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1

New ultrasound assisted chemical oxygen demand determination  

Microsoft Academic Search

A new method for the chemical oxygen demand (COD) determination assisted by ultrasonic radiation has been evaluated for the first time. The suggested method uses an instrumentation simpler and cheaper than the previous ones used for the same purpose. With this preliminary version of the method the optimized experimental conditions are: high ultrasonic power (143 W, 95% of maximum nominal

Antonio Canals; Angel Cuesta; Luis Gras; M Remedios Hernández

2002-01-01

2

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

3

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.

4

Chemical oxygen demand sensor employing a thin layer electrochemical cell  

Microsoft Academic Search

A chemical oxygen demand sensor employing a thin layer electrochemical cell was constructed using a sandwich-type thin layer working electrode. The electrode was constructed by attaching face to face glass and copper plates separated by PTFE spacers to create an extremely shallow cell. After filling the cell by capillary action, it was possible to measure reproducibly the coulometric charge required

Kyong-Hoon Lee; Tomoko Ishikawa; Scott McNiven; Yoko Nomura; Satoshi Sasaki; Yoshiko Arikawa; Isao Karube

1999-01-01

5

Ultrasound-assisted method for determination of chemical oxygen demand  

Microsoft Academic Search

A method for determination chemical oxygen demand (COD) assisted by use of ultrasound has been successfully evaluated for the first time. The method uses instrumentation simpler and cheaper and, in some instances, safer than that used by previous methods for the same purpose. The new device used for sonication is an all-glass cylindrical sonotrode that can be introduced directly into

Antonio Canals; M. del Remedio Hernández

2002-01-01

6

Chemical oxygen demand reduction in a whey fermentation  

Microsoft Academic Search

The efficiency of Chemical Oxygen Demand (COD) reduction ? in the fermentation of whey by Kluyveromyces fragilis IMAT 1872 was studied at various temperatures, lactose concentrations, air dilution ratios and stirring speeds. Their effects on the biomass yield (y) has been determined previously (Moresi et al. in press).

Mauro Moresi; Alberto Colicchio; Fabio Sansovini; Enzo Sebastiani

1980-01-01

7

Dichromate method for the determination of chemical oxygen demand  

Microsoft Academic Search

The oxidizability of organic substances of different classes was studied under the conditions of an official procedure for\\u000a the determination of chemical oxygen demand (COD) with and without using Ag2SO4 as a catalyst. Organic substances can be divided into three groups: easily oxidizable compounds that are oxidized by 80–100%\\u000a without a catalyst; medium-oxidizable compounds that are oxidized by 40–80% in

Yu. M. Dedkov; O. V. Elizarova; S. Yu. Kel’ina

2000-01-01

8

Uncertainty of chemical oxygen demand determination in wastewater samples  

Microsoft Academic Search

The measurement uncertainty of the result of chemical oxygen demand determination in wastewater was evaluated. The major\\u000a sources of uncertainty of the result of measurement were identified as the purity of reagents, volumetric operations, gravimetric\\u000a operations, bias, and the repeatability of the method. Identification and evaluation of uncertainty sources was followed by\\u000a combined uncertainty calculations. The combined uncertainty was compared

Andreja Drolc; M. Cotman; M. Roš

2003-01-01

9

EVALUATION OF MICROWAVE DIGESTION FOR CHEMICAL OXYGEN-DEMAND DETERMINATION  

Microsoft Academic Search

A microwave digestion procedure has been evaluated for use in the\\u000a determination of chemical oxygen demand (COD) by the dichromate method,\\u000a using small volumes of sample and reagents. Different organic\\u000a substances with COD values between 50 and 500 mg O2.1(-1) were analyzed\\u000a by both the proposed procedure and the standard method, obtaining\\u000a satisfactory results (mean recoveries 91-102\\\\%) with digestion times

M DELVALLE; M. Poch; J. Alonso; J. Bartroli

1990-01-01

10

Measuring Chemical Oxygen Demand of Cottage Cheese Whey Cultured with Kluyveromyces Fragilis1  

Microsoft Academic Search

A method previously used to measure the chemical oxygen demand of cheese whey cultured with Kluyveromycesfragilis appears to have detected considerably less chemical oxygen demand than was actually present. This study compared two methods for measuring chemical oxygen demand of such whey. The main difference between the two methods was the inclusion or exclusion of a refluxing apparatus during the

Stanley E. Gilliland

1979-01-01

11

Influence of endogenous respiration on the coloration and chemical oxygen demand of biologically purified wastewater  

Microsoft Academic Search

The influence of the endogenous respiration of active sludge on the bichromate oxidizability (chemical oxygen demand) and\\u000a coloration of coke-plant wastewater is investigated. The high chemical oxygen demand of purified wastewater is due to secondary\\u000a pollution by the oxidation products of the active sludge.

T. M. Sabirova; I. V. Nevolina; R. M. Stukov; B. L. Kopeliovich

2011-01-01

12

Development of a Fully Automatic Microwave Assisted Chemical Oxygen Demand (COD) Measurement Device  

Microsoft Academic Search

In this work, a fast and fully automatic microwave assisted chemical oxygen demand (COD) measurement device is described. In this instrument, the absorbance of Cr(III) generated during sample oxidation is measured at 590 nm. Chemical oxygen demand values can be obtained in just 12 min. This represents a significant reduction in digestion time, compared with the standard convective–conductive method; this is mainly

A. P. Beltrá; J. Iniesta; L. Gras; F. Gallud; V. Montiel; A. Aldaz; A. Canals

2003-01-01

13

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

14

Temporal and spatial variations of chemical oxygen demand in Lake Taihu, China, from 2005 to 2009  

Microsoft Academic Search

We undertook a study in Lake Taihu, China, from 2005 to 2009 including a total of 639 samples to determine: (i) the seasonal\\u000a dynamics and spatial distribution of the chemical oxygen demand (COD) and (ii) the relationships between the COD concentration\\u000a and the biochemical oxygen demand (BOD), phytoplankton pigment, total dissolved nitrogen (TDN), and total dissolved phosphorus\\u000a (TDP) concentrations, as

Yan Yin; Yunlin Zhang; Xiaohan Liu; Guangwei Zhu; Boqianq Qin; Zhiqiang Shi; Longqing Feng

2011-01-01

15

Photocatalytic sensor for the determination of chemical oxygen demand using flow injection analysis  

Microsoft Academic Search

A photocatalytic sensor for the determination of chemical oxygen demand (COD) with flow injection analysis (FIA) based on the photocatalysis of organic compounds in the presence of titanium dioxide (TiO2) beads in a photochemical column is described. The sensor was developed in conjunction with TiO2 beads in the photochemical column and with an oxygen electrode as the sensing part. The

Yoon-Chang Kim; Satoshi Sasaki; Kazuyoshi Yano; Kazunori Ikebukuro; Kazuhito Hashimoto; Isao Karube

2001-01-01

16

Typha angustifolia stress tolerance to wastewater with different levels of chemical oxygen demand  

Microsoft Academic Search

The stress tolerance of wetland plants is important to their potential use in wastewater treatment. In the present study, we investigated the physiological response of Typha angustifolia (T. angustifolia) to wastewater with different chemical oxygen demands (CODs) by bucket experiments. Activities of antioxidant enzymes such as catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) were measured. The content of total

Jingtao Xu; Cong Li; Fang Yang; Zhong Dong; Jian Zhang; Yingcan Zhao; Pengyu Qi; Zhen Hu

2011-01-01

17

A solid chemical oxygen demand (COD) method for determining biomass in waste waters  

Microsoft Academic Search

A method of biomass determination similar to volatile suspended solids (VSS) that used chemical oxygen demand (COD) as a detection method instead of gravimetric methods is described. The “solid COD” method has a strong correlation with VSS for biomass at different stages of growth on different wastewaters including municipal sewage and bleached kraft mill effluent. Soluble COD from the wastewaters

C. M. Bullock; P. A. Bicho; Y. Zhang; J. N. Saddler

1996-01-01

18

Chemical Oxygen Demand (COD) Reduction in Domestic Wastewater by Fly Ash and Brick Kiln Ash  

Microsoft Academic Search

The potential of fly ash, brick kiln ash and commercial activated carbon is determined for the reduction of chemical oxygen demand (COD) from domestic wastewater. Laboratory experiments are conducted for investigating the effect of treatment time, adsorbent dose, pH of the media, initial COD concentration, agitation speed and particle size of adsorbents on the COD reduction from the domestic wastewater.

Rani Devi; R. P. Dahiya

2006-01-01

19

A Mercury-Free Microwave Method for the Chemical Oxygen Demand Analysis of Sewage  

Microsoft Academic Search

A COD (chemical oxygen demand) method involving dichromate oxidation in a digestion bomb heated in a microwave oven, was developed and tested for sewage samples. Oxidation was complete within 2 min and the method gave comparable results to more conventional open reflux and closed tube methods, which require a 2 h oxidation. Lower sulphuric acid concentrations were required for full

E. Axán; G. M. Morrison

1995-01-01

20

Miniaturized closed reflux, colorimetric method for the determination of chemical oxygen demand  

Microsoft Academic Search

The standard technique for the closed reflux, colorimetric analysis of chemical oxygen demand (COD) utilizes several hazardous compounds, including mercury, silver, chromium, and sulfuric acid. A miniaturized version of this analytical technique was developed, thereby reducing the use and disposal of these hazardous compounds by 84%. The miniaturized method demonstrated a similar level of accuracy as the conventional technique for

Timothy M. LaPara; James E. Alleman; P. Greg Pope

2000-01-01

21

Identification mode of chemical oxygen demand in water based on remotely sensing technique and its application  

Microsoft Academic Search

This work was to give an identification mode of chemical oxygen demand (COD) within water body using remotely sensing technique. For this purpose the field data, including the spectral data of water body and the concentration of COD within water ,were collected at Huanjiang river, Rouyuan river and Malian river in Qingyang city , Gansu province of China on 6-7

Huang Miao-fen; Xing Xu-feng; Qi Xiao-ping; Yu Wu-yi; Zhang Yi-min

2007-01-01

22

Chemical oxygen demand fate from cottage cheese (acid) whey applied to a sodic soil  

Microsoft Academic Search

Cottage cheese (acid) whey is an effective amendment in sodic soil reclamation, but the high chemical oxygen demand (COD) of whey is of concern in land application. The objective of this research was to determine the fate of COD from cottage cheese whey applied to a sodic soil. Treatments of 0, 25, 50, and 100 mm (0, 20, 40, and

S. B. Jones; C. L. Hansen; C. W. Robbins

1993-01-01

23

Ultrasound assisted method to increase soluble chemical oxygen demand (SCOD) of sewage sludge for digestion  

Microsoft Academic Search

The aim of this study was to clarify the possibilities to increase the amount of soluble chemical oxygen demand (SCOD) and methane production of sludge using ultrasound technologies with and without oxidising agents. The study was done using multivariate data analyses. The most important factors affected were discovered. Ultrasonically assisted disintegration increased clearly the amount of SCOD of sludge. Also

Antti Grönroos; Hanna Kyllönen; Kirsi Korpijärvi; Pentti Pirkonen; Teija Paavola; Jari Jokela; Jukka Rintala

2005-01-01

24

Correction of hydrogen peroxide interference on standard chemical oxygen demand test  

Microsoft Academic Search

The chemical oxygen demand test, which is widely used as an indicator to identify the characteristics of wastewater, could be disturbed by the inorganic substances such as nitrite, chloride, hydrogen peroxide, etc. For hydrogen peroxide differently to the other inorganic substances, the method of overcoming its interference is not mentioned in Standard Methods [APHA (1995) Standard Methods for the Examination

Yun Whan Kang; Min-Jung Cho; Kyung-Yup Hwang

1999-01-01

25

Comparison of microcolorimetric and macrotitrimetric methods for chemical oxygen demand of oil shale wastewaters  

Microsoft Academic Search

Modifications are described for both the microcolorimetric and macrotitrimetric chemical oxygen demand (COD) procedures. For the former, a prolonged cooling period, followed by extensive mixing, minimizes the spectrophotometric interference from refractive index changes and catalyst-induced precipitate. For the latter, automated titration and absorbance monitoring near the chromate-chronic isosbestic point improves accuracy and reproducibility. The applicability of these modified methods for

Bonnie M. Jones; Richard H. Sakaji; Christian G. Daughton

1985-01-01

26

FISHERY WASTE EFFLUENTS: A METHOD TO DETERMINE RELATIONSHIPS BETWEEN CHEMICAL OXYGEN DEMAND AND RESIDUE  

E-print Network

1638, Kodiak, AK 99615. 2Tenney, R. D. 1972. COD for Industrial Waste Water, Tech. Rep. 97, 5 p.; 1972 of screened waste effluents from November 1973 to September 1974: shrimp using fresh or salt water processing. Chemical Oxygen Demand, Tech. Rep. 101, 12 p.; 1973. Shrimp Waste Streams and COD, Tech. Rep. 104, 3 p

27

Rapid determination of chemical oxygen demand using a focused microwave heating system featuring temperature control  

Microsoft Academic Search

This paper demonstrates the use of a microwave heating system, employed\\u000a in the chemical digestion step, for the determination of chemical oxygen\\u000a demand in wastewater. The results are first compared with those provided\\u000a by standard methods using reference substances. The problems arising\\u000a from abrupt heating of the sample and the potential thermal\\u000a decomposition of potassium dichromate are examined. Two different

Ramon Ramon; Francisco Valero; M del Valle

2003-01-01

28

Chemiluminescence system for automatic determination of chemical oxygen demand using flow injection analysis  

Microsoft Academic Search

A novel chemiluminescence (CL) system for automatic determination of chemical oxygen demand (COD) combined with flow injection analysis is proposed in this paper. In this system, potassium permanganate is reduced to Mn2+ which is first adsorbed on a strongly acid cation-exchange resin mini-column to be concentrated during chemical oxidation of the organic compounds at room temperature, while the excessive MnO4?

Baoxin Li; Zhujun Zhang; Juan Wang; Chunli Xu

2003-01-01

29

Amperometric determination of chemical oxygen demand using boron-doped diamond (BDD) sensor  

Microsoft Academic Search

A new application of boron-doped diamond (BDD) electrode was developed for detecting chemical oxygen demand (COD) by amperometric method. The effects of some basic experimental parameters including pH and applied potential on the response of the BDD electrode were investigated and the optimal operating conditions were obtained. In the COD tests of standard samples, a wide linear range of 20–9000mgl?1

Hongbin Yu; Hua Wang; Xie Quan; Shuo Chen; Yaobin Zhang

2007-01-01

30

A spectrophotometric method for determination of chemical oxygen demand using home-made reagents  

Microsoft Academic Search

A novel spectrophotometric assay method using home-made reagents that can be used to determine the chemical oxygen demand (COD) in real wastewater is described. The home-made reagents were used instead of the American Hach reagents. The principle of measurement was based on direct determination of the concentration change that Cr6+ is reduced intensely to Cr3+ resulting from potassium dichromate oxidation

Jun Li; Tao Tao; Xue-bin Li; Jiao-lan Zuo; Tong Li; Jin Lu; Shu-hui Li; Li-zhen Chen; Chun-yang Xia; Yong Liu; Yan-li Wang

2009-01-01

31

Estimation of chemical oxygen demand by ultraviolet spectroscopic profiling and artificial neural networks  

Microsoft Academic Search

A simple method based on the mathematical treatment of spectral absorbance profiles in conjunction with artificial neural\\u000a networks (ANNs) is demonstrated for rapidly estimating chemical oxygen demand (COD) values of wastewater samples. In order\\u000a to improve spectroscopic analysis and ANN training time as well as to reduce the storage space of the trained ANN algorithm,\\u000a it is necessary to decrease

Shoshana Fogelman; Michael Blumenstein; Huijun Zhao

2006-01-01

32

Rapid detection of chemical oxygen demand using least square support vector machines  

Microsoft Academic Search

A novel method to rapidly detect COD (Chemical Oxygen Demand) in polluted water with UV (ultra-violet) spectroanalysis is proposed in this paper. This method utilizes an on-line adaptive algorithm based upon LS-SVM (least square support vector machine), which can build adaptive models to predict the COD values of unknown water samples quickly and accurately. Practical application shows that this adaptive

Jun Fang; Liankui Dai

2004-01-01

33

Photocatalytic degradation of organic pollutants and detection of chemical oxygen demand by fluorescence methods  

Microsoft Academic Search

TiO2 photocatalyst was used to degrade organic pollutants in aqueous solutions and the detection of chemical oxygen demand was studied by fluorescence method. It was found that TiO2 dosage, initial solution pH, initial concentration electron acceptor Ce4+, the time of UV light irradiation and the temperature of solution affected the degradation of the organic pollutants. The optimum conditions were obtained

Chengfang Li; Gongwu Song

2009-01-01

34

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

Microsoft Academic Search

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

Hong Yao; Bin Wu; Haibin Qu; Yiyu Cheng

2009-01-01

35

Intensification of textile effluent chemical oxygen demand reduction by innovative hybrid methods  

Microsoft Academic Search

This study presents the reduction of textile effluent chemical oxygen demand (COD) by sonolysis, sorption, sono-sorption and sono-Fenton-sorption methods. Eco-friendly, cost effective, easily available tea waste activated using sodium hydroxide, formaldehyde, ultrasound irradiation (US), formaldehyde followed by US, and sodium hydroxide followed by US was used as an adsorbent. Better activation was obtained with formaldehyde followed by US treatment and

Senthilnathan Nachiappan; Karuppan Muthukumar

2010-01-01

36

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

Microsoft Academic Search

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

Dezhong Dan; Fulai Dou; Dianjie Xiu; Yuanqing Qin

2000-01-01

37

Reduction of chloride ion interference in chemical oxygen demand (COD) determinations using bismuth-based adsorbents  

Microsoft Academic Search

An efficient method for the reduction of chloride interference in the determination of chemical oxygen demand (COD) without the use of Hg(II) as a masking agent is described. Chloride ion is removed as hydrochloric acid gas from acidified sample solutions at 150°C in a closed reaction tube and captured by a bismuth-based adsorbent suspended above the heated solution. The effects

Bikas Vaidya; Steve W. Watson; Shelley J. Coldiron; Marc D. Porter

1997-01-01

38

Photoelectro-synergistic catalysis combined with a FIA system application on determination of chemical oxygen demand  

Microsoft Academic Search

In this paper, photoelectro-synergistic catalysis oxidation of organics in the water on Ti\\/TiO2\\/PbO2 electrode was investigated. The prepared TiO2 film was investigated with Atomic force micrograph (AFM). Furthermore, the results were compared with those obtained from electrocatalysis (EC) and electro-assisted photocatalysis (PC). The method proposed employed photoelectro-synergistic catalysis (PEC), together with flow injection analysis, to determine the chemical oxygen demand

Jiaqing Li; Lei Zheng; Luoping Li; Guoyue Shi; Yuezhong Xian; Litong Jin

2007-01-01

39

Determination of the chemical oxygen demand (COD) using a copper electrode: a clean alternative method  

Microsoft Academic Search

A clean alternative method for the determination of chemical oxygen demand (COD) was developed using a copper electrode as\\u000a an electrocatalytic sensor. The measuring principle is based on oxidation current of organic compounds in the wastewater.\\u000a The effects of important experimental conditions, such as electrolytic solution concentration and potential scan rate, on\\u000a analytical performance have been investigated. Analytical linear range

Claudineia R. Silva; Cleone D. C. Conceição; Viviane G. Bonifácio; Orlando Fatibello Filho; Marcos F. S. Teixeira

2009-01-01

40

A nano-copper electrochemical sensor for sensitive detection of chemical oxygen demand  

Microsoft Academic Search

Copper nanoparticle (nano-Cu) was electrodeposited on the surface of Cu disk electrode under ?1V for 60s, and then used to construct an electrochemical sensor for chemical oxygen demand (COD). The electrochemical oxidation behavior of glycine, a standard compound for evaluating the COD, was investigated. The potential shifts negatively, and the current increases greatly at the surface of nano-Cu, indicating remarkable

Jinquan Yang; Jianwei Chen; Yikai Zhou; Kangbing Wu

2011-01-01

41

Temporal and spatial characteristics of chemical oxygen demand in Tokyo Bay  

Microsoft Academic Search

Chemical oxygen demand (COD) at the sea surface in Tokyo Bay was examined using monthly data during 1980–89. The long-term\\u000a mean and the annual-cycle amplitude of COD are largest in the northwestern region, decrease southward, and are smallest near\\u000a the entrance of the bay. Based on their spatial properties, Tokyo Bay was divided into northwest, northeast, southwest, and\\u000a southeast regions,

Midori Kawabe; Masaki Kawabe

1997-01-01

42

A modified method for estimation of chemical oxygen demand for samples having high suspended solids  

Microsoft Academic Search

Determination of chemical oxygen demand (COD) of samples having high suspended solids concentration such as cattle dung slurry with open reflux method of APHA–AWWA–WPCF did not give consistent results. This study presents a modification of the open reflux method (APHA–AWWA–WPCF) to make it suitable for samples with high percentage of suspended solids. The new method is based on a different

Yadvika; Asheesh Kumar Yadav; T. R. Sreekrishnan; Santosh Satya; Sangeeta Kohli

2006-01-01

43

DETERMINATION OF CHEMICAL OXYGEN DEMAND IN URBAN AND INDUSTRIAL WASTEWATER USING MICROWAVE SAMPLE DIGESTION  

Microsoft Academic Search

This work is presented as a continuation of our previous work where optimum time and power were studied to determine the chemical oxygen demand in standard solutions prepared from potassium hydrogenphthalate using a microwave oven.A gradual digestion in microwave oven was compared with conventional oven digestion at 150±2°C during 2 hours. The method was applied to urban and industrial wastewater coming

Ignacio Gómez; Roberto Ivorra; Ana Pérez; Ana María Santacruz; Juan Navarro; Jorge Mataix; Raul Moral

2002-01-01

44

Simultaneous Determination of Chemical Oxygen Demand\\/Inorganic Carbon by Flow Injection-Pervaporation  

Microsoft Academic Search

A method for the simultaneous determination of chemical oxygen demand (COD) and inorganic carbon by spectrophotometric and potentiometric (pH) detection, respectively, is described. The carbon dioxide is removed by pervaporation and accepted at the upper part of the separation unit by a buffer stream, the pH change of which is measured by a pH-electrode situated on the top of the

I. Papaefstathiou; M. D. Luque De Castro

1997-01-01

45

Correlating Biochemical and Chemical Oxygen Demand of Effluents - A Case Study of Selected Industries in Kumasi, Ghana  

Microsoft Academic Search

The study aims at establishing an empirical correla tion between biochemical oxygen demand (BOD 5) and chemical oxygen demand (COD) of effluents from selected industries in the Kumasi Metropolis to facilitate speed y effluent quality assessment or optimal process control. Hour ly effluent samples were collected for an 8-h perio d three times per week for analysis of the principal

F. K. Attiogbe; Mary Glover-Amengor; K. T. Nyadziehe

46

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

Microsoft Academic Search

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

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

1999-01-01

47

Photoelectrochemical determination of chemical oxygen demand based on an exhaustive degradation model in a thin-layer cell  

Microsoft Academic Search

This work focuses on the experimental optimisation of a newly developed photoelectrochemical system for the determination of chemical oxygen demand (PECOD). This method is developed based on a photoelectrochemical degradation principle. Chemical oxygen demand (COD) is directly quantified by measuring the amount of electron transferred at a TiO2 nanoporous thin-film electrode during an exhaustive photoelectrocatalytic degradation process in a thin-layer

Shanqing Zhang; Huijun Zhao; Dianlu Jiang; Richard John

2004-01-01

48

Rapid Determination of the Chemical Oxygen Demand in Water with the Use of High-Temperature Solid-Electrolyte Cells  

Microsoft Academic Search

A new procedure is proposed for the determination of the oxidazibility of organic and inorganic matter in water (an analogue of the chemical oxygen demand (COD)). The procedure is based on high-temperature oxidation in a controlled binary oxygen–inert gas mixture and the determination of the amount of oxygen consumed for oxidation in a solid-electrolyte cell. A new design for the

B. K. Zuev; A. A. Korotkov; V. G. Filonenko; A. N. Mashkovtsev; V. P. Zvolinskii

2004-01-01

49

Ceriometry, a combined method for chemical oxygen demand and dissolved oxygen (with a discussion on the precision of the winkler technique)  

Microsoft Academic Search

A ceriometric method is described in which Ce3+ salts are used for the determination of dissolved oxygen and Ce4+ salts for the determination of the chemical oxygen demand. The interference of COD in the O2 determination, a common feature of most Winkler determinations, is corrected. The standard deviation is typically about 1% of the mean, and bias (inaccuracy) is very

H. L. Golterman; A. G. Wisselo

1981-01-01

50

Electrochemical treatment of rice grain-based distillery effluent: chemical oxygen demand and colour removal.  

PubMed

The electrochemical (EC) treatment of rice grain-based distillery wastewater was carried out in a 1.5 dm3 electrolytic batch reactor using aluminium plate electrodes. With the four-plate configurations, a current density (j) of 89.3 A/m2 and pH 8 was found to be optimal, obtaining a maximum chemical oxygen demand (COD) and colour removal of 93% and 87%, respectively. The chemical dissolution of aluminium was strongly influenced by initial pH (pHi). At higher pHi (pH 9.5) anode consumption decreased while energy consumption increased. At the optimal current density 89.3 A/m2, the aluminium electrode consumption was 16.855 g/dm3 wastewater and energy consumption was 31.4 Wh/dm3 achieving a maximum COD removal of 87%. The settling and filterability characteristics ofelectrochemically treated sludge were also analysed at different pH. It was noted that treated slurry at pHi 9.5 gave best settling characteristic, which decreased with increase in pH. EC-treated effluent at pHi 8 had provided best filterability. Characteristics of scum and residues are also analysed at different pH. PMID:24600862

Prajapati, Abhinesh Kumar; Chaudhari, Parmesh Kumar

2014-01-01

51

Analysis of chemical compositions contributable to chemical oxygen demand (COD) of oilfield produced water  

Microsoft Academic Search

This work was to give a comprehensive estimation for the chemical compositions contributable to COD of the produced water treatment system. For this purpose, the wastewater samples were collected from an onshore wastewater treatment plant. The chemical compositions of the wastewater were investigated, and the COD contributed by each component was estimated. The results showed that the COD levels of

Jinren Lu; Xiulin Wang; Baotian Shan; Ximing Li; Weidong Wang

2006-01-01

52

Determination of chemical oxygen demand (COD) using ultrasound digestion and oxidation-reduction potential-based titration  

Microsoft Academic Search

A new method for determining wastewater chemical oxygen demand (COD) using ultrasonic digestion and titration based on oxidation reduction potential (ORP) was developed. COD values of potassium hydrogen phthalate solution obtained by ultrasonic digestion were well matched with those obtained using Standard Methods. When applied to determine COD of real wastewater collected from a local treatment plant, results from the

Hyunook Kim; Honglae Lim; Mark F. Colosimo

2007-01-01

53

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

Microsoft Academic Search

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

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

2007-01-01

54

Pecan shell-based granular activated carbon for treatment of chemical oxygen demand (COD) in municipal wastewater  

Microsoft Academic Search

The present investigation was undertaken to compare the adsorption efficiency of pecan shell-based granular activated carbon with the adsorption efficiency of the commercial carbon Filtrasorb 200 with respect to uptake of the organic components responsible for the chemical oxygen demand (COD) of municipal wastewater. Adsorption efficiencies for these two sets of carbons (experimental and commercial) were analyzed by the Freundlich

R. R. Bansode; J. N. Losso; W. E. Marshall; R. M. Rao; R. J. Portier

2004-01-01

55

Removal of soluble chemical oxygen demand from domestic wastewaters in a laboratory-scale anaerobic waste stabilization pond  

Microsoft Academic Search

Anaerobic waste stabilization ponds (AWSPs) have been extensively used to treat both domestic and industrial wastewaters. In this study two laboratory-scale AWS columns (591 each) were operated using domestic wastewater in a repeated batch model. Data from one of the reactors was used to develop a dynamic model to describe the removal of soluble chemical oxygen demand (SCOD). This model

1995-01-01

56

Effects of chitosan on growth of an aquatic plant ( Hydrilla verticillata) in polluted waters with different chemical oxygen demands  

Microsoft Academic Search

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. verricillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg\\/L) and decreased with low COD (63

Qiu-jin XU; Yue-gang NIAN; Xiang-can JIN; Chang-zhou YAN; Jin LIU; Gao-ming Jiang

2007-01-01

57

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

PubMed

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

Yao, Na; Wang, Jinqi; Zhou, Yikai

2014-01-01

58

Chemical oxygen demand reduction in coffee wastewater through chemical flocculation and advanced oxidation processes  

Microsoft Academic Search

The removal of the natural organic matter present in coffee processing wastewater through chemical coagulation-flocculation and advanced oxidation processes (AOP) had been studied. The effectiveness of the removal of natural organic matter using commercial flocculants and UV\\/H2O2,UV\\/O3 and UV\\/H2O2\\/O3 processes was determined under acidic conditions. For each of these processes, different operational conditions were explored to optimize the treatment efficiency

Teresa ZAYAS Péerez; Gunther GEISSLER; Fernando HERNANDEZ

2007-01-01

59

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

Microsoft Academic Search

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

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

2005-01-01

60

A surface-fluorinated-TiO 2–KMnO 4 photocatalytic system for determination of chemical oxygen demand  

Microsoft Academic Search

A new method for chemical oxygen demand (COD) determination has been developed, based on photocatalytic oxidative degradation by using a fluorinated-TiO2–KMnO4 system. In such a system, a linear correlation is observed between the amount of oxidizable dissolved organic matter and the amount of MnO4? consumed by the coupled reduction process. Thus, the COD determination is transformed to a simple and

Lihua Zhu; Yu’e Chen; Yinghui Wu; Xiurong Li; Heqing Tang

2006-01-01

61

Trivalent manganese as an environmentally friendly oxidizing reagent for microwave- and ultrasound-assisted chemical oxygen demand determination  

Microsoft Academic Search

In the present work manganese(III) has been used as oxidant and microwave radiation and ultrasound energy have been assessed to speed up and to improve the efficiency of digestion step for the determination of chemical oxygen demand (COD). Microwave (MW) and ultrasound-assisted COD determination methods have been optimized by means of experimental design and the optimum conditions are: 40psi pressure,

Claudia E. Domini; Lorena Vidal; Antonio Canals

2009-01-01

62

EFFECT OF INFLUENT CHEMICAL OXYGEN DEMAND TO NITROGEN RATIO ON A PARTIAL NITRIFICATION\\/COMPLETE DENITRIFICATION PROCESS  

Microsoft Academic Search

A novel single-sludge process for achieving partial nitrification and complete denitrification (the PN\\/CD process) was tested at the bench-scale over a range of influent ratios of chemical oxygen demand (COD) to total Kjeldahl nitrogen (TKN). Mean ammonia nitrogen concentrations in PN\\/CD process effluent varied from 6.5 to 8.4 mg\\/liter at influent COD\\/TKN ratios varying from 3.7 to 9.8. Ammonia nitrogen

CHIE-CHIEN TSENG; THOMAS G. POTTER; BEN KOOPMAN

1998-01-01

63

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

Microsoft Academic Search

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

Chun-Han Ko; Chihhao Fan

2010-01-01

64

A portable miniature UV-LED-based photoelectrochemical system for determination of chemical oxygen demand in wastewater  

Microsoft Academic Search

A portable, cost-effective, environmental friendly and miniature thin-layer photoelectrochemical system in conjunction with an ultraviolet light emitting diode (UV-LED) is developed for determination of chemical oxygen demand (COD), namely UV-LED PeCOD. The COD value is directly quantified by measuring the amount of electrons captured at a nanostructured TiO2 electrode during the exhaustive photoelectrocatalytic degradation of organic species in the thin-layer

Shanqing Zhang; Lihong Li; Huijun Zhao; Guiying Li

2009-01-01

65

A modified method for the determination of chemical oxygen demand (COD) for samples with high salinity and low organics  

Microsoft Academic Search

This study proposes a modification to the standard method for the determination of the chemical oxygen demand of samples with a salinity up to 40g NaCl\\/L and low organic concentrations (20–230mg COD\\/L). The masking of chloride by the use of a HgSO4:Cl ratio of 20:1 prior to digestion, and the use of 3g K2Cr2O7\\/L in the digestion solution resulted in

I. Vyrides; D. C. Stuckey

2009-01-01

66

Rh2O3\\/Ti electrode preparation using laser anneal and its application to the determination of chemical oxygen demand  

Microsoft Academic Search

The method of preparation of a Rh2O3\\/Ti electrode by using laser calcination and the characterization by x-ray diffractometer were proposed. The electrode, which could develop organic electrocatalytical oxidation, was employed as an amperometric sensor, together with a flow injection analysis, to measure chemical oxygen demand (COD) of waste water in a speedy way. The measuring principle was based on the

Jiaqing Li; Luoping Li; Lei Zheng; Yuezhong Xian; Litong Jin

2006-01-01

67

Amperometric determination of chemical oxygen demand with flow injection analysis using F-PbO 2 modified electrode  

Microsoft Academic Search

An electrochemical detection system with an F-PbO2 modified electrode for flow injection analysis to determine chemical oxygen demand (COD) was proposed and experimentally validated. The measuring principle was based on the current response on the modified electrode which was proportional to the COD value. Under the optimized experiment condition, the linear range was 100–1200mgl?1, and the detection limit was 15mgl?1.

Jiaqing Li; Luoping Li; Lei Zheng; Yuezhong Xian; Shiyun Ai; Litong Jin

2005-01-01

68

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

69

TiO2 nanotube sensor for online chemical oxygen demand determination in conjunction with flow injection technique.  

PubMed

A simple, rapid and environmental friendly online chemical oxygen demand (COD) analytical method based on TiO2 nanotube sensor in conjunction with the flow injection technique was proposed to determine the COD of aqueous samples, especially for refractory organics, low-concentration wastewater, and surface water. The new method can overcome the drawbacks of the conventional COD determination methods. The results show that with the new method, each analysis takes only about 1 to 3 min, the linear range is up to 1 to 500 mg x L(-1) of the compound of interest, and the detection limit is 1 mg x L(-1). The COD values obtained by the proposed method are more accurate than those obtained by the conventional method. PMID:25109199

Li, Xuejin; Yin, Weiping; Li, Jianyong; Bai, Jing; Huang, Ke; Li, Jinhua; Zhou, Baoxue

2014-06-01

70

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands.  

PubMed

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. verticillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water. PMID:17915732

Xu, Qiu-jin; Nian, Yue-gang; Jin, Xiang-can; Yan, Chang-zhou; Liu, Jin; Jiang, Gao-ming

2007-01-01

71

From microbial fuel cell (MFC) to microbial electrochemical snorkel (MES): maximizing chemical oxygen demand (COD) removal from wastewater.  

PubMed

The paper introduces the concept of the microbial electrochemical snorkel (MES), a simplified design of a "short-circuited" microbial fuel cell (MFC). The MES cannot provide current but it is optimized for wastewater treatment. An electrochemically active biofilm (EAB) was grown on graphite felt under constant polarization in an urban wastewater. Controlling the electrode potential and inoculating the bioreactor with a suspension of an established EAB improved the performance and the reproducibility of the anodes. Anodes, colonized by an EAB were tested for the chemical oxygen demand (COD) removal from urban wastewater using a variety of bio-electrochemical processes (microbial electrolysis, MFC, MES). The MES technology, as well as a short-circuited MFC, led to a COD removal 57% higher than a 1000 ?-connected MFC, confirming the potential for wastewater treatment. PMID:21409654

Erable, Benjamin; Etcheverry, Luc; Bergel, Alain

2011-03-01

72

A simple chemiluminescence method for determination of chemical oxygen demand values in water  

Microsoft Academic Search

In this paper, a low cost chemiluminescence detector with a photodiode instead of photo-multiplier tube (PMT) was developed for environmental monitoring of water quality. Based on the chemiluminescent reaction of luminol–H2O2–Cr3+ system, light emission caused by luminol–H2O2–Cr3+ system was detected by the photodiode, and its intensity caused by the appearance of Cr3+ after samples digestion was proportional to the chemical

Yonggang Hu; Zeyu Yang

2004-01-01

73

PRIMARY RESEARCH PAPER Water column oxygen demand and sediment oxygen flux  

E-print Network

PRIMARY RESEARCH PAPER Water column oxygen demand and sediment oxygen flux: patterns of oxygen of the USA. We analyzed rates of oxygen loss as water-column biochemical oxygen demand (BOD5) and sediment, chemical and biological data were collected to identify factors related to oxygen loss. BOD5 rates ranged

Mallin, Michael

74

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

75

Flow injection method for the rapid determination of chemical oxygen demand based on microwave digestion and chromium speciation in flame atomic absorption spectrometry  

Microsoft Academic Search

The present paper describes a new flow injection method for the determination of Chemical Oxygen Demand (COD). This method consists of a first digestion step, where the sample is heated by microwave radiation, a second one where an anionic exchange resin retains the Cr(VI) that has not been reduced by the organic matter of the sample and a third one

A. Cuesta; J. L. Todoli; A Canals

1996-01-01

76

An experimental investigation of chemical oxygen demand removal from the wastewater containing oxalic acid using three-phase three-dimensional electrode reactor  

Microsoft Academic Search

The removal of chemical oxygen demand (COD) from wastewater containing oxalic acid was experimentally investigated using a three-phase three-dimensional electrode reactor. The experimental results show that the removal efficiency depends on the applied cell voltage, airflow, electrolysis time and the number of repeated runs. The former four factors all had a positive effect while the last factor generally had a

Ya Xiong; Hans T. Karlsson

2002-01-01

77

Replacement of chemical oxygen demand (COD) with total organic carbon (TOC) for monitoring wastewater treatment performance to minimize disposal of toxic analytical waste  

Microsoft Academic Search

Chemical oxygen demand (COD) is widely used for wastewater monitoring, design, modeling and plant operational analysis. However this method results in the production of hazardous wastes including mercury and hexavalent chromium. The study examined the replacement of COD with total organic carbon (TOC) for general performance monitoring by comparing their relationship with influent and effluent samples from 11 wastewater treatment

Donata Dubber; Nicholas F. Gray

2010-01-01

78

Feasibility of using ornamental plants ( Zantedeschia aethiopica) in subsurface flow treatment wetlands to remove nitrogen, chemical oxygen demand and nonylphenol ethoxylate surfactants—a laboratory-scale study  

Microsoft Academic Search

A lab-scale subsurface flow wetland (SSFW) was studied to assess the effectiveness of using calla lily (Zantedeschia aethiopica) in SSFW to remove nitrate, ammonium, chemical oxygen demand (COD), and nonylphenol ethoxylate (NPEO) surfactants. Reduction of inorganic nitrogen and COD from wastewater is one of the most important objectives in any water treatment process and is usually used to evaluate the

Marco A Belmont; Chris D Metcalfe

2003-01-01

79

An interlaboratory study as useful tool for proficiency testing of chemical oxygen demand measurements using solid substrates and liquid samples with high suspended solid content  

Microsoft Academic Search

In 2008, the first Proficiency Testing Scheme of Chemical Oxygen Demand (1stCOD-PTADG) was conducted to assess the results obtained for different research groups whose field work is mainly anaerobic digestion. This study was performed using four samples, two solid samples as raw materials and two solid samples to prepare high concentration suspended solid solutions. Invitations were sent to a large

F. Raposo; M. A. de la Rubia; R. Borja; M. Alaiz; J. Beltrán; C. Cavinato; M. Clinckspoor; G. Demirer; E. Diamadopoulos; B. Helmreich; P. Jenicek; N. Martí; R. Méndez; J. Noguerol; F. Pereira; S. Picard; M. Torrijos

2009-01-01

80

Co-Digestion of Palm Oil Mill Effluent and Refined Glycerin Wash Water for Chemical Oxygen Demand Removal and Methane Production  

Microsoft Academic Search

Problem statement: Refined Glycerin Wash Water (RGWW) from the oleochemical industry contains high Chemical Oxygen Demand (COD) and requires proper treatment before disposal. Unfortunately the wash water also contain s high concentration of sodium chloride (NaCl) that could cause inhibition to the normal biological tre atment process. However, there is feasibility of co - digesting the RGWW and Palm Oil

A. Sulaiman; M. R. Zakaria; M. A. Hassan; Y. Shirai; Z. Busu

2009-01-01

81

In line measurement of chemical oxygen demand by means of multipulse amperometry at a rotating Pt ring — Pt\\/PbO 2 disc electrode  

Microsoft Academic Search

In this paper an amperometric method that makes use of a the rotating ring-disc electrode (RRDE) configuration is described for the determination of the chemical oxygen demand (COD). It is shown that the strong oxidant necessary in COD measurements can be generated by an electrolytic in situ formation of an aggressive species, at the disc part of the ring-disc electrode,

P Westbroek; E Temmerman

2001-01-01

82

Quality improvement in determination of chemical oxygen demand in samples considered difficult to analyze, through participation in proficiency-testing schemes  

Microsoft Academic Search

Chemical oxygen demand (COD) is a critical analytical parameter in waste and wastewater treatment, more specifically in anaerobic digestion, although little is known about the quality of measuring COD of anaerobic digestion samples. Proficiency testing (PT) is a powerful tool that can be used to test the performance achievable in the participants’ laboratories, so we carried out a second PT

V. Fernández-Cegrí; M. A. De la Rubia; R. Borja; J. Beltrán; C. Cavinato; M. Clinckspoor; G. Demirer; E. Diamadopoulos; J. C. Frigon

2010-01-01

83

Rapid, sensitive and on-line measurement of chemical oxygen demand by novel optical method based on UV photolysis and chemiluminescence  

Microsoft Academic Search

A novel on-line method based on the combination of UV photolysis and chemiluminescence detection was established and experimentally validated for the determination of chemical oxygen demand (COD). A quantitative amount of free radicals can be produced by analytes in the UV irradiation process. By utilizing the phenomenon that luminol can be oxidized by the free radicals to produce luminescence, COD

Yingying Su; Xiaohong Li; He Chen; Yi Lv; Xiandeng Hou

2007-01-01

84

Rapid determination of chemical oxygen demand by a semi-automated method based on microwave sample digestion, chromium(VI) organic solvent extraction and flame atomic absorption spectrometry  

Microsoft Academic Search

In the present work, a new flow injection analysis (FIA) manifold for the rapid determination of chemical oxygen demand is presented and evaluated. The FIA manifold combines sample digestion by means of an oxidant solution (i.e., potassium dichromate and mercury sulfate) and an acid solution (sulfuric acid and silver sulfate) in a domestic microwave oven with the liquid–liquid extraction of

Angel Cuesta; José L Todol??; Juan Mora; Antonio Canals

1998-01-01

85

Recalcitrant organic compounds (chemical oxygen demand sources) in biologically treated pulp and paper mill effluents: Their fate and environmental impact in receiving waters  

Microsoft Academic Search

Most North American pulp and paper mills now biologically treat (biotreat) their liquid effluent. However, treated water still contains effluent-derived recalcitrant organic material (EROM), measured as chemical oxygen demand (COD), for which emission limits exist in Europe and are being considered in the US. Production of microbially resistant, dissolved natural organic material (NOM) typically found in Canadian stream and lake

F. Archibald; L. Roy-Arcand; M. Methot; L. Valeanu

1998-01-01

86

Pecan shell-based granular activated carbon for treatment of chemical oxygen demand (COD) in municipal wastewater.  

PubMed

The present investigation was undertaken to compare the adsorption efficiency of pecan shell-based granular activated carbon with the adsorption efficiency of the commercial carbon Filtrasorb 200 with respect to uptake of the organic components responsible for the chemical oxygen demand (COD) of municipal wastewater. Adsorption efficiencies for these two sets of carbons (experimental and commercial) were analyzed by the Freundlich adsorption model. The results indicate that steam-activated and acid-activated pecan shell-based carbons had higher adsorption for organic matter measured as COD, than carbon dioxide-activated pecan shell-based carbon or Filtrasorb 200 at all the carbon dosages used during the experiment. The higher adsorption may be related to surface area as the two carbons with the highest surface area also had the highest organic matter adsorption. These results show that granular activated carbons made from agricultural waste (pecan shells) can be used with greater effectiveness for organic matter removal from municipal wastewater than a coal-based commercial carbon. PMID:15158504

Bansode, R R; Losso, J N; Marshall, W E; Rao, R M; Portier, R J

2004-09-01

87

Water column oxygen demand and sediment oxygen flux: patterns of oxygen depletion in tidal creeks  

Microsoft Academic Search

Low dissolved oxygen (DO) levels often occur during summer in tidal creeks along the southeastern coast of the USA. We analyzed\\u000a rates of oxygen loss as water-column biochemical oxygen demand (BOD5) and sediment oxygen flux (SOF) at selected tidal creek sites monthly over a 1-year period. Ancillary physical, chemical\\u000a and biological data were collected to identify factors related to oxygen

Tara A. MacPherson; Lawrence B. Cahoon; Michael A. Mallin

2007-01-01

88

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

Microsoft Academic Search

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× 5 m2 and 8× 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

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

89

Spatial distribution and diurnal variation of chemical oxygen demand at the beginning of the rainy season in the Changjiang (Yangtze) River Estuary  

Microsoft Academic Search

A field observation was carried out in the Changjiang (Yangtze) River Estuary from May 19 to 26, 2003. A total of 29 stations,\\u000a including 2 anchored stations, were occupied through almost the whole salinity gradient. Based on the observation data, biogeochemistry\\u000a of chemical oxygen demand (COD) was examined. Spatial distribution pattern of COD shows that it decreased downstream. The\\u000a COD

Xuelu Gao; Jinming Song; Ning Li; Xuegang Li

2007-01-01

90

Effect of spent cotton stalks on color removal and chemical oxygen demand lowering in olive oil mill wastewater by white rot fungi  

Microsoft Academic Search

Wastewater from olive oil mill was decolorized (and its chemical oxygen demand reduced in static cultivation) using the fungiCoriolus versicolor, Funalia trogii, Phanerochœte chrysosporium andPleurotus sajor-caju. The effect of cotton stalk on decolorizing and COD removing capability was demonstrated.P. chrysosporium (in 20% medium with cotton stalk) reduced the COD by 48% and color by 58%,F. trogii (in 30% medium with

S. Kahraman

1999-01-01

91

Study on photocatalytic oxidation for determination of the low chemical oxygen demand using a nano-TiO 2–Ce(SO 4) 2 coexisted system  

Microsoft Academic Search

A new photocatalytic system, nano-TiO2–Ce(SO4)2 coexisted system, which can be used to determine the low chemical oxygen demand (COD) is described. Nano-TiO2 powders is used as photocatalyst in this system. The measuring method is based on direct determination of the concentration change of Ce(IV) resulting from photocatalytic oxidation of organic compounds. The mechanism of the photocatalytic oxidation for COD determination

Yihao Chai; Hongchun Ding; Zhonghai Zhang; Yuezhong Xian; Zhensheng Pan; Litong Jin

2006-01-01

92

Study on photocatalytic oxidation for determination of chemical oxygen demand using a nano-TiO 2–K 2Cr 2O 7 system  

Microsoft Academic Search

A photocatalytic method for the determination of chemical oxygen demand (COD) using a nano-TiO2–K2Cr2O7 system is described. The measuring principle is based on direct determination of the change of Cr(III) concentration resulting from photocatalytic oxidation of organic compounds and simultaneous photocatalytic reduction of stoichiometrically involved K2Cr2O7 in the solution. The operation conditions were optimized. The determinative COD value using this

Shiyun Ai; Jiaqing Li; Ya Yang; Mengnan Gao; Zhensheng Pan; Litong Jin

2004-01-01

93

Assessment of a modified and optimised method for determining chemical oxygen demand of solid substrates and solutions with high suspended solid content  

Microsoft Academic Search

A modified approach to determine the chemical oxygen demand (COD) of solid substrates based on the DIN 38414-S9 standard method is proposed. The adapted procedure is assessed and compared with standard methods widely used for water and wastewater such as the American Public Health Association–American Water Works Association–Water Pollution Control Federation (APHA–AWWA–WPCF) standard methods 5220 B-open reflux (SM-OR) and 5220

F. Raposo; M. A. de la Rubia; R. Borja; M. Alaiz

2008-01-01

94

Dissolved Oxygen and Biochemical Oxygen Demand  

NSDL National Science Digital Library

This 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.

Agency, U. S.

95

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.

2010-03-02

96

Removal of chemical oxygen demand, nitrogen, and heavy metals using a sequenced anaerobic-aerobic treatment of landfill leachates at 10–30°C  

Microsoft Academic Search

As a first step of treatment of landfill leachates (total chemical oxygen demand [COD]: 1.43–3.81 g\\/L; total nitrogen: 90–162\\u000a mg\\/L), performance of laboratory upflow anaerobic sludge bed reactors was investigated under mesophilic (30?C), submesophilic\\u000a (20?C), and psychrophilic (10?C) conditions. Under hydraulic retention times (HRTs) of about 0.3 d, when the average organic\\u000a loading rates (OLRs) were about 5 g of

Sergey Kalyuzhnyi; Marina Gladchenko; Andrey Epov; Vasu Appanna

2003-01-01

97

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

Microsoft Academic Search

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

Parmesh Kumar Chaudhari; Indra Mani Mishra; Shri Chand

2007-01-01

98

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...

99

Use of flow injection analysis based on iodometry for automation of dissolved oxygen (Winkler method) and chemical oxygen demand (dichromate method) determinations  

Microsoft Academic Search

Summary Two analytical methods for water analysis were miniaturized and partly automated by the flow injection analytical approach. In the standard Winkler method for dissolved oxygen determination, the final step, the titration of liberated iodine with Na2S2O3, was replaced by amperometric detection in a flowing stream. The concentration of dissolved oxygen was determined by the standard addition method using KIO3

M. Novi?; B. Pihlar; M. Dular

1988-01-01

100

TRANSIENT BIOGEOCHEMICAL CYCLING AND SEDIMENT OXYGEN DEMAND  

EPA Science Inventory

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

101

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; Eckstadt, Hartmut

2013-01-01

102

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

PubMed

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

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

2013-01-01

103

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

104

Enhanced removal of chemical oxygen demand, nitrogen and phosphorus using the ameliorative anoxic/anaerobic/oxic process and micro-electrolysis.  

PubMed

Synthetic wastewater was treated using a novel system integrating the reversed anoxic/anaerobic/oxic (RAAO) process, a micro-electrolysis (ME) bed and complex biological media. The system showed superior chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removal rates. Performance of the system was optimised by considering the influences of three major controlling factors, namely, hydraulic retention time (HRT), organic loading rate (OLR) and mixed liquor recirculation (MLR). TP removal efficiencies were 69, 87, 87 and 83% under the HRTs of 4, 8, 12 and 16 h. In contrast, HRT had negligible effects on the COD and TN removal efficiencies. COD, TN and TP removal efficiencies from synthetic wastewater were 95, 63 and 87%, respectively, at an OLR of 1.9 g/(L·d). The concentrations of COD, TN and TP in the effluent were less than 50, 15 and 1 mg/L, respectively, at the controlled MLR range of 75-100%. In this system, organics, TN and TP were primarily removed from anoxic tank regardless of the operational conditions. PMID:22766877

Bao, K Q; Gao, J Q; Wang, Z B; Zhang, R Q; Zhang, Z Y; Sugiura, N

2012-01-01

105

Quantitative relations between chemical oxygen demand concentration and its influence factors in the sluice-controlled river reaches of Shaying River, China.  

PubMed

Recent research on the effects of dam and sluice construction on the water environment has attracted extensive attention from academia and governments alike. Because the operation of sluices greatly alters environmental factors such as water flow and sediment load, the water quality in sluice-controlled river reaches (SCRRs) undergoes complex changes compared with those in normal reaches. This work used river reaches near the Huaidian Sluice in Shaying River of China as a case study to analyse the effects of sluice operation on water quality evolution in SCRRs. The most influential factors affecting the rate of change in chemical oxygen demand (COD) concentration in SCRRs were identified through water quality monitoring experiments performed under various modes of sluice operation and by applying a statistical method 'partial correlation analysis'. Then, a hydrodynamic model incorporating sluice operation and a water quality transport and transform model incorporating the release of endogenous loads were developed. Using these two models, the processes of temporal and spatial change of COD concentrations in the SCRRs were simulated under various scenarios designed to represent the dominant factors of influence. Finally, the simulation results were used to develop empirical relationships between the rate of change in COD concentrations and the dominant factors of influence. The results reveal that three factors, i.e., water inflow concentration, gate opening size, and gate opening number, are the dominant factors of influence, and there are logarithmic relationships between the rate of change in COD concentration in the SCRRs and these factors. PMID:25410948

Dou, Ming; Li, Guiqiu; Li, Congying

2015-01-01

106

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

EPA Science Inventory

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

107

Effect of aeration and material composition in soil mixture block on the removal of colored substances and chemical oxygen demand in livestock wastewater using multi-soil-layering systems  

Microsoft Academic Search

To investigate the efficiency of multi-soil-layering (MSL) systems on the removal of colored substances and chemical oxygen demand (COD) from livestock wastewater, four MSL systems with different soil mixture block (SMB) compositions were constructed in four 50 cm × 10 cm × 68 cm acrylic boxes. Livestock wastewater (diluted 10-fold) with an absorbance of 0.9215 at a wavelength of 406 nm and a COD concentration of approximately 3,000 mg L

Xin Chen; Kuniaki Sato; Toshiyuki Wakatsuki; Tsugiyuki Masunaga

2007-01-01

108

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

Microsoft Academic Search

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

H. Grootaerd; B. Liessens; W. Verstraete

1997-01-01

109

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 2.1c #12;Figure 2.1d #12;FIGURE 2.2: CHEMICAL OXYGEN DEMAND VERSUS POLITICAL RIGHTS Figure 2.2a;Figure 2.2b #12;Figure 2.2c #12;Figure 2.2d #12;FIGURE 2.3: CHEMICAL OXYGEN DEMAND VERSUS PER CAPITA GDP

Lin, C.-Y. Cynthia

110

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...

111

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...

112

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

113

A chemiluminescence biochemical oxygen demand measuring method.  

PubMed

A new chemiluminescence biochemical oxygen demand (BOD(CL)) determining method was studied by employing redox reaction between quinone and Baker's yeast. The measurement was carried out by utilizing luminol chemiluminescence (CL) reaction catalyzed by ferricyanide with oxidized quinone of menadione, and Saccharomyces cerevisiae using a batch-type luminometer. In this study, dimethyl sulfoxide was used as a solvent for menadione. After optimization of the measuring conditions, the CL response to hydrogen peroxide in the incubation mixture had a linear response between 0.1 and 100 microM H2O2 (r2=0.9999, 8 points, n=3, average of relative standard deviation; R.S.D.(av)=4.22%). Next, a practical relationship between the BOD(CL) response and the glucose glutamic acid concentration was obtained over a range of 11-220 mg O2 L(-1) (6 points, n=3, R.S.D.(av) 3.71%) with a detection limit of 5.5 mg O2 L(-1) when using a reaction mixture and incubating for only 5 min. Subsequently, the characterization of this method was studied. First, the BOD(CL) responses to 16 pure organic substances were examined. Second, the influences of chloride ions, artificial seawater, and heavy metal ions on the BOD(CL) response were investigated. Real sample measurements using river water were performed. Finally, BOD(CL) responses were obtained for at least 8 days when the S. cerevisiae suspension was stored at 4 degrees C (response reduction, 69.9%; R.S.D. for 5 testing days, 18.7%). BOD(CL) responses after 8 days and 24 days were decreased to 69.9% and 35.8%, respectively, from their original values (R.S.D. for 8 days involving 5 testing days, 18.7%). PMID:17936112

Nakamura, Hideaki; Abe, Yuta; Koizumi, Rui; Suzuki, Kyota; Mogi, Yotaro; Hirayama, Takumi; Karube, Isao

2007-10-17

114

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

115

Biochemical oxygen demand sensor using Serratia marcescens LSY 4  

Microsoft Academic Search

A microbial biochemical oxygen demand (BOD) sensor consisting of Serratia marcescens LSY 4 and an oxygen electrode was prepared for estimation of the biochemical oxygen demand. The response of the BOD sensor was insensitive to pH in the range of pH 6.0?8.0, and the baseline drift of the signal was nearly absent even in unbuffered aqueous solution. Because heavy metal

Mal-Nam Kim; Hee-Sun Kwon

1999-01-01

116

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...

117

Biochemical Oxygen Demand and Dissolved Oxygen. Training Module 5.105.2.77.  

ERIC Educational Resources Information Center

This document is an instructional module package prepared in objective form for use by an instructor familiar with the azide modification of the Winkler dissolved oxygen test and the electronic dissolved oxygen meter test procedures for determining the dissolved oxygen and the biochemical oxygen demand of a wastewater sample. Included are…

Kirkwood Community Coll., Cedar Rapids, IA.

118

Potential oxygen demand of sediments from Lake Erie  

USGS Publications Warehouse

Dreissenid mussels (Dreissena polymorpha and D. bugensis) biodeposit large quantities of filtered materials (i.e., feces and pseudofeces) directly on bottom substrates. These biodeposits have the potential to increase oxygen demand in sediments and overlying waters and thus contribute to hypolimnetic anoxia in Lake Erie. We hypothesized that higher potential oxygen demand of sediments would occur in areas near shore than in offshore hypolimnetic waters as a result of biodeposits carried by currents from littoral water where mussels, available foods, and biodeposits may be most abundant. To address this hypothesis, we measured potential oxygen demand (mg O2/L/120 h incubation) at six sites near shore and six sites offshore monthly June to September 2002 and August 2003. In addition, we compared, in post priori hypothesis, seven sites with and five sites without dreissenid mussels. Contrary to our hypotheses, potential oxygen demand was not significantly higher in bottles containing nearshore sediments than offshore sediments. Similarly, potential oxygen demand was not significantly higher at sites with dreissenid mussels than at sites without mussels. Data are consistent with pre-dreissenid studies which show oxygen demand and percent ash-free dry weights of sediments were higher offshore than near shore and ash-free dry weight of sediments decreased June to September. Therefore, the present study provides no evidence that dreissenid mussels have contributed directly-via biodeposition-to increased anoxia observed in Lake Erie in the mid to late 1990s.

Schloesser, D. W.; Stickel, R. G.; Bridgeman, T. B.

2005-01-01

119

Modeling In situ sediment oxygen demand in the Arroyo Colorado  

E-print Network

and are targeted for rehabilitation under the Total Maximum Daily Load (TMDL) program. In some rivers, sediment oxygen demand (SOD) accounts for as much as 50% of the total oxygen depletion, making SOD a critical element in water quality modeling studies. SOD...

Kasprzak, Kevin Ray

2012-06-07

120

REVIEW: Chemically pumped oxygen---iodine laser  

Microsoft Academic Search

A review is given of the principles of operation of the oxygen---iodine laser. Various types of chemical generators of singlet oxygen, which are key components in oxygen---iodine lasers, are considered. Experimental investigations of cw and pulsed oxygen---iodine lasers are described. The state-of-the-art theoretical investigations and potential applications of oxygen---iodine lasers are discussed.

Nikolai N. Yuryshev

1996-01-01

121

Oxygen demand of calcium-tolerant adult cardiac myocytes.  

PubMed

Isolated Ca2+-tolerant myocytes are mechanically at rest. Therefore, minimal oxygen demands should be expected. If oxygen consumption is measured without mechanical agitation of the cells, consumption rates comparable to those of the arrested myocardium are measured. In the current literature, much higher values are usually reported. It is suggested that these are due to mechanical stimulation of the cells in stirred suspensions. PMID:4062837

Spieckermann, P G; Piper, H M

1985-01-01

122

Glucagon increases hepatic oxygen supply-demand ratio in pigs  

SciTech Connect

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

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

1987-05-01

123

The chemically pumped oxygen-iodine laser  

Microsoft Academic Search

The present status of the chemical oxygen-iodine laser is discussed. The pertinent processes occurring in the chemical O2 generator, the O2(1Delta) transport region, and the nozzle are reviewed. The energy transfer kinetics, laser gain, and the performance and device efficiency are examined.

P. V. Avizonis; G. Hasen; K. A. Truesdell

1990-01-01

124

Methods for assessing biochemical oxygen demand (BOD): a review.  

PubMed

The Biochemical Oxygen Demand (BOD) is one of the most widely used criteria for water quality assessment. It provides information about the ready biodegradable fraction of the organic load in water. However, this analytical method is time-consuming (generally 5 days, BOD5), and the results may vary according to the laboratory (20%), primarily due to fluctuations in the microbial diversity of the inoculum used. Work performed during the two last decades has resulted in several technologies that are less time-consuming and more reliable. This review is devoted to the analysis of the technical features of the principal methods described in the literature in order to compare their performances (measuring window, reliability, robustness) and to identify the pros and the cons of each method. PMID:24316182

Jouanneau, S; Recoules, L; Durand, M J; Boukabache, A; Picot, V; Primault, Y; Lakel, A; Sengelin, M; Barillon, B; Thouand, G

2014-02-01

125

Inhibitory effect of nitrobenzene on oxygen demand in lake sediments.  

PubMed

Nitrobenzene is an important raw material and product, which presents a heavy threat to the ecosystem. The potential impacts of nitrobenzene on sediment oxygen demand (SOD) were studied in lake sediment simulating reactors receiving relatively low inputs of nitrobenzene. Oxygen microprofiles were measured in these sediment reactors using microelectrodes. After an initial microprofile measurement as a control, nitrobenzene was added to the overlying water resulting in concentrations of 0, 50, 100, and 150 microg/L. Microprofiles were measured on day 1, 2, 4 and 7 following the addition of nitrobenzene. SODs were determined from the microprofiles using a reaction-diffusion model. Results showed that the SODs increased relative to the initial values measured in the pre-treatment period in reactors exposed to all nitrobenzene concentrations on day 1. However, the values decreased gradually on the following days, which eventually resulted in a 50% loss in SODs after 7 days of exposure to nitrobenzene in all reactors. In addition, the inhibition effect of nitrobenzene on SOD exhibited a weak relationship with its concentration. The microscopic observation and count of algae in the sediment showed that the exposure to nitrobenzene did not change the composition of algae greatly, however, it decreased the number of dominant algae species sharply after 7 days of exposure. These results suggested that nitrobenzene could significantly alter SOD in lakes, which could ultimately affect the pollutant recovery in aquatic-sediment systems. PMID:22893973

Zhou, Xiaohong; Wang, Xuying; Shi, Hanchang

2012-01-01

126

Oxygen demand and long term changes of profundal zoobenthos  

Microsoft Academic Search

The paper attempts to combine the low oxygen content of the hypolimnion during stratification and the oxygen uptake of zoobenthos. Data of declining oxygen content in the hypolimnion and critical limits of respiration are combined for Chironomus anthracinus, Potamothrix hammoniensis and three species of Pisidium, P. casertanum, P. subtruncatum and P. henslowanum. The respiratory adaptation to low oxygen content influences

Petur M. Jónasson

1984-01-01

127

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

PubMed

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

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

2007-09-01

128

Sedimentary microbial oxygen demand for laminar flow over a sediment bed of finite length.  

PubMed

Dead organic material accumulated on the bed of a lake, reservoir or wetland often provides the substrate for substantial microbial activity as well as chemical processes that withdraw dissolved oxygen (DO) from the water column. A model to estimate the actual DO profile and the "sedimentary oxygen demand (SOD)" must specify the rate of microbial or chemical activity in the sediment as well as the diffusive supply of DO from the water column through the diffusive boundary layer into the sediment. Most previous experimental and field studies have considered this problem with the assumptions that the diffusive boundary layer is (a) turbulent and (b) fully developed. These assumptions require that (a) the flow velocity above the sediment bed is fast enough to produce turbulent mixing in the boundary layer, and (b) the sediment bed is long. In this paper a model for laminar flow and SOD over a sediment bed of finite length is presented and the results are compared with those for turbulent flow. Laminar flow near a sediment bed is encountered in quiescent water bodies such as lakes, reservoirs, river backwaters, wetlands and ponds under calm wind conditions. The diffusive oxygen transfer through the laminar diffusive boundary layer above the sediment surface can restrict the microbial or chemical oxygen uptake inside the sediment significantly. The developing laminar diffusive boundary layer above the sediment/water interface is modeled based on the analogy with heat transfer, and DO uptake inside the sediment is modeled by Michaelis-Menten microbial growth kinetics. The model predicts that the rate of SOD at the beginning of the reactive sediment bed is solely dependent on microbial density in the sediment regardless of flow velocity and type. The rate of SOD, and the DO penetration depth into the sediment decrease in stream-wise direction over the length of the sediment bed, as the diffusive boundary layer above the sediment/water interface thickens. With increasing length of the sediment bed both SOD rate and DO penetration depth into the sediment tend towards zero if the flow is laminar, but tend towards a finite value if the flow is turbulent. That value can be determined as a function of both flow velocity and microbial density. The effect of the developing laminar boundary layer on SOD is strongest at the very lowest flow velocity and/or highest microbial density inside the sediment. Under quiescent conditions, the effective SOD exerted by a reactive sediment bed of a lake or wetland approaches zero, i.e. no or very little oxygen demand is exerted on the overlying water column, except at the leading edge. PMID:16054191

Higashino, Makoto; Stefan, Heinz G

2005-09-01

129

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...

130

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

131

Prepared in cooperation with the U.S. Fish and Wildlife Service Benthic Oxygen Demand in Three Former  

E-print Network

:...................................................................................................................................3 Dissolved-Oxygen Flux Estimates Based on Diffusion .............................................................................................................................6 Dissolved Oxygen (DOPrepared in cooperation with the U.S. Fish and Wildlife Service Benthic Oxygen Demand in Three

132

Demand and supply of hydrogen as chemical feedstock in USA  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

133

Interplay between oxygen demand reactions and kinetic gas-water transfer in porous media.  

PubMed

Gas-water phase transfer associated with the dissolution of trapped gas in porous media is a key process that occurs during pulsed gas sparging operations in contaminated aquifers. Recently, we applied a numerical model that was experimentally validated for abiotic situations, where multi-species kinetic inter-phase mass transfer and dissolved gas transport occurred during pulsed gas penetration-dissolution events [Balcke, G.U., Meenken, S., Hoefer, C. and Oswald, S.E., 2007. Kinetic gas-water transfer and gas accumulation in porous media during pulsed oxygen sparging. Environmental Science & Technology 41(12), 4428-4434]. Here we extend the model by using a reactive term to describe dissolved oxygen demand reactions via the formation of a reaction product, and to study the effects of such an aerobic degradation process on gas-water mass transfer and dissolution of trapped gas in porous media. As a surrogate for microbial oxygen reduction, first-order oxygen demand reactions were based on the measured oxidation of alkaline pyrogallol in column experiments. This reaction allows for adjusting the rate to values close to expected biodegradation rates and detection of the reaction product. The experiments and model consistently demonstrated accelerated oxygen gas-water mass transfer with increasing oxygen demand rates associated with an influence on the partitioning of other gases. Thus, as the oxygen demand accelerates, less gas phase residues, consisting mainly of nitrogen, are observed, which is in general beneficial to the performance of field biosparging operations. Model results additionally predict how oxygen demand influences oxygen mass transfer for a range of biodegradation rates. A typical field case scenario was simulated to illustrate the observed coupling of oxygen consumption and gas bubble dissolution. The model provides a tool to improve understanding of trapped gas behavior in porous media and contributes to a model-assisted biosparging. PMID:18662823

Oswald, Sascha E; Griepentrog, Marco; Schirmer, Mario; Balcke, Gerd U

2008-08-01

134

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

PubMed

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

Liu, Changyu; Jia, Jianbo; Dong, Shaojun

2013-04-15

135

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

136

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

137

Chemical oxygen — iodine laser with mixing of supersonic jets  

Microsoft Academic Search

The results are reported of the first investigation of a chemical oxygen — iodine laser with supersonic mixing of parallel jets of oxygen and of a mixture of nitrogen with iodine. It was found that, in principle, such a laser system is feasible. The maximum output power was 160 and 130 W with the chemical efficiency 13% and 14.3%, respectively.

V N Azyazov; M V Zagidullin; V D Nikolaev; V S Safonov

1997-01-01

138

The standard chemical oxygen-iodine laser kinetics package  

Microsoft Academic Search

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

Glen P. Perram; Gordon D. Hager

1988-01-01

139

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

140

Stream Depth Significance During In-Situ Sediment Oxygen Demand Measurements in Shallow Streams  

Microsoft Academic Search

Ninety-one sediment oxygen demand (SOD) samples from six designated sites along the stretch of Lower Rapid Creek, South Dakota, were conducted using an in-situ SOD chamber. Inside the chamber, readings of dissolved oxygen (DO), water temperature, pH, and specific conductance were recorded every minute for more than one hour using the Datasonde 3 Hydrolab. Initial readings of such parameters were

Anf H. Ziadat; Bruce W. Berdanier

2004-01-01

141

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

142

Efficient chemical oxygen-iodine laser powered by a centrifugal bubble singlet oxygen generator  

NASA Astrophysics Data System (ADS)

Efficient production of singlet delta oxygen in a bubble singlet oxygen generator (BSOG) under the influence of centrifugal acceleration, 136g, has been obtained. An output power of 770W with chemical efficiency of 25.6% has been achieved in a small-scale, supersonic chemical oxygen-iodine laser supplied by the centrifugal BSOG. The ratio of the output power to the basic hydrogen peroxide volumetric flow rate was 4.3KJ/liter. Efficient chemical oxygen-iodine laser (COIL) operation with the centrifugal BSOG demonstrates the potential for mobile COIL applications.

Nikolaev, V. D.; Svistun, M. I.; Zagidullin, M. V.; Hager, G. D.

2005-06-01

143

Efficient chemical oxygen-iodine laser powered by a centrifugal bubble singlet oxygen generator  

Microsoft Academic Search

Efficient production of singlet delta oxygen in a bubble singlet oxygen generator (BSOG) under the influence of centrifugal acceleration, 136 g, has been obtained. An output power of 770 W with chemical efficiency of 25.6% has been achieved in a small-scale, supersonic chemical oxygen-iodine laser supplied by the centrifugal BSOG. The ratio of the output power to the basic hydrogen

V. D. Nikolaev; M. I. Svistun; M. V. Zagidullin; G. D. Hager

2005-01-01

144

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

145

Rapid method of determining biological oxygen demand (BOD) in coking plant wastewater  

SciTech Connect

The biochemical oxygen demand (BOD) is an important characteristic of coking plant wastewaters because it shows the concentration of substances in the water which can be oxidized by biochemical means. At present, the dilution method is the most widely used method for determining BOD in the Soviet Union. In the article presented, an improved method for determining BOD is discussed. (JMT)

Paekov, G.I.; Stanetskaya, A.M.

1982-01-01

146

Ethanol Demand in United States Production of Oxygenate-limited Gasoline  

Microsoft Academic Search

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

Hadder

2000-01-01

147

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

USGS Publications Warehouse

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

Heckathorn, Heather A.; Gibs, Jacob

2010-01-01

148

OPTIMIZING HIGH PRESSURE CHEMICAL OXYGEN-IODINE LASERS  

Microsoft Academic Search

The Blaze II chemical laser model was baselined to existing oxygen-iodine research assessment and device improvement chemical laser (RADICL) gain data. Subsequent Fabry-Perot power calculations with Blaze II were an average of 33% higher than the corresponding stable resonator power data. With the Blaze II model baselined to RADICL gain data, a genetic algorithm (GA) was used to predict optimal

David L. Carroll

1996-01-01

149

The effect of heavy metals on nitrogen and oxygen demand removal in constructed wetlands  

Microsoft Academic Search

The objective of this study is to investigate the respective effects of Zn, Pb and Cd as well as the combined effect of Zn, Pb, Cd and Cu on the removal of nitrogen and oxygen demand in constructed wetlands. Four laboratory-scale gravel-filled subsurface-flow constructed wetland units planted with cattails (Typha latifolia) were operated outdoors and fed with primary-treated domestic wastewater

P. E Lim; M. G Tay; K. Y Mak; N Mohamed

2003-01-01

150

Geostatistical modeling of the spatial distribution of sediment oxygen demand within a Coastal Plain blackwater watershed  

PubMed Central

Blackwater streams are found throughout the Coastal Plain of the southeastern United States and are characterized by a series of instream floodplain swamps that play a critical role in determining the water quality of these systems. Within the state of Georgia, many of these streams are listed in violation of the state’s dissolved oxygen (DO) standard. Previous work has shown that sediment oxygen demand (SOD) is elevated in instream floodplain swamps and due to these areas of intense oxygen demand, these locations play a major role in determining the oxygen balance of the watershed as a whole. This work also showed SOD rates to be positively correlated with the concentration of total organic carbon. This study builds on previous work by using geostatistics and Sequential Gaussian Simulation to investigate the patchiness and distribution of total organic carbon (TOC) at the reach scale. This was achieved by interpolating TOC observations and simulated SOD rates based on a linear regression. Additionally, this study identifies areas within the stream system prone to high SOD at representative 3rd and 5th order locations. Results show that SOD was spatially correlated with the differences in distribution of TOC at both locations and that these differences in distribution are likely a result of the differing hydrologic regime and watershed position. Mapping of floodplain soils at the watershed scale shows that areas of organic sediment are widespread and become more prevalent in higher order streams. DO dynamics within blackwater systems are a complicated mix of natural and anthropogenic influences, but this paper illustrates the importance of instream swamps in enhancing SOD at the watershed scale. Moreover, our study illustrates the influence of instream swamps on oxygen demand while providing support that many of these systems are naturally low in DO. PMID:20938491

Todd, M. Jason; Lowrance, R. Richard; Goovaerts, Pierre; Vellidis, George; Pringle, Catherine M.

2010-01-01

151

Comparison of wetland and agriculture drainage as sources of biochemical oxygen demand to the San Joaquin River, California  

Microsoft Academic Search

For many years, the San Joaquin River (SJR) has had low dissolved oxygen conditions intermittently during the late summer and early fall. The low dissolved oxygen conditions are impacting critical fish habitat and the SJR is being regulated under a state of California remediation plan that includes the development of a total maximum daily load (TMDL) allocation for oxygen demanding

William T. Stringfellow; Jeremy S. Hanlon; Sharon E. Borglin; Nigel W. T. Quinn

2008-01-01

152

Chemical generation of atomic iodine for chemical oxygen–iodine laser. I. Modelling of reaction systems  

Microsoft Academic Search

The mathematical modelling of reaction systems for chemical generation of atomic iodine is presented. This process is aimed to be applied in the chemical oxygen–iodine laser (COIL), where it can save a substantial part of energy of singlet oxygen and so increase the laser output power. In the suggested method, gaseous reactants for I atoms generation are admixed into the

V??t Jirásek; Otomar Špalek; Jarmila Kodymová; Miroslav ?enský

2001-01-01

153

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

USGS Publications Warehouse

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

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

2003-01-01

154

Chemical production of chondrule oxygen isotopic composition  

NASA Technical Reports Server (NTRS)

Defining the source of observed meteoritic O isotopic anomalies remains a fundamental challenge. The O isotopic composition of chondrules are particularly striking. There are at least three types of chemical processes that produce the isotopic compositions observed in chondrules and Ca-Al-rich inclusions (CAI's). The processes are rather general, viz, they require no specialized processes and the processes associated with chondrule production are likely to produce the observed compositions.

Thiemens, M. H.

1994-01-01

155

Biochemical oxygen demand and algae: Fractionation of phytoplankton and nonphytoplankton respiration in a large river  

SciTech Connect

Mass balance equations for dissolved oxygen in streams are formulated to account for, among other variables, algal respiration (R), and biochemical oxygen demand (BOD). The oxygen consumption measured in primary productivity-respiration analyses is not R but is total community oxygen consumption (TCOC), and BOD measurements are complicated by undefined algal components. Ultimate BOD was found to be 0.24 mg of O{sub 2} consumed per {mu}g chlorophyll a and carbonaceous BOD was 0.20 per {mu}g chlorophyll a in excess of background BOD. The results were similar for live and dead algae. Phytoplankton respiration was fractionated from nonphytoplankton oxygen consumption (NPOC) by the regression of respiration against chlorophyll a to obtain a y intercept of zero chlorophyll. The intercepts, NPOC, closely matched O{sub 2} consumption measured when phytoplankton biomass was very low. Phytoplankton respiration, calculated as the residual of the difference between TCOC and NPOC,ranged from 0.2 to 1.5 (mean = 0.88) mg O{sub 2} per mg chlorophyll a per hour, close to the literature value of 1 (in cultures). Depth-integrated (DI) phytoplankton respiration was 1/4 to 1/3 of DI gross primary productivity and 1-3% of maximum primary productivity. The separation of phytoplankton R and NPOC permitted the demonstration that R probably is not a simple function of productivity.

Cohen, R.R.H. (Colorado School of Mines, Golden (United States))

1990-04-01

156

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

157

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

Microsoft Academic Search

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

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

2003-01-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

159

Chemical generation of atomic iodine for the chemical oxygen–iodine laser. II. Experimental results  

Microsoft Academic Search

A new method for the chemical generation of atomic iodine intended for use in a chemical oxygen–iodine laser (COIL) was investigated experimentally. The method is based on the fast reaction of hydrogen iodide with chemically produced chlorine atoms. Effects of the initial ratio of reactants and their mixing in a flow of nitrogen were investigated experimentally and interpreted by means

Otomar Špalek; V??t Jirásek; Miroslav ?enský; Jarmila Kodymová; Ivo Jakubec; Gordon D. Hager

2002-01-01

160

Stream Depth Significance During In-Situ Sediment Oxygen Demand Measurements in Shallow Streams  

NASA Astrophysics Data System (ADS)

Ninety-one sediment oxygen demand (SOD) samples from six designated sites along the stretch of Lower Rapid Creek, South Dakota, were conducted using an in-situ SOD chamber. Inside the chamber, readings of dissolved oxygen (DO), water temperature, pH, and specific conductance were recorded every minute for more than one hour using the Datasonde 3 Hydrolab. Initial readings of such parameters were recorded for the overlaying water before the deployment of the SOD chamber. Characteristics of the stream conditions, air temperature, barometric pressure, average flow velocity of the stream, depth of the stream, and the flow velocity by the chamber were recorded. Single and multiple linear regression analyses on all parameters indicated that the velocity of the stream is the least critical parameter for SOD in shallow streams.

Ziadat, Anf H.; Berdanier, Bruce W.

2004-06-01

161

Chemical oxygen-iodine laser with cryosorption vacuum pump  

NASA Astrophysics Data System (ADS)

In a chemical oxygen-iodine laser (COIL), chemically prepared, gaseous gain medium at 3-10 Torr pressure is drawn through the laser cavity by vacuum suction. Multiple-stage vacuum pumps such as Roots blowers or steam ejectors are typically used to receive and compress the gas flowing from the laser and exhaust it to the atmosphere. The size and weight of such vacuum pumps present a significant challenge to engineering and packaging a transportable COIL system.

Vetrovec, John

2000-05-01

162

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

Microsoft Academic Search

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.

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

2004-01-01

163

Iodine dissociation in chemical oxygen-iodine lasers (COILs)  

Microsoft Academic Search

Iodine dissociation has been measured in the supersonic cavity of a chemical oxygen-iodine laser during lasing under a wide variety of flow conditions. By varying flow conditions, measured dissociations from 0 to 100 percent were observed. A simple model of the initial step in the dissociation process was developed that adequately rationalizes the measurements.

Charles A. Helms; J. Shaw; Gordon D. Hager; Keith A. Truesdell; David N. Plummer; J. Copland

1995-01-01

164

Research on advanced chemical and discharge oxygen-iodine lasers  

NASA Astrophysics Data System (ADS)

Generation of singlet oxygen and atomic iodine for operation of the chemical or discharge oxygen-iodine laser (COIL/DOIL) is described, employing novel methods and device configurations proposed in our laboratory. A centrifugal spray generator of singlet oxygen was developed, based on the conventional reaction between chlorine and basic hydrogen peroxide. Recent results of theoretical and experimental investigation of the generator parameters are presented. A new conception of the discharge generator of singlet oxygen was initiated, based on a combined DC arc jet and RF discharge techniques. Principle of the generator currently developed and constructed is described. A new device configuration was designed for the alternative method of atomic iodine generation using a radiofrequency discharge decomposition of iodine compounds like CH3I or CF3I. Some recent experimental results of this research are also presented.

Kodymová, Jarmila; Jirásek, Vít; Schmiedberger, Josef; Spalek, Otomar; Censký, Miroslav

2009-02-01

165

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

166

Valid Inequalities Based on Demand Propagation for Chemical ...  

E-print Network

Department of Chemical and Biological Engineering. University of ... there are two major types of chemical processing, sequential and network. In sequential .... the conversion of A to B via reaction A ? B is a task), which implies that a schedule may include multiple ..... zero to eliminate more combinations. In total there are ...

sara

2012-10-04

167

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

168

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

169

Oxygen Abundances and Chemical Evolution in Low Surface Brightness Galaxies  

E-print Network

We report the oxygen abundances of the HII regions of a sample of low surface brightness (LSB) galaxies. We provide analytic functions describing the McGaugh (1991) calibration of the R_23 method. We use this and the equivalent width (EW) method to determine oxygen abundances, and also make direct estimates in a few cases where the temperature sensitive [OIII] 4363 line is available. We find LSB galaxies to be metal poor, consistent with the L-Z relation of other galaxies. The large gas mass fractions of these objects provide an interesting test of chemical evolution models. We find no obvious deviation from the closed-box model of galactic chemical evolution. Based on our abundance and gas mass fraction measurements, we infer that LSB galaxies are not fundamentally different than other galaxy types but are perhaps at an early stage of evolution.

Rachel Kuzio de Naray; Stacy S. McGaugh; W. J. G. de Blok

2004-09-11

170

Spatial gain measurements in a chemical oxygen iodine laser (COIL)  

Microsoft Academic Search

The spatial distribution of small signal gain has been investigated on the RADICL device, a supersonic chemical oxygen-iodine laser (COIL). A frequency-stabilized, narrow linewidth diode laser system operating on the F=3?F=4 hyperfine levels of the (2 P1\\/2) to (2P3\\/2) spin-orbit transition in atomic iodine was used as a small signal probe. A peak gain of 1.2%\\/cm was measured along the

R. F. Tate; B. S. Hunt; C. A. Helms; K. A. Kruesdell; G. D. Hager

1995-01-01

171

Mode locking of a cw supersonic chemical oxygen iodine laser  

Microsoft Academic Search

This paper presents the results of the first mode locking experiments on a supersonic chemical oxygen iodine laser (COIL). Mode locking has been achieved using an acousto-optic modulator (AOM) and lasing demonstrated on the TEM00 modes with a small intracavity aperture. A dc magnetic field was used to increase the number of axial modes and a peak power of 2.5

S. P. Phipps; Charles A. Helms; Richard J. Copland; Wolfgang G. Rudolph; Keith A. Truesdell; Gordon D. Hager

1997-01-01

172

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

SciTech Connect

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

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

2008-08-01

173

Correlation of various oxygen demanding parameters in advanced waste-water treatment plants  

SciTech Connect

This study was designed to examine the various oxygen demand parameters and their relationship in a waste-water stream on a unit operation basis as it moves through a variety of state-of-the-art waste-water treatment facilities. Regression techniques were utilized to evaluate if analytical tools can be developed which provide plant operators with fast accurate monitoring techniques for evaluating and interpreting plant performance. Results of this study indicated that the failure to consistently obtain statistical correlations among operational control parameters, including BOD{sub 5}, in similar waste-water treatment facilities may be due to the varying types of compounds present in the raw sewage, and the increase in amount of variability of the non-biodegradable organics as treatment proceeds. The use of surrogate parameters to predict BOD{sub 5} was not warranted.

Rhodes, K.A.

1988-01-01

174

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

175

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

176

On oxygen-containing groups in chemically modified graphenes.  

PubMed

Reduced graphenes (belonging to the class of chemically modified graphenes, CMG) are one of the most investigated and utilized materials in current research. Oxygen functionalities on the CMG surfaces have dramatic influences on material properties. Interestingly, these functionalities are rarely comprehensively characterized. Herein, the four most commonly used CMGs, mainly electrochemically reduced graphene oxide (ER-GO), thermally reduced graphene oxide (TR-GO), and the corresponding starting materials, that is, graphene oxide and graphite oxide, were comprehensively characterized by a wide variety of methods, such as high-resolution X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, UV/Vis spectroscopy, transmission electron microscopy (TEM), and voltammetry, to establish connections between the structures of these materials that carry different oxygen functionalities and their electrochemical behaviors. This was followed by the quantification of the negatively charged oxygen-containing groups (OCGs) by UV/Vis spectroscopy and of the electrochemically reducible OCGs by voltammetry. Lastly, a biofunctionalization with gold nanoparticle (AuNP)-modified DNA sequences was performed by the formation of covalent bonds with the carboxylic groups (-COOH) on the CMG surfaces. There was an evident predominance of functionalizable -COOH groups on the ER-GO surface, as confirmed by a higher amount of Au detected both with differential-pulse voltammetry and impedance spectroscopy, coupled with visualization by TEM. We exploited the DNA-Au bioconjugates as highly specific stains to localize and visualize the positions of carboxylic groups. Our findings are very important to clearly identify the presence, nature, and distribution of oxygen functionalities on different chemically modified graphenes. PMID:22415893

Bonanni, Alessandra; Ambrosi, Adriano; Pumera, Martin

2012-04-10

177

Algal Biomass as an Indicator for Biochemical Oxygen Demand in the San Joaquin River, California.  

NASA Astrophysics Data System (ADS)

Episodes of hypoxia (DO < 2 mg/L) occur in the lower San Joaquin River (SJR), California, and are typically most acute in the late summer and fall. The oxygen deficit can stress and kill aquatic organisms, and often inhibits the upstream migration of fall-run Chinook salmon. Hypoxia is most pronounced downstream from the Stockton Deep Water Ship Channel, which has been dredged from a depth of 2-3 m to about 11 m to allow ocean-going ships to reach the Port of Stockton. To protect aquatic organisms and facilitate the upstream migration of fall-run Chinook salmon, the minimum water quality standard for DO is 6 mg/L during September through November, and 5 mg/L for the remainder of the year. A five year study examined components contributing to biochemical oxygen demand (BOD): ammonia, algal biomass, non-algal particulate organic matter, and dissolved organic carbon. BOD shows a significant increase in loading rates as the SJR flows downstream, which parallels the load of algal biomass due to instream growth. BOD loading rates from tributaries accounts for 28% in a wet year and 39% in a dry year. Regression analysis revealed that chlorophyll-a + pheophyton-a was the only significant (p<0.05) predictor for BOD (r2 = 0.71). Less than 20% of the BOD was found in the dissolved fraction (<0.45 ?m). The average BOD decomposition rate of the SJR and tributaries is 0.0841 d-1. We conclude that algal biomass is the primary contributor to BOD loads in the San Joaquin River.

Volkmar, E. C.; Dalhgren, R. A.

2005-12-01

178

Analytical applications of microbial fuel cells. Part I: Biochemical oxygen demand.  

PubMed

Microbial fuel cells (MFCs) are bio-electrochemical devices, where usually the anode (but sometimes the cathode, or both) contains microorganisms able to generate and sustain an electrochemical gradient which is used typically to generate electrical power. In the more studied set-up, the anode contains heterotrophic bacteria in anaerobic conditions, capable to oxidize organic molecules releasing protons and electrons, as well as other by-products. Released protons could reach the cathode (through a membrane or not) whereas electrons travel across an external circuit originating an easily measurable direct current flow. MFCs have been proposed fundamentally as electric power producing devices or more recently as hydrogen producing devices. Here we will review the still incipient development of analytical uses of MFCs or related devices or set-ups, in the light of a non-restrictive MFC definition, as promising tools to asset water quality or other measurable parameters. An introduction to biological based analytical methods, including bioassays and biosensors, as well as MFCs design and operating principles, will also be included. Besides, the use of MFCs as biochemical oxygen demand sensors (perhaps the main analytical application of MFCs) is discussed. In a companion review (Part 2), other new analytical applications are reviewed used for toxicity sensors, metabolic sensors, life detectors, and other proposed applications. PMID:24856922

Abrevaya, Ximena C; Sacco, Natalia J; Bonetto, Maria C; Hilding-Ohlsson, Astrid; Cortón, Eduardo

2015-01-15

179

Oxygen demand, nitrogen and copper removal by free-water-surface and subsurface-flow constructed wetlands under tropical conditions  

Microsoft Academic Search

This study was conducted to: (1) assess the role of wetland vegetation in the removal of oxygen demand and nitrogen under tropical conditions, (2) estimate the uptake of nitrogen and copper by wetland plants and (3) investigate the speciation of Cu in wetland media among four operationally defined host fractions, namely exchangeable, carbonate, reducible and organically bound. Four laboratory-scale wetland

P. E. Lim; T. F. Wong; D. V. Lim

2001-01-01

180

PROPOSED MODIFICATIONS OF K2-TEMPERATURE RELATION AND LEAST SQUARES ESTIMATES OF BOD (BIOCHEMICAL OXYGEN DEMAND) PARAMETERS  

EPA Science Inventory

A technique is presented for finding the least squares estimates for the ultimate biochemical oxygen demand (BOD) and rate coefficient for the BOD reaction without resorting to complicated computer algorithms or subjective graphical methods. This may be used in stream water quali...

181

USE OF SYNCHRONOUS FLUORESCENCE SPECTRA TO ESTIMATE BIOCHEMICAL OXYGEN DEMAND (BOD) OF URBAN RIVERS AFFECTED BY TREATED SEWAGE  

Microsoft Academic Search

Synchronous fluorescence spectra and the first derivative spectra of urban rivers affected by treated sewage were studied to find the optimum index for biochemical oxygen demand (BOD) estimation. In addition, various sample treatment methods as well as the multiple regression method using available monitoring parameters were examined to improve the BOD estimation capability of the indices. From July to November

J. Hur

2008-01-01

182

Multikilowatt chemical oxygen-iodine laser with chemical generation of molecular iodine  

NASA Astrophysics Data System (ADS)

A multikilowatt chemical oxygen-iodine laser (COIL) using molecular iodine generated chemically as the iodine source was developed and tested. The COIL, with a gain length of 26.5cm, was energized by a square pipe-array jet singlet oxygen generator (JSOG), with a nozzle bank having a designed Mach number of 2.5. The JSOG, operating without a primary buffer gas, has a much better operation stability during basic hydrogen peroxide pumping circulations. Iodine injectors/nozzles made of polyimide were used. An output power of 7.8kW and a chemical efficiency of 24.5% were achieved with a chlorine flow rate of 353mmole/s.

Zhang, Yuelong; Sang, Fengting; Zhang, Peng; Jin, Yuqi; Fang, Benjie; Zhao, Weili; Chen, Fang; Li, Qingwei; Xu, Mingxiu

2007-07-01

183

Chemical oxygen-iodine laser with a new method of atomic iodine generation  

Microsoft Academic Search

A study of recently proposed chemical method of atomic iodine production in the Chemical Oxygen-Iodine Laser (COIL) was performed. The process using gaseous reactants is based on the fast reaction of hydrogen iodide with chemically produced atomic chlorine. In the absence of singlet oxygen, the high yield of atomic iodine was attained (80 to 100 %). In the flow of

Otomar Spalek; Miroslav Censky; Vít Jirásek; Jarmila Kodymová; Ivo Jakubec; Gordon D. Hager

2003-01-01

184

Power optimization of small-scale chemical oxygen-iodine laser with jet-type singlet oxygen generator  

Microsoft Academic Search

Studies of power optimization of a 5-cm gain length chemical oxygen-iodine laser (COIL) energized by a jet-type singlet oxygen generator (JSOG) are presented. For 10 mmol\\/s of Cl2 flow rate, output power of 132 W with chemical efficiency of 14.5% was obtained without a water vapor trap, 163 W and 18% were achieved when coholed (173 K). He was introduced

I. Blayvas; B. D. Barmashenko; D. Furman; S. Rosenwaks; M. V. Zagidullin

1996-01-01

185

Simulation of dissolved oxygen and biochemical oxygen demand, Plantation Canal, Broward County, Florida with an evaluation of the QUAL-I model for use in south Florida  

USGS Publications Warehouse

A mathematical model; QUAL-I, developed by the Texas Water Development Board, was evaluated as a management tool in predicting the spatial and temporal distribution of dissolved oxygen and biochemical oxygen demand in Plantation Canal. Predictions based on the QUAL-I model, which was verified only against midday summer-flow conditions, showed that improvement of quality of inflows from sewage treatment plants and use of at least 130 cubic feet per second of dilution water would improve water quality in the canal significantly. The model was not fully amenable to use on Plantation Canal because: (1) it did not consider photosynthetic production, nitrification, and benthic oxygen demand as sources and sinks of oxygen; (2) the model assumptions of complete mixing, transport, and steady state were not met; and (3) the data base was inadequate because it consisted of only one set of data for each case. However, it was felt that meaningful results could be obtained for some sets of conditions. (Woodard-USGS)

Russo, Thomas N.; McQuivey, Raul S.

1975-01-01

186

A double exponential model for biochemical oxygen demand Ian G. Mason a,*, Robert I. McLachlan b  

E-print Network

2005 Abstract Biochemical oxygen demand (BOD) exertion patterns in anaerobically treated farm dairy exponential model of BOD exertion as follows: BODt ¼ BOD0 u1ð1 � e�k1t � þ BOD0 u2ð1 � e�k2t � where t is time, BOD0 u1 and BOD0 u2 are apparent ultimate BOD (BODu) values, and k1 and k2 are rate constants

McLachlan, Robert

187

Development of an Improved Test for the Determination of Biochemical Oxygen Demand  

E-print Network

. Comparative effect of natural and artificial seeds on oxygen consumption and BOO in unsterilized wastewater 5 increase the rate of oxygen consumption with either seed cultures retained high concentrations of viable cells for 2-3 months in several different simple media, suggesting a stabilized, consistent seed could

District of Columbia, University of the

188

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

PubMed

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

Ayyaru, Sivasankaran; Dharmalingam, Sangeetha

2014-03-25

189

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

190

Efficient chemical oxygen-iodine laser with longitudinal flow of the active medium  

SciTech Connect

A chemical oxygen-iodine laser with fast flow of the active medium along the optic axis was constructed. Lasing with an output power of 186 W and a chemical efficiency in excess of 20% were achieved. (lasers)

Zagidullin, M V; Nikolaev, V D; Svistun, M I; Khvatov, N A [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

1999-02-28

191

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

192

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

Microsoft Academic Search

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

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

2011-01-01

193

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

Microsoft Academic Search

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

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

2011-01-01

194

Lasing performance of a chemical oxygen iodine laser (COIL) with advanced ejector nozzle banks  

Microsoft Academic Search

Experimental lasing results for the Chemical Oxygen Iodine Laser, (COIL), using four different ejector nozzle configurations are presented. These nozzle banks differed in the location of Iodine injection, the area of the oxygen nozzles, and the nozzle contour of the primary driver nitrogen. The aerodynamic choking of the oxygen jets caused by the under expanded primary driver nitrogen resulted in

Nickolay A. Khvatov; Valeri D. Nikolaev; Michael I. Svistun; Marsel V. Zagidullin; Gordon D. Hager

2002-01-01

195

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

PubMed Central

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

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

2011-01-01

196

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

PubMed

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

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

2011-05-15

197

High-power chemical oxygen-iodine laser welding  

NASA Astrophysics Data System (ADS)

The present paper describes the welding characteristics with a 10 kW class Chemical Oxygen-Iodine Laser (COIL), whose wavelength is 1.32 micrometer. Bead-on-plate welding tests of 304 stainless steel plates were carried out at laser power 8.5 kW and 11 kW. Three different shielding gases (N2, Ar and He) were used through a coaxial conical shape nozzle under the lens. In COIL welding, the interaction between the laser beam and the laser induced plasma is very small because the wavelength of COIL is shorter than that of CO2 laser, so that the laser beam reaches on the workpiece without absorption by the plasma. As the result of the welding tests, the welded bead shapes did not depend on a type of the shielding gas. Radiograph and longitudinal section tests of the welded beads were carried out. When He and Ar gases were used as the shielding gas, there were several porosities. On the other hand, the use of N2 gas made no porosity. The full penetration on 10 mm thick plate was achieved in the high aspect ratio without the welding defects under the condition of laser power 8.5 kW and welding speed 1.5 m/min.

Nakabayashi, Tokuhiro; Muro, Mikio

2000-02-01

198

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

199

Experimental results on chemical generation of atomic iodine via Cl atoms for chemical oxygen-iodine laser  

Microsoft Academic Search

An alternative chemical way of atomic iodine generation for the chemical oxygen-iodine laser (COIL) was studied. This development was aimed at the laser power increase and simplification of the laser operation control. The method is based on the fast reaction of hydrogen iodide with chemically produced chlorine atoms. Kinetics of the process was studied in two types of the small-scale

Otomar Spalek; Vít Jirásek; Miroslav Censky; Jarmila Kodymová; Ivo Jakubec; Gordon D. Hager

2003-01-01

200

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

PubMed

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

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

2013-01-01

201

High-efficiency operation of chemical oxygen-iodine laser using nitrogen as buffer gas  

Microsoft Academic Search

High-efficiency operation of supersonic chemical oxygen-iodine laser (COIL) with an advanced jet-type singlet oxygen generator using nitrogen as buffer gas was demonstrated. Laser output was remarkably increased when buffer gas was cooled with liquid nitrogen. The effects of buffer gas temperature on the characteristics of the oxygen-iodine laser medium was discussed. A net chemical efficiency of 23.4% was obtained at

M. Endo; S. Nagatomo; S. Takeda; M. V. Zagidullin; V. D. Nikolaev; H. Fujii; F. Wani; D. Sugimoto; K. Sunako; K. Nanri; T. Fujioka

1998-01-01

202

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

203

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

Microsoft Academic Search

The CaSO4 based oxygen carrier has been proposed as an alternative low cost oxygen carrier for Chemical-looping combustion (CLC) of coal. The reduction of CaSO4 to CaS is an important step for the cyclic process of reduction\\/oxidation in CLC of coal with CaSO4 based oxygen carrier. Thermodynamic analysis of CaSO4 oxygen carrier with CO based on the principle of Gibbs

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

2010-01-01

204

On a new method for chemical production of iodine atoms in a chemical oxygen-iodine laser  

SciTech Connect

A new method is proposed for generating iodine atoms in a chemical oxygen-iodine laser. The method is based on a branched chain reaction of dissociation of the alkyl iodide CH{sub 3}I in a medium of singlet oxygen and chlorine. (active media)

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

2004-11-30

205

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

206

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

207

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

208

Chemical complexity in the winds of the oxygen-rich supergiant star VY Canis Majoris  

E-print Network

LETTERS Chemical complexity in the winds of the oxygen-rich supergiant star VY Canis Majoris L. M Canis Majoris (VY CMa). A variety of unexpected chemical com- pounds have been identified, including Na is further modified by interstellar ultraviolet radiation3,4 . Chemical compounds in these shells apparently

Ziurys, Lucy M.

209

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.

210

Singlet oxygen generator for a solar powered chemically pumped iodine laser. Final Report  

Microsoft Academic Search

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

Busch

1984-01-01

211

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

212

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

E-print Network

. Emerson School of Oceanography This study used measurements of dissolved neon, nitrogen, argon, and oxygenApplications of neon, nitrogen, argon and oxygen to physical, chemical and biological cycles in the ocean Roberta Claire Hamme A dissertation submitted in partial fulfillment of the requirements

Hamme, Roberta C.

213

Syngas chemical looping gasification process: oxygen carrier particle selection and performance  

Microsoft Academic Search

The syngas chemical looping (SCL) process coproduces hydrogen and electricity. The process involves reducing metal oxides with syngas followed by regeneration of reduced metal oxides with steam and air in a cyclic manner. Iron oxide is determined to be a desired oxygen carrier for hydrogen production considering overall properties including oxygen carrying capacity, thermodynamic properties, reaction kinetics, physical strength, melting

Fanxing Li; Hyung Ray Kim; Deepak Sridhar; Fei Wang; Liang Zeng; Joseph Chen; L.-S. Fan

2009-01-01

214

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

Microsoft Academic Search

\\u000a The CaSO4 based oxygen carrier has been proposed as an alternative low cost oxygen carrier for Chemical-looping combustion (CLC) of\\u000a coal. The reduction of CaSO4 to CaS is an important step for the cyclic process of reduction\\/oxidation in CLC of coal with CaSO4 based oxygen carrier. Thermodynamic analysis of CaSO4 oxygen carrier with CO based on the principle of Gibbs

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

215

Efficient, small scale chemical oxygen-iodine laser  

SciTech Connect

More than 40% extractable power efficiency has been achieved in a transverse flow, small scale, chemically pumped iodine-atom laser. 5 W of cw laser emission at 1315 nm has been obtained via energy transfer from chemically generated O/sub 2/(/sup 1/..delta..) to I atoms in a 10 x 1 cm/sup 2/ rectangular flow duct. Simple construction materials, safely handled chemicals, and a medium size vacuum pump were used for fabricating and operating the laser. The importance of minimizing quenching of excited species by collision with water molecules or with the wall is demonstrated.

Bachar, J.; Rosenwaks, S.

1982-07-01

216

Possibility of operation of a chemical oxygen–iodine laser without a cooled trap  

Microsoft Academic Search

A new proposal is made and discussed that it should be possible to operate a chemical oxygen–iodine laser not with the aid of a cooled trap for freezing out water vapor and hydrogen peroxide, but by deep cooling of a chemical generator. This may improve considerably the operating characteristics of such a laser.

M V Zagidullin; Valerii I Igoshin; V A Katulin; N L Kupriyanov

1983-01-01

217

Performance of a high-efficiency 5-cm gain length supersonic chemical oxygen-iodine laser  

Microsoft Academic Search

The Air Force Phillips Laboratory has developed a small-scale supersonic chemical oxygen-iodine laser (COIL) test stand (VertiCOIL) to rapidly evaluate emerging potential technology improvements. VertiCOIL was designed to address issues relevant to military and commercial applications such as long run time, high-efficiency operation, and compact design. VertiCOIL demonstrated an overall chemical efficiency of nearly 27%, one of the highest chemical

Tilghman L. Rittenhouse; Stephen P. Phipps; Charles A. Helms

1999-01-01

218

Chemical oxygen-iodine laser with atomic iodine generated via Cl or F atoms  

Microsoft Academic Search

Two alternative chemical methods of atomic iodine generation for a chemical oxygen-iodine laser (COIL) were studied. These methods are based on fast reactions of gaseous hydrogen iodide with chemically produced chlorine and fluorine atoms. Both processes were studied first in small-scale reactors. A yield of atomic iodine in the Cl system and nitrogen (non-reactive) atmosphere exceeded 80%, while in the

Otomar Spalek; Vit Jirasek; Miroslav Censky; Jarmila Kodymova; Ivo Jakubec; Gordon D. Hager

2005-01-01

219

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

Microsoft Academic Search

Mist singlet oxygen generator (Mist-SOG) has been developed in order to increase the BHP utilization. On the other hand, Mist-SOG generates much more water vapor than conventional SOG because the heat capacity of the BHP is small. It is well known that the water vapor deactivates the excited iodine. In order to remove the water vapor, we developed a jet-cold

Shigeki Muto; Masamori Endo; Kenzo Nanri; Tomoo Fujioka

2003-01-01

220

Atomic oxygen-MoS/sub 2/ chemical interactions  

SciTech Connect

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

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

1989-01-01

221

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

222

Kinetic bottlenecks to chemical exchange rates for deep-sea animals - Part 1: Oxygen  

NASA Astrophysics Data System (ADS)

Ocean warming will reduce dissolved oxygen concentrations which can pose challenges to marine life. Oxygen limits are traditionally reported simply as a static concentration thresholds with no temperature, pressure or flow rate dependency. Here we treat the oceanic oxygen supply potential for heterotrophic consumption as a dynamic molecular exchange problem analogous to familiar gas exchange processes at the sea surface. A combination of the purely physico-chemical oceanic properties temperature, hydrostatic pressure, and oxygen concentration defines the ability of the ocean to supply oxygen to any given animal. This general oceanic oxygen supply potential is modulated by animal specific properties such as the diffusive boundary layer thickness to define and limit maximal oxygen supply rates. Here we combine all these properties into formal, mechanistic equations defining novel oceanic properties that subsume various relevant classical oceanographic parameters to better visualize, map, comprehend, and predict the impact of ocean deoxygenation on aerobic life. By explicitly including temperature and hydrostatic pressure into our quantities, various ocean regions ranging from the cold deep-sea to warm, coastal seas can be compared. We define purely physico-chemical quantities to describe the oceanic oxygen supply potential, but also quantities that contain organism-specific properties which in a most generalized way describe general concepts and dependencies. We apply these novel quantities to example oceanic profiles around the world and find that temperature and pressure dependencies of diffusion and partial pressure create zones of greatest physical constriction on oxygen supply typically at around 1000 m depth, which coincides with oxygen concentration minimum zones. In these zones, which comprise the bulk of the world ocean, ocean warming and deoxygenation have a clear negative effect for aerobic life. In some shallow and warm waters the enhanced diffusion and higher partial pressure due to higher temperatures might slightly overcompensate for oxygen concentration decreases due to decreases in solubility.

Hofmann, A. F.; Peltzer, E. T.; Brewer, P. G.

2012-10-01

223

A pulsed oxygen - iodine chemical laser excited by a longitudinal electric discharge  

SciTech Connect

The dependence of the energy parameters of an oxygen - iodine chemical laser with a bulk generation of iodine atoms in a longitudinal electric discharge on the length of the discharge gap is studied for various discharge energies and voltages and various working mixture compositions (at constant oxygen and iodine pressures). Analyses of the results suggests that temperature effects account for a twofold decrease in the specific energy yield for the lasing initiated by a longitudinal electric discharge compared to the photolytic initiation. (lasers)

Vagin, Nikolai P; Yuryshev, Nikolai N [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2002-07-31

224

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

225

Chemical-looping with oxygen uncoupling using combined Mn-Fe oxides, testing in batch fluidized bed  

Microsoft Academic Search

Chemical-looping with oxygen uncoupling (CLOU) has been studied with gaseous and solid fuel in a small fluidized bed batch reactor, using new Fe-Mn-based oxygen carriers. CLOU is a development of chemical-looping combustion, using oxygen carriers with the ability to release oxygen, which can react directly with the fuel. The carbon dioxide from the combustion is inherently obtained as separated from

Golnar Azimi; Henrik Leion; Tobias Mattisson; Anders Lyngfelt

2011-01-01

226

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

227

Semi-specific Microbacterium phyllosphaerae-based microbial sensor for biochemical oxygen demand measurements in dairy wastewater.  

PubMed

Although the long incubation time of biochemical oxygen demand (BOD7) measurements has been addressed by the use of microbial biosensors, the resulting sensor-BOD values gained from the measurements with specific industrial wastewaters still underestimates the BOD value of such samples. This research aims to provide fast and more accurate BOD measurements in the dairy wastewater samples. Unlike municipal wastewater, wastewater from the dairy industry contains many substrates that are not easily accessible to a majority of microorganisms. Therefore, a bacterial culture, Microbacterium phyllosphaerae, isolated from dairy wastewater was used to construct a semi-specific microbial biosensor. A universal microbial biosensor based on Pseudomonas fluorescens, which has a wide substrate spectrum but is nonspecific to dairy wastewater, was used as a comparison. BOD biosensors were calibrated with OECD synthetic wastewater, and experiments with different synthetic and actual wastewater samples were carried out. Results show that the semi-specific M. phyllosphaerae-based microbial biosensor is more sensitive towards wastewaters that contain milk derivates and butter whey than the P. fluorescens-based biosensor. Although the M. phyllosphaerae biosensor underestimates the BOD7 value of actual dairy wastewaters by 25-32%, this bacterial culture is more suitable for BOD monitoring in dairy wastewater than P. fluorescens, which underestimated the same samples by 46-61%. PMID:22961489

Kibena, Elo; Raud, Merlin; Jõgi, Eerik; Kikas, Timo

2013-04-01

228

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

229

Physiological responses of Phragmites australis to wastewater with different chemical oxygen demands  

Microsoft Academic Search

Constructed wetlands have been widely used to treat various wastewaters with large differences in their concentration of pollutants. The capability of wetland plants to resist these wastewaters is crucial for a wetland's healthy development. Phragmites australis has been shown to have the capability to grow in simulated wastewater containing a wide concentration of pollutants. In this study, the physiological responses

Jingtao Xu; Jian Zhang; Huijun Xie; Cong Li; Nan Bao; Chenglu Zhang; Qianqian Shi

2010-01-01

230

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

NASA Astrophysics Data System (ADS)

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

Ay, Murat; Kisi, Ozgur

2014-04-01

231

Effects of seasonal climate change on Chemical Oxygen Demand (COD) concentration in the Anzali Wetland (Iran)  

Microsoft Academic Search

The Anzali Wetland is a distinguished coastal wetland in the southern coast of the Caspian Sea in north of Iran. This wetland is connected to the Caspian Sea through a channel and is supported with freshwater by 10 major rivers. The Anzali Wetland plays a key role as a habitat for many indigenous plants and animal species. It is believed

A. Tahershamsi; A. Bakhtiary; A. Mousavi

2009-01-01

232

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...

233

Simultaneous electrochemical removal of copper and chemical oxygen demand using a packed-bed electrode cell  

Microsoft Academic Search

Copper ions and chelating agents in water were treated simultaneously by using a packed-bed electrode cell. The cathode packings were graphite particles or graphite felt; the anode packings were platinum-plated titanium pellets, ß-PbO2 particles or oxidized lead spheres. The catholyte contained ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), iminodiacetic acid (IDA) or glycine chelate of copper, while the anolyte contained the

Katsuki Kusakabe; Hiroshi Nishida; Shigeharu Morooka; Yasuo Kato

1986-01-01

234

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

Microsoft Academic Search

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

Chiehming J. Chang

1992-01-01

235

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...

236

Nephelometric determination of the chemical oxygen demand in filtrates after the ultrafiltration purification of used lubricants  

SciTech Connect

Regions with developed industry are characterized by a large amount of lubricants in wastewater, and controlling the amount of mineral oil in the water in these regions is of prime importance. One of the methods of purifying used lubricants is ultrafiltration. In most cases, ultrafiltration purification is performed in BTU-0.5/2 tubular units with F-1 Teflon membranes. It is known that, in the case of the ultrafiltration purification of dispersed systems, the part of the dispersed phase with a particle size smaller than the diameter of membrane pores usually penetrates to the filtrate. The formation of the dispersed phase with a smaller size of particles is also possible because oil particles of a larger size are pressed through the membrane due to the wetting of the membrane material with the dispersed phase, which is the case of Teflon membranes. As a result, water produced by the ultrafiltration purification of lubricant-containing wastes contains oil particles 10-100 nm in size, which is comparable to the membrane pores. The amount of these particles can be small, which makes their determination difficult. Moreover, the method of controlling the amount of oil in the filtrate should be rapid, sensitive, and simple enough to allow its application in industrial conditions.

Bykadorov, N.U.; Radchenko, S.S. [Volgograd State Technical Univ. (Russian Federation)

1995-11-01

237

Nitrification in the Surface Water of the W?oc?awek Dam Reservoir. The Process Contribution to Biochemical Oxygen Demand (N-BOD)  

Microsoft Academic Search

Nitrifying activity in the surface water of the W?oc?awek Dam Reservoir (WDR) was determined by use of a nitrification selective inhibitor (ATU). The highest values of nitrification were observed in the stations nearer the dam, with lower flow velocity, where the activity amounted to up to 120 µg N\\/dm 3 \\/day. Nitrification process (%) involvement in biochemical oxygen demand increased

J. Polak

238

Purdue AgronomyPurdue AgronomyCrop, Soil, and EnvironmEntal SCiEnCES Wastewater Biological Oxygen Demand in Septic Systems  

E-print Network

can determine the waste stream's biochemical oxygen demand (or, BOD). BOD refers to the amount in a liter of wastewater. This is important, because a high BOD number means potential septic system problems for homeowners, while a low BOD means fewer problems for homeowners. This publication describes the environmental

Holland, Jeffrey

239

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

Microsoft Academic Search

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

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

2000-01-01

240

Experiment and modeling of a small-scale, supersonic chemical oxygen-iodine laser  

Microsoft Academic Search

We report on detailed experiment and modeling of a small-scale, supersonic chemical oxygen-iodine laser. The laser has a 5 cm long active medium and utilizes a simple sparger-type O2(1?) chemical generator and a medium-size pumping system. A grid nozzle is used for iodine injection and supersonic expansion. 25 W of cw laser emission at 1.315 µm are obtained in the

A. Elior; B. D. Barmashenko; E. Lebiush; S. Rosenwaks

1995-01-01

241

Two-dimensional gain measurements in a chemical oxygen-iodine laser (COIL) device  

Microsoft Academic Search

The spatial distribution of gain has been investigated on the Research Assessment and Device Improvement Chemical Laser, a supersonic chemical oxygen-iodine laser (COIL). A frequency-stabilized, narrow linewidth diode laser system operating on the F equals 3 yields F equals 4 hyperfine levels of the (2P1\\/2) to (2P3\\/2) spin-orbit transition in atomic iodine was used as a small signal probe. A

R. F. Tate; B. Scott Hunt; Gordon D. Hager; Charles A. Helms; Keith A. Truesdell

1995-01-01

242

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

Microsoft Academic Search

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

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

2008-01-01

243

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

NASA Astrophysics Data System (ADS)

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

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

244

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

NASA Astrophysics Data System (ADS)

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 ~1.5 mole s-1 achieving a typical chemical efficiency of about 18%.

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.

2011-05-01

245

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

246

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

247

Efficient operation of a chemically pumped oxygen iodine laser utilizing dilute hydrogen peroxide  

Microsoft Academic Search

A chemically pumped oxygen iodine laser system has been operated employing 35 wt pct H2O2 rather than commonly used 90 wt pct H2O2. Laser power as high as 40 W has been extracted. The maximum overall efficiency of 20.7 percent, which is almost 25 percent higher than the previously reported best data, has been achieved.

S. Yoshida; H. Fujii; T. Sawano; M. Endo; T. Fujioka

1987-01-01

248

Performance of a Multistream Injection Chemical OxygenIodine Laser with Starlet Ejectors  

E-print Network

A variant of an ejector-mixing nozzle for a chemical oxygen­iodine laser was experimentally tested that the starlets provide faster mixing. Hot-flow testing demonstrated that the starlet design improved laser performance by 20­30% above the basic cylindrical ejector design. Furthermore, a conical ejector design

Carroll, David L.

249

History of chemical oxygen-iodine laser (COIL) development in the USA  

Microsoft Academic Search

This is an overview of the development of Chemical Oxygen-Iodine Laser (COIL) technology in the United States. Key technical developments will be reviewed, beginning in 1960 and culminating in 1977 with the first COIL lasing demonstration at the Air Force Weapons Laboratory (now the Phillips Laboratory). The discussion will then turn to subsonic laser development, supersonic lasing demonstration and efficiency

Keith A. Truesdell; Charles A. Helms; Gordon D. Hager

1995-01-01

250

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

Microsoft Academic Search

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

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

2004-01-01

251

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

PubMed

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

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

2013-07-01

252

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

PubMed

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

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

2013-02-01

253

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

254

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

255

Calculation of the mixing chamber of an ejector chemical oxygen - iodine laser  

SciTech Connect

Gas parameters are calculated at the outlet of the mixing chamber of an ejector chemical oxygen-iodine laser with a nozzle unit consisting of nozzles of three types, which provides a total pressure of the active medium that substantially exceeds a pressure in the generator of singlet oxygen. This technique of forming the laser active medium substantially facilitates the ejection of the exhaust gas to the atmosphere by using a diffuser and single-stage vacuum systems based on water circulating pumps. (lasers, active media)

Zagidullin, M V; Nikolaev, V D [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2001-06-30

256

Can fluorescence spectrometry be used as a surrogate for the Biochemical Oxygen Demand (BOD) test in water quality assessment? An example from South West England  

Microsoft Academic Search

The fluorescence intensities of tryptophan-like, tyrosine-like and humic-like materials were determined using excitation-emission-matrices (EEMs) for a wide range of samples including natural surface waters, sewage and industrial effluents and waters that have experienced known pollution events from the South West of England (n=469). Fluorescence intensities reported in arbitrary fluorescence units (AFU) were correlated with standard five day Biochemical Oxygen Demand

Naomi Hudson; Andy Baker; David Ward; Darren M. Reynolds; Chris Brunsdon; Cynthia Carliell-Marquet; Simon Browning

2008-01-01

257

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

258

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

2006-09-01

259

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

Microsoft Academic Search

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

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

2002-01-01

260

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

261

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

262

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

263

Reverse engineering of oxygen transport in the lung: adaptation to changing demands and resources through space-filling networks.  

PubMed

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

264

Efficient generation in a chemical oxygen - iodine laser with a low buffer-gas flow rate  

SciTech Connect

The efficient generation in a chemical oxygen - iodine laser (COIL) with a low buffer-gas flow rate for Mach numbers M {<=} 1 is demonstrated. The maximum output power of the COIL was 415 W for a molecular chlorine flow rate of 20 mmol s{sup -1}, which corresponds to a chemical efficiency {eta}{sub ch} =23%. It is shown that the substitution of the buffer gas CO{sub 2} for N{sub 2} does not cause any significant variation in the dependence of the output power on the degree of dilution of the active medium. (lasers)

Azyazov, V N; Safonov, V S; Ufimtsev, N I [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2002-09-30

265

Magnetic modulation of gain in a chemical oxygen-iodine laser  

Microsoft Academic Search

A magnetic modulation of gain in a continuous-wave (CW) chemical oxygen-iodine laser (COIL) is proposed for several regimes of laser generation. The principle of the method proposed is based on a direct magnetic modulation of gain in the active zone of a COIL utilizing the Zeeman effect on the laser transition 2P1\\/2 -2P3\\/2 of iodine atoms. The possible applications of

Josef Schmiedberger; Jarmila Kodymova; Jiri Kovar; Otomar Spalek; Pavel Trenda

1991-01-01

266

Chemical oxygen-iodine laser power generation with an off-axis hybrid resonator  

Microsoft Academic Search

A rectangular negative branch off-axis hybrid resonator was coupled to a 10 kW class chemical oxygen-iodine laser. Resonator setup and alignment turned out to be straightforward. The extracted power was 6.6 kW and reached approximately 70% of the power for an optimized stable resonator. The divergence of the emitted laser beam in the unstable direction was lower than two times

Jürgen Handke; Wolfgang O. Schall; Thomas Hall; Frank Duschek; Karin M. Grünewald

2006-01-01

267

Optical saturation and extraction from the chemical oxygen-iodine laser medium  

Microsoft Academic Search

A rate equation model for the loaded gain of a flowing chemical oxygen-iodine laser is described. It includes pumping of the upper laser level by O2(1?), deactivation by water and energy pooling with O2(1?), stimulated emission on the 3?4 transition, hyperfine relaxation (HFR) of the 2P1\\/2 and 2P3\\/2 iodine sublevels, and velocity cross-relaxation (VCR) of the iodine atoms. The solution

D. A. Copeland; A. H. Bauer

1993-01-01

268

Experimental study of gain and output coupling characteristics of a CW chemical oxygen-iodine laser  

Microsoft Academic Search

Gain and output coupling characteristics of the CW chemical oxygen-iodine laser (COIL) are determined experimentally by means of varying the output coupling method. Under the conditions that the Cl2 flow rate is 11.8 mmol\\/s, the I2 molar flow rate is from 20 to 50 ?mol\\/s, and the duct pressure is 200 Pa, the following were obtained from the experimental data:

Josef Schmiedberger; Jarmila Kodymova; Otomar Spalek; Jiri Kovar

1991-01-01

269

Efficient operation of a chemically pumped oxygen iodine laser utilizing dilute hydrogen peroxide  

SciTech Connect

A chemically pumped oxygen iodine laser system has been operated employing 35 wt. % H/sub 2/O/sub 2/ rather than commonly used 90 wt. % H/sub 2/O/sub 2/. Laser power as high as 40 W has been extracted. The maimum overall efficiency of 20.7%, which is almost 25% higher than the previously reported best data, has been achieved.

Yoshida, S.; Fujii, H.; Sawano, T.; Endo, M.; Fujioka, T.

1987-11-09

270

Demonstration of a repetitively pulsed magnetically gain-switched chemical oxygen iodine laser  

Microsoft Academic Search

Recently, modulation of the output from a chemical oxygen iodine laser (COIL) has been demonstrated by applying a pulsed magnetic field directly to the laser cavity. A peak-to- average power enhancement of 3.2 was obtained. The rate of change of the magnetic field in these experiments, however, was relatively slow, 0.5 gauss\\/microsecond(s) . In this article, we report the demonstration

Gordon D. Hager; D. Kopf; David N. Plummer; T. Salsich; Peter G. Crowell

1993-01-01

271

Mode locking of a CW supersonic chemical oxygen-iodine laser  

Microsoft Academic Search

This paper presents the results of the first mode-locking experiments on a supersonic chemical oxygen-iodine laser (COIL). Mode locking has been achieved using an acoustooptic modulator (AOM) and lasing demonstrated on the TEM00 modes with a small intracavity aperture. A dc magnetic field was used to increase the number of axial modes and a peak power of 2.5 kW has

Stephen P. Phipps; Charles A. Helms; R. James Copland; Wolfgang Rudolph; Keith A. Truesdell; Gordon D. Hager

1996-01-01

272

Determination of riboflavin by the perturbation of active oxygen on a chemical oscillating reaction  

Microsoft Academic Search

This paper studies the perturbation of active oxygen (O2??H2O2) produced from the irradiated riboflavin on a chemical oscillating reaction, and a new and sensitive methodological approach for the determination of riboflavin is proposed based on it. An automatic experimental setup is designed to combine the irradiation of riboflavin with the analogous Belousov–Zhabotinskii reaction, which is implemented in a continuous-flow stirred

Zhang Ke; Ma Wanhong; Cai Ruxiu; Lin Zhixin; Gan Nanqin

2000-01-01

273

Impact of hydrogen and oxygen defects on the lattice parameter of chemical vapor deposited zinc sulfide  

NASA Astrophysics Data System (ADS)

The lattice parameter of cubic chemical vapor deposited (CVD) ZnS with measured oxygen concentrations <0.6 at. % and hydrogen impurities of <0.015 at. % has been measured and found to vary between -0.10% and +0.09% relative to the reference lattice parameter (5.4093 Å) of oxygen-free cubic ZnS as reported in the literature. Defects other than substitutional O must be invoked to explain these observed volume changes. The structure and thermodynamic stability of a wide range of native and impurity induced defects in ZnS have been determined by ab initio calculations. Lattice contraction is caused by S-vacancies, substitutional O on S sites, Zn vacancies, H in S vacancies, peroxy defects, and dissociated water in S-vacancies. The lattice is expanded by interstitial H, H in Zn vacancies, dihydroxy defects, interstitial oxygen, Zn and [ZnHn] complexes (n = 1,…,4), interstitial Zn, and S2 dumbbells. Oxygen, though present, likely forms substitutional defects for sulfur resulting in lattice contraction rather than as interstitial oxygen resulting in lattice expansion. It is concluded based on measurement and calculations that excess zinc atoms either at anti-sites (i.e., Zn atoms on S-sites) or possibly as interstitial Zn are responsible for the relative increase of the lattice parameter of commercially produced CVD ZnS.

McCloy, J. S.; Wolf, W.; Wimmer, E.; Zelinski, B. J.

2013-01-01

274

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.

275

Atomic resolution chemical bond analysis of oxygen in La2CuO4  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

276

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

277

Oxygen contaminants affecting on the electronic structures of the carbon nano tubes grown by rapid thermal chemical vapor deposition  

Microsoft Academic Search

Oxygen-related electronic structures of CNTs (carbon nanotubes) grown by rapid thermal chemical vapor deposition (RT-CVD) have been investigated by using partial electron yield near edge X-ray absorption spectroscopy (PEY-NEXAFS) and X-ray photoelectron spectroscopy (XPS). On the CNT surface with increased oxygen resulting from e-beam irradiation under the O2 gas environment, C k-edge NEXAFS spectra showed an increase of the oxygen-related

Kyuwook Ihm; Tai-Hee Kang; Dae Ho Lee; Ki-Jeong Kim; Bongsoo Kim; Ji Hoon Yang; Chong Yun Park

2006-01-01

278

Biomass Direct Chemical Looping Conversion in a Fluidized Bed Reactor with Natural Hematite as an Oxygen Carrier  

Microsoft Academic Search

Biomass direct chemical looping (BDCL) process has the potential to thermochemically convert biomass to hydrogen\\/synthesis gas and\\/or electricity with high efficiency and CO2 capture. BDCL gasification involves the use of an oxygen carrier which transfers oxygen from air to biomass to convert the biomass into synthesis gas, and the traditional gasifying agents, such as oxygen enriched air or high temperature

Fang He; Zhen Huang; Haibin Li; Zengli Zhao

2011-01-01

279

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 the principle design change of moving the iodine injectors closer to throat. Index Terms--Chemical lasers, gas lasers, iodine, laser appli- cations, laser materials-processing applications, lasers, nitrogen, oxygen

Carroll, David L.

280

LASERS: Highly efficient supersonic chemical oxygen --- iodine laser with a chlorine flow rate of 10 mmol s-1  

Microsoft Academic Search

An experimental parametric investigation was made of a compact supersonic chemical oxygen --- iodine laser. The output power of the laser was increased by displacing the point where iodine vapour was added to singlet oxygen from the subsonic to the transonic region of gas flow and by cooling of nitrogen. The output power was 200 W for a Mach number

M. V. Zagidullin; V. D. Nikolaev; M. I. Svistun; N. A. Khvatov; N. I. Ufimtsev

1997-01-01

281

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

SciTech Connect

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

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

1994-10-01

282

Interface redox engineering of Cu(In,Ga)Se 2 – based solar cells: oxygen, sodium, and chemical bath effects  

Microsoft Academic Search

The chemical effects of oxygenation of Cu(In,Ga)Se2 (CIGS) interfaces are analyzed and are shown to involve passivation of Se deficiencies and Cu removal. The former effect is beneficial at grain boundaries, but detrimental at the CdS\\/CIGS interface. The latter effect is purely detrimental. Na and chemical bath deposition (CBD) treatments are shown to isolate the ‘good’ oxygenation effect from the

Leeor Kronik; Uwe Rau; Jean-François Guillemoles; Dieter Braunger; Hans-Werner Schock; David Cahen

2000-01-01

283

Unveiling the Nature of the "Green Pea" Galaxies: Oxygen and Nitrogen Chemical Abundances  

NASA Astrophysics Data System (ADS)

We present recent results on the oxygen and nitrogen chemical abundances in the extremely compact, low-mass starburst galaxies at redshifts 0.1-0.3 usually referred to as "green pea" galaxies. We show that they are metal-poor galaxies (~1/5 solar) with lower oxygen abundances than star-forming galaxies of similar mass and N/O ratios unusually high for galaxies of the same metallicity. Recent, rapid, and massive inflows of cold gas, possibly coupled with enriched outflows from supernova winds, are used to explain the results. This is consistent with the known "pea" galaxy properties and suggest that these rare objects are experiencing a short and extreme phase in their evolution.

Amorín, R. O.; Pérez-Montero, E.; Vílchez, J. M.

2011-07-01

284

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

285

Time dependent chemical interactions of lithium, deuterium, and oxygen on lithium-coated graphite surfaces  

NASA Astrophysics Data System (ADS)

Lithium conditioning of plasma facing components has been used for particle control in fusion devices such as TFTR, CDX-U, FTU, T-11M, TJ-II and NSTX and has yielded improved plasma performance. A PMI probe has been installed on NSTX to provide an in-situ diagnostic for surface chemistry and deuterium retention measurements. Recent controlled laboratory experiments at Purdue University are investigating the chemical functionalities in lithiated graphite and the mechanism by which D is retained. XPS results show that Li reacts readily with residual oxygen in ATJ graphite, and immediately begins to intercalate into the substrate. Additionally, it has been found that Li-O and Li-C react to D proportional to the lithium thickness, suggesting a D saturation threshold. This work investigates the transient nature of the lithium and oxygen functionalities, their response to time varying D flux, and the implications to NSTX.

Taylor, C. N.; Allain, J. P.; Heim, B.; Skinner, C. H.; Kugel, H. W.; Kaita, R.; Roquemore, A. L.

2009-11-01

286

Preparation of biofilm electrode with Xanthomonas sp. and carbon nanotubes and the application to rapid biochemical oxygen demand analysis in high-salt condition.  

PubMed

A Xanthomonas sp. was isolated from the sludge on the drain outlet of a pharmaceutical factory. Then, the bacterium and carbon nanotubes (CNTs) were co-attached to an oxygen electrode for rapid analysis of biochemical oxygen demand (BOD). The response current was linear with BOD values in the range 10 to 300 mg/L for standard BOD solution with a response time of 35 seconds (R = 0.9994) and 20 to 580 mg/L for pharmaceutical wastewater with a response time < or =200 seconds (R = 0.9985), which means that this modified electrode might be used for online BOD analysis of pharmaceutical wastewater. Further studies revealed that the modified electrode can be used for BOD measurement in a high-salt condition. Also, the bacterium/CNTs biofilm can maintain its activity and good performance, even after being sealed and stored at 4 degrees C for 50 days. PMID:18751533

Chen, Jing; Yu, Zhiguo; Sun, Jinfeng; Jia, Jianbo; Li, Genxi

2008-08-01

287

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

288

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

289

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

290

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

291

On demand fusion and triggering of confined chemical reactions in femtoliter volume aqueous droplets controlled by interfacial tension  

NASA Astrophysics Data System (ADS)

Droplet-based microfluidic platforms offer many opportunities to confine chemical and biochemical reactants in discrete ultrasmall reaction volumes, and investigate the effects of increased confinement on reaction dynamics. Current state-of-the-art microfluidic sampling strategies for creating ultrasmall reaction volumes are predominately steady-state approaches, which result in difficulty in trapping reacting species with a well-defined time-zero for initiation of biochemical reactions in the confined space. This talk describes stepwise, on-demand generation and fusion of femtoliter aqueous droplets based on interfacial tension. Sub-millisecond reaction times from droplet fusion were demonstrated, as well as a reversible chemical toggle switch based on alternating fusion of droplets containing acidic or basic solution, monitored with the pH-dependent emission of fluorescein.

Collier, Pat; Jung, Seung-Yong; Retterer, Scott

2011-03-01

292

Pulsed chemical oxygen - iodine laser initiated by a transverse electric discharge  

SciTech Connect

A pulsed chemical oxygen - iodine laser with a volume production of atomic iodine in a pulsed transverse electric discharge is studied. An increase in the partial oxygen pressure was shown to increase the pulse energy with retention of the pulse duration. At the same time, an increase in the iodide pressure and the discharge energy shortens the pulse duration. Pulses with a duration of 6.5 {mu}s were obtained, which corresponds to a concentration of iodine atoms of 1.8 x 10{sup 15} cm{sup -3}. This concentration is close to the maximum concentration attained in studies of both cw and pulsed oxygen-iodine lasers. A specific energy output of 0.9 J litre{sup -1} and a specific power of 75 kW litre{sup -1} were obtained. The ways of increasing these parameters were indicated. It was found that SF{sub 6} is an efficient buffer gas favouring improvements in the energy pulse parameters. (lasers)

Vagin, Nikolai P; Yuryshev, Nikolai N [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2001-02-28

293

Electronic structure and chemical nature of oxygen dopant States in carbon nanotubes.  

PubMed

We performed low temperature photoluminescence (PL) studies on individual oxygen-doped single-walled carbon nanotubes (SWCNTs) and correlated our observations to electronic structure simulations. Our experiment reveals multiple sharp asymmetric emission peaks at energies 50-300 meV red-shifted from that of the E11 bright exciton peak. Our simulation suggests an association of these peaks with deep trap states tied to different specific chemical adducts. In addition, oxygen doping is also observed to split the E11 exciton into two or more states with an energy splitting <40 meV. We attribute these states to dark states that are brightened through defect-induced symmetry breaking. While the wave functions of these brightened states are delocalized, those of the deep-trap states are strongly localized and pinned to the dopants. These findings are consistent with our experimental observation of asymmetric broadening of the deep trap emission peaks, which can result from interaction between pinned excitons and one-dimensional phonons. Exciton pinning also increases the sensitivity of the deep traps to the local dielectric environment, leading to a large inhomogeneous broadening. Observations of multiple spectral features on single nanotubes indicate the possibility of different chemical adducts coexisting on a given nanotube. PMID:25265272

Ma, Xuedan; Adamska, Lyudmyla; Yamaguchi, Hisato; Yalcin, Sibel Ebru; Tretiak, Sergei; Doorn, Stephen K; Htoon, Han

2014-10-28

294

On the Oxygen and Nitrogen Chemical Abundances and the Evolution of the "Green Pea" Galaxies  

NASA Astrophysics Data System (ADS)

We have investigated the oxygen and nitrogen chemical abundances in extremely compact star-forming galaxies (SFGs) with redshifts between ~0.11 and 0.35, popularly referred to as "green peas." Direct and strong-line methods sensitive to the N/O ratio applied to their Sloan Digital Sky Survey (SDSS) spectra reveal that these systems are genuine metal-poor galaxies, with mean oxygen abundances ~20% solar. At a given metallicity these galaxies display systematically large N/O ratios compared to normal galaxies, which can explain the strong difference between our metallicities measurements and previous ones. While their N/O ratios follow the relation with stellar mass of local SFGs in the SDSS, we find that the mass-metallicity relation of the "green peas" is offset gsim0.3 dex to lower metallicities. We argue that recent interaction-induced inflow of gas, possibly coupled with a selective metal-rich gas loss, driven by supernova winds, may explain our findings and the known galaxy properties, namely high specific star formation rates, extreme compactness, and disturbed optical morphologies. The "green pea" galaxy properties seem to be uncommon in the nearby universe, suggesting a short and extreme stage of their evolution. Therefore, these galaxies may allow us to study in great detail many processes, such as starburst activity and chemical enrichment, under physical conditions approaching those in galaxies at higher redshifts.

Amorín, Ricardo O.; Pérez-Montero, Enrique; Vílchez, J. M.

2010-06-01

295

Biological and chemical interaction of oxygen on the reduction of Fe(III)EDTA in a chemical absorption-biological reduction integrated NOx removal system.  

PubMed

A promising chemical absorption-biological reduction integrated process has been proposed. A major problem of the process is oxidation of the active absorbent, ferrous ethylenediaminetetraacetate (Fe(II)EDTA), to the ferric species, leading to a significant decrease in NO removal efficiency. Thus the biological reduction of Fe(III)EDTA is vitally important for the continuous NO removal. Oxygen, an oxidizing agent and biological inhibitor, is typically present in the flue gas. It can significantly retard the application of the integrated process. This study investigated the influence mechanism of oxygen on the regeneration of Fe(II)EDTA in order to provide insight on how to eliminate or decrease the oxygen influence. The experimental results revealed that the dissolved oxygen and Fe(III)EDTA simultaneously served as electron acceptor for the microorganism. The Fe(III)EDTA reduction activity were directly inhibited by the dissolved oxygen. When the bioreactor was supplied with 3% and 8% oxygen in the gas phase, the concentration of initial dissolved oxygen in the liquid phase was 0.28 and 0.68 mg l(-1). Correspondingly, the instinct Fe(III)EDTA reduction activity of the microorganism determined under anoxic condition in a rotation shaker decreased from 1.09 to 0.84 and 0.49 mM h(-1). The oxidation of Fe(II)EDTA with dissolved oxygen prevented more dissolved oxygen access to the microorganism and eased the inhibition of dissolved oxygen on the microorganisms. PMID:21931973

Zhang, Shi-Han; Shi, Yao; Li, Wei

2012-03-01

296

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

Federal Register 2010, 2011, 2012, 2013

...designs. Relocating the supplemental oxygen supply can also complicate activating the oxygen flow, since that is generally accomplished...requirements of Sec. 25.1443, Minimum mass flow of supplemental oxygen. E. Related Actions As...

2013-01-09

297

The chemical action of oxygen on a heater during growth of refractory oxide crystals from melt  

SciTech Connect

The behavior of the W-O{sub 2} system has been investigated at 2400 K in the pressure range from 1 to 1 x 10{sup -5} bar. The chemical composition of the solid and vapor phases for the ratio W: O{sub 2} = 1: 1 was calculated by minimizing the Gibbs free energy. It is shown that the only solid phase in the system is metallic tungsten (0.333-0.355 mol), whereas trioxide WO{sub 3} dominates in the vapor phase; its concentration may reach 99%. It is concluded that providing an inert atmosphere in the growth chamber with a pressure of 1 bar decreases the concentration of atomic and molecular oxygen in the vapor phase and decreases its effect on the tungsten heater.

Kostomarov, D. V.; Bagdasarov, Kh. S., E-mail: bagdasarov@ns.crys.ras.ru; Kobzareva, S. A.; Antonov, E. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2009-01-15

298

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

SciTech Connect

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

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

2009-03-15

299

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

300

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

Microsoft Academic Search

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

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

2008-01-01

301

Chemical-looping combustion of coal with metal oxide oxygen carriers  

SciTech Connect

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

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

2009-08-15

302

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

303

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

PubMed Central

We have analyzed the possibility that chemical signaling does not entirely account for the effect of water deficit on the maize (Zea mays L.) leaf elongation rate (LER) under high evaporative demand. We followed time courses of LER (0.2-h interval) and spatial distribution of elongation rate in leaves of either water-deficient or abscisic acid (ABA)-fed plants subjected to varying transpiration rates in the field, in the greenhouse, and in the growth chamber. At low transpiration rates the effect of the soil water status on LER was related to the concentration of ABA in the xylem sap and could be mimicked by feeding artificial ABA. Transpiring plants experienced a further reduction in LER, directly linked to the transpiration rate or leaf water status. Leaf zones located at more than 20 mm from the ligule stopped expanding during the day and renewed expansion during the night. Neither ABA concentration in the xylem sap, which did not appreciably vary during the day, nor ABA flux into shoots could account for the effect of evaporative demand. In particular, maximum LER was observed simultaneously with a minimum ABA flux in the droughted plants, but with a maximum ABA flux in ABA-fed plants. All data were interpreted as the superposition of two additive effects: the first involved ABA signaling and was observed during the night and in ABA-fed plants, and the second involved the transpiration rate and was observed even in well-watered plants. We suggest that a hydraulic signal is the most likely candidate for this second effect. PMID:12223750

Salah, HBH.; Tardieu, F.

1997-01-01

304

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

305

The I2 dissociation mechanisms in the chemical oxygen-iodine laser revisited.  

PubMed

The recently suggested mechanism of I(2) dissociation in the chemical oxygen-iodine laser (COIL) [K. Waichman, B. D. Barmashenko, and S. Rosenwaks, J. Appl. Phys. 106, 063108 (2009); and J. Chem. Phys. 133, 084301 (2010)] was largely based on the suggestion of V. N. Azyazov, S. Yu. Pichugin, and M. C. Heaven [J. Chem. Phys. 130, 104306 (2009)] that the vibrational population of O(2)(a) produced in the chemical generator is high enough to play an essential role in the dissociation. The results of model calculations based on this mechanism agreed very well with measurements of the small signal gain g, I(2) dissociation fraction F, and temperature T in the COIL. This mechanism is here revisited, following the recent experiments of M. V. Zagidullin [Quantum Electron. 40, 794 (2010)] where the observed low population of O(2)(b, v = 1) led to the conclusion that the vibrational population of O(2)(a) at the outlet of the generator is close to thermal equilibrium value. This value corresponds to a very small probability, ?0.05, of O(2)(a) energy pooling to the states O(2)(X,a,b, v > 0). We show that the dissociation mechanism can reproduce the experimentally observed values of g, F, and T in the COIL only if most of the energy released in the processes of O(2)(a) energy pooling and O(2)(b) quenching by H(2)O ends up as vibrational energy of the products, O(2)(X,a,b), where the vibrational states v = 2 and 3 are significantly populated. We discuss possible reasons for the differences in the suggested vibrational population and explain how these differences can be reconciled. PMID:22755574

Waichman, K; Barmashenko, B D; Rosenwaks, S

2012-06-28

306

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

E-print Network

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

Azad, Abdul-Majeed

307

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

308

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

309

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

SciTech Connect

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

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

2010-05-15

310

Role of N2 molecules in pulse discharge production of I atoms for a pulsed chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

A pulsed electric discharge is the most effective means to turn chemical oxygen-iodine laser (COIL) operation into the pulse mode by fast production of iodine atoms. Experimental studies and numerical simulations are performed on a pulsed COIL initiated by an electric discharge in a mixture CF3I : N2 : O2(3X) : O2(a 1?g) flowing out of a chemical singlet oxygen generator. A transverse pulsed discharge is realized at various iodide pressures. The model comprises a system of kinetic equations for neutral and charged species, the electric circuit equation, the gas thermal balance equation and the photon balance equation. Reaction rate coefficients for processes involving electrons are repeatedly re-calculated by the electron Boltzmann equation solver when the plasma parameters are changed. The processes accounted for in the Boltzmann equation include direct and stepwise excitation and ionization of atoms and molecules, dissociation of molecules, electron attachment processes, electron-ion recombination, electron-electron collisions and second-kind collisions. The last processes are particularly important because of a high singlet oxygen concentration in gas flow from the singlet oxygen chemical generator. A conclusion is drawn about satisfactory agreement between the theory and the experiment.

Kochetov, I. V.; Napartovich, A. P.; Vagin, N. P.; Yuryshev, N. N.

2011-09-01

311

Determination of singlet-oxygen generator efficiency on a 10kW class supersonic chemical oxygen-iodine laser (RADICL)  

Microsoft Academic Search

With the advent of the Air Force Airborne Laser program, the emphasis of chemical oxggen-iodine laser (COIL) research has shifted toward improving the overall efficiency. A key component of the COIL is the singlet-oxygen generator (SOG). To assess the efficiency of the SOG, an accurate method of determining the yield of O2(a1 ?g), [O2(a1?g )]\\/[O2(total)] where [O2(total)]=[O2 (a1?g)]+[O2(X3 ?g-)], has

Kip R. Kendrick; Charles A. Helms; Brian G. Quillen

1999-01-01

312

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

313

CARBON COATED (CARBONOUS) CATALYST IN EBULLATED BED REACTOR FOR PRODUCTION OF OXYGENATED CHEMICALS FROM SYNGAS/CO2  

SciTech Connect

There are a number of exothermic chemical reactions which might benefit from the temperature control and freedom from catalyst fouling provided by the ebullated bed reactor technology. A particularly promising area is production of oxygenated chemicals, such as alcohols and ethers, from synthesis gas, which can be economically produced from coal or biomass. The ebullated bed operation requires that the small-diameter ({approx}1/32 inch) catalyst particles have enough mechanical strength to avoid loss by attrition. However, all of the State Of The Art (SOTA) catalysts and advanced catalysts for the purpose are low in mechanical strength. The patented carbon-coated catalyst technology developed in our laboratory converts catalyst particles with low mechanical strength to strong catalysts suitable for ebullated bed application. This R&D program is concerned with the modification on the mechanical strength of the SOTA and advanced catalysts so that the ebullated bed technology can be utilized to produce valuable oxygenated chemicals from syngas/CO{sub 2} efficiently and economically. The objective of this R&D program is to study the technical and economic feasibility of selective production of high-value oxygenated chemicals from synthesis gas and CO{sub 2} mixed feed in an ebullated bed reactor using carbon-coated catalyst particles.

Peizheng Zhou

2001-10-26

314

Determination of chemical oxygen demand using flow injection with Ti\\/TiO2 electrode prepared by laser anneal  

Microsoft Academic Search

The method of Ti\\/TiO2 photoelectrode preparation using laser-assisted sol-gel is introduced. The prepared TiO2 film is investigated by x-ray diffraction (XRD), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and amperometry, and it illustrates that the TiO2 film mainly consists of anatase TiO2 nanoparticles on its surface and exhibits a superior photocatalytic activity when compared with that calcined by oven.

Jiaqing Li; Lei Zheng; Luoping Li; Guoyue Shi; Yuezhong Xian; Litong Jin

2007-01-01

315

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

316

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

317

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

318

Mechanism of dark decomposition of iodine donor in the active medium of a pulsed chemical oxygen - iodine laser  

SciTech Connect

A scheme is proposed that describes the dark decomposition of iodide - the donor of iodine - and the relaxation of singlet oxygen in the chlorine-containing active medium of a pulsed chemical oxygen - iodine laser (COIL). For typical compositions of the active media of pulsed COILs utilising CH{sub 3}I molecules as iodine donors, a branching chain reaction of the CH{sub 3}I decomposition accompanied by the efficient dissipation of singlet oxygen is shown to develop even at the stage of filling the active volume. In the active media with CF{sub 3}I as the donor, a similar chain reaction is retarded due to the decay of CF{sub 3} radicals upon recombination with oxygen. The validity of this mechanism is confirmed by a rather good agreement between the results of calculations and the available experimental data. The chain decomposition of alkyliodides accompanied by an avalanche production of iodine atoms represents a new way of efficient chemical production of iodine for a COIL. (active media)

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

2002-06-30

319

Chemical influences on the luminescence of ruthenium diimine complexes and its response to oxygen  

Microsoft Academic Search

Different luminescent, hydrophillic ruthenium diimine cationic complexes are rendered soluble in the hydrophobic medium of a plasticised polymer through ion-pair coupling with a hydrophobic anion, such as tetraphenyl borate. Based on this approach, a number of different oxygen sensitive films, i.e., luminescent, thin plastic films which respond to oxygen — the latter quenches the luminescence — were prepared, using the

Andrew Mills; Francine Collé Williams

1997-01-01

320

An Inexpensive Electrode and Cell for Measurement of Oxygen Uptake in Chemical and Biochemical Systems.  

ERIC Educational Resources Information Center

The continuous measurement of oxygen consumption in an enzymatic reaction is a frequent experimental fact and extremely important in the enzymatic activity of oxygenase. An electrochemical system, based on a polarographic method, has been developed to monitor the oxygen uptake. The system developed and electrode used are described. (JN)

Brunet, Juan E.; And Others

1983-01-01

321

Parametric study of the gain in a small scale, grid nozzle, supersonic chemical oxygen-iodine laser  

Microsoft Academic Search

We report on experiments and model calculations of the small-signal gain and the gain profile in a grid nozzle supersonic chemical oxygen-iodine laser. The laser has a 5-cm long active medium and the gain is measured using a diode laser. The calculations are based on a simple one-dimensional semiempirical model previously developed in our laboratory. The gain is studied as

E. Lebiush; B. D. Barmashenko; A. Elior; S. Rosenwaks

1995-01-01

322

The chemical oxygen iodine laser in the presence of a magnetic field. I. Gain measurements and polarization effects  

Microsoft Academic Search

For pt.II, see ibid., vol.29, no.3, p.944-53 (1993). The results from a combined experimental\\/theoretical investigation of the influence of a magnetic field on the gain and polarization in a supersonic chemical oxygen laser are described. Theoretical calculations are presented for the normalized gain as a function of magnetic field strength and are shown to be in good agreement with the

G. D. Hager; D. Kopf; B. S. Hunt; B. Anderson; C. Woolhiser; P. Crowell

1993-01-01

323

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

Microsoft Academic Search

This paper describes the development of a simplified saturation model (SSM) for predicting power extraction from a chemical oxygen-iodine laser (COIL). Using the Fabry-Perot gain saturation assumption, analytic expressions for COIL extraction efficiency are presented for both constant-density and variable-density cavity conditions. The model treats mirror scattering, nonsaturable distributed losses, and diffractive losses from the mode-limiting aperture and is shown

G. D. Hager; C. A. Helms; K. A. Truesdell; D. Plummer; J. Erkkila; P. Crowell

1996-01-01

324

Effect of temperature on reduction reactivity of oxygen carrier particles in a fixed bed chemical-looping combustor  

Microsoft Academic Search

In a chemical-looping combustor (CLC), gaseous fuel is oxidized by metal oxide particle, e.g. oxygen carrier, in a reduction\\u000a reactor (combustor), and the greenhouse gas CO2 is separated from the exhaust gases during the combustion. In this study, NiO\\/bentonite particle was examined on the basis\\u000a of reduction reactivity, carbon deposition during reduction, and NOx formation during oxidation. Reactivity data for

Ho-Jung Ryu; Dal-Hee Bae; Gyoung-Tae Jin

2003-01-01

325

Chemical flame inhibition using molecular beam mass spectrometry bromotrifluoromethane in low pressure methane--oxygen--argon flames  

Microsoft Academic Search

A molecular beam-mass spectrometer-low pressure flat flame apparatus has been constructed for the purpose of examining the chemical microstructure of normal methane-oxygen-argon flames and those inhibited with Halon extinguishants. Details of construction and performance of this apparatus and of related flame temperature measurements are given. Particular attention is paid to the empirical characterization of the perturbation to the flame caused

J. C. Biordi; C. P. Lazzara; J. F. Papp

1973-01-01

326

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

327

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

328

Metabolic Response of Perfused Livers to Various Oxygenation Conditions  

E-print Network

in perfusate without RBCs was just sufficient to meet the average oxygen demand of the liver but wouldARTICLE Metabolic Response of Perfused Livers to Various Oxygenation Conditions Mehmet A. Orman,1 Marianthi G. Ierapetritou,1 Ioannis P. Androulakis,1,2 Francois Berthiaume2 1 Department of Chemical

Androulakis, Ioannis (Yannis)

329

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.

330

Chemical Modification of a Tetrapyrrole-Type Photosensitizer: Tuning Application and Photochemical Action beyond the Singlet Oxygen Channel.  

PubMed

Reactive oxygen species (ROS) formed by light activated photosensitizers (PSs) are the hallmark of photodynamic therapy (PDT). It is generally accepted that commonly used PSs generate singlet oxygen ((1)O2) as the cell-toxic species via type II photosensitization. We explored here the consequences of chemical modification and the influence of the net charge of a cationic tetrahydroporphyrin derivative (THPTS) relative to the basic molecular structure on the red-shift of absorption, solubility, mechanistic features, and photochemical as well as cell-toxic activity. In order to shed light into the interplay between chemical modification driven intra- and intermolecular photochemistry, intermolecular interaction, and function, a number of different spectroscopic techniques were employed and our experimental studies were accompanied by quantum chemical calculations. Here we show that for THPTS neither (1)O2 nor other toxic ROS (superoxide and hydroxyl radicals) are produced directly in significant quantities in aqueous solution (although the formation of singlet oxygen is energetically feasible and as such observed in acetonitrile). Nevertheless, the chemically modified tetrapyrrole photosensitizer displays efficient cell toxicity after photoexcitation. The distribution and action of THPTS in rat bladder caricinoma AY27 cells measured with fluorescence lifetime imaging microscopy shows accumulation of the THPTS in lysosomes and efficient cell death after irradiation. We found evidence that THPTS in water works mainly via the type I mechanism involving the reduction rather than oxidation of the excited triplet state THPTS(T1) via efficient electron donors in the biosystem environment and subsequent electron transfer to produce ROS indirectly. These intriguing structure-activity relationships may indeed open new strategies and avenues in developing PSs and PDT in general. PMID:25207950

Riyad, Yasser M; Naumov, Sergej; Schastak, Stanislaw; Griebel, Jan; Kahnt, Axel; Häupl, Tilmann; Neuhaus, Jochen; Abel, Bernd; Hermann, Ralf

2014-10-01

331

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

SciTech Connect

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

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

2010-05-15

332

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

333

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

334

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

335

Diode-laser-based absorption spectroscopy diagnostics of a jet-type O2(1?) generator for chemical oxygen-iodine lasers  

Microsoft Academic Search

Using diode-laser-based diagnostics, O2(1?) yield and water vapor fraction were measured at the exit of a jet-type singlet oxygen generator (JSOG) for a chemical oxygen-iodine laser (COIL). Chlorine utilization and gas temperature at the generator exit were also measured, simultaneously. For conditions corresponding to the maximum chemical efficiency of the supersonic COIL energized by the JSOG, the O2(1?) yield, water

D. Furman; B. D. Barmashenko; S. Rosenwaks

1999-01-01

336

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

337

Mechanism of pulse discharge production of iodine atoms from CF3I molecules for a chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The pulsed chemical oxygen-iodine laser (COIL) development is aimed at many new applications. Pulsed electric discharge is most effective in turning COIL operation into the pulse mode by instant production of iodine atoms. A numerical model is developed for simulations of the pulsed COIL initiated by an electric discharge. The model comprises a system of kinetic equations for neutral and charged species, electric circuit equation, gas thermal balance equation and the photon balance equation. Reaction rate coefficients for processes involving electrons are found by solving the electron Boltzmann equation, which is re-calculated in a course of computations when plasma parameters changed. The processes accounted for in the Boltzmann equation include excitation and ionization of atoms and molecules, dissociation of molecules, electron attachment processes, electron-ion recombination, electron-electron collisions, second-kind collisions and stepwise excitation of molecules. The last processes are particularly important because of a high singlet oxygen concentration in gas flow from the singlet oxygen chemical generator. Results of numerical simulations are compared with experimental laser pulse waveforms. It is concluded that there is satisfactory agreement between theory and the experiment. The prevailing mechanism of iodine atom formation from the CF3I donor in a very complex kinetic system of the COIL medium under pulse discharge conditions, based on their detailed numerical modelling and by comparing these results both with experimental results of other authors and their own experiments, is established. The dominant iodine atom production mechanism for conditions under study is the electron-impact dissociation of CF3I molecules. It was proved that in the conditions of the experiment the secondary chemical reactions with O atoms play an insignificant role.

Kochetov, I. V.; Napartovich, A. P.; Vagin, N. P.; Yuryshev, N. N.

2009-03-01

338

Safety in the Chemical Laboratory: Handling of Oxygen in Research Experiments.  

ERIC Educational Resources Information Center

Examines some of the considerations involved in setting up a typical oxygen/organic reaction. These considerations (including protection for personnel/equipment, adequate ventilation, reactor design, maximum reactor charge, operating procedures, and others) influence how the reaction is to be conducted and what compromises the scientist must…

Burnett, R. J.; Cole, J. E., Jr.

1985-01-01

339

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

Microsoft Academic Search

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

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

2010-01-01

340

Chemical diffusion of oxygen in dense, textured (Bi,Pb) 2Sr 2Ca 2Cu 3O x  

NASA Astrophysics Data System (ADS)

Dense polycrystalline (Bi,Pb) 2Sr 2Ca 2Cu 3O y specimens were fabricated by sinter forging. The specimens exhibited excellent phase purity and strong texture of c-axes, which were preferentially aligned parallel to the forging direction. The chemical diffusion coefficient of oxygen, D˜, measured in pure O 2 could be represented as D˜ab?1.78×10 -3 exp(-0.96 eV/ kT), where the subscript ab refers to diffusion within the a- b-plane. The measurements suggested that D˜ab? D˜c, where the subscript c refers to diffusion in the c-direction.

Park, J.-H.; Goretta, K. C.; Murayama, Norimitsu

1999-02-01

341

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

342

CARBON COATED (CARBONOUS) CATALYST IN EBULLATED BED REACTOR FOR PRODUCTION OF OXYGENATED CHEMICALS FROM SYNGAS/CO2  

SciTech Connect

This report summarizes the work completed under DOE's Support of Advanced Fuel Research program, Contract No. DE-FG26-99FT40681. The contract period was October 2000 through September 2002. This R&D program investigated the modification of the mechanical strength of catalyst extrudates using Hydrocarbon Technologies, Inc. (HTI) carbon-coated catalyst technology so that the ebullated bed technology can be utilized to produce valuable oxygenated chemicals from syngas/CO{sub 2} efficiently and economically. Exothermic chemical reactions benefit from the temperature control and freedom from catalyst fouling provided by the ebullated bed reactor technology. The carbon-coated extrudates prepared using these procedures had sufficient attrition resistance and surface area for use in ebullated bed operation. The low cost of carbon coating makes the carbon-coated catalysts highly competitive in the market of catalyst extrudates.

Peizheng Zhou

2002-12-30

343

The Effects of Oxygen Plasma on the Chemical Composition and Morphology of the Ru Capping Layer of the Extreme Ultraviolet (EUV) Mask Blanks  

SciTech Connect

Contamination removal from extreme ultraviolet (EUV) mask surfaces is one of the most important aspects to improve reliability for the next generation of EUV lithography. We report chemical and morphological changes of the ruthenium (Ru) mask surface after oxygen plasma treatment using surface sensitive analytical methods: X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and transmission electron microscopy (TEM). Chemical analysis of the EUV masks shows an increase in the subsurface oxygen concentration, Ru oxidation and surface roughness. XPS spectra at various photoelectron takeoff angles suggest that the EUV mask surface was covered with chemisorbed oxygen after oxygen plasma treatment. It is proposed that the Kirkendall effect is the most plausible mechanism that explains the Ru surface oxidation. The etching rate of the Ru capping layer by oxygen plasma was estimated to be 1.5 {+-} 0.2 {angstrom}/min, based on TEM cross sectional analysis.

Belau, Leonid; Park, Jeong Y.; Liang, Ted; Somorjai, Gabor A.

2008-06-07

344

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

E-print Network

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

Jester-Weinstein, Jack (Jack L.)

2013-01-01

345

Detection of vibrationally excited O{sub 2} in the active medium of a chemical oxygen - iodine laser  

SciTech Connect

The presence of vibrationally excited oxygen in the active medium of a chemical oxygen - iodine laser is discovered using the emission technique. Using the analysis of the luminescence spectra of oxygen molecules on O{sub 2}(b{sup 1{Sigma}}{sub g}{sup +}, v=i){yields}O{sub 2}(X{sup 3{Sigma}}{sub g}{sup -}, v'=i) (i=0, 1, 2) electronic vibrational - rotational transitions, it is shown that {approx}22 % of O{sub 2}(b{sup 1{Sigma}}{sub g}{sup +}) molecules are at the first vibrational level and {approx}10 % are at the second one. Moreover, due to the fast EE energy exchange, a mean number of vibrational quanta per one molecule in each of the O{sub 2}(X{sup 3{Sigma}}{sub g}{sup -}), O{sub 2}(a{sup 1{Delta}}{sub g}) and O{sub 2}(b{sup 1{Sigma}}{sub g}{sup +}) components is approximately the same and amounts to 30 % - 40 %. (active media. lasers)

Azyazov, V N; Antonov, I O; Pichugin, S Yu; Safonov, V S; Svistun, M I; Ufimtsev, N I [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2003-09-30

346

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

347

Chemical bonding of oxygen in intergranular amorphous layers in high-purity {beta}-SiC ceramics  

SciTech Connect

An amorphous intergranular layer, 0.4 nm thick, is found by high-resolution transmission electron microscopy of {beta}-SiC ceramics fabricated by the HIP glass-encapsulation technique without the use of additives. The intergranular layer is found to contain oxygen, which may also be present in the SiC grains near the grain boundary. The mean composition of the intergranular layer is determined to be SiO{sub 010{+-}0.01}C{sub 0.93{+-}0.04}, whose C/O ratio is close to a hypothetical Si-oxycarbide stoichiometry. Electron energy loss spectroscopy shows that both the Si-L{sub 23} and O-K edges from the intergranular layer are distinctive compared to those of SiC and/or SiO{sub 2}. This provides direct evidence of the presence of oxygen in a chemical environment different to that in glassy SiO{sub 2}, that can also be found in the intergranular layer. First principle calculations by the DV-X{alpha} method using an interface model cluster, satisfactorily reproduce the chemical shifts of the energy loss near edge structure (ELNES) for both the Si-L{sub 23} and O-K edges.

Kaneko, K. [JST, Atsuta, Nagoya (Japan). Ceramics Superplasticity Project] [JST, Atsuta, Nagoya (Japan). Ceramics Superplasticity Project; Yoshiya, M.; Tanaka, I. [Kyoto Univ., Sakyo, Kyoto (Japan)] [Kyoto Univ., Sakyo, Kyoto (Japan); Tsurekawa, S. [Tohoku Univ., Aoba, Sendai (Japan). Dept. of Machine Intelligence and System Engineering] [Tohoku Univ., Aoba, Sendai (Japan). Dept. of Machine Intelligence and System Engineering

1999-03-10

348

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

PubMed

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

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

2014-07-01

349

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

SciTech Connect

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

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

2005-05-15

350

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

351

The chemical character and behaviour of phosphorus in poorly oxygenated sediments from open sea to organic-rich inner bay in the Baltic Sea  

Microsoft Academic Search

The chemical composition and vertical distribution of phosphorus (P) in poorly oxygenated sediments in a continuum extending\\u000a from the open Baltic Sea towards an organic-rich inner bay were characterized by sequential extraction to examine the potential\\u000a for release of sediment P. The chemical composition of P was related to chemical and physical characteristics of the sediments\\u000a and the chemistry of

K. Lukkari; M. Leivuori; A. Kotilainen

2009-01-01

352

Lasing operation of chemical oxygen-iodine laser without water-vapor trap  

SciTech Connect

cw laser action from chemically pumped iodine atoms was achieved without a cold trap to freeze water vapor. An alkaline solution of H/sub 2/O/sub 2/ was circulated in a porous pipe generator, which made it possible to cool the solution externally. A lasing operation time of about 100 s with a constant output power of 5 W was obtained.

Takehisa, K.; Kikuchi, T.; Uchiyama, T.

1988-03-01

353

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

PubMed

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

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

2014-07-15

354

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

SciTech Connect

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

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

2010-03-15

355

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

356

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

SciTech Connect

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

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

2010-10-22

357

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

358

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

Microsoft Academic Search

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

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

2009-01-01

359

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

Microsoft Academic Search

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

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

2009-01-01

360

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

NASA Technical Reports Server (NTRS)

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

Carson, G. T., Jr.

1974-01-01

361

Chemical bonding between uranium and oxygen in U 6+-containing compounds  

NASA Astrophysics Data System (ADS)

Electronic parameters of a suite of hexavalent uranium compounds measured with X-ray photoelectron spectroscopy (XPS) have been collected. The binding energy difference, ?BE = BE (O 1s) - BE (U 4f 7/2), was used to characterize the valence electron transfer on the formation of the U-O bonds. The chemical bonding effects were considered on the basis of published structural and XPS data for U 6+-bearing compounds. An empirical relationship is obtained between ?BE and the mean U-O bond distance, L(U-O).

Atuchin, Victor V.; Zhang, Zhaoming

2012-01-01

362

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

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

363

The oxygen-18 isotope approach for measuring aquatic metabolism in high-productivity waters  

E-print Network

respiration and chemical O2 demand but excluding other respiration reactions such as denitrification). ManyThe oxygen-18 isotope approach for measuring aquatic metabolism in high-productivity waters Craig R carbon, oxygen, and nutrient processing on water- shed scales (Mulholland et al. 1997; Sabater et al

364

The K(C) channel in the cbb3-type respiratory oxygen reductase from Rhodobacter capsulatus is required for both chemical and pumped protons.  

PubMed

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

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

2014-05-01

365

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, Gulgez Gokce; Gennis, Robert B.; Daldal, Fevzi

2014-01-01

366

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

367

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

SciTech Connect

The expression of manganese peroxidase (MnP) in nitrogen-limited cultures of the lignin-degrading fungus Phanerochaete chrysosporium is regulated at the level of gene transcription by H{sub 2}O{sub 2} and various chemicals, including ethanol, sodium arsenite, and 2,4-dichlorophenol, as well as by Mn(II) and heat shock. Northern (RNA) blot analysis demonstrates that the addition of 1.0 mM H{sub 2}O{sub 2} to 5-day-old cultures grown in the absence of Mn results in the appearance of mnp mRNA within 15 min. Higher levels of mnp mRNA are obtained with simultaneous induction by Mn and H{sub 2}O{sub 2} than with H{sub 2}O{sub 2} alone. Although neither MnP activity nor associated protein is detectable in H{sub 2}O{sub 2}-induced cultures grown in the absence of Mn, simultaneous induction with Mn and H{sub 2}O{sub 2} results in a 1.6-fold increase in MnP activity compared with the MnP activity resulting resulting from Mn induction alone. In the presence of Mn, purging of low-nitrogen cultures with 100% O{sub 2}, in contrast to incubation under air, results in an increase in the accumulation of mnp mRNA and a 13-fold increase in MnP activity on day 5. However, in contrast to the effects of H{sub 2}O{sub 2} and heat shock, O{sub 2} purging of Mn-deficient cultures results in negligible accumulation of mnp mRNA. 48 refs., 6 figs.

Li, D.; Alic, M.; Brown, J.A.; Gold, M.H. [Oregon Graduate Institute of Science and Technology, Portland, OR (United States)

1995-01-01

368

Low dissolved oxygen sludge bulking in sequencing batch reactors  

Microsoft Academic Search

In this paper, the effect of aeration rate on sludge bulking in sequencing batch reactors is considered. Cycles of 8?h, including 6?h aeration period, were applied. Raw wastewater with chemical oxygen demand equal 350?±?20?mg\\/l was prepared using dried confectionery milk and tap water. Standard oxygen transfer efficiency equation in test condition was defined as y?=?1.24981ln(x)?+?13.86231. In low aeration rates that

S. H. Hashemi; A. A. Azimi; A. Torabian; G. Nabi Bidhendi; R. Mahmoodkhani

2005-01-01

369

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

SciTech Connect

A volume self-sustained discharge (VSD) in iodides (C{sub 3}H{sub 7}I, C{sub 4}H{sub 9}I) and in their mixtures with SF{sub 6}, N{sub 2}, and O{sub 2} in the presence of small-scale inhomogeneities on the cathode surface is shown to develop in the form of a self-initiating volume discharge (SIVD), i.e., a volume discharge without any preionisation including discharge gaps with a strong edge enhancement of the electric field. Additions of SF{sub 6} or N{sub 2} to the iodides improves the stability and homogeneity of the SIVD, while adding up to 300 % (relative to the partial iodide pressure) of O{sub 2} to these mixtures has only an insignificant effect on the discharge stability. The possibility of SIVD initiation was modelled experimentally in a 1.5-L discharge volume. For the C{sub 4}H{sub 9}I:O{sub 2}:SF{sub 6}=0.083:0.25:0.67 mixture at a pressure of 72 Torr, the specific energy input into the discharge plasma ranged up to 130 J L{sup -1} in this geometry. A conclusion was drawn that the SIVD is promising for the production of atomic iodine in the pulsed and repetitively pulsed operating regimes of a chemical oxygen - iodine laser. (lasers)

Belevtsev, A A [Institute for High Energy Densities, Associated Institute for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation); Kazantsev, S Yu; Saifulin, A V; Firsov, K N [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2003-06-30

370

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

NASA Astrophysics Data System (ADS)

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 2O 4/Na 2CO 3/Na(Mn 1/3Fe 2/3)O 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 1-xMn 1/3Fe 2/3O 2-? phases were observed together with the expected MnFe 2O 4/Na 2CO 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.

Seralessandri, L.; Bellusci, M.; Alvani, C.; La Barbera, A.; Padella, F.; Varsano, F.

2008-08-01

371

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 of moving the iodine injectors closer to throat. 1. Introduction Lasers made their debut for materials, HF/DF and the chemical oxygen-iodine laser (COIL) [2,3]. Of these other laser technologies, COIL

Carroll, David L.

372

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

373

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

374

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

375

Kinetic-fluid dynamics modeling of I{sub 2} dissociation in supersonic chemical oxygen-iodine lasers  

SciTech Connect

The mechanism of I{sub 2} dissociation in supersonic chemical oxygen-iodine lasers (COILs) is studied applying kinetic-fluid dynamics modeling, where pathways involving the excited species I{sub 2}(X {sup 1}SIGMA{sub g}{sup +},10<=v<25), I{sub 2}(X {sup 1}SIGMA{sub g}{sup +},25<=v<=47), I{sub 2}(A{sup '} {sup 3}PI{sub 2u}), I{sub 2}(A {sup 3}PI{sub 1u}), O{sub 2}(X {sup 3}SIGMA{sub g}{sup -},v), O{sub 2}(a {sup 1}DELTA{sub g},v), O{sub 2}(b {sup 1}SIGMA{sub g}{sup +},v), and I({sup 2}P{sub 1/2}) as intermediate reactants are included. The gist of the model is adding the first reactant and reducing the contribution of the second as compared to previous models. These changes, recently suggested by Azyazov, et al. [J. Chem. Phys. 130, 104306 (2009)], significantly improve the agreement with the measurements of the gain in a low pressure supersonic COIL for all I{sub 2} flow rates that have been tested in the experiments. In particular, the lack of agreement for high I{sub 2} flow rates, which was encountered in previous models, has been eliminated in the present model. It is suggested that future modeling of the COIL operation should take into account the proposed contribution of the above mentioned reactants.

Waichman, K. [Department of Physics, NRCN, P.O. Box 9001, Beer Sheva 89140 (Israel); Barmashenko, B. D.; Rosenwaks, S. [Department of Physics, Ben-Gurion University of the Negev, Beer Sheva 84105 (Israel)

2009-09-15

376

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

377

Separation of aromatic-carbon 13C NMR signals from di-oxygenated alkyl bands by a chemical-shift-anisotropy filter  

Microsoft Academic Search

Selection of alkyl-carbon and suppression of aromatic-carbon 13C nuclear magnetic resonance (NMR) signals has been achieved by exploiting the symmetry-based, systematic difference in their 13C chemical-shift anisotropies (CSAs). Simple three- or five-pulse CSA-recoupling sequences with “gamma-integral” cleanly suppress the signals of all sp2- and sp-hybridized carbons. The chemical-shift-anisotropy-based dephasing is particularly useful for distinguishing the signals of di-oxygenated alkyl (O–C–O)

J.-D. Mao; K. Schmidt-Rohr

2004-01-01

378

A quality-control method for physical and chemical monitoring data. Application to dissolved oxygen levels in the river Loire (France)  

Microsoft Academic Search

A quality-control method is proposed for examining continuous physical and chemical measurements, including temperature, dissolved oxygen, pH and electrical conductivity. Firstly, measurement consistency is evaluated by various modelling approaches: internal series structure, inter-variable relations or relations with external variables, spatial coherence and deterministic models. Secondly, outliers or systematic errors are detected using classical statistical tests. The method was evaluated for

F. Moatar; J. Miquel; A. Poirel

2001-01-01

379

Experimental study of cutting thick aluminum and steel with a chemical oxygen-iodine laser using an N2 or O2 gas assist  

Microsoft Academic Search

A chemical oxygen-iodine laser (COIL) was used for cutting aluminum and carbon steel. Cut depths of 20 mm were obtained in aluminum and 41 mm in carbon steel using an N2 gas assist and 5-6 kW of power on target. The same laser at the same power level produced a cut depth of 65 mm in carbon steel with an

David L. Carroll; James A. Rothenflue

1997-01-01

380

Pulsed chemical oxygen-iodine laser with volume generation of iodine as a model of a high-power supersonic cw laser  

SciTech Connect

In view of the identity of the kinetic processes and of the active-medium parameters of cw and pulsed chemical oxygen-iodine lasers, a repetitively pulsed laser with volume generation of iodine atoms and with a low average output power can be used as a simulator of a high-power cw laser. A comparison is made of experimental results with the parameters of a cw laser predicted by a numerical model. (lasers and amplifiers)

Yuryshev, Nikolai N [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

1998-05-31

381

Oxygen diffusion pathways in brownmillerite SrCoO2.5: influence of structure and chemical potential.  

PubMed

To design and discover new materials for next-generation energy materials such as solid-oxide fuel cells (SOFCs), a fundamental understanding of their ionic properties and behaviors is essential. The potential applicability of a material for SOFCs is critically determined by the activation energy barrier of oxygen along various diffusion pathways. In this work, we investigate interstitial-oxygen (Oi) diffusion in brownmillerite oxide SrCoO2.5, employing a first-principles approach. Our calculations indicate highly anisotropic ionic diffusion pathways, which result from its anisotropic crystal structure. The one-dimensional-ordered oxygen vacancy channels are found to provide the easiest diffusion pathway with an activation energy barrier height of 0.62 eV. The directions perpendicular to the vacancy channels have higher energy barriers for Oint diffusion. In addition, we have studied migration barriers for oxygen vacancies that could be present as point defects within the material. This in turn could also facilitate the transport of oxygen. Interestingly, for oxygen vacancies, the lowest barrier height was found to occur within the octahedral layer with an energy of 0.82 eV. Our results imply that interstitial migration would be highly one-dimensional in nature. Oxygen vacancy transport, on the other hand, could preferentially occur in the two-dimensional octahedral plane. PMID:25173033

Mitra, Chandrima; Meyer, Tricia; Lee, Ho Nyung; Reboredo, Fernando A

2014-08-28

382

Oxygen diffusion pathways in brownmillerite SrCoO2.5: Influence of structure and chemical potential  

NASA Astrophysics Data System (ADS)

To design and discover new materials for next-generation energy materials such as solid-oxide fuel cells (SOFCs), a fundamental understanding of their ionic properties and behaviors is essential. The potential applicability of a material for SOFCs is critically determined by the activation energy barrier of oxygen along various diffusion pathways. In this work, we investigate interstitial-oxygen (Oi) diffusion in brownmillerite oxide SrCoO2.5, employing a first-principles approach. Our calculations indicate highly anisotropic ionic diffusion pathways, which result from its anisotropic crystal structure. The one-dimensional-ordered oxygen vacancy channels are found to provide the easiest diffusion pathway with an activation energy barrier height of 0.62 eV. The directions perpendicular to the vacancy channels have higher energy barriers for Oint diffusion. In addition, we have studied migration barriers for oxygen vacancies that could be present as point defects within the material. This in turn could also facilitate the transport of oxygen. Interestingly, for oxygen vacancies, the lowest barrier height was found to occur within the octahedral layer with an energy of 0.82 eV. Our results imply that interstitial migration would be highly one-dimensional in nature. Oxygen vacancy transport, on the other hand, could preferentially occur in the two-dimensional octahedral plane.

Mitra, Chandrima; Meyer, Tricia; Lee, Ho Nyung; Reboredo, Fernando A.

2014-08-01

383

Chemical bonding, interface strength, and oxygen K electron-energy-loss near-edge structure of the Cu/Al{sub 2}O{sub 3} interface  

SciTech Connect

Chemical bondings and oxygen K electron-energy-loss near-edge structures (ELNES) of oxygen terminated Cu/Al{sub 2}O{sub 3} 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 weakness of the on-top configuration originates from the strong antibonding interactions between an interfacial oxygen and the second near neighbor Cu. Detailed analysis using overlap population diagrams revealed the formation mechanism of the strong antibonding interactions in the on-top configuration. In the oxygen K ELNES calculation, a prepeak feature appears in both configurations and it was predicted that the prepeak for the on-top configuration is larger than that for the hollow configuration. The overlap population diagrams elucidated that the prepeak is mainly composed of the O-Cu antibonding interactions, and the larger prepeak of the on-top configuration originates from the larger O-Cu interactions. The dependence of O-K ELNES on the direction of the momentum transfer vector was also discussed. Knowledge of the responsible direction of the momentum transfer vector in relation to the interface orientation was concluded to be indispensable in order to discuss detailed profiles of the ELNES from metal/ceramic heterointerfaces. This study reveals the effect of the atomic configuration of the interface to the chemical bondings, interface strength, and ELNES.

Mizoguchi, Teruyasu; Sasaki, Takeo; Matsunaga, Katsuyuki; Ikuhara, Yuichi [Institute of Engineering Innovation, The University of Tokyo, Yayoi, Bunkyo, Tokyo 113-8656 (Japan); Tanaka, Shingo; Kohyama, Masanori [Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda 563-8577 (Japan); Yamamoto, Takahisa [Department of Advanced Materials Science, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan)

2006-12-15

384

Supplemental Oxygen (Oxygen Therapy)  

MedlinePLUS

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

385

Simultaneous removal of chemical oxygen demand and nitrate in aerobic treatment of sewage wastewater using an immobilized photosynthetic bacterium of porous ceramic plates  

Microsoft Academic Search

A denitrifying photosynthetic bacterium (PSB), Rhodobacter sphaeroides S was immobilized on a porous ceramic plate (10?×?10?×?0.5?cm) using a small amount of agar. In the bioreactor (3.5 l liquid) using this plate, repeated batch treatments of sewage wastewater (acetic acid as a carbon source) were carried out under aerobic conditions (DO 5?mg\\/l) for two weeks. The simultaneous and effective removal of

H. Nagadomi; T. Takahasi; K. Sasaki; H. C. Yang

2000-01-01

386

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

Microsoft Academic Search

A stratified sand filter column, operated in recirculation mode and treating synthetic effluent resembling high-strength dairy wastewaters was studied over a 342-d duration. The aim of this paper was to examine the organic, total suspended solids (TSS) and nutrient removal rates of the sand filter, operated in recirculation mode, under incrementally increasing hydraulic and organic loading rates and to propose

M. G. Healy; M. Rodgers; J. Mulqueen

2007-01-01

387

Biodegradation of aromatic hydrocarbons by Haloarchaea and their use for the reduction of the chemical oxygen demand of hypersaline petroleum produced water.  

PubMed

Ten halophilic Archaea (Haloarchaea) strains able to degrade aromatic compounds were isolated from five hypersaline locations; salt marshes in the Uyuni salt flats in Bolivia, crystallizer ponds in Chile and Cabo Rojo (Puerto Rico), and sabkhas (salt flats) in the Persian Gulf (Saudi Arabia) and the Dead Sea (Israel and Jordan). Phylogenetic identification of the isolates was determined by 16S rRNA gene sequence analysis. The isolated Haloarchaea strains were able to grow on a mixture of benzoic acid, p-hydroxybenzoic acid, and salicylic acid (1.5mM each) and a mixture of the polycyclic aromatic hydrocarbons, naphthalene, anthracene, phenanthrene, pyrene and benzo[a]anthracene (0.3mM each). Evaluation of the extent of degradation of the mixed aromatic hydrocarbons demonstrated that the isolates could degrade these compounds in hypersaline media containing 20% NaCl. The strains were shown to reduce the COD of hypersaline crude oil reservoir produced waters significantly beyond that achieved using standard hydrogen peroxide treatment alone. PMID:21621813

Bonfá, Maricy R L; Grossman, Matthew J; Mellado, Encarnacion; Durrant, Lucia R

2011-09-01

388

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

PubMed

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

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

2013-11-21

389

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

Microsoft Academic Search

The problem of uncontrolled oxygen contamination of intermetallic TiAl ingots is considered for the application of crucibles\\u000a and molds based on traditional oxide ceramics. A synthesized Ti-45.9Al-8Nb (at %) alloy is solidified in alternative oxygen-free\\u000a crucibles made of high-purity aluminum nitride (99.99% AlN) upon holding at 1670°C for 5, 12, and 25 min and subsequent quenching\\u000a in a high-purity argon

A. V. Kartavykh; V. V. Cherdyntsev

2008-01-01

390

Origin of Oxygen Reduction Reaction Activity on "Pt3Co" Nanoparticles: Atomically Resolved Chemical Compositions and Structures  

E-print Network

Compositions and Structures Shuo Chen, Wenchao Sheng, Naoaki Yabuuchi, Paulo J. Ferreira,§ Lawrence F. Allard, Materials Science and Engineering Program, UniVersity of Texas at Austin, Austin, Texas 78712, and High-treated "Pt3Co" nanoparticles showed specific oxygen reduction reaction (ORR) activity (0.7 mA/cmPt 2 at 0.9 V

Ferreira, Paulo J.

391

Deactivation rate of I{sub 2} molecules (X, v {>=} 30) in the medium of a chemical oxygen-iodine laser  

SciTech Connect

The effective deactivation rate constants are calculated for I{sub 2}(X) molecules at vibrational levels with v {>=} 30 colliding with N{sub 2} and O{sub 2} molecules in the medium of a chemical oxygen-iodine laser. The calculated constants (4x10{sup -12} cm{sup 3} s{sup -1} and 3x10{sup -12} cm{sup 3} s{sup -1}) are less by half plus than the corresponding constants found earlier in the paper of Lawrence et al., where the dissociation of I{sub 2} was neglected in calculations. (lasers, active media)

Pichugin, S Yu [Samara Branch of the P. N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2008-08-31

392

Differential role of reactive oxygen species in chemical hypoxia-induced cell injury in opossum kidney cells and rabbit renal cortical slices.  

PubMed

This study was undertaken to evaluate the role of reactive oxygen species (ROS) and lipid peroxidation in chemical hypoxia in opossum kidney (OK) cells and rabbit renal cortical slices. Chemical hypoxia was induced by incubating cells or slices with antimycin A, an inhibitor of mitochondrial electron transport. Exposure of OK cells to chemical hypoxia resulted in a time-dependent cell death and parallel depletion of intracellular ATP. In OK cells subjected to chemical hypoxia, the generation of ROS was increased, and this was prevented by the H(2)O(2) scavenger catalase, but not by the hydroxyl radical scavenger dimethylthiourea (DMTU). Catalase prevented OK cell death induced by chemical hypoxia, but [Cu, Zn]-superoxide dismutase (SOD) and DMTU were not effective. The iron chelators deferoxamine and phenanthroline prevented chemical hypoxia-induced OK cell death, but the potent antioxidants N,N'-diphenyl-p-phenylenediamine (DPPD) and butylated hydroxyanisole (BHA) showed no beneficial effect. Antimycin A in OK cells increased lipid peroxidation, which was prevented by DPPD and phenanthroline. In rabbit renal cortical slices, antimycin A caused an increase in LDH release and lipid peroxidation, and these effects were prevented by ROS scavengers (SOD, catalase, and DMTU), iron chelator (deferoxamine), and antioxidants (DPPD and BHA). However, in primary cultured rabbit proximal tubular cells the antimycin A-induced cell death was not altered by antioxidants. The extent of ATP depletion was similar in renal cortical slices and primary cultured cells treated with antimycin A. These results indicate that chemical hypoxia-induced cell injury is not directly resulted from lipid peroxidation in OK cells, but this cell injury is mediated by lipid peroxidation in rabbit renal cortical slices. This discrepancy may be due to the difference in cell preparation (freshly prepared tubules and cultured cells). PMID:12097831

Kim, Yong Keun; Lee, Sung Keun; Ha, Mi Suk; Woo, Jae Suk; Jung, Jin Sup

2002-01-01

393

Induction of biochemical stress markers and apoptosis in transgenic Drosophila melanogaster against complex chemical mixtures: Role of reactive oxygen species  

Microsoft Academic Search

The study was aimed to investigate the effect of leachates of solid waste from a flashlight battery factory and a pigment plant on 70kDa heat shock protein (Hsp70) expression, generation of reactive oxygen species (ROS), antioxidant enzymes activities and apoptosis in Drosophila. Third instar larvae of Drosophila melanogaster transgenic for hsp70 (hsp70-lacZ) were fed on diet mixed with leachates of

Hifzur R. Siddique; Subash C. Gupta; Kalyan Mitra; Ramesh C. Murthy; Daya K. Saxena; Debapratim K. Chowdhuri

2007-01-01

394

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

395

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

396

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  

Microsoft Academic Search

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

Tamara L Andreeva; S V Kuznetsova; Aleksandr I Maslov; Vadim N Sorokin

2009-01-01

397

The story of oxygen.  

PubMed

The history of oxygen from discovery to clinical application for patients with chronic lung disease represents a long and storied journey. Within a relatively short period, early investigators not only discovered oxygen but also recognized its importance to life and its role in respiration. The application of oxygen to chronic lung disease, however, took several centuries. In the modern era, physiologists pursued the chemical nature of oxygen and its physiologic interaction with cellular metabolism and gas transport. It took brazen clinicians, however, to pursue oxygen as a therapeutic resource for patients with chronic lung disease because of the concern in the 20th century of the risks of oxygen toxicity. Application of ambulatory oxygen devices allowed landmark investigations of the long-term effects of continuous oxygen that established its safety and efficacy. Although now well established for hypoxic patients, many questions remain regarding the benefits of oxygen for varying severity and types of chronic lung disease. PMID:23271817

Heffner, John E

2013-01-01

398

Oxygen content, crystal structure and chemical expansion of PrBaCo(2-x)Fe(x)O(6-?) double perovskites.  

PubMed

PrBaCo2-xFexO6-? (x = 0-0.6) double perovskites were shown to have a tetragonal P4/mmm structure in air over the complete temperature range investigated despite the oxygen content reaching a threshold value of 5.5 at temperatures from 850 °C for x = 0 up to 1078 °C for x = 0.6. However the P4/mmm?Pmmm structure transition was found to occur in PrBaCo2O6-? under reducing conditions at temperatures from 500 °C at pO2 = 10(-3) atm down to 350 °C at pO2 = 10(-4) atm. The lattice chemical expansion along the a-axis and contraction along the c-axis, with decreasing oxygen content, 6 - ?, were found to completely compensate each other in the double perovskites and, therefore, their volume chemical expansion became negligible. As a result the cell volume linearly increases with temperature contrary to simple cubic perovskites. PMID:24964366

Tsvetkov, D S; Ivanov, I L; Malyshkin, D A; Zuev, A Yu

2014-08-21

399

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

Microsoft Academic Search

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

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

1987-01-01

400

Experimental determination of the carboxylate oxygen electric-field-gradient and chemical shielding tensors in L-alanine and L-phenylalanine  

NASA Astrophysics Data System (ADS)

We report a solid-state 17O NMR study of the 17O electric-field-gradient (EFG) and chemical shielding (CS) tensors for each carboxylate group in polycrystalline L-alanine and L-phenylalanine. The magic angle spinning (MAS) and stationary 17O NMR spectra of these compounds were obtained at 9.4, 14.1, and 16.4 T. Analyzes of these 17O NMR spectra yielded reliable experimental NMR parameters including 17O CS tensor components, 17O quadrupole coupling parameters, and the relative orientations between the 17O CS and EFG tensors. The extensive quantum chemical calculations at both the restricted Hartree-Fock and density-functional theories were carried out with various basis sets to evaluate the quality of quantum chemical calculations for the 17O NMR tensors in L-alanine. For 17O CS tensors, the calculations at the B3LYP/D95 ?? level could reasonably reproduce 17O CS tensors, but they still showed some discrepancies in the ?11 components by approximately 36 ppm. For 17O EFG calculations, it was advantageous to use calibrated Q value to give acceptable CQ values. The calculated results also demonstrated that not only complete intermolecular hydrogen-bonding networks to target oxygen in L-alanine, but also intermolecular interactions around the NH3+ group were significant to reproduce the 17O NMR tensors.

Yamada, Kazuhiko; Asanuma, Miwako; Honda, Hisashi; Nemoto, Takahiro; Yamazaki, Toshio; Hirota, Hiroshi

2007-10-01

401

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

402

Oxygen transfer in membrane bioreactors treating synthetic greywater  

Microsoft Academic Search

Mass transfer coefficients (kLa) were studied in two pilot scale membrane bioreactors (MBR) with different setup configurations treating 200L\\/h of synthetic greywater with mixed liquor suspended solids' (MLSS) concentrations ranging from 4.7 to 19.5g\\/L. Besides the MLSS concentration, mixed liquor volatile suspended solids (MLVSS), total solids (TS), volatile solids (VS), chemical oxygen demand (COD) and anionic surfactants of the sludge

Jochen Henkel; Mladen Lemac; Martin Wagner; Peter Cornel

2009-01-01

403

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

404

Chemical structure of silicon-, oxygen- and nitrogen-containing aC:H films prepared by RF plasma beam CVD  

Microsoft Academic Search

Si-, SiOx- and SiNx-containing a-C:H films (denoted as DLCSi, DLCSiO and DLCSiN) were deposited respectively from tetramethylsilane, hexamethyldisiloxane and hexamethyldisilazane precursors onto silicon wafer and aluminium substrates by electron cyclotron wave resonance (ECWR) RF plasma beam CVD. The chemical composition and the bonding states of the constituent elements were characterised by X-ray photoelectron spectroscopy and X-ray induced Auger electron spectroscopy.Compared

A. Toth; M. Mohai; T. Ujvari; I. Bertóti

2005-01-01

405

Experimental Effects of Atomic Oxygen on the Development of an Electric Discharge Oxygen Iodine Laser  

E-print Network

of the electric discharge iodine laser continues, the role of oxygen atoms downstream of the discharge region temperature. Keywords: chemical oxygen-iodine laser, COIL, ElectriCOIL, RF excitation of oxygen, singlet-delta oxygen, DOIL 1.0 INTRODUCTION The classic chemical oxygen-iodine laser (COIL) system1 operates on the I(2

Carroll, David L.

406

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

407

Pressure-induced electrical and structural anomalies in Pb1-xCaxTiO3 thin films grown at various oxygen pressures by chemical solution route  

NASA Astrophysics Data System (ADS)

Lead calcium titanate (Pb1-xCaxTiO3 or PCT) thin films have been thermally treated under different oxygen pressures, 10, 40 and 80 bar, by using the so-called chemical solution deposition method. The structural, morphological, dielectric and ferroelectric properties were characterized by x-ray diffraction, FT-infrared and Raman spectroscopy, atomic force microscopy and polarization-electric-field hysteresis loop measurements. By annealing at a controlled pressure of around 10 and 40 bar, well-crystallized PCT thin films were successfully prepared. For the sample submitted to 80 bar, the x-ray diffraction, Fourier transformed-infrared and Raman data indicated deviation from the tetragonal symmetry. The most interesting feature in the Raman spectra is the occurrence of intense vibrational modes at frequencies of around 747 and 820 cm-1, whose presence depends strongly on the amount of the pyrochlore phase. In addition, the Raman spectrum indicates the presence of symmetry-breaking disorder, which would be expected for an amorphous (disorder) and mixed pyrochlore-perovskite phase. During the high-pressure annealing process, the crystallinity and the grain size of the annealed film decreased. This process effectively suppressed both the dielectric and ferroelectric behaviour. Ferroelectric hysteresis loop measurements performed on these PCT films exhibited a clear decrease in the remanent polarization with increasing oxygen pressure.

Pontes, F. M.; Galhiane, M. S.; Santos, L. S.; Rissato, S. R.; Pontes, D. S. L.; Longo, E.; Leite, E. R.; Chiquito, A. J.; Pizani, P. S.; Jardim, R. F.; Escote, M. T.

2008-06-01

408

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

409

Preparation of atomic oxygen resistant polymeric materials  

NASA Technical Reports Server (NTRS)

Polyphenyl quinoxalines (PPQs) are an important family of high performance polymers that offer good chemical and thermal stability coupled with excellent mechanical properties. These aromatic heterocyclic polymers are potentially useful as films, coatings, adhesives, and composite materials that demand stability in harsh environments. Our approach was to prepare PPQs with pendent siloxane groups using the appropriate chemistry and then evaluate these polymers before and after exposure to simulated atomic oxygen. Either monomer, the bis(o-diamine)s or the bis(alpha-diketone)s can be synthesized with a hydroxy group to which the siloxane chain will be attached. Several novel materials were prepared.

Tortorelli, Victor J.; Hergenrother, P. M.; Connell, J. W.

1991-01-01

410

Therapeutics, Targets, and Chemical Biology Prostate Cancer Radiosensitization through  

E-print Network

Therapeutics, Targets, and Chemical Biology Prostate Cancer Radiosensitization through Poly(P)H:quinone oxido- reductase 1 (NQO1) metabolic bioactivation, triggering a massive induction of reactive oxygen cancers are in great demand. -Lapachone (-lap; 3,4-dihydro-2,2-dimethyl-2H-naphtho [1,2-b]pyran-5,6-dione

Gao, Jinming

411

Chemical and microstructural study of the oxygen passivation behaviour of nanocrystalline Mg and MgH 2  

NASA Astrophysics Data System (ADS)

Nanocrystalline Mg and MgH 2 samples have been prepared by high-energy ball milling and gas phase condensation methods. Starting from these materials in their "as received" state without air exposure, a study of the oxygen and air passivation behaviour was carried out by "in situ" analysis of the samples by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The binding energy and photoemission Auger parameters have been determined for metallic magnesium as well as for magnesium hydride, oxide and hydroxide species. Values of the MgH 2 material were reported for the first time. The study clearly shows the formation of an oxide passivation layer of ca. 3-4 nm in thickness for all the nanocrystalline magnesium samples handled under controlled inert gas atmospheres. A hydroxide like amorphous layer is formed at the topmost surface layers of the nanocrystalline Mg and MgH 2 samples. The implication of these studies for H 2 storage and transport applications of nanocrystalline magnesium is discussed.

Friedrichs, O.; Sánchez-López, J. C.; López-Cartes, C.; Dornheim, M.; Klassen, T.; Bormann, R.; Fernández, A.

2006-01-01

412

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

PubMed Central

alpha-Oxyprotohemin IX, an early intermediate in heme catabolism, was synthesized and its autoxidation to biliverdin IX alpha was studied. In anaerobic aqueous pyridine, alpha-oxyprotohemin (hexacoordinated) underwent autoreduction to yield an Fe(II) alpha-oxyprotoporphyrin pi-neutral radical bis(pyridine) complex, which reacted with an equimolar amount of dioxygen to give pyridine.verdohemochrome IX alpha and CO in 75-80% yield via an intermediate with an absorption maximum at 893 nm. Verdohemochrome IX alpha did not react with further dioxygen. Reconstituted apomyoglobin.alpha-oxyprotohemin IX complex (pentacoordinated) reacted with an equimolar amount of dioxygen to form an Fe(II) oxyporphyrin pi-neutral radical intermediate, which rearranged to a green compound (lambda max 660 and 704 nm) with elision of CO. The green product, which is probably an apomyoglobin.verdoheme pi-radical complex, reacted with another equimolar amount of dioxygen to give Fe(III).biliverdin IX alpha. Demetallation of this gave biliverdin IX alpha in overall yield of 70-75%. These results indicate that the sequence of oxyheme autoxidation in the presence of apomyoglobin is alpha-oxyprotoheme IX O2----CO----verdohemochrome IX alpha pi-radical O2----Fe(III).biliverdin IX alpha. A similar mechanism may prevail in vivo. The hexa- and pentacoordinated Fe(II) pi-radical form of the oxyporphyrin is crucial in triggering the autoxidation of the complex to verdohemochrome IX alpha. Further oxygenation of verdohemochrome IX alpha to Fe(III).biliverdin IX alpha occurred only in the pentacoordinated apomyoglobin.verdoheme Fe(II) complex. PMID:3456152

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

1986-01-01

413

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

414

Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution  

E-print Network

We present deep echelle spectrophotometry of the brightest emission-line knots of the star-forming galaxies He 2-10, Mkn 1271, NGC 3125, NGC 5408, POX 4, SDSS J1253-0312, Tol 1457-262, Tol 1924-416 and the HII region Hubble V in the Local Group dwarf irregular galaxy NGC 6822. The data have been taken with the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the 3100-10420 $\\AA$ range. We determine electron densities and temperatures of the ionized gas from several emission-line intensity ratios for all the objects. We derive the ionic abundances of C$^{2+}$ and/or O$^{2+}$ from faint pure recombination lines (RLs) in several of the objects, permitting to derive their C/H and C/O ratios. We have explored the chemical evolution at low metallicities analysing the C/O vs. O/H, C/O vs. N/O and C/N vs. O/H relations for Galactic and extragalactic HII regions and comparing with results for halo stars and DLAs. We find that HII regions in star-forming dwarf galaxies occupy a different locus in the C/O...

Esteban, C; Carigi, L; Peimbert, M; Bresolin, F; López-Sánchez, A R; Mesa-Delgado, A

2014-01-01

415

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

2014-10-14

416

ACTIVE MEDIA: 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  

Microsoft Academic Search

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

Tamara L. Andreeva; S. V. Kuznetsova; Aleksandr I. Maslov; Vadim N. Sorokin

2009-01-01

417

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  

Microsoft Academic Search

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

Tamara L Andreeva; S V Kuznetsova; Aleksandr I Maslov; Vadim N Sorokin

2009-01-01

418

Oxygen concentrators.  

PubMed

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

Howell, R S

1985-10-01

419

Neutron and X-ray investigations on the oxygen bonding in YBa 2 Cu 3 O 7-x combined with physico-chemical methods  

Microsoft Academic Search

The occupancy of the oxygen lattice positions at different annealing conditions in YBa2Cu3O(7-x) were determined by Rietveld refinements using neutron and X-ray diffraction data. The occupation density for the oxygen positions O1 to O4 were ascertained. The values of the oxygen content of the samples from this method were compared with those measured by thermoanalysis. The O1 and O4 oxygen

M. Große; G. Schuster; K. Teske; W. Anwand; K. Henkel

1994-01-01

420

Numerical study of He/CF3I pulsed discharge used to produce iodine atom in chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The pulsed discharge for producing iodine atoms from the alkyl and perfluoroalky iodides (CH3I, CF3I, 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 CF3I-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 CF3I 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 CF3I is needed to obtain the maximum iodine atom concentration.

Zhang, Jiao; Wang, Yanhui; Duo, Liping; Li, Guofu; Wang, Dezhen

2013-04-01

421

Effect of hydrogen sulfide on chemical looping of coal-derived synthesis gas over bentonite-supported metal---oxide oxygen carriers  

SciTech Connect

The effect of hydrogen sulfide (H2S) on the chemical looping combustion of coal-derived synthesis gas with bentonite-supported metal oxidesssuch as iron oxide, nickel oxide, manganese oxide, and copper oxideswas investigated by thermogravimetric analysis, mass spectrometry, and X-ray photoelectron spectroscopy (XPS). During the reaction with synthesis gas containing H2S, metal-oxide oxygen carriers were first reduced by carbon monoxide and hydrogen, and then interacted with H2S to form metal sulfide, which resulted in a weight gain during the reduction/sulfidation step. The reduced/sulfurized compounds could be regenerated to form sulfur dioxide and oxides during the oxidation reaction with air. The reduction/oxidation capacities of iron oxide and nickel oxide were not affected by the presence of H2S, but both manganese oxide and copper oxide showed decreased reduction/oxidation capacities. However, the rates of reduction and oxidation decreased in the presence of H2S for all four metal oxides.

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

2009-01-01

422

Development and Testing of a Dissolved Oxygen Model for a Hypereutrophic Lake  

Microsoft Academic Search

A mechanistic, two-layer mass balance model for dissolved oxygen (DO) in Onondaga Lake, a hypereutrophic, urban system, has been developed and tested. The model accommodates the processes of reaeration, algal photosynthesis and respiration, carbonaceous biochemical oxygen demand (CBOD), nitrogenous biochemical oxygen demand (NBOD), sediment oxygen demand (SOD) and water column oxidation of reduced species. Most model inputs, and many of

Rakesh K. Gelda; Martin T. Auer

1996-01-01

423

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

424

Published: November 03, 2011 r 2011 American Chemical Society 19306 dx.doi.org/10.1021/ja2083398 |J. Am. Chem. Soc. 2011, 133, 1930619309  

E-print Network

, and stored for use upon demand. Storing solar energy directly in high- energy chemical bonds, suchassolarPublished: November 03, 2011 r 2011 American Chemical Society 19306 dx.doi.org/10.1021/ja2083398 |J water splitting to hydrogen and oxygen, is one of the most attractive approaches.2 A single semi

Yang, Peidong

425

Feasibility of physico-chemical treatment and Advanced Oxidation Processes (AOPs) as a means of pretreatment of olive mill effluent (OME)  

Microsoft Academic Search

The efficiency of alternative pretreatment methods for an olive mill effluent (OME) in producing a final effluent conforming to Turkish Water Pollution Standards for discharge into the public sewage was studied. For this purpose, various treatment alternatives such as acid cracking, chemical coagulation, adsorption and Advanced Oxidation Processes (AOPs) were studied. A significant amount of Chemical Oxygen Demand (COD), total

Kadir Kestio?lu; Taner Yonar; Nuri Azbar

2005-01-01

426

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

PubMed

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

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

2005-08-01

427

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

428

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

429

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

430

Atmospheric Oxygen  

NSDL National Science Digital Library

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

Foundation, Wgbh E.

2003-09-26

431

VideoonDemandVideoonDemandVideoonDemand Video on Demand Testbed  

E-print Network

Control Application Server Distributed Server Network VoD Testbed ArchitectureVoD Testbed Architecture Video-pump VideoonDemandVideoonDemandVideoonDemand #12;Analyzer Video Packets Application Server Network Signalling Network · ATM · Internet · Wireless Video-pump Distributed Server Videoon

Eleftheriadis, Alexandros

432

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

433

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

434

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

435

Electrical Demand Control  

E-print Network

1. One Demand Interval Showfng Usage (kwh) vs. Time PO0 kw x 0.25 hour = 323 pulses 0.6966 kwh= If the demand limiter allows no more than 323 pulses in any 15-minute period, the demand 1 imit will be maintained. The simplest method of 1 imi... importantly, equipment start/stops are avoided. Most centrifugal chi 1 lers are installed with manual demand limiting systems. Interfacing this equipment with demand 1 imi ters is relati be limited relatively simple. With unitary equipment the by simply...

Eppelheimer, D. M.

1984-01-01

436

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

437

Electrochemical oxygen concentrator as an oxygen compressor  

NASA Technical Reports Server (NTRS)

A solid polymer electrolyte (SPE) oxygen compressor is described which generates pressures of 3000 psi. The SPE is a cation exchange membrane with chemical compatibility, and has the capability of withstanding 5000 psi. Other features of the compressor described include: gasketless sealing, porus plate cell supports, and conductive cooling. Results are presented of a computer program which defines the power of the system as a function of density, temperature, pressure, membrane thickness, and water content.

1975-01-01

438

Hyperbaric oxygen therapy ameliorates stress-impaired dermal wound healing  

Microsoft Academic Search

Psychological stress has been shown to dysregulate healing in both humans and animals. Studies indicate the possibility for decreased oxygen supply, and increased oxygen demand, in the wounds of the stressed animals. Oxygen is an important mediator of wound healing, and its availability can limit healing rate. Hence, in a mouse model of stress-impaired healing, the hypothesis that hyperbaric oxygen

Praveen K. Gajendrareddy; Chandan K. Sen; Michael P. Horan; Phillip T. Marucha

2005-01-01

439

Optimal energy demand management  

SciTech Connect

A solution to the problem of controlling energy demand is described. In particular, it is shown that the problem may be characterized as a probabilistic order level inventory system with instantaneous demand. The equivalence of the problems is illustrated as well as the techniques of solution. The results provide a useful tool for initial justification and feasibility considerations for a user contemplating the installation of an energy demand control system. 7 refs.

Gingher, G.C.

1981-01-01

440

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

441

10.1021/ol401787n r 2013 American Chemical Society Published on Web 08/20/2013  

E-print Network

10.1021/ol401787n r 2013 American Chemical Society Published on Web 08/20/2013 ORGANIC LETTERS 2013 of an intramolecular vinyl quinone DielsÃ?Alder (VQDA)6,7 reaction with neutral elec- tron demand, the implementation be introduced through a singlet oxygen ene reaction in the side chain, while the alkenyl hydroquinone moiety

Trauner, Dirk

442

10.1021/ol3003139 r 2012 American Chemical Society Published on Web 03/13/2012  

E-print Network

10.1021/ol3003139 r 2012 American Chemical Society Published on Web 03/13/2012 ORGANIC LETTERS 2012-arylglycosides where a carbon atom substitutes the anomeric glycosidic oxygen.3 The most common method for 1-C 2,3-unsaturated products due to -elimination processes.4Ã?7 Although the high demand

Davis, Ben G.

443

Ruminal waste stream as a source of industrial chemicals  

Microsoft Academic Search

Acetic, propionic, and butyric acids, which are volatile fatty acids (VFAs), are present in significant concentration in the rumen of cattle and other ruminant animals. The chemical oxygen demand (COD) burden carried by rumen wastes and ways to salvage the value-added enzymes, ?-amylase and cellulases, which are present in substantial quantities are presented. An average COD for grain\\/grass-fed animals was

Ajoy Koppolu; L. Davis Clements

2004-01-01

444

Demand Response Programs for Oregon  

E-print Network

Demand Response Programs for Oregon Utilities Public Utility Commission May 2003 Public Utility ....................................................................................................................... 1 Types of Demand Response Programs............................................................................ 3 Demand Response Programs in Oregon

445

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

446

Supply and Demand  

NSDL National Science Digital Library

This lesson from Illuminations allows students to learn about linear equations in a real-world setting. The material applies linear equations to the concept of supply and demand. Students will be able to translate between table, graph and equation representations for supply and demand data. The lesson is intended for grades 9-12 and should require two class periods to complete.

2010-12-03

447

Advanced chemical lasers  

Microsoft Academic Search

A review of recent advances in chemical laser technology is presented. New technology and concepts related to the Chemical Oxygen Iodine Laser (COIL), All Gas-phase Iodine Laser (AGIL), and HF Overtone Laser are discussed.

Gerald C. Manke II; Kevin B. Hewett; Timothy J. Madden; John E. McCord; Charles F. Wisniewski; Gordon D. Hager

2004-01-01

448

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

449

Oxygen transfer in membrane bioreactors treating synthetic greywater.  

PubMed

Mass transfer coefficients (k(L)a) were studied in two pilot scale membrane bioreactors (MBR) with different setup configurations treating 200L/h of synthetic greywater with mixed liquor suspended solids' (MLSS) concentrations ranging from 4.7 to 19.5g/L. Besides the MLSS concentration, mixed liquor volatile suspended solids (MLVSS), total solids (TS), volatile solids (VS), chemical oxygen demand (COD) and anionic surfactants of the sludge were measured. Although the pilot plants differed essentially in their configurations and aeration systems, similar alpha-factors at the same MLSS concentration could be determined. A comparison of the results to the published values of other authors showed that not the MLSS concentration but rather the MLVSS concentration seems to be the decisive parameter which influences the oxygen transfer in activated sludge systems operating at a high sludge retention time (SRT). PMID:19217638

Henkel, Jochen; Lemac, Mladen; Wagner, Martin; Cornel, Peter

2009-04-01