These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Downscaling the chemical oxygen demand test.  

PubMed

The usefulness of the standard chemical oxygen demand (COD) test for water characterization is offset to some extent by its requirement for highly toxic or expensive Cr, Ag, and Hg species. In addition, oxidation of the target samples by chromate requires a 2-3 h heating step. We have downscaled this method to obtain a reduction of up to ca. 80% in the use and generation of toxic residues and a time reduction of up to ca. 67%. This also translates into considerable energy savings by reducing the time required for heating as well as costly labour time. Such reductions can be especially important for analytical laboratories with heavy loads of COD analyses. Numerical results obtained with the standard COD method for laboratory KHP samples (potassium hydrogen phthalate) show an average relative error of 1.41% vs. an average of 2.14% obtained with the downsized or small-scale version. The average % standard deviation when using the former is 2.16% vs. 3.24% obtained with the latter. When analysing municipal wastewater samples, the relative error is smaller for the proposed small-scale method than for the standard method (0.05 vs. 0.58, respectively), and the % std. dev. is 1.25% vs. 1.06%. The results obtained with various industrial wastewaters show good agreement with those obtained using the standard method. Chloride ions do not interfere at concentrations below 2000 mg Nacl/L. This highly encouraging proof-of-concept offers a potentially alternative greener approach to COD analysis. PMID:24701932

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

2014-01-01

2

Chemical Oxygen Demand. Training Module 5.107.2.77.  

ERIC Educational Resources Information Center

This document is an instructional module package prepared in objective form for use by an instructor familiar with standard method procedures for determining the Chemical Oxygen Demand (COD) of a wastewater sample. Included are objectives, instructor guides, student handouts, and transparency masters. This module considers analytical procedures,…

Kirkwood Community Coll., Cedar Rapids, IA.

3

Estimation of Biological Oxygen Demand and Chemical Oxygen Demand for Combined Sewer Systems Using Synchronous Fluorescence Spectra  

PubMed Central

Real-time monitoring of water quality for sewer system is required for efficient sewer network design because it provides information on the precise loading of pollutant to wastewater treatment facilities and the impact of loading on receiving water. In this study, synchronous fluorescence spectra and its first derivatives were investigated using a number of wastewater samples collected in sewer systems in urban and non-urban areas, and the optimum fluorescence feature was explored for the estimation of biochemical oxygen demand (BOD) and chemical oxygen demand (COD) concentrations of sewer samples. The temporal variations in BOD and COD showed a regular pattern for urban areas whereas they were relatively irregular for non-urban areas. Irrespective of the sewer pipes and the types of the areas, two distinct peaks were identified from the synchronous fluorescence spectra, which correspond to protein-like fluorescence (PLF) and humic-like fluorescence (HLF), respectively. HLF in sewer samples appears to be associated with fluorescent whitening agents. Five fluorescence characteristics were selected from the synchronous spectra and the first-derivatives. Among the selected fluorescence indices, a peak in the PLF region (i.e., Index I) showed the highest correlation coefficient with both BOD and COD. A multiple regression approach based on suspended solid (SS) and Index I used to compensate for the contribution of SS to BOD and COD revealed an improvement in the estimation capability, showing good correlation coefficients of 0.92 and 0.94 for BOD and COD, respectively. PMID:22319257

Hur, Jin; Lee, Bo-Mi; Lee, Tae-Hwan; Park, Dae-Hee

2010-01-01

4

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

5

[Determination of chemical oxygen demand in water using near infrared transmission and UV absorbance method].  

PubMed

Chemical oxygen demand (COD) is a synthetical indicator which represents the degree of organic pollution in water. The near-infrared (NIR) transmission and the UV absorbance method based on photoelectric detection technology and spectroscopy analysis have some advantages such as high precision, speed, non-contact, no secondary pollution etc compared to conventional wet chemical method. The NIR transmission spectra and UV absorbance spectra of standard solution configured with phthalate hydrogen potassium were collected respectively by MPA FTIR spectrometer (Bruker Optics Inc.) made in Germany and AvaSpec-2048-2 UV spectrometer (Avantes Inc.) made in Netherlands. After different pretreatment to the spectra, COD quantitative analysis model was established using partial least squares regression (PLS) and linear regression. The statistical analysis of COD quantitative model was implemented, and the result showed that UV absorbance method had a higher relevance but lower forecast accuracy and precision than NIR transmission method. PMID:21847915

Wu, Guo-Qing; Bi, Wei-Hong; Lui, Jia-Ming; Fu, Guang-Wei

2011-06-01

6

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. PMID:22829788

Zhao, Xiaofeng; Huang, Xianjin; Liu, Yibo

2012-01-01

7

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

8

Peroxone mineralization of chemical oxygen demand for direct potable water reuse: Kinetics and process control.  

PubMed

Mineralization of organics in secondary effluent by the peroxone process was studied at a direct potable water reuse research treatment system serving an occupied four-bedroom, four bath university residence hall apartment. Organic concentrations were measured as chemical oxygen demand (COD) and kinetic runs were monitored at varying O3/H2O2 dosages and ratios. COD degradation could be accurately described as the parallel pseudo-1st order decay of rapidly and slowly-oxidizable fractions, and effluent COD was reduced to below the detection limit (<0.7 mg/L). At dosages ?4.6 mg L(-1) h(-1), an O3/H2O2 mass ratio of 3.4-3.8, and initial COD <20 mg/L, a simple first order decay was indicated for both single-passed treated wastewater and recycled mineral water, and a relationship is proposed and demonstrated to estimate the pseudo-first order rate constant for design purposes. At this O3/H2O2 mass ratio, ORP and dissolved ozone were found to be useful process control indicators for monitoring COD mineralization in secondary effluent. Moreover, an average second order rate constant for OH oxidation of secondary effluent organics (measured as MCOD) was found to be 1.24 × 10(7) ± 0.64 × 10(7) M(-1) S(-1). The electric energy demand of the peroxone process is estimated at 1.73-2.49 kW h electric energy for removal of one log COD in 1 m(3) secondary effluent, comparable to the energy required for desalination of medium strength seawater. Advantages/disadvantages of the two processes for municipal wastewater reuse are discussed. PMID:25704155

Wu, Tingting; Englehardt, James D

2015-04-15

9

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. PMID:24940868

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

2014-01-01

10

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

11

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

NASA Astrophysics Data System (ADS)

This paper proposes integration of k-means clustering and multi-layer perceptron (k-means-MLP) methods in modelling chemical oxygen demand (COD) concentration. This proposed method was tested by using daily measured water suspended solids, pH, temperature, discharge and COD concentration data of upstream of the municipal wastewater treatment plant system in Adapazari province of Turkey. Performance of the k-means-MLP method was compared with multi-linear regression, multi-layer perceptron, radial-based neural network, generalized regression neural network, and two different adaptive neuro-fuzzy inference system techniques (subtractive clustering and grid partition). Root mean square error, mean absolute error, mean absolute relative error and determination coefficient statistics were employed for the evaluation accuracy of each model. It was found that the k-means-MLP performed better than the other techniques in estimating COD. Moreover, the k-means clustering combined with the MLP could be used as a tool in modelling daily COD concentration.

Ay, Murat; Kisi, Ozgur

2014-04-01

12

Electrochemical nanocomposite-derived sensor for the analysis of chemical oxygen demand in urban wastewaters.  

PubMed

This work reports on the fabrication and comparative analytical assessment of electrochemical sensors applied to the rapid analysis of chemical oxygen demand (COD) in urban waste waters. These devices incorporate a carbon nanotube-polystyrene composite, containing different inorganic electrocatalysts, namely, Ni, NiCu alloy, CoO, and CuO/AgO nanoparticles. The sensor responses were initially evaluated using glucose as standard analyte and then by analyzing a set of real samples from urban wastewater treatment plants. The estimated COD values in the samples were compared with those provided by an accredited laboratory using the standard dichromate method. The sensor prepared with the CuO/AgO-based nanocomposite showed the best analytical performance. The recorded COD values of both the sensor and the standard method were overlapped, considering the 95% confidence intervals. In order to show the feasible application of this approach for the detection of COD online and in continuous mode, the CuO/AgO-based nanocomposite sensor was integrated in a compact flow system and applied to the detection of wastewater samples, showing again a good agreement with the values provided by the dichromate method. PMID:25594378

Gutiérrez-Capitán, Manuel; Baldi, Antoni; Gómez, Raquel; García, Virginia; Jiménez-Jorquera, Cecilia; Fernández-Sánchez, César

2015-02-17

13

Rapid Determination of the Chemical Oxygen Demand of Water Using a Thermal Biosensor  

PubMed Central

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

14

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

15

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

16

Removal of chemical oxygen demand and dissolved nutrients by a sunken lawn infiltration system during intermittent storm events.  

PubMed

Urban surface water runoff typically contains high but varying amounts of organic matter and nutrients that require removal before reuse. Infiltration systems such as sunken lawns can improve water quality. However, there is currently insufficient information describing the treatment efficiency of lawn-based infiltration systems. In this study, novel sunken lawn infiltration systems (SLISs) were designed and their pollutant removal effectiveness was assessed. The results revealed that SLISs with Poa pratensis and Lolium perenne effectively removed most chemical oxygen demand (CODCr) and dissolved nutrients. Average CODCr, total nitrogen (TN), ammonium-nitrogen (NH4(+)-N) and total phosphorus (TP) concentrations were reduced by 78.93, 66.64, 71.86 and 75.83%, respectively, and the corresponding effluent concentrations met the standard for urban miscellaneous water consumption in China. The NH4(+)-N in the synthetic runoff was shown to be removed by adsorption during the stormwater dosing and nitrification during subsequent dry days, as well as through uptake by plants. Phosphorus was mainly removed by adsorption and chemical precipitation. The NH4(+)-N and phosphorus Langmuir isotherm model fitted the clay loam soil adsorption process better than the Freundlich model. Overall, these results indicate that an SLIS provides an alternative means of removing runoff pollutants owing to its efficiency, easy operation and maintenance. PMID:24473312

Hou, Lizhu; Yang, Huan; Li, Ming

2014-01-01

17

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

Microsoft Academic Search

This study investigated the ability of an anaerobic\\/anoxic\\/oxic (A\\/O) system to treat a slaughterhouse wastewater. The system employed two identical continuous-flow reactors (10 l 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

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

2011-01-01

18

Performance of on-site pilot static granular bed reactor (SGBR) for treating dairy processing wastewater and chemical oxygen demand balance modeling under different operational conditions.  

PubMed

The performance and operational stability of a pilot-scale static granular bed reactor (SGBR) for the treatment of dairy processing wastewater were investigated under a wide range of organic and hydraulic loading rates and temperature conditions. The SGBR achieved average chemical oxygen demand (COD), biological oxygen demand (BOD), and total suspended solids (TSS)-removal efficiencies higher than 90 % even at high loading rates up to 7.3 kg COD/m(3)/day, with an hydraulic retention time (HRT) of 9 h, and at low temperatures of 11 °C. The average methane yield of 0.26 L CH4/g CODremoved was possibly affected by a high fraction of particulate COD and operation at low temperatures. The COD mass balance indicated that soluble COD was responsible for most of the methane production. The reactor showed the capacity of the methanogens to maintain their activity and withstand organic and hydraulic shock loads. PMID:25164570

Oh, Jin Hwan; Park, Jaeyoung; Ellis, Timothy G

2015-02-01

19

Dissolved Oxygen and Biochemical Oxygen Demand  

NSDL National Science Digital Library

This Environmental Protection Agency (EPA) website provides general information about dissolved oxygen, including what it is, sampling and equipment considerations, and sampling and analysis protocols. The site also features a chart of dissolved oxygen solubility as a function of temperature.

20

ENHANCED COD (CHEMICAL OXYGEN DEMAND) REMOVAL FROM PHARMACEUTICAL WASTEWATER USING POWDERED ACTIVATED CARBON ADDITION TO AN ACTIVATED SLUDGE SYSTEM  

EPA Science Inventory

Wastewater generated by the pharmaceutical manufacturing point source Sub-categories A (Fermentation Products) and C (Chemical Synthesis Products) are characterized by high COD concentrations (10,000 mg/l and higher). Plants in these subcategories typically employ secondary treat...

21

Ozonation of sludge-press liquors: Determination of carbonyl compounds by the PFBOA method and the effect on the chemical oxygen demand  

SciTech Connect

The European Community Urban Waste Water Treatment Directive, May 1991, requires water service companies to provide sufficient wastewater treatment to meet a new limit set for the Chemical Oxygen Demand (COD) in final effluent and new legislation has placed limits on the levels of COD that can be discharged from wastewater treatment works using secondary treatment processes. The current permitted upper level for COD in the final effluent is 125 mg per litre. Ozone is a strong oxidant and disinfectant and in contrast to chlorine, does not produce chlorinated by-products from its reaction with natural organic matter in water. In spite of the successful use of ozone for the treatment of potable waters since the early part of the century very few studies have been undertaken into possible chemical by-products which might arise from ozonation. Since the amount of ozone applied is always lower than that required to oxidize all the organic matter to carbon dioxide and water, a number of semi-oxidation products such as aromatic, phenolic and aliphatic carboxylic acids, aldehydes and ketones can be expected to be formed. The ozonation of sludge-press liquors and the resultant effect on COD was investigated. The concentration of carbonyl compounds was analyzed using O-(pentafluorobenzyl) hydroxylamine (PFBOA) as a derivatising agent in Gas Chromatographic (GC) determination.

Boyle, L.L.; McCullough, N.H. [Univ. Chemical Lab., Kent (United Kingdom); Poppelen, P. van [Southern Water Services Limited, Kent (United Kingdom)

1996-12-31

22

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

23

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

PubMed

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 m(3)/(m(2)?d). Various COD concentrations were used to adjust organic loading rates from 1.5 to 4.5 kg COD/(m(3)?d). An average COD removal efficiency of (85.10±6.40)% was achieved in all wastewater concentrations at a hydraulic loading of 6.4 m(3)/(m(2)?d). The results lead to a design organic load of 1.5 kg COD/(m(3)?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. PMID:24101209

Habte Lemji, Haimanot; Eckstädt, Hartmut

2013-10-01

24

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. PMID:24101209

Habte Lemji, Haimanot; Eckstädt, Hartmut

2013-01-01

25

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

26

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...

27

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...

28

Scalable chemical oxygen - iodine laser  

SciTech Connect

The problem of scaling chemical oxygen - iodine lasers (COILs) is discussed. The results of experimental study of a twisted-aerosol singlet oxygen generator meeting the COIL scalability requirements are presented. The energy characteristics of a supersonic COIL with singlet oxygen and iodine mixing in parallel flows are also experimentally studied. The output power of {approx}7.5 kW, corresponding to a specific power of 230 W cm{sup -2}, is achieved. The maximum chemical efficiency of the COIL is {approx}30%.

Adamenkov, A A; Bakshin, V V; Vyskubenko, B A; Efremov, V I; Il'in, S P; Ilyushin, Yurii N; Kolobyanin, Yu V; Kudryashov, E A; Troshkin, M V [Russian Federal Nuclear Center 'All-Russian Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod region (Russian Federation)

2011-12-31

29

Role of H2O2 in the fluctuating patterns of COD (chemical oxygen demand) during the treatment of palm oil mill effluent (POME) using pilot scale triple frequency ultrasound cavitation reactor.  

PubMed

Palm oil mill effluent (POME) is a highly contaminating wastewater due to its high chemical oxygen demand (COD) and biochemical oxygen demand (BOD). Conventional treatment methods require longer residence time (10-15 days) and higher operating cost. Owing to this, finding a suitable and efficient method for the treatment of POME is crucial. In this investigation, ultrasound cavitation technology has been used as an alternative technique to treat POME. Cavitation is the phenomenon of formation, growth and collapse of bubbles in a liquid. The end process of collapse leads to intense conditions of temperature and pressure and shock waves which assist various physical and chemical transformations. Two different ultrasound systems i.e. ultrasonic bath (37 kHz) and a hexagonal triple frequency ultrasonic reactor (28, 40 and 70 kHz) of 15 L have been used. The results showed a fluctuating COD pattern (in between 45,000 and 60,000 mg/L) while using ultrasound bath alone, whereas a non-fluctuating COD pattern with a final COD of 27,000 mg/L was achieved when hydrogen peroxide was introduced. Similarly for the triple frequency ultrasound reactor, coupling all the three frequencies resulted into a final COD of 41,300 mg/L compared to any other individual or combination of two frequencies. With the possibility of larger and continuous ultrasonic cavitational reactors, it is believed that this could be a promising and a fruitful green process engineering technique for the treatment of POME. PMID:24485395

Manickam, Sivakumar; Abidin, Norhaida binti Zainal; Parthasarathy, Shridharan; Alzorqi, Ibrahim; Ng, Ern Huay; Tiong, Timm Joyce; Gomes, Rachel L; Ali, Asgar

2014-07-01

30

FIGURE 1.1: BIOLOGICAL OXYGEN DEMAND VERSUS CIVIL LIBERTIES: Figure 1.1a  

E-print Network

-value: 0.3636 #12;Figure 1.3b #12;Figure 1.3c #12;Figure 1.3d #12;FIGURE 2.1: CHEMICAL OXYGEN DEMAND VERSUS.929653966824" "coef.vec: - 0.432628405197114" #12;Figure 2.3b #12;Figure 2.3c #12;Figure 2.3d #12;FIGURE 3APPENDIX 1 FIGURE 1.1: BIOLOGICAL OXYGEN DEMAND VERSUS CIVIL LIBERTIES: Figure 1.1a Estimate Std

Lin, C.-Y. Cynthia

31

Chapter A7. Section 7.0. Five-Day Biochemical Oxygen Demand  

USGS Publications Warehouse

The presence of a sufficient concentration of dissolved oxygen is critical to maintaining the aquatic life and aesthetic quality of streams and lakes. Determinng how organic matter affects the concentration of dissolved oxygen (DO) in a stream or lake is integral to water-quality management. The decay of organic matter in water is measured as biochemical or chemical oxygen demand. This report describes the field protocols used by U.S. Geological Survey (USGS) personnel to determine the five-day test for biochemical oxygen demand.

Delzer, Gregory C.; McKenzie, Stuart W.

1999-01-01

32

PRIMARY RESEARCH PAPER Water column oxygen demand and sediment oxygen flux  

E-print Network

creeks Introduction Tidal creeks along the coast of the southeastern United States periodicallyPRIMARY RESEARCH PAPER Water column oxygen demand and sediment oxygen flux: patterns of oxygen metals and sediments are heavily influenced by oxygen consumption or uptake (Medine et al., 1980). Toxic

Mallin, Michael

33

Modeling In situ sediment oxygen demand in the Arroyo Colorado  

E-print Network

MODELING IN SITU SEDIMENT OXYGEN DEMAND IN THE ARROYO COLORADO A Thesis by KEVIN RAY KASPRZAK Submitted to the Office of Graduate Studies of Texas Ab'cM University in partial fulfillment of the requirements for the degree of MASTER... OF SCIENCE May 2001 Major Subject: Agricultural Engineering MODELING IJYSITU SEDIMENT OXYGEN DEMAND IN THE ARROYO COLORADO A Thesis By KEVIN RAY KASPRZAK Submitted to Texas A&M University in partial fulfillment of the requirements for the degree...

Kasprzak, Kevin Ray

2001-01-01

34

Effects of arteriovenous fistulas on cardiac oxygen supply and demand  

Microsoft Academic Search

Effects of arteriovenous fistulas on cardiac oxygen supply and demand.BackgroundArteriovenous (AV) fistulas used for hemodialysis access may affect cardiac load by increasing the preload while decreasing the afterload. In dogs, AV fistulas have also been shown to affect coronary perfusion negatively. We investigated the net effect of AV fistulas on cardiac oxygen supply and demand.MethodsAortic pressure waves were reconstructed from

Willem Jan W. Bos; Robert Zietse; Karel H. Wesseling; Nico Westerhof

1999-01-01

35

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...

36

Impact of food to microorganism (F/M) ratio and colloidal chemical oxygen demand on nitrification performance of a full-scale membrane bioreactor treating thin film transistor liquid crystal display wastewater.  

PubMed

This study investigated impact of food to microorganism (F/M) ratio and colloidal chemical oxygen demand (COD) on nitrification performance in one full-scale membrane bioreactor (MBR) treating monoethanolamine (MEA)/dimethyl sulfoxide (DMSO)-containing thin film transistor liquid crystal display (TFT-LCD) wastewater. Poor nitrification was observed under high organic loading and high colloidal COD conditions, suggesting that high F/M ratio and colloidal COD situations should be avoided to minimize their negative impacts on nitrification. According to the nonmetric multidimensional scaling (NMS) statistical analyses on terminal restriction fragment length polymorphism (T-RFLP) results of ammonia monooxygenase (amoA) gene, the occurrence of Nitrosomonas oligotropha-like ammonia oxidizing bacteria (AOB) was positively related to successful nitrification in the MBR systems, while Nitrosomonas europaea-like AOB was positively linked to nitrification rate, which can be attributed to the high influent total nitrogen condition. Furthermore, Nitrobacter- and Nitrospira-like nitrite oxidizing bacteria (NOB) were both abundant in the MBR systems, but the continuously low nitrite environment is likely to promote the growth of Nitrospira-like NOB. PMID:23561953

Wu, Yi-Ju; Whang, Liang-Ming; Chang, Ming-Yu; Fukushima, Toshikazu; Lee, Ya-Chin; Cheng, Sheng-Shung; Hsu, Shu-Fu; Chang, Cheng-Huey; Shen, Wason; Yang, Charn-Yi; Fu, Ryan; Tsai, Tsair-Yuan

2013-08-01

37

Multikilowatt supersonic chemical oxygen iodine laser  

Microsoft Academic Search

The chemical oxygen iodine laser (COIL) is an attractive candidate for efficient power scaling at short wavelengths. High specific power output from supersonic operation leads to compact devices. The German Aerospace Research Establishment (DLR) started experimental investigations of a multikilowatt supersonic COIL at its Lampoldshausen rocket test site in 1994. The excited oxygen is produced by a rotating disk generator.

Juergen Handke; Wolfgang O. Schall; Willy L. Bohn; Lutz V. Entress-Fuersteneck; Karin Gruenewald; G. R. Kwirandt; Anke Werner

1996-01-01

38

Modeling biological oxygen demand of the Melen River in Turkey using an artificial neural network technique.  

PubMed

Artificial neural networks (ANNs) are being used increasingly to predict and forecast water resources' variables. The feed-forward neural network modeling technique is the most widely used ANN type in water resources applications. The main purpose of the study is to investigate the abilities of an artificial neural networks' (ANNs) model to improve the accuracy of the biological oxygen demand (BOD) estimation. Many of the water quality variables (chemical oxygen demand, temperature, dissolved oxygen, water flow, chlorophyll a and nutrients, ammonia, nitrite, nitrate) that affect biological oxygen demand concentrations were collected at 11 sampling sites in the Melen River Basin during 2001-2002. To develop an ANN model for estimating BOD, the available data set was partitioned into a training set and a test set according to station. In order to reach an optimum amount of hidden layer nodes, nodes 2, 3, 5, 10 were tested. Within this range, the ANN architecture having 8 inputs and 1 hidden layer with 3 nodes gives the best choice. Comparison of results reveals that the ANN model gives reasonable estimates for the BOD prediction. PMID:18691805

Dogan, Emrah; Sengorur, Bülent; Koklu, Rabia

2009-02-01

39

OVERVIEW OF USEPA/CLEAR LAKE ERIE - SEDIMENT OXYGEN DEMAND INVESTIGATIONS DURING 1979  

EPA Science Inventory

In situ hypolimnetic oxygen depletion measurements were conducted during four summer cruises in 1979 at two central basin stations in Lake Erie to evaluate the relative contribution of the sediments to the oxygen demand. ediment oxygen demand (SOD) rates were determined by measur...

40

A finite difference model for predicting sediment oxygen demand in streams  

E-print Network

Sediment oxygen demand (SOD) is a significant part of the dissolved oxygen budget in waterways, comprising up to 50% in some systems. It, therefore, has the potential of having a significant impact on the environment. As such, an accurate...

Charbonnet, Danielle Andrea

2003-01-01

41

Demand Oxygen System using Mechanomyography Amber Xu1, Arianna Golden1, Brad Holden1, Marco Dyer1, Suyog Sonwalkar1, Youngeun Kim1  

E-print Network

the oxygen tank lasts, constricRng their mobility. Therefore, demand oxygen systemsDemand Oxygen System using Mechanomyography Amber Xu1, Arianna Golden1, Brad available oxygen therapy systems for children waste oxygen because the oxygen flows

McGaughey, Alan

42

Biochemical oxygen demand measurement by mediator method in flow system.  

PubMed

Using mediator as electron acceptor for biochemical oxygen demand (BOD) measurement was developed in the last decade (BODMed). However, until now, no BODMed in a flow system has been reported. This work for the first time describes a flow system of BODMed method (BODMed-FS) by using potassium ferricyanide as mediator and carbon fiber felt as substrate material for microbial immobilization. The system can determine the BOD value within 30min and possesses a wider analytical linear range for measuring glucose-glutamic acid (GGA) standard solution from 2 up to 200mgL(-1) without the need of dilution. The analytical performance of the BODMed-FS is comparable or better than that of the previously reported BODMed method, especially its superior long-term stability up to 2 months under continuous operation. Moreover, the BODMed-FS has same determination accuracy with the conventional BOD5 method by measuring real samples from a local wastewater treatment plant (WWTP). PMID:25863368

Liu, Ling; Bai, Lu; Yu, Dengbin; Zhai, Junfeng; Dong, Shaojun

2015-06-01

43

The oxygen supply-demand balance: a monitoring challenge.  

PubMed

The principal task of acute critical care is to avoid or correct oxygen debt by increasing oxygen delivery (DO2) and/or decreasing oxygen consumption (VO2). The most commonly used methods to assess the relationship of adequate delivery and consumption are mixed venous oxygen saturation and its surrogate, central venous oxygen saturation (ScvO2). The purpose of this article is to review the values and limitations of the two parameters and evaluate the clinical use of ScvO2 in certain clinical scenarios, such as anaemia and transfusion, hypovolaemia, major surgery, septic shock, and in difficult-to-wean patients. PMID:24012232

Tánczos, Krisztián; Molnár, Zsolt

2013-06-01

44

14 CFR 23.1450 - Chemical oxygen generators.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Chemical oxygen generators. 23.1450 Section 23...Miscellaneous Equipment § 23.1450 Chemical oxygen generators. (a) For the purpose of this section, a chemical oxygen generator is defined as a device...

2011-01-01

45

49 CFR 173.168 - Chemical oxygen generators.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Chemical oxygen generators. 173.168 Section 173.168 Transportation...Than Class 1 and Class 7 § 173.168 Chemical oxygen generators. An oxygen generator, chemical (defined in § 171.8...

2012-10-01

46

14 CFR 25.1450 - Chemical oxygen generators.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Chemical oxygen generators. 25.1450 Section 25...Miscellaneous Equipment § 25.1450 Chemical oxygen generators. (a) For the purpose of this section, a chemical oxygen generator is defined as a device...

2012-01-01

47

14 CFR 25.1450 - Chemical oxygen generators.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Chemical oxygen generators. 25.1450 Section 25...Miscellaneous Equipment § 25.1450 Chemical oxygen generators. (a) For the purpose of this section, a chemical oxygen generator is defined as a device...

2010-01-01

48

49 CFR 173.168 - Chemical oxygen generators.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Chemical oxygen generators. 173.168 Section 173.168 Transportation...Than Class 1 and Class 7 § 173.168 Chemical oxygen generators. An oxygen generator, chemical (defined in § 171.8...

2013-10-01

49

14 CFR 23.1450 - Chemical oxygen generators.  

Code of Federal Regulations, 2014 CFR

...2014-01-01 2014-01-01 false Chemical oxygen generators. 23.1450 Section 23...Miscellaneous Equipment § 23.1450 Chemical oxygen generators. (a) For the purpose of this section, a chemical oxygen generator is defined as a device...

2014-01-01

50

14 CFR 23.1450 - Chemical oxygen generators.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Chemical oxygen generators. 23.1450 Section 23...Miscellaneous Equipment § 23.1450 Chemical oxygen generators. (a) For the purpose of this section, a chemical oxygen generator is defined as a device...

2012-01-01

51

49 CFR 173.168 - Chemical oxygen generators.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Chemical oxygen generators. 173.168 Section 173.168 Transportation...Than Class 1 and Class 7 § 173.168 Chemical oxygen generators. An oxygen generator, chemical (defined in § 171.8...

2011-10-01

52

14 CFR 23.1450 - Chemical oxygen generators.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Chemical oxygen generators. 23.1450 Section 23...Miscellaneous Equipment § 23.1450 Chemical oxygen generators. (a) For the purpose of this section, a chemical oxygen generator is defined as a device...

2013-01-01

53

49 CFR 173.168 - Chemical oxygen generators.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Chemical oxygen generators. 173.168 Section 173.168 Transportation...Than Class 1 and Class 7 § 173.168 Chemical oxygen generators. An oxygen generator, chemical (defined in § 171.8...

2014-10-01

54

14 CFR 25.1450 - Chemical oxygen generators.  

Code of Federal Regulations, 2014 CFR

...2014-01-01 2014-01-01 false Chemical oxygen generators. 25.1450 Section 25...Miscellaneous Equipment § 25.1450 Chemical oxygen generators. (a) For the purpose of this section, a chemical oxygen generator is defined as a device...

2014-01-01

55

14 CFR 25.1450 - Chemical oxygen generators.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Chemical oxygen generators. 25.1450 Section 25...Miscellaneous Equipment § 25.1450 Chemical oxygen generators. (a) For the purpose of this section, a chemical oxygen generator is defined as a device...

2011-01-01

56

14 CFR 23.1450 - Chemical oxygen generators.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Chemical oxygen generators. 23.1450 Section 23...Miscellaneous Equipment § 23.1450 Chemical oxygen generators. (a) For the purpose of this section, a chemical oxygen generator is defined as a device...

2010-01-01

57

14 CFR 25.1450 - Chemical oxygen generators.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Chemical oxygen generators. 25.1450 Section 25...Miscellaneous Equipment § 25.1450 Chemical oxygen generators. (a) For the purpose of this section, a chemical oxygen generator is defined as a device...

2013-01-01

58

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

59

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

60

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...

61

Ventilatory accommodation of changing oxygen demand in sciurid rodents  

Microsoft Academic Search

Ventilation was measured across a range of O2 consumption rates in four sciurid rodents: Tamias minimus (47 g), Spermophilus lateralis (189 g), S. beecheyi (531 g), and Marmota flaviventris juveniles (1054 g) and adults (2989 g). Maximum thermogenic oxygen consumption was measured for all but adult M. flaviventris. Aerobic scopes (maximum\\/minimum O2 consumption rates) were 4.6, 3.8, 5.4, and 4.8

Mark A. Chappell

1992-01-01

62

The effect of mayfly (Hexagenia spp.) burrowing activity on sediment oxygen demand in western Lake Erie  

USGS Publications Warehouse

Previous studies support the hypothesis that large numbers of infaunal burrow-irrigating organisms in the western basin of Lake Erie may increase significantly the sediment oxygen demand, thus enhancing the rate of hypolimnetic oxygen depletion. We conducted laboratory experiments to quantify burrow oxygen dynamics and increased oxygen demand resulting from burrow irrigation using two different year classes of Hexagenia spp. nymphs from western Lake Erie during summer, 2006. Using oxygen microelectrodes and hot film anemometry, we simultaneously determined oxygen concentrations and burrow water flow velocities. Burrow oxygen depletion rates ranged from 21.7 mg/nymph/mo for 15 mm nymphs at 23 °C to 240.7 mg/nymph/mo for 23 mm nymphs at 13 °C. Sealed microcosm experiments demonstrated that mayflies increase the rate of oxygen depletion by 2-5 times that of controls, depending on size of nymph and water temperature, with colder waters having greater impact. At natural population densities, nymph pumping activity increased total sediment oxygen demand 0.3-2.5 times compared to sediments with no mayflies and accounted for 22-71% of the total sediment oxygen demand. Extrapolating laboratory results to the natural system suggest that Hexagenia spp. populations may exert a significant control on oxygen depletion during intermittent stratification. This finding may help explain some of the fluctuations in Hexagenia spp. population densities in western Lake Erie and suggests that mayflies, by causing their own population collapse irrespective of other environmental conditions, may need longer term averages when used as a bio-indicator of the success of pollution-abatement programs in western Lake Erie and possibly throughout the Great Lakes.

Edwards, William J.; Soster, Frederick M.; Matisoff, Gerald; Schloesser, Donald W.

2009-01-01

63

Ventilatory accommodation of changing oxygen demand in sciurid rodents.  

PubMed

Ventilation was measured across a range of O2 consumption rates in four sciurid rodents: Tamias minimus (47 g), Spermophilus lateralis (189 g), S. beecheyi (531 g), and Marmota flaviventris juveniles (1054 g) and adults (2989 g). Maximum thermogenic oxygen consumption was measured for all but adult M. flaviventris. Aerobic scopes (maximum/minimum O2 consumption rates) were 4.6, 3.8, 5.4, and 4.8 in T. minimus, S. lateralis, S. beecheyi, and juvenile M. flaviventris, respectively. Aerobic scope was at least 4.1 in adult M. flaviventris. Ventilatory accommodation of changing O2 consumption rate was qualitatively similar in the four species, with the bulk of accommodation resulting from changes in minute volume. Nevertheless, there were significant differences in the relative importance of frequency, tidal volume, and O2 extraction in accommodation. In all species, frequency and minute volume were strongly correlated to O2 consumption rate. Tidal volume was significantly correlated to O2 consumption rate in T. minimus and S. beecheyi, but not in the other species. Oxygen extraction was not significantly correlated to O2 consumption rate in any species. Analysis of factorial ventilation changes across a standardized 3.8-fold change in O2 consumption rate revealed significant differences among species in frequency and O2 extraction, but not in tidal or minute volume. When compared to a generalized allometry for mammalian resting ventilation, the four sciurid species had consistently lower respiration frequency and higher O2 extraction than predicted, perhaps because the sciurid measurements were made on unrestrained animals. There was no indication that ventilation constrained maximum O2 consumption rate. PMID:1494030

Chappell, M A

1992-01-01

64

Detailed chemical kinetic modeling of diesel combustion with oxygenated fuels  

Microsoft Academic Search

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

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

1999-01-01

65

A source of atomic oxygen for a chemical CO laser  

Microsoft Academic Search

A supersonic chemical CO laser employing a CS2\\/O2 mixture is proposed in which the equilibrium products of the combustion of sulfur in oxygen are used as a source of atomic oxygen. Theoretical calculations are presented which show that supersonic flows containing about 15 percent of oxygen atoms can be generated by this method over a wide range of pressures and

T. V. Bystrova; Iu. L. Chizhov

1985-01-01

66

In situ global method for measurement of oxygen demand and mass transfer  

SciTech Connect

Two aerobic microorganisms, Saccharomycopsis lipolytica and Brevibacterium lactofermentum, have been used in a study of mass transfer and oxygen uptake from a global perspective using a closed gas system. Oxygen concentrations in the gas and liquid were followed using oxygen electrodes, and the results allowed for easy calculation of in situ oxygen transport. The cell yields on oxygen for S. lipolytica and B. lactofermentum were 1.01 and 1.53 g/g respectively. The mass transfer coefficient was estimated as 10 h{sup {minus}1} at 500 rpm for both fermentations. The advantages with this method are noticeable since the use of model systems may be avoided, and the in situ measurements of oxygen demand assure reliable data for scale-up.

Klasson, K.T. [Oak Ridge National Lab., TN (United States). Chemical Technology Div.; Lundbaeck, K.M.O.; Clausen, E.C.; Gaddy, J.L. [Univ. of Arkansas, Fayetteville, AR (United States). Dept. of Chemical Engineering

1997-05-01

67

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

PubMed Central

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

Hatay, M; Haas, AF; Robinett, NL; Barott, K; Vermeij, MJA; Marhaver, KL; Meirelles, P; Thompson, F; Rohwer, F

2013-01-01

68

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

69

A Novel Microbial Sensor Immobilized Arxula adeninivorans for Biochemical Oxygen Demand Measure in High Salt Condition  

Microsoft Academic Search

A microbial sensor, based on an immobilized mixed the yeast Arxula adeninivorans with a Clark-type oxygen electrode, has been developed for the measurement of Biochemical Oxygen Demand(BOD) in high salt wastewater. Arxula is immobilized in the Polyvinyl Alcohol (PVA). Arxula is salt tolerant, it can give a stable signal up to 100g\\/L NaCl in sample. The influence of pH, temperature

Hu Lei; Li Yi

2010-01-01

70

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

71

Simulating unsteady transport of nitrogen, biochemical oxygen demand, and dissolved oxygen in the Chattahoochee River downstream from Atlanta, Georgia  

USGS Publications Warehouse

As part of an intensive water-quality assessment of the Chattahoochee River, repetitive water-quality measurements were made at 12 sites along a 69-kilometer reach of the river downstream of Atlanta, Georgia. Concentrations of seven constituents (temperature, dissolved oxygen, ultimate carbonaceous biochemical oxygen demand (BOD), organic nitrogen, ammonia, nitrite, and nitrate) were obtained during two periods of 36 hours, one starting on August 30, 1976, and the other starting on May 31, 1977. The study reach contains one large and several small sewage outfalls and receives the cooling water from two large powerplants. An unsteady water-quality model of the Lagrangian type was calibrated using the 1977 data and verified using the 1976 data. The model provided a good means of interpreting these data even though both the flow and the pollution loading rates were highly unsteady. A kinetic model of the cascade type accurately described the physical and biochemical processes occurring in the river. All rate coefficients, except reaeration coefficients and those describing the resuspension of BOD, were fitted to the 1977 data and verified using the 1976 data. The study showed that, at steady low flow, about 38 percent of the BOD settled without exerting an oxygen demand. At high flow, this settled BOD was resuspended and exerted an immediate oxygen demand. About 70 percent of the ammonia extracted from the water column was converted to nitrite, but the fate of the remaining 30 percent is unknown. Photosynthetic production was not an important factor in the oxygen balance during either run.

Jobson, Harvey E.

1985-01-01

72

SEPARATING THE EFFECTS OF PARTIAL SUBMERGENCE AND SOIL OXYGEN DEMAND ON PLANT PHYSIOLOGY  

Microsoft Academic Search

In wetlands, a distinct zonation of plant species composition occurs along moisture gradients, due to differential flooding tolerance of the species involved. However, ''flooding'' comprises two important, distinct stressors (soil oxygen demand (SOD) and partial submergence) that affect plant survival and growth. To investigate how these two flooding stressors affect plant performance, we executed a factorial experiment (water depth 3

Peter M. van Bodegom; Brian K. Sorrell; Annelies Oosthoek; Chris Bakker; Rien Aerts

2008-01-01

73

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

Federal Register 2010, 2011, 2012, 2013, 2014

...Category Airplanes Equipped with Chemical Oxygen Generators Installed in...Because COGs produce oxygen through a chemical reaction that generates heat, there are...7\\ PS-ANM-25-04, Chemical Oxygen Generator...

2013-01-09

74

A Method for Generating Oxygen from Consumer Chemicals  

NASA Astrophysics Data System (ADS)

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.

Wright, Stephen W.

2003-10-01

75

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

76

Rate of Biochemical oxygen demand during formation of hypoxia in Amur Bay, Sea of Japan  

NASA Astrophysics Data System (ADS)

In May 2011, a Water Quality Monitor (WQM) hydrological station was maintained in the hypoxia area of Amur Bay one meter above the bottom, at the depth of 19 m. The temperature, electric conductivity, pressure, and content of dissolved oxygen were registered every four hours for more than three months. On the basis of these data, it was found that the period of hypoxia at the observation point lasted 93 days and a model of calculation of the rate of biochemical oxygen demand and the velocity of ventilation of the bottom waters is suggested.

Tishchenko, P. P.; Tishchenko, P. Ya.; Zvalinskii, V. I.; Semkin, P. Yu.

2014-12-01

77

Unexpected hypoxia-dependent erythropoietin secretion during experimental conditions not affecting tissue oxygen supply\\/demand ratio  

Microsoft Academic Search

Unexpected hypoxia-dependent erythropoietin secretion during experimental conditions not affecting tissue oxygen supply\\/demand ratio. Although a great deal of evidence supports the hypothesis that plasma erythropoietin (EPO) levels of mammals are related to the oxygen supply to the tissues relative to their oxygen needs, several observations millitate against its inherent simplicity. This study presents our results obtained from in vivo experiments

Carlos E Bozzini; Ana C Barceló; María I Conti; María P Martínez; Christian E Lezón; Clarisa Bozzini; Rosa M Alippi

1997-01-01

78

Improvement of the analysis of the biochemical oxygen demand (BOD) of Mediterranean seawater by seeding control  

Microsoft Academic Search

Biochemical oxygen demand (BOD) is a useful parameter for assessing the biodegradability of dissolved organic matter in water. At the same time, this parameter is used to evaluate the efficiency with which certain processes remove biodegradable natural organic matter (NOM). However, the values of BOD in seawater are very low (around 2mgO2L?1) and the methods used for its analysis are

F. Xavier Simon; Ywann Penru; Andrea R. Guastalli; Joan Llorens; Sylvie Baig

2011-01-01

79

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.

1998-01-01

80

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

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

Chemical diffusion of oxygen in tin dioxide: Effects of dopants and oxygen partial pressure  

SciTech Connect

Tin dioxide SnO{sub 2-{delta}} is a pronounced n-type electron conductor due to its oxygen deficiency. This study investigates the rate of chemical diffusion of oxygen in SnO{sub 2-{delta}} single crystals, which is a crucial step in the overall stoichiometry change of the material. The chemical diffusion coefficient D{sup {delta}} was determined from conductivity- and EPR-relaxation methods. The temperature dependence was found to be D{sup {delta}}=exp(-4+/-2)cm{sup 2}s{sup -1}exp(-(1.1+/-0.3)eV/kT). The dependence on crystal orientation, dopant content and oxygen partial pressure was below experimental error. The latter observation leads to the conclusion that the chemical diffusion coefficient is close to the diffusion coefficient of oxygen vacancies. Along with the relaxation process resulting from the chemical diffusion of oxygen, additional processes were observed. One of these was attributed to complications in the defect chemistry of the material. The relevance of the results for the kinetics of drift processes of Taguchi sensors is discussed.

Kamp, B. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany); Merkle, R. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany)]. E-mail: s.weiglein@fkf.mpg.de; Lauck, R. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany); Maier, J. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany)

2005-10-15

83

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

84

Benthic Oxygen Demand in Three Former Salt Ponds Adjacent to South San Francisco Bay, California  

USGS Publications Warehouse

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 2 meters). The water column at all deployment sites was monitored with dataloggers for ancillary water-quality parameters (including dissolved oxygen, salinity, specific conductance, temperature, and pH) to facilitate the interpretation of benthic-flux results. 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 micromoles per square centimeter per second (site averages depicted in table 2). Assuming pond areas of 1.0, 1.4, and 2.3 square kilometers for ponds A16, A14, and A3W, respectively, this converts to an oxygen mass flux into the ponds' sediment ranging from -1 to -72 kilograms per 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 micromoles per square centimeter per second) compared with diffusive flux estimates for ponds A16 and A3W (site averages -26 x 10-6 to -35 x 10-6 and -34 x 10-6 to -37 x 10-6 micromoles per square centimeter per second, respectively). These initial diffusive-flux estimates are of the order of magnitude of those measured in the South Bay using core-incubation experiments (Topping and others, 2004), which include bioturbation and bioirrigation effects. Estimates of benthic oxygen demand reported herein, based on molecular diffusion, serve as conservative estimates of benthic flux because solute transport across the sediment-water interface can be enhanced by multidisciplinary processes including bioturbation, bioirrigation, ground-water advection, and wind resuspension (Kuwabara and others, 2009).

Topping, Brent R.; Kuwabara, James S.; Athearn, Nicole D.; Takekawa, John Y.; Parchaso, Francis; Henderson, Kathleen D.; Piotter, Sara

2009-01-01

85

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

86

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

87

Fine sediment impacts on Salmonid spawning success: Relative effects of pore blockage and oxygen demand  

NASA Astrophysics Data System (ADS)

Salmonids act as geomorphic agents constructing a spawning habitat (redd) with fine sediment being washed out of the bed, increasing porosity around the incubating eggs. However, during the incubation period fine sediment infiltrates back into the river bed and degrades the habitat quality. Fine sediment has been found to reduce survival rates of salmonid eggs in both field and laboratory experiments, with the main hypotheses used to explain this being (a) fine sediment reduces gravel permeability and intra-gravel flow velocities; (b) intra-gravel O2 concentrations decrease due to reduced supply and increased consumption by organic sediments; and (c) clay particles block the exchange of O2 across the egg membrane. The SIDO (Sediment Intrusion and Dissolved Oxygen)-UK model is a physically based numerical model which stimulates the effect of fine sediment intrusion on the abiotic characteristics of the salmonid redd, along with the consequences for egg development and survival. This has been used to assess the sensitivity of salmonid egg survival to changes in the quantity and composition of fine sediment, including particle size and sediment oxygen demand. Results indicate that egg survival is highly sensitive to the discharge and the suspended sediment concentrations, particularly to changes in the supply rate of sand particles, rather than silt and clay. This can be explained by the increased likelihood of blocking of intra-gravel pores by larger sand particles, which reduce intra-gravel flow velocities and the supply of oxygen rich water. Furthermore, this effect of sediment mass has been found to be more important than the sediment oxygen consumption process. These findings have implications for how we manage the sediment delivery problem, especially as future projections indicate increased sediment delivery under climate and land management change.

Pattison, I.; Sear, D.; Collins, A.; Jones, I.; Naden, P.

2013-12-01

88

Development of a chemical oxygen - iodine laser with production of atomic iodine in a chemical reaction  

SciTech Connect

The alternative method of atomic iodine generation for a chemical oxygen - iodine laser (COIL) in chemical reactions with gaseous reactants is investigated experimentally. The influence of the configuration of iodine atom injection into the laser cavity on the efficiency of the atomic iodine generation and small-signal gain is studied. (lasers)

Censky, M; Spalek, O; Jirasek, V; Kodymova, J [Institute of Physics, Czech Academy of Sciences, Prague (Czech Republic); Jakubec, I [Institute of Inorganic Chemistry, Czech Academy of Sciences, Rez (Czech Republic)

2009-11-30

89

Separating the effects of partial submergence and soil oxygen demand on plant physiology.  

PubMed

In wetlands, a distinct zonation of plant species composition occurs along moisture gradients, due to differential flooding tolerance of the species involved. However, "flooding" comprises two important, distinct stressors (soil oxygen demand [SOD] and partial submergence) that affect plant survival and growth. To investigate how these two flooding stressors affect plant performance, we executed a factorial experiment (water depth x SOD) for six plant species of nutrient-rich and nutrient-poor conditions, occurring along a moisture gradient in Dutch dune slacks. Physiological, growth, and biomass responses to changed oxygen availability were quantified for all species. The responses were consistent with field zonation, but the two stressors affected species differently. Increased SOD increased root oxygen deprivation, as indicated by either raised porosity or increased alcohol dehydrogenase (ADH) activity in roots of flood-intolerant species (Calamagrostis epigejos and Carex arenaria). While SOD affected root functioning, partial submergence tended more to reduce photosynthesis (as shown both by gas exchange and 13C assimilation), leaf dark respiration, 13C partitioning from shoots to roots, and growth of these species. These processes were especially affected if the root oxygen supply was depleted by a combination of flooding and increased SOD. In contrast, the most flood-tolerant species (Juncus subnodulosus and Typha latifolia) were unaffected by any treatment and maintained high internal oxygen concentrations at the shoot : root junction and low root ADH activity in all treatments. For these species, the internal oxygen transport capacity was well in excess of what was needed to maintain aerobic metabolism across all treatments, although there was some evidence for effects of SOD on their nitrogen partitioning (as indicated by 865N values) and photosynthesis. Two species intermediate in flooding tolerance (Carex nigra and Schoenus nigricans) responded more idiosyncratically, with different parameters responding to different treatments. These results show that partial submergence and soil flooding are two very different stressors to which species respond in different ways, and that their effects on physiology, survival, and growth are interactive. Understanding species zonation with water regimes can be improved by a better appreciation of how these factors affect plant metabolism independently and interactively. PMID:18376561

van Bodegom, Peter M; Sorrell, Brian K; Oosthoek, Annelies; Bakker, Chris; Aerts, Rien

2008-01-01

90

Rapid field estimation of biochemical oxygen demand in a subtropical eutrophic urban lake with chlorophyll a fluorescence.  

PubMed

Development of a technique for rapid field estimation of biochemical oxygen demand (BOD) is necessary for cost-effective monitoring and management of urban lakes. While several studies reported the usefulness of laboratory tryptophan-like fluorescence technique in predicting 5-day BOD (BOD?) of wastewater and leachates, little is known about the predictability of field chlorophyll fluorescence measurements for BOD of urban lake waters that are constantly exposed to the mixture of chemical compounds. This study was conducted to develop a numeric relationship between chlorophyll a fluorescence and BOD for a eutrophic urban lake that is widely representative of lake water conditions in the subtropical southern USA. From October 2012 to September 2013, in situ measurements at the studied lake were made every 2 weeks on chlorophyll a fluorescence and other water quality parameters including water temperature, pH, dissolved oxygen, and specific conductivity. Water samples were taken for 5-day BOD and 10-day BOD (BOD??) analysis with and without incubation. The results showed a clear seasonal trend of both BOD measurements being high during the summer and low during the winter. There was a linear, positive relationship between chlorophyll a fluorescence and BOD, and the relationship appeared to be stronger with the 10-day BOD (r(2)?=?0.83) than with the 5-day BOD (r(2)?=?0.76). BOD dropped each day with declining chlorophyll a fluorescence, suggesting that die-off of phytoplankton has been the main consumption of oxygen in the studied lake. Ambient conditions such as rainfall and water temperature may have partially affected BOD variation. PMID:25446719

Xu, Zhen; Xu, Y Jun

2015-01-01

91

Comparison of Instream and Laboratory Methods of Measuring Sediment Oxygen Demand  

USGS Publications Warehouse

Sediment oxygen demand (SOD) was determined at three sites in a gravel-bottomed central Missouri stream by: (1) two variations of an instream method, and (2) a laboratory method. SOD generally was greatest by the instream methods, which are considered more accurate, and least by the laboratory method. Disturbing stream sediment did not significantly decrease SOD by the instream method. Temperature ranges of up to 12 degree Celsius had no significant effect on the SOD. In the gravel-bottomed stream, the placement of chambers was critical to obtain reliable measurements. SOD rates were dependent on the method; therefore, care should be taken in comparing SOD data obtained by different methods. There is a need for a carefully researched standardized method for SOD determinations.

Hall, Dennis C.; Berkas, Wayne R.

1988-01-01

92

Overview on the chemical oxygen-iodine laser technology  

NASA Astrophysics Data System (ADS)

The "Chemical Oxygen-Iodine Laser" (COIL) has passed through a tremendous development from the first milliwatt to a multi-kilowatt power, and thus offered a great opportunity for investigations in the COIL technology based on a multidisciplinary science. This overview has been aimed at a demonstration of enormous endeavor of the international COIL community in the last years to bring this laser system soon to the end-users by a focusing on advanced concepts of the hardware design, improvement and scaling-up the existing facilities. The overall COIL technology is considered as a sequence of the coexistent technologies of main laser components with a mutual impact: a technology of the singlet oxygen generator, gasdynamic mixing and expansion nozzle, energy extraction and optical resonator, and the exhaust and pressure recovery system. Advanced concepts of the named technologies based on inherent supporting research disciplines - a computational modeling, kinetic studies and diagnostic techniques - are briefly described. A critical insight into the COIL performance via an energy flow, energy losses, power extraction, and a chemical efficiency of this laser system utilizes the established heuristic phenomenology. The paper ends with a reference to developed projects and suggested potential applications of the chemical oxygen-iodine laser technology.

Kodymová, Jarmila

2007-05-01

93

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

94

Chemical kinetics of discharge-driven oxygen-iodine lasers  

NASA Astrophysics Data System (ADS)

Oxygen-iodine lasers that utilize electrical discharges to produce O II(a1?) are currently being developed. The discharge generators differ from those used in chemical oxygen-iodine lasers in that they produce significant amounts of atomic oxygen and traces of ozone. As a consequence of these differences, the chemical kinetics of the discharge laser are markedly different from those of a conventional chemical oxygen-iodine laser (COIL). The reactions of O with iodine include channels that are both beneficial and detrimental to the laser. The beneficial reactions result in the dissociation of I II while the detrimental processes cause direct and indirect removal of I(2P 1/2) (denoted I*, the upper level of the laser). We have examined kinetic processes relevant to the laser through studies of photo-initiated reactions in N IIO/CO II/I II mixtures. The reactions have been monitored using absorption spectroscopy, laser induced fluorescence and time-resolved emission spectroscopy. It has been established that deactivation of I* by O atoms is a critical energy loss process. We have determined a rate constant of (1.2+/-0.1)×10 -11 cm 3 s -1 for this reaction. As part of this effort the branching fraction for the formation of O II(a) from the reaction of O(1D) with N IIO was determined to be 0.38. This result has implications for lasers based on photolysis of O 3/N IIO/I II mixtures and the formation of O II(a) in the upper atmosphere.

Azyazov, Valeriy N.; Kabir, Md. Humayun; Antonov, Ivan O.; Heaven, Michael C.

2007-05-01

95

Plasma chemical oxygen-iodine laser: problems of development  

NASA Astrophysics Data System (ADS)

Great success has been obtained in the R&D of a chemical oxygen-iodine laser (COIL) operating on the electronic transition of the iodine atom, which gets an excitation from the energy donor -singlet delta oxygen (SDO). The latter is normally produced in a chemical SDO generator using very toxic and dangerous chemicals, which puts a limit for civilian applications of COIL that is still a very unique apparatus. Totally new non-chemical SDO generator is needed to allow oxygen-iodine laser to achieve its full potential as a non-hazardous efficient source of high-power laser radiation. There was interest in producing SDO in electric discharge plasma since the 50's long before COIL appearing. The idea of using SDO as a donor for iodine laser was formulated in the 70's. However, the injection of iodine molecules into a low- pressure self-sustained discharge did not result in iodine lasing. One of the main factors that could prevent from lasing in many experiments is a rather high threshold yield approximately 15 percent at 300K, which is needed for obtaining an inversion population. An analysis of different attempts of producing SDO in different kinds of electric discharge plasma has been done which demonstrates that high yield at gas pressure of practical interest for modern COIL technology can be obtained only in non-self sustained electric discharge plasma. The reason is that the value of relatively low reduced electrical field strength E/N approximately 1E-16 V.cm2, which is an order of magnitude less than that for the self-sustained discharge, is extremely important for the efficient SDO production. Although different kinds of non-self sustained discharges can be used for SDO production, we got started experiments with e-beam sustained discharge in gas mixtures containing oxygen. High specific input energy up to approximately 3 - 5 kJ/ has been experimentally obtained. Theoretical calculations have been done for different experimental conditions indicating a feasibility of reasonable SDO yield. Experimental and theoretical research of self-sustained electric discharge in SDO produced in a chemical generator, which is very important for getting plasma-chemical kinetic data needed for an estimation of SDO yield, is also discussed.

Ionin, Andrei A.; Napartovich, Anatoly P.; Yuryshev, Nikolai N.

2002-05-01

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

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

PubMed

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 that the optimal hot-pressing conditions were 120 degrees C and 150 kg cm(-2) for 30 s. When the MEA fabricated under optimal conditions and an air cathode were utilized for the construction of the MFC type BOD sensor, coulombs increased to 4.65 C from 0.52 C and power increased to 69,080 mW m(-3) from 880 mW m(-3) (at a BOD concentration of 200 mg L(-1)), respectively, compared with the conventional MFC lacking a MEA. The increased power improved the performance of the MFC type BOD sensor: sensitivity increased from 1.2 x 10(-3) to 1.8 x 10(-2) C per mg L(-1) of BOD, with good linearity (r2 = 0.97) and over 97% repeatability. We conclude that the MEA can be successfully applied to MFCs to make them highly sensitive BOD sensors. PMID:19492544

Kim, Mia; Hyun, Moon Sik; Gadd, Geoffrey M; Kim, Gwang Tae; Lee, Sang-Joon; Kim, Hyung Joo

2009-04-01

98

Chemical oxygen diffusion coefficient measurement by conductivity relaxation--correlation between tracer diffusion  

E-print Network

Chemical oxygen diffusion coefficient measurement by conductivity relaxation--correlation between J. P., Grenier J. C., Loup J. P. ABSTRACT Chemical oxygen diusion coecient ¯(D)was measured the oxygen partial pressure in the surrounding atmosphere of the sample. The consequent evolution

Paris-Sud XI, Université de

99

Time series of oxygen demand in deltaic sediments obtained by a new benthic station: the Rhône delta (NW Mediterranean Sea)  

NASA Astrophysics Data System (ADS)

Deltas are critical interfaces between the land and sea, buffering organic matter (OM) fluxes which constitute an important link between continent and ocean carbon cycles. Due to the extreme variability of estuaries and coastal areas, on both spatial and temporal scales (hydrology, production-respiration balance, coastal circulation...), the balance between deposition and consumption of OM by the benthic ecosystem is largely unknown. Based on a combination of two in situ techniques, we studied the biogeochemical transformations of particulate inputs in the Rhône River delta and its temporal variability. The Rhône River is the main source of freshwater, sediments and organic matter to the Gulf of Lions. Oxygen micro-electrodes have long been used in the deep-ocean and the coastal sea in order to study oxygen cycling in sediments and to estimate diffusive oxygen uptake (DOU). This technique has seldom been used for performing time-series measurements of DOU because of several drawbacks linked to the fragile nature of oxygen micro-electrodes, their changing calibration with time, the expected small amplitude of DOU variation over short time-scales and the large natural heterogeneity of the sediment DOU which would prevent small temporal variations of DOU to be distinguished from the "spatial noise". Here, we present results obtained by two in situ techniques: i) an in situ oxygen micro-profiler ii) a new benthic station equipped with oxygen micro-electrodes and environmental sensors. This new device performs daily measurements of oxygen microprofiles, with a potential for high frequency measurements (4 per day) and uses continuous re-calibration by moored oxygen optodes carried by the benthic station together with turbidity, temperature and salinity sensors. Time series typically encompasses periods of 2-3 months. The lateral heterogeneity of the DOU is assessed by performing a 2D map of oxygen demands at the initial stage of the deployment. We deployed this benthic station in a deltaic environment at the mouth of the Rhone River together with the oxygen micro-profiler in order to study the fate of particulate organic matter delivered during floods from this Mediterranean River. First results measured during low flow condition and small turbidity showed that the measurement system is stable over time and records a limited lateral heterogeneity allowing temporal variation and floods to be recorded. During the turbidity events of spring 2012, oxygen demand rises by a factor of 3-4. We discuss the importance of flood events in controlling the variability of DOU in this system. Keywords: oxygen microelectrodes, marine biogeochemistry, coastal zone, River deltas, benthic observatory, mineralization

Toussaint, Flora; Rabouille, Christophe; Bombled, Bruno; Cathalot, Cécile; Lansard, Bruno; Abchiche, Abdel; Aouji, Oualid; Buschholz, Gilles

2013-04-01

100

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

101

[Effects of upper thoracic epidural anesthesia on hemodynamics and oxygen supply-demand relationship in hypovolemic dogs].  

PubMed

The purpose of the present study is to assess the influence of upper thoracic epidural anesthesia (TEA) on hemodynamics, the systemic oxygen supply-demand relationship, and several indications of stress in the presence of preexisting hypovolemia. Sixteen adult mongrel dogs were anesthetized with halothane and nitrous oxide, and blood was withdrawn at the rate of 3 ml.kg-1.min-1 for 10 min. The dogs were randomly assigned to two groups; one receiving TEA (TEA group, n = 8), and the other without (controls, n = 8). Mean arterial blood pressure, heart rate, arterial concentrations of epinephrine and norepinephrine remained significantly lower (P less than 0.05) in the TEA group than in the controls during the 100-min observation period following the start of TEA. Cardiac index, oxygen supply-demand ratio (O2 delivery/O2 consumption) and arterial lactate concentration showed no significant intergroup differences at any point during observation. By contrast, there was a significant difference in arterial pH between the TEA group (7.22 +/- 0.05, mean +/- SD) and the controls (7.15 +/- 0.08) after 100 min of TEA. These results indicate that in hypovolemic dogs anesthetized with halothane and nitrous oxide, TEA affects the acid-base balance favorably without significantly influencing the systemic oxygen supply-demand relationship. PMID:1770569

Shibata, K; Taki, Y; Futagami, A; Yamamoto, K; Kobayashi, T; Murakami, S

1991-12-01

102

Characterization of water quality and simulation of temperature, nutrients, biochemical oxygen demand, and dissolved oxygen in the Wateree River, South Carolina, 1996-98  

USGS Publications Warehouse

In May 1996, the U.S. Geological Survey entered into a cooperative agreement with the Kershaw County Water and Sewer Authority to characterize and simulate the water quality in the Wateree River, South Carolina. Longitudinal profiling of dissolved-oxygen concentrations during the spring and summer of 1996 revealed dissolved-oxygen minimums occurring upstream from the point-source discharges. The mean dissolved-oxygen decrease upstream from the effluent discharges was 2.0 milligrams per liter, and the decrease downstream from the effluent discharges was 0.2 milligram per liter. Several theories were investigated to obtain an improved understanding of the dissolved-oxygen dynamics in the upper Wateree River. Data suggest that the dissolved-oxygen concentration decrease is associated with elevated levels of oxygen-consuming nutrients and metals that are flowing into the Wateree River from Lake Wateree. Analysis of long-term streamflow and water-quality data collected at two U.S. Geological Survey gaging stations suggests that no strong correlation exists between streamflow and dissolved-oxygen concentrations in the Wateree River. However, a strong negative correlation does exist between dissolved-oxygen concentrations and water temperature. Analysis of data from six South Carolina Department of Health and Environmental Control monitoring stations for 1980.95 revealed decreasing trends in ammonia nitrogen at all stations where data were available and decreasing trends in 5-day biochemical oxygen demand at three river stations. The influence of various hydrologic and point-source loading conditions on dissolved-oxygen concentrations in the Wateree River were determined by using results from water-quality simulations by the Branched Lagrangian Transport Model. The effects of five tributaries and four point-source discharges were included in the model. Data collected during two synoptic water-quality samplings on June 23.25 and August 11.13, 1997, were used to calibrate and validate the Branched Lagrangian Transport Model. The data include dye-tracer concentrations collected at six locations, stream-reaeration data collected at four locations, and water-quality and water-temperature data collected at nine locations. Hydraulic data for the Branched Lagrangian Transport Model were simulated by using the U.S. Geological Survey BRANCH one-dimensional, unsteady-flow model. Data that were used to calibrate and validate the BRANCH model included time-series of water-level and streamflow data at three locations. The domain of the hydraulic model and the transport model was a 57.3- and 43.5-mile reach of the river, respectively. 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 changes in the boundary concentration inputs of water temperature and dissolved oxygen followed by sensitivity to the change in streamflow. A 35-percent increase in streamflow resulted in a negative normalized sensitivity index, indicating a decrease in dissolved-oxygen concentrations. The simulated dissolved-oxygen concentrations showed no significant sensitivity to changes in model input rate kinetics. To demonstrate the utility of the Branched Lagrangian Transport Model of the Wateree River, the model was used to simulate several hydrologic and water-quality scenarios to evaluate the effects on simulated dissolved-oxygen concentrations. The first scenario compared the 24-hour mean dissolved-oxygen concentrations for August 13, 1997, as simulated during the model validation, with simulations using two different streamflow patterns. The mean streamflow for August 13, 1997, was 2,000 cubic feet per second. Simulations were run using mean streamflows of 1,000 and 1,400 cubic feet per second while keeping the water-quality boundary conditions the same as were used during the validation simulations. When compared t

Feaster, Toby D.; Conrads, Paul A.

2000-01-01

103

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

104

Detailed Chemical Kinetic Modeling of Diesel Spray Combustion with Oxygenated Fuels  

Microsoft Academic Search

This paper confirms a structure for the soot formation process inside a burning diesel jet plume of oxygenated fuels. An explanation of how the soot formation process changes by the use of oxygenated fuel in comparison with that for using a conventional diesel fuel, and why oxygenated fuel drastically suppresses the soot forma- tion has been derived from the chemical

Takaaki Kitamura; Takayuki Ito; Jiro Senda; Hajime Fujimoto

2001-01-01

105

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

106

Applications of neon, nitrogen, argon and oxygen to physical, chemical and biological cycles in the ocean  

E-print Network

Applications of neon, nitrogen, argon and oxygen to physical, chemical and biological cycles;#12;University of Washington Abstract Applications of neon, nitrogen, argon and oxygen to physical, chemical and biological cycles in the ocean by Roberta Claire Hamme Chair of Supervisory Committee: Professor Steven R

Hamme, Roberta C.

107

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

108

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

109

A new method for the determination of biological oxygen demand in domestic wastewater by headspace gas chromatography.  

PubMed

A headspace gas chromatographic method (HS-GC) has been developed for the determination of biological oxygen demand (BOD) in the water samples from domestic wastewater treatment plants. The method is based on measuring the remaining oxygen in the headspace of the sample (that has been seeded with microorganisms) in a closed container after a period of incubation. The relative standard deviation of the method in replicate testing was <4.9%. Further, the results differed by less than 6% when compared with the widely used reference method (the ISO standard) for determining BOD5. The limit of quantification in BODn testing was about 1.8 mg/L. The new method is simple and suitable for use in the batch sample testing for BODn measurement. PMID:23953613

Gu, Juan-Juan; Hu, Hui-Chao; Chai, Xin-Sheng; Tian, Ying-Xin; Barnes, Donald G; Huang, Shaobin

2013-09-20

110

MICREDOX--development of a ferricyanide-mediated rapid biochemical oxygen demand method using an immobilised Proteus vulgaris biocomponent.  

PubMed

Biochemical oxygen demand (BOD) is an international regulatory environmental index for monitoring organic pollutants in wastewater and the current legislated standard test for BOD monitoring requires 5 days to complete (BOD5 test). We are developing a rapid microbial technique, MICREDOX, for measuring BOD by eliminating oxygen and, instead, quantifying an equivalent biochemical co-substrate demand, the co-substrate being a redox mediator. Elevated concentrations of Proteus vulgaris, either as free cells or immobilised in Lentikat disks, were incubated with an excess of redox mediator (potassium hexacyanoferrate(III)) and organic substrate for 1h at 37 degrees C without oxygen. The addition of substrate increased the catabolic activity of the microorganisms and the accumulation of reduced mediator, which was subsequently re-oxidised at a working electrode generating a current quantifiable by a coulometric transducer. The recorded currents were converted to their BOD5 equivalent with the only assumption being a fixed conversion of substrate and known stoichiometry. Measurements are reported both for the BOD5 calibration standard solution (150 mg l(-1) glucose, 150 mg l(-1) glutamic acid) and for filtered effluent sampled from a wastewater treatment plant. The inclusion of a highly soluble mediator in place of oxygen facilitated a high ferricyanide concentration in the incubation, which in turn permitted increased concentrations of microorganisms to be used. This substantially reduced the incubation time, from 5 days to 1h, for the biological oxidation of substrates equivalent to those observed using the standard BOD5 test. Stoichiometric conversion efficiencies for the oxidation of the standard substrate by P. vulgaris were typically 60% for free cells and 35-50% for immobilised cells. PMID:15494235

Pasco, Neil; Baronian, Keith; Jeffries, Cy; Webber, Judith; Hay, Joanne

2004-10-15

111

Cutting Performance of a Chemical Oxygen-Iodine Laser William P. Latham, James A. Rothenflue, and Charles A. Helms  

E-print Network

Cutting Performance of a Chemical Oxygen-Iodine Laser William P. Latham, James A. Rothenflue. Green Street Urbana,IL 61801 . Abstract Chemical Oxygen-Iodine Laser (COIL) is a member of the class cutting and drilling. Chemical Oxygen- Iodine Laser (COIL) technology has received considerable interest

Carroll, David L.

112

Influence of decomposing jellyfish on the sediment oxygen demand and nutrient dynamics  

Microsoft Academic Search

Jellyfish populations can grow rapidly to attain large biomasses and therefore can represent significant stocks of carbon\\u000a and nitrogen in the ecosystem. Blooms are also generally short-lived, lasting for just weeks or months, after which time the\\u000a population can decline rapidly, sink to the bottom and decompose. The influence of decomposing jellyfish (Catostylus mosaicus, Scyphozoa) on benthic dissolved oxygen and

Elizabeth Jane West; David Thomas Welsh; Kylie Anne Pitt

2009-01-01

113

Influence of decomposing jellyfish on the sediment oxygen demand and nutrient dynamics  

Microsoft Academic Search

Jellyfish populations can grow rapidly to attain large biomasses and therefore can represent significant stocks of carbon\\u000a and nitrogen in the ecosystem. Blooms are also generally short-lived, lasting for just weeks or months, after which time the\\u000a population can decline rapidly, sink to the bottom and decompose. The influence of decomposing jellyfish (Catostylus mosaicus, Scyphozoa) on benthic dissolved oxygen and

Elizabeth Jane West; David Thomas Welsh; Kylie Anne Pitt

114

Oxygen Enrichment in the Process and Chemical Industries  

E-print Network

separation plants still employ refinements of the low temperature (cryogenic) 1iquefaction/disti llation cycle. Modern plants can produce upwards of 2,000 T/D gaseous oxygen and nitrogen from a single train for delivery by pipeline to the end user.... The gases may also be shipped as pure cryogenic liquids in special insulated transports to customers remote from the plant. The availability of pure oxygen (typically 99.5%) in large quantities at a reasonable cost provided a stimulus...

Milne, R. T.

1984-01-01

115

Ion fluence dependence on chemical behavior of energetic deuterium implanted into oxygen-contained boron film  

NASA Astrophysics Data System (ADS)

Ion fluence dependence on chemical behavior of energetic deuterium implanted into oxygen-contained boron and pure boron films was investigated by XPS and TDS. It was found that large amount of D implanted into the oxygen-contained sample was quickly desorbed as D 2O by chemical sputtering during D2+ implantation. The D retention for both samples increased as the D2+ fluence increased. The implanted D was preferentially trapped by O with forming O-D bond, and thereafter by B with forming B-D bond. These facts indicate that the stability of D bound to O is higher than that bound to B. It was concluded that the chemical sputtering of oxygen by energetic particles and the chemical stability of O-D bond should be taken into consideration for the evaluation of tritium inventory in the oxygen-contained boron film.

Miyauchi, H.; Yoshikawa, A.; Oyaidzu, M.; Oya, Y.; Sagara, A.; Noda, N.; Okuno, K.

2007-06-01

116

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

117

Semi-insulating crystalline silicon formed by oxygen doping during low-temperature chemical vapor deposition  

E-print Network

Semi-insulating crystalline silicon formed by oxygen doping during low-temperature chemical vapor) In this letter we demonstrate the use of oxygen as a dopant in silicon to create semi-insulating, crystalline of the films exhibit classical characteristics of space-charge-limited current associated with insulators

118

In-situ sediment oxygen demand rates in Hammonton Creek, Hammonton, New Jersey, and Crosswicks Creek, near New Egypt, New Jersey, August-October 2009  

USGS Publications Warehouse

Sediment oxygen demand rates were measured in Hammonton Creek, Hammonton, New Jersey, and Crosswicks Creek, near New Egypt, New Jersey, during August through October 2009. These rates were measured as part of an ongoing water-quality monitoring program being conducted in cooperation with the New Jersey Department of Environmental Protection. Oxygen depletion rates were measured using in-situ test chambers and a non-consumptive optical electrode sensing technique for measuring dissolved oxygen concentrations. Sediment oxygen demand rates were calculated on the basis of these field measured oxygen depletion rates and the temperature of the stream water at each site. Hammonton Creek originates at an impoundment, then flows through pine forest and agricultural fields, and receives discharge from a sewage-treatment plant. The streambed is predominantly sand and fine gravel with isolated pockets of organic-rich detritus. Sediment oxygen demand rates were calculated at four sites on Hammonton Creek and were found to range from -0.3 to -5.1 grams per square meter per day (g/m2/d), adjusted to 20 degrees Celsius. When deployed in pairs, the chambers produced similar values, indicating that the method was working as expected and yielding reproducible results. At one site where the chamber was deployed for more than 12 hours, dissolved oxygen was consumed linearly over the entire test period. Crosswicks Creek originates in a marshy woodland area and then flows through woodlots and pastures. The streambed is predominantly silt and clay with some bedrock exposures. Oxygen depletion rates were measured at three sites within the main channel of the creek, and the calculated sediment oxygen demand rates ranged from -0.33 to -2.5 g/m2/d, adjusted to 20 degrees Celsius. At one of these sites sediment oxygen demand was measured in both a center channel flowing area of a pond in the stream and in a stagnant non-flowing area along the shore of the pond where organic-rich bottom sediments had accumulated and lower dissolved oxygen concentration conditions existed in the water column. Dissolved oxygen concentrations in the center channel test chamber showed a constant slow decrease over the entire test period. Oxygen consumption in the test chamber at the near-shore location began rapidly and then slowed over time as oxygen became depleted in the chamber. Depending on the portion of the near-shore dissolved oxygen depletion curve used, calculated sediment oxygen demand rates ranged from as low as -0.03 g/m2/d to as high as -10 g/m2/d. The wide range of sediment oxygen demand rates indicates that care must be taken when extrapolating sediment oxygen demand rates between stream sites that have different bottom sediment types and different flow regimes.

Wilson, Timothy P.

2014-01-01

119

Oxygen demand for the stabilization of the organic fraction of municipal solid waste in passively aerated bioreactors  

SciTech Connect

Highlights: • The use of an passively aerated reactor enables effective stabilization of OFMSW. • Convective air flow does not inhibit the aerobic stabilization of waste. • The use of an passively aerated reactor reduces the heat loss due to convection. • The volume of supplied air exceeds 1.7–2.88 times the microorganisms demand. - Abstract: Conventional aerobic waste treatment technologies require the use of aeration devices that actively transport air through the stabilized waste mass, which greatly increases operating costs. In addition, improperly operated active aeration systems, may have the adverse effect of cooling the stabilized biomass. Because active aeration can be a limiting factor for the stabilization process, passive aeration can be equally effective and less expensive. Unfortunately, there are few reports documenting the use of passive aeration systems in municipal waste stabilization. There have been doubts raised as to whether a passive aeration system provides enough oxygen to the organic matter mineralization processes. In this paper, the effectiveness of aeration during aerobic stabilization of four different organic fractions of municipal waste in a reactor with an integrated passive ventilation system and leachate recirculation was analyzed. For the study, four fractions separated by a rotary screen were chosen. Despite the high temperatures in the reactor, the air flow rate was below 0.016 m{sup 3}/h. Using Darcy’s equation, theoretical values of the air flow rate were estimated, depending on the intensity of microbial metabolism and the amount of oxygen required for the oxidation of organic compounds. Calculations showed that the volume of supplied air exceeded the microorganisms demand for oxidation and endogenous activity by 1.7–2.88-fold.

Kasinski, Slawomir, E-mail: slawomir.kasinski@uwm.edu.pl; Wojnowska-Baryla, Irena

2014-02-15

120

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

121

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

Microsoft Academic Search

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

Paul Cho; Tobias Mattisson; Anders Lyngfelt

2004-01-01

122

Recovery Act: Novel Oxygen Carriers for Coal-fueled Chemical Looping  

SciTech Connect

Chemical Looping Combustion (CLC) could totally negate the necessity of pure oxygen by using oxygen carriers for purification of CO{sub 2} stream during combustion. It splits the single fuel combustion reaction into two linked reactions using oxygen carriers. The two linked reactions are the oxidation of oxygen carriers in the air reactor using air, and the reduction of oxygen carriers in the fuel reactor using fuels (i.e. coal). Generally metal/metal oxides are used as oxygen carriers and operated in a cyclic mode. Chemical looping combustion significantly improves the energy conversion efficiency, in terms of the electricity generation, because it improves the reversibility of the fuel combustion process through two linked parallel processes, compared to the conventional combustion process, which is operated far away from its thermo-equilibrium. Under the current carbon-constraint environment, it has been a promising carbon capture technology in terms of fuel combustion for power generation. Its disadvantage is that it is less mature in terms of technological commercialization. In this DOE-funded project, accomplishment is made by developing a series of advanced copper-based oxygen carriers, with properties of the higher oxygen-transfer capability, a favorable thermodynamics to generate high purity of CO{sub 2}, the higher reactivity, the attrition-resistance, the thermal stability in red-ox cycles and the achievement of the auto-thermal heat balance. This will be achieved into three phases in three consecutive years. The selected oxygen carriers with final-determined formula were tested in a scaled-up 10kW coal-fueled chemical looping combustion facility. This scaled-up evaluation tests (2-day, 8-hour per day) indicated that, there was no tendency of agglomeration of copper-based oxygen carriers. Only trace-amount of coke or carbon deposits on the copper-based oxygen carriers in the fuel reactor. There was also no evidence to show the sulphidization of oxygen carriers in the system by using the high-sulfur-laden asphalt fuels. In all, the scaled-up test in 10 kW CLC facility demonstrated that the preparation method of copper-based oxygen carrier not only help to maintain its good reactivity, also largely minimize its agglomeration tendency.

Pan, Wei-Ping; Cao, Yan

2012-11-30

123

Measurement of biochemical oxygen demand from different wastewater samples using a mediator-less microbial fuel cell biosensor.  

PubMed

Microbial fuel cells (MFCs) have attracted considerable attention as potential biosensors. A MFC biosensor for rapid measurement of biochemical oxygen demand (BOD) has been recently studied. However, a standardized bacterial mixture inoculated in the MFC biosensor for BOD measurement is unavailable. Thus, the commercial application of a MFC biosensor is limited. In this study, a mediator-less MFC biosensor inoculated with known mixed cultures to quickly determine BOD concentration was tested. Optimal external resistance, operating temperature and measurement time for the MFC biosensor were determined to be 5000 omega, 35 degrees C and 12h, respectively. A good relationship between BOD concentration and voltage output, high reproducibility and long-term stability for the MFC biosensor was observed. The newly developed MFC biosensor was inoculated with a mixture of six bacterial strains (Thermincola carboxydiphila, Pseudomonas aeruginosa, Ochrobactrum intermedium, Shewanella frigidimarina, Citrobacter freundii and Clostridium acetobutylicum) capable of degrading complex organic compounds and surviving toxic conditions. The described MFC biosensor was able to successfully measure BOD concentrations below 240 mg L(-1) in real wastewater samples. PMID:25145173

Hsieh, Min-Chi; Chung, Ying-Chien

2014-01-01

124

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

125

Chemical analysis of surface oxygenated moieties of fluorescent carbon nanoparticles  

NASA Astrophysics Data System (ADS)

Water-soluble carbon nanoparticles were prepared by refluxing natural gas soot in concentrated nitric acid. The surface of the resulting nanoparticles was found to be decorated with a variety of oxygenated species, as suggested by spectroscopic measurements. Back potentiometric titration of the nanoparticles was employed to quantify the coverage of carboxylic, lactonic, and phenolic moieties on the particle surface by taking advantage of their vast difference of acidity (pKa). The results were largely consistent with those reported in previous studies with other carbonaceous (nano)materials. Additionally, the presence of ortho- and para-quinone moieties on the nanoparticle surface was confirmed by selective labelling with o-phenylenediamine, as manifested in X-ray photoelectron spectroscopy, photoluminescence, and electrochemical measurements. The results further supported the arguments that the surface functional moieties that were analogous to 9,10-phenanthrenequinone were responsible for the unique photoluminescence of the nanoparticles and the emission might be regulated by surface charge state, as facilitated by the conjugated graphitic core matrix.

Huang, Jie; Deming, Christopher P.; Song, Yang; Kang, Xiongwu; Zhou, Zhi-You; Chen, Shaowei

2012-01-01

126

Chemical Oxygen-Iodine Layer Device Simulation Using the 3D, unsteady Navier-Stokes Equations  

Microsoft Academic Search

The time-dependent, chemically reacting, viscous fluid dynamics within the chemical oxygen-iodine laser (COIL) flowfield are simulated using the unsteady, laminar, multi-component Navier-Stokes equations. The solutions of these equations are generated within simulations of COIL hardware at standard operating conditions; conditions predicted in previous simulations to be unsteady. These current simulations ascertain the effect of the flow unsteadiness upon the laser

T. J. Madden

2007-01-01

127

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...

128

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...

129

Test bed for a high throughput supersonic chemical oxygen - iodine laser  

SciTech Connect

The paper reports the development of a test bed for a chemical oxygen - iodine laser based on a high throughput jet flow singlet oxygen generator (JSOG). The system provides vertical singlet oxygen extraction followed by horizontal orientation of subsequent subsystems. This design enables the study of flow complexities and engineering aspects of a distributed weight system as an input for mobile and other platform-mounted systems developed for large scale power levels. The system under consideration is modular and consists of twin SOGs, plenum and supersonic nozzle modules, with the active medium produced in the laser cavity. The maximal chlorine flow rate for the laser is {approx}1.5 mole s{sup -1} achieving a typical chemical efficiency of about 18%. (lasers)

Singhal, Gaurav; Mainuddin; Rajesh, R; Varshney, A K; Dohare, R K; Kumar, Sanjeev; Singh, V K; Kumar, Ashwani; Verma, Avinash C; Arora, B S; Chaturvedi, M K; Tyagi, R K; Dawar, A L

2011-05-31

130

Metal Oxide Nanoparticle Growth on Graphene via Chemical Activation with Atomic Oxygen  

PubMed Central

Chemically interfacing the inert basal plane of graphene with other materials has limited the development of graphene-based catalysts, composite materials, and devices. Here, we overcome this limitation by chemically activating epitaxial graphene on SiC(0001) using atomic oxygen. Atomic oxygen produces epoxide groups on graphene, which act as reactive nucleation sites for zinc oxide nanoparticle growth using the atomic layer deposition precursor diethyl zinc. In particular, exposure of epoxidized graphene to diethyl zinc abstracts oxygen, creating mobile species which diffuse on the surface to form metal oxide clusters. This mechanism is corroborated with a combination of scanning probe microscopy, Raman spectroscopy, and density functional theory, and can likely be generalized to a wide variety of related surface reactions on graphene. PMID:24206242

Johns, James E.; Alaboson, Justice M. P.; Patwardhan, Sameer; Ryder, Christopher R.; Schatz, George C.

2013-01-01

131

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

Microsoft Academic Search

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

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

2000-01-01

132

Remote Microwave Plasma Enhanced Chemical Vapour Deposition of SiO 2 Films : Oxygen Plasma Diagnostic  

Microsoft Academic Search

Silicon oxide is deposited by remote microwave plasma enhanced chemical vapour deposition (RMPECVD). The silica films are produced by exciting oxygen in a microwave discharge while a mixture of 5% of silane diluted in argon is introduced downstream. In the afterglow, double Langmuir probe measurements and rotational temperatures deduced from optical emission spectroscopy (OES), show that the electron energy is

C. Regnier; J. Desmaison; P. Tristant; D. Merle

1995-01-01

133

Oxygen is a key element for biology and the cycling of geochemical elements, and has shaped the chemical  

E-print Network

Oxygen is a key element for biology and the cycling of geochemical elements, and has shaped the chemical and biological evolution of Earth. The oceans appear to be loosing oxygen due to on-going climate change, with resulting impacts on marine ecosystems and global biogeochemical cycles. As oxygen levels

Handy, Todd C.

134

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

135

Online biochemical oxygen demand monitoring for wastewater process control--full-scale studies at Los Angeles Glendale wastewater plant, California.  

PubMed

The main objective of this investigation is to determine whether or not it would be feasible to use the measured values of biochemical oxygen demand (BOD) of wastewater obtained by an online instrument at the Los Angeles/Glendale Water Reclamation Plant (California) for controlling its activated sludge process. This investigation is part of a project to develop online BOD monitoring for process control in the City of Los Angeles wastewater treatment plants. Tests studied the Siepmann und Teutscher GmbH (ISCO-STIP Inc., Lincoln, Nebraska) BIOX-1010, which uses a bioreactor containing a culture of microbes from the wastewater to measure soluble BOD in 2 minutes. This rapid approximation to the operation of secondary treatment allows anticipation of system response. Calibration measurements allow the operators to find a conversion factor for the instrument's microprocessor to compute values of BOD that agree well with the standard 5-day BOD (BOD5) measurement, despite the differences in the details of the two testing methods. This instrument has recently been used at other wastewater treatment plants, at a number of airports in Europe and the United States to monitor runway runoff, and is also being used on waste streams at an increasing number of food processing plants. A comparison was made between the plant influent BOD values obtained by the BIOX-1010 online monitor from the end of August, 2000, to late January, 2001, and the individual and average values obtained for the same period using the standard BOD5, 20 degrees C test, to determine the effectiveness of the Biox-1010 to identify shock loads and their duration. Individual BOD estimates and averages over periods of overly high biological loads (shock loads) were compared, and the instrument readings were evaluated for their effectiveness in detecting shock loads. The results were highly satisfactory, so the instrument was used to trigger a shock-load warning alarm since late September, 2000. This allowed flow diversion and temporary storage to prevent process upsets. PMID:18536480

Iranpour, Reza; Zermeno, Miguel

2008-04-01

136

Seasonal contribution of terrestrial organic matter and biological oxygen demand to the Baltic Sea from three contrasting river catchments  

NASA Astrophysics Data System (ADS)

To examine the potential influence of terrestrially derived DOM on the Baltic Sea, a year-long study of dissolved organic matter (DOM) was performed in three river catchments in Sweden. One catchment drains into the Bothnian Sea, while two southern catchments drain into the Baltic Proper. Dissolved organic carbon (DOC) concentrations were positively correlated with discharge from forested catchments over the year and while the overall concentrations of DOC were several times higher in the southern two catchments, annual loading of DOC was on the same order for all three catchments, due to differences in discharge. Biological oxygen demand (BOD) was used as a proxy for the lability of carbon in the system. The range of BOD values was similar for all three catchments, however, the ratio of BOD to DOC (an indication of the labile fraction) in Ume älv was four times higher than in the southern two catchments. Total annual BOD loading to the Baltic Sea was twice as high in the northern catchment. Lower winter temperatures and preservation of organic matter in the northern catchment combined with an intense spring flood help to explain the higher concentrations of labile carbon in the northern catchment. Lower lability of DOM as well as higher colour in the southern catchments suggest that wetlands (i.e. peat bogs) may be the dominant source of DOM in these catchments, particularly in periods of low flow. With climate change expected to increase precipitation events and temperatures across the region, the supply and quality of DOM delivered to the Baltic Sea can also be expected to change. Our results indicate that DOM supply will be more stable throughout the year, and potentially have a lower bioavailability.

Reader, H. E.; Stedmon, C. A.; Kritzberg, E. S.

2014-01-01

137

Seasonal contribution of terrestrial organic matter and biological oxygen demand to the Baltic Sea from three contrasting river catchments  

NASA Astrophysics Data System (ADS)

To examine the potential influence of terrestrially derived DOM on the Baltic Sea, a year-long study of dissolved organic matter (DOM) was performed in three river catchments in Sweden. One catchment drains into the Bothnian Sea, while two southern catchments drain into the Baltic proper. Dissolved organic carbon (DOC) concentrations were positively correlated with discharge from forested catchments over the year. While the overall concentrations of DOC were several times higher in the southern two catchments, higher discharge in the northern catchment resulted in the annual loadings of DOC being on the same order of magnitude for all three catchments. Biological oxygen demand (BOD) was used as a proxy for the lability of carbon in the system. The range of BOD values was similar for all three catchments, however, the ratio of BOD to DOC (an indication of the labile fraction) in Ume river was four times higher than in the southern two catchments. Total annual BOD loading to the Baltic Sea was twice as high in the northern catchment than in the two southern catchments. Lower winter temperatures and preservation of organic matter in the northern catchment combined with an intense spring flood help to explain the higher concentrations of labile carbon in the northern catchment. Lower lability of DOM as well as higher colour in the southern catchments suggest that wetlands (i.e. peat bogs) may be the dominant source of DOM in these catchments, particularly in periods of low flow. With climate change expected to increase precipitation events and temperatures across the region, the supply and quality of DOM delivered to the Baltic Sea can also be expected to change. Our results indicate that DOM supply to the Baltic Sea from boreal rivers will be more stable throughout the year, and potentially have a lower bioavailability.

Reader, H. E.; Stedmon, C. A.; Kritzberg, E. S.

2014-06-01

138

40 IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 36, NO. 1, JANUARY 2000 High-Performance Chemical OxygenIodine Laser  

E-print Network

Oxygen­Iodine Laser Using Nitrogen Diluent for Commercial Applications D. L. Carroll, D. M. King, L. Fockler, D. Stromberg, W. C. Solomon, L. H. Sentman, and C. H. Fisher Abstract--A chemical oxygen­iodine; these are the highest reported chemical effi- ciencies with room-temperature nitrogen diluent. A long duration, high

Carroll, David L.

139

Effect of vapor-phase oxygen on chemical vapor deposition growth of graphene  

NASA Astrophysics Data System (ADS)

To obtain a large-area single-crystal graphene, chemical vapor deposition (CVD) growth on Cu is considered the most promising. Recently, the surface oxygen on Cu has been found to suppress the nucleation of graphene. However, the effect of oxygen in the vapor phase was not elucidated sufficiently. Here, we investigate the effect of O2 partial pressure (PO2) on the CVD growth of graphene using radiation-mode optical microscopy. The nucleation density of graphene decreases monotonically with PO2, while its growth rate reaches a maximum at a certain pressure. Our results indicate that PO2 is an important parameter to optimize in the CVD growth of graphene.

Terasawa, Tomo-o.; Saiki, Koichiro

2015-03-01

140

Limb Blood Flow and Vascular Conductance Are Reduced With Age in Healthy Humans Relation to Elevations in Sympathetic Nerve Activity and Declines in Oxygen Demand  

Microsoft Academic Search

Background—We tested the hypothesis that basal (resting) limb blood flow and vascular conductance are reduced with age in adult humans and that these changes are related to elevations in sympathetic vasoconstrictor nerve activity and reductions in limb oxygen demand. Methods and Results—Sixteen young (28 61 years; mean6SEM) and 15 older (6361 years) healthy normotensive adult men were studied. Diastolic blood

Frank A. Dinenno; Pamela P. Jones; Douglas R. Seals; Hirofumi Tanaka

141

Impact of hydration state and molecular oxygen on the chemical stability of levothyroxine sodium.  

PubMed

Levothyroxine sodium is an important medication used primarily for treating patients with hypothyroidism. Levothyroxine sodium tablets have been recalled many times since their 1955 introduction to the US market. These recalls resulted from the failure of lots to meet their content uniformity and potency specifications. The purpose of this study is to test the hypothesis that the chemical stability of levothyroxine sodium pentahydrate is compromised upon exposing the dehydrated substance to molecular oxygen. The impact of temperature, oxygen and humidity storage conditions on the stability of solid-state levothyroxine sodium was examined. After exposure to these storage conditions for selected periods of time, high performance liquid chromatography (HPLC) was used to quantify the formation of impurities. The results showed that levothyroxine sodium samples degraded significantly over a 32-day test period when subjected to dry conditions in the presence of molecular oxygen. However, dehydrated samples remained stable when oxygen was removed from the storage chamber. Furthermore, hydrated samples were stable in the presence of oxygen and in the absence of oxygen. These results reveal conditions that will degrade levothyroxine sodium pentahydrate and elucidate measures that can be taken to stabilize the drug substance. PMID:24295156

Hamad, Mazen Lee; Engen, William; Morris, Kenneth R

2015-05-01

142

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

143

Oxygen abundances in the Galactic Bulge: evidence for fast chemical enrichment  

E-print Network

AIMS: We spectroscopically characterize the Galactic Bulge to infer its star formation timescale, compared to the other Galactic components, through the chemical signature on its individual stars. METHODS: We derived iron and oxygen abundances for 50 K giants in four fields towards the Galactic bulge. High resolution (R=45,000) spectra for the target stars were collected with FLAMES-UVES at the VLT. RESULTS: Oxygen, as measured from the forbidden line at 6300 \\AA, shows a well-defined trend with [Fe/H], with [O/Fe] higher in bulge stars than in thick disk ones, which were known to be more oxygen enhanced than thin disk stars. CONCLUSIONS: These results support a scenario in which the bulge formed before and more rapidly than the disk, and therefore the MW bulge can be regarded as a prototypical old spheroid, with a formation history similar to that of early-type (elliptical) galaxies.

M. Zoccali; A. Lecureur; B. Barbuy; V. Hill; A. Renzini; D. Minniti; Y. Momany; A. Gomez; S. Ortolani

2006-09-05

144

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

145

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

146

Real-time molecular monitoring of chemical environment in obligate anaerobes during oxygen adaptive response  

PubMed Central

Determining the transient chemical properties of the intracellular environment can elucidate the paths through which a biological system adapts to changes in its environment, for example, the mechanisms that enable some obligate anaerobic bacteria to survive a sudden exposure to oxygen. Here we used high-resolution Fourier transform infrared (FTIR) spectromicroscopy to continuously follow cellular chemistry within living obligate anaerobes by monitoring hydrogen bond structures in their cellular water. We observed a sequence of well orchestrated molecular events that correspond to changes in cellular processes in those cells that survive, but only accumulation of radicals in those that do not. We thereby can interpret the adaptive response in terms of transient intracellular chemistry and link it to oxygen stress and survival. This ability to monitor chemical changes at the molecular level can yield important insights into a wide range of adaptive responses. PMID:19541631

Holman, Hoi-Ying N.; Wozei, Eleanor; Lin, Zhang; Comolli, Luis R.; Ball, David A.; Borglin, Sharon; Fields, Matthew W.; Hazen, Terry C.; Downing, Kenneth H.

2009-01-01

147

Real-Time Molecular Monitoring of Chemical Environment in ObligateAnaerobes during Oxygen Adaptive Response  

SciTech Connect

Determining the transient chemical properties of the intracellular environment canelucidate the paths through which a biological system adapts to changes in its environment, for example, the mechanisms which enable some obligate anaerobic bacteria to survive a sudden exposure to oxygen. Here we used high-resolution Fourier Transform Infrared (FTIR) spectromicroscopy to continuously follow cellular chemistry within living obligate anaerobes by monitoring hydrogen bonding in their cellular water. We observed a sequence of wellorchestrated molecular events that correspond to changes in cellular processes in those cells that survive, but only accumulation of radicals in those that do not. We thereby can interpret the adaptive response in terms of transient intracellular chemistry and link it to oxygen stress and survival. This ability to monitor chemical changes at the molecular level can yield important insights into a wide range of adaptive responses.

Holman, Hoi-Ying N.; Wozei, Eleanor; Lin, Zhang; Comolli, Luis R.; Ball, David. A.; Borglin, Sharon; Fields, Matthew W.; Hazen, Terry C.; Downing, Kenneth H.

2009-02-25

148

Fiber Optic Chemical Sensor For The Measurement Of Partial Pressure Of Oxygen  

NASA Astrophysics Data System (ADS)

The estimation of partial pressure of oxygen in gaseous samples, aqueous samples and biological fluids has very important ramifications in environmental, medicinal and analytical chemistry. We have devised a fiber optic chemical sensor for the determination of oxygen concentration based on the dynamic luminescence quenching of a fluorophore bx oxygen. Ruthenium(II)tris(bipyridine), [Ru(bpy)3]4+, has been employed in our studies as the oxygen sensitive dye. The emission of Ru(bpy)32+ is centered at 610 nm and has a lifetime of 685 ns in argon purged aqueous solution. Our fiber optic chemical sensor consists of a custom built spectrometer containing argon ion laser light source, detector and associated electronics. A fiber optic cable is employed to guide light into and out of the spectrometer. A known amount of the sensing material in solution is used in a specially designed cell which has a gas permeable membrane at one end and the other end is coupled with the long cable to the spectrometer. Further research is being continued in improving the sensor chemistry and its dynamic detection range.

Goswami, Kisholoy; Klainer, Stanley M.; Tokar, John M.

1989-01-01

149

BRIEF COMMUNICATIONS: Chemical oxygen-iodine laser utilizing low-strength hydrogen peroxide  

Microsoft Academic Search

Efficient operation of a chemical oxygen-iodine laser was achieved using low-strength (50%) hydrogen peroxide. An output power of 5 W was obtained when the chlorine consumption was 1.2 mmol\\/sec. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query Results Return items starting with number Query Form Database:

Nikolai P. Vagin; A. F. Konoshenko; P. G. Kryukov; D. Kh Nurligareev; V. S. Pazyuk; V. N. Tomashov; Nikolai N. Yuryshev

1984-01-01

150

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. PMID:20865052

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

2010-01-01

151

Cutting performance of a chemical oxygen-iodine laser on aerospace and industrial materials William P. Latham, Kip R. Kendrick, James A. Rothenflue  

E-print Network

Cutting performance of a chemical oxygen-iodine laser on aerospace and industrial materials William Lab, 104 5. Wright St., Urbana, Illinois 61801 ABSTRACT A chemical oxygen-iodine laser (COIL) was used:YAG lasers are used for such applications. More recently, the chemical oxygen-iodine laser (COIL) has

Carroll, David L.

152

Variables effecting ozone treatment of physical-chemical effluent  

Microsoft Academic Search

The treatment of raw sewage from an on-site apartment area was ; investigated in a series of laboratory experiments in which changes in turbidity, ; pH, total organic carbon, chemical oxygen demand, and, in some cases, biochemical ; oxygen demands were determined. Raw sewage, but mainly the effluent following ; physical-chemical treatment, was examined for improvement in discharge quality by

R. N. Dietz; J. Pruzansky; M. Steinberg

1973-01-01

153

Extraction of the suppression effects of oxygenated fuels on soot formation using a detailed chemical kinetic model  

Microsoft Academic Search

The influence of oxygenated fuels on the soot formation process inside a burning diesel jet plume was examined using a detailed chemical kinetic reaction mechanism. Normal heptane was selected as a representative diesel fuel, and methanol, ethanol and dimethyl ether were used as oxygenated fuels. It was found that the production of soot precursors, such as small unsaturated hydrocarbons and

Takaaki Kitamura; Takayuki Ito; Jiro Senda; Hajime Fujimoto

2001-01-01

154

Temperature variations in the oxygen carrier particles during their reduction and oxidation in a chemical-looping combustion system  

Microsoft Academic Search

A particle reaction model including mass and heat transfer has been developed to know the temperature variations produced inside the oxygen carrier particles during the cyclic reduction and oxidation reactions taking place in a chemical-looping combustion (CLC) system. The reactions of the different oxygen carriers based on Cu, Co, Fe, Mn, and Ni during the reduction with fuel gas (CH4,

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

2005-01-01

155

High-performance chemical oxygen-iodine laser using nitrogen diluent for commercial applications  

SciTech Connect

A chemical oxygen-iodine laser (COIL), the VertiCOIL device, was transferred from the Air Force Research Laboratory (AFRL) to the University of Illinois at Urbana-Champaign (UIUC) and made operational. The performance of the high-power VertiCOIL laser was measured with nitrogen diluent. New nozzle designs were investigated and implemented to optimize nitrogen performance. Nitrogen diluent chemical efficiencies of 23% were achieved; these are the highest reported chemical efficiencies with room-temperature nitrogen diluent. A long duration, high chemical efficiency test was demonstrated with nitrogen diluent; a chemical efficiency of 18.5% at 30 mmol/s of chlorine was maintained for 45 min. The highest performance was obtained with new iodine injector blocks and a larger throat height. The new iodine injector blocks moved the injectors closer to the throat by 0.7 cm and the throat height was increased from 0.897 to 1.151 cm (0.353 to 0.453 in). The performance enhancements were in qualitative agreement with the system design predictions of the Blaze II chemical laser model. Three-dimensional computational fluid dynamics calculations using the general aerodynamic simulation program code confirmed the principle design change of moving the iodine injectors closer to throat. Several researchers have suggested that COIL has a significant future as an industrial laser and have identified decommissioning and decontamination (D and D) of nuclear facilities as an important market for COIL.

Carroll, D.L.; King, D.M.; Fockler, L.; Stromberg, D.; Solomon, W.C.; Sentman, L.H.; Fisher, C.H.

2000-01-01

156

Oxygen carrier development for chemical looping combustion of coal derived synthesis gas  

SciTech Connect

In the present work, NETL researchers have studied chemical looping combustion (CLC) with an oxygen carrier NiO/bentonite (60 wt.% NiO) for the IGCC systems utilizing simulated synthesis gas. Multi cycle CLC was conducted with NiO/Bentonite in TGA at atmospheric pressure and in a high pressure reactor in a temperature range between 700-900°C. Global reaction rates of reduction and oxidation as a function of conversion were calculated for all oxidation-reduction cycles utilizing the TGA data. The effect of particle size of the oxygen carrier on CLC was studied for the size between 20-200 mesh. The multi cycle CLC tests conducted in a high pressure packed bed flow reactor indicated constant total production of CO2 from fuel gas at 800°C and 900°C and full consumption of hydrogen during the reaction.

Siriwardane, R.V.; Chaudhari, K.; Zinn, A.N.; Simonyi, T.; Robinson, Clark; Poston, J.A.

2006-09-01

157

Liquid-jet O2(1Delta) generator for chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Results of experimental and theoretical study of the liquid jet O2(1(Delta) ) generator in P.N. Lebedev Institute Samara Branch are presented. This study includes hydrodynamic and gasdynamic effects, heat and mass transfer, droplet generation and separation. The dependence of O2(1(Delta) ) and Cl2 yields on geometrical and physical parameters of generator are presented. High O2(1(Delta) ) yield and operation of small scale subsonic chemical oxygen-iodine laser up to 100 torr of active gas pressure in jet liquid generator have been achieved. Counterflowing jet liquid O2(1(Delta) ) generator is a very perspective for high power supersonic oxygen-iodine laser without water vapor trap and droplet separator.

Zagidullin, Marsel V.

1995-03-01

158

Chemical oxygen-iodine laser with a cryosorption vacuum pump with different buffer gases  

NASA Astrophysics Data System (ADS)

A traditional pressure recovery system is the major obstacle to mobile chemical oxygen-iodine laser (COIL) for its huge volume. A cryosorption vacuum pump was used as the pressure recovery system for different buffer gases. It made COIL become a flexible, quiet and pressure-tight. Experiments were carried out on a verti- COIL, which was designed for N2 and energized by a square-pipe jet singlet oxygen generator (JSOG). The output power with CO2 was 27.3% lower than that with N2, but the zeolite bed showed an adsorption capacity threefold higher for CO2 than for N2 in the continuous operation. The great volume efficiency interested researchers.

Xu, Mingxiu; Fang, Benjie; Sang, Fengting; Geng, Zicai; Li, Yongzhao; JIn, Yuqi

2015-02-01

159

A polydimethylsiloxane-polycarbonate hybrid microfluidic device capable of generating perpendicular chemical and oxygen gradients for cell culture studies.  

PubMed

This paper reports a polydimethylsiloxane-polycarbonate (PDMS-PC) hybrid microfluidic device capable of performing cell culture under combinations of chemical and oxygen gradients. The microfluidic device is constructed of two PDMS layers with microfluidic channel patterns separated by a thin PDMS membrane. The top layer contains an embedded PC film and a serpentine channel for a spatially confined oxygen scavenging chemical reaction to generate an oxygen gradient in the bottom layer for cell culture. Using the chemical reaction method, the device can be operated with a small amount of chemicals, without bulky gas cylinders and sophisticated flow control schemes. Furthermore, it can be directly used in conventional incubators with syringe pumps to simplify the system setup. The bottom layer contains arrangements of serpentine channels for chemical gradient generation and a cell culture chamber in the downstream. The generated chemical and oxygen gradients are experimentally characterized using a fluorescein solution and an oxygen-sensitive fluorescent dye, respectively. For demonstration, a 48 hour cell-based drug test and a cell migration assay using human lung adenocarcinoma epithelial cells (A549) are conducted under various combinations of the chemical and oxygen gradients in the experiments. The drug testing results show an increase in A549 cell apoptosis due to the hypoxia-activated cytotoxicity of tirapazamine (TPZ) and also suggest great cell compatibility and gradient controllability of the device. In addition, the A549 cell migration assay results demonstrate an aerotactic behavior of the A549 cells and suggest that the oxygen gradient plays an essential role in guiding cell migration. The migration results, under combinations of chemokine and oxygen gradients, cannot be simply superposed with single gradient results. The device is promising to advance the control of in vitro microenvironments, to better study cellular responses under various physiological conditions for biomedical applications. PMID:25096368

Chang, Chia-Wen; Cheng, Yung-Ju; Tu, Melissa; Chen, Ying-Hua; Peng, Chien-Chung; Liao, Wei-Hao; Tung, Yi-Chung

2014-10-01

160

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

161

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

162

Influence of the organic matter composition on benthic oxygen demand in the Rhône River prodelta (NW Mediterranean Sea)  

NASA Astrophysics Data System (ADS)

Measurements of diffusive (DOU) and total (TOU) sediment oxygen uptakes, oxygen penetration depth, porosity, OC, TN, carbohydrate, lipid, amino acid, chlorophyll a and pheophytin a concentrations were assessed in surface sediments at 9 stations located in the Rhône River prodelta and the adjacent continental shelf during April 2007 (a period characterized by low flow and discharge regimes). Our results show that sedimentary organics in the Rhône River prodelta were mainly fueled by a single source of OM, namely continental inputs. Those inputs were relatively labile and decreased following an inshore-offshore gradient. The descriptors of sedimentary organics mostly resulted from dilution and degradation processes affecting OM during its transfer from the mouth of the Rhône River. TOU/DOU ratios were close to one, with a slight increase at offshore stations. This is coherent with the limitation of bioirrigation in response to organic enrichment. DOU correlated best with bulk quantitative descriptors of sedimentary organics, which probably resulted from the overall correlation between all biochemical descriptors linked with the predominance of a single source of organic matter in the whole studied area. Nevertheless, an influence of Chl a and Pheo a contents on oxygen consumptions, possibly due to freshwater or/and marine primary production, is not to be excluded. These small fractions (<0.08‰ to total OM) could then be responsible for the oxygen consumption, even if not visible in classical measurements as ?13C or C/N.

Pastor, Lucie; Deflandre, Bruno; Viollier, Eric; Cathalot, Cécile; Metzger, Edouard; Rabouille, Christophe; Escoubeyrou, Karine; Lloret, Emily; Pruski, Audrey M.; Vétion, Gilles; Desmalades, Martin; Buscail, Roselyne; Grémare, Antoine

2011-06-01

163

Atomic Oxygen Recombination and Chemical Energy Accommodation on Alumina at High Temperature  

SciTech Connect

To develop heat shields for space vehicles, materials must be characterized in simulation conditions close to those in space environments. The most important conditions for simulating the Earth re-entry phase of space vehicles are achieved through the MESOX set-up associating a 6 kW solar radiation concentrator and a 2450 MHz microwave plasma generator. This paper presents some experimental results for the recombination coefficient {gamma} and the chemical energy accommodation coefficient {beta} in the surface-catalyzed oxygen atom recombination based on experiments performed on the MESOX set-up. This set-up allows both the experimental measurements of the recombination coefficient {gamma} using Optical Emission Spectroscopy and the chemical energy accommodation coefficient {beta} using calorimetry according to a defined protocol. Experimental results are presented for three types of alumina in the temperature range 900-2400 K, for 200 Pa total air pressure. These three alumina differ essentially from their content of sintering additives.

Balat-Pichelin, Marianne J.H.; Bedra, L.; Badie, J.-M. [Laboratoire Procedes, Materiaux et Energie Solaire, PROMES-CNRS (ex IMP-CNRS), BP5, 66125 Odeillo, Font-Romeu (France); Boubert, P. [Institut Universitaire des Systemes Thermiques Industriels, IUSTI-CNRS, 5 rue E. Fermi, 13453 Marseille (France)

2005-05-16

164

Oxygen reduction reaction over silver particles with various morphologies and surface chemical states  

NASA Astrophysics Data System (ADS)

The oxygen reduction reaction (ORR) in an alkaline solution was carried out using Ag powders having various particle morphologies and surface chemical states (Size: ca. 40-110 nm in crystalline size. Shape: spherical, worm like, and angular. Surface: smooth with easily reduced AgOx, defective with AgOx, and Ag2CO3 surface layer). The various Ag powders were well characterized by X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption, scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, and stripping voltammetry of underpotential-deposited lead. Defective and oxidized surfaces enhanced the Ag active surface area during the ORR. The ORR activity was affected by the morphology and surface chemical state: Ag particles with defective and angular surfaces showed smaller electron exchange number between three and four but showed higher specific activity compared to Ag particles with smooth surfaces.

Ohyama, Junya; Okata, Yui; Watabe, Noriyuki; Katagiri, Makoto; Nakamura, Ayaka; Arikawa, Hidekazu; Shimizu, Ken-ichi; Takeguchi, Tatsuya; Ueda, Wataru; Satsuma, Atsushi

2014-01-01

165

Cephalopod-inspired design of electro-mechano-chemically responsive elastomers for on-demand fluorescent patterning.  

PubMed

Cephalopods can display dazzling patterns of colours by selectively contracting muscles to reversibly activate chromatophores--pigment-containing cells under their skins. Inspired by this novel colouring strategy found in nature, we design an electro-mechano-chemically responsive elastomer system that can exhibit a wide variety of fluorescent patterns under the control of electric fields. We covalently couple a stretchable elastomer with mechanochromic molecules, which emit strong fluorescent signals if sufficiently deformed. We then use electric fields to induce various patterns of large deformation on the elastomer surface, which displays versatile fluorescent patterns including lines, circles and letters on demand. Theoretical models are further constructed to predict the electrically induced fluorescent patterns and to guide the design of this class of elastomers and devices. The material and method open promising avenues for creating flexible devices in soft/wet environments that combine deformation, colorimetric and fluorescent response with topological and chemical changes in response to a single remote signal. PMID:25225837

Wang, Qiming; Gossweiler, Gregory R; Craig, Stephen L; Zhao, Xuanhe

2014-01-01

166

Cephalopod-inspired design of electro-mechano-chemically responsive elastomers for on-demand fluorescent patterning  

NASA Astrophysics Data System (ADS)

Cephalopods can display dazzling patterns of colours by selectively contracting muscles to reversibly activate chromatophores – pigment-containing cells under their skins. Inspired by this novel colouring strategy found in nature, we design an electro-mechano-chemically responsive elastomer system that can exhibit a wide variety of fluorescent patterns under the control of electric fields. We covalently couple a stretchable elastomer with mechanochromic molecules, which emit strong fluorescent signals if sufficiently deformed. We then use electric fields to induce various patterns of large deformation on the elastomer surface, which displays versatile fluorescent patterns including lines, circles and letters on demand. Theoretical models are further constructed to predict the electrically induced fluorescent patterns and to guide the design of this class of elastomers and devices. The material and method open promising avenues for creating flexible devices in soft/wet environments that combine deformation, colorimetric and fluorescent response with topological and chemical changes in response to a single remote signal.

Wang, Qiming; Gossweiler, Gregory R.; Craig, Stephen L.; Zhao, Xuanhe

2014-09-01

167

Optical resonator with nonuniform magnification for improving beam uniformity of chemical oxygen iodine lasers  

NASA Astrophysics Data System (ADS)

Unstable resonator with nonuniform magnification for improving the beam uniformity of chemical oxygen iodine lasers is explored for the first time. The magnification of the resonator is a function of the radial coordinate of the polar coordinate system on the front mirror surface. A resonator was designed to have a lower magnification at the center of the resonator than at the edge. The resonator consists of two aspherical mirrors. Method for designing the resonator is given. The energy conservation law and the aplanatic condition were used to derive the designing principle of the two aspherical mirrors. The design result was fitted to polynomial form which is suitable for manufacturing. Numerical experiment was carried out to evaluate the performance of the resonator. The computation was based on coupled simulation of wave optics model and computational fluid mechanics model. Results proved the effectiveness of the design method. The design tends to enhance the intensity near the center of the output beam and cripple that near the edge. Further analysis revealed that this effect is induced because rays of light are reflected more densely at the center of the pupil than at the edge. Therefore, this design affords for a potential approach for improving the near field uniformity of chemical oxygen iodine lasers.

Wu, Kenan; Sun, Yang; Huai, Ying; Jia, Shuqin; Chen, Xi; Jin, Yuqi

2015-02-01

168

LIFE Chamber Chemical Equilibrium Simulations with Additive Hydrogen, Oxygen, and Nitrogen  

SciTech Connect

In order to enable continuous operation of a Laser Inertial confinement Fusion Energy (LIFE) engine, the material (fill-gas and debris) in the fusion chamber must be carefully managed. The chamber chemical equilibrium compositions for post-shot mixtures are evaluated to determine what compounds will be formed at temperatures 300-5000K. It is desired to know if carbon and or lead will deposit on the walls of the chamber, and if so: at what temperature, and what elements can be added to prevent this from happening. The simulation was conducted using the chemical equilibrium solver Cantera with a Matlab front-end. Solutions were obtained by running equilibrations at constant temperature and constant specific volume over the specified range of temperatures. It was found that if nothing is done, carbon will deposit on the walls once it cools to below 2138K, and lead below 838K. Three solutions to capture the carbon were found: adding pure oxygen, hydrogen/nitrogen combo, and adding pure nitrogen. The best of these was the addition of oxygen which would readily form CO at around 4000K. To determine the temperature at which carbon would deposit on the walls, temperature solutions to evaporation rate equations needed to be found. To determine how much carbon or any species was in the chamber at a given time, chamber flushing equations needed to be developed. Major concerns are deposition of carbon and/or oxygen on the tungsten walls forming tungsten oxides or tungsten carbide which could cause embrittlement and cause failure of the first wall. Further research is needed.

DeMuth, J A; Simon, A J

2009-09-03

169

A NEW RAPID METHOD TO ASSESS OXYGEN DEMAND BASED ON THE HBOD Bruce E. Logan, David Kohler, and Booki Min  

E-print Network

, requiring ground-glass stoppered bottles, wet chemical techniques, and wastewater dilutions. Improvements five-day BOD (BOD5) test was developed over one hundred years ago to determine the strength of waste Rights Reserved. #12;strength or that better methods are not needed. The BOD5 test is a time

170

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

171

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

172

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

NASA Astrophysics Data System (ADS)

Output power enhancement of a chemical oxygen-iodine laser (COIL) by an injection of predissociated iodine was studied. Iodine molecules were dissociated into atoms by the microwave discharge prior to injection. It was determined that predissociation caused a negative effect on the output power enhancement when this technique was applied to a conventional supersonic COIL@. Model calculations revealed that the existence of atomic iodine at the plenum caused the dissipation of stored energy. It was demonstrated that decreasing the mixing point pressure was crucial to obtain output power enhancement by the predissociation technique. For this purpose, a low-pressure transonic mixing scheme with a grid nozzle array was developed. A 9% enhancement of output power was demonstrated.

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

2000-02-01

173

Seasonal variation in biological oxygen demand levels in the main stem of the Fraser River, British Columbia and an agriculturally impacted tributary  

NASA Astrophysics Data System (ADS)

The Fraser River basin is one of British Columbia's most diverse and valuable ecosystems. Water levels and temperatures along the Fraser are seasonally variable, with high flow during the spring freshet and low flow during winter months. In the Fraser River, dissolved oxygen (DO) concentrations impact many aquatic species. Biological oxygen demand (BOD) measures the amount of oxygen consumed by bacteria during the decomposition of organic matter and is an indicator of water quality in freshwater environments. We compared BOD, DO, and pH during winter (November 2011) and summer (July 2012) in the main stem of the Fraser River at Fort Langley and a tributary in an agricultural area of the Fraser Valley, Nathan Creek. In November the BOD of the main stem of the Fraser River was 2.36 mg/L, pH 7.26, and DO 9.13 mg/L. BOD and DO of Nathan Creek was not significantly lower at 1.68 mg/L and DO 8.28 mg/L, however, the pH was significantly lower (p=0.001) at 6.75. In July, the Fraser River had significantly higher BOD levels than in winter at 4.43 mg/L, but no significant change in pH and DO. Nathan Creek BOD was significantly higher than it was in winter and higher than the main stem at 7.34 mg/L, with no significant change in pH and DO. There were strong seasonal differences in BOD in the Fraser River and Nathan Creek, with the highest levels seen in July. The higher BOD seen in Nathan Creek in July may be an indication of agricultural impact. Although all BOD values fell in the range of 1-8 mg/L and are considered to be relatively unpolluted.

Gillies, S. L.; Fraser, H.; Marsh, S. J.; Peucker-Ehrenbrink, B.; Voss, B. M.; Marcotte, D.; Fanslau, J.; Epp, A.; Bennett, M.; Hanson-Carson, J.; Luymes, R.

2012-12-01

174

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.

175

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

176

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

SciTech Connect

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

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

2010-06-15

177

Effect of unintentionally introduced oxygen on the electron-cyclotron resonance chemical-vapor deposition of SiNX films  

NASA Astrophysics Data System (ADS)

We establish the role of oxygen atoms on the structural, chemical, and mechanical properties of SiOXNY films grown on Si and InP substrates by electron-cyclotron resonance chemical-vapor deposition (ECR CVD) using a diluted SiH4 and N2 mixture in Ar, under controlled conditions. The mechanical and chemical properties of ECR-CVD SiNX films depend on the oxygen contamination even when this element is present in low concentrations. The compressive stress of SiNX films deposited with a low (and constant) content of oxygen (less than 12%) is shown to be in qualitative agreement with a model of repulsive Coulomb forces related mainly to polar -N-H+ units in the SiNX network. We observe a decrease of the film compressive stress when the N2/SiH4 flow ratio increases, which is due to the increase of Si-N bonds in detriment of N-H bonds. Films deposited with high oxygen content in the plasma show a decrease of nitrogen incorporation. Oxygen radicals species compete with those of nitrogen in their reaction with silicon dangling bonds, which has as a consequence a decrease in the incorporation of nitrogen. Additional creation of oxygen radicals, with no hydrogen dilution, is more effective in decreasing the number of N-H bonds, or the compressive stress in the SiNX films, than the corresponding creation of nitrogen radicals. The mechanical properties of SiNX films contaminated with oxygen are controlled, in general, by the total number of both nitrogen plus oxygen atoms relative to silicon. The buffered HF (BHF) film etch rate is enhanced and thus is mainly controlled by the oxygen content. Low values of the compressive stress do not necessarily imply low values of BHF etch rate or a high N/Si ratio. We also present a discussion of the origin of the unintentional incorporation of oxygen in a ECR-CVD system designed for industrial production.

Cova, P.; Masut, R. A.; Grenier, O.; Poulin, S.

2002-07-01

178

Singlet oxygen (1O) generation upon 1270 nm laser irradiation of ground state oxygen (3O) dissolved in organic solvents: Simultaneous and independent determination of 1O production rate and reactivity with chemical traps  

NASA Astrophysics Data System (ADS)

Direct photo-production of singlet oxygen, via 1270 nm laser excitation of molecular oxygen, has been the focus of recent articles. The chemical traps 1,3-diphenylisobenzofuran and rubrene are used to monitor singlet oxygen production in organic solvents through the O[3?g-]?O[1?g] transition. In this Letter evolution of the trap concentration is monitored continuously and we propose a new and simple method to measure singlet oxygen production rate. We derive an analytical expression for the trap disappearance rate that allows simultaneous and independent determination of the 1270 nm absorption cross section and the half quenching concentration with the chemical trap.

Sivéry, A.; Anquez, F.; Pierlot, C.; Aubry, J. M.; Courtade, E.

2013-01-01

179

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. PMID:21076638

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

2010-01-01

180

Chemical oxygen-iodine laser (COIL) for the dismantlement of nuclear facilities  

NASA Astrophysics Data System (ADS)

The dismantlement of obsolete nuclear facilities is a major challenge for both the US Department of Energy and nuclear power utilities. Recent demonstrations have shown that lasers can be highly effective for size reduction cutting, especially for the efficient storage and recycling of materials. However, the full benefits of lasers can only be realized with high average power beams that can be conveniently delivered, via fiber optics, to remote and/or confined areas. Industrial lasers that can meet these requirements are not available now or for the foreseeable future. However, a military weapon laser, a Chemical Oxygen Iodine Laser (COIL), which has been demonstrated at over a hundred kilo Watts, could be adapted to meet these needs and enable entirely new industrial applications. An 'industrialized' COIL would enable rapid sectioning of thick and complex structures, such as glove boxes, reactor vessels, and steam generators, accelerating dismantlement schedules and reducing worker hazards. The full advantages of lasers in dismantlement could finally be realized with a portable COIL which is integrated with sophisticated robotics. It could be built and deployed in less than two years, breaking the paradigm of labor-intensive dismantlement operations and cutting processing times and costs dramatically.

Hallada, Marc R.; Seiffert, Stephan L.; Walter, Robert F.; Vetrovec, John

2000-05-01

181

Densification of chemical vapor deposition silicon dioxide film using oxygen radical oxidation  

NASA Astrophysics Data System (ADS)

Silicon dioxide (SiO2) films formed by chemical vapor deposition (CVD) were treated with oxygen radical oxidation using Ar/O2 plasma excited by microwave. The mass density depth profiles, carrier trap densities, and current-voltage characteristics of the radical-oxidized CVD-SiO2 films were investigated. The mass density depth profiles were estimated with x ray reflectivity measurement using synchrotron radiation of SPring-8. The carrier trap densities were estimated with x ray photoelectron spectroscopy time-dependent measurement. The mass densities of the radical-oxidized CVD-SiO2 films were increased near the SiO2 surface. The densities of the carrier trap centers in these films were decreased. The leakage currents of the metal-oxide-semiconductor capacitors fabricated by using these films were reduced. It is probable that the insulation properties of the CVD-SiO2 film are improved by the increase in the mass density and the decrease in the carrier trap density caused by the restoration of the Si-O network with the radical oxidation.

Kawase, Kazumasa; Teramoto, Akinobu; Umeda, Hiroshi; Suwa, Tomoyuki; Uehara, Yasushi; Hattori, Takeo; Ohmi, Tadahiro

2012-02-01

182

Densification of chemical vapor deposition silicon dioxide film using oxygen radical oxidation  

SciTech Connect

Silicon dioxide (SiO{sub 2}) films formed by chemical vapor deposition (CVD) were treated with oxygen radical oxidation using Ar/O{sub 2} plasma excited by microwave. The mass density depth profiles, carrier trap densities, and current-voltage characteristics of the radical-oxidized CVD-SiO{sub 2} films were investigated. The mass density depth profiles were estimated with x ray reflectivity measurement using synchrotron radiation of SPring-8. The carrier trap densities were estimated with x ray photoelectron spectroscopy time-dependent measurement. The mass densities of the radical-oxidized CVD-SiO{sub 2} films were increased near the SiO{sub 2} surface. The densities of the carrier trap centers in these films were decreased. The leakage currents of the metal-oxide-semiconductor capacitors fabricated by using these films were reduced. It is probable that the insulation properties of the CVD-SiO{sub 2} film are improved by the increase in the mass density and the decrease in the carrier trap density caused by the restoration of the Si-O network with the radical oxidation.

Kawase, Kazumasa; Uehara, Yasushi [Advanced Technology R and D Center, Mitsubishi Electric Corporation, 8-1-1 Tsukaguchi-honmachi, Amagasaki, Hyogo 661-8661 (Japan); Teramoto, Akinobu; Suwa, Tomoyuki; Hattori, Takeo; Ohmi, Tadahiro [New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aoba Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Umeda, Hiroshi [Process Technology Div., Production and Technology Unit, RENESAS Electronics Corporation, 751 Horiguchi, Hitachinaka, Ibaraki 312-8504 (Japan)

2012-02-01

183

Chemical-looping combustion of coal-derived synthesis gas over copper oxide oxygen carriers  

SciTech Connect

CuO/bentonite and CuO-BHA nanocomposites were studied as oxygen carriers in chemical-looping combustion (CLC) of simulated synthesis gas. Global reaction rates of reduction and oxidation, as the function of reaction conversion, were calculated from 10-cycle oxidation/reduction tests utilizing thermogravimetric analysis at atmospheric pressure between 700 and 900 °C. It was found that the reduction reactions are always faster than oxidation reactions; reaction temperature and particle size do not significantly affect the reaction performance of CuO/bentonite. Multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivity for production of CO2 from fuel gas at 800 and 900 °C and full consumption of hydrogen during the reaction. Results of the tapered element oscillating microbalance showed a negative effect of pressure on the global rates of reduction-oxidation reactions at higher fractional conversions. X-ray diffraction patterns confirmed the presence of CuO in the bulk phase of the oxidized sample. Electron microanalysis showed significant morphology changes of reacted CuO/bentonite samples after the 10 oxidation-reduction cycles above 700 °C in an atmospheric thermogravimetric analyzer. The nanostructured CuO-BHA carrier also showed excellent stability and, in comparison to the CuO/bentonite system, slightly accelerated redox kinetics albeit at the expense of significantly increased complexity of manufacturing. Overall, both types of CuO carriers exhibited excellent reaction performance and thermal stability for the CLC process at 700-900 °C.

Tian, H.; Chaudhari, K.; Simonyi, T.; Poston, J.; Liu, T.; Sanders, T.; Veser, G.; Siriwardane, R.

2008-01-01

184

Chemical-looping combustion of coal-derived synthesis gas over copper oxide oxygen carriers  

SciTech Connect

CuO/bentonite and CuO?BHA nanocomposites were studied as oxygen carriers in chemical-looping combustion (CLC) of simulated synthesis gas. Global reaction rates of reduction and oxidation, as the function of reaction conversion, were calculated from 10-cycle oxidation/reduction tests utilizing thermogravimetric analysis at atmospheric pressure between 700 and 900 °C. It was found that the reduction reactions are always faster than oxidation reactions; reaction temperature and particle size do not significantly affect the reaction performance of CuO/bentonite. Multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivity for production of CO2 from fuel gas at 800 and 900 °C and full consumption of hydrogen during the reaction. Results of the tapered element oscillating microbalance showed a negative effect of pressure on the global rates of reduction?oxidation reactions at higher fractional conversions. X-ray diffraction patterns confirmed the presence of CuO in the bulk phase of the oxidized sample. Electron microanalysis showed significant morphology changes of reacted CuO/bentonite samples after the 10 oxidation?reduction cycles above 700 °C in an atmospheric thermogravimetric analyzer. The nanostructured CuO?BHA carrier also showed excellent stability and, in comparison to the CuO/bentonite system, slightly accelerated redox kinetics albeit at the expense of significantly increased complexity of manufacturing. Overall, both types of CuO carriers exhibited excellent reaction performance and thermal stability for the CLC process at 700?900 °C.

Tian, Hanjing; Chaudhari, K.P.; Simonyi, Thomas; Poston, J.A.; Liu, Tengfei; Sanders, Tom; Veser, Goetz; Siriwardane, R.V.

2008-11-01

185

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

186

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

187

Chemical Oxygen-Iodine Laser Diluted by CO2/N2 Buffer Gases with a Cryosorption Vacuum Pump  

NASA Astrophysics Data System (ADS)

Experiments were carried out on a verti-chemical oxygen-iodine laser (COIL), which was designed for N2 and energized by a square-pipe jet singlet oxygen generator (JSOG). A cryosorption vacuum pump was used as the pressure recovery system for CO2 and N2 buffer gases. The output power with CO2 was 27.3% lower than that with N2, but the zeolite bed showed an adsorption capacity threefold higher for CO2 than for N2 in the continuous operation with a Cl2 flow rate of 155 mmol/s and a total flow rate of 430±3 mmol/s.

Xu, Mingxiu; Sang, Fengting; Jin, Yuqi; Fang, Benjie; Chen, Fang; Geng, Zicai; Li, Yongzhao

2008-11-01

188

No oxygen isotope exchange between water and APS-sulfate at surface temperature: Evidence from quantum chemical modeling and triple-oxygen isotope experiments  

NASA Astrophysics Data System (ADS)

In both laboratory experiments and natural environments where microbial dissimilatory sulfate reduction (MDSR) occurs in a closed system, the ?34S ((34S/32S)sample/(34S/32S)standard - 1) for dissolved SO42- has been found to follow a typical Rayleigh-Distillation path. In contrast, the corresponding ?18O ((18O/16O)sample/(18O/16O)standard) - 1) is seen to plateau with an apparent enrichment of between 23‰ and 29‰ relative to that of ambient water under surface conditions. This apparent steady-state in the observed difference between ?18O and ?18OO can be attributed to any of these three steps: (1) the formation of adenosine-5'-phosphosulfate (APS) from ATP and SO42-, (2) oxygen exchange between sulfite (or other downstream sulfoxy-anions) and water later in the MDSR reaction chain and its back reaction to APS and sulfate, and (3) the re-oxidation of produced H2S or precursor sulfoxy-anions to sulfate in environments containing Fe(III) or O2. This study examines the first step as a potential pathway for water oxygen incorporation into sulfate. We examined the structures and process of APS formation using B3LYP/6-31G(d,p) hybrid density functional theory, implemented in the Gaussian-03 program suite, to predict the potential for oxygen exchange. We conducted a set of in vitro, enzyme-catalyzed, APS formation experiments (with no further reduction to sulfite) to determine the degree of oxygen isotope exchange between the APS-sulfate and water. Triple-oxygen-isotope labeled water was used in the reactor solutions to monitor oxygen isotope exchange between water and APS sulfate. The formation and hydrolysis of APS were identified as potential steps for oxygen exchange with water to occur. Quantum chemical modeling indicates that the combination of sulfate with ATP has effects on bond strength and symmetry of the sulfate. However, these small effects impart little influence on the integrity of the SO42- tetrahedron due to the high activation energy required for hydrolysis of SO42- (48.94 kcal/mol). Modeling also indicates that APS dissociation via hydrolysis is achieved through cleavage of the P-O bond instead of S-O bond, further supporting the lack of APS-H2O-oxygen exchange. The formation of APS in our in vitro experiments was verified by HPLC fluorescence spectroscopy, and triple-oxygen isotope data of the APS-sulfate indicate no oxygen isotope exchange occurred between APS-sulfate and water at 30 °C for an experimental duration ranging from 2 to 120 h. The study excludes APS formation as one of the causes for sulfate-oxygen isotope exchange with water during MDSR.

Kohl, Issaku E.; Asatryan, Rubik; Bao, Huiming

2012-10-01

189

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

SciTech Connect

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.; Williams, D. S. [Materials Science and Engineering, Binghamton University, Binghamton, New York 13902 (United States); Butler, K. T.; Walsh, A. [Center for Sustainable Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Quackenbush, N. F. [Department of Physics, Applied Physics, and Astronomy, Binghamton University, Binghamton, New York 13902 (United States); Junda, M.; Podraza, N. J. [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States); Fischer, D. A.; Woicik, J. C. [Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); White, B. E.; Piper, L. F. J., E-mail: lpiper@binghamton.edu [Department of Physics, Applied Physics, and Astronomy, Binghamton University, Binghamton, New York 13902 (United States); Materials Science and Engineering, Binghamton University, Binghamton, New York 13902 (United States)

2014-06-09

190

Nitrogen-to-oxygen as a tracer of the chemical evolution of the Local and young Universe  

NASA Astrophysics Data System (ADS)

Oxygen optical emission-lines are used exhaustively as tracers of the metal content in gaseous nebulae ionized during different episodes of massive star formation. The high luminosity of these lines make them to be detected from the Local Universe up to starbursts at high redshift. Occasionally, in those cases where these lines cannot be measured due to the spectral coverage or to the redshift, nitrogen emission-lines are used instead. However, both nitrogen and oxygen have different nucleosynthetic origins, so the study of chemical abundances from nitrogen emission-lines introduces variables depending on the star formation history of each galaxy that must be taken into account. This contribution summarizes those risks involved in using metallicity tracers based on optical nitrogen emission lines and also describes the advantages of using instead the nitrogen-to-oxygen ratio as a tracer itself, based mainly on its independence on star formation rate, avoiding selection effects at high redshift.

Pérez-Montero, E.

2013-05-01

191

The effect of the structure and conformational dynamics on quenching of triplet states of porphyrins and their chemical dimers by molecular oxygen and on singlet oxygen generation  

NASA Astrophysics Data System (ADS)

Quantum-chemical calculations are performed to analyze the factors affecting rate constant k T of quenching of the lowest triplet state by molecular oxygen and quantum yield ?? of singlet oxygen generation in chemical dimers of porphyrins bound by phenyl spacers at one of the meso positions (OEP)2-Ph, (TPP)2, and their Zn complexes. It is established that, for both types of dimers, the triplet excitation is localized on one of the macrocycles. The steric hindrance of macrocycles at the site of the phenyl ring of (OEP)2-Ph, (ZnOEP)2-Ph, and their monomeric analogues OEP-Ph and ZnOEP-Ph facilitates its rotation by 90° in the triplet state. The lowest triplet state energy in this ( U) conformation is lower than 7800 cm-1, which makes impossible electronic excitation energy transfer to molecular oxygen. The potential barrier of transformation to the U conformation is considerably lower for dimers than for monomers. Because of this, the rate of conformational transformations for dimers is higher and some of the (OEP)2-Ph and (ZnOEP)2-Ph molecules have time to transform into the new U conformation before diffusion collision with O2 molecules in solution. This leads to a noticeable decrease in ?? in accordance with experimental data. It is shown that the behavior of k T in the series of the studied dimers, their monomeric analogues, and relative compounds corresponds to the model of dipole-dipole electronic excitation energy transfer 1(3M⋯3?{g/-}) ? 1(1M0⋯1?g) in collisional complexes.

Ivashin, N. V.; Shchupak, E. E.; Sagun, E. I.

2015-01-01

192

[The turbidity and pH impact analysis of low concentration water chemical oxygen demand ultraviolet absorption detection].  

PubMed

Configuration standard solution in the concentration range of 1 - 25 mg x L(-1) of potassium hydrogen phthalate was used as experimental subject, Ultraviolet absorption spectra was collected, the COD quantitative analysis model was established by partial least squares with different pretreatment methods and the turbidity of the compensation effect analysis was given. The results show the model uses smoothing first derivative pretreatment method, internal cross validation RMSECV root mean square value of 0.122 27, principal component number 4, the square of the prediction model correlation coefficient is 0.999 8, and the relative prediction error is in the range of 0.03%-1.7%; for 0-100 NTU's turbidity solution, the relative standard deviation RSD is 2.3% after compensation; with pH in the range of 3-10, influence can be ignored. PMID:24555385

Wu, Guo-Qing; Bi, Wei-Hong; Fu, Guang-Wei; Li, Jian-Guo; Ji, Hong-Yue

2013-11-01

193

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

194

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

195

Chemical-looping combustion of coal-derived synthesis gas over copper oxide oxygen carriers  

SciTech Connect

CuO/bentonite and CuO-BHA nanocomposites were studied as oxygen carriers in chemical-looping combustion (CLC) of simulated synthesis gas. Global reaction rates of reduction and oxidation, as the function of reaction conversion, were calculated from 10-cycle oxidation/reduction tests utilizing thermogravimetric analysis at atmospheric pressure between 700 and 900{degree}C. It was found that the reduction reactions are always faster than oxidation reactions; reaction temperature and particle size do not significantly affect the reaction performance of CuO/bentonite. Multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivity for production of CO{sub 2} from fuel gas at 800 and 900{degree}C and full consumption of hydrogen during the reaction. Results of the tapered element oscillating microbalance showed a negative effect of pressure on the global rates of reduction-oxidation reactions at higher fractional conversions. X-ray diffraction patterns confirmed the presence of CuO in the bulk phase of the oxidized sample. Electron microanalysis showed significant morphology changes of reacted CuO/bentonite samples after the 10 oxidation-reduction cycles above 700{degree}C in an atmospheric thermogravimetric analyzer. The nanostructured CuO-BHA carrier also showed excellent stability and, in comparison to the CuO/bentonite system, slightly accelerated redox kinetics albeit at the expense of significantly increased complexity of manufacturing. Overall, both types of CuO carriers exhibited excellent reaction performance and thermal stability for the CLC process at 700-900{degree}C. 48 refs., 12 figs., 8 tabs.

Hanjing Tian; Karuna Chaudhari; Thomas Simonyi; James Poston; Tengfei Liu; Tom Sanders; Goetz Veser; Ranjani Siriwardane [U.S. Department of Energy, Morgantown, WV (United States). National Energy Technology Laboratory

2008-11-15

196

Hemoglobin-based oxygen carriers do not alter platelet functions: study of three chemically modified hemoglobin solutions  

Microsoft Academic Search

Objective. Chemically modified hemoglobins are being developed as potential oxygen-carrying blood substitutes (HBOCs). Clinical and preclinical data demonstrate the vasoactive properties of HBOCs by trapping of nitric oxide, which is also known to have platelet inhibitory activities properties. This study evaluated the effects of three structurally different HBOCs (Hb-Dex-BTC, !!-Hb, and o-raffinose-poly-Hb) on platelet functions in vitro to compare to

Marie Toussaint; Véronique Latger-Cannard; Alexis Caron; Thomas Lecompte; Claude Vigneron; Patrick Menu

2003-01-01

197

Impacts of increasing dissolved inorganic nitrogen discharged from Changjiang on primary production and seafloor oxygen demand in the East China Sea from 1970 to 2002  

NASA Astrophysics Data System (ADS)

In recent years, benthic hypoxia has been observed in the outflow region of the Changjiang River in the East China Sea. Because the nitrogen input to the Changjiang watershed, mainly from human activities, has increased by 3 fold in the last four decades and the nitrogen load had grown exponentially, it is speculated that anthropogenic nutrients may be responsible for the hypoxia in the East China Sea shelf. We employ a coupled 3-D physical-biogeochemical model of the East China Sea to investigate how the changing Changjiang nutrient loads from 1970 to the end of 2002 may have impacted on primary production in the water column and the seafloor oxygen demand (SOD) on the seafloor. The model predicts an average value of 437 mgC m- 2 d- 1 for primary production and 10.0 mmol O2 m- 2 d- 1 for SOD for the ECS shelf over the entire modeling period. The model results compare reasonably with observations during the period from December 1997 to October 1998. Responding to the increase of the Changjiang DIN loading by a factor of ~ 2.4, the modeled primary production in the East China Sea shelf has increased by 17%, and the modeled SOD by 22%. In the inner shelf, where the impact is the strongest, the SOD increases by 30%. We are able to identify areas of potential hypoxia using two criteria: SOD > 30 mmol O2 m- 2 d- 1 and water depth > 25 m. The maximum area of potential hypoxic region in any month of a year has increased dramatically after 1991; the change appears related to the Changjiang DIN loads from May to July that showed a sudden increase after 1990. The responses in potential hypoxic area are more pronounced than the increases in DIN (dissolved inorganic nitrogen) loads, suggesting strong nonlinear effect in the development of hypoxia, which warrants further investigation. It is cautioned that the SOD calculation was based on the Redfield C/N ratio, but the actual C/N ratio may deviate from it. Direct observations of the sediment oxygen consumption are needed to validate our modeling approach. We also assessed the potential impacts of particulate organic matter from Changjiang by introducing a load of reactive particulate nitrogen (PN), which was assumed proportional to DIN based on estimated yields in the watershed. The modeled impacts on primary productivity and SOD are significant, but more accurate quantification of the monthly PN load and better characterization of its reactivity are required for better assessment.

Liu, Kon-Kee; Yan, Weijin; Lee, Hung-Jen; Chao, Shenn-Yu; Gong, Gwo-Ching; Yeh, Tzu-Ying

2015-01-01

198

Pilot investigation of the oxygen demands and metabolic cost of incremental shuttle walking and treadmill walking in patients with cardiovascular disease  

PubMed Central

Objective To determine if the metabolic cost of the incremental shuttle-walking test protocol is the same as treadmill walking or predicted values of walking-speed equations. Setting Primary care (community-based cardiac rehabilitation). Participants Eight Caucasian cardiac rehabilitation patients (7 males) with a mean age of 67±5.2?years. Primary and secondary outcome measures Oxygen consumption, metabolic power and energy cost of walking during treadmill and shuttle walking performed in a balanced order with 1?week between trials. Results Average overall energy cost per metre was higher during treadmill walking (3.22±0.55?J?kg/m) than during shuttle walking (3.00±0.41?J?kg/m). There were significant post hoc effects at 0.67?m/s (p<0.004) and 0.84?m/s (p<0.001), where the energy cost of treadmill walking was significantly higher than that of shuttle walking. This pattern was reversed at walking speeds 1.52?m/s (p<0.042) and 1.69?m/s (p<0.007) where shuttle walking had a greater energy cost per metre than treadmill walking. At all walking speeds, the energy cost of shuttle walking was higher than that predicted using the American College of Sports Medicine walking equations. Conclusions The energetic demands of shuttle walking were fundamentally different from those of treadmill walking and should not be directly compared. We warn against estimating the metabolic cost of the incremental shuttle-walking test using the current walking-speed equations. PMID:25227624

Almodhy, M; Beneke, R; Cardoso, F; Taylor, M J D; Sandercock, G R H

2014-01-01

199

Defining Nutrient and Biochemical Oxygen Demand Baselines for Tropical Rivers and Streams in São Paulo State (Brazil): A Comparison Between Reference and Impacted Sites  

NASA Astrophysics Data System (ADS)

Determining reference concentrations in rivers and streams is an important tool for environmental management. Reference conditions for eutrophication-related water variables are unavailable for Brazilian freshwaters. We aimed to establish reference baselines for São Paulo State tropical rivers and streams for total phosphorus (TP) and nitrogen (TN), nitrogen-ammonia (NH4 +) and Biochemical Oxygen Demand (BOD) through the best professional judgment and the trisection methods. Data from 319 sites monitored by the São Paulo State Environmental Company (2005 to 2009) and from the 22 Water Resources Management Units in São Paulo State were assessed ( N = 27,131). We verified that data from different management units dominated by similar land cover could be analyzed together (Analysis of Variance, P = 0.504). Cumulative frequency diagrams showed that industrialized management units were characterized by the worst water quality (e.g. average TP of 0.51 mg/L), followed by agricultural watersheds. TN and NH4 + were associated with urban percentages and population density (Spearman Rank Correlation Test, P < 0.05). Best professional judgment and trisection (median of lower third of all sites) methods for determining reference concentrations showed agreement: 0.03 & 0.04 mg/L (TP), 0.31 & 0.34 mg/L (TN), 0.06 & 0.10 mg-N/L (NH4 +) and 2 & 2 mg/L (BOD), respectively. Our reference concentrations were similar to TP and TN reference values proposed for temperate water bodies. These baselines can help with water management in São Paulo State, as well as providing some of the first such information for tropical ecosystems.

Cunha, Davi G. F.; Dodds, Walter K.; Carmo Calijuri, Maria Do

2011-11-01

200

Proceedings of the International Conference on Lasers `95, eds. V.J. Corcoran and T.A. Goldman, STS Press, McLean VA, 1996, pp. 225-231. OPTIMIZING HIGH PRESSURE CHEMICAL OXYGEN-IODINE LASERS  

E-print Network

Press, McLean VA, 1996, pp. 225-231. OPTIMIZING HIGH PRESSURE CHEMICAL OXYGEN-IODINE LASERS David L laser model was baselined to existing oxygen-iodine research assessment and device improvement chemical* by N2. I. Introduction The typical chemical oxygen-iodine laser (COIL) utilizes an energy transfer from

Carroll, David L.

201

Chemical alteration of poly(vinyl fluoride) Tedlar by hyperthermal atomic oxygen  

NASA Astrophysics Data System (ADS)

In this study the erosion of poly(vinyl fluoride) Tedlar by hyperthermal atomic oxygen (AO) has been examined using X-ray photoelectron spectroscopy (XPS). Initially the Tedlar film had F/C and O/C atom ratios of 0.45 and 0.11, which decrease to 0.018 and 0.04, respectively, after a 2-h exposure to a flux of 2 × 10 15 atoms/cm 2 s AO with an average kinetic energy of 5 eV. This exposure essentially produced a graphitic or amorphous carbon-like layer with a carbon content greater than 90 at.%. Longer AO exposures do not alter the composition of this layer significantly. Exposure to O 2 or air nearly doubles the oxygen content in the near-surface region. This is due to dissociative oxygen adsorption at reactive sites formed at the polymer surface during AO exposure. Further exposure to AO removes this chemisorbed oxygen.

Hoflund, Gar B.; Everett, Michael L.

2005-01-01

202

Silicon-on-glass pore network micromodels with oxygen-sensing fluorophore films for chemical imaging and defined spatial structure  

SciTech Connect

Pore network microfluidic models were fabricated by a silicon-on-glass technique that provides the precision advantage of dry etched silicon while creating a structure that is transparent across all microfluidic channels and pores, and can be imaged from either side. A silicon layer is bonded to an underlying borosilicate glass substrate and thinned to the desired height of the microfluidic channels and pores. The silicon is then patterned and through-etched by deep reactive ion etching (DRIE), with the underlying glass serving as an etch stop. After bonding on a transparent glass cover plate, one obtains a micromodel in oxygen impermeable materials with water wet surfaces where the microfluidic channels are transparent and structural elements such as the pillars creating the pore network are opaque. The micromodel can be imaged from either side. The advantageous features of this approach in a chemical imaging application are demonstrated by incorporating a Pt porphyrin fluorophore in a PDMS film serving as the oxygen sensing layer and a bonding surface, or in a polystyrene film coated with a PDMS layer for bonding. The sensing of a dissolved oxygen gradient was demonstrated using fluorescence lifetime imaging, and it is shown that different matrix polymers lead to optimal use in different ranges dissolved oxygen concentration. Imaging with the opaque pillars in between the observation direction and the continuous fluorophore film yields images that retain spatial information in the sensor image.

Grate, Jay W.; Kelly, Ryan T.; Suter, Jonathan D.; Anheier, Norman C.

2012-11-21

203

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

204

Silicon-on-glass pore network micromodels with oxygen-sensing fluorophore films for chemical imaging and defined spatial structure.  

PubMed

Pore network microfluidic models were fabricated by a silicon-on-glass technique that provides the precision advantage of dry etched silicon while creating a structure that is transparent across all microfluidic channels and pores, and can be imaged from either side. A silicon layer is bonded to an underlying borosilicate glass substrate and thinned to the desired height of the microfluidic channels and pores. The silicon is then patterned and through-etched by deep reactive ion etching (DRIE), with the underlying glass serving as an etch stop. After bonding on a transparent glass cover plate, one obtains a micromodel in oxygen impermeable materials with water-wet surfaces where the microfluidic channels are transparent and structural elements such as the pillars creating the pore network are opaque. The advantageous features of this approach in a chemical imaging application are demonstrated by incorporating a Pt porphyrin fluorophore in a PDMS film serving as the oxygen-sensing layer and a bonding surface, or in a polystyrene film coated with a PDMS layer for bonding. The sensing of a dissolved oxygen gradient was demonstrated using fluorescence lifetime imaging, and it is shown that different matrix polymers lead to optimal use in different ranges of oxygen concentration. Imaging with the opaque pillars in between the observation direction and the continuous fluorophore film yields images that retain defined spatial structure in the sensor image. PMID:22995983

Grate, Jay W; Kelly, Ryan T; Suter, Jonathan; Anheier, Norm C

2012-11-21

205

Chemical bonding, interface strength, and oxygen K electron-energy-loss near-edge structure of the Cu\\/Al2O3 interface  

Microsoft Academic Search

Chemical bondings and oxygen K electron-energy-loss near-edge structures (ELNES) of oxygen terminated Cu\\/Al2O3 heterointerfaces with hollow and on-top configurations were theoretically investigated by using a first principles orthogonalized linear combination of atomic orbitals method. From the chemical bonding analysis, it was found that the hollow configuration has stronger ionic and covalent bondings as compared with the on-top configuration, and the

Teruyasu Mizoguchi; Takeo Sasaki; Shingo Tanaka; Katsuyuki Matsunaga; Takahisa Yamamoto; Masanori Kohyama; Yuichi Ikuhara

2006-01-01

206

Chemical bonding, interface strength, and oxygen K electron-energy-loss near-edge structure of the Cu\\/AlâOâ interface  

Microsoft Academic Search

Chemical bondings and oxygen K electron-energy-loss near-edge structures (ELNES) of oxygen terminated Cu\\/AlâOâ heterointerfaces with hollow and on-top configurations were theoretically investigated by using a first principles orthogonalized linear combination of atomic orbitals method. From the chemical bonding analysis, it was found that the hollow configuration has stronger ionic and covalent bondings as compared with the on-top configuration, and the

Teruyasu Mizoguchi; Takeo Sasaki; Katsuyuki Matsunaga; Yuichi Ikuhara; Shingo Tanaka; Masanori Kohyama; Takahisa Yamamoto

2006-01-01

207

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

208

Combined effects of Ag nanoparticles and oxygen plasma treatment on PLGA morphological, chemical, and antibacterial properties.  

PubMed

The purpose of this study is to investigate the combined effects of oxygen plasma treatments and silver nanoparticles (Ag) on PLGA in order to modulate the surface antimicrobial properties through tunable bacteria adhesion mechanisms. PLGA nanocomposite films, produced by solvent casting with 1 wt % and 7 wt % of Ag nanoparticles were investigated. The PLGA and PLGA/Ag nanocomposite surfaces were treated with oxygen plasma. Surface properties of PLGA were investigated by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), static contact angle (CA), and high resolution X-ray photoelectron spectroscopy (XPS). Antibacterial tests were performed using an Escherichia coli RB (a Gram negative) and Staphylococcus aureus 8325-4 (a Gram positive). The PLGA surface becomes hydrophilic after the oxygen treatment and its roughness increases with the treatment time. The surface treatment and the Ag nanoparticle introduction have a dominant influence on the bacteria adhesion and growth. Oxygen-treated PLGA/Ag systems promote higher reduction of the bacteria viability in comparison to the untreated samples and neat PLGA. The combination of Ag nanoparticles with the oxygen plasma treatment opens new perspectives for the studied biodegradable systems in biomedical applications. PMID:23360180

Fortunati, Elena; Mattioli, Samantha; Visai, Livia; Imbriani, Marcello; Fierro, Josè Luis G; Kenny, Josè Maria; Armentano, Ilaria

2013-03-11

209

Regenerable MgO promoted metal oxide oxygen carriers for chemical looping combustion  

DOEpatents

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

Siriwardane, Ranjani V.; Miller, Duane D.

2014-08-19

210

On feasibility of decreasing metal fuel content in chemical oxygen generators  

Microsoft Academic Search

Sodium chlorate based mixtures for oxygen generators include metal fuels, which may produce instabilities and increase risk of fire. Eliminating or at least decreasing the metal content would improve the process stability and fire safety of the generators. In the present paper, thermal decomposition of sodium chlorate based mixtures with different concentrations of cobalt oxide catalyst and metals (iron and

E. Shafirovich; A. Garcia; A. K. Narayana Swamy; D. J. Mast; S. D. Hornung

211

REVIEW ARTICLE: Inorganic solid state chemically sensitive devices: electrochemical oxygen gas sensors  

Microsoft Academic Search

The principles of operation of potentiometric, amperometric, coulometric and impedance-based oxygen gas sensors are reviewed. Factors influencing the speed of response are considered in detail and related to the information obtainable from impedance measurements. The response of a sensor to gaseous mixtures not in equilibrium is discussed, particularly in relation to measurements in gases generated by the combustion of fossil

W. C. Maskell

1987-01-01

212

Chemical Constraints on the Water and Total Oxygen Abundances in the Deep Atmosphere of Saturn  

NASA Astrophysics Data System (ADS)

Thermochemical equilibrium and kinetic calculations for the trace gases CO, PH3, and SiH4 give three independent constraints on the water and total oxygen abundances of Saturn's deep atmosphere. A lower limit to the water abundance of H2O/H2>=(1.7+0.7-0.4)×10-3 is given by CO chemistry, whereas an upper limit of H2O/H2<=(5.5+0.8-2.5)×10-3 is given by PH3 chemistry. A combination of the CO and PH3 constraints indicates a water enrichment on Saturn of 1.9-6.1 times the solar system abundance (H2O/H2=8.96×10-4). The total oxygen abundance must be at least 1.7 times the solar system abundance (O/H2=1.16×10-3) in order for SiH4 to remain below the detection limit of SiH4/H2<2×10-10. A combination of the CO, PH3, and SiH4 constraints suggests that the total oxygen abundance on Saturn is 3.2-6.4 times the solar system abundance. Our results indicate that oxygen on Saturn is less enriched than other heavy elements (such as C and P) relative to the solar system composition.

Visscher, Channon; Fegley, Bruce, Jr.

2005-04-01

213

Homegrown Demand  

NSDL National Science Digital Library

The professor sells an announced number of M&M packets (or other inexpensive good) through an auction to derive a classroom demand schedule. The resulting demand schedule is displayed as a "curve" and facilitates discussion of consumer demand.

Todd Swarthout

214

Sustainable Irrigation to Balance Supply of Soil Water, Oxygen, Nutrients and AgroChemicals  

Microsoft Academic Search

\\u000a The socio-economic pressure for improvements in irrigation efficiencies is increasing due to intense competition for water\\u000a between agricultural, domestic and industrial users as well as demands for compliance with environmental regulations. Precision\\u000a irrigation technology involving less irrigation water and uniform application across the field is therefore important. In\\u000a the context of declining water allocation for irrigation and the variations in

Surya P. Bhattarai; David J. Midmore; Ninghu Su

215

Nitrogen and Oxygen Abundance Variations in the Outer Ejecta of Eta Carinae: Evidence for Recent Chemical Enrichment  

E-print Network

We present optical spectra of the ionized `Outer Ejecta' of Eta Carinae that reveal differences in chemical composition at various positions. In particular, young condensations just outside the dusty Homunculus Nebula show strong nitrogen lines and little or no oxygen -- but farther away, nitrogen lines weaken and oxygen lines become stronger. The observed variations in the apparent N/O ratio may signify either that the various blobs were ejected with different abundances, or more likely, that the more distant condensations are interacting with normal-composition material. The second hypothesis is supported by various other clues involving kinematics and X-ray emission, and would suggest that Eta Car is enveloped in a ``cocoon'' deposited by previous stellar-wind mass loss. In particular, all emission features where we detect strong oxygen lines are coincident with or outside the soft X-ray shell. In either case, the observed abundance variations suggest that Eta Car's ejection of nitrogen-rich material is a recent phenomenon -- taking place in just the last few thousand years. Thus, Eta Carinae may be at a critical stage of evolution when ashes of the CNO cycle have just appeared at its surface. Finally, these spectra reveal some extremely fast nitrogen-rich material, with Doppler velocities up to 3200 km/s, and actual space velocities that may be much higher. This is the fastest material yet seen in Eta Car's nebula, but with unknown projection angles its age is uncertain.

Nathan Smith; Jon A. Morse

2004-02-20

216

Chemical alteration of poly(vinyl fluoride) Tedlar by hyperthermal atomic oxygen  

Microsoft Academic Search

In this study the erosion of poly(vinyl fluoride) Tedlar by hyperthermal atomic oxygen (AO) has been examined using X-ray photoelectron spectroscopy (XPS). Initially the Tedlar film had F\\/C and O\\/C atom ratios of 0.45 and 0.11, which decrease to 0.018 and 0.04, respectively, after a 2-h exposure to a flux of 2 × 1015atoms\\/cm2s AO with an average kinetic energy

Gar B. Hoflund; Michael L. Everett

2005-01-01

217

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

218

Chemical Constraints on the Water and Total Oxygen Abundances in the Deep Atmosphere of Saturn  

E-print Network

Thermochemical equilibrium and kinetic calculations for the trace gases CO, PH3, and SiH4 give three independent constraints on the water and total oxygen abundances of Saturn's deep atmosphere. A lower limit to the water abundance of H2O/H2 > 1.7 x 10^-3 is given by CO chemistry while an upper limit of H2O/H2 Saturn of 1.9 to 6.1 times the solar system abundance (H2O/H2 = 8.96 x 10^-4). The total oxygen abundance must be at least 1.7 times the solar system abundance (O/H2 = 1.16 x 10^-3) in order for the SiH4 to remain below a detection limit of SiH4/H2 Saturn is 3.2 to 6.4 times the solar system abundance. Our results indicate that oxygen on Saturn is less enriched than other heavy elements (such as C and P) relative to a solar system composition. This work was supported by NASA NAG5-11958.

Channon Visscher; Bruce Fegley Jr

2005-01-07

219

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

220

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

221

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

222

Chemical reactivity of hydrogen, nitrogen, and oxygen atoms at temperatures below 100 k  

NASA Technical Reports Server (NTRS)

The synthesis of unusual compounds by techniques employing cryogenic cooling to retard their very extreme reactivity was investigated. Examples of such species that were studied are diimide (N2H2), cyclobutadiene (C4H4), cyclopropanone (C3H4O), oxirene (C2H2O), and many others. Special purpose cryogenically cooled inlet arrangements were designed such that the analyses incurred no warm-up of the cold, and frequently explosively unstable, compounds. Controlled energy electron impact techniques were used to measure critical potentials and to develop the molecular energetics and thermodynamics of these molecules and to gain some insight into their kinetic characteristics as well. Three and four carbon strained ring molecules were studied. Several reactions of oxygen and hydrogen atoms with simple molecules of H, N, C, and O in hard quench configurations were studied. And the quench stabilization of BH3 was explored as a model system in cryochemistry.

Mcgee, H. A., Jr.

1973-01-01

223

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. PMID:23807900

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

2013-01-01

224

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

PubMed

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. PMID:23807900

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

2010-10-01

225

Chemical deposition of platinum nanoparticles on iridium oxide for oxygen electrode of unitized regenerative fuel cell  

Microsoft Academic Search

Platinum nanoparticles were deposited on the surface of IrO2 by chemical reduction. The morphology and structure of nanostructural Pt\\/IrO2 composites were characterized by XRD, EDX and FE-SEM. The reduction of PtCl62- ions in sodium borohydride aqueous solution containing sodium dodecylbenzenesulfonate (SDBS) additive leads to a fine dispersion and high loading of platinum nanoparticles on IrO2 without serious aggregation. A slight

Wenli Yao; Jun Yang; Jiulin Wang; Yanna Nuli

2007-01-01

226

Data acquisition and control system with a programmable logic controller (PLC) for a pulsed chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

A user-friendly data acquisition and control system (DACS) for a pulsed chemical oxygen -iodine laser (PCOIL) has been developed. It is implemented by an industrial control computer?a PLC, and a distributed input/output (I/O) module, as well as the valve and transmitter. The system is capable of handling 200 analogue/digital channels for performing various operations such as on-line acquisition, display, safety measures and control of various valves. 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 PCOIL. The DACS system has been programmed using software programmable logic controller (PLC). Using this DACS, more than 200 runs were given performed successfully.

Yu, Haijun; Li, Guofu; Duo, Liping; Jin, Yuqi; Wang, Jian; Sang, Fengting; Kang, Yuanfu; Li, Liucheng; Wang, Yuanhu; Tang, Shukai; Yu, Hongliang

2015-02-01

227

Decontamination of chemical-warfare agent simulants by polymer surfaces doped with the singlet oxygen generator zinc octaphenoxyphthalocyanine.  

PubMed

Using reactive singlet oxygen (1O2), the oxidation of chemical-warfare agent (CWA) simulants has been demonstrated. The zinc octaphenoxyphthalocyanine (ZnOPPc) complex was demonstrated to be an efficient photosensitizer for converting molecular oxygen (O2) to 1O2 using broad-spectrum light (450-800 nm) from a 250 W halogen lamp. This photosensitization produces 1O2 in solution as well as within polymer matrices. The oxidation of 1-naphthol to naphthoquinone was used to monitor the rate of 1O2 generation in the commercially available polymer film Hydrothane that incorporates ZnOPPc. Using electrospinning, nanofibers of ZnOPPc in Hydrothane and polycarbonate were formed and analyzed for their ability to oxidize demeton-S, a CWA simulant, on the surface of the polymers and were found to have similar reactivity as their corresponding films. The Hydrothane films were then used to oxidize CWA simulants malathion, 2-chloroethyl phenyl sulfide (CEPS), and 2-chloroethyl ethyl sulfide (CEES). Through this oxidation process, the CWA simulants are converted into less toxic compounds, thus decontaminating the surface using only O2 from the air and light. PMID:24060426

Gephart, Raymond T; Coneski, Peter N; Wynne, James H

2013-10-23

228

Chemical equilibria involved in the oxygen-releasing step of manganese ferrite water-splitting thermochemical cycle  

SciTech Connect

Sodium ferrimanganite carbonatation reaction was investigated at different temperatures/carbon dioxide partial pressures to evaluate the feasibility of the thermochemical water-splitting cycle based on the MnFe{sub 2}O{sub 4}/Na{sub 2}CO{sub 3}/Na(Mn{sub 1/3}Fe{sub 2/3})O{sub 2} system. After thermal treatments in selected experimental conditions, the obtained powder samples were investigated by using the X-ray diffraction (XRD) technique and Rietveld analysis. Two different lamellar Na{sub 1-x}Mn{sub 1/3}Fe{sub 2/3}O{sub 2-{delta}} phases were observed together with the expected MnFe{sub 2}O{sub 4}/Na{sub 2}CO{sub 3} mixture. Different equilibrium regions among sodium-depleted lamellar phases, manganese ferrite and sodium carbonate were found as a function of the different reaction conditions. A hypothesis concerning the regeneration mechanism of the initial compounds is proposed. Chemical equilibrium between stoichiometric and sub-stoichiometric forms of sodium ferrimanganite and sodium carbonate formation/dissociation appears to be essential factors governing the oxygen-releasing step of the manganese ferrite thermochemical cycle. - Graphical abstract: Na(Mn{sub 1/3}Fe{sub 2/3})O{sub 2} disproportion reaction in the presence of CO{sub 2} was studied. Chemical equilibria among Na{sub 1-x}(Mn{sub 1/3}Fe{sub 2/3})O{sub 2}, MnFe{sub 2}O{sub 4} and Na{sub 2}CO{sub 3} compounds were evidenced and studied by means of Rietveld analysis performed on XRD patterns. Two different sodium-depleted lamellar structures were identified. The role of sodium carbonate formation/dissociation equilibrium in the oxygen-releasing step of the manganese ferrite thermochemical cycle has been highlighted.

Seralessandri, L.; Bellusci, M.; Alvani, C.; La Barbera, A.; Padella, F. [ENEA-C.R. Casaccia, Italian National Agency for New Technologies, Energy and the Environment, Via Anguillarese 301, 00123 Roma (Italy); Varsano, F. [ENEA-C.R. Casaccia, Italian National Agency for New Technologies, Energy and the Environment, Via Anguillarese 301, 00123 Roma (Italy)], E-mail: francesca.varsano@casaccia.enea.it

2008-08-15

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

Oxygen Gas Abundances at z~1.4: Implications for the Chemical Evolution History of Galaxies  

E-print Network

The 1consumed to build up both the disk and the bulge components of spiral galaxies. Finally, our analysis of the metallicity-luminosity relation at 0chemical evolution may take place progressively in lower mass systems as the universe ages. These results are consistent with a ``downsizing'' type picture in the sense that particular signatures (e.g., high [OIII]/[OII] or low [O/H]) are seen in progressively more luminous (massive) systems at higher redshifts.

C. Maier; S. J. Lilly; C. M. Carollo; K. Meisenheimer; H. Hippelein; A. Stockton

2005-11-09

231

Chemical compatibility of a TiAl-Nb melt with oxygen-free crucible ceramics made of aluminum nitride  

NASA Astrophysics Data System (ADS)

The problem of uncontrolled oxygen contamination of intermetallic TiAl ingots is considered for the application of crucibles and molds based on traditional oxide ceramics. A synthesized Ti-45.9Al-8Nb (at %) alloy is solidified in alternative oxygen-free crucibles made of high-purity aluminum nitride (99.99% AlN) upon holding at 1670°C for 5, 12, and 25 min and subsequent quenching in a high-purity argon atmosphere. The initial material and the solidified ingots are studied by scanning electron microscopy, optical microscopy, X-ray diffraction, electron-probe microanalysis, and gas-content chemical analysis. The key features of the interaction of the TiAl-Nb melt with AlN ceramics are revealed. Partial thermal dissociation of the crucible material according to the reaction AlN ? Al + N and the reaction of atomic nitrogen with the melt lead to the formation of a solid 6.4-?m-thick TiN coating on the ingot surface and provide perfect wettability of the crucible by the melt and easy removal of solidified casting items from the mold. The TiN coating serves as a diffusion barrier that hinders the diffusion of nitrogen and residual oxygen from the pores in the crucible toward the melt. As a result, no oxide particles are detected in the ingots. However, few single microprecipitates of two nitride phases ((Ti,Al) x N y , NbN) are detected in the near-bottom region, 300 ?m thick, in the alloy after holding at 1670°C for 25 min. The total oxygen contamination in a two-phase ?2 + ? ingot does not exceed 1100 wt ppm, which is 1.5-2 times lower than that obtained in the experiments performed with modern advanced oxide crucibles made of yttrium ceramics Y2O3. AlN is shown to be a promising crucible material that can be considered as an alternative to oxide ceramics in the metallurgy of TiAl intermetallics.

Kartavykh, A. V.; Cherdyntsev, V. V.

2008-12-01

232

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

PubMed Central

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 KC 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 KC 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 KC channel. PMID:24563037

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

2014-01-01

233

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

234

Chemical role of oxygen plasma in wafer bonding using borosilicate glasses  

NASA Astrophysics Data System (ADS)

Plasma-treated oxide layers are commonly used in wafer bonding applications. Borosilicate glass (BSG) layers deposited by low-pressure chemical vapor deposition treated with an O2 plasma in reactive ion etching mode for 5 min at 0.6 W/cm2 and rinsed with DI H2O readily bond to GaAs and Si. The chemical role of this prebonding treatment was investigated using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The peak intensities for both the Si-O and B-O absorbance bands decreased in intensity as a result of the plasma treatment is consistent with the uniform sputtering of 9.8 nm±0.8 nm of BSG. Polarization dependent ATR-FTIR revealed that the H2O/OH absorbance bands decreased in peak intensity with the OH groups being preferentially oriented perpendicular to the sample surface after the plasma treatment. The subsequent DI H2O rinse restores the water to the surface while removing B2O3 from the BSG layer. This prebonding treatment, therefore, results in a hydrophilic bond, but alters the composition of the BSG film at the bonded interface.

Hansen, D. M.; Albaugh, C. E.; Moran, P. D.; Kuech, T. F.

2001-11-01

235

Optimal operation of cryogenic air separation systems with demand uncertainty and contractual obligations  

Microsoft Academic Search

Cryogenic air separation is an efficient technology for supplying large quantities of nitrogen, argon, and oxygen to chemical, petroleum and manufacturing customers. However, numerous uncertainties make effective operation of these complex processes difficult. This work addresses the problem of determining an optimal operating strategy to maximize the total profit of a cryogenic air separation process while considering demand uncertainty and

Yu Zhu; Sean Legg; Carl D. Laird

2011-01-01

236

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. PMID:22408276

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

2012-01-01

237

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

238

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

239

Contribution of magnetic susceptibility effects to transmembrane chemical shift differences in the /sup 31/P NMR spectra of oxygenated erythrocyte suspensions  

SciTech Connect

Triethyl phosphate, dimethyl methylphosphonate, and the hypophosphite ion all contain the phosphoryl functional group. When added to an oxygenated erythrocyte suspension, the former compound gives rise to a single /sup 31/P NMR resonance, whereas the latter compounds give rise to separate intra- and extracellular /sup 31/P NMR resonances. On the basis of experiments with intact oxygenated cell suspensions (in which the hematocrit was varied) and with oxygenated cell lysates (in which the lysate concentration was varied) it was concluded that the chemical shifts of the intra- and extracellular populations of triethyl phosphate differ as a consequence of the diamagnetic susceptibility of intracellular oxyhemoglobin but that this difference is averaged by the rapid exchange of the compound across the cell membrane. The difference is the magnetic susceptibility of the intra- and extracellular compartments contributes to the observed separation of the intra- and extracellular resonances of dimethyl methylphosphonate and hypophosphite. The magnitude of this contribution is, however, substantially less than that calculated using a simple two-compartment model and varies with the hematocrit of the suspension. Furthermore, it is insufficient to fully account for the transmembrane chemical shift differences observed for dimethyl methylphosphonate and hypophosphite. An additional effect is operating to move the intracellular resonances of these compounds to a lower chemical shift. The effect is mediated by an intracellular component, and the magnitude of the resultant chemical shift variations depends upon the chemical structure of the phosphoryl compound involved.

Kirk, K.; Kuchel, P.W.

1988-01-05

240

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.

1990-07-01

241

Diffusion and interactions of carbon dioxide and oxygen in the vicinity of the active site of Rubisco: Molecular dynamics and quantum chemical studies  

NASA Astrophysics Data System (ADS)

Molecular dynamics (MD) at the molecular mechanical level and geometry optimisation at the quantum mechanical level have been performed to investigate the transport and fixation of oxygen and carbon dioxide in the cavity of ribulose-1,5-bisphosphate carboxylase/oxygenase, or Rubisco. Multiple MD simulations have been carried out to study the diffusive behaviour of O2 and CO2 molecules from the Mg2+ cation in Rubisco at 298 K and 1 bar, being one step in the overall process of carboxylation/oxygenation in Rubisco. In addition to this work, in order to gain additional perspective on the role of chemical reaction rates and thermodynamics, oxygen, and carbon dioxide uptake mechanisms have also been investigated by the aid of quantum chemical calculations. The results indicate that the activation barrier for carboxylation is slightly lower than that of oxygenation. This agrees qualitatively with experimental findings, and rationalises the observed competition between both catalytic processes in nature. Finally, the longer-lived persistence of CO2 in the vicinity of the active centre (i.e., slower self-diffusion) may serve to explain, in part, why carboxylation is the more kinetically favoured on an overall basis compared to oxygenation.

El-Hendawy, Morad M.; Garate, José-Antonio; English, Niall J.; O'Reilly, Stephen; Mooney, Damian A.

2012-10-01

242

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

PubMed

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

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

2014-05-01

243

Evaluation and use of a diffusion-controlled sampler for determining chemical and dissolved oxygen gradients at the sediment-water interface  

USGS Publications Warehouse

Field and laboratory evaluations were made of a simple, inexpensive diffusion-controlled sampler with ports on two sides at each interval which incorporates 0.2-??m polycarbonate membrane to filter samples in situ. Monovalent and divalent ions reached 90% of equilibrium between sampler contents and the external solution within 3 and 6 hours, respectively. Sediment interstitial water chemical gradients to depths of tens of centimeters were obtained within several days after placement. Gradients were consistent with those determined from interstitial water obtained by centrifugation of adjacent sediment. Ten milliliter sample volumes were collected at 1-cm intervals to determine chemical gradients and dissolved oxygen profiles at depth and at the interface between the sediment and water column. The flux of dissolved species, including oxygen, across the sediment-water interface can be assessed more accurately using this sampler than by using data collected from benthic cores. ?? 1985 Dr W. Junk Publishers.

Simon, N.S.; Kennedy, M.M.; Massoni, C.S.

1985-01-01

244

OXYGEN ABUNDANCES IN NEARBY FGK STARS AND THE GALACTIC CHEMICAL EVOLUTION OF THE LOCAL DISK AND HALO  

SciTech Connect

Atmospheric parameters and oxygen abundances of 825 nearby FGK stars are derived using high-quality spectra and a non-local thermodynamic equilibrium analysis of the 777 nm O I triplet lines. We assign a kinematic probability for the stars to be thin-disk (P {sub 1}), thick-disk (P {sub 2}), and halo (P {sub 3}) members. We confirm previous findings of enhanced [O/Fe] in thick-disk (P {sub 2} > 0.5) relative to thin-disk (P {sub 1} > 0.5) stars with [Fe/H] {approx}< -0.2, as well as a 'knee' that connects the mean [O/Fe]-[Fe/H] trend of thick-disk stars with that of thin-disk members at [Fe/H] {approx}> -0.2. Nevertheless, we find that the kinematic membership criterion fails at separating perfectly the stars in the [O/Fe]-[Fe/H] plane, even when a very restrictive kinematic separation is employed. Stars with 'intermediate' kinematics (P {sub 1} < 0.7, P {sub 2} < 0.7) do not all populate the region of the [O/Fe]-[Fe/H] plane intermediate between the mean thin-disk and thick-disk trends, but their distribution is not necessarily bimodal. Halo stars (P {sub 3} > 0.5) show a large star-to-star scatter in [O/Fe]-[Fe/H], but most of it is due to stars with Galactocentric rotational velocity V < -200 km s{sup -1}; halo stars with V > -200 km s{sup -1} follow an [O/Fe]-[Fe/H] relation with almost no star-to-star scatter. Early mergers with satellite galaxies explain most of our observations, but the significant fraction of disk stars with 'ambiguous' kinematics and abundances suggests that scattering by molecular clouds and radial migration have both played an important role in determining the kinematic and chemical properties of solar neighborhood stars.

Ramirez, I.; Lambert, D. L. [McDonald Observatory and Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205 (United States)] [McDonald Observatory and Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205 (United States); Allende Prieto, C. [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain)] [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain)

2013-02-10

245

Methanol synthesis on ZnO(0001 ¯). I. Hydrogen coverage, charge state of oxygen vacancies, and chemical reactivity  

NASA Astrophysics Data System (ADS)

Oxygen vacancies on ZnO(0001¯) have been proposed to be the catalytically active sites for methanol synthesis on pure ZnO. The charge state and thus the chemical reactivity of such vacancies on this polar O-terminated basal plane of ZnO is expected to be intimately connected to the degree of its hydroxylation in view of its Tasker type(3) unstable character. Here, the interplay between hydrogen adsorption and the thermodynamic stability of O vacancies in various charge states, corresponding formally to F++, F+, F0, F-, and F-- centers, is investigated using electronic structure calculations. Assuming thermodynamic equilibrium of the defective surface with a hydrogen containing gas phase the thermodynamically most stable O vacancy type is determined as a function of temperature and pressure. For the adsorption of H2 molecules at O vacancy sites it is found that the homolytic process leads to energetically more favorable structures than heterolytic adsorption and hydride formation. By homolytic adsorption and desorption one can switch between F++, F0, and F-- or between F+ and F-, a process which is believed to occur during methanol synthesis. However, the barrier for heterolytic dissociation of H2 at O vacancies is significantly lower compared to homolytic cleavage. Furthermore, the barrier for transforming hydridic hydrogen, i.e., ZnH species, to protonic hydrogen, i.e., OH species together with a reduction of ZnO itself, is quite high. This implies that hydridic H- species created as a result of heterolytic dissociation might have a long enough lifetime at O vacancies that they will be available for methanol synthesis. ZnH and OH vibrational frequencies have been computed in order to assist future experimental assignments.

Kiss, Janos; Witt, Alexander; Meyer, Bernd; Marx, Dominik

2009-05-01

246

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

247

Effect of chemical composition on the elastic and electrical properties of the boron-oxygen-yttrium system studied by ab initio and experimental means  

Microsoft Academic Search

The effect of chemical composition on the elastic and electrical properties is studied for the BOxYz system with 0.27<=x<=1.14 and 0.36<=z<=0.08. We use ab initio calculations to obtain the elastic constants and density of states for BO1.5 and the BOY phase (yttrium substituting for oxygen in the boron suboxide structure). For decreasing x values, the elastic modulus is predicted to

Valeriu Chirita; Jochen M. Schneider; Ulf Helmersson

2004-01-01

248

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

249

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

250

Nitrogen and Oxygen Isotopic Detection of Nitrate in Seawater by Chemical Conversion of Nitrate to Nitrous Oxide  

NASA Astrophysics Data System (ADS)

A fast, easy, and reliable method for nitrogen and oxygen isotopic detection of nitrate would be beneficial to many in the biogeochemical society. Here we present a novel method capable of natural isotopic detection in the nM range. In addition to a fast analysis time (batch preparation in less than one hour for nitrogen isotopes), this method is capable of very low blanks (less than 1 nanomole) with sample precision of 0.2 permil for nitrogen and 0.5 permil for oxygen. The first step of the method is reduction of nitrate to nitrite by use of either spongy cadmium or UV light. UV light reduction has the advantage of a short reaction time (13 minutes), but is not capable of oxygen isotope analysis due to exchange with water. Reduction using spongy cadmium retains the oxygen isotopic signature, but requires up to 3 hours to react. Both reactions are non-fractionating with respect to nitrogen. The next step is the reduction of nitrite to nitrous oxide using either hydroxylamine or azide. The hydroxylamine has the advantage of being nontoxic, but the reaction time is 2 hours and oxygen is exchanged with water. The azide-nitrite reaction is complete in only 3 minutes and retains both nitrogen and oxygen isotopes of nitrate. The produced nitrous oxide is then purged and trapped in liquid nitrogen, then released into a capillary GC column connected to an isotope ratio mass spectrometer.

McIlvin, M.; Altabet, M.

2003-12-01

251

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. PMID:21664270

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

2011-01-01

252

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

253

Sensory, chemical, and electronic tongue assessment of micro-oxygenated wines and oak chip maceration: assessing the commonality of analytical techniques.  

PubMed

Micro-oxygenation (MOX) was conducted in the presence and absence of oak chips at rates to mimic oxygen ingress during barrel maturation of red wine. Following MOX, wines were analyzed for chemical attributes pertaining to phenolic composition and assessed by a trained sensory panel. An electronic tongue (ET) was also used to assess the wines. Variations in chemical attributes were found to be mostly influenced by vintage, followed by oak chip maceration accounting for 48% and 16% of variation within the data set, respectively. MOX treatment accounted for 11% of variability within the physiochemical data set, with attributes pertaining to anthocyanin polymerization and levels of sulfur dioxide in the finished wine being most significantly influenced. A generalized Procrustes rotation and alignment of the chemical, electronic tongue, and sensory data sets followed by PLS1 regressions showed good prediction of the sensory characters oak, pencil shavings, stewed plum, vegetal, and spice over the range of sensory scores from the ET data; bitterness and astringency could also be predicted from the physicochemical data with good precision. PMID:20356080

Schmidtke, Leigh M; Rudnitskaya, Alisa; Saliba, Anthony J; Blackman, John W; Scollary, Geoffrey R; Clark, Andrew C; Rutledge, Douglas N; Delgadillo, Ivonne; Legin, Andrey

2010-04-28

254

Disruption of biofilms from sewage pipes under physical and chemical conditioning  

Microsoft Academic Search

Biofilms grown inside two sewage collecting pipes located in industrial and residential areas are studied. Bacterial biomass inside three layers of biofilms was evaluated. Biofilm cohesion under different mixing rate and ionic strength was also investigated. Effects of physical and chemical parameters in the biofilms were evaluated by monitoring turbidity, chemical and biochemical oxygen demands. Extracted organic matter from biofilms

Charbel Mahfoud; Antoine El Samrani; Rita Mouawad; Walid Hleihel; Rim El Khatib; Bruno S. Lartiges; Naïm Ouaïni

2009-01-01

255

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

256

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

257

Chemical bonding in the outer core: high-pressure electronic structures of oxygen and sulfur in metallic iron  

USGS Publications Warehouse

The electronic structures of oxygen and sulfur impurities in metallic iron are investigated to determine if pressure, temperature, and composition-induced changes in bonding might affect phase equilibria along the Fe-FeS and Fe-FeO binaries. -from Authors

Sherman, D.M.

1991-01-01

258

Oxygen nonstoichiometry and thermo-chemical stability of La{sub 0.6}Sr{sub 0.4}CoO{sub 3-{delta}}  

SciTech Connect

The oxygen nonstoichiometry of La{sub 0.6}Sr{sub 0.4}CoO{sub 3-{delta}} has been the topic of various reports in the literature, but has been exclusively measured at high oxygen partial pressures, pO{sub 2}, and/or elevated temperatures. For applications of La{sub 0.6}Sr{sub 0.4}CoO{sub 3-{delta}}, such as solid oxide fuel cell cathodes or oxygen permeation membranes, knowledge of the oxygen nonstoichiometry and thermo-chemical stability over a wide range of pO{sub 2} is crucial, as localized low pO{sub 2} could trigger failure of the material and device. By employing coulometric titration combined with thermogravimetry, the oxygen nonstoichiometry of La{sub 0.6}Sr{sub 0.4}CoO{sub 3-{delta}} was measured at high and intermediate pO{sub 2} until the material decomposed (at log(pO{sub 2}/bar) Almost-Equal-To -4.5 at 1073 K). For a gradually reduced sample, an offset in oxygen content suggests that La{sub 0.6}Sr{sub 0.4}CoO{sub 3-{delta}} forms a 'super-reduced' solid solution before decomposing. When the sample underwent alternate reduction-oxidation, a hysteresis-like pO{sub 2} dependence of the oxygen content in the decomposition pO{sub 2} range was attributed to the reversible formation of ABO{sub 3} and A{sub 2}BO{sub 4} phases. Reduction enthalpy and entropy were determined for the single-phase region and confirmed interpolated values from the literature. - Graphical abstract: Oxygen nonstoichiometry (shown as 3-{delta}) of La{sub 0.6}Sr{sub 0.4}CoO{sub 3-{delta}} as a function of pO{sub 2} at 773-1173 K. The experimental data were obtained by thermogravimetric analysis (TG) and coulometric titration (measured either by a simple reduction (CT1) or a 'two-step-forward one-step-back' reduction-oxidation (CT2) procedure). D1 and D2 denote the decomposition pO{sub 2}. The solid lines are the fit to the thermogravimetry and CT1 data. The dashed lines represent the non-equilibrium region where the sample shows a super-reduced state. Highlights: Black-Right-Pointing-Pointer Oxygen nonstoichiometry of La{sub 0.6}Sr{sub 0.4}CoO{sub 3-{delta}} at intermediate temperatures and p(O2). Black-Right-Pointing-Pointer Experimental confirmation of previously interpolated reduction enthalpy. Black-Right-Pointing-Pointer Decomposition p(O2) assessed by coulometric titration. Black-Right-Pointing-Pointer Hysteresis-like p(O2) dependence of oxygen content at decomposition p(O2).

Kuhn, M., E-mail: kuhnm@mit.edu [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aobaku, Sendai 980-8577 (Japan); Hashimoto, S. [Graduate School of Environmental Studies, Tohoku University, 6-6-01 Aoba, Aramaki, Aobaku, Sendai 980-8579 (Japan); Sato, K.; Yashiro, K.; Mizusaki, J. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aobaku, Sendai 980-8577 (Japan)

2013-01-15

259

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

Microsoft Academic Search

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

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

2010-01-01

260

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

261

Influence of chemical and physical properties of activated carbon powders on oxygen reduction and microbial fuel cell performance.  

PubMed

Commercially available activated carbon (AC) powders made from different precursor materials (coal, peat, coconut shell, hardwood, and phenolic resin) were electrochemically evaluated as oxygen reduction catalysts and tested as cathode catalysts in microbial fuel cells (MFCs). AC powders were characterized in terms of surface chemistry and porosity, and their kinetic activities were compared to carbon black and platinum catalysts in rotating disk electrode (RDE) tests. Cathodes using the coal-derived AC had the highest power densities in MFCs (1620 ± 10 mW m(-2)). Peat-based AC performed similarly in MFC tests (1610 ± 100 mW m(-2)) and had the best catalyst performance, with an onset potential of E(onset) = 0.17 V, and n = 3.6 electrons used for oxygen reduction. Hardwood based AC had the highest number of acidic surface functional groups and the poorest performance in MFC and catalysis tests (630 ± 10 mW m(-2), E(onset) = -0.01 V, n = 2.1). There was an inverse relationship between onset potential and quantity of strong acid (pKa < 8) functional groups, and a larger fraction of microporosity was negatively correlated with power production in MFCs. Surface area alone was a poor predictor of catalyst performance, and a high quantity of acidic surface functional groups was determined to be detrimental to oxygen reduction and cathode performance. PMID:23692057

Watson, Valerie J; Nieto Delgado, Cesar; Logan, Bruce E

2013-06-18

262

Oxygen pressure control for electrolysis cells  

NASA Technical Reports Server (NTRS)

Duty cycle of switched, constant current circuit controlled by pressure sensor provides oxygen at a constant pressure from a cell which electrolyzes water, eliminating possibility of cell damage by excessive oxygen demand.

Powell, J. D.

1972-01-01

263

Quantification of chemical states, dissociation constants and contents of oxygen-containing groups on the surface of biochars produced at different temperatures.  

PubMed

Surface functional groups such as carboxyl play a vital role in the environmental applications of biochar as a soil amendment. However, the quantification of oxygen-containing groups on a biochar surface still lacks systematical investigation. In this paper, we report an integrated method combining chemical and spectroscopic techniques that were established to quantitatively identify the chemical states, dissociation constants (pK(a)), and contents of oxygen-containing groups on dairy manure-derived biochars prepared at 100-700 °C. Unexpectedly, the dissociation pH of carboxyl groups on the biochar surface covered a wide range of pH values (pH 2-11), due to the varied structural microenvironments and chemical states. For low temperature biochars (? 350 °C), carboxyl existed not only as hydrogen-bonded carboxyl and unbonded carboxyl groups but also formed esters at the surface of biochars. The esters consumed OH(-) via saponification in the alkaline pH region and enhanced the dissolution of organic matter from biochars. For high temperature biochars (? 500 °C), esters came from carboxyl were almost eliminated via carbonization (ester pyrolysis), while lactones were developed. The surface density of carboxyl groups on biochars decreased sharply with the increase of the biochar-producing temperature, but the total contents of the surface carboxyls for different biochars were comparable (with a difference <3-fold) as a result of the expanded surface area at high pyrolytic temperatures. Understanding the wide pKa ranges and the abundant contents of carboxyl groups on biochars is a prerequisite to recognition of the multifunctional applications and biogeochemical cycling of biochars. PMID:25453912

Chen, Zaiming; Xiao, Xin; Chen, Baoliang; Zhu, Lizhong

2015-01-01

264

High Temperatures & Electricity Demand  

E-print Network

High Temperatures & Electricity Demand An Assessment of Supply Adequacy in California Trends.......................................................................................................1 HIGH TEMPERATURES AND ELECTRICITY DEMAND.....................................................................................................................7 SECTION I: HIGH TEMPERATURES AND ELECTRICITY DEMAND ..........................9 BACKGROUND

265

The effect of chemical composition and oxygen fugacity on the electrical conductivity of dry and hydrous garnet at high temperatures and pressures  

NASA Astrophysics Data System (ADS)

The in situ electrical conductivity of hydrous garnet samples (Py20Alm76Grs4-Py73Alm14Grs13) was determined at pressures of 1.0-4.0 GPa and temperatures of 873-1273 K in the YJ-3000t apparatus using a Solartron-1260 impedance/gain-phase analyzer for various chemical compositions and oxygen fugacities. The oxygen fugacity was controlled by five solid-state oxygen buffers (Fe2O3 + Fe3O4, Ni + NiO, Fe + Fe3O4, Fe + FeO, and Mo + MoO2). Experimental results indicate that within a frequency range from 10-2 to 106 Hz, electrical conductivity is strongly dependent on signal frequency. Electrical conductivity shows an Arrhenius increase with temperature. At 2.0 GPa, the electrical conductivity of anhydrous garnet single crystals with various chemical compositions (Py20Alm76Grs4, Py30Alm67Grs3, Py56Alm43Grs1, and Py73Alm14Grs13) decreases with increasing pyrope component (Py). With increasing oxygen fugacity, the electrical conductivity of dry Py73Alm14Grs13 garnet single crystal shows an increase, whereas that of a hydrous sample with 465 ppm water shows a decrease, both following a power law (exponents of 0.061 and -0.071, respectively). With increasing pressure, the electrical conductivity of this hydrous garnet increases, along with the pre-exponential factors, and the activation energy and activation volume of hydrous samples are 0.7731 ± 0.0041 eV and -1.4 ± 0.15 cm3/mol, respectively. The results show that small hopping polarons left( {{text{Fe}}_{text{Mg}}^{ \\cdot } } right) and protons ( {text{H}}^{ \\cdot } ) are the dominant conduction mechanisms for dry and wet garnet single crystals, respectively. Based on these results and the effective medium theory, we established the electrical conductivity of an eclogite model with different mineral contents at high temperatures and high pressures, thereby providing constraints on the inversion of field magnetotelluric sounding results in future studies.

Dai, Lidong; Li, Heping; Hu, Haiying; Shan, Shuangming; Jiang, Jianjun; Hui, Keshi

2012-04-01

266

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

267

Responses of Solid Tumor Cells in DMEM to Reactive Oxygen Species Generated by Non-Thermal Plasma and Chemically Induced ROS Systems.  

PubMed

In this study, we assessed the role of different reactive oxygen species (ROS) generated by soft jet plasma and chemical-induced ROS systems with regard to cell death in T98G, A549, HEK293 and MRC5 cell lines. For a comparison with plasma, we generated superoxide anion (O2(-)), hydroxyl radical (HO·), and hydrogen peroxide (H2O2) with chemicals inside an in vitro cell culture. Our data revealed that plasma decreased the viability and intracellular ATP values of cells and increased the apoptotic population via a caspase activation mechanism. Plasma altered the mitochondrial membrane potential and eventually up-regulated the mRNA expression levels of BAX, BAK1 and H2AX gene but simultaneously down-regulated the levels of Bcl-2 in solid tumor cells. Moreover, a western blot analysis confirmed that plasma also altered phosphorylated ERK1/2/MAPK protein levels. At the same time, using ROS scavengers with plasma, we observed that scavengers of HO· (mannitol) and H2O2 (catalase and sodium pyruvate) attenuated the activity of plasma on cells to a large extent. In contrast, radicals generated by specific chemical systems enhanced cell death drastically in cancer as well as normal cell lines in a dose-dependent fashion but not specific with regard to the cell type as compared to plasma. PMID:25715710

Kaushik, Neha; Uddin, Nizam; Sim, Geon Bo; Hong, Young June; Baik, Ku Youn; Kim, Chung Hyeok; Lee, Su Jae; Kaushik, Nagendra Kumar; Choi, Eun Ha

2015-01-01

268

Responses of Solid Tumor Cells in DMEM to Reactive Oxygen Species Generated by Non-Thermal Plasma and Chemically Induced ROS Systems  

NASA Astrophysics Data System (ADS)

In this study, we assessed the role of different reactive oxygen species (ROS) generated by soft jet plasma and chemical-induced ROS systems with regard to cell death in T98G, A549, HEK293 and MRC5 cell lines. For a comparison with plasma, we generated superoxide anion (O2-), hydroxyl radical (HO.), and hydrogen peroxide (H2O2) with chemicals inside an in vitro cell culture. Our data revealed that plasma decreased the viability and intracellular ATP values of cells and increased the apoptotic population via a caspase activation mechanism. Plasma altered the mitochondrial membrane potential and eventually up-regulated the mRNA expression levels of BAX, BAK1 and H2AX gene but simultaneously down-regulated the levels of Bcl-2 in solid tumor cells. Moreover, a western blot analysis confirmed that plasma also altered phosphorylated ERK1/2/MAPK protein levels. At the same time, using ROS scavengers with plasma, we observed that scavengers of HO. (mannitol) and H2O2 (catalase and sodium pyruvate) attenuated the activity of plasma on cells to a large extent. In contrast, radicals generated by specific chemical systems enhanced cell death drastically in cancer as well as normal cell lines in a dose-dependent fashion but not specific with regard to the cell type as compared to plasma.

Kaushik, Neha; Uddin, Nizam; Sim, Geon Bo; Hong, Young June; Baik, Ku Youn; Kim, Chung Hyeok; Lee, Su Jae; Kaushik, Nagendra Kumar; Choi, Eun Ha

2015-02-01

269

Responses of Solid Tumor Cells in DMEM to Reactive Oxygen Species Generated by Non-Thermal Plasma and Chemically Induced ROS Systems  

PubMed Central

In this study, we assessed the role of different reactive oxygen species (ROS) generated by soft jet plasma and chemical-induced ROS systems with regard to cell death in T98G, A549, HEK293 and MRC5 cell lines. For a comparison with plasma, we generated superoxide anion (O2?), hydroxyl radical (HO·), and hydrogen peroxide (H2O2) with chemicals inside an in vitro cell culture. Our data revealed that plasma decreased the viability and intracellular ATP values of cells and increased the apoptotic population via a caspase activation mechanism. Plasma altered the mitochondrial membrane potential and eventually up-regulated the mRNA expression levels of BAX, BAK1 and H2AX gene but simultaneously down-regulated the levels of Bcl-2 in solid tumor cells. Moreover, a western blot analysis confirmed that plasma also altered phosphorylated ERK1/2/MAPK protein levels. At the same time, using ROS scavengers with plasma, we observed that scavengers of HO· (mannitol) and H2O2 (catalase and sodium pyruvate) attenuated the activity of plasma on cells to a large extent. In contrast, radicals generated by specific chemical systems enhanced cell death drastically in cancer as well as normal cell lines in a dose-dependent fashion but not specific with regard to the cell type as compared to plasma. PMID:25715710

Kaushik, Neha; Uddin, Nizam; Sim, Geon Bo; Hong, Young June; Baik, Ku Youn; Kim, Chung Hyeok; Lee, Su Jae; Kaushik, Nagendra Kumar; Choi, Eun Ha

2015-01-01

270

Parameters of an electric-discharge generator of iodine atoms for a chemical oxygen-iodine laser  

SciTech Connect

Laser-induced fluorescence is used for measuring the concentration of iodine molecules at the output of an electric-discharge generator of atomic iodine. Methyl iodide CH{sub 3}I is used as the donor of atomic iodine. The fraction of iodine extracted from CH{sub 3}I in the generator is {approx}50%. The optimal operation regimes are found in which 80%-90% of iodine contained in the output flow of the generator was in the atomic state. This fraction decreased during the iodine transport due to recombination and was 20%-30% at the place where iodine was injected into the oxygen flow. The fraction of the discharge power spent for dissociation was {approx}3%. (elements of laser setups)

Azyazov, V N; Vorob'ev, M V; Voronov, A I; Kupryaev, Nikolai V; Mikheev, P A; Ufimtsev, N I [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2009-01-31

271

Atomic Oxygen Effects  

NASA Technical Reports Server (NTRS)

Atomic oxygen, which is the most predominant species in low Earth orbit, is highly reactive and can break chemical bonds on the surface of a wide variety of materials leading to volatilization or surface oxidation which can result in failure of spacecraft materials and components. This presentation will give an overview of how atomic oxygen reacts with spacecraft materials, results of space exposure testing of a variety of materials, and examples of failures caused by atomic oxygen.

Miller, Sharon K. R.

2014-01-01

272

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

273

Oxygen Therapy  

MedlinePLUS

Oxygen therapy is a treatment that provides you with extra oxygen. Oxygen is a gas that your body needs to function. Normally, your lungs absorb oxygen from the air you breathe. But some conditions ...

274

Oxygen isotope and chemical compositions of magnetite and olivine in the anomalous CK3 Watson 002 and ungrouped Asuka-881595 carbonaceous chondrites: Effects of parent body metamorphism  

NASA Astrophysics Data System (ADS)

We report in situ O isotope and chemical compositions of magnetite and olivine in chondrules of the carbonaceous chondrites Watson-002 (anomalous CK3) and Asuka (A)-881595 (ungrouped C3). Magnetite in Watson-002 occurs as inclusion-free subhedral grains and rounded inclusion-bearing porous grains replacing Fe,Ni-metal. In A-881595, magnetite is almost entirely inclusion-free and coexists with Ni-rich sulfide and less abundant Ni-poor metal. Oxygen isotope compositions of chondrule olivine in both meteorites plot along carbonaceous chondrite anhydrous mineral (CCAM) line with a slope of approximately 1 and show a range of ?17O values (from approximately -3 to -6‰). One chondrule from each sample was found to contain O isotopically heterogeneous olivine, probably relict grains. Oxygen isotope compositions of magnetite in A-881595 plot along a mass-dependent fractionation line with a slope of 0.5 and show a range of ?17O values from -2.4‰ to -1.1‰. Oxygen isotope compositions of magnetite in Watson-002 cluster near the CCAM line and a ?17O value of -4.0‰ to -2.9‰. These observations indicate that magnetite and chondrule olivine are in O isotope disequilibrium, and, therefore, not cogenetic. We infer that magnetite in CK chondrites formed by the oxidation of pre-existing metal grains by an aqueous fluid during parent body alteration, in agreement with previous studies. The differences in ?17O values of magnetite between Watson-002 and A-881595 can be attributed to their different thermal histories: the former experienced a higher degree of thermal metamorphism that led to the O isotope exchange between magnetite and adjacent silicates.

Davidson, Jemma; Krot, Alexander N.; Nagashima, Kazuhide; Hellebrand, Eric; Lauretta, Dante S.

2014-08-01

275

Oxygenated Derivatives of Hydrocarbons  

Technology Transfer Automated Retrieval System (TEKTRAN)

For the book entitled “Insect Hydrocarbons: Biology, Biochemistry and Chemical Ecology”, this chapter presents a comprehensive review of the occurrence, structure and function of oxygenated derivatives of hydrocarbons. The book chapter focuses on the occurrence, structural identification and functi...

276

U-Pt-Sm-Ba-O chemical pinning centers in Ag-doped Sm123 textured in reduced oxygen  

Microsoft Academic Search

In the U\\/n process enriched uranium is admixed to HTS powders, textured and then irradiated with thermal neutrons. Neutrons must penetrate several centimeters for such processing to be successful in textured materials. Bulk Sm123 cannot be U\\/n processed because thermal neutrons penetrate <1 mm. However, textured Sm123 can still benefit from chemical pinning centers that are formed during U\\/n processing.

Ravi-Persad Sawh; Roy Weinstein; Drew Parks; Noriko Chikumoto; Masato Murakami

2003-01-01

277

Radiation-induced chemical reactions of carbon monoxide and hydrogen mixture—II. Effects of reactant pressure and temperature on the yields of oxygen containing products  

NASA Astrophysics Data System (ADS)

The radiation chemical reaction of CO-H 2 mixture up to 8.4 x 10 5 Pa has been studied. The G values of oxygen containing organic compounds except methanol increased with increasing total pressure of reactant. The G values of most of products except trioxane and tetraoxane were increased with raising of temperature in the range from 210 to 350 K, while the G values of trioxane and tetraoxane reached the maxima at 243 K and decreased rapidly with raising of temperature. From the dependencies of G values of these cyclic ethers on pressure and temperature of the reactant, it is considered that these cyclic ethers produced from the neutralization reaction of HCO + (CO) n cluster ions with electrons in an atmosphere of relatively large amount of hydrogen. The effects of CO content on G values of products did not change with the pressure change of the reactant.

Sugimoto, Shun'ichi; Nishii, Masanobu; Sugiura, Toshio

278

Towards a better understanding of the origins, chemical composition and aging of oxygenated organic aerosols: case study of a Mediterranean industrialized environment, Marseille  

NASA Astrophysics Data System (ADS)

As part of the FORMES summer 2008 experiment, an Aerodyne compact time-of-flight aerosol mass spectrometer (cToF-AMS) was deployed at an urban background site in Marseille to investigate the sources and aging of organic aerosols (OA). France's second largest city and the largest port in the Mediterranean, Marseille, provides a locale that is influenced by significant urban industrialized emissions and an active photochemistry with very high ozone concentrations. Particle mass spectra were analyzed by positive matrix factorization (PMF2) and the results were in very good agreement with previous apportionments obtained using a chemical mass balance (CMB) approach coupled to organic markers and metals (El Haddad et al., 2011a). AMS/PMF2 was able to identify for the first time, to the best of our knowledge, the organic aerosol emitted by industrial processes. Even with significant industries in the region, industrial OA was estimated to contribute only ~ 5% of the total OA mass. Both source apportionment techniques suggest that oxygenated OA (OOA) constitutes the major fraction, contributing ~ 80% of OA mass. A novel approach combining AMS/PMF2 data with 14C measurements was applied to identify and quantify the fossil and non-fossil precursors of this fraction and to explicitly assess the related uncertainties. Results show with high statistical confidence that, despite extensive urban and industrial emissions, OOA is overwhelmingly non-fossil, formed via the oxidation of biogenic precursors, including monoterpenes. AMS/PMF2 results strongly suggest that the variability observed in the OOA chemical composition is mainly driven in our case by the aerosol photochemical age. This paper presents the impact of photochemistry on the increase of OOA oxygenation levels, formation of humic-like substances (HULIS) and the evolution of ?-pinene SOA (secondary OA) components.

El Haddad, I.; D'Anna, B.; Temime-Roussel, B.; Nicolas, M.; Boreave, A.; Favez, O.; Voisin, D.; Sciare, J.; George, C.; Jaffrezo, J.-L.; Wortham, H.; Marchand, N.

2013-08-01

279

The use of natural abundance stable isotopic ratios to indicate the presence of oxygen-containing chemical linkages between cellulose and lignin in plant cell walls.  

PubMed

Qualitative and quantitative understanding of the chemical linkages between the three major biochemical components (cellulose, hemicellulose and lignin) of plant cell walls is crucial to the understanding of cell wall structure. Although there is convincing evidence for chemical bonds between hemicellulose and lignin and the absence of chemical bonds between hemicellulose and cellulose, there is no conclusive evidence for the presence of covalent bonds between cellulose and lignin. This is caused by the lack of selectivity of current GC/MS-, NMR- and IR-based methods for lignin characterisation as none of these techniques directly targets the possible ester and ether linkages between lignin and cellulose. We modified the widely-accepted "standard" three-step extraction method for isolating cellulose from plants by changing the order of the steps for hemicellulose and lignin removal (solubilisation with concentrated NaOH and oxidation with acetic acid-containing NaClO(2), respectively) so that cellulose and lignin could be isolated with the possible chemical bonds between them intact. These linkages were then cleaved with NaClO(2) reagent in aqueous media of contrasting (18)O/(16)O ratios. We produced cellulose with higher purity (a lower level of residual hemicellulose and no detectable lignin) than that produced by the "standard" method. Oxidative artefacts may potentially be introduced at the lignin removal stage; but testing showed this to be minimal. Cellulose samples isolated from processing plant-derived cellulose-lignin mixtures in media of contrasting (18)O/(16)O ratios were compared to provide the first quantitative evidence for the presence of oxygen-containing ester and ether bonds between cellulose and lignin in Zea mays leaves. However, no conclusive evidence for the presence or lack of similar bonds in Araucaria cunninghamii wood was obtained. PMID:20362306

Zhou, Youping; Stuart-Williams, Hilary; Farquhar, Graham D; Hocart, Charles H

2010-06-01

280

Singlet oxygen in photosensitization.  

PubMed

Oxygen is a ubiquitous element and a vitally important substance for life on the Earth, and especially for human life. Living organisms need oxygen for most, if not all, of their cellular functions. On the other hand, oxygen can produce metabolites that are toxic and potentially lethal to the same cells. Being reactive and chemically unstable reactive oxygen species (ROS) are the most important metabolites that initiate reduction and oxidation (redox) reactions under physiological conditions. Oxygen in its excited singlet state (1O2) is probably the most important intermediate in such reactions. Since the discovery of oxygen by Joseph Priestley in 1775 it has been recognized that oxygen can be both beneficial and harmful to life. PMID:16566709

Moan, Johan; Juzenas, Petras

2006-01-01

281

Supplemental Oxygen (Oxygen Therapy)  

MedlinePLUS

... gas and is non-flammable, however, it supports combustion. Materials burn more readily in an oxygen-enriched ... avoid using lotions or creams containing petroleum. The combustion of flammable products containing petroleum can also be ...

282

Oxygen control with microfluidics.  

PubMed

Cellular function and behavior are affected by the partial pressure of O2, or oxygen tension, in the microenvironment. The level of oxygenation is important, as it is a balance of oxygen availability and oxygen consumption that is necessary to maintain normoxia. Changes in oxygen tension, from above physiological oxygen tension (hyperoxia) to below physiological levels (hypoxia) or even complete absence of oxygen (anoxia), trigger potent biological responses. For instance, hypoxia has been shown to support the maintenance and promote proliferation of regenerative stem and progenitor cells. Paradoxically, hypoxia also contributes to the development of pathological conditions including systemic inflammatory response, tumorigenesis, and cardiovascular disease, such as ischemic heart disease and pulmonary hypertension. Current methods to study cellular behavior in low levels of oxygen tension include hypoxia workstations and hypoxia chambers. These culture systems do not provide oxygen gradients that are found in vivo or precise control at the microscale. Microfluidic platforms have been developed to overcome the inherent limits of these current methods, including lack of spatial control, slow equilibration, and unachievable or difficult coupling to live-cell microscopy. The various applications made possible by microfluidic systems are the topic of this review. In order to understand how the microscale can be leveraged for oxygen control of cells and tissues within microfluidic systems, some background understanding of diffusion, solubility, and transport at the microscale will be presented in addition to a discussion on the methods for measuring the oxygen tension in microfluidic channels. Finally the various methods for oxygen control within microfluidic platforms will be discussed including devices that rely on diffusion from liquid or gas, utilizing on-or-off-chip mixers, leveraging cellular oxygen uptake to deplete the oxygen, relying on chemical reactions in channels to generate oxygen gradients in a device, and electrolytic reactions to produce oxygen directly on chip. PMID:25251498

Brennan, Martin D; Rexius-Hall, Megan L; Elgass, Laura Jane; Eddington, David T

2014-11-21

283

Using a dual plasma process to produce cobalt--polypyrrole catalysts for the oxygen reduction reaction in fuel cells -- part II: analysing the chemical structure of the films  

E-print Network

The chemical structure of cobalt--polypyrrole -- produced by a dual plasma process -- is analysed by means of X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption spectroscopy (NEXAFS), X-ray diffraction (XRD), energy-dispersive X-Ray spectroscopy (EDX) and extended x-ray absorption spectroscopy (EXAFS).It is shown that only nanoparticles of a size of 3\\,nm with the low temperature crystal structure of cobalt are present within the compound. Besides that, cobalt--nitrogen and carbon--oxygen structures are observed. Furthermore, more and more cobalt--nitrogen structures are produced when increasing the magnetron power. Linking the information on the chemical structure to the results about the catalytic activity of the films -- which are presented in part I of this contribution -- it is concluded that the cobalt--nitrogen structures are the probable catalytically active sites. The cobalt--nitrogen bond length is calculated as 2.09\\,\\AA\\ and the carbon--nitrogen bond length as 1.38\\,\\AA.

Walter, Christian; Vyalikh, Denis; Brüser, Volker; Quade, Antje; Weltmann, Klaus-Dieter; 10.1149/2.043209jes

2012-01-01

284

Effect of chemical composition on the elastic and electrical properties of the boron-oxygen-yttrium system studied by ab initio and experimental means  

NASA Astrophysics Data System (ADS)

The effect of chemical composition on the elastic and electrical properties is studied for the BOxYz system with 0.27?x?1.14 and 0.36?z?0.08. We use ab initio calculations to obtain the elastic constants and density of states for BO1.5 and the BOY phase (yttrium substituting for oxygen in the boron suboxide structure). For decreasing x values, the elastic modulus is predicted to increase from 11 to 340 GPa, while electronic structure calculations suggest a shift in electrical properties from insulating to metallic. Thin films in the B-O-Y system are grown by reactive rf magnetron sputtering. As x decreases from 1.14 to 0.27, the elastic modulus increases from 12 to 282 GPa, which is a factor of 24, while resistivity decreases from 7.6±0.4 to (3.8±0.1)×10-2 ?m. The observed shifts in elasticity and resistivity are shown to be induced by the associated changes in chemical bonding from van der Waals type in BO1.5 to icosahedral type in the BOY phase.

Music, Denis; Chirita, Valeriu; Schneider, Jochen M.; Helmersson, Ulf

2004-03-01

285

Enhancement of chemically induced reactive oxygen species production and DNA damage in human SH-SY5Y neuroblastoma cells by 872 MHz radiofrequency radiation.  

PubMed

The objective of the study was to investigate effects of 872 MHz radiofrequency (RF) radiation on intracellular reactive oxygen species (ROS) production and DNA damage at a relatively high SAR value (5 W/kg). The experiments also involved combined exposure to RF radiation and menadione, a chemical inducing intracellular ROS production and DNA damage. The production of ROS was measured using the fluorescent probe dichlorofluorescein and DNA damage was evaluated by the Comet assay. Human SH-SY5Y neuroblastoma cells were exposed to RF radiation for 1 h with or without menadione. Control cultures were sham exposed. Both continuous waves (CW) and a pulsed signal similar to that used in global system for mobile communications (GSM) mobile phones were used. Exposure to the CW RF radiation increased DNA breakage (p<0.01) in comparison to the cells exposed only to menadione. Comparison of the same groups also showed that ROS level was higher in cells exposed to CW RF radiation at 30 and 60 min after the end of exposure (p<0.05 and p<0.01, respectively). No effects of the GSM signal were seen on either ROS production or DNA damage. The results of the present study suggest that 872 MHz CW RF radiation at 5 W/kg might enhance chemically induced ROS production and thus cause secondary DNA damage. However, there is no known mechanism that would explain such effects from CW RF radiation but not from GSM modulated RF radiation at identical SAR. PMID:19135463

Luukkonen, Jukka; Hakulinen, Pasi; Mäki-Paakkanen, Jorma; Juutilainen, Jukka; Naarala, Jonne

2009-03-01

286

Study of the influence of micro-oxygenation and oak chip maceration on wine composition using an electronic tongue and chemical analysis.  

PubMed

The influence of micro-oxygenation (MOX) and maceration with oak chips treatments on wine was studied on wine samples from three vintages produced in the Yarra Valley, Australia. A full factorial design was employed where two factors (MOX and oak chips treatments) had two levels and one factor (vintage) had three levels. Three replicated treatments were run for each factor's setting. Wine samples were analysed using conventional laboratory methods with respect to the phenolic wine compounds and colour attributes since the phenolic fraction of wine is most affected by both MOX and oak maceration treatments. The same wine samples were measured with an electronic tongue based on potentiometric chemical sensors. The significance of treatments and vintage effects on wine phenolic compounds was assessed using ANOVA and ANOVA-Simultaneous Component Analysis (ASCA). Cross-validation was used for the ASCA sub-model optimisations and permutation test for evaluations of the significance of the factors. Main effects of vintage and maceration with oak chips were found to be significant for both physicochemical and the ET data. Main effect of MOX treatment was also found significant for the physicochemical parameters. The largest effect on the phenolic composition of wine was due to its vintage, which accounted for 70% and 33% of total variance in the physicochemical and ET data respectively. The ET was calibrated with respect to the total phenolic content, colour density and hue and chemical ages 1 and 2 and could predict these parameters of wine with good precision. PMID:19427482

Rudnitskaya, A; Schmidtke, L M; Delgadillo, I; Legin, A; Scollary, G

2009-05-29

287

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.

Sharon Harris

288

Proceedings of the International Conference on Lasers '98, ed. V.J. Corcoran, STS Press, McLean VA, 1999, in press. PERFORMANCE OF A HIGH POWER CHEMICAL OXYGEN-IODINE LASER  

E-print Network

, 1999, in press. PERFORMANCE OF A HIGH POWER CHEMICAL OXYGEN-IODINE LASER USING NITROGEN DILUENT D was maintained for 45 minutes. The highest performance was obtained with new iodine injector blocks and a larger throat height. The new iodine injector blocks moved the injectors closer to the throat by 0.7 cm

Carroll, David L.

289

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

290

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

291

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

2014-01-01

292

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

293

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

294

The Multistep, Eight-Electron Oxidation Catalyzed by the Cofactorless Oxidase, PqqC: Identification of Chemical Intermediates and their Dependence on Molecular Oxygen  

PubMed Central

The final step of the biosynthesis of the 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 HPLC separation and mass spectrometric analyses of reaction mixtures were performed in order to correlate the structures of intermediates with previously observed UV/Vis 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.

2013-01-01

295

Numerical study of He/CF{sub 3}I pulsed discharge used to produce iodine atom in chemical oxygen-iodine laser  

SciTech Connect

The pulsed discharge for producing iodine atoms from the alkyl and perfluoroalky iodides (CH{sub 3}I, CF{sub 3}I, etc.) is the most efficient method for achieving the pulse operating mode of a chemical oxygen-iodine laser. In this paper, a one-dimensional fluid model is developed to study the characteristics of pulsed discharge in CF{sub 3}I-He mixture. By solving continuity equation, momentum equation, Poisson equation, Boltzmann equation, and an electric circuit equation, the temporal evolution of discharge current density and various discharge products, especially the atomic iodine, are investigated. The dependence of iodine atom density on discharge parameters is also studied. The results show that iodine atom density increases with the pulsed width and pulsed voltage amplitude. The mixture ratio of CF{sub 3}I and helium plays a more significant role in iodine atom production. For a constant voltage amplitude, there exists an optimal mixture ratio under which the maximum iodine atom concentration is achieved. The bigger the applied voltage amplitude is, the higher partial pressure of CF{sub 3}I is needed to obtain the maximum iodine atom concentration.

Zhang Jiao; Wang Yanhui; Wang Dezhen [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Duo Liping; Li Guofu [Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116024 (China)

2013-04-15

296

Hydrogen-oxygen flame acceleration and transition to detonation in channels with no-slip walls for a detailed chemical reaction model  

NASA Astrophysics Data System (ADS)

The features of flame acceleration in channels with wall friction and the deflagration to detonation transition (DDT) are investigated theoretically and using high resolution numerical simulations of two-dimensional reactive Navier-Stokes equations, including the effects of viscosity, thermal conduction, molecular diffusion, and a detailed chemical reaction mechanism for hydrogen-oxygen gaseous mixture. It is shown that in a wide channel, from the beginning, the flame velocity increases exponentially for a short time and then flame acceleration decreases, ending up with the abrupt increase of the combustion wave velocity and the actual transition to detonation. In a thin channel with a width smaller than the critical value, the exponential increase of the flame velocity is not bounded and ends up with the transition to detonation. The transition to detonation occurs due to the pressure pulse, which is formed at the tip of the accelerating flame. The amplitude of the pressure pulse grows exponentially due to a positive feedback coupling between the pressure pulse and the heat released in the reaction. Finally, large amplitude pressure pulse steepens into a strong shock coupled with the reaction zone forming the overdriven detonation. The evolution from a temperature gradient to a detonation via the Zeldovich gradient mechanism and its applicability to the deflagration-to-detonation transition is investigated for combustible materials whose chemistry is governed by chain-branching kinetics. The results of the high resolution simulations are fully consistent with experimental observations of the flame acceleration and DDT.

Ivanov, M. F.; Kiverin, A. D.; Liberman, M. A.

2011-05-01

297

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

SciTech Connect

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/cm{sup 2} at a turn-on field of 1.3?V/?m. The as grown SWCNTs were further treated with Oxygen (O{sub 2}) plasma for 5?min and again field emission characteristics were measured. The O{sub 2} plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111?mA/cm{sup 2} 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 O{sub 2} plasma treatment and the findings are being reported in this paper.

Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad [Department of Physics, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Harsh [Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, New Delhi 110025 (India); Husain, Mushahid, E-mail: mush-reslab@rediffmail.com [Department of Physics, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, New Delhi 110025 (India)

2014-02-28

298

Analytic study of the chain dark decomposition reaction of iodides - atomic iodine donors - in the active medium of a pulsed chemical oxygen-iodine laser: 2. Limiting parameters of the branching chain dark decomposition reaction of iodides  

SciTech Connect

The final stages in the development of a branching chain decomposition reaction of iodide in the active medium of a pulsed chemical oxygen-iodine laser (COIL) are analysed. Approximate expressions are derived to calculate the limiting parameters of the chain reaction: the final degree of iodide decomposition, the maximum concentration of excited iodine atoms, the time of its achievement, and concentrations of singlet oxygen and iodide at that moment. The limiting parameters, calculated by using these expressions for a typical composition of the active medium of a pulsed COIL, well coincide with the results of numerical calculations. (active media)

Andreeva, Tamara L; Kuznetsova, S V; Maslov, Aleksandr I; Sorokin, Vadim N [P N Lebedev Physical Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2009-08-31

299

High Selectivity Oxygen Delignification  

SciTech Connect

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

Lucian A. Lucia

2005-11-15

300

Carbon and oxygen dynamics of shallow aquatic systems: Process vectors and bacterial productivity  

Microsoft Academic Search

In shallow aquatic systems subject to heavy allochthonous (terrestrial) organic loading, bacterial processing of organic matter can be a significant component in the ecosystem C-cycle. Because this bacterial processing of organic matter also produces reduced species (Fe+2, Mn+2, S?2, NH3, etc.), these processes also create an additional chemical oxygen demand. Hence, net ecosystem operation can deviate significantly from the “Redfield

Thomas Torgersen; Brett Branco

2007-01-01

301

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

302

Investigation on oxygen content and ordering in Y1(Ba,Sr)2(Cu,Co)3O7-d superconductors by means of wet chemical analysis, X-ray- and neutron-diffraction techniques  

Microsoft Academic Search

A series of Co-doped samples as well as a series of Co and Sr doped samples have been studied with respect to structural changes. Variations in oxygen content, lattice parameters and Cu-O bond distances have been investigated. X-ray and neutron powder diffraction techniques as well as wet chemical methods have been used and some of the materials have also been

Sten Eriksson; Lars-Gunnar Johansson; Lars Börjesson; Masato Kakihana

1989-01-01

303

On demand, non-halon, fire extinguishing systems  

NASA Astrophysics Data System (ADS)

A system and process for on-demand generation of inert, non-flammable gases and water vapor to decrease the available atmospheric oxygen in the ullage of a hydrocarbon fuel storage tank to a level that will not support combustion of the hydrocarbon fuel, is disclosed. One, or more, of a variety of non-Halon, fire suppressor charges are selectively contained in one or more gas generating cartridges. The gas generating cartridge(s), when activated, cause release of these charges to prOmote rapid chemical reactions and supply inert, non-flammable gases and water vapor to the tank ullage. Activation is accomplished in aircraft by either pilot action or by pressure and temperature sensors contained within the hydrocarbon fuel tank.

Smith, Benjamin D.

1995-06-01

304

On demand, non-halon, fire extinguishing systems  

NASA Astrophysics Data System (ADS)

A system and process for on-demand generation of inert, nonflammable gases and water vapor to decrease the available atmospheric oxygen in the ullage of a hydrocarbon fuel storage tank to a level that will not support combustion of the hydrocarbon fuel, is disclosed. One, or more, of a variety of non-Halon, fire suppressor charges are selectively contained in one or more gas generating cartridges. The gas generating cartridge(s), when activated, cause release of these charges to promote rapid chemical reactions and supply inert, nonflammable gases and water vapor to the tank ullage. Activation is accomplished in aircraft by, either pilot action or, by pressure and temperature sensors contained within the hydrocarbon fuel tank.

Smith, Bengamin D.

1993-06-01

305

Microchemical systems for singlet oxygen generation  

E-print Network

Chemical Oxygen-Iodine Lasers (COIL) are a technology of interest for industrial and military audiences. COILs are flowing gas lasers where the gain medium of iodine atoms is collisionally pumped by singlet delta oxygen ...

Hill, Tyrone F. (Tyrone Frank), 1980-

2008-01-01

306

1 Removal of Trace Organic Chemicals and Performance of a Novel 2 Hybrid Ultrafiltration-Osmotic Membrane Bioreactor  

E-print Network

, Australia 6 *S Supporting Information 7 ABSTRACT: A hybrid ultrafiltration-osmotic membrane bioreactor (UFO from municipal wastewater. The UFO-MBR 10 system uses both ultrafiltration (UF) and forward osmosis (FO flushing). Results from UFO-MBR investigation illustrated that the chemical oxygen 21 demand, total

307

Oxygen analyzer  

DOEpatents

An oxygen analyzer which identifies and classifies microgram quantities of oxygen in ambient particulate matter and for quantitating organic oxygen in solvent extracts of ambient particulate matter. A sample is pyrolyzed in oxygen-free nitrogen gas (N.sub.2), and the resulting oxygen quantitatively converted to carbon monoxide (CO) by contact with hot granular carbon (C). Two analysis modes are made possible: (1) rapid determination of total pyrolyzable oxygen obtained by decomposing the sample at 1135.degree. C., or (2) temperature-programmed oxygen thermal analysis obtained by heating the sample from room temperature to 1135.degree. C. as a function of time. The analyzer basically comprises a pyrolysis tube containing a bed of granular carbon under N.sub.2, ovens used to heat the carbon and/or decompose the sample, and a non-dispersive infrared CO detector coupled to a mini-computer to quantitate oxygen in the decomposition products and control oven heating.

Benner, William H. (Danville, CA)

1986-01-01

308

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.

2003-09-26

309

Ethanol Demand in United States Gasoline Production  

SciTech Connect

The Oak Ridge National Laboratory (OWL) Refinery Yield Model (RYM) has been used to estimate the demand for ethanol in U.S. gasoline production in year 2010. Study cases examine ethanol demand with variations in world oil price, cost of competing oxygenate, ethanol value, and gasoline specifications. For combined-regions outside California summer ethanol demand is dominated by conventional gasoline (CG) because the premised share of reformulated gasoline (RFG) production is relatively low and because CG offers greater flexibility for blending high vapor pressure components like ethanol. Vapor pressure advantages disappear for winter CG, but total ethanol used in winter RFG remains low because of the low RFG production share. In California, relatively less ethanol is used in CG because the RFG production share is very high. During the winter in California, there is a significant increase in use of ethanol in RFG, as ethanol displaces lower-vapor-pressure ethers. Estimated U.S. ethanol demand is a function of the refiner value of ethanol. For example, ethanol demand for reference conditions in year 2010 is 2 billion gallons per year (BGY) at a refiner value of $1.00 per gallon (1996 dollars), and 9 BGY at a refiner value of $0.60 per gallon. Ethanol demand could be increased with higher oil prices, or by changes in gasoline specifications for oxygen content, sulfur content, emissions of volatile organic compounds (VOCS), and octane numbers.

Hadder, G.R.

1998-11-24

310

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

311

Elastic and structural properties and buckling behavior of single-walled carbon nanotubes under chemical adsorption of atomic oxygen and hydroxyl  

NASA Astrophysics Data System (ADS)

Atomic decoration of carbon nanotubes (CNTs) is an effective way to alter the key properties of pristine CNTs. Elastic properties and axial buckling behavior of atomic oxygen and hydroxyl chemisorbed single-walled CNTs are explored employing molecular dynamics (MD) simulations. Our results demonstrate that the structure of chemisorbed CNTs changes compared to pristine CNT which considerably depends on the distribution pattern of chemisorbed oxygen and -hydroxyl. The results also demonstrate that chemisorption of atomic oxygen and -hydroxyl reduces Young's modulus and critical strain while increases the critical force of CNTs. Buckling mode shape of chemisorbed CNTs depends on the distribution pattern.

Ansari, R.; Ajori, S.; Ameri, A.

2014-11-01

312

Oxygen analyzer  

DOEpatents

An oxygen analyzer which identifies and classifies microgram quantities of oxygen in ambient particulate matter and for quantitating organic oxygen in solvent extracts of ambient particulate matter. A sample is pyrolyzed in oxygen-free nitrogen gas (N/sub 2/), and the resulting oxygen quantitatively converted to carbon monoxide (CO) by contact with hot granular carbon (C). Two analysis modes are made possible: (1) rapid determination of total pyrolyzable obtained by decomposing the sample at 1135/sup 0/C, or (2) temperature-programmed oxygen thermal analysis obtained by heating the sample from room temperature to 1135/sup 0/C as a function of time. The analyzer basically comprises a pyrolysis tube containing a bed of granular carbon under N/sub 2/, ovens used to heat the carbon and/or decompose the sample, and a non-dispersive infrared CO detector coupled to a mini-computer to quantitate oxygen in the decomposition products and control oven heating.

Benner, W.H.

1984-05-08

313

Analysis of the Atmospheric Distribution, Sources, and Sinks of Oxygenated Volatile Organic Chemicals Based on Measurements over the Pacific during TRACE-P  

NASA Technical Reports Server (NTRS)

Airborne measurements of a large number of oxygenated volatile organic chemicals (OVOC) were carried out in the Pacific troposphere (0.1-12 km) in winter/spring of 2001 (24 February to 10 April). Specifically, these measurements included acetone (CH3COCH3), methylethyl ketone (CH3COC2H5, MEK), methanol (CH3OH), ethanol (C2H5OH), acetaldehyde (CH3CHO), propionaldehyde (C2H5CHO), peroxyacylnitrates (PANs) (C(sub n)H(sub 2n+1)COO2NO2), and organic nitrates (C(sub n)H(sub 2n+1)ONO2). Complementary measurements of formaldehyde (HCHO), methyl hydroperoxide (CH3OOH), and selected tracers were also available. OVOC were abundant in the clean troposphere and were greatly enhanced in the outflow regions from Asia. Background mixing ratios were typically highest in the lower troposphere and declined toward the upper troposphere and the lowermost stratosphere. Their total abundance (Summation of OVOC) was nearly twice that of nonmethane hydrocarbons (Summation of C2-C8 NMHC). Throughout the troposphere, the OH reactivity of OVOC is comparable to that of methane and far exceeds that of NMHC. A comparison of these data with western Pacific observations collected some 7 years earlier (February-March 1994) did not reveal significant differences. Mixing ratios of OVOC were strongly correlated with each other as well as with tracers of fossil and biomass/biofuel combustion. Analysis of the relative enhancement of selected OVOC with respect to CH3Cl and CO in 12 plumes originating from fires and sampled in the free troposphere (3-11 km) is used to assess their primary and secondary emissions from biomass combustion. The composition of these plumes also indicates a large shift of reactive nitrogen into the PAN reservoir thereby limiting ozone formation. A three-dimensional global model that uses state of the art chemistry and source information is used to compare measured and simulated mixing ratios of selected OVOC. While there is reasonable agreement in many cases, measured aldehyde concentrations are significantly larger than predicted. At their observed levels, acetaldehyde mixing ratios are shown to be an important source of HCHO (and HO x ) and PAN in the troposphere. On the basis of presently known chemistry, measured mixing ratios of aldehydes and PANs are mutually incompatible. We provide rough estimates of the global sources of several OVOC and conclude that collectively these are extremely large (150-500 Tg C / yr) but remain poorly quantified.

Singh, H. B.; Salas, L. J.; Chatfield, r. B.; Czech, E.; Fried, A.; Walega, J.; Evans, M. J.; Field, B. D.; Jacob, D. J.; Blake, D.; Heikes, B.; Talbot, R.; Sachse, G.; Crawford, J. H.; Avery, M. A.; Sandholm, S.; Fuelberg, H.

2004-01-01

314

Structure of the oxygen-evolving complex of photosystem II: information on the S(2) state through quantum chemical calculation of its magnetic properties.  

PubMed

Twelve structural models for the S(2) state of the oxygen-evolving complex (OEC) of photosystem II are evaluated in terms of their magnetic properties. The set includes ten models based on the 'fused twist' core topology derived by polarized EXAFS spectra and two related models proposed in recent mechanistic investigations. Optimized geometries and spin population analyses suggest that Mn(iii), which is most often identified with the manganese ion at site D, is always associated with a penta-coordinate environment, unless a chloride is directly ligated to the metal. Exchange coupling constants were determined by broken-symmetry density functional theory calculations and the complete spectrum of magnetic sublevels was obtained by direct diagonalization of the Heisenberg Hamiltonian. Seven models display a doublet ground state and are considered spectroscopic models for the ground state corresponding to the multiline signal (MLS) of the S(2) state of the OEC, whereas the remaining five models display a sextet ground state and could be related to the g = 4.1 signal of the S(2) state. It is found that the sign of the exchange coupling constant between the Mn centres at positions A and B of the cluster is directly related to the ground state multiplicity, implying that interconversion between the doublet and sextet can be induced by only small structural perturbations. The recently proposed quantum chemical method for the calculation of (55)Mn hyperfine coupling constants is subsequently applied to the S(2) MLS state models and the quantities that enter into the individual steps of the procedure (site-spin expectation values, intrinsic site isotropic hyperfine parameters and projected (55)Mn isotropic hyperfine constants) are analyzed and discussed in detail with respect to the structural and electronic features of each model. The current approach performs promisingly. It reacts sensitively to structural distortions and hence may be able to distinguish between different structural proposals. Thus it emerges as a useful contributor to the ongoing efforts that aim at establishing correlations between the body of spectroscopic data available for the various S(i) states of the OEC and their actual geometric features. PMID:19639153

Pantazis, Dimitrios A; Orio, Maylis; Petrenko, Taras; Zein, Samir; Lubitz, Wolfgang; Messinger, Johannes; Neese, Frank

2009-08-21

315

Oxygen levels versus chemical pollutants: do they have similar influence on macrofaunal assemblages? A case study in a harbour with two opposing entrances.  

PubMed

Generally, harbours are polluted zones characterised by low values of hydrodynamism and oxygen in the water column and high concentrations of pollutants in sediments. The harbour of Ceuta, North Africa, has an unusual structure; it is located between two bays connected by a channel, which increases the water movement and exchange in the harbour, maintaining moderate oxygen levels in the water-sediment interface. Nevertheless, high concentration of organic matter, nutrients and heavy metals were measured in sediments from this harbour. Under these unusual conditions (high levels of pollution but total saturation of oxygen in the water column) we studied the responses of soft-bottom macrobenthic communities using uni and multivariate analyses. The number of species was similar inside and outside the harbour but the species composition differed between internal and external stations; oxygen levels seem to control the "quantity" of species whereas pollutants control the "quality" of them. PMID:15734588

Guerra-García, J M; García-Gómez, J C

2005-05-01

316

Reduction and oxidation kinetics of Mn 3O 4\\/Mg–ZrO 2 oxygen carrier particles for chemical-looping combustion  

Microsoft Academic Search

The kinetics of reduction with methane and oxidation with oxygen of Mn3O4 supported on Mg–ZrO2 prepared by freeze granulation has been investigated. The reactivity experiments were performed in a thermogravimetric analyzer (TGA) using different reacting gas concentrations and temperatures in the range of 1073–1223K. The oxygen carrier particles showed high reactivity during both reduction and oxidation at all investigated temperatures.

Qamar Zafar; Alberto Abad; Tobias Mattisson; Börje Gevert; Michael Strand

2007-01-01

317

I.~Synthesis of 1,2-dioxetanes by electron transfer oxygenation of vinyl ethers. II.~Chemically-triggered decomposition of chemiluminescent 1,2-dioxetanes  

Microsoft Academic Search

Three methods for the synthesis of dioxetanes by electron-transfer oxygenation have been developed. In the first method a series of vinyl ethers were reacted with molecular oxygen in the presence of catalytic amounts of tris-p-bromophenyl amminium hexachloro-antimonate to afford high yields of the corresponding 1,2-dioxetanes. In the second method a series of vinyl ethers were reacted with oxodiperoxo metal (VI)

Khaledur S. M Rashid

1988-01-01

318

The aerobic capacity of tunas: Adaptation for multiple metabolic demands  

Microsoft Academic Search

Tunas are pelagic, continuous swimmers, with numerous specializations for achieving a high aerobic scope. Tunas must maintain a high rate of energy turnover, and therefore require elevated levels of aerobic performance in multiple physiological functions simultaneously. Based on a model of oxygen demand and delivery to the swimming musculature, the yellowfin's total oxygen consumption at the predicted maximum sustainable (aerobic)

K. E. Korsmeyer; H. Dewar; N. C. Lai; J. B. Graham

1996-01-01

319

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

320

The effect of oxygen-containing reagents on the crystal morphology and orientation in tungsten oxide thin films deposited via atmospheric pressure chemical vapour deposition (APCVD) on glass substrates.  

PubMed

Thin films of monoclinic WO3 and WO(3-x) have been synthesized by atmospheric pressure chemical vapour deposition from WCl6 and three oxygen containing precursors; water, ethanol and ethanoic anhydride. A wide variation in the colour, crystal morphology and preferred orientation of the films was observed, depending on the chosen oxygen source. In particular contrast were the films formed from WCl6 and ethanol, which were blue and had needle-like crystallites, and those formed from WCl6 and water, which were yellow and had hexagonal shaped crystallites. Studies were also undertaken to form films from WCl6, ethanol and water simultaneously, in which the ratio of ethanol to water was varied, and this led to films in which the crystal morphology and orientation could be controlled. PMID:17955818

Hyett, Geoffrey; Blackman, Christopher S; Parkin, Ivan P

2007-01-01

321

Electrochemical studies of quinone oxygen  

SciTech Connect

Asphaltenes are a chemically complex mixture of aromatic and heteroaromatic compounds. This material contains oxygen in various functional groups. The distribution includes esters, carboxylic acids, phenolic and most probably quinone type oxygen functionalities. The present work details the complete electrochemical behaviour of quinone type oxygen. The method is quinone specific. A condensed aromatic quinone, 9,10-anthraquinone, was selected as representative of complex quinones. By this method quinones can be determined in the presence of other oxygen functional groups, alcohols, carboxylic acids, ethers, and other carbonyls.

Deanhardt, M.L. (Lander College, Greenwood, SC (US)); Mushrush, G.W.; Stalick, W.M. (Chemistry Dept., George mason Univ., Fairfax, VA (US)); Watkins, J.M. Jr. (Naval Research Lab., Fuels Section, Code 6180, Washington, DC (US))

1990-02-01

322

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

323

Appreciating Oxygen  

ERIC Educational Resources Information Center

Photosynthetic flora and microfauna utilize light from the sun to convert carbon dioxide and water into carbohydrates and oxygen. While these carbohydrates and their derivative hydrocarbons are generally considered to be fuels, it is the thermodynamically energetic oxygen molecule that traps, stores, and provides almost all of the energy that…

Weiss, Hilton M.

2008-01-01

324

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.

325

Demand analysis system elasticities  

Microsoft Academic Search

The Demand Analysis System (DAS) provides energy consumption projections for the residential, commercial, industrial, and transportation sectors to 1995. These projections are developed within an integrated supply\\/demand balance framework known as the Intermediate Future Forecasting System (IFFS). Each of the end-use sectors is represented by a detailed structural econometric model within IFFS. These models are fully described in documentation reports,

B. N. Cohen; J. A. Holte; P. J. Werbos

1985-01-01

326

Characterist Passenger Demand  

E-print Network

Passeng er Demand User Trip Rates Passenger Demand #12;11 #12;12 0.00 0.50 1.00 1.50 2.00 2.50 CityofBunyanTransit RenvilleCounty GrantCountyTransportation WesternCommunityAction,Inc. IsantiCounty Kandiyohi

Minnesota, University of

327

Novel oxygen-carrier materials for chemical-looping combustion and chemical-looping reforming; La x Sr 1? x Fe y Co 1? y O 3? ? perovskites and mixed-metal oxides of NiO, Fe 2O 3 and Mn 3O 4  

Microsoft Academic Search

Solid oxygen-carrier materials for chemical-looping applications have been examined by reduction with CH4 and oxidation with air in a fixed-bed quartz reactor at 900°C. Four perovskite materials, three metal-oxide materials and four metal-oxide mixtures have been studied. It was found that LaxSr1?xFeO3?? perovskites provided very high selectivity towards CO\\/H2 and should be well suited for chemical-looping reforming. Substituting La for

Magnus Rydén; Anders Lyngfelt; Tobias Mattisson; De Chen; Anders Holmen; Erlend Bjørgum

2008-01-01

328

Oxygen uptake, ammonia excretion and phosphate excretion by krill and other Antarctic zooplankton in relation to their body size and chemical composition  

Microsoft Academic Search

Oxygen uptake, ammonia excretion and phosphate excretion were measured in 14 Antarctic zooplankton species, including various size classes of krill (Euphausia superba), during a cruise to the Antarctic Ocean adjacent to Wilkes Land in the summer of 1980. Elemental composition (C, N and P) was also determined on the specimens used in these metabolic rate measurements. The values obtained for

T. Ikeda; A. W. Mitchell

1982-01-01

329

Simultaneous autotrophic denitrification and nitrification in a low-oxygen reaction environment.  

PubMed

The occurrence of autotrophic denitrification and nitrification activities by ammonia-oxidising bacteria and nitrite-oxidising bacteria is studied in a bioreactor system operable at low-dissolved oxygen (DO) and at variable oxygen influx rates. At a loading of 3.6 mg NH4(+)-N/h into the bioreactor, simultaneous autotrophic denitrification and nitrification contributed to NH4(+)-N removal over oxygen influxes of 2-14 mg O2/h and DO <0.5 mg/L. The maximum autotrophic denitrification (or total-N removal) rates were achieved in a narrow oxygen influx band of 3-5 mg O2/h, where it accounted for up to 36% of NH4(+)-N removal. At oxygen influx >16 mg O2/h and DO >2 mg/L, autotrophic denitrification ceases and roughly 90% of feed NH4(+)-N is oxidised to NOX(-)-N. The stability of total effluent chemical oxygen demand (COD) over the range of oxygen influxes tested confirms the absence of heterotrophic denitrification in the bioreactor. The long solids residence time of the stable biomass zone (21 days) led to production of effluent COD as a result of cell decay, and thus effluent COD was used to calculate more accurately the mean cell residence time. PMID:25116505

Ramanathan, Ganapathy; Sales, Christopher M; Shieh, Wen K

2014-01-01

330

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

331

Effect of plasma-chemical and thermal treatment in oxygen on the activity of Na3ZrM(PO4)3 phosphates (M = Zn, Co, Cu) in the transformation of butanol-2  

NASA Astrophysics Data System (ADS)

The catalytic properties of plasma-chemically and thermally treated triple zirconium orthophosphates Na3ZrM(PO4)3 (M = Zn, Co, Cu) in the transformation of butanol-2 are studied. X-ray photoelectron spectroscopy data indicate that the surface composition of the samples differs from the stoichiometry, especially in the case of M = Cu. The partial reduction of copper ions occurs during plasma-chemical treatment (PCT), while the amount of Cu on the surface of Na3ZrCu(PO4)3 diminishes. Treatment in an oxygen glow discharge results in a 3-8 times greater yield of the alcohol dehydrogenation product, methyl ethyl ketone. The energy of the alcohol's bonds with the surface is reduced and the dehydration active sites become fully inactivated. In contrast, thermal treatment (TT) results in an increase in the activity of Na3ZrM(PO4)3 in the dehydration of butanol-2.

Pylinina, A. I.; Povarova, E. I.; Mikhalenko, I. I.; Yagodovskaya, T. V.

2013-06-01

332

Analytic study of the chain dark decomposition reaction of iodides - atomic iodine donors - in the active medium of a pulsed chemical oxygen-iodine laser: 1. Criteria for the development of the branching chain dark decomposition reaction of iodides  

SciTech Connect

The scheme of chemical processes proceeding in the active medium of a pulsed chemical oxygen-iodine laser (COIL) is analysed. Based on the analysis performed, the complete system of differential equations corresponding to this scheme is replaced by a simplified system of equations describing in dimensionless variables the chain dark decomposition of iodides - atomic iodine donors, in the COIL active medium. The procedure solving this system is described, the basic parameters determining the development of the chain reaction are found and its specific time intervals are determined. The initial stage of the reaction is analysed and criteria for the development of the branching chain decomposition reaction of iodide in the COIL active medium are determined. (active media)

Andreeva, Tamara L; Kuznetsova, S V; Maslov, Aleksandr I; Sorokin, Vadim N [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2009-02-28

333

In situ reactive oxygen species production for tertiary wastewater treatment.  

PubMed

The goal of this research was to develop a new approach for tertiary water treatment, particularly disinfection and removal of refractory organic compounds, without adding any chemical. Hydrogen peroxide can indeed be produced from dissolved oxygen owing to electrochemical processes. Using various current intensities (1.0 to 4.0 A), it was possible to in situ produce relatively high concentration of H2O2 with a specific production rate of 0.05?×?10(-5) M/min/A. Likewise, by using ultraviolet-visible absorption spectroscopy method, it was shown that other reactive oxygen species (ROS) including HO(*) radical and O3 could be simultaneously formed during electrolysis. The ROS concentration passed from 0.45?×?10(-5) M after 20 min of electrolysis to a concentration of 2.87?×?10(-5) M after 100 min of electrolysis. The disinfection and the organic matter removal were relatively high during the tertiary treatment of municipal and domestic wastewaters. More than 90 % of organic compounds (chemical oxygen demand) can be removed, whereas 99 % of faecal coliform abatement can be reached. Likewise, the process was also effective in removing turbidity (more than 90 % of turbidity was removed) so that the effluent became more and more transparent. PMID:25483973

Guitaya, Léa; Drogui, Patrick; Blais, Jean François

2014-12-01

334

Oxygen-assisted low-pressure chemical vapor deposition for the low-temperature direct growth of graphitic nanofibers on fluorine-doped tin oxide glass as a counter electrode for dye-sensitized solar cell  

NASA Astrophysics Data System (ADS)

In this paper, we report an oxygen-assisted low-pressure chemical vapor deposition (LPCVD) method for the direct growth of graphitic nanofibers (GNFs) on a fluorine-doped tin oxide (FTO) glass substrate at a low temperature (550 °C). By adding moderate concentrations of oxygen in a gas mixture of argon, ethylene, and hydrogen during LPCVD, an extremely dense GNF forest can be obtained on a nickel-coated FTO glass substrate. Though this process, the graphitic nanofibers are grown homogenously on a large area of FTO glass. It was observed that oxygen-assisted LPCVD leads to the direct growth of high-quality GNFs as a counter electrode for dye-sensitized solar cells (DSSCs). In combination with an N719 dye-sensitized TiO2 working electrode and an iodine-based electrolyte, the DSSC with a GNF counter electrode showed a power conversion efficiency of 5.51% under AM 1.5 (100 mW cm?2) illumination, which approached that of the DSSC with a Pt counter electrode (5.44%). The results demonstrated that our directly grown GNFs could be promising candidates for counter electrodes to achieve high performance in DSSCs.

Chen, Chih-Sheng; Hsieh, Chien-Kuo

2014-11-01

335

Oxygen Therapy  

MedlinePLUS

... need oxygen therapy by testing the presence of gases in your blood. This test is called an ... is already in the air and removing other gases. The concentrator is powered by electricity. What is ...

336

A study of aluminum oxide thin films prepared by atmospheric-pressure chemical vapor deposition from trimethylaluminum + oxygen and\\/or nitrous oxide  

Microsoft Academic Search

A significant improvement in the deposition rate of thin films of aluminum oxide, using trimethylaluminum and oxygen at a\\u000a substrate temperature of 570° C, is demonstrated. Hard, transparent, strongly adherent films of refractive index 1.62–1.63\\u000a were consistently achieved with controlled growth rates from 15 Å\\/sec to 94 Å\\/sec, depending upon the Al mole fraction. Systematic\\u000a analysis of the growth rate

Kenneth Michael Gustin; Roy Gerald Gordon

1988-01-01

337

A study of aluminum oxide thin films prepared by atmospheric-pressure chemical vapor deposition from trimethylaluminum + oxygen and\\/or nitrous oxide  

Microsoft Academic Search

A significant improvement in the deposition rate of thin films of aluminum oxide, using trimethylaluminum and oxygen at a substrate temperature of 570° C, is demonstrated. Hard, transparent, strongly adherent films of refractive index 1.62-1.63 were consistently achieved with controlled growth rates from 15 Å\\/sec to 94 Å\\/sec, depending upon the Al mole fraction. Systematic analysis of the growth rate

Kenneth Michael Gustin; Roy Gerald Gordon

1988-01-01

338

Quantum-chemical study of the effect of oxygen on the formation of active sites of silver clusters during the selective adsorption of hydrocarbons  

NASA Astrophysics Data System (ADS)

Density functional theory (PBE with a modified Dirac-Coulomb-Breit Hamiltonian) is used to simulate the adsorption of hydrocarbons (C2H2, C2H4, C2H6) on the surface of a sorbent containing Ag0, Ag?+, and AgO sites. The dynamics of change in the structural characteristics of Ag n ( n ? 10) is analyzed and the adsorption of oxygen on Ag8 and Ag10 is studied to select the adsorption site model. Studying the interaction of hydrocarbons with Ag8, Ag10, Ag{10/+}, Ag10O, and Ag10O2 clusters reveals that the presence of oxygen leads to an increase in the activation of unsaturated hydrocarbons, and the adsorption energy of C2H2 increases tenfold. It is found that the role of adsorbed oxygen is not only to form adsorption sites of hydrocarbons (Ag?+) but also to bind C2H2 and C2H4 directly to the sorbent's surface.

Lanin, S. N.; Polynskaya, Yu. G.; Pichugina, D. A.; Nguen, V.; Beletskaya, A. V.; Kuz'menko, N. E.; Shestakov, A. F.

2013-09-01

339

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

340

Demand weakens; prices fall  

SciTech Connect

This document is a brief review of uranium transactions during the months of April/May 1994. Spot market prices are discussed, as is spot market volume. The trend during this time frame shows a weakening demand and falling prices.

NONE

1994-06-01

341

Cinema Demand In Germany  

Microsoft Academic Search

This paper examines the German cinema market using time series data covering the period 1950–2002. Applying estimation techniques such as OLS, 2SLS and SUR, we identify interrelations between the number of seats, the average real prices and the demand for movies per capita. Furthermore, we test for the long-run relationship between demand, prices and real income and estimate the elasticity

Ralf Dewenter; Michael Westermann

2005-01-01

342

CUMULATIVE OXYGEN ABUNDANCES OF SPIRAL GALAXIES  

SciTech Connect

Studying the global evolution of spiral galaxies requires determining their overall chemical compositions. However, since spirals tend to possess gradients in their chemical compositions, determining their overall chemical abundances poses a challenge. In this study, the framework for a newly proposed method for determining the overall oxygen abundance of a disk is established. By separately integrating the absolute amounts of hydrogen and oxygen out to large radii, the cumulative oxygen abundance is shown to approach an asymptotic value. In this manner, a reliable account of the overall chemical state of a disk is revealed.

Dack, Stuart; McCall, Marshall L., E-mail: studack@alumni.yorku.ca, E-mail: mccall@yorku.ca [Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, ON M3J 1P3 (Canada)

2012-05-10

343

Cumulative Oxygen Abundances of Spiral Galaxies  

E-print Network

Studying the global evolution of spiral galaxies requires determining their overall chemical compositions. However, since spirals tend to possess gradients in their chemical compositions, determining their overall chemical abundances poses a challenge. In this study, the framework for a newly proposed method for determining the overall oxygen abundance of a disk is established. By separately integrating the absolute amounts of hydrogen and oxygen out to large radii, the cumulative oxygen abundance is shown to approach an asymptotic value. In this manner, a reliable account of the overall chemical state of a disk is revealed.

Dack, Stuart

2012-01-01

344

Cumulative Oxygen Abundances of Spiral Galaxies  

NASA Astrophysics Data System (ADS)

Studying the global evolution of spiral galaxies requires determining their overall chemical compositions. However, since spirals tend to possess gradients in their chemical compositions, determining their overall chemical abundances poses a challenge. In this study, the framework for a newly proposed method for determining the overall oxygen abundance of a disk is established. By separately integrating the absolute amounts of hydrogen and oxygen out to large radii, the cumulative oxygen abundance is shown to approach an asymptotic value. In this manner, a reliable account of the overall chemical state of a disk is revealed.

Dack, Stuart; McCall, Marshall L.

2012-05-01

345

Evaluation of lead and COD removal from lead octoate drier effluent by chemical precipitation, coagulation–flocculation, and potassium persulfate oxidation processes  

Microsoft Academic Search

A range of treatment processes for the removal of mineral and organic pollutants from industrial wastewater have been investigated. This study was aimed to remove lead, turbidity, and chemical oxygen demand (COD) from lead octoate drier wastewater via potassium persulfate oxidation in the presence of UV and heat, chemical precipitation by sulfuric acid, and coagulation–flocculation processes. Al2(SO4)3, poly-aluminum chloride (PAC),

Anahita Rabii; Gholamreza Nabi Bidhendi; Naser Mehrdadi

2012-01-01

346

Oxygen and oxygenation in stem-cell therapy for myocardial infarction  

Microsoft Academic Search

Myocardial infarction (MI) is caused by deprivation of oxygen and nutrients to the cardiac tissue due to blockade of coronary artery. It is a major contributor to chronic heart disease, a leading cause of mortality in the modern world. Oxygen is required to meet the constant energy demands for heart contractility, and also plays an important role in the regulation

Mahmood Khan; Pawel Kwiatkowski; Brian K. Rivera; Periannan Kuppusamy

2010-01-01

347

Effects of biomass types and carbonization conditions on the chemical characteristics of hydrochars.  

PubMed

Effects of biomass types (bark mulch versus sugar beet pulp) and carbonization processing conditions (temperature, residence time, and phase of reaction medium) on the chemical characteristics of hydrochars were examined by elemental analysis, solid-state ¹³C NMR, and chemical and biochemical oxygen demand measurements. Bark hydrochars were more aromatic than sugar beet hydrochars produced under the same processing conditions. The presence of lignin in bark led to a much lower biochemical oxygen demand (BOD) of bark than sugar beet and increasing trends of BOD after carbonization. Compared with those prepared at 200 °C, 250 °C hydrochars were more aromatic and depleted of carbohydrates. Longer residence time (20 versus 3 h) at 250 °C resulted in the enrichment of nonprotonated aromatic carbons. Both bark and sugar beet pulp underwent deeper carbonization during water hydrothermal carbonization than during steam hydrothermal carbonization (200 °C, 3 h) in terms of more abundant aromatic C but less carbohydrate C in water hydrochars. PMID:24004410

Cao, Xiaoyan; Ro, Kyoung S; Libra, Judy A; Kammann, Claudia I; Lima, Isabel; Berge, Nicole; Li, Liang; Li, Yuan; Chen, Na; Yang, John; Deng, Baolin; Mao, Jingdong

2013-10-01

348

Oxygen-18 kinetic isotope effects in the dopamine beta-monooxygenase reaction: evidence for a new chemical mechanism in non-heme metallomonooxygenases.  

PubMed

Previous studies of dopamine beta-monooxygenase (D beta M) have implicated the formation of a substrate-derived benzylic radical via a hydrogen atom abstraction mechanism [Miller & Klinman (1985) Biochemistry 24, 2114]. We now address the nature of the oxygen species catalyzing C-H bond cleavage through the measurement of oxygen-18 isotope effects as a function of substrate structure. Using deuterium isotope effects, together with experimental O-18 isotope effects with protonated and deuterated substrates, it has been possible to calculate intrinsic O-18 isotope effects. Since the D beta M mechanism includes many steps which may involve changes in bond order at dioxygen, e.g., the reversible binding of O2 to the active-site copper and its reductive activation to a copper-hydroperoxide species, the intrinsic O-18 isotope effect is expected to be the product of two terms: (1) an overall equilibrium O-18 isotope effect on steps leading from O2 binding to the formation of the intermediate which catalyzes C-H bond cleavage and (2) a kinetic O-18 isotope effect on the C-H bond cleavage step. Thus, the magnitude of a single O-18 isotope effect measurement cannot reveal the nature of the bonding at oxygen during substrate activation. In the present study we have measured the change in O-18 isotope effect as a function of substrate structure and reactivity, finding values of 18(V/K) which decrease from 1.0281 +/- 0.001 to 1.0216 +/- 0.0003 as the rate of the C-H bond cleavage step decreases from 680 to 2 s-1.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8286345

Tian, G; Berry, J A; Klinman, J P

1994-01-11

349

Oxygen scavengers - The chemistry of sulfite under hydrothermal conditions  

SciTech Connect

Control of oxygen corrosion is critical to the reliability of steam generator systems. Mechanical deaeration and chemical oxygen scavenging effectively reduce oxygen levels in boiler feedwater systems. This paper reviews the use of sulfites to reduce oxygen and provide corrosion control throughout the boiler feedwater circuit as well as mechanical and operational oxygen reduction methods. The mechanism of oxygen pitting, electrochemical reactions, and the basis of operation of mechanical deaeration are discussed. Estimating techniques for the amount of steam required and a deaerator troubleshooting guide are included. The chemistry of sulfites is covered in detail. Also included are a functional definition of chemical oxygen scavengers and a general discussion of their various types.

Cotton, I.J.

1987-03-01

350

Study of regional cerebral metabolism and blood flow relationships in man using the method of continuously inhaling oxygen-15 and oxygen-15 labelled carbon dioxide  

Microsoft Academic Search

A new technique for assessing regional oxygen use and blood flow has been applied to a wide range of neurological patients. The method couples the brain's high metabolic demand for oxygen with a shortlived radioactive form of this metabolite, namely oxygen-15 (half life: 2.1 min). This combination produces during the continuous inhalation of either molecular oxygen-15 or labelled carbon dioxide,

G L Lenzi; T Jones; C G McKenzie; P D Buckingham; J C Clark; S Moss

1978-01-01

351

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...

352

Hospital demand for physicians.  

PubMed

This article develops a derived demand for physicians that is general enough to encompass physician control, simple profit maximization and hospital utility maximization models of the hospital. The analysis focuses on three special aspects of physician affiliations: the price of adding a physician to the staff is unobserved; the physician holds appointments at multiple hospitals, and physicians are not homogeneous. Using 1983 American Hospital Association data, a system of specialty-specific demand equations is estimated. The results are consistent with the model and suggest that physicians should be concerned about reduced access to hospitals, particularly as the stock of hospitals declines. PMID:10104050

Morrisey, M A; Jensen, G A

1990-01-01

353

A fast and environment-friendly method for determination of chemical oxygen demand by using the heterogeneous Fenton-like process (H2O2/Fe(3-x)Co(x)O4 nanoparticles) as an oxidant.  

PubMed

An easy, fast and environment-friendly method for COD determination in water is proposed. The procedure is based on the oxidation of organic matter by the H2O2/Fe(3-x)Co(x)O4 system. The Fe(3-x)Co(x)O4 nanoparticles activate the H2O2 molecule to produce hydroxyl radicals, which are highly reactive for oxidizing organic matter in an aqueous medium. After the oxidation step, the organic matter amounts can be quantified by comparing the quantity of H2O2 consumed. Moreover, the proposed COD method has several distinct advantages, since it does not use toxic reagents and the oxidation reaction of organic matter is conducted at room temperature and atmospheric pressure. Method detection limit is 2.0 mg L(-1) with intra- and inter-day precision lower than 1% (n=5). The calibration graph is linear in the range of 2.0-50 mg L(-1) with a sample throughput of 25 samples h(-1). Data are validated based on the analysis of six contaminated river water samples by the proposed method and by using a comparative method validated and marketed by Merck, with good agreement between the results (t test, 95%). PMID:25640128

Esteves, Lorena C R; Oliveira, Thaís R O; Souza, Elias C; Bomfeti, Cleide A; Gonçalves, Andrea M; Oliveira, Luiz C A; Barbosa, Fernando; Pereira, Márcio C; Rodrigues, Jairo L

2015-04-01

354

Chemically pretreating slaughterhouse solid waste to increase the efficiency of anaerobic digestion.  

PubMed

The combined effect of temperature and pretreatment of the substrate on the anaerobic treatment of the organic fraction of slaughterhouse solid waste was studied. The goal of the study was to evaluate the effect of pretreating the waste on the efficiency of anaerobic digestion. The effect was analyzed at two temperature ranges (the psychrophilic and the mesophilic ranges), in order to evaluate the effect of temperature on the performance of the anaerobic digestion process for this residue. The experiments were performed in 6 L batch reactors for 30 days. Two temperature ranges were studied: the psychrophilic range (at room temperature, 18°C average) and the mesophilic range (at 37°C). The waste was pretreated with NaOH before the anaerobic treatment. The result of pretreating with NaOH was a 194% increase in the soluble chemical oxygen demand (COD) with a dose of 0.6 g NaOH per g of volatile suspended solids (VSS). In addition, the soluble chemical oxygen demand/total chemical oxygen demand ratio (sCOD/tCOD) increased from 0.31 to 0.7. For the anaerobic treatment, better results were observed in the mesophilic range, achieving 70.7%, 47% and 47.2% removal efficiencies for tCOD, total solids (TS), and volatile solids (VS), respectively. PMID:24794850

Flores-Juarez, Cyntia R; Rodríguez-García, Adrián; Cárdenas-Mijangos, Jesús; Montoya-Herrera, Leticia; Godinez Mora-Tovar, Luis A; Bustos-Bustos, Erika; Rodríguez-Valadez, Francisco; Manríquez-Rocha, Juan

2014-10-01

355

Oxygen safety  

MedlinePLUS

... Products that are safe include: Aloe vera Water-based products, such as K-Y Jelly Avoid tripping over oxygen tubing. Try taping the tubing to the back of your shirt. Teach children not to get tangled in the tubing.

356

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. PMID:277209

Greenstock, C. L.; Biaglow, J. E.; Durand, R. E.

1978-01-01

357

Myocardial oxygen consumption during dobutamine infusion in endotoxemic pigs  

Microsoft Academic Search

Purpose: Dobutamine infusion is used to increase whole-body oxygen delivery in septic patients to satisfy unmet oxygen demand of hypoxic tissues. However, dobutamine infusion also increases myocardial work and myocardial oxygen consumption. Our goal was to determine the importance of this effect as a fraction of the increase in whole-body oxygen consumption, in a porcine model of septic shock.Materials and

Michael J. Herbertson; James A. Russell; Keith R. Walley

1999-01-01

358

Passive migration barriers using slow release oxygen compounds  

SciTech Connect

This paper describes passive barriers for controlling downgradient plume migration in contaminated aquifers. Numerous field studies using migration barriers to control benzene, toluene, ethylbenzene, and xylene (BTEX) plumes are briefly summarized. The barriers consist of a patented oxygen release compound placed in a row of wells transecting a BTEX plume. Oxygen is slowly released to the saturated zone, thus enhancing natural biodegradation. Migration is controlled by matching the oxygen release rate to the flux and oxygen demand of the dissolved contaminants.

Norris, R.D. [Eckenfelder, Inc., Nashville, TN (United States); Johnson, J. [GRAM, Inc., Albuquerque, NM (United States); Odencrantz, J. [TRI-S Environmental Corp., Newport Beach, CA (United States)] [and others

1995-12-31

359

Modeling the liquid-phase oxidation of hydrocarbons over a range of temperatures and dissolved oxygen concentrations with pseudo-detailed chemical kinetics  

Microsoft Academic Search

The ability of pseudo-detailed chemical kinetic modeling to simulate the oxidation behavior of Exxsol D-80, a paraffin blend whose oxidative characteristics are representative of severely hydrotreated jet fuels, is assessed. The effects of temperature and initial dissolved O2 concentration on oxidation are considered. A 17-step pseudo-detailed mechanism is shown to provide reasonable simulations of Exxsol D-80 oxidation over a range

Nicholas J. Kuprowicz; Jamie S. Ervin; Steven Zabarnick

2004-01-01

360

Ni and oxygen Kedge XAS investigation into the chemical bonding for lithiation of Li y Ni 1? x Al x O 2 cathode material  

Microsoft Academic Search

The local structure refinement for the chemically Li-ion extracted LiNi1?xAlxO2 system has been intensively carried out with Ni K-edge and O K-edge X-ray absorption spectroscopy. The Li-ion extraction gives rise to the substantial variation of unit cell dimension, which presents the systematic decrease of lattice parameter a and the increase of lattice parameter c. For Ni K-edge XANES spectra, the

Min Gyu Kim; Nak Eun Sung; Hyun Joon Shin; Nam Soo Shin; Kwang Sun Ryu; Chul Hyun Yo

2004-01-01

361

Migration and Tourism Demand  

Microsoft Academic Search

This study considers the relationship between immigration and Portuguese tourism demand for the period 1995-2008, using a dynamic panel data approach. The findings indicate that Portuguese tourism increased significantly during the period in accordance with the values expected for a developed country. The regression results show that income, shock of immigration, population, and geographical distance between Portugal and countries of

Nuno Carlos LEITÃO; Muhammad SHAHBAZ

2012-01-01

362

The future demands efficiency  

Technology Transfer Automated Retrieval System (TEKTRAN)

Increasing demand for food, feed, fuel, and fiber from agricultural production systems will require increased efficiency of production, resilience to climate change, enhanced quality of the product, and new insights into management. These may sound like impossible challenges; however, the solution l...

363

Demanding Divestment from Sudan  

ERIC Educational Resources Information Center

Bowing to student demands to "stop supporting genocide," the University of California regents voted earlier this year to divest millions of dollars from companies working in the war-torn African nation of Sudan, the first major public university in the nation to take such action. Since student protests on the subject began at Harvard University in…

Asquith, Christina

2006-01-01

364

PHYSICAL AND BIOLOGICAL CONTROLS ON DISSOLVED OXYGEN DYNAMICS IN PENSACOLA BAY, FL  

EPA Science Inventory

Nutrient enrichment of estuaries and coastal waters can contribute to hypoxia (low dissolved oxygen) by increasing primary production and biological oxygen demand. Other factors, however, contribute to hypoxia and affect the susceptibility of coastal waters to hypoxia. Hypoxia fo...

365

Long-term seasonal changes of the Danube River eco-chemical status in the region of Serbia.  

PubMed

Seasonal spatial and temporal changes of selected eco-chemical parameters in section of the Danube River flowing through Serbia were analyzed. Data for electrical conductivity (EC), dry and suspended matter, residue on ignition, chemical oxygen demand (COD), biochemical oxygen demand (BOD-5), ultraviolet extinction, dissolved oxygen (DO), oxygen saturation, pH, nitrates, total phosphorus, and nitrogen were collected between 1992 and 2006. The use of monthly medians combined with linear regression and two-sided t test has been proven to be the best approach for resolving trends from natural variability of investigated parameters and for determining trend significance. Patterns of temporal changes between different months were examined. It was also determined that spatial trends of some parameters oscillate in predictable manner, increasing in one part of the year and declining in the other. Regression slope coefficients, an excellent indicator for determining when the water quality is changing the most along the course of the Danube, reach their maximum during summer for temperature (t), electric conductivity, nitrates, and total N, while in the same season suspended matter, COD, BOD-5, DO, and oxygen saturation coefficients reach their minimum. Correlations for used data sets of selected parameters were analyzed for better understanding of their behavior and mutual relations. It was observed that as Danube flows through Serbia, its general eco-chemical status either stagnates or improves, but the rate of river self-purification often depends on the season of the year. PMID:21701890

Ilijevi?, Konstantin; Gržeti?, Ivan; Živadinov, Ivan; Popovi?, Aleksandar

2012-05-01

366

The Demand for the Arts  

Microsoft Academic Search

This paper discusses the demand for the arts from a theoretical and an empirical perspectives. We suggest that the demand for the arts is price elastic and that art is a luxury good. Education, and learning experiences are also important factors affecting that demand. Ce texte traite de la demande pour les arts d'un point de vue théorique et empirique.

Louis Lévy-Garboua; Claude Montmarquette

2002-01-01

367

Production and Consumption of Reactive Oxygen Species by Fullerenes  

EPA Science Inventory

Reactive oxygen species (ROS) are one of the most important intermediates in chemical, photochemical, and biological processes. To understand the environmental exposure and toxicity of fullerenes better, the production and consumption of ROS (singlet oxygen, superoxide, hydrogen ...

368

Oxygen Transport Ceramic Membranes  

SciTech Connect

The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. The in situ electrical conductivity and Seebeck coefficient measurements were made on LSFT at 1000 and 1200 C over the oxygen activity range from air to 10{sup -15} atm. The electrical conductivity measurements exhibited a p to n type transition at an oxygen activity of 1 x 10{sup -10} at 1000 C and 1 x 10{sup -6} at 1200 C. Thermogravimetric studies were also carried out over the same oxygen activities and temperatures. Based on the results of these measurements, the chemical and mechanical stability range of LSFT were determined and defect structure was established. The studies on the fracture toughness of the LSFT and dual phase membranes exposed to air and N{sub 2} at 1000 C was done and the XRD and SEM analysis of the specimens were carried out to understand the structural and microstructural changes. The membranes that are exposed to high temperatures at an inert and a reactive atmosphere undergo many structural and chemical changes which affect the mechanical properties. A complete transformation of fracture behavior was observed in the N{sub 2} treated LSFT samples. Further results to investigate the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appear to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. Recent results on transient kinetic data are presented. The 2-D modeling of oxygen movement has been undertaken in order to fit isotope data. The model is used to study ''frozen'' profiles in patterned or composite membranes.

S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

2005-02-01

369

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

370

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

371

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

372

Labeling graphene oxygen groups with europium.  

PubMed

Graphene-related materials contain chemically bonded oxygen atoms in the form of epoxy, hydroxy, carboxy, and carbonyl groups. It is important to determine the quantity of oxygen atoms and to understand their position on the graphene sheet. However, visualization of these groups by standard methods is a challenge. Here, we utilize europium(III) as a selective label for oxygen-containing groups. We studied three different graphene-related materials: 1) graphene oxide, 2) chemically reduced graphene oxide, and 3) thermally reduced graphene oxide (the number of oxygen containing groups decreases from material 1 to 3). We show that it is possible to efficiently use Eu as a label of oxygen-containing groups. This Eu label could be applied to determine the precise location of oxygen-containing groups on graphene sheets and also induce novel optical, electrochemical, and catalytic properties. PMID:25404532

Ambrosi, Adriano; Pumera, Martin

2015-02-01

373

HYDROGEN-OXYGEN ROCKETS  

NSDL National Science Digital Library

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

David Reierson

374

INCOMPATIBLE CHEMICAL LIST PRUDENT PRACTICES FOR HANDLING CHEMICALS IN LABORATORIES  

E-print Network

heavy metals Nitrites Acids Nitroparaffins Inorganic bases, amines Oxalic Acid Silver, mercury Oxygen of Incompatible Chemicals CHEMICAL IS INCOMPATIBLE WITH Acetic Acid Chromic acid, nitric acid, hydroxyl compounds, ethylene glycol, perchloric acid, peroxides, permanganates Acetylene Chlorine, bromine, copper, fluorine

Cho, Junghyun

375

On demand, non-halon, fire extinguishing systems  

Microsoft Academic Search

A system and process for on-demand generation of inert, nonflammable gases and water vapor to decrease the available atmospheric oxygen in the ullage of a hydrocarbon fuel storage tank to a level that will not support combustion of the hydrocarbon fuel, is disclosed. One, or more, of a variety of non-Halon, fire suppressor charges are selectively contained in one or

Bengamin D. Smith

1993-01-01

376

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

377

Titration biosensors for the estimation of the biochemical nitrate demand of municipal and industrial wastes.  

PubMed

An anoxic titrimetric test was investigated for measuring denitrification potential of different wastewaters, both municipal and industrial, and to quantify the denitrifying activity in an activated sludge system. The method measures the amount of acid that is required to maintain the pH set-point value in a batch denitrification experiment, and it was performed using a DENICON (denitrification controller) biosensor. The amount of acid is proportional to the nitrate used to oxidise the biodegradable chemical oxygen demand present in the wastewater, while the acid consumption rate is used to derive the denitrifying activity. The wastewaters tested were a municipal wastewater (MW), an industrial-municipal wastewater (MIW; 70% and 30%, respectively), and four industrial wastewaters drawn from an ice-cream factory (IW1), a beet-sugar factory (IW2), a brewery (IW3), and a tuna cannery industry (IW4). Good correlation between titration data and analyses was found. PMID:15856352

Onnis, A; Carucci, A; Cappai, G

2006-03-01

378

New method of detecting singlet oxygen production  

Microsoft Academic Search

SINGLET oxygen is receiving increasing attention as a reactive species in many chemical or biological reactions (see refs 1-3 for recent reviews). We report here a new method for detecting the formation of singlet oxygen by the generation of stable nitroxide radicals from sterically hindered amines.

Y. Lion; M. Delmelle; A. van de Vorst

1976-01-01

379

The debate on continuous home oxygen therapy.  

PubMed

Two studies published in the early 80s, namely the Nocturnal Oxygen Therapy Trial (NOTT) and the Medical Research Council Trial (MRC), laid the foundations for modern home oxygen therapy. Since then, little progress has been made in terms of therapeutic indications, and several prescription-associated problems have come to light. Advances in technology have gone hand in hand with growing disregard for the recommendations in clinical guidelines on oxygen therapy. The introduction of liquid oxygen brought with it a number of technical problems, clinical problems related to selecting candidate patients for portable delivery devices, and economic problems associated with the rising cost of the therapy. Continuous home oxygen therapy has been further complicated by the recent introduction of portable oxygen concentrators and the development in quick succession of a range of delivery devices with different levels of efficiency and performance. Modern oxygen therapy demands that clinicians evaluate the level of mobility of their patients and the mobility permitted by available oxygen sources, correctly match patients with the most appropriate oxygen source and adjust the therapy accordingly. The future of continuous home oxygen therapy lies in developing the ideal delivery device, improving the regulations systems and information channels, raise patient awareness and drive research. PMID:24976235

Díaz Lobato, Salvador; García González, José Luis; Mayoralas Alises, Sagrario

2015-01-01

380

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

381

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

382

An upflow microaerobic sludge blanket reactor operating at high organic loading and low dissolved oxygen levels.  

PubMed

The activated sludge process (ASP) has high operational costs due to the need for aeration at dissolved O(2) (DO) levels of ?2 mg l(-1) and high capital costs to construct large reactors due to a low organic loading [typically 1 kg chemical oxygen demand (COD) m(-3) day(-1)]. A novel method for improving the energy use and treatment efficiency of the ASP via limited oxygenation (0.4 mg DO l(-1)) and high organic loading (6.2 kg COD m(-3) day(-1)) is proposed based on a laboratory-scale ASP for ammonia-rich industrial wastewaters. The sludge blanket phenomenon and granulation occurred simultaneously in the upflow microaerobic reactor. PMID:21188615

Zheng, Shaokui; Li, Huijun; Cui, Cancan

2011-04-01

383

Dividends with Demand Response  

SciTech Connect

To assist facility managers in assessing whether and to what extent they should participate in demand response programs offered by ISOs, we introduce a systematic process by which a curtailment supply curve can be developed that integrates costs and other program provisions and features. This curtailment supply curve functions as bid curve, which allows the facility manager to incrementally offer load to the market under terms and conditions acceptable to the customer. We applied this load curtailment assessment process to a stylized example of an office building, using programs offered by NYISO to provide detail and realism.

Kintner-Meyer, Michael CW; Goldman, Charles; Sezgen, O.; Pratt, D.

2003-10-31

384

Customer focused collaborative demand planning  

E-print Network

Many firms worldwide have adopted the process of Sales & Operations Planning (S&OP) process where internal departments within a firm collaborate with each other to generate a demand forecast. In a collaborative demand ...

Jha, Ratan (Ratan Mohan)

2008-01-01

385

Effects of oxygen on fracturing fluids  

SciTech Connect

The stability of polysaccharide gels at high temperature is limited by such factors as pH, mechanical degradation, and oxidants. Oxygen is unavoidably placed in fracturing fluids through dissolution of air. To prevent premature degradation of the fracturing fluid by this oxidant, oxygen scavengers are commonly used. In this paper, the effects of oxygen and various oxygen scavengers on gel stability will be presented. Mechanical removal of oxygen resulted in surprisingly stable fracturing gels at 275 F. However, chemical removal of oxygen gave mixed results. Test data from sodium thiosulfate, sodium sulfite, and sodium erythorbate used as oxygen scavengers/gel stabilizers showed that the efficiency of oxygen removal from gels did not directly coincide with the viscosity retention of the gel, and large excesses of additives were necessary to provide optimum gel stabilization. The inability of some oxygen scavengers to stabilize the gel was the result of products created from the interaction of oxygen with the oxygen scavenger, which in turn, produced species that degraded the gel. The ideal oxygen scavenger should provide superior gel stabilization without creating detrimental side reaction products. Of the materials tested, sodium thiosulfate appeared to be the most beneficial.

Walker, M.L.; Shuchart, C.E.; Yaritz, J.G.; Norman, L.R.

1995-11-01

386

Demand Response: Load Management Programs  

E-print Network

CenterPoint Load Management Programs CATEE Conference October, 2012 Agenda Outline I. General Demand Response Definition II. General Demand Response Program Rules III. CenterPoint Commercial Program IV. CenterPoint Residential Programs... V. Residential Discussion Points Demand Response Definition of load management per energy efficiency rule 25.181: ? Load control activities that result in a reduction in peak demand, or a shifting of energy usage from a peak to an off...

Simon, J.

2012-01-01

387

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

388

China's Coal: Demand, Constraints, and Externalities  

SciTech Connect

This study analyzes China's coal industry by focusing on four related areas. First, data are reviewed to identify the major drivers of historical and future coal demand. Second, resource constraints and transport bottlenecks are analyzed to evaluate demand and growth scenarios. The third area assesses the physical requirements of substituting coal demand growth with other primary energy forms. Finally, the study examines the carbon- and environmental implications of China's past and future coal consumption. There are three sections that address these areas by identifying particular characteristics of China's coal industry, quantifying factors driving demand, and analyzing supply scenarios: (1) reviews the range of Chinese and international estimates of remaining coal reserves and resources as well as key characteristics of China's coal industry including historical production, resource requirements, and prices; (2) quantifies the largest drivers of coal usage to produce a bottom-up reference projection of 2025 coal demand; and (3) analyzes coal supply constraints, substitution options, and environmental externalities. Finally, the last section presents conclusions on the role of coal in China's ongoing energy and economic development. China has been, is, and will continue to be a coal-powered economy. In 2007 Chinese coal production contained more energy than total Middle Eastern oil production. The rapid growth of coal demand after 2001 created supply strains and bottlenecks that raise questions about sustainability. Urbanization, heavy industrial growth, and increasing per-capita income are the primary interrelated drivers of rising coal usage. In 2007, the power sector, iron and steel, and cement production accounted for 66% of coal consumption. Power generation is becoming more efficient, but even extensive roll-out of the highest efficiency units would save only 14% of projected 2025 coal demand for the power sector. A new wedge of future coal consumption is likely to come from the burgeoning coal-liquefaction and chemicals industries. If coal to chemicals capacity reaches 70 million tonnes and coal-to-liquids capacity reaches 60 million tonnes, coal feedstock requirements would add an additional 450 million tonnes by 2025. Even with more efficient growth among these drivers, China's annual coal demand is expected to reach 3.9 to 4.3 billion tonnes by 2025. Central government support for nuclear and renewable energy has not reversed China's growing dependence on coal for primary energy. Substitution is a matter of scale: offsetting one year of recent coal demand growth of 200 million tonnes would require 107 billion cubic meters of natural gas (compared to 2007 growth of 13 BCM), 48 GW of nuclear (compared to 2007 growth of 2 GW), or 86 GW of hydropower capacity (compared to 2007 growth of 16 GW). Ongoing dependence on coal reduces China's ability to mitigate carbon dioxide emissions growth. If coal demand remains on a high growth path, carbon dioxide emissions from coal combustion alone would exceed total US energy-related carbon emissions by 2010. Within China's coal-dominated energy system, domestic transportation has emerged as the largest bottleneck for coal industry growth and is likely to remain a constraint to further expansion. China has a low proportion of high-quality reserves, but is producing its best coal first. Declining quality will further strain production and transport capacity. Furthermore, transporting coal to users has overloaded the train system and dramatically increased truck use, raising transportation oil demand. Growing international imports have helped to offset domestic transport bottlenecks. In the long term, import demand is likely to exceed 200 million tonnes by 2025, significantly impacting regional markets.

Aden, Nathaniel; Fridley, David; Zheng, Nina

2009-07-01

389

Impact of Stream Channel Urbanization on Dissolved Oxygen Concentrations  

NASA Astrophysics Data System (ADS)

Dissolved oxygen concentration in freshwater streams is an important regulator of ecosystem processes and indicator of stream health. This study attempts to investigate the impacts of urbanization and temperature on dissolved oxygen fluctuations in streams. Field measurements, laboratory experiments, and analysis of diurnal cycles of dissolved oxygen are evaluated in eight streams of the Baltimore and Anacostia watersheds along an urban to rural gradient. Temperature and dissolved oxygen measurements were taken from 8 long-term monitoring sites (5 Baltimore Long Term Ecological Research sites and 3 Anacostia branch sites monitored by the U.S. Geological Survey) in order to characterize fluctuations in dissolved oxygen influenced by changes in land use and temperature. Laboratory experiments investigating changes in 5-day biochemical oxygen demand across 3 different temperatures (4, 15, and 20 degrees Celsius) across land use were conducted using a temperature controlled incubator. Biochemical oxygen demand typically increased with increasing temperature and varied with land use. There were strong relationships between routine dissolved oxygen and temperature seasonally in streams of the Baltimore Long-Term Ecological Research site and Anacostia watershed. Land use and temperature may influence biochemical oxygen demand in streams and impact seasonal dynamics of dissolved oxygen.

Van Orden, E. T.

2011-12-01

390

OXYGEN TRANSPORT IN THE MICROCIRCULATION AND ITS REGULATION  

PubMed Central

Cells require energy to carry out their functions and they typically use oxidative phosphorylation to generate the needed ATP. Thus, cells have a continuous need for oxygen which they receive by diffusion from the blood through the interstitial fluid. The circulatory system pumps oxygen-rich blood through a network of increasingly minute vessels, the microcirculation. The structure of the microcirculation is such that all cells have at least one nearby capillary for diffusive exchange of oxygen and red blood cells release the oxygen bound to hemoglobin as they traverse capillaries. This review focuses first on the historical development of techniques to measure oxygen at various sites in the microcirculation, including the blood, interstitium and cells. Next, approaches are described as to how these techniques have been employed to make discoveries about different aspects of oxygen transport. Finally, ways in which oxygen might participate in the regulation of blood flow toward matching oxygen supply to oxygen demand is discussed. Overall, the transport of oxygen to the cells of the body is one of the most critical functions of the cardiovascular system and it is in the microcirculation where the final local determinants of oxygen supply, oxygen demand and their regulation are decided. PMID:23025284

Pittman, Roland N.

2012-01-01

391

Renal oxygenation: preglomerular vasculature is an unlikely contributor to renal oxygen shunting.  

PubMed

The primary aim of this study was to assess the plausibility of preglomerular arterial-to-venous oxygen shunting in the kidney. To this end, we have developed a segment-wise three-dimensional computational model that takes into account transport processes in arteries, veins, cortical tissue, and capillaries. Our model suggests that the amount of preglomerular oxygen shunting is negligible. Consequently, it is improbable that preglomerular shunting contributes to the hypothesized regulation of renal oxygenation. Cortical tissue oxygenation is more likely determined by the interplay between oxygen supply, either from the preglomerular vasculature or from capillaries, and oxygen consumption. We show that reported differences in permeability to oxygen between perfused and unperfused tissue may be explained by what we refer to as advection-facilitated diffusion. We further show that the preglomerular vasculature is the primary source of oxygen for the tissue when cortical consumption is high or renal arterial blood is highly oxygenated, i.e., under hyperoxemic conditions. Conversely, when oxygen demand in the tissue is decreased, or under hypoxemic conditions, oxygen is supplied predominantly by capillaries. PMID:25503734

Olgac, Ufuk; Kurtcuoglu, Vartan

2015-04-01

392

Oxygen requirements of the earliest animals  

PubMed Central

A rise in the oxygen content of the atmosphere and oceans is one of the most popular explanations for the relatively late and abrupt appearance of animal life on Earth. In this scenario, Earth’s surface environment failed to meet the high oxygen requirements of animals up until the middle to late Neoproterozoic Era (850–542 million years ago), when oxygen concentrations sufficiently rose to permit the existence of animal life for the first time. Although multiple lines of geochemical evidence support an oxygenation of the Ediacaran oceans (635–542 million years ago), roughly corresponding with the first appearance of metazoans in the fossil record, the oxygen requirements of basal animals remain unclear. Here we show that modern demosponges, serving as analogs for early animals, can survive under low-oxygen conditions of 0.5–4.0% present atmospheric levels. Because the last common ancestor of metazoans likely exhibited a physiology and morphology similar to that of a modern sponge, its oxygen demands may have been met well before the enhanced oxygenation of the Ediacaran Period. Therefore, the origin of animals may not have been triggered by a contemporaneous rise in the oxygen content of the atmosphere and oceans. Instead, other ecological and developmental processes are needed to adequately explain the origin and earliest evolution of animal life on Earth. PMID:24550467

Mills, Daniel B.; Ward, Lewis M.; Jones, CarriAyne; Sweeten, Brittany; Forth, Michael; Treusch, Alexander H.; Canfield, Donald E.

2014-01-01

393

The oxygen paradox of neurovascular coupling  

PubMed Central

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

394

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

395

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

396

PROOF on Demand  

NASA Astrophysics Data System (ADS)

PROOF on Demand (PoD) is a set of utilities, which allows starting a PROOF cluster at user request, on any resource management system. It provides a plug-in based system, which allows to use different job submission frontends, such as LSF or gLite WMS. Main components of PoD are the PROOFAgent and the PAConsole. PROOFAgent provides the communication layer between the PROOF master on the local machine and the PROOF workers on the remote resources, possibly behind a firewall. PAConsole provides a user-friendly GUI, which is used to setup, manage, and shutdown the dynamic PROOF cluster. Installation is simple and doesn't require administrator privileges, and all the processes run in user space. PoD gives users, who don't have a centrally-administrated static PROOF cluster at their institute, the possibility to enjoy the full power of interactive analysis with PROOF.

Malzacher, Peter; Manafov, Anar

2010-04-01

397

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

398

Comparison of various advanced oxidation processes and chemical treatment methods for COD and color removal from a polyester and acetate fiber dyeing effluent  

Microsoft Academic Search

In this paper, a comparison of various advanced oxidation processes (O3, O3\\/UV, H2O2\\/UV, O3\\/H2O2\\/UV, Fe2+\\/H2O2) and chemical treatment methods using Al2(SO4)3·18H2O, FeCl3 and FeSO4 for the chemical oxygen demand (COD) and color removal from a polyester and acetate fiber dyeing effluent is undertaken. Advanced oxidation processes (AOPs) showed a superior performance compared to conventional chemical treatment, which maximum achievable color

N. Azbar; T. Yonar; K. Kestioglu

2004-01-01

399

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)

2009-04-01

400

Concepts of brain oxygen sufficiency during seizures.  

PubMed

To resolve conflicting evidence of oxygen sufficiency or insufficiency during seizures, signals of metabolic and circulatory function were monitored in rat cerebral cortex during recurrent seizures. Early seizures were accompanied by increased blood volume, increased tPO2, and oxidative shifts of cytochrome a,a3, indicative of oxygen sufficiency. Later seizures were accompanied by a smaller increment in blood volume, a fall in tPO2, and shifts toward reduction of cytochrome a,a3, suggesting that cerebral oxygen supply became insufficient to meet demand. Responses suggesting oxygen insufficiency occurred during short duration ictal bursts, interictal spikes or electrocortical stimulation at times when longer duration ictal episodes still were accompanied by responses signalling oxygen sufficiency. These data indicate that there is a progressive dissociation of the normally tight couple between neuronal activity, energy demand, and cerebral blood flow during status epilepticus. Systemic derrangements that often accompanied recurrent seizures also contributed to decreased cerebral oxygenation. These factors may cause the neuronal damage reported to follow prolonged status epilepticus. PMID:6099961

Kreisman, N R; Sick, T J; Rosenthal, M

1984-01-01

401

Why DNA Electrical Properties Change on Molecular Oxygen Doping:  

NASA Astrophysics Data System (ADS)

A detailed semiempirical quantum-chemical study is reported on homogeneous adenosine-thymidine and guanosine-cytidine base pair steps, both pure ones and their complexes with oxygen molecules. The results of this study help gain detailed insight into physico-chemical mechanisms of electrical conduction control in DNA molecules when doping them with molecular oxygen or related molecules.

Starikov, E. B.

402

State of oxygen in fine titanium nitride powders  

Microsoft Academic Search

Oxygen in fine titanium nitride powders produced by the plasma-chemical method can exist in three forms — replacing the nitrogen in the nitride, forming oxide films, and adsorbed on the surface. In the course of the plasma-chemical synthesis of titanium nitride 1–5 wt. % of oxygen from the starting reactants becomes statistically distributed throughout the particles, forming homogeneous titanium oxynitrides.

V. I. Torbov; V. N. Troitskii; A. P. Zuev; V. V. Kireiko; I. A. Domashnev; V. I. Berestenko; O. D. Torbova

1981-01-01

403

Microgels on-demand  

NASA Astrophysics Data System (ADS)

Three-dimensional (3D) hydrogel structures are finding use in fundamental studies of self-assembly, rheology, and 3D cell culture. Most techniques for 3D hydrogel formation are ‘single pot’, in which gels are not addressable after formation. For many applications, it would be useful to be able to form arrays of gels bearing mixtures of constituents and/or formed from composites of different gel materials. Here, in response to this challenge, we introduce a digital microfluidic method for ‘on-demand’ formation of arrays of microgels bearing arbitrary contents and shapes. On formation of the gels, each microgel is individually addressable for reagent delivery and analysis. We demonstrate the utility of the method for 3D cell culture and higher-order tissue formation by implementing the first sub-microlitre recapitulation of 3D kidney epithelialization. We anticipate this platform will enable new research that can exploit the flexible nature of this technique for forming and addressing arrays of hydrogels with unique geometries and contents.

Eydelnant, Irwin A.; Betty Li, Bingyu; Wheeler, Aaron R.

2014-02-01

404

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' ...

405

Home Oxygen Therapy  

MedlinePLUS

... oxygen is rarely delivered in the older large, steel gas cylinders any longer since frequent and costly ... just like the compressed oxygen in the older steel cylinders. An important advantage of liquid oxygen is ...

406

Physically-based demand modeling  

E-print Network

PHYSICALLY-BASED DEMAND MODELING A Thesis by TERRY MARSHALL CALLONAY Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE August 1980 Major Subject...: Electrical Engineering PHYSICALLY-BASED DEMAND MODELING A Thesis by TERRY MARSHALL CALLOWAY Approved as to style and content by: Chairman of Committee emb Member Hea f Department August 1980 ABSTRACT Physically-Based Demand Modeling (August 1980...

Calloway, Terry Marshall

1980-01-01

407

ELECTRICITY DEMAND FORECAST COMPARISON REPORT  

E-print Network

Valerie T. Hall Deputy Director Energy Efficiency and Demand Analysis Division Scott W. Matthews Acting.................................................................................................................................3 PACIFIC GAS & ELECTRIC PLANNING AREA...............................................................................................................................13 SOUTHERN CALIFORNIA EDISON PLANNING AREA ................................................................13

408

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

409

Development of advanced generator of singlet oxygen for a COIL  

Microsoft Academic Search

The generator of singlet oxygen (SOG) remains still a challenge for a chemical oxygen-iodine laser (COIL). Hitherto, only chemical generators based on the gas-liquid reaction system (chlorine-basic hydrogen peroxide) can supply singlet oxygen, O2(1Delta), in enough high yields and at pressures to maintain operation of the high power supersonic COIL facilities. Employing conventional generators of jet-type or rotating disc-type makes

Jarmila Kodymova; Otomar Spalek; Vít Jirásek; Miroslav Censký; Jan Hrubý

2006-01-01

410

The Global Oxygen Cycle  

NASA Astrophysics Data System (ADS)

One of the key defining features of Earth as a planet that houses an active and diverse biology is the presence of free molecular oxygen (O2) in the atmosphere. Biological, chemical, and physical processes interacting on and beneath the Earth's surface determine the concentration of O2 and variations in O2 distribution, both temporal and spatial. In the present-day Earth system, the process that releases O2 to the atmosphere (photosynthesis) and the processes that consume O2 (aerobic respiration, sulfide mineral oxidation, oxidation of reduced volcanic gases) result in large fluxes of O2 to and from the atmosphere. Even relatively small changes in O2 production and consumption have the potential to generate large shifts in atmospheric O2 concentration within geologically short periods of time. Yet all available evidence supports the conclusion that stasis in O2 variation is a significant feature of the Earth's atmosphere over wide spans of the geologic past. Study of the oxygen cycle is therefore important because, while an equable O2 atmosphere is central to life as we know it, our understanding of exactly why O2 concentrations remain nearly constant over large spans of geologic time is very limited.This chapter begins with a review of distribution of O2 among various reservoirs on Earth's surface: air, sea, and other natural waters. The key factors that affect the concentration of O2 in the atmosphere and surface waters are next considered, focusing on photosynthesis as the major process generating free O2 and various biological and abiotic processes that consume O2. The chapter ends with a synopsis of current models on the evolution of an oxygenated atmosphere through 4.5 billion years of Earth's history, including geochemical evidence constraining ancient O2 concentrations and numerical models of atmospheric evolution.

Petsch, S. T.

2003-12-01

411

Photodegradation of porous silicon induced by photogenerated singlet oxygen molecules  

NASA Astrophysics Data System (ADS)

We report on the mechanism of photodegradation of porous silicon luminescence in ambient containing molecular oxygen. Energy transfer from excitons confined in silicon nanocrystallites to molecular oxygen results in the generation of highly chemically reactive singlet oxygen molecules. The subsequent interaction of singlet oxygen molecules with the hydrogenated surface of silicon nanocrystals results in its photooxidation and the creation of additional nonradiative defects, i.e., the luminescence fatigue effect.

Kovalev, D.; Gross, E.; Diener, J.; Timoshenko, V. Yu.; Fujii, M.

2004-10-01

412

Dissolved oxygen in the Tualatin River, Oregon, during winter flow conditions, 1991 and 1992  

USGS Publications Warehouse

Throughout the winter period, November through April, wastewater treatment plants in the Tualatin River Basin discharge from 10,000 to 15,000 pounds per day of biochemical oxygen demand to the river. These loads often increase substantially during storms when streamflow is high. During the early winter season, when streamflow is frequently less than the average winter flow, the treatment plants discharge about 2,000 pounds per day of ammonia. This study focused on the capacity of the Tualatin River to assimilat oxygen-demanding loads under winter streamflow conditions during the 1992 water year, with an emphasis on peak-flow conditions in the river, and winter-base-flow conditions during November 1992. Concentrations of dissolved oxygen throughout the main stem of the river during the winter remained generally high relative to the State standard for Oregon of 6 milligrams per liter. The most important factors controlling oxygen consumption during winter-low-flow conditions were carbonaceous biochemical oxygen demand and input of oxygen-depleted waters from tributaries. During peak-flow conditions, reduced travel time and increased dilution associated with the increased streamflow minimized the effect of increased oxygen-demanding loads. During the base-flow period in November 1992, concentrations of dissolved oxygen were consistently below 6 milligrams per liter. A hydrodynamic water-quality model was used to identify the processes depleting dissolved oxygen, including sediment oxygen demand, nitrification, and carbonaceous biochemical oxygen demand. Sediment oxygen demand was the most significant factor; nitrification was also important. Hypothetical scenarios were posed to evaluate the effect of different wastewater treatment plant loads during winter-base-flow conditions. Streamflow and temperature were significant factors governing concentrations of dissolved oxygen in the main-stem river.

Kelly, V.J.

1996-01-01

413

Oxygenated feedwater treatment proves worth  

Microsoft Academic Search

This article describes a departure from traditional chemical-treatment practice. Oxygenated treatment (OT) methodology features maintenance of prescribed O[sub 2] concentrations in boiler feedwater. A southwestern utility logs positive experience, early performance gains, and lessons learned. OT was developed in Germany in the late 1960s. It has been adopted widely in Europe and has spread to Japan; the first US trial

D. Biser; J. Ellis; D. Clifton

1994-01-01

414

Spatially monitoring oxygen level in 3D microfabricated cell culture systems using optical oxygen sensing beads.  

PubMed

Capability of measuring and monitoring local oxygen concentration at the single cell level (tens of microns scale) is often desirable but difficult to achieve in cell culture. In this study, biocompatible oxygen sensing beads were prepared and tested for their potential for real-time monitoring and mapping of local oxygen concentration in 3D micro-patterned cell culture systems. Each oxygen sensing bead is composed of a silica core loaded with both an oxygen sensitive Ru(Ph2phen3)Cl2 dye and oxygen insensitive Nile blue reference dye, and a poly-dimethylsiloxane (PDMS) shell rendering biocompatibility. Human intestinal epithelial Caco-2 cells were cultivated on a series of PDMS and type I collagen based substrates patterned with micro-well arrays for 3 or 7 days, and then brought into contact with oxygen sensing beads. Using an image analysis algorithm to convert florescence intensity of beads to partial oxygen pressure in the culture system, tens of microns-size oxygen sensing beads enabled the spatial measurement of local oxygen concentration in the microfabricated system. Results generally indicated lower oxygen level inside wells than on top of wells, and local oxygen level dependence on structural features of cell culture surfaces. Interestingly, chemical composition of cell culture substrates also appeared to affect oxygen level, with type-I collagen based cell culture systems having lower oxygen concentration compared to PDMS based cell culture systems. In general, results suggest that oxygen sensing beads can be utilized to achieve real-time and local monitoring of micro-environment oxygen level in 3D microfabricated cell culture systems. PMID:23443975

Wang, Lin; Acosta, Miguel A; Leach, Jennie B; Carrier, Rebecca L

2013-04-21

415

Spatially monitoring oxygen level in 3D microfabricated cell culture systems using optical oxygen sensing beads  

PubMed Central

Capability of measuring and monitoring local oxygen concentration at the single cell level (tens of microns scale) is often desirable but difficult to achieve in cell culture. In this study, biocompatible oxygen sensing beads were prepared and tested for their potential for real-time monitoring and mapping of local oxygen concentration in 3D micro-patterned cell culture systems. Each oxygen sensing bead is composed of a silica core loaded with both an oxygen sensitive Ru(Ph2phen3)Cl2 dye and oxygen insensitive Nile blue reference dye, and a poly-dimethylsiloxane (PDMS) shell rendering biocompatibility. Human intestinal epithelial Caco-2 cells were cultivated on a series of PDMS and type I collagen based substrates patterned with micro-well arrays for 3 or 7 days, and then brought into contact with oxygen sensing beads. Using an image analysis algorithm to convert florescence intensity of beads to partial oxygen pressure in the culture system, tens of microns-size oxygen sensing beads enabled the spatial measurement of local oxygen concentration in the microfabricated system. Results generally indicated lower oxygen level inside wells than on top of wells, and local oxygen level dependence on structural features of cell culture surfaces. Interestingly, chemical composition of cell culture substrates also appeared to affect oxygen level, with type-I collagen based cell culture systems having lower oxygen concentration compared to PDMS based cell culture systems. In general, results suggest that oxygen sensing beads can be utilized to achieve real-time and local monitoring of micro-environment oxygen level in 3D microfabricated cell culture systems. PMID:23443975

Wang, Lin; Acosta, Miguel A.; Leach, Jennie B.; Carrier, Rebecca L.

2013-01-01

416

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

417

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.

418

Marketing Models of Consumer Demand  

Microsoft Academic Search

Marketing researchers have used models of consumer demand to forecast future sales; to describe and test theories of consumer behavior; and to measure the response to marketing interventions. The basic framework typically starts from microfoundations of expected utility theory to obtain a statistical system that describes consumers' choices over available options, and to thus characterize product demand. The basic model

Pradeep K. Chintagunta; Harikesh S. Nair

2010-01-01

419

Physical demands during folk dancing  

Microsoft Academic Search

Summary  This investigation was undertaken to evaluate the aerobic demands during one of the most popular and demanding Swedish folk dances the hambo.Six men and six women, ranging in age from 22 to 32, participated. Their physical work capacity was investigated on a bicycle ergometer and a treadmill, using two to three submaximal and one maximal loads. All subjects were moderately

Ewa Wigaeus; åsa Kilbom

1980-01-01

420

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

421

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

422

A novel Multi-Fiber Optode sensor system (MuFO) for monitoring oxygen  

NASA Astrophysics Data System (ADS)

In the marine environment, dissolved oxygen concentrations often vary significantly spatially as well as temporally. Monitoring these variations is essential for our understanding of the biological and chemical processes controlling the oxygen dynamics in water columns and sediments. Such investigations require a high number of measuring points and a high temporal resolution. A Multi-Fiber Optode sensor system (MuFO) was designed to assess these requirements. The MuFO system simultaneously controls 100 fiber optodes enabling continuous monitoring of oxygen in 100 positions within a 5-10m radius. The measurements are based on quenching of an oxygen sensitive luminophore, which is immobilised at the end of each fiber optode. The optical oxygen measurements are based on lifetime-imaging, which are converted into oxygen concentrations using a multipoint calibration. At a constant temperature of 21C, the system overall had a mean accuracy of 1.3%, a precision of 0.2% air saturation, the average 90% response time was 16 seconds and the detection limit was 0.1% air saturation. The MuFO set-up was build into a waterproof titanium casing for marine field applications. The system is battery-powered and has a maximum operational capacity of 15 hours for continuous measurements. The MuFO system was recently used for various research tasks in the marine environment: Mounted on a lander, the in situ MuFO system was used for investigations of oxygen dynamics in marine water columns placing the fiber optodes in a vertical line on a 7m high pole. For studies of oxygen dynamics in marine wetland rhizospheres, the sensing ends of the fiber optodes were covered with a 50cm protective sleeve made from stainless steel tubing, and the sensors were manually pushed into the rhizosphere. For laboratory measurements of sediment oxygen demand, the MuFO system was used to simultaneously monitor the oxygen consumption in multiple sediment slurry incubations. The MuFO system proved to be a useful tool for field studies as well as in the laboratory and the system has multiple applications in marine research. This work was supported by the 7th framework EU-projects SENSEnet and HYPOX.

Koop-Jakobsen, K.; Fischer, J.; Wenzhöfer, F.

2012-04-01

423

Automated Demand Response and Commissioning  

SciTech Connect

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 human intervention, but is initiated at a home, building, or facility through receipt of an external communications signal. We refer to this as Auto-DR. The evaluation of the control and communications must be properly configured and pass through a set of test stages: Readiness, Approval, Price Client/Price Server Communication, Internet Gateway/Internet Relay Communication, Control of Equipment, and DR Shed Effectiveness. New commissioning tests are needed for such systems to improve connecting demand responsive building systems to the electric grid demand response systems.

Piette, Mary Ann; Watson, David S.; Motegi, Naoya; Bourassa, Norman

2005-04-01

424

Oxygen Transport Ceramic Membranes  

SciTech Connect

The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In this report, in situ neutron diffraction was used to characterize the chemical and structural properties of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} (here after as L2SF55T) specimen, which was subject to measurements of neutron diffraction from room temperature to 900 C. It was found that space group of R3c yielded a better refinement than a cubic structure of Pm3m. Oxygen occupancy was nearly 3 in the region from room temperature to 700 C, above which the occupancy decreased due to oxygen loss. Dense OTM bars provided by Praxair were loaded to fracture at varying stress rates. Studies were done at room temperature in air and at 1000 C in a specified environment to evaluate slow crack growth behavior. The X-Ray data and fracture mechanisms points to non-equilibrium decomposition of the LSFCO OTM membrane. The non-equilibrium conditions could probably be due to the nature of the applied stress field (stressing rates) and leads to transition in crystal structures and increased kinetics of decomposition. The formations of a Brownmillerite or Sr2Fe2O5 type structures, which are orthorhombic are attributed to the ordering of oxygen vacancies. The cubic to orthorhombic transitions leads to 2.6% increase in strains and thus residual stresses generated could influence the fracture behavior of the OTM membrane. Continued investigations on the thermodynamic properties (stability and phase-separation behavior) and total conductivity of prototype membrane materials were carried out. The data are needed together with the kinetic information to develop a complete model for the membrane transport. Previously characterization, stoichiometry and conductivity measurements for samples of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} were reported. In this report, measurements of the chemical and thermal expansion as a function of temperature and p{sub O2} are described.

S. Bandopadhyay; N. Nagabhushana; X.-D Zhou; Q. Cai; J. Yang; W.B. Yelon; W.J. James; H.U. Anderson; Alan Jacobson; C.A. Mims

2004-05-01

425

Comparative quantification of oxygen release by wetland plants: electrode technique and oxygen consumption model.  

PubMed

Understanding oxygen release by plants is important to the design of constructed wetlands for wastewater treatment. Lab-scale systems planted with Phragmites australis were studied to evaluate the amount of oxygen release by plants using electrode techniques and oxygen consumption model. Oxygen release rate (0.14 g O2/m(2)/day) measured using electrode techniques was much lower than that (3.94-25.20 gO2/m(2)/day) calculated using the oxygen consumption model. The results revealed that oxygen release by plants was significantly influenced by the oxygen demand for the degradation of pollutants, and the oxygen release rate increased with the rising of the concentration of degradable materials in the solution. The summary of the methods in qualifying oxygen release by wetland plants demonstrated that variations existed among different measuring methods and even in the same measuring approach. The results would be helpful for understanding the contribution of plants in constructed wetlands toward actual wastewater treatment. PMID:23872897

Wu, Haiming; Liu, Jufeng; Zhang, Jian; Li, Cong; Fan, Jinlin; Xu, Xiaoli

2014-01-01

426

On demand, non-halon, fire extinguishing systems  

Microsoft Academic Search

A system and process for on-demand generation of inert, non-flammable gases and water vapor to decrease the available atmospheric oxygen in the ullage of a hydrocarbon fuel storage tank to a level that will not support combustion of the hydrocarbon fuel, is disclosed. One, or more, of a variety of non-Halon, fire suppressor charges are selectively contained in one or

Benjamin D. Smith

1995-01-01

427

Oxygen Transport Membranes  

SciTech Connect

The focus of this research was to develop new membrane materials by synthesizing different compounds and determining their defect structures, crystallographic structures and electrical properties. In addition to measuring electrical conductivity, oxygen vacancy concentration was also evaluated using thermogravimetry, Neutron diffraction and Moessbauer Spectroscopy. The reducing conditions (CO{sub 2}/CO/H{sub 2} gas mixtures with steam) as encountered in a reactor environment can be expected to have significant influence on the mechanical properties of the oxides membranes. Various La based materials with and without Ti were selected as candidate membrane materials for OTM. The maximum electrical conductivity of LSF in air as a function of temperature was achieved at < 600 C and depends on the concentration of Sr (acceptor dopant). Oxygen occupancy in LSF was estimated using Neutron diffractometry and Moessbauer Spectroscopy by measuring magnetic moment changes depending on the Fe{sup 3+} and Fe{sup 4+} ratio. After extensive studies of candidate materials, lanthanum ferrites (LSF and LSFT) were selected as the favored materials for the oxygen transport membrane (OTM). LSF is a very good material for an OTM because of its high electronic and oxygen ionic conductivity if long term stability and mechanical strength are improved. LSFT not only exhibits p-type behavior in the high oxygen activity regime, but also has n-type conduction in reducing atmospheres. Higher concentrations of oxygen vacancies in the low oxygen activity regime may improve the performance of LSFT as an OTM. The hole concentration is related to the difference in the acceptor and donor concentration by the relation p = [Sr'{sub La}]-[Ti{sm_bullet}{sub Fe}]. The chemical formulation predicts that the hole concentration is, p = 0.8-0.45 or 0.35. Experimental measurements indicated that p is about {approx} 0.35. The activation energy of conduction is 0.2 eV which implies that LSCF conducts via the small polaron conduction mechanism. Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) were used to develop strategies to detect and characterize vacancy creation, dopant segregations and defect association in the oxygen conducting membrane material. The pO{sub 2} and temperature dependence of the conductivity, non-stoichiometry and thermal-expansion behavior of compositions with increasing complexity of substitution on the perovskite A and B sites were studied. Studies with the perovskite structure show anomalous behavior at low oxygen partial pressures (<10{sup -5} atm). The anomalies are due to non-equilibrium effects and can be avoided by using very strict criteria for the attainment of equilibrium. The slowness of the oxygen equilibration kinetics arises from two different mechanisms. In the first, a two phase region occurs between an oxygen vacancy ordered phase such as brownmillerite SrFeO{sub 2.5} and perovskite SrFeO{sub 3-x}. The slow kinetics is associated with crossing the two phase region. The width of the miscibility gap decreases with increasing temperature and consequently the effect is less pronounced at higher temperature. The preferred kinetic pathway to reduction of perovskite ferrites when the vacancy concentration corresponds to the formation of significant concentrations of Fe{sup 2+} is via the formation of a Ruddlesden-Popper (RP) phases as clearly observed in the case of La{sub 0.5}Sr{sub 0.5}FeO{sub 3-x} where LaSrFeO{sub 4} is found together with Fe. In more complex compositions, such as LSFTO, iron or iron rich phases are observed locally with no evidence for the presence of discrete RP phase. Fracture strength of tubular perovskite membranes was determined in air and in reducing atmospheric conditions. The strength of the membrane decreased with temperature and severity of reducing conditions although the strength distribution (Weibull parameter, m) was relatively unaltered. Surface and volume dominated the fracture origins and the overall fracture was purely transgranular. The dual phas

S. Bandopadhyay

2008-08-30

428

Artificial oxygen transport protein  

DOEpatents

This invention provides heme-containing peptides capable of binding molecular oxygen at room temperature. These compounds may be useful in the absorption of molecular oxygen from molecular oxygen-containing atmospheres. Also included in the invention are methods for treating an oxygen transport deficiency in a mammal.

Dutton, P. Leslie

2014-09-30

429

Oxygen Therapy for Children  

MedlinePLUS

Why do some children need oxygen therapy? Oxygen is a basic need for all humans. The air we breathe contains about 21 percent oxygen at sea level. ... How do I know if my child needs oxygen? A healthcare provider will figure out if your ...

430

Dissolved Oxygen Protocol  

NSDL National Science Digital Library

The purpose of this resource is to measure the amount of oxygen dissolved in water. Students use a dissolved oxygen kit or meter to measure the dissolved oxygen in the water at their hydrology site. The exact procedure depends on the instructions in the dissolved oxygen kit or meter used. The meter requires calibration before use.

The GLOBE Program, UCAR (University Corporation for Atmospheric Research)

2003-08-01

431

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

432

Transition metal substituted SrTiO3 perovskite oxides as promising functional materials for oxygen sensor  

NASA Astrophysics Data System (ADS)

Modern industries employ several gases as process fluids. Leakage of these gases in the operating area could lead to undesirable consequences. Even in chemical industries, which use large quantities of inert gases in confined areas, accidental leakage of these process gases would result in the reduction of oxygen partial pressure in atmospheric air. For instance, large amounts of gaseous nitrogen and argon are used in pharmaceutical industries, gas filling/bottling plants, operating area of Fast Breeder reactors, etc. Fall of concentration of oxygen in air below 17% could lead to life risk (Asphyxiation) of the working personnel that has to be checked well in advance. Further, when the leaking gas is of explosive nature, its damage potential would be very high if its concentration level in air increases beyond its lower explosive limit. Surveillance of the ambient within these industries at the critical areas and also in the environment around them for oxygen therefore becomes highly essential. Sensitive and selective gas sensors made of advanced materials are required to meet this demand of monitoring environmental pollution. The perovskite class of oxides (ABO3) is chemically stable even at high temperatures and can tolerate large levels of dopants without phase transformations. The electronic properties of this parent functional material can be tailored by adding appropriate dopants that exhibit different valence states. Aliovalent transition metal substituted SrTiO3 perovskites are good mixed ionic and electronic conductors and potential candidates for sensing oxygen at percentage level exploiting their oxygen pressure dependent electrical conductivity. This paper presents the preparation, study of electrical conductivity and oxygen-sensing characteristics of iron and cobalt substituted SrTiO3.

Misra, Sunasira

2012-07-01

433

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

434

DEMAND CREATES ITS OWN SUPPLY  

E-print Network

As recent events attest, modern economies may have trouble enforcing Say’s Law. An economy with decentralized markets and trades between goods and a liquid asset, money, has two equilibria. In full-employment,