROS level and Treg function, we investigated the expression of an immunoregulatory enzyme, indoleamine 2,3-dioxygenase (IDO) which is induced by ROS, in PD lesions. Taken together, it was implied that appropriately elevated levels of ROS might prevent psoriasis through enhancing IDO expression and Treg function.

Choi, Eun-Jeong; Hong, Min-Pyo; Kie, Jeong-Hae; Lim, Woosung; Lee, Hyeon Kook; Moon, Byung-In; Seoh, Ju-Young

2014-01-01

304

Promoted combustion of nine structural metals in high-pressure gaseous oxygen - A comparison of ranking methods  

NASA Technical Reports Server (NTRS)

The 316, 321, 440C, and 17-4 PH stainless steels, as well as Inconel 600, Inconel 718, Waspaloy, Monel 400, and Al 2219, have been evaluated for relative nonflammability in a high-pressure oxygen environment with a view to the comparative advantages of four different flammability-ranking methods. The effects of changes in test pressure, sample diameter, promoter type, and sample configuration on ranking method results are evaluated; ranking methods employing velocity as the primary ranking criterion are limited by diameter effects, while those which use extinguishing pressure are nonselective for metals with similar flammabilities.

Steinberg, Theodore A.; Rucker, Michelle A.; Beeson, Harold D.

1989-01-01

305

TLR 9 Activation in Dendritic Cells Enhances Salmonella Killing and Antigen Presentation via Involvement of the Reactive Oxygen Species  

PubMed Central

Synthetic CpG containing oligodeoxynucleotide Toll like receptor-9 agonist (CpG DNA) activates innate immunity and can stimulate antigen presentation against numerous intracellular pathogens. It was observed that Salmonella Typhimurium growth can be inhibited by the CpG DNA treatment in the murine dendritic cells. This inhibitory effect was mediated by an increased reactive oxygen species production. In addition, it was noted that CpG DNA treatment of dendritic cells during Salmonella infection leads to an increased antigen presentation. Further this increased antigen presentation was dependent on the enhanced reactive oxygen species production elicited by Toll like receptor-9 activation. With the help of an exogenous antigen it was shown that Salmonella antigen could also be cross-presented in a better way by CpG induction. These data collectively indicate that CpG DNA enhance the ability of murine dendritic cells to contain the growth of virulent Salmonella through reactive oxygen species dependent killing.

Lahiri, Amit; Vani, Janakiraman; Shaila, M. S.; Chakravortty, Dipshikha

2010-01-01

306

Enhanced coal gasification heated by unmixed combustion integrated with an hybrid system of SOFC\\/GT  

Microsoft Academic Search

For clean utilization of coal, enhanced gasification by in situ CO2 capture has the advantage that hydrogen production efficiency is increased while no energy is required for CO2 separation. The unmixed fuel process uses a sorbent material as CO2 carrier and consists of three coupled reactors: a coal gasifier where CO2 is captured generating a H2-rich gas that can be

Pilar Lisbona; Luis M. Romeo

2008-01-01

307

An analysis of combustion studies in shock expansion tunnels and reflected shock tunnels  

NASA Technical Reports Server (NTRS)

The effect of initial nonequilibrium dissociated air constituents on the combustion of hydrogen in high-speed flows for a simulated Mach 17 flight condition was investigated by analyzing the results of comparative combustion experiments performed in a reflected shock tunnel test gas and in a shock expansion tunnel test gas. The results were analyzed and interpreted with a one-dimensional quasi-three-stream combustor code that includes finite rate combustion chemistry. The results of this study indicate that the combustion process is kinetically controlled in the experiments in both tunnels and the presence of the nonequilibrium partially dissociated oxygen in the reflected shock tunnel enhances the combustion. Methods of compensating for the effect of dissociated oxygen are discussed.

Jachimowski, Casimir J.

1992-01-01

308

Low-oxygen pretreatment enhances endothelial cell growth and retention under shear stress.  

PubMed

Oxygen (O(2)) tension is an important factor that regulates endothelial cell (EC) growth and adhesion. We hypothesized that low-O(2) treatment of ECs improves the endothelialization and cell retention upon physiologically relevant perfusion flow, due to enhanced cell proliferation and extracellular matrix (ECM) secretion. We assessed the effects of a low-O(2) tension of 5% O(2) upon growth and ECM production of human umbilical vein ECs (HUVECs), in comparison to their counterparts at 20% O(2) on poly(ethylene terephthalate) (PET) films. Low-O(2) pretreatment at 5% O(2) promoted HUVEC proliferation, ECM secretion, and intercellular adhesion. Cell retentions of the endothelialized PET films formed under 5% and 20% O(2) were analyzed by applying shear stress in the range of 5-20 dyn/cm(2) for up to 24 h under the O(2) of 12% and 20%, mimicking arterial and conventional experimental O(2), respectively. The 5% O(2)-pretreated samples exhibited significantly higher cell retention than their normoxic counterparts at high cell density (>30 x 10(3) cells/cm(2)) over extended exposure time (>12 h) when perfused under both 12% and 20% O(2). The endothelium formed under 5% O(2) maintained its ability to respond to perfusion flow by upregulating nitric oxide and prostacyclin production under both O(2) perfusion conditions. The results indicate that pretreatment at 5% O(2) is an effective strategy to enhance endothelialization of vascular grafts by promoting endothelium formation, cell retention, and function. PMID:19072661

Zhao, Feng; Sellgren, Katelyn; Ma, Teng

2009-06-01

309

Excavated fe-N-C sites for enhanced electrocatalytic activity in the oxygen reduction reaction.  

PubMed

Platinum (Pt) is the best electrocatalyst for the oxygen reduction reaction (ORR) in hydrogen fuel cells, but it is an extremely expensive resource. The successful development of a cost-effective non-Pt ORR electrocatalyst will be a breakthrough for the commercialization of hydrogen-air fuel cells. Ball milling has been used to incorporate metal and nitrogen precursors into micropores of carbon more effectively and in the direct nitrogen-doping of carbon under highly pressurized nitrogen gas in the process of the preparation of non-noble ORR catalysts. In this study, we first utilize ball milling to excavate the ORR active sites embedded in Fe-modified N-doped carbon nanofibers (Fe-N-CNFs) by pulverization. The facile ball-milling process resulted in a significant enhancement in the ORR activity and the selectivity of the Fe-N-CNFs owing to the higher exposure of the metal-based catalytically active sites. The degree of excavation of the Fe-based active sites in the Fe-N-CNFs for the ORR was investigated with cyclic voltammetry, X-ray photoelectron spectroscopy, and pore-size distribution analysis. We believe that this simple approach is useful to improve alternative ORR electrocatalysts up to the level necessary for practical applications. PMID:24700786

Jeong, Beomgyun; Shin, Dongyoon; Jeon, Hongrae; Ocon, Joey D; Mun, Bongjin Simon; Baik, Jaeyoon; Shin, Hyun-Joon; Lee, Jaeyoung

2014-05-01

310

Apogossypolone targets mitochondria and light enhances its anticancer activity by stimulating generation of singlet oxygen and reactive oxygen species  

PubMed Central

Apogossypolone (ApoG2), a novel derivative of gossypol, has been shown to be a potent inhibitor of antiapoptotic Bcl-2 family proteins and to have antitumor activity in multiple types of cancer cells. Recent reports suggest that gossypol stimulates the generation of cellular reactive oxygen species (ROS) in leukemia and colorectal carcinoma cells; however, gossypol-mediated cell death in leukemia cells was reported to be ROS-independent. This study was conducted to clarify the effect of ApoG2-induced ROS on mitochondria and cell viability, and to further evaluate its utility as a treatment for nasopharyngeal carcinoma (NPC). We tested the photocytotoxicity of ApoG2 to the poorly differentiated NPC cell line CNE-2 using the ROS-generating TL/10 illumination system. The rapid ApoG2-induced cell death was partially reversed by the antioxidant N-acetyl-L-cysteine (NAC), but the ApoG2-induced reduction of mitochondrial membrane potential (MMP) was not reversed by NAC. In the presence of TL/10 illumination, ApoG2 generated massive amounts of singlet oxygen and was more effective in inhibiting cell growth than in the absence of illumination. We also determined the influence of light on the anti-proliferative activity of ApoG2 using a CNE-2–xenograft mouse model. ApoG2 under TL/10 illumination healed tumor wounds and suppressed tumor growth more effectively than ApoG2 treatment alone. These results indicate that the ApoG2-induced CNE-2 cell death is partly ROS-dependent. ApoG2 may be used with photodynamic therapy (PDT) to treat NPC.

Hu, Zhe-Yu; Wang, Jing; Cheng, Gang; Zhu, Xiao-Feng; Huang, Peng; Yang, Dajun; Zeng, Yi-Xin

2011-01-01

311

Heats of combustion of high temperature polymers  

Microsoft Academic Search

The heats of combustion for forty-nine commercial and developmental polymers of known chemical structure were determined using an oxygen bomb calorimeter according to standard methods. The experimental results were compared to thermochemical calculations of the net heat of combustion from oxygen consumption and the gross heat of combustion from group additivity of the heats of formation of products and reactants.

Richard N. Walters; Stacey M. Hackett; Richard E. Lyon

2000-01-01

312

The application of profluorescent nitroxides to detect reactive oxygen species derived from combustion-generated particulate matter: Cigarette smoke - A case study  

NASA Astrophysics Data System (ADS)

Reactive oxygen species (ROS) and related free radicals are considered to be key factors underpinning the various adverse health effects associated with exposure to ambient particulate matter. Therefore, measurement of ROS is a crucial factor for assessing the potential toxicity of particles. In this work, a novel profluorescent nitroxide, BPEAnit, was investigated as a probe for detecting particle-derived ROS. BPEAnit has a very low fluorescence emission due to inherent quenching by the nitroxide group, but upon radical trapping or redox activity, a strong fluorescence is observed. BPEAnit was tested for detection of ROS present in mainstream and sidestream cigarette smoke. In the case of mainstream cigarette smoke, there was a linear increase in fluorescence intensity with an increasing number of cigarette puffs, equivalent to an average of 101 nmol ROS per cigarette based on the number of moles of the probe reacted. Sidestream cigarette smoke sampled from an environmental chamber exposed BPEAnit to much lower concentrations of particles, but still resulted in a clearly detectible increase in fluorescence intensity with sampling time. It was calculated that the amount of ROS was equivalent to 50 ± 2 nmol per mg of particulate matter; however, this value decreased with ageing of the particles in the chamber. Overall, BPEAnit was shown to provide a sensitive response related to the oxidative capacity of the particulate matter. These findings present a good basis for employing the new BPEAnit probe for the investigation of particle-related ROS generated from cigarette smoke as well as from other combustion sources.

Miljevic, B.; Fairfull-Smith, K. E.; Bottle, S. E.; Ristovski, Z. D.

2010-06-01

313

Smouldering Combustion Phenomena in Science and Technology  

Microsoft Academic Search

Smouldering is the slow, low-temperature, flameless form of combustion of a condensed fuel. It poses safety and environmental hazards and allows novel technological application but its fundamentals remain mostly unknown to the scientific community. The terms filtering combustion, smoking problem, deep seated fires, hidden fires, peat or peatlands fires, lagging fires, low oxygen combustion, in-situ combustion, fireflood and underground gasification,

Guillermo Rein

314

CH4 combustion cycles at Pd/Al2O3--important role of support and oxygen access.  

PubMed

This research is focused on the analysis of adsorbed CH4 intermediates at oxidized Pd9 nanoparticles supported on ?-alumina. From first-principle density functional theory calculations, several configurations, charge transfer and electronic density of states have been analyzed in order to determine feasible paths for the oxidation process. Methane oxidation cycles have been considered as a further step at differently oxidized Pd nanoparticles. For low oxidized Pd nanoparticles, activation of methane is observed, whereby hydrogen from methane is adsorbed at one oxygen atom. This reaction is exothermic with adsorption energy equal to -0.38 eV. In a subsequent step, desorption of two water molecules is observed. Additionally, a very interesting structural effect is evident, mainly Pd-carbide formation, which is also an exothermic reaction with an energy of -0.65 eV. Furthermore, oxidation of such carbidized Pd nanoparticles leads to CO2 formation, which is an endothermic reaction. Important result is that the support is involved in CO2 formation. A different mechanism of methane oxidation has been found for highly oxidized Pd nanoparticles. When the Pd nanoparticle is more strongly exposed to oxidative conditions, adsorption of methane is also possible, but it will proceed with carbonic acid production at the interface between Pd nanoparticles and support. However, this step is endothermic. PMID:23736223

Czekaj, Izabela; Kacprzak, Katarzyna A; Mantzaras, John

2013-07-21

315

Enhancement in Figure of Merit ( ZT) by Annealing of BiTe Nanostructures Synthesized by Microwave-Assisted Flash Combustion  

NASA Astrophysics Data System (ADS)

Uniform polycrystalline bismuth telluride (BiTe) nanowires of diameter 100 nm to 150 nm and hexagonal nanoplates with thickness of 50 nm to 100 nm have been successfully synthesized by the microwave-assisted flash combustion technique. The formation of BiTe nanostructures depends on the type of fuel and the oxidant-to-fuel ratio, which in turn affect the reaction time and reaction temperature. Spark plasma sintering has been employed for compaction and sintering of both as-synthesized as well as annealed BiTe powders. Increasing the sintering temperature while using faster sintering cycles reduced the porosity, resulting in high densification while preserving the nanostructures. The dimensionless figure of merit ( ZT) was evaluated from the Seebeck coefficient, electrical resistivity, and thermal conductivity values over the range from 300 K to 600 K. The effect of annealing on the enhancement of ZT is discussed. These evaluations suggest that the rarely studied BiTe is a potential candidate for thermoelectric applications at low temperatures.

Kaur, Harjeet; Sharma, Lalit; Singh, Simrjit; Sivaiah, Bathula; Reddy, G. B.; Senguttuvan, T. D.

2014-06-01

316

Enhancement in Figure of Merit (ZT) by Annealing of BiTe Nanostructures Synthesized by Microwave-Assisted Flash Combustion  

NASA Astrophysics Data System (ADS)

Uniform polycrystalline bismuth telluride (BiTe) nanowires of diameter 100 nm to 150 nm and hexagonal nanoplates with thickness of 50 nm to 100 nm have been successfully synthesized by the microwave-assisted flash combustion technique. The formation of BiTe nanostructures depends on the type of fuel and the oxidant-to-fuel ratio, which in turn affect the reaction time and reaction temperature. Spark plasma sintering has been employed for compaction and sintering of both as-synthesized as well as annealed BiTe powders. Increasing the sintering temperature while using faster sintering cycles reduced the porosity, resulting in high densification while preserving the nanostructures. The dimensionless figure of merit (ZT) was evaluated from the Seebeck coefficient, electrical resistivity, and thermal conductivity values over the range from 300 K to 600 K. The effect of annealing on the enhancement of ZT is discussed. These evaluations suggest that the rarely studied BiTe is a potential candidate for thermoelectric applications at low temperatures.

Kaur, Harjeet; Sharma, Lalit; Singh, Simrjit; Sivaiah, Bathula; Reddy, G. B.; Senguttuvan, T. D.

2013-11-01

317

Dissolved carbonic anhydrase for enhancing post-combustion carbon dioxide hydration in aqueous ammonia  

SciTech Connect

Aqueous ammonia solvents that capture CO2 as ionic complexes of carbonates with ammonium have recently been advanced as alternatives to amine-based solvents due to their lower energy requirements for thermal regeneration. In ammonia based solvents, the hydration of CO2 to form bicarbonate may become a rate-limiting step as the CO2 loading increases and the resulting pH level of the solvent decreases. Variants of the enzyme carbonic anhydrase can accelerate the reversible hydration of CO2 to yield bicarbonate by more than 10(6)-fold. The possible benefit of bovine carbonic anhydrase (BCA) addition to solutions of aqueous ammonia to enhance CO2 hydration was investigated in semi-batch reactions within continuously stirred tank reactors or in a bubble column gas-liquid contactor. Adding 154 mg/liter of BCA to 2 M aqueous ammonia provided a 34.1% overall increase in the rate of CO2 hydration (as indicated by the production of [H+]) as the pH declined from 9.6 to 8.6 during sparging with a 15% CO2, 85% N-2 gas at a flow rate of 3 lpm. The benefits of adding BCA to enhance CO2 hydration were only discernable below similar to pH 9. The implications of the apparent pH limitations on the utility of BCA are discussed in the context of absorber unit operation design. Possible embodiments of carbonic anhydrase as either an immobilized catalyst or as a dissolved, recirculating catalyst in potential plant scale aqueous ammonia systems are considered as well. (C) 2010 Published by Elsevier Ltd.

Collett, James R.; Heck, Robert W.; Zwoster, Andy

2011-04-01

318

Maternal exposure to combustion generated PM inhibits pulmonary Th1 maturation and concomitantly enhances postnatal asthma development in offspring  

PubMed Central

Background Epidemiological studies suggest that maternal exposure to environmental hazards, such as particulate matter, is associated with increased incidence of asthma in childhood. We hypothesized that maternal exposure to combustion derived ultrafine particles containing persistent free radicals (MCP230) disrupts the development of the infant immune system and results in aberrant immune responses to allergens and enhances asthma severity. Methods Pregnant C57/BL6 mice received MCP230 or saline by oropharyngeal aspiration on gestational days 10 and 17. Three days after the second administration, blood was collected from MCP230 or saline treated dams and 8-isoprostanes in the serum were measured to assess maternal oxidative stress. Pulmonary T cell populations were assayed in the infant mice at six days, three and six weeks of postnatal age. When the infant mice matured to adults (i.e. six weeks of age), an asthma model was established with ovalbumin (OVA). Airway inflammation, mucus production and airway hyperresponsiveness were then examined. Results Maternal exposure to MCP230 induced systemic oxidative stress. The development of pulmonary T helper (Th1/Th2/Th17) and T regulatory (Treg) cells were inhibited in the infant offspring from MCP230-exposed dams. As the offspring matured, the development of Th2 and Treg cells recovered and eventually became equivalent to that of offspring from non-exposed dams. However, Th1 and Th17 cells remained attenuated through 6 weeks of age. Following OVA sensitization and challenge, mice from MCP230-exposed dams exhibited greater airway hyperresponsiveness, eosinophilia and pulmonary Th2 responses compared to offspring from non-exposed dams. Conclusions Our data suggest that maternal exposure to MCP230 enhances postnatal asthma development in mice, which might be related to the inhibition of pulmonary Th1 maturation and systemic oxidative stress in the dams.

2013-01-01

319

21 CFR 173.350 - Combustion product gas.  

Code of Federal Regulations, 2010 CFR

...173.350 Combustion product gas. The food additive combustion product gas may be safely used in the...purpose of removing and displacing oxygen in accordance with the following...butane, propane, or natural gas. The combustion...

2010-01-01

320

Low oxygen levels as a trigger for enhancement of respiratory metabolism in Saccharomyces cerevisiae  

PubMed Central

Background The industrially important yeast Saccharomyces cerevisiae is able to grow both in the presence and absence of oxygen. However, the regulation of its metabolism in conditions of intermediate oxygen availability is not well characterised. We assessed the effect of oxygen provision on the transcriptome and proteome of S. cerevisiae in glucose-limited chemostat cultivations in anaerobic and aerobic conditions, and with three intermediate (0.5, 1.0 and 2.8% oxygen) levels of oxygen in the feed gas. Results The main differences in the transcriptome were observed in the comparison of fully aerobic, intermediate oxygen and anaerobic conditions, while the transcriptome was generally unchanged in conditions receiving different intermediate levels (0.5, 1.0 or 2.8% O2) of oxygen in the feed gas. Comparison of the transcriptome and proteome data suggested post-transcriptional regulation was important, especially in 0.5% oxygen. In the conditions of intermediate oxygen, the genes encoding enzymes of the respiratory pathway were more highly expressed than in either aerobic or anaerobic conditions. A similar trend was also seen in the proteome and in enzyme activities of the TCA cycle. Further, genes encoding proteins of the mitochondrial translation machinery were present at higher levels in all oxygen-limited and anaerobic conditions, compared to fully aerobic conditions. Conclusion Global upregulation of genes encoding components of the respiratory pathway under conditions of intermediate oxygen suggested a regulatory mechanism to control these genes as a response to the need of more efficient energy production. Further, cells grown in three different intermediate oxygen levels were highly similar at the level of transcription, while they differed at the proteome level, suggesting post-transcriptional mechanisms leading to distinct physiological modes of respiro-fermentative metabolism.

Rintala, Eija; Toivari, Mervi; Pitkanen, Juha-Pekka; Wiebe, Marilyn G; Ruohonen, Laura; Penttila, Merja

2009-01-01

321

Emission Assessment From Full-scale Co-combustion Tests Of Binder-enhanced dRDF Pellets And High Sulfur Coal At Argonne National Laboratory  

Microsoft Academic Search

Argonne National Laboratory (ANL) and University of North Texas (UNT) research teams collected over 800 emissions and ash samples during the combustion of over 650 tons of binder enhanced densified refuse-drived fuel (b-dRDF) pellets with high sulfur coal in a spreader-stoker boiler at ANL. This full-scale test burn was conducted to validate predictions from laboratory and pilot scale test results

O. O. OhIsson; C. D. Livengood; K. E. Daugherty

1990-01-01

322

Sorption-enhanced steam reforming of hydrocarbons with autothermal sorbent regeneration in a moving heat wave of a catalytic combustion reaction  

Microsoft Academic Search

A novel technological concept of sorption-enhanced steam reforming of hydrocarbons is suggested. The peculiarity of the concept\\u000a is the autothermal regeneration of the carbon dioxide scavenger in the moving super-adiabatic heat wave of an exothermic catalytic\\u000a combustion reaction performed directly inside the adsorption-catalytic bed. The capability and high efficiency of the proposed\\u000a technological approach are confirmed by process simulation. The

Andrey N. Zagoruiko; Alexey G. Okunev

2007-01-01

323

Enhanced brain stem 5HT?A receptor function under neonatal hypoxic insult: role of glucose, oxygen, and epinephrine resuscitation.  

PubMed

Molecular processes regulating brain stem serotonergic receptors play an important role in the control of respiration. We evaluated 5-HT(2A) receptor alterations in the brain stem of neonatal rats exposed to hypoxic insult and the effect of glucose, oxygen, and epinephrine resuscitation in ameliorating these alterations. Hypoxic stress increased the total 5-HT and 5-HT(2A) receptor number along with an up regulation of 5-HT Transporter and 5-HT(2A) receptor gene in the brain stem of neonates. These serotonergic alterations were reversed by glucose supplementation alone and along with oxygen to hypoxic neonates. The enhanced brain stem 5-HT(2A) receptors act as a modulator of ventilatory response to hypoxia, which can in turn result in pulmonary vasoconstriction and cognitive dysfunction. The adverse effects of 100% oxygenation and epinephrine administration to hypoxic neonates were also reported. This has immense clinical significance in neonatal care. PMID:21484469

Anju, T R; Korah, P K; Jayanarayanan, S; Paulose, C S

2011-08-01

324

Enhanced Oxygen-Tolerance of the Full Heterotrimeric Membrane-Bound [NiFe]-Hydrogenase of Ralstonia eutropha  

PubMed Central

Hydrogenases are oxygen-sensitive enzymes that catalyze the conversion between protons and hydrogen. Water-soluble subcomplexes of membrane-bound [NiFe]-hydrogenases (MBH) have been extensively studied for applications in hydrogen–oxygen fuel cells as they are relatively tolerant to oxygen, although even these catalysts are still inactivated in oxidative conditions. Here, the full heterotrimeric MBH of Ralstonia eutropha, including the membrane-integral cytochrome b subunit, was investigated electrochemically using electrodes modified with planar tethered bilayer lipid membranes (tBLM). Cyclic voltammetry and chronoamperometry experiments show that MBH, in equilibrium with the quinone pool in the tBLM, does not anaerobically inactivate under oxidative redox conditions. In aerobic environments, the MBH is reversibly inactivated by O2, but reactivation was found to be fast even under oxidative redox conditions. This enhanced resistance to inactivation is ascribed to the oligomeric state of MBH in the lipid membrane.

2014-01-01

325

Enhanced Oxygen-Tolerance of the Full Heterotrimeric Membrane-Bound [NiFe]-Hydrogenase of Ralstonia eutropha.  

PubMed

Hydrogenases are oxygen-sensitive enzymes that catalyze the conversion between protons and hydrogen. Water-soluble subcomplexes of membrane-bound [NiFe]-hydrogenases (MBH) have been extensively studied for applications in hydrogen-oxygen fuel cells as they are relatively tolerant to oxygen, although even these catalysts are still inactivated in oxidative conditions. Here, the full heterotrimeric MBH of Ralstonia eutropha, including the membrane-integral cytochrome b subunit, was investigated electrochemically using electrodes modified with planar tethered bilayer lipid membranes (tBLM). Cyclic voltammetry and chronoamperometry experiments show that MBH, in equilibrium with the quinone pool in the tBLM, does not anaerobically inactivate under oxidative redox conditions. In aerobic environments, the MBH is reversibly inactivated by O2, but reactivation was found to be fast even under oxidative redox conditions. This enhanced resistance to inactivation is ascribed to the oligomeric state of MBH in the lipid membrane. PMID:24866391

Radu, Valentin; Frielingsdorf, Stefan; Evans, Stephen D; Lenz, Oliver; Jeuken, Lars J C

2014-06-18

326

Method for providing oxygen ion vacancies in lanthanide oxides  

Microsoft Academic Search

A method for desulfurization of fuel gases resulting from the incomplete combustion of sulfur containing hydrocarbons whereby the gases are treated with lanthanide oxides containing large numbers of oxygen-ion vacancies providing ionic porosity which enhances the ability of the lanthanide oxides to react more rapidly and completely with the sulfur in the fuel gases whereby the sulfur in such gases

D. Alan R. Kay; William G. Wilson

1989-01-01

327

Method, System and Apparatus for an Enhanced Electrically Pumped Oxygen Iodine Laser.  

National Technical Information Service (NTIS)

In one embodiment of the present invention an oxygen iodine laser includes a gas mixing section. Ground state oxygen and a carrier gas are introduced into the first gas mixing section, sometimes separately. The laser includes a discharge region to generat...

D. L. Carroll D. M. King J. T. Verdeyen W. C. Solomon

2005-01-01

328

Oxygen Supplementing, Biocompatible Outer Membranes for Enhanced Performance of Implantable Glucose Sensors  

Microsoft Academic Search

Lack of linearity and sensitivity, oxygen dependence, biofouling and tissue inflammation hinder the development of implantable biosensors for continuous monitoring of glucose. Herein, we report the development of stacked outer membranes based on LBL\\/PVA hydrogels that improve sensor sensitivity, linearity, oxygen independence and counter biofouling and inflammation. While the inner LBL membrane affords tunable diffusivity, the outer PVA is capable

Hardeep Singh

2010-01-01

329

Enhancement effect of an adsorbed organic acid on oxygen reduction at various types of activated carbon loaded with platinum  

NASA Astrophysics Data System (ADS)

We have found that application of activated carbon as a support of platinum in electrocatalysts for polymer electrolyte fuel cells improves the activity for oxygen reduction, especially by using activated carbon with trifluoromethanesulfonic acid adsorbed in the pores. In the present study, we investigated this enhancement effect of the acid for oxygen reduction at activated carbon of various specific surface areas and mean pore diameters. After adsorption of potassium trifluoromethanesulfonate onto the activated carbon loaded with platinum, a catalyst layer was formed from the activated carbon and a polymer electrolyte, followed by replacing the potassium ions with protons. We measured the adsorption isotherms of trifluoromethanesulfonate onto the activated carbons and found that adsorption behavior was dependent on the kind of activated carbon. Electrochemical properties of the layer was evaluated by cyclic voltammetry and by the relationship between electrode potential and oxygen reduction current in perchloric acid solution, supporting the layer on a rotating glassy carbon disk electrode. The properties, and consequently the enhancement effect of the organic acid for oxygen reduction, were clearly dependent on the kind of activated carbon and were explicable based on the pore structure and the adsorption behavior.

Maruyama, Jun; Abe, Ikuo

330

Characterization study and five-cycle tests in a fixed-bed reactor of titania-supported nickel oxide as oxygen carriers for the chemical-looping combustion of methane.  

PubMed

Recent investigations have shown that in the combustion of carbonaceous compounds CO2 and NOx emissions to the atmosphere can be substantially reduced by using a two stage chemical-looping process. In this process, the reduction stage is undertaken in a first reactor in which the framework oxygen of a reducible inorganic oxide is used, instead of the usual atmospheric oxygen, for the combustion of a carbonaceous compound, for instance, methane. The outlet gas from this reactor is mostly composed of CO2 and steam as reaction products and further separation of these two components can be carried out easily by simple condensation of steam. Then, the oxygen carrier found in a reduced state is transported to a second reactor in which carrier regeneration with air takes place at relatively low temperatures, consequently preventing the formation of thermal NOx. Afterward, the regenerated carrier is carried to the first reactor to reinitiate a new cycle and so on for a number of repetitive cycles, while the carrier is able to withstand the severe chemical and thermal stresses involved in every cycle. In this paper, the performance of titania-supported nickel oxides has been investigated in a fixed-bed reactor as oxygen carriers for chemical-looping combustion of methane. Samples with different nickel oxide contents were prepared by successive incipient wet impregnations, and their performance as oxygen carriers was investigated at 900 degrees C and atmospheric pressure in five-cycle fixed-bed reactor tests using pure methane and pure air for the respective reduction and regeneration stages. The evolution of the outlet gas composition in each stage was followed by gas chromatography, and the involved chemical, structural, and textural changes of the carrier in the reactor bed were studied by using different characterization techniques. From the study, it is deduced that the reactivity of these nickel-based oxygen carriers is in the two involved stages and almost independent of the nickel loading. However, in the reduction stage, carbon deposition, from the thermal decomposition of methane, and CO emissions, mainly derived from the partial reduction of titania as support acting as an additional oxygen source, may impose some constraints to the efficiency of the overall chemical-looping combustion process in CO2 capture. PMID:16124317

Corbella, Beatriz M; de Diego, Luis F; García-Labiano, Francisco; Adánez, Juan; Palaciost, José M

2005-08-01

331

Film Characteristics of Low-Temperature Plasma-Enhanced Chemical Vapor Deposition Silicon Dioxide Using Tetraisocyanatesilane and Oxygen  

Microsoft Academic Search

Silicon dioxide films were deposited in a parallel-plate electrode RF plasma-enhanced chemical vapor deposition (PECVD) system using hydrogen-free tetraisocyanatesilane (TICS) and oxygen. The deposition parameters were varied systematically, and the films were characterized by measuring infrared spectra, density, etch rate, refractive index, and current-voltage (I V) and capacitance-voltage (C V) characteristics, as well as by examining their annealing behavior. At

Irman Idris; Osamu Sugiura

1998-01-01

332

Photogenerated charge carriers and reactive oxygen species in ZnO/Au hybrid nanostructures with enhanced photocatalytic and antibacterial activity.  

PubMed

Semiconductor nanostructures with photocatalytic activity have the potential for many applications including remediation of environmental pollutants and use in antibacterial products. An effective way for promoting photocatalytic activity is depositing noble metal nanoparticles (NPs) on a semiconductor. In this paper, we demonstrated the successful deposition of Au NPs, having sizes smaller than 3 nm, onto ZnO NPs. ZnO/Au hybrid nanostructures having different molar ratios of Au to ZnO were synthesized. It was found that Au nanocomponents even at a very low Au/ZnO molar ratio of 0.2% can greatly enhance the photocatalytic and antibacterial activity of ZnO. Electron spin resonance spectroscopy with spin trapping and spin labeling was used to investigate the enhancing effect of Au NPs on the generation of reactive oxygen species and photoinduced charge carriers. Deposition of Au NPs onto ZnO resulted in a dramatic increase in light-induced generation of hydroxyl radical, superoxide and singlet oxygen, and production of holes and electrons. The enhancing effect of Au was dependent on the molar ratio of Au present in the ZnO/Au nanostructures. Consistent with these results from ESR measurements, ZnO/Au nanostructures also exhibited enhanced photocatalytic and antibacterial activity. These results unveiled the enhanced mechanism of Au on ZnO and these materials have great potential for use in water purification and antibacterial products. PMID:24354568

He, Weiwei; Kim, Hyun-Kyung; Wamer, Wayne G; Melka, David; Callahan, John H; Yin, Jun-Jie

2014-01-15

333

Hydrogen-Enhanced Lunar Oxygen Extraction and Storage Using Only Solar Power  

NASA Technical Reports Server (NTRS)

The innovation consists of a thermodynamic system for extracting in situ oxygen vapor from lunar regolith using a solar photovoltaic power source in a reactor, a method for thermally insulating the reactor, a method for protecting the reactor internal components from oxidation by the extracted oxygen, a method for removing unwanted chemical species produced in the reactor from the oxygen vapor, a method for passively storing the oxygen, and a method for releasing high-purity oxygen from storage for lunar use. Lunar oxygen exists in various types of minerals, mostly silicates. The energy required to extract the oxygen from the minerals is 30 to 60 MJ/kg O. Using simple heating, the extraction rate depends on temperature. The minimum temperature is approximately 2,500 K, which is at the upper end of available oven temperatures. The oxygen is released from storage in a purified state, as needed, especially if for human consumption. This method extracts oxygen from regolith by treating the problem as a closed batch cycle system. The innovation works equally well in Earth or Lunar gravity fields, at low partial pressure of oxygen, and makes use of in situ regolith for system insulation. The innovation extracts oxygen from lunar regolith using a method similar to vacuum pyrolysis, but with hydrogen cover gas added stoichiometrically to react with the oxygen as it is produced by radiatively heating regolith to 2,500 K. The hydrogen flows over and through the heating element (HE), protecting it from released oxygen. The H2 O2 heat of reaction is regeneratively recovered to assist the heating process. Lunar regolith is loaded into a large-diameter, low-height pancake reactor powered by photovoltaic cells. The reactor lid contains a 2,500 K HE that radiates downward onto the regolith to heat it and extract oxygen, and is shielded above by a multi-layer tungsten radiation shield. Hydrogen cover gas percolates through the perforated tungsten shielding and HE, preventing oxidation of the shielding and HE, and reacting with the oxygen to form water vapor. The water vapor is filtered through solid regolith to remove unwanted extraction byproducts, and then condensed to a liquid state and stored at 300 to 325 K. Conversion to usable oxygen is achieved by pumping liquid water into a high-pressure electrolyzer, storing the gaseous oxygen at high pressure for use, and diverting the hydrogen back to the reactor or to storage. The results from this design effort show that this oxygen-generating concept can be developed in an efficient system with low specific mass. Advantages include use of regolith as an oxygen source, filter, and thermal insulator. The system can be tested in Earth gravity and can be expected to operate similarly in lunar gravity. The system is scalable, either by increasing the power level and output of a standard module, or by employing multiple modules.

Burton, rodney; King, Darren

2013-01-01

334

Combining oxygen plasma treatment with anchorage of cationized gelatin for enhancing cell affinity of poly(lactide-co-glycolide).  

PubMed

Surface characteristics greatly influence attachment and growth of cells on biomaterials. Although polylactone-type biodegradable polymers have been widely used as scaffold materials for tissue engineering, lack of cell recognition sites, poor hydrophilicity and low surface energy lead to a bad cell affinity of the polymers, which limit the usage of polymers as scaffolds in tissue engineering. In the present study, surface of poly (L-lactide-co-glycolide) (PLGA) was modified by a method of combining oxygen plasma treatment with anchorage of cationized gelatin. Modification effect of the method was compared with other methods of oxygen plasma treatment, cationized gelatin or gelatin coating and combining oxygen plasma treatment with anchorage of gelatin. The change of surface property was compared by contact angles, surface energy, X-ray photoelectron spectra (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM) measurement. The optimum oxygen pretreatment time determined by surface energy was 10 min when the power was 50 W and the oxygen pressure was 20 Pa. Analysis of the stability of gelatin and cationized gelatin anchored on PLGA by XPS, ATR-FTIR, contact angles and surface energy measurement indicated the cationized gelatin was more stable than gelatin. The result using mouse NIH 3T3 fibroblasts as model cells to evaluate cell affinity in vitro showed the cationized gelatin-anchored PLGA (OCG-PLGA) was more favorable for cell attachment and growth than oxygen plasma treated PLGA (O-PLGA) and gelatin-anchored PLGA (OG-PLGA). Moreover cell affinity of OCG-PLGA could match that of collagen-anchored PLGA (AC-PLGA). So the surface modification method combining oxygen plasma treatment with anchorage of cationized gelatin provides a universally effective way to enhance cell affinity of polylactone-type biodegradable polymers. PMID:17618682

Shen, Hong; Hu, Xixue; Yang, Fei; Bei, Jianzhong; Wang, Shenguo

2007-10-01

335

Plasma-assisted combustion: Systematic decoupling of the kinetic enhancement mechanisms of ignition, flame propagation, and flame stabilization by long-lifetime species  

NASA Astrophysics Data System (ADS)

The advancement of propulsion devices and combustion systems has created ever increasingly more restrictive reactive environments that push the limits of combustion technology. Precise combustion control for higher efficiencies, reduced emissions, and limited residence times to react can exceed what is possible with traditional combustion chemistry, and therefore require new and creative solutions. The application of plasma to combustion systems offers a promising solution, with significant enhancement having been shown by many researchers. Nevertheless, there remain many unknowns with respect to the key species and mechanisms of enhancement. Detailed systematic experimental and numerical investigations were performed to identify the kinetic mechanisms of combustion enhancement by long-lifetime species generated by non-equilibrium plasma discharges. Two burner systems were adopted and integrated with plasma discharge devices to establish unique combustion platforms to study ignition, flame propagation, and flame stabilization phenomena. A counterflow diffusion flame burner was adopted for the investigation of the effects of plasma on flame stabilization. A newly developed non-equilibrium magnetic gliding arc plasma discharge was integrated with a counterflow diffusion flame burner and was found to significantly extend the limits of flame stabilization when activating air. Laser diagnostic methods of planar Rayleigh scattering and OH planar laser-induced fluorescence were applied and comparison to numerical simulations showed that the extension of the extinction limits was predominately through thermal effects due to rapid recombination of radicals. To elucidate the kinetic effects of plasma, the counterflow burner was augmented for ignition experiments. The application of Fourier transform infrared spectroscopy and comparison to numerical simulations showed significant kinetic ignition enhancement by plasma-produced NOx when activating air. The results established the existence of new ignition regimes for NO x addition that were strongly dependent upon the strain rates (residence times) in the system. The addition of small concentrations of fuel to the air upstream of the plasma produced fuel fragments and partially oxidized products that inhibited ignition. The dominating effects of plasma-produced NOx significantly mitigated the inhibitive effects of these species on chain-branching reaction pathways. To further decouple the plasma-flame interaction, the two long-lifetime plasma species of O3 and O2(a1Delta g) were produced, isolated, measured, and transported to a lifted flame burner to investigate their effect on flame propagation speed. The effects of O3 at atmospheric and sub-atmospheric pressure were found to be significant because of the decomposition of O3 releasing O to rapidly react with the fuel and extract chemical heat early in the pre-heat zone of the flame. The effect of O2(a1Delta g) was isolated by the addition of NO to the plasma afterglow to eliminate O3 and O catalytically. The O2(a1Delta g) was isolated, measured quantitatively using high sensitivity off-axis integrated cavity output absorption spectroscopy, and observed to enhance flame speed. The comparison of experimental and numerical simulation results showed that the current enhancement mechanism including O2(a 1Deltag) could not accurately explain the increase in flame speed observed. Furthermore, a novel filter system was developed to minimize the concentration of all plasma-produced species other than O3 and O2(a1Deltag) through gas phase and wall surface quenching. Lastly, a new simplified and well-defined plasma-combustion system was developed to provide a platform to study the plasma-flame interaction. In addition, a flow visualization technique was proposed by using plasma activation and NO seeding which could be applied to a system where particle seeding of the flow is prohibitive.

Ombrello, Timothy M.

336

ENHANCED BIOREMEDIATION UTILIZING HYDROGEN PEROXIDE AS A SUPPLEMENTAL SOURCE OF OXYGEN: A LABORATORY AND FIELD STUDY  

EPA Science Inventory

Laboratory and field scale studies were conducted to investigate the feasibility of using hydrogen peroxide as a supplemental source of oxygen for bioremediation of an aviation gasoline fuel spill. Field samples of aviation gasoline contaminated aquifer material were artificially...

337

UNDERGROUNG PLACEMENT OF COAL PROCESSING WASTE AND COAL COMBUSTION BY-PRODUCTS BASED PASTE BACKFILL FOR ENHANCED MINING ECONOMICS  

SciTech Connect

This project has successfully demonstrated that the extraction ratio in a room-and-pillar panel at an Illinois mine can be increased from the current value of approximately 56% to about 64%, with backfilling done from the surface upon completion of all mining activities. This was achieved without significant ground control problems due to the increased extraction ratio. The mined-out areas were backfilled from the surface with gob, coal combustion by-products (CCBs), and fine coal processing waste (FCPW)-based paste backfill containing 65%-70% solids to minimize short-term and long-term surface deformations risk. This concept has the potential to increase mine productivity, reduce mining costs, manage large volumes of CCBs beneficially, and improve the miner's health, safety, and environment. Two injection holes were drilled over the demonstration panel to inject the paste backfill. Backfilling was started on August 11, 1999 through the first borehole. About 9,293 tons of paste backfill were injected through this borehole with a maximum flow distance of 300-ft underground. On September 27, 2000, backfilling operation was resumed through the second borehole with a mixture of F ash and FBC ash. A high-speed auger mixer (new technology) was used to mix solids with water. About 6,000 tons of paste backfill were injected underground through this hole. Underground backfilling using the ''Groutnet'' flow model was simulated. Studies indicate that grout flow over 300-foot distance is possible. Approximately 13,000 tons of grout may be pumped through a single hole. The effect of backfilling on the stability of the mine workings was analyzed using SIUPANEL.3D computer program and further verified using finite element analysis techniques. Stiffness of the backfill mix is most critical for enhancing the stability of mine workings. Mine openings do not have to be completely backfilled to enhance their stability. Backfill height of about 50% of the seam height is adequate to minimize surface deformations. Freeman United Coal Company performed engineering economic evaluation studies for commercialization. They found that the costs for underground management at the Crown III mine would be slightly higher than surface management at this time. The developed technologies have commercial potential but each site must be analyzed on its merit. The Company maintains significant interest in commercializing the technology.

Y.P. Chugh; D. Biswas; D. Deb

2002-06-01

338

Oxy-fuel combustion with integrated pollution control  

Microsoft Academic Search

An oxygen fueled integrated pollutant removal and combustion system includes a combustion system and an integrated pollutant removal system. The combustion system includes a furnace having at least one burner that is configured to substantially prevent the introduction of air. An oxygen supply supplies oxygen at a predetermine purity greater than 21 percent and a carbon based fuel supply supplies

Brian R. Patrick; Thomas Lilburn Ochs; Cathy Ann Summers; Danylo B. Oryshchyn; Paul Chandler Turner

2012-01-01

339

Effects of oxygen-containing terpenes as skin permeation enhancers on the lipoidal pathways of human epidermal membrane.  

PubMed

The present study investigated the effects of oxygen-containing terpenes as skin permeation enhancers on the lipoidal pathways of human epidermal membrane (HEM). The enhancement (E(HEM)) effects of menthol, thymol, carvacrol, menthone, and cineole on the transport of a probe permeant, corticosterone, across HEM were determined. It was found that the enhancer potencies of menthol, thymol, carvacrol, and menthone were essentially the same and higher than that of cineole based on their aqueous concentration in the diffusion cell chamber at E(HEM) = 4. Thymol and carvacrol also had the same E(HEM) = 10 concentration further supporting that they had the same enhancer potency based on the aqueous concentration. The uptake amounts of terpene into the HEM stratum corneum (SC) intercellular lipid under the same conditions indicate that the intrinsic potencies of the studied terpenes are the same based on their concentration in the SC and similar to those of n-alkanol and n-alkylphenyl alcohol. Moreover, they are all better enhancers compared to branched-chain alkanol. The approximately same uptake enhancement of beta-estradiol induced by the studied terpenes and alcohols at E(HEM) conditions into the SC intercellular lipids suggests that the mechanism of enhancement action for the terpenes and those of alcohols are essentially the same. PMID:19156845

Chantasart, Doungdaw; Pongjanyakul, Thaned; Higuchi, William I; Li, S Kevin

2009-10-01

340

Droplet Combustion Experiment  

NASA Technical Reports Server (NTRS)

Liquid fuel combustion provides a major portion of the world's energy supply. In most practical combustion devices, liquid burns after being separated into a droplet spray. Essential to the design of efficient combustion systems is a knowledge of droplet combustion behavior. The microgravity environment aboard spacecraft provides an opportunity to investigate the complex interactions between the physical and chemical combustion processes involved in droplet combustion without the complications of natural buoyancy. Launched on STS-83 and STS-94 (April 4 and July 1, 1997), the Droplet Combustion Experiment (DCE) investigated the fundamentals of droplet combustion under a range of pressures (0.25 to 1 atm), oxygen mole fractions (<0.5), and droplet sizes (1.5 to 5 mm). Principal DCE flight hardware features were a chamber to supply selected test environments, the use of crew-inserted bottles, and a vent system to remove unwanted gaseous combustion products. The internal apparatus contained the droplet deployment and ignition mechanisms to burn single, freely deployed droplets in microgravity. Diagnostics systems included a 35-mm high-speed motion picture camera (see the following sequence of photos) with a backlight to photograph burning droplets and a camcorder to monitor experiment operations. Additional diagnostics included an ultraviolet-light-sensitive CCD (charge couple discharge) camera to obtain flame radiation from hydroxyl radicals (see the final figure) and a 35-mm SLR (single-lens-reflex) camera to obtain color still photographs of the flames.

Nayagam, Vedha

1998-01-01

341

Evaluation of alkali concentration in conditions relevant to oxygen/natural gas glass furnaces by laser-induced breakdown spectroscopy.  

SciTech Connect

A number of industrial combustion systems are adopting oxygen-enhanced firing to improve heat transfer characteristics and reduce emissions. The exhaust gas from these systems is dominated by H2O and CO2 and therefore has substantially different gas properties from traditional combustion exhaust. In the past, laser-induced breakdown spectroscopy (LIBS) has been successfully used for the evaluation of alkali aerosol concentrations in air-based combustion systems. This paper presents results of LIBS measurements of alkali concentrations in a laboratory calibration setup and in an oxygen/natural gas container glass furnace. It shows how both gas conditions (composition and temperature) and the molecular form of the alkali species affect the LIBS signals. The paper proposes strategies for mitigating these effects in future applications of LIBS in oxygen-enhanced combustion systems.

Walsh, Peter M.; Molina, Alejandro; Shaddix, Christopher R.; Blevins, Linda Gail; Sickafoose, Shane M.

2005-01-01

342

LOX/Hydrocarbon Combustion Instability Investigation  

NASA Technical Reports Server (NTRS)

The LOX/Hydrocarbon Combustion Instability Investigation Program was structured to determine if the use of light hydrocarbon combustion fuels with liquid oxygen (LOX) produces combustion performance and stability behavior similar to the LOX/hydrogen propellant combination. In particular methane was investigated to determine if that fuel can be rated for combustion instability using the same techniques as previously used for LOX/hydrogen. These techniques included fuel temperature ramping and stability bomb tests. The hot fire program probed the combustion behavior of methane from ambient to subambient temperatures. Very interesting results were obtained from this program that have potential importance to future LOX/methane development programs. A very thorough and carefully reasoned documentation of the experimental data obtained is contained. The hot fire test logic and the associated tests are discussed. Subscale performance and stability rating testing was accomplished using 40,000 lb. thrust class hardware. Stability rating tests used both bombs and fuel temperature ramping techniques. The test program was successful in generating data for the evaluation of the methane stability characteristics relative to hydrogen and to anchor stability models. Data correlations, performance analysis, stability analyses, and key stability margin enhancement parameters are discussed.

Jensen, R. J.; Dodson, H. C.; Claflin, S. E.

1989-01-01

343

Optimization of perfluoro nano-scale emulsions: the importance of particle size for enhanced oxygen transfer in biomedical applications.  

PubMed

Nano-scale emulsification has long been utilized by the food and cosmetics industry to maximize material delivery through increased surface area to volume ratios. More recently, these methods have been employed in the area of biomedical research to enhance and control the delivery of desired agents, as in perfluorocarbon emulsions for oxygen delivery. In this work, we evaluate critical factors for the optimization of PFC emulsions for use in cell-based applications. Cytotoxicity screening revealed minimal cytotoxicity of components, with the exception of one perfluorocarbon utilized for emulsion manufacture, perfluorooctylbromide (PFOB), and specific w% limitations of PEG-based surfactants utilized. We optimized the manufacture of stable nano-scale emulsions via evaluation of: component materials, emulsification time and pressure, and resulting particle size and temporal stability. The initial emulsion size was greatly dependent upon the emulsion surfactant tested, with pluronics providing the smallest size. Temporal stability of the nano-scale emulsions was directly related to the perfluorocarbon utilized, with perfluorotributylamine, FC-43, providing a highly stable emulsion, while perfluorodecalin, PFD, coalesced over time. The oxygen mass transfer, or diffusive permeability, of the resulting emulsions was also characterized. Our studies found particle size to be the critical factor affecting oxygen mass transfer, as increased micelle size resulted in reduced oxygen diffusion. Overall, this work demonstrates the importance of accurate characterization of emulsification parameters in order to generate stable, reproducible emulsions with the desired bio-delivery properties. PMID:22652356

Fraker, Christopher A; Mendez, Armando J; Inverardi, Luca; Ricordi, Camillo; Stabler, Cherie L

2012-10-01

344

Using fluorochemical as oxygen carrier to enhance the growth of marine microalga Nannochloropsis oculata.  

PubMed

The commercial value of marine Nannochloropsis oculata has been recognized due to its high content of eicosapentaenoic acid (>50% w/w). To make it as a profitable bioresource, one of the most desirable goals is to develop a quality-controlled, cost-effective, and large-scale photobioreactor for N. oculata growth. Generally, closed culture system can offer many advantages over open system such as small space requirement, controllable process and low risk of contamination. However, oxygen accumulation is often a detrimental factor for enclosed microalgal culture that has seriously hampered the development of microalga-related industries. In this study, we proposed to use fluorochemical as oxygen carrier to overcome the challenge where four liquid fluorochemicals namely perfluorooctyl bromide, perfluorodecalin, methoxynonafluorobutane, and ethoxynonafluorobutane were investigated separately. Our results showed that the microalgal proliferation with different fluorinated liquids was similar and comparable to the culture without a fluorochemical. When cultured in the photobioreactor with 60% oxygen atmosphere, the N. oculata can grow up in all the fluorochemical photobioreactors, but completely inhibited in the chamber without a fluorochemical. Moreover, the perfluorooctyl bromide system exhibited the most robust efficacy of oxygen removal in the culture media (perfluorooctyl bromide > perfluorodecalin > methoxynonafluorobutane > ethoxynonafluorobutane), and yielded a >3-fold increase of biomass production after 5 days. In summary, the developed fluorochemical photobioreactors offer a feasible means for N. oculata growth in closed and large-scale setting without effect of oxygen inhibition. PMID:23178985

Lee, Yu-Hsiang; Yeh, Yu-Ling; Lin, Keng-Hsien; Hsu, Yu-Chih

2013-08-01

345

Photooxidation of alkaloids: considerable quantum yield enhancement by rose bengal-sensitized singlet molecular oxygen generation.  

PubMed

The photooxidation of sanguinarine, coralyne and berberine was studied in oxygenated alkaline methanol solutions. Rose bengal as photosensitizer significantly accelerates the process, indicating the importance of singlet molecular oxygen in the reaction mechanism. The quantum yield of sensitized oxidation was found to increase significantly with pH and reaches 0.4 for berberine at pH 13.8. The direct oxidation of alkaloids is less efficient, the quantum yield does not exceed 0.01 even in oxygen-saturated solutions. The photoinduced electron ejection does not play a role in the oxidation. The uncharged pseudobase forms, which are present in alkaline medium, are oxidized much more easily than the alkaloid cations. PMID:21883246

Görner, Helmut; Miskolczy, Zsombor; Megyesi, Mónika; Biczók, László

2011-01-01

346

Ligand-Enhanced Reactive Oxidant Generation by Nanoparticulate Zero-Valent Iron and Oxygen  

PubMed Central

The reaction of zero-valent iron or ferrous iron with oxygen produces reactive oxidants capable of oxidizing organic compounds. However, the oxidant yield in the absence of ligands is too low for practical applications. The addition of oxalate, nitrilotriacetic acid (NTA), or ethylenediaminetetraacetic acid (EDTA) to oxygen-containing solutions of nanoparticulate zero-valent iron (nZVI) significantly increases oxidant yield, with yields approaching their theoretical maxima near neutral pH. These ligands improve oxidant production by limiting iron precipitation and by accelerating the rates of key reactions, including ferrous iron oxidation by oxygen and hydrogen peroxide. Product yields indicate that the oxic nZVI system produces hydroxyl radical (OH·) over the entire pH range in the presence of oxalate and NTA. In the presence of EDTA, probe compound oxidation is attributed to OH· under acidic conditions and a mixture of OH· and ferryl ion (Fe[IV]) at circumneutral pH.

Keenan, Christina R.; Sedlak, David L.

2009-01-01

347

Enhancement of a laminar premixed methane/oxygen/nitrogen flame speed using femtosecond-laser-induced plasma  

SciTech Connect

We first investigate the effects of femtosecond-laser-induced plasma on the flame speed of a laminar premixed methane/oxygen/nitrogen flame with a wide range of the equivalence ratios (0.8-1.05) at atmospheric pressure. It is experimentally found that the flame speed increases 20.5% at equivalence ratios 1.05. The self-emission spectra from the flame and the plasma are studied and an efficient production of active radicals under the action of femtosecond (fs)-laser pulses has been observed. Based on the experimental data obtained, the presence of oxygen atom and hydrocarbon radicals is suggested to be a key factor enhancing flame speed.

Yu Xin; Peng Jiangbo; Yi Yachao; Zhao Yongpeng; Chen Deying; Yu Junhua [National Key Laboratory of Science and Technology on Tunable Laser, Harbin Institute of Technology, Harbin 150080 (China); Institute of Opto-electronics, Harbin Institute of Technology, Harbin 150080 (China); Yang Peng; Sun Rui [Institute of Combustion Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2010-07-05

348

Enhancement of a laminar premixed methane/oxygen/nitrogen flame speed using femtosecond-laser-induced plasma  

NASA Astrophysics Data System (ADS)

We first investigate the effects of femtosecond-laser-induced plasma on the flame speed of a laminar premixed methane/oxygen/nitrogen flame with a wide range of the equivalence ratios (0.8-1.05) at atmospheric pressure. It is experimentally found that the flame speed increases 20.5% at equivalence ratios 1.05. The self-emission spectra from the flame and the plasma are studied and an efficient production of active radicals under the action of femtosecond (fs)-laser pulses has been observed. Based on the experimental data obtained, the presence of oxygen atom and hydrocarbon radicals is suggested to be a key factor enhancing flame speed.

Yu, Xin; Peng, Jiangbo; Yang, Peng; Sun, Rui; Yi, Yachao; Zhao, Yongpeng; Chen, Deying; Yu, Junhua

2010-07-01

349

Enhancement of cisplatin-based TACE by a hemoglobin-based oxygen carrier in an orthotopic rat HCC model.  

PubMed

Abstract Objective: Hypoxic tumor cells are more resistant to standard chemotherapies. A number of studies indicated that improving oxygenation inside the tumor could serve as a potential strategy to target hypoxia-induced chemoresistance. In this study, we examined whether a hemoglobin-based oxygen carrier (OC89) could increase tumor oxygenation and thus enhance the efficiency of transarterial chemoembolization (TACE) in an orthotopic rat HCC model. Methods: Efficiency of the hemoglobin-based oxygen carrier (OC89) in improving tumor oxygenation was examined by OxyLab pO2. Sensitization of chemotherapy (cisplatin) in TACE by OC89 was evaluated in four different therapeutic regimens including cisplatin (1 mg/kg) + OC89 (0.2 g/kg), cisplatin (1 mg/kg) + OC89 (0.4 g/kg), cisplatin (3 mg/kg) + OC89 (0.2 g/kg), cisplatin (3 mg/kg) + OC89 (0.4 g/kg). For all the therapeutic regimens, a single delivery of OC89 via the tail vein was performed 1 h before TACE. Results: Compared with Ringer's buffer, systemic delivery of OC89 (0.4 g/kg) attenuated tumor hypoxia (p < 0.05). Additionally, partial pressure of oxygen (pO2) fraction of low readings (0-10 mmHg) inside the tumor decreased from 74.1% to 24.6% after OC89 delivery, while pO2 fraction of high readings (15-25 mmHg) increased from 22.2% to 41.5%. When cisplatin was combined with OC89, regimen cisplatin (3 mg/kg) + OC89 (0.4 g/kg) resulted in a significant inhibition of tumor growth at Day 21 after therapy (p < 0.05). Further investigation indicated that OC89 delivery influenced anti-apoptotic and pro-apoptotic balance of the UPR pathway in the tumor. Conclusions: Our data suggest that targeting tumor hypoxia with the hemoglobin-based O2 carrier serves as a promising approach to enhance the efficacy of cisplatin-based chemotherapy in HCC. PMID:23795724

Liu, Xiao-Bing; Cheng, Qiao; Geng, Wei; Ling, Chang-Chun; Liu, Yan; Ng, Kevin Tak-Pan; Yam, Judy Wai-Ping; Guan, Xin-Yuan; Lo, Chung-Mau; Man, Kwan

2014-08-01

350

Enhanced oxygen supply improves islet viability in a new bioartificial pancreas.  

PubMed

The current epidemic of diabetes with its overwhelming burden on our healthcare system requires better therapeutic strategies. Here we present a promising novel approach for a curative strategy that may be accessible for all insulin-dependent diabetes patients. We designed a subcutaneous implantable bioartificial pancreas (BAP)-the "?-Air"-that is able to overcome critical challenges in current clinical islet transplantation protocols: adequate oxygen supply to the graft and protection of donor islets against the host immune system. The system consists of islets of Langerhans immobilized in an alginate hydrogel, a gas chamber, a gas permeable membrane, an external membrane, and a mechanical support. The minimally invasive implantable device, refueled with oxygen via subdermally implanted access ports, completely normalized diabetic indicators of glycemic control (blood glucose intravenous glucose tolerance test and HbA1c) in streptozotocin-induced diabetic rats for periods up to 6 months. The functionality of the device was dependent on oxygen supply to the device as the grafts failed when oxygen supply was ceased. In addition, we showed that the device is immuno-protective as it allowed for survival of not only isografts but also of allografts. Histological examination of the explanted devices demonstrated morphologically and functionally intact islets; the surrounding tissue was without signs of inflammation and showed visual evidence of vasculature at the site of implantation. Further increase in islets loading density will justify the translation of the system to clinical trials, opening up the potential for a novel approach in diabetes therapy. PMID:23043896

Barkai, Uriel; Weir, Gordon C; Colton, Clark K; Ludwig, Barbara; Bornstein, Stefan R; Brendel, Mathias D; Neufeld, Tova; Bremer, Chezi; Leon, Assaf; Evron, Yoav; Yavriyants, Karina; Azarov, Dimitri; Zimermann, Baruch; Maimon, Shiri; Shabtay, Noa; Balyura, Maria; Rozenshtein, Tania; Vardi, Pnina; Bloch, Konstantin; de Vos, Paul; Rotem, Avi

2013-01-01

351

Enhanced Proliferation, Survival, and Dopaminergic Differentiation of CNS Precursors in Lowered Oxygen  

Microsoft Academic Search

Standard cell culture systems impose environmental oxygen (O2) levels of 20%, whereas actual tissue O2 levels in both developing and adult brain are an order of magnitude lower. To address whether proliferation and differentiation of CNS precursors in vitro are influenced by the O2 environment, we analyzed embryonic day 12 rat mesencephalic precursor cells in traditional cultures with 20% O2

Lorenz Studer; Marie Csete; Sang-Hun Lee; Nadine Kabbani; Jean Walikonis; Barbara Wold; Ron McKay

2000-01-01

352

Membrane?electrode assembly enhances performance of a microbial fuel cell type biological oxygen demand sensor  

Microsoft Academic Search

A membrane?electrode assembly (MEA) was applied to a microbial fuel cell (MFC) type biological oxygen demand (BOD) sensor and the performance of the sensor was assessed. To establish the optimal conditions for MEA fabrication, platinum?catalysed carbon cloth cathodic electrodes were assembled with cation exchange membranes under various temperatures and pressures. By analysing coulombs from the MFCs, it could be determined

Mia Kim; Moon Sik Hyun; Geoffrey M. Gadd; Gwang Tae Kim; Hyung Joo Kim

2009-01-01

353

Enhanced energy recovery from the exhaust gases of basic oxygen furnaces through operation at pressure  

Microsoft Academic Search

This theoretical preliminary-design study indicates that it is potentially possible to produce about 14 MW of net power from the exhaust gases of three small basic oxygen furnaces in the Helwan plant of the Egyptian Iron and Steel Company, Egypt. The turbine exhaust gases would flow through one or more rotary ceramic heat exchangers, incorporating a neutral-gas purge stage, heating

N. S. Shenoy; D. G. Wilson

1985-01-01

354

Oxygen-tension controlled matrices for enhanced osteogenic cell survival and performance.  

PubMed

The success of a clinically-applicable bone tissue engineering construct for large area bone defects depends on its ability to allow for homogeneous bone regeneration throughout the construct. Insufficient vascularization, and consequently inadequate oxygen tension, throughout constructs has been largely cited as the most significant obstacle facing successful bone regeneration in large area defects. The development of constructs that support bone and vessel-forming cell growth and function throughout the scaffold structure are desired for large-area bone defect repair. Here, we developed oxygen tension-controlled matrices that support more homogenous oxygen levels throughout the constructs. Specifically, we examined polylactic co-glycolic acid (PLGA) scaffolds with optimized pore distribution and the percent pore volumes, and demonstrated significantly decreased oxygen and pH gradient from the exterior of the construct to the interior after long-term cell culture in vitro. We confirmed the ability of these optimized constructs to support the cellular survival via live/dead assay. In addition, we examined their ability to support the maintenance of two clinically relevant progenitor cell populations for bone tissue engineering and vascularization, namely mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs), and confirmed the expression of key bone and vascular markers via immunofluorescence. PMID:24570389

Amini, A R; Nukavarapu, S P

2014-06-01

355

Enhancement of the electroreduction of oxygen on Pt alloys with Fe, Ni, and Co  

Microsoft Academic Search

Electrocatalytic activity of Pt alloys with Ni, Co, and Fe, formed by sputtering, was investigated with regard to the oxygen reduction reaction (ORR) in perchloric acid solution. Hydrodynamic voltammograms with rotated electrodes were used to measure the electrocatalytic activity. Maximum activity was observed at ca. 30, 40, and 50% content of Ni, Co, and Fe, respectively, by which 10, 15,

Takako Toda; Hiroshi Igarashi; Hiroyuki Uchida; Masahiro Watanabe

1999-01-01

356

Enhanced catalytic electrochemical reduction of dissolved oxygen with ultraclean cucurbituril[7]-capped gold nanoparticles.  

PubMed

Gold nanoparticles capped with cucurbituril[7] have been prepared in the absence of metallic cations and organic ligands. Remarkably, these nanohybrids encapsulate dissolved oxygen and are highly active in electrochemical reduction. The effect of the presence of sodium and ammonium salts on this catalysed process is also analysed. PMID:24993482

Lanterna, Anabel; Pino, Eduardo; Doménech-Carbó, Antonio; González-Béjar, María; Pérez-Prieto, Julia

2014-08-21

357

N-doped graphene natively grown on hierarchical ordered porous carbon for enhanced oxygen reduction.  

PubMed

A novel nitrogen doped hybrid material composed of in situ-formed graphene natively grown on hierarchical ordered porous carbon is prepared, which successfully combines the advantages of both materials, such as high surface area, high mass transfer, and high conductivity. The outstanding structural properties of the resultant material render it an excellent metal-free catalyst for electrochemical oxygen reduction. PMID:23963824

Liang, Ji; Du, Xin; Gibson, Christopher; Du, Xi Wen; Qiao, Shi Zhang

2013-11-20

358

Enhanced Adhesion of Campylobacter jejuni to Abiotic Surfaces Is Mediated by Membrane Proteins in Oxygen-Enriched Conditions  

PubMed Central

Campylobacter jejuni is responsible for the major foodborne bacterial enteritis in humans. In contradiction with its fastidious growth requirements, this microaerobic pathogen can survive in aerobic food environments, suggesting that it must employ a variety of protection mechanisms to resist oxidative stress. For the first time, C. jejuni 81–176 inner and outer membrane subproteomes were analyzed separately using two-dimensional protein electrophoresis (2-DE) of oxygen-acclimated cells and microaerobically grown cells. LC-MS/MS analyses successfully identified 42 and 25 spots which exhibited a significantly altered abundance in the IMP-enriched fraction and in the OMP-enriched fraction, respectively, in response to oxidative conditions. These spots corresponded to 38 membrane proteins that could be grouped into different functional classes: (i) transporters, (ii) chaperones, (iii) fatty acid metabolism, (iv) adhesion/virulence and (v) other metabolisms. Some of these proteins were up-regulated at the transcriptional level in oxygen-acclimated cells as confirmed by qRT-PCR. Downstream analyses revealed that adhesion of C. jejuni to inert surfaces and swarming motility were enhanced in oxygen-acclimated cells or paraquat-stressed cells, which could be explained by the higher abundance of membrane proteins involved in adhesion and biofilm formation. The virulence factor CadF, over-expressed in the outer membrane of oxygen-acclimated cells, contributes to the complex process of C. jejuni adhesion to inert surfaces as revealed by a reduction in the capability of C. jejuni 81–176 ?CadF cells compared to the isogenic strain. Taken together, these data demonstrate that oxygen-enriched conditions promote the over-expression of membrane proteins involved in both the biofilm initiation and virulence of C. jejuni.

Sulaeman, Sheiam; Hernould, Mathieu; Schaumann, Annick; Coquet, Laurent; Bolla, Jean-Michel; De, Emmanuelle; Tresse, Odile

2012-01-01

359

Incineration of combustible waste materials  

Microsoft Academic Search

A method is described here of incinerating combustible waste materials comprises subjecting the materials to a temperature from about 500°C to about 925°C. This temperature is sufficient to gasify most of the combustible content. In the presence of a mixture of hot air and steam containing insufficient oxygen to support free combustion, the resulting gases blend with further hot gases

1987-01-01

360

Coal Combustion Science  

SciTech Connect

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

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

1991-08-01

361

Study on MSW catalytic combustion by TGA  

Microsoft Academic Search

By thermogravimetric analysis (TGA), the influences of different catalysts on the ignition and combustion of municipal solid waste (MSW) have been investigated in this paper. MSW combustion can be divided into two steps. One is the emission and combustion of volatiles, and the second is the combustion of char. The existence of catalysts in the first step enhances the emission

Boxiong Shen; Qinlei

2006-01-01

362

CHARACTERIZATION OF MERCURY-ENRICHED COAL COMBUSTION RESIDUES FROM ELECTRIC UTILITIES USING ENHANCED SORBENTS FOR MERCURY CONTROL  

EPA Science Inventory

Leaching of mercury and other constituents of potential concern during land disposal or beneficial use of coal combustion residues (CCRs) is the environmental impact pathway evaluated in this report. The specific objectives of the research was to: (1) evaluate mercury, arsenic an...

363

Cytochrome C Enhancement of Singlet Molecular Oxygen Production by the NAPD-Dependent Adrenodoxin Reductase-Adrenodoxin System: The Role of Singlet Oxygen in Damaging Adrenal Mitochondrial Membranes.  

National Technical Information Service (NTIS)

In the presence of NADPH, cytochrome c stimulates approximately a 200-fold increase in the production of singlet oxygen by the bovine adrenodoxin reductase-adrenodoxin system. The formation of singlet oxygen, which was monitored by the attending chemilumi...

A. P. Schaap J. Chu K. Goda T. Kimura

1973-01-01

364

PhénobarbitalEnhances the Formation of Reactive Oxygen in Neoplastic Rat Liver Nodules1  

Microsoft Academic Search

The effect of treatment of rats with the liver monooxygenase inducer phénobarbital on the formation of reactive oxygen in neoplastic liver nodules and the surrounding normal tissue was investigated. Liver nodules were induced by treatment of rats with diethylnitrosamine (single i.p. injection of 0.15 ¿tmol\\/kg body weight on day 1 after birth) followed by chronic administration of phénobarbital-sodium (PB; 0.05%

Werner Scholz; Werner Kun; Michael Schwarz

365

Plasma-enhanced HC-SCR of NO x in the presence of excess oxygen  

Microsoft Academic Search

The oxidative potential of a non-thermal plasma (NTP) in engine off-gases with excess oxygen results in an effective conversion of NO to NO2 that can be converted synergistically to molecular nitrogen with appropriate catalysts by selective catalytic reduction of NO2 with hydrocarbons (HC-SCR). The hydrocarbon added has two essential functions: first, it assists the gas-phase oxidation of NO to NO2

Hans Miessner; Klaus-Peter Francke; Rolf Rudolph

2002-01-01

366

Computational and experimental study of oxygen-enhanced axisymmetric laminar methane flames  

Microsoft Academic Search

Three axisymmetric laminar coflow diffusion flames, one of which is a nitrogen-diluted methane\\/air flame (the ‘base case’) and the other two of which consist of nitrogen-diluted methane vs. pure oxygen, are examined both computationally and experimentally. Computationally, the local rectangular refinement method is used to solve the fully coupled nonlinear conservation equations on solution-adaptive grids. The model includes C2 chemistry

Beth Anne V. Bennett; Zhongxian Cheng; Robert W. Pitz; Mitchell D. Smooke

2008-01-01

367

Enhanced Shrinkage of Lanthanum Strontium Manganite (La0.90Sr0.10MnO3+?) Resulting from Thermal and Oxygen Partial Pressure Cycling  

SciTech Connect

Exposure of La0.9Sr0.1MnO3+? to repeated oxygen partial pressure cycles (air/10 ppm O2) resulted in enhanced densification rates, similar to behavior shown previously due to thermal cycling. Shrinkage rates in the temperature range 700 to 1000oC were orders of magnitude higher than Makipirtti-Meng model estimations based on stepwise isothermal dilatometry results at high temperature. A maximum in enhanced shrinkage due to oxygen partial pressure cycling occurred at 900oC. Shrinkage was greatest when LSM-10 bars that were first equilibrated in air were exposed to gas flows of lower oxygen fugacity than in the reverse direction. The former creates transient cation and oxygen vacancies well above the equilibrium concentration, resulting in enhanced mobility. These vacancies annihilate as Schottky equilibria is re-established, whereas the latter condition does not lead to excess vacancy concentrations.

McCarthy, Ben; Pederson, Larry R.; Anderson, Harlan U.; Zhou, Xiao Dong; Singh, Prabhakar; Coffey, Greg W.; Thomsen, Ed C.

2007-10-01

368

Enhanced interaction of Vibrio cholerae virulence regulators TcpP and ToxR under oxygen-limiting conditions.  

PubMed

Vibrio cholerae is the causative agent of the diarrheal disease cholera. The ability of V. cholerae to colonize and cause disease requires the intricately regulated expression of a number of virulence factors during infection. One of the signals sensed by V. cholerae is the presence of oxygen-limiting conditions in the gut. It has been shown that the virulence activator AphB plays a key role in sensing low oxygen concentrations and inducing the transcription of another key virulence activator, TcpP. In this study, we used a bacterial two-hybrid system to further examine the effect of oxygen on different virulence regulators. We found that anoxic conditions enhanced the interaction between TcpP and ToxR, identified as the first positive regulator of V. cholerae virulence genes. We further demonstrated that the TcpP-ToxR interaction was dependent on the primary periplasmic protein disulfide formation enzyme DsbA and cysteine residues in the periplasmic domains of both ToxR and TcpP. Furthermore, we showed that in V. cholerae, an interaction between TcpP and ToxR is important for virulence gene induction. Under anaerobic growth conditions, we detected ToxR-TcpP heterodimers, which were abolished in the presence of the reducing agent dithiothreitol. Our results suggest that V. cholerae may sense intestinal anoxic signals by multiple components to activate virulence. PMID:24491579

Fan, Fenxia; Liu, Zhi; Jabeen, Nusrat; Birdwell, L Dillon; Zhu, Jun; Kan, Biao

2014-04-01

369

Enhanced oxygen dissociation in a propagating constricted discharge formed in a self-pulsing atmospheric pressure microplasma jet  

NASA Astrophysics Data System (ADS)

We report on the propagation of a constricted discharge feature in a repetitively self-pulsing microplasma jet operated in helium with a 0.075 vol% molecular oxygen admixture in ambient air environment. The constricted discharge is about 1 mm in width and repetitively ignites at the point of smallest electrode distance in a wedge-shaped electrode configuration, propagates through the discharge channel towards the nozzle, extinguishes, and re-ignites at the inlet at frequencies in the kHz range. It co-exists with a homogeneous, volume-dominated low temperature (T ? 300 K) ?-mode glow. Time-resolved measurements of nitrogen molecule C-state and nitrogen molecule ion B-state emission bands reveal an increase of the rotational temperature within the constricted discharge to about 600 K within 50 µs. Its propagation velocity was determined by phase-resolved diagnostics to be similar to the gas velocity, in the order of 40 m s-1. Two-photon absorption laser-induced fluorescence spectroscopy synchronized to the self-pulsing reveals spatial regions of increased oxygen atom densities co-propagating with the constricted discharge feature. The generated oxygen pulse density is about ten times higher than in the co-existing homogeneous ?-mode. Densities reach about 1.5 × 1016 cm-3 at average temperatures of 450 K at the nozzle. This enhanced dissociation of about 80% is attributed to the continuous interaction of the constricted discharge to the co-propagating gas volume.

Schröder, Daniel; Burhenn, Sebastian; Kirchheim, Dennis; Schulz-von der Gathen, Volker

2013-11-01

370

A fluidized-bed combustion process with inherent CO 2 separation; application of chemical-looping combustion  

Microsoft Academic Search

For combustion with CO2 capture, chemical-looping combustion has the advantage that no energy is lost for the separation of CO2. In chemical-looping combustion oxygen is transferred from the combustion air to the gaseous fuel by means of an oxygen carrier. The fuel and the combustion air are never mixed, and the gases from the oxidation of the fuel, CO2 and

Anders Lyngfelt; Bo Leckner; Tobias Mattisson

2001-01-01

371

Structural features and enhanced high-temperature oxygen ion transport in SrFe{sub 1-x}Ta{sub x}O{sub 3-{delta}}  

SciTech Connect

Structural features, oxygen non-stoichiometry and transport properties are studied in the oxide series SrFe{sub 1-x}Ta{sub x}O{sub 3-{delta}}, where x=0.2, 0.3 and 0.4. X-ray diffraction and electron microscopy data evidence formation of the inhomogeneous materials at x=0.3 and 0.4, which include phase constituents with a cubic perovskite and a double perovskite structure types. The composition, the amount and the typical grain size of the phase inhomogeneities are shown to depend both on doping and oxygen content. The increased oxygen-ion conductivity is observed in oxygen depleted materials, which is explained by the increase in the amount of cubic perovskite-like phase and development of interfacial pathways favorable for enhanced oxygen ion transport. - Graphical abstract: The structural studies, oxygen content and conductivity measurements suggest that oxygen depletion from the double perovskite phase constituent of SrFe{sub 1-x}Ta{sub x}O{sub 3-{delta}} for x>0.2 is accompanied by formation of pathways for fast ion transport. Black-Small-Square Highlights: Black-Right-Pointing-Pointer The double perovskite type regions are shown to exist in SrFe{sub 1-x}Ta{sub x}O{sub 3-{delta}}. Black-Right-Pointing-Pointer The oxygen depletion is accompanied with phase separation. Black-Right-Pointing-Pointer The phase separation favors formation of pathways for enhanced oxygen ion transport.

Markov, Alexey A.; Shalaeva, Elizaveta V.; Tyutyunnik, Alexander P.; Kuchin, Vasily V. [Institute of Solid State Chemistry of Ural Branch of RAS, 91 Pervomaiskaya Str., 620990 Yekaterinburg (Russian Federation); Patrakeev, Mikhail V., E-mail: patrakeev@ihim.uran.ru [Institute of Solid State Chemistry of Ural Branch of RAS, 91 Pervomaiskaya Str., 620990 Yekaterinburg (Russian Federation); Leonidov, Ilya A.; Kozhevnikov, Victor L. [Institute of Solid State Chemistry of Ural Branch of RAS, 91 Pervomaiskaya Str., 620990 Yekaterinburg (Russian Federation)

2013-01-15

372

Enhanced Combustion Low NOx Pulverized Coal Burner. Preliminary Economic Analysis of the Enhanced Low NOx Pulverized Coal Burner. Topical Report October 1, 2004 - September 29, 2006.  

National Technical Information Service (NTIS)

ALSTOM Power Inc., Power Plant Laboratories (ALSTOM-PPL) is currently working to develop a new low NOx coal nozzle tip for tangentially-fired utility boilers. Under this program ALSTOM-PPL is performing 3-weeks of large pilot scale combustion testing in i...

A. Raino D. Towle R. Chamberland

2006-01-01

373

Flow enhances photosynthesis in marine benthic autotrophs by increasing the efflux of oxygen from the organism to the water  

PubMed Central

Worldwide, many marine coastal habitats are facing rapid deterioration due in part to human-driven changes in habitat characteristics, including changes in flow patterns, a factor known to greatly affect primary production in corals, algae, and seagrasses. The effect of flow traditionally is attributed to enhanced influx of nutrients and dissolved inorganic carbon (DIC) across the benthic boundary layer from the water to the organism however, here we report that the organism’s photosynthetic response to changes in the flow is nearly instantaneous, and that neither nutrients nor DIC limits this rapid response. Using microelectrodes, dual-pulse amplitude-modulated fluorometry, particle image velocimetry, and real time mass-spectrometry with the common scleractinian coral Favia veroni, the alga Gracilaria cornea, and the seagrass Halophila stipulacea, we show that this augmented photosynthesis is due to flow-driven enhancement of oxygen efflux from the organism to the water, which increases the affinity of the RuBisCO to CO2. No augmentation of photosynthesis was found in the absence of flow or when flow occurred, but the ambient concentration of oxygen was artificially elevated. We suggest that water motion should be considered a fundamental factor, equivalent to light and nutrients, in determining photosynthesis rates in marine benthic autotrophs.

Mass, Tali; Genin, Amatzia; Shavit, Uri; Grinstein, Mor; Tchernov, Dan

2010-01-01

374

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

SciTech Connect

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

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

2007-02-01

375

Structurally ordered FePt nanoparticles and their enhanced catalysis for oxygen reduction reaction.  

PubMed

We report the structure-controlled synthesis of FePt/MgO NPs and their catalysis for oxygen reduction reaction (ORR) in 0.5 M H(2)SO(4) solution. The synthesis yields fcc-FePt/MgO and fct-FePt/MgO NPs with the MgO coating being readily removed for catalytic studies. The fct-FePt NPs show higher activity and durability than the fcc-FePt in the ORR condition. The results indicate that the fully ordered fct-FePt could serve as a practical Pt-based catalyst for fuel cell applications. PMID:20297818

Kim, Jaemin; Lee, Youngmin; Sun, Shouheng

2010-04-14

376

Determining Heats of Combustion of Gaseous Hydrocarbons  

NASA Technical Reports Server (NTRS)

Enrichment-oxygen flow rate-ratio related to heat of combustion. Technique developed for determining heats of combustion of natural-gas samples. Based on measuring ratio m/n, where m is (volmetric) flow rate of oxygen required to enrich carrier air in which test gas flowing at rate n is burned, such that mole fraction of oxygen in combustion-product gases equals that in carrier air. The m/n ratio directly related to heats of combustion of saturated hydrocarbons present in natural gas.

Singh, Jag J.; Sprinkle, Danny R.; Puster, Richard L.

1987-01-01

377

Combustion enhancement of a premixed flame by acoustic forcing with emphasis on role of large-scale vortical structures  

Microsoft Academic Search

The response of a chemically reacting, turbulent shear flow subject to flow excitation is studied in a two-dimensional, laboratory combustor. The combustor employs a V-shaped bluff-body flame holder. A premixed propane-air mixture flows over the flame holder creating two turbulent mixing layers, in which combustion is initiated. The inlet flow is periodically surged by acoustically forcing the upstream flow and

K. Yu; A. Trouve; S. Candel

1991-01-01

378

Reduction of blood oxygen levels enhances postprandial cardiac hypertrophy in Burmese python (Python bivittatus).  

PubMed

Physiological cardiac hypertrophy is characterized by reversible enlargement of cardiomyocytes and changes in chamber architecture, which increase stroke volume and via augmented convective oxygen transport. Cardiac hypertrophy is known to occur in response to repeated elevations of O2 demand and/or reduced O2 supply in several species of vertebrate ectotherms, including postprandial Burmese pythons (Python bivittatus). Recent data suggest postprandial cardiac hypertrophy in P. bivittatus is a facultative rather than obligatory response to digestion, though the triggers of this response are unknown. Here, we hypothesized that an O2 supply-demand mismatch stimulates postprandial cardiac enlargement in Burmese pythons. To test this hypothesis, we rendered animals anemic prior to feeding, essentially halving blood oxygen content during the postprandial period. Fed anemic animals had heart rates 126% higher than those of fasted controls, which, coupled with a 71% increase in mean arterial pressure, suggests fed anemic animals were experiencing significantly elevated cardiac work. We found significant cardiac hypertrophy in fed anemic animals, which exhibited ventricles 39% larger than those of fasted controls and 28% larger than in fed controls. These findings support our hypothesis that those animals with a greater magnitude of O2 supply-demand mismatch exhibit the largest hearts. The 'low O2 signal' stimulating postprandial cardiac hypertrophy is likely mediated by elevated ventricular wall stress associated with postprandial hemodynamics. PMID:24311803

Slay, Christopher E; Enok, Sanne; Hicks, James W; Wang, Tobias

2014-05-15

379

Reduced oxygen concentration enhances conversion of embryonic stem cells to epiblast stem cells.  

PubMed

Recently, an additional type of pluripotent stem cell-line derived from mouse embryos has been established and termed epiblast stem cell (EpiSC), and is expected to be an important tool for studying the mechanisms of maintenance of pluripotency since they depend on basic fibroblast growth factor-MAPK and Activin A-Smad2/3 signaling to maintain pluripotency, unlike mouse embryonic stem cells (ESCs). Further, because of the similarities between mouse EpiSCs and human ESCs, EpiSCs are expected to be effective experimental models for human stem cell therapy. Recently, study for conversion from ESC state to EpiSC state or reversion from EpiSC state to ESC state has attracted interest since these techniques may lead to increasing the potential of pluripotent stem cells and our knowledge about their developmental status. In the present study, we find that a low oxygen concentration in culture environment accelerated, improved, and stabilized the EpiSC state of the converted cells from the ESC state using Oct4?PE-GFP transgenic ESCs. Induced EpiSCs (iEpiSCs) in hypoxia possess closer gene expression patterns to native EpiSCs, and bisulfite sequences for the promoter regions of Stella and Oct4 genes have elucidated that the iEpiSC gain EpiSC-specific methylation patterns in hypoxia. Our data provide evidence that oxygen concentration is an important factor for establishment of the EpiSC-specific state. PMID:21861689

Takehara, Toshiyuki; Teramura, Takeshi; Onodera, Yuta; Hamanishi, Chiaki; Fukuda, Kanji

2012-05-20

380

Low dose gamma irradiation enhances defined signaling components of intercellular reactive oxygen-mediated apoptosis induction  

NASA Astrophysics Data System (ADS)

Transformed cells are selectively removed by intercellular ROS-mediated induction of apoptosis. Signaling is based on the HOCl and the NO/peroxynitrite pathway (major pathways) and the nitryl chloride and the metal-catalyzed Haber-Weiss pathway (minor pathways). During tumor progression, resistance against intercellular induction of apoptosis is acquired through expression of membrane-associated catalase. Low dose radiation of nontransformed cells has been shown to enhance intercellular induction of apoptosis. The present study was performed to define the signaling components which are modulated by low dose gamma irradiation. Low dose radiation induced the release of peroxidase from nontransformed, transformed and tumor cells. Extracellular superoxide anion generation was strongly enhanced in the case of transformed cells and tumor cells, but not in nontransformed cells. Enhancement of peroxidase release and superoxide anion generation either increased intercellular induction of apoptosis of transformed cells, or caused a partial protection under specific signaling conditions. In tumor cells, low dose radiation enhanced the production of major signaling components, but this had no effect on apoptosis induction, due to the strong resistance mechanism of tumor cells. Our data specify the nature of low dose radiation-induced effects on specific signaling components of intercellular induction of apoptosis at defined stages of multistep carcinogenesis.

Bauer, G.

2011-01-01

381

Laboratory investigations of stable carbon and oxygen isotope ratio data enhance monitoring of CO2 underground  

NASA Astrophysics Data System (ADS)

Stable carbon and oxygen isotope data play an important role in monitoring CO2 in the subsurface, for instance during carbon capture and storage (CCS). This includes monitoring of supercritical and gaseous CO2 movement and reactions under reservoir conditions and detection of potential CO2 leakage scenarios. However, in many cases isotope data from field campaigns are either limited due to complex sample retrieval or require verification under controlled boundary conditions. Moreover, experimentally verified isotope fractionation factors are also accurately known only for temperatures and pressures lower than commonly found in CO2 reservoirs (Myrttinen et al., 2012). For this reason, several experimental series were conducted in order to investigate effects of elevated pressures, temperatures and salinities on stable carbon and oxygen isotope changes of CO2 and water. These tests were conducted with a heateable pressure device and with glass or metal gas containers in which CO2 reacted with fluids for time periods of hours to several weeks. The obtained results revealed systematic differences in 13C/12C-distributions between CO2 and the most important dissolved inorganic carbon (DIC) species under reservoir conditions (CO2(aq), H2CO3 and HCO3-). Since direct measurements of the pH, even immediately after sampling, were unreliable due to rapid CO2 de-gassing, one of the key results of this work is that carbon isotope fractionation data between DIC and CO2 may serve to reconstruct in situ pH values. pH values reconstructed with this approach ranged between 5.5 and 7.4 for experiments with 60 bars and up to 120 °C and were on average 1.4 pH units lower than those measured with standard pH electrodes directly after sampling. In addition, pressure and temperature experiments with H2O and CO2 revealed that differences between the oxygen isotope ratios of both phases depended on temperature, water-gas ratios as well as salt contents of the solutions involved. Such systematic knowledge of the extent of oxygen isotope fractionation between H2O and CO2 can help to reconstruct equilibration times, fluid-CO2 ratios as well as temperature and salinity conditions. Isotope results from systematic laboratory studies and the information they provide for assessing in situ reservoir conditions can be transferred to field applications concerning integrity of CO2 reservoirs. They can also apply to natural systems and other industrial uses that involve monitoring of gases in the subsurface under similar pressure and temperature conditions. Reference: Myrttinen, A., Becker, V., Barth, J.A.C., 2012. A review of methods used for equilibrium isotope fractionation investigations between dissolved inorganic carbon and CO2. Earth-Science Reviews, 115(3): 192-199.

Barth, Johannes A. C.; Myrttinen, Anssi; Becker, Veith; Nowak, Martin; Mayer, Bernhard

2014-05-01

382

Sunscreen enhancement of UV-induced reactive oxygen species in the skin.  

PubMed

The number of UV-induced (20 mJ cm(-2)) reactive oxygen species (ROS) generated in nucleated epidermis is dependent upon the length of time the UV filter octocrylene, octylmethoxycinnamate, or benzophenone-3 remains on the skin surface. Two-photon fluorescence images acquired immediately after application of each formulation (2 mg cm(-2)) to the skin surface show that the number of ROS produced is dramatically reduced relative to the skin-UV filter control. After each UV filter remains on the skin surface for t=20 min, the number of ROS generated increases, although it remains below the number generated in the control. By t=60 min, the filters generate ROS above the control. The data show that when all three of the UV filters penetrate into the nucleated layers, the level of ROS increases above that produced naturally by epidermal chromophores under UV illumination. PMID:17015167

Hanson, Kerry M; Gratton, Enrico; Bardeen, Christopher J

2006-10-15

383

Covalent grafting of carbon nanotubes with a biomimetic heme model compound to enhance oxygen reduction reactions.  

PubMed

The oxygen reduction reaction (ORR) is one of the most important reactions in both life processes and energy conversion systems. The replacement of noble-metal Pt-based ORR electrocatalysts by nonprecious-metal catalysts is crucial for the large-scale commercialization of automotive fuel cells. Inspired by the mechanisms of dioxygen activation by metalloenzymes, herein we report a structurally well-defined, bio-inspired ORR catalyst that consists of a biomimetic model compound-an axial imidazole-coordinated porphyrin-covalently attached to multiwalled carbon nanotubes. Without pyrolysis, this bio-inspired electrocatalyst demonstrates superior ORR activity and stability compared to those of the state-of-the-art Pt/C catalyst in both acidic and alkaline solutions, thus making it a promising alternative as an ORR electrocatalyst for application in fuel-cell technology. PMID:24842193

Wei, Ping-Jie; Yu, Guo-Qiang; Naruta, Yoshinori; Liu, Jin-Gang

2014-06-23

384

Enhanced oxygen evolution activity of IrO2 and RuO2 (100) surfaces  

SciTech Connect

The activities of the oxygen evolution reaction (OER) on IrO2 and RuO2 catalysts are among the highest known to date. However, the intrinsic OER activities of surfaces with defined crystallographic orientations are not well established experimentally. Here we report that the (100) surface of IrO2 and RuO2 is more active than the (110) surface that has been traditionally explored by density functional theory studies. The relation between the OER activity and density of coordinatively undersaturated metal sites exposed on each rutile crystallographic facet is discussed. The surface-orientation dependent activities can guide the design of high-surface-area catalysts with increased activity for electrolyzers, metal-air batteries, and photoelectrochemical water splitting applications.

Stoerzinger, Kelsey [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT); Qiao, Liang [ORNL] [ORNL; Biegalski, Michael D [ORNL] [ORNL; Christen, Hans M [ORNL] [ORNL; Shao-Horn, Yang [Massachusetts Institute of Technology (MIT)] [Massachusetts Institute of Technology (MIT)

2014-01-01

385

Hyperbaric oxygen preconditioning attenuates hyperglycemia enhanced hemorrhagic transformation after transient MCAO in rats  

PubMed Central

Background Hemorrhagic transformation (HT) can be a devastating complication of ischemic stroke. Hyperbaric oxygen preconditioning (HBO-PC) has been shown to improve blood-brain barrier (BBB) permeability in stroke models. The purpose of this study is to examine whether HBO-PC attenuates HT after focal cerebral ischemia, and to investigate whether the mechanism of HBO-PC against HT includes up-regulation of antioxidants in hyperglycemic rats. Methods Male Sprague-Dawley rats (280-320 g) were divided into the following groups: sham, middle cerebral artery occlusion (MCAO) for 2 h, and MCAO treated with HBO-PC. HBO-PC was conducted giving 100% oxygen at 2.5 atm absolute (ATA), for 1 h at every 24 h interval for 5 days. At 24 h after the last session of HBO-PC, rats received an injection of 50% glucose (6 ml/kg intraperitoneally) and were subjected to MCAO 15 min later. At 24 h after MCAO, neurological behavior tests, infarct volume, blood-brain barrier permeability, and hemoglobin content were measured to evaluate the effect of HBO-PC. Western blot analysis of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) was evaluated at multiple time-points before and after MCAO. Results HBO-PC improved neurological behavior test, and reduced infarction volume, HT and Evans blue extravasation in the ipsilateral hemisphere at 24 h after MCAO. Western blot analysis failed to demonstrate up-regulation of Nrf2 in HBO-PC group before and after MCAO. Paradoxically, HBO-PC decreased HO-1 expression at 24 h after MCAO, as compared with htMCAO group. Conclusions HBO-PC improved neurological deficits, infarction volume, BBB disruption, and HT after focal cerebral ischemia. However, its mechanism against focal cerebral ischemia and HT may not include activation of Nrf2 and subsequent HO-1 expression.

2012-01-01

386

Labor Contractions Enhance Oxygenation and Behavioral Activity of Newborn Rat Pups  

NASA Technical Reports Server (NTRS)

Labor contractions help instigate behavioral responses at birth (viz., breathing and suckling) that are vital for the newborn's adaptation to the extrauterine world (Ronca et al., 1996). In the present study, we analyzed the role of labor contractions in postpartum oxygenation and behavioral activity of newborn rat pups. Newborns were observed following either vaginal (V) or cesarean delivery. For cesarean delivery, day 21 pregnant dams' were administered a spinal transaction to eliminate lower body sensation, a laparotomy was performed and the uterus was maintained in a heated (37.5 C) bath. Four rat fetuses in one of the dams' paired uterine horn were compressed (C) to Simulate labor contractions (20 sec/min for 10 min) while four fetuses in the opposite horn were not compressed (NC). Fetuses were surgically removed from the uterus, stroked with a soft brush to mimic postnatal licking by the dam, the umbilical cord occluded. Pups were exposed to room temperature (22 C) for one hr, then nest temperature (33 C) for one hr. PO2, CO2, and O2, saturation were determined at 0, 30, 60, or 120 min post delivery using a blood gas analyzer. V and C delivered neonates showed comparable rates of PO2, CO2 and O2 saturation whereas NC neonates showed depressed levels at all time points (p<0.05). Respiratory rates of V, C and NC neonates increased significantly (p<0.05) over the first two postpartum hrs and did not differ across groups. Postpartum behavioral activity was significantly greater in V and C conditions and positively correlated with postnatal oxygenation. These findings provide further evidence for importance of labor contractions in early postpartum adaptation.

Mills, N. A.; Baer, L. A.; Ronca, A. E.; Balton, Bonnie (Technical Monitor)

2002-01-01

387

Enhancement of arsenic trioxide cytotoxicity by dietary isothiocyanates in human leukemic cells via a reactive oxygen species-dependent mechanism.  

PubMed

Although clearly effective in acute promyelocytic leukemia (APL), arsenic trioxide (ATO) demonstrates little clinical benefit as a single agent in the treatment of non-APL hematological malignancies. We screened a library of 2000 marketed drugs and naturally occurring compounds to identify agents that potentiate the cytotoxic effects of ATO in leukemic cells. Here, we report the identification of three isothiocyanates (sulforaphane, erysolin and erucin) found in cruciferous vegetables as enhancers of ATO cytotoxicity. Both erysolin and sulforaphane significantly enhanced ATO-mediated cytotoxicity and apoptosis in a panel of leukemic cell lines; erucin activity was variable among cell types. Cellular exposure to sulforaphane in combination with ATO resulted in a dramatic increase in levels of reactive oxygen species (ROS) compared to treatment with either agent alone. Sulforaphane, alone or with ATO, decreased intracellular glutathione (GSH) content. Furthermore, addition of the free radical scavenger N-acetyl-l-cysteine (NAC) rescued cells from ATO/isothiocyanate-mediated cytotoxicity. Our data suggest that isothiocyanates enhance the cytotoxic effects of ATO through a ROS-dependent mechanism. Combinatorial treatment with isothiocyanates and ATO might provide a promising therapeutic approach for a variety of myeloid malignancies. PMID:19540589

Doudican, Nicole A; Bowling, Benjamin; Orlow, Seth J

2010-02-01

388

A DETAILED CHEMICAL ANALYSIS OF CHANGES TO BITUMEN PRODUCED BY THE IN SITU COMBUSTION PROCESS AT THE OXYGEN WOLF LAKE PROJECT, ALBERTA PART 1: WHOLE OIL SAMPLES  

Microsoft Academic Search

The detailed chemical changes in bitumen brought about over a one year period by an in situ combustion process in an oil sands reservoir have been investigated. Relative to a core sample, the fireflood-produced oils exhibited a significant reduction in density and viscosity which began early in the production cycle. This behaviour was correlated with a marked increase in material

R. F. Alex; B. Fuhr; C. Reichert

1992-01-01

389

Motorcycle Exhaust Particulates Enhance Vasoconstriction in Organ Culture of Rat Aortas and Involve Reactive Oxygen Species  

Microsoft Academic Search

The effects of motorcycle exhaust particulate on vasoconstric- tion were determined using rat thoracic aortas under organ culture conditions treated with organic extracts of motorcycle exhaust particulate from a two-stroke engine. The motorcycle exhaust particulate extract (MEPE) induced a concentration-dependent enhancement of vasoconstriction elicited by phenylephrine in the organ cultures of both intact and endothelium-denuded aortas for 18 h. Nifedipine

Hui-Ping Tzeng; Rong-Sen Yang; Tzuu-Huei Ueng; Shoei-Yn Lin-Shiau; Shing-Hwa Liu

2003-01-01

390

A hybrid 2-zone\\/WAVE engine combustion model for simulating combustion instabilities during dilute operation  

Microsoft Academic Search

Internal combustion engines are operated under conditions of high exhaust gas recirculation (EGR) to reduce NO x emissions and promote enhanced combustion modes such as HCCI. However, high EGR under certain conditions also promotes nonlinear feedback between cycles, leading to the development of combustion instabilities and cyclic variability. We employ a two-zone phenomenological combustion model to simulate the onset of

Kevin Dean Edwards; Robert M Wagner; Veerathu K Chakravarthy; C Stuart Daw; Johney Boyd Green Jr

2006-01-01

391

Process for combusting solid sulfur-containing material  

Microsoft Academic Search

In a process for combusting solid, sulfur-containing material by contacting the material with gaseous oxygen in a combustion zone at combustion conditions to produce combustion products including at least one sulfur oxide, the improvement is described comprising carrying out the contacting in the presence of discrete particles containing a metal-containing spinel. This reduces the amount of sulfur oxide emitted from

J. S. Yoo; J. A. Jaecker

1988-01-01

392

Partial combustion of electrical insulation fluids: Final report  

Microsoft Academic Search

Recurring fire incidents involving transformers have led to a desire to acquire information about the combustion products that may be generated not only in situations of complete combustion, but also in incidents when limited oxygen is present and combustion is incomplete or partial. This report details some results from investigations designed to identify the products of incomplete combustion of five

Claiborne

1987-01-01

393

Carbon nanotube-wired and oxygen-deficient MoO3 nanobelts with enhanced lithium-storage capability  

NASA Astrophysics Data System (ADS)

Carbon nanotube (CNT) wired and oxygen-deficient MoO3-x/CNT structures are fabricated via a facile hydrothermal reaction followed by controlled reduction in Ar/H2. The MoO3-x/CNT, which consists of 63 mol% MoO3 and 37 mol% MoO2, exhibits a much improved Li-storage property compared with the original MoO3/CNT structure when evaluated as an anode in the 0.05-3.0 V region. It is able to retain a capacity of 421 mAh g-1 towards Li after 100 cycles at 200 mA g-1, and deliver 293 and 202 mAh g-1 at current densities of 2 and 4 A g-1, respectively. It is suggested that the formation and recovery of a metallic MoO2 phase over the conversion reaction may account for the enhanced performance.

Ni, Jiangfeng; Wang, Guibin; Yang, Juan; Gao, Dongliang; Chen, Jitao; Gao, Lijun; Li, Yan

394

Green synthesis of silver nanoclusters supported on carbon nanodots: enhanced photoluminescence and high catalytic activity for oxygen reduction reaction.  

PubMed

Metal nanoclusters exhibit unusual optical and catalytic properties due to their unique electronic structures. Here, surfactant-free silver nanoclusters supported on carbon nanodots were synthesized through a facile and green approach with only glucose and AgNO3 as precursors and without any other protecting ligands and reducing agents. The hybrid nanoclusters exhibited enhanced blue fluorescence compared to the carbon nanodots. More importantly, the "surface-clean" silver nanoclusters have remarkable electrocatalytic performance towards oxygen reduction reaction (ORR) with the most efficient four-electron transfer process. Moreover, compared with commercial Pt/C catalyst, the Pt-free hybrid clusters showed comparable catalytic performance for ORR but much higher tolerance to methanol crossover. Such silver nanoclusters will provide broad applications in fluorescence-related areas and in fuel cells as an efficient Pt-free catalyst with low cost and high catalytic performance. PMID:24173664

Liu, Minmin; Chen, Wei

2013-12-21

395

A pilot test of passive oxygen release for enhancement of in situ bioremediation of BTEX-contaminated ground water  

SciTech Connect

A pilot-scale field demonstration of the use of Oxygen Release Compound{trademark} (ORC) was conducted at the site of a former gasoline service station. ORC was installed into a barrier consisting of a tight pattern of treatment wells located relatively near the apparent source of hydrocarbon contamination. The purpose of the barrier was to enhance in situ biodegradation of BTEX in ground water by the passive release of oxygen from the unpumped treatment wells placed across the migration path of the plume. Detailed monitoring was carried out using fencelines of multilevel monitoring wells located up- and downgradient of the barrier. Total BTEX concentrations influent to the barrier were found to be highly variable in space and time. Total influent BTEX concentrations averaged on a cross section transverse to flow were less variable over time, ranging from 10 to 16 mg/L. Significant decreases in BTEX mass flux through the zone impacted by the treatment wells were observed. For the entire portion of the plume impacted by the treatment wells, estimated BTEX treatment efficiency was approximately 70% on Day 51 of the test and declined thereafter.

Chapman, S.W.; Byerley, B.T.; Smyth, D.J.A.; Mackay, D.M.

1997-09-01

396

Improvement of islet function in a bioartificial pancreas by enhanced oxygen supply and growth hormone releasing hormone agonist  

PubMed Central

Islet transplantation is a feasible therapeutic alternative for metabolically labile patients with type 1 diabetes. The primary therapeutic target is stable glycemic control and prevention of complications associated with diabetes by reconstitution of endogenous insulin secretion. However, critical shortage of donor organs, gradual loss in graft function over time, and chronic need for immunosuppression limit the indication for islet transplantation to a small group of patients. Here we present a promising approach to address these limitations by utilization of a macrochamber specially engineered for islet transplantation. The s.c. implantable device allows for controlled and adequate oxygen supply and provides immunological protection of donor islets against the host immune system. The minimally invasive implantable chamber normalized blood glucose in streptozotocin-induced diabetic rodents for up to 3 mo. Sufficient graft function depended on oxygen supply. Pretreatment with the growth hormone-releasing hormone (GHRH) agonist, JI-36, significantly enhanced graft function by improving glucose tolerance and increasing ?-cell insulin reserve in rats thereby allowing for a reduction of the islet mass required for metabolic control. As a result of hypervascularization of the tissue surrounding the device, no relevant delay in insulin response to glucose changes has been observed. Consequently, this system opens up a fundamental strategy for therapy of diabetes and may provide a promising avenue for future approaches to xenotransplantation.

Ludwig, Barbara; Rotem, Avi; Schmid, Janine; Weir, Gordon C.; Colton, Clark K.; Brendel, Mathias D.; Neufeld, Tova; Block, Norman L.; Yavriyants, Karina; Steffen, Anja; Ludwig, Stefan; Chavakis, Triantafyllos; Reichel, Andreas; Azarov, Dimitri; Zimermann, Baruch; Maimon, Shiri; Balyura, Mariya; Rozenshtein, Tania; Shabtay, Noa; Vardi, Pnina; Bloch, Konstantin; de Vos, Paul; Schally, Andrew V.; Bornstein, Stefan R.; Barkai, Uriel

2012-01-01

397

Enhancement of oxygen vacancies and solar photocatalytic activity of zinc oxide by incorporation of nonmetal  

SciTech Connect

B-doped ZnO and N-doped ZnO powders have been synthesized by mechanochemical method and characterized by TG-DTA, XRD, SEM-EDX, XPS, UV-visible and photoluminescence (PL) spectra. X-ray diffraction data suggests the hexagonal wurtzite structure for modified ZnO crystallites and the incorporation of nonmetal expands the lattice constants of ZnO. The room temperature PL spectra suggest more number of oxygen vacancies exist in nonmetal-doped ZnO than that of undoped zinc oxide. XPS analysis shows the substitution of some of the O atoms of ZnO by nonmetal atoms. Solar photocatalytic activity of B-doped ZnO, N-doped ZnO and undoped ZnO was compared by means of oxidative photocatalytic degradation (PCD) of Bisphenol A (BPA). B-doped ZnO showed better solar PCD efficiency as compare to N-doped ZnO and undoped ZnO. The PCD of BPA follows first order reaction kinetics. The detail mechanism of PCD of Bisphenol A was proposed with the identification of intermediates such as hydroquinone, benzene-1,2,4-triol and 4-(2-hydroxypropan-2-yl) phenol. - Graphical Abstract: B-doped ZnO and N-doped ZnO synthesized by mechanochemical method were characterized by various techniques. Solar photocatalytic degradation of Bisphenol-A is in the order of B-ZnO>N-ZnO>ZnO. Highlights: Black-Right-Pointing-Pointer B-doped ZnO and N-doped ZnO powders have been synthesized by mechanochemical method. Black-Right-Pointing-Pointer PL spectra suggest oxygen vacancies are in order of B-doped ZnO>N-doped ZnO>ZnO. Black-Right-Pointing-Pointer Solar PCD efficiency is in order of B-doped ZnO>N-doped ZnO>ZnO for Bisphenol A.

Patil, Ashokrao B. [Department of Chemistry, University of Pune, Ganeshkhind, Pune 411007 (India); Patil, Kashinath R. [Center for Materials Characterization, National Chemical Laboratory, Pune 411008 (India); Pardeshi, Satish K., E-mail: skpar@chem.unipune.ac.in [Department of Chemistry, University of Pune, Ganeshkhind, Pune 411007 (India)

2011-12-15

398

Multiple approaches for enhancing all-organic electronics photoluminescent sensors: simultaneous oxygen and pH monitoring.  

PubMed

Key issues in using organic light emitting diodes (OLEDs) as excitation sources in structurally integrated photoluminescence (PL)-based sensors are the low forward light outcoupling, the OLEDs' broad electroluminescence (EL) bands, and the long-lived remnant EL that follows an EL pulse. The outcoupling issue limits the detection sensitivity (S) as only ~20% of the light generated within standard OLEDs can be forward outcoupled and used for sensor probe excitation. The EL broad band interferes with the analyte-sensitive PL, leading to a background that reduces S and dynamic range. In particular, these issues hinder designing compact sensors, potentially miniaturizable, that are devoid of optical filters and couplers. We address these shortcomings by introducing easy-to-employ multiple approaches for outcoupling improvement, PL enhancement, and background EL reduction leading to novel, compact all-organic device architectures demonstrated for simultaneous monitoring of oxygen and pH. The sensor comprises simply-fabricated, directionally-emitting, narrower-band, multicolor microcavity OLED excitation and small molecule- and polymer-based organic photodetectors (OPDs) with a more selective spectral response. Additionally, S and PL intensity for oxygen are enhanced by using polystyrene (PS):polyethylene glycol (PEG) blends as the sensing film matrix. By utilizing higher molecular weight PS, the ratio ?0/?100 (PL decay time ? at 0% O2/? at 100% O2) that is often used to express S increases ×1.9 to 20.7 relative to the lower molecular weight PS, where this ratio is 11.0. This increase reduces to ×1.7 when the PEG is added (?0/?100=18.2), but the latter results in an increase ×2.7 in the PL intensity. The sensor's response time is <10s in all cases. The microporous structure of these blended films, with PEG decorating PS pores, serves a dual purpose. It results in light scattering that reduces the EL that is waveguided in the substrate of the OLEDs and consequently enhances light outcoupling from the OLEDs by ~60%, and it increases the PL directed toward the OPD. The multiple functional structures of multicolor microcavity OLED pixels/microporous scattering films/OPDs enable generation of enhanced individually addressable sensor arrays, devoid of interfering issues, for O2 and pH as well as for other analytes and biochemical parameters. PMID:23639401

Liu, Rui; Xiao, Teng; Cui, Weipan; Shinar, Joseph; Shinar, Ruth

2013-05-17

399

Oxygen vacancy-mediated enhanced ferromagnetism in undoped and Fe-doped TiO2 nanoribbons  

NASA Astrophysics Data System (ADS)

We have investigated the structural, optical and ferromagnetic properties of undoped and Fe-doped TiO2 nanoribbons (NRbs) grown by a solvothermal method. A strong room temperature ferromagnetism (RTFM) is observed in both undoped and Fe-doped TiO2 NRbs. Fe-doped TiO2 NRbs exhibited a ?4.8-fold enhancement in RTFM as compared to the undoped NRbs grown under similar conditions. However, the RTFM decreases at higher Fe concentration, possibly due to antiferromagnetic ordering between nearby Fe3+ ions caused by a super exchange interaction. X-ray diffraction patterns reveal the pure TiO2(B) phase, the TiO2(B)–anatase mixed phase and the anatase–rutile mixed phase of the TiO2 structure. Field emission scanning electron microscopy and transmission electron microscopy observations reveal NRbs with uniform pore distribution and nanopits formed on the surface for both undoped and Fe-doped NRbs. These samples exhibit strong visible photoluminescence associated with oxygen vacancies and the ferromagnetic hysteresis loop, both of which are strongly enhanced after vacuum annealing. Optical absorption, electron spin resonance and x-ray photoelectron spectroscopic analyses are performed to elucidate the origin of RTFM. The observed RTFM in undoped and Fe-doped TiO2 NRbs is qualitatively explained through a model involving bound magnetic polarons, which include an electron locally trapped by an oxygen vacancy with the trapped electron occupying an orbital overlapping with the unpaired electron (3d1) of a Ti3+ ion and/or the unpaired electron (3d5) of a Fe3+ ion. The development of TiO2 NRbs with tunable optical and magnetic properties constitutes an important step towards realizing improved magneto-optical and spintronic devices from novel TiO2 nanostructures.

Santara, Batakrushna; Giri, P. K.; Dhara, Soumen; Imakita, Kenji; Fujii, Minoru

2014-06-01

400

Green synthesis of silver nanoclusters supported on carbon nanodots: enhanced photoluminescence and high catalytic activity for oxygen reduction reaction  

NASA Astrophysics Data System (ADS)

Metal nanoclusters exhibit unusual optical and catalytic properties due to their unique electronic structures. Here, surfactant-free silver nanoclusters supported on carbon nanodots were synthesized through a facile and green approach with only glucose and AgNO3 as precursors and without any other protecting ligands and reducing agents. The hybrid nanoclusters exhibited enhanced blue fluorescence compared to the carbon nanodots. More importantly, the ``surface-clean'' silver nanoclusters have remarkable electrocatalytic performance towards oxygen reduction reaction (ORR) with the most efficient four-electron transfer process. Moreover, compared with commercial Pt/C catalyst, the Pt-free hybrid clusters showed comparable catalytic performance for ORR but much higher tolerance to methanol crossover. Such silver nanoclusters will provide broad applications in fluorescence-related areas and in fuel cells as an efficient Pt-free catalyst with low cost and high catalytic performance.Metal nanoclusters exhibit unusual optical and catalytic properties due to their unique electronic structures. Here, surfactant-free silver nanoclusters supported on carbon nanodots were synthesized through a facile and green approach with only glucose and AgNO3 as precursors and without any other protecting ligands and reducing agents. The hybrid nanoclusters exhibited enhanced blue fluorescence compared to the carbon nanodots. More importantly, the ``surface-clean'' silver nanoclusters have remarkable electrocatalytic performance towards oxygen reduction reaction (ORR) with the most efficient four-electron transfer process. Moreover, compared with commercial Pt/C catalyst, the Pt-free hybrid clusters showed comparable catalytic performance for ORR but much higher tolerance to methanol crossover. Such silver nanoclusters will provide broad applications in fluorescence-related areas and in fuel cells as an efficient Pt-free catalyst with low cost and high catalytic performance. Electronic supplementary information (ESI) available: UV-Vis absorption spectra, XPS, additional fluorescence, CV and RDE data of the samples. See DOI: 10.1039/c3nr04054b

Liu, Minmin; Chen, Wei

2013-11-01

401

High thermal sensitivity of blood enhances oxygen delivery in the high-flying bar-headed goose.  

PubMed

The bar-headed goose (Anser indicus) crosses the Himalaya twice a year at altitudes where oxygen (O2) levels are less than half those at sea level and temperatures are below -20°C. Although it has been known for over three decades that the major hemoglobin (Hb) component of bar-headed geese has an increased affinity for O2, enhancing O2 uptake, the effects of temperature and interactions between temperature and pH on bar-headed goose Hb-O2 affinity have not previously been determined. An increase in breathing of the hypoxic and extremely cold air experienced by a bar-headed goose at altitude (due to the enhanced hypoxic ventilatory response in this species) could result in both reduced temperature and reduced levels of CO2 at the blood-gas interface in the lungs, enhancing O2 loading. In addition, given the strenuous nature of flapping flight, particularly in thin air, blood leaving the exercising muscle should be warm and acidotic, facilitating O2 unloading. To explore the possibility that features of blood biochemistry in this species could further enhance O2 delivery, we determined the P50 (the partial pressure of O2 at which Hb is 50% saturated) of whole blood from bar-headed geese under conditions of varying temperature and [CO2]. We found that blood-O2 affinity was highly temperature sensitive in bar-headed geese compared with other birds and mammals. Based on our analysis, temperature and pH effects acting on blood-O2 affinity (cold alkalotic lungs and warm acidotic muscle) could increase O2 delivery by twofold during sustained flapping flight at high altitudes compared with what would be delivered by blood at constant temperature and pH. PMID:23470665

Meir, Jessica U; Milsom, William K

2013-06-15

402

Dichloroacetate enhances adriamycin-induced hepatoma cell toxicity in vitro and in vivo by increasing reactive oxygen species levels.  

PubMed

A unique bioenergetic feature of cancer, aerobic glycolysis is considered an attractive therapeutic target for cancer therapy. Recently, dichloroacetate (DCA), a small-molecule metabolic modulator, was shown to reverse the glycoly