Science.gov

Sample records for flux rates measured

  1. RATES OF PHOTOSPHERIC MAGNETIC FLUX CANCELLATION MEASURED WITH HINODE

    SciTech Connect

    Park, Soyoung; Chae, Jongchul; Litvinenko, Yuri E.

    2009-10-10

    Photospheric magnetic flux cancellation on the Sun is generally believed to be caused by magnetic reconnection occurring in the low solar atmosphere. Individual canceling magnetic features are observationally characterized by the rate of flux cancellation. The specific cancellation rate, defined as the rate of flux cancellation divided by the interface length, gives an accurate estimate of the electric field in the reconnecting current sheet. We have determined the specific cancellation rate using the magnetograms taken by the Solar Optical Telescope (SOT) aboard the Hinode satellite. The specific rates determined with SOT turned out to be systematically higher than those based on the data taken by the Michelson Doppler Imager (MDI) aboard the Solar and Heliospheric Observatory. The median value of the specific cancellation rate was found to be 8 x 10{sup 6} G cm s{sup -1}-a value four times that obtained from the MDI data. This big difference is mainly due to a higher angular resolution and better sensitivity of the SOT, resulting in magnetic fluxes up to five times larger than those obtained from the MDI. The higher rates of flux cancellation correspond to either faster inflows or stronger magnetic fields of the reconnection inflow region, which may have important consequences for the physics of photospheric magnetic reconnection.

  2. Relationship between neutron yield rate of tokamak plasmas and spectrometer measured flux for different sight lines

    SciTech Connect

    Gorini, G.; Kaellne, J.; Ognissanto, F.; Tardocchi, M.

    2011-03-15

    A parametric relationship between total neutron yield rate and collimated fluxes related to the brightness (B) of plasma chords ({lambda}) is developed for different emissivity distributions of tokamak plasmas. Specifically, the brightness was expressed as a function of chord coordinates of radial position using a simple model for the emissivity profiles of width parameter w. The functional brightness dependence B({lambda},w) was calculated to examine the relationship between measured flux and deduced yield rate, and its plasma profile dependence. The results were used to determine the chord range of minimum profile sensitivity in order to identify the preferred collimator sight for the determination of yield rate from neutron emission spectroscopy (YNES) measurements. The YNES method is discussed in comparison to conventional methods to determine the total neutron yield rates and related plasma fusion power relying on uncollimated flux measurements and a different calibration base for the flux-yield relationship. The results have a special bearing for tokamaks operating with both deuterium and deuterium-tritium plasmas and future high power machines such as for ITER, DEMO, and IGNITOR.

  3. FFTF (FAST FLUX TEST FACILITY) REACTOR CHARACTERIZATION PROGRAM ABSOLUTE FISSION RATE MEASUREMENTS

    SciTech Connect

    FULLER JL; GILLIAM DM; GRUNDL JA; RAWLINS JA; DAUGHTRY JW

    1981-05-01

    Absolute fission rate measurements using modified National Bureau of Standards fission chambers were performed in the Fast Flux Test Facility at two core locations for isotopic deposits of {sup 232}Th, {sup 233}U, {sup 235}U, {sup 238}U, {sup 237}Np, {sup 239}Pu, {sup 240}Pu, and {sup 241}Pu. Monitor chamber results at a third location were analyzed to support other experiments involving passive dosimeter fission rate determinations.

  4. FFTF (Fast Flux Test Facility) Reactor Characterization Program: Absolute Fission-rate Measurements

    SciTech Connect

    Fuller, J.L.; Gilliam, D.M.; Grundl, J.A.; Rawlins, J.A.; Daughtry, J.W.

    1981-05-01

    Absolute fission rate measurements using modified National Bureau of Standards fission chambers were performed in the Fast Flux Test Facility at two core locations for isotopic deposits of {sup 232}Th, {sup 233}U, {sup 235}U, {sup 238}U, {sup 237}Np, {sup 239}Pu, {sup 240}Pu, and {sup 241}Pu. Monitor chamber results at a third location were analyzed to support other experiments involving passive dosimeter fission rate determinations.

  5. Heat generation rate measurement in a Li-ion cell at large C-rates through temperature and heat flux measurements

    NASA Astrophysics Data System (ADS)

    Drake, S. J.; Martin, M.; Wetz, D. A.; Ostanek, J. K.; Miller, S. P.; Heinzel, J. M.; Jain, A.

    2015-07-01

    Understanding the rate of heat generation in a Li-ion cell is critical for safety and performance of Li-ion cells and systems. Cell performance, cycle life, and system safety all depend on temperature distribution in the cell, which, in turn, depends on heat generation rate within the cell and on heat removal rate at the cell surface. Despite the existence of a number of theoretical models to predict heat generation rate, there is not much literature on experimental measurement at high C-rates. This paper reports measurement of heat generation rate from a Li-ion cell at high discharge rates, up to 9.6C, using measurements of cell temperature and surface heat flux. As opposed to calorimetry-based approaches, this method can be applied in situ to yield measurements of heat generation rate in laboratory or field use provided that at least one a priori test is performed to measure the temperature gradient within a cell in the same ambient condition. This method is based on simultaneous determination of heat stored and heat lost from the cell through heat flux and temperature measurements. A novel method is established for measurement of the internal temperature of the cell. Heat generation measurements are shown to agree with well-established theoretical models. The effect of actively cooling the cell is briefly discussed.

  6. GNSS measurement of EUV photons flux rate during strong and mid solar flares

    NASA Astrophysics Data System (ADS)

    HernáNdez-Pajares, M.; GarcíA-Rigo, A.; Juan, J. M.; Sanz, J.; Monte, E.; Aragón-ÀNgel, A.

    2012-12-01

    A new GNSS Solar Flare Activity Indicator (GSFLAI) is presented, given by the gradient of the ionospheric Vertical Total Electron Content (VTEC) rate, in terms of the solar-zenithal angle, measured from a global network of dual-frequency GPS receivers. It is highly correlated with the Extreme Ultraviolet (EUV) photons flux rate at the 26-34 nm spectral band, which is geo-effective in the ionization of the mono-atomic oxygen in the Earth's atmosphere. The results are supported by the comparison of GSFLAI with direct EUV observations provided by SEM instrument of SOHO spacecraft, for all the X-class solar flares occurring between 2001 and 2011 (more than 1000 direct comparisons at the 15 s SEM EUV sampling rate). The GSFLAI sensitivity enables detection of not only extreme X-class flares, but also of variations of one order of magnitude or even smaller (such as for M-class flares). Moreover, an optimal detection algorithm (SISTED), sharing the same physical fundamentals as GSFLAI, is also presented, providing 100% successful detection for all the X-class solar flares during 2000-2006 with registered location outside of the solar limb (i.e., detection of 94% of all of X-class solar-flares) and about 65% for M-class ones. As a final conclusion, GSFLAI is proposed as a new potential proxy of solar EUV photons flux rate for strong and mid solar flares, presenting high sensitivity with high temporal resolution (1 Hz, greater than previous solar EUV irradiance instruments), using existing ground GNSS facilities, and with the potential use as a solar flare detection parameter.

  7. Eddy covariance N2O flux measurements at low flux rates: results from the InGOS campaign in a Danish willow field.

    NASA Astrophysics Data System (ADS)

    Ibrom, Andreas; Brümmer, Christian; Hensen, Arjan; van Asperen, Hella; Carter, Mette S.; Gasche, Rainer; Famulari, Daniela; Kutsch, Werner; Pilegaard, Kim; Ambus, Per

    2014-05-01

    Nitrous oxide (N2O) fluxes from soils are characterised by their high spatial and temporal variability. The fluxes depend on the availability of the substrates for nitrification and denitrification and soil physical and chemical conditions that control the metabolic microbial activity. The sporadic nature of the fluxes and their high sensitivity to alterations of the soil climate put very high demands on measurement approaches. Laser spectroscopy enables accurate and fast response detection of atmospheric N2O concentrations and is used for eddy covariance (EC) flux measurements. Alternatively N2O fluxes can be measured with chambers together with high precision analysers. Differences in the measurement approaches and system designs are expected to have a considerable influence on the accuracy of the flux estimation. This study investigates how three different eddy covariance systems perform in a situation of low N2O fluxes from a flat surface. Chamber flux measurements with differing chamber and analyser designs are used for comparison. In April 2013, the EU research infrastructure project InGOS (http://www.ingos-infrastructure.eu/) organised a campaign of N2O flux measurements in a willow plantation close to the Risø Campus of the Technical University of Denmark. The willow field was harvested in February 2013 and received mineral fertiliser equivalent to 120 kg N ha-1 before the campaign started. Three different eddy covariance systems took part in the campaign: two Aerodyne quantum cascade laser (QCL) based systems and one Los Gatos Research off-axis integrated-cavity-output spectroscopy (ICOS) system for N2O and CO. The sonic anemometers were all installed at 2 m height above the bare ground. Gill R3 type sonic anemometers were used with QCL systems and a Gil HS-50 with the ICOS system. The 10 Hz raw data were analysed with group specific softwares and procedures. The local conditions in the exceptionally cold and dry spring 2013 did not lead to large N2O flux rates. All three EC systems showed 30 min. flux values varying around zero nmol m-2 s-1. This noise was considerably lower in the EC systems that used QCL analysers. The maximum daily averages of the uncorrected fluxes from two of the EC systems reached 0.26 (ICOS/HS50) and 0.28 (QCL/R3) nmol m-2 s-1.Spectral correction increased the flux estimates up to, e.g., 180% equivalent to 0.54 nmol m-2 s-1. The flux estimates from the soil chambers were with one exception higher than the flux estimates obtained from the EC systems with highest daily averages ranging from 0.1 up to 2 nmol m-2 s-1. These large differences were unexpected, because at least two of the EC systems were shown to accurately measure fluxes at such higher levels at another InGOS campaign in a fertilised Scottish grazed meadow. We use spectral analysis to examine the raw data for the effects of sensor noise on the flux estimates and discuss strategies on how to correct or account for it. Furthermore possible causes for the observed differences between the observed EC and chamber flux estimates will be discussed.

  8. Seasonal measurements of total OH reactivity fluxes, total ozone loss rates and missing emissions from Norway spruce in 2011

    NASA Astrophysics Data System (ADS)

    Nölscher, A. C.; Bourtsoukidis, E.; Bonn, B.; Kesselmeier, J.; Lelieveld, J.; Williams, J.

    2012-10-01

    Numerous reactive volatile organic compounds (VOCs) are emitted into the atmosphere by vegetation. Most biogenic VOCs are highly reactive towards the atmosphere's most important oxidant, the hydroxyl (OH) radical. One way to investigate the chemical interplay between biosphere and atmosphere is through the measurement of total OH reactivity, the total loss rate of OH radicals. This study presents the first determination of total OH reactivity emission rates (measurements via the Comparative Reactivity Method) based on a branch cuvette enclosure system mounted on a Norway spruce (Picea abies) throughout spring, summer and autumn 2011. In parallel separate VOC emission rates were monitored by a Proton Transfer Reaction-Mass Spectrometer (PTR-MS), and total ozone (O3) loss rates were obtained inside the cuvette. Total OH reactivity emission rates were in general temperature and light dependent, showing strong diel cycles with highest values during daytime. Monoterpene emissions contributed most, accounting for 56-69% of the measured total OH reactivity flux in spring and early summer. However, during late summer and autumn the monoterpene contribution decreased to 11-16%. At this time, a large missing fraction of the total OH reactivity emission rate (70-84%) was found when compared to the VOC budget measured by PTR-MS. Total OH reactivity and missing total OH reactivity emission rates reached maximum values in late summer corresponding to the period of highest temperature. Total O3 loss rates within the closed cuvette showed similar diel profiles and comparable seasonality to the total OH reactivity fluxes. Total OH reactivity fluxes were also compared to emissions from needle storage pools predicted by a temperature-only dependent algorithm. Deviations of total OH reactivity fluxes from the temperature-only dependent emission algorithm were observed for occasions of mechanical and heat stress. While for mechanical stress, induced by strong wind, measured VOCs could explain total OH reactivity emissions, during heat stress they could not. The temperature driven algorithm matched the diel course much better in spring than in summer, indicating a different production and emission scheme for summer and early autumn. During these times, unmeasured and possibly unknown primary biogenic emissions contributed significantly to the observed total OH reactivity flux.

  9. Combined radiocarbon and CO2 flux measurements used to determine in situ chlorinated solvent mineralization rate.

    PubMed

    Boyd, T J; Montgomery, M T; Cuenca, R H; Hagimoto, Y

    2015-03-01

    A series of combined measurements was made at the Naval Air Station North Island (NASNI) Installation Restoration Site 5, Unit 2 during July and August 2013. Combined measurements included CO2 respiration rate, CO2 radiocarbon content to estimate chlorinated hydrocarbon (CH) mineralization and a zone of influence (ZOI) model. CO2 was collected continuously over 2 two-week periods by recirculating monitoring well headspace gas through NaOH traps. A series of 12 wells in the main CH plume zone and a background well with no known historical contamination were sampled. The background well CO2 was used to determine radiocarbon content derived from respired natural organic matter. A two end-member mixing model was then used to determine the amount of CH-derived carbon present in the CO2 collected from plume region wells. The ZOI model provided an estimate for the soil volume sampled at each well. CH mineralization rates were highest upgradient and at the plume fringe for areas of high historical contamination and ranged from 0.02 to 5.6 mg CH carbon per day. Using the ZOI model volume estimates, CH-carbon removal ranged from 0.2 to 32 mg CH-carbon m(-3) per day. Because the rate estimates were based on a limited sampling (temporally), they were not further extrapolated to long-term contaminant degradation estimates. However, if the site manager or regulators required them, estimates - subject to long-term variability uncertainties - could be made using volume and rate data determined over short timescales. A more comprehensive seasonal sampling is needed to constrain long-term remediation models for the entire impacted area and identify environmental conditions related to more rapid turnover times amongst the wells. PMID:25686305

  10. MEASUREMENT OF GASEOUS EMISSION RATES FROM LAND SURFACES USING AN EMISSION ISOLATION FLUX CHAMBER. USER'S GUIDE

    EPA Science Inventory

    A promising method for monitoring ground emissions involves the use of an emission isolation flux chamber. The method is simple, easily available, and inexpensive. Applications would include RCRA and CERCLA facilities. To date, a uniform method operations does not exist. For this...

  11. Quantifying Methane Oxidation Rates and Flux During the Deepwater Horizon Oil Spill with Measurements of Methane Stable Isotopic Ratios and Concentrations

    NASA Astrophysics Data System (ADS)

    Du, M.; Kessler, J. D.; Sylva, S.

    2014-12-01

    Several independent techniques have been developed to measure the rate of methane oxidation and the source flux. However, none of these methods measure them concurrently. Here we present a stable isotope model incorporating measurements of methane stable isotopic ratios and concentrations, and current velocity, which can be used to determine methane oxidation rates, as well as the flux from the seafloor. This model was tested on 20 samples taken from 1 to 12 km from the wellhead from 11 June through 20 June 2010 during the Deepwater Horizon oil spill. Results suggest that rate of methane oxidation ranged from 22 to 844 nM d-1 in mid-June 2010 and that the flux from the seafloor was 8.4×107 moles d-1. Both estimated here are in agreement with previous estimates determined independently.

  12. Neutrino flux predictions for cross section measurements

    SciTech Connect

    Hartz, Mark

    2015-05-15

    Experiments that measure neutrino interaction cross sections using accelerator neutrino sources require a prediction of the neutrino flux to extract the interaction cross section from the measured neutrino interaction rate. This article summarizes methods of estimating the neutrino flux using in-situ and ex-situ measurements. The application of these methods by current and recent experiments is discussed.

  13. Measuring ammonia emission rates from livestock buildings and manure stores—part 1: development and validation of external tracer ratio, internal tracer ratio and passive flux sampling methods

    NASA Astrophysics Data System (ADS)

    Scholtens, R.; Dore, C. J.; Jones, B. M. R.; Lee, D. S.; Phillips, V. R.

    There is a need for robust methods for measuring ammonia emission rates from livestock buildings and manure stores, to guide efforts to abate emissions from livestock farming. This paper reports research to develop and validate three candidate measurement techniques: An external tracer ratio method, where concentrations of ammonia and sulphur hexafluoride are measured downwind of an animal house or manure store. An internal tracer ratio (ITR) method, suited to animal housings, where concentrations of ammonia and sulphur hexafluoride are measured just before air leaves the building. A flux sampler method, which uses sets of passive flux sampling devices positioned so as to intersect all significant flows of air out of an animal house or manure store source. All three of the measurement techniques were validated at a building section simulating a naturally ventilated (space-boarded) cattle house, with the external tracer ratio method also being validated at a simulated slurry store. In the validation tests on the external tracer ratio method the derived ammonia emission rates from the slurry store and cattle house validation studies were 25% below and 43% above the measured release rate, respectively. These biases were shown by t-tests to be statistically highly significant, but no clear explanation could be found for the different signs and magnitudes in the two cases. For the ITR method, recovery rates of 78% and 101% of released NH 3 were achieved, with low and high release rates, respectively. Validation tests conducted on the flux samplers gave an average of 66% (standard deviation 2.9%) ammonia recovery. The cause of this non-ideal level of recovery has not yet been identified. However, given the low standard deviation, it was concluded that these samplers could be used to measure ammonia emission rates from real farm buildings, provided that a correction factor for the non-ideal recovery was applied.

  14. A process-based model to estimate gas exchange and monoterpene emission rates in the mediterranean maquis - comparisons between modelled and measured fluxes at different scales

    NASA Astrophysics Data System (ADS)

    Vitale, M.; Matteucci, G.; Fares, S.; Davison, B.

    2009-02-01

    This paper concerns the application of a process-based model (MOCA, Modelling of Carbon Assessment) as an useful tool for estimating gas exchange, and integrating the empirical algorithms for calculation of monoterpene fluxes, in a Mediterranean maquis of central Italy (Castelporziano, Rome). Simulations were carried out for a range of hypothetical but realistic canopies of the evergreen Quercus ilex (holm oak), Arbutus unedo (strawberry tree) and Phillyrea latifolia. More, the dependence on total leaf area and leaf distribution of monoterpene fluxes at the canopy scale has been considered in the algorithms. Simulation of the gas exchange rates showed higher values for P. latifolia and A. unedo (2.39±0.30 and 3.12±0.27 gC m-2 d-1, respectively) with respect to Q. ilex (1.67±0.08 gC m-2 d-1) in the measuring campaign (May-June). Comparisons of the average Gross Primary Production (GPP) values with those measured by eddy covariance were well in accordance (7.98±0.20 and 6.00±1.46 gC m-2 d-1, respectively, in May-June), although some differences (of about 30%) were evident in a point-to-point comparison. These differences could be explained by considering the non uniformity of the measuring site where diurnal winds blown S-SW direction affecting thus calculations of CO2 and water fluxes. The introduction of some structural parameters in the algorithms for monoterpene calculation allowed to simulate monoterpene emission rates and fluxes which were in accord to those measured (6.50±2.25 vs. 9.39±4.5?g g-1DW h-1 for Q. ilex, and 0.63±0.207?g g-1DW h-1 vs. 0.98±0.30?g g-1DW h-1 for P. latifolia). Some constraints of the MOCA model are discussed, but it is demonstrated to be an useful tool to simulate physiological processes and BVOC fluxes in a very complicated plant distributions and environmental conditions, and necessitating also of a low number of input data.

  15. Beta ray flux measuring device

    DOEpatents

    Impink, Jr., Albert J. (Murrysville, PA); Goldstein, Norman P. (Murrysville, PA)

    1990-01-01

    A beta ray flux measuring device in an activated member in-core instrumentation system for pressurized water reactors. The device includes collector rings positioned about an axis in the reactor's pressure boundary. Activated members such as hydroballs are positioned within respective ones of the collector rings. A response characteristic such as the current from or charge on a collector ring indicates the beta ray flux from the corresponding hydroball and is therefore a measure of the relative nuclear power level in the region of the reactor core corresponding to the specific exposed hydroball within the collector ring.

  16. Monte Carlo simulations for high-rate fast neutron flux measurements made at the RAON neutron science facility by using MICROMEGAS

    NASA Astrophysics Data System (ADS)

    Hwang, Dae Hee; Hong, Ser Gi; Kim, Jae Cheon; Kim, Gi Dong; Kim, Yong Kyun

    2015-10-01

    RAON is a Korean heavy-ion accelerator complex that is planned to be built by 2021. Deuterons (53 MeV) and protons (88 MeV) accelerated by using a low-energy driver linac (SCL1) are delivered to the neutron production target in the Neutron Science Facility (NSF) to produce high-energy neutrons in the interval from 1 to 88 MeV with high fluxes of the order of 1012 n/cm2-sec. The repetition rate of the neutron beam ranges from 1 kHz to 1 MHz, and the maximum beam current is ~12 ?A at 1 MHz. The beam width is 1 ~ 2 ns. The high-energy and high-rate fast neutrons are used to estimate accurate neutron-induced cross sections for various nuclides at the NSF. A MICROMEGAS (MICRO Mesh Gaseous Structure), which is a gaseous detector initially developed for tracking in high-rate, high-energy physics experiments, is tentatively being considered as a neutron beam monitor. It can be used to measure both the energy distribution and the flux of the neutron beam. In this study, a MICROMEGAS detector for installation at the NSF was designed and investigated. 6Li, 10B, 235U and 238U targets are being considered as neutron/charged particle converters. For the low-energy region, 6Li(n,?)t and 10B(n,?)7Li are used in the energy range from thermal to 1 MeV. 235U(n,f) and 238U(n,f) reactions are used for high-energy region up to 90 MeV. All calculations are performed by using the GEANT4 toolkit.

  17. Measuring and modeling C flux rates through the central metabolic pathways in microbial communities using position-specific 13C-labeled tracers

    NASA Astrophysics Data System (ADS)

    Dijkstra, P.; van Groenigen, K.; Hagerty, S.; Salpas, E.; Fairbanks, D. E.; Hungate, B. A.; KOCH, G. W.; Schwartz, E.

    2012-12-01

    The production of energy and metabolic precursors occurs in well-known processes such as glycolysis and Krebs cycle. We use position-specific 13C-labeled metabolic tracers, combined with models of microbial metabolic organization, to analyze the response of microbial community energy production, biosynthesis, and C use efficiency (CUE) in soils, decomposing litter, and aquatic communities. The method consists of adding position-specific 13C -labeled metabolic tracers to parallel soil incubations, in this case 1-13C and 2,3-13C pyruvate and 1-13C and U-13C glucose. The measurement of CO2 released from the labeled tracers is used to calculate the C flux rates through the various metabolic pathways. A simplified metabolic model consisting of 23 reactions is solved using results of the metabolic tracer experiments and assumptions of microbial precursor demand. This new method enables direct estimation of fundamental aspects of microbial energy production, CUE, and soil organic matter formation in relatively undisturbed microbial communities. We will present results showing the range of metabolic patterns observed in these communities and discuss results from testing metabolic models.

  18. Latent Heat in Soil Heat Flux Measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The surface energy balance includes a term for soil heat flux. Soil heat flux is difficult to measure because it includes conduction and convection heat transfer processes. Accurate representation of soil heat flux is an important consideration in many modeling and measurement applications. Yet, the...

  19. Carbon Dioxide Flux Measurement Systems (CO2Flux) Handbook

    SciTech Connect

    Fischer, M

    2005-01-01

    The Southern Great Plains (SGP) carbon dioxide flux (CO2 flux) measurement systems provide half-hour average fluxes of CO2, H2O (latent heat), and sensible heat. The fluxes are obtained by the eddy covariance technique, which computes the flux as the mean product of the vertical wind component with CO2 and H2O densities, or estimated virtual temperature. A three-dimensional sonic anemometer is used to obtain the orthogonal wind components and the virtual (sonic) temperature. An infrared gas analyzer is used to obtain the CO2 and H2O densities. A separate sub-system also collects half-hour average measures of meteorological and soil variables from separate 4-m towers.

  20. Metabolic rate measurement system

    NASA Technical Reports Server (NTRS)

    Koester, K.; Crosier, W.

    1980-01-01

    The Metabolic Rate Measurement System (MRMS) is an uncomplicated and accurate apparatus for measuring oxygen consumption and carbon dioxide production of a test subject. From this one can determine the subject's metabolic rate for a variety of conditions, such as resting or light exercise. MRMS utilizes an LSI/11-03 microcomputer to monitor and control the experimental apparatus.

  1. Rates of total oxygen uptake of sediments and benthic nutrient fluxes measured using an in situ autonomous benthic chamber in the sediment of the slope off the southwestern part of Ulleung Basin, East Sea

    NASA Astrophysics Data System (ADS)

    Lee, Jae Seong; An, Sung-Uk; Park, Young-Gyu; Kim, Eunsoo; Kim, Dongseon; Kwon, Jung No; Kang, Dong-Jin; Noh, Jae-Hoon

    2015-09-01

    We have developed a new autonomous benthic lander for deep-sea research, the Korea Institute of Ocean Science and Technology (KIOST) Belc II and Belp II. The benthic lander was successfully tested at 950 and 1450 m water depths on the slope off the southwestern part of the Ulleung Basin in the East Sea of Korea. The ex situ measurements of the total oxygen uptake (TOU) rates at all the stations exceeded the in situ measurement values, and may indicate artificial effects from onboard incubation. The TOU rates were estimated to be 5.80 mmol m-2 d-1 and 3.77 mmol m-2 d-1 at water depths of 950 m and 1450 m, respectively. The benthic nutrient fluxes were also higher at water depths of 950 m, which indicates a partitioning of organic degradation with water depth. In addition, the negative phosphate and nitrogen benthic flux ratios and the higher nitrate removal flux via the sediment-water interface at the slope imply that the nitrogen in the bottom water may be preferentially removed via microbial respiration processes in the sediments, and may be coupled with the low nitrogen-to-phosphate ratio found in the deep water. Although our measurements comprised just two experiments in the slope sediment, the robust in situ measurement of the benthic fluxes in the slope sediment is a forerunner for new research into the biogeochemical cycles across the shelf edge-slope-basin system in the East Sea.

  2. Measuring zebrafish turning rate.

    PubMed

    Mwaffo, Violet; Butail, Sachit; di Bernardo, Mario; Porfiri, Maurizio

    2015-06-01

    Zebrafish is becoming a popular animal model in preclinical research, and zebrafish turning rate has been proposed for the analysis of activity in several domains. The turning rate is often estimated from the trajectory of the fish centroid that is output by commercial or custom-made target tracking software run on overhead videos of fish swimming. However, the accuracy of such indirect methods with respect to the turning rate associated with changes in heading during zebrafish locomotion is largely untested. Here, we compare two indirect methods for the turning rate estimation using the centroid velocity or position data, with full shape tracking for three different video sampling rates. We use tracking data from the overhead video recorded at 60, 30, and 15 frames per second of zebrafish swimming in a shallow water tank. Statistical comparisons of absolute turning rate across methods and sampling rates indicate that, while indirect methods are indistinguishable from full shape tracking, the video sampling rate significantly influences the turning rate measurement. The results of this study can aid in the selection of the video capture frame rate, an experimental design parameter in zebrafish behavioral experiments where activity is an important measure. PMID:25844837

  3. Crystal microbalance measures condensable molecular fluxes

    NASA Technical Reports Server (NTRS)

    Stephens, J. B.

    1967-01-01

    Quartz crystal quantitatively measures molecular fluxes emanating from and condensing on spacecraft surfaces. Vibrating in a thickness shear mode, the crystal is frequency sensitive to changes in mass on its surface and can measure a fractional monolayer of a condensate.

  4. Pyrolytic graphite gauge for measuring heat flux

    NASA Technical Reports Server (NTRS)

    Bunker, Robert C. (Inventor); Ewing, Mark E. (Inventor); Shipley, John L. (Inventor)

    2002-01-01

    A gauge for measuring heat flux, especially heat flux encountered in a high temperature environment, is provided. The gauge includes at least one thermocouple and an anisotropic pyrolytic graphite body that covers at least part of, and optionally encases the thermocouple. Heat flux is incident on the anisotropic pyrolytic graphite body by arranging the gauge so that the gauge surface on which convective and radiative fluxes are incident is perpendicular to the basal planes of the pyrolytic graphite. The conductivity of the pyrolytic graphite permits energy, transferred into the pyrolytic graphite body in the form of heat flux on the incident (or facing) surface, to be quickly distributed through the entire pyrolytic graphite body, resulting in small substantially instantaneous temperature gradients. Temperature changes to the body can thereby be measured by the thermocouple, and reduced to quantify the heat flux incident to the body.

  5. Calving fluxes and basal melt rates of Antarctic ice shelves.

    PubMed

    Depoorter, M A; Bamber, J L; Griggs, J A; Lenaerts, J T M; Ligtenberg, S R M; van den Broeke, M R; Moholdt, G

    2013-10-01

    Iceberg calving has been assumed to be the dominant cause of mass loss for the Antarctic ice sheet, with previous estimates of the calving flux exceeding 2,000?gigatonnes per year. More recently, the importance of melting by the ocean has been demonstrated close to the grounding line and near the calving front. So far, however, no study has reliably quantified the calving flux and the basal mass balance (the balance between accretion and ablation at the ice-shelf base) for the whole of Antarctica. The distribution of fresh water in the Southern Ocean and its partitioning between the liquid and solid phases is therefore poorly constrained. Here we estimate the mass balance components for all ice shelves in Antarctica, using satellite measurements of calving flux and grounding-line flux, modelled ice-shelf snow accumulation rates and a regional scaling that accounts for unsurveyed areas. We obtain a total calving flux of 1,321?±?144?gigatonnes per year and a total basal mass balance of -1,454?±?174?gigatonnes per year. This means that about half of the ice-sheet surface mass gain is lost through oceanic erosion before reaching the ice front, and the calving flux is about 34 per cent less than previous estimates derived from iceberg tracking. In addition, the fraction of mass loss due to basal processes varies from about 10 to 90 per cent between ice shelves. We find a significant positive correlation between basal mass loss and surface elevation change for ice shelves experiencing surface lowering and enhanced discharge. We suggest that basal mass loss is a valuable metric for predicting future ice-shelf vulnerability to oceanic forcing. PMID:24037377

  6. Eddy Correlation Flux Measurement System (ECOR) Handbook

    SciTech Connect

    Cook, DR

    2011-01-31

    The eddy correlation (ECOR) flux measurement system provides in situ, half-hour measurements of the surface turbulent fluxes of momentum, sensible heat, latent heat, and carbon dioxide (CO2) (and methane at one Southern Great Plains extended facility (SGP EF) and the North Slope of Alaska Central Facility (NSA CF). The fluxes are obtained with the eddy covariance technique, which involves correlation of the vertical wind component with the horizontal wind component, the air temperature, the water vapor density, and the CO2 concentration.

  7. Noninvasive measurement of pulmonary transvascular protein flux in normal man.

    PubMed Central

    Gorin, A B; Kohler, J; DeNardo, G

    1980-01-01

    Onset of lung edema is usually associated with increase in the pulmonary transvascular flux of water and proteins. Clinical measurement of these parameters may aid in early diagnosis of pulmonary edema, and allow differentiation between "cardiogenic" and "noncardiogenic" types base on the magnitude of the detected changes. We have previously described a noninvasive method for estimating transvascular protein flux in lung (Gorin, A. B., W. J. Weidner, R. H. Demling, and N. C. Staub, 1978. Noninvasive measurement of pulmonary transvascular protein flux in sheep. J. Appl. Physiol. 45: 225-233). Using this method we measured the net transvascular flux of [113mIn]transferrin (mol wt, 76,000 in lungs of nine normal human volunteers. Plasma clearance of [113In]transferrin occurred with a T1/2 = 7.0 +/- 2.6 h (mean +/- SD). The pulmonary transvascular flux coefficient, alpha, was 2.9 +/- 1.4 X 10(-3) ml/s (mean +/- SD) in man, slightly greater than that previously measured in sheep (2.7 +/- 0.7 X 10(-3) ml/s; mean +/- SD). The pulmonary transcapillary escape rate is twofold greater than the transcapillary escape rate for the vascular bed as a whole, indicating a greater "porosity" of exchanging vessels in the lung than exists for the "average" microvessel in the body. Time taken to reach half-equilibrium concentration of tracer protein in the lung interstitium was quite short, 52 +/- 13 min (mean +/- SD). We have shown that measurement of pulmonary transvascular protein flux in man is practical. The coefficient of variation of measurements of alpha (between subjects) was 0.48, and of measurements of pulmonary transcapillary escape rates was 0.39. In animals, endothelial injury commonly results in a two- to threefold increase in transvascular protein flux. Thus, external radioflux detection should be a suitable means of quantitating lung vascular injury in human disease states. PMID:7430349

  8. Cosmic muon flux measurements at the Kimballton Underground Research Facility

    NASA Astrophysics Data System (ADS)

    Kalousis, L. N.; Guarnaccia, E.; Link, J. M.; Mariani, C.; Pelkey, R.

    2014-08-01

    In this article, the results from a series of muon flux measurements conducted at the Kimballton Underground Research Facility (KURF), Virginia, United States, are presented. The detector employed for these investigations, is made of plastic scintillator bars readout by wavelength shifting fibers and multianode photomultiplier tubes. Data was taken at several locations inside KURF, spanning rock overburden values from ~ 200 to 1450 m.w.e. From the extracted muon rates an empirical formula was devised, that estimates the muon flux inside the mine as a function of the overburden. The results are in good agreement with muon flux calculations based on analytical models and MUSIC.

  9. Measuring Flux Density Of Monatomic Oxygen

    NASA Technical Reports Server (NTRS)

    Carruth, M. R., Jr.; Dehaye, R. F.; Norwood, J. K.; Whitaker, A. F.

    1991-01-01

    Improved version of catalytic-probe technique yields more accurate measurements of flux density of neutral, monatomic oxygen. Two probes measure heat of recombination on catalytic surface. Principal application of technique in experiments in which oxygen plasmas used to examine degradation of various materials by monatomic oxygen.

  10. Fundamentals of heat measurement. [heat flux transducers

    NASA Technical Reports Server (NTRS)

    Gerashchenko, O. A.

    1979-01-01

    Various methods and devices for obtaining experimental data on heat flux density over wide ranges of temperature and pressure are examined. Laboratory tests and device fabrication details are supplemented by theoretical analyses of heat-conduction and thermoelectric effects, providing design guidelines and information relevant to further research and development. A theory defining the measure of correspondence between transducer signal and the measured heat flux is established for individual (isolated) heat flux transducers subject to space and time-dependent loading. An analysis of the properties of stacked (series-connected) transducers of various types (sandwich-type, plane, and spiral) is used to derive a similarity theory providing general governing relationships. The transducers examined are used in 36 types of derivative devices involving direct heat loss measurements, heat conduction studies, radiation pyrometry, calorimetry in medicine and industry and nuclear reactor dosimetry.

  11. Experimental flux measurements on a network scale

    SciTech Connect

    Schwender, J.

    2011-10-11

    Metabolic flux is a fundamental property of living organisms. In recent years, methods for measuring metabolic flux in plants on a network scale have evolved further. One major challenge in studying flux in plants is the complexity of the plant's metabolism. In particular, in the presence of parallel pathways in multiple cellular compartments, the core of plant central metabolism constitutes a complex network. Hence, a common problem with the reliability of the contemporary results of {sup 13}C-Metabolic Flux Analysis in plants is the substantial reduction in complexity that must be included in the simulated networks; this omission partly is due to limitations in computational simulations. Here, I discuss recent emerging strategies that will better address these shortcomings.

  12. Dual neutron flux/temperature measurement sensor

    DOEpatents

    Mihalczo, J.T.; Simpson, M.L.; McElhaney, S.A.

    1994-10-04

    Simultaneous measurement of neutron flux and temperature is provided by a single sensor which includes a phosphor mixture having two principal constituents. The first constituent is a neutron sensitive 6LiF and the second is a rare-earth activated Y203 thermophosphor. The mixture is coated on the end of a fiber optic, while the opposite end of the fiber optic is coupled to a light detector. The detected light scintillations are quantified for neutron flux determination, and the decay is measured for temperature determination. 3 figs.

  13. Dual neutron flux/temperature measurement sensor

    DOEpatents

    Mihalczo, John T. (Oak Ridge, TN); Simpson, Marc L. (Knoxville, TN); McElhaney, Stephanie A. (Oak Ridge, TN)

    1994-01-01

    Simultaneous measurement of neutron flux and temperature is provided by a single sensor which includes a phosphor mixture having two principal constituents. The first constituent is a neutron sensitive 6LiF and the second is a rare-earth activated Y203 thermophosphor. The mixture is coated on the end of a fiber optic, while the opposite end of the fiber optic is coupled to a light detector. The detected light scintillations are quantified for neutron flux determination, and the decay is measured for temperature determination.

  14. Observational biases in flux magnification measurements

    E-print Network

    Hildebrandt, Hendrik

    2015-01-01

    Flux magnification is an interesting complement to shear-based lensing measurements, especially at high redshift where sources are harder to resolve. One measures either changes in the source density (magnification bias) or in the shape of the flux distribution (e.g. magnitude-shift). The interpretation of these measurements relies on theoretical estimates of how the observables change under magnification. Here we present simulations to create multi-band photometric mock catalogues of Lyman-break galaxies in a CFHTLenS-like survey that include several observational effects that can change these relations, making simple theoretical estimates unusable. In particular, we show how the magnification bias can be affected by photometric noise, colour selection, and dust extinction. We find that a simple measurement of the slope of the number-counts is not sufficient for the precise interpretation of virtually all observations of magnification bias. We also explore how sensitive the shift in the mean magnitude of a s...

  15. Plasma momentum meter for momentum flux measurements

    DOEpatents

    Zonca, Fulvio (Rome, IT); Cohen, Samuel A. (Hopewell, NJ); Bennett, Timothy (Princeton, NJ); Timberlake, John R. (Allentown, NJ)

    1993-01-01

    Invention comprises an instrument in which momentum flux onto a biasable target plate is transferred via a suspended quartz tube onto a sensitive force transducer--a capacitance-type pressure gauge. The transducer is protected from thermal damage, arcing and sputtering, and materials used in the target and pendulum are electrically insulating, rigid even at elevated temperatures, and have low thermal conductivity. The instrument enables measurement of small forces (10.sup.-5 to 10.sup.3 N) accompanied by high heat fluxes which are transmitted by energetic particles with 10's of eV of kinetic energy in a intense magnetic field and pulsed plasma environment.

  16. Applications and theory of micrometeorological flux measurement

    NASA Astrophysics Data System (ADS)

    Warland, Jon Steven

    1999-12-01

    Several aspects of micrometeorological flux measurement are explored in this thesis. After a brief sketch of the history of the topic, the field testing of a tunable diode laser trace gas analyzer system (TDLTGAS) is reported. This system uses infrared absorption spectroscopy to monitor atmospheric ammonia concentrations. We monitored ammonia concentration gradients over 3 plots receiving different manure applications. From the gradients, fluxes of ammonia were calculated every 15 min, allowing continuous monitoring of the three treatments. The system functioned well and analysis of the response showed no problems with ammonia adsorption to the walls of the system. A technique for monitoring flux ratios from small (<5 m2) microplots was also field tested. This method monitors concentration profiles close to the surface, and from these the ratio of gradients, which is equal to the ratio of fluxes, is calculated. The field test of this method used acetylene inhibition of denitrification. Acetylene prevents the reduction of N2O to N2 by denitrifying bacteria, thereby increasing the flux of N2O by an amount equal to the N2 flux that would have been. By comparing the ratio of N2O fluxes from microplots with and without acetylene, an estimate of N2 production by denitrification was obtained. Field testing showed the technique to be practical and easily implemented. The final chapter of this thesis analyzes the relationship between a canopy scalar source profile and the resulting concentration profile. The model developed here translates the temporal near-field into a spatial near-field, allowing a concentration profile to be calculated from a source distribution through a mixing matrix. The mixing matrix sums up the contribution of each source to the gradient at each height, and the gradient profile is then integrated to determine the concentration profile. Comparison of the model with a wind tunnel dispersion experiment shows excellent agreement, though field testing of the model is still required.

  17. Infrared Camera Diagnostic for Heat Flux Measurements on NSTX

    SciTech Connect

    D. Mastrovito; R. Maingi; H.W. Kugel; A.L. Roquemore

    2003-03-25

    An infrared imaging system has been installed on NSTX (National Spherical Torus Experiment) at the Princeton Plasma Physics Laboratory to measure the surface temperatures on the lower divertor and center stack. The imaging system is based on an Indigo Alpha 160 x 128 microbolometer camera with 12 bits/pixel operating in the 7-13 {micro}m range with a 30 Hz frame rate and a dynamic temperature range of 0-700 degrees C. From these data and knowledge of graphite thermal properties, the heat flux is derived with a classic one-dimensional conduction model. Preliminary results of heat flux scaling are reported.

  18. Micrometeorological flux measurements at a coastal site

    NASA Astrophysics Data System (ADS)

    Song, Guozheng; Meixner, Franz X.; Bruse, Michael; Mamtimin, Buhalqem

    2014-05-01

    The eddy covariance (EC) technique is the only direct measurement of the momentum, heat, and trace gas (e.g. water vapor, CO2 and ozone) fluxes. The measurements are expected to be most accurate over flat terrain where there is an extended homogenous surface upwind from the tower, and when the environmental conditions are steady. Additionally, the one dimensional approach assumes that vertical turbulent exchange is the dominant flux, whereas advective influences should be negligible. The application of EC method under non-ideal conditions, for example in complex terrain, has yet to be fully explored. To explore the possibilities and limitations of EC technique under non-ideal conditions, an EC system was set up at Selles beach, Crete, Greece (35.33°N, 25.71°E) in the beginning of July 2012. The dominant wind direction was west, parallel to the coast. The EC system consisted of a sonic anemometer (CSAT3 Campbell Scientific), an infrared open-path CO2/H2O gas analyzer (LI-7500, Li-COR Biosciences) and a fast chemiluminescence ozone analyzer (enviscope GmbH). All the signals of these fast response instruments were sampled at 10 Hz and the measurement height was 3 m. Besides, another gradient system was setup. Air temperature, relative humidity (HYGROMER MP 103 A), and wind speed (WMT700 Vaisala) were measured every 10 seconds at 3 heights (0.7, 1.45, 3 m). Air intakes were set up at 0.7m and 3m. A pump drew the air through a flow system and a telflon valve alternately switched between the two heights every 30 seconds. H2O, CO2 (LI-840A, Li-COR Biosciences) and ozone mixing ratio s (model 205, 2BTechnologies) were measured every 10 seconds. Momentum, heat, CO2 and ozone fluxes were evaluated by both EC and gradient technique. For the calculation of turbulent fluxes, TK3 algorithm (Department of Micrometeorology, University Bayreuth, Germany) was applied. We will present the measured fluxes of the two systems and assess the data quality under such non-ideal condition.

  19. High heat flux measurements and experimental calibrations/characterizations

    NASA Technical Reports Server (NTRS)

    Kidd, Carl T.

    1992-01-01

    Recent progress in techniques employed in the measurement of very high heat-transfer rates in reentry-type facilities at the Arnold Engineering Development Center (AEDC) is described. These advances include thermal analyses applied to transducer concepts used to make these measurements; improved heat-flux sensor fabrication methods, equipment, and procedures for determining the experimental time response of individual sensors; performance of absolute heat-flux calibrations at levels above 2,000 Btu/cu ft-sec (2.27 kW/cu cm); and innovative methods of performing in-situ run-to-run characterizations of heat-flux probes installed in the test facility. Graphical illustrations of the results of extensive thermal analyses of the null-point calorimeter and coaxial surface thermocouple concepts with application to measurements in aerothermal test environments are presented. Results of time response experiments and absolute calibrations of null-point calorimeters and coaxial thermocouples performed in the laboratory at intermediate to high heat-flux levels are shown. Typical AEDC high-enthalpy arc heater heat-flux data recently obtained with a Calspan-fabricated null-point probe model are included.

  20. A new disjunct eddy-covariance system for BVOC flux measurements - validation on CO2 and H2O fluxes

    NASA Astrophysics Data System (ADS)

    Baghi, R.; Durand, P.; Jambert, C.; Jarnot, C.; Delon, C.; Serça, D.; Striebig, N.; Ferlicoq, M.; Keravec, P.

    2012-12-01

    The disjunct eddy covariance (DEC) method is an interesting alternative to the conventional eddy covariance (EC) method because it allows the estimation of turbulent fluxes of species for which fast sensors are not available. We have developed and validated a new disjunct sampling system (called MEDEE). This system is built with chemically inert materials. Air samples are taken quickly and alternately in two cylindrical reservoirs, the internal pressures of which are regulated by a moving piston. The MEDEE system was designed to be operated either on the ground or aboard an aircraft. It is also compatible with most analysers since it transfers the air samples at a regulated pressure. To validate the system, DEC and EC measurements of CO2 and latent heat fluxes were performed concurrently during a field campaign. EC fluxes were first compared to simulated DEC (SDEC) fluxes and then to actual DEC fluxes. Both the simulated and actual DEC fluxes showed a good agreement with EC fluxes in terms of correlation. The determination coefficients (R2) were 0.93 and 0.91 for DEC and SDEC latent heat fluxes, respectively. For DEC and SDEC CO2 fluxes R2 was 0.69 in both cases. The conditions of low fluxes experienced during the campaign impaired the comparison of the different techniques especially for CO2 flux measurements. Linear regression analysis showed an 14% underestimation of DEC fluxes for both CO2 and latent heat compared to EC fluxes. A first field campaign, focusing on biogenic volatile organic compound (BVOC) emissions, was carried out to measure isoprene fluxes above a downy oak (Quercus Pubescens) forest in the south-east of France. The measured standard emission rate was in the lower range of reported values in earlier studies. Further analysis will be conducted through ground-based and airborne campaigns in the coming years.

  1. Rapid and Precise Determination of Cellular Amino Acid Flux Rates

    E-print Network

    Wikswo, John

    Rapid and Precise Determination of Cellular Amino Acid Flux Rates Using HPLC with Automated Derivatization with Absorbance Detection Abstract A method is presented for analyzing primary amino acids detection. Amino acids are derivatized with orthophthaldildehyde (OPA) using an online injector program

  2. ACCURACY OF SOIL HEAT FLUX MEASUREMENTS MADE WITH FLUX PLATES OF CONTRASTING PROPERTIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Flux plate measurements of soil heat flux (G) may include significant errors unless the plates are carefully installed and known errors accounted for. The objective of this research was to quantify potential errors in G when using soil heat flux plates of contrasting designs. Five flux plates with...

  3. Untangling autophagy measurements: all fluxed up.

    PubMed

    Gottlieb, Roberta A; Andres, Allen M; Sin, Jon; Taylor, David P J

    2015-01-30

    Autophagy is an important physiological process in the heart, and alterations in autophagic activity can exacerbate or mitigate injury during various pathological processes. Methods to assess autophagy have changed rapidly because the field of research has expanded. As with any new field, methods and standards for data analysis and interpretation evolve as investigators acquire experience and insight. The purpose of this review is to summarize current methods to measure autophagy, selective mitochondrial autophagy (mitophagy), and autophagic flux. We will examine several published studies where confusion arose in data interpretation, to illustrate the challenges. Finally, we will discuss methods to assess autophagy in vivo and in patients. PMID:25634973

  4. A storage-extended rating curve for sediment flux estimation

    NASA Astrophysics Data System (ADS)

    Fink, Gabriel; Wüest, Alfred

    2014-05-01

    An empirical suspended sediment concentration (SSC) estimation method was tested, which incorporates sediment storage, erosion, and sedimentation history of the upstream river system. It is based on the common rating curve method of which inaccurate SSC estimation is prevailingly caused by the assumption of an over-proportional relationship between SSC and discharge. However, this ignores the fact that SSC depends on the availability of sediments in the river basin as well. Hence, the tested method includes non-linear processes such as the clockwise and counter-clockwise hysteresis during flood discharges. The main characteristic of this new approach is that sediment flux is described as a composition of (i) the base transport of sediments from the catchment area into the river system, (ii) erosion, and (iii) in-situ sedimentation. The first two components are approximated with classical rating curves. The second component depends on (i) a threshold discharge for erosion and (ii) on the sediment availability. Sedimentation is factored as a constant value and it is zero if the discharge exceeds the threshold value. This new model formulation was tested with daily SSC and discharge measurements from the Alpine Rhine River for the period 1 June 2012 to 31 May 2013 at gauging station Diepoldsau, which is located a few kilometres upstream of Lake Constance. The seven empirical parameters of the model were estimated by using an evolutionary algorithm. This optimization algorithm found a threshold for erosion at a discharge of about 500 m3 s-1, a mean concentration of 124 mg l-1 that is lost due to sedimentation, and the mean content of sediment storage in the river bed of about 1.82×1011 kg, which is available for erosion. The results show an clear improvement of SSC estimation: R2 increased to 0.93 while it was 0.73 for the rating curve. Moreover, the new method calculated flood loads, which fitted perfect to measured sediments: e.g. the measured flood load of 7392 mg l-1 (4 June 2013) was approximated with 7357 mg l-1 by the model. To conclude, the additional consideration of erosion and sedimentation processes significantly improves SSC estimations especially during flood events and it offers a reliable way to estimate SSC time series with runoff data.

  5. ERRORS IN SOIL HEAT FLUX MEASUREMENT: EFFECTS OF FLUX PLATE DESIGN AND VARYING SOIL THERMAL PROPERTIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The flux plate method is the most commonly employed method for measuring soil heat flux (G) in surface energy balance studies. Nonetheless, significant errors in G measured with flux plates can occur unless proper installation techniques are used and necessary corrections made. The objective of th...

  6. A Push-Pull Test to Measure Volatilization Fluxes of Organic Pollutants without Flux Chambers

    NASA Astrophysics Data System (ADS)

    Reid, M. C.; Jaffe, P. R.

    2011-12-01

    Volatilization of organic contaminants is a potentially significant removal mechanism from wetlands, but field measurements are scarce and the physiochemical controls on volatilization from wetland soils remain poorly understood. It has been established that volatilization rates of certain pollutants are enhanced by vegetation and are strongly correlated with evapotranspiration (ET). These observations rely on flux chambers measurements, which are characterized by significant uncertainty due the chamber's effects on the meteorological variables around the plant and consequent impact on the biophysical processes governing ET and plant uptake of soil contaminants. Here we present data from a mesocosm study using a modified single-well push-pull test to measure in-situ volatilization rates from inundated soils vegetated with the wetland macrophytes Scirpus acutus and Typha latifolia, as well as from unplanted soil. This new method uses a test solution containing the volatile tracers sulfur hexafluoride (SF6), helium (He), and dichlorodifluoromethane (CFC-12) to estimate first-order volatilization rates and examine the relationship between physiochemical properties and volatilization rates. The test also yields an estimate for the volume of subsurface gas bubbles, which is used to derive a retardation factor for the effect of interphase partitioning on the estimation of kinetic parameters. We evaluate models to partition observed fluxes into different pathways for plant-mediated volatilization: transpirational uptake and consequent volatilization, and gas-phase diffusion through porous root aerenchyma. Those models are then used to scale tracer-derived volatilization fluxes to priority organic pollutants including benzene, trichloroethylene, and vinyl chloride. We also discuss the implementation of this method at field scales to estimate volatilization as a component of phytoremediation applications.

  7. Deformational injection rate measuring method

    NASA Astrophysics Data System (ADS)

    Mar?i?, Milan

    2002-09-01

    After completing the diesel engine endurance testing, we detected various traces of thermal load on the walls of combustion chambers located in the engine pistons. The engines were fitted with ? combustion chambers. The thermal load of different intensity levels occurred where the spray of fuel, fuel vapor, and air interacted with the combustion chamber wall. The uneven thermal load distribution of the combustion chamber wall results from varying injection rates in each injection nozzle hole. The most widely applied controlling methods so far for injection rate measurement, such as the Zeuch and Bosch concepts, allow measurement of only the total injection rate in multihole nozzles, without providing any indication whatsoever of the injection rate differences in individual injection nozzle holes. The new deformational measuring method described in the article allows the injection rate to be measured in each hole of the multihole nozzle. The results of the measurements using this method showed that the differences occurred in injection rates of individual injection nozzle holes. These differences may be the cause of various thermal loads on the combustion chamber walls. The criterion for injection rate is the deformation of the membrane due to an increase in the fuel quantity in the measuring space and due to the pressure waves resulting from the fuel being injected into the measuring space. The membrane deformation is measured using strain gauges, glued to the membrane and forming the Wheatstone's bridge. We devoted special attention to the temperature compensation of the Wheatstone's bridge and the membrane, heated up during the measurements.

  8. Data assimilation tool to reconstruct particle flux measurements

    NASA Astrophysics Data System (ADS)

    Bourdarie, Sebastien A.; Maget, Vincent; Lazaro, Didier; Sandberg, Ingmar

    2014-05-01

    In the framework of the EU-FP7 MAARBLE project, the Salammbô code and an ensemble Kalman filter is being used to reproduce the electron radiation belt dynamics during storms: (1) The ONERA data assimilation tool has been improved to ingest count rates instead of flux when the instrument response function is available. As an example, the ESA/SREM radiation monitor has complex response functions (proton and electron events are mixed, and for a given specie the instrument responds to a broad range of energies with different efficiencies) which makes very challenging to get fluxes out of count rates. (2) INTEGRAL/SREM, GIOVE-B/SREM, XMM/ERMD and GOES/SEM data assimilation is performed to reproduce with high fidelity the electron belt dynamics during magnetic storms. (3) Because the outputs of the tool are phase space densities, it is then possible to reconstruct INTEGRAL/SREM and GIOVE-B/SREM fluxes time series. In the present talk, an overview of the data assimilation tool will be given. The advantage of using assimilation tool to reconstruct particle flux measurements will be discussed. MAARBLE has received fundings from the European Community's Seventh Framework Programme (FP7-SPACE-.2010-1, SP1 Cooperation, Collaborative project) under grant agreement n284520. This paper reflects only the authors' views and the European Union is not liable for any use that may be made of the information contained therein.

  9. Novel Sensor for the In Situ Measurement of Uranium Fluxes

    SciTech Connect

    Hatfield, Kirk

    2015-02-10

    The goal of this project was to develop a sensor that incorporates the field-tested concepts of the passive flux meter to provide direct in situ measures of flux for uranium and groundwater in porous media. Measurable contaminant fluxes [J] are essentially the product of concentration [C] and groundwater flux or specific discharge [q ]. The sensor measures [J] and [q] by changes in contaminant and tracer amounts respectively on a sorbent. By using measurement rather than inference from static parameters, the sensor can directly advance conceptual and computational models for field scale simulations. The sensor was deployed in conjunction with DOE in obtaining field-scale quantification of subsurface processes affecting uranium transport (e.g., advection) and transformation (e.g., uranium attenuation) at the Rifle IFRC Site in Rifle, Colorado. Project results have expanded our current understanding of how field-scale spatial variations in fluxes of uranium, groundwater and salient electron donor/acceptors are coupled to spatial variations in measured microbial biomass/community composition, effective field-scale uranium mass balances, attenuation, and stability. The coupling between uranium, various nutrients and micro flora can be used to estimate field-scale rates of uranium attenuation and field-scale transitions in microbial communities. This research focuses on uranium (VI), but the sensor principles and design are applicable to field-scale fate and transport of other radionuclides. Laboratory studies focused on sorbent selection and calibration, along with sensor development and validation under controlled conditions. Field studies were conducted at the Rifle IFRC Site in Rifle, Colorado. These studies were closely coordinated with existing SBR (formerly ERSP) projects to complement data collection. Small field tests were conducted during the first two years that focused on evaluating field-scale deployment procedures and validating sensor performance under controlled field conditions. In the third and fourth year a suite of larger field studies were conducted. For these studies, the uranium flux sensor was used with uranium speciation measurements and molecular-biological tools to characterize microbial community and active biomass at synonymous wells distributed in a large grid. These field efforts quantified spatial changes in uranium flux and field-scale rates of uranium attenuation (ambient and stimulated), uranium stability, and quantitatively assessed how fluxes and effective reaction rates were coupled to spatial variations in microbial community and active biomass. Analyses of data from these field experiments were used to generate estimates of Monod kinetic parameters that are ‘effective’ in nature and optimal for modeling uranium fate and transport at the field-scale. This project provided the opportunity to develop the first sensor that provides direct measures of both uranium (VI) and groundwater flux. A multidisciplinary team was assembled to include two geochemists, a microbiologist, and two quantitative contaminant hydrologists. Now that the project is complete, the sensor can be deployed at DOE sites to evaluate field-scale uranium attenuation, source behavior, the efficacy of remediation, and off-site risk. Because the sensor requires no power, it can be deployed at remote sites for periods of days to months. The fundamental science derived from this project can be used to advance the development of predictive models for various transport and attenuation processes in aquifers. Proper development of these models is critical for long-term stewardship of contaminated sites in the context of predicting uranium source behavior, remediation performance, and off-site risk.

  10. Latent heat sink in soil heat flux measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The surface energy balance includes a term for soil heat flux. Soil heat flux is difficult to measure because it includes conduction and convection heat transfer processes. Accurate representation of soil heat flux is an important consideration in many modeling and measurement applications. Yet, the...

  11. NIST Measurement Services: Heat-Flux Sensor Calibration

    E-print Network

    -flux sensors (test number 35101C in SP250, NIST Calibration Services Users Guide). Inquiries concerningNIST Measurement Services: Heat-Flux Sensor Calibration NIST Special Publication 250-65 Benjamin K Special Publication 250-65 NIST MEASUREMENT SERVICES: Heat-Flux Sensor Calibration Benjamin K. Tsai

  12. Plasma momentum meter for momentum flux measurements

    DOEpatents

    Zonca, F.; Cohen, S.A.; Bennett, T.; Timberlake, J.R.

    1993-08-24

    An apparatus is described for measuring momentum flux from an intense plasma stream, comprising: refractory target means oriented normal to the flow of said plasma stream for bombardment by said plasma stream where said bombardment by said plasma stream applies a pressure to said target means, pendulum means for communicating a translational displacement of said target to a force transducer where said translational displacement of said target is transferred to said force transducer by an elongated member coupled to said target, where said member is suspended by a pendulum configuration means and where said force transducer is responsive to said translational displacement of said member, and force transducer means for outputting a signal representing pressure data corresponding to said displacement.

  13. In situ measurement of mesopelagic particle sinking rates and the control of carbon transfer to the ocean interior during the Vertical Flux in the Global Ocean (VERTIGO) voyages in the North Pacific

    NASA Astrophysics Data System (ADS)

    Trull, T. W.; Bray, S. G.; Buesseler, K. O.; Lamborg, C. H.; Manganini, S.; Moy, C.; Valdes, J.

    2008-07-01

    Among the parameters affecting carbon transfer to the ocean interior, particle sinking rates vary three orders of magnitude and thus more than primary production, f-ratios, or particle carbon contents [e.g., Boyd, P.W., Trull, T.W., 2006. Understanding the export of marine biogenic particles: is there consensus? Progress in Oceanography 4, 276-312, doi:10.1016/j.pocean.2006.10.007]. Very few data have been obtained from the mesopelagic zone where the majority of carbon remineralization occurs and the attenuation of the sinking flux is determined. Here, we report sinking rates from ˜300 m depth for the subtropical (station ALOHA, June 2004) and subarctic (station K2, July 2005) North Pacific Ocean, obtained from short (6.5 day) deployments of an indented rotating sphere (IRS) sediment trap operating as an in situ settling column [Peterson, M.L., Wakeham, S.G., Lee, C., Askea, M.A., Miquel, J.C., 2005. Novel techniques for collection of sinking particles in the ocean and determining their settling rates. Limnology and Oceanography Methods 3, 520-532] to separate the flux into 11 sinking-rate fractions ranging from >820 to >2 m d -1 that are collected by a carousel for further analysis. Functioning of the IRS trap was tested using a novel programming sequence to check that all particles have cleared the settling column prior to the next delivery of particles by the 6-hourly rotation cycle of the IRS. There was some evidence (from the flux distribution among the cups and photomicroscopy of the collected particles) that very slow-sinking particles may have been under-collected because they were unable to penetrate the brine-filled collection cups, but good evidence for appropriate collection of fast-settling fractions. Approximately 50% of the particulate organic carbon (POC) flux was sinking at greater than 100 m d -1 at both stations. At ALOHA, more than 15% of the POC flux sank at >820 m d -1, but low fluxes make this uncertain, and precluded resolution of particles sinking slower than 137 m d -1. At K2, less than 1% of the POC flux sank at >820 m d -1, but a large fraction (˜15-45%) of the flux was contributed by other fast-sinking classes (410 and 205 m d -1). PIC and BSi minerals were not present in higher proportions in the faster sinking fractions, but the observations were too limited to rule out a ballasting contribution to the control of sinking rates. Photographic evidence for a wide range of particle types within individual sinking-rate fractions suggests that biological processes that set the porosity and shape of particles are also important and may mask the role of minerals. Comparing the spectrum of sinking rates observed at K2 with the power-law profile of flux attenuation with depth obtained from other VERTIGO sediment traps deployed at multiple depths [Buesseler, K.O., Lamborg, C.H., Boyd, P.W., Lam, P.J., Trull, T.W., Bidigare, R.R., Bishop, J.K.B., Casciotti, K.L., Dehairs, F., Elskens, M., Honda, M., Karl, D.M., Siegel, D., Silver, M., Steinberg, D., Valdes, J., Van Mooy, B., Wilson, S.E., 2007b. Revisiting carbon flux through the Ocean's twilight zone. Science 316(5824), 567-570, doi: 10.1126/science.1137959] emphasizes the importance of particle transformations within the mesopelagic zone in the control of carbon transport to the ocean interior.

  14. Flux Rope Acceleration and Enhanced Magnetic Reconnection Rate

    SciTech Connect

    C.Z. Cheng; Y. Ren; G.S. Choe; Y.-J. Moon

    2003-03-25

    A physical mechanism of flares, in particular for the flare rise phase, has emerged from our 2-1/2-dimensional resistive MHD simulations. The dynamical evolution of current-sheet formation and magnetic reconnection and flux-rope acceleration subject to continuous, slow increase of magnetic shear in the arcade are studied by employing a non-uniform anomalous resistivity in the reconnecting current sheet under gravity. The simulation results directly relate the flux rope's accelerated rising motion with an enhanced magnetic reconnection rate and thus an enhanced reconnection electric field in the current sheet during the flare rise phase. The simulation results provide good quantitative agreements with observations of the acceleration of flux rope, which manifests in the form of SXR ejecta or erupting filament or CMEs, in the low corona. Moreover, for the X-class flare events studied in this paper the peak reconnection electric field is about O(10{sup 2} V/m) or larger, enough to accelerate p articles to over 100 keV in a field-aligned distance of 10 km. Nonthermal electrons thus generated can produce hard X-rays, consistent with impulsive HXR emission observed during the flare rise phase.

  15. Measurement of Integrated Low Frequency Flux Noise in Superconducting Flux/Phase Qubits

    SciTech Connect

    Mao Bo; Qiu Wei; Han Siyuan

    2008-11-07

    We measured the integrated low frequency flux noise ({approx}1 m{phi}{sub 0}) of an rf SQUID as a flux qubit by fitting the resonant peaks from photon assistant tunneling (PAT). The energy relaxation time Tl between the ground and first excited states in the same potential well, measured directly in time domain, is 3 ns. From these results we identified low frequency flux noise as the dominant source of decoherence. In addition, we found that the measured values of integrated flux noise in three qubits of various sizes differ more than an order of magnitude.

  16. Wind tunnels vs. flux chambers: Area source emission measurements and the necessity for VOC and odour correction factors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind tunnels and flux chambers have been used to measure fluxes of volatile organic compounds (VOC), odour, and ammonia (NH3) with little regard to air velocity or sweep air flow rates. As a result, flux measurements have been highly variable and scientists have been in disagreement as to the better...

  17. Heat flux microsensor measurements and calibrations

    NASA Technical Reports Server (NTRS)

    Terrell, James P.; Hager, Jon M.; Onishi, Shinzo; Diller, Thomas E.

    1992-01-01

    A new thin-film heat flux gage has been fabricated specifically for severe high temperature operation using platinum and platinum-10 percent rhodium for the thermocouple elements. Radiation calibrations of this gage were performed at the AEDC facility over the available heat flux range (approx. 1.0 - 1,000 W/cu cm). The gage output was linear with heat flux with a slight increase in sensitivity with increasing surface temperature. Survivability of gages was demonstrated in quench tests from 500 C into liquid nitrogen. Successful operation of gages to surface temperatures of 750 C has been achieved. No additional cooling of the gages is required because the gages are always at the same temperature as the substrate material. A video of oxyacetylene flame tests with real-time heat flux and temperature output is available.

  18. AmeriFlux Measurement Network: Science Team Research

    SciTech Connect

    Law, B E

    2012-12-12

    Research involves analysis and field direction of AmeriFlux operations, and the PI provides scientific leadership of the AmeriFlux network. Activities include the coordination and quality assurance of measurements across AmeriFlux network sites, synthesis of results across the network, organizing and supporting the annual Science Team Meeting, and communicating AmeriFlux results to the scientific community and other users. Objectives of measurement research include (i) coordination of flux and biometric measurement protocols (ii) timely data delivery to the Carbon Dioxide Information and Analysis Center (CDIAC); and (iii) assurance of data quality of flux and ecosystem measurements contributed by AmeriFlux sites. Objectives of integration and synthesis activities include (i) integration of site data into network-wide synthesis products; and (ii) participation in the analysis, modeling and interpretation of network data products. Communications objectives include (i) organizing an annual meeting of AmeriFlux investigators for reporting annual flux measurements and exchanging scientific information on ecosystem carbon budgets; (ii) developing focused topics for analysis and publication; and (iii) developing data reporting protocols in support of AmeriFlux network goals.

  19. Soil Flux Chamber Measurements with Five Species CRDS and New Realtime Chamber Flux Processor

    NASA Astrophysics Data System (ADS)

    Saad, N.; Alstad, K. P.; Arata, C.; Franz, P.

    2014-12-01

    Continuous soil flux chamber measurements remains a key tool for determining production and sequestration of direct and indirect greenhouse gases. The Picarro G2508 Cavity Ring-down Spectrometer has radically simplified soil flux studies by providing simultaneous measurements of five gases: CO2, CH4, N2O, NH3, and H2O, and by lending itself to field deployment. Successful use of the Picarro G2508 for continuous soil flux measurements in a variety of ecosystem types has already been demonstrated. Most recently, Picarro is developing a real-time processing software to simplify chamber measurements of soil flux with the G2508 CRDS. The new Realtime Chamber Flux Processor is designed to work with all chamber types and sizes, and provides real-time flux values of N2O, CO2 & CH4. The software features include chamber sequence table, flexible data tagging feature, ceiling concentration measurement shut-off parameter, user-defined run-time interval, temperature/pressure input for field monitoring and volumetric conversion, and manual flux measurement start/stop override. Realtime Chamber Flux Processor GUI interface is presented, and results from a variety of sampling designs are demonstrated to emphasize program flexibility and field capability.

  20. Dual physiological rate measurement instrument

    NASA Technical Reports Server (NTRS)

    Cooper, Tommy G. (inventor)

    1990-01-01

    The object of the invention is to provide an instrument for converting a physiological pulse rate into a corresponding linear output voltage. The instrument which accurately measures the rate of an unknown rectangular pulse wave over an extended range of values comprises a phase-locked loop including a phase comparator, a filtering network, and a voltage-controlled oscillator, arranged in cascade. The phase comparator has a first input responsive to the pulse wave and a second input responsive to the output signal of the voltage-controlled oscillator. The comparator provides a signal dependent on the difference in phase and frequency between the signals appearing on the first and second inputs. A high-input impedance amplifier accepts an output from the filtering network and provides an amplified output DC signal to a utilization device for providing a measurement of the rate of the pulse wave.

  1. Heat flux measurements on ceramics with thin film thermocouples

    NASA Technical Reports Server (NTRS)

    Holanda, Raymond; Anderson, Robert C.; Liebert, Curt H.

    1993-01-01

    Two methods were devised to measure heat flux through a thick ceramic using thin film thermocouples. The thermocouples were deposited on the front and back face of a flat ceramic substrate. The heat flux was applied to the front surface of the ceramic using an arc lamp Heat Flux Calibration Facility. Silicon nitride and mullite ceramics were used; two thicknesses of each material was tested, with ceramic temperatures to 1500 C. Heat flux ranged from 0.05-2.5 MW/m2(sup 2). One method for heat flux determination used an approximation technique to calculate instantaneous values of heat flux vs time; the other method used an extrapolation technique to determine the steady state heat flux from a record of transient data. Neither method measures heat flux in real time but the techniques may easily be adapted for quasi-real time measurement. In cases where a significant portion of the transient heat flux data is available, the calculated transient heat flux is seen to approach the extrapolated steady state heat flux value as expected.

  2. Thrombin flux and wall shear rate regulate fibrin fiber deposition state during polymerization under flow

    NASA Astrophysics Data System (ADS)

    Illing, Damian; Neeves, Keith

    2009-10-01

    Thrombin is released as a soluble enzyme from the platelet surface to trigger fibrin polymerization during thrombosis under flow conditions. While isotropic fibrin polymerization under static conditions involves protofibril extension and lateral aggregation leading to a gel, factors regulating fiber diameter and orientation are poorly quantified under hemodynamic flow due to the difficulty of setting thrombin fluxes. A membrane microfluidic device allowed combined control of both thrombin wall flux (10-13 to 10-11 nmol/? m^2 s) and the wall shear rate (10 to 100 s-1) of a flowing fibrinogen solution. At the thrombin flux of 10-12 nmol/? m^2 s, both fibrin deposition and fiber thickness decreased as the wall shear rate increased from 10 to 100 s-1. Direct measurement and transport-reaction simulations at 12 different thrombin flux-wall shear rate conditions demonstrated that two dimensionless numbers, the Peclet number (Pe) and the Damkohler number (Da),defined a phase diagram to predict fibrin morphology. For Da<10,we only observed thin films at all Pe. For 10900 and Pe<100, we observed three-dimensional gels. These results indicate that increase wall shear rate first quenches lateral aggregation and then protofibril extension.

  3. Eddy covariance measurements in screenhouses: turbulence characteristics and flux gradients

    NASA Astrophysics Data System (ADS)

    Dicken, U.; Cohen, S.; Tanny, J.

    2012-04-01

    Shading banana and other orchard crops with screens is popular in arid and semi-arid regions for decreasing water use and increasing fruit quality. However, crop water use within this unique environment is much less studied than for canopies in the open. Previous studies of our research group have established the use of the Eddy Covariance (EC) technique for reliable evapotranspiration and sensible heat flux measurements within screenhouses. These studies focused on operating conditions of the system. The present paper is a comprehensive study which examined the performance of the EC system in different types of screenhouses (shading and insect-proof), different crops (banana and pepper) at different development stages (small and large plants) and different climatic regions in Israel. The main goal was to establish guidelines for optimal application of the EC technique in screenhouses. The research consisted of 6 field campaigns: in 3 campaigns two EC systems were simultaneously deployed either vertically or horizontally, and in 3 other campaigns a single EC system was deployed at one measurement height. EC systems were deployed at different normalized system heights, Zs, which define the relative measurement heights within the air gap between the canopy top and the horizontal screened roof. System performance was examined using quality tests like energy balance closure, flux variance similarity, friction velocity, footprint modeling, energy spectrum, turbulence intensity and vertical and horizontal flux gradient analyses. Resulting energy balance closure slopes averaged 0.81±0.08 and 0.91±0.08 for the smaller and larger plants, respectively. Turbulent flows were found to be marginally developed within the air gap between the top of the plants and the horizontal screened roof. Turbulence intensity, flux variance similarity test, energy spectrum decay rate and friction velocity were essentially independent of the measurement height and were within the common range for flows in the open. Insect proof screenhouses were found to inhibit turbulence development. Considering common dimensions of commercial screenhouses, a footprint model, originally derived for canopies in the open, suggested that the normalized EC system height for which 90% of the measurements are within the available fetch is within the range 0.04 < Zs < 0.29. Vertical gradients of water vapor, sensible heat and CO2 fluxes were within the range of expected deviations (up to 26% difference between two vertically deployed EC systems) and were not correlated with advection effects. Hence, it is suggested that these gradients originated either due to non perfect energy balance closure or limitations of raw data corrections. We conclude that there is a constant flux layer in the screenhouse environment. The horizontal gradient of the vertical latent heat flux, measured in one campaign, was very small, suggesting that measurements were done in a position where the surface layer was already in equilibrium with the vegetation below.

  4. Heat flux measurement in SSME turbine blade tester

    SciTech Connect

    Liebert, C.H.

    1990-11-01

    Surface heat flux values were measured in the turbine blade thermal cycling tester located at NASA-Marshall. This is the first time heat flux has been measured in a space shuttle main engine turbopump environment. Plots of transient and quasi-steady state heat flux data over a range of about 0 to 15 MW/sq m are presented. Data were obtained with a miniature heat flux gage device developed at NASA-Lewis. The results from these tests are being incorporated into turbine design models. Also, these gages are being considered for airfoil surface heat flux measurement on turbine vanes mounted in SSME turbopump test bed engine nozzles at Marshall. Heat flux effects that might be observed on degraded vanes are discussed.

  5. Measuring biogenic carbon flux in the ocean

    SciTech Connect

    Boyd, P.; Newton, P.

    1997-01-24

    Richard B. Rivkin et al. propose that neither food-web structure nor new production can be used to predict the magnitude or patterns of downward export of biogenic organic carbon (BC) from the euphotic zone, at least for the duration of their study. These conclusions depend critically on the observations that while both food-web structure and new production estimates were different during and after the spring phytoplankton bloom, the BC flux-as estimated using shallow surface-tethered sediment traps-was similar for the two periods. The authors argue that the uncertainties associated with the trap-derived BC flux estimates are too large to support these conclusions, and they offer an alternative explanation for the apparent similarity of bloom and post-bloom export fluxes. The response of the authors of the original article is also given. 22 refs., 1 fig.

  6. Sound power flux measurements in strongly exited ducts with flow.

    PubMed

    Holland, Keith R; Davies, Peter O A L; van der Walt, Danie C

    2002-12-01

    This contribution describes new robust procedures for the measurement of sound power flux at appropriate axial positions along a duct with flow, using pairs of flush wall mounted microphones, or pressure transducers. The technology includes the application of selective averaging, order tracking, and optimized sampling rate methods to identify the small fraction of the total fluctuating wave energy that is being propagated along the flow path in a reverberent, or highly reactive duct system. Such measurements can also be used to quantify the local acoustic characteristics that govern the generation, transfer, and propagation of wave energy in the system. Illustrative examples include the determination of the acoustic characteristics of individual silencing elements installed in IC engine intakes and exhausts both on the flow bench and during controlled acceleration or run down on a test bed, where the wave component spectral levels approached 170 dB. PMID:12509008

  7. Calculation of turbulent shear stress, heat flux, mass flux, and mixing length from mean flow measurements

    NASA Astrophysics Data System (ADS)

    Clark, R. L.; Crouse, R. F.; Borek, G. T.

    1992-05-01

    A numerical technique to calculate the turbulent mass flux, shear stress, heat flux, and mixing length directly from measurable mean flow quantities is presented. The development of this technique was motivated by the desire to make aero-optical calculations based directly on experimentally obtained mean flow data. The technique is based upon the direct integration of the Navier-Stokes equations of compressible turbulent flow. The results of the integrations are the shear stress, heat flux, mass flux and mixing length distributions (i.e., all data that are necessary for application of the Aero-Optical Quality Code (AOQ).

  8. Measurement of Flux Density of Cas A at Low Frequencies

    NASA Astrophysics Data System (ADS)

    Patil, Ajinkya; Fisher, R.

    2012-01-01

    Cas A is used as a flux calibrator throughout the radio spectrum. Therefore it is important to know the spectral and secular variations in its flux density. Earlier observations by Scott et. al. (1969) and Baars et. al. (1972) suggested a secular decrease in flux density of Cas A at a rate of about 1% per year at all frequencies. However later observations by Erickson & Perley (1975) and Read (1977) indicated anomalously high flux from Cas A at 38 MHz. Also, these observations suggested that the original idea of faster decay of the flux density rate at low frequencies may be in error or that something more complex than simple decay is affecting the flux density at low frequencies. The source changes at 38 MHz still remains a mystery. We intend to present the results of follow up observations made from 1995 to 1998 with a three element interferometer in Green Bank operating in frequency range 30 to 120 MHz. We will discuss the problems at such low frequencies due to large beamwidth and unstable ionosphere. We will also discuss the strategies we have used so far to to find the flux density of Cas A by calculating the ratio of flux density of Cas A to that of Cyg A, assuming flux density of Cyg A to be constant. Above mentioned work was performed in summer student program sponsored by National Radio Astronomy Observatory.

  9. Measurements of the total ion flux from vacuum arc cathodespots

    SciTech Connect

    Anders, Andre; Oks, Efim M.; Yushkov, Georgy Yu; Savkin,Konstantin P.; Brown, Ian G.; Nikolaev, Alexey G.

    2005-05-25

    The ion flux from vacuum arc cathode spots was measured in two vacuum arc systems. The first was a vacuum arc ion source which was modified allowing us to collect ions from arc plasma streaming through an anode mesh. The second discharge system essentially consisted of a cathode placed near the center of a spherically shaped mesh anode. In both systems, the ion current streaming through the mesh was measured by a biased collector. The mesh anodes had geometric transmittances of 60 percent and 72 percent, respectively, which were taken into account as correction factors. The ion current from different cathode materials was measured for 50-500 A of arc current. The ion current normalized by the arc current was found to depend on the cathode material, with values in the range from 5 percent to 19 percent. The normalized ion current is generally greater for elements of low cohesive energy. The ion erosion rates were determined from values of ion current and ion charge states, which were previously measured in the same ion source. The absolute ion erosion rates range from 16-173 mu g/C.

  10. Calibration system for measuring the radon flux density.

    PubMed

    Onishchenko, A; Zhukovsky, M; Bastrikov, V

    2015-06-01

    The measurement of radon flux from soil surface is the useful tool for the assessment of radon-prone areas and monitoring of radon releases from uranium mining and milling residues. The accumulation chambers with hollow headspace and chambers with activated charcoal are the most used devices for these purposes. Systematic errors of the measurements strongly depend on the geometry of the chamber and diffusion coefficient of the radon in soil. The calibration system for the attestation of devices for radon flux measurements was constructed. The calibration measurements of accumulation chambers and chambers with activated charcoal were conducted. The good agreement between the results of 2D modelling of radon flux and measurements results was observed. It was demonstrated that reliable measurements of radon flux can be obtained by chambers with activated charcoal (equivalent volume ~75 l) or by accumulation chambers with hollow headspace of ~7-10 l and volume/surface ratio (height) of >15 cm. PMID:25977351

  11. First eddy covariance flux measurements by PTR-TOF

    PubMed Central

    Müller, M.; Graus, M.; Ruuskanen, T. M.; Schnitzhofer, R.; Bamberger, I.; Kaser, L.; Titzmann, T.; Hörtnagl, L.; Wohlfahrt, G.; Karl, T.; Hansel, A.

    2014-01-01

    The recently developed PTR-TOF instrument was evaluated to measure methanol fluxes emitted from grass land using the eddy covariance method. The high time resolution of the PTR-TOF allowed storing full mass spectra up to m/z 315 with a frequency of 10 Hz. Three isobaric ions were found at a nominal mass of m/z 33 due to the high mass resolving power of the PTR-TOF. Only one of the three peaks contributed to eddy covariance fluxes. The exact mass of this peak agrees well with the exact mass of protonated methanol (m/z 33.0335). The eddy covariance methanol fluxes measured with PTR-TOF were compared to virtual disjunct eddy covariance methanol fluxes simultaneously measured with a conventional PTR-MS. The methanol fluxes from both instruments show excellent agreement. PMID:24465280

  12. Sensitivity of shortwave radiative flux density, forcing, and heating rates to the aerosol vertical profile

    SciTech Connect

    Guan, Hong; Schmid, Beat; Bucholtz, Anthony; Bergstrom, Robert

    2010-03-31

    The effect of the aerosol vertical distribution on the solar radiation profiles, for idealized and measured profiles of optical properties (extinction and single-scattering albedo (SSA)) during the May 2003 Atmospheric Radiation Measurement (ARM) Aerosol Intensive Observation Period (AIOP), has been investigated using the Rapid Radiative Transfer Model Shortwave (RRTM_SW) code. Calculated profiles of down-welling and up-welling solar fluxes during the AIOP have been compared with the data measured by up- and down-looking solar broadband radiometers aboard a profiling research aircraft. The measured profiles of aerosol extinction, SSA, and water vapor obtained from the same aircraft that carried the radiometers served as the inputs for the model calculations. It is noteworthy that for this study, the uplooking radiometers were mounted on a stabilized platform that kept the radiometers parallel with respect to the earth’s horizontal plane. The results indicate that the shape of the aerosol extinction profiles has very little impact on direct radiative forcings at the top of atmosphere and surface in a cloud-free sky. However, as long as the aerosol is not purely scattering, the shape of the extinction profiles is important for forcing profiles. Identical extinction profiles with different absorption profiles drastically influence the forcing and heating rate profiles. Using aircraft data from 19 AIOP profiles over the Southern Great Plains (SGP), we are able to achieve broadband down-welling solar flux closure within 0.8% (bias difference) or 1.8% (rms difference), well within the expected measurement uncertainty of 1 to 3%. The poorer agreement in up-welling flux (bias -3.7%, rms 10%) is attributed to the use of inaccurate surface albedo data. The sensitivity tests reveal the important role accurate, vertically resolved aerosol extinction data plays in tightening flux closure. This study also suggests that in the presence of a strongly absorbing substance, aircraft flux measurements from a stabilized platform have the potential to determine heating rate profiles. These measurement-based heating rate profiles provide useful data for heating rate closure studies and indirect estimates of single scattering albedo assumed in radiative transfer calculations.

  13. Metabolic flux analysis using 13C peptide label measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    13C metabolic flux analysis (MFA) has become the experimental method of choice to investigate cellular metabolism. MFA has established flux maps of central metabolism for dozens of microbes, cell cultures, and plant seeds. Steady-state MFA utilizes isotopic labeling measurements of amino acids obtai...

  14. Spatially averaged heat flux and convergence measurements at the ARM regional flux experiment

    SciTech Connect

    Porch, W.; Barnes, F.; Buchwald, M.; Clements, W.; Cooper, D.; Hoard, D. ); Doran, C.; Hubbe, J.; Shaw, W. ); Coulter, R.; Martin, T. ); Kunkel, K. )

    1991-01-01

    Cloud formation and its relation to climate change is the greatest weakness in current numerical climate models. Surface heat flux in some cases causes clouds to form and in other to dissipate and the differences between these cases are subtle enough to make parameterization difficult in a numerical model. One of the goals of the DOE Atmospheric Radiation Measurement program is to make long term measurements at representative sites to improve radiation and cloud formation parameterization. This paper compares spatially averaged optical measurements of heat flux and convergence with a goal of determining how point measurements of heat fluxes scale up to the larger scale used for climate modeling. It was found that the various optical techniques used in this paper compared well with each other and with independent measurements. These results add confidence that spatially averaging optical techniques can be applied to transform point measurements to the larger scales needed for mesoscale and climate modeling. 10 refs., 6 figs. (MHB)

  15. Measurement of advective soil gas flux: Results of field and laboratory experiments with CO2

    SciTech Connect

    Amonette, James E.; Barr, Jonathan L.; Erikson, Rebecca L.; Dobeck, Laura M.; Barr, Jamie L.; Shaw, Joseph A.

    2013-10-01

    We modified our multi-channel, steady-state flow-through (SSFT), soil-CO2 flux monitoring system to include an array of inexpensive pyroelectric non-dispersive infrared detectors for full-range (0-100%) coverage of CO2 concentrations without dilution, and a larger-diameter vent tube. We then conducted field testing of this system from late July through mid-September 2010 at the Zero Emissions Research and Technology (ZERT) project site located in Bozeman, MT, and subsequently, laboratory testing at the Pacific Northwest National Laboratory (PNNL) in Richland, WA using a flux bucket filled with dry sand. In the field, an array of twenty-five SSFT and three non-steady-state (NSS) flux chambers was installed in a 10x4 m area, the long boundary of which was directly above a shallow (2-m depth) horizontal injection well located 0.5 m below the water table. Two additional chambers (one SSFT and one NSS) were installed 10 m from the well for background measurements. Volumetric soil moisture sensors were installed at each SSFT chamber to measure mean levels in the top 0.15 m of soil. A total flux of 52 kg CO2 d-1 was injected into the well for 27 d and the efflux from the soil was monitored by the chambers before, during, and for 27 d after the injection. Overall, the results were consistent with those from previous years, showing a radial efflux pattern centered on a known “hot spot”, rapid responses to changes in injection rate and wind power, evidence for movement of the CO2 plume during the injection, and nominal flux levels from the SSFT chambers that were up to 6-fold higher than those measured by adjacent NSS chambers. Soil moisture levels varied during the experiment from moderate to near saturation with the highest levels occurring consistently at the hot spot. The effects of wind on measured flux were complex and decreased as soil moisture content increased. In the laboratory, flux bucket testing with the SSFT chamber showed large measured-flux enhancement due to the Venturi effect on the chamber vent, but an overall decrease in measured flux when wind also reached the sand surface. Flux-bucket tests at a high flux (comparable to that at the hot spot) also showed that the measured flux levels increase linearly with the chamber-flushing rate until the actual level is reached. At the SSFT chamber-flushing rate used in the field experiment the measured flux in the laboratory was only about a third of the actual flux. The ratio of measured to actual flux increased logarithmically as flux decreased, and reached parity at low levels typical of diffusive flux systems. Taken together, our results suggest that values for advective CO2 flux measured by SSFT and NSS chamber systems are likely to be significantly lower than the actual values due to back pressure developed in the chamber that diverts flux from entering the chamber. Chamber designs that counteract the back pressure and also avoid large Venturi effects associated with vent tubes, such as the SSFT with a narrow vent tube operated at a high chamber-flushing rate, are likely to yield flux measurements closer to the true values.

  16. Scaling in situ cosmogenic nuclide production rates using analytical approximations to atmospheric cosmic-ray fluxes

    NASA Astrophysics Data System (ADS)

    Lifton, Nathaniel; Sato, Tatsuhiko; Dunai, Tibor J.

    2014-01-01

    Several models have been proposed for scaling in situ cosmogenic nuclide production rates from the relatively few sites where they have been measured to other sites of interest. Two main types of models are recognized: (1) those based on data from nuclear disintegrations in photographic emulsions combined with various neutron detectors, and (2) those based largely on neutron monitor data. However, stubborn discrepancies between these model types have led to frequent confusion when calculating surface exposure ages from production rates derived from the models. To help resolve these discrepancies and identify the sources of potential biases in each model, we have developed a new scaling model based on analytical approximations to modeled fluxes of the main atmospheric cosmic-ray particles responsible for in situ cosmogenic nuclide production. Both the analytical formulations and the Monte Carlo model fluxes on which they are based agree well with measured atmospheric fluxes of neutrons, protons, and muons, indicating they can serve as a robust estimate of the atmospheric cosmic-ray flux based on first principles. We are also using updated records for quantifying temporal and spatial variability in geomagnetic and solar modulation effects on the fluxes. A key advantage of this new model (herein termed LSD) over previous Monte Carlo models of cosmogenic nuclide production is that it allows for faster estimation of scaling factors based on time-varying geomagnetic and solar inputs. Comparing scaling predictions derived from the LSD model with those of previously published models suggest potential sources of bias in the latter can be largely attributed to two factors: different energy responses of the secondary neutron detectors used in developing the models, and different geomagnetic parameterizations. Given that the LSD model generates flux spectra for each cosmic-ray particle of interest, it is also relatively straightforward to generate nuclide-specific scaling factors based on recently updated neutron and proton excitation functions (probability of nuclide production in a given nuclear reaction as a function of energy) for commonly measured in situ cosmogenic nuclides. Such scaling factors reflect the influence of the energy distribution of the flux folded with the relevant excitation functions. Resulting scaling factors indicate 3He shows the strongest positive deviation from the flux-based scaling, while 14C exhibits a negative deviation. These results are consistent with a recent Monte Carlo-based study using a different cosmic-ray physics code package but the same excitation functions.

  17. FLUX MEASUREMENTS FROM A TALL TOWER IN A COMPLEX LANDSCAPE

    SciTech Connect

    Kurzeja, R.; Weber, A.; Chiswell, S.; Parker, M.

    2010-07-22

    The accuracy and representativeness of flux measurements from a tall tower in a complex landscape was assessed by examining the vertical and sector variability of the ratio of wind speed to momentum flux and the ratio of vertical advective to eddy flux of heat. The 30-60 m ratios were consistent with theoretical predictions which indicate well mixed flux footprints. Some variation with sector was observed that were consistent with upstream roughness. Vertical advection was negligible compared with vertical flux except for a few sectors at night. This implies minor influence from internal boundary layers. Flux accuracy is a function of sector and stability but 30-60 m fluxes were found to be generally representative of the surrounding landscape. This paper will study flux data from a 300 m tower, with 4 levels of instruments, in a complex landscape. The surrounding landscape will be characterized in terms of the variation in the ratio of mean wind speed to momentum flux as a function of height and wind direction. The importance of local advection will be assessed by comparing vertical advection with eddy fluxes for momentum and heat.

  18. "Influence Method" applied to measure a moderated neutron flux

    NASA Astrophysics Data System (ADS)

    Rios, I. J.; Mayer, R. E.

    2016-01-01

    The "Influence Method" is conceived for the absolute determination of a nuclear particle flux in the absence of known detector efficiency. This method exploits the influence of the presence of one detector, in the count rate of another detector when they are placed one behind the other and define statistical estimators for the absolute number of incident particles and for the efficiency. The method and its detailed mathematical description were recently published (Rios and Mayer, 2015 [1]). In this article we apply it to the measurement of the moderated neutron flux produced by an 241AmBe neutron source surrounded by a light water sphere, employing a pair of 3He detectors. For this purpose, the method is extended for its application where particles arriving at the detector obey a Poisson distribution and also, for the case when efficiency is not constant over the energy spectrum of interest. Experimental distributions and derived parameters are compared with theoretical predictions of the method and implications concerning the potential application to the absolute calibration of neutron sources are considered.

  19. High rates of energy expenditure and water flux in free-ranging Point Reyes mountain beavers Aplodontia rufa phaea

    USGS Publications Warehouse

    Crocker, D.E.; Kofahl, N.; Fellers, G.D.; Gates, N.B.; Houser, D.S.

    2007-01-01

    We measured water flux and energy expenditure in free-ranging Point Reyes mountain beavers Aplodontia rufa phaea by using the doubly labeled water method. Previous laboratory investigations have suggested weak urinary concentrating ability, high rates of water flux, and low basal metabolic rates in this species. However, free-ranging measurements from hygric mammals are rare, and it is not known how these features interact in the environment. Rates of water flux (210 ?? 32 mL d-1) and field metabolic rates (1,488 ?? 486 kJ d-1) were 159% and 265%, respectively, of values predicted by allometric equations for similar-sized herbivores. Mountain beavers can likely meet their water needs through metabolic water production and preformed water in food and thus remain in water balance without access to free water. Arginine-vasopressin levels were strongly correlated with rates of water flux and plasma urea : creatinine ratios, suggesting an important role for this hormone in regulating urinary water loss in mountain beavers. High field metabolic rates may result from cool burrow temperatures that are well below lower critical temperatures measured in previous laboratory studies and suggest that thermoregulation costs may strongly influence field energetics and water flux in semifossorial mammals. ?? 2007 by The University of Chicago. All rights reserved.

  20. A Preliminary Study of CO2 Flux Measurements by Lidar

    NASA Technical Reports Server (NTRS)

    Gibert, Fabien; Koch, Grady J.; Beyon, Jeffrey Y.; Hilton, T.; Davis, Kenneth J.; Andrews, Arlyn; Ismail, Syed; Singh, Upendra N.

    2008-01-01

    A mechanistic understanding of the global carbon cycle requires quantification of terrestrial ecosystem CO2 fluxes at regional scales. In this paper, we analyze the potential of a Doppler DIAL system to make flux measurements of atmospheric CO2 using the eddy-covariance and boundary layer budget methods and present results from a ground based experiment. The goal of this study is to put CO2 flux point measurements in a mesoscale context. In June 2007, a field experiment combining a 2-m Doppler Heterodyne Differential Absorption Lidar (HDIAL) and in-situ sensors of a 447-m tall tower (WLEF) took place in Wisconsin. The HDIAL measures simultaneously: 1) CO2 mixing ratio, 2) atmosphere structure via aerosol backscatter and 3) radial velocity. We demonstrate how to synthesize these data into regional flux estimates. Lidar-inferred fluxes are compared with eddy-covariance fluxes obtained in-situ at 396m AGL from the tower. In cases where the lidar was not yet able to measure the fluxes with acceptable precision, we discuss possible modifications to improve system performance.

  1. A calorimeter for neutron flux measurement. Final report

    SciTech Connect

    Chupp, T.E.

    1993-04-01

    A calorimeter for absolute neutron flux measurement has been built and tested. The calorimeter measures the heat produced in a 10{degrees}K thick LiPb target when neutrons are captured via the {sup 6}Li(n,{sup 3}H){sup 4}He reaction. The sensitivity achieved was 1.3x10{sup 6} n/s for a 1 hour measurement. Separate flux measurements with the calorimeter and a {sup 238}U fission chamber are in agreement and show that systematic errors are less than 3%. An improved calorimeter has been built which is sensitive to 10{sup 5} n/s for a 1 hour measurement.

  2. Measurements of eddy correlation oxygen fluxes in shallow freshwaters: Towards routine applications and analysis

    NASA Astrophysics Data System (ADS)

    McGinnis, Daniel F.; Berg, Peter; Brand, Andreas; Lorrai, Claudia; Edmonds, Theresa J.; Wüest, Alfred

    2008-02-01

    Benthic fluxes of dissolved oxygen are measured in a shallow reservoir using the eddy correlation technique. Flux variations depict the diurnal production-consumption cycle, with daytime oxygen release following the solar radiation trend. The average nighttime uptake of -40 +/- 11 mmol m-2 d-1 is in excellent agreement with the rate of -35 +/- 3 mmol m-2 d-1 derived from sediment oxygen microprofiles. Separating large-scale advective and turbulent fluctuations is a crucial and uncertain component of the flux computation and the largest source of error. To compensate for the 2.25 s oxygen sensor response time, the oxygen flux calculations are corrected by only ~5% using a first-order spectral enhancement. This work demonstrates that only a slightly faster oxygen sensor would be needed to resolve the entire flux spectrum. The 18 hours of data are the first measurements obtained in a freshwater reservoir that capture the diurnal oxygen production-consumption cycle.

  3. Error Evaluation of Methyl Bromide Aerodynamic Flux Measurements

    USGS Publications Warehouse

    Majewski, M.S.

    1997-01-01

    Methyl bromide volatilization fluxes were calculated for a tarped and a nontarped field using 2 and 4 hour sampling periods. These field measurements were averaged in 8, 12, and 24 hour increments to simulate longer sampling periods. The daily flux profiles were progressively smoothed and the cumulative volatility losses increased by 20 to 30% with each longer sampling period. Error associated with the original flux measurements was determined from linear regressions of measured wind speed and air concentration as a function of height, and averaged approximately 50%. The high errors resulted from long application times, which resulted in a nonuniform source strength; and variable tarp permeability, which is influenced by temperature, moisture, and thickness. The increase in cumulative volatilization losses that resulted from longer sampling periods were within the experimental error of the flux determination method.

  4. Radiant Flux of Near Field in Temperature Measurements

    SciTech Connect

    Suarez-Romero, J. G.; Resendiz Barron, A. J.; Farias Arguello, J. O.

    2008-04-15

    In this work we present a calculation of the radiant flux exiting from an object which is at a constant temperature. The flux calculation is based in the propagation model of irradiance and it permit to predict the small variations in measurements of infrared radiation sources when the pyrometer is going far from the source, this variation is known as distance effect. The classical radiometry defines the quantity radiance, which is used in temperature measurements of objects through the infrared radiation they emit. Unfortunately the radiance does not permit to take into account the variations of the radiant flux measured by the pyrometer due to the wave propagation of the radiation given that the radiance definition is based in ray propagation, the geometrical model. Due to the anterior in this work we present a radiant flux calculation using wave model and considering the approximation of the near field or Fresnel approximation. We show experimental results that confirm our proposal.

  5. Design of a differential radiometer for atmospheric radiative flux measurements

    SciTech Connect

    LaDelfe, P.C.; Weber, P.G.; Rodriguez, C.W.

    1994-11-01

    The Hemispherical Optimized NEt Radiometer (HONER) is an instrument under development at the Los Alamos National Laboratory for deployment on an unmanned aerospace vehicle as part of the Atmospheric Radiation Measurements (ARM/UAV) program. HONER is a differential radiometer which will measure the difference between the total upwelling and downwelling fluxes and is intended to provide a means of measuring the atmospheric radiative flux divergence. Unlike existing instruments which measure the upwelling and downwelling fluxes separately, HONER will achieve an optical difference by chopping the two fluxes alternately onto a common pyroelectric detector. HONER will provide data resolved into two spectral bands; one covering the solar dominated region from less than 0.4 micrometer to approximately 4.5 micrometers and the other covering the region from approximately 4.5 micrometers to greater than 50 micrometers, dominated by thermal radiation. The means of separating the spectral regions guarantees seamless summation to calculate the total flux. The fields-of-view are near-hemispherical, upward and downward. The instrument can be converted, in flight, from the differential mode to absolute mode, measuring the upwelling and downwelling fluxes separately and simultaneously. The instrument also features continuous calibration from on-board sources. We will describe the design and operation of the sensor head and the on-board reference sources as well as the means of deployment.

  6. Airborne flux measurements of biogenic volatile organic compounds over California

    NASA Astrophysics Data System (ADS)

    Misztal, P. K.; Karl, T.; Weber, R.; Jonsson, H. H.; Guenther, A. B.; Goldstein, A. H.

    2014-03-01

    Biogenic Volatile Organic Compound (BVOC) fluxes were measured onboard the CIRPAS Twin Otter aircraft as part of the California Airborne BVOC Emission Research in Natural Ecosystem Transects (CABERNET) campaign during June 2011. The airborne virtual disjunct eddy covariance (AvDEC) approach used measurements from a PTR-MS and a wind radome probe to directly determine fluxes of isoprene, MVK + MAC, methanol, monoterpenes, and MBO over ∼10 000 km of flight paths focusing on areas of California predicted to have the largest emissions of isoprene. The Fast Fourier Transform (FFT) approach was used to calculate fluxes over long transects of more than 15 km, most commonly between 50 and 150 km. The Continuous Wavelet Transformation (CWT) approach was used over the same transects to also calculate "instantaneous" fluxes with localization of both frequency and time independent of non-stationarities. Vertical flux divergence of isoprene is expected due to its relatively short lifetime and was measured directly using "racetrack" profiles at multiple altitudes. It was found to be linear and in the range 5% to 30% depending on the ratio of aircraft altitude to PBL height (z / zi). Fluxes were generally measured by flying consistently at 400 ± 50 m (a.g.l.) altitude, and extrapolated to the surface according to the determined flux divergence. The wavelet-derived surface fluxes of isoprene averaged to 2 km spatial resolution showed good correspondence to Basal Emission Factor (BEF) landcover datasets used to drive biogenic VOC (BVOC) emission models. The surface flux of isoprene was close to zero over Central Valley crops and desert shrublands, but was very high (up to 15 mg m-2 h-1) above oak woodlands, with clear dependence of emissions on temperature and oak density. Isoprene concentrations of up to 8 ppb were observed at aircraft height on the hottest days and over the dominant source regions. While isoprene emissions from agricultural crop regions, shrublands, and coniferous forests were extremely low, high concentrations of methanol and monoterpenes were found above some of these regions. These observations demonstrate the ability to measure fluxes from specific sources by eddy covariance from an aircraft, and suggest the utility of measurements using fast response chemical sensors to constrain emission inventories and map out source distributions for a much broader array of trace gases than was observed in this study. This paper reports the first regional direct eddy covariance fluxes of isoprene. The emissions of VOCs measured from aircraft with 2 km spatial resolution can quantify the distribution of major sources providing the observations required for testing statewide emission inventories of these important trace gases. These measurements will be used in a future study to assess BVOC emission models and their driving variable datasets.

  7. Solar Model Parameters and Direct Measurements of Solar Neutrino Fluxes

    E-print Network

    Abhijit Bandyopadhyay; Sandhya Choubey; Srubabati Goswami; S. T. Petcov

    2006-08-30

    We explore a novel possibility of determining the solar model parameters, which serve as input in the calculations of the solar neutrino fluxes, by exploiting the data from direct measurements of the fluxes. More specifically, we use the rather precise value of the $^8B$ neutrino flux, $\\phi_B$ obtained from the global analysis of the solar neutrino and KamLAND data, to derive constraints on each of the solar model parameters on which $\\phi_B$ depends. We also use more precise values of $^7Be$ and $pp$ fluxes as can be obtained from future prospective data and discuss whether such measurements can help in reducing the uncertainties of one or more input parameters of the Standard Solar Model.

  8. Analysis of field measurements of carbon dioxide and water vapor fluxes

    NASA Technical Reports Server (NTRS)

    Verma, Shashi B.

    1991-01-01

    Analysis of the field measurements of carbon dioxide and water vapor fluxes is discussed. These data were examined in conjunction with reflectance obtained from helicopter mounted Modular Multiband Radiometer. These measurements are representative of the canopy scale (10 to 100 m)(exp 2) and provide a good basis for investigating the hypotheses/relationship potentially useful in remote sensing applications. All the micrometeorological data collected during FIFE-89 were processed and fluxes of CO2, water vapor, and sensible heat were calculated. Soil CO2 fluxes were also estimated. Employing these soil CO2 flux values, in conjunction with micrometeorological measurements, canopy photosynthesis is being estimated. A biochemical model of leaf photosynthesis was adapted to the prairie vegetation. The modeled leaf photosynthesis rates were scaled up to the canopy level. This model and a multiplicative stomatal conductance model are also used to calculate canopy conductance.

  9. Surface Catalysis and Oxidation on Stagnation Point Heat Flux Measurements in High Enthalpy Arc Jets

    NASA Technical Reports Server (NTRS)

    Nawaz, Anuscheh; Driver, David M.; Terrazas-Salinas

    2013-01-01

    Heat flux sensors are routinely used in arc jet facilities to determine heat transfer rates from plasma plume. The goal of this study is to assess the impact of surface composition changes on these heat flux sensors. Surface compositions can change due to oxidation and material deposition from the arc jet. Systematic surface analyses of the sensors were conducted before and after exposure to plasma. Currently copper is commonly used as surface material. Other surface materials were studied including nickel, constantan gold, platinum and silicon dioxide. The surfaces were exposed to plasma between 0.3 seconds and 3 seconds. Surface changes due to oxidation as well as copper deposition from the arc jets were observed. Results from changes in measured heat flux as a function of surface catalycity is given, along with a first assessment of enthalpy for these measurements. The use of cupric oxide is recommended for future heat flux measurements, due to its consistent surface composition arc jets.

  10. Accuracy of quantum sensors measuring yield photon flux and photosynthetic photon flux

    NASA Technical Reports Server (NTRS)

    Barnes, C.; Tibbitts, T.; Sager, J.; Deitzer, G.; Bubenheim, D.; Koerner, G.; Bugbee, B.; Knott, W. M. (Principal Investigator)

    1993-01-01

    Photosynthesis is fundamentally driven by photon flux rather than energy flux, but not all absorbed photons yield equal amounts of photosynthesis. Thus, two measures of photosynthetically active radiation have emerged: photosynthetic photon flux (PPF), which values all photons from 400 to 700 nm equally, and yield photon flux (YPF), which weights photons in the range from 360 to 760 nm according to plant photosynthetic response. We selected seven common radiation sources and measured YPF and PPF from each source with a spectroradiometer. We then compared these measurements with measurements from three quantum sensors designed to measure YPF, and from six quantum sensors designed to measure PPF. There were few differences among sensors within a group (usually <5%), but YPF values from sensors were consistently lower (3% to 20%) than YPF values calculated from spectroradiometric measurements. Quantum sensor measurements of PPF also were consistently lower than PPF values calculated from spectroradiometric measurements, but the differences were <7% for all sources, except red-light-emitting diodes. The sensors were most accurate for broad-band sources and least accurate for narrow-band sources. According to spectroradiometric measurements, YPF sensors were significantly less accurate (>9% difference) than PPF sensors under metal halide, high-pressure sodium, and low-pressure sodium lamps. Both sensor types were inaccurate (>18% error) under red-light-emitting diodes. Because both YPF and PPF sensors are imperfect integrators, and because spectroradiometers can measure photosynthetically active radiation much more accurately, researchers should consider developing calibration factors from spectroradiometric data for some specific radiation sources to improve the accuracy of integrating sensors.

  11. Quantum reaction rate from higher derivatives of the thermal flux-flux autocorrelation function at time zero

    NASA Astrophysics Data System (ADS)

    Ceotto, Michele; Yang, Sandy; Miller, William H.

    2005-01-01

    A quantum theory of thermal reaction rates is presented which may be viewed as an extension of the recently developed "quantum instanton" (QI) model [W. H. Miller, Y. Zhao, M. Ceotto, and S. Yang, J. Chem. Phys. 119, 1329 (2003)]. It is based on using higher derivatives of the flux-flux autocorrelation function C(t) (as given by Miller, Schwartz, and Tromp) at t=0 to construct a short time approximation for C(t). Tests of this theory on 1d and collinear reactions, both symmetric and asymmetric, show it to be more accurate than the original QI model, giving rate constants to ˜5% for a wide range of temperature.

  12. Constraining isoprene emission factors using airborne flux measurements during CABERNET

    NASA Astrophysics Data System (ADS)

    Misztal, P. K.; Karl, T.; Jiang, X.; Avise, J. C.; Scott, K.; Jonsson, H.; Guenther, A. B.; Goldstein, A. H.

    2012-12-01

    An aircraft flux study was conducted to assess biogenic volatile organic compound (BVOC) emissions from California ecosystems targeting oak woodlands and isoprene for most transects. The direct eddy covariance approach featured high speed proton transfer reaction mass spectrometry onboard a CIRPAS (Center for Interdisciplinary Remotely-Piloted Aircraft Studies) Twin Otter aircraft during June 2011 as part of the CABERNET (California Airborne BVOC Emission Research in Natural Ecosystem Transects) project. Isoprene fluxes were calculated using wavelet analysis and scaled to surface fluxes using a divergence term obtained by measuring fluxes at multiple altitudes over homogenous oak terrain. By normalization of fluxes to standard temperature and photosynthetically active radiation levels using standard BVOC modeling equations, the resulting emission factors could be directly compared with those used by MEGAN (Model of Emissions of Gases and Aerosols from Nature) and BEIGIS (Biogenic Emission Inventory Geographic Information System) models which are the most commonly used BVOC emission models for California. As expected, oak woodlands were found to be the dominant source of isoprene in all areas surrounding and in the Central Valley of California. The airborne fluxes averaged to 2 km spatial resolution matched remarkably well with current oak woodland distributions driving the models and hence the correspondence of modeled and aircraft derived emission factors was also good, although quantitative differences were encountered depending on the region and driving variables used. Fluxes measured from aircraft proved to be useful for the improvement of the accuracy of modeled predictions for isoprene and other important ozone and aerosol precursor compounds. These are the first regional isoprene flux measurements using direct eddy covariance on aircraft.

  13. Intercomparison of gas analyzers for methane flux measurements

    NASA Astrophysics Data System (ADS)

    Haapanala, S.; Rinne, J.; Vesala, T.

    2010-12-01

    Four gas analyzers, capable of measuring methane concentration at a response time necessary for eddy covariance flux measurements, were operated in parallel for about six months between March and August 2010. Their reliability, need of maintenance, user friendliness, data coverage, and data quality were evaluated. The primary aim of this campaign was to provide an instrumentation suggestion for the European Research Infrastructure ICOS (Integrated Carbon Observation System). The instruments used were TGA100A (Campbell Scientific Inc.), RMT-200 (Los Gatos Research Inc.) , G1301-f (Picarro Inc.), and LI-7700 (Li-Cor Inc.). The last one, LI-7700, was a prototype of a later commercialized open path analyzer. The other instruments were closed path analyzers. The measurement site is an oligotrophic open fen Siikaneva, located in southern Finland. The site provides spatially quite uniform methane flux within the footprint. The methane flux rises in the spring, peaks in early August and falls down during the autumn. This provides excellent opportunity to study the performance of the analyzers at different CH4 flux levels from near zero up to about 5 mg m-2 h-1. The preliminary results show great similarity among the instruments in both concentrations and fluxes. Detailed numbers of the measurement characteristics will be provided later. The reliability and need of maintenance are difficult to evaluate quantitatively during that short period.

  14. Measurements of The Neutrino Flux Using Fine-Grained Tracker

    NASA Astrophysics Data System (ADS)

    Tian, Xinchun; Mishra, Sanjib; Petti, Roberto; Duyang, Hongyue; LBNE Collaboration

    2015-04-01

    The reference design of the near detector for the LBNE/F experiment is a high-resolution Fine-Grained Tracker (FGT) capable of precisely measuring all four species of neutrinos: ??, ?e, ?? and ?e. The goals of the FGT is to constrain the systematic errors, below the corresponding statistical error in the far detector, for all oscillation studies; and to conduct a panoply of precision measurements and searches in neutrino physics. We present sensitivity studies - critical to constraining the systematics in oscillation searches - of measurements of the absolute and relative neutrino flux using the various techniques: 1) neutrino electron NC (CC) scattering, 2) ?? proton QE scattering, 3) Coherent ? production for absolute flux and 4) Low- ? method for relative flux.

  15. Densitometric tomography using the measurement of muon flux

    NASA Astrophysics Data System (ADS)

    Hivert, F.; Busto, J.; Brunner, J.; Salin, P.; Gaffet, S.

    2013-12-01

    The knowledge of the subsurface properties is essentially obtained by geophysical methods, e.g. seismic imaging, electric prospection or gravimetry. The present work develops a recent method to investigate the in situ density of rocks using atmospheric the muon flux measurement , its attenuation depending on the rock density and thickness. This new geophysical technique have been mainly applied in volcanology (Lesparre N., 2011) using scintillator detectors. The present project (T2DM2) aims to realize underground muons flux measurements in order to characterizing the rock massif density variations above the LSBB underground research facility in Rustrel (France). The muon flux will be measure with a new Muon telescope instrumentation using Micromegas detectors in Time Projection Chambers (TPC) configuration. The first step of the work presented considers the muon flux simulation using the Gaisser model, for the interactions between muons and atmospheric particles, and the MUSIC code (Kudryavtsev V. A., 2008) for the muons/rock interactions. The results show that the muon flux attenuation caused by density variations are enough significant to be observed until around 500 m depth and for period of time in the order of one month. Such a duration scale and depth of investigation is compatible with the duration of the water transfer processes involved within the Karst unsaturated zone where LSBB is located. Our work now concentrates on the optimization of the spatial distribution of detectors that will be deployed in future.

  16. Denitrification Rates, Nitrous Oxide, and Methane Fluxes Along Soil Moisture Gradients In Stormwater Control Structures.

    NASA Astrophysics Data System (ADS)

    Bettez, N. D.; Morse, J. L.; Groffman, P. M.

    2014-12-01

    Urbanization has significant impacts on the landscape resulting in increased volume and velocity of stormwater runoff following precipitation events. The primary method used to control stormwater discharge and prevent downstream erosion is the use of best management practices (BMP's) such as retention basins, detention basins and rain gardens. Although the BMP's were designed to mitigate hydrologic impacts associated with urban development they have the potential to remove nitrogen through denitrification. In this study we set up transects along moisture gradients in two BMP's in Baltimore MD, USA and measured denitrification rates using the Nitrogen Free Air Removal Method (N-FARM) method and monitored both soil conditions (oxygen, moisture and temperature measured hourly) and trace gas fluxes (methane, carbon dioxide, and nitrous oxide measured monthly) for 1 year.

  17. Measurement of emission fluxes from Technical Area 54, Area G and L. Final report

    SciTech Connect

    Eklund, B.

    1995-03-15

    The emission flux (mass/time-area) of tritiated water from TA-54 was measured to support the characterization of radioactive air emissions from waste sites for the Radioactive Air Emissions Management (RAEM) program and for the Area G Performance Assessment. Measurements were made at over 180 locations during the summers of 1993 and 1994, including randomly selected locations across Area G, three suspected areas of contamination at Area G, and the property surrounding TA-54. The emission fluxes of radon were measured at six locations and volatile organic compounds (VOCs) at 30 locations. Monitoring was performed at each location over a several-hour period using the U.S. EPA flux chamber approach. Separate samples for tritiated water, radon, and VOCs were collected and analyzed in off-site laboratories. The measured tritiated water emission fluxes varied over several orders of magnitude, from background levels of about 3 pCi/m{sup 2}-min to 9.69 x 10{sup 6} pCi/m{sup 2}-min near a disposal shaft. Low levels of tritiated water were found to have migrated into Pajarito Canyon, directly south of Area G. The tritium flux data were used to generate an estimated annual emission rate of 14 Curies/yr for all of Area G, with the majority of this activity being emitted from relatively small areas adjacent to several disposal shafts. The estimated total annual release is less than 1% of the total tritium release from all LANL in 1992 and results in a negligible off-site dose. Based on the limited data available, the average emission flux of radon from Area G is estimated to be 8.1 pCi/m{sup 2}-min. The measured emission fluxes of VOCs were < 100 {mu}g/m{sup 2}-min, which is small compared with fluxes typically measured at hazardous waste landfills. The air quality impacts of these releases were evaluated in a separate report.

  18. Evapotranspiration: Mass balance measurements compared with flux estimation methods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evapotranspiration (ET) may be measured by mass balance methods and estimated by flux sensing methods. The mass balance methods are typically restricted in terms of the area that can be represented (e.g., surface area of weighing lysimeter (LYS) or equivalent representative area of neutron probe (NP...

  19. IMPROVING EMISSION INVENTORIES USING DIRECT FLUX MEASUREMENTS AND MODELING

    EPA Science Inventory

    This project uses a novel approach to measure real-world pollutant fluxes on an extended spatial and temporal scale, and to infer from those the source-specific pollutant emissions needed for a comparison to and an improvement of current emissions inventories. Air pollutants a...

  20. Estimating terrestrial uranium and thorium by antineutrino flux measurements

    E-print Network

    Mcdonough, William F.

    Estimating terrestrial uranium and thorium by antineutrino flux measurements Stephen T. Dye, and approved November 16, 2007 (received for review July 11, 2007) Uranium and thorium within the Earth produce of uranium and thorium concentrations in geological reservoirs relies largely on geochemi- cal model

  1. Sizing of Multiple Cracks Using Magnetic Flux Leakage Measurements

    E-print Network

    Reilly, James P.

    of the cracks. Then, an inversion procedure based on space mapping (SM) is used in order to estimate the crack, magnetic flux leakage (MFL), edge detection, space mapping optimization. 1. Introduction Magnetic, erosion and abrasive wear. In most practical cases, the MFL technique is used to measure cracks having

  2. Measurement of the 8B Solar Neutrino Flux with KamLAND

    SciTech Connect

    Abe, S.; Furuno, K.; Gando, A.; Gando, Y.; Ichimura, K.; Ikeda, H.; Inoue, K.; Kibe, Y.; Kimura, W.; Kishimoto, Y.; Koga, M.; Minekawa, Y.; Mitsui, T.; Morikawa, T.; Nagai, N.; Nakajima, K.; Nakamura, K.; Nakamura, M.; Narita, K.; Shimizu, I.; Shimizu, Y.; Shirai, J.; Suekane, F.; Suzuki, A.; Takahashi, H.; Takahashi, N.; Takemoto, Y.; Tamae, K.; Watanabe, H.; Xu, B.D.; Yabumoto, H.; Yonezawa, E.; Yoshida, H.; Yoshida, S.; Enomoto, S.; Kozlov, A.; Murayama, H.; Grant, C.; Keefer, G.; McKee, D.; Piepke, A.; Banks, T.I.; Bloxham, T.; Detwiler, J.A.; Freedman, S.J.; Fujikawa, B.K.; Han, K.; Kadel, R.; O'Donnell, T.; Steiner, H.M.; Winslow, L.A.; Dwyer, D.A.; Mauger, C.; McKeown, R.D.; Zhang, C.; Berger, B.E.; Lane, C.E.; Maricic, J.; Miletic, T.; Batygov, M.; Learned, J.G.; Matsuno, S.; Pakvasa, S.; Sakai, M.; Horton-Smith, G.A.; Tang, A.; Downum, K.E.; Gratta, G.; Tolich, K.; Efremenko, Y.; Kamyshkov, Y.; Perevozchikov, O.; Karwowski, H.J.; Markoff, D.M.; Tornow, W.; Heeger, K.M.; Piquemal, F.; Ricol, J.-S.; Decowski, M.P.

    2011-06-04

    We report a measurement of the neutrino-electron elastic scattering rate from {sup 8}B solar neutrinos based on a 123 kton-day exposure of KamLAND. The background-subtracted electron recoil rate, above a 5.5-MeV analysis threshold is 1.49 {+-} 0.14(stat) {+-} 0.17(syst) events per kton-day. Interpreted as due to a pure electron flavor flux with a {sup 8}B neutrino spectrum, this corresponds to a spectrum integrated flux of 2.77 {+-} 0.26(stat) {+-} 0.32(syst) x 10{sup 6} cm{sup -2}s{sup -1}. The analysis threshold is driven by {sup 208}Tl present in the liquid scintillator, and the main source of systematic uncertainty is due to background from cosmogenic {sup 11}Be. The measured rate is consistent with existing measurements and with standard solar model predictions which include matter-enhanced neutrino oscillation.

  3. Airborne flux measurements of Biogenic Isoprene over California

    SciTech Connect

    Misztal, P.; Karl, Thomas G.; Weber, Robin; Jonsson, H. H.; Guenther, Alex B.; Goldstein, Allen H.

    2014-10-10

    Biogenic Volatile Organic Compound (BVOC) fluxes were measured onboard the CIRPAS Twin Otter aircraft as part of the California Airborne BVOC Emission Research in Natural Ecosystem Transects (CABERNET) campaign during June 2011. The airborne virtual disjunct eddy covariance (AvDEC) approach used measurements from a PTR-MS and a wind radome probe to directly determine fluxes of isoprene, MVK+MAC, methanol, monoterpenes, and MBO over ~10,000-km of flight paths focusing on areas of California predicted to have the largest emissions of isoprene. The Fast Fourier Transform (FFT) approach was used to calculate fluxes over long transects of more than 15 km, most commonly between 50 and 150 km. The Continuous Wavelet Transformation (CWT) approach was used over the same transects to also calculate "instantaneous" fluxes with localization of both frequency and time independent of non-stationarities. Vertical flux divergence of isoprene is expected due to its relatively short lifetime and was measured directly using "racetrack" profiles at multiple altitudes. It was found to be linear and in the range 5% to 30% depending on the ratio of aircraft altitude to PBL height (z/zi). Fluxes were generally measured by flying consistently 1 at 400 m ±50 m (a.g.l.) altitude, and extrapolated to the surface according to the determined flux divergence. The wavelet-derived surface fluxes of isoprene averaged to 2 km spatial resolution showed good correspondence to Basal Emission Factor (BEF) landcover datasets used to drive biogenic VOC (BVOC) emission models. The surface flux of isoprene was close to zero over Central Valley crops and desert shrublands, but was very high (up to 15 mg m-2 h-1) above oak woodlands, with clear dependence of emissions on temperature and oak density. Isoprene concentrations of up to 8 ppb were observed at aircraft height on the hottest days and over the dominant source regions. While isoprene emissions from agricultural crop regions, shrublands, and coniferous forests were extremely low, high concentrations of methanol and monoterpenes were found above some of these regions. These observations demonstrate the ability to measure fluxes from specific sources by eddy covariance from an aircraft, and suggest the utility of measurements using fast response chemical sensors to constrain emission inventories and map out source distributions for a much broader array of trace gases than was observed in this study. This paper reports the first regional direct eddy covariance fluxes of isoprene. The emissions of VOCs measured from aircraft with 2 km spatial resolution can quantify the distribution of major sources providing the observations required for testing statewide emission inventories of these important trace gases. These measurements will be used in a future study to assess BVOC emission models and their driving variable datasets.

  4. Biogenic silica fluxes and accumulation rates in the Gulf of California

    SciTech Connect

    Thunell, R.C.; Pride, C.J.; Tappa, E. ); Muller-Karger, F.E. )

    1994-04-01

    The Gulf of California, though small in size, plays an important role in the global silica cycle. The seasonal pattern of biogenic silica flux in the gulf is closely related to that of phytoplankton biomass levels and is controlled by changes in weather and hydrographic conditions. The highest opal fluxes ([approximately] 0.35 g[center dot]m[sup [minus]2][center dot]d[sup [minus]1]) occur during winter and spring, and they are comparable to those measured in some of the most productive ecosystems of the world. Approximately 15%-25% of the biogenic silica produced in surface waters is preserved in gulf sediments, a figure significantly higher than the average global ocean preservation rate. However, the flux of opal at 500 m water depth is less than 25% of that being produced at the surface, suggesting that most of the recycling of biogenic silica in the Gulf of California occurs in the upper water column. 28 refs., 3 figs.

  5. Automatic magnetic flux measurement of micro plastic-magnetic rotors

    NASA Astrophysics Data System (ADS)

    Wang, Qingdong; Lin, Mingxing; Song, Aiwei

    2015-07-01

    Micro plastic-magnetic rotors of various sizes and shapes are widely used in industry, their magnetic flux measurement is one of the most important links in the production process, and therefore some technologies should be adopted to improve the measurement precision and efficiency. In this paper, the automatic measurement principle of micro plastic-magnetic rotors is proposed and the integration time constant and the integrator drift’s suppression and compensation in the measurement circuit are analyzed. Two other factors influencing the measurement precision are also analyzed, including the relative angles between the rotor magnetic poles and the measurement coil, and the starting point of the rotors in the coil where the measurement begins. An instrument is designed to measure the magnetic flux of the rotors. Measurement results show that the measurement error is within??±1%, which meets the basic requirements in industry application, and the measurement efficiency is increased by 10 times, which can cut down labor cost and management cost when compared with manual measurement.

  6. A disjunct eddy accumulation system for the measurement of BVOC fluxes: instrument characterizations and field deployment

    NASA Astrophysics Data System (ADS)

    Edwards, G. D.; Martins, D. K.; Starn, T.; Pratt, K.; Shepson, P. B.

    2012-09-01

    Biological volatile organic compounds (BVOCs), such as isoprene and monoterpenes, are emitted in large amounts from forests. Quantification of the flux of BVOCs is critical in the evaluation of the impact of these compounds on the concentrations of atmospheric oxidants and on the production of secondary organic aerosol. A disjunct eddy accumulation (DEA) sampler system was constructed for the measurement of speciated BVOC fluxes. Unlike traditional eddy covariance (EC), the relatively new technique of disjunct sampling differs by taking short, discrete samples that allow for slower sampling frequencies. Disjunct sample airflow is directed into cartridges containing sorbent materials at sampling rates proportional to the magnitude of the vertical wind. Compounds accumulated on the cartridges are then quantified by thermal desorption and gas chromatography. Herein, we describe our initial tests to evaluate the disjunct sampler including the application of vertical wind measurements to create optimized sampling thresholds. Measurements of BVOC fluxes obtained from DEA during its deployment above a mixed hardwood forest at the University of Michigan Biological Station (Pellston, MI) during the 2009 CABINEX field campaign are reported. Daytime (09:00 a.m. to 05:00 p.m. LT) isoprene fluxes, when averaged over the footprint of the tower, were 1.31 mg m-2 h-1 which are comparable to previous flux measurements at this location. Speciated monoterpene fluxes are some of the first to be reported from this site. Daytime averages were 26.7 ?g m-2 h-1 for ?-pinene and 10.6 ?g m-2 h-1 for ?-pinene. These measured concentrations and fluxes were compared to the output of an atmospheric chemistry model, and were found to be consistent with our knowledge of the variables that control BVOCs fluxes at this site.

  7. CO2-flux measurements above the Baltic Sea at two heights: flux gradients in the surface layer?

    NASA Astrophysics Data System (ADS)

    Lammert, A.; Ament, F.

    2015-11-01

    The estimation of CO2 exchange between the ocean and the atmosphere is essential to understand the global carbon cycle. The eddy-covariance technique offers a very direct approach to observe these fluxes. The turbulent CO2 flux is measured, as well as the sensible and latent heat flux and the momentum flux, a few meters above the ocean in the atmosphere. Assuming a constant-flux layer in the near-surface part of the atmospheric boundary layer, this flux equals the exchange flux between ocean and atmosphere. The purpose of this paper is the comparison of long-term flux measurements at two different heights above the Baltic Sea to investigate this assumption. The results are based on a 1.5-year record of quality-controlled eddy-covariance measurements. Concerning the flux of momentum and of sensible and latent heat, the constant-flux layer theory can be confirmed because flux differences between the two heights are insignificantly small more than 95 % of the time. In contrast, significant differences, which are larger than the measurement error, occur in the CO2 flux about 35 % of the time. Data used for this paper are published at http://doi.pangaea.de/10.1594/PANGAEA.808714.

  8. CO2-flux measurements above the Baltic Sea at two heights: flux gradients in the surface layer

    NASA Astrophysics Data System (ADS)

    Lammert, A.; Ament, F.

    2015-07-01

    The estimation of CO2 exchange between the ocean and the atmosphere is essential to understand the global carbon cycle. The eddy-covariance technique offers a very direct approach to observe these fluxes. The turbulent CO2 flux is measured as well as the sensible and latent heat flux and the momentum flux, a few meters above the ocean in the atmosphere. Assuming a constant-flux layer in the near surface part of the atmospheric boundary, this flux equals the exchange flux between ocean and atmosphere. The goal of this paper is the comparison of long-term flux measurements at two different heights above the Baltic Sea due to this assumption. The results are based on an one-and-a-half year record of quality controlled eddy covariance measurements. Concerning the flux of momentum and of sensible and latent heat, the constant-flux layer theory can be validated because flux gradients between the two heights are more than 95 % of the time insignificantly small. In contrast, significant gradients, which are larger than the measurement error, occur for the CO2 flux in nearly 35 % of the time. Data, used for this paper are published at http://doi.pangaea.de/10.1594/PANGAEA.808714.

  9. Measuring cardiac autophagic flux in vitro and in vivo.

    PubMed

    Gurney, Michael A; Huang, Chengqun; Ramil, Jennifer M; Ravindran, Nandini; Andres, Allen M; Sin, Jon; Linton, Phyllis-Jean; Gottlieb, Roberta A

    2015-01-01

    Autophagy is a lysosomal-dependent catabolic pathway that recycles various cytoplasmic-borne components, such as organelles and proteins, through the lysosomes. This process creates energy and biomolecules that are used to maintain homeostasis and to serve as an energy source under conditions of acute stress. Autophagic flux is a measure of efficiency or throughput of the pathway. Here, we describe a method for determining autophagic flux in vitro and in vivo using the autophagosomal/lysosomal fusion inhibitors chloroquine or bafilomycin A1 and then probing for the autophagosomal marker LC3-II via Western Blot. PMID:25308270

  10. A Novel Detector for High Neutron Flux Measurements

    SciTech Connect

    Singo, T. D.; Wyngaardt, S. M.; Papka, P.; Dobson, R. T.

    2010-01-05

    Measuring alpha particles from a neutron induced break-up reaction with a mass spectrometer can be an excellent tool for detecting neutrons in a high neutron flux environment. Break-up reactions of {sup 6}Li and {sup 12}C can be used in the detection of slow and fast neutrons, respectively. A high neutron flux detection system that integrates the neutron energy sensitive material and helium mass spectrometer has been developed. The description of the detector configuration is given and it is soon to be tested at iThemba LABS, South Africa.

  11. Eddy correlation measurements of NO, NO{sub 2}, and O{sub 3} fluxes

    SciTech Connect

    Gao, W.; Wesely, M.L.; Cook, D.R.; martin, T.J.

    1996-06-01

    The micrometeorological technique of eddy correlation was used to measure the vertical fluxes of NO, NO{sub 2}, and ozone in rural North Carolian during spring 1995 as part of the Natural emission of Oxidant precurssors-Validation of techniques and Assessment (NOVA) field experiment. Net flux densities were measured at heights 5 and 10 m above an agricultural field with short corn plants and large amount of exposed bare soil between the rows. Large upward eddy fluxes of NO{sub 2} were seen, and strong NO emissions from the soil were measured by collaborators using environmental enclosures on the soil surface. Data indicate that about 50% of the nitrogen emitted from the soil as NO was converted into NO{sub 2} at 5 m. Rest of the emitted nitrogen may remain as NO flux and be returned back to the vegetation and soil by deposition. Divergence of the NO{sub 2} and O{sub 3} fluxes were detected between 5 and 10 m. This is consistent with likely net NO{sub 2} and O{sub 3} destruction rates. The data will be used to help develop parameterizations of the flux of nitrogen oxides into the lower troposphere.

  12. Measurement of Heat Flux at Metal-Mold Interface during Casting Solidification

    SciTech Connect

    Sabau, Adrian S

    2006-01-01

    All previous studies on interfacial heat transfer coefficient have been based on indirect methods for estimating the heat flux that employed either inverse heat transfer analysis procedures or instrumentation arrangements to measure temperatures and displacements near the metal-mold interface. In this paper, the heat transfer at the metal-mold interfaces is investigated using a sensor for the direct measurement of heat flux. The heat flux sensor (HFS) was rated for 700oC and had a time response of less than 10 ms. Casting experiments were conducted using graphite molds for aluminum alloy A356. Several casting experiments were performed using a graphite coating and a boron nitride coating. The measurement errors were estimated. The temperature of the mold surface was provided by the HFS while the temperature of the casting surface was measured using a thermocouple. Results for the heat transfer coefficients were obtained based on measured heat flux and temperatures. Four stages were clearly identified for the variation in time of the heat flux. Values of the heat transfer coefficient were in good agreement with data from previous studies.

  13. A mobile detector for measurements of the atmospheric muon flux in underground sites

    NASA Astrophysics Data System (ADS)

    Mitrica, Bogdan; Margineanu, Romul; Stoica, Sabin; Petcu, Mirel; Brancus, Iliana; Jipa, Alexandru; Lazanu, Ionel; Sima, Octavian; Haungs, Andreas; Rebel, Heinigerd; Petre, Marian; Toma, Gabriel; Saftoiu, Alexandra; Stanca, Denis; Apostu, Ana; Gomoiu, Claudia

    2011-10-01

    Muons comprise an important contribution of the natural radiation dose in air (approx. 30 nSv/h of a total dose rate of 65-130 nSv/h), as well as in underground sites even when the flux and relative contribution are significantly reduced. The flux of muons observed underground can be used as an estimator for the depth in mwe (meter water equivalent) of the underground site. The water equivalent depth is important information to devise physics experiments feasible for a specific site. A mobile detector for performing measurements of the muon flux was developed in IFIN-HH, Bucharest. Consisting of two scintillator plates (approx. 0.9 m2) which measure in coincidence, the detector is installed on a van which facilitates measurements at different locations at the surface or underground. The detector was used to determine muon fluxes at different sites in Romania. In particular, data were taken and the values of meter water equivalents were assessed for several locations at the salt mine in Slanic-Prahova, Romania. The measurements have been performed in two different galleries of the Slanic mine at different depths. In order to test the stability of the method, also measurements of the muon flux at the surface at different elevations were performed. The results were compared with predictions of Monte-Carlo simulations using the CORSIKA and MUSIC codes.

  14. Scales, Growth Rates, and Spectral Fluxes of Baroclinic Instability in the Ocean

    E-print Network

    Tulloch, Ross

    An observational, modeling, and theoretical study of the scales, growth rates, and spectral fluxes of baroclinic instability in the ocean is presented, permitting a discussion of the relation between the local instability ...

  15. Methane fluxes measured by eddy covariance at a temperate upland forest

    NASA Astrophysics Data System (ADS)

    Wang, J.; Murphy, J. G.; Winsborough, C. L.; Basiliko, N.; Geddes, J. A.; Thomas, S.

    2012-12-01

    Methane flux measurements were carried out at a temperate upland forest in Central Ontario, Haliburton Forest and Wildlife Reserve (45.28° N, 78.55° W) using the eddy covariance (EC) method. An off-axis integrated cavity output spectrometer (OA-ICOS) Fast Greenhouse Gas Analyzer (FGGA from Los Gatos Research, Inc.) operated at a sampling rate of 10 Hz allowed for simultaneous measurement of methane (CH4), carbon dioxide (CO2), and water (H2O) over five months from June to October in 2011. Air was pulled from the top of a 32 m tower, 8 m above the forest canopy, to the bottom of the tower through 40 m of tubing to the instrument. A sonic anemometer and a LI-7500 open-path sensor were also used at the top of the tower to provide high frequency wind data and comparative open-path measurements of CO2 and H2O. A nearby soil station measured soil water content and soil temperature at 0, 3, and 10 cm below the surface. Observed methane fluxes showed net uptake of CH4 over the measurement period with an average uptake flux value (± standard deviation of the mean) of -2.7±0.13 nmol m-2 s-1. In early June when measurements commenced, the soil moisture was relatively high and CH4 flux values showed net emission. As the season advanced the soil became progressively drier, and there was an increasing trend in CH4 uptake, peaking in mid-September. There was also a diurnal trend in the CH4 flux, with increased uptake during the day, and decreased uptake between 0:00 and 08:00. The CH4 flux values correlated well with the horizontal wind speed measured within the forest canopy. We hypothesize that this may be due to a ventilation effect in which higher wind speed facilitates the introduction of CH4-rich air and removes CH4-depleted air near the methanotrophs in the soil. The measurements were made in an uneven-aged managed forest stand last harvested 15 years ago containing sandy and acidic soils (pH 4.0 - 5.0). Chamber flux measurements of CH4 were also performed at seven toposequences around the tower, every two weeks from June to October. These chamber flux values are qualitatively consistent with those measured by eddy covariance in terms of magnitude and seasonality. While the flux measurements indicate net uptake by soils, the diurnal cycle of mixing ratios often showed nighttime accumulation of methane, indicating that over the broader landscape around the tower, emissions may dominate.

  16. A mobile detector for measurements of the atmospheric muon flux

    NASA Astrophysics Data System (ADS)

    Mitrica, B.; Brancus, I. M.; Margineanu, R.; Petcu, M.; Dima, M.; Sima, O.; Haungs, A.; Rebel, H.; Petre, M.; Toma, G.; Saftoiu, A.; Apostu, A.

    2011-04-01

    Measurements of the underground atmospheric muon flux are important in order to determine accurately the overburden in mwe (meter water equivalent) of an underground laboratory for appreciating which kind of experiments are feasible for that location. Slanic- Prohava is one of the 7 possible locations for the European large underground experiment LAGUNA (Large Apparatus studying Grand Unification and Neutrino Astrophysics). A mobile device consisting of 2 scintillator plates (?0.9 m2, each) one above the other and measuring in coincidence, was set-up for determining the muon flux. The detector it is installed on a van which facilitates measurements on different positions at the surface or in the underground and it is in operation since autumn 2009. The measurements of muon fluxes presented in this contribution have been performed in the underground salt mine Slanic-Prahova, Romania, where IFIN-HH has built a low radiation level laboratory, and at the surface on different sites of Romania, at different elevations from 0 m a.s.l up to 655 m a.s.l. Based on our measurements we can say that Slanic site is a feasible location for LAGUNA in Unirea salt mine at a water equivalent depth of 600 mwe. The results have been compared with Monte-Carlo simulations performed with the simulation codes CORSIKA and MUSIC.

  17. Maximal Sum of Metabolic Exchange Fluxes Outperforms Biomass Yield as a Predictor of Growth Rate of

    E-print Network

    Ruppin, Eytan

    Maximal Sum of Metabolic Exchange Fluxes Outperforms Biomass Yield as a Predictor of Growth Rate National Laboratory, Argonne, Illinois, United States of America Abstract Growth rate has long been accessible and informative in laboratory cultures, maximal growth rate is often a prime determinant

  18. CAN COSMIC-RAY NUCLEON MEASUREMENTS BE USED TO SCALE PRODUCTION RATES OF COSMOGENIC NUCLIDES?

    E-print Network

    Zreda, Marek

    CAN COSMIC-RAY NUCLEON MEASUREMENTS BE USED TO SCALE PRODUCTION RATES OF COSMOGENIC NUCLIDES variability of nuclide production rates on the earth's surface. Direct measurements of cosmic-ray fluxes have spatial variations of cosmic-ray neu- tron intensity and production rates of in-situ cosmogenic nuclides

  19. Can organic matter flux profiles be diagnosed using remineralisation rates derived from observed tracers and modelled ocean transport rates?

    NASA Astrophysics Data System (ADS)

    Wilson, J. D.; Ridgwell, A.; Barker, S.

    2015-09-01

    The average depth in the ocean at which the majority of sinking organic matter particles remineralise is a fundamental parameter in the ocean's role in regulating atmospheric CO2. Observed spatial patterns in sinking fluxes and relationships between the fluxes of different particles in the modern ocean have widely been used to invoke controlling mechanisms with important implications for CO2 regulation. However, such analyses are limited by the sparse spatial sampling of the available sediment trap data. Here we explore whether model ocean circulation rates, in the form of a transport matrix, can be used to derive remineralisation rates and infer sinking particle flux curves from the much more highly resolved observations of dissolved nutrient concentrations. Initially we show an example of the method using a transport matrix from the MITgcm model and demonstrate that there are a number of potential uncertainties associated with the method. We then use the Earth system model GENIE to generate a synthetic tracer data set to explore the method and its sensitivity to key sources of uncertainty arising from errors in the tracer observations and in the model circulation. We use a 54-member ensemble of different, but plausible, estimates of the modern circulation to explore errors associated with model transport rates. We find that reconstructed re-mineralisation rates are very sensitive to both errors in observations and model circulation rates, such that a simple inversion cannot provide a robust estimate of particulate flux profiles. Estimated remineralisation rates are particularly sensitive to differences between the "observed" and modelled circulation because remineralisation rates are 3-4 magnitudes smaller than transport rates. We highlight a potential method of constraining the uncertainty associated with using modelled circulation rates, although its success is limited by the observations currently available. Finally, we show that there are additional uncertainties when inferring particle flux curves from reliable estimates of remineralisation rates due to processes that are not restricted to the vertical water column transport, such as the cycling of dissolved organic matter.

  20. New constraints on methane fluxes and rates of anaerobic methane oxidation in a Gulf of Mexico brine pool via in situ mass spectrometry

    E-print Network

    Girguis, Peter R.

    New constraints on methane fluxes and rates of anaerobic methane oxidation in a Gulf of Mexico Keywords: Methane flux Mass spectrometer Brine pool Methane oxidation Gulf of Mexico a b s t r a c t Deep report direct measurements of methane concentrations made in a Gulf of Mexico brine pool located

  1. Saharan Airborne Dust Flux Measurements from the Fennec Campaign

    NASA Astrophysics Data System (ADS)

    Rosenberg, Phil; Parker, Doug; Ryder, Claire; Garcia-Carreras, Luis; Marsham, John; Dorsey, James; Brooks, Ian; Dean, Angela; Crosier, Jonathan; McQuaid, Jim; Washington, Richard

    2013-04-01

    The Fennec campaign of 2011involved deployment of the Facility for Airborne Atmospheric Measurements BAe 146 (FAAM Bae 146) scientific research aircraft to Fuerteventura with research flights over the remote Saharan desert in Mali and Mauritania. The aims of the Fennec campaign were to characterise the dynamics, radiation and dust environment in this inaccessible region. The FAAM BAe 146 operated a suite of instruments which measured size distributions of dust including a Passive Cavity Aerosol Spectrometer Probe, a Cloud Droplet Probe and a Cloud Imaging Probe (part of a Cloud, Aerosol and Precipitation Spectrometer). These instruments were able to reliably generate particle size distributions over the approximate range 0.1 to 200 ?m and for the first time were simultaneously operated at high temporal resolution of at least 10 Hz. Combining these dust measurements with the measured 3D wind vectors has allowed size resolved dust flux estimates to be derived using the eddy covariance method. To the authors' knowledge this is the first time such estimates have been successfully derived from aircraft data. Although the FAAM BAe 146 is capable of low level flying with straight and level runs at minimum altitudes of ~100 m (higher in poor visibility), this is still significantly higher than mast based flux measurements making comparison of the total flux with surface based observations difficult. However, these observations give useful measures of the size dependence of the particle flux and the spectral signature of the dynamics of vertical dust transport. The size resolved measurements show that dust mass flux includes significant contributions up to particle diameters ~100 ?m. This is much larger than the limit seen by other studies and is even more surprising given that the measurements were made at heights so far above the saltation layer. Spectral analysis shows three distinct dynamical regimes. The first appears to be linked to chaotic turbulence with horizontal scales of ~100 m. The second seems to be linked to features on scales ~1 km, similar to the order of the boundary layer depth. Finally, in the third regime, the concentration and wind measurements have a very asymmetric cross correlation series in the along flight direction which may indicate a preferred orientation for turbulent eddies caused buy e.g. shear. These characteristics are linked to the weather conditions and dust uplift mechanisms for each case.

  2. Measurement of a surface heat flux and temperature

    NASA Technical Reports Server (NTRS)

    Davis, R. M.; Antoine, G. J.; Diller, T. E.; Wicks, A. L.

    1994-01-01

    The Heat Flux Microsensor is a new sensor which was recently patented by Virginia Tech and is just starting to be marketed by Vatell Corp. The sensor is made using the thin-film microfabrication techniques directly on the material that is to be measured. It consists of several thin-film layers forming a differential thermopile across a thermal resistance layer. The measured heat flux q is proportional to the temperature difference across the resistance layer q= k(sub g)/delta(sub g) x (t(sub 1) - T(sub 2)), where k(sub g) is the thermal conductivity and delta (sub g) is the thickness of the thermal resistance layer. Because the gages are sputter coated directly onto the surface, their total thickness is less than 2 micrometers, which is two orders of magnitude thinner than previous gages. The resulting temperature difference across the thermal resistance layer (delta is less than 1 micrometer) is very small even at high heat fluxes. To generate a measurable signal many thermocouple pairs are put in series to form a differential thermopile. The combination of series thermocouple junctions and thin-film design creates a gage with very attractive characteristics. It is not only physically non-intrusive to the flow, but also causes minimal disruption of the surface temperature. Because it is so thin, the response time is less than 20 microsec. Consequently, the frequency response is flat from 0 to over 50 kHz. Moreover, the signal of the Heat Flux Microsensor is directly proportional to the heat flux. Therefore, it can easily be used in both steady and transient flows, and it measures both the steady and unsteady components of the surface heat flux. A version of the Heat Flux Microsensor has been developed to meet the harsh demands of combustion environments. These gages use platinum and platinum-10 percent rhodium as the thermoelectric materials. The thermal resistance layer is silicon monoxide and a protective coating of Al2O3 is deposited on top of the sensor. The superimposed thin-film pattern of all six layers is presented. The large pads are for connection with pins used to bring the signal out the back of the ceramic. In addition to the heat flux measurement, the surface temperature is measured with a platinum resistance layer (RTS). The resistance of this layer increases with increasing temperature. Therefore, these gages simultaneously measure the surface temperature and heat flux. The demonstrated applications include rocket nozzles, SCRAM jet engines, gas turbine engines, boiling heat transfer, flame experiments, basic fluid heat transfer, hypersonic flight, and shock tube testing. The laboratory involves using one of these sensors in a small combustion flame. The sensor is made on a 2.5 cm diameter piece of aluminum nitride ceramic.

  3. Time and Space Resolved Heat Flux Measurements During Nucleate Boiling with Constant Heat Flux Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Yerramilli, Vamsee K.; Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Kim, Jungho

    2005-01-01

    The lack of temporally and spatially resolved measurements under nucleate bubbles has complicated efforts to fully explain pool-boiling phenomena. The objective of this current work was to acquire time and space resolved temperature distributions under nucleating bubbles on a constant heat flux surface using a microheater array with 100x 100 square microns resolution, then numerically determine the wall to liquid heat flux. This data was then correlated with high speed (greater than l000Hz) visual recordings of The bubble growth and departure from the heater surface acquired from below and from the side of the heater. The data indicate that microlayer evaporation and contact line heat transfer are not major heat transfer mechanisms for bubble growth. The dominant heat transfer mechanism appears to be transient conduction into the liquid as the liquid rewets the wall during the bubble departure process.

  4. Airborne flux measurements of biogenic isoprene over California

    NASA Astrophysics Data System (ADS)

    Misztal, P. K.; Karl, T.; Weber, R.; Jonsson, H. H.; Guenther, A. B.; Goldstein, A. H.

    2014-10-01

    Biogenic isoprene fluxes were measured onboard the CIRPAS Twin Otter aircraft as part of the California Airborne Biogenic volatile organic compound (BVOC) Emission Research in Natural Ecosystem Transects (CABERNET) campaign during June 2011. The airborne virtual disjunct eddy covariance (AvDEC) approach used measurements from a proton transfer reaction mass spectrometer (PTR-MS) and a wind radome probe to directly determine fluxes of isoprene over 7400 km of flight paths focusing on areas of California predicted to have the largest emissions. The fast Fourier transform (FFT) approach was used to calculate fluxes of isoprene over long transects of more than 15 km, most commonly between 50 and 150 km. The continuous wavelet transformation (CWT) approach was used over the same transects to also calculate instantaneous isoprene fluxes with localization of both frequency and time independent of non-stationarities. Fluxes were generally measured by flying consistently at 400 m ± 50 m (a.g.l.) altitude, and extrapolated to the surface according to the determined flux divergence determined in the racetrack-stacked profiles. The wavelet-derived surface fluxes of isoprene averaged to 2 km spatial resolution showed good correspondence to basal emission factor (BEF) land-cover data sets used to drive BVOC emission models. The surface flux of isoprene was close to zero over Central Valley crops and desert shrublands, but was very high (up to 15 mg m-2 h-1) above oak woodlands, with clear dependence of emissions on temperature and oak density. Isoprene concentrations of up to 8 ppb were observed at aircraft height on the hottest days and over the dominant source regions. Even though the isoprene emissions from agricultural crop regions, shrublands, and coniferous forests were extremely low, observations at the Walnut Grove tower south of Sacramento demonstrate that isoprene oxidation products from the high emitting regions in the surrounding oak woodlands accumulate at night in the residual layer above the valley and mix down into the valley in the morning. Thus, the isoprene emissions surrounding the valley have relevance for the regional photochemistry that is not immediately apparent solely from the direct emission flux distribution. This paper reports the first regional observations of fluxes from specific sources by eddy covariance from an aircraft which can finally constrain statewide isoprene emission inventories used for ozone simulations by state agencies. While previously there was no available means to constrain the biogenic models, our results provide a good understanding of what the major sources of isoprene are in California, their magnitude, and how they are distributed. This data set on isoprene fluxes will be particularly useful for evaluating potential model alternatives which will be dealt with in a separate paper to assess isoprene emission models and their driving variable data sets.

  5. Automation of soil flux chamber measurements: potentials and pitfalls

    NASA Astrophysics Data System (ADS)

    Görres, C.-M.; Kammann, C.; Ceulemans, R.

    2015-09-01

    Recent technological advances have enabled the wider application of automated chambers for soil greenhouse gas (GHG) flux measurements, several of them commercially available. However, only few studies addressed the difficulties and challenges associated with operating these systems. In this contribution we compared two commercial soil GHG chamber systems-the LI-8100A Automated Soil CO2 Flux System and the Greenhouse Gas Monitoring System AGPS. From April 2014 until August 2014, the two systems monitored in parallel soil respiration (SR) fluxes at a recently harvested poplar plantation, which provided a bare field situation directly after the harvest as well as a closed canopy later on. For the bare field situation (15 April-30 June 2014), the cumulated average SR obtained from the unfiltered datasets of the LI-8100A and the AGPS were 520 and 433 g CO2 m-2, respectively. For the closed canopy phase (01 July-31 August 2014), which was characterized by a higher soil moisture content, the cumulated average SR estimates were not significantly different with 507 and 501 g CO2 m-2 for the AGPS and the LI-8100A, respectively. Flux quality control and filtering did not significantly alter the results obtained by the LI-8100A, whereas the AGPS SR estimates were reduced by at least 20 %. The main reasons for the observed differences in the performance of the two systems were (i) a lower data coverage provided by the AGPS due to technical problems; (ii) incomplete headspace mixing in the AGPS chambers; (iii) lateral soil CO2 diffusion below the collars during AGPS chamber measurements; (iv) increased root growth within the LI-8100A collars; and (v) a possible overestimation of nighttime SR fluxes by the LI-8100A. In contrast to the LI-8100A, the AGPS had the gas sample inlets installed inside the collars and not the chambers. This unique design feature enabled for the first time the detection of disturbed chamber measurements during nights with a stratified atmosphere, resulting in unbiased nighttime SR estimates. Thus besides providing high temporal frequency flux data, automated chamber systems offer another possibility to greatly improve our understanding of SR fluxes.

  6. First measurement of the flux of solar neutrinos from the sun at the Sudbury Neutrino Observatory

    NASA Astrophysics Data System (ADS)

    Wittich, Peter

    2000-12-01

    The Sudbury Neutrino Observatory (SNO) is a second generation solar neutrino detector. SNO is the first experiment that is able to measure both the electron neutrino flux and a flavor-blind flux of all active neutrino types, allowing a model-independent determination if the deficit of solar neutrinos known as the solar neutrino problem is due to neutrino oscillation. The Sudbury Neutrino Observatory started taking production data in November, 1999. A measurement of the charged current rate will be the first indication if SNO too sees a suppression of the solar neutrino signal relative to the theoretical predictions. Such a confirmation is the first step in SNO's ambitious science program. In this thesis, we present evidence that SNO is seeing solar neutrinos and a preliminary ratio of the measured vs predicted rate of electrons as induced by 8B neutrinos in the ?e, + d --> p + p + e charged-current (CC) reaction.

  7. Radioastronomical measurement of ultrahigh-energy cosmic particle fluxes

    NASA Astrophysics Data System (ADS)

    Filonenko, A. D.

    2012-08-01

    The basic principles underlying the radio telescope measurement of ultrahigh-energy particle fluxes are reviewed. Experimental lunar regolith emission data are presented for the 10^{20} eV energy range. Some conclusions from theoretical work are discussed, as is the influence of a number of factors on the intensity of the radio pulse due to the cascade disk under the Moon's surface.

  8. Measuring the Magnetic Flux Density in the CMS Steel Yoke

    E-print Network

    V. I. Klyukhin; N. Amapane; A. Ball; B. Curé; A. Gaddi; H. Gerwig; A. Hervé; M. Mulders; R. Loveless

    2012-12-06

    The Compact Muon Solenoid (CMS) is a general purpose detector, designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive features include a 4 T superconducting solenoid with 6-m-diameter by 12.5-m-length free bore, enclosed inside a 10000-ton return yoke made of construction steel. The return yoke consists of five dodecagonal three-layered barrel wheels and four end-cap disks at each end comprised of steel blocks up to 620 mm thick, which serve as the absorber plates of the muon detection system. Accurate characterization of the magnetic field everywhere in the CMS detector is required. To measure the field in and around the steel, a system of 22 flux-loops and 82 3-D Hall sensors is installed on the return yoke blocks. Fast discharges of the solenoid (190 s time-constant) made during the CMS magnet surface commissioning test at the solenoid central fields of 2.64, 3.16, 3.68 and 4.01 T were used to induce voltages in the flux-loops. The voltages are measured on-line and integrated off-line to obtain the magnetic flux in the steel yoke close to the muon chambers at full excitations of the solenoid. The 3-D Hall sensors installed on the steel-air interfaces give supplementary information on the components of magnetic field and permit to estimate the remanent field in steel to be added to the magnetic flux density obtained by the voltages integration. A TOSCA 3-D model of the CMS magnet is developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. The results of the measurements and calculations are presented, compared and discussed.

  9. Estimation of rainfall interception in grassland using eddy flux measurements

    NASA Astrophysics Data System (ADS)

    Maruyama, A.; Miyazawa, Y.; Inoue, A.

    2014-12-01

    Rainfall interception plays an important role in the water cycle in natural ecosystems. Interception by the forest canopies have been widely observed or estimated over various ecosystems, such as tropical rainforest, evergreen forest and deciduous forest. However interception by the short canopies, e.g. shrubby plant, grassland and crop, has been rarely observed since it has been difficult to obtain reliable precipitation measurements under the canopy. In this study, we estimated monthly and annual rainfall interception in grassland using evapotranspiration data of eddy flux measurements. Experiments were conducted in grassland (Italian ryegrass) from 2010 to 2012 growing season in Kumamoto, Japan. Evapotranspiration (latent heat flux) were observed throughout the year based on the eddy covariance technique. A three dimensional sonic anemometer and an open path CO2/H2O analyzer were used to calculate 30 min flux. Other meteorological factors, such as air temperature, humidity and solar radiation, were also observed. Rainfall interception was estimated as follows. 1) Using evapotranspiration data during dry period, environmental response of surface conductance (gc) was inversely calculated based on the big-leaf model. 2) Evapotranspiration without interception during precipitation period was estimated using above model and environmental response of gc. 3) Assuming that evaporation of intercepted rainfall is equal to the difference in evapotranspiration between above estimation and actual measurements, rainfall interception was estimated over experimental period. The account of rainfall interception in grassland using this technique will be presented at the meeting.

  10. DIRECT MEASUREMENT OF HEAT FLUX FROM COOLING LAKE THERMAL IMAGERY

    SciTech Connect

    Garrett, A; Eliel Villa-Aleman, E; Robert Kurzeja, R; Malcolm Pendergast, M; Timothy Brown, T; Saleem Salaymeh, S

    2007-12-19

    Laboratory experiments show a linear relationship between the total heat flux from a water surface to air and the standard deviation of the surface temperature field, {sigma}, derived from thermal images of the water surface over a range of heat fluxes from 400 to 1800 Wm{sup -2}. Thermal imagery and surface data were collected at two power plant cooling lakes to determine if the laboratory relationship between heat flux and {sigma} exists in large heated bodies of water. The heat fluxes computed from the cooling lake data range from 200 to 1400 Wm{sup -2}. The linear relationship between {sigma} and Q is evident in the cooling lake data, but it is necessary to apply band pass filtering to the thermal imagery to remove camera artifacts and non-convective thermal gradients. The correlation between {sigma} and Q is improved if a correction to the measured {sigma} is made that accounts for wind speed effects on the thermal convection. Based on more than a thousand cooling lake images, the correlation coefficients between {sigma} and Q ranged from about 0.8 to 0.9.

  11. An ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements

    NASA Astrophysics Data System (ADS)

    Wohlfahrt, G.; Amelynck, C.; Ammann, C.; Arneth, A.; Bamberger, I.; Goldstein, A. H.; Gu, L.; Guenther, A.; Hansel, A.; Heinesch, B.; Holst, T.; Hörtnagl, L.; Karl, T.; Laffineur, Q.; Neftel, A.; McKinney, K.; Munger, J. W.; Pallardy, S. G.; Schade, G. W.; Seco, R.; Schoon, N.

    2015-01-01

    Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates reflecting uncertainties in the approaches used to model, and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis of the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land-atmosphere methanol exchange. Our study shows that the controls of plant growth on the production, and thus the methanol emission magnitude, and stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem-level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; they are however neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow taking full advantage of the rich information content of micrometeorological flux measurements.

  12. An ecosystem-scale perspective of the net land methanol flux. Synthesis of micrometeorological flux measurements

    DOE PAGESBeta

    Wohlfahrt, G.; Amelynck, C.; Ammann, C.; Arneth, A.; Bamberger, I.; Goldstein, A. H.; Gu, L.; Guenther, A.; Hansel, A.; Heinesch, B.; et al

    2015-07-09

    Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates, reflecting uncertainties in the approaches used to model and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis ofmore »the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land–atmosphere methanol exchange. Our study shows that the controls of plant growth on production, and thus the methanol emission magnitude, as well as stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; however, they are neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow for full advantage to be taken of the rich information content of micrometeorological flux measurements.« less

  13. An ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements

    NASA Astrophysics Data System (ADS)

    Wohlfahrt, G.; Amelynck, C.; Ammann, C.; Arneth, A.; Bamberger, I.; Goldstein, A. H.; Gu, L.; Guenther, A.; Hansel, A.; Heinesch, B.; Holst, T.; Hörtnagl, L.; Karl, T.; Laffineur, Q.; Neftel, A.; McKinney, K.; Munger, J. W.; Pallardy, S. G.; Schade, G. W.; Seco, R.; Schoon, N.

    2015-07-01

    Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates, reflecting uncertainties in the approaches used to model and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis of the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land-atmosphere methanol exchange. Our study shows that the controls of plant growth on production, and thus the methanol emission magnitude, as well as stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; however, they are neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow for full advantage to be taken of the rich information content of micrometeorological flux measurements.

  14. An ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements

    PubMed Central

    Wohlfahrt, G.; Amelynck, C.; Ammann, C.; Arneth, A.; Bamberger, I.; Goldstein, A. H.; Gu, L.; Guenther, A.; Hansel, A.; Heinesch, B.; Holst, T.; Hörtnagl, L.; Karl, T.; Laffineur, Q.; Neftel, A.; McKinney, K.; Munger, J. W.; Pallardy, S. G.; Schade, G. W.; Seco, R.; Schoon, N.

    2015-01-01

    Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates reflecting uncertainties in the approaches used to model, and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis of the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land–atmosphere methanol exchange. Our study shows that the controls of plant growth on the production, and thus the methanol emission magnitude, and stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem-level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; they are however neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow taking full advantage of the rich information content of micrometeorological flux measurements. PMID:25983744

  15. An ecosystem-scale perspective of the net land methanol flux. Synthesis of micrometeorological flux measurements

    SciTech Connect

    Wohlfahrt, G.; Amelynck, C.; Ammann, C.; Arneth, A.; Bamberger, I.; Goldstein, A. H.; Gu, L.; Guenther, A.; Hansel, A.; Heinesch, B.; Holst, T.; Hörtnagl, L.; Karl, T.; Laffineur, Q.; Neftel, A.; McKinney, K.; Munger, J. W.; Pallardy, S. G.; Schade, G. W.; Seco, R.; Schoon, N.

    2015-07-09

    Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates, reflecting uncertainties in the approaches used to model and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis of the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land–atmosphere methanol exchange. Our study shows that the controls of plant growth on production, and thus the methanol emission magnitude, as well as stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; however, they are neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow for full advantage to be taken of the rich information content of micrometeorological flux measurements.

  16. Momentum Flux Measuring Instrument for Neutral and Charged Particle Flows

    NASA Technical Reports Server (NTRS)

    Chavers, Greg; Chang-Diaz, Franklin; Schafer, Charles F. (Technical Monitor)

    2002-01-01

    An instrument to measure the momentum flux (total pressure) of plasma and neutral particle jets onto a surface has been developed. While this instrument was developed for magnetized plasmas, the concept works for non-magnetized plasmas as well. We have measured forces as small as 10(exp -4) Newtons on a surface immersed in the plasma where small forces are due to ionic and neutral particles with kinetic energies on the order of a few eV impacting the surface. This instrument, a force sensor, uses a target plate (surface) that is immersed in the plasma and connected to one end of an alumina rod while the opposite end of the alumina rod is mechanically connected to a titanium beam on which four strain gauges are mounted. The force on the target generates torque causing strain in the beam. The resulting strain measurements can be correlated to a force on the target plate. The alumina rod electrically and thermally isolates the target plate from the strain gauge beam and allows the strain gauges to be located out of the plasma flow while also serving as a moment arm of several inches to increase the strain in the beam at the strain gauge location. These force measurements correspond directly to momentum flux and may be used with known plasma conditions to place boundaries on the kinetic energies of the plasma and neutral particles. The force measurements may also be used to infer thrust produced by a plasma propulsive device. Stainless steel, titanium, molybdenum, and aluminum flat target plates have been used. Momentum flux measurements of H2, D2, He, and Ar plasmas produced in a magnetized plasma device have been performed.

  17. Spatial and temporal variations of methane flux measured by autochambers in a temperate ombrotrophic peatland

    NASA Astrophysics Data System (ADS)

    Lai, Derrick Y. F.; Moore, Tim R.; Roulet, Nigel T.

    2014-05-01

    We measured CH4 flux at high temporal resolution with triplicate autochambers from three different plant communities at the ombrotrophic Mer Bleue bog in Canada to investigate the spatial and temporal variations, and factors that related to the CH4 flux. Our results show that seasonal mean CH4 fluxes from the Eriophorum-dominated community were 1.4-2.2 and 3.7-5.5 times higher than those from Maianthemum/Ledum and Chamaedaphne communities, respectively. Significant interannual variations in CH4 flux were observed in Maianthemum/Ledum and Chamaedaphne communities, attributable to a 55-60% reduction of mean summer (July-September) CH4 flux in 2010 as a consequence of a 5.5-9.0 cm lower mean summer water table compared to 2009. The Eriophorum community showed a much larger rate of increase in CH4 flux with peat temperature in the early growing season than in midsummer, which might be caused by a concomitant increase in root exudation of labile carbon for methanogenesis. Temporal variability of log-transformed CH4 flux was correlated (r ? 0.4) with peat temperature only when water table was less than 20, 30, and 40 cm below the peat surface for Maianthemum/Ledum, Chamaedaphne, and Eriophorum communities, respectively. This difference in water table threshold among communities might partly be related to differences in rooting depth and hence the ability of plants to sustain CH4 flux in dry conditions. These results suggest that modeling of CH4 flux from ombrotrophic peatlands over time should take into account the role of different vegetation types, since the relationships between CH4 emissions and environmental factors vary among vascular plant communities.

  18. Development of a Passive Sensor for Measuring Water and Solute Mass Flux in the Hyporheic Zone

    NASA Astrophysics Data System (ADS)

    Annable, Michael D.; Layton, Leif; Hatfield, Kirk; Newman, Mark C.; Cho, Jaehyun; Klammler, Harald

    2014-05-01

    Measuring water, pollutant and nutrient exchange at the groundwater-surface water interface is challenging due to the dynamic nature of the hyporheic zone. Quantifying the exchange is critical to understanding mass balance across this interface. Technologies currently exist to identify groundwater discharge zones and infer estimates of contaminant mass flux based on total contaminant concentration in bulk sediment, though it is generally accepted that freely dissolved concentration in pore water is a better measure of potential exposure. Laboratory and preliminary field testing has been completed to demonstrate a new tool with potential to provide more accurate characterization of water, pollutant and nutrient flux at the groundwater-surface water interface through direct in-situ measurement. The sediment bed passive flux meter (SBPFM) was designed for passively and directly providing in-situ measurements of volumetric water flux and solute mass flux vertically through the upper surface sediment layer and into the overlying water column. The SBPFM consists of an internal permeable sorbent which is impregnated with one or more water soluble tracers (typically alcohols) and is contained in a dedicated drive-point with upper and lower screened openings for fluid intake and exhaust. This configuration generates water flow through the device proportional to the vertical gradient between the sediment bed and the water column. Once the SBPFM has been deployed, the tracers are displaced from the sorbent at rates proportional to the average vertical specific discharge. The mass loss of tracers during deployment can be used to calculate the cumulative water flux. Similarly, the cumulative mass of sorbed pollutants or nutrients provide a direct measurement of the vertical mass flux during deployment. The SBPFM prototype has been tested in controlled laboratory sediment interface models. The results show good agreement between the SBPFM calculated and the applied water and contaminant fluxes through the laboratory aquifer model. Flow reversals are anticipated for tidal sites and sorbent layers within the PFM are segmented and used to determine next flux magnitude and direction averaged over the deployment period. Preliminary field testing is underway focusing on an areas with chlorinated solvent contamination discharging to surface water. The SBPFM is deployed to quantify the net mass discharge of contaminants to a small stream over a short reach. The integrated mass discharge can be compared to concentrations and mass discharge observed in surface water. The SBPFM provides a new tool to assess water and solute flux at point locations and can provide spatial variability that can be integrated to support mass balance studies on segments of surface water reaches.

  19. Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign in Värriö field station

    NASA Astrophysics Data System (ADS)

    Ruuskanen, T. M.; Kaasik, M.; Aalto, P. P.; Horrak, U.; Vana, M.; Mårtensson, M.; Yoon, Y. J.; Keronen, P.; Mordas, G.; Ceburnis, D.; Nilsson, E. D.; O'Dowd, C.; Noppel, M.; Alliksaar, T.; Ivask, J.; Sofiev, M.; Prank, M.; Kulmala, M.

    2007-01-01

    The LAPBIAT measurement campaign took place in the SMEAR I measurement station located in Eastern Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the measurement campaign, concentrations and fluxes of aerosol particles, air ions and trace gases, paying special attention to an aerosol particle formation event broken by a polluted air mass approaching from industrial areas of Kola Peninsula, Russia. Aerosol particle number flux measurements show strong downward fluxes during that time. Concentrations of coarse aerosol particles were high for 1-2 days before the nucleation event (i.e. 28-29 April), very low immediately before and during the observed aerosol particle formation event (30 April) and increased moderately from the moment of sudden break of the event. In general particle deposition measurements based on snow samples show the same changes. Measurements of the mobility distribution of air ions showed elevated concentrations of intermediate air ions during the particle formation event. We estimated the growth rates in the nucleation mode size range. For particles <10 nm, the growth rate increases with size on 30 April. Dispersion modelling made with model SILAM support the conclusion that the nucleation event was interrupted by an outbreak of sulphate-rich air mass in the evening of 30 April that originated from the industry at Kola Peninsula, Russia. The results of this campaign highlight the need for detailed research in atmospheric transport of air constituents for understanding the aerosol dynamics.

  20. Measuring the Sources of the Intergalactic Ionizing Flux

    E-print Network

    L. L. Cowie; A. J. Barger; L. Trouille

    2008-11-06

    We use a wide-field (0.9 square degree) X-ray sample with optical and GALEX ultraviolet observations to measure the contribution of Active Galactic Nuclei (AGNs) to the ionizing flux as a function of redshift. Our analysis shows that the AGN contribution to the metagalactic ionizing background peaks around z=2. The measured values of the ionizing background from the AGNs are lower than previous estimates and confirm that ionization from AGNs is insufficient to maintain the observed ionization of the intergalactic medium (IGM) at z>3. We show that only sources with broad lines in their optical spectra have detectable ionizing flux and that the ionizing flux seen in an AGN is not correlated with its X-ray color. We also use the GALEX observations of the GOODS-N region to place a 2-sigma upper limit of 0.008 on the average ionization fraction fnu(700 A)/fnu(1500 A) for 626 UV selected galaxies in the redshift range z=0.9-1.4. We then use this limit to estimate an upper bound to the galaxy contribution in the redshift range z=0-5. If the z~1.15 ionization fraction is appropriate for higher redshift galaxies, then contributions from the galaxy population are also too low to account for the IGM ionization at the highest redshifts (z>4).

  1. Momentum Flux Measurements Using an Impact Thrust Stand

    NASA Technical Reports Server (NTRS)

    Chavers, Greg; Chang-Diaz, Franklin; Breizman, Boris; Bengtson, Roger

    2004-01-01

    A device has been developed to measure the force caused by a beam of charged and neutral particles impacting a target plate. This device, an impact thrust stand, was developed to allow thrusters, during early stages of development, to be quickly and easily exhausted and compared to other thrusters. Since some thruster concepts are tested using laboratory equipment that is heavy and cumbersome, measuring the momentum flux of the particles in the plume can be much simpler than placing the entire thruster on a thrust stand. Conservation of momentum requires the momentum flux measured in the plume to be related to the thrust produced by the thruster. The impact thrust stand was designed to be placed in the plume of an electric thruster and has been tested and compared to the thrust measured from a Hall thruster placed on a pendulum thrust stand. Force measurements taken at several axial locations in the magnetic nozzle region of the Variable Specific Impulse Magnetoplasma Rocket will be presented.

  2. The Adjustment of Avian Metabolic Rates and Water Fluxes to Desert Environments

    E-print Network

    Williams, Jos. B.

    461 The Adjustment of Avian Metabolic Rates and Water Fluxes to Desert Environments B. Irene on phylogenetically independent contrasts, we showed that birds from desert habitats have re- duced basal and field metabolic rates compared with species from mesic areas. Previous work showed that desert birds have reduced

  3. The abundance, vertical flux, and still-water and apparent sinking rates of marine snow in a shallow coastal water column

    NASA Astrophysics Data System (ADS)

    Shanks, Alan L.

    2002-09-01

    In Cape Lookout Bight, NC, measurements were made of marine snow (e.g., aggregates >0.5 mm in diameter) abundance and size, the vertical flux of material through the water column, the vertical flux of marine snow, and the measured still-water sinking rate of marine snow. The abundance and size of marine snow was determined from photographs taken by SCUBA divers. Sampled marine snow were used to determine aggregate dry weight. Marine snow flux and measured still-water sinking rate were made using a time-lapse camera that photographed a sediment trap mounted on a drogue. Flow over the drogue mounted sediment trap was <3 cm s -1. Knowing the flux of marine snow into the trap and the abundance of marine snow in the water column, the sinking rate of marine snow sinking freely in the water column (apparent marine snow sinking rate) was calculated. Throughout the study, marine snow was always present and usually abundant (average 125 l -1). The water-column particulate matter load ranged from 8 to 18 mg l -1. The vertical flux of particulate matter through the water column was large (average 74 g m -2 day -1). The average vertical flux was roughly equal to the sedimentation rate estimated from geochronology studies of sediment deposition in Cape Lookout Bight. More than 90% of the variation in the vertical flux of particulate matter through the water column was due to variations in the flux of marine snow. Variations in the vertical flux of marine snow were, however, not significantly correlated to the abundance of marine snow. Measured sinking rates ranged from around 10 to about 150 m day -1, increased with aggregate size, and varied little between days. The calculated apparent sinking rates of marine snow varied a great deal between days and were not similar to the measured sinking rates. The distribution and orientation of marine snow in the water column photographs appeared to delineate small (mm to cm diameter) eddies. Eddies in a random selection of water column photographs were measured. The upper limit to aggregate size appeared to have been set by the size of small turbulent eddies in the water column. The apparent sinking rate of marine snow, the total vertical flux and the flux of marine snow were all significantly correlated ( r>0.97) to the ratio of aggregate dry weight and eddy diameter. The data suggest that marine snow sinking rates were modified by turbulence in the water column.

  4. SIERRA-Flux: Measuring Regional Surface Fluxes of Carbon Dioxide, Methane, and Water Vapor from an Unmanned Aircraft System

    NASA Technical Reports Server (NTRS)

    Fladeland; Yates, Emma Louise; Bui, Thaopaul Van; Dean-Day, Jonathan; Kolyer, Richard

    2011-01-01

    The Eddy-Covariance Method for quantifying surface-atmosphere fluxes is a foundational technique for measuring net ecosystem exchange and validating regional-to-global carbon cycle models. While towers or ships are the most frequent platform for measuring surface-atmosphere exchange, experiments using aircraft for flux measurements have yielded contributions to several large-scale studies including BOREAS, SMACEX, RECAB by providing local-to-regional coverage beyond towers. The low-altitude flight requirements make airborne flux measurements particularly dangerous and well suited for unmanned aircraft.

  5. Ozone flux of an urban orange grove: multiple scaled measurements and model comparisons

    NASA Astrophysics Data System (ADS)

    Alstad, K. P.; Grulke, N. E.; Jenerette, D. G.; Schilling, S.; Marrett, K.

    2009-12-01

    There is significant uncertainty about the ozone sink properties of the phytosphere due to a complexity of interactions and feedbacks with biotic and abiotic factors. Improved understanding of the controls on ozone fluxes is critical to estimating and regulating the total ozone budget. Ozone exchanges of an orange orchard within the city of Riverside, CA were examined using a multiple-scaled approach. We access the carbon, water, and energy budgets at the stand- to leaf- level to elucidate the mechanisms controlling the variability in ozone fluxes of this agro-ecosystem. The two initial goals of the study were 1. To consider variations and controls on the ozone fluxes within the canopy; and, 2. To examine different modeling and scaling approaches for totaling the ozone fluxes of this orchard. Current understanding of the total ozone flux between the atmosphere near ground and the phytosphere (F-total) include consideration of a fraction which is absorbed by vegetation through stomatal uptake (F-absorb), and fractional components of deposition on external, non-stomatal, surfaces of the vegetation (F-external) and soil (F-soil). Multiplicative stomatal-conductance models have been commonly used to estimate F-absorb, since this flux cannot be measured directly. We approach F-absorb estimates for this orange orchard using chamber measurement of leaf stomatal-conductance, as well as non-chamber sap-conductance collected on branches of varied aspect and sun/shade conditions within the canopy. We use two approaches to measure the F-total of this stand. Gradient flux profiles were measured using slow-response ozone sensors collecting within and above the canopy (4.6 m), and at the top of the tower (8.5 m). In addition, an eddy-covariance system fitted with a high-frequency chemiluminescence ozone system will be deployed (8.5 m). Preliminary ozone gradient flux profiles demonstrate a substantial ozone sink strength of this orchard, with diurnal concentration differentials from tower to above canopy as high as 16 ppb, and from above to within canopy as high as 30 ppb. Preliminary leaf-conductance data also demonstrate substantial variability in diurnal e.g., south facing canopy conductance-rates were steady through a wide range of vpd conditions, while conductance of the other aspects were more variable within narrow ranges of leaf vpd conditions. Estimates of cumulative leaf- and branch-level ozone uptake, with consideration of within canopy variations, will be scaled to the stand-level using leaf-area-to-stem diameter allometric regression models. These scaled fluxes will represent the total vegetation uptake parameter in a Soil-Atmosphere-Vegetation-Transfer (SVAT) ozone flux model.

  6. Determining heat fluxes from temperature measurements made in massive walls

    SciTech Connect

    Balcomb, J.D.; Hedstrom, J.C.

    1980-01-01

    A technique is described for determining heat fluxes at the surfaces of masonry walls or floors using temperature data measured at two points within the wall, usually near the surfaces. The process consists of solving the heat diffusion equation in one dimension using finite difference techniques given two measured temperatures as input. The method is fast and accurate and also allows for an in-situ measurement of wall thermal diffusivity if a third temperature is measured. The method is documented in sufficient detail so that it can be readily used by the reader. Examples are given for heat flow through walls. Annual results for two cases are presented. The method has also been used to determine heat flow into floors.

  7. Progress on a Rayleigh Scattering Mass Flux Measurement Technique

    NASA Technical Reports Server (NTRS)

    Mielke-Fagan, Amy F.; Clem, Michelle M.; Elam, Kristie A.; Hirt, Stefanie M.

    2010-01-01

    A Rayleigh scattering diagnostic has been developed to provide mass flux measurements in wind tunnel flows. Spectroscopic molecular Rayleigh scattering is an established flow diagnostic tool that has the ability to provide simultaneous density and velocity measurements in gaseous flows. Rayleigh scattered light from a focused 10 Watt continuous-wave laser beam is collected and fiber-optically transmitted to a solid Fabry-Perot etalon for spectral analysis. The circular interference pattern that contains the spectral information that is needed to determine the flow properties is imaged onto a CCD detector. Baseline measurements of density and velocity in the test section of the 15 cm x 15 cm Supersonic Wind Tunnel at NASA Glenn Research Center are presented as well as velocity measurements within a supersonic combustion ramjet engine isolator model installed in the tunnel test section.

  8. Three-years of SO 2 flux measurements of Mt. Etna using an automated UV scanner array: Comparison with conventional traverses and uncertainties in flux retrieval

    NASA Astrophysics Data System (ADS)

    Salerno, G. G.; Burton, M. R.; Oppenheimer, C.; Caltabiano, T.; Randazzo, D.; Bruno, N.; Longo, V.

    2009-05-01

    Routine measurements of SO 2 flux using the traverse method on Mt. Etna (Italy) were augmented in late 2004 when an array of automatic scanning ultraviolet spectrometers was installed. Each instrument allows one SO 2 scan to be recorded every ~ 6 min. Here we report the methods that we developed to automatically and robustly transform SO 2 profiles into SO 2 flux data. Radian geometry and Fast Fourier Transform algorithm were used for reducing plume cross-sections and for discriminating between volcanic plumes from those produced by water vapour clouds. Uncertainty in flux measurements depends on the accuracy of plume-height estimation, on assumptions concerning plume-geometry, and on the quality of the retrieved SO 2 amounts. We compare 3 years of flux measurements made using both the automated network and "conventional" traverse methods beneath the plume. We found a good agreement between the datasets, both in terms of magnitude and in temporal variations. These results validate the Etna SO 2 flux monitoring system. Emission rates are available to the 24-hour manned operations room via intranet, providing real-time information on degassing rates and plume location.

  9. Measurement of Tree Stems O2 and CO2 Fluxes -New Approach in Tree Respiration B. Hilman* and A. Angert

    E-print Network

    Einat, Aharonov

    Measurement of Tree Stems O2 and CO2 Fluxes - New Approach in Tree Respiration B. Hilman* and A are major players in the global carbon cycle and emit respired CO2 at a rate which is estimated to be about 50% of the annual gross photosynthesis rate1 . Therefore, tree respiration has an important global

  10. Measurements of Correlation-Enhanced Collision Rates

    E-print Network

    California at San Diego, University of

    measurements of collision rate in laser-cooled magnesium ion plasmas with density n 107cm-3 and temperature 2.5×10-6 low temperature), the collision rate quantitatively with standard collisional theory in the high temperature plasma regime; and agree quantitatively

  11. Measuring Rates of Sexual Development in Female

    E-print Network

    Galef Jr., Bennett G.

    Measuring Rates of Sexual Development in Female Mongolian Gerbils MERTICE M. CLARK BENNETT G. GALEF, and aggressive behavior of female Mongolian gerbils. In the present series of studies, we explored the relationship in gerbils between age at vaginal patency and three other indices of rate of female sexual

  12. Are far-IR fluxes good measures of cloud mass?

    NASA Astrophysics Data System (ADS)

    Wagle, Gururaj; Ferland, G. J.; Troland, T. H.; Abel, N.

    2014-01-01

    It is commonly assumed that the Herschel far-IR fluxes are a measure of column density, hence, mass of interstellar clouds. The Polaris Flare, a high galactic latitude cirrus cloud, with several starless molecular cores, has been previously observed with the Herschel Space Telescope. We used Cloudy version 13.02 to model a molecular cloud MCLD 123.5+24.9, one of the denser regions of the Polaris Flare. These models include a detailed calculation of far-IR grain opacities, subject to various assumptions about grain composition, and predict far-IR fluxes. The models suggest that the observed fluxes reflect the incident stellar UV radiation field rather than the column density, if N(H) > a few times 1021 cm2 (AV > 1). For higher column densities, the models show that dust temperatures decline rapidly into the cloud. Therefore, the cloud interiors contribute very little additional far-IR flux, and column densities based upon far-IR fluxes can be significantly underestimated. The Polaris Flare, 150 pc distant, is well within the Galactic disc. There are no nearby hot stars. Therefore, the stellar UV radiation field incident on the cloud should be close to the mean interstellar radiation field (ISRF). In addition, the calculated grain opacities required to reproduce the far-IR fluxes in the Cloudy models are a few factors larger than that calculated for standard ISM graphite and silicate grains. This result suggests that the grains in dense regions are coated with water and ammonia ices, increasing their sizes and opacities. The Cloudy models also predict mm-wavelength CO line strengths for comparison with published observations at the IRAM 30-m telescope. In order to reproduce the observed CO line strengths for cores in MCLD 123.5+24.9, the models require that CO molecules be partially frozen out onto the grains. This result places age constraints upon the cores. We have also modeled CO emission from inter-core regions in MCLD 123.5+24.9. For these regions, the models significantly under predict the observed CO line strengths unless the molecular gas is clumped into high-density regions.

  13. Design and measurement of improved capacitively-shunted flux qubits

    NASA Astrophysics Data System (ADS)

    Sears, Adam; Birenbaum, Jeffrey; Hover, David; Gudmundsen, Theodore; Kerman, Andrew; Welander, Paul; Yoder, Jonilyn L.; Gustavsson, Simon; Jin, Xiaoyue; Kamal, Archana; Clarke, John; Oliver, William

    2014-03-01

    The addition of a capacitive or inductive shunt across one of the junctions can alter the coherence properties of a classic flux or RF-SQUID qubit. We have studied the performance of capacitively shunted flux qubits fabricated with MBE aluminum, starting from a 2D coplanar waveguide geometry used in similar high-performance transmon qubits, and measured dispersively. We will detail the importance of design parameters that preserve the flux qubit's anharmonicity and discuss conclusions about materials quality based on calculations of the participation of junction, dielectric, and superconductor components. This research was funded in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA); and by the Assistant Secretary of Defense for Research & Engineering under Air Force Contract number FA8721-05-C-0002. All statements of fact, opinion or conclusions contained herein are those of the authors and should not be construed as representing the official views or policies of IARPA, the ODNI, or the U.S. Government Present address: SLAC National Accelerator Laboratory, Menlo Park, CA.

  14. The first geothermal heat flux measurement below the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Fisher, A. T.; Mankoff, K. D.; Tulaczyk, S. M.; Foley, N.; Hossainzadeh, S.

    2014-12-01

    The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow and mass balance of outlet glaciers and ice sheets. We measured directly the geothermal heat flux below the West Antarctic Ice Sheet (WAIS), under Subglacial Lake Whillans (SLW), as part of the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project. The one-dimensional, conductive heat flux is the product of thermal gradient and thermal conductivity. We developed and fielded a tool to determine the thermal gradient in lake sediments, after penetrating ~800 m of ice using a hot water drilling system. We used the needle-probe method to measure the thermal conductivity of sediments recovered from the bottom of the lake with a gravity-driven multi-corer. The thermal gradient was determined during two separate deployments of the geothermal tool, which penetrated ~1.1 m into the till below SLW, yielding essentially identical results: 0.21±0.07 °C/m. Fifteen sediment thermal conductivity measurements yield an average value of 1.36±0.12 W/m-K. The heat flux determined from these measurements is 285±85 W/m2. This value is somewhat higher than that estimated from the WAIS-Divide ice core site, 230 mW/m2, ~800 km away, and much higher than regional estimates based on magnetics and a global seismic model, generally ?100 mW/m2. Elevated heat flux in this area could result from thermal perturbations associated with rifting, crustal thinning, or volcanic activity. Heat flux of this magnitude is likely to cause basal melt rate of a few cm/year. If this value is representative of conditions below this part of the WAIS, it might help to explain the occurrence of active subglacial lakes and fast-moving ice streams and the ice dynamics of WAIS more broadly.

  15. The AmeriFlux Network of Long-Term CO{sub 2} Flux Measurement Stations: Methodology and Intercomparability

    SciTech Connect

    Hollinger, D. Y.; Evans, R. S.

    2003-05-20

    A portable flux measurement system has been used within the AmeriFlux network of CO{sub 2} flux measurement stations to enhance the comparability of data collected across the network. No systematic biases were observed in a comparison between portable system and site H, LE, or CO{sub 2} flux values although there were biases observed between the portable system and site measurement of air temperature and PPFD. Analysis suggests that if values from two stations differ by greater than 26% for H, 35% for LE, and 32% for CO{sub 2} flux they are likely to be significant. Methods for improving the intercomparability of the network are also discussed.

  16. Measurement of autophagy flux in the nervous system in vivo

    PubMed Central

    Castillo, K; Valenzuela, V; Matus, S; Nassif, M; Oñate, M; Fuentealba, Y; Encina, G; Irrazabal, T; Parsons, G; Court, F A; Schneider, B L; Armentano, D; Hetz, C

    2013-01-01

    Accurate methods to measure autophagic activity in vivo in neurons are not available, and most of the studies are based on correlative and static measurements of autophagy markers, leading to conflicting interpretations. Autophagy is an essential homeostatic process involved in the degradation of diverse cellular components including organelles and protein aggregates. Autophagy impairment is emerging as a relevant factor driving neurodegeneration in many diseases. Moreover, strategies to modulate autophagy have been shown to provide protection against neurodegeneration. Here we describe a novel and simple strategy to express an autophagy flux reporter in the nervous system of adult animals by the intraventricular delivery of adeno-associated viruses (AAV) into newborn mice. Using this approach we efficiently expressed a monomeric tandem mCherry-GFP-LC3 construct in neurons of the peripheral and central nervous system, allowing the measurement of autophagy activity in pharmacological and disease settings. PMID:24232093

  17. Work flux density measurements in a pulse tube engine

    NASA Astrophysics Data System (ADS)

    Yoshida, T.; Yazaki, T.; Futaki, H.; Hamaguchi, K.; Biwa, T.

    2009-07-01

    A heat engine called a pulse tube engine has been recently proposed, which consists of only a few parts, namely, differentially heated stacked metal meshes in a cylinder and one piston, coupled to a flywheel. We built the prototype engine and tested its working mechanism from the standpoint of a thermoacoustic framework. We measured the work flux density distribution over the cross section of the pulse tube to elucidate the work source of the engine. This engine belongs to the standing wave engine group and the work source resides not in the stacked metal meshes but in the pulse tube.

  18. System having unmodulated flux locked loop for measuring magnetic fields

    DOEpatents

    Ganther, Jr., Kenneth R. (Olathe, KS); Snapp, Lowell D. (Blue Springs, MO)

    2006-08-15

    A system (10) for measuring magnetic fields, wherein the system (10) comprises an unmodulated or direct-feedback flux locked loop (12) connected by first and second unbalanced RF coaxial transmission lines (16a, 16b) to a superconducting quantum interference device (14). The FLL (12) operates for the most part in a room-temperature or non-cryogenic environment, while the SQUID (14) operates in a cryogenic environment, with the first and second lines (16a, 16b) extending between these two operating environments.

  19. Automated Soil Flux Chamber Measurements with Five Species Cavity Ring-Down Spectroscopy and New Realtime Soil Flux Processor

    NASA Astrophysics Data System (ADS)

    Alstad, Karrin; Saad, Nabil; Tan, Sze

    2015-04-01

    Continuous soil flux chamber measurements remains a key tool for determining production and sequestration of direct and indirect greenhouse gases. Cavity Ring-Down Spectroscopy has radically simplified soil flux studies by providing simultaneous measurements of five gases: CO2, CH4, N2O, NH3, and H2O in one analyzer (Picarro G2508) and by lending itself to field deployment. Successful use of the Picarro G2508 for continuous soil flux measurements in a variety of ecosystem types has already been demonstrated. Most recently, we have developed a real-time processing software to simplify chamber measurements and calculations of soil flux with the G2508 CRDS analyzer. The new Realtime Soil Flux Processor is designed to work with all chamber types and sizes, and provides a multi-option for real-time flux curve mathematical fitting and generation of flux values of N2O, CO2 & CH4 in addition to NH3 and H2O. The software features include: Sequence table Flexible data tagging feature Ceiling concentration shut-off parameter Set run-time interval Temperature/pressure input for field monitoring and volumetric conversion Manual start/stop override The Realtime Soil Flux Processor GUI interface and functionalities are presented, and results from a variety of sampling designs are demonstrated to emphasize program flexibility and field capability.

  20. Evaluation of scintillometery measurements of fluxes of momentum and sensible heat in the roughness sublayer

    NASA Astrophysics Data System (ADS)

    Sugawara, Hirofumi; Inagaki, Atsushi; Roth, Matthias; Kanda, Manabu

    2015-08-01

    Scintillometer measurements of turbulent fluxes of momentum and sensible heat in the roughness sublayer over a regular array of cubes in an outdoor environment were tested with direct measurement from sonic anemometers. The dissipation rate, ?, and temperature structure parameter, C T 2 , obtained from the scintillometer agreed well with those from four sonic anemometers located along the scintillometer path. The fluxes measured by the scintillometer also corresponded well to those from the line-averaged eddy covariance approach, although this agreement was greatly influenced by the choice of the zero-plane displacement length and the form of the similarity function used in the scintillometer software. A guide for choosing the appropriate similarity function for the urban roughness sublayer is proposed.

  1. Solid motor aft closure insulation erosion. [heat flux correlation for rate analysis

    NASA Technical Reports Server (NTRS)

    Stampfl, E.; Landsbaum, E. M.

    1973-01-01

    The erosion rate of aft closure insulation in a number of large solid propellant motors was empirically analyzed by correlating the average ablation rate with a number of variables that had previously been demonstrated to affect heat flux. The main correlating parameter was a heat flux based on the simplified Bartz heat transfer coefficient corrected for two-dimensional effects. A multiplying group contained terms related to port-to-throat ratio, local wall angle, grain geometry and nozzle cant angle. The resulting equation gave a good correlation and is a useful design tool.

  2. Measurement of Urban fluxes of CO2 and water

    NASA Astrophysics Data System (ADS)

    Grimmond, S.; Crawford, B.; Offerle, B.; Hom, J.

    2006-05-01

    Measurements of surface-atmosphere fluxes of carbon dioxide (FCO2) and latent heat in urban environments are rare even though cities are a major source of atmospheric CO2 and users of water. In this paper, an overview of urban FCO2 measurements will be presented to illustrate how and where such measurements are being conducted and emerging results to date. Most of these studies have been conducted over short periods of time; few studies have considered annual sources/sinks. More investigations have been conducted, and are planned, in European cities than elsewhere, most commonly in areas of medium density urban development. The most dense urban sites are significant net sources of carbon. However, in areas where there is large amounts of vegetation present, there is a net sink of carbon during the summertime. In the second part of the presentation, more detailed attention will be directed to an ongoing measurement program in Baltimore, MD (part of the Baltimore Ecosystem Study). Eddy covariance instrumentation mounted on a tall-tower at 41.2 m has continuously measured local-scale fluxes of carbon dioxide from a suburban environment since 2001. Several features make this particular study unique: 1) for an urban area, the study site is extensively vegetated, 2) the period of record (2001-2005) is among the longest available for urban FCO2 measurements, 3) both closed-path and open-path infrared gas analyzers are used for observations, and 4) several unique data quality control and gap-filling methods have been developed for use in an urban environment. Additionally, detailed surface datasets and GIS software are used to perform flux source area analysis. Results from Baltimore indicate that FCO2 is very dependent on source area land-cover characteristics, particularly the proportion of vegetated and built surfaces. Over the course of a year, the urban surface is a strong net source of CO2, though there is considerable inter-annual variability depending on environmental conditions (e.g. average temperature, total precipitation, cicada infestation). During the growing season, there is net uptake of CO2 by the surface, but this uptake is less than in forested areas and is not enough to offset CO2 emissions for the entire year

  3. Comparison of buried soil sensors, surface chambers and above ground measurements of carbon dioxide fluxes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil carbon dioxide (CO2) flux is an important component of the terrestrial carbon cycle. Accurate measurements of soil CO2 flux aids determinations of carbon budgets. In this study, we investigated soil CO2 fluxes with time and depth and above ground CO2 fluxes in a bare field. CO2 concentrations w...

  4. Eddy covariance measurements of the sea spray aerosol flux over the open ocean

    NASA Astrophysics Data System (ADS)

    Norris, Sarah J.; Brooks, Ian M.; Hill, Martin K.; Brooks, Barbara J.; Smith, Michael H.; Sproson, David A. J.

    2012-04-01

    Direct eddy covariance measurements of size-segregated sea spray aerosol fluxes over the open Atlantic Ocean are presented, along with a source function derived from them for a wind speed range of 4 to 18 m s-1 and a size range of 0.176 < R80 < 6.61 ?m. This is in broad agreement with other recent estimates of the source function over this size range but shows a more rapid decrease with size above R80 = 2 ?m than most other functions. The measurements were made during a 3 week cruise in the North Atlantic as part of the UK contribution to the international Surface Ocean-Lower Atmosphere Study (SOLAS) program. They utilized the new high-rate Compact Lightweight Aerosol Spectrometer Probe (CLASP), providing a 16-channel size spectrum (0.17 measurements demonstrate the high variability in sea spray aerosol flux compared with other air-sea fluxes, both between individual estimates and in the scales contributing to the flux.

  5. Heat flux measurements in stagnation point methane/air flames with thermographic phosphors

    NASA Astrophysics Data System (ADS)

    Salem, Mohamed; Staude, Susanne; Bergmann, Ulf; Atakan, Burak

    2010-10-01

    Light-induced phosphorescence from thermographic phosphors was used to study the wall temperatures and heat fluxes from nearly one-dimensional flat premixed flames. The investigated flames were stoichiometric, lean and rich laminar methane/air flames with equivalence ratios of ? = 1, ? = 0.75 and ? = 1.25 at ambient pressure. The flames were burning in a stagnation point arrangement against a water-cooled plate. The central part of this plate was an alumina ceramic plate coated from both sides with chromium-doped alumina (ruby) and excited with a Nd:YAG laser or a green light-emitting diode (LED) array to measure the wall temperature from both sides and thus the heat flux rate from the flame. The outlet velocity of the gases was varied from 0.1 to 1.2 m/s. The burner to plate distance (H) ranged from 0.5 to 2 times the burner exit diameter ( d = 30 mm). The measured heat flux rates indicate the change of the flame stabilization mechanism from a burner stabilized to a stagnation plate stabilized flame. The results were compared to modeling results of a one-dimensional stagnation point flow, with a detailed reaction mechanism. In order to prove the model, gas phase temperatures were measured by OH-LIF for a stoichiometric stagnation point flame. It turns out that the flame stabilization mechanism and with it the heat fluxes change from low to high mass fluxes. This geometry may be well suited for further studies of the elementary flame wall interaction.

  6. Heat flux measurements for use in physiological and clothing research

    NASA Astrophysics Data System (ADS)

    Niedermann, R.; Psikuta, A.; Rossi, R. M.

    2014-08-01

    Scientists use passive heat flow meters to measure body heat exchanges with the environment. In recent years, several such sensors have been developed and concerns about their proper calibration have been addressed. However, calibration methods have differed in the geometry of the heated device as well as in the heat transfer mechanism. Therefore, a comparison of calibration methods is needed in order to understand the obtained differences in calibration lines. We chose three commercially available heat flux sensors and placed them on four different heated devices: a hot plate, double hot plate, nude cylinder and a cylinder covered with a spacer material. We found differences between the calibration line of the manufacturer and our own measurements, especially when forced convection was involved as the main heat transfer mechanism. The results showed clearly that the calibration method should be chosen according to the intended purpose of use. In addition, we recommend use a thin, light heat flux sensor with good thermal conduction in human subject studies.

  7. Heat flux measurements for use in physiological and clothing research.

    PubMed

    Niedermann, R; Psikuta, A; Rossi, R M

    2014-08-01

    Scientists use passive heat flow meters to measure body heat exchanges with the environment. In recent years, several such sensors have been developed and concerns about their proper calibration have been addressed. However, calibration methods have differed in the geometry of the heated device as well as in the heat transfer mechanism. Therefore, a comparison of calibration methods is needed in order to understand the obtained differences in calibration lines. We chose three commercially available heat flux sensors and placed them on four different heated devices: a hot plate, double hot plate, nude cylinder and a cylinder covered with a spacer material. We found differences between the calibration line of the manufacturer and our own measurements, especially when forced convection was involved as the main heat transfer mechanism. The results showed clearly that the calibration method should be chosen according to the intended purpose of use. In addition, we recommend use a thin, light heat flux sensor with good thermal conduction in human subject studies. PMID:23824222

  8. Combining two complementary micrometeorological methods to measure CH4 and N2O fluxes over pasture

    NASA Astrophysics Data System (ADS)

    Laubach, J.; Barthel, M.; Fraser, A.; Hunt, J. E.; Griffith, D. W. T.

    2015-09-01

    New Zealand's largest industrial sector is pastoral agriculture, giving rise to a large fraction of the country's emissions of methane (CH4) and nitrous oxide (N2O). We designed a system to continuously measure CH4 and N2O fluxes at the field scale on two adjacent pastures that differed with respect to management. At the core of this system was a closed-cell Fourier-transform infrared spectrometer (FTIR), measuring the mole fractions of CH4, N2O and carbon dioxide (CO2) at two heights at each site. In parallel, CO2 fluxes were measured using eddy-covariance instrumentation. We applied two different micrometeorological ratio methods to infer the CH4 and N2O fluxes from their respective mole fractions and the CO2 fluxes. The first is a variant of the flux-gradient method, where it is assumed that the turbulent diffusivities of CH4 and N2O equal that of CO2. This method was reliable when the CO2 mole-fraction difference between heights was at least 4 times greater than the FTIR's resolution of differences. For the second method, the temporal increases of mole fractions in the stable nocturnal boundary layer, which are correlated for concurrently-emitted gases, are used to infer the unknown fluxes of CH4 and N2O from the known flux of CO2. This method was sensitive to "contamination" from trace gas sources other than the pasture of interest and therefore required careful filtering. With both methods combined, estimates of mean daily CH4 and N2O fluxes were obtained for 60 % of days at one site and 77 % at the other. Both methods indicated both sites as net sources of CH4 and N2O. Mean emission rates for one year at the unfertilised, winter-grazed site were 8.2 (± 0.91) nmol CH4 m-2 s-1 and 0.40 (± 0.018) nmol N2O m-2 s-1. During the same year, mean emission rates at the irrigated, fertilised and rotationally-grazed site were 7.0 (± 0.89) nmol CH4 m-2 s-1 and 0.57 (± 0.019) nmol N2O m-2 s-1. At this site, the N2O emissions amounted to 1.19 (± 0.15) % of the nitrogen inputs from animal excreta and fertiliser application.

  9. Heat flux measurement from thermal infrared imagery in low-flux fumarolic zones: Example of the Ty fault (La Soufrire de Guadeloupe)

    E-print Network

    Beauducel, François

    Heat flux measurement from thermal infrared imagery in low-flux fumarolic zones: Example of the Ty flux Low flux fumarolic zone Thermal infrared Remote sensing Thermal anomaly Sensible flux Monitoring mainly condensates in the soil close to surface and produces a thermal anomaly detectable at the surface

  10. Cosmic rays muon flux measurements at Belgrade shallow underground laboratory

    SciTech Connect

    Veselinovi?, N. Dragi?, A. Maleti?, D. Jokovi?, D. Savi?, M. Banjanac, R. Udovi?i?, V. Ani?in, I.

    2015-02-24

    The Belgrade underground laboratory is a shallow underground one, at 25 meters of water equivalent. It is dedicated to low-background spectroscopy and cosmic rays measurement. Its uniqueness is that it is composed of two parts, one above ground, the other bellow with identical sets of detectors and analyzing electronics thus creating opportunity to monitor simultaneously muon flux and ambient radiation. We investigate the possibility of utilizing measurements at the shallow depth for the study of muons, processes to which these muons are sensitive and processes induced by cosmic rays muons. For this purpose a series of simulations of muon generation and propagation is done, based on the CORSIKA air shower simulation package and GEANT4. Results show good agreement with other laboratories and cosmic rays stations.

  11. Fieldable computer system for determining gamma-ray pulse-height distributions, flux spectra, and dose rates from Little Boy

    SciTech Connect

    Moss, C.E.; Lucas, M.C.; Tisinger, E.W.; Hamm, M.E.

    1984-01-01

    Our system consists of a LeCroy 3500 data acquisition system with a built-in CAMAC crate and eight bismuth-germanate detectors 7.62 cm in diameter and 7.62 cm long. Gamma-ray pulse-height distributions are acquired simultaneously for up to eight positions. The system was very carefully calibrated and characterized from 0.1 to 8.3 MeV using gamma-ray spectra from a variety of radioactive sources. By fitting the pulse-height distributions from the sources with a function containing 17 parameters, we determined theoretical repsonse functions. We use these response functions to unfold the distributions to obtain flux spectra. A flux-to-dose-rate conversion curve based on the work of Dimbylow and Francis is then used to obtain dose rates. Direct use of measured spectra and flux-to-dose-rate curves to obtain dose rates avoids the errors that can arise from spectrum dependence in simple gamma-ray dosimeter instruments. We present some gamma-ray doses for the Little Boy assembly operated at low power. These results can be used to determine the exposures of the Hiroshima survivors and thus aid in the establishment of radation exposure limits for the nuclear industry.

  12. Comparative soil CO2 flux measurements and geostatistical estimation methods on Masaya volcano, Nicaragua

    USGS Publications Warehouse

    Lewicki, J.L.; Bergfeld, D.; Cardellini, C.; Chiodini, G.; Granieri, D.; Varley, N.; Werner, C.

    2005-01-01

    We present a comparative study of soil CO2 flux (FCO2) measured by five groups (Groups 1-5) at the IAVCEI-CCVG Eighth Workshop on Volcanic Gases on Masaya volcano, Nicaragua. Groups 1-5 measured (FCO2) using the accumulation chamber method at 5-m spacing within a 900 m2 grid during a morning (AM) period. These measurements were repeated by Groups 1-3 during an afternoon (PM) period. Measured (FCO2 ranged from 218 to 14,719 g m-2 day-1. The variability of the five measurements made at each grid point ranged from ??5 to 167%. However, the arithmetic means of fluxes measured over the entire grid and associated total CO2 emission rate estimates varied between groups by only ??22%. All three groups that made PM measurements reported an 8-19% increase in total emissions over the AM results. Based on a comparison of measurements made during AM and PM times, we argue that this change is due in large part to natural temporal variability of gas flow, rather than to measurement error. In order to estimate the mean and associated CO2 emission rate of one data set and to map the spatial FCO2 distribution, we compared six geostatistical methods: Arithmetic and minimum variance unbiased estimator means of uninterpolated data, and arithmetic means of data interpolated by the multiquadric radial basis function, ordinary kriging, multi-Gaussian kriging, and sequential Gaussian simulation methods. While the total CO2 emission rates estimated using the different techniques only varied by ??4.4%, the FCO2 maps showed important differences. We suggest that the sequential Gaussian simulation method yields the most realistic representation of the spatial distribution of FCO2, but a variety of geostatistical methods are appropriate to estimate the total CO2 emission rate from a study area, which is a primary goal in volcano monitoring research. ?? Springer-Verlag 2005.

  13. Measurement of the 36Cl deposition flux in central Japan: natural background levels and seasonal variability.

    PubMed

    Tosaki, Yuki; Tase, Norio; Sasa, Kimikazu; Takahashi, Tsutomu; Nagashima, Yasuo

    2012-04-01

    Essential parameters for the applications of (36)Cl as a tracer in groundwater studies include the initial (36)Cl/Cl ratio, at the time of recharge, and/or the natural background deposition flux of (36)Cl in the recharge area. To facilitate the hydrological use of (36)Cl in central Japan, this study aimed to obtain a precise estimate of the long-term average local (36)Cl flux and to characterize its seasonal variability. The (36)Cl in precipitation was continuously monitored in Tsukuba, central Japan over a period of >5 years. The (36)Cl flux showed a clear seasonal variation with an annual peak during the spring, which was attributed to the seasonal variability of tropopause height. The long-term average (36)Cl flux (32±2atoms m(-2)s(-1)), estimated from the measured data, was consistent with the prediction from the (36)Cl latitudinal fallout model scaled using the global mean production rate of 20atoms m(-2)s(-1). The initial (36)Cl/Cl ratio was estimated to be (41±6)×10(-15), which is similar to that of pre-bomb groundwater in the Tsukuba Upland. An observation period covering an 11-year solar cycle would yield more accurate estimates of the values, given the increased (36)Cl flux during the solar minimum. PMID:22305003

  14. A Novel Approach for Direct Measurement of Cumulative Water and Solute Mass Fluxes using a Passive Surface Water Flux Meter

    NASA Astrophysics Data System (ADS)

    Padowski, J. C.; Jawitz, J. W.; Hatfield, K.; Annable, M. D.; Cho, J.; Klammler, H.

    2005-12-01

    This work describes the development of a novel technique for passive measurement of pollutant loads in flowing surface water systems. Recent changes to the Clean Water Act have prompted a major initiative for the development of a national list of impaired surface waters. According to the law, every state is now responsible for defining the use of each water body and creating a Total Maximum Daily Load (TMDL) to regulate all pollutant loads entering these systems. Current methods for determining pollutant loads typically involve collecting separate instantaneous measurements of water velocities and solute concentrations at discrete points in space and time. The data must be combined, interpolated and integrated after collection to arrive at estimates of local cumulative solute flux and discharge. The frequency with which these parameters are measured typically rely upon the availability of resources (time, money, manpower, etc.) and are often undersampled. A method is presented here for direct measurement of cumulative surface water flux (discharge) and solute flux using a Passive Surface Water Flux Meter (PSFM). The PSFM is designed to directly measure local cumulative water and solute mass fluxes in surface water flow without any active components transmitting or logging data over time. This passive integration of water and solute mass fluxes eliminates the need for independent water flux and concentration measurements and any additional computations. Laboratory trials under steady state and transient conditions were used to test the appropriateness of the PSFM as a device for collecting water quality data. Results from steady state experiments verified the ability of PSFM to accurately measure cumulative water and solute mass flux. Preliminary results from investigations under transient flow conditions also showed promise for measuring pollutant loads in natural systems with this device.

  15. Direct measurement of the 7Be solar neutrino flux with 192 days of borexino data.

    PubMed

    Arpesella, C; Back, H O; Balata, M; Bellini, G; Benziger, J; Bonetti, S; Brigatti, A; Caccianiga, B; Cadonati, L; Calaprice, F; Carraro, C; Cecchet, G; Chavarria, A; Chen, M; Dalnoki-Veress, F; D'Angelo, D; de Bari, A; de Bellefon, A; de Kerret, H; Derbin, A; Deutsch, M; di Credico, A; di Pietro, G; Eisenstein, R; Elisei, F; Etenko, A; Fernholz, R; Fomenko, K; Ford, R; Franco, D; Freudiger, B; Galbiati, C; Gatti, F; Gazzana, S; Giammarchi, M; Giugni, D; Goeger-Neff, M; Goldbrunner, T; Goretti, A; Grieb, C; Hagner, C; Hampel, W; Harding, E; Hardy, S; Hartman, F X; Hertrich, T; Heusser, G; Ianni, Aldo; Ianni, Andrea; Joyce, M; Kiko, J; Kirsten, T; Kobychev, V; Korga, G; Korschinek, G; Kryn, D; Lagomarsino, V; Lamarche, P; Laubenstein, M; Lendvai, C; Leung, M; Lewke, T; Litvinovich, E; Loer, B; Lombardi, P; Ludhova, L; Machulin, I; Malvezzi, S; Manecki, S; Maneira, J; Maneschg, W; Manno, I; Manuzio, D; Manuzio, G; Martemianov, A; Masetti, F; Mazzucato, U; McCarty, K; McKinsey, D; Meindl, Q; Meroni, E; Miramonti, L; Misiaszek, M; Montanari, D; Monzani, M E; Muratova, V; Musico, P; Neder, H; Nelson, A; Niedermeier, L; Oberauer, L; Obolensky, M; Orsini, M; Ortica, F; Pallavicini, M; Papp, L; Parmeggiano, S; Perasso, L; Pocar, A; Raghavan, R S; Ranucci, G; Rau, W; Razeto, A; Resconi, E; Risso, P; Romani, A; Rountree, D; Sabelnikov, A; Saldanha, R; Salvo, C; Schimizzi, D; Schönert, S; Shutt, T; Simgen, H; Skorokhvatov, M; Smirnov, O; Sonnenschein, A; Sotnikov, A; Sukhotin, S; Suvorov, Y; Tartaglia, R; Testera, G; Vignaud, D; Vitale, S; Vogelaar, R B; von Feilitzsch, F; von Hentig, R; von Hentig, T; Wojcik, M; Wurm, M; Zaimidoroga, O; Zavatarelli, S; Zuzel, G

    2008-08-29

    We report the direct measurement of the 7Be solar neutrino signal rate performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso. The interaction rate of the 0.862 MeV 7Be neutrinos is 49+/-3stat+/-4syst counts/(day.100 ton). The hypothesis of no oscillation for 7Be solar neutrinos is inconsistent with our measurement at the 4sigma C.L. Our result is the first direct measurement of the survival probability for solar nu(e) in the transition region between matter-enhanced and vacuum-driven oscillations. The measurement improves the experimental determination of the flux of 7Be, pp, and CNO solar nu(e), and the limit on the effective neutrino magnetic moment using solar neutrinos. PMID:18851600

  16. Local Heat Flux Measurements with Single Element Coaxial Injectors

    NASA Technical Reports Server (NTRS)

    Jones, Gregg; Protz, Christopher; Bullard, Brad; Hulka, James

    2006-01-01

    To support the mission for the NASA Vision for Space Exploration, the NASA Marshall Space Flight Center conducted a program in 2005 to improve the capability to predict local thermal compatibility and heat transfer in liquid propellant rocket engine combustion devices. The ultimate objective was to predict and hence reduce the local peak heat flux due to injector design, resulting in a significant improvement in overall engine reliability and durability. Such analyses are applicable to combustion devices in booster, upper stage, and in-space engines, as well as for small thrusters with few elements in the injector. In this program, single element and three-element injectors were hot-fire tested with liquid oxygen and ambient temperature gaseous hydrogen propellants at The Pennsylvania State University Cryogenic Combustor Laboratory from May to August 2005. Local heat fluxes were measured in a 1-inch internal diameter heat sink combustion chamber using Medtherm coaxial thermocouples and Gardon heat flux gauges. Injectors were tested with shear coaxial and swirl coaxial elements, including recessed, flush and scarfed oxidizer post configurations, and concentric and non-concentric fuel annuli. This paper includes general descriptions of the experimental hardware, instrumentation, and results of the hot-fire testing for three of the single element injectors - recessed-post shear coaxial with concentric fuel, flush-post swirl coaxial with concentric fuel, and scarfed-post swirl coaxial with concentric fuel. Detailed geometry and test results will be published elsewhere to provide well-defined data sets for injector development and model validatation.

  17. Evidence for electron neutrino flavor change through measurement of the (8)B solar neutrino flux at the Sudbury Neutrino Observatory

    NASA Astrophysics Data System (ADS)

    Neubauer, Mark Stephen

    2001-11-01

    The Sudbury Neutrino Observatory (SNO) is a water Cerenkov detector designed to study solar neutrinos. Using 1 kiloton of heavy water as the target and detection medium, SNO is able to separately determine the flux of electron neutrinos (?e) and the flux of all active neutrinos from the Sun by measuring the rate of charged current (CC) and neutral current (NC) interactions with deuterons. A comparison of these interaction rates allows for direct observation of solar neutrino oscillations. SNO can also search for oscillations by comparing the rate of CC and neutrino- electron elastic scattering (ES) events, since ES has both charged current and neutral current sensitivity. In this thesis, we present measurement of the 8B solar ? e flux of 1.78+0.13-0.14 (stat+syst) × 106cm-2s -1 (35% BP2000 SSM) through measurement of the CC rate over 169.3 days of livetime. We have also measured the 8B flux from the ES reaction to be 2.56+0.48-0.45 (stat+syst), consistent with measurements by previous water Cerenkov experiments. A flavor analysis comparing the CC measured flux with that determined through ES by SuperKamiokande yields a non- ?e active neutrino flux from 8B of 3.62+1.06-1.08 × 106cm-2s-1 , providing evidence for ?e --> ? ?,? oscillations as a solution to the solar neutrino problem. This result excludes pure solar ?e --> ? s oscillations at greater than the 99.7% C.I. The total active 8B neutrino flux has been measured to be 5.39+1.07-1.09 × 106cm-2s-1 , consistent with BP2000 SSM predictions. First analyses of the CC (NHit) spectrum and hep flux in SNO are presented. The CC spectrum is found to be a good fit to expectations from an undistorted 8B spectrum, and global best fit vacuum oscillation solutions are disfavored over the other solutions by the data. Through observations near the 8B endpoint with consideration of energy systematics, hep flux limits of 4.1 (90% C.I.) and 6.9 (99% C.I.) times SSM expectations are obtained. A statistical fit for the hep flux signal yields a 3? upper limit of 3.2 times the SSM expected flux.

  18. TITLE: Effects of Nitrogen Fertilizer Types and Rates and Irrigation on Nitrous Oxide Fluxes in Turfgrass

    E-print Network

    in concentrations of atmospheric nitrous oxide (N2O), a greenhouse gas, and agriculture is considered a significant%, but fertilizer type had no significant effect. The amount of N volatilized into the atmosphere as N2O ranged from28 TITLE: Effects of Nitrogen Fertilizer Types and Rates and Irrigation on Nitrous Oxide Fluxes

  19. Nitrous Oxide Fluxes in Turfgrass: Effects of Nitrogen Fertilization Rates and Types Dale J. Bremer*

    E-print Network

    Nitrous Oxide Fluxes in Turfgrass: Effects of Nitrogen Fertilization Rates and Types Dale J. Bremer* ABSTRACT Urban ecosystems are rapidly expanding and their effects on atmo- spheric nitrous oxide (N2O; and (iii) evaluate effects of urea and ammonium sulfate on N2O emissions in turfgrass. Nitrogen fertilizers

  20. Author's personal copy How large is the subducted water flux? New constraints on mantle regassing rates

    E-print Network

    Mukhopadhyay, Sujoy

    cycling and the return flux of water to the deep Earth. Estimates of magma production rates and water Earth water cycle. The simulation is con- strained by reconstructions of Phanerozoic sea level change (Fig. 1). A quantitative assessment of the long-term water cycle is critical to our understanding

  1. Effect of wind tunnel air velocity on VOC flux rates from CAFO manure and wastewater

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind tunnels and flux chambers are often used to estimate volatile organic compound (VOC) emissions from animal feeding operations (AFOs) without regard to air velocity or sweep air flow rates. Laboratory experiments were conducted to evaluate the effect of wind tunnel air velocity on VOC emission ...

  2. Chamber and Diffusive Based Carbon Flux Measurements in an Alaskan Arctic Ecosystem

    NASA Astrophysics Data System (ADS)

    Wilkman, E.; Oechel, W. C.; Zona, D.

    2013-12-01

    Eric Wilkman, Walter Oechel, Donatella Zona Comprising an area of more than 7 x 106 km2 and containing over 11% of the world's organic matter pool, Arctic terrestrial ecosystems are vitally important components of the global carbon cycle, yet their structure and functioning are sensitive to subtle changes in climate and many of these functional changes can have large effects on the atmosphere and future climate regimes (Callaghan & Maxwell 1995, Chapin et al. 2002). Historically these northern ecosystems have acted as strong C sinks, sequestering large stores of atmospheric C due to photosynthetic dominance in the short summer season and low rates of decomposition throughout the rest of the year as a consequence of cold, nutrient poor, and generally water-logged conditions. Currently, much of this previously stored carbon is at risk of loss to the atmosphere due to accelerated soil organic matter decomposition in warmer future climates (Grogan & Chapin 2000). Although there have been numerous studies on Arctic carbon dynamics, much of the previous soil flux work has been done at limited time intervals, due to both the harshness of the environment and labor and time constraints. Therefore, in June of 2013 an Ultraportable Greenhouse Gas Analyzer (UGGA - Los Gatos Research Inc.) was deployed in concert with the LI-8100A Automated Soil Flux System (LI-COR Biosciences) in Barrow, AK to gather high temporal frequency soil CO2 and CH4 fluxes from a wet sedge tundra ecosystem. An additional UGGA in combination with diffusive probes, installed in the same location, provides year-round soil and snow CO2 and CH4 concentrations. When used in combination with the recently purchased AlphaGUARD portable radon monitor (Saphymo GmbH), continuous soil and snow diffusivities and fluxes of CO2 and CH4 can be calculated (Lehmann & Lehmann 2000). Of particular note, measuring soil gas concentration over a diffusive gradient in this way allows one to separate both net production and consumption, whereas chamber and eddy covariance methodologies only document net production from the surface. Also, the capability to measure spring, summer and fall chamber fluxes, and to continuously determine year-round CO2 and CH4 fluxes under even the most extreme weather conditions, allows an unprecedented level of data continuity and local spatial coverage. Comparison to a nearby eddy covariance tower measuring CO2 and CH4 fluxes with an LGR Fast Greenhouse Gas Analyzer add additional power to this set of measurements. Thus, inter-comparison between diffusive, chamber, and tower-based carbon fluxes should lend much insight into the spatial and temporal controls on carbon cycling in this ecosystem.

  3. Measuring star formation rates in blue galaxies

    NASA Technical Reports Server (NTRS)

    Gallagher, John S., III; Hunter, Deidre A.

    1987-01-01

    The problems associated with measurements of star formation rates in galaxies are briefly reviewed, and specific models are presented for determinations of current star formation rates from H alpha and Far Infrared (FIR) luminosities. The models are applied to a sample of optically blue irregular galaxies, and the results are discussed in terms of star forming histories. It appears likely that typical irregular galaxies are forming stars at nearly constant rates, although a few examples of systems with enhanced star forming activity are found among HII regions and luminous irregular galaxies.

  4. Measuring Degradation Rates Without Irradiance Data

    SciTech Connect

    Pulver, S.; Cormode, D.; Cronin, A.; Jordan, D.; Kurtz, S.; Smith, R.

    2011-02-01

    A method to report PV system degradation rates without using irradiance data is demonstrated. First, a set of relative degradation rates are determined by comparing daily AC final yields from a group of PV systems relative to the average final yield of all the PV systems. Then, the difference between relative and absolute degradation rates is found from a statistical analysis. This approach is verified by comparing to methods that utilize irradiance data. This approach is significant because PV systems are often deployed without irradiance sensors, so the analysis method described here may enable measurements of degradation using data that were previously thought to be unsuitable for degradation studies.

  5. Interplanetary dust fluxes measurements using the Waves instrument on STEREO

    NASA Astrophysics Data System (ADS)

    Zaslavsky, A.; Meyer-Vernet, N.; Mann, I.; Czechowski, A.; Issautier, K.; Le Chat, G.; Maksimovic, M.; Kasper, J. C.

    2010-12-01

    Dust particles provide an important fraction of the matter composing the interplanetary medium, their mass density at 1 A.U. being comparable to the one of the solar wind. The impact of a dust particle on a spacecraft produces a plasma cloud whose associated electric field is detected by the on-board electric antennas. The signal measured by the wave instruments thus reveals the dust properties. We analyse the dust particle impacts on the STEREO spacecraft during the 2007-2010 period. We use the TDS waveform sampler of the STEREO/WAVES instrument, which enables us to deduce considerably more informations than in a previous study based on the LFR spectral analyzer [Meyer-Vernet et al., 2009]. We observe two distinct populations of dust that we infer to be nano and micron sized dust particles and we derive their fluxes at 1 AU and the evolution of these fluxes with time (and solar longitude). The observations are also in accord with the dynamics of nanometer-sized and micrometer-sized dust particles in the interplanetary medium.

  6. Measurement of the Atmospheric ?e Flux in IceCube

    NASA Astrophysics Data System (ADS)

    Aartsen, M. G.; Abbasi, R.; Abdou, Y.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Altmann, D.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Baum, V.; Bay, R.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker Tjus, J.; Becker, K.-H.; Bell, M.; Benabderrahmane, M. L.; BenZvi, S.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bernhard, A.; Bertrand, D.; Besson, D. Z.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohaichuk, S.; Bohm, C.; Bose, D.; Böser, S.; Botner, O.; Brayeur, L.; Brown, A. M.; Bruijn, R.; Brunner, J.; Buitink, S.; Carson, M.; Casey, J.; Casier, M.; Chirkin, D.; Christy, B.; Clark, K.; Clevermann, F.; Cohen, S.; Cowen, D. F.; Cruz Silva, A. H.; Danninger, M.; Daughhetee, J.; Davis, J. C.; De Clercq, C.; De Ridder, S.; Desiati, P.; de Vries-Uiterweerd, G.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; Dreyer, J.; Dunkman, M.; Eagan, R.; Eberhardt, B.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feintzeig, J.; Feusels, T.; Filimonov, K.; Finley, C.; Fischer-Wasels, T.; Flis, S.; Franckowiak, A.; Franke, R.; Frantzen, K.; Fuchs, T.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Golup, G.; Goodman, J. A.; Góra, D.; Grant, D.; Groß, A.; Gurtner, M.; Ha, C.; Haj Ismail, A.; Hallgren, A.; Halzen, F.; Hanson, K.; Heereman, D.; Heimann, P.; Heinen, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Homeier, A.; Hoshina, K.; Huelsnitz, W.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Ishihara, A.; Jacobi, E.; Jacobsen, J.; Japaridze, G. S.; Jero, K.; Jlelati, O.; Kaminsky, B.; Kappes, A.; Karg, T.; Karle, A.; Kelley, J. L.; Kiryluk, J.; Kislat, F.; Kläs, J.; Klein, S. R.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Krasberg, M.; Kroll, G.; Kunnen, J.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Landsman, H.; Larson, M. J.; Lesiak-Bzdak, M.; Leute, J.; Lünemann, J.; Madsen, J.; Maruyama, R.; Mase, K.; Matis, H. S.; McNally, F.; Meagher, K.; Merck, M.; Mészáros, P.; Meures, T.; Miarecki, S.; Middell, E.; Milke, N.; Miller, J.; Mohrmann, L.; Montaruli, T.; Morse, R.; Nahnhauer, R.; Naumann, U.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke, A.; Odrowski, S.; Olivas, A.; Olivo, M.; O'Murchadha, A.; Panknin, S.; Paul, L.; Pepper, J. A.; Pérez de los Heros, C.; Pfendner, C.; Pieloth, D.; Pirk, N.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Rädel, L.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Richman, M.; Riedel, B.; Rodrigues, J. P.; Rott, C.; Ruhe, T.; Ruzybayev, B.; Ryckbosch, D.; Saba, S. M.; Salameh, T.; Sander, H.-G.; Santander, M.; Sarkar, S.; Schatto, K.; Scheel, M.; Scheriau, F.; Schmidt, T.; Schmitz, M.; Schoenen, S.; Schöneberg, S.; Schönherr, L.; Schönwald, A.; Schukraft, A.; Schulte, L.; Schulz, O.; Seckel, D.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Sheremata, C.; Smith, M. W. E.; Soiron, M.; Soldin, D.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stasik, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strahler, E. A.; Ström, R.; Sullivan, G. W.; Taavola, H.; Taboada, I.; Tamburro, A.; Ter-Antonyan, S.; Tilav, S.; Toale, P. A.; Toscano, S.; Usner, M.; van der Drift, D.; van Eijndhoven, N.; Van Overloop, A.; van Santen, J.; Vehring, M.; Voge, M.; Vraeghe, M.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Wasserman, R.; Weaver, Ch.; Wellons, M.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Williams, D. R.; Wissing, H.; Wolf, M.; Wood, T. R.; Woschnagg, K.; Xu, C.; Xu, D. L.; Xu, X. W.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; Ziemann, J.; Zierke, S.; Zilles, A.; Zoll, M.

    2013-04-01

    We report the first measurement of the atmospheric electron neutrino flux in the energy range between approximately 80 GeV and 6 TeV, using data recorded during the first year of operation of IceCube’s DeepCore low-energy extension. Techniques to identify neutrinos interacting within the DeepCore volume and veto muons originating outside the detector are demonstrated. A sample of 1029 events is observed in 281 days of data, of which 496±66(stat)±88(syst) are estimated to be cascade events, including both electron neutrino and neutral current events. The rest of the sample includes residual backgrounds due to atmospheric muons and charged current interactions of atmospheric muon neutrinos. The flux of the atmospheric electron neutrinos is consistent with models of atmospheric neutrinos in this energy range. This constitutes the first observation of electron neutrinos and neutral current interactions in a very large volume neutrino telescope optimized for the TeV energy range.

  7. Measurements for the JASPER Program Flux Monitor Experiment

    SciTech Connect

    Muckenthaler, F.J.; Spencer, R.R.; Hunter, H.T.; Hull, J.L.; Shono, A.

    1993-02-01

    The Flux Monitor Experiment was conducted at the Oak Ridge National Laboratory (ORNL) Tower Shielding Facility (TSF) during the months of May and June 1992, as part of the continuing series of eight experiments planned for the Japanese-American Shielding Program for Experimental Research (JASPER) program that was started in 1986. This series of experiments was designed to examine shielding concerns and radiation transport effects pertaining to in-vessel flux monitoring systems (FMS) in current reactor shield designs proposed for both the Advanced Liquid Metal Reactor (ALMR) design and the Japanese loop-type design. The program is a cooperative effort between the United States Department of Energy (US DOE) and the Japanese Power Reactor and Nuclear Fuel Development Corporation (PNC). The Tower Shielding Reactor H (TSR-II) neutron source was altered by the spectrum modifier (SM) used previously in the Axial Shield Experiment, and part of the Japanese Removable Radial Shield (RRS) before reaching the axial shield. In the axial shield were placed six homogeneous boron carbide (B{sub 4}C) hexagons around a center hexagon of aluminum used to represent sodium. Shield designs to be studied were placed beyond the axial shield, each design forming a void directly behind the axial shield. Measurements were made in the void and behind each slab as successive slabs were added.

  8. Measurement of the Atmospheric $?_e$ flux in IceCube

    E-print Network

    IceCube Collaboration; M. G. Aartsen; R. Abbasi; Y. Abdou; M. Ackermann; J. Adams; J. A. Aguilar; M. Ahlers; D. Altmann; K. Andeen; J. Auffenberg; X. Bai; M. Baker; S. W. Barwick; V. Baum; R. Bay; K. Beattie; J. J. Beatty; S. Bechet; J. Becker Tjus; K. -H. Becker; M. Bell; M. L. Benabderrahmane; S. BenZvi; J. Berdermann; P. Berghaus; D. Berley; E. Bernardini; D. Bertrand; D. Z. Besson; D. Bindig; M. Bissok; E. Blaufuss; J. Blumenthal; D. J. Boersma; S. Bohaichuk; C. Bohm; D. Bose1; S. Boser; O. Botner; L. Brayeur; A. M. Brown; R. Bruijn; J. Brunner; S. Buitink; M. Carson; J. Casey; M. Casier; D. Chirkin; B. Christy; K. Clark; F. Clevermann; S. Cohen; D. F. Cowen; A. H. Cruz Silva; M. Danninger; J. Daughhetee; J. C. Davis; C. De Clercq; S. De Ridder; F. Descamps; P. Desiati; G. de Vries-Uiterweerd; T. DeYoung; J. C. Diaz-Velez; J. Dreyer; J. P. Dumm; M. Dunkman; R. Eagan; B. Eberhardt; J. Eisch; R. W. Ellsworth; O. Engdegard; S. Euler; P. A. Evenson; O. Fadiran; A. R. Fazely; A. Fedynitch; J. Feintzeig; T. Feusels; K. Filimonov; C. Finley; T. Fischer-Wasels; S. Flis; A. Franckowiak; R. Franke; K. Frantzen; T. Fuchs; T. K. Gaisser; J. Gallagher; L. Gerhardt; L. Gladstone; T. Glusenkamp; A. Goldschmidt; G. Golup; J. A. Goodman; D. Gora; D. Grant; A. Gross; S. Grullon; M. Gurtner; C. Ha; A. Haj Ismail; A. Hallgren; F. Halzen; K. Hanson; D. Heereman; P. Heimann; D. Heinen; K. Helbing; R. Hellauer; S. Hickford; G. C. Hill; K. D. Hoffman; R. Hoffmann; A. Homeier; K. Hoshina; W. Huelsnitz; P. O. Hulth; K. Hultqvist; S. Hussain; A. Ishihara; E. Jacobi; J. Jacobsen; G. S. Japaridze; O. Jlelati; A. Kappes; T. Karg; A. Karle; J. Kiryluk; F. Kislat; J. Klas; S. R. Klein; J. -H. Kohne; G. Kohnen; H. Kolanoski; L. Kopke; C. Kopper; S. Kopper; D. J. Koskinen; M. Kowalski; M. Krasberg; G. Kroll; J. Kunnen; N. Kurahashi; T. Kuwabara; M. Labare; H. Landsman; M. J. Larson; R. Lauer; M. Lesiak-Bzdak; J. Lunemann; J. Madsen; R. Maruyama; K. Mase; H. S. Matis; F. McNally; K. Meagher; M. Merck; P. Meszaros; T. Meures; S. Miarecki; E. Middell; N. Milke; J. Miller; L. Mohrmann; T. Montaruli; R. Morse; R. Nahnhauer; U. Naumann; S. C. Nowicki; D. R. Nygren; A. Obertacke; S. Odrowski; A. Olivas; M. Olivo; A. O'Murchadha; S. Panknin; L. Paul; J. A. Pepper; C. Perez de los Heros; D. Pieloth; N. Pirk; J. Posselt; P. B. Price; G. T. Przybylski; L. Radel; K. Rawlins; P. Redl; E. Resconi; W. Rhode; M. Ribordy; M. Richman; B. Riedel; J. P. Rodrigues; C. Rott; T. Ruhe; B. Ruzybayev; D. Ryckbosch; S. M. Saba; T. Salameh; H. -G. Sander; M. Santander; S. Sarkar; K. Schatto; M. Scheel; F. Scheriau; T. Schmidt; M. Schmitz; S. Schoenen; S. Schoneberg; L. Schonherr; A. Schonwald; A. Schukraft; L. Schulte; O. Schulz; D. Seckel; S. H. Seo; Y. Sestayo; S. Seunarine; C. Sheremata; M. W. E. Smith; M. Soiron; D. Soldin; G. M. Spiczak; C. Spiering; M. Stamatikos; T. Stanev; A. Stasik; T. Stezelberger; R. G. Stokstad; A. Stoss; E. A. Strahler; R. Strom; G. W. Sullivan; H. Taavola; I. Taboada; A. Tamburro; S. Ter-Antonyan; S. Tilav; P. A. Toale; S. Toscano; M. Usner; D. van der Drift; N. van Eijndhoven; A. Van Overloop; J. van Santen; M. Vehring; M. Voge1; M. Vraeghe; C. Walck; T. Waldenmaier; M. Wallraff; M. Walter; R. Wasserman; Ch. Weaver; C. Wendt; S. Westerhoff; N. Whitehorn; K. Wiebe; C. H. Wiebusch; D. R. Williams; H. Wissing; M. Wolf; T. R. Wood; K. Woschnagg; C. Xu; D. L. Xu; X. W. Xu; J. P. Yanez; G. Yodh; S. Yoshida; P. Zarzhitsky; J. Ziemann; S. Zierke; A. Zilles; M. Zoll

    2013-03-22

    We report the first measurement of the atmospheric electron neutrino flux in the energy range between approximately 80 GeV and 6 TeV, using data recorded during the first year of operation of IceCube's DeepCore low energy extension. Techniques to identify neutrinos interacting within the DeepCore volume and veto muons originating outside the detector are demonstrated. A sample of 1029 events is observed in 281 days of data, of which 496 $\\pm$ 66(stat.) $\\pm$ 88(syst.) are estimated to be cascade events, including both electron neutrino and neutral current events. The rest of the sample includes residual backgrounds due to atmospheric muons and charged current interactions of atmospheric muon neutrinos. The flux of the atmospheric electron neutrinos is consistent with models of atmospheric neutrinos in this energy range. This constitutes the first observation of electron neutrinos and neutral current interactions in a very large volume neutrino telescope optimized for the TeV energy range.

  9. Measurement of the atmospheric ?e flux in IceCube.

    PubMed

    Aartsen, M G; Abbasi, R; Abdou, Y; Ackermann, M; Adams, J; Aguilar, J A; Ahlers, M; Altmann, D; Auffenberg, J; Bai, X; Baker, M; Barwick, S W; Baum, V; Bay, R; Beattie, K; Beatty, J J; Bechet, S; Becker Tjus, J; Becker, K-H; Bell, M; Benabderrahmane, M L; BenZvi, S; Berdermann, J; Berghaus, P; Berley, D; Bernardini, E; Bernhard, A; Bertrand, D; Besson, D Z; Bindig, D; Bissok, M; Blaufuss, E; Blumenthal, J; Boersma, D J; Bohaichuk, S; Bohm, C; Bose, D; Böser, S; Botner, O; Brayeur, L; Brown, A M; Bruijn, R; Brunner, J; Buitink, S; Carson, M; Casey, J; Casier, M; Chirkin, D; Christy, B; Clark, K; Clevermann, F; Cohen, S; Cowen, D F; Cruz Silva, A H; Danninger, M; Daughhetee, J; Davis, J C; De Clercq, C; De Ridder, S; Desiati, P; de Vries-Uiterweerd, G; de With, M; DeYoung, T; Díaz-Vélez, J C; Dreyer, J; Dunkman, M; Eagan, R; Eberhardt, B; Eisch, J; Ellsworth, R W; Engdegård, O; Euler, S; Evenson, P A; Fadiran, O; Fazely, A R; Fedynitch, A; Feintzeig, J; Feusels, T; Filimonov, K; Finley, C; Fischer-Wasels, T; Flis, S; Franckowiak, A; Franke, R; Frantzen, K; Fuchs, T; Gaisser, T K; Gallagher, J; Gerhardt, L; Gladstone, L; Glüsenkamp, T; Goldschmidt, A; Golup, G; Goodman, J A; Góra, D; Grant, D; Groß, A; Gurtner, M; Ha, C; Haj Ismail, A; Hallgren, A; Halzen, F; Hanson, K; Heereman, D; Heimann, P; Heinen, D; Helbing, K; Hellauer, R; Hickford, S; Hill, G C; Hoffman, K D; Hoffmann, R; Homeier, A; Hoshina, K; Huelsnitz, W; Hulth, P O; Hultqvist, K; Hussain, S; Ishihara, A; Jacobi, E; Jacobsen, J; Japaridze, G S; Jero, K; Jlelati, O; Kaminsky, B; Kappes, A; Karg, T; Karle, A; Kelley, J L; Kiryluk, J; Kislat, F; Kläs, J; Klein, S R; Köhne, J-H; Kohnen, G; Kolanoski, H; Köpke, L; Kopper, C; Kopper, S; Koskinen, D J; Kowalski, M; Krasberg, M; Kroll, G; Kunnen, J; Kurahashi, N; Kuwabara, T; Labare, M; Landsman, H; Larson, M J; Lesiak-Bzdak, M; Leute, J; Lünemann, J; Madsen, J; Maruyama, R; Mase, K; Matis, H S; McNally, F; Meagher, K; Merck, M; Mészáros, P; Meures, T; Miarecki, S; Middell, E; Milke, N; Miller, J; Mohrmann, L; Montaruli, T; Morse, R; Nahnhauer, R; Naumann, U; Niederhausen, H; Nowicki, S C; Nygren, D R; Obertacke, A; Odrowski, S; Olivas, A; Olivo, M; O'Murchadha, A; Panknin, S; Paul, L; Pepper, J A; Pérez de los Heros, C; Pfendner, C; Pieloth, D; Pirk, N; Posselt, J; Price, P B; Przybylski, G T; Rädel, L; Rawlins, K; Redl, P; Resconi, E; Rhode, W; Ribordy, M; Richman, M; Riedel, B; Rodrigues, J P; Rott, C; Ruhe, T; Ruzybayev, B; Ryckbosch, D; Saba, S M; Salameh, T; Sander, H-G; Santander, M; Sarkar, S; Schatto, K; Scheel, M; Scheriau, F; Schmidt, T; Schmitz, M; Schoenen, S; Schöneberg, S; Schönherr, L; Schönwald, A; Schukraft, A; Schulte, L; Schulz, O; Seckel, D; Seo, S H; Sestayo, Y; Seunarine, S; Sheremata, C; Smith, M W E; Soiron, M; Soldin, D; Spiczak, G M; Spiering, C; Stamatikos, M; Stanev, T; Stasik, A; Stezelberger, T; Stokstad, R G; Stößl, A; Strahler, E A; Ström, R; Sullivan, G W; Taavola, H; Taboada, I; Tamburro, A; Ter-Antonyan, S; Tilav, S; Toale, P A; Toscano, S; Usner, M; van der Drift, D; van Eijndhoven, N; Van Overloop, A; van Santen, J; Vehring, M; Voge, M; Vraeghe, M; Walck, C; Waldenmaier, T; Wallraff, M; Wasserman, R; Weaver, Ch; Wellons, M; Wendt, C; Westerhoff, S; Whitehorn, N; Wiebe, K; Wiebusch, C H; Williams, D R; Wissing, H; Wolf, M; Wood, T R; Woschnagg, K; Xu, C; Xu, D L; Xu, X W; Yanez, J P; Yodh, G; Yoshida, S; Zarzhitsky, P; Ziemann, J; Zierke, S; Zilles, A; Zoll, M

    2013-04-12

    We report the first measurement of the atmospheric electron neutrino flux in the energy range between approximately 80 GeV and 6 TeV, using data recorded during the first year of operation of IceCube's DeepCore low-energy extension. Techniques to identify neutrinos interacting within the DeepCore volume and veto muons originating outside the detector are demonstrated. A sample of 1029 events is observed in 281 days of data, of which 496±66(stat)±88(syst) are estimated to be cascade events, including both electron neutrino and neutral current events. The rest of the sample includes residual backgrounds due to atmospheric muons and charged current interactions of atmospheric muon neutrinos. The flux of the atmospheric electron neutrinos is consistent with models of atmospheric neutrinos in this energy range. This constitutes the first observation of electron neutrinos and neutral current interactions in a very large volume neutrino telescope optimized for the TeV energy range. PMID:25167245

  10. Occurrence rates of magnetic activities and flux maintenance in quiet regions

    NASA Astrophysics Data System (ADS)

    Iida, Yusuke

    We investigate occurrence rates of magnetic activities, namely merging, splitting, cancellation, and emergence as functions of flux content in quiet regions by means of feature tracking technique. The structure of magnetic field on the solar surface is important not only because it is the but also because it is actual magneto-convection on the stellar surface which we can observe for the most details. Recent satellite observation reveals scaling nature of magnetic patches on the solar surface. Parnell et al. (2009) found a power-law distribution with an index of -1.85 for flux content in each magnetic patch and Thornton & Parnell (2011) found a power-law distribution with an index of -2.7 for flux content of emerging flux. However, it is not still understood what mechanism makes these power-law nature. We try this issue by developing auto-tracking technique and quantization of patch activities. We use two data sets of line-of-sight magnetograms by Solar Optical Telescope (SOT)/ Narrowband Filter Imager (NFI) on board Hinode satellite. One has the high temporal cadence, 1 minute, and the other has the longest observational period, 140 hours. More than 3000 and 40000 patches are tracked in the data sets, respectively. We found that the occurrence of merging and splitting is larger than those of emergence and cancellation by one-order of magnitude, which means that the frequency distribution of flux content is maintained by the surface activities not by flux supply itself. The frequency dependence of cancellation on flux amount is also investigated. We found that a power-law distribution with an index of -2.48 with an error bar of 0.24, which is same as that of emergence in Thornton & Parnell (2011). In the discussion, we want to suggest flux re-cycling in quiet regions, which can explain these characters. begin{enumerate} Frequency distribution of flux content is formed to a power-law distribution by merging and splitting on the solar surface. Transport of patches of surface convection results in steep power-law distribution of flux content of cancellation. The submerged fluxes though cancellations re-appear to the solar surface, which results in small-scale flux emergences on the solar surface.

  11. Careful Measurements and Energy Balance Closure - The Case of Soil Heat Flux

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An area of persistent concern in micrometeorological measurements is the failure to close the energy balance at surface flux stations. While most attention has focused on corrections associated with the eddy fluxes, none of the energy balance terms are measured without error. The flux plate method i...

  12. Standardization of flux chambers and wind tunnels for area source emission measurements at animal feeding operations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Researchers and practitioners have used many varied designs of wind tunnels and flux chambers to measure the flux of volatile organic compounds, odor, and ammonia from area sources at animal feeding operations. The measured fluxes are used to estimate emission factors or compare treatments. We sho...

  13. Optimization of magnetic flux density measurement using multiple RF receiver coils and multi-echo in MREIT

    NASA Astrophysics Data System (ADS)

    Jeong, Woo Chul; Chauhan, Munish; Sajib, Saurav Z. K.; Kim, Hyung Joong; Serša, Igor; In Kwon, Oh; Woo, Eung Je

    2014-09-01

    Magnetic Resonance Electrical Impedance Tomography (MREIT) is an MRI method that enables mapping of internal conductivity and/or current density via measurements of magnetic flux density signals. The MREIT measures only the z-component of the induced magnetic flux density B = (Bx, By, Bz) by external current injection. The measured noise of Bz complicates recovery of magnetic flux density maps, resulting in lower quality conductivity and current-density maps. We present a new method for more accurate measurement of the spatial gradient of the magnetic flux density gradient (? Bz). The method relies on the use of multiple radio-frequency receiver coils and an interleaved multi-echo pulse sequence that acquires multiple sampling points within each repetition time. The noise level of the measured magnetic flux density Bz depends on the decay rate of the signal magnitude, the injection current duration, and the coil sensitivity map. The proposed method uses three key steps. The first step is to determine a representative magnetic flux density gradient from multiple receiver coils by using a weighted combination and by denoising the measured noisy data. The second step is to optimize the magnetic flux density gradient by using multi-echo magnetic flux densities at each pixel in order to reduce the noise level of ? Bz and the third step is to remove a random noise component from the recovered ? Bz by solving an elliptic partial differential equation in a region of interest. Numerical simulation experiments using a cylindrical phantom model with included regions of low MRI signal to noise (‘defects’) verified the proposed method. Experimental results using a real phantom experiment, that included three different kinds of anomalies, demonstrated that the proposed method reduced the noise level of the measured magnetic flux density. The quality of the recovered conductivity maps using denoised ? Bz data showed that the proposed method reduced the conductivity noise level up to 3-4 times at each anomaly region in comparison to the conventional method.

  14. MAVEN Measurements of the Ion Escape Rate from Mars

    NASA Astrophysics Data System (ADS)

    Brain, Dave; Dong, Yaxue; Fortier, Kier; Fang, Xiaohua; McFadden, James; Halekas, Jasper; Connerney, Jack; Eparvier, Frank; Dong, Chuanfei; Bougher, Stephen; Ma, Yingjuan; Modolo, Ronan; Lillis, Rob; Luhmann, Janet; Curry, Shannon; Seki, Kanako; Jakosky, Bruce

    2015-04-01

    The loss of atmospheric particles (neutral atoms, neutral molecules, ions) to space is thought to have played a role in the evolution of Martian climate over the past ~4 billion years. Due to the lack of a global magnetic field on Mars, the solar wind has direct access to the upper layers of the Martian atmosphere, and can drive non-thermal escape of charged particles (ions) from the atmosphere. Two spacecraft (Phobos 2 and Mars Express) have previously measured escaping ions at Mars. The recently arrived MAVEN spacecraft is equipped with instruments to measure escaping ions with high time cadence and high energy and mass resolution, as well as instruments to provide contextual information about what controls the variation in escape rates. We report on the total escape rate of heavy planetary ions from the Martian atmosphere measured by MAVEN. Heavy ions are identified in data from the SupraThermal And Thermal Ion Composition (STATIC) instrument. Rudimentary estimates of ion escape rate are obtained by summing the measured ion fluxes over a surface downstream from Mars with respect to the solar wind flow. This estimate can then be refined to account for the limited field of view of the instrument (investigation of measured particle distributions) and the limited spatial coverage of the spacecraft orbit trajectory. Variability in measured escape rates can also be grouped according to upstream conditions and the orientation of Mars (and its crustal magnetic fields) with respect to the solar wind. Important upstream drivers include the solar Extreme Ultraviolet (EUV) flux, solar wind pressure, and the interplanetary magnetic field strength and direction. These drivers are measured directly by MAVEN's EUV, SWIA, and MAG instruments. We will provide an initial estimate of ion escape rates based on the first several months of MAVEN data. We will then report on progress to refine these estimates to correct for instrument field of view and spacecraft coverage effects, as well as the influence of external drivers. We will place these estimates in context with previously published ion escape rates, and address the implications for atmospheric loss over the history of the planet

  15. A high sensitivity momentum flux measuring instrument for plasma thruster exhausts and diffusive plasmas

    SciTech Connect

    West, Michael D.; Charles, Christine; Boswell, Rod W.

    2009-05-15

    A high sensitivity momentum flux measuring instrument based on a compound pendulum has been developed for use with electric propulsion devices and radio frequency driven plasmas. A laser displacement system, which builds upon techniques used by the materials science community for surface stress measurements, is used to measure with high sensitivity the displacement of a target plate placed in a plasma thruster exhaust. The instrument has been installed inside a vacuum chamber and calibrated via two different methods and is able to measure forces in the range of 0.02-0.5 mN with a resolution of 15 {mu}N. Measurements have been made of the force produced from the cold gas flow and with a discharge ignited using argon propellant. The plasma is generated using a Helicon Double Layer Thruster prototype. The instrument target is placed about 1 mean free path for ion-neutral charge exchange collisions downstream of the thruster exit. At this position, the plasma consists of a low density ion beam (10%) and a much larger downstream component (90%). The results are in good agreement with those determined from the plasma parameters measured with diagnostic probes. Measurements at various flow rates show that variations in ion beam velocity and plasma density and the resulting momentum flux can be measured with this instrument. The instrument target is a simple, low cost device, and since the laser displacement system used is located outside the vacuum chamber, the measurement technique is free from radio frequency interference and thermal effects. It could be used to measure the thrust in the exhaust of other electric propulsion devices and the momentum flux of ion beams formed by expanding plasmas or fusion experiments.

  16. A comparison of methane flux rates from the margins of a permanent wetland and an ephemeral wetland in southern Minnesota

    NASA Astrophysics Data System (ADS)

    Nelson, L. C.; Kannenberg, S.; Ludwig, S.; Rich, H.; Spawn, S.; Porterfield, J.; Schade, J. D.

    2012-12-01

    The degree of expansion and contraction of wetlands is likely to change as climate change alters drought and precipitation events. As wetland size becomes more dynamic, the extent and duration of inundation of soils on their margins will change. The amount of methane released from wetlands will also change since methanogens thrive in anoxic, saturated soils. It is critical to study the factors that influence methane emissions from wetlands because methane is 20 times more effective at trapping heat in the atmosphere than carbon dioxide. The objective of our research was to compare methane flux rates from the margins of a permanent wetland and an ephemeral wetland. We also assessed the impact of Reed Canary Grass (Phalaris arundinacea) on transport of methane from the soil to the atmosphere. Methane flux emissions were measured using portable gas flux chambers at Bakko Pond (a permanent wetland) and East Coyote Pond (an ephemeral wetland) on the St. Olaf College Natural Lands in southern Minnesota. At each wetland, we measured methane emissions from plots of clipped and unclipped Reed Canary Grass. We found no statistical difference between clipped and unclipped plots, suggesting that a diffusive gas transport system rather than a coupling of a diffusive and convective gas transport emits methane. We also found that the average rate of methane flux was higher at East Coyote Pond at both the wet Reed Canary Grass and dry Reed Canary Grass sites, when compared to the dry Reed Canary Grass site at Bakko Pond. Higher methane emission rates at East Coyote Pond is consistent with the characteristics of a wetland with a shallow bank where marginal soil is frequently inundated with water, creating a favorable anoxic environment for active methanogens. In contrast, Bakko Pond has a steep embankment, reducing soil saturation. We also found that soil moisture was strongly correlated with methane flux rates between the sites and over time within a site. Overall, our results suggest that increases in the intensity of precipitation events due to climate change may lead to increased methane emissions from wetlands by increasing the extent of soil saturation. The total impact of these changes on annual methane flux will depend, however, on changes in the frequency of these events and the resulting changes in duration of soil saturation.

  17. Molecular fluxes from a spacecraft measured with quartz microbalances

    NASA Technical Reports Server (NTRS)

    Scialdone, J. J.

    1975-01-01

    A technique has been developed to obtain a characterization of the self-generated environment of a spacecraft and its variation with time, angular position, and distance. The density, pressure, outgassing flux, total weight loss, and other important parameters were obtained from data provided by two mass measuring crystal microbalances, mounted back to back, at a distance of 1 m from the spacecraft equivalent surface. The strongest source appeared to be caused by a material diffusion process which produced a directional density at 1 m distance of about 160 billion molecules per cu cm after 1 h in vacuum and decayed to 1.6 billion molecules per cu cm after 200 h. Self-contamination of the spacecraft was equivalent to that which occurs in a 300-km altitude orbit.

  18. Vacuum test fixture improves leakage rate measurements

    NASA Technical Reports Server (NTRS)

    Maier, H.; Marx, H.

    1966-01-01

    Cylindrical chamber, consisting of two matching halves, forms a vacuum test fixture for measuring leakage rates of individual connections, brazed joints, and entrance ports used in closed fluid flow line systems. Once the chamber has been sufficiently evacuated, atmospheric pressure holds the two halves together.

  19. Objective Measures as Predictors of Reputational Ratings.

    ERIC Educational Resources Information Center

    Saunier, Margaret Ellen

    1985-01-01

    A statistical prediction of National Research Council graduate department ratings in six disciplines (from faculty size and characteristics, student body size and characteristics, physical facilities, funding, and program productivity) found at least one measure of faculty or student size to be a significant predictor in all disciplines, and…

  20. Energetic ion diagnostics using neutron flux measurements during pellet injection

    SciTech Connect

    Heidbrink, W.W.

    1986-01-01

    Neutron measurements during injection of deuterium pellets into deuterium plasmas on the Tokamak Fusion Test Reactor (TFTR) indicate that the fractional increase in neutron emission about 0.5 msec after pellet injection is proportional to the fraction of beam-plasma reactions to total fusion reactions in the unperturbed plasma. These observations suggest three diagnostic applications of neutron measurements during pellet injection: (1) measurement of the beam-plasma reaction rate in deuterium plasmas for use in determining the fusion Q in an equivalent deuterium-tritium plasma, (2) measurement of the radial profile of energetic beam ions by varying the pellet size and velocity, and (3) measurement of the ''temperature'' of ions accelerated during wave heating. 18 refs., 3 figs.

  1. On the constancy of solar particle fluxes from track, thermoluminescence and solar wind measurements in lunar rocks

    NASA Technical Reports Server (NTRS)

    Zinner, E.

    1980-01-01

    Evidence contained within lunar rocks concerning possible variations in solar activity over the last 1 to 2 million years is reviewed. The effects of solar wind particles, which are implanted at shallow depths, solar flare protons, which produce thermoluminescence as well as stable and radionuclides, and solar flare heavy nuclei, which produce tracks, are considered, and the quality and limitations of nuclear tracks measurements as indicators of solar flare flux histories are discussed. Methods used for the determination of the solar flare track production rate, which must be known in order to measure lunar rock surface exposure times, are compared, and it is concluded that most of the evidence favors the rate obtained by Blanford et al. (1975). Information on the constancy of the solar flare particle flux obtained by comparison of the effects of different surface phenomena with solar particle effects is then illustrated for the cases of comparisons between solar flare tracks and microcrater densities, solar flare particle fluxes measured over different periods, and comparisons of the solar flare track production rate with the solar wind flux and microcratering rate. It is noted that these studies provide no evidence for a change in solar particle flux by more than a factor of two over the last 10,000 to 1 million years, or for a change in the solar flare Fe/H ratio in the last 2 million years.

  2. Measurement of particulate matter emission fluxes from a beef cattle feedlot using Flux-gradient technique

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Data on air emissions from open-lot beef cattle feedlots are limited. This research was conducted to determine PM10 emission fluxes from a commercial beef cattle feedlot in Kansas using the flux-gradient technique, a widely-used micrometeorological method for gaseous emissions from open sources. V...

  3. Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign at Värriö field station

    NASA Astrophysics Data System (ADS)

    Ruuskanen, T. M.; Kaasik, M.; Aalto, P. P.; Hõrrak, U.; Vana, M.; Mårtensson, M.; Yoon, Y. J.; Keronen, P.; Mordas, G.; Ceburnis, D.; Nilsson, E. D.; O'Dowd, C.; Noppel, M.; Alliksaar, T.; Ivask, J.; Sofiev, M.; Prank, M.; Kulmala, M.

    2007-07-01

    The LAPBIAT measurement campaign took place in the Värriö SMEAR I measurement station located in Eastern Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the measurement campaign, concentrations and fluxes of aerosol particles, air ions and trace gases, paying special attention to an aerosol particle formation event broken by a air mass change from a clean Arctic air mass with new particle formation to polluted one approaching from industrial areas of Kola Peninsula, Russia, lacking new particle formation. Aerosol particle number flux measurements show strong downward fluxes during that time. Concentrations of coarse aerosol particles were high for 1-2 days before the nucleation event (i.e. 28-29 April), very low immediately before and during the observed aerosol particle formation event (30 April) and increased moderately from the moment of sudden break of the event. In general particle deposition measurements based on snow samples show the same changes. Measurements of the mobility distribution of air ions showed elevated concentrations of intermediate air ions during the particle formation event. We estimated the growth rates in the nucleation mode size range. For particles <10 nm, the growth rate increases with size on 30 April. Dispersion modelling made with model SILAM support the conclusion that the nucleation event was interrupted by an outbreak of sulphate-rich air mass in the evening of 30 April that originated from the industry at Kola Peninsula, Russia. The results of this campaign highlight the need for detailed research in atmospheric transport of air constituents for understanding the aerosol dynamics.

  4. Flow rate measurement in aggressive conductive fluids

    NASA Astrophysics Data System (ADS)

    Dubovikova, Nataliia; Kolesnikov, Yuri; Karcher, Christian

    2014-03-01

    Two non-contact experimental methods of flow rate measurements for aggressive conductive liquids are described. The techniques are based on electromagnetic forces and Faraday's law: Lorentz force is induced inside moving conductive liquid under influence of variable magnetic field of permanent magnets. They are mounted along a liquid metal channel or (in case of the second method) inserted into rotated metal wheels. The force acts in the opposite of fluids' velocity direction and hence it is possible to measure reaction force of it that takes place according to Newton's law on magnetic field source - permanent magnets. And by knowing the force, which linearly depends on velocity, one can calculate mean flow rate of liquid. In addition experimental "dry" calibration and its results are described for one of the measurements' techniques.

  5. Aeolian sediment fluxes measured over various plant/soil complexes in the Chihuahuan desert

    NASA Astrophysics Data System (ADS)

    Bergametti, G.; Gillette, D. A.

    2010-09-01

    Measurements of horizontal flux of sediment were performed over the period 1998-2005 at different vegetated areas within the Jornada Long Term Ecological Research site. Sediment trap samples were collected during successive nominal 3-month periods at 15 sites: three independent sites at each of the five dominant plant/soil complexes encountered in this part of the Chihuahuan desert (mesquite, creosote, tarbush, grama grass, and playa grass). Mesquite vegetated areas have significantly higher sediment fluxes than the four other plant/soil complexes. The other types of vegetation complexes yield sediment fluxes that cannot be statistically distinguished from each other. An analysis of the temporal variability of the sediment fluxes indicates that only the annual sediment fluxes from mesquite sites are correlated with the annual occurrence of high wind speeds. Examination of the vertical profile of the fluxes of sediment and the fast response Sensit measurements confirms that a local saltation mechanism is responsible for sediment fluxes measured at mesquite sites. However, the local saltation mechanism cannot explain sediment fluxes measured on nonmesquite sites. Sediment fluxes at nonmesquite sites are only rarely carried in from upwind sources. Additionally, our data for sediment flux showed that off-site (drifting in) flux of sediment cannot explain the differences of mesquite and nonmesquite sediment fluxes. We suggest dust devils to be the mechanism that causes sediment emissions at both nonmesquite and mesquite lands, but their effect is trivial compared to the fluxes caused by mesoscale meteorological winds at the mesquite sites.

  6. Recommended Procedures for Measuring Radon Fluxes from Disposal Sites of Residual Radioactive Materials

    SciTech Connect

    Young,, J. A.; Thomas, V. W.; Jackson, P. 0.

    1983-03-01

    This report recornmenrls instrumentation and methods suitable for measuring radon fluxes emanating from covered disposal sites of residual radioactive materials such as uranium mill tailings. Problems of spatial and temporal variations in radon flux are discussed and the advantages and disadvantages of several instruments are examined. A year-long measurement program and a two rnonth measurement rnethodology are then presented based on the inherent difficulties of measuring average radon flux over a cover using the recommended instrumentation.

  7. Heat flux measured acoustically at Grotto Vent, a hydrothermal vent cluster on the Endeavour Segment, Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Xu, G.; Jackson, D. R.; Bemis, K. G.; Rona, P. A.

    2013-12-01

    Over the past several decades, quantifying the heat output has been a unanimous focus of studies at hydrothermal vent fields discovered around the global ocean. Despite their importance, direct measurements of hydrothermal heat flux are very limited due to the remoteness of most vent sites and the complexity of hydrothermal venting. Moreover, almost all the heat flux measurements made to date are snapshots and provide little information on the temporal variation that is expected from the dynamic nature of a hydrothermal system. The Cabled Observatory Vent Imaging Sonar (COVIS, https://sites.google.com/a/uw.edu/covis/) is currently connected to the Endeavour node of the NEPTUNE Canada observatory network (http://www.neptunecanada.ca) to monitor the hydrothermal plumes issuing from a vent cluster (Grotto) on the Endeavour Segment of the Juan de Fuca Ridge. COVIS is acquiring a long-term (20-months to date) time series of the vertical flow rate and volume flux of the hydrothermal plume above Grotto through the Doppler analysis of the acoustic backscatter data (Xu et al., 2013). We then estimate the plume heat flux from vertical flow rate and volume flux using our newly developed inverse method. In this presentation, we will briefly summarize the derivation of the inverse method and present the heat-flux time series obtained consequently with uncertainty quantification. In addition, we compare our heat-flux estimates with the one estimated from the plume in-situ temperatures measured using a Remotely Operative Vehicle (ROV) in 2012. Such comparison sheds light on the uncertainty of our heat flux estimation. Xu, G., Jackson, D., Bemis, K., and Rona, P., 2013, Observations of the volume flux of a seafloor hydrothermal plume using an acoustic imaging sonar, Geochemistry, Geophysics Geosystems, 2013 (in press).

  8. The BESS-Polar Proton & Helium flux measurements

    NASA Astrophysics Data System (ADS)

    Hams, T.; Yamamoto, A.; Mitchell, J.W.; Abe, K.; Fuke, H.; Haino, S.; Hasegawa, M.; Horikoshi, A.; Itazaki, A.; Kim, K.C.; Kumazawal, T.; Lee, M.H.; Makida, Y.; Matsuda, S.; Matsukawa, Y.; Matsumoto, K.; Moiseev, A.A.; Meyers, Z.; Nishimura, J.; Nozaki, M.; Orito, R.; Ormes, J.F.; Sakai, K.; Sasaki, M.; Seo, E.S.; Shikaze, Y.; Shinoda, R.; Streitmatter, R.E.; Suzuki, J.; Takasugi, Y.; Takeuchi, K.; Tanaka, K.; Thakur, N.; Yamagami, T.; Yoshida, T.; Yoshimura, K.

    The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) instrument pro-vides precise measurements of the elemental and isotopic composition of the light Galactic cosmic radiation (GCR) component. The ability to determine the charge sign of incident par-ticles enables the instrument to search for GCR antimatter, which is a major objective of the BESS program. Since 1993, the US-Japan BESS collaboration has conducted 11 successful balloon flights, nine northern-latitude flights of 1-day duration and most recently two long-duration balloon flights (8.5 days in 2004 & 24.5 days in 2007/2008), with the BESS-Polar instrument. The BESS-Polar instrument is the current effort of BESS program specifically designed for long-duration, low-geomagnetic cutoff Antarctic flights with significantly increased transparency for incident CR particle allowing to study anti/proton down to 100 MeV and a faster data acquisition enables processing of all CR events without event selection. The first BESS-Polar flight was launched on Dec 13, 2004 from Williams Field, near McMurdo Station in Antarctica. The instrument recorded data for 8.5 days, limited by the cryogenic life time of the superconducting magnet. During this flight the BESS-Polar instrument recorded 0.9 x 109 CR events. In this paper, we present the absolute proton and helium flux for the first BESS-Polar flight as well as the time variation of the fluxes due to solar activity.

  9. MEASURING TINY MASS ACCRETION RATES ONTO YOUNG BROWN DWARFS

    SciTech Connect

    Herczeg, Gregory J.; Cruz, Kelle L.; Hillenbrand, Lynne A.

    2009-05-10

    We present low-resolution Keck I/LRIS spectra spanning from 3200 to 9000 A of nine young brown dwarfs and three low-mass stars in the TW Hya Association and in Upper Sco. The optical spectral types of the brown dwarfs range from M5.5 to M8.75, though two have near-IR spectral types of early L dwarfs. We report new accretion rates derived from excess Balmer continuum emission for the low-mass stars TW Hya and Hen 3-600A and the brown dwarfs 2MASS J12073347-3932540, UScoCTIO 128, SSSPM J1102-3431, USco J160606.29-233513.3, DENIS-P J160603.9-205644, and Oph J162225-240515B, and upper limits on accretion for the low-mass star Hen 3-600B and the brown dwarfs UScoCTIO 112, Oph J162225-240515A, and USco J160723.82-221102.0. For the six brown dwarfs in our sample that are faintest at short wavelengths, the accretion luminosity or upper limit is measurable only when the image is binned over large wavelength intervals. This method extends our sensitivity to accretion rate down to {approx}10{sup -13} M{sub sun}yr{sup -1} for brown dwarfs. Since the ability to measure an accretion rate from excess Balmer continuum emission depends on the contrast between excess continuum emission and the underlying photosphere, for objects with earlier spectral types the upper limit on accretion rate is much higher. Absolute uncertainties in our accretion rate measurements of {approx}3-5 include uncertainty in accretion models, brown dwarf masses, and distance. The accretion rate of 2 x 10{sup -12} M {sub sun} yr{sup -1} onto 2MASS J12073347-3932540 is within 15% of two previous measurements, despite large changes in the H{alpha} flux.

  10. The effect of cumulus cloud field anisotropy on solar radiative fluxes and atmospheric heating rates

    NASA Astrophysics Data System (ADS)

    Hinkelman, Laura M.

    The effect of fair-weather cumulus cloud field anisotropy on domain average surface fluxes and atmospheric heating profiles was studied. Causes of anisotropy were investigated using a large-eddy simulation (LES) model. Cloud formation under a variety of environmental conditions was simulated and the degree of anisotropy in the output fields was calculated. Wind shear was found to be the single greatest factor in the development of both vertically tilted and horizontally stretched cloud structures. A stochastic field generation algorithm was used to produce twenty three-dimensional liquid water content fields based on the statistical properties of the LES cloud scenes. Progressively greater degrees of tilt and stretching were imposed on each of these scenes, so that an ensemble of scenes were produced for each level of distortion. The resulting scenes were used as input to a three-dimensional Monte Carlo model. Domain-average transmission, reflection, and absorption of broadband solar radiation were computed for each scene along with the average heating rate profile. Both tilt and horizontal stretching were found to significantly affect calculated fluxes, with the amount and sign of flux differences depending strongly on sun position relative to cloud distortion geometry. For nearly all solar geometries, domain-averaged fluxes and atmospheric heating rate profiles calculated using the Independent Pixel Approximation differed substantially from the corresponding three-dimensional Monte Carlo results.

  11. Outer atmospheres of cool stars. II - Mg II flux profiles and chromospheric radiative loss rates

    NASA Technical Reports Server (NTRS)

    Basri, G. S.; Linsky, J. L.

    1979-01-01

    International Ultraviolet Explorer high-resolution spectra of the Mg II lines at 2796, 2803 A in 15 stars of spectral type G2-M2 including a wide range of luminosities are presented. These spectra are calibrated in absolute flux units at earth and at the stellar surface, and the chromospheric radiative loss rates in the Mg II lines are compared with corresponding rates in the Ca II H, K, and 8542 lines. The ratio of Mg II surface flux to total surface flux is found to be independent of stellar luminosity and thus gravity; may decrease slowly with decreasing effective temperature, and increases with decreasing period among RS Canum Venaticorum binaries. The factor of 10 range in this ratio at each effective temperature may be due to differences in the fractional surface area covered by plages and may indicate that stars of all luminosity classes have chromospheric plages. In this small data sample no evidence is found that the Mg II line surface fluxes indicate whether a star possesses a transition region and hot corona.

  12. A highly portable, rapidly deployable system for eddy covariance measurements of CO2 fluxes

    SciTech Connect

    Billesbach, David P.; Fischer, Marc L.; Torn, Margaret S.; Berry, Joe A.

    2001-09-19

    To facilitate the study of flux heterogeneity within a region, the authors have designed, built, and field-tested a highly portable, rapidly deployable, eddy covariance CO{sub 2} flux measurement system. The system is built from off-the-shelf parts and was assembled at a minimal cost. The unique combination of features of this system allow for a very rapid deployment with a minimal number of field personnel. The system is capable of making high precision, unattended measurements of turbulent CO{sub 2} fluxes, latent heat (LE) fluxes, sensible heat fluxes (H), and momentum transfer fluxes. In addition, many of the meteorological and ecosystem variables necessary for quality control of the fluxes and for running ecosystem models are measured. A side-by-side field comparison of the system at a pair of established AmeriFlux sites has verified that, for single measurements, the system is capable of CO{sub 2} flux accuracy of about {+-} 1.2 {micro}mole/m{sup 2}/sec, LE flux accuracy of about {+-} 15 Watts/m{sup 2}, H flux accuracy of about {+-} 7 Watts/m{sup 2}, and momentum transfer flux accuracy of about {+-} 11 gm-m/sec/sec. System deployment time is between 2 and 4 hours by a single person. The system was measured to draw between 30 and 35 Watts of power and may be run from available line power, storage batteries, or solar panels.

  13. Direct Measurement of CO2 Fluxes in Marine Whitings

    SciTech Connect

    Lisa L. Robbins; Kimberly K. Yates

    2001-07-05

    Clean, affordable energy is a requisite for the United States in the 21st Century Scientists continue to debate over whether increases in CO{sub 2} emissions to the atmosphere from anthropogenic sources, including electricity generation, transportation and building systems may be altering the Earth's climate. While global climate change continues to be debated, it is likely that significant cuts in net CO{sub 2} emissions will be mandated over the next 50-100 years. To this end, a number of viable means of CO{sub 2} sequestration need to be identified and implemented. One potential mechanism for CO{sub 2} sequestration is the use of naturally-occurring biological processes. Biosequestration of CO{sub 2} remains one of the most poorly understood processes, yet environmentally safe means for trapping and storing CO{sub 2}. Our investigation focused on the biogeochemical cycling of carbon in microbial precipitations of CaCO{sub 3}. Specifically, we investigated modern whitings (microbially-induced precipitates of the stable mineral calcium carbonate) as a potential, natural mechanism for CO{sub 2} abatement. This process is driven by photosynthetic metabolism of cyanobacteria and microalgae. We analyzed net air: sea CO{sub 2} fluxes, net calcification and photosynthetic rates in whitings. Both field and laboratory investigations have demonstrated that atmospheric CO{sub 2}decreases during the process of microbial calcification.

  14. Erosion rates for polymers measured on LDEF

    NASA Technical Reports Server (NTRS)

    Gregory, John C.

    1992-01-01

    The summary and viewgraphs of work presented at the Long Duration Exposure Facility (LDEF) materials workshop are given. Experimental data for erosion depths and rates for polymers measured on LDEF are given. In general, agreement is reasonably good between erosion rates from the University of Alabama in Huntsville (UAH) LDEF experiment and prior data obtained at much lower mission fluences. Agreement is particularly satisfying in the case of Kapton where the prior data base is large. In spite of the known presence of silicaceous contamination on LDEF surfaces, the erosion rates of the highly erodible materials are hardly affected, if at all. Graphs showing changes in optical properties (reflectance and transmittance) of metal films are included.

  15. Validation of the doubly labeled water method under low and high humidity to estimate metabolic rate and water flux

    E-print Network

    Williams, Jos. B.

    rate and water flux in a tropical snake (Boiga irregularis) Nancy L. Anderson, Thomas E. Hetherington, and Joseph B. Williams Department of Evolution, Ecology, and Organismal Biology, The Ohio State University and high humidity to estimate metabolic rate and water flux in a tropical snake (Boiga irregularis). J Appl

  16. Airborne Flux Measurements of Volatile Organic Compounds and NOx over a European megacity

    NASA Astrophysics Data System (ADS)

    Shaw, Marvin; Lee, James; Davison, Brian; Misztal, Pawel; Karl, Thomas; Hewitt, Nick; Lewis, Alistair

    2014-05-01

    Ground level ozone (O3) and nitrogen dioxide (NO2) are priority pollutants whose concentrations are closely regulated by European Union Air Quality Directive 2008/50/EC. O3 is a secondary pollutant, produced from a complex chemical interplay between oxides of nitrogen (NOx = NO + NO2) and volatile organic compounds (VOCs). Whilst the basic atmospheric chemistry leading to O3 formation is generally well understood, there are substantial uncertainties associated with the magnitude of emissions of both VOCs and NOx. At present our knowledge of O3 precursor emissions in the UK is primarily derived from National Atmospheric Emission inventories (NAEI) that provide spatially disaggregated estimates at 1x1km resolution, and these are not routinely tested at city or regional scales. Uncertainties in emissions propagate through into uncertainties in predictions of air quality in the future, and hence the likely effectiveness of control policies on both background and peak O3 and NO2 concentrations in the UK. The Ozone Precursor Fluxes in the Urban Environment (OPFUE) project aims to quantify emission rates for NOx and selected VOCs in and around the megacity of London using airborne eddy covariance (AEC). The mathematical foundation for AEC has been extensively reviewed and AEC measurements of ozone, dimethyl sulphide, CO2 and VOCs have been previously reported. During the summer of 2013, approximately 30 hours of airborne flux measurements of toluene, benzene, NO and NO2 were obtained from the NERC Airborne Research and Survey Facility's (ARSF) Dornier-228 aircraft. Over SE England, flights involved repeated south west to north east transects of ~50 km each over Greater London and it's surrounding suburbs and rural areas, flying at the aircraft's minimum operating flight altitude and airspeed (~300m, 80m/s). Mixing ratios of benzene and toluene were acquired at 2Hz using a proton transfer reaction mass spectrometer (PTR-MS) and compared to twice hourly whole air canister samples (WAS) which were quantitatively determined post-flight via TD-GCMS. Mixing ratios between the PTR-MS and WAS-TD-GCMS were in good agreement with R2 values of 0.8 and 1.0 for Toluene and Benzene respectively. Mixing ratios of NO and NO2 were acquired at 10Hz using a 2 channel NOx chemiluminescence detector with photolytic converter. These measurements were used with 20 Hz 3-D wind vector data from an AIMMS-20 turbulence probe on the aircraft to calculate highly spatially resolved (1 km) surface-to-atmosphere emission flux rates of these compounds using the eddy covariance method of Karl et al. (2013). Measured surface to atmosphere emission fluxes of NOx, benzene and toluene from London were between 40 - 91 mg m2 h-1, 0.1 - 0.4 mg m2 h-1 and 0.2 - 2 mg m2 h-1 respectively, showing the spatial flux heterogeneity over the city. This demonstrates for the first time the feasibility of airborne eddy covariance flux measurements of reactive NOx species. We also show the applicability of wavelet analysis using virtually disjunct eddy covariance measurements of anthropogenic compounds in estimating regional fluxes over a European megacity. We compare our measured emission rates with those estimated from 'bottom-up' emissions inventories and highlight the agreement between the two.

  17. Methane fluxes measured by eddy covariance and static chamber techniques at a temperate forest in central Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Wang, J. M.; Murphy, J. G.; Geddes, J. A.; Winsborough, C. L.; Basiliko, N.; Thomas, S. C.

    2013-06-01

    Methane flux measurements were carried out at a temperate forest (Haliburton Forest and Wildlife Reserve) in central Ontario (45°17´11´´ N, 78°32´19´´ W) from June to October 2011. Continuous measurements were made by an off-axis integrated cavity output spectrometer that measures methane (CH4) at 10 Hz sampling rates. Fluxes were calculated from the gas measurements in conjunction with wind data collected by a 3-D sonic anemometer using the eddy covariance (EC) method. Observed methane fluxes showed net uptake of CH4 over the measurement period with an average uptake flux (±standard deviation of the mean) of -2.7 ± 0.13 nmol m-2 s-1. Methane fluxes showed a seasonal progression with average rates of uptake increasing from June through September and remaining high in October. This pattern was consistent with a decreasing trend in soil moisture content at the monthly timescale. On the diurnal timescale, there was evidence of increased uptake during the day, when the mid-canopy wind speed was at a maximum. These patterns suggest that substrate supply of CH4 to methanotrophs, and in certain cases hypoxic soil conditions supporting methanogenesis in low-slope areas, drives the observed variability in fluxes. A network of soil static chambers used at the tower site showed reasonable agreement with the seasonal trend and overall magnitude of the eddy covariance flux measurements. This suggests that soil-level microbial processes, and not abiological leaf-level CH4 production, drive overall CH4 dynamics in temperate forest ecosystems such as Haliburton Forest.

  18. Methane fluxes measured by eddy covariance and static chamber techniques at a temperate forest in central ontario, Canada

    NASA Astrophysics Data System (ADS)

    Wang, J. M.; Murphy, J. G.; Geddes, J. A.; Winsborough, C. L.; Basiliko, N.; Thomas, S. C.

    2012-12-01

    Methane flux measurements were carried out at a temperate forest (Haliburton Forest and Wildlife Reserve) in central Ontario (45°17´11´´ N, 78°32´19´´ W) from June-October, 2011. Continuous measurements were made by an off-axis integrated cavity output spectrometer Fast Greenhouse Gas Analyzer (FGGA) from Los Gatos Research Inc. that measures methane (CH4) at 10 Hz sampling rates. Fluxes were calculated from the gas measurements in conjunction with wind data collected by a 3-D sonic anemometer using the eddy covariance (EC) method. Observed methane fluxes showed net uptake of CH4 over the measurement period with an average uptake flux (± standard deviation of the mean) of -2.7 ± 0.13 nmol m-2 s-1. Methane fluxes showed a seasonal progression with average rates of uptake increasing from June through September and remaining high in October. This pattern was consistent with a decreasing trend in soil moisture content at the monthly time scale. On the diurnal timescale, there was evidence of increased uptake during the day, when the mid-canopy wind speed was at a maximum. These patterns suggest that substrate supply of CH4 and oxygen to methanotrophs, and in certain cases hypoxic soil conditions supporting methanogenesis in low-slope areas, drive the observed variability in fluxes. A network of soil static chambers used at the tower site showed close agreement with the eddy covariance flux measurements. This suggests that soil-level microbial processes, and not abiological leaf-level CH4 production, drive overall CH4 dynamics in temperate forest ecosystems such as Haliburton Forest.

  19. Ultrasonic rate measurement of multiphase flow

    SciTech Connect

    Dannert, D.A.; Horne, R.N.

    1993-01-01

    On of the most important tools in production logging and well testing is the downhole flowmeter. Unfortunately, existing tools are inaccurate outside of an idealized single phase flow, regime. Spinner tools are inaccurate at extremely high or low, flow rates and when the flow rate is variable. Radioactive tracer tools have similar inaccuracies and are extremely sensitive to the flow regime. Both tools completely fail in the presence of multiphase flow, whether gas/ oil, gas/water or fluid/solid. Downhole flowmetering is important for locating producing zones and thief zones and monitoring production and injection rates. The effects of stimulation can also be determined. This goal of this project is the investigation of accurate downhole flowmetering techniques for all single phase flow regimes and multiphase flows. The measurement method investigated in this report is the use of ultrasound. There are two ways to use ultrasound for fluid velocity measurement. The first method, examined in Chapter 2, is the contrapropagation, or transit-time, method which compares travel times with and against fluid flow. Chapter 3 details the second method which measures the Doppler frequency shift of a reflected sound wave in the moving fluid. Both of these technologies need to be incorporated in order to build a true multiphase flowmeter. Chapter 4 describes the proposed downhole multiphase flowmeter. It has many advantages besides the ones previously mentioned and is in full in that chapter.

  20. Tall tower landscape scale N2O flux measurements in a Danish agricultural and urban, coastal area

    NASA Astrophysics Data System (ADS)

    Ibrom, Andreas; Lequy, Émeline; Loubet, Benjamin; Pilegaard, Kim; Ambus, Per

    2015-04-01

    Both technical and natural processes emit the greenhouse gas nitrous oxide (N2O) into the atmosphere. The abundant use of nitrogen (N) as fertiliser increases the concentration of reactive nitrogen (Nr) in the atmosphere, the hydrosphere and in the biosphere, i.e. in terrestrial and aquatic ecosystems. Surplus Nr is distributed across linkages to other spheres until most of it is emitted to the atmosphere as NO, N2O or N2. A complete estimate of the effects from human activities on N2O emissions must therefore include all emissions, the direct emissions and the indirect emissions that happen in interlinked spheres. For this it is necessary to assess the fluxes at least at the landscape scale. The episodic nature and the large spatial variability make it difficult to estimate the direct and indirect emissions in a landscape. Modelling requires not only to include the highly variable microbial processes in the ecosystems that produce N2O but as well the accurate simulation of lateral Nr fluxes and their effects on N2O fluxes in places remote from the primary Nr sources. In this context tall tower N2O flux measurements are particularly useful as they integrate over larger areas and can be run, continuously without disturbing the fluxes. On the other hand these measurements can be difficult to interpret due to difficulties to measure the small concentration fluctuations in the atmosphere at small flux rates and to accurately attribute the measured flux at the tower to the area that generates the flux, i.e. the source area. The Technical University of Denmark (DTU) has established eddy covariance N2O flux measurements on a 125 m tall tower at its Risø Campus as part of the EU research infrastructure project the 'Integrated non-CO2 Greenhouse gas Observing System' (InGOS). The eddy covariance system consisted of a N2O/CO quantum cascade laser, Los Gatos, Mountain View, CA, USA and a 3D sonic anemometer (USA-1), Metek, Elmshorn, Germany. The Risø peninsula lies at the eastern coastline of the Roskilde fjord on the Danish island Zealand. The tower is surrounded by the fjord, by agricultural area, forests and, in the South by the urban area of the City of Roskilde. The City of Roskilde operates a waste incinerator and a waste water treatment plant, which drains treated waste water into the fjord. The level of the measured flux values was generally relatively low. Based on the clear definition of the lag time between N2O concentrations and the vertical wind speed, fluxes were measureable over larger periods. The fluxes showed clear directional relationships indicating their large spatial and temporal variability in the landscape. Footprint calculations were performed to attribute source areas to the measured fluxes ...(Kormann and Meixner, 2001; Neftel et al., 2008). The footprint of the flux measurement included areas between 200 m and several kilometres distance from the tower. A preliminary approach was developed to generate monthly maps of N2O fluxes around the tower. Here we present the results from the first seven months of flux measurements. Based on these results we discuss the potential and the limitations of tall tower eddy covariance measurements to estimate maps of N2O fluxes and the integral value of the landscape N2O flux. Acknowledgements: This work was funded by the EU-FP7 InGOS project. We thank Ebba Dellwik (Technical University of Denmark) for providing sonic anemometer data. References: Kormann, R. and Meixner, F.X., 2001. An Analytical Footprint Model For Non-Neutral Stratification. Boundary-Layer Meteorology, 99(2): 207-224. Neftel, A., Spirig, C. and Ammann, C., 2008. Application and test of a simple tool for operational footprint evaluations. Environmental Pollution, 152(3): 644-652.

  1. International Photolysis Frequency Measurement and Model Intercomparison (IPMMI): Spectral actinic solar flux measurements and modeling

    NASA Astrophysics Data System (ADS)

    Bais, A. F.; Madronich, S.; Crawford, J.; Hall, S. R.; Mayer, B.; van Weele, M.; Lenoble, J.; Calvert, J. G.; Cantrell, C. A.; Shetter, R. E.; Hofzumahaus, A.; Koepke, P.; Monks, P. S.; Frost, G.; McKenzie, R.; Krotkov, N.; Kylling, A.; Swartz, W. H.; Lloyd, S.; Pfister, G.; Martin, T. J.; Roeth, E.-P.; Griffioen, E.; Ruggaber, A.; Krol, M.; Kraus, A.; Edwards, G. D.; Mueller, M.; Lefer, B. L.; Johnston, P.; Schwander, H.; Flittner, D.; Gardiner, B. G.; Barrick, J.; Schmitt, R.

    2003-08-01

    The International Photolysis Frequency Measurement and Model Intercomparison (IPMMI) took place in Boulder, Colorado, from 15 to 19 June 1998, aiming to investigate the level of accuracy of photolysis frequency and spectral downwelling actinic flux measurements and to explore the ability of radiative transfer models to reproduce the measurements. During this period, 2 days were selected to compare model calculations with measurements, one cloud-free and one cloudy. A series of ancillary measurements were also performed and provided parameters required as input to the models. Both measurements and modeling were blind, in the sense that no exchanges of data or calculations were allowed among the participants, and the results were objectively analyzed and compared by two independent referees. The objective of this paper is, first, to present the results of comparisons made between measured and modeled downwelling actinic flux and irradiance spectra and, second, to investigate the reasons for which some of the models or measurements deviate from the others. For clear skies the relative agreement between the 16 models depends strongly on solar zenith angle (SZA) and wavelength as well as on the input parameters used, like the extraterrestrial (ET) solar flux and the absorption cross sections. The majority of the models (11) agreed to within about ±6% for solar zenith angles smaller than ˜60°. The agreement among the measured spectra depends on the optical characteristics of the instruments (e.g., slit function, stray light rejection, and sensitivity). After transforming the measurements to a common spectral resolution, two of the three participating spectroradiometers agree to within ˜10% for wavelengths longer than 310 nm and at all solar zenith angles, while their differences increase when moving to shorter wavelengths. Most models agree well with the measurements (both downwelling actinic flux and global irradiance), especially at local noon, where the agreement is within a few percent. A few models exhibit significant deviations with respect either to wavelength or to solar zenith angle. Models that use the Atmospheric Laboratory for Applications and Science 3 (ATLAS-3) solar flux agree better with the measured spectra, suggesting that ATLAS-3 is probably more appropriate for radiative transfer modeling in the ultraviolet.

  2. Soft defect printability: correlation to optical flux-area measurements

    NASA Astrophysics Data System (ADS)

    Taylor, Darren; Fiekowsky, Peter

    2001-01-01

    Soft defects on photomasks have, historically, been difficult to measure, and predict how the measured size of a soft defect will correlate to what prints, if at all. Over the past few years KLA-Tencor STARlight surface inspection has become the inspection of choice for soft defects. Though the capture rate of this tool is exceptional, the defect sizing capability has lacked in accuracy. Customer specifications have traditionally been built around defect size and transmission. If a given defect cannot be accurately sized then it cannot be accurately dispositioned. In this study we are attempting to show a correlation between the AVI defect measurement tool sizing and what actually prints on the wafer. We will show defect sizing both from the KLA-Tencor STARlight and pattern tools, the AVI tool, AIMS and VSS printability data.

  3. Long-term measurements of CO2 flux and evapotranspiration in a Chihuahuan desert grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We measured CO2 and evapotranspiration (ET) fluxes above a Chihuahuan desert grassland from 1996 through 2001. Averaged across six years, this ecosystem was a source (positive flux)of CO2 in every month. Over that period, sustained periods of carbon uptake (negative flux)were rare. Averaged across a...

  4. MEASURED AND PREDICTED FLUXES OF BIOGENIC SILICA IN LAKE MICHIGAN

    EPA Science Inventory

    Diatom production in the offshore waters of Lake Michigan is limited by silica supplies in late summer and can be predicted from the seasonal disappearance of silica from the trophogenic zone. Biogenic silica fluxes obtained from sediment trap collections were compared with fluxe...

  5. Influence of thermal and resonance neutron on fast neutron flux measurement by 239Pu fission chamber

    NASA Astrophysics Data System (ADS)

    Zeng, Li-Na; Wang, Qiang; Song, Ling-Li; Zheng, Chun

    2015-01-01

    The 239Pu fission chambers are widely used to measure fission spectrum neutron flux due to a flat response to fast neutrons. However, in the meantime the resonance and thermal neutrons can cause a significant influence on the measurement if they are moderated, which could be eliminated by using 10B and Cd covers. At a column enriched uranium fast neutron critical assembly, the fission reaction rates of 239Pu are measured as 1.791×10-16, 2.350×10-16 and 1.385×10-15 per second for 15 mm thick 10B cover, 0.5 mm thick Cd cover, and no cover respectively, while the fission reaction rate of 239Pu is rapidly increased to 2.569×10-14 for a 20 mm thick polythene covering fission chamber. The average 239Pu fission cross-section of thermal and resonance neutrons is calculated to be 500 b and 24.95 b with the assumption of 1/v and 1/E spectra respectively, then thermal, resonance and fast neutron flux are achieved to be 2.30×106, 2.24×106 and 1.04×108 cm-2·s-1.

  6. Compact Instruments Measure Helium-Leak Rates

    NASA Technical Reports Server (NTRS)

    Stout, Stephen; Immer, Christopher

    2003-01-01

    Compact, lightweight instruments have been developed for measuring small flows of helium and/or detecting helium leaks in solenoid valves when the valves are nominally closed. These instruments do not impede the flows when the valves are nominally open. They can be integrated into newly fabricated valves or retrofitted to previously fabricated valves. Each instrument includes an upstream and a downstream thermistor separated by a heater, plus associated analog and digital heater-control, signal- conditioning, and data-processing circuits. The thermistors and heater are off-the-shelf surface mount components mounted on a circuit board in the flow path. The operation of the instrument is based on a well-established thermal mass-flow-measurement technique: Convection by the flow that one seeks to measure gives rise to transfer of heat from the heater to the downstream thermistor. The temperature difference measured by the thermistors is directly related to the rate of flow. The calibration curve from temperature gradient to helium flow is closely approximated via fifth-order polynomial. A microprocessor that is part of the electronic circuitry implements the calibration curve to compute the flow rate from the thermistor readings.

  7. Continuous monitoring of fluid flow rate and contemporaneous biogeochemical fluxes in the sub-seafloor; the Mosquito flux meter

    NASA Astrophysics Data System (ADS)

    Culling, D. P.; Solomon, E. A.; Kastner, M.; Berg, R. D.

    2013-12-01

    Fluid flow through marine sediments and oceanic crust impacts seawater chemistry as well as diagenetic, thermal, seismic, and magmatic processes at plate boundaries, creates ore and gas hydrate deposits at and below seafloor, and establishes and maintains deep microbial ecosystems. However, steady-state fluid flow rates, as well as the temporal and spatial variability of fluid flow and composition are poorly constrained in many marine environments. A new, low-cost instrument deployable by ROV or submersible, named the Mosquito, was recently developed to provide continuous, long-term and campaign style monitoring of fluid flow rate and contemporaneous solute fluxes at multiple depths below the sea floor. The Mosquito consists of a frame that houses several osmotic pumps (Osmo-Samplers [OS]) connected to coils of tubing that terminate with an attachment to long thin titanium (Ti) needles, all of which are mounted to a release plate. The OS's consist of an acrylic housing which contains a brine chamber (BC) and a distilled water chamber (DWC) separated by semi permeable membranes. The osmotic gradient between the chambers drives the flow of distilled water into the BC. The DWC is connected to the Teflon tubing coil and a Ti needle, both of which are also filled with distilled water, thus the OS pulls fluid from the base of the needle through the tubing coil. One central Ti needle is attached to a custom-made tracer injection assembly, filled with a known volume of tracer, which is triggered, injecting a point source in the sediment. On a typical Mosquito, 4 needles are mounted vertically at varying depths with respect to the tracer injection needle, and 4 needles are mounted at equal depth but set at variable horizontal distances away from the tracer injection. Once the Mosquito has been placed on the seafloor, the release plate is manually triggered pushing the Ti needles into the sediment, then the tracer injection assembly is actuated. As the tracer is advected, the OS's monitor the tracer concentrations through time, which are modeled for fluid flow rates. Simultaneously the Mosquito provides a continuous record of fluid, at high-resolution, for chemical analysis. The fluid chemistry time series, in combination with the fluid flow rate record, provide a serial record of biogeochemical fluxes. The robust nature and adaptable layout of the Mosquito allows for a wide variety of deployment settings from mid ocean ridges to the continental shelf as well as lacustrine environments. Preliminary results are being presented for three major deployments of the new flow meters; a 5-day campaign style deployment at Hydrate Ridge offshore of Oregon, a recently recovered 2-year deployment at Hydrate Ridge, and two transects of Mosquito deployments spanning from the deformation front to the upper slope at the Cascadia subduction zone off the coast of Washington.

  8. Wide Range Neutron Flux Measuring Channel for Aerospace Application

    SciTech Connect

    Cibils, R. M.; Busto, A.; Gonella, J. L.; Martinez, R.; Chielens, A. J.; Otero, J. M.; Nunez, M.; Tropea, S. E.

    2008-01-21

    The use of classical techniques for neutron flux measurements in nuclear reactors involves the switching between several detection chains as the power grows up to 10 decades. In space applications where mass and size constraints are of key significance, such volume of hardware represents a clear disadvantage. Instead of requiring different instruments for each reactor operating range (start-up, ramping-up, and nominal power), a single instrument chain should be desirable. A Wide Range Neutron Detector (WRND) system, combining a classic pulse Counting Channel with a Campbell's theorem based Fluctuation Channel can be implemented for the monitoring and control of a space nuclear reactor. Such an instrument will allow for a reduction in the complexity of space-based nuclear instrumentation and control systems. In this presentation we will discuss the criteria and tradeoffs involved in the development of such a system. We will focus particularly on the characteristics of the System On Chip (SOC) and the DSP board used to implement this instrument.

  9. Bayesian calibration of reactor neutron flux spectrum using activation detectors measurements: Application to CALIBAN reactor

    SciTech Connect

    Cartier, J.; Casoli, P.; Chappert, F.

    2013-07-01

    In this paper, we present calibration methods in order to estimate reactor neutron flux spectrum and its uncertainties by using integral activation measurements. These techniques are performed using Bayesian and MCMC framework. These methods are applied to integral activation experiments in the cavity of the CALIBAN reactor. We estimate the neutron flux and its related uncertainties. The originality of this work is that these uncertainties take into account measurements uncertainties, cross-sections uncertainties and model error. In particular, our results give a very good approximation of the total flux and indicate that neutron flux from MCNP simulation for energies above about 5 MeV seems to overestimate the 'real flux'. (authors)

  10. Measurement of the {sup 8}B solar neutrino flux with the KamLAND liquid scintillator detector

    SciTech Connect

    Abe, S.; Furuno, K.; Gando, A.; Gando, Y.; Ichimura, K.; Ikeda, H.; Kibe, Y.; Kimura, W.; Kishimoto, Y.; Minekawa, Y.; Mitsui, T.; Morikawa, T.; Nagai, N.; Nakajima, K.; Nakamura, M.; Narita, K.; Shimizu, I.; Shimizu, Y.; Shirai, J.; Suekane, F.

    2011-09-15

    We report a measurement of the neutrino-electron elastic scattering rate from {sup 8}B solar neutrinos based on a 123 kton-day exposure of KamLAND. The background-subtracted electron recoil rate, above a 5.5-MeV analysis threshold is 1.49 {+-} 0.14(stat) {+-} 0.17(syst) events per kton-day. Interpreted as due to a pure electron flavor flux with a {sup 8}B neutrino spectrum, this corresponds to a spectrum integrated flux of 2.77 {+-} 0.26(stat) {+-} 0.32(syst) x10{sup 6} cm{sup -2}s{sup -1}. The analysis threshold is driven by {sup 208}Tl present in the liquid scintillator, and the main source of systematic uncertainty is due to background from cosmogenic {sup 11}Be. The measured rate is consistent with existing measurements and with standard solar model predictions which include matter-enhanced neutrino oscillation.

  11. Decoupled cantilever arms for highly versatile and sensitive temperature and heat flux measurements

    E-print Network

    Burg, Brian R.

    Microfabricated cantilever beams have been used in microelectromechanical systems for a variety of sensor and actuator applications. Bimorph cantilevers accurately measure temperature change and heat flux with resolutions ...

  12. Estimation of hydrocarbon biodegradation rates in gasoline-contaminated sediment from measured respiration rates

    USGS Publications Warehouse

    Baker, R.J.; Baehr, A.L.; Lahvis, M.A.

    2000-01-01

    An open microcosm method for quantifying microbial respiration and estimating biodegradation rates of hydrocarbons in gasoline-contaminated sediment samples has been developed and validated. Stainless-steel bioreactors are filled with soil or sediment samples, and the vapor-phase composition (concentrations of oxygen (O2), nitrogen (N2), carbon dioxide (CO2), and selected hydrocarbons) is monitored over time. Replacement gas is added as the vapor sample is taken, and selection of the replacement gas composition facilitates real-time decision-making regarding environmental conditions within the bioreactor. This capability allows for maintenance of field conditions over time, which is not possible in closed microcosms. Reaction rates of CO2 and O2 are calculated from the vapor-phase composition time series. Rates of hydrocarbon biodegradation are either measured directly from the hydrocarbon mass balance, or estimated from CO2 and O2 reaction rates and assumed reaction stoichiometries. Open microcosm experiments using sediments spiked with toluene and p-xylene were conducted to validate the stoichiometric assumptions. Respiration rates calculated from O2 consumption and from CO2 production provide estimates of toluene and p- xylene degradation rates within about ??50% of measured values when complete mineralization stoichiometry is assumed. Measured values ranged from 851.1 to 965.1 g m-3 year-1 for toluene, and 407.2-942.3 g m-3 year-1 for p- xylene. Contaminated sediment samples from a gasoline-spill site were used in a second set of microcosm experiments. Here, reaction rates of O2 and CO2 were measured and used to estimate hydrocarbon respiration rates. Total hydrocarbon reaction rates ranged from 49.0 g m-3 year-1 in uncontaminated (background) to 1040.4 g m-3 year-1 for highly contaminated sediment, based on CO2 production data. These rate estimates were similar to those obtained independently from in situ CO2 vertical gradient and flux determinations at the field site. In these experiments, aerobic conditions were maintained in the microcosms by using air as the replacement gas, thus preserving the ambient aerobic environment of the subsurface near the capillary zone. This would not be possible with closed microcosms.

  13. Solids flow rate measurement in dense slurries

    SciTech Connect

    Porges, K.G.; Doss, E.D.

    1993-09-01

    Accurate and rapid flow rate measurement of solids in dense slurries remains an unsolved technical problem, with important industrial applications in chemical processing plants and long-distance solids conveyance. In a hostile two-phase medium, such a measurement calls for two independent parameter determinations, both by non-intrusive means. Typically, dense slurries tend to flow in laminar, non-Newtonian mode, eliminating most conventional means that usually rely on calibration (which becomes more difficult and costly for high pressure and temperature media). These issues are reviewed, and specific solutions are recommended in this report. Detailed calculations that lead to improved measuring device designs are presented for both bulk density and average velocity measurements. Cross-correlation, chosen here for the latter task, has long been too inaccurate for practical applications. The cause and the cure of this deficiency are discussed using theory-supported modeling. Fluid Mechanics are used to develop the velocity profiles of laminar non-Newtonian flow in a rectangular duct. This geometry uniquely allows the design of highly accurate `capacitive` devices and also lends itself to gamma transmission densitometry on an absolute basis. An absolute readout, though of less accuracy, is also available from a capacitive densitometer and a pair of capacitive sensors yields signals suitable for cross-correlation velocity measurement.

  14. Mild solutions to a measure-valued mass evolution problem with flux boundary conditions

    NASA Astrophysics Data System (ADS)

    Evers, Joep H. M.; Hille, Sander C.; Muntean, Adrian

    2015-08-01

    We investigate the well-posedness and approximation of mild solutions to a class of linear transport equations on the unit interval [ 0, 1 ] endowed with a linear discontinuous production term, formulated in the space M ([ 0, 1 ]) of finite Borel measures. Our working technique includes a detailed boundary layer analysis in terms of a semigroup representation of solutions in spaces of measures able to cope with the passage to the singular limit where thickness of the layer vanishes. We obtain not only a suitable concept of solutions to the chosen measure-valued evolution problem, but also derive convergence rates for the approximation procedure and get insight in the structure of flux boundary conditions for the limit problem.

  15. Comparison of eddy covariance and modified Bowen ratio methods for measuring gas fluxes and implications for measuring fluxes of persistent organic pollutants

    NASA Astrophysics Data System (ADS)

    Bolinius, D. J.; Jahnke, A.; MacLeod, M.

    2015-11-01

    Semi-volatile persistent organic pollutants (POPs) cycle between the atmosphere and terrestrial surfaces, however measuring fluxes of POPs between the atmosphere and other media is challenging. Sampling times of hours to days are required to accurately measure trace concentrations of POPs in the atmosphere, which rules out the use of eddy covariance techniques that are used to measure gas fluxes of major air pollutants. An alternative, the modified Bowen ratio (MBR) method, has been used instead. In this study we used data from FLUXNET for CO2 and water vapor (H2O) to compare fluxes measured by eddy covariance to fluxes measured with the MBR method using vertical concentration gradients in air derived from averaged data that simulates the long sampling times typically required to measure POPs. When concentration gradients are strong and fluxes are unidirectional, the MBR method and the eddy covariance method agree within a factor of 3 for CO2, and within a factor of 10 for H2O. To remain within the range of applicability of the MBR method field, studies should be carried out under conditions such that the direction of net flux does not change during the sampling period. If that condition is met then the performance of the MBR method is not strongly affected by the length of sample duration nor the use of a fixed value for the transfer coefficient.

  16. Mass Flux Measurements of Arsenic in Groundwater (Battelle Conference)

    EPA Science Inventory

    Concentration trends of arsenic are typically used to evaluate the performance of remediation efforts designed to mitigate arsenic contamination in groundwater. A complementary approach would be to track changes in mass flux of the contaminant through the subsurface, for exampl...

  17. The flux measure of influence in engineering networks

    E-print Network

    Schwing, Kyle Michael

    2009-01-01

    The objective of this project is to characterize the influence of individual nodes in complex networks. The flux metric developed here achieves this goal by considering the difference between the weighted outdegree and ...

  18. Chemical weathering rates of a soil chronosequence on granitic alluvium: III. Hydrochemical evolution and contemporary solute fluxes and rates

    USGS Publications Warehouse

    White, A.F.; Schulz, M.S.; Vivit, D.V.; Blum, A.E.; Stonestrom, D.A.; Harden, J.W.

    2005-01-01

    Although long-term changes in solid-state compositions of soil chronosequences have been extensively investigated, this study presents the first detailed description of the concurrent hydrochemical evolution and contemporary weathering rates in such sequences. The most direct linkage between weathering and hydrology over 3 million years of soil development in the Merced chronosequence in Central California relates decreasing permeability and increasing hydrologic heterogeneity to the development of secondary argillic horizons and silica duripans. In a highly permeable, younger soil (40 kyr old), pore water solutes reflect seasonal to decadal-scale variations in rainfall and evapotranspiration (ET). This climate signal is strongly damped in less permeable older soils (250 to 600 kyr old) where solutes increasingly reflect weathering inputs modified by heterogeneous flow. Elemental balances in the soils are described in terms of solid state, exchange and pore water reservoirs and input/output fluxes from precipitation, ET, biomass, solute discharge and weathering. Solute mineral nutrients are strongly dependent on biomass variations as evidenced by an apparent negative K weathering flux reflecting aggradation by grassland plants. The ratios of solute Na to other base cations progressively increase with soil age. Discharge fluxes of Na and Si, when integrated over geologic time, are comparable to solid-state mass losses in the soils, implying similar past weathering conditions. Similarities in solute and sorbed Ca/Mg ratios reflect short-term equilibrium with the exchange reservoir. Long-term consistency in solute ratios, when contrasted against progressive decreases in solid-state Ca/Mg, requires an additional Ca source, probably from dry deposition. Amorphous silica precipitates from thermodynamically-saturated pore waters during periods of high evapotranspiration and result in the formation of duripans in the oldest soils. The degree of feldspar and secondary gibbsite and kaolinite saturation varies both spatially and temporally due to the seasonality of plant-respired CO2 and a decrease in organically complexed Al. In deeper pore waters, K-feldspar is in equilibrium and plagioclase is about an order of magnitude undersaturated. Hydrologic heterogeneity produces a range of weathering gradients that are constrained by solute distributions and matrix and macropore flow regimes. Plagioclase weathering rates, based on precipitation-corrected Na gradients, vary between 3 and 7 ?? 10-16 mol m-2 s-1. These rates are similar to previously determined solid-state rates but are several orders of magnitude slower than for experimental plagioclase dissolution indicating strong inhibitions to natural weathering, partly due to near-equilibrium weathering reactions. Copyright ?? 2005 Elsevier Ltd.

  19. Comparison of measured and modeled radiation, heat and water vapor fluxes: FIFE pilot study

    NASA Technical Reports Server (NTRS)

    Blad, Blaine L.; Hubbard, Kenneth G.; Verma, Shashi B.; Starks, Patrick; Norman, John M.; Walter-Shea, Elizabeth

    1987-01-01

    The feasibility of using radio frequency receivers to collect data from automated weather stations to model fluxes of latent heat, sensible heat, and radiation using routine weather data collected by automated weather stations was tested and the estimated fluxes were compared with fluxes measured over wheat. The model Cupid was used to model the fluxes. Two or more automated weather stations, interrogated by radio frequency and other means, were utilized to examine some of the climatic variability of the First ISLSCP (International Satellite Land-Surface Climatology Project) Field Experiment (FIFE) site, to measure and model reflected and emitted radiation streams from various locations at the site and to compare modeled latent and sensible heat fluxes with measured values. Some bidirectional reflected and emitted radiation data were collected from 23 locations throughout the FIFE site. Analysis of these data along with analysis of the measured sensible and latent heat fluxes is just beginning.

  20. Measurements of NO(x) and NO(y) concentrations and fluxes over Arctic tundra

    SciTech Connect

    Bakwin, P.S.; Wofsy, S.C.; Fan, Songmiao; Fitzjarrald, D.R. New York State Univ., Albany )

    1992-10-01

    Measurements of the atmospheric concentrations of NO, NO[sub 2], total NO(y), and O[sub 3] were made during the NASA Arctic Boundary Layer Expedition (ABLE 3A) at a remote location in a tundra bog ecosystem in southeastern Alaska during the growing season (July-August 1988). Concentrations of NO(x) and NO(y) were found to be very low compared to other remote continental sites, indicating that anthropogenic influences were small at this site during this time of year. The NO(y) emission rate from the soil were 0.13 +/- 0.05 x 10 exp 9 molecules/sq cm/s. Direct measurements of the flux of total NO(y) were made for the first time, indicating downward flux of NO(y) at all times of day, with maximum deposition of 2.5 +/- 0.9 x 10 exp 9 molecules/sq cm/s in the afternoon. Deposition of HNO3 appears to dominate the atmosphere/surface exchange of NO(y). The mean dry deposition rate of NO(y) to the tundra was 1.8 +/- 1.0 x 10 exp 9 molecules/sq cm/s. 58 refs.

  1. Measurements of NO(x) and NO(y) concentrations and fluxes over Arctic tundra

    NASA Technical Reports Server (NTRS)

    Bakwin, Peter S.; Wofsy, Steven C.; Fan, Song-Miao; Fitzjarrald, David R.

    1992-01-01

    Measurements of the atmospheric concentrations of NO, NO2, total NO(y), and O3 were made during the NASA Arctic Boundary Layer Expedition (ABLE 3A) at a remote location in a tundra bog ecosystem in southeastern Alaska during the growing season (July-August 1988). Concentrations of NO(x) and NO(y) were found to be very low compared to other remote continental sites, indicating that anthropogenic influences were small at this site during this time of year. The NO(y) emission rate from the soil were 0.13 +/- 0.05 x 10 exp 9 molecules/sq cm/s. Direct measurements of the flux of total NO(y) were made for the first time, indicating downward flux of NO(y) at all times of day, with maximum deposition of 2.5 +/- 0.9 x 10 exp 9 molecules/sq cm/s in the afternoon. Deposition of HNO3 appears to dominate the atmosphere/surface exchange of NO(y). The mean dry deposition rate of NO(y) to the tundra was 1.8 +/- 1.0 x 10 exp 9 molecules/sq cm/s.

  2. Measuring Mars Sand Flux Seasonality from a Time Series of Hirise Images

    NASA Astrophysics Data System (ADS)

    Ayoub, F.; Avouac, J.; Bridges, N. T.; Leprince, S.; Lucas, A.

    2012-12-01

    The volumetric transport rate of sand, or flux, is a fundamental quantity that relates to the rate of landscape evolution through surface deposition and erosion. Measuring this quantity on Mars is particularly relevant as wind is the dominant geomorphic agent active at present on the planet. Measuring sand flux on Mars has been made possible thanks to the availability of times series of high resolution images acquired by the High Resolution Imaging Science Experiment (HiRISE) and precise image registration and correlation methods which permits the quantification of movement to sub-pixel precision. In this study, focused on the Nili Patera dune field, we first measured the migration rate of sand ripples and dune lee fronts over 105 days, using a pair of HiRISE images acquired in 2007, correlated and co-registered with COSI-Corr. From these measurements and the estimation of the ripple and dune heights, we derived the reptation and saltation sand fluxes. We next applied the same methodology to a time-series of eight images acquired in 2010-2011 covering one Mars year. Pairs of sequential images, were processed with COSI-Corr yielding a times series of 8 displacement maps. A Principal Component Analysis (PCA) was applied to the time-series to quantify more robustly the time evolution of the signal and filter out noise, in particular due to misalignment of CCDs. Using the first two components, which account for 84% of the variance, the seasonal variation of the ripple migration rate was estimated. We clearly observe continuously active migration throughout the year with a strong seasonal quasi-sinusoidal variation which peaks at perihelion. Ripple displacement orientation is stable in time, toward ~N115°E. The wind direction is thus relatively constant in this area, a finding consistent with the barchan morphology and orientation of the dunes. The dataset require that sand moving winds must occur daily to weekly throughout the year. The amplitude of the seasonal variation is about twice the mean signal.

  3. Galileo Probe Measurements of Thermal and Solar Radiation Fluxes in the Jovian Atmosphere

    NASA Technical Reports Server (NTRS)

    Sromovsky, L. A.; Collard, A. D.; Fry, P. M.; Orton, G. S.; Lemmon, M. T.; Tomasko, M. G.; Freedman, R. S.

    1998-01-01

    The Galileo probe net flux radiometer (NFR) measured radiation fluxes in Jupiter's atmosphere from about 0.44 to 14 bars, using five spectral channels to separate solar and thermal components. Onboard calibration results confirm that the NFR responded to radiation approximately as expected. NFR channels also responded to a superimposed thermal perturbation, which can be approximately removed using blind channel measurements and physical constraints. Evidence for the expected NH3 cloud was seen in the spectral character of spin-induced modulations of the direct solar beam signals. These results are consistent with an overlying cloud of small NH3 ice particles (0.5-0.75 microns in radius) of optical depth 1.5-2 at 0.5 microns. Such a cloud would have so little effect on thermal fluxes that NFR thermal channels provide no additional constraints on its properties. However, evidence for heating near 0.45 bar in the NFR thermal channels would seem to require either an additional opacity source beyond this small-particle cloud, implying a heterogeneous-cloud structure to avoid conflicts with solar modulation results, or a change in temperature lapse rate just above the probe measurements. The large thermal flux levels imply water vapor mixing ratios that are only 6% of solar at 10 bars, but possibly increasing with depth, and significantly subsaturated ammonia at pressures less than 3 bars. If deep NH3 mixing ratios at the probe entry site are 3-4 times ground-based inferences, as suggested by probe radio signal attenuation, then only half as much water is needed to match NFR observations. No evidence of a water cloud was seen near the 5-bar level. The 5 microns thermal channel detected the presumed NH4SH cloud base near 1.35 bars. Effects of this cloud were also seen in the solar channel upflux measurements but not in the solar net fluxes, implying that the cloud is a conservative scatterer of sunlight. The minor thermal signature of this cloud is compatible with particle radii near 3 microns, but it cannot rule out smaller particles. Deeper than about 3 bars, solar channels indicate unexpectedly large absorption of sunlight at wavelengths longer than 0.6 microns, which might be due to unaccounted-for absorption by NH3 between 0.65 and 1.5 microns.

  4. Galileo Probe Measurements of Thermal and Solar Radiation Fluxes in the Jovian Atmosphere

    NASA Technical Reports Server (NTRS)

    Sromovsky, L. A.; Collard, A. D.; Fry, P. M.; Orton, G. S.; Lemmon, M. T.; Tomasko, M. G.; Freedman, R. S.

    1998-01-01

    The Galileo probe net flux radiometer (NFR) measured radiation fluxes in Jupiter's atmosphere from about 0.44 to 14 bars, using five spectral channels to separate solar and thermal components. Onboard calibration results confirm that the NFR responded to radiation approximately as expected. NFR channels also responded to a superimposed thermal perturbation, which can be approximately removed using blind channel measurements and physical constraints. Evidence for the expected NH3 cloud was seen in the spectral character of spin-induced modulations of the direct solar beam signals. These results are consistent with an overlying cloud of small NH3 ice particles (0.5-0.75 microns in radius) of optical depth 1.5-2 at 0.5 microns. Such a cloud would have so little effect on thermal fluxes that NFR thermal channels provide no additional constraints on its properties. However, evidence for heating near 0.45 bar in the NFR thermal channels would seem to require either an additional opacity source beyond this small-particle cloud, implying a heterogeneous cloud structure to avoid conflicts with solar modulation results, or a change in temperature lapse rate just above the probe measurements. The large thermal flux levels imply water vapor mixing ratios that are only 6% of solar at 10 bars, but possibly increasing with depth, and significantly subsaturated ammonia at pressures less than 3 bars. If deep NH3 mixing ratios at the probe entry site are 3-4 times ground-based inferences, as suggested by probe radio signal attenuation, then only half as much water is needed to match NFR observations. No evidence of a water cloud was seen near the 5-bar level. The 5-microns thermal channel detected the presumed NH4SH cloud base near 1.35 bars. Effects of this cloud were also seen in the solar channel upflux measurements but not in the solar net fluxes, implying that the cloud is a conservative scatterer of sunlight. The minor thermal signature of this cloud is compatible with particle radii near 3 gm, but it cannot rule out smaller particles. Deeper than about 3 bars, solar channels indicate unexpectedly large absorption of sunlight at wavelengths longer than 0.6 microns, which might be due to unaccounted-for absorption by NH3 between 0.65 and 1.5 microns.

  5. Direct Measurements of Reconnection Rate Attenuation by Plasmasphere Plumes

    NASA Astrophysics Data System (ADS)

    Sanchez, E. R.; Takahashi, K.

    2013-12-01

    It is widely hypothesized that mass loading of the magnetosphere (the process whereby the average mass density of the magnetosphere increases from its nominal value) significantly impacts solar wind-magnetosphere coupling and circulation within the magnetosphere. One important way in which mass loading can affect the magnetosphere occurs when enhanced convection after a lull in geomagnetic activity brings super-dense plasma from the plasmasphere (the so-called plasmsphere plume) into the dayside reconnection site. We measured the magnetic flux across the dayside polar cap boundary (a proxy of the dayside magnetic field reconnection rate) and tracked the sunward migration of the plasma plume for three storms that occurred after long intervals of quiet conditions. Significant intermittent reduction in the dayside reconnection potential (approximately 66% in the most pronounced case) was observed in the hours following the onset of negative IMF Bz condition, in agreement with the hypothesis that super-dense magnetospheric plasma convected into the dayside magnetopause inhibits reconnection.

  6. Evaluation of the flux chamber method for measuring volatile organic emissions from surface impoundments. Final report

    SciTech Connect

    Gholson, A.R.; Albritton, J.R.; Jayanty, R.K.M.

    1989-01-01

    The research deals with the validation of the flux-chamber method for measuring volatile organic emissions from liquid surfaces in treatment, storage, and disposal facilities (TSDF). A simulated surface impoundment was constructed so that method precision and accuracy could be determined under controlled conditions. Operational parameters studied included sweep flow rate, sampling time, sweep flow position and chamber depth in the liquid. Environmental factors included wind velocity, solar intensity, emission rate, and chemical composition. Field testing was performed at two TSDFs, a waste-water treatment facility at a chemical plant, and a waste stabilization facility. The results showed that good precision can be obtained under a variety of conditions, but that the method suffers from a negative bias that varies with the compound under analysis.

  7. Eddy covariance flux measurements of gaseous elemental mercury using cavity ring-down spectroscopy.

    PubMed

    Pierce, Ashley M; Moore, Christopher W; Wohlfahrt, Georg; Hörtnagl, Lukas; Kljun, Natascha; Obrist, Daniel

    2015-02-01

    A newly developed pulsed cavity ring-down spectroscopy (CRDS) system for measuring atmospheric gaseous elemental mercury (GEM) concentrations at high temporal resolution (25 Hz) was used to successfully conduct the first eddy covariance (EC) flux measurements of GEM. GEM is the main gaseous atmospheric form, and quantification of bidirectional exchange between the Earth's surface and the atmosphere is important because gas exchange is important on a global scale. For example, surface GEM emissions from natural sources, legacy emissions, and re-emission of previously deposited anthropogenic pollution may exceed direct primary anthropogenic emissions. Using the EC technique for flux measurements requires subsecond measurements, which so far has not been feasible because of the slow time response of available instrumentation. The CRDS system measured GEM fluxes, which were compared to fluxes measured with the modified Bowen ratio (MBR) and a dynamic flux chamber (DFC). Measurements took place near Reno, NV, in September and October 2012 encompassing natural, low-mercury (Hg) background soils and Hg-enriched soils. During nine days of measurements with deployment of Hg-enriched soil in boxes within 60 m upwind of the EC tower, the covariance of GEM concentration and vertical wind speed was measured, showing that EC fluxes over an Hg-enriched area were detectable. During three separate days of flux measurements over background soils (without Hg-enriched soils), no covariance was detected, indicating fluxes below the detection limit. When fluxes were measurable, they strongly correlated with wind direction; the highest fluxes occurred when winds originated from the Hg-enriched area. Comparisons among the three methods showed good agreement in direction (e.g., emission or deposition) and magnitude, especially when measured fluxes originated within the Hg-enriched soil area. EC fluxes averaged 849 ng m(-2) h(-1), compared to DFC fluxes of 1105 ng m(-2) h(-1) and MBR fluxes of 1309 ng m(-2) h(-1). This study demonstrated that a CRDS system can be used to measure GEM fluxes over Hg-enriched areas, with a conservative detection limit estimate of 32 ng m(-2) h(-1). PMID:25608027

  8. Solid He: Progress, Status, and Outlook for Mass Flux Measurements

    NASA Astrophysics Data System (ADS)

    Hallock, R. B.

    2015-07-01

    After a brief introduction, what is provided there is brief summary of work with solid He done at the University of Massachusetts Amherst and an outlook for future work. What is presented here is based on a presentation made at the Quantum Gases Fluids and Solids Workshop in Sao Paulo, Brazil in August of 2014. Our work with solid He is aimed at the question: Can a sample cell filled with solid He support a mass flux through the cell? The answer, as will be shown here, is yes. Evidence for this from several types of experiments will be reviewed. There will be an emphasis on more recent work, work that explores how the flux observed depends on temperature and on the He impurity level. The behavior observed suggests that solid He may be an example of a material that demonstrates Bosonic Luttinger liquid behavior. The normalized He flux has a universal temperature dependence. The presence of He at different impurity levels shows that the He blocks the flux at a characteristic temperature. The behavior appears to be consistent with the cores of dislocations as the entity that carries the flux, but it is clear that more work needs to be done to fully understand solid He.

  9. Measuring radon flux across active faults: Relevance of excavating and possibility of satellite discharges

    E-print Network

    Klinger, Yann

    Measuring radon flux across active faults: Relevance of excavating and possibility of satellite January 2010 Keywords: Exhalation flux Radon-222 Carbon dioxide Faults Earthquake Trench a b s t r a c on the Xidatan segment of the Kunlun Fault, Qinghai Province, China, using measurement of the radon- 222

  10. Water flux and drainage from soil measured with automated passive capillary wick samplers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Various soil water samplers are used to monitor measure and estimate drainage water, fluxes and solute transport in the soil vadose zone. Passive capillary samplers (PCAPs) have shown potential to provide better measurements and estimates of soil water drainage and fluxes than other lysimeters.Twelv...

  11. MERCURY FLUX MEASUREMENTS OVER AIR AND WATER IN KEJIMKUJIK NATIONAL PARK, NOVA SCOTIA

    E-print Network

    Folkins, Ian

    MERCURY FLUX MEASUREMENTS OVER AIR AND WATER IN KEJIMKUJIK NATIONAL PARK, NOVA SCOTIA F. S. BOUDALA. Mercury flux measurements were conducted at two lakes and three soil sites in Kejimkujik National Park, located in the eastern Canadian province of Nova Scotia. One of the lakes had high levels of both mercury

  12. LEAF, BRANCH, STAND & LANDSCAPE SCALE MEASUREMENTS OF VOLATILE ORGANIC COMPOUND FLUXES FROM U.S. WOODLANDS

    EPA Science Inventory

    Natural volatile organic compounds (VOC) fluxes were measured in three U.S. woodlands in summer 1993. Fluxes from individual leaves and branches were estimated with enclosure techniques and used to initialize and evaluate VOC emission model estimates. Ambient measurements were us...

  13. A comparison of methods for deriving solute flux rates using long-term data from streams in the mirror lake watershed

    USGS Publications Warehouse

    Bukaveckas, P.A.; Likens, G.E.; Winter, T.C.; Buso, D.C.

    1998-01-01

    Calculation of chemical flux rates for streams requires integration of continuous measurements of discharge with discrete measurements of solute concentrations. We compared two commonly used methods for interpolating chemistry data (time-averaging and flow-weighting) to determine whether discrepancies between the two methods were large relative to other sources of error in estimating flux rates. Flux rates of dissolved Si and SO42- were calculated from 10 years of data (1981-1990) for the NW inlet and Outlet of Mirror Lake and for a 40-day period (March 22 to April 30, 1993) during which we augmented our routine (weekly) chemical monitoring with collection of daily samples. The time-averaging method yielded higher estimates of solute flux during high-flow periods if no chemistry samples were collected corresponding to peak discharge. Concentration-discharge relationships should be used to interpolate stream chemistry during changing flow conditions if chemical changes are large. Caution should be used in choosing the appropriate time-scale over which data are pooled to derive the concentration-discharge regressions because the model parameters (slope and intercept) were found to be sensitive to seasonal and inter-annual variation. Both methods approximated solute flux to within 2-10% for a range of solutes that were monitored during the intensive sampling period. Our results suggest that errors arising from interpolation of stream chemistry data are small compared with other sources of error in developing watershed mass balances.

  14. Arrangement Analysis of Leaves Optimized on Photon Flux Density or Photosynthetic Rate

    NASA Astrophysics Data System (ADS)

    Obara, Shin'ya; Tanno, Itaru

    By clarifying a plant evolutive process, useful information may be obtained on engineering. Consequently, an analysis algorithm that investigates the optimal arrangement of plant leaves was developed. In the developed algorithm, the Monte Carlo method is introduced and sunlight is simulated. Moreover, the arrangement optimization of leaves is analyzed using a Genetic Algorithm (GA). The number of light quanta (photon flux density) that reaches leaves, or the average photosynthetic rate of the same was set as the objective function, and leaf models of a dogwood and a ginkgo tree were analyzed. The number of leaf models was set between two to four, and the position of the leaf was expressed in terms of the angle of direction, elevation angle, rotation angle, and the representative length of the branch of a leaf. The chromosome model introduced into GA consists of information concerning the position of the leaf. Based on the analysis results, the characteristics of the leaf of an actual plant could be simulated by ensuring the algorithm had multiple constrained conditions. The optimal arrangement of leaves differs in maximization of the photon flux density, and that of the average value of a photosynthetic rate. Furthermore, the leaf form affecting the optimal arrangement of leave and also having a significant influence also on a photosynthetic rate was shown.

  15. Measurements and Phenomenological Modeling of Magnetic FluxBuildup in Spheromak Plasmas

    SciTech Connect

    Romero-Talamas, C A; Hooper, E B; Jayakumar, R; McLean, H S; Wood, R D; Moller, J M

    2007-12-14

    Internal magnetic field measurements and high-speed imaging at the Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, R. H. Bulmer, Nucl. Fusion 39, 863 (1999)] are used to study spheromak formation and field buildup. The measurements are analyzed in the context of a phenomenological model of magnetic helicity based on the topological constraint of minimum helicity in the open flux before reconnecting and linking closed flux. Two stages are analyzed: (1) the initial spheromak formation, i. e. when all flux surfaces are initially open and reconnect to form open and closed flux surfaces, and (2) the stepwise increase of closed flux when operating the gun on a new mode that can apply a train of high-current pulses to the plasma. In the first stage, large kinks in the open flux surfaces are observed in the high-speed images taken shortly after plasma breakdown, and coincide with large magnetic asymmetries recorded in a fixed insertable magnetic probe that spans the flux conserver radius. Closed flux (in the toroidal average sense) appears shortly after this. This stage is also investigated using resistive magnetohydrodynamic simulations. In the second stage, a time lag in response between open and closed flux surfaces after each current pulse is interpreted as the time for the open flux to build helicity, before transferring it through reconnection to the closed flux. Large asymmetries are seen during these events, which then relax to a slowly decaying spheromak before the next pulse.

  16. Heat flux measurement from vertical temperature profile and thermal infrared imagery in low-flux fumarolic zones

    NASA Astrophysics Data System (ADS)

    Gaudin, Damien; Finizola, Anthony; Beauducel, François; Brothelande, Elodie; Allemand, Pascal; Delacourt, Christophe; Delcher, Eric; Peltier, Aline

    2014-05-01

    Hydrothermal systems are associated to most of the dormant volcanoes. Heat is transported by steam from the hot magma body in the connected porosity and the fissures of the rock to the surface. If the flux is low enough (<500 W/m²), the steam mainly condensates in the soil close to surface, and a significant proportion of the heat is transported to the surface by conduction, producing a gradient of temperature and a thermal anomaly detectable at the surface. Detecting and monitoring these fluxes is crucial for hazard management, since it reflects the state of the magma body in depth. In order to quantify this flux two methods are considered. First, a vertical profile of temperature is measured by a series of thermocouples, and the conducted flux is estimated thanks to the Fourier law. Secondly, a more recent method uses the thermal infrared imagery to monitor the surface temperature anomaly (STA) between the studied zone and an equivalent zone not affected by the geothermal flux. The heat flux from the soil to the atmosphere is computed as the sum of (1) the radiative flux, (2) the sensible flux and (3) the residual steam flux. These two methods are complementary and have an equivalent uncertainty of approximately 20%, which would allow to track the major changes in the hydrothermal system. However, the surface and sub-surface temperatures are strongly influenced by the climate. For instance, it has been widely demonstrated that the surface temperature dramatically decreases after a rainfall. In order to estimate the reliability of the measurements, a numerical model simulating the evolution of the subsurface temperature in low flux fumarolic zone has been built. In depth, the heat can be transported either by conduction, or by the rising steam, or by condensed water. In surface, both the radiative flux and the sensible flux (convection of the atmosphere) are taken into account. This model allows to estimate the changes of temperature due to a variation of solar illumination, wind, or rainfalls. It has been successfully tested during 5 months with a permanent station built on the Ty fault on La Soufrière volcano (Guadeloupe, Lesser Antilles). Results show that the diurnal cycle has a significant influence on the temperature up to ca. 30 cm depth, hindering the use of the thermal gradient in this zone, while the STA has a negligible variation. Rain has a more dramatic influence: the surface temperature and the STA are significantly affected, even for small rains. The model shows that the drop of temperature and the affected thickness are mainly controlled by the amount of rain, while the relaxation time is primarily a function of the heat flux. These results have strong implications in the interpretation and the reliability of the temperature surveys, and could be used to correct them from the climate fluctuations.

  17. Evaluation and gap-filling of soil NO flux dataset measured at a Hungarian semi-arid grassland

    NASA Astrophysics Data System (ADS)

    Horvath, Laszlo; Hidy, Dora; Weidinger, Tamas

    2015-04-01

    An Integrated Project ÉCLAIRE (http://www.eclaire-fp7.eu/) started in 2011 among others to study the effect of climate change on air pollution impacts. One of the main measurement tasks of this project was the continuous monitoring of soil NO emission at different kinds of lands (forest, arable, grass). Among the tree grass stations Bugacpuszta (central part of Hungary between the Danube and the Tisza) was selected to monitor and report soil NO fluxes continuously for 17 months on hourly basis. The climate is semi-arid temperate continental, the mean annual temperature is 10.7 ° C, and the average annual precipitation is around 550 mm. Nitric oxide soil emission flux was measured by 2-2 parallel manual and auto dynamic chambers on hourly basis above a semi-arid, sandy grassland between August 2012 and January 2014. Each chamber was sampled for 10 minutes at a flow rate of 2 L min-1 in sequence each hour all together for 40 minutes; in the remaining 20 minutes concentration gradients were measured by a mast at two heights. Soil temperature and moisture were measured a few meters apart from the chambers. A computer controlled valve system was switched the different channels in turn. The output concentrations of nitric oxide and ozone were measured by HORIBA gas monitors through Teflon tubing. Micrometeorological measurements (energy budget components, CO2 and O3 fluxes) were also provided. The initial NO flux datasets covered 43-85% of time period depending on chambers. Measured flux data ranges within 0-6 nmol m-2 s-1. We applied a gap-filling method based on multivariable analysis (Sigma Plot) combined with maximum likelihood method using the soil temperature and moisture data. Trend of gap-filled flux dataset shows large peaks mostly in summer and early fall. When soil parameters are far from the optimum (dry, warm conditions) the fluxes are negligible. Application of manual chambers closed for longer period results in substantial positive bias in flux estimation compared to auto chambers a consequence of measurement setup, different temperature and drier soil conditions below the chamber. Mean fluxes applying permanently closed dynamic chambers are approximately three times higher compared with auto chambers, 0.176 ±0.489 nmol m-2 s-1 and 0.058 ±0.130 nmol m-2 s-1 respectively from the all measured and gap filled data.

  18. Towards a Measurement of the $e^+e^-$ Flux above 1 TeV with HAWC

    E-print Network

    BenZvi, Segev; Hampel-Arias, Zigfried

    2015-01-01

    The High-Altitude Water Cherenkov (HAWC) Observatory records the air showers produced by cosmic rays and gamma rays at a rate of about 20 kHz. While the events observed by HAWC are 99.9% hadronic cosmic rays, this background can be strongly suppressed using topological cuts that preferentially select electromagnetic air showers. Using this capability of HAWC, we can create a sample of air showers dominated by gamma rays and cosmic electrons and positrons. HAWC is one of the few operating observatories capable of measuring showers produced by electron and positron primaries above 1 TeV, and can record these showers from two-thirds of the sky each day. We describe the sensitivity of HAWC to leptonic cosmic rays, and discuss prospects for the measurement of the combined $e^+e^-$ flux and possible approaches for positron and electron charge separation with the HAWC detector.

  19. Rn-222 tracing and stable isotope measurements of biogenic gas fluxes from methane saturated sediments

    NASA Technical Reports Server (NTRS)

    Martens, Christopher S.; Green, C. D.; Blair, Neal; Chanton, J. P.

    1985-01-01

    Transport of reduced biogenic gases from anoxic sediments and soils to the atmosphere can be quantitatively studied through measurement of radon-222/radium-226 disequilibrium. In previous work, seasonal variations in biogenic gas transport mechanisms, net fluxes and overall composition were documented. Now presented are direct field measurements of radon-222 activity in gases exiting organic rich sediments which show their usefulness for tracing of the stripping of dissolved biogenic gases from within the sediment column and transport via bubble ebullition. Methane is depleted in deuterium during the summer as compared with winter months and is in general lighter than in most marine sediments signaling the probable importance of acetate as an important precursor molecule. The significant seasonal isotopic variations observed illustrate the importance of understanding mechanisms and rates of biogenic gas production in order to interpret observed tropospheric isotopic data.

  20. Satellite Angular Rate Estimation From Vector Measurements

    NASA Technical Reports Server (NTRS)

    Azor, Ruth; Bar-Itzhack, Itzhack Y.; Harman, Richard R.

    1996-01-01

    This paper presents an algorithm for estimating the angular rate vector of a satellite which is based on the time derivatives of vector measurements expressed in a reference and body coordinate. The computed derivatives are fed into a spacial Kalman filter which yields an estimate of the spacecraft angular velocity. The filter, named Extended Interlaced Kalman Filter (EIKF), is an extension of the Kalman filter which, although being linear, estimates the state of a nonlinear dynamic system. It consists of two or three parallel Kalman filters whose individual estimates are fed to one another and are considered as known inputs by the other parallel filter(s). The nonlinear dynamics stem from the nonlinear differential equation that describes the rotation of a three dimensional body. Initial results, using simulated data, and real Rossi X ray Timing Explorer (RXTE) data indicate that the algorithm is efficient and robust.

  1. Identifying and Managing Data Validity Challenges with Automated Data Checks in the AmeriFlux Flux Measurement Network

    NASA Astrophysics Data System (ADS)

    Poindexter, C.; Pastorello, G.; Papale, D.; Trotta, C.; Ribeca, A.; Canfora, E.; Faybishenko, B.; Samak, T.; Gunter, D.; Hollowgrass, R.; Agarwal, D.

    2014-12-01

    AmeriFlux is a network of sites managed by independent investigators measuring carbon, water and heat fluxes. Individual investigators perform many data validity checks. Network-level data validity checks are also being applied to increase network-wide data consistency. A number of different types or errors occur in flux data, and while corrections have been developed to address some types of errors, other error types can be difficult to detect. To identify errors rapidly and consistently, we have developed automated data validity checks that rely on theoretical limits or relationships for specific measured variables. We present an example of a data validity check that is being developed for the friction velocity u*. The friction velocity is a crucial variable used to identify when low turbulent mixing in the atmospheric boundary layer invalidates eddy covariance measurements of fluxes. It is measured via sonic anemometer and is related to the wind speed WS, the measurement height relative to the canopy height, and the surface roughness, through the log law. Comparing independent measurements of WS and u* can help identify issues related to the sensor but doesn't take into consideration changes in the canopy (e.g. due to leaf emergence). The u* data check proposed relies on recent work comparing multiple methods for determining the aerodynamic roughness length z0 and zero plane displacement d (Graf, A., A. van de Boer, A. Moene & H. Vereecken, 2014, Boundary-Layer Meteorol., 151, 373-387). These methods, each of which is most robust across a different atmospheric stability range, yield multiple estimates for z0 and d at daily resolution. We use these multiple estimates for z0 and d, as well as half-hourly wind speeds and Obukhov length scales and their uncertainties to generate a predicted u* and a tolerance around this predicted value. In testing, this check correctly identified as invalid u* data known to be erroneous but did not flag data that could look anomalous but instead reflect real changes in the vegetation canopy. This and other validity checks both manual and automated are serving to increase accuracy and inter-comparability of all data within the AmeriFlux and FLUXNET networks preceding the upcoming release of a new global data set of fluxes.

  2. Comparative soil CO2 flux measurements and geostatisticalestimation methods on masaya volcano, nicaragua

    SciTech Connect

    Lewicki, J.L.; Bergfeld, D.; Cardellini, C.; Chiodini, G.; Granieri, D.; Varley, N.; Werner, C.

    2004-04-27

    We present a comparative study of soil CO{sub 2} flux (F{sub CO2}) measured by five groups (Groups 1-5) at the IAVCEI-CCVG Eighth Workshop on Volcanic Gases on Masaya volcano, Nicaragua. Groups 1-5 measured F{sub CO2} using the accumulation chamber method at 5-m spacing within a 900 m{sup 2} grid during a morning (AM) period. These measurements were repeated by Groups 1-3 during an afternoon (PM) period. All measured F{sub CO2} ranged from 218 to 14,719 g m{sup -2}d{sup -1}. Arithmetic means and associated CO{sub 2} emission rate estimates for the AM data sets varied between groups by {+-}22%. The variability of the five measurements made at each grid point ranged from {+-}5 to 167% and increased with the arithmetic mean. Based on a comparison of measurements made by Groups 1-3 during AM and PM times, this variability is likely due in large part to natural temporal variability of gas flow, rather than to measurement error. We compared six geostatistical methods (arithmetic and minimum variance unbiased estimator means of uninterpolated data, and arithmetic means of data interpolated by the multiquadric radial basis function, ordinary kriging, multi-Gaussian kriging, and sequential Gaussian simulation methods) to estimate the mean and associated CO{sub 2} emission rate of one data set and to map the spatial F{sub CO2} distribution. While the CO{sub 2} emission rates estimated using the different techniques only varied by {+-}1.1%, the F{sub CO2} maps showed important differences. We suggest that the sequential Gaussian simulation method yields the most realistic representation of the spatial distribution of F{sub CO2} and is most appropriate for volcano monitoring applications.

  3. MEASURING CO2 FLUX OVER NORTHERN GREAT PLAINS RANGELANDS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The role of rangelands in regulating atmospheric CO2 levels is a critical issue in global climate change research. Rangelands are complex systems occupying more than 40% of the land area in the world and USA. We studied the effects of seasonal grazing on CO2 flux on small plots located on a silty ra...

  4. Soil erosion rates (particulate and dissolved fluxes) variations in a temperate river basin

    NASA Astrophysics Data System (ADS)

    Cerdan, Olivier; Gay, Aurore; Négrel, Philippe; Pételet-Giraud, Emmanuelle; Salvador Blanes, Sébastien; Degan, Francesca

    2015-04-01

    Soil erosion is one of the major drivers of landscape evolution in Western Europe. However, depending on the land use characteristics and on the geological and topographical settings, miscellaneous forms of erosion may lead to a very diverse morphological evolution. To understand these landscape evolutions different scientific questions remain to be answered or quantified. The main difficulty arises from the nonlinear interactions between different erosional processes that act at different temporal and spatial scales. This study proposes to investigate different datasets describing particulate and dissolved sediment fluxes within a French River basin (The Loire River) at different spatial scales and at temporal scales ranging from the flood event to several decades. The particulate sediment load values at the outlet of the catchments range from 2.5 102 to 8.6 105 t yr-1, and the sediment yield values range from 2.9 to 32.4 t km 2 yr-1. Sediment exports from the Loire and Brittany river basins are low compared with mountainous regions and European exports. However, a strong spatial variability within this territory exists. The expected results on the sediment yield spatial pattern distribution and the correlation between SY values and basin sizes are not observed. An analysis of the sediment yield values at different time steps shows a strong effect of the seasonal availability of detached particles to be transported. High concentrations of suspended sediments during the winter and lower values during the summer and autumn are observed. Inter-annual variations are also observed, with export values varying by a factor 2 to 10 between years for one catchment. The influence of rainfall on the sediment exports is predominant, but investigations on physical characteristics of each catchment (e.g., lithology, slope, land use) are required to better understand the production and transfer processes within a drainage basin. These inter-annual variations imply that long-term data are required to provide mean SY values representative of the catchment functioning. From our calculations, 18 complete years of data are required to obtain a mean sediment yield value with less than 10% of variation on average around the mean. The specific dissolved fluxes vary from 13.7 to 199.9 t.km-2. t yr-1. Contrary to particulate matters, the impact of the lithology is illustrated by higher total dissolved solid fluxes on limestone catchments compared with graniteous or schisteous catchments. Nitrates and ammonium are indicators of anthropogenic perturbation and their fluxes vary respectively from 0.4 to 31.4 t.km-2. yr-1 and from 7.8*10-3 to 7.7 t.km-2. yr-1 and evolve differently according to land uses: nitrates fluxes are lower in the upstream Loire and higher downstream in the region where agricultural pressure is higher. The analysis of these datasets at different spatial and temporal scales permits to identify some of the dominant processes, and also to distinguish natural from anthropogenic influences. Concerning upland physical soil surface erosion rates, we find that the average travel distance of eroded particles may be limited, implying a strong decrease in physical erosion rates when moving from the local scale (m²) to the river basin scale (> 103 km²). Chemical erosion rates are less sensitive to scale and can either decrease or increase with increasing area in function of lithology, land management and topography. The results also highlight the predominant role of surface connectivity to characterize the fraction of sediment exported out of river drainage areas by physical soil surface erosion. For the export of dissolved sediment originating from weathering processes, the catchment physiography and connectivity does no longer play the dominant role. A direct link between soil production rates and exported dissolved fluxes tends to show that, contrary to the suspended particles, which are transport-limited, the dissolved matter seems to be supply-limited.

  5. Quantitative method for measuring heat flux emitted from a cryogenic object

    DOEpatents

    Duncan, Robert V. (Tijeras, NM)

    1993-01-01

    The present invention is a quantitative method for measuring the total heat flux, and of deriving the total power dissipation, of a heat-fluxing object which includes the steps of placing an electrical noise-emitting heat-fluxing object in a liquid helium bath and measuring the superfluid transition temperature of the bath. The temperature of the liquid helium bath is thereafter reduced until some measurable parameter, such as the electrical noise, exhibited by the heat-fluxing object or a temperature-dependent resistive thin film in intimate contact with the heat-fluxing object, becomes greatly reduced. The temperature of the liquid helum bath is measured at this point. The difference between the superfluid transition temperature of the liquid helium bath surrounding the heat-fluxing object, and the temperature of the liquid helium bath when the electrical noise emitted by the heat-fluxing object becomes greatly reduced, is determined. The total heat flux from the heat-fluxing object is determined as a function of this difference between these temperatures. In certain applications, the technique can be used to optimize thermal design parameters of cryogenic electronics, for example, Josephson junction and infra-red sensing devices.

  6. Quantitative method for measuring heat flux emitted from a cryogenic object

    DOEpatents

    Duncan, R.V.

    1993-03-16

    The present invention is a quantitative method for measuring the total heat flux, and of deriving the total power dissipation, of a heat-fluxing object which includes the steps of placing an electrical noise-emitting heat-fluxing object in a liquid helium bath and measuring the superfluid transition temperature of the bath. The temperature of the liquid helium bath is thereafter reduced until some measurable parameter, such as the electrical noise, exhibited by the heat-fluxing object or a temperature-dependent resistive thin film in intimate contact with the heat-fluxing object, becomes greatly reduced. The temperature of the liquid helum bath is measured at this point. The difference between the superfluid transition temperature of the liquid helium bath surrounding the heat-fluxing object, and the temperature of the liquid helium bath when the electrical noise emitted by the heat-fluxing object becomes greatly reduced, is determined. The total heat flux from the heat-fluxing object is determined as a function of this difference between these temperatures. In certain applications, the technique can be used to optimize thermal design parameters of cryogenic electronics, for example, Josephson junction and infrared sensing devices.

  7. Intercomparison of fast response commercial gas analysers for nitrous oxide flux measurements under field conditions

    NASA Astrophysics Data System (ADS)

    Rannik, Ü.; Haapanala, S.; Shurpali, N. J.; Mammarella, I.; Lind, S.; Hyvönen, N.; Peltola, O.; Zahniser, M.; Martikainen, P. J.; Vesala, T.

    2015-01-01

    Four gas analysers capable of measuring nitrous oxide (N2O) concentration at a response time necessary for eddy covariance flux measurements were operated from spring until winter 2011 over a field cultivated with reed canary grass (RCG, Phalaris arundinacea, L.), a perennial bioenergy crop in eastern Finland. The instruments were TGA100A (Campbell Scientific Inc.), CW-TILDAS-CS (Aerodyne Research Inc.), N2O / CO-23d (Los Gatos Research Inc.) and QC-TILDAS-76-CS (Aerodyne Research Inc.). The period with high emissions, lasting for about 2 weeks after fertilization in late May, was characterized by an up to 2 orders of magnitude higher emission, whereas during the rest of the campaign the N2O fluxes were small, from 0.01 to 1 nmol m-2 s-1. Two instruments, CW-TILDAS-CS and N2O / CO-23d, determined the N2O exchange with minor systematic difference throughout the campaign, when operated simultaneously. TGA100A produced the cumulatively highest N2O estimates (with 29% higher values during the period when all instruments were operational). QC-TILDAS-76-CS obtained 36% lower fluxes than CW-TILDAS-CS during the first period, including the emission episode, whereas the correspondence with other instruments during the rest of the campaign was good. The reasons for systematic differences were not identified, suggesting further need for detailed evaluation of instrument performance under field conditions with emphasis on stability, calibration and any other factors that can systematically affect the accuracy of flux measurements. The instrument CW-TILDAS-CS was characterized by the lowest noise level (with a standard deviation of around 0.12 ppb at 10 Hz sampling rate) as compared to N2O / CO-23d and QC-TILDAS-76-CS (around 0.50 ppb) and TGA100A (around 2 ppb). We identified that for all instruments except CW-TILDAS-CS the random error due to instrumental noise was an important source of uncertainty at the 30 min averaging level and the total stochastic error was frequently of the same magnitude as the fluxes when N2O exchange was small at the measurement site. Both instruments based on continuous-wave quantum cascade laser, CW-TILDAS-CS and N2O / CO-23d, were able to determine the same sample of low N2O fluxes with a high mutual coefficient of determination at the 30 min averaging level and with minor systematic difference over the observation period of several months. This enables us to conclude that the new-generation instrumentation is capable of measuring small N2O exchange with high precision and accuracy at sites with low fluxes.

  8. Characteristics of microbial volatile organic compound flux rates from soil and plant litter

    NASA Astrophysics Data System (ADS)

    Gray, C. M.; Fierer, N.

    2013-12-01

    Our knowledge of microbial production and consumption of volatile organic compounds (VOCs) from soil and litter, as well as which microorganisms are involved, is relatively limited compared to what we know about VOC emissions from terrestrial plants. With climate change expecting to alter plant community composition, nitrogen (N) deposition rates, mean annual temperatures, precipitation patterns, and atmospheric VOC concentrations, it is unknown how microbial production and consumption of VOCs from litter and soil will respond. We have spent the last 5 years quantifying VOC flux rates in decaying plant litter, mineral soils and from a subalpine field site using a proton transfer reaction mass spectrometer (PTR-MS). Microbial production, relative to abiotic sources, accounted for 78% to 99% of the total VOC emissions from decomposing litter, highlighting the importance of microbial metabolisms in these systems. Litter chemistry correlated with the types of VOCs emitted, of which, methanol was emitted at the highest rates from all studies. The net emissions of carbon as VOCs was found to be up to 88% of that emitted as CO2 suggesting that VOCs likely represent an important component of the carbon cycle in many terrestrial systems. Nitrogen additions drastically reduced VOC emissions from litter to near zero, though it is still not understood whether this was due to an increase in consumption or a decrease in production. In the field, the root system contributed to 53% of the carbon that was emitted as VOCs from the soil with increasing air temperatures correlating to an increase in VOC flux rates from the soil system. Finally, we are currently utilizing next generation sequencing techniques (Illumina MiSeq) along with varying concentrations of isoprene, the third most abundant VOC in the atmosphere behind methane and methanol, above soils in a laboratory incubation to determine consumption rates and the microorganisms (bacteria, archaea and fungi) associated with the consumption of isoprene in soils. To our knowledge, this is a novel technique for identifying microorganisms associated with consumption without the use of culturing or isotopic labeling. Together, these series of studies are moving us toward a predictive understanding of VOC fluxes and microbial ecology in soil and litter.

  9. Influence of Steel Grade on Surface Cooling Rates and Heat Flux during Quenching

    NASA Astrophysics Data System (ADS)

    Prasanna Kumar, T. S.

    2013-07-01

    Immersion quenching is one of the most widely used processes for achieving martensitic and bainitic steels. The efficiency and quality of quenching are generally tested using standard quench probes for obtaining the cooling curves. A host of parameters like quenchant type, steel grade, bath agitation, section thickness, etc., affect the cooling curves. Cooling curve analyses covered under ASTM standards cannot be used to assess the performance of a quenchant for different grades of steel, as they use a common material for the probe. This article reports the development of equipment, which, in conjunction with mathematical models, can be used for obtaining cooling curves for a specific steel/quenchant combination. The mathematical models couple nonlinear transient inverse heat transfer with phase transformation, resulting in cooling curves specific to the steel grade-quenchant combination. The austenite decomposition models were based on an approach consistent with both the TTT diagram of the steel and Fe-C equilibrium phase diagrams. The TTT diagrams for the specific chemistry of the specimens and the thermophysical properties of the individual phases as functions of temperature were obtained using JMatPro software. Experiments were conducted in the laboratory for computing surface temperature and heat flux at the mid-section of a 25-mm diameter by 100-mm-long cylindrical specimen of two types of steels in two different quenchants. A low alloy steel (EN19) and a plain carbon steel (C45) were used for bringing out the influence of austenite transformation on surface cooling rates and heat flux. Two types of industrial quenchants (i) a mineral oil, and (ii) an aqueous solution of polymer were used. The results showed that the cooling curves, cooling rate curves, and the surface heat flux depended on the steel grade with the quenchant remaining the same.

  10. A measurement of the absolute flux of cosmic-ray electrons

    NASA Technical Reports Server (NTRS)

    Golden, R. L.; Mauger, B. G.; Badhwar, G. D.; Daniel, R. R.; Lacy, J. L.; Stephens, S. A.; Zipse, J. E.

    1984-01-01

    A balloon-borne superconducting magnet spectrometer was used to measure the absolute flux of cosmic-ray electrons. The instrument consisted of a gas Cerenkov detector, a momentum spectrometer, and a lead-scintillator shower counter. In order to determine electron flux in the interstellar medium, observed fluxes for energy loss in the atmosphere and the payload were corrected, taking into account solar modulation effects and bremsstrahlung energy losses. Fluxes were measured at an average atmospheric depth of 5.8 g/sq cm, and the solar modulation was 300 MeV. A cosmic-ray electron flux of 367 E to the exp(3.15 + or -0.2) per sq m/sr s GeV was obtained in the energy range 4.5-63.5 GeV. The uncertainty of the absolute (electron-positron) flux was 10 percent. A summary of the electron data is given in a table.

  11. Aerosol Fluxes over Amazon Rain Forest Measured with the Eddy Covariance Method

    NASA Astrophysics Data System (ADS)

    Ahlm, L.; Nilsson, E. D.; Krejci, R.; Mårtensson, E. M.; Vogt, M.; Artaxo, P.

    2008-12-01

    We present measurements of vertical aerosol fluxes over the Amazon carried out on top of K34, a 50 meter high tower in the Cuieiras Reserve about 50 km north of Manaus in northern Brazil. The turbulent fluxes were measured with the eddy covariance method. The covariance of vertical wind speed from a sonic anemometer Gill Windmaster and total aerosol number concentration from a condensation particle counter (CPC) TSI 3010 provided the total number flux (diameter >0.01 ?m). The covariance of vertical wind speed and size resolved number concentrations from an optical particle counter (OPC) Grimm 1.109 provided size resolved number fluxes in 15 bins from 0.25 ?m to 2.5 ?m diameter. Additionally fluxes of CO2 and H2O were derived from Li-7500 observations. The observational period, from early March to early August, includes both wet and dry season. OPC fluxes generally show net aerosol deposition both during wet and dry season with the largest downward fluxes during midday. CPC fluxes show different patterns in wet and dry season. During dry season, when number concentrations are higher, downward fluxes clearly dominate. In the wet season however, when number concentrations are lower, our data indicates that upward and downward fluxes are quite evenly distributed during course of a day. On average there is a peak in upward flux during late morning and another peak during the afternoon. Since the OPC fluxes in the same time show net deposition, there is an indication of net source of primary aerosol particles with diameters between 10 and 250 nm emitted from the rain forest. Future data analysis will hopefully shed light on origin and formation mechanism of these particles and thus provide a deeper insight in the rain forest - atmosphere interactions. The aerosol flux measurements were carried out as a part of the AMAZE project in collaboration with University of Sao Paulo, Brazil, and financial support was provided by Swedish International Development Cooperation Agency (SIDA).

  12. Continuous Measurement of Methane Ebullition Flux from a Northern Peatland using a Fast Methane Analyzer

    NASA Astrophysics Data System (ADS)

    Zhongjie, Y.; Schafer, K. V.; Slater, L. D.; Varner, R. K.; Amante, J.; Comas, X.; Reeve, A. S.; Alcivar, W.; Gonzalez, D.

    2012-12-01

    Northern peatlands are an important source of methane (CH4) release to the atmosphere, estimated at between 20 and 50 Tg/yr. Recent work on CH4 emissions from peatlands has demonstrated that ebullition can be a more important emission pathway than previously assumed. However, accurate quantification of the atmospheric CH4 burden due to ebullition is still very limited because ebullition exhibits high spatiotemporal variability such that sudden episodic events are difficult to capture and quantify with existing experimental methods. We have initiated a novel measurement program to better quantify the spatiotemporal variability in CH4 flux in peatlands, and to examine potential effects of vegetation and environmental factors, e.g. atmospheric pressure, water table, etc on these releases. A flow-through system was designed, consisting of a closed static chamber and a fast methane analyzer (FMA) (LI-COR model 7700) that has been employed at both the field and laboratory scale. The CH4 concentration in the air flowing through the chamber is continuously measured by the analyzer and used to reconstruct continuous CH4 emission fluxes. The high sampling rate of the FMA makes it sensitive to both ebullition and diffusion of gaseous CH4, capturing short duration, episodic ebullition fluxes. Non-steady static chamber measurements were also conducted to cross-validate the continuous measurements. Results acquired during summer 2011 show that episodic ebullition occurred more frequently at the pool site where previous studies indicate extensive wood layers at depth and the vegetation was a mix of Sphagnum and wooded heath. During a 3 day period of continuous measurements captured the passage of a tropical storm Irene, where short term episodic releases of CH4, ranging from 113 mg CH4/m2/d to 202 mg CH4/m2/d, were observed at the time of lowest atmospheric pressure, providing new evidence that atmospheric pressure is an important factor to controlling CH4 ebullition from peatlands. While traditional techniques, e.g. static chamber measurement can only occasionally detect the occurrence of ebullition, the continuous measurement by using a flow-through system is able to resolve spatiotemporal complexity of episodic CH4 ebullition events. These continuous CH4 measurements provide new insights into the timing of CH4 ebullition from peatlands to the atmosphere as climate changes and the role of environmental variables in regulating these CH4 releases.

  13. Measuring Methane Emissions from Industrial and Waste Processing Sites Using the Dual Tracer Flux Ratio Method

    NASA Astrophysics Data System (ADS)

    Herndon, S.; Floerchinger, C.; Roscioli, J. R.; Yacovitch, T.; Franklin, J. P.; Shorter, J. H.; Kolb, C. E.; Subramanian, R.; Robinson, A. L.; Molina, L. T.; Allen, D.

    2013-12-01

    In order to directly quantify facility scale methane emissions during recent multi-state measurement campaigns we have deployed novel tracer release emission characterization approaches to investigate a wide variety of facility types. The development and application of a dual tracer flux ratio methodology will be discussed. Using known release rates of two (or more) inert tracer species, downwind methane plume measurements can be used to quantify and evaluate the uncertainty in known releases and unknown emissions of methane. Results from experiments designed to challenge the experimental methodology will be presented, which determined that for downwind sampling distances in excess of ~200 m, the dual tracer release method is quite robust (<20% emission rate error) under many atmospheric conditions and landscape variations. At downwind distances less than ~200 m, the assumption of equivalent dispersion between spatially separated release points can break down. For some facilities, this can be used to distinguish and estimate the magnitude of methane emissions taking place at different spatial points within the facility. Measured emissions for selected facilities will be presented and, where possible, the accurate quantification of the episodic releases during specific activities, as well as continuous fugitive emissions are identified and will be discussed . Collaboration with on-site operators allows these measurements to inform the design and implementation of effective mitigation strategies.

  14. Evaluating the value of enhanced atmospheric measurements and models to improve interpretation of flux data

    NASA Astrophysics Data System (ADS)

    Osuna, J. L.; Wharton, S.; Falk, M.; Pyles, R. D.; Ma, S.; Baldocchi, D. D.

    2013-12-01

    Gaps in trace-gas fluxes measured via eddy-covariance occur for many reasons. One of these reasons is that many sites are equipped with flux measurements at only one height above the canopy. The optimal height for detecting fluxes, however, changes in time with the environmental conditions at the site. In some instances, a measurement such as friction velocity (u*) can indicate when data should be eliminated. When u* is high however, data are not eliminated but sensors may not actually be detecting fluxes from the ecosystem of interest. This latter scenario often occurs at night when the surface layer of the atmosphere is stably stratified and may be lower than the tower measurement height. Here, we propose that increased information about atmospheric structure near the surface and the processes occurring within the surface layer can inform an improved interpretation of fluxes as measured at a single point above the canopy. We adjusted and tuned the Advanced Canopy-Atmosphere-Soil Algorithm (ACASA) for modeling a California mediterranean oak savanna, the Tonzi AmeriFlux Site near Ione, CA, USA. We fused datasets of wind profiles, temperature profiles, and fluxes from standard eddy-covariance measurements, radiosonde launches, and upward-facing LIDAR measurements to determine surface layer depth and then drive ACASA from the top of the surface layer. By combining modeled profiles of the surface layer with flux measurements above and below the canopy, we were able to better interpret when flux signals were true indications of canopy processes, and the sources of flux anomalies.

  15. Intercomparison of fast response commercial gas analysers for nitrous oxide flux measurements under field conditions

    NASA Astrophysics Data System (ADS)

    Rannik, Ü.; Haapanala, S.; Shurpali, N. J.; Mammarella, I.; Lind, S.; Hyvönen, N.; Peltola, O.; Zahniser, M.; Martikainen, P. J.; Vesala, T.

    2014-08-01

    Four gas analysers capable of measuring nitrous oxide (N2O) concentration at a response time necessary for eddy covariance flux measurements were operated from spring till winter 2011 over a field cultivated with reed canary grass (RCG, Phalaris arundinaceae, L.), a perennial bioenergy crop in Eastern Finland. The instruments were TGA100A (Campbell Scientific Inc.), CW-TILDAS-CS (Aerodyne Research Inc.), N2O/CO-23d (Los Gatos Research Inc.) and QC-TILDAS-76-CS (Aerodyne Research Inc.). The period with high emission, lasting for about two weeks after fertilization in late May, was characterised by an up to two orders of magnitude higher emission, whereas during the rest of the campaign the N2O fluxes were small, from 0.1 to 1 nmol m-2 s-1. Two instruments, CW-TILDAS-CS and N2O/CO-23d, determined the N2O exchange with minor systematic difference throughout the campaign, when operated simultaneously. TGA100A produced cumulatively highest N2O estimates (with 29% higher value during the period when all instruments were operational). QC-TILDAS-76-CS obtained 36% lower fluxes than CW-TILDAS-CS during the first period, including the emission episode, whereas the correspondence with other instruments during the rest of the campaign was good. The reason for these episodic higher and lower estimates by the two instruments is not currently known, suggesting further need for detailed evaluation of instrument performance under field conditions with emphasis on stability, calibration and, in particular, simultaneous accurate determination of water vapour concentration due to its large impact on small N2O fluxes through spectroscopic and dilution corrections. The instrument CW-TILDAS-CS was characterised by the lowest noise level (std around 0.12 ppb at 10 Hz sampling rate), as compared to N2O/CO-23d and QC-TILDAS-76-CS (around 0.50 ppb) and TGA100A (around 2 ppb). Both instruments based on Continuous-Wave Quantum Cascade Lasers, CW-TILDAS-CS and N2O/CO-23d, were able to determine the same sample of low N2O fluxes with high mutual coefficient of determination at 30 min averaging level and with minor systematic difference over the observation period of several months.

  16. Measurement of cosmic ray muon flux in the Belgrade ground level and underground laboratories

    NASA Astrophysics Data System (ADS)

    Dragi?, A.; Jokovi?, D.; Banjanac, R.; Udovi?i?, V.; Pani?, B.; Puzovi?, J.; Ani?in, I.

    2008-07-01

    The cosmic-ray muon count rate and energy loss spectra in plastic scintillator detectors are recorded in the Institute of Physics, Belgrade. Measurements are performed at two different levels: at the surface level (78 m a.s.l.) and in the Belgrade underground laboratory at the depth of 25 m.w.e. From experimental data and with the use of GEANT4 computer simulation the flux and vertical intensities have been determined. At ground level the muon flux is determined to be J1G=(1.37±0.06)×10-2 s-1 cm-2 and vertical intensity IvG=(8.4±0.4)×10-3 s-1 cm-2 sr-1 while the same quantities underground are J1U=(4.5±0.2)×10-3 s-1 cm-2 and IvU=(2.5±0.2)×10-3 s-1 cm-2 sr-1. Their relation to the results of similar measurements worldwide is discussed.

  17. Time and Space Resolved Wall Temperature Measurements during Nucleate Boiling with Constant Heat Flux Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Yerramilli, Vamsee K.; Kim, Jungho

    2005-01-01

    The lack of temporally and spatially resolved measurements under nucleate bubbles has complicated efforts to fully explain pool-boiling phenomena. The objective of this current work is to acquire time and space resolved temperature distributions under nucleate bubbles on a constant heat flux surface. This was performed using a microheater array with 100 micron resolution that allowed effectively simultaneous measurements of surface temperature while supplying a constant dissipative heat flux. This data is then correlated with high speed (> 1000Hz) visual recordings of the bubble growth and departure from the heater surface acquired from below and from the side of the heater. The data indicate that a significant source of energy during bubble nucleation and initial growth is the superheated layer around the bubble. Bubble coalescence was not observed to decrease surface temperature as significantly as bubble departure from the surface. Since bubble departure is typically followed by a sharp increase in the heater surface temperature, it is surmised that the departing bubble effectively removes the superheated layer, allowing a high local heat transfer rate with the bulk fluid through transient conduction/micro-convection during rewetting.

  18. Up-scaling methods of greenhouse gas fluxes between the soil and the atmosphere using a measuring tunnel as well as open-path measurement techniques for the flux-gradient method

    NASA Astrophysics Data System (ADS)

    Schäfer, K.; Jahn, C.; Emeis, S.; Wiwiorra, M.; von der Heide, C.; Böttcher, J.; Deurer, M.; Weymann, D.; Schleichardt, A.; Raabe, A.

    2009-09-01

    For up-scaling the emissions of N2O, CO2 and CH4 (GHG) from arable field soils a measuring tunnel for controlled enrichment of released gases was installed at the soil surface covering an area of 495 or 306 m2. The concentrations of GHG and humidity were measured by the path-averaging, multi-component Fourier Transform Infrared (FTIR) absorption spectrometry at an open path of 100 m length across the whole measuring tunnel. During a 2-years-time frame the N2O fluxes between the soil and the atmosphere at the agricultural field varied between 1.0 and 21 µg N2O-N m-2 h-1. These results were compared with N2O emission rates that were simultaneously measured with a conventional closed chamber technique. The resulting N2O fluxes between the soil and the atmosphere of both methods had the same order of magnitude. However, we found an extreme spatial variability of N2O fluxes at the scale of the closed chambers. The hypothesis that an enlargement of the measured soil surface area is an appropriate measure to avoid the problems of up-scaling results of small scale chamber measurements was confirmed by the results obtained with the measuring tunnel. Currently, a non-intrusive emission and flux measurement method at a scale from 100 m up to. 27.000 m2 on the basis of the flux-gradient method (0.50 and 2.70 m height above surface) is developed and tested by means of open-path multi-component measurement methods (FTIR, GHG) and area averaging meteorological measurements (determination of horizontal winds, friction velocity using acoustic tomography). Two campaigns in October 2007 and June 2008 were performed with this new methodology when wind speeds were low. Due to the very low wind speeds and insufficient turbulence for the application of the usual flux-gradient method a new concept introducing the viscosity instead of stability corrections was developed. It requires a direct measurement of the friction velocity and the vertical gradient of the horizontal wind speeds by ultra-sonic anemometers. The mean results of this measurement method during both campaigns and the measuring tunnel results differ by about 25 % to the mean measuring tunnel results. The calculated single values on the basis of 10-minutes-mean data varied from 2 up to 42 µg N2O-N m-2 h-1.

  19. Remote Measurement of Heat Flux from Power Plant Cooling Lakes

    SciTech Connect

    Garrett, A.; Kurzeja, R.; Villa-Aleman, E.; Bollinger, J.

    2013-01-01

    Laboratory experiments have demonstrated a correlation between the rate of heat loss q? from an experimental fluid to the air above and the standard deviation ? of the thermal variability in images of the fluid surface. These experimental results imply that q? can be derived directly from thermal imagery by computing ?. This paper analyses thermal imagery collected over two power plant cooling lakes to determine if the same relationship exists. Turbulent boundary layer theory predicts a linear relationship between q? and ? when both forced (wind driven) and free (buoyancy driven) convection are present. Datasets derived from ground- and helicopter-based imagery collections had correlation coefficients between ? and q? of 0.45 and 0.76, respectively. Values of q? computed from a function of ? and friction velocity u* derived from turbulent boundary layer theory had higher correlations with measured values of q? (0.84 and 0.89). This research may be applicable to the problem of calculating losses of heat from the ocean to the atmosphere during high-latitude cold-air outbreaks because it does not require the information typically needed to compute sensible, evaporative, and thermal radiation energy losses to the atmosphere.

  20. The home-made in situ passive flux sampler for the measurement of monoterpene emission flux: preliminary studies.

    PubMed

    Mar?, Mariusz; Namie?nik, Jacek; Zabiega?a, Bo?ena

    2015-09-01

    The paper presents the construction and metrological characteristics of the home-made in situ passive flux sampler, an analytical tool representing small-scale emission chambers working in situ and passively sampling analytes from the gaseous phase. The sorption element was a cylindrical container made of stainless steel net, packed with a carbon sorbent bed-graphitized charcoal, Carbograph 4 (35/50 mesh). The recommended working/exposure time of the constructed passive device was determined by carrying out model tests in the laboratory. In addition, a preliminary study was conducted to determine the rate of the emission flux of selected monoterpenes released from the surface of wood-based indoor materials (laminated chipboard) used in residential areas. PMID:26116240

  1. Novel Surface Thermocouple Probes for Divertor Heat Flux Measurement

    NASA Astrophysics Data System (ADS)

    Gangadhara, S.; Labombard, B.; Lipschultz, B.; Pierce, N.

    1996-11-01

    An array of novel surface thermocouple probes have been installed and tested in the outer divertor of Alcator C-Mod. These sensors can, in principle, record divertor surface temperatures with fast time response (? >= 10 ? sec), allowing a direct estimate of the plasma heat flux to be inferred. The design is an adaptation of a commercially available device(``The Self-Renewing Thermocouple,'' Nanmac Corp., Framingham, MA), employing a coaxial-like geometry with a single tungsten-rhenium ribbon wire embedded inside a 6.35 mm diameter molybdenum rod. Various prototypes were tested, including probes with flush and 5^circ angles with respect to the divertor surface, and probes with and without protective surface coatings. Typical surface temperature rises are ~ 300-700 ^circC, corresponding to signals of ~ 3-9 mV. RC filters with 10 ms time constants are used to reduce noise introduced by the plasma environment. The surface temperature corresponding to typical RMS noise levels is ~ 25 ^circC. Using a one-dimensional, semi-infinite slab model, parallel heat fluxes in the range of 50-500 MW/m^2 are estimated. A comparison with heat flux estimates from Langmuir probes located adjacent to the thermocouple array will be presented. Supported by U.S. DOE Contract No. DE-AC02-78ET51013

  2. Measurement of the Cosmic Ray and Neutrino-Induced Muon Flux at the Sudbury Neutrino Observatory

    SciTech Connect

    SNO collaboration; Aharmim, B.; Ahmed, S.N.; Andersen, T.C.; Anthony, A.E.; Barros, N.; Beier, E.W.; Bellerive, A.; Beltran, B.; Bergevin, M.; Biller, S.D.; Boudjemline, K.; Boulay, M.G.; Burritt, T.H.; Cai, B.; Chan, Y.D.; Chen, M.; Chon, M.C.; Cleveland, B.T.; Cox-Mobrand, G.A.; Currat, C.A.; Dai, X.; Dalnoki-Veress, F.; Deng, H.; Detwiler, J.; Doe, P.J.; Dosanjh, R.S.; Doucas, G.; Drouin, P.-L.; Duncan, F.A.; Dunford, M.; Elliott, S.R.; Evans, H.C.; Ewan, G.T.; Farine, J.; Fergani, H.; Fleurot, F.; Ford, R.J.; Formaggio, J.A.; Gagnon, N.; Goon, J.TM.; Grant, D.R.; Guillian, E.; Habib, S.; Hahn, R.L.; Hallin, A.L.; Hallman, E.D.; Hargrove, C.K.; Harvey, P.J.; Harvey, P.J.; Heeger, K.M.; Heintzelman, W.J.; Heise, J.; Helmer, R.L.; Hemingway, R.J.; Henning, R.; Hime, A.; Howard, C.; Howe, M.A.; Huang, M.; Jamieson, B.; Jelley, N.A.; Klein, J.R.; Kos, M.; Kruger, A.; Kraus, C.; Krauss, C.B.; Kutter, T.; Kyba, C.C.M.; Lange, R.; Law, J.; Lawson, I.T.; Lesko, K.T.; Leslie, J.R.; Levine, I.; Loach, J.C.; Luoma, S.; MacLellan, R.; Majerus, S.; Mak, H.B.; Maneira, J.; Marino, A.D.; Martin, R.; McCauley, N.; McDonald, A.B.; McGee, S.; Mifflin, C.; Miller, M.L.; Monreal, B.; Monroe, J.; Noble, A.J.; Oblath, N.S.; Okada, C.E.; O?Keeffe, H.M.; Opachich, Y.; Orebi Gann, G.D.; Oser, S.M.; Ott, R.A.; Peeters, S.J.M.; Poon, A.W.P.; Prior, G.; Rielage, K.; Robertson, B.C.; Robertson, R.G.H.; Rollin, E.; Schwendener, M.H.; Secrest, J.A.; Seibert, S.R.; Simard, O.; Simpson, J.J.; Sinclair, D.; Skensved, P.; Smith, M.W.E.; Sonley, T.J.; Steiger, T.D.; Stonehill, L.C.; Tagg, N.; Tesic, G.; Tolich, N.; Tsui, T.; Van de Water, R.G.; VanDevender, B.A.; Virtue, C.J.; Waller, D.; Waltham, C.E.; Wan Chan Tseung, H.; Wark, D.L.; Watson, P.; Wendland, J.; West, N.; Wilkerson, J.F.; Wilson, J.R.; Wouters, J.M.; Wright, A.; Yeh, M.; Zhang, F.; Zuber, K.

    2009-02-16

    Results are reported on the measurement of the atmospheric neutrino-induced muon flux at a depth of 2 kilometers below the Earth's surface from 1229 days of operation of the Sudbury Neutrino Observatory (SNO). By measuring the flux of through-going muons as a function of zenith angle, the SNO experiment can distinguish between the oscillated and un-oscillated portion of the neutrino flux. A total of 514 muon-like events are measured between -1 {le} cos {theta}{sub zenith} 0.4 in a total exposure of 2.30 x 10{sup 14} cm{sup 2} s. The measured flux normalization is 1.22 {+-} 0.09 times the Bartol three-dimensional flux prediction. This is the first measurement of the neutrino-induced flux where neutrino oscillations are minimized. The zenith distribution is consistent with previously measured atmospheric neutrino oscillation parameters. The cosmic ray muon flux at SNO with zenith angle cos {theta}{sub zenith} > 0.4 is measured to be (3.31 {+-} 0.01 (stat.) {+-} 0.09 (sys.)) x 10{sup -10} {micro}/s/cm{sup 2}.

  3. Measurement of erosion rate by absorption spectroscopy in a Hall thruster

    SciTech Connect

    Yamamoto, Naoji; Yokota, Shigeru; Matsui, Makoto; Komurasaki, Kimiya; Arakawa, Yoshihiro

    2005-08-15

    The erosion rate of a Hall thruster was estimated with the objective of building a real-time erosion rate monitoring system using a 1 kW class anode layer type Hall thruster. This system aids the understanding of the tradeoff between lifetime and performance. To estimate the flux of the sputtered wall material, the number density of the sputtered iron was measured by laser absorption spectroscopy using an absorption line from ground atomic iron at 371.9935 nm. An ultravioletAl{sub x}In{sub y}Ga{sub (1-x-y)}N diode laser was used as the probe. The estimated number density of iron was 1.1x10{sup 16} m{sup -3}, which is reasonable when compared with that measured by duration erosion tests. The relation between estimated erosion rate and magnetic flux density also agreed with that measured by duration erosion tests.

  4. A comparison of two nitrification inhibitors used to measure nitrification rates in estuarine sediments

    USGS Publications Warehouse

    Caffrey, J.M.; Miller, L.G.

    1995-01-01

    Nitrification rates were measured using intact sediment cores from South San Francisco Bay and two different nitrification inhibitors: acetylene and methyl fluoride. Sediment oxygen consumption and ammonium and nitrate fluxes were also measured in these cores. Four experiments were conducted in the spring, and one in the fall of 1993. There was no significant difference in nitrification rates measured using the two inhibitors, which suggests that methyl fluoride can be used as an effective inhibitor of nitrification. Nitrification was positively correlated with sediment oxygen consumption and numbers of macrofauna. This suggests that bioturbation by macrofauna is an important control of nitrification rates. Irrigation by the tube-dwelling polychaete, Asychis elongata, which dominates the benthic biomass at this location, appears particularly important. Ammonium fluxes out of the sediment were greatest about one week after the spring bloom, while nitrification peaked about one month later.

  5. A comparison of six methods for measuring soil-surface carbon dioxide fluxes

    USGS Publications Warehouse

    Norman, J.M.; Kucharik, C.J.; Gower, S.T.; Baldocchi, D.D.; Crill, P.M.; Rayment, M.; Savage, K.; Striegl, R.G.

    1997-01-01

    Measurements of soil-surface CO2 fluxes are important for characterizing the carbon budget of boreal forests because these fluxes can be the second largest component of the budget. Several methods for measuring soil-surface CO2 fluxes are available: (1) closed-dynamic-chamber systems, (2) closed-static-chamber systems, (3) open-chamber systems, and (4) eddy covariance systems. This paper presents a field comparison of six individual systems for measuring soil-surface CO2 fluxes with each of the four basic system types represented. A single system is used as a reference and compared to each of the other systems individually in black spruce (Picea mariana), jack pine (Pinus banksiana), or aspen (Populus tremuloides) forests. Fluxes vary from 1 to 10 ??mol CO2 m-2 s-1. Adjustment factors to bring all of the systems into agreement vary from 0.93 to 1.45 with an uncertainty of about 10-15%.

  6. Summary We analyzed assumptions and measurement er-rors in estimating canopy transpiration (EL) from sap flux (JS)

    E-print Network

    Oren, Ram

    ) from sap flux (JS) measured with Granier-type sensors, and in calculating canopy stomatal conductance- tively. Sap flux measured in stems did not lag JS measured in branches, and time and frequency domain of varia- tion. Recently, has been approximated from sap flux (JS) measurements scaled to EL (Köstner

  7. Increasing fluxes of S5 1044+71 measured with RATAN-600 radio telescope

    NASA Astrophysics Data System (ADS)

    Trushkin, S. T.; Mingaliev, M. G.; Sotnikova, Yu. V.; Erkenov, A.; Udovitskij, R. Yu.; Mufakharov, T. V.

    2014-02-01

    We report about the growing fluxes of the quasar S5 1044+71, identified with the FERMI source 2FGL J1048.3+714, since detection of the high state in the rest of January 2014 (ATEL #5792). We continue measurements and again detect the increase of the flux densities at frequencies 8.2-21.7 GHz in February.

  8. Balloon-borne measurements of the ultraviolet flux in the Arctic stratosphere during winter

    NASA Technical Reports Server (NTRS)

    Schiller, Cornelius; Mueller, Martin; Klein, Erich; Schmidt, Ulrich; Roeth, Ernst-Peter

    1994-01-01

    Filter radiometers sensitive from 280 to 320 nm and from 280 to 400 nm, respectively, were used for measurements of the actinic flux in the stratosphere. Since the instruments are calibrated for absolute spectral sensitivity the data can be compared with model calculations of the actinic flux. Data were obtained during seven balloon flights during the European Arctic Stratospheric Ozone Experiment (EASOE).

  9. Estimating components of forest evapotranspiration: A footprint approach for scaling sap flux measurements

    E-print Network

    Oren, Ram

    Estimating components of forest evapotranspiration: A footprint approach for scaling sap flux of sap flux density (JS) measured with the popular thermal dissipation probes (Granier, 1987; Oren et al styraciflua Sap flow Quercus spp. a b s t r a c t Forest evapotranspiration (ET) estimates that include scaled

  10. Measuring the Ion Flux to the Deposition Substrate in the Hollow Cathode Plasma Jet

    SciTech Connect

    Virostko, P.; Hubicka, Z.; Cada, M.; Adamek, P.; Kment, S.; Jastrabik, L.; Tichy, M.

    2008-03-19

    Measurements of positive ion flux to a negatively biased substrate for deposition of TiO{sub x} thin films by the hollow cathode plasma jet system are presented. Different methods of obtaining the bias of substrate and measuring the resulting ion flux were used for different bias frequencies. Pulsed DC bias, middle frequency 500 kHz bias, and 13.56 MHz RF bias were compared. For 13.56 MHz two different methods of ion flux determination were used. These measurements were performed for different bias voltage and discharge conditions.

  11. Measurement of NOx fluxes by eddy covariance from the BT tower, London during the ClearfLo project

    NASA Astrophysics Data System (ADS)

    Lee, James; Helfter, Carole; Nemitz, Eiko; Tremper, Anja; Stocker, Jenny; Carruthers, David

    2014-05-01

    The vast majority of air pollutants are emitted directly into the atmosphere from activities occurring at the Earth's surface. One of the key anthropogenic pollutants is NOx (defined as the sum of NO and NO2), which is emitted as a result of most anthropogenic combustion processes. Whilst the chemical reactions and atmospheric processing of NOx are reasonably well understood, and can be modelled with some skill, large uncertainties arise in models due to uncertainty associated with the rate of emissions. In recent years it has become clear that measured trends in certain pollutants, for example NO2, have not followed trends predicted by inventories. Continued exceedances of certain air pollution targets are of significant concern to governments, who have identified reducing this uncertainty associated with emissions as key evidence need. As part of the UK Natural Environment Research Council (NERC) Clean Air for London (ClearfLo) project, concentrations and fluxes of NOx were measured from the top of the BT tower, which is a 188m high telecommunications tower, situated in central London (51o31'17.4'N; 0o8'20.04W). The tower is surrounded by a mixture of commercial and residential buildings with an average height of 15 m. The typical daytime flux footprint of the tower is dominated by commercial/residential buildings and roads (82%) but also includes urban parkland (13%) and impervious ground (5%). High time resolution (10 Hz) chemiluminescence measurements of NO and NO2 (photolytic conversion to NO followed by chemiluminescence) were combined with fast turbulence measurements from a sonic anemometer to calculate fluxes using the eddy covariance technique. In brief, NOx fluxes per notional half-hourly averaging period were obtained by maximising the covariance between instantaneous (i.e. mean for the averaging period subtracted from each 10 Hz data point) fluctuations of NOx mixing ratio and vertical wind velocity. 24 hour NOx flux measurements were made on 36 days during June, July and August 2012 and 28 days in March and April 2013. The data showed a clear diurnal cycle, with NOx flux broadly following measured traffic flow in the surrounding streets, with a typical maximum daytime flux of 4?g m-2 s-1. Mixing ratios of NOx can be seen to be a function of the NOx flux and the boundary layer height evolution during the day. A clear weekday / weekend dependence is seen on the NOx flux measurements, again following the traffic flow data. The measured fluxes were averaged over 24 hours and scaled up to give a 'top down' estimate of the annual emission rate of 79.6 T km-2 yr-1. This compares well to estimates from the UK National Atmospheric Emissions Inventory, however some differences are seen when the data is separated into different wind sectors. Conversely, a 'bottom up' dispersion model (ADMS-Urban) was run using measured meteorological data and the detailed London Atmospheric Emissions Inventory as input. ADMS-Urban has previously been validated using near-surface measurements, but the current work demonstrates that the model gives good agreement with the flux measurements, both in terms of magnitude and diurnal cycle.

  12. Tropical Controls on the CO2 Atmospheric Growth Rate 2010-2011 from the NASA Carbon Monitoring System Flux (CMS-Flux) Project

    NASA Astrophysics Data System (ADS)

    Bowman, K. W.; Liu, J.; Parazoo, N.; Lee, M.; Menemenlis, D.; Gierach, M. M.; Brix, H.; Gurney, K. R.; Collatz, G. J.; Bousserez, N.; Henze, D. K.

    2014-12-01

    Interannual variations in the atmospheric growth rate of CO2 have been attributed to the tropical regions and the controls are correlated with temperature anomalies. We investigate the spatial drivers of the atmospheric growth rate and the processes controlling them over the exceptional period of 2010-2011. This period was marked by a marked shift from an El Nino to La Nina period resulting in historically high sea surface temperature anomalies in the tropical Atlantic leading to serious droughts in the Amazon. However, in 2011, unusual precipitation in Australia was linked to gross primary productivity anomalies in semi-arid regions. We use satellite observations of CO2, CO, and solar induced fluorescence assimilated into the NASA Carbon Monitoring System Project (CMS-Flux) to attribute the atmospheric growth rate to global, spatially resolved fluxes. This system is based upon observationally-constrained "bottom-up" estimates from the Fossil Fuel Data Assimilation System (FFDAS), the ECCO2­-Darwin physical and biogeochemical adjoint ocean state estimation system, and CASA-GFED3 land-surface biogeochemical model. The system is used to compute regional tropical and extra-tropical fluxes and quantify the role of biomass burning and gross primary productivity in controlling those fluxes.

  13. Enhancing the precision and accuracy within and among AmeriFlux site measurements

    SciTech Connect

    Law, Bev

    2013-11-25

    This is the final report for AmeriFlux QA/QC at Oregon State University. The major objective of this project is to contribute to the AmeriFlux network by continuing to build consistency in AmeriFlux measurements by addressing objectives stated in the AmeriFlux strategic plan and self evaluation, the North American Carbon Program, and the US Carbon Cycle Science Program. The project directly contributes to NACP and CCSP goals to establish an integrated, near-real time network of observations to inform climate change science.

  14. Magnetic hysteresis and magnetic flux patterns measured by acoustically stimulated electromagnetic response in a steel plate

    NASA Astrophysics Data System (ADS)

    Yamada, Hisato; Watanabe, Kakeru; Ikushima, Kenji

    2015-08-01

    Magnetic hysteresis loops are measured by ultrasonic techniques and used in visualizing the magnetic-flux distribution in a steel plate. The piezomagnetic coefficient determines the amplitude of acoustically stimulated electromagnetic (ASEM) fields, yielding the hysteresis behavior of the intensity of the ASEM response. By utilizing the high correspondence of the ASEM response to the magnetic-flux density, we image the specific spatial patterns of the flux density formed by an artificial defect in a steel plate specimen. Magnetic-flux probing by ultrasonic waves is thus shown to be a viable method of nondestructive material inspection.

  15. Absolute beam flux measurement at NDCX-I using gold-melting calorimetry technique

    SciTech Connect

    Ni, P.A.; Bieniosek, F.M.; Lidia, S.M.; Welch, J.

    2011-04-01

    We report on an alternative way to measure the absolute beam flux at the NDCX-I, LBNL linear accelerator. Up to date, the beam flux is determined from the analysis of the beam-induced optical emission from a ceramic scintilator (Al-Si). The new approach is based on calorimetric technique, where energy flux is deduced from the melting dynamics of a gold foil. We estimate an average 260 kW/cm2 beam flux over 5 {micro}s, which is consistent with values provided by the other methods. Described technique can be applied to various ion species and energies.

  16. Mapping methane sources and emissions over California from direct airborne flux and VOC source tracer measurements

    NASA Astrophysics Data System (ADS)

    Guha, A.; Misztal, P. K.; Peischl, J.; Karl, T.; Jonsson, H. H.; Woods, R. K.; Ryerson, T. B.; Goldstein, A. H.

    2013-12-01

    Quantifying the contributions of methane (CH4) emissions from anthropogenic sources in the Central Valley of California is important for validation of the statewide greenhouse gas (GHG) inventory and subsequent AB32 law implementation. The state GHG inventory is largely based on activity data and emission factor based estimates. The 'bottom-up' emission factors for CH4 have large uncertainties and there is a lack of adequate 'top-down' measurements to characterize emission rates. Emissions from non-CO2 GHG sources display spatial heterogeneity and temporal variability, and are thus, often, poorly characterized. The Central Valley of California is an agricultural and industry intensive region with large concentration of dairies and livestock operations, active oil and gas fields and refining operations, as well as rice cultivation all of which are known CH4 sources. In order to gain a better perspective of the spatial distribution of major CH4 sources in California, airborne measurements were conducted aboard a Twin Otter aircraft for the CABERNET (California Airborne BVOC Emissions Research in Natural Ecosystems Transects) campaign, where the driving research goal was to understand the spatial distribution of biogenic VOC emissions. The campaign took place in June 2011 and encompassed over forty hours of low-altitude and mixed layer airborne CH4 and CO2 measurements alongside coincident VOC measurements. Transects during eight unique flights covered much of the Central Valley and its eastern edge, the Sacramento-San Joaquin delta and the coastal range. We report direct quantification of CH4 fluxes using real-time airborne Eddy Covariance measurements. CH4 and CO2 were measured at 1-Hz data rate using an instrument based on Cavity Ring Down Spectroscopy (CRDS) along with specific VOCs (like isoprene, methanol, acetone etc.) measured at 10-Hz using Proton Transfer Reaction Mass Spectrometer - Eddy Covariance (PTRMS-EC) flux system. Spatially resolved eddy covariance fluxes were obtained using the virtual disjunct eddy covariance method and from Wavelet Analysis along flight tracks flown in the mixed layer. Preliminary analysis of mixing ratio measurements indicate that high concentrations of CH4 occur consistently while flying above the Central Valley that are correlated to large enhancements of methanol which is an important dairy and livestock emissions tracer. The elevated CH4 mixing ratios along the eastern edge of the San Joaquin Valley highlight the contribution of topography and emissions transport to local ambient levels of CH4. Large enhancements of CH4, benzene and toluene are also observed while flying over the oil production facilities in western part of Kern county (state's top oil producing county, 10% of US production) suggesting the likelihood of fugitive emissions in the region. VOC tracer analysis is used to evaluate the source of high CH4 emissions encountered along the eastern edge of the central Sacramento valley where fugitive emissions from natural gas fields and cultivation of rice are likely sources. Plumes from biomass burning, landfills and refineries encountered during different flights are also investigated. Eddy covariance based CH4 flux estimates are derived for various sources and compared with ';bottom-up' inventory estimates to verify/validate the CA methane inventory for major sources.

  17. Renewed activity beneath Nea Kameni, Santorini volcano (Greece), identified from deformation and soil gas CO2 flux measurements

    NASA Astrophysics Data System (ADS)

    Parks, M.; Biggs, J.; Pyle, D. M.; Mather, T. A.; Caliro, S.; Chiodini, G.; Edmonds, M.; Nomikou, P.

    2011-12-01

    As part of an ongoing study since 2010, a programme of soil CO2 gas sampling and deformation monitoring was undertaken at Santorini volcano. A change was recently detected in both CO2 emission rate and deformation measurements. These have coincided with an ongoing cluster of small earthquakes beneath the volcanic islands of Nea Kameni and Palea Kameni. We believe our results indicate a new phase of unrest at Santorini volcano, which has been quiescent since the last eruption in 1950. We have combined InSAR measurements with soil gas fluxes, to better understand the nature of this system over the past 18 years. C-band (5.65 cm wavelength), L-band (23.6 cm) and X-band (3.1 cm) radar data acquired between 1993 and 2011 constrain deformation rates at Santorini. Soil gas CO2 flux measurements were made across a network of sites on Nea Kameni using the accumulation chamber method and gas samples were collected using a GC syringe during the CO2 flux measurements in April 2011, for isotopic analysis. The gas samples were analysed using a continuous flow isotope ratio mass spectrometer (Thermo-Finnigan Delta XP) to determine variations in magmatic and biogenic components. Our preliminary findings show a dramatic switch from an extended period of slow subsidence (at ~1 cm/yr) at Nea Kameni from 1993-2010, to an episode of inflation which commenced in early 2011, and is continuing at a rate of ~ 2 cm per month. Variations in CO2 flux from 4 soil gas surveys, acquired between April 2010 and July 2011, were analysed using various geostatistical techniques. These show a significant increase in total CO2 emission rate over the past 18 months (current flux is ~ 6500 tonnes/year); the high-flux end member gas has a carbon isotopic composition of ?13C ~ 0%. This is consistent with an origin from a high-temperature hydrothermal source dominated by magmatic C. Source modelling was undertaken to determine the optimal parameters for the source of the deformation observed and comparisons were made between InSAR measurements, CO2 effluxes, GPS measurements and seismicity to better constrain the physical processes involved. These changes may be the first precursory events in the lead up to an eruption, but it is also possible that activity may cease without an eruption. Whatever the outcome of this unrest, we have a rare opportunity to capture the changes in degassing and deformation field associated with a shallow crustal disturbance at a quiescent but potentially dangerous volcano.

  18. Apparatus for measuring high-flux heat transfer in radiatively heated compact exchangers

    NASA Technical Reports Server (NTRS)

    Olson, Douglas A.

    1989-01-01

    An apparatus is described which can deliver uniform heat flux densities of up to 80 W/sq cm over an area 7.8 cm x 15.2 cm for use in measuring the heat transfer and pressure drop in thin (6 mm or less), compact heat exchangers. Helium gas at flow rates of 0 to 40 kg/h and pressures to 6.9 MPa (1000 psi) is the working fluid. The instrumentation used in the apparatus and the methods for analyzing the data is described. The apparatus will be used initially to test the performance of prototype cooling jackets for the engine struts of the National Aerospace Plane (NASP).

  19. Eddy-covariance methane flux measurements over a European beech forest

    NASA Astrophysics Data System (ADS)

    Gentsch, Lydia; Siebicke, Lukas; Knohl, Alexander

    2015-04-01

    The role of forests in global methane (CH4) turnover is currently not well constrained, partially because of the lack of spatially integrative forest-scale measurements of CH4 fluxes. Soil chamber measurements imply that temperate forests generally act as CH4 sinks. Upscaling of chamber observations to the forest scale is however problematic, if the upscaling is not constrained by concurrent 'top-down' measurements, such as of the eddy-covariance type, which provide sufficient integration of spatial variations and of further potential CH4 flux components within forest ecosystems. Ongoing development of laser absorption-based optical instruments, resulting in enhanced measurement stability, precision and sampling speed, has recently improved the prospects for meaningful eddy-covariance measurements at sites with presumably low CH4 fluxes, hence prone to reach the flux detection limit. At present, we are launching eddy-covariance CH4 measurements at a long-running ICOS flux tower site (Hainich National Park, Germany), located in a semi natural, unmanaged, beech dominated forest. Eddy-covariance measurements will be conducted with a laser spectrometer for parallel CH4, H2Ov and CO2 measurements (FGGA, Los Gatos Research, USA). Independent observations of the CO2 flux by the FGGA and a standard Infrared Gas Analyser (LI-7200, LI-COR, USA) will allow to evaluate data quality of measured CH4 fluxes. Here, we want to present first results with a focus on uncertainties of the calculated CH4 fluxes with regard to instrument precision, data processing and site conditions. In future, we plan to compare eddy-covariance flux estimates to side-by-side turbulent flux observations from a novel eddy accumulation system. Furthermore, soil CH4 fluxes will be measured with four automated chambers situated within the tower footprint. Based on a previous soil chamber study at the same site, we expect the Hainich forest site to act as a CH4 sink. However, we hypothesize that our measurements might also reveal short CH4 emission periods when soils become water-saturated. Nonetheless, CH4 emissions by plants could also result in a close to neutral net CH4 flux.

  20. Measuring eddy covariance fluxes of ozone with a slow-response analyser

    PubMed Central

    Wohlfahrt, Georg; Hörtnagl, Lukas; Hammerle, Albin; Graus, Martin; Hansel, Armin

    2013-01-01

    Ozone (O3) fluxes above a temperate mountain grassland were measured by means of the eddy covariance (EC) method using a slow-response O3 analyser. The resultant flux loss was corrected for by a series of transfer functions which model the various sources of high- and, in particular, low-pass filtering. The resulting correction factors varied on average between 1.7 and 3.5 during night and day time, respectively. A cospectral analysis confirmed the accuracy of this approach. O3 fluxes were characterised by a comparatively large random uncertainty, which during daytime typically amounted to 60 %. EC O3 fluxes were compared against O3 flux measurements made concurrently with the flux-gradient (FG) method. The two methods generally agreed well, except for a period between sun rise and early afternoon, when the FG method was suspected of being affected by the presence of photochemical sources/sinks. O3 flux magnitudes and deposition velocities determined with the EC method compared nicely with the available literature from grassland studies. We conclude that our understanding of the causes and consequences of various sources of flux loss (associated with any EC system) has sufficiently matured so that also less-than-ideal instrumentation may be used in EC flux applications, albeit at the cost of relatively large empirical corrections. PMID:24348085

  1. Evapotranspiration components determined by eddy covariance and sap flux measurements in oil palm plantations in Sumatra, Indonesia

    NASA Astrophysics Data System (ADS)

    Meijide, Ana; Röll, Alexander; Niu, Furong; June, Tania; Hölscher, Dirk; Knohl, Alexander

    2015-04-01

    The expansion of oil palm cultivation fueled by the increasing global demand for palm oil is leading to massive land transformations in tropical areas, particularly in South-East Asia. Conversions of forest land to oil palm plantations likely affect ecosystem water fluxes. However, there is a lack of information on water fluxes from oil palm plantations as well as on the partitioning of these fluxes into its different components such as transpiration and evaporation. It is expected that water fluxes from oil palm plantations vary temporally, both long-term, i.e. between different age-classes of plantations, and short-term, i.e. from day to day within a certain plantation (e.g. during or after periods of rainfall). A proper evaluation of water fluxes from oil palm plantations thus requires an experimental design encompassing these types of variability. To assess evapotranspiration (ET) rates, an eddy covariance tower was installed in a 2-year-old oil palm plantation in the lowlands of Jambi, Sumatra; it was subsequently moved to a 12-year-old oil palm plantation located in the same region. In parallel to the ET, sap flux density was measured on 16 leaf petioles on four oil palms; stand transpiration rates were derived from these measurements with stand inventory data. The parallel measurements ran for several weeks in both plantations. Preliminary results for our period of study show that the average ET rate of the 2-year-old oil palm plantation was 5.2 mm day-1; values up to 7.0 mm day-1 were observed on dry, sunny days with non-limiting soil moisture. Stand transpiration (T) by the young oil palms was very low, 0.3 mm day-1on average, and only showed a small variation between days. Under optimal environmental conditions, the ratio of T to total ET was up to 0.08 in the young plantation, while in the mature, 12-year-old plantation, it was significantly higher and reached 0.5. Transpiration rates in the mature oil palm plantation were about six- to seven-fold higher than in the young plantation and again showed very small fluctuations between days (1.8-2.2 mm day-1). Regardless of the age class, evapotranspiration followed changes in environmental conditions more closely than transpiration. This uncoupling of the oil palm transpiration response from environmental drivers may have severe effects on both the magnitude and the spatial and temporal variability of ecosystem water fluxes and needs to be investigated further.

  2. Description of heat flux measurement methods used in hydrocarbon and propellant fuel fires at Sandia.

    SciTech Connect

    Nakos, James Thomas

    2010-12-01

    The purpose of this report is to describe the methods commonly used to measure heat flux in fire applications at Sandia National Laboratories in both hydrocarbon (JP-8 jet fuel, diesel fuel, etc.) and propellant fires. Because these environments are very severe, many commercially available heat flux gauges do not survive the test, so alternative methods had to be developed. Specially built sensors include 'calorimeters' that use a temperature measurement to infer heat flux by use of a model (heat balance on the sensing surface) or by using an inverse heat conduction method. These specialty-built sensors are made rugged so they will survive the environment, so are not optimally designed for ease of use or accuracy. Other methods include radiometers, co-axial thermocouples, directional flame thermometers (DFTs), Sandia 'heat flux gauges', transpiration radiometers, and transverse Seebeck coefficient heat flux gauges. Typical applications are described and pros and cons of each method are listed.

  3. Neutral hydrogen flux measured at 100- to 200-km altitude in an electron aurora

    NASA Technical Reports Server (NTRS)

    Iglesias, G. E.; Anderson, H. R.

    1975-01-01

    Neutral hydrogen fluxes were measured at altitudes of 120-200 km by a rocket payload that also measured electron and proton fluxes and vector magnetic fields. An intense electron arc was crossed, while an upper limit to the flux of 0.5- to 20-keV protons was 1,000,000 per sq cm s sr keV. A neutral flux of 50,000,000 per sq cm s sr was observed, assuming hydrogen with greater than 1-keV energy, with greater north-south extent than the electron flux. Its pitch angle distribution was peaked toward 90 deg, tending toward isotropy in the center. This is fitted to a model describing spreading of an initial proton arc above 500 km.

  4. Eddy covariance flux measurements of pollutant gases in urban Mexico City

    E-print Network

    Velasco, Erik

    Eddy covariance (EC) flux measurements of the atmosphere/surface exchange of gases over an urban area are a direct way to improve and evaluate emissions inventories, and, in turn, to better understand urban atmospheric ...

  5. Geothermal Flux, Basal Melt Rates, and Subglacial Lakes in Central East Antarctica

    NASA Astrophysics Data System (ADS)

    Carter, S. P.; Blankenship, D. D.; Morse, D. L.

    2002-12-01

    The lakes beneath the East Antarctic ice sheet represent a unique environment on Earth, entirely untouched by human interference. Life forms which survive in this cold, lightless, high pressure environment may resemble the life forms which survived through "snowball earth" and evolved into the life forms we know today (Kirchvink, 2000). Recent airborne radar surveys over Dome C and the South Pole regions allow us to assess where these lakes are most likely to exist and infer melting and freezing rates at base of the ice sheet. Lakes appear as strong, flat basal reflectors in airborne radar sounding data. In order to determine the absolute strength of the reflector it is important to accurately estimate signal loss due to absorption by the ice. As this quantity is temperature sensitive, especially in regions where liquid water is likely to exist, we have developed a one dimensional heat transfer model, incorporating surface temperature, accumulation, ice sheet thickness, and geothermal flux. Of the four quantities used for our temperature model, geothermal flux has usually proven to be the most difficult to asses, due to logistical difficulties. A technique developed by Fahnestock et al 2001 is showing promise for inferring geothermal flux, with airborne radar data. This technique assumes that internal reflectors, which result from varying electrical properties within the ice column, can be approximated as constant time horizons. Using ice core data from our study area, we can place dates upon these internal layers and develop an age versus depth relationship for the surveyed region, with margin of error of +- 50 m for each selected layer. Knowing this relationship allows us to infer the vertical strain response of the ice to the stress of vertical loading by snow accumulation. When ice is frozen to the bed the deeper ice will accommodate the increased stress of by deforming and thinning (Patterson 1994). This thinning of deeper layers occurs throughout most of our study area. However, analysis of dated internal layers over several bright, flat, "lake-like" reflectors reveals a very different age versus depth relationship in which deeper layers actually thicken with depth. This thickening of deep layers results from ice flowing in from the sides to accommodate significant liquid water production at the base of the ice sheet. This melt is occurring today and can be quantified. With our knowledge of melt rates we can begin to estimate inputs and assess hydrologic parameters for the subglacial lake systems of East Antarctica.

  6. Automated modeling of ecosystem CO2 fluxes based on closed chamber measurements: A standardized conceptual and practical approach

    NASA Astrophysics Data System (ADS)

    Hoffmann, Mathias; Jurisch, Nicole; Albiac Borraz, Elisa; Hagemann, Ulrike; Sommer, Michael; Augustin, Jürgen

    2015-04-01

    Closed chamber measurements are widely used for determining the CO2 exchange of small-scale or heterogeneous ecosystems. Among the chamber design and operational handling, the data processing procedure is a considerable source of uncertainty of obtained results. We developed a standardized automatic data processing algorithm, based on the language and statistical computing environment R© to (i) calculate measured CO2 flux rates, (ii) parameterize ecosystem respiration (Reco) and gross primary production (GPP) models, (iii) optionally compute an adaptive temperature model, (iv) model Reco, GPP and net ecosystem exchange (NEE), and (v) evaluate model uncertainty (calibration, validation and uncertainty prediction). The algorithm was tested for different manual and automatic chamber measurement systems (such as e.g. automated NEE-chambers and the LI-8100A soil CO2 Flux system) and ecosystems. Our study shows that even minor changes within the modelling approach may result in considerable differences of calculated flux rates, derived photosynthetic active radiation and temperature dependencies and subsequently modeled Reco, GPP and NEE balance of up to 25%. Thus, certain modeling implications will be given, since automated and standardized data processing procedures, based on clearly defined criteria, such as statistical parameters and thresholds are a prerequisite and highly desirable to guarantee the reproducibility, traceability of modelling results and encourage a better comparability between closed chamber based CO2 measurements.

  7. On Using CO2 Concentration Measurements at Mountain top and Valley Locations in Regional Flux Studies.

    NASA Astrophysics Data System (ADS)

    de Wekker, S. F.; Song, G.; Stephens, B. B.

    2007-12-01

    Data from the Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON) are used to investigate atmospheric controls on temporal and spatial variability of CO2 in mountainous terrain and the usefulness of mountain top and valley measurement for the estimation of regional CO2 fluxes. Rocky RACCOON consists of four sites installed in fall of 2005 and spring of 2006: Niwot Ridge, near Ward, Colorado; Storm Peak Laboratory near Steamboat Springs, Colorado; Fraser Experimental Forest, near Fraser Colorado; and Hidden Peak, near Snowbird, Utah. The network uses the NCAR-developed Autonomous Inexpensive Robust CO2 Analyzer. These units measure CO2 concentrations at three levels on a tower, producing individual measurements every 2.5 minutes precise to 0.1 ppm CO2 and closely tied to the WMO CO2 scale. Three of the sites are located on a mountain top while one site is located in a valley. Initial analyses show interesting relationships between CO2 concentration and atmospheric parameters, such as wind speed and direction, temperature, and incoming solar radiation. The nature of these relationships is further investigated with an atmospheric mesoscale model. Idealized and realistic simulations are able to capture the observed behavior of spatial and temporal CO2 variability and reveal the responsible physical processes. The implications of the results and the value of the measurements for providing information on local to regional scale respiration and photosynthesis rates in the Rockies are discussed.

  8. Differential radiometry for measuring the net radiative flux in the earth`s atmosphere

    SciTech Connect

    La Delfe, P.C.; Love, S.P.; Weber, P.G.

    1996-11-01

    The Hemispheric Optimized NEt Radiometer (HONER) is very briefly described. HONER was developed to resolve technical issues impeding the accurate measurement of atmospheric radiative flux. HONER uses differential radiometry, chopping the signal from upwelling and downwelling fluxes onto a single AC detector system, allowing true optical differencing as well as measurements of the individual fluxes. Wavelength coverage encompasses ultraviolet to more than 50 micrometers. HONER has been used in a ground-based version and will be tested on the Perseus B Unmanned Aerospace Vehicle.

  9. Annual sediment flux estimates in a tidal strait using surrogate measurements

    USGS Publications Warehouse

    Ganju, N.K.; Schoellhamer, D.H.

    2006-01-01

    Annual suspended-sediment flux estimates through Carquinez Strait (the seaward boundary of Suisun Bay, California) are provided based on surrogate measurements for advective, dispersive, and Stokes drift flux. The surrogates are landward watershed discharge, suspended-sediment concentration at one location in the Strait, and the longitudinal salinity gradient. The first two surrogates substitute for tidally averaged discharge and velocity-weighted suspended-sediment concentration in the Strait, thereby providing advective flux estimates, while Stokes drift is estimated with suspended-sediment concentration alone. Dispersive flux is estimated using the product of longitudinal salinity gradient and the root-mean-square value of velocity-weighted suspended-sediment concentration as an added surrogate variable. Cross-sectional measurements validated the use of surrogates during the monitoring period. During high freshwater flow advective and dispersive flux were in the seaward direction, while landward dispersive flux dominated and advective flux approached zero during low freshwater flow. Stokes drift flux was consistently in the landward direction. Wetter than average years led to net export from Suisun Bay, while dry years led to net sediment import. Relatively low watershed sediment fluxes to Suisun Bay contribute to net export during the wet season, while gravitational circulation in Carquinez Strait and higher suspended-sediment concentrations in San Pablo Bay (seaward end of Carquinez Strait) are responsible for the net import of sediment during the dry season. Annual predictions of suspended-sediment fluxes, using these methods, will allow for a sediment budget for Suisun Bay, which has implications for marsh restoration and nutrient/contaminant transport. These methods also provide a general framework for estimating sediment fluxes in estuarine environments, where temporal and spatial variability of transport are large. ?? 2006 Elsevier Ltd. All rights reserved.

  10. Flow rate measuring devices for gas flows

    NASA Astrophysics Data System (ADS)

    Bonfig, K. W.

    1985-07-01

    Flowrate measuring devices are described: volume meter with fixed or mobile walls; turbine meter; throttling procedure; ultrasonic and Doppler methods; vortex method; rotary flowmeter; and swinging body flow measuring procedure. Flowrate can also be measured from the force exerted on bodies immersed in a fluid or based on thermodynamical principles. The characteristics and operating envelope of each device/method are given.

  11. Contribution of the finite volume point dilution method for measurement of groundwater fluxes in a fractured aquifer.

    PubMed

    Jamin, P; Goderniaux, P; Bour, O; Le Borgne, T; Englert, A; Longuevergne, L; Brouyère, S

    2015-11-01

    Measurement of groundwater fluxes is the basis of all hydrogeological study, from hydraulic characterization to the most advanced reactive transport modeling. Usual groundwater flux estimation with Darcy's law may lead to cumulated errors on spatial variability, especially in fractured aquifers where local direct measurement of groundwater fluxes becomes necessary. In the present study, both classical point dilution method (PDM) and finite volume point dilution method (FVPDM) are compared on the fractured crystalline aquifer of Ploemeur, France. The manipulation includes the first use of the FVPDM in a fractured aquifer using a double packer. This configuration limits the vertical extent of the tested zone to target a precise fracture zone of the aquifer. The result of this experiment is a continuous monitoring of groundwater fluxes that lasted for more than 4days. Measurements of groundwater flow rate in the fracture (Qt) by PDM provide good estimates only if the mixing volume (Vw) (volume of water in which the tracer is mixed) is precisely known. Conversely, the FVPDM allows for an independent estimation of Vw and Qt, leading to better precision in case of complex experimental setup such as the one used. The precision of a PDM does not rely on the duration of the experiment while a FVPDM may require long experimental duration to guarantees a good precision. Classical PDM should then be used for rapid estimation of groundwater flux using simple experimental setup. On the other hand, the FVPDM is a more precise method that has a great potential for development but may require longer duration experiment to achieve a good precision if the groundwater fluxes investigated are low and/or the mixing volume is large. PMID:26519822

  12. Contribution of the finite volume point dilution method for measurement of groundwater fluxes in a fractured aquifer

    NASA Astrophysics Data System (ADS)

    Jamin, P.; Goderniaux, P.; Bour, O.; Le Borgne, T.; Englert, A.; Longuevergne, L.; Brouyère, S.

    2015-11-01

    Measurement of groundwater fluxes is the basis of all hydrogeological study, from hydraulic characterization to the most advanced reactive transport modeling. Usual groundwater flux estimation with Darcy's law may lead to cumulated errors on spatial variability, especially in fractured aquifers where local direct measurement of groundwater fluxes becomes necessary. In the present study, both classical point dilution method (PDM) and finite volume point dilution method (FVPDM) are compared on the fractured crystalline aquifer of Ploemeur, France. The manipulation includes the first use of the FVPDM in a fractured aquifer using a double packer. This configuration limits the vertical extent of the tested zone to target a precise fracture zone of the aquifer. The result of this experiment is a continuous monitoring of groundwater fluxes that lasted for more than 4 days. Measurements of groundwater flow rate in the fracture (Qt) by PDM provide good estimates only if the mixing volume (Vw) (volume of water in which the tracer is mixed) is precisely known. Conversely, the FVPDM allows for an independent estimation of Vw and Qt, leading to better precision in case of complex experimental setup such as the one used. The precision of a PDM does not rely on the duration of the experiment while a FVPDM may require long experimental duration to guarantees a good precision. Classical PDM should then be used for rapid estimation of groundwater flux using simple experimental setup. On the other hand, the FVPDM is a more precise method that has a great potential for development but may require longer duration experiment to achieve a good precision if the groundwater fluxes investigated are low and/or the mixing volume is large.

  13. Effects of trapped proton flux anisotropy on dose rates in low Earth orbit.

    PubMed

    Badhwar, G D; Kushin, V V; Akatov YuA; Myltseva, V A

    1999-06-01

    Trapped protons in the South Atlantic Anomaly (SAA) have a rather narrow pitch angle distribution and exhibit east-west anisotropy. In low Earth orbits, the E-W effect results in different amounts of radiation dose received by different sections of the spacecraft. This effect is best studied on missions in which the spacecraft flies in a fixed orientation. The magnitude of the effect depends on the particle energy and altitude through the SAA. In this paper, we describe a clear example of this effect from measurements of radiation dose rates and linear energy transfer spectra made on Space Shuttle flight STS-94 (28.5 degree inclination x 296 km altitude). The ratio of dose rates from the two directions at this location in the mid-deck was 2.7. As expected from model calculations, the spectra from the two directions are different, that is the ratio is energy dependent. The data can be used to distinguish the anisotropy models. The flight carried an active tissue equivalent proportional counter (TEPC), and passive thermoluminscent detectors (TLDs), and two types of nuclear emulsions. Using nuclear emulsions, charged particles and secondary neutron energy spectra were measured. The combined galactic cosmic radiation+trapped charged particle lineal energy spectra measured by the TEPC and the linear energy transfer spectrum measured by nuclear emulsions are in good agreement. The charged particle absorbed dose rates varied from 112 to 175 microGy/day, and dose equivalent rates from 264.3 to 413 microSv/day. Neutrons in the 1-10 MeV contributed a dose rate of 3.7 microGy/day and dose equivalent rate of 30.8 microSv/day, respectively. PMID:11543145

  14. Cluster electric current density measurements within a magnetic flux rope in the plasma sheet

    NASA Technical Reports Server (NTRS)

    Slavin, J. A.; Lepping, R. P.; Gjerloev, J.; Goldstein, M. L.; Fairfield, D. H.; Acuna, M. H.; Balogh, A.; Dunlop, M.; Kivelson, M. G.; Khurana, K.

    2003-01-01

    On August 22, 2001 all 4 Cluster spacecraft nearly simultaneously penetrated a magnetic flux rope in the tail. The flux rope encounter took place in the central plasma sheet, Beta(sub i) approx. 1-2, near the leading edge of a bursty bulk flow. The "time-of-flight" of the flux rope across the 4 spacecraft yielded V(sub x) approx. 700 km/s and a diameter of approx.1 R(sub e). The speed at which the flux rope moved over the spacecraft is in close agreement with the Cluster plasma measurements. The magnetic field profiles measured at each spacecraft were first modeled separately using the Lepping-Burlaga force-free flux rope model. The results indicated that the center of the flux rope passed northward (above) s/c 3, but southward (below) of s/c 1, 2 and 4. The peak electric currents along the central axis of the flux rope predicted by these single-s/c models were approx.15-19 nA/sq m. The 4-spacecraft Cluster magnetic field measurements provide a second means to determine the electric current density without any assumption regarding flux rope structure. The current profile determined using the curlometer technique was qualitatively similar to those determined by modeling the individual spacecraft magnetic field observations and yielded a peak current density of 17 nA/m2 near the central axis of the rope. However, the curlometer results also showed that the flux rope was not force-free with the component of the current density perpendicular to the magnetic field exceeding the parallel component over the forward half of the rope, perhaps due to the pressure gradients generated by the collision of the BBF with the inner magnetosphere. Hence, while the single-spacecraft models are very successful in fitting flux rope magnetic field and current variations, they do not provide a stringent test of the force-free condition.

  15. Measurements of Protein Crystal Face Growth Rates

    NASA Technical Reports Server (NTRS)

    Gorti, S.

    2014-01-01

    Protein crystal growth rates will be determined for several hyperthermophile proteins.; The growth rates will be assessed using available theoretical models, including kinetic roughening.; If/when kinetic roughening supersaturations are established, determinations of protein crystal quality over a range of supersaturations will also be assessed.; The results of our ground based effort may well address the existence of a correlation between fundamental growth mechanisms and protein crystal quality.

  16. A flux-gradient system for simultaneous measurement of the CH4, CO2, and H2O fluxes at a lake-air interface.

    PubMed

    Xiao, Wei; Liu, Shoudong; Li, Hanchao; Xiao, Qitao; Wang, Wei; Hu, Zhenghua; Hu, Cheng; Gao, Yunqiu; Shen, Jing; Zhao, Xiaoyan; Zhang, Mi; Lee, Xuhui

    2014-12-16

    Inland lakes play important roles in water and greenhouse gas cycling in the environment. This study aims to test the performance of a flux-gradient system for simultaneous measurement of the fluxes of water vapor, CO2, and CH4 at a lake-air interface. The concentration gradients over the water surface were measured with an analyzer based on the wavelength-scanned cavity ring-down spectroscopy technology, and the eddy diffusivity was measured with a sonic anemometer. Results of a zero-gradient test indicate a flux measurement precision of 4.8 W m(-2) for water vapor, 0.010 mg m(-2) s(-1) for CO2, and 0.029 ?g m(-2) s(-1) for CH4. During the 620 day measurement period, 97%, 69%, and 67% of H2O, CO2, and CH4 hourly fluxes were higher in magnitude than the measurement precision, which confirms that the flux-gradient system had adequate precision for the measurement of the lake-air exchanges. This study illustrates four strengths of the flux-gradient method: (1) the ability to simultaneously measure the flux of H2O, CO2, and CH4; (2) negligibly small density corrections; (3) the ability to resolve small CH4 gradient and flux; and (4) continuous and noninvasive operation. The annual mean CH4 flux (1.8 g CH4 m(-2) year(-1)) at this hypereutrophic lake was close to the median value for inland lakes in the world (1.6 g CH4 m(-2) year(-1)). The system has adequate precision for CH4 flux for broad applications but requires further improvement to resolve small CO2 flux in many lakes. PMID:25377990

  17. Inverse estimation of radon flux distribution for East Asia using measured atmospheric radon concentration.

    PubMed

    Hirao, S; Hayashi, R; Moriizumi, J; Yamazawa, H; Tohjima, Y; Mukai, H

    2015-11-01

    In this study, the (222)Rn flux density distribution at surface was estimated in East Asia with the Bayesian synthesis inversion using measurement data and a long-range atmospheric (222)Rn transport model. Surface atmospheric (222)Rn concentrations measured at Hateruma Island in January 2008 were used. The estimated (222)Rn flux densities were generally higher than the prior ones. The area-weighted mean (222)Rn flux density for East Asia in January 2008 was estimated to be 44.0 mBq m(-2) s(-1). The use of the estimated (222)Rn flux density improved the discrepancy of the model-calculated concentrations with the measurements at Hateruma Island. PMID:25904695

  18. Comparison of measured and modeled radiation, heat and water vapor fluxes: FIFE pilot study

    NASA Technical Reports Server (NTRS)

    Blad, Blaine L.; Verma, Shashi B.; Hubbard, Kenneth G.; Starks, Patrick; Hays, Cynthia; Norman, John M.; Waltershea, Elizabeth

    1988-01-01

    The primary objectives of the 1985 study were to test the feasibility of using radio frequency receivers to collect data from automated weather stations and to evaluate the use of the data collected by the automated weather stations for modeling the fluxes of latent heat, sensible heat, and radiation over wheat. The model Cupid was used to calculate these fluxes which were compared with fluxes of these entities measured using micrometeorological techniques. The primary objectives of the 1986 study were to measure and model reflected and emitted radiation streams at a few locations within the First International Satellite Land-Surface Climatology Project Field Experiment (FIFE) site and to compare modeled and measured latent heat and sensible heat fluxes from the prairie vegetation.

  19. Flux correction for closed-path laser spectrometers without internal water vapor measurements

    NASA Astrophysics Data System (ADS)

    Hiller, R. V.; Zellweger, C.; Knohl, A.; Eugster, W.

    2012-01-01

    Recently, instruments became available on the market that provide the possibility to perform eddy covariance flux measurements of CH4 and many other trace gases, including the traditional CO2 and H2O. Most of these instruments employ laser spectroscopy, where a cross-sensitivity to H2O is frequently observed leading to an increased dilution effect. Additionally, sorption processes at the intake tube walls modify and delay the observed H2O signal in closed-path systems more strongly than the signal of the sampled trace gas. Thereby, a phase shift between the trace gas and H2O fluctuations is introduced that dampens the H2O flux observed in the sampling cell. For instruments that do not provide direct H2O measurement in the sampling cell, transfer functions from externally measured H2O fluxes are needed to estimate the effect of H2O on trace gas flux measurements. The effects of cross-sensitivity and the damping are shown for an eddy covariance setup with the Fast Greenhouse Gas Analyzer (FGGA, Los Gatos Research Inc.) that measures CO2, CH4, and H2O fluxes. This instrument is technically identical with the Fast Methane Analyzer (FMA, Los Gatos Research Inc.) that does not measure H2O concentrations. Hence, we used measurements from a FGGA to derive a modified correction for the FMA accounting for dilution as well as phase shift effects in our instrumental setup. With our specific setup for eddy covariance flux measurements, the cross-sensitivity counteracts the damping effects, which compensate each other. Hence, the new correction only deviates very slightly from the traditional Webb, Pearman, and Leuning density correction, which is calculated from separate measurements of the atmospheric water vapor flux.

  20. Canopy-scale flux measurements and bottom-up emission estimates of volatile organic compounds from a mixed oak and hornbeam forest in northern Italy

    NASA Astrophysics Data System (ADS)

    Acton, W. J. F.; Schallhart, S.; Langford, B.; Valach, A.; Rantala, P.; Fares, S.; Carriero, G.; Tillmann, R.; Tomlinson, S. J.; Dragosits, U.; Gianelle, D.; Hewitt, C. N.; Nemitz, E.

    2015-10-01

    This paper reports the fluxes and mixing ratios of biogenically emitted volatile organic compounds (BVOCs) 4 m above a mixed oak and hornbeam forest in northern Italy. Fluxes of methanol, acetaldehyde, isoprene, methyl vinyl ketone + methacrolein, methyl ethyl ketone and monoterpenes were obtained using both a proton transfer reaction-mass spectrometer (PTR-MS) and a proton transfer reaction-time of flight-mass spectrometer (PTR-ToF-MS) together with the methods of virtual disjunct eddy covariance (PTR-MS) and eddy covariance (PTR-ToF-MS). Isoprene was the dominant emitted compound with a mean day-time flux of 1.9 mg m-2 h-1. Mixing ratios, recorded 4 m above the canopy, were dominated by methanol with a mean value of 6.2 ppbv over the 28 day measurement period. Comparison of isoprene fluxes calculated using the PTR-MS and PTR-ToF-MS showed very good agreement while comparison of the monoterpene fluxes suggested a slight over estimation of the flux by the PTR-MS. A basal isoprene emission rate for the forest of 1.7 mg m-2 h-1 was calculated using the MEGAN isoprene emissions algorithms (Guenther et al., 2006). A detailed tree species distribution map for the site enabled the leaf-level emissions of isoprene and monoterpenes recorded using GC-MS to be scaled up to produce a "bottom-up" canopy-scale flux. This was compared with the "top-down" canopy-scale flux obtained by measurements. For monoterpenes, the two estimates were closely correlated and this correlation improved when the plant species composition in the individual flux footprint was taken into account. However, the bottom-up approach significantly underestimated the isoprene flux, compared with the top-down measurements, suggesting that the leaf-level measurements were not representative of actual emission rates.

  1. Rates of insulin secretion in INS-1 cells are enhanced by coupling to anaplerosis and Kreb's cycle flux independent of ATP synthesis

    SciTech Connect

    Cline, Gary W.; Pongratz, Rebecca L.; Zhao, Xiaojian; Papas, Klearchos K.

    2011-11-11

    Highlights: Black-Right-Pointing-Pointer We studied media effects on mechanisms of insulin secretion of INS-1 cells. Black-Right-Pointing-Pointer Insulin secretion was higher in DMEM than KRB despite identical ATP synthesis rates. Black-Right-Pointing-Pointer Insulin secretion rates correlated with rates of anaplerosis and TCA cycle. Black-Right-Pointing-Pointer Mitochondria metabolism and substrate cycles augment secretion signal of ATP. -- Abstract: Mechanistic models of glucose stimulated insulin secretion (GSIS) established in minimal media in vitro, may not accurately describe the complexity of coupling metabolism with insulin secretion that occurs in vivo. As a first approximation, we have evaluated metabolic pathways in a typical growth media, DMEM as a surrogate in vivo medium, for comparison to metabolic fluxes observed under the typical experimental conditions using the simple salt-buffer of KRB. Changes in metabolism in response to glucose and amino acids and coupling to insulin secretion were measured in INS-1 832/13 cells. Media effects on mitochondrial function and the coupling efficiency of oxidative phosphorylation were determined by fluorometrically measured oxygen consumption rates (OCRs) combined with {sup 31}P NMR measured rates of ATP synthesis. Substrate preferences and pathways into the TCA cycle, and the synthesis of mitochondrial 2nd messengers by anaplerosis were determined by {sup 13}C NMR isotopomer analysis of the fate of [U-{sup 13}C] glucose metabolism. Despite similar incremental increases in insulin secretion, the changes of OCR in response to increasing glucose from 2.5 to 15 mM were blunted in DMEM relative to KRB. Basal and stimulated rates of insulin secretion rates were consistently higher in DMEM, while ATP synthesis rates were identical in both DMEM and KRB, suggesting greater mitochondrial uncoupling in DMEM. The relative rates of anaplerosis, and hence synthesis and export of 2nd messengers from the mitochondria were found to be similar in DMEM to those in KRB. And, the correlation of total PC flux with insulin secretion rates in DMEM was found to be congruous with the correlation in KRB. Together, these results suggest that signaling mechanisms associated with both TCA cycle flux and with anaplerotic flux, but not ATP production, may be responsible for the enhanced rates of insulin secretion in more complex, and physiologically-relevant media.

  2. Estimating Scalar Fluxes in Tropical Forests from Concentration/Temperature Profile Measurements

    NASA Astrophysics Data System (ADS)

    Silva, R.; Siqueira, M.; Katul, G.; Rocha, H.; Goulden, M.; Miller, S.

    2004-12-01

    Eddy Covariance (EC) flux measurements are now widely used for estimating long-term biosphere-atmosphere gas exchange. However, gap-filling and constraining these EC estimates using other techniques that are sensitive to different assumptions remains a high priority. Improved ability to recover fluxes from concentration and temperature profile data could serve as one such constraining and gap-filling method. Furthermore, if successful, concentration profiles permit estimating fluxes of chemical fluxes for which high frequency gas analyzers are not currently available. We investigate the ability of higher order closure models to estimate CO2 fluxes from a 40 m tall tropical forest on the Floresta Nacional do Tapajós, Para, Brazil. Eddy covariance measurements of sensible and latent heat, CO2 and momentum fluxes were collected along with profile measurements of CO2 and water vapor concentrations and temperature as part of the LBA program. To this end, we extended a 2nd order Eulerian approach for CO2 along with the appropriate stability correction regimes. Also, we included in the model transient term in an attempt to improve estimates over periods in which storage and turbulent fluxes may be of comparable magnitude. For comparison, we performed calculations using a 1st order closure model and a "dummy" model where perfect similarity between heat and CO2 transfer is assumed.

  3. Field intercomparison of two optical analyzers for CH4 eddy covariance flux measurements

    NASA Astrophysics Data System (ADS)

    Tuzson, B.; Hiller, R. V.; Zeyer, K.; Eugster, W.; Neftel, A.; Ammann, C.; Emmenegger, L.

    2010-07-01

    Fast response optical analyzers based on laser absorption spectroscopy are the preferred tools to measure field-scale mixing ratios and fluxes of a range of trace gases. Several state-of-the-art instruments have become commercially available and are gaining in popularity. This paper aims for a critical field evaluation and intercomparison of two compact, cryogen-free and fast response instruments: a quantum cascade laser based absorption spectrometer from Aerodyne Research, Inc., and an off-axis integrated cavity output spectrometer from Los Gatos Research, Inc. In this paper, both analyzers are characterized with respect to precision, accuracy, response time and also their sensitivity to water vapour. The instruments were tested in a field campaign to assess their behaviour under various meteorological conditions. The instrument's suitability for eddy covariance flux measurements was evaluated by applying an artificial flux of CH4 generated above a managed grassland with otherwise very low methane flux. This allowed an independent verification of the flux measurements accuracy, including the overall eddy covariance setup and data treatment. The retrieved fluxes were in good agreement with the known artificial emission flux, which is more than satisfactory, given that the analyzers were attached to separate sonic anemometers placed on individual eddy towers with different data acquisition systems but similar data treatment that are specific to the best practice used by the involved research teams.

  4. A new method for simultaneous measurement of convective and radiative heat flux in car underhood applications

    NASA Astrophysics Data System (ADS)

    Khaled, M.; Garnier, B.; Harambat, F.; Peerhossaini, H.

    2010-02-01

    A new experimental technique is presented that allows simultaneous measurement of convective and radiative heat flux in the underhood. The goal is to devise an easily implemented and accurate experimental method for application in the vehicle underhood compartment. The new method is based on a technique for heat-flux measurement developed by the authors (Heat flow (flux) sensors for measurement of convection, conduction and radiation heat flow 27036-2, © Rhopoint Components Ltd, Hurst Green, Oxted, RH8 9AX, UK) that uses several thermocouples in the thickness of a thermal resistive layer (foil heat-flux sensor). The method proposed here uses a pair of these thermocouples with different radiative properties. Measurements validating this novel technique are carried out on a flat plate with a prescribed constant temperature in both natural- and forced-convection flow regimes. The test flat plate is instrumented by this new technique, and also with a different technique that is intrusive but very accurate, used as reference here (Bardon J P and Jarny Y 1994 Procédé et dispositif de mesure transitoire de température et flux surfacique Brevet n°94.011996, 22 February). Discrepancies between the measurements by the two techniques are less than 10% for both convective and radiative heat flux. Error identification and sensitivity analysis of the new method are also presented.

  5. Seasonal measurements of total OH reactivity emission rates from Norway spruce in 2011

    NASA Astrophysics Data System (ADS)

    Nölscher, A. C.; Bourtsoukidis, E.; Bonn, B.; Kesselmeier, J.; Lelieveld, J.; Williams, J.

    2013-06-01

    Numerous reactive volatile organic compounds (VOCs) are emitted into the atmosphere by vegetation. Most biogenic VOCs are highly reactive towards the atmosphere's most important oxidant, the hydroxyl (OH) radical. One way to investigate the chemical interplay between biosphere and atmosphere is through the measurement of total OH reactivity, the total loss rate of OH radicals. This study presents the first determination of total OH reactivity emission rates (measurements via the comparative reactivity method) based on a branch cuvette enclosure system mounted on a Norway spruce (Picea abies) throughout spring, summer and autumn 2011. In parallel VOC emission rates were monitored by a second proton-transfer-reaction mass spectrometer (PTR-MS), and total ozone (O3) loss rates were obtained inside the cuvette. Total OH reactivity emission rates were in general temperature and light dependent, showing strong diel cycles with highest values during daytime. Monoterpene emissions contributed most, accounting for 56-69% of the measured total OH reactivity flux in spring and early summer. However, during late summer and autumn the monoterpene contribution decreased to 11-16%. At this time, a large missing fraction of the total OH reactivity emission rate (70-84%) was found when compared to the VOC budget measured by PTR-MS. Total OH reactivity and missing total OH reactivity emission rates reached maximum values in late summer corresponding to the period of highest temperature. Total O3 loss rates within the closed cuvette showed similar diel profiles and comparable seasonality to the total OH reactivity fluxes. Total OH reactivity fluxes were also compared to emissions from needle storage pools predicted by a temperature-only-dependent algorithm. Deviations of total OH reactivity fluxes from the temperature-only-dependent emission algorithm were observed for occasions of mechanical and heat stress. While for mechanical stress, induced by strong wind, measured VOCs could explain total OH reactivity emissions, during heat stress they could not. The temperature-driven algorithm matched the diel variation of total OH reactivity emission rates much better in spring than in summer, indicating a different production and emission scheme for summer and early autumn. During these times, unmeasured and possibly unknown primary biogenic emissions contributed significantly to the observed total OH reactivity flux.

  6. Measurement of the sky photon background flux at the Auger Observatory

    SciTech Connect

    Caruso, R.; Insolia, A.; Petrera, Sergio; Privitera, P.; Salamida, F.; Verzi, V.

    2005-07-01

    The sky photon background flux has been measured at the southern Auger site in Malargue, Argentina, using the observatory's fluorescence detectors (FD). The analysis is based on ADC variances of pixels not triggered by the First Level Trigger. Photon fluxes are calculated for each individual pixel at each telescope. The statistics from each night of data taking allows a study of local variations in the photon flux. Results show a clear dependence of the flux on elevation angle. Time variations, possibly related to different atmospheric conditions, do not mask this dependence. In particular the flux excess above the horizon shows a rather stable and reproducible behavior with elevation. Correlation of this dependence with atmospheric parameters can be of interest as it offers the promise of extracting those parameters directly from FD data, thus allowing cross checks with independent methods based on different monitoring devices.

  7. Measurement of the Sky Photon Background Flux at the Auger Observatory

    E-print Network

    R. Caruso; A. Insolia; S. Petrera; P. Privitera; F. Salamida; V. Verzi

    2005-07-05

    The sky photon background flux has been measured at the southern Auger site in Malargue, Argentina, using the observatory's fluorescence detectors (FD). The analysis is based on ADC variances of pixels not triggered by the First Level Trigger. Photon fluxes are calculated for each individual pixel at each telescope. The statistics from each night of data taking allows a study of local variations in the photon flux. Results show a clear dependence of the flux on elevation angle. Time variations, possibly related to different atmospheric conditions, do not mask this dependence. In particular the flux excess above the horizon shows a rather stable and reproducible behaviour with elevation. Correlation of this dependence with atmospheric parameters can be of interest as it offers the promise of extracting those parameters directly from FD data, thus allowing cross checks with independent methods based on different monitoring devices.

  8. An Absolute Flux Density Measurement of the Supernova Remnant Casseopia A at 32 GHz

    E-print Network

    Brian S. Mason; Erik M. Leitch; Steven T. Myers; John K. Cartwright; A. C. S. Readhead

    1999-08-31

    We report 32 GHz absolute flux density measurements of the supernova remnant Cas A, with an accuracy of 2.5%. The measurements were made with the 1.5-meter telescope at the Owens Valley Radio Observatory. The antenna gain had been measured by NIST in May 1990 to be $0.505 \\pm 0.007 \\frac{{\\rm mK}}{{\\rm Jy}}$. Our observations of Cas A in May 1998 yield $S_{cas,1998} = 194 \\pm 5 {\\rm Jy}$. We also report absolute flux density measurements of 3C48, 3C147, 3C286, Jupiter, Saturn and Mars.

  9. Field intercomparison of four methane gas analyzers suitable for eddy covariance flux measurements

    NASA Astrophysics Data System (ADS)

    Peltola, O.; Mammarella, I.; Haapanala, S.; Burba, G.; Vesala, T.

    2013-06-01

    Performances of four methane gas analyzers suitable for eddy covariance measurements are assessed. The assessment and comparison was performed by analyzing eddy covariance data obtained during summer 2010 (1 April to 26 October) at a pristine fen, Siikaneva, Southern Finland. High methane fluxes with pronounced seasonality have been measured at this fen. The four participating methane gas analyzers are commercially available closed-path units TGA-100A (Campbell Scientific Inc., USA), RMT-200 (Los Gatos Research, USA), G1301-f (Picarro Inc., USA) and an early prototype open-path unit Prototype-7700 (LI-COR Biosciences, USA). The RMT-200 functioned most reliably throughout the measurement campaign, during low and high flux periods. Methane fluxes from RMT-200 and G1301-f had the smallest random errors and the fluxes agree remarkably well throughout the measurement campaign. Cospectra and power spectra calculated from RMT-200 and G1301-f data agree well with corresponding temperature spectra during a high flux period. None of the gas analyzers showed statistically significant diurnal variation for methane flux. Prototype-7700 functioned only for a short period of time, over one month, in the beginning of the measurement campaign during low flux period, and thus, its overall accuracy and season-long performance were not assessed. The open-path gas analyzer is a practical choice for measurement sites in remote locations due to its low power demand, whereas for G1301-f methane measurements interference from water vapor is straightforward to correct since the instrument measures both gases simultaneously. In any case, if only the performance in this intercomparison is considered, RMT-200 performed the best and is the recommended choice if a new fast response methane gas analyzer is needed.

  10. Direct measurements of CO2 fluxes in an urban area of Beijing city

    NASA Astrophysics Data System (ADS)

    Liu, H.; Feng, J.

    2009-12-01

    Direct measurements of CO2 fluxes in an urban area of Beijing city Huizhi Liu and Jianwu Feng LAPC, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029 Abstract Direct measurements of CO2 fluxes using an eddy covariance (EC) system were conducted from 2006 to 2008 in an urban environment of Beijing city. The EC measurements were made at the height of 47 m above the canopy on a 325 m tower. Stationarity test and cospectral analyses of the turbulence measurements met the requirement of EC assumptions. Analyses of the data revealed a clear annual cycle of CO2 fluxes with the maximum in the winter and the minimum in the summer. The positive fluxes of CO2 demonstrated that the urban surface was consistently a net source of CO2 emissions to the atmosphere. The mean daily CO2 fluxes were 0.48 ± 0.17 mg m-2 s-1 and 0.78 ± 0.28 mg m-2 s-1 (mean ± std) in the summer and the winter respectively, indicating that vehicle emissions and residential heating both contributed to the higher magnitude of CO2 fluxes in winter time. Diurnal pattern of CO2 fluxes were largely associated with traffic volumn. Two distinct peaks were observed in the morning and evening traffic peak hours, with the winter morning peak averaging up to 1.3 mg m-2 s-1. Minimum CO2 fluxes usually occurred before sunrise. The two peaks of CO2 fluxes in the weekend were a little lower than in the weekday all the year around. In summer time, the two peaks occurred about 2 hour later in the weekend compared to the weekday, but this phenomenon was not obvious in the winter. Restricted driving and other related measures to reduce CO2 emission during the time of Olympic Games (July 20 to September 20, 2008) had significant impact on the magnitude of CO2 fluxes, resulting in a mean daily value of 0.39 ± 0.13 mg m-2 s-1 (mean ± std). This research in Beijing city aims at furthering the understanding of the level and dynamics of CO2 fluxes in mega cities in China. Keywords: Carbon dioxide fluxes, eddy covariance, urban area, Beijing

  11. Elemental weathering fluxes and saprolite production rate in a Central African lateritic terrain (Nsimi, South Cameroon)

    NASA Astrophysics Data System (ADS)

    Braun, Jean-Jacques; Marechal, Jean-Christophe; Riotte, Jean; Boeglin, Jean-Loup; Bedimo Bedimo, Jean-Pierre; Ndam Ngoupayou, Jules Remy; Nyeck, Brunot; Robain, Henri; Sekhar, M.; Audry, Stéphane; Viers, Jérôme

    2012-12-01

    The comparison between contemporary and long-term weathering has been carried out in the Small Experimental Watershed (SEW) of Nsimi, South Cameroon in order to quantify the export fluxes of major and trace elements and the residence time of the lateritic weathering cover. We focus on the hillside system composed of a thick lateritic weathering cover topped by a soil layer. This study is built on the recent improvements of the hillside hydrological functioning and on the analyses of major and trace elements. The mass balance calculation at the weathering horizon scale performed with the parent rock as reference indicates (i) strong depletion profiles for alkalis (Na, K, Rb) and alkaline earths (Mg, Ca, Sr, Ba), (ii) moderate depletion profiles for Si, P, Cd, Cu, Zn, Ni and Co, (iii) depletion/enrichment profiles for Al, Ga, Ge, Sn, Pb, LREE, HREE, Y, U, Fe, V, Cr, Mn. It is noteworthy that (i) Mn and Ce are not significantly redistributed according to oxidative processes as it is the case for Fe, V and Cr, and (ii) Ge is fractionated compared to silica with enrichment in Fe-rich horizons. The calculations performed for the topsoil with iron crust as parent material reference reveal that the degradation of the iron crust is accompanied by the loss of most of the constituting elements, among which are those specifically accumulated as the redox sensitive elements (Fe, V, Cr) and iron oxide related elements like Th. The overall current elemental fluxes from the hillside system at the springs and the seepage zones are extremely low due to the inert lateritic mineralogy. Ninety-four percent of the whole Na flux generated from the hillside corrected from atmospheric deposits (77 mol/ha/yr) represents the current weathering rates of plagioclase (oligoclase) in the system, the other remaining 6% may be attributed to the dissolution of hornblende. The silica hillside flux is 300 mol/ha/yr and can be mostly attributed to the plagioclase and kaolinite dissolution. Al and Ga are exported from the lateritic regolith and maybe due to the dissolution of kaolinite crystals. Compared to the other immobile elements (Zr, Hf, Nb and Th), Ti is significantly exported. Among redox-sensitive elements (Fe, V, Cr, Mn, Ce), only Ce and Mn are exported out of the hillside system. The other elements (Fe, V, Cr) are likely able to be mobilized but over a short distance only. Rb, Sr, Ba, Ni, Cu, Zn are affected by export processes. LREE and Y are exported but in very low amounts (in the range from ?mol/ha/yr to mmol/ha/yr) while HREE and U are exported in negligible quantities. A first attempt is carried out to compare the mature ridge top profile from Nsimi SEW with the immature ridge top weathering profile from the Mule Hole SEW (South India), developed on similar granodioritic basement, in order to get deeper insight into (i) the contemporary saprolite production rates and (ii) the combined effect of precipitation (in terms of Mean Annual Rainfall, MAR) and evapotranspiration on the aggressiveness of the draining solutions. Considering (i) the contemporary Na flux as representative of the dissolution of plagioclase crystals and conservative during saprolitization processes and (ii) steady state of the inter-annual recharge (R) over a 10 years period, the current saprolite production rates (?r) are of 22 mm/kyr for Mule Hole SEW and 2 mm/kyr for Nsimi SEW, respectively. Even with a very low R/MAR ratio (0.04) compared to Nsimi, the chemical weathering at Mule Hole is active and related to the groundwater exports. At Mule Hole, plagioclase crystals are still present in the saprolite and the soil cover leading to a diffuse weathering front. The high Nsimi R/MAR ratio (0.2) allows the solution to be still aggressive with respect to the plagioclase and other weatherable minerals at the bedrock interface resulting in their complete breakdown in a few centimetres (sharp weathering front) leading to a mature saprolite. For the Nsimi SEW, if we consider (i) the low contemporary saprolite production rate (2 mm/kyr), (ii) the Miocene age (average 15 Myr) o

  12. Automated Speech Rate Measurement in Dysarthria

    ERIC Educational Resources Information Center

    Martens, Heidi; Dekens, Tomas; Van Nuffelen, Gwen; Latacz, Lukas; Verhelst, Werner; De Bodt, Marc

    2015-01-01

    Purpose: In this study, a new algorithm for automated determination of speech rate (SR) in dysarthric speech is evaluated. We investigated how reliably the algorithm calculates the SR of dysarthric speech samples when compared with calculation performed by speech-language pathologists. Method: The new algorithm was trained and tested using Dutch…

  13. Evaluation of laser absorption spectroscopic techniques for eddy covariance flux measurements of ammonia.

    PubMed

    Whitehead, James D; Twigg, Marsailidh; Famulari, Daniela; Nemitz, Eiko; Sutton, Mark A; Gallagher, Martin W; Fowler, David

    2008-03-15

    An intercomparison was made between eddy covariance flux measurements of ammonia by a quantum cascade laser absorption spectrometer (QCLAS) and a lead-salt tunable diode laser absorption spectrometer (TDLAS). The measurements took place in September 2004 and again in April 2005 over a managed grassland site in Southern Scotland, U.K. These were also compared with a flux estimate derived from an "Ammonia Measurement by ANnular Denuder with online Analysis" (AMANDA), using the aerodynamic gradient method (AGM). The concentration and flux measurements from the QCLAS correlated well with those of the TDLAS and the AGM systems when emissions were high, following slurry application to the field. Both the QCLAS and TDLAS, however, underestimated the flux when compared with the AMANDA system, by 64%. A flux loss of 41% due to chemical reaction of ammonia in the QCLAS (and 37% in the TDLAS) sample tube walls was identified and characterized using laboratory tests but did not fully accountforthis difference. Recognizing these uncertainties, the agreement between the systems was nevertheless very close (R2 = 0.95 between the QCLAS and the TDLAS; R2 = 0.84 between the QCLAS and the AMANDA) demonstrating the suitability of the laser absorption methods for quantifying the temporal dynamics of ammonia fluxes. PMID:18409634

  14. Heat and mass flux measurement from thermal infrared imagery: Example of the Soufrière Volcano (Guadeloupe)

    NASA Astrophysics Data System (ADS)

    Gaudin, D.; Beauducel, F.; Finizola, A.; Allemand, P.; Delacourt, C.; Richon, P.; Coutant, O.; de Chabalier, J.

    2012-12-01

    The estimation of mass and heat emissions is crucial for volcano monitoring. These fluxes may be diffuse or concentrated on precise zones of the volcano : gas fumaroles, thermal anomalies, hot springs. The total flux evolution is good indicator of the volcanic activity global behavior, while local flux at focused zones may help to characterize the hydrothermal system. However, large-scale surveys using classical methods are difficult to carry on, since field conditions may prevent permanent instrument installation. Thermal infrared pictures (7.5 - 14 ?m) can be used to map temperatures of surfaces and gases. In this study, we investigated relationships between temperature anomalies and heat flux, in order to evaluate the potential of thermal imagery for volcano monitoring. Two surveys have been achieved in 2010 and 2012 on la Soufrière Volcano (Guadeloupe, Lesser Antilles), both by airborne and handled thermal cameras. We first calibrate the uncooled microbolometers cameras, then we correct images from atmospheric absorption according to sensor elevation and atmospheric humidity, pressure and temperature. To correct effects of surface reflexion, we estimate surface emissivity and incoming flux at surface. Finally, the absolute precision of measurements is 2 K while the relative sensitivity is about 0.2 K. In order to estimate the total heat flux, we map thermal anomalies on the volcano edifice by overlapping infrared airborne images on visible orthorectified images. Active zones are clearly identified at the top (actives and potential fumaroles) and on the slopes (former active fumaroles and hot springs). At the summit active fumaroles, we estimate the mass flux of gas by measuring the panache dilution into the atmosphere. Indeed, it is shown that temperature profile along the plume is a function of the wind velocity, distance and mass flux at the source vent. Measured fluxes of 30 m3/s for the South Crater and 5 m3/s for the Tarissan Pit are estimated, and compared to other methods results. At the Ty Fault thermal anomaly (low flux fumarolian zone), we conducted an experiment to estimate the heat flux from thermal gradient anomaly at surface. This implies the measurement of external parameters describing the atmosphere dynamics (surface roughness, wind velocity, rainfall, etc.). We validate our interpretative model of surface flux with in situ vertical temperature gradient measurements. The surface flux is integrated over all spatial areas to provide the total flux of the zone. Our measurements on La Soufrière Volcano show that the fluxes emitted in hot springs and in sub-fumarolian zones (1.5 MW for the Ty Fault zone) represents a few percents of the total budget of heat (50 MW). However, the evolution of the localization and of the power of different heat sources shows a clear evolution from 2010 to 2012, with an increase of the summit activity and a decrease of the peripheral sub-fumarolian heat flux. These observations are in good agreement with the seismic, tectonic and geochemical observations, showing a pressurization of the volcano since 1997. Finally, thermal infrared imaging enables a precise mapping of mass and heat fluxes. It has a great potential in volcano monitoring, because of its ease of use, and the large variety of measurements which can be achieved from a single image.

  15. CO{sub 2} flux measurements across portions of the Dixie Valley geothermal system, Nevada

    SciTech Connect

    Bergfeld, D.; Goff, F.; Janik, C.J.; Johnson, S.D.

    1998-12-31

    A map of the CO{sub 2} flux across a newly formed area of plant kill in the NW part of the Dixie Valley geothermal system was constructed to monitor potential growth of a fumarole field. Flux measurements were recorded using a LI-COR infrared analyzer. Sample locations were restricted to areas within and near the dead zone. The data delineate two areas of high CO{sub 2} flux in different topographic settings. Older fumaroles along the Stillwater range front produce large volumes of CO{sub 2} at high temperatures. High CO{sub 2} flux values were also recorded at sites along a series of recently formed ground fractures at the base of the dead zone. The two areas are connected by a zone of partial plant kill and moderate flux on an alluvial fan. Results from this study indicate a close association between the range front fumaroles and the dead zone fractures. The goals of this study are to characterize recharge to the geothermal system, provide geochemical monitoring of reservoir fluids and to examine the temporal and spatial distribution of the CO{sub 2} flux in the dead zone. This paper reports the results of the initial CO{sub 2} flux measurements taken in October, 1997.

  16. Can CO2 Turbulent Flux Be Measured by Lidar? A Preliminary Study

    NASA Technical Reports Server (NTRS)

    Gilbert, Fabien; Koch, Grady; Beyon, Jeffrey Y.; Hilton, Timothy W.; Davis, Kenneth J.; Andrews, Arlyn; Flamant, Pierre H.; Singh, Upendra N.

    2011-01-01

    The vertical profiling ofCO2 turbulent fluxes in the atmospheric boundary layer (ABL) is investigated using a coherent differential absorption lidar (CDIAL) operated nearby a tall tower in Wisconsin during June 2007. A CDIAL can perform simultaneous range-resolved CO2 DIAL and velocity measurements. The lidar eddy covariance technique is presented. The aims of the study are (i) an assessment of performance and current limitation of available CDIAL for CO2 turbulent fluxes and (ii) the derivation of instrument specifications to build a future CDIAL to perform accurate range-resolved CO2 fluxes. Experimental lidar CO2 mixing ratio and vertical velocity profiles are successfully compared with in situ sensors measurements. Time and space integral scales of turbulence in the ABL are addressed that result in limitation for time averaging and range accumulation. A first attempt to infer CO2 fluxes using an eddy covariance technique with currently available 2-mm CDIAL dataset is reported.

  17. Improved Eddy Flux Measurements by Open-Path Gas Analyzer and Sonic Anemometer Co-Location

    NASA Astrophysics Data System (ADS)

    Bogoev, Ivan

    2014-05-01

    A novel instrument design combines the sensing paths of an open-path gas analyzer and a 3-D sonic anemometer and integrates the sensors in a single aerodynamic body. Common electronics provide fast-response, synchronized measurements of wind vector, sonic temperature, CO2 and H2O densities, and atmospheric pressure. An instantaneous CO2 mixing ratio, relative to dry air, is computed in real time. The synergy of combined sensors offers an alternative to the traditional density-based flux calculation method historically used for standalone open-path analyzers. A simple method is described for a direct, in-situ, mixing-ratio-based flux calculation. The method consists of: (i) correcting sonically derived air temperature for humidity effects using instantaneous water vapor density and atmospheric pressure measurements, (ii) computing water vapor pressure based on water-vapor density and humidity-corrected sonic temperature, (iii) computing fast-response CO2 mixing ratio based on CO2 density, sonic temperature, water vapor, and atmospheric pressures, and (iv) computing CO2 flux from the covariance of the vertical wind speed and the CO2 mixing ratio. Since CO2 mixing ratio is a conserved quantity, the proposed method simplifies the calculations and eliminates the need for corrections in post-processing by accounting for temperature, water-vapor, and pressure-fluctuation effects on the CO2 density. A field experiment was conducted using the integrated sensor to verify performance of the mixing-ratio method and to quantify the differences with density-derived CO2 flux corrected for sensible and latent-heat fluxes. The pressure term of the density corrections was also included in the comparison. Results suggest that the integrated sensor with co-located sonic and gas sensing paths and the mixing-ratio-based method minimize or eliminate the following uncertainties in the measured CO2 flux: (i) correcting for frequency-response losses due to spatial separation of measured quantities, (ii) correcting sonically-derived, sensible-heat flux for humidity, (iii) correcting latent-heat flux for sensible-heat flux and water-vapor self-dilution, (iv) correcting CO2 flux for sensible- and latent-heat fluxes, (v) correcting CO2 flux for pressure-induced density fluctuations.

  18. Use of airborne thermal imaging to quantify heat flux and flow rate of surface geothermal fluids at Pilgrim Hot Springs, Alaska

    NASA Astrophysics Data System (ADS)

    Haselwimmer, C. E.; Prakash, A.

    2011-12-01

    Measuring the temperature and flow rate of hot springs is important for quantifying convective heat losses from low to moderate temperature geothermal systems. When coupled with sub-surface measurements of convective and conductive heat flow (e.g. with shallow-temperature probes, temperature gradient drilling), total surface heat losses from a geothermal system may be estimated, which can be used in assessment of undeveloped resources or monitoring of existing developments. A novel approach to estimating the heat flux and flow rate of surface geothermal waters using airborne thermal imagery is presented that has been applied and validated at Pilgrim Hot Springs near Nome in Alaska. Over this study site thermal imagery was acquired using a broadband FLIR camera during two airborne surveys undertaken in fall 2010 and early spring 2011. Calibrated surface temperature data for surface hot springs and pools was input into a thermal budget model that calculates the geothermal heat input on a pixel-by-pixel basis by accounting for radiative, evaporative/sensible, short-wave solar, and long-wave atmospheric heat fluxes. The sum of geothermal heat fluxes for geothermal waters was used to estimate the outflow rate of hot springs based upon values of the specific enthalpy of water at the average spring temperature (81°C, derived from field measurements) and average temperature of non-geothermal surface waters (measured from the thermal images). The results of applying these methods to fall and spring airborne thermal data from Pilgrim Hot Springs yield geothermal heat fluxes supporting surface geothermal fluids of 3.28 MW, and 3.80 MW respectively that correspond to outflow rates from hot springs of 192.39 and 198.04 gpm (gallons per minute). These estimates are considerably higher than previous field based results (~2 MW or 100 gpm) derived from direct measurement of the flow rate of the main hot pool at the site. This outcome demonstrates the value of the synoptic coverage of airborne thermal imaging that can map all sources of hot fluids including small lower temperature springs and diffuse outflow. This work has demonstrated the potential of airborne thermal imaging for providing estimates of heat flux associated with hot spring outflow in a rapid and repeatable manner.

  19. Lidar Based Particulate Flux Measurements of Agricultural Field

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A three-wavelength portable scanning lidar system was developed to derive information on particulate spatial aerosol distribution over remote distances. The lidar system and retrieval approach has been tested during several field campaigns measuring agricultural emissions from a swine feeding operat...

  20. Feed rate measuring method and system

    DOEpatents

    Novak, J.L.; Wiczer, J.J.

    1995-12-05

    A system and method are provided for establishing the feed rate of a workpiece along a feed path with respect to a machine device. First and second sensors each having first and second sensing electrodes which are electrically isolated from the workpiece are positioned above, and in proximity to the desired surfaces of the workpiece along a feed path. An electric field is developed between the first and second sensing electrodes of each sensor and capacitance signals are developed which are indicative of the contour of the workpiece. First and second image signals representative of the contour of the workpiece along the feed path are developed by an image processor. The time delay between corresponding portions of the first and second image signals are then used to determine the feed rate based upon the separation of the first and second sensors and the amount of time between corresponding portions of the first and second image signals. 18 figs.

  1. Feed rate measuring method and system

    DOEpatents

    Novak, James L. (Albuquerque, NM); Wiczer, James J. (Albuquerque, NM)

    1995-01-01

    A system and method are provided for establishing the feed rate of a workpiece along a feed path with respect to a machine device. First and second sensors each having first and second sensing electrodes which are electrically isolated from the workpiece are positioned above, and in proximity to the desired surfaces of the workpiece along a feed path. An electric field is developed between the first and second sensing electrodes of each sensor and capacitance signals are developed which are indicative of the contour of the workpiece. First and second image signals representative of the contour of the workpiece along the feed path are developed by an image processor. The time delay between corresponding portions of the first and second image signals are then used to determine the feed rate based upon the separation of the first and second sensors and the amount of time between corresponding portions of the first and second image signals.

  2. Rotation Rate of Saturn's Magnetosphere using CAPS Plasma Measurements

    NASA Technical Reports Server (NTRS)

    Sittler, E.; Cooper, J.; Hartle, R.; Simpson, D.; Johnson, R.; Thomsen, M.; Arridge, C.

    2011-01-01

    We present the present status of an investigation of the rotation rate of Saturn's magnetosphere using a 3D velocity moment technique being developed at Goddard which is similar to the 2D version used by Sittler et al. for SOI and similar to that used by Thomsen et al.. This technique allows one to nearly cover the full energy range of the Cassini Plasma Spectrometer (CAPS) IMS from 1 V . E/Q < 50 kV. Since our technique maps the observations into a local inertial frame, it does work during roll maneuvers. We make comparisons with the bi-Maxwellian fitting technique developed by Wilson et al. and the similar velocity moment technique by Thomsen et al. . We concentrate our analysis when ion composition data is available, which is used to weight the non-compositional data, referred to as singles data, to separate H+, H2+ and water group ions (W+) from each other. The chosen periods have high enough telemetry rates (4 kbps or higher) so that coincidence ion data, similar to that used by Sittler et al. for SOI is available. The ion data set is especially valuable for measuring flow velocities for protons, which are more difficult to derive using singles data within the inner magnetosphere, where the signal is dominated by heavy ions (i.e., proton peak merges with W+ peak as low energy shoulder). Our technique uses a flux function, which is zero in the proper plasma flow frame, to estimate fluid parameter uncertainties. The comparisons investigate the experimental errors and potential for systematic errors in the analyses, including ours. The rolls provide the best data set when it comes to getting 4PI coverage of the plasma but are more susceptible to time aliasing effects. In the future we will then make comparisons with magnetic field observations, Saturn ionosphere conductivities as presently known and the field aligned currents necessary for the planet to enforce corotation of the rotating plasma.

  3. 29 CFR 530.202 - Piece rates-work measurement.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 3 2011-07-01 2011-07-01 false Piece rates-work measurement. 530.202 Section 530.202 Labor... Piece rates—work measurement. (a) No certificate will be issued pursuant to § 530.101 of subpart B to an... different types of items produced using stop watch time studies or other work measurement...

  4. 29 CFR 530.202 - Piece rates-work measurement.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 3 2013-07-01 2013-07-01 false Piece rates-work measurement. 530.202 Section 530.202 Labor... Piece rates—work measurement. (a) No certificate will be issued pursuant to § 530.101 of subpart B to an... different types of items produced using stop watch time studies or other work measurement...

  5. 29 CFR 530.202 - Piece rates-work measurement.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 3 2012-07-01 2012-07-01 false Piece rates-work measurement. 530.202 Section 530.202 Labor... Piece rates—work measurement. (a) No certificate will be issued pursuant to § 530.101 of subpart B to an... different types of items produced using stop watch time studies or other work measurement...

  6. Simultaneous Flux Measurements of CO2, its Stable Isotope Ratios and Trace Gases Based on Eddy Accumulation Technique for Flux Partitioning

    NASA Astrophysics Data System (ADS)

    Takahashi, Y.; Hirata, R.

    2007-12-01

    For the purpose of determining the CO2 uptake by terrestrial ecosystem, eddy covariance method (EC) is commonly used in the tower-flux measurements. The flux measured by this method is called 'enet ecosystem exchange (NEE)'. NEE has the meaning of difference between two component fluxes, photosynthetic uptake and respiratory release of CO2. Magnitude of both the component fluxes is far larger than NEE. Both the component fluxes have difference in response function against changes in environmental factors, such as temperature and water. Therefore it is important to evaluate the characteristics of variations in the comporent fluxes individually in the future prediction of CO2 uptake by terrestrial ecosystem. Separation of NEE into the componet fluxes is usually done by using an approximate temperature expression of respiratory flux. This approximate expression is based on the assumption that the NEE observed at nighttime equals to the respiratory flux. The photosynthetic uptake of CO2 is defined as difference between the observed NEE and 'respiration' approximated as a temperature-function. Because of its technical simplicity, this approach has provided useful information about climatology of the gross CO2 fluxes. However, the temperature expression of respiratory flux has several limitations in its application. We are now developing a flux-partitioning method using chemical tracers (e.g. stable isotopes of CO2 and carbonyl sulfide) as additional constraints. The flux partitioning using stable isotopes of CO2 is based on the imbalance of net flux of the CO2 isotopes between 'respiration' and 'photosynthesis'. On the other hand, because of this similarity in the control factors for uptake ratio, the net flux of carbonyl sulfide (COS) is regarded as a possible constraint for the functioning of variations in photosynthetic CO2 uptake by terrestrial ecosystem. Field observation of fluxes of those chemical tracers by EC method is difficult due to stringent requirements for on-site measurement. Therefore, as a first step, we are planning to measure those fluxes based on an eddy accumulation technique coupled with flask sampling and high precision lab analysis. We report current progress of the development.

  7. Pool size measurements facilitate the determination of fluxes at branching points in non-stationary metabolic flux analysis: the case of Arabidopsis thaliana

    PubMed Central

    Heise, Robert; Fernie, Alisdair R.; Stitt, Mark; Nikoloski, Zoran

    2015-01-01

    Pool size measurements are important for the estimation of absolute intracellular fluxes in particular scenarios based on data from heavy carbon isotope experiments. Recently, steady-state fluxes estimates were obtained for central carbon metabolism in an intact illuminated rosette of Arabidopsis thaliana grown photoautotrophically (Szecowka et al., 2013; Heise et al., 2014). Fluxes were estimated therein by integrating mass-spectrometric data of the dynamics of the unlabeled metabolic fraction, data on metabolic pool sizes, partitioning of metabolic pools between cellular compartments and estimates of photosynthetically inactive pools, with a simplified model of plant central carbon metabolism. However, the fluxes were determined by treating the pool sizes as fixed parameters. Here we investigated whether and, if so, to what extent the treatment of pool sizes as parameters to be optimized in three scenarios may affect the flux estimates. The results are discussed in terms of benchmark values for canonical pathways and reactions, including starch and sucrose synthesis as well as the ribulose-1,5-bisphosphate carboxylation and oxygenation reactions. In addition, we discuss pathways emerging from a divergent branch point for which pool sizes are required for flux estimation, irrespective of the computational approach used for the simulation of the observable labeling pattern. Therefore, our findings indicate the necessity for development of techniques for accurate pool size measurements to improve the quality of flux estimates from non-stationary flux estimates in intact plant cells in the absence of alternative flux measurements. PMID:26082786

  8. Measuring rates of outdoor airflow into HVAC systems

    SciTech Connect

    Fisk, William J.; Faulkner, David; Sullivan, Douglas P.; Delp, Woody

    2002-10-01

    During the last few years, new technologies have been introduced for measuring the flow rates of outside air into HVAC systems. This document describes one particular technology for measuring these airflows, a system and a related protocol developed to evaluate this and similar measurement technologies under conditions without wind, and the results of our evaluations. We conclude that the measurement technology evaluated can provide a reasonably accurate measurement of OA flow rate over a broad range of flow, without significantly increasing airflow resistance.

  9. Urban greenhouse gas mole fraction in-situ measurements: Results from the Indianapolis Flux Experiment (INFLUX)

    NASA Astrophysics Data System (ADS)

    Miles, Natasha; Lauvaux, Thomas; Davis, Kenneth; Richardson, Scott; Sarmiento, Daniel; Sweeney, Colm; Karion, Anna; Hardesty, Robert Michael; Turnbull, Jocelyn; Iraci, Laura; Gurney, Kevin; Razlivanov, Igor; Obiminda Cambaliza, Maria; Shepson, Paul; Whetstone, James

    2014-05-01

    The Indianapolis Flux Experiment (INFLUX) was designed to develop and evaluate methods for the measurement and modeling of greenhouse gas fluxes from urban environments. Determination of greenhouse gas fluxes and uncertainty bounds is essential for the evaluation of the effectiveness of mitigation strategies. The current INFLUX observation network includes twelve in-situ tower-based, continuous measurements of CO2, CO, and CH4, flask sampling of 14CO2 and other trace gases, and periodic aircraft sampling of greenhouse gases and meteorological conditions. Eddy covariance and radiative flux are measured at four of the tower sites, and a scanning Doppler lidar was installed in April 2013; both are used to quantify key boundary layer meteorological properties and evaluate model performance. Additionally, a total carbon column observing network (TCCON) column remote sensing station was deployed August - December 2012. The data from the towers, TCCON, and aircraft measurements are being used in an inverse-modeling approach to yield estimates of the urban area flux at 1 km2 resolution. Very high space/time resolution estimates of fossil fuel carbon emissions (Hestia project) offer state-of-the-art "bottom up" emissions estimates for the city and its surroundings. Here we present an overview of the progress from INFLUX, with a focus on tower-based results. With this high density of urban tower-based greenhouse gas measurements, we will quantify horizontal and vertical spatial patterns in atmospheric mole fractions of CO2, CO, and CH4 in Indianapolis. The consistency of the observed horizontal gradients with that expected based on differences in land-cover contributions according to footprint analysis will be evaluated. The ability to correctly model transport and mixing in the atmospheric boundary layer, responsible for carrying greenhouse gases from their source to the point of measurement, is essential. Thus we investigate differences between the modeled and observed sensible heat flux, latent heat flux, air temperature, and wind speed.

  10. Field intercomparison of four methane gas analysers suitable for eddy covariance flux measurements

    NASA Astrophysics Data System (ADS)

    Peltola, O.; Mammarella, I.; Haapanala, S.; Burba, G.; Vesala, T.

    2012-12-01

    Performances of four methane gas analyzers suitable for eddy covariance measurements are assessed. The assessment and comparison was performed by analyzing eddy covariance data obtained during summer 2010 (1 April to 26 October) at a pristine fen, Siikaneva, Southern Finland. High methane fluxes with pronounced seasonality have been measured at this fen. The four participating methane gas analyzers are commercially available closed-path units TGA-100A (Campbell Scientific Inc., USA), RMT-200 (Los Gatos Research, USA), G1301-f (Picarro Inc., USA) and an early prototype open-path unit Prototype-7700 (LI-COR Biosciences, USA). The RMT-200 functioned most reliably throughout the measurement campaign, during low and high flux periods. Methane fluxes from RMT-200 and G1301-f had the smallest random errors and the fluxes agree remarkably well throughout the measurement campaign. Cospectra and power spectra calculated from RMT-200 and G1301-f data agree well with corresponding temperature spectra during a high flux period. None of the gas analysers showed statistically significant diurnal variation for methane flux. Prototype-7700 functioned only for a short period of time, over one month, in the beginning of the measurement campaign during low flux period, and thus, its overall accuracy and long-term performance were not assessed. Prototype-7700 is a practical choice for measurement sites in remote locations due to its low power demand, however if only the performance in this intercomparison is considered, RMT-200 performed the best and is the recommended choice if a new fast response methane gas analyser is needed.

  11. First measurements of the flux integral with the NIST-4 watt balance

    E-print Network

    Haddad, D; Chao, L S; Cao, A; Sineriz, G; Pratt, J R; Newell, D B; Schlamminger, S

    2015-01-01

    In early 2014, construction of a new watt balance, named NIST-4, has started at the National Institute of Standards and Technology (NIST). In a watt balance, the gravitational force of an unknown mass is compensated by an electromagnetic force produced by a coil in a magnet system. The electromagnetic force depends on the current in the coil and the magnetic flux integral. Most watt balances feature an additional calibration mode, referred to as velocity mode, which allows one to measure the magnetic flux integral to high precision. In this article we describe first measurements of the flux integral in the new watt balance. We introduce measurement and data analysis techniques to assess the quality of the measurements and the adverse effects of vibrations on the instrument.

  12. High geothermal heat flux measured below the West Antarctic Ice Sheet.

    PubMed

    Fisher, Andrew T; Mankoff, Kenneth D; Tulaczyk, Slawek M; Tyler, Scott W; Foley, Neil

    2015-07-01

    The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow, and mass balance of ice sheets, but measurements of this parameter are difficult to make in ice-covered regions. We report the first direct measurement of geothermal heat flux into the base of the West Antarctic Ice Sheet (WAIS), below Subglacial Lake Whillans, determined from the thermal gradient and the thermal conductivity of sediment under the lake. The heat flux at this site is 285 ± 80 mW/m(2), significantly higher than the continental and regional averages estimated for this site using regional geophysical and glaciological models. Independent temperature measurements in the ice indicate an upward heat flux through the WAIS of 105 ± 13 mW/m(2). The difference between these heat flux values could contribute to basal melting and/or be advected from Subglacial Lake Whillans by flowing water. The high geothermal heat flux may help to explain why ice streams and subglacial lakes are so abundant and dynamic in this region. PMID:26601210

  13. High geothermal heat flux measured below the West Antarctic Ice Sheet

    PubMed Central

    Fisher, Andrew T.; Mankoff, Kenneth D.; Tulaczyk, Slawek M.; Tyler, Scott W.; Foley, Neil

    2015-01-01

    The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow, and mass balance of ice sheets, but measurements of this parameter are difficult to make in ice-covered regions. We report the first direct measurement of geothermal heat flux into the base of the West Antarctic Ice Sheet (WAIS), below Subglacial Lake Whillans, determined from the thermal gradient and the thermal conductivity of sediment under the lake. The heat flux at this site is 285 ± 80 mW/m2, significantly higher than the continental and regional averages estimated for this site using regional geophysical and glaciological models. Independent temperature measurements in the ice indicate an upward heat flux through the WAIS of 105 ± 13 mW/m2. The difference between these heat flux values could contribute to basal melting and/or be advected from Subglacial Lake Whillans by flowing water. The high geothermal heat flux may help to explain why ice streams and subglacial lakes are so abundant and dynamic in this region. PMID:26601210

  14. Field intercomparison of two optical analyzers for CH4 eddy covariance flux measurements

    NASA Astrophysics Data System (ADS)

    Tuzson, B.; Hiller, R. V.; Zeyer, K.; Eugster, W.; Neftel, A.; Ammann, C.; Emmenegger, L.

    2010-11-01

    Fast response optical analyzers based on laser absorption spectroscopy are the preferred tools to measure field-scale mixing ratios and fluxes of a range of trace gases. Several state-of-the-art instruments have become commercially available and are gaining in popularity. This paper aims for a critical field evaluation and intercomparison of two compact, cryogen-free and fast response instruments: a quantum cascade laser based absorption spectrometer from Aerodyne Research, Inc., and an off-axis integrated cavity output spectrometer from Los Gatos Research, Inc. In this paper, both analyzers are characterized with respect to precision, accuracy, response time and also their sensitivity to water vapour. The instruments were tested in a field campaign to assess their behaviour under various meteorological conditions. The instrument's suitability for eddy covariance flux measurements was evaluated by applying an artificial flux of CH4 generated above a managed grassland with otherwise very low methane exchange. This allowed an independent verification of the flux measurements accuracy, including the overall eddy covariance setup and data treatment. The retrieved fluxes were in good agreement with the known artificial emission flux, which is more than satisfactory, given that the analyzers were attached to separate sonic anemometers placed on individual eddy towers with different data acquisition systems but similar data treatment that are specific to the best practice used by the involved research teams.

  15. Measurement of turbulent water vapor fluxes using a lightweight unmanned aerial vehicle system

    NASA Astrophysics Data System (ADS)

    Thomas, R. M.; Lehmann, K.; Nguyen, H.; Jackson, D. L.; Wolfe, D.; Ramanathan, V.

    2012-01-01

    We present here the first application of a lightweight unmanned aerial vehicle (UAV) system designed to measure turbulent properties and vertical latent heat fluxes (?E). Such measurements are crucial to improve our understanding of linkages between surface moisture supply and boundary layer clouds and phenomena such as atmospheric rivers. The application of UAVs allows for measurements on spatial scales complimentary to satellite, aircraft, and tower derived fluxes. Key system components are: a turbulent gust probe; a fast response water vapor sensor; an inertial navigation system (INS) coupled to global positioning system (GPS); and a 100 Hz data logging system. We present measurements made in the continental boundary layer at the National Aeronautics and Space Administration (NASA) Dryden Research Flight Facility located in the Mojave Desert. Two flights consisting of several horizontal straight flux run legs up to ten kilometers in length and between 330 and 930 m above ground level (m a.g.l.) are compared to measurement from a surface tower. Surface measured ?E ranged from -53 W m-2 to 41 W m-2, and the application of a Butterworth High Pass Filter (HPF) to the datasets improved agreement to within +/-12 W m-2 for 86% of flux runs, by removing improperly sampled low frequency flux contributions. This result, along with power and co-spectral comparisons and consideration of the differing spatial scales indicates the system is able to resolve vertical fluxes for the measurement conditions encountered. Challenges remain, and the outcome of these measurements will be used to inform future sampling strategies and further system development.

  16. Measurement of turbulent water vapor fluxes using a lightweight unmanned aerial vehicle system

    NASA Astrophysics Data System (ADS)

    Thomas, R. M.; Lehmann, K.; Nguyen, H.; Jackson, D. L.; Wolfe, D.; Ramanathan, V.

    2011-08-01

    We present here the first application of a lightweight unmanned aerial vehicle (UAV) system designed to measure turbulent properties and vertical latent heat fluxes (?E). Such measurements are crucial to improve our understanding of linkages between surface moisture supply and boundary layer clouds and phenomena such as atmospheric rivers. The application of UAVs allows for measurements on spatial scales complimentary to satellite, aircraft, and tower derived fluxes. Key system components are: a turbulent gust probe; a fast response water vapor sensor; an inertial navigation system (INS) coupled to global positioning system (GPS); and a 100 Hz data logging system. We present measurements made in the continental boundary layer at the National Aeronautics and Space Administration (NASA) Dryden Research Flight Facility located in the Mojave Desert. Two flights consisting of several horizontal straight flux run legs up to ten kilometers in length and between 330 and 930 m above ground level (m a.g.l.) are compared to measurement from a surface tower. Surface measured ?E ranged from -53 W m-2 to 41 W m-2, and the application of a Butterworth High Pass Filter (HPF) to the datasets improved agreement to within ± 12 W m-2 for 86 % of flux runs, by removing improperly sampled low frequency flux contributions. This result, along with power and co-spectral comparisons and consideration of the differing spatial scales indicates the system is able to resolve vertical fluxes for the measurement conditions encountered. Challenges remain, and the outcome of these measurements will be used to inform future sampling strategies and further system development.

  17. Standardization of flux chamber and wind tunnel flux measurements for quantifying volatile organic compound and ammonia emissions from area sources at animal feeding operations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A variety of wind tunnels and flux chambers have been used to measure fluxes of volatile organic compounds (VOC) and ammonia (NH3) at animal feeding operations (AFO). However, there has been little regard to the extreme variation and potential inaccuracies caused by inappropriate air velocity or sw...

  18. Inverse Heat Conduction Using Measured Back Surface Temperature and Heat Flux

    E-print Network

    Zhang, Yuwen

    . (1) h = convection heat transfer coefficient, W=m2 K k = thermal conductivity, W=m K L = thicknessInverse Heat Conduction Using Measured Back Surface Temperature and Heat Flux Jianhua Zhou, Yuwen are not directly measurable, but they can be estimated by solving an inverse heat conduction problem based

  19. Airborne Measurements of Methane Fluxes over Mid-Latitude and Sub-Arctic Wetlands

    NASA Astrophysics Data System (ADS)

    Hartmann, J.; Sachs, T.

    2012-04-01

    For a quantification of the natural GHG budget of the atmosphere the emission of methane from the vast arctic wetlands need to be assessed accurately. The conventional methods of flux measurements made by closed chambers and eddy towers need to be upscaled, introducing a potentially large source of uncertainty, due to the heterogeneity of the emitting sources at the surface. In order to obtain a large area coverage and thus a higher spacial representativeness we performed airborne measurements of methane fluxes over mid-latitude and sub-arctic wetlands, for flight legs of tens of kilometres length. We installed a fast trace gas analyser, a Los Gatos RMT200, in the research aircraft Polar 5, together with the noseboom mounted turbulence sensor package. Measurement flights have been carried out in June 2011 over wetlands in Germany and in northern Finland in a convectively mixed boundary layer. Reference data have been optained at the surface by tower mounted eddy correlation measurements. A spectral analysis of the first measurements shows that the system is well suitable to measure the vertical flux of methane from natural surfaces transported by the dominating eddies in the convective boundary layer. Our flux measurements compare well to those obtained at the surface. On the high-frequency end of the spectrum the measurement accuracy is not sufficient to resolve the inertial subrange.

  20. Measurements of instantaneous heat flux to metal and ceramic surfaces in a diesel engine

    SciTech Connect

    Huang, J.C.; Borman, G.L.

    1987-02-01

    The effects of surface materials and extent of insulation on the heat transfer to the head of an open-chamber diesel were studied. A large instrumentation plug designed to incorporate plates of various materials on the gas-side surface was utilized with a special research head. Instantaneous rates of heat transfer to the plate gas-side surface were measured. Measurement results obtained with a zirconia plate and an insulated metal plate are compared to data for an inunsulated metal plate. The insulation of the metal plate increased its gas-side surface temperature over the uninsulated case by about the same amount achieved with a 6.35-mm-thick zirconia plate. The magnitude of the surface temperature swing for zirconia is not as high as expected from conduction theory, but is substantially higher than that for the uninsulated metal. Significant reductions of steady-state heat fluxes were achieved with both the zirconia and the insulated metal compared to the uninsulated metal.

  1. Measurements of ambient HONO concentrations and vertical HONO flux above a northern Michigan forest canopy

    NASA Astrophysics Data System (ADS)

    Zhang, N.; Zhou, X.; Bertman, S.; Tang, D.; Alaghmand, M.; Shepson, P. B.; Carroll, M. A.

    2012-09-01

    Systems have been developed and deployed at a North Michigan forested site to measure ambient HONO and vertical HONO flux. The modified HONO measurement technique is based on aqueous scrubbing of HONO using a coil sampler, followed by azo dye derivatization and detection using a long-path absorption photometer (LPAP). A Na2CO3-coated denuder is used to generate "zero HONO" air for background correction. The lower detection limit of the method, defined by 3 times of the standard deviation of the signal, is 1 pptv for 1-min averages, with an overall uncertainty of ±(1 + 0.05 [HONO]) pptv. The HONO flux measurement technique has been developed based on the relaxed eddy accumulation approach, deploying a 3-D sonic anemometer and two HONO measurement systems. The overall uncertainty is estimated to be within ±(8 × 10-8 + 0.15 FHONO) mol m-2 h-1, with a 20-min averaged data point per 30 min. Ambient HONO and vertical HONO flux were measured simultaneously at the PROPHET site from 17 July to 7 August 2008. The forest canopy was found to be a net HONO source, with a mean upward flux of 0.37 × 10-6 moles m-2 h-1. The HONO flux reached a maximal mean of ~0.7 × 10-6 moles m-2 h-1 around solar noon, contributing a major fraction to the HONO source strength required to sustain the observed ambient concentration of ~70 pptv. There were no significant correlations between [NOx] and daytime HONO flux and between JNO2 × [NO2] and HONO flux, suggesting that NOx was not an important precursor responsible for HONO daytime production on the forest canopy surface in this low-NOx rural environment. Evidence supports the hypothesis that photolysis of HNO3 deposited on the forest canopy surface is a major daytime HONO source.

  2. A case study of eddy covariance flux of N2O measured within forest ecosystems: quality control and flux error analysis

    NASA Astrophysics Data System (ADS)

    Mammarella, I.; Werle, P.; Pihlatie, M.; Eugster, W.; Haapanala, S.; Kiese, R.; Markkanen, T.; Rannik, Ü.; Vesala, T.

    2009-07-01

    Eddy covariance (EC) flux measurements of nitrous oxide obtained by using a 3-D sonic anemometer and a tunable diode laser gas analyzer for N2O were investigated. Two datasets (Sorø, Denmark and Kalevansuo, Finland) from different measurement campaigns including sub-canopy flux measurements of energy and carbon dioxide are discussed with a focus on selected quality control aspects and flux error analysis. Although fast response trace gas analyzers based on spectroscopic techniques are increasingly used in ecosystem research, their suitability for reliable estimates of eddy covariance fluxes is still limited, and some assumptions have to be made for filtering and processing data. The N2O concentration signal was frequently dominated by offset drifts (fringe effect), which can give an artificial extra contribution to the fluxes when the resulting concentration fluctuations are correlated with the fluctuations of the vertical wind velocity. Based on Allan variance analysis of the N2O signal, we found that a recursive running mean filter with a time constant equal to 50~s was suitable to damp the influence of the periodic drift. Although the net N2O fluxes over the whole campaign periods were quite small at both sites (~5 ?g N m-2 h-1 for Kalevansuo and ~10 ?g N m-2 h-1 for Sorø), the calculated sub-canopy EC fluxes were in good agreement with those estimated by automatic soil chambers. However EC N2O flux measurements show larger random uncertainty than the sensible heat fluxes, and classification according to statistical significance of single flux values indicates that downward N2O fluxes have larger random error.

  3. A case study of eddy covariance flux of N2O measured within forest ecosystems: quality control and flux error analysis

    NASA Astrophysics Data System (ADS)

    Mammarella, I.; Werle, P.; Pihlatie, M.; Eugster, W.; Haapanala, S.; Kiese, R.; Markkanen, T.; Rannik, Ü.; Vesala, T.

    2010-02-01

    Eddy covariance (EC) flux measurements of nitrous oxide (N2O) obtained by using a 3-D sonic anemometer and a tunable diode laser gas analyzer for N2O were investigated. Two datasets (Sorø, Denmark and Kalevansuo, Finland) from different measurement campaigns including sub-canopy flux measurements of energy and carbon dioxide are discussed with a focus on selected quality control aspects and flux error analysis. Although fast response trace gas analyzers based on spectroscopic techniques are increasingly used in ecosystem research, their suitability for reliable estimates of EC fluxes is still limited, and some assumptions have to be made for filtering and processing data. The N2O concentration signal was frequently dominated by offset drifts (fringe effect), which can give an artificial extra contribution to the fluxes when the resulting concentration fluctuations are correlated with the fluctuations of the vertical wind velocity. Based on Allan variance analysis of the N2O signal, we found that a recursive running mean filter with a time constant equal to 50 s was suitable to damp the influence of the periodic drift. Although the net N2O fluxes over the whole campaign periods were quite small at both sites (~5 ?g N m-2 h-1 for Kalevansuo and ~10 ?g N m-2 h-1 for Sorø), the calculated sub-canopy EC fluxes were in good agreement with those estimated by automatic soil chambers. However, EC N2O flux measurements show larger random uncertainty than the sensible heat fluxes, and classification according to statistical significance of single flux values indicates that downward N2O fluxes have larger random error.

  4. Areal-averaged trace gas emission rates from long-range open-path measurements in stable boundary layer conditions

    NASA Astrophysics Data System (ADS)

    Schäfer, K.; Grant, R. H.; Emeis, S.; Raabe, A.; von der Heide, C.; Schmid, H. P.

    2012-07-01

    Measurements of land-surface emission rates of greenhouse and other gases at large spatial scales (10 000 m2) are needed to assess the spatial distribution of emissions. This can be readily done using spatial-integrating micro-meteorological methods like flux-gradient methods which were evaluated for determining land-surface emission rates of trace gases under stable boundary layers. Non-intrusive path-integrating measurements are utilized. Successful application of a flux-gradient method requires confidence in the gradients of trace gas concentration and wind, and in the applicability of boundary-layer turbulence theory; consequently the procedures to qualify measurements that can be used to determine the flux is critical. While there is relatively high confidence in flux measurements made under unstable atmospheres with mean winds greater than 1 m s-1, there is greater uncertainty in flux measurements made under free convective or stable conditions. The study of N2O emissions of flat grassland and NH3 emissions from a cattle lagoon involves quality-assured determinations of fluxes under low wind, stable or night-time atmospheric conditions when the continuous "steady-state" turbulence of the surface boundary layer breaks down and the layer has intermittent turbulence. Results indicate that following the Monin-Obukhov similarity theory (MOST) flux-gradient methods that assume a log-linear profile of the wind speed and concentration gradient incorrectly determine vertical profiles and thus flux in the stable boundary layer. An alternative approach is considered on the basis of turbulent diffusivity, i.e. the measured friction velocity as well as height gradients of horizontal wind speeds and concentrations without MOST correction for stability. It is shown that this is the most accurate of the flux-gradient methods under stable conditions.

  5. Measuring Transpiration to Regulate Winter Irrigation Rates

    SciTech Connect

    Samuelson, Lisa

    2006-11-08

    Periodic transpiration (monthly sums) in a young loblolly pine plantation between ages 3 and 6 was measured using thermal dissipation probes. Fertilization and fertilization with irrigation were better than irrigation alone in increasing transpiration of young loblolly pines during winter months, apparently because of increased leaf area in fertilized trees. Irrigation alone did not significantly increase transpiration compared with the non-fertilized and non-irrigated control plots.

  6. Heart Rate Variability: Measures and Models

    E-print Network

    Malvin C. Teich; Steven B. Lowen; Bradley M. Jost; Karin Vibe-Rheymer; Conor Heneghan

    2000-08-07

    We focus on various measures of the fluctuations of the sequence of intervals between beats of the human heart, and how such fluctuations can be used to assess the presence or likelihood of cardiovascular disease. We examine sixteen such measures and their suitability for correctly classifying heartbeat records of various lengths as normal or revealing the presence of cardiac dysfunction, particularly congestive heart failure. Using receiver-operating-characteristic analysis we demonstrate that scale-dependent measures prove substantially superior to scale-independent ones. The wavelet-transform standard deviation at a scale near 32 heartbeat intervals, and its spectral counterpart near 1/32 cycles/interval, turn out to provide reliable results using heartbeat records just minutes long. We further establish for all subjects that the human heartbeat has an underlying stochastic origin rather than arising from a chaotic attractor. Finally, we develop a mathematical point process that emulates the human heartbeat time series for both normal subjects and heart-failure patients.

  7. Natural Gas Seepage Along the Edge of the Aquitaine Shelf (France): Origin and Flux Measurements

    NASA Astrophysics Data System (ADS)

    Ruffine, L.; Donval, J. P.; Battani, A.; Bignon, L.; Croguennec, C.; Caprais, J. C.; Birot, D.; Bayon, G.; Lantéri, N.; Levaché, D.; Dupré, S.

    2014-12-01

    A newly discovered and highly active seepage area has been acoustically mapped at the western edge of the Aquitaine Shelf in the Bay of Biscay [Dupré et al., 2014]. Three selected seeping sites have been investigated with a Remotely Operated Vehicle. All sites were characterized by vigorous gas emissions, and the occurrence of massive carbonate crusts and bacterial mats at the seafloor. Nine seeps have been sampled with the PEGAZ sampler. The latter allowed gas-bubble sampling and preservation at in situpressure, together with gas-flux measurement through its graduated transparent cone. The C2+ fraction of the gas samples accounts for less than 0.06 %-mol of the total composition. Both the abundance of methane and dD and d13C isotopic analyses of the hydrocarbons indicate a biogenic source generated by microbial reduction of carbon dioxide [Whiticar et al., 1986]. The analyses of the associated noble gases also provide further support for a shallow-depth generation. While sharing the same origin, the collected samples are different in other respects, such as the measured d13C values for carbon dioxide and the hydrocarbons. This is the case in particular for methane, with displays values in between -66.1 and -72.7 ‰. We hypothesized that such variations are the result of multiple gas-transport processes along with the occurrence of hydrocarbon oxidation at different rates within the sedimentary column. The measured gas fluxes are extremely heterogeneous from one seep to another, ranging from 18 to 193 m3.yr-1. These values will be discussed in detail by comparing them with values obtained from different measurement techniques at other gas-seeping sites. The GAZCOGNE study is co-funded by TOTAL and IFREMER as part of the PAMELA (Passive Margin Exploration Laboratories) scientific project. References:Dupré, S., L. Berger, N. Le Bouffant, C. Scalabrin, and J. F. Bourillet (2014), Fluid emissions at the Aquitaine Shelf (Bay of Biscay, France): a biogenic origin or the expression of hydrocarbon leakage?, Continental Shelf Research, doi:10.1016/j.csr.2014.07.004. Whiticar, M. J., E. Faber, and M. Schoell (1986), Biogenic methane formation in marine and freshwater environments: CO2 reduction vs. acetate fermentation--Isotope evidence, Geochimica et Cosmochimica Acta, 50(5), 693-709.

  8. The exchange of acetaldehyde between plants and the atmosphere: Stable carbon isotope and flux measurements

    NASA Astrophysics Data System (ADS)

    Jardine, Kolby Jeremiah

    The exchange of acetaldehyde between plant canopies and the atmosphere may significantly influence regional atmospheric chemistry and plant metabolism. While plants are known to both produce and consume acetaldehyde, the exchange of this compound with forested ecosystems is complicated by physical, biological, and chemical processes that range from being poorly understood to completely unknown. This precludes a quantitative understanding of acetaldehyde exchange rates between the atmosphere and the biosphere. In this study, the processes controlling the exchange of acetaldehyde with plant canopies was investigated using concentration, flux, and natural abundance 13C measurements of gas phase acetaldehyde from individual plants, soils, and entire ecosystems. Although previously only considered important in anoxic tissues, it was discovered that acetaldehyde is produced and consumed in leaves through ethanolic fermentation coupled to the pyruvate dehydrogenase bypass system under normal aerobic conditions. These coupled pathways determine the acetaldehyde compensation point, a major factor controlling its exchange with the atmosphere. Carbon isotope analysis suggests a new pathway for acetaldehyde production from plants under stress involving the peroxidation of membrane fatty acids. This pathway may be a major source of acetaldehyde to the atmosphere from plants under biotic and abiotic stresses. Plant stomata were found to be the dominant pathway for the exchange of acetaldehyde with the atmosphere with stomatal conductance influencing both emission and uptake fluxes. In addition, increasing temperature and solar radiation was found to increase the compensation point by increasing the rates of acetaldehyde production relative to consumption. Under ambient conditions, bare soil was neutral to the exchange of acetaldehyde while senescing and decaying leaves were found to be strong source of acetaldehyde to the atmosphere due to increased decomposition processes and the loss of biological sink(s). Vertical concentration profiles and within-canopy turbulence characterization allowed for the estimation of fine scale source/sink profiles of acetaldehyde in forested ecosystems in Michigan, California, and North Carolina. The different vertical and temporal acetaldehyde exchange patterns between the sites were well described using a simple canopy exchange model based on the results from the process based branch studies. We find that net ecosystem acetaldehyde emission rates are inversely related to foliage density by influencing the extinction of sunlight in a plant canopy. While high foliage density canopies can effectively mitigate regional air pollution by behaving as a net sink of atmospheric acetaldehyde, lower density canopies may aggravate it by acting as a net source.

  9. A literature overview of micrometeorological CH4 and N2O flux measurements in terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Nicolini, Giacomo; Castaldi, Simona; Fratini, Gerardo; Valentini, Riccardo

    2013-12-01

    The use of micrometeorological (MM) techniques for methane (CH4) and nitrous oxide (N2O) flux measurements in terrestrial ecosystems is increasing and a general outline which summarizes key results is needed. This work provides an overview of the current status of global flux measurements of CH4 and N2O by MM techniques in terrestrial ecosystems. Published studies were grouped into four main terrestrial land cover categories and the reported flux ranges, the consistency of different MM approaches over the same ecosystem types, the variability of the MM technique performances as regards the flux detection limit and environmental conditions, were analysed. Furthermore, the issue of the comparability between MM and soil chambers measurements was evaluated. The existing dataset, although temporally and spatially limited, shows that CH4 and N2O fluxes are extremely variable in both time and space with mean fluxes spanning within interquartile ranges of 1.33 ÷ 5.45, 11.02 ÷ 68.48, 5.38 ÷ 29.28, 13.87·103 ÷ 47.60·103 nmol CH4 m-2 s-1 in forest, wetlands, croplands and artificial lands respectively, and of 0.09 ÷ 0.42, 0.24 ÷ 1.47, 9.13 ÷ 20.89 nmol N2O m-2 s-1 in forest, croplands and artificial lands (no published works were found for wetlands). When environmental conditions were comparable, a general agreement of flux ranges was found within each ecosystem type, in particular when estimates were based on accurate footprint analysis. Exceptions were mainly related to site-specific aspects or to particular measurement periods. Not all the measurement set-ups were suitable for all ecosystems, environmental conditions, turbulence characteristics and flux intensity, however the latest technological improvements make the detection of fluxes feasible virtually in all ecosystems. MM studies of CH4 and N2O fluxes were unevenly distributed around the globe and, in particular, were lacking in sensitive areas like Africa, South America and Central Asia.

  10. Flux measurements of energy and trace gases in urban Houston, Texas

    NASA Astrophysics Data System (ADS)

    Boedeker, I.; Schade, G. W.; Adams, S.; Park, C.

    2008-12-01

    We describe the setup and some first year results of a new flux measurements tower in an urban area. An existing radio communications tower 4 km north of downtown Houston was equipped with micrometeorological instrumentation and trace gas sampling lines in spring 2007. Wind speed, temperature and relative humidity are recorded at five levels between 12 and 60 m above ground; 3-D wind speed measurements, solar and net radiances, and trace gas sampling are established from the 60 m level. A closed path IRGA is used for CO2 and water vapor fluxes, and independent instrumentation for criteria pollutant and VOC fluxes. Two CSI data loggers and software control the measurements, and EdiRe software is used to analyze turbulence data and compute fluxes. A project description is provided at http://atmo.tamu.edu/yellowcabtower. Surface properties as calculated from the gradient measurements show the site to be surprisingly uniform, with displacement heights between 5 and 9 m and roughness lengths between 0.4 and 0.7 m, despite urban heterogeneity. The latter is investigated through visible/near IR orthoimagery and LIDAR data, which are incorporated into a local GIS. Net radiation was also only marginally affected by surface heterogeneity. At this urban location it is balanced by roughly equal amounts of sensible heat, latent heat, and storage fluxes. Latent heat flux, however, is smaller outside the growing season, with an equivalent increase in winter storage fluxes, as expected. Significant differences are also observed with direction during summer, showing decreased Bowen ratios and lower CO2 emissions from sectors with a larger urban tree canopy cover in the footprint. The largely mature, dominantly oak urban canopy cover alleviates approximately 100 W m- 2 during typical summer days. On the other hand, anthropogenic CO2 emissions dominate over photosynthetic uptake all year round. Measured carbon fluxes peak during morning rush-hour traffic, especially when increasing stretches of the main commuter road fall into the footprint. Outside the rush hour, daytime carbon fluxes typically ranged from 0.4 to 1.6 g C m-2 h-1. A seasonal comparison shows that up to 75% of midday anthropogenic carbon flux is removed via photosynthesis in the dominant wind sector, S, which bears typical tree canopy covers of 25-50% on pervious surfaces.

  11. A Fast, Portable, Fiber Optic Spectrofluorometer for Eddy Correlation Flux Measurement in the Aquatic Environment

    NASA Astrophysics Data System (ADS)

    Hu, I. H.; Senft-Grupp, S.; Hemond, H.

    2014-12-01

    The measurement of chemical fluxes between natural waters and their benthic sediments by most existing methods, such as benthic chambers and sediment core incubations, is slow, cumbersome, and often inaccurate. One promising new method for determining benthic fluxes is eddy correlation (EC), a minimally invasive, in situ technique based on high-speed velocity and concentration measurements. Widespread application of EC to a large range of chemicals of interest is currently limited, however, by the availability of rapid, high-resolution chemical sensors capable of precisely measuring concentrations at a point location and at sufficient speed (several Hz). A proof of concept spectrofluorometry instrument has been created that is capable of high-frequency concentration measurements of naturally fluorescent substances. Designed with the EC application in mind, the system utilizes optical fibers to transmit excitation and emission light, enabling in situ measurements at high spatial resolution. Emitted fluorescence light is passed through a tunable monochromator before reaching a photomultiplier tube; photons are quantified by a custom miniaturized, low-power photon counting circuit board. Preliminary results indicate that individual measurements made at 100 Hz of a 10 ppm humic acid solution were precise within 10%, thus yielding a precision of the order of +/- 1% in a second. Used in an EC system, this instrument will enable flux measurements of substances such as naturally occurring fluorescent dissolved organic material (FDOM). Measurement of fluxes of FDOM is significant in its own right, and also will allow the indirect measurement of the numerous other chemical fluxes that are associated with FDOM by using tracer techniques. The use of a tunable monochromator not only allows flexibility in detection wavelength, but also enables full wavelength scans of the emission spectrum, making the spectrofluorometer a dual-function device capable of both characterizing the chemistry of the water (e.g. characterizing the FDOM present, or identifying additional compounds), and measuring fluorescence at selected wavelengths for EC and other applications.

  12. Uncertainty analysis of steady state incident heat flux measurements in hydrocarbon fuel fires.

    SciTech Connect

    Nakos, James Thomas

    2005-12-01

    The objective of this report is to develop uncertainty estimates for three heat flux measurement techniques used for the measurement of incident heat flux in a combined radiative and convective environment. This is related to the measurement of heat flux to objects placed inside hydrocarbon fuel (diesel, JP-8 jet fuel) fires, which is very difficult to make accurately (e.g., less than 10%). Three methods will be discussed: a Schmidt-Boelter heat flux gage; a calorimeter and inverse heat conduction method; and a thin plate and energy balance method. Steady state uncertainties were estimated for two types of fires (i.e., calm wind and high winds) at three times (early in the fire, late in the fire, and at an intermediate time). Results showed a large uncertainty for all three methods. Typical uncertainties for a Schmidt-Boelter gage ranged from {+-}23% for high wind fires to {+-}39% for low wind fires. For the calorimeter/inverse method the uncertainties were {+-}25% to {+-}40%. The thin plate/energy balance method the uncertainties ranged from {+-}21% to {+-}42%. The 23-39% uncertainties for the Schmidt-Boelter gage are much larger than the quoted uncertainty for a radiative only environment (i.e ., {+-}3%). This large difference is due to the convective contribution and because the gage sensitivities to radiative and convective environments are not equal. All these values are larger than desired, which suggests the need for improvements in heat flux measurements in fires.

  13. Analysis of Neutron Flux in Preparation for Reaction Measurements with Radioactive Targets

    NASA Astrophysics Data System (ADS)

    Bauer, Katherine; McMahan, M. A.

    2004-10-01

    At the 88-Inch Cyclotron, at Lawrence Berkeley National Laboratory researchers are trying to measure the cross section for the reaction 89Zr(n, 2n)88Zr. Accurately knowing this cross-section is important for the US Stockpile Stewardship Program; in addition, neutron cross-sections of other isotopes in this region are useful to understand nucleosynthesis. A large neutron flux is important for this project because the target is radioactive. By replicating the experiment with non-radioactive activation foils using identical geometry we can evaluate the neutron flux and get some energy information. The neutrons will induce radioactivity in the foils. Radioactive counts from the decay of these foils can be measured by using a Ge-Li counter, which can then be used to quantify the neutron flux. These same measurements will also identify which thresholds are too high to take place in the given beam. Knowing the neutron flux for other foils will allow researchers to determine what the neutron flux will be in the Zr-89 experiment and if it will be high enough to effectively measure the (n, 2n) cross-section.

  14. Denitrification in the Upper Mississippi River: Rates, controls, and contribution to nitrate flux

    USGS Publications Warehouse

    Richardson, W.B.; Strauss, E.A.; Bartsch, L.A.; Monroe, E.M.; Cavanaugh, J.C.; Vingum, L.; Soballe, D.M.

    2004-01-01

    We evaluated patterns of denitrification and factors effecting denitrification in the upper Mississippi River. Measurements were taken over 2 years, during which river discharge ranged from record flooding to base flow conditions. Over the period of study, average denitrification enzyme activity was highest in backwater lakes and lowest in the main channel. Throughout the study reach, highest denitrification enzyme activity occurred during fall and lowest occurred in winter. Rates during spring floods (2001) were only slightly higher than during the preceding winter. Mean unamended denitrification rates ranged from 0.02 (fall 2001 in backwaters) to 0.40 ??g N??cm -2??h-1 (spring 2001 in backwaters). Laboratory experiments showed that denitrification rates increased significantly with addition of NO3- regardless of sediment C content, while rates increased little with addition of labile C (glucose). Denitrification in this reach of the upper Mississippi River appears to be NO3- limited throughout the growing season and the delivery of NO 3- is strongly controlled by river discharge and hydrologie connectivity across the floodplain. We estimate that denitrification removes 6939 t N??year-1 or 6.9% of the total annual NO 3- input to the reach. Hydrologic connectivity and resultant NO3- delivery to high-C sediments is a critical determinant of reach-scale processing of N in this floodplain system.

  15. Interstellar Hydrogen Fluxes Measured by IBEX-Lo in 2009: Numerical Modeling and Comparison with the Data

    NASA Astrophysics Data System (ADS)

    Katushkina, O. A.; Izmodenov, V. V.; Alexashov, D. B.; Schwadron, N. A.; McComas, D. J.

    2015-10-01

    In this paper, we perform numerical modeling of the interstellar hydrogen fluxes measured by IBEX-Lo during orbit 23 (spring 2009) using a state-of-the-art kinetic model of the interstellar neutral hydrogen distribution in the heliosphere. This model takes into account the temporal and heliolatitudinal variations of the solar parameters as well as the non-Maxwellian kinetic properties of the hydrogen distribution due to charge exchange in the heliospheric interface. We found that there is a qualitative difference between the IBEX-Lo data and the modeling results obtained with the three-dimensional, time-dependent model. Namely, the model predicts a larger count rate in energy bin 2 (20–41 eV) than in energy bin 1 (11–21 eV), while the data shows the opposite case. We perform study of the model parameter effects on the IBEX-Lo fluxes and the ratio of fluxes in two energy channels. We show that the most important parameter, which has a major influence on the ratio of the fluxes in the two energy bins, is the solar radiation pressure. The parameter fitting procedure shows that the best agreement between the model result and the data occurs when the ratio of the solar radiation pressure to the solar gravitation, ?0, is {1.26}-0.076+0.06, and the total ionization rate of hydrogen at 1 AU is {? }E,0={3.7}-0.35+0.39× {10}-7 s?1. We have found that the value of ?0 is much larger than ?0 = 0.89, which is the value derived from the integrated solar Ly? flux data for the period of time studied. We discuss possible reasons for the differences.

  16. Thin film heat flux sensors fabricated on copper substrates for thermal measurements in microfluidic environments

    NASA Astrophysics Data System (ADS)

    Jasperson, Benjamin A.; Schmale, Joshua; Qu, Weilin; Pfefferkorn, Frank E.; Turner, Kevin T.

    2014-12-01

    Micro-scale heat flux sensors are fabricated on bulk copper surfaces using a combination of lithography-based microfabrication and micro end milling. The heat flux sensors are designed to enable heat transfer measurements on an individual pin in a copper micro pin fin heat sink. Direct fabrication of the sensors on copper substrates minimizes the thermal resistance between the sensor and pin. To fabricate the devices, copper wafers were polished to a flatness and roughness suitable for microfabrication and standard processes, including photolithography, polyimide deposition via spinning, and metal deposition through physical vapor deposition were tailored for use on the unique copper substrates. Micro end milling was then used to create 3D pin features and segment the devices from the copper substrate. Temperature calibrations of the sensors were performed using a tube furnace and the heat flux sensing performance was assessed through laser-based tests. This paper describes the design, fabrication and calibration of these integrated heat flux sensors.

  17. Measured and parameterized energy fluxes estimated for Atlantic transects of RV Polarstern

    NASA Astrophysics Data System (ADS)

    Bumke, Karl; Macke, Andreas; Kalisch, John; Kleta, Henry

    2013-04-01

    Even to date energy fluxes over the oceans are difficult to assess. As an example the relative paucity of evaporation observations and the uncertainties of currently employed empirical approaches lead to large uncertainties of evaporation products over the ocean (e.g. Large and Yeager, 2009). Within the frame of OCEANET (Macke et al., 2010) we performed such measurements on Atlantic transects between Bremerhaven (Germany) and Cape Town (South Africa) or Punta Arenas (Chile) onboard RV Polarstern during the recent years. The basic measurements of sensible and latent heat fluxes are inertial-dissipation (e.g. Dupuis et al., 1997) flux estimates and measurements of the bulk variables. Turbulence measurements included a sonic anemometer and an infrared hygrometer, both mounted on the crow's nest. Mean meteorological sensors were those of the ship's operational measurement system. The global radiation and the down terrestrial radiation were measured on the OCEANET container placed on the monkey island. At least about 1000 time series of 1 h length were analyzed to derive bulk transfer coefficients for the fluxes of sensible and latent heat. The bulk transfer coefficients were applied to the ship's meteorological data to derive the heat fluxes at the sea surface. The reflected solar radiation was estimated from measured global radiation. The up terrestrial radiation was derived from the skin temperature according to the Stefan-Boltzmann law. Parameterized heat fluxes were compared to the widely used COARE-parameterization (Fairall et al., 2003), the agreement is excellent. Measured and parameterized heat and radiation fluxes gave the total energy budget at the air sea interface. As expected the mean total flux is positive, but there are also areas, where it is negative, indicating an energy loss of the ocean. It could be shown that the variations in the energy budget are mainly due to insolation and evaporation. A comparison between the mean values of measured and parameterized sensible and latent heat fluxes shows that the data are suitable to validate satellite derived fluxes at the sea surface and re-analysis data. References Dupuis, H., P. K. Taylor, A. Weill, and K. Katsaros, 1997: Inertial dissipation method applied to derive turbulent fluxes over the ocean during the surface of the ocean. J. Geophys. Res., 102 (C9), 21 115-21 129. Fairall, C. W., E. F. Bradley, J. E. Hare, A. A. Grachev, J. B. Edson, 2003: Bulk Parameterization of Air-Sea Fluxes: Updates and Verification for the COARE Algorithm. J. Climate, 16, 571-591. Large, W.G., and S.G. Yeager, 2009: The global climatology of an interannually varying air-sea flux data set. Climate Dynamics 33, 341-364. Macke, A., Kalisch, J., Zoll, Y., and Bumke, K., 2010: Radiative effects of the cloudy atmosphere from ground and satellite based observations, EPJ Web of Conferences, 5 9, 83-94

  18. Development of airborne eddy-correlation flux measurement capabilities for reactive oxides of nitrogen

    NASA Technical Reports Server (NTRS)

    Bradshaw, John (Principal Investigator); Zheng, Xiaonan; Sandholm, Scott T.

    1996-01-01

    This research is aimed at producing a fundamental new research tool for characterizing the source strength of the most important compound controlling the hemispheric and global scale distribution of tropospheric ozone. Specifically, this effort seeks to demonstrate the proof-of-concept of a new general purpose laser-induced fluorescence based spectrometer for making airborne eddy-correlation flux measurements of nitric oxide (NO) and other reactive nitrogen compounds. The new all solid-state laser technology being used in this advanced sensor will produce a forerunner of the type of sensor technology that should eventually result in highly compact operational systems. The proof-of-concept sensor being developed will have over two orders-of-magnitude greater sensitivity than present-day instruments. In addition, this sensor will offer the possibility of eventual extension to airborne eddy-correlation flux measurements of nitrogen dioxide (NO2) and possibly other compounds, such as ammonia (NH3), peroxyradicals (HO2), nitrateradicals (NO3) and several iodine compounds (e.g., I and IO). Demonstration of the new sensor's ability to measure NO fluxes will occur through a series of laboratory and field tests. This proof-of-concept demonstration will show that not only can airborne fluxes of important ultra-trace compounds be made at the few parts-per-trillion level, but that the high accuracy/precision measurements currently needed for predictive models can also. These measurement capabilities will greatly enhance our current ability to quantify the fluxes of reactive nitrogen into the troposphere and significantly impact upon the accuracy of predictive capabilities to model O3's distribution within the remote troposphere. This development effort also offers a timely approach for producing the reactive nitrogen flux measurement capabilities that will be needed by future research programs such as NASA's planned 1999 Amazon Biogeochemistry and Atmospheric Chemistry Experimental portion of LBA.

  19. Combined analysis of neutron and photon flux measurements for the Jules Horowitz reactor core mapping

    SciTech Connect

    Fourmentel, D.; Villard, J. F.; Lyoussi, A.; Reynard-Carette, C.; Bignan, G.; Chauvin, J. P.; Gonnier, C.; Guimbal, P.; Malo, J. Y.; Carette, M.; Janulyte, A.; Merroun, O.; Brun, J.; Zerega, Y.; Andre, J.

    2011-07-01

    We study the combined analysis of nuclear measurements to improve the knowledge of the irradiation conditions in the experimental locations of the future Jules Horowitz Reactor (JHR). The goal of the present work is to measure more accurately neutron flux, photon flux and nuclear heating in the reactor. In a Material Testing Reactor (MTR), nuclear heating is a crucial parameter to design the experimental devices to be irradiated in harsh nuclear conditions. This parameter drives the temperature of the devices and of the samples. The numerical codes can predict this parameter but in-situ measurements are necessary to reach the expected accuracy. For this reason, one objective of the IN-CORE program [1] is to study the combined measurements of neutron and photon flux and their cross advanced interpretation. It should be reminded that both neutron and photon sensors are not totally selective as their signals are due to neutron and photon interactions. We intend to measure the neutron flux by three different kinds of sensors (Uranium Fission chamber, Plutonium Fission chamber and Self Powered Neutron Detector), the photon flux by two different sensors (Ionization chamber and Self Powered Gamma Detector) and the nuclear heating by two different ones (Differential calorimeter and Gamma Thermometer). For the same parameter, we expect that the use of different kinds of sensors will allow a better estimation of the aimed parameter by mixing different spectrum responses and different neutron and gamma contributions. An experimental test called CARMEN-1 is scheduled in OSIRIS reactor (CEA Saclay - France) at the end of 2011, with the goal to map irradiation locations in the reactor reflector to get a first validation of the analysis model. This article focuses on the sensor selection for CARMEN-1 experiment and to the way to link neutron and photon flux measurements in view to reduce their uncertainties but also to better assess the neutron and photon contributions to nuclear heating. (authors)

  20. Interstellar hydrogen fluxes measured by IBEX-Lo in 2009: numerical modeling and comparison with the data

    E-print Network

    Katushkina, O A; Alexashov, D B; Schwadron, N A; McComas, D J

    2015-01-01

    In this paper, we perform numerical modeling of the interstellar hydrogen fluxes measured by IBEX-Lo during orbit 23 (spring 2009) using a state-of-the-art kinetic model of the interstellar neutral hydrogen distribution in the heliosphere. This model takes into account the temporal and heliolatitudinal variations of the solar parameters as well as non-Maxwellian kinetic properties of the hydrogen distribution due to charge exchange in the heliospheric interface. We found that there is a qualitative difference between the IBEX-Lo data and the modeling results obtained with the three-dimensional, time-dependent model. Namely, the model predicts a larger count rate in energy bin~2 (20-41 eV) than in energy bin~1 (11-21 eV), while the data shows the opposite case. We perform study of the model parameter effects on the IBEX-Lo fluxes and the ratio of fluxes in two energy channels. We shown that the most important parameter, which has a major influence on the ratio of the fluxes in the two energy bins, is the solar...

  1. Remote Heat Flux Measurement Using a Self Calibration Multiwavelength Pyrometer and a Transparent Material

    NASA Technical Reports Server (NTRS)

    Ng, Daniel

    1998-01-01

    A self calibrating multiwavelength pyrometer was used to conduct remote heat flux measurements using a transparent sapphire disk by determining the sapphire disk's front and back surface temperatures. Front surface temperature (Tfs) was obtained from detection of surface emitted radiation at long wavelengths (lambda > 6 micrometers). Back surface temperature (Tbs) was obtained from short wavelength (1 to 5 micrometers) radiation transmitted through the sapphire disk. The thermal conductivity k of the sapphire disk and the heat transfer coefficients h(sub 1) and h(sub 2) of its surfaces are determined experimentally. An analysis of the heat flux measurement is presented.

  2. DETECTION AND FLUX DENSITY MEASUREMENTS OF THE MILLISECOND PULSAR J2145–0750 BELOW 100 MHz

    SciTech Connect

    Dowell, J.; Taylor, G. B.; Craig, J.; Henning, P. A.; Schinzel, F.; Ray, P. S.; Blythe, J. N.; Clarke, T.; Helmboldt, J. F.; Ellingson, S. W.; Wolfe, C. N.; Lazio, T. J. W.; Stovall, K.

    2013-09-20

    We present flux density measurements and pulse profiles for the millisecond pulsar PSR J2145–0750 spanning 37 to 81 MHz using data obtained from the first station of the Long Wavelength Array. These measurements represent the lowest frequency detection of pulsed emission from a millisecond pulsar to date. We find that the pulse profile is similar to that observed at 102 MHz. We also find that the flux density spectrum between ?40 MHz to 5 GHz is suggestive of a break and may be better fit by a model that includes spectral curvature with a rollover around 730 MHz rather than a single power law.

  3. Device accurately measures and records low gas-flow rates

    NASA Technical Reports Server (NTRS)

    Branum, L. W.

    1966-01-01

    Free-floating piston in a vertical column accurately measures and records low gas-flow rates. The system may be calibrated, using an adjustable flow-rate gas supply, a low pressure gage, and a sequence recorder. From the calibration rates, a nomograph may be made for easy reduction. Temperature correction may be added for further accuracy.

  4. Neutron flux measurements in the side-core region of Hunterston B advanced gas-cooled reactor

    SciTech Connect

    Allen, D.A.; Shaw, S.E.; Huggon, A.P.; Steadman, R.J.; Thornton, D.A.; Whiley, G.S.

    2011-07-01

    The core restraints of advanced gas-cooled reactors are important structural components that are required to maintain the geometric integrity of the cores. A review of neutron dosimetry for the sister stations Hunterston B and Hinkley Point B identified that earlier conservative assessments predicted high thermal neutron dose rates to key components of the restraint structure (the restraint rod welds), with the implication that some of them may be predicted to fail during a seismic event. A revised assessment was therefore undertaken [Thornton, D. A., Allen, D. A., Tyrrell, R. J., Meese, T. C., Huggon, A.P., Whiley, G. S., and Mossop, J. R., 'A Dosimetry Assessment for the Core Restraint of an Advanced Gas Cooled Reactor,' Proceedings of the 13. International Symposium on Reactor Dosimetry (ISRD-13, May 2008), World Scientific, River Edge, NJ, 2009, W. Voorbraak, L. Debarberis, and P. D'hondt, Eds., pp. 679-687] using a detailed 3D model and a Monte Carlo radiation transport program, MCBEND. This reassessment resulted in more realistic fast and thermal neutron dose recommendations, the latter in particular being much lower than had been thought previously. It is now desirable to improve confidence in these predictions by providing direct validation of the MCBEND model through the use of neutron flux measurements. This paper describes the programme of work being undertaken to deploy two neutron flux measurement 'stringers' within the side-core region of one of the Hunterston B reactors for the purpose of validating the MCBEND model. The design of the stringers and the determination of the preferred deployment locations have been informed by the use of detailed MCBEND flux calculations. These computational studies represent a rare opportunity to design a flux measurement beforehand, with the clear intention of minimising the anticipated uncertainties and obtaining measurements that are known to be representative of the neutron fields to which the vulnerable steel restraint components are exposed. (authors)

  5. Validation of the doubly-labeled water (H/sup 3/H/sup 18/O) method for measuring water flux and energy metabolism in tenebrionid beetles

    SciTech Connect

    Cooper, P.D.

    1981-01-01

    Doubly-labeled water (H/sup 3/H/sup 18/O) has been used to determine water flux and energy metabolism in a variety of vertebrates. This study examines the applicability of this technique to arthropods. The theory of the technique depends upon the assumption that doubly-labeled water introduced into the animal's body water equilibrates with water and carbon dioxide by the action of carbonic anhydrase. Tritium (/sup 3/H) is lost from the animal only with water while oxygen-18 is lost with both water and carbon dioxide. The difference bwtween the rates of loss of the two isotopes is proportional to CO/sub 2/ loss rate. Validation of the use of tritiated water for measuring water flux was accomplished by comparing gravimetric measurements of water gain with flux rates determined by loss of tritiated water. At room humidity, an overestimate for influx calculated from labeled water calculations was found, averaging 12 mg H/sub 2/O (g.d)/sup -1/. Comparison of CO/sub 2/ loss rate determined isotopically with rates of CO/sub 2/ loss determined by standard metabolic rates also yielded overestimates for the isotopic technique, overestimates ranging between 20 and 30%. The relevance of this for studies using labeled water for studying water fluxes and free metabolism of free-ranging arthropods is discussed.

  6. Modeling magnetic fields measured by surface probes embedded in a cylindrical flux conserver.

    PubMed

    Golingo, R P

    2007-03-01

    Calculating magnetic fields at the surface of a flux conserver, perfect conductor, for displaced plasma currents is useful for understanding modes of a Z-pinch. The magnetic fields measured at the flux conserver are a sum of the magnetic fields from the plasma current and the eddy currents which form in the walls to keep the flux constant. While the magnetic field at the wall from the plasma current alone is easily calculated using the Biot-Savart law, finding the eddy currents in the flux conserver which satisfy the boundary conditions can be a tedious process. A simple method of calculating the surface magnetic field for a given Z-pinch displacement off-axis is derived for a cylindrical flux conserver. This relationship does not require the explicit calculation of the eddy currents, saving time when analyzing surface magnetic probe measurements. Analytic expressions can be used to describe the surface magnetic field which increase the understanding of the magnetic probe measurements. PMID:17411182

  7. Coronal mass ejections: The long-term variation of their occurrence rate and the solar wind mass flux

    NASA Technical Reports Server (NTRS)

    Webb, David F.

    1987-01-01

    Solar Coronal Mass Ejections (CMEs) from the Sun are an important aspect of coronal physics, and a potentially important contributor to the solar wind mass flux. However, despite significant progress in studies of CMEs since their discovery in the early 70's, questions remain about their effects on the interplanetary medium. A study is done of the long-term variations of the occurrence rates of CMEs, of activity tracers related to CMEs, and of the solar wind particle flux. CMEs are most directly detected by scattered electron radiation in white light. To estimate their long-term occurrence frequency and their contributions to the in-ecliptic solar wind mass flux, observed CME rates must be corrected for instrumental duty cycles, detection efficiency out of the plane of the sky, mass detection thresholds, and geometrical considerations. These corrections are evaluated using data on solar CMEs from the spaceborne Skylab, SMM, and SOLWIND coronagraphs and on interplanetary plasma clouds from the HELIOS white light photometers. Variations in the CME rate and the contribution of CMEs to the solar wind mass flux are traced over nearly a complete solar activity cycle.

  8. Measurements of ambient HONO concentrations and vertical HONO flux above a northern Michigan forest canopy

    NASA Astrophysics Data System (ADS)

    Zhang, N.; Zhou, X.; Bertman, S.; Tang, D.; Alaghmand, M.; Shepson, P. B.; Carroll, M. A.

    2012-03-01

    Systems have been developed and deployed at a North Michigan forested site to measure ambient HONO and vertical HONO flux. The modified HONO measurement technique is based on aqueous scrubbing of HONO using a coil sampler, followed by azo dye derivatization and detection using an optical fiber spectrometer with a 1-m long path flow cell. A Na2CO3-coated denuder is used to generate "zero HONO" air for background correction. The lower detection limit of the method, defined by 3 times of the standard deviation of the signal, is 1 pptv for 2-min averages, with an overall uncertainty of ±(1 + 0.05 [HONO]) pptv. The HONO flux measurement technique has been developed based on the relaxed eddy accumulation approach, deploying a 3-D sonic anemometer and two HONO measurement systems. The overall uncertainty is estimated to be within ±(8 × 10-8 + 0.15 FHONO) mol m-2 h-1, with a 20-min averaged data point per 30 min. Ambient HONO and vertical HONO flux were measured simultaneously at the PROPHET site from 17 July to 7 August 2008. The forest canopy was found to be a net HONO source, with a mean upward flux of 0.37 × 10-6 moles m-2 h-1. The HONO flux reached a maximum mean of ~0.7 × 10-6 moles m-2 h-1 around solar noon, contributing a major fraction (~60%) to the HONO source strength required to sustain the observed ambient concentration of ~70 pptv. There was no significant correlation between NOx and daytime HONO flux, suggesting that NOx was not an important precursor responsible for HONO daytime production on the forest canopy surface in the low-NOx rural environment. Evidence suggests that photolysis of HNO3 deposited on the forest canopy surface is a major daytime HONO source.

  9. Effects of acute fresh water exposure on water flux rates and osmotic responses in Kemp's ridley sea turtles (Lepidochelys kempi)

    NASA Technical Reports Server (NTRS)

    Ortiz, R. M.; Patterson, R. M.; Wade, C. E.; Byers, F. M.

    2000-01-01

    Water flux rates and osmotic responses of Kemp's Ridley sea turtles (Lepidochelys kempi) acutely exposed to fresh water were quantified. Salt-water adapted turtles were exposed to fresh water for 4 d before being returned to salt water. During the initial salt water phase, absolute and relative water flux rates were 1.2+/-0.1 l d(-1) and 123.0+/-6.8 ml kg(-1) d(-1), respectively. When turtles were exposed to fresh water, rates increased by approximately 30%. Upon return to salt water, rates decreased to original levels. Plasma osmolality, Na(+), K(+), and Cl(-) decreased during exposure to fresh water, and subsequently increased during the return to salt water. The Na(+):K(+) ratio was elevated during the fresh water phase and subsequently decreased upon return to salt water. Aldosterone and corticosterone were not altered during exposure to fresh water. Elevated water flux rates during fresh water exposure reflected an increase in water consumption, resulting in a decrease in ionic and osmotic concentrations. The lack of a change in adrenocorticoids to acute fresh water exposure suggests that adrenal responsiveness to an hypo-osmotic environment may be delayed in marine turtles when compared to marine mammals.

  10. Oil palm water use: calibration of a sap flux method and a field measurement scheme.

    PubMed

    Niu, Furong; Röll, Alexander; Hardanto, Afik; Meijide, Ana; Köhler, Michael; Hendrayanto; Hölscher, Dirk

    2015-05-01

    Oil palm (Elaeis guineensis Jacq.) water use was assessed by sap flux density measurements with the aim to establish the method and derive water-use characteristics. Thermal dissipation probes were inserted into leaf petioles of mature oil palms. In the laboratory, we tested our set-up against gravimetric measurements and derived new parameters for the original calibration equation that are specific to oil palm petioles. In the lowlands of Jambi, Indonesia, in a 12-year-old monoculture plantation, 56 leaves on 10 palms were equipped with one sensor per leaf. A 10-fold variation in individual leaf water use among leaves was observed, but we did not find significant correlations to the variables trunk height and diameter, leaf azimuthal orientation, leaf inclination or estimated horizontal leaf shading. We thus took an un-stratified approach to determine an appropriate sampling design to estimate stand transpiration (Es, mm day(-1)) rates of oil palm. We used the relative standard error of the mean (SEn, %) as a measure for the potential estimation error of Es associated with sample size. It was 14% for a sample size of 13 leaves to determine the average leaf water use and four palms to determine the average number of leaves per palm. Increasing these sample sizes only led to minor further decreases of the SEn of Es. The observed 90-day average of Es was 1.1 mm day(-1) (error margin ± 0.2 mm day(-1)), which seems relatively low, but does not contradict Penman-Monteith-derived estimates of evapotranspiration. Examining the environmental drivers of Es on an intra-daily scale indicates an early, pre-noon maximum of Es rates (11 am) due to a very sensitive reaction of Es to increasing vapor pressure deficit in the morning. This early peak is followed by a steady decline of Es rates for the rest of the day, despite further rising levels of vapor pressure deficit and radiation; this results in pronounced hysteresis, particularly between Es and vapor pressure deficit. PMID:25787332

  11. Using Airborne Microwave Remotely Sensed Root-Zone Soil Moisture and Flux Measurements to Improve Regional Predictions of Carbon Fluxes in a Terrestrial Biosphere Model

    NASA Astrophysics Data System (ADS)

    Zhang, K.; Antonarakis, A. S.; Medvigy, D.; Burgin, M. S.; Crow, W. T.; Milak, S.; Jaruwatanadilok, S.; Truong-Loi, M.; Moghaddam, M.; Saatchi, S. S.; Cuenca, R. H.; Moorcroft, P. R.

    2013-12-01

    North American ecosystems are critical components of the global carbon cycle, exchanging large amounts of carbon dioxide and other gases with the atmosphere. Net ecosystem exchange (NEE) of CO2 between atmosphere and ecosystems quantifies these carbon fluxes, but current continental-scale estimates contain high levels of uncertainty. Root-zone soil moisture (RZSM) and its spatial and temporal heterogeneity influences NEE and improved estimates can help reduce uncertainty in NEE estimates. We used the RZSM measurements from the Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) mission, and the carbon, water and energy fluxes observed by the eddy-covariance flux towers to constrain the Ecosystem Demography Model 2.2 (ED2.2) to improve its predictions of carbon fluxes. The parameters of the ED2.2 model were first optimized at seven flux tower sites in North America, which represent six different biomes, by constraining the model against a suite of flux measurements and forest inventory measurements through a Bayesian Markov-Chain Monte Carlo framework. We further applied the AirMOSS RZSM products to constrain the ED2.2 model to achieve better estimates of regional NEE. Evaluation against flux tower measurements and forest dynamics measurements shows that the constrained ED2.2 model produces improved predictions of monthly to annual carbon fluxes. The remote sensing based RZSM can further help improve the spatial patterns and temporal variations of model NEE. The results demonstrate that model-data fusion can substantially improve model performance and highlight the important role of RZSM in regulating the spatial and temporal heterogeneities of carbon fluxes.

  12. Measurement of tracheal mucous transport rate in the horse

    SciTech Connect

    Nelson, R.; Hampe, D.W.

    1983-06-01

    Tracheal mucous transport rates were measured in 12 nonanesthetized horses after an intratracheal injection of 99mtechnetium-sulfur colloid. The transport rate of the subsequent bolus of radioactivity was determined, using a portable scaler rate meter fitted with a high-energy gamma-scintillation probe. A gamma-scintillation camera was used to verify bolus form and movement in 1 horse. The mean tracheal mucous transport rate was 1.66 +/- 0.24 cm/min.

  13. Marine particle dynamics : sinking velocities, size distributions, fluxes, and microbial degradation rates

    E-print Network

    McDonnell, Andrew M. P

    2011-01-01

    The sinking flux of particulate matter into the ocean interior is an oceanographic phenomenon that fuels much of the metabolic demand of the subsurface ocean and affects the distribution of carbon and other elements ...

  14. Nano-engineering the boiling surface for optimal heat transfer rate and critical heat flux

    E-print Network

    Phillips, Bren Andrew

    2011-01-01

    The effects on pool boiling characteristics such as critical heat flux and the heat transfer coefficient of different surface characteristics such as surface wettability, roughness, morphology, and porosity are not well ...

  15. ECH Absorbed Power Evaluation Method Compensated for Temporal Response of Diamagnetic Flux Measurements on LHD

    NASA Astrophysics Data System (ADS)

    Makino, Ryohei; Kubo, Shin; Ido, Takeshi; Shimozuma, Takashi; Yoshimura, Yasuo; Nishiura, Masaki; Igami, Hiroe; Takhashi, Hiromi; Ogasawara, Shinya; Mutoh, Takashi

    Evaluation methods of electron cyclotron resonance heating (ECH) power absorption are discussed. ECH power absorption can be evaluated from changes in the time derivative of the plasma stored energy. On the Large Helical Device (LHD), absorbed power is usually evaluated from the difference between the time derivative of the stored energy estimated from diamagnetic flux just before and after ECH injection. The temporal response of the diamagnetic flux measurement is slow with a time constant of several milliseconds because of uncompensated effects of image currents, and it affects the ECH absorbed power estimation. Therefore, a new method taking the slow response into account is developed. ECH power absorption has been evaluated from the plasma kinetic energy and compared with the power absorption evaluated by the new method. The evaluated power absorption values were approximately consistent with each other. Absorbed power evaluation using diamagnetic flux measurements is more accurate by taking the slow response into account.

  16. Potentials and challenges associated with automated closed dynamic chamber measurements of soil CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Görres, Carolyn-Monika; Kammann, Claudia; Ceulemans, Reinhart

    2015-04-01

    Soil respiration fluxes are influenced by natural factors such as climate and soil type, but also by anthropogenic activities in managed ecosystems. As a result, soil CO2 fluxes show a large intra- and interannual as well as intra- and intersite variability. Most of the available soil CO2 flux data giving insights into this variability have been measured with manually closed static chambers, but technological advances in the past 15 years have also led to an increased use of automated closed chamber systems. The great advantage of automated chambers in comparison to manually operated chambers is the higher temporal resolution of the flux data. This is especially important if we want to better understand the effects of short-term events, e.g. fertilization or heavy rainfall, on soil CO2 flux variability. However, the chamber method is an invasive measurement method which can potentially alter soil CO2 fluxes and lead to biased measurement results. In the peer-reviewed literature, many papers compare the field performance and results of different closed static chamber designs, or compare manual chambers with automated chamber systems, to identify potential biases in CO2 flux measurements, and thus help to reduce uncertainties in the flux data. However, inter-comparisons of different automated closed dynamic chamber systems are still lacking. Here we are going to present a field comparison of the most-cited automated chamber system, the LI-8100A Automated Soil Flux System, with the also commercially available Greenhouse Gas Monitoring System AGPS. Both measurement systems were installed side by side at a recently harvested poplar bioenergy plantation (POPFULL, http://uahost.uantwerpen.be/popfull/) from April 2014 until August 2014. The plantation provided optimal comparison conditions with a bare field situation after the harvest and a regrowing canopy resulting in a broad variety of microclimates. Furthermore, the plantation was planted in a double-row system with the row width alternating between 1.50 m and 0.75 m, creating spatial differences in e.g. dry bulk density and soil organic carbon content. The soil CO2 flux data sets were split into four subsets each characterized by different environmental conditions, thus presenting different challenges for the measurement equipment, namely 1) daytime, calm conditions, 2) daytime, windy conditions, 3) nighttime, calm conditions, and 4) nighttime, windy conditions. In parallel to the chamber measurements, soil CO2 concentrations were manually measured in the topsoil. Soil CO2 fluxes calculated from this dataset were used as a reference range of soil CO2 fluxes at the field site. Funding support: ERC Advanced Grant agreement (# 233366) POPFULL under the EC 7th Framework Program (FP7/2007-2013), Flemish Hercules Foundation as Infrastructure contract # ZW09-06, and the Methusalem Program of the Flemish Government.

  17. Productivity and carbon dioxide exchange of leguminous crops: estimates from flux tower measurements

    USGS Publications Warehouse

    Gilmanov, Tagir G.; Baker, John M.; Bernacchi, Carl J.; Billesbach, David P.; Burba, George G.; Castro, Saulo; Chen, Jiquan; Eugster, Werner; Fischer, Marc L.; Gamon, John A.; Gebremedhin, Maheteme T.; Glenn, Aaron J.; Griffis, Timothy J.; Hatfield, Jerry L.; Heuer, Mark W.; Howard, Daniel M.; Leclerc, Monique Y.; Loescher, Henry W.; Marloie, Oliver; Meyers, Tilden P.; Olioso, Albert; Phillips, Rebecca L.; Prueger, John H.; Skinner, R. Howard; Suyker, Andrew E.; Tenuta, Mario; Wylie, Bruce K.

    2014-01-01

    Net CO2 exchange data of legume crops at 17 flux tower sites in North America and three sites in Europe representing 29 site-years of measurements were partitioned into gross photosynthesis and ecosystem respiration by using the nonrectangular hyperbolic light-response function method. The analyses produced net CO2 exchange data and new ecosystem-scale ecophysiological parameter estimates for legume crops determined at diurnal and weekly time steps. Dynamics and annual totals of gross photosynthesis, ecosystem respiration, and net ecosystem production were calculated by gap filling with multivariate nonlinear regression. Comparison with the data from grain crops obtained with the same method demonstrated that CO2 exchange rates and ecophysiological parameters of legumes were lower than those of maize (Zea mays L.) but higher than for wheat (Triticum aestivum L.) crops. Year-round annual legume crops demonstrated a broad range of net ecosystem production, from sinks of 760 g CO2 m–2 yr–1 to sources of –2100 g CO2 m–2 yr–1, with an average of –330 g CO2 m–2 yr–1, indicating overall moderate CO2–source activity related to a shorter period of photosynthetic uptake and metabolic costs of N2 fixation. Perennial legumes (alfalfa, Medicago sativa L.) were strong sinks for atmospheric CO2, with an average net ecosystem production of 980 (range 550–1200) g CO2 m–2 yr–1.

  18. An inverse approach to estimate bubble-mediated air-sea gas flux from inert gas measurements

    E-print Network

    Khatiwala, Samar

    in equilibrium with local sea level pressure (slp). As convention here, a positive flux is from atmosphereAn inverse approach to estimate bubble-mediated air-sea gas flux from inert gas measurements David, Ar, N2/Ar and Kr/Ar) to constrain the magnitude of bubble mediated air-sea gas flux. We illustrate

  19. A multi-site analysis of random error2 in tower-based measurements of carbon and energy fluxes3

    E-print Network

    open-path, gas analyzer is22 used.23 #12;RANDOM ERRORS IN ENERGY AND CO2 FLUX MEASUREMENTS Richardson Forest Service, 271 Mast Road, Durham, NH 03824 USA.25 #12;RANDOM ERRORS IN ENERGY AND CO2 FLUX (sensible heat, H, and latent heat,2 LE) and CO2 (FCO2) represent the "true" flux plus or minus potential

  20. High CO2 emissions through porous media: Transport mechanisms and implications for flux measurement and fractionation

    USGS Publications Warehouse

    Evans, William C.; Sorey, M.L.; Kennedy, B.M.; Stonestrom, D.A.; Rogie, J.D.; Shuster, D.L.

    2001-01-01

    Diffuse emissions of CO2 are known to be large around some volcanoes and hydrothermal areas. Accumulation-chamber measurements of CO2 flux are increasingly used to estimate the total magmatic or metamorphic CO2 released from such areas. To assess the performance of accumulation chamber systems at fluxes one to three orders of magnitude higher than normally encountered in soil respiration studies, a test system was constructed in the laboratory where known fluxes could be maintained through dry sand. Steady-state gas concentration profiles and fractionation effects observed in the 30-cm sand column nearly match those predicted by the Stefan-Maxwell equations, indicating that the test system was functioning successfully as a uniform porous medium. Eight groups of investigators tested their accumulation chamber equipment, all configured with continuous infrared gas analyzers (IRGA), in this system. Over a flux range of ~ 200-12,000 g m-2 day-1, 90% of their 203 flux measurements were 0-25% lower than the imposed flux with a mean difference of - 12.5%. Although this difference would seem to be within the range of acceptability for many geologic investigations, some potential sources for larger errors were discovered. A steady-state pressure gradient of -20 Pa/m was measured in the sand column at a flux of 11,200 g m-2 day-1. The derived permeability (50 darcies) was used in the dusty-gas model (DGM) of transport to quantify various diffusive and viscous flux components. These calculations were used to demonstrate that accumulation chambers, in addition to reducing the underlying diffusive gradient, severely disrupt the steady-state pressure gradient. The resultant diversion of the net gas flow is probably responsible for the systematically low flux measurements. It was also shown that the fractionating effects of a viscous CO2 efflux against a diffusive influx of air will have a major impact on some important geochemical indicators, such as N2/Ar, ??15N-N2, and 4He/22Ne. Published by Elsevier Science B.V.

  1. Remotely sensed dune sand flux measurements in the dustiest place on Earth (Bodélé, Chad)

    NASA Astrophysics Data System (ADS)

    Vermeesch, P.

    2009-12-01

    The Bodélé Depression of northern Chad is the dustiest place on Earth, thanks to a unique combination of two factors. First, the Bodélé is located downwind of a narrow gap between the Tibesti and Ennedi mountain ranges, which act as a funnel creating the strong winds of the Bodélé Low Level Jet. Second, the depression forms the deepest part of palaeo-lake Megachad, which once rivaled the Caspian Sea in size. When the lake dried out during the Holocene, it left behind thick deposits of diatomite, which currently provide an abundant and readily available source of dust. Previous work has shown that dust is primarily produced by eddies near the horns of barchan dunes. Using a new remote sensing technique called COSI-Corr, these barchans were shown to be not only the largest, but also the fastest on Earth, featuring the highest sand fluxes. Quantifying sand flux with field measurements is an expensive and time-consuming process. COSI-Corr -which stands for 'Co-registration of Optically Sensed Images and Correlation' and was originally developed for the purpose of detecting surface deformation caused by earthquakes- offers an alternative approach to measuring sand flux, using remote sensing. From pairs of ASTER imagery, dune migration in the Bodélé depression was successfully measured over time intervals of one month to 6.5 years. The displacement maps produced by COSI-Corr can be used to automatically distinguish dunes from interdunes, which is a crucial step towards calculating sand flux. Dune heights and volumes were obtained by interpolating a surface between the interdune areas and subtracting it from a digital elevation model. Multiplying height with celerity yields a pixel-by-pixel estimate of the sand flux. Applying this method to large diatomite dunes in the Bodélé confirms that these are some of the world’s fastest moving barchans. Plotting dune height against inverse celerity reveals sand flux at the dune crest of >200 m3/m/yr. Average dune sand flux values for the eastern and western Bodélé are 76 and 99 m3/m/yr, respectively. The contribution of the dunes to the total area-averaged sand flux is 24-29 m3/m/yr, which is ~10% of the saltation flux determined by previously published field measurements. The displacement field of quartz dunes in the northeastern Bodélé displayed as a vector field.

  2. Comparison of CO2 fluxes from eddy covariance and soil chambers measurements in a vineyard

    NASA Astrophysics Data System (ADS)

    Vendrame, Nadia; Tezza, Luca; Meggio, Franco; Pitacco, Andrea

    2015-04-01

    In order to study the processes involved in the carbon balance of a vineyard, we set up a long-term monitoring station of CO2, water vapour and energyfluxes. The experimental site is located in an extensive flat vineyard in the north-east of Italy. We measure the net ecosystem exchange with the eddy covariance (EC) technique using a Campbell Scientific closed-path IRGA and sonic anemometer, and the soil CO2 flux using a Li-Cor multiplexed system connected with six automatic dynamic chambers. Ancillary meteorological and soil variables are also measured. The vineyard is planted with north-south oriented rows spaced 2.2 m apart. Floor is grass covered, and a strip 0.6 m wide on the rows is chemically treated. To represent the different soil conditions existing in the EC footprint and to study the components of the CO2 soil flux, we placed dark soil chambers both on the vineyard rows and in the inter-row space. A well-known limit of the EC technique is the underestimation of fluxes during calm wind periods, mainly occurring at night. In the autumn/winter vine dormancy period, the EC and soil chambers CO2 fluxes should be similar. We compared the CO2 fluxes measured using the two methods to evaluate the reliability of EC measurements at different atmospheric turbulent mixing conditions and stability. The EC technique underestimates the ecosystem respiration during night time periods with friction velocity lower than 0.1 m/s. The present comparison could enable the assessment of a friction velocity threshold, representing the limit above which the EC fluxes can be considered representative of the vegetation-atmosphere exchanges at our specific site.

  3. Gravity wave momentum fluxes from MF and meteor radar measurements in the polar MLT region

    NASA Astrophysics Data System (ADS)

    Placke, Manja; Hoffmann, Peter; Latteck, Ralph; Rapp, Markus

    2015-01-01

    Annual cycles of horizontal winds and gravity wave (GW) momentum fluxes in the mesosphere/lower thermosphere (MLT) are presented for the medium frequency Doppler radar at Saura (SMF radar, located at 69°N, 16°E) for the first time. Four year mean wind and momentum flux fields for 2008 through 2011 clearly show the coupling and interactions between GWs and the mean flow especially in the summer months. GW breaking at mesopause heights results in momentum flux divergence and affects the wind field by forcing a reversal of the wind profile in summer. Height-time cross sections for the individual years (2008 to 2011) illustrate the year-to-year variation of horizontal winds and the vertical fluxes of zonal and meridional momentum. They show similar annual patterns from year to year which are more consistent in the summer months than during winter and have maximum absolute values in 2009. Furthermore, the precise SMF radar measurements give an excellent possibility to evaluate momentum flux estimates from the colocated meteor radar at Andenes. Both radars have different capabilities, and different techniques are applied to derive momentum fluxes. They show comparable results for the 4 year mean annual cycles of horizontal winds and momentum fluxes especially in summer. This holds for both structure and magnitudes in the overlapping heights, where the SMF radar data provide a wider vertical coverage. The best agreement is found for the zonal components of both radars, whereas there are some larger discrepancies in the meridional components, especially in the vertical flux of meridional momentum.

  4. Validation of flux measurements with artificial sources: simulating CH4 from cows and NH3 emissions from medium plot scales

    NASA Astrophysics Data System (ADS)

    Sintermann, Jörg; Felber, Raphael; Häni, Christoph; Ammann, Christof; Neftel, Albrecht

    2014-05-01

    Mitigation of ammonia (NH3) emissions with detrimental environmental effects as well as of greenhouse gas emissions (GHG: CO2, N2O, CH4) are key challenges faced by the agricultural production sector. While NH3 originates mainly from polluted surfaces, e.g. after slurry application, the main source for CH4 emissions are cows and other ruminating animals, representing point sources. There are two widespread state-of-the-art techniques to determine agricultural emissions: eddy covariance (EC) flux measurements and Lagrangian stochastic (LS) dispersion modelling, namely the WindTrax (WT) model. Whereas GHG emissions can be measured with both techniques, NH3 emissions are usually not feasible with EC measurements due to the stickiness of NH3 molecules on surfaces. In addition, point sources render difficulties for the interpretation of EC flux data. We tested the EC technique and the WT model using artificial sources with known gas release rates. i) The effect of a point source on EC fluxes was investigated by placing an artificial CH4 source with known release rate upwind of the EC tower at two different heights and during different wind conditions. ii) The WT model was checked with a NH3 release grid of 314 m2 of known source strength. Ambient NH3 concentrations were measured by open path DOAS systems and impinger sampling. The CH4 concentration timeseries influenced by the point source showed a similar pattern as in the presence of cows upwind of the EC system. CH4 release rates from the point source were reproduced by the EC flux measurement with stationary background conditions only. The experiments with the NH3 release showed that WT performs well for emission determination, even in complex terrain (asphalt surrounded by grassland) with associated micrometeorology, given a realistic description of the vertical profile of wind velocity. Calculated gas recoveries ranged between 73 to 105%. Such a result is encouraging considering the immanent uncertainties from a NH3 experiment (variable background concentration, relatively small downwind concentrations, NH3 interception on ground/tubing).

  5. Supersonic Mass Flux Measurements via Tunable Diode Laser Absorption and Non-Uniform Flow Modeling

    NASA Technical Reports Server (NTRS)

    Chang, Leyen S.; Strand, Christopher L.; Jeffries, Jay B.; Hanson, Ronald K.; Diskin, Glenn S.; Gaffney, Richard L.; Capriotti, Diego P.

    2011-01-01

    Measurements of mass flux are obtained in a vitiated supersonic ground test facility using a sensor based on line-of-sight (LOS) diode laser absorption of water vapor. Mass flux is determined from the product of measured velocity and density. The relative Doppler shift of an absorption transition for beams directed upstream and downstream in the flow is used to measure velocity. Temperature is determined from the ratio of absorption signals of two transitions (lambda(sub 1)=1349 nm and lambda(sub 2)=1341.5 nm) and is coupled with a facility pressure measurement to obtain density. The sensor exploits wavelength-modulation spectroscopy with second-harmonic detection (WMS-2f) for large signal-to-noise ratios and normalization with the 1f signal for rejection of non-absorption related transmission fluctuations. The sensor line-of-sight is translated both vertically and horizontally across the test section for spatially-resolved measurements. Time-resolved measurements of mass flux are used to assess the stability of flow conditions produced by the facility. Measurements of mass flux are within 1.5% of the value obtained using a facility predictive code. The distortion of the WMS lineshape caused by boundary layers along the laser line-of-sight is examined and the subsequent effect on the measured velocity is discussed. A method for correcting measured velocities for flow non-uniformities is introduced and application of this correction brings measured velocities within 4 m/s of the predicted value in a 1630 m/s flow.

  6. MAGNETIC FLUX DENSITY MEASURED IN FAST AND SLOW SOLAR WIND STREAMS

    SciTech Connect

    Erdos, G.; Balogh, A.

    2012-07-10

    The radial component of the heliospheric magnetic field vector is used to estimate the open magnetic flux density of the Sun. This parameter has been calculated using observations from the Ulysses mission that covered heliolatitudes from 80 Degree-Sign S to 80 Degree-Sign N, from 1990 to 2009 and distances from 1 to 5.4 AU, the Advanced Composition Explorer mission at 1 AU from 1997 to 2010, the OMNI interplanetary database from 1971, and the Helios 1 and 2 missions that covered the distance range from 0.3 to 1 AU. The flux density was found to be much affected by fluctuations in the magnetic field which make its calculated value dependent on heliospheric location, type of solar wind (fast or slow), and the level of solar activity. However, fluctuations are distributed symmetrically perpendicular to the average Parker direction. Therefore, distributions of the field vector in the two-dimensional plane defined by the radial and azimuthal directions in heliospheric coordinates provide a way to reduce the effects of the fluctuations on the measurement of the flux density. This leads to a better defined flux density parameter; the distributions modified by removing the effects of fluctuations then allow a clearer assessment of the dependence of the flux density on heliospheric location, solar wind type, and solar activity. This assessment indicates that the flux density normalized to 1 AU is independent of location and solar wind type (fast or slow). However, there is a residual dependence on solar activity which can be studied using the modified flux density measurements.

  7. Surface Measurements of Oxygen, Carbon Dioxide and Water Vapor Fluxes Using AN Automated Chamber System

    NASA Astrophysics Data System (ADS)

    Fentabil, M. M.; Fazackerley, S.; Nichol, C. F.

    2011-12-01

    The various soil respiration measurements that are available depend on measuring the emitted CO2 flux as organic carbon is respired aerobically. Comparative studies among the four well known methods (the open-flow infra-red gas analyzer method; the closed chamber method; the dynamic closed chamber method; and the alkali absorption method) under field conditions and laboratory experiments show differences. The discrepancies observed in these methods under field conditions could be evaluated by incorporating O2 flux measurement in addition to CO2 flux measurement. However, this is hampered by the absence of suitable equipment for measuring oxygen influx at the soil surface. A system to measure O2 fluxes at the soil surface using chamber methods has been developed. A gas handling subsystem and O2 analyser has been incorporated into an existing non-steady state automated chamber system originally designed for CO2 and H2O flux monitoring. The system consists of four 60 L soil chambers connected to temperature-controlled datalogger housing. During a measurement cycle, the chamber lid closes and the system measures changes of CO2/H2O and depletion of O2in the chamber headspace. Samples for CO2 /H2O circulate in a closed path between the chamber and an IR gas analyser. An air sample for O2 analysis is sub-sampled from this circulating air stream. Air samples for O2 are first dried using a two-stage Nafion drier. Mass flows and pressures are balanced at the pascal level prior to the gas passing into a ppm level fuel-cell oxygen analyser (Sable Systems Oxzilla). The chamber sample airstream is measured against a reference gas identically handled in a parallel air stream. A makeup gas of dry N2 is injected back to the chamber to return equimolar amounts of gas to replace the wet air removed, and hence prevent pressure fluctuation in the headspace of the chamber. The implementation of automated control of gas drying and sampling, pressure balancing, flow regulation and self calibration of the differential oxygen analyser enabled measuring O2 at the ppm level. The system is being tested utilizing a laboratory column experiment in which known O2 consumption is generated via oxidation of lead in electrochemical oxygen gas sensor (Model GC33-200, GC. Industrial Inc., Fremont, CA). This system marks one of the first successful direct measurement of oxygen flux across soil surface.

  8. Eddy covariance methane flux measurements over a grazed pasture: effect of cows as moving point sources

    NASA Astrophysics Data System (ADS)

    Felber, R.; Münger, A.; Neftel, A.; Ammann, C.

    2015-02-01

    Methane (CH4) from ruminants contributes one third to global agricultural greenhouse gas emissions. Eddy covariance (EC) technique has been extensively used at various flux sites to investigate carbon dioxide exchange of ecosystems. Since the development of fast CH4 analysers the instrumentation at many flux sites have been amended for these gases. However the application of EC over pastures is challenging due to the spatial and temporal uneven distribution of CH4 point sources induced by the grazing animals. We applied EC measurements during one grazing season over a pasture with 20 dairy cows (mean milk yield: 22.7 kg d-1) managed in a rotational grazing system. Individual cow positions were recorded by GPS trackers to attribute fluxes to animal emissions using a footprint model. Methane fluxes with cows in the footprint were up to two orders of magnitude higher than ecosystem fluxes without cows. Mean cow emissions of 423 ± 24 g CH4 head-1 d-1 (best guess of this study) correspond well to animal respiration chamber measurements reported in the literature. However a systematic effect of the distance between source and EC tower on cow emissions was found which is attributed to the analytical footprint model used. We show that the EC method allows to determine CH4 emissions of grazing cows if the data evaluation is adjusted for this purpose and if some cow distribution information is available.

  9. Eddy covariance methane flux measurements over a grazed pasture: effect of cows as moving point sources

    NASA Astrophysics Data System (ADS)

    Felber, R.; Münger, A.; Neftel, A.; Ammann, C.

    2015-06-01

    Methane (CH4) from ruminants contributes one-third of global agricultural greenhouse gas emissions. Eddy covariance (EC) technique has been extensively used at various flux sites to investigate carbon dioxide exchange of ecosystems. Since the development of fast CH4 analyzers, the instrumentation at many flux sites has been amended for these gases. However, the application of EC over pastures is challenging due to the spatially and temporally uneven distribution of CH4 point sources induced by the grazing animals. We applied EC measurements during one grazing season over a pasture with 20 dairy cows (mean milk yield: 22.7 kg d-1) managed in a rotational grazing system. Individual cow positions were recorded by GPS trackers to attribute fluxes to animal emissions using a footprint model. Methane fluxes with cows in the footprint were up to 2 orders of magnitude higher than ecosystem fluxes without cows. Mean cow emissions of 423 ± 24 g CH4 head-1 d-1 (best estimate from this study) correspond well to animal respiration chamber measurements reported in the literature. However, a systematic effect of the distance between source and EC tower on cow emissions was found, which is attributed to the analytical footprint model used. We show that the EC method allows one to determine CH4 emissions of cows on a pasture if the data evaluation is adjusted for this purpose and if some cow distribution information is available.

  10. Gas flow meter and method for measuring gas flow rate

    DOEpatents

    Robertson, Eric P.

    2006-08-01

    A gas flow rate meter includes an upstream line and two chambers having substantially equal, fixed volumes. An adjustable valve may direct the gas flow through the upstream line to either of the two chambers. A pressure monitoring device may be configured to prompt valve adjustments, directing the gas flow to an alternate chamber each time a pre-set pressure in the upstream line is reached. A method of measuring the gas flow rate measures the time required for the pressure in the upstream line to reach the pre-set pressure. The volume of the chamber and upstream line are known and fixed, thus the time required for the increase in pressure may be used to determine the flow rate of the gas. Another method of measuring the gas flow rate uses two pressure measurements of a fixed volume, taken at different times, to determine the flow rate of the gas.

  11. Benthic remineralisation rates in southern North Sea - from point measurements to areal estimates

    NASA Astrophysics Data System (ADS)

    Neumann, Andreas; Friedrich, Jana; van Beusekom, Justus; Naderipour, Céline

    2015-04-01

    The southern North Sea is enclosed by densely populated hinterland with intensive use by agriculture and industry and thus substantially affected by anthropogenic influences. As a coastal subsystem, this applies especially to the German Wadden Sea, a system of back-barrier tidal flats along the whole German Bight. Ongoing efforts to implement environmental protection policies during the last decades changed the significance of various pollutants such as reactive nitrogen or phosphate, which raises the desire for constant monitoring of the coastal ecosystem to assess the efficiency of the employed environmental protection measures. Environmental monitoring is limited to point measurements which thus have to be interpolated with appropriate models. However, existing models to estimate various sediment characteristics for the interpolation of point measurements appear insufficient when compared with actual field measurements in the southern North Sea. We therefore seek to improve these models by identifying and quantifying key variables of benthic solute fluxes by comprehensive measurements which cover the complete spatial and seasonal variability. We employ in-situ measurements with the eddy-correlation technique and flux chambers in combination with ex-situ incubations of sediment cores to establish benthic fluxes of oxygen and nutrients. Additional ex-situ measurements determine basic sediment characteristics such as permeability, volumetric reaction rates, and substrate concentration. With our first results we mapped the distribution of measured sediment permeability, which suggest that areas with water depth greater than 30 m are impervious whereas sediment in shallower water at the Dogger Bank and along the coast is substantially permeable with permeability between 10-12 m2 and 10-10 m2. This implies that benthic fluxes can be estimated with simple diffusion-type models for water depths >30 m, whereas estimates especially for coastal sediments require percolation modelling. We are further able to estimate sediment permeability and volumetric oxygen consumption rate on the basis of grain size distribution. Since grain size distribution is already mapped with high spatial resolution, we now have the prerequisites to interpolate two key variables for benthic consumption and influx of oxygen. With our next step we intend to assess model-based estimates of benthic oxygen and nutrient fluxes with our in-situ measurements as references to refine the underlying models. Our field measurements contribute to the NOAH project (North Sea; Observation and Assessment of Habitats), the established methods for routine monitoring contribute to the WiMO project (Wissenschaftliches Monitoring / Scientific Monitoring).

  12. Measuring denitrification after grassland renewal and grassland conversion to cropland by using the 15N gas-flux method

    NASA Astrophysics Data System (ADS)

    Buchen, Caroline; Eschenbach, Wolfram; Flessa, Heinz; Giesemann, Anette; Lewicka-Szczebak, Dominika; Well, Reinhard

    2015-04-01

    Denitrification, the reduction of oxidized forms of inorganic N to N2O and N2 is an important pathway of gaseous nitrogen losses. Measuring denitrification, especially the reduction of N2O to N2, expressed in the product ratio (N2O/(N2O + N2)), is rather difficult and hence rarely performed under field conditions. But using the 15N gas-flux method allows determining N transformation processes in their natural environment. In order to develop effective climate mitigation strategies understanding the N2O source is essential. We used the 15N gas-flux method to determine N2O and N2 emissions following grassland renewal and conversion techniques. Therefore we selected three different treatments: control (C), mechanical grassland renovation (GR) (autumn 2013) and grassland conversion to maize (GM) (spring 2014) from field plot trials on two different sites (Histic Gleysoil and Plaggic Anthrosol) near Oldenburg, Lower Saxony, Germany. We applied 15N labeled KNO3- (60 atom. % 15N) at a rate equivalent to common farming practices (150 kg N*ha-1) using needle injection of fertilizer solution in three different depths (10 cm, 15 cm, 20 cm) for homogeneous soil labeling up to 30 cm in microplots. During the first 10 days after application (May 2014) gas flux measurements from closed chambers were performed every second day and then weekly following a period of 8 weeks. Gas samples were analyzed for ?15N of N2 and N2O by IRMS according to Lewicka-Szczebak et al. (2013). Concentration and 15N enrichment of NO3- in soil water was determined on weekly samples using the SPIN-MAS technique (Stange et al. 2007). Fluxes of N2 and N2O evolved from the 15N labeled soil nitrogen pool were calculated using the equations of Spott et al. (2006). Peak events of N2 and N2O emissions occurred during the first 10 days of measurement, showing differences in soil types, as well as treatment variations. N2 fluxes up to 178 g*ha-1*day-1 and N2O fluxes up to 280 g*ha-1*day-1 were measured on the Plaggic Anthrosol in the GR treatment, while on the Histic Gleysoil, the GM treatment showed highest fluxes with N2 fluxes up to 1260 g*ha-1*day-1 and N2O fluxes up to 747 g*ha-1*day-1. Alike the product ratio of initial fluxes was higher on the Plaggic Anthrosol and lower on the Histic Gleysoil. Data analysis is still in progress and further results will be provided. References: Lewicka-Szczebak, D., R. Well, A. Giesemann, L. Rohe and U. Wolf (2013). "An enhanced technique for automated determination of 15N signatures of N2, (N2+N2O) and N2O in gas samples." Rapid Communications in Mass Spectrometry 27(13): 1548-1558. Spott, O., R. Russow, B. Apelt and C. F. Stange (2006). "A 15N-aided artificial atmosphere gas flow technique for online determination of soil N2 release using the zeolite Köstrolith SX6®." Rapid Communications in Mass Spectrometry 20(22): 3267-3274. Stange, F., O. Spott, B. Apelt and R. W. Russow (2007). "Automated and rapid online determination of 15N abundance and concentration of ammonium, nitrite, or nitrate in aqueous samples by the SPINMAS technique." Isotopes in Environmental and Health Studies 43(3): 227-236.

  13. Calculating the detection limits of chamber-based soil greenhouse gas flux measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Renewed interest in quantifying greenhouse gas emissions from soil has lead to an increase in the application of chamber-based flux measurement techniques. Despite the apparent conceptual simplicity of chamber-based methods, nuances in chamber design, deployment, and data analyses can have marked ef...

  14. Measurement of the flux of ultra high energy cosmic rays using data from very inclined air

    E-print Network

    Hebbeker, Thomas

    Measurement of the flux of ultra high energy cosmic rays using data from very inclined air showers.1.2 Cosmic rays above 100 TeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.2 Extensive air-model of the hadronic cascade . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3 Very inclined air showers

  15. Measuring Fast-Temporal Sediment Fluxes with an Analogue Acoustic Sensor: A Wind Tunnel Study

    PubMed Central

    Poortinga, Ate; van Minnen, Jan; Keijsers, Joep; Riksen, Michel; Goossens, Dirk; Seeger, Manuel

    2013-01-01

    In aeolian research, field measurements are important for studying complex wind-driven processes for land management evaluation and model validation. Consequently, there have been many devices developed, tested, and applied to investigate a range of aeolian-based phenomena. However, determining the most effective application and data analysis techniques is widely debated in the literature. Here we investigate the effectiveness of two different sediment traps (the BEST trap and the MWAC catcher) in measuring vertical sediment flux. The study was performed in a wind tunnel with sediment fluxes characterized using saltiphones. Contrary to most studies, we used the analogue output of five saltiphones mounted on top of each other to determine the total kinetic energy, which was then used to calculate aeolian sediment budgets. Absolute sediment losses during the experiments were determined using a balance located beneath the test tray. Test runs were conducted with different sand sizes and at different wind speeds. The efficiency of the two traps did not vary with the wind speed or sediment size but was affected by both the experimental setup (position of the lowest trap above the surface and number of traps in the saltation layer) and the technique used to calculate the sediment flux. Despite this, good agreement was found between sediment losses calculated from the saltiphone and those measured using the balance. The results of this study provide a framework for measuring sediment fluxes at small time resolution (seconds to milliseconds) in the field. PMID:24058512

  16. Uncertainty analysis for chromaticity coordinates and luminous flux measurements of LEDs

    NASA Astrophysics Data System (ADS)

    Qi, Rui; Bajorins, David P.

    2014-09-01

    This paper introduces an uncertainty analysis model and its experimental implementation for chromaticity coordinates and luminous flux measurements of light-emitting diode (LED) sources. The uncertainty model applies the theory of the numerical method to estimate both the chromaticity coordinates and luminous flux uncertainties. The modeling process follows the steps described in GUM for determining the uncertainties. First, the mathematical functions for chromaticity coordinates and luminous flux are expressed according to both the sphere calibration and the LED measurement procedures. Based on the functions, the uncertainty contributors are identified as the input quantities of the model, and luminous flux and chromaticity coordinates are the output quantities. Second, the uncertainty contributors are categorized as random variables and systematic variables. Contributors such as spectrometer wavelength and spectral value repeatability are random variables; thus, their standard uncertainties are analyzed with statistical methods. The other contributors, such as spectrometer wavelength offsets and stray light, are systematic variables; thus, their standard uncertainties are estimated with non-statistical methods. In order to measure these contributors, several simple methods are developed for spectrometers and source measure units (SMU). Third, the sensitivity coefficients for the uncertainty contributors are calculated based on the numerical approach by calculating the output quantities with a change of the input quantities. Fourth, the uncertainties caused by each contributor are calculated using their standard uncertainties and sensitivity coefficients, and then combined. Finally, the expanded uncertainty is obtained with a coverage factor (k=2). The calculation for each step is conducted by a Matlab program.

  17. Confronting model predictions of carbon fluxes with measurements of Amazon forests subjected to experimental

    E-print Network

    Malhi, Yadvinder

    rainforest. Summary Considerable uncertainty surrounds the fate of Amazon rainforests in response to climate are projected to be one of the biggest consequences for the Amazon rainforest as global climate changeConfronting model predictions of carbon fluxes with measurements of Amazon forests subjected

  18. Flux Measurements of Volatile Organic Compounds from an Urban Tower Platform 

    E-print Network

    Park, Chang Hyoun

    2011-08-08

    surface layer. We describe a new relaxed eddy accumulation system combined with a dual-channel gas chromatography - flame ionization detection used for volatile organic compound (VOC) flux measurements in the urban area, focusing on the results... ................................................................... 18 2.4.1. Setup for sample flow path ........................................................ 18 2.4.2. Relaxed eddy accumulation (REA) setup .................................. 19 2.4.3. GC...

  19. FIELD MEASUREMENTS OF CONTAMINANT FLUX BY INTEGRAL PUMPING TESTS (SAN FRANCISCO, CA)

    EPA Science Inventory

    Current remedial techniques are unable to completely eliminate all dense nonaqueous phase liquid (DNAPL) from source zone areas and conflicting views on the benefits of partial DNAPL source zone remediation exist in the literature. A comparison of flux measurements before and af...

  20. Reconciling Measured and Modeled Distributed Snowpack Temperatures and Subsurface Heat Fluxes

    NASA Astrophysics Data System (ADS)

    Huwald, H.; Higgins, C. W.; Diebold, M.; Lehning, M.; Williams, S. R.; Selker, J. S.; Parlange, M. B.

    2014-12-01

    While many common snow cover models allow for spatially distributed representation of the snow pack, most in-situ measurement techniques determining snow properties and state variables are invasive, destructive, and in most cases single point measurements. Fiber optic distributed temperature sensing (FO-DTS) provides a way to obtain hundreds of data points in the snow at a time in various problem-adapted configurations with cable lengths of several hundred meters. We present several experiments employing different geometrical FO cable arrangements in the snow in an attempt to obtain small-scale statistical information on snow temperature distribution and variability and the resulting subsurface (conductive) heat fluxes. The spatially distributed conductive heat fluxes are computed based on the Fourier heat equation using snow temperature and snow depth data, and an effective snow thermal conductivity derived from collocated density measurements. The temperature measurements and the simple heat flux calculations are then compared to corresponding results from the detailed SNOWPACK model. These comparisons investigate the closure of the local energy balance and show the relation between DTS temperatures and model estimations of snow thermal conductivity and conductive heat fluxes.

  1. Measurement of the Light Flux of Stars and the Night-Sky

    E-print Network

    Hebbeker, Thomas

    Measurement of the Light Flux of Stars and the Night-Sky with Silicon Photomultipliers Von der-High-Energy Cosmic Rays and Extensive Air Showers 5 2.1 Energy spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.2 Fluorescence detector . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.3 Event

  2. EVALUATION OF THE FLUX CHAMBER METHOD FOR MEASURING VOLATILE ORGANIC EMISSIONS FROM SURFACE IMPOUNDMENTS

    EPA Science Inventory

    This research deals with the validation of the flux chamber method for measuring volatile organic emissions from liquid surfaces in treatment, storage and disposal facilities (TSDF). A simulated surface impoundment was constructed so that method precision and accuracy could be de...

  3. Tropospheric ozone reduces carbon assimilation in trees: estimates from analysis of continuous flux measurements

    E-print Network

    Goldstein, Allen

    Tropospheric ozone reduces carbon assimilation in trees: estimates from analysis of continuous flux Abstract High ground-level ozone concentrations are typical of Mediterranean climates. Plant exposure to this oxidant is known to reduce carbon assimilation. Ozone damage has been traditionally measured through

  4. Energy budget components, ammonia concentration and flux measurements on an agricultural landscape near Bjerringbro, Denmark

    NASA Astrophysics Data System (ADS)

    Pogány, Andrea; Weidinger, Tamás.; Bienkowski, Jerzy; Bordás, Árpád.; Bozóki, Zoltán.; Eredics, Attila; Hensen, Arjan; Janku, Krzysztof; Kiss, Gy?z?; Kraai, Aline; Istenes, Zoltán.; Mohácsi, Árpád.; Szabó, Gábor; Schelde, Kirsten; Theobald, Mark

    2010-05-01

    As a part of the NitroEurope common field experiment, energy budget components and ammonia concentrations were measured by various methods on an agricultural field near Bjerringbro, Denmark in April 2009. Several sources of ammonia (pig farms, nearby fertilized fields) were present in the landscape and the field itself was also fertilized with pig slurry during the campaign. Turbulent fluxes were calculated using micrometeorological measurement data (standard meteorological parameters, radiation and surface energy budget components) as well as three different methods: (i) the gradient, (ii) the Bowen ratio and (iii) the eddy covariance method using 15 min average time. Results obtained using different methodologies for flux calculations and local effects on energy budget closure were compared. Instrumentation used for measuring ammonia concentrations included two wet-chemical (AMANDA) instruments and two photoacoustic instruments (a mid-IR CO2 laser based Nitolux and a self-developed near-IR diode laser based WaSul instrument). The WaSul instrument was operated in gradient configuration, which also enables the calculation of ammonia fluxes. The instruments were placed at different points of the field to gain more information on the spatial concentration distribution. Ammonia concentration data measured by the different instruments and wind speed and direction data were used to estimate the location of ammonia sources within the landscape. After fertilization of the field ammonia emission fluxes were calculated from the gradient data.

  5. Shipboard Measurements and Estimations of AirSea Fluxes in the Western Tropical Pacific Ocean

    E-print Network

    California at Irvine, University of

    Ship­board Measurements and Estimations of Air­Sea Fluxes in the Western Tropical Pacific Ocean E dur­ ing the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean and Atmospheric Response of the surface­layer turbulence properties are compared with those from previous land and ocean results. Momentum

  6. Measurement of greenhouse gas flux from agricultural soils using static chambers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Measurement of greenhouse gas (GHG) fluxes between the soil and the atmosphere, in both managed and unmanaged ecosystems, is critical to understanding the biogeochemical drivers of climate change and to the development and evaluation of GHG mitigation strategies based on modulation of landscape mana...

  7. USDA-ARS GRACEnet Project Protocols, Chapter 3. Chamber-based trace gas flux measurements4

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This protocol addresses N2O, CO2 and CH4 flux measurement by soil chamber methodology. The reactivities of other gasses of interest such as NOx O3, CO, and NH3 will require different chambers and associated instrumentation. Carbon dioxide is included as an analyte with this protocol; however, when p...

  8. Productivity and carbon dioxide exchange of the leguminous crops: Estimates from flux tower measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Net CO2 exchange data on legume crops at 17 flux tower sites in North America and 3 sites in Europe representing 29 site-years of measurements were partitioned into gross photosynthesis and ecosystem respiration using a light-response function method, resulting in new estimates of ecosystem-scale ec...

  9. Partitioning forest carbon fluxes with overstory and understory eddy-covariance measurements: A synthesis based

    E-print Network

    Cohen, Ronald C.

    , with a range of 32­79%. Understory in deciduous forests (62%) had higher contributions to ecosystem respiration; Photosynthesis; Respiration; Forest floor; Evergreen; Deciduous 1. Introduction Forests influence atmosphericPartitioning forest carbon fluxes with overstory and understory eddy-covariance measurements

  10. MEASUREMENT OF BI-DIRECTIONAL AMMONIA FLUXES OVER SOYBEAN USING MODIFIED BOWEN-RATIO TECHNIQUE

    EPA Science Inventory

    Measurements of bi-directional ammonia exchange over a fertilized soybean canopy are presented for an 8-week period during the summer of 2002. The modified Bowne-ratio approach was used to determine fluxes from vertical NH3 and temperature gradients in combination with eddy covar...

  11. Use of Nitrogen Budgets and N2 Flux Measurements to Estimate the Role of Denitrification in Brownfield Stormwater Wetlands

    NASA Astrophysics Data System (ADS)

    Palta, M. M.; Groffman, P. M.; Findlay, S.

    2012-12-01

    Wetlands are constructed or restored in urban and agricultural areas to reduce inorganic nitrogen (N) contamination of surface water runoff. Few studies, however, have examined the performance of unrestored but highly impacted wetlands within an urban context. These wetlands tend to be the primary recipient of nitrate (NO3-)-enriched storm and rainwater due to their ubiquity in low-lying portions of the urban landscape. Wetland studies anticipate high rates of NO3- removal via the microbial process of denitrification when labile carbon (C) and NO3- are high and O2 is low. The ability to quantify and predict the role of denitrification within particular systems is limited, however, and denitrification estimates are compromised by our inability to accurately measure N2 flux. In this study, we calculated loading rates of inorganic N and used measurements of N2/Ar, O2/Ar, and NO3- flux in sediments to generate inorganic N budgets for brownfield stormwater wetland sites. Loading of inorganic N via rain and stormwater ranged from 4-533 mg N/m2/d, and large amounts of NH4+ were additionally created from mineralization of decomposing organic matter, leading to high fluxes of NH4+ out of sediment into water (2-117 mg N/m2/d). Hydrology was a strong driving force of N2 flux; lowering of the water table allowed surface sediments to oxidize, leading to production of NO3-, which fueled N2 production lower in the sediment profile. Overall, the wetlands are denitrifying NO3- at a rate of around 620-2,580 ?g N/m2/day. Flux of NO3- out of sediments was higher in some cases (630-1,900 ?g N/m2/day), likely due to plant uptake. These wetlands appeared to be serving as a sink for NO3-, but were net sources of NH4+; periodic drainage of the wetlands to promote oxidation of NH4+ may be a strategy for promoting higher inorganic nitrogen removal from these sites.

  12. Emissions of volatile organic compounds inferred from airborne flux measurements over a megacity

    NASA Astrophysics Data System (ADS)

    Karl, T.; Apel, E.; Hodzic, A.; Riemer, D. D.; Blake, D. R.; Wiedinmyer, C.

    2009-01-01

    Toluene and benzene are used for assessing the ability to measure disjunct eddy covariance (DEC) fluxes of Volatile Organic Compounds (VOC) using Proton Transfer Reaction Mass Spectrometry (PTR-MS) on aircraft. Statistically significant correlation between vertical wind speed and mixing ratios suggests that airborne VOC eddy covariance (EC) flux measurements using PTR-MS are feasible. City-median midday toluene and benzene fluxes are calculated to be on the order of 14.1±4.0 mg/m2/h and 4.7±2.3 mg/m2/h, respectively. For comparison the adjusted CAM2004 emission inventory estimates toluene fluxes of 10 mg/m2/h along the footprint of the flight-track. Wavelet analysis of instantaneous toluene and benzene measurements during city overpasses is tested as a tool to assess surface emission heterogeneity. High toluene to benzene flux ratios above an industrial district (e.g. 10-15 g/g) including the International airport (e.g. 3-5 g/g) and a mean flux (concentration) ratio of 3.2±0.5 g/g (3.9±0.3 g/g) across Mexico City indicate that evaporative fuel and industrial emissions play an important role for the prevalence of aromatic compounds. Based on a tracer model, which was constrained by BTEX (BTEX- Benzene/Toluene/Ethylbenzene/m, p, o-Xylenes) compound concentration ratios, the fuel marker methyl-tertiary-butyl-ether (MTBE) and the biomass burning marker acetonitrile (CH3CN), we show that a combination of industrial, evaporative fuel, and exhaust emissions account for >87% of all BTEX sources. Our observations suggest that biomass burning emissions play a minor role for the abundance of BTEX compounds in the MCMA (2-13%).

  13. Micrometeorological and flux measurements over a permafrost black spruce forest in Interior Alaska

    NASA Astrophysics Data System (ADS)

    Nakai, T.; Kim, Y.; Busey, R.; Suzuki, R.

    2011-12-01

    A measurement site of energy, water, and carbon fluxes was established in a black spruce forest at the center of a flat basin of Poker Flat Research Range (PFRR), University of Alaska Fairbanks (UAF), located in Interior Alaska, as a key observation site of JAMSTEC-IARC Collaboration Study (JICS). This forest is characterized by an open canopy structure of a black spruce stand with its floor covered by vegetation such as sphagnum moss, tussock sedges, shrubs, and herbs, which is typical in Interior Alaska associated with the presence of permafrost. To obtain reliable flux data for a long period with minimum data loss, an improved closed-path CO2/H2O gas analyzer LI-7200 (LI-COR) was used. In addition, to consider the effect of the angle of attack dependent errors of ultrasonic anemometer on eddy fluxes, a WindMaster Pro ultrasonic anemometer (Gill) was employed. Measurements started in October 2010. Comparing the fluxes measured on the tower (11m) and forest floor (1.85m), the ratio of the CO2 flux of the overstory black spruce to the total CO2 flux was almost 1 until the understory plants emerged, and gradually decreased as the understory plants grew. On the other hand, most of the evapotranspiration was explained by the forest floor, and the contribution of the overstory black spruce trees was negligibly small. The decoupling coefficient of the whole canopy was almost less than 0.1, and typically less than 0.05, indicating that the leaf and surface of this black spruce forest were strongly coupled to the prevailing weather. In fact, most of evapotranspiration was explained by the adiabatic term with saturation deficit and wind speed, and the contribution of the available energy was less important. This low decoupling coefficient may be due to the high surface roughness with the open canopy structure of the black spruce forest.

  14. Estimates of surface heat flux from sodar and laser scintillation measurements in the unstable boundary layer

    SciTech Connect

    Coulter, R.L.; Wesely, M.L.

    1980-10-01

    Measurements of acoustic backscatter in the lower planetary boundary layer and optical line-of-sight scintillation in the surface layer are each used to compute sensible heat fluxes in the unstable surface layer. Comparisons with simultaneous low-level point measurements by eddy correlation show good agreement, indicating that remote-sensing methods can be successful over less homogeneous terrain where conventional surface layer measurement techniques are less accurate. Corrections to take into account the effects of humidity fluctuations are found necessary in order to achieve accuracies within 10%. Free convection is assumed to permit interpretation of the sodar data, while either forced or free convection is assumed for the scintillation data. A systematic overestimate of heat fluxes is found from sodar measurements made during the morning, when the height of the convectively mixed layer is increasing rapidly.

  15. A method for obtaining distributed surface flux measurements in complex terrain

    NASA Astrophysics Data System (ADS)

    Daniels, M. H.; Pardyjak, E.; Nadeau, D. F.; Barrenetxea, G.; Brutsaert, W. H.; Parlange, M. B.

    2011-12-01

    Sonic anemometers and gas analyzers can be used to measure fluxes of momentum, heat, and moisture over flat terrain, and with the proper corrections, over sloping terrain as well. While this method of obtaining fluxes is currently the most accurate available, the instruments themselves are costly, making installation of many stations impossible for most campaign budgets. Small, commercial automatic weather stations (Sensorscope) are available at a fraction of the cost of sonic anemometers or gas analyzers. Sensorscope stations use slow-response instruments to measure standard meteorological variables, including wind speed and direction, air temperature, humidity, surface skin temperature, and incoming solar radiation. The method presented here makes use of one sonic anemometer and one gas analyzer along with a dozen Sensorscope stations installed throughout the Val Ferret catchment in southern Switzerland in the summers of 2009, 2010 and 2011. Daytime fluxes are calculated using Monin-Obukhov similarity theory in conjunction with the surface energy balance at each Sensorscope station as well as at the location of the sonic anemometer and gas analyzer, where a suite of additional slow-response instruments were co-located. Corrections related to slope angle were made for wind speeds and incoming shortwave radiation measured by the horizontally-mounted cup anemometers and incoming solar radiation sensors respectively. A temperature correction was also applied to account for daytime heating inside the radiation shield on the slow-response temperature/humidity sensors. With these corrections, we find a correlation coefficient of 0.77 between u* derived using Monin-Obukhov similarity theory and that of the sonic anemometer. Calculated versus measured heat fluxes also compare well and local patterns of latent heat flux and measured surface soil moisture are correlated.

  16. Measuring the cascade rate in anisotropic turbulence through 3rd order structure functions.

    NASA Astrophysics Data System (ADS)

    Verdini, Andrea; Landi, Simone; Hellinger, Petr

    2014-05-01

    We employ the Von-Karman-Howart-Yaglom-Politano-Poquet (KHYPP)law, to compute the cascade rate by means of 3rd order structure functions in homogeneous, forced, DNS at high resolution. We consider first the isotropic case (no guide field) and verify that the cascade rate is consistent with the dissipation rate. Then we consider an anisotropic case (with guide field) for which the isotropic KHYPP law does not apply. We compute the parallel and perpendicular cascade rates and find that the latter basically accounts for the total dissipation rate, as expected for anisotropic turbulence. Also, the cascade rate derived from the isotropic law is found to be a good approximation for the total cascade rate. Recent works have shown that the hypothesis of stationary turbulence must be probably relaxed in the solar wind. We present preliminary results on the measure of the cascade rate in the expanding solar wind, obtained with DNS of MHD turbulence in the expanding box model. Such model incorporates the basic physic of expansion thus inducing anisotropies driven by both the magnetic field and expansion, along with an energy decrease due to the conservation of linear invariants (angular momentum and magnetic flux). The correction due to non-stationary conditions is found to be important and to become negligible only at small scales, thus suggesting that solar wind measurements over- estimate the actual cascade rate.

  17. TRAPPED PROTON FLUXES AT LOW EARTH ORBITS MEASURED BY THE PAMELA EXPERIMENT

    SciTech Connect

    Adriani, O.; Bongi, M.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Bruno, A.; Boezio, M.; Bonvicini, V.; Carbone, R.; Bogomolov, E. A.; Bottai, S.; Cafagna, F.; Campana, D.; Carlson, P.; Casolino, M.; De Donato, C.; De Santis, C.; De Simone, N.; Felice, V. Di; Castellini, G.; and others

    2015-01-20

    We report an accurate measurement of the geomagnetically trapped proton fluxes for kinetic energy above ?70 MeV performed by the PAMELA mission at low Earth orbits (350 ÷ 610 km). Data were analyzed in the frame of the adiabatic theory of charged particle motion in the geomagnetic field. Flux properties were investigated in detail, providing a full characterization of the particle radiation in the South Atlantic Anomaly region, including locations, energy spectra, and pitch angle distributions. PAMELA results significantly improve the description of the Earth's radiation environment at low altitudes, placing important constraints on the trapping and interaction processes, and can be used to validate current trapped particle radiation models.

  18. New ground-based lidar enables volcanic CO2 flux measurements.

    PubMed

    Aiuppa, Alessandro; Fiorani, Luca; Santoro, Simone; Parracino, Stefano; Nuvoli, Marcello; Chiodini, Giovanni; Minopoli, Carmine; Tamburello, Giancarlo

    2015-01-01

    There have been substantial advances in the ability to monitor the activity of hazardous volcanoes in recent decades. However, obtaining early warning of eruptions remains challenging, because the patterns and consequences of volcanic unrests are both complex and nonlinear. Measuring volcanic gases has long been a key aspect of volcano monitoring since these mobile fluids should reach the surface long before the magma. There has been considerable progress in methods for remote and in-situ gas sensing, but measuring the flux of volcanic CO2-the most reliable gas precursor to an eruption-has remained a challenge. Here we report on the first direct quantitative measurements of the volcanic CO2 flux using a newly designed differential absorption lidar (DIAL), which were performed at the restless Campi Flegrei volcano. We show that DIAL makes it possible to remotely obtain volcanic CO2 flux time series with a high temporal resolution (tens of minutes) and accuracy (<30%). The ability of this lidar to remotely sense volcanic CO2 represents a major step forward in volcano monitoring, and will contribute improved volcanic CO2 flux inventories. Our results also demonstrate the unusually strong degassing behavior of Campi Flegrei fumaroles in the current ongoing state of unrest. PMID:26324399

  19. New ground-based lidar enables volcanic CO2 flux measurements

    PubMed Central

    Aiuppa, Alessandro; Fiorani, Luca; Santoro, Simone; Parracino, Stefano; Nuvoli, Marcello; Chiodini, Giovanni; Minopoli, Carmine; Tamburello, Giancarlo

    2015-01-01

    There have been substantial advances in the ability to monitor the activity of hazardous volcanoes in recent decades. However, obtaining early warning of eruptions remains challenging, because the patterns and consequences of volcanic unrests are both complex and nonlinear. Measuring volcanic gases has long been a key aspect of volcano monitoring since these mobile fluids should reach the surface long before the magma. There has been considerable progress in methods for remote and in-situ gas sensing, but measuring the flux of volcanic CO2—the most reliable gas precursor to an eruption—has remained a challenge. Here we report on the first direct quantitative measurements of the volcanic CO2 flux using a newly designed differential absorption lidar (DIAL), which were performed at the restless Campi Flegrei volcano. We show that DIAL makes it possible to remotely obtain volcanic CO2 flux time series with a high temporal resolution (tens of minutes) and accuracy (<30%). The ability of this lidar to remotely sense volcanic CO2 represents a major step forward in volcano monitoring, and will contribute improved volcanic CO2 flux inventories. Our results also demonstrate the unusually strong degassing behavior of Campi Flegrei fumaroles in the current ongoing state of unrest. PMID:26324399

  20. Technical Note: Semi-rigid chambers for methane gas flux measurements on tree-stems

    NASA Astrophysics Data System (ADS)

    Siegenthaler, A.; Welch, B.; Pangala, S. R.; Peacock, M.; Gauci, V.

    2015-09-01

    There is increasing interest in the measurement of methane (CH4) emissions from tree stems in a wide range of ecosystems so as to determine how they contribute to the total ecosystem flux. To date, tree CH4 fluxes are commonly measured using rigid closed chambers (static or dynamic), which often pose challenges as these are bulky and limit measurement of CH4 fluxes to only a very narrow range of tree stem sizes and shapes. To overcome these challenges we aimed to design, describe and test new semi-rigid stem-flux chambers (or sleeves). We compared semi-rigid chamber's gas permeability to CH4 against the traditional rigid chamber approach, in the laboratory and in the field, with continuous flow or syringe injections. We found that the semi-rigid chambers performed well, and had numerous benefits including reduced gas permeability and optimal stem gas exchange surface to total chamber volume ratio (Sc/Vtot) allowing better headspace mixing, especially when connected in a dynamic mode to a continuous flow gas analyser. Semi-rigid sleeves can easily be constructed and transported in multiple sizes, are extremely light, cheap to build and fast to deploy. This makes them ideal for use in remote ecosystems where access logistics are complicated.

  1. Flux density measurements of GPS candidate pulsars at 610 MHz using interferometric imaging technique

    E-print Network

    Dembska, M; Kijak, J; Lewandowski, W

    2015-01-01

    We conducted radio interferometric observations of six pulsars at 610 MHz using the Giant Metrewave Radio Telescope (GMRT). All these objects were claimed or suspected to be the gigahertz-peaked spectra (GPS) pulsars. For a half of the sources in our sample the interferometric imaging provides the only means to estimate their flux at 610 MHz due to a strong pulse scatter-broadening. In our case, these pulsars have very high dispersion measure values and we present their spectra containing for the first time low-frequency measurements. The remaining three pulsars were observed at low frequencies using the conventional pulsar flux measurement method. The interferometric imaging technique allowed us to re-examine their fluxes at 610 MHz. We were able to confirm the GPS feature in the PSR B1823$-$13 spectrum and select a GPS candidate pulsar. These results clearly demonstrate that the interferometric imaging technique can be successfully applied to estimate flux density of pulsars even in the presence of strong s...

  2. First air-sea flux mooring measurements in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Schulz, E. W.; Josey, S. A.; Verein, R.

    2012-08-01

    The Southern Ocean is a key component of the global climate system: insulating the Antarctic polar region from the subtropics, transferring climate signals throughout the world's oceans and forming the southern component of the global overturning circulation. However, the air-sea fluxes that drive these processes are severely under-observed due to the harsh and remote location. This paucity of reference observations has resulted in large uncertainties in ship-based, numerical weather prediction, satellite and derived flux products. Here, we report observations from the Southern Ocean Flux Station (SOFS); the first successful air-sea flux mooring deployment in this ocean. The mooring was deployed at 47°S, 142°E for March 2010 to March 2011 and returned measurements of near surface meteorological variables and radiative components of the heat exchange. These observations enable the first accurate quantification of the annual cycle of net air-sea heat exchange and wind stress from a Southern Ocean location. They reveal a high degree of variability in the net heat flux with extreme turbulent heat loss events, reaching -470 Wm-2 in the daily mean, associated with cold air flowing from higher southern latitudes. The observed annual mean net air-sea heat flux is a small net ocean heat loss of -10 Wm-2, with seasonal extrema of 139 Wm-2 in January and -79 Wm-2 in July. The novel observations made with the SOFS mooring provide a key point of reference for addressing the high level of uncertainty that currently exists in Southern Ocean air-sea flux datasets.

  3. Methane flux measurements from paddy fields in the tropical Indian region

    NASA Astrophysics Data System (ADS)

    Lal, Shyam; Venkataramani, S.; Subbaraya, B. H.

    Methane flux measurements have been made from paddy fields in the Thanjavur region in southern India from September 1991 to January 1992. This is a major rice growing area having plenty of river and rain water. A perspex chamber was used to cover the plants. Samples from this chamber were collected using a metal bellows pump in small sample bottles. The methane flux values estimated from the analysis of these samples are mostly in the range of 15-25 mg m -2h -1. These preliminary results, from natural fields, give higher flux values than estimates from some other regions in India, as well as average values for the mid-latitude region, but values lower than from China.

  4. Rocket-based measurement of particle fluxes and currents in an auroral arc.

    NASA Technical Reports Server (NTRS)

    Vondrak, R. R.; Anderson, H. R.; Spiger, R. J.

    1971-01-01

    The rocket with the experiment was fired from Fort Churchill, Canada, over a homogeneous arc at 2000 local time on Feb. 26, 1969. Detectors measured the pitch-angle distribution of the fluxes of electrons with energies in the range from 2 to 18 and energies above 50 keV, and of protons with energies in the range from 2 to 18 and in the range from 80 to 1000 keV. The total backscattered flux was about 20% of the downward flux in the same energy range. No protons in the range from 2 to 18 keV, or any higher energy particles, were found in significant quantities. It was found that the energetic auroral electrons carry a substantial part of the Birkeland current. The arc extended at least 1500 km in an east-west direction and was not associated with substorm activity.

  5. Compact, Low-power Nitrous Oxide Monitor for Eddy Flux Soil Emission Measurements

    NASA Astrophysics Data System (ADS)

    Shorter, Joanne; Nelson, David; McManus, Barry; Zahniser, Mark

    2015-04-01

    Nitrous oxide, N2O, is one of the most important greenhouse and ozone-depleting gases. The concentration of N2O in the atmosphere has been increasing at a rate of 0.3% per year, with this rise believed to be largely due to soil emissions and agricultural practices (Park et al. 2011; Park et al. 2012). The eddy covariance technique, which requires fast (~10 Hz) measurement of mixing ratios and wind data, is perhaps the most effective technique available to quantify the exchange of gases between the atmosphere and the biosphere. It is very useful for addressing the high spatial and temporal variability of nitrous oxide emissions from soils. Nitrous oxide monitors appropriate for eddy covariance measurements generally require large flow rates (~10 - 15 slpm) and high speed, high power vacuum pumps (500 lpm, 600 W). These requirements complicate and in some environments prevent successful field deployment. We have addressed this by developing a compact, low-power nitrous oxide monitor for eddy flux or soil chamber measurements with a dramatically reduced sample cell volume. The sample volume is reduced nearly 5 fold (from 500 to 108 cm3) with only a two-fold reduction in optical path length (from 76 m to 36 m). The new multi-pass cell has an aluminum tube insert with a tapered internal volume that follows the mode envelope of the multi-pass spot pattern. This permits the use of a much smaller, lower power pump while still achieving high precision and fast response. Precision of 26 parts per trillion (ppt) in 1 sec was achieved with a 1/e response time of 0.14 s using a relatively low speed vacuum pump (100 lpm, 350 W). Further reductions in cell volume are planned which should permit sensitive eddy covariance measurements of nitrous oxide using an even smaller, lower power pump (60 lpm, 160 W) and modest sample flow rates (~2 slpm). We have also recently studied the application of a standard ARI nitrous oxide monitor to measurement of N2O isotopologues emitted into soil chambers. We measured nitrous oxide isotopologues, 14N15N16O (456), 14N14N16O (446), and15N14N16O (546), in the headspace of soil incubation jars. No significant interferences were observed and differences in isotopic ratios between distinctive soil samples were observed. Park, S., P. Croteau, K. A. Boering, D. M. Etheridge, D. Ferretti, P. J. Fraser, K. R. Kim, P. B. Krummel, R. L. Langenfelds, T. D. van Ommen, L. P. Steele and C. M. Trudinger (2012). "Trends and seasonal cycles in the isotopic composition of nitrous oxide since 1940." Nature Geosci 5(4): 261-265. Park, S., T. Pérez, K. Boering, S. Trumbore, J. Gil, S. Marquina and S. Tyler (2011). "Can N2O stable isotopes and isotopomers be useful tools to characterize sources and microbial pathways of N2O production and consumption in tropical soils?" Global Biogeochemical Cycles 25(1): GB1001.

  6. Acoustic measurement of the Deepwater Horizon Macondo well flow rate

    E-print Network

    Camilli, Richard

    On May 31, 2010, a direct acoustic measurement method was used to quantify fluid leakage rate from the Deepwater Horizon Macondo well prior to removal of its broken riser. This method utilized an acoustic imaging sonar and ...

  7. Dendritic flux avalanches and the accompanied thermal strain in type-II superconducting films: effect of magnetic field ramp rate

    NASA Astrophysics Data System (ADS)

    Jing, Ze; Yong, Huadong; Zhou, You-He

    2015-07-01

    Dendritic flux avalanches and the accompanying thermal stress and strain in type-II superconducting thin films under transverse magnetic fields are numerically simulated in this paper. The influence of the magnetic field ramp rate, edge defects, and the temperature of the surrounding coolant are considered. Maxwell's equations and the highly nonlinear E-J power-law characteristics of superconductors, coupled with the heat diffusion equation, are adopted to formulate these phenomena. The fast Fourier transform-based iteration scheme is used to track the evolution of the magnetic flux and the temperature in the superconducting film. The finite element method is used to analyze the thermal stress and strain induced in the superconducting film. It is found that the ramp rate has a significant effect on the flux avalanche process. The avalanches nucleate more easily for a film under a large magnetic field ramp rate than for a film under a small one. In addition, the avalanches always initiate from edge defects or areas that experience larger magnetic fields. The superconducting films experience large thermal strain induced by the large temperature gradient during the avalanche process, which may even lead to the failure of the sample.

  8. Measurements of microparticle fluxes on orbital stations in 1978-2011

    NASA Astrophysics Data System (ADS)

    Novikov, Lev; Baranov, Dmitrii; Dergachev, Valentin; Gagarin, Yurii; Samokhina, Maria S.; Bednyakov, Sergey A.

    The important task of ISO WG4/SC14 activity is the development of standards for the micrometeoroids/space debris environment. To develop such standards it is necessary to have a large amount of experimental data. This paper presents results of flight experiments for measuring fluxes of hard particles with sizes of 1-500 mum, that were carried out on “Salut-6” (1978-1979), “Salut-7” (1984-1985) and “Mir” (1988-1997) orbital space stations, and on ISS (1998-2011). Particle fluxes were determined by analyzing holes in thermal protective shields of plastic track detectors for heavy nuclei of cosmic rays, that were used in PLATAN experiment on “Salut” and “Mir” stations, and on ISS (2002-2004), and by studying craters in polished metal samples and at the surface of a specimen cartridge of KOMPLAST experiment on ISS (1998-2011). Differential and integral dependences of particle fluxes on their diameter were obtained for various assumptions about the correlation between diameters of craters/holes and of incident particles. The elemental composition analysis of remainders in craters, carried out with an electron microprobe, enabled to distinguish craters created by micrometeoroids from the ones made by space debris particles. The data obtained on particle fluxes are compared with existing models of natural and artificial particle fluxes. KOMPLAST results for particles with size of 5-50 mum exceed corresponding values of ORDEM2000 model for the ISS orbit.

  9. Suspended sediment fluxes in a tidal wetland: Measurement, controlling factors, and error analysis

    USGS Publications Warehouse

    Ganju, N.K.; Schoellhamer, D.H.; Bergamaschi, B.A.

    2005-01-01

    Suspended sediment fluxes to and from tidal wetlands are of increasing concern because of habitat restoration efforts, wetland sustainability as sea level rises, and potential contaminant accumulation. We measured water and sediment fluxes through two channels on Browns Island, at the landward end of San Francisco Bay, United States, to determine the factors that control sediment fluxes on and off the island. In situ instrumentation was deployed between October 10 and November 13, 2003. Acoustic Doppler current profilers and the index velocity method were employed to calculate water fluxes. Suspended sediment concentrations (SSC) were determined with optical sensors and cross-sectional water sampling. All procedures were analyzed for their contribution to total error in the flux measurement. The inability to close the water balance and determination of constituent concentration were identified as the main sources of error; total error was 27% for net sediment flux. The water budget for the island was computed with an unaccounted input of 0.20 m 3 s-1 (22% of mean inflow), after considering channel flow, change in water storage, evapotranspiration, and precipitation. The net imbalance may be a combination of groundwater seepage, overland flow, and flow through minor channels. Change of island water storage, caused by local variations in water surface elevation, dominated the tidalty averaged water flux. These variations were mainly caused by wind and barometric pressure change, which alter regional water levels throughout the Sacramento-San Joaquin River Delta. Peak instantaneous ebb flow was 35% greater than peak flood flow, indicating an ebb-dominant system, though dominance varied with the spring-neap cycle. SSC were controlled by wind-wave resuspension adjacent to the island and local tidal currents that mobilized sediment from the channel bed. During neap tides sediment was imported onto the island but during spring tides sediment was exported because the main channel became ebb dominant Over the 34-d monitoring period 14,000 kg of suspended sediment were imported through the two channels. The water imbalance may affect the sediment balance if the unmeasured water transport pathways are capable of transporting large amounts of sediment. We estimate a maximum of 2,800 kg of sediment may have been exported through unmeasured pathways, giving a minimum net import of 11,200 kg. Sediment flux measurements provide insight on tidal to fortnightly marsh sedimentation processes, especially in complex systems where sedimentation is spatially and temporally variable. ?? 2005 Estuarine Research Federation.

  10. Estimation of regional CO2 fluxes in northern Wisconsin using the ring of towers concentration measurements

    NASA Astrophysics Data System (ADS)

    Uliasz, M.; Denning, A. S.; Corbin, K.; Miles, N.; Richardson, S.; Davis, K.

    2006-12-01

    The WLEF TV tower in northern Wisconsin is instrumented to take continuous measurements of CO2 mixing ratio at 6 levels from 11 to 396m. During the spring and summer of 2004 additional CO2 measurements were deployed on five 76 m communication towers forming a ring around the WLEF tower with a 100-150 km radius. The data from the ring of towers are being used to estimate regional fluxes of CO2. The modeling framework developed for this purpose is based on SiB-RAMS: Regional Atmospheric Modeling System linked to Simple Biosphere model. The RAMS domain extends over the entire continental US with nested grids centered in northern Wisconsin. The CO2 lateral boundary conditions are provided by a global transport model PCTM (Parameterized Chemistry and Transport Model). This model system is capable to realistically reproduce diurnal cycle of CO2 fluxes as well as their spatial patterns in regional scale related to different vegetation types. However, there is still significant uncertainty in simulating atmospheric transport of CO2 due to synoptic and mesoscale circulations. We are attempting to assimilate available CO2 tower data into our modeling system in order to provide corrections for the fluxes simulated by the SiB-RAMS. These corrections applied separately to respiration and assimilation fluxes have spatial patterns but are assumed constant in time during a period of 10 days. Another correction is estimated for the CO2 inflow concentration entering the regional domain. The CO2 data assimilation is based the Lagrangian Particle Dispersion (LPD) model and the Bayessian inversion technique. The LPD model is driven by meteorological fields from the SiB-RAMS and is used for a regional domain in its adjoint mode to trace particles backward in time to derive influence functions for each concentration sample. The influence functions provide information on potential contributions both from surface sources and inflow fluxes that make their way through the modeling domain boundaries into the CO2 concentration sample. Then the Bayesian inversion technique is applied to estimate unknown corrections (model biases) for the CO2 fluxes. Several tests of the modeling framework were performed with the aid of model generated concentration pseudo- data. Finally, real data, CO2 concentration time series, observed at the towers were used to estimate CO2 regional fluxes. Different configurations of source areas within the radius up to 500 km from the WLEF tower and different assumptions concerning expected model-data mismatch error were investigated. The estimated fluxes are consistent with eddy covariance measurements from the WLEF tower.

  11. Sources and sinks of ozone in savanna and forest areas during EXPRESSO: Airborne turbulent flux measurements

    NASA Astrophysics Data System (ADS)

    Cros, B.; Delon, C.; Affre, C.; Marion, T.; Druilhet, A.; Perros, P. E.; Lopez, A.

    2000-12-01

    An airborne study of ozone concentrations and fluxes in the lower layers of the atmosphere was conducted over the Central African Republic (CAR) and northern Congo in November/December 1996, within the framework of the Experiment of Regional Sources and Sinks of Oxidants (EXPRESSO). The first 4 km of the atmosphere above savanna, rain forest, and the transitional area between them, were investigated with the French research aircraft Avion de Recherche Atmosphérique et de Télédétection (ARAT). Turbulent fluxes and deposition velocities of ozone were determined using the Eddy Correlation (EC) method. A specific methodology was developed to obtain accurate airborne turbulent flux measurements. This methodology is linked to the turbulence stationarity. The average values of ozone fluxes and ozone deposition velocities in the Atmospheric Boundary Layer (ABL) increase appreciably from savanna to forest. Near the ground, the ozone fluxes range between -0.115 +/-0.073 ppbv m/s above savanna and -0.350 +/-0.115 ppbv m/s above forest; for the deposition, the ranges are 0.0042 +/-0.0018 m/s and 0.015 +/-0.004 m/s. A simple empirical relationship between deposition velocity and Leaf Area Index (LAI) is proposed, giving an estimation of the deposition velocity for a whole latitudinal band. Vertical inputs of ozone to the ABL are estimated according to entrainment fluxes. The role of advection is neglected for horizontal transport of ozone in the ABL. The photochemical ozone production is deduced from the photo-stationary state deviation, and compared to the net ozone increase in the ABL during the flights performed above the forest. A tentative ozone budget based on the aircraft measurements is proposed in the ABL of the rain forest. Around noon, the photochemical production dominates with a net production of about 10 ppbv/h.

  12. Measuring proton energies and fluxes using EIT (SOHO) CCD areas outside the solar disk images

    E-print Network

    L. V. Didkovsky; D. L. Judge; A. R. Jones; E. J. Rhodes, Jr.; J. B. Gurman

    2006-04-20

    An indirect proton flux measuring tool based on discrimination of the energy deposited by protons in 128 x 128 pixel EIT CCD areas outside the solar disk images is presented. Single pixel intensity events are converted into proton incident energy flux using modeled energy deposition curves for angles of incidence 60 deg in four EIT spatial areas with different proton stopping power. The extracted proton flux is corrected for both the loss of one-pixel events in the range of angles of incidence as well as for the contribution to the single pixel events resulting from scattered middle-energy protons (low-energy or high-energy particles are stopped by the EIT components or pass through them, accordingly). A simple geometrical approach was found and applied to correct for a non-unique relation between the proton-associated CCD output signal and the incident proton energy. With this geometrical approximation four unique proton incident energy ranges were determined as 45--49, 145--154, 297--335, and 390--440 MeV. The indirect proton flux measuring tool has been tested by comparing Solar Energetic Particles (SEP) flux temporal profiles extracted from the EIT CCD frames and downloaded from the GOES database for the Bastille Day (BD) of 2000 July 14 and the more recent 2005 January 20 events. The SEP flux temporal profiles and proton spectra extracted from the EIT in the relatively narrow energy ranges between 45 and 440 MeV reported here are consistent with the related GOES profiles. The four additional EIT extracted ranges provide higher energy resolution of the SEP data.

  13. Confidence bands for measured economically optimal nitrogen rates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    While numerous researchers have computed economically optimal N rate (EONR) values from measured yield – N rate data, nearly all have neglected to compute or estimate the statistical reliability of these EONR values. In this study, a simple method for computing EONR and its confidence bands is descr...

  14. STATISTICAL MODEL OF LABORATORY DEATH RATE MEASUREMENTS FOR AIRBORNE BACTERIA

    EPA Science Inventory

    From 270 published laboratory airborne death rate measurements, two regression models relating the death rate constant for 15 bacterial species to aerosol age in the dark, Gram reaction, temperature, and an evaporation factor which is a function of RH and temperature were obtaine...

  15. Heart rate measurement based on a time-lapse image.

    PubMed

    Takano, Chihiro; Ohta, Yuji

    2007-10-01

    Using a time-lapse image acquired from a CCD camera, we developed a non-contact and non-invasive device, which could measure both the respiratory and pulse rate simultaneously. The time-lapse image of a part of the subject's skin was consecutively captured, and the changes in the average image brightness of the region of interest (ROI) were measured for 30s. The brightness data were processed by a series of operations of interpolation as follows a first-order derivative, a low pass filter of 2 Hz, and a sixth-order auto-regressive (AR) spectral analysis. Fourteen sound and healthy female subjects (22-27 years of age) participated in the experiments. Each subject was told to keep a relaxed seating posture with no physical restriction. At the same time, heart rate was measured by a pulse oximeter and respiratory rate was measured by a thermistor placed at the external naris. Using AR spectral analysis, two clear peaks could be detected at approximately 0.3 and 1.2 Hz. The peaks were thought to correspond to the respiratory rate and the heart rate. Correlation coefficients of 0.90 and 0.93 were obtained for the measurement of heart rate and respiratory rate, respectively. PMID:17074525

  16. Bacteriophage Flux in Endosymbionts (Wolbachia): Infection Frequency, Lateral Transfer, and Recombination Rates

    E-print Network

    Bordenstein, Seth

    Bacteriophage Flux in Endosymbionts (Wolbachia): Infection Frequency, Lateral Transfer in the free-living microbial world--bacteriophages. This study yields three results that show bacteriophages endosymbiont of invertebrates, Wolbachia. First, we show that bacteriophage WO is more widespread in Wolbachia

  17. Integral measurements of neutron and gamma-ray leakage fluxes from the Little Boy replica

    SciTech Connect

    Muckenthaler, F.J.

    1984-03-01

    This report presents integral measurements of neutron and gamma-ray leakage fluxes from a critical mockup of the Hiroshima bomb Little Boy at Los Alamos National Laobratory with detector systems developed by Oak Ridge National Laboratory. Bonner ball detectors were used to map the neutron fluxes in the horizontal midplane at various distances from the mockup and for selected polar angles, keeping the source-detector separation constant. Gamma-ray energy deposition measurements were made with thermoluminescent detectors at several locations on the iron shell of the source mockup. The measurements were performed as part of a larger progam to provide benchmark data for testing the methods used to calculate the radiation released from the Little Boy bomb over Hiroshima. 3 references, 10 figures.

  18. Integral emission factors for methane determined using urban flux measurements and local-scale inverse models

    NASA Astrophysics Data System (ADS)

    Christen, Andreas; Johnson, Mark; Molodovskaya, Marina; Ketler, Rick; Nesic, Zoran; Crawford, Ben; Giometto, Marco; van der Laan, Mike

    2013-04-01

    The most important long-lived greenhouse gas (LLGHG) emitted during combustion of fuels is carbon dioxide (CO2), however also traces of the LLGHGs methane (CH4) and nitrous oxide (N2O) are released, the quantities of which depend largely on the conditions of the combustion process. Emission factors determine the mass of LLGHGs emitted per energy used (or kilometre driven for cars) and are key inputs for bottom-up emission modelling. Emission factors for CH4 are typically determined in the laboratory or on a test stand for a given combustion system using a small number of samples (vehicles, furnaces), yet associated with larger uncertainties when scaled to entire fleets. We propose an alternative, different approach - Can integrated emission factors be independently determined using direct micrometeorological flux measurements over an urban surface? If so, do emission factors determined from flux measurements (top-down) agree with up-scaled emission factors of relevant combustion systems (heating, vehicles) in the source area of the