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1

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

PubMed

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

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

2013-01-01

2

Chemical oxygen demand determination in environmental waters by mixed-acid digestion and single sweep polarography  

Microsoft Academic Search

A new variant of the method for chemical oxygen demand (COD; 20–1100mg O2l?1) determination in environmental waters is described. The method is based on determination of excess Cr(VI) in a mixed-acid (H3PO4–H2SO4) digestion solution by single sweep polarography instead of titrimetry; COD is measured indirectly. The reflux time is shortened to 15min by mixed-acid digestion. The effects of mixed-acid concentration,

Dezhong Dan; Fulai Dou; Dianjie Xiu; Yuanqing Qin

2000-01-01

3

Determination of Chemical Oxygen Demand in Substrates from Anaerobic Treatment of Solid Organic Waste  

Microsoft Academic Search

A modified method is described for the determination of the chemical oxygen demand (COD) of samples with high solids content,\\u000a especially those used in biogas production. The modified method is based on ISO 6060 and DIN 38414 methods. Analyses with\\u000a potassium hydrogen phthalate solution standard showed that the modified method is valid and gives equal results to standard\\u000a method (9,960 mg\\/L

Gregor D. Zupan?i?; Milenko Roš

4

A high throughput chemiluminescence method for determination of chemical oxygen demand in waters  

Microsoft Academic Search

A novel and high throughput chemiluminescence (CL) method for determination of chemical oxygen demand (COD) in water sample was originally developed based on potassium permanganate–glutaraldehyde CL system. With this method, dissolved organic matter in water samples was digested by excess acid potassium permanganate, the reacted mixture solutions containing surplus KMnO4 were added in wells of a 96-well plate, followed by

Hong Yao; Bin Wu; Haibin Qu; Yiyu Cheng

2009-01-01

5

Use of Chemical Oxygen Demand Values of Bacterial Cells in Waste-Water Purification  

PubMed Central

Four methods for determining substrate recoveries in studies concerned with the partition of substrate between sludge synthesis and respiration were investigated. An energy balance comparing chemical oxygen demand (COD) removed with the summation of oxygen uptake and the COD of the cells produced yielded average recoveries closer to 100% than any of the other three methods tested. The standard COD test was shown to yield highly reproducible values when used to determine the COD of activated sludge. Although the protein and carbohydrate content of the cells varied with cell age, a concomitant variation in cell COD was not noted.

Gaudy, A. F.; Bhatla, M. N.; Gaudy, E. T.

1964-01-01

6

Evaluation of chemical oxygen demand (COD) based on coulometric determination of electrochemical oxygen demand (EOD) using a surface oxidized copper electrode  

Microsoft Academic Search

Chemical oxygen demand (COD) was estimated by exhaustive electrolysis using a home-made cell with a copper working electrode in 0.1M NaOH. The net Faradaic charge, corresponding to the number of electrons consumed in electrolyzing (oxidizing) the organic species, was correlated to the COD evaluated by the conventional methods using dichromate or permanganate. The time taken for a single measurement was

Kyong-Hoon Lee; Tomoko Ishikawa; S. J McNiven; Yoko Nomura; Atsunori Hiratsuka; Satoshi Sasaki; Yoshiko Arikawa; Isao Karube

1999-01-01

7

Evaluation of Activated Carbon for Enhanced COD (Chemical Oxygen Demand) Removal from Pharmaceutical Wastewater. Volume 1. Final Report.  

National Technical Information Service (NTIS)

From September to December, 1984 pharmaceutical plant wastewater containing high concentrations of total chemical oxygen demand (TCOD) in the raw waste and treated effluent was treated in trailer mounted pilot plants. The biological treatment train used t...

R. Osantowski R. Wullschleger

1985-01-01

8

Evaluation of Activated Carbon for Enhanced COD (Chemical Oxygen Demand) Removal from Pharmaceutical Wastewater. Volume 2. Appendices.  

National Technical Information Service (NTIS)

From September to December, 1984 pharmaceutical plant wastewater containing high concentrations of total chemical oxygen demand (TCOD) in the raw waste and treated effluent was treated in trailer mounted pilot plants.The biological treatment train used to...

R. Osantowski R. Wullschleger

1985-01-01

9

Replacing dichromate with hydrogen peroxide in the chemical oxygen demand (COD) test.  

PubMed

The widely used standard method for chemical oxygen demand (COD) involves hazardous chromium species, and its two-hour heating protocol entails a substantial amount of energy expenditure. In the present work we report a proof of concept for a major modification of this method in the range 10-800 mgCOD/L, whereby H2O2 is proposed as a replacement oxidizer. This modification not only reduces the use of unsafe chromium species but also allows for the use of milder conditions that decrease the total energy outlay. The results are comparable with those obtained either with the standard method or with a commercial Hach® kit. PMID:22797236

Carbajal-Palacios, Patricia; Balderas-Hernández, Patricia; Ibanez, Jorge G; Roa-Morales, Gabriela

2012-01-01

10

Determination of Oxygen Demand  

NASA Astrophysics Data System (ADS)

Oxygen demand is a commonly used parameter to evaluate the potential effect of organic pollutants on either a wastewater treatment process or a receiving water body. Because microorganisms utilize these organic materials, the concentration of dissolved oxygen is greatly depleted from the water. The oxygen depletion in the environment can have a detrimental effect on fish and plant life.

Hang, Yong D.

11

Reduction of chemical oxygen demand of industrial wastes using subcritical water oxidation  

SciTech Connect

If wastes have strong toxicity, high organic content, and a deep hue, they are difficult to handle in the waste disposal. It is very practical that waste of this kind is treated by Subcritical Water Oxidation (SWO). In our work, caprolactum (CPL) waste, purged from a petrochemical plant, and dyeing waste, purged from a textile plant, were individually treated by a semi-batch SWO process. Within a one-hour treatment, Chemical Oxygen Demand (COD) reduction reached 89% for CPL waste (6.90 MPa, 260[degree]C) and 95% for dyeing waste (6.90 MPa, 240[degree]C). There is also a great improvement in hue, especially for the dyeing waste. When CPL wastewater was treated by the SWO process using a chromium metal powder as a catalyst, COD reduction improved further under the same operating conditions. A kinetic model was used to illustrate the oxidation mechanism and the effectiveness of the catalyst. The oxygen concentration in the effluent showed that oxygen consumption corresponded to COD reduction. With the monitoring of concentrations of total soluble chromium in the effluent, a suitable reaction period could be found in order to meet the standard of the Environmental Protection Agency (EPA). 12 refs., 11 figs., 2 tabs.

Lin, J.C.; Chang, C.J. (Yuan-Ze Inst. of Technology, Taoyuan (Taiwan, Province of China))

1992-10-01

12

Spatial Autocorrelation Analysis of Chinese Inter-Provincial Industrial Chemical Oxygen Demand Discharge  

PubMed Central

A spatial autocorrelation analysis method is adopted to process the spatial dynamic change of industrial Chemical Oxygen Demand (COD) discharge in China over the past 15 years. Studies show that amount and intensity of industrial COD discharges are on a decrease, and the tendency is more remarkable for discharge intensity. There are large differences between inter-provincial discharge amount and intensity, and with different spatial differentiation features. Global spatial autocorrelation analysis reveals that Global Moran’s I of discharge amount and intensity is on the decrease. In space, there is an evolution from an agglomeration pattern to a discretization pattern. Local spatial autocorrelation analysis shows that the agglomeration area of industrial COD discharge amount and intensity varies greatly in space with time. Stringent environmental regulations and increased funding for environmental protections are the crucial factors to cut down industrial COD discharge amount and intensity.

Zhao, Xiaofeng; Huang, Xianjin; Liu, Yibo

2012-01-01

13

High-sulfate, high-chemical oxygen demand wastewater treatment using aerated methanogenic fluidized beds  

SciTech Connect

Many industrial wastewaters have both high organic pollution and sulfate (SO{sub 4}{sup {minus}2}) concentrations. Although biological conversion of organics to methane may be an economical chemical oxygen demand (COD) removal option, significant inhibition of methane production results from reduction of SO{sub 4}{sup {minus}2} to hydrogen sulfide (H{sub 2}S), which is inhibitory to methanogenic microorganisms. Therefore, sulfate-containing wastewater is often not amenable to conventional anaerobic treatment. Recently, limited aeration of recycle flow to hybrid and baffled reactors has been used to treat this wastewater and has been shown to reduce aqueous H{sub 2}S concentrations by causing production of uninhibitory sulfur (S{degree}) and thiosulfate (S{sub 2}O{sub 3}{sup {minus}2}) as well as gas stripping volatile H{sub 2}S. In this study, directly aerated methanogenic fluidized bed reactors (FBRs) achieved increased methane production compared to strictly anaerobic FBRs treating high-sulfate wastewater. Oxygen transfer satisfying up to 28% of the COD load resulted in maximum specific oxygen utilization rates of 0.20 mg oxygen/g volatile solids{center{underscore}dot}min, with significant, concomitant methane production. Under typically inhibitory SO{sub 4}{sup {minus}2} loading, higher aeration caused increased effluent SO{sub 4}{sup {minus}2}, increased H{sub 2}S mass in the offgas, and lower reactor H{sub 2}S concentration. As a result, COD removal increased from 25% for a strictly anaerobic FBR to 87% for an aerated FBR. In addition, aerated systems required significantly less alkalinity supplementation to maintain a pH value of 7, ostensibly because of stripping of acidic carbon dioxide. The potential pH increase associated with aeration also shifts sulfide speciation to less toxic disulfide. Direct, limited aeration of methanogenic FBRs is described as a method for increased COD removal when treating high-COD, high-sulfate wastewater.

Zitomer, D.H.; Shrout, J.D.

2000-02-01

14

Chromium (VI) biosorption and removal of chemical oxygen demand by Spirulina platensis from wastewater-supplemented culture medium  

Microsoft Academic Search

The inappropriate discharge of wastewater containing high concentrations of toxic metals is a serious threat to the environment. Given that the microalga Spirulina platensis has demonstrated a capacity for chromium VI (Cr (VI) biosorption, we assessed the ideal concentration of chromium-containing wastewater required for maximum removal of Cr (VI) and chemical oxygen demand (COD) from the environment by using this

Clinei D. Magro; Maitê C. Deon; Andreia De Rossi; Christian O. Reinehr; Marcelo Hemkemeier; Luciane M. Colla

2012-01-01

15

Grey and neural network prediction of suspended solids and chemical oxygen demand in hospital wastewater treatment plant effluent  

Microsoft Academic Search

Grey model (GM) and artificial neural network (ANN) was employed to predict suspended solids (SS) and chemical oxygen demand (COD) in the effluent from sequence batch reactors of a hospital wastewater treatment plant (HWWTP). The results indicated that the minimum mean absolute percentage errors (MAPEs) of 23.14% and 51.73% for SS and COD could be achieved using genetic algorithm ANN

T. Y. Pai; Y. P. Tsai; H. M. Lo; C. H. Tsai; C. Y. Lin

2007-01-01

16

A portable photoelectrochemical probe for rapid determination of chemical oxygen demand in wastewaters.  

PubMed

A photoelectrochemical probe for rapid determination of chemical oxygen demand (COD) is developed using a nanostructured mixed-phase TiO2 photoanode, namely PeCOD probe. A UV-LED light source and a USB mircroelectrochemical station are powered and controlled by a laptop computer, which makes the probe portable for onsite COD analyses. The photoelectrochemical measurement of COD was optimized in terms of light intensity, applied bias, and pH. Under the optimized conditions, the net steady state currents originated from the oxidation of organic compounds were found to be directly proportional to COD concentrations. A practical detection limit of 0.2 ppm COD and a linear range of 0-120 ppm COD were achieved. The analytical method using the portable PeCOD probe has the advantages of being rapid, low cost, robust, user-friendly, and environmental friendly. It has been successfully applied to determine the COD values of the synthetic samples consisting of potassium hydrogen phthalate, D-glucose, glutamic acid, glutaric acid, succinic acid, and malonic acid, and real samples from various industries, such as bakery, oil and grease manufacturer, poultry, hotel, fine food factory, and fresh food producer, commercial bread manufacturer. Excellent agreement between the proposed method and the conventional COD method (dichromate) was achieved. PMID:19921898

Zhang, Shanqing; Li, Lihong; Zhao, Huijun

2009-10-15

17

WO3/W Nanopores Sensor for Chemical Oxygen Demand (COD) Determination under Visible Light  

PubMed Central

A sensor of a WO3 nanopores electrode combined with a thin layer reactor was proposed to develop a Chemical Oxygen Demand (COD) determination method and solve the problem that the COD values are inaccurately determined by the standard method. The visible spectrum, e.g., 420 nm, could be used as light source in the sensor we developed, which represents a breakthrough by limiting of UV light source in the photoelectrocatalysis process. The operation conditions were optimized in this work, and the results showed that taking NaNO3 solution at the concentration of 2.5 mol·L?1 as electrolyte under the light intensity of 214 ?W·cm?2 and applied bias of 2.5 V, the proposed method is accurate and well reproducible, even in a wide range of pH values. Furthermore, the COD values obtained by the WO3 sensor were fitted well with the theoretical COD value in the range of 3–60 mg·L?1 with a limit value of 1 mg·L?1, which reveals that the proposed sensor may be a practical device for monitoring and controlling surface water quality as well as slightly polluted water.

Li, Xuejin; Bai, Jing; Liu, Qiang; Li, Jianyong; Zhou, Baoxue

2014-01-01

18

A high throughput chemiluminescence method for determination of chemical oxygen demand in waters.  

PubMed

A novel and high throughput chemiluminescence (CL) method for determination of chemical oxygen demand (COD) in water sample was originally developed based on potassium permanganate-glutaraldehyde CL system. With this method, dissolved organic matter in water samples was digested by excess acid potassium permanganate, the reacted mixture solutions containing surplus KMnO(4) were added in wells of a 96-well plate, followed by injection of glutaraldehyde in the wells, and CL was then produced along with the reaction of the added glutaraldehyde with the surplus KMnO(4) and detected by a photomultiplier tube (PMT). The difference (DeltaI) between the CL intensity for distilled water and that for sample water was proportional to the COD value of water sample. The calibration graph was linear in the range of 0.16-19.24 mg L(-1) with a detection limit of 0.1 mg L(-1). A complete analysis could be performed in 40 min including digestion and detection, giving a very high throughput of 3 x 96 samples in about 60 min. Compared with the conventional methods, this method is simple and sensitive and consumes very limited and cheap reagents. Owing to its rapid, automatic, high throughput and low cost characteristics, the presented CL method has been applied successfully to the determination of COD in real water samples (n=32) with satisfactory results. PMID:19110119

Yao, Hong; Wu, Bin; Qu, Haibin; Cheng, Yiyu

2009-02-01

19

Rapid determination of the chemical oxygen demand of water using a thermal biosensor.  

PubMed

In this paper we describe a thermal biosensor with a flow injection analysis system for the determination of the chemical oxygen demand (COD) of water samples. Glucose solutions of different concentrations and actual water samples were tested, and their COD values were determined by measuring the heat generated when the samples passed through a column containing periodic acid. The biosensor exhibited a large linear range (5 to 3000 mg/L) and a low detection limit (1.84 mg/L). It could tolerate the presence of chloride ions in concentrations of 0.015 M without requiring a masking agent. The sensor was successfully used for detecting the COD values of actual samples. The COD values of water samples from various sources were correlated with those obtained by the standard dichromate method; the linear regression coefficient was found to be 0.996. The sensor is environmentally friendly, economical, and highly stable, and exhibits good reproducibility and accuracy. In addition, its response time is short, and there is no danger of hazardous emissions or external contamination. Finally, the samples to be tested do not have to be pretreated. These results suggest that the biosensor is suitable for the continuous monitoring of the COD values of actual wastewater samples. PMID:24915178

Yao, Na; Wang, Jinqi; Zhou, Yikai

2014-01-01

20

WO?/W nanopores sensor for chemical oxygen demand (COD) determination under visible light.  

PubMed

A sensor of a WO3 nanopores electrode combined with a thin layer reactor was proposed to develop a Chemical Oxygen Demand (COD) determination method and solve the problem that the COD values are inaccurately determined by the standard method. The visible spectrum, e.g., 420 nm, could be used as light source in the sensor we developed, which represents a breakthrough by limiting of UV light source in the photoelectrocatalysis process. The operation conditions were optimized in this work, and the results showed that taking NaNO3 solution at the concentration of 2.5 mol·L(-1) as electrolyte under the light intensity of 214 ?W·cm(-2) and applied bias of 2.5 V, the proposed method is accurate and well reproducible, even in a wide range of pH values. Furthermore, the COD values obtained by the WO3 sensor were fitted well with the theoretical COD value in the range of 3-60 mg·L(-1) with a limit value of 1 mg·L(-1), which reveals that the proposed sensor may be a practical device for monitoring and controlling surface water quality as well as slightly polluted water. PMID:24940868

Li, Xuejin; Bai, Jing; Liu, Qiang; Li, Jianyong; Zhou, Baoxue

2014-01-01

21

Preparation and application of TiO 2 photocatalytic sensor for chemical oxygen demand determination in water research  

Microsoft Academic Search

In this work, a TiO2 photocatalytic sensor was prepared and utilized into flow injection analysis (FIA) for chemical oxygen demand (COD) determination. With a positive bias potential of 0.4V (vs. Ag\\/AgCl) applied to the sensor and a 12-W quartz UV lamp illuminating it, photocurrent, due to the charge transfer at the interface of TiO2 sensor and the passing solution, was

Junshui Chen; Jidong Zhang; Yuezhong Xian; Xiangyang Ying; Meichuan Liu; Litong Jin

2005-01-01

22

Nitrogen and chemical oxygen demand removal from septic tank wastewater in subsurface flow constructed wetlands: substrate (cation exchange capacity) effects.  

PubMed

The current article focuses on chemical oxygen demand (COD) and nitrogen (ammonium and nitrate) removal performance from synthetic human wastewater as affected by different substrate rocks having a range of porosities and cation exchange capacities (CECs). The aggregates included lava rock, lightweight expanded shale, meta-basalt (control), and zeolite. The first three had CECs of 1 to 4 mequiv/100 gm, whereas the zeolite CEC was much greater (-80 mequiv/100 gm). Synthetic wastewater was gravity fed to each constructed wetland system, resulting in a 4-day retention time. Effluent samples were collected, and COD and nitrogen species concentrations measured regularly during four time periods from November 2008 through June 2009. Chemical oxygen demand and nitrogen removal fractions were not significantly different between the field and laboratory constructed wetland systems when corrected for temperature. Similarly, overall COD and nitrogen removal fractions were practically the same for the aggregate substrates. The important difference between aggregate effects was the zeolite's ammonia removal process, which was primarily by adsorption. The resulting single-stage nitrogen removal process may be an alternative to nitrification and denitrification that may realize significant cost savings in practice. PMID:24851327

Collison, Robert S; Grismer, Mark E

2014-04-01

23

High removal of chemical and biochemical oxygen demand from tequila vinasses by using physicochemical and biological methods.  

PubMed

The goal of this research is to find a more effective treatment for tequila vinasses (TVs) with potential industrial application in order to comply with the Mexican environmental regulations. TVs are characterized by their high content of solids, high values of biochemical oxygen demand (BODs), chemical oxygen demand (COD), low pH and intense colour; thus, disposal of untreated TVs severely impacts the environment. Physicochemical and biological treatments, and a combination of both, were probed on the remediation of TVs. The use of alginate for the physicochemical treatment of TVs reduced BOD5 and COD values by 70.6% and 14.2%, respectively. Twenty white-rot fungi (WRF) strains were tested in TV-based solid media. Pleurotus ostreatus 7992 and Trametes trogii 8154 were selected due to their ability to grow on TV-based solid media. Ligninolytic enzymes' production was observed in liquid cultures of both fungi. Using the selected WRF for TVs' bioremediation, both COD and BOD5 were reduced by 88.7% and 89.7%, respectively. Applying sequential physicochemical and biological treatments, BOD5 and COD were reduced by 91.6% and 93.1%, respectively. Results showed that alginate and selected WRF have potential for the industrial treatment of TVs. PMID:24956770

Retes-Pruneda, Jose Luis; Davila-Vazquez, Gustavo; Medina-Ramírez, Iliana; Chavez-Vela, Norma Angelica; Lozano-Alvarez, Juan Antonio; Alatriste-Mondragon, Felipe; Jauregui-Rincon, Juan

2014-08-01

24

Chromium (VI) biosorption and removal of chemical oxygen demand by Spirulina platensis from wastewater-supplemented culture medium.  

PubMed

The inappropriate discharge of wastewater containing high concentrations of toxic metals is a serious threat to the environment. Given that the microalga Spirulina platensis has demonstrated a capacity for chromium VI (Cr (VI) biosorption, we assessed the ideal concentration of chromium-containing wastewater required for maximum removal of Cr (VI) and chemical oxygen demand (COD) from the environment by using this microalga. The Paracas and Leb-52 strains of S. platensis, with initial wastewater concentrations of 0%, 12.5%, 25%, and 50%, were cultured in Zarrouk medium diluted to 50% under controlled air, temperature, and lighting conditions. The cultures were maintained for 28 days, and pH, biomass growth, COD, and Cr (VI) were assessed. The wastewater concentration influenced microalgal growth, especially at high concentrations. Removal of 82.19% COD and 60.92% Cr (VI) was obtained, but the COD removal was greater than the Cr (VI) removal in both strains of S. platensis. PMID:22755529

Magro, Clinei D; Deon, Maitê C; De Rossi, Andreia; Reinehr, Christian O; Hemkemeier, Marcelo; Colla, Luciane M

2012-01-01

25

Effects of organic carbon source, chemical oxygen demand/N ratio and temperature on autotrophic nitrogen removal.  

PubMed

To assess the feasibility of the Anammox process as a cost-effective post-treatment step for anaerobic sewage treatment, the simultaneous effects of organic carbon source, chemical oxygen demand (COD)/N ratio, and temperature on autotrophic nitrogen removal was studied. In batch experiments, three operating conditions were evaluated at 14, 22 and 30 °C, and at COD/N ratios of 2 and 6. For each operating condition, containing 32 ± 2 mg NH4(+)-N/L and 25 ± 2 mg NO2(-)-N/L, three different substrate combinations were tested to simulate the presence of readily biodegradable and slowly biodegradable organic matter (RBCOD and SBCOD, respectively): (i) acetate (RBCOD); (ii) starch (SBCOD); and (iii) acetate + starch. The observed stoichiometric NO2(-)-N/NH4(+)-N conversion ratios were in the range of 1.19-1.43, and the single or simultaneous presence of acetate and starch did not affect the Anammox metabolism. High Anammox nitrogen removal was observed at 22 °C (77-84%) and 30 °C (73-79%), whereas there was no nitrogen removal at 14 °C; the Anammox activity was strongly influenced by temperature, in spite of the COD source and COD/N ratios applied. These results suggest that the Anammox process could be applied as a nitrogen removal post-treatment for anaerobic sewage systems in warm climates. PMID:24845324

Sánchez Guillén, J A; Yimman, Y; Lopez Vazquez, C M; Brdjanovic, D; van Lier, J B

2014-01-01

26

Repetitive determination of chemical oxygen demand by cyclic flow injection analysis using on-line regeneration of consumed permanganate.  

PubMed

A cyclic flow injection analysis (cyclic FIA) for the repetitive determination of chemical oxygen demand (COD) was developed. The acidic KMnO4 method was carried out by adopting a single-line circulating flow system. The oxidant (KMnO4) consumed by the oxidation of organic substances was regenerated and reused repeatedly, resulting in an extreme reduction of hazardous wastes. Only 50 ml of the reagent carrier solution containing 0.2 mM KMnO4 and 1 mM HIO4 in 0.8 M H2SO4 solution was continuously circulated through the system. The KMnO4 could play two roles: acting as an oxidant of the organic substances and/or a spectrophotometric reagent. The co-existing HIO4 acted as a regenerator of KMnO4, which made it possible to recycle the system repeatedly. Under two different digestions (70 and 130 degrees C), 50 repetitive determinations of standard sodium oxalate (6.5 mg COD L(-1)) and D-glucose (7.2 mg COD L(-1)) were skillfully carried out with a slightly decreased baseline. The analytical frequency was 30 samples per hour for COD determination. The proposed method saved consumption of the used reagents, KMnO4 and H2SO4, and thus these wastes were extremely reduced. The obtained COD values with the proposed method were co-related with those provided by the manual standard method, but were fairly low owing to the insufficient digestion step. PMID:16429777

Zenki, Michio; Fujiwara, Satoru; Yokoyama, Takashi

2006-01-01

27

Decolourization and removal of chemical oxygen demand (COD) with energy recovery: Treatment of biodigester effluent of a molasses-based alcohol distillery using inorganic coagulants  

Microsoft Academic Search

The removal of molasses-derived colour and chemical oxygen demand from the biodigester effluent of a molasses-based alcohol distillery effluent treatment plant was studied using inorganic coagulants—FeCl3, AlCl3 and polyaluminium chloride (PAC). The coagulation\\/flocculation yield about 55, 60 and 72% COD reductions and about 83, 86 and 92% colour reductions, with the use of 60mM\\/l AlCl3, 60mM\\/l FeCl3 and 30ml\\/l of

Parmesh Kumar Chaudhari; Indra Mani Mishra; Shri Chand

2007-01-01

28

Chemical oxygen demand removal efficiency and limited factors study of aminosilicone polymers in a water emulsion by iron-carbon micro-electrolysis.  

PubMed

Micro-electrolysis was applied in the present study to investigate the effect of pH, iron-carbon mass ratio, contact time, and treatment batch on the removal efficiency of chemical oxygen demand (COD) within an aminosilicone emulsion. The results exhibited that the removal efficiency of COD decreased linearly with the batch increase, and this tendency was consistent under the various conditions. The adsorption of activated carbons contributes a large portion to the elimination of COD within the aminosilicone emulsion. The oxidation action of iron-carbon micro-electrolysis was proven and the aminosilicone emulsion's COD removal contribution was approximately 16%. Aminosilicone polymers were adsorbed on the surface of activated carbons and iron chips, which contributes to the decline of COD removal efficiency and limits the contribution of oxidation action. PMID:24645546

Yang, Shangyuan; Liang, Zhiwei; Yu, Huadong; Wang, Yunlong; Chen, Yingxu

2014-02-01

29

Treatment of a slaughterhouse wastewater: effect of internal recycle rate on chemical oxygen demand, total Kjeldahl nitrogen and total phosphorus removal.  

PubMed

This study investigated the ability of an anaerobic/anoxic/oxic (A2/O) system to treat a slaughterhouse wastewater. The system employed two identical continuous-flow reactors (101 total liquid volume each) running in parallel with the main operational variable, being the internal recycle (IR) rate. The chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and total phosphorus (TP) performance was evaluated as the IR flowrate was increased from a Q of 151d(-1) to 4Q at a system hydraulic retention time of 16 h and a solids retention time of 10 d. The COD:TKN and COD:TP ratios were 8.2:1 and 54:1, which supported both nitrogen and phosphorus removal. For all IR multiples of Q, the COD removal was in excess of 90%. The TKN removal showed a modest improvement (a 4-5% increase, depending on the dissolved oxygen (DO)) as the IR doubled from Q to 2Q, but no further increase was observed at the 4Q IR rate. The TP removal reached its optimum (around 85%-89% (again depending on the DO)) at the 2Q rate. PMID:22439562

Fongsatitkul, P; Wareham, D G; Elefsiniotis, P; Charoensuk, P

2011-12-01

30

TRANSIENT BIOGEOCHEMICAL CYCLING AND SEDIMENT OXYGEN DEMAND  

EPA Science Inventory

Through this research, the effects of variable sediment accumulation and oxygen concentration on SOD and soluble chemical fluxes will be quantified. This study will enable correct estimates of “diffuser-induced” SOD to be made that will facilitate appropriate desig...

31

Performance of a stratified sand filter in removal of chemical oxygen demand, total suspended solids and ammonia nitrogen from high-strength wastewaters.  

PubMed

A stratified sand filter column, operated in recirculation mode and treating synthetic effluent resembling high-strength dairy wastewaters was studied over a 342-d duration. The aim of this paper was to examine the organic, total suspended solids (TSS) and nutrient removal rates of the sand filter, operated in recirculation mode, under incrementally increasing hydraulic and organic loading rates and to propose a field filter-sizing criterion. Best performance was obtained at a system hydraulic loading rate of 10 L m(-2) d(-1); a higher system hydraulic loading rate (of 13.4 L m(-2) d(-1)) caused surface ponding. The system hydraulic loading rate of 10 L m(-2) d(-1) gave a filter chemical oxygen demand (COD), TSS, and total kjeldahl nitrogen (TKN) loading rate of 14, 3.7, and 2.1 g m(-2) d(-1), respectively, and produced consistent COD and TSS removals of greater than 99%, and an effluent NO(3)-N concentration of 42 mg L(-1) (accounting for an 86% reduction in total nitrogen (Tot-N)). As the proportional surface area requirement for the sand filter described in this study is less than the recommended surface area requirement of a free-water surface (FWS) wetland treating an effluent of similar quality, it could provide an economic and sustainable alternative to conventional wetland treatment. PMID:16814452

Healy, M G; Rodgers, M; Mulqueen, J

2007-06-01

32

Coupling of anodic oxidation and adsorption by granular activated carbon for chemical oxygen demand removal from 4,4'-diaminostilbene-2,2'-disulfonic acid wastewater.  

PubMed

Experiments were performed to reduce chemical oxygen demand (COD) from 4,4'-diaminostilbene-2,2'-disulfonic (DSD) acid manufacturing wastewater using electrochemical oxidation coupled with adsorption by granular activated carbon. The COD removal is affected by the residence time and applied voltage. When the residence time is increased, lower value of COD effluent could be obtained, however, the average current efficiency (ACE) decreased rapidly, and so does the applied voltage. In addition, aeration could effectively enhance COD removal efficiency and protect anodes from corrosion. Furthermore, the acidic condition is beneficial to the rapid decrease of COD and the values of pH effluent are independent of the initial solution pH. The optimization conditions obtained from these experiments are applied voltage of 4.8 V, residence time of 180 min and air-liquid ratio of 4.2 with the COD effluent of about 690 mg L?¹. In these cases, the ACE and energy consumption are 388% and 4.144 kW h kg?¹ COD, respectively. These perfect results from the experiments illustrate that the combined process is a considerable alternative for the treatment of industrial wastewater containing high concentration of organic pollutants and salinity. PMID:21099056

Wang, Lizhang; Zhao, Yuemin

2010-01-01

33

Chemical oxygen demand, total organic carbon and colour reduction in slaughterhouse wastewater by unmodified and iron-modified clinoptilolite-rich tuff.  

PubMed

In this study, reduction of chemical oxygen demand (COD), colour, and total organic carbon in effluents from a slaughterhouse in central Mexico was performed using clinoptilolite-rich tuff. The experimental parameters considered were initial concentration of the adsorbate, pH, adsorbent dosage, and contact time. Surface morphology of the materials was tested by using scanning electron microscopy. Specific surface area was analysed by using Brunauer-Emmett-Teller (BET) and phase composition was analysed by using X-ray diffraction. The experimental adsorption data were fitted to the first- and pseudo-second-order kinetic models. The highest COD removal was observed in slightly acidic pH conditions. The maximum reduction efficiency of COD was accomplished with unmodified clinoptilolite-rich tuff at a contact time of 1440 min. In these conditions, the adsorbent was efficient for treating wastewater from a slaughterhouse. Moreover, after several regeneration cycles with Fenton reagent or hydrogen peroxide, the regenerated zeolite with H2O2 (3%) showed the best reduction efficiencies. PMID:24701954

Torres-Pérez, J; Solache-Ríos, M; Martínez-Miranda, V

2014-01-01

34

Accuracy of different sensors for the estimation of pollutant concentrations (total suspended solids, total and dissolved chemical oxygen demand) in wastewater and stormwater.  

PubMed

Many field investigations have used continuous sensors (turbidimeters and/or ultraviolet (UV)-visible spectrophotometers) to estimate with a short time step pollutant concentrations in sewer systems. Few, if any, publications compare the performance of various sensors for the same set of samples. Different surrogate sensors (turbidity sensors, UV-visible spectrophotometer, pH meter, conductivity meter and microwave sensor) were tested to link concentrations of total suspended solids (TSS), total and dissolved chemical oxygen demand (COD), and sensors' outputs. In the combined sewer at the inlet of a wastewater treatment plant, 94 samples were collected during dry weather, 44 samples were collected during wet weather, and 165 samples were collected under both dry and wet weather conditions. From these samples, triplicate standard laboratory analyses were performed and corresponding sensors outputs were recorded. Two outlier detection methods were developed, based, respectively, on the Mahalanobis and Euclidean distances. Several hundred regression models were tested, and the best ones (according to the root mean square error criterion) are presented in order of decreasing performance. No sensor appears as the best one for all three investigated pollutants. PMID:23863442

Lepot, Mathieu; Aubin, Jean-Baptiste; Bertrand-Krajewski, Jean-Luc

2013-01-01

35

Surface runoff pollution by cattle slurry and inorganic fertilizer spreading: chemical oxygen demand, ortho-phosphates, and electrical conductivity levels for different buffer strip lengths.  

PubMed

As a way of dealing with the removal of pollutants from farming practices generated wastewater in the EU, we investigate the effect of spreading cattle slurry and inorganic fertiliser on 8 x 5 m2 and 8 x 3 m2 areas, referred to surface runoff chemical oxygen demand (COD), ortho-phosphates (o-P) and electrical conductivity (EC) levels, and the efficiency of grass buffer strips of various lengths in removing pollutants from runoff. The experimental plot was a 15% sloped Lolium perenne pasture. Surface runoff was generated by means of a rainfall simulator working at 47 mm h-1 rainfall intensity. Runoff was sampled by using Gerlach-type troughs situated 2, 4, 6 and 8 m downslope from the amended areas. During the first rainfall simulation, COD, o-P and EC levels were consistently higher in the slurry zone, more evidently in the larger amended area. During the second and third rainfall simulations, concentration and mass levels show a downslope drift into the buffer zones, with no clear buffer strip length attenuation. Correlation between runoff and mass drift is clearly higher in the slurry zone. Percentage attenuation in COD and o-P levels, referred to initial slurry concentrations--including rainfall dilution--were higher than 98%, and higher than 90% for EC. PMID:11496670

Núñez-Delgado, A; López-Periago, E; Quiroga-Lago, F; Díaz-Fierros Viqueira, F

2001-01-01

36

A pilot scale trickling filter with pebble gravel as media and its performance to remove chemical oxygen demand from synthetic brewery wastewater*  

PubMed Central

Evaluating the performance of a biotrickling filter for the treatment of wastewaters produced by a company manufacturing beer was the aim of this study. A pilot scale trickling filter filled with gravel was used as the experimental biofilter. Pilot scale plant experiments were made to evaluate the performance of the trickling filter aerobic and anaerobic biofilm systems for removal of chemical oxygen demand (COD) and nutrients from synthetic brewery wastewater. Performance evaluation data of the trickling filter were generated under different experimental conditions. The trickling filter had an average efficiency of (86.81±6.95)% as the hydraulic loading rate increased from 4.0 to 6.4 m3/(m2?d). Various COD concentrations were used to adjust organic loading rates from 1.5 to 4.5 kg COD/(m3?d). An average COD removal efficiency of (85.10±6.40)% was achieved in all wastewater concentrations at a hydraulic loading of 6.4 m3/(m2?d). The results lead to a design organic load of 1.5 kg COD/(m3?d) to reach an effluent COD in the range of 50–120 mg/L. As can be concluded from the results of this study, organic substances in brewery wastewater can be handled in a cost-effective and environmentally friendly manner using the gravel-filled trickling filter.

Habte Lemji, Haimanot; Eckstadt, Hartmut

2013-01-01

37

FLUX OF REDUCED CHEMICAL CONSTITUENTS (FE(2+), MN(2+), NH4(1+) AND CH4) AND SEDIMENT OXYGEN DEMAND IN LAKE ERIE  

EPA Science Inventory

Sediment pore water concentrations of Fe(2+), Mn(2+), NH4(+), and CH4 were analyzed from both diver-collected cores and an in situ equilibration device (peeper) in Lake Erie's central basin. Sediment oxygen demand (SOD) was measured at the same station with a hemispheric chamber ...

38

Organic-coated nanoparticulate zero valent iron for remediation of chemical oxygen demand (COD) and dissolved metals from tropical landfill leachate.  

PubMed

The use of nanoparticulate zero valent iron (NZVI) in the treatment of inorganic contaminants in landfill leachate and polluted plumes has been the subject of many studies, especially in temperate, developed countries. However, NZVI's potential for reduction of chemical oxygen demand (COD) and treatment of metal ion mixtures has not been explored in detail. We investigated the efficiency of NZVI synthesized in the presence of starch, mercaptoacetic, mercaptosuccinic, or mercaptopropenoic acid for the reduction of COD, nutrients, and metal ions from landfill leachate in tropical Sri Lanka. Synthesized NZVI were characterized with X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis, Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller. Of the samples tested, Starch-NZVI (S-NZVI) and mercaptoacetic-NZVI (MA-NZVI) performed well for treatment both COD and metal mixture. The removal percentages for COD, nitrate-nitrogen, and phosphate from S-NZVI were 50, 88, and 99 %, respectively. Heavy metal removal was higher in S-NZVI (>95 %) than others. MA-NZVI, its oxidation products, and functional groups of its coating showed the maximum removal amounts for both Cu (56.27 mg g(-1)) and Zn (28.38 mg g(-1)). All mercapto-NZVI showed well-stabilized nature under FTIR and XRD investigations. Therefore, we suggest mercapto acids as better agents to enhance the air stability for NZVI since chemically bonded thiol and carbonyl groups actively participation for stabilization process. PMID:24535668

Wijesekara, S S R M D H R; Basnayake, B F A; Vithanage, Meththika

2014-06-01

39

Effects of directly soluble and fibrous rapidly acidifying chemical oxygen demand and reactor liquid surface tension on granulation and sludge-bed stability in upflow anaerobic sludge-blanket reactors  

Microsoft Academic Search

In recent years, it has become clear that the rapidly acidifying chemical oxygen demand (RACOD) content of the waste water\\u000a and the surface tension of the reactor liquid contribute to the phenomenon of granular growth in upflow anaerobic sludge-blanket\\u000a reactors (UASB). By adding 20% of directly soluble RACOD, in the form of a sucrose\\/starch mixture, on top of the original

H. Grootaerd; B. Liessens; W. Verstraete

1997-01-01

40

COMPARISON OF METHODS TO DETERMINE OXYGEN DEMAND FOR BIOREMEDIATION OF A FUEL CONTAMINATED AQUIFER  

EPA Science Inventory

Four analytical methods were compared for estimating concentrations of fuel contaminants in subsurface core samples. he methods were total organic carbon, chemical oxygen demand, oil and grease, and a solvent extraction of fuel hydrocarbons combined with a gas chromatographic tec...

41

COMPARISON OF METHODS TO DETERMINE OXYGEN DEMAND FOR BIOREMEDIATION OF A FUEL CONTAMINATED AQUIFER  

EPA Science Inventory

Four analytical methods were compared for estimating concentrations of fuel contaminants in subsurface core samples. The methods were total organic carbon, chemical oxygen demand, oil and grease, and a solvent extraction of fuel hydrocarbons combined with a gas chromatographic te...

42

DIAGENETIC OXYGEN EQUIVALENTS MODEL OF SEDIMENT OXYGEN DEMAND  

EPA Science Inventory

The consumption of oxygen in the overlying water by sediments is an important component in the oxygen balance of most natural waters. Conventional practice is to specify the magnitude of this sink using direct uptake measurements. Unfortunately, if the management alternative bein...

43

Glucagon increases hepatic oxygen supply-demand ratio in pigs  

SciTech Connect

The present study was performed on eight young pigs to test the hypothesis that glucagon increases hepatic oxygen supply to a greater extent than hepatic oxygen uptake, providing a better hepatic oxygen supply-demand relationship. The experiments were performed under pentobarbital sodium anesthesia and controlled ventilation. Splanchnic blood flow was studied using radioactive microspheres. Glucagon was administered in doses of 1 and 5 ..mu..g x kg/sup -1/ x min/sup -1/. During glucagon infusion, hepatic arterial blood flow substantially increased, splenic and pancreatic blood flows increased moderately, while stomach and intestinal blood flows, as well as portal blood flow did not change significantly. Shunting of both 9- and 15-..mu..m spheres through preportal tissues did not change significantly. Oxygen content in arterial or portal venous blood did not change significantly, while it increased in hepatic venous blood by 30%. There were no differences in the effects between the doses of glucagon administered. There was no correlation found between changes in hepatic oxygen supply and cardiac output or blood pressure. The changes observed during glucagon administration resulted in an increase in oxygen delivery to the liver and hepatic oxygen supply-uptake ratio.

Gelman, S.; Dillard, E.; Parks, D.A.

1987-05-01

44

[Postoperatively increased oxygen demand and hemoptysis after extubation].  

PubMed

A 22-year-old man on postoperative day 1 after open reduction with internal fixation of a distal fibula fracture presented with hemoptysis and increased oxygen demand. X-ray and contrast-enhanced computed tomography revealed bilateral patchy opacities and mediastinal emphysema. After bronchoscopy and bronchoalveolar lavage, a diagnosis of alveolar hemorrhage was made. The medical history revealed regular abuse of marihuana and cocaine. PMID:22349534

Kloth, J K; Wiebel, M; Weber, M-A

2012-03-01

45

Biochemical mediator demand--a novel rapid alternative for measuring biochemical oxygen demand.  

PubMed

The biochemical oxygen demand (BOD) test (BOD5) is a crucial environmental index for monitoring organic pollutants in waste water but is limited by the 5-day requirement for completing the test. We have optimised a rapid microbial technique for measuring the BOD of a standard BOD5 substrate (150 mg glucose/l, 150 mg glutamic acid/l) by quantifying an equivalent biochemical mediator demand in the absence of oxygen. Elevated concentrations of Escherichia coli were incubated with an excess of redox mediator, potassium hexacyanoferrate(III), and a known substrate for 1 h at 37 degrees C without oxygen. The addition of substrate increased the respiratory activity of the microorganisms and the accumulation of reduced mediator; the mediator was subsequently re-oxidised at a working electrode generating a current quantifiable by a coulometric transducer. Catabolic conversion efficiencies exceeding 75% were observed for the oxidation of the standard substrate. The inclusion of a mediator allowed a higher co-substrate concentration compared to oxygen and substantially reduced the incubation time from 5 days to 1 h. The technique replicates the traditional BOD5 method, except that a mediator is substituted for oxygen, and we aim to apply the principle to measure the BOD of real waste streams in future work. PMID:10855725

Pasco, N; Baronian, K; Jeffries, C; Hay, J

2000-05-01

46

Umbilical cord vitamin D, ionized calcium and myocardial oxygen demand.  

PubMed

Abstract Objective: Systemic blood vitamin D and total calcium are correlates of birthweight and cardiovascular disease but whether umbilical cord blood vitamin D and ionized calcium are correlates of birthweight and cardiovascular function is not known. This cross-sectional study correlates umbilical cord vitamin D, ionized calcium and birthweight with the heart rate-systolic pressure product (RPP), an indicator of myocardial oxygen demand. Methods: Cord blood vitamin D and ionized calcium concentrations were compared for vitamin D normal (?50?nM, 20?ng/mL) and vitamin D deficiency (<50?nM, 20?ng/mL) in normal weight (?2500?g) and low birthweight (LBW, <2500?g) newborns. Heart rate and blood pressure were measured during postnatal transition and RPP was computed. Results: RPP was positively correlated with birthweight (r?=?+0.52, p?oxygen demand, in LBW newborns appears to correlate with low umbilical cord vitamin D and ionized calcium levels, suggestive of pathological heart development. PMID:24102390

Reeves, Inez; Liang, Willie; Asadi, M Sadegh; Millis, Richard M

2014-07-01

47

Sediment oxygen demand in the lower Willamette River, Oregon, 1994  

USGS Publications Warehouse

An investigation of sediment oxygen demand (SOD) at the interface of the stream and stream bed was performed in the lower Willamette River (river mile 51 to river mile 3) during August, 1994, as part of a cooperative project with the Oregon Department of Environmental Quality. The primary goals of the investigation were to measure the spatial variability of SOD in the lower Willamette River and to relate SOD to bottom-sediment characteristics. The SOD chambers used in the study were open-bottomed, opaque plastic cylinders that were seated and sealed on the river bottom by scuba divers. When seated, the chambers contained 52 liters of isolated river water, which was slowly recirculated for at least 2 hours over 0.225 square meters of relatively undisturbed bottom sediment. These chambers could not be deployed in areas with gravels and cobbles, which represent about 55 percent of the study area above Willamette Falls and 30 percent of the river below Willamette Falls. Sediment oxygen demand is commonly reported as grams of oxygen consumed per square meter of bottom sediment per day (g/m2 p day). The measured SOD rates, corrected to a temperature of 20 degrees C, ranged from 1.3 to 4.1 g/m2' day in the lower Willamette River. The SOD measured above and below Willamette Falls averaged 2.0 and 2.1 g/m2 ' day, respectively. After adjusting for the amount of bottom material composed of gravels and cobbles, the best estimates for reachwide SOD rates above and below Willamette Falls are 1.4 (+ 0.5) and 1.8 (+ 0.3) g/m2' day, respectively Sediment samples were collected near each chamber and analyzed for percent water, percent sand, and percent organics. The sand content ranged from 0.1 to 6.2 percent and averaged 1.8 percent. The organic content ranged from 1.4 to 9.6 and averaged 5.6 percent. No statistically significant correlations were found between these sediment characteristics and sediment oxygen demand.

Caldwell, J. M.; Doyle, M. C.

1995-01-01

48

Micro Chemical Oxygen-Iodine Laser (COIL).  

National Technical Information Service (NTIS)

It has been previously proposed to improve the performance and compactness of chemical oxygen-iodine lasers (COIL) through the replacement of some of their macroscale components with arrays of higher-performing microscale (MEMS) components. In this progra...

C. Livermore-Clifford

2007-01-01

49

Measurement of biochemical oxygen demand of the leachates.  

PubMed

Biochemical oxygen demand (BOD) of the leachates originally from the different types of landfill sites was studied based on the data measured using the two manometric methods. The measurements of BOD using the dilution method were carried out to assess the typical physicochemical and biological characteristics of the leachates together with some other parameters. The linear regression analysis was used to predict rate constants for biochemical reactions and ultimate BOD values of the different leachates. The rate of a biochemical reaction implicated in microbial biodegradation of pollutants depends on the leachate characteristics, mass of contaminant in the leachate, and nature of the leachate. Character of leachate samples for BOD analysis of using the different methods may differ significantly during the experimental period, resulting in different BOD values. This work intends to verify effect of the different dilutions for the manometric method tests on the BOD concentrations of the leachate samples to contribute to the assessment of reaction rate and microbial consumption of oxygen. PMID:23001555

Fulazzaky, Mohamad Ali

2013-06-01

50

Sediment Oxygen Demand in the Arroyo Colorado River  

NASA Astrophysics Data System (ADS)

The lower reaches of the Arroyo Colorado have historically failed to meet their use under subsection 303(b) of the U.S. Clean Water Act due to fecal coliform bacteria and low dissolved oxygen (DO). Fish kills, especially at the tidal confluence at the Port of Harlingen, Texas, have been reported. Oxygen demand from sediment (SOD) for a river typically has two states -- diffusion limited SOD (SOD) and potential SOD (pSOD), expressed when sediment is resuspended through increased flow or other disturbances. The objective of this research was to measure SOD in the Arroyo Colorado River in situ, estimate pSOD ex situ, and evaluate the relationship between SOD and the depositional environment. We measured SOD and pSOD in the Arroyo Colorado River at up to eight sites over three sampling events. We identified the sample sites based on a modified Rosgen geomorphic index for streambed stabilization. Sites with high sediment deposition potential had high SOD. The average values of SOD between sites were 0.62 g/m2/day (standard deviation 0.38 g/m2/day) and ranged from 0.13 to 1.2 g/m2/day. Potential SOD values ranged from as low as 19.2 to as high as 2,779 g/m3 sediment/ day. Potential SOD can serve as an indicator of the possible impact of SOD from resuspended sediment in stream systems.

Matlock, Marty D.; Kasprzak, Kevin Ray; Osborn, G. Scott

2003-04-01

51

Petroleum industry effluents and other oxygen-demanding wastes in Niger Delta, Nigeria.  

PubMed

In this article, we review the fundamental phenomenon of oxygenation within the overriding context of petroleum-industry effluents and the other oxygen demanding wastes in Niger Delta, Nigeria. Drill cuttings, drilling mud (fluids used to stimulate the production processes), and accidental discharges of crude petroleum constitute serious land and water pollution in the oil-bearing province. Effluents from other industrial establishments such as distilleries, pulp and paper mills, fertilizer plants, and breweries, as well as thermal effluents, plant nutrients (such as nitrates and phosphates), and eroded sediments have also contributed to the pollution of their surrounding environment. Since these wastes are oxygen-demanding in nature, their impact on the recipient environment can be reversed by the direct application of simple chemistry. The wastes can be reduced, particularly in natural bodies of water, by direct oxidation-reduction processes or simple chemical combinations, acid-base reactions, and solubility equilibria; these are pH- and temperature-dependent. A shift in pH and alkalinity affects the solubility equilibria of Na+, Cl-, SO(2-), NO3(-), HCO3(-), and PO4(3-), and other ions and compounds. PMID:17193303

Osuji, Leo C; Uwakwe, Augustine A

2006-07-01

52

Effects of dilution on dissolved oxygen depletion and microbial populations in the biochemical oxygen demand determination.  

PubMed

The biochemical oxygen demand (BOD) value is still a key parameter that can determine the level of organics, particularly the content of biodegradable organics in water. In this work, the effects of sample dilution, which should be done inevitably to get appropriate dissolved oxygen (DO) depletion, on the measurement of 5-day BOD (BOD(5)), was investigated with and without seeding using natural and synthetic water. The dilution effects were also evaluated for water samples taken in different seasons such as summer and winter because water temperature can cause a change in the types of microbial species, thus leading to different oxygen depletion profiles during BOD testing. The predation phenomenon between microbial cells was found to be dependent on the inorganic nutrients and carbon sources, showing a change in cell populations according to cell size after 5-day incubation. The dilution of water samples for BOD determination was linked to changes in the environment for microbial growth such as nutrition. The predation phenomenon between microbial cells was more important with less dilution. BOD(5) increased with the specific amount of inorganic nutrient per microbial mass when the natural water was diluted. When seeding was done for synthetic water samples, the seed volume also affected BOD due to the rate of organic uptake by microbes. BOD(5) increased with the specific bacterial population per organic source supplied at the beginning of BOD measurement. For more accurate BOD measurements, specific guidelines on dilution should be established. PMID:17602220

Seo, Kyo Seong; Chang, Ho Nam; Park, Joong Kon; Choo, Kwang-Ho

2007-09-01

53

A comparison between the multiple linear regression model and neural networks for biochemical oxygen demand estimations  

Microsoft Academic Search

The most common test for determining the strength of organic content in wastewaters is the biochemical oxygen demand (BOD). The variables of water quality are temperature, pH value (pH), dissolved oxygen (DO), substance solid (SS), total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3N), nitrate (NO3), total phosphorous(T-P), and total coliform bacteria (T-coliform). These water quality indices affect biochemical oxygen demand. The

S. Areerachakul; S. Sanguansintukul

2009-01-01

54

MODELING SEDIMENT-NUTRIENT FLUX AND SEDIMENT OXYGEN DEMAND  

EPA Science Inventory

Depositional flux of particulate organic matter in bottom sediments affects nutrients cycling at the sediment-water interface and consumes oxygen from the overlying water in streams, lakes, and estuaries. This project deals with analytical modeling of nitrogen and carbon producti...

55

Demand and supply of hydrogen as chemical feedstock in USA  

NASA Technical Reports Server (NTRS)

Projections are made for the demand and supply of hydrogen as chemical feedstock in USA. Industrial sectors considered are petroleum refining, ammonia synthesis, methanol production, isocyanate manufacture, edible oil processing, coal liquefaction, fuel cell electricity generation, and direct iron reduction. Presently, almost all the hydrogen required is produced by reforming of natural gas or petroleum fractions. Specific needs and emphases are recommended for future research and development to produce hydrogen from other sources to meet the requirements of these industrial sectors. The data and the recommendations summarized in this paper are based on the Workshop 'Supply and Demand of Hydrogen as Chemical Feedstock' held at the University of Houston on December 12-14, 1977.

Huang, C. J.; Tang, K.; Kelley, J. H.; Berger, B. J.

1979-01-01

56

Biochemical oxygen demand. (Latest citations from the NTIS bibliographic database). Published Search  

SciTech Connect

The bibliography contains citations concerning biochemical oxygen demand (BOD) in sewage, industrial waste treatment, runoff, and limnology. The effects of salinity on BOD, aerobic, and anaerobic waste treatment processes are described. The use of algae and water hyacinths in wastewater treatment is explored, along with the water quality and biological oxygen demand of specific bodies of water. (Contains 250 citations and includes a subject term index and title list.)

Not Available

1994-03-01

57

Determination of Biochemical Oxygen Demand of Area Waters: A Bioassay Procedure for Environmental Monitoring  

ERIC Educational Resources Information Center

A graphical method for determining the 5-day biochemical oxygen demand (BOD5) for a body of water is described. In this bioassay, students collect a sample of water from a designated site, transport it to the laboratory, and evaluate the amount of oxygen consumed by naturally occurring bacteria during a 5-day incubation period. An accuracy check,…

Riehl, Matthew

2012-01-01

58

Biofilm reactor based real-time analysis of biochemical oxygen demand.  

PubMed

We reported a biofilm reactor (BFR) based analytical system for real-time biochemical oxygen demand (BOD) monitoring. It does not need a blank solution and other chemical reagents to operate. The initial dissolved oxygen (DO) in sample solution was measured as blank, while DO in the BFR effluent was measured as response. The DO difference obtained before and after the sample solution flowed through the BFR was regarded as an indicator of real-time BOD. The analytical performance of this reagent-free BFR system was equal to the previous BFR system operated using phosphate buffer saline (PBS) and high purity deionized water in reproducibility, accuracy and long-term stability. Besides, this method embraces many notable advantages, such as no secondary pollution. Additionally, the sample solutions are free from temperature controlling and air-saturation before injection. Significantly, this is a real-time BOD analysis method. This method was successfully carried out in a simulated emergency, and the obtained results agreed well with conventional BOD?. These advantages, coupled with simplicity in device, convenience in operation and minimal maintenance, make such a reagent-free BFR analytical system promising for practical BOD real-time warning. PMID:23228491

Liu, Changyu; Jia, Jianbo; Dong, Shaojun

2013-04-15

59

Biological oxygen demand optode analysis of coral reef-associated microbial communities exposed to algal exudates.  

PubMed

Algae-derived dissolved organic matter has been hypothesized to induce mortality of reef building corals. One proposed killing mechanism is a zone of hypoxia created by rapidly growing microbes. To investigate this hypothesis, biological oxygen demand (BOD) optodes were used to quantify the change in oxygen concentrations of microbial communities following exposure to exudates generated by turf algae and crustose coralline algae (CCA). BOD optodes were embedded with microbial communities cultured from Montastraea annularis and Mussismilia hispida, and respiration was measured during exposure to turf and CCA exudates. The oxygen concentrations along the optodes were visualized with a low-cost Submersible Oxygen Optode Recorder (SOOpR) system. With this system we observed that exposure to exudates derived from turf algae stimulated higher oxygen drawdown by the coral-associated bacteria than CCA exudates or seawater controls. Furthermore, in both turf and CCA exudate treatments, all microbial communities (coral-, algae-associated and pelagic) contributed significantly to the observed oxygen drawdown. This suggests that the driving factor for elevated oxygen consumption rates is the source of exudates rather than the initially introduced microbial community. Our results demonstrate that exudates from turf algae may contribute to hypoxia-induced coral stress in two different coral genera as a result of increased biological oxygen demand of the local microbial community. Additionally, the SOOpR system developed here can be applied to measure the BOD of any culturable microbe or microbial community. PMID:23882444

Gregg, Ak; Hatay, M; Haas, Af; Robinett, Nl; Barott, K; Vermeij, Mja; Marhaver, Kl; Meirelles, P; Thompson, F; Rohwer, F

2013-01-01

60

The diluter-demand oxygen system used during the international Himalayan expedition to Mount Everest.  

NASA Technical Reports Server (NTRS)

The diluter-demand regulators are designed in such a way that as the individual inspires he simultaneously draws ambient air and pure oxygen from a tank into his mask. The size of the ambient air orifice is made directly proportional to the barometric pressure by use of a passive aneroid valve. As altitude increases the ambient air orifice is automatically made smaller and the individual inspires a greater proportion of oxygen.

Blume, F. D.; Pace, N.

1972-01-01

61

The standard chemical oxygen-iodine laser kinetics package  

Microsoft Academic Search

This report presents the Air Force Weapons Laboratory Standard Chemical Oxygen-Iodine Laser Kinetics Package. A complete reaction scheme including recommended rate coefficients for modeling the gas phase kinetics of chemical oxygen-iodine lasers (COIL) was established to provide a common basis for the research and development of COIL devices. A review of the experimental kinetic data base from which this model

Glen P. Perram; Gordon D. Hager

1988-01-01

62

A reagent-free tubular biofilm reactor for on-line determination of biochemical oxygen demand.  

PubMed

We reported a reagent-free tubular biofilm reactor (BFR) based analytical system for rapid online biochemical oxygen demand (BOD) determination. The BFR was cultivated using microbial seeds from activated sludge. It only needs tap water to operate and does not require any chemical reagent. The analytical performance of this reagent-free BFR system was found to be equal to or better than the BFR system operated using phosphate buffer saline (PBS) and high purity deionized water. The system can readily achieve a limit of detection of 0.25 mg O2 L(-1), possessing superior reproducibility, and long-term operational and storage stability. More importantly, we confirmed for the first time that the BFR system is capable of tolerating common toxicants found in wastewaters, such as 3,5-dichlorophenol and Zn(II), Cr(VI), Cd(II), Cu(II), Pb(II), Mn(II) and Ni(II), enabling the method to be applied to a wide range of wastewaters. The sloughing and clogging are the important attributes affecting the operational stability, hence, the reliability of most online wastewater monitoring systems, which can be effectively avoided, benefiting from the tubular geometry of the reactor and high flow rate conditions. These advantages, coupled with simplicity in device, convenience in operation and minimal maintenance, make such a reagent-free BFR analytical system promising for practical BOD online determination. PMID:23500366

Liu, Changyu; Zhao, Huijun; Gao, Shan; Jia, Jianbo; Zhao, Limin; Yong, Daming; Dong, Shaojun

2013-07-15

63

In-situ determination of sediment oxygen demand in cultivation ponds  

NASA Astrophysics Data System (ADS)

This paper presents a method for in-situ determining sediment oxygen demand (SOD) in cultivation pond. This method based on sediment surface structure, temperature, and other determining conditions like those in shrimp cultivation environments, overcomes defects of old methods and provides more accurate estimation of SOD's effect on dissolved oxygen in culture waters. Our experiment shows that the sediment surface structure and temperature had imortant effect on SOD in culture water. Different SOD values were derived from different parts of oxygen consumption curves of sediment, because the curves were not linear. According to the oxygen consumption curves of sediment and saturated DO in culture water, it was thought more suitable to calculate SOD with dissolved oxygen reduction from 5.0 to 2.0 mg/l. This method to determine the SOD of shrimp ponds yielded satisfactory results.

Sun, Yao; Chen, Ju-Fa; Yin, Li; Song, Yun-Li

2000-06-01

64

Sediment Oxygen Demand in the Tualatin River Basin, Oregon, 1992-96.  

National Technical Information Service (NTIS)

The report discusses the USGC measurements of sediment oxygen demand (SOD) in the Tualatin River Basin. Specifically, this investigation of SOD in the Tualatin River Basin was designed to: determine the magnitude of the SOD rate in the main stem and the t...

S. A. Rounds M. C. Doyle

1997-01-01

65

Membrane?electrode assembly enhances performance of a microbial fuel cell type biological oxygen demand sensor  

Microsoft Academic Search

A membrane?electrode assembly (MEA) was applied to a microbial fuel cell (MFC) type biological oxygen demand (BOD) sensor and the performance of the sensor was assessed. To establish the optimal conditions for MEA fabrication, platinum?catalysed carbon cloth cathodic electrodes were assembled with cation exchange membranes under various temperatures and pressures. By analysing coulombs from the MFCs, it could be determined

Mia Kim; Moon Sik Hyun; Geoffrey M. Gadd; Gwang Tae Kim; Hyung Joo Kim

2009-01-01

66

Sediment oxygen demand in the Saddle River and Salem River watersheds, New Jersey, July-August 2008  

USGS Publications Warehouse

Many factors, such as river depth and velocity, biochemical oxygen demand, and algal productivity, as well as sediment oxygen demand, can affect the concentration of dissolved oxygen in the water column. Measurements of sediment oxygen demand, in conjunction with those of other water-column water-quality constituents, are useful for quantifying the mechanisms that affect in-stream dissolved-oxygen concentrations. Sediment-oxygen-demand rates are also needed to develop and calibrate a water-quality model being developed for the Saddle River and Salem River Basins in New Jersey to predict dissolved-oxygen concentrations. This report documents the methods used to measure sediment oxygen demand in the Saddle River and Salem River watersheds along with the rates of sediment oxygen demand that were obtained during this investigation. In July and August 2008, sediment oxygen demand was measured in situ in the Saddle River and Salem River watersheds. In the Saddle River Basin, sediment oxygen demand was measured twice at two sites and once at a third location; in the Salem River Basin, sediment oxygen demand was measured three times at two sites and once at a third location. In situ measurements of sediment oxygen demand in the Saddle River and Salem River watersheds ranged from 0.8 to 1.4 g/m2d (grams per square meter per day) and from 0.6 to 7.1 g/m2d at 20 degrees Celsius, respectively. Except at one site in this study, rates of sediment oxygen demand generally were low. The highest rate of sediment oxygen demand measured during this investigation, 7.1 g/m2d, which occurred at Courses Landing in the Salem River Basin, may be attributable to the consumption of oxygen by a large amount of organic matter (54 grams per kilogram as organic carbon) in the streambed sediments or to potential error during data collection. In general, sediment oxygen demand increased with the concentration of organic carbon in the streambed sediments. Repeated measurements made 6 to 7 days apart at the same site locations resulted in similar values.

Heckathorn, Heather A.; Gibs, Jacob

2010-01-01

67

Atomic oxygen-MoSâ chemical interactions  

Microsoft Academic Search

The present study shows that, at 1.5 eV O-atom translation energy, SOâ is generated and outgases from an anhydrous MoSâsurface with an initial reactivity nearly 50% that of kapton. The reaction of atomic oxygen with MoSâ has little or no translational energy barier; i.e., thermally generated atomic oxygen reacts as readily as that having 1.5 eV of translational energy. It

J. B. Cross; J. A. Martin; L. E. Pope; S. L. Koontz

1989-01-01

68

Improvement of a mediator-type biochemical oxygen demand sensor for on-site measurement  

Microsoft Academic Search

We characterized a mediator-type biochemical oxygen demand (BOD) sensor with a three-electrode system using potassium ferricyanide (FC) and Pseudomonas fluorescens in our previous study. In the present study, we have utilized the advantages of a mediator-type biosensor, which does not require air-supply equipment for on-site measurements, and made a fully disposable sensor tip for a portable device. The tip consists

Nobuyuki Yoshida; Junko Hoashi; Takashi Morita; Scott J. McNiven; Hideaki Nakamura; Isao Karube

2001-01-01

69

A Method for Generating Oxygen from Consumer Chemicals  

Microsoft Academic Search

The rapidly accelerated combustion of wood, paper, carbon, a candle, and steel wool in oxygen gas is presented. The oxygen gas is generated as needed in the bottles used for the demonstration using chemicals readily available on the retail market: liquid chlorine bleach and 3% hydrogen peroxide.

Stephen W. Wright

2003-01-01

70

Prediction of Benthic Impact for Salmon Net-Pens Based on the Balance of Benthic Oxygen Supply and Demand  

Microsoft Academic Search

The ratio between oxygen supply and oxygen demand was examined as a predictor of benthic response to organic enrichment caused by salmon net-pen aquaculture. Oxygen supply to the benthos was calculated based on Fickian diffusion and near-bottom flow velocities. A strong linear correlation was found between measured carbon sedimentation rates and rates of benthic metabolism. This relationship allowed an estimation

R. H. Findlay; Les Watling

1997-01-01

71

Detailed chemical kinetic modeling of diesel combustion with oxygenated fuels  

SciTech Connect

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

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

1999-10-28

72

Optimization of jet singlet oxygen generator for chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Experimental investigation of a jet singlet oxygen generator for a supersonic chemical oxygen-iodine laser was performed aimed to evaluation of the effects of BHP temperature and composition on the water content and other output generator parameters. Laser experiments on a small-scale system were realized to prove the obtained results.

Spalek, Otomar; Kodymova, Jarmila; Zagidullin, Marsel V.; Nikolaev, Valeri D.

1997-04-01

73

Simulation of Temperature, Nutrients, Biochemical Oxygen Demand, and Dissolved Oxygen in the Catawba River, South Carolina, 1996-97  

USGS Publications Warehouse

Time-series plots of dissolved-oxygen concentrations were determined for various simulated hydrologic and point-source loading conditions along a free-flowing section of the Catawba River from Lake Wylie Dam to the headwaters of Fishing Creek Reservoir in South Carolina. The U.S. Geological Survey one-dimensional dynamic-flow model, BRANCH, was used to simulate hydrodynamic data for the Branched Lagrangian Transport Model. Waterquality data were used to calibrate the Branched Lagrangian Transport Model and included concentrations of nutrients, chlorophyll a, and biochemical oxygen demand in water samples collected during two synoptic sampling surveys at 10 sites along the main stem of the Catawba River and at 3 tributaries; and continuous water temperature and dissolved-oxygen concentrations measured at 5 locations along the main stem of the Catawba River. A sensitivity analysis of the simulated dissolved-oxygen concentrations to model coefficients and data inputs indicated that the simulated dissolved-oxygen concentrations were most sensitive to watertemperature boundary data due to the effect of temperature on reaction kinetics and the solubility of dissolved oxygen. Of the model coefficients, the simulated dissolved-oxygen concentration was most sensitive to the biological oxidation rate of nitrite to nitrate. To demonstrate the utility of the Branched Lagrangian Transport Model for the Catawba River, the model was used to simulate several water-quality scenarios to evaluate the effect on the 24-hour mean dissolved-oxygen concentrations at selected sites for August 24, 1996, as simulated during the model calibration period of August 23 27, 1996. The first scenario included three loading conditions of the major effluent discharges along the main stem of the Catawba River (1) current load (as sampled in August 1996); (2) no load (all point-source loads were removed from the main stem of the Catawba River; loads from the main tributaries were not removed); and (3) fully loaded (in accordance with South Carolina Department of Health and Environmental Control National Discharge Elimination System permits). Results indicate that the 24-hour mean and minimum dissolved-oxygen concentrations for August 24, 1996, changed from the no-load condition within a range of - 0.33 to 0.02 milligram per liter and - 0.48 to 0.00 milligram per liter, respectively. Fully permitted loading conditions changed the 24-hour mean and minimum dissolved-oxygen concentrations from - 0.88 to 0.04 milligram per liter and - 1.04 to 0.00 milligram per liter, respectively. A second scenario included the addition of a point-source discharge of 25 million gallons per day to the August 1996 calibration conditions. The discharge was added at S.C. Highway 5 or at a location near Culp Island (about 4 miles downstream from S.C. Highway 5) and had no significant effect on the daily mean and minimum dissolved-oxygen concentration. A third scenario evaluated the phosphorus loading into Fishing Creek Reservoir; four loading conditions of phosphorus into Catawba River were simulated. The four conditions included fully permitted and actual loading conditions, removal of all point sources from the Catawba River, and removal of all point and nonpoint sources from Sugar Creek. Removing the point-source inputs on the Catawba River and the point and nonpoint sources in Sugar Creek reduced the organic phosphorus and orthophosphate loadings to Fishing Creek Reservoir by 78 and 85 percent, respectively.

Feaster, Toby D.; Conrads, Paul A.; Guimaraes, Wladmir B.; Sanders, Curtis L., Jr.; Bales, Jerad D.

2003-01-01

74

Non-steady response of BOD biosensor for the determination of biochemical oxygen demand in wastewater.  

PubMed

A biochemical oxygen demand (BOD) biosensor for effective and expeditious BOD(7) estimations was constructed and the non-steady phase of the output signal was extensively studied. The modelling approach introduced allows response curve reconstruction and a curve fitting procedure of good quality, resulting in parameters indicating the relationship between response and organic substrate concentration and stability properties of the BOD biosensor. Also, the immobilization matrixes of different thicknesses were characterized to determine their suitability for bio-sensing measurements in non-stationary conditions, as well as for the determination of the mechanical durability of the BOD biosensor in time. The non-steady response of the experimental output of the BOD biosensor was fitted according to the developed model that enables to determine the stability of the biosensor output and dependency on biodegradable organic substrate concentration. The calibration range of the studied BOD biosensor in OECD synthetic wastewater was 15-110 mg O(2) L(-1). Repeatability tests showed relative standard deviation (RSD) values of 2.8% and 5.8% for the parameter ?(d), characterizing the transient output of the amperometric oxygen sensor in time, and ?(s), describing the dependency of the transient response of the BOD biosensor on organic substrate concentration, respectively. BOD biosensor experiments for the evaluation of the biochemical oxygen demand of easily degradable and refractory municipal wastewater showed good concurrence with traditional BOD(7) analysis. PMID:21042614

Velling, Siiri; Mashirin, Alexey; Hellat, Karin; Tenno, Toomas

2011-01-01

75

Light-responsive polymer nanoreactors: a source of reactive oxygen species on demand.  

PubMed

Various domains present the challenges of responding to stimuli in a specific manner, with the desired sensitivity or functionality, and only when required. Stimuli-responsive systems that are appropriately designed can effectively meet these challenges. Here, we introduce nanoreactors that encapsulate photosensitizer-protein conjugates in polymer vesicles as a source of "on demand" reactive oxygen species. Vesicles made of poly(2-methyloxazoline)-poly(dimethylsiloxane)-poly(2-methyloxazoline) successfully encapsulated the photosensitizer Rose Bengal-bovine serum albumin conjugate (RB-BSA) during a self-assembly process, as demonstrated by UV-Vis spectroscopy. A combination of light scattering and transmission electron microscopy indicated that the nanoreactors are stable over time. They serve a dual role: protecting the photosensitizer in the inner cavity and producing in situ reactive oxygen species (ROS) upon irradiation with appropriate electromagnetic radiation. Illumination with appropriate wavelength light allows us to switch on/off and to control the production of ROS. Because of the oxygen-permeable nature of the polymer membrane of vesicles, ROS escape into the environment around vesicles, as established by electron paramagnetic resonance. The light-sensitive nanoreactor is taken up by HeLa cells in a Trojan horse fashion: it is nontoxic and, when irradiated with the appropriate laser light, produces ROS that induce cell death in a precise area corresponding to the irradiation zone. These nanoreactors can be used in theranostic approaches because they can be detected via the fluorescent photosensitizer signal and simultaneously produce ROS efficiently "on demand". PMID:23154601

Baumann, Patric; Balasubramanian, Vimalkumar; Onaca-Fischer, Ozana; Sienkiewicz, Andrzej; Palivan, Cornelia G

2013-01-01

76

The locus coeruleus-norepinephrine network optimizes coupling of cerebral blood volume with oxygen demand  

PubMed Central

Given the brain's uniquely high cell density and tissue oxygen levels bordering on hypoxia, the ability to rapidly and precisely match blood flow to constantly changing patterns in neural activity is an essential feature of cerebrovascular regulation. Locus coeruleus-norepinephrine (LC-NE) projections innervate the cerebral vasculature and can mediate vasoconstriction. However, function of the LC-mediated constriction in blood-flow regulation has never been addressed. Here, using intrinsic optical imaging coupled with an anesthesia regimen that only minimally interferes with LC activity, we show that NE enhances spatial and temporal aspects of functional hyperemia in the mouse somatosensory cortex. Increasing NE levels in the cortex using an ?2-adrenergic receptor antagonist paradoxically reduces the extent of functional hyperemia while enhancing the surround blood-flow reduction. However, the NE-mediated vasoconstriction optimizes spatial and temporal focusing of the hyperemic response resulting in a sixfold decrease in the disparity between blood volume and oxygen demand. In addition, NE-mediated vasoconstriction accelerated redistribution to subsequently active regions, enhancing temporal synchronization of blood delivery. These observations show an important role for NE in optimizing neurovascular coupling. As LC neuron loss is prominent in Alzheimer and Parkinson diseases, the diminished ability to couple blood volume to oxygen demand may contribute to their pathogenesis.

Bekar, Lane K; Wei, Helen S; Nedergaard, Maiken

2012-01-01

77

Oxygen centered radicals in iodine chemical oscillators.  

PubMed

The existence of free radicals in iodine-based oscillatory systems has been debated for some time. Recently, we have reported the presence of reactive oxygen species (ROS) in the iodide-peroxide system in acidic medium, which is common to all iodine--based oscillatory systems ( J. Phys. Chem. A 2011 , 115 , 2247--2249 ). In this work, the goal was to identify the ROS produced in this system using an EPR spin trap which can distinguish between hydroxyl (HO(•)) and hydroperoxyl (HOO(•)) radicals. The formation of the hydroperoxyl radical was observed and a possible explanation for the low EPR signal of hydroxyl radical was proposed. PMID:21692499

Stanisavljev, Dragomir R; Milenkovi?, Maja C; Mojovi?, Milos D; Popovi?-Bijeli?, Ana D

2011-07-14

78

Oxygenate Supply/Demand Balances in the Short-Term Integrated Forecasting Model (Released in the STEO March 1998)  

EIA Publications

The blending of oxygenates, such as fuel ethanol and methyl tertiary butyl ether (MTBE), into motor gasoline has increased dramatically in the last few years because of the oxygenated and reformulated gasoline programs. Because of the significant role oxygenates now have in petroleum product markets, the Short-Term Integrated Forecasting System (STIFS) was revised to include supply and demand balances for fuel ethanol and MTBE. The STIFS model is used for producing forecasts in the Short-Term Energy Outlook. A review of the historical data sources and forecasting methodology for oxygenate production, imports, inventories, and demand is presented in this report.

Information Center

1998-03-01

79

Development and characterization of a novel immobilized microbial membrane for rapid determination of biochemical oxygen demand load in industrial waste-waters  

Microsoft Academic Search

The rapid determination of waste-water quality of waste-water treatment plants in terms of pollutional strength, i.e. biochemical oxygen demand (BOD) is difficult or even impossible using the chemical determination method. The present study reports the determination of BOD within minutes using microbial BOD sensors, as compared to the 5-day determination using the conventional method. Multiple criteria establish the basis for

Shikha Rastogi; Anil Kumar; N. K Mehra; S. D Makhijani; A Manoharan; V Gangal; Rita Kumar

2003-01-01

80

Benthic Oxygen Demand in Former Salt Ponds as Estimated by Porewater Profiles  

NASA Astrophysics Data System (ADS)

In recent years, several ponds near Alviso, California, previously used in commercial salt production, were modified for wetland restoration and management as part of the South Bay Salt Pond Restoration Project. Algal growth and subsequent decay often leads to suboxic or anoxic water conditions in the ponds. Sampling trips were coordinated in the second half of 2008 to examine the interstitial water in the sediment and the overlying bottom waters of three shallow (average depth <1 m) ponds adjacent to the southern reach of San Francisco Bay. A pore-water profiler, modified for dissolved-oxygen sampling, was used to obtain the first centimeter-scale estimates of the vertical concentration gradients for diffusive-flux determinations. In each pond, profilers were deployed in triplicate at two sites: a shallow site (< 1 m) and a deep site (> 2 m). Calculated diffusive benthic flux of dissolved (0.2-micron filtered) oxygen was consistently negative (that is, drawn from the water column into the sediment) and ranged between -0.5 x 10-6 and -37 x 10-6 µmol/cm2/sec. Assuming pond areas of 1.0, 1.4, and 2.3 square kilometers for the three ponds (named A16, A14, and A3W, respectively), this converts to an oxygen mass flux into the ponds’ sediment ranging from -1 to -72 kg/day. Diffusive oxygen flux into the benthos (listed as negative) was lowest in pond A14 (-0.5 x 10-6 to -1.8 x 10-6 µmol/cm2/sec) compared with diffusive flux estimates for ponds A16 and A3W (site averages -26 x 10-6 to -35 x10-6 and -34 x 10-6 to -37 x10-6 µmol/cm2/sec). These initial diffusive-flux estimates are of the order of magnitude of those previously measured in the nearby open Bay waters using core-incubation experiments, which include bioturbation and bioirrigation effects. Since the porewater profiles are unable to capture these biological effects, the benthic oxygen demand within the ponds is likely larger than reported. It should then be understood that the 2008 estimates of benthic oxygen demand, based on molecular diffusion, serve as conservative, and perhaps strongly conservative, estimates of benthic flux because solute transport across the sediment-water interface can be enhanced by myriad processes including bioturbation, bioirrigation, ground-water advection, and wind resuspension.Dissovled Oxygen Flux within Salt Ponds

Kuwabara, J. S.; Topping, B.; Athearn, N. D.; Takekawa, J. Y.; Parchaso, F.; Henderson, K.; Piotter, S.

2009-12-01

81

Development of a biochemical oxygen demand sensor using gold-modified boron doped diamond electrodes.  

PubMed

Gold-modified boron doped diamond (BDD) electrodes were examined for the amperometric detection of oxygen as well as a detector for measuring biochemical oxygen demand (BOD) using Rhodotorula mucilaginosa UICC Y-181. An optimum potential of -0.5 V (vs Ag/AgCl) was applied, and the optimum waiting time was observed to be 20 min. A linear calibration curve for oxygen reduction was achieved with a sensitivity of 1.4 ?A mg(-1) L oxygen. Furthermore, a linear calibration curve in the glucose concentration range of 0.1-0.5 mM (equivalent to 10-50 mg L(-1) BOD) was obtained with an estimated detection limit of 4 mg L(-1) BOD. Excellent reproducibility of the BOD sensor was shown with an RSD of 0.9%. Moreover, the BOD sensor showed good tolerance against the presence of copper ions up to a maximum concentration of 0.80 ?M (equivalent to 50 ppb). The sensor was applied to BOD measurements of the water from a lake at the University of Indonesia in Jakarta, Indonesia, with results comparable to those made using a standard method for BOD measurement. PMID:23088708

Ivandini, Tribidasari A; Saepudin, Endang; Wardah, Habibah; Harmesa; Dewangga, Netra; Einaga, Yasuaki

2012-11-20

82

Light-responsive polymer nanoreactors: a source of reactive oxygen species on demand  

NASA Astrophysics Data System (ADS)

Various domains present the challenges of responding to stimuli in a specific manner, with the desired sensitivity or functionality, and only when required. Stimuli-responsive systems that are appropriately designed can effectively meet these challenges. Here, we introduce nanoreactors that encapsulate photosensitizer-protein conjugates in polymer vesicles as a source of ``on demand'' reactive oxygen species. Vesicles made of poly(2-methyloxazoline)-poly(dimethylsiloxane)-poly(2-methyloxazoline) successfully encapsulated the photosensitizer Rose Bengal-bovine serum albumin conjugate (RB-BSA) during a self-assembly process, as demonstrated by UV-Vis spectroscopy. A combination of light scattering and transmission electron microscopy indicated that the nanoreactors are stable over time. They serve a dual role: protecting the photosensitizer in the inner cavity and producing in situ reactive oxygen species (ROS) upon irradiation with appropriate electromagnetic radiation. Illumination with appropriate wavelength light allows us to switch on/off and to control the production of ROS. Because of the oxygen-permeable nature of the polymer membrane of vesicles, ROS escape into the environment around vesicles, as established by electron paramagnetic resonance. The light-sensitive nanoreactor is taken up by HeLa cells in a Trojan horse fashion: it is nontoxic and, when irradiated with the appropriate laser light, produces ROS that induce cell death in a precise area corresponding to the irradiation zone. These nanoreactors can be used in theranostic approaches because they can be detected via the fluorescent photosensitizer signal and simultaneously produce ROS efficiently ``on demand''.Various domains present the challenges of responding to stimuli in a specific manner, with the desired sensitivity or functionality, and only when required. Stimuli-responsive systems that are appropriately designed can effectively meet these challenges. Here, we introduce nanoreactors that encapsulate photosensitizer-protein conjugates in polymer vesicles as a source of ``on demand'' reactive oxygen species. Vesicles made of poly(2-methyloxazoline)-poly(dimethylsiloxane)-poly(2-methyloxazoline) successfully encapsulated the photosensitizer Rose Bengal-bovine serum albumin conjugate (RB-BSA) during a self-assembly process, as demonstrated by UV-Vis spectroscopy. A combination of light scattering and transmission electron microscopy indicated that the nanoreactors are stable over time. They serve a dual role: protecting the photosensitizer in the inner cavity and producing in situ reactive oxygen species (ROS) upon irradiation with appropriate electromagnetic radiation. Illumination with appropriate wavelength light allows us to switch on/off and to control the production of ROS. Because of the oxygen-permeable nature of the polymer membrane of vesicles, ROS escape into the environment around vesicles, as established by electron paramagnetic resonance. The light-sensitive nanoreactor is taken up by HeLa cells in a Trojan horse fashion: it is nontoxic and, when irradiated with the appropriate laser light, produces ROS that induce cell death in a precise area corresponding to the irradiation zone. These nanoreactors can be used in theranostic approaches because they can be detected via the fluorescent photosensitizer signal and simultaneously produce ROS efficiently ``on demand''. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr32380j

Baumann, Patric; Balasubramanian, Vimalkumar; Onaca-Fischer, Ozana; Sienkiewicz, Andrzej; Palivan, Cornelia G.

2012-12-01

83

Ethanol Demand in United States Production of Oxygenate-limited Gasoline  

SciTech Connect

Ethanol competes with methyl tertiary butyl ether (MTBE) to satisfy oxygen, octane, and volume requirements of certain gasolines. However, MTBE has water quality problems that may create significant market opportunities for ethanol. Oak Ridge National Laboratory (ORNL) has used its Refinery Yield Model to estimate ethanol demand in gasolines with restricted use of MTBE. Reduction of the use of MTBE would increase the costs of gasoline production and possibly reduce the gasoline output of U.S. refineries. The potential gasoline supply problems of an MTBE ban could be mitigated by allowing a modest 3 vol percent MTBE in all gasoline. In the U.S. East and Gulf Coast gasoline producing regions, the 3 vol percent MTBE option results in costs that are 40 percent less than an MTBE ban. In the U.S. Midwest gasoline producing region, with already high use of ethanol, an MTBE ban has minimal effect on ethanol demand unless gasoline producers in other regions bid away the local supply of ethanol. The ethanol/MTBE issue gained momentum in March 2000 when the Clinton Administration announced that it would ask Congress to amend the Clean Air Act to provide the authority to significantly reduce or eliminate the use of MTBE; to ensure that air quality gains are not diminished as MTBE use is reduced; and to replace the existing oxygenate requirement in the Clean Air Act with a renewable fuel standard for all gasoline. Premises for the ORNL study are consistent with the Administration announcement, and the ethanol demand curve estimates of this study can be used to evaluate the impact of the Administration principles and related policy initiatives.

Hadder, G.R.

2000-08-16

84

Detailed chemical kinetic mechanisms for combustion of oxygenated fuels  

Microsoft Academic Search

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

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

2000-01-01

85

Chemical arms treaty makes unprecedented demands of industry  

SciTech Connect

It took nearly a quarter of a century of grueling negotiations to craft the text of the comprehensive and verifiable chemical weapons treaty. But that may have been the easy part. Now representatives from about 90 of the more than 140 nations that have signed the treaty are at The Hague participating in a two-year exercise called the Preparatory Commission, or PrepCom. PrepCom's charge is to make concrete what are now merely words on paper. When it completes its work, the chemical industry will be ensnared in a web of requirements far surpassing any mandated by existing domestic legislation. PrepCom's agenda was scripted by the same Conference on Disarmament negotiators who labored in Geneva hammering out the treaty banning the production, stockpiling, transfer, and use of chemical weapons. They wanted to make certain that a structure was in place to monitor and verify compliance with the treaty once it entered into force, or becomes effective. The negotiators' agenda was approved by those countries that signed the treaty this past January in Pairs. It set out some 40 individual tasks for PrepCom, many of them highly technical and most of them potentially politically volatile. This paper discusses the problems facing PrepCom.

Ember, L.R.

1993-06-07

86

Application of commercial biochemical oxygen demand inocula for biodegradable dissolved organic carbon determination.  

PubMed

Biochemical oxygen demand (BOD) and biodegradable dissolved organic carbon (BDOC) measure the amount of biodegradable organics in water samples using mixed culture seeds. The BOD method relies on the dissolved oxygen reduction while the BDOC procedure, which is more novel, is based on the dissolved organic carbon decrease during the incubation. In this study, three commercial BOD seeds, namely BOD Seed, Bi-Chem and Polyseed, were tested as inocula for BDOC measurement. Standard solutions, secondary effluent and raw surface water samples were used. BDOC exertions provided by the commercial seeds were compared with those obtained from two existing BDOC inocula, indigenous and mixed liquor suspended solid (MLSS) seeds. The commercial and indigenous inocula provided similar exertion trends and BDOC results that were not significantly different for surface water samples while the results for secondary effluent samples were inconclusive. The MLSS inoculum tend to provide slightly higher BDOC values and faster exertion kinetics than the commercial and indigenous inocula. The exertions by all five inocula could be expressed well with first-order kinetics for all cases that enough data were available for kinetics evaluation. The commercial seeds were similar in terms of BDOC determination accuracy and precision, and exertion kinetics. It is possible to use the commercial BOD inocula as seeds for BDOC determination but the results might not be statistically the same as those of the indigenous inoculum for certain types of samples. PMID:16278006

Khan, Eakalak; Sy-Savane, Ousmane; Jittawattanarat, Rungrod

2005-11-01

87

The chemical effects of auroral oxygen precipitation at Jupiter  

NASA Technical Reports Server (NTRS)

A numerical model of the auroral ionosphere and thermosphere of Jupiter, which includes odd oxygen species, is presented. Density profiles of neutral species O, OH, and H2O and the ion species H2(+), H3(+), H(+), H2O(+), H3O(+), O(+), and OH(+) are calculated. The total neutral odd oxygen density is found to be about 10 exp 5/cu cm near the auroral ionosphere peak. The major ionospheric ion, H(+) reacts rapidly with both O and H2O and the presence of these species in the model calculations significantly reduces the H(+) density and thus the electron density. The chemical lifetime against reaction of H(+) with odd oxygen is about 1000 s near the peak, whereas the radiative recombination lifetime is roughly 10,000 s.

Cravens, T. E.; Eisenhower, G. M.

1992-01-01

88

Chemical oxygen-iodine laser (COIL) thermal management  

NASA Astrophysics Data System (ADS)

The chemical oxygen-iodine laser (COIL) has been studied at the Phillips Laboratory since its invention in 1978. One of the most difficult challenges in COIL technology is to produce constant power for more than a few seconds; an essential feature for most applications. The key to developing a laser with these operational characteristics is management of the heat released during the production of singlet delta oxygen. Approximately 10 joules is deposited into the singlet delta oxygen generator (SOG) for every joule extracted as laser power. A recent test series demonstrated run times of 120 seconds at 9 kW by controlling the SOG reaction temperature with a flowing aqueous solution of cold hydroperoxide (BHP). This method of managing the energy released is quite effective but requires a large reservoir of cold BHP.

Truesdell, Keith A.; Helms, Charles A.; Longergan, Thomas; Wisniewski, Charles F.; Scott, Joseph E.; Healey, Keith P.

1995-03-01

89

Multiphase reacting flow modeling of singlet oxygen generators for chemical oxygen iodine lasers.  

SciTech Connect

Singlet oxygen generators are multiphase flow chemical reactors used to generate energetic oxygen to be used as a fuel for chemical oxygen iodine lasers. In this paper, a theoretical model of the generator is presented along with its solutions over ranges of parameter space and oxygen maximizing optimizations. The singlet oxygen generator (SOG) is a low-pressure, multiphase flow chemical reactor that is used to produce molecular oxygen in an electronically excited state, i.e. singlet delta oxygen. The primary product of the reactor, the energetic oxygen, is used in a stage immediately succeeding the SOG to dissociate and energize iodine. The gas mixture including the iodine is accelerated to a supersonic speed and lased. Thus the SOG is the fuel generator for the chemical oxygen iodine laser (COIL). The COIL has important application for both military purposes--it was developed by the US Air Force in the 1970s--and, as the infrared beam is readily absorbed by metals, industrial cutting and drilling. The SOG appears in various configurations, but the one in focus here is a crossflow droplet generator SOG. A gas consisting of molecular chlorine and a diluent, usually helium, is pumped through a roughly rectangular channel. An aqueous solution of hydrogen peroxide and potassium hydroxide is pumped through small holes into the channel and perpendicular to the direction of the gas flow. So doing causes the solution to become aerosolized. Dissociation of the potassium hydroxide draws a proton from the hydrogen peroxide generating an HO{sub 2} radical in the liquid. Chlorine diffuses into the liquid and reacts with the HO{sub 2} ion producing the singlet delta oxygen; some of the oxygen diffuses back into the gas phase. The focus of this work is to generate a predictive multiphase flow model of the SOG in order to optimize its design. The equations solved are the so-called Eulerian-Eulerian form of the multiphase flow Navier-Stokes equations wherein one set of the equations represents the gas phase and another equation set of size m represents the liquid phase. In this case, m is representative of the division of the liquid phase into distinct representations of the various droplet sizes distributed in the reactor. A stabilized Galerkin formulation is used to solve the equation set on a computer. The set of equations is large. There are five equations representing the gas phase: continuity, vector momentum, heat. There are 5m representing the liquid phase: number density, vector momentum, heat. Four mass transfer equations represent the gas phase constituents and there are m advection diffusion equations representing the HO{sub 2} ion concentration in the liquid phase. Thus we are taking advantage of and developing algorithms to harness the power of large parallel computing architectures to solve the steady-state form of these equations numerous times so as to explore the large parameter space of the equations via continuation methods and to maximize the generation of singlet delta oxygen via optimization methods. Presented here will be the set of equations that are solved and the methods we are using to solve them. Solutions of the equations will be presented along with solution paths representing varying aerosol loading-the ratio of liquid to gas mass flow rates-and simple optimizations centered around maximizing the oxygen production and minimizing the amount of entrained liquid in the gas exit stream. Gas-entrained liquid is important to minimize as it can destroy the lenses and mirrors present in the lasing cavity.

Salinger, Andrew Gerhard; Pawlowski, Roger Patrick; Hewett, Kevin B. (Air Force Research Laboratory, Albuquerque, NM); Madden, Timothy J. (Air Force Research Laboratory, Albuquerque, NM); Musson, Lawrence Cale

2008-08-01

90

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

91

Chemical oxygen-iodine laser with a centrifugal spray generator of singlet oxygen  

NASA Astrophysics Data System (ADS)

A chemical oxygen-iodine laser driven by the centrifugal spray generator of singlet oxygen was developed and experimentally studied. Modeling and experimental studies showed that the designed generator can produce singlet oxygen, O2(1?g), with a high efficiency (chlorine utilization 0.68 - 0.87 and O2(1?g) yield 0.35 - 0.7) even at very high generator pressures (25 - 70 kPa), which cannot be attained by other O2(1?g) generators. This high-pressure operation should be beneficial for a pressure recovery system of the laser. Another specific feature of the generator is a very high BHP utilization (0.24-0.6). The developed separator can effectively remove even small droplets (> 1 ?m) from gas at the generator exit. Preliminary experiments on the COIL driven the centrifugal spray generator provided the small signal gain up to 0.5 % cm-1.

Špalek, Otomar; Jirásek, Vít; ?enský, Miroslav; Kodymová, Jarmila

2010-09-01

92

Development and characterization of microbial biosensors for evaluating low biochemical oxygen demand in rivers.  

PubMed

Five microorganisms were used to construct a biosensor for the evaluation of low biochemical oxygen demand (BOD) in rivers. Characterization and comparison of BOD biosensors were performed using two standard solutions: glucose and glutamic acid (GGA) and artificial wastewater (AWW). Pseudomonas putida SG10 demonstrated the best response when using AWW. Trichosporon cutaneum IFO10466, however, had an extremely poor response. When evaluating the biosensor response to each component of AWW, all of the microorganisms except T. cutaneum displayed the highest response to tannic acid. In a comparison of the two standard solutions for all the microorganisms, the biosensor responses of GGA were approximately three times higher than those of AWW were. In the BOD determination of environmental samples, the biosensor BOD values evaluated using AWW were slightly lower or equivalent to BOD5 values, whereas the biosensor BOD values evaluated using GGA were considerably lower. These results suggest that GGA is suitable for the detection of high BOD in industrial wastewaters and factory effluents, while AWW is suitable for the detection of low BOD in rivers. PMID:24209354

Chee, Gab-Joo

2013-12-15

93

Water Quality Impacts of Biochemical Oxygen Demand Under Transferable Discharge Permit Programs  

NASA Astrophysics Data System (ADS)

Biochemical oxygen demand is an important example of water pollutants that degrade biochemically and affect water quality according to the location as well as the strength of the discharge. Therefore, it is important to examine carefully the potential water quality impacts of a program of transferable discharge permits (TDP's) to regulate these discharges prior to the implementation of such a program. This paper provides a framework for evaluating these impacts and illustrates trade-offs among cost efficiency, equity, and uncertainty with respect to meeting water quality goals. Examples are given for the Delaware River estuary and the Willamette River. It is shown that violations of the standard could occur under a TDP program. Restrictions on the market could be used, however, to control or possibly to eliminate such violations. Limits on the total discharge in sections of the basin, zone boundaries for markets, and revaluation factors for transferred permits were shown to be effective individually or in various combinations. Even with these restrictions, however, there is sufficient flexibility so that significantly more cost-efficient solutions are obtained than under direct regulation programs that treat all dischargers uniformly.

Brill, E. Downey, Jr.; Eheart, J. Wayland; Kshirsagar, Sudhir R.; Lence, Barbara J.

1984-04-01

94

Compensatory vasodilatation during hypoxic exercise: mechanisms responsible for matching oxygen supply to demand.  

PubMed

Hypoxia can have profound influences on the circulation. In humans, acute exposure to moderate hypoxia has been demonstrated to result in vasodilatation in the coronary, cerebral, splanchnic and skeletal muscle vascular beds. The combination of submaximal exercise and hypoxia produces a 'compensatory' vasodilatation and augmented blood flow in contracting skeletal muscles relative to the same level of exercise under normoxic conditions. This augmented vasodilatation exceeds that predicted by a simple sum of the individual dilator responses to hypoxia alone and normoxic exercise. Additionally, this enhanced hypoxic exercise hyperaemia is proportional to the hypoxia-induced fall in arterial oxygen (O(2)) content, thus preserving muscle O(2) delivery and ensuring it is matched to demand. Several vasodilator pathways have been proposed and examined as likely regulators of skeletal muscle blood flow in response to changes in arterial O(2) content. The purpose of this review is to put into context the present evidence regarding mechanisms responsible for the compensatory vasodilatation observed during hypoxic exercise in humans. Along these lines, this review will highlight the interactions between various local metabolic and endothelial derived substances that influence vascular tone during hypoxic exercise. PMID:22988134

Casey, Darren P; Joyner, Michael J

2012-12-15

95

System Dynamics Approach to Modelling the Degradation of Biochemical Oxygen Demand in A Constructed Wetland Receiving Stormwater Runoff.  

National Technical Information Service (NTIS)

The objective of this research was to develop a tool to aid the Air Force Environmental Manager in the identification of the design parameters of a constructed wetland system that may be optimized to provide a desired biochemical oxygen demand (BOD) remov...

L. A. Mudgett

1995-01-01

96

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

97

Respiratory demand during rigorous physical work in a chemical protective ensemble.  

PubMed

Protection afforded by a respirator filter depends on many factors, among them chemical or biological agent and flow rate. Filtration mechanisms, such as chemical adsorption, depend on sufficient residence time for the filter media to extract noxious agents from the airstream. Consequently, filter efficiency depends on inspiratory air velocities, among other factors. Filter designs account for this by adjusting bed depth and cross-sectional area to anticipated flow rates. Many military and commercial filters are designed and tested at 32-40 L/min. The present study investigated respiratory demand while U.S. Marines (n=32) completed operationally relevant tasks in chemical protective ensembles, including M-40 masks and C2A1 filters. Respiratory demand greatly exceeded current test conditions during the most arduous tasks: minute ventilation=96.4+/-18.9 L/min (mean+/-SD) with a maximum of 131.7 L/min observed in one subject. Mean peak inspiratory flow rate (PIF) reached 238.7+/-34.0 L/min with maximum PIF often exceeding 300 L/min (maximum observed value=356.3 L/min). The observed respiratory demand was consistent with data reported in previous laboratory studies of very heavy workloads. This study is among the few to report on respiratory demand while subjects perform operationally relevant tasking in chemical protective ensembles. The results indicate that military and industrial filters will probably encounter higher flow rates than previously anticipated during heavy exertion. PMID:15764530

Kaufman, Jonathan; Hastings, Sherri

2005-02-01

98

Centrifugal spray generator of singlet oxygen for a chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

A centrifugal spray generator of singlet oxygen, O2(1?g), for driving a chemical oxygen-iodine laser was developed and its operation was experimentally studied. Modeling of the liquid separation from the gas flow showed that the separator designed could remove droplets larger than 0.5 ?m from gas, which is very important for the laser operation. This result was confirmed by experiments. Experimental studies proved that O2(1?g) could be produced with a high efficiency (chlorine utilization 0.68-0.87 and O2(1?g) yield 0.35-0.7) even at very high generator pressures (25-70 kPa), which cannot be attained by other O2(1?g) generators.

Špalek, O.; Hrubý, J.; ?enský, M.; Jirásek, V.; Kodymová, J.

2010-09-01

99

Detailed Chemical Kinetic Modeling of Diesel Combustion with Oxygenated Fuels  

SciTech Connect

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

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

2000-01-11

100

Standard chemical oxygen-iodine laser kinetics package. Revision. Final report, August 1987March 1988  

Microsoft Academic Search

It has been long recognized that continuous-wave (CW) chemical lasers represent an extremely complex interaction between fluid mechanics, chemical kinetics, and optical physics. The chemical oxygen-iodine laser presents additional problems in that the energy-storage medium, singlet oxygen, is generated by a liquid-gas phase reaction. The kinetics of chemical oxygen-iodine lasers can be divided into five categories: (1) the chemistry of

G. P. Perram; G. D. Hager

1988-01-01

101

Removal of Water Vapor in a Mist Singlet Oxygen Generator for Chemical Oxygen Iodine Laser  

NASA Astrophysics Data System (ADS)

The mist singlet oxygen generator (Mist-SOG) for a chemical oxygen iodine laser (COIL) has been developed in order to increase basic hydrogen peroxide (BHP) utilization. It was clarified that the Mist-SOG generated much more water vapor than conventional SOGs because the heat capacity of BHP is small. The water vapor deactivates the excited iodine and depresses the laser power. Therefore, a jet-cold trap was developed in order to remove the water vapor while maintaining a minimum deactivation of singlet oxygen. In this method, a nozzle was used to spray chilled H2O2 at 238 K as a thin layer directly to the gas flow to achieve a large specific surface area for water vapor. As a result, the water vapor mole fraction was reduced to 7% from 18% with the BHP utilization of 21% at the Cl2 consumption rate of 3.5 mmol/s (Cl2 input flow rate of 8.0 mmol/s) for 65-?m-diameter BHP droplets.

Muto, Shigeki; Endo, Masamori; Nanri, Kenzo; Fujioka, Tomoo

2004-02-01

102

Spray generator of singlet oxygen for a chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

A spray type of singlet oxygen generator for driving the Chemical Oxygen-Iodine Laser was developed. Singlet oxygen, O2(1?g), is generated by a fast reaction of chlorine with basic hydrogen peroxide solution in the form of a dense spray. A mathematical model of this reaction system showed that O2(1?g) can be generated in this system with a high yield (0.70-0.80), high utilization of chlorine (0.75-0.95), and effective utilization of liquid (0.36-0.54) at very high generator pressures (35-75 kPa). Experimental studies of this reaction system without an efficient separation of liquid proved an efficient O2(1?g) production characterized by a rather high product of chlorine utilization and O2(1?g) yield (0.4-0.9) at very high generator pressures (30-80 kPa). This pressure is much higher than the operation pressure used in other generators, which should be beneficial for a pressure recovery system of the COIL. These results provided the basis for designing a centrifugal spray generator with an efficient separation of liquid from the gas flow, which is the subject of the following paper.

Jirásek, V.; Hrubý, J.; Špalek, O.; ?enský, M.; Kodymová, J.

2010-09-01

103

Improving the dynamic response of a mediator-less microbial fuel cell as a biochemical oxygen demand (BOD) sensor  

Microsoft Academic Search

The dynamic behavior of a mediator-less, microbial fuel cell (MFC) was studied as a continuous biochemical oxygen demand (BOD) sensor. The response time and the sensitivity were analyzed through the step-change testing of the fuel concentration. The MFC of 25 ml had the shortest response time of 36± 2 min at the fuel-feeding rate of 0.53 ml min-1 and the resistance of 10O

Hyunsoo Moon; In Seop Chang; Kui Hyun Kang; Jae Kyung Jang; Byung Hong Kim

2004-01-01

104

XPS chemical analysis of tholins: the oxygen contamination  

NASA Astrophysics Data System (ADS)

In Titan's atmosphere, solid organic aerosols are initiated in the upper atmosphere by the photo-dissociation and photo-ionization of N2 and CH4. In order to simulate this complex chemistry several experimental setups have been built, among them plasma experiments. The aerosol analogues produced in such plasma discharges contain oxygen, as a few percents of the elemental composition, despite the absence of oxygen source in the reactive medium [1]. The present study aims at studying the origin of such systematic oxygen incorporation in tholins. A low pressure (0.9mbar) RF CCP discharge is used described in [2]. Gas mixtures of N2 and CH4 (from 1 to 10% of CH4) are injected continuously. The plasma discharge leads to the production of analogues of Titan's atmospheric aerosols: both as grains in the volume [1] and as thin films on the surface of the reactor [3]. SiO2 substrates of 1cm diameter and 1mm thickness are placed on the grounded electrode of the discharge. Organic films are deposited during 2 hours in order to have films thickness less than 1?m. After the two hours, samples are recovered at ambient air for ex-situ analysis. Two complementary analyses are performed to analyse the thin film chemical composition: XPS and SIMS, in order to probe both the surface and depth profile. References [1] Sciamma-O'brien E., Carrasco N., Szopa C., Buch A., Cernogora G. Icarus 209, 2 (2010) 704-714 [2] Alcouffe G., Cavarroc M., Cernogora G., Ouni F., Jolly A., Boufendi L., Szopa C. Plasma Sources Science and Technology 19, 1 (2010) 015008 (11pp) [3] Mahjoub A., Carrasco N., Dahoo P.-R., Gautier T., Szopa C., Cernogora G. Icarus 221, 2 (2012) 670-677.

Carrasco, N.; Jomard, F.; Vigneron, J.; Cernogora, G.

2013-12-01

105

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

PubMed

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

Ayyaru, Sivasankaran; Dharmalingam, Sangeetha

2014-03-25

106

Aircraft and runway deicers at General Mitchell International Airport, Milwaukee, Wisconsin, USA. 1. Biochemical oxygen demand and dissolved oxygen in receiving streams  

USGS Publications Warehouse

Aircraft and runway deicers are used during cold weather at many of the world's airports to facilitate safe air travel. Propylene glycol-, ethylene glycol-, and urea-based deicers are known to have very high biochemical oxygen demand. At General Mitchell International Airport (GMIA) in Milwaukee, Wisconsin, USA, deicer application, water chemistry, and dissolved oxygen (DO) data were collected for two deicing seasons in order to evaluate and define premanagement water quality parameters prior to the implementation of a glycol management program. Calculations using stream-monitoring data during a controlled release of deicer provided an estimate of 0.8/d for the first-order decay rate constant, substantially higher than published laboratory test results. For eight precipitation events with deicing activities, between 2.4 and 99% of propylene and ethylene glycol applied to aircraft was delivered directly to receiving streams. The percentage of glycol runoff during an event increased with increasing storm-flow volume. Elevated concentrations of glycol and biochemical oxygen demand were measured downstream from the airport. However, the frequency of low DO concentrations in the receiving streams is comparable with that at an upstream reference site. This is possibly due to slowed bacteria metabolism at low water temperatures, short travel times, and dilution from downstream tributaries.

Corsi, S. R.; Booth, N. L.; Hall, D. W.

2001-01-01

107

Applications of the chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The Chemical Oxygen-Iodine Laser (COIL) has been developed at the Air Force Research Laboratory for military applications. For example, the COIL is to be use as the laser device for the ABL. A high power laser is useful for applications that require the delivery of a substantial amount of energy to a very small focused laser spot. The COIL is a member of the class of high power lasers that are also useful for industrial applications, including the materials processing task of high speed cutting and drilling. COIL technology has received considerable interest over the last several years due to its short, fiber- deliverable wavelength, scalability to very high powers, and demonstrated nearly diffraction-limited optical quality. These unique abilities make it an ideal candidate for nuclear reactor decommissioning and nuclear warhead dismantlement. Japanese researchers envision using a COIL for disaster cleanup and survivor rescue. It is also being studied by the oil and gas industry for well drilling. Any commercial or industrial application that requires very rapid, precise, and noninvasive cutting or drilling, could be readily accomplished with a COIL. Because of the substantial power levels available with a COIL, the laser could also be used for broad area applications such as paint stripping. This paper includes a collection of experiments accomplished at the Air Force Research Laboratory Chemical Laser Facility, including metal cutting, hole drilling, high power fiber optic transmission, and rock crushing.

Latham, William P.; Kendrick, Kip R.; Quillen, Brian

2000-01-01

108

Impact of the renewable oxygenate standard for reformulated gasoline on ethanol demand, energy use, and greenhouse gas emissions  

SciTech Connect

To assure a place for renewable oxygenates in the national reformulated gasoline (RFG) program, the US Environmental Protection Agency has promulgated the renewable oxygenate standard (ROS) for RFG. It is assumed that ethanol derived from corn will be the only broadly available renewable oxygenate during Phase I of the RFG program. This report analyzes the impact that the ROS could have on the supply of ethanol, its transported volume, and its displacement from existing markets. It also considers the energy and crude oil consumption and greenhouse gas (GHG) emissions that could result from the production and use of various RFGs that could meet the ROS requirements. The report concludes that on the basis of current and projected near-term ethanol capacity, if ethanol is the only available renewable oxygenate used to meet the requirements of the ROS, diversion of ethanol from existing use as a fuel is likely to be necessary. Year-round use of ethanol and ETBE would eliminate the need for diversion by reducing winter demand for ethanol. On an RFG-program-wide basis, using ethanol and ETBE to satisfy the ROS can be expected to slightly reduce fossil energy use, increase crude oil use, and have essentially no effect on GHG emissions or total energy use relative to using RFG oxygenated only with MTBE.

Stork, K.C.; Singh, M.K.

1995-04-01

109

Oxygen-17 nuclear magnetic resonance spectroscopy of sulfoxides and sulfones. Alkyl substituent induced chemical shift effects  

SciTech Connect

Oxygen-17 NMR chemical shifts have been determined for a number of cyclic and acyclic as well as aliphatic, olefinic, and aryl sulfoxides and sulfones. The /sup 17/O NMR chemical shifts for the acyclic, aliphatic, and aromatic sulfoxides reported here absorb in the narrow range between delta -20 and +20, while the cyclic, aliphatic sulfoxides absorb between delta -13 and +66 relative to external (but naturally abundant) H/sub 2//sup 17/O. The sulfonyl oxygens are deshielded relative to the sulfinyl oxygens, exhibiting chemical shifts for acyclic and cyclic sulfonyl oxygens between delta 120 and 183 for the sulfones reported here. Diastereotopic sulfonyl oxygens exhibit chemical shift nonequivalence. Substituent-induced chemical shift effects by a methyl or methylene group on the sulfinyl and sulfonyl oxygens are discussed.

Dyer, J.C.; Harris, D.L.; Evans, S.A. Jr.

1982-09-10

110

Detailed Chemical Kinetic Mechanisms for Combustion of Oxygenated Fuels  

SciTech Connect

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

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

2000-01-11

111

Proceeding of US Army Corps of Engineers Workshop on Sediment Oxygen Demand Held in Providence, Rhode Island on 21-22 August 1990.  

National Technical Information Service (NTIS)

Sediment oxygen demand (SOD) and related processes control many water quality conditions. An understanding of SOD processes and their quantification is needed to assess the effects of US Army Corps of Engineers (CE) projects on sediment-water interactions...

C. Cerco D. Gunnison C. B. Price

1992-01-01

112

Effect of olprinone, a phosphodiesterase III inhibitor, on balance of cerebral oxygen supply and demand during cardiopulmonary bypass.  

PubMed

Neuropsychological dysfunction with cardiopulmonary bypass (CPB) may be facilitated by inadequate cerebral oxygen balance during CPB. Olprinone, a phosphodiesterase III inhibitor, augments cerebral blood flow by a direct vasodilator effect on cerebral arteries. We conducted the present randomized study in patients undergoing cardiac surgery with CPB to investigate whether olprinone improved the balance of cerebral oxygen supply and demand during the rewarming period of CPB. After anesthesia, a 5.5 F fiberoptic oximeter catheter was inserted into the right jugular bulb retrogradely for monitoring the jugular venous oxyhemoglobin saturation (SjO2), and a probe of transcranial near-infrared spectroscopy was placed over the forehead for monitoring the bilateral regional cerebral oxygen saturation (rSO2). Patients were randomly assigned to 3 groups, and olprinone was administered at 0, 0.2, or 0.4 ?g·kg(-1)·min(-1) after establishment of hypothermic CPB. Olprinone significantly prevented the reduction of the SjO2 at 5 and 10 minutes after the start of rewarming, although it did not alter rSO2. Furthermore, there was a minor reduction of the bilateral rSO2 at low doses of olprinone (0.2 ?g·kg(-1)·min(-1)). We conclude that olprinone prevents the decrease of the SjO2 at the rewarming period and improves the balance of cerebral oxygen supply and demand during the rewarming period of CPB. In addition, a future extended study may be required to elucidate the effect of low dose of olprinone. PMID:21326107

Yamanaka, Hiroo; Hayashi, Yukio; Kamibayashi, Takahiko; Mashimo, Takashi

2011-05-01

113

Impact of oxygen cut off and starvation conditions on biological activity and physico-chemical properties of activated sludge.  

PubMed

Physico-chemical and biological parameters were monitored both throughout different oxygen cut off and starvation (OCS) times (6 h-72 h) and after the restoration of normal operational conditions. Sludge apparent viscosity and soluble extracellular polymeric substances (EPS) characteristics were measured to determine the activated sludge (AS) properties. Oxygen transfer, biological activity with specific oxygen uptake rate (SOUR) measurements during endogenous/exogenous conditions (without any external substrate/with external substrate consumption) and chemical oxygen demand (COD) removal were measured to assess the AS performances. During the different stress times, AS deflocculated as a decrease of apparent viscosity was observed and microorganisms biodegraded the released EPS to survive. After aeration return, and under endogenous conditions, size exclusion chromatographic fingerprints of soluble EPS were modified and macromolecules probably of type humic-like substances appeared in significant quantities. These new macromolecules presumably acted as biosurfactants. Consequently, the liquid surface tension, as well as the oxygen transfer rate (OTR), decreased. Under exogenous conditions, high biological activity (SOUR = 11.8 +/- 2.1 mg(O2 x g(MLVSS)(-1) x h(-1)) compensated the decrease of oxygen transfer. Finally, AS biomass maintained a constant COD degradation rate (15.7 +/- 1.9 mg(O2) x g(MLVSS)(-1) x h(-1)) before and after the disturbances for all times tested. This work demonstrates that AS microorganisms can counteract concomitant oxygen and nutrients shortage when the duration of such a condition does not exceed 72 h. Dissociation of endogenous/exogenous conditions appears to offer an ideal laboratory model to study EPS and biomass activity effects on oxygen transfer. PMID:23837341

Villain, Maud; Clouzot, Ludiwine; Guibaud, Gilles; Marrot, Benoit

2013-01-01

114

Chemical oxygen iodine laser (COIL) technology and development  

NASA Astrophysics Data System (ADS)

In the late 1960's researchers realized that producing a population inversion in a moving medium could be used to generate high-energy laser beams. The first lasers to scale to the 10 kW size with good beam quality were supersonic flows of N2 - CO2, emitting radiation from the CO2 at 10.6 microns. In the 1970's gas dynamic CO2 lasers were scaled to hundreds of kilowatts and engineered into a KC-135 aircraft. This aircraft (The Airborne Laser Laboratory) was used to shoot down Sidewinder AIM-9B missiles in the early 1980"s. During this same time period (1970-1990) hydrogen fluoride and deuterium fluoride lasers were scaled to the MW scale in ground-based facilities. In 1978, the Iodine laser was invented at the Air Force Research Laboratory and scaled to the 100 kW level by the early 1990"s. Since the 60s, the DOD Chemical Laser development efforts have included CO2, CO, DF, HF, and Iodine. Currently, the DOD is developing DF, HF, and Iodine lasers, since CO2 and CO have wavelengths and diffraction limitations which make them less attractive for high energy weapons applications. The current military vision is to use chemical lasers to prove the principles and field ground and air mounted laser systems while attempting to develop weight efficient solid-state lasers at the high power levels for use in future Strategic and Tactical situations. This paper describes the evolution of Chemical Oxygen Iodine Lasers, their selection for use in the Airborne Laser (ABL), and the Advanced Tactical Laser (ATL). COIL was selected for these early applications because of its power scalability, its short wavelength, its atmospheric transmittance, and its excellent beam quality. The advantages and challenges are described, as well as some of the activities to improve magazine depth and logistics supportability. COIL lasers are also potentially applicable to mobile ground based applications, and future space based applications, but challenges exist. In addition, COIL is being considered for civil commercial applications in the US and overseas.

Duff, Edward A.; Truesdell, Keith A.

2004-09-01

115

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

Microsoft Academic Search

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

Qingjie Guo; Jianshe Zhang; Hongjing Tian

2012-01-01

116

Cerebral oxygen demand for short-lived and steady-state events  

PubMed Central

Due to importance of oxidative energetics for cerebral function, extraction of oxygen consumption (CMRO2) from blood oxygenation level dependent (BOLD) signal using multi-modal measurements of blood flow (CBF) and volume (CBV) has become an accepted functional magnetic resonance imaging (fMRI) technique. This approach, termed calibrated fMRI, is based on a biophysical model which describes tissue oxygen extraction at steady-state. A problem encountered for calculating dynamic CMRO2 relates to concerns whether the conventional BOLD model can be applied transiently. In particular, it is unclear whether calculation of CMRO2 differs between short and long stimuli. Linearity was experimentally demonstrated between BOLD-related components and neural activity, thereby making it possible to use calibrated fMRI in a dynamic manner. We used multi-modal fMRI and electrophysiology, in ?-chloralose anesthetized rats during forepaw stimulation to show that respective transfer functions (of BOLD, CBV, CBF) generated by deconvolution with neural activity are time invariant, for events in the millisecond to minute range. These results allowed extraction of a significant component of the BOLD signal that can be ascribed to CMRO2 transients. We discuss the importance of minimizing residual signal, represented by the difference between modeled and raw signals, in convolution analysis using multi-modal signals.

Herman, Peter; Sanganahalli, Basavaraju G.; Blumenfeld, Hal; Hyder, Fahmeed

2009-01-01

117

Cerebral oxygen demand for short-lived and steady-state events.  

PubMed

Because of the importance of oxidative energetics for cerebral function, extraction of oxygen consumption (CMR(O2)) from blood oxygenation level-dependent (BOLD) signal using multi-modal measurements of blood flow (CBF) and volume (CBV) has become an accepted functional magnetic resonance imaging (fMRI) technique. This approach, termed calibrated fMRI, is based on a biophysical model which describes tissue oxygen extraction at steady-state. A problem encountered for calculating dynamic CMR(O2) relates to concerns whether the conventional BOLD model can be applied transiently. In particular, it is unclear whether calculation of CMR(O2) differs between short and long stimuli. Linearity was experimentally demonstrated between BOLD-related components and neural activity, thereby making it possible to use calibrated fMRI in a dynamic manner. We used multi-modal fMRI and electrophysiology, in alpha-chloralose anesthetized rats during forepaw stimulation to show that respective transfer functions (of BOLD, CBV, CBF) generated by deconvolution with neural activity are time invariant, for events in the millisecond to minute range. These results allowed extraction of a significant component of the BOLD signal that can be ascribed to CMR(O2) transients. We discuss the importance of minimizing residual signal, represented by the difference between modeled and raw signals, in convolution analysis of multi-modal signals. PMID:19393011

Herman, Peter; Sanganahalli, Basavaraju G; Blumenfeld, Hal; Hyder, Fahmeed

2009-05-01

118

Oxygen diffusion in basalt and andesite melts: experimental results and discussion of chemical versus tracer diffusion  

NASA Astrophysics Data System (ADS)

Chemical diffusion coefficients for oxygen in melts of Columbia River basalt (Ice Harbor Dam flow) and Mt. Hood andesite have been determined at 1 atm. The diffusion model is that of sorption or desorption of oxygen into a sphere of uniform initial concentration from a constant and semi-infinite atmosphere. The experimental design utilizes a thermogravimetric balance to monitor the rate of weight change arising from the response of the sample redox state to an imposed fO2. Oxygen diffusion coefficients are approximately an order-ofmagnitude greater for basaltic melt than for andesitic melt. At 1260° C, the oxygen diffusion coefficients are: D=1.65×10-6cm2/s and D=1.43×10-7cm2/s for the basalt and andesite melts, respectively. The high oxygen diffusivity in basaltic melt correlates with a high ratio of nonbridging oxygen/tetrahedrally coordinated cations, low melt viscosity, and high contents of network-modifying cations. The dependence of the oxygen diffusion coefficient on temperature is: D=36.4exp(-51,600±3200/ RT)cm2/s for the basalt and D=52.5exp(-60,060±4900/ RT)cm2/s for the andesite ( R in cal/deg-mol; T in Kelvin). Diffusion coefficients are independent of the direction of oxygen diffusion (equilibrium can be approached from extremely oxidizing or reducing conditions) and thus, melt redox state. Characteristic diffusion distances for oxygen at 1260° C vary from 10-2 to 102 m over the time interval of 1 to 106 years. A compensation diagram shows two distinct trends for oxygen chemical diffusion and oxygen tracer diffusion. These different linear relationships are interpreted as supporting distinct oxygen transport mechanisms. Because oxygen chemical diffusivities are generally greater than tracer diffusivities and their Arrhenius activation energies are less, transport mechanisms involving either molecular oxygen or vacancy diffusion are favored.

Wendlandt, Richard F.

1991-10-01

119

Oxidation kinetics of chemically vapor-deposited silicon carbide in wet oxygen  

Microsoft Academic Search

The oxidation kinetics of chemically vapor-deposited SiC in dry oxygen and wet oxygen at temperatures between 1,200 and 1,400 C were monitored using thermogravimetric analysis. It was found that in a clean environment, 10% water vapor enhanced the oxidation kinetics of SiC only very slightly compared to rates found in dry oxygen. Oxidation kinetics were examined in terms of the

Elizabeth J. Opila

1994-01-01

120

The chemical diffusivity of oxygen in liquid iron oxide and a calcium ferrite  

Microsoft Academic Search

Measurements have been made of the chemical diffusion coefficient of oxygen in liquid iron oxide at temperatures from 1673\\u000a to 1888 K and in a calcium ferrite (Fe\\/Ca = 2.57) at temperatures from 1573 to 1873 K. A gravimetric method was used to measure\\u000a the oxygen uptake during the oxidation of the melts by oxygen or CO2-CO mixtures. The rate

Y. Li; R. J. Fruehan; J. A. Lucas; G. R. Belton

2000-01-01

121

Evaluation of oxygen utilization as an indicator of municipal solid-waste compost stability  

Microsoft Academic Search

This research evaluated oxygen utilization parameters as indicators of MSW compost stability. Parameters evaluated were the oxygen utilization rate (OUR), specific oxygen uptake rate (SOUR), five-day biochemical oxygen demand, and chemical oxygen demand. In addition, other suggested indicators of stability were investigated including percent volatile solids, volatile solids reduction, nitrogen content, carbon: nitrogen ratio, and reheating potential (RP). OUR is

1991-01-01

122

A 12-kW continuous-wave chemical oxygen-iodine laser  

SciTech Connect

A 12-kW continuous-wave chemical oxygen-iodine laser, provided with an original jet-type singlet oxygen generator, is developed and tested. The experimental and numerical techniques applied for the diagnostics and mathematical simulation of processes in the laser active medium are introduced. Some of the calculation and experimental results are presented. (lasers)

Boreysho, A S; Mal'kov, V M; Savin, Aleksandr V; Vasil'ev, D N; Evdokimov, I M; Trilis, A V; Strakhov, S Yu [Institute of Laser Instruments and Technologies, D F Ustinov 'VOENMEKh' Baltic State Technical University, St Petersburg (Russian Federation)

2003-04-30

123

Oxygen diffusion in basalt and andesite melts: experimental results and discussion of chemical versus tracer diffusion  

Microsoft Academic Search

Chemical diffusion coefficients for oxygen in melts of Columbia River basalt (Ice Harbor Dam flow) and Mt. Hood andesite have been determined at 1 atm. The diffusion model is that of sorption or desorption of oxygen into a sphere of uniform initial concentration from a constant and semi-infinite atmosphere. The experimental design utilizes a thermogravimetric balance to monitor the rate

Richard F. Wendlandt

1991-01-01

124

Standard Chemical Oxygen-Iodine Laser Kinetics Package. Final report, August 1987March 1988  

Microsoft Academic Search

This report presents the Air Force Weapons Laboratory Standard Chemical Oxygen-Iodine Laser Kinetics Package. A complete reaction scheme including recommended rate coefficients for modeling the gas-phase kinetics of chemical oxygen-iodine lasers (COIL) was established to provide a common basis for the research and development of COIL devices. A review of the experimental kinetic data base from which this model was

G. P. Perram; G. D. Hager

1988-01-01

125

Limited Influence of Oxygen on the Evolution of Chemical Diversity in Metabolic Networks  

PubMed Central

Oxygen is thought to promote species and biomolecule diversity. Previous studies have suggested that oxygen expands metabolic networks by acquiring metabolites with different chemical properties (higher hydrophobicity, for example). However, such conclusions are typically based on biased evaluation, and are therefore non-conclusive. Thus, we re-investigated the effect of oxygen on metabolic evolution using a phylogenetic comparative method and metadata analysis to reduce the bias as much as possible. Notably, we found no difference in metabolic network expansion between aerobes and anaerobes when evaluating phylogenetic relationships. Furthermore, we showed that previous studies have overestimated or underestimated the degrees of differences in the chemical properties (e.g., hydrophobicity) between oxic and anoxic metabolites in metabolic networks of unicellular organisms; however, such overestimation was not observed when considering the metabolic networks of multicellular organisms. These findings indicate that the contribution of oxygen to increased chemical diversity in metabolic networks is lower than previously thought; rather, phylogenetic signals and cell-cell communication result in increased chemical diversity. However, this conclusion does not contradict the effect of oxygen on metabolic evolution; instead, it provides a deeper understanding of how oxygen contributes to metabolic evolution despite several limitations in data analysis methods.

Takemoto, Kazuhiro; Yoshitake, Ikumi

2013-01-01

126

Atomic oxygen-MoS/sub 2/ chemical interactions  

SciTech Connect

The present study shows that, at 1.5 eV O-atom translation energy, SO/sub 2/ is generated and outgases from an anhydrous MoS/sub 2/surface with an initial reactivity nearly 50% that of kapton. The reaction of atomic oxygen with MoS/sub 2/ has little or no translational energy barier; i.e., thermally generated atomic oxygen reacts as readily as that having 1.5 eV of translational energy. It is also shown that water, present in the flowing afterglow apparatus used to study thermal O-atom reactivity, formed sulfates on the MoS/sub 2/ surface and that the sulfate is not likely in the form of sulfuric acid. These results imply that water dumps or outgasing in low earth orbit have the potential of forming sulfuric acid covered surfaces on MoS/sub 2/ lubricants. For MoS/sub 2/ films sputter-deposited at 50-70/degree/C, friction measurements show a high initial friction coefficient for O-atom exposed MoS/sub 2/ surfaces (up to 0.25) which drops to the normal low values after several cycles of operation in air and ultrahigh vacuum. For MoS/sub 2/ films deposited at 200/degree/C, the friction coefficient was not affected by the O-atom exposure. 11 refs., 3 figs.

Cross, J.B.; Martin, J.A.; Pope, L.E.; Koontz, S.L.

1989-01-01

127

GENETIC ALGORITHMS AND OPTIMIZING CHEMICAL OXYGEN-IODINE LASERS  

Microsoft Academic Search

This paper presents results from the first known application of the genetic algorithm (GA) technique for optimizing the performance of a laser system (chemical, solid-state, or gaseous). The effects of elitism, single point and uniform crossover, creep mutation, different random number seeds, population size, niching and the number of children per pair of parents on the performance of the GA

David L. Carroll

1996-01-01

128

Factors affecting the performance of a single-chamber microbial fuel cell-type biological oxygen demand sensor.  

PubMed

Microbial fuel cells (MFCs) are devices that exploit microorganisms as biocatalysts to degrade organic matter or sludge present in wastewater (WW), and thereby generate electricity. We developed a simple, low-cost single-chamber microbial fuel cell (SCMFC)-type biochemical oxygen demand (BOD) sensor using carbon felt (anode) and activated sludge, and demonstrated its feasibility in the construction of a real-time BOD measurement system. Further, the effects of anodic pH and organic concentration on SCMFC performance were examined, and the correlation between BOD concentration and its response time was analyzed. Our results demonstrated that the SCMFC exhibited a stable voltage after 132 min following the addition of synthetic WW (BOD concentration: 200 mg/L). Notably, the response signal increased with an increase in BOD concentration (range: 5-200 mg/L) and was found to be directly proportional to the substrate concentration. However, at higher BOD concentrations (>120 mg/L) the response signal remained unaltered. Furthermore, we optimized the SCMFC using synthetic WW, and tested it with real WW. Upon feeding real WW, the BOD values exhibited a standard deviation from 2.08 to 8.3% when compared to the standard BOD5 method, thus demonstrating the practical applicability of the developed system to real treatment effluents. PMID:24225089

Yang, Gai-Xiu; Sun, Yong-Ming; Kong, Xiao-Ying; Zhen, Feng; Li, Ying; Li, Lian-Hua; Lei, Ting-Zhou; Yuan, Zhen-Hong; Chen, Guan-Yi

2013-01-01

129

Simplified Laboratory Procedures for COD (Chemical Oxygen Demand) Determination Using Dichromate Reflux Method.  

National Technical Information Service (NTIS)

Under sponsorship of Water Pollution Control Federation the laboratory procedures for COD determination as outlined in the 15th and 16th editions of the APHA/AWWA/WPCF Standard Methods for the Examination of Water and Wastewater was simplified by the WPCF...

L. K. Wang E. DeMichele M. H. Wang

1985-01-01

130

A STUDY OF NEW CATALYTIC AGENTS TO DETERMINE CHEMICAL OXYGEN DEMAND  

EPA Science Inventory

This study was made to find a catalyst to replace silver sulfate in the COD method in order to reduce the cost of the determination. The results show that comparable results to the standard method for concentration of 50-500 mg/l could be obtained using a reduced amount of silver...

131

Reduction of chemical oxygen demand of industrial wastes using subcritical water oxidation  

Microsoft Academic Search

If wastes have strong toxicity, high organic content, and a deep hue, they are difficult to handle in the waste disposal. It is very practical that waste of this kind is treated by Subcritical Water Oxidation (SWO). In our work, caprolactum (CPL) waste, purged from a petrochemical plant, and dyeing waste, purged from a textile plant, were individually treated by

Chiehming J. Chang

1992-01-01

132

IMPROVED MICROBIAL, VOLATILE SOLIDS, AND COD (CHEMICAL OXYGEN DEMAND) REDUCTIONS IN AN AUTOHEATED AEROBIC DIGESTER  

EPA Science Inventory

The report is a summary of some of the work performed by Cornell University in which modifications to an aerobic digester permitted the digester to comply with PSRP requirements in cold climates. The modifications included addition of an insulated cover to prevent escape of the h...

133

Modelling of chemical oxygen demand by using ANNs, ANFIS and k-means clustering techniques  

NASA Astrophysics Data System (ADS)

COD estimates of k-means-MLP method integrated are compared with other AI techniques.The k-means-MLP method performs better than the other AI techniques.SS, T and pH parameters are quite effective in estimating daily COD concentration.

Ay, Murat; Kisi, Ozgur

2014-04-01

134

Removal of color and residual chemical oxygen demand from synfuel wastewater  

SciTech Connect

Color has been classified as a nonconventional'' water pollutant by the Clean Water Act of 1977. This designation allows the government to regulate the amount of color in discharged effluent where warranted. Discharged color detracts from the aesthetic value of the receiving water, and can be a source of public concern. Color may also have negative effects on aquatic life due to decreased light transmittance and toxic effects. The production of synthetic natural gas from coal results in a wastewater with high levels of phenols, ammonia, and organics. This wastewater requires a multiple-stage treatment process to meet discharge regulations. Treatment processes commonly used for coal conversion wastewaters include solvent extraction, stream stripping, and biological oxidation and nitrification. An additional concern with these wastewaters is the presence of color. High levels of color are common in coal conversion wastewaters, even subsequent to secondary treatment. Since the discharge of colored water presents an environmental concern as discussed above, the need for economical, effective methods to remove this color exists. The objective of this research is to evaluate color removal from a coal conversion wastewater by solvent extraction, adsorption, and biological methods. 15 refs., 9 figs., 9 tabs.

Gallagher, J.R.; San, T.M.; Mayer, G.G.

1988-06-01

135

Determination of the chemical diffusion of oxygen in liquid iron oxide at 1615 °c  

Microsoft Academic Search

The chemical diffusion of oxygen in liquid iron oxide has been studied by the oxidation of a melt in a long capillary at 1615\\u000a °C. When pure oxygen was used as the oxidizing agent, the surface composition of the slag was found to be in close agreement\\u000a with the expected gas-slag equilibrium, suggesting that diffusion is the controlling step. This

Y. Sayadyaghoubi; S. Sun; S. Jahanshahi

1995-01-01

136

Development of a mist singlet oxygen generator for a chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Mist singlet oxygen generator (Mist-SOG) has been developed in order to increase the BHP utilization. On the other hand, Mist-SOG generates much more water vapor than conventional SOG because the heat capacity of the BHP is small. It is well known that the water vapor deactivates the excited iodine. In order to remove the water vapor, we developed a jet-cold trap. In this method, a nozzle sprayed a chilled H2O2 at 238K with a thin layer form to the gas flow directly in order to get the large specific surface for the water vapor. As a result of experiment, Water vapor partial pressure reduced from 3.3 Torr at the BHP flow rate of 2.2 ml/s and Cl2 flow rate of 3.5 mmol/s for the 65?m BHP droplets.

Muto, Shigeki; Endo, Masamori; Nanri, Kenzo; Fujioka, Tomoo

2003-11-01

137

Effect of Oxygen Injection on Argon Induction Plasmas by Chemically Non-equilibrium Modeling  

NASA Astrophysics Data System (ADS)

Thermal plasmas have simply been used as a high temperature source. This indicates that thermal plasmas may have more capabilities in material processing, especially production of high-quality and high-performance materials, if thermal plasmas are utilized effectively as chemically reactive gases. Therefore, characteristics of thermal plasmas with chemically reactive gas should be investigated. The purpose of this work is to investigate the effective injection location of oxygen into argon induction plasmas. A non-equilibrium modeling of argon-oxygen induction thermal plasmas was performed without chemical equilibrium assumptions. The thermofluid and concentration fields were obtained by solving of two-dimensional modeling. Chemical reaction kinetics rates of the dissociation and recombination as well as the ionization were taken into account in this modeling. The transport properties were estimated using Chapman-Enskog method with higher order of Sonine polynomial expansion with collision integrals at each of the calculation step. As a result, the high-temperature region and high-concentration region of dissociated oxygen spread toward the wall in the chemically non-equilibrium model. Deviation from the LTE assumption at the coil region is not negligible in argon-oxygen induction plasmas under atmospheric pressure.

Atsuchi, Nobuhiko; Shigeta, Masaya; Watanabe, Takayuki

2004-09-01

138

A sensitive ferricyanide-mediated biochemical oxygen demand assay for analysis of wastewater treatment plant influents and treated effluents.  

PubMed

Representative and fast monitoring of wastewater influent and effluent biochemical oxygen demand (BOD) is an elusive goal for the wastewater industry and regulatory bodies alike. The present study describes a suitable assay, which incorporates activated sludge as the biocatalyst and ferricyanide as the terminal electron acceptor for respiration. A number of different sludges and sludge treatments were investigated, primarily to improve the sensitivity of the assay. A limit of detection (LOD) (2.1 mg BOD? L?¹) very similar to that of the standard 5-day BOD? method was achieved in 4 h using raw influent sludge that had been cultured overnight as the biocatalyst. Reducing the microbial concentration was the most effective means to improve sensitivity and reduce the contribution of the sludge's endogenous respiration to total ferricyanide-mediated (FM) respiration. A strong and highly significant relationship was found (n = 33; R = 0.96; p < 0.001; slope = 0.94) between BOD? and FM-BOD equivalent values for a diverse range of samples including wastewater treatment plant (WWTP) influent and treated effluent, as well as several grey water samples. The activated sludge FM-BOD assay presented here is an exceptional surrogate method to the standard BOD? assay, providing representative, same-day BOD analysis of WWTP samples with a comparable detection limit, a 4-fold greater analytical range and much faster analysis time. The industry appeal of such an assay is tremendous given that ~90% of all BOD? analysis is dedicated to measurement of WWTP samples, for which this assay is specifically designed. PMID:23200506

Jordan, Mark A; Welsh, David T; John, Richard; Catterall, Kylie; Teasdale, Peter R

2013-02-01

139

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

NASA Astrophysics Data System (ADS)

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

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

140

The Effects of Dissolved Oxygen upon Amide Proton Relaxation and Chemical Shift in a Perdeuterated Protein  

NASA Astrophysics Data System (ADS)

The effects of dissolved molecular oxygen upon amide proton ( 1H N) longitudinal and transverse relaxation rates and chemical shifts were studied for a small protein domain, the second type 2 module of fibronectin ( 2F2)—isotopically enriched to 99% 2H, 98% 15N. Longitudinal relaxation rate enhancements, R O 2( 1H N), of individual backbone 1H N nuclei varied up to 14 fold between a degassed and oxygenated (1 bar) solution, indicating that the oxygen distribution within the protein is inhomogeneous. On average, smaller relaxation rate enhancements were observed for 1H N nuclei associated with the core of the protein compared to 1H N nuclei closer to the surface, suggesting restricted oxygen accessibility to some regions. In agreement with an O 2- 1H N hyperfine interaction in the extreme narrowing limit, the 1H N transverse relaxation rates showed no significant change, up to an oxygen pressure of 9.5 bar (the maximum pressure used in this study). For most 1H N resonances, small ?? O 2( 1H N) hyperfine chemical shifts could be detected between oxygen pressures of 1 bar and 9.5 bar.

Ulmer, Tobias S.; Campbell, Iain D.; Boyd, Jonathan

2002-08-01

141

Operational characteristics of high-pressure subsonic mode chemical oxygen-iodine lasers  

NASA Astrophysics Data System (ADS)

High-pressure subsonic mode operation of chemical oxygen- iodine laser (COIL) is studied. In this mode, the singlet oxygen generated by the liquid-jet singlet oxygen generator (SOG) is directly utilized in the optical cavity without supersonic expansion. Drastic reduction of the required vacuum pump capacity, and iodine consumption was obtained. We have demonstrated a 25.0 percent of chemical efficiency with a small-scale device. The scale-up version of the COIL is developed and initial tests are conducted. The device is so designed that it will operate for 2 hours at 1kW laser output. Due to the inadequate heat exchanger of basic hydrogen peroxide (BHP), performance of the system was not yet satisfactory. However, a 30-minute continuous operation o the counter-flow type jet SOG with recirculation of BHP was demonstrated for the first time.

Endo, Masamori; Sugimoto, Daichi; Tei, Kazuyoku; Takeda, Shuzaburo; Nanri, Kenzo; Fujioka, Tomoo

2000-05-01

142

Application of a telescopic resonator to high-power chemical oxygen-iodine lasers  

Microsoft Academic Search

The application of an intraresonator telescope to high-power chemical oxygen-iodine lasers to decrease the output beam divergence is analyzed and demonstrated. A theoretical formula based on the ABCD matrix theory is developed to analyze the characteristics of the telescopic resonator. Calculations are carried out using Galilean type telescopes with magnification factors in the range of two to four, and our

Sanichiro Yoshida; Kouki Shimizu; Hari Tahil; Ikuzo Tanaka

1994-01-01

143

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

PubMed

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

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

2013-07-01

144

Singlet oxygen generator for a solar powered chemically pumped iodine laser  

NASA Technical Reports Server (NTRS)

The potential of solid phase endoperoxides as a means to produce single-delta oxygen in the gas phase in concentrations useful to chemical oxygen-iodine lasers was investigated. The 1,4 - endoperoxide of ethyl 3- (4-methyl - 1-naphthyl) propanoate was deposited over an indium-oxide layer on a glass plate. Single-delta oxygen was released from the endoperoxide upon heating the organic film by means of an electrical discharge through the conductive indium oxide coating. The evolution of singlet-delta oxygen was determined by measuring the dimol emission signal at 634 nm. Comparison of the measured signal with an analytic model leads to two main conclusions: virtually all the oxygen being evolved is in the singlet-delta state and in the gas phase, and there is no significant quenching other than energy pooling on the time scale of the experiment (approximately 10 msec). The use of solid phase endoperoxide as a singlet-delta oxygen generator for an oxygen-iodine laser appears promising.

Busch, G. E.

1984-01-01

145

The correlation of the indices of the biochemical oxygen requirement and chemical oxygen absorption in the purification of the effluent of the viscose sector  

Microsoft Academic Search

of the results, the large error (10 - 20%), and the time required (5 - 20 days) so that the usefulness of the BOR index for operational and process control is limited. Along with the BOR use is made of the index of chemical oxygen absorption (COA) which is the oxygen equivalent of the concentration of the organic substances being

A. Ya. Rudomir; I. A. Evilevich; V. L. Kolin; A. P. Zalipaeva

1976-01-01

146

Determination of the chemical diffusion of oxygen in liquid iron oxide at 1615 °c  

NASA Astrophysics Data System (ADS)

The chemical diffusion of oxygen in liquid iron oxide has been studied by the oxidation of a melt in a long capillary at 1615 °C. When pure oxygen was used as the oxidizing agent, the surface composition of the slag was found to be in close agreement with the expected gas-slag equilibrium, suggesting that diffusion is the controlling step. This was not the case when air, 5 pct oxygen in argon or pure CO2 was used to oxidize the slag. The deviation of the surface composition from the expected equilibrium was in accordance with a mechanism of mixed control by both the gas-slag reaction and diffusion in the bulk. The average value of the chemical diffusivity of oxygen (or iron) in liquid iron oxide with Fe2+/Fe T between 0.25 and 0.77 was established to be 3(±1) × 10-7 m2/s. This value is one to two orders of magnitude higher than those from earlier studies. There seems to be a reasonable correlation between the chemical and the ionic self-diffusivities through the Darken equation. A quantitative analysis in this respect and on the role of electron hole migration depends on the availability of data on the ionic conductivity and the tracer diffusivities.

Sayadyaghoubi, Y.; Sun, S.; Jahanshahi, S.

1995-08-01

147

Reverse Engineering of Oxygen Transport in the Lung: Adaptation to Changing Demands and Resources through Space-Filling Networks  

PubMed Central

The space-filling fractal network in the human lung creates a remarkable distribution system for gas exchange. Landmark studies have illuminated how the fractal network guarantees minimum energy dissipation, slows air down with minimum hardware, maximizes the gas- exchange surface area, and creates respiratory flexibility between rest and exercise. In this paper, we investigate how the fractal architecture affects oxygen transport and exchange under varying physiological conditions, with respect to performance metrics not previously studied. We present a renormalization treatment of the diffusion-reaction equation which describes how oxygen concentrations drop in the airways as oxygen crosses the alveolar membrane system. The treatment predicts oxygen currents across the lung at different levels of exercise which agree with measured values within a few percent. The results exhibit wide-ranging adaptation to changing process parameters, including maximum oxygen uptake rate at minimum alveolar membrane permeability, the ability to rapidly switch from a low oxygen uptake rate at rest to high rates at exercise, and the ability to maintain a constant oxygen uptake rate in the event of a change in permeability or surface area. We show that alternative, less than space-filling architectures perform sub-optimally and that optimal performance of the space-filling architecture results from a competition between underexploration and overexploration of the surface by oxygen molecules.

Hou, Chen; Gheorghiu, Stefan; Huxley, Virginia H.; Pfeifer, Peter

2010-01-01

148

Growth of polycrystalline oxygenated three dimensional cadmium telluride thin films by chemical synthesis  

NASA Astrophysics Data System (ADS)

Oxygenated crystalline cadmium telluride (CdTeO3) thin films have been achieved via chemical synthesis onto glass substrate at room temperature. The morphology of the deposited film shows the three dimensional polycrystalline structures of well alignment of the crystallites with each other and the uniform rectangular structure compressed with one another having different sizes. XRD of films shows the peaks corresponding to single phase face centered cubic of crystalline oxygenated cadmium telluride are well defined. Energy-dispersive spectroscopy confirms the elemental composition of cadmium and telluride.

Kapadnis, Ramesh S.; Bansode, Sanjay B.; Kale, Sampat S.; Pathan, Habib M.

2013-06-01

149

Use of basic deuterium peroxide in the chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The chemical oxygen-iodine laser (COIL) uses a reaction of gaseous chorine and aqueous solution of basic oxygen peroxide (BHP) to produce oxygen singlet delta molecules, O2(1(Delta) ). Quenching of O2(1(Delta) ) during its extraction from the BHP solution and quenching of excited atomic iodine I* by water vapor from the O2(1(Delta) ) production process are well-known parasitic effects in COIL. This paper shows that both of these effects can be significantly reduced by replacing the hydrogen 1H1 isotope atoms in BHP by the 1H2 isotope atoms. In addition to restoring laser power lost to parasitic quenching, use of basic deuterium peroxide (BDP) rather than BHP is expected to allow generation of O2(1(Delta) ) at elevated temperature. This approach promises to save refrigerant, reduce the risk of BDP freezing, and delay precipitation of salt form BDP solution. Methods for producing BDP are outlined.

Vetrovec, John; Yang, Tientsai T.; Copeland, Drew A.

2000-05-01

150

Oxidation Kinetics of Chemically Vapor-Deposited Silicon Carbide in Wet Oxygen  

NASA Technical Reports Server (NTRS)

The oxidation kinetics of chemically vapor-deposited SiC in dry oxygen and wet oxygen (P(sub H2O) = 0.1 atm) at temperatures between 1200 C and 1400 C were monitored using thermogravimetric analysis. It was found that in a clean environment, 10% water vapor enhanced the oxidation kinetics of SiC only very slightly compared to rates found in dry oxygen. Oxidation kinetics were examined in terms of the Deal and Grove model for oxidation of silicon. It was found that in an environment containing even small amounts of impurities, such as high-purity Al2O3 reaction tubes containing 200 ppm Na, water vapor enhanced the transport of these impurities to the oxidation sample. Oxidation rates increased under these conditions presumably because of the formation of less protective sodium alumino-silicate scales.

Opila, Elizabeth J.

1994-01-01

151

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

SciTech Connect

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

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

2013-06-01

152

LASERS: Efficient chemical oxygen — iodine laser with a high total pressure of the active medium  

NASA Astrophysics Data System (ADS)

A new concept of obtaining a high total pressure of the active medium of a chemical oxygen — iodine laser (OIL) is proposed and verified. The nozzle unit of the laser consists of the alternating vertical arrays of cylindrical nozzles to produce high-pressure nitrogen jets, plane slotted nozzles for the flow of O2(1?) oxygen, and vertical arrays of cylindrical nozzles to inject the N2 — I2 mixture between the first two streams. For a molar chlorine flow rate of 39.2 mmol s-1, the output power was 700 W and the chemical efficiency was 19.7 %. The combined use of the ejector nozzle unit proposed to obtain the active medium and a super-sonic diffuser allows a significant simplification of the ejection system for the exhaust active medium of the OIL.

Zagidullin, M. V.; Nikolaev, V. D.; Svistun, M. I.; Khvatov, N. A.; Heiger, G. D.; Madden, T. J.

2001-01-01

153

Application of a telescopic resonator to high-power chemical oxygen-iodine lasers  

SciTech Connect

The application of an intraresonator telescope to high-power chemical oxygen-iodine lasers to decrease the output beam divergence is analyzed and demonstrated. A theoretical formula based on the ABCD matrix theory is developed to analyze the characteristics of the telescopic resonator. Calculations are carried out using Galilean type telescopes with magnification factors in the range of two to four, and the high-power chemical oxygen-iodine laser as an analysis model. By locating the telescope at a proper position on the optical axis, the overall telescopic resonator can be conveniently tailored to the hardware of this model laser in a way that the beam divergence and the resonator stability can be improved simultaneously. Experiments are carried out for one of the conditions used in the calculations. Measured divergence angles are in excellent agreement with the theoretical values.

Yoshida, Sanichiro; Shimizu, Kouki; Tahil, Hari; Tanaka, Ikuzo (Inst. of Research and Innovation, Chiba (Japan). Laser Lab.)

1994-01-01

154

Chemical Activity of Oxygen Atoms in Magnetron Sputter-Deposited ZnO Films during Film Growth  

NASA Astrophysics Data System (ADS)

The role of oxygen atoms in the growth of magnetron sputter-deposited ZnO films was studied by alternating the deposition of a several-nanometer-thick ZnO layer and an O2/Ar mixed plasma exposure, i.e., a layer-by-layer (LbL) technique. Film crystallization was promoted by suppressing the formation of oxygen vacancies and interstitial defects by adjusting the exposure conditions of the O2/Ar plasma. These findings suggest that the chemical potential of oxygen atoms influences film crystallization and the electronic state. The diffusion and effusion of oxygen atoms at the growing surface have effects similar to those of thermal annealing, namely, the promotion of film crystallization and the creation and annihilation of oxygen- and zinc-related defects. The role of oxygen atoms reaching the growing film surface is discussed in terms of chemical annealing, and a possible oxygen diffusion mechanism is proposed.

Morita, Aya; Watanabe, Ikuo; Ohta, Naoki; Shirai, Hajime

2011-08-01

155

Reduced oxygen tension and EDTA improve bovine zygote development in a chemically defined medium1  

Microsoft Academic Search

Bovine zygotes produced by in vitro oo- cyte maturation and fertilization were cultured for 7.5 d in a chemically defined medium without serum or proteins, except .12 IU\\/mL of insulin. In Exp. 1, embryos were cultured in approximately 20% oxygen (i.e., 5% CO2 in air) or 5% CO2 ;5 % O 2; 90% N2, with the metal chelators EDTA or

S. E. Olson; G. E. Seidel

156

Changes in chemical states of PET films due to low and high energy oxygen ion beam  

Microsoft Academic Search

The effects of low (1.0, 3.0 keV) and high (1.0 MeV) energy reactive oxygen ion beam irradiation on surface nano-morphology and chemical state of the constituent elements in the surface layer of a polyethylene terephthalate thin film (thickness 25 ?m) are studied in this paper. PET thin film, which has a high potential as a material for biomedical and electrical

A. M Ektessabi; K Yamaguchi

2000-01-01

157

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

Microsoft Academic Search

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

Tobias Mattisson; Marcus Johansson; Anders Lyngfelt

2006-01-01

158

Synthesis gas production through biomass direct chemical looping conversion with natural hematite as an oxygen carrier.  

PubMed

Biomass direct chemical looping (BDCL) conversion with natural hematite as an oxygen carrier was conducted in a fluidized bed reactor under argon atmosphere focusing on investigation the cyclic performance of oxygen carrier. The presence of oxygen carrier can evidently promote the biomass conversion. The gas yield and carbon conversion increased from 0.75 Nm(3)/kg and 62.23% of biomass pyrolysis to 1.06 Nm(3)/kg and 87.63% of BDCL, respectively. The components of the gas product in BDCL were close to those in biomass pyrolysis as the cyclic number increased. The gas yield and carbon conversion decreased from 1.06 Nm(3)/kg and 87.63% at 1st cycle to 0.93 Nm(3)/kg and 77.18% at 20th cycle, respectively, due to the attrition and structural changes of oxygen carrier. X-ray diffraction (XRD) analysis showed that the reduction extent of oxygen carrier increased with the cycles. Scanning electron microscope (SEM) and pore structural analysis displayed that agglomeration was observed with the cycles. PMID:23707909

Huang, Zhen; He, Fang; Feng, Yipeng; Zhao, Kun; Zheng, Anqing; Chang, Sheng; Li, Haibin

2013-07-01

159

Seasonal variation in benthic community oxygen demand: A response to an ice algal bloom in the Beaufort Sea, Canadian Arctic?  

Microsoft Academic Search

Understanding pathways of carbon cycling on Arctic shelves is critical if we are to evaluate the potential effects of climate change on these systems. We investigated the relationship between ice algal standing stock and benthic respiration between January and July 2004 at a time series station in the southeastern Beaufort Sea. Both ice algal chlorophyll a and benthic sediment oxygen

Paul E. Renaud; Andrea Riedel; Christine Michel; Nathalie Morata; Michel Gosselin; Thomas Juul-Pedersen; Amy Chiuchiolo

2007-01-01

160

How does the character of oxygen demand control the structure of hypoxia on the Texas–Louisiana continental shelf?  

Microsoft Academic Search

A realistic hydrodynamic model of the Texas–Louisiana shelf is configured with various simple oxygen respiration models to isolate the effects of stratification and circulation on the formation and maintenance of hypoxia. Biological activity is parameterized through various forms of respiration rather than using a complex biogeochemical model. The model domain covers the region that has historically been observed to be

Robert D. Hetland; Steven F. DiMarco

2008-01-01

161

On the chemical processing of hydrocarbon surfaces by fast oxygen ions.  

PubMed

Solid methane (CH(4)), ethane (C(2)H(6)), and ethylene (C(2)H(4)) ices (thickness: 120 ± 40 nm; 10 K), as well as high-density polyethylene (HDPE: [C(2)H(4)](n)) films (thickness: 130 ± 20 nm; 10, 100, and 300 K), were irradiated with mono-energetic oxygen ions (? ~ 6 × 10(15) cm(-2)) of a kinetic energy of 5 keV to simulate the exposure of Solar System hydrocarbon ices and aerospace polymers to oxygen ions sourced from the solar wind and planetary magnetospheres. On-line Fourier-transform infrared spectroscopy (FTIR) was used to identify the following O(+) induced reaction pathways in the solid-state: (i) ethane formation from methane ice via recombination of methyl (CH(3)) radicals, (ii) ethane conversion back to methane via methylene (CH(2)) retro-insertion, (iii) ethane decomposing to acetylene via ethylene through successive hydrogen elimination steps, and (iv) ethylene conversion to acetylene via hydrogen elimination. No changes were observed in the irradiated PE samples via infrared spectroscopy. In addition, mass spectrometry detected small abundances of methanol (CH(3)OH) sublimed from the irradiated methane and ethane condensates during controlled heating. The detection of methanol suggests an implantation and neutralization of the oxygen ions within the surface where atomic oxygen (O) then undergoes insertion into a C-H bond of methane. Atomic hydrogen (H) recombination in forming molecular hydrogen and recombination of implanted oxygen atoms to molecular oxygen (O(2)) are also inferred to proceed at high cross-sections. A comparison of the reaction rates and product yields to those obtained from experiments involving 5 keV electrons, suggests that the chemical alteration of the hydrocarbon ice samples is driven primarily by electronic stopping interactions and to a lesser extent by nuclear interactions. PMID:21901185

Ennis, Courtney; Yuan, Hanqiu; Sibener, S J; Kaiser, Ralf I

2011-10-21

162

Semi-gas kinetics model for performance modeling of flowing chemical oxygen-iodine lasers (COIL)  

NASA Astrophysics Data System (ADS)

A semi-gas kinetics (SGK) model for performance analyses of flowing chemical oxygen-iodine laser (COIL) is presented. In this model, the oxygen-iodine reaction gas flow is treated as a continuous medium, and the effect of thermal motions of particles of different laser energy levels on the performances of the COIL is included and the velocity distribution function equations are solved by using the double-parameter perturbational method. For a premixed flow, effects of different chemical reaction systems, different gain saturation models and temperature, pressure, yield of excited oxygen, iodine concentration and frequency-shift on the performances of the COIL are computed, and the calculated output power agrees well with the experimental data. The results indicate that the power extraction of the SGK model considering 21 reactions is close to those when only the reversible pumping reaction is considered, while different gain saturation, models and adjustable parameters greatly affect the output power, the optimal threshold gain range, and the length of power extraction.

Gao, Zhi; Hu, Limin; Shen, Yiqing

2004-05-01

163

Atomic resolution chemical bond analysis of oxygen in La2CuO4  

NASA Astrophysics Data System (ADS)

The distorted CuO6 octahedron in La2CuO4 was studied using aberration-corrected scanning transmission electron microscopy at atomic resolution. The near-edge structure in the oxygen K-edge electron energy-loss spectrum was recorded as a function of the position of the electron probe. After background subtraction, the measured spectrum image was processed using a recently developed inversion process to remove the mixing of signals on the atomic columns due to elastic and thermal scattering. The spectra were then compared with first-principles band structure calculations based on the local-density approximation plus on-site Coulomb repulsion (LDA + U) approach. In this article, we describe in detail not only anisotropic chemical bonding of the oxygen 2p state with the Cu 3d state but also with the Cu 4p and La 5d/4f states. Furthermore, it was found that buckling of the CuO2 plane was also detectable at the atomic resolution oxygen K-edge. Lastly, it was found that the effects of core-hole in the O K-edge were strongly dependent on the nature of the local chemical bonding, in particular, whether it is ionic or covalent.

Haruta, M.; Nagai, T.; Lugg, N. R.; Neish, M. J.; Nagao, M.; Kurashima, K.; Allen, L. J.; Mizoguchi, T.; Kimoto, K.

2013-08-01

164

A pared-down gas-phase kinetics for the chemical oxygen-iodine laser medium  

NASA Astrophysics Data System (ADS)

Kinetic data obtained in the last decade has resulted in revisions of some mechanisms of excitation and deactivation of excited states in the chemical oxygen-iodine laser (COIL) medium. This review considers new kinetic data and presents analyses of the mechanisms of pumping and quenching of electronically and vibrationally excited states in the oxygen-iodine laser media. An effective three-level model of I2 molecule excitation and relaxation has been developed. The calculated effective rate constants for deactivation of I2(X,11 ? ? ? 24) by O2, N2, He and CO2 are presented. A simplified kinetic package for the COIL active medium is recommended. This model consists of a 30-reaction set with 14 species. The results of calculations utilizing simplified model are in good agreement with the experimental data.

Pichugin, S. Yu.; Heaven, M. C.

2013-11-01

165

Isotropic chemical shifts and quadrupolar parameters of oxygen-17 using dynamic-angle spinning NMR  

SciTech Connect

Several oxygen-17-enriched silicates were studied using dynamic-angle spinning (DAS) NMR spectroscopy at two magnetic field strengths. The DAS method averages second-order quadrupolar interactions by reorienting a sample about a time-dependent axis, thereby yielding high-resolution spectra for half-odd integer spin quadrupolar nuclei such as oxygen-17. A narrow spectral line is observed for each distinct oxygen site in a powdered sample at the sum of the isotropic chemical shift and the field-dependent isotropic second-order quadrupolar shift. Using equations for the total shift observed at two field strengths, the chemical shift is uniquely determined together with a product of the quadrupolar coupling constant (C{sub Q} = e{sup 2}qQ/h) and the quadrupolar asymmetry parameter ({eta}). For one silicate, the authors demonstrate a computer program that uses the isotropic shifts and quadrupolar products as constraints and provides simulations of overlapped magic-angle spinning line shapes. In this way the quadrupolar parameters, C{sub Q} and {eta}, are determined separately for each crystallographic site. The silicates studied include the discrete orthosilicates larnite (Ca{sub 2}SiO{sub 4}) and forsterite (Mg{sub 2}SiO{sub 4}), as well as diopside (CaMgSi{sub 2}O{sub 6}), wollastonite (CaSiO{sub 3}), and clinoenstatite (MgSiO{sub 3}), which are minerals composed of chains of silicon-oxygen tetrahedra. 49 refs., 2 figs., 2 tabs.

Mueller, K.T.; Baltisberger, J.H.; Wooten, E.W.; Pines, A. [Lawrence Berkeley Laboratory, CA (United States)

1992-08-20

166

Active-medium inhomogeneities and optical quality of radiation of supersonic chemical oxygen-iodine lasers  

SciTech Connect

Optical inhomogeneities of the active medium of a supersonic chemical oxygen-iodine laser (COIL) and their effect on the radiation parameters are studied in the case when an unstable resonator is used. Classification of optical inhomogeneities and the main factors affecting the quality of COIL radiation are considered. The results of numerical simulation of a three-dimensional gas-dynamic active medium and an unstable optical resonator in the diffraction approximation are presented. The constraints in the fabrication of large-scale COILs associated with a deterioration of the optical quality of radiation are determined. (lasers)

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

2007-09-30

167

Unstable resonators of high-power chemical oxygen-iodine lasers  

SciTech Connect

Configurations of unstable resonators are considered depending on the basic parameters of a high-power chemical oxygen-iodine laser and the design of an unstable resonator is proposed which provides the compensation of the inhomogeneity of the small-signal gain downstream of the active medium, a high energy efficiency, and stability to intracavity aberrations. The optical scheme of this resonator is presented and its properties are analysed by simulating numerically the kinetics of the active medium and resonator itself in the diffraction approximation. (laser beams and resonators)

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

2006-09-30

168

17O NMR spectroscopy of substituted methyleneindanones: relationship between chemical shift and oxygen atom electron density  

NASA Astrophysics Data System (ADS)

17O NMR spectroscopic data for eigth ?-substituted methyleneindanones obtained at natural abundance in acetonitrile at 75°C are reported. 17O NMR data for ten para-substituted E-benzalindanones, enriched with 17O, were recorded in acetonitrile at 75°C. The 17O NMR data for the E-benzalindanones gave good correlations with sigma plus values, with literature carbonyl IR stretching frequencies, and with literature 17O NMR carbonyl data of chalcones and 5-aryl-2,3-furandiones. The carbonyl oxygen atom electron density (AM1) gave good correlation with the carbonyl 17O NMR chemical shift of both ?-substituted methyleneindanones and the E-benzalindanones.

Kumar, Arvind; Boykin, David W.

1993-07-01

169

Practical use of chemical probes for reactive oxygen species produced in biological systems by ?-irradiation  

NASA Astrophysics Data System (ADS)

Application of chemical probes, for detection of reactive oxygen species (ROS), was tested during ?-irradiation. The ethanol/?-(4-pyridyl-1-oxide)- N- tert-butylnitrone (4-POBN) and 3,3'-diaminobenzidine (DAB) were structurally stable enough to detect rad OH and H 2O 2, increasingly generated by ?-irradiation up to 1000 Gy. Interestingly, the production rate of H 2O 2, but not rad OH, during ?-irradiation, was significantly different between in vitro systems of lettuce and spinach. These results suggest that 4-POBN and DAB could be utilized as a semi-quantitative probe to quantify rad OH and H 2O 2, produced by ?-irradiation up to 1000 Gy.

Lee, Min Hee; Moon, Yu Ran; Chung, Byung Yeoup; Kim, Jae-Sung; Lee, Kang-Soo; Cho, Jae-Young; Kim, Jin-Hong

2009-05-01

170

Direct spectroscopic observation of singlet oxygen quenching and kinetic studies of physical and chemical singlet oxygen quenching rate constants of synthetic antioxidants (BHA, BHT, and TBHQ) in methanol.  

PubMed

Singlet oxygen quenching by synthetic antioxidants (BHA, BHT, and TBHQ) was directly observed by spectroscopic monitoring of luminescence at 1268 nm. The luminescence data showed unambiguous evidence of singlet oxygen quenching by synthetic phenolic antioxidants with the highest activity for TBHQ, followed by BHA and BHT. The protective activities of these synthetic antioxidants on alpha-terpinene oxidation with chemically-induced singlet oxygen under dark further confirmed their singlet oxygen quenching abilities. Total singlet oxygen quenching rate constants (k(r) + k(q)) of BHA, BHT, and TBHQ were determined in a system containing alpha-terpinene (as a singlet oxygen trap) and methylene blue (as a sensitizer) during light irradiation, and the values were 5.14 x 10(7), 3.41 x 10(6), and 1.99 x 10(8) M(-1)s(-1), respectively. After the k(r) value of alpha-terpinene was first determined, the k(r) values of the synthetic antioxidants were calculated by measuring their relative reaction rates with singlet oxygen to that of alpha-terpinene under the identical conditions. The k(r) values of the BHA, BHT, and TBHQ were 3.90 x 10(5), 1.23 x 10(5), and 2.93 x 10(6), M(-1)s(-1). The percent partition of chemical quenching over total singlet oxygen quenching (k(r) x 100)/(k(r) + k(q)) for BHA, BHT, and TBHQ were 0.76%, 3.61%, and 1.47%, respectively. The results showed that the synthetic antioxidants quench singlet oxygen almost exclusively through the mechanism of physical quenching. This represents the first report on the singlet oxygen quenching mechanism of these synthetic antioxidants. Practical Application: The synthetic antioxidants, especially TBHQ, have been found to have a strong singlet oxygen quenching ability. This article also clearly showed that singlet oxygen quenching by synthetic antioxidants was mainly by the physical quenching mechanism. The results suggested that these synthetic antioxidants, especially TBHQ, could be used practically for the protection of the food components such as edible oils and vitamins against singlet oxygen induced oxidations without significant losses of antioxidant activity during storage under light. PMID:20722904

Lee, Jun Hyun; Jung, Mun Yhung

2010-08-01

171

Syngas production via methane steam reforming with oxygen: plasma reactors versus chemical reactors  

NASA Astrophysics Data System (ADS)

Steam reforming with oxygen (SRO) is a combination of non-catalytic partial oxidation and steam reforming of methane, industrially used for syngas production. There are several models of the chemical reactors used for this purpose but in the last decade a new direction has developed - plasma devices. The aim of the present paper is to make a comparative analysis between the autothermal reformers, including their improved variants, and the plasma reactors. The study is conceived in terms of advantages and disadvantages coming from the exploitation parameters, methane conversion, selectivity, energy efficiency and investment costs. Although SRO by means of chemical reactors may be the most efficient, plasma reactors represent an incisive approach by their simplicity, compactness and low price.

Cormier, Jean Marie; Rusu, Iulian

2001-09-01

172

ON THE OXYGEN AND NITROGEN CHEMICAL ABUNDANCES AND THE EVOLUTION OF THE 'GREEN PEA' GALAXIES  

SciTech Connect

We have investigated the oxygen and nitrogen chemical abundances in extremely compact star-forming galaxies (SFGs) with redshifts between {approx}0.11 and 0.35, popularly referred to as 'green peas'. Direct and strong-line methods sensitive to the N/O ratio applied to their Sloan Digital Sky Survey (SDSS) spectra reveal that these systems are genuine metal-poor galaxies, with mean oxygen abundances {approx}20% solar. At a given metallicity these galaxies display systematically large N/O ratios compared to normal galaxies, which can explain the strong difference between our metallicities measurements and previous ones. While their N/O ratios follow the relation with stellar mass of local SFGs in the SDSS, we find that the mass-metallicity relation of the 'green peas' is offset {approx_gt}0.3 dex to lower metallicities. We argue that recent interaction-induced inflow of gas, possibly coupled with a selective metal-rich gas loss, driven by supernova winds, may explain our findings and the known galaxy properties, namely high specific star formation rates, extreme compactness, and disturbed optical morphologies. The 'green pea' galaxy properties seem to be uncommon in the nearby universe, suggesting a short and extreme stage of their evolution. Therefore, these galaxies may allow us to study in great detail many processes, such as starburst activity and chemical enrichment, under physical conditions approaching those in galaxies at higher redshifts.

Amorin, Ricardo O.; Perez-Montero, Enrique; Vilchez, J. M., E-mail: amorin@iaa.e, E-mail: epm@iaa.e, E-mail: jvm@iaa.e [Instituto de Astrofisica de Andalucia (CSIC), Glorieta de la Astronomia S/N, E-18008 Granada (Spain)

2010-06-01

173

Control of Leaf Expansion Rate of Droughted Maize Plants under Fluctuating Evaporative Demand (A Superposition of Hydraulic and Chemical Messages?).  

PubMed Central

We have analyzed the possibility that chemical signaling does not entirely account for the effect of water deficit on the maize (Zea mays L.) leaf elongation rate (LER) under high evaporative demand. We followed time courses of LER (0.2-h interval) and spatial distribution of elongation rate in leaves of either water-deficient or abscisic acid (ABA)-fed plants subjected to varying transpiration rates in the field, in the greenhouse, and in the growth chamber. At low transpiration rates the effect of the soil water status on LER was related to the concentration of ABA in the xylem sap and could be mimicked by feeding artificial ABA. Transpiring plants experienced a further reduction in LER, directly linked to the transpiration rate or leaf water status. Leaf zones located at more than 20 mm from the ligule stopped expanding during the day and renewed expansion during the night. Neither ABA concentration in the xylem sap, which did not appreciably vary during the day, nor ABA flux into shoots could account for the effect of evaporative demand. In particular, maximum LER was observed simultaneously with a minimum ABA flux in the droughted plants, but with a maximum ABA flux in ABA-fed plants. All data were interpreted as the superposition of two additive effects: the first involved ABA signaling and was observed during the night and in ABA-fed plants, and the second involved the transpiration rate and was observed even in well-watered plants. We suggest that a hydraulic signal is the most likely candidate for this second effect.

Salah, HBH.; Tardieu, F.

1997-01-01

174

Regeneration of basic hydrogen peroxide for chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Regeneration of Basic Hydrogen Peroxide (BHP) for Chemical Oxygen Iodine Laser (COIL) has been studied. The apparatus is an electrolyte H2O2 generator, which is composed of anode chamber, cathode chamber with gas diffusion electrode and cation exchange membrane. BHP containing 5 to 10 weight percent (wt%) of H2O2 is supplied to the apparatus and the change in the H2O2 concentration is measured for various operational conditions. A 5.11wt% BHP is regenerated with current efficiency of 92% and a 10.4wt% BHP is regenerated with current efficiency of 73%. It is found that the BHP flow rate and temperature of the BHP are critical to obtain high current efficiency.

Hano, Masami; Wakita, Syuhei; Uno, Masaharu; Endo, Masamori; Nanri, Kenzo; Takeda, Shuzaburo; Fujioka, Tomoo

2003-11-01

175

Real-time data acquisition and control system for a chemical oxygen iodine laser  

NASA Astrophysics Data System (ADS)

A user-friendly data acquisition and control system (DACS) for a chemical oxygen-iodine laser (COIL) has been developed. The system is capable of handling 117 analogue/digital channels for performing various operations such as on-line acquisition, control, display, safety measures and status indication of various subsystems. These operations are controlled either by control switches configured on a PC while not running or by a pre-determined sequence or timings during the run. The system is capable of real-time acquisition and on-line estimation of important diagnostic parameters for optimization of a COIL. The DACS system has been programmed using Advantech-GeniDAQ software. This software has also been used to convert the acquired data into graphical form. Using this DACS, more than 200 runs were given performed successfully.

Mainuddin; Tyagi, R. K.; Rajesh, R.; Singhal, Gaurav; Dawar, A. L.

2003-08-01

176

Lasing in supersonic chemical oxygen-iodine lasers: recent modeling and comparison with experiment  

NASA Astrophysics Data System (ADS)

Simple models are developed, describing the power extraction in chemical oxygen-iodine lasers (COILs) with stable and unstable resonators. For stable resonators the model is applied to the ejector high pressure COIL and the results are compared with the experimental data (see also a preceding paper by Rosenwaks et al.). The positive and negative branch unstable resonators with cylindrical mirrors that have been recently used in COILs are studied theoretically using a geometrical optics model. The optical extraction efficiency, spatial distributions of the intracavity radiation intensity in the flow direction and the intensity in the far field are calculated for both kinds of resonators as a function of both the resonator and COIL parameters. The optimal resonator magnifications corresponding to the maximum intensity in the far field are found.

Barmashenko, Boris D.; Waichman, Karol; Rosenwaks, Salman

2010-09-01

177

Modelling chemical reactions in dc plasma inside oxygen bubbles in water  

NASA Astrophysics Data System (ADS)

Plasmas generated inside oxygen bubbles in water have been developed for water purification. Zero-dimensional numerical simulations were used to investigate the chemical reactions in plasmas driven by dc voltage. The numerical and experimental results of the concentrations of hydrogen peroxide and ozone in the solution were compared with a discharge current between 1 and 7 mA. Upon increasing the water vapour concentration inside bubbles, we saw from the numerical results that the concentration of hydrogen peroxide increased with discharge current, whereas the concentration of ozone decreased. This finding agreed with the experimental results. With an increase in the discharge current, the heat flux from the plasma to the solution increased, and a large amount of water was probably vaporized into the bubbles.

Takeuchi, N.; Ishii, Y.; Yasuoka, K.

2012-02-01

178

Plasma chemical and electrical modelling of a negative DC corona in pure oxygen  

NASA Astrophysics Data System (ADS)

A complex plasma chemical and electrical model of a negative stationary wire-to-cylinder corona discharge in pure oxygen is presented. The corona discharge is assumed to have axial and azimuthal symmetry. The experimental current-voltage characteristic is required as input data, but there are no other adjustable or empirical parameters. The experimental validation of the results of the model comes from its prediction of the ozone concentration. The role played by different reactions and species is analysed in detail using the results of the simulation. The effect of the gas temperature and of the decomposition of ozone at the electrodes is also investigated. The agreement between the model and the experiments is excellent when the effect of ozone decomposition at the electrodes is taken into account.

Soria, C.; Pontiga, F.; Castellanos, A.

2004-02-01

179

Chemical kinetics of radio-frequency driven atmospheric-pressure helium-oxygen plasmas in humid air  

NASA Astrophysics Data System (ADS)

We describe the chemical kinetics of radio-frequency (rf) driven atmospheric-pressure helium-based plasmas in ambient air as determined through a zero-dimensional time-dependent global model. The effects of humid-air admixtures on the plasma-induced chemical reactions and the evolution of species concentrations in the helium-oxygen mixture (He-O2, helium with 5000 ppm admixture of oxygen) are studied for wide air impurity levels of 1-5000 ppm with the relative humidity of 0-100%. Comparisons made with experiments using an rf driven micro-scale atmospheric pressure plasma jet and one-dimensional simulations suggest that the plausible air impurity level in the experiments is not more than hundreds ppm. Effects of the air impurity containing water-humidity on electro-negativity and chemical activity are clarified with particular emphasis on reactive oxygen species.

Murakami, Tomoyuki; Niemi, Kari; Gans, Timo; O'Connell, Deborah; Graham, William

2011-11-01

180

Cellulose nanobiocomposites with reinforcement of boron nitride: study of thermal, oxygen barrier and chemical resistant properties.  

PubMed

A series of cellulose based nanobiocomposites (cellulose/BN) were prepared with incorporation of various percentage of nano boron nitride (BN). The interaction between cellulose and boron nitride was studied by Fourier transform infrared spectroscopy (FTIR). The structure of cellulose/BN nanobiocomposites was investigated by XRD, FESEM, and HRTEM. It was observed that the boron nitride nanoparticles were dispersed within cellulose matrix due to intercalation and partial exfoliation. The quantitative identification of nanobiocomposites was investigated by selected area electron diffraction (SAED). Thermal stabilities of the prepared nanobiocomposites were measured by thermo gravimetric analysis (TGA) and it was found that thermal stability of the nanobiocomposites was higher than the virgin cellulose. The oxygen barrier property of cellulose/BN nanobiocomposites was measured using a gas permeameter and a substantial reduction in oxygen permeability due to increase in boron nitride loading was observed. Further it was noticed that the chemical resistance of the nanobiocomposites was more than the virgin cellulose. Hence, the prepared nanobiocomposite may be widely used for insulating and temperature resistant packaging materials. PMID:23648034

Swain, Sarat K; Dash, Satyabrata; Behera, Chandini; Kisku, Sudhir K; Behera, Lingaraj

2013-06-20

181

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

PubMed

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

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

2007-08-15

182

A Chemical Kinetic Modeling Study of the Effects of Oxygenated Hydrocarbons on Soot Emissions from Diesel Engines  

SciTech Connect

A detailed chemical kinetic modeling approach is used to examine the phenomenon of suppression of sooting in diesel engines by addition of oxygenated hydrocarbon species to the fuel. This suppression, which has been observed experimentally for a few years, is explained kinetically as a reduction in concentrations of soot precursors present in the hot products of a fuel-rich diesel ignition zone when oxygenates are included. Oxygenates decrease the overall equivalence ratio of the igniting mixture, producing higher ignition temperatures and more radical species to consume more soot precursor species, leading to lower soot production. The kinetic model is also used to show how different oxygenates, ester structures in particular, can have different soot-suppression efficiencies due to differences in molecular structure of the oxygenated species.

Westbrook, C K; Pitz, W J; Curran, H J

2005-11-14

183

Chemical activity of oxygen atoms in the magnetron sputter-deposited ZnO films during film growth.  

PubMed

The role of oxygen atoms in the growth of magnetron sputter-deposited ZnO films was studied in a deposition and post-deposition study in which the deposition of a several-nanometer-thick ZnO layer altered with an exposure to an O2/Ar mixed plasma, i.e., a layer-by-layer (LbL) technique. The film crystallization was promoted by suppressing the oxygen vacancy and interstitial defects by adjusting the exposure conditions of the O2/Ar plasma. These findings suggest that the chemical potential of the oxygen atom influences the film crystallization and the electronic state. The diffusion and effusion of oxygen atoms at the growing surface have an effect similar to that of thermal annealing, promoted film crystallization and the creation and the annihilation of oxygen- and zinc-related defects. The role of oxygen atoms reaching the growing film surface is discussed in terms of chemical annealing and a possible oxygen diffusion mechanism is proposed. PMID:22097531

Watanabe, Fumiya; Morita, Aya; Shirai, Hajime

2011-09-01

184

Chemicals and energy co-generation from direct hydrocarbons/oxygen proton exchange membrane fuel cell  

NASA Astrophysics Data System (ADS)

A proton exchange membrane fuel cell for chemicals and energy co-generation was set up with hydrocarbons ethane, propane and butane as fuels, and the electrochemical performance of the cell was studied by using linear potential sweep, alternating current impedance and gas chromatography. The cell performance can be improved to a great extent by increasing the platinum load in the catalyst, by treating the membrane with phosphoric acid and by elevating temperature. The improvement of cell performance by the increase of platinum load is ascribed to the increase of reaction sites for hydrocarbon oxidation, that by phosphoric acid treatment to the increase of proton conductivity in Nafion membrane, and that by elevating temperature to the improvement in thermodynamic as well as kinetic aspects. Only a small fraction of the hydrocarbon is converted to carbon dioxide in this cell during its power generation. The current efficiency is 5% for the conversion of ethane to carbon dioxide in the ethane/oxygen fuel cell with 20% carbon-supported platinum as catalyst and phosphoric acid-treated membrane as proton exchange membrane at 0.2 V, 80 °C and ambient pressure. The reaction activity of hydrocarbons at the anode is in the order of propane, butane and ethane. The possible chemicals produced from the cell were hydrocarbons with more than six carbons, which are inactive at the anode under cell conditions.

Li, W. S.; Lu, D. S.; Luo, J. L.; Chuang, K. T.

185

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

SciTech Connect

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

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

2009-03-15

186

Chemical-looping combustion of coal with metal oxide oxygen carriers  

SciTech Connect

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

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

2009-08-15

187

CAN GALACTIC CHEMICAL EVOLUTION EXPLAIN THE OXYGEN ISOTOPIC VARIATIONS IN THE SOLAR SYSTEM?  

SciTech Connect

A number of objects in primitive meteorites have oxygen isotopic compositions that place them on a distinct, mass-independent fractionation line with a slope of one on a three-isotope plot. The most popular model for describing how this fractionation arose assumes that CO self-shielding produced {sup 16}O-rich CO and {sup 16}O-poor H{sub 2}O, where the H{sub 2}O subsequently combined with interstellar dust to form relatively {sup 16}O-poor solids within the solar nebula. Another model for creating the different reservoirs of {sup 16}O-rich gas and {sup 16}O-poor solids suggests that these reservoirs were produced by Galactic chemical evolution (GCE) if the solar system dust component was somewhat younger than the gas component and both components were lying on the line of slope one in the O three-isotope plot. We argue that GCE is not the cause of mass-independent fractionation of the oxygen isotopes in the solar system. The GCE scenario is in contradiction with observations of the {sup 18}O/{sup 17}O ratios in nearby molecular clouds and young stellar objects. It is very unlikely for GCE to produce a line of slope one when considering the effect of incomplete mixing of stellar ejecta in the interstellar medium. Furthermore, the assumption that the solar system dust was younger than the gas requires unusual timescales or the existence of an important stardust component that is not theoretically expected to occur nor has been identified to date.

Lugaro, Maria [Monash Centre for Astrophysics (MoCA), Building 28, Monash University, Clayton, VIC 3800 (Australia); Liffman, Kurt [CSIRO/MSE, P.O. Box 56, Highett, VIC 3190 (Australia); Ireland, Trevor R. [Planetary Science Institute and Research School of Earth Sciences, Australian National University, Canberra, ACT 0200 (Australia); Maddison, Sarah T., E-mail: maria.lugaro@monash.edu [Centre for Astrophysics and Supercomputing, Swinburne University, H39, P.O. Box 218, Hawthorn, VIC 3122 (Australia)

2012-11-01

188

Parametric studies of a small-scale chemical oxygen-iodine laser/jet generator system: recent achievements  

NASA Astrophysics Data System (ADS)

Recent results of parametric studies of an efficient supersonic chemical oxygen-iodine laser are presented. The laser is energized by a jet type singlet oxygen generator, operated without primary buffer gas and applies simple nozzle geometry and transonic mixing of iodine and oxygen. Output power of 190 W with chemical efficiency of 18% was obtained in a 5 cm gain length for Cl2 flow rate of 11.8 mmole/s. The power is studied as a function of the distance between the optical axis and the supersonic nozzle exit plane, the molar flow rates of various reagents, the BHP and gas pressures in the generator, the type of the secondary buffer gas (N2 or He) and the stagnation temperature of the gas. It is found that the power under the present operation conditions is almost unaffected by water vapor in the medium. The role of buffer gas under different conditions is discussed.

Furman, Dov; Barmashenko, Boris D.; Rosenwaks, Salman

1998-05-01

189

Gain and Temperature in a Slit Nozzle Supersonic Chemical Oxygen-Iodine Laser with Transonic and Supersonic Injection of Iodine.  

National Technical Information Service (NTIS)

Spatial distributions of the gain and temperature across the flow were studied for transonic and supersonic schemes of the iodine injection in a slit nozzle supersonic chemical oxygen-iodine laser as a function of the iodine and secondary nitrogen flow ra...

B. D. Barmashenko D. Furman E. Bruins S. Rosenwaks V. Rybalkin

2002-01-01

190

Preparation of photocatalytic nano-ZnO\\/TiO 2 film and application for determination of chemical oxygen demand  

Microsoft Academic Search

A composite nano-ZnO\\/TiO2 film as photocatalyst was fabricated with vacuum vaporized and sol–gel methods. The nano-ZnO\\/TiO2 film improved the separate efficiency of the charge and extended the range of spectrum, which showed a higher efficiency of photocatalytic than the pure nano-TiO2 and nano-ZnO film. The photocatalytic mechanism of nano-ZnO\\/TiO2 film was discussed, too. A new method for determination of low

Zhonghai Zhang; Yuan Yuan; Yanju Fang; Linhong Liang; Hongchun Ding; Litong Jin

2007-01-01

191

Chemical Oxygen Demand (COD) For Monitoring Reduction-Oxidation (Redox) Equilibrium During High Level Waste (HLW) Vitrification  

SciTech Connect

High-level nuclear waste is being immobilized at the Savannah River Site by vitrification into borosilicate glass at the Defense Waste Processing Facility. Control of the REDuction/OXidation (REDOX) equilibrium in the DWPF melter is critical for processing high level liquid wastes. Based upon previous research, an acceptable iron REDOX ratio was defined for the DWPF melts as 0.09 Fe2/SFe 0.33. Controlling the DWPF melter at a REDuction/OXidation (REDOX) equilibrium ofFe2/SFe 0.33 prevents the potential for metallic and metallic sulfide species to form and accumulate on the floor of the melter. Control of foaming due to deoxygenation of manganic species is achieved by converting 66-100 of the MnO2 or Mn2O3 species in a waste feed to MnO before the waste is fed to the DWPF melter. At the lower redox limit of Fe 2/SFe 0.09 about 99 of the Mn 4/Mn 3 is converted to Mn 2. Therefore, the lower REDOX limit eliminates melter foaming from deoxygenation. Organic and nitrate concentrations in the DWPF melter feed are the major parameters influencing melt REDOX. Organics such as formates act as reductants while nitrates, nitrites, and manganic (Mn 4 and Mn 3) species act as oxidants. During melting, the REDOX of the melt pool cannot be measured. Therefore, the Fe 2/SFe ratio in the glass poured from the melter must be related to melter feed organic and oxidant concentrations to ensure production of a high quality glass without impacting production rate (e.g., from foaming) or melter life (e.g., from metal formation and accumulation).

JANTZEN, CAROLM.

2004-04-30

192

Effects of translational nonequilibrium on the performance of a flowing chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The effect of the translational nonequilibrium on performance modeling of flowing chemical oxygen-iodine lasers (COIL) is emphasized in this paper. The spectral line broadening (SLB) model is a basic factor for predicting the performances of flowing COIL. The Voigt profile function is a well-known SLB model and is usually utilized. In the case of gas pressure in laser cavity less than 5 torr, a low pressure limit expression of the Voigt profile function is used. These two SLB models imply that all lasing particles can interact with monochromatic laser radiation. Basically, the inhomogeneous broadening effects are not considered in these two SLB models and they cannot predict the spectral content. The latter requires consideration of finite translational relaxation rate. Unfortunately, it is rather difficult to solve simultaneously the Navier-Stokes (NS) equations and the conservation equations of the number of lasing particles per unit volume and per unit frequency interval. In the operating condition of flowing COIL, it is possible to obtain a perturbational solution of the conservational equations for lasing particles and deduce a new relation between the gain and the optical intensity, i.e., a new gain-saturation relation. By coupling the gain-saturation relation with other governing equations (such as the NS equations, chemical reaction equations and the optical model of gain-equal-loss), we have numerically calculated the performances of flowing COIL. The present results are compared with those obtained by the common rate-equation (RE) model, in which the Voigt profile function and its low pressure limit expression are used. The difference of different model"s results is great. For instance, in the case of lasing frequency coinciding with the central frequency of line profile and very low gas pressure, the gain saturation relation of the present model is quite different with that of the RE model.

Gao, Zhi; Yan, Hai-Xing; Hu, Li-Min

2003-12-01

193

Galactic chemical evolution and the oxygen isotopic composition of the solar system  

NASA Astrophysics Data System (ADS)

We review current observational and theoretical constraints on the galactic chemical evolution (GCE) of oxygen isotopes to explore whether GCE plays a role in explaining the lower 17O/18O ratio of the Sun, relative to the present-day interstellar medium, or the existence of distinct 16O-rich and 16O-poor reservoirs in the solar system. Although the production of both 17O and 18O are related to the metallicity of progenitor stars, 17O is most likely produced in stars that evolve on longer timescales than those that produce 18O. Therefore, the 17O/18O ratio need not have remained constant over time, contrary to preconceptions and the simplest models of GCE. An apparent linear, slope-one correlation between ?17O and ?18O in the ISM need not necessarily reflect an O isotopic gradient, and any slope-one galactocentric gradient need not correspond to evolution in time. Instead, increasing 17O/18O is consistent both with observational data from molecular clouds and with modeling of the compositions of presolar grains. Models in which the rate of star formation has decelerated over the past few Gyr or in which an enhanced period of star formation occurred shortly before solar birth ("starburst") can explain the solar-ISM O-isotopic difference without requiring a local input of supernova ejecta into the protosolar cloud. "Cosmic chemical memory" models in which interstellar dust is on average older than interstellar gas predict that primordial solar system solids should be 16O-rich, relative to the Sun, in conflict with observations. However, scenarios can be constructed in which the 16O-rich contribution of very massive stars could lead to 16O-poor solids and a 16O-rich bulk Sun, if the solar system formed shortly after a starburst, independent of the popular scenario of photochemical self-shielding of CO.

Nittler, Larry R.; Gaidos, Eric

2012-12-01

194

Chemical potential of oxygen for iron-rutile-ilmenite and iron-ilmenite-ulvospinel equilibria  

NASA Astrophysics Data System (ADS)

The chemical potential of oxygen corresponding to the iron-rutile-ilmenite (IRI) and iron-ilmenite-ulvospinel (IIU) equilibria has been measured employing solid-state galvanic cells, 11663_2007_Article_BF02654037_TeX2GIFE1.gif Pt, Fe + TiO_2 + FeTiO_3 //(Y_2 O_3 ) ZrO_2 //Fe + FeO, Pt and 11663_2007_Article_BF02654037_TeX2GIFE2.gif {text{Pt, Fe + FeTiO}}_{text{3}} {text{ + Fe}}_{text{2}} {text{TiO}}_{text{4}} {text{//(Y}}_{text{2}} {text{0}}_{text{3}} {text{) ZrO}}_{text{2}} {text{//Fe + FeO, Pt}} in the temperature range of 875 to 1275 K and 900 to 1373 K, respectively. The cells are written such that the right-hand electrodes are positive. The electromotive force (emf) of both the cells was found to be reversible and to vary linearly with temperature over the entire range of measurement. The chemical potential of oxygen for IRI equilibrium is represented by ??o2(IRI) = -550,724 - 29.445 T + 20.374 T In T(±210) J mol-1 (875 <- T<- 1184 K) = -620,260 + 369.593 T - 27.716T ln T(±210) J mol-1 (1184 <- T<- 1275 K) and that for IIU equilibrium by ??o2(IIU) = -501,800 - 49.035T + 20.374 T ln T(±210) J mol-1 (900 <- T<- 1184 K) = -571,336 + 350.003 T- 27.716T ln T(=-210) J mol-1 (1184 <- T<- 1373 K) The standard Gibbs energy changes for IRI and IIU equilibria have been deduced from the measured oxygen potentials. Since ilmenite contains small amounts of Ti³+ ions, a correction for the activity of FeTiO3 has been incorporated by assuming ideal mixing on each cation sublattice in the FeTiO3-Ti2O3 system. Similarly, the ulvospinel contains some Fe³+ ions and a correction for the activity of Fe2TiO4 has been included by modeling the Fe2TiO4-Fe3O4 system. The third-law analysis of the results obtained for IRI equilibrium gives ?H{298/0} = -575 (±1.0) kJ mol-1 and for IIU equilibrium yields ?H{298/0} = -523.7 (±0.7) kJ mol-1}. The present results suggest that Fe2+ and Ti4+ cations mix almost ideally on the octahedral site of spinel lattice in Fe2TiO4, giving rise to a configurational contribution of 2R In 2 (11.5256 J mol-1 K-1) to the entropy of Fe2TiO4.

Kale, G. M.; Jacob, K. T.

1992-01-01

195

Chemical oxygen-iodine laser for decommissioning and dismantlement of nuclear facilities  

NASA Astrophysics Data System (ADS)

Conceptual designs of a chemical oxygen-iodine laser (COIL) facility for decommissioning and dismantlement (DD) of nuclear facility is proposed. The requisite output power and beam quality was determined base don our preliminary experiments of nonmetal material processing. Assuming the laser power of 30kW, it is derived that the beam quality of M2 equals 36 required to cut a biological shield wall of a nuclear power plant at a cutting speed of 10mm/min. Then the requisite specification of an optical fiber to deliver the laser is calculated. It turned to be quite extreme, core diameter of 1.7mm and NA equals 0.018. The mass flow and heat balance of proposed facility is calculated based on our recent COIL studies. With the high-pressure subsonic mode, the vacuum pump size is minimized compared to the supersonic operation. Finally, the size of the facility is estimated assuming tow-hour continuous operation. It is revealed that such a system can be packed in five railway containers.

Tei, Kazuyoku; Sugimoto, Daichi; Endo, Masamori; Takeda, Shuzaburo; Fujioka, Tomoo

2000-01-01

196

Chemical Quenching of Singlet Oxygen by Carotenoids in Plants1[C][W  

PubMed Central

Carotenoids are considered to be the first line of defense of plants against singlet oxygen (1O2) toxicity because of their capacity to quench 1O2 as well as triplet chlorophylls through a physical mechanism involving transfer of excitation energy followed by thermal deactivation. Here, we show that leaf carotenoids are also able to quench 1O2 by a chemical mechanism involving their oxidation. In vitro oxidation of ?-carotene, lutein, and zeaxanthin by 1O2 generated various aldehydes and endoperoxides. A search for those molecules in Arabidopsis (Arabidopsis thaliana) leaves revealed the presence of 1O2-specific endoperoxides in low-light-grown plants, indicating chronic oxidation of carotenoids by 1O2. ?-Carotene endoperoxide, but not xanthophyll endoperoxide, rapidly accumulated during high-light stress, and this accumulation was correlated with the extent of photosystem (PS) II photoinhibition and the expression of various 1O2 marker genes. The selective accumulation of ?-carotene endoperoxide points at the PSII reaction centers, rather than the PSII chlorophyll antennae, as a major site of 1O2 accumulation in plants under high-light stress. ?-Carotene endoperoxide was found to have a relatively fast turnover, decaying in the dark with a half time of about 6 h. This carotenoid metabolite provides an early index of 1O2 production in leaves, the occurrence of which precedes the accumulation of fatty acid oxidation products.

Ramel, Fanny; Birtic, Simona; Cuine, Stephan; Triantaphylides, Christian; Ravanat, Jean-Luc; Havaux, Michel

2012-01-01

197

Predicting dissolved oxygen concentration using kernel regression modeling approaches with nonlinear hydro-chemical data.  

PubMed

Kernel function-based regression models were constructed and applied to a nonlinear hydro-chemical dataset pertaining to surface water for predicting the dissolved oxygen levels. Initial features were selected using nonlinear approach. Nonlinearity in the data was tested using BDS statistics, which revealed the data with nonlinear structure. Kernel ridge regression, kernel principal component regression, kernel partial least squares regression, and support vector regression models were developed using the Gaussian kernel function and their generalization and predictive abilities were compared in terms of several statistical parameters. Model parameters were optimized using the cross-validation procedure. The proposed kernel regression methods successfully captured the nonlinear features of the original data by transforming it to a high dimensional feature space using the kernel function. Performance of all the kernel-based modeling methods used here were comparable both in terms of predictive and generalization abilities. Values of the performance criteria parameters suggested for the adequacy of the constructed models to fit the nonlinear data and their good predictive capabilities. PMID:24338099

Singh, Kunwar P; Gupta, Shikha; Rai, Premanjali

2014-05-01

198

Electrochemical methods for autonomous chemical (phosphate and oxygen) monitoring in the ocean in the Oxygen Minimum Zone  

NASA Astrophysics Data System (ADS)

Oxygen Minimum Zones (OMZ), mainly localized in the EBUS, are known to play a crucial role on climate evolution via greenhouse gases budgets and on marine ecosystems (respiratory barrier, modifications of the nitrogen cycle). Deoxygenation will have widespread consequences due to the role oxygen plays in the biogeochemical cycling of carbon, nitrogen, phosphorus and other important elements such as Fe, S. Developing new sensors for improving our understanding of the coupled biogeochemical cycles (P-O-C-N) in these regions constitutes an immense challenge. Electrochemistry provides promising liquid reagentless methods by going further in miniaturization, decreasing the response time and energy requirements and thus increasing our observing capacities in the ocean. We present an electrochemical method for phosphate determination in seawater based on the anodic oxidation of molybdenum in seawater in order to create molybdophosphate complexes amperometrically detected on a gold electrode by means of amperometry or square-wave voltammetry. We propose a solution to address the silicate interference issue based on an appropriate ratio of proton/molybdate within an electrochemical cell using specialized membrane technology. The detection limit can be as low as 180 nM. An application of this method is presented in the OMZ offshore Peru. The results show excellent agreement when compared to colorimetry with an average deviation of 5.1%. This work is a first step to develop an autonomous in situ sensor for electrochemical detection of phosphate in seawater. The STOX sensor for the measurements of ultra-low oxygen concentrations was improved by decreasing the distance between the sensing and guard cathodes. The modification of the sensor tip was done by development of a method for gold plating on the front silicone rubber membrane in order to form a guard cathode. Then, the traditional and modified STOX sensors were compared and the preliminary studies showed a great potential in STOX sensors with the modified guard cathode. The results show higher sensitivity and faster response time (t90 = 7.3 s) for the modified sensor. The temperature calibrations show an increasing signal with temperature (2.36 %/°C) similar for both sensor types. The improvement makes the sensor particularly suitable for use with CTD (Conductivity, Temperature, Depth) type instruments.

Jonca, J.; Thouron, D.; Comtat, C.; Revsbech, N. P.; Garçon, V.

2012-04-01

199

Influence of Matrices on Oxygen Sensing of Three Sensing Films with Chemically Conjugated Platinum Porphyrin Probes and Preliminary Application for Monitoring of Oxygen Consumption of Escherichia coli (E. coli)  

PubMed Central

Oxygen sensing films were synthesized by a chemical conjugation of functional platinum porphyrin probes in silica gel, polystyrene (PS), and poly(2-hydroxyethyl methacrylate) (PHEMA) matrices. Responses of the sensing films to gaseous oxygen and dissolved oxygen were studied and the influence of the matrices on the sensing behaviors was investigated. Silica gel films had the highest fluorescence intensity ratio from deoxygenated to oxygenated environments and the fastest response time to oxygen. PHEMA films had no response to gaseous oxygen, but had greater sensitivity and a faster response time for dissolved oxygen than those of PS films. The influence of matrices on oxygen response, sensitivity and response time was discussed. The influence is most likely attributed to the oxygen diffusion abilities of the matrices. Since the probes were chemically immobilized in the matrices, no leaching of the probes was observed from the sensing films when applied in aqueous environment. One sensing film made from the PHEMA matrix was used to preliminarily monitor the oxygen consumption of Escherichia coli (E. coli) bacteria. E. coli cell density and antibiotics ampicillin concentration dependent oxygen consumption was observed, indicating the potential application of the oxygen sensing film for biological application.

Tian, Yanqing; Shumway, Bradley R.; Gao, Weimin; Youngbull, Cody; Holl, Mark R.; Johnson, Roger H.; Meldrum, Deirdre R.

2010-01-01

200

Origin of deep subgap states in amorphous indium gallium zinc oxide: Chemically disordered coordination of oxygen  

NASA Astrophysics Data System (ADS)

The origin of the deep subgap states in amorphous indium gallium zinc oxide (a-IGZO), whether intrinsic to the amorphous structure or not, has serious implications for the development of p-type transparent amorphous oxide semiconductors. We report that the deep subgap feature in a-IGZO originates from local variations in the oxygen coordination and not from oxygen vacancies. This is shown by the positive correlation between oxygen composition and subgap intensity as observed with X-ray photoelectron spectroscopy. We also demonstrate that the subgap feature is not intrinsic to the amorphous phase because the deep subgap feature can be removed by low-temperature annealing in a reducing environment. Atomistic calculations of a-IGZO reveal that the subgap state originates from certain oxygen environments associated with the disorder. Specifically, the subgap states originate from oxygen environments with a lower coordination number and/or a larger metal-oxygen separation.

Sallis, S.; Butler, K. T.; Quackenbush, N. F.; Williams, D. S.; Junda, M.; Fischer, D. A.; Woicik, J. C.; Podraza, N. J.; White, B. E.; Walsh, A.; Piper, L. F. J.

2014-06-01

201

Thermal, Mechanical and Chemical Analysis for VELOX -Verification Experiments for Lunar Oxygen Production  

NASA Astrophysics Data System (ADS)

One major aspect for the development of a long-term human presence on the moon will be sustainability and autonomy of any kind of a permanent base. Important resources, such as breathable air and water for the survival of the crew on the lunar surface will have to be extracted in-situ from the lunar regolith, the major resource on the Moon, which covers the first meter of the lunar surface and contains about 45 At the DLR Bremen we are interested in a compact and flexible lab experimenting facility, which shall demonstrate the feasibility of this process by extracting oxygen out of lunar Regolith, respectively soil simulants and certain minerals in the laboratory case. For this purpose, we have investigated important boundary conditions such as temperatures during the process, chemical reaction characteristics and material properties for the buildup of the facility and established basic requirements which shall be analyzed within this paper. These requirements have been used for the concept development and outline of the facility, which is currently under construction and will be subject to initial tests in the near future. This paper will focus mainly on the theoretical aspects of the facility development. Great effort has been put into the thermal and mechanical outline and pre-analysis of components and the system in a whole. Basic aspects that have been investigated are: 1. Selection of suitable materials for the furnace chamber configuration to provide a high-temperature capable operating mode. 2. Theoretical heat transfer analysis of the designed furnace chamber assembly with subsequent validation with the aid of measured values of the constructed demonstration plant. 3. Description of chemical conversion processes for Hydrogen reduction of Lunar Regolith with corresponding analysis of thermal and reaction times under different boundary conditions. 4. Investigation of the high-temperature mechanical behavior of the constructed furnace chamber with regard to thermal stability and especially to the hermetically sealed reactor due to internal Hydrogen atmosphere. In the end, we will give a first glimpse into the development of the test setup and first test results on the way to a superior test set-up and infrastructure with pre-and post-processing units such as feeding and extraction units and analysis of reaction products.

Lange, Caroline; Ksenik, Eugen; Braukhane, Andy; Richter, Lutz

202

Oxygenated Organic Chemicals in the Pacific Troposphere: Distribution, Sources and Chemistry  

NASA Technical Reports Server (NTRS)

Airborne measurements of a large number of oxygenated organic chemicals (Oxorgs) were carried out in the Pacific troposphere (0.1-12 km) in the Spring of 2001 (Feb. 24-April 10). Specifically these measuremen ts included acetone, methylethyl ketone (MEK), methanol, ethanol, ace taldehyde, propionaldehyde, PANS, and organic nitrates. Complementary measurements of formaldehyde, organic peroxides, and tracers were al so available. Ox-orgs were abundant in the clean troposphere and were greatly enhanced in the outflow regions from Asia. Their mixing ratios were typically highest in the lower troposphere and declined toward s the upper troposphere and the lowermost stratosphere. Their total a bundance (Ox-orgs) significantly exceeded that of NMHC (C2-C8 NMHC). A comparison of these data with observations collected some seven yea rs earlier (Feb.-March, 1994), did not reveal any significant changes . Throughout the troposphere mixing ratios of Ox-orgs were strongly c orrelated with each other as well as with tracers of fossil and bioma sshiof'uel combustion. Analysis of the relative enhancement of selected Oxorgs with respect to CH3Cl and CO in twelve sampled plumes, origi nating from fires, is used to assess their primary and secondary sour ces from biomass combustion. The composition of these plumes also ind icates a large shift of reactive nitrogen into the PAN reservoir ther eby limiting ozone formation. The Harvard 3-D photochemical model, th at uses state of the art chemistry and source information, is used to compare simulated and observed mixing ratios of selected species. A 1 -D model is used to explore the chemistry of aldehydes. These results will be presented.

Singh, Hanwant B.; Salas, L.; Chatfield, R.; Czech, E.; Fried, A.; Evans, M.; Jacob, D. J.; Blake, D.; Heikes, B.; Talbot, R.

2003-01-01

203

Chemical luminescence measurement of singlet oxygen generated by photodynamic therapy in solutions in real time  

NASA Astrophysics Data System (ADS)

Photodynamic therapy (PDT) is a cancer therapy that utilizes optical energy to activate a photosensitizer drug in a target tissue. Reactive oxygen species (ROS), such as 1O2 and superoxide, are believed to be the major cytotoxic agents involved in PDT. Although current PDT dosimetry mostly involves measurements of light and photosensitizer doses delivered to a patient, the quantification of ROS production during a treatment would be the ultimate dosimetry of PDT. Technically, it is very difficult and expensive to directly measure the fluorescence from 1O2, due to its extreme short lifetime and weak signal strength. In this paper, Photofrin® and 635nm laser were used to generate 1O2 and superoxide in a PDT in solution. Compound 3,7- dihydro-6-{4-[2-(N"-(5-fluoresceinyl) thioureido) ethoxy] phenyl}-2- methylimidazo{1,2-a} pyrazin-3-one sodium salt,an Cyp- ridina luciferin analog commonly referred as FCLA, was used as a chemical reporter of ROS. The 532nm chemiluminescence (CL) from the reaction of the FCLA and ROS was detected with a photon multiplier tube (PMT) system operating at single photon counting mode. With the setup, we have made detections of ROS generated by PDT in real time. By varying the amount of conventional PDT dosage (photosensitizer concentration, light irradiation fluence and its delivery rate) and the amount of FCLA, the intensity of CL and its consumption rate were investigated. The results show that the intensity and temporal profile of CL are highly related to the PDT treatment parameters. This suggests that FCLA CL may provide a highly potential alternative for ROS detection during PDT.

Luo, Shiming; Xing, Da; Zhou, Jing; Qin, Yanfang; Chen, Qun

2005-04-01

204

Chemical diffusion of oxygen in crushed single-crystal YBa 2Cu 3O 7- ? investigated by thermogravimetry  

NASA Astrophysics Data System (ADS)

The kinetics of oxygen in- and out-diffusion in the crushed YBa 2Cu 3O 7- ? single-crystal prepared by the top-seeded solution-growth (TSSG) were studied by thermogravimetry. By fitting these experimental curves, the chemical in-diffusion coefficient in the temperature range from 375 to 475 °C were determined as on the order of 10 -10 cm 2/s for the samples with oxygen deficiencies ? < 0.1. The activation energy in the same samples was also determined as 1.04 ± 0.10 eV. The out-diffusion exhibited similar kinetics behavior as in the in-diffusion process at a fixed oxygen partial pressure.

Zhang, Yulong; Yao, Xin; Zhang, Hong; Jin, Yanping

2004-11-01

205

Highly efficient cw chemical oxygen-iodine laser with transsonic iodine injection and a nitrogen buffer gas  

SciTech Connect

Methods of increasing the efficiency of low-pressure chemical oxygen-iodine lasers (COILs) with transsonic injection of molecular iodine, in which nitrogen is used as a buffer gas, are studied. A two-layer gas-dynamic model is used for a parametric analysis of physicochemical processes occurring in the transsonic iodine injector and in the COIL resonator, including mixing and generation of radiation. The 3D-RANS computer simulation software is used to study the flow structures resulting from an injection of iodine-containing flow into the transsonic zone of the oxygen nozzle. Experiments with a 10-kW modified laser have resulted in a chemical efficiency of 31.5% for a lasing power of 13.5 kW. The results of experimental studies of the cryosorption COIL exhaust system are presented. (lasers)

Boreysho, A S; Barkan, A B; Vasil'ev, D N; Evdokimov, I M; Savin, A V [D. F. Ustinov Voenmekh Baltic State Technical University, Laser Systems Ltd., St. Petersburg (Russian Federation)

2005-06-30

206

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

Microsoft Academic Search

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

Irman Idris; Osamu Sugiura

1998-01-01

207

A queueing approach to production-inventory planning for supply chain with uncertain demands: Case study of PAKSHOO Chemicals Company  

Microsoft Academic Search

In some industries such as the consumable product industry because of small differences between products made by various companies, customer loyalty is directly related to the availability of products required at that time. In other words, in such industries demand cannot be backlogged but can be totally or partly lost. So companies of this group use make-to-stock (MTS) production policy.

E. Teimoury; M. Modarres; F. Ghasemzadeh; M. Fathi

2010-01-01

208

Contamination of Oxygen-Consuming Organics in the Yellow River of China  

Microsoft Academic Search

Contamination of oxygen-consuming organics (OCOs) was one of the most serious problems in the Yellow River of China. This\\u000a study was conducted to analyze monitoring of the data on OCOs contamination for the river in 1980 and during 1992–1999 as\\u000a well as examining the effect of suspended solids (SS) on chemical oxygen demand (CODMn) and biochemical oxygen demand (BOD5) of

Xinghui Xia; Zhifeng Yang; Ran Wang; Lihong Meng

2005-01-01

209

Natural gas to fuels and chemicals: improved methane aromatization in an oxygen-permeable membrane reactor.  

PubMed

Adding value with membranes: Improved methane aromatization was achieved by using an oxygen-permeable membrane. The resulting membrane reactor shows a superior methane conversion and a higher resistance towards catalyst deactivation. PMID:24346953

Cao, Zhengwen; Jiang, Heqing; Luo, Huixia; Baumann, Stefan; Meulenberg, Wilhelm A; Assmann, Jens; Mleczko, Leslaw; Liu, Yi; Caro, Jürgen

2013-12-16

210

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

SciTech Connect

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

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

2010-05-15

211

Radioactivity, Physical and Chemical Parameters of Underground and Surface Waters in Qua Iboe River Estuary, Nigeria  

Microsoft Academic Search

Radioactivity, physical and chemical parameters of underground boreholes and surface waters in the region of Qua Iboe River Estuary involved in oil production activities were measured. The physical and chemical parameters measured included pH, temperature, turbidity, and concentrations of total dissolved and suspended solids, dissolved oxygen, chemical and biochemical oxygen demand, oils and grease, salinity, hardness (carbonates and bicarbonates), chlorine,

NSE M. Ekpo; L. E. D. Inyang

2000-01-01

212

An improved chemical scheme for the reactions of atomic oxygen and simple unsaturated hydrocarbons - implications for star-forming regions  

NASA Astrophysics Data System (ADS)

Recent laboratory experiments have demonstrated that even though contribution from other reaction channels cannot be neglected, unsaturated hydrocarbons easily break their multiple C-C bonds to form CO after their interactions with atomic oxygen. Here, we present an upgraded chemical modelling including a revision of the reactions between oxygen atoms and small unsaturated hydrocarbons for different astrochemical environments. The first conclusion is that towards hot cores/corinos atomic oxygen easily degrades unsaturated hydrocarbons directly to CO or to its precursor species (such as HCCO or HCO) and destroys the double or triple bond of alkenes and alkynes. Therefore, environments rich in atomic oxygen at a relatively high temperature are not expected to be rich in large unsaturated hydrocarbons or polycyclic aromatic hydrocarbons. In contrast, in O-poor and C-rich objects, hydrocarbon growth can occur to a large extent. In addition, new radical species, namely ketyl and vinoxy radicals, generated from other reaction channels can influence the abundances of hydrocarbons towards hot cores. We, therefore, suggest that they should be included in the available databases. Hydrocarbon column densities are calculated in the 1013-1015 cm-2 range, in good agreement with their observed values, despite the small number of data currently published in the literature.

Occhiogrosso, Angela; Viti, Serena; Balucani, Nadia

2013-07-01

213

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

SciTech Connect

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

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

2009-03-15

214

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

Microsoft Academic Search

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

Carl Linderholm; Alberto Abad; Tobias Mattisson; Anders Lyngfelt

2008-01-01

215

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

SciTech Connect

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

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

2007-07-31

216

Oxygen chemical diffusion in three basaltic liquids at elevated temperatures and pressures  

NASA Astrophysics Data System (ADS)

The diffusivity of oxygen has been measured in three basaltic liquids from 1280 to 1450°C and 4 to 21 kilobars using a solid media piston-cylinder apparatus. The measurements were done by monitoring the reduction of ferric iron in previously oxidized spheres of basalt melt. The compositions studied were olivine nephelinite, alkali basalt, and 1921 Kilauea tholeiite. The isobaric temperature dependence of oxygen diffusivity is adequately described by Arrhenius relationships for the three liquids studied. Arrhenius activation energies were determined at 12 kilobars for olivine nephelinite (62± 6 kcal/mole) and tholeiite (51 ± 4 kcal/mole) and at 4, 12, and 20 kilobars for alkali basalt (70 ± 7, 86 ± 6, and 71 ± 14 kcal/mole, respectively). The Arrhenius parameters for the three compositions define a compensation law which is indistinguishable from those for oxygen diffusion in simple silicate melts (DUNN, 1982) and for divalent cation diffusion in basaltic melts ( HOFMANN, 1980). These results suggest that the principal species contributing to the total diffusivity of oxygen is the oxide anion (O 2-). The isothermal pressure dependence of oxygen diffusion is complex and quite different from that observed for cationic diffusion in silicate melts. All three compositions show a sharp decrease in oxygen diffusivity at approximately the same pressure as the change in the liquidus phase from olivine to pyroxene, but otherwise the pressure dependence can be described by Arrhenius type equations. The equations yield negative activation volumes for the olivine nehpelinite and the alkali basalt. The activation volumes determined for the tholeiite are near zero at low pressure and positive at high pressure. A negative activation volume represents a decrease in the average size of the principal diffusing species. The results of this study are consistent with a melt model which includes both continuous changes in the relative proportions of the various anionic species in the melt with pressure and the occurrence of anionic disproportionation reactions within narrow pressure ranges.

Dunn, Todd

1983-11-01

217

Chemical Kinetics of Reaction Systems Carbon Monoxide + Hydroxy Radical and Methyl Radical + Oxygen  

Microsoft Academic Search

Experimental and modeling studies were carried out on kinetics and mechanism of two key reactions of natural gas combustion. Five mixtures of hydrogen, oxygen, and carbon dioxide diluted in argon were studied behind reflected -shock waves in the temperature range from 1420 to 2640 K. The production of CO molecules and OH radicals was measured in-situ by laser absorption. The

Ching-Len Yu

1996-01-01

218

78 FR 1765 - Requirements for Chemical Oxygen Generators Installed on Transport Category Airplanes  

Federal Register 2010, 2011, 2012, 2013

...airplanes do not comply with the requirements of Sec. Sec. 25.1447, 121.329, and 121.333. The AD contained a provisional...presentation are contained in Sec. Sec. 25.1443 and 25.1447. The supplemental oxygen systems are necessary safety...

2013-01-09

219

Oxygen chemical diffusion in three basaltic liquids at elevated temperatures and pressures  

Microsoft Academic Search

The diffusivity of oxygen has been measured in three basaltic liquids from 1280 to 1450°C and 4 to 21 kilobars using a solid media piston-cylinder apparatus. The measurements were done by monitoring the reduction of ferric iron in previously oxidized spheres of basalt melt. The compositions studied were olivine nephelinite, alkali basalt, and 1921 Kilauea tholeiite. The isobaric temperature dependence

Todd Dunn

1983-01-01

220

Comparison of one- and three-dimensional computational fluid dynamics models of the supersonic chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

A simple one-dimensional (1D) computational fluid dynamics (CFD) model of the chemical oxygen iodine laser (COIL) with supersonic mixing is compared with three-dimensional (3D) CFD models and with experimental measurements of the COIL parameters. Dependence of the gain, iodine dissociation fraction and temperature at the resonator optical axis and of the output lasing power on the iodine flow rate predicted by the 1D model is in good agreement with that found using 3D models and experimental results. Hence the 1D model can be used instead of much more complicated 3D models for estimates of the working parameters of supersonic COILs.

Brami-Rosilio, I.; Barmashenko, B. D.; Rosenwaks, S.

2012-09-01

221

A Heterogeneous Chemical Origin for the Mass-Independent Distribution of Oxygen Isotopes in the Solar System?  

NASA Astrophysics Data System (ADS)

One of the longest standing problems in planetary science is the origin of the mass-independently fractionated oxygen isotopic reservoirs in the solar system. The oldest minerals formed in the solar system, calcium-aluminum-rich inclusions (CAIs), are 16O enriched compared to the terrestrial bodies (Earth, Mars, asteroids, and comets). In contrast to most terrestrial solids, whose enrichment-depletion patterns in 18O/16O and 17O/16O are well understood to result from mass-dependent processes, the oxygen isotopic distribution of the solar system requires one (or more) physical processes that produced distinct 16O enriched and 16O depleted reservoirs. Several mechanism have been proposed to date including: I) The injection of pure 16O by a supernova II) isotope selective photo-dissociation of CO and, III) symmetry-dependent chemical fractionation processes in the pre-solar nebula. Mechanism I has been ruled out, while recent experimental tests of mechanism II have cast doubt on the basic assumptions that underlie self-shielding models. Recently it was proposed that the 16O-rich and 16O-poor reservoirs present in the early solar system were produced by the heterogeneous chemical processes that produce H2O on the surface of interstellar dust grains in dense molecular clouds, the astrophysical setting where star formation is observed to occur (1). The production of mass-independently fractionated H2O is expected because its major precursors in these environments, O3(surf.) and HO2 (surf.) are well-known carriers of mass-independently fractionated oxygen isotopic anomalies in Earth’s atmosphere. The formation of complex molecular species in molecular clouds is widely believed to be dominated by chemical reactions that occur on the surfaces of cold interstellar dust grains. This talk will review how these heterogeneous chemical reactions, which in many ways mimic the photo-chemistry present in Earth’s atmosphere, leads to the formation of molecular species such as O2, O3, CO, CO2, and H2O on the surfaces of interstellar dust grains. If the formation of O3 on cold dust grains is mass-independently fractionated with a ?17O ~ 25-35‰, as it is in Earth’s atmosphere, then the triple-oxygen isotopic composition of water inherited from the parent molecular cloud would be consistent with constraints provided by studies of the oxygen isotopic composition of primitive meteorites, cometary water, and the preliminary measurements of the solar wind by Genesis. In this talk, we present the first triple-oxygen isotopic measurements of O3 formed in molecular cloud conditions and will discuss the implications for planetary system formation. (1)Dominguez, Gerardo, A Heterogeneous Chemical Origin for the 17O-enriched and O-depleted Reservoirs of the Early Solar System. The Astrophysical Journal Letters 713, L59 (2010).

Dominguez, G.; Chakraborty, S.; Jackson, T. L.; Thiemens, M. H.

2010-12-01

222

Intra-/inter-laboratory validation study on reactive oxygen species assay for chemical photosafety evaluation using two different solar simulators.  

PubMed

A previous multi-center validation study demonstrated high transferability and reliability of reactive oxygen species (ROS) assay for photosafety evaluation. The present validation study was undertaken to verify further the applicability of different solar simulators and assay performance. In 7 participating laboratories, 2 standards and 42 coded chemicals, including 23 phototoxins and 19 non-phototoxic drugs/chemicals, were assessed by the ROS assay using two different solar simulators (Atlas Suntest CPS series, 3 labs; and Seric SXL-2500V2, 4 labs). Irradiation conditions could be optimized using quinine and sulisobenzone as positive and negative standards to offer consistent assay outcomes. In both solar simulators, the intra- and inter-day precisions (coefficient of variation; CV) for quinine were found to be below 10%. The inter-laboratory CV for quinine averaged 15.4% (Atlas Suntest CPS) and 13.2% (Seric SXL-2500V2) for singlet oxygen and 17.0% (Atlas Suntest CPS) and 7.1% (Seric SXL-2500V2) for superoxide, suggesting high inter-laboratory reproducibility even though different solar simulators were employed for the ROS assay. In the ROS assay on 42 coded chemicals, some chemicals (ca. 19-29%) were unevaluable because of limited solubility and spectral interference. Although several false positives appeared with positive predictivity of ca. 76-92% (Atlas Suntest CPS) and ca. 75-84% (Seric SXL-2500V2), there were no false negative predictions in both solar simulators. A multi-center validation study on the ROS assay demonstrated satisfactory transferability, accuracy, precision, and predictivity, as well as the availability of other solar simulators. PMID:24384453

Onoue, Satomi; Hosoi, Kazuhiro; Toda, Tsuguto; Takagi, Hironori; Osaki, Naoto; Matsumoto, Yasuhiro; Kawakami, Satoru; Wakuri, Shinobu; Iwase, Yumiko; Yamamoto, Toshinobu; Nakamura, Kazuichi; Ohno, Yasuo; Kojima, Hajime

2014-06-01

223

Synthesis of thermal and chemical resistant oxygen barrier starch with reinforcement of nano silicon carbide.  

PubMed

Starch/silicon carbide (starch/SiC) bionanocomposites were synthesized by solution method using different wt% of silicon carbide with starch matrix. The interaction between starch and silicon carbide was studied by Fourier transform infrared (FTIR) spectroscopy. The structure of the bionanocomposites was investigated by X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). Thermal property of starch/SiC bionanocomposites was measured and a significant enhancement of thermal resistance was noticed. The oxygen barrier property of the composites was studied and a substantial reduction in permeability was observed as compared to the virgin starch. The reduction of oxygen permeability with enhancement of thermal stability of prepared bionanocomposites may enable the materials suitable for thermal resistant packaging and adhesive applications. PMID:23911512

Dash, Satyabrata; Swain, Sarat K

2013-09-12

224

Influence of the chemical bond on the K emission spectrum of oxygen and fluorine.  

NASA Technical Reports Server (NTRS)

The K emission spectrum of oxygen and fluorine from a number of simple oxides and fluorides is divided into three to six sub-peaks. The spectra of many of these oxides and fluorides resemble one another owing to their basically ionic bonding. Certain sub-peaks, however, are ascribed to cross-over transitions and partially covalent energy levels. The different fluorine spectrum of Teflon is due to the hybrid nature of its covalent bonds.

Koster, A. S.

1971-01-01

225

Chemical Technology at the Community College of Rhode Island: Curricular Approaches Designed To Reflect the Demands of a Diverse Population Entering Chemical Technology Programs.  

ERIC Educational Resources Information Center

In an effort to provide nontraditional students with the same opportunity as traditional students to reach the highest level of skills and competencies associated with hi-tech, high-wage employment, the Community College of Rhode Island (CCRI) offers alternatives to its historically successful full-time day program in chemical technology.…

Hajian, Harry

226

Chemical analysis and molecular models for calcium-oxygen-carbon interactions in black carbon found in fertile amazonian anthrosoils.  

PubMed

Carbon particles containing mineral matter promote soil fertility, helping it to overcome the rather unfavorable climate conditions of the humid tropics. Intriguing examples are the Amazonian Dark Earths, anthropogenic soils also known as "Terra Preta de Índio'' (TPI), in which chemical recalcitrance and stable carbon with millenary mean residence times have been observed. Recently, the presence of calcium and oxygen within TPI-carbon nanoparticles at the nano- and mesoscale ranges has been demonstrated. In this work, we combine density functional theory calculations, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transformed infrared spectroscopy, and high resolution X-ray photoelectron spectroscopy of TPI-carbons to elucidate the chemical arrangements of calcium-oxygen-carbon groups at the molecular level in TPI. The molecular models are based on graphene oxide nanostructures in which calcium cations are strongly adsorbed at the oxide sites. The application of material science techniques to the field of soil science facilitates a new level of understanding, providing insights into the structure and functionality of recalcitrant carbon in soil and its implications for food production and climate change. PMID:24892495

Archanjo, Braulio S; Araujo, Joyce R; Silva, Alexander M; Capaz, Rodrigo B; Falcão, Newton P S; Jorio, Ado; Achete, Carlos A

2014-07-01

227

Oxygen Content of the Earth's Core and Chemical Interaction at the Core-Mantle Boundary  

NASA Astrophysics Data System (ADS)

The possibility of oxygen being an important light element in the Earth's core is supported by new experimental data from our group and from Takefuji et al. (2005, GRL). Our investigation of FeO partitioning between magnesiowüstite and liquid Fe up to 25 GPa and 3173 K shows that oxygen solubility in liquid Fe increases strongly with temperature, decreases weakly with pressure up to 10-15 GPa and then increases at higher pressures. The change in the pressure dependence is due to the volume change of reaction changing sign at 10-15 GPa due to the FeO component being more compressible in Fe liquid than in magnesiowüstite. The results of Takefuji et al. (2005) obtained at 25-97 GPa are consistent with our results. The combined data sets are fitted with a thermodynamic model that enables the solubility of O in liquid Fe to be estimated under conditions of the outer core. According to this model, the core must be undersaturated in oxygen with respect to the bulk of the mantle, thus indicating core-mantle disequilibrium. The oxygen content of the core was likely fixed during core formation, as was the case for the partitioning of siderophile elements between mantle and core. Based on chondritic bulk compositions, a preliminary core formation model predicts the incorporation of up to 8 wt% oxygen in liquid Fe during metal-silicate segregation in a magma ocean 1000-1500 km deep. The exact O content depends on the O content of the chondritic starting material which is poorly constrained. However, 8 wt% O in the core was also predicted by Alfie et al. (2002, EPSL) based on the density contrast between the inner and outer cores. The new model has implications for reactions occurring at the CMB. Magnesiowüstite coexisting with liquid Fe that contains up to 8 wt% O would be very MgO-rich, with XMgO ~ 0.98 at CMB conditions. This means that the base of the mantle must be strongly depleted in the FeO component. However, such an MgO-rich layer might be very thin because Fe-Mg diffusion, at least in silicate perovskite, is extremely slow at CMB conditions (Holzapfel et al. 2005, Science).

Rubie, D. C.; Asahara, Y.; Frost, D. J.

2006-12-01

228

Chemical reaction of atomic oxygen with evaporated films of copper, part 4  

NASA Technical Reports Server (NTRS)

Evaporated copper films were exposed to an atomic oxygen flux of 1.4 x 10(exp 17) atoms/sq cm per sec at temperatures in the range 285 to 375 F (140 to 191 C) for time intervals between 2 and 50 minutes. Rutherford backscattering spectroscopy (RBS) was used to determine the thickness of the oxide layers formed and the ratio of the number of copper to oxygen atoms in the layers. Oxide film thicknesses ranged from 50 to 3000 A (0.005 to 0.3 microns, or equivalently, 5 x 10(exp -9) to 3 x 10(exp -7); it was determined that the primary oxide phase was Cu2O. The growth law was found to be parabolic (L(t) varies as t(exp 1/2)), in which the oxide thickness L(t) increases as the square root of the exposure time t. The analysis of the data is consistent with either of the two parabolic growth laws. (The thin-film parabolic growth law is based on the assumption that the process is diffusion controlled, with the space charge within the growing oxide layer being negligible. The thick-film parabolic growth law is also based on a diffusion controlled process, but space-charge neutrality prevails locally within very thick oxides.) In the absence of a voltage measurement across the growing oxide, a distinction between the two mechanisms cannot be made, nor can growth by the diffusion of neutral atomic oxygen be entirely ruled out. The activation energy for the reaction is on the order of 1.1 eV (1.76 x 10(exp -19) joule, or equivalently, 25.3 kcal/mole).

Fromhold, A. T.; Williams, J. R.

1990-01-01

229

Food energy supply and demand: A discrepancy between particulate organic carbon flux and sediment community oxygen consumption in the deep ocean  

Microsoft Academic Search

Sediment community oxygen consumption (SCOC) and particulate organic carbon (POC) flux to the benthic boundary layer were concurrently measured at five deep-sea stations on a transect across the eastern and central North Pacific at various times of year. A free vehicle grab respirometer and Alvin-manipulated grab respirometer were used to measure SCOC. Paired particle interceptor traps (PITS) were used to

K. L. JR SMITH

1987-01-01

230

Chemicals and energy co-generation from direct hydrocarbons\\/oxygen proton exchange membrane fuel cell  

Microsoft Academic Search

A proton exchange membrane fuel cell for chemicals and energy co-generation was set up with hydrocarbons ethane, propane and butane as fuels, and the electrochemical performance of the cell was studied by using linear potential sweep, alternating current impedance and gas chromatography. The cell performance can be improved to a great extent by increasing the platinum load in the catalyst,

W. S. Li; D. S. Lu; J. L. Luo; K. T. Chuang

2005-01-01

231

TRPV4 inhibition counteracts edema and inflammation and improves pulmonary function and oxygen saturation in chemically induced acute lung injury.  

PubMed

The treatment of acute lung injury caused by exposure to reactive chemicals remains challenging because of the lack of mechanism-based therapeutic approaches. Recent studies have shown that transient receptor potential vanilloid 4 (TRPV4), an ion channel expressed in pulmonary tissues, is a crucial mediator of pressure-induced damage associated with ventilator-induced lung injury, heart failure, and infarction. Here, we examined the effects of two novel TRPV4 inhibitors in mice exposed to hydrochloric acid, mimicking acid exposure and acid aspiration injury, and to chlorine gas, a severe chemical threat with frequent exposures in domestic and occupational environments and in transportation accidents. Postexposure treatment with a TRPV4 inhibitor suppressed acid-induced pulmonary inflammation by diminishing neutrophils, macrophages, and associated chemokines and cytokines, while improving tissue pathology. These effects were recapitulated in TRPV4-deficient mice. TRPV4 inhibitors had similar anti-inflammatory effects in chlorine-exposed mice and inhibited vascular leakage, airway hyperreactivity, and increase in elastance, while improving blood oxygen saturation. In both models of lung injury we detected increased concentrations of N-acylamides, a class of endogenous TRP channel agonists. Taken together, we demonstrate that TRPV4 inhibitors are potent and efficacious countermeasures against severe chemical exposures, acting against exaggerated inflammatory responses, and protecting tissue barriers and cardiovascular function. PMID:24838754

Balakrishna, Shrilatha; Song, Weifeng; Achanta, Satyanarayana; Doran, Stephen F; Liu, Boyi; Kaelberer, Melanie M; Yu, Zhihong; Sui, Aiwei; Cheung, Mui; Leishman, Emma; Eidam, Hilary S; Ye, Guosen; Willette, Robert N; Thorneloe, Kevin S; Bradshaw, Heather B; Matalon, Sadis; Jordt, Sven-Eric

2014-07-15

232

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

SciTech Connect

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

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

2010-03-15

233

Numerical study on the performance of nozzle flow for supersonic chemical oxygen-iodine lasers  

NASA Astrophysics Data System (ADS)

Laser performance is greatly dependent on its operating conditions due to the strong coupling among multi-physics such as gas-dynamics, chemical reaction kinetics and optics in the mixing nozzle of COIL. In this paper, 3D CFD technology is used to simulate the mixing and reactive flow of subsonic cross jet scheme at different conditions. Results obtained show that the jet penetration depth plays a dominant role in the spatial distribution of small signal gains. In the case of over-penetration, unsteady flow structures are induced by impinging between the opposing jets. The optimum spatial distribution of the chemical performance cannot be obtained even if the full penetration condition is achieved through the subsonic transverse jet mixing scheme in the COIL nozzle flow.

Hu, Zongmin; Lü, Junming; Jiang, Zonglin; Myong, Rho-Shin; Cho, Tae-Hwan

2008-04-01

234

Electrochemical and Structural Study of a Chemically Dealloyed PtCu Oxygen Reduction Catalyst  

SciTech Connect

A carbon-supported, dealloyed platinum-copper (Pt-Cu) oxygen reduction catalyst was prepared using a multistep synthetic procedure. Material produced at each step was characterized using high-angle annular dark-field scanning transmission electron microscopy, electron energy loss spectroscopy mapping, X-ray absorption spectroscopy, X-ray diffraction, and cyclic voltammetry, and its oxygen reduction reaction (ORR) activity was measured by a thin-film rotating disk electrode technique. The initial synthetic step, a coreduction of metal salts, produced a range of poorly crystalline Pt, Cu, and Pt-Cu alloy nanoparticles that nevertheless exhibited good ORR activity. Annealing this material alloyed the metals and increased particle size and crystallinity. Transmission electron microscopy shows the annealed catalyst to include particles of various sizes, large (>25 nm), medium (12-25 nm), and small (<12 nm). Most of the small and medium-sized particles exhibited a partial or complete core-shell (Cu-rich core and Pt shell) structure with the smaller particles typically having more complete shells. The appearance of Pt shells after annealing indicates that they are formed by a thermal diffusion mechanism. Although the specific activity of the catalyst material was more than doubled by annealing, the concomitant decrease in Pt surface area resulted in a drop in its mass activity. Subsequent dealloying of the catalyst by acid treatment to partially remove the copper increased the Pt surface area by changing the morphology of the large and some medium particles to a 'Swiss cheese' type structure having many voids. The smaller particles retained their core-shell structure. The specific activity of the catalyst material was little reduced by dealloying, but its mass activity was more than doubled due to the increase in surface area. The possible origins of these results are discussed in this report.

Dutta, Indrajit; Carpenter, Michael K.; Balogh, Michael P.; Ziegelbauer, Joseph M.; Moylan, Thomas E.; Atwan, Mohammed H.; Irish, Nicholas P. (Trison Business Solutions); (General Motors Corp.)

2010-10-22

235

Electrochemical and Structural Study of a Chemically Dealloyed PtCu Oxygen Reduction Catalyst  

PubMed Central

A carbon-supported, dealloyed platinum-copper (Pt-Cu) oxygen reduction catalyst was prepared using a multi-step synthetic procedure. Material produced at each step was characterized using high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), electron energy loss spectroscopy (EELS) mapping, x-ray absorption spectroscopy (XAS), x-ray diffraction (XRD), and cyclic voltammetry (CV), and its oxygen reduction reaction (ORR) activity was measured by a thin-film rotating disk electrode (TF-RDE) technique. The initial synthetic step, a co-reduction of metal salts, produced a range of poorly crystalline Pt, Cu, and Pt-Cu alloy nanoparticles that nevertheless exhibited good ORR activity. Annealing this material alloyed the metals and increased particle size and crystallinity. TEM shows the annealed catalyst to include particles of various sizes, large (>25 nm), medium (12–25 nm), and small (<12 nm). Most of the small and medium-sized particles exhibited a partial or complete coreshell (Cu-rich core and Pt shell) structure with the smaller particles typically having more complete shells. The appearance of Pt shells after annealing indicates that they are formed by a thermal diffusion mechanism. Although the specific activity of the catalyst material was more than doubled by annealing, the concomitant decrease in Pt surface area resulted in a drop in its mass activity. Subsequent dealloying of the catalyst by acid treatment to partially remove the copper increased the Pt surface area by changing the morphology of the large and some medium particles to a “Swiss cheese” type structure having many voids. The smaller particles retained their core-shell structure. The specific activity of the catalyst material was little reduced by dealloying, but its mass activity was more than doubled due to the increase in surface area. The possible origins of these results are discussed in this report.

Dutta, Indrajit; Carpenter, Michael K; Balogh, Michael P; Ziegelbauer, Joseph M; Moylan, Thomas E; Atwan, Mohammed H; Irish, Nicholas P

2013-01-01

236

Study of oxygen-containing groups in a series of graphite oxides: Physical and chemical characterization  

Microsoft Academic Search

Some graphite oxides with different degrees of oxidation have been prepared by using a modified Staudenmaier method. The oxidation process has been studied by using different techniques: elementary analysis, gas adsorption, X-ray diffraction, FT-IR, XPS and 13C-NMR. The influence of the oxidation degree on the appearance and evolution of new chemical groups in the samples has been analyzed. The oxidation

C. Hontoria-Lucas; A. J. López-Peinado; J. de D. López-González; M. L. Rojas-Cervantes; R. M. Martín-Aranda

1995-01-01

237

Numerical study on the performance of nozzle flow for supersonic chemical oxygen–iodine lasers  

Microsoft Academic Search

Laser performance is greatly dependent on its operating conditions due to the strong coupling among multi-physics such as\\u000a gas-dynamics, chemical reaction kinetics and optics in the mixing nozzle of COIL. In this paper, 3D CFD technology is used\\u000a to simulate the mixing and reactive flow of subsonic cross jet scheme at different conditions. Results obtained show that\\u000a the jet penetration

Zongmin Hu; Junming Lü; Zonglin Jiang; Rho-Shin Myong; Tae-Hwan Cho

2008-01-01

238

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

Microsoft Academic Search

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

Laihong Shen; Jiahua Wu; Jun Xiao

2009-01-01

239

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

Microsoft Academic Search

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

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

2009-01-01

240

Oxygen isotopic and chemical zoning of melilite crystals in a type A Ca-Al-rich inclusion of Efremovka CV3 chondrite  

NASA Astrophysics Data System (ADS)

Different oxygen isotopic reservoirs have been recognized in the early solar system. Fluffy type A Ca-Al-rich inclusions (CAIs) are believed to be direct condensates from a solar nebular gas, and therefore, have acquired oxygen from the solar nebula. Oxygen isotopic and chemical compositions of melilite crystals in a type A CAI from Efremovka CV3 chondrite were measured to reveal the temporal variation in oxygen isotopic composition of surrounding nebular gas during CAI formation. The CAI is constructed of two domains, each of which has a core-mantle structure. Reversely zoned melilite crystals were observed in both domains. Melilite crystals in one domain have a homogeneous 16O-poor composition on the carbonaceous chondrite anhydrous mineral (CCAM) line of ?18O = 5-10‰, which suggests that the domain was formed in a 16O-poor oxygen isotope reservoir of the solar nebula. In contrast, melilite crystals in the other domain have continuous variations in oxygen isotopic composition from 16O-rich (?18O = -40‰) to 16O-poor (?18O = 0‰) along the CCAM line. The oxygen isotopic composition tends to be more 16O-rich toward the domain rim, which suggests that the domain was formed in a variable oxygen isotope reservoir of the solar nebula. Each domain of the type A CAI has grown in distinct oxygen isotope reservoir of the solar nebula. After the domain formation, domains were accumulated together in the solar nebula to form a type A CAI.

Kawasaki, Noriyuki; Sakamoto, Naoya; Yurimoto, Hisayoshi

2012-12-01

241

A simplified analytic model for gain saturation and power extraction in the flowing chemical oxygen-iodine laser  

SciTech Connect

This paper describes the development of a simplified saturation model (SSM) for predicting power extraction from a chemical oxygen-iodine laser (COIL). Using the Fabry-Perot gain saturation assumption, analytic expressions for COIL extraction efficiency are presented for both constant-density and variable-density cavity conditions. The model treats mirror scattering, nonsaturable distributed losses, and diffractive losses from the mode-limiting aperture and is shown to be in excellent agreement with experimental COIL power extraction data. A comparison of the model with the Rigrod power extraction model is presented showing that the Rigrod model accurately predicts COIL extraction efficiency only in the limit that the COIL device no longer behaves as a transfer laser.

Hager, G.D.; Helms, C.A.; Truesdell, K.A. [Phillips Lab., Kirtland AFB, NM (United States)] [Phillips Lab., Kirtland AFB, NM (United States); Plummer, D.; Erkkila, J.; Crowell, P. [Logicon RDA, Albuquerque, NM (United States)] [Logicon RDA, Albuquerque, NM (United States)

1996-09-01

242

Spin-trapping of oxygen free radicals in chemical and biological systems: New traps, radicals and possibilities  

NASA Astrophysics Data System (ADS)

The choice of the spin-trap that is to be applied in any EPR study represents the crossroad between a comprehensive investigation and an "ordinary" quantification of production of radicals. So, the scope of our study was to compare the performance of different spin-traps for qualitative analysis of radical-generating systems, and their ability to recognize previously unnoticed radicals. In addition, we present a brief account of the difficulties involved in the detection of oxygen-centered radicals in chemical and biological systems accompanied by the rationale for using the EPR spin-trapping technique in quantitative studies of such reactive species. Certain technical aspects of EPR experiments related to efficient trapping of free radicals in biochemical systems are also discussed. As an example we present here results obtained using EPR spectroscopy and the spin-trap DEPMPO, which show that the Fenton reaction, as well as various biological systems generate a previously unappreciated hydrogen ( rad H) atom.

Ba?i?, Goran; Spasojevi?, Ivan; Še?erov, Bojana; Mojovi?, Miloš

2008-05-01

243

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

NASA Technical Reports Server (NTRS)

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

Carson, G. T., Jr.

1974-01-01

244

The chemical kinetics and thermodynamics of sodium species in oxygen-rich hydrogen flames  

NASA Technical Reports Server (NTRS)

Results are presented which, it is claimed, lead to a correction of previous misconceptions over the relative importance and kinetics of NaO2. It is shown that its rapid conversion to NaO and NaOH is such that it can severely perturb the NaOH/Na ratio and produce significant concentration overshoots over that predicted from the balance of the reaction of Na with H2O. This becomes increasingly the case in flames of large O2 concentrations and temperatures below 2500 K; and the corresponding large rate constants for the termolecular formation of the other alkali peroxides imply that similar considerations will be necessary for them. Depending on the rate constants for the exothermic conversions of MO2 to MO or MOH, the steady-state concentrations of MO2 could be more or less significant than for sodium. Owing to numerous reactions that produce these conversions, the MOH species will probably be the dominant species in all cases in oxygen-rich hydrogen or hydrocarbon flames, with MO concentrations at not greater than 1 percent of the bound metal.

Hynes, A. J.; Steinberg, M.; Schofield, K.

1984-01-01

245

The production of oxygenated polycrystalline graphene by one-step ethanol-chemical vapor deposition  

PubMed Central

Large-area mono- and bilayer graphene films were synthesized on Cu foil (~ 1 inch2) in about 1 min by a simple ethanol-chemical vapor deposition (CVD) technique. Raman spectroscopy and high resolution transmission electron microscopy revealed the synthesized graphene films to have polycrystalline structures with 2–5 nm individual crystallite size which is a function of temperature up to 1000°C. X-ray photoelectron spectroscopy investigations showed about 3 atomic% carboxylic (COOH) functional groups were formed during growth. The field-effect transistor devices fabricated using polycrystalline graphene as conducting channel (Lc=10 ?m; Wc=50 ?m) demonstrated a p-type semiconducting behavior with high drive current and Dirac point at ~35 V. This simple one-step method of growing large area polycrystalline graphene films with semiconductor properties and easily functionalizable groups should assist in the realization of potential of polycrystalline graphene for nanoelectronics, sensors and energy storage devices.

Paul, Rajat K.; Badhulika, Sushmee; Niyogi, Sandip; Haddon, Robert C.; Boddu, Veera M.; Costales-Nieves, Carmen; Bozhilov, Krassimir N.; Mulchandani, Ashok

2012-01-01

246

The KC Channel in the cbb3-Type Respiratory Oxygen Reductase from Rhodobacter capsulatus Is Required for Both Chemical and Pumped Protons.  

PubMed

The heme-copper superfamily of proton-pumping respiratory oxygen reductases are classified into three families (A, B, and C families) based on structural and phylogenetic analyses. Most studies have focused on the A family, which includes the eukaryotic mitochondrial cytochrome c oxidase as well as many bacterial homologues. Members of the C family, also called the cbb3-type oxygen reductases, are found only in prokaryotes and are of particular interest because of their presence in a number of human pathogens. All of the heme-copper oxygen reductases require proton-conducting channels to convey chemical protons to the active site for water formation and to convey pumped protons across the membrane. Previous work indicated that there is only one proton-conducting input channel (the K(C) channel) present in the cbb3-type oxygen reductases, which, if correct, must be utilized by both chemical protons and pumped protons. In this work, the effects of mutations in the K(C) channel of the cbb3-type oxygen reductase from Rhodobacter capsulatus were investigated by expressing the mutants in a strain lacking other respiratory oxygen reductases. Proton pumping was evaluated by using intact cells, and catalytic oxygen reductase activity was measured in isolated membranes. Two mutations, N346M and Y374F, severely reduced catalytic activity, presumably by blocking the chemical protons required at the active site. One mutation, T272A, resulted in a substantially lower proton-pumping stoichiometry but did not inhibit oxygen reductase activity. These are the first experimental data in support of the postulate that pumped protons are taken up from the bacterial cytoplasm through the K(C) channel. PMID:24563037

Y?ld?z, Gülgez Gökçe; Gennis, Robert B; Daldal, Fevzi; Oztürk, Mehmet

2014-05-01

247

Theory of chemical bonds in metalloenzymes - Manganese oxides clusters in the oxygen evolution center -  

NASA Astrophysics Data System (ADS)

In early 1980 we have initiated broken-symmetry (BS) MO theoretical calculations of transition-metal oxo species M = O (M = Ti,V,Cr,Mn,Fe,Ni,Cu) to elucidate the nature of d?-p? and d?-p? bonds. It has been concluded that high-valent M = O species such as [Mn(IV) = O]2+ and [Fe(IV) = O]2+ exhibit electrophilic property in a sharp contrast with nucleophilic character of low-valent M = O bonds: [M(II)O2-]0, and closed-shell d?-p? bonds of high-valent M = O species often suffer the triplet-instability, giving rise to open-shell (BS) configurations with significant metal-diradical (MDR) character: •M-O•: note that these bonds are therefore regarded as typical examples of strongly correlated electron systems. Because of the MDR character, 1,4-metal diradical mechanism was indeed preferable to four-centered mechanism in the case of addition reaction of naked Mn(IV) = O to ethylene. Recently the manganese-oxo species have been receiving renewed interest in relation to catalytic cycle of oxygen evolution from water molecules in the photosynthesis II (PSII) system. Accumulated experimental results indicate that this process is catalyzed with four manganese oxide clusters coordinated with calcium ion (CaMn4O4). Past decade we have performed BS MO theoretical investigations of manganese oxide clusters related to CaMn4O4. These calculations have elucidated that high-valent Mn(X) = O (X = IV,V) bonds exhibit intermediate MDR character (y=40-60%) in the case of total low-spin (LS) configuration but the MDR character decreases with coordination of Ca2+ and water molecules. While the MDR character of the Mn-oxo bonds becomes very high at the high-spin (HS) configuration. Our computational results enabled us to propose two possible mechanisms on the theoretical ground: (A) electrophilic (EP) mechanism and (B) radical coupling (RC) mechanism. The theoretical results indicate that the EP mechanism is preferable for the low-spin (LS) state in polar media like in the protein environments (native OEC), whereas the RC mechanism is feasible at the state without such environmental stabilization: local singlet and local triplet diradical mechanisms are proposed for the OO coupling process. Possibilities of EP and RC mechanisms are examined in comparison with a lot of experimental results accumulated and theoretical results with several groups.

Yamaguchi, K.; Shoji, M.; Saito, T.; Isobe, H.; Yamada, S.; Nishihara, S.; Kawakami, T.; Kitagawa, Y.; Yamanaka, S.; Okumura, M.

2012-12-01

248

Thermo-chemical fuel removal from porous materials by oxygen and nitrogen dioxide  

NASA Astrophysics Data System (ADS)

Thermo-chemical removal (TCR), or baking in reactive gases, is a candidate method to control the co-deposit related tritium inventory in fusion devices. TCR can be understood as reaction–diffusion processes in a porous material. O2-TCR was applied to 150–550 nm thick a-C:D layers with similar textures. A linear relation between the integral TCR rate and the layer thickness, as predicted by the understanding, was observed in the experiment, i.e. the time to remove the hydrogen inventory is independent of its initial amount. TCR with nitrogen dioxide (NO2) at temperatures of 200–350 °C was conducted with a set of a-C:D and W–C–H layers. At 350 °C NO2 removed ? 15% porosity a-C:D within 3 min. The O retention in remaining a-C:D was ? 1017 O cm?2. An activation energy of ? 0.78 eV for reactions of NO2 with D and C was determined. The results were applied for predictions of the TCR effectivity in ITER. The treatment of W–C–H led to O uptake (O/W ? 2–3), while W and C contents remained unchanged.

Möller, S.; Alegre, D.; Kreter, A.; Petersson, P.; Esser, H. G.; Samm, U.

2014-04-01

249

Efficient electrocatalytic oxygen reduction by the 'blue' copper oxidase, laccase, directly attached to chemically modified carbons.  

PubMed

This discussion describes efforts to produce a stable, efficient electrocatalyst for four-electron O2 reduction through the direct attachment of fungal laccase, a 'blue' copper oxidase, to functionalised carbon electrode materials. Commercially available carbons, including fibrous and porous materials, offer important opportunities for achieving high conductivity over high surface areas that can be chemically functionalised. A promising approach for attaching laccase to a carbon surface is to use the diazonium coupling reaction to generate protrusive aromatic functionalities that can bind to hydrophobic residues close to the 'blue' Cu site: this site provides a fast, intramolecular electron relay into the buried trinuclear Cu active site that converts O2 rapidly and cleanly to H2O. This enhancement procedure makes possible the stable, direct electrocatalytic reduction of O2 at high potential with high efficiency in terms of turnover frequency per enzyme active site engaged with the electrode. The absence of electron-transfer mediators and simplicity of electrode system reveals the more inherent characteristics of the electrocatalytic mechanism that are masked in the waveform when a mediator is used. The study includes experiments to assess the effects of methanol and chloride ions on laccase electrocatalysis, complementing studies carried out by other groups, particularly those in which laccase is embedded in an electron-mediating gel. PMID:19213324

Blanford, Christopher F; Foster, Carina E; Heath, Rachel S; Armstrong, Fraser A

2008-01-01

250

Regulation of manganese peroxidase gene transcription by hydrogen peroxide, chemical stress, and molecular oxygen.  

PubMed Central

The expression of manganese peroxidase (MnP) in nitrogen-limited cultures of the lignin-degrading fungus Phanerochaete chrysosporium is regulated at the level of gene transcription by H2O2 and various chemicals, including ethanol, sodium arsenite, and 2,4-dichlorophenol, as well as by Mn(II) and heat shock. Northern (RNA) blot analysis demonstrates that the addition of 1.0 mM H2O2 to 5-day-old cultures grown in the absence of Mn results in the appearance of mnp mRNA within 15 min. Higher levels of mnp mRNA are obtained with simultaneous induction by Mn and H2O2 than with H2O2 alone. Although neither MnP activity nor associated protein is detectable in H2O2-induced cultures grown in the absence of Mn, simultaneous induction with Mn and H2O2 results in a 1.6-fold increase in MnP activity compared with the MnP activity resulting from Mn induction alone. In the presence of Mn, purging of low-nitrogen cultures with 100% O2, in contrast to incubation under air, results in an increase in the accumulation of mnp mRNA and a 13-fold increase in MnP activity on day 5. However, in contrast to the effects of H2O2 and heat shock, O2 purging of Mn-deficient cultures results in negligible accumulation of mnp mRNA.

Li, D; Alic, M; Brown, J A; Gold, M H

1995-01-01

251

Potential nutritional assessment of dwarf elephant grass ( Pennisetum purpureum Schum. cv. Mott) by chemical composition, digestion and net portal flux of oxygen in cattle  

Microsoft Academic Search

This study was conducted to evaluate changes in chemical composition of dwarf elephant grass hay cut at 30, 40, 50 and 60 days of growth, and its effect on apparent digestibility and particle-phase passage through the gastrointestinal tract (Experiment 1) and on oxygen utilization by the portal-drained viscera of cattle (Experiment 2). The experiments were carried out using four Holstein

G. V Kozloski; J Perottoni; M. L. S Ciocca; J. B. T Rocha; A. G Raiser; L. M. B Sanchez

2003-01-01

252

Extended Hartree-Fock theory of chemical reactions. IX. Diradical and perepoxide mechanisms for oxygenations of ethylene with molecular oxygen and iron-oxo species are revisited  

NASA Astrophysics Data System (ADS)

Symmetry and broken symmetry (BS) in molecular orbital description of transition structures and intermediates in oxygenation reactions have been revisited to elucidate states correlation diagrams and mechanisms for addition reactions of molecular oxygen and metal-oxo M=O (M = Mn(II) and Fe(II)) species to C=C double bonds. Relative stabilities between diradical (DR) and perepoxide (PE) intermediates were thoroughly investigated by several BS hybrid DFT (HDFT) methods and BS CCSD(T) method with and without spin projection. It has been found that recovery of spin symmetry, namely eliminating spin contamination error from the BS solutions, is crucial for the elucidation of reasonable state correlation diagrams and energy differences of the key structures in the oxygenation reactions because the singlet-triplet energy gap for molecular oxygen is large (22 kcal/mol). The BS HDFT followed by spin correction reproduced activation barriers for transition structures along both PE and DR reaction pathways by the use of the CASPT2 method. Basis set dependence on the relative stability between PE and DR intermediates were also examined thoroughly. Solvation effect for DR and PE intermediates was further examined with self-consistent reaction field (SCRF) and SCIPCM methods. Both BS HDFT and CASPT2 have concluded that the DR mechanism is favorable for the addition reaction of singlet oxygen to ethylene, supporting our previous conclusions. The BS HDFT with spin correction was concluded to be useful enough for theoretical investigations of mechanisms of oxygenation reactions. Implications of the computational results were discussed in relation to the theoretical framework (four configuration model) for elucidation of possible mechanisms of epoxidation reactions with Fe(IV)=O cores in metalloenzymes on the basis of isolobal analogies among O, O=O, and Fe(IV)=O. Correspondence between magnetic coupling mode and radical pathway in oxygenations with these species was clarified based on the BS MO interaction diagrams, leading to local singlet and triplet diradical mechanisms for epoxidations.

Yamaguchi, Kizashi; Yamanaka, Syusuke; Shimada, Jiro; Isobe, Hiroshi; Saito, Toru; Shoji, Mitsuo; Kitagawa, Yasutaka; Okumura, Mitsutaka

253

Chemical studies of chloride and stable oxygen isotopes in two conifer afforested and moorland sites in the British uplands  

NASA Astrophysics Data System (ADS)

Chloride concentration variations for three streams in the Crinan Canal region of southwest Scotland, draining heather ( Calluna vulgaris) and immature and mature sitka spruce conifer forest ( Picea sitchensis (Bong.) Carr) are compared with incident rainfall values. Results show the importance, and correspondence, of in-catchment processes for attenuating atmospheric inputs of chloride before its entry to the stream. All three streams exhibit a damped chloride concentration variation compared with rainfall. The chloride chemistries for the three streams are intercorrelated. The weekly data show a net accumulation of chloride into the catchment over the 1 year sampling period. This is associated with an inappropriate stream sampling frequency and/or large yearly fluctuations, in the rainfall input; 80% of the rainfall chloride contribution was introduced during four of the 52 weeks of sampling. The yearly flux of chloride leaving the catchment as stream flow is remarkably similar for all three catchments. The study highlights the need for long and detailed data records from which information can be obtained on chemical budgets and the deficiencies in the measurement of atmospheric inputs of chloride. Although mature conifers are known to capture significant inputs of chemicals to a catchment, not measured by a standard rainfall collector in uplands areas, analogous results are not inferred in the lowland Crinal Canal case. Far more detailed studies are required if a definitive statement is to be made. The chloride results from the Crinan Canal Study are compared with analogous data for streams draining the Hafren Forest at Plynlimon in mid-Wales. Similar degrees of damping are observed and seasonal oscillations occur which do not have the same phase or amplitude. In addition, oxygen isotopic data are presented for the Plynlimon case to highlight a higher degree of damping than for chloride.

Neal, Colin; Rosier, Paul T. W.

254

Gain and temperature in a slit nozzle supersonic chemical oxygen-iodine laser with transonic and supersonic injection of iodine  

NASA Astrophysics Data System (ADS)

Spatial distributions of the gain and temperament across the flow were studied for transonic and supersonic schemes of the iodine injection in a slit nozzle supersonic chemical oxygen-iodine laser as a function of the iodine and secondary nitrogen flow rate, jet penetration parameter and gas pumping rate. The mixing efficiency for supersonic injection of iodine is found to be much larger than for transonic injection, the maximum values of the gain being approximately 0.65 percent/cm for both injection schemes. Measurements of the gain distribution as a function of the iodine molar flow rate nI2 were carried out. For transonic injection the optimal value of nI2 at the flow centerline is smaller than that at the off axis location. The temperature is distributed homogeneously across the flow, increasing only in the narrow boundary layers near the walls. Opening a leak downstream of the cavity in order to decease the Mach number results in a decrease of the gain and increase of the temperature. The mixing efficiency in this case is much larger than for closed leak.

Rosenwaks, Salman; Barmashenko, Boris D.; Bruins, Esther; Furman, Dov; Rybalkin, Victor; Katz, Arje

2002-05-01

255

LASERS: Self-initiating volume discharge in iodides used for producing atomic iodine in pulsed chemical oxygen — iodine lasers  

NASA Astrophysics Data System (ADS)

A volume self-sustained discharge (VSD) in iodides (C3H7I, C4H9I) and in their mixtures with SF6, N2, and O2 in the presence of small-scale inhomogeneities on the cathode surface is shown to develop in the form of a self-initiating volume discharge (SIVD), i.e., a volume discharge without any preionisation including discharge gaps with a strong edge enhancement of the electric field. Additions of SF6 or N2 to the iodides improves the stability and homogeneity of the SIVD, while adding up to 300 % (relative to the partial iodide pressure) of O2 to these mixtures has only an insignificant effect on the discharge stability. The possibility of SIVD initiation was modelled experimentally in a 1.5-L discharge volume. For the C4H9I:O2:SF6=0.083:0.25:0.67 mixture at a pressure of 72 Torr, the specific energy input into the discharge plasma ranged up to 130 J L-1 in this geometry. A conclusion was drawn that the SIVD is promising for the production of atomic iodine in the pulsed and repetitively pulsed operating regimes of a chemical oxygen — iodine laser.

Belevtsev, A. A.; Kazantsev, S. Yu; Saifulin, A. V.; Firsov, K. N.

2003-06-01

256

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

Microsoft Academic Search

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

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

2008-01-01

257

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

Microsoft Academic Search

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

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

2008-01-01

258

Oxygenated volatile organic chemicals in the oceans: Inferences and implications based on atmospheric observations and air-sea exchange models  

NASA Astrophysics Data System (ADS)

Airborne measurements of oxygenated volatile organic chemicals (OVOC), OH free radicals, and tracers of pollution were performed over the Pacific during Winter/Spring of 2001. We interpret atmospheric observations of acetaldehyde, propanal, methanol, and acetone with the help of a global 3-D model and an air-sea exchange model to assess their oceanic budgets. We infer that surface waters of the Pacific are greatly supersaturated with acetaldehyde and propanal. Bulk surface seawater concentration of 7 nM (10-9 mol L-1) and 2 nM and net fluxes of 1.1 × 10-12 g cm-2 s-1 and 0.4 × 10-12 g cm-2 s-1 are calculated for acetaldehyde and propanal, respectively. Large surface seawater concentrations are also estimated for methanol (100 nM) and acetone (10 nM) corresponding to an under-saturation of 6% and 14%, and a deposition velocity of 0.08 cm s-1 and 0.10 cm s-1, respectively. These data imply a large oceanic source for acetaldehyde and propanal, and a modest sink for methanol and acetone. Assuming a 50-100 meter mixed layer, an extremely large oceanic reservoir of OVOC, exceeding the atmospheric reservoir by an order of magnitude, can be inferred to be present. Available seawater data are both preliminary and extremely limited but indicate rather low bulk OVOC concentrations and provide no support for the existence of a large oceanic reservoir. We speculate on the causes and implications of these findings.

Singh, H. B.; Tabazadeh, A.; Evans, M. J.; Field, B. D.; Jacob, D. J.; Sachse, G.; Crawford, J. H.; Shetter, R.; Brune, W. H.

2003-08-01

259

The effect of silver coating on magnetic properties of oxygen-stabilized tetragonal Ni nanoparticles prepared by chemical reduction  

NASA Astrophysics Data System (ADS)

Ni-nickel oxide and Ni-Ag nanoparticles with core-shell morphology have been synthesized by a simple two-step chemical route. It involves the reduction of Ni2+ cations to Ni particles with sodium borohydride (NaBH4) in aqueous solution, followed by coating part of the sample with a surface layer of silver. The coating was accomplished via a simple transmetallation reaction, \\mathrm {Ni+ 2Ag^{+} \\to 2Ag+Ni^{2+}} , in aqueous AgNO3 solution at room temperature. Particles left uncoated have a thin spontaneous surface oxide layer of nickel oxide, presumably non-stoichiometric, as a passivating layer. From x-ray diffraction patterns, the Ni in as-prepared samples, both coated and uncoated, has been identified as being in a tetragonal crystal structure, different from its usual fcc form. This structural modification is due to the presence of interstitial oxygen atoms in the Ni lattice, and results in appreciably modified magnetic properties in this new phase of Ni, for example a linear non-hysteretic magnetization response with applied field at room temperature. A comparative magnetic study of the uncoated and silver coated Ni particles exemplifies the role played by the Ag shell in modifying the magnetic properties of the coated sample. This is evident from the smaller coercivity and remnant magnetization in the hysteresis loop at 5 K in the case of the Ag coated as-prepared sample, larger magnetic moment but smaller saturation magnetization and susceptibility of the Ag coated air annealed sample, and higher blocking temperature for this sample in comparison to the uncoated counterparts. These features have been coherently explained on the basis of the structural modifications induced in these samples by Ag coating.

Roy, Aparna; Srinivas, V.; Ram, S.; Chandrasekhar Rao, T. V.

2007-08-01

260

Oxygen-aromatic contacts in intra-strand base pairs: Analysis of high-resolution DNA crystal structures and quantum chemical calculations.  

PubMed

Three-dimensional structures of biomolecules are stabilized by a large number of non-covalent interactions and some of them such as van der Waals, electrostatic and hydrogen bond interactions are well characterized. Delocalized ?-electron clouds of aromatic residues are known to be involved in cation-?, CH-?, OH-? and ?-? interactions. In proteins, many examples have been found in which the backbone carbonyl oxygen of one residue makes close contact with the aromatic center of aromatic residues. Quantum chemical calculations suggest that such contacts may provide stability to the protein secondary structures. In this study, we have systematically analyzed the experimentally determined high-resolution DNA crystal structures and identified 91 examples in which the aromatic center of one base is in close contact (<3.5?) with the oxygen atom of preceding (Group-I) or succeeding base (Group-II). Examples from Group-I are overwhelmingly observed and cytosine or thymine is the preferred base contributing oxygen atom in Group-I base pairs. A similar analysis of high-resolution RNA structures surprisingly did not yield many examples of oxygen-aromatic contact of similar type between bases. Ab initio quantum chemical calculations on compounds based on DNA crystal structures and model compounds show that interactions between the bases in base pairs with oxygen-aromatic contacts are energetically favorable. Decomposition of interaction energies indicates that dispersion forces are the major cause for energetically stable interaction in these base pairs. We speculate that oxygen-aromatic contacts in intra-strand base pairs in a DNA structure may have biological significance. PMID:24816369

Jain, Alok; Krishna Deepak, R N V; Sankararamakrishnan, Ramasubbu

2014-07-01

261

Mössbauer Study of Structural-Chemical Transformation in Two-Dimensional Iron-Oxygen Nanostructures in the Course of Transport Reduction  

NASA Astrophysics Data System (ADS)

Structural-chemical transformations of quasi-two-dimensional iron-oxygen nanostructures occurring at transport reduction were studied using NGR spectroscopy. It has been found that isolated iron-oxygen groups [i.e. groups containing iron and oxygen atoms: ?Si-O-Fe(OH)2 and (?Si-O-)2-FeOH] forming surface monolayers were not reduced at T = 400-600°C because of their covalent bonding with the silica surface. Reduction of iron oxide microparticles (microstructures) at T >= 600°C resulted in the formation of metal iron in the form of ?-Fe. It has been revealed that in the course of transport reduction (TR) of the samples with deposited monolayers (one or four monolayers) at T >= 600°C bulk phases of iron silicate and metal iron were formed. It has also been shown that the features of structural-chemical transformations of supported iron-oxygen nanolayers were in relation with the specific character of phase formation within nanoscale structures.

Smirnov, V. M.; Voronkov, G. P.; Semenov, V. G.; Povarov, V. G.; Murin, I. V.

262

Chemical ionization of phenyl n -propyl ether and methyl substituted analogs: Propene loss initiated by competing proton transfer to the oxygen atom and the aromatic ring  

Microsoft Academic Search

The mechanism of propene loss from protonated phenyl n-propyl ether and a series of mono-, di-, and trimethylphenyl n-propyl ethers has been examined by chemical ionization (CI) mass spectrometry in combination with tandem mass spectrometry\\u000a experiments. The role of initial proton transfer to the oxygen atom and the aromatic ring, respectively, has been probed with\\u000a the use of deuterated CI

Bogdan Bogdanov; Henri E. K. Matimba; Steen Ingemann; Nico M. M. Nibbering

1996-01-01

263

Technical Note: Performance of Chemical Ionization Reaction Time-of-Flight Mass Spectrometry (CIR-TOF-MS) for the measurement of atmospherically significant oxygenated volatile organic compounds  

Microsoft Academic Search

The performance of a new chemical ionization re- action time-of-flight mass spectrometer (CIR-TOF-MS) util- ising the environment chamber SAPHIR (Simulation of At- mospheric Photochemistry In a large Reaction Chamber- Forschungzentrum Julich, Germany) is described. The work took place as part of the ACCENT (Atmospheric Composi- tion and Change the European NeTwork for excellence) sup- ported oxygenated volatile organic compound (OVOC)

K. P. Wyche; R. S. Blake; A. M. Ellis; P. S. Monks; T. Brauers; R. Koppmann; E. C. Apel

2007-01-01

264

Performance of Chemical Ionization Reaction Time-of-Flight Mass Spectrometry (CIR-TOF-MS) for the measurement of atmospherically significant oxygenated volatile organic compounds  

Microsoft Academic Search

The performance of a new chemical ionization reaction time-of-flight mass spectrometer (CIR-TOF-MS) utilising the environment chamber SAPHIR (Simulation of Atmospheric Photochemistry In a large Reaction Chamber - Forschungzentrum Jülich, Germany) is described. The work took place as part of the ACCENT (Atmospheric Composition and Change the European NeTwork for excellence) supported oxygenated volatile organic compound (OVOC) measurement intercomparison during January

K. P. Wyche; R. S. Blake; A. M. Ellis; P. S. Monks; T. Brauers; R. Koppmann; E. Apel

2006-01-01

265

Technical Note: Performance of Chemical Ionization Reaction Time-of-Flight Mass Spectrometry (CIR-TOF-MS) for the measurement of atmospherically significant oxygenated volatile organic compounds  

Microsoft Academic Search

The performance of a new chemical ionization reaction time-of-flight mass spectrometer (CIR-TOF-MS) utilising the environment chamber SAPHIR (Simulation of Atmospheric Photochemistry In a large Reaction Chamber- Forschungzentrum Jülich, Germany) is described. The work took place as part of the ACCENT (Atmospheric Composition and Change the European NeTwork for excellence) supported oxygenated volatile organic compound (OVOC) measurement intercomparison during January 2005.

K. P. Wyche; R. S. Blake; A. M. Ellis; P. S. Monks; T. Brauers; R. Koppmann; E. C. Apel

2007-01-01

266

Numerical analysis of spatial evolution of the small signal gain in a chemical oxygen–iodine laser operating without primary buffer gas  

Microsoft Academic Search

A chemical oxygen–iodine laser (COIL) that operates without primary buffer gas has become a new way of facilitating the compact integration of laser systems. To clarify the properties of spatial gain distribution, three-dimensional (3-D) computational fluid dynamics (CFD) technology was used to study the mixing and reactive flow in a COIL nozzle with an interleaving jet configuration in the supersonic

Zongmin Hu; Zonglin Jiang; Rhoshin Myong; Taehwan Cho

2008-01-01

267

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

SciTech Connect

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

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

2010-01-01

268

Comparison of sodium carbonate-oxygen and sodium hydroxide-oxygen pretreatments on the chemical composition and enzymatic saccharification of wheat straw.  

PubMed

Pretreatment of wheat straw with a combination of sodium carbonate (Na2CO3) or sodium hydroxide (NaOH) with oxygen (O2) 0.5MPa was evaluated for its delignification ability at relatively low temperature 110°C and for its effect on enzymatic hydrolysis efficiency. In the pretreatment, the increase of alkali charge (as Na2O) up to 12% for Na2CO3 and 6% for NaOH, respectively, resulted in enhancement of lignin removal, but did not significantly degrade cellulose and hemicellulose. When the pretreated solid was hydrolyzed with a mixture of cellulases and hemicellulases, the sugar yield increased rapidly with the lignin removal during the pretreatment. A total sugar yield based on dry matter of raw material, 63.8% for Na2CO3-O2 and 71.9% for NaOH-O2 was achieved under a cellulase loading of 20FPU/g-cellulose. The delignification efficiency and total sugar yield from enzymatic hydrolysis were comparable to the previously reported results at much higher temperature without oxygen. PMID:24686372

Geng, Wenhui; Huang, Ting; Jin, Yongcan; Song, Junlong; Chang, Hou-Min; Jameel, Hasan

2014-06-01

269

Effect of pentachlorophenol and chemical oxygen demand mass concentrations in influent on operational behaviors of upflow anaerobic sludge blanket (UASB) reactor  

Microsoft Academic Search

Upflow anaerobic sludge blanket (UASB) reactor that was seeded with anaerobic sludge acclimated to chlorophenols was used to investigate the feasibility of anaerobic biotreatment of synthetic wastewater containing pentachlorophenol (PCP) with additional sucrose as carbon source. Two sets of UASB reactors were operated at one time. But the seeded sludge for the two reactors was different and Reactor I was

Dong-Sheng Shen; Ruo He; Xin-Wen Liu; Yan Long

2006-01-01

270

Identification, design and synthesis of oxygenated hydrocarbon-based carbon dioxide-soluble polymers for chemical and petroleum engineering applications  

NASA Astrophysics Data System (ADS)

Over the past two decades the use of sub/supercritical CO2 has received much attention as a green alternative to organic solvents for chemical processes because of its pressure-tunable physicochemical properties and economic advantages. However the advantages are diminished because of a relative narrow range of CO2-soluble materials. The goal of this work is to identify, design and synthesize oxygenated hydrocarbon-based CO 2-soluble polymers that are able to serve as construction blocks for copolymers, dispersants, surfactants, and thickeners. Without concerning on the cost and the environmental persistence like fluorinated materials, the inexpensive and environmentally benign materials would significantly enhance the viability of sub/supercritical CO2-based technology. Based on both experimental heuristics and ab initio simulation of molecular modeling (performed by Dr. Johnson's group), we proposed specific new polymer structures: poly (3-acetoxy oxetane) (PAO), poly (vinyl methoxymethyl ether) (PVMME), poly (vinyl 1-methoxyethyl ether) (PVMEE), and cellulose triacetate (CTA) oligomers. Phase behavior studies were also performed with novel CO 2-philic compounds containing vinyl acetate, propylene glycol, or multiple tert-butyl groups. PAO, PVMME and PVMME were soluble in CO2, but not as soluble as poly (vinyl acetate). Oligomers of cellulose triacetate with as many as four repeat units solubilized into dense CO2 less than 14 MPa in the concentration range of 1-5 wt%. Phase behaviors of more than twenty compounds in dense CO2 were studied in this project. A new type of phase behavior for solid CO2-philes that melt and dissolve in CO 2 was detailed using a model binary mixture of beta-D-maltose octaacetate and CO2. Copolymers of tetrafluoroethylene (TFE) and vinyl acetate (VAc) exhibited lower miscibility pressures than either of the homopolymers, probably due to quadradentate binding configurations with CO 2. Phase behavior investigation of poly (propylene glycol) (PPG) monobutyl ether in CO2 demonstrated ether-CO2 interactions should receive as much attention as carbonyl-CO2 interactions when designing CO2-philic functional groups. 1,3,5-tri-tert-butylbenzene and 2,4,6-tri-tert-butylphenol were both extraordinarily soluble in CO2, and are excellent candidates for CO2-soluble sand binders. In summary, although a new CO2 thickener was not identified, new non-fluorous CO2-soluble materials were identified, which were, in general, acetate-rich with flexible chains, weak self-interactions, and multidentate interaction between CO2 and solute functional groups.

Hong, Lei

271

Oxygen Microelectrode That Is Insensitive to Medium Chemical Composition: Use in an Acid Microbial Mat Dominated by Cyanidium caldarium  

PubMed Central

A novel oxygen microelectrode with a tip diameter of 2 to 20 ?m was constructed which could function satisfactorily under a variety of environmental conditions and in a variety of media, including human blood serum, citric acid at pH 2.5, moist air, and paraffin oil. Measurement of oxygen by this electrode does not require stirring of the medium. Electrodes could be made so that the 90% response time necessary to detect changes in oxygen concentration was less than 0.2 s, and response was linear with oxygen concentration. To demonstrate the performance of the electrode, oxygen and photosynthesis profiles of an acid microbial mat (pH 2.8) dominated by the eucaryotic alga Cyanidium caldarium were made. Photosynthetic rates as high as 95 mmol of O2 dm?3 h?1 were measured within the most active 0.1-mm layer, which was ca. 0.2 mm below the surface of the microbial mat. The total photosynthetic activity was 47 mmol of O2 m?2 h?1. Vertical profiles of photosynthesis at different light intensities showed that the microalgae within the mat were not photoinhibited at bright sunlight (2,090 ?Einsteins m?2 s?1).

Revsbech, Niels Peter; Ward, David M.

1983-01-01

272

Role of preferential weak hybridization between the surface-state of a metal and the oxygen atom in the chemical adsorption mechanism.  

PubMed

We report on the chemical adsorption mechanism of atomic oxygen on the Pt(111) surface using angle-resolved-photoemission spectroscopy (ARPES) and density functional calculations. The detailed band structure of Pt(111) from ARPES reveals that most of the bands near the Fermi level are surface-states. By comparing band maps of Pt and O/Pt, we identify that dxz (dyz) and dz(2) orbitals are strongly correlated in the surface-states around the symmetry point M and K, respectively. Additionally, we demonstrate that the s- or p-orbital of oxygen atoms hybridizes preferentially with the dxz (dyz) orbital near the M symmetry point. This weak hybridization occurs with minimal charge transfer. PMID:24097254

Kim, Yong Su; Jeon, Sang Ho; Bostwick, Aaron; Rotenberg, Eli; Ross, Philip N; Walter, Andrew L; Chang, Young Jun; Stamenkovic, Vojislav R; Markovic, Nenad M; Noh, Tae Won; Han, Seungwu; Mun, Bongjin Simon

2013-11-21

273

CONTROL OF LASER RADIATION PARAMETERS: Enhancement of the efficiency and control of emission parameters of an unstable-resonator chemical oxygen—iodine laser  

NASA Astrophysics Data System (ADS)

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

Boreisho, A. S.; Lobachev, V. V.; Savin, A. V.; Strakhov, S. Yu; Trilis, A. V.

2007-07-01

274

Effect of an oxygen plasma on the physical and chemical properties of several fluids for the liquid droplet radiator  

NASA Technical Reports Server (NTRS)

The Liquid Droplet Radiator is one of several radiator systems currently under investigation by NASA Lewis Research Center. It involves the direct exposure of the radiator working fluid to the space environment. An area of concern is the potential harmful effects of the low-Earth-orbit atomic oxygen environment on the radiator working fluid. To address this issue, seven candidate fluids were exposed to an oxygen plasma environment in a laboratory plasma asher. The fluids studied included Dow Corning 705 Diffusion Pump Fluid, polymethylphenylsiloxane and polydimethlsiloxane, both of which are experimental fluids made by Dow Corning, Fomblin Z25, made by Montedison, and three fluids from the Krytox family of fluids, Krytox 143AB, 1502, and 16256, which are made by DuPont. The fluids were characterized by noting changes in visual appearance, physical state, mass, and infrared spectra. Of the fluids tested, the Fomblin and the three Krytoxes were the least affected by the oxygen plasma. The only effect noted was a change in mass, which was most likely due to an oxygen-catalyzed deploymerization of the fluid molecule.

Gulino, D. A.; Coles, C. E.

1986-01-01

275

Effect of an oxygen plasma on the physical and chemical properties of several fluids for the Liquid Droplet Radiator  

NASA Technical Reports Server (NTRS)

The Liquid Droplet Radiator is one of several radiator systems currently under investigation by NASA Lewis Research Center. It involves the direct exposure of the radiator working fluid to the space environment. An area of concern is the potential harmful effects of the low-Earth-orbit atomic oxygen environment on the radiator working fluid. To address this issue, seven candidate fluids were exposed to an oxygen plasma environment in a laboratory plasma asher. The fluids studied included Dow Corning 705 Diffusion Pump Fluid, polymethylphenylsiloxane and polydimethylsiloxane, both of which are experimental fluids made by Dow Corning, Fomblin Z25, made by Montedison, and three fluids from the Krytox family of fluids, Krytox 143AB, 1502, and 16256, which are made by DuPont. The fluids were characterized by noting changes in visual appearance, physical state, mass, and infrared spectra. Of the fluids tested, the Fomblin and the three Krytoxes were the least affected by the oxygen plasma. The only effect noted was a change in mass, which was most likely due to an oxygen-catalyzed depolymerization of the fluid molecule.

Gulino, Daniel A.; Coles, Carolyn E.

1987-01-01

276

Chemical kinetics and reactive species in atmospheric pressure helium-oxygen plasmas with humid-air impurities  

NASA Astrophysics Data System (ADS)

In most applications helium-based plasma jets operate in an open-air environment. The presence of humid air in the plasma jet will influence the plasma chemistry and can lead to the production of a broader range of reactive species. We explore the influence of humid air on the reactive species in radio frequency (rf)-driven atmospheric-pressure helium-oxygen mixture plasmas (He-O2, helium with 5000 ppm admixture of oxygen) for wide air impurity levels of 0-500 ppm with relative humidities of from 0% to 100% using a zero-dimensional, time-dependent global model. Comparisons are made with experimental measurements in an rf-driven micro-scale atmospheric pressure plasma jet and with one-dimensional semi-kinetic simulations of the same plasma jet. These suggest that the plausible air impurity level is not more than hundreds of ppm in such systems. The evolution of species concentration is described for reactive oxygen species, metastable species, radical species and positively and negatively charged ions (and their clusters). Effects of the air impurity containing water humidity on electronegativity and overall plasma reactivity are clarified with particular emphasis on reactive oxygen species.

Murakami, Tomoyuki; Niemi, Kari; Gans, Timo; O'Connell, Deborah; Graham, William G.

2013-02-01

277

Determination of zinc speciation in basic oxygen furnace flying dust by chemical extractions and X-ray spectroscopy  

Microsoft Academic Search

There is a growing concern regarding the environmental and public health risks associated with airborne particulate matter (PM). The basic oxygen furnace is one of the most important atmospheric dust sources of the steel manufacturing process. It emits dust enriched in heavy metal such as Zn, which is assumed to contribute to the toxic potential of atmospheric PM. Dust collected

M. L. Sammut; J. Rose; A. Masion; E. Fiani; M. Depoux; A. Ziebel; J. L. Hazemann; O. Proux; D. Borschneck; Y. Noack

2008-01-01

278

PHYSICAL PROCESSES IN LASERS AND CONTROL OF LASER RADIATION PARAMETERS: Control of the duration of optical pulses from an oxygen-iodine chemical laser  

NASA Astrophysics Data System (ADS)

It is shown that long radiation pulses needed in applications of lasers in technology may be emitted efficiently by an oxygen-iodine chemical laser. Slow photolysis can increase the output pulse duration to approximately 1 ms while retaining a high efficiency. Calculations yield the dependence of the lasing characteristics on all the parameters of interest. It is demonstrated that at high active medium pressures (up to 100 Torr) and low iodine concentrations, the pulse duration may be regulated with a high specific output energy and a high photolysis efficiency.

Zagidullin, M. V.; Zaikin, A. P.; Igoshin, Valerii I.

1989-04-01

279

Buffer gas mixing with active gas on chemical oxygen-iodine laser performance with jet type SOG  

NASA Astrophysics Data System (ADS)

The increasing of stagnation pressure and Re number of gas flow is a very important for supersonic oxygen-iodine laser (COIL). This goal can be achieved with the aid of high pressure singlet oxygen generator (SOG) and high dilution of oxygen with buffer gas of high molecular weight downstream of SOG. The study of COIL operated with jet type SOG at 10 and 20 mmole/s of chlorine flow rate and 50 torr output of pure oxygen is presented. Two experimental set-up were tested. In the first one the mixing of chlorine with buffer gas was provided upstream of SOG gas inlet. In the second one the pure chlorine was injected into SOG and oxygen was mixed with buffer gas downstream of SOG outlet. The stability of jet SOG in the first set-up strongly depended on partial buffer gas pressure and its molecular weight: at higher pressures and molecular weight the stability of SOG operation was worse. In the second set-up the operation of SOG didn't depend on buffer gas pressure and its molecular weight. COIL output power was highest for first set-up with dilution of chlorine by buffer gas until SOG stable operated. In the second set-up the output power was in twice less and strongly depend on type and position of buffer gas injector between SOG and iodine injector. This dependence strongly demonstrated the importance of gas mixing to molecular level for achieving highest COIL power. Another problem considered in this work is connected with BHP heating that important for recirculation of liquid in long time duration COIL operating system. The correlation of BHP heating and O2(1(Delta) ) yield is presented. It is shown that nacsent O2(1(Delta) ) yield is close to 100%.

Zagidullin, Marsel V.; Nikolaev, Valeri D.; Svistun, Michael I.; Safonov, Vladimir S.; Ufimtsev, Nikolay I.

1996-03-01

280

The Rate of Oxygen Utilization by Cells  

PubMed Central

The discovery of oxygen is considered by some to be the most important scientific discovery of all time – from both physical-chemical/astrophysics and biology/evolution viewpoints. One of the major developments during evolution is the ability to capture dioxygen in the environment and deliver it to each cell in the multicellular, complex mammalian body -- on demand, i.e. just-in-time. Humans use oxygen to extract approximately 2550 Calories (10.4 MJ) from food to meet daily energy requirements. This combustion requires about 22 moles of dioxygen per day, or 2.5 × 10-4 mol s-1. This is an average rate of oxygen utilization of 2.5 × 10-18 mol cell-1 s-1, i.e. 2.5 amol cell-1 s-1. Cells have a wide range of oxygen utilization, depending on cell type, function, and biological status. Measured rates of oxygen utilization by mammalian cells in culture range from <1 to >350 amol cell-1 s-1. There is a loose positive linear correlation of the rate of oxygen consumption (OCR) by mammalian cells in culture with cell volume and cell protein. The use of oxygen by cells and tissues is an essential aspect of the basic redox biology of cells and tissues. This type of quantitative information is fundamental to investigations in quantitative redox biology, especially redox systems biology.

Wagner, Brett A.; Venkataraman, Sujatha; Buettner, Garry R.

2011-01-01

281

Chemical analysis at atomic resolution of isolated extended defects in an oxygen-deficient, complex manganese perovskite.  

PubMed

A general approach to the structural and analytical characterization of complex bulk oxides that exploits the advantage of the atomic spatial resolution and the analytical capability of aberration-corrected microscopy is described. The combined use of imaging and spectroscopic techniques becomes necessary to the complete characterization of the oxygen-deficient colossal magnetoresistant La(0.56)Sr(0.44)MnO(2.5)-related perovskite. In this compound, the formation of isolated (La/Sr)O and MnO rock-salt-type planar defects are identified from atomically resolved High Angle Annular Dark Field (HAADF) images. The location of the oxygen atomic columns from Annular Bright Field (ABF) images indicates edge-sharing MnO6 octahedra in the MnO planes and the study performed by Electron Energy Loss Spectroscopy (EELS) reveals different Mn oxidation states derived from the corner- or edge-sharing MnO6 octahedra environment. PMID:24375704

Ruiz-González, M Luisa; Cortés-Gil, Raquel; Torres-Pardo, Almudena; González-Merchante, Daniel; Alonso, José M; González-Calbet, José M

2014-01-27

282

The Interconversion of Electrical and Chemical Energy: The Electrolysis of Water and the Hydrogen-Oxygen Fuel Cell.  

ERIC Educational Resources Information Center

Discusses some of the drawbacks of using a demonstration of the electrolysis of water to illustrate the interconversion between electrical and chemical energy. Illustrates a simple apparatus allowing demonstration of this concept while overcoming these drawbacks. (CW)

Roffia, Sergio; And Others

1988-01-01

283

Oxygen plasma-treated gold nanoparticle-based field-effect devices as transducer structures for bio-chemical sensing  

Microsoft Academic Search

EIS (electrolyte-insulator-semiconductor) sensors based on the functionalization of uncoated gold nanoparticles supported\\u000a on a Si\\/SiO2 structure are presented. Oxygen plasma etching at moderate power (<200 W) provides a convenient and efficient way to remove\\u000a organic capping agents from the gold nanoparticles without significant damage. Higher power intensities destroy the linkage\\u000a between the SiO2 and the gold nanoparticles, and some of the

Jenny Gun; Dan Rizkov; Ovadia Lev; Maryam H. Abouzar; Arshak Poghossian; Michael J. Schöning

2009-01-01

284

IDENTIFICATION OF MINOR OXYGEN HETEROCYCLIC COMPOUNDS OF CITRUS ESSENTIAL OILS BY LIQUID CHROMATOGRAPHY-ATMOSPHERIC PRESSURE CHEMICAL IONISATION MASS SPECTROMETRY  

Microsoft Academic Search

The oxygen heterocyclic compounds (coumarins, psoralens, and polymethoxylated flavones (PMFs)) present in citrus essential oils (lemon, mandarin, sweet orange, bitter orange, bergamot, grapefruit, and lime) were analysed by an HPLC-MS system equipped with an APcI source. The mass spectra obtained at different voltages of the “sample cone” have been used to build a library.Citrus essential oils have been analysed with

P. Dugo; L. Mondello; E. Sebastiani; R. Ottanà; G. Errante; G. Dugo

1999-01-01

285

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

Microsoft Academic Search

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

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

2010-01-01

286

Chemical Exchange at the Sediment-Water Interface of Cannonsville Reservoir  

Microsoft Academic Search

Rates of chemical exchange at the sediment-water interface of Cannonsville Reservoir were determined using intact sediment cores. Reference sites for coring were selected based on the results of a surficial sediment survey. Higher levels of volatile suspended solids, chemical oxygen demand, total organic carbon, total nitrogen, and total phosphorus were noted at deep water stations proximate to the dam and

Michael J. Erickson; Martin T. Auer

1998-01-01

287

Treatment of chemical mechanical polishing wastewater by electrocoagulation: system performances and sludge settling characteristics  

Microsoft Academic Search

Treatment of copper chemical mechanical polishing (CMP) wastewater from a semiconductor plant by electrocoagulation is investigated. The CMP wastewater was characterized by high suspended solids (SS) content, high turbidity (NTU), chemical oxygen demand (COD) concentration up to 500 mgl?1 and copper concentration up to 100 mgl?1. In the present study, electrocoagulation was employed to treat the CMP wastewater with an

Chen L. Lai; Sheng H. Lin

2004-01-01

288

Oxygen Sag and Stream Purification.  

ERIC Educational Resources Information Center

Presents a literature review of water quality related to oxygen sag and stream purification, covering publications of 1976-77. This review includes: (1) self-purification models; (2) oxygen demand; and (3) reaeration and oxygen transfer. A list of 60 references is also presented. (HM)

Neal, Larry; Herwig, Roy

1978-01-01

289

Chemical reactions of caesium, tellurium and oxygen with fast breeder reactor cladding alloys. Part I — The corrosion by tellurium  

NASA Astrophysics Data System (ADS)

The corrosion of the alloys PE16, M316 and FV448 by liquid Te in sealed capsules has been studied after 168 h at 948 K both with and without a buffer of Mo/MoO 2. This buffer sets the thermodynamic oxygen potential at ? ?o 2 = -417 kJ mol -1 O 2. All three alloys were severely corroded and the extent was in the order M316 > PE16 = FV448. Oxygen diminished the extent of corrosion but did not change the order. All three alloys carried two layers of corrosion products on top of a damaged metal surface. The outer layer contained Fe 1.5 Ni 1.5 Te 2 for PE16 but Fe 2.25 Te 2 for M316 and FV448. The inner layer contained Cr 2Te 3 for all three alloys. The damaged metal surface was largely Cr 2Te 3. The substrate alloys (PE16 and FV448) were penetrated intergranularly by Te, but M316 exhibited an even band of Cr-depleted steel. The results are explained by the diffusion of Te into the alloy and the diffusion of the alloy components in the opposite direction. The corrosion is exacerbated by dissolution of alloy into the liquid Te from which the metal tellurides subsequently precipitate.

Pulham, R. J.; Richards, M. W.

1990-05-01

290

Reactivity and molecular structure of silicon-oxygen-carbon-containing films derived from organometallic chemical vapor deposition (OMCVD)  

Microsoft Academic Search

The organometallic chemical vapor deposition (OMCVD) of non-crystalline solids is an attractive method to provide surface protection. The drawback of large scale processing is the difficulty in depositing films reproducibly with long-term reliability. Hence, there is continuing research for the preparation of ceramic films, such as metal carbides, which are reliable with respect to composition and performance. The purpose of

Terence J. Clark

1996-01-01

291

A comparison of measured radionuclide release rates from Three Mile Island Unit2 core debris for different oxygen chemical potentials  

Microsoft Academic Search

Chemical and radiochemical analyses of reactor coolant samples taken during defueling of the Three Mile Island Unit-2 (TMI-2) reactor provide relevant data to assist in understanding the solution chemistry of the radionuclides retained within the TMI-2 reactor coolant system. Hydrogen peroxide was added to various plant systems to provide disinfection for microbial contamination and has provided the opportunity to observe

V. F. Baston; K. J. Hofstetter; R. F. Ryan

1987-01-01

292

The industry demands better demand response  

Microsoft Academic Search

The promise and hype surrounding the Smart Grid far exceeds its current capabilities. In no area is this truer than with Demand Response (DR) programs for the commercial building sector, which is responsible for 20 percent of energy demand and emissions in the United States. These concentrated pools of demand are a nightmare for ever-more strained utility grids, especially in

Mike Zimmerman

2012-01-01

293

STRUCTURAL FEATURES ASSOCIATED WITH DEGRADABLE AND PERSISTENT CHEMICALS  

EPA Science Inventory

A multivariate statistical method and a heuristic method were employed to examine the structural features associated with the persistence of degradation of 287 chemicals tested with the standard biochemical oxygen demand(BOD) procedure. The data base consisted of 196 'degradable'...

294

On Ammonia Binding to the Oxygen-Evolving Complex of Photosystem?II: A Quantum Chemical Study.  

PubMed

A recent EPR study (M. Perrez Navarro et?al., Proc. Natl. Acad. Sci.- 2013, 110, 15561) provided evidence that ammonia binding to the oxygen-evolving complex (OEC) of photosystem?II in its S2 state takes place at a terminal-water binding position (W1) on the "dangler" manganese center MnA . This contradicted earlier interpretations of (14) N electron-spin-echo envelope modulation (ESEEM) and extended X-ray absorption fine-structure (EXAFS) data, which were taken to indicate replacement of a bridging oxo ligand by an NH2 unit. Here we have used systematic broken-symmetry density functional theory calculations on large (ca. 200 atom) model clusters of an extensive variety of substitution patterns and core geometries to examine these contradictory pieces of evidence. Computed relative energies clearly favor the terminal substitution pattern over bridging-ligand arrangements (by about 20-30?kcal?mol(-1) ) and support W1 as the preferred binding site. Computed (14) N EPR nuclear-quadrupole coupling tensors confirm previous assumptions that the appreciable asymmetry may be accounted for by strong, asymmetric hydrogen bonding to the bound terminal NH3 ligand (mainly by Asp61). Indeed, bridging NH2 substitution would lead to exaggerated asymmetries. Although our computed structures confirm that the reported elongation of an Mn-Mn distance by about 0.15?Å inferred from EXAFS experiments may only be reproduced by bridging NH2 substitution, it seems possible that the underlying EXAFS data were skewed by problems due to radiation damage. Overall, the present data clearly support the suggested terminal NH3 coordination at the W1 site. The finding is significant for the proposed mechanistic scenarios of OEC catalysis, as this is not a water substrate site, and effects of this ammonia binding on catalysis thus must be due to more indirect influences on the likely substrate binding site at the O5 bridging-oxygen position. PMID:24806267

Schraut, Johannes; Kaupp, Martin

2014-06-10

295

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

SciTech Connect

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

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

1992-01-01

296

Enhanced indirect ferromagnetic p-d exchange coupling of Mn in oxygen rich ZnO:Mn nanoparticles synthesized by wet chemical method  

NASA Astrophysics Data System (ADS)

This paper investigates the ferromagnetism in ZnO:Mn powders and presents our findings about the role played by the doping concentration and the structural defects towards the ferromagnetic signal. The narrow-size-distributed ZnO:Mn nanoparticles based powders with oxygen rich stoichiometery were synthesized by wet chemical method using zinc acetate dihydrate and manganese acetate tetrahydrate as precursors. A consistent increase in the lattice cell volume, estimated from x-ray diffraction spectra and the presence of Mn 2p3/2 peak at ~640.9 eV, in x-ray photoelectron spectroscopic spectra, confirmed a successful incorporation of manganese in its Mn2+ oxidation state in ZnO host matrix. Extended deep level emission spectra in Mn doped ZnO powders exhibited the signatures of oxygen interstitials and zinc vacancies except for the sample with 5 at. % Mn doping. The nanocrystalline powders with 2 and 5 at. % Mn doping concentration were ferromagnetic at room temperature while the 10 at. % Mn doped sample exhibited paramagnetic behavior. The maximum saturation magnetization of 0.05 emu/g in the nanocrystalline powder with 5 at. % Mn doping having minimum defects validated the ferromagnetic signal to be due to strong p-d hybridization of Mn ions.

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

2012-02-01

297

Degradation modes of austenitic and ferritic-martensitic stainless steels in He-CO-CO2 and liquid sodium environments of equivalent oxygen and carbon chemical potentials  

NASA Astrophysics Data System (ADS)

The objective of this work is to explore possible thermodynamic correlations between the degradation modes of austenitic and ferritic-martensitic alloys observed in high temperature He-CO-CO2 environments with oxygen and carbon chemical potentials equivalent to that in a liquid sodium environment containing 2-5 molppm oxygen and 0.02-0.2 molppm carbon at temperatures 500-700 °C. Two He-CO-CO2 environments (Pco/Pco2 = 1320, Pco = 1980 molppm, and Pco/Pco2 = 9, Pco = 13.5 molppm) were selected to test alloys NF616 and 316L at 700 and 850 °C. Upon exposure to He environments at 850 °C, 316L samples exhibited thick surface Cr2O3 scales and substantial internal oxidation; however at 700 °C no significant internal oxidation was observed. NF616 samples exhibited relatively thinner surface Cr2O3 scales compared to 316L samples at both temperatures. NF616 samples exposed to liquid sodium at 700 °C and He-Pco/Pco2 = 9 at 850 °C showed decarburization. No surface oxide formation was observed on the sample exposed to the Na environment. Results obtained from He exposure experiments provide insight into what may occur during long exposure times in a sodium environment.

Gulsoy, G.; Was, G. S.; Pawel, S. J.; Busby, J. T.

2013-10-01

298

Xas Studies of Chemical Bonding of Nitrogen And Oxygen Atoms in Ti/ZrHf High-K Gate Dielectrics  

SciTech Connect

Near edge x-ray absorption spectroscopy (NEXAS) has been used to study bonding in Ti/Zr/Hf (hereafter TM) Si oxynitrides and silicates. Comparisons between O K{sub 1} and N K{sub 1} spectra are particularly informative since O and N anti-bonding molecular orbitals (MO) display distinct features from nearest- and next-nearest-neighbor TM and Si atoms. MO TM-atom spectral features are qualitatively different in TM silicates and Si oxynitrides. NEXAS studies of TM silicates identity chemical phase separation (CPS) into TM-dioxides and SiO{sub 2} for annealing to 900{sup o}C.

Seo, H.; Lee, S.; Ju, B.; Lucovsky, G.; Luning, J.

2009-06-05

299

On the mechanism of the chemical and enzymic oxygenations of alpha-oxyprotohemin IX to Fe.biliverdin IX alpha.  

PubMed Central

alpha-Oxyprotohemin IX, an early intermediate in heme catabolism, was synthesized and its autoxidation to biliverdin IX alpha was studied. In anaerobic aqueous pyridine, alpha-oxyprotohemin (hexacoordinated) underwent autoreduction to yield an Fe(II) alpha-oxyprotoporphyrin pi-neutral radical bis(pyridine) complex, which reacted with an equimolar amount of dioxygen to give pyridine.verdohemochrome IX alpha and CO in 75-80% yield via an intermediate with an absorption maximum at 893 nm. Verdohemochrome IX alpha did not react with further dioxygen. Reconstituted apomyoglobin.alpha-oxyprotohemin IX complex (pentacoordinated) reacted with an equimolar amount of dioxygen to form an Fe(II) oxyporphyrin pi-neutral radical intermediate, which rearranged to a green compound (lambda max 660 and 704 nm) with elision of CO. The green product, which is probably an apomyoglobin.verdoheme pi-radical complex, reacted with another equimolar amount of dioxygen to give Fe(III).biliverdin IX alpha. Demetallation of this gave biliverdin IX alpha in overall yield of 70-75%. These results indicate that the sequence of oxyheme autoxidation in the presence of apomyoglobin is alpha-oxyprotoheme IX O2----CO----verdohemochrome IX alpha pi-radical O2----Fe(III).biliverdin IX alpha. A similar mechanism may prevail in vivo. The hexa- and pentacoordinated Fe(II) pi-radical form of the oxyporphyrin is crucial in triggering the autoxidation of the complex to verdohemochrome IX alpha. Further oxygenation of verdohemochrome IX alpha to Fe(III).biliverdin IX alpha occurred only in the pentacoordinated apomyoglobin.verdoheme Fe(II) complex.

Sano, S; Sano, T; Morishima, I; Shiro, Y; Maeda, Y

1986-01-01

300

Electrocoagulation of chemical mechanical polishing (CMP) wastewater from semiconductor fabrication  

Microsoft Academic Search

Treatment of chemical mechanical polishing (CMP) wastewater is investigated. The CMP wastewater, as obtained from a large semiconductor manufacturer, was characterized by high suspended solids (SS) content, high Nephelometric turbidity unit (NTU), chemical oxygen demand (COD) concentration up to 500mg\\/l, copper concentration over 100mg\\/l and a milky color. This study was to explore the feasibility of treating the CMP wastewater

Chen L Lai; Sheng H Lin

2003-01-01

301

Growth patterns, chemical composition and oxygen consumption in early juvenile Hyas araneus (Decapoda: Majidae) reared in the laboratory  

NASA Astrophysics Data System (ADS)

Early (instar I and II) juveniles of the spider crab Hyas araneus were reared under constant conditions (12 °C, 32‰S) in the laboratory, and their growth, biochemical composition, and respiration were studied. Every second day, dry weight (W), ash-free dry weight (AFW), and contents of ash, organic and inorganic carbon (C), nitrogen (N), hydrogen (H), protein, chitin, lipid, and carbohydrates were measured, as well as oxygen consumption. Changes in the absolute amounts of W. AFW, and C, N, and H during the moulting cycle are described with various regression equations as functions of age within a given instar. These patterns of growth differ in part from those that have been observed during previous studies in larval stages of the same and some other decapod species, possibly indicating different growth strategies in larvae and juveniles. There were clear periodic changes in ash (% of W) and inorganic C (as % of total C), with initially very low and then steeply increasing values in postmoult, a maximum in intermoult, and decreasing figures during the premoult phase of each moulting cycle. Similar patterns were observed in the chitin fraction, reaching a maximum of 16% of W (31% of AFW). Ash, inorganic C, and chitin represent the major components of the exoskeleton and hence, changes in their amounts are associated with the formation and loss of cuticle material. Consequently, a high percentage of mineral matter was lost with the exuvia (76% of the late premoult [LPM] ash content, 74% of inorganic C), but relatively small fractions of LPM organic matter (15% of AFW, 11% of organic C, 5 6% of N and H). These cyclic changes in the cuticle caused an inverse pattern of variation in the percentage values (% of W) of AFW, organic C, N, H, and biochemical constituents other than chitin. When these measures of living biomass were related to, exclusively, the organic body fraction (AFM), much less variation was found during individual moulting cycles, with values of about 43 52% in organic C, 9 10% in N, 6 9% H, 31 49% of AFW in protein, 3 10% in lipid, and <1% in carbohydrates. All these constituents showed, on the average, a decreasing tendency during the first two crab instars, whereas N remained fairly constant. It cannot be explained at present, what other elements and biochemical compounds, respectively, might replace these decreasing components of AFW. Decreasing tendencies during juvenile growth were observed also in the organic C/N and in the lipid/protein weight ratios, both indicating that the proportion of lipid decreased at a higher rate than that of protein. Changes were observed also in the composition of inorganic matter, with significantly lower inorganic C in early postmoult (2 4% of ash) than in later stages of the moult cycle (about 9%). This reflected probably an increase in the degree of calcification, i.e. in the calcium carbonate content of the exoskeleton. As a fraction of total C, inorganic C reached maximum values of 17 and 20% in the crab I and II instars, respectively. The energy content of juvenile spider crabs was estimated independently from organic C and biochemical constituents, with a significant correlation between these values. However, the former estimates of energy were, on the average, significantly lower than the latter (slope of the regression ?1). Since organic C should be a reliable integrator of organic substances, but the sum of protein, lipid, chitin, and carbohydrates amounted to only 60 91% of AFW, it is concluded that the observed discrepancy between these two estimates of energy was caused by energy from biochemical constituents that had not been determined in our analyses. Thus, energy values obtained from these biochemical fractions alone may underestimate the actual amount of organic matter and energy. Respiration per individual in juvenile spider crabs was higher than that in larval stages of the same species (previous studies), but their W-specific values of oxygen consumption (QO2) were lower than in conspecific larvae (0.6 2?g O2·[mg W]-1). QO2 showed a consiste

Anger, K.; Harms, J.; Christiansen, M. E.; Süsens, U.; Wilmes, B.

1992-03-01

302

rf Power dependence on the chemical and structural properties of copper oxide thin films obtained at various oxygen fractions  

NASA Astrophysics Data System (ADS)

Copper oxide (CuOx) thin films were deposited on flexible polyethyleneterephthalate (PET) substrates by rf magnetron sputtering and the effects of the rf power and the O2 fraction on the physical and chemical properties of the films were examined. The obtained films were characterized with a surface profiler, X-ray diffraction (XRD), scanning electron microscopy (SEM), four points probe, and X-ray photoelectron spectroscopy (XPS). The trend of surface resistance of CuOx films was almost identical as rf power varied from 200 to 300 W. The surface resistance of the films increased as the O2 fraction increased up to 14.3%. After this point it decreased. The propensity of surface resistance of the films, however, monotonically increased as a function of O2 fraction at 400 W of rf power. XRD study revealed that the preferential phase of CuOx changed from metallic cubic Cu(1 1 1) through cubic Cu2O(1 1 1) to monoclinic CuO(1¯ 1 1) as the O2 fraction increased. The compositional ratio of Cu species with different oxidation state in CuOx films was investigated by X-ray induced Auger electron spectroscopy (XAES). XAES study revealed that the compositional ratio of Cu was dependent with the rf power. The higher rf power applied, the more Cu+ species and less Cu2+ species formed in CuOx films.

Lim, Kyounga; Park, Juyun; Kim, Do-Geun; Kim, Jong-Kuk; Kang, Jae-Wook; Kang, Yong-Cheol

2012-09-01

303

Living Without Oxygen: Oxygen Tolerance in Bacteria  

NSDL National Science Digital Library

This activity focuses on chemical processes, such as nitrogen fixation and denitrification, which are carried out by bacteria. Often the efficacy of these processes is determined by the amount of oxygen present in the environment in which the bacteria live. Much of the time, these processes are carried out by facultatively anaerobic bacteria in the suboxic region of lakes, oceans, sediments, and leaf litter. Students will discover whether facultatively anaerobic photoautotrophs share the same tolerance for oxygen, how differences in oxygen tolerance can be tested, and of what significance the tolerance for oxygen is in the nitrogen cycle. They will practice aseptic technique, monitor the growth of bacterial cultures, display their results graphically, and propose environmental problems associated with the oxygen tolerance of nitrogen fixers and denitifiers.

Harris, Sharon

304

Oxygen concentrators.  

PubMed

Oxygen concentrators offer an alternative source of oxygen to conventional methods of supply. The disadvantage of their high initial purchase price is offset by low running costs. In hospitals they may find a place in providing "oxygen" for some gas pipeline systems. They are the method of choice for supplying oxygen for long-term domiciliary oxygen therapy. PMID:4092132

Howell, R S

1985-10-01

305

Effect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system  

NASA Astrophysics Data System (ADS)

Field emission properties of single wall carbon nanotubes (SWCNTs) grown on iron catalyst film by plasma enhanced chemical vapour deposition system were studied in diode configuration. The results were analysed in the framework of Fowler-Nordheim theory. The grown SWCNTs were found to be excellent field emitters, having emission current density higher than 20 mA/cm2 at a turn-on field of 1.3 V/?m. The as grown SWCNTs were further treated with Oxygen (O2) plasma for 5 min and again field emission characteristics were measured. The O2 plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111 mA/cm2 at a much lower turn on field of 0.8 V/?m. The as grown as well as plasma treated SWCNTs were also characterized by various techniques, such as scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy before and after O2 plasma treatment and the findings are being reported in this paper.

Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad; Harsh; Husain, Mushahid

2014-02-01

306

Chemical Composition, Aroma Evaluation, and Oxygen Radical Absorbance Capacity of Volatile Oil Extracted from Brassica rapa cv. "Yukina" Used in Japanese Traditional Food.  

PubMed

The chemical composition of the volatile oil extracted from the aerial parts of Brassica rapa cv. "yukina" was analyzed using GC-MS, GC-PFPD, and GC-O. A total of 50 compounds were identified. The most prominent constituents were (E)-1,5-heptadiene (40.27%), 3-methyl-3-butenenitrile (25.97%) and 3-phenylpropanenitrile (12.41%). With regard to aroma compounds, 12 compounds were identified by GC-O analysis. The main aroma-active compounds were dimethyl tetrasulfide (sulphury-cabbage, FD = 64), 3-phenylpropanenitrile (nutty, FD = 64), 3-methylindole (pungent, FD = 64), and methional (potato, FD = 32). The antioxidant activity of the aroma-active compounds of the oil was determined using an oxygen radical absorbance capacity (ORAC) assay using fluorescein as the fluorescent probe. The ORAC values were found to be 785 ± 67 trolox equivalents (?mol TE/g) for B. rapa cv. "yukina" oil. The results obtained showed that the volatile oil extracted from the aerial parts is a good dietary source of antioxidants. PMID:24919480

Usami, Atsushi; Motooka, Ryota; Takagi, Ayumi; Nakahashi, Hiroshi; Okuno, Yoshiharu; Miyazawa, Mitsuo

2014-06-27

307

Chemical kinetics modelling of a decaying SF6 arc plasma in the presence of a solid organic insulator, copper, oxygen and water  

NASA Astrophysics Data System (ADS)

The composition variations occurring in decaying SF6 arc plasmas in the presence of atoms released from the vaporization of organic insulators (e.g. Teflon, polyethylene, polypropylene, megelit, nylon), copper, oxygen and water were studied between 12 000 K and 300 K by means of a chemical kinetics model. From the results obtained at 300 K and a pressure of 101.3 kPa: (i) the role of the impurities on the formation of the SF6 decomposition products: SF4 , SOF2 , SO2 F2 and S2 F10 , was determined; (ii) it was confirmed that the vaporization of an organic insulator leads to the appearance of CF4 and an increase in the generation of the major byproduct (SF4 +SOF2 ) which is correlated to the production of CF4 ; (iii) it was seen that, for a given amount of vaporized insulator, insulators that contain fluorine atoms brought about less SF6 decomposition than those that did not.

Coll, I.; Casanovas, A. M.; Vial, L.; Gleizes, A.; Casanovas, J.

2000-02-01

308

Multistep, eight-electron oxidation catalyzed by the cofactorless oxidase, PqqC: identification of chemical intermediates and their dependence on molecular oxygen.  

PubMed

The final step of the biosynthesis of prokaryotic cofactor PQQ is catalyzed by PqqC, a cofactorless oxidase that brings about a ring closure and overall eight-electron oxidation of its substrate. Time-dependent acid quenching and subsequent high-performance liquid chromatography separation and mass spectrometric analyses of reaction mixtures were performed to correlate the structures of intermediates with previously observed UV-visible signatures. The reaction is composed of four stepwise oxidations: three steps use O2 as the two-electron acceptor, and the fourth uses hydrogen peroxide (H2O2). The chemical nature of the intermediates, the stoichiometry of the reaction, and their dependence on the oxygen concentration indicate that the third oxidation uses the product, H2O2, from the preceding step to produce water. The last oxidation step can also be studied separately and is a reaction between O2 and PQQH2 trapped in the active site. This oxidation is approximately 10 times slower than the reoxidation of PQQH2 in solution. From the order of the four oxidation steps and their sensitivity to O2 concentration, we propose a progressive closure of the active site as the enzyme proceeds through its catalytic cycle. PMID:23718207

Bonnot, Florence; Iavarone, Anthony T; Klinman, Judith P

2013-07-01

309

Application of high resolution Chemical Ionization Mass Spectrometry (CI-ToFMS) to study SOA composition: focus on formation of oxygenated species via aqueous phase processing  

NASA Astrophysics Data System (ADS)

This paper demonstrates the capabilities of Chemical Ionization Mass Spectrometry (CIMS) to study secondary organic aerosol (SOA) composition with a high resolution (HR) time-of-flight mass analyzer (aerosol-CI-ToFMS). In particular, by studying aqueous oxidation of Water Soluble Organic Compounds (WSOC) extracted from ?-pinene ozonolysis SOA, we assess the capabilities of three common CIMS reagent ions: (a) protonated water clusters (H2O)nH+, (b) acetate CH3C(O)O- and (c) iodide water clusters I(H2O)n- to monitor SOA composition. As well, we report the relative sensitivity of these reagent ions to a wide range of common organic aerosol constituents. We find that (H2O)nH+ is more selective to the detection of less oxidized species, so that the range of O/C and OSC (carbon oxidation state) in the SOA spectra is considerably lower than those measured using CH3C(O)O- and I(H2O)n-. Specifically, (H2O)nH+ ionizes organic compounds with OSC ? 1.3, whereas CH3C(O)O- and I(H2O)n- both ionize highly oxygenated organics with OSC up to 4 with I(H2O)n- being more selective towards multi-functional organic compounds. In the bulk O/C and H/C space, i.e. in a Van Krevelen plot, there is a remarkable agreement in both absolute magnitude and oxidation trajectory between CI-ToFMS data and those from a high resolution aerosol mass spectrometer (HR-AMS). This indicates that the CI-ToFMS data captures much of the chemical change occurring in the particle and that gas phase species, which are not detected by the HR-AMS, do not dominate the overall ion signal. Finally, the data illustrate the capability of aerosol-CI-ToFMS to monitor specific chemical change, including the fragmentation and functionalization reactions that occur during organic oxidation, and the oxidative conversion of dimeric SOA species into monomers. Overall, aerosol-CI-ToFMS is a valuable, selective complement to some common SOA characterization methods, such as AMS and spectroscopic techniques. Both laboratory and ambient SOA samples can be analyzed using the techniques illustrated in the paper.

Aljawhary, D.; Lee, A. K. Y.; Abbatt, J. P. D.

2013-07-01

310

Ambient Oxygen Promotes Tumorigenesis  

PubMed Central

Oxygen serves as an essential factor for oxidative stress, and it has been shown to be a mutagen in bacteria. While it is well established that ambient oxygen can also cause genomic instability in cultured mammalian cells, its effect on de novo tumorigenesis at the organismal level is unclear. Herein, by decreasing ambient oxygen exposure, we report a ?50% increase in the median tumor-free survival time of p53?/? mice. In the thymus, reducing oxygen exposure decreased the levels of oxidative DNA damage and RAG recombinase, both of which are known to promote lymphomagenesis in p53?/? mice. Oxygen is further shown to be associated with genomic instability in two additional cancer models involving the APC tumor suppressor gene and chemical carcinogenesis. Together, these observations represent the first report directly testing the effect of ambient oxygen on de novo tumorigenesis and provide important physiologic evidence demonstrating its critical role in increasing genomic instability in vivo.

Starost, Matthew F.; Lago, Cory U.; Lim, Philip K.; Sack, Michael N.; Kang, Ju-Gyeong; Wang, Ping-yuan; Hwang, Paul M.

2011-01-01

311

Electricity demand curtailment planning  

SciTech Connect

The state of electricity demand curtailment planning for long term electricity supply disruptions is reviewed. Legal, institutional and technological problems associated with demand curtailment plans are examined, and the existence of well defined social objectives on the part of planners is questioned. A linear programming approach to electricity demand curtailment planning is presented.

Allentuck, J; Carroll, O; Schnader, M

1980-01-01

312

Supply and Demand  

MedlinePLUS

... Baby > Breastfeeding > Supply and Demand Ages & Stages Listen Supply and Demand Article Body As natural as it is, breastfeeding ... rhythm with your baby. In reality, the efficient supply-and-demand rhythm of normal breastfeeding—in which your baby’s ...

313

Defect equilibria and chemical expansion in undoped and doped ceria and strontium doped lanthanum cobalt iron oxide oxygen conducting materials and their applications in solid-state electrochemical cells  

NASA Astrophysics Data System (ADS)

Ceramic oxygen conducting materials are used in many energy-related applications from fuel reforming to electricity generation. In a typical ceramic oxygen conductor, oxygen ions are transmitted through a dense membrane via defects in the material. Hence, defects control the performance of these materials. In low oxygen partial pressure, ceria based materials become non-stoichiometric and can form defect complexes that hinder ionic conductivity. In addition, oxygen non-stoichiometry induces strain (chemical expansion) that can result in stresses for composite or constrained applications. In this dissertation the non-stoichiometry and chemical expansion behavior is reported as a function of PO2 for undoped ceria, gadolinium doped ceria (GDC) and strontium doped lanthanum cobalt iron oxide (LSCF). Undoped ceria was measured at 800°C and GDC and LSCF at 600--900°C in a wide PO2 range. It was found that defect interactions could effectively be modeled in ceria based materials using defect complex formation in a mass action formalism and the results were used to model nonlinear chemical expansion behavior. In LSCF, non-stoichiometry and chemical expansion were modeled using using metallic and semi-conductor models. A semi-conductor model with B-site small polarons best represented the measured behavior. The resulting models and parameters can be used to predict mechanical and electrical behavior of SOFC components. Surface oxygen non-stoichiometry has also been measured by comparing low surface area to high surface area samples. It was found that surface defect concentration previously ignored in the literature can result in erroneous non-stoichiometry measurements. In the latter half of this dissertation these materials are applied in SOFC and ceramic oxygen generator (COG) technology. A strategy is presented here for advanced life support systems employs a catalytic layer combined with a COG cell so that CO2 is reduced all the way to solid carbon and oxygen without carbon buildup on the COG cell and subsequent deactivation. In addition, a highly porous GDC anode support is developed that is infiltrated with metal. SOFCs are fabricated that utilize the highly porous support and operate on hydrocarbon fuels that show initial performance > 250 mW/cm 2 at 600 °C on vaporized dodecane.

Bishop, Sean R.

314

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

PubMed

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

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

2005-08-01

315

Chemical and physical characteristics of water in estuaries of Texas, October 1976-September 1978  

USGS Publications Warehouse

This report presents basic data on the chemical and physical characteristics of water in the estuaries of Texas for the period October 1976-September 1978. The properties or constituents that are measured in the field are dissolved oxygen (DO), specific conductance, temperature, pH, and transparency by Secchi disk. Analyses conducted in the laboratory include the principal inorganic ions, biochemical oxygen demand (BOD), total organic carbon (TOC), ammonium, nitrite, nitrate, and total phosphate. (USGS)

Fisher, J. C.

1982-01-01

316

Oxygen nonstoichiometry and chemical stability of Nd{sub 2-x}Sr{sub x}NiO{sub 4+{delta}}  

SciTech Connect

Nonstoichiometric variation of oxygen content in Nd{sub 2-x}Sr{sub x}NiO{sub 4+{delta}} (x=0, 0.2, 0.4) and decomposition P(O{sub 2}) were determined by means of high temperature gravimetry and coulometric titration. The measurements were carried out in the temperature range from 873 to 1173 K and the P(O{sub 2}) range from 10{sup -20} to 1 bar. Nd{sub 2-x}Sr{sub x}NiO{sub 4+{delta}} shows the oxygen excess and the oxygen deficient composition depending on P(O{sub 2}), temperature, and the Sr content. To evaluate the characteristics of oxygen nonstoichiometric behavior, partial molar enthalpy of oxygen was calculated. The value of partial molar enthalpy of oxygen slightly approaches zero as delta increases in the oxygen excess region while that is independent of delta in the oxygen deficient region. Discussion was made by comparing data of this study with nonstoichiometric and thermodynamic data of La{sub 2-x}Sr{sub x}NiO{sub 4+{delta}}: Nd{sub 2-x}Sr{sub x}NiO{sub 4+{delta}} show more oxygen excess than La{sub 2-x}Sr{sub x}NiO{sub 4+{delta}} in the higher P(O{sub 2}) region, while the nonstoichiometric behavior in the oxygen deficient composition is almost the same. The variation of partial molar enthalpy of oxygen with delta for Nd{sub 2-x}Sr{sub x}NiO{sub 4+{delta}} in the oxygen excess region is much smaller than that of La{sub 2-x}Sr{sub x}NiO{sub 4+{delta}}. The oxygen nonstoichiometric behavior of Nd{sub 2-x}Sr{sub x}NiO{sub 4+{delta}} is more ideal-solution-like than that of La{sub 2-x}Sr{sub x}NiO{sub 4+{delta}}. - Graphical abstract: We synthesized Nd{sub 2-x}Sr{sub x}NiO{sub 4+{delta}} by citric acid method and measured oxygen nonstoichiometry in the temperature range between 873 and 1173 K. They showed both oxygen excess and oxygen deficient composition depending on P(O{sub 2}), temperature, and. the Sr content. The results are compared with the oxygen nonstoichiometry of La{sub 2-x}Sr{sub x}NiO{sub 4+{delta}}.

Nakamura, Takashi, E-mail: t-naka@mail.tagen.tohoku.ac.j [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1, Katahira, Aoba-Ku, Sendai 980-8577 (Japan); Yashiro, Keiji; Sato, Kazuhisa; Mizusaki, Junichiro [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1, Katahira, Aoba-Ku, Sendai 980-8577 (Japan)

2009-06-15

317

Determination of biodegradability of phenolic compounds, characteristic to wastewater of the oil-shale chemical industry, on activated sludge by oxygen uptake measurement.  

PubMed

The aim of this study was to investigate the biodegradation of phenol, o-cresol and p-cresol individually and as bi-substrate mixtures at low initial substrate concentrations. Activated sludge was taken from the Kohtla-Järve wastewater treatment plant, Estonia, which is also treating phenolic wastewater from the oil-shale chemical industry and is considered to be acclimated to the phenolic compounds. Respirometric data have been used for evaluation of the kinetic parameters describing the bio-oxidation of substrates. Activated sludge was able to degrade phenol and p-cresol faster than o-cresol, showing better affinity to p-cresol. However, at higher concentrations, phenol and p-cresol exhibited also an inhibitory effect to the microorganisms. The highest values for maximum rate of oxygen uptake (V(O2,max)) were obtained for the bi-substrate system of phenol--p-cresol among the mixtures containing both substrates at equal concentrations from 0.005 mM to 0.050 mM. Concerning the systems containing one substrate at 0.1 mM and the other substrate varied in the abovementioned range, the highest V(O2,max) values were found for phenol--o-cresol(0.1 mM). The interaction parameters indicated that phenol had a stronger inhibition effect on the biodegradation of p-cresol than p-cresol had on the biodegradation of phenol. However, the obtained interaction parameters for systems of phenol--o-cresol indicated that o-cresol had a stronger inhibition effect on the biodegradation of phenol, which in turn had a mild inhibition or even enhancing effect on the biodegradation of o-cresol. In the case of a 1:1 mixture, phenol and o-cresol had a similar mild inhibition effect on each other's biodegradation. PMID:22519119

Lepik, Riina; Tenno, Toomas

2012-01-01

318

Characterization of singlet oxygen production and its involvement in photodamage of Photosystem II in the cyanobacterium Synechocystis PCC 6803 by histidine-mediated chemical trapping.  

PubMed

Singlet oxygen production in intact cells of the cynobacterium Synechocystis 6803 was studied using chemical trapping by histidine, which leads to O2 uptake during illumination. The rate of O2 uptake, measured by a standard Clark-type electrode, is enhanced in the presence of D2O, which increases the lifetime of (1)O2, and suppressed by the (1)O2 quencher NaN3. Due to the limited mobility of (1)O2 these data demonstrate that exogenous histidine reaches close vicinity of (1)O2 production sites inside the cells. Flash induced chlorophyll fluorescence measurements showed that histidine does not inhibit Photosystem II activity up to 5mM concentration. By applying the histidine-mediated O2 uptake method we showed that (1)O2 production linearly increases with light intensity even above the saturation of photosynthesis. We also studied (1)O2 production in site directed mutants in which the Gln residue at the 130th position of the D1 reaction center subunit was changed to either Glu or Leu, which affect the efficiency of nonradiative charge recombination from the primary radical pair (Rappaport et al. 2002, Biochemistry 41: 8518-8527; Cser and Vass 2007, BBA 1767:233-243). We found that the D1-Gln130Glu mutant showed decreased (1)O2 production concomitant with decreased rate of photodamage relative to the WT, whereas both (1)O2 production and photodamage were enhanced in the D1-Gln130Leu mutant. The data are discussed in the framework of the model of photoinhibition in which (3)P680 mediated (1)O2 production plays a key role in PSII photodamage, and nonradiative charge recombination of the primary charge separated state provides a photoprotective pathway. PMID:23466334

Rehman, Ateeq Ur; Cser, Krisztián; Sass, László; Vass, Imre

2013-06-01

319

Simultaneous analysis of oxygenated and nitrated polycyclic aromatic hydrocarbons on standard reference material 1649a (urban dust) and on natural ambient air samples by gas chromatography–mass spectrometry with negative ion chemical ionisation  

Microsoft Academic Search

This study deals with the development of a routine analytical method using gas chromatography–mass spectrometry with negative ion chemical ionisation (GC\\/NICI-MS) for the determination of 17 nitrated polycyclic aromatic hydrocarbons (NPAHs) and 9 oxygenated polycyclic aromatic hydrocarbons (OPAHs) present at low concentrations in the atmosphere. This method includes a liquid chromatography purification procedure on solid-phase extraction (SPE) cartridge. Application of

A. Albinet; E. Leoz-Garziandia; H. Budzinski; E. ViIlenave

2006-01-01

320

Simultaneous determination by ultra-performance liquid chromatography–atmospheric pressure chemical ionization time-of-flight mass spectrometry of nitrated and oxygenated PAHs found in air and soot particles  

Microsoft Academic Search

An ultra-performance liquid chromatographic-atmospheric pressure chemical ionization time-of-flight mass spectrometric (UPLC-APCIToFMS)\\u000a method for rapid analysis of twelve nitrated polycyclic aromatic hydrocarbons (NPAHs) and nine oxygenated polycyclic aromatic\\u000a hydrocarbons (OPAHs) in particle samples has been developed. The extraction step using pressurized liquid extraction was optimized\\u000a by experimental design methods and the concentrated extracts were analyzed without further clean-up. Matrix effects resulting

Giovanni Mirivel; Véronique Riffault; Jean-Claude Galloo

2010-01-01

321

Electrocatalysis of anodic oxygen-transfer reactions: The electrochemical incineration of benzoquinone  

Microsoft Academic Search

The electrochemical performance of several anode materials is compared for the electrochemical incineration of p-benzoquinone in acetate buffer media (pH 5). The chemical oxygen demand (COD) estimated for benzoquinone by titration with standard permanganate solution can be decreased to virtually zero by electrolysis at electrodes comprised of Fe(III)-doped β-PbOâ films on Ti substrates. Carbon dioxide is a product of the

Jianren Feng; L. L. Houk; D. C. Johnson; S. N. Lowery; J. J. Carey

1995-01-01

322

Supply and Demand  

NSDL National Science Digital Library

This lesson from Illuminations allows students to learn about linear equations in a real-world setting. The material applies linear equations to the concept of supply and demand. Students will be able to translate between table, graph and equation representations for supply and demand data. The lesson is intended for grades 9-12 and should require two class periods to complete.

2010-12-03

323

The Demand for Insurance  

Microsoft Academic Search

This note provides a simple model of the demand for insurance. We derive the insurance demand equation for a risk-averse individual with logarithmic utility. Comparative statics are derived, and simple proofs of the Bernoulli principle and the Arrow theorem are shown.

James R. Garven

324

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

325

Hyperbaric Oxygenation.  

National Technical Information Service (NTIS)

The characteristics and possibilities of hyperbaric oxygenation were studied. The effect of hyperoxygenation of the organism under various conditions was examined, and periods of same exclusion of circulation when breathing oxygen under increased pressure...

I. P. Berezin

1974-01-01

326

Continuous Recording of Physico-Chemical Measurement of Quantities of Bacterial Cultures. I. Building of Apparatus for the Recording of Relative Turbidity, Redoxpotential and Dissolved Oxygen.  

National Technical Information Service (NTIS)

In this report an apparatus is described which in growing bacteria cultures makes possible continuous recording of the dissolved oxygen, redoxpotential and turbidity. The results of measurements obtained with the apparatus in 5 different varieties of bact...

G. Horn H. E. Jacob W. Bockel

1965-01-01

327

Controlled release of singlet oxygen using diphenylanthracene functionalized polymer nanoparticles.  

PubMed

Functionalized polymer nanoparticles react and store molecular oxygen for several weeks in the form of endoperoxides. On-demand controlled release of singlet oxygen by the particles is achieved by thermolysis. PMID:24531381

Martins, S; Farinha, J P S; Baleizão, C; Berberan-Santos, M N

2014-03-28

328

Oxygen deficiency and excretion of metabolites by strictly aerobic bacteria  

Microsoft Academic Search

Summary Alcaligenes eutrophus, Pseudomonas acidovorans, Pseudomonas delafieldii and Paracoccus denitrificans excrete metabolites when the oxygen demand of cells is not satisfied. The mechanism by which various metabolites are excreted at different degrees of oxygen deficiency is discussed.

D. Vollbrecht

1980-01-01

329

Chemical State of Surface Oxygen on Carbon and Its Effects on the Capacity of the Carbon Anode in a Lithium-Ion Battery Investigated  

NASA Technical Reports Server (NTRS)

In a lithium-ion battery, the lithium-storage capacity of the carbon anode is greatly affected by a surface layer formed during the first half cycle of lithium insertion and release into and out of the carbon anode. The formation of this solid-electrolyte interface, in turn, is affected by the chemistry of the carbon surface. A study at the NASA Glenn Research Center examined the cause-and-effect relations. Information obtained from this research could contribute in designing a high-capacity lithium-ion battery and, therefore, small, powerful spacecraft. In one test, three types of surfaces were examined: (1) a surface with low oxygen content (1.5 at.%) and a high concentration of active sites, (2) a surface with 4.5 at.% -OH or -OC type oxygen, and (3) a surface with 6.5 at.% O=C type oxygen. The samples were made from the same precursor and had similar bulk properties. They were tested under a constant current of 10 mA/g in half cells that used lithium metal as the counter electrode and 0.5 M lithium iodide in 50/50 (vol%) ethylene carbonate and dimethyl carbonate as the electrolyte. For the first cycle of the electrochemical test, the graph describes the voltage of the carbon anode versus the lithium metal as a function of the capacity (amount of lithium insertion or release). From these data, it can be observed that the surface with low oxygen and a high concentration of active sites could result in a high irreversible capacity. Such a high irreversible capacity could be prevented if the active sites were allowed to react with oxygen in air, producing -OH or -OC type oxygen. The O=C type oxygen, on the other hand, could greatly reduce the capacity of lithium intercalation and, therefore, needs to be avoided during battery fabrication.

Hung, Ching-Cheh

2001-01-01

330

Residential Demand Module  

EIA Publications

Model Documentation - Documents the objectives, analytical approach, and development of the National Energy Modeling System (NEMS) Residential Sector Demand Module. The report catalogues and describes the model assumptions, computational methodology, parameter estimation techniques, and FORTRAN source code.

Owen Comstock

2013-11-05

331

Industrial Demand Module  

EIA Publications

Documents the objectives, analytical approach, and development of the National Energy Modeling System (NEMS) Industrial Demand Module. The report catalogues and describes model assumptions, computational methodology, parameter estimation techniques, and model source code.

Kelly Perl

2013-09-30

332

Oxygen therapies.  

PubMed

Oxygen therapies are unproven alternatives promoted as a cure for cancer, acquired immune deficiency syndrome (AIDS), and other degenerative diseases. These "therapies" are offered at clinics in Mexico, the United States, and Europe. Proponents claim that many diseases, including cancer, are caused by oxygen deficiency and that oxygenation can restore health by destroying cancer cells, eliminating pathogens, stimulating metabolism, and by producing "oxidative detoxification." There is no scientific evidence to support any of these claims. Oxygen therapies include: (1) hydrogen peroxide therapy involving intravenous infusion, ingestion, colonic administration, or soaking in hydrogen peroxide solution; (2) ozone colonies and ozone autohemotherapy, in which blood is withdrawn and treated with ozone before reinfusion, and (3) "oxygenated" water, pills, and solutions. The use of oxygen therapies has resulted in serious adverse events and several deaths. Oxygen therapies should not be confused with those commonly used in respiratory care. PMID:20043470

Cassileth, Barrie

2009-11-30

333

Hyperbaric oxygen therapy ameliorates stress-impaired dermal wound healing  

Microsoft Academic Search

Psychological stress has been shown to dysregulate healing in both humans and animals. Studies indicate the possibility for decreased oxygen supply, and increased oxygen demand, in the wounds of the stressed animals. Oxygen is an important mediator of wound healing, and its availability can limit healing rate. Hence, in a mouse model of stress-impaired healing, the hypothesis that hyperbaric oxygen

Praveen K. Gajendrareddy; Chandan K. Sen; Michael P. Horan; Phillip T. Marucha

2005-01-01

334

Oxygen for Limelight  

Microsoft Academic Search

THE employment of oxygen for limelight and other purposes has increased enormously since the commercial introduction of the Brin method, by which the gas is separated from atmospheric air by a now well-known chemical process. The gas so obtained is practically pure, analysis showing that as now supplied by the Brin companies it contains on an average 95 per cent.

T. C. Hepworth

1892-01-01

335

Evaluation of oxygen utilization as an indicator of municipal solid-waste compost stability  

SciTech Connect

This research evaluated oxygen utilization parameters as indicators of MSW compost stability. Parameters evaluated were the oxygen utilization rate (OUR), specific oxygen uptake rate (SOUR), five-day biochemical oxygen demand, and chemical oxygen demand. In addition, other suggested indicators of stability were investigated including percent volatile solids, volatile solids reduction, nitrogen content, carbon: nitrogen ratio, and reheating potential (RP). OUR is a measure of the rate of oxygen utilization by the microorganisms in the decomposition of organic matter in compost. OUR was observed to be sensitive to the degree of stabilization and decreased with increasing compost age and stability. OUR values near zero indicate that the compost microorganisms are in a state of endogenous respiration, which is characteristic of a stable compost. Therefore, OUR is an excellent indicator of stability. A number of disadvantages are associated with OUR for practical application. Therefore, other parameters were evaluated as indicators of stability based on their statistical correlation to OUR. RP exhibited the strongest correlation to OUR. In combination, RP and SOUR were the two parameters which exhibited the strongest correlation to OUR. OUR, RP, and SOUR are all measures of microbial activity which reflect the degree of organic decomposition, and therefore, stability. Based on the results of this research; OUR, RP, and SOUR are useful parameters in assessing compost stability.

Zimmerman, R.A.

1991-01-01

336

Reactive Oxygen Species and Cellular Oxygen Sensing  

PubMed Central

Many organisms activate adaptive transcriptional programs to help them cope with decreased oxygen levels, or hypoxia, in their environment. These responses are triggered by various oxygen sensing systems in bacteria, yeast and metazoans. In metazoans, the hypoxia inducible factors (HIFs) mediate the adaptive transcriptional response to hypoxia by upregulating genes involved in maintaining bioenergetic homeostasis. The HIFs in turn are regulated by HIF-specific prolyl hydroxlase activity, which is sensitive to cellular oxygen levels and other factors such as tricarboxylic acid cycle metabolites and reactive oxygen species (ROS). Establishing a role for ROS in cellular oxygen sensing has been challenging since ROS are intrinsically unstable and difficult to measure. However, recent advances in fluorescence energy transfer resonance (FRET)-based methods for measuring ROS are alleviating some of the previous difficulties associated with dyes and luminescent chemicals. In addition, new genetic models have demonstrated that functional mitochondrial electron transport and associated ROS production during hypoxia are required for HIF stabilization in mammalian cells. Current efforts are directed at how ROS mediate prolyl hydroxylase activity and hypoxic HIF stabilization. Progress in understanding this process has been enhanced by the development of the FRET-based ROS probe, an vivo prolyl hydroxylase reporter and various genetic models harboring mutations in components of the mitochondrial electron transport chain.

Cash, Timothy P; Pan, Yi; Simon, M. Celeste

2008-01-01

337

Influence of oxygen pressure on critical current density and magnetic flux pinning structures in YBa2Cu3O7-x fabricated by chemical solution deposition  

NASA Astrophysics Data System (ADS)

This paper studies the effect of oxygen partial pressure on the fabrication of YBa2Cu3O7-x films on (00l) LaAlO3 substrates by metalorganic deposition using trifluoroacetates (TFA-MOD). As the oxygen partial pressure increases to 1500 Pa, a great increase in the superconducting properties is observed at high magnetic fields parallel to the YBCO c axis. The cross-sectional transmission electron microscope images show that a high density of stacking faults in the size range of 10-15 nm may act as flux pinning centres to enhance the critical current density of the YBCO films

Ding, Fa-Zhu; Gu, Hong-Wei; Zhang, Teng; Dai, Shao-Tao; Xiao, Li-Ye

2011-02-01

338

Lesson on Demand. Lesson Plan.  

ERIC Educational Resources Information Center

This lesson plan helps students understand the role consumer demand plays in the market system, i.e., how interactions in the marketplace help determine pricing. Students will participate in an activity that demonstrates the concepts of demand, demand schedule, demand curve, and the law of demand. The lesson plan provides student objectives;…

Weaver, Sue

339

Oxygen toxicity.  

PubMed

Oxygen is one of the most widely available and used therapeutic agents in the world. However, it is all too easy forget that oxygen is a prescribable drug with specific biochemical and physiologic actions, a distinct range of effective doses and well-defined adverse effects at high doses. The human body is affected in different ways depending on the type of exposure. Short exposures to high partial pressures at greater than atmospheric pressure lead to central nervous system toxicity, most commonly seen in divers or in hyperbaric oxygen therapy. Pulmonary and ocular toxicity results from longer exposure to elevated oxygen levels at normal atmospheric pressure. PMID:24767867

Thomson, Louise; Paton, James

2014-06-01

340

Energy demand forecasting  

NASA Astrophysics Data System (ADS)

Energy demand forecasting and its connection with national energy policies and decisions is examined in light of recent, sharply revised estimates of future energy requirements. Techniques of economic projects are examined. Modeling of energy demands is discussed. Renewable energy sources are discussed. The shift away from reliance of domestic users on oil and natural gas toward electricity as a primary energy resource is examined in the context of the need to conserve energy and expand generating capacity in order to avoid a significant electricity shortfall.

341

Screening of physical–chemical methods for removal of organic material, nitrogen and toxicity from low strength landfill leachates  

Microsoft Academic Search

Physical–chemical methods have been suggested for the treatment of low strength municipal landfill leachates. Therefore, applicability of nanofiltration and air stripping were screened in laboratory-scale for the removal of organic matter, ammonia, and toxicity from low strength leachates (NH4-N 74–220 mg\\/l, chemical oxygen demand (COD) 190–920 mg O2\\/l, EC50=2–17% for Raphidocelis subcapitata). Ozonation was studied as well, but with the

S. K Marttinen; R. H Kettunen; K. M Sormunen; R. M Soimasuo; J. A Rintala

2002-01-01

342

Demand, Growth, and Evolution  

ERIC Educational Resources Information Center

The paradigm shift to engaged and collaborative learning delivered via distance education technologies has been led by practitioners in adult and continuing education. Online and blended courses are experiencing increased demand and continued growth at all levels of higher education, professional development, and K-12 education. Adult and…

Hoskins, Barbara

2011-01-01

343

Commercial Demand Module  

EIA Publications

Documents the objectives, analytical approach and development of the National Energy Modeling System (NEMS) Commercial Sector Demand Module. The report catalogues and describes the model assumptions, computational methodology, parameter estimation techniques, model source code, and forecast results generated through the synthesis and scenario development based on these components.

Kevin Jarzomski

2013-10-10

344

Residential Energy Demand  

Microsoft Academic Search

This paper provides a concise review of the empirical literature on residential energy demand. It also discusses the findings in the reviewed literature and their implications for the choice of policy instruments. While there is a plethora of studies on the technical possibilities, i.e. the potential energy savings that new technologies allow, it is plain that energy consumption also depends

Bengt Kriström

2008-01-01

345

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

Microsoft Academic Search

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

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

2009-01-01

346

LDEF atomic oxygen fluence update  

NASA Technical Reports Server (NTRS)

The definition of LDEF atomic oxygen exposure involves theoretical prediction of fluxes, modeling of shielding and scattering effects, and comparison of predicted with observed atomic oxygen effects on LDEF experiments. Work is proceeding as follows: atomic oxygen fluxes and fluences have been recalculated using a more detailed orbit prediction program; a micro-environments program is being developed to account for the effects of experiment geometry on atomic oxygen flux; and chemical and physical measurements are being made on copper grounding straps to verify correspondence between predicted exposures and observed surface property variations. These three areas of work are reported briefly.

Bourassa, Roger J.; Gillis, J. R.

1992-01-01

347

Oxygen Metabolism of Some Reef Substrate Microcosms.  

National Technical Information Service (NTIS)

Measurements of oxygen demand by individual reef microcosms (deadheads) contained under plastic hemispheres were made at Hydro-Lab in February 1974. After baseline O2 consumption data were acquired, attempts were made to alter O2 demand rates of microcosm...

L. H. DiSalvo H. C. Ross

1974-01-01

348

Use of Potassium Ferrate in Oxygen Demand Measurement.  

National Technical Information Service (NTIS)

This research project was initiated with the primary objective of improving the commonly used COD test by the use of ferrate (VI) ion as an alternate or preliminary oxidant. The oxidation of NH3 and more general oxidation of organic compounds was desired....

J. D. Carr

1977-01-01

349

MODELING SEDIMENT-NUTRIENT FLUX AND SEDIMENT OXYGEN DEMAND  

EPA Science Inventory

This project builds upon previous advances in modeling bottom sediment processes in eutrophication models. It develops algorithms for simulating processes responsible for nitrogen (nitrate, ammonium, organic-N) and carbon transformation and cycling (organic-N and methane) in bott...

350

USE OF POTASSIUM FERRATE IN OXYGEN DEMAND MEASUREMENT  

EPA Science Inventory

This research project was initiated with the primary objective of improving the commonly used COD test by the use of ferrate (VI) ion as an alternate or preliminary oxidant. The oxidation of NH3 and more general oxidation of organic compounds was desired. A secondary objective wa...

351

Demand surge following earthquakes  

USGS Publications Warehouse

Demand surge is understood to be a socio-economic phenomenon where repair costs for the same damage are higher after large- versus small-scale natural disasters. It has reportedly increased monetary losses by 20 to 50%. In previous work, a model for the increased costs of reconstruction labor and materials was developed for hurricanes in the Southeast United States. The model showed that labor cost increases, rather than the material component, drove the total repair cost increases, and this finding could be extended to earthquakes. A study of past large-scale disasters suggested that there may be additional explanations for demand surge. Two such explanations specific to earthquakes are the exclusion of insurance coverage for earthquake damage and possible concurrent causation of damage from an earthquake followed by fire or tsunami. Additional research into these aspects might provide a better explanation for increased monetary losses after large- vs. small-scale earthquakes.

Olsen, Anna H.

2012-01-01

352

The Demand for Pornography  

Microsoft Academic Search

The market for pornography acquired great economic relevance in the 1970s with diffusion of the videocassette recorder, and\\u000a went onto gain increasing relevance as from the 1990s, with the ICT revolution. Nonetheless, it has been totally ignored in\\u000a economic investigation. The present paper focuses on the demand side of this market, with the main aim of proposing a preliminary\\u000a theoretical

Fabio D’Orlando

2011-01-01

353

Lunar Oxygen as Monopropellant  

NASA Astrophysics Data System (ADS)

This paper explores the feasibility of beamed energy propulsion to provide transportation to and from the lunar surface to low lunar orbit using lunar oxygen as propellant. Oxygen, as an Electro-Thermal Propulsion (ETP) monopropellant, has specific impulse comparing favorably with chemical bipropellants, though not as high as cryogenic LO2+LH2. Lunar hydrogen is not available in non-polar regions and costly to transport from earth for use as fuel for lunar operations. However, oxygen is a major component of lunar soil and available given ISRU (In Situ Resource Utilization) infrastructure. Low-gravity and vacuum environment plus low velocity increments are distinct advantages favoring lunar-based beamed energy propulsion. In lunar vacuum and low gravity environment, energy storage devices such as SMES (Superconductor Magnet Energy Storage) and FES (Flywheel Energy Storage) should exhibit improved efficiency. Microwave source design also favors vacuum operation.

Johansen, Donald G.

2008-04-01

354

Quantum dots as a possible oxygen sensor.  

PubMed

Results of studies on optical properties of low toxicity quantum dots (QDs) obtained from copper doped zinc sulfate are discussed in the paper. The effect of copper admixture concentration and solution pH on the fluorescence emission intensity of QDs was investigated. Quenching of QDs fluorescence by oxygen was reported and removal of the oxygen from the environment by two methods was described. In the chemical method oxygen was eliminated by adding sodium sulfite, in the other method oxygen was removed from the solution using nitrogen gas. For elimination of oxygen by purging the solution with nitrogen the increase of fluorescence intensity with decreasing oxygen concentration obeyed Stern-Volmer equation indicating quenching. For the chemical method Stern-Volmer equation was not fulfilled. The fluorescence decays lifetimes were determined and the increase of mean lifetimes at the absence of oxygen support hypothesis that QDs fluorescence is quenched by oxygen. PMID:24568848

Zió?czyk, Paulina; Kur-Kowalska, Katarzyna; Przybyt, Ma?gorzata; Miller, Ewa

2014-05-21

355

Quantum dots as a possible oxygen sensor  

NASA Astrophysics Data System (ADS)

Results of studies on optical properties of low toxicity quantum dots (QDs) obtained from copper doped zinc sulfate are discussed in the paper. The effect of copper admixture concentration and solution pH on the fluorescence emission intensity of QDs was investigated. Quenching of QDs fluorescence by oxygen was reported and removal of the oxygen from the environment by two methods was described. In the chemical method oxygen was eliminated by adding sodium sulfite, in the other method oxygen was removed from the solution using nitrogen gas. For elimination of oxygen by purging the solution with nitrogen the increase of fluorescence intensity with decreasing oxygen concentration obeyed Stern-Volmer equation indicating quenching. For the chemical method Stern-Volmer equation was not fulfilled. The fluorescence decays lifetimes were determined and the increase of mean lifetimes at the absence of oxygen support hypothesis that QDs fluorescence is quenched by oxygen.

Zió?czyk, Paulina; Kur-Kowalska, Katarzyna; Przybyt, Ma?gorzata; Miller, Ewa

356

A DETAILED CHEMICAL ANALYSIS OF CHANGES TO BITUMEN PRODUCED BY THE IN SITU COMBUSTION PROCESS AT THE OXYGEN WOLF LAKE PROJECT, ALBERTA PART 1: WHOLE OIL SAMPLES  

Microsoft Academic Search

The detailed chemical changes in bitumen brought about over a one year period by an in situ combustion process in an oil sands reservoir have been investigated. Relative to a core sample, the fireflood-produced oils exhibited a significant reduction in density and viscosity which began early in the production cycle. This behaviour was correlated with a marked increase in material

R. F. Alex; B. Fuhr; C. Reichert

1992-01-01

357

Chemical and Structural Dependences of the Fractionation of Oxygen and Silicon Isotopes Between Rock-forming Minerals: a First-Principles Density Functional Study  

Microsoft Academic Search

Ab initio methods based on density functional theory have proven to be successful in reproducing the physical and chemical properties of complex systems. Within this framework, we have recently developed a methodology to predict equilibrium fractionation factors as a function of temperature (1). We use PBE functionals, combined with the use of pseudopotentials and planewave basis sets. Our previous work

M. Meheut; E. A. Schauble

2008-01-01

358

Erythropoiesis-stimulating agents and other methods to enhance oxygen transport  

Microsoft Academic Search

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

S Elliott

2008-01-01

359

electrocatalysts for oxygen reduction  

Microsoft Academic Search

Experience gained during efforts towards optimization of noble-metal-free electrocatalysts for oxygen reduction is simultaneously used to understand the chemical and morphological necessities for inducing efficient multi-electron transfer catalysis. The analysis of many preparative experimental steps between the moderately performing metal porphyrines and the highly efficient transition metal- and sulfur- containing pyrolised catalyst material contributes to the following model of the

Helmut Tributsch; Ulrike I. Koslowski; Iris Dorbandt

360

Rhenium-Oxygen Interactions at High Temperatures  

NASA Technical Reports Server (NTRS)

The reaction of pure rhenium metal with dilute oxygen/argon mixtures was studied from 600 to 1400 C. Temperature, oxygen pressure, and flow rates were systematically varied to determine the rate-controlling steps. At lower temperatures the oxygen/rhenium chemical reaction is rate limiting; at higher temperatures gas-phase diffusion of oxygen through the static boundary layer is rate limiting. At all temperatures post-reaction microstructures indicate preferential attack along certain crystallographic planes and defects.

Jacobson, Nathan S.; Myers, Dwight L.; Zhu, Dongming; Humphrey, Donald

2000-01-01

361

Meeting increased demand.  

PubMed

New Zealand is a little country with a little economy but with a population that's rapidly aging. New Zealand's population is only 4.3 million people. It's GDP is only $US58.6 billion (2002). New Zealand's expenditure on health as a percentage of GDP is not out of line with that of other countries. As a nation we have been increasing expenditure on health over recent years. In 1990 we spent 7% of GDP on health. In 1995 that increased to 7.65% and is now 8.3%. However, in per capita terms our expenditure on health does not compare so well with like countries. The size of New Zealand's economy is restricting what our country spends on health. Health is already the second highest demand on the New Zealand tax dollar. The tolerance of New Zealanders would be challenged if a Government attempted to increase taxes further to meet the growing demands for expenditure on health, but at the same time the population's expectations are increasing. This is the challenging situation we face today. What lies ahead? Like all industrialized countries New Zealand is facing an aging population. The population below age 40 is decreasing, but it is increasing significantly over that age. 16% of the population is currently aged over 60. By 2051 this proportion will almost double to just over 31%. Coupled with the aging population is increased awareness and expectations, as access to options for treatment and technology becomes readily accessible to the population through such media as the internet. The extent of the impact of the aging population can be clearly represented by focusing on one specialty such as orthopaedics. The New Zealand Orthopaecic Association undertook a study in July 2003 which concluded (among other things) that as a result of the projected aging of the population, over the next 50 years: Musculo-skeletal operations will increase by over 30%. The number of hip replacements will nearly double. The incidence of osteoporosis will increase by a massive 201%. The number of people affected by arthritis will increase by nearly 50%. A huge increase in numbers affected with musculoskeletal conditions will require significant increases in health care resources, including hospital beds and facilities, orthopaedic surgeons and other health care professionals. New Zealand has been slow to acknowledge and plan for the increased demand for health services which is looming. Growing New Zealand's economy will help, but alone will not be enough. It is more than just finding the financial resources to better meet the demand. The enormous demands on the availability of treatment resources including hospital facilities and trained health care professionals must be addressed. There are major workforce issues to be faced. The change in population distribution between young and old will have an impact and it will be necessary to ensure that there are sufficient numbers of properly trained health care professionals available at all levels. It is hoped that improvements in preventative care programmes and new technologies and treatment techniques may reduce the rate of demand. As the health of our population is improved through targeted programmes dealing with obesity, diabetes, smoking and accident prevention, it may be possible to reallocate or change the focus of resources within the health and hospital sectors. Many countries are developing national strategies for their aging population. Clearly the New Zealand Government needs to move swiftly to develop a plan to manage the increased burden that is developing as a result of the aging population. That plan must create an environment which facilitates, encourages and supports greater private investment in healthcare facilities and healthcare delivery. Incentives must be created to motivate individuals to take greater responsibility for their healthcare needs and the funding of it. The development of a long term strategy to meet the challenges of the aging population is a priority. PMID:19195249

Blair, Andrew

2004-07-01

362

An Electronic Transition Chemical Laser.  

National Technical Information Service (NTIS)

This report covers unclassified laser research performed at the Air Force Weapons Laboratory. The two reports included herein describe the first operation of an oxygen-iodine chemical laser and the first transverse flow high efficiency oxygen-iodine chemi...

W. E. McDermott N. R. Pchelkin D. J. Bernard R. R. Bousek

1978-01-01

363

Effects of sensitizers on cell respiration: II. The effects of hypoxic cell sensitizers on oxygen utilization in cellular and chemical models.  

PubMed Central

The metabolic activity of nitroheterocyclic sensitizers could limit their usefulness in vivo. Biochemical mechanisms of drug metabolism, toxicity and effects on cell respiration have been studied in microsomes, and the kinetics of the simulated redox reactions determined by pulse radiolysis. Stimulated oxidation of coenzyme, glucose, ascorbate or glutathione substrate radicals by nitroheterocyclic sensitizers, with the concomitant appearance of the respective nitro radical anions, is observed. Under hypoxia, the nitro radical anions decay slowly by second order processes, forming reduced metabolites. In air, the nitro radical anions react with oxygen forming superoxide radical anions, peroxide and regenerating the drug. Nitro radical-anions also react with cytochrome-c indicating a possible interference with mitochondrial energy metabolism.

Greenstock, C. L.; Biaglow, J. E.; Durand, R. E.

1978-01-01

364

Chemical etch rates in HF solutions as a function of thickness of thermal SiO2 and buried SiO2 formed by oxygen implantation  

Microsoft Academic Search

A comparative study of chemical etch rates in diluted HF or a mixture of HF, H2O, and HNO3 (P etch) was performed on conventional thermal silicon oxides (1050–1120 °C; O2 pressure ≊1.1 atm; one type with addition of 0.02% C2H3Cl3) and buried oxide layers. The latter were formed by single or multiple implanting n- and p-type (100) Si maintained at

K. Vanheusden; A. Stesmans

1991-01-01

365

Studies on the preparation of active oxygen-deficient copper ferrite and its application for hydrogen production through thermal chemical water splitting  

Microsoft Academic Search

Hydrogen generation through thermal chemical water splitting technology has recently received increasingly international interest\\u000a in the nuclear hydrogen production field. Besides the main known sulfur-iodine (S-I) cycle developed by the General Atomics\\u000a Company and the UT3 cycle (iron, calcium, and bromine) developed at the University of Tokyo, the thermal cycle based on metal\\u000a oxide two-step water splitting methods is also

Bo Yu; Ping Zhang; Lei Zhang; Jing Chen; JingMing Xu

2008-01-01

366

On the nitrogen and oxygen incorporation in plasma-enhanced chemical vapor deposition (PECVD) SiO x N y films  

Microsoft Academic Search

Silicon oxynitride films were deposited by plasma-enhanced chemical vapor deposition at low temperatures using nitrous oxide (N2O) and silane (SiH4) as gas precursors. The influence of the N2O\\/SiH4 flow ratio (varied from 0.25 up to 5) and the thickness of the films on the optical and structural properties of the material was analyzed. The films were characterized by ellipsometry, Fourier-transform

M. I Alayo; I Pereyra; W. L Scopel; M. C. A Fantini

2002-01-01

367

DEMAND RELATIONSHIPS AMONG JUICE BEVERAGES: A DIFFERENTIAL DEMAND SYSTEM APPROACH  

Microsoft Academic Search

Nielsen ScanTrack data were used to study how income and prices influenced consumer juice beverage demand in the United States during the period from 1988-89 through 1991-92. Alternative differential demand models combining the features of the Rotterdam model and the almost ideal demand system (AIDS) were tested. Results indicate the CBS type demand responses describe consumer behavior better than the

Mark G. Brown; Jonq-Ying Lee; James L. Seale Jr.

1994-01-01

368

Tools for a New Demand Forecasting Paradigm 'Individual Demand Forecasting  

Microsoft Academic Search

Notwithstanding the increasing importance to forecast individual demands, tools for forecasting individual demands has received few attention so far. In this paper we presented three kinds of tools for individual demand forecasting: (1) tools for total customer participation, (2) tools for total value fusion, and (3) tool for net change forecasting. We describe important requirements for the development of each

Zhongjun Tang; Jing Xiao

2009-01-01

369

Establishing Chemical Technology Programs.  

ERIC Educational Resources Information Center

In light of the increasing demand for well-prepared chemical technicians, this paper provides suggestions for two-year colleges interested in initiating or upgrading a chemical technology program. Introductory comments indicate that, from the industry standpoint, chemical technicians are invaluable, but inadequate in numbers and often unprepared.…

Hajian, Harry G.

370

Effect of light transmittance and oxygen permeability of various packaging materials on keeping quality of low fat pasteurized milk: chemical and sensorial aspects  

Microsoft Academic Search

Chemical and sensory changes in low fat (15gkg?1) pasteurized milk stored under fluorescent light at 4°C in 500mL bottles made of (a) multilayer pigmented [HDPE (high-density polyethylene)+20gkg?1 TiO2\\/HDPE+40gkg?1 carbon black\\/HDPE+20gkg?1 TiO2], (b) monolayer pigmented [HDPE+20gkg?1 TiO2], (c) clear PET (polyethylene terephthalate) and (d) pigmented [PET+20gkg?1 TiO2] were monitored for a period of 7 days. Milk packaged in coated paperboard cartons

Theodora Moyssiadi; Anastasia Badeka; Efthymia Kondyli; Theodora Vakirtzi; Ioannis Savvaidis; Michael G Kontominas

2004-01-01

371

Oxygen-Concentrating Cell  

NASA Technical Reports Server (NTRS)

High-purity oxygen produced from breathing air or from propellantgrade oxygen in oxygen-concentrating cell. Operating economics of concentrator attractive: Energy consumption about 4 Wh per liter of oxygen, slightly lower than conventional electrochemical oxygen extractors.

Buehler, K.

1986-01-01

372

Black rice (Oryza sativa L. indica) pigmented fraction suppresses both reactive oxygen species and nitric oxide in chemical and biological model systems.  

PubMed

Anthocyanins, present in fruits and vegetables as natural colorants, have been well characterized to possess bioactive properties. Anthocyanin components extracted from black rice (Oryza sativa L. indica) separated by gel filtration and identified using LC-MS were cyanidin 3-glucoside and peonidin 3-glucoside. A standardized extract of black rice pigmented fraction (BRE) containing known proportions of cyanidin 3-glucoside and peonidin 3-glucoside exhibited marked antioxidant activities and free radical scavenging capacities in a battery of in vitro model systems. Significant (p < 0.05) prevention of supercoiled DNA strand scission induced by reactive oxygen species (specifically, peroxyl radical and hydroxyl radicals) and suppression of the oxidative modification of human low-density lipoprotein was obtained with BRE. In addition, BRE reduced (p < 0.05) the formation of nitric oxide by suppressing inducible nitric oxide synthase expression in murine macrophage RAW264.7 cells, without introducing cell toxicity. The results of this study show that black rice contains anthocyanin pigments with notable antioxidant and anti-inflammatory properties for potential use in nutraceutical or functional food formulations. PMID:12926869

Hu, Chun; Zawistowski, Jerzy; Ling, Wenhua; Kitts, David D

2003-08-27

373

Automated Demand Response and Commissioning  

Microsoft Academic Search

This paper describes the results from the second season of research to develop and evaluate the performance of new Automated Demand Response (Auto-DR) hardware and software technology in large facilities. Demand Response (DR) is a set of activities to reduce or shift electricity use to improve the electric grid reliability and manage electricity costs. Fully-Automated Demand Response does not involve

Mary Ann Piette; David S. Watson; Naoya Motegi; Norman Bourassa

2005-01-01

374

Demand for gasoline in Kuwait  

Microsoft Academic Search

This paper estimates the demand for gasoline in Kuwait for the period 1970–1989 using a cointegration and error correction model (ECM). It is found that gasoline demand is inelastic with respect to price in the short and long run, and while it is elastic in the long run, gasoline demand is inelastic with respect to income in the short run.

M. N. Eltony; N. H. Al-Mutairi

1995-01-01

375

Comparison of airline passenger oxygen systems.  

PubMed

The principal sources of oxygen for inflight passenger use, scheduled and unscheduled, are examined. Present practices of assessment of the passenger's "fitness to fly" are described. Three partner airlines, British Airways, U.S. Air, and Qantas, catering for more than 8000 oxygen requests annually, are compared. Analysis of customer use suggests that medical oxygen requests are frequently not clinically justified. The growth in demand, for both scheduled and unscheduled use of an expensive resource, supports the need for a "recommended best practice" among carriers. Passengers with respiratory disorders who will most benefit from inflight oxygen are vulnerable either to hypoxia or asthma. PMID:7487813

Byrne, N J

1995-08-01

376

Oxygen Releasing Biomaterials for Tissue Engineering  

PubMed Central

Due to the increasing demand to generate thick and vascularized tissue engineered constructs, novel strategies are currently being developed. An emerging example is the generation of oxygen-releasing biomaterials to tackle mass transport and diffusion limitations within engineered tissue-like constructs. Biomaterials containing oxygen releasing molecules can be fabricated in various forms such as, hybrid thin films, microparticles, or three dimensional (3D) scaffolds. In this perspective, we will summarize various oxygen-releasing reagents and their potential applications in regenerative engineering. Moreover, we will review the main approaches to fabricate oxygen-releasing biomaterials for a range of tissue engineering applications.

Camci-Unal, Gulden; Alemdar, Neslihan; Annabi, Nasim; Khademhosseini, Ali

2013-01-01

377

Chemical vapor deposition of yttrium barium(2) copper(3) oxygen(x) thin films for wire applications. Final report, May 88-Dec 91  

SciTech Connect

The chemical vapor deposition of superconducting ytterbium barium copper oxide thin films onto continuous lengths of ceramic fiber tows has been investigated. This project couples two areas of current interest in the materials field: continuous fiber coating and the deposition of one of the unique high temperature superconducting oxides. The YBa2Cu3Ox material has zero resistance at temperatures above 77 K (the boiling point of nitrogen), and the film form has been shown to have high critical current densities. By coating ceramic fiber tows, a strong, flexible superconducting material in the form of wire can be developed and used for several applications, including coils for magnets and transmission lines. Over 900 deposition runs were completed using a horizontal CVD furnace and over 150 continuous fiber coating experiments were completed. The deposition was performed on fiber tows, flat samples, and flexible tapes; the continuous substrates were moved and held stationary in the furnace.

Lackey, W.J.; Hanigofsky, J.A.; Hill, D.N.; Carter, W.B.; Barefield, E.K.

1991-12-01

378

The research of Iodine pool pressure of chemical oxygen-iodine laser in non-equilibrium condition and its automatic control system design  

NASA Astrophysics Data System (ADS)

In the working process of chemical oxy-iodigenne laser(COIL), the change of iodine pool pressure is complicated. As a result, it causes some mis-judgements, such as the damage of heater and the leakage of iodine steam. Further more, when the heater electric circuit is in a single working status, and after the heater switch is on or off, there exists a buffer time for the stabilization of iodine pool pressure, which is a relatively long time, and the minimum buffer pressure exceeds to 19 torr . Of course, it increases the preparing time for steady operation of laser, and reduces the quality of laser beam. In this paper, we study the iodine pool pressure of COIL in non-equilibrium condition, and analyze the mutation and the serious buffer phenomenon of iodine steam pressure. At the same time, we design an automatic control system for iodine pool pressure, which consists of five modules, such as data collection, automatic control, manual control, heater electric circuit, and the setting and display of pressure. This system uses two kinds of heater electric circuits, in this way, the serious buffer phenomenon of iodine pool pressure is effectively avoided. As a result, the maximal buffer pressure reduces to 4 torr, this makes sure that the iodine steam pressure is suitable for the operation of COIL, which produces a good condition for the steady operation of laser system and an excellent laser output.

Zhou, Songqing; Qu, Pubo; Ren, Weiyan

2013-05-01

379

OXYGEN TRANSPORT CERAMIC MEMBRANES  

SciTech Connect

Conversion of natural gas to liquid fuels and chemicals is a major goal for the Nation as it enters the 21st Century. Technically robust and economically viable processes are needed to capture the value of the vast reserves of natural gas on Alaska's North Slope, and wean the Nation from dependence on foreign petroleum sources. Technologies that are emerging to fulfill this need are all based syngas as an intermediate. Syngas (a mixture of hydrogen and carbon monoxide) is a fundamental building block from which chemicals and fuels can be derived. Lower cost syngas translates directly into more cost-competitive fuels and chemicals. The currently practiced commercial technology for making syngas is either steam methane reforming (SMR) or a two-step process involving cryogenic oxygen separation followed by natural gas partial oxidation (POX). These high-energy, capital-intensive processes do not always produce syngas at a cost that makes its derivatives competitive with current petroleum-based fuels and chemicals. This project has the following 6 main tasks: Task 1--Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. Task 2--Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. Task 3--Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. Task 4--Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. Task 5--Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. Task 6--Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

2001-12-01

380

Oxygen transfer in a full-depth biological aerated filter.  

PubMed

The City of San Diego, California, evaluated the performance capabilities of biological aerated filters (BAFs) at the Point Loma Wastewater Treatment Plant. The City conducted a 1-year pilot-plant evaluation of BAF technology supplied by two BAF manufacturers. This paper reports on the first independent oxygen-transfer test of BAFs at full depth using the offgas method. The tests showed process-water oxygen-transfer efficiencies of 1.6 to 5.8%/m (0.5 to 1.8%/ft) and 3.9 to 7.9%/m (1.2 to 2.4%/ft) for the two different pilot plants, at their nominal design conditions. Mass balances using chemical oxygen demand and dissolved organic carbon corroborated the transfer rates. Rates are higher than expected from fine-pore diffusers for similar process conditions and depths and clean-water conditions for the same column and are mostly attributed to extended bubble retention time resulting from interactions with the media and biofilm. PMID:18710150

Stenstrom, Michael K; Rosso, Diego; Melcer, Henryk; Appleton, Ron; Occiano, Victor; Langworthy, Alan; Wong, Pete

2008-07-01

381

An integrated communications demand model  

NASA Astrophysics Data System (ADS)

A computer model of communications demand is being developed to permit dynamic simulations of the long-term evolution of demand for communications media in the U.K. to be made under alternative assumptions about social, economic and technological trends in British Telecom's business environment. The context and objectives of the project and the potential uses of the model are reviewed, and four key concepts in the demand for communications media, around which the model is being structured are discussed: (1) the generation of communications demand; (2) substitution between media; (3) technological convergence; and (4) competition. Two outline perspectives on the model itself are given.

Doubleday, C. F.

1980-11-01

382

Workshop on Oxygen in Asteroids and Meteorites  

NASA Technical Reports Server (NTRS)

Contents include the following: Constraints on the detection of solar nebula's oxidation state through asteroid observation. Oxidation/Reduction Processes in Primitive Achondrites. Low-Temperature Chemical Processing on Asteroids. On the Formation Location of Asteroids and Meteorites. The Spectral Properties of Angritic Basalts. Correlation Between Chemical and Oxygen Isotopic Compositions in Chondrites. Effect of In-Situ Aqueous Alteration on Thermal Model Heat Budgets. Oxidation-Reduction in Meteorites: The Case of High-Ni Irons. Ureilite Atmospherics: Coming up for Air on a Parent Body. High Temperature Effects Including Oxygen Fugacity, in Pre-Planetary and Planetary Meteorites and Asteroids. Oxygen Isotopic Variation of Asteroidal Materials. High-Temperature Chemical Processing on Asteroids: An Oxygen Isotope Perspective. Oxygen Isotopes and Origin of Opaque Assemblages from the Ningqiang Carbonaceous Chondrite. Water Distribution in the Asteroid Belt. Comparative Planetary Mineralogy: V Systematics in Planetary Pyroxenes and fo 2 Estimates for Basalts from Vesta.

2005-01-01

383

Aerobic treatment of a nitrogen-limited chemical process wastewater.  

PubMed

Nitrogen transformations and their effect on aerobic suspended growth treatment of an industrial wastewater were studied in three parallel bench-scale reactors operated at 5 degrees C at mean cell residence times (MCRT) of 15, 30, and 60 days. In normal process wastewater, the bulk of influent nitrogen was in organic form, and the fraction transformed was almost totally incorporated into synthesized biomass. Assimilative control by heterotrophs maintained ammonia-nitrogen levels below permitted effluent levels, and nitrification was not significant. Although volatile suspended solids had a nitrogen content of only 5% to 8%, effective organics removal was maintained, and total organic carbon and filtered daily average five-day biochemical oxygen demand (BOD5) were below permitted effluent levels. A marked improvement in settleability and lower effluent total suspended solids was achieved by adding ammonia-nitrogen to the wastewater in excess of stoichiometric growth requirements. During a batch production cycle of a cationic chemical, the ratio of nitrogen to chemical oxygen demand and the fraction of the total influent nitrogen in soluble form increased in the wastewater. Reactor effluent ammonia levels increased to above permit levels at all three MCRTs during treatment of wastewater containing cationic production effluents. The magnitude of ammonia increase was greater for longer MCRTs, suggesting that synthesis of cell mass was not capable of assimilating the increased ammonia supply under these non-steady conditions. The experimental results suggest several potential strategies for operating the aerobic process at the treatment facility, including adding nitrogen to improve settleability and discontinuing these additions when wastewater contains a high ratio of nitrogen to chemical oxygen demand and an elevated soluble nitrogen fraction. PMID:9028176

Smith, D P

1996-06-01

384

Bifunctional oxygen electrodes  

NASA Astrophysics Data System (ADS)

The objective of the research on bifunctional oxygen electrodes for alkaline electrolytes was to improve significantly both the cathodic and anodic polarization as well as the cycle life of such electrodes. The research has focused on finding high-efficiency, long-life electrocatalysts for O2 reduction and generation and achieving an understanding of the mechanisms of the catalysis. Catalyst systems which have been examined in alkaline electrolytes have included the following:various types of carbons and graphites; chemically-modified carbons and graphites using adsorptive attachment (e.g., various quinones, macrocycles and chemical linkages); silver and various intermetallics; various oxide systems including perovskites, spinels, pyrochlores and other mixed transition metal oxides; transition metal macrocycles including porphyrins, phthalocyanines, naphthalocyanines and tetraazaannulenes; and thermally-treated macrocycles. Mechanistic studies have particularly focused on the reduction of O2 on various carbon/graphite surfaces and the role of the O2(-) radical ion.

Tryk, D.; Aldred, W.; Chen, Z.; Fierro, C.; Hashiguchi, J.; Hossain, M.; Zhang, Z.; Zhao, F.

1985-01-01

385

Monitoring oxygenation.  

PubMed

Cyanosis was used for a century after dentists began pulling teeth under 100% N(2)O in 1844 because brief (2 min) severe hypoxia is harmless. Deaths came with curare and potent anesthetic respiratory arrest. Leland Clark's invention of a polarographic blood oxygen tension electrode (1954) was introduced for transcutaneous PO2 monitoring to adjust PEEP and CPAP PO2 to prevent premature infant blindness from excess O2 (1972). Oximetry for warning military aviators was tried after WW II but not used for routine monitoring until Takuo Aoyagi (1973) discovered an equation to measure SaO2 by the ratio of ratios of red and IR light transmitted through tissue as it changed with arterial pulses. Pulse oximetry (1982) depended on simultaneous technology improvements of light emitting red and IR diodes, tiny cheap solid state sensors and micro-chip computers. Continuous monitoring of airway anesthetic concentration and oxygen also became very common after 1980. Death from anesthesia fell 10 fold between 1985 and 2000 as pulse oximetry became universally used, but no proof of a causative relationship to pulse oximetry exists. It is now assumed that all anesthesiologist became much more aware of the dangers of prolonged hypoxia, perhaps by using the pulse oximeters. PMID:21717228

Severinghaus, John W

2011-06-01

386

Oxygen plasmas used to synthesize superoxides  

NASA Technical Reports Server (NTRS)

Production of alkali metal superoxides by interaction of molecular oxygen with alkali metals or their salts is discussed. Diagram of reactor to show components and operating principles is provided. Analysis of chemical reactions involved is developed.

Hollahan, J. R.; Wydeven, T.

1972-01-01

387

Universal Non-Pressurized Aircraft Oxygen System.  

National Technical Information Service (NTIS)

This report describes the development of a laboratory working model of a solid chemical oxygen generating system. A design study was conducted to aid in designing a system which would satisfy program specifications and provide operational flexibility and ...

R. L. Rankin F. Roehlich M. J. McGoff

1972-01-01

388

Demand Activated Manufacturing Architecture  

SciTech Connect

Honeywell Federal Manufacturing & Technologies (FM&T) engineers John Zimmerman and Tom Bender directed separate projects within this CRADA. This Project Accomplishments Summary contains their reports independently. Zimmerman: In 1998 Honeywell FM&T partnered with the Demand Activated Manufacturing Architecture (DAMA) Cooperative Business Management Program to pilot the Supply Chain Integration Planning Prototype (SCIP). At the time, FM&T was developing an enterprise-wide supply chain management prototype called the Integrated Programmatic Scheduling System (IPSS) to improve the DOE's Nuclear Weapons Complex (NWC) supply chain. In the CRADA partnership, FM&T provided the IPSS technical and business infrastructure as a test bed for SCIP technology, and this would provide FM&T the opportunity to evaluate SCIP as the central schedule engine and decision support tool for IPSS. FM&T agreed to do the bulk of the work for piloting SCIP. In support of that aim, DAMA needed specific DOE Defense Programs opportunities to prove the value of its supply chain architecture and tools. In this partnership, FM&T teamed with Sandia National Labs (SNL), Division 6534, the other DAMA partner and developer of SCIP. FM&T tested SCIP in 1998 and 1999. Testing ended in 1999 when DAMA CRADA funding for FM&T ceased. Before entering the partnership, FM&T discovered that the DAMA SCIP technology had an array of applications in strategic, tactical, and operational planning and scheduling. At the time, FM&T planned to improve its supply chain performance by modernizing the NWC-wide planning and scheduling business processes and tools. The modernization took the form of a distributed client-server planning and scheduling system (IPSS) for planners and schedulers to use throughout the NWC on desktops through an off-the-shelf WEB browser. The planning and scheduling process within the NWC then, and today, is a labor-intensive paper-based method that plans and schedules more than 8,000 shipped parts per month based on more than 50 manually-created document types. The fact that DAMA and FM&T desired to move from paper-based manual architectures to digitally based computer architectures gave further incentive for the partnership to grow. FM&T's greatest strength was its knowledge of NWC-wide scheduling and planning with its role as the NWC leader in manufacturing logistics. DAMA's asset was its new knowledge gained in the research and development of advanced architectures and tools for supply chain management in the textiles industry. These complimentary strengths allowed the two parties to provide both the context and the tools for the pilot. Bender: Honeywell FM&T participated in a four-site supply chain project, also referred to as an Inter-Enterprise Pipeline Evaluation. The MSAD project was selected because it involves four NWC sites: FM&T, Pantex, Los Alamos National Laboratory (LANL), and Lawrence Livermore National Laboratory (LLNL). FM&T had previously participated with Los Alamos National Laboratory in FY98 to model a two-site supply chain project, between FM&T and LANL. Evaluation of a Supply Chain Methodology is a subset of the DAMA project for the AMTEX consortium. LANL organization TSA-7, Enterprise Modeling and Simulation, has been involved in AMTEX and DAMA through development of process models and simulations for LANL, the NWC, and others. The FY 1998 and this FY 1999 projects directly involved collaboration between Honeywell and the Enterprise Modeling and Simulation (TSA-7) and Detonation Science and Technology (DX1) organizations at LANL.

Bender, T.R.; Zimmerman, J.J.

2001-02-07

389

Partial Oxidation Reactions of Methane and Oxygen  

Microsoft Academic Search

In considering the typical experimental conditions used for studies of methane oxidation to oxygenates or hydrocarbons in the presence of catalysts, it is clear that a significant potential exists for the appearance of non-catalyzed, thermally activated gas-phase reactions of methane and oxygen. In order to identify and describe the contribution of the gas phase processes during catalyzed reactions, a chemical

M. W. Droege; L. M. Hair; W. J. Pitz; C. K. Westbrook

1989-01-01

390

Making Excited Oxygen Molecules And Atoms  

NASA Technical Reports Server (NTRS)

Oxidation of semiconductors and high-temperature superconductors achieved at lower temperatures by use of oxygen molecules or atoms raised into specific excited states. Use of excited oxygen (or other species) of interest in research on kinetics and mechanisms of chemical reactions. Used in ultra-high-vacuum chamber also equipped for such surface-analytical techniques as x-ray photoelectron spectroscopy.

Vasquez, Richard P.

1989-01-01

391

Predicting anaerobic biogasification potential of ingestates and digestates of a full-scale biogas plant using chemical and biological parameters  

Microsoft Academic Search

The aim of this work was to develop simple and fast tests to predict anaerobic biogasification potential (ABP) of ingestates and digestates from a biogas plant. Forty-six samples of both ingestates and digestates were collected within an eight-month observation period and were analyzed in terms of biological and chemical parameters, namely, ABP test, oxygen demand in a 20-h respirometric test

Andrea Schievano; Michele Pognani; Giuliana D’Imporzano; Fabrizio Adani

2008-01-01

392

Harnessing the power of demand  

SciTech Connect

Demand response can provide a series of economic services to the market and also provide ''insurance value'' under low-likelihood, but high-impact circumstances in which grid reliablity is enhanced. Here is how ISOs and RTOs are fostering demand response within wholesale electricity markets. (author)

Sheffrin, Anjali; Yoshimura, Henry; LaPlante, David; Neenan, Bernard

2008-03-15

393

CAREER GUIDE FOR DEMAND OCCUPATIONS.  

ERIC Educational Resources Information Center

THIS PUBLICATION UPDATES THE "CAREER GUIDE FOR DEMAND OCCUPATIONS" PUBLISHED IN 1959 AND PROVIDES COUNSELORS WITH INFORMATION ABOUT OCCUPATIONS IN DEMAND IN MANY AREAS WHICH REQUIRE PREEMPLOYMENT TRAINING. IT PRESENTS, IN COLUMN FORM, THE EDUCATION AND OTHER TRAINING USUALLY REQUIRED BY EMPLOYERS, HIGH SCHOOL SUBJECTS OF PARTICULAR PERTINENCE TO…

LEE, E.R.; WELCH, JOHN L.

394

The demand for league football  

Microsoft Academic Search

A demand equation is estimated for total Football League attendances for the period 1948\\/49 to 1979\\/80. Plausible values are obtained for the elasticities of demand with respect to income and to a price variable which includes the cost of travel to the stadium. The values imply that football spectating is an inferior good with a low price elasticity. Equations are

Peter J. W. N. Bird

1982-01-01

395

Global energy demand to 2060  

Microsoft Academic Search

The projection of global energy demand to the year 2060 is of particular interest because of its relevance to the current greenhouse concerns. The long-term growth of global energy demand in the time scale of climatic change has received relatively little attention in the public discussion of national policy alternatives. The sociological, political, and economic issues have rarely been mentioned

Starr

1989-01-01

396

China, India demand cushions prices  

SciTech Connect

Despite the hopes of coal consumers, coal prices did not plummet in 2006 as demand stayed firm. China and India's growing economies, coupled with solid supply-demand fundamentals in North America and Europe, and highly volatile prices for alternatives are likely to keep physical coal prices from wide swings in the coming year.

Boyle, M.

2006-11-15

397

Promotion and Fast Food Demand  

Microsoft Academic Search

Many believe that fast food promotion is a significant cause of the obesity epidemic in North America. Industry members argue that promotion only reallocates brand shares and does not increase overall demand. We study the effect of fast food promotion on market share and total demand by estimating a discrete / continuous model of fast food restaurant choice and food

Timothy J. Richards; Luis Padilla

2009-01-01

398

Demand Response for Ancillary Services  

SciTech Connect

Many demand response resources are technically capable of providing ancillary services. In some cases, they can provide superior response to generators, as the curtailment of load is typically much faster than ramping thermal and hydropower plants. Analysis and quantification of demand response resources providing ancillary services is necessary to understand the resources economic value and impact on the power system. Methodologies used to study grid integration of variable generation can be adapted to the study of demand response. In the present work, we describe and illustrate a methodology to construct detailed temporal and spatial representations of the demand response resource and to examine how to incorporate those resources into power system models. In addition, the paper outlines ways to evaluate barriers to implementation. We demonstrate how the combination of these three analyses can be used to translate the technical potential for demand response providing ancillary services into a realizable potential.

Alkadi, Nasr E [ORNL; Starke, Michael R [ORNL

2013-01-01

399

Simultaneous analysis of oxygenated and nitrated polycyclic aromatic hydrocarbons on standard reference material 1649a (urban dust) and on natural ambient air samples by gas chromatography-mass spectrometry with negative ion chemical ionisation.  

PubMed

This study deals with the development of a routine analytical method using gas chromatography-mass spectrometry with negative ion chemical ionisation (GC/NICI-MS) for the determination of 17 nitrated polycyclic aromatic hydrocarbons (NPAHs) and 9 oxygenated polycyclic aromatic hydrocarbons (OPAHs) present at low concentrations in the atmosphere. This method includes a liquid chromatography purification procedure on solid-phase extraction (SPE) cartridge. Application of this analytical procedure has been performed on standard reference material (SRM 1649a: urban dust), giving results in good agreement with the few data available in the literature. The analytical method was also applied on ambient air samples (on both gas and particulate phases) from the French POVA program (POllution des Vallées Alpines). NPAHs concentrations observed for a rural site during the Winter period are about 0.2-100.0pgm(-3) in the particulate phase and about 0.0-20.0pgm(-3) in the gas phase. OPAHs present concentrations 10-100 times higher (0.1-2.0ngm(-3) and 0.0-1.4ngm(-3) for the particulate and the gas phases, respectively). These preliminary results show a good correlation between the characteristics of the sampling site and the compound origins (primary or secondary). PMID:16682050

Albinet, A; Leoz-Garziandia, E; Budzinski, H; Viilenave, E

2006-07-14

400

Simultaneous determination by ultra-performance liquid chromatography-atmospheric pressure chemical ionization time-of-flight mass spectrometry of nitrated and oxygenated PAHs found in air and soot particles.  

PubMed

An ultra-performance liquid chromatographic-atmospheric pressure chemical ionization time-of-flight mass spectrometric (UPLC-APCIToFMS) method for rapid analysis of twelve nitrated polycyclic aromatic hydrocarbons (NPAHs) and nine oxygenated polycyclic aromatic hydrocarbons (OPAHs) in particle samples has been developed. The extraction step using pressurized liquid extraction was optimized by experimental design methods and the concentrated extracts were analyzed without further clean-up. Matrix effects resulting in suppression or enhancement of the response during the ionization step were not observed. The suitability of the developed method is demonstrated by analysis of six different particle samples including standard reference materials, atmospheric particles collected by a high-volume sampler at an urban background site, and a soot sample from a burner. Results from these measurements showed clear differences between the different kinds of samples. Concentrations from reference materials are in good agreement with those from previous studies. Additionally a clear seasonal trend could be observed in atmospheric NPAH and OPAH concentrations found in real samples, with higher concentrations in winter. PMID:20101503

Mirivel, Giovanni; Riffault, Véronique; Galloo, Jean-Claude

2010-05-01

401

OXYGEN TRANSPORT CERAMIC MEMBRANES  

SciTech Connect

Conversion of natural gas to liquid fuels and chemicals is a major goal for the Nation as it enters the 21st Century. Technically robust and economically viable processes are needed to capture the value of the vast reserves of natural gas on Alaska's North Slope, and wean the Nation from dependence on foreign petroleum sources. Technologies that are emerging to fulfill this need are all based syngas as an intermediate. Syngas (a mixture of hydrogen and carbon monoxide) is a fundamental building block from which chemicals and fuels can be derived. Lower cost syngas translates directly into more cost-competitive fuels and chemicals. The currently practiced commercial technology for making syngas is either steam methane reforming (SMR) or a two-step process involving cryogenic oxygen separation followed by natural gas partial oxidation (POX). These high-energy, capital-intensive processes do not always produce syngas at a cost that makes its derivatives competitive with current petroleum-based fuels and chemicals.

Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

2002-01-01

402

Chemical feedstocks from coal  

Microsoft Academic Search

In theory, coal can provide all the chemical feedstocks now derived from oil; however, coal-chemistry technology has become outdated and needs to be improved to meet today's economic and technical demands. To bridge this gap, this collection of essays (translated from German) presents the current possibilities for producing organic chemicals from coal and suggests some routes for future developmental work.

J. Falbe; E. Ahland; G. Baron

1982-01-01

403

Modelling electricity demand with representative load curves  

Microsoft Academic Search

Models for electricity planning require inclusion of demand. Depending on the type of planning, the demand is usually represented as an annual demand for electricity (GWh), a peak demand (MW) or in the form of annual load–duration curves. The demand for electricity varies with the seasons, economic activities, etc. Existing schemes do not capture the dynamics of demand variations that

P. Balachandra; Vijay Chandru

1999-01-01

404

Demand responsive passenger transport in low-demand situations  

Microsoft Academic Search

Demand responsive services (DRT) are seen as a cure for high-cost bus services in low-demand areas. DRT services cover a wide spectrum and international experience shows mixed success. In 2009\\/10 Booz and Company investigated DRT services to understand common success and failures. An international literature review was conducted, as well as assessing three New Zealand\\/Australian case studies as follows:• community

R. A. Scott

2010-01-01

405

Temperature and pressure dependent solubility of oxygen in water: a thermodynamic analysis  

Microsoft Academic Search

A thermodynamic analysis of the temperature dependent equilibrium between oxygen solubility (activity) in pure water and oxygen partial pressure PO2 was undertaken. Experimental oxygen solubility sources were used to determine a set of self consistent values for the chemical potential, entropy and partial molar heat capacity of dissolved oxygen. These were combined with established thermodynamic data for gaseous oxygen to

Desmond Tromans

1998-01-01

406

Visualizing chemical reactions and crossover processes in a fuel cell inserted in the ESR resonator: detection by spin trapping of oxygen radicals, nafion-derived fragments, and hydrogen and deuterium atoms.  

PubMed

We present experiments in an in situ fuel cell (FC) inserted in the resonator of the ESR spectrometer that offered the ability to observe separately processes at anode and cathode sides and to monitor the formation of HO and HOO radicals, H and D atoms, and radical fragments derived from the Nafion membrane. The presence of the radicals was determined by spin-trapping electron spin resonance (ESR) with 5,5-dimethylpyrroline N-oxide (DMPO) as a spin trap. The in situ FC was operated at 300 K with a membrane-electrode assembly (MEA) based on Nafion 117 and Pt as catalyst, at closed and open circuit voltage conditions, CCV and OCV, respectively. Experiments with H(2) or D(2) at the anode and O(2) at the cathode were performed. The DMPO/OH adduct was detected only at the cathode for CCV operation, suggesting generation of hydroxyl radicals from H(2)O(2) formed electrochemically via the two-electron reduction of oxygen. The DMPO/OOH adduct, detected in this study for the first time in a FC, appeared at the cathode and anode for OCV operation, and at the cathode after CCV FC operation of >or=2 h. These results were interpreted in terms of electrochemical generation of HOO at the cathode (HO + H(2)O(2) --> H(2)O + HOO) and its chemical generation at the anode from hydrogen atoms and crossover oxygen (H + O(2) --> HOO). DMPO/H and DMPO/D adducts were detected at the anode and cathode sides, for CCV and OCV operation; H and D are aggressive radicals capable of abstracting fluorine from the tertiary carbon in the polymer membrane chain and of leading to chain fragmentation. Carbon-centered radical (CCR) adducts were detected at the cathode after CCV FC operation; weak CCR signals were also detected at the anode. CCRs can originate only from the Nafion membranes, and their presence indicates membrane fragmentation. Taken together, this study has demonstrated that FC operation involves processes such as gas crossover, reactions at the catalyst surface, and possible attack of the membrane by reactive H or D that do not occur in ex situ experiments in the laboratory, thus implying different mechanistic pathways in the two types of experiments. PMID:19453175

Danilczuk, Marek; Coms, Frank D; Schlick, Shulamith

2009-06-11

407

Physical, chemical, and biological characteristics of compounds used in hydraulic fracturing.  

PubMed

Hydraulic fracturing (HF), a method to enhance oil and gas production, has become increasingly common throughout the U.S. As such, it is important to characterize the chemicals found in HF fluids to evaluate potential environmental fate, including fate in treatment systems, and human health impacts. Eighty-one common HF chemical additives were identified and categorized according to their functions. Physical and chemical characteristics of these additives were determined using publicly available chemical information databases. Fifty-five of the compounds are organic and twenty-seven of these are considered readily or inherently biodegradable. Seventeen chemicals have high theoretical chemical oxygen demand and are used in concentrations that present potential treatment challenges. Most of the HF chemicals evaluated are non-toxic or of low toxicity and only three are classified as Category 2 oral toxins according to standards in the Globally Harmonized System of Classification and Labeling of Chemicals; however, toxicity information was not located for thirty of the HF chemicals evaluated. Volatilization is not expected to be a significant exposure pathway for most HF chemicals. Gaps in toxicity and other chemical properties suggest deficiencies in the current state of knowledge, highlighting the need for further assessment to understand potential issues associated with HF chemicals in the environment. PMID:24853136

Stringfellow, William T; Domen, Jeremy K; Camarillo, Mary Kay; Sandelin, Whitney L; Borglin, Sharon

2014-06-30

408

Integrated Oxygen-Recovery System  

NASA Technical Reports Server (NTRS)

System for revitalizing breathing air in enclosed environment converts carbon dioxide and water to oxygen and methane. Chemical conversions take place in reactor module containing solid-metal-cathode water electrolyzer integrated with Sabatier reactor. According to design estimates, fully developed version of system sized to maintain breathable air for four persons, occupies 67 percent less volume, weighs 60 percent less, and consumes 3.4 percent less power than system of same capacity in which electrolyzer and Sabatier reactor are distinct components. Although oxygen primary desired end product in system originally contemplated, product methane also of value in industrial version of system.

Schubert, F. H.; Davenport, R. J.; Lee, M. G.

1996-01-01

409

Guidelines for Forecasting Energy Demand.  

National Technical Information Service (NTIS)

Four methodologies for forecasting energy demand are reviewed after considering the role of energy in the economy and the analysis of energy use in different economic sectors. The special case of Israel is considered throughout, and some forecasts for ene...

T. Sonnino

1976-01-01

410

Probability Distribution of Leadtime Demand.  

National Technical Information Service (NTIS)

This study examines 11 probability distributions to determine which distribution best describes demand during leadtime for 1H Cognizance Symbol (Cog) material. Proper selection of the distribution is critical in the accurate calculation of reorder levels....

A. P. Urban J. A. Mellinger G. Evans

1984-01-01

411

Saving Electricity and Demand Response  

NASA Astrophysics Data System (ADS)

A lot of people lost their lives in the tremendous earthquake in Tohoku region on March 11. A large capacity of electric power plants in TEPCO area was also damaged and large scale power shortage in this summer is predicted. In this situation, electricity customers are making great effort to save electricity to avoid planned outage. Customers take actions not only by their selves but also by some customers' cooperative movements. All actions taken actually are based on responses to request form the government or voluntary decision. On the other hand, demand response based on a financial stimulus is not observed as an actual behavior. Saving electricity by this demand response only discussed in the newspapers. In this commentary, the events regarding electricity-saving measure after this disaster are described and the discussions on demand response, especially a raise in power rate, are put into shapes in the context of this electricity supply-demand gap.

Yamaguchi, Nobuyuki

412

The jumbo squid, Dosidicus gigas (Ommastrephidae), living in oxygen minimum zones II: Blood-oxygen binding  

NASA Astrophysics Data System (ADS)

Dosidicus gigas is a large, metabolically active squid that migrates across a strong oxygen and temperature gradient in the Eastern Pacific. Here we analyze the oxygen-binding properties of the squid's respiratory protein (hemocyanin, Hc) that facilitate such activity. A high Hc-oxygen affinity, strong temperature dependence, and pronounced pH sensitivity (P50=0.009T2.03, pH 7.4; Bohr coefficient=?logP50/?pH=-1.55+0.034T) of oxygen binding facilitate night-time foraging in the upper water column, and support suppressed oxygen demand in hypoxic waters at greater depths. Expanding hypoxia may act to alter the species habitable depth range. This analysis supports the contention that ocean acidification could limit oxygen carrying capacity in squids at warmer temperature leading to reduced activity levels or altered distribution.

Seibel, Brad A.

2013-10-01

413

Copper-Exchanged Zeolite L Traps Oxygen  

NASA Technical Reports Server (NTRS)

Brief series of simple chemical treatments found to enhance ability of zeolite to remove oxygen from mixture of gases. Thermally stable up to 700 degrees C and has high specific surface area which provides high capacity for adsorption of gases. To increase ability to adsorb oxygen selectively, copper added by ion exchange, and copper-exchanged zeolite reduced with hydrogen. As result, copper dispersed atomically on inner surfaces of zeolite, making it highly reactive to oxygen, even at room temperature. Reactivity to oxygen even greater at higher temperatures.

Sharma, Pramod K.; Seshan, Panchalam K.

1991-01-01

414

Demand Response Spinning Reserve Demonstration  

SciTech Connect

The Demand Response Spinning Reserve project is a pioneeringdemonstration of how existing utility load-management assets can providean important electricity system reliability resource known as spinningreserve. Using aggregated demand-side resources to provide spinningreserve will give grid operators at the California Independent SystemOperator (CAISO) and Southern California Edison (SCE) a powerful, newtool to improve system reliability, prevent rolling blackouts, and lowersystem operating costs.

Eto, Joseph H.; Nelson-Hoffman, Janine; Torres, Carlos; Hirth,Scott; Yinger, Bob; Kueck, John; Kirby, Brendan; Bernier, Clark; Wright,Roger; Barat, A.; Watson, David S.

2007-05-01

415

Personalized Demand Responsive Transit Systems  

Microsoft Academic Search

An aging population in the US, low-density urban sprawl and the accessibility needs of certain groups (particularly disabled and aged) increasingly point to more flexible demand-responsive transit systems in the future. This paper describes the important aspects of a consumer-oriented Personalized Demand Responsive Transit (PDRT) service. The system will provide services to the traveling public for journeys to work and

Y. B. Yim; Asad J. Khattak

2000-01-01

416

The oxygen paradox of neurovascular coupling.  

PubMed

The coupling of cerebral blood flow (CBF) to neuronal activity is well preserved during evolution. Upon changes in the neuronal activity, an incompletely understood coupling mechanism regulates diameter changes of supplying blood vessels, which adjust CBF within seconds. The physiologic brain tissue oxygen content would sustain unimpeded brain function for only 1?second if continuous oxygen supply would suddenly stop. This suggests that the CBF response has evolved to balance oxygen supply and demand. Surprisingly, CBF increases surpass the accompanying increases of cerebral metabolic rate of oxygen (CMRO2). However, a disproportionate CBF increase may be required to increase the concentration gradient from capillary to tissue that drives oxygen delivery. However, the brain tissue oxygen content is not zero, and tissue pO2 decreases could serve to increase oxygen delivery without a CBF increase. Experimental evidence suggests that CMRO2 can increase with constant CBF within limits and decreases of baseline CBF were observed with constant CMRO2. This conflicting evidence may be viewed as an oxygen paradox of neurovascular coupling. As a possible solution for this paradox, we hypothesize that the CBF response has evolved to safeguard brain function in situations of moderate pathophysiological interference with oxygen supply. PMID:24149931

Leithner, Christoph; Royl, Georg

2014-01-01

417

Oxygen chemisorption cryogenic refrigerator  

Microsoft Academic Search

The present invention relates to a chemisorption compressor cryogenic refrigerator which employs oxygen to provide cooling at 60 to 100 K. The invention includes dual vessels containing an oxygen absorbent material, alternately heated and cooled to provide a continuous flow of high pressure oxygen, multiple heat exchangers for precooling the oxygen, a Joule-Thomson expansion valve system for expanding the oxygen

Jack A. Jones

1987-01-01

418

Oxygen-iodine laser research at RFNC-VNIIEF  

Microsoft Academic Search

The paper presents the most important efforts in the Chemical Oxygen-Iodine Laser (COIL) research carried on at Russian Federal Nuclear Center VNIIEF and some of their results. In particular, they include experimental data on the laser generation output of subsonic COIL on the water vapor concentration in singlet oxygen, calculated generation values of a supersonic COIL having high singlet oxygen

Anatoliy A. Adamenkov; Yuri N. Deryugin; Boris A. Vyskubenko; S. P. Ilyin; V. V. Kalinovsky; Yuriy V. Kolobyanin; V. V. Konovalov; Ivan M. Krukovsky; Evgeniy A. Kudryashov; V. D. Nikolaev

1998-01-01

419

Erythrocytes: Oxygen Sensors and Modulators of Vascular Tone  

NSDL National Science Digital Library

Through oxygen-dependent release of the vasodilator ATP, the mobile erythrocyte plays a fundamental role in matching microvascular oxygen supply with local tissue oxygen demand. Signal transduction within the erythrocyte and microvessels as well as feedback mechanisms controlling ATP release have been described. Our understanding of the impact of this novel control mechanism will rely on the integration of in vivo experiments and computational models.

Mary L. Ellsworth (Saint Louis University); Christopher Ellis (University of Western Ontario); Hans Dietrich (Washington University School of Medicine)

2009-04-01

420

Hyperbaric oxygen therapy  

MedlinePLUS

Hyperbaric oxygen therapy uses a special chamber, sometimes called a pressure chamber, to increase the amount of oxygen in ... the atmosphere. This helps your blood carry more oxygen to organs ... therapy can help wounds, especially infected wounds, heal more ...

421

Living with Oxygen Therapy  

MedlinePLUS

... page from the NHLBI on Twitter. Living With Oxygen Therapy Oxygen therapy helps many people function better and be ... chronic obstructive pulmonary disease) Although you may need oxygen therapy continuously or for long periods, it doesn' ...

422

Oxygen Injection System.  

National Technical Information Service (NTIS)

The oxygen injection system is for afterburners and ramjets which employs a particular type of flameholder structure for assisting in the distribution of oxygen. The design of the concentric flameholders is such that only a single oxygen line is required ...

R. E. Meyer W. E. Helfrich

1965-01-01

423

Oxygen incorporation in rubrene single crystals.  

PubMed

Single crystal rubrene is a model organic electronic material showing high carrier mobility and long exciton lifetime. These properties are detrimentally affected when rubrene is exposed to intense light under ambient conditions for prolonged periods of time, possibly due to oxygen up-take. Using photoelectron, scanning probe and ion-based methods, combined with an isotopic oxygen exposure, we present direct evidence of the light-induced reaction of molecular oxygen with single crystal rubrene. Without a significant exposure to light, there is no reaction of oxygen with rubrene for periods of greater than a year; the crystal's surface (and bulk) morphology and chemical composition remain essentially oxygen-free. Grand canonical Monte Carlo computations show no sorbtion of gases into the bulk of rubrene crystal. A mechanism for photo-induced oxygen inclusion is proposed. PMID:24786311

Mastrogiovanni, Daniel D T; Mayer, Jeff; Wan, Alan S; Vishnyakov, Aleksey; Neimark, Alexander V; Podzorov, Vitaly; Feldman, Leonard C; Garfunkel, Eric

2014-01-01

424

Oxygen Incorporation in Rubrene Single Crystals  

NASA Astrophysics Data System (ADS)

Single crystal rubrene is a model organic electronic material showing high carrier mobility and long exciton lifetime. These properties are detrimentally affected when rubrene is exposed to intense light under ambient conditions for prolonged periods of time, possibly due to oxygen up-take. Using photoelectron, scanning probe and ion-based methods, combined with an isotopic oxygen exposure, we present direct evidence of the light-induced reaction of molecular oxygen with single crystal rubrene. Without a significant exposure to light, there is no reaction of oxygen with rubrene for periods of greater than a year; the crystal's surface (and bulk) morphology and chemical composition remain essentially oxygen-free. Grand canonical Monte Carlo computations show no sorbtion of gases into the bulk of rubrene crystal. A mechanism for photo-induced oxygen inclusion is proposed.

Mastrogiovanni, Daniel D. T.; Mayer, Jeff; Wan, Alan S.; Vishnyakov, Aleksey; Neimark, Alexander V.; Podzorov, Vitaly; Feldman, Leonard C.; Garfunkel, Eric

2014-05-01

425

Oxygen Incorporation in Rubrene Single Crystals  

PubMed Central

Single crystal rubrene is a model organic electronic material showing high carrier mobility and long exciton lifetime. These properties are detrimentally affected when rubrene is exposed to intense light under ambient conditions for prolonged periods of time, possibly due to oxygen up-take. Using photoelectron, scanning probe and ion-based methods, combined with an isotopic oxygen exposure, we present direct evidence of the light-induced reaction of molecular oxygen with single crystal rubrene. Without a significant exposure to light, there is no reaction of oxygen with rubrene for periods of greater than a year; the crystal's surface (and bulk) morphology and chemical composition remain essentially oxygen-free. Grand canonical Monte Carlo computations show no sorbtion of gases into the bulk of rubrene crystal. A mechanism for photo-induced oxygen inclusion is proposed.

Mastrogiovanni, Daniel D. T.; Mayer, Jeff; Wan, Alan S.; Vishnyakov, Aleksey; Neimark, Alexander V.; Podzorov, Vitaly; Feldman, Leonard C.; Garfunkel, Eric

2014-01-01

426

Oxygen delivery from red cells.  

PubMed Central

This paper deals with the theoretical analysis of the unloading of oxygen from a red cell. A scale analysis of the governing transport equations shows that the solutions have a boundary layer structure near the red-cell membrane. The boundary layer is a region of chemical nonequilibrium, and it owes its existence to the fact that the kinetic time scales are shorter than the diffusion time scales in the red cell. The presence of the boundary layer allows an analytical solution to be obtained by the method of matched asymptotic expansions. A very useful result from the analysis is a simple, lumped-parameter description of the oxygen delivery from a red cell. The accuracy of the lumped-parameter description has been verified by comparing its predictions with results obtained by numerical integration of the full equations for a one-dimensional slab. As an application, we calculate minimum oxygen unloading times for red cells.

Clark, A; Federspiel, W J; Clark, P