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

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

2000-10-01

2

Combustion and radiation characteristics of oxygen-enhanced inverse diffusion flame  

Microsoft Academic Search

The characteristics of combustion and radiation heat transfer of an oxygen-enhanced diffusion flame was experimentally analyzed.\\u000a An infrared radiation heat flux gauge was used to measure the thermal radiation of various types of flames with fuel, air\\u000a and pure oxygen. And the Laser Induced Incandescence (LII) technique was applied to characterize the soot concentrations which\\u000a mainly contribute to the continuum

Sang Soon Hwang; Jay P Gore

2002-01-01

3

Mult-Pollutant Control Through Novel Approaches to Oxygen Enhanced Combustion  

SciTech Connect

Growing concerns about global climate change have focused effortss on identifying approaches to stabilizing carbon dioxide levels in the atmosphere. One approach utilizes oxy-fuel combustion to produce a concentrated flue gas that will enable economical CO{sub 2} capture by direct methods. Oxy-fuel combustion rewuires an Air Separation Unit (ASU) to provide a high-purity stream of oxygen as well as a Compression and Purification Unit (CPU) to clean and compress the CO{sub 2} for long term storage. Overall plant efficiency will suffer from the parasitic load of both the ASU and CPU and researchers are investigating techniques to enhance other aspects of the combustion and gas cleanup proceses to improve the benefit-to-cost ratio. This work examines the influence of oxy-fuel combustion and non-carbon based sorbents on the formation and fate of multiple combustion pollutants both numerically and experimentally.

Richard Axelbaum; Pratim Biswas

2009-02-28

4

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

5

Hydrogen-oxygen powered internal combustion engine  

NASA Technical Reports Server (NTRS)

Hydrogen at 300 psi and oxygen at 800 psi are injected sequentially into the combustion chamber to form hydrogen-rich mixture. This mode of injection eliminates difficulties of preignition, detonation, etc., encountered with carburated, spark-ignited, hydrogen-air mixtures. Ignition at startup is by means of a palladium catalyst.

Cameron, H.; Morgan, N.

1970-01-01

6

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...

7

Pulse enhanced fluidized bed combustion  

SciTech Connect

Various technologies are available for the combustion of high-sulfur, high-ash fuels, particularly coal. From performance, economic and environmental standpoints, fluidized bed combustion (FBC) is the leading candidate for utilization of high sulfur coals. ThermoChem, Inc., and the South Carolina Energy Research and Development Center (SCERDC) are installing a hybrid fluidized bed combustion system at Clemson University. This hybrid system, known as the Pulsed Atmospheric Fluidized Bed Combustor (PAFBC), will augment the University`s steam system by providing 50--60,000 lbs/hr of saturated process steam. The PAFBC, developed by Manufacturing and Technology Conversion International, Inc., (MTCI), integrates a pulse combustor with a bubbling-bed-type atmospheric fluidized bed coal combustor. The pulse combustion system imparts an acoustic effect that enhances combustion efficiency, SO{sub 2} capture, low NO{sub x} emissions, and heat transfer efficiency in the fluidized bed. These benefits of pulse combustion result in modestly sized PAFBC units with high throughput rates and lower costs when compared to conventional fluidized bed units.

Mueller, B.; Golan, L. [South Carolina Energy Research and Development Center, Clemson, SC (United States); Toma, M.; Mansour, M. [Manufacturing and Technology Conversion International, Inc., Columbia, MD (United States)

1996-12-31

8

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

9

Test Would Quantify Combustion Oxygen From Different Sources  

NASA Technical Reports Server (NTRS)

Proposed isotope-enrichment scheme enables determination of contributions of dual sources of oxygen for combustion. Liquid oxygen or other artificial stream enriched with O(18) to about 1 percent by weight. Combustion products analyzed by mass spectrometer to measure relative abundances of H2O(18) and H2O(16). From relative abundances of water products measured, one computes relative contribution of oxygen extracted from stream compared to other source of oxygen in combustion process. Used to determine contributions of natural oxygen in air and liquid oxygen supplied in separate stream mixed with air or sent directly into combustion chamber.

Tapphorn, Ralph M.

1993-01-01

10

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

11

Quantitative Measurement of Oxygen in Microgravity Combustion  

NASA Technical Reports Server (NTRS)

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

Silver, Joel A.

1997-01-01

12

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

13

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

14

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

15

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

16

The combustion kinetics of coal chars in oxygen-enriched environments.  

SciTech Connect

Oxygen-enhanced and oxygen-fired pulverized coal combustion is actively being investigated to achieve emission reductions and reductions in flue gas cleanup costs, as well as for coal-bed methane and enhanced oil recovery applications. To fully understand the results of pilot scale tests and to accurately predict scale-up performance through CFD modeling, accurate rate expressions are needed to describe coal char combustion under these unconventional combustion conditions. In the work reported here, the combustion rates of two pulverized coal chars have been measured in both conventional and oxygen-enriched atmospheres. A combustion-driven entrained flow reactor equipped with an optical particle-sizing pyrometry diagnostic and a rapid-quench sampling probe has been used for this investigation. Highvale subbituminous coal and a high-volatile eastern United States bituminous coal have been investigated, over oxygen concentrations ranging from 6 to 36 mol% and gas temperatures of 1320-1800 K. The results from these experiments demonstrate that pulverized coal char particles burn under increasing kinetic control in elevated oxygen environments, despite their higher burning rates in these environments. Empirical fits to the data have been successfully performed over the entire range of oxygen concentrations using a single-film oxidation model. Both a simple nth-order Arrhenius expression and an nth-order Langmuir-Hinshelwood kinetic equation provide good fits to the data. Local fits of the nth-order Arrhenius expression to the oxygen-enriched and oxygen-depleted data produce lower residuals in comparison to fits of the entire dataset. These fits demonstrate that the apparent reaction order varies from 0.1 under near-diffusion-limit oxygen-depleted conditions to 0.5 under oxygen-enriched conditions. Burnout predictions show good agreement with measurements. Predicted char particle temperatures tend to be low for combustion in oxygen-depleted environments.

Shaddix, Christopher R.; Murphy, Jeffrey J.

2004-09-01

17

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...

18

Engine valve actuation for combustion enhancement  

DOEpatents

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

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

2008-03-04

19

Engine Valve Actuation For Combustion Enhancement  

DOEpatents

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

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

2004-05-18

20

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

EPA Science Inventory

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

21

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

22

Praxair's dilute oxygen combustion technology for pyrometallurgical applications  

NASA Astrophysics Data System (ADS)

Dilute oxygen combustion (DOC) technology uses separate high-velocity fuel and oxygen jets to generate strong in-furnace gas recirculation, producing combustion between the fuel and a highly diluted oxygen and furnace-gas mixture. These very low NOx oxy-fuel burners have been developed and commercially demonstrated in steel reheating furnaces. The burner design meets industry needs for increased productivity and lower operating costs with minimal capital expense and low maintenance. The performance of DOC technology has been measured under laboratory and industrial conditions encompassing both natural gas and coke oven gas firing, and a wide range of furnace temperatures and nitrogen levels that simulate air infiltration. This paper describes the results of the tests using natural gas as the fuel and lists potential applications for DOC technology in the non-ferrous metals industry.

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

2001-05-01

23

Powdered aluminum and oxygen rocket propellants: Subscale combustion experiments  

NASA Technical Reports Server (NTRS)

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

Meyer, Mike L.

1993-01-01

24

Combustion of coal chars in oxygen-enriched atmospheres  

SciTech Connect

This work pertains to the high-temperature combustion of pulverized coal chars under oxygen-enriched atmospheres. Single char particles were burned in a drop-tube furnace, electrically-heated to 1300-1500 K, in 21%, 50% and 100% O{sub 2}, in a balance of N{sub 2}. Their luminous combustion histories were observed with two-color ratio pyrometry. A solution of the Planckian ratio-pyrometry equation for temperature was implemented, extending on Wien's approximation. The temperature and time histories for 45-53 {mu}m bituminous chars experienced wide particle-to-particle disparity, and varied depending on oxygen mole fraction and furnace temperature. Average char surface temperatures increased from 1600-1800 K in air, to 2100-2300 K in 50% O-2, to 2300-2400 K in 100% O{sub 2}, at gas temperatures of 1300-1500 K, respectively. Combustion durations decreased from 25-45 ms in air, to 8-17 ms in 50% O{sub 2}, to 6-13 in 100% O{sub 2}. Thus, average particle temperatures increased by up to 45%, whereas burnout times decreased by up to 87% as combustion was progressively enriched in O{sub 2} until 100% was attained. The apparent and intrinsic reactivity of the chars burning at 1500 K gas temperature were found to increase by factors of to 8 and 35, respectively, as the oxygen mole fraction increased by a factor of five, from 21% to 100%.

Bejarano, P.A.; Levendis, Y.A. [Northeastern University, Boston, MA (United States)

2007-07-01

25

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

26

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

27

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

28

Simulation of the Combustion of Thin Iron Rods in Oxygen in the Adiabatic Approximation  

NASA Astrophysics Data System (ADS)

A mathematical model of the combustion of a thin iron rod in the atmosphere of oxygen with no forced air flow around it has been constructed. This model includes an adjustment parameter that relates the rate of combustion of the rod with its diameter and the content of oxygen. The problem on the combustion of a thin iron rod in oxygen was solved analytically in the adiabatic approximation. The results of calculations were compared with the corresponding experimental data.

Shabunya, S. I.; Martynenko, V. V.; Ignatenko, V. I.; Rostaing, J.-Ch.

2014-11-01

29

Enhanced Combustion Low NOx Pulverized Coal Burner  

SciTech Connect

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

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

2007-06-30

30

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

NASA Technical Reports Server (NTRS)

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

Klich, G. F.

1976-01-01

31

Chemically enhanced combustion of water-slurry fuels  

Microsoft Academic Search

A method of enhancing the combustion of solid fuel\\/-water slurries by the addition of about 100 to 5,000 ppm of a stable water-soluble explosive, which will detonate early in the combustion process, thereby producing a secondary dispersion of fuel particles, and an 80-65% coal\\/20-35% water composition suitable for secondary dispersion during combustion containing about 100-5,000 ppm of a water-soluble explosive,

Olen

1984-01-01

32

An investigation of plasma enhanced combustion  

NASA Astrophysics Data System (ADS)

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

Kim, Woo Kyung

33

Combustion characteristics of a swirling inverse diffusion flame upon oxygen content variation  

Microsoft Academic Search

The combustion characteristics of a swirling inverse diffusion flame (IDF) upon variation of the oxygen content in the oxidizer were experimentally studied. The oxidizer jet was a mixture mainly composed of oxygen and nitrogen gases, with a volumetric oxygen fraction of 20%, 21% and 26%, and liquefied petroleum gas (LPG) was used as the fuel. Each set of experiment was

H. S. Zhen; C. W. Leung; C. S. Cheung

2011-01-01

34

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

NASA Technical Reports Server (NTRS)

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

Palaszewski, Bryan

1994-01-01

35

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

36

National Combustion Code Parallel Performance Enhancements  

NASA Technical Reports Server (NTRS)

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

Quealy, Angela; Benyo, Theresa (Technical Monitor)

2002-01-01

37

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

38

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

E-print Network

M. A. Delano Union Carbide Corp. Tarrytown, NY ABSTRACT EVALUATION OF ADVANCED PSA AND OXYGEN COMBUSTION SYSTEM FOR INDUSTRIAL FURNACE APPLICATIONS D. Lagree Union Carbide Corp. Tonawanda, NY The performance of a pilot scale advanced PSA... oxygen generation system and a low NO x oxygen burner was evaluated for industrial furnace applications. The PSA system employs a two-bed vacuum cycle design with a capacity of 1.3 TPD at 90% O 2 purity. The oxygen generated from the PSA system...

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

39

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

NASA Astrophysics Data System (ADS)

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

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

40

Rocket combustion chamber life-enhancing design concepts  

NASA Technical Reports Server (NTRS)

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

Quentmeyer, Richard J.

1990-01-01

41

Rocket combustion chamber life-enhancing design concepts  

SciTech Connect

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

Quentmeyer, R.J.

1990-07-01

42

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 ...

43

Chemically enhanced combustion of water-slurry fuels  

SciTech Connect

A method of enhancing the combustion of solid fuel/-water slurries by the addition of about 100 to 5,000 ppm of a stable water-soluble explosive, which will detonate early in the combustion process, thereby producing a secondary dispersion of fuel particles, and an 80-65% coal/20-35% water composition suitable for secondary dispersion during combustion containing about 100-5,000 ppm of a water-soluble explosive, preferably selected from at least one member of a group consisting of picric acid; alkali picrates, such as ammonium picrate, sodium picrate, potassium picrate, calcium picrate, etc., and heavy metal picrates, such as iron picrate, lead picrate, zinc picrate, etc.; guanidine and nitroguanidine. The addition of the explosive may be made to the water makeup of the slurry or may be added to the formed slurry.

Olen, K.R.

1984-06-19

44

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

45

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

46

New type of microengine using internal combustion of hydrogen and oxygen  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

47

Investigation of spontaneous combustion of hydrogen-oxygen mixture using DSMC simulation  

NASA Astrophysics Data System (ADS)

Combustion has been widely studied in the literature, but very little work was focused on the microscopic level. In this paper, the DSMC method is applied to simulate the microscopic behavior of the spontaneous combustion of hydrogen oxygen mixture. It is found that the ignition delay time of the mixture depends on many factors, such as the physical size, temperature, pressure, and dilution. Comparison between DSMC and CFD results shows that more atomic hydrogen is consumed through reaction HO2+ H ? H2+ O2 at temperature close to the extended second explosion limit due to localized distribution of reactants, which may indicate the importance of microscopic behavior on low temperature combustion.

Yang, Chao; Sun, Quanhua

2014-12-01

48

Enriched Oxygen Combustion Simulation for Rotary Kiln Application  

Microsoft Academic Search

Rotary kilns are important key equipment for the production of cement clinker in the cement manufacturing process. These kilns are fired with fossil fuels which release CO2, NOx and other gases into the atmosphere. Oxy-fuel combustion reduces emission of pollutants (CO2 and NOx) from the rotary kiln as well as it increases the efficiency of cement production due to higher

B. Manickam; F. Dinkelacker; T. Lobe; M. Tertychnyy

2009-01-01

49

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

50

Enhanced Efficiency of Internal Combustion Engines By Employing Spinning Gas  

SciTech Connect

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 gain in fuel efficiency of several percent 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 the efficiency.

Geyko, Vasily; Fisch, Nathaniel

2014-02-27

51

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

52

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

53

Reduced Gravity Combustion of Propanol Droplets in Oxygen-Inert Environments  

Microsoft Academic Search

Reduced gravity combustion experiments were performed with individual fiber-supported propanol droplets that were initially about 1 mm in diameter. The environment was composed of an oxygen-inert mixture. Helium, argon, xenon, nitrogen, and carbon dioxide were used as inerts, the oxygen mole fraction was 0.21, and the pressure was 0.03, 0.1, or 0.3 MPa. Use of helium caused extinction at 0.03 MPa and 0.1 MPa,

J. B. Wei; B. D. Shaw

2009-01-01

54

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

PubMed Central

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

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

2013-01-01

55

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

56

FIELD DEMONSTRATION OF THE LINDE OXYGEN COMBUSTION SYSTEM ON THE EPA MOBILE INCINERATOR  

EPA Science Inventory

This paper summarizes the various system performance tests and the long-term operating experience of the LINDE(r) Oxygen Combustion System (OCS) installed on the U.S. Environmental Protection Agency's (EPA) Mobile Incineration System (MIS) when it was in operation at the Denney F...

57

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

SciTech Connect

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

John M. Veranth; Gautham Krishnamoorthy

2001-04-01

58

FIELD DEMONSTRATION OF THE LINDE OXYGEN COMBUSTION SYSTEM ON THE EPA MOBILE INCINERATOR  

EPA Science Inventory

This paper summarizes the various system performance tests and the long-term operating experience of the LINDE Oxygen Combustion System installed on the U.S. Environmental Protection Agency's Mobile Incineration System (MIS) when it was in operation at the Denney Farm site in sou...

59

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

Microsoft Academic Search

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

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

1982-01-01

60

High density adsorbed oxygen on Rh,,111... and enhanced routes to metallic oxidation using atomic oxygen  

E-print Network

High density adsorbed oxygen on Rh,,111... and enhanced routes to metallic oxidation using atomic oxygen K. D. Gibson, Mark Viste, Errol C. Sanchez, and S. J. Sibener The James Franck Institute; accepted 30 November 1998 Exposure of Rh 111 to atomic oxygen leads to the facile formation of a full

Sibener, Steven

61

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

62

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

63

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

64

Study of using oxygen-enriched combustion air for locomotive diesel engines  

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 output 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 can improve 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 with its attendant higher combustion temperatures, reduces emissions of particulates and visible smoke but increases NO emissions (by up to three times at 26% oxygen content). Therefore, exhaust gas after-treatment and heat recovery would be required if the full potential of oxygen enrichment for improving the performance of locomotive diesel engines is to be realized.

Poola, R.B.; Sekar, R. [Argonne National Lab., IL (United States); Assanis, D.N. [Univ. of Michigan, Ann Arbor, MI (United States); Cataldi, G.R. [Association of American Railroads, Washington, DC (United States)

1996-12-31

65

EFFECT OF OXYGEN - ENHANCEMENT ON HAZARDOUS WASTE INCINERATION  

EPA Science Inventory

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

66

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

67

Functionalized graphene sheet colloids for enhanced fuel/propellant combustion.  

PubMed

We have compared the combustion of the monopropellant nitromethane with that of nitromethane containing colloidal particles of functionalized graphene sheets or metal hydroxides. The linear steady-state burning rates of the monopropellant and colloidal suspensions were determined at room temperature, under a range of pressures (3.35-14.4 MPa) using argon as a pressurizing fluid. The ignition temperatures were lowered and burning rates increased for the colloidal suspensions compared to those of the liquid monopropellant alone, with the graphene sheet suspension having significantly greater burning rates (i.e., greater than 175%). The relative change in burning rate from neat nitromethane increased with increasing concentrations of fuel additives and decreased with increasing pressure until at high pressures no enhancement was found. PMID:19925013

Sabourin, Justin L; Dabbs, Daniel M; Yetter, Richard A; Dryer, Frederick L; Aksay, Ilhan A

2009-12-22

68

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

69

Photographic Study of Combustion in a Rocket Engine I : Variation in Combustion of Liquid Oxygen and Gasoline with Seven Methods of Propellant Injection  

NASA Technical Reports Server (NTRS)

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

Bellman, Donald R; Humphrey, Jack C

1948-01-01

70

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

71

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

72

Enhanced Combustion Woodstove (ECW) technology. Report for January 1991-July 1993  

SciTech Connect

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. ECW technology is based on the fact that woodstove emissions are caused by the incomplete combustion and pyrolysis of wood in the primary combustion zone. To achieve low emissions, the stove must incorporate a secondary combustion zone above the wood which will hold flame at all times. Current noncatalytic woodstoves can achieve satisfactory secondary combustion only under fairly ideal conditions. Stable secondary combustion may not be achieved at typical low-fire conditions, leading to high emissions. Initial work focused on using an electrical glowplug (ECW electric) to ignite and add energy to the secondary combustion zone. Later work has focused on using a gaseous fuel (ECW gaseous or ECWG) for this purpose.

McCrillis, R.C.; Abbott, J.H.; Ponder, W.H.; Butts, N.L.; Henry, D.S.

1994-01-01

73

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

NASA Technical Reports Server (NTRS)

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

Linne, Diane L.

1991-01-01

74

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

NASA Technical Reports Server (NTRS)

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

Linne, Diane L.

1991-01-01

75

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

PubMed Central

Emission factors (EFs) of parent polycyclic aromatic (pPAHs), nitrated PAHs (nPAHs), and oxygenated PAHs (oPAHs) were measured for indoor corn straw burned in a cooking brick stove in both normal and controlled burning conditions. EFs of total 28 pPAHs, 6 nPAHs and 4 oPAHs were 7.9±3.4, 6.5±1.6×10-3, and 6.1±1.4×10-1 mg/kg, respectively. By controlling the burning conditions, it was found that the influence of fuel charge size on EFs of the pPAHs and derivatives was insignificant. Measured EFs increased significantly in a fast burning mainly because of the oxygen deficient atmosphere formed in the stove chamber with a small volume. In both restricted and enhance air supply conditions, EFs of pPAHs, nPAHs and oPAHs were significantly higher than those measured in normal burning conditions. Though EFs varied in 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 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, Bin; Wu, Haisuo; Tao, Shu

2014-01-01

76

CONTROL OF TRANSIENT INCINERATOR EMISSIONS WITH AN OXYGEN BASED COMBUSTION SYSTEM  

EPA Science Inventory

The subject of this paper is the experience with a novel and field-proven method for the enhanced control of transient emissions from rotary kiln incinerators using oxygen enrichment. hen high-BTU content wastes are fed into rotary kiln incinerators in an intermittent mode (typic...

77

Catalytic enhancement of singlet oxygen for hybrid electric discharge oxygen-iodine laser systems  

Microsoft Academic Search

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

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

2010-01-01

78

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

79

Low Oxygen Tension Enhances Hepatitis C Virus Replication  

PubMed Central

Low oxygen tension exerts a significant effect on the replication of several DNA and RNA viruses in cultured cells. In vitro propagation of hepatitis C virus (HCV) has thus far been studied under atmospheric oxygen levels despite the fact that the liver tissue microenvironment is hypoxic. In this study, we investigated the efficiency of HCV production in actively dividing or differentiating human hepatoma cells cultured under low or atmospheric oxygen tensions. By using both HCV replicons and infection-based assays, low oxygen was found to enhance HCV RNA replication whereas virus entry and RNA translation were not affected. Hypoxia signaling pathway-focused DNA microarray and real-time quantitative reverse transcription-PCR (qRT-PCR) analyses revealed an upregulation of genes related to hypoxic stress, glycolytic metabolism, cell growth, and proliferation when cells were kept under low (3% [vol/vol]) oxygen tension, likely reflecting cell adaptation to anaerobic conditions. Interestingly, hypoxia-mediated enhancement of HCV replication correlated directly with the increase in anaerobic glycolysis and creatine kinase B (CKB) activity that leads to elevated ATP production. Surprisingly, activation of hypoxia-inducible factor alpha (HIF-?) was not involved in the elevation of HCV replication. Instead, a number of oncogenes known to be associated with glycolysis were upregulated and evidence that these oncogenes contribute to hypoxia-mediated enhancement of HCV replication was obtained. Finally, in liver biopsy specimens of HCV-infected patients, the levels of hypoxia and anaerobic metabolism markers correlated with HCV RNA levels. These results provide new insights into the impact of oxygen tension on the intricate HCV-host cell interaction. PMID:23269812

Kalliampakou, K. I.; Kotta-Loizou, I.; Befani, C.; Liakos, P.; Simos, G.; Mentis, A. F.; Kalliaropoulos, A.; Doumba, P. P.; Smirlis, D.; Foka, P.; Bauhofer, O.; Poenisch, M.; Windisch, M. P.; Lee, M. E.; Koskinas, J.; Bartenschlager, R.

2013-01-01

80

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

PubMed

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

Zhuang, Ye; Pavlish, John H

2012-04-17

81

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

82

Mathematical modeling and experimental investigations of oxygen-methane fuel combustion at coaxial-jet supply into the combustion chamber of liquid-propellant rocket engine  

Microsoft Academic Search

The numerical results are presented for the case of coaxial-jet supply at the different ratio of mass component velocities\\u000a at the combustion chamber inlet with the constant and variable relationship of oxygen-methane components. The experimental\\u000a investigations of coaxial-jet mixing elements as part of the model setup chamber operating on corrosive producer gas and gaseous\\u000a methane were carried out. A qualitative

V. R. Rubinskii; S. P. Khrisanfov; V. Yu. Klimov; A. V. Kretinin

2010-01-01

83

Does oxygen enhance the radiation-induced inactivation of penicillinase  

SciTech Connect

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

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

1980-04-01

84

Embryonic oxygen enhances learning ability in hatchling lizards  

PubMed Central

Introduction Producing smart offspring is an important fitness trait; individuals with enhanced cognitive ability should be more adept at responding to complex environmental demands. Cognitive ability can be influenced by conditions experienced during embryonic development. Although oxygen is necessary for embryonic development, availability can be limited within the nest environment because of substrate type, hydric conditions, and temperature. We do not yet understand, however, whether oxygen availability during embryonic development influences offspring fitness, especially cognitive ability. To address this question we incubated Mongolian Racerunner lizard (Eremias argus) eggs under hypoxic (12% O2), normoxic (21% O2), and hyperoxic conditions (30% O2). Results Hypoxia not only slowed hatching time, but also resulted in constrained cognitive ability relative to hatchlings experiencing normoxic or hyperoxic incubation conditions. Oxygen did not influence hatching success, body size or sprint speed of hatchlings. Conclusions Oxygen availability during embryonic development has important influences on incubation duration and cognitive ability of hatchling lizards. This study provides the first evidence that oxygen availability during embryonic development can modify cognitive ability of oviparous reptiles. PMID:24589451

2014-01-01

85

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

PubMed Central

While no doubt thought about for thousands of years, it was Antoine Lavoisier in the late 18th century who is largely credited with the first “modern” investigations of biological energy exchanges. From Lavoisier’s work with combustion and respiration a scientific trend emerges that extends to the present day: the world gains a credible working hypothesis but validity goes missing, often for some time, until later confirmed using proper measures. This theme is applied to glucose/glycogen metabolism where energy exchanges are depicted as conversion from one form to another and, transfer from one place to another made by both the anaerobic and aerobic biochemical pathways within working skeletal muscle, and the hypothetical quantification of these components as part of an oxygen (O2) uptake measurement. The anaerobic and aerobic energy exchange components of metabolism are represented by two different interpretations of O2 uptake: one that contains a glycolytic component (1 L O2 = 21.1 kJ) and one that does not (1 L O2 = 19.6 kJ). When energy exchange transfer and oxygen-related expenditures are applied separately to exercise and recovery periods, an increased energy cost for intermittent as compared to continuous exercise is hypothesized to be a direct result. PMID:24833508

Scott, Christopher B.

2014-01-01

86

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

87

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

88

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

89

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

PubMed

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

2014-09-01

90

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

91

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

92

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

SciTech Connect

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

John M. Veranth; Gautham Krishnamoorthy

2002-02-28

93

Carbon deposition model for oxygen-hydrocarbon combustion, volume 2. Interim final report  

SciTech Connect

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.

1987-09-01

94

Carbon deposition model for oxygen-hydrocarbon combustion, volume 1. Interim final report  

SciTech Connect

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.

1987-09-01

95

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

96

Combustion  

NSDL National Science Digital Library

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

2014-01-28

97

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

98

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

99

Effect of temperature on reduction of CaSO oxygen carrier in chemical-looping combustion of simulated coal gas in a fluidized bed reactor  

Microsoft Academic Search

Chemical-looping combustion (CLC) is a promising combustion technology for gaseous and solid fuel with efficient use of energy and inherent separation of CO. The concept of a coal-fueled CLC system using, calcium sulfate (CaSO) as oxygen carrier is proposed in this study. Reduction tests of CaSO oxygen carrier with simulated coal gas were performed in a laboratory-scale fluidized bed reactor

Q. L. Song; R. Xiao; Z. Y. Deng; L. H. Shen; J. Xiao; M. Y. Zhang

2008-01-01

100

Enhancing the combustible properties of bamboo by torrefaction.  

PubMed

Bamboo has wide range of moisture content, low bulk energy density and is difficult to transport, handle, store and feed into existing combustion and gasification systems. Because of its important fuel characteristics such as low ash content, alkali index and heating value, bamboo is a promising energy crop for the future. The aim of this study was to evaluate the effects of torrefaction on the main energy properties of Bambusa vulgaris. Three different torrefaction temperatures were employed: 220, 250 and 280°C. The elemental characteristics of lignite and coal were compared to the torrefied bamboo. The characteristics of the biomass fuels tend toward those of low rank coals. Principal component analysis of FTIR data showed a clear separation between the samples by thermal treatment. The loadings plot indicated that the bamboo samples underwent chemical changes related to carbonyl groups, mostly present in hemicelluloses, and to aromatic groups present in lignin. PMID:21703854

Rousset, Patrick; Aguiar, Clarissa; Labbé, Nicole; Commandré, Jean-Michel

2011-09-01

101

Preliminary Study of Oxygen-Enhanced Longitudinal Relaxation in MRI: A Potential Novel Biomarker of Oxygenation Changes in Solid Tumors  

SciTech Connect

Purpose: There is considerable interest in developing non-invasive methods of mapping tumor hypoxia. Changes in tissue oxygen concentration produce proportional changes in the magnetic resonance imaging (MRI) longitudinal relaxation rate (R{sub 1}). This technique has been used previously to evaluate oxygen delivery to healthy tissues and is distinct from blood oxygenation level-dependent (BOLD) imaging. Here we report application of this method to detect alteration in tumor oxygenation status. Methods and materials: Ten patients with advanced cancer of the abdomen and pelvis underwent serial measurement of tumor R{sub 1} while breathing medical air (21% oxygen) followed by 100% oxygen (oxygen-enhanced MRI). Gadolinium-based dynamic contrast-enhanced MRI was then performed to compare the spatial distribution of perfusion with that of oxygen-induced DELTAR{sub 1}. Results: DELTAR{sub 1} showed significant increases of 0.021 to 0.058 s{sup -1} in eight patients with either locally recurrent tumor from cervical and hepatocellular carcinomas or metastases from ovarian and colorectal carcinomas. In general, there was congruency between perfusion and oxygen concentration. However, regional mismatch was observed in some tumor cores. Here, moderate gadolinium uptake (consistent with moderate perfusion) was associated with low area under the DELTAR{sub 1} curve (consistent with minimal increase in oxygen concentration). Conclusions: These results provide evidence that oxygen-enhanced longitudinal relaxation can monitor changes in tumor oxygen concentration. The technique shows promise in identifying hypoxic regions within tumors and may enable spatial mapping of change in tumor oxygen concentration.

O'Connor, James P.B. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom) and Cancer Research UK Department of Medical Oncology, Christie Hospital, Manchester (United Kingdom); Naish, Josephine H.; Parker, Geoff J.M. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); Waterton, John C. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); AstraZeneca, Cheshire (United Kingdom); Watson, Yvonne [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); Jayson, Gordon C. [Cancer Research UK Department of Medical Oncology, Christie Hospital, Manchester (United Kingdom); Buonaccorsi, Giovanni A.; Cheung, Sue; Buckley, David L.; McGrath, Deirdre M. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); West, Catharine M.L. [Academic Department of Radiation Oncology, University of Manchester, Manchester (United Kingdom); Davidson, Susan E. [Department of Clinical Oncology, Christie Hospital, Manchester (United Kingdom); Roberts, Caleb; Mills, Samantha J. [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom); Mitchell, Claire L.; Hope, Lynn; Ton, N. Chan [Cancer Research UK Department of Medical Oncology, Christie Hospital, Manchester (United Kingdom); Jackson, Alan [Imaging Science and Biomedical Engineering, University of Manchester, Manchester (United Kingdom)

2009-11-15

102

Measurements of combustion properties in a microwave enhanced flame  

SciTech Connect

Microwave induced flame speed enhancement is quantified in a laminar, premixed CH{sub 4}/air wall stagnation flat flame. Experiments were performed in a high Q microwave cavity with the cavity tuned so that the maximum microwave field is located in the vicinity of a flat flame front. Equivalence ratios were varied between 0.6 and 0.8. When the flame is radiated by a continuous wave microwave field of approximately 5 kV/cm, the flame front is observed to move towards the burner exit and stabilize at a standoff distance corresponding to a flame speed increase of up to 20%. No microwave discharge is observed, indicating that the enhanced flame speed arises from microwave energy deposited directly into the reaction zone through coupling to the weakly ionized gas in that region. Laser diagnostics were performed to quantify temperature increase, the laminar flame speed enhancement, and changes in the OH radical concentration through filtered Rayleigh scattering, particle image velocimetry, and planar laser induced fluorescence, respectively. These measurements indicate that microwave radiation may prove to be an effective means to non-invasively control and enhance flame stability in combustors. (author)

Stockman, Emanuel S.; Zaidi, Sohail H.; Miles, Richard B. [Engineering Quadrangle - Mechanical and Aerospace Engineering, Olden Street, Princeton University, Princeton, NJ 08544 (United States); Carter, Campbell D. [US Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, OH 45433 (United States); Ryan, Michael D. [Universal Technology Corporation, Dayton, OH 45332 (United States)

2009-07-15

103

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

Microsoft Academic Search

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

Mitsuteru Ogawa; Naohiro Yoshida

2005-01-01

104

Liquid oxygen/hydrogen testing of a single swirl coaxial injector element in a windowed combustion chamber  

NASA Astrophysics Data System (ADS)

A modular, high pressure, liquid rocket single element combustion chamber was developed at Aerojet for use with nonintrusive combustion diagnostics. The hardware is able to accommodate full-size injection elements and includes a recessed annular injector around the single element to provide a source for hot gas background flow, which reduces recirculation in the chamber and provides additional injection mass to elevate chamber pressure. Experiments are being conducted to develop the diagnostics required to characterize a single-element combustion spray field for combustion modeling, benchmark data for CFD model validation, and development of the transfer functions between single element cold flow and multielement hot fire. The latter task is being pursued using an injector element identical to elements that had been previously cold-flow tested in single element tests to ambient backpressure and hot fire tested in a multielement injector. Preliminary tests conducted to date without hydrogen flowing through the annular coaxial orifice of the single element show the general flow characteristics of a reacting, unconfined, liquid oxygen hollow cone swirl spray.

Hulka, J.; Makel, D.

1993-06-01

105

Combustion synthesis of TiO2-Al-C/Al2O3 mixture in the presence of oxygen  

NASA Astrophysics Data System (ADS)

Quasi-adiabatic combustion synthesis of optimized 3TiO2+4Al+(3+x)C mixture in the presence of oxygen was carried out to produce TiC-Al2O3 composite. The influence of Al2O3 diluent in combusted (3TiO2+4Al+3.5C+yAl2O3) reactant mixture was investigated. Thermodynamics studies of the system shown that self-sustaining (SS) mode of combustion wave propagation can occur for large amounts of diluents (y = 2.5). Diluent reduced combustion temperature and rate of reaction kinetics. Oxide (Ti2O, Ti3O5) and intermetallic (AlTi2) phases were detected when extra Al2O3 was added to the mixture. Semi-quantitative XRD analysis was employed to study the phase formation of products for various amounts of diluent content in the mixture. The boundary between SS and non-SS modes of wave propagation was determined. Adding Al2O3 diluent slightly increased density that resulted in better thermal conductivity.

Rahbari G, R.; Saw, L. H.; Hamdi, M.; Yahya, R.

2009-03-01

106

Development of Nanofiller-Modulated Polymeric Oxygen Enrichment Membranes for Reduction of Nitrogen Oxides in Coal Combustion  

SciTech Connect

North Carolina A&T State University in Greensboro, North Carolina, has undertaken this project to develop the knowledge and the material to improve the oxygen-enrichment polymer membrane, in order to provide high-grade oxygen-enriched streams for coal combustion and gasification applications. Both experimental and theoretical approaches were used in this project. The membranes evaluated thus far include single-walled carbon nano-tube, nano-fumed silica polydimethylsiloxane (PDMS), and zeolite-modulated polyimide membranes. To document the nanofiller-modulated polymer, molecular dynamics simulations have been conducted to calculate the theoretical oxygen molecular diffusion coefficient and nitrogen molecular coefficient inside single-walled carbon nano-tube PDMS membranes, in order to predict the effect of the nano-tubes on the gas-separation permeability. The team has performed permeation and diffusion experiments using polymers with nano-silica particles, nano-tubes, and zeolites as fillers; studied the influence of nano-fillers on the self diffusion, free volume, glass transition, oxygen diffusion and solubility, and perm-selectivity of oxygen in polymer membranes; developed molecular models of single-walled carbon nano-tube and nano-fumed silica PDMS membranes, and zeolites-modulated polyimide membranes. This project partially supported three graduate students (two finished degrees and one transferred to other institution). This project has resulted in two journal publications and additional publications will be prepared in the near future.

Jianzhong Lou; Shamsuddin Ilias

2010-12-31

107

Polarographic Determination of Glycyrrhizic Acid Based on Double Enhancement Action of Surfactant and Dissolved Oxygen  

Microsoft Academic Search

A method for the determination of glycyrrhizic acid (GA) is described based on polarographic current of GA enhanced doubly by both cation surfactant (cetyl trimethyl ammonium bromide (CTMAB)), and dissolved oxygen (including oxygen-derived species). The doubly enhanced current of GA includes two additional currents. One is the increased reduction current of adsorbed GA induced by CTMAB. The other is the

Guo Wei; Kang Xiao-feng; Song Jun-feng

1999-01-01

108

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

109

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

110

Microprocessor Based Combustion Monitoring and Control Systems Utilizing in Situ Opacity, Oxygen and CO Measurement  

E-print Network

by detecting variations in the output of a zirconium oxide fuel cell oxygen sensor. As the oxygen concentration varies, an output signal is generated which can be directly related to the oxygen content of the flue gas. An In Situ Oxygen Analyzer is mounted... conditioning systems while providing a more representative sample of the gas to be measured. Fuel cell oxygen sensor consists of a ceramic tU!;le made of yttria-stabilized zirconium oxide. When this c~1t is heated above I 100 degrees F (600 degrees C...

Molloy, R. C.

1981-01-01

111

Application of MOBILE (mapping of oxygen by imaging lipids relaxation enhancement) to study variations in tumor oxygenation.  

PubMed

The aim of the study was to sensitively monitor changes in tumor oxygen using the MOBILE (mapping of oxygen by imaging lipids relaxation enhancement) technique. This method was applied in mammary tumor mouse models on an 11.7T Bruker MRI system. MOBILE was compared with functional imaging R2*, R1 of water and with pO2 measurements (using EPR oximetry and O2-dependent fluorescence quenching measurements). MOBILE was shown to be capable to monitor changes in oxygenation in tumor tissues. PMID:23852506

Jordan, Bénédicte F; Magat, Julie; Colliez, Florence; Ozel, Elif; Fruytier, Anne-Catherine; Marchand, Valérie; Mignion, Lionel; Gallez, Bernard

2013-01-01

112

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

113

High-pressure calorimeter chamber tests for liquid oxygen/kerosene (LOX/RP-1) rocket combustion  

SciTech Connect

An experimental program was conducted to investigate the rocket combustion and heat transfer characteristics of liquid oxygen/kerosene (LOX/RP-1) mixtures at high chamber pressures. Two water-cooled calorimeter chambers of different combustion lengths were tested using 37- and 61-element oxidizer-fuel-oxidizer triplet injectors. The tests were conducted at nominal chamber pressures of 4.1, 8.3, and 13.8 MPa abs (600, 1200, and 2000 psia). Heat flux Q/A data were obtained for the entire calorimeter length for oxygen/fuel mixture ratios of 1.8 to 3.3. Test data at 4.1 MPa abs compared favorably with previous test data from another source. Using an injector with a fuel-rich outer zone reduced the throat heat flux by 47 percent with only a 4.5 percent reduction in the characteristic exhaust velocity efficiency C* sub eff. The throat heat transfer coefficient was reduced approximately 40 percent because of carbon deposits on the chamber wall.

Masters, P.A.; Armstrong, E.S.; Price, H.G.

1988-12-01

114

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

Microsoft Academic Search

We are investigating catalytically enhanced production of singlet oxygen, O2(a1▵g), observed by reaction of O2\\/He discharge effluents over an iodine oxide film surface in a microwave discharge-flow reactor at 320 K. We have previously reported a two-fold increase in the O2(a) yields by this process, and corresponding enhancement of I(2P1\\/2) excitation and small-signal gain upon injection of I2 and NO2.

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

2011-01-01

115

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

116

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

SciTech Connect

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

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

2011-12-22

117

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

E-print Network

variations in the output of a zirconium oxide fuel cell oxygen sensor. As the oxygen concentration varies, an output signal is generated which can be directly related to the oxygen content of the flue gas. it to instantaneously react to dynamic... to maintain the desired fuel/air mixture ratio for each level of load demand such that the air will lead the fuel on increasing fuel-load demand and lag on de creasing fuel-load demand. See Figure 2. Figure 2. The zirconium oxide fuel cell is an ideal...

Molloy, R. C.

1980-01-01

118

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

119

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

120

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

E-print Network

Lithium-oxygen batteries have a great potential to enhance the gravimetric energy density of fully packaged batteries by two to three times that of lithium ion cells. Recent studies have focused on finding stable electrolytes ...

Oh, Dahyun

121

STRENGTH ENHANCEMENT OF A FIBER NETWORK BY CARBOXYMETHYL CELLULOSE DURING OXYGEN DELIGNIFICATION OF KRAFT PULP  

Microsoft Academic Search

Sorption of carboxymethyl cellulose (CMC) on the fiber surface was applied during oxygen delignification to enhance the strength properties of softwood kraft pulp. Unlike many previous efforts, the focus was not set on the improvement of selectivity of oxygen delignification, i.e. retaining stable viscosity vs. decreasing kappa number. Instead, without an improved selectivity, handsheets from CMC-treated fibers exhibited a 15%

Eero Kontturi; Mia Mitikka-Eklund; Tapani Vuorinen

122

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

123

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

124

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

125

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

Microsoft Academic Search

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

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

2004-01-01

126

Fibronectin coating of oxygenator membranes enhances endothelial cell attachment  

PubMed Central

Background Extracorporeal membrane oxygenation (ECMO) can replace the lungs’ gas exchange capacity in refractory lung failure. However, its limited hemocompatibility, the activation of the coagulation and complement system as well as plasma leakage and protein deposition hamper mid- to long-term use and have constrained the development of an implantable lung assist device. In a tissue engineering approach, lining the blood contact surfaces of the ECMO device with endothelial cells might overcome these limitations. As a first step towards this aim, we hypothesized that coating the oxygenator’s gas exchange membrane with proteins might positively influence the attachment and proliferation of arterial endothelial cells. Methods Sheets of polypropylene (PP), polyoxymethylpentene (TPX) and polydimethylsiloxane (PDMS), typical material used for oxygenator gas exchange membranes, were coated with collagen, fibrinogen, gelatin or fibronectin. Tissue culture treated well plates served as controls. Endothelial cell attachment and proliferation were analyzed for a period of 4 days by microscopic examination and computer assisted cell counting. Results Endothelial cell seeding efficiency is within range of tissue culture treated controls for fibronectin treated surfaces only. Uncoated membranes as well as all other coatings lead to lower cell attachment. A confluent endothelial cell layer develops on fibronectin coated PDMS and the control surface only. Conclusions Fibronectin increases endothelial cells’ seeding efficiency on different oxygenator membrane material. PDMS coated with fibronectin shows sustained cell attachment for a period of four days in static culture conditions. PMID:23356939

2013-01-01

127

Regenerable MgO promoted metal oxide oxygen carriers for chemical looping combustion  

DOEpatents

The disclosure provides an oxygen carrier comprised of a plurality of metal oxide particles in contact with a plurality of MgO promoter particles. The MgO promoter particles increase the reaction rate and oxygen utilization of the metal oxide when contacting with a gaseous hydrocarbon at a temperature greater than about 725.degree. C. The promoted oxide solid is generally comprised of less than about 25 wt. % MgO, and may be prepared by physical mixing, incipient wetness impregnation, or other methods known in the art. The oxygen carrier exhibits a crystalline structure of the metal oxide and a crystalline structure of MgO under XRD crystallography, and retains these crystalline structures over subsequent redox cycles. In an embodiment, the metal oxide is Fe.sub.2O.sub.3, and the gaseous hydrocarbon is comprised of methane.

Siriwardane, Ranjani V.; Miller, Duane D.

2014-08-19

128

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

129

METALLIZED GELLED PROPELLANTS: OXYGEN\\/RP1 \\/ALUMINUM ROCKET HEAT TRANSFER AND COMBUSTION MEASUREMENTS  

Microsoft Academic Search

A series of rocket engine heat transfer experiments using metallized gelled liquid propellants was conducted. These experiments used a small 20- to 40-lbf thrust engine composed of a modular injector, igniter, chamber and nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-wt% loadings of aluminum particles. Gaseous oxygen was used as the oxidizer.

Bryan Palaszewski; James S. Zakany

130

Combustion of polymers in a low pressure and low oxygen environment  

NASA Astrophysics Data System (ADS)

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

Zarzecki, Mariusz

131

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

132

Strong photoluminescence enhancement of MoS(2) through defect engineering and oxygen bonding.  

PubMed

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

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

2014-06-24

133

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

134

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

135

Numerical investigation of influence of homogeneous\\/heterogeneous ignition\\/combustion mechanisms on ignition point position during pulverized coal combustion in oxygen enriched and recycled flue gases atmosphere  

Microsoft Academic Search

It is expected that pulverized coal combustion will continue to play a major role in electricity generation for the foreseeable future. Oxy-fuel coal combustion is actively being investigated, as alternative to conventional pulverized-coal combustion, due to its potential to easier carbon dioxide sequestration. This paper presents experimental and numerical analysis of ignition phenomena in oxy-fuel conditions. A modification of standard

Rastko Jovanovic; Aleksandra Milewska; Bartosz Swiatkowski; Adrian Goanta; Hartmut Spliethoff

2011-01-01

136

Study of using oxygen-enriched combustion air for locomotive diesel engines  

SciTech Connect

A thermodynamic simulation is used to study effects of O2-enriched intake air on performance and NO emissions of a locomotive diesel engine. Parasitic power of the air separation membrane required to supply the O2-enriched air is also estimated. For a given constraint on peak cylinder pressure, gross and net power output of an engine operating under different levels of O2 enrichment are compared with those obtained when a high-boost turbocharged engine is used. A 4% increase in peak cylinder pressure can result in 13% increase in net engine power when intake air with 28 vol% O2 is used and fuel injection timing retarded by 4 degrees. When the engine is turbocharged to a higher inlet boost, the same increase in peak cylinder pressure can result in only 4% improvement in power. If part of the higher exhaust enthalpies from the O2 enrichment is recovered, the power requirements of the air separator membrane can be met. O2 enrichment with its higher combustion temperatures reduces emissions of particulates and visible smoke but increases NO emissions (by up to 3 times at 26% O2 content). Therefore, exhaust gas after-treatment and heat recovery would be required if the full potential of O2 enrichment for improving the performance of locomotive diesel engines is to be realized.

Poola, R.B.; Sekar, R. [Argonne National Lab., IL (United States); Assanis, D.N. [Michigan Univ., Ann Arbor, MI (United States); Cataldi, G.R. [Association of American Railroads, Washington, DC (United States)

1996-10-01

137

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

138

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

Tambutté, Eric; Allemand, Denis; Tambutté, Sylvie

2014-01-01

139

Implementation of multiple-pulse injection strategies to enhance the homogeneity for simultaneous low-NOx and -soot diesel combustion  

Microsoft Academic Search

The diesel combustion implemented with the use of a homogeneous lean charge has shown to produce simultaneous reduction of nitrogen oxides (NOx) and soot emissions at low-load conditions. Similarly, at higher load levels, a cylinder charge mixture weakened by the use of exhaust gas recirculation (EGR) and enhanced homogeneity has also shown to result in simultaneous reduction of NOx and

Ming Zheng; Raj Kumar

2009-01-01

140

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

141

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

142

Normal and inverse laminar jet-diffusion flames under oxygen enhancement and gravity-variation  

Microsoft Academic Search

A computational study (emphasizing the effects of oxygen enhancement, gravity and inverse burning on species mass-fraction, velocity, temperature, radiative losses, transport properties, reaction rates, species emission and flame size) has been performed for ethane fueled laminar gas jet diffusion flames. Fire safety, efficient energy utilization and fundamental research, both on earth and in space, are the areas where this study

Pramod Bhatia

2008-01-01

143

Evidence of oxygen vacancy enhanced room-temperature ferromagnetism in Co-doped ZnO  

E-print Network

The annealing effects on structure and magnetism for Co-doped ZnO films under air, Ar, and Ar/H2 atmospheres diluted magnetic semiconductor structures. By comparison of the x-ray near edge spectraEvidence of oxygen vacancy enhanced room-temperature ferromagnetism in Co-doped ZnO H. S. Hsu and J

Huang, Jung-Chun

144

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

145

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

NASA Astrophysics Data System (ADS)

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

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

1987-01-01

146

Liquid oxygen\\/hydrogen testing of a single swirl coaxial injector element in a windowed combustion chamber  

Microsoft Academic Search

A modular, high pressure, liquid rocket single element combustion chamber was developed at Aerojet for use with nonintrusive combustion diagnostics. The hardware is able to accommodate full-size injection elements and includes a recessed annular injector around the single element to provide a source for hot gas background flow, which reduces recirculation in the chamber and provides additional injection mass to

J. Hulka; D. Makel

1993-01-01

147

Investigation of chemical looping combustion by solid fuels. 2. redox reaction kinetics and product characterization with coal, biomass, and solid waste as solid fuels and CuO as an oxygen carrier  

Microsoft Academic Search

This paper is the second in a series of two on the investigation of the chemical looping combustion (CLC) of solid fuels. The first paper put forward the concept of the CLC of solid fuels using a circulating fluidized bed as a reactor and Cu-CuO as the oxygen carrier, which was based on an analysis of oxygen transfer capability, reaction

Yan Cao; Bianca Casenas; Wei-Ping Pan

2006-01-01

148

Enhanced oxygen transfer rate and bioprocess yield by using magnetite nanoparticles in fermentation media of erythromycin.  

PubMed

BackgroundMagnetite nanoparticles have widespread biomedical applications. In the aerobic bioprocesses, oxygen is a limiting factor for the microbial metabolic rate; hence a high availability of oxygen in the medium is crucial for high fermentation productivity. This study aimed to examine the effect of using magnetite nanoparticles on oxygen transfer rate in erythromycin fermentation culture.MethodsMagnetite nanoparticles were synthetized through co-precipitation method. After observing the enhanced oxygen transfer rate in deionized water enriched with magnetite nanoparticles, these nanoparticles were used in the media of by Saccharopolyspora erythraea growth to explore their impact on erythromycin fermentation titer. Treatments comprised different concentrations of magnetite nanoparticles, (0, 0.005, 0.02 v/v).ResultsIn the medium containing 0.02 v/v magnetite nanoparticles, KLa was determined to be 1.89 time higher than that in magnetite nanoparticle-free broth. An improved 2.25 time higher erythromycin titer was obtained in presence of 0.02 v/v nanoparticles.ConclusionsOur results, demonstrate the potential of magnetite nanoparticles for enhancing the productivity of aerobic pharmaceutical bioprocesses. PMID:25223458

Labbeiki, Ghazal; Attar, Hossein; Heydarinasab, Amir; Sorkhabadi, Sayed; Rashidi, Alimorad

2014-09-16

149

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

150

Power enhancement in chemical oxygen-iodine lasers by iodine predissociation via corona/glow discharge  

NASA Astrophysics Data System (ADS)

The gain and power in a supersonic chemical oxygen-iodine laser (COIL) are enhanced by applying dc corona/glow discharge in the transonic section of the secondary flow in the supersonic nozzle, dissociating I2 prior to its mixing with O2(?1). The loss of O2(?1) consumed for dissociation is thus reduced, and the consequent dissociation rate downstream of the discharge increases, resulting in up to 80% power enhancement. The implication of this method for COILs operating beyond the specific conditions reported here is assessed.

Katz, A.; Dahan, Z.; Rybalkin, V.; Waichman, K.; Barmashenko, B. D.; Rosenwaks, S.

2007-04-01

151

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

152

Modelling of the oxygen enhancement ratio for ion beam radiation therapy  

NASA Astrophysics Data System (ADS)

The poor treatment prognosis for tumours with oxygen-deficient areas is usually attributed to the increased radioresistance of hypoxic cells. It can be expressed by the oxygen enhancement ratio (OER), which decreases with increasing linear energy transfer (LET) suggesting a potential clinical advantage of high-LET radiotherapy with heavy ion beams compared to low-LET photon or proton irradiation. The aim of this work is to review the experimental cell survival data from the literature and, based on them, to develop a simple OER model to estimate the clinical impact of OER variations. For this purpose, the standard linear-quadratic model and the Alper-Howard-Flanders model are used. According to our calculations for a carbon ion spread-out Bragg peak at clinically relevant intermediate oxygen levels (0.5-20 mmHg), the advantage of carbon ions might be relatively moderate, with OER values about 1%-15% smaller than for protons. Furthermore, the variations of OER with LET are much smaller in vivo than in vitro due to different oxygen partial pressures used in cell experiments or measured inside tumours. The proposed OER model is a simple tool to quantify the oxygen effect in a practical way and provides the possibility to do hypoxia-based biological optimization in treatment planning.

Wenzl, Tatiana; Wilkens, Jan J.

2011-06-01

153

Enhanced oxygen separation through robust freeze-cast bilayered dual-phase membranes.  

PubMed

Dual-phase oxygen-permeable asymmetric membranes with enhanced oxygen permeation were prepared by combining freeze-casting, screen-printing, and constraint-sintering techniques. The membranes were evaluated under oxyfuel operating conditions. The prepared membranes are composed of an original ice-templated La(0.6)Sr(0.4)Co(0.2)Fe(0.8)O(3-?) support with hierarchically oriented porosity and a top fully densified bilayered coating comprising a 10??m-thick La(0.6)Sr(0.4)Co(0.2)Fe(0.8)O(3-?) layer and a top protective 8??m-thick layer made of an optimized NiFe2O4/Ce(0.8)Tb(0.2)O(2-?) composite synthesized by the one-pot Pechini method. Preliminary analysis confirmed the thermochemical compatibility of the three involved phases at high temperature without any additional phase detected. This membrane exhibited a promising oxygen permeation value of 4.8?mL?min(-1) ?cm(-2) at 1000?°C upon using Ar and air as the sweep and feed gases, respectively. Mimicking oxyfuel operating conditions by switching argon to pure CO2 as a sweep gas at 1000?°C and air as feed enabled an oxygen flux value of 5.6?mL?min(-1) ?cm(-2) to be reached. Finally, under the same conditions and increasing the oxygen partial pressure to 0.1?MPa in the feed, the oxygen permeation reached 12?mL?min(-1) ?cm(-2). The influence of CO2 content in the sweep gas was studied and its reversible and positive effect over oxygen permeation at temperatures equal to or above 950?°C was revealed. Finally, the membrane stability over a period of 150?h under CO2-rich sweep gas showed a low degradation rate of 2.4×10(-2) ?mL?min(-1) ?cm(-2) per day. PMID:25070608

Gaudillere, Cyril; Garcia-Fayos, Julio; Balaguer, María; Serra, José M

2014-09-01

154

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

155

Carbon attrition during the fluidized combustion and gasification of coal. Quarterly technical progress report, 1 March-31 May 1982. [By fragmentation or attrition; with and without oxygen  

SciTech Connect

The work during the period 1 March-31 May 1982 has been mainly directed to exploring the effect of oxygen concentration on the instantaneous rates of generation of carbon fines by attrition during the fluidized combustion of batches of 4760-6350 ..mu..m South African coal. Time-resolved bed carbon particle size distributions are determined under the same conditions as attrition experiments have been carried out. Instantaneous attrition rates have been correlated to bed carbon loading and exposed surface for various oxidizing conditions.

Massimilla, L.; Cammarota, A.; Chirone, R.; D& #x27; Amore, M.

1982-01-01

156

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...

157

Chemical kinetic modeling of oxy-fuel combustion of sour gas for enhanced oil recovery  

E-print Network

Oxy-fuel combustion of sour gas, a mixture of natural gas (primarily methane (CH 4 )), carbon dioxide (CO 2 ), and hydrogen sulfide (H 2 S), could enable the utilization of large natural gas resources, especially when ...

Bongartz, Dominik

2014-01-01

158

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

159

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

160

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

SciTech Connect

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

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

2013-11-28

161

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

162

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

NASA Astrophysics Data System (ADS)

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; Choi, Changrok; Woong Jang, Chi; Lee, Seok; Min Jhon, Young

2013-02-01

163

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

164

Plasma-Enhanced Combustion of Hydrocarbon Fuels and Fuel Blends Using Nanosecond Pulsed Discharges  

SciTech Connect

This project had as its goals the study of fundamental physical and chemical processes relevant to the sustained premixed and non-premixed jet ignition/combustion of low grade fuels or fuels under adverse flow conditions using non-equilibrium pulsed nanosecond discharges.

Cappelli, Mark; Mungal, M Godfrey

2014-10-28

165

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

E-print Network

undergoing in-situ combustion. Six runs were performed with Jobo crude oil (9-11ºAPI) from the Orinoco Belt in Venezuela. Four of the runs were successful. Two of them are base runs; the remaining ones are with tetralin with concentration of 5 wt% (of oil...

Huseynzade, Samir

2009-05-15

166

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...

167

Sol-gel-derived NiO/NiAl{sub 2}O{sub 4} oxygen carriers for chemical-looping combustion by coal char  

SciTech Connect

This paper focuses on the investigation of Ni-based oxygen carriers for CLC by coal char. First, Al(OC{sub 3}H{sub 7}){sub 3} and Ni(NO{sub 3}){sub 2} are selected as the main raw materials to prepare sol-gel-derived NiO/NiAl{sub 2}O{sub 4} oxygen carriers. The oxygen carrier with a mass content of 60% NiO, a sintering temperature of 1300{sup o}C, and a sintering time of 6 h performs comparatively well. Second, the reduction reaction of the NiO/NiAl{sub 2}O{sub 4} oxygen carriers with char and the circular reduction/oxidation reactions of the NiO/NiAl{sub 2}O{sub 4} oxygen carriers with char/air or hydrogen/air are carried out in a thermogravimetric analysis (TGA) instrument to investigate the reactivities and chemical life of the prepared NiO/NiAl{sub 2}O{sub 4} oxygen carriers. The experimental results show that (a) when the TGA temperature is higher than 850{sup o}C, NiO/NiAl{sub 2}O{sub 4} starts to react with coal char rapidly, which indicates that CLC of coal char using NiO/NiAl{sub 2}O{sub 4} as oxygen carriers is a feasible technology of energy utilization in principle; (b) NiO/NiAl{sub 2}O{sub 4}, which maintains its activity over single-cycle reduction/oxidation reactions with char/air or multiple-cycle reduction/oxidation reactions with hydrogen/air, exhibits extremely good recyclablity; (c) the porous beehive structure of the NiO/NiAl{sub 2}O{sub 4} particle is maintained, and the sintering behavior between different particles is not observed during cyclic studies. Those experimental results prove the sol-gel-derived oxygen carrier NiO/NiAl{sub 2}O{sub 4} is capable of being used in chemical-looping combustion fueled by coal char or H{sub 2}. 51 refs., 5 figs., 5 tabs.

Haibo Zhao; Liming Liu; Baowen Wang; Di Xu; Linlin Jiang; Chuguang Zheng [Huazhong University of Science and Technology, Wuhan (China). State Key Laboratory of Coal Combustion

2008-03-15

168

Frequent low-load ischemic resistance exercise to failure enhances muscle oxygen delivery and endurance capacity.  

PubMed

This study investigated the effects of frequent low-load ischemic resistance exercise performed to failure on quadriceps size and performance, muscle activation, oxygen kinetics and cardiovascular responses. Ten healthy males performed knee-extension exercise for 4 weeks (4 sessions/week) at 15% maximal voluntary muscle contraction (MVC). One leg was trained with free blood flow (C-leg) while in the other leg (I-leg) ischemia was induced by an inflatable cuff (?230 mmHg). Quadriceps cross-sectional area (CSA) of the I-leg increased by 3.4% (P<0.05). A tendency for smaller increase in muscle CSAs at the cuff level was observed. MVC force did not change in either leg, whereas the number of repetitions during exercise test to failure increased (P<0.01) by 63% in I-leg and 36% in C-leg. The decrease in muscle oxygenated hemoglobin concentration acquired by NIRS was attenuated (P<0.01) by 56% in I-leg and 21% in C-leg. Electromyographic amplitude of rectus femoris in I-leg was ?45% lower (P<0.025) during the ischemic test. Also, ?9% increase (P<0.05) in pre-exercise diastolic pressure was observed. In conclusion, substantial gains in muscle endurance capacity were induced, which were associated with enhanced muscle oxygen delivery. The potential negative effects of ischemic exercise with high cuff pressure on muscle and nerve and on arterial pressure regulation need further investigation. PMID:21385216

Kacin, A; Strazar, K

2011-12-01

169

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

170

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

E-print Network

the Orinoco Belt in Venezuela. Four of the runs were successful. Two of them are base runs; the remaining ones are with tetralin with concentration of 5 wt% (of oil) and catalyst with concentration of 750 ppm. For all runs, the following were kept... (base run)……………... 29 5.3 Temperature profiles, run no.1 (base run)………………………………... 31 5.4 Combustion front velocity, run no.1 (base run)...………………………… 32 5.5 Cumulative oil and water production, run no.1...

Huseynzade, Samir

2008-10-10

171

Effects of oxygen functional groups on the enhancement of the hydrogen spillover of Pd-doped activated carbon.  

PubMed

The hydrogen storage performance of Pd-doped oxidized activated carbon (Pd/AC-ox) with various oxygen contents or functional groups was investigated. The surface chemistry of the Pd/AC-ox sample was modified by treatment with hydrogen gas. Temperature-programmed desorption was performed to characterize the oxygen functional groups in each sample. In this study, low- and high-pressure hydrogen adsorption isotherm experiments were conducted using a static volumetric measurement at room temperature (RT) and pressures of up to 8MPa. The results showed that increasing the oxygen content and functional groups on the surface of the Pd/AC-ox significantly improved the reversible RT hydrogen storage capacity due to the spillover effect. The hydrogen spillover enhancement factors at 0.12MPa were greater than 100% for all samples. The hydrogen uptake of Pd/AC-ox1 at RT and 8MPa with an oxygen content of 8.94wt.% was 0.37wt.%, which was 48% greater than that of Pd-free AC-ox (0.25wt.%). In addition, the hydrogen uptake of Pd/AC-ox3 with lower oxygen contents demonstrates that the hydrogen spillover enhancement gradually disappears when the pressure is increased to more than 2MPa (i.e., a transition from spillover to physisorption). The surface diffusion, or reversible adsorption, of the spiltover H atoms, which is enhanced by oxygen functional groups, was affected by a threshold amount of oxygen groups (such as hydroxyl groups). PMID:25490569

Chung, Tsui-Yun; Tsao, Cheng-Si; Tseng, Hui-Ping; Chen, Chien-Hung; Yu, Ming-Sheng

2015-03-01

172

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

173

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

174

Carbon deposition model for oxygen-hydrocarbon combustion. Task 6: Data analysis and formulation of an empirical model. Final report, April 1989-May 1990  

SciTech Connect

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, D.B.; Rosenberg, S.D.

1990-05-01

175

Research Combustion Lab Facility Capabilities and Throughput Enhanced by New Test Stands  

NASA Technical Reports Server (NTRS)

The original test stand location has a small copper rocket engine mounted on the stand. The new stand, located about 4 feet to the left, has a long pulse detonation combustion engine mounted on it. To the rear of the two stands can be seen a bulkhead with feed line outlets that can be switched at common valves behind the bulkhead to supply either stand. A gauge panel is visible through a doorway in the bulkhead at which various purge pressures are set. A connection panel for instrumentation wiring can be seen above the stands.

2003-01-01

176

Oxygen-enhanced models for globular cluster stars. III - Horizontal-branch sequences  

NASA Technical Reports Server (NTRS)

A large grid of horizontal-branch (HB) evolutionary sequences which have been calculated with core expansion and semiconvection and with enhanced oxygen composition are presented and described. Tracks for 10 different metallicities are computed; they range from (Fe/H) = -0.47 to -2.26 and comprise a total of 115 sequences. The evolution is traced from the zero-age horizontal-branch (ZAHB) to the lower AGB at a point where log L/solar luminosity = 2.25. All of the sequences are illustrated on both the theoretical H-R diagram and on the B, V color-magnitude diagram. A complete set of tables for the ZAHB models and a representative sample of tabulations of the track parameters are provided. The phenomena which control HB evolution morphology, and existing certainties in theoretical HB models are discussed.

Dorman, Ben

1992-01-01

177

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

178

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

PubMed

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

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

2013-07-01

179

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

180

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

181

Enhancement of chemical-oxygen demand and color removal of distillery spent-wash by ozonation.  

PubMed

Distillery spent-wash has very high organic content (75,000 to 125,000 mg/L chemical-oxygen demand [COD]), color, and contains difficult-to-biodegrade organic compounds. For example, anaerobic treatment of the distillery spent-wash used in this study resulted in 60% COD reduction and low color removal. Subsequent aerobic treatment of the anaerobic effluent resulted in enhancement of COD removal to 66%. In this paper, the effect of ozonation on various properties of the anaerobically treated distillery effluent, including the effect on its subsequent aerobic biodegradation, was investigated. Ozonation of the anaerobically treated distillery effluent at various ozone doses resulted in the reduction of total-organic carbon (TOC), COD, COD/TOC ratio, absorbance, color, and increase in the biochemical-oxygen demand (BOD)/COD ratio of the effluent. Further, ozonation of the anaerobically treated distillery effluent at an ozone dose of 2.08 mg/mg initial TOC and subsequent aerobic biodegradation resulted in 87.4% COD removal, as compared to 66% removal when ozonation was not used. PMID:16749309

Srivastava, S; Bose, P; Tare, V

2006-04-01

182

Atomic Ordering Enhanced Electrocatalytic Activity of Nanoalloys for Oxygen Reduction Reaction  

SciTech Connect

For oxygen reduction reaction (ORR) over alloy electrocatalysts, the understanding of how the atomic arrangement of the metal species in the nanocatalysts is responsible for the catalytic enhancement is challenging for achieving better design and tailoring of nanoalloy catalysts. This paper reports results of an investigation of the atomic structures and the electrocatalytic activities of ternary and binary nanoalloys, aiming at revealing a fundamental insight into the unique atomic-scale structure?electrocatalytic activity relationship. PtIrCo catalyst and its binary counterparts (PtCo and PtIr) are chosen as a model system for this study. The effect of thermochemical treatment temperature on the atomic-scale structure of the catalysts was examined as a useful probe to the structure?activity correlation. The structural characterization of the binary and ternary nanoalloy catalysts was performed by combining surface sensitive techniques such as XPS and 3D atomic ordering sensitive techniques such as high-energy X-ray diffraction (HE-XRD) coupled to atomic pair distribution function (PDF) analysis (HE-XRD/PDFs) and computer simulations. The results show that the thermal treatment temperature tunes the nanoalloy’s atomic and chemical ordering in a different way depending on the chemical composition, leading to differences in the nanoalloy’s mass and specific activities. A unique structural tunability of the atomic ordering in a platinum?iridium?cobalt nanoalloy has been revealed for enhancing greatly the electrocatalytic activity toward oxygen reduction reaction, which has significant implication for rational design and nanoengineering of advanced catalysts for electrochemical energy conversion and storage.

Loukrakpam, Rameshwori; Shan, Shiyao; Petkov, Valeri; Yang, Lefu; Luo, Jin; Zhong, Chuan-Jian

2013-10-01

183

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

184

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

SciTech Connect

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

Arvind Atreya

2007-02-16

185

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

186

Intrinsic relationship between enhanced oxygen reduction reaction activity and nanoscale work function of doped carbons.  

PubMed

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

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

2014-06-25

187

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

188

BUFFER ADDITIVES FOR LIME/LIMESTONE SLURRY SCRUBBING: SULFITE OXIDATION WITH ENHANCED OXYGEN ABSORPTION CATALYZED BY TRANSITION METALS  

EPA Science Inventory

The report gives results of a study of sulfite oxidation, involving the measurement of the rate of enhanced oxygen absorption across an unbroken interface into solution containing sulfite (2-100 mM) and catalyst (0.01-100 mM) at pH 4-6 and 50 C. Fe, Mn, Co, Cu and Cr ions were po...

189

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

PubMed Central

Psoriasis is a chronic inflammatory skin disease resulting from immune dysregulation. Regulatory T cells (Tregs) are important in the prevention of psoriasis. Traditionally, reactive oxygen species (ROS) are known to be implicated in the progression of inflammatory diseases, including psoriasis, but many recent studies suggested the protective role of ROS in immune-mediated diseases. In particular, severe cases of psoriasis vulgaris have been reported to be successfully treated by hyperbaric oxygen therapy (HBOT), which raises tissue level of ROS. Also it was reported that Treg function was closely associated with ROS level. However, it has been only investigated in lowered levels of ROS so far. Thus, in this study, to clarify the relationship between ROS level and Treg function, as well as their role in the pathogenesis of psoriasis, we investigated imiquimod-induced psoriatic dermatitis (PD) in association with Treg function both in elevated and lowered levels of ROS by using knockout mice, such as glutathione peroxidase-1?/? and neutrophil cytosolic factor-1?/? mice, as well as by using HBOT or chemicals, such as 2,3-dimethoxy-1,4-naphthoquinone and N-acetylcysteine. The results consistently showed Tregs were hyperfunctional in elevated levels of ROS, whereas hypofunctional in lowered levels of ROS. In addition, imiquimod-induced PD was attenuated in elevated levels of ROS, whereas aggravated in lowered levels of ROS. For the molecular mechanism that may link ROS level and Treg function, we investigated the expression of an immunoregulatory enzyme, indoleamine 2,3-dioxygenase (IDO) which is induced by ROS, in PD lesions. Taken together, it was implied that appropriately elevated levels of ROS might prevent psoriasis through enhancing IDO expression and Treg function. PMID:24608112

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

2014-01-01

190

Combustion-enhancement and pollutant-control research with acoustically induced mixing. Final report  

SciTech Connect

The application of acoustic energy to a pulverized-coal flame was investigated to determine its influence on NO/sub x/ generation, combustion intensity and turndown ratio. A bench-scale, research combustor utilizing plug flow and burning 5 lb/hr of Illinois No. 6C coal was tested as both a two-stage and single-staged combustor with and without acoustics applied. Sound intensities up to 149 dB at frequencies from 1100 Hz to 3000 Hz were evaluated. The experiments showed that NO/sub x/ generation was unaffected by acoustic mixing in the low first-stage stoichiometric ratio (SR/sub 1/) range of a two-staged combustor and increased up to 20% by use of acoustics in the high SR/sub 1/ range. A similar increase in NO/sub x/ with acoustics was seen in a single stage combustor operating with 5% to 20% excess air. The testing further showed that carbon burnup efficiency could be increased by 7 to 9 percentage points (in the 90 to 100% range) when acoustics were applied. Limited test data indicated that volumetric heat release and turndown ratio could be increased by a factor of 2.8. 21 figures, 3 tables.

Faeser, R.J.; Rudnicki, M.I.

1983-03-01

191

Supersonic Inlet with Pylons Set and Star-Shaped Forebody for Mixing, Combustion and Thrust Enhancement  

NASA Technical Reports Server (NTRS)

Two new approaches are discussed in this paper for application in the Scramjet inlet of an air-breathing propulsion system: 1) In the first approach, the pylon set is installed in the rectangular inlet near the cowl front edge. For a quasi-axisymmetric inlet, a similar set is installed along the Star-shaped forebody axis. This set contains 3 - 4 airfoil-shaped strips or cross-sectional rings depending on the type of inlet. The inlets: rectangular, axisymmetric or star-shaped, are located at different distances from the forebody. Fuel injection takes place through these pylons, which provides for uniform mixing downstream. The locations, sizes and angles of these pylons are very important for efficient application. Optimal values of geometrical parameters were determined from multi-parametric NSE-based numerical simulations of the laminar and turbulent external/internal flows. These simulations have shown significant benefits for mixing, combustion and thrust of the proposed approach by comparison with traditional well-known designs. Experimental tests will be conducted soon at the NASA LaRC and Institute of Mechanics at Moscow State University. Preliminary estimates are very promising.

Gilinsky, M.; Gonor, A. L.; Khaikine, V. A.; Blankson, I. M.

2003-01-01

192

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; Farré, Ramon

2014-01-01

193

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

PubMed

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

Zhao, Feng; Sellgren, Katelyn; Ma, Teng

2009-06-01

194

Effects of EGR, water/N2/CO2 injection and oxygen enrichment on the availability destroyed due to combustion for a range of conditions and fuels  

E-print Network

combustion of iso octane.................................................................................................... 24 3 Percentage availability destroyed for different ?Cooled? EGR fractions as a function of reactant temperature for constant... volume combustion of iso octane, reactant pressure of 500 kPa......................................................... 24 4 Product temperature for different ?Cooled? EGR fractions as a function of reactant temperature for constant pressure combustion...

Sivadas, Hari Shanker

2009-06-02

195

Smouldering Combustion Phenomena in Science and Technology  

Microsoft Academic Search

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

Guillermo Rein

196

Enhancement of activity of RuSex electrocatalyst by modification with nanostructured iridium towards more efficient reduction of oxygen  

NASA Astrophysics Data System (ADS)

Electrocatalytic activity of carbon (Vulcan XC-72) supported selenium-modified ruthenium, RuSex/C, nanoparticles for reduction of oxygen was enhanced through intentional decoration with iridium nanostructures (dimensions, 2-3 nm). The catalytic materials were characterized in oxygenated 0.5 mol dm-3 H2SO4 using cyclic and rotating ring disk voltammetric techniques as well as using transmission electron microscopy and scanning electron microscopy equipped with X-ray dispersive analyzer. Experiments utilizing gas diffusion electrode aimed at mimicking conditions existing in the low-temperature fuel cell. Upon application of our composite catalytic system, the reduction of oxygen proceeded at more positive potentials, and higher current densities were observed when compared to the behavior of the simple iridium-free system (RuSex/C) investigated under the analogous conditions. The enhancement effect was more pronounced than that one would expect from simple superposition of voltammetric responses for the oxygen reduction at RuSex/C and iridium nanostructures studied separately. Nanostructured iridium acted here as an example of a powerful catalyst for the reduction of H2O2 (rather than O2) and, when combined with such a moderate catalyst as ruthenium-selenium (for O2 reduction), it produced an integrated system of increased electrocatalytic activity in the oxygen reduction process. The proposed system retained its activity in the presence of methanol that could appear in a cathode compartment of alcohol fuel cell.

Dembinska, Beata; Kiliszek, Malgorzata; Elzanowska, Hanna; Pisarek, Marcin; Kulesza, Pawel J.

2013-12-01

197

Reactive oxygen species enhance differentiation of human embryonic stem cells into mesendodermal lineage.  

PubMed

Recently, reactive oxygen species (ROS) have been studied as a regulator of differentiation into specific cell types in embryonic stem cells (ESCs). However, ROS role in human ESCs (hESCs) is unknown because mouse ESCs have been used mainly for most studies. Herein we suggest that ROS generation may play a critical role in differentiation of hESCs; ROS enhances differentiation of hESCs into bi-potent mesendodermal cell lineage via ROS-involved signaling pathways. In ROS-inducing conditions, expression of pluripotency markers (Oct4, Tra 1-60, Nanog, and Sox2) of hESCs was decreased, while expression of mesodermal and endodermal markers was increased. Moreover, these differentiation events of hESCs in ROS-inducing conditions were decreased by free radical scavenger treatment. hESC-derived embryoid bodies (EBs) also showed similar differentiation patterns by ROS induction. In ROS-related signaling pathway, some of the MAPKs family members in hESCs were also affected by ROS induction. p38 MAPK and AKT (protein kinases B, PKB) were inactivated significantly by buthionine sulfoximine (BSO) treatment. JNK and ERK phosphorylation levels were increased at early time of BSO treatment but not at late time point. Moreover, MAPKs family-specific inhibitors could prevent the mesendodermal differentiation of hESCs by ROS induction. Our results demonstrate that stemness and differentiation of hESCs can be regulated by environmental factors such as ROS. PMID:20164681

Ji, Ae-Ri; Ku, Seung-Yup; Cho, Myung Soo; Kim, Yoon Young; Kim, Yong Jin; Oh, Sun Kyung; Kim, Seok Hyun; Moon, Shin Yong; Choi, Young Min

2010-03-31

198

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

PubMed

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

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

2014-05-01

199

Oxygen-plasma-modified biomimetic nanofibrous scaffolds for enhanced compatibility of cardiovascular implants  

PubMed Central

Summary Electrospun nanofibrous scaffolds have been extensively used in several biomedical applications for tissue engineering due to their morphological resemblance to the extracellular matrix (ECM). Especially, there is a need for the cardiovascular implants to exhibit a nanostructured surface that mimics the native endothelium in order to promote endothelialization and to reduce the complications of thrombosis and implant failure. Thus, we herein fabricated poly-?-caprolactone (PCL) electrospun nanofibrous scaffolds, to serve as coatings for cardiovascular implants and guide tissue regeneration. Oxygen plasma treatment was applied in order to modify the surface chemistry of the scaffold and its effect on cell attachment and growth was evaluated. The conditions of the surface modification were properly adjusted in order to define those conditions of the treatment that result in surfaces favorable for cell growth, while maintaining morphological integrity and mechanical behavior. Goniometry (contact angle measurements), scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) measurements were used to evaluate the morphological and chemical changes induced by the plasma treatment. Moreover, depth-sensing nanoindentation was performed to study the resistance of the plasma-treated scaffolds to plastic deformation. Lastly, the cell studies indicated that all scaffolds were cytocompatible, with the plasma-treated ones expressing a more pronounced cell viability and adhesion. All the above findings demonstrate the great potential of these biomimetic tissue-engineering constructs as efficient coatings for enhanced compatibility of cardiovascular implants. PMID:25671169

Pappa, Anna Maria; Krol, Silke; Kassavetis, Spyros; Konstantinou, Dimitris; Pitsalidis, Charalampos; Tzounis, Lazaros; Pliatsikas, Nikos; Logothetidis, Stergios

2015-01-01

200

Platinum-Based Nanowire Networks with Enhanced Oxygen-Reduction Activity  

NASA Astrophysics Data System (ADS)

Pt-Al and Pt-Y-Al thin-film electrodes on yttria-stabilized zirconia electrolytes were prepared by dealloying of cosputtered Pt-Al or Pt-Y-Al films. The selective dissolution of Al from the Pt-alloy compound causes the formation of a highly porous nanowire network with a mean branch thickness below 25 nm and a pore intercept length below 35 nm. The oxygen-reduction capability of the resulting electrodes is analyzed in a micro-solid-oxide fuel-cell setup at elevated temperatures (598-873 K). Here, we demonstrate that these nanoporous thin films excel "state-of-the-art" fuel-cell electrodes in terms of catalytic activity and thermal stability. The nanoporous Pt electrodes exhibit exchange-current densities that are up to 13 times higher than conventional Pt electrodes, measured at 648 K. It is shown that the enhanced intrinsic electrocatalytic activity of these Pt electrodes is achieved by the addition of yttrium as a ternary constituent, which allows for an engineering of the material's band structure.

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

2014-11-01

201

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

PubMed

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

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

2013-07-21

202

High pressure ignition of boron in reduced oxygen atmospheres  

SciTech Connect

Boron ignition delay times for 24 {micro}m diameter particles have been measured behind the reflected shock at a shock tube endwall in reduced oxygen atmospheres and in a combustion bomb at higher pressures in the products of a hydrogen/oxygen/nitrogen reaction. The shock tube study independently varies temperature (1,400 -- 3,200 K), pressure (8.5, 34 atm), and ignition-enhancer additives (water vapor, fluorine compounds). A combustion chamber is used at a peak pressure of 157 atm and temperature in excess of 2,800 K to study ignition delays at higher pressures than are possible in the shock tube.

Foelsche, R.O.; Spalding, M.J.; Burton, R.L.; Krier, H. [Univ. of Illinois, Urbana, IL (United States)

1996-07-01

203

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

204

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

205

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

PubMed Central

Background The industrially important yeast Saccharomyces cerevisiae is able to grow both in the presence and absence of oxygen. However, the regulation of its metabolism in conditions of intermediate oxygen availability is not well characterised. We assessed the effect of oxygen provision on the transcriptome and proteome of S. cerevisiae in glucose-limited chemostat cultivations in anaerobic and aerobic conditions, and with three intermediate (0.5, 1.0 and 2.8% oxygen) levels of oxygen in the feed gas. Results The main differences in the transcriptome were observed in the comparison of fully aerobic, intermediate oxygen and anaerobic conditions, while the transcriptome was generally unchanged in conditions receiving different intermediate levels (0.5, 1.0 or 2.8% O2) of oxygen in the feed gas. Comparison of the transcriptome and proteome data suggested post-transcriptional regulation was important, especially in 0.5% oxygen. In the conditions of intermediate oxygen, the genes encoding enzymes of the respiratory pathway were more highly expressed than in either aerobic or anaerobic conditions. A similar trend was also seen in the proteome and in enzyme activities of the TCA cycle. Further, genes encoding proteins of the mitochondrial translation machinery were present at higher levels in all oxygen-limited and anaerobic conditions, compared to fully aerobic conditions. Conclusion Global upregulation of genes encoding components of the respiratory pathway under conditions of intermediate oxygen suggested a regulatory mechanism to control these genes as a response to the need of more efficient energy production. Further, cells grown in three different intermediate oxygen levels were highly similar at the level of transcription, while they differed at the proteome level, suggesting post-transcriptional mechanisms leading to distinct physiological modes of respiro-fermentative metabolism. PMID:19804647

Rintala, Eija; Toivari, Mervi; Pitkänen, Juha-Pekka; Wiebe, Marilyn G; Ruohonen, Laura; Penttilä, Merja

2009-01-01

206

Enhanced oxygen-tolerance of the full heterotrimeric membrane-bound [NiFe]-hydrogenase of Ralstonia eutropha.  

PubMed

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

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

2014-06-18

207

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

208

Enhanced reactive oxygen species overexpression by CuO nanoparticles in poorly differentiated hepatocellular carcinoma cells  

NASA Astrophysics Data System (ADS)

Copper oxide nanoparticles (CuO NPs) are known to exhibit toxic effects on a variety of cell types and organs. To determine the oxidative impact of CuO NPs on hepatocellular carcinoma (HCC) cells, well-differentiated (HepG2) and poorly differentiated (SK-Hep-1) cells were exposed to CuO NPs. Cell viability assay showed that the median inhibition concentration (IC50) for SK-Hep-1 and HepG2 cells was 25 ?g ml-1 and 85 ?g ml-1, respectively. Cellular fluorescence intensity using DCFH-DA staining analysis revealed significant intracellular reactive oxygen species (ROS) generation of up to 242% in SK-Hep-1 cells, compared with 86% in HepG2 cells. HPLC analysis demonstrated that a CuO NP treatment caused cellular GSH depletion of 58% and a GSH/GSSG ratio decrease to ~0.1 in SK-Hep-1 cells. The oxidative stress caused by enhanced superoxide anion production was observed in both HepG2 (146%) and SK-Hep-1 (192%) cells. The Griess assay verified that CuO NPs induced NO production (170%) in SK-Hep-1 cells. Comet assay and western blot further demonstrated that CuO NPs induced severe DNA strand breakage (70%) in SK-Hep-1 cells and caused DNA damage via increased ?-H2AX levels. These results suggest that well-differentiated HepG2 cells possess a robust antioxidant defense system against CuO NP-induced ROS stress and exhibit more tolerance to oxidative stress. Conversely, poorly differentiated SK-Hep-1 cells exhibited a deregulated antioxidant defense system that allowed accumulation of CuO NP-induced ROS and resulted in severe cytotoxicity.Copper oxide nanoparticles (CuO NPs) are known to exhibit toxic effects on a variety of cell types and organs. To determine the oxidative impact of CuO NPs on hepatocellular carcinoma (HCC) cells, well-differentiated (HepG2) and poorly differentiated (SK-Hep-1) cells were exposed to CuO NPs. Cell viability assay showed that the median inhibition concentration (IC50) for SK-Hep-1 and HepG2 cells was 25 ?g ml-1 and 85 ?g ml-1, respectively. Cellular fluorescence intensity using DCFH-DA staining analysis revealed significant intracellular reactive oxygen species (ROS) generation of up to 242% in SK-Hep-1 cells, compared with 86% in HepG2 cells. HPLC analysis demonstrated that a CuO NP treatment caused cellular GSH depletion of 58% and a GSH/GSSG ratio decrease to ~0.1 in SK-Hep-1 cells. The oxidative stress caused by enhanced superoxide anion production was observed in both HepG2 (146%) and SK-Hep-1 (192%) cells. The Griess assay verified that CuO NPs induced NO production (170%) in SK-Hep-1 cells. Comet assay and western blot further demonstrated that CuO NPs induced severe DNA strand breakage (70%) in SK-Hep-1 cells and caused DNA damage via increased ?-H2AX levels. These results suggest that well-differentiated HepG2 cells possess a robust antioxidant defense system against CuO NP-induced ROS stress and exhibit more tolerance to oxidative stress. Conversely, poorly differentiated SK-Hep-1 cells exhibited a deregulated antioxidant defense system that allowed accumulation of CuO NP-induced ROS and resulted in severe cytotoxicity. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05843g

Kung, Mei-Lang; Hsieh, Shu-Ling; Wu, Chih-Chung; Chu, Tian-Huei; Lin, Yu-Chun; Yeh, Bi-Wen; Hsieh, Shuchen

2015-01-01

209

Enhanced reactive oxygen species overexpression by CuO nanoparticles in poorly differentiated hepatocellular carcinoma cells.  

PubMed

Copper oxide nanoparticles (CuO NPs) are known to exhibit toxic effects on a variety of cell types and organs. To determine the oxidative impact of CuO NPs on hepatocellular carcinoma (HCC) cells, well-differentiated (HepG2) and poorly differentiated (SK-Hep-1) cells were exposed to CuO NPs. Cell viability assay showed that the median inhibition concentration (IC50) for SK-Hep-1 and HepG2 cells was 25 ?g ml(-1) and 85 ?g ml(-1), respectively. Cellular fluorescence intensity using DCFH-DA staining analysis revealed significant intracellular reactive oxygen species (ROS) generation of up to 242% in SK-Hep-1 cells, compared with 86% in HepG2 cells. HPLC analysis demonstrated that a CuO NP treatment caused cellular GSH depletion of 58% and a GSH/GSSG ratio decrease to ?0.1 in SK-Hep-1 cells. The oxidative stress caused by enhanced superoxide anion production was observed in both HepG2 (146%) and SK-Hep-1 (192%) cells. The Griess assay verified that CuO NPs induced NO production (170%) in SK-Hep-1 cells. Comet assay and western blot further demonstrated that CuO NPs induced severe DNA strand breakage (70%) in SK-Hep-1 cells and caused DNA damage via increased ?-H2AX levels. These results suggest that well-differentiated HepG2 cells possess a robust antioxidant defense system against CuO NP-induced ROS stress and exhibit more tolerance to oxidative stress. Conversely, poorly differentiated SK-Hep-1 cells exhibited a deregulated antioxidant defense system that allowed accumulation of CuO NP-induced ROS and resulted in severe cytotoxicity. PMID:25521936

Kung, Mei-Lang; Hsieh, Shu-Ling; Wu, Chih-Chung; Chu, Tian-Huei; Lin, Yu-Chun; Yeh, Bi-Wen; Hsieh, Shuchen

2015-01-22

210

Enhanced singlet oxygen production by photodynamic therapy and a novel method for its intracellular measurement.  

PubMed

Abstract The generation of singlet oxygen (SO) in the presence of specific photosensitizers (PSs) or semiconductor quantum dots (QDs) and its application in photodynamic therapy (PDT) is of great interest to develop cancer therapies with no need of surgery, chemotherapy, and/or radiotherapy. This work was focused on the identification of the main factors leading to the enhancement of SO production using Rose Bengal (RB), and Methylene Blue (MB) as PS species in organic and aqueous mediums. Subsequently, the capacity of zinc oxide (ZnO), zinc sulfide (ZnS), and ZnO/ZnS core-shell QDs as well as manganese (Mn(+2)) doped ZnO and ZnS nanoparticles (NPs) as potential PS was also investigated. Many variable parameters such as type of quencher, PSs, NPs, as well as its different concentrations, light source, excitation wavelength, reaction time, distance from light source, and nature of solvent were used. The degradation kinetics of the quenchers generated by SO species and the corresponding quantum yields were determined by monitoring the photo-oxidation of the chemical quencher and measuring its disappearance by fluorometry and spectrophotometry in the presence of NPs. Small intracellular changes of SO induced by these metal Zn (zinc) NPs and PDT could execute and accelerate deadly programs in these leukemic cells, providing in this way an innovative modality of treatment. In order to perform further more specific in vitro cytotoxic studies on B-chronic lymphocytic leukemia cells exposed to Zn NPs and PDT, we needed first to measure and ascertain those possible intracellular SO variations generated by this type of treatment; for this purpose, we have also developed and tested a novel method first described by us. PMID:25490599

Luengas, Sandra L Pena; Marin, Gustavo Horacio; Aviles, Kevin; Acuña, Ricardo Cruz; Roque, Gustavo; Nieto, Felipe Rodríguez; Sanchez, Francisco; Tarditi, Adrián; Rivera, Luis; Mansilla, Eduardo

2014-12-01

211

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

212

Responses to Oxygen Deprivation and Potential for Enhanced Flooding Tolerance in Maize  

Technology Transfer Automated Retrieval System (TEKTRAN)

Although plants release oxygen as a byproduct during the process of photosynthesis, they are obligatory aerobes requiring the gas for their survival, growth and productivity. Oxygen limitation, the predominant stress in flooded plants, dramatically affects the gene expression, development and produc...

213

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

214

Materials problems in fluidized-bed-combustion and coal-gasification systems: further studies of corrosion chemistry in low-oxygen activity atmospheres. Final report  

SciTech Connect

This report presents the results of additional studies on corrosion chemistry in low-oxygen activity atmospheres that are characteristic of gasified or incompletely combusted coal. The objective of the work was to identify those factors in alloy composition and structure and in gas composition and temperature that govern both the formation and eventual breakdown of protective-oxide scales in low-P/sub O//sub 2// to high-P/sub S//sub 2// atmospheres. It was found that protective chromic-oxide scales of uniform composition and structure formed only on cold-worked or ultrafine grain surfaces of alloys containing >1% Fe or Mn. Breakdown or failure of normally protective chromic-oxide scales was studied as a function of alloy composition (Fe, Ni, Co, Mn, Cr) and atmosphere conditions (P/sub O//sub 2//, P/sub S//sub 2// temperature). The most protective scales were those formed on Ni-Cr alloys low in Fe and Mn (<1%). These scales failed eventually by mechanical breakdown; i.e., cracking or spalling. The least-protective scales were those formed on alloys containing Fe and Mn. Internal sulfidation did not appear to be a major factor in breakaway sulfidation of alloys. Chromic-oxide scales formed in the absence of sulfur were found to be excellent barriers to the inward transport of sulfur. It is concluded that the best alloys for resisting sulfidation in these atmospheres are Ni or Co-Ni based with 30 to 50% Cr and <0.1% Fe and Mn. Yttrium or rare earths should be added to reduce the rate of oxide growth and to retard failure by oxide cracking or spalling.

Perkins, R.A.; Coons, W.C.; Vonk, S.J.

1982-06-01

215

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

216

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

EPA Science Inventory

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

217

Enhanced electrocatalysis of the oxygen reduction reaction based on patterning 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, M.; Kodama, K.; Stamenkovic, V. R.; Cuesta, A.; Markovic, N. M. (Materials Science Division); (Inst. de Quimica Fisica); (Toyota Central R& D Labs.)

2010-10-01

218

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

219

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

220

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

221

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

222

A review of the compatibility of structural materials with oxygen  

NASA Technical Reports Server (NTRS)

Consideration of the problem of ignition and combustion of structural materials, particularly metals, which may come in contact with oxygen during its production, transport, and use. Following a review of the historical development of compatibility problems and research, a detailed account is given of compatibility testing methods aimed at detecting probable ignition sources, such as mechanical impact, electric sparks or flashes, heat, sound waves, abrasion, and surface fractures. A summary is presented of the ignition and combustion research reported in the literature, dwelling particularly on papers concerning oxygen-related accidents and the compatibility of metals with high-pressure oxygen. The relative oxygen compatibility of a number of common materials is discussed, including that of nickel and copper alloys, stainless steels, aluminum alloys, and titanium alloys. Finally, an effort is made to pinpoint research areas which would enhance understanding of the compatibility of bulk materials.

Clark, A. F.; Hust, J. G.

1974-01-01

223

Oxygen plasma immersion ion implantation treatment to enhance data retention of tungsten nanocrystal nonvolatile memory  

SciTech Connect

Data retention characteristics of tungsten nanocrystal (W-NC) memory devices using an oxygen plasma immersion ion implantation (PIII) treatment are investigated. With an increase of oxygen PIII bias voltage and treatment time, the capacitance–voltage hysteresis memory window is increased but the data retention characteristics become degraded. High-resolution transmission electron microscopy images show that this poor data retention is a result of plasma damage on the tunneling oxide layer, which can be prevented by lowering the bias voltage to 7?kV. In addition, by using the elevated temperature retention measurement technique, the effective charge trapping level of the WO{sub 3} film surrounding the W-NCs can be extracted. This measurement reveals that a higher oxygen PIII bias voltage and treatment time induces more shallow traps within the WO{sub 3} film, degrading the retention behavior of the W-NC memory.

Wang, Jer-Chyi, E-mail: jcwang@mail.cgu.edu.tw; Chang, Wei-Cheng; Lai, Chao-Sung, E-mail: cslai@mail.cgu.edu.tw [Department of Electronic Engineering, Chang Gung University, Kweishan 333, Taoyuan, Taiwan (China); Chang, Li-Chun [Department of Material Engineering and Center for Thin Film Technologies and Applications, Ming Chi University of Technology, Taishan 24301, New Taipei City, Taiwan (China); Ai, Chi-Fong; Tsai, Wen-Fa [Institute of Nuclear Energy Research, Atomic Energy Council, Longtan 325, Taoyuan, Taiwan (China)

2014-03-15

224

Superoxide dismutase enhances the formation of hydroxyl radicals in the reaction of 3-hydroxyanthranilic acid with molecular oxygen.  

PubMed Central

Superoxide dismutase (SOD) enhanced the formation of hydroxyl radicals, which were detected by using the e.s.r. spin-trapping technique, in a reaction mixture containing 3-hydroxyanthranilic acid (or p-aminophenol), Fe3+ ions, EDTA and potassium phosphate buffer, pH 7.4. The hydroxyl-radical formation enhanced by SOD was inhibited by catalase and desferrioxamine, and stimulated by EDTA and diethylenetriaminepenta-acetic acid, suggesting that both hydrogen peroxide and iron ions participate in the reaction. The hydroxyl-radical formation enhanced by SOD may be considered to proceed via the following steps. First, 3-hydroxyanthranilic acid is spontaneously auto-oxidized in a process that requires molecular oxygen and yields superoxide anions and anthranilyl radicals. This reaction seems to be reversible. Secondly, the superoxide anions formed in the first step are dismuted by SOD to generate hydrogen peroxide and molecular oxygen, and hence the equilibrium in the first step is displaced in favour of the formation of superoxide anions. Thirdly, hydroxyl radicals are generated from hydrogen peroxide through the Fenton reaction. In this Fenton reaction Fe2+ ions are available since Fe3+ ions are readily reduced by 3-hydroxyanthranilic acid. The superoxide anions do not seem to participate in the reduction of Fe3+ ions, since superoxide anions are rapidly dismuted by SOD present in the reaction mixture. PMID:2843167

Iwahashi, H; Ishii, T; Sugata, R; Kido, R

1988-01-01

225

Enhanced Adhesion of Campylobacter jejuni to Abiotic Surfaces Is Mediated by Membrane Proteins in Oxygen-Enriched Conditions  

PubMed Central

Campylobacter jejuni is responsible for the major foodborne bacterial enteritis in humans. In contradiction with its fastidious growth requirements, this microaerobic pathogen can survive in aerobic food environments, suggesting that it must employ a variety of protection mechanisms to resist oxidative stress. For the first time, C. jejuni 81–176 inner and outer membrane subproteomes were analyzed separately using two-dimensional protein electrophoresis (2-DE) of oxygen-acclimated cells and microaerobically grown cells. LC-MS/MS analyses successfully identified 42 and 25 spots which exhibited a significantly altered abundance in the IMP-enriched fraction and in the OMP-enriched fraction, respectively, in response to oxidative conditions. These spots corresponded to 38 membrane proteins that could be grouped into different functional classes: (i) transporters, (ii) chaperones, (iii) fatty acid metabolism, (iv) adhesion/virulence and (v) other metabolisms. Some of these proteins were up-regulated at the transcriptional level in oxygen-acclimated cells as confirmed by qRT-PCR. Downstream analyses revealed that adhesion of C. jejuni to inert surfaces and swarming motility were enhanced in oxygen-acclimated cells or paraquat-stressed cells, which could be explained by the higher abundance of membrane proteins involved in adhesion and biofilm formation. The virulence factor CadF, over-expressed in the outer membrane of oxygen-acclimated cells, contributes to the complex process of C. jejuni adhesion to inert surfaces as revealed by a reduction in the capability of C. jejuni 81–176 ?CadF cells compared to the isogenic strain. Taken together, these data demonstrate that oxygen-enriched conditions promote the over-expression of membrane proteins involved in both the biofilm initiation and virulence of C. jejuni. PMID:23029510

Sulaeman, Sheiam; Hernould, Mathieu; Schaumann, Annick; Coquet, Laurent; Bolla, Jean-Michel; Dé, Emmanuelle; Tresse, Odile

2012-01-01

226

Coal Combustion Science  

SciTech Connect

The objective of this activity is to support the Office of Fossil Energy in executing research on coal combustion science. This activity consists of basic research on coal combustion that supports both the Pittsburgh Energy Technology Center Direct Utilization Advanced Research and Technology Development Program, and the International Energy Agency Coal Combustion Science Project. Specific tasks for this activity include: (1) coal devolatilization - the objective of this risk is to characterize the physical and chemical processes that constitute the early devolatilization phase of coal combustion as a function of coal type, heating rate, particle size and temperature, and gas phase temperature and oxidizer concentration; (2) coal char combustion -the objective of this task is to characterize the physical and chemical processes involved during coal char combustion as a function of coal type, particle size and temperature, and gas phase temperature and oxygen concentration; (3) fate of mineral matter during coal combustion - the objective of this task is to establish a quantitative understanding of the mechanisms and rates of transformation, fragmentation, and deposition of mineral matter in coal combustion environments as a function of coal type, particle size and temperature, the initial forms and distribution of mineral species in the unreacted coal, and the local gas temperature and composition.

Hardesty, D.R. (ed.); Fletcher, T.H.; Hurt, R.H.; Baxter, L.L. (Sandia National Labs., Livermore, CA (United States))

1991-08-01

227

Enhancement of the electroreduction of oxygen on Pt alloys with Fe, Ni, and Co  

Microsoft Academic Search

Electrocatalytic activity of Pt alloys with Ni, Co, and Fe, formed by sputtering, was investigated with regard to the oxygen reduction reaction (ORR) in perchloric acid solution. Hydrodynamic voltammograms with rotated electrodes were used to measure the electrocatalytic activity. Maximum activity was observed at ca. 30, 40, and 50% content of Ni, Co, and Fe, respectively, by which 10, 15,

Takako Toda; Hiroshi Igarashi; Hiroyuki Uchida; Masahiro Watanabe

1999-01-01

228

ENHANCEMENT OF OXYGEN TRANSFER RATE IN TRICKLING FILTER USING RADIAL JET NOZZLE  

Microsoft Academic Search

Oxygen Transfer Rate (OTR) is considered one of the most important factors that affect trickling filter performance, insufficient OTR limits trickling filter performance and generate malodor, another factor that affects trickling filter performance is the percent wetting of the media surface. Effective distribution system may achieve increase in OTR and maintain maximum wetting of the media surface. The present study

Kamal T. Ewida; Sameh M. El-Mokadem; Radwan M. Kamal; Ayman M. Ali

229

Combustion enhancement and pollutant control research with acoustically induced mixing. Technical progress report, March-June, 1981  

SciTech Connect

An experimental research program has been initiated to evaluate the possibility that beneficial effects can result when acoustic energy is impressed on the combustion zone of pulverized coal furnaces. These benefits include the reduction in NO/sub x/ generation, the increase in combustion intensity, and the increase in turndown ratio (maximum flow/minimum flow). The postulated reason for these possible benefits is the fine stirring action of high frequency acoustic waves. The first three-month period of this program was devoted to the formulation of a test plan, the design of the 5 lb/hr coal rate combustor with acoustic driver attachments, and the specification of the test facility.

Faeser, R.J.; Rudnicki, M.I.

1981-07-01

230

Reduced No.sub.x combustion method  

DOEpatents

A combustion method enabling reduced NO.sub.x formation wherein fuel and oxidant are separately injected into a combustion zone in a defined velocity relation, combustion gases are aspirated into the oxidant stream prior to intermixture with the fuel, and the fuel is maintained free from contact with oxygen until the intermixture.

Delano, Mark A. (Briarcliff Manor, NY)

1991-01-01

231

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

232

Enhanced oxygen dissociation in a propagating constricted discharge formed in a self-pulsing atmospheric pressure microplasma jet  

NASA Astrophysics Data System (ADS)

We report on the propagation of a constricted discharge feature in a repetitively self-pulsing microplasma jet operated in helium with a 0.075 vol% molecular oxygen admixture in ambient air environment. The constricted discharge is about 1 mm in width and repetitively ignites at the point of smallest electrode distance in a wedge-shaped electrode configuration, propagates through the discharge channel towards the nozzle, extinguishes, and re-ignites at the inlet at frequencies in the kHz range. It co-exists with a homogeneous, volume-dominated low temperature (T ? 300 K) ?-mode glow. Time-resolved measurements of nitrogen molecule C-state and nitrogen molecule ion B-state emission bands reveal an increase of the rotational temperature within the constricted discharge to about 600 K within 50 µs. Its propagation velocity was determined by phase-resolved diagnostics to be similar to the gas velocity, in the order of 40 m s-1. Two-photon absorption laser-induced fluorescence spectroscopy synchronized to the self-pulsing reveals spatial regions of increased oxygen atom densities co-propagating with the constricted discharge feature. The generated oxygen pulse density is about ten times higher than in the co-existing homogeneous ?-mode. Densities reach about 1.5 × 1016 cm-3 at average temperatures of 450 K at the nozzle. This enhanced dissociation of about 80% is attributed to the continuous interaction of the constricted discharge to the co-propagating gas volume.

Schröder, Daniel; Burhenn, Sebastian; Kirchheim, Dennis; Schulz-von der Gathen, Volker

2013-11-01

233

Effects of Pin-up Oxygen on [60]Fullerene for Enhanced Antioxidant Activity  

PubMed Central

The introduction of pin-up oxygen on C60, such as in the oxidized fullerenes C60O and C60On, induced noticeable increase in the antioxidant activity as compared to pristine C60. The water-soluble inclusion complexes of fullerenes C60O and C60Onreacted with linoleic acid peroxyl radical 1.7 and 2.4 times faster, respectively.

2008-01-01

234

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

235

Biotic enhancement of weathering, atmospheric oxygen and carbon dioxide in the Neoproterozoic  

NASA Astrophysics Data System (ADS)

The Neoproterozoic (1000-544Ma BP) was a time of severe glaciations and a major transition from microscopic to macroscopic life forms. Here we develop the hypothesis that a rise in atmospheric oxygen in the Neoproterozoic was driven by the biological colonization of the land surface. If early forms of photosynthetic land life selectively weathered continental rock in order to extract nutrients, this would have led to an increase in the flux of biologically available phosphorus to the ocean. We show that recent models for coupled biogeochemical cycles, despite differences in the feedback mechanisms represented, predict this would lead to a rise in atmospheric oxygen concentration, consistent with biological and geochemical evidence. A rise in oxygen may in turn have provided a necessary condition for the evolution of animals with hard skeletons seen in the Cambrian explosion. Increased weathering of silicate rocks would also have caused a decline in atmospheric carbon dioxide, which could have been a causal factor in the Neoproterozoic glaciations.

Watson, A.; Lenton, T.

2003-04-01

236

Oxygenation and exercise performance-enhancing effects attributed to the breathe-right nasal dilator.  

PubMed

Recently, many professional football players have elected to wear spring-loaded nasal dilators during competition. Many athletes believe that wearing the "Breathe-Right" nasal dilator will increase nasal gas conduction and oxygenation to their body, subsequently improving their performance. The purpose of this experiment was to investigate the advantages of wearing a nasal dilator while performing aerobic and anaerobic exercise, as opposed to not wearing a nasal dilator. It was hypothesized that the "Breathe-Right" nasal dilator, manufactured by CNS, Inc (Chanhassen, MN) would increase nasal gaseous conduction and increase oxygenation to the body. Nasal gaseous conduction and oxygenation are essential components for using aerobic power. We examined whether wearing a nasal dilator improves performance by using a ramped cycle ergometer stress test on athletes until they reached VO(2) maximum progressing from aerobic to anaerobic exercise. Baseline data were collected (ie, VO(2), VO(2)/Kg, respiratory exchange ratio, anaerobic threshold time, and onset of VO(2) max) using a MedGraphics CardiO(2) System. The subjects included 16 college-aged male athletes. Dependent t-tests implemented on each physiological response; VO(2) max, peak VO(2) kg, onset of anaerobic threshold, onset of VO(2) max, respiratory exchange ratio at VO(2) max, and maximum WATT output, showed there was no difference in the athletes' performance when they wore the nasal dilators and when they did not wear the dilators. PMID:16558338

Trocchio, M; Fisher, J; Wimer, J W; Parkman, A W

1995-09-01

237

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

238

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...

239

Enhanced Cellular Responses and Distinct Gene Profiles in Human Fetoplacental Artery Endothelial Cells under Chronic Low Oxygen1  

PubMed Central

ABSTRACT Fetoplacental endothelial cells are exposed to oxygen levels ranging from 2% to 8% in vivo. However, little is known regarding endothelial function within this range of oxygen because most laboratories use ambient air (21% O2) as a standard culture condition (SCN). We asked whether human umbilical artery endothelial cells (HUAECs) that were steadily exposed to the physiological chronic normoxia (PCN, 3% O2) for ?20–25 days differed in their proliferative and migratory responses to FGF2 and VEGFA as well as in their global gene expression compared with those in the SCN. We observed that PCN enhanced FGF2- and VEGFA-stimulated cell proliferation and migration. In oxygen reversal experiments (i.e., when PCN cells were exposed to SCN for 24 h and vice versa), we found that preexposure to 21% O2 decreased the migratory ability, but not the proliferative ability, of the PCN-HUAECs in response to FGF2 and VEGFA. These PCN-enhanced cellular responses were associated with increased protein levels of HIF1A and NOS3, but not FGFR1, VEGFR1, and VEGFR2. Microarray analysis demonstrated that PCN up-regulated 74 genes and down-regulated 86, 14 of which were directly regulated by hypoxia-inducible factors as evaluated using in silico analysis. Gene function analysis further indicated that the PCN-regulated genes were highly related to cell proliferation and migration, consistent with the results from our functional assays. Given that PCN significantly alters cellular responses to FGF2 and VEGFA as well as transcription in HUAECs, it is likely that we may need to reexamine the current cellular and molecular mechanisms controlling fetoplacental endothelial functions, which were largely derived from endothelial models established under ambient O2. PMID:24152727

Jiang, Yi-Zhou; Wang, Kai; Li, Yan; Dai, Cai-Feng; Wang, Ping; Kendziorski, Christina; Chen, Dong-Bao; Zheng, Jing

2013-01-01

240

Combustion of White Phosphorus  

NASA Astrophysics Data System (ADS)

The reaction of white phosphorus with pure oxygen is conveniently and safely demonstrated by carrying out the reaction in a retort that has its open end submerged in water. After filling the retort with oxygen gas, a small amount of white phosphorus is introduced and heated with a hot-plate until it ignites. The spectacular reaction leads to consumption and expulsion of oxygen gas, creation of a partial vacuum in the retort, and back suction of water that extinguishes the combustion. Featured on the Cover

Keiter, Richard L.; Gamage, Chaminda P.

2001-07-01

241

Efficiency evaluation of oxygen enrichment in energy conversion processes  

Microsoft Academic Search

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

Bomelburg

1983-01-01

242

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

243

Combustion enhancement and pollutant-control research with acoustically induced mixing. Technical progress report, June-September 1981  

SciTech Connect

An experimental research program has been initiated to evaluate the possibility that beneficial effects can result when acoustic energy is impressed on the combustion zone of pulverized coal furnaces. These benefits include the reduction in NO/sub x/ generation, the increase in combustion intensity, and the increase in turndown ratio (maximum flow/minimum flow). The postulated reason for these possible benefits is the increased relative motion of the gas and coal particles and the fine stirring action resulting from high frequency acoustic waves. During the second, three-month period of this contract, the design and fabrication of the combustor were completed and the test facility buildup was 70% completed. A checkout test of the acoustic equipment and a preliminary acoustic survey test of the combustor response were also completed.

Faeser, R.J.; Rudnicki, M.I.

1981-09-01

244

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

245

Enhancing nitrogen use efficiency of cereal crops by optimizing temperature, moisture, balanced nutrients, and oxygen bioavailability  

Technology Transfer Automated Retrieval System (TEKTRAN)

Enhancement of nutrient use efficiency is imperative for increasing economic returns and reduction of environmental pollution caused by fertilization in crop production systems. In this paper, we have demonstrated at a given soil temperature and nitrogen (N) rate, N loss via ammonia (NH3) emission f...

246

Enhancement of antibody-induced arthritis via Toll-like receptor 2 stimulation is regulated by granulocyte reactive oxygen species.  

PubMed

The suppressive role of phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX2) complex-derived reactive oxygen species (ROS) in adaptive immunity-driven arthritis models is well established. In this study, we aimed to investigate the role of NOX2 complex-derived ROS in a model of innate immunity-driven arthritis and to identify the ROS-regulated innate receptors that control arthritis. We used collagen antibody-induced arthritis (CAIA), which is a T and B lymphocyte-independent model of the effector phase of arthritis and is induced by well-defined monoclonal arthritogenic antibodies and enhanced by injection of lipopolysaccharide (LPS). CAIA was induced in both wild-type and Ncf1 mutant mice that lack phagocyte oxidative burst, and stimulated with LPS and other agents to activate innate immune responses. We found that both LPS and lipomannan enhanced CAIA more potently in the presence of functional phagocyte ROS production than in its absence. The ROS-dependent enhancement of CAIA was regulated by TLR2, but not by TLR4 stimulation, and was driven by granulocytes, whereas macrophages did not contribute to the phenotype. In addition, we report that collagen-induced arthritis was not affected by the functionality of the TLR4. We report that TLR2 signaling as an important ROS-regulated proinflammatory pathway leads to severe neutrophil-dependent inflammation in murine CAIA and conclude that the TLR2 pathway is modulated by phagocyte ROS to stimulate the development of arthritis. PMID:22642907

Kelkka, Tiina; Hultqvist, Malin; Nandakumar, Kutty Selva; Holmdahl, Rikard

2012-07-01

247

Hydrothermal Continuous Flow Synthesis and Exfoliation of NiCo Layered Double Hydroxide Nanosheets for Enhanced Oxygen Evolution Catalysis.  

PubMed

We report the controlled synthesis of NiCo layered double hydroxide (LDH) nanoplates using a newly developed high temperature high pressure hydrothermal continuous flow reactor (HCFR), which enables direct growth onto conductive substrates in high yield and, most importantly, better control of the precursor supersaturation and, thus, nanostructure morphology and size. The solution coordination chemistry of metal-ammonia complexes was utilized to synthesize well-defined NiCo LDH nanoplates directly in a single step without topochemical oxidation. The as-grown NiCo LDH nanoplates exhibit a high catalytic activity toward the oxygen evolution reaction (OER). By chemically exfoliating LDH nanoplates to thinner nanosheets, the catalytic activity can be further enhanced to yield an electrocatalytic current density of 10 mA cm(-2) at an overpotential of 367 mV and a Tafel slope of 40 mV dec(-1). Such enhancement could be due to the increased surface area and more exposed active sites. X-ray photoelectron spectroscopy (XPS) suggests the exfoliation also caused some changes in electronic structure. This work presents general strategies to controllably grow nanostructures of LDH and ternary oxide/hydroxides in general and to enhance the electrocatalytic performance of layered nanostructures by exfoliation. PMID:25633476

Liang, Hanfeng; Meng, Fei; Cabán-Acevedo, Miguel; Li, Linsen; Forticaux, Audrey; Xiu, Lichen; Wang, Zhoucheng; Jin, Song

2015-02-11

248

Laboratory investigations of stable carbon and oxygen isotope ratio data enhance monitoring of CO2 underground  

NASA Astrophysics Data System (ADS)

Stable carbon and oxygen isotope data play an important role in monitoring CO2 in the subsurface, for instance during carbon capture and storage (CCS). This includes monitoring of supercritical and gaseous CO2 movement and reactions under reservoir conditions and detection of potential CO2 leakage scenarios. However, in many cases isotope data from field campaigns are either limited due to complex sample retrieval or require verification under controlled boundary conditions. Moreover, experimentally verified isotope fractionation factors are also accurately known only for temperatures and pressures lower than commonly found in CO2 reservoirs (Myrttinen et al., 2012). For this reason, several experimental series were conducted in order to investigate effects of elevated pressures, temperatures and salinities on stable carbon and oxygen isotope changes of CO2 and water. These tests were conducted with a heateable pressure device and with glass or metal gas containers in which CO2 reacted with fluids for time periods of hours to several weeks. The obtained results revealed systematic differences in 13C/12C-distributions between CO2 and the most important dissolved inorganic carbon (DIC) species under reservoir conditions (CO2(aq), H2CO3 and HCO3-). Since direct measurements of the pH, even immediately after sampling, were unreliable due to rapid CO2 de-gassing, one of the key results of this work is that carbon isotope fractionation data between DIC and CO2 may serve to reconstruct in situ pH values. pH values reconstructed with this approach ranged between 5.5 and 7.4 for experiments with 60 bars and up to 120 °C and were on average 1.4 pH units lower than those measured with standard pH electrodes directly after sampling. In addition, pressure and temperature experiments with H2O and CO2 revealed that differences between the oxygen isotope ratios of both phases depended on temperature, water-gas ratios as well as salt contents of the solutions involved. Such systematic knowledge of the extent of oxygen isotope fractionation between H2O and CO2 can help to reconstruct equilibration times, fluid-CO2 ratios as well as temperature and salinity conditions. Isotope results from systematic laboratory studies and the information they provide for assessing in situ reservoir conditions can be transferred to field applications concerning integrity of CO2 reservoirs. They can also apply to natural systems and other industrial uses that involve monitoring of gases in the subsurface under similar pressure and temperature conditions. Reference: Myrttinen, A., Becker, V., Barth, J.A.C., 2012. A review of methods used for equilibrium isotope fractionation investigations between dissolved inorganic carbon and CO2. Earth-Science Reviews, 115(3): 192-199.

Barth, Johannes A. C.; Myrttinen, Anssi; Becker, Veith; Nowak, Martin; Mayer, Bernhard

2014-05-01

249

Covalent grafting of carbon nanotubes with a biomimetic heme model compound to enhance oxygen reduction reactions.  

PubMed

The oxygen reduction reaction (ORR) is one of the most important reactions in both life processes and energy conversion systems. The replacement of noble-metal Pt-based ORR electrocatalysts by nonprecious-metal catalysts is crucial for the large-scale commercialization of automotive fuel cells. Inspired by the mechanisms of dioxygen activation by metalloenzymes, herein we report a structurally well-defined, bio-inspired ORR catalyst that consists of a biomimetic model compound-an axial imidazole-coordinated porphyrin-covalently attached to multiwalled carbon nanotubes. Without pyrolysis, this bio-inspired electrocatalyst demonstrates superior ORR activity and stability compared to those of the state-of-the-art Pt/C catalyst in both acidic and alkaline solutions, thus making it a promising alternative as an ORR electrocatalyst for application in fuel-cell technology. PMID:24842193

Wei, Ping-Jie; Yu, Guo-Qiang; Naruta, Yoshinori; Liu, Jin-Gang

2014-06-23

250

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

2014-01-01

251

Production of Oxygen  

NSDL National Science Digital Library

In this chemistry activity, learners use yeast and hydrogen peroxide to generate a gas (oxygen) and test some of its properties. This resource includes brief questions for learners to answer after the experiment. Use this activity to introduce learners to oxygen as well as combustion. Note: this activity involves an open flame.

2014-01-28

252

Hyperbaric oxygen preconditioning attenuates hyperglycemia enhanced hemorrhagic transformation after transient MCAO in rats  

PubMed Central

Background Hemorrhagic transformation (HT) can be a devastating complication of ischemic stroke. Hyperbaric oxygen preconditioning (HBO-PC) has been shown to improve blood-brain barrier (BBB) permeability in stroke models. The purpose of this study is to examine whether HBO-PC attenuates HT after focal cerebral ischemia, and to investigate whether the mechanism of HBO-PC against HT includes up-regulation of antioxidants in hyperglycemic rats. Methods Male Sprague-Dawley rats (280-320 g) were divided into the following groups: sham, middle cerebral artery occlusion (MCAO) for 2 h, and MCAO treated with HBO-PC. HBO-PC was conducted giving 100% oxygen at 2.5 atm absolute (ATA), for 1 h at every 24 h interval for 5 days. At 24 h after the last session of HBO-PC, rats received an injection of 50% glucose (6 ml/kg intraperitoneally) and were subjected to MCAO 15 min later. At 24 h after MCAO, neurological behavior tests, infarct volume, blood-brain barrier permeability, and hemoglobin content were measured to evaluate the effect of HBO-PC. Western blot analysis of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) was evaluated at multiple time-points before and after MCAO. Results HBO-PC improved neurological behavior test, and reduced infarction volume, HT and Evans blue extravasation in the ipsilateral hemisphere at 24 h after MCAO. Western blot analysis failed to demonstrate up-regulation of Nrf2 in HBO-PC group before and after MCAO. Paradoxically, HBO-PC decreased HO-1 expression at 24 h after MCAO, as compared with htMCAO group. Conclusions HBO-PC improved neurological deficits, infarction volume, BBB disruption, and HT after focal cerebral ischemia. However, its mechanism against focal cerebral ischemia and HT may not include activation of Nrf2 and subsequent HO-1 expression. PMID:22494892

2012-01-01

253

Labor Contractions Enhance Oxygenation and Behavioral Activity of Newborn Rat Pups  

NASA Technical Reports Server (NTRS)

Labor contractions help instigate behavioral responses at birth (viz., breathing and suckling) that are vital for the newborn's adaptation to the extrauterine world (Ronca et al., 1996). In the present study, we analyzed the role of labor contractions in postpartum oxygenation and behavioral activity of newborn rat pups. Newborns were observed following either vaginal (V) or cesarean delivery. For cesarean delivery, day 21 pregnant dams' were administered a spinal transaction to eliminate lower body sensation, a laparotomy was performed and the uterus was maintained in a heated (37.5 C) bath. Four rat fetuses in one of the dams' paired uterine horn were compressed (C) to Simulate labor contractions (20 sec/min for 10 min) while four fetuses in the opposite horn were not compressed (NC). Fetuses were surgically removed from the uterus, stroked with a soft brush to mimic postnatal licking by the dam, the umbilical cord occluded. Pups were exposed to room temperature (22 C) for one hr, then nest temperature (33 C) for one hr. PO2, CO2, and O2, saturation were determined at 0, 30, 60, or 120 min post delivery using a blood gas analyzer. V and C delivered neonates showed comparable rates of PO2, CO2 and O2 saturation whereas NC neonates showed depressed levels at all time points (p<0.05). Respiratory rates of V, C and NC neonates increased significantly (p<0.05) over the first two postpartum hrs and did not differ across groups. Postpartum behavioral activity was significantly greater in V and C conditions and positively correlated with postnatal oxygenation. These findings provide further evidence for importance of labor contractions in early postpartum adaptation.

Mills, N. A.; Baer, L. A.; Ronca, A. E.; Balton, Bonnie (Technical Monitor)

2002-01-01

254

Survival curves of irradiated glutathione-deficient human fibroblasts: indication of a reduced enhancement of radiosensitivity by oxygen and misonidazole  

SciTech Connect

Fibroblasts derived from a patient with 5-oxoprolinuria are genetically deficient in glutathione synthetase. This deficiency causes a dramatic decrease in intracellular glutathione (GSH) level. The radiosensitivity of GSH deficient cells (GSH) was studied in vitro using colony forming ability as an endpoint. Cells with normal GSH level, obtained from the healthy brother of the patient, were used as controls. When irradiated in 95% air-5% CO/sub 2/, GSH/sup -/ cells are slightly but significantly more radiosensitive than GSH/sup +/ controls (dose modifying factor (DMF) of 1.2). When irradiated in argon, the survival curve of GSH/sup -/ cells indicates an oxygen enhancement ratio (OER) of 1.5 when compared to the curve obtained in oxic conditions. The OER of control cells in the same conditions is 2.9. In comparison to results obtained in air, 100% oxygen moderately increases the radiosensitivity of GSH/sup +/ cells (DMF 1,23), while it has a very low effect on GSH/sup -/ cells (DMF 1.06). These results suggest that intracellular GSH plays an essential protective role in hypoxia, its effect is reduced in air and practically disappears in 100% oxygen. When cells are incubated with 8 mM misonidazole 2 hours before irradiation, the drug has a much greater sensitizing effect on GSH/sup +/ cells (DMF 2.33) than on GSH/sup -/ cells (DMF 1.55). The results demonstrate that intracellular GSH level plays a major role in the response of hypoxic cells, irradiated either alone or in the presence of misonidazole.

Midander, J. (Karolinska Inst., Stockholm, Sweden); Deschavanne, P.J.; Malaise, E.P.; Revesz, L.

1982-03-01

255

Dichloroacetate enhances adriamycin-induced hepatoma cell toxicity in vitro and in vivo by increasing reactive oxygen species levels.  

PubMed

A unique bioenergetic feature of cancer, aerobic glycolysis is considered an attractive therapeutic target for cancer therapy. Recently, dichloroacetate (DCA), a small-molecule metabolic modulator, was shown to reverse the 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

Dai, Yunhai; Xiong, Xiaopeng; Huang, Gang; Liu, Jianjun; Sheng, Shile; Wang, Hongjian; Qin, Wenxin

2014-01-01

256

The oxycoal process with cryogenic oxygen supply.  

PubMed

Due to its large reserves, coal is expected to continue to play an important role in the future. However, specific and absolute CO2 emissions are among the highest when burning coal for power generation. Therefore, the capture of CO2 from power plants may contribute significantly in reducing global CO2 emissions. This review deals with the oxyfuel process, where pure oxygen is used for burning coal, resulting in a flue gas with high CO2 concentrations. After further conditioning, the highly concentrated CO2 is compressed and transported in the liquid state to, for example, geological storages. The enormous oxygen demand is generated in an air-separation unit by a cryogenic process, which is the only available state-of-the-art technology. The generation of oxygen and the purification and liquefaction of the CO2-enriched flue gas consumes significant auxiliary power. Therefore, the overall net efficiency is expected to be lowered by 8 to 12 percentage points, corresponding to a 21 to 36% increase in fuel consumption. Oxygen combustion is associated with higher temperatures compared with conventional air combustion. Both the fuel properties as well as limitations of steam and metal temperatures of the various heat exchanger sections of the steam generator require a moderation of the temperatures during combustion and in the subsequent heat-transfer sections. This is done by means of flue gas recirculation. The interdependencies among fuel properties, the amount and the temperature of the recycled flue gas, and the resulting oxygen concentration in the combustion atmosphere are investigated. Expected effects of the modified flue gas composition in comparison with the air-fired case are studied theoretically and experimentally. The different atmosphere resulting from oxygen-fired combustion gives rise to various questions related to firing, in particular, with regard to the combustion mechanism, pollutant reduction, the risk of corrosion, and the properties of the fly ash or the deposits that form. In particular, detailed nitrogen and sulphur chemistry was investigated by combustion tests in a laboratory-scale facility. Oxidant staging, in order to reduce NO formation, turned out to work with similar effectiveness as for conventional air combustion. With regard to sulphur, a considerable increase in the SO2 concentration was found, as expected. However, the H2S concentration in the combustion atmosphere increased as well. Further results were achieved with a pilot-scale test facility, where acid dew points were measured and deposition probes were exposed to the combustion environment. Besides CO2 and water vapour, the flue gas contains impurities like sulphur species, nitrogen oxides, argon, nitrogen, and oxygen. The CO2 liquefaction is strongly affected by these impurities in terms of the auxiliary power requirement and the CO2 capture rate. Furthermore, the impurity of the liquefied CO2 is affected as well. Since the requirements on the liquid CO2 with regard to geological storage or enhanced oil recovery are currently undefined, the effects of possible flue gas treatment and the design of the liquefaction plant are studied over a wide range. PMID:19495717

Kather, Alfons; Scheffknecht, Günter

2009-09-01

257

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

258

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

259

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

260

A biofilm enhanced miniature microbial fuel cell using Shewanella oneidensis DSP10 and oxygen reduction cathodes.  

PubMed

A miniature-microbial fuel cell (mini-MFC, chamber volume: 1.2 mL) was used to monitor biofilm development from a pure culture of Shewanella oneidensis DSP10 on graphite felt (GF) under minimal nutrient conditions. ESEM evidence of biofilm formation on GF is supported by substantial power density (per device cross-section) from the mini-MFC when using an acellular minimal media anolyte (1500 mW/m2). These experiments demonstrate that power density per volume for a biofilm flow reactor MFC should be calculated using the anode chamber volume alone (250W/m3), rather than with the full anolyte volume. Two oxygen reduction cathodes (uncoated GF or a Pt/vulcanized carbon coating on GF) were also compared to a cathode using uncoated GF and a 50mM ferricyanide catholyte solution. The Pt/C-GF (2-4% Pt by mass) electrodes with liquid cultures of DSP10 produced one order of magnitude larger power density (150W/m3) than bare graphite felt (12W/m3) in this design. These advances are some of the required modifications to enable the mini-MFC to be used in real-time, long-term environmental power generating situations. PMID:16939710

Biffinger, Justin C; Pietron, Jeremy; Ray, Ricky; Little, Brenda; Ringeisen, Bradley R

2007-03-15

261

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

262

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

263

Phenolic extract of Dialium guineense pulp enhances reactive oxygen species detoxification in aflatoxin B? hepatocarcinogenesis.  

PubMed

This study investigated the effect of Dialium guineense pulp phenolic extract on aflatoxin B1 (AFB1)-induced oxidative imbalance in rat liver. Reactive oxygen species (ROS) scavenging potentials of free and bound phenolic extract of D. guineense (0.2-1.0?mg/mL) were investigated in vitro using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, superoxide ion (O2(-)), hydrogen peroxide (H2O2), hydroxyl radical, and ferric ion reducing system. In the in vivo study, 35 animals were randomized into seven groups of five rats each. Free and bound phenolic extract (1?mg/mL) produced 66.42% and 93.08%, 57.1% and 86.0%, 62.0% and 90.05%, and 60.11% and 72.37% scavenging effect on DPPH radical, O2(-) radical, H2O2, and hydroxyl radical, while ferric ion was significantly reduced. An AFB1-mediated decrease in the activities of ROS detoxifying enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glucose 6 phosphate dehydrogenase) was significantly attenuated (P<.05). AFB1-mediated elevation in the concentrations of oxidative stress biomarkers; malondialdehyde, conjugated dienes, lipid hydroperoxides, protein carbonyl, and percentage DNA fragmentation were significantly lowered by D. guineense phenolic extract (P<.05). Overall, the in vitro and in vivo effects suggest that D. guineense phenolic extract elicited ROS scavenging and detoxification potentials, as well as the capability of preventing lipid peroxidation, protein oxidation, and DNA fragmentation. PMID:24892362

Adeleye, Abdulwasiu O; Ajiboye, Taofeek O; Iliasu, Ganiyat A; Abdussalam, Folakemi A; Balogun, Abdulazeez; Ojewuyi, Oluwayemisi B; Yakubu, Musa T

2014-08-01

264

Construction of a reusable, high-fidelity model to enhance extracorporeal membrane oxygenation training through simulation.  

PubMed

Initiation of extracorporeal membrane oxygenation (ECMO) is stressful, especially for inexperienced extracorporeal life support providers. The main objective of this study was to create a novel, reusable mannequin for high-fidelity simulation of ECMO initiation. We modified a Laerdal neonatal mannequin (SimNewB; Stavanger, Norway) so that it could be used to simulate an ECMO initiation. A simulation of a neonatal patient suffering from meconium aspiration was performed in the pediatric intensive care unit, and participants included new extracorporeal life support specialists in addition to the composition of the clinical ECMO team. A total of 17 individuals participated in the neonatal ECMO initiation simulation. Questionnaire results showed that 88% of participants felt better prepared to assist in an ECMO initiation after the simulation. All participants (100%) agreed that the modified mannequin and the environment were realistic and that this simulation helps teamwork and communication in future initiations of ECMO. Simulation can be used for the prevention, identification, and reduction of anxiety-related crisis situations that novice providers may infrequently encounter during routine clinical use of mechanical circulatory support. Use of a reusable, high-fidelity mannequin may be beneficial for effective team training of complex pediatric ECMO-related procedures. PMID:24675629

Thompson, Jess L; Grisham, Lisa M; Scott, Jeanne; Mogan, Chris; Prescher, Hannes; Biffar, David; Jarred, John; Meyer, Robyn J; Hamilton, Allan J

2014-04-01

265

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

266

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

Microsoft Academic Search

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

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

2012-01-01

267

Solvothermal, chloroalkoxide-based synthesis of monoclinic WO(3) 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

268

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

269

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

270

Laser irradiation of mouse spermatozoa enhances in-vitro fertilization and Ca2+ uptake via reactive oxygen species  

NASA Astrophysics Data System (ADS)

630 nm He-Ne laser irradiation was found to have a profound influence on Ca2+ uptake in mouse spermatozoa and the fertilizing potential of these cells. Laser irradiation affected mainly the mitochondrial Ca2+ transport mechanisms. Furthermore, the effect of light was found to be Ca2+-dependent. We demonstrate that reactive oxygen species (ROS) are involved in the cascade of biochemical events evoked by laser irradiation. A causal association between laser irradiation, ROS generation, and sperm function was indicated by studies with ROS scavengers, superoxide dismutase (SOD) and catalase, and exogenous hydrogen peroxide. SOD treatment resulted in increased Ca2+ uptake and in enhanced fertilization rate. Catalase treatment impaired the light-induced stimulation in Ca2+ uptake and fertilization rate. Exogenous hydrogen peroxide was found to enhance Ca2+ uptake in mouse spermatozoa and the fertilizing capability of these cells in a dose-dependent manner. These results suggest that the effect of 630 nm He-Ne laser irradiation is mediated through the generation of hydrogen peroxide by the spermatozoa and that this effect plays a significant role in the augmentation of the sperm cells' capability to fertilize metaphase II-arrested eggs in-vitro.

Cohen, Natalie; Lubart, Rachel; Rubinstein, Sara; Breitbart, Haim

1996-11-01

271

Vertical distribution of specific ventilation in normal supine humans measured by oxygen-enhanced proton MRI  

PubMed Central

Specific ventilation (SV) is the ratio of fresh gas entering a lung region divided by its end-expiratory volume. To quantify the vertical (gravitationally dependent) gradient of SV in eight healthy supine subjects, we implemented a novel proton magnetic resonance imaging (MRI) method. Oxygen is used as a contrast agent, which in solution changes the longitudinal relaxation time (T1) in lung tissue. Thus alterations in the MR signal resulting from the regional rise in O2 concentration following a sudden change in inspired O2 reflect SV—lung units with higher SV reach a new equilibrium faster than those with lower SV. We acquired T1-weighted inversion recovery images of a sagittal slice of the supine right lung with a 1.5-T MRI system. Images were voluntarily respiratory gated at functional residual capacity; 20 images were acquired with the subject breathing air and 20 breathing 100% O2, and this cycle was repeated five times. Expired tidal volume was measured simultaneously. The SV maps presented an average spatial fractal dimension of 1.13 ± 0.03. There was a vertical gradient in SV of 0.029 ± 0.012 cm?1, with SV being highest in the dependent lung. Dividing the lung vertically into thirds showed a statistically significant difference in SV, with SV of 0.42 ± 0.14 (mean ± SD), 0.29 ± 0.10, and 0.24 ± 0.08 in the dependent, intermediate, and nondependent regions, respectively (all differences, P < 0.05). This vertical gradient in SV is consistent with the known gravitationally induced deformation of the lung resulting in greater lung expansion in the dependent lung with inspiration. This SV imaging technique can be used to quantify regional SV in the lung with proton MRI. PMID:20930129

Cronin, Matthew V.; Cortney Henderson, A.; Holverda, Sebastiaan; Theilmann, Rebecca J.; Arai, Tatsuya J.; Dubowitz, David J.; Hopkins, Susan R.; Buxton, Richard B.; Kim Prisk, G.

2010-01-01

272

Simultaneous synthesis of gold nanoparticle/graphene nanocomposite for enhanced oxygen reduction reaction  

NASA Astrophysics Data System (ADS)

We report here on a novel and facile technique for the simultaneous synthesis of a highly active and stable gold (Au) nanoparticle/reduced graphene oxide (rGO) sheet nanocomposite as an efficient electrocatalyst to facilitate the oxygen reduction reaction (ORR). X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray (EDX) spectroscopy and electrochemical methods were employed to characterize the Au and rGO nanocomposites formed on the electrode surface. The major advantage of the simultaneous synthetic method is the integration of the superb properties of both Au nanoparticles and graphene in a single-step with a 100% usage of the precursors. The Au/rGO nanocomposites exhibited pronounced electrocatalytic performance towards ORR with approximately three times higher than that of Au nanoparticles. The nanocomposites show the ORR onset peak potentials at 0.12 and -0.03 V (vs Ag/AgCl), with reduction peaks at -0.06 and -0.16 V (vs Ag/AgCl) in 0.1 M H2SO4 and KOH media, which is ?120-190 mV more positive than that of Au nanoparticles and a commercial Pt/C catalyst. Moreover, the nanocomposites exhibit excellent methanol tolerance and high durability in comparison with the commercial Pt/C. The new method demonstrated in this study provides an efficient route for the generation of ultrafine and highly dense Au nanoparticles that are homogeneously dispersed on rGO sheets for ORR.

Govindhan, Maduraiveeran; Chen, Aicheng

2015-01-01

273

Feasibility study of enhanced combustion via improved wood stove firebox design. Final report Nov 84-Jul 85  

SciTech Connect

The report gives results of an examination of materials that might be used to line the firebox of a wood-burning stove to produce more uniform and complete combustion. (Emissions from incomplete combustion in wood-burning stoves are becoming an increasing environmental problem.) Although many materials were considered initially, refractory materials appear to possess the qualities desired relative to heat transfer, resistance to the firebox environment, availability, and cost. Further investigation of specific refractory materials was carried out, resulting in a list of material properties of potentially useful refractories and a determination of the relative costs of installed refractory. The approach used in the study was to establish the conditions for a basic stove, then to apply various candidate lining materials to the basic stove and analytically estimate the effect of the lining addition. Basic heat-transfer calculations were used. The use of refractory materials permitted an increase in stove inner-wall temperatures and an increased cool-down time for a stove. The study shows that refractory materials can aid in maintaining internal firebox temperatures above the ignition temperatures of common emissions. This would not be practical for an uninsulated stove. The study concludes that there is a need for actual tests to confirm results cited in the study.

Fuentes, K.T.; Hodas, L.J.

1985-10-01

274

Droplet Combustion Experiment movie  

NASA Technical Reports Server (NTRS)

The Droplet Combustion Experiment (DCE) was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1 mission (STS-83, April 4-8 1997; the shortened mission was reflown as MSL-1R on STS-94). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (1.1 MB, 12-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available)A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300164.html.

2003-01-01

275

Enhanced Oxygen Diffusion Within the Internal Oxidation Zone of Alloy 617 in Controlled Impurity Helium Environments from 1023 K to 1123 K (750 °C to 850 °C)  

NASA Astrophysics Data System (ADS)

Alloy 617 was exposed to He-CO-CO2 environments with P_{{CO}} /P_{{{{CO}}2 }} of either 9 or 1320 at temperatures from 1023 K to 1123 K (750 °C to 850 °C) to determine the oxygen diffusion coefficients within the internal oxidation zone of the alloy. The oxygen diffusion coefficients determined based on both intergranular and transgranular oxidation rates were several orders of magnitude greater than those reported in pure nickel and in nickel-based binary alloys, indicating that the rapid internal aluminum oxidation of Alloy 617 was primarily due to enhanced oxygen diffusion along the incoherent Al2O3-alloy interfaces. The range of activation energy values determined for oxygen diffusion associated with the intergranular aluminum oxidation was from 149.6 to 154.7 kJ/mol, and that associated with the transgranular aluminum oxidation was from 244.7 to 283.5 kJ/mol.

Gulsoy, Gokce; Was, Gary S.

2015-01-01

276

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

277

Breaking Up with Combustion  

NSDL National Science Digital Library

This activity teaches combustion as the interaction of a fuel source and oxygen. A burning candle is observed, then extinguished—first by a glass cup placed over it to cut off the oxygen supply, then using carbon dioxide generated by vinegar and baking soda. Some background information is provided about how car engines use gasoline as fuel, and how humans use food as fuel— both are similar to how the candle uses wax as fuel. The activity is written for a kit that can be checked out of the library, but the kit is not required.

2012-06-26

278

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

279

Aging Enhances Production of Reactive Oxygen Species and Bactericidal Activity in Peritoneal Macrophages by Up-Regulating Classical Activation Pathways  

PubMed Central

Maintenance of macrophages in their basal state and their rapid activation in response to pathogen detection is central to the innate immune system, acting to limit nonspecific oxidative damage and promote pathogen killing following infection. To identify possible age-related alterations in macrophage function, we have assayed the function of peritoneal macrophages from young (3–4 mo) and aged (14–15 mo) Balb/c mice. In agreement with prior suggestions, we observe age-dependent increases in macrophage recruitment into the peritoneum, as well as ex vivo functional changes involving enhanced nitric oxide production under resting conditions that contribute to a reduction in the time needed for full activation of senescent macrophages following exposure to LPS. Further, we observe enhanced bactericidal activity following Salmonella uptake by macrophages isolated from aged Balb/c mice in comparison with those isolated from young animals. Pathways responsible for observed phenotypic changes were interrogated using tandem mass spectrometry, which identified age-dependent increases in proteins linked to immune cell pathways under both basal conditions and following LPS activation. Immune pathways up-regulated in macrophages isolated from aged mice include proteins critical to formation of the immunoproteasome. Detection of these latter proteins are dramatically enhanced following LPS exposure for macrophages isolated from aged animals; in comparison, the identification of immunoproteasome subunits is insensitive to LPS exposure for macrophages isolated from young animals. Consistent with observed global changes in the proteome, quantitative proteomic measurements indicate that there are age-dependent abundance changes involving specific proteins linked to immune cell function under basal conditions. LPS exposure selectively increases many proteins involved in immune cell function in aged Balb/c mice. Collectively these results indicate that macrophages isolated from old mice are in a pre-activated state that enhances their sensitivities of LPS exposure. The hyper-responsive activation of macrophages in aged animals may act to minimize infection to general bacterial threats that arise due to age-dependent declines in adaptive immunity. However, this hypersensitivity and the associated increase in the formation of reactive oxygen species is likely to contribute to observed age-dependent increases in oxidative damage that underlie many diseases of the elderly. PMID:21981794

Smallwood, Heather S.; López-Ferrer, Daniel; Squier, Thomas C.

2011-01-01

280

Aging Enhances the Production of Reactive Oxygen Species and Bactericidal Activity in Peritoneal Macrophages by Upregulating Classical Activation Pathways  

SciTech Connect

Maintenance of macrophages in their basal state and their rapid activation in response to pathogen detection are central to the innate immune system, acting to limit nonspecific oxidative damage and promote pathogen killing following infection. To identify possible age-related alterations in macrophage function, we have assayed the function of peritoneal macrophages from young (3?4 months) and aged (14?15 months) Balb/c mice. In agreement with prior suggestions, we observe age-dependent increases in the extent of recruitment of macrophages into the peritoneum, as well as ex vivo functional changes involving enhanced nitric oxide production under resting conditions that contribute to a reduction in the time needed for full activation of senescent macrophages following exposure to lipopolysaccharides (LPS). Further, we observe enhanced bactericidal activity following Salmonella uptake by macrophages isolated from aged Balb/c mice in comparison with those isolated from young animals. Pathways responsible for observed phenotypic changes were interrogated using tandem mass spectrometry, which identified age-dependent increases in levels of proteins linked to immune cell pathways under basal conditions and following LPS activation. Immune pathways upregulated in macrophages isolated from aged mice include proteins critical to the formation of the immunoproteasome. Detection of these latter proteins is dramatically enhanced following LPS exposure for macrophages isolated from aged animals; in comparison, the identification of immunoproteasome subunits is insensitive to LPS exposure for macrophages isolated from young animals. Consistent with observed global changes in the proteome, quantitative proteomic measurements indicate that there are age-dependent abundance changes involving specific proteins linked to immune cell function under basal conditions. LPS exposure selectively increases the levels of many proteins involved in immune cell function in aged Balb/c mice. Collectively, these results indicate that macrophages isolated from old mice are in a preactivated state that enhances their sensitivities to LPS exposure. The hyper-responsive activation of macrophages in aged animals may act to minimize infection by general bacterial threats that arise due to age-dependent declines in adaptive immunity. However, this hypersensitivity and the associated increase in the level of formation of reactive oxygen species are likely to contribute to observed age-dependent increases in the level of oxidative damage that underlie many diseases of the elderly.

Smallwood, Heather S.; Lopez-Ferrer, Daniel; Squier, Thomas C.

2011-10-07

281

Enhanced growth and recombinant protein production of Escherichia coli by a perfluorinated oxygen carrier in miniaturized fed-batch cultures  

Microsoft Academic Search

Background  Liquid perfluorochemicals (PFCs) are interesting oxygen carriers in medicine and biotechnology with a high solubility for\\u000a oxygen. They have been repeatedly used for improving oxygen transfer into prokaryotic and eukaryotic cell cultures, however\\u000a their application is still limited. Here we show the great benefit of air\\/oxygen saturated perfluorodecalin (PFD) for high\\u000a cell density cultivation of Escherichia coli in microwell plates

Maciej Pilarek; Julia Glazyrina; Peter Neubauer

2011-01-01

282

Droplet Combustion Experiment (DCE)  

NASA Technical Reports Server (NTRS)

The first space-based experiments were performed on the combustion of free, individual liquid fuel droplets in oxidizing atmospheres. The fuel was heptane, with initial droplet diameters ranging about from 1 mm to 4 mm. The atmospheres were mixtures of helium and oxygen, at pressures of 1.00, 0.50 and 0.25 bar, with oxygen mole fractions between 20% and 40%, as well as normal Spacelab cabin air. The temperatures of the atmospheres and of the initial liquid fuel were nominally 300 K. A total of 44 droplets were burned successfully on the two flights, 8 on the shortened STS-83 mission and 36 on STS-94. The results spanned the full range of heptane droplet combustion behavior, from radiative flame extinction at larger droplet diameters in the more dilute atmospheres to diffusive extinction in the less dilute atmospheres, with the droplet disappearing prior to flame extinction at the highest oxygen concentrations. Quasisteady histories of droplet diameters were observed along with unsteady histories of flame diameters. New and detailed information was obtained on burning rates, flame characteristics and soot behavior. The results have motivated new computational and theoretical investigations of droplet combustion, improving knowledge of the chemical kinetics, fluid mechanics and heat and mass transfer processes involved in burning liquid fuels.

Haggard, John B., Jr.; Nayagan, Vedha; Dryer, Frederick L.; Williams, Forman A.

1998-01-01

283

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

284

The Combustive Sound Source  

NASA Astrophysics Data System (ADS)

This thesis describes a unique type of low frequency underwater sound source, the Combustive Sound Source (CSS). The fundamental operating principle of CSS is the following: Electrolysis of water produces hydrogen and oxygen gas, which is a combustible mixture. The gas mixture is captured in a combustion chamber and ignited with a spark. The ensuing combustion produces expanding gases which in turn produce high intensity, low frequency acoustic pulses. The thesis begins by discussing the background of the project and initial feasibility work. It continues by briefly discussing electrolysis and gas production. Fundamental combustion theory is discussed, along with two experiments that relate the acoustic output of CSS to theory. Additional experiments were conducted in order to compare the first bubble period in the CSS pressure signature with the predictions of the Rayleigh-Willis equation. The dependence of the radiated acoustic waveform on the volume and depth of the bubble was investigated. The first bubble period of the CSS pressure signature agrees with Rayleigh-Willis theory in trend, but not in absolute value. Empirical equations are presented which predict the first bubble period for three different situations, a depth of nine meters for various stoichiometric volumes, a stoichiometric volume of 0.5 STP liters for various depths, and a stoichiometric volume of 500 cubic centimeters for various depths. High speed filming of the CSS bubble is presented. The high speed films confirm that CSS produces a bubble of high temperature combustion products. The bubble oscillates and generates acoustic output. The motion of the bubble is shown to be related to the acoustic output in the classic manner, with pressure peaks associated with minimum bubble volumes. Finally, several other factors that affect the acoustic output of CSS are discussed. These include the shape of the CSS combustion chamber, the ignition source, the oxidizer, the presence of high pressure bubble collapses, and the presence of high frequency components.

Wilson, Preston S.

1994-04-01

285

Oxygen rich p-type ZnO thin films using wet chemical route with enhanced carrier concentration by temperature-dependent tuning of acceptor defects  

NASA Astrophysics Data System (ADS)

This paper reports the temperature-dependent tailoring of acceptor defects in oxygen rich ZnO thin films, for enhanced p-type conductivity. The oxygen rich p-type ZnO thin films were successfully grown by pulsed laser deposition on silicon substrate at different postdeposition annealing temperatures (500-800 °C). The oxygen rich ZnO powder was synthesized by wet chemical method using zinc acetate dihydrate [Zn(CH3COO)2.2H2O] and potassium hydroxide (KOH) as precursors. The powder was then compressed and sintered to make pellets for pulsed laser deposition system. The x-ray diffraction analysis exhibits an improved crystallinity in thin films annealed at elevated temperatures with a temperature-dependent variation in lattice constants. An analysis of Auger Zn L3M4,5M4,5 peak reveals a consistent decrease in interstitial zinc (Zni) exhibiting its temperature-dependent reversion to zinc lattice sites. Room temperature photoluminescence of the p-type ZnO shows a dominant deep level emission peak at ˜3.12 eV related to oxygen interstitials (acceptors). The relative concentration of oxygen interstitials (Oi) increases with increase in annealing temperature, resulting in enhanced hole carrier concentration. The maximum hole carrier concentration of 6.8 × 1014 cm-3 (indicating p-type conductivity) was estimated using Hall probe measurements for the thin film sample annealed at 700 °C.

Ilyas, Usman; Rawat, R. S.; Tan, T. L.; Lee, P.; Chen, R.; Sun, H. D.; Fengji, Li; Zhang, Sam

2011-11-01

286

Strongly coupled Pd nanotetrahedron/tungsten oxide nanosheet hybrids with enhanced catalytic activity and stability as oxygen reduction electrocatalysts.  

PubMed

The design and synthesis of highly active oxygen reduction reaction (ORR) catalysts with strong durability at low cost is extremely desirable but still remains a significant challenge. Here we develop an efficient strategy that utilizes organopalladium(I) complexes containing palladium-palladium bonds as precursors for the synthesis of strongly coupled Pd tetrahedron-tungsten oxide nanosheet hybrids (Pd/W18O49) to improve the electrocatalytic activity and stability of Pd nanocrystals. The hybrid materials are synthesized by direct nucleation, growth, and anchoring of Pd tetrahedral nanocrystals on the in situ-synthesized W18O49 nanosheets. Compared to supportless Pd nanocrystals and W18O49, their hybrids exhibited not only surprisingly high activity but also superior stability to Pt for the ORR in alkaline solutions. X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and electrochemical analyses indicated that the enhanced electrocatalytic activity and durability are associated with the increased number and improved catalytic activity of active sites, which is induced by the strong interaction between the Pd tetrahedrons and W18O49 nanosheet supports. The present study provides a novel strategy for synthesizing hybrid catalysts with strong chemical attachment and electrical coupling between nanocatalysts and supports. The strategy is expected to open up exciting opportunities for developing a novel class of metal-support hybrid nanoelectrocatalysts with improved ORR activity and durability for both fuel cells and metal-air batteries. PMID:25054583

Lu, Yizhong; Jiang, Yuanyuan; Gao, Xiaohui; Wang, Xiaodan; Chen, Wei

2014-08-20

287

Carbonization of self-assembled nanoporous hemin with a significantly enhanced activity for the oxygen reduction reaction.  

PubMed

The scarcity and high cost of Pt-based electrocatalysts for the oxygen reduction reaction (ORR) hinder the practical application of proton exchange membrane fuel cells (PEMFCs). It is critical to replace platinum with non-noble metal electrocatalysts (NNMEs). Carbonized metalloporphyrins represent an important class of NNMEs, but most metalloporphyrins are costly and the corresponding NNMEs do not possess a high ORR activity. Herein, we report that the self-assembly of inexpensive hemin leads to porous nanomaterials in water under ambient conditions and subsequent heat-treatment of the unprecedented nanoporous hemin results in a magnetic NNME with a much enhanced ORR activity compared with directly carbonized hemin without self-assembly. The improvement of the ORR activity likely originates from the exposure of more ORR active sites, caused by the surface area increase of the nanoporous hemin after carbonization over that of micro-scale pristine hemin crystals. Moreover, the ORR activity of heat-treated nanoporous hemin is actually comparable to that of commercial Pt/C in alkaline solution. Additionally, the carbonized nanoporous hemin is much better than commercial Pt/C in terms of durability and tolerance to methanol. This study opens up a new avenue to the production of inexpensive metalloporphyrin-based NNMEs with a high ORR performance by using a self-assembly method in combination with traditional pyrolysis. PMID:25406677

Xie, Yan; Tang, Chizhou; Hao, Zhiqiang; Lv, Yang; Yang, Ruixia; Wei, Xuming; Deng, Weiqiao; Wang, Anjie; Yi, Baolian; Song, Yujiang

2014-11-14

288

Targeted lung expression of interleukin-11 enhances murine tolerance of 100% oxygen and diminishes hyperoxia-induced DNA fragmentation.  

PubMed Central

Acute lung injury is a frequent and treatment-limiting consequence of therapy with hyperoxic gas mixtures. To determine if IL-11 is protective in oxygen toxicity, we compared the effects of 100% O2 on transgenic mice that overexpress IL-11 in the lung and transgene (-) controls. IL-11 markedly enhanced survival in 100% O2 with 100% of transgene (-) animals dying within 72-96 h and > 90% of transgene (+) animals surviving for more than 10 d. This protection was associated with markedly diminished alveolar-capillary protein leak, endothelial and epithelial membrane injury, lipid peroxidation, and pulmonary neutrophil recruitment. Significant differences in copper zinc superoxide dismutase and catalase activities were not noted and the levels of total, reduced and oxidized glutathione were similar in transgene (+) and (-) animals. Glutathione reductase, glutathione peroxidase, and manganese superoxide dismutase activities were slightly higher in transgene (+) as versus (-) mice after 100% O2 exposure, and IL-11 diminished hyperoxia-induced expression of IL-1 and TNF. Hyperoxia also caused cell death with DNA fragmentation in the lungs of transgene (-) animals and IL-11 markedly diminished this cell death response. These studies demonstrate that IL-11 markedly diminishes hyperoxic lung injury. They also demonstrate this protection is associated with small changes in lung antioxidants, diminished hyperoxia-induced IL-1 and TNF production, and markedly suppressed hyperoxia-induced DNA fragmentation. PMID:9576762

Waxman, A B; Einarsson, O; Seres, T; Knickelbein, R G; Warshaw, J B; Johnston, R; Homer, R J; Elias, J A

1998-01-01

289

3-Methyl pyruvate enhances radiosensitivity through increasing mitochondria-derived reactive oxygen species in tumor cell lines  

PubMed Central

Considerable interest has recently been focused on the special characteristics of cancer metabolism, and several drugs designed to modulate cancer metabolism have been tested as potential anticancer agents. To date, however, very few studies have been conducted to investigate the combined effects of anticancer drugs and radiotherapy. In this study, to evaluate the role of mitochondria-derived reactive oxygen species (ROS) in the radiation-induced cell death of tumor cells, we have examined the effect of 3-methyl pyruvate (MP). MP is a membrane-permeable pyruvate derivative that is capable of activating mitochondrial energy metabolism in human lung carcinoma A549 cells and murine squamous carcinoma SCCVII cells. Pretreatment with MP significantly enhanced radiation-induced cell death in both cell lines, and also led to increases in the mitochondrial membrane potential, intracellular adenosine triphosphate content, and mitochondria-derived ROS production following the exposure of the cells to X-rays. In A549 cells, MP-induced radiosensitization was completely abolished by vitamin C. In contrast, it was partially abolished in SCCVII cells. These results therefore suggest that the treatment of the cells with MP induced radiosensitization via the production of excess mitochondria-derived ROS in tumor cells. PMID:24385472

Nishida, Naoya; Yasui, Hironobu; Nagane, Masaki; Yamamori, Tohru; Inanami, Osamu

2014-01-01

290

Docosahexaenoic acid prevents paraquat-induced reactive oxygen species production in dopaminergic neurons via enhancement of glutathione homeostasis.  

PubMed

Omega-3 polyunsaturated fatty acid levels are reduced in the substantia nigra area in Parkinson's disease patients and animal models, implicating docosahexaenoic acid (DHA) as a potential treatment for preventing Parkinson's disease and suggesting the need for investigations into how DHA might protect against neurotoxin-induced dopaminergic neuron loss. The herbicide paraquat (PQ) induces dopaminergic neuron loss through the excessive production of reactive oxygen species (ROS). We found that treatment of dopaminergic SN4741 cells with PQ reduced cell viability in a dose-dependent manner, but pretreatment with DHA ameliorated the toxic effect of PQ. To determine the toxic mechanism of PQ, we measured intracellular ROS content in different organelles with specific dyes. As expected, all types of ROS were increased by PQ treatment, but DHA pretreatment selectively decreased cytosolic hydrogen peroxide content. Furthermore, DHA treatment-induced increases in glutathione reductase and glutamate cysteine ligase modifier subunit (GCLm) mRNA expression were positively correlated with glutathione (GSH) content. Consistent with this increase in GCLm mRNA levels, Western blot analysis revealed that DHA pretreatment increased nuclear factor-erythroid 2 related factor 2 (Nrf2) protein levels. These findings indicate that DHA prevents PQ-induced neuronal cell loss by enhancing Nrf2-regulated GSH homeostasis. PMID:25545062

Lee, Hyoung Jun; Han, Jeongsu; Jang, Yunseon; Kim, Soo Jeong; Park, Ji Hoon; Seo, Kang Sik; Jeong, Soyeon; Shin, Soyeon; Lim, Kyu; Heo, Jun Young; Kweon, Gi Ryang

2015-01-30

291

Improvement of Gas Utilization Ratio in the Gaseous Reduction of Iron Oxide and Suppression of Dioxins Formation in Combustion Processes by the Enhancement of Carbon Deposition  

NASA Astrophysics Data System (ADS)

Carbon deposition from CO-CO2 mixture is examined on metallic iron at temperatures ranging from 650 to 950K. The CO-CO2 mixture was introduced in an alumina tube, in which the high purity electrolytic iron powder was packed, and the ingoing and the outgoing gas compositions were measured by a quadrupole mass spectrometer. The lowering limit of the partial pressure of CO (PCO/(PCO+PCO2)), at which the carbon deposition substantially occurs, is investigated. The condition, under which carbon deposition occurs, is clarified in Fe-CO-CO2 system. The improvement of the gas utilization ratio in the reduction of iron oxide and the suppression of dioxins formation in combustion processes by the enhancement of carbon deposition are discussed. From the present thermodynamic calculation, it is concluded that dioxins formation can be suppressed by lowering the PCO/(PCO+PCO2) value under 0.2 to 0.3 according to the enhancement of the carbon deposition at 700 to 750K.

Ono-Nakazato, Hideki; Koyama, Tomotsugu; Usui, Tateo

292

Feasibility study of enhanced combustion via improved wood stove firebox design. Rept. for December 1984-March 1985  

SciTech Connect

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 relative to heat transfer, resistance to the firebox environment, availability, and cost. Further investigation of specific refractory materials has been carried out, resulting in a listing of material properties of potentially useful refractories and a determination of relative installed costs. Basic heat-transfer calculations were used to determine the effects of the addition of refractory materials in the firebox. The use of refractory materials permitted an increase in stove inner-wall temperatures and an increased cooldown time for a stove. The study showed that refractory materials could aid in maintaining internal firebox temperatures above the ignition temperatures of common emissions. This would not be a practical operational mode for an uninsulated stove. The study concluded that there is a need for actual testing to confirm the results cited in this study.

Fuentes, K.T.; Hodas, L.J.; Osborne, M.C.

1985-01-01

293

Simple method to enhance positive bias stress stability of in-ga-zn-o thin-film transistors using a vertically graded oxygen-vacancy active layer.  

PubMed

We proposed a simple method to deposit a vertically graded oxygen-vacancy active layer (VGA) to enhance the positive bias stress (PBS) stability of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). We deposited a-IGZO films by sputtering (target composition; In2O3:Ga2O3:ZnO = 1:1:1 mol %), and the oxygen partial pressure was varied during deposition so that the front channel of the TFTs was fabricated with low oxygen partial pressure and the back channel with high oxygen partial pressure. Using this method, we were able to control the oxygen vacancy concentration of the active layer so that it varied with depth. As a result, the turn-on voltage shift following a 10?000 s PBS of optimized VGA TFT was drastically improved from 12.0 to 5.6 V compared with a conventional a-IGZO TFT, without a significant decrease in the field effect mobility. These results came from the self-passivation effect and decrease in oxygen-vacancy-related trap sites of the VGA TFTs. PMID:25402628

Park, Ji Hoon; Kim, Yeong-Gyu; Yoon, Seokhyun; Hong, Seonghwan; Kim, Hyun Jae

2014-12-10

294

Non-equilibrium Plasma-Assisted Combustion  

NASA Astrophysics Data System (ADS)

As a promising method to enhance combustion, plasma-assisted combustion has drawn considerable attention. Due to the fast electron impact excitation and dissociation of molecules at low temperatures, plasma introduces new reaction pathways, changes fuel oxidation timescales, and can dramatically modify the combustion processes. In this dissertation, the radical generation from the plasma and its effect on flame extinction and ignition were investigated experimentally together with detailed numerical simulation on a counterflow CH4 diffusion flame. It was found that the atomic oxygen production played a dominant role in enhancing the chain-branching reaction pathways and accelerating fuel oxidation at near limit flame conditions. To understand the direct coupling effect between plasma and flame, a novel plasma-assisted combustion system with in situ discharge in a counterflow diffusion flame was developed. The ignition and extinction characteristics of CH4/O 2/He diffusion flames were investigated. For the first time, it was demonstrated that the strong plasma-flame coupling in in situ discharge could significantly modify the ignition/extinction characteristics and create a new fully stretched ignition S-curve. To understand low temperature kinetics of combustion, it is critical to measure the formation and decomposition of H2O2. A molecular beam mass spectrometry (MBMS) system was developed and integrated with a laminar flow reactor. H2O2 measurements were directly calibrated, and compared to kinetic models. The results confirmed that low and intermediate temperature DME oxidation produced significant amounts of H2O2. The experimental characterizations of important intermediate species including H2O2, CH2O and CH3OCHO provided new capabilities to investigate and improve the chemical kinetics especially at low temperatures. A numerical scheme for model reduction was developed to improve the computational efficiency in the simulation of combustion with detailed kinetics. A multi-generation Path Flux Analysis (PFA) method for kinetic mechanism reduction is proposed and validated. In this method, the formation and consumption fluxes of each species at multiple reaction path generations were analyzed and used to identify the important reaction pathways. The comparisons of the ignition delays, flame speeds, and flame structures showed that the PFA method presented a higher accuracy than that of current existing methods in a broad range of initial pressures and temperatures.

Sun, Wenting

295

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...

296

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

297

Low Oxygen Tension Enhances Osteogenic Potential of Bone Marrow-Derived Mesenchymal Stem Cells with Osteonecrosis-Related Functional Impairment  

PubMed Central

Objective. Glucocorticoids can affect the function of bone marrow-derived mesenchymal stem cells (BMMSCs) adversely and merit the requirement for a strategy to correct this anomaly; we assessed the effect of low oxygen (2%) on BMMSCs from rabbits with osteonecrosis. Methods. Bone marrow-derived mesenchymal stem cells from normal rabbits and rabbits with osteonecrosis were divided into four groups: (1) normal-normoxia group, with normal BMMSCs cultured under 20% oxygen; (2) osteonecrosis-normoxia group, with BMMSCs from rabbits with osteonecrosis cultured under 20% oxygen; (3) osteonecrosis-low oxygen treated group, with BMMSCs from rabbits with osteonecrosis cultured under 2% oxygen; (4) normal-low oxygen treated group, with normal BMMSCs cultured under 2% oxygen. The proliferation, osteogenic, and adipogenic differentiation of MSCs and expression of stemness genes, osteogenic, and adipogenic differentiation markers were investigated. Results. Compared with BMMSCs from normal rabbits, those from osteonecrosis rabbits showed significantly reduced proliferation ability, repressed expression of stemness genes, decreased osteoblasts formation, and increased adipocytes formation, indicating an osteonecrosis-related impairment. Low oxygen (2%) treated BMMSCs from osteonecrosis rabbits showed not only increased proliferation and osteogenic potential but also decreased adipogenic potential. Conclusion. Low oxygen (2%) culture represents a novel strategy to augment BMMSC function affected by glucocorticoids and holds significance for future strategies to treat femoral head osteonecrosis.

Fan, Lihong; Liu, Ruiyu; Shi, Zhibin; Dang, Xiaoqian; Wang, Kunzheng

2015-01-01

298

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

299

Light carbon doping by oxygen-free paraffin wax to enhance the current density of MgB2 in the entire field regime  

NASA Astrophysics Data System (ADS)

An oxygen-free hydrocarbon, paraffin wax, was evenly doped into MgB2 by a new method to enhance the electromagnetic properties. A 5 wt% paraffin addition resulted in significant enhancements of the upper critical field (Hc2), irreversible critical field (Hirr), and critical current density (Jc) properties in the entire field range at both 5 and 20 K. This excellent low-field and high-temperature Jc performance may be ascribed to the small carbon substitution, high critical temperature (Tc) and non-degraded grain coupling in the optimum paraffin-doped MgB2 sample.

Jiang, C. H.; Dou, S. X.; Cheng, Z. X.; Wang, X. L.

2008-06-01

300

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

301

Unraveling the enhanced photocatalytic activity and phototoxicity of ZnO/metal hybrid nanostructures from generation of reactive oxygen species and charge carriers.  

PubMed

An effective way for promoting photocatalytic activity of a semiconductor is deposition of noble metal nanoparticles (NPs) onto it. In this paper, we deposited Ag and Pd onto ZnO NPs to form ZnO/Ag and ZnO/Pd hybrid nanostructures. It was found that both Ag and Pd nanocomponents can greatly enhance the photocatalytic activity and phototoxicity of ZnO toward human skin cells. Using electron spin resonance spectroscopy with spin trapping and spin labeling techniques, we observed that either deposition of Ag or Pd resulted in a significant increase in photogenerated electrons and holes and production of reactive oxygen species including hydroxyl radicals, superoxide, and singlet oxygen. We compared the enhancing effects of Ag and Pd and found that Pd is more effective than Ag in promoting the generation of hydroxyl radicals and holes and the photocatalytic activity of ZnO. Conversely, Ag is more effective than Pd in enhancing electron transfer and the generation of superoxide and singlet oxygen. The mechanism underlying the differences in the effects of Ag and Pd may be related to differences in Fermi levels for Ag and Pd and band bending accompanied by effects on Schottky barriers. The results of these studies provide information valuable for designing hybrid nanomaterials having photocatalytic and photobiological activities useful for applications such as water purification and formulation of antibacterial products. PMID:25116236

He, Weiwei; Wu, Haohao; Wamer, Wayne G; Kim, Hyun-Kyung; Zheng, Jiwen; Jia, Huimin; Zheng, Zhi; Yin, Jun-Jie

2014-09-10

302

Waste plastics as supplemental fuel in the blast furnace process: improving combustion efficiencies.  

PubMed

The possibility of using waste plastics as a source of secondary fuel in a blast furnace has been of recent interest. The success of this process, however, will be critically dependent upon the optimization of operating systems. For instance, the supply of waste plastics must be reliable as well as economically attractive compared with conventional secondary fuels such as heavy oil, natural gas and pulverized coal. In this work, we put special importance on the improvement of the combustibility of waste plastics as a way to enhance energy efficiency in a blast furnace. As experimental variables to approach this target, the effects of plastic particle size, blast temperature, and the level of oxygen enrichment were investigated using a custom-made blast model designed to simulate a real furnace. Lastly, the combustion efficiency of the mixture of waste plastics and pulverized coal was tested. The observations made from these experiments led us to the conclusion that with the increase of both blast temperature and the level of oxygen enrichment, and with a decrease in particle size, the combustibility of waste polyethylene could be improved at a given distance from the tuyere. Also it was found that the efficiency of coal combustion decreased with the addition of plastics; however, the combustion efficiency of mixture could be comparable at a longer distance from the tuyere. PMID:12220825

Kim, Dongsu; Shin, Sunghye; Sohn, Seungman; Choi, Jinshik; Ban, Bongchan

2002-10-14

303

Assessment of the effect of high ash content in pulverized coal combustion  

SciTech Connect

The existing literature on CFD-based coal combustion modelling is applicable mainly for coals of low ash content and the calculations are done on an ash-free basis. In Indian coals, the ash content may be significantly higher, up to 40% or more. Studies reported in the literature show that the mineral matter in the coal may have a number of effects on the combustion characteristics. In the present study, a sensitivity analysis is performed, using the CFD code CFX of AEA Technology, on the likely effect of ash content on the char reactivity, oxygen diffusion rate for char combustion and on the radiative heat transfer parameters. The results show that the effect of enhanced char reactivity is negligible whereas reduced oxygen diffusion rates due to a thicker ash layer may result in a significant reduction in char oxidation rates with a resultant decrease in the peak temperature in the furnace. The global parameters such as the peak temperature and the flue gas temperature remain relatively insensitive to the presence of high ash content. These results are consistent with the experimental observations of Kurose et al. . Kurose, M. Ikeda, H. Makino, Combustion characteristics of high ash coal in pulverized coal combustion, J. Fuel 80 (2001) 1447-1455).

Jayanti, S.; Maheswaran, K.; Saravanan, V. [Indian Institute of Technology, Madras (India). Dept. of Chemical Engineering

2007-05-15

304

Summary of Simplified Two Time Step Method for Calculating Combustion Rates and Nitrogen Oxide Emissions for Hydrogen/Air and Hydrogen/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 (greater than l x 10(exp -20)) moles per cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and water mole concentrations, pressure and temperature (T(sub 4)). 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 H2/O2. A similar correlation is also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium temperature (T(sub 4)) as a function of overall fuel/air ratio, pressure and initial temperature (T(sub 3)). High values of the regression coefficient R squared are obtained.

Marek, C. John; Molnar, Melissa

2005-01-01

305

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

306

Microgravity Combustion Diagnostics Workshop  

NASA Technical Reports Server (NTRS)

Through the Microgravity Science and Applications Division (MSAD) of the Office of Space Science and Applications (OSSA) at NASA Headquarters, a program entitled, Advanced Technology Development (ATD) was promulgated with the objective of providing advanced technologies that will enable the development of future microgravity science and applications experimental flight hardware. Among the ATD projects one, Microgravity Combustion Diagnostics (MCD), has the objective of developing advanced diagnostic techniques and technologies to provide nonperturbing measurements of combustion characteristics and parameters that will enhance the scientific integrity and quality of microgravity combustion experiments. As part of the approach to this project, a workshop was held on July 28 and 29, 1987, at the NASA Lewis Research Center. A small group of laser combustion diagnosticians met with a group of microgravity combustion experimenters to discuss the science requirements, the state-of-the-art of laser diagnostic technology, and plan the direction for near-, intermediate-, and long-term programs. This publication describes the proceedings of that workshop.

Santoro, Gilbert J. (editor); Greenberg, Paul S. (editor); Piltch, Nancy D. (editor)

1988-01-01

307

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

308

Oxygen vacancy tuned Ohmic-Schottky conversion for enhanced performance in ?-Ga2O3 solar-blind ultraviolet photodetectors  

NASA Astrophysics Data System (ADS)

?-Ga2O3 epitaxial thin films were deposited using laser molecular beam epitaxy technique and oxygen atmosphere in situ annealed in order to reduce the oxygen vacancy. Metal/semiconductor/metal structured photodetectors were fabricated using as-grown film and annealed film separately. Au/Ti electrodes were Ohmic contact with the as-grown films and Schottky contact with the annealed films. In compare with the Ohmic-type photodetector, the Schottky-type photodetector takes on lower dark current, higher photoresponse, and shorter switching time, which benefit from Schottky barrier controlling electron transport and the quantity of photogenerated carriers trapped by oxygen vacancy significant decreasing.

Guo, D. Y.; Wu, Z. P.; An, Y. H.; Guo, X. C.; Chu, X. L.; Sun, C. L.; Li, L. H.; Li, P. G.; Tang, W. H.

2014-07-01

309

Ventilation effects on combustion products.  

PubMed

The effects of fire ventilation on combustion products are expressed in terms of relationship between concentration of products and equivalence ratio, phi. For well-ventilated fires, phi < 1.0, where mostly heat and products of complete combustion (such as CO2 and water) are generated. For ventilation-controlled fires, phi > 1.0, where mostly products of incomplete combustion are generated with very high concentrations in a transition region for phi between 1.0 and 3.5. The high concentrations of the products of incomplete combustion are dangerous to life and property. For halogenated materials, this condition occurs for phi < 1.0. The non-flaming region for fires is found to exist for phi > 3.5. Correlations have been developed for the prediction of concentrations of products at various phi values for the assessment of combustion toxicity and smoke damage hazards by zone fire models, such as Hazard 1. The correlations show good agreement with the measured concentrations. The concentrations of the products of incomplete combustion depend on the chemical structures of the materials. For the same phi values, the carbon monoxide concentrations are higher for materials with oxygen atoms in the structure, whereas smoke concentrations are higher for materials with carbon and hydrogen atoms in the structure. The results of the study suggest that it is necessary to examine the combustion behaviour of advanced materials for use in aircraft and other critical applications at various phi values, along with the toxicity experiments. PMID:9016749

Tewarson, A

1996-12-31

310

Furnace combustion zone temperature control method  

SciTech Connect

This patent describes a method for controlling temperature in a combustion zone in a furnace, independent of flue gas oxygen content. It comprises: supplying combustion air to the furnace for combustion of a fuel therein; providing a plurality of low volume gas flow entry ports to the combustion zone in the furnace with carrier gas continuously flowing through the ports into the combustion zone; selecting a set point value for the combustion zone temperature which, upon the temperature exceeding the set point value, commences generation of a fine water mist external the combustion zone by mist generating means within the carrier gas, the mist flowing into the combustion zone with the carrier gas and reducing temperature within the combustion zone by vaporization therein; and adding a proportionately greater amount of water mist to the carrier gas as the temperature of the combustion zone deviates above the set point value, the amount of water mist added limited by the capacity of the mist generating means, and ceasing the water mist generation upon the combustion zone temperature falling to or below the set point value.

McIntyre, G.C.; Lacombe, R.J.; Forbess, R.G.

1991-05-28

311

Comparison of Different Global Reaction Mechanisms for MILD Combustion of Natural Gas  

Microsoft Academic Search

Emissions of nitrogen oxides from fossil fuel combustion are a major environmental problem because they have been shown to contribute to the formation of acid rain and photochemical smog. MILD (Moderate and Intensive Low oxygen Dilution) combustion is a promising technology to decrease pollutant emissions and to improve combustion efficiency. A combination of air preheating and fuel dilution with combustion

Ju Pyo Kim; Uwe Schnell; Günter Scheffknecht

2008-01-01

312

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

313

A study of the current group evaporation/combustion theories  

NASA Technical Reports Server (NTRS)

Liquid fuel combustion can be greatly enhanced by disintegrating the liquid fuel into droplets, an effect achieved by various configurations. A number of experiments carried out in the seventies showed that combustion of droplet arrays and sprays do not form individual flames. Moreover, the rate of burning in spray combustion greatly deviates from that of the single combustion rate. Such observations naturally challenge its applicability to spray combustion. A number of mathematical models were developed to evaluate 'group combustion' and the related 'group evaporation' phenomena. This study investigates the similarity and difference of these models and their applicability to spray combustion. Future work that should be carried out in this area is indicated.

Shen, Hayley H.

1990-01-01

314

Activation and Enhancement of Room-Temperature Ferromagnetism in Cu-Doped Anatase TiO2 Films by Bound Magnetic Polaron and Oxygen Defects.  

PubMed

Cu-doped anatase TiO2 films grown by magnetron sputtering at room temperature showed the unexpected observation of room-temperature ferromagnetism, which was enhanced or destroyed corresponding to low or high impurity concentration via vacuum annealing. On the basis of the analysis of composition and structure, the most important factor for activating ferromagnetism can be identified as the creation of grain boundary defects. In addition, oxygen defects can be the dominating factor for increasing the saturation moment of the 0.19 at. % Cu-doped TiO2 film from 0.564 to 26.41 emu/cm(3). These results help elucidate the origin of ferromagnetism and emphasize the role of oxygen defects for the application of ferromagnetic films. PMID:25437752

Zheng, Jian-Yun; Bao, Shan-Hu; Lv, Yan-Hong; Jin, Ping

2014-12-24

315

Enhanced ferromagnetic and metal insulator transition in Sm0.55Sr0.45MnO3 thin films: Role of oxygen vacancy induced quenched disorder  

NASA Astrophysics Data System (ADS)

Effect of quenched disorder (QD) caused by oxygen vacancy (OV) and substrate induced inhomogeneous compressive strain, on the magnetic and transport properties of oriented polycrystalline Sm0.55Sr0.45MnO3 thin films is investigated. QD is related intimately to the ordering/disordering of the OVs and controls the paramagnetic-ferromagnetic/insulator-metal transition. OV ordered films show enhanced TC/TIM˜165 K, which is depressed by oxygen annealing. OV disordering realized by quenching reduces TC/TIM. The first order IM transition observed in SSMO single crystals is transformed into nonhysteretic and continuous one in the OV ordered films. QD appears to be diluted by OV disorder/annihilation and results in stronger carrier localization.

Srivastava, M. K.; Siwach, P. K.; Kaur, A.; Singh, H. K.

2010-11-01

316

Influence of oxygen content of room temperature TiO2-x deposited films for enhanced resistive switching memory performance  

NASA Astrophysics Data System (ADS)

In this work, we demonstrate that TiO2-x based Resistive Random Access Memory devices can function without an initial electroforming process and a wide range of switching ratios could be achieved by controlling the oxygen content, the compliance current, the sweep bias amplitude, and the width of the voltage pulse applied on the memory cell. The influence of deposition ambient and more particularly of oxygen flux during thin film sputtering at room temperature to the resistive properties of titanium oxide will be discussed in detail. By controlling the density of oxygen vacancies into the dielectric matrix, we can also improve the repeatability and the operation of the device, in terms of distribution of the SET/RESET voltages. We propose that ultra high density of vacancies deteriorate the switching phenomenon, whereas high vacancy density results in better switching behavior. Moreover, we conclude that the oxygen vacancies density and distribution have a direct impact on the conducting filament diameter, in terms of sensitivity of the conducting paths (high OFF/ON ratio). By increasing the oxygen content, we reduce the size of vacancy based filaments, resulting in a more stable operation of our device. In addition, manipulation of population of oxygen ions into the Ti top electrode enables the creation of multilevel switching states. Switching speed, endurance, and retention performance reveals the excellent functionality of our device as a non-volatile memory element and conduction mechanism analysis demonstrates the manifestation of Poole-Frenkel emission in conjunction with trap-assisted tunneling, which is also deployed in order to interpret the gradual increase of current during SET process.

Bousoulas, P.; Michelakaki, I.; Tsoukalas, D.

2014-01-01

317

Strategies to overcome oxygen transfer limitations during hairy root cultivation of Azadiracta indica for enhanced azadirachtin production.  

PubMed

The vast untapped potential of hairy root cultures as a stable source of biologically active chemicals has focused the attention of scientific community toward its commercial exploitation. However, the major bottleneck remains its successful scale-up. Due to branching, the roots form an interlocked matrix that exhibits resistance to oxygen transfer. Thus, present work was undertaken to develop cultivation strategies like optimization of inlet gas composition (in terms of % (v/v) O(2) in air), air-flow rate and addition of oxygen vectors in the medium, to curb the oxygen transfer limitations during hairy root cultivation of Azadirachta indica for in vitro azadirachtin (a biopesticide) production. It was found that increasing the oxygen fraction in the inlet air (in the range, 20-100% (v/v) O(2) in air) increased the azadirachtin productivity by approximately threefold, to a maximum of 4.42 mg/L per day (at 100% (v/v) O(2) in air) with respect to 1.68 mg/L per day in control (air with no oxygen supplementation). Similarly, increasing the air-flow rate (in the range, 0.3-2 vvm) also increased the azadirachtin productivity to a maximum of 1.84 mg/L per day at 0.8 vvm of air-flow rate. On the contrary, addition of oxygen vectors (in the range, 1-4% (v/v); hydrogen peroxide, toluene, Tween 80, kerosene, silicone oil, and n-hexadecane), decreased the azadirachtin productivity with respect to control (1.76 mg/L per day). PMID:22246729

Srivastava, Smita; Srivastava, Ashok Kumar

2012-07-01

318

Bubble Combustion  

NASA Technical Reports Server (NTRS)

A method of energy production that is capable of low pollutant emissions is fundamental to one of the four pillars of NASA s Aeronautics Blueprint: Revolutionary Vehicles. Bubble combustion, a new engine technology currently being developed at Glenn Research Center promises to provide low emissions combustion in support of NASA s vision under the Emissions Element because it generates power, while minimizing the production of carbon dioxide (CO2) and nitrous oxides (NOx), both known to be Greenhouse gases. and allows the use of alternative fuels such as corn oil, low-grade fuels, and even used motor oil. Bubble combustion is analogous to the inverse of spray combustion: the difference between bubble and spray combustion is that spray combustion is spraying a liquid in to a gas to form droplets, whereas bubble combustion involves injecting a gas into a liquid to form gaseous bubbles. In bubble combustion, the process for the ignition of the bubbles takes place on a time scale of less than a nanosecond and begins with acoustic waves perturbing each bubble. This perturbation causes the local pressure to drop below the vapor pressure of the liquid thus producing cavitation in which the bubble diameter grows, and upon reversal of the oscillating pressure field, the bubble then collapses rapidly with the aid of the high surface tension forces acting on the wall of the bubble. The rapid and violent collapse causes the temperatures inside the bubbles to soar as a result of adiabatic heating. As the temperatures rise, the gaseous contents of the bubble ignite with the bubble itself serving as its own combustion chamber. After ignition, this is the time in the bubble s life cycle where power is generated, and CO2, and NOx among other species, are produced. However, the pollutants CO2 and NOx are absorbed into the surrounding liquid. The importance of bubble combustion is that it generates power using a simple and compact device. We conducted a parametric study using CAVCHEM, a computational model developed at Glenn, that simulates the cavitational collapse of a single bubble in a liquid (water) and the subsequent combustion of the gaseous contents inside the bubble. The model solves the time-dependent, compressible Navier-Stokes equations in one-dimension with finite-rate chemical kinetics using the CHEMKIN package. Specifically, parameters such as frequency, pressure, bubble radius, and the equivalence ratio were varied while examining their effect on the maximum temperature, radius, and chemical species. These studies indicate that the radius of the bubble is perhaps the most critical parameter governing bubble combustion dynamics and its efficiency. Based on the results of the parametric studies, we plan on conducting experiments to study the effect of ultrasonic perturbations on the bubble generation process with respect to the bubble radius and size distribution.

Corrigan, Jackie

2004-01-01

319

Combustion energy of fullerene soot  

SciTech Connect

The standard energy of combustion of fullerene soot generated in arc discharge was determined to be [minus]36.0 [+-] 0.5 kJ g[sup [minus]1] by oxygen-bomb combustion calorimetry. The value was much closer to those of C[sub 60] and C[sub 70] than that of graphite. This result provides an energetic reason for the remarkable yield of fullerenes in arc discharge and supports the mechanism of fullerene formation, where fullerenes are the lowest energy products. Fullerene onion formation is interpreted in terms of energy relaxation of the fullerene soot. 20 refs., 1 tab.

Man, Naoki; Nagano, Yatsuhisa; Kiyobayashi, Tetsu; Sakiyama, Minoru (Osaka Univ., Toyonaka (Japan))

1995-02-23

320

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

321

Reference particles for toxicological studies of wood combustion: formation, characteristics, and toxicity compared to those of real wood combustion particulate mass.  

PubMed

Multiple studies show that particulate mass (PM) generated from incomplete wood combustion may induce adverse health issues in humans. Previous findings have shown that also the PM from efficient wood combustion may induce enhanced production of reactive oxygen species (ROS), inflammation, and cytotoxicity in vitro and in vivo. Underlying factors of these effects may be traced back to volatile inorganic transition metals, especially zinc, which can be enriched in the ultrafine fraction of biomass combustion particulate emission. In this study, nanoparticles composed of potassium, sulfur, and zinc, which are the major components forming inorganic fine PM, were synthesized and tested in vitro. In addition, in vitro toxicity of PM from efficient combustion of wood chips was compared with that of the synthesized particles. Cytotoxicity, cell cycle arrest, ROS generation, and tumor necrosis factor alpha release were related to zinc concentration in PM. Potassium sulfate and potassium carbonate did not induce toxic responses. In light of the provided data, it can be concluded that zinc, enriched in wood combustion emissions, caused the toxicity in all of the measured end points. PMID:25063562

Torvela, Tiina; Uski, Oskari; Karhunen, Tommi; Lähde, Anna; Jalava, Pasi; Sippula, Olli; Tissari, Jarkko; Hirvonen, Maija-Riitta; Jokiniemi, Jorma

2014-09-15

322

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

323

Nitrogen-doped carbon dots decorated on graphene: a novel all-carbon hybrid electrocatalyst for enhanced oxygen reduction reaction.  

PubMed

An all-carbon hybrid, composed of coal-based nitrogen-doped carbon dots decorated on graphene, was prepared via hydrothermal treatment. The hybrid possesses comparable electrocatalytic activity, better durability and methanol tolerance than those of the commercial Pt-based electrocatalysts for oxygen reduction reaction, indicative of its great potential in fuel cells. PMID:25626119

Hu, Chao; Yu, Chang; Li, Mingyu; Wang, Xiuna; Dong, Qiang; Wang, Gang; Qiu, Jieshan

2015-02-10

324

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

325

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

326

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

327

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

328

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

329

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

330

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

331

Smoldering Combustion Experiments in Microgravity  

NASA Technical Reports Server (NTRS)

The Microgravity Smoldering Combustion (MSC) experiment is part of a study of the smolder characteristics of porous combustible materials in a microgravity environment. Smoldering is a non-flaming form of combustion that takes place in the interior of porous materials and takes place in a number of processes ranging from smoldering of porous insulation materials to high temperature synthesis of metals. The objective of the study is to provide a better understanding of the controlling mechanisms of smolder, both in microgravity and normal-gravity. As with many forms of combustion, gravity affects the availability of oxidizer and transport of heat, and therefore the rate of combustion. Microgravity smolder experiments, in both a quiescent oxidizing environment, and in a forced oxidizing flow have been conducted aboard the NASA Space Shuttle (STS-69 and STS-77 missions) to determine the effect of the ambient oxygen concentration and oxidizer forced flow velocity on smolder combustion in microgravity. The experimental apparatus is contained within the NASA Get Away Special Canister (GAS-CAN) Payload. These two sets of experiments investigate the propagation of smolder along the polyurethane foam sample under both diffusion driven and forced flow driven smoldering. The results of the microgravity experiments are compared with identical ones carried out in normal gravity, and are used to verify present theories of smolder combustion. The results of this study will provide new insights into the smoldering combustion process. Thermocouple histories show that the microgravity smolder reaction temperatures (Ts) and propagation velocities (Us) lie between those of identical normal-gravity upward and downward tests. These observations indicate the effect of buoyancy on the transport of oxidizer to the reaction front.

Walther, David C.; Fernandez-Pello, A. Carlos; Urban, David L.

1997-01-01

332

Effect of diluted and preheated oxidizer on the emission of methane flameless combustion  

NASA Astrophysics Data System (ADS)

In combustion process, reduction of emissions often accompanies with output efficiency reduction. It means, by using current combustion technique it is difficult to obtainlow pollution and high level of efficiency in the same time. In new combustion system, low NOxengines and burners are studied particularly. Recently flameless or Moderate and Intensive Low oxygen Dilution (MILD) combustion has received special attention in terms of low harmful emissions and low energy consumption. Behavior of combustion with highly preheated air was analyzed to study the change of combustion regime and the reason for the compatibility of high performance and low NOx production. Sustainability of combustion under low oxygen concentration was examined when; the combustion air temperature was above the self-ignition temperature of the fuel. This paper purposes to analyze the NOx emission quantity in conventional combustion and flameless combustion by Chemical Equilibrium with Applications (CEA) software.

Hosseini, Seyed Ehsan; Salehirad, Saber; Wahid, M. A.; Sies, Mohsin Mohd; Saat, Aminuddin

2012-06-01

333

Enhanced brain stem 5HT 2A receptor function under neonatal hypoxic insult: role of glucose, oxygen, and epinephrine resuscitation  

Microsoft Academic Search

Molecular processes regulating brain stem serotonergic receptors play an important role in the control of respiration. We\\u000a evaluated 5-HT2A receptor alterations in the brain stem of neonatal rats exposed to hypoxic insult and the effect of glucose, oxygen, and\\u000a epinephrine resuscitation in ameliorating these alterations. Hypoxic stress increased the total 5-HT and 5-HT2A receptor number along with an up regulation

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

2011-01-01

334

Oxidation of glyoxylic acid by cerium(IV): Oxygen-induced enhancement of the primary radical concentration  

SciTech Connect

In order to help understand the role of oxygen in Ce(IV)-induced oxidation of small carbonic acids, we investigated the reaction of glyoxylic acid (HCOCOOH) and Ce(IV) in 1 M sulfuric acid. Spectrophotometric data showed that in excess of glyoxylic acid the consumption of Ce(IV) obeys pseudo-first-order kinetics, with a rate constant of 8.8 L mol{sup -1} s{sup -1} at 25{degree}C and an activation energy of 80 kJ mol{sup -1}. Rapid-flow EPR measurements revealed an approximately 1:2:1 triplet with a g value of 2.0071{+-}0.0005 and a hyperfine splitting of 7.1{+-}0.2 G, assignable to the primary radical formed by abstraction of a hydrogen atom from hydrated glyoxylic acid. The rate constant for the anaerobic self-decay of the radical was measured as approximately 3.7x10{sup 9} L mol{sup -1} s{sup -1}. Surprisingly, oxygen had no effect on the Ce(IV) kinetics, while the radical decay was significantly inhibited under aerobic conditions (ratio of experimental rate constants = 6.3). Amperometric measurements revealed accompanying oxygen consumption. Analyses based on numerical simulations show that the observed oxygen-induced increase in radical concentration cannot be explained in the framework of standard autooxidation mechanisms. An alternative reaction scheme is suggested which reproduces the observed aerobic radical kinetics and which thus could be relevant to similar oxidation reactions. 30 refs., 7 figs., 2 tabs.

Neumann, B. [Max-Planck-Institut fuer Molekulare Physiologie, Dortmund (Germany)] [Max-Planck-Institut fuer Molekulare Physiologie, Dortmund (Germany); [Florida State Univ., Tallahassee, FL (United States); [West Virginia Univ., Morgantown, WV (United States); Steinbock, O.; Dalal, N.S. [Florida State Univ., Tallahassee, FL (United States)] [Florida State Univ., Tallahassee, FL (United States); [West Virginia Univ., Morgantown, WV (United States); Mueller, S.C. [Max-Planck-Institut fuer Molekulare Physiologie, Dortmund (Germany)] [Max-Planck-Institut fuer Molekulare Physiologie, Dortmund (Germany); [Otto-von-Guericke-Universitaet, Magdeburg (Germany); [Florida State Univ., Tallahassee, FL (United States); [West Virginia Univ., Morgantown, WV (United States)

1996-07-25

335

Formation of a long-lived electron-transfer state in mesoporous silica-alumina composites enhances photocatalytic oxygenation reactivity  

PubMed Central

A simple donor-acceptor linked dyad, 9-mesityl-10-methylacridinium ion (Acr+-Mes) was incorporated into nanosized mesoporous silica-alumina to form a composite, which in acetonitrile is highly dispersed. In this medium, upon visible light irradiation, the formation of an extremely long-lived electron-transfer state (Acr•-Mes•+) was confirmed by EPR and laser flash photolysis spectroscopic methods. The composite of Acr+-Mes-incorporated mesoporous silica-alumina with an added copper complex [(tmpa)CuII] (tmpa = tris(2-pyridylmethyl)amine) acts as an efficient and robust photocatalyst for the selective oxygenation of p-xylene by molecular oxygen to produce p-tolualdehyde and hydrogen peroxide. Thus, incorporation of Acr+-Mes into nanosized mesoporous silica-alumina combined with an O2-reduction catalyst ([(tmpa)CuII]2+) provides a promising method in the development of efficient and robust organic photocatalysts for substrate oxygenation by dioxygen, the ultimate environmentally benign oxidant. PMID:22543164

Fukuzumi, Shunichi; Doi, Kaoru; Itoh, Akinori; Suenobu, Tomoyoshi; Ohkubo, Kei; Yamada, Yusuke; Karlin, Kenneth D.

2012-01-01

336

Method for providing oxygen ion vacancies in lanthanide oxides  

DOEpatents

A method for desulfurization of fuel gases resulting from the incomplete combustion of sulfur containing hydrocarbons whereby the gases are treated with lanthanide oxides containing large numbers of oxygen-ion vacancies providing ionic porosity which enhances the ability of the lanthanide oxides to react more rapidly and completely with the sulfur in the fuel gases whereby the sulfur in such gases is reduced to low levels suitable for fuels for firing into boilers of power plants generating electricity with steam turbine driven generators, gas turbines, fuel cells and precursors for liquid fuels such as methanol and the like.

Kay, D. Alan R. (4305 Lakeshore Rd., Burlington, CA); Wilson, William G. (820 Harden Dr., Pittsburgh, PA 15229)

1989-12-05

337

Flame propagation enhancement by plasma excitation of oxygen. Part II: Effects of O{sub 2}(a{sup 1}{delta}{sub g})  

SciTech Connect

The isolated effect of O{sub 2}(a{sup 1}{delta}{sub g}) on the propagation of C{sub 2}H{sub 4} lifted flames was studied at reduced pressures (3.61 kPa and 6.73 kPa). The O{sub 2}(a{sup 1}{delta}{sub g}) was produced in a microwave discharge plasma and was isolated from O and O{sub 3} by NO addition to the plasma afterglow in a flow residence time on the order of 1 s. The concentrations of O{sub 2}(a{sup 1}{delta}{sub g}) and O{sub 3} were measured quantitatively through absorption by sensitive off-axis integrated-cavity-output spectroscopy and one-pass line-of-sight absorption, respectively. Under these conditions, it was found that O{sub 2}(a{sup 1}{delta}{sub g}) enhanced the propagation speed of C{sub 2}H{sub 4} lifted flames. Comparison with the results of enhancement by O{sub 3} found in part I of this investigation provided an estimation of 2-3% of flame speed enhancement for 5500 ppm of O{sub 2}(a{sup 1}{delta}{sub g}) addition from the plasma. Numerical simulation results using the current kinetic model of O{sub 2}(a{sup 1}{delta}{sub g}) over-predicts the flame propagation enhancement found in the experiments. However, the inclusion of collisional quenching rate estimations of O{sub 2}(a{sup 1}{delta}{sub g}) by C{sub 2}H{sub 4} mitigated the over-prediction. The present isolated experimental results of the enhancement of a hydrocarbon fueled flame by O{sub 2}(a{sup 1}{delta}{sub g}), along with kinetic modeling results suggest that further studies of C{sub n}H{sub m} + O{sub 2}(a{sup 1}{delta}{sub g}) collisional and reactive quenching are required in order to correctly predict combustion enhancement by O{sub 2}(a{sup 1}{delta}{sub g}). The present experimental results will have a direct impact on the development of elementary reaction rates with O{sub 2}(a{sup 1}{delta}{sub g}) at flame conditions to establish detailed plasma-flame kinetic mechanisms. (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

338

Update for combustion properties of wood components  

Microsoft Academic Search

The combustion properties of various biomass and wood materials from various references and from our laboratory were reanalysed. The net heat of combustion for cellulosic materials was found to be 13.23 kJ\\/g times the ratio of stoichiometric oxygen mass to fuel mass, ro, regardless of the material composition. Bomb calorimeter data for original, charred and volatilized material components provide gross

Mark Dietenberger

2002-01-01

339

The anion-transport inhibitor H2DIDS cross-links hemoglobin interdimerically and enhances oxygen unloading.  

PubMed

Human hemoglobin treated with equal concentrations of the anion-transport inhibitor H2DIDS produces a right shift in the oxygen dissociation curve. concomitantly, the Hill coefficient is reduced from n = 2.7 to 2.1. When higher concentrations of H2DIDS are applied (H2DIDS: hemoglobin = 5:0.5 mM), the Hill coefficient decreases further to 1.5 and the oxygen dissociation curve of hemoglobin is shifted slightly to the left of the control. Similar results were also obtained with DIDS instead of H2DIDS. SDS-PAGE shows that H2DIDS cross-links hemoglobin monomers mainly into dimers. Cross-linking is more effective under anaerobic conditions. With tritiated H2DIDS the larger part of the radioactivity is found in the dimer position of hemoglobin. Separation of the alpha and beta units of hemoglobin reacted with tritiated H2DIDS demonstrated a stoichiometry of 2.2 and 2.4 molecules H2DIDS per molecule alpha and beta unit hemoglobin, leading to about 8-9 H2DIDS molecules per native hemoglobin. The right shift produced in the hemoglobin oxygen dissociation curve and the cross-linking of monomers into dimers, especially under anaerobic condition, suggest that H2DIDS can also react with those amino groups of hemoglobin which are involved in 2,3-DPG binding. A comparison of H2DIDS, DIDS and 2,3-DPG at three different concentrations close to the hemoglobin concentration revealed a concentration dependent right shift in the oxygen dissociation curve with the order of potency 2,3-DPG greater than H2DIDS greater than DIDS. The Hill coefficients (n) at the three concentrations of 2,3-DPG demonstrated no changes, but H2DIDS and DIDS reduced in a concentration-dependent manner the cooperativity of hemoglobin. Again, H2DIDS is more potent than DIDS, especially at the low concentration. These anion-transport inhibitors provide novel approaches to the exploration of hemoglobin function. PMID:3207730

Fuhrmann, G F; Kreutzfeldt, C; Rudolphi, K; Fasold, H

1988-12-01

340

Enhancements of a Combustion Vessel to Determine Laminar Flame Speeds of Hydrocarbon Blends with Helium Dilution at Elevated Temperatures and Pressures  

E-print Network

speeds were those of methane, ethane, and propane fuel blends, as well as pure methane, at an elevated pressure of 5 atm and temperatures of 298 and 473 K, using a constant-volume, cylindrical combustion vessel. The current Aramco mechanism developed...

Plichta, Drew

2013-04-03

341

Hyperbaric oxygen preconditioning attenuates hyperglycemia-enhanced hemorrhagic transformation by inhibiting matrix metalloproteinases in focal cerebral ischemia in rats  

PubMed Central

Hyperglycemia dramatically aggravates brain infarct and hemorrhagic transformation (HT) after ischemic stroke. Oxidative stress and matrix metalloproteinases (MMPs) play an important role in the pathophysiology of HT. Hyperbaric oxygen preconditioning (HBO-PC) has been proved to decrease oxidative stress and be neuroprotective in experimental stroke models. The present study determined whether HBO-PC would ameliorate HT by a pre-ischemic increase of reactive oxygen species (ROS) generation, and a suppression of MMP-2 and MMP-9 in hyperglycemic middle cerebral artery occlusion (MCAO) rats. Rats were pretreated with HBO (100% O2, 2.5 atmospheres absolute) 1 h daily for 5 days before MCAO. Acute hyperglycemia was induced by an injection of 50% dextrose. Neurological deficits, infarction volume and hemorrhagic volume were assessed 24 h and 7 days after ischemia. ROS scavenger n-acetyl cysteine (NAC), hypoxia-inducible factor-1? (HIF-1?) inhibitor 2-methoxyestradiol (2ME2) and activator cobalt chloride (CoCl2), and MMPs inhibitor SB-3CT were administrated for mechanism study. The activity of MMP-2 and MMP-9, and the expression HIF-1? were measured. HBO-PC improved neurological deficits, and reduced hemorrhagic volume; the expression of HIF-1? was significantly decreased, and the activity of MMP-2 and MMP-9 was reduced by HBO-PC compared with vehicle group. Our results suggested that HBO-PC attenuated HT via decreasing HIF-1? and its downstream MMP-2 and MMP-9 in hyperglycemic MCAO rats. PMID:23537951

Soejima, Yoshiteru; Hu, Qin; Krafft, Paul R.; Fujii, Mutsumi; Tang, Jiping; Zhang, John H.

2013-01-01

342

Handbook of infrared radiation from combustion gases  

NASA Technical Reports Server (NTRS)

The treatment of radiant emission and absorption by combustion gases are discussed. Typical applications include: (1) rocket combustion chambers and exhausts, (2) turbojet engines and exhausts, and (3) industrial furnaces. Some mention is made of radiant heat transfer problems in planetary atmospheres, in stellar atmospheres, and in reentry plasmas. Particular consideration is given to the temperature range from 500K to 3000K and the pressure range from 0.001 atmosphere to 30 atmospheres. Strong emphasis is given to the combustion products of hydrocarbon fuels with oxygen, specifically to carbon dioxide, water vapor, and carbon monoxide. In addition, species such as HF, HC1, CN, OH, and NO are treated.

Ludwig, C. B.; Malkmus, W.; Reardon, J. E.; Thomson, J. A. L.; Goulard, R. (editor)

1973-01-01

343

Mathematics of combustion  

Microsoft Academic Search

The applications of numerical techniques to the study of combustion processes is considered. The basic equations governing combustion processes are introduced, and some novel approaches to combustion reaction modelling are described. Among the specific applications discussed are: the Burger and Korteweg-de Vries equations of detonation processes; turbulent combustion modelling; and analysis of finite amplitude waves in combustible gases.

J. D. Buckmaster; H. Rabitz; F. A. Williams; W. Fickett; J. F. Clarke

1985-01-01

344

Combustion pressure sensor  

Microsoft Academic Search

A combustion pressure sensor is described for mounting on an internal combustion engine so as to have access to the interior of a combustion cylinder. The sensor consists of: a first diaphragm means adjacent a combustion region for deflecting as a function of the magnitude of adjacent pressure in the combustion region, and for acting as a gas tight seal

Bettman

1986-01-01

345

A hybrid 2-zone/WAVE engine combustion model for simulating combustion instabilities during dilute operation  

SciTech Connect

Internal combustion engines are operated under conditions of high exhaust gas recirculation (EGR) to reduce NO x emissions and promote enhanced combustion modes such as HCCI. However, high EGR under certain conditions also promotes nonlinear feedback between cycles, leading to the development of combustion instabilities and cyclic variability. We employ a two-zone phenomenological combustion model to simulate the onset of combustion instabilities under highly dilute conditions and to illustrate the impact of these instabilities on emissions and fuel efficiency. The two-zone in-cylinder combustion model is coupled to a WAVE engine-simulation code through a Simulink interface, allowing rapid simulation of several hundred successive engine cycles with many external engine parametric effects included. We demonstrate how this hybrid model can be used to study strategies for adaptive feedback control to reduce cyclic combustion instabilities and, thus, preserve fuel efficiency and reduce emissions.

Edwards, Kevin Dean [ORNL; Wagner, Robert M [ORNL; Chakravarthy, Veerathu K [ORNL; Daw, C Stuart [ORNL; Green Jr, Johney Boyd [ORNL

2006-01-01

346

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

347

Chemical Looping Combustion Kinetics  

SciTech Connect

One of the most promising methods of capturing CO{sub 2} emitted by coal-fired power plants for subsequent sequestration is chemical looping combustion (CLC). A powdered metal oxide such as NiO transfers oxygen directly to a fuel in a fuel reactor at high temperatures with no air present. Heat, water, and CO{sub 2} are released, and after H{sub 2}O condensation the CO{sub 2} (undiluted by N{sub 2}) is ready for sequestration, whereas the nickel metal is ready for reoxidation in the air reactor. In principle, these processes can be repeated endlessly with the original nickel metal/nickel oxide participating in a loop that admits fuel and rejects ash, heat, and water. Our project accumulated kinetic rate data at high temperatures and elevated pressures for the metal oxide reduction step and for the metal reoxidation step. These data will be used in computational modeling of CLC on the laboratory scale and presumably later on the plant scale. The oxygen carrier on which the research at Utah is focused is CuO/Cu{sub 2}O rather than nickel oxide because the copper system lends itself to use with solid fuels in an alternative to CLC called 'chemical looping with oxygen uncoupling' (CLOU).

Edward Eyring; Gabor Konya

2009-03-31

348

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

349

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 is focused on spray physics and associated combustion instability phenomena. Results concerning high pressure droplet gasification model, droplet turbulent dispersion model, and spray atomization model will contribute to the development of new computational tools for design of stable liquid propellant rocket engines.

Liang, Pak-Yan; Jeng, San-Mou; Litchford, Ronald

1989-01-01

350

Combustion Control  

E-print Network

casing of the fuel control regulator with the combustion air piping. The upstream pressure on the burner air orifice is applied to the main diaphragm of the pressure balanced regulator. Assuming sufficient gas pressure at the regulator inlet..., the outlet gas pressure will equal the air impulse pressLre. As the primary control drive moves to open or close the air valve, the outlet pressure will "track" changes in air pressure. The burner is an orifice for the air (assuming that it is in good...

Riccardi, R. C.

1984-01-01

351

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

352

Continuous-flow Mass Production of Silicon Nanowires via Substrate-Enhanced Metal-Catalyzed Electroless Etching of Silicon with Dissolved Oxygen as an Oxidant  

NASA Astrophysics Data System (ADS)

Silicon nanowires (SiNWs) are attracting growing interest due to their unique properties and promising applications in photovoltaic devices, thermoelectric devices, lithium-ion batteries, and biotechnology. Low-cost mass production of SiNWs is essential for SiNWs-based nanotechnology commercialization. However, economic, controlled large-scale production of SiNWs remains challenging and rarely attainable. Here, we demonstrate a facile strategy capable of low-cost, continuous-flow mass production of SiNWs on an industrial scale. The strategy relies on substrate-enhanced metal-catalyzed electroless etching (MCEE) of silicon using dissolved oxygen in aqueous hydrofluoric acid (HF) solution as an oxidant. The distinct advantages of this novel MCEE approach, such as simplicity, scalability and flexibility, make it an attractive alternative to conventional MCEE methods.

Hu, Ya; Peng, Kui-Qing; Liu, Lin; Qiao, Zhen; Huang, Xing; Wu, Xiao-Ling; Meng, Xiang-Min; Lee, Shuit-Tong

2014-01-01

353

The combination of hypoxia-response enhancers and an oxygen-dependent proteolytic motif enables real-time imaging of absolute HIF-1 activity in tumor xenografts  

SciTech Connect

The transcriptional activity of hypoxia-inducible factor-1 (HIF-1) is associated with tumor malignancies; therefore, it is important to comprehend its dynamism in solid tumors. However, a molecular imaging strategy to accurately access it remains to be developed. We constructed here a novel HIF-1-dependent reporter gene, 5HREp-ODD-luc, in which 5 copies of the hypoxia-response element (5HRE) enhance expression of the oxygen-dependent degradation (ODD) domain and luciferase (luc) fusion under hypoxia. Because the ODD domain caused the oxygen-dependent degradation of the ODD-Luc protein, the novel reporter gene showed little leak of luminescence under normoxia. Such a property caused an increase of the hypoxia-responsiveness up to about 4.7 x 10{sup 4}-fold. Moreover, the ODD domain caused rapid degradation of the ODD-Luc protein under normoxia, the luminescence reflected the dynamism of HIF-1 activity in real-time. The superiority of the novel reporter gene will surely accelerate analysis of the intratumoral HIF-1 activity during tumor progression and cancer treatments.

Harada, Hiroshi [Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan) and Nano-Medicine Merger Education Unit, Kyoto University, Kyoto (Japan)]. E-mail: hharada@kuhp.kyoto-u.ac.jp; Kizaka-Kondoh, Shinae [Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan); COE Formation for Genomic Analysis of Disease Model Animals with Multiple Genetic Alterations, Kyoto University Graduate School of Medicine, Kyoto (Japan); Itasaka, Satoshi [Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan); Shibuya, Keiko [Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan); Morinibu, Akiyo [Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan); Shinomiya, Kazumi [Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan); Hiraoka, Masahiro [Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507 (Japan); Nano-Medicine Merger Education Unit, Kyoto University, Kyoto (Japan)

2007-09-07

354

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

355

Effects of the differentiating agents sodium butyrate and N-methylformamide on the oxygen enhancement ratio of human colon tumor cells.  

PubMed

We have previously shown that chronic adaptation of human tumor cells to the differentiation-inducing agents N-methylformamide (NMF) and sodium butyrate (NAB) increases the sensitivity of oxic cells to graded single doses of X rays. These studies were carried out to define the sensitivity of hypoxic cells after adaptation. Clone A colon tumor cells were grown for three passages in medium containing 170 mM NMF or 2 mM NAB and irradiated in suspension culture, after gassing with either oxygen (60 min) or ultrapure nitrogen (90 min), and complete survival curves were generated. Using the linear-quadratic equation to describe the data, it was found that NMF and NAB produced increased X-ray killing of hypoxic cells. At the 10% level of survival, the dose-modifying factors were about 1.20 and 1.25 for NMF- and NAB-adapted hypoxic cells, respectively, as compared to hypoxic control cells. However, since both oxic and hypoxic cells exhibited increased sensitivity after NMF and NAB adaptation, there was no major change in the oxygen enhancement ratio. PMID:3340722

Hallows, K R; Bliven, S F; Leith, J T

1988-01-01

356

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

357

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 oxygenated species. The hydroxyl moiety in n-butanol results in the direct production of the oxygenated species such as butanal, acetaldehyde, and formaldehyde. The formation of these compounds sequesters carbon from forming soot precursors, but they may introduce other adverse environmental and health effects. Biodiesel is a mixture of long chain fatty acid methyl esters derived from fats and oils. This research study presents high quality experimental data for one large fatty acid methyl ester, methyl decanoate, and models its combustion using an improved skeletal mechanism. The results indicate that methyl decanoate is consumed via abstraction of hydrogen atoms to produce fuel radicals, which ultimately lead to the production of alkenes. The ester moiety in methyl decanoate leads to the formation of low molecular weight oxygenated compounds such as carbon monoxide, formaldehyde, and ketene. The study concludes that the oxygenated molecules in biofuels follow similar combustion pathways to the hydrocarbons in petroleum fuels. The oxygenated moiety's ability to sequester carbon from forming soot precursors is highlighted. However, the direct formation of oxygenated hydrocarbons warrants further investigation into the environmental and health impacts of practical biofuel combustion systems.

Sarathy, Subram Maniam

358

The enhanced electrocatalytic activity of okara-derived N-doped mesoporous carbon for oxygen reduction reaction  

NASA Astrophysics Data System (ADS)

Nitrogen-doped carbon (N-C) catalysts can potentially offer high ORR (oxygen reduction reaction) electrocatalytic activity comparable to Pt/C catalysts. Here, we establish a correlation between N-species (pyridinic-N and graphitic-N) with high ORR activity and a key role for Fe in their preparation. N-C catalysts are prepared from okara (a cheap, nitrogen-rich, biomass precursor) using a facile synthesis method with inclusion of FeCl3 at different steps of synthesis. Mesoporous N-C catalyst is produced that had ORR activity comparable to that of commercial Pt/C catalyst. High ORR-activity N-C results from the presence of FeCl3 at a specific step during synthesis. Detailed investigation by XPS reveals that increased levels of pyridinic-N and graphitic-N arose from pyridinic-N-oxide conversion in the presence of Fe. We conclude that transforming inert N species to active N species underlies the increase in active catalytic sites on the carbon surface and offers a means to improve N-C catalyst performance.

Wang, Rongfang; Wang, Hui; Zhou, Tianbao; Key, Julian; Ma, Yanjiao; Zhang, Zheng; Wang, Qizhao; Ji, Shan

2015-01-01

359

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

360

Size-Dependent Enhancement of Electrocatalytic Oxygen-Reduction and Hydrogen-Evolution Performance of MoS2 Particles.  

PubMed

MoS2 particles with different size distributions were prepared by simple ultrasonication of bulk MoS2 followed by gradient centrifugation. Relative to the inert microscale MoS2 , nanoscale MoS2 showed significantly improved catalytic activity toward the oxygen-reduction reaction (ORR) and hydrogen-evolution reaction (HER). The decrease in particle size was accompanied by an increase in catalytic activity. Particles with a size of around 2?nm exhibited the best dual ORR and HER performance with a four-electron ORR process and an HER onset potential of -0.16?V versus the standard hydrogen electrode (SHE). This is the first investigation on the size-dependent effect of the ORR activity of MoS2 , and a four-electron transfer route was found. The exposed abundant Mo edges of the MoS2 nanoparticles were proven to be responsible for the high ORR catalytic activity, whereas the origin of the improved HER activity of the nanoparticles was attributed to the plentiful exposed S edges. This newly discovered process provides a simple protocol to produce inexpensive highly active MoS2 catalysts that could easily be scaled up. Hence, it opens up possibilities for wide applications of MoS2 nanoparticles in the fields of energy conversion and storage. PMID:23873743

Wang, Tanyuan; Gao, Dongliang; Zhuo, Junqiao; Zhu, Zhiwei; Papakonstantinou, Pagona; Li, Yan; Li, Meixian

2013-07-19

361

Carbon dioxide power plant for total emission control and enhanced oil recovery. [Removal, storage, and use of CO/sub 2/  

SciTech Connect

The design of a compact environmentally acceptable carbon dioxide diluted coal-oxygen fired power plant is described. The plant releases no combustion products to the atmosphere. The oxygen for combustion is separated in an air liquefaction plant and the effluent nitrogen is available for use in oil well production. Recycle carbon dioxide mixed with oxygen replaces the nitrogen for the combustion of coal in the burners. The carbon dioxide produced is used in enhanced oil recovery operations and injected into spent wells and excavated salt cavities for long-term storage. The recovery of CO/sub 2/ from a coal-burning power plant by this method appears to have the lowest energy expenditure and the lowest byproduct cost compared to alternative removal and recovery processes.

Horn, F L; Steinberg, M

1981-08-01

362

Fluidization, combustion and emission behavior of biomass in fluidized bed combustion units  

SciTech Connect

Gaseous components were measured over the height and the cross section inside a circulating fluidized bed riser with a thermal power of 60 kW. The combustion behavior of lignite (German brown coal), hard coal, biomass (China reed), and sewage sludge was investigated. The burn-out behavior was investigated by in-situ and real time measurement of the oxygen consumption using solid electrolyte sensor probes within a bubbling fluidized bed combustor with 15 kW thermal power. Non-uniform oxygen concentration profiles were found over the small riser cross-section which differed for the various fuels. The feed location and the fuel distribution also influences the horizontal oxygen profile. The reasons for the non-uniformity of the horizontal oxygen concentration profile are the combustion of volatile matter and the recirculation of char near the walls. A simulation model was developed to calculate the hydrodynamics and the oxygen consumption for the difference fuels inside the CFBC riser.

Kaeferstein, P.; Tepper, H.; Gohla, M.; Reimer, H. [Otto-von-Guericke-Univ. of Magdeburg (Germany). Dept. Heat Transfer and Energy Economy

1997-12-31

363

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

364

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

365

Combustion chemistry  

SciTech Connect

This research is concerned with the development and use of sensitivity analysis tools to probe the response of dependent variables to model input variables. Sensitivity analysis is important at all levels of combustion modeling. This group`s research continues to be focused on elucidating the interrelationship between features in the underlying potential energy surface (obtained from ab initio quantum chemistry calculations) and their responses in the quantum dynamics, e.g., reactive transition probabilities, cross sections, and thermal rate coefficients. The goals of this research are: (i) to provide feedback information to quantum chemists in their potential surface refinement efforts, and (ii) to gain a better understanding of how various regions in the potential influence the dynamics. These investigations are carried out with the methodology of quantum functional sensitivity analysis (QFSA).

Brown, N.J. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01

366

Apparatus for photocatalytic destruction of internal combustion engine emissions during cold start  

DOEpatents

A method and apparatus for the destruction of emissions from an internal combustion engine wherein a substrate coated with TiO.sub.2 is exposed to a light source in the exhaust system of an internal combustion engine thereby catalyzing oxidation/reduction reactions between gaseous hydrocarbons, carbon monoxide, nitrogen oxides and oxygen in the exhaust of the internal combustion engine.

Janata, Jiri (Richland, WA); McVay, Gary L. (Richland, WA); Peden, Charles H. (West Richland, WA); Exarhos, Gregory J. (Richland, WA)

1998-01-01

367

Apparatus for photocatalytic destruction of internal combustion engine emissions during cold start  

Microsoft Academic Search

A method and apparatus are disclosed for the destruction of emissions from an internal combustion engine wherein a substrate coated with TiOâ is exposed to a light source in the exhaust system of an internal combustion engine thereby catalyzing oxidation\\/reduction reactions between gaseous hydrocarbons, carbon monoxide, nitrogen oxides and oxygen in the exhaust of the internal combustion engine. 4 figs.

J. Janata; G. L. McVay; C. H. Peden; G. J. Exarhos

1998-01-01

368

Apparatus for photocatalytic destruction of internal combustion engine emissions during cold start  

Microsoft Academic Search

A method and apparatus for the destruction of emissions from an internal combustion engine wherein a substrate coated with TiO.sub.2 is exposed to a light source in the exhaust system of an internal combustion engine thereby catalyzing oxidation\\/reduction reactions between gaseous hydrocarbons, carbon monoxide, nitrogen oxides and oxygen in the exhaust of the internal combustion engine.

Jiri Janata; Gary L. McVay; Charles H. Peden; Gregory J. Exarhos

1998-01-01

369

A study of thermodynamic cycle and system configurations of hydrogen combustion turbines  

Microsoft Academic Search

A hydrogen combustion turbine is powered by steam generated from the internal combustion of hydrogen as a fuel mixed with stoichiometric oxygen. As it is possible to use a closed cycle system, benefits in cycle efficiency and a reduction of environmental pollution effects.Three different closed hydrogen combustion turbine cycles are evaluated. These are the Bottoming reheat cycle (A), the Topping

H. Sugisita; H. Mori; K. Uematsu

1998-01-01

370

High Selectivity Oxygen Delignification  

SciTech Connect

Project Objective: The objectives of this project are as follows: (1) Examine the physical and chemical characteristics of a partner mill pre- and post-oxygen delignified pulp and compare them to lab generated oxygen delignified pulps; (2) Apply the chemical selectivity enhancement system to the partner pre-oxygen delignified pulps under mill conditions (with and without any predetermined amounts of carryover) to determine how efficiently viscosity is preserved, how well selectivity is enhanced, if strength is improved, measure any yield differences and/or bleachability differences; and (3) Initiate a mill scale oxygen delignification run using the selectivity enhancement agent, collect the mill data, analyze it, and propose any future plans for implementation.

Lucian A. Lucia

2005-11-15

371

The Combustion of Methane at High Temperatures  

Microsoft Academic Search

The combustion at about 1000 degrees C of methane\\/air mixtures containing up to 5% of methane has been studied using a flow system. Under such conditions the reaction takes place in a few milliseconds. It is little influenced by surface, is retarded by methane and accelerated by oxygen. Below 500 to 600 degrees C there appears to be a change

J. H. Burgoyne; H. Hirsch

1954-01-01

372

Enhanced visible-light activity of F-N co-doped TiO2 nanocrystals via nonmetal impurity, Ti3+ ions and oxygen vacancies  

NASA Astrophysics Data System (ADS)

A visible light active F-N co-doped TiO2 photocatalysts with varying molar ratio of TiO2/NH4F were successfully prepared using an effective yet simple ethanol-water solvothermal method. The photocatalytic activities of the prepared catalysts were tested for the degradation of methylene blue (MB) under visible light irradiation. Superior photocatalytic activity relative to that of undoped TiO2 was observed on the F-N co-doped catalyst with TiO2:NH4F molar ratio of 1.0. Based on the characterization results including FT-IR, XRD, Raman analysis, UV-vis DRS, XPS and ESR, the F and N dopants were effectively incorporated into the anatase TiO2 lattice, and resulted in a decrease in the energy gap, especially for the TONF-2 sample, which shows two optical absorption edge at 2.32 eV and 2.99 eV, respectively. The ESR data showed that the presence of fluorine and nitrogen in the lattice induces the formation of reduced Ti3+ centers and oxygen vacancies. In addition, the surface O2rad - radicals were also detected by ESR analysis, which together with rad OH radicals are responsible for the MB solution decoloration under visible light. According to the experimental results, it is believed that the enhanced visible light activity arises from the synergistic effect of F-N co-doping, the presence of Ti3+ centers and oxygen vacancies, and thus possible mechanism for both visible light absorption and charge separation were proposed.

Yang, Guidong; Wang, Ting; Yang, Bolun; Yan, Zifeng; Ding, Shujiang; Xiao, Tiancun

2013-12-01

373

Multi-component nanoporous platinum-ruthenium-copper-osmium-iridium alloy with enhanced electrocatalytic activity towards methanol oxidation and oxygen reduction  

NASA Astrophysics Data System (ADS)

Multi-component nanoporous platinum-ruthenium-copper-osmium-iridium (np-PtRuCuOsIr) electrocatalyst has been facilely fabricated by chemical dealloying of mechanically alloyed AlCuPtRuOsIr precursor. The np-PtRuCuOsIr catalyst exhibits a typical three-dimensional bi-continuous interpenetrating ligament/channel structure with a length scale of ?2.5 nm. The np-PtRuCuOsIr catalyst reaches a higher level in the mass activity (857.5 mA mgPt-1) and specific activity (3.0 mA cm-2) towards methanol oxidation compared to the commercial PtC catalyst (229.5 mA mgPt-1 and 0.5 mA cm-2 respectively). Moreover, the CO stripping peak of np-PtRuCuOsIr is 0.54 V (vs. SCE), 130 mV negative shift in comparison with the commercial PtC (0.67 V vs. SCE). The half-wave potential of np-PtRuCuOsIr is 0.900 V vs. RHE, 36 mV positive compared with that of the commercial PtC (0.864 V vs. RHE). The np-PtRuCuOsIr catalyst also shows 1.8 and 3.8 times enhancement in the mass and specific activity towards oxygen reduction than the commercial PtC. Moreover, the np-PtRuCuOsIr alloy exhibits superior oxygen reduction activities even after 15 K cycles, indicating its excellent long-term stability. The present np-PtRuCuOsIr can act as a promising candidate for the electrocatalyst in direct methanol fuel cells (DMFCs).

Chen, Xiaoting; Si, Conghui; Gao, Yulai; Frenzel, Jan; Sun, Junzhe; Eggeler, Gunther; Zhang, Zhonghua

2015-01-01

374

Comparison of photoacoustically derived hemoglobin and oxygenation measurements with contrast-enhanced ultrasound estimated vascularity and immunohistochemical staining in a breast cancer model.  

PubMed

In this preliminary study, we compared two noninvasive techniques for imaging intratumoral physiological conditions to immunohistochemical staining in a murine breast cancer model. MDA-MB-231 tumors were implanted in the mammary pad of 11 nude rats. Ultrasound and photoacoustic (PA) scanning were performed using a Vevo 2100 scanner (Visualsonics, Toronto, Canada). Contrast-enhanced ultrasound (CEUS) was used to create maximum intensity projections as a measure of tumor vascularity. PAs were used to determine total hemoglobin signal (HbT), oxygenation levels in detected blood (SO2 Avg), and oxygenation levels over the entire tumor area (SO2 Tot). Tumors were then stained for vascular endothelial growth factor (VEGF), cyclooxygenase-2 (Cox-2), and the platelet endothelial cell adhesion molecule CD31. Correlations between findings were analyzed using Pearson's coefficient. Significant correlation was observed between CEUS-derived vascularity measurements and both PA indicators of blood volume (r = 0.49 for HbT, r = 0.50 for SO2 Tot). Cox-2 showed significant negative correlation with SO2 Avg (r = -0.49, p = 0.020) and SO2 Tot (r = -0.43, p = 0.047), while CD31 showed significant negative correlation with CEUS-derived vascularity (r = -0.47, p = 0.036). However, no significant correlation was observed between VEGF expression and any imaging modality (p > 0.08). Photoacoustically derived HbT and SO2 Tot may be a good indicator of tumor fractional vascularity. While CEUS correlates with CD31 expression, photoacoustically derived SO2 Avg appears to be a better predictor of Cox-2 expression. PMID:24652195

Eisenbrey, John R; Merton, Daniel A; Marshall, Andrew; Liu, Ji-Bin; Fox, Traci B; Sridharan, Anush; Forsberg, Flemming

2015-01-01

375

Combustion Fundamentals Research  

NASA Technical Reports Server (NTRS)

Increased emphasis is placed on fundamental and generic research at Lewis Research Center with less systems development efforts. This is especially true in combustion research, where the study of combustion fundamentals has grown significantly in order to better address the perceived long term technical needs of the aerospace industry. The main thrusts for this combustion fundamentals program area are as follows: analytical models of combustion processes, model verification experiments, fundamental combustion experiments, and advanced numeric techniques.

1983-01-01

376

Particle behavior and char burnout mechanisms under pressurized combustion conditions  

SciTech Connect

Combined cycle systems with coal-fired gas turbines promise highest cycle efficiencies for this fuel. Pressurized pulverized coal combustion, in particular, yields high cycle efficiencies due to the high flue gas temperatures possible. The main problem, however, is to ensure a flue gas clean enough to meet the high gas turbine standards with a dirty fuel like coal. On the one hand, a profound knowledge of the basic chemical and physical processes during fuel conversion under elevated pressures is required whereas on the other hand suitable hot gas cleaning systems need to be developed. The objective of this work was to provide experimental data to enable a detailed description of pressurized coal combustion processes. A series of experiments were performed with two German hvb coals, Ensdorf and Goettelborn, and one German brown coal, Garzweiler, using a semi-technical scale pressurized entrained flow reactor. The parameters varied in the experiments were pressure, gas temperature and bulk gas oxygen concentration. A two-color pyrometer was used for in-situ determination of particle surface temperatures and particle sizes. Flue gas composition was measured and solid residue samples taken and subsequently analyzed. The char burnout reaction rates were determinated varying the parameters pressure, gas temperature and initial oxygen concentration. Variation of residence time was achieved by taking the samples at different points along the reaction zone. The most influential parameters on char burnout reaction rates were found to be oxygen partial pressure and fuel volatile content. With increasing pressure the burn-out reactions are accelerated and are mostly controlled by product desorption and pore diffusion being the limiting processes. The char burnout process is enhanced by a higher fuel volatile content.

Bauer, C.M.; Spliethoff, H.; Hein, K.R.G.

1999-07-01

377

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

378

Application of pulse combustion to solid and hazardous-waste incineration  

SciTech Connect

The paper discusses the application of pulse combustion to solid and hazardous waste incineration. A rotary kiln incinerator simulator was retrofitted with a frequency-tunable pulse combustor to enhance the efficiency of combustion. The pulse combustor excites pulsations in the kiln and increases the completeness of combustion by promoting better mixing within the system. Tests were performed using toluene sorbed onto a ground corn cob sorbent and placed in cardboard containers. The burner was operated in a non-pulse mode as a baseline condition, and then in a pulse mode in which the frequency of the pulse combustor was adjusted to the natural frequency of the combustion chamber, creating resonant pulsations of large magnitude. The test was also performed using polyethylene tube bundles to simulate a solid waste and to investigate a surrogate which produces different puff characteristics. The addition of turbulence in the rotary kiln due to high amplitude acoustic pulsations has a strong tendency to reduce the amount of soot and/or semivolatile and non-volatile hydrocarbons. Mass emissions of soot were consistently reduced in all tests. Carbon monoxide increased during acoustic pulsations in the toluene tests. The paper also discusses unsatisfied oxygen demand and carbon penetration and how pulsations affect them.

Stewart, C.R.; Lemieux, P.M.; Zinn, B.T.

1991-01-01

379

Iron deficiency leads to inhibition of oxygen transfer and enhanced formation of virulence factors in cultures of Pseudomonas aeruginosa PAO1  

Microsoft Academic Search

growth media with varied iron concentrations. In a computer-controlled bioreactor cultivation system for controlled dissolved oxygen tension (pO2), a strong correlation between the exhaustion of iron and the onset of oxygen limitation was observed. The oxygen transfer rate of the culture, characterized by the volumetric oxygen transfer coefficient, kLa, significantly decreased under iron-limited conditions. The formation of alginate and capsule

Eun-Jin Kim; Wael Sabra; An-Ping Zeng

2003-01-01

380

Combustion Characteristics of a Swirling LOX Type Hybrid Rocket Engine  

NASA Astrophysics Data System (ADS)

We have proposed a swirling oxidizer type hybrid rocket engine. In this paper, liquid oxygen (LOX) was used as oxidizer. Combustion tests of a hybrid rocket engine with a swirling LOX flow were conducted by changing the swirl strength. Ignition was rapid and reliable, and combustion of PMMA with swirling LOX was stable. Fuel regression rates, C* efficiency and specific impulse of the hybrid rocket engine with swirling LOX flow were smaller than those with swirling gaseous oxygen (GOX). This low performance may be restraint of atomization and vaporization of LOX by formation of a liquid layer on the PMMA fuel and a decline of angular momentum of the swirling LOX during vaporization. Combustion oscillation occurred when the ratios of differential pressure between injector pressure and chamber pressure to chamber pressure were small. This combustion oscillation was confirmed to be a “Chugging” mode due to combustion time lag of LOX.

Kitagawa, Koki; Yuasa, Saburo

381

Coal combustion by wet oxidation  

SciTech Connect

The combustion of coal by wet oxidation was studied by the Center for Waste Management Programs, of Michigan Technological University. In wet oxidation a combustible material, such as coal, is reacted with oxygen in the presence of liquid water. The reaction is typically carried out in the range of 204/sup 0/C (400/sup 0/F) to 353/sup 0/C (650/sup 0/F) with sufficient pressure to maintain the water present in the liquid state, and provide the partial pressure of oxygen in the gas phase necessary to carry out the reaction. Experimental studies to explore the key reaction parameters of temperature, time, oxidant, catalyst, coal type, and mesh size were conducted by running batch tests in a one-gallon stirred autoclave. The factors exhibiting the greatest effect on the extent of reaction were temperature and residence time. The effect of temperature was studied from 204/sup 0/C (400/sup 0/F) to 260/sup 0/C (500/sup 0/F) with a residence time from 600 to 3600 seconds. From this data, the reaction activation energy of 2.7 x 10/sup 4/ calories per mole was determined for a high-volatile-A-Bituminous type coal. The reaction rate constant may be determined at any temperature from the activation energy using the Arrhenius equation. Additional data were generated on the effect of mesh size and different coal types. A sample of peat was also tested. Two catalysts were evaluated, and their effects on reaction rate presented in the report. In addition to the high temperature combustion, low temperature desulfurization is discussed. Desulfurization can improve low grade coal to be used in conventional combustion methods. It was found that 90% of the sulfur can be removed from the coal by wet oxidation with the carbon untouched. Further desulfurization studies are indicated.

Bettinger, J.A.; Lamparter, R.A.; McDowell, D.C.

1980-11-15

382

Buoyancy and Pressure Effects on Bulk Metal-Oxygen Reactions  

NASA Technical Reports Server (NTRS)

The combustion behavior of metal-oxygen reactions if a weakly buoyant environment is studied to understand the rate-controlling mechanisms in the homogeneous and heterogeneous combustion of bulk metals. Cylindrical titanium and magnesium specimens are ignited in pure-oxygen at pressures ranging from 0.1 to 4.0 atm. Reduced gravity is obtained from an aircraft flying parabolic trajectories. A weakly buoyant environment is generated at low pressures under normal gravity and also at 1 atm under reduced gravity (0.01g). The similarity between these two experimental conditions comes from the p(exp 2)g buoyancy scale extracted from the Grashof number. Lower propagation rates of the molten interface on titanium samples are found at progressively lower pressures at 1 g. These rates are compared to theoretical results from heat conduction analyses with a diffusion/convection controlled reaction. The close agreement found between experimental and theoretical values indicate the importance values indicate the importance of natural convection enhanced oxygen transport on combustion rates. For magnesium, progressively longer burning times are experienced at lower pressures and 1 g. Under reduced gravity conditions at 1 atm, a burning time twice as long as in 1 g is exhibited. However, in this case, the validity of the p(exp 2)g buoyancy scale remains untested due to the inability to obtain steady gas-phase burning of the magnesium sample at 0.1 atm. Nevertheless, longer burning times and larger flame standoff distance at low pressures and at low gravity points to a diffusion/convection controlled reaction.

Abbud-Madrid, A.; McKnight, C.; Branch, M. C.; Daily, J. W.; Friedman, R. (Technical Monitor)

1998-01-01

383

Wogonin-enhanced reactive oxygen species-induced apoptosis and potentiated cytotoxic effects of chemotherapeutic agents by suppression Nrf2-mediated signaling in HepG2 cells.  

PubMed

Cancer cells, compared with normal cells, are under increased oxidative stress with higher level of reactive oxygen species (ROS). When exposed to environmental stresses such as ROS, NFE-related factor 2 (Nrf2) is the key to antioxidant response by transcriptionally activating various detoxification and antioxidant enzymes. Previously, we have shown that wogonin, a flavonoid isolated from the root of Scutellaria baicalensis Georgi, could reverse drug resistance in MCF-7/DOX cells by blocking the translocation of Nrf2 into nucleus. However, the exact mechanism underlying the effect remains unclear. In this study, we observed that wogonin reduced the Nrf2 nuclear translocation, and therefore elevated the level of intracellular ROS to accomplish the purpose of killing malignant cells. Furthermore, the suppression of Nrf2 by wogonin can potentiate cytotoxic effects of chemotherapeutic agents in HepG2 cells. On one hand, down-regulation of Nrf2 lead to reduction of cytoprotective effect by inducing phage II enzymes which sensitize cells to chemotherapeutic agents. On the other hand, inhibition of multidrug resistance-associated proteins (MRPs) by wogonin enhances the effective drug level in cancer cells and potentiates their chemotherapeutic effects. Finally, we found that the decrease of Nrf2 may be related to overexpression of p53. Using p53 siRNA to knock down the endogenous p53 expression, the levels of both c-myc and Nrf2 in nucleus increased when exposed to wogonin. The present study indicates that wogonin can be used in chemotherapy not only because of its own antitumor ability, but also due to the enhanced cytotoxic effects of chemotherapeutic agents. PMID:24666416

Qian, C; Wang, Y; Zhong, Y; Tang, J; Zhang, J; Li, Z; Wang, Q; Hu, R

2014-05-01

384

Overexpression of copper/zinc superoxide dismutase from mangrove Kandelia candel in tobacco enhances salinity tolerance by the reduction of reactive oxygen species in chloroplast  

PubMed Central

Na+ uptake and transport in Kandelia candel and antioxidative defense were investigated under rising NaCl stress from 100 to 300 mM. Salinized K. candel roots had a net Na+ efflux with a declined flux rate during an extended NaCl exposure. Na+ buildup in leaves enhanced H2O2 levels, superoxide dismutase (SOD) activity, and increased transcription of CSD gene encoding a Cu/Zn SOD. Sequence and subcellular localization analyses have revealed that KcCSD is a typical Cu/Zn SOD in chloroplast. The transgenic tobacco experimental system was used as a functional genetics model to test the effect of KcCSD on salinity tolerance. KcCSD-transgenic lines were more Na+ tolerant than wild-type (WT) tobacco in terms of lipid peroxidation, root growth, and survival rate. In the latter, 100 mM NaCl led to a remarkable reduction in chlorophyll content and a/b ratio, decreased maximal chlorophyll a fluorescence, and photochemical efficiency of photosystem II. NaCl stress in WT resulted from H2O2 burst in chloroplast. Na+ injury to chloroplast was less pronounced in KcCSD-transgenic plants due to upregulated antioxidant defense. KcCSD-transgenic tobacco enhanced SOD activity by an increment in SOD isoenzymes under 100 mM NaCl stress from 24 h to 7 day. Catalase activity rose in KcCSD overexpressing tobacco plants. KcCSD-transgenic plants better scavenged NaCl-elicited reactive oxygen species (ROS) compared to WT ones. In conclusion, K. candel effectively excluded Na+ in roots during a short exposure; and increased CSD expression to reduce ROS in chloroplast in a long-term and high saline environment. PMID:25657655

Jing, Xiaoshu; Hou, Peichen; Lu, Yanjun; Deng, Shurong; Li, Niya; Zhao, Rui; Sun, Jian; Wang, Yang; Han, Yansha; Lang, Tao; Ding, Mingquan; Shen, Xin; Chen, Shaoliang

2015-01-01

385

Overexpression of copper/zinc superoxide dismutase from mangrove Kandelia candel in tobacco enhances salinity tolerance by the reduction of reactive oxygen species in chloroplast.  

PubMed

Na(+) uptake and transport in Kandelia candel and antioxidative defense were investigated under rising NaCl stress from 100 to 300 mM. Salinized K. candel roots had a net Na(+) efflux with a declined flux rate during an extended NaCl exposure. Na(+) buildup in leaves enhanced H2O2 levels, superoxide dismutase (SOD) activity, and increased transcription of CSD gene encoding a Cu/Zn SOD. Sequence and subcellular localization analyses have revealed that KcCSD is a typical Cu/Zn SOD in chloroplast. The transgenic tobacco experimental system was used as a functional genetics model to test the effect of KcCSD on salinity tolerance. KcCSD-transgenic lines were more Na(+) tolerant than wild-type (WT) tobacco in terms of lipid peroxidation, root growth, and survival rate. In the latter, 100 mM NaCl led to a remarkable reduction in chlorophyll content and a/b ratio, decreased maximal chlorophyll a fluorescence, and photochemical efficiency of photosystem II. NaCl stress in WT resulted from H2O2 burst in chloroplast. Na(+) injury to chloroplast was less pronounced in KcCSD-transgenic plants due to upregulated antioxidant defense. KcCSD-transgenic tobacco enhanced SOD activity by an increment in SOD isoenzymes under 100 mM NaCl stress from 24 h to 7 day. Catalase activity rose in KcCSD overexpressing tobacco plants. KcCSD-transgenic plants better scavenged NaCl-elicited reactive oxygen species (ROS) compared to WT ones. In conclusion, K. candel effectively excluded Na(+) in roots during a short exposure; and increased CSD expression to reduce ROS in chloroplast in a long-term and high saline environment. PMID:25657655

Jing, Xiaoshu; Hou, Peichen; Lu, Yanjun; Deng, Shurong; Li, Niya; Zhao, Rui; Sun, Jian; Wang, Yang; Han, Yansha; Lang, Tao; Ding, Mingquan; Shen, Xin; Chen, Shaoliang

2015-01-01

386

Gravity Effects on Combustion Synthesis of Glasses  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

387

Exhaust gas purifying device for internal combustion engine  

Microsoft Academic Search

An oxygen sensor is disposed upstream of a three-way catalyst in an exhaust system of an internal combustion engine and includes a sensing element of metal oxide whose electromotive force or resistance value varies in response to the concentration of oxygen in the engine exhaust gases. A catalytic body including a catalytic metal material exhibiting the same catalytic performance as

M. Asano; K. Kondo; Y. Segawa

1981-01-01

388

Synthesis of octopus-tentacle-like Cu nanowire-Ag nanocrystals heterostructures and their enhanced electrocatalytic performance for oxygen reduction reaction.  

PubMed

In this article, the novel octopus-tentacle-like Cu nanowire-Ag nanocrystals heterostructures have been fabricated in solution phase via heterogeneous nucleation and growth of Ag nanocrystals on presynthesized Cu nanowires. The growth environment and dynamic factors of Ag nanocrystals play an important role for formation of such heterostructures. Combined the physical constants of Cu and Ag with a series of control experiments, the epitaxial growth means of Ag nanocrystals on Cu nanowire is found to abide by "layer-plus-island" (Stranski-Krastanow) mode. Because of the presence of multiple junctions and strong synergistic effect of their constituents, the obtained heterostructures exhibit greatly enhanced electrocatalytic performance toward oxygen reduction reaction compared with that of pure Ag nanocrystals, Cu nanowires, and mechanically mixed dual components as well as recently reported some non-Pt materials, which can be served as an alternative cathodic electrocatalyst to apply in alkaline fuel cells. Moreover, our method can be extended to fabricate octopus-tentacle-like Cu nanowire-Au nanocrystals and Cu nanowire-Pd nanocrystals heterostructures. PMID:23157177

Han, Min; Liu, Suli; Zhang, Linyan; Zhang, Can; Tu, Wenwen; Dai, Zhihui; Bao, Jianchun

2012-12-01

389

Photoinduced enhancement of the c-axis conductivity in oxygen-deficient YBa{sub 2}Cu{sub 3}O{sub x} thin films  

SciTech Connect

High quality thin films of oxygen-depleted YBa{sub 2}Cu{sub 3}O{sub x} (x{approx}6.6) were prepared by pulsed-laser deposition on SrTiO{sub 3}, substrates that were cut with tilt angles of 10{degree} and 20{degree} with respect to the [001] direction, resulting in a steplike growth of the layers. The resistance showed a semiconducting behavior along the projection of the c axis to the film surface, but a metallic behavior in the perpendicular direction, indicating that the former is dominated by the c-axis resistivity and the latter by the ab-plane resistivity of YBa{sub 2}Cu{sub 3}O{sub x}. Long-term illumination of the samples with a 100 W halogen lamp resulted in a significant conductivity enhancement in both directions. The photoinduced change of the out-of-plane resistance vs temperature characteristics is comparable to the effect of large hydrostatic pressure, introducing structural changes similar to that of photoexcitation. {copyright} {ital 1997 American Institute of Physics.}

Markowitsch, W.; Stockinger, C.; Lang, W. [Ludwig Boltzmann Institut fuer Festkoerperphysik, A-1060 Wien (Austria)] [Ludwig Boltzmann Institut fuer Festkoerperphysik, A-1060 Wien (Austria); [and Institut fuer Materialphysik der Universitaet Wien, A-1090 Wien (Austria); Bierleutgeb, K.; Pedarnig, J.D.; Baeuerle, D. [Angewandte Physik, Johannes-Kepler-Universitaet Linz, A-4040 Linz (Austria)] [Angewandte Physik, Johannes-Kepler-Universitaet Linz, A-4040 Linz (Austria)

1997-09-01

390

Maize ABP9 enhances tolerance to multiple stresses in transgenic Arabidopsis by modulating ABA signaling and cellular levels of reactive oxygen species.  

PubMed

The phytohormone abscisic acid (ABA) and reactive oxygen species (ROS) play critical roles in mediating abiotic stress responses in plants. It is well known that ABA is involved in the modulation of ROS levels by regulating ROS-producing and ROS-scavenging genes, but the molecular mechanisms underlying this regulation are poorly understood. Here we show that the expression of maize ABP9 gene, which encodes a bZIP transcription factor capable of binding to the ABRE2 motif in the maize Cat1 promoter, is induced by ABA, H(2)O(2), drought and salt. Constitutive expression of ABP9 in transgenic Arabidopsis leads to remarkably enhanced tolerance to multiple stresses including drought, high salt, freezing temperature and oxidative stresses. ABP9 expressing Arabidopsis plants also exhibit increased sensitivity to exogenously applied ABA during seed germination, root growth and stomatal closure and improved water-conserving capacity. Moreover, constitutive expression of ABP9 causes reduced cellular levels of ROS, alleviated oxidative damage and reduced cell death, accompanied by elevated expression of many stress/ABA responsive genes including those for scavenging and regulating ROS. Taken together, these results suggest that ABP9 may play a pivotal role in plant tolerance to abiotic stresses by fine tuning ABA signaling and control of ROS accumulation. PMID:21327835

Zhang, Xia; Wang, Lei; Meng, Hui; Wen, Hongtao; Fan, Yunliu; Zhao, Jun

2011-03-01

391

Field-scale investigation of enhanced petroleum hydrocarbon biodegradation in the vadose zone combining soil venting as an oxygen source with moisture and nutrient addition. Doctoral thesis  

SciTech Connect

Soil venting is effective for the physical removal of volatile hydrocarbons from unsaturated soils, and is also effective as a source of oxygen for biological degradation of the volatile and non-volatile fractions of hydrocarbons in contaminated soil. Treatment of soil venting off-gas is expensive, constituting a minimum of 50% of soil venting remediation costs. In this research, methods for enhancing biodegradation through soil venting were investigated, with the goal of eliminating the need for expensive off-gas treatment. A seven-month field investigation was conducted at Tyndall Air Force Base (AFB), Florida, where past jet fuel storage had resulted in contamination of a sandy soil. The contaminated area was dewatered to maintain approximately 1.6 meters of unsaturated soil. Soil hydrocarbon concentrations ranged from 30 to 23,000 mg/kg. Contaminated and uncontaminated test plots were vented for 188 days. Venting was interrupted five times during operation to allow for measurement of biological activity (CO{sub 2} production and O{sub 2} consumption) under varying moisture and nutrient conditions.

Miller, R.N.

1990-01-01

392

Sol-flame synthesis of cobalt-doped TiO2 nanowires with enhanced electrocatalytic activity for oxygen evolution reaction.  

PubMed

Doping nanowires (NWs) is of crucial importance for a range of applications due to the unique properties arising from both impurities' incorporation and nanoscale dimensions. However, existing doping methods face the challenge of simultaneous control over the morphology, crystallinity, dopant distribution and concentration at the nanometer scale. Here, we present a controllable and reliable method, which combines versatile solution phase chemistry and rapid flame annealing process (sol-flame), to dope TiO2 NWs with cobalt (Co). The sol-flame doping method not only preserves the morphology and crystallinity of the TiO2 NWs, but also allows fine control over the Co dopant profile by varying the concentration of Co precursor solution. Characterizations of the TiO2:Co NWs show that Co dopants exhibit 2+ oxidation state and substitutionally occupy Ti sites in the TiO2 lattice. The Co dopant concentration significantly affects the oxygen evolution reaction (OER) activity of TiO2:Co NWs, and the TiO2:Co NWs with 12 at% of Co on the surface show the highest OER activity with a 0.76 V reduction of the overpotential with respect to undoped TiO2 NWs. This enhancement of OER activity for TiO2:Co NWs is attributed to both improved surface charge transfer kinetics and increased bulk conductivity. PMID:24820239

Cai, Lili; Cho, In Sun; Logar, Manca; Mehta, Apurva; He, Jiajun; Lee, Chi Hwan; Rao, Pratap M; Feng, Yunzhe; Wilcox, Jennifer; Prinz, Fritz B; Zheng, Xiaolin

2014-06-28

393

Combustion 2000  

SciTech Connect

This report is a presentation of work carried out on Phase II of the HIPPS program under DOE contract DE-AC22-95PC95144 from June 1995 to March 2001. The objective of this report is to emphasize the results and achievements of the program and not to archive every detail of the past six years of effort. These details are already available in the twenty-two quarterly reports previously submitted to DOE and in the final report from Phase I. The report is divided into three major foci, indicative of the three operational groupings of the program as it evolved, was restructured, or overtaken by events. In each of these areas, the results exceeded DOE goals and expectations. HIPPS Systems and Cycles (including thermodynamic cycles, power cycle alternatives, baseline plant costs and new opportunities) HITAF Components and Designs (including design of heat exchangers, materials, ash management and combustor design) Testing Program for Radiative and Convective Air Heaters (including the design and construction of the test furnace and the results of the tests) There are several topics that were part of the original program but whose importance was diminished when the contract was significantly modified. The elimination of the subsystem testing and the Phase III demonstration lessened the relevance of subtasks related to these efforts. For example, the cross flow mixing study, the CFD modeling of the convective air heater and the power island analysis are important to a commercial plant design but not to the R&D product contained in this report. These topics are of course, discussed in the quarterly reports under this contract. The DOE goal for the High Performance Power Plant System ( HIPPS ) is high thermodynamic efficiency and significantly reduced emissions. Specifically, the goal is a 300 MWe plant with > 47% (HHV) overall efficiency and {le} 0.1 NSPS emissions. This plant must fire at least 65% coal with the balance being made up by a premium fuel such as natural gas. To achieve these objectives requires a change from complete reliance of coal-fired systems on steam turbines (Rankine cycles) and moving forward to a combined cycle utilizing gas turbines (Brayton cycles) which offer the possibility of significantly greater efficiency. This is because gas turbine cycles operate at temperatures well beyond current steam cycles, allowing the working fluid (air) temperature to more closely approach that of the major energy source, the combustion of coal. In fact, a good figure of merit for a HIPPS design is just how much of the enthalpy from coal combustion is used by the gas turbine. The efficiency of a power cycle varies directly with the temperature of the working fluid and for contemporary gas turbines the optimal turbine inlet temperature is in the range of 2300-2500 F (1260-1371 C). These temperatures are beyond the working range of currently available alloys and are also in the range of the ash fusion temperature of most coals. These two sets of physical properties combine to produce the major engineering challenges for a HIPPS design. The UTRC team developed a design hierarchy to impose more rigor in our approach. Once the size of the plant had been determined by the choice of gas turbine and the matching steam turbine, the design process of the High Temperature Advanced Furnace (HITAF) moved ineluctably to a down-fired, slagging configuration. This design was based on two air heaters: one a high temperature slagging Radiative Air Heater (RAH) and a lower temperature, dry ash Convective Air Heater (CAH). The specific details of the air heaters are arrived at by an iterative sequence in the following order:-Starting from the overall Cycle requirements which set the limits for the combustion and heat transfer analysis-The available enthalpy determined the range of materials, ceramics or alloys, which could tolerate the temperatures-Structural Analysis of the designs proved to be the major limitation-Finally the commercialization issues of fabrication and reliability, availability and maintenance. The program that has s

A. Levasseur; S. Goodstine; J. Ruby; M. Nawaz; C. Senior; F. Robson; S. Lehman; W. Blecher; W. Fugard; A. Rao; A. Sarofim; P. Smith; D. Pershing; E. Eddings; M. Cremer; J. Hurley; G. Weber; M. Jones; M. Collings; D. Hajicek; A. Henderson; P. Klevan; D. Seery; B. Knight; R. Lessard; J. Sangiovanni; A. Dennis; C. Bird; W. Sutton; N. Bornstein; F. Cogswell; C. Randino; S. Gale; Mike Heap

2001-06-30

394

Chemical Kinetic Models for HCCI and Diesel Combustion  

SciTech Connect

Hydrocarbon fuels for advanced combustion engines consist of complex mixtures of hundreds or even thousands of different components. These components can be grouped into a number of chemically distinct classes, consisting of n-paraffins, branched paraffins, cyclic paraffins, olefins, oxygenates, and aromatics. Biodiesel contains its own unique chemical class called methyl esters. The fractional amounts of these chemical classes are quite different in gasoline, diesel fuel, oil-sand derived fuels and bio-derived fuels, which contributes to the very different combustion characteristics of each of these types of combustion systems. The objectives of this project are: (1) Develop detailed chemical kinetic models for fuel components used in surrogate fuels for diesel and HCCI engines; (2) Develop surrogate fuel models to represent real fuels and model low temperature combustion strategies in HCCI and diesel engines that lead to low emissions and high efficiency; and (3) Characterize the role of fuel composition on low temperature combustion modes of advanced combustion engines.

Pitz, W J; Westbook, C K; Mehl, M

2008-10-30

395

HYDROGEN-OXYGEN ROCKETS  

NSDL National Science Digital Library

During this activity students build a plastic pipette rocket. The first concept will to learn how igniting varying mixtures of hydrogen and oxygen will affect how far the rocket will fly. Second students will observe and manipulate variables to better understand the fundamental chemistry concepts: principles of combustion reactions, kinetics, stoichiometry, gas mixtures, rocketry, and different types of chemical reactions. Finally, students will assess their own understanding of these chemistry concepts by investigating how NASA scientists launch real rockets into space. One follow-up activity would be to investigate and collect data on a launching a heavier object at the school football field.

Reierson, David

396

Combustion 2000  

SciTech Connect

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

None

1999-12-31

397

Fundamentals of Gas Turbine combustion  

NASA Technical Reports Server (NTRS)

Combustion problems and research recommendations are discussed in the areas of atomization and vaporization, combustion chemistry, combustion dynamics, and combustion modelling. The recommendations considered of highest priority in these areas are presented.

Gerstein, M.

1979-01-01

398

Ignition and combustion of metallized propellants  

NASA Technical Reports Server (NTRS)

An experimental program was conducted to investigate the ignition and combustion properties of a gelled, metallized fuel, A1/JP20, burned with gaseous oxygen, and to compare the results to the ignition and combustion properties of neat RP1. Both a Cstar efficiency and a specific impulse efficiency were calculated by comparing experimental values with those from a one-dimensional chemical equilibrium computer code. For most operating conditions, the efficiencies of the A1/JP10 were only 2 to 6 percent less than those of the neat RP1.

Galecki, Diane L.

1989-01-01

399

Combustion Modeling in Internal Combustion Engines  

Microsoft Academic Search

The fundamental assumptions of the Blizard and Keck combustion model for internal combustion engines are examined and a generalization of that model is derived. The most significant feature of the model is that it permits the occurrence of unburned hydrocarbons in the thermodynamic-kinetic modeling of exhaust gases. The general formulas are evaluated in two specific cases that are likely to

FRANK J. ZELEZNIK

1976-01-01

400

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

401

BOOK REVIEW: Turbulent Combustion  

Microsoft Academic Search

The book Turbulent Combustion by Norbert Peters is a concise monograph on single-phase gaseous low Mach number turbulent combustion. It is compiled from the author's review papers on this topic plus some additional material. Norbert Peters characterizes turbulent combustion both by the way fuel and air are mixed and by the ratio of turbulent and chemical time scales. This approach

Norbert Peters

2001-01-01

402

Adiabatic internal combustion engine  

Microsoft Academic Search

An adiabatic internal combustion engine is described comprising a cylinder having a piston movably disposed therein, means for admitting air and fuel to the cylinder to be combusted therein and means for discharging the combustion gases therefrom, the cylinder including a piston guide and seal structure having stationary seal rings associated therewith and, the cylinder having an inner wall structure

C. E. Kraus; C. B. Lohr

1989-01-01

403

Internal combustion engine  

Microsoft Academic Search

An internal combustion engine is described which utilizes a combustion cylinder formed in part of material which can withstand high temperatures in conjunction with a displacement or power piston having a ringless section capable of withstanding high temperatures and being backed up by a relatively low temperature lubricated ringed piston section. Means to inject fuel and water into the combustion

Thomas

1976-01-01

404

Combustion synthesis and nanomaterials  

Microsoft Academic Search

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

Singanahally T. Aruna; Alexander S. Mukasyan

2008-01-01

405

Atmospheric Oxygen  

NSDL National Science Digital Library

In this feature, adapted from Interactive NOVA: Earth, students explore the relationship between oxygen concentration and the well-being of various organisms by simulating a change in oxygen levels and observing what happens.

Foundation, Wgbh E.

2003-09-26

406

On-Line Measurement of Heat of Combustion of Gaseous Hydrocarbon Fuel Mixtures  

NASA Technical Reports Server (NTRS)

A method for the on-line measurement of the heat of combustion of gaseous hydrocarbon fuel mixtures has been developed and tested. The method involves combustion of a test gas with a measured quantity of air to achieve a preset concentration of oxygen in the combustion products. This method involves using a controller which maintains the fuel (gas) volumetric flow rate at a level consistent with the desired oxygen concentration in the combustion products. The heat of combustion is determined form a known correlation with the fuel flow rate. An on-line computer accesses the fuel flow data and displays the heat of combustion measurement at desired time intervals. This technique appears to be especially applicable for measuring heats of combustion of hydrocarbon mixtures of unknown composition such as natural gas.

Sprinkle, Danny R.; Chaturvedi, Sushil K.; Kheireddine, Ali

1996-01-01

407

Increased Polyamine Biosynthesis Enhances Stress Tolerance by Preventing the Accumulation of Reactive Oxygen Species: T-DNA Mutational Analysis of Oryza sativa Lysine Decarboxylase-like Protein 1  

PubMed Central

A highly oxidative stress-tolerant japonica rice line was isolated by T-DNA insertion mutation followed by screening in the presence of 50 mM H2O2. The T-DNA insertion was mapped to locus Os09g0547500, the gene product of which was annotated as lysine decarboxylase-like protein (GenBank accession No. AK062595). We termed this gene OsLDC-like 1, for Oryza sativa lysine decarboxylase-like 1. The insertion site was in the second exon and resulted in a 27 amino acid N-terminal deletion. Despite this defect in OsLDC-like 1, the mutant line exhibited enhanced accumulation of the polyamines (PAs) putrescine, spermidine, and spermine under conditions of oxidative stress. The generation of reactive oxygen species (ROS) in the mutant line was assessed by qRT-PCR analysis of NADPH oxidase (RbohD and RbohF), and by DCFH-DA staining. Cellular levels of ROS in osldc-like 1 leaves were significantly lower than those in the wild-type (WT) rice after exposure to oxidative, high salt and acid stresses. Exogenously-applied PAs such as spermidine and spermine significantly inhibited the stress-induced accumulation of ROS and cell damage in WT leaves. Additionally, the activities of ROS-detoxifying enzymes were increased in the homozygous mutant line in the presence or absence of H2O2. Thus, mutation of OsLDC-like 1 conferred an oxidative stress-tolerant phenotype. These results suggest that increased cellular PA levels have a physiological role in preventing stress-induced ROS and ethylene accumulation and the resultant cell damage. PMID:22965749

Jang, Su Jin; Wi, Soo Jin; Choi, Yoo Jin; An, Gynheung; Park, Ky Young

2012-01-01

408

Increased Tumor Oxygenation and Drug Uptake During Anti-Angiogenic Weekly Low Dose Cyclophosphamide Enhances the Anti-Tumor Effect of Weekly Tirapazamine  

PubMed Central

Metronomic cyclophosphamide treatment is associated with anti-angiogenic activity and is anticipated to generate exploitable hypoxia using hypoxia-activated prodrugs. Weekly administration of tirapazamine (TPZ; 5 mg/kg body weight i.p.) failed to inhibit the growth of 9L gliosarcoma tumors grown s.c. in scid mice. However, the anti-tumor effect of weekly cyclophosphamide (CPA) treatment (140 mg/kg BW i.p.) was substantially enhanced by weekly TPZ administration. An extended tumor free period and increased frequency of tumor eradication without overt toxicity were observed when TPZ was given 3, 4 or 5 days after each weekly CPA treatment. Following the 2nd CPA injection, Electron Paramagnetic Resonance (EPR) Oximetry indicated significant increases in tumor pO2, starting at 48 hr, which further increased after the 3rd CPA injection. pO2 levels were, however, stable in growing untreated tumors. A strong negative correlation (?0.81) between tumor pO2 and tumor volume during 21 days of weekly CPA chemotherapy was observed, indicating increasing tumor pO2 with decreasing tumor volume. Furthermore, CPA treatment resulted in increased tumor uptake of activated CPA. CPA induced increases in VEGF RNA, which reached a maximum on day 1, and in PLGF RNA which was sustained throughout the treatment, while anti-angiogenic host thrombospondin-1 increased dramatically through day 7 post-CPA treatment. Weekly cyclophosphamide treatment was anticipated to generate exploitable hypoxia. However, our findings suggest that weekly CPA treatment induces a functional improvement of tumor vasculature, which is characterized by increased tumor oxygenation and drug uptake in tumors, thus counter-intuitively, benefiting intratumoral activation of TPZ and perhaps other bioreductive drugs. PMID:19754361

Doloff, J.C.; Khan, N.; Ma, J.; Demidenko, E.; Swartz, H.M.; Jounaidi, Y.

2010-01-01

409

Metabolic Agents that Enhance ATP can Improve Cognitive Functioning: A Review of the Evidence for Glucose, Oxygen, Pyruvate, Creatine, and L-Carnitine  

PubMed Central

Over the past four or five decades, there has been increasing interest in the neurochemical regulation of cognition. This field received considerable attention in the 1980s, with the identification of possible cognition enhancing agents or “smart drugs”. Even though many of the optimistic claims for some agents have proven premature, evidence suggests that several metabolic agents may prove to be effective in improving and preserving cognitive performance and may lead to better cognitive aging through the lifespan. Aging is characterized by a progressive deterioration in physiological functions and metabolic processes. There are a number of agents with the potential to improve metabolic activity. Research is now beginning to identify these various agents and delineate their potential usefulness for improving cognition in health and disease. This review provides a brief overview of the metabolic agents glucose, oxygen, pyruvate, creatine, and L-carnitine and their beneficial effects on cognitive function. These agents are directly responsible for generating ATP (adenosine triphosphate) the main cellular currency of energy. The brain is the most metabolically active organ in the body and as such is particularly vulnerable to disruption of energy resources. Therefore interventions that sustain adenosine triphosphate (ATP) levels may have importance for improving neuronal dysfunction and loss. Moreover, recently, it has been observed that environmental conditions and diet can affect transgenerational gene expression via epigenetic mechanisms. Metabolic agents might play a role in regulation of nutritional epigenetic effects. In summary, the reviewed metabolic agents represent a promising strategy for improving cognitive function and possibly slowing or preventing cognitive decline. PMID:22254121

Owen, Lauren; Sunram-Lea, Sandra I.

2011-01-01

410