Electron Flow Measurements Research Articles

Spectroelectrochemical testing of a proposed mechanism for a redox-based therapeutic intervention: Ascorbate treatment of severe paraquat poisoning

The toxicity of paraquat is believed to involve a redox-cycling mechanism that can disrupt cellular redox homeostasis and, also, generate damaging free radicals. It has been suggested that for cases of severe paraquat poisoning the administration of ascorbate (i.e., vitamin C) can confer benefit by quenching the paraquat free radical (PQ+·). Here, we used an electrochemical approach that abstracts-away many of the (bio)chemical complexities and isolates the redox-interactions between paraquat and ascorbate. Specifically, we used a series of experiments that coupled electrochemical measurements of electron flow with optical measurements of paraquat's redox-state switching. Our results demonstrate that the reduced absorbate cannot quench the PQ+·-radical because they are both reductants. However, oxidation of ascorbate does allow PQ+·-radical scavenging. More broadly, we believe this study demonstrates the potential for developing electrochemical approaches to complement existing experimental methods in redox biology.

Upgrades to improve the usability, reliability, and spectral range of the MST Thomson scattering diagnostic.

The Thomson scattering diagnostic on MST records both equilibrium and fluctuating electron temperature with a range capability of 10 eV-5 keV. Standard operation with two modified commercial Nd:YAG lasers allows measurements at rates of 1 kHz-25 kHz. Several subsystems of the diagnostic are being improved. The power supplies for the avalanche photodiode detectors (APDs) that record the scattered light are being replaced to improve usability, reliability, and maintainability. Each of the 144 APDs will have an individual rack mounted switching supply, with bias voltage adjustable to match the APD. Long-wavelength filters (1140 nm center, 80 nm bandwidth) have been added to the polychromators to improve capability to resolve non-Maxwellian distributions and to enable directed electron flow measurements. A supercontinuum (SC) pulsed white light source has replaced the tungsten halogen lamp previously used for spectral calibration of the polychromators. The SC source combines substantial brightness produced in nanosecond pulses with a spectrum that covers the entire range of the polychromators.

Increasing Operations Profitability Using an End-to-End, Wireless Internet, Gas Monitoring System

Abstract Smart-Alek ™ is an example of a fully integrated, end-to-end gas measurement and production analysis system utilizing public wireless communications and a Web-browser-only delivery system to provide seamless well visibility to any desktop. Capitalizing on the technology's cost effectiveness and ease of deployment, Northrock Resources Ltd. (a wholly-owned subsidiary of Unocal Corporation) has adopted a grass roots shift in their operations strategy that implements on-the-ground, timely decision- making at the field level. This technology fits Northrock's operations business needs of easy to use, complete, reliable, and cost effective production information delivered in a timely manner to everyone on the team. Previously, Northrock has found that these needs were not adequately met by conventional SCADA technologies. This type of end-to-end wireless and Web technology has enabled Northrock to increase gas volumes with more accurate measurement (Electronic Flow Measurement vs. mechanical chart), and less downtime. Reductions in operating osts were achieved by decreases in well visitation frequency and a redirection of operator "windshield time" to activities that Introduction Although advances in SCADA (Supervisory Control And Data Acquisition) have improved gas measurement technology from the 100-year-old mechanical chart methods, costs can be prohibitive to implement an electronic alternative. The following case study investigates how Northrock increased profitability deploying and utilizing Smart-Alek ™ company-wide while avoiding these high mplementation costs. Smart-Alek ™ is an example of a new type of end-to-end electronic Gas Flow Measurement (GFM) system, entitled FINE ™. FINE ™ is an acronym meaning Field Intelligence (FI), Network (N), and End-User Interface (E)(1, 2). Background A comparison of GFM information flow between mechanical charts, SCADA, and FINE ™ is given in Figure 1. On the left of this figure is the information flow path of the mechanical chart method. Data gathering using mechanical charts, typically involves daily site visitations by an operator who estimates the previous day's volume from chart readings. This rough estimate is then manually entered into a Field Data Capture system (FDC). Once captured, these rough production volumes are then accessible by operations staff, engineers, and management who use them to make daily business decisions. Use of the rough volumes in FDC and integrated chart volumes for accounting is error prone and time intensive, and it introduces significant business challenges in the flow of information from the wellhead to the producers bank account. The business impacts of these inefficiencies and errors are as follows:Obtaining on-site daily estimates requires significant operator time.Both on-site estimating and chart integration can be highly inaccurate because of the numerous manual steps required by many people.Accuracy of integrated volumes is highly dependent on fixed meter run parameters and gas composition. These parameters are error prone because they are also stored manually in multiple systems (i.e., log books, spreadsheets, meter detail, and chart integration files), which translates into increased rework costs and potential lost revenue.Chart integrated volumes are typically not reconciled with field estimates. This can result in undetected errors that have a direct impact on cash flow, which can be large and long term.

Gas Well Production Optimization with Remote Performance Monitoring

Abstract Monitoring gas production with mechanical chart recorders and the associated business practices results in significant loss of earnings due to data inaccuracies, late identification of well shutdown, and operational inefficiencies. To solve this, several current technologies have now been integrated into a low cost end-to-end system called FINE. This technical note describes FINE and provides field data demonstrating the benefits. Introduction Gas flow measurement has been dominated by 100-year-old circular chart technology. "Charts" record differential pressures generated across an orifice plate (and the static pressures and inflow temperatures) at a gas meter. These differential pressures are converted into flow rates by standardized AGA flow calculations(1,2). The process of chart measurement involves a laborious cycle of collecting charts, chart integration and data entry, which often takes weeks to return information to the decision makers. This mechanical measurement necessarily involves lost earnings due to data inaccuracies, late identification of well shutdown, and operational inefficiencies. Electronic flow measurement (EFM) has been an alternative to charts for many years. It is based upon electronic gas measurement standards established by the American Petroleum Institute(3). However, the cost and construct of acquisition and dissemination with engineered SCADA (Supervisory Control and Data Acquisition) solutions have prevented widespread acceptance or use by a large number of stakeholders within an organization who could add value. Integrated technologies now permit practical acquisition of electronic gas flow measurement from every well, and dissemination for use by everyone within an organization. These technologies all adhere to a basic system structure T. Ito calls "FINE"(4). FINE Technology FINE stands for Field Instrument (FI), Network (N) and End user (E). FINE is a seamless system design that, in spite of the measurement complexity, simplifies data acquisition so that monitoring costs are similar to that of a chart, and dissemination is seamless to everyone from managers to investors on their PCs. (See Figure 1.) FINE's structure is revolutionary, involving end-to-end, internet- based metrology systems and preferably built on autonomous networkable transmitters. FINE integrates:transmitters with digital sensor cores,public wireless communications,high performance embedded processors, micro-power electronics (FI), and solar power operation,central digital nervous system (N), anddatabase and web interface tools (E). The transmitter connects wirelessly through a network to an Internet information delivery system using full-duplex asynchronous communication made possible by embedded processors. Increase Revenues, Reduced Costs When gas producers and transmission companies apply FINE systems to gas well monitoring, they can realize increased revenues and reduced operating costs. Revenues are increased by:Reduced downtime (e.g., by exception alarming)Improved allocations (e.g., by higher accuracy)Optimized field production (e.g., by daily monitoring of wells, well testing, and regular gas-in-place estimates) FINE reduces costs by:Improved operator efficiency (e.g., focusing on operations)

Improved Production Operating Efficiencies Through Automation

Abstract During 1994 – 1995, Wascana Energy Inc. implemented a supervisory control and data acquisition system.(SCADA) covering its entire southeast Saskatchewan operating area. This SCADA system was implemented to improve operating efficiencies by reducing operating costs and increasing production volumes. The system provided for remote monitoring and control of certain production facilities and wells. Wascana contracted an automation system integrator to assist in customizing. the graphical user interface and configuring the PC based computer system to communicate with various end devices in several fields. The master polling station and backup PC are located in Wascana's Estevan office. Data communications between the Estevan office, the field and district offices is accomplished with a UHF radio system and existing phone lines. Selected real time data is stored on an SQL database server, located on Wascana's local and wide area networks (LAN, WAN) to support corporate wide data sharing. Field automation includes wellhead managers (WHM) on all horizontal producers for pump off control and real time dynamometer analysis, remote tank level monitoring, electronic flow measurement, water injection facility control and flowline leak detection. Introduction In 1994, Wascana Energy (WEI) increased the focus on production automation as one means to improve operating performance, through reduced operating costs and increased production volumes. Published literature, personal project visits and discussions with other companies, active in automation, confirmed that opportunities existed for improving cost and production performance. Although Wascana already had several operations with field level automation (programmable logic controllers (PLCs) controlling a number of facilities, SCADA in a small number of gas fields and initial experience with pump off control for beampumped oil wells), a consistent area or corporate wide approach did not exist. Electronic flow measurement and remote monitoring andlor control were limited. Initial experience with wellhead managers (WHM) for pump off control (POC) began in 1993 on a horizontal well drilled by WEI in the Weyburn area of southeast Saskatchewan. Since that initial installation, WEI has installed WHMs on over 40 horizontal wells in the southeast area. These horizontal wells account for more than 50% of WEI production from southeast Saskatchewan. WHMs are now routinely installed on new wells and monitored by the SCADA system from the company's area office at Estevan. The initial SCADA system utilized during 1993/1994 consisted of VHF radio communications between several WHMs (horizontal wells) and Estevan using a basic, DOS-based, Graphical User Interface (GUI), provided by the WHM vendor. The radio communications was subsequently upgraded to UHF frequencies and a sophisticated, Windows-based, GUI was installed that includes a comprehensive voice callout and alarm system. Wellhead managers are polled directly from the Estevan control centre and other remote monitoring is accomplished via field level remote terminal units (RTUs) and PLCs. Other field level sensors, end devices and electronic flow measurement devices are tied into these field RTUs and PLCs. Although primary control is at the field level, the SCADA system can pass certain control commands from the control centre to the field RTUs.

Changes in Photosystem II Account for the Circadian Rhythm in Photosynthesis in Gonyaulax polyedra

Cell-free extracts that show activity in photosynthetic electron flow have been prepared from the unicellular dinoflagellate, Gonyaulax polyedra. Electron flow, as O(2) uptake, was measured through both photo-system I and II from water to methyl viologen, through photosystem I alone from reduced 2,6-dichlorophenol indophenol to methyl viologen which does not include the plastoquinone pool or from duroquinol to methyl viologen which includes the plastoquinone pool. Electron flow principally through photosystem II was measured from water to diaminodurene and ferricyanide, as O(2) evolution. Cultures of Gonyaulax were grown on a 12-hour light:12 hour dark cycle to late log phase, then transferred to constant light at the beginning of a light period. After 3 days, measurements of electron flow were made at the maximum and minimum of the photosynthetic rhythm, as determined from measurements of the rhythm of bioluminescence. Photosynthesis was also measured in whole cells, either as (14)C fixation or O(2) evolution. Electron flow through both photosystems and through photosystem II alone were clearly rhythmic, while electron flow through photosystem I, including or excluding the plastoquinone pool, was constant with time in the circadian cycle. Thus, only changes in photosystem II account for the photosynthesis rhythm in Gonyaulax.

The H+/e- stoicheiometry of respiration-linked proton translocation in the cytochrome system of mitochondria.

1. The -->H(+)/e(-) quotients for proton release from mitochondria associated with electron flow from succinate and duroquinol to O(2), ferricyanide or ferricytochrome c, and from NNN'N'-tetramethyl-p-phenylenediamine+ascorbate to O(2), were determined from rate measurements of electron flow and proton translocation. 2. Care was taken to avoid, or to take into account, unrelated electron flow and proton translocation, which might take place in addition to the oxido-reductions that were the subject of our analysis. Spectrophotometric techniques were chosen to provide accurate measurement of the rate of consumption of oxidants and reductants. The rate of proton translocation was measured with fast pH meters with a precision of 10(-3) pH unit. 3. The -->H(+)/O quotient for succinate or duroquinol oxidation was, at neutral pH, 4, when computed on the basis of spectrophotometric determinations of the rate of O(2) consumption or duroquinol oxidation. Higher -->H(+)/O quotients for succinate oxidation, obtained from polarographic measurements of O(2) consumption, resulted from underestimation of the respiratory rate. 4. The -->H(+)/2e(-) quotient for electron flow from succinate and duroquinol to ferricyanide or ferricytochrome c ranged from 3.9 to 3.6. 5. Respiration elicited by NNN'N'-tetramethyl-p-phenylenediamine+ascorbate by antimycin-inhibited mitochondria resulted in extra proton release in addition to that produced for oxidation of ascorbate to dehydroascorbate. Accurate spectrophotometric measurement of respiration showed that the -->H(+)/e(-) ratio was only 0.25 and not 0.7-1.0 as obtained with the inadequate polarographic assay of respiration. Proton release was practically suppressed when mitochondria were preincubated aerobically in the absence of antimycin. Furthermore, the rate of scalar proton consumption for water production was lower than that expected from the stoicheiometry. Thus the extra proton release observed during respiration elicited by NNN'N'-tetramethyl-p-phenylenediamine+ascorbate is caused by oxidation of endogenous hydrogenated reductants. 6. It is concluded that (i) the -->H(+)/O quotient for the cytochrome system is, at neutral pH, 4 and not 6 or 8 as reported by others; (ii) all the four protons are released during electron flow from quinol to cytochrome c; (iii) the oxidase transfers electrons from cytochrome c to protons from the matrix aqueous phase and does not pump protons from the matrix to the outer aqueous phase.