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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 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

2

THE SITE DEMONSTRATION OF THE AMERICAN COMBUSTION PYRETRON OXYGEN-ENHANCED BURNER  

EPA Science Inventory

A demonstration of the American Combustion PyretronTM oxygen-enhanced burner ws conducted under the Superfund Innovative Technology Evaluation (SITE) program. The Demonstration was conducted at the U.S. EPA's Combustion Research Facility (CRF) in Jefferson, Arkansas....

3

SITE DEMONSTRATION OF THE AMERICAN COMBUSTION PYRETRON OXYGEN-ENHANCED BURNER  

EPA Science Inventory

A demonstration of the American Combustion Pyretron TM oxygen-enhanced burner was conducted under the Superfund Innovative Technology Evaluation (SITE) program. he Demonstration was conducted at the U.S. EPA's Combustion Research Facility (CRF) in Jefferson, Arkansas. n eight wee...

4

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

5

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

6

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

7

Dilute Oxygen Combustion Phase 3 Final Report  

SciTech Connect

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 75 tph to 100 tph. The fuel rate is essentially unchanged, with the fuel savings expected from oxy-fuel combustion being offset by higher flue gas temperatures. When allowance is made for the high nitrogen level and high gas phase temperature in the furnace, measured NOx emissions are in line with laboratory data on DOC burners developed in Phase 1 of the project. Burner performance has been good and there have been no operating or maintenance problems. The DOC system continues to be used as part of Auburn Steel?s standard reheat furnace practice. High gas phase temperature is a result of the high firing density needed to achieve high production rates, and little opportunity exists for improvement in that area. However, fuel and NOx performance can be improved by further conversion of furnace zones to DOC burners, which will lower furnace nitrogen levels. Major obstacles are cost and concern about increased formation of oxide scale on the steel. Oxide scale formation may be enhanced by exposure of the steel to higher concentrations of oxidizing gas components (primarily products of combustion) in the higher temperature zones of the furnace. Phase 4 of the DOC project will examine the rate of oxide scale formation in these higher temperature zones and develop countermeasures that will allow DOC burners to be used successfully in these furnace zones.

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

2000-05-31

8

Dilute Oxygen Combustion - Phase 3 Report  

SciTech Connect

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 75 tph to 100 tph. The fuel rate is essentially unchanged, with the fuel savings expected from oxy-fuel combustion being offset by higher flue gas temperatures. When allowance is made for the high nitrogen level and high gas phase temperature in the furnace, measured NOx emissions are in line with laboratory data on DOC burners developed in Phase 1 of the project. Burner performance has been good, and there have been no operating or maintenance problems. The DOC system continues to be used as part of Auburn Steel's standard reheat furnace practice. High gas phase temperature is a result of the high firing density needed to achieve high production rates, and little opportunity exists for improvement in that area. However, fuel and NOx performance can be improved by further conversion on furnace zones to DOC burners, which will lower furnace nitrogen levels. Major obstacles are cost and concern about increased formation of oxide scale on the steel. Oxide scale formation may be enhanced by exposure of the steel to higher concentrations of oxidizing gas components (primarily products of combustion) in the higher temperature zones of the furnace. Phase 4 of the DOC project will examine the rate of oxide scale formation in these higher temperature zones and develop countermeasures that will allow DOC burners to be used successfully in these furnace zones.

Riley, Michael F.

2000-05-31

9

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

10

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...

11

Oxygen Enriched Combustion System Performance Study  

E-print Network

}ched combustlon systems are technically, envlronmentally and economically feasible and offer significant energy savings and/or productivity improvement, and then to verify the performance of selected systems in research furnaces. Tests of several commercial... for 35 - 100 percent oxygen. The absolute levels of the NO x emissions also depended on the furnace temperature. INTRODUCTION Oxygen enriched combustion has been found to have significant energy saving potential in industrial furnace applications...

Chen, S. L.; Kwan, Y.; Abele, A. R.; Silver, L. S.; Kobayashi, H.

12

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...

13

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

14

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

15

Reactive Oxygen Species in Combustion Aerosols  

NASA Astrophysics Data System (ADS)

Research on airborne particulate matter (PM) has received increased concern in recent years after it was identified as a major component of the air pollution mix that is strongly associated with premature mortality and morbidity. Particular attention has been paid to understanding the potential health impacts of fine particles (PM2.5), which primarily originate from combustion sources. One group of particulate-bound chemical components of health concern is reactive oxygen species (ROS), which include molecules such as hydrogen peroxide (H2O2), ions such as hypochlorite ion (OCl-), free radicals such as hydroxyl radical (·OH) and superoxide anion (·O2-) which is both an ion and a radical. However, the formation of ROS in PM is not clearly understood yet. Furthermore, the concentration of ROS in combustion particles of different origin has not been quantified. The primary objective of this work is to study the effect of transition metals on the production of ROS in PM2.5 by determining the concentrations of ROS and metals. Both soluble and total metals were measured to evaluate their respective associations with ROS. PM2.5 samples were collected from several outdoor and indoor combustion sources, including those emitted from on-road vehicles, food cooking, incense sticks, and cigarette smoke. PM2.5 samples were also collected from the background air in both the ambient outdoor and indoor environments to assess the levels of particulate-bound transition metals and ROS with no combustion activities in the vicinity of sampling locations. Results obtained from this comprehensive study on particulate-bound ROS will be presented and discussed.

Balasubramanian, R.; See, S.

2007-12-01

16

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

17

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

18

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

19

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

20

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...

21

Infrared multiphoton ignition and enhancement of combustion. Final report  

Microsoft Academic Search

The research demonstrated the feasibility of obtaining reliable ignition and enhancement of combustion by a novel concept, Infrared Multiphoton Absorption\\/Dissociation (IRMPA\\/IRMPD). A methanol-oxygen system was chosen to test this concept because methanol is a potential alternative fuel susceptible to IRMPD. Multiphoton absorption, dissociation, and ignition experiments were conducted in closed pyrex reaction cells with IR-transmitting NaCl windows. Various pressures of

M. Lavid; A. T. Poulos

1986-01-01

22

Oxygen isotopic signature of CO2 from combustion processes  

NASA Astrophysics Data System (ADS)

For a comprehensive understanding of the global carbon cycle precise knowledge of all processes is necessary. Stable isotope (13C and 18O) abundances provide information for the qualification and the quantification of the diverse source and sink processes. This study focuses on the ?18O signature of CO2 from combustion processes, which are widely present both naturally (wild fires), and human induced (fossil fuel combustion, biomass burning) in the carbon cycle. All these combustion processes use atmospheric oxygen, of which the isotopic signature is assumed to be constant with time throughout the whole atmosphere. The combustion is generally presumed to take place at high temperatures, thus minimizing isotopic fractionation. Therefore it is generally supposed that the 18O signature of the produced CO2 is equal to that of the atmospheric oxygen. This study, however, reveals that the situation is much more complicated and that important fractionation effects do occur. From laboratory studies fractionation effects on the order of up to 26%permil; became obvious in the derived CO2 from combustion of different kinds of material, a clear differentiation of about 7‰ was also found in car exhausts which were sampled directly under ambient atmospheric conditions. We investigated a wide range of materials (both different raw materials and similar materials with different inherent 18O signature), sample geometries (e.g. texture and surface-volume ratios) and combustion circumstances. We found that the main factor influencing the specific isotopic signatures of the combustion-derived CO2 and of the concomitantly released oxygen-containing side products, is the case-specific rate of combustion. This points firmly into the direction of (diffusive) transport of oxygen to the reaction zone as the cause of the isotope fractionation. The original total 18O signature of the material appeared to have little influence, however, a contribution of specific bio-chemical compounds to individual combustion products released from the involved material became obvious.

Schumacher, M.; Werner, R. A.; Meijer, H. A. J.; Jansen, H. G.; Brand, W. A.; Geilmann, H.; Neubert, R. E. M.

2011-02-01

23

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

24

Oxygen isotopic signature of CO2 from combustion processes  

NASA Astrophysics Data System (ADS)

For a comprehensive understanding of the global carbon cycle precise knowledge of all processes is necessary. Stable isotope (13C and 18O) abundances provide information for the qualification and the quantification of the diverse source and sink processes. This study focuses on the ?18O signature of CO2 from combustion processes, which are widely present both naturally (wild fires), and human induced (fossil fuel combustion, biomass burning) in the carbon cycle. All these combustion processes use atmospheric oxygen, of which the isotopic signature is assumed to be constant with time throughout the whole atmosphere. The combustion is generally presumed to take place at high temperatures, thus minimizing isotopic fractionation. Therefore it is generally supposed that the 18O signature of the produced CO2 is equal to that of the atmospheric oxygen. This study, however, reveals that the situation is much more complicated and that important fractionation effects do occur. From laboratory studies fractionation effects in the order of about 26‰ became obvious, a clear differentiation of about 7‰ was also found in car exhausts which were sampled directly under ambient atmospheric conditions. We investigated a wide range of materials (both different raw materials and similar materials with different inherent 18O signature), sample geometries (e.g. texture and surface-volume ratios) and combustion circumstances. We found that the main factor influencing the specific isotopic signatures of the combustion-derived CO2 and of the concomitantly released oxygen-containing side products, is the case-specific rate of combustion. This points firmly into the direction of (diffusive) transport of oxygen to the reaction zone as the cause of the isotope fractionation. The original 18O signature of the material appeared to have little or no influence.

Schumacher, M.; Neubert, R. E. M.; Meijer, H. A. J.; Jansen, H. G.; Brand, W. A.; Geilmann, H.; Werner, R. A.

2008-11-01

25

Characteristics of non-premixed oxygen-enhanced combustion: II. Flame structure effects on soot precursor kinetics resulting in soot-free flames  

SciTech Connect

A detailed computational study was performed to understand the effects of the flame structure on the formation and destruction of soot precursors during ethylene combustion. Using the USC Mech Version II mechanism the contributions of different pathways to the formation of benzene and phenyl were determined in a wide domain of Z{sub st} values via a reverse-pathway analysis. It was shown that for conventional ethylene-air flames two sequential reversible reactions play primary roles in the propargyl (C{sub 3}H{sub 3}) chemistry, namely (1) C{sub 2}H{sub 2}+CH{sub 3}= pC{sub 3} H{sub 4}+H, (2) pC{sub 3} H{sub 4}= C{sub 3} H{sub 3}+ H with the corresponding overall endothermic reaction of propargyl formation (3) C{sub 2} H{sub 2}+CH{sub 3}= C{sub 3} H{sub 3}+2H. The contributions of these reactions to propyne (pC{sub 3}H{sub 4}) and propargyl formation and propargyl self-combination leading to benzene and phenyl were studied as a function of physical position, temperature, Z{sub st}, and H concentration. In particular, the role of H radicals on soot precursor destruction was studied in detail. At low Z{sub st}, Reactions 1 and 2 contribute significantly to propyne and propargyl formation on the fuel side of the radical pool at temperatures greater than approx. 1600 K. At higher local temperatures near the radical pool where the concentration of H is significant, the reverse reactions begin to dominate resulting in soot precursor destruction. As Z{sub st} is increased, these regions merge and only net propargyl consumption is observed. Based on the equilibrium constant of Reaction 3, a Z{sub st} value was estimated above which the rate of propargyl formation as a soot precursor is greatly reduced (Z{sub st} = 0.3). This condition compares well with the experimental results for permanently blue counterflow flames in the literature. (author)

Skeen, S.A.; Axelbaum, R.L. [Department of Energy, Environmental, Chemical Engineering, Washington University in St. Louis, St. Louis, MO (United States); Yablonsky, G. [Department of Energy, Environmental, Chemical Engineering, Washington University in St. Louis, St. Louis, MO (United States); Parks College, Saint Louis University, St. Louis, MO (United States)

2010-09-15

26

Infrared multiphoton ignition and enhancement of combustion. Final report  

SciTech Connect

The research demonstrated the feasibility of obtaining reliable ignition and enhancement of combustion by a novel concept, Infrared Multiphoton Absorption/Dissociation (IRMPA/IRMPD). A methanol-oxygen system was chosen to test this concept because methanol is a potential alternative fuel susceptible to IRMPD. Multiphoton absorption, dissociation, and ignition experiments were conducted in closed pyrex reaction cells with IR-transmitting NaCl windows. Various pressures of pure methanol and methanol-oxygen mixtures were irradiated with single pulses from a TEA CO/sub 2/ laser usually tuned at 10.33 micrometers and focused to fluences in the range 1-80 J/cm2. Temporal and spatial ignition behaviors were investigated and successful ignitions were obtained by multiphoton absorption processes. The research scope was expanded to include a second alcohol, 2-propanol.

Lavid, M.; Poulos, A.T.

1986-08-01

27

REDUCTION OF NOx EMISSION FROM COAL COMBUSTION THROUGH OXYGEN ENRICHMENT  

SciTech Connect

BOC Process Gas Solutions and Western Research Institute (WRI) conducted a pilot-scale test program to evaluate the impact of oxygen enrichment on the emissions characteristics of pulverized coal. The combustion test facility (CTF) at WRI was used to assess the viability of the technique and determine the quantities of oxygen required for NOx reduction from coal fired boiler. In addition to the experimental work, a series of Computational Fluid Dynamics (CFD) simulations were made of the CTF under comparable conditions. A series of oxygen enrichment test was performed using the CTF. In these tests, oxygen was injected into one of the following streams: (1) the primary air (PA), (2) the secondary air (SA), and (3) the combined primary and secondary air. Emission data were collected from all tests, and compared with the corresponding data from the baseline cases. A key test parameter was the burner stoichiometry ratio. A series of CFD simulation models were devised to mimic the initial experiments in which secondary air was enriched with oxygen. The results from these models were compared against the experimental data. Experimental evidence indicated that oxygen enrichment does appear to be able to reduce NOx levels from coal combustion, especially when operated at low over fire air (OFA) levels. The reductions observed however are significantly smaller than that reported by others (7-8% vs. 25-50%), questioning the economic viability of the technique. This technique may find favor with fuels that are difficult to burn or stabilize at high OFA and produce excessive LOI. While CFD simulation appears to predict NO amounts in the correct order of magnitude and the correct trend with staging, it is sensitive to thermal conditions and an accurate thermal prediction is essential. Furthermore, without development, Fluent's fuel-NO model cannot account for a solution sensitive fuel-N distribution between volatiles and char and thus cannot predict the trends seen in the experiment.

Western Research Institute

2006-07-01

28

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

29

Studies of MHD generator performance with oxygen enriched coal combustion  

NASA Astrophysics Data System (ADS)

This paper presents calculations made using the Aerodyne PACKAGE (Plasma Analysis, Chemical Kinetics, and Generator Efficiency) computer code which bear on two questions which arise in connection with choices between oxygen enrichment and air preheating to attain the high combustion temperatures needed for open-cycle, coal-fired MHD power generation. The first question is which method produces the highest enthalpy extraction per unit channel length. The second is, in test facilities intended to study tradeoffs between oxygen enrichment and preheated air, can good generator performance be obtained from the same physical channel for different combustor compositions. The answer to the first question is found to depend on what combustor conditions are taken to be comparable. As for the second question, it is found that operation with channel input from off-design combustor conditions can cause serious problems, which can be partially alleviated by changing the channel load factors.

Wormhoudt, J.; Yousefian, V.; Kolb, C. E.; Martinez-Sanchez, M.

1980-07-01

30

Initiation of diffusion combustion in a supersonic flow of H2 air mixture by electrical-discharge-excited oxygen molecules  

NASA Astrophysics Data System (ADS)

The methodology of arranging a stable combustion in a diffusion mode in a supersonic non-premixed H2-air flow at a short distance and at a low air temperature due to excitation of O2 molecules to the a 1?g and b\\,^{1}\\!\\Sigma _g^+ states in the electrical discharge is considered. It is shown that for initiation of combustion in this case, it is sufficient to subject the oxygen molecules to an electrical discharge in a thin (with a thickness of 0.5-1 cm) layer located between hydrogen and air streams. It is shown that the mechanism of combustion enhancement is caused by accelerating the chain reactions due to the abundance of excited oxygen molecules in a shear layer and has a non-thermal character. This paper was presented at the Third International Symposium on Nonequilibrium Processes, Combustion, and Atmospheric Phenomena (Dagomys, Sochi, Russia, 25-29 June 2007).

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

2008-06-01

31

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

32

Combustion of hydrogen-oxygen mixture in electrochemically generated nanobubbles  

NASA Astrophysics Data System (ADS)

Ignition of exothermic chemical reactions in small volumes is considered as difficult or impossible due to the large surface-to-volume ratio. Here observation of the spontaneous reaction is reported between hydrogen and oxygen in bubbles whose diameter is smaller than a threshold value around 150 nm. The effect is attributed to high Laplace pressure and to fast dynamics in nanobubbles and is the first indication on combustion in the nanoscale. In this study the bubbles were produced by water electrolysis using successive generation of H2 and O2 above the same electrode with short voltage pulses in the microsecond range. The process was observed in a microsystem at current densities >1000 A/cm2 and relative supersaturations >1000.

Svetovoy, Vitaly B.; Sanders, Remko G. P.; Lammerink, Theo S. J.; Elwenspoek, Miko C.

2011-09-01

33

Combustion Enhancement Using a Silent Discharge Plasma Reactor  

NASA Astrophysics Data System (ADS)

Electric fields affect flame propagation speed, stability, and combustion chemistry. External electrodes, arc discharges, and plasma jets have been used to combust gas mixtures outside their flammability limits. Experiments with silent electrical discharges (SEDs) and propagating flames have shown that flame propagation velocity is actually decreased (combustion retarded) when an SED is applied directly to the flame region, but velocity is increased (combustion promoted) when applied to the unburned gas mixture upstream of a flame. More recent work has proposed electric arc/microwave-driven plasma-generating fuel nozzles to produce dissociated fuel or ionized fuel for aircraft gas turbine engine combustor mixers. In contrast to prior works, we have used a silent discharge plasma (SDP) reactor to break up large fuel molecules into smaller molecules and create free radicals/active species in a gas stream before the fuel is mixed with an oxidizer and combusted. 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 for fuel and combustion products are observed (i.e., combustion is enhanced). Results of changes in the degree of combustion will be discussed in terms of variations in the plasma specific energy.

Rosocha, Louis; Platts, David; Coates, Don; Stange, Sy

2003-10-01

34

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

35

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

36

Algorithmic Enhancements for Unsteady Aerodynamics and Combustion Applications  

NASA Technical Reports Server (NTRS)

Research in the FY01 focused on the analysis and development of enhanced algorithms for unsteady aerodynamics and chemically reacting flowfields. The research was performed in support of NASA Ames' efforts to improve the capabilities of the in-house computational fluid dynamics code, OVERFLOW. Specifically, the research was focused on the four areas: (1) investigation of stagnation region effects; (2) unsteady preconditioning dual-time procedures; (3) dissipation formulation for combustion; and (4) time-stepping methods for combustion.

Venkateswaran, Sankaran; Olsen, Michael (Technical Monitor)

2001-01-01

37

Use of coal as fuel for chemical-looping combustion with Ni-based oxygen carrier  

Microsoft Academic Search

Chemical-looping combustion is an indirect combustion technology with inherent separation of the greenhouse gas CO. The feasibility of using NiO as an oxygen carrier during chemical-looping combustion of coal has been investigated experimentally at 800-960°C in the present work. The experiments were carried out in a fluidized bed, where the steam acted as the gasification-fluidization medium. Coal gasification and the

Zhengping Gao; Laihong Shen; Jun Xiao; Cuijuan Qing; Qilei Song

2008-01-01

38

Oxygen and Opacity Stack Emission Monitoring Systems To Optimize Combustion Efficiency and Meet EPA Requirements  

E-print Network

The combustion efficiency of industrial fuel burning equipment can be optimized through the use of oxygen and opacity stack emission monitoring systems. By providing the operator with the means to obtain accurate, continuous, dynamic feedback...

Molloy, R. C.

1980-01-01

39

Comparison of iron-, nickel-, copper- and manganese-based oxygen carriers for chemical-looping combustion  

Microsoft Academic Search

For combustion with CO2 capture, chemical-looping combustion (CLC) with inherent separation of CO2 is a promising technology. Two interconnected fluidized beds are used as reactors. In the fuel reactor, a gaseous fuel is oxidized by an oxygen carrier, e.g. metal oxide particles, producing carbon dioxide and water. The reduced oxygen carrier is then transported to the air reactor, where it

Paul Cho; Tobias Mattisson; Anders Lyngfelt

2004-01-01

40

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

Microsoft Academic Search

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

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

2010-01-01

41

A hybrid process combining oxygen enriched air combustion and membrane separation for post-combustion carbon dioxide capture  

Microsoft Academic Search

For carbon dioxide capture and storage (CCS), similar to a large majority of industrial processes, the separation (i.e. capture) step dominates the costs of the technological chain. Based on a concept of minimal work of concentration, the evaluation of a tentative capture framework which combines an oxygen enrichment step before combustion and a CO2 capture step from flue gas has

Eric Favre; Roda Bounaceur; Denis Roizard

2009-01-01

42

Combustion control in domestic boilers using an oxygen sensor  

Microsoft Academic Search

This paper deals with the problem of controlling the combustion process in a domestic boiler fed with natural gas. Combustion control is of particular interest because of its implications with respect to safety, energy saving and reduction of pollution. Traditionally, the control system of a domestic boiler is conceived in such a way to regulate simply the water temperature by

G. Conte; M. Cesaretti; D. Scaradozzi

2006-01-01

43

COMBUSTION ENHANCEMENT OF A GAS FLARE USING ACOUSTICAL EXCITATION  

Microsoft Academic Search

The effect of acoustical excitation on flame stability, trajectory, exhaust emissions, and gas temperatures from a gas flare stack in a crossflow was experimentally investigated. Circular, elliptical, and cup nozzle configurations were examined and compared with a sinusoidal wave excitation. It was found that increasing the pulsation amplitude enhances the combusting efficiency up to the quenching limit. Increasing the Strouhal

R. E. EL BEHERY; A. A. MOHAMAD; M. M. KAMAL

2005-01-01

44

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

45

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

46

Tubular amperometric high-temperature sensors: simultaneous determination of oxygen, nitrogen oxides and combustible components  

Microsoft Academic Search

Tubular amperometric sensors based on stabilized zirconia solid electrolyte with two working electrodes have been studied experimentally with respect to the simultaneous measurements of oxygen and nitrogen oxides, and of oxygen and combustible gas mixtures. Sensors with different types of working electrodes have been optimized for specific gas analytical problems. An almost complete separation of the sensor signals to defined

S. I Somov; G Reinhardt; U Guth; W Göpel

2000-01-01

47

Combustion of solid fuel in very low speed oxygen streams  

NASA Technical Reports Server (NTRS)

In reduced gravity, the combustion of solid fuel in low-speed flow can be studied. The flame behavior in this low-speed regime will fill a void in our understanding of the flow effect on combustion. In addition, it is important for spacecraft fire safety considerations. In this work, modeling and experimental work on low-speed forced-concurrent-flow flame spread are carried out. In addition, experiments on reduced-gravity buoyant-flow flame spread are performed.

Tien, James S.; Sacksteder, Kurt R.; Ferkul, Paul V.; Grayson, Gary D.

1993-01-01

48

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

49

Simulation of surface profile formation in oxygen laser cutting of mild steel due to combustion cycles  

NASA Astrophysics Data System (ADS)

A physicomathematical model of cyclic iron combustion in an oxygen flow during oxygen laser cutting of metal sheets is developed. The combustion front is set into motion by focused laser radiation and a heterogeneous oxidation reaction in oxygen. The burning rate is limited by oxygen supply from the gas phase towards the metal surface, and the interface motion depends on the local temperature. A 3D numerical simulation predicts wavy structures on the metal surface; their linear sizes depend on the scanning speed of the laser beam, the thickness of the produced liquid oxide film and the parameters of the oxygen jet flow. Simulation results help in understanding the mechanism of striation formation during oxygen gas-laser cutting of mild steel and are in qualitative agreement with experimental findings.

Ermolaev, G. V.; Kovalev, O. B.

2009-09-01

50

Pressurized chemical-looping combustion of coal with an iron ore-based oxygen carrier  

SciTech Connect

Chemical-looping combustion (CLC) is a new combustion technology with inherent separation of CO{sub 2}. Most of the previous investigations on CLC of solid fuels were conducted under atmospheric pressure. A pressurized CLC combined cycle (PCLC-CC) system is proposed as a promising coal combustion technology with potential higher system efficiency, higher fuel conversion, and lower cost for CO{sub 2} sequestration. In this study pressurized CLC of coal with Companhia Valedo Rio Doce (CVRD) iron ore was investigated in a laboratory fixed bed reactor. CVRD iron ore particles were exposed alternately to reduction by 0.4 g of Chinese Xuzhou bituminous coal gasified with 87.2% steam/N{sub 2} mixture and oxidation with 5% O{sub 2} in N{sub 2} at 970 C. The operating pressure was varied between 0.1 MPa and 0.6 MPa. First, control experiments of steam coal gasification over quartz sand were performed. H{sub 2} and CO{sub 2} are the major components of the gasification products, and the operating pressure influences the gas composition. Higher concentrations of CO{sub 2} and lower fractions of CO, CH{sub 4}, and H{sub 2} during the reduction process with CVRD iron ore was achieved under higher pressures. The effects of pressure on the coal gasification rate in the presence of the oxygen carrier were different for pyrolysis and char gasification. The pressurized condition suppresses the initial coal pyrolysis process while it also enhances coal char gasification and reduction with iron ore in steam, and thus improves the overall reaction rate of CLC. The oxidation rates and variation of oxygen carrier conversion are higher at elevated pressures reflecting higher reduction level in the previous reduction period. Scanning electron microscope and energy-dispersive X-ray spectroscopy (SEM-EDX) analyses show that particles become porous after experiments but maintain structure and size after several cycles. Agglomeration was not observed in this study. An EDX analysis demonstrates that there is very little coal ash deposited on the oxygen carrier particles but no appreciable crystalline phases change as verified by X-ray diffraction (XRD) analysis. Overall, the limited pressurized CLC experiments carried out in the present work suggest that PCLC of coal is promising and further investigations are necessary. (author)

Xiao, Rui; Song, Min; Zhang, Shuai; Shen, Laihong [School of Energy and Environment, Southeast University, Sipailou No. 2, Nanjing 210096 (China); Song, Qilei [School of Energy and Environment, Southeast University, Sipailou No. 2, Nanjing 210096 (China); Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA (United Kingdom); Lu, Zuoji [School of Energy and Environment, Southeast University, Sipailou No. 2, Nanjing 210096 (China); GCL Engineering Limited, Zhujiang No. 1, Nanjing 210008 (China)

2010-06-15

51

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 ...

52

New type of microengine using internal combustion of hydrogen and oxygen  

PubMed Central

Microsystems become part of everyday life but their application is restricted by lack of strong and fast motors (actuators) converting energy into motion. For example, widespread internal combustion engines cannot be scaled down because combustion reactions are quenched in a small space. Here we present an actuator with the dimensions 100 × 100 × 5??m3 that is using internal combustion of hydrogen and oxygen as part of its working cycle. Water electrolysis driven by short voltage pulses creates an extra pressure of 0.5–4?bar for a time of 100–400??s in a chamber closed by a flexible membrane. When the pulses are switched off this pressure is released even faster allowing production of mechanical work in short cycles. We provide arguments that this unexpectedly fast pressure decrease is due to spontaneous combustion of the gases in the chamber. This actuator is the first step to truly microscopic combustion engines. PMID:24599052

Svetovoy, Vitaly B.; Sanders, Remco G. P.; Ma, Kechun; Elwenspoek, Miko C.

2014-01-01

53

New type of microengine using internal combustion of hydrogen and oxygen  

E-print Network

Microsystems become part of everyday life but their application is restricted by lack of strong and fast motors (actuators) converting energy into motion. For example, widespread internal combustion engines cannot be scaled down because combustion reactions are quenched in a small space. Here we present an actuator with the dimensions 100x100x5 um^3 that is using internal combustion of hydrogen and oxygen as part of its working cycle. Water electrolysis driven by short voltage pulses creates an extra pressure of 0.5-4 bar for a time of 100-400 us in a chamber closed by a flexible membrane. When the pulses are switched off this pressure is released even faster allowing production of mechanical work in short cycles. We provide arguments that this unexpectedly fast pressure decrease is due to spontaneous combustion of the gases in the chamber. This actuator is the first step to truly microscopic combustion engines.

Vitaly B. Svetovoy; Remco G. P. Sanders; Kechun Ma; Miko C. Elwenspoek

2014-02-27

54

Enhanced efficiency of internal combustion engines by employing spinning gas.  

PubMed

The efficiency of the internal combustion engine might be enhanced by employing spinning gas. A gas spinning at near sonic velocities has an effectively higher heat capacity, which allows practical fuel cycles, which are far from the Carnot efficiency, to approach more closely the Carnot efficiency. A remarkable gain in fuel efficiency is shown to be theoretically possible for the Otto and Diesel cycles. The use of a flywheel, in principle, could produce even greater increases in efficiency. PMID:25215720

Geyko, V I; Fisch, N J

2014-08-01

55

Enhanced efficiency of internal combustion engines by employing spinning gas  

NASA Astrophysics Data System (ADS)

The efficiency of the internal combustion engine might be enhanced by employing spinning gas. A gas spinning at near sonic velocities has an effectively higher heat capacity, which allows practical fuel cycles, which are far from the Carnot efficiency, to approach more closely the Carnot efficiency. A remarkable gain in fuel efficiency is shown to be theoretically possible for the Otto and Diesel cycles. The use of a flywheel, in principle, could produce even greater increases in efficiency.

Geyko, V. I.; Fisch, N. J.

2014-08-01

56

Reduction Kinetics of a CasO 4 Based Oxygen Carrier for Chemical-Looping Combustion  

Microsoft Academic Search

\\u000a The CaSO4 based oxygen carrier has been proposed as an alternative low cost oxygen carrier for Chemical-looping combustion (CLC) of\\u000a 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

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

57

Combustion Effects in Laser-oxygen Cutting: Basic Assumptions, Numerical Simulation and High Speed Visualization  

NASA Astrophysics Data System (ADS)

Laser-oxygen cutting is very complicated for theoretical description technological process. Iron-oxygen combustion playing a leading role making it highly effective, able to cut thicker plates and, at the same time, producing special types of striations and other defects on the cut surface. In this paper results of numerical simulation based on elementary assumptions on iron-oxygen combustion are verified with high speed visualization of laser-oxygen cutting process. On a base of assumption that iron oxide lost its protective properties after melting simulation of striation formation due cycles of laser induced non self-sustained combustion is proposed. Assumption that reaction limiting factor is oxygen transport from the jet to cutting front allows to calculate reaction intensity by solving Navier - Stokes and diffusion system in gas phase. Influence of oxygen purity and pressure is studied theoretically. The results of numerical simulation are examined with high speed visualization of laser-oxygen cutting of 4-20 mm mild steel plates at cutting conditions close to industrial.

Zaitsev, Alexander V.; Ermolaev, Grigory V.

58

Combustion and Performance 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, performance, and combustion stability analyses of several of the configurations. This paper summarizes the analyses of combustion and performance as a follow-up to a paper published in the 2008 JANNAF/LPS meeting. Combustion stability analyses are presented in a separate paper. The current paper includes test and analysis results of coaxial element injectors using liquid oxygen and liquid methane or gaseous methane propellants. Several thrust chamber configurations have been modeled, including thrust chambers with multi-element swirl coax element injectors tested at the NASA MSFC, and a uni-element chamber with shear and swirl coax injectors tested at The Pennsylvania State University. Configurations were modeled with two one-dimensional liquid rocket combustion analysis codes, the Rocket Combustor Interaction Design and Analysis (ROCCID), and the Coaxial Injector Combustion Model (CICM). Significant effort was applied to show how these codes can be used to model combustion and performance with oxygen/methane propellants a priori, and what anchoring or calibrating features need to be applied or developed in the future. This paper describes the test hardware configurations, presents the results of all the analyses, and compares the results from the two analytical methods

Hulka, J. R.; Jones, G. W.

2010-01-01

59

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

60

PHYSICAL REVIEW E 90, 022139 (2014) Enhanced efficiency of internal combustion engines by employing spinning gas  

E-print Network

PHYSICAL REVIEW E 90, 022139 (2014) Enhanced efficiency of internal combustion engines by employing; published 28 August 2014) The efficiency of the internal combustion engine might be enhanced by employing Optimizing the internal combustion engine to achieve the highest possible fuel efficiency can be approached

61

Injection Principles from Combustion Studies in a 200-Pound-Thrust Rocket Engine Using Liquid Oxygen and Heptane  

NASA Technical Reports Server (NTRS)

The importance of atomizing and mixing liquid oxygen and heptane was studied in a 200-pound-thrust rocket engine. Ten injector elements were used with both steel and transparent chambers. Characteristic velocity was measured over a range of mixture ratios. Combustion gas-flow and luminosity patterns within the chamber were obtained by photographic methods. The results show that, for efficient combustion, the propellants should be both atomized and mixed. Heptane atomization controlled the combustion rate to a much larger extent than oxygen atomization. Induced mixing, however, was required to complete combustion in the smallest volume. For stable, high-efficiency combustion and smooth engine starts, mixing after atomization was most promising.

Heidmann, M. F.; Auble, C. M.

1955-01-01

62

Numerical Simulation in Combustion Space of an Oxy-fuel Glass Furnace with Different Jet Angles of Auxiliary Oxygen  

Microsoft Academic Search

Numerical simulation in the combustion space of an oxy-fuel glass furnace was carried out. In order to obtain better combustion efficiency, the cases by adding auxiliary oxygen inlet with different jet angles of auxiliary oxygen from 0 degrees to 90 degrees were compared. The gas phase is expressed with two-equation model, while the combustion with non-premixed model and the radiation

Xinjie Fu; Hailiang Zhang; Junlin Xie; Shuxia Mei

2010-01-01

63

Transcritical oxygen\\/transcritical or supercritical methane combustion  

Microsoft Academic Search

Injection of liquid fluid initially at subcritical temperature into an environment in which the temperature and pressure exceed the thermodynamic critical conditions is an important phenomenon in many high performance devices like liquid propellant rocket engines. This is found, for example, in the Space Shuttle main engines or in the Ariane 5 Vulcain engine both operating with liquid oxygen (LOx)

G. Singla; P. Scouflaire; C. Rolon; S. Candel

2005-01-01

64

Development of Cu-based oxygen carriers for chemical-looping combustion  

Microsoft Academic Search

In a chemical-looping combustion (CLC) process, gas (natural gas, syngas, etc.) is burnt in two reactors. In the first one, a metallic oxide that is used as oxygen source is reduced by the feeding gas to a lower oxidation state, being CO2 and steam the reaction products. In the second reactor, the reduced solid is regenerated with air to the

Luis F de Diego; Francisco Garc??a-Labiano; Juan Adánez; Pilar Gayán; Alberto Abad; Beatriz M Corbella; Jose Mar??a Palacios

2004-01-01

65

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

66

Comparison of Oxygen-Bomb Combustion with Standard Ignition Techniques for Determining Author(s): William A. Reiners and Norma M. Reiners  

E-print Network

Comparison of Oxygen-Bomb Combustion with Standard Ignition Techniques for Determining Total Ash. http://www.jstor.org #12;COMPARISON OF OXYGEN-BOMB COMBUSTION WITH STANDARD IGNITION TECHNIQUES samples by oxygen- bomb combustion and by a simple muffle-furnacetechnique. The influence of using

Minnesota, University of

67

Performance and Stability Analyses of Rocket Combustion Devices Using 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 flight-qualified engine systems, so limited test data and analysis results are available at this stage of early development. NASA has funded several hardware-oriented programs 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, NASA Marshall Space Flight Center has conducted combustion, performance, and combustion stability analyses of several of the configurations on these programs. This paper summarizes these analyses. Test and analysis results of impinging and coaxial element injectors using liquid oxygen and liquid methane propellants are included. Several cases with gaseous methane are included for reference. Several different thrust chamber configurations have been modeled, including thrust chambers with multi-element like-on-like and swirl coax element injectors tested at NASA MSFC, and a unielement chamber with shear and swirl coax injectors tested at The Pennsylvania State University. Configurations were modeled with two one-dimensional liquid rocket combustion analysis codes, the Rocket Combustor Interaction Design and Analysis (ROCCID), and the Coaxial Injector Combustion Model (CICM). Significant effort was applied to show how these codes can be used to model combustion and performance with oxygen/methane propellants a priori, and what anchoring or calibrating features need to be applied or developed in the future. This paper describes the test hardware configurations, presents the results of all the analyses, and compares the results from the two analytical methods.

Hulka, James R.; Jones, G. W.

2010-01-01

68

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

69

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

70

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

71

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

72

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

73

Chemical-looping combustion of methane with CaSO 4 oxygen carrier in a fixed bed reactor  

Microsoft Academic Search

Chemical-looping combustion is a promising technology for the combustion of gas or solid fuel with efficient use of energy and inherent separation of CO2. Chemical-looping combustion of methane with calcium sulfate as a novel oxygen carrier was conducted in a laboratory scale fixed bed reactor. The effects of reaction temperature, gas flow rate, sample mass, and particle size on reduction

Qilei Song; Rui Xiao; Zhongyi Deng; Huiyan Zhang; Laihong Shen; Jun Xiao; Mingyao Zhang

2008-01-01

74

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

75

Upgrading and enhanced recovery of Jobo heavy oil using hydrogen donor under in-situ combustion  

E-print Network

UPGRADING AND ENHANCED RECOVERY OF JOBO HEAVY OIL USING HYDROGEN DONOR UNDER IN-SITU COMBUSTION A... UPGRADING AND ENHANCED RECOVERY OF JOBO HEAVY OIL USING HYDROGEN DONOR UNDER IN-SITU COMBUSTION A Thesis by SAMIR HUSEYNZADE Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements...

Huseynzade, Samir

2008-10-10

76

Experimental and analytical study to model temperature profiles and stoichiometry in oxygen-enriched in-situ combustion  

E-print Network

EXPERIMENTAL AND ANALYTICAL STUDY TO MODEL TEMPERATURE PROFILES AND STOICHIOMETRY IN OXYGEN-ENRICHED IN-SITU COMBUSTION A Dissertation by JOSE RAMON RODRIGUEZ Submitted to the Office of Graduate Studies of Texas A... AND STOICHIOMETRY IN OXYGEN-ENRICHED IN-SITU COMBUSTION A Dissertation by JOSE RAMON RODRIGUEZ Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR...

Rodriguez, Jose Ramon

2004-09-30

77

Combustion Gas Turbine Power Enhancement by Refrigeration of Inlet Air  

E-print Network

Combustion gas turbines have gained widespread acceptance for mechanical drive and power generation applications. One key drawback of a combustion turbine is that its specific output and thermal efficiency vary quite significantly with variations...

Meher-Homji, C. B.; Mani, G.

1983-01-01

78

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

E-print Network

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 due to cost. We then show that a conceivable global use of hydrogen in complete replacement of fossil fuels would imply the permanent removal from our atmosphere of 2.8875x10^7 metric tons O_2/day. Fuel cells are briefly discussed to point out similarly serious environmental problems, again, for large uses. We propose the possibility of resolving these problems by upgrading hydrogen to the new combustible fuel called magnegas^TM, whose chemical structure is composed by the new chemical species of magnecules, whose energy content and other features are beyond the descriptive capacities of quantum chemistry. In fact, magnegas contains up to 50% hydrogen, while having combustion exhaust with: 1) a positive oxygen balance (releasing more oxygen in the exhaust than that used in the combustion); 2) no appreciable carcinogenic or toxic substances; 3) considerably reduced carbon dioxide as compared to fossil fuels; 4) considerably reduced nitrogen oxides; and 5) general reduction of pollutants in the exhaust up to 96% of current EPA standards.

R. M. Santilli

2000-09-04

79

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

80

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

81

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.

82

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

83

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

84

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

85

Infrared multiphoton ignition and combustion enhancement of natural gas  

Microsoft Academic Search

The unique chemistry of methane combustion, including strong C-H bond energy, leads to difficulties in use of natural gas as an engine fuel. Problems include low combustion efficiency, knocking, unreliable ignition (misfiring), and NOx emission. It is well established that improvement of the above-mentioned combustion phenomena requires the presence of high concentration of chain-initiating and chain-branching reactive radicals. This project

Moshe Lavid; Arthur T. Poulos; Suresh K. Gulati

1993-01-01

86

Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis  

NASA Astrophysics Data System (ADS)

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.

Song, Fang; Hu, Xile

2014-07-01

87

On the triple oxygen isotope composition of carbon dioxide from some combustion processes  

NASA Astrophysics Data System (ADS)

The triple oxygen isotope composition (?17O) of CO2 from different sources is gaining in importance as possible tracer of gross carbon exchanges between major reservoirs. Here we present the ?17O of CO2 from natural gas and propane-butane combustion, wood chips burning, car exhaust and human breath. All investigated CO2 samples had negative ?17O value compared to the CO2-water equilibration line (slope ? = 0.522; zero intercept), which was inherited from the oxidant air O2. However, for all combustion experiments, the ?17O value of CO2 was significantly higher than the ?17O value of air O2. The oxygen isotope composition of CO2 from natural gas (?18O = 21.6 ± 0.7‰; ?17O = -0.30 ± 0.02‰) and from propane-butane (?18O = 22.5 ± 0.8‰; ?17O = -0.32 ± 0.02‰) combustion is explained by kinetic fractionation of ambient air O2. In case of wood chips burning (?18O = 19.4 ± 1.0‰; ?17O = -0.21 ± 0.02‰) the wood inherent O also affected the triple oxygen isotope composition of the CO2. Car exhaust CO2 (?18O = 32.6 ± 3.0‰; ?17O = -0.32 ± 0.03‰) might have likely equilibrated with the condensed water in the exhaust line. The isotope composition of breath CO2 (?18O = 35 ± 1‰; ?17O = -0.03 ± 0.03‰) was controlled by equilibration with body water. We assess the ?17O value of CO2 as a potential tracer for anthropogenic CO2 emission.

Horváth, B.; Hofmann, M. E. G.; Pack, A.

2012-10-01

88

Emissions of Parent, Nitro, and Oxygenated Polycyclic Aromatic Hydrocarbons from Residential Wood Combustion in Rural China  

PubMed Central

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 (EFPAH28), 9 nPAHs (EFPAHn9) and 4 oPAHs (EFPAHo4) were measured for residential combustion of 27 wood fuels in rural China. The measured EFPAH28, EFPAHn9, and EFPAHo4 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.

2012-01-01

89

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

90

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

91

The effect of carbon dioxide-oxygen mixtures on oil recovery by in-situ combustion  

E-print Network

has, in recent years, become interested in in-situ combustion to recover low-gravity, high viscosity crude oils from underground reservoirs. In this process in-situ oil is ignited forming a burning front which is propagated through the formation... and analyzed. Temperature and rate of advance of the burning front, along with inlet and outlet pressures, were measured throughout the run . Burns made with a carbon dioxide-oxygen mixture were compared with those made using air as the injection gas. Three...

Broussard, Neal Joseph

2012-06-07

92

Infrared multiphoton ignition and combustion enhancement of natural gas. Final report, November 1989October 1992  

Microsoft Academic Search

This research program has demonstrated the feasibility of using Infrared Multiphoton (IRMP) processes for reliable ignition and combustion enhancement of natural gas. Hydrocarbon constituents of natural gas are excited with focused, pulsed infrared lasers tuned to discrete resonant frequencies causing their dissociation to very reactive radicals. These radicals participate in chain-branching and chain-propagating reactions significantly improving the combustion of natural

M. Lavid; A. T. Poulos; S. K. Gulati; J. G. Stevens; W. R. Lempert

1993-01-01

93

Measurement and modelling of oxygenated organic compounds from smoldering combustion of biomass  

SciTech Connect

Biomass fires emit a myriad of compounds, some of which are toxic and/or globally significant as photochemically reactive, tropospheric trace gases, greenhouse gases and precursors to stratospheric ozone-destroying radicals. 35 oxygenated organic compounds in condensed (-45{degrees}C) smoke from 29 bench scale fires of ponderosa pine sapwood, needles, bark, litter, duff, and humus have been identified and quantified. These fires ranged from flaming to low intensity smoldering. In addition, five low intensity fires of intact ponderosa pine forest floor (litter, duff, and humus) were carried out on a larger scale in a combustion chamber. The condensates were analyzed by gas chromatography/mass spectrometry and the gas phase was analyzed by gas chromatography/flame ionization detection. Acetic acid, vinyl acetate and acetol were major condensable emissions. The dependence of oxygenated organic emissions on fuel chemistry and combustion efficiency has been investigated, along with correlations between emissions. Molar emission ratios of individual compounds to CO have been calculated and used to estimate possible exposure levels for wildland firefighters.

McKenzie, L.M.; Richards, G.N. [Univ. of Montana, Missoula, MT (United States)

1995-12-01

94

Emissions of parent, nitrated, and oxygenated polycyclic aromatic hydrocarbons from indoor corn straw burning in normal and controlled combustion conditions.  

PubMed

Emission factors (EFs) of parent polycyclic aromatic hydrocarbons (pPAHs), nitrated PAHs (nPAHs), and oxygenated PAHs (oPAHs) were measured for indoor corn straw burned in a brick cooking stove under different burning conditions. The EFs of total 28 pPAHs, 6 nPAHs and 4 oPAHs were (7.9 +/- 3.4), (6.5 +/- 1.6) x 10(-3), and (6.1 +/- 1.4) x 10(-1) mg/kg, respectively. Fuel charge size had insignificant influence on the pollutant emissions. Measured EFs increased significantly in a fast burning due to the oxygen deficient atmosphere formed in the stove chamber. In both restricted and enhanced air supply conditions, the EFs of pPAHs, nPAHs and oPAHs were significantly higher than those measured in normal burning conditions. Though EFs varied among different burning conditions, the composition profiles and calculated isomer ratios were similar, without significant differences. The results from the stepwise regression model showed that fuel burning rate, air supply amount, and modified combustion efficiency were the three most significant influencing factors, explaining 72%-85% of the total variations. PMID:24494494

Shen, Guofeng; Xue, Miao; Wei, Siye; Chen, Yuanchen; Wang, Bin; Wang, Rong; Lv, Yan; Shen, Huizhong; Li, Wei; Zhang, Yanyan; Huang, Ye; Chen, Han; Wei, Wen; Zhao, Qiuyue; Li, Bing; Wu, Haisuo; Tao, Shu

2013-10-01

95

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

96

Burning of solids in oxygen-rich environments in normal and reduced gravity. [combustion of cellulose acetates  

NASA Technical Reports Server (NTRS)

An experimental program was conducted to investigate the combustion characteristics of solids burning in a weightless environment. The combustion characteristics of thin cellulose acetate material were obtained from specimens burned in supercritical as well as in low pressure oxygen atmospheres. Flame spread rates were measured and found to depend on material thickness and pressure in both normal gravity (1-g) and reduced gravity (0-g). A gravity effect on the burning process was also observed; the ratio of 1-g to 0-g flame spread rate becomes larger with increasing material thickness. Qualitative results on the combustion characteristics of metal screens (stainless steel, Inconel, copper, and aluminum) burning in supercritical oxygen and normal gravity are also presented. Stainless steel (300 sq mesh) was successfully ignited in reduced gravity; no apparent difference in the flame spread pattern was observed between 1-g and 0-g.

Andracchio, C. R.; Cochran, T. H.

1974-01-01

97

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

98

Heat Release Rate and Effective Heat of Combustion Measurements: A Comparative Study of Thermal and Oxygen Consumption Techniques  

Microsoft Academic Search

A new calorimeter especially built for the measurement of the heat release rate and effective heat of combustion of composite materials is pre sented. Two procedures can be used to obtain these data: the first one is based on the direct measurement of the convective and radiant heat liberated by the flame, the second involves oxygen consumption measurement. Preliminary ex

Fatima Moussan; Jean-Louis Delfau; Christian Vovelle; Christian Pham Van Cang; Gérard Bosseboeuf

1995-01-01

99

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

100

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

101

Steam-enhanced regime for liquid hydrocarbons combustion: velocity distribution in the burner flame  

NASA Astrophysics Data System (ADS)

The lab-scale burner device with proprietary design was used for combustion of diesel fuel in a steam-enhanced regime. This operation mode ensures drastic intensification of liquid hydrocarbon combustion due to supply of superheated steam jet to the combustion zone. The particle image velocimetry technique was used for study of velocity field in the burner flame. The method of seeding of flow zone with new kind of tracers (micro-sized silica particles produced from silicon oil added to liquid fuel) was tested.

Alekseenko, S. V.; Anufriev, I. S.; Vigriyanov, M. S.; Dulin, V. M.; Kopyev, E. P.; Sharypov, O. V.

2014-06-01

102

Combustion, respiration and intermittent exercise: a theoretical perspective on oxygen uptake and energy expenditure.  

PubMed

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. PMID:24833508

Scott, Christopher B

2014-01-01

103

Catalytic enhancement of singlet oxygen for hybrid 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 on 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. In this paper we report further observations of the effects of elevated temperature up to 410 K, and correlations of the catalytically generated O2(a) with atomic oxygen over a large range of discharge-flow conditions. We have applied a diffusion-limited reaction rate model to extrapolate the catalytic reaction rates to the highpressure, fast-flow conditions of the subsonic plenum of a supersonic EOIL test reactor. Using the model and the flow reactor results, we have designed and implemented a first-generation catalytic module for the PSI supersonic MIDJet/EOIL reactor. We describe preliminary tests with this module for catalyst coating deposition and enhancement of the small-signal gain observed in the supersonic flow. The observed catalytic effect could significantly benefit the development of high-power electrically driven oxygen-iodine laser systems.

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

2010-02-01

104

Clinical oxygen enhancement ratio of tumors in carbon ion radiotherapy: the influence of local oxygenation changes  

PubMed Central

The effect of carbon ion radiotherapy on hypoxic tumors has recently been questioned because of low linear energy transfer (LET) values in the spread-out Bragg peak (SOBP). The aim of this study was to investigate the role of hypoxia and local oxygenation changes (LOCs) in fractionated carbon ion radiotherapy. Three-dimensional tumors with hypoxic subvolumes were simulated assuming interfraction LOCs. Different fractionations were applied using a clinically relevant treatment plan with a known LET distribution. The surviving fraction was calculated, taking oxygen tension, dose and LET into account, using the repairable–conditionally repairable (RCR) damage model with parameters for human salivary gland tumor cells. The clinical oxygen enhancement ratio (OER) was defined as the ratio of doses required for a tumor control probability of 50% for hypoxic and well-oxygenated tumors. The resulting OER was well above unity for all fractionations. For the hypoxic tumor, the tumor control probability was considerably higher if LOCs were assumed, rather than static oxygenation. The beneficial effect of LOCs increased with the number of fractions. However, for very low fraction doses, the improvement related to LOCs did not compensate for the increase in total dose required for tumor control. In conclusion, our results suggest that hypoxia can influence the outcome of carbon ion radiotherapy because of the non-negligible oxygen effect at the low LETs in the SOBP. However, if LOCs occur, a relatively high level of tumor control probability is achievable with a large range of fractionation schedules for tumors with hypoxic subvolumes, but both hyperfractionation and hypofractionation should be pursued with caution. PMID:24728013

Antonovic, Laura; Lindblom, Emely; Dasu, Alexandru; Bassler, Niels; Furusawa, Yoshiya; Toma-Dasu, Iuliana

2014-01-01

105

Enhanced performance of an electric oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Experiments and modeling have led to continued enhancements in the Electric Oxygen-Iodine Laser (ElectricOIL) system. This continuous wave (cw) laser operating on the 1315 nm transition of atomic iodine is pumped by the production of O2(a) in a radio-frequency (RF) discharge in an O2/He/NO gas mixture. New discharge geometries have led to improvements in O2(a) production and efficiency. A 95% enhancement in cw laser power was achieved via a 50% increase in gain length, flow rates, and discharge power. A further 87% increase in extracted laser power was obtained using a larger mode volume resonator. The gain has improved by more than 100-fold from the initial demonstration of 0.002% cm-1 to 0.26% cm-1, and similarly the outcoupled laser power has improved more than 500-fold from 0.16 W to 102 W.

Carroll, D. L.; Benavides, G. F.; Zimmerman, J. W.; Woodard, B. S.; Day, M. T.; Palla, A. D.; Verdeyen, J. T.; Solomon, W. C.

2010-02-01

106

Complex effects arising in smoke plume simulations due to inclusion of direct emissions of oxygenated organic species from biomass combustion  

NASA Astrophysics Data System (ADS)

Oxygenated volatile organic species (oxygenates), including HCOOH, H2CO, CH3OH, HOCH2CHO (hydroxyacetaldehyde), CH3COOH, and C6H5OH, have recently been identified by Fourier transform infrared measurements as a significant component of the direct emissions from biomass combustion. These oxygenates have not generally been included in the hydrocarbon-based initial emission profiles used in previous photochemical simulations of biomass combustion smoke plumes. We explore the effects of oxygenates on this photochemistry by using an established initial emission hydrocarbon profile and comparing simulation results obtained both with and without addition of the above six oxygenates. Simulations are started at noon and carried out for 30 hours in an expanding Lagrangian plume. After an initial transient period during which [NOx] falls rapidly, conditions within the oxygenated smoke plume are found to be strongly NOx-sensitive, and the simulated final species profile is thus strongly dependent upon the ?[NO]/?[CO] initial emission profile. Oxygenate addition results in very significant and complex effects on net O3 production, as well as on the relative amounts of long-lived HOx and NOx reservoir species (H2O2, organic hydroperoxides, HNO3, and peroxyacetyl nitrate (PAN)) that are mixed into the surrounding atmosphere. Oxygenates may either increase or decrease net O3 production (depending upon the initial ?[NO]/?[CO]). However, they always increase H2O2 and organic hydroperoxide production as a result of increased rates of radical + radical reactions. These effects spring largely from accelerated removal of NOx from the smoke plume due to increased radical concentrations resulting both from photolysis of oxygenates (mainly CH2O) and from their relatively high reactivity. Predicted concentrations of H2O2, ?[O3]/?[CO], ?[NH3]/?[CO], and ?[HCOOH]/?[CO] are compared with some available measured values.

Mason, Sherri A.; Field, Richard J.; Yokelson, Robert J.; Kochivar, Michael A.; Tinsley, Mark R.; Ward, Darold E.; Hao, Wei Min

2001-01-01

107

Combustion  

NASA Technical Reports Server (NTRS)

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

Bulzan, Dan

2007-01-01

108

Combustion  

NSDL National Science Digital Library

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

House, The S.

2014-01-28

109

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

110

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

NASA Astrophysics Data System (ADS)

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.

Edenburn, Michael W.

1990-07-01

111

Sulfur behavior in chemical looping combustion with NiO/Al{sub 2}O{sub 3} oxygen carrier  

SciTech Connect

Chemical looping combustion (CLC) is a novel technology where CO{sub 2} is inherently separated during combustion. Due to the existence of sulfur contaminants in the fossil fuels, the gaseous products of sulfur species and the interaction of sulfur contaminants with oxygen carrier are a big concern in the CLC practice. The reactivity of NiO/Al{sub 2}O{sub 3} oxygen carrier reduction with a gas mixture of CO/H{sub 2} and H{sub 2}S is investigated by means of a thermogravimetric analyzer (TGA) and Fourier Transform Infrared spectrum analyzer in this study. An X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscope (SEM) are used to evaluate the phase characterization of reacted oxygen carrier, and the formation mechanisms of the gaseous products of sulfur species are elucidated in the process of chemical looping combustion with a gaseous fuel containing hydrogen sulfide. The results show that the rate of NiO reduction with H{sub 2}S is higher than the one with CO. There are only Ni and Ni{sub 3}S{sub 2} phases of nickel species in the fully reduced oxygen carrier, and no evidence for the existence of NiS or NiS{sub 2}. The formation of Ni{sub 3}S{sub 2} is completely reversible during the process of oxygen carrier redox. A liquid phase sintering on the external surface of reduced oxygen carriers is mainly attributed to the production of the low melting of Ni{sub 3}S{sub 2} in the nickel-based oxygen carrier reduction with a gaseous fuel containing H{sub 2}S. Due to the sintering of metallic nickel grains on the external surface of the reduced oxygen carrier, further reaction of the oxygen carrier with H{sub 2}S is constrained, and there is no increase of the sulfidation index of the reduced oxygen carrier with the cyclical reduction number. Also, a continuous operation with a syngas of carbon monoxide and hydrogen containing H{sub 2}S is carried out in a 1 kW{sub th} CLC prototype based on the nickel-based oxygen carrier, and the effect of the fuel reactor temperature on the release of gaseous products of sulfur species is investigated. (author)

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

2010-05-15

112

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

113

The Tapioca Bomb: A Demonstration to Enhance Learning about Combustion and Chemical Safety  

ERIC Educational Resources Information Center

In any demonstration to students, producing light and sound usually ensures interest and can enhance understanding and retention of the concepts involved. A guided inquiry (Predict, Observe, Explain: POE) approach was used to involve the students actively in their learning about the explosive combustion of fine flour particles in air in the…

Keeratichamroen, Wasana; Dechsri, Precharn; Panijpan, Bhinyo; Ruenwongsa, Pintip

2010-01-01

114

Super-linear Enhancement of the Electric Oxygen-Iodine Laser David L. Carrolla  

E-print Network

Super-linear Enhancement of the Electric Oxygen-Iodine Laser David L. Carrolla , Brian S. Woodardb., Urbana, Illinois, 61801, United States ABSTRACT Continuing experiments with Electric Oxygen-Iodine Laser: electric discharge oxygen-iodine laser, ElectricOIL, EOIL, DOIL, singlet delta oxygen 1. INTRODUCTION

Carroll, David L.

115

Infrared multiphoton ignition and combustion enhancement of natural gas. Final report, November 1989-October 1992  

SciTech Connect

This research program has demonstrated the feasibility of using Infrared Multiphoton (IRMP) processes for reliable ignition and combustion enhancement of natural gas. Hydrocarbon constituents of natural gas are excited with focused, pulsed infrared lasers tuned to discrete resonant frequencies causing their dissociation to very reactive radicals. These radicals participate in chain-branching and chain-propagating reactions significantly improving the combustion of natural gas. Experimental and computational tasks were performed to discern IR laser conditions needed to reliably obtain IRMP ignition and reduction in ignition delay time.

Lavid, M.; Poulos, A.T.; Gulati, S.K.; Stevens, J.G.; Lempert, W.R.

1993-11-30

116

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

117

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

118

Reactivity of a CaSO 4 -oxygen carrier in chemical-looping combustion of methane in a fixed bed reactor  

Microsoft Academic Search

Chemical-looping combustion (CLC) is a promising technology for the combustion of gas or solid fuel with efficient use of\\u000a energy and inherent separation of CO2. A reactivity study of CaSO4 oxygen carrier in CLC of methane was conducted in a laboratory scale fixed bed reactor. The oxygen carrier particles were\\u000a exposed in six cycles of alternating reduction methane and oxidation

Qilei Song; Rui Xiao; Zhongyi Deng; Laihong Shen; Mingyao Zhang

2009-01-01

119

Shock enhancement and control of hypersonic mixing and combustion  

Microsoft Academic Search

Experimental and computational analyses of the possibility that shock-enhanced mixing can substantially increase the rate of mixing between coflowing streams of hydrogen and air are discussed. Numerical computations indicate that the steady interaction between a weak shock in air with a coflowing hydrogen jet can be approximated by the two-dimensional time-dependent interaction between a weak shock and an initially circular

Frank E. Marble; Edward E. Zukoski; Jeffrey Jacobs; Gavin Hendricks; Ian Waitz

1990-01-01

120

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

121

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

122

Shock enhancement and control of hypersonic mixing and combustion  

NASA Technical Reports Server (NTRS)

Experimental and computational analyses of the possibility that shock-enhanced mixing can substantially increase the rate of mixing between coflowing streams of hydrogen and air are discussed. Numerical computations indicate that the steady interaction between a weak shock in air with a coflowing hydrogen jet can be approximated by the two-dimensional time-dependent interaction between a weak shock and an initially circular region filled with hydrogen imbedded in air. Experimental results obtained in a shock tube and contoured wall injector are presented. It is shown that the shock impinging process causes the light gas cylinder to split into two parts; one of these mixes rapidly with air and the other forms a stably stratified vortex pair which mixes more slowly. The geometry of the flow field and the mixing process and scaling parameters are assessed.

Marble, Frank E.; Zukoski, Edward E.; Jacobs, Jeffrey; Hendricks, Gavin; Waitz, Ian

1990-01-01

123

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

124

Infrared multiphoton ignition and combustion enhancement of natural gas. Final report, February 1988-May 1989  

SciTech Connect

The Phase I feasibility study has demonstrated the potential of using Infrared Multiphoton (IRMP) processes for ignition and combustion enhancement of natural gas. Experiments with IR lasers were conducted to investigate the effects of IRMP techniques on methane, ethane, isotopically substituted surrogates, and sensitized mixtures. Major findings include: (1) Identification of HF/DF laser as an appropriate source for IRMP; (2) Demonstration of IRMP decomposition of deuterated methane with CO{sub 2} laser; (3) Successful IRMP ignition of deuterated methane and ethane mixtures; (4) Successful IRMP ignition of methane mixtures using photo-sensitizers. These experimental findings support the concept that IRMP processes are capable of dissociating methane, other minor constituents of natural gas, or sensitizers to reactive, combustion-enhancing radicals. A comprehensive Phase II contract to bring the concept closer to commercial implementation is underway.

Lavid, M.; Poulos, A.T.

1990-08-14

125

Enhanced formation of dioxins and furans from combustion devices by addition of trace quantities of bromine  

SciTech Connect

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 tetrachloroethylene, generated as PICs from the fuel-lean combustion of methylene chloride, were enhanced by up to 3 orders of magnitude by introducing Br in the form of methylene bromide at a constant halogen molar input rate with a 1:10 Br/chlorine (Cl) molar ratio. The two chlorinated PICs in question are both potential ring growth precursors, which could lead to enhanced formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs). The experiments described in this paper expand on this earlier work by examining the effect of trace amounts of Br on the formation of PCDDs/PCDFs, in addition to other chlorinated, brominated, and mixed bromo-chloro organic PICs.

Lemieux, P.M.; Ryan, J.V. [Environmental Protection Agency, Research Triangle Park, NC (United States). Air Pollution Prevention and Control Div.] [Environmental Protection Agency, Research Triangle Park, NC (United States). Air Pollution Prevention and Control Div.

1998-12-31

126

Progress in an oxygen-carrier reaction kinetics experiment for rotary-bed chemical looping combustion  

E-print Network

The design process for an experimental platform measuring reaction kinetics in a chemical looping combustion (CLC) process is documented and justified. To enable an experiment designed to characterize the reaction kinetics ...

Jester-Weinstein, Jack (Jack L.)

2013-01-01

127

A UV light enhanced TiO2/graphene device for oxygen sensing at room temperature  

E-print Network

temperature oxygen sensor based on TiO2/graphene device was developed with an enhanced sensing performance the oxygen gas typically use potentiometric1 and amperometric sensors.2 However, their complex structures structures and improve sensing performances. To overcome the common drawbacks of the TiO2-based oxygen sensor

Cao, Wenwu

128

Experimental investigation on heat loss and combustion in methane\\/oxygen micro-tube combustor  

Microsoft Academic Search

To understand working features of a micro-tube combustor, combustion of CH4\\/O2 was carried out in three types of micro-tubes with the same outer diameter of 3mm. In the tests, combustion characteristics and heat loss in micro-tubes were studied. It is shown that when equivalence ratio was lower than unity, CH4 was not completely oxidized and a great amount of gas

Junwei Li; Beijing Zhong

2008-01-01

129

Evaluation of Novel Ceria-Supported Metal Oxides As Oxygen Carriers for Chemical-Looping Combustion  

E-print Network

is oxidized with oxygen provided by solid oxygen carrier particles, rather than with O2 direct from air reactor. In the air reactor, oxygen depleted particles are exposed to a flow of air, whereby) Reduced particles are transferred back to the air reactor for reoxidation by reaction 1, and the cycle can

Azad, Abdul-Majeed

130

Enhancement of electric oxygen-iodine laser performance using larger mode volume resonators  

E-print Network

Enhancement of electric oxygen-iodine laser performance using larger mode volume resonators Brian S.4130, 140.4780, 230.5750. The electrically driven oxygen-iodine laser (Electric- OIL) that was first report on the demonstration of an 87% enhancement in cw laser power on the 1315 nm transition of atomic

Carroll, David L.

131

Enhancement of electric oxygen-iodine laser performance using a rectangular discharge and longer gain length  

E-print Network

Enhancement of electric oxygen-iodine laser performance using a rectangular discharge and longer of Physics. doi:10.1063/1.3269811 The electrically driven oxygen-iodine laser Electri- cOIL that was first on the demonstration of a 95% enhancement in continuous-wave laser power on the 1315 nm transition of atomic iodine via

Carroll, David L.

132

Enhanced performance of an electric oxygen-iodine laser D. L. Carrolla  

E-print Network

Enhanced performance of an electric oxygen-iodine laser D. L. Carrolla , G. F. Benavidesa,b , J. W and modeling have led to continued enhancements in the Electric Oxygen-Iodine Laser (ElectricOIL) system. This continuous wave (cw) laser operating on the 1315 nm transition of atomic iodine is pumped by the production

Carroll, David L.

133

Oxygen-diffusion limited metal combustions in Zr, Ti, and Fe foils: Time- and angle-resolved x-ray diffraction studies  

NASA Astrophysics Data System (ADS)

The transient phase and chemical transformations of diffusion controlled metal combustions in bulk Zr, Ti, and Fe foils have been investigated, in situ, using novel time- and angle-resolved x-ray diffraction (TARXD). The TARXD employs monochromatic synchrotron x-rays and a fast-rotating diffracted beam chopper resolving the diffraction image temporally in time-resolution of ˜45 ?s along the azimuth on a 2D pixel array detector. The metal foil strips (10-25 ?m in thickness) are ignited using a pulsed electrical heating with a typical heating rate of ˜106 K/s. The x-ray results indicate that the combustion occurs in molten metals, producing a wide range of stoichiometric solid oxides. It reflects an enhanced oxygen solubility and mobility of molten metals with respect to those of solid metals. However, the initial oxides formed are mainly oxygen-deficient metal oxides of ZrO, TiO, and FeO/Fe3O4 —the lowest suboxides stable at these high temperatures. These transition metal monoxides further react with unreacted molten metals, yielding the secondary products of Zr3O, Ti3O, and Ti2O — but not in FeO/Fe3O4. On the other hand, the higher stoichiometric oxides of ZrO2 and TiO2 are formed in the later time only on the metal surface. These results clearly indicate that the combustion process of metal strips is diffusion limited and strongly depends on the solubility and diffusivity of oxygen into molten metals. The time-resolved diffraction data reveals no evidence for metal oxidation in solids, but a series of temperature-induced polymorphic phase transitions. The dynamic thermal expansibility of Fe measured in the present fast heating experiments is similar to those in static conditions (3.3*10-5/K vs 3.5*10-5/K for ?-Fe and 6.5*10-5/K versus 7.0*10-5/K for ?-Fe).

Wei, Haoyan; Yoo, Choong-Shik; Chen, Jing-Yin; Shen, Guoyin

2012-03-01

134

Oxygen-diffusion limited metal combustions in Zr, Ti, and Fe foils: Time- and angle-resolved x-ray diffraction studies  

SciTech Connect

The transient phase and chemical transformations of diffusion controlled metal combustions in bulk Zr, Ti, and Fe foils have been investigated, in situ, using novel time- and angle-resolved x-ray diffraction (TARXD). The TARXD employs monochromatic synchrotron x-rays and a fast-rotating diffracted beam chopper resolving the diffraction image temporally in time-resolution of {approx}45 {mu}s along the azimuth on a 2D pixel array detector. The metal foil strips (10-25 {mu}m in thickness) are ignited using a pulsed electrical heating with a typical heating rate of {approx}10{sup 6} K/s. The x-ray results indicate that the combustion occurs in molten metals, producing a wide range of stoichiometric solid oxides. It reflects an enhanced oxygen solubility and mobility of molten metals with respect to those of solid metals. However, the initial oxides formed are mainly oxygen-deficient metal oxides of ZrO, TiO, and FeO/Fe{sub 3}O{sub 4} - the lowest suboxides stable at these high temperatures. These transition metal monoxides further react with unreacted molten metals, yielding the secondary products of Zr{sub 3}O, Ti{sub 3}O, and Ti{sub 2}O - but not in FeO/Fe{sub 3}O{sub 4}. On the other hand, the higher stoichiometric oxides of ZrO{sub 2} and TiO{sub 2} are formed in the later time only on the metal surface. These results clearly indicate that the combustion process of metal strips is diffusion limited and strongly depends on the solubility and diffusivity of oxygen into molten metals. The time-resolved diffraction data reveals no evidence for metal oxidation in solids, but a series of temperature-induced polymorphic phase transitions. The dynamic thermal expansibility of Fe measured in the present fast heating experiments is similar to those in static conditions (3.3*10{sup -5}/K vs 3.5*10{sup -5}/K for {alpha}-Fe and 6.5*10{sup -5}/K versus 7.0*10{sup -5}/K for {gamma}-Fe).

Wei, Haoyan; Yoo, Choong-Shik; Chen, Jing-Yin; Shen, Guoyin (CIW); (WSU)

2012-04-30

135

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

136

Enhanced oxygen delivery by perflubron emulsion during acute hemodilution.  

PubMed

A high-concentration 90% w/v perflubron (perfluorooctyl bromide [PFOB]) emulsion (Oxygent HT) is being evaluated as an oxygen carrier for use during surgery. This study was done to assess oxygen delivery by Oxygent HT during acute normovolemic hemodilution. Anesthetized mongrel dogs, instrumented with femoral and pulmonary artery catheters, were hemodiluted to a hematocrit of 25% with 3:1 (v/v) of Ringers-lactate (R-L). Dogs were then ventilated with 100% O2 and hemodiluted to a Hct approximately 11% with 1.5 (v/v) of colloid (autologous plasma and 5% albumin). Dogs then received either 3.3 mL/kg Oxygent HT (n = 5) or 3.3 mL/kg R-L (n = 4), and were monitored for 3 hours. Total oxygen delivery (DO2), blood oxygen content, cardiac output, mixed venous PO2, and mixed venous Hb saturation was higher in Oxygent HT treated dogs compared to the R-L controls. The percentage of total DO2 contributed by perflubron-dissolved oxygen was about 8-10% and accounted for 25-30% of total oxygen consumption (VO2). The percentage of VO2 contributed by Hb-carried oxygen was significantly higher in R-L controls (46 +/- 4%) than in the treated dogs (15 +/- 3%), indicating that the availability of the perflubron-dissolved oxygen allowed for a reserve of oxygen to remain available in the red blood cells. PMID:7849918

Keipert, P E; Faithfull, N S; Bradley, J D; Hazard, D Y; Hogan, J; Levisetti, M S; Peters, R M

1994-01-01

137

Determination of fluorine, chlorine and bromine in household products by means of oxygen bomb combustion and ion chromatography.  

PubMed

A method for routine determination of fluorine, chlorine and bromine in household products was developed and validated. In this work, halogen analyses were made based on oxygen bomb combustion followed by ion chromatography (IC). The chromatographic analysis was performed by an IonPac AS19 hydroxide-selective anion-exchange column, a reagent free ion chromatograph eluent generator and an anion self-regenerating suppressor in 10 min. The response was linear (r ? 0.9995) in the entire investigated domain. The limit of detection for the halogens was in the range of 2 to 9 × 10(-3) mg/L and the limit of quantification was lower than 8 mg/Kg with 20 µL of injection volume. The certified reference material of ERM-EC 681k was pretreated using an oxygen bomb combustion procedure to demonstrate the precision of the proposed method. The quantitative analysis results obtained by IC for the target elements were 797 ± 9 mg/Kg chlorine and 786 ± 25 mg/Kg bromine, which were in good agreement with the certified values of 800 ± 4 mg/Kg chlorine, 770 ± 5 mg/Kg bromine for ERM-EC 681k, respectively. This validated method was successfully applied for the analysis of fluorine, chlorine and bromine in household product samples, and the variation of halogen contained among the tested samples was remarkable. PMID:22752184

Zhang, Shuai; Zhao, Tianbo; Wang, Jia; Qu, Xiaoling; Chen, Wei; Han, Yin

2013-01-01

138

Supplemental Oxygen (Oxygen Therapy)  

MedlinePLUS

... mind when using oxygen. Oxygen is a safe gas and is non-flammable, however, it supports combustion. Materials burn more readily in an oxygen-enriched environment. Follow these tips for safe oxygen use: Post "No Smoking" and "No Open Flames" signs in and outside ...

139

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

140

Characteristics of oxygen-blown gasification for combustible waste in a fixed-bed gasifier  

Microsoft Academic Search

With increasing environmental considerations and stricter regulations, gasification of waste is considered to be a more attractive technology than conventional incineration for energy recovery as well as material recycling. The experiment for combustible waste mixed with plastic and cellulosic materials was performed in a fixed-bed gasifier to investigate the gasification behaviour with the operating conditions. Waste pelletized to a diameter

Jae Ik Na; So Jin Park; Yong Koo Kim; Jae Goo Lee; Jae Ho Kim

2003-01-01

141

Characteristics Evaluation of a CO2-Caputuring Power Generation System with Reheat Cycle Utilizing Regenerative Oxygen-Combustion Steam-Superheater  

Microsoft Academic Search

A new CO2-capturing power generation system is proposed that can be easily realized by applying conventional technologies. In the proposed system, the temperature of middle-pressure steam in a thermal power plant is raised by utilizing oxygen-combusting regenerative steam-superheater. The generated CO2 by combusting fuel in the superheater can be easily separated and captured from the exhaust gas at condenser outlet,

Pyong Sik Pak

2006-01-01

142

Effect of Ozone Addition on Combustion Efficiency of Hydrogen: Liquid-Oxygen Propellant in Small Rockets  

NASA Technical Reports Server (NTRS)

An experimental study shows that 2 percent by weight ozone in oxygen has little effect on overall reactivity for a range of oxidant-fuel weight ratios from 1 to 6. This conclusion is based on characteristic-velocity measurements in 200-pound-thrust chambers at a pressure of 300 pounds per square inch absolute with low-efficiency injectors. The presence of 9 percent ozone in oxygen also did not affect performance in an efficient chamber. Explosions were encountered when equipment or procedure permitted ozone to concentrate locally. These experiments indicate that even small amounts of ozone in oxygen can cause operational problems.

Miller, Riley O.; Brown, Dwight D.

1959-01-01

143

Turbulence in a gaseous hydrogen-liquid oxygen rocket combustion chamber  

NASA Technical Reports Server (NTRS)

The intensity of turbulence and the Lagrangian correlation coefficient for a LOX-GH2 rocket combustion chamber was determined from experimental measurements of tracer gas diffusion. A combination of Taylor's turbulent diffusion theory and a numerical method for solving the conservation equations of fluid mechanics was used to calculate these quantities. Taylor's theory was extended to consider the inhomogeneity of the turbulence field in the axial direction of the combustion chamber, and an exponential function was used to represent the Lagrangian correlation coefficient. The results indicate that the value of the intensity of turbulence reaches a maximum of 14% at a location about 7" downstream from the injector. The Lagrangian correlation coefficient associated with this value is given by the above exponential expression where alpha = 10,000/sec.

Lebas, J.; Tou, P.; Ohara, J.

1975-01-01

144

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

145

Application of oxygen-enriched combustion for locomotive diesel engines. Phase 1  

SciTech Connect

A thermodynamic simulation is used to study the effects of oxygen-enriched intake air on the performance and nitrogen oxide (NO) emissions of a locomotive diesel engine. The parasitic power of the air separation membrane required to supply the oxygen-enriched air is also estimated. For a given constraint on peak cylinder pressure, the gross and net power outputs of an engine operating under different levels of oxygen enrichment are compared with those obtained when a high-boost turbocharged engine is used. A 4% increase in peak cylinder pressure can result in an increase in net engine power of approximately 13% when intake air with an oxygen content of 28% by volume is used and fuel injection timing is retarded by 4 degrees. When the engine is turbocharged to a higher inlet boost, the same increase in peak cylinder pressure improves power by only 4%. If part of the significantly higher exhaust enthalpies available as a result of oxygen enrichment are recovered, the power requirements of the air separator membrane can be met, resulting in substantial net power improvements. Oxygen enrichment reduces particulate and visible smoke emissions but increases NO emissions. However, a combination of retarded fuel injection timing and post-treatment of exhaust gases may be adequate to meet the locomotive diesel engine NO{sub x} standards. Exhaust gas after-treatment and heat recovery would be required to realize the full potential of oxygen enrichment. Economic analysis shows that oxygen-enrichment technology is economically feasible and provides high returns on investment. The study also indicates the strong influence of membrane parasitic requirements and exhaust energy recovery on economic benefits. To obtain an economic advantage while using a membrane with higher parasitic power requirements, it is necessary to recover a part of the exhaust energy.

Poola, R.B.; Sekar, R.R.; Assanis, D.N.

1996-09-01

146

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

147

Determination of Standard Molar Enthalpy of Formation for Crystalline endo-Tricyclo(5.2.1.0 2,6 )decane by an Isoperibol Oxygen-Bomb Combustion Calorimeter  

Microsoft Academic Search

The construction and principle of the new-established isoperibol oxygen-bomb combustion calorimeter are described. The energy equivalent (?calor) of the calorimeter has been determined from ten combustion experiments using about 0.7 g of NIST 39i benzoic acid with a certified mass energy of combustion, ?cU = ?(26434 ± 3) J g ?1 , under experimental conditions: ?calor = (13572 ± 2)

J.-T. CHEN; Z.-C. TAN; H.-T. ZHANG; L.-X. SUN

2005-01-01

148

Discharge-driven electric oxygen-iodine laser superlinear enhancement via increasing g0L  

E-print Network

Discharge-driven electric oxygen-iodine laser superlinear enhancement via increasing g0L G. F the development of an electric oxygen-iodine laser with higher output using a larger product of gain and gain length, g0L. A factor of 4.4 increase in laser power output on the 1315 nm atomic iodine transition

Carroll, David L.

149

Electric Oxygen-Iodine Laser Performance Enhancement using Larger Discharge and Resonator Mode Volumes  

E-print Network

Electric Oxygen-Iodine Laser Performance Enhancement using Larger Discharge and Resonator Mode that significantly higher power was available in the electric oxygen-iodine laser gas flow which could be extracted length of the laser cavity, plus the addition of an iodine pre-dissociator discharge are expected

Carroll, David L.

150

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

151

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

152

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

153

Evaluation of Advanced PSA and Oxygen Combustion System for Industrial Furnace Applications  

E-print Network

of use. In contrast, high purity (99.999% pure) oxygen is produced by the Y. Kwan Energy and Environmental Research Corp. Irvine, CA distillation of liquid air at a remote plant and usually transported to the point of use either as cryogenic liquid... expense items. Referring to Figure 3, the PSA system produces 90% product purity, whereas the membrane system produces 35%, and the cryogenic and liquid systems supply 99.9% oxygen. The cost curves show PSA supply to be particUlarly attractive...

Delano, M. A.; Lagree, D.; Kwan, Y.

154

Materials for temperature independent resistive oxygen sensors for combustion exhaust gas control  

Microsoft Academic Search

Acceptor and donor doped SrTi1?xFexO3?? materials for novel temperature independent resistive oxygen sensors for lean-burn engine exhaust gases were prepared and characterized by X-ray diffraction. Their electrical resistance, R, was investigated in the oxygen partial pressure range from 10?4 to 1 bar between 700°C and 1000°C. Doped and undoped samples with x=0.3 obey an R?pO2?1\\/5 power law. Undoped samples show

Ralf Moos; Wolfgang Menesklou; Hans-Jürgen Schreiner; Karl Heinz Härdtl

2000-01-01

155

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

156

Erythropoiesis-stimulating agents and other methods to enhance oxygen transport  

PubMed Central

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

2008-01-01

157

Medium-Pressure Hydrogen-Oxygen Combustion Turbine Systems for Utilization of Industrial Waste Heat  

NASA Astrophysics Data System (ADS)

Recovery of waste heat is an effective means of achieving energy conservation, and the total amount of industrial waste heat is still notable. However, the value of waste heat as an energy source is low (low exergy). Its utilization therefore requires larger recovery systems with increased costs. The concept of introducing a second, high-quality heat source in the form of H2-O2 combustion in order to improve the system's performance is presented here. System analysis of the combination effect (higher output from combined than from separate sources) was conducted. The investigation results show that the systems under consideration have the potential for significant merits under moderate conditions. The proposed combination of low- and high-quality heat sources also permits reductions in the system size and cost.

Furutani, Hirohide; Uzunow, Nikolaj

158

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 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 +/- 20% of the localized mean pressure to an acceptable range of +/- 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 arc 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

159

Output Power Enhancement of a Chemical Oxygen-Iodine Laser by Predissociated Iodine Injection  

Microsoft Academic Search

Output power enhancement of a chemical oxygen-iodine laser (COIL) by an injection of predissociated iodine was studied. Iodine molecules were dissociated into atoms by the microwave discharge prior to injection. It was determined that predissociation caused a negative effect on the output power enhancement when this technique was applied to a conventional supersonic COIL@. Model calculations revealed that the existence

Masamori Endo; Daichi Sugimoto; Hideo Okamoto; Kenzo Nanri; Taro Uchiyama; Shuzaburo Takeda; Tomoo Fujioka

2000-01-01

160

Instructions for use Role of Cerium Oxide in the Enhancement of Activity for the Oxygen  

E-print Network

Instructions for use #12;Role of Cerium Oxide in the Enhancement of Activity for the Oxygen proved to be effective for the enhancement of ORR activity.9-14 Cerium oxide (CeOx) is known to the inhibition of Pt oxide formation by the CeOx layer, of which Ce3+ was oxidized to Ce4+ instead of Pt

Tsunogai, Urumu

161

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

162

Optimization of perfluorocarbon emulsion properties for enhancing oxygen mass transfer in a bio-artificial liver support system  

Microsoft Academic Search

The oxygen carrying performance of a perfluorooctyl bromide (PFOB) emulsion is considered. The intended purpose is to enhance hepatocyte growth and function in a bio-artificial liver support system (BALSS). Such oxygen carrying emulsions have previously been used in biological systems (e.g. cell culturing). However, optimum emulsion characteristics for enhanced oxygen mass transfer have not been established nor was consideration given

F. S. Moolman; H. Rolfes; S. W. van der Merwe; W. W. Focke

2004-01-01

163

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. PMID:12676601

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

2003-01-01

164

Sulfur evolution in chemical looping combustion of coal with MnFe2O4 oxygen carrier.  

PubMed

Chemical looping combustion (CLC) of coal has gained increasing attention as a novel combustion technology for its advantages in CO2 capture. Sulfur evolution from coal causes great harm from either the CLC operational or environmental perspective. In this research, a combined MnFe2O4 oxygen carrier (OC) was synthesized and its reaction with a typical Chinese high sulfur coal, Liuzhi (LZ) bituminous coal, was performed in a thermogravimetric analyzer (TGA)-Fourier transform infrared (FT-IR) spectrometer. Evolution of sulfur species during reaction of LZ coal with MnFe2O4 OC was systematically investigated through experimental means combined with thermodynamic simulation. TGA-FTIR analysis of the LZ reaction with MnFe2O4 indicated MnFe2O4 exhibited the desired superior reactivity compared to the single reference oxides Mn3O4 or Fe2O3, and SO2 produced was mainly related to oxidization of H2S by MnFe2O4. Experimental analysis of the LZ coal reaction with MnFe2O4, including X-ray diffraction and X-ray photoelectron spectroscopy analysis, verified that the main reduced counterparts of MnFe2O4 were Fe3O4 and MnO, in good agreement with the related thermodynamic simulation. The obtained MnO was beneficial to stabilize the reduced MnFe2O4 and avoid serious sintering, although the oxygen in MnO was not fully utilized. Meanwhile, most sulfur present in LZ coal was converted to solid MnS during LZ reaction with MnFe2O4, which was further oxidized to MnSO4. Finally, the formation of both MnS and such manganese silicates as Mn2SiO4 and MnSiO3 should be addressed to ensure the full regeneration of the reduced MnFe2O4. PMID:25079636

Wang, Baowen; Gao, Chuchang; Wang, Weishu; Zhao, Haibo; Zheng, Chuguang

2014-05-01

165

Experimental study of O{sub 2}-CO{sub 2} production for the oxyfuel combustion using a Co-based oxygen carrier  

SciTech Connect

Production of O{sub 2}-CO{sub 2} mixed gases for the oxyfuel combustion using a Co-based oxygen carrier packed in a fixed bed reactor was investigated. The reaction kinetics of CoO with O{sub 2} and the decomposition kinetics of Co{sub 3}O{sub 4} in CO{sub 2} atmosphere at different temperatures were studied using thermogravimetric analysis (TGA). Both desorption and sorption processes exhibit a high reaction rate. Multiple sorption and desorption cycles indicated that Co-based oxygen carrier has high reactivity and cyclic stability. The results of X-ray diffraction indicated that Co-based oxygen carrier does not react with CO{sub 2} during the desorption stage, and this is especially important for oxyfuel combustion. The high temperature sorption process for production of O{sub 2}-CO{sub 2} gas mixtures in a fixed bed reactor packed with Co-based oxygen carrier particles through air separation with carbon dioxide as the purge gas is investigated. Oxygen is absorbed, and heat is stored by the Co-based oxygen carrier particles with air being fed. An O{sub 2}-CO{sub 2} stream can be obtained when the fixed bed is regenerated with carbon dioxide as the desorption gas. O{sub 2} fraction in the O{sub 2}-CO{sub 2} gas mixtures can be controlled by adjusting the flow rate of CO{sub 2} regeneration gas. This Co-based oxygen carrier offers potential for further study in the O{sub 2}-CO{sub 2} production for the oxyfuel coal combustion process.

Li, Z.S.; Zhang, T.; Cai, N.S. [Tsinghua University, Beijing (China)

2008-10-01

166

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. PMID:24883242

Tambutte, Eric; Allemand, Denis; Tambutte, Sylvie

2014-01-01

167

Enhanced oxidative vaporization of Cr2O3 and chromium by oxygen atoms  

NASA Technical Reports Server (NTRS)

Rates of oxidative vaporization of Cr2O3 have been found to be markedly enhanced in the presence of oxygen atoms. Investigations were conducted over the temperature range 200-1250 C. For Cr2O3 the enhancement was about 10 to the 9th power at 550 C in oxygen containing 2.5% atoms. Rapid oxidative vaporization of bare chromium was observed below 800 C, 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

168

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

169

Waste to energy operability enhancement under waste uncertainty via oxygen enrichment.  

PubMed

Waste to energy (WTE) performance is evaluated by maximization of electrical energy production and throughput, while maintaining low operational costs and complying with emission limits. Uncertainty in the quantities, composition and heating values of received wastes, pose severe operability problems and impair performance and emissions. The present work demonstrates and quantifies the possibility of improving WTE efficiency under feedstock uncertainty via oxygen enrichment of the combustion air. Acting essentially as a nitrogen depletion mechanism, oxygen enrichment has reverse effects compared to excess air (EA); synergistic use provides extended capabilities for performance improvement, without impairing final emissions, while satisfying capacity constraints. Increased oxygen enrichment is required at higher EA to maintain temperature. Lower charging rates of rich wastes (plastics, paper, etc.) or diminishing heating values, require higher oxygen enrichment or lower EA. The opposite holds for lower charging rates of poor wastes (biodegradables, biosludge, inerts, etc.) or rising heating values. The results establish the possibility of nominal designs to respond to feedstock variations and may be useful for low range excess air operation (low cost) or adiabatic operation (high EA, combustor temperature controlled by large fluegas volumes). The vector formulation facilitates digital coding for applications featuring multiple waste mixture variability. A 700000 tpa WTE facility in Athens, now under public-private-partnership contract tender is investigated. PMID:25036380

Tsiliyannis, Christos Aristeides

2014-08-19

170

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

171

High-Index-Contrast Ridge Waveguide Lasers Fabricated Via Oxygen-Enhanced Wet Thermal Oxidation  

E-print Network

High-Index-Contrast Ridge Waveguide Lasers Fabricated Via Oxygen-Enhanced Wet Thermal Oxidation Di etch plus wet thermal oxidization process is demonstrated which enables high-index- contrast (HIC radius as low as 10 µm. A wet thermal oxidation process modified through addition of

Bowers, John

172

Astrocyte-Enhanced Neuronal Survival is Mediated by Scavenging of Extracellular Reactive Oxygen Species  

Microsoft Academic Search

The survival of cultured neurons is promoted by the presence of antioxidants or astrocytes. This indicates that extracellular reactive oxygen species (ROS) impair neuronal survival and suggests that astrocytes exert their survival-enhancing effect through inactivation of these toxicants. However, to our knowledge, data supporting this hypothesis are lacking. Previously, we showed that loss of the antioxidant glutathione abolishes the neuronal

Benjamin Drukarch; Eric Schepens; Johannes C. Stoof; Cornelis H. Langeveld; Freek L. Van Muiswinkel

1998-01-01

173

Combustion optimization in a hydrogen-enhanced lean burn SI engine  

E-print Network

Lean operation of spark ignition (SI) automotive engines offers attractive performance incentives. Lowered combustion temperatures inhibit NO[sub]x pollutant formation while reduced manifold throttling minimizes pumping ...

Goldwitz, Joshua A. (Joshua Arlen), 1980-

2004-01-01

174

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

175

Efficiency evaluation of oxygen enrichment in energy conversion processes  

SciTech Connect

The extent to which energy conversion efficiencies can be increased by using oxygen or oxygen-enriched air for combustion was studied. Combustion of most fuels with oxygen instead of air was found to have five advantages: increases combustion temperature and efficiency, improves heat transfer at high temperatures, reduces nitrous oxide emissions, permits a high ration of exhaust gas recirculation and allows combustion of certain materials not combustible in air. The same advantages, although to a lesser degree, are apparent with oxygen-enriched air. The cost-effectiveness of the process must necessarily be improved by about 10% when using oxygen instead of air before such use could become justifiable on purely economic terms. Although such a modest increase appears to be attainable in real situations, this study ascertained that it is not possible to generally assess the economic gains. Rather, each case requires its own evaluation. For certain processes industry has already proven that the use of oxygen leads to more efficient plant operation. Several ideas for essentially new applications are described. Specifically, when oxygen is used with exhaust gas recirculation in external or internal combustion engines. It appears also that the advantages of pulse combustion can be amplified further if oxygen is used. When burning wet fuels with oxygen, direct steam generation becomes possible. Oxygen combustion could also improve processes for in situ gasification of coals, oil shales, peats, and other wet fuels. Enhanced oil recovery by fire flooding methods might also become more effective if oxygen is used. The cold energy contained in liquid oxygen can be substantially recovered in the low end of certain thermodynamic cycles. Further efforts to develop certain schemes for using oxygen for combustion appear to be justified from both the technical and economic viewpoints.

Bomelburg, H.J.

1983-12-01

176

Quantitative analysis of combustion by-products using resonance enhanced multiphoton ionization mass spectrometry  

SciTech Connect

We have combined one-color Resonance Enhanced Multiphoton Ionization (REMPI) Time-of-Flight Mass Spectrometry with on-line flame sampling to determine the spatial distribution of naphthalene in a pure methane + oxygen/argon(1/4) diffusion flame. Naphthalene concentrations between 100 ppbv and 6 ppmv were measured in real-time by performing gas phase standard additions to the flame sample. Liquid standard additions are commonly used to determine the relation between absorbance and species concentration in solution. Gas phase standard additions are used equivalently to quantify the relation between REMPI signal and partial pressure. By utilizing two-color REMPI, our technique can be extended to larger polycyclic aromatic hydrocarbons (PAHs) such as anthracene, perylene, and benzo[a]pyrene. Recent results showing concentration profiles of larger PAHs in the flame will be presented. The real-time measurements of absolute PAH concentrations has important applications to process monitoring and kinetic modeling of soot growth.

Gittins, C.M.; Rohlfing, E.A. [Sandia National Lab., Livermore, CA (United States)

1996-12-31

177

Gain and continuous-wave laser power enhancement with a multiple discharge electric oxygen-iodine laser  

E-print Network

Gain and continuous-wave laser power enhancement with a multiple discharge electric oxygen-iodine in an electric oxygen-iodine laser. O2 a 1 is produced by two parallel radio-frequency-excited electric.1063/1.2948860 The electrically driven oxygen-iodine laser Electri- cOIL that was first demonstrated by Carroll et al.1,2 operates

Carroll, David L.

178

The Effect of Varying Magnetic Field Gradient on Combustion Dynamic  

NASA Astrophysics Data System (ADS)

The focus of the recent experimental research is to provide control of the combustion dynamics and complex measurements (flame temperature, heat production rate, and composition of polluting emissions) for pelletized wood biomass using a non-uniform magnetic field that produces magnetic force interacting with magnetic moment of paramagnetic oxygen. The experimental results have shown that a gradient magnetic field provides enhanced mixing of the flame compounds by increasing combustion efficiency and enhancing the burnout of volatiles.

Suzdalenko, Vera; Zake, Maija; Barmina, Inesa; Gedrovics, Martins

2011-01-01

179

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

E-print Network

We investigate the effect of enhancing gravity on saturated nucleate pool boiling of oxygen for effective gravities of 1g, 6.0g, 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 (boiling curve over our applied gravity range.

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

2007-02-01

180

Effect of Hydrologic and Geochemical Conditions on Oxygen-Enhanced Bioremediation in a Gasoline-Contaminated Aquifer  

Microsoft Academic Search

Oxygen addition to enhance bioremediation of gasoline-contaminated ground water was performed in two locations of a shallow aquifer in South Carolina characterized by benzene, toluene, and methyl tert-butyl ether (MTBE) at concentrations greater than 1 mg\\/L, respectively. Oxygen addition with an oxygen-release compound (a proprietary form of magnesium peroxide [MgO2]) produced markedly different results with respect to dissolved oxygen (DO)

James E. Landmeyer; Paul M. Bradley

2003-01-01

181

Contrast enhancement for in vivo visible reflectance imaging of tissue oxygenation.  

PubMed

Results are presented illustrating a straightforward algorithm to be used for real-time monitoring of oxygenation levels in blood cells and tissue based on the visible spectrum of hemoglobin. Absorbance images obtained from the visible reflection of white light through separate red and blue bandpass filters recorded by monochrome charge-coupled devices (CCDs) are combined to create enhanced images that suggest a quantitative correlation between the degree of oxygenated and deoxygenated hemoglobin in red blood cells. The filter bandpass regions are chosen specifically to mimic the color response of commercial 3-CCD cameras, representative of detectors with which the operating room laparoscopic tower systems are equipped. Adaptation of this filter approach is demonstrated for laparoscopic donor nephrectomies in which images are analyzed in terms of real-time in vivo monitoring of tissue oxygenation. PMID:17716397

Crane, Nicole J; Schultz, Zachary D; Levin, Ira W

2007-08-01

182

Contrast Enhancement for in vivo Visible Reflectance Imaging of Tissue Oxygenation  

PubMed Central

Results are presented illustrating a straightforward algorithm to be used for real time monitoring of oxygenation levels in blood cells and tissue based on the visible spectrum of hemoglobin. Absorbance images obtained from the visible reflection of white light through separate red and blue bandpass filters recorded by monochrome CCDs are combined to create enhanced images that suggest a quantitative correlation to the degree of oxygenated and deoxygenated hemoglobin in red blood cells. The filter bandpass regions are chosen specifically to mimic the color response of commercial 3-CCD cameras, representative of detectors with which the operating room laparoscopic tower systems are equipped. Adaptation of this filter approach is demonstrated for laparoscopic donor nephrectomies in which images are analyzed in terms of real time, in vivo monitoring of tissue oxygenation. PMID:17716397

Crane, Nicole J.; Schultz, Zachary D.; Levin, Ira W.

2009-01-01

183

Combustion lean limits fundamentals and their application to a SI hydrogen-enhanced engine concept  

E-print Network

Operating an engine with excess air, under lean conditions, has significant benefits in terms of increased engine efficiency and reduced emissions. However, under high dilution levels, a lean limit is reached where combustion ...

Ayala, Ferran A. (Ferran Alberto), 1976-

2006-01-01

184

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...

185

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. PMID:20667843

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

2011-01-01

186

Characteristics Evaluation of a CO2-Caputuring Power Generation System with Reheat Cycle Utilizing Regenerative Oxygen-Combustion Steam-Superheater  

NASA Astrophysics Data System (ADS)

A new CO2-capturing power generation system is proposed that can be easily realized by applying conventional technologies. In the proposed system, the temperature of middle-pressure steam in a thermal power plant is raised by utilizing oxygen-combusting regenerative steam-superheater. The generated CO2 by combusting fuel in the superheater can be easily separated and captured from the exhaust gas at condenser outlet, and is liquefied. The superheated steam is used to drive a steam turbine power generation system. By adopting a high efficient combined cycle power generation system as an example, it has been shown that the proposed system can increase power output by 10.8%, decrease the CO2 emission amount of the total integrated system by 18.6% with power generation efficiency drop of 2.36% compared with the original power plant without CO2-capture, when superheated steam temperature is 750°C

Pak, Pyong Sik

187

Reaction kinetics of plutonium with oxygen, water and humid air: moisture enhancement of the corrosion rate  

Microsoft Academic Search

Kinetic measurements for the reactions of unalloyed plutonium with water vapor and oxygen in the 35 to 400°C range show that moisture enhancement of the corrosion rate is confined to a temperature regime below 200°C. In combination with kinetic data from literature sources and measurements with air at 25°C, the data define a rate-temperature envelope in which the corrosion reaction

John M. Haschke; Thomas H. Allen; Jerry L. Stakebake

1996-01-01

188

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

PubMed

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. PMID:23712529

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

2013-07-01

189

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

190

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

191

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. PMID:22952902

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

2012-01-01

192

Design and implementation of Carbon Monoxide and Oxygen emissions measurement in swirl-stabilized oxy-fuel combustion  

E-print Network

Oxy-fuel combustion in natural gas power generation is a technology of growing interest as it provides the most efficient means of carbon capture. Since all the emissions from these power plants are sequestered, there are ...

Sommer, Andrew (Andrew Zhang)

2013-01-01

193

Flame propagation enhancement by plasma excitation of oxygen. Part I: Effects of O{sub 3}  

SciTech Connect

The thermal and kinetic effects of O{sub 3} on flame propagation were investigated experimentally and numerically by using C{sub 3}H{sub 8}/O{sub 2}/N{sub 2} laminar lifted flames. Ozone produced by a dielectric barrier plasma discharge was isolated and measured quantitatively by using absorption spectroscopy. Significant kinetic enhancement by O{sub 3} was observed by comparing flame stabilization locations with and without O{sub 3} production. Experiments at atmospheric pressures showed an 8% enhancement in the flame propagation speed for 1260 ppm of O{sub 3} addition to the O{sub 2}/N{sub 2} oxidizer. Numerical simulations showed that the O{sub 3} decomposition and reaction with H early in the pre-heat zone of the flame produced O and OH, respectively, from which the O reacted rapidly with C{sub 3}H{sub 8} and produced additional OH. The subsequent reaction of OH with the fuel and fuel fragments, such as CH{sub 2}O, provided chemical heat release at lower temperatures to enhance the flame propagation speed. It was shown that the kinetic effect on flame propagation enhancement by O{sub 3} reaching the pre-heat zone of the flame for early oxidation of fuel was much greater than that by the thermal effect from the energy contained within O{sub 3}. For non-premixed laminar lifted flames, the kinetic enhancement by O{sub 3} also induced changes to the hydrodynamics at the flame front which provided additional enhancement of the flame propagation speed. The present results will have a direct impact on the development of detailed plasma-flame kinetic mechanisms and provided a foundation for the study of combustion enhancement by O{sub 2}(a{sup 1}{delta}{sub g}) in part II of this investigation. (author)

Ombrello, Timothy; Won, Sang Hee; Ju, Yiguang [Department of Mechanical and Aerospace Engineering, Engineering Quadrangle, Olden Street, Princeton, NJ 08544 (United States); Williams, Skip [Air Force Research Laboratory, Propulsion Directorate, 1950 Fifth Street, Wright-Patterson AFB, OH 45433 (United States)

2010-10-15

194

Cathodic current enhancement via manganese and oxygen related reactions in marine biofilms  

NASA Astrophysics Data System (ADS)

Corrosion is a threat that has economic, and environmental impacts worldwide. Many types of corrosive attack are the subject of ongoing research. One of these areas of research is microbiologically influenced corrosion, which is the enhancement and/or initiation of corrosion events caused by microorganisms. It is well known that colonies of microorganisms can enhance cathodic currents through biofilm formation. The aim of the present work was to elucidate the role of manganese in enhancing cathodic currents in the presence of biofilms. Repeated polarizations conducted in Delaware Bay waters, on biofilm coated Cr identified potentially sustainable reduction reactions. The reduction of MnO2 and the enhancement of the oxygen reduction reaction (ORR) were proven to be factors that influence cathodic current enhancement. The removal of ambient oxygen during polarizations resulted in a shutdown of cathodic current enhancement. These field data led to an exploration of the synergistic relationship between MnO2 and the ORR. Laboratory studies of the catalysis of peroxide disproportionation by MnO2 were monitored using a hanging mercury drop electrode. Experiments were run at an ambient sweater pH of 8 and pH 9, which simulated the near-surface conditions typical of cathodes immersed in seawater. Rapid reoxidation at the more basic pH was shown to allow manganese to behave as a persistent catalyst under the typical electrochemical surface conditions of a cathode. As a result a mechanism for ORR enhancement by manganese was proposed as a unique mechanism for cathodic current enhancement in biofilms. A separate field study of Delaware biofilms on stainless steel coupled to a sacrificial Al anode was carried out to identify the ORR enhancement mechanism and sustainable redox reactions at the cathode. Chemical treatments of glutaraldehyde and formaldoxime were applied to cathodes with biofilms to distinguish between enzymatic and MnO2 related ORR enhancement. The results ruled out the enzymatic catalysis of ORR and supported the catalysis by MnO2. Sustainable redox reactions at the cathode were evaluated by monitoring the cathodic current of biofilm coated stainless steel for a year under different polarization intensities. The results showed that sustainable cathodic reactions were present in marine biofilms but their influence on the cathodic current was negligible until a potential was reached where the ORR could take place. Additionally seasonal variability was observed in the enhanced cathodic current in Delaware Bay biofilms. This was attributed to the seasonal variability of manganese in the water column.

Strom, Matthew James

195

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

196

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

PubMed Central

Lithium-oxygen batteries have a great potential to enhance the gravimetric energy density of fully packaged batteries by 2–3 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 since it plays 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. PMID:24220635

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

2014-01-01

197

Combustion-derived flame generated ultrafine soot generates reactive oxygen species and activates Nrf2 antioxidants differently in neonatal and adult rat lungs  

PubMed Central

Background Urban particulate matter (PM) has been epidemiologically correlated with multiple cardiopulmonary morbidities and mortalities, in sensitive populations. Children exposed to PM are more likely to develop respiratory infections and asthma. Although PM originates from natural and anthropogenic sources, vehicle exhaust rich in polycyclic aromatic hydrocarbons (PAH) can be a dominant contributor to the PM2.5 and PM0.1 fractions and has been implicated in the generation of reactive oxygen species (ROS). Objectives Current studies of ambient PM are confounded by the variable nature of PM, so we utilized a previously characterized ethylene-combusted premixed flame particles (PFP) with consistent and reproducible physiochemical properties and 1) measured the oxidative potential of PFP compared to ambient PM, 2) determined the ability of PFPs to generate oxidative stress and activate the transcription factor using in vitro and ex vivo models, and 3) we correlated these responses with antioxidant enzyme expression in vivo. Methods We compared oxidative stress response (HMOX1) and antioxidant enzyme (SOD1, SOD2, CAT, and PRDX6) expression in vivo by performing a time-course study in 7-day old neonatal and young adult rats exposed to a single 6-hour exposure to 22.4 ?g/m3 PFPs. Results We showed that PFP is a potent ROS generator that induces oxidative stress and activates Nrf2. Induction of the oxidative stress responsive enzyme HMOX1 in vitro was mediated through Nrf2 activation and was variably upregulated in both ages. Furthermore, antioxidant enzyme expression had age and lung compartment variations post exposure. Of particular interest was SOD1, which had mRNA and protein upregulation in adult parenchyma, but lacked a similar response in neonates. Conclusions We conclude that PFPs are effective ROS generators, comparable to urban ambient PM2.5, that induce oxidative stress in neonatal and adult rat lungs. PFPs upregulate a select set of antioxidant enzymes in young adult animals, that are unaffected in neonates. We conclude that the inability of neonatal animals to upregulate the antioxidant response may, in part, explain enhanced their susceptibility to ultrafine particles, such as PFP. PMID:23902943

2013-01-01

198

Gene and Enhancer Trap Transposable Elements Reveal Oxygen Deprivation regulated Genes and their Complex Patterns of Expression in Arabidopsis  

Microsoft Academic Search

Transposon tagging with modified maize Ds-GUS constructs was used to isolate genes induced by oxygen deprivation in Arabidopsis thaliana. Seedlings of 800 gene-trap (DsG) and 600 enhancer-trap (DsE) lines were grown on vertically positioned plates for 1 week, oxygen deprived for up to 24 h and stained for GUS activity. Oxygen deprivation induced intricate patterns of gene expression in seedlings

AIRICA B AXTER-BURRELL; R UTH C HANG; S PRINGER; JULIA B AILEY-SERRES

2003-01-01

199

Combustion enhancement of a premixed flame by acoustic forcing with emphasis on role of large-scale vortical structures  

SciTech Connect

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 the flame response is investigated in the near wake region behind the stabilizer. Experimental observations combine acoustic pressure measurements, C2 radical spectroscopy, and direct-shadow spark visualization. It is shown that forcing may produce significant increases in overall combustion rate by generating periodic large-scale vortical structures. These orderly structures accelerate the entrainment and improve the mixing between incoming fresh reactants and recirculating hot gases. The magnitude of the increase is a sensitive function of forcing frequency. Data indicate that maximum combustion enhancement occurs when the forcing frequency matches the preferred mode of the hydrodynamic field in the near wake region. 13 refs.

Yu, K.; Trouve, A.; Candel, S. (Naval Weapons Center, China Lake, CA (USA) Stanford Univ., CA (USA) Ecole Centrale des Arts et Manufactures, Chatenay-Malabry (France))

1991-01-01

200

Experimental and Modeling Studies of the Characteristics of Liquid Biofuels for Enhanced Combustion  

SciTech Connect

The objectives of this project have been to develop a comprehensive set of fundamental data regarding the combustion behavior of biodiesel fuels and appropriately associated model fuels that may represent biodiesels in automotive engineering simulation. Based on the fundamental study results, an auxiliary objective was to identify differentiating characteristics of molecular fuel components that can be used to explain different fuel behavior and that may ultimately be used in the planning and design of optimal fuel-production processes. The fuels studied in this project were BQ-9000 certified biodiesel fuels that are certified for use in automotive engine applications. Prior to this project, there were no systematic experimental flame data available for such fuels. One of the key goals has been to generate such data, and to use this data in developing and verifying effective kinetic models. The models have then been reduced through automated means to enable multi-dimensional simulation of the combustion characteristics of such fuels in reciprocating engines. Such reliable kinetics models, validated against fundamental data derived from laminar flames using idealized flow models, are key to the development and design of optimal engines, engine operation and fuels. The models provide direct information about the relative contribution of different molecular constituents to the fuel performance and can be used to assess both combustion and emissions characteristics. During this project, we completed a major and thorough validation of a set of biodiesel surrogate components, allowing us to begin to evaluate the fundamental combustion characteristics for B100 fuels.

E. Meeks; A. U. Modak; C.V. Naik; K. V. Puduppakkam; C. Westbrook; F. N. Egolfopoulos; T. Tsotsis; S. H. Roby

2009-07-01

201

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...

202

Upgrading and enhanced recovery of Jobo heavy oil using hydrogen donor under in-situ combustion  

E-print Network

In-situ upgrading of oil using hydrogen donors is a new process. In particular, very little research has been conducted with respect to in-situ oil upgrading using hydrogen donor under in-situ combustion. Several papers describe the use of metal...

Huseynzade, Samir

2009-05-15

203

Enhanced Surgical Imaging: Laparoscopic Vessel Identification and Assessment of Tissue Oxygenation  

PubMed Central

Background Inherent to minimally invasive procedures are loss of tactile feedback and loss of three dimensional assessment. Tasks such as vessel identification and dissection are not trivial for the inexperienced laparoscopic surgeon. Advanced surgical imaging, such as 3-CCD (charge-coupled device) image enhancement, can be used to assist with these more challenging tasks and, in addition, offers a method to non-invasively monitor tissue oxygenation during surgery. Study Design In this study, 3-CCD image enhancement is used for the identification of vessels in 25 laparoscopic donor and partial nephrectomy cases. The algorithm is then applied to two laparoscopic nephrectomy cases involving multiple renal arteries. We also utilize the 3-CCD camera to qualitatively monitor renal parenchymal oxygenation during 10 laparoscopic donor nephrectomies (LDNs). Results The mean ROI (region of interest) intensity values obtained for the renal artery and vein (68.40 ± 8.44 and 45.96 ± 8.65, respectively) are used to calculate a threshold intensity value (59.00) that allows for objective vessel differentiation. In addition, we examined the renal parenchyma during LDNs. Mean ROI intensity values were calculated for the renal parenchyma at two distinct time points, prior to vessel stapling (non-ischemic) and just before extraction from the abdomen (ischemic). The non-ischemic mean ROI intensity values are statistically different from the ischemic mean ROI intensity values (p < 0.05), even with short ischemia times. Conclusions We have developed a technique, 3-CCD image enhancement, for the identification of vasculature and for the monitoring of parenchymal oxygenation. This technique requires no additional laparoscopic operating room equipment and has real-time video capability. PMID:18501814

Crane, Nicole J.; McHone, Ben; Hawksworth, Jason; Pearl, Jonathan P.; Denobile, John; Tadaki, Doug; Pinto, Peter A.; Levin, Ira W.; Elster, Eric A.

2009-01-01

204

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

205

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

206

Cation interdiffusion model for enhanced oxygen kinetics at oxide heterostructure interfaces.  

PubMed

An interface between the perovskite La(0.8)Sr(0.2)CoO(3-?) (LSC-113) and the K(2)NiF(4)-type (La(0.5)Sr(0.5))(2)CoO(4-?) (LSC-214) heterostructure was recently shown to enhance oxygen surface exchange and the rate of the oxygen reduction reaction (ORR) by orders of magnitude compared to either the LSC-113 or LSC-214 phase alone. This result is of interest to develop better optimized materials for solid-state electrochemical devices, e.g. solid oxide fuel cells. The effect has been attributed to the interface itself, rather than changes in the bulk LSC-113 or LSC-214 phases. Using density functional theory (DFT)-based simulations, we demonstrate that there is a ?0.9 eV (?1.3 eV) energy gain for exchanging a Sr from LSC-113(25%Sr) (LSC-113(40%Sr)) with a La from LSC-214(50%Sr). These changes in energy create a large driving force for interdiffusion across the heterostructure interface from Sr into LSC-214 and La into LSC-113. We estimate that the Sr concentrations (in the LSC-214 phase) in a typical experimental temperature range of 500-600 °C and in equilibrium with LSC-113(25%Sr) and LSC-113(40%Sr), may be about 75% Sr and 90% Sr, respectively. Based on the bulk behavior of the LSC-214 phase (Vashook et al., Solid State Ionics, 2000, 138, 99-104), an Sr enrichment from x = 0.5 to x = 0.75 in (La(1-x)Sr(x))(2)CoO(4-?) is expected to enhance the oxygen vacancy concentration by 2-2.5 orders of magnitude under typical experimental conditions. An increased vacancy concentration in LSC-214 near the interface can explain most of the enhanced oxygen kinetics observed up until now in these heterostructures. PMID:22270079

Gadre, Milind J; Lee, Yueh-Lin; Morgan, Dane

2012-02-28

207

Oxygen stabilization induced enhancement in superconducting characteristics of high-Tc oxides  

NASA Technical Reports Server (NTRS)

In an attempt to enhance the electrical and mechanical properties of the high temperature superconducting oxides, high T(sub c) composites were prepared composed of the 123 compounds and AgO. The presence of extra oxygen due to the decomposition of AgO at high temperature is found to stabilize the superconducting 123 phase. Ag is found to serve as clean flux for grain growth and precipitates as pinning center. Consequently, almost two orders of magnitude enhancement in critical current densities were also observed in these composites. In addition, these composites also show much improvement in workability and shape formation. On the other hand, proper oxygen treatment of Y5Ba6Cu11Oy was found to possibly stabilize superconducting phase with T(sub c) near 250 K. I-V, ac susceptibility, and electrical resistivity measurements indicate the existence of this ultra high T(sub c) phase in this compound. Detailed structure, microstructure, electrical, magnetic and thermal studies of the superconducting composites and the ultra high T(sub c) compound are presented and discussed.

Wu, M. K.; Chen, J. T.; Huang, C. Y.

1991-01-01

208

Low Oxygen Tension Enhances Proliferation and Maintains Stemness of Adipose Tissue-Derived Stromal Cells  

PubMed Central

Abstract Recent evidence indicates that low oxygen tension or hypoxia alters the characteristics of stem cells. The actions of hypoxia are mediated through the hypoxia-inducible factor, a critical mediator of the cellular response to hypoxia. Adipose tissue–derived stromal cells (ASCs) are one of the most promising cell sources for tissue engineering applications. This study investigated the effect of hypoxia on ASCs in terms of the ability to proliferate and differentiate. ASCs were extracted from mice and maintained under hypoxic atmosphere (2% O2) for up to eight in vitro passages. The proliferation rate was examined as a growth curve, and the potency of differentiation was evaluated. To investigate the cell characteristics, we checked several stem-cell markers and growth factors. Compared with the normoxic state (20% O2), hypoxia enhances proliferation with an approximately six- to sevenfold higher ASC expansion over 6 weeks. The expression of Oct3/4 and Nanog (stem-cell marker) and the amount of secreted growth factors were increased under the hypoxic condition. These results suggest that low oxygen tension enhances proliferation and maintains stemness of ASCs. Thus, this study emphasizes the profitability of hypoxic culture for expansion of ASCs and maintenance of their undifferentiated state for further therapeutic use. PMID:23741631

Fujita, Masanori; Tanaka, Yuji; Kojima, Itaru; Kanatani, Yasuhiro; Ishihara, Masayuki; Tachibana, Shoichi

2013-01-01

209

Analysis of Acid Gas Emissions in the Combustion of the Binder Enhanced D-Rdf by Ion Chromatography.  

NASA Astrophysics Data System (ADS)

Waste-to-energy has become an attractive alternative to landfills. One concern in this development is the release of pollutants in the combustion process. The binder enhanced d-RDF pellets satisfy the requirements of environmental acceptance, chemical/biological stability, and being storeable. The acid gas emissions of combusting d-RDF pellets with sulfur -rich coal were analyzed by ion chromatography and decreased when d-RDF pellets were utilized. The results imply the possibility of using d-RDF pellets to substitute for sulfur -rich coal as fuel, and also substantiate the effectiveness of a binder, calcium hydroxide, in decreasing emissions of SOx. In order to perform the analysis of the combustion sample, sampling and sample pretreatment methods prior to the IC analysis and the first derivative detection mode in IC are investigated as well. At least two trapping reagents are necessary for collecting acid gases: one for hydrogen halides, and the other for NOx and SOx. Factors affecting the absorption of acid gases are studied, and the strength of an oxidizing agent is the main factor affecting the collection of NOx and SOx. The absorption preference series of acid gases are determined and the absorption models of acid gases in trapping reagents are derived from the analytical results. To prevent the back-flushing of trapping reagents between impingers when leak-checking, a design for the sampling train is suggested, which can be adopted in sample collections. Several reducing agents are studied for pretreating the sample collected in alkali -permanganate media. Besides the recommendation of the hydrogen peroxide solution in EPA method, methanol and formic acid are worth considering as alternate reducing agents in the pretreatment of alkaline-permanganate media prior to IC analysis. The first derivative conductivity detection mode is developed and used in IC system. It is efficient for the detection and quantification of overlapping peaks as well as being applicable for nonoverlapping peaks.

Jen, Jen-Fon

1988-12-01

210

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

211

Identification of combustion intermediates in a low-pressure premixed laminar 2,5-dimethylfuran/oxygen/argon flame with tunable synchrotron photoionization  

SciTech Connect

Low-pressure (4.0 kPa) premixed laminar 2,5-dimethylfuran (DMF)/oxygen/argon flame with an equivalence ratio of 2.0 was studied with tunable vacuum ultraviolet (VUV) synchrotron radiation photoionization and molecular-beam mass spectrometry. Photoionization mass spectra of DMF/O{sub 2}/Ar flame were recorded and the photoionization efficiency curves of the combustion intermediates were measured. Flame species, including isomeric intermediates, are identified by comparing the measured ionization energies with those reported in literatures or those calculated with Gaussian-3 procedure. More than 70 species have been detected, including furan and its derivatives, aromatics, and free radicals. Possible reaction pathways of DMF, 2-methylfuran, and furan are proposed based on the intermediates identified. DMF can be consumed by H-abstraction and pyrolysis reactions. 2-Methylfuran and furan can be consumed by H-abstraction, H-addition and pyrolysis reactions. (author)

Wu, Xuesong; Huang, Zuohua; Wei, Lixia [State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an 710049 (China); Yuan, Tao; Zhang, Kuiwen [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China)

2009-07-15

212

Reversed flow fluidized-bed combustion apparatus  

DOEpatents

The present invention is directed to a fluidized-bed combustion apparatus provided with a U-shaped combustion zone. A cyclone is disposed in the combustion zone for recycling solid particulate material. The combustion zone configuration and the recycling feature provide relatively long residence times and low freeboard heights to maximize combustion of combustible material, reduce nitrogen oxides, and enhance sulfur oxide reduction.

Shang, Jer-Yu (Fairfax, VA); Mei, Joseph S. (Morgantown, WV); Wilson, John S. (Morgantown, WV)

1984-01-01

213

Enhanced decomposition of dimethyl phthalate via molecular oxygen activated by Fe@Fe2O3/AC under microwave irradiation.  

PubMed

In this study, we demonstrate that the decomposition of dimethyl phthalate under microwave irradiation could be greatly enhanced over Fe@Fe(2)O(3) nanowires supported on activated carbon (Fe@Fe(2)O(3)/AC). The great enhanced decomposition of dimethyl phthalate could be attributed to a unique microwave induced molecular oxygen activation process. Upon microwave irradiation, electrons could be transferred from activated carbon to zero-valent iron, and then react with molecular oxygen to form O(2)(-) and OH radicals for the decomposition of dimethyl phthalate. The deactivation and the regeneration of Fe@Fe(2)O(3)/AC catalyst were systematically studied. We also found that microwave heating could accelerate the electron transferring from AC to Fe@Fe(2)O(3) to generate more reactive oxygen species for the decomposition of DMP than conventional oil bath heating. This novel molecular oxygen activation approach may find applications for wastewater treatment and drinking water purification. PMID:22883705

Chen, Yiling; Ai, Zhihui; Zhang, Lizhi

2012-10-15

214

Measurements of peak power enhancement and power conservation in magnetically gain-modulated chemical oxygen-iodine laser  

SciTech Connect

The chemical oxygen-iodine laser (COIL) operates in the near infrared region (1.315 [mu]m) on the magnetic dipole transition between the first electronic metastable state and the basic state of atomic iodine. A periodically pulsed regime of the magnetically gain-switched chemical oxygen iodine laser was investigated. The effects of different magnetic field intensity and pulse length on the laser power pulse enhancement and the mean power conservation were studied experimentally.

Schmiedberger, J.; Kodymova, J.; Kokes, A. (Czech Academy of Sciences, Prague (Czechoslovakia). Inst. of Physics); Spalek, O. (Inst. of Inorganic Chemistry, Prague (Czechoslovakia))

1994-10-01

215

Effect of food deprivation on oxygen consumption and body composition of growth-enhanced transgenic Atlantic salmon ( Salmo salar)  

Microsoft Academic Search

The influence of food deprivation on the rate of oxygen consumption and the rate of mobilization\\/utilization of energy reserves in F2 generation growth-enhanced transgenic Atlantic salmon were compared relative to their non-transgenic counterparts, over a pre-smolt weight interval of 8 to 55 g.Throughout most of the 8 weeks of food deprivation, transgenic fish exhibited a greater rate of oxygen consumption

J. T Cook; A. M Sutterlin; M. A McNiven

2000-01-01

216

Role of Metal Coordination Structures in Enhancement of Electrocatalytic Activity of Ternary Nanoalloys for Oxygen Reduction Reaction  

SciTech Connect

The ability to harness the metal-metal and metal-oxygen coordination structures of nanoalloy catalysts is critical for catalyzing the oxygen reduction reaction because such a detailed atomic-scale structure dictates the surface binding site and strength for molecular oxygen and oxygenated intermediate species in the electrocatalytic process. This report describes the results of an investigation of the metal-metal and metal-oxygen coordination structures of ternary nanoalloys and their manipulation to enhance the electrocatalytic activity for oxygen reduction reaction. The basic hypothesis is that such atomic-scale structure can be manipulated by oxidative-reductive thermal treatment to influence the binding site and strength of molecular oxygen and oxygenated species on the nanoalloy surface. The results have revealed remarkable increases in both mass activity and specific activity for the catalysts processed by the oxidative-reductive treatment over those treated under non-reactive or low-degree oxidative atmospheres before the reductive treatment. In comparison with non-reactive-reductive treatment, an increased degree of heteroatomic alloying among the three metal components in the ternary catalysts and a decreased percentage of oxides (NiO and CoO) have been revealed by X-ray absorption fine structure spectroscopy for the catalysts treated by the oxidative-reductive treatment. An enrichment of surface Pt has also been detected by x-ray photoelectron spectroscopy for such catalysts. A combination of the increase in the heteroatomic alloying, the decrease in metal oxides, and the enrichment of surface Pt by the oxidative-reductive thermal treatment has therefore been concluded to be responsible for the enhanced electrocatalytic activity. The demonstration of this new approach to manipulating the metal-metal and metal-oxygen coordination structures forms the basis for an effective strategy in engineering ternary nanoalloy catalysts, and has provided new insights into the role of such structures in the enhancement of the electrocatalytic activity.

Wanjala, Bridgid N.; Fang, Bin; Loukrakpam, Rameshwori; Chen, Yongsheng; Engelhard, Mark H.; Luo, Jin; Yin, Jun; Yang, Lefu; Shan, Shiyao; Zhong, Chuan-Jian

2012-04-04

217

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

PubMed Central

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. PMID:24264379

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

2013-01-01

218

Lipopolysaccharide infusion enhances dynamic cerebral autoregulation without affecting cerebral oxygen vasoreactivity in healthy volunteers  

PubMed Central

Introduction Sepsis may be associated with disturbances in cerebral oxygen transport and cerebral haemodynamic function, thus rendering the brain particularly susceptible to hypoxia. The purpose of this study was to assess the impact of isocapnic hypoxia and hyperoxia on dynamic cerebral autoregulation in a human-experimental model of the systemic inflammatory response during the early stages of sepsis. Methods A total of ten healthy volunteers were exposed to acute isocapnic inspiratory hyperoxia (FIO2?=?40%) and hypoxia (FIO2?=?12%) before and after a 4-hour lipopolysaccharide (LPS) infusion (2 ng kg-1). Middle cerebral artery blood follow velocity was assessed using transcranial Doppler ultrasound, and dynamic autoregulation was evaluated by transfer function analysis. Results Transfer function analysis revealed an increase in the phase difference between mean arterial blood pressure and middle cerebral artery blood flow velocity in the low frequency range (0.07–0.20 Hz) after LPS (P<0.01). In contrast, there were no effects of either isocapnic hyperoxia or hypoxia on dynamic autoregulation, and the cerebral oxygen vasoreactivity to both hyperoxia and hypoxia was unaffected by LPS. Conclusions The observed increase in phase suggests that dynamic cerebral autoregulation is enhanced after LPS infusion and resistant to any effects of acute hypoxia; this may protect the brain from ischaemia and/or blood–brain barrier damage during the early stages of sepsis. PMID:24131656

2013-01-01

219

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

220

Enhanced phagocytosis, chemotaxis, and production of reactive oxygen intermediates by interstitial lung macrophages following acute endotoxemia.  

PubMed

Endotoxemia is associated with enhanced release of a variety of cytotoxic and/or proinflammatory mediators from locally activated tissue macrophages. The lung is highly sensitive to damage induced by endotoxin, suggesting that pulmonary macrophages are activated by this bacterially derived product to release mediators that contribute to the pathogenesis of tissue injury. In the present studies, we used a rat model of acute endotoxemia induced by a single intravenous injection of animals with lipopolysaccharide (LPS) to determine the extent to which different lung macrophage subpopulations are activated. Alveolar macrophages (AM) and interstitial macrophages (IM) were isolated sequentially from the lung by lavage, followed by digestion with collagenase and selective adherence to tissue culture dishes. Both AM and IM were found to produce superoxide anion, as well as hydrogen peroxide in response to inflammatory stimuli. AM produced greater quantities of these reactive oxygen intermediates than did IM. Treatment of rats with LPS resulted in a significant increase in production of reactive oxygen intermediates by IM, but not by AM. Similarly, while AM from untreated rats phagocytized more opsonized sheep red blood cells than did IM, LPS treatment of rats significantly enhanced phagocytosis only in IM. In addition, this treatment caused a significant increase in chemotaxis of IM towards C5a. In contrast, although LPS treatment of rats had no effect on tumor necrosis factor-alpha release by AM, a significant reduction was observed in IM. Taken together, these data demonstrate that IM play a role in the inflammatory response of the lung to acute endotoxemia. PMID:8086172

Wizemann, T M; Laskin, D L

1994-09-01

221

Large Enhancement in Oxygen Mobility in the Superconductors RBa2Cu3O7 with Increasing Rare-Earth Size.  

PubMed

Ultrasonic composite oscillator measurements of the mechanical relaxation in RBa(2)Cu(3)O(7-8) arising from oxygen hopping in the basal chain layer show enhancements in oxygen mobility of 20, 50, and 100 times for R = gadolinium, neodymium, and lanthanum, respectively, above that for R = yttrium. The use of the larger rare earths offers a practical solution to the major problem of slow oxygen diffusion in single crystals and bulk, dense material for wires and melt-textured monolithic bodies. PMID:17777029

Tallon, J L; Mellander, B E

1992-10-30

222

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

223

A novel formulation of oxygen-carrying matrix enhances liver-specific function of cultured hepatocytes  

Microsoft Academic Search

Oxygen is an important component of the cellular microenvironment, mediating cell survival, differentiation, and function. Oxygen supply is a limit- ing factor during culture of highly metabolic cells such as hepatocytes. Here we present a simple formulation of a fluorocarbon-based oxygen carrier embedded in collagen gel that increases oxygen concentration in culture 6-fold. Rat hepatocytes cultured on oxygen carrier-collagen showed

Yaakov Nahmias; Yiannos Kramvis; Laurent Barbe; Monica Casali; Francois Berthiaume; Martin L. Yarmush

2006-01-01

224

Self-assembled nanoporous Pt-based nanowire networks with enhanced oxygen-reduction activity  

E-print Network

The development of "alternative" power sources poses one of the central scientific challenges of this century. The fuel cell is one of the potential alternatives which can be used for various forms of portable power generation. But in order to stand up to batteries, the fuel cell needs to be safe, reliable and economically competitive. Even though the implementation of nano-engineered thin-film electrolytes recently caused a leap in evolution of miniaturised fuel cells, the development of a new generation of electrodes has been less effective. This situation is based on the intricate demand to enhance the oxygen-reduction activity while reducing the cost-intensive Pt content of those electrodes. Despite this central challenge, the integrity of those electrodes has to be conserved over a time span of 10000 hours. Here, we show a solution for both problems, as the nano-porous Pt-based nanowire networks investigated in this contribution guarantee for an enhanced catalytic activity which is up to a factor 13 high...

Galinski, Henning; Lin, Yang; Scherrer, Barbara; Evans, Anna; Döbeli, Max; Gauckler, Ludwig J

2014-01-01

225

Oxidation of Glyoxylic Acid by Cerium(IV): Oxygen-Induced Enhancement of the Primary Radical Concentration  

E-print Network

Oxidation of Glyoxylic Acid by Cerium(IV): Oxygen-Induced Enhancement of the Primary Radical in Ce(IV)-induced oxidation of small carbonic acids, we investigated the reaction of glyoxylic acid could be relevant to similar oxidation reactions. Introduction Over the past several decades

Steinbock, Oliver

226

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

227

Enhancement in sensitivity and detection of luminescent quenching based oxygen sensing by gold nanoparticles  

NASA Astrophysics Data System (ADS)

The field of plasmonics has shown a great promise in the enhancement of luminescence detection. Here, a simple method to enhance oxygen detection by quenching of Ru[(4,7-diphenyl-1,10-anthroline)3]2+ (or Ru[dpp]2+) in a sol-gel matrix by localized surface plasmon resonance (LSPR) of gold nanoparticles (AuNP) is presented. In the experiments, AuNP (10 +/- 1.5 nm diameter) were added to a sol that was prepared by hydrolysis of trimethoxysilane, octyltrimethoxysilane and ethanol in the presence of Ru[dpp]2+ luminophore. The resulting sol of the mixture was spincoated on glass and allowed to age in the dark for one week to form the sol-gel film. A control sample was also prepared using the procedure, except that AuNP was not added to the sol. The resulting AuNP embedded sol-gel shows 8.3 times improvement in the baseline (0% O2) intensity (I0) over the control. Moreover, there is a dramatic improvement in the sensitivity from 0.0011 per % O2 in the control to 0.059 per % O2 with AuNP, for O2 level below 15%. Signal to noise ratio also improved, thus leading to a 100-fold improvement in the detection limit. Using phaseluminometry, it was determined that there is a reduction in the luminescence lifetime when AuNP is added to the sol-gel matrix. This reduction in the lifetime can be explained by the near-field interaction between the luminophores and the AuNP.

Cheung, Maurice C.-K.; Roche, Philip J. R.; Yao, Lei; Kirk, Andrew G.; Chodavarapu, Vamsy P.

2010-06-01

228

Low oxygen tension enhances the generation of lung progenitor cells from mouse embryonic and induced pluripotent stem cells  

PubMed Central

Abstract Whole?organ decellularization technology has emerged as a new alternative for the fabrication of bioartificial lungs. Embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) are potentially useful for recellularization since they can be directed to express phenotypic marker genes of lung epithelial cells. Normal pulmonary development takes place in a low oxygen environment ranging from 1 to 5%. By contrast, in vitro ESC and iPSC differentiation protocols are usually carried out at room?air oxygen tension. Here, we sought to determine the role played by oxygen tension on the derivation of Nkx2.1+ lung/thyroid progenitor cells from mouse ESC and iPSC. A step?wise differentiation protocol was used to generate Nkx2.1+ lung/thyroid progenitors under 20% and 5% oxygen tension. On day 12, gene expression analysis revealed that Nkx2.1 and Foxa2 (endodermal and early lung epithelial cell marker) were significantly upregulated at 5% oxygen tension in ESC and iPSC differentiated cultures compared to 20% oxygen conditions. In addition, quantification of Foxa2+Nkx2.1+Pax8? cells corresponding to the lung field, with exclusion of the potential thyroid fate identified by Pax8 expression, confirmed that the low physiologic oxygen tension exerted a significant positive effect on early pulmonary differentiation of ESC and iPSC. In conclusion, we found that 5% oxygen tension enhanced the derivation of lung progenitors from mouse ESC and iPSC compared to 20% room?air oxygen tension. PMID:25347858

Garreta, Elena; Melo, Esther; Navajas, Daniel; Farre, Ramon

2014-01-01

229

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. PMID:21192843

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

2011-01-01

230

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

231

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

232

Hydroxyl radical-PLIF measurements and accuracy investigation in high pressure gaseous hydrogen/gaseous oxygen combustion  

NASA Astrophysics Data System (ADS)

In-flow species concentration measurements in reacting flows at high pressures are needed both to improve the current understanding of the physical processes taking place and to validate predictive tools that are under development, for application to the design and optimization of a range of power plants from diesel to rocket engines. To date, non intrusive measurements have been based on calibrations determined from assumptions that were not sufficiently quantified to provide a clear understanding of the range of uncertainty associated with these measurements. The purpose of this work is to quantify the uncertainties associated with OH measurement in a oxygen-hydrogen system produced by a shear, coaxial injector typical of those used in rocket engines. Planar OH distributions are obtained providing instantaneous and averaged distribution that are required for both LES and RANS codes currently under development. This study has evaluated the uncertainties associated with OH measurement at 10, 27, 37 and 53 bar respectively. The total rms error for OH-PLIF measurements from eighteen different parameters was quantified and found as 21.9, 22.8, 22.5, and 22.9% at 10, 27, 37 and 53 bar respectively. These results are used by collaborators at Georgia Institute of Technology (LES), Pennsylvania State University (LES), University of Michigan (RANS) and NASA Marshall (RANS).

Vaidyanathan, Aravind

233

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

234

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

235

Enhancement of electrical property by oxygen doping to copper phthalocyanine in inverted top emitting organic light emitting diodes  

SciTech Connect

We reported the evidence of oxygen doping to copper-phthalocyanine (CuPc) by O{sub 2}-plasma treatment to inverted top-emitting organic light-emitting diodes (ITOLEDs). In situ synchrotron-radiation photoelectron spectroscopy results showed that a new Cu-O bond appeared and the energy difference between the highest-occupied molecular orbital and E{sub F} is lowered by 0.15 eV after plasma treatment. The oxygen ions chemically interacted with Cu atoms and transferred charges to the CuPc. Thus the hole injection barrier was lowered, enhancing the electroluminescent property of ITOLEDs.

Hong, Kihyon; Kim, Kisoo; Lee, Jong-Lam [Department of Materials Science and Engineering and Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, Kyungbuk 790-784 (Korea, Republic of)

2009-11-23

236

Faster pulmonary oxygen uptake kinetics in children vs adults due to enhancements in oxygen delivery and extraction.  

PubMed

This study aimed to examine if the faster pulmonary oxygen uptake (VO2p) phase 2 in children could be explained by increased O2 availability or extraction at the muscle level. For that purpose, O2 availability and extraction were assessed using deoxyhemoglobin (HHb) estimated by near-infrared spectroscopy during moderate-intensity constant load cycling exercise in children and young adults. Eleven prepubertal boys and 12 men volunteered to participate in the study. They performed one maximal graded exercise to determine the power associated with the gas exchange threshold (GET) and four constant load exercises at 90% of GET. VO2p and HHb were continuously monitored. VO2p , HHb, and estimated capillary blood flow (Qcap) kinetics were modelled after a time delay and characterized by the time to achieve 63% of the amplitude (?) and by mean response time (MRT: time delay + ?), respectively. Mean values of ? for VO2p (P < 0.001), of MRT for HHb (P < 0.01) and of MRT for Qcap (P < 0.001) were significantly shorter in children. Faster VO2p kinetics have been shown in children; these appear due to both faster O2 extraction and delivery kinetics as indicated by faster HHb and Qcap kinetics, respectively. PMID:22353227

Leclair, E; Berthoin, S; Borel, B; Thevenet, D; Carter, H; Baquet, G; Mucci, P

2013-12-01

237

Turbulent combustion  

SciTech Connect

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

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

1993-12-01

238

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. PMID:24866391

2014-01-01

239

Enhancement of singlet oxygen production based on FRET between Coumarin tri-compound and CdSe/ZnS QDs  

NASA Astrophysics Data System (ADS)

The compatibility between coumarin-derived dendrimer (CdD)-captured silica particles (SiCdDs) and watersoluble CdSe/ZnS quantum dots (QDs) in the FRET process improved the excited state of QDs in the reaction of singlet oxygen production under LED irradiation. Sol-gel GA was successfully used to improve the binding between SiCdDs and QDs. Singlet oxygen production using QDs coated with SiCdDs through sol-gel GA was enhanced by about 80 % compared to that achieved using QDs only. The single oxygen produced by the QDs, the QDs/GA-SiCdDs complexes and the SiCdDs/GA-QDs complexes in this study could be used in the treatment of HeLa cells.

Duong, Hong Dinh; Lee, Jee Won; Rhee, Jong Il

2014-08-01

240

TECHNOLOGY DEMONSTRATION SUMMARY: THE AMERICAN COMBUSTION PYRETRON THERMAL DESTRUCTION SYSTEM AT THE U.S. EPA'S COMBUSTION FACILITY  

EPA Science Inventory

The American Combustion Pyretron Thermal Destruction System at the U.S. EPA's Combustion Research Facility. Under the auspices of the Superfund Innovative Technology Evaluation, or SITE, program, a critical assessment was made of the American Combustion Pyretron? oxygen enha...

241

A carbon-nanotube-supported graphene-rich non-precious metal oxygen reduction catalyst with enhanced performance durability.  

PubMed

A non-precious metal catalyst for oxygen reduction in acid media, enriched in graphene sheets/bubbles during a high-temperature synthesis step, has been developed from an Fe precursor and in situ polymerized polyaniline, supported on multi-walled carbon nanotubes. The catalyst showed no performance loss for 500 hours in a hydrogen/air fuel cell. The improved durability is correlated with the graphene formation, apparently enhanced in the presence of carbon nanotubes. PMID:23420477

Wu, Gang; More, Karren L; Xu, Ping; Wang, Hsing-Lin; Ferrandon, Magali; Kropf, Arthur J; Myers, Deborah J; Ma, Shuguo; Johnston, Christina M; Zelenay, Piotr

2013-04-25

242

Modulation of reactive oxygen species by antioxidants in chronic myeloid leukemia cells enhances imatinib sensitivity through survivin downregulation.  

PubMed

Survivin, a member of the inhibitor of apoptosis protein family and a target for new drugs, is modulated by reactive oxygen species in several types of neoplasms including leukemias. The aim of this study is to find mechanisms to enhance sensitivity to imatinib in imatinib-responsive cells. In this study, we demonstrated through fluorescein isothiocyanate-labeled annexin V for apoptotic cells detection and western blotting that by inhibiting catalase activity, imatinib apoptosis induction was significantly enhanced (P<0.05) through diminishing survivin expression in K562 cells. These findings might be of clinical relevance and might help improve the chemotherapeutic use of imatinib mesylate. PMID:18827562

Kwee, Jolie Kiemlian; Luque, Diogo Gomes; Ferreira, Ana Carolina dos Santos; Vasconcelos, Flavia da Cunha; Silva, Karina Lani; Klumb, Claudete Esteves; Maia, Raquel Ciuvalschi

2008-11-01

243

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

244

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

245

Gene and Enhancer Trap Transposable Elements Reveal Oxygen Deprivation?regulated Genes and their Complex Patterns of Expression in Arabidopsis  

PubMed Central

Transposon tagging with modified maize Ds–GUS constructs was used to isolate genes induced by oxygen deprivation in Arabidopsis thaliana. Seedlings of 800 gene?trap (DsG) and 600 enhancer?trap (DsE) lines were grown on vertically positioned plates for 1 week, oxygen deprived for up to 24 h and stained for GUS activity. Oxygen deprivation induced intricate patterns of gene expression in seedlings of 65 lines. The insertion site and phenotypes of 15 lines were examined. Surprisingly, none of the insertions were into genes that encode known anaerobic polypeptides. Insertions were identified within or adjacent to genes encoding proteins of regulatory, enzymatic, mitochondrial protein import and unknown function, as well as adjacent to genes encoding a putative receptor?like kinase and putative sensor?histidine kinase. Four lines had significantly lower ADH activity after 24 h of oxygen deprivation and three of these showed reduced stress tolerance. Two lines with wild?type levels of ADH were low?oxygen intolerant. Paradoxically, several lines had significantly higher ADH activity after 12 h of oxygen deprivation but reduced stress tolerance. Caffeine treatment, which increased ADH specific activity in wild?type seedlings under aerobic conditions, was sufficient to increase GUS staining in seven of the 15 lines, providing evidence that these genes may be regulated by cytosolic calcium levels. These results demonstrate the effectiveness of the Ds–GUS tagging system in the identification of genes that are regulated in response to oxygen deprivation and a calcium second messenger. PMID:12509334

BAXTER?BURRELL, AIRICA; CHANG, RUTH; SPRINGER, PATRICIA; BAILEY?SERRES, JULIA

2003-01-01

246

Oxygen Vacancy Enhanced Photocatalytic Activity of Pervoskite SrTiO3.  

PubMed

A facile and general method has been developed to fabricate oxygen vacancies on perovskite SrTiO3 (STO) nanocrystals through a controllable solid-state reaction of NaBH4 and SrTiO3 nanocrystals. STO samples with tunable color, oxygen vacancy concentration on nanocrystal surface have been synthesized. TEM results reveal that these STO samples have a crystalline core/amorphous shell structure (SrTiO3@SrTiO3-x). XPS and EPR results disclose that the oxygen vacancy concentration increases with the increase of reaction time and temperature. The concentration of oxygen vacancies calculated from TGA data, could reach 5.07% (atom) in this study. UV-vis spectra and photocatalytic results indicate that oxygen vacancies on STO surface play an important role in influencing the light absorption and photocatalytic performance. However, an excess amount of oxygen vacancies leads to a decrease of photocatalytic performance. The optimal photocatalytic activity for H2 production under UV-vis irradiation is up to 2.2 mmol h(-1) g(-1), which is about 2.3 times than the original SrTiO3, corresponding to 3.28% (atom) of oxygen vacancy concentration. PMID:25311356

Tan, Huaqiao; Zhao, Zhao; Zhu, Wan-Bin; Coker, Eric N; Li, Binsong; Zheng, Min; Yu, Weixing; Fan, Hongyou; Sun, Zaicheng

2014-11-12

247

Interagency assessment of oxygenated fuels  

SciTech Connect

Oxygenates have been used as octane enhancers in gasoline since the late 1970s, due to the phaseout of lead. During the 1980s, oxygenates came in to wider use as some States implemented oxygenated gasoline programs for the control of carbon monoxide (CO) pollution in cold weather. People with coronary artery disease are particularly sensitive to the adverse effects of this air pollutant. The first winter oxygenated gasoline program in the United States was implemented in Denver, Colorado in 1988. The 1990 Clean Air Act Amendments required the use of oxygenated gasoline in several areas of the country that failed to attain the National Ambient Air Quality Standard (NAAQS) for CO. During the winter months of 1992-1993, many new oxygenated gasoline programs were implemented to increase combustion efficiency in cold weather and thereby reduce CO emissions. Methyl tertiary-butyl ether (MTBE) has become the most widely used motor vehicle oxygenate in the U.S., though in some areas, ethanol is the dominant oxygenate used in motor vehicle fuels. Other fuel oxygenates that are in use or may potentially be used include ethyl tertiary-butyl ether (ETBE), tertiary-amyl methyl ether (TAME), diisopropyl ether (DIPE), tertiary-butyl alcohol (TBA), and methanol. Because of limitations in available data, there is less emphasis in this report on these other oxygenates. The Clean Air Act requires at least 2.7% by weight oxygen content for gasoline sold in CO nonattainment areas, and about 15% by volume MTBE or about 7.5% by volume ethanol to achieve this requirement. The purpose of this report is to provide a review of the scientific literature on oxygenated fuels and to assess effects of the winter oxygenated fuels program on air quality, water quality, fuel economy and engine performance, and public health.

NONE

1997-12-31

248

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

249

Experimental and theoretical analysis of magnetic moment enhancement in oxygen-deficient EuO  

NASA Astrophysics Data System (ADS)

We have carried out both experimental and theoretical studies of the magnetic properties of thin films of oxygen-deficient EuO. Accurate control of the oxygen vacancy concentration in these films was achieved by sputter codeposition of Eu and Eu2O3 . The films were characterized by superconducting quantum interference device, x-ray reflectometry and polarized neutron reflectometry and the magnetic moment was found to increase monotonically with oxygen vacancy concentration. The electronic structure of EuO1-x was calculated using density-functional theory (DFT+U) . In agreement with previous studies, these calculations show that oxygen vacancies act as n -type dopants in EuO and that the excess electrons preferentially populate the majority spin branch of the spin-polarized conduction band. The observed increase in the magnetic moment originating from these excess electrons was accurately determined experimentally and found to be in good agreement with our quantitative predictions.

Barbagallo, M.; Hine, N. D. M.; Cooper, J. F. K.; Steinke, N.-J.; Ionescu, A.; Barnes, C. H. W.; Kinane, C. J.; Dalgliesh, R. M.; Charlton, T. R.; Langridge, S.

2010-06-01

250

Enhanced electrocatalysis of the oxygen reduction reaction based on pattering of platinum surfaces with cyanide.  

SciTech Connect

The slow rate of the oxygen reduction reaction in the phosphoric acid fuel cell is the main factor limiting its wide application. Here, we present an approach that can be used for the rational design of cathode catalysts with potential use in phosphoric acid fuel cells, or in any environments containing strongly adsorbing tetrahedral anions. This approach is based on molecular patterning of platinum surfaces with cyanide adsorbates that can efficiently block the sites for adsorption of spectator anions while the oxygen reduction reaction proceeds unhindered. We also demonstrate that, depending on the supporting electrolyte anions and cations, on the same CN-covered Pt(111) surface, the oxygen reduction reaction activities can range from a 25-fold increase to a 50-fold decrease. This behaviour is discussed in the light of the role of covalent and non-covalent interactions in controlling the ensemble of platinum active sites required for high turn over rates of the oxygen reduction reaction.

Strmcnik, D.; Escudero-Escribano, M.; Kodama, K.; Stamenkovic, V. R.; Cuesta, A.; Markovic, N. M.; Materials Science Division; Inst. de Quimica Fisica; Toyota Central R& D Labs., Inc.

2010-08-15

251

Specificity of oxygen radical scavengers and assessment of free radical scavenger efficiency using luminol enhanced chemiluminescence.  

PubMed

The selective scavenging capacities of 19 important oxygen radical scavengers were determined by adding them individually to each of the four oxy radical standards, (superoxide, hydroxy, alkoxy and hydroperoxy, and singlet O2), calculating the percent chemiluminescence inhibited, and extrapolating O2 equivalents neutralized from baseline. The sensitivity (0.01 nm/ml) and selectivity of this method not only allows identification of individual oxygen free radical species but also quantitates the efficiency of free radical scavengers. PMID:2827676

Rao, P S; Luber, J M; Milinowicz, J; Lalezari, P; Mueller, H S

1988-01-15

252

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

PubMed

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

Zhang, Chaoyang; Wen, Yushi; Xue, Xianggui

2014-08-13

253

Asthma: Comparison of Dynamic Oxygen-enhanced MR Imaging and Quantitative Thin-Section CT for Evaluation of Clinical Treatment.  

PubMed

Purpose To compare the use of dynamic oxygen-enhanced magnetic resonance (MR) imaging with the use of quantitatively assessed computed tomography (CT) for assessment of clinical stage and evaluation of pulmonary functional change due to treatment in patients with asthma. Materials and Methods The institutional review board of Kobe University Hospital approved this study, and written informed consent was obtained from each subject. Thirty consecutive patients with asthma (17 men and 13 women; age range, 27-78 years) underwent dynamic oxygen-enhanced MR imaging, multidetector CT, and assessment of forced expiratory volume in 1 second. All patients were classified as having one of four stages of asthma according to the guidelines of the National Asthma Education and Prevention Program. Relative enhancement ratio ( RER relative enhancement ratio ) and wash-in time maps were generated by means of pixel-by-pixel analyses. Regions of interest were placed on images of the lung in all sections, and all measurements were averaged to determine mean RER relative enhancement ratio and mean wash-in time for each subject. Percentage of airway wall area and mean lung density were determined at quantitative CT. For comparison of the modalities for assessment of clinical stage, indexes of subjects at all clinical stages were compared by means of the Tukey honestly significant difference test. Evaluation of pulmonary functional improvement was assessed by correlating improvement of each index with that of forced expiratory volume. Results Mean wash-in time was significantly different among patients with asthma of different clinical stages (P < .05), but significant differences between mean RER relative enhancement ratio and percentage of airway wall area were observed for a limited number of clinical stages (P < .05). Improvement of mean RER relative enhancement ratio (r = 0.63, P = .0002) and mean wash-in time (r = -0.75, P < .0001) was significantly correlated with forced expiratory volume. Conclusion Dynamic oxygen-enhanced MR imaging has potential as a tool for assessment of clinical stage and evaluation of pulmonary functional change due to treatment in patients with asthma. © RSNA, 2014. PMID:25102370

Ohno, Yoshiharu; Nishio, Mizuho; Koyama, Hisanobu; Seki, Shinichiro; Yoshikawa, Takeshi; Matsumoto, Sumiaki; Obara, Makoto; van Cauteren, Marc; Sugimura, Kazuro

2014-12-01

254

Tripropellant combustion process  

NASA Technical Reports Server (NTRS)

The addition of small amounts of hydrogen to the combustion of LOX/hydrocarbon propellants in large rocket booster engines has the potential to enhance the system stability. Programs being conducted to evaluate the effects of hydrogen on the combustion of LOX/hydrocarbon propellants at supercritical pressures are described. Combustion instability has been a problem during the development of large hydrocarbon fueled rocket engines. At the higher combustion chamber pressures expected for the next generation of booster engines, the effect of unstable combustion could be even more destructive. The tripropellant engine cycle takes advantage of the superior cooling characteristics of hydrogen to cool the combustion chamber and a small amount of the hydrogen coolant can be used in the combustion process to enhance the system stability. Three aspects of work that will be accomplished to evaluate tripropellant combustion are described. The first is laboratory demonstration of the benefits through the evaluation of drop size, ignition delay and burning rate. The second is analytical modeling of the combustion process using the empirical relationship determined in the laboratory. The third is a subscale demonstration in which the system stability will be evaluated. The approach for each aspect is described and the analytical models that will be used are presented.

Kmiec, T. D.; Carroll, R. G.

1988-01-01

255

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

256

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

257

Nutrients and oxygen alter reservoir biochemical characters and enhance oil recovery during biostimulation.  

PubMed

Biostimulation of petroleum reservoir to improve oil recovery has been conducted in a large number of oilfields. However, the roles and linkages of organic nutrients, inorganic salts and oxygen content during biostimulation have not been effectively elucidated. Therefore, we investigated the relationships between carbon source, nitrogen source, phosphorus source, oxygen content, and microbial stimulation, oil emulsification, and oil degradation. The organic nutrients (molasses) accelerated microbial growth, and promoted oil emulsification under aerobic conditions. The added molasses also promoted metabolites production (CO2, CH4 and acetic acid) and microbial anaerobic hydrocarbon degradation under anaerobic conditions. (NH4)2HPO4 improved gases production by neutralizing the acidic production and molasses. NaNO3 could also improve gases production by inhibiting sulfate-reducing bacteria to adjust pH value. Oxygen supply was necessary for oil emulsification, but bountiful supply of oxygen aggravated oil degradation, leading the entire ranges of alkanes and some aromatic hydrocarbons were degraded. Core-flooding experiments showed an oil displacement efficiency of 13.81 % in test with air package injected, 8.56 % without air package injection, and 4.77 % in control test with air package injection and 3.61 % without air package injection. The results suggest that the combined effect of organic nutrients, inorganic salts and oxygen content determines microbial growth, while production of metabolites, oil emulsification and biodegradation alter the reservoir biochemical characters and influence oil recovery during stimulation. PMID:23700126

Gao, Peike; Li, Guoqiang; Dai, Xuecheng; Dai, Liubing; Wang, Hongbo; Zhao, Lingxia; Chen, Yuehua; Ma, Ting

2013-11-01

258

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

259

Strongly enhanced incorporation of oxygen into barium titanate based multilayer ceramic capacitors using water vapor  

NASA Astrophysics Data System (ADS)

The reoxidation of sintered BaTiO3-based multilayer ceramic capacitors (MLCCs) is currently an empirically determined, but poorly understood, procedure. In this work, the incorporation of oxygen into BaTiO3-based MLCCs has been studied by means of isotope exchange annealing (O182/O162, H12O18/H12O16 or H22O16/H12O16) and subsequent determination of the isotope profiles in the solid by secondary ion mass spectrometry. Oxygen isotope profiles in the barium titanate dielectric can be described by a bulk diffusion coefficient D? and a surface exchange coefficient k?. The values obtained for k? indicate that oxygen incorporation from H2O is much faster than from dry O2; it thus plays the key role in the reoxidation process.

Kessel, M.; De Souza, R. A.; Yoo, H.-I.; Martin, M.

2010-07-01

260

An algorithm for sensing venous oxygenation using ultrasound-modulated light enhanced by microbubbles  

NASA Astrophysics Data System (ADS)

Near-infrared spectroscopy (NIRS) can provide an estimate of the mean oxygen saturation in tissue. This technique is limited by optical scattering, which reduces the spatial resolution of the measurement, and by absorption, which makes the measurement insensitive to oxygenation changes in larger deep blood vessels relative to that in the superficial tissue. Acousto-optic (AO) techniques which combine focused ultrasound (US) with diffuse light have been shown to improve the spatial resolution as a result of US-modulation of the light signal, however this technique still suffers from low signal-to-noise when detecting a signal from regions of high optical absorption. Combining an US contrast agent with this hybrid technique has been proposed to amplify an AO signal. Microbubbles are a clinical contrast agent used in diagnostic US for their ability to resonate in a sound field: in this work we also make use of their optical scattering properties (modelled using Mie theory). A perturbation Monte Carlo (pMC) model of light transport in a highly absorbing blood vessel containing microbubbles surrounded by tissue is used to calculate the AO signal detected on the top surface of the tissue. An algorithm based on the modified Beer-Lambert law is derived which expresses intravenous oxygen saturation in terms of an AO signal. This is used to determine the oxygen saturation in the blood vessel from a dual wavelength microbubble-contrast AO measurement. Applying this algorithm to the simulation data shows that the venous oxygen saturation is accurately recovered, and this measurement is robust to changes in the oxygenation of the superficial tissue layer.

Honeysett, Jack E.; Stride, Eleanor; Deng, Jing; Leung, Terence S.

2012-02-01

261

Peculiar surface-interface properties of nanocrystalline ceria-cobalt oxides with enhanced oxygen storage capacity.  

PubMed

Peculiar surface-interface properties of nanocrystalline ceria-cobalt oxides were evidenced by X-ray diffraction, transmission electron microscopy and X-ray absorption spectroscopy. It was found that cobalt foreign cations modify the surface oxygen vacancies of ceria at the atomic level, inducing the exposure of well-defined reactive faces between the ceria-host and the cobalt oxide interface. These modifications of the surface-interface structure promoted a remarkable increase in the oxygen storage capacity of ceria nanocrystals. PMID:25231060

Qiu, Nan; Zhang, Jing; Wu, Ziyu

2014-11-01

262

The influence of oxygen on the fluorescence enhancement of fatty-acid-capped CdS nanocrystals.  

PubMed

CdS nanocrystals were synthesized in 1-octadecene (ODE) solution with oleic acid (OA) as a capping agent. Freshly prepared CdS nanocrystals showed a weak orangelike fluorescence due to defects on the particle surface. After several weeks' storage, the bulk fluorescence of CdS nanocrystals was dramatically enhanced, which gave the nanocrystals a blue or violet appearance. UV and photoluminescence (PL) measurements were employed to investigate this process. It has been found that the oxygen in the air played the most important role. The oxygen atoms could absorb on the surface of particles and a layer of oxide was gradually formed, which effectively passivated the surface of CdS nanocrystals. Interestingly, this oxidative process had no relation to UV illumination. PMID:16112677

Wang, Chunlei; Zhang, Hao; Zhang, Junhu; Li, Minjie; Han, Kun; Yang, Bai

2006-02-01

263

Enhanced native acceptor-related blue emission of ZnO thin films annealed in an oxygen ambient  

NASA Astrophysics Data System (ADS)

The thermodynamic behaviors of charged point defects in unintentionally-doped ZnO thin films were investigated. The as-grown sample displayed two different types of blue-emission bands: one at ˜2.95 eV from native-donor zinc interstitial (Zn i ) and the other at ˜3.17 eV from native-acceptor zinc vacancies (V Zn ). In the samples annealed at oxygen ambience, V Zn -related emission was dramatically enhanced, and Zn i -related emission was drastically reduced. The behavior was observed to become more apparent when the annealing temperature was increased. The results can be explained by both the increased generation probability and the lowered formation enthalpy of V Zn in an oxygen-rich environment, particularly at higher temperatures.

Shim, Eunhee; Lee, Choeun; Jung, Eiwhan; Lee, Jinyong; Kim, Doo Soo; Lee, Youngmin; Kim, Deuk Young; Lee, Sejoon

2012-06-01

264

Enhancement on the Hypocrellin B Singlet Oxygen Generation Quantum Yield in the Presence of Rare Earth Ions  

NASA Astrophysics Data System (ADS)

This paper shows a study of the optical properties of the photosensitizer hypocrellin B and its complexes formed with the rare earth ions lanthanum, europium and terbium, in ethanol and dimethyl sulfoxide (DMSO) solutions, with the purpose of verify its potentiality for use in Photodynamic Therapy. Indeed, lanthanide ions are able to modify hypocrellin B energy levels and radiative decay probabilities. Lifetime and infrared emission measurements were employed in order to reveal the capacity of the complexes at generating singlet oxygen. Hypocrellin B complex with lanthanum in ethanol showed the best results regarding ideal photosensitizers, since it displaced hypocrellin B absorption peak at 584 nm to 614 nm, as well as enhanced singlet oxygen generation from 0.47 to 0.62 (reference: methylene blue, ?? = 0,52).

Toffoli, Daniel José; Gomes, Laércio; Junior, Nilson Dias Vieira; Courrol, Lilia Coronato

2008-04-01

265

Measuring Absolute Oxygen Pressure  

NASA Technical Reports Server (NTRS)

Sensor determines absolute pressure of oxygen without reference pressure source. Absolute oxygen pressure transducer with control circuit enables measurement without reference pressure. Transducer, two part device, combines solid electrolyte membranes sensor with diffusional orifice. Device adapted for direct control of oxygen pressure in combustion mixtures.

Richter, R.

1985-01-01

266

Enhanced oxygen uptake rates in dragonfly nymphs ( Somatochlora cingulata ) as an indication of stress from naphthalene  

Microsoft Academic Search

The problem of pollutant bioaccumulation and subsequent physiological trauma is often reflected in the oxygen-uptake rate either through disrupted metabolism or in the mobilization of a compensatory homeostatic mechanism. Consequently, the respiration rate provides a critical index of environmental suitability and the cost for survival. While the resort to diversity indices to assess areas of stress is conloletely valid, such

Manuel Correa; Robert Coler

1983-01-01

267

Enhanced Oxygen Delivery Reverses Anaerobic Metabolic States in Prolonged Sandwich Rat Hepatocyte Culture  

Microsoft Academic Search

It must be assumed that current petri dish primary hepatocyte culture models do not supply sufficient amounts of oxygen and thus cause anaerobic metabolism of the cells. This is contrary to the physiologic state of the cells.In vivothe liver is a highly vascularized organ with a rather high blood flow rate of a mixture of arterial and venous blood. The

A. Bader; N. Frühauf; M. Tiedge; M. Drinkgern; L. De Bartolo; J. T. Borlak; G. Steinhoff; A. Haverich

1999-01-01

268

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

269

Enhancing the Oxygen Plasma Resistance of Low-k Methylsilsesquioxane by H2 Plasma Treatment  

Microsoft Academic Search

The organic silsesquioxane, methylsilsesquioxane (MSQ), has a low dielectric constant because of its low film density compared to thermal oxide. However, the quality of the MSQ film is degraded by the damage caused by oxygen plasma and hygroscopic behavior during photoresist stripping. In this work, we have studied the ability of H2 plasma treatment to improve the quality of MSQ.

Po-Tsun Liu; Ting-Chang Chang; Yi-Shian Mor; Simon M. Sze

1999-01-01

270

Pt-Cu bimetallic electrocatalysts with enhanced catalytic properties for oxygen reduction.  

PubMed

A highly active Pt-Cu bimetallic catalyst for the electrocatalytic oxygen reduction reaction, with an average diameter of 2.9 nm and a Cu/Pt ratio of 0.30 for the bimetallic nanoparticles, was prepared by capturing Pt-Cu alloy nanoparticles on melem-modified carbon, followed by removing 90% of copper from the alloy NPs. PMID:25089299

Zhu, Chun-Mei; Gao, Ang; Wang, Yuan; Liu, Yan

2014-10-16

271

The positive influence of boron-doped graphene for its supported Au clusters: enhancement of SERS and oxygen molecule adsorption.  

PubMed

The interactions between Au clusters and graphene sheets with and without doping have been studied systematically. It is found that B-doped graphene is a good support for Au clusters, not only because of the charge transfer from the graphene sheet to its supported Au clusters, but also due to its stronger interaction at the interface resulting from the doped B atom, which will facilitate more electrons being transferred to the upper surface of the Au cluster. This is good for surface-enhanced Raman scattering (SERS) and molecule oxygen adsorption, beneficial to the material preparation and apparatus design for high active SERS substrates and nano-catalysts. PMID:22955956

Kong, Xiangkai; Sun, Zhiyuan; Chen, Qianwang

2012-10-21

272

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...

273

Gain and continuous-wave laser power enhancement with a multiple discharge electric oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Herein the authors report on the demonstration of a 70% enhancement in gain and 98% enhancement in continuous-wave laser power on the 1315nm transition of atomic iodine via an increase in flow rates and pressure using multiple discharges in an electric oxygen-iodine laser. O2(a?1) is produced by two parallel radio-frequency-excited electric discharges sustained in an O2-He-NO gas mixture, a secondary discharge predissociated the molecular iodine, and I(P1/22) is then pumped using energy transferred from O2(a?1). A gain of 0.17%cm-1 was obtained and the total laser output power was 12.3W.

Zimmerman, J. W.; Woodard, B. S.; Benavides, G. F.; Carroll, D. L.; Verdeyen, J. T.; Palla, A. D.; Solomon, W. C.

2008-06-01

274

Enhanced catalytic electrochemical reduction of dissolved oxygen with ultraclean cucurbituril[7]-capped gold nanoparticles  

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information (ESI) available: Experimental methods, AuNP concentration calculation, UV-Visible and TEM pictures. See DOI: 10.1039/c4nr01967a

Lanterna, Anabel; Pino, Eduardo; Doménech-Carbó, Antonio; González-Béjar, María; Pérez-Prieto, Julia

2014-07-01

275

Enhanced uptake of dissolved oxygen and glucose by Escherichia coli in a turbulent flow  

Microsoft Academic Search

Laboratory experiments were conducted to study the effect of turbulence on Escherichia coli cells in an oscillating grid reactor under conditions of no oxygen transfer to the liquid phase. Fluid flow was quantified\\u000a at a submillimeter resolution using a particle image velocimetry measuring technique. The root-mean-square estimates of the\\u000a velocity gradient tensor components indicated the dominance of shear rate deformation

Amer Al-Homoud; Miki Hondzo

2008-01-01

276

Strongly enhanced incorporation of oxygen into barium titanate based multilayer ceramic capacitors using water vapor  

SciTech Connect

The reoxidation of sintered BaTiO{sub 3}-based multilayer ceramic capacitors (MLCCs) is currently an empirically determined, but poorly understood, procedure. In this work, the incorporation of oxygen into BaTiO{sub 3}-based MLCCs has been studied by means of isotope exchange annealing ({sup 18}O{sub 2}/{sup 16}O{sub 2}, {sup 1}H{sub 2}{sup 18}O/{sup 1}H{sub 2}{sup 16}O or {sup 2}H{sub 2}{sup 16}O/{sup 1}H{sub 2}{sup 16}O) and subsequent determination of the isotope profiles in the solid by secondary ion mass spectrometry. Oxygen isotope profiles in the barium titanate dielectric can be described by a bulk diffusion coefficient D* and a surface exchange coefficient k*. The values obtained for k* indicate that oxygen incorporation from H{sub 2}O is much faster than from dry O{sub 2}; it thus plays the key role in the reoxidation process.

Kessel, M.; De Souza, R. A.; Martin, M. [Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen (Germany); Yoo, H.-I. [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)

2010-07-12

277

Inhibition of Pathogenic Enteric Bacteria by Hyperbaric Oxygen: Enhanced Antibacterial Activity in the Absence of Carbon Dioxide  

PubMed Central

The antibacterial effects of 24-h exposures to high-pressure oxygen in relation to environmental CO2 were studied at 3 atm absolute (ata) and at 1 ata. Eight gram-negative, aerobic and facultatively aerobic, pathogenic enteric bacteria (Salmonella typhosa, Salmonella paratyphi, Salmonella schottmuelleri, Shigella dysenteriae, Shigella flexneri, Proteus vulgaris, Pseudomonas aeruginosa, and Escherichia coli) were exposed as shallow-broth cultures and agar surface cultures. Although broths supplemented with 0.2% glucose permitted some growth of Salmonella typhosa, Salmonella schottmuelleri, Shigella dysenteriae, and Shigella flexneri during exposure to high-pressure oxygen in the presence of CO2, the other species grew only after the exposure, indicating a bacteriostatic effect. Both bacteriostatic and bactericidal effects were demonstrated on the surface of Trypticase soy agar, where killing of Salmonellea typhosa, Proteus vulgaris, and Pseudomonas aeruginosa was significantly greater after exposure to pure O2 at 3 ata than at 1 ata. At 3 ata, significantly more killing occurred upon exposure of all species (except Shigella dysenteriae and S. flexneri) on an agar surface to 100% O2 as compared with exposure to a mixture of 95% O2 + 5% CO2. Thus, deprivation of CO2 during exposure to pure O2 enhanced the bactericidal effect of high-pressure oxygen. PMID:238466

Bornside, George H.; Pakman, Leonard M.; Ordonez, Alfred A.

1975-01-01

278

Enhanced Interaction of Vibrio cholerae Virulence Regulators TcpP and ToxR under Oxygen-Limiting Conditions  

PubMed Central

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

2014-01-01

279

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. PMID:20133799

Mass, Tali; Genin, Amatzia; Shavit, Uri; Grinstein, Mor; Tchernov, Dan

2010-01-01

280

Oxygen stabilization induced enhancement in J(sub c) and T(sub c) of superconducting oxides  

NASA Technical Reports Server (NTRS)

In an attempt to enhance the electrical and mechanical properties of the high temperature superconducting oxides, high T(sub c) composites were prepared composed of the 123 compounds and AgO. The presence of extra oxygen due to the decomposition of AgO at high temperature is found to stabilize the superconducting 123 phase. Ag is found to serve as clean flux for grain growth and precipitates as pinning center. Consequently, almost two orders of magnitude enhancement in critical current densities were also observed in these composites. In addition, these composites also show much improvement in workability and shape formation. On the other hand, proper oxygen treatment of Y5Ba6Cu11Oy was found to possibly stabilize superconducting phase with T(sub c) near 250 K. I-V, ac susceptibility, and electrical resistivity measurements indicate the existence of this ultra high T(sub c) phase in this compound. Detailed structure, microstructure, electrical, magnetic and thermal studies of the superconducting composites and the ultra high T(sub c) compound are presented and discussed.

Wu, M. K.; Chen, J. T.; Huang, C. Y.

1990-01-01

281

Flow enhances photosynthesis in marine benthic autotrophs by increasing the efflux of oxygen from the organism to the water.  

PubMed

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 CO(2). 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. PMID:20133799

Mass, Tali; Genin, Amatzia; Shavit, Uri; Grinstein, Mor; Tchernov, Dan

2010-02-01

282

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

283

Effect of oxygen addition to methane on growth of vertically oriented carbon nanotubes by radio-frequency plasma-enhanced chemical-vapor deposition  

SciTech Connect

We have investigated the effect of oxygen addition to methane on the growth of vertically oriented carbon nanotubes (VCNTs) by radio-frequency plasma-enhanced chemical-vapor deposition (RFCVD). By adding moderate concentrations of oxygen to methane during RFCVD, highly crystalline VCNTs were densely grown at 430 deg. C. With increasing oxygen concentration, the length of the VCNTs was increased and the linearity was degraded, whereas when excess oxygen was added to methane, no VCNTs were grown. Plasma states were investigated by optical emission spectroscopy during RFCVD. In the case of RFCVD with oxygen added to methane, peaks due to CO and OH radicals were dominant. The CO species appear to be one of the key factors in the growth of well-crystallized VCNTs. Moreover, VCNTs were grown at temperatures as low as 350 deg. C with the addition of moderate amounts of oxygen to methane in RFCVD.

Ikuno, Takashi; Honda, Shin-ichi; Kamada, Kazunori; Oura, Kenjiro; Katayama, Mitsuhiro [Department of Electronic Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)

2005-05-15

284

Oxygen-enhanced 3D radial ultrashort echo time magnetic resonance imaging in the healthy human lung.  

PubMed

The purpose of this work was to use 3D radial ultrashort echo time (UTE) MRI to perform whole-lung oxygen-enhanced (OE) imaging in humans. Eight healthy human subjects underwent two 3D radial UTE MRI acquisitions (TE?=?0.08?ms): one while breathing 21% O2 and the other while breathing 100% O2 . Scans were each performed over 5?min of free breathing, using prospective respiratory gating. For comparison purposes, conventional echo time (TE?=?2.1?ms) images were acquired simultaneously during each acquisition using a radial " outward-inward" k-space trajectory. 3D percent OE maps were generated from these images. 3D OE maps showing lung signal enhancement were generated successfully in seven subjects (technical failure in one subject). Mean percent signal enhancement was 6.6%?±?1.8%, near the value predicted by theory of 6.3%. No significant enhancement was seen using the conventional echo time data, confirming the importance of UTE for this acquisition strategy. 3D radial UTE MRI shows promise as a method for OE MRI that enables whole-lung coverage and isotropic spatial resolution, in comparison to existing 2D OE methods, which rely on a less time-efficient inversion recovery pulse sequence. These qualities may help OE MRI become a viable low-cost method for 3D imaging of lung function in human subjects. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24984695

Kruger, Stanley J; Fain, Sean B; Johnson, Kevin M; Cadman, Robert V; Nagle, Scott K

2014-12-01

285

Effects of Enhanced External Counterpulsation on Arterial Stiffness and Myocardial Oxygen Demand in Patients with Chronic Angina Pectoris  

PubMed Central

Enhanced external counterpulsation (EECP) is a non-invasive modality for treatment of symptomatic coronary disease (CAD) in patients not amenable to revascularization procedures. However, the mechanism(s) underlying the benefits of EECP remain unknown. We hypothesized that reductions in arterial stiffness and aortic wave reflection are a therapeutic target for EECP. CAD patients with chronic angina pectoris were randomized (2:1 ratio) to either 35 1-hr sessions of EECP (n=28) or Sham-EECP (n=14). Central and peripheral arterial pulse wave velocity (PWV) and aortic wave reflection (augmentation index; AIx) were measured using applanation tonometry before, and after 17 and 35 1-hr treatment sessions. Wasted left ventricular pressure energy and aortic systolic tension time index, markers of left-ventricular myocardial oxygen demand were derived from the synthesized aortic pressure wave. Exercise duration, anginal threshold, and peak oxygen consumption were measured using a graded treadmill test. Central arterial stiffness and AIx were reduced following 17- and 35-sessions in the treatment group. Measures of peripheral arterial stiffness were reduced following 35 sessions in the treatment group. Changes in aortic pressure wave reflection resulted in decreased measures of myocardial oxygen demand and wasted left ventricular energy. No changes in either central or peripheral arterial stiffness were observed in the Sham group. Furthermore, measures of exercise capacity were improved in the EECP group, but unchanged in the Sham group. In conclusion, EECP therapy reduces central and peripheral arterial stiffness, which may explain improvements in myocardial oxygen demand in patients with chronic angina pectoris following treatment. PMID:21420062

Casey, Darren P.; Beck, Darren T.; Nichols, Wilmer W.; Conti, C. Richard; Choi, Calvin Y.; Khuddus, Matheen A.; Braith, Randy W.

2011-01-01

286

Effects of enhanced external counterpulsation on arterial stiffness and myocardial oxygen demand in patients with chronic angina pectoris.  

PubMed

Enhanced external counterpulsation (EECP) is a noninvasive technique for treatment of symptomatic coronary artery disease in patients not amenable to revascularization procedures. However, the mechanisms underlying the benefits of EECP remain unknown. We hypothesized that decreases in arterial stiffness and aortic wave reflection are a therapeutic target for EECP. Patients with coronary artery disease and chronic angina pectoris were randomized (2:1 ratio) to 35 1-hour sessions of EECP (n = 28) or sham EECP (n = 14). Central and peripheral arterial pulse-wave velocity and aortic wave reflection (augmentation index) were measured using applanation tonometry before, and after 17 and 35 1-hour treatment sessions. Wasted left ventricular pressure energy and aortic systolic tension-time index, markers of left-ventricular myocardial oxygen demand, were derived from the synthesized aortic pressure wave. Exercise duration, anginal threshold, and peak oxygen consumption were measured using a graded treadmill test. Central arterial stiffness and augmentation index were decreased after 17 and 35 sessions in the treatment group. Measurements of peripheral arterial stiffness were decreased after 35 sessions in the treatment group. Changes in aortic pressure wave reflection resulted in decreased measurements of myocardial oxygen demand and wasted left ventricular energy. No changes in central or peripheral arterial stiffness were observed in the sham group. Furthermore, measurements of exercise capacity were improved in the EECP group but unchanged in the sham group. In conclusion, EECP therapy decreases central and peripheral arterial stiffness, which may explain improvements in myocardial oxygen demand in patients with chronic angina pectoris after treatment. PMID:21420062

Casey, Darren P; Beck, Darren T; Nichols, Wilmer W; Conti, C Richard; Choi, Calvin Y; Khuddus, Matheen A; Braith, Randy W

2011-05-15

287

Ames Hybrid Combustion Facility  

NASA Technical Reports Server (NTRS)

The report summarizes the design, fabrication, safety features, environmental impact, and operation of the Ames Hybrid-Fuel Combustion Facility (HCF). The facility is used in conducting research into the scalability and combustion processes of advanced paraffin-based hybrid fuels for the purpose of assessing their applicability to practical rocket systems. The facility was designed to deliver gaseous oxygen at rates between 0.5 and 16.0 kg/sec to a combustion chamber operating at pressures ranging from 300 to 900. The required run times were of the order of 10 to 20 sec. The facility proved to be robust and reliable and has been used to generate a database of regression-rate measurements of paraffin at oxygen mass flux levels comparable to those of moderate-sized hybrid rocket motors.

Zilliac, Greg; Karabeyoglu, Mustafa A.; Cantwell, Brian; Hunt, Rusty; DeZilwa, Shane; Shoffstall, Mike; Soderman, Paul T.; Bencze, Daniel P. (Technical Monitor)

2003-01-01

288

Discharge-driven electric oxygen-iodine laser superlinear enhancement via increasing g0L.  

PubMed

The authors report the development of an electric oxygen-iodine laser with higher output using a larger product of gain and gain length, g0L. A factor of 4.4 increase in laser power output on the 1315 nm atomic iodine transition was achieved with a factor of 3 increase in gain length. I(2P1/2) is pumped using energy transferred from O2(a1?) produced by flowing a gas mixture of O2-He-NO through three coaxial geometry radio-frequency discharges. Continuous wave (CW) average total laser power of 481 W was extracted with g0L=0.042. PMID:22555687

Benavides, G F; Zimmerman, J W; Woodard, B S; Day, M T; King, D M; Carroll, D L; Palla, A D; Verdeyen, J T; Solomon, W C

2012-05-01

289

Effect of Li +-ion on enhancement of photoluminescence in Gd 2O 3:Eu 3+ nanophosphors prepared by combustion technique  

Microsoft Academic Search

Gd2O3:Eu3+ (4mol%) nanophosphor co-doped with Li+ ions have been synthesized by low-temperature solution combustion technique in a short time. Powder X-ray diffractometer (PXRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV–VIS and photoluminescence (PL) techniques have been employed to characterize the synthesized nanoparticles. It is found that the lattice of Gd2O3:Eu3+ phosphor transforms from monoclinic to cubic as

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

2011-01-01

290

The enhancement of low-temperature combustion of diesel PM through concerted application of FBC and perovskite  

Microsoft Academic Search

In this study, we attempted to improve diesel particulate matter (PM) combustion by the simultaneous application of a fuel-born catalyst and a perovskite catalyst. The experiment was simulated by mixing fuel-borne catalyst (FBC)-incorporated PM with perovskite catalyst in a physical manner. FBC-incorporated PM was achieved satisfactorily using a self-constructed PM generator. Through temperature-programmed oxidation (TPO), the catalyst combination of Fe\\/Ce

Dae-Won Lee; Ju Young Sung; Jai Hyun Park; Yoon-Ki Hong; Seong Ho Lee; Seung-Hoon Oh; Kwan-Young Lee

2010-01-01

291

Evidence for enhanced phosphorus regeneration from marine sediments overlain by oxygen depleted waters  

SciTech Connect

Phosphorus regeneration and burial fluxes determined from in situ benthic flux chamber and solid phase measurements at sites on the Californian continental margin, Peruvian continental slope, North Carolina continental slope, and from the Santa Monica basin, California are reported. Comparison of these sites indicates that O{sub 2}-depleted bottomwaters enhance P regeneration from sediments, diminishing overall phosphorus burial efficiency. Based on these observations, a positive feedback, linking ocean anoxia, enhanced benthic phosphorus regeneration, and marine productivity is proposed. On shorter timescales, these results also suggest that O{sub 2} depletion in coastal regions caused by eutrophication may enhance P regeneration from sediments, thereby providing additional P necessary for increased biological productivity. 42 refs., 2 figs., 2 tabs.

Ingall, E.; Jahnki, R. [Skidaway Institute of Oceanography, Savannah, GA (United States)] [Skidaway Institute of Oceanography, Savannah, GA (United States)

1994-06-01

292

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

293

Engineering the oxygen sensing regulation results in an enhanced recombinant human hemoglobin production by Saccharomyces cerevisiae.  

PubMed

Efficient production of appropriate oxygen carriers for transfusions (blood substitutes or artificial blood) has been pursued for many decades, and to date several strategies have been used, from synthetic polymers to cell-free hemoglobin carriers. The recent advances in the field of metabolic engineering also allowed the generation of different genetically modified organisms for the production of recombinant human hemoglobin. Several studies have showed very promising results using the bacterium Escherichia coli as a production platform, reporting hemoglobin titers above 5% of the total cell protein content. However, there are still certain limitations regarding the protein stability and functionality of the recombinant hemoglobin produced in bacterial systems. In order to overcome these limitations, yeast systems have been proposed as the eukaryal alternative. We recently reported the generation of a set of plasmids to produce functional human hemoglobin in Saccharomyces cerevisiae, with final titers of active hemoglobin exceeding 4% of the total cell protein. In this study, we propose a strategy for further engineering S. cerevisiae by altering the oxygen sensing pathway by deleting the transcription factor HAP1, which resulted in an increase of the final recombinant active hemoglobin titer exceeding 7% of the total cellular protein. Biotechnol. Bioeng. 2015;112: 181-188. © 2014 Wiley Periodicals, Inc. PMID:25082441

Martínez, José L; Liu, Lifang; Petranovic, Dina; Nielsen, Jens

2015-01-01

294

EGR control device for internal combustion engine  

Microsoft Academic Search

This patent describes an EGR control device for an internal combustion engine comprising an EGR control valve installed in EGR passageway communicating with an exhaust system and an intake system of an internal combustion engine, an oxygen sensor for detecting the oxygen content of the intake air installed in the downstream of the opening of the EGR passageway in the

M. Nishida; N. Inoue; Y. Asayama; H. Suzuki

1988-01-01

295

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

296

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

297

Enhanced Oxygen Reduction Activity In Acid By Tin-Oxide Supported Au Nanoparticle Catalysts  

SciTech Connect

Gold nanoparticles supported on hydrous tin-oxide (Au-SnO{sub x}) are active for the four-electron oxygen reduction reaction in an acid electrolyte. The unique electrocatalytic of the Au-SnO is confirmed by the low amount of peroxide detected with rotating ring-disk electrode voltammetry and Koutecky-Levich analysis. In comparison, 10 wt % Au supported on Vulcan carbon and SnO{sub x} catalysts both produce significant peroxide in the acid electrolyte, indicating only a two-electron reduction reaction. Characterization of the Au-SnO{sub x} catalyst reveals a high-surface area, amorphous support with 1.7 nm gold metal particles. The high catalytic activity of the Au-SnO is attributed to metal support interactions. The results demonstrate a possible path to non-Pt catalysts for proton exchange membrane fuel cell cathodes.

Baker,W.; Pietron, J.; Teliska, M.; Bouwman, P.; Ramaker, D.; Swider-Lyons, K.

2006-01-01

298

Enhanced performance from a hybrid quenchometric deoxyribonucleic Acid (DNA) silica xerogel gaseous oxygen sensing platform.  

PubMed

A complex of salmon milt deoxyribonucleic acid (DNA) and the cationic surfactant cetyltrimethylammonium (CTMA) forms an organic-soluble biomaterial that can be readily incorporated within an organically modified silane-based xerogel. The photoluminescence (PL) intensity and excited-state luminescence lifetime of tris(4,7'-diphenyl-1,10'-phenanathroline) ruthenium(II) [(Ru(dpp)3](2+), a common O2 responsive luminophore, increases in the presence of DNA-CTMA within the xerogel. The increase in the [Ru(dpp)3](2+)excited-state lifetime in the presence of DNA-CTMA arises from DNA intercalation that attenuates one or more non-radiative processes, leading to an increase in the [Ru(dpp)3](2+) excited-state lifetime. Prospects for the use of these materials in an oxygen sensor are demonstrated. PMID:25280266

Zhou, Bin; Liu, Ke; Liu, Xin; Yung, Ka Yi; Bartsch, Carrie M; Heckman, Emily M; Bright, Frank V; Swihart, Mark T; Cartwright, Alexander N

2014-11-01

299

Enhanced production of validamycin A by H2O2-induced reactive oxygen species in fermentation of Streptomyces hygroscopicus 5008.  

PubMed

A novel fermentation strategy to enhance antibiotics production was demonstrated by inducing reactive oxygen species (ROS), and validamycin A (VAL-A) production by Streptomyces hygroscopicus 5008 in agro-industrial residues containing medium was taken as an example. By optimizing H2O2 amount and addition time, the intracellular ROS level was increased, and VAL-A production titer was enhanced by 40% on day 4 when 25 ?M H2O2 was added at 8th h of fermentation. Addition of diphenyleneiodonium chloride (ROS inhibitor) reduced the H2O2 induction effect. The transcription level of eight VAL-A structure genes was enhanced by ROS, and activities of glucose-6-phosphate dehydrogenase and ValG enzyme were increased while glyceraldehyde 3-phosphate dehydrogenase activity was inhibited. This work demonstrated that ROS induction was a useful strategy for VAL-A fermentation, and the information on gene transcription and enzyme activities may be helpful to further understanding the mechanism of ROS effect on the antibiotic biosynthesis. PMID:20952185

Wei, Zhen-Hua; Bai, Linquan; Deng, Zixin; Zhong, Jian-Jiang

2011-01-01

300

Enhanced Work Function of Al-Doped Zinc-Oxide Thin Films by Oxygen Inductively Coupled Plasma Treatment  

NASA Astrophysics Data System (ADS)

Al-doped zinc-oxide (AZO) thin films treated by oxygen and chlorine inductively coupled plasma (ICP) were compared. Kelvin probe (KP) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the effect of treatment. The results of KP measurement show that the surface work function of AZO thin films can increase up to 5.92 eV after oxygen ICP (O-ICP)'s treatment, which means that the work function was increased by at least 1.1 eV. However, after the treatment of chlorine ICP (Cl-ICP), the work function increased to 5.44 eV, and the increment was 0.6 eV. And 10 days later, the work function increment was still 0.4 eV after O-ICP's treatment, while the work function after Cl-ICP's treatment came back to the original value only after 48 hours. The XPS results suggested that the O-ICP treatment was more effective than Cl-ICP for enhancing the work function of AZO films, which is well consistent with KP results.

Li, Zebin; Wu, Zhonghang; Ju, Jiaqi; He, Kongduo; Chen, Zhenliu; Yang, Xilu; Yan, Hang; Ou, Qiongrong; Liang, Rongqing

2014-01-01

301

Structurally ordered intermetallic platinum-cobalt core-shell nanoparticles with enhanced activity and stability as oxygen reduction electrocatalysts  

NASA Astrophysics Data System (ADS)

To enhance and optimize nanocatalyst performance and durability for the oxygen reduction reaction in fuel-cell applications, we look beyond Pt-metal disordered alloys and describe a new class of Pt-Co nanocatalysts composed of ordered Pt3Co intermetallic cores with a 2-3 atomic-layer-thick platinum shell. These nanocatalysts exhibited over 200% increase in mass activity and over 300% increase in specific activity when compared with the disordered Pt3Co alloy nanoparticles as well as Pt/C. So far, this mass activity for the oxygen reduction reaction is the highest among the Pt-Co systems reported in the literature under similar testing conditions. Stability tests showed a minimal loss of activity after 5,000 potential cycles and the ordered core-shell structure was maintained virtually intact, as established by atomic-scale elemental mapping. The high activity and stability are attributed to the Pt-rich shell and the stable intermetallic Pt3Co core arrangement. These ordered nanoparticles provide a new direction for catalyst performance optimization for next-generation fuel cells.

Wang, Deli; Xin, Huolin L.; Hovden, Robert; Wang, Hongsen; Yu, Yingchao; Muller, David A.; Disalvo, Francis J.; Abruña, Héctor D.

2013-01-01

302

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

303

Enhancement of electric oxygen-iodine laser performance using larger mode volume resonators.  

PubMed

Herein the authors report on the demonstration of an 87% enhancement in cw laser power on the 1315 nm transition of atomic iodine via a 100% increase in the resonator mode volume. O(2)(a1Delta) is produced by a single rf-excited electric discharge sustained in an O(2)-He-NO gas mixture flowing through a rectangular geometry, and I(P2(1/2)) is then pumped using energy transferred from O(2)(a1Delta). A total laser output power of 102.5 W was obtained using a Z-pass resonator configuration. PMID:20479825

Woodard, Brian S; Benavides, Gabriel F; Zimmerman, Joseph W; Carroll, David L; Palla, Andrew D; Day, Michael T; Verdeyen, Joseph T; Solomon, Wayne C

2010-05-15

304

Enhancement of electric oxygen-iodine laser performance using a rectangular discharge and longer gain length  

NASA Astrophysics Data System (ADS)

Herein the authors report on the demonstration of a 95% enhancement in continuous-wave laser power on the 1315 nm transition of atomic iodine via a 50% increase in gain length, flow rates, and discharge power. O2(a ?1) is produced by a single radio-frequency-excited electric discharge sustained in an O2-He-NO gas mixture flowing through a rectangular geometry, and I(P21/2) is then pumped using energy transferred from O2(a ?1). A gain of 0.26% cm-1 was obtained and the total laser output power was 54.8 W.

Benavides, G. F.; Zimmerman, J. W.; Woodard, B. S.; Carroll, D. L.; Palla, A. D.; Day, M. T.; Verdeyen, J. T.; Solomon, W. C.

2009-11-01

305

Superparamagnetic iron oxide nanoparticles as radiosensitizer via enhanced reactive oxygen species formation  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Ultrasmall citrate-coated SPIONs with {gamma}Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4} structure were prepared. Black-Right-Pointing-Pointer SPIONs uptaken by MCF-7 cells increase the ROS production for about 240%. Black-Right-Pointing-Pointer The SPION induced ROS production is due to released iron ions and catalytically active surfaces. Black-Right-Pointing-Pointer Released iron ions and SPION surfaces initiate the Fenton and Haber-Weiss reaction. Black-Right-Pointing-Pointer X-ray irradiation of internalized SPIONs leads to an increase of catalytically active surfaces. -- Abstract: Internalization of citrate-coated and uncoated superparamagnetic iron oxide nanoparticles by human breast cancer (MCF-7) cells was verified by transmission electron microscopy imaging. Cytotoxicity studies employing metabolic and trypan blue assays manifested their excellent biocompatibility. The production of reactive oxygen species in iron oxide nanoparticle loaded MCF-7 cells was explained to originate from both, the release of iron ions and their catalytically active surfaces. Both initiate the Fenton and Haber-Weiss reaction. Additional oxidative stress caused by X-ray irradiation of MCF-7 cells was attributed to the increase of catalytically active iron oxide nanoparticle surfaces.

Klein, Stefanie; Sommer, Anja [Department of Chemistry and Pharmacy, Physical Chemistry I and ICMM, Friedrich-Alexander University of Erlangen-Nuremberg, Egerlandstr. 3, D-91058 Erlangen (Germany)] [Department of Chemistry and Pharmacy, Physical Chemistry I and ICMM, Friedrich-Alexander University of Erlangen-Nuremberg, Egerlandstr. 3, D-91058 Erlangen (Germany); Distel, Luitpold V.R. [Department of Radiation Oncology, Friedrich Alexander University Erlangen-Nuremberg, Universitaetsstrasse 27, D-91054 Erlangen (Germany)] [Department of Radiation Oncology, Friedrich Alexander University Erlangen-Nuremberg, Universitaetsstrasse 27, D-91054 Erlangen (Germany); Neuhuber, Winfried [Department of Anatomy, Chair of Anatomy I, Friedrich Alexander University Erlangen-Nuremberg, Krankenhausstr. 9, D-91054 Erlangen (Germany)] [Department of Anatomy, Chair of Anatomy I, Friedrich Alexander University Erlangen-Nuremberg, Krankenhausstr. 9, D-91054 Erlangen (Germany); Kryschi, Carola, E-mail: kryschi@chemie.uni-erlangen.de [Department of Chemistry and Pharmacy, Physical Chemistry I and ICMM, Friedrich-Alexander University of Erlangen-Nuremberg, Egerlandstr. 3, D-91058 Erlangen (Germany)] [Department of Chemistry and Pharmacy, Physical Chemistry I and ICMM, Friedrich-Alexander University of Erlangen-Nuremberg, Egerlandstr. 3, D-91058 Erlangen (Germany)

2012-08-24

306

Enhanced nitrogen removal in constructed wetlands: effects of dissolved oxygen and step-feeding.  

PubMed

Four horizontal subsurface flow constructed wetlands (HSFCWs), named HSFCW1 (three-stage, without step-feeding), HSFCW2 (three-stage, with step-feeding), HSFCW3 (five-stage, without step-feeding) and HSFCW4 (five-stage, with step-feeding) were designed to investigate the effects of dissolved oxygen (DO) and step-feeding on nitrogen removal. High removal of 90.9% COD, 99.1% ammonium nitrogen and 88.1% total nitrogen (TN) were obtained simultaneously in HSFCW4 compared with HSFCW1-3. The excellent TN removal of HSFCW4 was due to artificial aeration provided sufficient DO for nitrification and the favorable anoxic environment created for denitrification. Step-feeding was a crucial factor because it provided sufficient carbon source (high COD: nitrate ratio of 14.3) for the denitrification process. Microbial activities and microbial abundance in HSFCW4 was found to be influenced by DO distribution and step-feeding, and thus improve TN removal. These results suggest that artificial aeration combined with step-feeding could achieve high nitrogen removal in HSFCWs. PMID:25069093

Li, Fengmin; Lu, Lun; Zheng, Xiang; Ngo, Huu Hao; Liang, Shuang; Guo, Wenshan; Zhang, Xiuwen

2014-10-01

307

Enhancement of oxygen vacancies and solar photocatalytic activity of zinc oxide by incorporation of nonmetal  

NASA Astrophysics Data System (ADS)

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.

Patil, Ashokrao B.; Patil, Kashinath R.; Pardeshi, Satish K.

2011-12-01

308

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

309

Dichloroacetate Enhances Adriamycin-Induced Hepatoma Cell Toxicity In Vitro and In Vivo by Increasing Reactive Oxygen Species Levels  

PubMed Central

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 glycolytic phenotype, induce reactive oxygen species (ROS) generation, and trigger apoptosis in various tumor cells. In this work, the capacity of DCA to enhance Adriamycin (ADM) efficacy in hepatoma cells by modulating glucose metabolism and redox status was evaluated. Two human hepatoma (HCC-LM3 and SMMC-7721) and a normal liver (LO2) cell lines were treated with DCA or ADM alone, or in combination. Exposure of hepatoma cells to DCA/ADM combination resulted in significantly decreased cell viability and increased percentage of apoptotic cells as well as intracellular ROS levels, in comparison with treatment with DCA or ADM alone. However, simultaneous treatment with the thiol antioxidant N-acetylcysteine (NAC, 10 mmol/L) reduced the elevated ROS levels and protected hepatoma cells from the cytotoxic effects of DCA/ADM combination. L-buthionine-[S,R]-sulfoximine, an inhibitor of glutathione synthesis, enhanced hepatoma cell sensitivity to DCA/ADM combination. Interestingly, treatment with DCA/ADM combination did not significantly increase cytotoxicity in normal hepatocytes in comparison with the drugs administered individually. Finally, DCA reduced tumor growth and enhanced ADM efficacy on HCC-LM3 hepatoma in mice. Overall, our data suggest that DCA enhances ADM cytotoxicity in hepatoma cells by increasing intracellular ROS levels and provide a strong biochemical rationale for the use of DCA in combination with ADM for treatment of hepatoma. PMID:24728083

Huang, Gang; Liu, Jianjun; Sheng, Shile; Wang, Hongjian; Qin, Wenxin

2014-01-01

310

Combustion noise  

NASA Technical Reports Server (NTRS)

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

Strahle, W. C.

1977-01-01

311

Enhanced thermoelectric properties via oxygen non-stoichiometry in La2NiO4 and SrTiO3  

NASA Astrophysics Data System (ADS)

We present the results of transport properties calculations and experiments on various oxides. A large enhancement of the thermoelectric properties is predictedfootnotetextPRB 86, 165114 (2012). via ab initio calculations for La2NiO4+?, with electronic-only thermoelectric figure of merit (zT) values exceeding unity for oxygen excess ? <= 0.10. The effects of lattice strain (caused, e.g. by growth of thin films on different substrates) enhance even further the thermoelectric response. A similar result is obtained at very low electron-doping in bulk SrTiO3 via oxygen removal. This is analyzed experimentally via thermal annealing that depletes oxygen (˜ 1 oxygen vacancy per 10^6 unit cells). In both these systems, the increase in conductivity reached in the metallic limit retains a large thermopower, with the corresponding enhancement of zT. In the case of SrTiO3, experiments indicatefootnotetextarxiv:1211.1615. that such a small oxygen vacancy level reduces drastically the thermal conductivity by introducing random scattering centers. In the talk, we will discuss the electronic structure origin of the enhancement of the thermoelectric response and how this can be tuned. Results are general and applicable to other non-stoichiometric oxides.

Pardo, Victor; Botana, Antia S.; Bach, Paul M.; Leboran, Victor; Rivadulla, Francisco; Baldomir, Daniel

2013-03-01

312

Toward a Full Simulation of the Basic Oxygen Furnace: Deformation of the Bath Free Surface and Coupled Transfer Processes Associated with the Post-Combustion in the Gas Region  

NASA Astrophysics Data System (ADS)

The present article treats different phenomena taking place in a steelmaking converter through the development of two separate models. The first model describes the cavity produced at the free surface of the metal bath by the high-speed impinging oxygen jet. The model is based on a zonal approach, where gas compressibility effects are taken into account only in the high velocity jet region, while elsewhere the gas is treated as incompressible. The volume of fluid (VOF) method is employed to follow the deformation of the bath free surface. Calculations are presented for two- and three-phase systems and compared against experimental data obtained in a cold model experiment presented in the literature. The influence on the size and shape of the cavity of various parameters and models (including the jet inlet boundary conditions, the VOF advection scheme, and the turbulence model) is studied. Next, the model is used to simulate the interaction of a supersonic oxygen jet with the surface of a liquid steel bath in a pilot-scale converter. The second model concentrates on fluid flow, heat transfer, and the post-combustion reaction in the gas phase above the metal bath. The model uses the simple chemical reaction scheme approach to describe the transport of the chemical species and takes into account the consumption of oxygen by the bath and thermal radiative transfer. The model predictions are in reasonable agreement with measurements collected in a laboratory experiment and in a pilot-scale furnace.

Doh, Y.; Chapelle, P.; Jardy, A.; Djambazov, G.; Pericleous, K.; Ghazal, G.; Gardin, P.

2013-06-01

313

Solvothermal, Chloroalkoxide-based Synthesis of Monoclinic WO3 Quantum Dots and Gas-Sensing Enhancement by Surface Oxygen Vacancies.  

PubMed

We report for the first time the synthesis of monoclinic WO3 quantum dots. A solvothermal processing at 250 °C in oleic acid of W chloroalkoxide solutions was employed. It was shown that the bulk monoclinic crystallographic phase is the stable one even for the nanosized regime (mean size 4 nm). The nanocrystals were characterized by X-ray diffraction, High resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis, Fourier transform infrared and Raman spectroscopy. It was concluded that they were constituted by a core of monoclinic WO3, surface covered by unstable W(V) species, slowly oxidized upon standing in room conditions. The WO3 nanocrystals could be easily processed to prepare gas-sensing devices, without any phase transition up to at least 500 °C. The devices displayed remarkable response to both oxidizing (nitrogen dioxide) and reducing (ethanol) gases in concentrations ranging from 1 to 5 ppm and from 100 to 500 ppm, at low operating temperatures of 100 and 200 °C, respectively. The analysis of the electrical data showed that the nanocrystals were characterized by reduced surfaces, which enhanced both nitrogen dioxide adsorption and oxygen ionosorption, the latter resulting in enhanced ethanol decomposition kinetics. PMID:25211288

Epifani, Mauro; Comini, Elisabetta; Díaz, Raül; Andreu, Teresa; Genç, Aziz; Arbiol, Jordi; Siciliano, Pietro; Faglia, Guido; Morante, Joan R

2014-10-01

314

Induction of apoptosis in human multiple myeloma cell lines by ebselen via enhancing the endogenous reactive oxygen species production.  

PubMed

Ebselen a selenoorganic compound showing glutathione peroxidase like activity is an anti-inflammatory and antioxidative agent. Its cytoprotective activity has been investigated in recent years. However, experimental evidence also shows that ebselen causes cell death in several cancer cell types whose mechanism has not yet been elucidated. In this study, we examined the effect of ebselen on multiple myeloma (MM) cell lines in vitro. The results showed that ebselen significantly enhanced the production of reactive oxygen species (ROS) accompanied by cell viability decrease and apoptosis rate increase. Further studies revealed that ebselen can induce Bax redistribution from the cytosol to mitochondria leading to mitochondrial membrane potential ??m changes and cytochrome C release from the mitochondria to cytosol. Furtherly, we found that exogenous addition of N-acetyl cysteine (NAC) completely diminished the cell damage induced by ebselen. This result suggests that relatively high concentration of ebselen can induce MM cells apoptosis in culture by enhancing the production of endogenous ROS and triggering mitochondria mediated apoptotic pathway. PMID:24587987

Zhang, Liang; Zhou, Liwei; Du, Jia; Li, Mengxia; Qian, Chengyuan; Cheng, Yi; Peng, Yang; Xie, Jiayin; Wang, Dong

2014-01-01

315

Sensitive determination of reactive oxygen species in cigarette smoke using microchip electrophoresis-localized surface plasmon resonance enhanced fluorescence detection.  

PubMed

A sensitive approach to the determination of reactive oxygen species (ROS) in puffs of cigarette smoke (CS) has been developed. The experimental system consists of a microfluidic chip electrophoresis and a laser induced fluorescence (LIF) device enhanced by localized surface plasmon resonance. Core-shell Ag@SiO2 nanoparticles were prepared and then immobilized on the surface of the microchannel to increase the fluorescence intensity based on localized surface plasmon resonance-enhanced fluorescence (LSPREF) effect. The ROS in puffs of CS were trapped via the oxidation of 2',7'-dichlorodihydrofluorescein (DCHF) that had been loaded on polyacrylonitrile (PAN) nanofibers in a micro-column. Determination of ROS was based on the amount of 2',7'-dichlorofluorescein (DCF), which is the sole product from DCHF oxidation. With the optimization of the trapping efficiency, we detected about 8.0 pmol of ROS per puff in the mainstream CS. This microchip electrophoresis-SPREF system enables sensitive quantitation of ROS in CS with low consumption of reagent, material, and analysis time. PMID:24458305

Wang, Huai-Song; Xiao, Fang-Nan; Li, Zhong-Qiu; Ouyang, Jun; Wu, Zeng-Qiang; Xia, Xing-Hua; Zhou, Guo-Jun

2014-03-21

316

An Increase in Reactive Oxygen Species by Deregulation of ARNT Enhances Chemotherapeutic Drug-Induced Cancer Cell Death  

PubMed Central

Background Unique characteristics of tumor microenvironments can be used as targets of cancer therapy. The aryl hydrocarbon receptor nuclear translocator (ARNT) is an important mediator of tumor progression. However, the functional role of ARNT in chemotherapeutic drug-treated cancer remains unclear. Methodology/Principal Findings Here, we found that knockdown of ARNT in cancer cells reduced the proliferation rate and the transformation ability of those cells. Moreover, cisplatin-induced cell apoptosis was enhanced in ARNT-deficient cells. Expression of ARNT also decreased in the presence of cisplatin through proteasomal degradation pathway. However, ARNT level was maintained in cisplatin-treated drug-resistant cells, which prevented cell from apoptosis. Interestingly, reactive oxygen species (ROS) dramatically increased when ARNT was knocked down in cancer cells, enhancing cisplatin-induced apoptosis. ROS promoted cell death was inhibited in cells treated with the ROS scavenger, N-acetyl-cysteine (NAC). Conclusions/Significance These results suggested that the anticancer activity of cisplatin is attributable to its induction of the production of ROS by ARNT degradation. Targeting ARNT could be a potential strategy to eliminate drug resistance in cancer cells. PMID:24921657

Shieh, Jiunn-Min; Shen, Chih-Jie; Chang, Wei-Chiao; Cheng, Hung-Chi; Chan, Ya-Yi; Huang, Wan-Chen; Chang, Wen-Chang; Chen, Ben-Kuen

2014-01-01

317

Induction of Apoptosis in Human Multiple Myeloma Cell Lines by Ebselen via Enhancing the Endogenous Reactive Oxygen Species Production  

PubMed Central

Ebselen a selenoorganic compound showing glutathione peroxidase like activity is an anti-inflammatory and antioxidative agent. Its cytoprotective activity has been investigated in recent years. However, experimental evidence also shows that ebselen causes cell death in several cancer cell types whose mechanism has not yet been elucidated. In this study, we examined the effect of ebselen on multiple myeloma (MM) cell lines in vitro. The results showed that ebselen significantly enhanced the production of reactive oxygen species (ROS) accompanied by cell viability decrease and apoptosis rate increase. Further studies revealed that ebselen can induce Bax redistribution from the cytosol to mitochondria leading to mitochondrial membrane potential ??m changes and cytochrome C release from the mitochondria to cytosol. Furtherly, we found that exogenous addition of N-acetyl cysteine (NAC) completely diminished the cell damage induced by ebselen. This result suggests that relatively high concentration of ebselen can induce MM cells apoptosis in culture by enhancing the production of endogenous ROS and triggering mitochondria mediated apoptotic pathway. PMID:24587987

Du, Jia; Li, Mengxia; Qian, Chengyuan; Cheng, Yi; Peng, Yang; Xie, Jiayin; Wang, Dong

2014-01-01

318

Pyruvate Induces Transient Tumor Hypoxia by Enhancing Mitochondrial Oxygen Consumption and Potentiates the Anti-Tumor Effect of a Hypoxia-Activated Prodrug TH-302  

PubMed Central

Background TH-302 is a hypoxia-activated prodrug (HAP) of bromo isophosphoramide mustard that is selectively activated within hypoxic regions in solid tumors. Our recent study showed that intravenously administered bolus pyruvate can transiently induce hypoxia in tumors. We investigated the mechanism underlying the induction of transient hypoxia and the combination use of pyruvate to potentiate the anti-tumor effect of TH-302. Methodology/Results The hypoxia-dependent cytotoxicity of TH-302 was evaluated by a viability assay in murine SCCVII and human HT29 cells. Modulation in cellular oxygen consumption and in vivo tumor oxygenation by the pyruvate treatment was monitored by extracellular flux analysis and electron paramagnetic resonance (EPR) oxygen imaging, respectively. The enhancement of the anti-tumor effect of TH-302 by pyruvate treatment was evaluated by monitoring the growth suppression of the tumor xenografts inoculated subcutaneously in mice. TH-302 preferentially inhibited the growth of both SCCVII and HT29 cells under hypoxic conditions (0.1% O2), with minimal effect under aerobic conditions (21% O2). Basal oxygen consumption rates increased after the pyruvate treatment in SCCVII cells in a concentration-dependent manner, suggesting that pyruvate enhances the mitochondrial respiration to consume excess cellular oxygen. In vivo EPR oxygen imaging showed that the intravenous administration of pyruvate globally induced the transient hypoxia 30 min after the injection in SCCVII and HT29 tumors at the size of 500–1500 mm3. Pretreatment of SCCVII tumor bearing mice with pyruvate 30 min prior to TH-302 administration, initiated with small tumors (?550 mm3), significantly delayed tumor growth. Conclusions/Significance Our in vitro and in vivo studies showed that pyruvate induces transient hypoxia by enhancing mitochondrial oxygen consumption in tumor cells. TH-302 therapy can be potentiated by pyruvate pretreatment if started at the appropriate tumor size and oxygen concentration. PMID:25254649

Takakusagi, Yoichi; Matsumoto, Shingo; Saito, Keita; Matsuo, Masayuki; Kishimoto, Shun; Wojtkowiak, Jonathan W.; DeGraff, William; Kesarwala, Aparna H.; Choudhuri, Rajani; Devasahayam, Nallathamby; Subramanian, Sankaran; Munasinghe, Jeeva P.; Gillies, Robert J.; Mitchell, James B.; Hart, Charles P.; Krishna, Murali C.

2014-01-01

319

COMBUSTION OF COAL IN AN OPPOSED FLOW DIFFUSION BURNER  

E-print Network

rank, particle size, heat of combustion, porosity, and otherheat transfer from high temperature product gases or the combustionheat loss, it is not possible to burn coal samples in air, but oxygen enrichment is required to sustain combustion.

Chin, W.K.

2010-01-01

320

Esterified dendritic TAM radicals with very high stability and enhanced oxygen sensitivity.  

PubMed

In this work, we have developed a new class of dendritic TAM radicals (TG, TdG, and dTdG) through a convergent method based on the TAM core CT-03 or its deuterated analogue dCT-03 and trifurcated Newkome-type monomer. Among these radicals, dTdG exhibits the best EPR properties with sharpest EPR singlet and highest O(2) sensitivity due to deuteration of both the ester linker groups and the TAM core CT-03. Like the previous dendritic TAM radicals, these new compounds also show extremely high stability toward various reactive species owing to the dendritic encapsulation. The highly charged nature of these molecules resulting from nine carboxylate groups prevents concentration-dependent EPR line broadening at physiological pH. Furthermore, we demonstrate that these TAM radicals can be easily derivatized (e.g., PEGylation) at the nine carboxylate groups and the resulting PEGylated analogue dTdG-PEG completely inhibits the albumin binding, thereby enhancing suitability for in vivo applications. These new dendritic TAM radicals show great potential for in vivo EPR oximetric applications and provide insights on approaches to develop improved and targeted EPR oximetric probes for biomedical applications. PMID:23343531

Song, Yuguang; Liu, Yangping; Hemann, Craig; Villamena, Frederick A; Zweier, Jay L

2013-02-15

321

Combustion front propagation in underground coal gasification  

SciTech Connect

Reverse Combustion (RC) enhances coal seam permeability prior to Underground Coal Gasification. Understanding RC is necessary to improve its reliability and economics. A curved RC front propagation model is developed, then solved by high activation energy asymptotics. It explicitly incorporates extinction (stoichiometric and thermal) and tangential heat transport (THT) (convection and conduction). THT arises from variation in combustion front temperature caused by tangential variation in the oxidant gas flux to the channel surface. Front temperature depends only weakly on THT; front velocity is strongly affected, with heat loss slowing propagation. The front propagation speed displays a maximum with respect to gas flux. Combustion promoters speed front propagation; inhibitors slow front propagation. The propagation model is incorporated into 2-D simulations of RC channel evolution utilizing the boundary element method with cubic hermetian elements to solve the flow from gas injection wells through the coal to the convoluted, temporally evolving, channel surface, and through the channel to a gas production well. RC channel propagation is studied using 17 cm diameter subbituminous horizontally drilled coal cores. Sixteen experiments at pressures between 2000 and 3600 kPa, injected gas oxygen contents between 21% and 75%, and flows between 1 and 4 standard liters per minute are described. Similarity analysis led to scaling-down of large RC ({approx}1 m) to laboratory scale ({approx}5 cm). Propagation velocity shows a strong synergistic increase at high levels of oxygen, pressure, and gas flow. Char combustion is observed, leaving ash-filled, irregularly shaped channels. Cracks are observed to penetrate the char zone surrounding the channel cores. 69 refs., 54 figs., 4 tabs.

Dobbs, R.L. II; Krantz, W.B.

1990-10-01

322

Enhanced combustion of fossil-fuel particles and droplets in oscillating flow. Annual technical report, 1 September 1978-31 August 1979  

Microsoft Academic Search

The objective of this research is to determine the effect of oscillating flow on the rates of combustion of fossil fuel particles or droplets. Under certain conditions, an oscillatory (pulsating) flow may produce significantly increased rates of burning of fuel particles or droplets and thus provide more effective fuel utilization, with reduced excess air and improved combustion efficiency. The combustion

F. A. Lyman; J. S. Sabnis

1979-01-01

323

Enhancement of optical absorption by modulation of the oxygen flow of TiO2 films deposited by reactive sputtering  

NASA Astrophysics Data System (ADS)

Oxygen-deficient TiO2 films with enhanced visible and near-infrared optical absorption have been deposited by reactive sputtering using a planar diode radio frequency magnetron configuration. It is observed that the increase in the absorption coefficient is more effective when the O2 gas supply is periodically interrupted rather than by a decrease of the partial O2 gas pressure in the deposition plasma. The optical absorption coefficient at 1.5 eV increases from about 1 × 102 cm-1 to more than 4 × 103 cm-1 as a result of the gas flow discontinuity. A red-shift of ˜0.24 eV in the optical absorption edge is also observed. High resolution transmission electron microscopy with composition analysis shows that the films present a dense columnar morphology, with estimated mean column width of 40 nm. Moreover, the interruptions of the O2 gas flow do not produce detectable variations in the film composition along its growing direction. X-ray diffraction and micro-Raman experiments indicate the presence of the TiO2 anatase, rutile, and brookite phases. The anatase phase is dominant, with a slight increment of the rutile and brookite phases in films deposited under discontinued O2 gas flow. The increase of optical absorption in the visible and near-infrared regions has been attributed to a high density of defects in the TiO2 films, which is consistent with density functional theory calculations that place oxygen-related vacancy states in the upper third of the optical bandgap. The electronic structure calculation results, along with the adopted deposition method and experimental data, have been used to propose a mechanism to explain the formation of the observed oxygen-related defects in TiO2 thin films. The observed increase in sub-bandgap absorption and the modeling of the corresponding changes in the electronic structure are potentially useful concerning the optimization of efficiency of the photocatalytic activity and the magnetic doping of TiO2 films.

Pereira, André L. J.; Lisboa Filho, Paulo N.; Acuña, Javier; Brandt, Iuri S.; Pasa, André A.; Zanatta, Antonio R.; Vilcarromero, Johnny; Beltrán, Armando; Dias da Silva, José H.

2012-06-01

324

Oxygen-Enhanced Wet Thermal Oxidation of In0.53Ga0.47As Christopher S. Seibert, Jinyang Li, Wangqing Yuan, Douglas C. Hall  

E-print Network

Oxygen-Enhanced Wet Thermal Oxidation of In0.53Ga0.47As Christopher S. Seibert, Jinyang Li oxidation has allowed for the oxidation of various low aluminum content and aluminum-free compound semiconductor alloys that are traditionally difficult to thermally oxidize, including those latticed matched

325

Pyrolysis reactor and fluidized bed combustion chamber  

DOEpatents

A solid carbonaceous material is pyrolyzed in a descending flow pyrolysis reactor in the presence of a particulate source of heat to yield a particulate carbon containing solid residue. The particulate source of heat is obtained by educting with a gaseous source of oxygen the particulate carbon containing solid residue from a fluidized bed into a first combustion zone coupled to a second combustion zone. A source of oxygen is introduced into the second combustion zone to oxidize carbon monoxide formed in the first combustion zone to heat the solid residue to the temperature of the particulate source of heat.

Green, Norman W. (Upland, CA)

1981-01-06

326

Fabrication of novel oxygen-releasing alginate beads as an efficient oxygen carrier for the enhancement of aerobic bioremediation of 1,4-dioxane contaminated groundwater.  

PubMed

Oxygen-releasing alginate beads (ORABs), a new concept of oxygen-releasing compounds (ORCs) designed to overcome some limitations regarding the fast oxygen release rate and the high pH equilibrium of ORCs, were fabricated to promote the stimulation of aerobic biodegradation in anaerobic groundwater. Slow oxygen-releasing rate and maintenance of constant pH were achieved by changing the parameters (ionic radius and valence) related to the cross-linking ions composing ORABs, and the best results were obtained for ORABs cross-linked with Al (Al-ORABs). Furthermore, the mechanism of the improved aerobic biodegradation using Al-ORABs under oxygen-limiting groundwater conditions was elucidated in batch and column studies with 1,4-dioxane and Mycrobacterium sp. PH-06 as a model contaminant and aerobic microbes, respectively. Maximum 1,4-dioxane degradations of 99% and 68.1% were achieved when Al-ORABs were applied in batch and column conditions, respectively, whereas 34.3% and 18% of 1,4-dioxane were degraded without Al-ORABs in batch and column conditions, respectively. PMID:25189509

Lee, Chung-Seop; Le Thanh, Thao; Kim, Eun-Ju; Gong, Jianyu; Chang, Yoon-Young; Chang, Yoon-Seok

2014-11-01

327

Mechanism of smokeless diesel combustion with oxygenated fuels based on the dependence of the equivalence ration and temperature on soot particle formation  

Microsoft Academic Search

The equivalence ratio ? and temperature T are well known to have a significant effect on the quality of particulate formation, such as the soot volume fraction, particle diameter and number density. The purpose of this work is to clarify the ?-T dependence of soot formation for various kinds of fuels, including paraffinic hydrocarbon, aromatic hydrocarbon and oxygenated hydrocarbon, and

T Kitamura; T Ito; J Senda; H Fujimoto

2002-01-01

328

Development of nanoparticle applications in cell imaging, bioassay and reactive oxygen species detection based on surface-enhanced raman spectroscopy  

NASA Astrophysics Data System (ADS)

Surface-enhanced Raman scattering (SERS) has been developed over forty years with a wide variety of applications. Signals enhanced from single molecule absorbed on the surface of metallic nanoparticles can be up to 14-order-of-magnitude. This is due to the resonance between the optical field and surface plasmon of the metal substrate. Nanoshells have been chosen as substrates since they do not need to pre-aggregate due to their tunable optical property. We developed Raman imaging system by incorporating functionalized nanoshells, cells and SERS. Nanoshells have been coated with different self-assembled monolayers containing poly(ethylene glycol) (PEG) molecules. Probes have been designed by coating nanoshells with Raman active PEG molecules and delivered into macrophage cells. The imaging technique requires less preparation and provides the information of nanoshells in semi-quantitative way in vitro. We developed half-sandwich bioassay by detecting low volume of antigens on nitrocellulose membrane, detected by SERS. Antibodies were grafted to the surface of nanoshells and were conjugated to the antigens on the nitrocellulose membrane for detection. Raman active PEGs were conjugated onto the metal substrate for recognition and quantification. The benefits of this assay are that it is faster, easier to execute and requires less volume of antigen to conjugate onto the substrate. We also developed reactive oxygen species (ROS) sensors by incubating PEGs and either 4-nitrobenzenethiol (4-NBT) or 4-mercaptophenol (4-MP) on the surface of nanoshells. By analyzing the changes of SERS spectrum, the production of hydroxyl radicals produced in the Fenton reaction can be tracked in low concentrations. The sensors were designed to track ROS production within cells when they are under oxidative stress. The methods developed in this thesis are versatile, and can be broadly applied to the study of different subtracts, such as gold colloid.

Huang, Yiming

329

Mitochondrial targeting of cyclosporin A enables selective inhibition of cyclophilin-D and enhanced cytoprotection after glucose and oxygen deprivation  

PubMed Central

CsA (cyclosporin A) is a hydrophobic undecapeptide that inhibits CyPs (cyclophilins), a family of PPIases (peptidylprolyl cis–trans isomerases). In some experimental models, CsA offers partial protection against lethal cell injury brought about by transient ischaemia; this is believed to reflect inhibition of CyP-D, a mitochondrial isoform that facilitates formation of the permeability transition pore in the mitochondrial inner membrane. To evaluate this further, we have targeted CsA to mitochondria so that it becomes selective for CyP-D in cells. This was achieved by conjugating the inhibitor to the lipophilic triphenylphosphonium cation, enabling its accumulation in mitochondria due to the inner membrane potential. In a cell-free system and in B50 neuroblastoma cells the novel reagent (but not CsA itself) preferentially inhibited CyP-D over extramitochondrial CyP-A. In hippocampal neurons, mitochondrial targeting markedly enhanced the capacity of CsA to prevent cell necrosis brought about by oxygen and glucose deprivation, but largely abolished its capacity to inhibit glutamate-induced cell death. It is concluded that CyP-D has a major pathogenic role in ‘energy failure’, but not in glutamate excitotoxicity, where cytoprotection primarily reflects CsA interaction with extramitochondrial CyPs and calcineurin. Moreover, the therapeutic potential of CsA against ischaemia/reperfusion injuries not involving glutamate may be improved by mitochondrial targeting. PMID:19832699

Malouitre, Sylvanie; Dube, Henry; Selwood, David; Crompton, Martin

2009-01-01

330

Modeling of Laser-Induced Metal Combustion  

SciTech Connect

Experiments involving the interaction of a high-power laser beam with metal targets demonstrate that combustion plays an important role. This process depends on reactions within an oxide layer, together with oxygenation and removal of this layer by the wind. We present an analytical model of laser-induced combustion. The model predicts the threshold for initiation of combustion, the growth of the combustion layer with time, and the threshold for self-supported combustion. Solutions are compared with detailed numerical modeling as benchmarked by laboratory experiments.

Boley, C D; Rubenchik, A M

2008-02-20

331

Utilization of oxygen-enriched air in diesel engines: Fundamental considerations  

SciTech Connect

Utilization of oxygen-enriched air in diesel engines holds potential for low exhaust smoke and particulate emissions. The majority of the oxygen-enriched-air combustion-related studies so far are experimental in nature, where the observed results are understood on an overall basis. This paper deals with the fundamental considerations associated with the oxygen-enriched air-fuel combustion process to enhance understanding of the concept. The increase in adiabatic flame temperature, the composition of exhaust gases at equilibrium, and also the changes in thermodynamic and transport properties due to oxygen-enrichment of standard intake air are computed. The effects of oxygen-enrichment on fuel evaporation rate, ignition delay, and premixed burnt fraction are also evaluated. Appropriate changes in the ignition delay correlation to reflect the effects of oxygen-enrichment are proposed. The notion of oxygen-enrichment of standard intake air as being akin to leaning of the fuel-air mixture is refuted on the basis of the fundamentally different requirements for the oxygen-enriched combustion process.

Lahiri, D.; Mehta, P.S. [Indian Inst. of Tech., Madras (India); Poola, R.B.; Sekar, R. [Argonne National Lab., IL (United States)

1997-09-01

332

The roles of density-tunable surface oxygen vacancy over bouquet-like Bi2O3 in enhancing photocatalytic activity.  

PubMed

Bouquet-like hierarchical Bi2O3 photocatalyst materials with high-density surface oxygen vacancy are synthesized via a hydrothermal method by the synergetic control of NaOH and a polyvinyl alcohol (PVA) stabilizer. The OH(-) ion addition led to the formation of more relaxed PVA macromolecular clusters, as a result, a thinner PVA film was formed, the species adsorbed on the surface of the produced Bi2O3 crystal nucleus could tune both the surface microstructure size and oxygen vacancy density via controlling the velocity, transfer and reaction of the OH(-) ions. The significant enhancement of photocatalytic performances could be attributed to the high density of the surface oxygen vacancy which was propitious to the charge separation efficiencies, distribution characteristic, and its role in a photo-redox reaction. A turnable-bending self-assembly mechanism was proposed to clarify the formation process of the bouquet-like hierarchical structure. PMID:24452180

Wu, Yuqi; Lu, Gongxuan

2014-03-01

333

FORMATION AND CONTROL OF PRODUCTS OF INCOMPLETE COMBUSTION  

EPA Science Inventory

Oxygenated organic products of incomplete combustion, including oxygenated PAHs and phthalates, have been found in combustor emissions. Some have substantial health effects and significantly influence the risk assessment calculations. Others are found that may or may not be a...

334

Real-time quantitative analysis of combustion-generated polycyclic aromatic hydrocarbons by resonance-enhanced multiphoton ionization time-of-flight mass spectrometry  

SciTech Connect

We have combined resonance-enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry with on-line flame sampling to determine the centerline concentrations of naphthalene, fluorene, and anthracene in a pure methane + oxygen/argon (1:5) diffusion flame. Naphthalene concentrations between 100 parts per billion by volume (ppbV) and 6 parts per million by volume (ppmV) and fluorene concentrations below 50 ppbV are determined using one-color REMPI on jet-cooled samples extracted from the flame; anthracene concentrations in the 5-40 ppbV range are determined using two-color REMPI. The REMPI ion signals are converted to absolute concentrations in real time by performing gas-phase standard additions to the flame sample. Isomer-selective detection of larger polycyclic aromatic hydrocarbons, such as perylene and benzo[a]pyrene, is possible using the two-color REMPI approach. 38 refs., 8 figs.

Gittins, C.M.; Rohlfing, E.A. [Sandia National Lab., Livermore, CA (United States)] [Sandia National Lab., Livermore, CA (United States); Castaldi, M.J.; Senkan, S.M. [Univ. of California, Los Angeles, CA (United States)] [Univ. of California, Los Angeles, CA (United States)

1997-02-01

335

Real-Time Quantitative Analysis of Combustion-Generated Polycyclic Aromatic Hydrocarbons by Resonance-Enhanced Multiphoton Ionization Time-of-Flight Mass Spectrometry.  

PubMed

We have combined resonance-enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry with on-line flame sampling to determine the centerline concentrations of naphthalene, fluorene, and anthracene in a pure methane + oxygen/argon (1:5) diffusion flame. Naphthalene concentrations between 100 parts per billion by volume (ppbV) and 6 parts per million by volume (ppmV) and fluorene concentrations below 50 ppbV are determined using one-color REMPI on jet-cooled samples extracted from the flame; anthracene concentrations in the 5-40 ppbV range are determined using two-color REMPI. The REMPI ion signals are converted to absolute concentrations in real time by performing gas-phase standard additions to the flame sample. Isomer-selective detection of larger polycyclic aromatic hydrocarbons, such as perylene and benzo[a]pyrene, is possible using the two-color REMPI approach. PMID:21639183

Gittins, C M; Castaldi, M J; Senkan, S M; Rohlfing, E A

1997-02-01

336

Nitrogen oxide pollution abatement using catalytic combustion  

SciTech Connect

A process is claimed for purifying nitric acid plant tail gases in which there is catalytic combustion of a hydrogen containing gas with the oxygen contained in the tail gases, the improvement in which heat produced from the catalytic combustion is used for catalytic reforming of a stream of hydrocarbon and steam to produce the hydrogen containing gas.

James, G.

1980-04-15

337

Lack of enhanced preservation of organic matter in sediments under the oxygen minimum on the Oman Margin  

Microsoft Academic Search

The impingement of oxygen minima on continental margins is widely thought to promote the accumulation of sedimentary facies enriched in well-preserved organic matter. It is shown here, however, that such a relationship does not clearly apply to the productive Oman Margin in the Arabian Sea, which hosts one of the most severe oxygen minima in the oceans. Measurements made on

T. F. Pedersen; G. B. Shimmield; N. B. Price

1992-01-01

338

Forced cocurrent smoldering combustion  

NASA Technical Reports Server (NTRS)

An analytical model of cocurrent smoldering combustion through a very porous solid fuel is developed. Smoldering is initiated at the top of a long radially insulated uniform fuel cylinder, so that the smolder wave propagates downward, opposing an upward-forced flow of oxidizer, with the solid fuel and the gaseous oxidizer entering the reaction zone from the same direction (hence, cocurrent). Radiative heat transfer was incorporated using a diffusion approximation, and smoldering was modeled using a one-step reaction mechanism. The results indicate that, for a given fuel, the final temperature depends only on the initial oxygen mass flux, increasing logarithmically with the mass flux. The smolder velocity is linearly dependent on the initial oxygen mass flux, and, at a fixed value of the flux, increases with initial oxygen mass fraction. The mathematical relationship determining the conditions for steady smolder propagation is presented.

Dosanjh, Sudip S.; Pagni, Patrick J.; Fernandez-Pello, A. Carlos

1987-01-01

339

Antipollution combustion chamber  

SciTech Connect

The invention concerns a combustion chamber for turbojet engines. The combustion chamber is of the annular type and consists of two coaxial flame tubes opening into a common dilution and mixing zone. The inner tube is designed for low operating ratings of the engine, the outer tube for high ratings. Air is injected as far upstream as possible into the dilution zone, to enhance the homogenization of the gaseous flow issuing from the two tubes prior to their passage into the turbine and to assure the optimum radial distribution of temperatures. The combustion chamber according to the invention finds application in a particularly advantageous manner in turbojet engines used in aircraft propulsion because of the reduced emission of pollutants it affords.

Caruel, J.E.; Gastebois, P.M.

1981-01-27

340

Microgravity Smoldering Combustion Takes Flight  

NASA Technical Reports Server (NTRS)

The Microgravity Smoldering Combustion (MSC) experiment lifted off aboard the Space Shuttle Endeavour in September 1995 on the STS-69 mission. This experiment is part of series of studies focused on the smolder characteristics of porous, combustible materials in a microgravity environment. Smoldering is a nonflaming form of combustion that takes place in the interior of combustible materials. Common examples of smoldering are nonflaming embers, charcoal briquettes, and cigarettes. The objective of the study is to provide a better understanding of the controlling mechanisms of smoldering, both in microgravity and Earth gravity. As with other forms of combustion, gravity affects the availability of air and the transport of heat, and therefore, the rate of combustion. Results of the microgravity experiments will be compared with identical experiments carried out in Earth's gravity. They also will be used to verify present theories of smoldering combustion and will provide new insights into the process of smoldering combustion, enhancing our fundamental understanding of this frequently encountered combustion process and guiding improvement in fire safety practices.

1996-01-01

341

Nano-structured manganese oxide as a cathodic catalyst for enhanced oxygen reduction in a microbial fuel cell fed with a synthetic wastewater  

Microsoft Academic Search

Microbial fuel cells (MFCs) provide new opportunities for the simultaneous wastewater treatment and electricity generation. Enhanced oxygen reduction capacity of cost-effective metal-based catalysts in an air cathode is essential for the scale-up and commercialization of MFCs in the field of wastewater treatment. We demonstrated that a nano-structured MnOx material, prepared by an electrochemically deposition method, could be an effective catalyst

Xian-Wei Liu; Xue-Fei Sun; Yu-Xi Huang; Guo-Ping Sheng; Kang Zhou; Raymond J. Zeng; Fang Dong; Shu-Guang Wang; An-Wu Xu; Zhong-Hua Tong; Han-Qing Yu

2010-01-01

342

Formation of oxygenated compounds from isooctane flames  

Microsoft Academic Search

The formation of three families of oxygenated compounds is studied in the case of isooctane combustion. Stoichiometric, lean and rich conditions are studied at different distances from a flat burner. Nine carbonyl compounds, five alcohols and three organic acids are found in detectable concentrations in the combustion products. These oxygenated compounds are formed very quickly, their concentrations increase or remain

Efthimios Zervas; Stavros Poulopoulos; Constantinos Philippopoulos

2006-01-01

343

Simplified Two-Time Step Method for Calculating Combustion Rates and Nitrogen Oxide Emissions for Hydrogen/Air and Hydorgen/Oxygen  

NASA Technical Reports Server (NTRS)

A simplified single rate expression for hydrogen combustion and nitrogen oxide production was developed. Detailed kinetics are predicted for the chemical kinetic times using the complete chemical mechanism over the entire operating space. These times are then correlated to the reactor conditions using an exponential fit. Simple first order reaction expressions are then used to find the conversion in the reactor. The method uses a two-time step kinetic scheme. The first time averaged step is used at the initial times with smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, temperature, and pressure. The second instantaneous step is used at higher water concentrations (> 1 x 10(exp -20) moles/cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and water mole concentrations, pressure and temperature (T4). The simple correlations are then compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. This time is regressed over the complete initial conditions using the Excel regression routine. Chemical kinetic time equations for H2 and NOx are obtained for H2/air fuel and for the H2/O2. A similar correlation is also developed using data from NASA s Chemical Equilibrium Applications (CEA) code to determine the equilibrium temperature (T4) as a function of overall fuel/air ratio, pressure and initial temperature (T3). High values of the regression coefficient R2 are obtained.

Molnar, Melissa; Marek, C. John

2005-01-01

344

Effect of Hydrologic and Geochemical Conditions on Oxygen-Enhanced Bioremediation in a Gasoline-Contaminated Aquifer  

USGS Publications Warehouse

The effect of pre-existing factors, e.g., hydrologic, geochemical, and microbiological properties, on the results of oxygen addition to a reformulated gasoline-contaminated groundwater system was studied. Oxygen addition with an oxygen-release compound (a proprietary form of magnesium peroxide produced different results with respect to dissolved oxygen (DO) generation and contaminant decrease in the two locations. Oxygen-release compound injected at the former UST source area did not significantly change measured concentrations of DO, benzene, toluene, or MTBE. Conversely, oxygen-release compound injected 200 m downgradient of the former UST source area rapidly increased DO levels, and benzene, toluene, and MTBE concentrations decreased substantially. The different results could be related to differences in hydrologic and geochemical conditions that characterized the two locations prior to oxygen addition. The lack of recharge to ground water in the paved UST source area led to a much larger geochemical sink for DO compared to ground water in the unpaved area.

Landmeyer, J. E.; Bradley, P. M.

2003-01-01

345

Hybrid membrane--PSA system for separating oxygen from air  

DOEpatents

A portable, non-cryogenic, oxygen generation system capable of delivering oxygen gas at purities greater than 98% and flow rates of 15 L/min or more is described. The system consists of two major components. The first component is a high efficiency membrane capable of separating argon and a portion of the nitrogen content from air, yielding an oxygen-enriched permeate flow. This is then fed to the second component, a pressure swing adsorption (PSA) unit utilizing a commercially available, but specifically formulated zeolite compound to remove the remainder of the nitrogen from the flow. The system is a unique gas separation system that can operate at ambient temperatures, for producing high purity oxygen for various applications (medical, refining, chemical production, enhanced combustion, fuel cells, etc . . . ) and represents a significant advance compared to current technologies.

Staiger, Chad L. (Albuquerque, NM); Vaughn, Mark R. (Albuquerque, NM); Miller, A. Keith (Albuquerque, NM); Cornelius, Christopher J. (Blackburg, VA)

2011-01-25

346

Modelling Spontaneous Combustion of Coal  

Microsoft Academic Search

Spontaneous combustion of coal is an important problem in mining and storage, in terms of both safety and economics. This is because coal reacts with oxygen in the air and an exothermic reaction occurs, even in ambient conditions. The heat of the reaction accumulates and the reaction becomes progressively faster and thermal runaway may take place to the point of

Ahmet ARISOY; B. Basil BEAMISH

347

On-line measurement of heat of combustion  

NASA Technical Reports Server (NTRS)

An experimental method for an on-line measurement of heat of combustion of a gaseous hydrocarbon fuel mixture of unknown composition is developed. It involves combustion of a test gas with a known quantity of air to achieve a predetermined oxygen concentration level in the combustion products. This is accomplished by a feedback controller which maintains the gas volumetric flow rate at a level consistent with the desired oxygen concentration in the products. The heat of combustion is determined from a known correlation with the gas volumetric flow rate. An on-line microcomputer accesses the gas volumetric flow data, and displays the heat of combustion values at desired time intervals.

Chaturvedi, S. K.; Chegini, H.

1988-01-01

348

Flameless Combustion for Gas Turbines  

NASA Astrophysics Data System (ADS)

An experimental study of a novel flameless combustor for gas turbine engines is presented. Flameless combustion is characterized by distributed flame and even temperature distribution for high preheat air temperature and large amount of recirculating low oxygen exhaust gases. Extremely low emissions of NOx, CO, and UHC are reported. Measurements of the flame chemiluminescence, CO and NOx emissions, acoustic pressure, temperature and velocity fields as a function of the preheat temperature, inlet air mass flow rate, exhaust nozzle contraction ratio, and combustor chamber diameter are described. The data indicate that larger pressure drop promotes flameless combustion and low NOx emissions at the same flame temperature. High preheated temperature and flow rates also help in forming stable combustion and therefore are favorable for flameless combustion.

Gutmark, Ephraim; Li, Guoqiang; Overman, Nick; Cornwell, Michael; Stankovic, Dragan; Fuchs, Laszlo; Milosavljevic, Vladimir

2006-11-01

349

Coencapsulation of oxygen carriers and glucose oxidase in polyelectrolyte complex capsules for the enhancement of D-gluconic acid and delta-gluconolactone production.  

PubMed

A novel encapsulated oxidative biocatalyst comprising glucose oxidase (GOD) coencapsulated with oxygen carriers within polyelectrolyte complex capsules was developed for the production of D-gluconic acid and delta-gluconolactone. The capsules containing immobilized GOD were produced by polyelectrolyte complexation with sodium alginate (SA) and cellulose sulfate (CS) as polyanions, poly(methylene-co-guanidine) (PMCG) as the polycation, CaCl(2) as the gelling agent and NaCl as the antigelling agent (GOD-SA-CS/PMCG capsules). Poly(dimethylsiloxane) (PDMS) and an emulsion of n-dodecane (DOD) or perfluorodecaline (PFD) with PDMS were used as the oxygen carriers and MnO(2) was used as a hydrogen peroxide decomposition catalyst. Water-soluble PDMS was found to act as both an oxygen carrier and an emulsifier of water-insoluble DOD and PFD. Stable microcapsules could be produced with concentrations of up to 4% (w/w) of PDMS, 10% (w/w) of DOD and PFD, and 25% (w/w) of MnO(2) in the polyanion solution of SA and CS. Roughly a two-fold increase in the GOD activity from 21.0+/-1.1 to 38.4+/-2.0 U*g(-1) and product space-time yields (STY) from 44.3+/-2.0 to 83.4+/-3.4 g*H*day(-1) could be achieved utilizing coencapsulated oxygen carriers compared to GOD encapsulated in the absence of oxygen carriers. This enhanced production does not significantly depend on the selected oxygen carrier under the conditions used in this study. PMID:20222845

Bucko, Marek; Gemeiner, Peter; Vikartovská, Alica; Mislovicová, Danica; Lacík, Igor; Tkác, Ján

2010-04-01

350

Enhanced Kosterlitz-Thouless Transitions in Yttrium BARIUM(2) COPPER(3) OXYGEN(7-X)/PRASEODYMIUM BARIUM(2) COPPER(3) OXYGEN(7-X) Superlattices  

NASA Astrophysics Data System (ADS)

The superconducting properties of YBa _2Cu_3O_ {7-x}/PrBa_2Cu _3O_{7-x} superlattices with ultrathin YBa_2 Cu_3O_{7 -x} layers were studied. The superlattices were multilayered films grown epitaxially on (100) SrTiO_3 and LaAlO_3 substrates by pulsed-laser deposition. They were characterized by several methods and found to have good structural and electrical characteristics. Strongly enhanced Kosterlitz-Thouless transitions were observed in the multilayers composed of two and four unit cells of YBa_2Cu_3 O_{7-x}, separated by insulating PrBa_2Cu_3 O_{7-x}. The parameter tau_{KT} = (T_{co} - T_{KT})/ T_{co} was up to an order of magnitude larger than in single crystals or in thicker films of YBa_2Cu _3O_{7-x}, showing that two-dimensional behavior is more closely approached in the multilayers. Here T_{co} is the mean-field transition temperature and T_{KT} is the Kosterlitz-Thouless transition temperature. Our results confirm that the enhancement of two -dimensionality is accompanied by a lowering of T _{co} in the ultrathin layers of YBa_2Cu_3 O_{7-x}. We interpret this as direct evidence that interlayer coupling is essential for the higher transition temperature observed in the bulk.

Vadlamannati, Sharma S.

1991-02-01

351

Prooxidant action of maltol: role of transition metals in the generation of reactive oxygen species and enhanced formation of 8-hydroxy-2'-deoxyguanosine formation in DNA.  

PubMed

Maltol (3-hydroxy-2-methyl-4-pyrone) produced reactive oxygen species as a complex with transition metals. Maltol/iron complex inactivated aconitase the most sensitive enzyme to oxidative stress. The inactivation of aconitase was iron-dependent, and prevented by TEMPOL, a scavenger of reactive oxygen species, suggesting that the maltol/iron-mediated generation of superoxide anion is responsible for the inactivation of aconitase. Addition of maltol effectively enhanced the ascorbate/copper-mediated formation of 8-hydroxy-2'-deoxyguanosine in DNA. Oxidation of ascorbic acid by CuSO(4) was effectively stimulated by addition of maltol, and the enhanced oxidation rate was markedly inhibited by the addition of catalase and superoxide dismutase. These results suggest that maltol can stimulate the copper reduction coupled with the oxidation of ascorbate, resulting in the production of superoxide radical which in turn converts to hydrogen peroxide and hydroxyl radical. Cytotoxic effect of maltol can be explained by its prooxidant properties: maltol/transition metal complex generates reactive oxygen species causing the inactivation of aconitase and the production of hydroxyl radical causing the formation of DNA base adduct. PMID:16799863

Murakami, Keiko; Ishida, Kumiko; Watakabe, Kyoko; Tsubouchi, Ryoko; Haneda, Miyako; Yoshino, Masataka

2006-06-01

352

Highly-precise measurements of ambient oxygen using near-infrared cavity-enhanced laser absorption spectrometry.  

PubMed

Highly precise measurements of ambient oxygen have been used to constrain the carbon budget, study photosynthesis, estimate marine productivity, and prescribe individual pollution events to their point of origin. These studies require analyzers that can measure ambient oxygen with ppm-level precision. In this work, we utilize near-infrared off-axis integrated cavity output spectroscopy (off-axis ICOS) to quantify ambient oxygen with a precision (1?, 100s) of ±7 ppm. By periodically calibrating the instrument, the analyzer is capable of making oxygen measurements to better than ±1 ppm (1?). The sensor is highly linear (R(2) > 0.9999) over a wide dynamic range (0-100% oxygen). The sensor was combined with a commercial CO(2)/CH(4)/H(2)O Analyzer, and used to make measurements of respiration and fossil fuel pollution events with oxidative ratios ranging from 1.15-1.60. Future improvements will increase the analyzer precision (1?, 100s) to better than ±1.4 ppm, and decrease the periodic referencing interval to >1 h. By including an additional diode laser, the instrument can be extended to make simultaneous measurements of O(2), CO(2), and H(2)O to enable improved understanding of carbon dioxide production and loss. PMID:22924385

Gupta, Manish

2012-09-18

353

Enhanced response of microbial fuel cell using sulfonated poly ether ether ketone membrane as a biochemical oxygen demand sensor.  

PubMed

The present study is focused on the development of single chamber microbial fuel cell (SCMFC) using sulfonated poly ether ether ketone (SPEEK) membrane to determine the biochemical oxygen demand (BOD) matter present in artificial wastewater (AW). The biosensor produces a good linear relationship with the BOD concentration up to 650 ppm when using artificial wastewater. This sensing range was 62.5% higher than that of Nafion(®). The most serious problem in using MFC as a BOD sensor is the oxygen diffusion into the anode compartment, which consumes electrons in the anode compartment, thereby reducing the coulomb yield and reducing the electrical signal from the MFC. SPEEK exhibited one order lesser oxygen permeability than Nafion(®), resulting in low internal resistance and substrate loss, thus improving the sensing range of BOD. The system was further improved by making a double membrane electrode assembly (MEA) with an increased electrode surface area which provide high surface area for electrically active bacteria. PMID:24626398

Ayyaru, Sivasankaran; Dharmalingam, Sangeetha

2014-03-25

354

Biofuels Combustion  

NASA Astrophysics Data System (ADS)

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

Westbrook, Charles K.

2013-04-01

355

Biofuels combustion.  

PubMed

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

Westbrook, Charles K

2013-01-01

356

Internal and surface phenomena in metal combustion  

NASA Technical Reports Server (NTRS)

Combustion of metals has been widely studied in the past, primarily because of their high oxidation enthalpies. A general understanding of metal combustion has been developed based on the recognition of the existence of both vapor-phase and surface reactions and involvement of the reaction products in the ensuing heterogeneous combustion. However, distinct features often observed in metal particle combustion, such as brightness oscillations and jumps (spearpoints), disruptive burning, and non-symmetric flames are not currently understood. Recent metal combustion experiments using uniform high-temperature metal droplets produced by a novel micro-arc technique have indicated that oxygen dissolves in the interior of burning particles of certain metals and that the subsequent transformations of the metal-oxygen solutions into stoichiometric oxides are accompanied with sufficient heat release to cause observed brightness and temperature jumps. Similar oxygen dissolution has been observed in recent experiments on bulk iron combustion but has not been associated with such dramatic effects. This research addresses heterogeneous metal droplet combustion, specifically focusing on oxygen penetration into the burning metal droplets, and its influence on the metal combustion rate, temperature history, and disruptive burning. A unique feature of the experimental approach is the combination of the microgravity environment with a novel micro-arc Generator of Monodispersed Metal Droplets (GEMMED), ensuring repeatable formation and ignition of uniform metal droplets with controllable initial temperature and velocity. The droplet initial temperatures can be adjusted within a wide range from just above the metal melting point, which provides means to ignite droplets instantly upon entering an oxygen containing environment. Initial droplet velocity will be set equal to zero allowing one to organize metal combustion microgravity experiments in a fashion similar to usual microgravity liquid fuel droplet combustion studies. In addition, the internal compositions of rapidly quenched metal particles will be analyzed using SEM technique. Such compositions are similar to those existing during the combustion and provide new insight on metal combustion processes. The results of this experimental work will be used to model the fundamental mechanisms of metal combustion. Preliminary experimental results on Al and Zr particle combustion at normal gravity are discussed here.

Dreizin, Edward L.; Molodetsky, Irina E.; Law, Chung K.

1995-01-01

357

Kinetics of oxygen-enhanced water gas shift on bimetallic catalysts and the roles of metals and support  

NASA Astrophysics Data System (ADS)

The post-processing of reformate is an important step in producing hydrogen (H2) with low carbon monoxide (CO) for low temperature fuel cells from syn-gas. However, the conventional process consists of three steps, i.e. two steps of water gas shift (WGS) and preferential oxidation (PROX) of CO, and it is not suitable for mobile applications due to the large volume of water gas shift (WGS) catalysts and conditioning and/or regeneration necessary for these catalysts. Aiming at replacing those three steps by a simple one-step process, small amount of oxygen was added to WGS (the reaction called oxygen-enhanced water gas shift or OWGS) to promote the reaction kinetics and low pyrophoric ceria-supported bimetallic catalysts were employed for stable performance in this reaction. Not only CO conversion, but also H2 yield was found to increase by the O2 addition on CeO2-supported catalysts. The characteristics of OWGS, high H2 production rate at 200 to 300°C at short contact time where unreacted O2 exists, evidenced the impact of O2 addition on surface species on the catalyst. Around 1.5 of reaction order in CO for various CeO2-supported metal catalysts for OWGS compared to reaction orders in CO ranging from -0.1 to 0.6 depending on metal species for WGS shows O2 addition decreases CO coverage to free up the active sites for co-reactant (H2O) adsorption and activation. Among the monometallic and bimetallic catalysts, Pt-Cu and Pd-Cu bimetallic catalysts were superior to monometallic catalysts in OWGS. These bimetallic components were found to form alloys where noble metal is surrounded mainly by Cu to have strong interaction between noble metal and copper resulting in high OWGS activity and low pyrophoric property. The metal loadings were optimized for CeO2-supported Pd-Cu bimetallic system and 2 wt% Pd with 5 -- 10 wt% Cu were found to be the optimum for the present OWGS condition. In the kinetic study, Pd in Pd-Cu was shown to increase the active sites for H2O dissociation and/or the subsequent reaction with chemisorbed CO as well as Pd keeps Cu in reduced state. Cu was found to keep Pd dispersed, suppress H2 activation on Pd, and facilitate CO 2 desorption from catalyst surface. While composition and structure of metal have large impacts on OWGS performance, CeO2 was shown to create new sites for H2O activation at metal-ceria interfacial region in concert with metal. These new sites strongly activate H2O to drive OWGS and WGS compared to the pure metallic sites which are present in majority on Al2O3-supported catalyst. The observed two regimes of turnover rate, the one dependent on catalyst surface area and the other independent of surface area, strongly suggested bifunctional reaction pathway where the reaction rate is determined by activation of H2O and by association of chemisorbed CO and H 2O. The associative route was also evidenced by pulse response study where the reaction occurs only when CO and H2O pulses are supplied together, and thus pre-adsorbed species such as formate and carbonate identified by FT-IR are proven to be spectators. No correlation between WGS rate and isotopic exchange rate of molecularly adsorbed D2O with H 2 showed H2O dissociation is necessary for WGS to occur. Long duration tests revealed CeO2-supported Pd-Cu, Pt-Cu and Cu catalysts are stable in OWGS condition compared to Pt, Pd, and Al 2O3-supported Pd-Cu catalysts which exhibited continuous deactivation during about 70 hours of test. The addition of Cu prevents agglomeration of monometallic Pd and carbonate formation on monometallic Pt during the reaction. The better activity and stability of Pd-Cu and Pt-Cu bimetallic catalysts in the realistic OWGS condition were ascribed to the unique active sites consisting of highly dispersed Pd in Cu or Pt in Cu on CeO2, which are good for H2O activation with low reaction inhibition by the product gases. Pt monometallic catalyst showed and highest activity in OWGS in the absence of product gases, but this was found vulnerable in the presence of product gases due to strong adsorption of H2 and CO2 on t

Kugai, Junichiro

358

Extracellular Matrix Degradation Products and Low-Oxygen Conditions Enhance the Regenerative Potential of Perivascular Stem Cells  

PubMed Central

Tissue and organ injury results in alterations of the local microenvironment, including the reduction in oxygen concentration and degradation of the extracellular matrix (ECM). The response of perivascular stem cells to these microenvironment changes are of particular interest because of their wide distribution throughout the body and their potential involvement in tissue and organ response to injury. The chemotactic, mitogenic, and phenotypic responses of this stem cell population were evaluated in response to a combination of decreased oxygen concentration and the presence of ECM degradation products. Culture in low-oxygen conditions resulted in increased proliferation and migration of the cells and increased activation of the ERK signaling pathway and associated integrins without a change in cell surface marker phenotype. The addition of ECM degradation products were additive to these processes. Reactive oxygen species within the cells were increased in association with the mitogenic and chemotactic responses. The increased proliferation and chemotactic properties of this stem cell population without any changes in phenotype and differentiation potential has important implications for both in vitro cell expansion and for in vivo behavior of these cells at the site of injury. PMID:20653348

Tottey, Stephen; Corselli, Mirko; Jeffries, Eric M.; Londono, Ricardo; Peault, Bruno

2011-01-01

359

Lack of enhanced preservation of organic matter in sediments under the oxygen minimum on the Oman Margin  

SciTech Connect

The impingement of oxygen minima on continental margins is widely thought to promote the accumulation of sedimentary facies enriched in well-preserved organic matter. It is shown here, however, that such a relationship does not clearly apply to the productive Oman Margin in the Arabian Sea, which hosts one of the most severe oxygen minima in the oceans. Measurements made on the 0-1 cm depth interval from fourteen box cores collected from the outer shelf-upper continental slope area off Oman show that (1) deposited organic matter is overwhelmingly of marine origin, (2) there is no significant correlation between the abundance of sedimentary organic carbon (C{sub org}) and the bottom-water O{sub 2} concentration, (3) there is no relation between the sedimentary C{sub org}:N ratio and bottom-water O{sub 2}, and (4) there is no correlation between the hydrogen index (HI) of the organic matter and bottom water oxygen. There are, however, significant correlations between the C{sub org}:N ratio and the I:C{sub org}, Cr:Al, and Zr:Al ratios, as well as between the C{sub org}:N ratio and the hydrogen index. Overall, these data suggest that the bottom water oxygen concentration has little effect in governing either the distribution of the degree of preservation of organic matter on this margin. Thus, the generally high but spatially variable C{sub org} content of the sediments on the Oman Margin may not reflect the occurrence of an oxygen minimum but instead be the result of a high settling flux of organic matter, supported by monsoon-driven upwelling, and post-depositional redistribution of the organic material by hydrodynamic influences.

Pedersen, T.F. (Univ. of British Columbia, Vancouver (Canada)); Shimmield, G.B.; Price, N.B. (Univ. of Edinburgh (United Kingdom))

1992-01-01

360

Combustion & Health  

E-print Network

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

Hamilton, W.

2012-01-01

361

Study of methods for applying and enhancing transfer film coatings of polytetrafluoroethylene (PTEE) to Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbo Pump (HPOTP) bearings  

NASA Technical Reports Server (NTRS)

Machines were constructed and evaluated for burnishing polytetrafluoroethylene on balls for use in the high pressure oxygen turbopump (HPOTP). The most positive performance was obtained with single-ball burnishing, but one technique for burnishing three balls simultaneously holds promise. Evaluations of the coatings in a HPOTP bearing of earlier design (employed smaller diameter balls) showed very little life enhancement before high torque and ball and race wear initiated. Other coating techniques, such as molybdenum disulfide combined with PTFE transfer films, hold promise for providing the more durable quantities of solid lubricant needed for the bearings.

Kannel, J. W.; Dufrane, K. F.; Zugaro, F. F.

1981-01-01

362

Oxygen and hydrogen atom concentration profiles in the premixed propane/oxygen flame  

NASA Technical Reports Server (NTRS)

The oxygen and hydrogen free radical (atom) concentration profiles in the premixed propane/oxygen flame at 92.5% oxygen were determined using electron spin resonance (ESR) spectroscopy techniques. The ESR instrument was specially modified so that the flame can be probed for determining the oxygen and hydrogen atom population densities during the actual combustion process of propane burning in oxygen. The technique used for propane is similar to that suggested by Fristrom and Westenberg to measure the free radical concentration profiles in C-C hydrocarbon/oxygen combustion.

Downs, W. R.; Simmons, E. L.

1974-01-01

363

Gain and continuous-wave laser power enhancement with a secondary discharge to predissociate molecular iodine in an electric oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Herein the authors report on the demonstration of a 50% enhancement in gain and 38% enhancement in continuous-wave laser power on the 1315nm transition of atomic iodine through the addition of a secondary discharge to predissociate the molecular iodine in an electric oxygen-iodine laser. In the primary discharge the O2(a?1) is produced by a radio-frequency-excited electric discharge sustained in an O2-He-NO gas mixture, and I(P1/22) is then pumped using energy transferred from O2(a?1). A gain of 0.10%cm-1 was obtained and the total laser output power was 6.2W.

Benavides, G. F.; Zimmerman, J. W.; Woodard, B. S.; Carroll, D. L.; Verdeyen, J. T.; Field, T. H.; Palla, A. D.; Solomon, W. C.

2008-01-01

364

Microfluidic surface-enhanced Raman scattering sensors based on nanopillar forests realized by an oxygen-plasma-stripping-of-photoresist technique.  

PubMed

A novel surface-enhanced Raman scattering (SERS) sensor is developed for real-time and highly repeatable detection of trace chemical and biological indicators. The sensor consists of a polydimethylsiloxane (PDMS) microchannel cap and a nanopillar forest-based open SERS-active substrate. The nanopillar forests are fabricated based on a new oxygen-plasma-stripping-of-photoresist technique. The enhancement factor (EF) of the SERS-active substrate reaches 6.06 × 10(6) , and the EF of the SERS sensor is about 4 times lower due to the influence of the PDMS cap. However, the sensor shows much higher measurement repeatability than the open substrate, and it reduces the sample preparation time from several hours to a few minutes, which makes the device more reliable and facile for trace chemical and biological analysis. PMID:23606301

Mao, Haiyang; Wu, Wengang; She, Didi; Sun, Gongchen; Lv, Pengpeng; Xu, Jun

2014-01-15

365

Facial Synthesis of PtM (M = Fe, Co, Cu, Ni) Bimetallic Alloy Nanosponges and Their Enhanced Catalysis for Oxygen Reduction Reaction.  

PubMed

Constructing electrocatalysts with enhanced activity and stability is necessary due to the increasing demands of the fuel cell industry. This work demonstrates a facile approach to synthesize well-defined three-dimensional (3D) PtM (M = Fe, Co, Cu, Ni) bimetallic alloy nanosponges (BANs) in the presence of Al. Significantly, with the aid of Al, the as-prepared BANs exhibit greatly enhanced electrochemistry catalytic activity in an oxygen reduction reaction (ORR), and PtFe BANs appear the best ORR property among the four BANs and commercial Pt/C catalysts. This work may provide a universal approach for convenient and large-scale fabrication of porous bimetallic nanocatalysts, thus providing promising potential application as an efficient cathodic component in fuel cells for industrial production. PMID:25223424

Zhu, Zhijun; Zhai, Yanling; Dong, Shaojun

2014-10-01

366

Enhancement of the efficiency and control of emission parameters of an unstable-resonator chemical oxygen-iodine laser  

SciTech Connect

The outlook is considered for the development of a high-power supersonic flowing chemical oxygen-iodine laser operating as an amplifier and controlled by radiation from a master oscillator by using an unstable resonator with a hole-coupled mirror. The influence of the seed radiation intensity, the coupling-hole diameter, the active-medium length, and the magnification factor on the parameters of laser radiation is analysed. It is shown that the use of such resonators is most advisable in medium-power oxygen-iodine lasers for which classical unstable resonators are inefficient because of their low magnification factors. The use of unstable resonators with a hole-coupled mirror and injection provides the control of radiation parameters and a considerable increase in the output power and brightness of laser radiation. (control of laser radiation parameters)

Boreisho, A S; Lobachev, V V; Savin, A V; Strakhov, S Yu; Trilis, A V [Institute of Laser Instruments and Technologies, D F Ustinov 'VOENMEKh' Baltic State Technical University, St Petersburg (Russian Federation)

2007-07-31

367

Spray combustion stability  

NASA Technical Reports Server (NTRS)

The central purpose of this project is the improvement of liquid-fueled rocket motor design technology in order to assist the establishment of economical commercial access to space through the development of engines with enhanced performance and reliability. Specific research effort in the project is focused on spray physics and associated combustion instability phenomena. Results garnered from this work will contribute to the development of new computational tools for design of stable liquid propellant rocket engines. The specific objectives of the research effort include identifying and evaluating physical submodels which pertain to spray combustion stability with the idea of enhancing or refining existing submodels with a more comprehensive approach. In particular, any refinements to the spray combustion physical submodels which are achieved during the project will be channeled back to Rocketdyne for incorporation in their ARICC liquid rocket combustor code as second generation improvements. Also, as the ARICC code forms the basis or future CFD development, some effort is devoted to an evaluation of the code's capability for modeling oscillating pressure waves within the combustor.

Liang, Pak-Yan; Jeng, S. M.; Litchford, Ronald

1995-01-01

368

Enhanced chemical oxygen demand removal and flux reduction in pulp and paper wastewater treatment using laccase-polymerized membrane filtration  

Microsoft Academic Search

The purpose of this present study is to investigate the removal efficiency of chemical oxygen demand (COD) from pulp and paper wastewater using laccase-polymerized membrane filtration process. The membranes with molecular weight cut-off (MWCO) of 5000 and 10,000, 30,000 and 54,000 were used in a cross-flow module to treat the pulp and paper wastewater containing high phenolic constituents and COD.

Chun-Han Ko; Chihhao Fan

2010-01-01

369

Enhancement of oxygen reduction activity with addition of carbon support for non-precious metal nitrogen doped carbon catalyst  

Microsoft Academic Search

An improved synthesis scheme of non-precious metal N-doped carbon catalysts for oxygen reduction reaction is reported. The non-precious metal N-doped carbon catalysts were prepared by pyrolysis of the mixture (phenol resin, Ketjen black carbon support and cobalt phenanthroline complex). The drastic improvement of distribution state of Ketjen black supported non-precious metal N-doped carbon catalysts was observed by means of transmission

Taigo Onodera; Shuichi Suzuki; Takaaki Mizukami; Hisao Kanzaki

2011-01-01

370

Rapid quantification of oxygen tension in blood flow with a fluorine nanoparticle reporter and a novel blood flow-enhanced-saturation-recovery sequence.  

PubMed

We present a novel blood flow-enhanced-saturation-recovery (BESR) sequence, which allows rapid in vivo T1 measurement of blood for both (1)H and (19)F nuclei. BESR sequence is achieved by combining homogeneous spin preparation and time-of-flight image acquisition and therefore preserves high time efficiency and signal-to-noise ratio for (19)F imaging of circulating perfluorocarbon nanoparticles comprising a perfluoro-15-crown-5-ether core and a lipid monolayer (nominal size = 250 nm). The consistency and accuracy of the BESR sequence for measuring T1 of blood was validated experimentally. With a confirmed linear response feature of (19)F R1 with oxygen tension in both salt solution and blood sample, we demonstrated the feasibility of the BESR sequence to quantitatively determine the oxygen tension within mouse left and right ventricles under both normoxia and hyperoxia conditions. Thus, (19)F BESR MRI of circulating perfluorocarbon nanoparticles represents a new approach to noninvasively evaluate intravascular oxygen tension. PMID:22915328

Hu, Lingzhi; Chen, Junjie; Yang, Xiaoxia; Caruthers, Shelton D; Lanza, Gregory M; Wickline, Samuel A

2013-07-01

371

Process modeling and analysis of CO? purification for oxy-coal combustion  

E-print Network

Oxy-coal combustion technology has great potential as one of the major CO2 capture technologies for power generation from coal. The distinguishing feature of oxy-coal combustion is that the oxygen source is a high concentration ...

Iloeje, Chukwunwike Ogbonnia

2011-01-01

372

Enthalpies of Combustion and Formation of Cyclopropylamine. The C-N Thermochemical Bond Energy.  

National Technical Information Service (NTIS)

The standard enthalpy of combustion of liquid cyclopropylamine was found by oxygen-bomb combustion calorimetry. The enthalpy of vaporization was derived from vapor pressure measurements, and the standard enthalpy of formation in the ideal gaseous state wa...

R. T. Moore, W. D. Good

1971-01-01

373

Alkene and arene combustion on Pd(111)  

SciTech Connect

Palladium-catalyzed combustion reactions can play a significant role in the control of auto emissions in the three-way catalytic converter. Oxidation reactions of ethene, propene, 1-butene, 1,3-butadiene, benzene, and toluene were studied on oxygen-precovered Pd(111) (0.25 ML--1.2 ML) using temperature-programmed reaction spectroscopy (TPRS). Combustion is the sole reaction pathway; no partial oxidation products are formed. Comparison of these results with those from Pd(100) demonstrates that the structure of the metal surface does not significantly affect the mechanism of catalytic oxidation of most of the olefins or aromatic hydrocarbons studied, although, in general, combustion occurs at higher temperatures on Pd(111). Only for benzene combustion is there an appreciable structure sensitivity. For all the hydrocarbons studied the CO{sub 2} and CO yields are maximized for an oxygen precoverage of 0.34 oxygen atoms per surface palladium atom. Abrupt increases in carbon oxide production at specific oxygen coverages indicate that oxygen-induced surface reconstructions may play a role in the combustion activity.

Harris, T.D.; Madix, R.J. [Stanford Univ., CA (United States)] [Stanford Univ., CA (United States)

1998-09-10

374

Platelet-activating factor enhances tumour metastasis via the reactive oxygen species-dependent protein kinase casein kinase 2-mediated nuclear factor-?B activation.  

PubMed

Platelet-activating factor (PAF) promotes tumour metastasis via activation of the transcription factor nuclear factor-?B (NF-?B). We here investigated the role of the protein kinase CK2 (formerly Casein Kinase 2 or II) in PAF-induced NF-?B activation and tumour metastasis, given that PAF has been reported to increase CK2 activity, and that CK2 plays a key role in NF-?B activation. PAF increased CK2 activity, phosphorylation and protein expression in vivo as well as in vitro. CK2 inhibitors inhibited the PAF-mediated NF-?B activation and expression of NF-?B-dependent pro-inflammatory cytokines and anti-apoptotic factors. Pre-treatment with the antioxidant N-Acetyl-L-Cysteine (NAC) resulted in a significant inhibition in PAF-induced enhancement of CK2 activity, phosphorylation and protein expression in vivo as well as in vitro. H2 O2 and known reactive oxygen species inducers, lipopolysaccharide (LPS) and tumour necrosis factor-? (TNF-?) enhanced CK2 activity, phosphorylation and protein expression, which was again inhibited by antioxidant. PAF, LPS and TNF-? induced increased CK2 activity, phosphorylationand protein expression, which were inhibited by p38 inhibitor. PAF, LPS or TNF-? increased pulmonary metastasis of B16F10, which was inhibited by antioxidants, CK2 inhibitor and p38 inhibitor. Our data suggest that (i) reactive oxygen species activate CK2 via p38, which, in turn, induces NF-?B activation, and (ii) PAF, LPS and TNF-? increase pulmonary tumour metastasis via the induction of the reactive oxygen species (ROS)/p38/CK2/NF-?B pathway. PMID:24628121

Kim, Kyoung-Jin; Cho, Kyung-Deuk; Jang, Kyu Yun; Kim, Han-A; Kim, Hae-Kyoung; Lee, Hern-Ku; Im, Suhn-Young

2014-09-01

375

Combustion control  

Microsoft Academic Search

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

Zabielski

1990-01-01

376

Advanced Combustion  

SciTech Connect

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

Holcomb, Gordon R. [NETL

2013-03-11

377

Combustion characteristics of ethanol in a porous ceramic burner and ignition improved by enhancement of liquid-fuel intrusion in the pore with ultrasonic irradiation  

Microsoft Academic Search

Porous burner has a potential of lower-emission in a combustion of liquid fuels. However, it would be less attractive owing to its complexity and inefficiency in operations of the fuel vaporizing, in view of a practical application. To solve the problem described above, an ignition promoted system is proposed with taking advantages of characteristics of the porous burner. In this

Takuya Fuse; Noriyuki Kobayashi; Masanobu Hasatani

2005-01-01

378

Enhanced magnetoresistance induced by oxygen deficiency in La0.4Ca0.6MnO3-? oxides  

NASA Astrophysics Data System (ADS)

We report electrical features and magnetoresistance behavior of the oxygen deficient La0.4Ca0.6MnO3-? perovskites (? = 0, 0.15, and 0.2). These samples will be referred to as S0, S15, and S20, respectively. The dependence of electrical transport on temperature and magnetic field is systematically investigated between 2 K and 400 K in magnetic field ranging up to 5 T. The parent compound shows a stable charge ordering/antiferromagnetic state with a semiconductor-like behavior in all considered temperature range. The variable range hopping and thermally activated hopping models are found to fit well with the electrical resistivity data at low and high temperatures, respectively. Oxygen deficiency tends to weaken the charge ordering and induce ferromagnetism and metallicity at low temperature. Metal insulator transition appears at higher fields for lower oxygen deficit (S15 sample) and without field for the S20 sample. The resistivity data for S15 sample are discussed in the framework of the variable-range hopping model. Abnormal transport properties were observed in the S20 sample, characterized by the double metal-insulator transitions and low minimum behavior. These results are discussed in terms of phenomenological percolation model, based on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions. While the parent compound shows no magnetoresistance, a large magnetoresistance is observed in the deficient samples at low temperature reaching 90% and 75% at 2 T for S15 and S20 samples, respectively. Noticeably, these values reached 98% and 91% at 5 T. The appearance of colossal magnetoresistance is attributed to the spin dependent hopping between spin clusters and/or ferromagnetic domains.

Triki, M.; Dhahri, E.; Hlil, E. K.; Garden, J. L.

2014-03-01

379

Enhancement of oxygen reduction activity with addition of carbon support for non-precious metal nitrogen doped carbon catalyst  

NASA Astrophysics Data System (ADS)

An improved synthesis scheme of non-precious metal N-doped carbon catalysts for oxygen reduction reaction is reported. The non-precious metal N-doped carbon catalysts were prepared by pyrolysis of the mixture (phenol resin, Ketjen black carbon support and cobalt phenanthroline complex). The drastic improvement of distribution state of Ketjen black supported non-precious metal N-doped carbon catalysts was observed by means of transmission electron microscopy (TEM). In addition, the non-precious metal N-doped carbon catalyst synthesized with Ketjen black carbon support showed much higher oxygen reduction reaction (ORR) activity relative to unsupported non-precious metal N-doped carbon catalyst in O2-saturated 0.5 mol l-1 H2SO4 at 35 °C. Moreover, the highest ORR activity was obtained with addition of optimum amount of Ketjen black carbon support was thirtyfold compared to unsupported non-precious metal N-doped carbon catalyst at 0.7 V. Similarly, the performance of a polymer electrolyte fuel cell (PEFC) using the non-precious metal N-doped carbon catalyst as the cathode electrode catalyst was obviously better than that of the non-precious metal N-doped carbon catalyst before optimization. Microstructure, specific surface area and surface composition of the non-precious metal N-doped carbon catalysts were analyzed by XRD, XPS and BET measurement with nitrogen physisorption, respectively.

Onodera, Taigo; Suzuki, Shuichi; Mizukami, Takaaki; Kanzaki, Hisao

2011-10-01

380

The Economics of Oxygen Enriched Air Production Via Membranes  

E-print Network

Oxygen enriched air combustion is a recognized approach to energy conservation. Conventional methods of producing oxygen enriched air: Pressure Swing Adsorption and Cryogenics, are energy-intensive and expensive. In this paper the economics of using...

Gollan, A.; Kleper, M. H.

1984-01-01

381

Chemical, color, and sensory attributes of sorghum bran-enhanced beef patties in a high oxygen environment  

E-print Network

Bottom rounds were shipped to the Rosenthal Meat Science and Technology Center, ground and enhanced with one of the following predetermined treatments: control; 0.4% sodium phosphates and 0.3% salt; 0.25% sorghum bran; 2.0% sorghum bran; 0...

Jenschke, Blaine Edward

2006-04-12

382

HEAT TRANSFER IN A PULSE COMBUSTION WATER HEATER  

Microsoft Academic Search

Pulse combustion devices offer several potential advantages over conventional burners, including enhanced efficiency, reduced size, automatic rejection of exhaust gases and consistency of operation over long time periods. This project was conducted in order to acquire an understanding of the heat transfer characteristics and pressure oscillations occurring in pulse combustion devices.^ A gas-fired pulse combustion water heater was utilized. This

HSIN-CHENG GARY HUANG; H. C. G

1984-01-01

383

Catalyzing the Combustion of Coal  

NASA Technical Reports Server (NTRS)

Reaction rate of coal in air can be increased by contacting or coating coal with compound such as calcium acetate. The enhanced reaction rate generates more heat, reducing furnace size. Increase in combustion rate is about 26 percent, and internal pollutants in powerplant are reduced.

Humphrey, M. F.; Dokko, W.

1982-01-01

384

OxLDL enhances L-type Ca2+ currents via lysophosphatidylcholine-induced mitochondrial reactive oxygen species (ROS) production  

Microsoft Academic Search

Objective: To examine the mechanisms underlying oxidised LDL- (oxLDL)-induced alterations in Ca2+ currents, an effect which underlies altered vascular contractility and cardiac myocyte function. Methods: Ca2+ currents (ICa) were recorded by whole-cell patch-clamp in HEK293 cells expressing L-type Ca 2+ channel a1C subunits or isolated rat ventricular myocytes. oxLDL (but not native LDL) significantly enhanced recombinant ICa, an effect mimicked

Ian M. Fearon

385

Enhancement of p-type conduction in Ag-doped ZnO thin films via Mg alloying: The role of oxygen vacancy  

NASA Astrophysics Data System (ADS)

ZnO, ZnMgO, Ag-doped ZnO (ZnO:Ag), and Ag-doped ZnMgO (ZnMgO:Ag) thin films have been prepared by pulsed laser deposition. All the films have a preferred orientation with the c-axis perpendicular to the substrates. Hall-effect measurements indicate that the ZnO:Ag film exhibits p-type conduction, but obviously worse than that of the ZnMgO:Ag film. A comparative study of p-type ZnO:Ag and ZnMgO:Ag films using photoluminescence and x-ray photoelectron spectroscopy measurements shows that the enhanced p-type conduction in ZnMgO:Ag film is closely related to the increase of the activation energy of the intrinsic donors and the suppression of charge-compensating oxygen-related defects after Mg incorporation.

Cao, Ling; Zhu, Liping; Ye, Zhizhen

2013-05-01

386

Assessing the end-organ in peripheral arterial occlusive disease--from contrast--enhanced ultrasound to blood-oxygen-level-dependent MR imaging  

PubMed Central

Peripheral arterial occlusive disease (PAOD) is a result of atherosclerotic disease which is currently the leading cause of morbidity and mortality in the western world. Patients with PAOD may present with intermittent claudication or symptoms related to critical limb ischemia. PAOD is associated with increased mortality rates. Stenoses and occlusions are usually detected by macrovascular imaging, including ultrasound and cross-sectional methods. From a pathophysiological view these stenoses and occlusions are affecting the microperfusion in the functional end-organs, such as the skin and skeletal muscle. In the clinical arena new imaging technologies enable the evaluation of the microvasculature. Two technologies currently under investigation for this purpose on the end-organ level in PAOD patients are contrast-enhanced ultrasound (CEUS) and blood-oxygen-level-dependent (BOLD) MR imaging (MRI). The following article is providing an overview about these evolving techniques with a specific focus on skeletal muscle microvasculature imaging in PAOD patients. PMID:24834413

Partovi, Sasan; Jacobi, Bjoern; Fergus, Nathan; Schulte, Anja-Carina; Robbin, Mark R.; Bilecen, Deniz; Staub, Daniel

2014-01-01

387

Sequential oxygen and alkali intercalation of epitaxial graphene on Ir(111): enhanced many-body effects and formation of pn-interfaces  

NASA Astrophysics Data System (ADS)

High quality epitaxial graphene films can be applied as templates for tailoring graphene–substrate interfaces that allow for precise control of the charge carrier behavior in graphene through doping and many-body effects. By combining scanning tunneling microscopy, angle-resolved photoemission spectroscopy and density functional theory we demonstrate that oxygen intercalated epitaxial graphene on Ir(111) has high structural quality, is quasi free-standing, and shows signatures of many-body interactions. Using this system as a template, we show that pn-interfaces can be patterned by adsorption and intercalation of rubidium, and that the n-doped graphene regions exhibit a reduced Coulomb screening via enhanced electron–plasmon coupling. These findings are central for understanding and tailoring the properties of graphene-metal contacts e.g. for realizing quantum tunneling devices.

Ulstrup, Søren; Andersen, Mie; Bianchi, Marco; Barreto, Lucas; Hammer, Bjørk; Hornekær, Liv; Hofmann, Philip

2014-09-01

388

Enhancement by Tumor Necrosis Factor Alpha of Dengue Virus-Induced Endothelial Cell Production of Reactive Nitrogen and Oxygen Species Is Key to Hemorrhage Development?  

PubMed Central

Hemorrhage is a severe manifestation of dengue disease. Virus strain and host immune response have been implicated as the risk factors for hemorrhage development. To delineate the complex interplay between the virus and the host, we established a dengue hemorrhage model in immune-competent mice. Mice inoculated intradermally with dengue virus develop hemorrhage within 3 days. In the present study, we showed by the presence of NS1 antigen and viral nuclei acid that dengue virus actively infects the endothelium at 12 h and 24 h after inoculation. Temporal studies showed that beginning at day 2, there was macrophage infiltration into the vicinity of the endothelium, increased tumor necrosis factor alpha (TNF-?) production, and endothelial cell apoptosis in the tissues. In the meantime, endothelial cells in the hemorrhage tissues expressed inducible nitric oxide synthase (iNOS) and nitrotyrosine. In vitro studies showed that primary mouse and human endothelial cells were productively infected by dengue virus. Infection by dengue virus induced endothelial cell production of reactive nitrogen and oxygen species and apoptotic cell death, which was greatly enhanced by TNF-?. NG-Nitro-l-arginine methyl ester and N-acetyl cysteine reversed the effects of dengue virus and TNF-? on endothelial cells. Importantly, hemorrhage development and the severity of hemorrhage were greatly reduced in mice lacking iNOS or p47phox or treatment with oxidase inhibitor, pointing to the critical roles of reactive nitrogen and oxygen species in dengue hemorrhage. PMID:18842737

Yen, Yu-Ting; Chen, Hseun-Chin; Lin, Yang-Ding; Shieh, Chi-Chang; Wu-Hsieh, Betty A.

2008-01-01

389

Wheat Oxophytodienoate Reductase Gene TaOPR1 Confers Salinity Tolerance via Enhancement of Abscisic Acid Signaling and Reactive Oxygen Species Scavenging1[C][W  

PubMed Central

The 12-oxo-phytodienoic acid reductases (OPRs) are classified into the two subgroups OPRI and OPRII. The latter proteins participate in jasmonic acid synthesis, while the function of the former ones is as yet unclear. We describe here the characterization of the OPRI gene TaOPR1, isolated from the salinity-tolerant bread wheat (Triticum aestivum) cultivar SR3. Salinity stress induced a higher level of TaOPR1 expression in the seedling roots of cv SR3 than in its parental cultivar, JN177. This induction was abolished when abscisic acid (ABA) synthesis was inhibited. The overexpression of TaOPR1 in wheat significantly enhanced the level of salinity tolerance, while its heterologous expression in Arabidopsis alleviated root growth restriction in the presence of salinity and oxidants and raised the sensitivity to ABA. In Arabidopsis, TaOPR1 promoted ABA synthesis and the ABA-dependent stress-responsive pathway, partially rescued the sensitivity of the Arabidopsis aba2 mutant defective in ABA synthesis to salinity, and improved the activities of reactive oxygen species scavengers and the transcription of their encoding genes while reducing malondialdehyde and reactive oxygen species levels. TaOPR1 did not interact with jasmonate synthesis or the jasmonate signaling pathway. Rather than serving purely as an antioxidant, we believe that TaOPR1 acts during episodes of abiotic stress response as a signaling compound associated with the regulation of the ABA-mediated signaling network. PMID:23321418

Dong, Wei; Wang, Mengcheng; Xu, Fei; Quan, Taiyong; Peng, Keqin; Xiao, Langtao; Xia, Guangmin

2013-01-01

390

Efficiency enhancement of organic light-emitting diodes with an oxygen-plasma-treated ITO substrate and an electron-injection layer of alkali-metal carbonates  

NASA Astrophysics Data System (ADS)

The efficiency enhancement of organic light-emitting diodes with an oxygen-plasma-treated substrate and an electron-injection layer of alkali-metal carbonates (Li2CO3 and Cs2CO3) was studied. The Li2CO3 and the Cs2CO3 carbonates were thermally evaporated to a thickness of 1 nm. For the device with a Li2CO3 layer, the luminance at 9.25 V of the device with the plasma-treated ITO substrate was found to be improved by approximately 10% compared to that of the device with the plasma-untreated ITO substrate, and the maximum luminance driving voltage was lowered by 1.0 V. For the device with a Cs2CO3 layer, the luminance at 11.25 V of the device with the oxygenplasma-treated ITO substrate was found to be improved by approximately 42.3% compared to that of the device with plasma-untreated ITO substrate, and the maximum luminance driving voltage was lowered by 1.25 V. Especially, the luminous efficiencies of the devices with the Li2CO3 and the Cs2CO3 layers were confirmed to have been increased by 50.0% and 78.1%, respectively, when the oxygen-plasma-treated ITO substrate was used.

Kang, Yong-Gil; Kim, Seung-Tae; Lee, Jong-Yong; Hong, Jin-Woong; Shin, Jong-Yeol; Kim, Tae-Wan

2014-05-01

391

Quantification of aromatic oxygenase genes to evaluate enhanced bioremediation by oxygen releasing materials at a gasoline-contaminated site.  

PubMed

Subsurface injection of oxygen-releasing materials (ORMs) is frequently performed at petroleum-contaminated sites to stimulate aerobic bioremediation of benzene, toluene, ethylbenzene, and xylenes (BTEX). In this study, qPCR enumeration of aromatic oxygenase genes and PCR-DGGE profiles of bacterial 16S rRNA genes were combined with groundwater monitoring to determine the impact of ORM injection on BTEX bioremediation at a gasoline-contaminated site. Prior to injection, BTEX concentrations were greater than 3 mg/L and DO levels were typically lessthan 2 mg/L, butphenol hydroxylase (PHE) and ring-hydroxylating toluene monooxygenase (RMO) genes were detected in impacted wells indicating the potential for aerobic BTEX biodegradation. Following injection, DO increased, BTEX concentrations decreased substantially, and PHE and RMO genes copies increased by 1-3 orders of magnitude. In addition, naphthalene dioxygenase (NAH) and xylene monooxygenase (TOL) genes were intermittently detected during periods of increased DO. Following depletion of the ORM, DO decreased, BTEX concentrations rebounded, and oxygenase genes were no longer detected. Temporal changes in PCR-DGGE microbial community profiles reflected the dynamic changes in subsurface conditions. Overall, the combination of chemical and geochemical analyses with quantification of aromatic oxygenase genes demonstrated that injection stimulated BTEX biodegradation until the ORM was depleted. PMID:19368209

Nebe, Jennifer; Baldwin, Brett R; Kassab, Raymond L; Nies, Loring; Nakatsu, Cindy H

2009-03-15

392

Enhanced Electrocatalytic Performance for Oxygen Reduction via Active Interfaces of Layer-By-Layered Titanium Nitride/Titanium Carbonitride Structures.  

PubMed

Cathode materials always limit the performance of fuel cells while the commercial platinum-based catalysts hardly meet the requirements of low cost, durable and stable. Here a non-precious metal oxygen reduction reaction (ORR) electocatalyst based on titanium nitride/titanium carbonitride hierarchical structures (TNTCNHS) is demonstrated as high activity as Pt/C. In alkaline condition, tuning interface/mass ratio of TiN/TiCN, we observed the onset potential of ~0.93?V vs. RHE and a limit diffusion current density of ~5.1?mA cm(-2) (at a rotating speed of 1600?rpm) on TNTCNHS with a relative low catalyst loading of ~0.1?mg cm(-2). The kinetic current, durability and tolerance to crossover effect studies reveal even more efficient than carbon-supported platinum. The architecture fabrication for such electrocatalyst is easy to realize in industrial-scale facilities, for the use of chemical vapor deposition (CVD) technique could support a huge area production (more than 10000?cm(2) for one pot) to satisfy the enormous market requirements in the future. PMID:25335930

Jin, Zhaoyu; Li, Panpan; Xiao, Dan

2014-01-01

393

Enhanced Electrocatalytic Performance for Oxygen Reduction via Active Interfaces of Layer-By-Layered Titanium Nitride/Titanium Carbonitride Structures  

NASA Astrophysics Data System (ADS)

Cathode materials always limit the performance of fuel cells while the commercial platinum-based catalysts hardly meet the requirements of low cost, durable and stable. Here a non-precious metal oxygen reduction reaction (ORR) electocatalyst based on titanium nitride/titanium carbonitride hierarchical structures (TNTCNHS) is demonstrated as high activity as Pt/C. In alkaline condition, tuning interface/mass ratio of TiN/TiCN, we observed the onset potential of ~0.93 V vs. RHE and a limit diffusion current density of ~5.1 mA cm-2 (at a rotating speed of 1600 rpm) on TNTCNHS with a relative low catalyst loading of ~0.1 mg cm-2. The kinetic current, durability and tolerance to crossover effect studies reveal even more efficient than carbon-supported platinum. The architecture fabrication for such electrocatalyst is easy to realize in industrial-scale facilities, for the use of chemical vapor deposition (CVD) technique could support a huge area production (more than 10000 cm2 for one pot) to satisfy the enormous market requirements in the future.

Jin, Zhaoyu; Li, Panpan; Xiao, Dan

2014-10-01

394

Enhanced Electrocatalytic Performance for Oxygen Reduction via Active Interfaces of Layer-By-Layered Titanium Nitride/Titanium Carbonitride Structures  

PubMed Central

Cathode materials always limit the performance of fuel cells while the commercial platinum-based catalysts hardly meet the requirements of low cost, durable and stable. Here a non-precious metal oxygen reduction reaction (ORR) electocatalyst based on titanium nitride/titanium carbonitride hierarchical structures (TNTCNHS) is demonstrated as high activity as Pt/C. In alkaline condition, tuning interface/mass ratio of TiN/TiCN, we observed the onset potential of ~0.93?V vs. RHE and a limit diffusion current density of ~5.1?mA cm?2 (at a rotating speed of 1600?rpm) on TNTCNHS with a relative low catalyst loading of ~0.1?mg cm?2. The kinetic current, durability and tolerance to crossover effect studies reveal even more efficient than carbon-supported platinum. The architecture fabrication for such electrocatalyst is easy to realize in industrial-scale facilities, for the use of chemical vapor deposition (CVD) technique could support a huge area production (more than 10000?cm2 for one pot) to satisfy the enormous market requirements in the future. PMID:25335930

Jin, Zhaoyu; Li, Panpan; Xiao, Dan

2014-01-01

395

Atomic layer-by-layer deposition of Pt on Pd nanocubes for catalysts with enhanced activity and durability toward oxygen reduction.  

PubMed

An effective strategy for reducing the Pt content while retaining the activity of a Pt-based catalyst is to deposit the Pt atoms as ultrathin skins of only a few atomic layers thick on nanoscale substrates made of another metal. During deposition, however, the Pt atoms often take an island growth mode because of a strong bonding between Pt atoms. Here we report a versatile route to the conformal deposition of Pt as uniform, ultrathin shells on Pd nanocubes in a solution phase. The introduction of the Pt precursor at a relatively slow rate and high temperature allowed the deposited Pt atoms to spread across the entire surface of a Pd nanocube to generate a uniform shell. The thickness of the Pt shell could be controlled from one to six atomic layers by varying the amount of Pt precursor added into the system. Compared to a commercial Pt/C catalyst, the Pd@PtnL (n = 1-6) core-shell nanocubes showed enhancements in specific activity and durability toward the oxygen reduction reaction (ORR). Density functional theory (DFT) calculations on model (100) surfaces suggest that the enhancement in specific activity can be attributed to the weakening of OH binding through ligand and strain effects, which, in turn, increases the rate of OH hydrogenation. A volcano-type relationship between the ORR specific activity and the number of Pt atomic layers was derived, in good agreement with the experimental results. Both theoretical and experimental studies indicate that the ORR specific activity was maximized for the catalysts based on Pd@Pt2-3L nanocubes. Because of the reduction in Pt content used and the enhancement in specific activity, the Pd@Pt1L nanocubes showed a Pt mass activity with almost three-fold enhancement relative to the Pt/C catalyst. PMID:24797061

Xie, Shuifen; Choi, Sang-Il; Lu, Ning; Roling, Luke T; Herron, Jeffrey A; Zhang, Lei; Park, Jinho; Wang, Jinguo; Kim, Moon J; Xie, Zhaoxiong; Mavrikakis, Manos; Xia, Younan

2014-06-11

396

Combustive management of oil spills  

SciTech Connect

Extensive experiments with in situ incineration were performed on a desert site at the University of Arizona with very striking results. The largest incinerator, 6 feet in diameter with a 30 foot chimney, developed combustion temperatures of 3000, F, and attendant soot production approximately 1000 times less than that produced by conventional in situ burning. This soot production, in fact, is approximately 30 times less than current allowable EPA standards for incinerators and internal combustion engines. Furthermore, as a consequence of the high temperature combustion, the bum rate was established at a very high 3400 gallons per hour for this particular 6 foot diameter structure. The rudimentary design studies we have carried out relative to a seagoing 8 foot diameter incinerator have predicted that a continuous burn rate of 7000 gallons per hour is realistic. This structure was taken as a basis for operational design because it is compatible with C130 flyability, and will be inexpensive enough ($120,000 per copy) to be stored at those seaside depots throughout the US coast line in which the requisite ancillary equipments (booms, service tugs, etc.) are already deployed. The LOX experiments verified our expectations with respect to combustion of debris and various highly weathered or emulsified oils. We have concluded, however, that the use of liquid oxygen in actual beach clean up is not promising because the very high temperatures associated with this combustion are almost certain to produce environmentally deleterious effects on the beach surface and its immediately sublying structures. However, the use of liquid oxygen augmentation for shore based and flyable incinerators may still play an important role in handing the problem of accumulated debris.

Not Available

1992-01-01

397

HIGH PRESSURE COAL COMBUSTION KINETICS PROJECT  

SciTech Connect

The HPCCK project was initiated with a kickoff meeting held on June 12, 2001 in Morgantown, WV, which was attended by all project participants. SRI's existing g-RCFR reactor was reconfigured to a SRT-RCFR geometry (Task 1.1). This new design is suitable for performing the NBFZ experiments of Task 1.2. It was decided that the SRT-RCFR apparatus could be modified and used for the HPBO experiments. The purchase, assembly, and testing of required instrumentation and hardware is nearly complete (Task 1.1 and 1.2). Initial samples of PBR coal have been shipped from FWC to SRI (Task 1.1). The ECT device for coal flow measurements used at FWC will not be used in the SRI apparatus and a screw type feeder has been suggested instead (Task 5.1). NEA has completed a upgrade of an existing Fluent simulator for SRI's RCFR to a version that is suitable for interpreting results from tests in the NBFZ configuration (Task 1.3) this upgrade includes finite-rate submodels for devolatilization, secondary volatiles pyrolysis, volatiles combustion, and char oxidation. Plans for an enhanced version of CBK have been discussed and development of this enhanced version has begun (Task 2.5). A developmental framework for implementing pressure and oxygen effects on ash formation in an ash formation model (Task 3.3) has begun.

Chris Guenther; Bill Rogers

2001-09-15

398

Oxygen-atom transfer reactivity of axially ligated mn(v)-oxo complexes: evidence for enhanced electrophilic and nucleophilic pathways.  

PubMed

Addition of anionic donors to the manganese(V)-oxo corrolazine complex Mn(V)(O)(TBP8Cz) has a dramatic influence on oxygen-atom transfer (OAT) reactivity with thioether substrates. The six-coordinate anionic [Mn(V)(O)(TBP8Cz)(X)](-) complexes (X = F(-), N3(-), OCN(-)) exhibit a ?5 cm(-1) downshift of the Mn-O vibrational mode relative to the parent Mn(V)(O)(TBP8Cz) complex as seen by resonance Raman spectroscopy. Product analysis shows that the oxidation of thioether substrates gives sulfoxide product, consistent with single OAT. A wide range of OAT reactivity is seen for the different axial ligands, with the following trend determined from a comparison of their second-order rate constants for sulfoxidation: five-coordinate ? thiocyanate ? nitrate < cyanate < azide < fluoride ? cyanide. This trend correlates with DFT calculations on the binding of the axial donors to the parent Mn(V)(O)(TBP8Cz) complex. A Hammett study was performed with p-X-C6H4SCH3 derivatives and [Mn(V)(O)(TBP8Cz)(X)](-) (X = CN(-) or F(-)) as the oxidant, and unusual "V-shaped" Hammett plots were obtained. These results are rationalized based upon a change in mechanism that hinges on the ability of the [Mn(V)(O)(TBP8Cz)(X)](-) complexes to function as either an electrophilic or weak nucleophilic oxidant depending upon the nature of the para-X substituents. For comparison, the one-electron-oxidized cationic Mn(V)(O)(TBP8Cz(•+)) complex yielded a linear Hammett relationship for all substrates (? = -1.40), consistent with a straightforward electrophilic mechanism. This study provides new, fundamental insights regarding the influence of axial donors on high-valent Mn(V)(O) porphyrinoid complexes. PMID:25238495

Neu, Heather M; Yang, Tzuhsiung; Baglia, Regina A; Yosca, Timothy H; Green, Michael T; Quesne, Matthew G; de Visser, Sam P; Goldberg, David P

2014-10-01

399

Enhanced reactive oxygen species scavenging by overproduction of superoxide dismutase and catalase delays postharvest physiological deterioration of cassava storage roots.  

PubMed

Postharvest physiological deterioration (PPD) of cassava (Manihot esculenta) storage roots is the result of a rapid oxidative burst, which leads to discoloration of the vascular tissues due to the oxidation of phenolic compounds. In this study, coexpression of the reactive oxygen species (ROS)-scavenging enzymes copper/zinc superoxide dismutase (MeCu/ZnSOD) and catalase (MeCAT1) in transgenic cassava was used to explore the intrinsic relationship between ROS scavenging and PPD occurrence. Transgenic cassava plants integrated with the expression cassette p54::MeCu/ZnSOD-35S::MeCAT1 were confirmed by Southern-blot analysis. The expression of MeCu/ZnSOD and MeCAT1 was verified by quantitative reverse transcription-polymerase chain reaction and enzymatic activity analysis both in the leaves and storage roots. Under exposure to the ROS-generating reagent methyl viologen or to hydrogen peroxide (H2O2), the transgenic plants showed higher enzymatic activities of SOD and CAT than the wild-type plants. Levels of malondialdehyde, chlorophyll degradation, lipid peroxidation, and H2O2 accumulation were dramatically reduced in the transgenic lines compared with the wild type. After harvest, the storage roots of transgenic cassava lines show a delay in their PPD response of at least 10 d, accompanied by less mitochondrial oxidation and H2O2 accumulation, compared with those of the wild type. We hypothesize that this is due to the combined ectopic expression of Cu/ZnSOD and CAT leading to an improved synergistic ROS-scavenging capacity of the roots. Our study not only sheds light on the mechanism of the PPD process but also develops an effective approach for delaying the occurrence of PPD in cassava. PMID:23344905

Xu, Jia; Duan, Xiaoguang; Yang, Jun; Beeching, John R; Zhang, Peng

2013-03-01

400

Enhance  

NSDL National Science Digital Library

It doesn't take a Photoshop expert to create attractive graphics for the Web. To prove this, the folks at MicroFrontier have released three graphic creation/editing packages for the Macintosh, each aimed at a different user level. All three applications support Photoshop 3.0 compatible plug-ins and basic features such as scanner support, image and resolution scaling, and basic image enhancement. Enhance, aimed at the graphics professionals, adds even more features, including multiple layers, opacity control, sixteen levels of undo, convolution filter effects, and CYMK support. A save-disabled demo version of each application is available at the MicroFrontier Website. The price for Enhance is $100 .

1998-01-01

401

Quercetin enhances apoptotic effect of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in ovarian cancer cells through reactive oxygen species (ROS) mediated CCAAT enhancer-binding protein homologous protein (CHOP)-death receptor 5 pathway.  

PubMed

Although tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has shown efficacy in a phase 2 clinical trial, development of resistance to TRAIL by tumor cells is a major roadblock. We investigated whether quercetin, a flavonoid, can sensitize human ovarian cancer cells to TRAIL. Results indicate that quercetin sensitized cancer cells to TRAIL. The quercetin induced expression of death receptor DR5 but did not affect expression of DR4 in cancer cells. The induction of DR5 was mediated through activation of JNK and through upregulation of a transcription factor CCAAT enhancer-binding protein homologous protein (CHOP); as silencing of these signaling molecules abrogated the effect of quercetin. Upregulation of DR5 was mediated through the generation of reactive oxygen species (ROS), as ROS scavengers reduced the effect of quercetin on JNK activation, CHOP upregulation, DR induction, TRAIL sensitization, downregulated the expression of cell survival proteins and upregulated the proapoptotic proteins. Furthermore, quercetin enhances TRAIL mediated inhibition of tumor growth of human SKOV-3 xenograft was associated with induction of apoptosis, activation of caspase-3, CHOP and DR5. Overall, our data suggest that quercetin enhances apoptotic death of ovarian cancer cells to TRAIL through upregulation of CHOP-induced DR5 expression following ROS mediated endoplasmic reticulum-stress. PMID:24612139

Yi, Liu; Zongyuan, Yang; Cheng, Gong; Lingyun, Zhang; Guilian, Yu; Wei, Gong

2014-05-01

402

Chemical Kinetic Modeling of Biofuel Combustion  

NASA Astrophysics Data System (ADS)

Bioalcohols, such as bioethanol and biobutanol, are suitable replacements for gasoline, while biodiesel can replace petroleum diesel. Improving biofuel engine performance requires understanding its fundamental combustion properties and the pathways of combustion. This study's contribution is experimentally validated chemical kinetic combustion mechanisms for biobutanol and biodiesel. Fundamental combustion data and chemical kinetic mechanisms are presented and discussed to improve our understanding of biofuel combustion. The net environmental impact of biobutanol (i.e., n-butanol) has not been studied extensively, so this study first assesses the sustainability of n-butanol derived from corn. The results indicate that technical advances in fuel production are required before commercializing biobutanol. The primary contribution of this research is new experimental data and a novel chemical kinetic mechanism for n-butanol combustion. The results indicate that under the given experimental conditions, n-butanol is consumed primarily via abstraction of hydrogen atoms to produce fuel radical molecules, which subsequently decompose to smaller hydrocarbon and